JP6270379B2 - Fine cellulose fiber composite and method for producing the same - Google Patents

Description

  The present invention relates to a fine cellulose fiber composite and a method for producing the same. More specifically, the present invention relates to a fine cellulose fiber composite containing fine cellulose fibers and a natural and / or synthetic resin emulsion and a method for producing the same.

  A technique for improving hardness and modulus by mixing fibers with rubber is known. Fibers with a large diameter are easy to disperse in the rubber, but the physical properties such as fatigue resistance decrease, but mixing fibers with a small diameter into the rubber improves the fatigue resistance, but the fibers are entangled and become rubber. There is a tendency for the dispersibility of to deteriorate. Therefore, we proposed a fiber that has both dispersibility and fatigue resistance by dispersing mixed yarn fibers with a sea-island cross section in rubber and fibrillating with shearing force during mixing to increase the contact area with rubber. (Patent Document 1). However, since this fiber forms a sea-island structure by phase separation of the resin, the thickness and length are non-uniform, specifically, the diameter is 1 μm and 0.7 μm thick, and the contact area with rubber is sufficiently large Therefore, a large reinforcing effect cannot be expected.

  Moreover, in patent document 2, the rubber composition containing the fine cellulose fiber hydrophobized by mixing after hydrophobizing the fine cellulose fiber and rubber latex in an aqueous medium, and drying is produced. However, in the mixing step in the aqueous medium, since the fine cellulose fibers hydrophobized by chemical modification are not uniformly dispersed with the rubber latex in the aqueous medium, the fine cellulose fibers aggregate in the obtained rubber composition, The performance originally possessed by the fine cellulose fibers cannot be sufficiently extracted. In addition, after preparing fine cellulose fibers, organic solvent substitution is performed and chemical modification is performed. However, since fine cellulose fibers are prepared as a low-concentration aqueous dispersion and are extremely hydrophilic, Water removal in the solvent replacement step becomes very complicated, and it is difficult to efficiently produce hydrophobized fine cellulose fibers.

 In Patent Document 3, a natural cellulose raw material is reacted with an oxyl compound such as 2,2,6,6, -tetramethyl-1-piperidine-N-oxyl (TEMPO) together with a co-oxidant to form C6 position of cellulose. By oxidizing a part of the primary hydroxyl group to aldehyde and carboxyl group via aldehyde, a fine cellulose fiber having a number average fiber diameter of 200 nm or less can be obtained by a relatively mild mechanical treatment by electrostatic repulsion. Have been described. This fine cellulose fiber has good dispersibility without agglomeration in an aqueous medium due to electrostatic repulsion. A fine cellulose fiber and a resin emulsion are mixed in an aqueous medium and then dried to produce a composite having a good fiber dispersion state. However, in the composite with the hydrophobic resin, since the fine cellulose fiber has very high hydrophilicity, the affinity is poor and the reinforcing effect is not sufficient.

Japanese Patent Laid-Open No. 10-7811 JP 2009-84564 A JP 2012-25949 A

  The present invention has been made to solve the above-mentioned problems of the prior art, and fine cellulose fibers can be uniformly dispersed in natural and / or synthetic resin emulsion components. It is an object to be solved to provide a fine cellulose fiber composite having a high affinity with natural and / or synthetic resins and a method for producing the same.

  As a result of intensive studies on the above problems, the present inventors have mixed a fine cellulose fiber in which a hydrophobic group and an anionic group are introduced into cellulose and a natural and / or synthetic resin emulsion to produce a fine cellulose fiber composite. By manufacturing, it discovered that the said subject could be solved and came to complete this invention.

That is, according to the present invention, the following inventions are provided.
(1) A cellulose fiber composite containing (a) fine cellulose fibers in which a hydrophobic group and an anionic group are introduced into cellulose, and (b) a natural and / or synthetic resin emulsion.
(2) The cellulose fiber composite according to (1), wherein the fine cellulose fiber is produced by a step of introducing a compound having both a hydrophobic group and an anionic group with respect to the hydroxyl group of the cellulose fiber raw material.
(3) A fine cellulose fiber is (a) a cellulose half-esterification process in which a cellulose fiber raw material is treated with succinic anhydride substituted with a hydrophobic group, and (b) a half-esterification obtained in the half-esterification process. (1) or (2) which is a fine cellulose fiber produced by a method comprising an alkali treatment step of treating the obtained cellulose with an alkali solution, and (c) a defibration treatment step of defibrating the alkali-treated cellulose. ) Cellulose fiber composites.

(4) including a step of mixing a dispersion of fine cellulose fibers in which a hydrophobic group and an anionic group are introduced into cellulose and a natural and / or synthetic resin emulsion to obtain a cellulose-resin emulsion dispersion ( The method for producing a cellulose fiber composite according to any one of 1) to (3).
(5) After the step of mixing a dispersion of fine cellulose fibers in which a hydrophobic group and an anionic group are introduced into cellulose and a natural and / or synthetic resin emulsion to obtain a cellulose-resin emulsion dispersion, a solvent The method according to (4), further comprising a step of removing the solid and recovering the solid content.
(6) A fiber reinforcing material comprising the fine cellulose fiber composite according to any one of (1) to (3).
(7) A molded product obtained by molding a fiber reinforcement containing the fine cellulose fiber composite according to any one of (1) to (3).

  According to the present invention, when the fine cellulose fiber dispersion in which the hydrophobic group and the anionic group are introduced into the cellulose and the natural and / or synthetic resin emulsion are mixed, the fine cellulose fiber is mixed in the mixed solution by the anionic group. Disperses well and can mix uniformly with the resin emulsion. In addition, according to the present invention, not only can a composite with a good fiber dispersion state be obtained by removing water from the mixed solution, but also the hydrophobic groups in cellulose increase the affinity with the resin, The reinforcing effect can be greatly increased. Furthermore, by utilizing electrostatic repulsion of the anionic group of the obtained cellulose fiber, it becomes possible to prepare a fine cellulose fiber having a hydrophobic group and an anionic group by a mild mechanical treatment, and a manufacturing process Can be simplified.

