JP2012241166A - Poly(3-hydroxyalkanoate)-based preliminarily foamed particle and in-mold expansion-molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a poly(3-hydroxyalkanoate)-based preliminarily foamed particle which has biodegradability, is excellent in moldability and physical properties, and has a high expansion ratio and a high closed cell ratio, and to provide an in-mold expansion-molded body.SOLUTION: The poly(3-hydroxyalkanoate)-based preliminarily foamed particle is obtained by expanding a particle comprising a poly(3-hydroxyalkanoate)-based resin composition containing 1-10 pts.wt. of glycerin triester in which constituent fatty acids are 1-12C aliphatic acids, with respect to 100 pts.wt. of a resin containing ≥70% of a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer in which the composition ratio of 3-hydroxyhexanoate is 6-12 mol%, at 105-125°C and has ≥20 of expansion ratio and ≥90% of closed cell ratio and also is not cross-linked. The poly(3-hydroxyalkanoate)-based preliminarily foamed particles are fused mutually in a metallic mold to produce the in-mold expansion-molded body.

Description

  The present invention relates to pre-expanded particles obtained by foaming resin composition particles mainly composed of biodegradable poly (3-hydroxyalkanoate) resin, and an in-mold foam-molded article using the pre-expanded particles.

  Conventionally, plastics have been made disposable because of ease of processing and hygiene problems, while being easy to process or use. However, as plastics are used and disposed of in large quantities, the problems associated with landfilling and incineration are becoming more and more important, and there is a shortage of landfills and the ecosystem due to non-degradable plastics remaining in the environment. Impacts, generation of harmful gases during combustion, global warming due to a large amount of heat of combustion, etc. In recent years, biodegradable plastics have been actively developed as a solution to the problem of plastic waste.

  Above all, carbon dioxide produced when burning plant-derived biodegradable plastic was originally in the air, and carbon dioxide in the atmosphere does not increase. This is called carbon neutral and tends to be regarded as important. Since carbon dioxide fixation is expected to be effective in preventing global warming, a parliamentary deliberation for ratification was approved in Russia in August 2003, especially against the Kyoto Protocol that imposed carbon dioxide reduction target values. The effectiveness of the Protocol has come to a certainty, and carbon dioxide-fixed substances are very attractive and are expected to be used actively.

  On the other hand, aromatic polyesters are produced and consumed in large quantities as general-purpose polymers, but they are not biodegradable and are also produced from fossil fuels in terms of carbon dioxide fixation and prevention of global warming. Therefore, carbon dioxide immobilized in the ground is released into the atmosphere, which is not a preferable material in terms of carbon neutrality.

  From the viewpoint of biodegradability and carbon neutral, aliphatic polyester-based resins have attracted attention as plant-derived plastics, and in particular, polylactic acid-based resins, poly (3-hydroxyalkanoates) (hereinafter sometimes referred to as P3HA) Poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer (hereinafter sometimes referred to as PHBH), poly (3-hydroxybutyrate-co) among P3HA resins, and P3HA resins -3-Hydroxyvalerate) copolymers and the like are attracting attention.

  In particular, PHBH has high heat resistance due to crystallinity, and further has flexibility, impact resistance, and high tensile elongation due to 3-hydroxyhexanoate (hereinafter sometimes referred to as 3HH) which is a copolymerization component. It attracts attention as a resin material with balanced physical properties having characteristics similar to those of general-purpose resins such as polyethylene resins and polypropylene resins.

  On the other hand, foams made of general-purpose resins such as polyethylene resins and polypropylene resins have been widely used as cushioning materials for packaging, agricultural boxes, fish boxes, automobile members, building materials, civil engineering materials, and the like. However, when these foams made of general-purpose resins are left in a natural environment after use, they are not decomposed by microorganisms in the soil, which may cause environmental pollution problems. Development of foams using resin is underway.

  Patent Document 1 discloses a pre-expanded particle using PHBH as a biodegradable resin and a method for obtaining a molded body thereof. In this patent, there is reported a method of obtaining an aliphatic polyester-based pre-foamed particle having two melting points and an in-mold foam-molded product comprising the pre-foamed particle, using PHBH as a dispersion medium in water and isobutane as a foaming agent. Has been. However, since high-viscosity PHBH is used, high-expansion pre-expanded particles cannot be obtained when foamed at low temperatures.

  For this reason, pre-expanded particles with a high magnification are obtained by slowly raising the temperature to a desired foaming temperature and setting the foaming temperature to a high temperature while growing the crystal. For this reason, the foaming process takes a long time, the productivity is poor, and the manufacturing cost is increased. Further, since the resin particles and water coexist in the pressure resistant container for a long time due to foaming at a high temperature, hydrolysis is significant and stable quality aliphatic polyester pre-foamed particles and molded products cannot be obtained.

  In addition, development related to a foam of a polylactic acid resin, which is a representative biodegradable resin, has been actively conducted. Patent Documents 2 and 3 include a step of impregnating a polylactic acid resin particle with a foaming agent, It has been reported about polylactic acid-based pre-expanded particles obtained from the step of foaming foaming agent-impregnated polylactic acid-based resin particles with steam and molded articles thereof. Patent Document 2 discloses a method for improving the expansion ratio by adding a castor oil-based aliphatic ester to a polylactic acid-based resin modified or cross-linked with isocyanate. However, since the glass transition temperature is lowered by adding a castor oil-based aliphatic ester to the polylactic acid-based resin, when the polylactic acid-based resin particles are impregnated with a foaming agent, and the foaming agent-impregnated polylactic acid-based resin particles are steamed. When foaming, blocking may easily occur. Moreover, since the isocyanate is generally considered to be toxic, the usable applications are limited.

  Patent Document 3 discloses a technique for containing a fusibility improver such as a glycerin derivative in order to improve the fusibility of polylactic acid-based pre-foamed particles. In this patent, in order to selectively have a fusing improver on the surface of polylactic acid-based pre-expanded particles, polylactic acid-based resin particles heavier than water are impregnated with a foaming agent in an aqueous medium, It is necessary to add a lighter adhesion improver. For this reason, the impregnation variation of the fusing property improving agent occurs, and the polylactic acid-based pre-expanded particles having a uniform quality may not be obtained. In addition, the amount of impregnation of the fusibility improver is different between the inside and the surface of the polylactic acid resin particles, so that the effect of improving the expansion ratio is not sufficient.

  Patent Document 4 describes a resin composition comprising a poly (3-hydroxyalkanoate) resin and a plasticizer mainly composed of polyglycerol acetate having an acetylation rate of 50% or more. The effect of the patent is a method for improving deterioration of physical properties of the resin composition and the molded body thereof over time, and although it is described that the resin composition can be made into a foam, it is particularly effective to increase the expansion ratio and increase the independence. There is no description about making the bubble rate.

