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

Abstract

Provided are poly(3-hydroxyalkanoate) foamed particles having a high foaming ratio, which are obtained by one foaming process, and poly(3-hydroxyalkanoate) foamed molded bodies. The present invention provides poly(3-hydroxyalkanoate) foamed particles and foamed molded bodies formed from 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] The massive amounts of plastics derived from petroleum are discarded annually, leading to insufficient landfill capacity and environmental pollution, which are considered serious problems. Furthermore, microplastics have become a significant issue in the marine environment in recent years. Therefore, biodegradable plastics, which decompose through microbial action in (a) marine and soil environments, and (b) landfills and composting facilities, are of great interest.

[0003] For biodegradable plastics, development is underway with the aim of widespread application in (a) agricultural, forestry, and fishery materials that are utilized in the environment, and (b) food containers, packaging materials, hygiene products, garbage bags, etc., which are difficult to recycle and reuse after use. Furthermore, foams formed from biodegradable plastics are expected to find applications in packaging cushioning materials, agricultural product boxes, fish boxes, automotive parts, building materials, civil engineering materials, etc.

[0004] Among the aforementioned biodegradable plastics, poly(3-hydroxyalkanoates) (hereinafter sometimes referred to as "P3HA"), as a plastic derived from plant materials, has attracted much attention from the perspective of excellent biodegradability and carbon neutrality.

[0005] There has been ongoing active development of technologies related to biodegradable plastics. For example, Patent Document 1 discloses a resin composition made by mixing polyepoxide in a specific proportion with an aliphatic polyester copolymer produced by microorganisms. More specifically, Patent Document 1 discloses a biodegradable resin with a low glass transition temperature and high toughness at low temperatures that can be obtained by mixing polyepoxide in a specific proportion with an aliphatic polyester copolymer produced by microorganisms.

[0006] Patent Document 2 discloses non-crosslinked pre-foamed particles formed by foaming particles of a resin composition mainly composed of biodegradable poly(3-hydroxyalkanoate) resin, and an in-mold foamed article using the pre-foamed particles. More specifically, Patent Document 2 discloses obtaining non-crosslinked poly(3-hydroxyalkanoate) pre-foamed particles and an in-mold foamed article with high expansion ratio and closed-cell ratio by foaming particles formed of a resin composition containing poly(3-hydroxyalkanoate) resin and a specific triglyceride under specific conditions.

[0007] Patent Document 3 discloses aliphatic polyester foams and aliphatic polyester porous particles with uniform porous structures, as well as methods for manufacturing them. More specifically, Patent Document 3 discloses obtaining biodegradable aliphatic polyester foams or aliphatic polyester porous particles with a desired foaming ratio, high porosity, and small pore size deviation by foaming aliphatic polyester in the presence of polyols.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Publication No. 2010-229407

[0011] Patent Document 2: Japanese Patent Publication No. 2012-241166

[0012] Patent Document 3: International Publication No. 2014 / 136746 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] However, the expansion ratio of poly(3-hydroxyalkanoate) foam particles obtained by the above-mentioned existing technology through a single foaming process is not high enough, and there is still room for improvement from the point of view of expansion ratio.

[0015] In view of the above, an embodiment of the present invention aims to provide poly(3-hydroxyalkanoate) foamed particles with high foaming ratio obtained by a single foaming process, and poly(3-hydroxyalkanoate) foamed molded articles.

[0016] Methods for solving problems

[0017] That is, in one embodiment of the present invention, the poly(3-hydroxyalkanoate) foam particles comprise a poly(3-hydroxyalkanoate) resin (A) and a nonionic water-soluble polymer (B).

[0018] Relative to 100 parts by weight of the above-mentioned poly(3-hydroxyalkanoate) resin (A), the content of the above-mentioned nonionic water-soluble polymer (B) is 0.10 parts by weight to 5.00 parts by weight.

[0019] The closed-cell rate of the above-mentioned poly(3-hydroxyalkanoate) foam particles is over 90%.

[0020] The effects of the invention

[0021] According to one aspect of the present invention, it is possible to provide poly(3-hydroxyalkanoate) foamed particles with high expansion ratio obtained by a single foaming process, as well as poly(3-hydroxyalkanoate) foamed molded articles. Detailed Implementation

[0022] The following describes one embodiment of the present invention, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications can be made within the scope shown in the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included within the technical scope of the present invention. In addition, new technical features can be formed by combining the technical means disclosed in each embodiment. It should be noted that all academic and patent documents described in this specification are incorporated herein by reference. Furthermore, in this specification, unless otherwise specified, "A~B" indicating a numerical range means "A or more (inclusive of A and greater than A) and B or less (inclusive of B and less than B)".

[0023] [1. Technical concept of one embodiment of the present invention]

[0024] Patent Document 1 does not describe the effect of polyepoxide on the foaming ratio of foamed particles when a resin composition containing polyepoxide mixed with an aliphatic polyester copolymer is used to form foamed particles. It should be noted that Patent Document 1 discloses an example in which 5.26 parts by weight or more of polyepoxide are used relative to 100 parts by weight of the aliphatic polyester copolymer. However, it is preferable to minimize by-products other than the resin, and from this perspective, there is still room for improvement.

[0025] The technology described in Patent Document 2 relates to non-crosslinked foamed particles. Patent Document 2 discloses increasing the foaming ratio by using a large amount of a specific triglyceride, a poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate) copolymer (PHBH) with a high MFR, and a small amount of triglyceride. However, it is preferable to minimize byproducts other than the resin, and there is still room for improvement in this regard. Furthermore, the use of a high MFR PHBH results in poor moldability and a narrowed process window, which also allows for improvement. Additionally, the use of a plasticizer in the technology described in Patent Document 2 reduces the strength of the foamed molded article, which also allows for improvement.

[0026] The inventors have independently discovered that the technology described in Patent Document 3 results in aliphatic polyester foams or porous particles with low closed-cell ratios, making it impossible to apply them to secondary processing such as in-mold foaming.

[0027] Through in-depth research, the inventors discovered that if the foamed particles are poly(3-hydroxyalkanoate) containing a specific amount of nonionic, water-soluble polymers, the foaming ratio increases with a single foaming treatment, thus eliminating the need for a second foaming treatment, thereby completing this invention. It should be noted that eliminating the need for a second foaming treatment offers significant advantages, including simplifying the manufacturing process of the foamed particles and reducing manufacturing costs.

[0028] [2. Poly(3-hydroxyalkanoate) foam particles]

[0029] In this specification, "poly(3-hydroxyalkanoate) foamed particles" are sometimes referred to as "foamed particles", "poly(3-hydroxyalkanoate) foamed particles of one embodiment of the present invention" are sometimes referred to as "the foamed particles", "poly(3-hydroxyalkanoate) foamed molded body" are sometimes referred to as "foamed molded body", and "poly(3-hydroxyalkanoate) foamed molded body of one embodiment of the present invention" are sometimes referred to as "the foamed molded body".

[0030] These foamed particles are obtained by foaming poly(3-hydroxyalkanoate) resin particles formed from a poly(3-hydroxyalkanoate) resin composition. In this specification, "poly(3-hydroxyalkanoate) resin composition" is sometimes referred to as "resin composition," and "poly(3-hydroxyalkanoate) resin particles" is sometimes referred to as "resin particles."

[0031] In this specification, repeating units derived from monomer X are sometimes referred to as "unit X". Repeating units may also be called structural units.

[0032] One embodiment of the present invention provides poly(3-hydroxyalkanoate) foamed particles comprising 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 relative to 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.

[0033] Because of the above-described structure, these foamed particles have the advantage of achieving a high foaming ratio. This foamed molded body can be manufactured by molding these foamed particles using known methods.

[0034] (2-1. Poly(3-hydroxyalkanoate) resins (A))

[0035] One embodiment of the poly(3-hydroxyalkanoate) foamed particles of the present invention comprises a poly(3-hydroxyalkanoate) resin (A) as a component. In this specification, "poly(3-hydroxyalkanoate) resin (A)" is sometimes referred to as "poly(3-hydroxyalkanoate)" or "P3HA". This component will be described below.

[0036] P3HA is a polymer having a 3-hydroxyalkanoate unit as an essential structural unit (monomer unit). In this specification, "3-hydroxyalkanoate" is sometimes referred to as "3HA". Specifically, a polymer containing repeating units represented by the following general formula (1) is preferred as P3HA:

[0037] [-CHR-CH2-CO-O-]···(1).

[0038] In general formula (1), R represents C n H 2n+1 The alkyl group is represented by n, which is an integer from 1 to 15. Examples of R include straight-chain or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, and hexyl. Preferably, n is 1 to 10, more preferably 1 to 8.

[0039] As P3HA, microbially produced P3HA is particularly preferred. Microbially produced P3HA is poly[(R)-3HA] in which all 3HA units are (R)-3HA.

[0040] For P3HA, it is preferable to include 50 mol% or more of 3HA units (especially repeating units of general formula (1)) in 100 mol% of all repeating units of P3HA, more preferably 70 mol% or more, and even more preferably 80 mol% or more. In addition, as repeating units (monomer units), they may be only 3HA units, or they may include repeating units from monomers other than 3HA (e.g., 4-hydroxyalkanoate units, etc.).

[0041] 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, in one embodiment of the present invention, the P3HA preferably comprises a 3-hydroxybutyrate unit. In this specification, "3-hydroxybutyrate" is sometimes referred to as "3HB".

[0042] When P3HA contains two or more repeating units, the monomer that becomes the source of the repeating unit other than the most abundant repeating unit is called a comonomer. In this specification, "repeating unit derived from comonomer" is sometimes referred to as "comonomer unit".

[0043] As a comonomer, there are no particular limitations, but 3-hydroxyhexanoate (hereinafter sometimes referred to as 3HH) or 4-hydroxybutyrate (hereinafter sometimes referred to as 4HB) are preferred.

[0044] P3HA is preferably selected from one or more of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-copolymer-3-hydroxyvalerate), poly(3-hydroxybutyrate-copolymer-3-hydroxyvalerate-copolymer-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copolymer-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-copolymer-4-hydroxybutyrate). From the viewpoint of processability and the physical properties of the foamed molded article, poly(3-hydroxybutyrate-copolymer-3-hydroxyhexanoate) and poly(3-hydroxybutyrate-copolymer-4-hydroxybutyrate) are more preferred.

