JP5143374B2 - Biodegradable resin composition - Google Patents

Description

  The present invention relates to a biodegradable resin composition.

  General-purpose resins made from petroleum such as polypropylene and polyvinyl chloride are used in various fields such as daily goods, household appliances, automobile parts, building materials, and food packaging because of their good processability and durability. It is used. However, these resin products have a disadvantage of good durability at the stage of finishing and discarding their functions, and are inferior in degradability in nature, and thus may affect the ecosystem.

  In order to solve such problems, thermoplastic resins and biodegradable resins include polylactic acid and copolymers of lactic acid and other aliphatic hydroxycarboxylic acids, aliphatic polyhydric alcohols and aliphatic polycarboxylic acids. Biodegradable resin compositions such as aliphatic polyesters derived from have been developed.

  Among these biodegradable resin compositions, polylactic acid resin is limited to the field of hard molded products due to its brittleness, hardness and lack of flexibility, and lacks flexibility when molded into a film or the like. However, there is a problem such as whitening when it is bent, and the current situation is that it is not sufficiently spread in the soft or semi-rigid field.

  Various methods for adding a plasticizer have been proposed as techniques for applying polylactic acid resin to soft and semi-rigid fields. For example, a technique of adding a plasticizer such as tributyl acetylcitrate or diglycerin tetraacetate is disclosed. When these plasticizers are added to polylactic acid and a film or sheet is formed by extrusion or the like, good flexibility is obtained, but because the resin is in an amorphous state, flexibility due to temperature changes near the glass transition point is obtained. The property changes markedly (temperature sensitivity) and the heat resistance at high temperatures is insufficient, so that the physical properties change significantly depending on the season, making it difficult to use in a high temperature environment. In order to solve this problem, a method of improving the heat resistance and the like by crystallizing polylactic acid by adding a crystal nucleating agent such as talc (Patent Document 1) has been proposed. However, when the molded product is left under high temperature and high humidity, there is a problem that the plasticizer bleeds.

  Patent Document 2 discloses an aliphatic polyester having a weight average molecular weight of 100,000 or more and a residual monomer amount of 5000 ppm or less, a low molecular compound having an amide group, talc, a carbodiimide compound, an isocyanate compound, and an oxazoline. An aliphatic polyester composition comprising at least one hydrolysis inhibitor selected from the group consisting of a series compound is disclosed. However, an aliphatic polyester molded article having flexibility, good moldability, and excellent both heat resistance and impact resistance has not been obtained.

  Patent Document 3 discloses a biodegradable resin composition containing a polylactic acid resin, a specific plasticizer, and an organic nucleating agent. Although an aliphatic polyester molded article having good moldability and excellent heat resistance and impact resistance has been obtained, further improvement in heat resistance is desired.

Further, Patent Document 4 or Patent Document 5 discloses a resin composition characterized by containing a kenaf fiber obtained by subjecting a polylactic acid resin to delignification treatment or a kenaf fiber having an average fiber length of 3 to 5 mm. Yes. However, an aliphatic polyester molded article having good moldability and excellent both heat resistance and impact resistance has not been obtained.
Japanese Patent No. 3410075 JP 2005-60474 A International publication 05/108501 A1 pamphlet JP 2005-60556 A International publication 04/066282 A1 pamphlet

  An object of the present invention is to provide a biodegradable resin composition having good moldability and excellent heat resistance and impact resistance.

  The present invention is a biodegradable resin composition containing a biodegradable resin, a plasticizer, a vegetable fiber material, and a crystal nucleating agent, wherein the plasticizer has two or more ester groups in the molecule. The biodegradable resin composition which is a compound whose average added mole number of ethylene oxide is 3-9 is provided.

  The biodegradable resin composition of the present invention has good moldability and excellent heat resistance and impact resistance.

[Biodegradable resin]
The biodegradable resin used in the present invention has a biodegradability based on JIS K6953 (ISO 14855) “Aerobic and ultimate biodegradability and disintegration test under controlled aerobic compost conditions”. The polyester resin which has is preferable.

