CN114450334A

CN114450334A - Cellulose acetate particles

Info

Publication number: CN114450334A
Application number: CN202080067146.1A
Authority: CN
Inventors: 水野将宏; 小山田直广
Original assignee: Daicel Corp
Current assignee: Daicel Corp
Priority date: 2020-01-16
Filing date: 2020-01-16
Publication date: 2022-05-06
Anticipated expiration: 2040-01-16
Also published as: TWI839566B; CN114450334B; WO2021144914A1; TW202128776A

Abstract

An object of the present disclosure is to provide cellulose acetate particles capable of obtaining a molded article of cellulose acetate having good strength and high transparency. A cellulose acetate particle comprising a cellulose acetate and a plasticizer, wherein the cellulose acetate particle has a melt flow rate of more than 1.0g/10min and less than 2.8g/10min, a total sulfuric acid content of 20ppm or more and 170ppm or less, and a calcium concentration of 22ppm or more and 37ppm or less, the cellulose acetate has an acetyl substitution degree of 2.2 or more and 2.6 or less, and the plasticizer content is 30 parts by weight or more and 44 parts by weight or less relative to 100 parts by weight of the cellulose acetate.

Description

Cellulose acetate particles

Technical Field

The present disclosure relates to a cellulose acetate particle.

Background

Cellulose acetate is one of organic acid esters of cellulose as a cellulose derivative, and its use is in various fields such as clothing fibers, cigarette filters, plastics, films, paints, pharmaceuticals, foods, cosmetics, and construction applications, and the production amount is also large in cellulose derivatives, and it is an industrially important substance.

As a typical industrial production method of cellulose acetate, there is a so-called acetic acid method in which acetic anhydride is used as an acetylating agent, acetic acid is used as a diluent, and sulfuric acid is used as a catalyst. The basic steps of the acetic acid method are composed of the following steps (patent document 1, non-patent document 1): (1) a pretreatment step of dissociating and/or crushing a pulp raw material (dissolving pulp) having a high alpha-cellulose content, and spraying mixed acetic acid; (2) an acetylation step of subjecting the pretreated pulp of (1) to an acetylation reaction using a mixed acid composed of acetic anhydride, acetic acid, and an acetylation catalyst (e.g., sulfuric acid); (3) a ripening step of hydrolyzing cellulose acetate to produce cellulose acetate having a desired degree of acetylation; and (4) a post-treatment step of separating, purifying, stabilizing and drying the cellulose acetate precipitate after the completion of the hydrolysis reaction from the reaction solution.

Fibers, films and plastics obtained by molding cellulose acetate produced by the above-described method as a raw material generally have a yellowish hue, and even if other various properties are satisfied, they have a defect in appearance, which leads to a reduction in commercial value.

Therefore, in order to reduce the yellowness of cellulose acetate, a secondary treatment is usually performed by adding a white pigment, a fluorescent whitening agent, a bleaching agent, an antioxidant, or the like at the time of molding. For example, it is common to add pigments such as titanium dioxide to cigarette filters. This countermeasure is not an essential solution, and its effect is limited.

On the other hand, attempts have been made to directly obtain cellulose acetate having excellent hue by lowering yellowness. For example, a cause of yellowing of hemicellulose components in wood pulp is pointed out (non-patent documents 2 and 3), and the following are disclosed: cellulose acetate having excellent transparency can be obtained by adding an organic solvent to the cellulose acetate (patent document 2) or by dissolving cellulose diacetate in a solvent having good solubility once and then recovering the solution (patent document 3).

In recent years, it has been desired to add a light color to a molded article of cellulose acetate, and fashionability to develop higher transparency has been demanded, and therefore a molded article of cellulose acetate having a higher level of yellowing resistance, a more excellent hue, and excellent transparency has been demanded.

Molded bodies of cellulose acetate are produced mainly as follows: first, cellulose acetate (sheet), a plasticizer, and, if necessary, an optional additive and the like are melt-kneaded to prepare cellulose acetate pellets (a granular composition containing cellulose acetate and a plasticizer), and then the pellets are subjected to molding processing such as melt extrusion.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 56-059801

Patent document 2: japanese laid-open patent publication No. H06-157601

Patent document 3: japanese laid-open patent publication No. H06-157602

Non-patent document

Non-patent document 1: macromol. Symp.2004,208,49-60

Non-patent document 2: wilson, R.S.Tabke, Tappi,57,77(1974)

Non-patent document 3: F.L.Wells, W.C.Shattner, A.Walker, Tappi,46,581(1963)

Disclosure of Invention

Problems to be solved by the invention

If the transparency of the cellulose acetate particles is insufficient, a molded article having high transparency cannot be obtained. However, even when cellulose acetate (sheet) having a low yellow hue and an excellent hue is used, cellulose acetate particles having a low yellow hue and an excellent hue are not necessarily obtained, and it is difficult to produce cellulose acetate particles having high transparency. Further, in various applications such as fiber materials for clothing and the like, frames for glasses or sunglasses, and building materials, strength of molded articles is required, but it is difficult to obtain molded articles of cellulose acetate having good strength and high transparency.

