Cellulose-based resin composition and molded article using same

Abstract

Provided is a cellulose-based resin composition that can form a molded article having a high designability. An aspect of the present disclosure relates to a cellulose-based resin composition comprising (A) cellulose acetate having a degree of acetyl substitution of at least 2.0 and (B) at least one polymer selected from the group consisting of polyvinyl acetate and polyvinyl alcohol that has a degree of saponification of not more than 40 mol%.

Description

Cellulose-based resin composition and molded article using the same

[0001] The present invention relates to a cellulose-based resin composition and a molded article using the same.

[0002] Bioplastics made from plant components can contribute to combating oil depletion and global warming, and are therefore used in durable products such as electronic devices and automobiles, in addition to general products such as packaging, containers, and textiles.

[0003] Conventional bioplastics, such as polylactic acid, polyhydroxyalkanoates, and modified starch, are all made from starch-based materials, i.e., edible parts of plants. Therefore, concerns about future food shortages have led to the development of new bioplastics made from inedible parts.

[0004] A typical raw material for inedible parts is cellulose, a major component of wood and plants, and various bioplastics using this have been developed and commercialized. Among cellulose resins, cellulose acetate is the most widely produced industrially.

[0005] In recent years, there has been a demand for resin molded articles that have high-quality appearance and excellent design, even without painting. By not painting resin molded articles, it is possible to reduce the emissions of volatile organic compounds (VOCs) and the painting costs during production, and also to solve the problem of poor appearance of the resulting molded articles due to peeling and deterioration of the paint film.

[0006] As a cellulose-based resin composition for molding, for example, Patent Document 1 discloses a transparent water-soluble cellulose acetate-based resin composition containing cellulose acetate having a total acetyl substitution degree of 0.4 to 1.6 and polyvinyl alcohol having a saponification degree of 50 mol % or more.

[0007] WO2016 / 203657

[0008] However, Patent Document 1 (Table 4, etc.) describes that the use of cellulose acetate with a high degree of acetyl substitution results in cloudiness. On the other hand, there is a demand for the use of cellulose acetate with a high degree of acetyl substitution from the viewpoint of water resistance, etc., and there has been a need for the development of a cellulose-based resin composition that can form a molded article with excellent appearance even in such cases.

[0009] In view of the above-mentioned problems, the present invention has an object to provide a cellulose-based resin composition containing cellulose acetate with a high degree of acetyl substitution and capable of forming a molded body with excellent appearance, and a molded body (molded article) using the same.

[0010] One aspect of the present disclosure relates to the following.

[0011] A cellulose-based resin composition comprising: (A) cellulose acetate having a degree of acetyl substitution of 2.0 or more; and (B) at least one polymer selected from the group consisting of polyvinyl acetate and polyvinyl alcohol having a degree of saponification of 40 mol % or less.

[0012] According to the present disclosure, it is possible to provide a cellulose-based resin composition that can form a molded article with excellent appearance, and a molded article molded using the same.

[0013] One embodiment of the cellulose-based resin composition (also simply referred to as "resin composition" or "composition") of the present disclosure comprises: cellulose acetate (A) having an acetyl substitution degree of 2.0 or more; and at least one polymer (B) selected from the group consisting of polyvinyl acetate and polyvinyl alcohol having a saponification degree of 40 mol% or less. One embodiment of the cellulose-based resin composition of the present disclosure is a cellulose-based resin composition for molding.

[0014] Resin compositions based on cellulose acetate often contain large amounts of plasticizer, resulting in problems such as leaching and volatilization of low-molecular-weight plasticizers. Meanwhile, the inventors of the present application have discovered that the use of polymeric resin additives such as polybutylene succinate as plasticizers results in cloudiness, making it difficult to obtain molded articles with excellent appearance. The cellulose-based resin composition of the present disclosure solves these problems and enables the formation of molded articles with excellent moldability and designability. Furthermore, the cellulose-based resin composition of the present disclosure has excellent thermal stability because it allows the amount of volatile low-molecular-weight plasticizer used to be reduced. Each component will be described below.

[0015] <Component (A)> The cellulose-based resin composition of the present disclosure contains cellulose acetate (also referred to as "component (A)") having an acetyl substitution degree of 2.0 or more. In this specification, cellulose acetate is also referred to as "CA."

[0016] As the cellulose acetate, one in which acetyl groups have been introduced into at least some of the hydroxy groups of cellulose as a raw material can be used.

[0017] Cellulose is a linear polymer formed by the polymerization of β-D-glucose molecules (β-D-glucopyranose) via β(1→4) glycosidic bonds, as shown in the following formula (1). Each glucose unit constituting cellulose has three hydroxy groups (n in the formula is a natural number). The cellulose acetate of this embodiment is such cellulose in which acetyl groups have been introduced using these hydroxy groups.

[0018]

[0019] Cellulose is a major component of plants and can be obtained by separating other components such as lignin from plants. In addition to those obtained in this way, cotton (e.g., cotton linters) and pulp (e.g., wood pulp) with a high cellulose content can be used either as is or after purification. Regarding the shape, size, and form of cellulose or its derivatives used as raw materials, it is preferable to use cellulose or its derivatives in powder form with an appropriate particle size and shape in terms of reactivity, solid-liquid separation, and handleability. For example, fibrous or powdery materials with a diameter of 1 to 100 μm (preferably 10 to 50 μm) and a length of 10 μm to 100 mm (preferably 100 μm to 10 mm) can be used.

[0020] The degree of polymerization of cellulose, expressed as the glucose polymerization degree (average polymerization degree), is preferably in the range of 50 to 5,000, more preferably 100 to 3,000, and even more preferably 100 to 1,000. If the degree of polymerization is too low, the strength, heat resistance, etc. of the produced resin may be insufficient. Conversely, if the degree of polymerization is too high, the melt viscosity of the produced resin may become too high, which may cause problems in molding.

