Poly(3-hydroxyalkanoate) foamed particles and poly(3-hydroxyalkanoate) foamed molded articles

Abstract

The present invention addresses the problem of providing poly(3-hydroxyalkanoate)-based foam particles that have a high foaming ratio and are obtained through a one-time foaming treatment, and a poly(3-hydroxyalkanoate)-based foam molded body. Provided are poly(3-hydroxyalkanoate)-based foam particles and a foam molded body that are composed of a poly(3-hydroxyalkanoate) composition containing a non-ionic water-soluble polymer.

Description

[Technical Field]

[0001] One embodiment of the present invention relates to poly(3-hydroxyalkanoate) foamed particles and poly(3-hydroxyalkanoate) foamed molded articles. [Background technology]

[0002] Large quantities of petroleum-derived plastics are discarded every year, and the resulting shortage of landfills and environmental pollution are serious problems. In recent years, microplastics have also become a major problem in the marine environment. For these reasons, biodegradable plastics, which are broken down by microorganisms in (a) the environment such as the sea and soil, and (b) landfills and compost, are attracting attention.

[0003] Biodegradable plastics are being developed with the aim of having a wide range of applications, including (a) agricultural, forestry, and fisheries materials used in the environment, and (b) food containers, packaging materials, hygiene products, garbage bags, etc., which are difficult to recover and reuse after use. Furthermore, foams made from biodegradable plastics are expected to be used in packaging cushioning materials, agricultural product boxes, fish boxes, automotive components, building materials, civil engineering materials, and the like.

[0004] Among the aforementioned biodegradable plastics, poly(3-hydroxyalkanoate) (hereinafter sometimes referred to as "P3HA") is attracting attention as a plant-derived plastic due to its excellent biodegradability and carbon neutrality.

[0005] The development of technologies related to biodegradable plastics has been actively pursued for some time. For example, Patent Document 1 discloses a resin composition obtained by mixing a polyalkylene oxide in a specific ratio with an aliphatic polyester copolymer produced from microorganisms. More specifically, Patent Document 1 discloses that by mixing polyalkylene oxide in a specific ratio with an aliphatic polyester copolymer produced from microorganisms, a biodegradable resin with a low glass transition temperature and high toughness at low temperatures can be obtained.

[0006] Patent Document 2 discloses uncrosslinked pre-foamed particles obtained by foaming particles made from a resin composition mainly composed of a biodegradable poly(3-hydroxyalkanoate) resin, and an in-molded foamed molded article using said pre-foamed particles. More specifically, Patent Document 2 discloses that by foaming particles made from a resin composition containing a poly(3-hydroxyalkanoate) resin and a specific glycerin triester under specific conditions, uncrosslinked poly(3-hydroxyalkanoate) pre-foamed particles and an in-molded foamed molded article with a high foaming ratio and closed-cell ratio can be obtained.

[0007] Patent Document 3 discloses aliphatic polyester foam and aliphatic polyester porous particles having a uniform porosity structure, as well as methods for producing them. More specifically, Patent Document 3 discloses that by foaming an aliphatic polyester in the presence of a polyol, a biodegradable aliphatic polyester foam or aliphatic polyester porous particles can be obtained that have a desired foaming ratio, high porosity, and small variation in pore size. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2010-229407 [Patent Document 2] Japanese Patent Publication No. 2012-241166 [Patent Document 3] International Publication No. 2014 / 136746 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the conventional technology described above does not produce poly(3-hydroxyalkanoate) foamed particles with a sufficiently high foaming ratio in a single foaming process, and there is room for improvement from the standpoint of foaming ratio.

[0010] In view of the above circumstances, an object of one embodiment of the present invention is to provide poly(3-hydroxyalkanoate) foamed particles with a high foaming ratio obtained by a single foaming treatment, and poly(3-hydroxyalkanoate) foamed molded articles. [Means for solving the problem]

[0011] In other words, the poly(3-hydroxyalkanoate) foamed particles according to one embodiment of the present invention are The material comprises a poly(3-hydroxyalkanoate) resin (A) and a nonionic water-soluble polymer (B), The content of the nonionic water-soluble polymer (B) is 0.10 to 5.00 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A). The closed-cell ratio of the poly(3-hydroxyalkanoate) foamed particles is 90% or more. [Effects of the Invention]

[0012] According to one aspect of the present invention, it is possible to provide poly(3-hydroxyalkanoate) foamed particles with a high foaming ratio obtained by a single foaming treatment, and poly(3-hydroxyalkanoate) foamed molded articles. [Modes for carrying out the invention]

[0013] One embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Moreover, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic and patent documents mentioned herein are incorporated herein by reference. Furthermore, unless otherwise specified herein, "A to B" representing a numerical range means "A or greater (including A and greater than A) and B or less (including B and less than B)."

[0014] [1. Technical Concept of One Embodiment of an Embodiment] Patent Document 1 does not describe the effect of polyalkylene oxide on the foaming ratio of foamed particles when a resin composition obtained by mixing polyalkylene oxide with an aliphatic polyester copolymer is made into foamed particles. The technology described in Patent Document 1 discloses an example in which 5.26 parts by weight or more of polyalkylene oxide is used per 100 parts by weight of aliphatic polyester copolymer. However, it is preferable to reduce the amount of by-components other than the resin as much as possible, and there is room for improvement in this respect.

[0015] The technology described in Patent Document 2 relates to non-crosslinked foamed particles. Patent Document 2 discloses that the foaming ratio can be improved by using a large amount of a specific glycerin triester, or by using a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer (PHBH) with a high MFR and a small amount of glycerin triester. However, it is preferable to reduce the amount of auxiliary components other than the resin as much as possible, and there is room for improvement in this respect. Also, using a PHBH with a high MFR results in poor moldability and a narrow process window, and there is room for improvement in this respect as well. Furthermore, the technology described in Patent Document 2 uses a plasticizer, which reduces the strength of the foamed molded article, and there is room for improvement in this respect as well.

[0016] In the technique described in Patent Document 3, the present inventors have independently found that the closed-cell porosity of the obtained aliphatic polyester foam or porous particles is low and they cannot be applied to secondary processing such as in-mold foaming molding.

[0017] As a result of intensive studies, the present inventors have found that poly(3-hydroxyalkanoate)-based foamed particles containing a specific amount of nonionic water-soluble polymer have a high expansion ratio by a single foaming treatment, and thus the second foaming treatment is not necessarily required, leading to the completion of the present invention. If the second foaming treatment becomes unnecessary, there are great advantages that not only can the manufacturing process of the foamed particles be simplified, but also the manufacturing cost of the foamed particles can be reduced.

[0018] [2. Poly(3-hydroxyalkanoate)-based foamed particles] In this specification, "poly(3-hydroxyalkanoate)-based foamed particles" may be referred to as "foamed particles", "poly(3-hydroxyalkanoate)-based foamed particles according to an embodiment of the present invention" may be referred to as "the present foamed particles", "poly(3-hydroxyalkanoate)-based foamed molded article" may be referred to as "foamed molded article", and "poly(3-hydroxyalkanoate)-based foamed molded article according to an embodiment of the present invention" may be referred to as "the present foamed molded article".

[0019] [[ID=I5]] The present foamed particles are foamed particles obtained by foaming poly(3-hydroxyalkanoate)-based resin particles composed of a poly(3-hydroxyalkanoate)-based resin composition. In this specification, "poly(3-hydroxyalkanoate)-based resin composition" may be referred to as "resin composition", and "poly(3-hydroxyalkanoate)-based resin particles" may be referred to as "resin particles".

[0020] In this specification, the repeating unit derived from the X monomer may be referred to as "X unit". The repeating unit can also be said to be a constituent unit.

[0021] Poly(3-hydroxyalkanoate) foamed particles according to one embodiment of the present invention include a poly(3-hydroxyalkanoate) resin (A) and a nonionic water-soluble polymer (B). The content of the nonionic water-soluble polymer (B) is 0.10 parts by weight to 5.00 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A), and the closed-cell ratio of the poly(3-hydroxyalkanoate) foamed particles is 90% or more.

[0022] Because these foamed particles have the above-described structure, they have the advantage of being able to achieve a high foaming ratio. These foamed molded articles can be manufactured by molding these foamed particles by a known method.

[0023] (2-1. Poly(3-hydroxyalkanoate) resin (A)) Poly(3-hydroxyalkanoate) foamed particles according to one embodiment of the present invention contain a poly(3-hydroxyalkanoate) resin (A) as a component. In this specification, "poly(3-hydroxyalkanoate) resin (A)" may be referred to as "poly(3-hydroxyalkanoate)" or "P3HA". The component will be described below.

[0024] P3HA is a polymer having a 3-hydroxyalkanoate unit as an essential constituent unit (monomer unit). In this specification, "3-hydroxyalkanoate" may also be referred to as "3HA". Specifically, a polymer containing the repeating unit shown in the following general formula (1) is preferred as P3HA: [-CHR-CH2-CO-O-]···(1).

[0025] In general formula (1), R is C n H 2n+1 R represents an alkyl group, where n is an integer from 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl groups. n is preferably 1 to 10, and more preferably 1 to 8.

[0026] As for P3HA, P3HA produced from microorganisms is particularly preferred. P3HA produced from microorganisms is poly[(R)-3HA] in which all 3HA units are (R)-3HA.

[0027] P3HA preferably contains 50 mol% or more of 3HA units (particularly the repeating unit of general formula (1)) out of 100 mol% of the total repeating units of P3HA, more preferably 70 mol% or more, and even more preferably 80 mol% or more. Furthermore, the repeating units (monomer units) may consist only of 3HA units, or in addition to 3HA units, it may also contain repeating units derived from monomers other than 3HA (for example, 4-hydroxyalkanoate units).

[0028] Specific examples of 3HA units include 3-hydroxybutyrate units, 3-hydroxyvalerate units, and 3-hydroxyhexanoate units. 3-hydroxybutyrate has a melting point and tensile strength close to that of propylene. Therefore, P3HA according to one embodiment of the present invention preferably contains 3-hydroxybutyrate units. In this specification, "3-hydroxybutyrate" may also be referred to as "3HB".

[0029] When P3HA contains two or more repeating units, the monomers from which the repeating units other than the most abundant one originate are referred to as comonomers. In this specification, "repeating units derived from comonomers" may also be referred to as "comonomer units."

[0030] The comonomer is not particularly limited, but 3-hydroxyhexanoate (hereinafter sometimes referred to as 3HH) or 4-hydroxybutyrate (hereinafter sometimes referred to as 4HB) are preferred.

[0031] P3HA is preferably one or more selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate). From the viewpoint of processability and the physical properties of the foamed molded product, among these, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) are more preferred.

[0032] P3HA preferably has 3HB units as essential repeating units (constituent units) and also has comonomer units. In other words, P3HA is preferably a copolymer having 3HB units and comonomer units.

[0033] More specifically, P3HA is a copolymer having 3-hydroxybutyrate units and comonomer units, and the ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of the total repeating units in the copolymer is preferably 99 / 1 (mol% / mol%) to 85 / 15 (mol% / mol%). From the viewpoint of increasing the foaming ratio, the ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of the total repeating units in the copolymer is more preferably 97 / 3 (mol% / mol%) to 87 / 13 (mol% / mol%), and even more preferably 95 / 5 (mol% / mol%) to 89 / 11 (mol% / mol%).

