Crosslinked resin particles and thermoplastic resin modifier

Abstract

The present invention addresses the problem of providing novel biodegradable crosslinked resin particles. Specifically provided are crosslinked resin particles that have a gel fraction of 50% or higher and contain a biodegradable resin having a glass transition temperature lower than 0°C.

Description

Crosslinked resin particles and modifiers for thermoplastic resins

[0001] The present invention relates to crosslinked resin particles and a modifier for thermoplastic resins.

[0002] BACKGROUND ART Conventionally, a technique of adding various modifiers (for example, crosslinked particles) to a thermoplastic resin in order to improve the mechanical strength, such as impact strength, of the thermoplastic resin has been known.

[0003] Known examples of crosslinked resin particles include crosslinked resin particles made of resins such as acrylic resins, acrylic silicone resins, and polystyrene (see, for example, Patent Documents 1 and 2).

[0004] Meanwhile, in recent years, from the viewpoint of consideration for the environment during and after the disposal of resin products, there has been active development of biodegradable resins (hereinafter, sometimes referred to as "biodegradable resins"). For example, Patent Document 3 describes crosslinking of poly(3-hydroxyalkanoate), a type of biodegradable resin, by melt-kneading the resin in the presence of an organic peroxide. However, it describes that the crosslinked resin produced by such melt-kneading is used to form a film and / or sheet, and there is no description whatsoever about producing small particle size crosslinked resin particles.

[0005] Japanese Patent Publication No. 2009-56770 Japanese Patent Publication No. 2003-82191 International Publication No. 2019 / 022008

[0006] To date, no biodegradable crosslinked resin particles have been known.

[0007] One embodiment of the present invention has been made in view of the above-mentioned current situation, and its object is to provide novel crosslinked resin particles having biodegradability.

[0008] As a result of intensive research to solve the above problems, the present inventors have succeeded in producing novel crosslinked resin particles using various biodegradable resins, thereby completing one embodiment of the present invention.

[0009] The crosslinked resin particles according to one embodiment of the present invention contain a biodegradable resin (A) having a glass transition temperature of less than 0° C. and have a gel fraction of 50% or more.

[0010] A modifier for thermoplastic resin according to one embodiment of the present invention comprises crosslinked resin particles, and the crosslinked resin particles comprise a biodegradable resin (A) having a glass transition temperature of less than 0°C and a gel fraction of 50% or more.

[0011] According to one embodiment of the present invention, it is possible to provide novel crosslinked resin particles having biodegradability.

[0012] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and less than B)."

[0013] 1. Crosslinked Resin Particles The crosslinked resin particles according to one embodiment of the present invention contain a biodegradable resin (A) having a glass transition temperature of less than 0° C. and have a gel fraction of 50% or more.

[0014] In this specification, "glass transition temperature" may be referred to as "Tg," and "crosslinked resin particles according to one embodiment of the present invention" may be referred to as "the present crosslinked resin particles."

[0015] The crosslinked resin particles have the advantage of being biodegradable because they contain a biodegradable resin (A). Therefore, they are expected to be useful as environmentally friendly crosslinked resin particles that address the problem of plastic waste. Furthermore, because the crosslinked resin particles are biodegradable, resin compositions and molded articles containing the crosslinked resin particles can prevent soil pollution due to disposal. This can contribute to the achievement of Sustainable Development Goals (SDGs), such as Goal 12, "Ensure sustainable consumption and production patterns." Furthermore, if the biodegradable resin (A) is both soil and marine degradable, resin compositions and molded articles containing the crosslinked resin particles can prevent marine pollution in addition to preventing soil pollution due to disposal.

[0016] In a preferred embodiment of the present invention, a molded article obtained by molding a resin composition containing the present crosslinked resin particles and a thermoplastic resin also has the advantage of excellent tensile elongation at break. In a further preferred embodiment of the present invention, a molded article obtained by molding a resin composition containing the present crosslinked resin particles and a thermoplastic resin also has the advantage of excellent tensile impact strength.

[0017] <Biodegradable Resin (A)> The biodegradable resin (A) is not particularly limited as long as it has a Tg of less than 0°C and is biodegradable.

[0018] Examples of biodegradable resins (including both biodegradable resins with a Tg of less than 0° C. and biodegradable resins with a Tg of 0° C. or higher) include aliphatic polyesters and aliphatic aromatic polyesters.

[0019] Examples of the aliphatic polyester include (i) polyhydroxyalkanoate resins (hereinafter, also referred to as "PHA"), (ii) polylactic acid (hereinafter, also referred to as "PLA"), (iii) polycaprolactone (hereinafter, also referred to as "PCL"), and (iv) aliphatic polyesters other than PHA, PLA, and PCL.

[0020] "PHA" is a general term for polymers containing hydroxyalkanoic acid as a monomer unit (monomer repeating unit), and is generally biodegradable. PHA is an aliphatic polyester, preferably a polyester not containing an aromatic ring. In this specification, "PHA" refers to a polymer containing hydroxyalkanoic acid repeating units in an amount of 50 mol% or more of all monomer repeating units (100 mol%). PHA preferably contains hydroxyalkanoic acid repeating units in an amount of 60 mol% or more, more preferably 70 mol% or more, of all monomer repeating units (100 mol%).

[0021] The PHA is not particularly limited. Examples of PHA include polyglycolic acid, poly(3-hydroxyalkanoate)-based resin (hereinafter sometimes referred to as "P3HA"), and poly(4-hydroxyalkanoate)-based resin. One type of PHA may be used alone, or two or more types may be used in combination. The PHA preferably contains a poly(3-hydroxyalkanoate)-based resin, and more preferably is a poly(3-hydroxyalkanoate)-based resin (in other words, composed solely of a poly(3-hydroxyalkanoate)-based resin).

[0022] In this specification, "polyglycolic acid" refers to a group of all monomer repeating units (100 mol%) containing [—CH ２ The term "polyglycolic acid" refers to a resin containing 50 mol % or more of repeating units represented by the formula [—CH—CO—O—]. ２ The repeating units represented by the formula [—CO—O—] may account for 60 mol % or more, 70 mol % or more, 80 mol % or more, or 90 mol % or more of all the monomer repeating units (100 mol %).

[0023] The polyglycolic acid may be a homopolymer of glycolic acid, or a copolymer of glycolic acid and a monomer other than glycolic acid (for example, a copolymer of glycolic acid and lactic acid, or a copolymer of glycolic acid and caprolactone).

[0024] Polyglycolic acid can be obtained by known methods such as condensation polymerization of glycolic acid and ring-opening polymerization of glycolide.

[0025] The P3HA has the formula: [—CHR—CH ２ 3-hydroxyalkanoic acid repeating units represented by the formula: —CO—O— (wherein R is C ｎ H ２ｎ＋１ where n is an integer of 1 or more and 15 or less.) is a polyhydroxyalkanoate containing the 3-hydroxyalkanoic acid repeating unit as an essential repeating unit. In this specification, "P3HA" refers to a resin containing 50 mol % or more of the 3-hydroxyalkanoic acid repeating units out of all monomer repeating units (100 mol %). The P3HA preferably contains 60 mol % or more, and more preferably 70 mol % or more, of all monomer repeating units (100 mol %).

[0026] P3HA is not particularly limited and may be a homopolymer containing the repeating unit described above, or a copolymer containing the repeating unit described above. Examples of the copolymer include copolymers of 3-hydroxybutanoic acid (hereinafter sometimes referred to as "3HB") and one or more monomers selected from the group consisting of 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, 3-hydroxyundecanoic acid, 3-hydroxydodecanoic acid, 3-hydroxytridecanoic acid, 3-hydroxytetradecanoic acid, 3-hydroxyhexadecanoic acid, and 3-hydroxyoctadecanoic acid. Alternatively, another example of the copolymer may be a copolymer of 3HB and one or more monomers selected from the group consisting of 4-hydroxybutanoic acid, 4-hydroxypentanoic acid, 4-hydroxyhexanoic acid, 4-hydroxyheptanoic acid, 4-hydroxyoctanoic acid, 4-hydroxynonanoic acid, 4-hydroxydecanoic acid, 4-hydroxyundecanoic acid, 4-hydroxydodecanoic acid, 4-hydroxytridecanoic acid, 4-hydroxytetradecanoic acid, 4-hydroxyhexadecanoic acid, and 4-hydroxyoctadecanoic acid.

[0027] Examples of P3HA include poly(3-hydroxybutyrate) (hereinafter sometimes referred to as "P3HB"), which is a homopolymer of 3HB, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (hereinafter sometimes referred to as "P3HB3HH"), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate) (hereinafter sometimes referred to as "P3HB3HH3HO"), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (hereinafter sometimes referred to as "P3HB4HB"). Only one type of P3HA may be used, or two or more types may be used in combination. As used herein, "poly(X-co-Y)" refers to a copolymer containing X repeating units and Y repeating units, and is intended to mean a copolymer obtained by copolymerizing a monomer from which the X repeating unit is derived and a monomer from which the Y repeating unit is derived. Furthermore, during the production of P3HA by microorganisms, a small amount (less than 1 mol%) of a monomer may be copolymerized. However, if this does not significantly affect the physical properties of the resulting P3HA, the monomer is considered to be uncopolymerized, and the product will be referred to by a name that does not include that monomer.

[0028] P3HA can be produced by microorganisms. Such microbially produced P3HA is typically P3HA composed only of D-form (R-form) 3-hydroxyalkanoic acid repeating units. Among microbially produced P3HAs, P3HB, P3HB3HH, P3HB3HH3HO, and P3HB4HB are preferred, with P3HB3HH, P3HB3HH3HO, and P3HB4HB being more preferred, due to ease of industrial production.

[0029] It is also preferred that P3HA contains 3-hydroxybutanoic acid (3HB) repeating units. When P3HA contains 3HB repeating units, from the viewpoint of the balance between flexibility and strength, the composition ratio of 3HB repeating units in all monomer repeating units (100 mol%) is preferably 60 mol% to 99 mol%, more preferably 61 mol% to 97 mol%, and even more preferably 62 mol% to 95 mol%. When the composition ratio of 3HB repeating units in P3HA is 60 mol% or more, there is an advantage that the rigidity of the crosslinked resin particles can be further improved. On the other hand, when the composition ratio of 3HB repeating units in P3HA is 99 mol% or less, there is an advantage that the flexibility of the crosslinked resin particles tends to be further improved. The monomer composition ratio of P3HA can be measured by gas chromatography or the like (see, for example, WO 2014 / 020838). As P3HA, two or more types having different composition ratios of 3HB repeating units may be used in combination.

