JP2022128430A - Method for producing esterified cellulose nanofiber and resin composition - Google Patents

Abstract

An object of the present invention is to provide an esterified cellulose nanofiber and a resin composition capable of producing a resin composition capable of forming a molded article having good and stable appearance and physical properties with good process efficiency while using the esterified cellulose nanofiber. A manufacturing method is provided.
An ester comprising a modification step of esterifying a pulp containing cellulose to obtain an esterified pulp, and a defibration and purification step of defibrating and purifying the esterified pulp to produce esterified cellulose nanofibers. In the method for producing cellulose nanofibers, the esterified pulp comprises a high DS component having a degree of esterification (DS) of 1.5 or more and 3 or less and a high DS component having a degree of esterification (DS) of 0.2 or more and less than 1.5. and said purification is removal of at least a portion of said high DS component.
[Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a method for producing an esterified cellulose nanofiber and a resin composition.

Thermoplastic resins are light and have excellent processing characteristics, so they are widely used in various fields such as automobile parts, electrical and electronic parts, office equipment housings, and precision parts. is often insufficient, composites of resins and various fillers are generally used. In recent years, the use of organic fibers such as cellulose fibers as such fillers has been studied. Cellulose is a material with low environmental load, has a low specific gravity, and can have an excellent property-improving effect for resin compositions, so it is promising as a filler for environmentally friendly resin compositions. is. In particular, cellulose nanofibers, due to their fine structure, can exhibit an excellent reinforcing effect on resin compositions even in a small amount, and thus their use as fillers for resin compositions has been studied in recent years. However, cellulose nanofibers are extremely prone to aggregation due to hydrogen bonding between cellulose molecules and the like, and uniform dispersion in resins is not always easy. In order to allow the cellulose nanofibers to be well dispersed in the resin while exhibiting an excellent reinforcing effect on the cellulose nanofibers, various techniques have conventionally been proposed in which the cellulose nanofibers are chemically modified to make them hydrophobic and then mixed with the resin. ing.

For example, Patent Document 1 discloses a fiber-reinforced resin composition containing chemically modified cellulose nanofibers and a thermoplastic resin, wherein the ratio of the solubility parameter of the chemically modified cellulose nanofibers to the solubility parameter of the thermoplastic resin is 0.87 to 1.88, and the chemically modified cellulose nanofibers have a crystallinity of 42.7% or more.

Patent Document 2 discloses a masterbatch containing acylated modified microfibrillated plant fibers, a thermoplastic resin, and a compatibilizer, and mixed with a diluent resin to produce a fiber-reinforced resin composition, wherein the acyl The acylation-modified microfibrillated plant fiber has a solubility parameter of 10 or more, the thermoplastic resin has a solubility parameter of 9 to 15 and is equal to or greater than the solubility parameter of the diluent resin, and the compatibilizer has a solubility parameter of the acylation-modified microfibrillated microfibrillated A masterbatch is described that is below the solubility parameter of plant fibers.

JP 2016-176052 A JP 2017-171713 A

Normally, when kneading the cellulose nanofibers and the resin, the water-containing slurry of the cellulose nanofibers is dehydrated and concentrated to increase the solid content concentration. However, when esterified cellulose nanofibers are used as cellulose nanofibers, the filter used for dehydration and concentration may become clogged, resulting in a decrease in process efficiency. Furthermore, in the resin composition containing the esterified cellulose nanofibers and the molded article formed using the same, unexpected appearance and/or physical properties different from those in the case of using the unesterified cellulose nanofibers. There were occasional problems.

Patent Documents 1 and 2 attempt to obtain a resin composition in which cellulose nanofibers or microfibrillated plant fibers are well dispersed in a resin, but there are inherent disadvantages when using esterified cellulose nanofibers. There is no focus on

The present invention solves the above-mentioned problems, and enables production of a resin composition capable of forming a molded article having good and stable appearance and physical properties with good process efficiency while using esterified cellulose nanofibers. An object of the present invention is to provide a method for manufacturing fibers and resin compositions.

The present disclosure includes the following aspects.
[1] A modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
a defibration and purification step of defibrating and purifying the esterified pulp to produce esterified cellulose nanofibers;
A method for producing an esterified cellulose nanofiber comprising
The esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5,
A method, wherein said purification is removal of at least a portion of said high DS component.
[2] The method according to aspect 1, wherein the difference in the degree of esterification (DS) between the high DS component and the low DS component is 0.3 or more.
[3] The method according to aspect 1 or 2 above, wherein in the defibration and purification step, the purification is performed before defibration.
[4] The method according to aspect 1 or 2 above, wherein in the defibration and purification step, the purification is performed during fibrillation.
[5] The method according to aspect 1 or 2 above, wherein in the defibration and purification step, the purification is performed after fibrillation.
[6] The method according to any one of aspects 1 to 5 above, wherein the purification is performed by dissolving and removing the high DS component in a solvent.
[7] The method according to aspect 6, wherein the high DS component is removed by filtration after the dissolution.
[8] The method according to aspect 6 or 7, wherein the solvent contains one or more selected from the group consisting of ketones, esters, nitrogen-containing compounds, sulfur-containing compounds, ethers, and halogenated hydrocarbons.
[9] The method according to any one of the above aspects 1 to 5, wherein the purification is performed using a separation solvent that separates the high DS component and the low DS component.
[10] The method according to aspect 9, wherein the high DS component is removed together with the separation solvent.
[11] Dispersing the high DS component in the separation solvent to form dispersed particles, and then filtering the dispersed particles and the separation solvent through a filter to trap and remove the dispersed particles in the filter. 10. The method of aspect 9 above, wherein said purification is performed by
[12] The method according to any one of aspects 9 to 11 above, wherein the separation solvent contains one or more selected from the group consisting of water and alcohol.
[13] The method according to any one of the above aspects 1 to 12, wherein the esterified pulp has a degree of esterification (DS) of more than 1.0 and not more than 2.0.
[14] The method according to any one of aspects 1 to 13, wherein the esterified cellulose nanofiber has a degree of esterification (DS) of 0.3 or more and 1.2 or less.
[15] The method according to any one of the above aspects 1 to 14, wherein the pulp is cotton linter-derived pulp.
[16] The method according to any one of the above aspects 1 to 15, wherein the esterification is performed in dimethylsulfoxide (DMSO).
[17] The method according to any one of the above aspects 1 to 16, wherein a carboxylic acid vinyl ester is used as an esterifying agent for the esterification.
[18] The method according to any one of the above aspects 1 to 17, wherein the esterification is acetylation.
[19] The method according to any one of the above aspects 1 to 18, wherein the high DS component removed by the purification comprises an acetylated polysaccharide having a cellulose type I crystallinity of less than 50%.
[20] a modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
a refining step of refining the esterified pulp;
A defibration and mixing step of mixing the purified esterified pulp with a resin and defibrating it to produce a resin composition containing the esterified cellulose nanofibers and the resin;
A method for producing a resin composition comprising
The esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5,
A method, wherein said purification is removal of at least a portion of said high DS component.
[21] a modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
A defibration and mixing step of mixing the esterified pulp with a resin and defibrating it to produce a resin composition containing the esterified cellulose nanofibers and the resin;
A method for producing a resin composition comprising
The esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5,
A method, wherein at least part of the high DS component is transferred from the esterified pulp into a resin phase in the defibration and mixing step.
[22] a modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
a refining step of refining the esterified pulp;
A defibration step of defibrating the purified esterified pulp to generate esterified cellulose nanofibers;
a mixing step of mixing the esterified cellulose nanofibers obtained in the fibrillation step and a resin to produce a resin composition;
A method for producing a resin composition comprising
The esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5,
A method, wherein said purification is removal of at least a portion of said high DS component.

According to one aspect of the present invention, esterified cellulose nanofibers can be used to produce a resin composition capable of forming a molded article having good and stable appearance and physical properties with good process efficiency. Methods of making fibers and resin compositions can be provided.

Illustrative embodiments of the present invention (hereinafter abbreviated as "present embodiments") will be described below, but the present invention is not limited to these embodiments. Unless otherwise specified, the characteristic values of the present disclosure are values measured by the method described in the [Examples] section of the present disclosure or a method understood to be equivalent thereto by those skilled in the art.

<<Method for producing esterified cellulose nanofiber>>
One aspect of the present invention provides a method for producing esterified cellulose nanofibers. In one aspect, the method includes a modification step of esterifying a pulp containing cellulose to obtain an esterified pulp, and a defibration and purification step of defibrating and purifying the esterified pulp to produce esterified cellulose nanofibers. . In one embodiment, the esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5, and is purified is the removal of at least part of the high DS component.

The presence of a high DS component and a low DS component in the esterified pulp is confirmed by a method of extracting with a solvent that dissolves only the high DS component (in one embodiment, dimethylsulfoxide (DMSO)) and separating the low DS component. . In one aspect, the high DS component is solvent-soluble, and the crystallinity of cellulose (in one aspect, the crystallinity of cellulose type I) is low or in an amorphous state, but the low DS component is in a general-purpose organic solvent. , the crystallinity of cellulose (in one aspect, the crystallinity of cellulose type I) is maintained at a high retention rate, and has a fiber shape similar to that of pulp. In the method of this embodiment, purification may remove some or all of the high DS components. In one aspect, the content of high DS components in the esterified pulp is reduced after refining compared to before refining, or contains the high DS component, it can be confirmed that at least a portion of the high DS component has been removed from the esterified pulp.

Esterified cellulose nanofibers are relatively resistant to agglomeration of cellulose nanofibers due to hydrophobization of cellulose molecules. shows a strong reinforcing effect. However, when producing a resin composition and a molded article using esterified cellulose nanofibers, as described above, the process efficiency is lowered due to clogging of the filter, and the appearance and/or physical properties of the molded article are affected. There were occasional problems.

The present inventors focused on the fact that some undesired components generated during the production of esterified cellulose nanofibers contribute to filter clogging, deterioration of the physical properties of molded articles, and poor appearance, and made further studies. The undesirable component is an excessively esterified portion in the esterified cellulose nanofiber, specifically a portion having a degree of esterification (DS) of 1.5 or more (in the present disclosure, a high DS component Also called.). Such a high DS component tends to have a low degree of crystallinity, and thus has a small reinforcing effect on the molded body. It is thought that they bleed out or act as a plasticizer for the resin, thereby degrading the physical properties of the molded product, and furthermore, partly decomposing to cause problems such as appearance defects such as silver streaks and black streaks. In addition, the high DS component tends to cause the esterified cellulose nanofibers to aggregate, and is thought to reduce the dispersibility of the esterified cellulose nanofibers in the resin.

By removing such a high DS component, the method of the present embodiment avoids problems such as filter clogging during production of esterified cellulose nanofibers, and further imparts good physical properties and appearance to the molded product. obtain.
Each step of the method for producing an esterified cellulose nanofiber according to the present embodiment will be described below.

