Cellulose acetate resin compositions, melt-molded articles, injection-molded articles, and sheets or films

Abstract

The cellulose acetate resin composition of this invention comprises: cellulose acetate (A) with a total degree of acetyl substitution of 2.60 or less, filler (B), and plasticizer (C). Filler (B) is selected from the group consisting of (b1) specific inorganic compounds, (b2) specific metal salts, (b3) cellulose or hemicellulose, and (b4) wood flour. Plasticizer (C) is selected from (c1) glycerol ester plasticizers, (c2) ether plasticizers, and (c3) glycol ester plasticizers. The content of component (A) is 45-90% by mass. The total content of component (B) is 5-50% by mass. The total content of component (C) is 5-35% by mass.

Description

Technical Field

[0001] This invention relates to a cellulose acetate resin composition. More specifically, this invention relates to a cellulose acetate resin composition for melt molding. Prior Technology

[0002] Cellulose acetate is known to be biodegradable and can be broken down by activated sludge. Due to increasing global environmental concerns, the demand for biodegradable manufactured products, especially membranes and sheets, is growing.

[0003] Cellulose acetate exhibits poor thermal fusibility due to hydrogen bonds formed by residual hydroxyl groups in its molecular chain. The lower the total degree of acetyl substitution (DS) of cellulose acetate, the higher its melting temperature tends to be. Conversely, the higher the total degree of acetyl substitution of cellulose acetate, the higher its crystallinity, thus tending to decrease its solubility and fusibility. Various methods for forming sheets or films from cellulose acetate using melt deposition have been studied.

[0004] Patent Document 1 discloses a biodegradable sheet composed of an acetate composition containing cellulose acetate and polyethylene glycol. Patent Document 2 discloses a biodegradable film or sheet with cellulose acetate having an acetyl substitution degree of 2.3 to 2.7 and a biodegradable plasticizer as the main components. The plasticizer is selected from the group consisting of (1) compounds represented by H5C3(OH)3-n(OOCCH3)n(0≦n≦3) and (2) glycerol alkylates, ethylene glycol alkylates, polyethylene glycol alkylates with ethylene repeating units of 5 or less, aliphatic monocarboxylic acid alkyl esters, aliphatic dicarboxylic acid alkyl esters, and aliphatic tricarboxylic acid alkyl esters.

[0005] Patent Document 3 discloses a cellulose acetate-based resin composition, which is formed by melting and mixing cellulose acetate with a weight average molecular weight of 100,000 to 250,000 and an average degree of substitution of 1.0 to 2.5 with a plasticizer with an average molecular weight of 300 or more, and includes a region with a glass transition temperature of 200°C or higher. Patent Document 4 discloses a water-soluble cellulose acetate-based resin composition containing cellulose acetate with a total degree of acetyl substitution of 0.5 to 1.0 and water-soluble organic additives.

[0006] Patent document 5 discloses a technology in which an alkaline additive with a pH of 13 or lower and 7 or higher is added to a 1% aqueous solution (20°C) of polymers such as cellulose esters to improve their biodegradability. [Previous Technical Documents] [Patent Literature]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 8-53575 [Patent Document 2] Japanese Patent Application Publication No. 2002-60545 [Patent Document 3] Japanese Patent Application Publication No. 11-255959 [Patent Document 4] Japanese Patent Application Publication No. 2015-140432 [Patent Document 5] Japanese Patent Publication No. 2018-500416 Summary of the Invention

[0008] [The problem that the invention aims to solve] The compositions disclosed in Patent Documents 1-3 are all melt-spun at temperatures exceeding 200°C to obtain sheets with a thickness exceeding 100 μm. If the melting temperature exceeds 200°C, there is a problem of coloring due to the thermal decomposition of cellulose acetate. The resin composition in Patent Document 4 is melt-spun at a temperature below 200°C, but this resin composition uses cellulose acetate with a low degree of substitution.

[0009] According to the inventors, resin compositions containing cellulose acetate with a relatively high degree of substitution have insufficient melt flow at temperatures below 200°C, and the melt's extensibility or flexibility is also insufficient. Therefore, it is particularly difficult to produce films with a thickness of less than 100 μm.

[0010] Patent Document 5's polymer composition is mainly used for film formation by casting method, and does not mention melt film formation. Previously, various problems were pointed out with resin compositions containing inorganic substances such as alkaline substances: due to the high melting temperature, cellulose acetate undergoes thermal decomposition or color deterioration; side reactions occur with inorganic additives; the melt tension decreases, resulting in poor film formation; and so on.

[0011] Furthermore, as mentioned above, it is known that cellulose acetate decomposes in activated sludge, but there is also the following problem: in water systems with fewer bacteria than activated sludge, such as seawater, a satisfactory decomposition rate cannot be obtained.

[0012] The purpose of this invention is to provide a cellulose acetate resin composition that can be melt-molded to obtain a molded article with excellent marine biodegradability. [Technical means to solve the problem]

[0013] The cellulose acetate resin composition of the present invention comprises: cellulose acetate (A) with a total degree of acetyl substitution of 2.60 or less, filler (B), and plasticizer (C). The filler (B) is selected from one or more of the group consisting of (b1) to (b4) below. (b1) Inorganic compounds containing oxygen atoms bonded to any of the metals Na, K, Ca, or Mg; (b2) A metal salt comprising one or more metal ions selected from Na+, K+, Ca2+ or Mg2+ and one or more anions selected from carbonate ion, bicarbonate ion, silicate ion or aluminate ion; (b3) Cellulose or hemicellulose; and (b4) Wood flour.

[0014] Plasticizer (C) is selected from one or more of the group consisting of (c1) to (c3) below. (c1) Glyceryl esters in which at least one hydroxyl group of glycerol has been esterified are plasticizers; (c2) An ether-based plasticizer having at least one terminal hydroxyl group of a polyalkylene glycol etherified; and (c3) A diol ester plasticizer of polyalkylene glycol with at least one terminal hydroxyl group esterified.

[0015] Relative to the resin composition as a whole, the content of cellulose acetate (A) is 45% by mass or more and 90% by mass or less, the total content of filler (B) is 5% by mass or more and 50% by mass or less, and the total content of plasticizer (C) is 5% by mass or more and 35% by mass or less.

[0016] Preferably, the total content of cellulose acetate (A), filler (B) and plasticizer (C) in the resin composition is 85% by mass or more.