[0030] The microorganism that produces P3HA is not particularly limited as long as it has the ability to produce P3HA. For example, the first P3HB-producing bacterium was Bacillus megaterium, discovered in 1925, and other naturally occurring microorganisms such as Cupriavidus necator (formerly classified as Alcaligenes eutrophus and Ralstonia eutropha) and Alcaligenes latus are known. In these microorganisms, P3HB accumulates intracellularly.

[0031] Known examples of bacteria that produce copolymers of 3HB and other hydroxyalkanoic acids include Aeromonas caviae, which produces P3HB3HH, and Alcaligenes eutrophus, which produces poly(3-hydroxybutyrate-co-4-hydroxybutyrate). In particular, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bacteriol., 179, pp. 4821-4830 (1997)), into which genes encoding P3HA synthases have been introduced, is preferred for increasing P3HB3HH productivity. Microbial cells obtained by culturing such microorganisms under appropriate conditions and allowing P3HA to accumulate within the cells are used. In addition to the above, genetically modified microorganisms into which various P3HA synthesis-related genes have been introduced may be used depending on the P3HA to be produced, or culture conditions, including the type of substrate, may be optimized.

[0032] The weight-average molecular weight of the PHA is not particularly limited. The weight-average molecular weight of the PHA is preferably 50,000 to 3,000,000, preferably 100,000 to 2,000,000, and more preferably 150,000 to 1,500,000. A PHA with a weight-average molecular weight of 50,000 or more has the advantage of reducing or avoiding the tendency for the crosslinked resin particles to have low strength. Furthermore, a PHA with a weight-average molecular weight of 50,000 or more has the advantage of reducing or avoiding the tendency for the PHA to become sticky due to low molecular weight components. On the other hand, a PHA with a weight-average molecular weight of 3,000,000 or less may have the advantage of being easy to manufacture and / or easy to handle in order to achieve the object of one embodiment of the present invention. The numerical value of the weight-average molecular weight of the PHA is a value obtained by measurement using the PHA before crosslinking treatment.

[0033] The weight-average molecular weight can be measured using gel permeation chromatography (GPC) (Shimadzu Corporation's "High Performance Liquid Chromatograph 20A System"), a polystyrene gel column (Showa Denko K.K.'s "K-G 4A" or "K-806M" or the like), and chloroform as the mobile phase. The weight-average molecular weight can be determined as a polystyrene-equivalent molecular weight using a calibration curve obtained by measuring polystyrenes with known molecular weights using the same measurement method. In this case, the calibration curve can be prepared using polystyrenes with weight-average molecular weights of 31,400, 197,000, 668,000, and 1,920,000. As the column for the GPC, a column appropriate for measuring the molecular weight can be used.

[0034] In this specification, "polylactic acid" refers to a compound having a repeating unit of [-CHCH ３ The term "polylactic acid" refers to a resin containing 50 mol % or more of repeating units represented by the formula [-CHCH ３ The repeating units represented by the formula [—CO—O—] may account for 60 mol % or more, 70 mol % or more, 80 mol % or more, or 90 mol % or more of all the monomer repeating units (100 mol %).

[0035] As the polylactic acid, any conventionally known polylactic acid can be used. The polylactic acid may be crystalline polylactic acid, amorphous polylactic acid, or a mixture of crystalline polylactic acid and amorphous polylactic acid.

[0036] The polylactic acid may be a homopolymer of lactic acid, a copolymer of lactic acid and other monomers, or a blend of a homopolymer of lactic acid and a copolymer of lactic acid and other monomers.

[0037] Examples of the other monomers include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polycarboxylic acids, polyfunctional polysaccharides, and caprolactone.

[0038] The lactic acid raw material for producing polylactic acid is not particularly limited, and can be L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof, or L-lactide, D-lactide, meso-lactide, or a mixture thereof, etc. Lactic acid obtained by microbial fermentation from renewable plant-derived raw materials such as starch can be suitably used.

[0039] The method for producing polylactic acid is not particularly limited, and known methods such as dehydration condensation polymerization and ring-opening polymerization can be applied.

[0040] The weight-average molecular weight of polylactic acid is not particularly limited, but is preferably 50,000 to 1,000,000, more preferably 70,000 to 700,000, and even more preferably 100,000 to 400,000. When the weight-average molecular weight of polylactic acid is 50,000 or more, the crosslinked resin particles, as well as the resin composition containing the crosslinked resin particles and the molded article thereof, can have sufficient rigidity and / or strength. On the other hand, polylactic acid having a weight-average molecular weight of 1,000,000 or less can have the advantage that the polylactic acid is easy to produce and / or easy to handle in order to achieve the object of one embodiment of the present invention.

[0041] "Polycaprolactone" includes, but is not limited to, polymers obtained by ring-opening polymerization of ε-caprolactone. In one embodiment of the present invention, PCL obtained by other manufacturing methods can also be used. An organometallic catalyst can also be used to promote the polymerization of PCL. In this specification, "PCL" also includes copolymers of ε-caprolactone and monomers other than ε-caprolactone (e.g., lactide, glycolic acid, etc.).

[0042] PCL typically has a melting point of 50°C to 65°C, a crystallization temperature of 10°C to 30°C, and a glass transition temperature of -50°C to -60°C.

[0043] The weight-average molecular weight of PCL is preferably 30,000 to 500,000, and more preferably 100,000 to 400,000. When the weight-average molecular weight of PCL is 30,000 or more, the present crosslinked resin particles, as well as a resin composition containing the crosslinked resin particles and a molded article thereof, can have sufficient rigidity and / or strength. When the weight-average molecular weight of PCL is 500,000 or less, the present crosslinked resin particles can be advantageously easily processed.

[0044] Commercially available PCL products include, for example, Ingevity's "Capa 6506" (powder, Mw = 130,000), "Capa 6500" (pellet, Mw = 130,000), "Capa 6806" (powder, Mw = 230,000), "Capa 6800" (pellet, Mw = 230,000), and "FB100" (pellet, Mw = 300,000, contains cross-linked PCL).

[0045] Examples of the aliphatic polyester other than PHA include (i) polycaprolactone (PCL), (ii) polylactic acid (PLA), and (iii) aliphatic polyesters having a structure obtained by polycondensation of an aliphatic diol and an aliphatic dicarboxylic acid. Specific examples of the aliphatic polyester having a structure obtained by polycondensation of an aliphatic diol and an aliphatic dicarboxylic acid include polyethylene succinate, polybutylene succinate (hereinafter also referred to as "PBS"), polyhexamethylene succinate, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polybutylene succinate adipate (hereinafter also referred to as "PBSA"), polyethylene sebacate, and polybutylene sebacate.

[0046] In this specification, "PBS" refers to an aliphatic polyester copolymer synthesized by an esterification reaction and / or transesterification reaction, and a condensation polymerization reaction, between an aliphatic diol component mainly composed of 1,4-butanediol and an aliphatic dicarboxylic acid component mainly composed of a succinic acid component such as succinic acid and / or a derivative thereof.

[0047] PBS is, for example, [—CO—(CH ２ ) ２ —CO—O—(CH ２ ) ４-O-].

[0048] PBS can be produced from petroleum or non-petroleum-based materials (e.g., plants).

[0049] In this specification, "PBS" also includes a "PBS-based resin" which is a copolymer of the above-mentioned PBS with a monomer other than 1,4-butanediol and succinic acid (for example, L-lactic acid and / or caprolactone).

[0050] Commercially available PBS can also be used, such as "BioPBS FZ71" and "BioPBS FZ91" manufactured by Mitsubishi Chemical Corporation.

[0051] In this specification, "PBSA" refers to an aliphatic polyester copolymer synthesized by an esterification reaction and a condensation polymerization reaction between an aliphatic diol component mainly composed of 1,4-butanediol, an aliphatic dicarboxylic acid component mainly composed of a succinic acid component such as succinic acid and / or a derivative thereof, and adipic acid.

[0052] As long as the effects of one embodiment of the present invention are achieved, the PBSA may contain, in addition to butanediol repeating units, succinic acid repeating units, and adipic acid repeating units, any diol repeating units other than butanediol, any dicarboxylic acid repeating units other than succinic acid and adipic acid, and / or hydroxyalkanoic acid repeating units. Examples of the optional diols include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. Examples of the optional dicarboxylic acids include suberic acid, sebacic acid, dodecanoic acid, succinic anhydride, and adipic anhydride.

[0053] In this specification, "PBSA" also includes "PBSA-based resins" which are copolymers of the above-mentioned PBSA with monomers other than 1,4-butanediol, succinic acid, and adipic acid (e.g., lactic acid, terephthalic acid, malic acid, sebacic acid, azelaic acid, etc.) within the range that does not impair biodegradability.

[0054] Commercially available PBSA may also be used, such as "BioPBS FD72" and "BioPBS FD92" manufactured by Mitsubishi Chemical Corporation.

[0055] As the aliphatic polyester, one of the various resins described above may be used alone, or two or more of them may be used in combination. Furthermore, among the various resins described above, one of the resins described above may be used alone, or two or more of them may be used in combination.

[0056] Examples of the aliphatic aromatic polyester include aliphatic aromatic polyesters obtained by using both an aliphatic compound and an aromatic compound as monomers and copolymerizing these monomers (using both an aliphatic compound and an aromatic compound as monomers).

[0057] Examples of the aliphatic aromatic polyester include polybutylene adipate terephthalate (hereinafter sometimes referred to as "PBAT"), polybutylene sebacate terephthalate (hereinafter sometimes referred to as "PBSeT"), polybutylene azelate terephthalate (hereinafter sometimes referred to as "PBAzT"), polybutylene succinate terephthalate (hereinafter sometimes referred to as "PBST"), and polybutylene succinate adipate terephthalate (hereinafter sometimes referred to as "PBSAT").

[0058] As used herein, "PBAT" refers to a random copolymer of 1,4-butanediol with adipic acid and terephthalic acid.

[0059] The PBAT is not particularly limited, but is preferably a PBAT obtained by reacting (a) a mixture consisting essentially of 35 to 95 mol % of adipic acid or an ester-forming derivative thereof, or a mixture thereof, and 5 to 65 mol % of terephthalic acid or an ester-forming derivative thereof, or a mixture thereof (the sum of the individual mol % is 100 mol %) with (b) a mixture containing butanediol (wherein the molar ratio of (a) to (b) is 0.4:1 to 1.5:1), as described in JP 10-508640 A and the like.