[0021] Cellulose acetate can be obtained by introducing acetyl groups into hydroxyl groups of cellulose. Commercially available cellulose acetate may be used.

[0022] The acetyl group can be introduced by reacting a hydroxy group in cellulose with an acylating agent. The acetyl group corresponds to an organic group introduced in place of the hydrogen atom of the hydroxy group in cellulose. The acylating agent is a compound having at least one functional group capable of reacting with the hydroxy group in cellulose, such as a compound having a carboxyl group, a carboxylic acid halide group, or a carboxylic acid anhydride group. Specific examples include aliphatic monocarboxylic acids (acetic acid), their acid halides, and their acid anhydrides (acetic anhydride).

[0023] The average number of acetyl groups introduced per glucose unit of cellulose (DS ＡＣ) (acetyl group introduction ratio, acetyl substitution degree, also referred to as "DS"), i.e., the average number of hydroxy groups substituted with acetyl groups per glucose unit, is preferably 2.0 or more, and can be set in the range of 2.0 to 3.0. In order to fully obtain the effect of introducing acetyl groups, particularly from the viewpoint of water resistance, flowability, etc., the DS ＡＣ is preferably 2.0 or more, more preferably 2.2 or more, and even more preferably 2.4 or more. From the viewpoint of obtaining the effect of introducing an acetyl group while fully obtaining the effect of other groups (hydroxyl group, etc.), DS ＡＣ is preferably 2.9 or less, more preferably 2.8 or less.

[0024] By introducing acetyl groups into cellulose, the intermolecular forces (intermolecular bonds) of cellulose can be reduced, and the plasticity of the cellulose acetate resin composition can be improved.

[0025] The degree of acetyl substitution of cellulose acetate can be measured by known methods, and may be measured by the method described in Patent Document 1. The degree of acetyl substitution can be determined by converting the acetylation degree determined according to the method for measuring acetylation degree in ASTM D-817-91 (Test Methods for Cellulose Acetate, etc.) using the following formula. This is a common method for determining the degree of substitution of cellulose acetate. DS = 162.14 × AV × 0.01 / (60.052 - 42.037 × AV × 0.01) DS: acetylation degree AV: acetylation degree (%) First, 500 mg of dried cellulose acetate (sample) was precisely weighed and dissolved in 50 ml of a mixed solvent of ultrapure water and acetone (volume ratio 4:1). After that, 50 ml of 0.2 N aqueous sodium hydroxide solution was added, and the mixture was saponified at 25°C for 2 hours. Next, 50 ml of 0.2 N hydrochloric acid is added, and the amount of acetic acid released is titrated with 0.2 N aqueous sodium hydroxide (0.2 N normal sodium hydroxide solution) using phenolphthalein as an indicator. A blank test (a test without using a sample) is also conducted using the same method. The AV (acetylation degree) (%) is then calculated according to the following formula:

[0026] AV (%) = (A - B) x F x 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

[0027] The degree of acetyl substitution of cellulose acetate may also be measured by propionylating the hydroxyl groups of cellulose acetate, dissolving the cellulose acetate in deuterated chloroform, and then measuring the degree of acetyl substitution by NMR.

[0028] The greater the residual amount of hydroxy groups, the greater the maximum strength and heat resistance of the cellulose acetate resin composition, but the greater the water absorption. On the other hand, the greater the conversion rate (degree of substitution) of hydroxy groups, the lower the water absorption and the greater the plasticity and breaking strain, but the lower the maximum strength and heat resistance. Taking these trends into consideration, the conversion rate of hydroxy groups can be appropriately set.

[0029] The average number of remaining hydroxy groups per glucose unit of cellulose acetate (residual hydroxyl group degree) can be set in the range of 0 to 1.0, and is preferably less than 1.0. Hydroxy groups may remain from the viewpoint of the maximum strength and heat resistance of the cellulose acetate resin composition. For example, the residual hydroxyl group degree may be 0.01 or more, and even 0.1 or more. In particular, from the viewpoint of the fluidity of the cellulose acetate resin composition, the residual hydroxyl group degree of the final cellulose acetate product is preferably 1.0 or less, more preferably less than 1.0, more preferably 0.8 or less, and even more preferably 0.6 or less. Furthermore, from the viewpoint of the fluidity of the cellulose acetate resin composition as well as water resistance and impact resistance, the residual hydroxyl group degree is preferably 0.6 or less, more preferably 0.5 or less, even more preferably 0.4 or less, and particularly preferably 0.2 or less.

[0030] The molecular weight of cellulose acetate is preferably in the range of 10,000 to 400,000 in terms of weight average molecular weight, more preferably 50,000 to 350,000, even more preferably 100,000 to 300,000, and even more preferably 150,000 to 250,000. If the molecular weight is too large, the fluidity of the cellulose acetate resin composition may be reduced, making processing difficult and homogeneous mixing difficult. Conversely, if the molecular weight is too small, the physical properties of the cellulose acetate resin composition, such as impact resistance, may be reduced. This weight average molecular weight can be determined by gel permeation chromatography (GPC) (commercially available standard polystyrene can be used as the standard sample).

[0031] <Component (B)> The resin composition of the present disclosure contains at least one polymer (B) (also referred to as "component (B)") selected from the group consisting of polyvinyl acetate and polyvinyl alcohol having a saponification degree of 40 mol% or less. By including component (B), the cellulose-based resin composition can improve the moldability of the resin composition, and the molded article obtained by molding the resin composition can have excellent appearance (design). Furthermore, by including component (B), the amount of volatile plasticizer used can be reduced, which results in excellent thermal stability of the composition and is also preferable from the viewpoints of workability and reduced environmental impact. Furthermore, the amount of low-molecular-weight plasticizer used can be reduced, thereby preventing plasticizer leaching.