[0017] The preferred glyceryl ester is a plasticizer (c1) that is an acetylated glyceryl acetate with an acetyl substitution degree of 0 or more and 3 or less.

[0018] The preferred ether-based plasticizer (c2) is a polyalkylene glycol with a molecular weight of less than 150 etherified by hydrocarbon groups and an average degree of substitution of 0 or more and 2 or less for the terminal hydroxyl groups. The polyalkylene glycol has repeating alkoxy groups with 2 or more and 4 or less carbon atoms, and its degree of polymerization is 23 or less.

[0019] The preferred glycol ester plasticizer (C3) is a polyalkylene glycol esterified with a carboxylic acid of molecular weight less than 150 and with an average degree of substitution of 0 or more and 2 or less for the terminal hydroxyl groups. The polyalkylene glycol has repeating alkoxy groups with 2 or more and 4 or less carbon atoms, and its degree of polymerization is less than 23.

[0020] Preferably, the sulfuric acid content of cellulose acetate (A) is below 350 ppm.

[0021] Preferably, the total degree of acetylation of cellulose acetate (A) is 2.0 or more and 2.60 or less.

[0022] In other views, the present invention refers to a melt-molded article obtained using any of the above-described cellulose acetate resin compositions. Preferably, it is an injection-molded article obtained using any of the above-described resin compositions. More preferably, it is a film or sheet obtained using any of the above-described resin compositions. [Effects of the Invention]

[0023] The cellulose acetate resin composition of this invention exhibits excellent marine biodegradability by including a specific amount of filler (B). Furthermore, by further including a specific amount of plasticizer (C), this resin composition can be melt-formed at relatively low temperatures regardless of the presence of filler (B). Moreover, this resin composition has high melt tension, and therefore can also be used in injection-molded articles, especially films. Implementation

[0024] The present invention will now be described in detail based on preferred embodiments. The scope of the present invention is not limited to these descriptions; appropriate modifications may be made without prejudice to the spirit of the invention, except as illustrated below. Furthermore, the present invention is not limited to the following embodiments, and various modifications may be made within the scope indicated in the claims. The technical scope of the present invention also includes other embodiments obtained by appropriately combining the technical means disclosed in various embodiments.

[0025] Furthermore, in this specification, the range "X~Y" refers to "above X and below Y". Also, unless otherwise specified, "ppm" refers to "weight ppm" or "mass ppm". Furthermore, "weight" and "mass", "parts by weight" and "parts by mass", and "weight%" and "mass%" are considered synonyms.

[0026] [Cellulose acetate resin composition] The cellulose acetate resin composition of the present invention comprises: cellulose acetate (A), filler (B), and plasticizer (C). The total degree of acetylation of cellulose acetate (A) is 2.60 or less. The filler (B) is selected from one or more of the group consisting of (b1) to (b4) below: (b1) Inorganic compounds containing oxygen atoms bonded to any of the metals Na, K, Ca, or Mg; (b2) A metal salt comprising one or more metal ions selected from Na+, K+, Ca2+ or Mg2+ and one or more anions selected from carbonate ion, bicarbonate ion, silicate ion or aluminate ion; (b3) Cellulose or hemicellulose; and (b4) Wood flour. Plasticizer (C) is selected from one or more of the group consisting of (c1) to (c3) below: (c1) Glyceryl esters in which at least one hydroxyl group of glycerol has been esterified are plasticizers; (c2) An ether-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified; and (c3) A diol ester plasticizer of polyalkylene glycol with at least one terminal hydroxyl group esterified. In the resin composition, the content of cellulose acetate (A) is 45% by mass or more and 90% by mass or less, the total content of filler (B) is 5% by mass or more and 50% by mass or less, and the total content of plasticizer (C) is 5% by mass or more and 35% by mass or less.

[0027] The resin composition contains 5% by mass and 50% by mass of filler (B) selected from (b1) to (b4) above. This resin composition exhibits excellent biodegradability, particularly in seawater. The resin composition also contains 5% by mass and 35% by mass of plasticizer selected from (c1) to (c3) above, along with filler (B). This plasticizer (C) has high compatibility with cellulose acetate (A) with a total acetyl substitution degree of 2.60 or less. By incorporating this plasticizer (C), the resin composition, even with filler (B), can be melt-molded at a temperature lower than the thermal decomposition temperature of cellulose acetate, specifically below 200°C, and coloring caused by thermal decomposition can be avoided.

[0028] Furthermore, it is believed that the plasticizer (C) obtained by etherifying or esterifying the terminal hydroxyl groups during the melting of this resin composition enhances the entanglement between the molecular chains of cellulose acetate (A). Therefore, this resin composition exhibits lower melt viscosity and higher melt tension in the temperature range below 200°C. Due to its lower melt viscosity and higher melt tension, this resin composition can not only be melt-formed but also extended into thin films. Furthermore, the blow-forming method, previously difficult to apply to cellulose acetate, can also be used for film formation.

[0029] From the viewpoint of obtaining excellent biodegradability, the total content of cellulose acetate (A), filler (B), and plasticizer (C) in the resin composition is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. There is no particular upper limit to this total content, and it can be 100% by mass.

[0030] [Packaging (B)] In the resin composition of the present invention, one or more fillers (B) selected from the group consisting of (b1) to (b4) below are incorporated. (b1) Inorganic compounds containing oxygen atoms bonded to any of the metals Na, K, Ca, or Mg; (b2) A metal salt comprising one or more metal ions selected from Na+, K+, Ca2+ or Mg2+ and one or more anions selected from carbonate ion, bicarbonate ion, silicate ion or aluminate ion; (b3) Cellulose or hemicellulose; and (b4) Wood flour. [ ]

[0031] In particular, resin compositions containing fillers (B) selected from inorganic compounds (b1) and metal salts (b2) exhibit significantly increased seawater biodegradability. This is believed to be because inorganic compounds (b1) and metal salts (b2) are alkaline in seawater, thereby promoting the hydrolysis of cellulose acetate. From this perspective, resin compositions containing at least one of (b1) and (b2) as filler (B) are preferred.