[0045] P3HA preferably has 3HB units as essential repeating units (structural units) and comonomer units. That is, P3HA is preferably a copolymer having 3HB units and comonomer units.

[0046] More specifically, P3HA is preferably 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 all repeating units in the copolymer is 99 / 1 (mol% / mol%) to 85 / 15 (mol% / mol%). From the viewpoint of further improving the foaming ratio, the ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of all 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%).

[0047] A P3HA having such a ratio of monomer units can be produced according to methods known to those skilled in the art, such as those described in International Publication WO2009 / 145164. The ratio of monomer units in a P3HA can be determined by methods known to those skilled in the art, such as those described in International Publication 2013 / 147139.

[0048] In one embodiment of the present invention, the method for manufacturing P3HA is not particularly limited, and can be a chemical synthesis-based method or a microbial-based method. Preferably, a microbial-based method is used. For the microbial-based P3HA manufacturing method, known methods can be applied, and preferably include a cultivation step, a purification step, and a drying step.

[0049] There are no particular limitations on the method for culturing microorganisms that produce P3HA through a culturing process; for example, the method described in International Publication No. WO2019 / 142717 can be used.

[0050] Examples of microorganisms that produce copolymers of 3HB with other hydroxyalkyl esters include: *Aeromonas caviae* as a producer of P3HB3HV and P3HB3HH, and *Alcaligenes eutrophus* as a producer of P3HB4HB. Particularly regarding P3HB3HH, *Alcaligenes eutrophus* strain AC32 (FERMBP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, p4821-4830 (1997)) is preferred. In the method for manufacturing P3HA, it is preferable to use microbial cells from which *Alcaligenes eutrophus* strain AC32 and other microorganisms are cultured under appropriate conditions, allowing P3HB3HH to accumulate within the cells. In addition to the above, regarding the copolymer-producing microorganisms, recombinant microorganisms incorporating various P3HA synthesis-related genes can also be used, depending on the desired P3HA production. Furthermore, regarding the culture conditions of the microorganisms, simply optimize all culture conditions, including the type of substrate, according to the desired P3HA production.

[0051] There are no particular limitations on the method for purifying P3HA obtained from microbial culture through a purification process; known physical, and / or chemical, and / or biological treatments can be applied. The purification method described, for example, in International Publication No. 2010 / 067543, is preferred.

[0052] There are no particular limitations on the method for drying P3HA obtained by microbial culture and purification through the drying process. Spray drying, fluidized bed drying, airflow drying, rotary drying, vibration drying, and belt drying can be used. The drying method described in International Publication No. 2018 / 070492 is preferred.

[0053] The drying process may include:

[0054] (a) The process of preparing an aqueous suspension A comprising 100 parts by weight of P3HA and 0.10 to 5.00 parts by weight of the nonionic water-soluble polymer described below, and

[0055] (b) The process of spray drying the aqueous suspension A prepared in step (a).

[0056] By including steps (a) and (b), P3HA containing 0.10 to 5.00 parts by weight of nonionic water-soluble polymer relative to 100 parts by weight of P3HA can be obtained.

[0057] In step (b) of the manufacturing method of P3HA of the present invention, the aqueous suspension A prepared in step (a) is spray-dried. Examples of spray-drying methods include supplying the aqueous suspension A in the form of fine droplets into a dryer, where it is brought into contact with hot air and dried. The method (atomizer) for supplying the aqueous suspension A in the form of fine droplets into the dryer is not particularly limited; known methods such as using a rotating disc or a nozzle can be cited. The manner in which the droplets come into contact with the hot air in the dryer is not particularly limited; parallel flow, counter-flow, or a combination thereof can be cited.

[0058] In step (b), the spray drying temperature should be such that most of the aqueous medium is removed from the droplets of the aqueous suspension A. This temperature should allow drying to reach the target moisture content and be appropriately set to minimize quality degradation (reduction in molecular weight, color tone) and melting. Furthermore, the airflow rate of the hot air inside the dryer can be appropriately set based on factors such as the size of the dryer.

[0059] One embodiment of the P3HA manufacturing method of the present invention may include a step of further drying the obtained P3HA after step (b). Alternatively, one embodiment of the P3HA manufacturing method of the present invention may include other steps (e.g., a step of adding various additives to an aqueous suspension A, etc.).

[0060] According to one embodiment of the P3HA manufacturing method of the present invention, P3HA in a dried state with high productivity and excellent thermal stability can be obtained. In particular, the P3HA manufacturing method of the present invention can reduce the cost (equipment cost, utility) of the drying process. Furthermore, the P3HA manufacturing method of the present invention can obtain P3HA in powder form (P3HA powder), thus enabling the efficient production of P3HA with excellent operability.

[0061] (2-2. Nonionic water-soluble polymers (B))

[0062] One embodiment of the poly(3-hydroxyalkanoate) foam particles of the present invention comprises a nonionic, water-soluble polymer (B) as a component. This component will be described below.

[0063] The nonionic water-soluble polymer (B) in this invention refers to a polymer that does not ionize when dissolved in water and becomes an ion.

[0064] The content of the nonionic water-soluble polymer (B) in this foamed particle is 0.10 parts by weight to 5.00 parts by weight, preferably 0.10 parts by weight to 4.00 parts by weight, more preferably 0.10 parts by weight to 3.00 parts by weight, even more preferably 0.10 parts by weight to 2.00 parts by weight, and even more preferably 0.10 parts by weight to 1.50 parts by weight, relative to 100 parts by weight of P3HA. It should be noted that within these ranges, the lower limit is not limited to 0.10, and can be 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, or 1.00. According to this configuration, the foaming ratio of poly(3-hydroxyalkanoate) foamed particles obtained by a single foaming process can be increased. Furthermore, this composition can reduce the content of nonionic water-soluble polymer (B) in poly(3-hydroxyalkanoate) foam particles, thereby preventing various effects of nonionic water-soluble polymer (B) on poly(3-hydroxyalkanoate) foam particles.

[0065] There is no particular limitation on the method for quantifying the content of nonionic water-soluble polymer (B) in foamed particles. The content of nonionic water-soluble polymer (B) in foamed particles can be analyzed using analytical instruments. The content of nonionic water-soluble polymer (B) in foamed particles can be determined by, for example, the following methods (1) to (4): (1) dissolving 20 mg of foamed particles in 0.8 ml of dichloroform; (2) further adding 20 mg of 1,1,2,2-tetrachloroethane as an internal standard to the dichloroform solution prepared in (1) above; (3) for (a) the dichloroform 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 dichloroform, and (b) the dichloroform solution prepared in (2) above, respectively, by... 1 (3) The NMR spectrum of the nonionic water-soluble polymer (B) contained in these dichloroform solutions was determined by H-NMR; (4) The amount of nonionic water-soluble polymer (B) in the foamed particles was quantified by referring to the determination results of the dichloroform solution containing the nonionic water-soluble polymer (B) (standard) and by calculating the signal intensity ratio of the nonionic water-soluble polymer (B) from the two obtained NMR spectra. This method is sometimes also called the separation method.

[0066] It should be noted that foamed particles obtained using crosslinking agents (some of which may have a crosslinked structure) sometimes do not completely dissolve in organic solvents. Foamed particles obtained using crosslinking agents are also referred to as "foamed particles X". For the content of nonionic water-soluble polymer (B) in foamed particles X, a foamed particle (hereinafter sometimes referred to as "foamed particle Y") obtained under the exact same manufacturing conditions as foamed particles X, except without the use of a crosslinking agent, is used as a sample. The content of nonionic water-soluble polymer (B) in foamed particle Y, determined by the above-described separation method, is considered as the content of nonionic water-soluble polymer (B) in foamed particles X.

[0067] The nonionic water-soluble polymer (B) has hydrophilic groups. Preferably, the nonionic water-soluble polymer (B) further has hydrophobic groups. Because it has hydrophilic groups, the nonionic water-soluble polymer (B) 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 leakage from resin particles and foam particles. This configuration is preferred from the viewpoint of increasing the foaming ratio and compatibility with P3HA.

[0068] The hydrophilic group is not limited and can include, for example, oxyvinyl, hydroxyl, carboxyl, and ether groups. From the viewpoint of easily achieving a balance between hydrophilicity and hydrophobicity, oxyvinyl and hydroxyl groups are preferred. The hydrophobic group is not limited and can include, for example, straight-chain alkyl, branched-chain alkyl, oxypropylene, fluoroalkyl, and alkylsiloxane groups. From the viewpoint of easily achieving a balance between hydrophilicity and hydrophobicity, straight-chain alkyl, branched-chain alkyl, and oxypropylene groups are preferred.

[0069] Nonionic water-soluble polymers (B) can be categorized as: 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.

[0070] The nonionic, water-soluble polymer (B) is preferably a biodegradable substance. Based on this configuration, the resulting P3HA-type foamed particles and P3HA-type foamed molded articles are biodegradable, and are therefore preferred. It should be noted that a biodegradable substance refers to a substance that is biodegradable according to OECD TG301.

[0071] The aforementioned biodegradable, nonionic, water-soluble polymer (B) is not limited and can include: natural polymers, semi-synthetic polymers, and synthetic polymers. Specifically, examples of natural polymers include: starch, guar gum, carrageenan, and xanthan gum. Examples of semi-synthetic polymers include: cellulose derivatives and starch derivatives. Examples of synthetic polymers include: polyepoxides, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, and poly(N-vinylacetamide). From the viewpoint of easily achieving a balance between hydrophilicity and hydrophobicity, starch derivatives, cellulose derivatives, polyvinyl alcohol, and polyepoxides are preferred.

[0072] The nonionic water-soluble polymer (B) is preferably selected from at least one of polyepoxides, polyvinyl alcohol, and cellulose derivatives. In this case, the content of the nonionic water-soluble polymer (B) relative to 100 parts by weight of P3HA is preferably 0.10 to 1.00 parts by weight. It should be noted that within this range, the lower limit is not limited to 0.10, and can be 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or 0.90. According to this configuration, the foaming ratio of poly(3-hydroxyalkanoate) foamed particles obtained by a single foaming process can be further improved. Furthermore, according to this configuration, the content of the nonionic water-soluble polymer (B) in the poly(3-hydroxyalkanoate) foamed particles can be further reduced, resulting in further prevention of various effects of the nonionic water-soluble polymer (B) on the poly(3-hydroxyalkanoate) foamed particles.