[0034] P3HA having such ratios of each monomer unit can be prepared by methods known to those skilled in the art, for example, by the method described in International Publication WO2009 / 145164. The ratio of each monomer unit in P3HA can be determined by methods known to those skilled in the art, for example, by the method described in International Publication 2013 / 147139.

[0035] In one embodiment of the present invention, the method for producing P3HA is not particularly limited and may be a chemical synthesis method or a microbial method. Among these, the microbial method is preferred. Known methods can be applied to the microbial method for producing P3HA, but it is preferable to include a culture step, a purification step, and a drying step.

[0036] The method for culturing microorganisms that produce P3HA in the culture process is not particularly limited, and for example, the method described in International Publication No. WO2019 / 142717 can be used.

[0037] Examples of microorganisms that produce copolymers of 3HB with other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with respect to P3HB3HH, Alcaligenes eutrophus AC32 strain (FERM BP-6038) (T.Fukui, Y.Doi, J.Bateriol., 179, p4821-4830 (1997)) is more preferred, as its P3HB3HH productivity has been improved by introducing genes for the P3HA synthase group. In the method for producing P3HA, microbial cells that have accumulated P3HB3HH in their cells by culturing microorganisms such as Alcaligenes eutrophus AC32 strain under appropriate conditions are preferably used. Furthermore, regarding copolymer-producing microorganisms, in addition to those mentioned above, genetically modified microorganisms into which various P3HA synthesis-related genes have been introduced may be used, depending on the P3HA to be produced. Also, the culture conditions of the microorganisms (bacteria) should be optimized, including the type of substrate, according to the P3HA to be produced.

[0038] The method for purifying P3HA obtained by microbial culture in the purification process is not particularly limited, and known physical treatments and / or chemical treatments and / or biological treatments can be applied. For example, the purification method described in International Publication No. 2010 / 067543 can be preferably applied.

[0039] The method for drying P3HA obtained by microbial culture and purification in the drying process is not particularly limited, and spray drying, fluidized bed drying, airflow drying, rotary drying, vibration drying, and band drying can be applied. For example, the drying method described in International Publication No. 2018 / 070492 is preferably applied.

[0040] The drying process is (a) A step of preparing an aqueous suspension A containing 100 parts by weight of P3HA and 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer described later, (b) The step of spray-drying the aqueous suspension A prepared in step (a) may also be included.

[0041] By including steps (a) and (b), a P3HA is obtained that contains 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer per 100 parts by weight of P3HA.

[0042] In step (b) of the method for producing P3HA of the present invention, the aqueous suspension A prepared in step (a) is spray-dried. A spray-drying method may include, for example, supplying the aqueous suspension A as fine droplets into a dryer and drying it in contact with hot air within the dryer. The method for supplying the aqueous suspension A as fine droplets into the dryer (atomizer) is not particularly limited and includes known methods such as using a rotating disk or a nozzle. The method of contact between the droplets and hot air within the dryer is not particularly limited and includes parallel flow, counterflow, or a combination thereof.

[0043] The drying temperature during spray drying in step (b) should be set appropriately so as to remove most of the aqueous medium from the droplets of aqueous suspension A, while allowing drying to the desired moisture content and minimizing quality deterioration (decreased molecular weight, decreased color) and melting. The amount of hot air in the dryer can also be set appropriately according to, for example, the size of the dryer.

[0044] A P3HA production method according to one embodiment of the present invention may include a step of further drying the obtained P3HA after step (b). Furthermore, a P3HA production method according to one embodiment of the present invention may include other steps (for example, a step of adding various additives to aqueous suspension A).

[0045] According to the P3HA manufacturing method of one embodiment of the present invention, it is possible to obtain P3HA in a dry state with high productivity and excellent thermal stability. According to the P3HA manufacturing method of one embodiment of the present invention, it is possible to reduce the cost of the drying process in particular (equipment costs, utilities). Furthermore, according to the P3HA manufacturing method of one embodiment of the present invention, it is possible to obtain P3HA in powder form (P3HA powder), so that P3HA with excellent handling properties can be obtained with high efficiency.

[0046] (2-2. Nonionic water-soluble polymers (B)) Poly(3-hydroxyalkanoate) foamed particles according to one embodiment of the present invention contain a nonionic water-soluble polymer (B) as a component. This component will be described below.

[0047] In this invention, the nonionic water-soluble polymer (B) refers to a polymer that does not ionize when dissolved in water.

[0048] The content of the nonionic water-soluble polymer (B) in these foamed particles is 0.10 to 5.00 parts by weight, preferably 0.10 to 4.00 parts by weight, more preferably 0.10 to 3.00 parts by weight, more preferably 0.10 to 2.00 parts by weight, and more preferably 0.10 to 1.50 parts by weight, relative to 100 parts by weight of P3HA. In all of these numerical ranges, the lower limit is not limited to 0.10, but may be 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, or 1.00. With this configuration, the foaming ratio of the poly(3-hydroxyalkanoate) foamed particles obtained by a single foaming treatment can be increased. Furthermore, with this configuration, the amount of nonionic water-soluble polymer (B) contained in the poly(3-hydroxyalkanoate) foam particles can be reduced, and as a result, various effects that the nonionic water-soluble polymer (B) has on the poly(3-hydroxyalkanoate) foam particles can be prevented.

[0049] There are no particular limitations on the method for quantifying the nonionic water-soluble polymer (B) content in foamed particles. The nonionic water-soluble polymer (B) content in foamed particles can be analyzed by analytical laboratories, etc. The nonionic water-soluble polymer (B) content in foamed particles can be measured, for example, by the following methods (1) to (4): (1) Dissolve 20 mg of foamed particles in 0.8 ml of deuterated chloroform; (2) Add 20 mg of 1,1,2,2-tetrachloroethane as an internal standard to the deuterated chloroform solution prepared in (1); (3) For each of (a) a deuterated chloroform solution prepared by dissolving any amount (e.g., 10 mg) of nonionic water-soluble polymer (B) (standard) and 20 mg of 1,1,2,2-tetrachloroethane in 0.8 ml of deuterated chloroform, and (b) the deuterated chloroform solution prepared in (2), 1(4) Using 1H-NMR, measure the NMR spectrum derived from the nonionic water-soluble polymer (B) contained in the deuterated chloroform solution; (5) While referring to the measurement results of the deuterated chloroform solution containing the nonionic water-soluble polymer (B) (standard), quantify the amount of nonionic water-soluble polymer (B) in the foam particles based on the signal intensity ratio derived from the nonionic water-soluble polymer (B) calculated from both obtained NMR spectra. This method is sometimes referred to as the liquid-liquid separatory method.

[0050] Furthermore, foamed particles obtained using a crosslinking agent (foamed particles that may have a partially crosslinked structure) may not be completely soluble in organic solvents. Foamed particles obtained using a crosslinking agent are also referred to as "foamed particles X". Regarding the nonionic water-soluble polymer (B) content in foamed particles X, the nonionic water-soluble polymer (B) content in foamed particles Y, obtained by measuring using the liquid-liquid separation method described above, using foamed particles (hereinafter sometimes referred to as "foamed particles Y") obtained under exactly the same conditions as the manufacturing method of foamed particles X except that a crosslinking agent is not used, is considered to be the nonionic water-soluble polymer (B) content in foamed particles X.

[0051] The nonionic water-soluble polymer (B) has hydrophilic groups. Preferably, the nonionic water-soluble polymer (B) also has hydrophobic groups. Since the nonionic water-soluble polymer (B) has hydrophilic groups, it has the advantage of being able to increase the foaming ratio. On the other hand, if the nonionic water-soluble polymer (B) has hydrophobic groups, it has the advantage of being able to suppress bleeding from resin particles and foam particles. This configuration is preferable from the viewpoint of improving the foaming ratio and compatibility with P3HA.

[0052] The hydrophilic group is not limited to, but can include oxyethylene group, hydroxyl group, carboxyl group, ether group, etc. From the viewpoint of easily achieving a balance between hydrophilicity and hydrophobicity, among these, the oxyethylene group and hydroxyl group are preferred. The hydrophobic group is not limited to, but can include linear alkyl group, branched alkyl group, oxypropylene group, fluoroalkyl group, alkylsiloxane group, etc. From the viewpoint of easily achieving a balance between hydrophilicity and hydrophobicity, among these, the linear alkyl group, branched alkyl group, and oxypropylene group are preferred.

[0053] Examples of nonionic water-soluble polymers (B) include combinations of hydrophilic and hydrophobic blocks, combinations of hydrophilic main chains and hydrophobic side chains, and combinations of hydrophobic main chains and hydrophilic side chains.

[0054] The nonionic water-soluble polymer (B) is preferably a biodegradable substance. This configuration is preferable because the resulting P3HA-based foam particles and P3HA-based foam molded articles are biodegradable. A biodegradable substance is defined as a substance that is biodegradable in accordance with OECD TG301.

[0055] The biodegradable nonionic water-soluble polymer (B) is not limited to natural polymers, semi-synthetic polymers, or synthetic polymers. Specifically, natural polymers include starch, guar gum, carrageenan xanthan gum, etc. Semi-synthetic polymers include cellulose derivatives and starch derivatives, etc. Synthetic polymers include polyalkylene oxides, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, and poly-N-vinylacetamide, etc. Among these, starch derivatives, cellulose derivatives, polyvinyl alcohol, and polyalkylene oxides are preferred because they allow for an easy balance between hydrophilicity and hydrophobicity.

[0056] The nonionic water-soluble polymer (B) is preferably at least one selected from the group consisting of polyalkylene oxide, polyvinyl alcohol, and cellulose derivatives. In this case, the content of the nonionic water-soluble polymer (B) is preferably 0.10 to 1.00 parts by weight per 100 parts by weight of P3HA. Within this numerical range, the lower limit is not limited to 0.10, but may be 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or 0.90. With this configuration, the foaming ratio of the poly(3-hydroxyalkanoate) foamed particles obtained by a single foaming treatment can be increased. Furthermore, with this configuration, the content of the nonionic water-soluble polymer (B) contained in the poly(3-hydroxyalkanoate) foamed particles can be reduced, and as a result, various effects of the nonionic water-soluble polymer (B) on the poly(3-hydroxyalkanoate) foamed particles can be better prevented.

[0057] The polyalkylene oxide is not particularly limited, and commercially available products can be used, for example. Examples of commercially available products include Pluronic 10400 (BASF), Pluronic 10500 (BASF), Genapol PF80 (Clariant), Unilube DP60-600B (NOF Corporation), Unilube DP60-950B (NOF Corporation), Pronon 208 (NOF Corporation), Epan U105 (Daiichi Kogyo Seiyaku Co., Ltd.), Epan U108 (Daiichi Kogyo Seiyaku Co., Ltd.), Epan 750 (Daiichi Kogyo Seiyaku Co., Ltd.), Emulsogen EPN 287 (CLARIANT), Emulsogen LCN 407 (CLARIANT), Neugen TDS (Daiichi Kogyo Seiyaku Co., Ltd.), DKS NL (Daiichi Kogyo Seiyaku Co., Ltd.), and Neugen SD (Daiichi Kogyo Seiyaku Co., Ltd.).

