Thermoplastic resin composition

Abstract

The thermoplastic resin composition of the present invention contains a cellulose ester, a polyester, and a plasticizer. The number average molecular weight of the plasticizer is 1000 or less. The amount of the polyester is 120 parts by weight or less relative to 100 parts by weight of the cellulose ester. The amount of the plasticizer is less than 100 parts by weight relative to 100 parts by weight of the cellulose ester.

Description

TECHNICAL FIELD

[0001] The present application relates to a thermoplastic resin composition. In detail, the present application relates to a thermoplastic resin composition comprising a cellulose ester. BACKGROUND

[0002] Most cellulose esters have poor thermal melt properties due to hydrogen bonding caused by the residual hydroxyl groups in the molecular chain. In particular, there is a tendency for the lower the degree of substitution of the cellulose ester, the higher the melting temperature. Furthermore, if the degree of substitution of the cellulose ester is high, its crystallinity becomes high, and thus there is a tendency for the solubility and melt properties to decrease. In the past, studies have been conducted to improve the processability by adding a plasticizer to the cellulose ester to lower the melting temperature, but the resulting molded articles have insufficient elongation and the like, and thus there are problems particularly in the processability of films and sheets having a thin film thickness.

[0003] On the other hand, cellulose esters such as cellulose acetate are known to have biodegradability and are decomposed using activated sludge. In recent years, due to increasing concerns about the global environment, biodegradable molded articles are desired in various technical fields.

[0004] For example, in Japanese Patent Application Publication No. 2001-294792 (Patent Literature 1), a biodegradable coating agent is disclosed, which is characterized by containing: at least one biodegradable resin selected from polylactic acid, cellulose acetate, polyvinyl alcohol, polycaprolactone, polybutylene succinate, and polyethylene succinate; and an edible coloring agent. Furthermore, in Japanese Patent Application Publication No. 2003-276094 (Patent Literature 2), a foamed molded body is disclosed, which is formed by mixing and foaming a water solution of a binder selected from at least one component selected from polyvinyl alcohol and / or starch, polyethylene glycol, carboxymethyl cellulose, polyethylene succinate, polybutylene succinate, polybutylene succinate / adipate, polycaprolactone, cellulose acetate, and polylactic acid, and a fibrous substance.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Publication No. 2001-294792

[0008] Patent Literature 2: Japanese Patent Application Publication No. 2003-276094 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] The biodegradable coating agent disclosed in Patent Literature 1 is targeted for application to inks, paints, and the like, and cannot be applied to molded articles such as films. The molded body disclosed in Patent Literature 2 is a porous body obtained by mixing a binder composed of a biodegradable polymer and a fibrous substance, and is not a technology that can be applied to molded articles such as films obtained by melt molding.

[0011] An object of the present disclosure is to provide a thermoplastic resin composition that enables a molded article having excellent biodegradability and good elongation to be obtained.

[0012] Technical Solution

[0013] The thermoplastic resin composition of the present disclosure contains a cellulose ester, a polyester, and a plasticizer. The number average molecular weight of the plasticizer is 1000 or less. The amount of the polyester is 120 parts by weight or less relative to 100 parts by weight of the cellulose ester. The amount of the plasticizer is less than 100 parts by weight relative to 100 parts by weight of the cellulose ester.

[0014] It is preferable that the total degree of substitution of the cellulose ester be 2.1 or more and 2.6 or less. It is preferable that the degree of substitution at 2 and the degree of substitution at 3 of the cellulose ester both be greater than the degree of substitution at 6.

[0015] It is preferable that the plasticizer be one or two or more selected from the group consisting of citric acid esters, glycerol esters, adipic acid esters, and polyethylene glycol esters.

[0016] It is preferable that the polyester have a structural unit resulting from the dehydration condensation of a dicarboxylic acid and a diol as a repeating structure. In the polyester, the proportion of a structural unit containing an aromatic ring relative to the total structural units can be 50% or less. It is preferable that the dicarboxylic acid be selected from the group consisting of succinic acid, adipic acid, and terephthalic acid. It is preferable that the diol be selected from the group consisting of ethylene glycol, propylene glycol, and butanediol.

