Cellulose acetate resin composition

Abstract

This cellulose acetate resin composition comprises (A) cellulose acetate having a total degree of acetyl substitution of 2.60 or less, (B) a filler and (C) a plasticizer. The filler (B) is selected from the group consisting of (b1) a specific inorganic compound, (b2) a specific metal salt, (b3) cellulose or hemicellulose, and (b4) a wood powder. The plasticizer (C) is selected from (c1) a glycerin ester-based plasticizer, (c2) an ether-based plasticizer and (c3) a glycol ester-based plasticizer. The content of the component (A) is 45 to 90% by mass. The total content of the component (B) is 5 to 50% by mass. The total content of the component (C) is 5 to 35% by mass.

Description

Technical Field

[0001] The present invention relates to a cellulose acetate resin composition. Specifically, the present invention relates to a cellulose acetate resin composition used for melt molding.

Background Art

[0002] Cellulose acetate has biodegradability and is known to be decomposed by activated sludge. Due to the increasing interest in the global environment, biodegradable molded articles, particularly films and sheets, are in demand.

[0003] Cellulose acetate has poor heat meltability due to hydrogen bonds caused by hydroxyl groups remaining in the molecular chain. The lower the total degree of substitution of acetyl groups (DS) in cellulose acetate, the higher the melting temperature tends to be. On the other hand, the higher the total degree of substitution of acetyl groups in cellulose acetate, the higher its crystallinity, and thus the solubility and meltability tend to decrease. Various methods for forming cellulose acetate into sheets or films by melt casting have been studied.

[0004] Patent Document 1 discloses a biodegradable sheet composed of an acetate composition containing cellulose acetate and polyoxyethylene glycol. Patent Document 2 discloses a biodegradable film or sheet mainly composed of cellulose acetate with an acetyl group substitution degree of 2.3 to 2.7 and a biodegradable plasticizer. This plasticizer is (1) H5C3(OH) 3-n (OOCCH3) n (0≦n≦3) and (2) a compound selected from the group consisting of glycerin alkylate, ethylene glycol alkylate, polyethylene glycol alkylate with 5 or less ethylene repeating units, aliphatic monocarboxylic acid alkyl ester, aliphatic dicarboxylic acid alkyl ester, and aliphatic tricarboxylic acid alkyl ester.

[0005] In Patent Document 3, a cellulose acetate resin composition is proposed which is obtained by melting and mixing cellulose acetate having 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 having an average molecular weight of 300 or more and includes a region where the glass transition temperature is 200°C or higher. Patent Document 4 discloses a water-soluble cellulose acetate resin composition containing cellulose acetate having a total degree of acetylation of 0.5 to 1.0 and a water-soluble organic additive.

[0006] Patent Document 5 discloses a technique for improving the biodegradability of a polymer such as a cellulose ester by adding a basic additive having a pH of 13 or less and 7 or more in a 1% aqueous solution (20°C).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

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

[0009] According to the findings of the present inventors, in a resin composition containing cellulose acetate with a relatively high degree of substitution, the melt fluidity at temperatures lower than 200°C is not sufficient, and the melt elongation and bending flexibility are also insufficient. In particular, it has been difficult to form a thin film with a thickness of 100 μm or less.

[0010] The polymer composition of Patent Document 5 is mainly used for film formation by the casting method and is not mentioned with respect to melt film formation. Conventionally, in a resin composition containing an inorganic substance such as a basic substance, since the melting temperature becomes high, various problems such as thermal decomposition of cellulose acetate, deterioration of the hue accompanying it, generation of side reactions with additives such as inorganic substances, and film formation defects due to a decrease in melt tension have been pointed out.

[0011] As described above, although it is known that cellulose acetate is decomposed in activated sludge, there has also been a problem that a satisfactory decomposition rate cannot be obtained in an aqueous system with a smaller number of bacteria than activated sludge, for example, seawater.

[0012] An object of the present invention is to provide a cellulose acetate resin composition capable of obtaining a molded article excellent in marine biodegradability by melt molding.

Means for Solving the Problems

[0013] The cellulose acetate resin composition according to the present invention contains cellulose acetate (A) having a total degree of acetylation of 2.60 or less, a filler (B), and a plasticizer (C). The filler (B) is one or more selected from the group consisting of the following (b1)-(b4). (b1) An inorganic compound containing an oxygen atom that binds to a metal element of any one of Na, K, Ca, or Mg (b2) Na + , K + , Ca 2+ or Mg 2+ A metal salt containing one or more metal ions selected from and one or more anions selected from carbonate ions, bicarbonate ions, silicate ions, or aluminate ions (b3) Cellulose or hemicellulose (b4) Wood flour

[0014] The plasticizer (C) is one or more selected from the group consisting of the following (c1) - (c3). (c1) A glycerin ester - type plasticizer in which at least one hydroxyl group of glycerin is esterified (c2) An ether - type plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified (c3) A glycol ester - type plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified

[0015] The content of cellulose acetate (A) in the whole resin composition 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 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 this resin composition is 85% by mass or more.

