Resin composition for injection molding and injection molded article

Abstract

In the present invention, a poly(3-hydroxyalkanoate) resin component includes a copolymer (A) of a 3-hydroxybutyrate unit and another hydroxyalkanoate unit, in which the content proportion of the other hydroxyalkanoate unit is 1-6 mol%, and a copolymer (B) of a 3-hydroxybutyrate unit and another hydroxyalkanoate unit, in which the content proportion of the other hydroxyalkanoate unit is 24 mol% or greater. This resin composition also includes a layered clay mineral (C). The proportion of (A) is 72-93 wt%, and the proportion of (B) is 7-28 wt%. The (C) content is 5-45 parts by weight per 100 total parts by weight of the poly(3-hydroxyalkanoate) resin component.

Description

Technical Field

[0001] The present invention relates to an injection molding resin composition containing a poly(3-hydroxyalkanoate) - based resin component and an injection molded article.

Background Art

[0002] In recent years, environmental problems caused by waste plastics have been spotlighted. In particular, it has been found that plastics that have flowed into the sea via ocean dumping or rivers are drifting in large quantities on a global scale in the ocean. Since such plastics maintain their shape over a long period of time, they are pointed out to have an impact on the ecosystem, such as so-called ghost fishing that restrains and captures marine organisms, or when ingested by marine organisms, they remain in the digestive tract and cause feeding disorders.

[0003] Furthermore, it has also been pointed out that microplastics formed by the disintegration and particle formation of plastics due to ultraviolet rays and the like adsorb harmful compounds in the ocean, and when marine organisms ingest these, the harmful substances are incorporated into the food chain.

[0004] Regarding such ocean pollution caused by plastics, the use of biodegradable plastics is expected. However, in a report compiled by the United Nations Environment Programme in 2015, it was pointed out that plastics that are biodegradable in composts such as polylactic acid cannot be a countermeasure against ocean pollution because they cannot be expected to decompose in a short period in the actual ocean where the temperature is low.

[0005] Under such circumstances, poly(3-hydroxyalkanoate) - based resins are attracting attention as materials to solve the above problems because they can undergo biodegradation even in seawater.

[0006] In Patent Document 1, a resin composition containing a poly(3-hydroxyalkanoate)-based resin such as poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), pentaerythritol, and a filler is disclosed for the purpose of improving the slow crystallization of the poly(3-hydroxyalkanoate)-based resin and improving the surface smoothness and mold transferability of the resulting molded article.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] For example, injection molded articles such as spoons are often required to have a high balance between elastic modulus (rigidity) and toughness (resistance to breakage).

[0009] However, according to the method of simply adding a filler to a poly(3-hydroxyalkanoate)-based resin as described in Patent Document 1, the resulting injection molded article may have reduced toughness and be prone to breakage.

[0010] On the other hand, as a method for improving breakage resistance, a method of adding another soft biodegradable resin, such as a polybutylene succinate-based resin or a polybutylene adipate terephthalate-based resin, to a poly(3-hydroxyalkanoate)-based resin can also be considered. However, when these resins are added, the seawater degradability of the injection molded article may deteriorate, the elastic modulus may decrease, and the molding cycle may be prolonged, resulting in a decrease in productivity.

[0011] There is a demand for an injection molded article that has a practical balance between elastic modulus and toughness, is excellent in productivity, while using a poly(3-hydroxyalkanoate)-based resin having seawater degradability as a main resin component.

[0012] In view of the above situation, the present invention aims to provide a resin composition containing a poly(3-hydroxyalkanoate)-based resin component, which can form an injection molded article having a practical balance between elastic modulus and toughness with good productivity.

Means for Solving the Problems

[0013] As a result of intensive studies to solve the above problems, the present inventors have found that by using two types of poly(3-hydroxyalkanoate)-based resins having different content ratios of constituent monomers at a specific ratio and adding a specific amount of a specific filler, an injection molded article having a practical balance between elastic modulus and toughness can be formed with good productivity, and thus the present invention has been completed.