[0073] There are no particular limitations on the aforementioned polyepoxides; for example, commercially available products can be used. Commercially available products include, for example: Pluronic 10400 (manufactured by BASF), Pluronic 10500 (manufactured by BASF), Genapol PF80 (manufactured by Clariant), UNILUBE DP60-600B (manufactured by Nippon Yuko Co., Ltd.), UNILUBE DP60-950B (manufactured by Nippon Yuko Co., Ltd.), PLONON 208 (manufactured by Nippon Yuko Co., Ltd.), EPAN U105 (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), EPANU108 (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), EPAN 750 (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), Emulsogen EPN287 (manufactured by CLARIANT), Emulsogen LCN 407 (manufactured by CLARIANT), NOIGEN TDS (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), DKS NL (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), NO IGEN SD (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), etc.

[0074] There are no particular limitations on the polyvinyl alcohol used; for example, commercially available products can be used. Commercially available products include, for example: 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.), GOHSENOL GH-22 (manufactured by Mitsubishi Chemical Corporation), GOHSENOL GH-20R (manufactured by Mitsubishi Chemical Corporation), GOHSENOL GH-17R (manufactured by Mitsubishi Chemical Corporation), GOHSENOL GM-14R (manufactured by Mitsubishi Chemical Corporation), GOHSENOL GL-05 (manufactured by Mitsubishi Chemical Corporation), GOHSENOL GL-03 (manufactured by Mitsubishi Chemical Corporation), GOHSENOL... KH-20 (manufactured by Mitsubishi Chemical Co., Ltd.), GOHSENOL KH-17 (manufactured by Mitsubishi Chemical Co., Ltd.), GO HSENOL KL-05 (manufactured by Mitsubishi Chemical Co., Ltd.), GOHSENOL KL-03 (manufactured by Mitsubishi Chemical Co., Ltd.), GOHSENOL NK-05R (manufactured by Mitsubishi Chemical Co., Ltd.), etc.

[0075] There are no particular limitations on the aforementioned cellulose derivatives; for example, commercially available products can be used. Examples of commercially available products include: METOLOSE MCE-100 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), METOLOSE MCE-400 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), METOLOSE MCE-4000 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), METOLOSE SFE-4000 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), METOLOSE SFE-4000 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), METOLOSE SE-50 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), and METOLOSE NE-100 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.).

[0076] (2-3. Additives)

[0077] The foamed particles may further contain additives (other additives) other than poly(3-hydroxyalkanoate) resins (A) and nonionic water-soluble polymers (B). These other additives may include, depending on the purpose, crystallizing nucleating agents, bubble modifiers, lubricants, plasticizers, antistatic agents, flame retardants, conductive agents, heat insulation agents, crosslinking agents, antioxidants, UV absorbers, colorants, inorganic fillers, organic fillers, hydrolysis inhibitors, etc. Biodegradable additives are particularly preferred.

[0078] Examples of nucleating agents for crystallization include pentaerythritol, orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. One of these nucleating agents can be used alone, or two or more can be used in combination. Furthermore, when using two or more nucleating agents in combination, the mixing ratio can be adjusted appropriately according to the intended purpose.

[0079] The content of the nucleating agent in the foamed particles is not particularly limited. The content of the nucleating agent relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A) 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. The lower limit of the content of the nucleating agent in the poly(3-hydroxyalkanoate) resin (A) is not particularly limited; for example, it can be 0.1 parts by weight or more relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A).

[0080] Examples of bubble modifiers include talc, silica, calcium silicate, calcium carbonate, alumina, titanium dioxide, diatomaceous earth, clay, sodium bicarbonate, alumina, barium sulfate, alumina, and bentonite. Among these bubble modifiers, talc is preferred from the viewpoint of its particularly excellent dispersibility in P3HA. Furthermore, one of these bubble modifiers can be used alone, or two or more can be used in combination. When using two or more bubble modifiers in combination, the mixing ratio can be appropriately adjusted according to the desired effect.

[0081] The content of the bubble modifier in the 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, relative to 100 parts by weight of poly(3-hydroxyalkanoate) resin (A).

[0082] Examples of plasticizers include glyceryl esters such as diacetyl monolaurate, citrates such as tributyl acetyl citrate, sebacic acid esters such as dibutyl sebacate, adipate compounds, polyether esters, benzoate compounds, phthalate compounds, isosorbide compounds, polycaprolactone compounds, and diesters such as benzyl methyl diethylene glycol adipate. Among these, glyceryl esters, citrates, sebacic acid esters, and diesters are preferred for their superior plasticizing effect on P3HA. One of these plasticizers can be used alone, or two or more can be used in combination. Furthermore, when using two or more plasticizers in combination, the mixing ratio can be adjusted appropriately according to the intended purpose.

[0083] The content of plasticizer in the 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 relative to 100 parts by weight of poly(3-hydroxyalkanoate) resin (A).

[0084] These foamed particles may contain compounds having isocyanate groups (hereinafter sometimes referred to as isocyanate compounds). However, isocyanate compounds are sometimes toxic. In addition, when the foamed particles contain isocyanate compounds, the resulting foamed particles and foamed molded products may sometimes turn yellow.

[0085] Therefore, the content of isocyanate compounds in the foamed particles is preferably less than 3.0 parts by weight, more preferably less than 1.0 parts by weight, and even more preferably less than 0.1 parts by weight, relative to 100 parts by weight of poly(3-hydroxyalkanoate) resin (A). Most preferably, the foamed particles do not contain isocyanate compounds.

[0086] 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, as (a) aromatic isocyanate compounds, isocyanate compounds with toluene, diphenylmethane, naphthalene, bitoluidine, xylene, and / or triphenylmethane as their backbone can be listed. As (b) alicyclic isocyanate compounds, isocyanate compounds with isophorone and / or hydrogenated diphenylmethane as their backbone can be cited. As (c) aliphatic isocyanate compounds, isocyanate compounds with hexamethylene and / or lysine as their backbone can be cited, etc. Furthermore, mixtures obtained by combining two or more of these isocyanate compounds can also be used. When using isocyanate compounds, from the perspectives of versatility, processability, and weather resistance, isocyanate compounds with toluene and / or diphenylmethane as the backbone are preferred, and isocyanate compounds with diphenylmethane as the backbone (polyisocyanates) are particularly preferred.

[0087] Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearyl behenamide, N-stearyl erucamide, ethylene bis-stearamide, ethylene bis-oleamide, ethylene bis-erucamide, ethylene bis-laurateamide, ethylene bis-decanoamide, p-phenylene bis-stearamide, ethylenediamine, stearic acid, and sebacic acid condensates. Among these, behenamide and erucamide are preferred from the viewpoint of particularly excellent lubricating effect on P3HA. The amount of lubricant 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 relative to 100 parts by weight of P3HA. Furthermore, the lubricant may be not a single type, but two or more types can be mixed, and the mixing ratio can be adjusted appropriately according to the purpose.

[0088] Examples of antistatic agents include coconut oil fatty acid diethanolamide. The content of antistatic agents in these foamed particles is not specifically limited.

[0089] (2-4. Physical properties of poly(3-hydroxyalkanoate) foamed particles)

[0090] (apparent density)

[0091] The apparent density of the foamed 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. Based on this configuration, a poly(3-hydroxyalkanoate) foamed molded body achieving a balance between mechanical strength and lightweight can be obtained. It should be noted that the apparent density can be determined simply by following the measurement method described in the examples below.

[0092] (Expansion ratio)

[0093] The expansion ratio of the foamed particles is not limited, but is preferably 18 times or more, more preferably 19 times or more, further preferably 20 times or more, even 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 expansion ratio of the foamed particles is not limited, and can be, for example, 50 times, 40 times, 30 times, 25 times, or 23 times. Based on this configuration, a poly(3-hydroxyalkanoate) foamed molded article achieving a balance between mechanical strength and lightweight can be obtained. It should be noted that the expansion ratio can be determined simply by following the determination method described in the examples described later.

[0094] (Heat on the high-temperature side)

[0095] The high-temperature heat of this foamed particle 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. Based on this configuration, poly(3-hydroxyalkanoate) foamed particles with excellent in-mold foaming properties can be produced without the poly(3-hydroxyalkanoate) foamed particles obtained in the foaming process adhering to each other. It should be noted that the high-temperature heat can be measured simply by following the measurement method described in the examples below.

[0096] (Bubble diameter)

[0097] The pore diameter of the foamed particles is not limited, but is preferably 50 μm to 500 μm, more preferably 100 μm to 450 μm, even more preferably 150 μm to 400 μm, even more preferably 200 μm to 350 μm, even more preferably 220 μm to 300 μm, further preferably 240 μm to 280 μm, and particularly preferably 245 μm to 270 μm. Based on this configuration, poly(3-hydroxyalkanoate) foamed particles with excellent in-mold foaming properties can be produced. It should be noted that the pore diameter can be measured simply by following the measurement method described in the examples below.

[0098] (Gel fraction)

[0099] 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, and can be, for example, 90% by weight, 80% by weight, or 75% by weight. According to this configuration, it has the advantage of providing a widened process window for the foamed molded article during in-mold foaming. It should be noted that the gel fraction can be determined simply by following the determination method described in the examples below.

[0100] (Closed-pore ratio)

[0101] The closed-cell ratio of this foamed particle 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 this foamed particle is not limited, and can be, for example, 100%, 99%, 98%, or 97%. Based on this configuration, poly(3-hydroxyalkanoate) foamed particles with excellent in-mold foaming properties can be produced. It should be noted that the closed-cell ratio can be determined simply by following the measurement method described in the examples below.

[0102] [3. Method for manufacturing poly(3-hydroxyalkanoate) foamed particles]

[0103] There are no particular limitations on the method for manufacturing poly(3-hydroxyalkanoate) foamed particles, and known methods can be used (e.g., the method described in International Publication No. 2019 / 146555). In this specification, "method for manufacturing poly(3-hydroxyalkanoate) foamed particles" is sometimes referred to as "manufacturing method," and "method for manufacturing poly(3-hydroxyalkanoate) foamed particles according to an embodiment of the present invention" is sometimes referred to as "this manufacturing method."

[0104] As a specific embodiment of this manufacturing method, examples include a manufacturing method that sequentially includes a resin particle preparation step of adjusting the resin particles and a foaming step of foaming the resin particles, but it is not limited to such a manufacturing method.