[0017] It is preferable that the polyester be selected from the group consisting of polybutylene succinate (PBS), poly(butylene succinate-co-adipate) (PBSA), and poly(butylene adipate-co-terephthalate) (PBAT).

[0018] In the thermoplastic resin composition of the present disclosure, the cellulose ester can also be cellulose acetate.

[0019] Advantageous Effects

[0020] According to the thermoplastic resin composition of the present disclosure, a molded article having excellent biodegradability and good elongation can be obtained by melt molding. In particular, the thermoplastic resin composition of the present disclosure can be preferably used as a material for a melt-molded article, an injection-molded article, and in particular, a molded article having a thin film thickness such as a film or a sheet. DETAILED DESCRIPTION

[0021] Hereinafter, one example of the preferred embodiment will be described in detail. Each of the configurations in each of the embodiments and combinations thereof are one example, and addition, omission, substitution, and other changes can be made to the configurations as appropriate without departing from the scope of the gist of the present disclosure. The present disclosure is not limited by the embodiments, but is defined only by the claims. Furthermore, the various aspects disclosed in the present specification can be combined with any of the other features disclosed in the present specification.

[0022] Note that, in the present specification, "X to Y" indicating a range means "X or more and Y or less". Furthermore, unless otherwise noted, the test temperature is room temperature (20°C ± 5°C) throughout.

[0023] [Thermoplastic resin composition]

[0024] The thermoplastic resin composition of the present disclosure contains a cellulose ester, a polyester, and a plasticizer. The number average molecular weight of the plasticizer is 1000 or less. The amount of the polyester is 120 parts by weight or less with respect to 100 parts by weight of the cellulose ester. The amount of the plasticizer is less than 100 parts by weight with respect to 100 parts by weight of the cellulose ester.

[0025] The thermoplastic resin composition can be melt-formed in a lower temperature region by containing the plasticizer in the amount described above. In the resin composition, the resulting molded product is imparted with good elongation by the polyester in the amount described above. Furthermore, the cellulose ester and the polyester have good biodegradability. The plasticizer having a number average molecular weight of 1000 or less does not hinder the biodegradability of the cellulose ester and the polyester. According to the thermoplastic resin composition of the present disclosure, a molded product having excellent biodegradability and good elongation can be obtained. By melt-forming the resin composition as a material, particularly, a film, a sheet, or the like having a thin film thickness can be obtained.

[0026] [Cellulose ester]

[0027] The cellulose ester has an acyl group as a substituent. As examples of the acyl group, acetyl group, propionyl group, butyryl group, carboxyl group, carboxymethyl group, 2-hydroxyethyl group, 2-hydroxypropyl group, methyl group, and the like can be listed. From the viewpoint of easily obtaining good biodegradability, as the substituent of the cellulose ester, an acetyl group, a propionyl group, and a butyryl group are preferred, and an acetyl group is more preferred. The cellulose ester can have two or more acyl groups. The cellulose ester can contain a substituent other than the acyl group within a range that does not hinder the effects of the present disclosure.

[0028] As a specific example of the cellulose ester contained in the thermoplastic resin composition of the present disclosure, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, and the like can be listed. From the aspect of being able to obtain a molded product having excellent strength, cellulose acetate is preferred.

[0029] [total degree of substitution]

[0030] The total degree of substitution of the cellulose ester is preferably 2.6 or less, more preferably 2.5 or less, and even more preferably 2.4 or less, from the viewpoint of improved biodegradability. The total degree of substitution of the cellulose ester is preferably 1.9 or more, more preferably 2.0 or more, and even more preferably 2.1 or more, from the viewpoint of high melt flowability. The cellulose ester having a total degree of substitution of 1.9 or more and 2.6 or less is preferred. The total degree of substitution of the cellulose ester can be 1.9 to 2.5, 1.9 to 2.4, 1.9 to 2.3, 2.0 to 2.6, 2.0 to 2.5, 2.0 to 2.4, 2.0 to 2.3, 2.1 to 2.6, 2.1 to 2.5, 2.1 to 2.4, or 2.1 to 2.3.