[0014] That is, the present invention is a resin composition for injection molding containing a poly(3-hydroxyalkanoate)-based resin component, wherein the poly(3-hydroxyalkanoate)-based resin component is a copolymer (A) of a 3-hydroxybutyrate unit and other hydroxyalkanoate units, in which the content ratio of other hydroxyalkanoate units is 1 to 6 mol%, and a copolymer (B) of a 3-hydroxybutyrate unit and other hydroxyalkanoate units, in which the content ratio of other hydroxyalkanoate units is 24 mol% or more, the resin composition further contains a layered clay mineral (C), in the poly(3-hydroxyalkanoate)-based resin component, the ratio of the copolymer (A) is 72 to 93% by weight, the ratio of the copolymer (B) is 7 to 28% by weight, and the content of the layered clay mineral (C) is 5 to 45 parts by weight with respect to 100 parts by weight in total of the poly(3-hydroxyalkanoate)-based resin component, and relates to a resin composition for injection molding. Preferably, the average content ratio of the other hydroxyalkanoate units in all monomer units constituting the poly(3-hydroxyalkanoate)-based resin component is 2 to 35 mol%. Preferably, the other hydroxyalkanoate unit is a 3-hydroxyhexanoate unit. Preferably, the layered clay mineral (C) is at least one selected from the group consisting of mica, talc, and kaolinite. The present invention also relates to an injection molded article made of the resin composition for injection molding.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a resin composition that contains a poly(3-hydroxyalkanoate) resin component and can form an injection molded article having a practical balance between elastic modulus and toughness with good productivity.

Brief Description of the Drawings

[0016]

Figure 1

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0018] One embodiment of the present invention is a resin composition used for producing a molded article by subjecting it to injection molding. The resin composition contains, as a resin component, at least a poly(3-hydroxyalkanoate) resin component.

[0019] (Poly(3-hydroxyalkanoate) resin component) As the poly(3-hydroxyalkanoate) resin component, a mixture of at least two types of poly(3-hydroxyalkanoate) resins having different content ratios of constituent monomers is used. By using such a mixture, an injection molded article having a practical balance between elastic modulus and toughness can be formed with good productivity.

[0020] The poly(3-hydroxyalkanoate) resin is preferably a polymer having 3-hydroxyalkanoate units, specifically, a polymer containing units represented by the following general formula (1). [-CHR-CH2-CO-O-] (1)

[0021] In general formula (1), R represents an alkyl group represented by C p H 2p+1 and p represents an integer from 1 to 15. Examples of R include linear or branched alkyl groups such as methyl group, ethyl group, propyl group, methylpropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, hexyl group, etc. As p, 1 to 10 is preferable, and 1 to 8 is more preferable.

[0022] As the poly(3-hydroxyalkanoate) resin, a poly(3-hydroxyalkanoate) resin produced from microorganisms is particularly preferable. In the poly(3-hydroxyalkanoate) resin produced from microorganisms, all 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0023] The poly(3-hydroxyalkanoate) resin preferably contains 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of 3-hydroxyalkanoate units (particularly, units represented by general formula (1)) based on all the constituent units. The poly(3-hydroxyalkanoate) resin may contain only one or more 3-hydroxyalkanoate units as the constituent units of the polymer, or may contain other units (for example, 4-hydroxyalkanoate units, etc.) in addition to one or more 3-hydroxyalkanoate units.

[0024] The poly(3-hydroxyalkanoate) resin may be a homopolymer or copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units. In particular, it is preferable that all the 3-hydroxybutyrate units are (R)-3-hydroxybutyrate units. Further, the poly(3-hydroxyalkanoate) resin is preferably a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0025] Specific examples of the poly(3-hydroxyalkanoate) resin include, for example, poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), and the like. In particular, from the viewpoints of productivity and mechanical properties of injection molded articles, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferable, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferable.

[0026] The poly(3-hydroxyalkanoate) resin component contains at least one highly crystalline poly(3-hydroxyalkanoate)-based resin and at least one low-crystalline poly(3-hydroxyalkanoate)-based resin. Generally, a highly crystalline poly(3-hydroxyalkanoate)-based resin has excellent productivity but poor mechanical strength, while a low-crystalline poly(3-hydroxyalkanoate)-based resin has poor productivity but excellent mechanical properties. When these two resins are mixed, it is presumed that the highly crystalline poly(3-hydroxyalkanoate)-based resin forms fine resin crystal particles, and the low-crystalline poly(3-hydroxyalkanoate)-based resin forms tie molecules that crosslink these resin crystal particles. By using these resins in combination, the productivity can be good, and the mechanical properties of the injection molded article can be significantly improved.

[0027] The highly crystalline poly(3-hydroxyalkanoate)-based resin is a copolymer (A) of a 3-hydroxybutyrate unit and other hydroxyalkanoate units. The content ratio of the 3-hydroxybutyrate unit contained in the highly crystalline poly(3-hydroxyalkanoate)-based resin is preferably higher than the average content ratio of the 3-hydroxybutyrate unit in all monomer units constituting the poly(3-hydroxyalkanoate) resin component. Specifically, the content ratio of other hydroxyalkanoate units in the copolymer (A) is preferably 1 mol% or more and 6 mol% or less, more preferably 2 mol% or more and 5 mol% or less, and still more preferably 3 mol% or more and 5 mol% or less.

