Cellulose acetate composition

Abstract

This cellulose acetate composition comprises cellulose acetate, a plasticizer, and a polymer having a structural unit derived from a (meth)acrylic acid ester. The weight average molecular weight of the (meth)acrylic acid ester–based polymer is 500 to less than 5000. The amount of the (meth)acrylic acid ester–based polymer in the composition is less than 2 parts by mass per 100 parts by mass of the cellulose acetate. A molded article is formed from the cellulose acetate composition.

Description

Technical Field

[0001] The present disclosure relates to a cellulose acetate composition. Specifically, the present disclosure relates to a thermoplastic cellulose acetate composition.

Background Art

[0002] Cellulose acetate has poor thermoplasticity due to hydrogen bonds caused by hydroxyl groups remaining in the molecular chain. In particular, the lower the degree of acetyl substitution of cellulose acetate, the higher the molding temperature tends to be. When the molding temperature is high and close to the thermal decomposition temperature of cellulose acetate, thermal decomposition of cellulose acetate starts during molding, resulting in a problem of deterioration in the quality of the obtained molded product. And, the higher the degree of acetyl substitution of cellulose acetate, the higher its crystallinity, and thus the thermoplasticity tends to decrease. Conventionally, a measure has been taken to improve the processability and the quality of the molded product by adding a plasticizer to the cellulose ester to lower the molding temperature.

[0003] In Patent Document 1 (Japanese Patent Application Laid-Open No. 2018-100351), a cellulose acetate having a weight average degree of polymerization of 120 or more and 330 or less and an acetyl group substitution degree of 2.10 or more and 2.60 or less is blended with a (meth)acrylic polymer having a weight average molecular weight of 1000 or more and 30000 or less and a plasticizer to improve thermoplasticity (thermal fluidity). For example, Patent Document 1 discloses, as a specific composition, an example containing 2.0 parts by mass of a (meth)acrylic polymer having a weight average molecular weight of 1700 and a comparative example containing 1.5 parts by mass of a (meth)acrylic polymer having a weight average molecular weight of 14000.

[0004] Patent Document 2 (Japanese Patent Publication No. 2015-168708) discloses a cellulose ester composition containing 2 to 100 parts by mass of a plasticizer and 1 to 10 parts by mass of a polymer with a weight-average molecular weight of 5,000 to 30,000, per 100 parts by mass of cellulose ester. Methyl methacrylate resins are preferred as the polymer. For example, Patent Document 2 discloses an example in which a specific composition contains 1.5 parts by mass of a methyl methacrylate resin with a weight-average molecular weight of 14,000. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-100351 [Patent Document 2] Japanese Patent Publication No. 2015-168708 [Overview of the project] [Problems that the invention aims to solve]

[0006] As described in Patent Documents 1 and 2, compositions containing (meth)acrylic polymers, etc., along with plasticizers allow for thermoforming at temperatures lower than the decomposition temperature of cellulose acetate. However, the technology proposed in Reference Document 1 has the problem that it is not possible to obtain molded products with sufficient mechanical strength because only cellulose acetate with a low molecular weight can be used. Furthermore, although cellulose acetate has recently attracted attention as a biodegradable material, if a large amount of (meth)acrylic polymers, etc., is incorporated into the composition, the physical properties as an acrylic alloy become dominant, and the desired biodegradability may not be obtained. Moreover, while cellulose acetate can be produced from bio-derived raw materials such as cellulose and acetic acid, (meth)acrylic polymers, etc., can only be obtained from so-called petroleum-derived raw materials. From the viewpoint of sustainability, there is a need for compositions with a small amount of (meth)acrylic polymers, etc.

[0007] Furthermore, it was confirmed that compositions containing large amounts of (meth)acrylic polymers, as disclosed extensively in Patent Documents 1 and 2, exhibited an off-odor. This off-odor was attributed to the (meth)acrylic polymer itself. Moreover, according to the present disclosers' findings, when the amount of (meth)acrylic polymer is high, even molded products obtained at low molding temperatures may generate odors during molding or during post-molding storage. From the viewpoint of improving the quality of the resulting molded products and ensuring safety during operation, there is a need for cellulose acetate compositions that produce less odor during molding and in the molded products themselves.

[0008] The purpose of this disclosure is to provide a cellulose acetate composition in which odor is suppressed during thermoforming and storage. [Means for solving the problem]

[0009] As a result of diligent research, the Disclosing Parties have found that by using a very small amount of (meth)acrylic acid ester polymer in combination with a plasticizer, not only is sufficient thermoplasticity obtained, but odor generation during molding is significantly suppressed, and odor generation during long-term storage of molded products is also significantly suppressed.

[0010] That is, the cellulose acetate composition of this disclosure comprises cellulose acetate, a plasticizer, and a polymer having structural units derived from (meth)acrylic acid ester. The weight-average molecular weight of this polymer is 500 or more and less than 5,000. The content of this polymer in the cellulose acetate composition is less than 2 parts by weight per 100 parts by weight of cellulose acetate.