[0032] Component (B) is at least one polymer selected from the group consisting of polyvinyl acetate and polyvinyl alcohol having a saponification degree of 40 mol % or less, and preferably contains polyvinyl alcohol having a saponification degree of 40 mol % or less. Component (B) may be one type of polymer or a combination of two or more types of polymers.

[0033] Polyvinyl alcohol (also referred to as "PVA") is a saponified product of a vinyl ester polymer (a polymer containing at least a vinyl ester as a polymerization component). The vinyl ester (vinyl ester monomer) is not particularly limited, but examples thereof include vinyl esters of fatty acids (e.g., vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caprylate, vinyl versatate, vinyl monochloroacetate, and other alkanoic acid vinyl esters (preferably C １－１６ alkanoic acid vinyl esters), aromatic carboxylic acid vinyl esters (e.g., vinyl arene carboxylates such as vinyl benzoate (preferably C ７－１２ arenecarboxylic acid-vinyl esters). The vinyl esters may be used alone or in combination of two or more.

[0034] The vinyl ester may be at least a fatty acid vinyl ester (e.g., C vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl butyrate). １－１０ It is preferable that the polyvinyl alcohol contains a polyvinyl alcohol (alkanoic acid-vinyl ester), and from an industrial viewpoint, it is preferable that the polyvinyl alcohol contains vinyl acetate. In one aspect of the present embodiment, the polyvinyl alcohol is preferably a compound obtained by saponifying polyvinyl acetate.

[0035] The vinyl ester polymer may have a unit derived from another monomer (a monomer copolymerizable with the vinyl ester) as needed (it may be modified with another monomer). The other monomer is not particularly limited, but examples thereof include alkyl vinyl ethers (e.g., preferably C １－１６alkyl vinyl ether), epoxy group-containing vinyl monomers {for example, vinyl glycidyl ethers (for example, allyl glycidyl ether, (meth)acryl glycidyl ether, 4-(meth)acrylamidophenyl glycidyl ether, 3-(meth)acrylamidophenyl glycidyl ether, N-glycidoxymethyl(meth)acrylamide, N-glycidoxyethyl(meth)acrylamide, N-glycidoxypropyl(meth)acrylamide, N-glycidoxybutyl(meth)acrylamide, 4-(meth)acrylamidomethyl-2,5-dimethyl-phenyl glycidyl ether), epoxy group-containing α-olefins (for example, 1,2-epoxy-5-hexene, 1,2-epoxy-7-octene, 1,2-epoxy-9-decene, 8-hydroxy-6,7-epoxy-1-octene, 8-acetoxy-6,7-epoxy-1-octene), N-(2,3-epoxy)propyl(meth)acrylamide, (meth)acrylamidopropyldimethyl(2,3-epoxy)propylammonium chloride, glycidyl (meth)acrylate, etc.}, α-olefins (for example, ethylene, propylene, etc.), (meth)acrylic acid esters [for example, (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, diacetone (meth)acrylate], unsaturated amides [for example, (meth)acrylamide, diacetone (meth)acrylamide, N-methylolacrylamide, etc.], unsaturated acids {for example, unsaturated acids [for example, (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, etc.], unsaturated acid esters [unsaturated acid esters other than (meth)acrylic acid, esters, for example, alkyl (methyl, ethyl, propyl, etc.) esters, unsaturated acid anhydrides (such as maleic anhydride), salts of unsaturated acids [for example, alkali metal salts (for example, sodium salts, potassium salts, etc.), ammonium salts, etc.], glycidyl group-containing monomers [for example, allyl glycidyl ether, glycidyl (meth)acrylate, etc.], sulfonic acid group-containing monomers (for example, 2-acrylamido-2-methylpropanesulfonic acid and its salts, etc.), phosphate group-containing monomers [for example, acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, etc.], allyl alcohol, diacetone (meth)acrylamide, etc., but are not particularly limited to these. These other monomers may be used alone or in combination of two or more.

[0036] The vinyl ester-derived structural units and structural units derived from other monomers may be modified to the extent that the effects of the present invention are not impaired. Modification of vinyl ester-derived units may be, for example, acetalization, etherification, acetoacetylation, cationization, polyoxyalkylene modification, etc. Modification of units derived from other monomers may be, for example, ring-opening reaction of epoxy groups (e.g., reaction of epoxy groups with thiols), etc.

[0037] The method for producing PVA is not particularly limited, and known methods such as saponifying a vinyl ester polymer (preferably polyvinyl acetate) may be used. The polymerization method for vinyl ester polymers is not particularly limited, and examples include conventionally known bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. However, solution polymerization (e.g., solution polymerization using methanol as a solvent) is industrially preferred. Known initiators such as peroxides and azo initiators can be used in the solution polymerization, and the degree of polymerization of the resulting vinyl ester polymer can be adjusted by changing the blending ratio of the vinyl ester monomer to the solvent and the polymerization yield. In this embodiment, commercially available PVA may be used.

[0038] As a method for saponifying a vinyl ester polymer, a known saponification method using an alkali catalyst or an acid catalyst can be used. Among these, a method of adding an alkali such as sodium hydroxide to a methanol solution of a vinyl ester polymer or a mixed solution of a vinyl ester polymer in methanol, water, methyl acetate, or the like, and stirring to mix the mixture, followed by alcoholysis, is industrially preferred. The resulting lumps, gels, or granules may then be pulverized, the added alkali neutralized as needed, and the solid and liquid components may be separated. The solid may then be dried to obtain a PVA. When modification is performed, the timing of modification is not particularly limited, and the modification may be performed before or after the saponification of the vinyl ester polymer.