Hereinafter, the present invention will be described in more detail.
<Cellulose fiber raw material>
Cellulose fiber materials used as raw materials for fine cellulose fibers include paper pulp, cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw and bagasse, cellulose isolated from sea squirts and seaweeds, etc. Is mentioned. Among these, paper pulp is preferable in terms of availability. Paper pulp includes hardwood kraft pulp (bleached kraft pulp (LBKP), unbleached kraft pulp (LUKP), oxygen bleached kraft pulp (LOKP), etc.), softwood kraft pulp (bleached kraft pulp (NBKP), unbleached kraft pulp) (NUCKP, oxygen bleached kraft pulp (NOKP), etc.), sulfite pulp (SP), chemical pulp such as soda pulp (AP), semi-chemical pulp (SCP), semi-chemical pulp such as chemiground wood pulp (CGP) In addition, mechanical pulp such as groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP), non-wood pulp using raw material such as cocoon, sardine, hemp, kenaf and the like, and deinked pulp using raw paper as a raw material. Among these, kraft pulp, deinked pulp, and sulfite pulp are preferable because they are more easily available. A cellulose fiber raw material may be used individually by 1 type, and may be used in mixture of 2 or more types.

<Chemical treatment process>
In the present invention, a fine cellulose fiber in which a hydrophobic group and an anionic group are introduced into cellulose by a step of introducing a hydrophobic group and an anionic group to the hydroxyl group of cellulose of the cellulose fiber raw material can be produced. it can. The step of introducing the hydrophobic group and the anionic group with respect to the hydroxyl group of the cellulose of the cellulose fiber raw material can be preferably performed in the presence of an alkali.

  Specifically, as a step of introducing a hydrophobic group and an anionic group to the hydroxyl group of cellulose, the cellulose fiber raw material is treated with a compound having both a hydrophobic group and an anionic group (preferably in the presence of an alkali). A method of treating (hereinafter referred to as Method A) or a cellulose fiber raw material (preferably in the presence of an alkali) with an anionizing agent, and a chemical modification for introducing a hydrophobic group (preferably in the presence of an alkali) And a step of treating with an agent (hereinafter, method B). Method A is preferable because both a hydrophobic group (hydrophobic bulky group) and a carboxy group can be introduced simultaneously, the reaction becomes very simple, and the production process can be simplified. Hereinafter, method A and method B will be described.

(About Method A)
In one example of the present invention, the cellulose fiber raw material can be treated with a compound having both a hydrophobic group and an anionic group. As a compound having both a hydrophobic group and an anionic group, specifically, succinic anhydride substituted with a hydrophobic group can be used. As an example of Method A, a cellulose half-esterification step in which a cellulose fiber raw material is treated with succinic anhydride substituted with a hydrophobic group, and after completion of the half-esterification, cellulose into which a carboxy group has been introduced is treated with an alkaline solution. By the alkali treatment step, fine cellulose fibers in which a hydrophobic group and an anionic group are introduced into cellulose can be produced.

  The kind of the hydrophobic group in the succinic anhydride substituted with the hydrophobic group is not particularly limited, and specific examples of the succinic anhydride substituted with the hydrophobic group include alkyl or alkenyl succinic anhydride. Specific examples of the alkyl or alkenyl succinic anhydride include, but are not particularly limited to, compounds having a skeleton derived from an olefin having 1 to 24 carbon atoms and a maleic anhydride skeleton. Specifically, 2-methyl succinic anhydride, 2,3-dimethyl succinic anhydride, itaconic anhydride, allyl succinic anhydride, (2-methyl-2-propynyl) succinic anhydride, octyl succinic anhydride, nonyl anhydride Alkyl succinic anhydrides such as succinic acid, decyl succinic anhydride, dodecyl succinic anhydride, tetradecyl succinic anhydride, hexadecyl succinic anhydride, octadecyl succinic anhydride, 2-hexen-1-yl succinic anhydride, pentenyl succinic anhydride, Hexenyl succinic anhydride, octenyl succinic anhydride, decenyl succinic anhydride, undecenyl succinic anhydride, dodecenyl succinic anhydride, tridecenyl succinic anhydride, hexadecenyl succinic anhydride, octadecenyl succinic anhydride, isoocta Alkenyl succinic anhydride such as decenyl succinic anhydride That, without being limited thereto. These can be used alone or in combination of two or more.

  The amount of succinic anhydride substituted with a hydrophobic group is preferably about 0.1 to 1000 parts by weight, more preferably about 0.5 to 500 parts by weight, and 1 to 500 parts by weight with respect to 100 parts by weight of the cellulose fiber raw material. Is more preferable.

  The treatment temperature when treating with succinic anhydride substituted with a hydrophobic group is preferably 250 ° C. or less from the viewpoint of the thermal decomposition temperature of cellulose. Furthermore, when water is contained in the treatment, the temperature is preferably 80 to 200 ° C, more preferably 100 to 170 ° C.

  The reaction conditions of the cellulose fiber raw material and succinic anhydride substituted with a hydrophobic group are not particularly limited. For example, the cellulose fiber raw material, an aqueous alkali solution (for example, an aqueous sodium hydroxide solution), and anhydrous anhydrous substituted with a hydrophobic group Examples thereof include a method of mixing succinic acid, heating and stirring to evaporate and remove moisture.

  The concentration of the cellulose fiber raw material in the mixed solution is not particularly limited, but the dehydration process can be shortened, the fiber raw material and the succinic anhydride substituted with a hydrophobic group are easily contacted, and the reactivity is increased. Is preferably 10% by mass or more, and more preferably 20% by mass or more. On the other hand, 90 mass% or less is preferable, 80 mass% or less is more preferable, and 70 mass% or less is especially preferable in order not to impair the swelling property of the fiber raw material.

  In the present invention, the cellulose fiber raw material can be treated with succinic anhydride substituted with a hydrophobic group, preferably in the presence of alkali, to half-esterify the cellulose. The alkali may be an inorganic alkali compound or an organic alkali compound. Examples of the inorganic alkali compound include alkali metal hydroxides and alkaline earth metal hydroxides. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and examples of the alkaline earth metal hydroxide include calcium hydroxide. Examples of the organic alkali compound include ammonia, aliphatic amines, and aromatic amines. The solvent in the alkaline solution may be either water or an organic solvent, but a polar solvent (polar organic solvent such as water or alcohol) is preferred, and an aqueous solvent containing at least water is more preferred.