  Patent Document 5 discloses a cup composed of paper laminated with a poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) / triacetin / polyhydroxybutyrate mixture, and the cups are made of PHA. It describes that it is molded from a foam material. However, the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer used only describes the 3-hydroxyhexanoate ratio, and no specific description of the foam material is given at all. It has not been. Further, since a chemical foaming agent is used as the foaming agent, the foaming temperature is as high as 155 ° C., and when the foaming temperature is lowered, the foaming ratio is greatly reduced. Furthermore, there is no description regarding specific foaming ratio and closed cell ratio.

  Patent Document 6 discloses a packaging material composed of a poly (3-hydroxybutyrate) resin and glycerin triester, and merely describes that the packaging material may be a foam. There is no description on increasing the expansion ratio and increasing the closed cell ratio.

JP 2000-319438 A JP 2007-138097 A JP 2006-282750 A International Publication Number WO2008 / 018567 Special table 2003-518998 gazette Japanese Patent Laid-Open No. 4-136066

  An object of the present invention is to provide P3HA-based pre-expanded particles and in-mold foam-molded articles that are biodegradable, have good moldability and physical properties, and have a high expansion ratio and closed cell ratio.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention premixed particles obtained by mixing PHBH with a specific amount of triacetin and foaming in a specific temperature range have an expansion ratio of 20 times. As a result, the present inventors have found that the closed cell ratio is 90% or more and have completed the present invention.

  That is, according to the first aspect of the present invention, a poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer having a composition ratio of 3-hydroxyhexanoate of 6 to 12 mol% is 70% or more. Particles comprising a poly (3-hydroxyalkanoate) resin composition containing 1 to 10 parts by weight of glycerin triester whose constituent fatty acid is an aliphatic acid having 1 to 12 carbon atoms with respect to 100 parts by weight of the contained resin The present invention relates to non-crosslinked poly (3-hydroxyalkanoate) -based pre-expanded particles which are foamed at 105 to 125 ° C., have an expansion ratio of 20 times or more and a closed cell ratio of 90% or more. In a preferred embodiment, the poly (3-hydroxyalkanoate) -based resin composition has a melt flow rate measured at 190 ° C. and 2.16 kgf of 7 to 25 g / 10 min. Ate) based pre-expanded particles. More preferably, the poly (3-hydroxyalkanoate) -based pre-foamed particles described above formed by foaming using carbon dioxide as a foaming agent, more preferably, the resin composition is obtained by melt kneading. The poly (3-hydroxyalkanoate) -based pre-expanded particles described above, particularly preferably poly (3-hydroxybutyrate-co-3-hydroxy) having a composition ratio of 3-hydroxyhexanoate of 6 to 12 mol% Hexanoate) From a resin composition containing 1 to 10 parts by weight of a glycerin triester whose fatty acid is an aliphatic acid having 1 to 12 carbon atoms with respect to 100 parts by weight of a resin containing 70% or more of a copolymer The resulting poly (3-hydroxyalkanoate) resin composition particles are dispersed in an aqueous dispersion medium in a closed container together with a dispersant, and then the foaming agent is sealed in the sealed container. After being heated to the softening temperature of the resin composition particles or higher, one end of the sealed container is opened, and the resin composition particles and the aqueous dispersion medium are released in an atmosphere at a pressure lower than the pressure of the sealed container. And the poly (3-hydroxyalkanoate) -based pre-expanded particles described above, wherein the resin particles are expanded. A second aspect of the present invention is a poly (3-hydroxyalkanoate) -based type characterized in that the poly (3-hydroxyalkanoate) -based pre-expanded particles described above are fused together in a mold. The present invention relates to an inner foam molding.

  According to the present invention, it is possible to provide P3HA pre-expanded particles and in-mold foam-molded articles that are biodegradable, have good moldability and physical properties, and have a high expansion ratio and closed cell ratio.

  Hereinafter, the present invention will be described in more detail. The poly (3-hydroxyalkanoate) -based pre-expanded particles of the present invention are non-crosslinked without using isocyanate or the like, and particles made of a poly (3-hydroxyalkanoate) -based resin composition are expanded at a specific temperature. It becomes.

  In the present invention, the term “non-crosslinked” refers to a case where the proportion of insoluble matter in the poly (3-hydroxyalkanoate) -based pre-expanded particles is 3% by weight or less, preferably 1% by weight or less, and 0% by weight. % Is most preferred. The reason is that a crosslinking agent or the like is not necessary, and there is a cost merit such that the pressure of the molding heating steam at the time of in-mold foam molding can be kept low, and it is easy to reuse.

  In addition, the ratio of the insoluble content of the P3HA pre-expanded particles is measured as follows. A 150 ml flask is charged with 1 g of P3HA pre-expanded particles and 100 ml of chloroform, heated under reflux at 62 ° C. for 8 hours under atmospheric pressure, and the resulting heat-treated product is suction filtered using a 200-mesh wire mesh. And filter. The obtained filtered product on the wire mesh is dried in an oven at 80 ° C. under a vacuum of 30 to 40 Torr for 8 hours. At this time, the dry matter weight W1 (g) obtained is measured. The weight ratio of this weight W1 (g) to 1 g of P3HA pre-expanded particles is defined as insoluble matter.

  The poly (3-hydroxyalkanoate) -based resin composition of the present invention comprises a resin containing 70% by weight or more of a poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer and glycerin triester. contains. The content of the copolymer in the resin is preferably 90% by weight or more, and more preferably 100% by weight. The resin composition is preferably obtained by melt kneading. The copolymer is preferably a product produced by microorganisms from the viewpoint of carbon dioxide fixation.

  The poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer of the present invention comprises a repeating unit of 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) and 3-hydroxyhexanoate It is used as a general term for copolymers consisting of the above repeating units. Therefore, other monomer components may be included. The polymerization method for obtaining the copolymer is not particularly limited, and any copolymerization method such as random copolymerization, alternating copolymerization, or block copolymerization may be applied.

  The constitutional ratio of the repeating unit of the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer is 3-hydroxybutyrate unit / 3 from the viewpoint of molding processability and molded product quality. -Hydroxyhexanoate unit = 94/6 to 88/12 (mol / mol) is preferable, and 93/7 to 89/11 (mol / mol) is more preferable.

  The 3HH composition ratio of PHBH can be measured by gas chromatography as follows. To 20 mg of dry PHBH, 2 ml of a sulfuric acid-methanol mixture (15:85) and 2 ml of chloroform are added and sealed, and heated at 100 ° C. for 140 minutes to obtain a methyl ester of a PHBH decomposition product. After cooling, 1.5 g of sodium hydrogen carbonate is added little by little to neutralize it, and the mixture is allowed to stand until the generation of carbon dioxide gas stops. After adding 4 ml of diisopropyl ether and mixing well, it is centrifuged, and the monomer unit composition of the PHBH degradation product in the supernatant is analyzed by capillary gas chromatography to obtain the 3HH ratio.