<Degeneration step>
In this step, a pulp containing cellulose is esterified to obtain an esterified pulp. Pulp includes wood pulp obtained from wood species (hardwood or softwood), non-wood pulp obtained from non-wood species (bamboo, hemp fiber, bagasse, kenaf, linter, etc.), and purified pulp of these (purified linter, etc.) ) can be used. As the non-wood pulp, cotton-derived pulp including cotton linter pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, straw-derived pulp, and the like can be used. Cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp are cotton lints, cotton linters, hemp-based abaca (e.g., from Ecuador or the Philippines), zeisal, respectively. , bagasse, kenaf, bamboo, straw, etc., through a refining process such as delignification by digestion, a bleaching process, and the like. The pulp is preferably cotton linter-derived pulp, since it has a high degree of crystallinity and can produce esterified cellulose nanofibers with excellent mechanical properties.

Esterification may be carried out in a solvent in the presence of an esterifying agent. As the solvent used in the esterification (also referred to as an esterification solvent in the present disclosure), aprotic solvents such as alkylsulfoxides, alkylamides, pyrrolidones, etc. can be used alone or in combination of two or more. .

Examples of alkylsulfoxides include di-C1-4 alkylsulfoxides such as dimethylsulfoxide (DMSO), methylethylsulfoxide and diethylsulfoxide.

Examples of alkylamides include N,N-dimethylformamide (DMF), N,N-diC1-4 alkylformamide such as N,N-diethylformamide; N,N-dimethylacetamide (DMAc), N,N -N,N-diC1-4 alkylacetamides such as diethylacetamide.

Examples of pyrrolidones include pyrrolidones such as 2-pyrrolidone and 3-pyrrolidone; N—C1-4 alkylpyrrolidones such as N-methyl-2-pyrrolidone (NMP).

As the esterification solvent, dimethylsulfoxide (DMSO) is particularly preferable from the viewpoint of obtaining good esterification efficiency.

Acid halides, acid anhydrides and carboxylic acid vinyl esters are preferred as the esterifying agent, and carboxylic acid vinyl esters are particularly preferred from the viewpoint of esterification efficiency. In a particularly preferred embodiment the esterification is acetylation.

The acid halide may be at least one selected from the group consisting of compounds represented by the following formulas.
R ¹ -C(=O)-X
(wherein R ¹ represents an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 24 carbon atoms, or an aryl group having 6 to 24 carbon atoms, and X represents Cl , Br or I.)
Specific examples of acid halides include acetyl chloride, acetyl bromide, acetyl iodide, propionyl chloride, propionyl bromide, propionyl iodide, butyryl chloride, butyryl bromide, butyryl iodide, benzoyl chloride, benzoyl bromide, iodine Examples include, but are not limited to, benzoyl chloride and the like. Among them, acid chlorides can be preferably used from the viewpoint of reactivity and handleability. In addition, in the reaction of the acid halide, one or more alkaline compounds may be added for the purpose of acting as a catalyst and at the same time neutralizing the by-product acidic substances. Specific examples of alkaline compounds include, but are not limited to: tertiary amine compounds such as triethylamine and trimethylamine; and nitrogen-containing aromatic compounds such as pyridine and dimethylaminopyridine.

Any appropriate acid anhydrides can be used as the acid anhydride. for example,
Saturated aliphatic monocarboxylic acid anhydrides such as acetic acid, propionic acid, (iso)butyric acid, and valeric acid; (meth)acrylic acid, unsaturated aliphatic monocarboxylic acid anhydrides such as oleic acid;
Alicyclic monocarboxylic acid anhydrides such as cyclohexanecarboxylic acid and tetrahydrobenzoic acid;
Aromatic monocarboxylic acid anhydrides such as benzoic acid and 4-methylbenzoic acid;
Examples of dibasic carboxylic anhydrides include saturated aliphatic dicarboxylic anhydrides such as succinic anhydride and adipic acid, unsaturated aliphatic dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride, and 1-cyclohexene-1 anhydride. , 2-dicarboxylic acid, hexahydrophthalic anhydride, alicyclic dicarboxylic anhydrides such as methyltetrahydrophthalic anhydride, and aromatic dicarboxylic anhydrides such as phthalic anhydride and naphthalic anhydride;
Examples of polybasic carboxylic acid anhydrides having 3 or more bases include (anhydrous) polycarboxylic acids such as trimellitic anhydride and pyromellitic anhydride.
In the acid anhydride reaction, an acidic compound such as sulfuric acid, hydrochloric acid, phosphoric acid, etc., or a Lewis acid (for example, a Lewis acid compound represented by MYn, where M is B, As, Ge, etc.) is used as a catalyst. or a base metal element such as Al, Bi, In, or a transition metal element such as Ti, Zn, Cu, or a lanthanoid element, n is an integer corresponding to the valence of M, 2 or 3 and Y represents a halogen atom, OAc, OCOCF ₃ , ClO ₄ , SbF ₆ , PF ₆ or OSO ₂ CF ₃ (OTf).), or adding one or more of an alkaline compound such as triethylamine or pyridine You may

As the carboxylic acid vinyl ester, the following formula:
R-COO-CH= _CH2
{In the formula, R is an alkyl group having 1 to 24 carbon atoms, an alkenyl group having 2 to 24 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 24 carbon atoms. } is preferred. Carboxylic acid vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl cyclohexanecarboxylate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, pivaline It is more preferably at least one selected from the group consisting of vinyl acid, vinyl octylate, divinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl pivalate, vinyl octylate, vinyl benzoate, and vinyl cinnamate. . For the esterification reaction with a carboxylic acid vinyl ester, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogencarbonates, primary to tertiary grades are used as catalysts. One or more selected from the group consisting of amines, quaternary ammonium salts, imidazole and its derivatives, pyridine and its derivatives, and alkoxides may be added.

Alkali metal hydroxides and alkaline earth metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide and the like. Alkali metal carbonates, alkaline earth metal carbonates and alkali metal hydrogen carbonates include lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, carbonate Examples include potassium hydrogen and cesium hydrogen carbonate.

Primary to tertiary amines are primary amines, secondary amines, and tertiary amines, and specific examples include ethylenediamine, diethylamine, proline, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, tris(3-dimethylaminopropyl)amine, Examples include N,N-dimethylcyclohexylamine and triethylamine.

Imidazole and its derivatives include 1-methylimidazole, 3-aminopropylimidazole, carbonyldiimidazole and the like.

Pyridine and its derivatives include N,N-dimethyl-4-aminopyridine, picoline and the like.

Alkoxides include sodium methoxide, sodium ethoxide, potassium-t-butoxide and the like.

Examples of carboxylic acids include at least one selected from the group consisting of compounds represented by the following formulas.
R-COOH
(Wherein, R represents an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms.)

Specific examples of carboxylic acids include acetic acid, propionic acid, butyric acid, caproic acid, cyclohexanecarboxylic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, pivalic acid, methacrylic acid, crotonic acid, and pivaline. At least one selected from the group consisting of acid, octylic acid, benzoic acid, and cinnamic acid is included.

Among these carboxylic acids, at least one selected from the group consisting of acetic acid, propionic acid, and butyric acid, particularly acetic acid, is preferable from the viewpoint of reaction efficiency.
In the carboxylic acid reaction, the catalyst used is an acidic compound such as sulfuric acid, hydrochloric acid, phosphoric acid, or a Lewis acid (for example, a Lewis acid compound represented by MYn, where M is B, As, Ge, etc.). represents a metalloid element, or a base metal element such as Al, Bi, In, or a transition metal element such as Ti, Zn, Cu, or a lanthanoid element, n is an integer corresponding to the valence of M, and 2 or 3 and Y represents a halogen atom, OAc, _OCOCF3 , _{ClO4 , SbF6} , PF6 or _{OSO2CF3 (} OTf)), or one or more of an alkaline compound such as triethylamine or pyridine may

Among these esterifying agents, in particular, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, vinyl butyrate, and acetic acid, especially acetic anhydride and vinyl acetate, reacts It is preferable from the viewpoint of efficiency.

The esterified pulp produced in the esterification step includes a high DS component having a degree of esterification (DS) of 1.5 or more and 3 or less (that is, a component to be removed by the method of the present embodiment) and a degree of esterification (DS) of 0 .2 or more and less than 1.5 low DS components. In one aspect, the degree of esterification (DS) of the high DS component is 1.5 or more, or 1.6 or more, or 1.7 or more, from the viewpoint of obtaining the effect of removing the high DS component satisfactorily, In one aspect, it is 3 or less, or 2.9 or less, or 2.8 or less. In one aspect, the degree of esterification (DS) of the low DS component is 0.2 from the viewpoint of obtaining esterified cellulose nanofibers that are excellent in resin dispersibility, heat resistance (that is, high thermal decomposition initiation temperature), etc. or more, or 0.3 or more, or 0.4 or more, or 0.5 or more, or 0.6 or more, and has good mechanical properties inherent to cellulose (especially tensile strength, dimensional stability, etc.). From the viewpoint of obtaining cellulose nanofibers, in one aspect, it is less than 1.5, or 1.4 or less, or 1.3 or less, or 1.2 or less, or 1.1 or less, or 1.0 or less.

The difference in DS value between the high DS component and the low DS component of the esterified pulp is preferably 0.3 or more, or 0.4 or more, or 0.5 or more, or 0.6 or more, or 0.7 or more, or 0.8 or more. The difference may be, for example, 2.5 or less, 2.0 or less, or 1.5 or less from the viewpoint of obtaining a desired degree of DS of the low DS component.

Here, the DS of the esterified pulp is considered to be the averaged DS of the esterified cellulose that constitutes the esterified pulp. It is the average degree of esterification of a given glucose. When cellulose, which is a polymer, is modified, the degree of esterification of glucose, which is a monomer unit, is either 0, 1, 2, or 3, but is averaged as the DS of the esterified cellulose, and further as the DS of the esterified pulp averaged. Therefore, when a certain esterification reaction is carried out, the DS of a plurality of pulp fibers esterified at the same time will converge in a narrow range and not have a wide distribution. That is, the difference in DS value between the high DS component and the low DS component represents not just the DS distribution but also the difference in the degree of progress of esterification. The removal contributes to the development of the desired effect by changing the properties of the esterified pulp.

The degree of esterification (DS) of the esterified pulp (that is, the DS of the entire esterified pulp) is 1.0 in one aspect from the viewpoint of obtaining esterified cellulose nanofibers that are excellent in dispersibility in resins, heat resistance, etc. from the viewpoint of obtaining an esterified cellulose nanofiber having a higher, or 1.2 or more, or 1.3 or more, and having good mechanical properties inherent to cellulose, in one embodiment, 2.0 or less, or 1.9 or less, or 1.8 or less.