  In the reaction, a quaternary ammonium salt such as quaternary ammonium hydroxide or quaternary ammonium chloride can be used to improve the reactivity. The types of quaternary ammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylbenzylammonium hydroxide, dimethyldibenzylammonium Examples include hydroxide. Examples of the quaternary ammonium chloride include tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, trimethylethylammonium chloride, trimethylbenzylammonium chloride, dimethyldibenzylammonium chloride and the like. . These act as phase transfer catalysts that facilitate the reaction of succinic anhydride substituted with hydrophobic groups with hydrophilic cellulose. The amount of catalyst used is preferably 0.01 to 100 moles per mole of cellulose glucose units.

  In addition, by using an organic solvent in which succinic anhydride substituted with a hydrophobic group is dissolved, succinic anhydride substituted with a hydrophobic group penetrates into the inside of the cellulose to facilitate the reaction. As the organic solvent, water is preferable because it is easily mixed with water, such as ketone solvents such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, ethylene glycol, propylene glycol, polyethylene glycol, and other ethers such as dimethyl and diethylated compounds. Amide solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone; dimethyl sulfoxide and the like. Moreover, you may use 2 or more types of mixed solvents chosen from these. Although there will be no restriction | limiting in particular if the usage-amount will have sufficient quantity which can dissolve the succinic anhydride substituted by the hydrophobic group, 5-90 mass% of the total amount of solvent is preferable.

  The alkali concentration at 25 ° C. of the mixed solution consisting of alkali solution / cellulose fiber raw material / succinic anhydride substituted with a hydrophobic group is preferably 0.1% by mass or more, and preferably 0.5 to 12% by mass. Further preferred.

  The reaction apparatus is not particularly limited as long as it can be heated and stirred, but examples thereof include a reaction vessel equipped with stirring blades, a reaction vessel having a stirring bar, a kneader, a twin screw extruder, a lab plast mill, a bead mill, a ball mill, and the like. It is done. Since the reaction is basically a solid-liquid reaction, a stirrer with high stirring efficiency is preferable in order to increase the reaction efficiency. Specific examples include a kneader, a twin screw extruder, a lab plast mill, a bead mill, and a ball mill. Is done.

The cellulose half-esterified with succinic anhydride substituted with hydrophobic groups is then treated with an alkaline solution.
Although it does not specifically limit as a method of an alkali treatment, For example, the method of immersing the cellulose half-esterified with the succinic anhydride substituted by the hydrophobic group in an alkaline solution is mentioned. The alkali compound contained in the alkali solution may be an inorganic alkali compound or an organic alkali compound. Examples of inorganic alkali compounds include alkali metal hydroxides or alkaline earth metal hydroxides, alkali metal carbonates or alkaline earth metal carbonates, alkali metal phosphates or alkaline earth metal phosphoric acids. Salt. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and examples of the alkaline earth metal hydroxide include calcium hydroxide.

Examples of the alkali metal carbonate include lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate. Examples of the alkaline earth metal carbonate include calcium carbonate.
Examples of the alkali metal phosphate include lithium phosphate, potassium phosphate, trisodium phosphate, and disodium hydrogen phosphate. Examples of alkaline earth metal phosphates include calcium phosphate and calcium hydrogen phosphate.

Examples of the organic alkali compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammoniums, aromatic ammoniums, heterocyclic compounds and their hydroxides, carbonates, and phosphates.
For example, ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, Tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, N, N-dimethyl-4-aminopyridine, ammonium carbonate, ammonium hydrogen carbonate, diammonium hydrogen phosphate, etc. Can be mentioned.

  The pH of the reaction solution at 25 ° C. in the alkali treatment step is preferably 9 or more, more preferably 10 or more, and still more preferably 11-14. If the pH of the reaction solution is at least the lower limit, the yield of fine cellulose fibers will be higher. However, when pH exceeds 14, the handleability of an alkaline solution will fall.

  After the alkali treatment, in order to improve the handleability, it is preferable to wash the alkali-treated cellulose with water or an organic solvent before the defibrating treatment step.

(Method B)
In another example of the present invention, a cellulose fiber raw material is treated with an anionizing agent (preferably in the presence of alkali), and a chemical modifier for introducing a hydrophobic group (preferably in the presence of alkali). To produce a fine cellulose fiber in which a part of hydrogen atoms of the hydroxyl group of cellulose is substituted with a hydrophobic group and a part of hydrogen atoms of another hydroxyl group of cellulose is further substituted with an anionic group. be able to. The order of the step of treating the cellulose fiber raw material with the anionizing agent and the step of treating the cellulose fiber raw material with the chemical modifier for introducing the hydrophobic group are not particularly limited, and after performing the step of treating the cellulose fiber raw material with the anionic agent. The step of treating with a chemical modifier for introducing a hydrophobic group may be performed. Or after performing the process of processing a cellulose fiber raw material with the chemical modifier for introduce | transducing a hydrophobic group, you may perform the process of processing with an anionizing agent.

  Examples of the anionic group include a carboxy group, a phosphoric acid group, and a sulfonic acid group.

As a method of introducing a carboxy group into a cellulose fiber raw material, a method of oxidizing a part of the hydroxyl group of cellulose to a carboxy group using an oxidizing agent can be mentioned.
Oxidizing agents include ozone, chlorine dioxide, hydrogen peroxide, peracetic acid, persulfuric acid, permanganic acid, chlorine, hypochlorous acid, chlorous acid, chloric acid, perchloric acid or an aqueous solution thereof such as six salts. Chromic acid sulfuric acid mixture, Jones reagent (acidic sulfuric acid solution of chromic anhydride), chromic acid oxidizing reagent such as pyridilinium chlorochromate (PCC reagent), activated dimethyl sulfoxide reagent used for Swern oxidation, etc., and catalytic oxidation And N-oxyl compounds such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and the like. Of these, ozone, TEMPO, hydrogen peroxide, and chlorine dioxide are preferred, and ozone and TEMPO are more preferred because of the high efficiency of introducing carboxy groups into cellulose fibers.

As a method for introducing a carboxy group into a cellulose fiber raw material, a method using a carboxylic acid compound having two or more carboxy groups in the molecule is also preferred.
In the treatment with the carboxylic acid compound, the hydroxy group of the cellulose molecule and the carboxylic acid compound undergo a dehydration reaction to form a polar group (—COO ⁻ ). Thereby, the bond strength between cellulose fibers becomes weak and defibration improves.