[0028] As the copolymer (A), a copolymer containing the 3-hydroxybutyrate unit described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0029] The low-crystalline poly(3-hydroxyalkanoate) resin is a copolymer (B) of 3-hydroxybutyrate units and other hydroxyalkanoate units. The content ratio of 3-hydroxybutyrate units contained in the low-crystalline poly(3-hydroxyalkanoate) resin is preferably lower than the average content ratio of 3-hydroxybutyrate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin component. Specifically, the content ratio of other hydroxyalkanoate units in the copolymer (B) is preferably 24 mol% or more and 99 mol% or less, more preferably 24 mol% or more and 50 mol% or less, still more preferably 24 mol% or more and 35 mol% or less, and particularly preferably 24 mol% or more and 30 mol% or less.

[0030] As the copolymer (B), the copolymers containing 3-hydroxybutyrate units described above can be used, but poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0031] The proportion of the copolymer (A) is 72% by weight or more and 93% by weight or less, and the proportion of the copolymer (B) is 7% by weight or more and 28% by weight or less, based on the total amount of the copolymer (A) and the copolymer (B). By using the copolymer (A) and the copolymer (B) in combination within this range, it becomes possible to form an injection molded article having an excellent balance between elastic modulus and toughness with good productivity. When the proportion of the copolymer (B), which is a low-crystalline poly(3-hydroxyalkanoate)-based resin, is less than 7% by weight, the toughness of the injection molded article tends to be insufficient, and when it exceeds 28% by weight, the molding cycle of the injection molded article tends to become longer and the productivity tends to decrease. The proportion of the copolymer (A) is preferably 75% by weight or more and 90% by weight or less, and the proportion of the copolymer (B) is preferably 10% by weight or more and 25% by weight or less. More preferably, the proportion of the copolymer (A) is 77% by weight or more and 88% by weight or less, and the proportion of the copolymer (B) is 12% by weight or more and 23% by weight or less. Even more preferably, the proportion of the copolymer (A) is 75% by weight or more and 85% by weight or less, and the proportion of the copolymer (B) is 15% by weight or more and 25% by weight or less.

[0032] The poly(3-hydroxyalkanoate)-based resin component may contain only the copolymer (A) and the copolymer (B), or may further contain other poly(3-hydroxyalkanoate)-based resins in addition to the copolymer (A) and the copolymer (B). The other poly(3-hydroxyalkanoate)-based resin may be a homopolymer of 3-hydroxybutyrate, or a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, and the copolymer may not fall under the definition of either the copolymer (A) or the copolymer (B) in terms of the content ratio of the other hydroxyalkanoate units.

[0033] The average content ratios of 3-hydroxybutyrate units and other hydroxyalkanoate units in all monomer units constituting the poly(3-hydroxyalkanoate)-based resin component are preferably 3-hydroxybutyrate units / other hydroxyalkanoate units = 98 / 2 to 65 / 35 (mol% / mol%), more preferably 96 / 4 to 75 / 25 (mol% / mol%), still more preferably 95 / 5 to 80 / 20 (mol% / mol%), and particularly preferably 96 / 6 to 85 / 15 (mol% / mol%) from the viewpoint of achieving both the mechanical properties and productivity of the injection molded article.

[0034] The average content ratio of each monomer unit in all monomer units constituting the poly(3-hydroxyalkanoate)-based resin component can be determined by a method known to those skilled in the art, for example, the method described in paragraph

[0047] of WO 2013 / 147139. The average content ratio means the molar ratio of each monomer unit in all monomer units in the entire poly(3-hydroxyalkanoate)-based resin component, and means the molar ratio of each monomer unit contained in the entire mixture of two or more poly(3-hydroxyalkanoate)-based resins constituting the poly(3-hydroxyalkanoate)-based resin component.

[0035] The weight average molecular weight of the poly(3-hydroxyalkanoate)-based resin component is not particularly limited, but is preferably 50,000 to 3,000,000, more preferably 200,000 to 2,000,000, still more preferably 250,000 to 1,500,000, and particularly preferably 300,000 to 800,000 from the viewpoint of achieving both the mechanical properties and productivity of the injection molded article.