[0031] [degree of substitution at 2-position, 3-position, and 6-position]

[0032] The degree of substitution at 2-position, 3-position, and 6-position of the cellulose ester contained in the resin composition of the present disclosure is not particularly limited, and a cellulose ester in which both the degree of substitution at 2-position and the degree of substitution at 3-position are greater than the degree of substitution at 6-position is preferred from the viewpoint of improved biodegradability. Here, the degree of substitution at 2-position, 3-position, and 6-position refers to the average number of substituents of hydrogen atoms of the hydroxyl groups at 2-position, 3-position, and 6-position of the repeating unit (glucopyranose unit) of the substituted cellulose.

[0033] It is preferred that the degree of substitution at 6-position of the cellulose ester is 0.8 or less, more preferably 0.75 or less, and even more preferably 0.7 or less. The degree of substitution at 6-position of the cellulose ester can be 0, or 0.1 or more.

[0034] [Method for measuring degree of substitution]

[0035] The degree of substitution of the cellulose ester can be measured by the following method. For example, it can be measured by NMR method according to the method of Tezuka (Carbonydr. Res. 273, 83 (1995)). That is, the free hydroxyl groups of the cellulose ester are acylated with carboxylic anhydride in pyridine. The kind of carboxylic anhydride to be used here should be selected according to the analysis target, for example, in the case of analyzing the acetyl degree of substitution of cellulose acetate, butyric anhydride is preferable, and in the case of analyzing the butyryl degree of substitution of cellulose butyrate, acetic anhydride is preferable. The obtained sample is dissolved in deuterated chloroform, and the degree of substitution is measured by NMR. 13C-NMR spectrum. In the case of citing acetyl group as an example of the substituent, the carbon signal of acetyl group appears in the region of 169 to 171 ppm in the order of 2-position, 3-position, 6-position from the high magnetic field. If other examples are cited, in the case of analyzing the propionyl substitution degree in the cellulose ester having propionyl group or the cellulose ester not having propionyl group treated with propionic anhydride, the signal of the carbonyl carbon of propionyl group appears in the region of 172 to 174 ppm in the same order. The total substitution degree of the cellulose ester treated with carboxylic anhydride according to the method of Tezuka's method is 3.0, and therefore, if the sum of the area of the carbonyl carbon signal of the acyl group originally possessed by the cellulose ester and the carbonyl signal of the acyl group introduced by the treatment with carboxylic anhydride is normalized to 3.0, the existence ratio of each acyl group at each corresponding position (in other words, the area ratio of each signal) is obtained, which can be used as each acyl substitution degree at 2-position, 3-position, 6-position of the glucose ring in the cellulose ester. Note that it is self-evident that the substituent containing acyl group which can be analyzed by this method is only the substituent not corresponding to the carboxylic anhydride used in the treatment of the analysis target. In addition, the analysis method is not limited to C-NMR, and 13 C-NMR, but also 1 H-NMR analysis.

[0036] [Viscosity average polymerization degree of cellulose ester]

[0037] The viscosity average polymerization degree of the cellulose ester is not particularly limited, and is preferably 10 or more and 400 or less. The resin composition containing the cellulose ester having a viscosity average polymerization degree in this range is excellent in melt molding properties. From this viewpoint, the viscosity average polymerization degree is more preferably 15 or more and 300 or less, and further preferably 20 or more and 200 or less. The viscosity average polymerization degree of the cellulose ester can be 10 or more and 300 or less. It can be 10 or more and 200 or less, 15 or more and 400 or less, 15 or more and 200 or less, 20 or more and 400 or less, or 20 or more and 300 or less.

[0038] The viscosity average polymerization degree (DPv) is calculated based on the intrinsic viscosity number ([η], unit: cm 3 / g) of the cellulose ester.