[0017] A preferred glycerin ester - type plasticizer (c1) is glycerin acetate with an acetyl substitution degree of 0 or more and 3 or less.

[0018] A preferred ether - type plasticizer (c2) is a polyalkylene glycol etherified with a hydrocarbon group having a molecular weight of 150 or less and having an average substitution degree of terminal hydroxyl groups of 0 or more and 2 or less. This polyalkylene glycol has an alkyleneoxy group having 2 to 4 carbon atoms as a repeating unit, 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 having a molecular weight of 150 or less and having an average substitution degree of terminal hydroxyl groups of 0 or more and 2 or less. This polyalkylene glycol has an alkyleneoxy group having 2 to 4 carbon atoms as a repeating unit, and its degree of polymerization is 23 or less.

[0020] Preferably, the sulfuric acid component amount of cellulose acetate (A) is 350 ppm or less.

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

[0022] From another viewpoint, the present invention is a melt-molded article obtained by using any of the above-described cellulose acetate resin compositions. Preferably, it is an injection molded article obtained by using any of the above-described resin compositions. Preferably, it is a film or sheet obtained by using any of the above-described resin compositions.

Advantages of the Invention

[0023] The cellulose acetate resin composition according to the present invention has excellent marine biodegradability by containing a predetermined amount of filler (B). Further, this resin composition can be melt-molded in a relatively low temperature range even though it contains a filler (B) by further containing a predetermined amount of plasticizer (C). Furthermore, in this resin composition, since a high melt tension can be obtained, it can also be applied to injection molded articles, particularly films.

Modes for Carrying Out the Invention

[0024] Hereinafter, the present invention will be described in detail based on preferred embodiments. The scope of the present invention is not limited to these descriptions, and it can be appropriately modified and implemented within the scope that does not impair the gist of the present invention other than those exemplified below. Further, the present invention is not limited to the following embodiments, and various modifications are possible within the scope shown in the claims. Other embodiments obtained by appropriately combining the technical means disclosed for each of the plurality of embodiments are also included in the technical scope of the present invention.

[0025] In addition, in the present specification, "X to Y" indicating a range means "X or more and Y or less". Further, unless otherwise noted, "ppm" means "weight ppm" or "mass ppm". Furthermore, "weight" and "mass", "parts by weight" and "parts by mass", "weight %" and "mass %" are treated as synonyms, respectively.

[0026] [Cellulose acetate resin composition] The cellulose acetate resin composition according to the present disclosure contains cellulose acetate (A), a filler (B), and a plasticizer (C). The total degree of acetylation of cellulose acetate (A) is 2.60 or less. The filler (B) is (b1) an inorganic compound containing an oxygen atom that binds to a metal element of any one of Na, K, Ca, or Mg, (b2) a metal salt containing one or more metal ions selected from Na + , K + , Ca 2+ or Mg 2+ and one or more anions selected from carbonate ions, bicarbonate ions, silicate ions, or aluminate ions, (b3) cellulose or hemicellulose and (b4) wood flour and is one or two or more selected from the group consisting of. The plasticizer (C) is (c1) a glycerin ester-based plasticizer in which at least one hydroxyl group of glycerin is esterified, (c2) an ether-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified and (c3) a glycol ester plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified It is one or more selected from the group consisting of. In this 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] In this resin composition, the filler (B) selected from the above (b1)-(b4) is blended in an amount of 5% by mass or more and 50% by mass or less. This resin composition is excellent in biodegradability, particularly biodegradability in seawater. In this resin composition, together with the filler (B), a plasticizer selected from the above (c1)-(c3) is blended in an amount of 5% by mass or more and 35% by mass or less. The compatibility between this plasticizer (c) and cellulose acetate (A) having an acetyl total substitution degree of 2.60 or less is high. By blending this plasticizer (C), this resin composition can be melt-molded at a temperature lower than the thermal decomposition temperature of cellulose acetate, specifically less than 200°C, despite containing the filler (B), and coloring due to thermal decomposition can be avoided.

[0028] Also, this resin composition is considered to exhibit an action of improving the entanglement between the molecular chains of cellulose acetate (A) when the plasticizer (C) whose terminal hydroxyl group is etherified or esterified is melted. Therefore, in this resin composition, the melt viscosity in the temperature range below 200°C is low and the melt tension is high. Due to the low melt viscosity and high melt tension, this resin composition can not only be melt-molded into a film, but can also be further stretched to form a thin film. Furthermore, film formation by the inflation method, which has been difficult to apply to cellulose acetate in the past, becomes possible.