[0105] (3-1. Resin particle preparation process)

[0106] This manufacturing method preferably includes a resin particle preparation step prior to the foaming step, wherein the resin particle preparation step prepares (a) resin particles comprising 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 composed of 100 parts by weight of P3HA and 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer. The resin particle preparation step can be considered as a step of molding the resin into a shape easily used for foaming. The method of resin particle preparation is not particularly limited as long as resin particles can be obtained.

[0107] The preferred steps in resin particle preparation include:

[0108] (a) A melt-blending process comprising 100 parts by weight of P3HA and 0.10 to 5.00 parts by weight of a nonionic water-soluble polymer resin composition; and

[0109] (b) A particle molding process that shapes the melt-blended resin composition into a shape that is easy to use for foaming.

[0110] As for the melt mixing process, there are no particular limitations as long as the melt-mixed resin composition can be obtained. Specific examples of the melt mixing process include methods such as (a1) and (a2) below:

[0111] (a1) A resin composition is prepared 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. The resin composition is then fed to a melt-blending device for melt-blending.

[0112] (a2) A method of preparing (completing) a resin composition in a melt-blending apparatus by feeding 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, into a melt-blending apparatus, and melt-blending the resin composition.

[0113] In method (a1) above, the order in which 100 parts by weight of P3HA, 0.10 to 5.00 parts by weight of the nonionic water-soluble polymer, and other additives added as needed are mixed or blended (dry blending) 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 the nonionic water-soluble polymer, and other additives added as needed are supplied to the melt-blending apparatus is not particularly limited.

[0114] In the method described above (a1), there is no particular limitation on the mixing device, and examples include: belt mixer, high-speed mixer, drum mixer, super mixer, etc.

[0115] In the methods described in (a1) and (a2) above, there are no particular limitations on the melt mixing apparatus, and examples include: extruders, kneaders, Banbury mixers, and rollers. From the perspective of superior productivity and convenience, an extruder is preferred as the melt mixing apparatus, and a twin-screw extruder is even more preferred.

[0116] In the method described in (a1) above, the amount of nonionic water-soluble polymer and other additives used for mixing or blending is the content of nonionic water-soluble polymer and other additives in the obtained resin particles. Furthermore, in the method described in (a2) above, the amount of nonionic water-soluble polymer and other additives supplied to the melt-blending apparatus is the content of nonionic water-soluble polymer and other additives in the obtained resin particles. Therefore, regarding the above-mentioned amount and supply amount of nonionic water-soluble polymer and other additives, the descriptions in the (nonionic water-soluble polymer) and (other additives) sections above are referenced. It should be noted that in the melt-blending process of one embodiment of the present invention, the P3HA used may already contain a nonionic water-soluble polymer. When the P3HA used already contains a nonionic water-soluble polymer, the nonionic water-soluble polymer may not be used in the melt-blending process. Furthermore, the sum of the content of nonionic polymers contained in P3HA and the amount of nonionic water-soluble polymers used in the melt mixing process is taken as the content of nonionic water-soluble polymers in the obtained resin particles. Additionally, it is not necessary to use all other additives used in this manufacturing method in the resin particle preparation process. In other words, it is possible to omit all or some of the other additives used in this manufacturing method (e.g., crosslinking agents and plasticizers) in the resin particle preparation process, i.e., they can be omitted from the resin particles and added to the dispersion in the dispersion process described later.

[0117] In the melt-blending process, the temperature at which the resin composition is melt-blended depends on the physical properties of P3HA (melting point, weight-average molecular weight, etc.) and the type of additives used, and therefore cannot be limited in a general way. Regarding the temperature at which the resin composition is melt-blended, for example, it is preferable to set the temperature of the melt-blended resin composition (hereinafter sometimes referred to as the composition temperature) ejected from the nozzle of the die head to be 150°C to 200°C, more preferably 160°C to 195°C, and even more preferably 170°C to 190°C. When the composition temperature is above 150°C, there is no risk of insufficient melt-blending of the resin composition. On the other hand, when the composition temperature is below 200°C, there is no risk of thermal decomposition of P3HA.

[0118] As for the particle forming process, there are no particular limitations as long as the melt-mixed resin composition can be formed into the desired shape. By using a melt-mixing apparatus equipped with a die and a cutting device, the melt-mixed resin composition can be easily formed into the desired shape during the particle forming process. Specifically, the melt-mixed resin composition is ejected from the nozzle of the die provided in the melt-mixing apparatus, and the resin composition is cut using the cutting device at the same time or after ejection, thereby forming the desired shape. The shape of the obtained resin particles is not particularly limited, but cylindrical, elliptical, spherical, cubic, or cuboid shapes are preferred from the perspective of ease of foaming.

[0119] In the particle molding process, the resin composition ejected from the nozzle of the die head can be cooled. When cooling the resin composition ejected from the nozzle of the die head, the resin composition can be cut using a cutting device during or after cooling.

[0120] In the particle molding process, when the resin composition ejected from the nozzle of the die head is cooled, the temperature exhibited by 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. According to this configuration, the crystallization of the resin composition after melt mixing is fast enough, thus having the advantage of good resin particle productivity.

[0121] 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. Based on this configuration, poly(3-hydroxyalkanoate) foamed particles with high expansion ratio and high closed-cell ratio can be obtained. It should be noted that the melt flow rate of the resin particles can be measured simply by following the measurement method described in the examples below.

[0122] (3-2. Foaming process)

[0123] As a foaming step in this manufacturing method, there is no particular limitation as long as it enables the resin particles to foam. In one embodiment of the invention, the foaming step may include a dispersion step of dispersing the resin particles in an aqueous dispersion medium. The specific method of the dispersion step is not particularly limited; for example, it may be a step of dispersing the resin particles, aqueous dispersion medium, crosslinking agent, foaming agent, dispersant, crosslinking aid, dispersing aid, and / or plasticizer in a container. Preferably, the foaming step includes the following steps after the dispersion step as additional steps besides the dispersion step:

[0124] (a) A heating-pressurization process in which the temperature inside the container is raised to a certain temperature and the pressure inside the container is increased to a certain pressure;

[0125] (b) A process for maintaining the temperature and pressure inside a container at a certain temperature and pressure; and

[0126] (c) A discharge process in which the dispersion in the container is released from one end of the container into a region (space) with a lower pressure than the foaming pressure (i.e., the pressure inside the container).

[0127] (Distributed processes)

[0128] The dispersion process can be considered, for example, as the process of preparing a dispersion in an aqueous dispersion medium containing resin particles, a crosslinking agent, a foaming agent, and dispersants, crosslinking aids, dispersing auxiliaries, and plasticizers as needed. It should be noted that in the dispersion, (a) the crosslinking agent and crosslinking aids are consumed through reaction with P3HA in the resin particles and may be absent, and (b) the foaming agent and plasticizer are impregnated in the resin particles and may not exist in a dispersed state.

[0129] There are no particular limitations on the container, but it is preferred to be a container that can withstand the foaming temperature and foaming pressure described later, for example, a pressure-resistant container is preferred.

[0130] As an aqueous dispersion medium, there are no particular limitations as long as it can uniformly disperse resin particles, crosslinking agents, foaming agents, etc. For example, tap water and / or industrial water can also be used as an aqueous dispersion medium. From the viewpoint of being able to stably produce 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, deionized water (water purified by ion exchange resin), etc., as an aqueous dispersion medium.

[0131] There is no particular limitation on the amount of aqueous dispersion medium used, but it is preferably 100 to 1000 parts by weight relative to 100 parts by weight of resin particles.

[0132] In this manufacturing method, a crosslinking agent is preferably used. By using a crosslinking agent, the P3HA in the obtained foamed particles becomes P3HA with a crosslinked structure. Since the crosslinking reaction of P3HA in the resin particles also occurs during the foaming process, the foaming process can also be called the crosslinking process.

[0133] As a crosslinking agent, any agent capable of crosslinking P3HA is acceptable and is not particularly limited. Organic peroxides are preferred as crosslinking agents. In other words, poly(3-hydroxyalkanoate) foamed particles are preferably crosslinked using organic peroxides. Organic peroxides (a) can be used in the resin particle preparation process, (b) in the dispersion process, and (c) in both the resin particle preparation and dispersion processes. More specifically, to allow the organic peroxide to react with P3HA, (a) the organic peroxide and P3HA can be melt-blended in the resin particle preparation process, (b) the resin particles and organic peroxide can be dispersed in an aqueous dispersion medium in the dispersion process, and (c) the organic peroxide and P3HA can be melt-blended, and the resin particles and organic peroxide can be further dispersed in an aqueous dispersion medium. In the dispersion process, by dispersing the resin particles produced in the resin particle preparation process and the organic peroxide in an aqueous dispersion medium, the organic peroxide can impregnate the resin particles and react. For this reason, in this method of manufacturing foamed particles, organic peroxides are preferred as crosslinking agents. It should be noted that when organic peroxides are used as crosslinking agents, crosslinking structures are formed by direct bonding of P3HA molecular chains to each other (without the structure derived from the crosslinking agent).

[0134] Although it depends on the type of P3HA used, the organic peroxide used as a crosslinking agent is preferably an organic peroxide with a 1-hour half-life temperature of 90°C to 160°C, and more preferably an organic peroxide with a 1-hour half-life temperature of 115°C to 125°C. Examples of such organic peroxides include: benzoyl peroxide (1-hour half-life temperature: 92℃), 2-ethylhexyl tert-butyl peroxide (1-hour half-life temperature: 121℃), isopropyl tert-butyl peroxide (1-hour half-life temperature: 118℃), 2-ethylhexyl tert-amyl peroxide (1-hour half-life temperature: 117℃), isopropyl tert-amyl peroxide (1-hour half-life temperature: 115℃), tert-butyl peroxide isobutyrate (1-hour half-life temperature: 93℃), tert-butyl peroxide 2-ethylhexanoate (1-hour half-life temperature: 95℃), tert-butyl peroxide isononanoate (1-hour half-life temperature: 123℃), and tert-butyl peracetate (1-hour half-life temperature: 95℃). The following organic peroxides have a half-life temperature of 1 hour: 123℃, tert-butyl peroxide (1-hour half-life temperature: 125℃), tert-amyl peroxide isobutyrate (1-hour half-life temperature: 93℃), tert-amyl peroxide-2-ethylhexylhexanoate (1-hour half-life temperature: 92℃), tert-amyl peroxide-isononanoate (1-hour half-life temperature: 114℃), tert-amyl peracetate (1-hour half-life temperature: 120℃), tert-amyl peroxide benzoate (1-hour half-life temperature: 122℃), dicumyl peroxide (1-hour half-life temperature: 137℃), 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane (1-hour half-life temperature: 140℃), and di-tert-butyl peroxide (1-hour half-life temperature: 149℃). When using organic peroxides with a half-life temperature of 90℃ or higher, there is a tendency to produce foaming particles with the desired gel fraction. On the other hand, when using organic peroxides with a half-life of less than 160°C, there is an advantage that there is no risk of unreacted crosslinking agent residue in the final product.