[0039] The intrinsic viscosity number ([η], unit: cm 3 / g) is calculated according to JIS-K-7367-1 and ISO 1628-1. Specifically, a sample solution in which dimethyl sulfoxide (DMSO) is used as a solvent is prepared, and the logarithmic relative viscosity at 25°C measured by using an Ubbelohde viscometer is divided by the concentration of the sample solution.

[0040] Using the obtained intrinsic viscosity number [η], the viscosity average molecular weight was calculated according to the following equation based on the document by Kamide et al. (Polymer Journal, 13, 421-431 (1981)).

[0041] Viscosity average molecular weight = (intrinsic viscosity number [η] / 0.171) (1 / 0.61)

[0042] Using the calculated viscosity average molecular weight, the viscosity average degree of polymerization (DPv) was calculated according to the following equation.

[0043] Viscosity average degree of polymerization (DPv) = viscosity average molecular weight / (162.14 + 42.037 x DS)

[0044] Note that, in the equation, DS is the total degree of substitution of the cellulose ester.

[0045] [Weight average molecular weight of cellulose ester]

[0046] The weight average molecular weight of the cellulose ester is not particularly limited, and from the viewpoint of being able to obtain a molded product having excellent tensile properties, it is preferably 100,000 or more, more preferably 120,000 or more. From the viewpoint of being able to obtain moderate flowability at the time of melting, the weight average molecular weight of the cellulose ester is preferably 1,500,000 or less, more preferably 1,200,000 or less.

[0047] The weight average molecular weight of the cellulose ester can be calculated using a publicly known method. In detail, the weight average molecular weight of the cellulose ester is determined by performing size exclusion chromatography (GPC) measurement under the following apparatus and conditions (GPC-light scattering method).

[0048] Apparatus: GPC "SYSTEM-21H" by Shodex.

[0049] Solvent: Acetone.

[0050] Chromatography column: GMHxl (Tosoh) 2, guard column (TSKgel guard column HXL-H by Tosoh).

[0051] Flow rate: 0.8 ml / min.

[0052] Temperature: 29°C.

[0053] Sample concentration: 0.25% (wt / vol).

[0054] Injection amount: 100 μl.

[0055] Detection: MALLS (multi-angle light scattering detector) (DAWN-EOS by Wyatt).

[0056] Standard substance for MALLS correction: PMMA (molecular weight 27600).

[0057] [Content of cellulose ester]

[0058] The content of the cellulose ester in the thermoplastic resin composition of the present disclosure is preferably 30% by weight or more and 90% by weight or less with respect to the entire resin composition. From the viewpoint of obtaining a molded product with high strength, the content of the cellulose ester is more preferably 35% by weight or more. From the viewpoint of obtaining good elongation, the content of the cellulose ester is more preferably 85% by weight or less. The content of the cellulose ester in the resin composition of the present disclosure can be 30% by weight to 85% by weight, can be 35% by weight to 90% by weight, or can be 35% by weight to 85% by weight. In the case where two or more kinds of cellulose esters are used in combination, the total amount thereof is preferably adjusted to the above numerical range.

[0059] [Polyester]

[0060] The polyester contained in the thermoplastic resin composition of the present disclosure is not particularly limited, and a polyester that exhibits biodegradability can be preferably used. It can be an aliphatic polyester, or an aliphatic-aromatic polyester. Furthermore, from the viewpoint of the polymer structure, it can be a polyester having a structural unit derived from polycondensation of a hydroxycarboxylic acid as a repeating unit, or a polyester having a structural unit derived from dehydration condensation of a dicarboxylic acid and a diol as a repeating unit.

[0061] As the polyester having a structural unit derived from polycondensation of a hydroxycarboxylic acid as a repeating unit, polyglycolic acid, polylactic acid, poly(β-hydroxybutyric acid), poly(β-hydroxyvaleric acid), poly(lactic acid-co-glycolic acid), poly(β-hydroxybutyric acid-co-β-hydroxyvaleric acid), poly(β-propiolactone), poly(ε-caprolactone), and the like can be exemplified. As the polyester having a structural unit derived from dehydration condensation of a dicarboxylic acid and a diol as a repeating unit, polyethylene succinate, polybutylene succinate, poly(butylene succinate-co-adipate), poly(butylene adipate terephthalate), and the like can be exemplified. From the viewpoint that polymer design is easy, the polyester having a structural unit derived from dehydration condensation of a dicarboxylic acid and a diol as a repeating unit is preferred.