  The gas chromatograph uses “GC-17A” manufactured by Shimadzu Corporation, and the capillary column uses “NEUTRA BOND-1” manufactured by GL Science Co., Ltd. (column length 25 m, column inner diameter 0.25 mm, liquid film thickness 0.4 μm). He is used as the carrier gas, the column inlet pressure is set to 100 kPa, and 1 μl of the sample is injected. As for the temperature condition, the temperature is raised at a rate of 8 ° C./min from the initial temperature of 100 ° C. to 200 ° C., and further, the temperature is raised at a rate of 30 ° C./min from 200 ° C. to 290 ° C.

  The PHBH is preferably a product produced by a microorganism. Examples of the microorganism include Alcaligenes eutrophus AC32 strain in which a PHA synthase gene derived from Aeromonas caviae has been introduced into Alcaligenes eutrophus (International Deposit under the Budapest Treaty, International Depositary: National Institute of Advanced Industrial Science and Technology, Patent Biology Center) Kunibara, Tsukuba, Higashi 1-chome, 1-Chuo 1-Chuo 6), original deposit date: August 12, 1996, transferred to August 7, 1997, deposit number FERM BP-6038, original deposit FERM P-15786 (Transfer)) (J. Bacteriol., 179, 4821 (1997)) and the like. For example, according to WO09 / 145164, PHBH produced by microorganisms can be obtained.

  As a resin other than PHBH contained in the entire resin of the present invention in an amount of 30% by weight or less, a resin having good compatibility with PHBH and having biodegradability is preferable. Examples thereof include poly (3-hydroxyalkanoate) -based resins other than PHBH, polylactic acid, polybutylene succinate, polybutylene adipate terephthalate, and the like, and at least one selected from these groups can be used.

  As the glycerol triester contained in the poly (3-hydroxyalkanoate) resin composition of the present invention, the constituent fatty acid is preferably an aliphatic acid having 1 to 12 carbon atoms, and the constituent fatty acid is 8 to 12 carbon atoms. More preferably, it is an aliphatic acid. When the number of carbon atoms of the constituent fatty acid exceeds 12, the compatibility with the P3HA resin is deteriorated, and it may be easy to bleed out.

  Specific examples of the glycerin triester include triacetin, glycerin diacetyl monolaurate, C8 and C10 fatty acid triglycerides ("Coconard MT" manufactured by Kao Corporation), C8 fatty acid triglycerides ("Coconard RK" manufactured by Kao Corporation), and the like. Among them, glycerin diacetyl monolaurate, C8 and C10 fatty acid triglycerides (“Coconard MT” manufactured by Kao Corporation) are preferable, and glycerin diacetyl monolaurate is more preferable.

  The amount of the glycerin triester used is 1 to 10 parts by weight with respect to 100 parts by weight of a resin containing 70% by weight or more of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer. It is preferable that it is 1 to 5 parts by weight. If it is less than 1 part by weight, the effect of improving the expansion ratio may not be obtained so much. Moreover, when it exceeds 10 weight part, a plasticizer may become easy to bleed out on the surface of an in-mold foaming molding.

  The weight average molecular weight of the resin containing 70% by weight or more of the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer of the present invention (hereinafter sometimes referred to as Mw1) is 300,000 to 3 million is preferable, 350,000 to 2.5 million is more preferable, and 350,000 to 2 million is more preferable. When the weight average molecular weight is less than 300,000, mechanical properties and the like may be inferior, and when it exceeds 3 million, molding may be difficult.

  The weight average molecular weight was measured using gel permeation chromatography (Waters), polystyrene gel (“Shodex K-804”, Showa Denko KK) as the column, chloroform as the mobile phase, and polystyrene equivalent. The molecular weight can be obtained. At this time, the calibration curve was prepared using polystyrene having a weight average molecular weight of 31400, 197000, 668000, and 1920,000.

  The poly (3-hydroxyalkanoate) resin composition has a melt flow rate measured at 190 ° C. and 2.16 kgf in order that the pre-expanded particles using the resin composition have a high expansion ratio and a high closed cell ratio. (Hereinafter, it may be referred to as MFR2) is preferably 7 to 25 g / 10 minutes, and the resin composition as described above satisfies the above melt flow rate in most cases. If the MFR2 is less than 7 g / 10 minutes, the expansion ratio may be difficult to increase unless the foaming temperature is increased. If the foaming temperature exceeds 25 g / 10 minutes, the bubbles in the resulting P3HA pre-expanded particles are continuous and foamed in the mold. Molding may be difficult.

  The method for measuring the melt flow rate of the P3HA resin composition is a value measured at 190 ° C. under a 2.16 kg load according to JIS K7210. When the value exceeds 100 g / 10 min, measurement is impossible.

  The P3HA resin composition in the present invention may contain various additives as long as the effects of the present invention are not impaired. Here, the additive may be, for example, an air conditioner, an antioxidant, an ultraviolet absorber, a colorant such as a dye or a pigment, a lubricant, a crystallization nucleating agent, an inorganic filler, etc., depending on the purpose. Biodegradable additives are preferred.

  As crystallization nucleating agents, 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 bis stearic acid amide, ethylene bis olein Acid amide, ethylene biserucic acid amide, ethylene bislauric acid amide, ethylene biscapric acid amide, p-phenylenebisstearic acid amide, and the like. The amount used is preferably 0.5 to 5 parts by weight. .

  Examples of the air conditioner include inorganic agents such as talc, silica, calcium silicate, calcium carbonate, aluminum oxide, titanium oxide, diatomaceous earth, clay, baking soda, alumina, barium sulfate, aluminum oxide, bentonite, and the amount used is Usually, it is preferably 0.005 to 1 part by weight.

  Inorganic fillers include carbon black, calcium carbonate, silicon oxide and silicate, zinc white, high-site clay, kaolin, basic magnesium carbonate, mica, talc, quartz powder, diatomaceous earth, dolomite powder, titanium oxide, Examples thereof include zinc oxide, antimony oxide, barium sulfate, calcium sulfate, alumina, calcium silicate and the like.

  Examples of other fillers include inorganic fibers such as carbon fibers and organic fibers such as human hair and wool. In addition, natural fibers such as bamboo fiber, pulp fiber, kenaf fiber, other similar plant substitute species, Mallow family annual plant, linden annual plant plant and the like can also be used. From the viewpoint of reducing carbon dioxide, plant-derived natural fibers are preferable, and kenaf fibers are particularly preferable.