[0058] The polyvinyl alcohol is not particularly limited, and commercially available products can be used, for example. Examples of commercially available products include Kuraray Poval PVA-205 (manufactured by Kuraray Co., Ltd.), Kuraray Poval PVA-217 (manufactured by Kuraray Co., Ltd.), Kuraray Poval PVA-224 (manufactured by Kuraray Co., Ltd.), Exceval RS-1713 (manufactured by Kuraray Co., Ltd.), Exceval RS-1717 (manufactured by Kuraray Co., Ltd.), Gosenol GH-22 (manufactured by Mitsubishi Chemical Corporation), Gosenol GH-20R (manufactured by Mitsubishi Chemical Corporation), and Gosenol GH-17R (manufactured by Mitsubishi Chemical Corporation). Examples include Gosenol GM-14R (manufactured by Mitsubishi Chemical Corporation), Gosenol GL-05 (manufactured by Mitsubishi Chemical Corporation), Gosenol GL-03 (manufactured by Mitsubishi Chemical Corporation), Gosenol KH-20 (manufactured by Mitsubishi Chemical Corporation), Gosenol KH-17 (manufactured by Mitsubishi Chemical Corporation), Gosenol KL-05 (manufactured by Mitsubishi Chemical Corporation), Gosenol KL-03 (manufactured by Mitsubishi Chemical Corporation), Gosenol NK-05R (manufactured by Mitsubishi Chemical Corporation), etc.

[0059] The cellulose derivative is not particularly limited, and commercially available products can be used, for example. Examples of commercially available products include Metroz MCE-100 (manufactured by Shin-Etsu Chemical Co., Ltd.), Metroz MCE-400 (manufactured by Shin-Etsu Chemical Co., Ltd.), Metroz MCE-4000 (manufactured by Shin-Etsu Chemical Co., Ltd.), Metroz SFE-400 (manufactured by Shin-Etsu Chemical Co., Ltd.), Metroz SFE-4000 (manufactured by Shin-Etsu Chemical Co., Ltd.), Metroz SE-50 (manufactured by Shin-Etsu Chemical Co., Ltd.), Metroz NE-100 (manufactured by Shin-Etsu Chemical Co., Ltd.), and the like.

[0060] (2-3. Additives) These foamed particles may further contain additives other than the poly(3-hydroxyalkanoate) resin (A) and the nonionic water-soluble polymer (B). Other additives may include, for example, nucleating agents, foam regulators, lubricants, plasticizers, antistatic agents, flame retardants, conductive agents, heat insulating agents, crosslinking agents, antioxidants, UV absorbers, colorants, inorganic fillers, organic fillers, hydrolysis inhibitors, etc., depending on the purpose. Among the other additives, biodegradable additives are particularly preferred.

[0061] Examples of nucleating agents include pentaerythritol, orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. These nucleating agents may be used individually or in combination of two or more. When using a mixture of two or more nucleating agents, the mixing ratio may be adjusted as appropriate depending on the purpose.

[0062] The content of the nucleating agent in the foamed particles is not particularly limited. The content of the nucleating agent is preferably, for example, 5.0 parts by weight or less, more preferably 3.0 parts by weight or less, and even more preferably 1.5 parts by weight or less, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A). The lower limit of the content of the nucleating agent in the poly(3-hydroxyalkanoate) resin (A) is not particularly limited, but for example, it may be 0.1 parts by weight or more per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A).

[0063] Examples of foam regulators include talc, silica, calcium silicate, calcium carbonate, aluminum oxide, titanium dioxide, diatomaceous earth, clay, baking soda, alumina, barium sulfate, aluminum oxide, and bentonite. Among these foam regulators, talc is preferred because of its excellent dispersibility in P3HA. One of these foam regulators may be used alone, or two or more may be used in combination. When using a mixture of two or more foam regulators, the mixing ratio may be adjusted as appropriate depending on the purpose.

[0064] The content of the foaming agent in these foamed particles is not particularly limited, but is preferably 0.01 to 1.00 parts by weight, more preferably 0.03 to 0.50 parts by weight, and even more preferably 0.05 to 0.30 parts by weight per 100 parts by weight of poly(3-hydroxyalkanoate) resin (A).

[0065] Examples of plasticizers include glycerin ester compounds such as glycerin diacetomolaurate, citrate ester compounds such as tributyl acetylcitrate, sebacate ester compounds such as dibutyl sebacate, adipate ester compounds, polyether ester compounds, benzoate ester compounds, phthalate ester compounds, isosorbide ester compounds, polycaprolactone compounds, and dibasic acid ester compounds such as benzylmethyldiethylene glycol adipate. Among these, glycerin ester compounds, citrate ester compounds, sebacate ester compounds, and dibasic acid ester compounds are preferred because they have excellent plasticizing effects on P3HA. One of these plasticizers may be used alone, or two or more may be used in combination. When two or more plasticizers are used in combination, the mixing ratio may be adjusted as appropriate depending on the purpose.

[0066] The content of the plasticizer in these foamed particles 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 per 100 parts by weight of poly(3-hydroxyalkanoate) resin (A).

[0067] These foamed particles may contain compounds having an isocyanate group (hereinafter sometimes referred to as isocyanate compounds). However, isocyanate compounds may be toxic. Also, if the foamed particles contain isocyanate compounds, the resulting foamed particles and foamed molded products may turn yellow.

[0068] Therefore, the isocyanate compound content in these foamed particles is preferably less than 3.0 parts by weight, more preferably less than 1.0 part by weight, and even more preferably less than 0.1 parts by weight, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A). It is most preferable that these foamed particles do not contain any isocyanate compound.

[0069] As isocyanate compounds, for example, polyisocyanate compounds having two or more isocyanate groups in one molecule can be used. Specific types of isocyanate compounds include aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds. For example, (a) aromatic isocyanate compounds include isocyanate compounds with a skeleton of torylene, diphenylmethane, naphthylene, tolidine, xylene, and / or triphenylmethane. (b) alicyclic isocyanate compounds include isocyanate compounds with a skeleton of isophorone and / or hydrogenated diphenylmethane. (c) aliphatic isocyanate compounds include isocyanate compounds with a skeleton of hexamethylene and / or lysine. Furthermore, mixtures obtained by combining two or more of these isocyanate compounds can also be used. When using isocyanate compounds, it is preferable to use isocyanate compounds with a trilene and / or diphenylmethane backbone, particularly isocyanate compounds with a diphenylmethane backbone (polyisocyanates), due to their versatility, ease of handling, and weather resistance.

[0070] Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearate, ethylenebisoleamide, ethylenebiserucamide, ethylenebislaurylamide, ethylenebiscaprate, p-phenylenebisstearate, and polycondensates of ethylenediamine, stearic acid, and sebacic acid. Among these, behenamide and erucamide are preferred because they have particularly excellent lubricating effects on P3HA. The amount of lubricant used is not particularly limited, but is preferably 0.01 to 5.00 parts by weight, more preferably 0.05 to 3.00 parts by weight, and even more preferably 0.10 to 1.50 parts by weight per 100 parts by weight of P3HA. Furthermore, not only one type of lubricant but two or more types may be mixed, and the mixing ratio can be appropriately adjusted according to the purpose.

[0071] Examples of antistatic agents include coconut oil fatty acid diethanolamide. The amount of antistatic agent in these foamed particles is not particularly limited.

[0072] (2-4. Physical properties of poly(3-hydroxyalkanoate) foamed particles) (Apparent density) The apparent density of the foam particles is not limited, but is preferably 20 g / L to 67 g / L, more preferably 25 g / L to 65 g / L, and even more preferably 30 g / L to 63 g / L. This configuration allows for the production of a poly(3-hydroxyalkanoate) foam molded article with a balanced combination of mechanical strength and lightweight properties. The apparent density can be measured according to the measurement method described in the examples below.

[0073] (Expansion ratio) The foaming ratio of these foam particles is not limited, but is preferably 18 times or more, more preferably 19 times or more, more preferably 20 times or more, more preferably 21 times or more, more preferably 22 times or more, and even more preferably 23 times or more. The upper limit of the foaming ratio of these foam particles is not limited, but may be, for example, 50 times, 40 times, 30 times, 25 times, or 23 times. With this configuration, a poly(3-hydroxyalkanoate) foamed molded article with a good balance of mechanical strength and lightweight properties can be obtained. The foaming ratio may be measured according to the measurement method described in the examples below.

[0074] (heat amount on high temperature side) The high-temperature heat content of these foamed particles is not limited, but is preferably 0.1 J / g to 20.0 J / g, more preferably 0.3 J / g to 18.0 J / g, and even more preferably 0.5 J / g to 15.0 J / g. With this configuration, the poly(3-hydroxyalkanoate) foamed particles obtained in the foaming process are free from adhesion and exhibit excellent in-mold foaming properties. The high-temperature heat content can be measured according to the measurement method described in the examples below.

[0075] (Cell diameter) The cell diameter of the foamed particles is not limited, but is preferably 50 μm to 500 μm, more preferably 100 μm to 450 μm, more preferably 150 μm to 400 μm, more preferably 200 μm to 350 μm, more preferably 220 μm to 300 μm, even more preferably 240 μm to 280 μm, and particularly preferably 245 μm to 270 μm. With this configuration, poly(3-hydroxyalkanoate) foamed particles with excellent in-mold foaming properties can be obtained. The cell diameter can be measured according to the measurement method described in the examples below.

[0076] (Gel fraction) The gel fraction of the foamed particles is not limited, but is preferably 30% by weight or more, more preferably 40% by weight or more, and even more preferably 50% by weight or more. The upper limit of the gel fraction of the foamed particles is not limited, but may be, for example, 90% by weight, 80% by weight, or 75% by weight. This configuration has the advantage of widening the process window in which a good foamed molded product can be provided when in-mold foam molding is performed. The gel fraction can be measured according to the measurement method described in the examples below.

[0077] (Percentage of closed cells) The closed-cell ratio of these foamed particles is 90% or more, more preferably 91% or more, more preferably 92% or more, more preferably 93% or more, more preferably 94% or more, more preferably 95% or more, more preferably 96% or more, more preferably 97% or more, and even more preferably 98% or more. The upper limit of the closed-cell ratio of these foamed particles is not limited, but could be, for example, 100%, 99%, 98%, or 97%. This configuration allows for poly(3-hydroxyalkanoate)-based foamed particles with excellent in-mold foaming properties. The closed-cell ratio can be measured according to the measurement method described in the examples below.

[0078] [3. Method for producing poly(3-hydroxyalkanoate) foamed particles] The method for producing poly(3-hydroxyalkanoate) foamed particles is not particularly limited, and known methods (for example, the method described in International Publication No. 2019 / 146555) can be used. In this specification, "method for producing poly(3-hydroxyalkanoate) foamed particles" may be referred to as "production method," and "method for producing poly(3-hydroxyalkanoate) foamed particles according to one embodiment of the present invention" may be referred to as "this production method."

[0079] Specific embodiments of this manufacturing method include, for example, a manufacturing method that sequentially includes a resin particle preparation step for adjusting resin particles and a foaming step for foaming the resin particles, but is not limited to such a manufacturing method.