[0029] From the viewpoint of obtaining excellent biodegradability, the total content of cellulose acetate (A), filler (B), and plasticizer (C) in this resin composition is preferably 85% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit of this total content is not particularly limited and may be 100% by mass.

[0030] [Filler (B)] The resin composition according to the present disclosure is blended with one or more fillers (B) selected from the group consisting of the following (b1)-(b4). (b1) An inorganic compound containing an oxygen atom that binds to a metal element of any one of Na, K, Ca, or Mg (b2) Na + , K + , Ca 2+ or Mg 2+ A metal salt containing one or more metal ions selected from and one or more anions selected from carbonate ions, bicarbonate ions, silicate ions, or aluminate ions (b3) Cellulose or hemicellulose (b4) Wood flour

[0031] In particular, in a resin composition containing a filler (B) selected from the inorganic compound (b1) and the metal salt (b2), its seawater biodegradability is significantly improved. This is presumably because the inorganic compound (b1) and the metal salt (b2) exhibit basicity in seawater, thereby promoting the hydrolysis of cellulose acetate. From this viewpoint, a resin composition containing at least one selected from (b1) and (b2) as the filler (B) is preferred.

[0032] The total content of the filler (B) in the resin composition of the present disclosure is 5% by mass or more and 50% by mass or less with respect to the entire resin composition. From the viewpoint of improving seawater biodegradability, the total content of the filler (B) is preferably 10% by mass or more, and more preferably 15% by mass or more. From the viewpoint of excellent melt moldability, the total content of the filler (B) is preferably 45% by mass or less, and more preferably 40% by mass or less. The total content of the filler (B) in the resin composition of the present disclosure may be 5 to 45% by mass, 5 to 40% by mass, 10 to 50% by mass, 10 to 45% by mass, 10 to 40% by mass, 15 to 50% by mass, 15 to 45% by mass, or 15 to 40% by mass. When a plurality of fillers (B) are used in combination, the total amount is adjusted to the above-mentioned numerical range.

[0033] Examples of the inorganic compound (b1) containing an oxygen atom bonded to any one of the metal elements Na, K, Ca, and Mg include oxides, hydroxides, and composite oxides of any one of the metal elements Na, K, Ca, and Mg. From the viewpoints of improving biodegradability and easy handling, preferred inorganic compounds (b1) are magnesium oxide, magnesium hydroxide, talc, hydrotalcite, bentonite, calcium oxide, and calcium hydroxide.

[0034] Na + , K + , Ca 2+ or Mg 2+One or more metal ions selected from the group consisting of, and one or more anions selected from carbonate ions, bicarbonate ions, silicate ions, or aluminate ions. Specific examples of the metal salt (b2) include sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, magnesium bicarbonate, calcium silicate, magnesium silicate, magnesium aluminate, magnesium metasilicate aluminate, and the like. From the viewpoint of obtaining high biodegradability and good moldability, preferred metal salts (b2) are calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, magnesium aluminate, and magnesium metasilicate aluminate.

[0035] Cellulose and hemicellulose (b3) are not particularly limited, and conventionally known ones can be appropriately used. From the viewpoint of excellent melt kneadability, fine cellulose and hemicellulose are preferred. They may be in powder form or fibrous form. In the case of powder form, the average particle diameter (median diameter) measured by a Microtrac particle size analyzer is preferably 10 μm or more and 200 μm or less.

[0036] As the wood flour (b4), conventionally known pulverized wood can be used. From the viewpoint of excellent melt kneadability, the average particle diameter (median diameter) of the wood flour is preferably 10 μm or more and 200 μm or less. The average particle diameter (median diameter) of the wood flour is measured by a Microtrac particle size analyzer.

[0037] [Plasticizer (C)] In the resin composition according to the present disclosure, one or more plasticizers (C) selected from the group consisting of the following (c1)-(c3) are blended. (c1) Glycerol ester plasticizers in which at least one hydroxyl group of glycerol is esterified (c2) Ether plasticizers in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified (c3) Glycol ester plasticizers in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified

[0038] From the viewpoint that a melting temperature lower than the decomposition temperature of cellulose acetate is achieved, a resin composition containing at least one selected from ether plasticizers (c2) and glycol ester plasticizers (c3) as a plasticizer (C) is preferable.

[0039] The total content of the plasticizer (C) in the resin composition of the present disclosure is 5% by mass or more and 35% by mass or less with respect to the entire resin composition. From the viewpoint of high melt fluidity, the total content of the plasticizer (C) is preferably 7% by mass or more, more preferably 9% by mass or more. From the viewpoint of obtaining a low melt viscosity below 200°C, the total content of the plasticizer (C) is preferably 33% by mass or less. The total content of the plasticizer (C) in the resin composition of the present disclosure may be 5 to 33% by mass, may be 7 to 35% by mass, may be 7 to 33% by mass, may be 9 to 35% by mass, or may be 9 to 33% by mass. When a plurality of plasticizers (C) are used in combination, the total amount thereof is adjusted to the above numerical range.

