Cellulose acetate resin composition

Abstract

This cellulose acetate resin composition contains: a cellulose acetate in which the total substitution degree of acetyl is from 1.9 to 2.6 inclusive; and a plasticizer. The cellulose acetate has a number average molecular weight of 45,000 or more and a weight-average molecular weight of 70,000 or more. This plasticizer is selected from among: (1) ether plasticizers in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified; and (2) ester plasticizers in which at least on terminal hydroxyl group of a polyalkylene glycol is esterified. The degree of polymerization of polyalkylene glycol in the ether plasticizers (1) and the ester plasticizers (2) is at least 3 and less than 10. This plasticizer does not contain an aromatic ring at its terminal group.

Description

[Technical Field]

[0001] The present disclosure relates to a cellulose acetate resin composition. More specifically, the present disclosure relates to a cellulose acetate resin composition for use in melt molding. [Background technology]

[0002] Cellulose acetate is biodegradable and is known to be decomposed by activated sludge. With growing concern about the global environment, there is a demand for biodegradable films and sheets.

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

[0004] Patent Document 1 discloses a biodegradable sheet made of an acetate composition containing cellulose acetate and polyoxyethylene glycol. Patent Document 2 discloses a biodegradable film or sheet whose main components are cellulose acetate having 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) selected from the group consisting of glycerin alkylate, ethylene glycol alkylate, polyethylene glycol alkylate having 5 or less ethylene repeating units, aliphatic monocarboxylic acid alkyl ester, aliphatic dicarboxylic acid alkyl ester, and aliphatic tricarboxylic acid alkyl ester.

[0005] Patent Document 3 proposes a cellulose acetate resin composition comprising 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, melted and mixed with a plasticizer having an average molecular weight of 300 or more, and having a glass transition temperature in a range of 200° C. or higher. Patent Document 4 discloses a water-soluble cellulose acetate resin composition comprising cellulose acetate having a total acetyl substitution degree of 0.5 to 1.0 and a water-soluble organic additive.

[0006] Patent Document 5 describes a composition and film containing cellulose acetate with an acetyl substitution degree of 1.5-2.8 and 1-45% of triethylene glycol or the like as a plasticizer. Patent Document 6 discloses a composition and film containing cellulose acetate with an acetyl substitution degree of 2.0-2.6 and a plasticizer. Patent Document 7 discloses a compound in which the terminal of the oxyalkylene group is alkylated or acylated as a plasticizer for cellulose acetate resins. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 8-53575 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-60545 [Patent Document 3] Japanese Patent Application Publication No. 11-255959 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-140432 [Patent Document 5] Chinese Patent Application Publication No. 11113872 [Patent Document 6] Japanese Patent Application Publication No. 2018-524463 [Patent Document 7] Japanese Patent Application Laid-Open No. 2007-77300 Summary of the Invention [Problem 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 exceeding 100 μm in thickness. Melting temperatures exceeding 200°C pose the problem of coloration due to thermal decomposition of cellulose acetate. The resin composition of Patent Document 4 is melt-spun at temperatures below 200°C, and a low-substituted cellulose acetate is used in this resin composition. In the examples of Patent Document 5, melt-molding is performed at temperatures below 200°C, and a low-molecular-weight cellulose acetate is used in this composition. Patent Document 6 uses a special plasticizer with an aromatic ring, which is of concern for its environmental impact. Patent Document 7 does not mention cellulose acetate in detail, and does not provide a plasticizer that is particularly suitable for thinning cellulose acetate.

[0009] According to the findings of the present inventors, resin compositions containing cellulose acetate with a relatively high degree of substitution do not have sufficient melt fluidity at temperatures below 200°C, and the molten product is also insufficient in terms of extensibility and bending flexibility, making it particularly difficult to form films with a thickness of 100 µm or less. Furthermore, there is a demand for further improvements in the strength of molded articles, but it has been difficult to apply high-molecular-weight cellulose acetate, which is expected to have an increased melt viscosity, particularly in melt film formation.

[0010] An object of the present disclosure is to provide a cellulose acetate resin composition that can be formed into a film at a melting temperature of less than 200°C. [Means for solving the problem]

[0011] The cellulose acetate composition according to the present disclosure contains cellulose acetate having a total degree of acetyl substitution of 1.9 to 2.6, and a plasticizer. The cellulose acetate has a number-average molecular weight Mn of 45,000 or more and a weight-average molecular weight Mw of 70,000 or more. The plasticizer is (1) An ether-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified, the degree of polymerization of this polyalkylene glycol is 3 or more but less than 10, and the terminal group does not contain an aromatic ring. and (2) An ester-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified, the degree of polymerization of this polyalkylene glycol is 3 or more but less than 10, and the terminal group does not contain an aromatic ring. is selected from.

[0012] Preferably, the total content of the plasticizer in the entire resin composition is 5% by weight or more and 50% by weight or less.

[0013] Preferably, the polyalkylene glycol has an alkyleneoxy group having 2 to 4 carbon atoms as a repeating unit.