[0080] (3-1. Resin particle preparation process) The present manufacturing method preferably includes a resin particle preparation step, which involves preparing either (a) resin particles containing 100 parts by weight of P3HA and 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer, or (b) resin particles consisting of 100 parts by weight of P3HA and 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer, before the foaming step. The resin particle preparation step can also be described as a step of molding the resin into a shape that is easily used for foaming. The form of the resin particle preparation step is not particularly limited as long as resin particles can be obtained.

[0081] The resin particle preparation process is as follows: (a) A melt-kneading step in which a resin composition containing 100 parts by weight of P3HA and 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer is melt-kneaded, (b) Preferably includes a particle molding step of shaping the melt-kneaded resin composition into a shape that is easy to use for foaming.

[0082] The form of the melt-kneading process is not particularly limited, as long as a melt-kneaded resin composition can be obtained. Specific examples of the melt-kneading process include, for example, the following methods (a1) and (a2): (a1) Prepare a resin composition by mixing or blending 100 parts by weight of P3HA, 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer, and other additives as needed, using a mixing device or similar. Then, supply the resin composition to a melt-kneading device and melt-knead it. (a2) A method of supplying 100 parts by weight of P3HA, 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer, and other additives as needed, to a melt-kneading apparatus, preparing (completing) a resin composition in the melt-kneading apparatus, and melt-kneading the resin composition.

[0083] In method (a1) above, the order in which 100 parts by weight of P3HA, 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer, and other additives as needed, is mixed or blended (dry blended) is not particularly limited. In method (a2) above, the order in which 100 parts by weight of P3HA, 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer, and other additives as needed, are supplied to a melt-kneading apparatus is not particularly limited.

[0084] In the method described in (a1) above, the mixing device is not particularly limited and includes ribbon blenders, flash blenders, tumbler mixers, super mixers, and the like.

[0085] In the methods described in (a1) and (a2) above, the melting and kneading apparatus is not particularly limited and includes extruders, kneaders, Banbar mixers, and rolls. Extruders are preferred as the melting and kneading apparatus due to their superior productivity and convenience, and twin-screw extruders are even more preferred.

[0086] In method (a1) above, the amount of nonionic water-soluble polymer and other additives used for mixing or blending becomes the content of nonionic water-soluble polymer and other additives in the resulting resin particles. Also, in method (a2) above, the amount of nonionic water-soluble polymer and other additives supplied to the melt-kneading apparatus becomes the content of nonionic water-soluble polymer and other additives in the resulting resin particles. Therefore, the descriptions in the sections on (nonionic water-soluble polymer) and (other additives) above apply to the amounts of nonionic water-soluble polymer and other additives used and supplied. In addition, in the melt-kneading step according to one embodiment of the present invention, the P3HA used may already contain a nonionic water-soluble polymer. If the P3HA used already contains a nonionic water-soluble polymer, it is not necessary to use a nonionic water-soluble polymer in the melt-kneading step. Furthermore, the sum of the content of nonionic polymer in the P3HA and the amount of nonionic water-soluble polymer used in the melt-kneading step becomes the content of nonionic water-soluble polymer in the resulting resin particles. Furthermore, it is not necessary to use all of the other additives used in this manufacturing method in the resin particle preparation step. In other words, all or some of the other additives used in this manufacturing method (e.g., crosslinking agents and plasticizers) may be added to the dispersion in the dispersion step described later without being used in the resin particle preparation step, i.e., without being included in the resin particles.

[0087] In the melt-mixing process, the temperature at which the resin composition is melt-mixed cannot be specified in general terms, as it depends on the physical properties of P3HA (melting point, weight-average molecular weight, etc.) and the type of additive used. Regarding the temperature at which the resin composition is melt-mixed, for example, it is preferable that the temperature of the melt-mixed resin composition discharged from the die nozzle (hereinafter sometimes referred to as the composition temperature) be 150°C to 200°C, more preferably 160°C to 195°C, and even more preferably 170°C to 190°C. If the composition temperature is 150°C or higher, there is no risk of insufficient melt-mixing of the resin composition. On the other hand, if the composition temperature is 200°C or lower, there is no risk of thermal decomposition of P3HA.

[0088] The particle molding process is not particularly limited, as long as the molten and kneaded resin composition can be molded into a desired shape. By using a molten and kneading apparatus equipped with a die and a cutting device, the molten and kneaded resin composition can be easily molded into a desired shape in the particle molding process. Specifically, the molten and kneaded resin composition can be extruded from the nozzle of a die provided in the molten and kneading apparatus, and the resin composition can be cut by a cutting device simultaneously with or after extrusion to form the desired shape. The shape of the resulting resin particles is not particularly limited, but cylindrical, elliptical, spherical, cubic, and rectangular parallelepiped shapes are preferred because they are easy to use for foaming.

[0089] In the particle molding process, the resin composition extruded from the die nozzle may be cooled. When cooling the resin composition extruded from the die nozzle, the resin composition may be cut by a cutting device simultaneously with or after the cooling process.

[0090] In the particle molding process, when the resin composition discharged from the die nozzle is cooled, the temperature of the cooled resin composition (hereinafter sometimes referred to as the cooling temperature) is not particularly limited. The cooling temperature is preferably 20°C to 80°C, more preferably 30°C to 70°C, and even more preferably 40°C to 60°C. This configuration has the advantage of good resin particle productivity because the crystallization of the melt-kneaded resin composition is sufficiently fast.

[0091] The melt flow rate (MFR) of the resin particles is not particularly limited, but is preferably 1 g / 10 min to 20 g / min, more preferably 1 g / 10 min to 17 g / min, and even more preferably 1 g / min to 15 g / min. With this configuration, poly(3-hydroxyalkanoate) foamed particles with a high foaming ratio and a high closed-cell ratio can be obtained. The melt flow rate of the resin particles can be measured according to the measurement method described in the examples below.

[0092] (3-2. Foaming Process) The foaming step in this manufacturing method is not particularly limited as long as it can foam the resin particles. In one embodiment of the present invention, the foaming step may include a dispersion step of dispersing the resin particles in an aqueous dispersion medium. The specific form of the dispersion step is not particularly limited, but the dispersion step is, for example, a step of dispersing the resin particles, an aqueous dispersion medium, a crosslinking agent, a foaming agent, and optionally a dispersant, a crosslinking aid, a dispersion aid, and / or a plasticizer in a container. The foaming step, as a step other than the dispersion step, follows the dispersion step, (a) A heating-pressure step in which the temperature inside the container is raised to a certain temperature and the pressure inside the container is raised to a certain pressure, (b) A holding step for maintaining the temperature and pressure inside the container at a constant temperature and constant pressure, (c) Preferably includes a discharge step of opening one end of the container and releasing the dispersion liquid inside the container into a region (space) with a pressure lower than the foaming pressure (i.e., the pressure inside the container).

[0093] (Dispersion process) The dispersion process can also be described as a process of preparing a dispersion in which resin particles, a crosslinking agent, a blowing agent, and optionally a dispersant, crosslinking aid, dispersion aid, and plasticizer are dispersed in an aqueous dispersion medium. In the dispersion, (a) the crosslinking agent and crosslinking aid may be consumed by reaction with P3HA in the resin particles and may not be present, and (b) the blowing agent and plasticizer may be impregnated into the resin particles and may not be present in a dispersed state.

[0094] The container is not particularly limited, but it is preferable that it be able to withstand the foaming temperature and pressure described later, for example, a pressure-resistant container is preferred.

[0095] The aqueous dispersion medium is not particularly limited, as long as it can uniformly disperse resin particles, crosslinking agents, foaming agents, etc. As the aqueous dispersion medium, for example, tap water and / or industrial water can be used. In order to enable stable production of foaming particles, it is preferable to use pure water and ultrapure water such as RO water (water purified by reverse osmosis membrane method), distilled water, and deionized water (water purified by ion exchange resin) as the aqueous dispersion medium.

[0096] The amount of aqueous dispersion medium used is not particularly limited, but 100 to 1000 parts by weight is preferred per 100 parts by weight of resin particles.

[0097] In this manufacturing method, it is preferable to use a crosslinking agent. By using a crosslinking agent, the P3HA in the resulting foamed particles becomes P3HA with a crosslinked structure. Since the crosslinking reaction of P3HA in the resin particles also proceeds during the foaming process, the foaming process can also be considered a crosslinking process.

[0098] The crosslinking agent is not particularly limited as long as it can crosslink P3HA. Organic peroxides are preferred as crosslinking agents. In other words, it is preferable that poly(3-hydroxyalkanoate) foamed particles are crosslinked with organic peroxides. The organic peroxide may be used (a) in the resin particle preparation step, (b) in the dispersion step, or (c) in both the resin particle preparation step and the dispersion step. More specifically, in order to react the organic peroxide with P3HA, (a) the organic peroxide and P3HA may be melt-kneaded in the resin particle preparation step, (b) the resin particles and organic peroxide may be dispersed in an aqueous dispersion medium in the dispersion step, or (c) the organic peroxide and P3HA may be melt-kneaded, and the resin particles and organic peroxide may also be dispersed in an aqueous dispersion medium. In the dispersion step, the resin particles produced in the resin particle preparation step and the organic peroxide can be dispersed in an aqueous dispersion medium to impregnate and react with the resin particles. For these reasons, organic peroxides are preferred as crosslinking agents in this foam particle manufacturing method. When organic peroxides are used as crosslinking agents, the crosslinked structure is formed by the direct bonding of P3HA molecular chains (without the need for structures derived from the crosslinking agent).

[0099] Depending on the type of P3HA used, organic peroxides with a 1-hour half-life temperature of 90°C to 160°C are preferred as crosslinking agents, and organic peroxides with a 1-hour half-life temperature of 115°C to 125°C are more preferred. Such organic peroxides include, specifically, benzoyl peroxide (half-life temperature: 92°C), t-butyl peroxy-2-ethylhexyl carbonate (half-life temperature: 121°C), t-butyl peroxyisopropyl carbonate (half-life temperature: 118°C), t-amyl peroxy-2-ethylhexyl carbonate (half-life temperature: 117°C), t-amyl peroxyisopropyl carbonate (half-life temperature: 115°C), t-butyl peroxyisobutyrate (half-life temperature: 93°C), t-butyl peroxy-2-ethylhexanoate (half-life temperature: 95°C), t-butyl peroxyisononanoate (half-life temperature: 123°C), and t-butyl peroxyacetate ( Examples include t-butyl peroxydibenzoate (1 hour half-life temperature: 125°C), t-amyl peroxyisobutyrate (1 hour half-life temperature: 93°C), t-amyl peroxy-2-ethylhexanoate (1 hour half-life temperature: 92°C), t-amyl peroxyisononanoate (1 hour half-life temperature: 114°C), t-amyl peroxyacetate (1 hour half-life temperature: 120°C), t-amyl peroxybenzoate (1 hour half-life temperature: 122°C), dicumyl peroxide (1 hour half-life temperature: 137°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (1 hour half-life temperature: 140°C), and di-t-butyl peroxide (1 hour half-life temperature: 149°C). When using organic peroxides with a half-life temperature of 90°C or higher, there is an advantage in that foamed particles with the desired gel fraction tend to be obtained. On the other hand, when using organic peroxides with a half-life temperature of 160°C or lower, there is an advantage in that there is no risk of unreacted crosslinking agents remaining in the final product.