[0062] The polyester having a structural unit derived from dehydration condensation of a dicarboxylic acid and a diol as a repeating unit is preferred. From the aspects that biodegradability is excellent and the load on the environment is small, the proportion of the structural unit containing an aromatic ring with respect to the total structural units is preferably 50% or less, more preferably 45% or less, and further preferably 40% or less, and can also be 0%.

[0063] As the dicarboxylic acid component constituting the polyester, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid, and the like can be exemplified. The dicarboxylic acid is preferably selected from the group consisting of succinic acid, adipic acid, and terephthalic acid.

[0064] As the diol component constituting the polyester, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, ethyl propylene glycol, butylene glycol, and the like can be exemplified. The diol is preferably selected from the group consisting of ethylene glycol, propylene glycol, and butylene glycol.

[0065] From the viewpoint of imparting good elongation to the obtained molded product, the polyester is preferably selected from the group consisting of polybutylene succinate (PBS), poly(butylene succinate-co-butylene adipate) (PBSA), and poly(butylene adipate-co-terephthalate) (PBAT). Two or more kinds of the polyester can be used in combination. Other polyesters can also be further incorporated within a range not impeding the effects of the present disclosure.

[0066] [Weight average molecular weight of the polyester]

[0067] From the viewpoint of obtaining a molded product excellent in strength, the weight average molecular weight of the polyester is preferably 100,000 or more, more preferably 120,000 or more. From the viewpoint of easy mixing with the cellulose ester, the weight average molecular weight of the polyester is preferably 1,000,000 or less, more preferably 800,000 or less. The weight average molecular weight of the polyester is measured by the method described with respect to the cellulose ester.

[0068] From the viewpoint of uniformly mixing the cellulose ester and the plasticizer, the number of carbon atoms of the dicarboxylic acid component constituting the polyester is preferably 8 or less, more preferably 6 or less.

[0069] From the viewpoint of uniformly mixing the cellulose ester and the plasticizer, the number of carbon atoms of the diol component constituting the polyester is preferably 8 or less, more preferably 6 or less.

[0070] [Content of the polyester]

[0071] In the thermoplastic resin composition of the present disclosure, the amount of the polyester is 120 parts by weight or less relative to 100 parts by weight of the cellulose ester, while from the viewpoint of obtaining high strength, the amount is preferably 100 parts by weight or less, more preferably 80 parts by weight or less. From the viewpoint of imparting good elongation to the molded article, the amount of the polyester is preferably 3 parts by weight or more, more preferably 5 parts by weight or more, and further preferably 10 parts by weight or more, relative to 100 parts by weight of the cellulose. The amount of the polyester relative to 100 parts by weight of the cellulose ester can be more than 0 and 120 parts by weight or less, can be more than 0 and 100 parts by weight or less, can be more than 0 and 80 parts by weight or less, can be 3 parts by weight to 120 parts by weight, can be 3 parts by weight to 100 parts by weight, can be 3 parts by weight to 80 parts by weight, can be 5 parts by weight to 120 parts by weight, can be 5 parts by weight to 100 parts by weight, can be 5 parts by weight to 80 parts by weight, can be 10 parts by weight to 120 parts by weight, can be 10 parts by weight to 100 parts by weight, or can be 10 parts by weight to 80 parts by weight. In the case where two or more kinds of polyester are blended, the total amount thereof is adjusted to the range described above.

[0072] [Plasticizer]

[0073] The plasticizer contained in the thermoplastic resin composition of the present disclosure is a compound having a number average molecular weight of 1000 or less, while from the viewpoint of obtaining a large effect of improving the plasticity of cellulose acetate, the number average molecular weight is preferably 800 or less, more preferably 700 or less. From the viewpoint of reducing bleeding from the obtained molded article, the number average molecular weight of the plasticizer is preferably 50 or more, more preferably 100 or more, and particularly preferably 200 or more. The number average molecular weight of the plasticizer is measured by the method described above with respect to the cellulose ester.