  The biodegradable resin used in the present invention is not particularly limited as long as it has a biodegradability capable of being decomposed into a low molecular weight compound with the participation of microorganisms in nature. For example, aliphatic polyesters such as polyhydroxybutyrate, polycaprolactone, polybutylene succinate, polybutylene succinate / adipate, polyethylene succinate, polylactic acid resin, polymalic acid, polyglycolic acid, polydioxanone, poly (2-oxetanone) Aliphatic aliphatic copolyesters such as polybutylene succinate / terephthalate, polybutylene adipate / terephthalate, polytetramethylene adipate / terephthalate; starch, cellulose, chitin, chitosan, gluten, gelatin, zein, soy protein, collagen, keratin, etc. And a mixture of the above natural polymer and the above aliphatic polyester or aliphatic aromatic copolyester.

  Among these, polylactic acid resin is preferable from the viewpoint of processability, economical efficiency, availability in large quantities, and physical properties. Here, the polylactic acid resin is polylactic acid or a copolymer of lactic acid and hydroxycarboxylic acid. Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid and the like, and glycolic acid and hydroxycaproic acid are preferable. A preferred molecular structure of polylactic acid is composed of 20 to 100 mol% of either L-lactic acid or D-lactic acid and 0 to 20 mol% of each enantiomer. The copolymer of lactic acid and hydroxycarboxylic acid is composed of 85 to 100 mol% of either L-lactic acid or D-lactic acid and 0 to 15 mol% of hydroxycarboxylic acid units. These polylactic acid resins can be obtained by dehydrating polycondensation using L-lactic acid, D-lactic acid and hydroxycarboxylic acid as a raw material by selecting those having the required structure. Preferably, it can be obtained by ring-opening polymerization by selecting a desired structure from lactide, which is a cyclic dimer of lactic acid, glycolide, which is a cyclic dimer of glycolic acid, and caprolactone. Lactide includes L-lactide which is a cyclic dimer of L-lactic acid, D-lactide which is a cyclic dimer of D-lactic acid, meso-lactide obtained by cyclic dimerization of D-lactic acid and L-lactic acid, and D-lactide. There is DL-lactide, which is a racemic mixture of lactide and L-lactide. Any lactide can be used in the present invention. However, the main raw material is preferably D-lactide or L-lactide.

  Among the polylactic acid resins, from the viewpoint of heat resistance, a crystal having an optical purity of 90% or more and a ratio of crystalline polylactic acid having an optical purity of 90% or more and polylactic acid having an optical purity of less than 90% by weight is preferable. Polylactic acid / polylactic acid having an optical purity of less than 90% = 100/0 to 10/90, preferably 100/0 to 25/75.

Examples of the commercially available polylactic acid resin include Mitsui Chemicals, Inc., trade name Lacia; Nature Works, trade name Nature works; Toyota Motor Corporation, U's, and the like.
Among these polylactic acid resins, from the viewpoint of crystallization speed and physical properties, L-lactic acid is a high-purity product, particularly a grade of L-lactic acid, particularly LACEA H-400, LACEA H-100, LACEA H-440, manufactured by Mitsui Chemicals. A polylactic acid resin having an L-lactic acid purity of 95% or more, particularly, LACEA H-400, LACEA H-100, manufactured by Mitsui Chemicals, Inc. is more preferable.

[Plasticizer]
The plasticizer used in the present invention is a compound having 2 or more ester groups in the molecule and having an average addition mole number of ethylene oxide of 3 to 9, and comprising succinic acid or adipic acid and polyethylene glycol monomethyl ether. It is preferably at least one selected from the group consisting of an ester and an ester of acetic acid and an ethylene oxide adduct of glycerin or ethylene glycol.

The average molecular weight of the plasticizer used in the present invention is preferably from 250 to 700, more preferably from 300 to 600, still more preferably from 350 to 550, particularly preferably from the viewpoint of bleed resistance and volatile resistance. Is 400-500. The average molecular weight can be obtained by calculating the saponification value by the method described in JIS K0070 and calculating from the following formula.
Average molecular weight = 56108 × (number of ester groups) / saponification value