[0036] In addition, the weight average molecular weight of each poly(3-hydroxyalkanoate)-based resin constituting the poly(3-hydroxyalkanoate)-based resin component is not particularly limited. However, from the viewpoint of achieving both the mechanical properties and productivity of the injection molded article, the weight average molecular weight of the copolymer (A), which is a highly crystalline poly(3-hydroxyalkanoate)-based resin, is preferably from 200,000 to 1,000,000, more preferably from 220,000 to 800,000, and still more preferably from 250,000 to 600,000. On the other hand, from the viewpoint of achieving both the mechanical properties and productivity of the injection molded article, the weight average molecular weight of the copolymer (B), which is a low crystalline poly(3-hydroxyalkanoate)-based resin, is preferably from 200,000 to 2,500,000, more preferably from 250,000 to 2,300,000, still more preferably from 300,000 to 2,000,000, and particularly preferably from 350,000 to 1,500,000.

[0037] Incidentally, the weight average molecular weight of the poly(3-hydroxyalkanoate)-based resin or the poly(3-hydroxyalkanoate)-based resin component can be measured in terms of polystyrene using gel permeation chromatography (HPLC GPC system manufactured by Shimadzu Corporation) using a chloroform solvent. As the column in the gel permeation chromatography, a column suitable for measuring the weight average molecular weight may be used.

[0038] The poly(3-hydroxyalkanoate)-based resin component is preferably not crosslinked using a crosslinking agent such as an organic peroxide, that is, it is preferably a resin component having no crosslinked structure.

[0039] The method for producing the poly(3-hydroxyalkanoate) resin is not particularly limited, and it may be a production method by chemical synthesis or a production method by microorganisms. Among them, the production method by microorganisms is preferred. Regarding the production method by microorganisms, known methods can be applied. For example, as copolymer-producing bacteria of 3-hydroxybutyrate and other hydroxyalkanoates, Aeromonas caviae, which is a P3HB3HV and P3HB3HH-producing bacterium, Alcaligenes eutrophus, which is a P3HB4HB-producing bacterium, etc. are known. In particular, regarding P3HB3HH, in order to increase the productivity of P3HB3HH, Alcaligenes eutrophus AC32 strain (Alcaligenes eutrophus AC32, FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, p4821-4830 (1997)) into which the genes of the P3HA synthase group have been introduced, etc. are more preferred, and microbial cells in which P3HB3HH has been accumulated in the cells by culturing these microorganisms under appropriate conditions are used. In addition to the above, according to the poly(3-hydroxyalkanoate) resin to be produced, genetically modified microorganisms into which various genes related to the synthesis of poly(3-hydroxyalkanoate) resins have been introduced may be used, or the culture conditions including the type of substrate may be optimized.

[0040] The method for obtaining a blend of two or more poly(3-hydroxyalkanoate) resins is not particularly limited, and it may be a method for obtaining a blend by microbial production or a method for obtaining a blend by chemical synthesis. Also, two or more resins may be melt-kneaded using an extruder, kneader, Banbury mixer, roll, etc. to obtain a blend, or two or more resins may be dissolved in a solvent, mixed, and dried to obtain a blend.

[0041] (Other resin) The resin composition for injection molding according to one embodiment may contain other resins other than the poly(3-hydroxyalkanoate) resin as long as the effects of the invention are not impaired. Examples of such other resins include aliphatic polyester resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate, polybutylene sebacate terephthalate, and polybutylene azelate terephthalate. Only one kind of other resin may be included, or two or more kinds may be included.

[0042] The content of the other resin is not particularly limited. However, from the viewpoint of the seawater degradability of the injection molded article, it is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less with respect to a total of 100 parts by weight of the poly(3-hydroxyalkanoate) resin component. The lower limit of the content of the other resin is not particularly limited and may be 0 parts by weight.

[0043] (Layered clay mineral (C)) The resin composition for injection molding according to one embodiment further contains a layered clay mineral (C). Thereby, an injection molded article excellent in the balance between elastic modulus and toughness can be formed. Here, the layered clay mineral refers to a mineral mainly composed of layered silicate.

[0044] The layered clay mineral (C) is not particularly limited, and known ones can be used. However, from the viewpoint of easily achieving the effect of improving productivity, one or more selected from the group consisting of smectite, mica, talc, pyrophyllite, vermiculite, chlorite, kaolinite, and serpentine are preferred. From the viewpoint of versatility, mica, talc, and kaolinite are preferred, and talc is particularly preferred.

[0045] Examples of the mica include wet-ground mica and dry-ground mica. Specifically, mica manufactured by Yamaguchi Mica Co., Ltd. and Keiwa Furnace Materials Co., Ltd. are exemplified.

[0046] Examples of the talc include general-purpose talc and surface-treated talc. Specifically, examples include "Micro Ace" (registered trademark) manufactured by Nippon Talc Co., Ltd., "Talkan Powder" (registered trademark) manufactured by Hayashi Kasei Co., Ltd., and talc manufactured by Takehara Chemical Industry Co., Ltd. and Maruo Calcium Co., Ltd.