[0040] The glycerin ester plasticizer (c1) is a compound in which at least one hydroxyl group of glycerin is esterified, and is preferably a compound esterified with a carboxylic acid having a molecular weight of 150 or less, more preferably 130 or less.

[0041] The carboxylic acid may be an aliphatic carboxylic acid (fatty acid) or an aromatic carboxylic acid. From the viewpoint of reducing the environmental load, a fatty acid is preferable. It may be a saturated fatty acid or an unsaturated fatty acid. Preferably, it is an ester plasticizer esterified with a saturated fatty acid. Specific examples of the saturated fatty acid include formic acid, acetic acid, propionic acid, butyric acid, etc. A particularly preferable glycerin ester plasticizer (c1) is glycerin acetate having an acetyl substitution degree of 0 or more and 3 or less.

[0042] The ether plasticizer (C2) is a compound in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified, preferably a compound etherified with a hydrocarbon group having a molecular weight of 150 or less, more preferably 130 or less, and particularly preferably 100 or less. The average degree of substitution of the terminal hydroxyl groups of the etherified polyalkylene glycol may be from 0 to 2.

[0043] The hydrocarbon group may be linear, branched or cyclic. An aliphatic hydrocarbon group is preferred, and a saturated aliphatic hydrocarbon group (alkyl group) is more preferred. Specific examples of the alkyl group having a molecular weight of 150 or less include a methyl group, an ethyl group, a propyl group, etc.

[0044] In the ether plasticizer (C2), the polyalkylene glycol has an alkyleneoxy group as a repeating unit. From the viewpoint of suppressing decomposition during melting, the number of carbon atoms of the alkyleneoxy group as a repeating unit is preferably 2 or more, and from the viewpoint of improving compatibility with cellulose acetate (A), the number of carbon atoms is preferably 4 or less. Examples of such an alkyleneoxy group include an ethyleneoxy group, a propyleneoxy group, and a butyleneoxy group.

[0045] From the viewpoint of obtaining a high melt tension, the number of repeating units (hereinafter referred to as the 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 preferred degree of polymerization is 23 or less, and 15 or less is more preferred.

[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 15 or less is more preferred. From the viewpoint of obtaining a high melt tension, an ether plasticizer (C2) having a number average degree of polymerization of 3 or more is preferred. The number average degree of polymerization of the ether plasticizer (C2) is calculated from the number average molecular weight measured by size exclusion chromatography (GPC) using polystyrene as a standard substance.

[0047] Specific examples of the ether plasticizer (c2) used in the resin composition of the present disclosure 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, and the like.

[0048] The glycol ester plasticizer (c3) is a compound in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified, preferably a compound esterified with a carboxylic acid having a molecular weight of 150 or less, more preferably 130 or less, and particularly preferably 100 or less. The average degree of substitution of the terminal hydroxyl groups of the esterified polyalkylene glycol may be from 0 to 2.

[0049] The carboxylic acid may be an aliphatic carboxylic acid (fatty acid) or an aromatic carboxylic acid. From the viewpoint of reducing the environmental load, fatty acids are preferred. It may be a saturated fatty acid or an unsaturated fatty acid. Preferably, it is a glycol ester plasticizer (c3) esterified with a saturated fatty acid. Specific examples of the saturated fatty acid include formic acid, acetic acid, propionic acid, butyric acid, and the like.

[0050] In the glycol ester plasticizer (C3), the polyalkylene glycol has an alkyleneoxy group as a repeating unit. From the viewpoint of suppressing decomposition during melting, the number of carbon atoms in the alkyleneoxy 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 an alkyleneoxy group include an ethyleneoxy group, a propyleneoxy group, and a butyleneoxy group.

[0051] From the viewpoint of obtaining high 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 preferred degree of polymerization is 23 or less, and more preferably 15 or less.

[0052] From the viewpoints of suppressing volatilization during melting and improving melt tension, the number average molecular weight of the glycol ester plasticizer (C3) is preferably 200 or more. From the viewpoint of excellent compatibility with cellulose acetate (A), a glycol ester plasticizer (C3) having a number average molecular weight of 1000 or less is preferred. The number average molecular weight of the glycol ester plasticizer (C3) is measured by size exclusion chromatography (GPC) using polystyrene as a standard substance.

[0053] Specific examples of the glycol ester plasticizer (C3) used in the resin composition of the present disclosure include triethylene glycol monoacetate, triethylene glycol diacetate, triethylene glycol dipropionate, triethylene glycol dibenzoate, tetraethylene glycol diacetate, and the like.