  As a plasticizer used in the present invention, from the viewpoint of excellent moldability and impact resistance of the biodegradable resin molded product, an ester of acetic acid and glycerol with an average of 3 to 9 moles of ethylene oxide adduct, acetic acid and ethylene oxide Alkyl ether esters of polyhydric alcohols such as esters with polyethylene glycol having an average addition mole number of 4 to 9, esters of polyethylene glycol monomethyl ether with an average addition mole number of succinic acid and ethylene oxide of 2 to 4, adipic acid and Esters with polyethylene glycol monomethyl ether having an average addition mole number of ethylene oxide of 2-3, esters of polyethylene glycol monomethyl ether with 1,3,6-hexanetricarboxylic acid and ethylene oxide having an average addition mole number of 2-3, etc. Polyhydric carboxylic acids and polyethylene Esters of glycol monomethyl ether is more preferable. From the viewpoint of excellent moldability, impact resistance and bleed resistance of the plasticizer of the biodegradable resin molded article, an ester of acetic acid and glycerin with an average of 3 to 6 mol of ethylene oxide adduct, an average addition mol of acetic acid and ethylene oxide Esters of polyethylene glycol having a number of 4-6, esters of polyethylene glycol monomethyl ether having an average addition mole number of succinic acid and ethylene oxide of 2-3, esters of adipic acid and diethylene glycol monomethyl ether, 1, 3, 6 -Ester of hexanetricarboxylic acid and diethylene glycol monomethyl ether is more preferable. From the viewpoint of moldability of the biodegradable resin molded article, impact resistance, bleed resistance of the plasticizer, volatility resistance, and irritating odor, an ester of succinic acid and triethylene glycol monomethyl ether is particularly preferable.

  In addition, it is preferable that the ester of this invention is all the esterified saturated ester from a viewpoint of fully exhibiting the function as a plasticizer.

  The reason why the effect of the present invention is improved by a specific plasticizer is not clear, but the plasticizer is a polyoxyethylene chain having 2 or more ester groups in the molecule and an average added mole number of ethylene oxide of 3 to 9 If it is a compound having a (which preferably further has a methyl group, preferably 2 or more), its heat resistance and compatibility with the biodegradable resin will be good. Therefore, the bleed resistance is improved and the softening effect of the biodegradable resin is also improved. It is considered that when the biodegradable resin is crystallized, the growth rate is improved by improving the softening of the biodegradable resin. As a result, since the biodegradable resin retains flexibility even at a low mold temperature, crystallization of the biodegradable resin progresses in a short mold holding time, and good moldability is expected.

[Crystal nucleating agent]
In the present invention, as the crystal nucleating agent, at least one selected from an organic nucleating agent and an inorganic nucleating agent can be used.
As the organic nucleating agent used in the present invention, from the viewpoint of moldability, heat resistance, impact resistance of the biodegradable resin molded article and bloom resistance of the organic nucleating agent, ester groups, hydroxyl groups and An aliphatic compound having at least two groups selected from amide groups is preferred, and an aliphatic compound having two or more hydroxyl groups and two or more ester groups or amide groups is more preferred. The melting point of the organic nucleating agent is preferably 65 ° C or higher, more preferably 70 to 220 ° C, and still more preferably 80 to 190 ° C.

  The reason why the effect of the present invention is improved by the organic nucleating agent is not clear, but if it has two or more of the above functional groups, the interaction with the biodegradable resin is improved and the compatibility is improved. It is thought that it is caused by fine dispersion in the resin, and it is considered that dispersibility in the biodegradable resin is improved by having one or more, preferably two or more hydroxyl groups, and one or more amide groups or ester groups. It is considered that the compatibility with the biodegradable resin is preferably improved by having two or more. When the melting point of the crystal nucleating agent is higher than the heat treatment temperature and below the kneading temperature of the resin composition, the dispersibility is improved by dissolving the crystal nucleating agent at the time of kneading. And the heat treatment temperature is increased, which is preferable from the viewpoint of improving the crystallization speed. The preferred crystal nucleating agent is considered to precipitate a large number of fine crystals quickly in the cooling process from the resin melt state, and is also preferable from the viewpoint of improving transparency and crystallization speed.

  Examples of the organic nucleating agent used in the present invention include hydroxy fatty acid monoamides such as 12-hydroxy stearic acid monoethanolamide, methylene bis 12-hydroxy stearic acid amide, ethylene bis 12-hydroxy stearic acid amide, hexamethylene bis 12-hydroxy stearic acid. Examples thereof include hydroxy fatty acid bisamides such as amides and hydroxy fatty acid esters such as 12-hydroxystearic acid triglyceride. From the viewpoints of moldability, heat resistance, impact resistance and bloom resistance of organic nucleating agent of biodegradable resin moldings, ethylene bis 12-hydroxystearic acid amide, hexamethylene bis 12-hydroxystearic acid amide, 12-hydroxy Stearic acid triglyceride is preferred.