[0039] The saponification degree of the PVA (preferably partially saponified polyvinyl acetate) of this embodiment is preferably 40 mol% or less, more preferably 38 mol% or less. The lower limit of the saponification degree of the PVA is not particularly limited, but is preferably 0.5 mol% or more, more preferably 1 mol% or more, more preferably 3 mol% or more, even more preferably 8 mol% or more, even more preferably 20 mol% or more, and even more preferably 30 mol% or more, and may even be 35 mol% or more. When the saponification degree of the PVA is 40 mol% or less, the transparency when mixed with cellulose acetate (component (A)) is high, the haze value can be reduced, and a molded article with excellent appearance can be produced. When a molded article obtained from a mixture of component (A) and PVA is highly transparent, it is possible to obtain a molded article with good color development and excellent appearance, even when a colorant is contained. On the other hand, when the saponification degree of the PVA is too high, mixing with cellulose acetate may result in cloudiness. In one embodiment, when the resin composition contains a partially saponified vinyl ester polymer (preferably polyvinyl acetate), the PVA has hydroxyl groups, which makes it easier for interactions such as hydrogen bonds to occur with cellulose acetate, thereby making them more compatible with each other.

[0040] The saponification degree and average polymerization degree of polyvinyl alcohol can be measured by a method in accordance with JIS K 6726. For example, the saponification degree and polymerization degree when polyvinyl acetate is partially saponified are expressed by the following formulas.

[0041]

[0042] The average polymerization degrees of polyvinyl acetate and polyvinyl alcohol are not particularly limited, but are preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more, and are preferably 3000 or less, more preferably 2000 or less, even more preferably 1500 or less, even more preferably 1000 or less, and even more preferably 500 or less. If the polymerization degree of the polymer of component (B) is too low, bleeding may occur easily, while if the polymerization degree is too high, the thermoplasticity (processability) of the resin composition may be reduced. The average polymerization degrees of polyvinyl acetate and polyvinyl alcohol can be measured, for example, by the methods specified in JIS K6725 and JIS K6726.

[0043] The viscosity of a 4% aqueous solution of polyvinyl alcohol at 20° C. is not particularly limited, but is, for example, preferably 300 mPa·s or less, more preferably 100 mPa·s or less, even more preferably 10 mPa·s or less, and even more preferably 5 mPa·s or less, and is preferably 1 mPa·s or more, more preferably 2 mPa·s or more. The viscosity of a 4% aqueous solution of polyvinyl alcohol at 20° C. can be measured, for example, by the method specified in JIS K6726.

[0044] In the resin composition of the present disclosure, the content of component (B) relative to the total of 100% by mass of components (A) and (B) is not particularly limited, but is preferably 5% by mass or more, more preferably 8% by mass or more, even more preferably 15% by mass or more, and may be 20% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and may be 30% by mass or less. When the content of component (B) is within this range, a resin composition having high transparency and excellent moldability can be obtained.

[0045] In the resin composition of this embodiment, the content of component (A) relative to the total of components (A) and (B) (100% by mass) is not particularly limited, but is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and may be 70% by mass or more, and is preferably 95% by mass or less, more preferably 92% by mass or less, and even more preferably 85% by mass or less, and may be 80% by mass or less. When the content of component (A) is within this range, a resin composition having high transparency and excellent moldability can be obtained.

[0046] The total content of component (A) and component (B) relative to 100% by mass of the total amount of the cellulose-based resin composition is not particularly limited, but is, for example, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and still more preferably 95% by mass or more. It may be 100% by mass, but is preferably less than 99.8% by mass, more preferably 99.5% by mass or less, even more preferably 99% by mass or less, and still more preferably 98% by mass or less.

[0047] (Plasticizer) In one aspect, the cellulose-based resin composition of the present disclosure may contain a plasticizer. In this embodiment, the plasticizer is preferably a compound that has high compatibility with cellulose acetate of component (A) and does not become cloudy when mixed with cellulose acetate.

[0048] The plasticizer is not particularly limited, but various additives used in ordinary thermoplastic resins can be used as long as they do not impair the effects of the present invention. The addition of a plasticizer can improve the processability and elongation at break of the resin composition. A low-molecular-weight plasticizer is preferred as the plasticizer. Examples of plasticizers include phthalate esters such as dibutyl phthalate, diaryl phthalate, diethyl phthalate, dimethyl phthalate, di-2-methoxyethyl phthalate, ethylphthalyl-ethyl glycolate, and methylphthalyl-ethyl glycolate; tartaric acid esters such as dibutyl tartrate; adipic acid esters such as dioctyl adipate and diisononyl adipate; phosphate esters such as triethyl phosphate, triphenyl phosphate, and tricresyl phosphate; dibasic fatty acid esters such as dibutyl adipate, dioctyl adipate, dibutyl azelate, dioctyl azelate, and dioctyl sebacate; epoxidized vegetable oils such as epoxidized soybean oil and epoxidized linseed oil; castor oil and its derivatives; and the like. Among these, plasticizers such as dioctyl adipate, benzyl-2-butoxyethoxyethyl adipate, tricresyl phosphate, diphenylcresyl phosphate, and diphenyloctyl phosphate are particularly preferred.