[0060] In one embodiment of the present invention, in place of the 1,4-butanediol in the production of PBAT, glycol compounds such as ethylene glycol, propylene glycol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentaerythritol, bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol may be used. Also, in one embodiment of the present invention, in place of the adipic acid in the production of PBAT, dicarboxylic acids such as oxalic acid, succinic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis(p-carboxyphenyl)methane, anthracenedicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalic acid, and 5-tetrabutylphosphonium isophthalic acid may be used.

[0061] Commercially available PBAT may also be used, such as "Ecoflex C1200" manufactured by BASF.

[0062] In this specification, "PBSeT" refers to a random copolymer of 1,4-butanediol with sebacic acid and terephthalic acid. For each embodiment of PBSeT, the above-described embodiments of PBAT can be appropriately applied in which the "adipic acid" and "adipic acid or an ester-forming derivative thereof" moieties are replaced with "sebacic acid" and "sebacic acid or an ester-forming derivative thereof," respectively.

[0063] Commercially available PBSeT may also be used, such as "Ecoflex FS blend C2200" (registered trademark) manufactured by BASF.

[0064] In this specification, "PBAzT" refers to a random copolymer of 1,4-butanediol with azelaic acid and terephthalic acid. For each embodiment of PBAzT, the above-described embodiments of PBAT can be appropriately applied in which the "adipic acid" and "adipic acid or an ester-forming derivative thereof" moieties are replaced with "azelaic acid" and "azelaic acid or an ester-forming derivative thereof," respectively.

[0065] In this specification, "PBST" refers to a polymer obtained by introducing a terephthalate unit into the above-mentioned PBS. More specifically, "PBST" refers to an aliphatic-aromatic polyester copolymer synthesized by an esterification reaction and a condensation polymerization reaction between an aliphatic dicarboxylic acid component, the main component of which is succinic acid and / or a derivative thereof, and terephthalic acid.

[0066] As used herein, "PBSAT" refers to a copolymer containing, among aliphatic dicarboxylic acid residues, residues of succinic acid, adipic acid, and phthalic acid, preferably in a ratio of 70-90:5-15:5-15 mol %. Therefore, PBSAT can be produced, for example, by esterifying a dicarboxylic acid mixture containing succinic acid, adipic acid, and phthalic acid in the above-mentioned ratios with 1,4-butanediol, an aliphatic glycol, in a molar ratio of 1:1.2-2.0, followed by a condensation polymerization reaction. The reactive groups and reaction conditions used in the reaction can be those used in existing biodegradable resins such as PBS, as appropriate.

[0067] As the aliphatic aromatic polyester, one of the above-mentioned various resins may be used alone, or two or more of them may be used in combination. Furthermore, among the above-mentioned various resins, one of the above-mentioned resins may be used alone, or two or more of them may be used in combination.

[0068] The present crosslinked resin particles contain at least a biodegradable resin (A) having a glass transition temperature of less than 0°C as a biodegradable resin. The present crosslinked resin particles may further contain, in addition to the biodegradable resin (A) having a glass transition temperature of less than 0°C, a biodegradable resin having a glass transition temperature of 0°C or higher. The glass transition temperature of the resin can be easily measured by the method described in the section (Glass Transition Temperature (Tg)) in the section [Examples] below. In other words, the present crosslinked resin particles contain a biodegradable resin (A) having a glass transition temperature of less than 0°C, as determined by the measurement method described below.

[0069] Generally, PHA, PCL, PBS, PBSA, PBAT, PBSeT, PBAzT, PBST, and PBSAT other than polyglycolic acid have a Tg of less than 0°C. PCL generally has a Tg of -50°C to -60°C. PBS generally has a Tg of -30°C to -40°C. PBSA generally has a Tg of -40°C to -50°C. PBAT generally has a Tg of -30°C to -40°C. PBSeT generally has a Tg of -20°C to -40°C. PBAzT generally has a Tg of -20°C to -40°C. PBST generally has a Tg of -20°C to -40°C. PBSAT generally has a Tg of -20°C to -40°C.

[0070] Generally, polyglycolic acid and PLA have a Tg above 0° C. Polyglycolic acid generally has a Tg between 35° C. and 40° C. PLA generally has a Tg between 55° C. and 65° C.

[0071] On the other hand, the glass transition temperature of a resin depends on the structural units that make up the resin. Therefore, for example, polyglycolic acid, which is a copolymer of glycolic acid and caprolactone, may have a Tg of less than 0°C depending on the content of caprolactone. Also, polylactic acid, which is a copolymer of lactic acid and caprolactone, may have a Tg of less than 0°C depending on the content of caprolactone. Such polyglycolic acid having a glass transition temperature of less than 0°C and polylactic acid having a glass transition temperature of less than 0°C can also be considered as biodegradable resin (A).

[0072] For example, the Tg of a copolymer of P3HA with 3HB and a monomer other than 3HB may depend on the type and content of the monomer other than 3HB in the copolymer. For example, P3HB3HH, in which 3HH repeating units account for 10 mol% or more of all repeating units of P3HB3HH (100 mol%), has a Tg of less than 0°C. For example, P3HB4HB, in which 4HB repeating units account for 6 mol% or more of all repeating units of P3HB4HB (100 mol%), has a Tg of less than 0°C.

[0073] As the biodegradable resin (A), one of the various resins described above may be used alone, or two or more may be used in combination. Furthermore, among the various resins described above, one of the resins described above may be used alone, or two or more may be used in combination. In relation to this, the biodegradable resin (A) may be (i) composed of only one or more aliphatic polyesters, (ii) composed of only one or more aliphatic aromatic polyesters, (iii) composed of only a mixture of one or more aliphatic polyesters and one or more aliphatic aromatic polyesters, or (iv) composed of a mixture of one or more aliphatic polyesters, one or more aliphatic aromatic polyesters, and one or more resins other than aliphatic polyesters and aliphatic aromatic polyesters.

[0074] The biodegradable resin (A) preferably contains one or more selected from the group consisting of (i) poly(3-hydroxybutyrate-co-4-hydroxybutyrate), (ii) poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate), (iii) polycaprolactone, (iv) aliphatic polyesters having a structure obtained by polycondensation of an aliphatic diol and an aliphatic dicarboxylic acid, and (v) aliphatic aromatic polyesters, and more preferably is one or more selected from this group (consisting only of one or more selected from this group).

[0075] The present crosslinked resin particles preferably contain 60% by weight or more of a biodegradable resin, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more, based on 100% by weight of the resin component of the crosslinked resin particles. The present crosslinked resin particles may contain 100% by weight of a biodegradable resin, based on 100% by weight of the resin component of the crosslinked resin particles. In other words, the resin component of the present crosslinked resin particles may be composed solely of a biodegradable resin.

[0076] The present crosslinked resin particles preferably contain 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more of a biodegradable resin (A) having a glass transition temperature of less than 0°C, based on 100% by weight of the resin component of the crosslinked resin particles. The present crosslinked resin particles may contain 100% by weight of the biodegradable resin (A) based on 100% by weight of the resin component of the crosslinked resin particles. In other words, the resin component of the present crosslinked resin particles may be composed solely of the biodegradable resin (A).

[0077] One embodiment of the present invention may be configured such that the biodegradable resin (A) does not include crosslinked resin particles containing 50% by weight or more of P3HB3HH, or 60% by weight or more of P3HB3HH, or 70% by weight or more of P3HB3HH, or 80% by weight or more of P3HB3HH, or 90% by weight or more of P3HB3HH. The crosslinked resin particles in one embodiment of the present invention may not include P3HB3HH; in other words, one embodiment of the present invention may be configured such that the crosslinked resin particles containing P3HB3HH are not included.

[0078] One embodiment of the present invention may be configured such that, as the biodegradable resin (A), crosslinked resin particles containing 50% by weight or more of P3HA are excluded, crosslinked resin particles containing 60% by weight or more, crosslinked resin particles containing 70% by weight or more, crosslinked resin particles containing 80% by weight or more, or crosslinked resin particles containing 90% by weight or more are excluded. The crosslinked resin particles in one embodiment of the present invention may be free of P3HA; in other words, one embodiment of the present invention may be configured such that crosslinked resin particles containing P3HA are excluded.

[0079] One embodiment of the present invention may be configured such that, as the biodegradable resin (A), crosslinked resin particles containing 50% by weight or more of PHA are excluded, crosslinked resin particles containing 60% by weight or more are excluded, crosslinked resin particles containing 70% by weight or more are excluded, crosslinked resin particles containing 80% by weight or more are excluded, or crosslinked resin particles containing 90% by weight or more are excluded. The crosslinked resin particles in one embodiment of the present invention may be free of PHA; in other words, one embodiment of the present invention may be configured such that crosslinked resin particles containing PHA are excluded.

[0080] (Gel Fraction) In this specification, the term "crosslinked resin particles" refers to particles having a crosslinked structure in which molecular chains of the resin constituting the resin particles are bonded intramolecularly and / or intermolecularly. That is, the present crosslinked resin particles may have a crosslinked structure in which molecular chains of the biodegradable resin (A) are bonded together. The amount of crosslinked structures in the crosslinked resin particles affects the gel fraction of the crosslinked resin particles; specifically, the more crosslinked structures there are, the higher the gel fraction. The present crosslinked resin particles have a certain amount or more of crosslinked structures, and therefore exhibit a high gel fraction, specifically a gel fraction of 50% or more. Because the present crosslinked resin particles have a gel fraction of 50% or more, the crosslinked resin particles have excellent hardness, heat resistance, and solvent resistance.

[0081] The gel fraction value is preferably 60% or more, more preferably 70% or more, even more preferably 75% or more, and particularly preferably 80% or more. It may also be 85% or more, or 90% or more. The upper limit of the gel fraction is not particularly limited, and may be 100% or less. From the viewpoint of production efficiency of crosslinked resin particles, the upper limit of the gel fraction is preferably 99.5% or less, more preferably 99% or less. The upper limit of the gel fraction may also be 98% or less, 97% or less, or 96% or less.

[0082] The gel fraction is a value measured as follows: (1) A dried product of crosslinked resin particles is added to chloroform so that the concentration becomes 0.7% by weight, and the resulting mixture is kept at 60°C for 30 minutes to obtain a chloroform solution; (2) The chloroform solution is then left to stand at room temperature for 3 hours, and then the chloroform solution is filtered through a membrane filter with a pore size of 0.45 µm; (3) The gel remaining on the filter is dried, and the weight of the dried gel together with the filter is measured, and the gel fraction is calculated using the following formula: Gel fraction (%) = {(Weight of filter including dried gel - Weight of filter only) / Weight of dried product of crosslinked resin particles used for measurement} x 100.