[0100] The amount of crosslinking agent used is not particularly limited, but is preferably 0.1 to 5.0 parts by weight, more preferably 0.3 to 3.0 parts by weight, and even more preferably 0.5 to 2.5 parts by weight per 100 parts by weight of resin particles. When the amount of crosslinking agent used is 0.1 parts by weight or more per 100 parts by weight of resin particles, (a) the resulting foamed particles can be sufficiently crosslinked, and (b) the closed-cell ratio of the resulting foamed particles will be high, resulting in a good foamed molded article. On the other hand, when the amount of crosslinking agent used is 5.0 parts by weight or less per 100 parts by weight of resin particles, the effect corresponding to the amount of crosslinking agent added can be obtained, so there is no risk of economic waste. The amount of crosslinking agent used has a positive correlation with the gel fraction of the foamed particles and greatly affects the value of the gel fraction of the foamed particles. Therefore, it is desirable to strictly set the amount of crosslinking agent used considering the gel fraction of the resulting foamed particles. In the dispersion process according to one embodiment of the present invention, the resin particles used may already contain a crosslinking agent. In that case, it is preferable that the sum of the amount of crosslinking agent already contained in the resin particles before the dispersion process and the amount of crosslinking agent used in the dispersion process satisfies the aforementioned range.

[0101] Examples of blowing agents include inorganic gases such as nitrogen, carbon dioxide, and air; saturated hydrocarbons with 3 to 5 carbon atoms such as propane, n-butane, isobutane, n-pentane, isopentane, and neopentane; ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether; halogenated hydrocarbons such as monochloromethane, dichloromethane, and dichlorodifluoroethane; and water. At least one type of blowing agent selected from the group consisting of the inorganic gases, saturated hydrocarbons with 3 to 5 carbon atoms, ethers, halogenated hydrocarbons, and water can be used. Among these, nitrogen or carbon dioxide is preferred as the blowing agent from the viewpoint of environmental impact and blowing power. One of these blowing agents may be used alone, or two or more may be used in mixture. When two or more blowing agents are used in mixture, the mixing ratio may be appropriately adjusted according to the purpose.

[0102] The amount of foaming agent used is not particularly limited, but is preferably 2 to 10,000 parts by weight, more preferably 5 to 5,000 parts by weight, and even more preferably 10 to 1,000 parts by weight per 100 parts by weight of resin particles. When the amount of foaming agent used is 2 parts by weight or more per 100 parts by weight of resin particles, foamed particles with a high foaming ratio can be obtained. On the other hand, when the amount of foaming agent used is 10,000 parts by weight or less per 100 parts by weight of resin particles, the effect is obtained in proportion to the amount of foaming agent used, so there is no economic waste.

[0103] In this manufacturing method, it is preferable to use a dispersant. Using a dispersant has the advantage of suppressing the adhesion (sometimes referred to as blocking) between resin particles, thereby enabling the stable production of foamed particles. Examples of dispersants include inorganic substances such as tricalcium phosphate, trimagnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, clay, aluminum oxide, titanium oxide, and aluminum hydroxide. One of these dispersants may be used alone, or two or more may be used in mixture. Furthermore, when using a mixture of two or more dispersants, the mixing ratio may be appropriately adjusted depending on the purpose.

[0104] The amount of dispersant used is not particularly limited, but is preferably 0.1 to 3.0 parts by weight, and more preferably 0.5 to 1.5 parts by weight, per 100 parts by weight of resin particles.

[0105] In this manufacturing method, crosslinking aids may be used to improve the crosslinking efficiency of P3HA. Examples of crosslinking aids include compounds having at least one unsaturated bond in the molecule. Among these compounds, allyl esters, acrylic acid esters, methacrylic acid esters, and divinyl compounds are particularly preferred as crosslinking aids. One of these crosslinking aids may be used alone, or two or more may be used in combination. Furthermore, when using a mixture of two or more crosslinking aids, the mixing ratio may be appropriately adjusted depending on the purpose.

[0106] The amount of crosslinking aid used is not particularly limited, but preferably 0.01 to 3.00 parts by weight, more preferably 0.03 to 1.50 parts by weight, and even more preferably 0.05 to 1.00 parts by weight per 100 parts by weight of resin particles. If the amount of crosslinking aid used is 0.01 parts by weight or more per 100 parts by weight of resin particles, it will exhibit sufficient effect as a crosslinking aid.

[0107] In the dispersion process, when impregnating and reacting resin particles with a crosslinking agent and, if necessary, a crosslinking aid, it is preferable to lower the oxygen concentration in the container and the amount of dissolved oxygen in the dispersion in order to increase the crosslinking efficiency of P3HA. Methods for lowering the oxygen concentration in the container and the amount of dissolved oxygen in the dispersion include replacing the gas in the container and the gas dissolved in the dispersion with inorganic gases such as carbon dioxide and nitrogen, and evacuating the gas in the container.

[0108] In this manufacturing method, a dispersion aid may be used to improve the effect of suppressing the adhesion between resin particles. Examples of dispersion aids include anionic surfactants such as sodium alkanesulfonate, sodium alkylbenzenesulfonate, and sodium α-olefin sulfonate. One of these dispersion aids may be used alone, or two or more may be used in combination. When using a mixture of two or more dispersion aids, the mixing ratio may be adjusted as appropriate depending on the purpose.

[0109] The amount of dispersion aid used is not particularly limited, but preferably 0.001 to 0.500 parts by weight, and more preferably 0.010 to 0.200 parts by weight, per 100 parts by weight of resin particles. To further improve the effect of suppressing the adhesion between resin particles, it is preferable to use the dispersant and the dispersion aid in combination.

[0110] In this manufacturing method, plasticizers may be used. By using plasticizers, it is possible to obtain foamed particles with a high foaming ratio and flexibility.

[0111] Examples of plasticizers used in this manufacturing method, or preferred plasticizers, include those listed in the (additives) section of [2. Poly(3-hydroxyalkanoate) foamed particles] above.

[0112] The amount of plasticizer used is not particularly limited, but is preferably more than 0 parts by weight and 20 parts by weight or less, more preferably 1 to 15 parts by weight, and even more preferably 1 to 10 parts by weight per 100 parts by weight of resin particles. In the dispersion step according to one embodiment of the present invention, the resin particles used may already contain a plasticizer. If the resin particles used already contain a plasticizer, it is preferable that the sum of the amount of plasticizer contained in the resin particles and the amount of plasticizer used in the dispersion step satisfies the above range.

[0113] (Heating-pressure boosting process and holding process) The heating-pressure step is preferably performed after the dispersion step, and the holding step is preferably performed after the heating-pressure step. In this specification, (a) a constant temperature in the heating-pressure step and the holding step may be referred to as the foaming temperature, and (b) a constant pressure may be referred to as the foaming pressure.

[0114] The foaming temperature cannot be specified in general, as it varies depending on the type of P3HA, the type of foaming agent, the desired foaming ratio of the foamed particles, etc. For example, a foaming temperature of 100.0°C to 140.0°C is preferred, 110.0°C to 135.0°C is more preferred, and 115.0°C to 133.0°C is even more preferred. When the foaming temperature is 100°C or higher, foamed particles with a high foaming ratio tend to be obtained. On the other hand, when the foaming temperature is 140°C or lower, there is no risk of hydrolysis of the resin particles occurring in the container.

[0115] In the heating-pressure process, the rate at which the temperature is raised to the desired foaming temperature (hereinafter sometimes referred to as the heating rate) is preferably 1.0°C / min to 3.0°C / min, and more preferably 1.5°C / min to 3.0°C / min. If the heating rate is 1.0°C / min or higher, productivity is excellent. On the other hand, if the heating rate is 3.0°C / min or lower, there is no risk that the impregnation of the foaming agent into the resin particles and the reaction between the crosslinking agent and P3HA will be insufficient during heating.

[0116] The foaming pressure is preferably 1.0 MPa to 10.0 MPa (gauge pressure), more preferably 2.0 MPa to 5.0 MPa (gauge pressure), and even more preferably 2.5 MPa to 4.0 MPa. If the foaming pressure is 1.0 MPa (gauge pressure) or higher, foamed particles with a high foaming ratio can be obtained.

[0117] (Release process) The release step is preferably performed after the heating-pressure step or after the holding step. The release step can cause the resin particles to foam, resulting in foamed particles.

[0118] In the release process, the "region with a pressure lower than the foaming pressure" refers to the "region under a pressure lower than the foaming pressure" or the "space under a pressure lower than the foaming pressure," and can also be described as "an atmosphere with a pressure lower than the foaming pressure." The region with a pressure lower than the foaming pressure is not particularly limited as long as the pressure is lower than the foaming pressure; for example, it may be a region under atmospheric pressure.

[0119] In the discharge process, when discharging the dispersion into a region with a pressure lower than the foaming pressure, the dispersion can be discharged through an open orifice with a diameter of 1 mm to 5 mm for purposes such as adjusting the flow rate of the dispersion and reducing variations in the foaming ratio of the resulting foamed particles. Furthermore, when using resin particles with relatively high melting points, the low-pressure region (space) may be filled with saturated water vapor to improve foaming properties.

[0120] In the release process, a cleaning agent may be used after the resin particles have been foamed. Examples of cleaning agents include hot water and sodium hexametaphosphate. Using a cleaning agent allows for the adjustment of the dispersant adhering to the surface of the foamed particles.

[0121] In the release process, an antistatic agent may be used after the resin particles have been foamed. Examples of antistatic agents include coconut oil fatty acid diethanolamide. By using an antistatic agent, static electricity of the foamed particles can be suppressed, improving handling.

[0122] While the above-described manufacturing method is the most preferred method for producing these foamed particles, it is not limited thereto. For example, these foamed particles can also be obtained using the manufacturing methods described in (r1) to (r3) below: (r1) The resin particles obtained by the above (resin particle preparation step) are placed in a pressure vessel, and a foaming agent is injected into the pressure vessel under pressure without using an aqueous dispersion medium. If necessary, the pressure vessel is heated and maintained to obtain resin particles containing the foaming agent. Next, the pressure vessel is depressurized to return to atmospheric pressure, and the resin particles containing the foaming agent are heated in the pressure vessel or transferred to another pressure vessel using a heating means such as steam to foam the resin particles impregnated with the foaming agent and obtain foamed particles; (r2) In the (resin particle preparation step) and the (melt kneading step), when melting and kneading the resin composition, a crosslinking agent and a foaming agent are injected under pressure into the melt kneading apparatus to prepare a resin composition containing the crosslinking agent and the foaming agent. Then, the resin composition is discharged from the nozzle of a die provided in the melt kneading apparatus, and the resin composition is cut by a cutting device while being cooled simultaneously with the discharge to obtain resin particles containing the foaming agent. The resin particles are transferred to a pressure vessel and heated with a heating means such as steam to foam the resin particles and obtain foamed particles; (r3) In the (resin particle preparation step), in the (melt kneading step), when melting and kneading the resin composition, a crosslinking agent and a foaming agent are injected under pressure into the melt kneading apparatus to prepare a resin composition containing the crosslinking agent and the foaming agent. Then, the resin composition is discharged from the nozzle of a die provided in the melt kneading apparatus, and foamed at the same time as the discharge and cut by a cutting device to obtain foamed particles.