[0011] Polymers having structural units derived from (meth)acrylic acid esters may have at least one functional group at the end of the main chain or side chain. Preferably, this functional group is selected from a hydroxyl group, a carboxyl group, and an alkoxysilyl group.

[0012] The functional group equivalent of a polymer having constituent units derived from (meth)acrylic acid ester may be 100 g / mol or more and 1000 g / mol or less.

[0013] The degree of acetyl substitution of cellulose acetate may be between 1.9 and 2.6. The weight-average molecular weight of cellulose acetate may be between 70,000 and 250,000.

[0014] Preferably, the plasticizer is a citrate ester, glycerol ester, adipic acid ester, and a plasticizer of the general formula HO-(CH2-CH2-O) n The plasticizer is selected from esterified compounds of the compound represented by -H (wherein n is an integer from 2 to 10). The content of the plasticizer in the cellulose acetate composition may be 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of cellulose acetate.

[0015] A molded article of this disclosure is formed from a cellulose acetate composition described in any of the preceding descriptions. [Effects of the Invention]

[0016] The cellulose acetate composition of this disclosure suppresses odor during molding and storage. Moreover, the composition of this disclosure yields molded articles with improved strength. [Best Mode for Carrying Out the Invention]

[0017] The following describes a specific example of a preferred embodiment. Each configuration and combination thereof in each embodiment is an example, and additions, omissions, substitutions, and other modifications are possible as appropriate, without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments, but is limited only by the scope of the claims. Furthermore, each aspect disclosed herein can be combined with any other features disclosed herein.

[0018] In the present specification, "(meth)acrylic" means "acrylic and / or methacrylic". "X to Y" indicating a range means "X or more and Y or less". Also, unless otherwise noted, all test temperatures are room temperature (20°C ± 5°C).

[0019] [Cellulose acetate composition] The cellulose acetate composition according to the present disclosure includes cellulose acetate, a plasticizer, and a polymer having a structural unit derived from (meth)acrylate. The weight average molecular weight of this polymer is 500 or more and less than 5,000. In the cellulose acetate composition of the present disclosure, the content of this polymer is less than 2 parts by mass with respect to 100 parts by mass of cellulose acetate.

[0020] Here, the polymer having a structural unit derived from (meth)acrylate (hereinafter referred to as "(meth)acrylate polymer") means a polymer obtained using (meth)acrylate as a monomer. In the present specification, the (meth)acrylate polymer is a concept that also includes a copolymer obtained by copolymerizing two or more kinds of monomers.

[0021] By including a plasticizer, the cellulose acetate composition according to the present disclosure is easy to mold in a temperature range lower than the decomposition temperature of cellulose acetate. In this composition, by further including the (meth)acrylate polymer in the aforementioned amount, not only is the odor during molding and storage reduced, but the mechanical properties of the obtained molded product are also improved. The molded product obtained from this cellulose acetate composition is excellent in mechanical strength and high quality.

[0022] [(Meth)acrylate polymer] As described above, the cellulose acetate composition of the present disclosure contains a (meth)acrylate polymer. Examples of the (meth)acrylate from which the constituent units of this polymer are derived include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, glycidyl (meth)acrylate, γ-(methacryloyloxypropyl)trimethoxysilane, γ-(methacryloyloxypropyl)dimethoxymethylsilane, and the like. A copolymer obtained using two or more (meth)acrylates as monomers may also be used.

[0023] From the perspective of improving compatibility with cellulose acetate, the (meth)acrylate polymer is preferably a polymer of an aliphatic alkyl ester of (meth)acrylic acid, more preferably a polymer of an aliphatic alkyl ester having 8 or less carbon atoms. Similarly, from the perspective of improving compatibility with cellulose acetate, an acrylate polymer is preferred, a polymer of an aliphatic alkyl ester of acrylic acid is more preferred, a polymer of an aliphatic alkyl ester having 8 or less carbon atoms is even more preferred, and an acrylate polymer selected from methyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate is even more preferred.

[0024] As long as the effects of this disclosure are obtained, the (meth)acrylic acid ester polymer may be a copolymer of any of the above-mentioned (meth)acrylic acid esters with another monomer. Examples of such other monomers include (meth)acrylic acid, (meth)acrylamide, (meth)acrylonitrile, vinyl acetate, vinyl propionate, vinyl alcohol, ethylene, propylene, and styrene. In the case of a copolymer of (meth)acrylic acid esters with another monomer, from the viewpoint of odor reduction, the content of constituent units derived from (meth)acrylic acid esters in this copolymer is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, particularly preferably 90 mol% or more, and may be 100 mol%.

[0025] From the viewpoint of compatibility with cellulose acetate, it is preferable that the (meth)acrylic acid ester polymer has at least one functional group at the end of the main chain or side chain. A polymer having a functional group at the end of the main chain is more preferable, and a polymer having functional groups at the ends of both the main chain and side chains is even more preferable.