[0047] Examples of the kaolinite include dry kaolin, calcined kaolin, wet kaolin, etc. Specifically, examples include "TRANSLINK" (registered trademark), "ASP" (registered trademark), "SANTINTONE" (registered trademark), "ULTREX" (registered trademark) manufactured by Hayashi Kasei Co., Ltd., and kaolinite manufactured by Keiwa Furnace Materials Co., Ltd.

[0048] The average particle diameter of the layered clay mineral (C) is preferably 0.1 to 50 μm, more preferably 0.3 to 30 μm, still more preferably 0.5 to 15 μm, and particularly preferably 1 to 10 μm because it is excellent in the mechanical properties and productivity of the injection molded article. The average particle diameter can be measured using a laser diffraction / scattering type device such as "Microtrac MT3100II" manufactured by Nikkiso Co., Ltd.

[0049] The content of the layered clay mineral (C) is 5 parts by weight or more and 45 parts by weight or less with respect to 100 parts by weight in total of the poly(3-hydroxyalkanoate) resin component. By blending the layered clay mineral (C) within this range, it becomes possible to form an injection molded article excellent in the balance between elastic modulus and toughness with good productivity. When the content of the layered clay mineral (C) is less than 5 parts by weight, the elastic modulus of the injection molded article tends to decrease, and when it exceeds 45 parts by weight, the production of the injection molded article becomes difficult. The content is preferably 10 parts by weight or more and 40 parts by weight or less, more preferably 10 parts by weight or more and 35 parts by weight or less, and still more preferably 15 parts by weight or more and 30 parts by weight or less.

[0050] For the purpose of improving the dispersibility of the layered clay mineral (C), it is preferable to use the layered clay mineral (C) in combination with a dispersion aid.

[0051] Examples of the dispersion aid include glycerin ester compounds, adipic acid ester compounds, polyether ester compounds, phthalic acid ester compounds, isosorbide ester compounds, polycaprolactone compounds, etc. Among these, modified glycerin compounds such as glycerin diacetate monolaurate, glycerin diacetate monocaprylate, and glycerin diacetate monodecanoate; adipic acid ester compounds such as diethylhexyl adipate, dioctyl adipate, and diisononyl adipate; and polyether ester compounds such as polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate are preferred because of their excellent affinity for the resin component and difficulty in bleeding. Furthermore, those containing a large amount of biomass-derived components are particularly preferred because they can increase the biomass degree of the entire composition. Examples of such dispersion aids include the "Licmer" (registered trademark) PL series of Riken Vitamin Co., Ltd. and the Polysorb series of ROQUETTE. The dispersion aid can be used alone or in combination of two or more kinds.

[0052] The blending amount (total blending amount) of the dispersion aid is not particularly limited, but it is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight in total of the poly(3-hydroxyalkanoate) resin component. However, the dispersion aid may not be blended.

[0053] (Additive) The resin composition for injection molding according to one embodiment may contain an additive as long as it does not inhibit the effects of the invention. Examples of the additive include a nucleating agent, a lubricant, a plasticizer, an antistatic agent, a flame retardant, a conductive agent, a heat insulating agent, a crosslinking agent, an antioxidant, an ultraviolet absorber, a colorant, an inorganic filler, an organic filler, a hydrolysis inhibitor, etc., which can be used according to the purpose. Particularly preferred are additives having biodegradability.

[0054] Examples of the crystallization nucleating agent include pentaerythritol, orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, boron nitride, and the like. Among them, pentaerythritol is preferred in that it has an especially excellent effect of promoting the crystallization of the poly(3-hydroxyalkanoate) resin component. The amount of the crystallization nucleating agent used is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.7 to 1.5 parts by weight, based on 100 parts by weight in total of the poly(3-hydroxyalkanoate) resin component. Further, one kind of the crystallization nucleating agent may be used, or two or more kinds may be used, and the use ratio can be appropriately adjusted according to the purpose.

[0055] Examples of the lubricant include behenic acid amide, oleic acid amide, erucic acid amide, stearic acid amide, palmitic acid amide, N-stearyl behenic acid amide, N-stearyl erucic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, ethylene bislauric acid amide, ethylene biscapric acid amide, p-phenylene bisstearic acid amide, a polycondensate of ethylenediamine, stearic acid, and sebacic acid, and the like. Among them, behenic acid amide or erucic acid amide is preferred in that it has an especially excellent lubricant effect on the poly(3-hydroxyalkanoate) resin component. The amount of the lubricant used is not particularly limited, but is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1.5 parts by weight, based on 100 parts by weight in total of the poly(3-hydroxyalkanoate) resin component. Further, one kind of the lubricant may be used, or two or more kinds may be used, and the use ratio can be appropriately adjusted according to the purpose.