An object of the present disclosure is to provide cellulose acetate particles capable of obtaining a molded article of cellulose acetate having good strength and high transparency.

Technical scheme

The present disclosure relates to a cellulose acetate particle containing cellulose acetate and a plasticizer, the melt flow rate exceeding 1.0g/10min and less than 2.8g/10min, a total sulfuric acid of 20ppm or more and 170ppm or less, and a calcium concentration of 22ppm or more and 37ppm or less, the cellulose acetate having an acetyl substitution degree of 2.2 or more and 2.6 or less, the plasticizer being contained in an amount of 30 parts by weight or more and 44 parts by weight or less with respect to 100 parts by weight of the cellulose acetate.

Preferably, in the cellulose acetate particle, the plasticizer contains at least one selected from the group consisting of a glyceride-based plasticizer and a phthalate-based plasticizer.

Preferably, the YI (yellowness index) value in the cellulose acetate particles is 20 or less.

Preferably, in the cellulose acetate particles, the melt flow rate is 1.2g/10min or more and 2.3g/10min or less.

Effects of the invention

According to the cellulose acetate particles of the present disclosure, a molded body of cellulose acetate having good strength and high transparency can be obtained.

Detailed Description

[ cellulose acetate particles ]

Hereinafter, an example of a preferred embodiment will be specifically described. The cellulose acetate particle of the present disclosure contains cellulose acetate having a melt flow rate of more than 1.0g/10min and less than 2.8g/10min, a total sulfuric acid of 20ppm or more and 170ppm or less, and a calcium concentration of 22ppm or more and 37ppm or less, an acetyl group substitution degree of the cellulose acetate of 2.2 or more and 2.6 or less, and a plasticizer in an amount of 30 parts by weight or more and 44 parts by weight or less with respect to 100 parts by weight of the cellulose acetate.

The particles in the cellulose acetate particles are particles obtained by melt-kneading cellulose acetate, a plasticizer, and, if necessary, any additives, and the like, and are formed into a particle shape. The method of melt kneading is not particularly limited, but a method of forming strands by a melt extrusion method using a single-screw or twin-screw extruder and cutting them into pellets, and the like can be mentioned.

(melt flow Rate (MFR))

The Melt Flow Rate (MFR) of the cellulose acetate particles of the present disclosure is in excess of 1.0g/10min and less than 2.8g/10 min. The MFR is preferably 1.2g/10min or more, more preferably 1.5g/10min or more, and still more preferably 2.0g/10min or more. The MFR is preferably 2.5g/10min or less, more preferably 2.3g/10min or less.

When the MFR is 1.0g/10min or less, the resulting molded article will have a hue difference. In addition, when an attempt is made to obtain a molded article, the fluidity of the molten cellulose acetate particles is too high, and the possibility of leakage from the mold becomes high. On the other hand, when the MFR is 2.8g/10min or more, the mechanical strength is poor, and particularly, the tensile properties, bending properties, or toughness are poor. In addition, when an attempt is made to obtain a molded article, the fluidity of the molten cellulose acetate particles is low, and the surface smoothness of the obtained molded article may be deteriorated.

The MFR was determined in accordance with JIS-K7210 under the conditions of a temperature of 200 ℃ and a load of 2.16 kg.

(Total sulfuric acid)

The cellulose acetate particles of the present disclosure have a total sulfuric acid of 20ppm or more and 170ppm or less. The total sulfuric acid may be 30ppm or more, and may be 50ppm or more. The total sulfuric acid may be 150ppm or less, 120ppm or less, 100ppm or less, or 80ppm or less.

When the total sulfuric acid is within the above range, a molded article of cellulose acetate having good strength and high transparency can be obtained from the cellulose acetate particle of the present disclosure. If the total sulfuric acid content exceeds 170ppm, the resulting molded article will have a hue difference.

Total sulfuric acid is the amount of sulfuric acid in 1g of cellulose acetate particles in an absolutely dry state, and can be measured by the coulometry method for the dried cellulose acetate particles.

(calcium concentration)

The cellulose acetate particles of the present disclosure have a calcium concentration of 22ppm or more and 37ppm or less. The calcium concentration may be 23ppm or more, 26ppm or more, and 28ppm or more. The calcium concentration may be 34ppm or less, 33ppm or less, or 31ppm or less.

When the calcium concentration is within the above range, a molded article of cellulose acetate having good strength and high transparency can be obtained from the cellulose acetate particles of the present disclosure. If the calcium concentration is less than 22ppm or exceeds 37ppm, the resulting molded article is poor in color.

(magnesium concentration)

The magnesium concentration of the cellulose acetate particles of the present disclosure may be 1ppm or more and 50ppm or less, and may be 1ppm or more and 20ppm or less.

(calcium and magnesium concentration)

The cellulose acetate particles of the present disclosure may have a total concentration of calcium and magnesium of 0.5 to 3 μmol/g, or 0.9 to 2.0 μmol/g.