[0026] Examples of functional groups that (meth)acrylic acid ester polymers may have at the ends of their main chains or side chains include hydroxyl groups, alkoxy groups, carboxyl groups, epoxy groups, amino groups, amide groups, and alkoxysilyl groups. Examples of alkoxysilyl groups include trimethoxysilyl groups, triethoxysilyl groups, dimethoxyethoxysilyl groups, and diethoxymethoxysilyl groups. Functional groups selected from hydroxyl groups, carboxyl groups, and alkoxysilyl groups are preferred, and trimethoxysilyl groups are preferred as alkoxysilyl groups. (Meth)acrylic acid ester polymers may have two or more functional groups at the ends of their main chains or side chains.

[0027] The amount of functional groups in the main chain or side chain of a (meth)acrylic acid ester polymer is not particularly limited, but from the viewpoint of compatibility with cellulose acetate, the functional group equivalent of this polymer is preferably 100 g / mol or more, followed by 200 g / mol or more, 300 g / mol or more, 400 g / mol or more, 500 g / mol or more, and 600 g / mol or more. From the viewpoint of easy availability, a preferred functional group equivalent is 1,000 g / mol or less. The functional group equivalent is the number of grams of polymer containing 1 gram equivalent of functional groups, and can be measured by known analytical methods. For example, the hydroxyl group equivalent can be calculated by dividing the molecular weight of potassium hydroxide (KOH) by the hydroxyl value measured according to JIS K1557-1.

[0028] [Weight-average molecular weight of (meth)acrylic acid ester polymers] From the viewpoint of easy mixing with cellulose acetate, the weight-average molecular weight of the (meth)acrylic acid ester polymer is less than 5,000, preferably 4,500 or less, more preferably 4,000 or less, even more preferably 3,500 or less, and even more preferably 3,000 or less. From the viewpoint of reducing odor, particularly ester odor, the weight-average molecular weight of the (meth)acrylic acid ester polymer is 500 or more, preferably 750 or more, more preferably 1,000 or more, even more preferably 1,250 or more, and even more preferably 1,500 or more. The weight-average molecular weight of the (meth)acrylic acid ester polymer is measured by the method described later for cellulose ester.

[0029] [Viscosity of (meth)acrylic acid ester polymers] From the viewpoint of easy mixing with cellulose acetate, the viscosity of the (meth)acrylic acid ester polymer is preferably 30,000 mPa·s or less, more preferably 25,000 mPa·s or less, even more preferably 23,000 mPa·s or less, and still more preferably 21,000 mPa·s or less. In this specification, the viscosity of the (meth)acrylic acid ester polymer is the value measured using a B-type viscometer in an environment of 25°C and 50% relative humidity.

[0030] [Content of (meth)acrylic acid ester polymers] In the cellulose acetate composition of this disclosure, the content of the (meth)acrylic acid ester polymer is less than 2 parts by mass per 100 parts by mass of cellulose acetate. From the viewpoint of reducing odor, particularly ester odor, the amount is preferably 1.8 parts by mass or less, more preferably 1.5 parts by mass or less, even more preferably 1.0 part by mass or less, and even more preferably 0.625 parts by mass or less. On the other hand, from the viewpoint of reducing odor, particularly acetic acid odor associated with hydrolysis, the amount of the (meth)acrylic acid ester polymer is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of cellulose acetate. The content of (meth)acrylic acid ester polymers may be 0.01 parts by mass or more and less than 2.0 parts by mass, 0.01 parts by mass or more and 1.5 parts by mass or less, 0.01 parts by mass or more and 1.0 parts by mass or less, 0.01 parts by mass or more and 0.625 parts by mass or less, 0.05 parts by mass or more and less than 2.0 parts by mass, 0.05 parts by mass or more and 1.5 parts by mass or less, 0.05 parts by mass or more and 1.0 parts by mass or less, 0.05 parts by mass or more and 0.625 parts by mass or less, 0.1 parts by mass or more and less than 2.0 parts by mass, 0.1 parts by mass or more and 1.5 parts by mass or less, 0.1 parts by mass or more and 1.0 parts by mass or less, or 0.1 parts by mass or more and 0.625 parts by mass or less, per 100 parts by mass of cellulose acetate.

[0031] [Cellulose acetate (CA)] The cellulose acetate compositions of this disclosure include cellulose acetate. To the extent that the effects of this disclosure are obtained, the compositions of this disclosure may also include cellulose esters other than cellulose acetate.

[0032] [Degree of acetyl substitution] In the compositions of this disclosure, the degree of acetyl substitution of cellulose acetate is not particularly limited, but from the viewpoint of high melt fluidity, the degree of acetyl substitution of cellulose acetate is preferably 1.9 or higher, more preferably 2.0 or higher, and particularly preferably 2.1 or higher. Furthermore, from the viewpoint of improving compatibility with (meth)acrylic acid ester polymers, the degree of acetyl substitution of cellulose acetate is preferably 2.6 or lower, more preferably 2.5 or lower, and even more preferably 2.4 or lower. Two or more types of cellulose acetate with different degrees of substitution may be used in combination.