[0056] Examples of the plasticizer include glycerin ester compounds, citric acid ester compounds, sebacic acid ester compounds, adipic acid ester compounds, polyether ester compounds, benzoic acid ester compounds, phthalic acid ester compounds, isosorbide ester compounds, polycaprolactone compounds, dibasic acid ester compounds, etc. Among them, glycerin ester compounds, citric acid ester compounds, sebacic acid ester compounds, and dibasic acid ester compounds are preferable in that they have particularly excellent plasticizing effects on the poly(3-hydroxyalkanoate)-based resin component. Examples of the glycerin ester compound include glycerin diacetomonolaurate. Examples of the citric acid ester compound include tributyl acetylcitrate. Examples of the sebacic acid ester compound include dibutyl sebacate. Examples of the dibasic acid ester compound include benzyl methyl diethylene glycol adipate. The amount of the plasticizer used is not particularly limited, but is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, and even more preferably 3 to 10 parts by weight with respect to 100 parts by weight in total of the poly(3-hydroxyalkanoate)-based resin component. Further, one type of plasticizer may be used, or two or more types may be used, and the use ratio can be appropriately adjusted according to the purpose.

[0057] (Method for producing injection molded article) The injection molded article according to one embodiment can be produced by melt-kneading each component, obtaining pellets if necessary, and then using a known injection molding method. This will be specifically described below.

[0058] First, a poly(3-hydroxyalkanoate)-based resin component, a layered clay mineral (C), other resins if necessary, and optional additives are added, and melt-kneaded using an extruder, kneader, Banbury mixer, roll, etc. to prepare a resin composition, which is extruded into strands and then cut to obtain pellets having a particle shape such as a columnar shape, an elliptical columnar shape, a spherical shape, a cubic shape, a rectangular parallelepiped shape. It is desirable that the produced pellets be sufficiently dried at 40 to 80°C to remove moisture and then subjected to injection molding.

[0059] The temperature at which the melt-kneading is carried out cannot be generally specified because it depends on the melting point, melt viscosity, etc. of the resin used. However, it is preferable that the resin temperature at the die outlet of the melt-kneaded product is 135 to 200°C, more preferably 140 to 195°C, still more preferably 145 to 190°C, and particularly preferably 150 to 185°C. If the resin temperature of the melt-kneaded product is less than 135°C, the poly(3-hydroxyalkanoate) resin component may not be melted, and if it exceeds 200°C, the poly(3-hydroxyalkanoate) resin component may be thermally decomposed.

[0060] Next, an injection molded article can be molded by subjecting the produced pellets to injection molding. Injection molding is a method of obtaining a molded article by injecting a heat-melted resin composition into a mold, cooling and solidifying the resin composition in the mold, then opening the mold and demolding the molded article. As the injection molding method, in addition to the injection molding method generally employed when molding a thermoplastic resin, injection blow molding, gas assist molding method, injection compression molding method and other injection molding methods can be adopted. Also, in-mold molding method, gas press molding method, two-color molding method, sandwich molding method, PUSH-PULL, SCORIM, etc. can also be adopted. However, the available injection molding methods are not limited to the above methods.

[0061] The temperature during cooling by the mold after injection can be appropriately determined by those skilled in the art, but 20 to 70°C is preferable, 25 to 60°C is more preferable, 30 to 50°C is still more preferable, and 35 to 45°C is particularly preferable.

[0062] The injection molded article according to a preferred embodiment mainly comprises a poly(3-hydroxyalkanoate) resin as the resin component, and thus has good seawater degradability, and therefore can solve the environmental problems caused by marine disposal of plastics.

[0063] The applications of the injection-molded article according to one embodiment are not particularly limited. For example, they include tableware such as plates, cups, mugs, and lids; cutlery such as spoons, forks, knives, and ladles; capsules such as coffee capsules and toy containers; toys; agricultural materials; parts for office automation equipment; parts for household appliances; members for automobiles; various containers and boxes; daily sundries; stationery; bottle molded products, etc.

Examples

[0064] Hereinafter, the present invention will be specifically described by way of examples. However, the technical scope of the present invention is not limited by these examples.