[0014] Preferably, the ether substituent of the ether-based plasticizer is a hydrocarbon group having a molecular weight of not more than 150. Preferably, the hydrocarbon group is an alkyl group.

[0015] Preferably, the ester-based plasticizer is a polyalkylene glycol esterified with a carboxylic acid having a molecular weight of not more than 150. Preferably, the carboxylic acid is a saturated fatty acid.

[0016] Preferably, the molecular weight distribution Mw / Mn of the cellulose acetate is greater than 1.7.

[0017] The film according to the present disclosure can be obtained using any of the resin compositions described above, and has a thickness of 10 μm or more and 150 μm or less. [Effects of the Invention]

[0018] The cellulose acetate resin composition according to the present disclosure has high melt fluidity in the temperature range below 200°C, and therefore can be easily formed into a thin film, resulting in a film with excellent strength. Furthermore, this resin composition can be formed into a film at a temperature sufficiently lower than the thermal decomposition temperature of cellulose acetate, thereby suppressing coloration. Furthermore, this resin composition has high melt tension, and therefore can be applied to inflation film formation. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present disclosure will be described in detail below based on preferred embodiments. Each configuration and combination thereof in each embodiment is merely an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the scope of the gist of the present disclosure. The present disclosure is not limited by the embodiments, but is limited only by the scope of the claims.

[0020] In the present specification, the range "X to Y" means "X or more and Y or less." Furthermore, unless otherwise noted, "ppm" means "ppm by weight."

[0021] [Cellulose acetate resin composition] The cellulose acetate resin composition according to the present disclosure contains cellulose acetate and a plasticizer. The cellulose acetate has a total acetyl substitution degree of 1.9 or more and 2.6 or less, a number-average molecular weight Mn of 45,000 or more, and a weight-average molecular weight Mw of 70,000 or more. The plasticizer is (1) An ether-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified, the degree of polymerization of this polyalkylene glycol is 3 or more but less than 10, and the terminal group does not contain an aromatic ring. and (2) An ester-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified, the degree of polymerization of this polyalkylene glycol is 3 or more but less than 10, and the terminal group does not contain an aromatic ring. One or more selected from the above.

[0022] This resin composition contains a plasticizer in which at least one hydroxyl group at the terminal of a polyalkylene glycol is etherified or esterified. This plasticizer has high compatibility with cellulose acetate having a total acetyl substitution degree of 1.9 to 2.6, a number-average molecular weight Mn of 45,000 or more, and a weight-average molecular weight Mw of 70,000 or more. This resin composition suppresses bleed-out of the plasticizer. Furthermore, a resin composition containing this plasticizer can be melt-molded at temperatures lower than the thermal decomposition temperature of cellulose acetate, specifically below 200°C, thereby avoiding coloration due to decomposition products. This resin composition also has a low melt viscosity in the temperature range below 200°C. Therefore, even when a thin film is extruded by narrowing the die lip in a melt extrusion method, the viscosity of the molten material does not increase more than necessary, allowing for suitable film formation.

[0023] Furthermore, in this resin composition, the plasticizer, whose terminal hydroxyl groups have been etherified or esterified, is thought to improve the entanglement of the molecular chains of cellulose acetate during melting. In the resin composition according to the present disclosure, the action of this plasticizer improves the melt tension without excessively increasing the melt viscosity. Therefore, the film after melt extrusion can be further stretched to reduce its thickness. Furthermore, film formation by the inflation method, which has traditionally been difficult to apply to cellulose acetate, is also possible.

[0024] From the viewpoint of obtaining high melt fluidity, the MI value (190°C, 5 kg) of the resin composition of the present disclosure is preferably 6.0 or more, preferably 7.5 or more, and more preferably 9.0 or more. The MI value is measured in accordance with the description of JIS K7210-1 "Plastics - Determination of melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics - Part 1: Standard test method."

[0025] [Plasticizer] As described above, the plasticizer blended in the resin composition according to the present disclosure has at least one terminal hydroxyl group of the polyalkylene glycol etherified or esterified. Specifically, this plasticizer is etherified or esterified by a functional group that does not contain an aromatic ring. In other words, this plasticizer does not contain an aromatic ring in its terminal group. This plasticizer reduces the adverse environmental impact caused by aromatic compounds.

[0026] The polyalkylene glycol has an alkyleneoxy group as a repeating unit. From the viewpoint of suppressing decomposition during melting, the carbon number of the alkyleneoxy group as a repeating unit is preferably 2 or more, and from the viewpoint of excellent compatibility with cellulose acetate, the carbon number is preferably 4 or less. Examples of such alkyleneoxy groups include an ethyleneoxy group, a propyleneoxy group, and a butyleneoxy group.

[0027] From the viewpoint of obtaining a high melt tension, the number of repeating units in the polyalkylene glycol (hereinafter referred to as the degree of polymerization) is 3 or more, and preferably 4 or more. From the viewpoint of obtaining a low melt viscosity, the degree of polymerization of the polyalkylene glycol is less than 10, preferably 9 or less, and more preferably 8 or less.