[0033] The total acetyl substitution degree (sometimes referred to as the average substitution degree) of cellulose acetate can be determined by converting the degree of acetate AV, which is calculated according to the method for measuring the degree of acetate in ASTM:D-871-96 (Test methods for cellulose acetate, etc.), using the following formula. This is the most common method for determining the substitution degree of cellulose acetate. DS=162.14×AV×0.01 / (60.052-42.037×AV×0.01) DS: Total degree of acetyl substitution AV: Degree of acetic acid (%)

[0034] The method for measuring the degree of acetic acid (AV) is as follows:

[0035] First, 500 mg of dried cellulose acetate (sample) is accurately weighed and dissolved in 50 ml of a mixed solvent of ultrapure water and acetone (volume ratio 4:1). Then, 50 ml of 0.2 N sodium hydroxide aqueous solution is added, and saponification is carried out at 25°C for 2 hours. Next, 50 ml of 0.2 N hydrochloric acid is added, and the amount of acetic acid removed is titrated with 0.2 N sodium hydroxide aqueous solution (0.2 N sodium hydroxide normal solution) using phenolphthalein as an indicator. A blank test (test without a sample) is also performed in the same manner. Finally, AV (degree of acetate) (%) is calculated according to the following formula. AV(%) = (AB) × F × 1.201 / Sample weight (g) A: Titration volume (ml) of 0.2N sodium hydroxide normal solution B: Titration volume (ml) of 0.2N sodium hydroxide normal solution in the blank test. F: Factor of 0.2N sodium hydroxide normal solution

[0036] [Cellulose acetate: molecular weight and molecular weight distribution] In the compositions of this disclosure, the weight-average molecular weight of cellulose acetate is not particularly limited, but from the viewpoint of obtaining molded articles with excellent strength, it is preferably 70,000 or more, may be 83,000 or more, may be 90,000 or more, may be 100,000 or more, and may be 150,000 or more. From the viewpoint of obtaining appropriate fluidity when melted, the weight-average molecular weight of cellulose acetate is preferably 250,000 or less, and may be 200,000 or less. The weight-average molecular weight of cellulose acetate may be 7,000 to 250,000, 7,000 to 200,000, 83,000 to 250,000, 83,000 to 200,000, 90,000 to 250,000, 90,000 to 200,000, 100,000 to 250,000, 100,000 to 200,000, 150,000 to 250,000, or 150,000 to 200,000. If the weight-average molecular weight of cellulose acetate falls below 83,000, the resulting composition is likely to have insufficient mechanical strength.

[0037] The molecular weight distribution of cellulose acetate is evaluated by the ratio of the number-average molecular weight Mn to the weight-average molecular weight Mw (Mw / Mn). From the viewpoint of obtaining high melt fluidity, the molecular weight distribution Mw / Mn of cellulose acetate is preferably greater than 1.7, more preferably 1.8 or greater, even more preferably 2.0 or greater, and particularly preferably 2.1 or greater. From the viewpoint of production efficiency of cellulose acetate, the molecular weight distribution Mw / Mn is preferably 3.5 or less, more preferably 3.2 or less, and even more preferably 3.0 or less.

[0038] Cellulose acetate is a semi-synthetic polymer obtained from cellulose as a raw material. The maximum molecular weight of cellulose acetate is determined by the cellulose used as the raw material. Cellulose acetate with a large molecular weight distribution (Mw / Mn) can be obtained by performing hydrolysis in the shortest possible time in the manufacturing method described later. Furthermore, by using cellulose with different molecular weights as raw materials, cellulose acetate with a large molecular weight distribution (Mw / Mn) can be obtained. In addition, it is possible to increase the molecular weight distribution (Mw / Mn) by mixing multiple cellulose acetate flakes with different median degrees of polymerization. If the molecular weight distribution (Mw / Mn) is approximately 3.5 or less, it can be obtained by adjusting the reaction conditions in the cellulose acetate manufacturing method described later. To obtain a molecular weight distribution (Mw / Mn) greater than 3.5, methods of mixing multiple cellulose raw materials or mixing multiple cellulose acetate flakes are effective.