[0049] When the cellulose resin composition contains a plasticizer, its content is not particularly limited, but is preferably less than 15% by mass, more preferably 10% by mass or less, even more preferably 8% by mass or less, more preferably 5% by mass or less, even more preferably less than 5% by mass, relative to 100% by mass of the total of component (A), component (B), and plasticizer. It may also be 0% by mass, but is preferably 1% by mass or more, and more preferably 3% by mass or more. When the plasticizer content is within this range, a resin composition with high thermal stability and excellent fluidity and moldability can be provided. If the plasticizer content is too high, the plasticizer may bleed out, or the thermal stability of the resin composition may be reduced due to evaporation of the plasticizer.

[0050] The resin composition of the present disclosure may contain a colorant as described below, but in an embodiment that does not contain a colorant, it is preferable that the resin composition has high transparency. The resin composition may be colorless or colored, but is preferably colorless and transparent. High transparency results in good color development when a colorant or the like is added, and a molded product with a high-quality appearance, i.e., excellent design, can be formed.

[0051] In one aspect of this embodiment, the haze value of a 0.3 mm thick molded body formed from a resin composition containing no colorant is preferably 50% or less, more preferably 45% or less, even more preferably 40% or less, and even more preferably 30% or less.

[0052] (Colorant (C)) In one aspect of the present embodiment, the cellulose-based resin composition may contain a colorant such as a black colorant.

[0053] As the black colorant, for example, carbon black is preferred.

[0054] The average particle size of the carbon black is preferably 1 to 20 nm, more preferably 5 to 20 nm, and even more preferably 8 to 18 nm. The smaller the average particle size, the lower the brightness of the molded article, and the more likely it is that a high-quality black (jet black) appearance will be obtained. Conversely, the larger the average particle size, the higher the dispersibility. From these perspectives, it is preferable to use carbon black with a particle size within the above range.

[0055] This average particle size is the arithmetic mean particle size of carbon black particles determined by observing the particles under an electron microscope.

[0056] The specific surface area of ​​the carbon black is not limited, but is preferably 140 m from the viewpoint of jet blackness of the molded product. ２ / g or more is preferable, and 180m ２ / g or more is more preferable. ２ / g or less can be used, and ２ / g or less, and further, 500m ２ / g or less can be used. In terms of the relationship between particle size and specific surface area, the smaller the particle size, the larger the specific surface area. From the viewpoints of the brightness and appearance of the molded product and the dispersibility of the particles, it is preferable to use carbon black with a BET specific surface area within the above range. This specific surface area is the BET specific surface area (JIS K6217) calculated from the nitrogen adsorption amount using the S-BET equation.

[0057] Furthermore, although not limited thereto, the carbon black is preferably acidic, specifically preferably having a pH of 5 or less, more preferably a pH of 4 or less, and even more preferably a pH of 3.5 or less. By using such acidic (low pH) carbon black, the brightness of the molded article can be reduced. For example, carbon black having a pH of preferably 2.5 to 4, more preferably 2.5 to 3.5, can be suitably used.

[0058] This pH value was measured using a glass electrode pH meter on a mixture of carbon black and distilled water. The specific measurement method is as follows: 100 ml of boiled and degassed pure water is added to 10 g of sample, boiled on a hot plate for 15 minutes, cooled to room temperature, the supernatant liquid is removed, and the pH of the resulting muddy substance is measured using a glass electrode pH meter.

[0059] It is believed that the interaction or bonding between the acidic groups (e.g., carboxylic acid groups) on the surface of such acidic carbon black and the polar groups (e.g., hydroxyl groups) of cellulose acetate improves the affinity, resulting in high dispersion of the carbon black and contributing to a decrease in brightness.

[0060] As colorants other than the black colorant, organic or inorganic pigments or dyes can be used, specifically metal oxides such as red iron oxide, iron (III) oxide, and chromium (III) oxide.

[0061] The content of the colorant is not limited, but can be set, for example, in the range of 0.01 to 10 phr (meaning 0.01 to 10 parts by mass per 100 parts by mass of the total mass of the components other than the colorant in the cellulose-based resin composition; the same applies hereinafter to the standard for the colorant content) relative to the total mass of the components other than the colorant. From the viewpoint of obtaining a sufficient coloring effect, the content of the colorant is preferably 0.05 phr or more, more preferably 0.09 phr or more, and more preferably 0.1 phr or more, relative to the total mass of the components other than the colorant. From the viewpoint of suppressing the excess amount of colorant while obtaining a sufficient coloring effect, the content is preferably 5 phr or less, more preferably 3 phr or less, and even more preferably 2 phr or less.

[0062] From the viewpoint of appearance such as glossiness, the content of the colorant is not limited, but is preferably 1 phr or less, more preferably 0.3 phr or less, even more preferably 0.2 phr or less, and particularly preferably 0.1 phr or less.

[0063] The resin composition may contain, as other components, additives commonly used in ordinary molding resin materials, provided that the purpose of this embodiment is not impaired. Examples of such additives include phenolic or phosphorus-based antioxidants, light stabilizers, ultraviolet absorbers, antistatic agents, antibacterial and antifungal agents, fillers, and flame retardants.

[0064] If necessary, inorganic or organic granular or fibrous fillers can be added to the resin composition. Addition of the filler can further improve strength and rigidity. Examples of fillers include mineral particles (talc, mica, calcined silica, kaolin, sericite, bentonite, smectite, clay, silica, quartz powder, glass beads, glass powder, glass flakes, milled fiber, wollastonite (or wollastonite), etc.), boron-containing compounds (boron nitride, boron carbide, titanium boride, etc.), metal carbonates (magnesium carbonate, heavy calcium carbonate, light calcium carbonate, etc.), metal silicates (calcium silicate, aluminum silicate, magnesium silicate, magnesium aluminosilicate, etc.), metal oxides (magnesium oxide, etc.), metal sulfates (calcium sulfate, barium sulfate, etc.), metal carbides (silicon carbide, aluminum carbide, titanium carbide, etc.), metal nitrides (aluminum nitride, silicon nitride, titanium nitride, etc.), white carbon, and various metal foils. Examples of fibrous fillers include organic fibers (natural fibers, paper, etc.), inorganic fibers (glass fibers, asbestos fibers, carbon fibers, silica fibers, silica-alumina fibers, wollastonite, zirconia fibers, potassium titanate fibers, etc.), metal fibers, etc. These fillers can be used alone or in combination.