  Specific methods for treating the cellulose fiber raw material with the carboxylic acid compound include a method of mixing the gasified carboxylic acid compound with the cellulose fiber raw material, a method of adding the carboxylic acid compound to the dispersion of the cellulose fiber raw material, and the like. Can be mentioned. Among these, since the process is simple and the efficiency of introducing a carboxy group is high, a method of mixing a gasified carboxylic acid compound with a cellulose fiber raw material is preferable. Examples of the method for gasifying the carboxylic acid compound include a method for heating the carboxylic acid compound.

The carboxylic acid compound used in this treatment is at least one selected from the group consisting of a compound having two carboxy groups, an acid anhydride of a compound having two carboxy groups, and derivatives thereof. Of the compounds having two carboxy groups, compounds having two carboxy groups (dicarboxylic acid compounds) are preferred.
The compounds having two carboxy groups include propanedioic acid (malonic acid), butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), 2-methylpropanedioic acid, 2 -Methylbutanedioic acid, 2-methylpentanedioic acid, 1,2-cyclohexanedicarboxylic acid, 2-butenedioic acid (maleic acid, fumaric acid), 2-pentenedioic acid, 2,4-hexadienedioic acid, 2-methyl 2-butenedioic acid, 2-methyl-2-pentenedioic acid, 2-methylidenebutanedioic acid (itaconic acid), benzene-1,2-dicarboxylic acid (phthalic acid), benzene-1,3-dicarboxylic acid (isophthalic acid) ), Benzene-1,4-dicarboxylic acid (terephthalic acid), ethanedioic acid (oxalic acid), and the like.

Acid anhydrides of compounds having two carboxy groups include maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, pyromellitic anhydride, 1,2-cyclohexanedicarboxylic anhydride Examples thereof include acid anhydrides of dicarboxylic acid compounds such as acids and compounds containing a plurality of carboxy groups.
The acid anhydride derivative of the compound having two carboxy groups includes at least a part of the acid anhydride of the compound having a carboxy group, such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride. The hydrogen atom is substituted with a substituent (for example, an alkyl group, a phenyl group, etc.).
Of these, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are industrially applicable and easily gasified.

  As a method for introducing a phosphate group into a cellulose fiber raw material, a method of mixing a powder or an aqueous solution of phosphoric acid or a phosphoric acid derivative with a dry or wet cellulose fiber raw material, phosphoric acid or Examples thereof include a method of adding an aqueous solution of a phosphoric acid derivative. In these methods, dehydration treatment, heat treatment, and the like are usually performed after mixing or adding a powder or aqueous solution of phosphoric acid or phosphoric acid derivative.

Examples of the phosphoric acid or phosphoric acid derivative used here include at least one compound selected from an oxo acid, a polyoxo acid or a derivative thereof containing a phosphorus atom.
Specifically, phosphoric acid; sodium salt of phosphoric acid such as sodium dihydrogen phosphate, disodium hydrogen phosphate and trisodium phosphate; sodium salt of polyphosphoric acid such as sodium pyrophosphate and sodium metaphosphate; Potassium salts of phosphoric acid such as potassium hydrogen, dipotassium hydrogen phosphate and tripotassium phosphate; potassium salts of polyphosphoric acid such as potassium pyrophosphate and potassium metaphosphate; ammonium dihydrogen phosphate, diammonium hydrogen phosphate and phosphoric acid Examples thereof include ammonium salts of phosphoric acid such as triammonium; ammonium salts of polyphosphoric acid such as ammonium pyrophosphate and ammonium metaphosphate. These may be used alone or in combination of two or more. Among the above, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferable.

  The hydrophobic group in the present invention is not limited as long as it is a functional group exhibiting hydrophobicity, but is preferably a hydrophobic bulky group. Hydrophobic group is not particularly limited, but is a hydrocarbon group or acyl having 2 to 50 carbon atoms, saturated or unsaturated, linear or branched, containing an aromatic ring, or containing a saturated or unsaturated ring Groups and the like. Specific examples of hydrophobic groups include acetyl, acryloyl, methacryloyl, propionyl, propioyl, butyryl, 2-butyryl, pentanoyl, hexanoyl, heptanoyl, octanoyl, nonanoyl, decanoyl, undecanoyl. Group, dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, pivaloyl group and other acyl groups, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, tert-butyl group, pentyl group , Hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, alkyl group such as dodecyl group, myristyl group, palmityl group, stearyl group, and aromatic rings such as benzyl group, benzoyl group, naphthoyl group, etc. Functional groups etc. are mentioned, but these Not a constant.

  Reaction conditions of cellulose and a chemical modifier for introducing a hydrophobic group are not particularly limited, but a solvent, a catalyst, or the like can be used, heating, decompression, or the like can be performed as necessary.

  The type of chemical modifier for introducing a hydrophobic group is one or two selected from the group consisting of cyclic ethers such as acids, acid anhydrides, alcohols, halogenating reagents, isocyanates, alkoxysilanes, and oxiranes (epoxies). More than species.

  When the step of treating the cellulose fiber raw material with an anionizing agent and the step of treating with a chemical modifying agent for introducing a hydrophobic group are performed in the presence of alkali, the alkali used may be an inorganic alkali compound or an organic alkali. It may be a compound. Examples of the inorganic alkali compound include alkali metal hydroxides and alkaline earth metal hydroxides. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and examples of the alkaline earth metal hydroxide include calcium hydroxide. Examples of the organic alkali compound include ammonia, aliphatic amines, and aromatic amines. The solvent in the alkaline solution may be either water or an organic solvent, but a polar solvent (polar organic solvent such as water or alcohol) is preferred, and an aqueous solvent containing at least water is more preferred.

  The pH at 25 ° C. of each reaction solution in the step of treating the cellulose fiber raw material with an anionic agent and the step of treating with a chemical modifier for introducing a hydrophobic group is preferably 9 or more, and preferably 10 or more. More preferred is 11-14.

(Contents of anionic groups and hydrophobic groups in cellulose)
The anionic group content in cellulose is preferably 0.1 to 2.0 mmol / g, more preferably 0.1 to 1.5 mmol / g, and 0.2 to 1.2 mmol / g. More preferably it is. If content of an anionic group is the said range, the hydration property of a fine cellulose fiber will not become high too much, and the viscosity at the time of making a slurry will become low. If the content of the anionic group exceeds the above upper limit, the hydration property becomes too high, and the fine cellulose fibers may be dissolved, which is not preferable.