  Examples of the inorganic nucleating agent used in the present invention include silicates such as talc, smectite, kaolin, mica, and montmorillonite, silica, and inorganic compounds such as magnesium oxide. From the viewpoint of dispersibility, the average particle size is 0.1. An inorganic compound of ˜20 μm is preferable, and 0.1 to 10 μm is more preferable. Among inorganic compounds, silicate is preferable, talc or mica is more preferable, and talc is particularly preferable from the viewpoint of moldability and heat resistance of the biodegradable resin molded body. Silica is preferred from the viewpoint of moldability and transparency of the biodegradable resin molded product.

  In the present invention, it is preferable to use an organic nucleating agent and an inorganic nucleating agent in combination. By using an organic nucleating agent and an inorganic nucleating agent in combination, the moldability, heat resistance and impact resistance of the biodegradable resin molded body are increased. Is further improved, and the bloom resistance of the organic nucleating agent is also improved. The reason why the effect of the present invention is improved is not clear, but the biodegradable resin is crystallized by improving the dispersibility of the inorganic nucleating agent in the resin by using the inorganic nucleating agent and the organic nucleating agent together. It is thought that the starting point increases and microcrystallization occurs. As a result, since the crystallization speed is improved, crystallization of the biodegradable resin progresses with a short mold holding time and shows good moldability, and since the molded body is dense, the heat resistance and It is considered that the impact resistance is improved. In addition, the interaction between the hydrophilic surface of the inorganic nucleating agent and the polar group of the organic nucleating agent prevents the organic nucleating agent from precipitating (blooming) on the resin surface, thus preventing mold contamination. It is considered a thing.

[Plant fiber material]
The vegetable fiber material used in the present invention contains cellulose and is not particularly limited. Specific examples of vegetable fiber materials include okara, rice husks, wood chips, chips such as waste paper pulverized materials, cotton fibers, hemp fibers, bamboo fibers, wood fibers, kenaf fibers, jute fibers, banana fibers, coconuts Examples include plant fibers such as fibers, powders such as paper powder, wood powder, bamboo powder, and cellulose powder. From the viewpoint of moldability and heat resistance of biodegradable resin moldings, kenaf fibers, jute fibers, and wood powder And at least one selected from paper dust is preferable, and kenaf fibers and jute fibers are more preferable.

  The reason why the plant fiber material improves the heat resistance of the biodegradable resin molding is not clear, but the presence of the plant fiber material in the amorphous part alleviates softening of the amorphous part under high temperature. It is thought. Therefore, it is considered that the heat resistance of the amorphous part as well as the crystalline part having heat resistance is improved, and as a result, the heat resistance of the biodegradable resin molded product is improved.

  The plant fiber material used in the present invention may be subjected to delignification treatment by a known method such as heating and pressurization using a sodium hydroxide solution from the viewpoint of the color tone of the biodegradable resin molded product.

[Biodegradable resin composition]
The biodegradable resin composition of the present invention contains a biodegradable resin, a plasticizer, a vegetable fiber material, and a crystal nucleating agent. Particularly preferred combinations of the biodegradable resin, plasticizer, vegetable fiber material and crystal nucleating agent in the biodegradable resin composition of the present invention include polylactic acid as the biodegradable resin and succinic acid and triethylene glycol as the plasticizer. Ester with monomethyl ether, plant fiber material is kenaf fiber, crystal nucleating agent is at least one selected from ethylene bis 12-hydroxystearic acid amide, hexamethylene bis 12-hydroxystearic acid amide and 12-hydroxystearic acid triglyceride A combination of an organic nucleating agent and at least one inorganic nucleating agent selected from talc, mica and silica.

  As described above, the biodegradable resin composition of the present invention has the effects of the present invention by containing a biodegradable resin, a specific plasticizer, a vegetable fiber material, and a crystal nucleating agent. Therefore, even if a plasticizer other than the plasticizer of the present invention, a vegetable fiber material and a crystal nucleating agent are added to a biodegradable resin, particularly a polylactic acid resin, the effect of the present invention cannot be obtained.