The calcium concentration (or magnesium concentration) of the cellulose acetate particles can be determined by the following method. An undried sample (3.0 g) was charged into a crucible, carbonized on an electric heater, and then ashed in an electric furnace at 750 ℃ to 850 ℃ for about 2 hours. After cooling for about 30 minutes, 25mL of a 0.07 wt% hydrochloric acid solution was added and dissolved by heating at 220 to 230 ℃. After cooling, the dissolved solution was diluted to 200mL with distilled water, and the absorbance of the solution was measured as a detection solution together with a standard solution by using an atomic absorption spectrometer to determine the calcium concentration (or magnesium concentration) of the detection solution, and the calcium concentration (or magnesium concentration) of the sample was obtained by conversion according to the following equation. The water content in the sample can be measured, for example, by a KETT moisture meter (METTLER TOLEDO HB 43). About 2.0g of the sample in a hydrous state was placed in an aluminum receiving pan of a KETT moisture meter and heated at 120 ℃ until the weight was not changed, whereby the moisture (wt%) in the sample was calculated from the weight change before and after heating.

[ numerical formula 1]

(YI value)

The YI value of the cellulose acetate particle of the present disclosure is preferably 20 or less, more preferably 19 or less, further preferably 18 or less, and particularly preferably 17 or less. The lower this YI value means that the less yellow hue of the cellulose acetate, the more excellent the hue, and the lower limit of the YI value is not particularly limited, and may be 10 or more.

The YI value of the cellulose acetate particles can be measured in accordance with JIS K7373 plastic-determination method of yellowness and yellowness.

[ cellulose acetate ]

(degree of substitution with acetyl group)

The cellulose acetate particle of the present disclosure contains cellulose acetate having an acetyl group substitution degree of 2.2 or more and 2.6 or less. The degree of substitution with an acetyl group may be 2.3 or more, 2.4 or more, or 2.5 or less.

When the substitution degree of acetyl groups is less than 2.2, the resulting molded article has low dimensional stability, moisture resistance, heat resistance, or the like. On the other hand, when the substitution degree of acetyl group exceeds 2.6, the strength of the obtained molded article is excellent, but it becomes brittle, and for example, when the molded article is used as a fiber material for clothing or the like, or a molded article such as a frame of glasses or sunglasses, a large amount of plasticizer needs to be added in order to obtain flexibility such as elongation suitable for these applications, and the possibility of occurrence of bleeding increases.

The degree of substitution with an acetyl group can be determined by the following well-known titration method: the degree of substitution of cellulose acetate was determined by dissolving cellulose acetate in an appropriate solvent corresponding to the degree of substitution. The degree of acetyl substitution will be determined by the following ASTM: the degree of acetylation obtained by the measurement method of the degree of acetylation in D-817-91 (test method for cellulose acetate and the like) is determined by the following equation in terms of conversion. This is the most common way to determine the degree of substitution of cellulose acetate.

In the present disclosure, the degree of substitution with acetyl groups means the total degree of substitution with acetyl groups, that is, the sum of the degrees of substitution with acetyl groups at the 2, 3, and 6 positions of the glucose ring, which may also be referred to as cellulose acetate.

The degrees of substitution of the acetyl groups at the 2-, 3-and 6-positions in the glucose ring of cellulose acetate can be determined by the method according to Otsuka (Tezuka, Carboydr. Res.273, 83(1995)) by nuclear magnetic resonance spectroscopy (NMR)¹³C-NMR or¹H-NMR).

(6% viscosity)

The cellulose acetate contained in the cellulose acetate particle of the present disclosure may have a 6% viscosity of 50mPa · s or more and 120mPa · s or less. The 6% viscosity is preferably 55 mPas or more, more preferably 65 mPas or more, further preferably 70 mPas or more, particularly preferably 80 mPas or more. The 6% viscosity is preferably 110 mPas or less, more preferably 100 mPas or less, and still more preferably 90 mPas or less.

If the 6% viscosity of cellulose acetate is too low, the resulting molded article may have poor mechanical strength, particularly poor toughness. In addition, when an attempt is made to obtain a molded article, the fluidity of the molten cellulose acetate particles is too high, and the possibility of leakage from the mold becomes high. On the other hand, if the 6% viscosity is too high, the resulting molded article may have a hue difference or poor mechanical strength, and particularly, the tensile properties and bending properties may be poor. In addition, when an attempt is made to obtain a molded article, the fluidity of the molten cellulose acetate particles is low, and the surface smoothness of the obtained molded article may be deteriorated.

The 6% viscosity is determined by dissolving cellulose acetate in 95% acetone aqueous solution to 6 wt/vol% and measuring the fluidization time using an austenitic viscometer.

The 6% viscosity can be adjusted by appropriately changing the conditions such as the reaction time, the amount of catalyst, the reaction temperature, and the amount of neutralization agent in the acetylation step (2) and the hydrolysis step (3) in the production of cellulose acetate (sheet) described below.

[ constitutive sugar ratio ]

The ratio of glucose in the sum of glucose (Glc), xylose (Xyl), and mannose (Man) is preferably 97 mol% or more, more preferably 97.5 mol% or more, still more preferably 98.0 mol% or more, and most preferably 98.5 mol% or more, as the constituent sugar ratio of the cellulose acetate of the present disclosure. This is because cellulose acetate particles having more excellent hue, particularly high transparency, can be obtained.