[0083] (Median diameter (D50)) The median diameter of the present crosslinked resin particles is preferably 0.10 μm to 10.00 μm. This configuration enables the crosslinked resin particles to be suitably used in various applications as described below. From the viewpoint of practical use opportunities, the lower limit of the median diameter is more preferably 0.15 μm or more, and even more preferably 0.20 μm or more. Furthermore, from the viewpoint of productivity (production and / or crosslinking treatment of biodegradable resin (A)), the upper limit of the median diameter is more preferably 8.00 μm or less, and even more preferably 5.00 μm or less.

[0084] The median diameter is a value obtained by measurement using a dispersion liquid in which crosslinked resin particles are dispersed in an aqueous solvent. A general-purpose measuring device can be used as the measuring device, and an example of such a device is MicrotracMT3300EXII manufactured by Nikkiso Co., Ltd. More specifically, the particle diameter at which the larger and smaller sides are equal (50%) in the cumulative particle diameter distribution obtained by measurement is defined as the "median diameter (D50)".

[0085] <Peroxide> The crosslinked structure in the present crosslinked resin particles is not particularly limited, but is preferably crosslinked using a peroxide. That is, the present crosslinked resin particles are preferably crosslinked using a peroxide. When a peroxide is used, radicals generated by decomposition of the peroxide act on the molecules of the resin (e.g., biodegradable resin (A)) that constitute the resin particles. As a result, molecular chains of the resin that constitutes the resin particles are directly bonded to each other, thereby forming a crosslinked structure.

[0086] When the crosslinked resin particles are crosslinked using a peroxide, the aqueous dispersion containing the crosslinked resin particles may contain substances derived from the peroxide used to introduce the crosslinked structure (such as decomposition products of the peroxide and unreacted peroxide). Alternatively, when the crosslinked resin particles are crosslinked using a peroxide, substances derived from the peroxide used to introduce the crosslinked structure (such as decomposition products of the peroxide and unreacted peroxide) may adhere to the surface of the resulting crosslinked resin particles. In other words, when the crosslinked resin particles are crosslinked using a peroxide, the crosslinked resin particles may contain substances derived from the peroxide (such as decomposition products of the peroxide and unreacted peroxide). When the crosslinked resin particles contain substances derived from the peroxide, analysis of the crosslinked resin particles reveals that the crosslinked resin particles are crosslinked using a peroxide.

[0087] The peroxide may be an organic peroxide or an inorganic peroxide, but is preferably an organic peroxide because it can increase the gel fraction more efficiently.

[0088] As the organic peroxide, it is preferable to use at least one selected from the group consisting of diacyl peroxides, alkyl peroxy esters, dialkyl peroxides, hydroperoxides, peroxyketals, peroxycarbonates, and peroxydicarbonates, taking into consideration the heating temperature and / or time during the crosslinking treatment.

[0089] Specific examples of such organic peroxides include butyl peroxy neododecanoate, octanoyl peroxide, dilauroyl peroxide, succinic peroxide, a mixture of toluoyl peroxide and benzoyl peroxide, benzoyl peroxide, bis(butylperoxy)trimethylcyclohexane, butyl peroxylaurate, dimethyldi(benzoylperoxy)hexane, bis(butylperoxy)methylcyclohexane, bis(butylperoxy)cyclohexane, and butylperoxybenzo ester, butyl bis(butylperoxy)valerate, dicumyl peroxide, di-t-hexyl peroxide, t-butylperoxy 2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxymethyl monocarbonate, t-pentylperoxymethyl monocarbonate, t-hexylperoxymethyl monocarbonate, t-heptylperoxymethyl monocarbonate, t-octylperoxymethyl monocarbonate, 1 , 1,3,3-tetramethylbutylperoxymethyl monocarbonate, t-butylperoxyethyl monocarbonate, t-pentylperoxyethyl monocarbonate, t-hexylperoxyethyl monocarbonate, t-heptylperoxyethyl monocarbonate, t-octylperoxyethyl monocarbonate, 1,1,3,3-tetramethylbutylperoxyethyl monocarbonate, t-butylperoxy n-propyl monocarbonate, t-pentylperoxy n-propyl monocarbonate, t-hexylperoxy peroxy isopropyl monocarbonate, t-heptylperoxy isopropyl monocarbonate, t-octylperoxy isopropyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy isopropyl monocarbonate, t-butylperoxy isopropyl monocarbonate, t-pentylperoxy isopropyl monocarbonate, t-hexylperoxy isopropyl monocarbonate, t-heptylperoxy isopropyl monocarbonate, t-octylperoxy isopropyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy isopropyl monocarbonate, t-butylperoxy n-butyl monocarbonate, t-pentylperoxy n-butyl monocarbonate, t-hexylperoxy n-butyl monocarbonate, t-heptylperoxy n-butyl monocarbonate, t-octylperoxy n-butyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy n-butyl monocarbonate, t-butylperoxy isobutyl monocarbonate, t-pentylperoxy isobutyl monocarbonate, t -Hexylperoxy isobutyl monocarbonate, t-heptylperoxy isobutyl monocarbonate, t-octylperoxy isobutyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy isobutyl monocarbonate, t-butylperoxy sec-butyl monocarbonate, t-pentylperoxy sec-butyl monocarbonate, t-hexylperoxy sec-butyl monocarbonate, t-heptylperoxy sec-butyl monocarbonate, t-octylperoxy sec-butyl monocarbonate t-butylperoxy t-butyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy sec-butyl monocarbonate, t-butylperoxy t-butyl monocarbonate, t-pentylperoxy t-butyl monocarbonate, t-hexylperoxy t-butyl monocarbonate, t-heptylperoxy t-butyl monocarbonate, t-octylperoxy t-butyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy t-butyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t-pentylperoxy 2-ethylhexyl monocarbonate ethylhexyl monocarbonate, t-hexylperoxy 2-ethylhexyl monocarbonate, t-heptylperoxy 2-ethylhexyl monocarbonate, t-octylperoxy 2-ethylhexyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexyl monocarbonate, diisobutyl peroxide, cumyl peroxy neodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, bis(4-t-butylcyclohexyl) peroxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy) Examples of organic peroxides include hexane, t-hexylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butylperoxy-2-ethylhexyl carbonate, t-butylperoxyisopropyl carbonate, 1,6-bis(t-butylperoxycarbonyloxy)hexane, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxyacetate, t-butylperoxybenzoate, t-amylperoxy-3,5,5-trimethylhexanoate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, and 2,2-di-t-butylperoxybutane. One organic peroxide may be used alone, or two or more organic peroxides may be used in combination.

[0090] Among these, t-butylperoxyisopropyl monocarbonate, t-pentylperoxyisopropyl monocarbonate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy2-ethylhexyl monocarbonate, t-pentylperoxy2-ethylhexyl monocarbonate, t-hexylperoxy2-ethylhexyl monocarbonate, t-amylperoxyisopropyl monocarbonate, di-t-hexyl peroxide, t-butylperoxy2-ethylhexanoate Peroxymethylbutylperoxyisobutyrate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, and 1,1,3,3-tetramethylbutylperoxyneodecanoate are preferred organic peroxides because they can efficiently promote crosslinking of the resin that constitutes the resin particles.

[0091] Since the heating temperature during the crosslinking treatment can be set low, the peroxide is preferably a compound exhibiting a one-hour half-life temperature of 200° C. or less, more preferably a compound exhibiting a one-hour half-life temperature of 170° C. or less, and even more preferably a compound exhibiting a one-hour half-life temperature of 140° C. or less. The lower limit of the one-hour half-life temperature of the peroxide may be 50° C. or more, 60° C. or more, or 70° C. or more.

[0092] Particularly preferred organic peroxides exhibiting such a one-hour half-life temperature include t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, di-sec-butylperoxydicarbonate, t-butylperoxy 2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, and 1,1,3,3-tetramethylbutylperoxyneodecanoate.

[0093] The case where the peroxide is an inorganic peroxide will be described. Examples of the inorganic peroxide include hydrogen peroxide, potassium peroxide, calcium peroxide, sodium peroxide, magnesium peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate, taking into consideration the heating temperature and / or time during the crosslinking treatment. Among these, hydrogen peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate are preferred because they are easy to handle and have decomposition temperatures suitable for the heating temperature during the crosslinking treatment. The inorganic peroxide may be used alone or in combination of two or more. Furthermore, an organic peroxide and an inorganic peroxide may be used in combination.

[0094] <Multifunctional Compound> The crosslinked structure in the present crosslinked resin particles may be introduced using only a peroxide, or may be introduced using both a peroxide and a multifunctional compound. That is, the present crosslinked resin particles may be crosslinked in the presence of a peroxide and a multifunctional compound. When both a peroxide and a multifunctional compound are used, the gel fraction of the crosslinked resin particles can be increased with a smaller amount of peroxide than when only a peroxide is used.

[0095] The polyfunctional compound refers to a compound having two or more functional groups (e.g., radical reactive groups) per molecule that can crosslink the resin (e.g., biodegradable resin (A)) that constitutes the resin particles. The polyfunctional compound is not particularly limited, but is preferably a compound that is reactive with radicals generated from peroxides, and is particularly preferably a compound having two or more radical reactive groups per molecule. The radical reactive group is preferably at least one selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, and a methacryloyl group.

[0096] Such polyfunctional compounds are not particularly limited, but examples thereof include allyl (meth)acrylate, allyl alkyl (meth)acrylates, allyloxyalkyl (meth)acrylates, polyfunctional (meth)acrylates having two or more (meth)acrylic groups such as ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol (meth)acrylate, divinylbenzene, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, and divinylbenzene. Preferably, the polyfunctional compound is one or more selected from the group consisting of allyl methacrylate, triallyl isocyanurate, butanediol di(meth)acrylate, and divinylbenzene, and more preferably, the polyfunctional compound is one or more selected from the group consisting of allyl methacrylate and triallyl isocyanurate.

[0097] When a crosslinked structure is formed in the presence of a polyfunctional compound, the resulting crosslinked resin particles usually contain a structure derived from the polyfunctional compound, in which case the molecular chains of the resin constituting the resin particles are bonded to each other via the structure derived from the polyfunctional compound.

[0098] The crosslinked resin particles may be composed solely of the biodegradable resin (A) having a crosslinked structure, or may further contain components other than the biodegradable resin (A) having a crosslinked structure. Examples of the components other than the biodegradable resin (A) having a crosslinked structure include the above-mentioned biodegradable resins having a glass transition temperature of 0°C or higher, resins other than biodegradable resins, antioxidants, hydrolysis inhibitors, antiblocking agents, crystal nucleating agents, lubricants, and ultraviolet absorbers.