  Examples of the method for producing the P3HA pre-expanded particles and the in-mold foam-molded product of the present invention are shown below.

<Method for producing P3HA-based pre-expanded particles>
First, a resin containing 70% by weight or more of a poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer and a glycerin triester, and further, if necessary, the various additives as an extruder, Melting and kneading using a kneader, Banbury mixer, roll, etc. to produce a P3HA resin composition, extruding it into a strand, and then cutting it into a cylindrical, elliptical, spherical, cubic, cuboid, etc. The P3HA resin composition particles having a particle shape that can be easily used for foaming of the present invention are obtained. The weight per resin composition particle is preferably 0.1 to 10 mg, more preferably 0.5 to 7 mg. If it is less than 0.1 mg, it may be difficult to produce P3HA-based resin composition particles, and if it exceeds 10 mg, it may be difficult to reduce the thickness of the in-mold foam molded product.

  In the above, the temperature at which the resin containing 70% by weight or more of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer and glycerin triester are melt kneaded depends on the melting point and viscosity of the resin used. However, the temperature of the melt-kneaded product is preferably 120 to 170 ° C, more preferably 130 to 160 ° C, and still more preferably 135 to 150 ° C. If the temperature of the melt-kneaded product is less than 120 ° C., the kneaded state of the resin composition may be non-uniform, and if it exceeds 170 ° C., the resin composition is slow to solidify and the productivity is deteriorated. The composition may thermally decompose.

  The melting point of the P3HA resin composition particles obtained above (hereinafter sometimes referred to as Tm2) is preferably 110 to 160 ° C, and more preferably 120 to 150 ° C. When the melting point is less than 110 ° C., the heat resistance is low, and the resulting molded product may be easily deformed by heat. If the melting point exceeds 160 ° C., it is necessary to increase the temperature at which the P3HA resin composition particles are foamed, so that hydrolysis may easily occur when water is used as a solvent during the foaming step.

  In addition, the said melting | fusing point heats up 1-10 mg of P3HA type | system | group resin composition particle | grains from 10 degreeC to 180 degreeC at the rate of 10 degree-C / min using a differential scanning calorimeter (made by Seiko Instruments Inc.), In the endothermic curve obtained when cooling from 180 ° C. to 10 ° C. at a rate of 10 ° C./min and again raising the temperature to 180 ° C. at a rate of 10 ° C./min, it means the endothermic peak temperature appearing on the highest temperature side.

  In order to make Tm2 within the above range, the melting point of the resin containing 70% by weight or more of the raw material poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer (hereinafter referred to as Tm1). In some cases) is preferably 115 to 165 ° C, more preferably 125 to 155 ° C. If Tm1 is within the above range, Tm2 can be easily within the desired temperature range.

  In addition, the said melting | fusing point uses a differential scanning calorimeter (made by Seiko Instruments Inc.), and contains 1-10 mg of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer 70weight% or more. The resin is heated at a rate of 10 ° C./min from 10 ° C. to 180 ° C., then cooled at a rate of 10 ° C./min from 180 ° C. to 10 ° C., and again at a rate of 10 ° C./min from 180 ° C. In the endothermic curve obtained when the temperature is raised, the endothermic peak temperature that appears on the highest temperature side.

  Necessary after the P3HA resin composition particles obtained above are dispersed in an aqueous dispersion medium in a closed container together with a dispersant, and then a foaming agent is introduced into the sealed container and heated above the softening temperature of the resin composition particles. After holding for a certain period of time near the foaming temperature, one end of the sealed container is released, and the resin composition particles and the aqueous dispersion medium are released into an atmosphere at a pressure lower than the pressure of the sealed container. The resin composition particles are expanded (hereinafter, this series of operations may be referred to as decompression foaming) to obtain P3HA pre-expanded particles. In addition, the temperature in the airtight container at the time of discharge | release in a low pressure atmosphere is a foaming temperature, and the pressure in the airtight container at the time of discharge | release in a low pressure atmosphere is a foaming pressure.

  Examples of the dispersant include inorganic substances such as tricalcium phosphate, calcium pyrophosphate, kaolin, basic magnesium carbonate, aluminum oxide, basic zinc carbonate, and so on, for example, dodecylbenzene sulfonate sodium, α-olefin sulfonate sodium, normal Anionic surfactants such as paraffin sulfonic acid sodium can be mentioned, and it is preferable to use a combination of an inorganic substance and an anionic surfactant.

  The amount of the inorganic substance used is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the P3HA resin composition particles, and the amount of the anionic surfactant used is P3HA resin composition particles 100. It is preferable that it is 0.001-0.5 weight part with respect to a weight part, and it is more preferable that it is 0.001-0.2 weight part or less.

  As the aqueous dispersion medium, water is usually preferable from the viewpoints of economy and handleability, but is not limited thereto. The amount of the aqueous dispersion medium used is preferably 100 to 1000 parts by weight with respect to 100 parts by weight of the P3HA resin composition particles.

  Examples of blowing agents include inorganic gases such as carbon dioxide, nitrogen and air, saturated hydrocarbons having 3 to 5 carbon atoms such as propane, normal butane, isobutane, normal pentane, isopentane and neopentane, dimethyl ether, diethyl ether, and methyl ethyl ether. And halogenated hydrocarbons such as ether, monochloromethane, dichloromethane, dichlorodifluoroethane, water, etc., and at least one selected from these groups can be used. Among these, it is preferable to use carbon dioxide from the viewpoint of environmental load and foaming power.

  The amount of foaming agent added varies depending on the expansion ratio of the target pre-expanded particles, the type of foaming agent, the type of P3HA resin, the ratio of the P3HA resin composition particles to the dispersion medium, the space volume of the sealed container, the foaming temperature, etc. However, it is preferably 2 to 10000 parts by weight, more preferably 5 to 5000 parts by weight, and still more preferably 10 to 1000 parts by weight with respect to 100 parts by weight of the P3HA resin composition particles. If the foaming agent is less than 2 parts by weight, a sufficient foaming ratio may not be obtained, and even if the foaming agent exceeds 10,000 parts by weight, it is not possible to obtain the effect of addition, and it is economically wasteful. There is a case.

  The rate at which the temperature is raised to the desired foaming temperature (hereinafter sometimes referred to as the rate of temperature rise) is preferably 1 to 3 ° C / min, and more preferably 1.5 to 3 ° C / min. When the rate of temperature rise is less than 1 ° C./min, productivity is low and hydrolysis may occur remarkably. If the rate of temperature rise exceeds 3 ° C./min, annealing may not be sufficiently performed at the time of temperature rise.