  The content of an anionic group can be determined using a method of “Test Method T237 cm-08 (2008): Carboxyl Content of pull” of TAPPI, USA. In order to make it possible to measure the content of anionic groups in a wider range, among the test solutions used in the test method, sodium hydrogen carbonate (NaHCO 3) / sodium chloride (NaCl) = 0.84 g / 5.85 g was distilled water. According to TAPPI T237 cm-08 (2008), except that the test solution dissolved and diluted in 1000 ml was changed to 1.60 g of sodium hydroxide so that the concentration of the test solution was substantially 4-fold. In addition, when an anionic group is introduced, the difference in measured values in the cellulose fiber before and after the introduction of the anionic group is regarded as a substantial anionic group content. In addition, the absolutely dry cellulose fiber used as a measurement sample is one obtained by freeze-drying in order to avoid alteration of cellulose that may occur due to heating during heat drying.

  Since the anionic group content measuring method is a measuring method for a monovalent anionic group (carboxy group), when the anionic group to be quantified is multivalent, the monovalent anionic group is contained. A value obtained by dividing the value obtained as a quantity by the acid value is defined as an anionic group content.

  The content of hydrophobic groups in cellulose is preferably 0.1 to 2.0 mmol / g, more preferably 0.1 to 1.5 mmol / g, and 0.2 to 1.2 mmol / g. More preferably. If the content of the hydrophobic group exceeds the upper limit, the fine cellulose fibers may be dissolved, which is not preferable.

<Defibration process>
In the present invention, a cellulose fiber into which a hydrophobic group and an anionic group are introduced can be defibrated. In the defibrating process, the alkali-treated cellulose is usually defibrated using a defibrating apparatus to obtain a fine cellulose fiber suspension.

  High-speed defibrator, grinder (stone mill type crusher), high-pressure homogenizer and ultra-high pressure homogenizer, high-pressure collision type crusher, ball mill, disk type refiner, conical refiner, twin-screw kneader, vibration mill, high speed A wet milling apparatus such as a homomixer under rotation, an ultrasonic disperser, or a beater can be used as appropriate. These may be used alone, a plurality of the same devices may be used, or different types of devices may be combined. When combining different types of apparatuses, it is preferable to combine any two of a refiner, a high-pressure homogenizer, and a high-speed rotary defibrator.

  In the defibrating treatment, it is preferable to dilute cellulose into a slurry by diluting water and an organic solvent alone or in combination. The cellulose solid content concentration after dilution is preferably 0.1 to 20% by mass, and more preferably 0.2 to 10% by mass. If the solid content concentration of the diluted cellulose is equal to or higher than the lower limit, the efficiency of the defibrating process is improved, and if it is equal to or lower than the upper limit, blockage in the defibrating apparatus can be prevented.

<Purification process>
In this invention, you may perform the refinement | purification process which refine | purifies a fine cellulose fiber dispersion so that an average fiber width may be 2-100 nm after a defibration process process. The purification step may or may not be performed. If the fine cellulose fiber dispersion is purified by the purification step, fibers having a large fiber diameter are removed, the appearance of the fine cellulose fibers can be improved, and the physical properties can be further improved. When fine cellulose fibers are used in applications where strength is important, the number of fracture nuclei consisting of large fibers is reduced by the refining process, so that variations in strength and deterioration can be prevented.

  In the refining step, a refining apparatus that removes large fibers from fine cellulose fibers having an average fiber width of 2 to 1000 nm to have an average fiber width of 2 to 100 nm can be used. Examples of the refining device include a decanter using a difference in specific gravity, a centrifuge, a cleaner, a screen and a filter using a difference in shape, a flotator for separating by flotation, and a pressure levitation device. These may be used singly or a plurality of different types may be combined.

<Fine cellulose fiber>
The fine cellulose fiber is preferably a cellulose fiber or rod-like particle having an I-type crystal structure that is much thinner and shorter than the pulp fiber usually used for papermaking.
The fact that the fine cellulose fiber has a type I crystal structure is that 2θ = 14 to 17 ° in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418４) monochromatized with graphite. It can be identified by having typical peaks in the vicinity and two positions near 2θ = 22 to 23 °.

  The degree of crystallinity of fine cellulose fibers determined by the X-ray diffraction method is preferably 60% or more, more preferably 65% or more, and further preferably 70% or more. If the degree of crystallinity is not less than the lower limit, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion. The degree of crystallinity can be obtained by measuring an X-ray diffraction profile and using a conventional method (Segal et al., Textile Research Journal, 29, 786, 1959).

<Fiber width>
The fine cellulose fiber is preferably cellulose having an average fiber width of 2 to 1000 nm determined by observation with an electron microscope. The average fiber width of the fine cellulose fibers is more preferably 2 to 100 nm, further preferably 2 to 50 nm, particularly preferably 2 to 30 nm, and most preferably 2 to 15 nm. When the average fiber width of the fine cellulose fibers exceeds the above upper limit, the characteristics as the fine cellulose fibers (high strength, high rigidity, high dimensional stability, high dispersibility when combined with resin, transparency) are obtained. Becomes difficult. If the average fiber width of the fine cellulose fibers is less than the lower limit value, the cellulose molecules are dissolved in the dispersion medium, so that characteristics (high strength, high rigidity, high dimensional stability) as fine cellulose fibers can be obtained. It becomes difficult.

Measurement of the average fiber width by observation with an electron microscope of fine cellulose fibers is performed as follows. A slurry containing fine cellulose fibers is prepared, and the slurry is cast on a carbon film-coated grid that has been subjected to a hydrophilization treatment to obtain a transmission electron microscope (TEM) observation sample. When wide fibers are included, an operation electron microscope (SEM) image of the surface cast on glass may be observed. Observation by an electron microscope image is performed at any magnification of 1000 times, 5000 times, 10000 times, 20000 times, 40000 times, 50000 times, or 100000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicularly intersecting the straight line X is drawn in the same image, and 20 or more fibers intersect the straight line Y.

  For the electron microscope observation image as described above, the width (minor axis of the fiber) of at least 20 fibers (that is, at least 40 in total) is read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y. . In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber width of at least 40 × 3 sets (that is, at least 120 sets) is read. The fiber widths thus read are averaged to obtain the average fiber width. This average fiber width is equal to the number average fiber diameter.

  The maximum fiber width of the fine cellulose fibers is preferably 500 nm or less, and more preferably 300 nm or less.