[0039] The weight-average molecular weight and molecular weight distribution of cellulose acetate can be determined by known methods. Specifically, the weight-average molecular weight of cellulose esters is determined by size exclusion chromatography (GPC) measurement under the following apparatus and conditions (GPC-light scattering method). Equipment: Shodex GPC "SYSTEM-21H" Solvent: Acetone Columns: GMHxl (Tosoh) x 2, Guard column (Tosoh TSKgel guardcolumn HXL-H) Flow rate: 0.8ml / min Temperature: 29℃ Sample concentration: 0.25% (wt / vol) Injection volume: 100μl Detection: MALLS (Multi-angle light scattering detector) (Wyatt, "DAWN-EOS") MALLS correction standard material: PMMA (molecular weight 27600)

[0040] [Cellulose acetate content] In the cellulose acetate composition of this disclosure, the cellulose acetate content is preferably 30% by weight or more and 95% by weight or less of the total composition. From the viewpoint of obtaining a high-strength molded article, the cellulose acetate content is more preferably 40% by weight or more. From the viewpoint of obtaining good elongation, the cellulose acetate content is more preferably 90% by weight or less. When two or more types of cellulose acetate with different physical properties are used in combination, it is preferable that their total amount be adjusted to the above numerical range.

[0041] [Method for manufacturing cellulose acetate] The cellulose acetate used in the compositions of this disclosure can be produced by known methods for producing cellulose acetate. Such a method is the so-called acetic acid method, in which acetic anhydride is used as the acetic acid agent, acetic acid as the diluent, and sulfuric acid as the catalyst. The basic steps of the acetic acid method consist of: (1) a pretreatment step in which pulp raw material (dissolved pulp) with a relatively high α-cellulose content is disintegrated and crushed, and then sprayed and mixed with acetic acid; (2) an acetic acid step in which the pretreated pulp from (1) is reacted with a mixed acid consisting of acetic anhydride, acetic acid, and an acetic acid catalyst (e.g., sulfuric acid); (3) a maturation step in which the cellulose acetate is hydrolyzed to obtain cellulose acetate of the desired degree of acetic acid; and (4) a posttreatment step in which the cellulose acetate after the hydrolysis reaction is completed is precipitated, separated, purified, stabilized, and dried from the reaction solution. The total degree of acetyl substitution can be adjusted by adjusting the conditions of the maturation step (conditions such as time and temperature).

[0042] [Plasticizer] In the cellulose acetate composition of this disclosure, the type of plasticizer is not particularly limited. From the viewpoint of improving the plasticity of cellulose acetate, citrate esters, glycerol esters, adipic acid esters and the general formula HO-(CH2-CH2-O) n A plasticizer selected from the group consisting of esterified compounds represented by -H (wherein n is an integer from 2 to 10) is preferred. Two or more plasticizers may be used in combination. It is also possible to include other plasticizers to the extent that the effects of this disclosure are not inhibited.

[0043] Specific examples of citrate esters include acetyltriethyl citrate, acetyltributyl citrate, isodecyl citrate, isopropyl citrate, triethyl citrate, triethylhexyl citrate, and tributyl citrate. Specific examples of glycerin esters include triacetin, diacetin, and monoacetin.

[0044] Specific examples of adipate esters include dimethyl adipate, dibutyl adipate, diisostearyl adipate, diisodecyl adipate, diisononyl adipate, diisobutyl adipate, diisopropyl adipate, diethylhexyl adipate, dioctyl adipate, dioctyldodecyl adipate, dicapryl adipate, dihexyldecyl adipate, bis(2-methoxyethyl) adipate, bis[2-(2-methoxyethoxy)ethyl] adipate, and bis[2-(2-butoxyethoxy)ethyl] adipate. Adipate ester plasticizers commercially available under the trade name "DAIFATTY-101" (manufactured by Daihachi Chemical Industry Co., Ltd.) may also be used.

[0045] General formula HO-(CH2-CH2-O) n Specific examples of esterified compounds represented by -H (where n is an integer from 2 to 10) include diethylene glycol monoacetate, diethylene glycol diacetate, diethylene glycol dibenzoate, triethylene glycol monoacetate, triethylene glycol diacetate, triethylene glycol dipropionate, triethylene glycol dibenzoate, tetraethylene glycol monoacetate, tetraethylene glycol diacetate, tetraethylene glycol dipropionate, and tetraethylene glycol dibenzoate.

[0046] From the viewpoint of significantly improving the plasticity of cellulose acetate, the number average molecular weight of the plasticizer is preferably 1000 or less, more preferably 800 or less, even more preferably 600 or less, and even more preferably 500 or less. From the viewpoint of reducing bleeding from the resulting molded article, the number average molecular weight of the plasticizer is preferably 50 or more, more preferably 100 or more, and particularly preferably 200 or more. The number average molecular weight of the plasticizer is measured for cellulose acetate by the method described above.

[0047] [Plasticizer content] In the cellulose acetate composition of this disclosure, the amount of plasticizer is not particularly limited, but from the viewpoint of excellent shapeability, it is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, per 100 parts by mass of cellulose acetate. From the viewpoint of improving melt fluidity, the amount of plasticizer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more, per 100 parts by mass of cellulose acetate. When two or more plasticizers are used in combination, their total amount is adjusted to fall within the above range.