[0074] The plasticizer contained in the thermoplastic resin composition of the present disclosure is not particularly limited as long as the number average molecular weight is 1000 or less, and a plasticizer that improves the plasticity of cellulose acetate is preferred, and a plasticizer that improves the plasticity of both cellulose acetate and polyester is more preferred. A plasticizer selected from the group consisting of citric acid esters, glycerol esters, adipic acid esters, and polyethylene glycol esters is preferred. Two or more kinds of plasticizers can be used in combination. Other plasticizers can also be further contained within a range that does not hinder the effects of the present disclosure.

[0075] As specific examples of the citric acid esters, acetyltriethyl citrate, acetyltributyl citrate, isodecyl citrate, isopropyl citrate, triethyl citrate, triethylhexyl citrate, tributyl citrate, and the like can be given. As specific examples of the glycerol esters, glycerol triacetate, glycerol diacetate, glycerol monoacetate, and the like can be given. As specific examples of the adipic acid esters, dimethyl adipate, dibutyl adipate, diisostearyl adipate, diisodecyl adipate, diisononyl adipate, diisobutyl adipate, diisopropyl adipate, diethylhexyl adipate, dioctyl adipate, dioctyldodecyl adipate, didecyl adipate, dihexyldecyl adipate, and the like can be given. As specific examples of the polyethylene glycol esters, triethylene glycol monoacetate, triethylene glycol diacetate, triethylene glycol dipropionate, triethylene glycol dibenzoate, tetraethylene glycol diacetate, and the like can be given.

[0076] [Content of plasticizer]

[0077] In the thermoplastic resin composition of the present disclosure, the amount of the plasticizer is less than 100 parts by weight with respect to 100 parts by weight of the cellulose ester, while from the viewpoint of excellent extensibility, it is preferably 90 parts by weight or less, more preferably 80 parts by weight or less. From the viewpoint that the cellulose ester and the polyester can be uniformly melted, the amount of the plasticizer is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, particularly preferably 15 parts by weight or more with respect to 100 parts by weight of the cellulose. The amount of the plasticizer with respect to 100 parts by weight of the cellulose ester can be more than 0 and less than 100 parts by weight, can be more than 0 and 90 parts by weight or less, can be more than 0 and 80 parts by weight or less, can be 5 parts by weight or more and less than 100 parts by weight, can be 5 parts by weight to 90 parts by weight, can be 5 parts by weight to 80 parts by weight, can be 10 parts by weight or more and less than 100 parts by weight, can be 10 parts by weight to 90 parts by weight, can be 10 parts by weight to 80 parts by weight, can be 15 parts by weight or more and less than 100 parts by weight, can be 15 parts by weight to 90 parts by weight, or can be 15 parts by weight to 80 parts by weight. In the case where two or more kinds of plasticizers are used in combination, the total amount thereof is adjusted to the range described above.

[0078] [Method for producing thermoplastic resin composition]

[0079] The thermoplastic resin composition disclosed herein is obtained by melt-blending cellulose ester, polyester, and a plasticizer with a number average molecular weight of 1000 or less in the stated proportions. Preferably, the resin composition is obtained by melt-blending the cellulose ester and plasticizer, followed by melt-blending the resulting melt mixture with polyester. In this case, melt-blending can also be performed after mixing the cellulose ester and plasticizer. Through mixing before melt-blending, the plasticizer and cellulose ester are more uniformly integrated and fuse within a short time, thus homogenizing the resulting compound. This further facilitates melt-blending with polyester.

[0080] In mixing cellulose esters and plasticizers, known mixers such as Henschel mixers can be used. Both dry and wet mixing methods can be employed. When using a mixer such as a Henschel mixer, the temperature inside the mixer is preferably a temperature at which the cellulose ester does not melt, for example, above 20°C and below 200°C.