<Fiber length>
As for the average fiber length of a fine cellulose fiber, 0.1-5.0 micrometers is preferable. If average fiber length is more than the said lower limit, the strength improvement effect at the time of mix | blending a fine cellulose fiber with resin will fully be acquired. If average fiber length is below the said upper limit, the mixability at the time of mix | blending a fine cellulose fiber with resin will become more favorable. The fiber length can be determined by analyzing the electron microscope observation image used when measuring the average fiber width. That is, at least 20 fibers (that is, a total of at least 40 fibers) are read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y with respect to the electron microscope observation image as described above. In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber length of at least 40 × 3 sets (that is, at least 120 sets) is read. The average fiber length is obtained by averaging the fiber lengths thus read.

<Method for producing cellulose fiber composite>
According to the present invention, a step of obtaining a cellulose-resin emulsion dispersion by mixing a dispersion of fine cellulose fibers in which a hydrophobic group and an anionic group are introduced into cellulose and a natural and / or synthetic resin emulsion. A method for producing the cellulose fiber composite of the present invention is provided. According to the present invention, problems such as aggregation and sedimentation of fine cellulose fibers that could not be avoided by conventional techniques are solved, and a composite in which fine cellulose fibers are uniformly dispersed can be obtained. Moreover, the affinity with the resin is increased by the hydrophobic group, and an excellent reinforcing effect can be exhibited.

(Natural and / or synthetic resin emulsion)
Examples of natural and / or synthetic resin emulsions used in the present invention include resin emulsions and latexes. Among them, synthetic resin aqueous emulsions and rubber aqueous latexes are preferred. Examples of the synthetic resin aqueous emulsion include vinyl acetate, urethane, acrylic, polyester, epoxy, and polyvinyl alcohol resin emulsions. These 1 type may be used and 2 or more types may be used together. Examples of the aqueous rubber latex include natural rubber (N R), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butyl rubber (IIR), nitrile. Examples thereof include rubber (NBR), chloroprene rubber (CR), acrylic rubber (ACMM), and fluororubber (FKM). These 1 type may be used and 2 or more types may be used together. Among these, natural rubber latex is preferable.

(Production method of raw material dispersion)
The manufacturing method of a raw material dispersion liquid is not specifically limited, It can prepare by mixing each component used. Usually, it can be prepared by mixing a dispersion in which fine cellulose fibers are dispersed and a resin emulsion.

  The content of the cellulose fiber in the raw material dispersion is not particularly limited, but from the viewpoint of handling that the viscosity and liquid stability of the obtained fine cellulose dispersion are suitable, the content of the cellulose fiber is 0. 5 mass% or more is preferable, 1 mass% or more is more preferable, 50 mass% or less is preferable, and 40 mass% or less is more preferable.

  The content of the resin component in the raw material dispersion is not particularly limited, but from the viewpoint of handleability such that the viscosity and liquid stability of the resulting fine cellulose fiber dispersion are suitable, the total amount of the raw material dispersion, 2 mass% or more is preferable, 2.5 mass% or more is more preferable, 95 mass% or less is preferable, and 80 mass% or less is more preferable.

  The content of the dispersion medium in the raw material dispersion is not particularly limited, but from the viewpoint of handleability such that the viscosity and liquid stability of the resulting fine cellulose fiber dispersion are suitable, 10 mass% or more is preferable, 20 mass% or more is more preferable, 97.5 mass% or less is preferable, and 95 mass% or less is more preferable.

  The mass ratio of the resin component and the dispersion medium in the raw material dispersion is not particularly limited, but from the viewpoint of handleability such that the viscosity and liquid stability of the resulting fine cellulose fiber dispersion are suitable, the content of the solvent Is preferably 5 to 2000 parts by mass and more preferably 25 to 1000 parts by mass with respect to 100 parts by mass of the resin component.

  The mass ratio between the fine cellulose fiber and the resin component in the raw material dispersion is not particularly limited, but the fine cellulose fiber is preferred from the viewpoint of handleability such that the viscosity and liquid stability of the obtained fine cellulose fiber dispersion are suitable. The content of is preferably 2.5 parts by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, with respect to the total amount (100 parts by mass) of the cellulose fiber and the resin component, 97.5 It is preferably no greater than mass parts, more preferably no greater than 97 parts by mass, and even more preferably no greater than 95 parts by mass.

  In the step of preparing the raw material dispersion of the present invention, there is no particular limitation on the method of mixing the fine cellulose fiber dispersion, the resin emulsion, and other components. For example, a propeller type stirring device, a homogenizer, a rotary stirring device, an electromagnetic stirring device It can be performed by a general method such as manual stirring or natural diffusion without stirring.

  In order to remove water from the dispersion composed of the fine cellulose fiber and the resin emulsion of the present invention, in addition to the commonly used coagulation method of the resin emulsion, natural drying, oven drying, freeze drying, spray drying, pulse combustion, centrifugation A method such as separation can be used.

<Fiber reinforcement>
According to this invention, the fiber reinforcement containing the above-mentioned fine cellulose fiber composite is provided further. The fiber reinforcing material of the present invention is obtained from the above-described fine cellulose fiber composite, and fine cellulose fibers are dispersed in the resin. The fiber reinforcing material can be obtained, for example, by blending various additives into the fine cellulose fiber composite and kneading. It can also be obtained by further blending and kneading a resin with the fine cellulose fiber composite. Examples of additives include inorganic and organic fillers such as silica particles, carbon black, and fibers, silane coupling agents, vulcanizing agents, stearic acid, oils, cured resins, waxes, and antioxidants.

Moreover, a vulcanizing agent may be added before kneading to obtain a vulcanized fiber reinforcement.
As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent can be used. As the organic peroxide, various commonly used ones can be used, among which dicumyl peroxide, t-butylperoxybenzene, and di-t-butylperoxy-diisopropylbenzene are preferable. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example, and sulfur is particularly preferable. One of these vulcanizing agents may be used alone, or two or more thereof may be used in combination.

The addition amount of the vulcanizing agent is usually 7.0 parts by mass or less, preferably 6.0 parts by mass or less in the case of sulfur with respect to 100 parts by mass of the resin. Moreover, it is 1.0 mass part or more normally, Preferably it is 3.0 mass part or more, More preferably, it is 4.0 mass part or more.
In the case of vulcanization, a vulcanization accelerator and a vulcanization acceleration aid may be added together with the vulcanizing agent.