Crystallization of the polymer proceeds in two stages by generation of polymer crystal nuclei and diffusion of polymer segments. From the viewpoint of improving the crystallization speed, the organic nucleating agent dissolves in the resin melt state to improve dispersibility, and upon cooling, a large number of fine crystal nucleating agent crystals are instantly generated, thereby promoting polymer crystal nucleation, and The effect of increasing the number of crystal nuclei is considered to be remarkable. However, even if polymer crystal nuclei are formed, if the diffusion rate of the polymer segment is slow, the total crystallization rate is not satisfactory. In order to improve the diffusion rate of the polymer, the temperature may be increased, but it is not preferable because the crystal nucleus of the polymer becomes unstable. Since the plasticizer according to the present invention has a remarkably high effect of improving the crystal growth rate of the polymer, a sufficient crystallization rate can be obtained even at a low temperature of 50 to 90 ° C. Furthermore, from the viewpoint of improving heat resistance, the fine and dense crystalline parts obtained by the synergistic effect of the organic nucleating agent and the plasticizer according to the present invention and the non-crystalline part softened by the plant fiber material are biodegradable. It has the effect of synergistically improving the heat resistance of the resin molding. These effects can be realized only by combining the plasticizer, vegetable fiber material, and organic nucleating agent according to the present invention.
In addition, when an inorganic nucleating agent is further contained, the dispersibility in the resin is improved by the organic nucleating agent, and in particular, the effect of improving the crystal growth rate of the polymer at 90 ° C. or higher is exhibited. The effect of improving the crystal growth rate of the polymer can be obtained.

  In order to obtain a sufficient crystallization speed and impact resistance of the present invention, the amount of the plasticizer added is preferably 5 parts by weight or more, more preferably 7 parts by weight or more with respect to 100 parts by weight of the biodegradable resin.

  The content of the biodegradable resin in the biodegradable resin composition of the present invention is preferably 50% by weight or more, more preferably 70% by weight or more from the viewpoint of achieving the object of the present invention.

  The content of the plasticizer in the biodegradable resin composition of the present invention is preferably 5 to 30 parts by weight with respect to 100 parts by weight of the biodegradable resin from the viewpoint of obtaining a sufficient crystallization speed and impact resistance. More preferably, it is more preferably -30 parts by weight, and more preferably 10-30 parts by weight.

  From the viewpoint of obtaining sufficient heat resistance, the content of the vegetable fiber material in the biodegradable resin composition of the present invention is preferably 1 to 200 parts by weight, preferably 5 to 150 parts by weight with respect to 100 parts by weight of the biodegradable resin. Parts are more preferred, and 10 to 100 parts by weight are even more preferred.

  The content of the crystal nucleating agent in the biodegradable resin composition of the present invention is preferably 0.2 to 52 parts by weight, more preferably 0.6 to 42 parts by weight, with respect to 100 parts by weight of the biodegradable resin. -32 parts by weight are particularly preferred.

  In addition, the content of the organic nucleating agent in the biodegradable resin composition of the present invention is preferably 0.1 to 2 parts by weight, more preferably 0.3 to 2 parts by weight with respect to 100 parts by weight of the biodegradable resin. 0.5 to 1.5 parts by weight is particularly preferable.

From the viewpoint of obtaining sufficient crystallization speed and transparency, the content of the inorganic nucleating agent in the biodegradable resin composition of the present invention is preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the biodegradable resin. 0.3 to 2 parts by weight is more preferable, and 0.5 to 1.5 parts by weight is particularly preferable.
In addition, from the viewpoint of obtaining a sufficient crystallization speed, heat resistance and impact resistance, the content of the inorganic nucleating agent in the biodegradable resin composition of the present invention is 3 to 100 parts by weight of the biodegradable resin. 50 parts by weight is preferable, 5 to 40 parts by weight is still more preferable, and 5 to 30 parts by weight is particularly preferable.

  In the biodegradable resin composition of the present invention, the difference [Tg1-Tg2] between the glass transition point (Tg1) of the biodegradable resin and the glass transition point (Tg2) of the biodegradable resin composition is 10 to 80. The range of ° C is preferable, the range of 15 to 70 ° C is more preferable, and the range of 20 to 60 ° C is particularly preferable.

  The biodegradable resin composition of the present invention can further contain a hydrolysis inhibitor in addition to the crystal nucleating agent and the plasticizer of the present invention. Examples of the hydrolysis inhibitor include carbodiimide compounds such as polycarbodiimide compounds and monocarbodiimide compounds, polycarbodiimide compounds are preferred from the viewpoint of moldability of the biodegradable resin molded body, and the heat resistance of the biodegradable resin molded body, From the viewpoint of impact resistance and bloom resistance of the organic nucleating agent, a monocarbodiimide compound is preferred.