[0032] The total content of filler (B) in the resin composition of the present invention is 5% by mass or more and 50% by mass or less relative to the total resin composition. From the viewpoint of improving seawater biodegradability, the total content of filler (B) is preferably 10% by mass or more, and more preferably 15% by mass or more. From the viewpoint of excellent melt-forming properties, the total content of filler (B) is preferably 45% by mass or less, and more preferably 40% by mass or less. The total content of filler (B) in the resin composition of the present invention may also be 5-45% by mass, 5-40% by mass, 10-50% by mass, 10-45% by mass, 10-40% by mass, 15-50% by mass, 15-45% by mass, or 15-40% by mass. When multiple fillers (B) are used together, their total content is adjusted to the above-mentioned range.

[0033] Examples of inorganic compounds (b1) containing oxygen atoms bonded to any of the metal elements Na, K, Ca, or Mg include oxides, hydroxides, and complex oxides of any of the metal elements Na, K, Ca, or Mg. From the viewpoint of improving biodegradability and ease of handling, preferred inorganic compounds (b1) include magnesium oxide, magnesium hydroxide, talc, hydrotalcite, bentonite, calcium oxide, and calcium hydroxide.

[0034] Specific examples of metal salts (b2) containing one or more metal ions selected from Na+, K+, Ca2+, or Mg2+ and one or more anions selected from carbonate ions, bicarbonate ions, silicate ions, or aluminate ions include sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, magnesium bicarbonate, calcium silicate, magnesium silicate, magnesium aluminate, and magnesium aluminum silicate. From the viewpoint of obtaining higher biodegradability and good formability, preferred metal salts (b2) are calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, magnesium aluminate, and magnesium aluminum silicate.

[0035] There are no particular limitations on the cellulose and hemicellulose (b3), and previously known materials may be used as appropriate. From the viewpoint of excellent melt-mixing properties, fine cellulose and hemicellulose are preferred. It may be in powder or fibrous form. In the case of powder, it is preferred that the average particle size (median particle size) measured by a Microtrac particle size analyzer is 10 μm or more and 200 μm or less.

[0036] As wood flour (b4), it can be made from previously known wood powder. From the viewpoint of excellent melt-mixing properties, the average particle size (median particle size) of the wood flour is preferably 10 μm or more and 200 μm or less. The average particle size (median particle size) of the wood flour was determined using a Microtrac particle size analyzer.

[0037] [Plasticizer (C)] In the resin composition of the present invention, one or more plasticizers (C) selected from the group consisting of (c1) to (c3) below are incorporated. (c1) Glyceryl esters in which at least one hydroxyl group of glycerol has been esterified are plasticizers; (c2) An ether-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified; and (c3) A diol ester plasticizer of polyalkylene glycol with at least one terminal hydroxyl group esterified.

[0038] From the viewpoint of achieving a melting temperature lower than that of cellulose acetate, it is preferable to include a resin composition containing at least one of the plasticizers (C) selected from ether-based plasticizers (C2) and glycol ester-based plasticizers (C3).

[0039] The total content of plasticizer (C) in the resin composition of the present invention is 5% by mass or more and 35% by mass or less relative to the total resin composition. From the viewpoint of achieving high melt flowability, the total content of plasticizer (C) is preferably 7% by mass or more, and more preferably 9% by mass or more. From the viewpoint of obtaining a low melt viscosity without reaching 200°C, the total content of plasticizer (C) is preferably 33% by mass or less. The total content of plasticizer (C) in the resin composition of the present invention can be 5-33% by mass, 7-35% by mass, 7-33% by mass, 9-35% by mass, or 9-33% by mass. When multiple plasticizers (C) are used together, their total content is adjusted to the above-mentioned numerical range.

[0040] Glyceryl ester plasticizer (C1) is a compound obtained by esterification of at least one hydroxyl group of glycerol, and is obtained by esterification using a carboxylic acid with a molecular weight of less than 150, more preferably less than 130.

[0041] As a carboxylic acid, it can be an aliphatic carboxylic acid (fatty acid) or an aromatic carboxylic acid. From the viewpoint of reducing environmental impact, fatty acids are preferred. It can be a saturated fatty acid or an unsaturated fatty acid. It is more preferably an ester-based plasticizer obtained by esterification of saturated fatty acids. Specific examples of saturated fatty acids include formic acid, acetic acid, propionic acid, and butyric acid. A particularly preferred glyceryl ester plasticizer (C1) is glyceryl acetate with an acetyl substitution degree of 0 or more and less than 3.

[0042] The ether-based plasticizer (c2) is a compound obtained by etherifying at least one terminal hydroxyl group of a polyalkylene glycol, and is obtained by etherifying a hydrocarbon group with a molecular weight of less than 150, more preferably less than 130, and even more preferably less than 100. The average degree of substitution of the terminal hydroxyl group of the etherified polyalkylene glycol can be more than 0 and less than 2.

[0043] As a hydrocarbon group, it can be straight-chain, branched, or cyclic. It is preferably an aliphatic hydrocarbon group, and more preferably a saturated aliphatic hydrocarbon group (alkyl). Specific examples of alkyl groups with a molecular weight of 150 or less include methyl, ethyl, and propyl.

[0044] In the ether-based plasticizer (c2), the polyalkylene glycol has an alkoxy group as a repeating unit. From the viewpoint of suppressing decomposition during melting, the number of carbon atoms in the alkoxy group as the repeating unit is preferably 2 or more; from the viewpoint of improving compatibility with cellulose acetate (A), the number of carbon atoms is preferably 4 or less. Examples of such alkoxy groups include ethoxy, propoxy, and butoxy groups.

[0045] From the viewpoint of obtaining higher melt tension, the number of repeating units in the polyalkylene glycol (hereinafter referred to as degree of polymerization) is preferably 2 or more, and more preferably 3 or more. From the viewpoint of excellent compatibility with cellulose acetate (A), the degree of polymerization is preferably 23 or less, and more preferably 15 or less.

[0046] From the viewpoint of excellent compatibility with cellulose acetate (A), the number-average degree of polymerization of the ether plasticizer (c2) is preferably 23 or less, and more preferably 15 or less. From the viewpoint of obtaining higher melt tension, the number-average degree of polymerization of the ether plasticizer (c2) is preferably 3 or more. The number-average degree of polymerization of the ether plasticizer (c2) is calculated based on the number-average molecular weight measured by particle size chromatography (GPC) using polystyrene as a standard.

[0047] Specific examples of the ether-based plasticizer (c2) used in the resin composition of the present invention include: diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol dibutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether, polypropylene glycol monomethyl ether, etc.