  The foaming temperature varies depending on the type of P3HA resin to be used, the type / addition amount of glycerin triester, the type of foaming agent, the expansion ratio of the desired pre-expanded particles, etc. Preferably there is. If the foaming temperature is 105 ° C. or lower, the foaming ratio may be difficult to increase. If the foaming temperature is 125 ° C. or higher, the P3HA-based resin particles may be hydrolyzed in the sealed container. May be significantly reduced.

  The foaming pressure is preferably 1 to 10 MPa (gauge pressure), and more preferably 2.5 to 5 MPa (gauge pressure).

  The time for holding near the foaming temperature is preferably 1 to 60 minutes, and more preferably 5 to 40 minutes. If the holding time is less than 1 minute, the amount of foaming agent impregnated may be non-uniform. If it exceeds 60 minutes, the molecular weight may decrease significantly due to hydrolysis.

  When the dispersion in the sealed container is discharged into a low-pressure atmosphere, it can be discharged through an opening orifice having a diameter of 1 to 5 mm for the purpose of adjusting the flow rate and reducing the variation in magnification. For the P3HA resin composition particles having a relatively high melting point, the low-pressure atmosphere may be filled with saturated water vapor for the purpose of improving the expansion ratio.

  The P3HA-based pre-expanded particles of the present invention obtained as described above have a closed cell ratio of 90% or more, preferably 95% or more. When the closed cell ratio is less than 90%, the P3HA pre-expanded particles are unlikely to expand during in-mold foam molding. Moreover, according to said manufacturing method, it becomes easy to make an expansion ratio 20 times or more and an independent cell rate 90% or more.

  In the present invention, an expansion ratio of 20 times or more may not be obtained only by the decompression foaming method. In that case, after the pressure in the P3HA pre-expanded particles is made higher than the normal pressure by pressurizing the P3HA pre-expanded particles in an airtight container and impregnating with an inorganic gas such as air or carbon dioxide, the P3HA It is good also as P3HA type | system | group pre-expanded particle which heated the system pre-expanded particle with steam etc., and made it expand further, and raised the expansion ratio by what is called two-stage expansion. However, from the viewpoint of productivity and the like, it is preferable that the expansion ratio is 20 times or more only by decompression foaming.

  The pressure in the P3HA pre-expanded particles after the pressure treatment impregnating the inorganic gas (hereinafter sometimes referred to as expanded particle internal pressure) is preferably 0.15 to 0.65 MPa, More preferably, it is 30 to 0.65 MPa.

The internal pressure of the expanded particles is determined as follows. P3HA-based pre-expanded particles are not allowed to pass through, but inorganic gas is collected in an appropriate amount in a polyethylene bag of about 70 mm × 100 mm having a large number of fine pores that can freely pass through. The weight is measured in a temperature-controlled room. Let this weight be U (g). The weight of the P3HA pre-expanded particles after impregnating the P3HA pre-expanded particles contained in the polyethylene bag with an inorganic gas such as air or carbon dioxide is measured. Let this weight be Q (g). The difference between Q (g) and U (g) is taken as the impregnated inorganic gas amount m (g), and the foamed particle internal pressure P (MPa) is calculated by the following formula.
P = (m ÷ M) × R × T ÷ V1 + 0.1

  In the above formula, M is the molecular weight (g / mol) of the impregnated inorganic gas, R is the gas constant, T is the temperature in the constant temperature room (K), and V1 is the inorganic gas volume (L) in the P3HA-based pre-expanded particles. Then, R = 0.0083 (MPa · L / (K · mol)) is adopted. V1 is a value obtained by subtracting the volume of the base resin composition in the P3HA pre-expanded particles from the volume of the P3HA pre-expanded particles.

  The temperature in the sealed container when impregnating the P3HA pre-expanded particles with the inorganic gas is preferably 20 to 80 ° C, more preferably 40 to 80 ° C.

  The temperature of the steam or the like used in the two-stage foaming varies depending on the characteristics of the P3HA-based prefoamed particles to be used, the foaming ratio of the desired prefoamed particles, and cannot be defined unconditionally, but is generally 90 to 120 ° C. preferable.

  The P3HA-based pre-expanded particles obtained as described above can be made into a P3HA-based in-mold expanded molded body by a known molding method. For example, (A) pre-expanded particles are pressurized with an inorganic gas, impregnated with the inorganic gas in the pre-expanded particles, given a predetermined internal pressure of the expanded particles, filled into a mold, and heated and fused with water vapor. Method, (B) After filling the pre-expanded particles in the mold, compress the pre-expanded particles so that the volume of the pre-expanded particles is reduced by 15 to 50%, and heat-fuse with steam, (C) the pre-expanded particles at gas pressure A method of compressing and filling the mold, and using the recovery power of the pre-expanded particles to heat-fuse with steam, (D) without pretreatment, filling the mold with the pre-expanded particles, A method such as a heat fusion method can be used.

  The vapor pressure (hereinafter may be referred to as molding heating vapor pressure) when producing the P3HA-based in-mold foam molded product varies depending on the type of P3HA-based resin used, the type / addition amount of glycerin triester, and the like. However, it is generally preferably 0.05 to 0.25 MPa (gauge pressure), although it cannot be generally specified.

  As the inorganic gas of the method (A), air, nitrogen, carbon dioxide, helium, neon, argon, etc. can be used, and at least one selected from these groups can be used. Among these, air or carbon dioxide is preferable.

  The foamed particle internal pressure in the method (A) is preferably 0.15 to 0.40 MPa, more preferably 0.20 to 0.30 MPa.

  The temperature in the sealed container when impregnating the P3HA pre-expanded particles with the inorganic gas in the method (A) is preferably 20 to 80 ° C, more preferably 40 to 80 ° C or less.

  The in-mold foam-molded article of the present invention can be used for applications such as packaging cushioning materials, agricultural boxes, fish boxes, automobile members, building materials, and civil engineering materials.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” and “%” are based on weight.

<Measurement of 3HH ratio of PHBH>
To about 20 mg of dry PHBH, 2 ml of a sulfuric acid-methanol mixture (15:85) and 2 ml of chloroform were added and sealed, and heated at 100 ° C. for 140 minutes to obtain a methyl ester of a PHBH decomposition product. After cooling, 1.5 g of sodium hydrogen carbonate was added little by little to neutralize the solution, and the mixture was allowed to stand until generation of carbon dioxide gas stopped. After adding 4 ml of diisopropyl ether and mixing well, the mixture was centrifuged, and the monomer unit composition of the PHBH degradation product in the supernatant was analyzed by capillary gas chromatography to obtain the 3HH ratio. “GC-17A” manufactured by Shimadzu Corporation was used for the gas chromatograph, and “NEUTRA BOND-1” manufactured by GL Science (column length: 25 m, column inner diameter: 0.25 mm, liquid film thickness: 0.4 μm) was used as the capillary column. He was used as the carrier gas, the column inlet pressure was set to 100 kPa, and 1 μl of the sample was injected. As temperature conditions, the temperature was raised from an initial temperature of 100 ° C. to 200 ° C. at a rate of 8 ° C./min, and further from 200 to 290 ° C. at a rate of 30 ° C./min.