[0048] The plasticizer content in molded products can be measured by the following method. First, a solvent is selected that dissolves all polymers containing constituent units derived from cellulose acetate, plasticizers, and (meth)acrylic acid esters. Next, the molded product to be measured is pulverized to a size suitable for dissolution and dissolved in the selected solvent to obtain a dilute solution. By analyzing this dilute solution using gas chromatography-mass spectrometry (GC-MASS), the content of plasticizers and other components can be measured. Nuclear magnetic resonance (NMR) spectrometers can also be used to identify plasticizers.

[0049] [Method for producing cellulose acetate composition] The cellulose acetate composition of this disclosure is obtained by melt-kneading cellulose acetate, a plasticizer, and a (meth)acrylic acid ester polymer. This composition may also be obtained by melt-kneading cellulose acetate and a plasticizer, and then adding the (meth)acrylic acid ester polymer to the resulting molten mixture and melt-kneading it. Pre-melt-kneading the cellulose acetate and plasticizer facilitates uniform mixing with the (meth)acrylic acid ester polymer.

[0050] Cellulose acetate, plasticizer, and (meth)acrylic acid ester polymer may be mixed before melt kneading, and if necessary, cellulose acetate and plasticizer may be mixed before melt kneading. Known mixers such as Henschel mixers can be used for mixing before melt kneading. Dry mixing or wet mixing is acceptable. When using a mixer such as a Henschel mixer, the temperature inside the mixer should preferably be such that the cellulose acetate does not melt, for example, 20°C or higher and less than 200°C.

[0051] For melt-kneading cellulose acetate, plasticizer, and (meth)acrylic acid ester polymer, melt-kneading cellulose acetate and plasticizer, and melt-kneading a mixture of cellulose acetate and plasticizer with a (meth)acrylic acid ester polymer, extruders such as twin-screw extruders are used. From the viewpoint of uniformity of the mixture and suppression of thermal degradation, the mixing temperature (cylinder temperature) by the extruder is preferably 170°C to 230°C. When melt-kneading using a twin-screw extruder, the mixing temperature (also called cylinder temperature) may be 200°C. The mixture may be extruded in strand form from a die attached to the tip of the twin-screw extruder and then cut into pellets. In this case, the die temperature may be around 220°C.

[0052] The amount of (meth)acrylic acid ester polymer blended into the cellulose acetate composition of this disclosure is less than 2 parts by mass per 100 parts by mass of cellulose acetate. From the viewpoint of reducing odor, particularly ester odor, the amount is preferably 1.8 parts by mass or less, more preferably 1.5 parts by mass or less, even more preferably 1.0 part by mass or less, and even more preferably 0.625 parts by mass or less. On the other hand, from the viewpoint of reducing odor, particularly acetic acid odor associated with hydrolysis, the amount of (meth)acrylic acid ester polymer is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more per 100 parts by mass of cellulose acetate. The amount of (meth)acrylic acid ester polymer blended may be 0.01 parts by mass or more and less than 2.0 parts by mass, 0.01 parts by mass or more and 1.5 parts by mass or less, 0.01 parts by mass or more and 1.0 parts by mass or less, 0.01 parts by mass or more and 0.625 parts by mass or less, 0.05 parts by mass or more and less than 2.0 parts by mass, 0.05 parts by mass or more and 1.5 parts by mass or less, 0.05 parts by mass or more and 1.0 parts by mass or less, 0.05 parts by mass or more and 0.625 parts by mass or less, 0.1 parts by mass or more and less than 2.0 parts by mass, 0.1 parts by mass or more and 1.5 parts by mass or less, 0.1 parts by mass or more and 1.0 parts by mass or less, and 0.1 parts by mass or more and 0.625 parts by mass or less, per 100 parts by mass of cellulose acetate. When two or more (meth)acrylic acid ester polymers are blended, the total amount is adjusted to be less than 2 parts by mass.

[0053] Within limits that do not impair the effects of the present invention, known additives such as colorants, ultraviolet absorbers, light stabilizers, antioxidants, heat stabilizers, optical property modifiers, fluorescent whitening agents, flame retardants, lubricants, hydrolysis inhibitors, and water repellents may be added to this composition. In that case, it is preferable that the total content of cellulose acetate, plasticizers, and (meth)acrylic acid ester polymers in the composition be 90% by weight or more.

[0054] [Application] The cellulose acetate composition of this disclosure can be melt-molded at relatively low temperatures. Because the cellulose acetate composition of this disclosure has appropriate fluidity when melted, it can be suitably applied to the production of films or sheets by injection molding and melt deposition. Furthermore, it is possible to produce thin films by stretching or inflation molding after melt extrusion.

[0055] Molded articles formed from the cellulose acetate composition according to this disclosure are suitably used in applications such as tableware, packaging containers, trays, agricultural materials, fishing materials, office automation parts, building materials, medical parts, home appliance parts, automotive parts, daily necessities, stationery, and eyeglass frames. [Examples]

[0056] The present invention will be described in detail below with reference to examples, but the technical scope of the present invention is not limited by these examples. Unless otherwise specified, all tensile property evaluation tests were conducted indoors (temperature 25°C ± 5°C, humidity 50% RH).