The degree of esterification (DS) can be calculated from the reflection infrared absorption spectrum of the esterified pulp or the esterified cellulose nanofiber, based on the peak intensity ratio between the peak derived from the acyl group and the peak derived from the cellulose skeleton. . The peak of the C═O absorption band based on the acyl group appears at 1730 cm ⁻¹ , and the peak of the C—O absorption band based on the cellulose backbone chain appears at 1030 cm ⁻¹ . The DS of the esterified pulp or the esterified cellulose nanofiber is the DS obtained from the solid-state NMR measurement described later, and the peak intensity of the absorption band of C=O based on the acyl group with respect to the peak intensity of the absorption band of the cellulose backbone chain CO. Create a correlation graph with the modification rate (IR index 1030) defined by the ratio of the calibration curve degree of substitution DS = 4.13 × IR index (1030) calculated from the correlation graph
can be obtained by using

Solid-state NMR is used when it is difficult to perform appropriate measurements with the above reflection infrared absorption spectrum. The method for calculating DS by solid-state NMR is to perform ¹³ C solid-state NMR measurement on freeze-pulverized esterified pulp or esterified cellulose nanofibers, and the carbons C1-C6 derived from the pyranose ring of cellulose appearing in the range of 50 ppm to 110 ppm. It can be obtained by the following formula from the area intensity (Inf) of the signal attributed to one carbon atom derived from the modifying group with respect to the total area intensity (Inp) of the signal derived from the modification group.
DS = (Inf) x 6/(Inp)
For example, if the modifying group is an acetyl group, the 23 ppm signal attributed to --CH ₃ may be used.

The conditions for the ¹³ C solid-state NMR measurement to be used are, for example, as follows.
Apparatus: Bruker Biospin Avance500WB
Frequency: 125.77MHz
Measurement method: DD/MAS method Waiting time: 75 sec
NMR sample tube: 4mmφ
Accumulated times: 640 times (about 14 hours)
MAS: 14,500Hz
Chemical shift reference: glycine (external reference: 176.03 ppm)

As crystal forms of cellulose, type I, type II, type III, type IV and the like are known. Types I and II are commonly used, and types III and IV are not commonly used on an industrial scale. The crystal form of the esterified pulp is preferably type I or type II, more preferably type I, in terms of high structural mobility, low linear expansion coefficient, high tensile strength, bending strength and bending elongation. is.

The crystallinity of the high DS component of the esterified pulp is, in one aspect, less than 30%, or no more than 25%, or no more than 20%. In one aspect, the high DS component is highly esterified, and the degree of crystallinity is significantly reduced compared to before esterification. The crystallinity of the high DS component may, in one aspect, be 1% or greater, or 2% or greater, or 3% or greater. In one aspect, the high DS component removed by purification comprises acetylated polysaccharides with a cellulose type I crystallinity of less than 50%. Acetylated polysaccharides may include amorphous materials, such as, in addition to acetylated cellulose, acetylated hemicellulose and the like. In one aspect, the acetylated polysaccharide is cellulose type I and crystalline with a degree of crystallinity of less than 50%, or amorphous (amorphous).

The crystallinity of the low DS component of the esterified pulp is, in one aspect, 50% or more, or 60% or more, or 70% or more. In one aspect, the low DS component has a low degree of esterification, and the degree of crystallinity does not decrease significantly compared to before esterification. In addition, although it may be slightly fragmented by shearing due to stirring during the chemical modification reaction, it maintains the fiber shape of the same length and thickness as the raw material pulp. The crystallinity of the low DS component may, in one aspect, be 95% or less, or 90% or less, or 85% or less.
In one aspect, the crystallinity of the high DS component and the low DS component is the crystallinity of cellulose type I.

In the present disclosure, when the cellulose is a cellulose type I crystal (derived from natural cellulose), the crystallinity is obtained from the diffraction pattern (2θ/deg. of 10 to 30) when the sample is measured by wide-angle X-ray diffraction. It is obtained by the following formula according to the Segal method.
Crystallinity (%) = ([Diffraction intensity due to (200) plane at 2θ/deg.=22.5]-[Diffraction intensity due to amorphous at 2θ/deg.=18])/[2θ /deg. =22.5 diffraction intensity due to the (200) plane]×100

In addition, when the cellulose is a cellulose type II crystal (derived from regenerated cellulose), the crystallinity is, in wide-angle X-ray diffraction, at 2θ = 12.6°, which is attributed to the (110) plane peak of the cellulose type II crystal. It is obtained by the following formula from the absolute peak intensity h0 and the peak intensity h1 from the baseline at this interplanar spacing.
Crystallinity (%) = h1 / h0 × 100

<Fibrillation refining process>
In this step, the esterified pulp is defibrated and refined (that is, at least a portion of the high DS component is removed) to produce esterified cellulose nanofibers. In one aspect, defibration is performed in a solvent (also referred to in this disclosure as defibration solvent). For example, esterified cellulose nanofibers are obtained by defibrating the above-described esterified pulp in a defibrating solvent, typically in the form of a slurry, by a pulverization method such as a high-pressure homogenizer, microfluidizer, ball mill, or disc mill. be able to.

Examples of fibrillation solvents include water, DMSO (dimethylsulfoxide), DMF (dimethylformamide), DMAc (dimethylacetamide), NMP (N-methylpyrrolidone), acetic acid, and the like. Two or more of these solvents may be mixed and used.

In the defibration and refining step, refining may be performed before, during and/or after defibration. Purification methods may be, for example, one or a combination of two or more of solvent extraction, filtration, decantation, trapping of solids on filters, and the like. The above-mentioned solid matter as the refining removal material may be a solid matter detached from the esterified pulp and dispersed in the defibration solvent, a solid matter deposited after dissolving in the fibrillation solvent from the esterified pulp, or the like. In addition, since the high DS component may appear as foamy floating matter on the liquid surface of the slurry during fibrillation, such floating matter may be scooped out and removed as a refining removal material. More specific examples of purification methods include a combination of solvent extraction (i.e., dissolving the high DS component in a solvent) and filtration, a combination of solvent extraction and decantation, trapping solids in filters, For example, removal of foam-like suspended substances. The refining method may be selected according to the high DS component content in the esterified pulp, the type of fibrillation solvent, and the like.

In one aspect, purification is performed by dissolving and removing high DS components in a purification solvent. The high DS component dissolved in the refining solvent may be separated from the esterified pulp, for example by filtration. A method using a solvent capable of dissolving a high DS component (also referred to as a high DS component-dissolving solvent in the present disclosure) is preferable in that the high DS component adhering to the pulp surface can be removed with high efficiency. When a high DS component-dissolving solvent is used, the timing of purification is preferably before or after defibration from the viewpoint of purification efficiency.

The high DS component-dissolving solvent may be the same or different from the fibrillation solvent. For example, after dissolving and removing the high DS component in a high DS component-dissolving solvent before defibration, defibration may be performed by replacing the solvent with the defibration solvent. The solvent may be replaced with a component-dissolving solvent to dissolve and remove the high DS component. After fibrillation in the defibrating solvent, the high DS component-dissolving solvent is added, and the high DS component is dissolved and removed with a mixed solvent. may

The high DS component-dissolving solvent preferably contains one or more selected from the group consisting of ketones, esters, nitrogen-containing compounds, sulfur-containing compounds, ethers, and halogenated hydrocarbons. Solvents other than these may be included within the range in which the high DS component is soluble.
Ketones include acetone, methyl ethyl ketone (MEK), cyclohexanone, and the like.
Esters include methyl formate, methyl acetate, ethyl acetate, ethyl lactate, propylene carbonate and the like.
Examples of nitrogen-containing compounds include nitromethane, acetonitrile, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc) and the like.
Examples of sulfur-containing compounds include dimethylsulfoxide (DMSO) and the like.
Ethers include propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), γ-butyrolactone (GBL), tetrahydrofuran (THF), dioxane, dioxolane and the like.
Halogenated hydrocarbons include methylene chloride, chloroform, and the like.

In one aspect, purification may be performed using a separation solvent that separates high and low DS components. As the separation solvent, a mixture of a high DS component-dissolving solvent and a high DS component-insoluble solvent, or a high DS component-insoluble solvent can be used. When a mixture of a high DS component-dissolving solvent and a high DS component-insoluble solvent is used, the high DS component dissolved and/or swollen by the high DS component-dissolving solvent is dissolved in the solvent by the high DS component-insoluble solvent. deposits and/or peels off. When a high DS component insoluble solvent is used, the high DS component separated by mechanical action such as beating or strong stirring forms bubbles and is unevenly distributed. By these actions, the high DS component is separated from the low DS component site and dispersed in the solvent, thereby separating the high DS component and the low DS component.

Examples of the high DS component insoluble solvent include alcohols such as methanol, ethanol, isopropanol, isobutanol and t-butanol, polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin, and water. is preferred.

As a preferred combination of a high DS component-dissolving solvent and a high DS component-insoluble solvent, the high DS component-dissolving solvent is one selected from the group consisting of acetone, MEK, DMSO, NMP, DMF, and DMAc. The group consisting of alcohols such as methanol, ethanol, isopropanol, isobutanol and t-butanol, polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin, and water. A combination of one or more selected from can be exemplified. In this combination, the mass mixing ratio of the high DS component-dissolving solvent/high DS component-insoluble solvent is preferably 3 or less, or 2 or less, or 1 or less, from the viewpoint of good uneven distribution of the high DS component, Or it is 0.5 or less. On the other hand, the mixing ratio is, for example, 0.005 or more, or 0.005 or more, or 0.005 or more, from the viewpoint of favorably obtaining the advantage that the high DS component between fibrils is easily removed due to the swelling effect due to the combined use of the high DS component-dissolving solvent. 0.01 or greater, or 0.05 or greater.

In one aspect, the solubility of the high DS component at the solvent temperature during purification is 1 g or more per 100 g of the high DS component-dissolving solvent and less than 1 g per 100 g of the high DS component-insoluble solvent. , a high DS component soluble solvent and a high DS component insoluble solvent may be selected.

In one aspect, the high DS components may be removed, such as by decantation, along with the separation solvent. Alternatively, after the high DS component is dispersed in the separation solvent to form dispersed particles, the dispersed particles may be adsorbed on a filter and removed. The method using a separation solvent is preferable in that when a high DS component insoluble solvent is used as the fibrillation solvent, the steps of purification and solvent replacement can be carried out at the same time. When a separation solvent is used, the timing of purification is preferably during or after defibration from the viewpoint of purification efficiency. As the filter for adsorbing the dispersed particles, a filter cloth made of polypropylene, polyethylene terephthalate, nylon, or the like is suitable from the viewpoint of collection efficiency of the dispersed particles.