[0054] [Cellulose Acetate (A)] In the resin composition of the present disclosure, cellulose acetate (A) having an overall degree of acetylation (DS) of 2.60 or less is used. From the viewpoint of improving biodegradability, the overall degree of acetylation of cellulose acetate (A) is preferably 2.56 or less, more preferably 2.50 or less. From the viewpoint of high water resistance, the overall degree of acetylation of cellulose acetate (A) is preferably 2.0 or more, more preferably 2.1 or more. Cellulose acetate (A) having an overall degree of acetylation of 2.0 or more and 2.60 or less is preferred. The overall degree of acetylation of cellulose acetate (A) may be 2.0 to 2.56, may be 2.0 to 2.50, may be 2.1 to 2.60, may be 2.1 to 2.56, or may be 2.1 to 2.50.

[0055] The overall degree of acetylation (DS) of cellulose acetate (A) is determined by converting the degree of acetylation AV determined according to the method for measuring the degree of acetylation in ASTM: D-871-96 (Test Methods for Cellulose Acetate, etc.) by the following formula. This is the most 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: Overall degree of acetylation AV: Degree of acetylation (%)

[0056] The method for measuring the degree of acetylation (AV) is as follows.

[0057] First, 500 mg of dried cellulose acetate (sample) is precisely weighed and dissolved in 50 ml of a mixed solvent of ultrapure water and acetone (volume ratio 4:1). Then, 50 ml of 0.2N-sodium hydroxide aqueous solution is added, and saponification is carried out at 25°C for 2 hours. Next, 50 ml of 0.2N-hydrochloric acid is added, and using phenolphthalein as an indicator, the amount of acetic acid released is titrated with 0.2N-sodium hydroxide aqueous solution (0.2N-sodium hydroxide standard solution). Also, a blank test (a test without using a sample) is carried out in the same manner. Then, AV (degree of acetylation) (%) is calculated according to the following formula. AV (%) = (A - B)×F×1.201 / sample mass (g) A: Titration volume (ml) of 0.2N sodium hydroxide standard solution B: Titration volume (ml) of 0.2N sodium hydroxide standard solution in the blank test F: Factor of 0.2N sodium hydroxide standard solution

[0058] [Degree of acetyl substitution at the 2nd, 3rd and 6th positions] In the resin composition of the present disclosure, cellulose acetate (A) in which the degree of acetyl substitution C2 at the 2nd position, the degree of acetyl substitution C3 at the 3rd position, and the degree of acetyl substitution at the 6th position satisfy the following mathematical formula is preferred. (C2 + C3) / 2 > C6 Cellulose acetate (A) in which the total degree of acetyl substitution satisfies the above-mentioned range and the degrees of acetyl substitution at the 2nd, 3rd and 6th positions satisfy the above mathematical formula is excellent in biodegradability. In the present specification, the degrees of acetyl substitution at the 2nd, 3rd and 6th positions are 13 Measured by C-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 disclosure is not particularly limited, but is preferably 10 or more and 400 or less. A resin composition containing cellulose acetate (A) having a viscosity average degree of polymerization within this range is excellent in melt moldability. From this viewpoint, 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 determined based on the intrinsic viscosity number ([η], unit: cm 3 / g) of cellulose acetate (A).

[0061] The intrinsic viscosity number ([η], unit: cm 3 / g) is determined in accordance with JIS-K-7367-1 and ISO1628-1. Specifically, a sample solution using dimethyl sulfoxide (DMSO) as a solvent is prepared, and the logarithmic relative viscosity at 25°C measured using an Ubbelohde viscometer of size number 1C is divided by the concentration of the sample solution to obtain it.

[0062] Using the obtained intrinsic viscosity [η], in accordance with the literature by Kamide et al. (Polymer Journal, 13, 421-431 (1981)), the viscosity-average molecular weight was calculated by the following formula. Viscosity-average molecular weight = (intrinsic viscosity [η] / 0.171)(1 / 0.61)

[0063] Using the calculated viscosity-average molecular weight, the viscosity-average degree of polymerization (DPv) was determined by the following formula. Viscosity-average degree of polymerization (DPv) = viscosity-average molecular weight / (162.14 + 42.037 × DS) In the formula, DS is the total degree of acetyl substitution described 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 fluidity during melting, the weight-average degree of polymerization (DPw) is preferably 15 to 300, more preferably 20 to 200.