[0048] The glycol ester plasticizer (C3) is a compound obtained by esterification of at least one terminal hydroxyl group of a polyalkylene glycol, and is obtained by esterification with a carboxylic acid having a molecular weight of less than 150, more preferably less than 130, and even more preferably less than 100. The average degree of substitution of the terminal hydroxyl group of the esterified polyalkylene glycol can be more than 0 and less than 2.

[0049] As a carboxylic acid, it can be an aliphatic carboxylic acid (fatty acid) or an aromatic carboxylic acid. From the perspective of reducing environmental impact, fatty acids are preferred. It can be a saturated fatty acid or an unsaturated fatty acid. A diol ester plasticizer (C3) obtained by esterification of saturated fatty acids is preferred. Specific examples of saturated fatty acids include formic acid, acetic acid, propionic acid, and butyric acid.

[0050] In glycol ester plasticizers (c3), polyalkylene glycols have an alkoxy group as a repeating unit. From the viewpoint of suppressing decomposition during melting, the number of carbon atoms in the alkoxy group as the repeating unit is preferably 2 or more, and from the viewpoint of excellent compatibility with cellulose acetate (A), the number of carbon atoms is preferably 4 or less. Examples of such alkoxy groups include ethoxy, propoxy, and butoxy.

[0051] From the viewpoint of obtaining higher melt tension, the number of repeating units (degree of polymerization) in the polyalkylene glycol is preferably 2 or more, and more preferably 3 or more. From the viewpoint of excellent compatibility with cellulose acetate (A), the degree of polymerization is preferably 23 or less, and more preferably 15 or less.

[0052] From the viewpoint of suppressing volatilization during melting and increasing melt tension, the number average molecular weight of the glycol ester plasticizer (C3) is preferably 200 or higher. From the viewpoint of excellent compatibility with cellulose acetate (A), the number average molecular weight of the glycol ester plasticizer (C3) is preferably 1000 or lower. The number average molecular weight of the glycol ester plasticizer (C3) was determined by particle size chromatography (GPC) using polystyrene as a standard.

[0053] Specific examples of glycol ester plasticizers (c3) used in the resin composition of the present invention include triethylene glycol monoacetate, triethylene glycol diacetate, triethylene glycol dipropionate, triethylene glycol dibenzoate, tetraethylene glycol diacetate, etc.

[0054] [Cellulose acetate (A)] In the resin composition of the present invention, cellulose acetate (A) with a total degree of acetyl substitution (DS) of 2.60 or less is used. From the viewpoint of improving biodegradability, the total degree of acetyl substitution of cellulose acetate (A) is preferably 2.56 or less, more preferably 2.50 or less. From the viewpoint of higher water resistance, the total degree of acetyl substitution of cellulose acetate (A) is preferably 2.0 or more, more preferably 2.1 or more. Cellulose acetate (A) with a total degree of acetyl substitution of 2.0 or more and 2.60 or less is preferred. The total degree of acetyl substitution of cellulose acetate (A) can be 2.0~2.56, 2.0~2.50, 2.1~2.60, 2.1~2.56, or 2.1~2.50.

[0055] The total degree of acetylation (DS) of cellulose acetate (A) is calculated by converting the degree of acetylation AV obtained according to the determination of acetylation in ASTM:D-871-96 (Test Methods for Cellulose Acetate, etc.) using the following formula. This method is the most commonly used method for determining the degree of substitution of cellulose acetate. DS=162.14×AV×0.01 / (60.052-42.037×AV×0.01) DS: Total degree of acetyl substitution AV: Acetylation (%)

[0056] The method for determining acetylation degree (AV) is described below.

[0057] First, accurately weigh 500 mg of dried cellulose acetate (sample), dissolve it in 50 ml of a mixed solvent of ultrapure water and acetone (volume ratio 4:1), then add 50 ml of 0.2 N-sodium hydroxide aqueous solution and saponify at 25°C for 2 hours. Next, add 50 ml of 0.2 N-hydrochloric acid, and titrate the amount of acetic acid released using phenolphthalein as an indicator with 0.2 N-sodium hydroxide aqueous solution (0.2 N-sodium hydroxide standard solution). Then, perform a blank test (test without using the sample) using the same method. Finally, calculate AV (degree of acetylene) (%) according to the following formula. AV(%) = (AB) × F × 1.201 / sample mass (g) A: Titration volume (ml) of 0.2 N-sodium hydroxide standard solution B: Titration volume (ml) of the specified 0.2 N-sodium hydroxide solution in the blank test. F: 0.2 N-Sodium hydroxide standard solution coefficient

[0058] [Degree of acetyl substitution at positions 2, 3, and 6] In the resin composition of the present invention, it is preferred to be cellulose acetate (A) with an acetyl substitution degree of C2 at the 2-position, C3 at the 3-position, and C3 at the 6-position satisfying the following formula. (C2+C3) / 2>C6 Cellulose acetate (A) with a total acetyl substitution degree meeting the above range and acetyl substitution degrees at positions 2, 3, and 6 meeting the above formulas exhibits excellent biodegradability. In this specification, the acetyl substitution degrees at positions 2, 3, and 6 are determined by 13C-NMR.

[0059] [Viscosity-average degree of polymerization (DPv) of cellulose acetate (A)] The viscosity-average degree of polymerization (DPv) of cellulose acetate used in the resin composition of the present invention is not particularly limited, but is preferably 10 or more and 400 or less. Resin compositions containing cellulose acetate (A) within this range have excellent melt-forming properties. From this point of view, the viscosity-average degree of polymerization is more preferably 15 or more and 300 or less, and even more preferably 20 or more and 200 or less.

[0060] The viscosity-average degree of polymerization (DPv) is calculated based on the limiting viscosity value ([η], unit: cm3 / g) of cellulose acetate (A).

[0061] The limiting viscosity value ([η], unit: cm3 / g) is determined according to JIS-K-7367-1 and ISO1628-1. Specifically, a sample solution is prepared using dimethyl monoxide (DMSO) as the solvent, and the limiting viscosity is determined by dividing the logarithmic relative viscosity at 25°C, measured using an Ubbelohde viscometer of size 1C, by the concentration of the sample solution.