The separating solvent may be the same or different from the fibrillation solvent. For example, using a defibration solvent that can function as a separation solvent, the high DS component may be separated and removed at any time during defibration or after defibration, and after defibration in the defibration solvent, the solvent is replaced with the separation solvent. The high DS component may be separated and removed, or after defibration in the defibrating solvent, the separation solvent may be added and the high DS component may be separated and removed with a mixed solvent.
The separating solvent preferably contains one or more selected from the group consisting of water and alcohol. Alcohols include methanol, ethanol, propanol, butanol, and the like. Acids or bases may be added to adjust pH, and electrolytes may be added to adjust ionic strength.

<Characteristics of esterified cellulose nanofiber>
In one aspect, the average fiber diameter of the esterified cellulose nanofibers obtained by the method of the present embodiment is 2 to 1000 nm, preferably 4 nm or more, or 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, or 50 nm or more, or 100 nm or more, preferably 500 nm or less, or 450 nm or less, or 400 nm or less, or 350 nm or less, or 300 nm or less, or 250 nm or less, or 200 nm or less.

In one aspect, the number average fiber diameter (D), number average fiber length (L), and L/D ratio of the esterified cellulose nanofibers are measured using a scanning electron microscope (SEM) according to the following procedure. value. An aqueous dispersion of cellulose is substituted with tert-butanol, diluted to 0.001 to 0.1% by mass, and treated using a high-shear homogenizer (eg, IKA, product name “Ultra Turrax T18”), processing conditions: rotation. Dispersed at several 15,000 rpm for 3 minutes, cast on an osmium-deposited silicon substrate, air-dried, and used as a measurement sample. Specifically, the length (L) and diameter (D) of 100 randomly selected fibrous substances in an observation field whose magnification is adjusted so that at least 100 fibrous substances can be observed. is measured and the ratio (L/D) is calculated. Calculate the number average length (L), number average diameter (D), and number average ratio (L/D) values for the cellulose.

The crystallinity of the esterified cellulose nanofiber is preferably 55% or more, or 60% or more, or 70% or more, or 80%, from the viewpoint of obtaining a resin composition excellent in heat resistance, mechanical strength, and dimensional stability. That's it. When the crystallinity is in this range, the mechanical properties (heat resistance, strength, dimensional stability) of the cellulose itself are high, so when the cellulose is dispersed in the resin, the heat resistance, strength, and dimensional stability of the resin composition tend to be high. A higher crystallinity is preferable, but the preferable upper limit is 99% from the viewpoint of production.

The degree of polymerization of the esterified cellulose nanofiber is preferably 100 or more, or 150 or more, or 200 or more, or 300 or more, or 400 or more from the viewpoint of mechanical property expression, and is preferably , 3500 or less, or 3300 or less, or 3200 or less, or 3100 or less, or 3000 or less.

The degree of polymerization of cellulose means the average degree of polymerization measured according to the reduction specific viscosity method using a copper ethylenediamine solution described in the Confirmation Test (3) of "The Japanese Pharmacopoeia 15th Edition (published by Hirokawa Shoten)".

In one aspect, the weight average molecular weight (Mw) of the esterified cellulose nanofibers is 100,000 or more, more preferably 200,000 or more. The ratio (Mw/Mn) between the weight average molecular weight and the number average molecular weight (Mn) is 6 or less, preferably 5.4 or less. The larger the weight average molecular weight, the smaller the number of terminal groups of the cellulose molecule. In addition, since the ratio of the weight average molecular weight to the number average molecular weight (Mw/Mn) represents the width of the molecular weight distribution, the smaller the Mw/Mn, the smaller the number of ends of the cellulose molecules. Since the terminal of the cellulose molecule is the starting point of thermal decomposition, not only the weight average molecular weight of the cellulose molecule is large, but also when the weight average molecular weight is large and the width of the molecular weight distribution is narrow, especially highly heat-resistant cellulose and cellulose and a resin is obtained. The weight average molecular weight (Mw) of the esterified cellulose nanofibers may be, for example, 600,000 or less, or 500,000 or less, from the viewpoint of availability of cellulose raw materials. The ratio (Mw/Mn) of the weight-average molecular weight to the number-average molecular weight (Mn) may be, for example, 1.5 or more, or 2 or more from the viewpoint of ease of production of the esterified cellulose nanofibers. Mw can be controlled within the above range by selecting a cellulose raw material having an Mw suitable for the purpose, and by appropriately subjecting the cellulose raw material to physical and/or chemical treatments within an appropriate range. The Mw/Mn is also within the above range by selecting a cellulose raw material having Mw/Mn according to the purpose, by appropriately performing physical treatment and/or chemical treatment on the cellulose raw material in an appropriate range, etc. can be controlled to In both the control of Mw and the control of Mw/Mn, the physical treatment includes dry or wet grinding such as microfluidizer, ball mill, disk mill, crusher, homomixer, high-pressure homogenizer, and ultrasonic device. Examples of physical treatments that apply mechanical forces such as impact, shear, shear, friction, etc., include cooking, bleaching, acid treatment, regenerated cellulose, and the like.

The weight-average molecular weight and number-average molecular weight of the esterified cellulose nanofibers referred to here are obtained by dissolving the esterified cellulose nanofibers in N,N-dimethylacetamide to which lithium chloride has been added, followed by dissolving the N,N-dimethylacetamide. is a value obtained by gel permeation chromatography using as a solvent.

Methods for controlling the degree of polymerization (that is, the average degree of polymerization) or the molecular weight of esterified cellulose nanofibers include hydrolysis treatment after the defibration and purification step. The hydrolysis treatment promotes depolymerization of the amorphous cellulose inside the cellulose, thereby reducing the average degree of polymerization. At the same time, the hydrolysis treatment removes impurities such as hemicellulose and lignin in addition to the amorphous cellulose described above, so that the interior of the fiber becomes porous. As a result, in the step of applying a mechanical shearing force to the cellulose, such as during the kneading step described below, the cellulose is easily subjected to mechanical treatment, and the cellulose is easily pulverized.

In one aspect, the esterified cellulose nanofibers can include alkali-soluble polysaccharides. Alkali-soluble polysaccharides include β-cellulose and γ-cellulose in addition to hemicellulose. Alkali-soluble polysaccharides are components obtained as alkali-soluble parts of holocellulose obtained by solvent extraction and chlorine treatment of plants (for example, wood) (that is, components obtained by removing α-cellulose from holocellulose). It is understood by those skilled in the art. Alkali-soluble polysaccharides are polysaccharides containing hydroxyl groups, and can cause deterioration in heat resistance, physical properties, discoloration, and dispersibility in resins of esterified cellulose nanofibers. The smaller the content of alkali-soluble polysaccharides, the better.

In one embodiment, the average content of alkali-soluble polysaccharides in the esterified cellulose nanofibers is preferably , 20% by mass or less, or 18% by mass or less, or 15% by mass or less, or 12% by mass or less, or 11% by mass or less, or 8% by mass or less. From the viewpoint of ease of production of the esterified cellulose nanofibers, the content may be 1% by mass or more, 2% by mass or more, 3% by mass or more, or 6% by mass or more. In one aspect, the average content of alkali-soluble polysaccharides in the cellulose raw material may be 13% by weight or less, or 12% by weight or less, or 11% by weight or less, or 8% by weight or less, and most preferably 0% by weight. %, but it may be, for example, 3% by mass or more, or 6% by mass or more from the viewpoint of availability of the cellulose raw material.

The average content of alkali-soluble polysaccharides can be obtained by the method described in Non-Patent Document (Wood Science Experiment Manual, edited by Japan Wood Science Society, pp. 92-97, 2000), and the holocellulose content (Wise method) It is obtained by subtracting the α-cellulose content from This method is understood in the art as a method for measuring the amount of hemicellulose. The alkali-soluble polysaccharide content is calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide contents is taken as the average alkali-soluble polysaccharide content.

In one aspect, the average content of acid-insoluble components in the esterified cellulose nanofibers is preferably 10 per 100% by mass of the esterified cellulose nanofibers, from the viewpoint of avoiding a decrease in heat resistance of cellulose and accompanying discoloration. % by mass or less, or 5% by mass or less, or 3% by mass or less. From the viewpoint of ease of production of the esterified cellulose nanofibers, the content may be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more.

The average content of acid-insoluble components is determined by quantifying acid-insoluble components using the Clason method described in Non-Patent Document (Wood Science Experimental Manual, Japan Wood Science Society, pp. 92-97, 2000). This method is understood in the industry as a method for measuring the amount of lignin. After stirring the sample in a sulfuric acid solution to dissolve cellulose, hemicellulose, etc., the sample was filtered through a glass fiber filter paper, and the obtained residue corresponds to the acid-insoluble component. The acid-insoluble component content is calculated from this acid-insoluble component weight, and the number average of the acid-insoluble component content calculated for the three samples is taken as the acid-insoluble component average content.

From the viewpoint of obtaining esterified cellulose nanofibers having excellent dispersibility in resins, heat resistance, etc., the degree of esterification (DS) of the esterified cellulose nanofibers is, in one aspect, 0.3 or more, or 0.4 or more, or 0.5 or more, or 0.6 or more, or 0.7 or more, and from the viewpoint of obtaining an esterified cellulose nanofiber having good mechanical properties inherent to cellulose, in one embodiment, 1.2 or less, or 1 .1 or less, or 1.0 or less.

<<Method for producing resin composition>>
One aspect of the present invention also provides a method for producing a resin composition containing esterified cellulose nanofibers and a resin.

The amount of the esterified cellulose nanofibers relative to 100% by mass of the entire resin composition is preferably 0.1% by mass or more, or 0.5% by mass or more, from the viewpoint of obtaining a good reinforcing effect of the esterified cellulose nanofibers. Or 1% by mass or more, or 3% by mass or more, and from the viewpoint of maintaining good properties inherent in the resin, preferably 30% by mass or less, or 25% by mass or less, or 20% by mass or less, or 15% by mass It is below.

The amount of the resin with respect to 100% by mass of the entire resin composition is preferably 20% by mass or more, or 30% by mass or more, or 40% by mass or more, or 50% by mass or more, from the viewpoint of maintaining good properties inherent in the resin. , or 60% by mass or more, or 70% by mass or more, or 75% by mass or more, or 80% by mass or more, or 85% by mass or more, and from the viewpoint of obtaining the effects of other components well, preferably 99. 9% by mass or less, or 99.5% by mass or less, or 99% by mass or less, or 97% by mass or less, or 95% by mass or less, or 90% by mass or less.

<Resin>
The resin is appropriately selected according to the purpose of use of the resin composition. It may be a crystalline thermoplastic resin or the like. Examples of resins include polyolefin-based resins, polyamide-based resins, polyester-based resins, polyacetal-based resins, polyphenylene ether-based resins, polyphenylene sulfide-based resins, and mixtures of two or more of these. Polyolefin-based resins, polyamide-based resins, polyester-based resins, polyacetal-based resins, etc., are preferred, and polyamide-based resins and polyacetal-based resins are particularly preferred. From the viewpoint of increasing the heat resistance of the resin composition, the melting point of the thermoplastic resin (particularly the crystalline resin) is preferably 140°C or higher, or 150°C or higher, or 160°C or higher, or 170°C or higher, or 180°C or higher. , or 190° C. or higher, or 200° C. or higher, or 210° C. or higher, 220° C. or higher, or 230° C. or higher, or 240° C. or higher, or 245° C. or higher, or 250° C. or higher.