[0065] The weight-average degree of polymerization (DPw) of cellulose acetate (A) can be determined by a known method. Specifically, the weight-average degree of polymerization (DPw) of cellulose acetate (A) is determined by performing size exclusion chromatography (GPC) measurement under the following apparatus and conditions (GPC - light scattering method). Apparatus: GPC "SYSTEM-21H" manufactured by Shodex Solvent: Acetone Columns: 2 GMHxl (Tosoh), guard column (TSKgel guardcolumn HXL-H manufactured by Tosoh) Flow rate: 0.8 ml / min Temperature: 29 °C Sample concentration: 0.25% (wt / vol) Injection volume: 100 μl Detection: MALLS (multi-angle light scattering detector) (manufactured by Wyatt, "DAWN-EOS") Standard substance for MALLS correction: PMMA (molecular weight 27,600)

[0066] [Sulfuric acid component content of cellulose acetate (A)] From the viewpoint of suppressing coloring during melt molding, the sulfuric acid component content of cellulose acetate (A) is preferably 350 ppm or less, more preferably 300 ppm or less, and particularly preferably 250 ppm or less. Although it is preferable that the sulfuric acid component content is as small as possible, the lower limit is 30 ppm. In the present specification, the sulfuric acid component is a concept including bound sulfuric acid, free sulfuric acid, and sulfates neutralized by the addition of a base contained in cellulose acetate (A). Bound sulfuric acid includes sulfuric acid groups ester-bonded to cellulose acetate (A) and sulfuric acid components bonded as sulfonic acid groups.

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

[0068] [Content of cellulose acetate (A)] In the resin composition of the present disclosure, the content of cellulose acetate (A) is 45% by mass or more and 90% by mass or less with respect to the entire resin composition. From the viewpoint of obtaining good conformability, the content of cellulose acetate (A) is preferably 50% by mass or more. From the viewpoint of obtaining high melt fluidity, 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 disclosure may be 45 to 80% by mass, may be 50 to 90% by mass, or may be 50 to 80% by mass. When two or more types of cellulose acetate (A) are used in combination, the total amount thereof is adjusted to the above numerical range.

[0069] [Manufacturing method of cellulose acetate (A)] Cellulose acetate with an overall degree of acetylation of 2.60 or less can be produced by known methods for producing cellulose acetate. Such production methods include the so-called acetic acid method using acetic anhydride as an acetylating agent, acetic acid as a diluent, and sulfuric acid as a catalyst. The basic steps of the acetic acid method are: (1) a pretreatment step of spraying and mixing acetic acid after dissociating and crushing a pulp raw material (dissolving pulp) with a relatively high α-cellulose content; (2) an acetylation step of reacting the pretreated pulp in (1) with a mixed acid composed of acetic anhydride, acetic acid, and an acetylation catalyst (e.g., sulfuric acid); (3) an aging step of hydrolyzing cellulose acetate to obtain cellulose acetate with a desired degree of acetylation; and (4) a post-treatment step of precipitating, separating, purifying, stabilizing, and drying the cellulose acetate after the hydrolysis reaction from the reaction solution. Adjustment of the overall degree of acetylation can be achieved by adjusting the conditions (such as time and temperature) of the aging step.

[0070] [Method for producing resin composition] The resin composition of the present disclosure can be obtained by melt-kneading cellulose acetate (A) with an overall degree of acetylation of 2.60 or less, the filler (B) described above, and the plasticizer (C) described above. Preferably, this resin composition is obtained by mixing cellulose acetate (A), filler (B), and plasticizer (C) and then melt-kneading them. By mixing before melt-kneading, the filler (B) and plasticizer (C) and cellulose acetate (A) can be more uniformly and quickly incorporated, resulting in homogenization of the obtained kneaded product, and thus a resin composition with improved melt fluidity and processing accuracy can be obtained.

[0071] For mixing cellulose acetate (A), filler (B), and plasticizer (C), known mixers such as a Henschel mixer can be used. Either dry mixing or wet mixing may be used. When using a mixer such as a Henschel mixer, the temperature inside the mixer is preferably a temperature at which cellulose acetate (A) does not melt, for example, 20°C or higher and less than 200°C.

[0072] For the melt-kneading of cellulose acetate (A), filler (B) and plasticizer (C), or the melt-kneading after mixing cellulose acetate (A), filler (B) and plasticizer (C), an extruder such as a twin-screw extruder can be used. From the viewpoints of the uniformity of the kneaded product and suppression of heat deterioration, the kneading temperature (cylinder temperature) by the extruder is preferably 170 °C or higher and 230 °C or lower. The melting point of cellulose acetate (A) is approximately 230 °C to 280 °C depending on the degree of substitution, and since it is close to the decomposition temperature of cellulose acetate (A), usually, melt-kneading is difficult in this temperature range. However, in the resin composition of the present disclosure, since the plasticizing temperature is lowered by the aforementioned plasticizer (C), even when a predetermined amount of filler (B) is contained, a sufficiently uniform kneaded product can be obtained at a temperature of 230 °C or lower. For example, when melt-kneading using a twin-screw extruder, the kneading temperature (also referred to as the cylinder temperature) may be 200 °C. After extruding the kneaded product in a strand shape from the die attached to the tip of the twin-screw extruder, it may be hot cut into pellets. At this time, the die temperature may be about 220 °C.