[0081] In the melt blending of cellulose esters and plasticizers, and in the melt blending of cellulose esters and plasticizers with polyesters, extruders such as twin-screw extruders can be used. From the viewpoint of uniformity of the blend and suppression of thermal degradation, the blending temperature (barrel temperature) of the extruder is preferably 170°C or higher and 230°C or lower. When using a twin-screw extruder for melt blending, the blending temperature (also called the barrel temperature) can also be 200°C. After the blend is extruded into a rope-like form from the die mounted at the front end of the twin-screw extruder, it can also be hot-cut into granules. In this case, the die temperature can be around 220°C.

[0082] In the thermoplastic resin compositions disclosed herein, the amount of polyester incorporated is 120 parts by weight or less relative to 100 parts by weight of cellulose ester. When two or more polyesters are incorporated, their total amount is adjusted to 120 parts by weight or less.

[0083] In the thermoplastic resin compositions of this disclosure, the amount of plasticizer incorporated is less than 100 parts by weight relative to 100 parts by weight of cellulose ester. When two or more plasticizers are incorporated, their total amount is adjusted to less than 100 parts by weight.

[0084] Within the scope that does not impair the effects of the present invention, known additives such as colorants, ultraviolet absorbers, light stabilizers, antioxidants, heat stabilizers, optical property modifiers, fluorescent whitening agents, flame retardants, lubricants, hydrolysis inhibitors, and hydrophobic agents may also be added to the resin composition. In this case, it is preferable to add the additives such as cellulose esters, polyesters, and plasticizers in the resin composition in a manner that is 90% by weight or more.

[0085] [use]

[0086] The thermoplastic resin composition of the present disclosure can be melt-formed at a lower temperature. The thermoplastic resin composition of the present disclosure has moderate fluidity at the time of melting, and thus can also be preferably applied to injection molding. The molded product obtained using the thermoplastic resin composition has excellent biodegradability, and also has good elongation, and thus can be applied to the manufacture of films or sheets by injection molding and melt film formation. Furthermore, by stretching or blow molding after melt extrusion, a film that has been thinned can be produced.

[0087] The thermoplastic resin composition of the present disclosure can be preferably used, for example, as a material for tableware, packaging containers, trays, agricultural materials, fishery materials, parts for Office Automation (OA), building materials, medical parts, parts for household electrical appliances, automobile members, daily sundries, stationery, and eyeglass frames, and the like.

[0088] Examples

[0089] Hereinafter, the present application will be specifically described by way of examples, but the technical scope of the present application is not limited by these examples. Hereinafter, unless otherwise specified, the tensile property evaluation test was all performed indoors (temperature 25°C ± 5°C, humidity 50% RH).

[0090] [Example 1]

[0091] Cellulose acetate (total acetyl substitution degree = 2.44, 2-position substitution degree = 0.85, 3-position substitution degree = 0.85, 6-position substitution degree = 0.73, weight average molecular weight 175,000) 100 parts by weight was mixed with triacetin (manufactured by Daicel Corporation, molecular weight 218.21) 25 parts by weight as a plasticizer in a dry state, dried at 80°C for 3 hours or more, and further, mixed by stirring using a Henschel mixer to obtain a mixture of cellulose acetate and a plasticizer. The obtained mixture was supplied to a twin-screw extruder (manufactured by Kukye Co., Ltd., trade name "PCM30", barrel temperature: 200°C, die temperature: 220°C) to perform melt kneading, and the extruded strand-like material was hot cut to obtain granules.

[0092] The obtained granules were mixed with polybutylene succinate (manufactured by Sigma-Aldrich Japan K.K.) as a polyester in a dry state, and then supplied to a twin-screw extruder (PCM30 manufactured by Kukye Co., Ltd., barrel temperature 200°C, die temperature 220°C) to perform melt kneading and extrusion, thereby obtaining the thermoplastic resin composition of Example 1. The polybutylene succinate was compounded at 22 parts by weight with respect to 100 parts by weight of cellulose acetate.