[0028] In the ether-based plasticizer in which at least one terminal hydroxyl group of the polyalkylene glycol is etherified, the ether substituent is preferably a linear, branched, or cyclic hydrocarbon group. An aliphatic hydrocarbon group is preferred, and a saturated aliphatic hydrocarbon group (alkyl group) is more preferred. From the viewpoint of excellent compatibility with cellulose acetate, the molecular weight of this hydrocarbon group is preferably 150 or less, more preferably 140 or less, and even more preferably 100 or less.

[0029] From the viewpoint of excellent compatibility with cellulose acetate, the number-average degree of polymerization of the ether-based plasticizer is preferably 10 or less, more preferably 8 or less. From the viewpoint of high melt fluidity, ether-based plasticizers having a number-average degree of polymerization of 3 or more are preferred. The number-average degree of polymerization of the ether-based plasticizer is calculated from the number-average molecular weight measured by size exclusion chromatography (GPC) using polystyrene as a standard substance.

[0030] Specific examples of ether-based plasticizers used in the resin composition of the present disclosure include triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, polyethylene glycol monomethyl ether, etc. Further examples include monomethyl ethers, monoethyl ethers, dimethyl ethers, etc. of polyethylene glycols having a degree of polymerization of 3 or more and less than 10, and monomethyl ethers, monoethyl ethers, dimethyl ethers, etc. of polypropylene glycols having a degree of polymerization of 3 or more and less than 10.

[0031] In the resin composition of the present disclosure, the ester-based plasticizer in which at least one terminal hydroxyl group of the polyalkylene glycol is esterified has a number-average degree of polymerization of 2 or more. From the viewpoints of suppressing volatilization during melting and improving melt tension, the number-average degree of polymerization of the ester-based plasticizer is more preferably 3 or more. From the viewpoint of excellent compatibility with cellulose acetate, ester-based plasticizers with a number-average degree of polymerization of 10 or less are preferred. The number-average degree of polymerization of the ester-based plasticizer is calculated from the number-average molecular weight measured by size exclusion chromatography (GPC) using polystyrene as a standard substance.

[0032] An ester-based plasticizer is preferred in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified with a carboxylic acid having a molecular weight of preferably 150 or less, more preferably 130 or less. From the viewpoint of reducing the burden on the environment, a preferred carboxylic acid is an aliphatic carboxylic acid (fatty acid). The carboxylic acid may be a saturated fatty acid or an unsaturated fatty acid. An ester-based plasticizer esterified with a saturated fatty acid is preferred.

[0033] Specific examples of the ester-based plasticizer used in the resin composition of the present disclosure include triethylene glycol monoacetate, triethylene glycol diacetate, triethylene glycol dipropionate, and tetraethylene glycol diacetate.

[0034] The content of the plasticizer in the resin composition of the present disclosure is adjusted appropriately depending on the type of plasticizer, the physical properties of cellulose acetate, etc. From the viewpoint of easily obtaining the above-mentioned effect of the plasticizer, the total content of the plasticizer is preferably 5 wt% or more, more preferably 10 wt% or more, even more preferably 15 wt% or more, and particularly preferably 20 wt% or more, based on the entire resin composition. From the viewpoint of the strength of the obtained molded product, the total content of the plasticizer is preferably 50 wt% or less, more preferably 45 wt% or less, even more preferably 40 wt% or less, and particularly preferably 35 wt% or less. The total content of plasticizers in the resin composition of the present disclosure may be 10 to 45 wt%, 10 to 40 wt%, 10 to 35 wt%, 15 to 50 wt%, 15 to 45 wt%, 15 to 40 wt%, 15 to 35 wt%, 20 to 50 wt%, 20 to 45 wt%, 20 to 40 wt%, or 20 to 35 wt%. When multiple plasticizers are used in combination, it is preferable that the total amount be adjusted to the aforementioned numerical range.

[0035] [Cellulose acetate (CA)] The resin composition of the present disclosure uses cellulose acetate having a total degree of acetyl substitution (DS) of 1.9 or more and 2.6 or less. From the viewpoint of improving water resistance, the total degree of acetyl substitution of the cellulose acetate is preferably 2.0 or more, more preferably 2.1 or more. From the viewpoint of excellent biodegradability, the total degree of acetyl substitution of the cellulose acetate is preferably 2.56 or less, more preferably 2.50 or less, even more preferably 2.40 or less, even more preferably 2.30 or less, and particularly preferably 2.26 or less. The total degree of acetyl substitution of the cellulose acetate may be 1.9 to 2.56, or may be 1.9 to 2.50, or may be 1.9 to 2.40, or may be 1.9 to 2.30, or may be 1.9 to 2.26, or may be 2.0 to 2.6, or may be 2.0 to 2.56, or may be 2.0 to 2.50, or may be 2.0 to 2.40, or may be 2.0 to 2.30, or may be 2.0 to 2.26, or may be 2.1 to 2.6, or may be 2.1 to 2.56, or may be 2.1 to 2.50, or may be 2.1 to 2.40, or may be 2.1 to 2.30, or may be 2.1 to 2.26.