[0062] Using the obtained limiting viscosity value [η], the viscosity-average molecular weight was calculated using the following formula, based on the literature of Kamide et al. (Polymer Journal, 13, 421-431 (1981)). Viscosity-average molecular weight = (limiting viscosity value [η] / 0.171)(1 / 0.61)

[0063] Using the calculated viscosity-average molecular weight, the viscosity-average degree of polymerization (DPv) is determined using the following formula. Viscosity-average degree of polymerization (DPv) = Viscosity-average molecular weight / (162.14 + 42.037 × DS) Furthermore, in the formula, DS represents the total degree of substitution of the acetyl group mentioned above.

[0064] [Weight-average degree of polymerization (DPw)] The weight-average degree of polymerization (DPw) of cellulose acetate (A) is preferably in the range of 10 to 400. From the viewpoint of improving melt flowability, the weight-average degree of polymerization (DPw) is preferably 15 to 300, and more preferably 20 to 200.

[0065] The weight-average degree of polymerization (DPw) of cellulose acetate (A) can be determined using known methods. Specifically, the weight-average degree of polymerization (DPw) of cellulose acetate (A) is determined by particle size chromatography (GPC) under the following apparatus and conditions (GPC-light scattering method). Device: Shodex-manufactured GPC "SYSTEM-21H" Solvent: Acetone Tube Column: 2 GMHxl (Tosoh) tubes, guard column (Tosoh TSK gel guardcolumn HXL-H) Flow rate: 0.8 ml / min Temperature: 29℃ Sample concentration: 0.25% (wt / vol) Injection volume: 100 μl Detection: MALLS (Multi-Angle Light Scattering Detector) (Manufactured by Wyatt, "DAWN-EOS") MALLS calibration standard material: PMMA (molecular weight 27600)

[0066] [Sulfuric acid content of cellulose acetate (A)] From the viewpoint of suppressing coloring during melt molding, the sulfuric acid content of cellulose acetate (A) is preferably below 350 ppm, more preferably below 300 ppm, and even more preferably below 250 ppm. The lower the sulfuric acid content, the better, but the lower limit is 30 ppm. Furthermore, in this specification, the sulfuric acid content includes the concept of sulfates neutralized by adding bonded sulfuric acid, free sulfuric acid, and free base contained in cellulose acetate (A). Bonded sulfuric acid includes sulfuric acid components bonded in the form of sulfuric acid groups or sulfonic acid groups bonded to cellulose acetate (A) ester.

[0067] The sulfuric acid content was determined by heating cellulose acetate (A) at 1300°C, capturing the sublimated sulfurous acid gas in 10% hydrogen peroxide water, titrating it with sodium hydroxide aqueous solution, and then converting it to sulfuric acid.

[0068] [Content of cellulose acetate (A)] The content of cellulose acetate (A) in the resin composition of the present invention is 45% by mass or more and 90% by mass or less relative to the total resin composition. From the viewpoint of obtaining good formability, the content of cellulose acetate (A) is preferably 50% by mass or more. From the viewpoint of obtaining higher melt flowability, the content of cellulose acetate (A) is preferably 80% by mass or less. The content of cellulose acetate (A) in the resin composition of the present invention may also be 45-80% by mass, 50-90% by mass, or 50-80% by mass. When two or more types of cellulose acetate (A) are used together, their total amount is adjusted to the above-mentioned numerical range.

[0069] [Manufacturing method of cellulose acetate (A)] Cellulose acetate with a total degree of acetylation of 2.60 or less can be manufactured using known methods for manufacturing cellulose acetate. One such method is the so-called acetic acid process, which uses acetic anhydride as an acetylation agent, acetic acid as a diluent, and sulfuric acid as a catalyst. The basic steps of the acetic acid process include: (1) a pretreatment step, in which pulp raw material (dissolved pulp) with a relatively high α-cellulose content is dissociated, pulverized, and then dispersed and mixed with acetic acid; (2) an acetylation step, in which the pretreated pulp from step (1) is reacted with a mixed acid consisting of acetic anhydride, acetic acid, and an acetylation catalyst (e.g., sulfuric acid); (3) a aging step, in which cellulose acetate is hydrolyzed to the desired degree of acetylation; and (4) a post-treatment step, in which the cellulose acetate after hydrolysis is precipitated from the reaction solution, purified, stabilized, and dried. The degree of total substitution of acetyl can be adjusted by adjusting the conditions of the ripening process (time, temperature, etc.).

[0070] [Manufacturing method of resin composition] The resin composition of the present invention can be obtained by melt-blending cellulose acetate (A) with a total acetyl substitution degree of 2.60 or less, the filler (B) mentioned above, and the plasticizer (C) mentioned above. Preferably, the resin composition is obtained by melt-blending a mixture of cellulose acetate (A), filler (B), and plasticizer (C). The mixing before melt-blending allows the filler (B) and plasticizer (C) to fuse more uniformly and quickly with cellulose acetate (A), thereby homogenizing the obtained mixture and obtaining a resin composition with better melt flowability and processing precision.

[0071] The cellulose acetate (A), filler (B), and plasticizer (C) can be mixed using a known mixer such as a Henschel mixer. Both dry and wet mixing are acceptable. When using a mixer such as a Henschel mixer, the preferred temperature inside the mixer is the temperature at which cellulose acetate (A) has not melted, for example, above 20°C but below 200°C.

[0072] Melt-mixing of cellulose acetate (A), filler (B), and plasticizer (C), or melt-mixing of a mixture of cellulose acetate (A), filler (B), and plasticizer (C), can be performed using an extruder such as a twin-screw extruder. From the viewpoint of uniformity of the mixture and suppression of heat degradation, the mixing temperature (barrel temperature) of the extruder is preferably 170°C or higher and 230°C or lower. The melting point of cellulose acetate (A) varies depending on the degree of substitution, ranging from approximately 230°C to 280°C. Since this is close to the decomposition temperature of cellulose acetate (A), melt mixing is generally difficult within this temperature range. However, in the resin composition of the present invention, the aforementioned plasticizer (C) lowers the plasticizing temperature. Therefore, even when a specific amount of filler (B) is included, a sufficiently uniform mixture can be obtained at a temperature below 230°C. For example, when using a twin-screw extruder for melt mixing, the mixing temperature (also referred to as the barrel temperature) can be 200°C. The mixture can be extruded in strands from the die installed at the front end of a twin-shaft extruder and then thermally cut into granules. At this time, the temperature of the die head should be around 220℃.