[0099] The present crosslinked resin particles are different from the expanded resin particles disclosed in WO 2007 / 049694 and WO 2019 / 146555, and are preferably not expanded. In other words, the present crosslinked resin particles preferably contain substantially no air bubbles inside the particles. "Substantially no air bubbles inside the particles" means that the volume of air bubbles (voids) is 10% or less of the 100% volume of the crosslinked resin particles.

[0100] When the crosslinked resin particles are not expanded, the apparent density of the crosslinked resin particles is relatively large. The apparent density of the crosslinked resin particles is 0.6 g / cm. ３ It is preferable that the density exceeds 0.7 g / cm ３ More preferably, it is 0.9 g / cm or more. ３ The apparent density of the crosslinked resin particles can be determined by the method described in JIS K0061 (Method for measuring density and specific gravity of chemical products) or JIS Z8807 (Method for measuring density and specific gravity of solids).

[0101] The average weight per particle of the present crosslinked resin particles is not particularly limited. For example, when the median diameter of the crosslinked resin particles is 10.00 μm or less, the average weight per particle of the crosslinked resin particles can be much less than 0.1 mg.

[0102] The crosslinked resin particles may be dried, and the shape after drying may be powder, pellets, crumbs, a film, a sheet, or the like, depending on the drying method.

[0103] <Aqueous Dispersion> In one embodiment of the present invention, an aqueous dispersion is provided in which the present crosslinked resin particles are dispersed in an aqueous medium.

[0104] The aqueous medium contained in the aqueous dispersion may be water alone or a mixed solvent of water and a water-compatible organic solvent. In the mixed solvent, the concentration of the water-compatible organic solvent is not particularly limited as long as it is equal to or lower than the solubility of the organic solvent in water.

[0105] The organic solvent is not particularly limited, but examples thereof include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, pentanol, hexanol, and heptanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; nitriles such as acetonitrile and propionitrile; amides such as dimethylformamide and acetamide; dimethyl sulfoxide; pyridine; piperidine; and the like. Among these, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, acetonitrile, and propionitrile are preferred because they are easily removable. Furthermore, methanol, ethanol, 1-propanol, 2-propanol, butanol, and acetone are more preferred because they are easily available. Furthermore, methanol, ethanol, and acetone are particularly preferred.

[0106] The water content in the entire aqueous medium (100% by weight) constituting the aqueous dispersion is preferably 5% by weight to 100% by weight. The water content in 100% by weight of the aqueous medium is more preferably 10% by weight or more, more preferably 30% by weight or more, even more preferably 50% by weight or more, and particularly preferably 70% by weight or more. The water content in 100% by weight of the aqueous medium may be 90% by weight or more, or may be 95% by weight or more.

[0107] The concentration of the crosslinked resin particles in the aqueous dispersion is not particularly limited, but may be, for example, 1% by weight to 60% by weight. The aqueous dispersion may also contain a dispersant, which will be described later.

[0108] <Method for producing crosslinked resin particles> An example of a method for producing the present crosslinked resin particles will now be described in detail. The present crosslinked resin particles can be produced by crosslinking resin molecular chains in an aqueous dispersion containing resin particles before crosslinking treatment in the presence of peroxide. Note that the term "resin particles" refers to particles composed of the resin component that essentially constitutes the crosslinked resin particles. When the resin component is composed only of PHA, the resin particles can also be called PHA particles. In order to efficiently crosslink the resin molecular chains, it is preferable to heat the aqueous dispersion of resin particles containing peroxide to a temperature suitable for decomposing the peroxide.

[0109] More specifically, the method for producing crosslinked resin particles preferably includes the steps of: (1) preparing an aqueous dispersion of resin particles in which pre-crosslinked resin particles (e.g., PHA particles) are dispersed in water; (2) adding a peroxide to the aqueous dispersion of resin particles to impregnate the resin particles with the peroxide; and (3) heating the aqueous dispersion of resin particles impregnated with the peroxide to a heating temperature to crosslink the resin molecular chains (e.g., PHA molecular chains). Furthermore, the method more preferably includes the step of maintaining the heating temperature after all the peroxide has been added.

[0110] In step (1), for example, the aqueous dispersion of PHA particles may be an aqueous dispersion obtained by culturing a PHA-producing microorganism to accumulate PHA in the cells, disrupting the cells in the culture solution, and then separating and removing the cell components, or an aqueous dispersion obtained by concentrating or diluting the aqueous dispersion. According to such a method, the process from producing PHA particles by culturing a PHA-producing microorganism to crosslinking treatment can be carried out without separating the PHA particles from water.

[0111] Alternatively, the aqueous dispersion of resin particles (for example, PHA particles) can be prepared by dispersing dried resin particles (for example, PHA particles) in water.

[0112] The aqueous medium contained in the aqueous dispersion may be water alone or a mixed solvent of water and a water-compatible organic solvent. In the mixed solvent, the concentration of the water-compatible organic solvent is not particularly limited as long as it is equal to or lower than the solubility of the organic solvent in water.

[0113] The organic solvent is not particularly limited, but examples thereof include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, pentanol, hexanol, and heptanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; nitriles such as acetonitrile and propionitrile; amides such as dimethylformamide and acetamide; dimethyl sulfoxide; pyridine; piperidine; and the like. Among these, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, acetonitrile, and propionitrile are preferred because they are easily removable. Furthermore, methanol, ethanol, 1-propanol, 2-propanol, butanol, and acetone are more preferred because they are easily available. Furthermore, methanol, ethanol, and acetone are particularly preferred.

[0114] The water content in the entire aqueous medium (100% by weight) constituting the aqueous dispersion is preferably 5% by weight to 100% by weight. The water content in 100% by weight of the aqueous medium is more preferably 10% by weight or more, more preferably 30% by weight or more, even more preferably 50% by weight or more, and particularly preferably 70% by weight or more. The water content in 100% by weight of the aqueous medium may be 90% by weight or more, or may be 95% by weight or more.

[0115] In the aqueous dispersion, the median diameter of the resin particles is preferably within the same range as the median diameter of the crosslinked resin particles described above. In the case of PHA particles produced by a PHA-producing microorganism, the median diameter is usually within the above range, so that an aqueous dispersion of PHA particles having a desired median diameter can be obtained without carrying out a special step for adjusting the particle size.

[0116] The concentration of the resin particles in the aqueous dispersion is not particularly limited and can be set appropriately, but may be, for example, about 1 to 70% by weight, and preferably about 5 to 50% by weight.

[0117] The aqueous dispersion of resin particles preferably contains a dispersant to improve the dispersibility of the resin particles and promote the crosslinking reaction uniformly. Examples of dispersants include anionic surfactants such as dioctyl sodium sulfosuccinate, sodium dodecyl sulfate, sodium lauryl sulfate, and sodium oleate; cationic surfactants such as lauryl trimethylammonium chloride; nonionic surfactants such as glycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene polyoxypropylene glycol; and water-soluble polymers such as polyvinyl alcohol, ethylene-modified polyvinyl alcohol, polyvinylpyrrolidone, methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, polymethacrylic acid, and sodium polymethacrylate. These dispersants may be used alone or in combination of two or more.

[0118] When a dispersant is used, the content (addition amount) of the dispersant in the aqueous dispersion is not particularly limited. The content of the dispersant in the aqueous dispersion may be, for example, 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, and particularly preferably 0.5 to 3 parts by weight, relative to 100 parts by weight of the resin particles.

[0119] In step (2), a peroxide is added to the aqueous dispersion of resin particles obtained in step (1) to impregnate the resin particles with the peroxide. The peroxide may be any of those described above. The peroxide may be added in various forms, such as a solid or liquid. Alternatively, a liquid diluted with a diluent may be added. The peroxide may be added all at once, continuously, or in portions.

[0120] When a peroxide and the polyfunctional compound are used in combination, it is preferable to add the polyfunctional compound to the aqueous dispersion of resin particles in step (2). The polyfunctional compound can be any of those described above. The polyfunctional compound can be added in various forms, such as solid or liquid. Alternatively, a liquid diluted with a diluent or the like may be added. The polyfunctional compound may be added all at once, continuously, or in portions.

[0121] In step (2), the resin particles are impregnated with the peroxide and any polyfunctional compound by, for example, setting the temperature of the aqueous dispersion to, for example, 0°C or higher but lower than a temperature suitable for decomposing the peroxide employed in the next step (3) after or while adding these compounds to the aqueous dispersion of the resin particles, and maintaining this temperature for, for example, about 1 minute to 5 hours while stirring the aqueous dispersion. Specifically, the temperature of the aqueous dispersion during impregnation may be about 0°C to 80°C, or about 10°C to 60°C.

[0122] The amount of peroxide used can be appropriately set in consideration of the gel fraction of the crosslinked resin particles, and is, for example, preferably 0.01 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, even more preferably 0.3 to 5 parts by weight, and particularly preferably 0.5 to 3 parts by weight, per 100 parts by weight of the resin particles.

[0123] In the production method of crosslinking resin particles in an aqueous dispersion using a peroxide, crosslinking can be easily carried out while maintaining the particle size (volume) before crosslinking, thereby obtaining crosslinked resin particles. On the other hand, in the method of crosslinking a resin by melt-kneading in the presence of a peroxide, this can be difficult to achieve.

[0124] Furthermore, the manufacturing method of crosslinking resin particles in an aqueous dispersion using a peroxide has the advantage that it is easy to control the temperature rise caused by the heat generated during the crosslinking reaction, and crosslinked resin particles having a safe and stable crosslinked structure (quality) can be efficiently obtained.

[0125] The amount of the polyfunctional compound used may also be appropriately determined in consideration of the gel fraction of the crosslinked resin particles. The amount of the polyfunctional compound used is, for example, preferably 0.01 to 20 parts by weight, more preferably 0.05 to 15 parts by weight, even more preferably 0.1 to 10 parts by weight, still more preferably 0.2 to 5 parts by weight, and particularly preferably 0.3 to 3 parts by weight, relative to 100 parts by weight of the resin particles.

[0126] In step (3), the aqueous dispersion of resin particles impregnated with peroxide is heated to a temperature suitable for decomposing the peroxide. The heating temperature is preferably within a range of approximately 25°C above or below the one-hour half-life temperature of the peroxide (one-hour half-life temperature -25°C to one-hour half-life temperature +25°C). Specifically, the heating temperature is preferably 30°C to 140°C, more preferably 50°C to 135°C, and even more preferably 60°C to 130°C. This method allows the resin (e.g., PHA) to be crosslinked at a temperature lower than its melting temperature, thereby avoiding resin degradation due to heating during the crosslinking process. The melting temperature of PHA is, for example, 50°C to 210°C.