<Measurement of weight average molecular weight (Mw1, Mw2)>
The weight average molecular weight (Mw1) of the resin containing 70% or more of the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer or the weight average molecular weight (Mw2) of the P3HA-based resin composition particles is: Gel permeation chromatography (manufactured by Waters) was used, and polystyrene gel (“Shodex K-804” manufactured by Showa Denko KK) was used for the column. Chloroform was used as the mobile phase, and the molecular weight was calculated in terms of polystyrene. At this time, a calibration curve was prepared using polystyrene having a weight average molecular weight of 31400, 197000, 668000, and 1920,000.

<Measurement of melt flow rate (MFR1, MFR2)>
A resin or P3HA resin composition particle containing 70% or more of a sufficiently dried poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer is treated at 190 ° C. according to JIS K7210, 2 The values measured with a 16 kg load (the former: MFR1, the latter: MFR2).

<Measurement of melting point (Tm1, Tm2)>
The melting point of resin or P3HA resin composition particles containing 70% or more of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer is 1-10 mg of PHBH in differential scanning calorimetry. Alternatively, the P3HA-based resin composition particles are heated from 10 ° C. to 180 ° C. at a rate of 10 ° C./min, then cooled to 10 ° C. at a rate of 10 ° C./min, and again to 180 ° C. at a rate of 10 ° C./min. The endothermic peak temperature appearing on the highest temperature side in the endothermic curve obtained was read.

<Bleed-out property of P3HA resin composition particles>
The bleed state was evaluated from the state when the P3HA resin composition, which was at a high temperature immediately after melt-kneading the P3HA resin and glycerin triester, was immersed in a 60 ° C. hot water bath. The evaluation criteria at that time are as follows. ○: No bleed out, ×: With bleed out.

<Measurement of expansion ratio of P3HA pre-expanded particles>
A graduated cylinder containing ethanol at 23 ° C. was prepared, and 500 or more P3HA-based pre-expanded particles (weight W2 (g of expanded particle group) that were left in the graduated cylinder for 7 days under conditions of 50% relative humidity and 23 ° C. )) Is submerged using a wire mesh or the like, and the volume V2 (cm ³ ) of the expanded particle group read from the rise in the ethanol water level is determined from the density ρ1 (g / cm ³ ) of the P3HA resin composition. Calculated according to the formula.
Foaming ratio = V2 / W2 × ρ1

<Measurement of closed cell ratio of P3HA pre-expanded particles>
Using an air-comparing hydrometer (manufactured by BECKMAN), the closed cell volume of the obtained P3HA-based pre-expanded particles is obtained, and the closed cell volume is divided by the volume obtained by the ethanol immersion method separately. Was calculated.

<Measurement of Insoluble Content of P3HA Pre-foamed Particle>
A 150 ml flask is charged with 1 g of P3HA pre-expanded particles and 100 ml of chloroform, heated under reflux at 62 ° C. for 8 hours under atmospheric pressure, and the resulting heat-treated product is suction filtered using a 200-mesh wire mesh. And filtered. The obtained filtered product on the wire mesh was dried in an oven at 80 ° C. under a vacuum condition of 30 to 40 Torr for 8 hours. At this time, the obtained dry matter weight W1 (g) was measured. The weight ratio of this weight W1 (g) to 1 g of P3HA resin pre-expanded particles was defined as insoluble matter.

<Measurement of foamed particle internal pressure of P3HA pre-foamed particles>
P3HA pre-expanded particles are not allowed to pass through, but an appropriate amount is collected in a polyethylene bag of about 70 mm x 100 mm having a large number of fine pores through which inorganic gas can pass freely, and the temperature is constant at 23 ° C and 50% relative humidity under atmospheric pressure. The weight was measured indoors. This weight was defined as U (g). The weight of the P3HA pre-expanded particles after impregnating the P3HA pre-expanded particles contained in the polyethylene bag with an inorganic gas such as air or carbon dioxide was measured. This weight was defined as Q (g). The difference between Q (g) and U (g) was taken as the impregnated inorganic gas amount m (g), and the foamed particle internal pressure P (MPa) was calculated by the following formula.
P = (m ÷ M) × R × T ÷ V1 + 0.1

  In the above formula, M is the molecular weight (g / mol) of the impregnated inorganic gas, R is the gas constant, T is the temperature in the constant temperature room (K), and V1 is the inorganic gas volume (L) in the P3HA-based pre-expanded particles. Then, R = 0.0083 (MPa · L / (K · mol)) was adopted. V1 is a value obtained by subtracting the volume of the base resin composition in the P3HA pre-expanded particles from the volume of the P3HA pre-expanded particles.

<Measurement of molded body magnification>
The length, width and thickness of the in-mold foam molded body made of plate-like P3HA pre-expanded particles obtained by in-mold foam molding are measured with calipers to determine the volume of the in-mold foam molded body, and the in-mold foam is obtained. A value obtained by dividing the weight of the molded body by the volume of the in-mold foam molded body was defined as the density ρ2 (g / L) of the in-mold foam molded body. When the density ρ3 (g / L) of the P3HA resin composition was used, it was calculated according to the following formula.
Molded body magnification = ρ3 / ρ2

<Bleed-out property of molded body>
The in-mold foam molded body made of P3HA-based pre-expanded particles obtained in Examples and Comparative Examples was stored in an oven (manufactured by Tabai Espec) at a set temperature of 80 ° C. for 24 hours, and the in-mold foam molded body The bleed state was evaluated using the stickiness of the surface as an index. The evaluation criteria at that time are as follows. ○: No bleed out, ×: With bleed out.

(Production Example 1) Production of PHBH-1 PHBH-1 was produced according to [0064] to [0125] of International Publication No. 09/145164 pamphlet, in particular, Examples 4, 7 to 11 and Table 1. The characteristics of PHBH-1 were as follows. 3HH ratio = 7 mol%, Mw1 = 600,000, MFR1 = 10 g / 10 min, Tm1 = 142 ° C.

(Production Example 2) Production of PHBH-2 PHBH-2 was produced in accordance with [0064] to [0125] of International Publication No. 09/145164 pamphlet, in particular, Examples 2, 7 to 11 and Table 1. The characteristics of PHBH-2 were as follows. 3HH ratio = 11 mol%, Mw1 = 400,000, MFR1 = 15 g / 10 min, Tm1 = 132 ° C.