The proportion (mol%) of glucose in the sum of glucose, xylose and mannose can be determined by the following method.

The proportion (mol%) of glucose in the sum of glucose, xylose and mannose can be determined by hydrolyzing cellulose acetate (sample) with sulfuric acid, neutralizing with barium carbonate, filtering through a filter paper and an ion exchange filter, and calculating the contents of glucose, xylose and mannose from data obtained by a high performance liquid chromatography electrospray detector (HPLC-CAD) in a High Performance Liquid Chromatography (HPLC) method.

[ plasticizer ]

The cellulose acetate particles of the present disclosure contain a plasticizer. The content of the plasticizer is 30 to 44 parts by weight based on 100 parts by weight of the cellulose acetate. The content of the plasticizer may be 33 parts by weight or more and 35 parts by weight or more based on 100 parts by weight of the cellulose acetate. The content of the plasticizer may be 40 parts by weight or less.

If the content of the plasticizer is too small, the YI value of the cellulose acetate particle is high and the hue is poor. When the content of the plasticizer is too large, the YI value of the cellulose acetate particles is low, and even when an excellent hue is obtained, the mechanical strength of the obtained molded article is poor, and particularly, the tensile properties and bending properties are poor.

Content of plasticizer in cellulose acetate particles the solution is subjected to¹H-NMR measurement.

Examples of the plasticizer include the following. Aromatic carboxylate plasticizers [ phthalic acid plasticizers [ di-C1-12 alkyl phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, and di-2-ethylhexyl phthalate, C1-6 alkoxy C1-12 alkyl phthalates such as dimethoxyethyl phthalate, C1-12 alkyl/aryl C1-3 alkyl phthalates such as butylbenzyl phthalate, and C1-6 alkyl phthaloyl C2-4 alkylene glycol phthalates such as ethylphthaloyl glycol phthalate and butylphthaloyl butylene glycol ], trimellitic acid plasticizers (trimethyl trimellitate, triethyl trimellitate, trioctyl trimellitate, and the like ], tri-C1-12 alkyl trimellitates such as tri-2-ethylhexyl trimellitate, tetra-C1-12 alkyl pyromellitate such as tetraoctyl pyromellitate, etc.) ]; phosphate-based plasticizers [ tributyl phosphate, tricresyl phosphate, triphenyl phosphate, and the like ]; fatty acid ester plasticizers [ adipic acid esters such as dibutyl adipate, dioctyl adipate, butoxyethoxyethyl/benzyl adipate, and dibutoxyethoxyethyl adipate; azelaic acid esters such as diethyl azelate, dibutyl azelate and dioctyl azelate; sebacates such as dibutyl sebacate and dioctyl sebacate; butyl oleate; and methyl acetylricinoleate, etc. ]; glycerin-based plasticizers [ triacetin, diglycerin tetraacetate, and the like ] as lower fatty acid esters of polyhydric alcohols (glycerin, trimethylolpropane, pentaerythritol, sorbitol, and the like); glycol ester plasticizers [ dipropylene glycol dibenzoate, etc ]; citrate-based plasticizers [ acetyl tributyl citrate, etc. ]; amide plasticizers [ e.g., N-butylbenzenesulfonamide ]; ester oligomer-based plasticizers (caprolactone oligomers and the like); and epoxidized soybean oil. These plasticizers may be used alone, or two or more of them may be used in combination.

Among these plasticizers, at least one selected from the group consisting of a citrate-based plasticizer, a glyceride-based plasticizer, a phosphate-based plasticizer, and a phthalic acid-based plasticizer is preferably included, and at least one selected from the group consisting of a glyceride-based plasticizer and a phthalic acid-based plasticizer is more preferably included. In particular, since the cellulose acetate has excellent compatibility, it is more preferable to include at least one selected from the group consisting of diethyl phthalate and triacetin.

[ optional Components ]

The cellulose acetate particles of the present disclosure may contain any conventionally known component. Any component may be used as long as the type and amount thereof are adjusted according to the use and/or specification of the intended molded article. Examples of the optional components include: stabilizers such as antioxidants, ultraviolet absorbers, heat stabilizers, and light stabilizers; colorants such as dyes and pigments; an antistatic agent; a flame retardant aid; a lubricant; an anti-blocking agent; a dispersant; a fluidizing agent; an anti-drip agent; a chelating agent; and antibacterial agents, and the like. Cellulose esters other than cellulose acetate (for example, organic acid esters such as cellulose propionate and cellulose butyrate, inorganic acid esters such as cellulose nitrate, cellulose sulfate and cellulose phosphate) and other polymers may be contained as an optional component.

[ production of cellulose acetate particles ]

The cellulose acetate particles of the present disclosure are not particularly limited. For example, it is obtained by: cellulose acetate (sheet) and a plasticizer were mixed and dried to obtain plasticizer-adsorbed cellulose acetate, and then the plasticizer-adsorbed cellulose acetate was melt-kneaded to prepare a granular form. Specifically, examples thereof include: a method of kneading the cellulose acetate having the plasticizer adsorbed thereon with an extruder such as a single-screw or twin-screw extruder to form a pellet, and a method of melt-kneading the cellulose acetate with a kneader such as a heated roll or a banbury mixer to form a pellet.