[0065] The substances used in the examples and comparative examples are shown below. [Poly(3-hydroxyalkanoate) resin] PHBH1: P3HB3HH (average content ratio 3HB / 3HH = 95.4 / 4.6 (mol% / mol%), weight average molecular weight is 380,000 g / mol) Manufactured according to the method described in Example 2 of International Publication No. 2019 / 142845. PHBH2: P3HB3HH (average content ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight average molecular weight is 660,000 g / mol) Manufactured according to the method described in Example 9 of International Publication No. 2019 / 142845. PBSA: Polybutylene succinate adipate resin, BioPBS FD72PB manufactured by Mitsubishi Chemical Corporation PBAT: Polybutylene adipate terephthalate, Ecoflex F Blend C1200 manufactured by BASF

[0066] [Layered clay mineral (C)] Talc: Micro Ace K-1 (manufactured by Nippon Talc Co., Ltd.)

[0067] [Additive] Additive-1: Pentaerythritol (manufactured by Mitsubishi Chemical Corporation: Neutralizer P) Additive-2: Behenic acid amide (manufactured by Nippon Fine Chemical Co., Ltd.: BNT-22H) Regarding the evaluation methods implemented in the examples and comparative examples, they will be described below.

[0068] [Evaluation of Tensile Modulus] (Preparation of Test Specimens) The resin pellets dried at 60°C for 24 hours using a dehumidifying dryer were used with a Toyo Machine Metal injection molding machine Si-30V. The barrel temperature of the injection molding machine was set to nozzle / T1 / T2 / T3 = 155 / 145 / 135 / 125°C, the mold temperature was set to 35°C, and at an injection speed of 20 mm / sec, a JIS K7161 type 1A dumbbell with a thickness of 4 mm was obtained. (Measurement of Modulus) After the obtained dumbbell was left standing at 23°C for 168 hours, a tensile test was performed at 10 mm / sec based on JIS K 7161, and the tensile modulus was measured. When the obtained tensile modulus was 1400 MPa or more, it was evaluated as ○ (good), and when it was less than 1400 MPa, it was evaluated as × (insufficient).

[0069] [Bending Test] (Preparation of Test Specimens) The resin pellets dried at 60°C for 24 hours using a dehumidifying dryer were used with a Toyo Machine Metal injection molding machine Si-30V. The barrel temperature of the injection molding machine was set to nozzle / T1 / T2 / T3 = 155 / 145 / 135 / 125°C, the mold temperature was set to 35°C, and at an injection speed of 20 mm / sec, a small dessert spoon with a length of 9.8 cm, a thickness of 1 mm for the dish part, and a thickness of 1.5 mm for the handle was obtained. (Bending Evaluation) The left hand held the end of the dish part 11 of the spoon 10, and the right hand held the end of the spoon handle 12, and the bending test was carried out by bending vigorously in the direction of the arrow shown in Figure 1. The same bending test was performed on 5 spoons. When none of them broke, it was evaluated as ○ (good toughness), and when even one broke, it was evaluated as × (insufficient toughness).

[0070] [Evaluation of Molding Cycle] The resin pellets dried at 60°C for 24 hours using a dehumidifying dryer were used to obtain coffee capsules using an injection molding machine Si-30V manufactured by Toyo Machine Metal. The barrel temperature of the injection molding machine was set at nozzle / T1 / T2 / T3 = 155 / 145 / 135 / 125°C, the mold temperature was set at 35°C, and the injection speed was 20 mm / sec. When the molding cycle was less than 30 seconds, it was evaluated as 〇 (good productivity), and when it was 30 seconds or more, it was evaluated as × (insufficient productivity).

[0071] [Evaluation of seawater degradability] (Preparation of test pieces) Pellets dried at 60°C for 24 hours using a dehumidifying dryer were used. A film with a thickness of 30 μm was obtained using a single-screw extruder type D2020, a T-die type T150C (lip thickness 250 μm, lip width 15 cm), and a film take-up device type FT2W20 (roll temperature 30°C, take-up speed 2 m) on a Toyo Seiki Laboplastomill 3S150 under the molding temperature conditions C1 / C2 / C3 / die = 130 / 140 / 150 / 160°C. (Seawater degradation test) 10 L of seawater that had not rained for more than 3 consecutive days was collected from the Seto Inland Sea adjacent to Kaneka Takasago Kogyosho Co., Ltd., filtered through an 80-mesh filter, and then 5 g of ammonium chloride and 1 g of potassium dihydrogen phosphate were added and stirred until completely dissolved. The prepared seawater was filled to 60% of the volume of a container with a height of 37 × depth of 30 × width of 52 cm. A 10 × 10 cm piece cut from the film was immersed in the seawater and left for 2 months while air was bubbled. When the film was decomposed and disappeared, it was evaluated as 〇 (good seawater degradability), and when the film did not disappear, it was evaluated as × (insufficient seawater degradability).