The vulcanization temperature is preferably 60 ° C. or higher, and more preferably 100 ° C. or higher. In addition, from the point which suppresses decomposition | disassembly of a fine cellulose fiber, 250 degreeC or less is preferable and vulcanization temperature is 200 degrees C or less more preferable.
The vulcanization time is preferably 5 minutes or more, more preferably 10 minutes or more, and further preferably 15 minutes or more from the viewpoint of productivity. On the other hand, the vulcanization time is preferably 180 minutes or less.
Vulcanization may be carried out multiple times by changing the temperature and time.

The fiber reinforcement is usually formed into a molded product. The method for producing the molded product may be a method of molding after obtaining the fiber reinforcement, or a method of molding simultaneously with obtaining the fiber reinforcement. As the molding method, various molding methods such as extrusion molding, press molding, and injection molding can be applied.
The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

<Preparation of fine cellulose fiber>
(Production Example 1)
Hardwood kraft pulp (LBKP) having a solid content concentration of 30% is thoroughly mixed with 4 g of dry mass, 8 g of 4N sodium hydroxide and 2 g of octenyl succinic anhydride (50 parts by mass with respect to 100 parts by mass of dry pulp), And stirred for 2 hours. Next, the pulp treated with octenyl succinic anhydride was washed with 500 mL of water three times, and then ion-exchanged water was added to prepare 490 mL of a slurry. Then, while stirring the slurry, 10 mL of 4N aqueous sodium hydroxide solution was added little by little to adjust the pH of the slurry to 12 to 13, and the pulp was alkali treated. Thereafter, the pulp after alkali treatment was washed with water until the pH became 8 or less. When the amount of substituents (carboxy group amount) was measured, it was 0.44 mmol / g.

Next, ion exchange water was added to the pulp after the alkali treatment to prepare a slurry having a solid content concentration of 0.5% by mass. The slurry was defibrated for 30 minutes using a defibrating apparatus (Cleamix-2.2S, manufactured by MTechnic Co., Ltd.) under a condition of 21500 rotations / min to obtain a defibrated pulp slurry.
Ion exchanged water is added to the defibrated pulp slurry to adjust the slurry solid content concentration to 0.2% by mass, and this is centrifuged at 12000G using a cooling high-speed centrifuge (Kokusan, H-2000B). The supernatant liquid separated by 1 was recovered as an aqueous dispersion 1 of fine cellulose fibers.

(Production Example 2)
It was carried out in the same manner as in Production Example 1 except that octyl succinic anhydride was used instead of octenyl succinic anhydride, and recovered as an aqueous dispersion 2 of fine cellulose fibers. When the amount of substituents (carboxy group amount) was measured, it was 0.39 mmol / g.

(Production Example 3)
As a fiber raw material containing cellulose, a hardwood bleached kraft pulp (LBKP) having a carboxy group content of 0.06 mmol / g, a pulp concentration of 30% by mass (water content of 70% by mass), and an absolute dry mass conversion of 20 g was prepared. The LBKP was placed in a container, and 5 L of an ozone / oxygen mixed gas having an ozone concentration of 200 g / m 3 was introduced into the container and shaken at 25 ° C. for 2 minutes. The ozone addition rate at this time was 5 mass% with respect to the pulp dry mass. After standing for 6 hours, ozone and air in the container were removed, and the ozone oxidation treatment was completed.

  After the treatment, the suspension was washed with ion-exchanged water, and the washing was repeated until the pH of the washing water reached 6 or higher. Then, it filtered under reduced pressure using the filter paper, and obtained the oxidation treatment pulp with a cellulose fiber density | concentration of 30 mass%. The dry mass of 4 g of the above pulp, 8 g of 4N sodium hydroxide and 2 g of octenyl succinic anhydride (50 parts by mass with respect to 100 parts by mass of the dry pulp) were mixed well, and the mixture was heated and stirred at 130 ° C. for 2 hours. Next, the pulp treated with octenyl succinic anhydride was washed with 500 mL of water three times, and then ion-exchanged water was added to prepare 490 mL of a slurry. Then, while stirring the slurry, 10 mL of 4N aqueous sodium hydroxide solution was added little by little to adjust the pH of the slurry to 12 to 13, and the pulp was alkali treated. Thereafter, the pulp after alkali treatment was washed with water until the pH became 8 or less. When the amount of substituents (carboxy group amount) was measured, it was 0.81 mmol / g.

Next, ion exchange water was added to the pulp after the alkali treatment to prepare a slurry having a solid content concentration of 0.5% by mass. The slurry was defibrated for 30 minutes using a defibrating apparatus (Cleamix-2.2S, manufactured by MTechnic Co., Ltd.) under a condition of 21500 rotations / min to obtain a defibrated pulp slurry.
Ion exchanged water is added to the defibrated pulp slurry to adjust the slurry solid content concentration to 0.2% by mass, and this is centrifuged at 12000G using a cooling high-speed centrifuge (Kokusan, H-2000B). The supernatant liquid separated by 1 was recovered as an aqueous dispersion 3 of fine cellulose fibers.

(Production Example 4)
It was carried out in the same manner as in Production Example 3 except that octyl succinic anhydride was used instead of octenyl succinic anhydride, and recovered as an aqueous dispersion 4 of fine cellulose fibers. When the amount of substituents (carboxy group amount) was measured, it was 0.76 mmol / g.

(Production Example 5)
Except not using octenyl succinic anhydride, it carried out similarly to manufacture example 1 and collect | recovered as the aqueous dispersion 5 of the fine cellulose fiber.

(Production Example 6)
As a fiber raw material containing cellulose, a hardwood bleached kraft pulp (LBKP) having a carboxy group content of 0.06 mmol / g, a pulp concentration of 30% by mass (water content of 70% by mass), and an absolute dry mass conversion of 20 g was prepared. The LBKP was placed in a container, and 5 L of an ozone / oxygen mixed gas having an ozone concentration of 200 g / m 3 was introduced into the container and shaken at 25 ° C. for 2 minutes. The ozone addition rate at this time was 5 mass% with respect to the pulp dry mass. After standing for 6 hours, ozone and air in the container were removed, and the ozone oxidation treatment was completed. After the treatment, the suspension was washed with ion-exchanged water, and the washing was repeated until the pH of the washing water reached 6 or higher. Then, it filtered under reduced pressure using the filter paper, and obtained the oxidation treatment pulp with a cellulose fiber density | concentration of 30 mass%.