[0135] The amount of crosslinking agent 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 relative to 100 parts by weight of resin particles. When the amount of crosslinking agent is 0.1 parts by weight or more relative to 100 parts by weight of resin particles, (a) the obtained foamed particles can be fully crosslinked, and (b) the closed-cell ratio of the obtained foamed particles is increased, resulting in a good foamed molded body. On the other hand, when the amount of crosslinking agent is 5.0 parts by weight or less relative to 100 parts by weight of resin particles, an effect corresponding to the amount of crosslinking agent added can be obtained, thus avoiding the risk of economic waste. The amount of crosslinking agent is positively correlated with the gel fraction of the foamed particles and has a great influence on the value of the gel fraction of the foamed particles. Therefore, it is preferable to strictly set the amount of crosslinking agent considering the gel fraction of the obtained foamed particles. In the dispersion process of one embodiment of the present invention, the resin particles used sometimes already contain a crosslinking agent. In this case, 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 preferably satisfies the above-mentioned range.

[0136] Examples of foaming 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 chloromethane, dichloromethane, and dichlorodifluoroethane; and water. At least one of the above-mentioned inorganic gases, saturated hydrocarbons with 3 to 5 carbon atoms, ethers, halogenated hydrocarbons, and water can be used as a foaming agent. From the perspective of environmental impact and foaming capacity, nitrogen or carbon dioxide is preferred as a foaming agent. One of these foaming agents can be used alone, or two or more can be used in combination. Furthermore, when using two or more foaming agents in combination, the mixing ratio can be adjusted appropriately according to the purpose.

[0137] The amount of foaming agent 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 relative to 100 parts by weight of resin particles. When the amount of foaming agent is 2 parts or more relative to 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 is 10,000 parts or less relative to 100 parts by weight of resin particles, an effect commensurate with the amount of foaming agent can be obtained, thus avoiding economic waste.

[0138] In this manufacturing method, a dispersant is preferably used. By using a dispersant, the adhesion (sometimes called agglomeration) of resin particles to each other can be suppressed, providing the advantage of stably producing foamed particles. Examples of dispersants include: tricalcium phosphate, basic magnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, clay, alumina, titanium dioxide, aluminum hydroxide, and other inorganic substances. One of these dispersants can be used alone, or two or more can be used in combination. Furthermore, when using two or more dispersants in combination, the mixing ratio can be appropriately adjusted according to the desired effect.

[0139] The amount of dispersant is not particularly limited, but is preferably 0.1 to 3.0 parts by weight, more preferably 0.5 to 1.5 parts by weight, relative to 100 parts by weight of resin particles.

[0140] In this manufacturing method, a crosslinking aid can be used to improve the crosslinking efficiency of P3HA. Examples of crosslinking aids include compounds having at least one unsaturated bond within the molecule. Allyl esters, acrylates, methacrylates, and divinyl compounds are particularly preferred as crosslinking aids. One of these crosslinking aids can be used alone, or two or more can be used in combination. Furthermore, when two or more crosslinking aids are used in combination, the mixing ratio can be appropriately adjusted according to the intended purpose.

[0141] The amount of crosslinking aid is not particularly limited, but is 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, relative to 100 parts by weight of resin particles. When the amount of crosslinking aid is 0.01 parts by weight or more relative to 100 parts by weight of resin particles, it can exert a sufficient effect as a crosslinking aid.

[0142] In the dispersion process, when the crosslinking agent and crosslinking aids added as needed are impregnated in the resin particles and allowed to react, in order to improve the crosslinking efficiency of P3HA, it is preferable to reduce the oxygen concentration in the container and the dissolved oxygen content in the dispersion. Methods for reducing the oxygen concentration in the container and the dissolved oxygen content in the dispersion include: replacing the gas in the container and the dissolved gas in the dispersion with inorganic gases such as carbon dioxide and nitrogen, and evacuating the gas in the container.

[0143] In this manufacturing method, a dispersing agent can be used to improve the inhibition of mutual adhesion between resin particles. Examples of dispersing agents include anionic surfactants such as sodium alkane sulfonate, sodium alkylbenzene sulfonate, and sodium α-olefin sulfonate. One of these dispersing agents can be used alone, or two or more can be used in combination. Furthermore, when using two or more dispersing agents in combination, the mixing ratio can be appropriately adjusted according to the intended purpose.

[0144] The amount of dispersant is not particularly limited, but is preferably 0.001 to 0.500 parts by weight, more preferably 0.010 to 0.200 parts by weight, relative to 100 parts by weight of resin particles. To further improve the effect of inhibiting the mutual adhesion of resin particles, it is preferable to use the above-mentioned dispersant and the dispersant aid in combination.

[0145] In this manufacturing method, plasticizers can be used. By using plasticizers, foamed particles with high expansion ratio and softness can be obtained.

[0146] As a plasticizer used in this manufacturing method, or preferably used plasticizer, the plasticizer described in the above-mentioned item [2. Poly(3-hydroxyalkanoate) foam particles] (additives) can be cited.

[0147] The amount of plasticizer used is not particularly limited, but is preferably greater than 0 parts by weight and less than 20 parts by weight relative to 100 parts by weight of resin particles, more preferably 1 to 15 parts by weight, and even more preferably 1 to 10 parts by weight. In the dispersion step of one embodiment of the present invention, the resin particles used may already contain plasticizer. When the resin particles used already contain plasticizer, the sum of the plasticizer content in the resin particles and the amount of plasticizer used in the dispersion step preferably satisfies the above-described range.

[0148] (Heating-pressurization process and holding process)

[0149] The heating-pressurization process is preferably performed after the dispersion process, and the holding process is preferably performed after the heating-pressurization process. In this specification, sometimes the certain temperature (a) in the heating-pressurization process and the holding process is referred to as the foaming temperature, and sometimes the certain pressure (b) is referred to as the foaming pressure.

[0150] The foaming temperature varies depending on the type of P3HA, the type of foaming agent, and the desired expansion ratio of the foamed particles, and therefore cannot be limited in general. A preferred foaming temperature is, for example, 100.0℃ to 140.0℃, more preferably 110.0℃ to 135.0℃, and even more preferably 115.0℃ to 133.0℃. At foaming temperatures of 100℃ and above, there is a tendency to obtain foamed particles with a high expansion ratio. On the other hand, at foaming temperatures below 140℃, there is no risk of resin particle hydrolysis occurring within the container.

[0151] In the heating-pressurization 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, more preferably 1.5°C / min to 3.0°C / min. When 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 of insufficient impregnation of the foaming agent into the resin particles or inadequate reaction between the crosslinking agent and P3HA during heating.

[0152] 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. When the foaming pressure is 1.0 MPa (gauge pressure) or higher, foamed particles with a high foaming ratio can be obtained.

[0153] (Release process)

[0154] The release process is preferably performed after the heating-pressurization process or after the holding process. Through the release process, the resin particles can be foamed, resulting in foamed particles.

[0155] 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 called "the gas atmosphere with a pressure lower than the foaming pressure." The region with a pressure lower than the foaming pressure can be any pressure lower than the foaming pressure; there are no special limitations. For example, it can be a region at atmospheric pressure.

[0156] During the discharge process, when the dispersion is discharged to a region with a pressure lower than the foaming pressure, it can be discharged through an open nozzle orifice with a diameter of 1 mm to 5 mm to adjust the flow rate of the dispersion and reduce the deviation in the foaming ratio of the obtained foamed particles. Alternatively, when using resin particles with a higher melting point, the aforementioned low-pressure region (space) can be filled with saturated water vapor to improve foaming properties.

[0157] In the discharge process, a cleaning agent can be used after the resin particles have foamed. Examples of cleaning agents include warm water and sodium hexametaphosphate. By using a cleaning agent, the dispersant adhering to the surface of the foamed particles can be adjusted.

[0158] During the foaming process, an antistatic agent can be used after the resin particles have foamed. Examples of antistatic agents include coconut oil fatty acid diethanolamide. By using an antistatic agent, static electricity in the foamed particles can be suppressed, improving operability.

[0159] The method described above is the most preferred method for manufacturing the foamed particles, but it is not limited thereto. For example, the manufacturing methods described below (r1) to (r3) can also produce the foamed particles:

[0160] (r1) The resin particles obtained through the above (resin particle conditioning process) are placed in a pressure vessel, and a foaming agent is injected into the pressure vessel without using an aqueous dispersion medium. By heating and maintaining the pressure vessel as needed, resin particles containing a foaming agent are obtained. Next, after depressurizing the pressure vessel and restoring it to atmospheric pressure, the resin particles containing the foaming agent are heated in the pressure vessel or transferred to another pressure vessel by means of steam or other heating methods to foam the resin particles impregnated with the foaming agent, thereby obtaining foamed particles;

[0161] (r2) In the above-mentioned (melt mixing process) of the (resin particle adjustment process), when the resin composition is melt-mixed, a crosslinking agent and a foaming agent are pressed into a melt mixing apparatus to prepare a resin composition containing a crosslinking agent and a foaming agent. Next, the resin composition is ejected from a nozzle of a die provided in the melt mixing apparatus, cooled simultaneously, and cut using a cutting device to obtain resin particles containing a foaming agent. The resin particles are transferred to a pressure vessel and heated by a heating method such as steam to foam the resin particles and obtain foamed particles.

[0162] (r3) In the above-mentioned (melt mixing process) of the (resin particle adjustment process), when the resin composition is melt-mixed, a crosslinking agent and a foaming agent are pressed into a melt mixing apparatus to prepare a resin composition containing a crosslinking agent and a foaming agent. Then, the resin composition is ejected from a nozzle of a die provided in the melt mixing apparatus, and foaming is achieved during ejection. The mixture is then cut using a cutting device to obtain foamed particles.

[0163] In the above (r1), the pressure at which the foaming agent is pressed into the pressure-resistant container is preferably 0.01 MPa (gauge pressure) to 10.00 MPa (gauge pressure), more preferably 0.03 MPa (gauge pressure) to 5.00 MPa (gauge pressure).