[0036] The total acetyl substitution degree of cellulose acetate (sometimes referred to as the average substitution degree) can be determined by converting the acetylation degree AV determined according to the method for measuring the acetylation degree in ASTM: D-871-96 (Test methods for cellulose acetate, etc.) using the following formula. This is the most common method for determining the substitution degree of cellulose acetate. DS=162.14×AV×0.01 / (60.052-42.037×AV×0.01) DS: Total degree of acetyl substitution AV: Acetyl content (%)

[0037] The method for measuring the acetylation degree (AV) is as follows.

[0038] First, 500 mg of dried cellulose acetate (sample) is weighed and dissolved in 50 ml of a mixed solvent of ultrapure water and acetone (volume ratio 4:1). Then, 50 ml of 0.2 N aqueous sodium hydroxide is added and the solution is saponified at 25°C for 2 hours. Next, 50 ml of 0.2 N hydrochloric acid is added, and the amount of acetic acid released is titrated with 0.2 N aqueous sodium hydroxide (normal 0.2 N sodium hydroxide solution) using phenolphthalein as an indicator. A blank test (a test without sample) is also conducted using the same method. The AV (acetylation degree) (%) is then calculated using the following formula: AV (%) = (AB) × F × 1.201 / sample weight (g) A: Titration volume of 0.2N sodium hydroxide normal solution (ml) B: Titration volume (ml) of 0.2N sodium hydroxide normal solution in the blank test F: Factor of 0.2N sodium hydroxide normal solution

[0039] [Molecular weight and molecular weight distribution of cellulose acetate] The resin composition of the present disclosure contains cellulose acetate having a number-average molecular weight Mn of 45,000 or more and a weight-average molecular weight Mw of 70,000 or more. Resin compositions containing cellulose acetate having a number-average molecular weight Mn and a weight-average molecular weight Mw within these ranges can easily produce molded articles with high strength by melt molding. From the viewpoint of improving strength, the weight-average molecular weight Mw of the cellulose acetate is preferably 80,000 or more, more preferably 90,000 or more, and even more preferably 100,000 or more. While the upper limit of the weight-average molecular weight Mw is not particularly limited, from the viewpoint of ease of melt molding, it is preferably 250,000 or less, more preferably 240,000 or less, and even more preferably 230,000 or less.

[0040] From the viewpoint of improving strength, the number average molecular weight Mn of cellulose acetate is preferably 50,000 or more, more preferably 55,000 or more, and even more preferably 60,000 or more. Although there is no particular upper limit for the number average molecular weight Mn, from the viewpoint of ease of melt molding, it is preferably 125,000 or less, more preferably 120,000 or less, and even more preferably 115,000 or less.

[0041] The molecular weight distribution of cellulose acetate is evaluated by the ratio of number-average molecular weight Mn to weight-average molecular weight Mw (Mw / Mn). From the viewpoint of obtaining high melt fluidity, the molecular weight distribution Mw / Mn of cellulose acetate is preferably more than 1.7, more preferably 1.8 or more, even more preferably 2.0 or more, and particularly preferably 2.1 or more. From the viewpoint of production efficiency of cellulose acetate, the molecular weight distribution Mw / Mn is preferably 3.5 or less, more preferably 3.2 or less, and even more preferably 3.0 or less.

[0042] Cellulose acetate is a semi-synthetic polymer obtained from cellulose as a raw material. The maximum molecular weight of cellulose acetate is determined by the cellulose raw material. Cellulose acetate with a large molecular weight distribution Mw / Mn can be obtained by performing hydrolysis as quickly as possible in the production method described below. Cellulose acetate with a large molecular weight distribution Mw / Mn can also be obtained by using cellulose with different molecular weights as raw materials. Furthermore, it is possible to increase the molecular weight distribution Mw / Mn by mixing multiple cellulose acetate flakes with different median degrees of polymerization. A molecular weight distribution Mw / Mn of approximately 3.5 or less can be obtained by adjusting the reaction conditions in the cellulose acetate production method described below. To obtain a molecular weight distribution Mw / Mn exceeding 3.5, a method of mixing multiple cellulose raw materials or a method of mixing multiple cellulose acetate flakes is effective.