[0093] [Example 2 and Comparative Examples 1 to 4]

[0094] The compositions of cellulose acetate, glyceryl triacetate, and polybutylene succinate were set to the amounts shown in Table 1 below. Otherwise, the thermoplastic resin compositions of Examples 2 and Comparative Examples 1-4 were obtained in the same manner as in Example 1. In Comparative Example 2, the cellulose acetate and polybutylene succinate were not uniformly melted.

[0095] [Evaluation of Tensile Properties]

[0096] The thermoplastic resin compositions of Examples 1-2 and Comparative Examples 1-4 were injection molded (barrel temperature 230°C, mold temperature 50°C) to produce dumbbell-shaped test pieces. The resin composition of Comparative Example 2 did not melt uniformly during molding and could not be molded into the shape of the mold; therefore, the following tensile test was not performed.

[0097] Tensile tests were conducted using a tensile testing machine (manufactured by A&D Corporation, trade name "TENSILON Universal Testing Machine") according to ISO 527-1 standard (tensile speed 10 mm / min, clamp spacing 115 mm). The breaking strength (unit: MPa), nominal strain at break (%), and modulus of elasticity (MPa) of Examples 1-2, Comparative Examples 1 and 3-4 were measured. The average values ​​of 5 measurements for each example are shown in Table 1 below.

[0098] [Table 1]

[0099]

[0100] (Summarize)

[0101] It was confirmed that the resin compositions of Examples 1 and 2 exhibit high plasticity and can be uniformly melt-molded at a temperature of 180°C. Furthermore, as shown in Table 1, the resin compositions of the Examples exhibit higher tensile strength and superior elongation (nominal strain at break) compared to Comparative Example 1 (which does not contain polyester) and Comparative Example 3 (which contains excessive polyester). Moreover, the resin compositions of the Examples exhibit a higher elastic modulus compared to Comparative Example 4 (which is polyester alone).

[0102] As shown in Table 1, the resin compositions of the examples received higher evaluations compared to the resin compositions of the comparative examples. Based on these evaluation results, the advantages of the present invention are evident.

[0103] Industrial availability

[0104] The resin compositions described above can be applied to various fields using melt molding, injection molding, and melt film forming.

Claims

1. A thermoplastic resin composition comprising a cellulose ester, a polyester, and a plasticizer. The cellulose ester is cellulose acetate with a total degree of substitution of 2.1 or higher and 2.6 or lower. The plasticizer has a number average molecular weight of less than 1000. The polyester has a weight-average molecular weight of 100,000 or more and 1,000,000 or less. The polyester has repeating structural units formed by the dehydration condensation of succinic acid and butanediol, and the proportion of structural units containing aromatic rings to all structural units is less than 40%. The amount of the polyester is 10 parts by weight or more and 100 parts by weight less than 100 parts by weight of the cellulose ester. The amount of the plasticizer is 15 parts by weight or more and less than 100 parts by weight relative to 100 parts by weight of the cellulose ester. The cellulose ester has a weight-average molecular weight of 100,000 or more and 1,500,000 or less. The content of the cellulose ester is 35% by weight or more and 85% by weight or less relative to the total resin composition.

2. The thermoplastic resin composition according to claim 1, wherein, The degree of substitution at the 2-position and the 3-position of the cellulose ester are both greater than the degree of substitution at the 6-position.

3. The thermoplastic resin composition according to claim 1 or 2, wherein, The plasticizer is selected from one or more of citrate, glyceryl ester, adipate and polyethylene glycol ester.

4. The thermoplastic resin composition according to claim 1 or 2, wherein, In the case of the polyester, the proportion of structural units containing aromatic rings to all structural units is 0%.

5. The thermoplastic resin composition according to claim 1 or 2, wherein, The polyester also has a repeating structure consisting of a dicarboxylic acid and a diol formed by dehydration condensation, wherein the dicarboxylic acid is selected from the group consisting of adipic acid and terephthalic acid, and the diol is selected from the group consisting of ethylene glycol and propylene glycol.

6. The thermoplastic resin composition according to claim 1 or 2, wherein, The polyester is selected from the group consisting of polybutylene succinate PBS and poly(butylene succinate-co-butylene adipate) PBSA.

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