[0065] In one embodiment, the resin composition preferably contains a small amount of polylactic acid resin and aliphatic polyester (e.g., polybutylene succinate, polybutylene succinate adipate, polycaprolactone, polyhydroxybutyrate, polyhydroxybutyrate hexanate, etc.). If the content of these polylactic acid resins and aliphatic polyesters is high, the transparency when mixed with cellulose acetate decreases, making it difficult to obtain molded products with excellent appearance. In one embodiment, the content of these components is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass, relative to the total mass of the resin composition.

[0066] In one embodiment, the resin composition preferably contains a low content of polyvinyl alcohol with a high degree of saponification (preferably a degree of saponification of more than 40 mol%, more preferably a degree of saponification of 50 mol% or more). If the content of polyvinyl alcohol with a high degree of saponification is high, mixing with cellulose acetate may result in cloudiness. In one embodiment, the content of polyvinyl alcohol with a degree of saponification of, for example, more than 40 mol% or 50 mol% or more is preferably 5% by mass or less, more preferably less than 5% by mass, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0% by mass, relative to the total mass of the resin composition.

[0067] <Method for producing cellulose-based resin composition> In one embodiment of the present disclosure, the cellulose-based resin composition can be obtained by melt-mixing component (A) and component (B), and, if necessary, other components, in a conventional mixer (preferably, mixing to achieve uniformity). Examples of the mixer that can be used include compounding devices such as a tumbler mixer, ribbon blender, single-screw or multi-screw extruder, kneading kneader, and kneading roll. After melt-mixing, the mixture can be granulated into an appropriate shape as needed, and can be pelletized using, for example, a pelletizer.

[0068] <Molded Article> A molded article formed using the cellulose-based resin composition of the present disclosure can be formed into a desired shape by a conventional molding method, and the shape and thickness of the molded article are not limited. From the viewpoint of the strength of the molded article, for example, 0.5 mm or more is preferable, and 0.8 mm or more is more preferable. However, when producing a film, sheet, or the like by extrusion molding, hot press molding, or the like, the thickness is preferably 0.01 mm or more, more preferably 0.1 mm or more, and may be 0.3 mm or more. On the other hand, the upper limit of the thickness of the molded article is not particularly limited and can be appropriately set depending on the required shape, strength, etc., but even if the thickness is set to, for example, 10 mm or less, or even 5 mm or less, sufficient physical properties and a high-quality appearance can be obtained. In the molded article of this embodiment, the additive is distributed throughout the entire molded article (in any direction including the thickness direction), so that a high-quality appearance can be obtained in any shape without the need for painting, decorative films, or the like.

[0069] The cellulose-based resin composition according to the present disclosure can be molded into a molded article according to the intended use by a common molding method such as injection molding, injection compression molding, extrusion molding, or heat press molding.

[0070] Molded articles formed using the cellulose-based resin composition according to the present disclosure have excellent design properties and can be applied to housings, exteriors, decorative panels, decorative films, etc., and can be used in place of components used in, for example, electronic devices, home appliances, various containers, building materials, furniture, stationery, automobiles, and household goods. For example, they can be used in housings and exterior parts of electronic devices and home appliances, various storage cases, tableware, interior building materials, automobile interior materials, and other everyday items.

[0071] One aspect of this embodiment relates to products such as electronic devices, home appliances, automobiles, building materials, furniture, stationery, and household goods, which include a molded article formed using the resin composition of this embodiment.

[0072] Applications for electronic devices and home appliances include housings for personal computers, landline phones, mobile phone terminals, smartphones, tablets, POS terminals, routers, projectors, speakers, lighting equipment, calculators, remote controls, refrigerators, washing machines, humidifiers, dehumidifiers, video recorders / players, vacuum cleaners, air conditioners, rice cookers, electric shavers, electric toothbrushes, dishwashers, broadcasting equipment, clock faces and exteriors, and cases for mobile devices such as smartphones.

[0073] Automotive applications include interior instrument panels, dashboards, cup holders, door trim, armrests, door handles, door locks, steering wheels, brake levers, ventilators, and shift levers.

[0074] Examples of building materials include interior wall materials, floor materials, tiles, window frames, doorknobs, etc.

[0075] Furniture applications include the exteriors of dressers, bookshelves, tables, chairs, etc.

[0076] Stationery applications include the exteriors of pens, pencil cases, book covers, scissors, cutters, etc.

[0077] Examples of uses for everyday items include eyeglass frames, cosmetic containers, cosmetic boxes for products, the main body and exterior of accessories, decorative parts for clothing such as buttons, the exterior of earphones, the main body and exterior of cards, and business card trays.

[0078] Other examples of sports-related goods include golf tees and golf markers.

[0079] The present invention will be described in more detail below with reference to specific examples, but the present invention is not limited to these.

[0080] The components used in producing the resin compositions of the Examples and Comparative Examples are shown below.