[0043] The molecular weight and molecular weight distribution of cellulose acetate can be determined by a known method. Specifically, the molecular weight and molecular weight distribution of cellulose acetate are determined by size exclusion chromatography (GPC) measurement (GPC-light scattering method) using the following apparatus and conditions. Equipment: Shodex GPC "SYSTEM-21H" Solvent: Acetone Columns: 2 GMHxl (Tosoh), guard column (TSKgel guard column HXL-H manufactured by Tosoh) Flow rate: 0.8ml / min Temperature: 29℃ Sample concentration: 0.25% (wt / vol) Injection volume: 100μl Detection: MALLS (multi-angle light scattering detector) (Wyatt, "DAWN-EOS") MALLS correction standard material: PMMA (molecular weight 27600)

[0044] [Viscosity average degree of polymerization (DPv) of cellulose acetate] The viscosity-average degree of polymerization (DPv) of the cellulose acetate used in the resin composition of the present disclosure is not particularly limited, but is preferably 10 to 400. A resin composition containing cellulose acetate having a viscosity-average degree of polymerization in this range has excellent melt moldability. From this viewpoint, the viscosity-average degree of polymerization is more preferably 15 to 300, and even more preferably 20 to 200.

[0045] The viscosity-average degree of polymerization (DPv) is the intrinsic viscosity of cellulose acetate ([η], unit: cm 3 / g).

[0046] Intrinsic viscosity ([η], unit: cm 3 / g) can be determined in accordance with JIS-K-7367-1 and ISO 1628-1. Specifically, a sample solution is prepared using dimethyl sulfoxide (DMSO) as a solvent, and the logarithmic relative viscosity at 25°C measured using a size 1C Ubbelohde viscometer is divided by the concentration of the sample solution.

[0047] Using the obtained limiting viscosity number [η], the viscosity average molecular weight was calculated according to the following formula in accordance with the literature of Kamide et al. (Polymer Journal, 13, 421-431 (1981)). Viscosity average molecular weight = (intrinsic viscosity number [η] / 0.171) (1 / 0.61)

[0048] Using the calculated viscosity average molecular weight, the viscosity average degree of polymerization (DPv) was calculated according to 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.

[0049] [Method for producing cellulose acetate] Cellulose acetate with a total acetyl substitution degree of 1.9 to 2.6, a number-average molecular weight of 45,000 or more, and a weight-average molecular weight of 70,000 or more can be produced by known cellulose acetate production methods. Examples of such production methods include the so-called acetic acid process, which uses acetic anhydride as the acetylating agent, acetic acid as the diluent, and sulfuric acid as the catalyst. The basic steps of the acetic acid process are: (1) a pretreatment step in which a pulp raw material (dissolving pulp) with a relatively high α-cellulose content is disintegrated and crushed, and then acetic acid is sprayed and mixed with the pulp; (2) an acetylation step in which the pretreated pulp (1) is reacted with a mixed acid consisting of acetic anhydride, acetic acid, and an acetylation catalyst (e.g., sulfuric acid); (3) an aging step in which cellulose acetate is hydrolyzed to cellulose acetate with the desired acetylation degree; and (4) a post-treatment step in which the cellulose acetate after the hydrolysis reaction is precipitated, purified, stabilized, and dried from the reaction solution. The total acetyl substitution degree can be adjusted by adjusting the conditions of the aging step (e.g., time, temperature, etc.).

[0050] [Method of producing resin composition] The resin composition of the present disclosure can be obtained by melt-kneading cellulose acetate having a total acetyl substitution degree of 1.9 to 2.6, a number-average molecular weight of 45,000 or more, and a weight-average molecular weight of 70,000 or more with the above-mentioned plasticizer. Preferably, this resin composition is obtained by mixing cellulose acetate and the plasticizer, followed by melt-kneading. By mixing before melt-kneading, the plasticizer and cellulose acetate blend more uniformly and in a short time, and the resulting kneaded product becomes homogenous, resulting in a resin composition with improved melt fluidity and processing accuracy.

[0051] A known mixer such as a Henschel mixer can be used to mix the cellulose acetate and the plasticizer. 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 the cellulose acetate does not melt, for example, 20°C or higher and lower than 200°C.

[0052] An extruder such as a twin-screw extruder can be used to melt-knead cellulose acetate and a plasticizer, or to melt-knead cellulose acetate and a plasticizer after mixing. From the viewpoint of uniformity of the kneaded mixture and suppression of thermal degradation, the kneading temperature (cylinder temperature) of the extruder is preferably 160°C or higher and 230°C or lower, more preferably 170°C or higher and 210°C or lower. The melting point of cellulose acetate is approximately 230°C to 280°C, depending on the degree of substitution. This is close to the decomposition temperature of cellulose acetate, and melt-kneading is usually difficult within this temperature range. However, in the resin composition of the present disclosure, the plasticization temperature is lowered by the plasticizer, so a sufficiently uniform kneaded mixture can be obtained at temperatures of 230°C or lower. For example, when melt-kneading is performed using a twin-screw extruder, the kneading temperature (also referred to as the cylinder temperature) may be 200°C. The kneaded mixture may be extruded into strands from a die attached to the tip of the twin-screw extruder and then hot-cut into pellets. At this time, the die temperature may be about 200°C to 220°C.