In the case of mixing the plasticizer with the cellulose acetate (flake), the mixing of the cellulose acetate (flake) with the plasticizer may be performed by a mixer such as a planetary mill, a henschel mixer, a vibration mill, a ball mill, or the like. Since homogeneous mixing and dispersion can be carried out in a short time, a Henschel mixer is preferably used. The degree of mixing is not particularly limited, and in the case of a henschel mixer, for example, the mixing is preferably carried out for 10 minutes to 1 hour.

Further, drying may be performed after mixing of the cellulose acetate with the plasticizer. The drying method includes, for example, a method of drying by leaving it at 50 to 105 ℃ for 1 to 48 hours.

(production of cellulose acetate (sheet))

The cellulose acetate (sheet) can be obtained by a conventionally known production method. For example, a method for producing cellulose acetate (sheet) having the following steps: step (1) of bringing pulp into contact with acetic acid to carry out pretreatment; a step (2) (acetylation step) in which cellulose contained in the pulp is reacted with acetic anhydride after the pretreatment, and acetylation is performed; a step (3) (a curing step) of hydrolyzing the cellulose acetate obtained by the acetylation; and a step (4) of precipitating the cellulose acetate whose acetyl substitution degree has been adjusted by the hydrolysis.

Pulp can be used as a cellulose source that becomes a raw material of the cellulose acetate of the present disclosure. Examples of the pulp include wood pulp and linter pulp (linter pulp). In particular, wood pulp may be used.

In the step (1) of bringing the pulp into contact with acetic acid for pretreatment, acetic acid or acetic acid containing 1 to 10 wt% of sulfuric acid (sulfurous acetic acid) may be used.

In the step (2) of reacting the cellulose contained in the pulp with acetic anhydride to perform acetylation, the acetylation may be specifically started by, for example: adding cellulose contained in pulp activated by pretreatment to a mixture composed of acetic acid, acetic anhydride, and sulfuric acid; or adding a mixture of acetic acid and acetic anhydride and sulfuric acid to cellulose contained in the pulp activated by the pretreatment.

The cellulose acetate is in a state where almost all hydroxyl groups are substituted with acetyl groups by the acetylation, and hydrolysis may be performed to adjust the degree of substitution to a desired degree. In the case of using sulfuric acid as a catalyst for the acetylation reaction, since the sulfuric acid is bonded to the cellulose in the form of a sulfuric ester, the step (3) of performing hydrolysis is also intended to remove the sulfuric ester by hydrolysis in order to improve thermal stability after the acetylation reaction is completed.

In the step (3) for hydrolysis, the degree of substitution with an acetyl group can be adjusted by stopping the acetylation reaction by adding a neutralizing agent composed of water (including steam); dilute acetic acid; or carbonates, acetates, hydroxides or oxides of calcium, magnesium, iron, aluminum or zinc, etc.

In the step (4) of precipitating the cellulose acetate whose acetyl substitution degree is adjusted by the hydrolysis, the mixture containing the cellulose acetate may be mixed with a precipitating agent such as water or dilute acetic acid, and the formed cellulose acetate (precipitate) may be separated to obtain a precipitate. Furthermore, as the precipitant, dilute acetic acid is preferable.

After the step (4) of precipitating cellulose acetate, the free metal components, sulfuric acid components, and the like may be removed by washing with water. In addition to the water washing, the following may be further added as a stabilizer as required: alkali metal compounds and/or alkaline earth metal compounds, particularly calcium compounds such as calcium hydroxide. In addition, a stabilizer may be used in the washing with water.

The cellulose acetate may be dried immediately after the step (4) of precipitating the cellulose acetate or after any step such as washing with water. The drying method is not particularly limited, and a known method may be used, and for example, drying may be performed under conditions such as air blowing or reduced pressure. Examples of the drying method include hot air drying.

[ molded article ]

The cellulose acetate particles of the present disclosure may also be redissolved, for example, using a single-screw or twin-screw extruder equipped with a T-die, for molding. The molding of the cellulose acetate particles of the present disclosure may be carried out by a conventionally known molding method. Specific molding methods include: injection molding, extrusion molding, vacuum molding, profile molding, foam molding, injection molding (injection molding), press molding, blow molding (blow molding), gas injection molding, and the like.

The shape of the molded article obtained by molding the cellulose acetate particle of the present disclosure is not particularly limited, but may be, for example, a particle, a film, a sheet, a fiber, or the like. The shape of the molded article may be adjusted according to various uses such as OA (Office Automation)/home appliance field, electric/electronic field, communication equipment field, sanitary field, transportation vehicle field such as automobile, house-related field such as furniture and building materials, and miscellaneous goods field.

The aspects disclosed in this specification can be combined with any other feature disclosed in this specification.

Examples

The present disclosure will be specifically described below with reference to examples, but the technical scope thereof is not limited by these examples.

Physical properties described in examples below were evaluated by the following methods.