  Examples of the polycarbodiimide compound include poly (4,4′-diphenylmethanecarbodiimide), poly (4,4′-dicyclohexylmethanecarbodiimide), poly (1,3,5-triisopropylbenzene) polycarbodiimide, and poly (1,3,5). -Triisopropylbenzene and 1,5-diisopropylbenzene) polycarbodiimide and the like, and examples of the monocarbodiimide compound include N, N'-di-2,6-diisopropylphenylcarbodiimide.

  The carbodiimide compounds may be used alone or in combination of two or more in order to satisfy the moldability, heat resistance, impact resistance and bloom resistance of the organic nucleating agent of the biodegradable resin molded product. Poly (4,4′-dicyclohexylmethanecarbodiimide) is obtained from carbodilite LA-1 (manufactured by Nisshinbo Co., Ltd.), poly (1,3,5-triisopropylbenzene) polycarbodiimide and poly (1,3,5). -Triisopropylbenzene and 1,5-diisopropylbenzene) polycarbodiimide are stabuxol P and stabuxol P-100 (Rhein Chemie), N, N'-di-2,6-diisopropylphenylcarbodiimide is stabuxol I (Rhein Chemie) Can be purchased and used.

  The content of the hydrolysis inhibitor in the biodegradable resin composition of the present invention is 0.05 to 3 parts by weight with respect to 100 parts by weight of the biodegradable resin from the viewpoint of moldability of the biodegradable resin molded article. Preferably, 0.1 to 2 parts by weight is more preferable.

  In addition to the above, the biodegradable resin composition of the present invention further contains other components such as a hindered phenol or phosphite antioxidant, or a hydrocarbon wax or a lubricant that is an anionic surfactant. can do. The content of each of the antioxidant and the lubricant is preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the biodegradable resin.

  The biodegradable resin composition of the present invention includes an antistatic agent, an antifogging agent, a light stabilizer, an ultraviolet absorber, a pigment, an inorganic filler, an antifungal agent, an antibacterial agent and a foaming agent as components other than those described above. In addition, flame retardants and the like can be contained as long as the object of the present invention is not hindered.

  Since the biodegradable resin composition of the present invention has good processability and can be processed at a low temperature of, for example, 200 ° C. or less, there is also an advantage that the plasticizer is hardly decomposed. Etc., and can be used for various applications.

[Production method of biodegradable resin molding]
A biodegradable resin molded product can be obtained by molding the biodegradable resin composition of the present invention.
The method for producing the biodegradable resin molded article of the present invention comprises the step (1) of mixing the biodegradable resin composition of the present invention at a melting point (Tm) or higher of the biodegradable resin, and the biodegradable resin composition. And (2) a heat treatment at a temperature not lower than the glass transition temperature (Tg) and lower than Tm.

  In addition, after passing through the step (1), after cooling to an amorphous state (that is, a condition that the degree of crystallinity measured by high angle X-ray diffraction method is 1% or less), the method of performing the step (2) After the step (1), the method of cooling and immediately performing the step (2) is preferable. From the viewpoint of the crystallization speed improvement effect of the present invention, the step (1) is followed by cooling and the step (1). The method of performing 2) is more preferable.

  As a specific example of the step (1) in the method for producing a biodegradable resin molded body of the present invention, it can be performed by a usual method, for example, while melting the biodegradable resin using an extruder or the like, The method etc. which mix the plasticizer of this invention, vegetable fiber material, and a crystal nucleating agent are mentioned. The temperature of the step (1) is not less than the melting point (Tm) of the biodegradable resin, preferably in the range of Tm to Tm + 100 ° C., from the viewpoint of dispersibility of the plasticizer, plant fiber material and crystal nucleating agent of the present invention. More preferably, it is the range of Tm-Tm + 50 degreeC. For example, when the biodegradable resin is a polylactic acid resin, the temperature is preferably 170 to 240 ° C, more preferably 170 to 220 ° C.

  As a specific example of the step (2) in the method for producing a molded article of the present invention, it can be carried out by an ordinary method, for example, a method of heat-treating or injection of a biodegradable resin composition extruded by an extruder or the like. Examples thereof include a method in which a biodegradable resin composition is filled in a mold with a molding machine or the like and the biodegradable resin composition is heat-treated. From the viewpoint of improving the crystallization speed, the temperature in the step (2) is not less than the glass transition temperature (Tg) of the biodegradable resin composition and less than Tm, preferably in the range of Tg to Tg + 100 ° C., more preferably Tg + 10. It is the range of -Tg + 80 degreeC, Most preferably, it is the range of Tg + 20-Tg + 70 degreeC. For example, in the case of a biodegradable resin composition in which the biodegradable resin is a polylactic acid resin, 50 to 90 ° C is preferable, and 70 to 80 ° C is more preferable.