[0073] The blending amount of the filler (B) with respect to the entire obtained resin composition is 5% by mass or more and 50% by mass or less. When blending two or more types of fillers (B), the total amount thereof is adjusted to be 5% by mass or more and 50% by mass or less.

[0074] The blending amount of the plasticizer (C) with respect to the entire obtained resin composition is 5% by mass or more and 35% by mass or less. When blending two or more types of plasticizers (C), the total amount thereof is adjusted to be 5% by mass or more and 35% by mass or less.

[0075] Within a range that does not inhibit the effects of the present invention, a plasticizer other than the aforementioned plasticizer may be blended into this resin composition, and known additives such as a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, a heat stabilizer, an optical property adjuster, a fluorescent brightening agent, and a flame retardant may be blended. In that case, it is preferable to blend so that the total content of cellulose acetate (A), filler (B) and plasticizer (C) in the resin composition is 85% by mass or more.

[0076] [Melt-formed article] From another perspective, the present invention relates to a melt-formed article using the cellulose acetate resin composition described above. The molded article obtained by melt-molding the resin composition of the present disclosure has no coloring caused by thermal decomposition products and, moreover, has high marine biodegradability.

[0077] [Injection molded product] From still another perspective, the present invention relates to an injection molded product using the cellulose acetate resin composition described above. The resin composition of the present disclosure, which has excellent fluidity during melting, can be suitably applied to injection molding. Preferably, the present invention relates to a film or sheet using the cellulose acetate resin composition described above. In particular, a film obtained by using the resin composition of the present disclosure, which has a high melt tension, in a melt film-forming method that was conventionally difficult is thin and uniform. Preferably, the thickness of this film is less than 100 μm, more preferably 10 μm or more and 90 μm or less. As described later, by using a stretching or inflation method after melt extrusion, the thickness of the film can be made thinner, depending on the application, to 10 μm or more and 50 μm or less, and further to 10 μm or more and 30 μm or less.

[0078] [Film-forming method] The film of the present disclosure is manufactured by a melt film-forming method without using a solvent with a large environmental load. Specifically, this film is formed by heating and melting the resin composition of the present disclosure and extruding it from a press or a T-die. As the melting temperature, 210°C or lower is preferable, 200°C or lower is more preferable, and 190°C or lower is even more preferable. From the perspective of ease of film formation, a preferable melting temperature is 160°C or higher.

[0079] For example, by using a known melt extruder and extruding the melt onto a roll adjusted to a predetermined temperature from a T-die and solidifying it, an unstretched film can be obtained. The film thickness is adjusted by changing the melting temperature and the die lip. By increasing the roll speed after die extrusion, a more thinly stretched film can be obtained.

[0080] The film of the present disclosure may be obtained by the inflation method. In the inflation method, it is possible to form a film in a tubular shape. By fusing and sealing this tube, a bag with a handle can be easily formed into a film.

[0081] The inflation film obtained using the resin composition of the present disclosure is excellent in biodegradability, particularly marine biodegradability. This inflation film can be used as a low environmental impact shopping bag or garbage bag.

[0082] The resin composition according to the present disclosure can be suitably used, for example, as a base material for tableware, packaging containers, trays, agricultural materials, fishing materials, OA parts, household electrical appliance parts, automotive members, daily sundries, stationery, etc. [Examples]

[0083] Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be construed in a limited manner based on the description of these examples.

[0084] [Test 1] [Example 1] 70 parts by mass of cellulose acetate (manufactured by Daicel Corporation: total degree of acetylation DS = 2.46, sulfuric acid component amount 200 ppm), 20 parts by mass of calcium carbonate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) as a filler, and 30 parts by mass of triethylene glycol diacetate (manufactured by TCI, molecular weight 234.3) as a plasticizer were blended in a dry state, dried at 80 ° C for 3 hours or more, and further stirred and mixed using a Henschel mixer to obtain a mixture of cellulose acetate, filler, and plasticizer. The obtained mixture was supplied to a twin-screw extruder (manufactured by Ikegai Corporation, trade name "PCM30", cylinder temperature: 180 ° C, die temperature: 180 ° C), melt-kneaded, and then the extruded strand was hot-cut to obtain pellets.

[0085] [Examples 2 - 47 and Comparative Examples 2, 3, and 5 - 19] The melt extrusion was carried out in the same manner as in Example 1, except that the composition of the resin composition was as shown in Table 1-6 below.