[0073] The amount of filler (B) in the overall resin composition is 5% by mass or more and 50% by mass or less. When two or more fillers (B) are blended, the total amount is adjusted to 5% by mass or more and 50% by mass or less.

[0074] The amount of plasticizer (C) in the obtained resin composition is 5% by mass or more and 35% by mass or less. When two or more plasticizers (C) are added, the total amount is adjusted to 5% by mass or more and 35% by mass or less.

[0075] To the extent that it does not impair the effects of the present invention, plasticizers other than the plasticizers mentioned above may be incorporated into the resin composition, as well as known additives such as colorants, ultraviolet absorbers, light stabilizers, antioxidants, heat stabilizers, optical property modifiers, fluorescent whitening agents, and flame retardants. In this case, it is preferable to incorporate the plasticizers in such a way that the total content of cellulose acetate (A), filler (B), and plasticizer (C) in the resin composition is 85% by mass or more.

[0076] [Melted Molded Body] From another perspective, the present invention relates to a melt-molded article using the aforementioned cellulose acetate resin composition. The molded article obtained by melt-molding the resin composition of the present invention does not exhibit coloring caused by thermal decomposition products and has high marine biodegradability.

[0077] [Injection Molded Products] From another perspective, the present invention relates to an injection-molded article using the aforementioned cellulose acetate resin composition. The resin composition of the present invention, with its excellent melt flowability, is suitable for injection molding. Preferably, the present invention relates to a film or sheet using the aforementioned cellulose acetate resin composition. In particular, the film obtained by using the resin composition of the present invention, which has a high melt tension, in a melt film-forming method that was previously difficult to achieve is thinner and more uniform. The thickness of the film is preferably less than 100 μm, more preferably 10 μm or more and 90 μm or less. As described below, the film thickness can be reduced to 10 μm or more and 50 μm or less, and further to 10 μm or more and 30 μm or less, depending on the application, by using stretching or blow-drying methods after melt extrusion.

[0078] [Film Forming Method] The membrane of this invention is manufactured by a melt-film forming method and does not use solvents that impose a high burden on the environment. Specifically, the membrane is formed by heating and melting the resin composition of this invention, followed by pressure or extrusion from a T-die. The melting temperature is preferably below 210°C, more preferably below 200°C, and even more preferably below 190°C. From the viewpoint of facilitating membrane formation, a melting temperature of 160°C or higher is preferred.

[0079] For example, using a known melt extruder, molten material is extruded from a T-die onto rollers pre-set to a specific temperature to solidify, thereby obtaining an unstretched film. The film thickness can be adjusted by changing the melt temperature and the die lip. A thinner stretched film can be obtained by increasing the roller speed after extrusion from the die.

[0080] The membrane of this invention can also be obtained using a blow-blowing method. In the blow-blowing method, a tubular membrane can be formed. By melting the tube into a fusible link, a tote bag can be easily made.

[0081] The blown film obtained using the resin composition of this invention exhibits excellent biodegradability, especially marine biodegradability. This blown film can be used as a low-environmental-impact shopping bag or garbage bag.

[0082] The resin composition of the present invention can be suitably used as a base material for tableware, packaging containers, trays, agricultural materials, fishery materials, OA parts, home appliance parts, automotive components, daily necessities, stationery, etc. [Example]

[0083] The effects of the present invention are illustrated by the following examples, but the present invention should not be interpreted in a limited manner based on the description of these examples.

[0084] [Experiment 1] [Example 1] 70 parts by weight of cellulose acetate (manufactured by Daicel Co., Ltd.: total acetyl substitution degree DS=2.46, sulfuric acid content 200 ppm) was mixed with calcium carbonate (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.) as filler and 30 parts by weight of triethylene glycol diacetate (manufactured by TCI Co., Ltd., molecular weight 234.3) as plasticizer under dry conditions. The mixture was dried at 80°C for more than 3 hours and then stirred and mixed using a Henschel mixer to obtain a mixture of cellulose acetate, filler and plasticizer. The obtained mixture was fed into a twin-screw extruder (manufactured by Ikegai Co., Ltd., trade name "PCM30", barrel temperature: 180°C, die temperature: 180°C) for melt mixing and extrusion in strands. The granules were obtained by thermal cutting.

[0085] [Examples 2-47 and Comparative Examples 2, 3 and 5-19] The composition of the resin is shown in Tables 1-6 below. Otherwise, melt extrusion was performed in the same manner as in Example 1.

[0086] [Compare Examples 1 and 4] In Comparative Examples 1 and 4, no melt mixing was performed, and the cellulose acetate shown in Table 5 below was directly supplied to the following seawater biodegradation test.

[0087] [Evaluation of Formability] Based on whether there was an excessive increase in torque during melt extrusion and whether the obtained particles were colored, Examples 1-47 and Comparative Examples 2, 3 and 5-19 were graded according to the following criteria. The evaluation results are shown in Tables 1-6 below. A: It can be granulated, and no coloring was observed. B: It can be granulated, but staining is observed. C: Granulation is impossible due to increased torque during extrusion.

[0088] [Evaluation of the biodegradability of seawater] The seawater biodegradability of Examples 1-36 (rated A in formability) and Comparative Examples 2, 3, 5, and 6, as well as Comparative Examples 1 and 4, was evaluated. In Examples 1-36 and Comparative Examples 2, 3, 5, and 6, the particles obtained by melt extrusion were pulverized to an average particle size of approximately 20 μm and then used in the following biodegradation tests. In Comparative Examples 1 and 4, no melt mixing was performed, and the particles were directly used as controls in the following biodegradation tests. The cellulose acetate in Comparative Examples 1 and 4 was a powder with an average particle size of 20 μm.

[0089] Each sample (60 mg) was added to 250 g of seawater and stirred at 30°C. Carbon dioxide production was measured 90 and 120 days after sample addition. The theoretical carbon dioxide production was calculated based on the measured total organic carbon (TOC) of each sample. The ratio of the measured value (subtracting the measured value from the control group (seawater only)) to the theoretical carbon dioxide production was defined as the seawater biodegradability (%). The results are shown in Tables 1-5 below.