Production Example 3 Production of PHBH-3 PHBH-3 was produced according to [0064] to [0125] of International Publication No. 09/145164 pamphlet, in particular, Examples 1, 7 to 11 and Table 1. The characteristics of PHBH-3 were as follows. 3HH ratio = 12 mol%, Mw1 = 1.4 million, MFR1 = 3 g / 10 min, Tm1 = 128 ° C.

Example 1
According to the composition of Table 1, 100 parts by weight of PHBH-1 obtained in Production Example 1, 1 part by weight of glycerin diacetyl monolaurate (Additive 1, “Rikemar PL-012” manufactured by Riken Vitamin Co., Ltd.), talc ( 0.1 part by weight of a bubble adjusting agent) was melt-kneaded using a twin screw extruder, particle weight: 2.5 mg, Mw2 = 590,000, MFR2 = 10 g / 10 min, P3HA resin with Tm2 = 141 ° C. Composition particles were obtained. At this time, the temperature of the melt-kneaded product exiting from the twin screw extruder was 145 ° C., and no bleed out was observed when immersed in hot water at 60 ° C. The measurement and evaluation results for the obtained P3HA-based resin composition particles are summarized in Table 1.

  Subsequently, 100 parts by weight of the obtained P3HA-based resin composition particles, 200 parts by weight of water, 1.2 parts by weight of basic calcium triphosphate and 0.03 parts by weight of sodium dodecylbenzenesulfonate were charged into a pressure vessel and stirred. Then, after adding carbon dioxide as a foaming agent, the contents of the pressure vessel were heated from 60 ° C. to 120 ° C. at a temperature rising rate of 1.5 ° C./min. Thereafter, carbon dioxide was additionally injected and the pressure was increased to a foaming pressure of 4.0 MPa (gauge pressure). After maintaining the foaming temperature near the foaming pressure for 30 minutes, the valve at the bottom of the pressure vessel was opened and the diameter was 3.6 mm. The pressure-resistant container contents are discharged to atmospheric pressure through the opening orifice of P3HA to obtain P3HA-based pre-foamed particles. After washing the basic tricalcium phosphate adhering to the surface of the pre-foamed particles, drying is performed at 40 ° C. for 24 hours. And left for 7 days under conditions of relative humidity 50% and 23 ° C. to obtain P3HA-based pre-expanded particles. The obtained P3HA pre-expanded particles had an expansion ratio of 12 times, a closed cell ratio of 98%, and an insoluble content of 0% by weight. The results are summarized in Table 2.

The P3HA-based pre-expanded particles obtained above were charged into a 1 m ³ pressure-resistant container heated to 60 ° C. and subjected to pressure treatment with air, so that the internal pressure of the expanded particles was 0.20 MPa. The pre-expanded particles are filled in a block mold having a length of 400 mm, a width of 300 mm, and a thickness of 40 mm, and then compressed so that the volume of the pre-expanded particles is reduced by 10%, and then molded heating steam of 0.19 MPa (gauge pressure) An in-mold foam molded article was obtained by heating with pressure, dried at 40 ° C. for 24 hours, and allowed to stand for 7 days under conditions of 50% relative humidity and 23 ° C. The molded body magnification of the obtained in-mold foam molded product was 17 times, and no bleed out was observed on the surface of the in-mold foam molded product after being stored in an oven at a set temperature of 80 ° C. for 24 hours. The results regarding the in-mold foam molded product are summarized in Table 3.

(Example 2)
According to the composition of Table 1, P3HA-based pre-expanded particles and mold were the same as in Example 1 except that Additive-1 was 5 parts by weight, and the foamed particle internal pressure and the molding heating steam pressure were the values shown in Table 1. An inner foamed molded product was obtained. The evaluation results are summarized in Tables 2 and 3.

(Example 3)
According to the composition of Table 1, P-1HA pre-foaming was carried out in the same manner as in Example 1 except that Additive-1 was 10 parts by weight, and the foaming temperature, the foamed particle internal pressure and the molding heating steam pressure were the values shown in Table 1. Particles and an in-mold foam molding were obtained. The evaluation results are summarized in Tables 2 and 3.

Example 4
Except that the additive-1 is a C8, C10 fatty acid triglyceride (additive-2, “Coconard MT” manufactured by Kao Co., Ltd.) according to the formulation of Table 1, and the foamed particle internal pressure is the value shown in Table 1, Examples In the same manner as in Example 2, P3HA-based pre-expanded particles and in-mold expanded molded articles were obtained. The evaluation results are summarized in Tables 2 and 3.

(Example 5)
According to the composition of Table 1, Additive-1 was triacetin (Additive-3, “Triacetin” manufactured by Wako Pure Chemical Industries, Ltd.), and the foamed particle internal pressure and the molding heating steam pressure were the values shown in Table 1, In the same manner as in Example 2, P3HA-based pre-expanded particles and in-mold expanded molded articles were obtained. The evaluation results are summarized in Tables 2 and 3.

(Example 6)
Example 1 except that the P3HA-based resin was PHBH-2 obtained in Production Example 2 according to the formulation of Table 1, and the foaming temperature, the foamed particle internal pressure, and the molding heating steam pressure were the values shown in Tables 2 and 3. In the same manner as above, P3HA-based pre-expanded particles and in-mold expanded molded articles were obtained. The evaluation results are summarized in Tables 2 and 3.

(Example 7)
According to the composition of Table 1, P3HA-based pre-expanded particles and mold were the same as in Example 6 except that Additive-1 was 5 parts by weight, and the foamed particle internal pressure and the molding heating steam pressure were the values shown in Table 3. An inner foamed molded product was obtained. The evaluation results are summarized in Tables 2 and 3.

(Comparative Example 1)
According to the composition of Table 1, additive-1 was not used, and the same procedure as in Example 1 was performed except that the molding heating steam pressure was changed to the value shown in Table 3. Tables 2 and 3 summarize the evaluation results of the P3HA-based pre-expanded particles and the in-mold foam-molded product thus obtained. Compared with the Example using glycerin triester, the expansion ratio and the compact ratio were low.

(Comparative Example 2)
The same procedure as in Example 1 was carried out except that the additive-1 was 0.1 part by weight and the foamed particle internal pressure was the value shown in Table 3 according to the formulation in Table 1. Tables 2 and 3 summarize the evaluation results of the P3HA-based pre-expanded particles and the in-mold foam-molded product thus obtained. Since there was little addition amount of glycerol triester, there was almost no effect of this invention.

(Comparative Example 3)
According to the composition shown in Table 1, the same procedure as in Example 1 was conducted except that Additive-1 was 20 parts by weight and the foaming temperature, the foamed particle internal pressure and the molding heating steam pressure were set to the values shown in Table 3. Tables 2 and 3 summarize the evaluation results of the P3HA-based pre-expanded particles and the in-mold foam-molded product thus obtained. Since there was much addition amount of glycerol triester, additive-1 bleeded out from this molded object.