[0086] [Comparative Examples 1 and 4] In Comparative Examples 1 and 4, melt kneading was not performed, and the cellulose acetate shown in Table 5 below was directly subjected to the seawater biodegradation test described below.

[0087] [Evaluation of Moldability] Examples 1-47 and Comparative Examples 2, 3, and 5-19 were ranked according to the following criteria based on the presence or absence of excessive torque increase during melt extrusion and the presence or absence of coloring of the obtained pellets. The evaluation results are shown in Table 1-6 below. A: Pelletization was possible, and no coloring was observed. B: Pelletization was possible, but coloring was observed. C: Pelletization was not possible due to an increase in torque during extrusion.

[0088] [Evaluation of Seawater Biodegradability] The seawater biodegradabilities of Examples 1-36 and Comparative Examples 2, 3, 5, and 6, which had an A in the moldability evaluation, and Comparative Examples 1 and 4 were evaluated. Examples 1-36 and Comparative Examples 2, 3, 5, and 6 were each subjected to the following biodegradation test after pulverizing the pellets obtained by melt extrusion to an average particle size of about 20 μm. Comparative Examples 1 and 4 were directly subjected to the following biodegradation test as controls without melt kneading. The cellulose acetates of Comparative Examples 1 and 4 were both powders with an average particle size of 20 μm.

[0089] 60 mg of each sample was put into 250 g of seawater and stirred at a temperature of 30°C. The amount of carbon dioxide generated 90 days and 120 days after the sample was put in was measured. The theoretical amount of carbon dioxide generated was calculated from the total organic carbon (TOC) amount measured for each sample subjected to the test, and the ratio of the value obtained by subtracting the measured value of the blank (seawater only) from the measured value to this theoretical amount of carbon dioxide generated was defined as the seawater biodegradability (%). The results obtained are shown in Table 1-5 below.

[0090]

Table 1

[0091]

Table 2

[0092]

Table 3

[0093]

Table 4

[0094]

Table 5

[0095]

Table 6

[0096] (Summary) As shown in Tables 1-6, it was confirmed that the resin compositions of the examples have high plasticity and can be molded without problems by melt extrusion at a temperature of 180°C. Further, it was found that the resin compositions of the examples have a higher decomposition rate in seawater than the resin compositions of the comparative examples that do not contain cellulose acetate and filler.

[0097] As shown in Tables 1-6, the resin compositions of the examples have a higher evaluation than the resin compositions of the comparative examples. From this evaluation result, the superiority of the present invention is clear.

Industrial Applicability

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

Claims

1. A resin composition comprising cellulose acetate (A) having an overall degree of acetylation of 2.1 or more and 2.60 or less, a filler (B), and a plasticizer (C), wherein the filler (B) is (b1) magnesium oxide, (b2) Na ＋ , K ＋ , Ca ２＋ or Mg ２＋ A metal salt containing one or more metal ions selected from, and one or more anions selected from carbonate ions, bicarbonate ions, silicate ions or aluminate ions (b3) cellulose or hemicellulose and (b4) wood flour and is one or more selected from the group consisting of wherein the plasticizer (C) is (c1) a glycerin ester-based plasticizer in which at least one hydroxyl group of glycerin is esterified, (c2) an ether-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified and (c3) a glycol ester-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified and is one or more selected from the group consisting of wherein, based on the entire resin composition, 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, and the total content of the cellulose acetate (A), the filler (B), and the plasticizer (C) in the resin composition is 85% by mass or more and 100% by mass or less, a cellulose acetate resin composition.

2. The resin composition according to claim 1, wherein the glycerin ester-based plasticizer (c1) is glycerin acetate in which at least one hydroxyl group of glycerin is esterified with acetic acid.

3. The resin composition according to claim 1 or 2, wherein the ether-based plasticizer (c2) is a compound in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified with a hydrocarbon group having a molecular weight of 150 or less, and this polyalkylene glycol has an alkyleneoxy group having 2 to 4 carbon atoms as a repeating unit, and its degree of polymerization is 2 or more and 23 or less.

4. The resin composition according to any one of claims 1 to 3, wherein the glycol ester-based plasticizer (c3) is a compound in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified with a carboxylic acid having a molecular weight of 150 or less, and this polyalkylene glycol has an alkyleneoxy group having 2 to 4 carbon atoms as a repeating unit, and its degree of polymerization is 2 or more and 23 or less.

5. The resin composition according to any one of claims 1 to 4, wherein the sulfuric acid component amount of the cellulose acetate (A) is 350 ppm or less.

6. A melt-molded article obtained by using the resin composition according to any one of claims 1 to 5 above.

7. An injection-molded article obtained by using the resin composition according to any one of claims 1 to 5 above.

8. A sheet or film obtained by using the resin composition according to any one of claims 1 to 5 above.

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