The melting point of the thermoplastic resin is, for example, 150° C. to 190° C. or 160° C. to 180° C. for relatively low melting point resins (eg, polyolefin resins), and relatively high melting point resins (eg, polyamide resins). 220° C. to 350° C. or 230° C. to 320° C. can be exemplified.

In the present disclosure, the melting point of a resin refers to the peak top temperature of an endothermic peak that appears when the temperature is raised from 23° C. at a rate of 10° C./min using a differential scanning calorimeter (DSC). When two or more peaks appear, the peak top temperature of the endothermic peak on the highest temperature side is indicated.

In the present disclosure, the glass transition temperature of the resin is measured at an applied frequency of 10 Hz while increasing the temperature from 23 ° C. at a rate of 2 ° C./min using a dynamic viscoelasticity measuring device. The peak top temperature of the peak at which the modulus drops significantly and the loss modulus is maximized. When two or more loss modulus peaks appear, the peak top temperature of the peak on the highest temperature side is indicated.

Polyolefin resins that are preferable as thermoplastic resins are polymers obtained by polymerizing olefins (eg, α-olefins) or alkenes as monomer units. Specific examples of polyolefin-based resins include ethylene-based (co)polymers such as low-density polyethylene (e.g., linear low-density polyethylene), high-density polyethylene, ultra-low-density polyethylene, and ultra-high molecular weight polyethylene, polypropylene, and ethylene. - polypropylene-based (co)polymers exemplified by propylene copolymers, ethylene-propylene-diene copolymers, ethylene-acrylic acid copolymers, ethylene-methyl methacrylate copolymers, ethylene-glycidyl methacrylate copolymers Examples thereof include copolymers of α-olefins such as ethylene represented by coalescence.

Polypropylene is the most preferred polyolefin resin. In particular, polypropylene having a melt mass flow rate (MFR) of 3 g/10 min or more and 30 g/10 min or less measured at 230° C. under a load of 21.2 N in accordance with ISO 1133 is preferred. The lower limit of MFR is more preferably 5 g/10 minutes, still more preferably 6 g/10 minutes, and most preferably 8 g/10 minutes. Also, the upper limit is more preferably 25 g/10 minutes, still more preferably 20 g/10 minutes, and most preferably 18 g/10 minutes. The MFR desirably does not exceed the above upper limit from the viewpoint of improving toughness of the composition, and preferably does not exceed the above lower limit from the viewpoint of fluidity of the composition.

Acid-modified polyolefin resins are also suitable for use in order to increase affinity with cellulose. The acid in this case can be appropriately selected from maleic acid, fumaric acid, succinic acid, phthalic acid, their anhydrides, and polycarboxylic acids such as citric acid. Among these, maleic acid or its anhydride is preferable because the modification rate can be easily increased. The modification method is not particularly limited, but a method of heating above the melting point in the presence or absence of a peroxide to melt and knead is common. As the polyolefin resin to be acid-modified, all of the polyolefin resins described above can be used, but polypropylene is particularly suitable for use. Although the acid-modified polypropylene may be used alone, it is more preferable to use it in combination with unmodified polypropylene in order to adjust the modification rate of the resin as a whole. The ratio of acid-modified polypropylene to all polypropylene at this time is 0.5% by mass to 50% by mass. A more preferable lower limit is 1% by mass, still more preferably 2% by mass, still more preferably 3% by mass, particularly preferably 4% by mass, and most preferably 5% by mass. A more preferred upper limit is 45% by mass, still more preferably 40% by mass, still more preferably 35% by mass, particularly preferably 30% by mass, and most preferably 20% by mass. In order to maintain the interfacial strength between the resin and cellulose, the lower limit or more is preferable, and in order to maintain the ductility of the resin, the upper limit or less is preferable.

The melt mass flow rate (MFR) of the acid-modified polypropylene measured at 230° C. and a load of 21.2 N in accordance with ISO 1133 is preferably 50 g/10 minutes or more in order to increase the affinity with the cellulose interface. . A more preferred lower limit is 100 g/10 min, even more preferably 150 g/10 min, and most preferably 200 g/10 min. Although there is no particular upper limit, it is 500 g/10 minutes for maintenance of mechanical strength. By setting the MFR within this range, it is possible to enjoy the advantage of being likely to exist at the interface between the cellulose and the resin.

Polyamide resins include polyamide 6, polyamide 11, polyamide 12 obtained by polycondensation reaction of lactams, 1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 1,7-heptanediamine, 2-methyl-1-6-hexanediamine, 1,8-octanediamine, 2-methyl-1,7-heptanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10- Diamines such as decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, m-xylylenediamine, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid acid, decanedioic acid, benzene-1,2-dicarboxylic acid, benzene-1,3-dicarboxylic acid, benzene-1,4-dicarboxylic acid, etc., cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid Polyamide 6,6 obtained as a copolymer with dicarboxylic acids such as polyamide 6,6, polyamide 6,10, polyamide 6,11, polyamide 6,12, polyamide 6,T, polyamide 6,I, polyamide 9,T, polyamide 10, T, polyamide 2M5,T, polyamide MXD,6, polyamide 6,C, polyamide 2M5,C, and copolymers thereof, such as polyamide 6,T/6,I. mentioned.

Among these polyamide resins, aliphatic polyamides such as polyamide 6, polyamide 11, polyamide 12, polyamide 6,6, polyamide 6,10, polyamide 6,11, polyamide 6,12, polyamide 6,C, polyamide 2M5,C Alicyclic polyamides such as

The terminal carboxyl group concentration of the polyamide resin is not particularly limited, but is preferably 20 μmol/g or more, or 25 μmol/g or more, preferably 150 μmol/g or less, or 100 μmol/g. may be:

The terminal amino group concentration of the polyamide-based resin is preferably 20 μmol/g or more, or 30 μmol/g or more, and preferably 150 μmol/g or less, or 100 μmol/g or less.

The total concentration of the terminal amino group and the terminal carboxyl group of the polyamide resin is not particularly limited, but is preferably 10 μmol/g or more, or 50 μmol/g or more, or 100 μmol/g or more, or 135 μmol/g. or more, and from the viewpoint of preventing a decrease in viscosity due to an excessively low molecular weight of the resin and suppressing burr generation during molding, it is preferably 500 μmol/g or less, or 300 μmol/g or less, or 135 μmol/g or less, or 100 μmol/g or less.

The ratio of amino terminal groups to carboxyl terminal groups ([NH ₂ ]/[COOH]) of the polyamide resin is preferably greater than 1.00, or 1.01 or more, or 1.05 or more, or 1.10 or more. is. The upper limit of the amino terminal group ratio is not particularly limited, but it may be preferably 10000 or less, or 1000 or less, or 100 or less, or 10 or less from the viewpoint of maintaining good color tone of the resin composition.

A known method can be used as a method for adjusting the terminal group concentration of the polyamide-based resin. For example, a diamine compound, a monoamine compound, a dicarboxylic acid compound, a monocarboxylic acid compound, an acid anhydride, a monoisocyanate, a monoacid halide, a monoester, a monoalcohol, etc., can be used to obtain a predetermined terminal group concentration during the polymerization of the polyamide. A method of adding a terminal adjuster that reacts with the terminal group to the polymerization liquid can be used.

The amino terminal group and carboxyl terminal group concentrations of the polyamide-based resin can be determined from the integrated values of the characteristic signals corresponding to each terminal group by ¹ H-NMR. Specifically, the method described in JP-A-7-228775 is recommended.

The polyamide resin preferably has an intrinsic viscosity [η] of 0.6 to 2.0 dL/g, and preferably 0.7 to 1.4 dL/g, measured at 30°C in concentrated sulfuric acid. is more preferred, 0.7 to 1.2 dL/g is even more preferred, and 0.7 to 1.0 dL/g is particularly preferred. The use of a polyamide having an intrinsic viscosity within the above range has the advantage of increasing the fluidity of the resin composition in the mold during injection molding and improving the appearance of the molded piece.

In the present disclosure, "intrinsic viscosity" is synonymous with viscosity generally called intrinsic viscosity, and is described, for example, in Polymer Process Engineering (Prentice-Hall, Inc 1994), pages 291-294. can be measured by

Polyester-based resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polybutylene adipate terephthalate (PBAT). , polyhydroxyalkanoic acid (PHA), polylactic acid (PLA), polyarylate (PAR), polycarbonate (PC), and the like. PET, PBS, PBSA, PBT, and PEN are more preferred as the polyester-based resin, and PBS, PBSA, and PBT are even more preferred.

In addition, the terminal groups of the polyester resin can be freely changed depending on the monomer ratio during polymerization and the presence or absence and amount of addition of a terminal stabilizer. More preferably, the ratio ([COOH]/[total terminal groups]) is from 0.30 to 0.95. The carboxyl end group ratio lower limit is more preferably 0.35, still more preferably 0.40, and most preferably 0.45. Also, the upper limit of the carboxyl terminal group ratio is more preferably 0.90, still more preferably 0.85, and most preferably 0.80. The carboxyl terminal group ratio is desirably 0.30 or more from the viewpoint of dispersibility of cellulose in the composition, and desirably 0.95 or less from the viewpoint of the color tone of the resulting composition.

Polyacetal-based resins generally include homopolyacetal made from formaldehyde and copolyacetal containing trioxane as a main monomer and 1,3-dioxolane as a comonomer component. From the viewpoint of thermal stability, copolyacetal can be preferably used. In particular, the amount of comonomer component (eg, 1,3-dioxolane)-derived structure is more preferably in the range of 0.01 to 4 mol %. A preferred lower limit for the amount of comonomer component-derived structures is 0.05 mol %, more preferably 0.1 mol %, and even more preferably 0.2 mol %. A preferred upper limit is 3.5 mol %, more preferably 3.0 mol %, even more preferably 2.5 mol %, most preferably 2.3 mol %.

From the viewpoint of thermal stability during extrusion or molding, the lower limit is preferably within the above range, and from the viewpoint of mechanical strength, the upper limit is preferably within the above range.

As the resin, a resin having a hydrophilic group (for example, one or more selected from a hydroxyl group, an amino group and a carboxy group) is particularly preferable from the viewpoint of affinity with cellulose. Preferred examples of the resin having a hydrophilic group are selected from the group consisting of acid-modified polyolefin resins, polyacetal resins, polycarbonate resins, polyamide resins, polyester resins, polyphenylene ether resins, and acrylic resins. more than seeds. Among them, polyamide-based resins and maleated polypropylene are preferred.