[0057] [Test 1] [Example 1] The cellulose acetate composition of Example 1 was obtained by adding 100 parts by mass of cellulose acetate (total acetyl substitution degree = 2.45, weight-average molecular weight 170,000), 25 parts by mass of an adipic acid ester plasticizer (product name "DIAFATTY-101" manufactured by Daihachi Chemical Industry Co., Ltd.) as a plasticizer, 0.625 parts by mass of a hydroxyl group-containing methyl acrylate polymer (product name "Actflow UMM-1001" manufactured by Soken Chemical Co., Ltd.) as a (meth)acrylic acid ester polymer, and 0.3 parts by mass of an antioxidant (product name "Irgafos168" manufactured by BASF Japan Ltd.) to a Laboplast mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and kneading at 210°C for 5 minutes. Details of the (meth)acrylic acid ester polymer are shown in Table 1 below.

[0058] [Examples 2-5] Cellulose acetate compositions of Examples 2-5 were obtained in the same manner as in Example 1, except that the (meth)acrylic acid ester polymer was changed to one of those shown in Table 1 below.

[0059] [Comparative Example 1] A cellulose acetate composition of Comparative Example 1 was obtained in the same manner as in Example 1, except that a (meth)acrylic acid ester polymer was not added.

[0060] [Table 1]

[0061] Details of the compounds shown in Table 1 are as follows: UMM-1001 (Product name "Actflow UMM-1001" manufactured by Soken Chemical Co., Ltd., hydroxyl group-containing methyl acrylate polymer, weight-average molecular weight 1,000, functional group equivalent 600 g / mol, viscosity 8,000-13,500 mPa·s) CBB-3098 (product name "Actflow CBB-3098" manufactured by Soken Chemical Co., Ltd., carboxyl group-containing butyl acrylate polymer, weight-average molecular weight 3,000, functional group equivalent 570 g / mol, viscosity 12,500-20,500 mPa·s) CB-3098 (Product name "Actflow CB-3098" manufactured by Soken Chemical Co., Ltd., carboxyl group-containing 2-ethylhexyl acrylate polymer, weight-average molecular weight 3,000, functional group equivalent 570 g / mol, viscosity 10,000-20,000 mPa·s) NE-1000 (Product name "Actflow NE-1000" manufactured by Soken Chemical Co., Ltd., trimethoxysilyl group-containing butyl acrylate polymer, weight-average molecular weight 3,000, functional group equivalent 620 g / mol, viscosity 700-1,300 mPa·s) UT-1001 (Product name "Actflow UT-1001" manufactured by Soken Chemical Co., Ltd., hydroxyl group-containing 2-ethylhexyl acrylate polymer, weight-average molecular weight 3,500, functional group equivalent 970 g / mol, viscosity 2,000-5,000 mPa·s)

[0062] [Acetic acid generation amount 1] The cellulose acetate compositions of Examples 1-5 and Comparative Example 1 were freeze-dried and then 100 mg of powder was taken as a sample. Gas chromatography-mass spectrometry (GC / MS analysis) was performed under the following conditions, and the amount of acetic acid generated was quantified using a calibration curve. The measurement results are shown in Table 2 below. GC / MS instrument: Agilent GC7890 / 5977B-MSD Column: Rtx-624[U] 60m-0.32mmφ-1.8μm Heating temperature: 190℃ Heating time: 20 minutes Headspace: Agilent G1888 Vial volume: 20 ml

[0063] [Table 2]

[0064] As shown in Table 2, the cellulose acetate compositions of the examples containing (meth)acrylic acid ester polymers produced less acetic acid during heating than the compositions of the comparative examples.

[0065] [Exam 2] [Example 6] 100 parts by mass of cellulose acetate (total acetyl substitution degree = 2.45, weight-average molecular weight 170,000), 25 parts by mass of adipic acid ester plasticizer (product name "DIAFATTY-101" from Daihachi Chemical Industry Co., Ltd.) as a plasticizer, 0.625 parts by mass of hydroxyl group-containing methyl acrylate polymer (product name "Actflow UMM-1001" from Soken Chemical Co., Ltd.) as a (meth)acrylic acid ester polymer, and 0.3 parts by mass of an antioxidant (product name "Irgafos168" from BASF Japan Ltd.) were supplied to a twin-screw extruder (product name "PCM30" from Ikegai Co., Ltd., cylinder temperature: 200℃, die temperature: 230℃), melt-kneaded, and then extruded into strands which were cut to obtain pellets consisting of the cellulose acetate composition of Example 6.

[0066] [Example 7 and Comparative Examples 2-7] Pellets for Example 7 and Comparative Examples 2-7 were obtained in the same manner as in Example 6, except that the type of plasticizer and the amount of (meth)acrylic acid ester polymer were as shown in Table 2 below.