[0123] In (r1) above, the pressure at which the foaming agent is injected into the pressure vessel is preferably 0.01 MPa (gauge pressure) to 10.00 MPa (gauge pressure), and more preferably 0.03 MPa (gauge pressure) to 5.00 MPa (gauge pressure).

[0124] In (r1) and (r2) above, the temperature inside the pressure vessel when heating the resin particles containing the foaming agent with steam or the like is preferably 100°C to 150°C, and more preferably 105°C to 145°C.

[0125] In (r2) and (r3) above, the pressure at which the crosslinking agent and blowing agent are injected into the melting and mixing apparatus is preferably 3 MPa (gauge pressure) to 30 MPa (gauge pressure), and more preferably 5 MPa (gauge pressure) to 15 MPa (gauge pressure).

[0126] (Two-stage foaming process) In the foaming particle manufacturing method described above, foaming particles with the desired apparent density may not be obtained by the foaming step alone. In such cases, the foaming particle manufacturing method may further include a second foaming step in which the foamed particles obtained in the foaming step are further expanded. The second foaming step is not particularly limited as long as it is possible to obtain foamed particles with an apparent density even lower than that of the foamed particles obtained in the foaming step by further expanding the foamed particles obtained in the foaming step. For example, the following embodiments can be given for the second foaming step: (s1) supply the foamed particles obtained in the foaming step into a container; (s2) supply air or an inorganic gas such as carbon dioxide into the container to increase the pressure inside the container; (s3) impregnate the foamed particles with the inorganic gas as in (s2) and raise the pressure inside the foamed particles to a level higher than atmospheric pressure; (s4) then heat the foamed particles with steam or the like to further expand them and obtain foamed particles with the desired apparent density. Foamed particles obtained in the second foaming step are sometimes referred to as second foamed particles. Furthermore, when a two-stage foaming process is performed, the foaming process may be referred to as a single-stage foaming process, and the foamed particles obtained in the single-stage foaming process may be referred to as single-stage foamed particles.

[0127] In the two-stage foaming process, the internal pressure of the foamed particles is preferably 0.15 MPa to 0.60 MPa (absolute pressure), and more preferably 0.20 MPa to 0.50 MPa (absolute pressure).

[0128] In the two-stage foaming process (in s2 and s3), when impregnating the foamed particles with the inorganic gas, the container temperature is preferably 10°C to 90°C, more preferably 20°C to 90°C, even more preferably 30°C to 90°C, and still more preferably 40°C to 90°C.

[0129] In the two-stage foaming process (as described in s4 above), the pressure of steam or other heat used to heat the foam particles (hereinafter sometimes referred to as "two-stage foaming pressure") varies depending on the characteristics of the foam particles used and the desired apparent density, and cannot be specified in general terms. The two-stage foaming pressure is preferably 0.01 MPa to 0.17 MPa (gauge pressure), and more preferably 0.03 MPa to 0.11 MPa (gauge pressure).

[0130] The gel fraction of the two-stage foamed particles is preferably the same as that of the foamed particles. That is, the description in the (gel fraction) section above can be appropriately applied to the gel fraction of the two-stage foamed particles.

[0131] [4. Poly(3-hydroxyalkanoate) foamed molded articles] A poly(3-hydroxyalkanoate) foamed molded article according to one embodiment of the present invention consists of poly(3-hydroxyalkanoate) foamed particles according to one embodiment of the present invention. A poly(3-hydroxyalkanoate) foamed molded article according to one embodiment of the present invention may be formed by molding poly(3-hydroxyalkanoate) foamed particles according to one embodiment of the present invention. A poly(3-hydroxyalkanoate) foamed molded article according to one embodiment of the present invention may contain poly(3-hydroxyalkanoate) foamed particles according to one embodiment of the present invention. With this configuration, a poly(3-hydroxyalkanoate) foamed molded article with a high foaming ratio can be provided.

[0132] The method for manufacturing this foamed molded article (i.e., the method for molding the foamed particles) is not particularly limited, and known methods can be applied. For example, the following in-mold foaming methods (A) to (D) are examples, but are not particularly limited: (A) A method in which the foamed particles are pressurized with an inorganic gas in a container to impregnate the foamed particles with the inorganic gas, a predetermined internal pressure is applied to the foamed particles, the foamed particles are then filled into a mold, and heated with steam; (B) A method in which the foamed particles are filled into a mold, compressed so as to reduce the volume inside the mold by 10% to 75%, and heated with steam; (C) A method of compressing the foamed particles with gas pressure and filling them into a mold, and then heating them with steam using the recovery force of the foamed particles; (D) A method of filling a mold with the foamed particles without any special pretreatment and heating it with steam.

[0133] In the manufacture of this foamed molded article, the pressure of the steam used to heat the foam particles (hereinafter sometimes referred to as the molding pressure) varies depending on the characteristics of the foam particles used and cannot be specified in general terms. The molding pressure is preferably 0.05 MPa to 0.30 MPa (gauge pressure), more preferably 0.08 MPa to 0.25 MPa (gauge pressure), and even more preferably 0.10 MPa to 0.20 MPa (gauge pressure).

[0134] In the method for producing this foamed molded article, at least one inorganic gas selected from the group consisting of air, nitrogen, oxygen, carbon dioxide, helium, neon, argon, etc., can be used as the inorganic gas in method (A) above. Among these inorganic gases, air and / or carbon dioxide are preferred.

[0135] In the manufacturing method of this foamed molded article, the temperature inside the container when impregnating the foamed particles with inorganic gas in method (A) is preferably 10°C to 90°C, more preferably 20°C to 90°C, even more preferably 30°C to 90°C, and still more preferably 40°C to 90°C.

[0136] In the manufacturing method of this foamed molded article, the internal pressure of the foamed particles in method (A) described above is preferably 0.10 MPa to 0.30 MPa (absolute pressure), more preferably 0.11 MPa to 0.25 MPa (absolute pressure), and even more preferably 0.12 MPa to 0.20 MPa (absolute pressure). The internal pressure of the foamed particles can be measured according to the measurement method described in the examples below.

[0137] The foaming ratio of this foamed molded article is not limited, but is preferably 25 times or more, more preferably 27 times or more, even more preferably 30 times or more, and still more preferably 35 times or more. The upper limit of the foaming ratio of this foamed molded article is not limited, but could be, for example, 50 times, 40 times, or 35 times. With this configuration, a poly(3-hydroxyalkanoate)-based foamed molded article with a good balance of mechanical strength and lightweight properties can be provided.

[0138] One embodiment of the present invention may have the following configuration:

[0139] [1] Poly(3-hydroxyalkanoate) foamed particles comprising a poly(3-hydroxyalkanoate) resin (A) and a nonionic water-soluble polymer (B), wherein the content of the nonionic water-soluble polymer (B) is 0.10 parts by weight to 5.00 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A), and the closed-cell ratio of the poly(3-hydroxyalkanoate) foamed particles is 90% or more.

[0140] [2] The poly(3-hydroxyalkanoate) foamed particle according to [1], wherein the nonionic water-soluble polymer (B) has a hydrophobic group.

[0141] [3] Poly(3-hydroxyalkanoate) foamed particles according to [1] or [2], wherein the nonionic water-soluble polymer (B) is biodegradable.

[0142] [4] The poly(3-hydroxyalkanoate) foamed particle according to any one of [1] to [3], wherein the nonionic water-soluble polymer (B) is at least one selected from the group consisting of polyalkylene oxide, polyvinyl alcohol, and cellulose derivatives.

[0143] [5] The poly(3-hydroxyalkanoate) foamed particles according to [4], wherein the content of the nonionic water-soluble polymer (B) is 0.10 parts by weight to 1.00 part by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A).

[0144] [6] The poly(3-hydroxyalkanoate) foamed particle according to any one of [1] to [5], wherein the poly(3-hydroxyalkanoate) resin (A) is at least one selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0145] [7] The poly(3-hydroxyalkanoate) resin (A) is a copolymer having 3-hydroxybutyrate units and comonomer units, Poly(3-hydroxyalkanoate) foamed particles according to any one of [1] to [6], wherein the ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of the total repeating units in the copolymer is 99 / 1 (mol% / mol%) to 85 / 15 (mol% / mol%).

[0146] [8] Poly(3-hydroxyalkanoate) foamed particles as described in any one of [1] to [7], having an apparent density of 20 g / L to 67 g / L.

[0147] [9] Poly(3-hydroxyalkanoate) foamed particles as described in any one of [1] to [8], wherein the high-temperature heat content is 0.1 J / g to 20.0 J / g.

[0148]

[10] Poly(3-hydroxyalkanoate) foamed particles as described in any one of [1] to [9], having a cell diameter of 50 μm to 500 μm.

[0149]

[11] Poly(3-hydroxyalkanoate) foamed particles as described in any one of [1] to

[10] , wherein the gel fraction is 30% by weight or more.

[0150] A poly(3-hydroxyalkanoate) foamed molded article comprising poly(3-hydroxyalkanoate) foamed particles as described in any one of

[12] , [1], to

[11] .

[0151]

[13] A poly(3-hydroxyalkanoate) foamed molded article according to

[12] , wherein the foaming ratio is 25 times or more. [Examples]

[0152] The present invention will be specifically described below with reference to examples, but the technical scope of the present invention is not limited by these examples.

[0153] 〔material〕 The substances used in the examples and comparative examples are shown below.

[0154] (Water-soluble polymer) Water-soluble polymer-1: Nonionic polyvinyl alcohol (Kuraray POVA-205 manufactured by Kuraray Co., Ltd., degree of saponification 87.0 mol%~89.0 mol%, degree of polymerization 500, hydrophobic groups are acetate groups) Water-soluble polymer-2: Nonionic polyalkylene oxide (NOF Corporation Pronon #208, 80% by weight of ethylene oxide, average molecular weight 10,000, hydrophobic group is oxypropylene group) Water-soluble polymer-3: Nonionic cellulose derivative (Metholose MCE-4000, manufactured by Shin-Etsu Chemical Co., Ltd., 25.0% to 33.0% methoxy groups, hydrophobic groups are methoxy groups) Water-soluble polymer-4: Nonionic polyalkylene oxide (Emulsogen EPN 287, manufactured by CLARIANT, 28 mol% ethylene oxide, molecular weight 1404, hydrophobic group is oxypropylene group) Water-soluble polymer-5: Ionic polyalkylene oxide (Emulsogen EPA 073, manufactured by CLARIANT, 7 mol% ethylene oxide, molecular weight 577, hydrophobic group is oxypropylene group) All five water-soluble polymers mentioned above possess both hydrophilic and hydrophobic groups, and are biodegradable.

[0155] (Bubble regulator) Foam regulator: Talc (Talcan Powder PK-S, manufactured by Hayashi Chemical Co., Ltd.).

[0156] (Crystallizing agent) Crystallization agent: Pentaerythritol (Neurizer P, manufactured by Mitsubishi Chemical Corporation).

[0157] (Lubricant) Lubricant-1: Behenamide (Crodamide BR, manufactured by CRODA) Lubricant-2: Erucic acid amide (Crodamide ER, manufactured by CRODA).