  In addition, melting | fusing point (Tm) of biodegradable resin is a value calculated | required from the crystal melting endothermic peak temperature by the temperature rising method of differential scanning calorimetry (DSC) based on JIS-K7121. Moreover, the glass transition temperature (Tg) of a biodegradable resin composition is a value calculated | required from the peak temperature of the loss elastic modulus (E '') in the dynamic viscoelasticity measurement based on JIS-K7198.

  The thermal deformation temperature of the biodegradable resin molded article of the present invention cannot be determined unconditionally because it varies depending on the type and amount of biodegradable resin, plasticizer, vegetable fiber material, crystal nucleating agent, In particular, in the case of a polylactic acid resin, from the viewpoint of expressing the effect of the present invention, 80 ° C. or higher is preferable, 90 ° C. or higher is more preferable, and 100 ° C. or higher is further preferable. In addition, the heat distortion temperature of the biodegradable resin molding of this invention is a value measured by the measuring method described in the Example here.

  Although the impact resistance of the biodegradable resin molded product of the present invention varies depending on the type and amount of the biodegradable resin, plasticizer, vegetable fiber material, crystal nucleating agent, etc., it cannot be determined unconditionally. In particular, in the case of a polylactic acid resin, 60 (J / m) or more is preferable, 70 (J / m) or more is more preferable, and 80 (J / m) or more is more preferable from the viewpoint of expressing the effect of the present invention. Here, the impact resistance of the biodegradable resin molded product of the present invention is a value measured by the measurement method described in the examples.

  The degree of crystallinity of the biodegradable resin molded article of the present invention cannot be determined unconditionally because it varies depending on the type and amount of biodegradable resin, plasticizer, vegetable fiber material, crystal nucleating agent, In particular, in the case of a polylactic acid resin, it is preferably 30 to 70%, more preferably 40 to 70%, and particularly preferably 50 to 65% from the viewpoint of expressing the effect of the present invention. In addition, the crystallinity degree of the biodegradable resin molding of this invention is a value measured by the measuring method described in the Example here.

Examples 1-6 , Comparative Examples 1-7
The present invention products ( E to K) and comparative products (a to g) shown in Table 1 as the biodegradable resin composition were mixed at 180 ° C. for 10 minutes with a kneader (DS3-20MWB-E, manufactured by Moriyama Seisakusho) It is melt-kneaded, and then immediately stretched to a thickness of about 5 mm with an 8-inch roll (manufactured by Nippon Roll Manufacturing Co., Ltd.) at 80 ° C. and cut into a size of about 8 cm × 8 cm in length × width = 8 ° C. The product was pulverized by a pulverizer (S-20 manufactured by Daiko Seiki Co., Ltd.) to obtain a pulverized product of the biodegradable resin composition.

  The obtained pulverized product was dried at 70 ° C. under reduced pressure for 1 day, and the water content was adjusted to 500 ppm or less.

* 1: Polylactic acid resin (manufactured by Mitsui Chemicals, LACEA H-400)
* 2: Diester of succinic acid and triethylene glycol monomethyl ether * 3: Kenaf fiber ≡ 1-5 mm fiber length
* 4: Ethylene bis 12-hydroxystearic acid amide (Nippon Kasei Co., Ltd., SLIPAX H)
* 5: Nihon Talc Co., Ltd., Micro Ace P-6
* 6 : Nisshinbo product, Carbodilite LA-1
* 7 : 12-hydroxystearic acid triglyceride (Kao Corporation, Kao Wax 85P)
* 8 : Bis (diisopropylphenyl) carbodiimide * 9 : Hayashi Kasei Co., Ltd., Mica WG-325
* 10 : Caprylic acid monoglyceride diacetate * 11 : Polyethylene glycol, manufactured by Sanyo Chemical Co., Ltd.