[0053] The amount of plasticizer blended with respect to the entire resin composition obtained is preferably 5% by weight or more and 50% by weight or less. When two or more plasticizers are blended, the total amount is preferably 5% by weight or more and 50% by weight or less. This resin composition may be blended with plasticizers other than the above-mentioned plasticizers, and may also be blended with known additives such as colorants, ultraviolet absorbers, light stabilizers, antioxidants, heat stabilizers, optical property adjusters, fluorescent brighteners, and flame retardants, within a range that does not impair the effects of the present disclosure.

[0054] [film] From another perspective, the present disclosure relates to a film using the aforementioned cellulose acetate resin composition. The film obtained by using the resin composition of the present disclosure in a melt film-forming method, which has been difficult to achieve in the past, is thin and free from coloration due to thermal decomposition products. The thickness of this film is preferably 150 μm or less, more preferably 10 μm to 150 μm, even more preferably 10 μm to 100 μm, and particularly preferably 10 μm to 90 μm. As described below, by using a stretching or inflation method after melt extrusion, the film thickness can be reduced to 10 μm to 50 μm, or even 10 μm to 30 μm, depending on the application.

[0055] Films obtained using the resin composition of the present disclosure have excellent marine biodegradability. Preferably, 40% by weight or more of the organic carbon content decomposes into CO2 within 180 days in the ocean, more preferably 50% by weight or more, and particularly preferably 60% by weight or more. Marine biodegradability can be measured using a method in accordance with ASTM D6691.

[0056] [Film forming method] The film of the present disclosure is produced by a melt film-forming method without using solvents or plasticizers that have a large environmental impact. Specifically, the film is produced by heating and melting the resin composition of the present disclosure and extruding it through a press or a T-die. The melting temperature is preferably 210°C or lower, more preferably 200°C or lower, and even more preferably 190°C or lower. From the viewpoint of ease of film formation, the melting temperature is preferably 160°C or higher.

[0057] For example, using a known melt extruder, a melt is extruded through a T-die onto a roll adjusted to a predetermined temperature and solidified to obtain an unstretched film. The film thickness can be adjusted by changing the melt temperature and die lip. A thinner stretched film can be obtained by increasing the roll speed after die extrusion.

[0058] The film of the present disclosure may be obtained by an inflation method. The inflation method makes it possible to form a film in a tubular shape. By fusing this tube with a fusion seal, a bag with a handle can be easily formed. By forming a film using the highly biodegradable resin composition of the present disclosure by an inflation method, it is possible to produce a shopping bag or a garbage bag with a low environmental impact.

[0059] The resin composition according to the present disclosure can be suitably used as a base material for, for example, tableware, packaging containers, trays, agricultural materials, fishing materials, office automation parts, home appliance parts, automotive components, daily necessities, stationery, and the like. [Example]

[0060] The effects of the present disclosure will be clarified below by examples, but the present disclosure should not be interpreted as being limited based on the description of these examples.

[0061] [Test 1: Plasticity evaluation test] [Example 1-1] Cellulose acetate (manufactured by Daicel Corporation; total acetyl substitution degree DS = 2.45, number average molecular weight Mn = 85,000, weight average molecular weight Mw = 190,000, Mw / Mn = 2.2) 75 parts by weight and triethylene glycol diacetate (manufactured by TCI, molecular weight 234) 25 parts by weight 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 and plasticizer. The resulting mixture was fed into a twin-screw extruder (manufactured by Ikegai Corporation, product name "PCM30", cylinder temperature: 210 °C, die temperature: 210 °C), melt-kneaded, extruded, and pelletized to obtain a kneaded mixture.

[0062] [Examples 1-2 to 1-3 and Comparative Examples 1-1 to 1-6] A kneaded material was obtained in the same manner as in Example 1-1, except that the plasticizer was changed as shown in Table 1-2 below.

[0063] [Evaluation of plasticity] The transparency of the kneaded materials of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-6 was visually observed. Kneaded materials in which no opaque parts were observed were evaluated as having high plasticity (◯), and kneaded materials in which even a slight amount of opaque parts were observed were evaluated as having low plasticity (×). The evaluation results are shown in Table 1-2 below.

[0064] [MFR measurement] The MFR (g / 10 min) of the kneaded products of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-4, which were evaluated as having high plasticity, was measured at a temperature of 190°C and a load of 5 kg in accordance with the method described in JIS K7210-1, "Plastics - Determination of melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastic plastics - Part 1: Standard test method." A melt indexer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used for the measurement. The results obtained are shown in Table 1-2 below as MI values ​​(190°C, 5 kg). In addition, the state of the strands obtained during the MFR measurement was observed, and those with a uniform surface were evaluated as good (◯), and those with oily adhesion on the surface were evaluated as poor (×). Comparative Example 1-5 could not be measured under the same conditions due to its low melt fluidity.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Test 2: Film Creation Test] [Example 2-1] In the same manner as in Example 1-1, cellulose acetate (manufactured by Daicel Corporation: total degree of acetyl substitution DS = 2.45, number average molecular weight Mn = 85,000, weight average molecular weight Mw = 190,000, Mw / Mn = 2.2) and triethylene glycol diacetate (manufactured by TCI, molecular weight 234) were melt-kneaded to obtain pellets. The obtained pellets were fed into a melt extruder (twin-screw extruder) controlled at the temperature shown in Table 3 below, and the molten resin composition was extruded through a T-die onto a roll to form an unstretched film. The obtained film was colorless and transparent, and its thickness was 100 μm.