[0081] <Cellulose acetate> (a1): Cellulose acetate (CA) (manufactured by Daicel Corporation, product name: L-50, acetyl group introduction ratio (substitution degree) DS = 2.4, acetylation degree 55%, polymerization degree based on 6% viscosity 180)

[0082] <Resin Additives> (b1) to (b7), (b1′) to (b3′): Polyvinyl alcohol (PVA) (trade name: JMR series, manufactured by Japan Vinyl Acetate & Poval Co., Ltd.; the product number, degree of saponification, and degree of polymerization of the PVA used in each example and comparative example are shown in Table 1.) (b4′): Polylactic acid (trade name: Ingeo Biopolymer 3001D, manufactured by NatureWorks) (b5′): Polybutylene succinate (trade name: BioPBS FZ71PM, manufactured by PTT MCC Biochem)

[0083] <Plasticizer> (d1): Adipic acid ester mixture, manufactured by Daihachi Chemical Industry Co., Ltd., trade name: Daifatty 101

[0084] Example A: Examples A1 to A7, Comparative Examples A1 to A5 The above-mentioned cellulose acetate (a1) and resin additives (b1) to (b7) and (b1') to (b5') were prepared as constituent materials for the target cellulose-based resin composition. The constituent materials were then thoroughly mixed by hand mixing at the blending ratios shown in Table 1 to obtain a mixture. The "blending ratio of resin additives" in Table 1 represents the blending ratio of the resin additives relative to the total of 100% by mass of cellulose acetate (a1) and resin additives. The cellulose acetate, polylactic acid, and polybutylene succinate were previously dried at 80°C for 5 hours before hand mixing. A resin composition (pellets) was prepared using the resulting mixture according to the kneading method described below. Furthermore, the pellets were used to produce a molded product (film) according to the molding method described below. The resulting film was evaluated for haze. The results are shown in Table 1.

[0085] (Kneading method) The mixture obtained by hand mixing was kneaded using a kneader (manufactured by Thermo Scientific, product name: HAAKE MiniLab Rheomex CTW5) at a set temperature of 240°C and a rotation speed of 60 rpm to obtain pellets of the resin composition.

[0086] (Molding method (press molding)) The obtained pellets were dried at 80°C for 5 hours immediately before molding, and then press-molded using a hot press molding machine (manufactured by Tester Sangyo Co., Ltd., product name: SA-303-II-S benchtop test press) at 240°C for 1 minute and 100 kgf / cm２ and then immediately apply a pressure of 100 kgf / cm for 1 minute at room temperature. ２ The mixture was cooled while being pressed with a pressure of 0.3 mm to prepare a circular film having a thickness of 0.3 mm and a diameter of 60 mm.

[0087] <Haze Measurement> The film obtained by press molding was measured for haze (cloudiness), which is an index of transparency, using a haze meter (manufactured by Murakami Color Research Laboratory, trade name: Haze Meter HM-65W type, conforming to JIS K 7136). The haze value is expressed in %. The smaller the haze value, the higher the transparency, and the better the appearance when a colorant is used.

[0088]

[0089] As shown in Table 1, the haze of the molded articles obtained in Examples A1 to A7 was lower than that of Comparative Examples A1 to A5, and the molded articles were excellent in transparency.

[0090] Example B: Examples B1 to B8, Comparative Examples B1 to B10 Pellets and films were obtained in the same manner as in Example A, except that the type and blending ratio of the resin additives were changed as shown in Table 2. The haze of the obtained films was evaluated using the same evaluation method as in Example A. The results are shown in Table 2.

[0091]

[0092] Example C: Example C1, Comparative Example C1 The above-mentioned cellulose acetate (a1), polyvinyl alcohol (b7), and plasticizer (d1) were prepared as constituent materials for the target cellulose-based resin composition. The constituent materials were then thoroughly mixed by hand mixing at the blending ratios shown in Table 3 to obtain a mixture. In Table 3, the blending ratios of polyvinyl alcohol and plasticizer represent blending ratios relative to the total of 100% by mass of cellulose acetate (a1), polyvinyl alcohol (b7), and plasticizer (d1). The cellulose acetate was previously dried at 80°C for 5 hours before hand mixing. Using the resulting mixture, a resin composition (pellets) was prepared according to the same kneading method as in Example A. The melt flow rate (MFR) and thermal stability of the resulting pellets were evaluated. The results are shown in Table 3.

[0093] <Evaluation of Melt Flow Rate (MFR)> The melt flow rate (MFR), which is an index of fluidity, of the pellets obtained by kneading was evaluated as follows: The pellets were dried at 80°C for 5 hours, and then placed in a measuring device (Shimadzu Flow Tester CFT-500D, manufactured by Shimadzu Corporation), and the MFR was measured under conditions of 230°C, 5 kgf, and preheating for 2 minutes.

[0094] <Evaluation of Thermal Stability> The thermal stability of the pellets obtained by kneading was evaluated from the weight loss rate upon heating. 10 mg of pellets were placed in a thermogravimetric analyzer (manufactured by Seiko Instruments, product name: TG / DTA 6200), held at 80°C for 5 hours to dry, then heated to 220°C and held there for 1 hour. The weights before and after holding at 220°C for 1 hour were measured, and the weight loss rate was calculated according to the following formula: Weight loss rate (%) = 100 × (weight at start of holding - weight at end of holding) / weight at start of holding

[0095] The apparatus was filled with a nitrogen gas atmosphere and the temperature was increased at 10°C / min. When the weight loss rate was less than 2%, the thermal stability was evaluated as ◯, when it was 2% or more but less than 5%, the thermal stability was evaluated as △, and when it was 5% or more, the thermal stability was evaluated as ×.

[0096]

[0097] As shown in Table 3, Example C1 contained PVA, which reduced the plasticizer content compared to Comparative Example C1, improving thermal stability (i.e., suppressing the evaporation of the plasticizer) and achieving sufficient MFR (flowability, moldability).