(Comparative Example 4)
According to the composition of Table 1, Additive-1 was glycerin (Additive-4, “glycerin” manufactured by Wako Pure Chemical Industries, Ltd.), and the foamed particle internal pressure and the molding heating steam pressure were the values shown in Table 3, The same operation as in Example 2 was performed. Tables 2 and 3 summarize the evaluation results of the P3HA-based pre-expanded particles and the in-mold foam-molded product thus obtained. Since additive-4 is not glycerin triester, the weight average molecular weight of the obtained P3HA resin composition particles was lowered. Further, the obtained P3HA-based pre-expanded particles had a low closed cell ratio and could not be subjected to in-mold foam molding.

(Comparative Example 5)
According to the composition in Table 1, Additive-1 was glycerin monostearate (Additive-5, manufactured by Kao Corporation [Electrostopper TS-5]), and the same procedure as in Example 2 was performed. Since additive-5 was not glycerin triester, it was judged that the weight average molecular weight of the obtained P3HA-based resin composition particles was low and the melt flow rate was large, so that it could not be used for foaming.

(Comparative Example 6)
According to the composition of Table 1, the additive-1 was propylene glycol monostearate (additive-6, “Kaohomotex PS-200V” manufactured by Kao Corporation), and the same procedure as in Example 2 was performed. Since additive-6 is not glycerin triester, it was judged that the weight average molecular weight of the obtained P3HA-based resin composition particles was low and the melt flow rate was large, so that it could not be used for foaming.

(Comparative Example 7)
Additive-1 was sorbitan laurate (Additive-7, “Emazole L-10V” manufactured by Kao Corporation), and the same procedure as in Example 2 was performed. Since additive-7 was not glycerin triester, it was judged that the weight average molecular weight of the obtained P3HA-based resin composition particles was low and the melt flow rate was large, so that it could not be used for foaming.

(Comparative Example 8)
Additive-1 was sorbitan tristearate (Additive-8, “Emazole S-30V” manufactured by Kao Corporation), and the same procedure as in Example 2 was performed. Since additive-8 is not glycerin triester, it was judged that the weight average molecular weight of the obtained P3HA-based resin composition particles was low and the melt flow rate was large, so that it could not be used for foaming.

(Comparative Example 9)
Additive-1 was stearyl stearate (Additive-9, “Exepal SS” manufactured by Kao Corporation), and the same procedure as in Example 2 was performed. Since it was not glycerin triester, when the P3HA resin composition was immersed in a 60 ° C. hot water bath, it bleeded out, so the subsequent evaluation was not performed.

(Comparative Example 10)
The test was carried out in the same manner as Comparative Example 1 except that the foaming temperature, the foamed particle internal pressure and the molding heating steam pressure were set to the values shown in Tables 2 and 3. Tables 2 and 3 summarize the evaluation results of the P3HA-based pre-expanded particles and the in-mold foam-molded product thus obtained. Even if glycerin triester is not used, it is possible to improve the expansion ratio by raising the foaming temperature. However, since the closed cell ratio is lowered, an in-mold foam-molded product was not obtained.

(Comparative Example 11)
The same procedure as in Comparative Example 1 was performed except that the foaming temperature was changed to the value shown in Table 2. The evaluation results are summarized in Table 2. The P3HA resin composition particles were completely melted in the pressure vessel and could not be foamed.

(Comparative Example 12)
This was carried out in the same manner as Comparative Example 1 except that PHBH-2 was used and the foaming temperature, the foamed particle internal pressure, and the molding heating steam pressure were set to the values shown in Tables 2 and 3. Tables 2 and 3 summarize the evaluation results of the P3HA-based pre-expanded particles and the in-mold foam-molded product thus obtained. Even if glycerin triester is not used, it is possible to improve the expansion ratio by raising the foaming temperature, but the closed cell ratio is lowered, so that an in-mold foam-molded product was not obtained.

(Comparative Example 13)
This was carried out in the same manner as Comparative Example 1 except that PHBH-3 was used and the foaming temperature, the foamed particle internal pressure and the molding heating steam pressure were set to the values shown in Tables 2 and 3. Tables 2 and 3 summarize the evaluation results of the P3HA-based pre-expanded particles and the in-mold foam-molded product thus obtained. Since a high-viscosity P3HA resin was used, the expansion ratio and the compact ratio were low.

(Comparative Example 14)
The same procedure as in Comparative Example 13 was performed except that the foaming temperature was changed to the value shown in Table 2. The evaluation results are summarized in Table 2. The P3HA resin composition particles were completely melted in the pressure vessel and could not be foamed.

Claims (6)

Based on 100 parts by weight of a resin containing 70% or more of a poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer having a composition ratio of 3-hydroxyhexanoate of 6 to 12 mol% Particles made of a poly (3-hydroxyalkanoate) -based resin composition containing 1 to 10 parts by weight of glycerin triester, whose constituent fatty acid is an aliphatic acid having 1 to 12 carbon atoms, are foamed at 105 to 125 ° C. An uncrosslinked poly (3-hydroxyalkanoate) -based pre-expanded particle having an expansion ratio of 20 times or more and a closed cell ratio of 90% or more. The poly (3-hydroxyalkanoate) resin composition according to claim 1, wherein the poly (3-hydroxyalkanoate) resin composition has a melt flow rate measured at 190 ° C and 2.16 kgf of 7 to 25 g / 10 min. System pre-expanded particles. The poly (3-hydroxyalkanoate) -based pre-expanded particles according to claim 1 or 2, which are expanded using carbon dioxide as a foaming agent. The poly (3-hydroxyalkanoate) -based pre-expanded particles according to any one of claims 1 to 3, wherein the resin composition is obtained by melt kneading. Based on 100 parts by weight of a resin containing 70% or more of a poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer having a composition ratio of 3-hydroxyhexanoate of 6 to 12 mol% The poly (3-hydroxyalkanoate) resin composition particles comprising a resin composition containing 1 to 10 parts by weight of glycerin triester, which is an aliphatic acid having 1 to 12 carbon atoms, is sealed together with a dispersant. After dispersing in an aqueous dispersion medium in the container, a foaming agent is introduced into the sealed container, heated to a temperature higher than the softening temperature of the resin composition particles, and then one end of the sealed container is opened to disperse the resin composition particles and the aqueous dispersion. The poly (3-hydroxyalkanoate) -based pre-expanded particles according to any one of claims 1 to 4, wherein the resin particles are expanded by releasing the medium into an atmosphere at a pressure lower than the pressure in the sealed container. A poly (3-hydroxyalkanoate) -based pre-expanded particle according to any one of claims 1 to 5, which is fused to each other in a mold. In-mold foam molding.