[0067] [Liquidity Assessment] In accordance with ISO 1133, the melt flow rate (MFR, unit: g / 10min) of the pellets of Examples 6-7 and Comparative Examples 2-7 was measured using a melt indexer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) under conditions of a temperature of 220°C and a load of 10 kg. The average of five measurements for each is shown in Table 3 below.

[0068] [Tensile properties evaluation] The pellets from Examples 6-7 and Comparative Example 2-7 were injection molded (cylinder temperature 230°C, mold temperature 50°C) to create dumbbell-shaped test specimens. Tensile tests were performed using a tensile testing machine (manufactured by A&D Company, Limited, product name "Tensilon Universal Material Testing Machine") in accordance with ISO standards (tensile speed 10 mm / min, grip distance 115 mm), and the tensile strength (according to ISO 527-1, unit: MPa), flexural strength (according to ISO 178, unit: MPa), and flexural modulus (according to ISO 178, unit: MPa) were measured. The average of three measurements for each is shown in Table 3 below.

[0069] [Acetic acid generation amount 2] The pellets (3.0 g) from Examples 6-7 and Comparative Example 2-7 were each sealed in glass tubes (50 ml capacity) under a relative humidity of 75%, and left to stand at 60°C for 6 hours. After that, the inside was aspirated using an acetic acid detection tube (manufactured by Gastec Co., Ltd.), and the amount of acetic acid generated (unit: ppm) was measured. The measurement results are shown in Table 3 below.

[0070] [Sensory evaluation] The dumbbell-shaped test specimens used for tensile property evaluation were crushed into approximately 1 cm square pieces using pliers. Each crushed sample was placed in a 250 ml mayonnaise jar and stored in an 80°C hot air oven for 72 hours. After removing the mayonnaise jars from the hot air oven and allowing them to cool to room temperature, three panelists were asked to check the odor. The results are shown in Table 3 below.

[0071] [Table 3]

[0072] Details of the compounds shown in Table 3 are as follows: UMM-1001 (Product name "Actflow UMM-1001" manufactured by Soken Chemical Co., Ltd., hydroxyl group-containing methyl acrylate polymer, weight-average molecular weight 1,000, functional group equivalent 600 g / mol, viscosity 8,000-13,500 mPa·s) DAIFATTY-101 (an adipic acid ester-based plasticizer manufactured by Daihachi Chemical Industry Co., Ltd.)

[0073] As shown in Table 3, the cellulose acetate compositions of the examples containing less than 2 parts by mass of (meth)acrylic acid ester polymer showed reduced acetic acid generation during storage and suppressed ester odor caused by the (meth)acrylic acid ester polymer. Furthermore, the compositions of the examples yielded appropriate MFR and showed improved mechanical properties compared to the comparative examples.

[0074] The evaluation results from Tests 1 and 2 show that the cellulose acetate composition of the example suppresses odor generation during heat molding and storage, and moreover, yields molded articles with excellent mechanical properties. The advantages of this disclosure are clear from these evaluation results. [Industrial applicability]

[0075] The cellulose acetate compositions described above can be applied to various fields using melt molding, injection molding, and even melt film formation.

Claims

1. It comprises cellulose acetate, a plasticizer, and a polymer having structural units derived from (meth)acrylic acid ester, The degree of acetyl substitution of the above cellulose acetate is 1.9 or more and 2.6 or less. The weight-average molecular weight of the polymer having the above-mentioned (meth)acrylic acid ester-derived structural units is 500 or more and less than 5,000. A cellulose acetate composition in which the content of a polymer having structural units derived from the above (meth)acrylic acid ester is less than 2 parts by mass per 100 parts by mass of the above cellulose acetate.

2. The cellulose acetate composition according to claim 1, wherein the polymer having structural units derived from the above (meth)acrylic acid ester has at least one functional group at the end of the main chain or side chain.

3. The cellulose acetate composition according to claim 2, wherein the above-mentioned functional group is selected from a hydroxyl group, a carboxyl group, and an alkoxysilyl group.

4. The cellulose acetate composition according to claim 2 or 3, wherein the functional group equivalent of the polymer having the constituent units derived from the above (meth)acrylic acid ester is 100 g / mol or more and 1000 g / mol or less.

5. The cellulose acetate composition according to any one of claims 1 to 4, wherein the weight-average molecular weight of the cellulose acetate is 70,000 or more and 250,000 or less.

6. The above plasticizers include citrate esters, glycerol esters, adipic acid esters, and the general formula HO-(CH ２ -CH ２ -O) ｎ A cellulose acetate composition according to any one of claims 1 to 5, wherein one or more are selected from esterified compounds of compounds represented by -H (wherein n is an integer from 2 to 10).

7. The cellulose acetate composition according to any one of claims 1 to 6, wherein the content of the plasticizer is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the cellulose acetate.

8. A molded article formed from the cellulose acetate composition according to any one of claims 1 to 7.

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