[0158] (Dispersant) Dispersant: Tricalcium phosphate (manufactured by Taihei Chemical Industry Co., Ltd.).

[0159] (Dispersing agent) Dispersing agent: Sodium alkyl sulfonate (Latemul PS, manufactured by Kao Corporation).

[0160] (Crosslinking agent) Crosslinking agent: t-butyl peroxy-2-ethylhexyl carbonate (content 97%) (Perbutyl E manufactured by NOF Corporation).

[0161] (Cleaning agent) Cleaning agent: Sodium hexametaphosphate (manufactured by WUXI LOTUS ESSENCE).

[0162] (Antistatic agent) Antistatic agent: Coconut oil fatty acid diethanolamide (Profan 128 Extra, manufactured by Sanyo Chemical Industries).

[0163] [Measurement method] The evaluation methods used in the examples and comparative examples are described below.

[0164] (Measurement of the melting point of poly(3-hydroxyalkanoate) resin particles) Approximately 5 mg of poly(3-hydroxyalkanoate) resin particles were weighed using a differential scanning calorimeter (DSC7020, Hitachi High-Tech Science Corporation). Next, the poly(3-hydroxyalkanoate) resin particles were heated from 10°C to 190°C at a heating rate of 10°C / min. The temperature of the highest melting peak in the resulting DSC curve was defined as the melting point.

[0165] (Measurement of MFR of poly(3-hydroxyalkanoate) resin particles) Using a melt flow index tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), measurements were taken in accordance with JIS K7210, with a load of 5 kg and a measurement temperature of 5°C to 10°C above the melting end temperature, as read from the DSC curve obtained in the above-mentioned (measurement of the melting point of poly(3-hydroxyalkanoate) resin particles).

[0166] (Measurement of specific gravity of poly(3-hydroxyalkanoate) resin particles) Using an automatic hydrometer (DSG-1, manufactured by Toyo Seiki Seisakusho Co., Ltd.), the specific gravity (g / cm³) of poly(3-hydroxyalkanoate) resin particles was determined by the water displacement method in accordance with JIS K7112. 3 ) was measured.

[0167] (Measurement of apparent density of poly(3-hydroxyalkanoate) foam particles) The apparent density of poly(3-hydroxyalkanoate) foam particles was measured as follows (1) to (3): (1) A graduated cylinder containing ethanol was prepared, and weight Wd (g) of poly(3-hydroxyalkanoate) foam particles was submerged in the ethanol; (2) The volume of poly(3-hydroxyalkanoate) foam particles was read from the rise in the ethanol water level (submersion method) and measured as Vd (cm). 3 (3) The apparent density ρd of poly(3-hydroxyalkanoate) foamed particles was calculated using the following formula: Apparent density ρd (g / cm³) 3 ) = Wd / Vd.

[0168] (Measurement of foaming ratio of poly(3-hydroxyalkanoate) foaming particles) The foaming ratio of poly(3-hydroxyalkanoate) foamed particles was calculated based on the following formula: The foaming ratio (times) = specific gravity of poly(3-hydroxyalkanoate) resin particles / apparent density ρd of poly(3-hydroxyalkanoate) foamed particles.

[0169] (Measurement of gel fraction of poly(3-hydroxyalkanoate) foamed particles) The method for measuring the gel fraction of poly(3-hydroxyalkanoate) foam particles was as follows (a1) to (a5): (a1) 0.5 g of poly(3-hydroxyalkanoate) foam particles and 50 ml of chloroform were placed in a 100 ml flask; (a2) The mixture in the flask was heated under reflux at 62°C under atmospheric pressure for 8 hours; (a3) ​​The resulting heat-treated material was filtered using a suction filtration apparatus equipped with a 100-mesh wire mesh; (a4) The filtered material on the wire mesh was dried in an oven at 80°C under vacuum conditions for 8 hours, and the weight of the dried material Wg (g) was measured; (a5) The gel fraction was calculated using the following formula: Gel fraction (weight %) = Wg / 0.5 × 100.

[0170] (Measurement of high-temperature heat content of poly(3-hydroxyalkanoate) foamed particles) The high-temperature heat content of poly(3-hydroxyalkanoate) foam particles was measured using a differential scanning calorimeter (DSC7020, Hitachi High-Tech Science Corporation). The specific operating procedure was as follows (1) to (5): (1) Approximately 5 mg of poly(3-hydroxyalkanoate) foam particles were weighed out; (2) The temperature of the poly(3-hydroxyalkanoate) foam particles was increased from 10°C to 190°C at a heating rate of 10°C / min to melt the poly(3-hydroxyalkanoate) foam particles; (3) In the DSC curve obtained in the process of (2), a baseline was created by drawing a straight line connecting the point representing the temperature before the start of melting and the point representing the temperature after the end of melting; (4) A straight line passing through the maximum point between the high-temperature melting peak or the hottest melting peak and the adjacent melting peak was drawn perpendicular to the X-axis; (5) The amount of heat calculated from the high-temperature region enclosed by the baseline, the straight line passing through the maximum point, and the DSC curve was defined as the high-temperature heat quantity.

[0171] (Measurement of the average cell diameter of poly(3-hydroxyalkanoate) foamed particles) The method for measuring the average cell diameter of foam particles was as follows (1) to (5): (1) Using a razor (Feather High Stainless Double-Edged), the foam particle was cut so as to pass through its center; (2) The resulting cross-section of the foam particle was observed at 50x magnification using an optical microscope (Keyence VHX-100); (3) A straight line was drawn through the center or approximate center of the cross-section of the foam particle in the image obtained from the observation; (4) (4-1) The number of bubbles n present on the straight line was measured; (4-2) The length of the line segment cut off from the straight line at the intersection of the straight line and the surface of the foam particle was measured and defined as the foam particle diameter L; (5) The average cell diameter of the foam particle was calculated using the following formula: Average cell diameter (μm) = L / n.

[0172] (Measurement of the closed-cell ratio of poly(3-hydroxyalkanoate) foamed particles) The measurement of the closed cell ratio of poly(3-hydroxyalkanoate) based expanded particles was carried out in accordance with the method described in Procedure C of ASTM D2856-87. First, using an air comparison pycnometer [manufactured by Tokyo Science Co., Ltd., model 1000], the volume Vc (cm 3 ) was measured. Next, the total amount of the expanded particles after measuring Vc was immersed in a graduated cylinder containing ethanol, and the apparent volume Va (cm 3 ) of the expanded particles was determined from the increase in the water level of the graduated cylinder (water immersion method). The closed cell ratio of the expanded particles was determined from 100 - (Va - Vc) × 100 / Va (%).

[0173] (Measurement of the internal pressure of poly(3-hydroxyalkanoate) based expanded particles) The method for measuring the internal pressure of poly(3-hydroxyalkanoate) based expanded particles was as follows: (1) The weight W1 (g) of the poly(3-hydroxyalkanoate) based expanded particles after the pressurization step was measured; (2) The expanded particles were heated at 150 °C for 30 minutes to dissipate the inorganic gas inside the expanded particles; (3) For the poly(3-hydroxyalkanoate) based expanded particles from which the inorganic gas had been dissipated, the weight W2 (g) of the expanded particles was measured again; (4) The weight of the inorganic gas (ΔW) was calculated from the weight difference (W1 - W2) of the poly(3-hydroxyalkanoate) based expanded particles before and after dissipating the inorganic gas; (5) The internal pressure P (MPa) of the poly(3-hydroxyalkanoate) based expanded particles was calculated from the state equation of an ideal gas (specifically, the following formula): Internal pressure P (MPa) = (1 + ΔW / M × 0.082 × (273 + T) × (ρd × 1000 / W2)) / 9.87: In the above formula, M is the average molar molecular weight, T is the temperature (room temperature) (°C) when measuring the weight of the poly(3-hydroxyalkanoate) based expanded particles after the pressurization step. ρd is the apparent density (g / cm 3 ) of the poly(3-hydroxyalkanoate) based expanded particles (expanded particles with weight W1) after the pressurization step.

[0174] (Measurement of the expansion ratio of poly(3-hydroxyalkanoate) based expanded molded articles) The method for measuring the magnification of the poly(3-hydroxyalkanoate) foam molded article was as follows (1) to (4): (1) Using a digital caliper (manufactured by Mitutoyo Corporation), the length (mm) in the longitudinal direction (length) (mm), transverse direction (width) (width) and thickness direction (thickness) of the obtained poly(3-hydroxyalkanoate) foam molded article was measured, and the volume V (cm³) of the poly(3-hydroxyalkanoate) foam molded article was measured. 3 (1) The density of the foamed molded material was calculated; (2) The weight W (g) of the foamed molded material was measured; (3) The density ρ of the poly(3-hydroxyalkanoate) foamed molded material was calculated based on the following formula: density ρ (g / cm³) 3 ) = W / V; (4) The foaming ratio of the foamed molded product was calculated based on the following formula: Foaming ratio (times) = Specific gravity of resin particles / Density ρ of the foamed molded product.

[0175] The raw materials (P3HA-1 to P3HA-7) for the poly(3-hydroxyalkanoate) foamed particles were prepared by the following method.

[0176] [Manufacturing Example 1] Fabrication of P3HA-1 P3HA-1 was prepared by the method described in International Publication No. 2018 / 070492. In this preparation, 1.00 part by weight of water-soluble polymer-1 (Kuraray Poval PVA-205, manufactured by Kuraray Co., Ltd.) was used per 100 parts by weight of P3HA. The resulting P3HA-1 contained (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000, and (b) 1.00 part by weight of water-soluble polymer-1 per 100 parts by weight of P3HB3HH.

[0177] [Manufacturing Example 2] Fabrication of P3HA-2 P3HA-2 was prepared by the method described in International Publication No. 2018 / 070492. In this preparation, 1.00 part by weight of water-soluble polymer-2 (Pronon #208, manufactured by NOF Corporation) was used instead of water-soluble polymer-1 for every 100 parts by weight of P3HA. The resulting P3HA-2 contained (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000, and (b) 1.00 part by weight of water-soluble polymer-2 per 100 parts by weight of P3HB3HH.

[0178] [Manufacturing Example 3] Fabrication of P3HA-3 P3HA-3 was prepared by the method described in International Publication No. 2018 / 070492. In this preparation, 1.00 part by weight of water-soluble polymer-2 (Pronon #208, manufactured by NOF Corporation) and 0.50 parts by weight of water-soluble polymer-3 (Metholose MCE-4000, manufactured by Shin-Etsu Chemical Co., Ltd.) were used instead of water-soluble polymer-1 for 100 parts by weight of P3HA. The resulting P3HA-3 contained (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000, and (b) 1.00 part by weight of water-soluble polymer-2 and 0.50 parts by weight of water-soluble polymer-3 per 100 parts by weight of the said P3HB3HH.

[0179] [Manufacturing Example 4] Fabrication of P3HA-4 P3HA-4 was prepared using the method described in International Publication No. 2018 / 070492. In this preparation, 1.00 part by weight of water-soluble polymer-4 (Emulsogen EPN 287, manufactured by CLARIANT) was used instead of water-soluble polymer-1 for every 100 parts by weight of P3HA. The resulting P3HA-4 contained (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000, and (b) 1.00 part by weight of water-soluble polymer-4 per 100 parts by weight of P3HB3HH.