[0072] <Example 1> (Preparation of PHBH blend) The total amount of copolymer (A), copolymer (B), and other biodegradable resins was set to 100 parts by weight, where 100 parts by weight = 10 kg. Based on the formulation (unit: parts by weight) described in Table 2, each component other than talc was mixed. Specifically, using a 75L super mixer manufactured by Kawata Co., Ltd., 9.0 kg of PHBH1, 1.0 kg of PHBH2, 100 g of additive 1, and 50 g of additive 2 were added, and the mixture was stirred at 300 rpm for 3 minutes to obtain a PHBH blend.

[0073] (Compounding) In a Toshiba Machine TEM26SS (L / D = 60), the screw configuration, auxiliary equipment, and barrel set temperature described in Table 1 were adopted, and the screw rotation speed was set to 100 rpm. From the screw root, the above PHBH blend was fed from the main feed, and further, 1.0 kg of talc was added from the side feed. The total supply amount of the main feed and the side feed was set to 10 kg / hr, and based on the following calculation formula, the supply amounts of the main feed and the side feed were determined respectively. Side feed supply amount = 10 kg / hr × weight parts of talc ÷ total weight parts of compounding components Main feed supply amount = 10 kg / hr - side feed supply amount The strands coming out from the die tip were passed through a water tank filled with warm water at 45°C for solidification, and then cut by a pelletizer to obtain pellets. Using the obtained pellets, a tensile modulus, a bending test, and a molding cycle test were carried out, and the results were summarized in Table 3.

[0074] <Examples 2 to 16, Comparative Examples 1 to 22> Pellets were obtained in the same procedure as in Example 1 except that the preparation of the PHBH blend and compounding were carried out based on the formulation described in Table 2. A tensile modulus, a bending test, and a molding cycle test were carried out, and the results were summarized in Table 3. For Examples 4 and 8, and Comparative Examples 21 and 22, a seawater degradability test was also carried out, and the results were described in Table 3.

[0075]

Table 1

[0076] [Table 2]

[0077] [Table 3]

[0078] From Table 3, it can be seen that the injection-molded articles obtained in Examples 1 to 16 have both good elastic modulus and toughness shown in the bending test, a short molding cycle, and excellent productivity. On the other hand, all of the injection-molded articles obtained in Comparative Examples 1, 2, 6, 7, 9, 10, 12, 13, and 15 in which the content ratio of the copolymer (B) is less than 7% by weight were insufficient in toughness. Also, all of the injection-molded articles obtained in Comparative Examples 8, 11, 14, and 16 in which the content ratio of the copolymer (B) exceeds 28% by weight had a long molding cycle and insufficient productivity. Even when the content ratio of the copolymer (B) is in the range of 7 to 28% by weight, all of the injection-molded articles obtained in Comparative Examples 3 to 5 that do not contain talc were insufficient in elastic modulus. Also, in all of Comparative Examples 17 to 20 in which the talc content exceeds 45 parts by weight, pelletization was impossible, that is, injection-molded articles could not be manufactured. All of the injection-molded articles obtained in Comparative Examples 21 and 22 that do not contain the copolymer (B) but instead contain other biodegradable resins were insufficient in elastic modulus and also insufficient in seawater degradability. [Explanation of Signs]

[0079] 10 spoon 11 dish part 12 handle

Claims

1. An injection molding resin composition containing a poly(3-hydroxyalkanoate) resin component, wherein the poly(3-hydroxyalkanoate) resin component includes a copolymer (A) of a 3-hydroxybutyrate unit and other hydroxyalkanoate units, with the content ratio of the other hydroxyalkanoate units being 1 to 6 mol%, and a copolymer (B) of a 3-hydroxybutyrate unit and other hydroxyalkanoate units, with the content ratio of the other hydroxyalkanoate units being 24 mol% or more, the resin composition further includes a layered clay mineral (C), in the poly(3-hydroxyalkanoate) resin component, the proportion of the copolymer (A) is 72 to 93% by weight, and the proportion of the copolymer (B) is 7 to 28% by weight, an injection molding resin composition, wherein the content of the layered clay mineral (C) is 5 to 45 parts by weight based on 100 parts by weight in total of the poly(3-hydroxyalkanoate) resin component.

2. The injection molding resin composition according to Claim 1, wherein the average content ratio of the other hydroxyalkanoate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin component is 2 to 35 mol%.

3. The injection molding resin composition according to Claim 1 or 2, wherein the other hydroxyalkanoate unit is a 3-hydroxyhexanoate unit.

4. The injection molding resin composition according to any one of Claims 1 to 3, wherein the layered clay mineral (C) is at least one selected from the group consisting of mica, talc, and kaolinite.

5. An injection molded article comprising the injection molding resin composition according to any one of Claims 1 to 4.

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