[0127] In the subsequent step (4), it is preferable to maintain the heating temperature. This allows the crosslinking reaction using the peroxide to proceed sufficiently. The time for maintaining the heating temperature is not particularly limited, but is preferably 1 minute to 15 hours, and more preferably 1 hour to 10 hours.

[0128] After the crosslinking reaction is complete, the crosslinked resin particles are separated from the aqueous dispersion, and water is removed from the separated crosslinked resin particles to obtain dried crosslinked resin particles. The method for separating the crosslinked resin particles from the aqueous dispersion is not particularly limited, and examples thereof include filtration, centrifugation, heat drying, freeze drying, and spray drying. For example, spray drying can be used to obtain dried crosslinked resin particles directly from the aqueous dispersion. Furthermore, by extruding the crosslinked resin particles alone after separation from the aqueous dispersion, residual water can be completely removed, and crosslinked resin particles can be obtained in pellet form. Furthermore, an aggregation step using a coagulant and / or pH adjustment may be performed.

[0129] The aqueous dispersion itself after the crosslinking reaction has been completed, or an aqueous dispersion obtained by concentrating the aqueous dispersion after the crosslinking reaction to increase the concentration of crosslinked resin particles, or an aqueous dispersion obtained by diluting the aqueous dispersion after the crosslinking reaction by adding an aqueous medium, also constitute one aspect of the present invention. Also, (i) an aqueous dispersion with an adjusted pH and / or (ii) an aqueous dispersion to which other additives such as a dispersant, an antioxidant, a hydrolysis inhibitor, an antiblocking agent, a crystal nucleating agent, or an ultraviolet absorber have been added, also constitute one aspect of the present invention.

[0130] <Uses of Crosslinked Resin Particles> The uses of the crosslinked resin particles according to one embodiment of the present invention are not particularly limited, and they can be used in applications where conventionally known crosslinked resin particles are used. Specific examples include resin modifiers, rheology modifiers for paints or adhesives, paint pigments, paper coating agents, matting agents, antiblocking agents, cosmetic additives, toner additives, spacers for liquid crystal displays, coating agents, fillers for adhesive tapes, textile processing agents, medical diagnostic test particles, fillers, aqueous coating films, coated paper, resin tubes, foamed particles, packaging materials, containers, cosmetic containers, stain-resistant resin compositions, heat-sealable paper, handle molded articles, forks, films, resin films for twist packaging, bags, gloves, binding materials, multilayer films, stretched films, fibers, multifilaments, meltblown nonwoven fabrics, masks, pile fabrics, coffee filters, inflation molded articles, blow molded articles, calendered sheet molded articles, injection molded articles, laminates, films, and sheets. The uses of the crosslinked resin particles are not limited to these.

[0131] [2. Resin Composition] A thermoplastic resin composition according to one embodiment of the present invention contains a thermoplastic resin and the crosslinked resin particles described above in the section [1. Crosslinked Resin Particles].

[0132] In this specification, the "thermoplastic resin composition according to one embodiment of the present invention" may be referred to as the "resin composition".

[0133] Because the resin composition has the above-described structure, it can fully utilize the effect of improving mechanical strength such as impact strength provided by the crosslinked resin particles, and as a result, molded articles of the thermoplastic resin composition have the advantage of being excellent in impact resistance.

[0134] A molded article can be obtained by molding the thermoplastic resin composition by a known method.

[0135] The content of the crosslinked resin particles in the resin composition is not particularly limited. The content of the crosslinked resin particles in the resin composition may be 0.1 parts by weight or more, 0.3 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, or 30 parts by weight or more, based on 100 parts by weight of the total of the thermoplastic resin and the crosslinked resin particles. The content of the crosslinked resin particles in the resin composition is preferably 60 parts by weight or less, more preferably 55 parts by weight or less, even more preferably 53 parts by weight or less, and particularly preferably 50 parts by weight or less, based on 100 parts by weight of the total of the thermoplastic resin and the crosslinked resin particles. The content of the crosslinked resin particles in the present resin composition may be 45 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 12 parts by weight or less, or 10 parts by weight or less, based on 100 parts by weight of the total of the thermoplastic resin and the crosslinked resin particles.

[0136] <Thermoplastic Resin> In the present resin composition, the thermoplastic resin can also be referred to as a matrix resin. The thermoplastic resin is not particularly limited as long as it can be molded into a desired shape by heating to melt it and then cooling and solidifying it. Specific examples of the thermoplastic resin include polyolefin resins such as polyethylene and polypropylene, acrylic resins such as polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, polytetrafluoroethylene, and polymethyl methacrylate, AS resin, polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyester resin, and cyclic polyolefin. These thermoplastic resins may be used alone or in combination of two or more. The thermoplastic resin preferably has a gel fraction of less than 50%. The thermoplastic resin is preferably not crosslinked.

[0137] As the thermoplastic resin, polyester-based resins are particularly preferred, such as aliphatic polyesters (e.g., PHA, PLA, PCL, and aliphatic polyesters having a structure in which an aliphatic diol and an aliphatic dicarboxylic acid are polycondensed) and aliphatic aromatic polyesters.

[0138] Specific embodiments of the aliphatic polyester and the aliphatic aromatic polyester are the same as those explained in the section <Biodegradable resin (A)> above, and therefore, the explanation therefor is omitted here.

[0139] Since the crosslinked resin particles contain a biodegradable resin (A), it is preferable that the thermoplastic resin also contains a biodegradable resin, i.e., a biodegradable resin. For convenience, the biodegradable resin contained in the thermoplastic resin may be referred to as a "biodegradable resin (B)." In other words, it is preferable that the thermoplastic resin contains a biodegradable resin (B). This configuration has the advantage of being able to enhance the biodegradability of the entire thermoplastic resin composition and the entire molded product of the thermoplastic resin composition.

[0140] The biodegradable resin (B) contained in the thermoplastic resin may be a biodegradable resin having a glass transition temperature of less than 0°C, a biodegradable resin having a glass transition temperature of 0°C or higher, or a mixture of a biodegradable resin having a glass transition temperature of less than 0°C and a biodegradable resin having a glass transition temperature of 0°C or higher. Since the effects of the incorporation of crosslinked resin particles (e.g., the impact resistance improvement effect) can be more fully enjoyed, it is preferable that the biodegradable resin (B) contained in the thermoplastic resin contains a biodegradable resin having a glass transition temperature of 0°C or higher. The biodegradable resin (B) contained in the thermoplastic resin preferably contains 50% by weight or more of a biodegradable resin having a glass transition temperature of 0°C or higher, more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 80% by weight or more, based on 100% by weight of the biodegradable resin (B). The biodegradable resin (B) may be composed solely of a biodegradable resin having a glass transition temperature of 0°C or higher.

[0141] Furthermore, when the crosslinked resin particles contain a resin produced from a plant-derived raw material, from the viewpoint of resource circulation, it is preferable that the thermoplastic resin also contains a resin produced from a plant-derived raw material, and it is more preferable that the thermoplastic resin is composed only of a resin produced from a plant-derived raw material.

[0142] The case where the thermoplastic resin contains a biodegradable resin (B) will be described. The thermoplastic resin preferably contains 10 to 100% by weight of the biodegradable resin (B) relative to 100% by weight of the thermoplastic resin. The thermoplastic resin more preferably contains 30% by weight or more of the biodegradable resin (B) relative to 100% by weight of the thermoplastic resin, more preferably 50% by weight or more, even more preferably 70% by weight or more, and particularly preferably 90% by weight or more. The thermoplastic resin may be composed solely of the biodegradable resin (B).

[0143] Since the thermoplastic resin composition and its molded article can largely benefit from the impact resistance improving effect of the crosslinked resin particles, the biodegradable resin (B) preferably contains a polyester resin, more preferably contains an aliphatic polyester, and particularly preferably contains PHA and / or polylactic acid. The PHA used as the thermoplastic resin preferably has a gel fraction of less than 50%. The PHA used as the thermoplastic resin preferably does not have a crosslinked structure.

[0144] The case where the thermoplastic resin contains PHA and / or polylactic acid as the biodegradable resin (B) will be described below. The thermoplastic resin preferably contains 10% by weight to 100% by weight of PHA and polylactic acid in total, more preferably 30% by weight or more, even more preferably 50% by weight or more, even more preferably 70% by weight or more, and particularly preferably 90% by weight or more, based on 100% by weight of the thermoplastic resin.

[0145] There are no particular limitations on the PHA that can be used as the thermoplastic resin, and examples thereof include polyglycolic acid, P3HA, and poly(4-hydroxyalkanoate)-based resins. Only one type of PHA may be used, or two or more types may be used in combination. P3HA is particularly preferred as the PHA used as the thermoplastic resin.

[0146] A case where the crosslinked resin particles contain P3HA and the thermoplastic resin contains P3HA will be described. The P3HA that can be used as the thermoplastic resin is the same as the P3HA related to the crosslinked resin particles, and the various P3HAs described above can be used. The P3HA contained in the thermoplastic resin may be a resin having the same composition as the P3HA contained in the crosslinked resin particles, or may be a resin having a different composition and / or physical properties. The P3HA contained in the thermoplastic resin is preferably a resin having a different composition and / or physical properties from the P3HA contained in the crosslinked resin particles, and is more preferably a resin that is harder than the P3HA contained in the crosslinked resin particles.

[0147] The case where the P3HA used as the thermoplastic resin contains 3-hydroxybutanoic acid (3HB) repeating units will be described. In this case, from the viewpoint of the balance between flexibility and strength, the composition ratio of 3HB repeating units in all monomer repeating units (100 mol%) of the P3HA is preferably 80 mol% to 99 mol%, more preferably 82 mol% to 97 mol%. When the composition ratio of 3HB repeating units in the P3HA is 80 mol% or more, the rigidity of the P3HA can be further improved. On the other hand, when the composition ratio of 3HB repeating units in the P3HA is 99 mol% or less, the flexibility of the P3HA tends to be further improved. Two or more types of P3HA having different composition ratios of 3HB repeating units may be used in combination.

[0148] The weight-average molecular weight of the PHA used as the thermoplastic resin is not particularly limited, but is preferably 50,000 to 3,000,000, more preferably 100,000 to 2,000,000, and even more preferably 150,000 to 1,500,000. When the weight-average molecular weight of the PHA is 50,000 or more, sufficient rigidity and / or strength can be obtained in the resin composition and molded articles thereof. On the other hand, a PHA having a weight-average molecular weight of 3,000,000 or less can have the advantage of being easy to manufacture and / or easy to handle in order to achieve the object of one embodiment of the present invention.