[0098] Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0099] Some or all of the above embodiments can be described as in the following supplementary notes, but the disclosure of the present application is not limited to the following supplementary notes.

[0100] (Appendix 1) A cellulose-based resin composition comprising: (A) cellulose acetate having a degree of acetyl substitution of 2.0 or more; and (B) at least one polymer selected from the group consisting of polyvinyl acetate and polyvinyl alcohol having a degree of saponification of 40 mol % or less.

[0101] (Appendix 2) The cellulose-based resin composition according to Appendix 1, wherein the polymer (B) has an average degree of polymerization of 100 to 3,000.

[0102] (Appendix 3) The cellulose-based resin composition according to Appendix 1 or 2, wherein the polymer (B) is polyvinyl alcohol obtained by partially saponifying polyvinyl acetate and having a saponification degree of 40 mol% or less, preferably 38 mol% or less.

[0103] (Appendix 4) The cellulose-based resin composition according to any one of Appendices 1 to 3, wherein the content of the polymer (B) relative to the total mass of the cellulose acetate (A) and the polymer (B) is 5% by mass or more and 60% by mass or less.

[0104] (Appendix 5) The cellulose-based resin composition according to any one of the preceding appendices, wherein the polymer (B) has an average degree of polymerization of 100 to 1,500.

[0105] (Appendix 6) The cellulose-based resin composition according to any one of the preceding appendices, wherein the content of the polymer (B) relative to the total mass of the cellulose acetate (A) and the polymer (B) is 10% by mass or more and 50% by mass or less.

[0106] (Appendix 7) The cellulose-based resin composition according to any one of the preceding appendices, wherein the acetyl substitution degree of the cellulose acetate (A) is 2.0 or more and 2.9 or less, and the polymer (B) is a polyvinyl alcohol obtained by partially saponifying polyvinyl acetate and having a saponification degree of 1 mol % or more and 38 mol % or less.

[0107] (Appendix 8) The cellulose-based resin composition according to Appendix 7, wherein the polymer (B) has an average degree of polymerization of 100 to 1,500.

[0108] (Appendix 9) The cellulose-based resin composition according to appendix 7 or 8, wherein the content of the polymer (B) relative to the total mass of the cellulose acetate (A) and the polymer (B) is 10% by mass or more and 50% by mass or less.

[0109] (Appendix 10) The cellulose-based resin composition according to any one of the preceding appendices, further comprising a plasticizer, wherein the content of the plasticizer is less than 15% by mass relative to 100% by mass of the total of the cellulose acetate (A), the polymer (B), and the plasticizer.

[0110] (Appendix 11) The cellulose-based resin composition according to Appendix 10, wherein the content of the plasticizer is 8% by mass or less relative to 100% by mass of the total of the cellulose acetate (A), the polymer (B), and the plasticizer.

[0111] (Appendix 12) The cellulose-based resin composition according to appendix 10 or 11, wherein the plasticizer comprises an adipic acid ester.

[0112] (Appendix 13) The cellulose-based resin composition according to any one of the preceding appendices, wherein the content of polyvinyl alcohol having a saponification degree of 50 mol% or more is less than 5 mass%.

[0113] (Appendix 14) The cellulose-based resin composition according to any one of the preceding appendices, further comprising a colorant (C).

[0114] (Appendix 15) The cellulose-based resin composition according to Appendix 14, wherein the colorant (C) contains carbon black.

[0115] (Appendix 16) The cellulose-based resin composition according to any one of the preceding appendices, wherein a molded article having a thickness of 0.3 mm formed from the cellulose-based resin composition containing no colorant has a haze value of 50% or less.

[0116] (Appendix 17) A molded article formed using the cellulose resin composition according to any one of the preceding appendices.

[0117] (Appendix 18) A molded article formed using the cellulose resin composition according to Appendix 9.

[0118] (Supplementary Note 19) An electronic device or a home appliance, comprising the molded article according to Supplementary Note 17 or 18.

[0119] (Supplementary Note 20) An automobile comprising the molded article according to Supplementary Note 17 or 18.

[0120] This application claims priority based on Japanese Patent Application No. 2022-182383, filed November 15, 2022, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. Cellulose acetate (A) with an acetyl substitution degree of 2.0 or more, and at least one polymer (B) selected from the group consisting of polyvinyl acetate and polyvinyl alcohol with a saponification degree of 40 mol% or less. A cellulose-based resin composition containing the same.

2. The cellulose-based resin composition according to Claim 1, wherein the average polymerization degree of the polymer (B) is 100 to 3000.

3. The cellulose-based resin composition according to Claim 1 or 2, wherein the polymer (B) is polyvinyl alcohol in which polyvinyl acetate is partially saponified and has a saponification degree of 38 mol% or less.

4. The cellulose-based resin composition according to Claim 1 or 2, wherein the content of the polymer (B) relative to the total mass of cellulose acetate (A) and the polymer (B) is 5% by mass or more and 60% by mass or less.

5. The cellulose-based resin composition according to Claim 1 or 2, further containing a plasticizer, and the content of the plasticizer relative to 100% by mass of the total of cellulose acetate (A), the polymer (B), and the plasticizer is less than 15% by mass.

6. The cellulose-based resin composition according to Claim 5, wherein the plasticizer contains an adipic acid ester.

7. The cellulose-based resin composition according to Claim 1 or 2, further containing a colorant (C).

8. The cellulose-based resin composition according to Claim 7, wherein the colorant (C) contains carbon black.

9. The cellulose-based resin composition according to Claim 1 or 2, wherein the haze value of a molded article with a thickness of 0.3 mm formed from a cellulose-based resin composition not containing a colorant is 50% or less.

10. A molded article formed using the cellulose-based resin composition according to Claim 1 or 2.