[0164] In (r1) and (r2) above, the temperature inside the pressure vessel when heating the resin particles containing the foaming agent using water vapor or the like is preferably 100°C to 150°C, more preferably 105°C to 145°C.

[0165] In (r2) and (r3) above, the pressure at which the crosslinking agent and the foaming agent are pressed into the melt mixing device is preferably 3 MPa (gauge pressure) to 30 MPa (gauge pressure), and more preferably 5 MPa (gauge pressure) to 15 MPa (gauge pressure).

[0166] (Secondary foaming process)

[0167] In the above-described method for manufacturing foamed particles, sometimes the desired apparent density of foamed particles cannot be obtained through the foaming process alone. In such cases, the method for manufacturing foamed particles may further include a secondary foaming process that further expands the foamed particles obtained in the foaming process. As a secondary foaming process, it is not particularly limited as long as further expansion of the foamed particles obtained in the foaming process yields foamed particles with an apparent density lower than that obtained in the foaming process. Examples of secondary foaming processes include: (s1) supplying the foamed particles obtained in the foaming process into a container; (s2) supplying an inorganic gas such as air or carbon dioxide into the container to increase the pressure inside the container; (s3) impregnating the foamed particles with the inorganic gas as described in (s2), making the pressure inside the foamed particles higher than atmospheric pressure; (s4) then heating the foamed particles with steam or the like to further expand them, obtaining foamed particles with the desired apparent density. Foamed particles obtained through a secondary foaming process are sometimes referred to as secondary foamed particles. In addition, when a secondary foaming process is performed, the above-mentioned foaming process is sometimes referred to as a primary foaming process, and the foamed particles obtained through the primary foaming process are called primary foamed particles.

[0168] The internal pressure of the foamed particles in the secondary foaming process is preferably 0.15MPa to 0.60MPa (absolute pressure), and more preferably 0.20MPa to 0.50MPa (absolute pressure).

[0169] In the secondary foaming process (in s2 and s3 above), the container temperature at which the inorganic gas is impregnated with the foaming particles is preferably 10°C to 90°C, more preferably 20°C to 90°C, more preferably 30°C to 90°C, and even more preferably 40°C to 90°C.

[0170] In the secondary foaming process (s4 above), the pressure of water vapor or the like used to heat the foaming particles (hereinafter sometimes referred to as "secondary foaming pressure") varies depending on the characteristics of the foaming particles used and the desired apparent density, and cannot be limited in general. The secondary 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).

[0171] The gel fraction of the secondary foamed particles is preferably the same as the gel fraction of the foamed particles. That is, the description of the (gel fraction) item above can be appropriately cited as the gel fraction of the secondary foamed particles.

[0172] [4. Poly(3-hydroxyalkanoate) foamed molding compounds]

[0173] One embodiment of the present invention provides a poly(3-hydroxyalkanoate) foamed molded body formed from poly(3-hydroxyalkanoate) foamed particles of one embodiment of the present invention. The poly(3-hydroxyalkanoate) foamed molded body of one embodiment of the present invention can be obtained by molding the poly(3-hydroxyalkanoate) foamed particles of one embodiment of the present invention. The poly(3-hydroxyalkanoate) foamed molded body of one embodiment of the present invention may contain the poly(3-hydroxyalkanoate) foamed particles of one embodiment of the present invention. According to this configuration, a poly(3-hydroxyalkanoate) foamed molded body with a high expansion ratio can be provided.

[0174] The manufacturing method of this foamed molded body (i.e., the molding method of the foamed particles) is not particularly limited, and well-known methods can be used. Examples of in-mold foaming molding methods (A) to (D) below can be cited, but there are no particular limitations:

[0175] (A) Pressurize the foamed particles in a container with inorganic gas so that the inorganic gas is impregnated in the foamed particles. After applying a given internal pressure to the foamed particles, fill the foamed particles into a mold and heat them with steam.

[0176] (B) After filling the foamed particles into the mold, they are compressed to reduce the volume of the mold by 10% to 75%, and then heated by steam.

[0177] (C) The foamed particles are compressed by gas pressure and filled into a mold, and the restoring force of the foamed particles is used to heat them with steam.

[0178] (D) Without any special pretreatment, the foamed particles are filled into the mold and heated using steam.

[0179] In the manufacture of this foamed molded article, the pressure of the water vapor used to heat the foamed particles (hereinafter sometimes referred to as the molding pressure) varies depending on the characteristics of the foamed particles used and cannot be limited in a general sense. 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).

[0180] In this method for manufacturing a foamed molded article, at least one inorganic gas selected from 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.

[0181] In this method for manufacturing a foamed molded body, the temperature inside the container where the inorganic gas from method (A) is impregnated with the foamed particles is preferably 10°C to 90°C, more preferably 20°C to 90°C, more preferably 30°C to 90°C, and even more preferably 40°C to 90°C.

[0182] In the manufacturing method of this foamed molded article, the internal pressure of the foamed particles in method (A) 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 by following the measurement method described in the examples below.

[0183] The expansion ratio of this foamed molded article is not limited, but is preferably 25 times or more, more preferably 27 times or more, more preferably 30 times or more, and even more preferably 35 times or more. The upper limit of the expansion ratio of this foamed molded article is not limited, and can be, for example, 50 times, 40 times, or 35 times. Based on this configuration, a poly(3-hydroxyalkanoate) foamed molded article achieving a balance between mechanical strength and lightweight can be provided.

[0184] One embodiment of the present invention may have the following configuration.

[0185] [1] A poly(3-hydroxyalkanoate) foamed particle 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 relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A), and the closed-cell rate of the poly(3-hydroxyalkanoate) foamed particle is 90% or more.

[0186] [2] The poly(3-hydroxyalkanoate) foam particles according to [1], wherein the above-mentioned nonionic water-soluble polymer (B) has hydrophobic groups.

[0187] [3] The poly(3-hydroxyalkanoate) foam particles according to [1] or [2], wherein the above-mentioned nonionic water-soluble polymer (B) is a biodegradable water-soluble polymer.

[0188] [4] Poly(3-hydroxyalkanoate) foamed particles according to any one of [1] to [3], wherein the above-mentioned nonionic water-soluble polymer (B) is selected from at least one of polyepoxide, polyvinyl alcohol and cellulose derivatives.

[0189] [5] According to the poly(3-hydroxyalkanoate) foamed particles of [4], the content of the nonionic water-soluble polymer (B) is 0.10 parts by weight to 1.00 parts by weight relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A).

[0190] [6] Poly(3-hydroxyalkanoate) foamed particles according to any one of [1] to [5], wherein the poly(3-hydroxyalkanoate) resin (A) is selected from at least one of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-copolymer-3-hydroxyvalerate), poly(3-hydroxybutyrate-copolymer-3-hydroxyvalerate-copolymer-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copolymer-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-copolymer-4-hydroxybutyrate).

[0191] [7] Poly(3-hydroxyalkanoate) foamed particles according to any one of [1] to [6], wherein the poly(3-hydroxyalkanoate) resin (A) is a copolymer having 3-hydroxybutyrate units and comonomer units.

[0192] The ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of all repeating units in the above copolymer is 99 / 1 (mol% / mol%) to 85 / 15 (mol% / mol%).

[0193] [8] The poly(3-hydroxyalkanoate) foamed particles according to any one of [1] to [7] have an apparent density of 20 g / L to 67 g / L.

[0194] [9] The poly(3-hydroxyalkanoate) foamed particles according to any one of [1] to [8] have a high-temperature heat of 0.1 J / g to 20.0 J / g.

[0195]

[10] The poly(3-hydroxyalkanoate) foam particles according to any one of [1] to [9] have a pore diameter of 50 μm to 500 μm.

[0196]

[11] The poly(3-hydroxyalkanoate) foamed particles according to any one of [1] to

[10] have a gel fraction of 30% by weight or more.

[0197]

[12] A poly(3-hydroxyalkanoate) foamed molded body formed from poly(3-hydroxyalkanoate) foamed particles as described in any one of [1] to

[11] .

[0198]

[13] The poly(3-hydroxyalkanoate) foamed molded body according to

[12] has a foaming ratio of 25 times or more.

[0199] Example

[0200] The present invention will be specifically described below through embodiments, but the present invention is not limited to these embodiments.

[0201] 〔Material〕

[0202] The substances used in the examples and comparative examples are shown below.

[0203] (Water-soluble polymer)

[0204] Water-soluble polymer-1: Nonionic polyvinyl alcohol (Kuraray PVA-205 manufactured by Kuraray Corporation, degree of saponification 87.0 mol%~89.0 mol%, degree of polymerization 500, hydrophobic group is acetic acid group)

[0205] Water-soluble polymer-2: Nonionic polyepoxide (PLONON#208 manufactured by Nippon Oil Co., Ltd., 80% by weight of ethylene oxide, average molecular weight 10,000, hydrophobic group is oxypropylene group)

[0206] Water-soluble polymer-3: Nonionic cellulose derivative (METOLOSEMCE-4000 manufactured by Shin-Etsu Chemical Co., Ltd., 25.0%–33.0% methoxy group, hydrophobic group is methoxy group)

[0207] Water-soluble polymer-4: Nonionic polyepoxide (Clarian's Emulsogen EPN 287, ethylene oxide 28 mol%, molecular weight 1404, hydrophobic group is oxypropylene group)

[0208] Water-soluble polymer-5: Ionic polyepoxide (Clarian company's Emulsogen EP A 073, ethylene oxide 7 mol%, molecular weight 577, hydrophobic group is oxypropylene group)

[0209] All five water-soluble polymers mentioned above have both hydrophilic and hydrophobic groups and are biodegradable.

[0210] (Bubble control agent)

[0211] Bubble modifier: Talc (Talcum Powder PK-S manufactured by Hayashi Kasei Corporation).

[0212] (Crystallization nucleating agent)

[0213] Crystallization nucleating agent: Pentaerythritol (Neulizer P manufactured by Mitsubishi Chemical Corporation).

[0214] (Lubricant)

[0215] Lubricant-1: Behenamide (Crodamide BR manufactured by CRODA)

[0216] Lubricant-2: Erucamide (Crodamide ER manufactured by CRODA).

[0217] (Dispersant)

[0218] Dispersant: Tricalcium phosphate (manufactured by Taihei Chemical Industry Co., Ltd.)

[0219] (Dispersing agent)

[0220] Dispersing agent: Sodium alkyl sulfonate (LATEMUL PS, manufactured by Kao Corporation).