[0068] [Example 2-2] A 100 μm thick film (colorless and transparent) was obtained in the same manner as in Example 2-1, except that cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.15, number average molecular weight Mn = 81,000, weight average molecular weight Mw = 180,000, Mw / Mn = 2.2) was used.

[0069] [Examples 2-3, 2-4, and 2-9 to 2-12 and Comparative Examples 2-1 to 2-4] A 100 μm-thick film (colorless and transparent) was obtained in the same manner as in Examples 2-1 and 2-2, except that the specifications of the cellulose acetate and plasticizer were as shown in Tables 3 and 4. In Examples 2-3, 2-9, and 2-11 and Comparative Examples 2-1 to 2-4, cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.45, number average molecular weight Mn = 85,000, weight average molecular weight Mw = 190,000, Mw / Mn = 2.2) was used, and in Examples 2-4, 2-10, and 2-12, cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.15, number average molecular weight Mn = 81,000, weight average molecular weight Mw = 180,000, Mw / Mn = 2.2) was used. In Comparative Examples 2-1 to 2-4, insoluble matter was found in the obtained molded products, and it was confirmed that it was difficult to form a film with a uniform thickness at a temperature below 200°C.

[0070] [Examples 2-5 to 2-8 and 2-13 to 2-16] Stretched films having the thicknesses shown in Table 3 were obtained in the same manner as in Examples 2-1 and 2-2, except that the specifications of the cellulose acetate and plasticizer were as shown in Tables 3 and 4 below and the roll speed after extrusion from the T-die was changed. Cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.45, number average molecular weight Mn = 85,000, weight average molecular weight Mw = 190,000, Mw / Mn = 2.2) was used in Examples 2-5, 2-6, 2-13, and 2-14, and cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.15, number average molecular weight Mn = 81,000, weight average molecular weight Mw = 180,000, Mw / Mn = 2.2) was used in Examples 2-7, 2-8, 2-15, and 2-16.

[0071] [Comparative Examples 2-5 to 2-8] In Comparative Examples 2-5 and 2-7, the specifications of the cellulose acetate were as shown in Table 4 below, and a 100 μm thick film (colorless and transparent) was obtained in the same manner as in Comparative Example 2-1 except that the temperature of the melt extruder was controlled at 210° C. However, the workability was poor due to the high melt viscosity. In Comparative Examples 2-6 and 2-8, an attempt was made to reduce the thickness by changing the roll speed after extrusion from the T-die, but many chips occurred in the obtained film, making it unsuitable for practical use. In Comparative Examples 2-5 and 2-6, cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.45, number average molecular weight Mn = 85,000, weight average molecular weight Mw = 190,000, Mw / Mn = 2.2) was used, and in Comparative Examples 2-7 and 2-8, cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.15, number average molecular weight Mn = 81,000, weight average molecular weight Mw = 180,000, Mw / Mn = 2.2) was used.

[0072] [Table 3]

[0073] [Table 4]

[0074] [Test 3: Blown film creation test] [Example 3-1] As in Example 2-3, 67 parts by weight of cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.45, number average molecular weight Mn = 85,000, weight average molecular weight Mw = 190,000, Mw / Mn = 2.2) and 33 parts by weight of triethylene glycol diacetate (manufactured by TCI, molecular weight 234) 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 and plasticizer. The resulting mixture was fed into a twin-screw extruder (manufactured by Ikegai Corporation, product name "PCM30", cylinder temperature: 170 ° C, die temperature: 170 ° C), melt-kneaded, and extruded to obtain pellets. The pellets were placed in an inflation molding machine (die diameter 30 mm, lip width 1 mm) and an inflation film with a thickness of 100 μm and a folded width of 80 mm was obtained at a first half zone temperature of 170° C., a second half zone temperature of 170° C., and a die temperature of 170° C. The film was well formed and the obtained film was colorless and transparent.

[0075] [Examples 3-2 to 3-4] Except for the specifications of cellulose acetate and plasticizer shown in Table 5 below, inflation films with a thickness of 100 μm and a folded width of 80 mm were obtained in the same manner as in Example 3-1. The film formation state was good in all cases, and the obtained films were colorless and transparent. In Examples 3-2 and 3-4, cellulose acetate (manufactured by Daicel Corporation: total acetyl substitution degree DS = 2.15, number average molecular weight Mn = 81,000, weight average molecular weight Mw = 180,000, Mw / Mn = 2.2) was used.