<Additional ingredients>
The resin composition of the present embodiment may further contain additional components as necessary in order to improve its performance. Additional components include dispersants; filler components other than cellulose; compatibilizers; plasticizers; polysaccharides such as starches and alginic acid; Inorganic compounds such as oxides and metal powders; colorants; fragrances; pigments; flow control agents; leveling agents; . The content of any additional component in the resin composition is appropriately selected within a range that does not impair the desired effect of the present invention, for example, 0.01 to 50% by mass, or 0.1 to 30% by mass. can be

As the dispersing agent, a compound capable of reacting with or hydrogen bonding with hydroxyl groups of cellulose is preferred. Preferred examples of dispersants are one or more selected from the group consisting of cellulose derivatives, polyalkylene oxides, amides and amines. Among them, cellulose derivatives are preferable because they are cellulose-based substances and therefore have high affinity with cellulose, while they are also thermoplastic resins, and therefore have a high effect of improving the dispersion stability of cellulose in the resin composition. Dispersants having a boiling point higher than that of water are preferred. The boiling point higher than that of water refers to a boiling point higher than the boiling point at each pressure in the vapor pressure curve of water (for example, 100° C. under 1 atm).

In the resin composition, the amount of the dispersant with respect to 100 parts by mass of cellulose is preferably 1 part by mass or more, or 5 parts by mass or more, or 10 parts by mass or more, or 20 parts by mass, from the viewpoint of good dispersion and network formation of cellulose. It is at least 500 parts by mass, preferably 300 parts by mass or less, or 200 parts by mass or less from the viewpoint of reducing variations in performance of the resin composition.

Hereinafter, process examples of the method for producing a resin composition will be described.

[Method 1]
In one aspect, the method for producing a resin composition comprises:
A modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
a refining step of refining the esterified pulp;
A defibration and mixing step of mixing the purified esterified pulp with a resin and defibrating it to produce a resin composition containing the esterified cellulose nanofibers and the resin;
including.

The modification step may be carried out in the same manner as the <modification step> in the <<method for producing esterified cellulose nanofibers>> described above. Therefore, the esterified pulp may contain a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5.

The refining step may be performed in the same manner as the refining performed before defibration in <Defibering and refining step> of <<Method for producing esterified cellulose nanofibers>> described above. The purification is thus the removal of at least a portion of the high DS components.

In the defibration and mixing step, the purified esterified pulp is mixed with a resin and fibrillated. Specifically, the above-mentioned esterified pulp can be defibrated together with a thermoplastic resin by kneading means such as a mixing roller, a kneader, a Banbury mixer, or an extruder.

[Method 2]
In one aspect, the method for producing a resin composition comprises:
A modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
A defibration and mixing step of mixing the esterified pulp with a resin and fibrillating it to produce a resin composition containing the esterified cellulose nanofibers and the resin;
including.

The modification step may be carried out in the same manner as the <modification step> in the <<method for producing esterified cellulose nanofibers>> described above. Therefore, the esterified pulp may contain a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5.

In the defibration and mixing step, the esterified pulp is mixed with the resin and fibrillated. Specifically, the above-mentioned esterified pulp can be defibrated together with a thermoplastic resin by kneading means such as a mixing roller, a kneader, a Banbury mixer, or an extruder.
In this step, at least part of the high DS component of the esterified pulp is transferred from the esterified pulp into the resin phase. Suitable conditions for transferring the high DS component into the resin phase include a large difference in DS between the high DS component and the low DS component. The DS difference between the high DS component and the low DS component is preferably 0.5 or more, or 0.6 or more, or 0.7 or more. The DS difference is, for example, 2.5 or less, or 2.0 or less, or 1.5 or less from the viewpoint of obtaining an esterified cellulose nanofiber having both good physical properties and good dispersibility in a resin. may The DS difference can be adjusted by adjusting the esterification conditions so that the degree of esterification is high on the pulp surface and low inside the pulp.

A preferred process condition for the defibration and mixing step is to provide a zone with a damming effect in the middle of the twin-screw extrusion step. This zone consists of elements which serve to dam or reverse the mixture of esterified pulp and thermoplastic resin, usually provided with sealing discs, reverse flights, reverse kneading disc elements and the like. In particular, when using a large twin-screw extruder to increase productivity, it is necessary to increase the discharge rate, resulting in insufficient kneading and a high DS component at the interface between the resin and the esterified cellulose fiber. However, the use of a screw having the aforementioned element promotes migration of the high DS component into the resin.

[Method 3]
In one aspect, the method for producing a resin composition comprises:
A modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
A refining step of refining the esterified pulp;
A defibration step of defibrating the purified esterified pulp to generate esterified cellulose nanofibers;
a mixing step of mixing the esterified cellulose nanofibers obtained in the fibrillation step and a resin to produce a resin composition;
including.

The modification step may be carried out in the same manner as the <modification step> in the <<method for producing esterified cellulose nanofibers>> described above. Therefore, the esterified pulp may contain a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5.

The refining step may be performed in the same manner as the refining performed before defibration in <Defibering and refining step> of <<Method for producing esterified cellulose nanofibers>> described above. The purification is thus the removal of at least a portion of the high DS components.

The defibration step may be carried out in the same manner as the fibrillation performed after purification in the <fibrillation purification step> of the above-mentioned <<method for producing esterified cellulose nanofibers>>.

In the mixing step, the resin composition is produced by mixing the esterified cellulose nanofibers obtained in the fibrillation step with the resin. Esterified cellulose nanofibers may be melt-kneaded with a resin in the form of a dry body or a slurry (for example, an aqueous dispersion). The heating temperature during melt-kneading can be adjusted according to the resin to be used, and is preferably a temperature that is equal to or higher than the melting point of the resin but does not significantly exceed the melting point. The heating temperature is preferably the melting point of the resin or higher, or the melting point +20° C. or higher, or the melting point +30° C. or higher, or the melting point +40° C. or higher. The melting point is +90°C or less, or the melting point +80°C or less, or the melting point +70°C or less. The above melting point means the highest melting point when the resin composition contains a plurality of types of thermoplastic resins. The minimum processing temperatures recommended by thermoplastic resin suppliers are 255 to 270°C for nylon 66, 225 to 240°C for nylon 6, 170 to 190°C for polyacetal resin, and 160 to 180°C for polypropylene. Heat set temperatures may range from 20° C. above these recommended minimum processing temperatures.

The moisture content of the mixture to be melt-kneaded is preferably 0.2% by mass or less, or 0.1% by mass or less, or 0.07% by mass or less. The moisture content may be, for example, 0.001% by mass or more from the viewpoint of ease of process control.

For melt-kneading, an extruder such as a single-screw extruder or a twin-screw extruder can be used, but a twin-screw extruder is preferable for controlling the dispersibility of cellulose. L/D obtained by dividing the cylinder length (L) of the extruder by the screw diameter (D) is preferably 40 or more, particularly preferably 50 or more. Further, the screw rotation speed during kneading is preferably in the range of 100 to 800 rpm, more preferably in the range of 150 to 600 rpm. These will vary depending on the screw design. From the viewpoint of suppressing thermal deterioration of the resin composition, weak kneading (that is, kneading under a small shear force) is suitable. Weak kneading can be achieved, for example, by providing a large number of conveying zones in the screw configuration of the extruder, reducing the rotation speed of the screw, and the like. Each screw in the cylinder of the extruder is optimized by combining an elliptical two-blade screw-shaped full-flight screw, a kneading element called a kneading disk, and the like.

<<Shape of resin composition>>
The resin composition of this embodiment can be provided in various forms. Specifically, resin pellets, sheets, fibers, plates, rods, and the like may be used, but resin pellets are preferred from the standpoint of ease of post-processing and ease of transportation. Preferable resin pellet shapes include round, elliptical, and cylindrical shapes, and the shape may vary depending on the cutting method during extrusion. For example, pellets cut by a cutting method called underwater cutting are often round, and pellets cut by a cutting method called hot cutting are often round or oval. Pellets cut by the so-called cutting method often have a cylindrical shape. A preferable pellet diameter of round pellets is 1 mm or more and 3 mm or less. A preferable diameter of the cylindrical pellet is 1 mm or more and 3 mm or less, and a preferable length thereof is 2 mm or more and 10 mm or less. From the viewpoint of operational stability during extrusion, the above diameter and length are preferably at least the lower limit, and from the viewpoint of biting into a molding machine in post-processing, they are preferably at most the upper limit.

The resin composition of this embodiment can be used as various resin moldings. There are no particular restrictions on the method for producing the resin molded article, but injection molding, extrusion molding, blow molding, inflation molding, foam molding, and the like can be used. Among these, the injection molding method is particularly preferable from the viewpoint of design and cost.

≪Use of resin composition≫
The resin composition obtained by the method of the present embodiment is useful as a substitute for steel plates, fiber-reinforced plastics (for example, carbon-fiber-reinforced plastics, glass-fiber-reinforced plastics, etc.), resin composites containing inorganic fillers, and the like. Suitable uses of the resin composition include industrial machine parts, general machine parts, automobile/railway/vehicle/vessel/aerospace parts, electronic/electrical parts, construction/civil engineering materials, household goods, sports/leisure goods, Case members for wind power generation, containers/packaging members, and the like can be exemplified.

Hereinafter, exemplary embodiments of the present invention will be further described with reference to examples, but the present invention is not limited to the following examples.

≪Evaluation method≫
<Average Fiber Diameter and L/D of Esterified Pulp and Esterified Cellulose Nanofiber>
Dilute the wet cake with tert-butanol to 0.01% by mass, use a high shear homogenizer (manufactured by IKA, trade name "Ultra Turrax T18"), treatment conditions: rotation speed 25,000 rpm × 5 minutes Dispersed, Cast on mica, air-dried, and measured by high-resolution scanning electron microscopy. In the measurement, the magnification was adjusted so that at least 100 cellulose fibers were observed, and images were taken in a plurality of fields of view that do not overlap each other. Specifically, first, images are taken in 5 fields of view, and the total number of cellulose fibers in all fields of view is counted. If the number is less than 100, an additional 5 fields of view are added to obtain images of a total of 10 fields of view. The number of cellulose in was measured. This was repeated, and images were added for each 5 fields of view until the total number of cellulose lines in all fields of view reached 100 or more. In the image obtained in this way, the length (L) of 100 celluloses randomly selected from 100 or more celluloses, the major diameter (D), and the ratio of these are obtained, and the addition average of 100 celluloses is calculated. did.