[0149] Regarding the PHA and polylactic acid used as the thermoplastic resin, aspects other than those described above are the same as those explained in the section <Biodegradable resin (A)> above, so that the explanation therefor is incorporated by reference and will not be repeated here.

[0150] The content of the thermoplastic resin in the resin composition is not particularly limited. The content of the thermoplastic resin in the resin composition is preferably 40 to 99.9 parts by weight, more preferably 40 to 99.7 parts by weight, more preferably 40 to 99.5 parts by weight, even more preferably 40 to 99 parts by weight, and even more preferably 40 to 95 parts by weight, per 100 parts by weight of the total of the thermoplastic resin and the crosslinked resin particles. According to this configuration, the thermoplastic resin composition can provide a molded article with excellent impact resistance. The content of the thermoplastic resin in the resin composition may be 45 to 93 parts by weight, 47 to 90 parts by weight, 50 to 80 parts by weight, 50 to 75 parts by weight, or 50 to 70 parts by weight, per 100 parts by weight of the total of the thermoplastic resin and the crosslinked resin particles. The content of the thermoplastic resin in the present resin composition may be 55 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 88 parts by weight or more, or 90 parts by weight or more, based on 100 parts by weight of the total of the thermoplastic resin and the crosslinked resin particles.

[0151] <Crystal Nucleating Agent> The present resin composition may further contain a crystal nucleating agent. When the thermoplastic resin composition contains a crystal nucleating agent, crystallization during molding is promoted when the thermoplastic resin is a crystalline resin, and molding processability, productivity, etc. can be improved. When the present resin composition contains a crystal nucleating agent, there is also the advantage that a thermoplastic resin composition and a molded article thereof having excellent heat resistance or mechanical properties can be obtained.

[0152] The crystal nucleating agent is not particularly limited, and conventionally known ones can be used. Examples of the crystal nucleating agent include inorganic substances such as talc, kaolinite, montmorillonite, mica, synthetic mica, clay, zeolite, silica, carbon black, graphite, boron nitride, zinc oxide, titanium oxide, tin oxide, calcium carbonate, magnesium carbonate, aluminum oxide, neodymium oxide, barium sulfate, sodium chloride, and metal phosphates; sugar alcohol compounds derived from natural products such as erythritol, pentaerythritol, galactitol, mannitol, and arabitol; polysaccharides such as chitin and chitosan; polyols such as aliphatic alcohols (polyols), polyvinyl alcohol, and polyethylene oxide; sodium benzoate, potassium benzoate, lithium benzoate, calcium benzoate, magnesium benzoate, barium benzoate, lithium terephthalate, sodium terephthalate, and terephthalic acid salts. metal salts of organic carboxylic acids such as potassium phosphate, calcium oxalate, sodium laurate, potassium laurate, sodium myristate, potassium myristate, calcium myristate, sodium octacosanoate, calcium octacosanoate, sodium stearate, potassium stearate, lithium stearate, calcium stearate, magnesium stearate, barium stearate, sodium montanate, calcium montanate, sodium toluate, sodium salicylate, potassium salicylate, zinc salicylate, aluminum dibenzoate, potassium dibenzoate, lithium dibenzoate, sodium β-naphthalate, and sodium cyclohexanecarboxylate; organic sulfonates such as sodium p-toluenesulfonate and sodium sulfoisophthalate;Carboxylic acid amides such as ethylene stearic acid amide, ethylene bislauric acid amide, palmitic acid amide, hydroxystearic acid amide, erucic acid amide, and trimesic acid tris(t-butylamide), lauric acid esters, palmitic acid esters, oleic acid esters, stearic acid esters, erucic acid esters, N-oleyl palmitic acid ester, N-oleyl oleic acid ester, N-oleyl stearate, N-stearyl oleic acid ester, N-stearyl stearate, N-stearyl erucic acid ester, methylene bisstearate, ethylene bislauric acid ester, ethylene biscapric acid ester, ethylene bisoleic acid ester, ethylene bisstearate, ethylene biserucic acid ester, ethylene Examples of suitable crystal nucleating agents include carboxylic acid esters such as butylene bisisostearate, butylene bisstearate, and p-xylylene bisstearate; dicarboxylic acid derivatives such as dimethyl adipate, dibutyl adipate, diisodecyl adipate, and dibutyl sebacate; cyclic compounds having a functional group C═O and one or more functional groups selected from the group consisting of NH, S, and O in the molecule, such as indigo, quinacridone, and quinacridone magenta; sorbitol derivatives such as bisbenzylidene sorbitol and bis(p-methylbenzylidene)sorbitol; compounds containing a nitrogen-containing heteroaromatic nucleus, such as pyridine, triazine, and imidazole; phosphate ester compounds, bisamides of higher fatty acids, and metal salts of higher fatty acids; branched polylactic acid; and low-molecular-weight poly(3-hydroxybutyrate). These crystal nucleating agents may be used alone or in combination of two or more.

[0153] The content of the nucleating agent is not particularly limited as long as it can promote the crystallization of the thermoplastic resin. The content of the nucleating agent is preferably 0.05 to 12.00 parts by weight, more preferably 0.10 to 10.00 parts by weight, and even more preferably 0.50 to 8.00 parts by weight, per 100 parts by weight of the thermoplastic resin. When the content of the nucleating agent is within the above range, the effect of the nucleating agent can be obtained while suppressing a decrease in viscosity during molding and in the physical properties of the molded product.

[0154] <Lubricant> The resin composition may further contain a lubricant. When the thermoplastic resin composition contains a lubricant, the surface smoothness of the obtained molded article can be improved. The lubricant is not particularly limited. Examples of the lubricant include, but are not limited to, fatty acid metal salts such as magnesium stearate and calcium stearate; fatty acid amides such as behenic acid amide, stearic acid amide, erucic acid amide, oleic acid amide, methylenebisstearic acid amide, and ethylenebisstearic acid amide; polyethylene wax, oxidized polyester wax, glycerin monofatty acid esters such as glycerin monostearate, glycerin monobehenate, and glycerin monolaurate; organic acid monoglycerides such as succinic acid saturated fatty acid monoglycerides; sorbitan fatty acid esters such as sorbitan behenate, sorbitan stearate, and sorbitan laurate; polyglycerin fatty acid esters such as diglycerin stearate, diglycerin laurate, tetraglycerin stearate, tetraglycerin laurate, decaglycerin stearate, and decaglycerin laurate; and higher alcohol fatty acid esters such as stearyl stearate. Lubricants may be used alone or in combination of two or more.

[0155] The content of the lubricant (when multiple lubricants are used, the total content) is not particularly limited as long as it can impart lubricity to the molded body. The content of the lubricant is preferably 0.01 to 20.00 parts by weight, more preferably 0.05 to 10.00 parts by weight, even more preferably 0.10 to 10.00 parts by weight, even more preferably 0.20 to 5.00 parts by weight, and particularly preferably 0.30 to 4.00 parts by weight, relative to 100 parts by weight of the thermoplastic resin. When the content of the lubricant is within the above range, it is possible to obtain the effect of the lubricant while avoiding bleeding out of the lubricant onto the surface of the molded body.

[0156] <Other Components> The present resin composition may contain other components such as plasticizers; organic fillers; inorganic fillers; antioxidants; hydrolysis inhibitors; ultraviolet absorbers; colorants such as dyes and pigments; and antistatic agents, to the extent that the functionality of the resulting molded article is not impaired.

[0157] The plasticizer is not particularly limited. Examples of the plasticizer include polyester-based plasticizers such as polypropylene glycol sebacate ester; aliphatic dibasic acid ester-based plasticizers such as di-1-butyl adipate, di-n-butyl sebacate, and di-2-ethylhexyl azelate; glycerin-based plasticizers such as glycerin diacetomonolaurate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate; polycarboxylic acid ester-based plasticizers such as tri-2-ethylhexyl acetylcitrate and tributyl acetylcitrate; polyolefin plasticizers such as polyethylene glycol, polypropylene glycol, poly(ethylene oxide-propylene oxide) block and / or random copolymers, and polytetramethylene glycol. alkylene glycol-based plasticizers; phosphate ester-based plasticizers such as diphenyl-2-ethylhexyl phosphate and diphenyloctyl phosphate; epoxy-based plasticizers such as epoxidized soybean oil and epoxidized linseed oil fatty acid butyl esters; and castor oil-based plasticizers such as castor oil fatty acid esters, methyl ricinoleate, ethyl ricinoleate, isopropyl ricinoleate, butyl ricinoleate, ethylene glycol monoricylate, propylene glycol monoricylate, trimethylolpropane monoricylate, sorbitan monoricylate, castor oil fatty acid polyethylene glycol esters, castor oil ethylene oxide adducts, castor oil-based polyols, castor oil-based toluene, and castor oil-based diols. These plasticizers may be used alone or in combination of two or more.

[0158] The organic filler is not particularly limited. Examples of the organic filler include fillers made of naturally-derived materials such as wood-based materials (e.g., wood chips, wood flour, sawdust, etc.), rice husks, rice flour, starch, corn starch, rice straw, wheat straw, and natural rubber; organic fibers such as natural plant fibers, natural animal fibers, and synthetic fibers; and fillers made of synthetic resin materials such as polyester, polyacrylic, polyamide, nylon, polyethylene, polyolefin, polyvinyl alcohol, polyvinyl chloride, polyurethane, polyacetal, aramid, PBO (poly-p-phenylene benzobisoxazole), polyphenylene sulfide, acetyl cellulose, polybenzazole, polyarylate, polyvinyl acetate, and synthetic rubber.

[0159] The natural plant fibers are not particularly limited. Examples of the natural plant fibers include kenaf fiber, abaca fiber, bamboo fiber, jute fiber, hemp fiber, linen fiber, henequen (sisal), ramie fiber, hemp, cotton, banana fiber, coconut fiber, palm, paper mulberry, Mitsumata, bagasse, etc. Other examples include regenerated fibers such as pulp, cellulose fiber, and rayon processed from plant fibers. Examples of natural animal fibers include wool, silk, cashmere, and mohair.

[0160] The inorganic filler is not particularly limited. Examples of the inorganic filler include silica-based inorganic fillers (e.g., quartz, fumed silica, silicic anhydride, fused silica, crystalline silica, amorphous silica, fillers formed by condensing alkoxysilanes, ultrafine amorphous silica, etc.), alumina, zircon, iron oxide, zinc oxide, titanium oxide, silicon nitride, boron nitride, aluminum nitride, silicon carbide, glass, silicone rubber, silicone resin, titanium oxide, carbon fiber, mica, graphite, carbon black, ferrite, graphite, diatomaceous earth, clay, clay, talc, calcium carbonate, manganese carbonate, magnesium carbonate, barium sulfate, and silver powder. These inorganic fillers may be surface-treated to improve dispersibility in the resin composition. These inorganic fillers may be used alone or in combination of two or more.