< degree of acetylation/degree of acetyl substitution >

The degree of acetylation of cellulose acetate is determined by the method of measuring the degree of acetylation in ASTM-D-817-91 (test method for cellulose acetate and the like). 1.9g of dried cellulose acetate was accurately weighed, dissolved in 150mL of a mixed solvent of acetone and dimethyl sulfoxide (volume ratio: 4: 1), and 30mL of a 1N-sodium hydroxide aqueous solution was added thereto, followed by saponification at 25 ℃ for 2 hours. Phenolphthalein was added as an indicator and excess sodium hydroxide was titrated with 1N-sulfuric acid (concentration factor: F). Further, a blank test was performed in the same manner as described above, and the acetylation degree was calculated according to the following formula.

Degree of acetylation (%) [6.5 × (B-a) × F ]/W

(in the formula, A represents the titration amount (ml) of 1N-sulfuric acid in the sample, B represents the titration amount (ml) of 1N-sulfuric acid in the blank test, F represents the concentration factor of 1N-sulfuric acid, and W represents the weight of the sample).

The degree of substitution with an acetyl group is determined by converting the degree of acetylation into the following formula.

DS＝162.14×AV×0.01/(60.052-42.037×AV×0.01)

And (2) DS: degree of substitution by acetyl groups.

AV: degree of acetylation (%).

< 6% viscosity >

The 6% viscosity of cellulose acetate was determined by the following method. To the flask were added 3.00g of the dried sample and 61.67g of methylene chloride, followed by sealing and stirring for about 1 hour. Then, it was completely dissolved by shaking for about 1.5 hours with an inverted shaker. The resulting 6 wt/vol% solution was transferred to the specific Ostwald viscometer mark and tempered at 25 + -1 deg.C for about 30 minutes. The flow-down time between the lines was measured, and the 6% viscosity was calculated from the following formula (1).

6% viscosity (mPa. multidot.s) ═ downflow time(s) × viscometer coefficient (1)

The viscometer coefficient was determined from the following formula (2) by measuring the down flow time by the same procedure as described above using a standard solution for viscometer calibration [ product name "JS-200" (according to JIS Z8809, manufactured by Showa oil Co.).

Viscometer systemNumber { absolute viscosity of standard solution (mPa · s) × density of solution (0.827 g/cm)³) Density of the/{ Standard solution (g/cm)³) Times the second(s) of the flow of the standard solution } (2)

< YI value (yellow index value) >

The YI value of cellulose acetate is a value obtained by measuring the YI value in transmitted light of a cellulose acetate solution. The apparatus was manufactured under the trade name "Spectro Color Meter SQ 2000" manufactured by Nippon Denshoku industries, and the diameter of the apparatus was measured under a C light source, 2 ℃ visual field, and EXCLUDE (without regular reflection) under the selected measurement conditions. To 12g of dried cellulose acetate, 8.8g of methanol and 79.2g of methylene chloride were added and dissolved, and the defoamed solution was put into a 45mm (L) × 45mm (W) × 10mm (D) glass cuvette, and the YI value was measured. A lower YI value means that the cellulose acetate has a lower yellow hue and an excellent hue.

< ratio of constituent sugars >

Cellulose acetate was hydrolyzed with sulfuric acid, neutralized with barium carbonate, filtered through filter paper and an ion exchange filter, and then the molar contents of glucose, xylose and mannose were calculated by a High Performance Liquid Chromatography (HPLC) method using data obtained by HPLC-CAD (Agilent1200 series system), and the ratio of the molar content of glucose in the sum of the molar contents of glucose (Glc), xylose (Xyl) and mannose (Man) was determined.

The HPL-CADC measurement conditions are as follows.

A chromatographic column: asahipak NH 2P-504E (4.6mm I.D.. times.250 mm).

Protection of the column: asahipak NH2P-50G 4A (4.6mm I.D.. times.10 mm).

Temperature of the column: at 20 ℃.

Mobile phase: water/acetonitrile 25/75 (v/v).

Flow rate of mobile phase: 1.0 mL/min.

A detector: CoronaPlus CAD Detector (ESA Biosciences).

Nitrogen pressure: 35 psi.

An atomizer: at 30 ℃.

< tensile Strength at yield Point, tensile Strength at Break Point, and elongation >

Cellulose acetate particles were extruded by a twin-screw extruder, and the extruded cellulose acetate particles were formed into a sheet having a thickness of 6.4mm, and then punched to prepare a strip-shaped test piece (dumbbell No. 1). The tensile strength at yield point was determined under the condition of a tensile rate of 5mm/min in accordance with ASTM-D638 using this dumbbell No. 1. The tensile strength at break and the elongation were determined in accordance with ASTM-D638 using this No. 1 dumbbell.

< flexural Strength and flexural modulus >

The flexural strength and flexural modulus of the cellulose acetate pellets were determined in accordance with ASTM-D790 using a long piece (127 mm. times.12.7 mm. times.6.4 mm) obtained by extruding cellulose acetate pellets by means of a twin-screw extruder, molding the extruded cellulose acetate pellets into a sheet having a thickness of 6.4mm, and punching the sheet.

< Izod impact Strength >

The Izod impact strength of the cellulose acetate pellets was determined in accordance with ASTM-D256 using a long piece (63.5 mm. times.12.7 mm. times.6.4 mm) obtained by extruding cellulose acetate pellets by means of a twin-screw extruder, molding the extruded cellulose acetate pellets into a sheet having a thickness of 6.4mm, and punching the sheet.