[0180] [Manufacturing Example 5] Fabrication of P3HA-5 P3HA-5 was prepared using the method described in International Publication No. 2018 / 070492. In this preparation, 1.00 part by weight of water-soluble polymer-5 (Emulsogen EPA 073, manufactured by CLARIANT) was used instead of water-soluble polymer-1 for every 100 parts by weight of P3HA. The resulting P3HA-5 contained (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000, and (b) 1.00 part by weight of water-soluble polymer-5 per 100 parts by weight of P3HB3HH.

[0181] [Manufacturing Example 6] Fabrication of P3HA-6 P3HA-6 was prepared by the method described in International Publication No. 2018 / 070492. In this preparation, 0.05 parts by weight of water-soluble polymer-1 (Kuraray Poval PVA-205, manufactured by Kuraray Co., Ltd.) was used per 100 parts by weight of P3HA. The resulting P3HA-6 contained (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000, and (b) 0.05 parts by weight of water-soluble polymer-1 per 100 parts by weight of P3HB3HH.

[0182] [Manufacturing Example 7] Fabrication of P3HA-7 Instead of spray drying as described in International Publication No. 2018 / 070492, P3HA-7 was prepared by fluidized bed drying. No water-soluble polymer was used in this process. The resulting P3HA-7 was P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000. The obtained P3HA-7 contained (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000.

[0183] [Manufacturing Example 8] Fabrication of P3HA-8 P3HA-8 was prepared by the method described in International Publication No. 2018 / 070492. In this preparation, 0.50 parts by weight of water-soluble polymer-4 (Emulsogen EPN 287, manufactured by CLARIANT) was used instead of water-soluble polymer-1 for every 100 parts by weight of P3HA. The resulting P3HA-8 contained (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 89 / 11 (mol% / mol%) and a weight-average molecular weight of 580,000, and (b) 0.50 parts by weight of water-soluble polymer-4 per 100 parts by weight of P3HB3HH.

[0184] Table 1 summarizes the types and amounts of P3HA and water-soluble polymers used in each manufacturing example.

[0185] [Example 1] (Manufacturing of poly(3-hydroxyalkanoate) resin particles) Using P3HA-1, the following components were weighed out to the same amount: 100.0 parts by weight of P3HA-1, 0.10 parts by weight of a foam regulator, 1.0 part by weight of a crystal nucleating agent, 0.10 parts by weight of lubricant-1, and 0.10 parts by weight of lubricant-2. A mixture was prepared using a super mixer (SMV(G)-100, manufactured by Kawata Co., Ltd.). This mixture was melted and kneaded using a twin-screw extruder (TEM-26SX, manufactured by Toshiba Machine Co., Ltd.) at a cylinder setting temperature of 130°C to 160°C, and extruded from a nozzle on a die attached to the tip of the extruder. After the molten P3HA-based composition extruded from the nozzle at 180°C was water-cooled at 43°C, a small amount of water-diluted antistatic agent was applied to the surface of the strand of the P3HA-based composition (100 parts by weight), and then the strand was cut. The obtained poly(3-hydroxyalkanoate) resin particles had a weight of 2.0 mg per particle, a length / diameter ratio of 1.5, a Tmp of 145°C, and a melting end temperature of 152°C. Furthermore, the MFR of the resin particles, measured at a temperature of 160°C and a load of 5 kgf, was 2.2 g / 10 min.

[0186] (Manufacturing of poly(3-hydroxyalkanoate) foamed particles) 100 parts by weight of the obtained poly(3-hydroxyalkanoate) resin particles, 200 parts by weight of pure water, 1.0 part by weight of dispersant, 0.1 part by weight of dispersion aid, and 2.0 parts by weight of crosslinking agent were placed in a pressure vessel under stirring. Then, the oxygen in the pressure vessel was removed by thoroughly aerating with carbon dioxide. Next, carbon dioxide was introduced into the pressure vessel as a foaming agent. Subsequently, the dispersion in the pressure vessel was heated to a foaming temperature of 129.5°C. Then, additional carbon dioxide was introduced to increase the pressure to a foaming pressure of 3.3 MPa (gauge pressure), and it was held at around this foaming temperature and pressure for 60 minutes. After that, the valve at the bottom of the pressure vessel was opened, and the dispersion in the pressure vessel was released to atmospheric pressure through a 3.6 mm diameter open orifice to obtain poly(3-hydroxyalkanoate) foamed particles. The dispersant adhering to the surface of the foamed particles was removed to some extent with a water-diluted detergent and warm water, and then dried at 80°C. In this process, a small amount of water-diluted antistatic agent was sprayed onto the poly(3-hydroxyalkanoate) foamed particles to suppress static electricity. The resulting poly(3-hydroxyalkanoate) foamed particles had a foaming ratio of 21 times, a gel fraction of 69% by weight, a weight per particle of 2.0 mg, a length / diameter ratio of 0.9, a cell diameter of 260 μm, and a closed-cell ratio of 94%. The characteristics of the poly(3-hydroxyalkanoate) foamed particles are summarized in Tables 2 and 3.

[0187] (Manufacturing of poly(3-hydroxyalkanoate) foamed molded articles) The obtained poly(3-hydroxyalkanoate) foam particles were placed in a pressure-resistant container heated to 80°C and pressurized with air to achieve an internal pressure of 0.15 MPa (absolute pressure). These foam particles were then filled into a mold measuring 370 mm (length) x 320 mm (width) x 60 mm (thickness) in a molding machine (DAISEN EP-900L-M5). Next, the poly(3-hydroxyalkanoate) foam particles were heated with steam at a pressure of 0.15 MPa (gauge pressure) for 5 to 10 seconds to obtain a poly(3-hydroxyalkanoate) foam molded body, which was then dried at 75°C. The evaluation results for the poly(3-hydroxyalkanoate) foam molded body are summarized in Tables 2 and 3.

[0188] [Examples 2-5, Comparative Examples 1-3] Except for changing the poly(3-hydroxyalkanoate) resin and aqueous polymer used as shown in Tables 2 and 3, poly(3-hydroxyalkanoate) resin particles, poly(3-hydroxyalkanoate) foam particles, and poly(3-hydroxyalkanoate) foam molded articles were prepared in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The evaluation results are summarized in Tables 2 and 3. [Table 1] [Table 2]

[0189] [Table 3] [Consideration] From Tables 1 to 3, the following can be seen: (1) Examples 1 to 5 show that by using a poly(3-hydroxyalkanoate) resin and a small amount of nonionic water-soluble polymer to produce poly(3-hydroxyalkanoate) foamed particles, poly(3-hydroxyalkanoate) foamed particles with a high foaming ratio can be obtained in a single foaming treatment; (2) In Comparative Example 1, poly(3-hydroxyalkanoate) foamed particles were prepared using a poly(3-hydroxyalkanoate) resin and a small amount of ionic water-soluble polymer. In this case, thermal decomposition was accelerated during the melt-kneading process when preparing the poly(3-hydroxyalkanoate) resin particles, resulting in a very high MFR of the resin particles. As a result, in Comparative Example 1, although the foaming ratio of the poly(3-hydroxyalkanoate) foamed particles could be increased, a good poly(3-hydroxyalkanoate) foamed molded article could not be obtained due to the low percentage of closed cells. (3) In Comparative Example 2, poly(3-hydroxyalkanoate) foamed particles were prepared using a poly(3-hydroxyalkanoate) resin and a very small amount (0.05 by weight) of an ionic water-soluble polymer. In this case, it was not possible to increase the foaming ratio of the poly(3-hydroxyalkanoate) foamed particles. (4) In Comparative Example 3, poly(3-hydroxyalkanoate) foamed particles were prepared without using a water-soluble polymer, but in this case, it was not possible to increase the foaming ratio of the poly(3-hydroxyalkanoate) foamed particles. [Industrial applicability]

[0190] The present invention can be suitably used in fields such as packaging cushioning materials (for example, cushioning materials for packaging home appliances such as refrigerators, freezers, air conditioner bodies and their outdoor units, washing machines, air purifiers, humidifiers, rice cookers, microwave ovens, ovens, toasters, electric fans, and battery units; cushioning materials for packaging automotive parts such as transmissions, roofs, hoods, doors, batteries, and engines); automotive components (for example, bumper core materials, headrests, luggage boxes, toolboxes, floor spacers, seat core materials, child seat core materials, sun visor core materials, knee pads, etc.); thermal insulation materials (for example, temperature-controlled storage containers, temperature-controlled transport containers, etc.); casting model applications; agricultural product boxes; fish boxes; building materials; and civil engineering materials.

Claims

1. Poly(3-hydroxyalkanoate) foamed particles, The material comprises a poly(3-hydroxyalkanoate) resin (A) and a nonionic water-soluble polymer (B), The content of the nonionic water-soluble polymer (B) is 0.10 to 5.00 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A). The closed-cell ratio of the poly(3-hydroxyalkanoate) foamed particles is 90% or more. The nonionic water-soluble polymer (B) is at least one selected from the group consisting of polyalkylene oxide, polyvinyl alcohol, cellulose derivatives, and starch derivatives, and is a poly(3-hydroxyalkanoate) foamed particle.

2. The poly(3-hydroxyalkanoate) foamed particle according to claim 1, wherein the nonionic water-soluble polymer (B) has a hydrophobic group.

3. The poly(3-hydroxyalkanoate) foamed particle according to claim 1, wherein the nonionic water-soluble polymer (B) is biodegradable.

4. The poly(3-hydroxyalkanoate) foamed particle according to claim 1, wherein the nonionic water-soluble polymer (B) is at least one selected from the group consisting of polyalkylene oxide, polyvinyl alcohol, and cellulose derivatives.

5. The poly(3-hydroxyalkanoate) foamed particles according to claim 4, wherein the content of the nonionic water-soluble polymer (B) is 0.10 parts by weight to 1.00 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A).

6. The poly(3-hydroxyalkanoate) foamed particle according to claim 1, wherein the poly(3-hydroxyalkanoate) resin (A) is at least one selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

7. The poly(3-hydroxyalkanoate) resin (A) is a copolymer having 3-hydroxybutyrate units and comonomer units. The poly(3-hydroxyalkanoate) foamed particle according to claim 1, wherein the ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of the total repeating units in the copolymer is 99 / 1 (mol% / mol%) to 85 / 15 (mol% / mol%).

8. Poly(3-hydroxyalkanoate) foamed particles according to claim 1, having an apparent density of 20 g / L to 67 g / L.

9. Poly(3-hydroxyalkanoate) foamed particles according to claim 1, wherein the high-temperature heat content is 0.1 J / g to 20.0 J / g.

10. Poly(3-hydroxyalkanoate) foamed particles according to claim 1, wherein the cell diameter is 50 μm to 500 μm.

11. Poly(3-hydroxyalkanoate) foamed particles according to claim 1, wherein the gel fraction is 30% by weight or more.

12. A poly(3-hydroxyalkanoate) foamed molded article comprising poly(3-hydroxyalkanoate) foamed particles according to any one of claims 1 to 11.

13. A poly(3-hydroxyalkanoate) foamed molded article according to claim 12, wherein the foaming ratio is 25 times or more.

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