[0090] [Table 1] composition Formability Seawater biodegradability CA plasticizers filler 90 days later (%) 120 days later (%) Substitutability Sulfuric acid (ppm) quality% type quality% type quality% Example 1 2.46 200 58.3 Triethylene glycol diacetate 25.0 CaCO3 16.7 A 63.6 84.8 Example 2 2.46 200 58.3 Triethylene glycol diacetate 25.0 wood flour 16.7 A 61.7 78.0 Example 3 2.46 200 58.3 Triethylene glycol diacetate 25.0 Cellulose powder 16.7 A 61.6 78.3 Example 4 2.46 200 58.3 Triethylene glycol diacetate 25.0 talc 16.7 A 64.3 86.3 Example 5 2.46 200 58.3 Triethylene glycol diacetate 25.0 Magnesium aluminum silicate 16.7 A 74.0 99.4 Example 6 2.46 200 58.3 Triethylene glycol diacetate 25.0 magnesium oxide 16.7 A 77.1 97.6 Example 7 2.46 200 58.3 Triacetylglycerol 25.0 CaCO3 16.7 A 62.3 86.9 Example 8 2.46 200 58.3 Triacetylglycerol 25.0 wood flour 16.7 A 61.5 78.3 Example 9 2.46 200 58.3 Triacetylglycerol 25.0 Cellulose powder 16.7 A 61.7 78.5 Example 10 2.46 200 58.3 Triacetylglycerol 25.0 talc 16.7 A 64.3 85.5 Example 11 2.46 200 58.3 Triacetylglycerol 25.0 Magnesium aluminum silicate 16.7 A 73.1 97.1 Example 12 2.46 200 58.3 Triacetylglycerol 25.0 magnesium oxide 16.7 A 77.6 97.5

[0091] [Table 2] composition Formability Seawater biodegradability CA plasticizers filler 90 days later (%) 120 days later (%) Substitutability Sulfuric acid (ppm) quality% type quality% type quality% Example 13 2.46 200 50.0 Triethylene glycol diacetate 21.4 CaCO3 28.6 A 72.3 97.6 Example 14 2.46 200 50.0 Triethylene glycol diacetate 21.4 wood flour 28.6 A 64.5 80.9 Example 15 2.46 200 50.0 Triethylene glycol diacetate 21.4 Cellulose powder 28.6 A 67.2 81.2 Example 16 2.46 200 50.0 Triethylene glycol diacetate 21.4 talc 28.6 A 72.8 99.2 Example 17 2.46 200 50.0 Triethylene glycol diacetate 21.4 Magnesium aluminum silicate 28.6 A 83.6 98.3 Example 18 2.46 200 50.0 Triethylene glycol diacetate 21.4 magnesium oxide 28.6 A 87.0 98.2 Example 19 2.46 200 50.0 Triacetylglycerol 21.4 CaCO3 28.6 A 72.4 98.4 Example 20 2.46 200 50.0 Triacetylglycerol 21.4 wood flour 28.6 A 65.5 81.0 Example 21 2.46 200 50.0 Triacetylglycerol 21.4 Cellulose powder 28.6 A 66.6 84.9 Example 22 2.46 200 50.0 Triacetylglycerol 21.4 talc 28.6 A 71.9 99.3 Example 23 2.46 200 50.0 Triacetylglycerol 21.4 Magnesium aluminum silicate 28.6 A 82.5 97.0 Example 24 2.46 200 50.0 Triacetylglycerol 21.4 magnesium oxide 28.6 A 87.0 98.8

[0092] [Table 3] composition Formability Seawater biodegradability CA plasticizers filler 90 days later (%) 120 days later (%) Substitutability Sulfuric acid (ppm) quality% type quality% type quality% Example 25 2.15 200 58.3 Triethylene glycol diacetate 25.0 CaCO3 16.7 A 80.4 98.1 Example 26 2.15 200 58.3 Triethylene glycol diacetate 25.0 wood flour 16.7 A 72.5 98.4 Example 27 2.15 200 58.3 Triethylene glycol diacetate 25.0 Cellulose powder 16.7 A 73.8 98.8 Example 28 2.15 200 58.3 Triethylene glycol diacetate 25.0 talc 16.7 A 79.7 98.5 Example 29 2.15 200 58.3 Triethylene glycol diacetate 25.0 Magnesium aluminum silicate 16.7 A 93.6 97.1 Example 30 2.15 200 58.3 Triethylene glycol diacetate 25.0 magnesium oxide 16.7 A 96.0 97.8 Example 31 2.15 200 58.3 Triacetylglycerol 25.0 CaCO3 16.7 A 80.3 98.7 Example 32 2.15 200 58.3 Triacetylglycerol 25.0 wood flour 16.7 A 72.8 98.7 Example 33 2.15 200 58.3 Triacetylglycerol 25.0 Cellulose powder 16.7 A 72.6 98.2 Example 34 2.15 200 58.3 Triacetylglycerol 25.0 talc 16.7 A 79.9 97.7 Example 35 2.15 200 58.3 Triacetylglycerol 25.0 Magnesium aluminum silicate 16.7 A 92.8 98.3 Example 36 2.15 200 58.3 Triacetylglycerol 25.0 magnesium oxide 16.7 A 95.0 97.0

[0093] [Table 4] composition Formability Seawater biodegradability CA plasticizers filler 90 days later (%) 120 days later (%) Substitutability Sulfuric acid (ppm) quality% type quality% type quality% Example 37 2.46 550 58.3 Triethylene glycol diacetate 25.0 CaCO3 16.7 B - - Example 38 2.46 550 58.3 Triethylene glycol diacetate 25.0 wood flour 16.7 B - - Example 39 2.46 550 58.3 Triethylene glycol diacetate 25.0 Cellulose powder 16.7 B - - Example 40 2.46 550 58.3 Triethylene glycol diacetate 25.0 talc 16.7 B - - Example 41 2.46 550 58.3 Triethylene glycol diacetate 25.0 Magnesium aluminum silicate 16.7 B - - Example 42 2.46 550 58.3 Triethylene glycol diacetate 25.0 magnesium oxide 16.7 B - - Example 42 2.46 550 58.3 Triacetylglycerol 25.0 CaCO3 16.7 B - - Example 43 2.46 550 58.3 Triacetylglycerol 25.0 wood flour 16.7 B - - Example 44 2.46 550 58.3 Triacetylglycerol 25.0 Cellulose powder 16.7 B - - Example 45 2.46 550 58.3 Triacetylglycerol 25.0 talc 16.7 B - - Example 46 2.46 550 58.3 Triacetylglycerol 25.0 Magnesium aluminum silicate 16.7 B - - Example 47 2.46 550 58.3 Triacetylglycerol 25.0 magnesium oxide 16.7 B - -