  Next, the pulverized product obtained in this manner was subjected to a mold having good mold releasability shown in Table 2 using an injection molding machine (J75E-D manufactured by Nippon Steel Works) with a cylinder temperature of 200 ° C. Injection molding was performed at the mold temperature and the mold holding time. Mold releasability of the obtained test pieces [flat plate (70 mm × 40 mm × 3 mm), prismatic test piece (125 mm × 12 mm × 6 mm) and prismatic test piece (63 mm × 12 mm × 5 mm)] based on the following criteria evaluated. In addition, a prismatic specimen (125 mm × 12 mm × 6 mm) has a thermal deformation temperature, a prismatic specimen (63 mm × 12 mm × 5 mm) has impact resistance, and a flat plate (70 mm × 40 mm × 3 mm) has a crystallinity. Each was evaluated by the following methods. These results are shown in Table 2.

<Evaluation criteria for mold releasability>
○: Very easy to leave (the test piece is not deformed and can be taken out easily)
Δ: Slightly difficult to separate (test piece is slightly deformed and difficult to remove)
X: Not separated (the test piece is greatly deformed and does not leave the runner)
The mold releasability becomes better as the melt crystallization speed of the test piece increases in the mold and in the runner portion.

<Heat deformation temperature>
For a prismatic test piece (125 mm x 12 mm x 6 mm), the temperature at which the heat deflection temperature measuring machine (Toyo Seiki Seisakusho B-32) is deflected by 0.025 mm at a load of 0.45 MPa is based on JIS-K7191. It was measured.

<Impact resistance>
The Izod impact strength of a prismatic test piece (63 mm × 12 mm × 5 mm) was measured using an impact tester (type 863 manufactured by Ueshima Seisakusho Co., Ltd.) based on JIS-K7110.

<Crystallinity>
Use a wide-angle X-ray diffraction measurement device (RINT2500VPC, light source CuKα, tube voltage 40kV, tube current 120mA, manufactured by Rigaku Corporation) for the flat plate after injection molding (70mm × 40mm × 3mm) 2θ = 5-30 ° The crystallinity was determined by analyzing the amorphous and crystalline peak areas in the range.

From the results of Table 2, the biodegradable resin composition (E to K) of the present invention containing a specific plasticizer and an organic nucleating agent, a vegetable fiber material, and further containing an inorganic nucleating agent is 80 ° C. Molding was possible with a short mold holding time even at the mold temperature, and the molded product was excellent in exhibiting heat resistance of 110 ° C. or higher and impact resistance of 74 J / m or higher.

  On the other hand, the resin composition (ac) containing no vegetable fiber material, the resin composition (d and e) containing no specific plasticizer, and the resin composition (g) containing no plasticizer are in good molding. In order to obtain a good molded product, a resin composition (f) that requires a mold temperature of 80 ° C. or higher and a long mold holding time of 60 seconds or longer to obtain a product and does not contain a plasticizer and a crystal nucleating agent In this case, the mold temperature could not be raised, and it was in an amorphous state. Further, the obtained molded product could not achieve both excellent heat resistance and impact resistance.

From the above results, the biodegradable resin composition of the present invention containing a specific plasticizer, crystal nucleating agent, and vegetable fiber material exhibits excellent moldability at a low mold temperature, and has excellent heat resistance and resistance. It can be seen that the biodegradable resin composition of the present invention, which has both impact properties and further uses an organic nucleating agent and an inorganic nucleating agent in combination, is further improved in heat resistance.

Claims (3)

Relative to 100 parts by weight of the biodegradable resin, 5 to 30 parts by weight of a plasticizer, a polylactic acid resin composition containing 1 to 200 parts by weight vegetable fiber material, and 0.2 to 52 parts by weight of the crystal nucleating agent The plasticizer is a compound having 2 or more ester groups in the molecule and an average added mole number of ethylene oxide of 3 to 9, and an organic nucleating agent and an inorganic nucleating agent are used in combination as a crystal nucleating agent, and organic A polylactic acid resin composition, wherein the nucleating agent is at least one selected from ethylene bis 12-hydroxystearic acid amide, hexamethylene bis 12-hydroxystearic acid amide, and 12-hydroxystearic acid triglyceride. Plasticizer, and succinic acid or adipic acid and polyethylene glycol monomethyl ether ester, and acetic acid and, at least one kind of claim 1 wherein is selected from the group consisting of esters of ethylene oxide adducts of glycerol or ethylene glycol Polylactic acid resin composition. The polylactic acid resin composition according to claim 1 or 2 , wherein the vegetable fiber material is at least one selected from kenaf fiber, jute fiber, wood powder and paper powder.