< Rockwell hardness >

The Rockwell hardness of the cellulose acetate particles was determined in accordance with ASTM-D785.

< Heat distortion temperature (high load) >

The heat distortion temperature of the cellulose acetate particles was determined using a strip sheet in accordance with ASTM-D648.

< Melt Flow Rate (MFR) >

The MFR of the cellulose acetate particles was determined in accordance with JIS-K7210 under the conditions of a temperature of 200 ℃ and a load of 2.16 kg.

< calcium concentration/magnesium concentration >

An undried sample (3.0 g) was charged into a crucible, carbonized on an electric heater, and then ashed in an electric furnace at 750 ℃ to 850 ℃ for about 2 hours. After cooling for about 30 minutes, 25mL of a 0.07 wt% hydrochloric acid solution was added and dissolved by heating at 220 to 230 ℃. After cooling, the dissolved solution was brought to a constant volume of 200mL with distilled water, and the solution was used as a detection solution, and absorbance was measured using an atomic absorption spectrometer together with a standard solution to determine the calcium concentration (or magnesium concentration) of the detection solution, and the calcium concentration (or magnesium concentration) of the sample was determined by conversion of the following equation. The moisture in the sample is measured, for example, using a KETT moisture meter (METTLER TOLEDO HB 43). About 2.0g of the sample in a water-containing state was placed in an aluminum receiving pan of a KETT moisture meter, and heated at 120 ℃ until the weight was not changed, whereby the moisture (wt%) in the sample was calculated from the weight change before and after heating.

< Total sulfuric acid >

The total sulfuric acid of the cellulose acetate particles was determined as follows. An electrolyte solution prepared by adding sodium azide, acetic acid and potassium iodide to distilled water was prepared in a titration cell. About 0.01g of dried cellulose acetate particles (sample) were placed in a quartz boat, and burned in a tubular furnace in an argon/oxygen stream at 800 to 900 ℃ to introduce the generated sulfur dioxide into the electrolyte in the titration cell. Triiodide ions are generated in a titration cell by electrolysis, sulfur dioxide is titrated with the triiodide ions, and the amount of sulfuric acid is calculated from the amount of electricity required for the titration. Further, the dibutyl disulfide/toluene standard solution was similarly burned, and the amount of sulfuric acid in the sample was corrected based on the recovery rate thereof, and was defined as total sulfuric acid. The total sulfuric acid was expressed in ppm units as the amount of sulfuric acid in 1g of cellulose acetate particles in an absolutely dry state.

< YI value (yellow index value) >

The YI value of the cellulose acetate particles was measured in accordance with "JIS K7373 Plastic-determination method of yellow and yellowing". The device used a spectral color difference meter SD7000 manufactured by Nippon Denshoku industries Co., Ltd, and the measurement conditions selected D65 as the light source, 10 ℃ viewing angle, and reflection (SCE) as the measurement method. To the direction of

The YI value was determined by adding the particles to a round cell of 15H, shaking up and down about 20 times, and leveling with a bar or a spatula. The measurement values were averaged by 5 measurements.

< example 1>

The softwood pre-hydrolyzed sulfite pulp having an alpha cellulose content of 97.7 wt% was crushed into a cotton-like state by a disc refiner to obtain a crushed pulp. Acetic acid (26 parts by weight) was sprayed onto 100 parts by weight of crushed pulp (water content: 7.0%), sufficiently stirred, and then, as a pretreatment, the pulp was left to stand for 1.6 hours to be activated (activation step).

The activated pulp was added to a mixture consisting of 310 parts by weight of acetic acid, 250 parts by weight of acetic anhydride, and 13.3 parts by weight of sulfuric acid. The mixture was pre-cooled to-12 ℃. The temperature was adjusted from-16 ℃ to a maximum temperature of 46 ℃ over 40 minutes, and acetylation was carried out for 110 minutes from the time point of adding the pulp to the mixture (acetylation step). A neutralizer (24% magnesium acetate aqueous solution) was added over 3 minutes so as to adjust the amount of sulfuric acid (amount of aged sulfuric acid) to 2.5 parts by weight. Then, after water was added to make the water content (aging water) in the reaction bath 60 mol%, the temperature of the reaction bath was raised to 85 ℃ over 55 minutes. The aging water concentration is expressed in mol% by multiplying the ratio of the reaction bath water to acetic acid in terms of a molar ratio by 100. Then, aging was carried out at 85 ℃ for 80 minutes, and aging was stopped by neutralizing sulfuric acid with magnesium acetate to obtain a reaction mixture containing cellulose acetate (aging step).

To the resulting reaction mixture containing cellulose acetate, diluted acetic acid (10% by weight) was mixed using a twin-screw kneader, and cellulose acetate was precipitated by mixing in a precipitation manner. At this time, dilute acetic acid was mixed into the reaction mixture containing cellulose acetate 5 times.

The precipitated cellulose acetate was washed with water, immersed in a dilute aqueous calcium hydroxide solution (20ppm), filtered off, dried, and pulverized with a pulverizer to obtain a cellulose acetate flake.