[0094] [Table 5] composition Formability Seawater biodegradability CA plasticizers filler 90 days later (%) 120 days later (%) Substitutability Sulfuric acid (ppm) quality% type quality% type quality% Comparative Example 1 2.46 200 100.0 - - - - - 26.3 54.0 Comparative Example 2 2.46 200 70.0 Triethylene glycol diacetate 30.0 - - A 34.5 66.9 Comparative Example 3 2.46 200 70.0 Triacetylglycerol 30.0 - - A 35.6 66.5 Comparative Example 4 2.15 200 100.0 - - - - - 50.4 77.0 Comparative Example 5 2.15 200 70.0 Triethylene glycol diacetate 30.0 - - A 61.5 90.5 Comparative Example 6 2.15 200 70.0 Triacetylglycerol 30.0 - - A 61.3 90.3 Comparative Example 7 2.46 200 36.8 Triethylene glycol diacetate 15.8 CaCO3 47.4 C - - Comparative Example 8 2.46 200 36.8 Triethylene glycol diacetate 15.8 wood flour 47.4 C - - Comparative Example 9 2.46 200 36.8 Triethylene glycol diacetate 15.8 Cellulose powder 47.4 C - - Comparative Example 10 2.46 200 36.8 Triethylene glycol diacetate 15.8 talc 47.4 C - - Comparative Example 11 2.46 200 36.8 Triethylene glycol diacetate 15.8 Magnesium aluminum silicate 47.4 C - - Comparative Example 12 2.46 200 36.8 Triethylene glycol diacetate 15.8 magnesium oxide 47.4 C - -

[0095] [Table 6] composition Formability Seawater biodegradability CA plasticizers filler 90 days later (%) 120 days later (%) Substitutability Sulfuric acid (ppm) quality% type quality% type quality% Comparative Example 13 2.46 200 36.8 Triacetylglycerol 15.8 CaCO3 47.4 C - - Comparative Example 14 2.46 200 36.8 Triacetylglycerol 15.8 wood flour 47.4 C - - Comparative Example 15 2.46 200 36.8 Triacetylglycerol 15.8 Cellulose powder 47.4 C - - Comparative Example 16 2.15 200 36.8 Triacetylglycerol 15.8 talc 47.4 C - - Comparative Example 17 2.15 200 36.8 Triacetylglycerol 15.8 Magnesium aluminum silicate 47.4 C - - Comparative Example 18 2.15 200 36.8 Triacetylglycerol 15.8 magnesium oxide 47.4 C - - Comparative Example 19 2.46 200 43.8 Triethylene glycol diacetate 18.8 CaCO3 37.5 C - -

[0096] (Summarize) As shown in Tables 1-6, it is confirmed that the resin composition of the examples has higher plasticity and can be molded without hindrance by melt extrusion at a temperature of 180°C. Furthermore, it is known that the resin composition of the examples decomposes at a higher rate in seawater than the resin composition of the comparative examples that does not contain cellulose acetate or fillers.

[0097] As shown in Tables 1-6, the resin compositions of the Examples performed better than those of the Comparative Examples. Based on these evaluation results, the superiority of the present invention is more significant. [Industrial Applicability]

[0098] The resin composition described above can be applied to various fields using melt molding and, consequently, melt film formation.

Claims

1. A cellulose acetate resin composition comprising: cellulose acetate (A) having a total degree of acetyl substitution of 2.1 or more and 2.60 or less, a filler (B), and a plasticizer (C), wherein the filler (B) is selected from at least one of (b1) and (b2) below: (b1) an inorganic compound containing an oxygen atom bonded to any metal element selected from Na, K, Ca, or Mg; and (b2) a metal salt containing one or more metal ions selected from Na+, K+, Ca2+, or Mg2+ and one or more anions selected from carbonate ions, bicarbonate ions, silicate ions, or aluminate ions; wherein the plasticizer (C) is selected from one or more of the group consisting of (c1) to (c3) below: (c1) a glycerol ester having at least one hydroxyl group of glycerol esterified as a plasticizer; (c2) a polyalkylene glycol. (c3) An ether-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified; and (c4) an glycol ester-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified; and relative to the resin composition as a whole, the content of the cellulose acetate (A) is 45% by mass or more and 90% by mass or less, the total content of the filler (B) is 5% by mass or more and 50% by mass or less, and the total content of the plasticizer (C) is 7% by mass or more and 35% by mass or less.

2. The resin composition as claimed in claim 1, wherein, The total content of the above-mentioned cellulose acetate (A), filler (B) and plasticizer (C) in the above-mentioned resin composition is 85% by mass or more.

3. The resin composition as claimed in claim 1 or 2, wherein, The aforementioned glycerol ester is a plasticizer (c1) that is an acetylated glycerol acetate with an acetyl substitution degree of 0 or more and 3 or less.

4. The resin composition as claimed in claim 1 or 2, wherein, The aforementioned ether-based plasticizer (c2) is a polyalkylene glycol with a molecular weight of less than 150 etherified by hydrocarbon groups and an average degree of substitution of 0 or more and 2 or less of terminal hydroxyl groups. The polyalkylene glycol has repeating units of alkoxy groups with 2 or more and 4 or less carbon atoms, and its degree of polymerization is less than 23.

5. The resin composition as claimed in claim 1 or 2, wherein, The aforementioned glycol ester plasticizer (c3) is a polyalkylene glycol esterified with a carboxylic acid of molecular weight less than 150 and with an average degree of substitution of 0 or more and 2 or less at the terminal hydroxyl groups. The polyalkylene glycol has repeating units of alkoxy groups with 2 or more and 4 or less carbon atoms and has a degree of polymerization of 23 or less.

6. The resin composition as claimed in claim 1 or 2, wherein, The sulfuric acid content of the above-mentioned cellulose acetate (A) is above 30 ppm and below 250 ppm.

7. A melt-molded article obtained using a resin composition of any one of claims 1 to 6.

8. An injection-molded article obtained using a resin composition of any one of claims 1 to 6.

9. A sheet or film obtained by using the resin composition of any one of claims 1 to 6.