<Preparation of porous sheet of esterified pulp and esterified cellulose nanofiber>
First, the wet cake was added to tert-butanol, and then subjected to dispersion treatment using a mixer or the like until no aggregates were present. The concentration was adjusted to 0.5% by mass with respect to 0.5 g of cellulose solid content. 100 g of the obtained tert-butanol dispersion was filtered on a filter paper and dried at 150° C. After that, the filter paper was peeled off to obtain a sheet. A porous sheet having an air resistance of 100 sec/100 ml or less per 10 g/m ² sheet basis weight was used as a measurement sample.
Regarding the acetylated cellulose nanofibers in the resin composition, the composition is dissolved and dispersed in a solvent (hexafluoroisopropanol for polyamide) that dissolves the resin but does not dissolve the esterified pulp and the esterified cellulose nanofibers, followed by centrifugation. A sample obtained by washing the insoluble matter collected by separation or filtration with the solvent, ethanol, and water in this order was used as a measurement sample.

<Crystallinity of esterified pulp and esterified cellulose nanofiber>
The porous sheet described above was subjected to X-ray diffraction measurement, and the degree of crystallinity was calculated from the following formula.
Crystallinity (%) = [I ₍₂₀₀₎ - I _(amorphous) ] / I ₍₂₀₀₎ × 100
I ₍₂₀₀₎ : diffraction peak intensity by 200 plane (2θ = 22.5°) in cellulose type I crystal I _(amorphous) : halo peak intensity by amorphous in cellulose type I crystal, 4 from the diffraction angle of 200 plane .5° low angle side (2θ = 18.0°) peak intensity (X-ray diffraction measurement conditions)
Device MiniFlex (manufactured by Rigaku Corporation)
Operation axis 2θ/θ
Radiation source CuKα
Measurement method Continuous type Voltage 40 kV
Current 15mA
Start angle 2θ=5°
End angle 2θ=30°
Sampling width 0.020°
Scan speed 2.0°/min
Sample: Paste a porous sheet on the sample holder

<Esterification degree (DS) of esterified pulp and esterified cellulose nanofiber>
The infrared spectroscopy spectrum of the porous sheet described above was measured at three locations by the ATR-IR method with a Fourier transform infrared spectrophotometer (Nicolet Summit Pro manufactured by ThermoFisher Scientific). Infrared spectral measurement was performed under the following conditions.
Accumulated times: 16 times,
Wavenumber resolution: 4 cm ^-1
ATR Crystal: Diamond,
Incident angle: 45°
IR index from the obtained IR spectrum, the following formula:
IR index = H1730/H1030
Calculated according to In the formula, H1730 and H1030 are absorbances at 1730 cm ^-1 and 1030 cm ^-1 (absorption bands of cellulose backbone CO stretching vibration). However, a line connecting 1900 cm ^-1 and 1500 cm ^-1 and a line connecting 800 cm ^-1 and 1500 cm ^-1 are used as baselines, respectively, and the absorbance is defined as the absorbance of this baseline being 0.
Then, the average degree of substitution at each measurement location was calculated from the IR index according to the following formula, and the average value was taken as DS.
DS = 4.13 x IR index

<Confirmation of presence of high DS component and low DS component in esterified pulp>
A part of the slurry was extracted after the esterification reaction when producing the esterified pulp in the Production Examples described later. DMSO was added to the slurry at a room temperature of 20° C. or higher, and the slurry was filtered through a PTFE membrane filter with a pore size of 5 μm to separate the filtrate and the filtrate. The filtrate was dried on an ATR crystal of an infrared spectrophotometer, and the value obtained by measuring the IR spectrum of the film was taken as the DS of the high DS component. Further, the filter cake was further washed with water to prepare a porous sheet by the method described above, and the value obtained by measuring the IR spectrum was used as the DS of the low DS component.

<Confirmation of presence of high DS components in components removed by purification>
The powder obtained by drying the purification-removed material collected in the production example described later was subjected to X-ray diffraction measurement as a sample to confirm that the degree of crystallinity was less than 50%. It was re-dissolved in DMSO at room temperature, separated into a supernatant and a precipitate by a centrifuge, the supernatant was dried on an ATR crystal of an infrared spectrophotometer, and the DS value obtained by IR spectrum measurement of the film was 1.5. When it was 5 or more, it was determined that a high DS component was present in the purification removal.

<Confirmation of migration of high DS component into resin in resin composition>
The resin compositions obtained in Example 6, Reference Example 1, and Comparative Example 3, which will be described later, were dissolved and dispersed in hexafluoroisopropanol, and the insoluble matter was sedimented by centrifugation to separate the supernatant. After filtering the supernatant through a membrane filter with a pore size of 0.20 μm, the filtrate was dried to obtain a film-like sheet. The sheet was pulverized, DMSO was added, and the high DS component was extracted, and the liquid was analyzed by ATR-IR in the same manner as described above to confirm whether or not the high DS component migrated into the resin.

<Tensile yield strength and tensile elongation at break of the resin composition>
Using an injection molding machine, the resin composition pellets were molded into multi-purpose test specimens conforming to ISO294-3, and the molding was performed under the conditions conforming to JIS K6920-2 with n=10.

<Appearance of molded piece>
The appearance of the multipurpose test piece was visually observed.

<Comprehensive judgment>
The tensile yield strength, tensile elongation at break, and appearance of the molded piece were comprehensively judged, and the excellent one was evaluated as ◯, the particularly excellent one as ⊚, and the poor one as x.

≪Materials used≫
<Resin>
Polyamide 6 (hereinafter simply referred to as PA6)
UBE Nylon 1013B (manufactured by Ube Industries, Ltd.)
<Pulp>
Cotton linter pulp A pulp sheet obtained from Japan Pulp & Paper Co., Ltd. was used as it was.

≪Production of esterified pulp≫
<Production Example 1> (Purification by solvent dissolution)
Dimethyl sulfoxide (30 kg) was added to a jacketed 40 L reactor, and sodium bicarbonate catalyst (0.48 kg) and pulp raw material (1.5 kg) were added and stirred. Warm water was run through the jacket to heat the liquid to a temperature of 45°C. The inside of the reactor was replaced with nitrogen, and vinyl acetate (1.4 kg) was charged. After reacting for 1 hour, pure water (10 kg) was added to terminate the reaction. A filter cloth (PP9B, available from Nakao Filter Industry Co., Ltd.) was set in a 100 L Nutsche filter, pure water (50 kg) and the reaction solution were added, and pressure filtration was performed at room temperature (first filtration). Furthermore, pressure filtration with pure water (50 kg) at room temperature was repeated three times (second to fourth filtration), and pressure filtration was performed four times in total. Next, acetone (30 kg) was added at room temperature, pressure filtration was repeated twice (purification using acetone as a high DS component-dissolving solvent), and the filtrate was collected as a purified residue to confirm the presence of high DS components. The filtrate was obtained as acetylated pulp 1 containing the low DS component and having at least a portion of the high DS component removed.

<Production Example 2> (Purification by trapping in a filter)
After performing up to the first filtration in the same manner as in Production Example 1, pure water (50 kg) was added at room temperature, the mixture was stirred, and pressure filtration was performed (second filtration). The acetylated pulp was taken out, and the clay-like slurry (refined removal product 1) adsorbed on the filter cloth (PP9B) as a filter was removed (purification using a mixed solvent of DMSO and water as a separation solvent). The acetylated pulp was put back into the Nutsche filter and washed and filtered twice with pure water (50 kg) at room temperature (3rd and 4th filtration). The clay-like slurry (purification removal product 2) is removed from the filter cloth again (purification using a mixed solvent of DMSO and water as a separation solvent), while the acetylated pulp is washed and filtered twice with pure water at room temperature ( 5th and 6th filtration), and pressure filtration was carried out a total of 6 times to obtain acetylated pulp 2 containing a low DS component and from which at least part of the high DS component was removed. A combination of purified and removed products 1 and 2 was used to confirm the presence of high DS components.

<Production Example 3> (Dissolution in a solvent and purification by filtration)
The pulp was acetylated by the method described in Production Example 1, except that pure water (5 kg) was added to stop the reaction. The moisture content of the reaction solution at this point was about 14% by mass when the solution obtained by squeezing the pulp to remove the solid matter was measured with a Karl Fischer moisture meter. Such hydrous dimethyl sulfoxide can function as a high DS component-dissolving solvent. Next, a filter cloth (PP9B) is set on a 100 L Nutsche filter, the above reaction solution is added, and pressure filtration is performed at room temperature (a mixed solvent of low water content DMSO and water is used as a high DS component dissolving solvent. Purification used), the filtrate is recovered as a purification removal product, and the presence of high DS components is confirmed, and pure water (50 kg) is added to the filtrate at room temperature, stirred, and pressure filtration is repeated 6 times. Residual dimethyl sulfoxide was removed to obtain acetylated pulp 3 containing a low DS component and having at least a portion of the high DS component removed.

<Production Example 4> (Purification by removal of foamy suspended matter)
The pulp was acetylated by the method described in Production Example 1, except that washing with acetone was not performed. The acetylated pulp taken out was dispersed in water at room temperature and beaten with a beater manufactured by Toyo Seiki Seisakusho. The foam formed on the liquid surface by peeling from the acetylated pulp was collected by scooping it as a refining remover (refining using water as a separating solvent). The presence of the high DS component contained in the refined and removed material was confirmed, and an acetylated pulp 4 containing the low DS component and from which at least a part of the high DS component was removed was obtained as an aqueous dispersion.

<Production Example 5> (Unpurified)
Acetylated pulp 5, which had not been purified to remove high DS components, was obtained by the method described in Production Example 1, except that washing with acetone was not performed.

<Production Example 6> (Preparation of low DS component-free acetylated pulp)
Acetylated pulp 6 was obtained by the method described in Production Example 2, except that vinyl acetate (2.1 kg) was used and the reaction was carried out at 60° C. for 3 hours.

<<Production of acetylated cellulose nanofibers and resin composition>>
<Example 1> (Purification before fibrillation)
Acetylated pulp 1 prepared in Production Example 1 was added to pure water so that the solid content was 1.5% by mass, and was highly fibrillated by beating using a laboratory disc refiner manufactured by Aikawa Iron Works Co., Ltd. After that, fibrillation was performed with a high-pressure homogenizer (operating pressure: 10 times at 85 MPa) at the same concentration to obtain a dispersion liquid of acetylated cellulose nanofibers. The average fiber diameter, crystallinity and DS of the obtained acetylated cellulose nanofibers were measured by the methods described above.

The dispersion was filtered to obtain a wet cake state with a solid content of 20% by mass, and the above acetylated cellulose nanofiber (100 parts by mass in terms of dry mass) was added with Sannics GL-3000 (40% by mass) manufactured by Sanyo Chemical Industries, Ltd. parts by mass) was added and dried under reduced pressure at 50° C. to prepare a powdery mixture.

The powdery mixture produced above and a thermoplastic resin (UBE Nylon 1013B manufactured by Ube Industries, Ltd.) are blended at a ratio such that the cellulose fiber is 10% by mass in the resin composition, and the resin composition is obtained by the following procedure. manufactured things.