[0221] (Cross-linking agent)

[0222] Crosslinking agent: tert-butyl peroxide (97%) (manufactured by Nippon Oil Co., Ltd.).

[0223] (Cleaning agent)

[0224] Cleaning agent: Sodium hexametaphosphate (manufactured by WUXI LOTUS ESSENCE).

[0225] (Antistatic agent)

[0226] Antistatic agent: coconut oil fatty acid diethanolamide (PROFAN 128EXTRA manufactured by Sanyo Chemical Co., Ltd.)

[0227] [Measurement Method]

[0228] The evaluation methods implemented in the embodiments and comparative examples will be described below.

[0229] (Determination of the melting point of poly(3-hydroxyalkanoate) resin particles)

[0230] Approximately 5 mg of poly(3-hydroxyalkanoate) resin particles were measured using a differential scanning calorimeter (DSC7020, Hitachi High-Tech). The poly(3-hydroxyalkanoate) resin particles were then heated from 10°C to 190°C at a rate of 10°C / min. The temperature of the highest melting peak in the resulting DSC curve was taken as the melting point.

[0231] (Determination of MFR of poly(3-hydroxyalkanoate) resin particles)

[0232] Using a melt flow index tester (manufactured by Yasuda Seiki Co., Ltd.), the test was conducted according to JIS K7210 under the following conditions: a load of 5 kg and a test temperature of +5°C to +10°C from the melt end temperature obtained from the DSC curve obtained above (determination of the melting point of poly(3-hydroxyalkanoate) resin particles).

[0233] (Determination of the specific gravity of poly(3-hydroxyalkanoate) resin particles)

[0234] The specific gravity (g / cm³) of poly(3-hydroxyalkanoate) resin particles was determined using an automatic hydrometer (DSG-1, manufactured by Toyo Seiki Co., Ltd.) according to JIS K7112 via the water displacement method. 3 ).

[0235] (Determination of apparent density of poly(3-hydroxyalkanoate) foamed particles)

[0236] The method for determining the apparent density of poly(3-hydroxyalkanoate) foamed particles is as described in (1) to (3) below: (1) Prepare a graduated cylinder containing ethanol, and precipitate poly(3-hydroxyalkanoate) foamed particles weighing Wd (g) in the ethanol; (2) Set the volume of the poly(3-hydroxyalkanoate) foamed particles read from the rise in ethanol level (immersion method) as Vd (cm³). 3 (3) The apparent density ρd of poly(3-hydroxyalkanoate) foamed particles is calculated by the following formula;

[0237] Apparent density ρd (g / cm³) 3 = Wd / Vd.

[0238] (Determination of the expansion ratio of poly(3-hydroxyalkanoate) foamed particles)

[0239] The expansion ratio of poly(3-hydroxyalkanoate) foam particles is calculated based on the following formula:

[0240] Foaming ratio (times) = Specific gravity of poly(3-hydroxyalkanoate) resin particles / Apparent density ρd of poly(3-hydroxyalkanoate) foam particles.

[0241] (Determination of gel fraction in poly(3-hydroxyalkanoate) foamed particles)

[0242] The method for determining the gel fraction of poly(3-hydroxyalkanoate) foamed particles is as described in (a1) to (a5) below: (a1) Add 0.5 g of poly(3-hydroxyalkanoate) foamed particles and 50 ml of chloroform to a 100 ml flask; (a2) Heat the mixture in the flask under atmospheric pressure and at 62 °C for 8 hours under reflux; (a3) ​​Filter the obtained heat-treated material using a vacuum filter equipped with a 100-mesh metal mesh; (a4) Dry the filtered material on the metal mesh in an oven at 80 °C under vacuum for 8 hours, and determine the weight Wg (g) of the dried material; (a5) Calculate the gel fraction using the following formula:

[0243] Gel fraction (wt%) = Wg / 0.5 × 100.

[0244] (Determination of high-temperature heat of poly(3-hydroxyalkanoate) foamed particles)

[0245] The heat on the high-temperature side of poly(3-hydroxyalkanoate) foamed particles was measured using a differential scanning calorimeter (DSC7020 manufactured by Hitachi High-Tech). The specific operating steps are as follows (1) to (5): (1) Measure about 5 mg of poly(3-hydroxyalkanoate) foamed particles; (2) Increase the temperature of the poly(3-hydroxyalkanoate) foamed particles from 10°C to 190°C at a heating rate of 10°C / min to melt the poly(3-hydroxyalkanoate) foamed particles; (3) In the DSC curve obtained in the above process (2), connect the point representing the temperature before the start of melting and the point representing the temperature after the end of melting with a straight line to form a baseline; (4) Plot a straight line along the direction perpendicular to the X-axis through the melting peak on the high-temperature side or the maximum point between the melting peak at the highest temperature and the adjacent melting peak; (5) The heat calculated from the area on the high-temperature side enclosed by the straight line through the baseline and the maximum point and the DSC curve is taken as the heat on the high-temperature side.

[0246] (Determination of the average cell diameter of poly(3-hydroxyalkanoate) foam particles)

[0247] The method for determining the average pore diameter of the foamed particles is as follows (1) to (5): (1) Using a razor (FEATHER Hi-STAINLESS double-edged blade), the foamed particle is cut through the center; (2) The cut surface of the foamed particle is observed at 50x magnification using an optical microscope (Keyence VHX-100); (3) In the observed image, a straight line is drawn through the center or approximately the center of the cut surface of the foamed particle; (4) (4-1) The number of bubbles n present on the straight line is determined; (4-2) The length of the line segment cut from the straight line at the intersection of the straight line and the surface of the foamed particle is determined and set as the foamed particle diameter L; (5) The average pore diameter of the foamed particles is calculated using the following formula:

[0248] Average bubble diameter (μm) = L / n.

[0249] (Determination of closed-cell ratio of poly(3-hydroxyalkanoate) foam particles)

[0250] The closed-cell ratio of poly(3-hydroxyalkanoate) foam particles was determined according to the method described in Procedure C of ASTM D2856-87. First, the volume Vc (cm³) was measured using an air comparative hydrometer [Tokyo Science, Model 1000]. 3 Next, the entire volume of the foamed particles, after Vc measurement, was precipitated in a graduated cylinder containing ethanol. The apparent volume Va (cm³) of the foamed particles was calculated based on the rise in water level in the graduated cylinder (immersion method). 3 The closed-cell ratio of the foamed particles was calculated using 100 - (Va - Vc) × 100 / Va (%).

[0251] (Determination of internal pressure of poly(3-hydroxyalkanoate) foamed particles)

[0252] The method for determining the internal pressure of poly(3-hydroxyalkanoate) foamed particles is as follows (1) to (5): (1) The weight W1 (g) of the poly(3-hydroxyalkanoate) foamed particles after the pressurization process is measured; (2) The foamed particles are heated at 150°C for 30 minutes to dissipate the inorganic gas inside the foamed particles; (3) The weight W2 (g) of the poly(3-hydroxyalkanoate) foamed particles after the inorganic gas has been dissipated is measured again; (4) The weight (ΔW) of the inorganic gas is calculated based on the weight difference (W1-W2) of the poly(3-hydroxyalkanoate) foamed particles before and after the inorganic gas is dissipated; (5) The internal pressure P (MPa) of the poly(3-hydroxyalkanoate) foamed particles is calculated using the ideal gas equation of state (specifically the following formula):

[0253] Internal pressure P (MPa) = (1 + ΔW / M × 0.082 × (273 + T) × (ρd × 1000 / W2)) / 9.87

[0254] In the above formula, M is the average molar molecular weight, T is the temperature (room temperature) (°C) at which the weight of the poly(3-hydroxyalkanoate) foam particles after the pressurization process is measured, and Pd is the apparent density (g / cm³) of the poly(3-hydroxyalkanoate) foam particles (foam particles with weight W1) after the pressurization process. 3 ).

[0255] (Determination of the expansion ratio of poly(3-hydroxyalkanoate) foamed molded articles)

[0256] The method for determining the expansion ratio of poly(3-hydroxyalkanoate) foamed molded bodies is as described in (1) to (4) below: (1) The longitudinal (mm), transverse (mm), and thickness (mm) lengths of the poly(3-hydroxyalkanoate) foamed molded body are measured using a digital caliper (MITUTOYO). The volume V (cm³) of the poly(3-hydroxyalkanoate) foamed molded body is then calculated. 3 (2) Determine the weight W (g) of the foamed molded body; (3) Calculate the density ρ of the poly(3-hydroxyalkanoate) foamed molded body based on the following formula: density ρ (g / cm³) 3 )=W / V;(4) Calculate the foaming ratio of the foamed molded body based on the following formula: foaming ratio (times)=specific gravity of resin particles / density ρ of foamed molded body.

[0257] The raw materials (P3HA-1 to P3HA-7) for poly(3-hydroxyalkanoate) foamed particles are prepared by the following method.

[0258] [Manufacturing Example 1] Production of P3HA-1

[0259] P3HA-1 was prepared using the method described in International Publication No. 2018 / 070492. At this time, 1.00 part by weight of water-soluble polymer-1 (Kuraray Poval PVA-205 manufactured by Kuraray Co., Ltd.) was used relative to 100 parts by weight of P3HA. The resulting P3HA-1 comprised (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 relative to 100 parts by weight of P3HB3HH.

[0260] [Manufacturing Example 2] Production of P3HA-2

[0261] P3HA-2 was prepared using the method described in International Publication No. 2018 / 070492. In this process, 1.00 part by weight of water-soluble polymer-2 (PLONO N#208 manufactured by Nippon Oil Co., Ltd.) was used instead of water-soluble polymer-1, relative to 100 parts by weight of P3HA. The resulting P3HA-2 comprised (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 relative to 100 parts by weight of P3HB3HH.

[0262] [Manufacturing Example 3] Production of P3HA-3

[0263] P3HA-3 was prepared using the method described in International Publication No. 2018 / 070492. In this process, 1.00 parts by weight of water-soluble polymer-2 (PLONO N#208 manufactured by Nippon Oil Co., Ltd.) and 0.50 parts by weight of water-soluble polymer-3 (METOLO SE MCE-4000 manufactured by Shin-Etsu Chemical Co., Ltd.) were used instead of water-soluble polymer-1, relative to 100 parts by weight of P3HA. The resulting P3HA-3 comprised (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 parts by weight of water-soluble polymer-2 and 0.50 parts by weight of water-soluble polymer-3 relative to 100 parts by weight of P3HB3HH.