Cellulose acetate flakes (100 parts by weight), diethyl phthalate (Dai chemical industry, Inc.; DEP) as a plasticizer (35.5 parts by weight), tris (2, 4-di-t-butylphenyl) phosphite as an antioxidant (peroxide decomposer) (0.3 part by weight), epoxidized soybean oil as a plasticizer and a heat stabilizer (0.5 part by weight), and citric acid (0.02 part by weight) as a metal chelate agent for preventing a radical reaction were stirred and mixed using a Henschel mixer, and then fed to a twin-screw extruder (melting temperature (cylinder temperature: actual temperature): 194 ℃, set temperature of a die: 205 ℃) and extruded and granulated to obtain cellulose acetate granules.

< examples 2 to 5>

In examples 2 to 5, the concentration of the dilute aqueous calcium hydroxide solution was reduced (example 2); shortening the time of acetylation process and reducing the amount of water added in the maturation process (examples 3 and 5); a cellulose acetate sheet was obtained in the same manner as in example 1, except that the raw material was changed to linter pulp (example 4). Cellulose acetate particles were obtained in the same manner as in example 1, except that the temperature at the time of producing cellulose acetate particles using the cellulose sheet was adjusted as shown in table 1.

< example 6>

Cellulose acetate particles were obtained in the same manner as in example 1, except that triacetin was used as the plasticizer.

< comparative examples 1 to 2>

In comparative examples 1 to 2, the concentration of the dilute aqueous calcium hydroxide solution was 25ppm (comparative example 1); a cellulose acetate sheet was obtained in the same manner as in example 1 except that the concentration of the dilute aqueous calcium hydroxide solution was changed to 10ppm (comparative example 2). Cellulose acetate particles were obtained in the same manner as in example 1, except that the cellulose sheet was used.

< comparative examples 3 to 4>

Cellulose acetate particles were obtained in the same manner as in comparative example 1, except that the amount of the plasticizer was changed as shown in table 1.

< comparative example 5>

In the water washing of the precipitated cellulose acetate, the temperature and amount of water were changed to obtain a cellulose acetate sheet having a high total sulfuric acid content. Cellulose acetate particles were obtained using the cellulose sheet in the same manner as in example 1.

< comparative examples 6 to 7>

In comparative examples 6 to 7, the amount of water added in the aging step was increased while the time for the acetylation step was increased (comparative example 6); a cellulose acetate sheet adjusted to 6% viscosity was obtained in the same manner as in example 1, except that the time for the acetylation step was shortened and the amount of water added in the aging step was reduced (comparative example 7). Cellulose acetate particles were obtained in the same manner as in example 1, except that the temperature at the time of producing cellulose acetate particles using the cellulose sheet was set as shown in table 1.

The results of obtaining the physical properties of the cellulose acetate sheets and the cellulose acetate particles of the above examples and comparative examples are shown in table 1.

[ Table 1]

In comparative examples 1 and 2, the calcium concentration of comparative example 1 was high and the calcium concentration of comparative example 2 was low, compared with examples, and therefore the YI value of cellulose acetate particles was high, that is, the yellow hue was strong and the hue was poor.

In comparative example 6, the MFR was lower than that of the examples, and the YI value of the cellulose acetate particles was higher. In comparative example 3, since MFR was low and the content of plasticizer was small, YI value of cellulose acetate particles was high and hue difference was low.

In comparative example 4, the YI value was low even when the MFR was high because the plasticizer content was high, but the values of the tensile strength at break point, the flexural strength, the flexural modulus, the rockwell hardness, and the heat distortion temperature (high load) were low, and the tensile properties and the flexural properties were poor. That is, it is known that the deformation is easy.

In comparative example 5, the total sulfuric acid was higher than in the examples, and the YI value of the cellulose acetate particles was higher.

In comparative example 7, the MFR was higher than that of example. Therefore, cellulose acetate particles have a low YI value and excellent hue, but have a low value of Izod impact strength and poor toughness. That is, it is known that the impact resistance is poor.

On the other hand, the cellulose acetate particles of examples had a low YI value, excellent hue and good other physical properties, and thus it was found that a molded article of cellulose acetate having good strength and high transparency was obtained.

Claims

1. A cellulose acetate particle comprising cellulose acetate and a plasticizer,

a melt flow rate of more than 1.0g/10min and less than 2.8g/10min, a total sulfuric acid content of 20ppm or more and 170ppm or less, and a calcium content of 22ppm or more and 37ppm or less,

the cellulose acetate has an acetyl substitution degree of 2.2 or more and 2.6 or less,

the content of the plasticizer is 30 parts by weight or more and 44 parts by weight or less with respect to 100 parts by weight of the cellulose acetate.

2. The cellulose acetate particle according to claim 1,

the plasticizer includes at least one selected from the group consisting of a glyceride-based plasticizer and a phthalic acid-based plasticizer.

3. The cellulose acetate particle according to claim 1 or 2,

the YI value is 20 or less.

4. The cellulose acetate particle according to any one of claims 1 to 3,

the melt flow rate is 1.2g/10min or more and 2.3g/10min or less.