Using a small kneader (manufactured by Xplore Instruments, product name “Xplore”), the mixture was circulated and kneaded at 260° C. and 100 rpm (sia rate 1570 (1/s)) for 5 minutes to check the torque. The higher the dispersibility of the esterified cellulose nanofibers in the thermoplastic resin, the higher the melt viscosity. Subsequently, a strand of the resin composition having a diameter of 1 mm was obtained through a die. Using a resin composition pellet obtained by cutting the strand into a length of 1 cm, the tensile yield strength and tensile elongation at break were measured according to the evaluation method described above. For molded pieces that fractured before yielding, their ultimate strength was substituted as the tensile yield strength.
Since the polyamide resin changes due to moisture absorption, it was stored in an aluminum moisture-proof bag immediately after molding to suppress moisture absorption.

<Example 2> (purification before fibrillation)
An acetylated cellulose nanofiber and a resin composition were prepared and evaluated by the method described in Example 1, except that the acetylated pulp 2 prepared in Production Example 2 was used.

<Example 3> (purification before fibrillation)
An acetylated cellulose nanofiber and a resin composition were prepared and evaluated by the method described in Example 1, except that the acetylated pulp 3 prepared in Production Example 3 was used.

<Example 4> (purification before fibrillation)
The concentration of the aqueous dispersion of acetylated pulp 4 prepared in Production Example 4 was adjusted to a solid content of 1.5% by mass. ), acetylated cellulose nanofibers and a resin composition were prepared and evaluated by the method described in Example 1, except that a dispersion of acetylated cellulose nanofibers was obtained by fibrillation.

<Example 5> (Purification before fibrillation)
Acetylated pulp 3 prepared in Production Example 3 and a thermoplastic resin (UBE Nylon 1013B manufactured by Ube Industries, Ltd.) were blended in a ratio such that the acetylated pulp was 10% by mass in the resin composition, and the resin was produced in the following procedure. A composition was produced.

Kneading was performed at 260° C. using a twin-screw extruder (OMEGA30H manufactured by STEER, L/D=72) having 15 cylinder blocks. Incidentally, the cylinder 14 was provided with a vent port at the top of the cylinder so that vacuum suction could be performed, and vacuum suction was carried out. A 50 mesh screen mesh was attached between the die adapter and the die head.

As for the screw configuration, cylinders 1 to 3 are used as a transport zone composed only of transport screws, and two clockwise kneading discs (feed type kneading discs: hereinafter simply referred to as RKD from the upstream side to cylinder 4). ), and two neutral kneading discs (non-conveying type kneading discs: hereinafter sometimes simply referred to as NKD). Cylinder 5 was the transfer zone, cylinder 6 with 1 RKD followed by 2 NKDs, cylinders 7 and 8 were the transfer zones, cylinder 9 with 2 NKDs. The following cylinder 10 was the conveying zone, cylinder 11 had two NKDs followed by one counterclockwise screw, and cylinders 12 and 13 were the conveying zone.

Using resin composition pellets obtained by cutting the extruded strand into 1 cm lengths, the tensile yield strength and tensile elongation at break were measured according to the evaluation methods described above. For molded pieces that fractured before yielding, their ultimate strength was substituted as the tensile yield strength. The acetylated cellulose nanofibers in the resin composition were isolated by dissolving the polyamide resin in hexafluoroisopropanol, and the average fiber diameter, crystallinity and DS were measured by the methods described above.
Since the polyamide resin changes due to moisture absorption, it was stored in an aluminum moisture-proof bag immediately after molding to suppress moisture absorption.

<Comparative Example 1> (unpurified)
An acetylated cellulose nanofiber and a resin composition were prepared and evaluated by the method described in Example 1 except that the acetylated pulp 5 prepared in Production Example 5 was used.

<Comparative Example 2> (Use of low DS component-free acetylated pulp)
An acetylated cellulose nanofiber and a resin composition were prepared and evaluated by the method described in Example 1, except that the acetylated pulp 6 prepared in Production Example 6 was used.

As shown in Table 1, in Comparative Example 1 in which the high DS component was not removed, the tensile yield strength and tensile elongation at break were low, and the molded piece was highly colored. Moreover, in Comparative Example 2, in which the degree of substitution is high due to excessive chemical modification (that is, does not contain a low DS component), the reinforcing effect of the resin composition tends to be low.

<Example 6> (Migration of high DS component into thermoplastic resin)
Acetylated pulp 5 prepared in Production Example 5 and a thermoplastic resin (UBE Nylon 1013B manufactured by Ube Industries, Ltd.) were blended at a ratio of 10% by mass of the acetylated pulp in the resin composition and kneaded. A resin composition was prepared by defibrating and transferring the high DS component into the resin, and evaluated.

Kneading was performed at a temperature of 260° C. and a discharge rate of 20 kg/h using a twin-screw extruder (OMEGA30H manufactured by STEER, L/D=72) having 15 cylinder blocks. Incidentally, the cylinder 14 was provided with a vent port at the top of the cylinder so that vacuum suction could be performed, and vacuum suction was carried out. A 50 mesh screen mesh was attached between the die adapter and the die head.

As for the screw configuration, cylinders 1 to 3 are used as a transport zone composed only of transport screws, and two clockwise kneading discs (feed type kneading discs: hereinafter simply referred to as RKD from the upstream side to cylinder 4). ), and two neutral kneading discs (non-conveying type kneading discs: hereinafter sometimes simply referred to as NKD). Cylinder 5 was the transfer zone, cylinder 6 with 1 RKD followed by 2 NKDs, cylinders 7 and 8 were the transfer zones, cylinder 9 with 2 NKDs. The following cylinder 10 is used as a transfer zone, and two NKDs and one counterclockwise kneading disk (reverse feed type kneading disk: hereinafter sometimes simply referred to as LKD) are arranged in the cylinder 11. , cylinders 12 and 13 were the transport zones.

Using resin composition pellets obtained by cutting the extruded strand into 1 cm lengths, the tensile yield strength and tensile elongation at break were measured according to the evaluation methods described above. For molded pieces that fractured before yielding, their ultimate strength was substituted as the tensile yield strength.
Since the polyamide resin changes due to moisture absorption, it was stored in an aluminum moisture-proof bag immediately after molding to suppress moisture absorption.

<Reference example 1>
Example 6 except that pellets were prepared with a screw configuration that does not contain LKD using a small twin-screw extruder manufactured by Technobell Co., Ltd. (L / D = 45, screw diameter 15 mm, discharge rate 0.2 kg / h) Molding and evaluation of the resin composition were carried out in the same manner as in the above.

<Comparative Example 3>
The resin composition was molded and evaluated in the same manner as in Example 6, except that the pellets were prepared with a screw configuration using NKD instead of LKD.

As shown in Table 2, in Example 6 in which a screw element having a damming effect was combined, the effect of reinforcing the resin composition with the esterified cellulose nanofibers was good even when the discharge rate was large.

Since the resin composition containing the esterified cellulose nanofibers of the present disclosure can form a molded body having excellent appearance and physical properties, it can be used for industrial machine parts, general machine parts, automobiles, railways, vehicles, ships, and aviation. It can be suitably applied to a wide range of applications such as space-related parts, electronic/electrical parts, construction/civil engineering materials, daily goods, sports/leisure goods, housing members for wind power generation, containers/packaging members, and the like.

Claims (22)

A modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
a defibration and purification step of defibrating and purifying the esterified pulp to produce esterified cellulose nanofibers;
A method for producing an esterified cellulose nanofiber comprising
The esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5,
A method, wherein said purification is removal of at least a portion of said high DS component. 2. The method of claim 1, wherein the difference in degree of esterification (DS) between the high DS component and the low DS component is 0.3 or more. The method according to claim 1 or 2, wherein in the defibration and purification step, the purification is performed before defibration. 3. The method according to claim 1 or 2, wherein in the defibration and purification step, the purification is performed during defibration. The method according to claim 1 or 2, wherein in the defibration and purification step, the purification is performed after defibration. A method according to any one of claims 1 to 5, wherein said purification is carried out by dissolving and removing said high DS components in a solvent. 7. The method of claim 6, wherein after said dissolution, said high DS component is removed by filtration. 8. The method of claim 6 or 7, wherein the solvent comprises one or more selected from the group consisting of ketones, esters, nitrogen-containing compounds, sulfur-containing compounds, ethers, and halogenated hydrocarbons. The method according to any one of claims 1 to 5, wherein the purification is performed using a separation solvent that separates the high DS component and the low DS component. 10. The method of claim 9, wherein the high DS component is removed with the separation solvent. said purification by dispersing said high DS component in said separating solvent to form dispersed particles and then filtering said dispersed particles and said separating solvent through a filter to trap and remove said dispersed particles in said filter; 10. The method of claim 9, wherein: The method according to any one of claims 9 to 11, wherein said separating solvent comprises one or more selected from the group consisting of water and alcohol. The method according to any one of claims 1 to 12, wherein the esterified pulp has a degree of esterification (DS) of more than 1.0 and not more than 2.0. The method according to any one of claims 1 to 13, wherein the esterified cellulose nanofibers have a degree of esterification (DS) of 0.3 or more and 1.2 or less. 15. The method of any one of claims 1-14, wherein the pulp is cotton linter derived pulp. A method according to any one of claims 1 to 15, wherein said esterification is carried out in dimethylsulfoxide (DMSO). The method according to any one of claims 1 to 16, wherein a carboxylic acid vinyl ester is used as an esterification agent for said esterification. A method according to any one of claims 1 to 17, wherein said esterification is acetylation. 19. The method of any one of claims 1-18, wherein the high DS component removed by said purification comprises acetylated polysaccharides having a cellulose type I crystallinity of less than 50%. A modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
a refining step of refining the esterified pulp;
A defibration and mixing step of mixing the purified esterified pulp with a resin and defibrating it to produce a resin composition containing the esterified cellulose nanofibers and the resin;
A method for producing a resin composition comprising
The esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5,
A method, wherein said purification is removal of at least a portion of said high DS component. A modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
A defibration and mixing step of mixing the esterified pulp with a resin and defibrating it to produce a resin composition containing the esterified cellulose nanofibers and the resin;
A method for producing a resin composition comprising
The esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5,
A method, wherein at least part of the high DS component is transferred from the esterified pulp into a resin phase in the defibration and mixing step. A modification step of esterifying a pulp containing cellulose to obtain an esterified pulp;
a refining step of refining the esterified pulp;
A defibration step of defibrating the purified esterified pulp to generate esterified cellulose nanofibers;
a mixing step of mixing the esterified cellulose nanofibers obtained in the fibrillation step and a resin to produce a resin composition;
A method for producing a resin composition comprising
The esterified pulp contains a high DS component with a degree of esterification (DS) of 1.5 or more and 3 or less and a low DS component with a degree of esterification (DS) of 0.2 or more and less than 1.5,
A method, wherein said purification is removal of at least a portion of said high DS component.