[0264] [Manufacturing Example 4] Production of P3HA-4

[0265] P3HA-4 was prepared using the method described in International Publication No. 2018 / 070492. In this case, 1.00 part by weight of water-soluble polymer-4 (Emul sogen EPN 287, manufactured by CLARIANT) was used instead of water-soluble polymer-1 relative to 100 parts by weight of P3HA. The resulting P3HA-4 comprised (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 relative to 100 parts by weight of P3HB3HH.

[0266] [Manufacturing Example 5] Production of P3HA-5

[0267] P3HA-5 was prepared using the method described in International Publication No. 2018 / 070492. In this case, 1.00 part by weight of water-soluble polymer-5 (Emul sogen EPA 073, manufactured by CLARIANT) was used instead of water-soluble polymer-1, relative to 100 parts by weight of P3HA. The resulting P3HA-5 comprised (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 relative to 100 parts by weight of P3HB3HH.

[0268] [Manufacturing Example 6] Production of P3HA-6

[0269] P3HA-6 was prepared using the method described in International Publication No. 2018 / 070492. At this time, 0.05 parts by weight of water-soluble polymer-1 (Kuraray Poval PVA-205 manufactured by Kuraray Co., Ltd.) were used relative to 100 parts by weight of P3HA. The resulting P3HA-6 comprised (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 relative to 100 parts by weight of P3HB3HH.

[0270] [Manufacturing Example 7] Production of P3HA-7

[0271] 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 comprises (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000.

[0272] [Manufacturing Example 8] Production of P3HA-8

[0273] P3HA-8 was prepared using the method described in International Publication No. 2018 / 070492. In this process, 0.50 parts by weight of water-soluble polymer-4 (Emul sogen EPN 287, manufactured by CLARIANT) was used instead of water-soluble polymer-1, relative to 100 parts by weight of P3HA. The resulting P3HA-8 comprised (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 relative to 100 parts by weight of P3HB3HH.

[0274] Table 1 summarizes the types and amounts of P3HA and water-soluble polymers used in each manufacturing example.

[0275] [Example 1]

[0276] (Manufacturing of poly(3-hydroxyalkanoate) resin particles)

[0277] A mixture was prepared using P3HA-1 (100.0 parts by weight), bubble conditioner (0.10 parts by weight), crystallizer (1.0 part by weight), lubricant-1 (0.10 parts by weight), and lubricant-2 (0.10 parts by weight) using a super mixer (KAWATA SMV(G)-100). The mixture was melt-kneaded using a twin-screw extruder (Toshiba Machine Co., Ltd. TEM-26SX) at a drum temperature set to 130°C–160°C, and then extruded from a nozzle on a die mounted at the front of the extruder. The molten P3HA composition extruded from the nozzle at 180°C was water-cooled at 43°C. A small amount of water-diluted antistatic agent was then applied to the surface of the 100 parts by weight P3HA composition thread, and the thread was then cut. The average weight of each poly(3-hydroxyalkanoate) resin particle was 2.0 mg, the length / diameter ratio was 1.5, the Tmp was 145 °C, and the melt end temperature was 152 °C. Furthermore, the MFR of the resin particles measured at a test temperature of 160 °C and a loading of 5 kgf was 2.2 g / 10 min.

[0278] (Manufacturing of poly(3-hydroxyalkanoate) foamed particles)

[0279] 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 dispersing aid, and 2.0 parts by weight of crosslinking agent were added to a pressure-resistant container under stirring. Then, the container was thoroughly ventilated with carbon dioxide to remove oxygen. Next, carbon dioxide, acting as a foaming agent, was introduced into the pressure-resistant container. The dispersion in the pressure-resistant container was then heated to a foaming temperature of 129.5°C. Carbon dioxide was then added again, and the pressure was increased to a foaming pressure of 3.3 MPa (gauge pressure), maintained near this foaming temperature and pressure for 60 minutes. Then, the valve at the bottom of the pressure-resistant container was opened, and the dispersion was released to atmospheric pressure through a 3.6 mm diameter nozzle, yielding poly(3-hydroxyalkanoate) foamed particles. The dispersant adhering to the surface of the foamed particles was partially removed with a water-diluted cleaning agent and warm water, and the particles were dried at 80°C. At this point, to suppress static electricity in the poly(3-hydroxyalkanoate) foamed particles, a micro-spray of an antistatic agent diluted with water was applied. The resulting poly(3-hydroxyalkanoate) foamed particles had a foaming ratio of 21 times, a gel fraction of 69% by weight, an average weight of 2.0 mg per particle, a length / diameter ratio of 0.9, a cell diameter of 260 μm, and a closed-cell rate of 94%. The characteristics of the poly(3-hydroxyalkanoate) foamed particles are summarized in Tables 2 and 3.

[0280] (Manufacturing of poly(3-hydroxyalkanoate) foamed molded articles)

[0281] The obtained poly(3-hydroxyalkanoate) foam particles were placed in a pressure vessel heated to 80°C and pressurized in air to achieve an internal pressure of 0.15 MPa (absolute pressure). These foam particles were then filled into a mold (370 mm x 320 mm x 60 mm) using a molding machine (DAISEN EP-900L-M5). Next, the poly(3-hydroxyalkanoate) foam particles were heated with steam at 0.15 MPa (gauge pressure) for 5–10 seconds to obtain a poly(3-hydroxyalkanoate) foamed molded body, which was then dried at 75°C. The evaluation results of the poly(3-hydroxyalkanoate) foamed molded body are summarized in Tables 2 and 3.

[0282] [Examples 2-5, Comparative Examples 1-3]

[0283] The poly(3-hydroxyalkanoate) resins and waterborne polymers used were changed as shown in Tables 2 and 3. Otherwise, poly(3-hydroxyalkanoate) resin particles, poly(3-hydroxyalkanoate) foamed particles, and poly(3-hydroxyalkanoate) foamed molded articles were prepared in the same manner as in Example 1, and the same evaluation was performed as in Example 1. The evaluation results are summarized in Tables 2 and 3.

[0284]

[0285]

[0286] [Table 3]

[0287]

[0288] [Inspection]

[0289] The following conclusions can be drawn from Tables 1 to 3:

[0290] (1) As can be seen from Examples 1 to 5, when poly(3-hydroxyalkanoate) foam particles are made using poly(3-hydroxyalkanoate) resin and a small amount of nonionic water-soluble polymer, poly(3-hydroxyalkanoate) foam particles with high foaming ratio can be obtained by one foaming process.

[0291] (2) In Comparative Example 1, although poly(3-hydroxyalkanoate) foamed particles were prepared using poly(3-hydroxyalkanoate) resin and a small amount of ionic water-soluble polymer, thermal decomposition was promoted during melt mixing of the poly(3-hydroxyalkanoate) resin particles, resulting in a very high MFR of the resin particles. As a result, although the expansion ratio of the poly(3-hydroxyalkanoate) foamed particles could be increased in Comparative Example 1, a good poly(3-hydroxyalkanoate) foamed molded body could not be obtained due to the low closed-cell ratio.

[0292] (3) In Comparative Example 2, although poly(3-hydroxyalkanoate) foamed particles were made using poly(3-hydroxyalkanoate) resin and a very small amount (0.05 by weight) of ionic water-soluble polymer, the foaming ratio of the poly(3-hydroxyalkanoate) foamed particles could not be increased in this case.

[0293] (4) In Comparative Example 3, poly(3-hydroxyalkanoate) foam particles were made without the use of water-soluble polymers, but in this case, it was not possible to increase the foaming ratio of the poly(3-hydroxyalkanoate) foam particles.

[0294] Industrial applicability

[0295] This invention can be appropriately used in the fields of packaging cushioning materials (e.g., cushioning materials for household appliance packaging such as refrigerators, freezers, air conditioner main units and their outdoor units, washing machines, air purifiers, humidifiers, rice cookers, microwave ovens, drying ovens, baking ovens, electric fans, battery units, etc.; cushioning materials for automotive packaging such as gearboxes, roof covers, engine hoods, doors, batteries, engines, etc.), automotive parts (e.g., 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 (e.g., containers for constant temperature storage, containers for constant temperature transportation, etc.), casting molds, agricultural product boxes, fish boxes, building materials, and civil engineering materials.

Claims

1. A poly(3-hydroxyalkanoate) foamed particle, comprising 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, relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A). The closed-cell rate of the poly(3-hydroxyalkanoate) foam particles is over 90%. The nonionic water-soluble polymer (B) is selected from at least one of polyepoxides, polyvinyl alcohol, cellulose derivatives and starch derivatives.

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

3. The poly(3-hydroxyalkanoate) foamed particles according to claim 1, wherein, The content of the nonionic water-soluble polymer (B) is 0.10 to 1.00 parts by weight relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin (A).

4. The poly(3-hydroxyalkanoate) foamed particles according to claim 1 or 2, wherein, The poly(3-hydroxyalkanoate) resin (A) is selected from at least one of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-copolymer-3-hydroxyvalerate), poly(3-hydroxybutyrate-copolymer-3-hydroxyvalerate-copolymer-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copolymer-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-copolymer-4-hydroxybutyrate).

5. The poly(3-hydroxyalkanoate) foamed particles according to claim 1 or 2, wherein, The poly(3-hydroxyalkanoate) resin (A) is a copolymer having 3-hydroxybutyrate units and comonomer units. The ratio of 3-hydroxybutyrate units to comonomer units in 100 mol% of all repeating units in the copolymer is 99 / 1 to 85 / 15 in mol% / mol%.

6. The poly(3-hydroxyalkanoate) foamed particles according to claim 1 or 2, having an apparent density of 20 g / L to 67 g / L.

7. The poly(3-hydroxyalkanoate) foamed particles according to claim 1 or 2, wherein the heat on the high-temperature side is 0.1 J / g to 20.0 J / g.

8. The poly(3-hydroxyalkanoate) foam particles according to claim 1 or 2, wherein the pore diameter is 50 μm to 500 μm.

9. The poly(3-hydroxyalkanoate) foamed particles according to claim 1 or 2, wherein the gel fraction is 30% by weight or more.

10. A poly(3-hydroxyalkanoate) foamed molded article formed from poly(3-hydroxyalkanoate) foamed particles according to any one of claims 1 to 9.

11. The poly(3-hydroxyalkanoate) foamed molded article according to claim 10, wherein the foaming ratio is 25 times or more.

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