Subsequently, ion-exchange water was added to the pulp to prepare a slurry having a solid content concentration of 0.5% by mass. The slurry was defibrated for 30 minutes using a defibrating apparatus (Cleamix-2.2S, manufactured by MTechnic Co., Ltd.) under a condition of 21500 rotations / min to obtain a defibrated pulp slurry.
Ion exchanged water is added to the defibrated pulp slurry to adjust the slurry solid content concentration to 0.2% by mass, and this is centrifuged at 12000G using a cooling high-speed centrifuge (Kokusan, H-2000B). The supernatant liquid separated by 1 was recovered as an aqueous dispersion 6 of fine cellulose fibers.

<Manufacture of fine cellulose fiber composite>
Example 1
While stirring at 11000 rpm using an IKA homogenizer for 100 parts of natural rubber latex (solid content concentration: 20% by mass), 5 parts by mass of fine cellulose fiber dispersion 1 (0.2% by mass) obtained in Production Example 1 And stirred for another 10 minutes to obtain a mixed solution. The mixed solution was dried at 110 ° C. for 3 hours using a vacuum dryer to obtain a fine cellulose fiber composite 1.

(Example 2)
Using the fine cellulose fiber dispersion 2 obtained in Production Example 2, a fine cellulose fiber composite 2 was obtained in the same manner as in Example 1.

(Example 3)
A fine cellulose fiber composite 3 was obtained in the same manner as in Example 1 using the fine cellulose fiber dispersion 3 obtained in Production Example 3.

Example 4
A fine cellulose fiber composite 4 was obtained in the same manner as in Example 1 using the fine cellulose fiber dispersion 4 obtained in Production Example 4.

(Comparative Example 1)
Using the fine cellulose fiber dispersion 5 obtained in Production Example 5, a fine cellulose fiber composite 5 was obtained in the same manner as in Example 1.

(Comparative Example 2)
A fine cellulose fiber composite 6 was obtained in the same manner as in Example 1 using the fine cellulose fiber dispersion 6 obtained in Production Example 6.

(Comparative Example 3)
A solid rubber was obtained in the same manner as in Example 1 without adding the fine cellulose fiber dispersion.

  Table 1 shows the ratio between the solid content of the resin emulsion and the amount of fine cellulose fibers in the fine cellulose fiber dispersion in each Example and each Comparative Example.

<Evaluation>
The fine cellulose fiber composites of Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated as follows.
Additives were added to each fine cellulose fiber composite as described below, followed by vulcanization to prepare a fiber reinforcement made of a vulcanized rubber composition, and the mechanical properties of the fiber reinforcement were measured.

  Specifically, zinc white (No. 1 zinc white, Asaoka Ceramics) with respect to 105 parts by mass (rubber component: 100 parts by mass, fine cellulose fiber 1: 5 parts by mass) of each example and comparative example. 3 parts by mass of Raw Materials) and 3 parts by mass of stearic acid (Wako Pure Chemical Industries) were blended. Next, these were kneaded at 140 ° C. for 3 minutes using a kneading apparatus (Laboplast Mill μ, manufactured by Toyo Seiki Co., Ltd.). In the obtained kneaded product, 1 part by mass of a vulcanization accelerator (N-tert-butyl-2-benzothiazole sulfenamide, manufactured by Wako Pure Chemical Industries, Ltd.), sulfur (5 mass% oil-treated powder sulfur, Tsurumi Chemical Industry) 2 parts by mass) were added and kneaded at 80 ° C. for 3 minutes using the same kneader as described above to obtain a rubber composition. Subsequently, this rubber composition was pressure-pressed at 150 ° C. for 30 minutes and vulcanized to obtain a fiber reinforcing material having a thickness of 1 mm. A predetermined dumbbell-shaped test piece is prepared from the obtained fiber reinforcement, and the breaking strength and M300 (tensile modulus when the elongation is 300%) are measured by a tensile test according to JIS K6251 using the test piece. did. The measurement results are shown in Table 2. In addition, the breaking strength in Table 2 and the numerical value of M300 are relative indices with the value of Comparative Example 3 as 100. The larger the index, the better the mechanical properties.

The solid rubber of Comparative Example 3 was evaluated as follows.
That is, a fiber reinforcing material was obtained in the same manner as in the evaluation of the fine cellulose fiber composite except that 105 parts by mass of the fine cellulose fiber composite was changed to 100 parts by mass of the solid rubber. And the mechanical physical property of the fiber reinforcement was measured similarly to evaluation of the said fine cellulose fiber composite. The measurement results are shown in Table 1.

  The fiber reinforcements obtained from the fine cellulose fiber composites of Examples 1 to 4 had high elastic modulus and breaking strength. On the other hand, in Comparative Example 1, since there is no carboxy group, the dispersibility in water is low, and the resin emulsion is not uniformly mixed. In addition, since there is no hydrophobic functional group, the affinity with rubber is low. The mechanical properties were insufficient. Although the fiber reinforcement obtained from the fine cellulose fiber composite of Comparative Example 2 has excellent mechanical properties, it does not have a hydrophobic functional group and therefore has low affinity with rubber, and the value of M300 does not reach that of the Examples. It was. Since the solid rubber of Comparative Example 3 does not contain fine cellulose fibers, the fiber reinforcing material obtained from the solid rubber has insufficient mechanical properties.

Claims (2)

A method for producing a cellulose fiber composite comprising (a) fine cellulose fibers having a hydrophobic group and an anionic group introduced into cellulose, and (b) natural and / or synthetic resins,
A step of producing a fine cellulose fiber by introducing a compound having both a hydrophobic group and an anionic group in the presence of water to the hydroxyl group of the cellulose fiber raw material;
A cellulose fiber composite comprising a step of mixing a dispersion of fine cellulose fibers in which a hydrophobic group and an anionic group are introduced into cellulose and a natural and / or synthetic resin emulsion to obtain a cellulose-resin emulsion dispersion. Manufacturing method. After the step of mixing a dispersion of fine cellulose fibers in which a hydrophobic group and an anionic group are introduced into cellulose and a natural and / or synthetic resin emulsion to obtain a cellulose-resin emulsion dispersion, the solvent is removed. further comprising the step of recovering the solids, the method according to claim 1.