[0076] [Table 5]

[0077] [Test 4: Strength evaluation test] [Examples 4-1 to 4-4 and Comparative Examples 4-1 to 4-4] Cellulose acetate and a plasticizer were blended in a dry state according to the composition shown in Table 6 below, dried at 80°C for 3 hours or more, and then stirred and mixed using a Henschel mixer to obtain a mixture of cellulose acetate and a plasticizer. The resulting mixture was fed to a twin-screw extruder (manufactured by Ikegai Corporation, product name "PCM30", cylinder temperature: 210°C, die temperature: 210°C), melt-kneaded, and extruded to obtain pellets of the kneaded product.

[0078] (Creating dumbbell pieces) The pellets of the examples and comparative examples were injection molded (at 210° C.) to prepare dumbbell-shaped A-type test pieces (thickness 4 mm) as specified in ISO527.

[0079] (Creating film-like test pieces) The pellets of the examples and comparative examples were fed into a melt extruder (twin-screw extruder), and the molten resin composition was extruded from a T-die onto a roll at a first half zone temperature of 190°C, a second half zone temperature of 200°C, and a die temperature of 200°C, to obtain a film having a thickness of 100 μm.

[0080] [Tensile test] The tensile strength (maximum strength: MPa) of the dumbbell specimens and films of the examples and comparative examples was measured at room temperature (20°C ± 5°C) according to the method described in ISO 527. A tensile tester manufactured by A&D Co., Ltd. was used for the measurements. The test conditions were as follows: Tensile speed: 50 mm / min Grip distance: 115 mm Each measurement was carried out five times, and the average values ​​were calculated and the results are shown in Table 6. The film strength is the maximum strength in the machine direction (extrusion direction).

[0081] [Table 6]

[0082] (summary) As shown in Table 1-2, the resin compositions of Examples 1-1 to 1-3 were found to have high plasticity and exhibit higher melt fluidity (MI value) at a temperature of 190°C than the resin compositions of the comparative examples. Furthermore, as shown in Table 3, the resin compositions of Examples 2-1 to 2-16 were capable of good melt film formation at temperatures below 200°C. Furthermore, as in Examples 2-5 to 2-8 and 2-13 to 2-16, the melt tension of the molten material was high, making it possible to stretch the molten material to a thickness of less than 100 μm. On the other hand, as shown in Table 4, the resin compositions of Comparative Examples 2-1 to 2-4 were difficult to form into films at melting temperatures below 200°C. As in Comparative Examples 2-5 to 2-8, films could be formed at melting temperatures of 200°C or higher, but the high melt viscosity made workability poor and thin films could not be formed. Furthermore, as shown in Table 5, it was confirmed that the resin compositions of the examples were applicable to inflation film formation at temperatures below 200°C. Furthermore, as shown in Table 6, it was confirmed that the resin compositions of the Examples had higher tensile strength and better mechanical properties than the Comparative Examples.

[0083] As shown in Tables 1 to 6, the resin compositions of the examples were rated higher than the resin compositions of the comparative examples. These evaluation results clearly demonstrate the superiority of the present disclosure. [Industrial Applicability]

[0084] The resin composition described above can be applied to various fields using the melt film-forming method.

Claims

1. The present invention comprises a cellulose acetate having a total degree of acetyl substitution of 1.9 or more and 2.6 or less, and a plasticizer, The cellulose acetate has a number average molecular weight Mn of 45,000 or more and 125,000 or less, and a weight average molecular weight Mw of 70,000 or more and 250,000 or less, The plasticizer is (1) An ether-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is etherified, the degree of polymerization of this polyalkylene glycol is 3 or more but less than 10, and the terminal group does not contain an aromatic ring. and (2) An ester-based plasticizer in which at least one terminal hydroxyl group of a polyalkylene glycol is esterified, the degree of polymerization of this polyalkylene glycol is 3 or more but less than 10, and the terminal group does not contain an aromatic ring. A cellulose acetate resin composition selected from the following:

2. 2. The resin composition according to claim 1, wherein the total content of the plasticizer is 5% by weight or more and 50% by weight or less based on the total weight of the resin composition.

3. 3. The resin composition according to claim 1, wherein the polyalkylene glycol has an alkyleneoxy group having 2 to 4 carbon atoms as a repeating unit.

4. 4. The resin composition according to claim 1, wherein the ether-based plasticizer has an ether substituent which is a hydrocarbon group having a molecular weight of 150 or less.

5. The resin composition according to claim 4, wherein the hydrocarbon group is an alkyl group.

6. 6. The resin composition according to claim 1, wherein the ester-based plasticizer is a polyalkylene glycol esterified with a carboxylic acid having a molecular weight of 150 or less.

7. The resin composition according to claim 6, wherein the carboxylic acid is a saturated fatty acid.

8. The resin composition according to claim 1 , wherein the cellulose acetate has a molecular weight distribution Mw / Mn of more than 1.

7.

9. A film having a thickness of 10 μm or more and 150 μm or less, obtained using the resin composition according to any one of claims 1 to 8.

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