[0161] The antioxidant is not particularly limited. Examples of the antioxidant include phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. These antioxidants may be used alone or in combination of two or more.

[0162] The hydrolysis inhibitor is not particularly limited. Examples of the hydrolysis inhibitor include carbodiimide compounds, epoxy compounds, isocyanate compounds, and oxazoline compounds. These hydrolysis inhibitors may be used alone or in combination of two or more.

[0163] The ultraviolet absorber is not particularly limited. Examples of the ultraviolet absorber include benzophenone compounds, benzotriazole compounds, triazine compounds, salicylic acid compounds, cyanoacrylate compounds, and nickel complex salt compounds. These ultraviolet absorbers may be used alone or in combination of two or more.

[0164] The colorants such as pigments and dyes are not particularly limited. Examples of colorants include inorganic colorants such as titanium oxide, calcium carbonate, chromium oxide, cuprous oxide, calcium silicate, iron oxide, carbon black, graphite, titanium yellow, and cobalt blue; soluble azo pigments such as lake red, lithol red, and brilliant carmine; insoluble azo pigments such as dinitrile orange and fast yellow; phthalocyanine pigments such as monochlorophthalocyanine blue, polychlorophthalocyanine blue, and polybromophthalocyanine green; condensed polycyclic pigments such as indigo blue, perylene red, isoindolinone yellow, and quinacridone red; and dyes such as oracet yellow. These colorants may be used alone or in combination of two or more.

[0165] The antistatic agent is not particularly limited. Examples of the antistatic agent include low molecular weight antistatic agents such as fatty acid ester compounds, aliphatic ethanolamine compounds, and aliphatic ethanolamide compounds, and polymeric antistatic agents. These antistatic agents may be used alone or in combination of two or more.

[0166] The resin composition may further contain any of the following additives: catalyst deactivators (hindered phenol compounds, thioether compounds, vitamin compounds, triazole compounds, polyamine compounds, hydrazine derivative compounds, phosphorus compounds, etc.), mold release agents (montanic acid and its salts, esters thereof, half esters thereof, stearyl alcohol, stearamide, polyethylene wax, etc.), color inhibitors (phosphites, hypophosphites, etc.), silane coupling agents (epoxy silane coupling agents, amino silane coupling agents, (meth)acrylic silane coupling agents, isocyanate silane coupling agents, etc.), flame retardants (red phosphorus, phosphate esters, brominated polystyrene, brominated polyphenylene ether, brominated polyisocyanate, methyl methyl silane ... The composition may also contain: polycarbonate, aluminum hydroxide, magnesium hydroxide, melamine and cyanuric acid or salts thereof, silicon compounds, etc.), conductive agents (carbon black, etc.), sliding property improvers (graphite, fluororesin, etc.), epoxy compounds (glycidyl ether compounds, glycidyl ester compounds, polymer compounds grafted or copolymerized with a glycidyl compound, etc.), acid anhydride compounds (maleic anhydride, succinic anhydride, polymer compounds grafted or copolymerized with an acid anhydride, etc.), carbodiimide compounds (N,N'-di-2,6-diisopropylphenylcarbodiimide, 2,6,2',6'-tetraisopropyldiphenylcarbodiimide, polycarbodiimide, etc.), etc.

[0167] The content of each of the other components described above is not particularly limited as long as the effect of one embodiment of the present invention is exhibited, and can be appropriately determined by a person skilled in the art.

[0168] <Method for producing thermoplastic resin composition> The resin composition can be produced by a known method. Specifically, a method can be used in which a thermoplastic resin, crosslinked resin particles, and optional components such as a crystal nucleating agent, a lubricant, and other components are melt-kneaded using an extruder, kneader, Banbury mixer, kneading roll, or the like. When melt-kneading, it is preferable to mix the components while taking care to avoid a decrease in molecular weight due to thermal decomposition. Alternatively, the thermoplastic resin composition can be produced by dissolving all raw materials (components) in a soluble solvent and then removing the solvent.

[0169] When producing a thermoplastic resin composition by melt-kneading, each component may be charged separately into an extruder, etc., or the components may be mixed in advance and the resulting mixture may be charged into an extruder, etc. For example, an aqueous dispersion of a thermoplastic resin and an aqueous dispersion of crosslinked resin particles may be mixed, and then the resulting mixture may be dried in a dryer to obtain a mixed powder, which may then be charged into an extruder, etc.

[0170] When melt-kneading is performed using an extruder, the obtained thermoplastic resin composition may be extruded from the extruder into a strand shape and then cut, thereby processing the thermoplastic resin composition into particle shapes such as a bar shape, a cylindrical shape, an elliptical cylindrical shape, a sphere shape, a cube shape, a rectangular parallelepiped shape, or the like.

[0171] The resin temperature during melt-kneading cannot be generally defined because it depends on the melting point and melt viscosity of the resin used, etc. The resin temperature is preferably 140°C to 250°C, more preferably 150°C to 230°C, and even more preferably 160°C to 210°C, from the viewpoint of uniformly dispersing the crosslinked resin particles in the thermoplastic resin while avoiding thermal decomposition of the thermoplastic resin.

[0172] <Method for producing molded article> In one embodiment of the present invention, a molded article is provided, which is obtained by molding the present resin composition. The method for molding the thermoplastic resin composition is not particularly limited, and commonly used molding methods can be applied. Specific molding methods include inflation film molding, extrusion blow molding, injection blow molding, extrusion molding, calendar molding, vacuum molding, and injection molding. A molded article obtained by molding a thermoplastic resin composition can also be said to be a molded article containing a thermoplastic resin composition.

[0173] By carrying out the above-described molding method using the resin composition, molded articles having excellent impact resistance, specifically, film molded articles, sheet molded articles, blow molded articles, extrusion molded articles, vacuum molded articles, or injection molded articles, can be produced with good productivity. In this specification, the term "film molded article" refers to a product conforming to JIS 20108:2012, specifically a thin film having a thickness of less than 0.25 mm. In this specification, the term "sheet molded article" refers to a product conforming to JIS 20108:2012, specifically a thin plate having a thickness of 0.25 mm or more.

[0174] Molded articles containing the resin composition can be suitably used in agriculture, fisheries, forestry, horticulture, medicine, hygiene products, the food industry, clothing, non-clothing, packaging, automobiles, building materials, and other fields.

[0175] [3. Thermoplastic Resin Modifier] One embodiment of the present invention provides a thermoplastic resin modifier comprising crosslinked resin particles, the crosslinked resin particles comprising a biodegradable resin (A) having a glass transition temperature of less than 0° C. and having a gel fraction of 50% or more. When blended with a thermoplastic resin, the thermoplastic resin modifier according to one embodiment of the present invention can provide a resin composition that can provide a molded article having excellent impact resistance.

[0176] For each aspect of the thermoplastic resin modifier, the description in the above section [1. Crosslinked Resin Particles] is incorporated as appropriate.

[0177] An embodiment of the present invention may have the following configuration.

[0178] [1] Crosslinked resin particles containing a biodegradable resin (A) having a glass transition temperature of less than 0°C and having a gel fraction of 50% or more.

[0179] [2] The crosslinked resin particles according to [1], excluding those containing 90% by weight or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) as the biodegradable resin (A).

[0180] [3] The crosslinked resin particles according to [1] or [2], wherein the biodegradable resin (A) is at least one selected from the group consisting of (i) poly(3-hydroxybutyrate-co-4-hydroxybutyrate), (ii) poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate), (iii) polycaprolactone, (iv) aliphatic polyesters having a structure in which an aliphatic diol and an aliphatic dicarboxylic acid are polycondensed, and (v) aliphatic aromatic polyesters.

[0181] [4] The crosslinked resin particles according to any one of [1] to [3], wherein the median diameter of the crosslinked resin particles is 0.10 μm to 10.00 μm.

[0182] [5] The crosslinked resin particles according to any one of [1] to [4], wherein the crosslinked resin particles are crosslinked using a peroxide.

[0183] [6] The crosslinked resin particles according to [5], wherein the crosslinked resin particles are crosslinked in the presence of the peroxide and a polyfunctional compound.

[0184] [7] The crosslinked resin particles according to any one of [1] to [6], wherein the crosslinked resin particles are not foamed.

[0185] [8] A thermoplastic resin composition comprising a thermoplastic resin and the crosslinked resin particles according to any one of [1] to [7].

[0186] [9] The thermoplastic resin composition according to [8], wherein the thermoplastic resin contains a biodegradable resin (B).

[0187]

[10] The thermoplastic resin composition according to [9], wherein the biodegradable resin (B) includes a polyester resin.

[0188]

[11] The thermoplastic resin composition according to any one of [8] to

[10] , further comprising a crystal nucleating agent and / or a lubricant.

[0189]

[12] A molded article obtained by molding the thermoplastic resin composition according to any one of [8] to

[11] .

[0190]

[13] The molded article according to

[12] , which is a film molded article, a sheet molded article, a blow molded article, an extrusion molded article, a vacuum molded article, or an injection molded article.

[0191]

[14] A modifier for thermoplastic resins, comprising crosslinked resin particles, the crosslinked resin particles comprising a biodegradable resin (A) having a glass transition temperature of less than 0°C and a gel fraction of 50% or more.

[0192]

[15] The crosslinked resin particles contain 90% by weight or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) as the biodegradable resin (A), excluding those containing the thermoplastic resin modifier according to

[14] .

[0193] EXAMPLES The following examples will be used to more specifically explain one embodiment of the present invention, but the present invention is not limited to these examples in any way.

[0194] [Measurement Conditions] (Median Diameter (D50)) The median diameter of the crosslinked resin particles was measured using an aqueous dispersion of crosslinked resin particles as a sample. The measuring device used was a Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd. More specifically, the particle diameter at which the larger and smaller sides of the cumulative particle diameter distribution obtained by the measurement were equal (50%) was defined as the "median diameter (D50)."

[0195] (Gel Fraction) The dried crosslinked resin particles were added to chloroform to a concentration of 0.7 wt % and maintained at 60°C for 30 minutes to obtain a chloroform solution. After allowing to stand at room temperature for 3 hours, the chloroform solution was filtered through a membrane filter with a pore size of 0.45 μm. Losses were prevented by pouring chloroform over the inside of the container and the filter multiple times while thoroughly washing. The gel remaining on the filter was dried and weighed together with the filter, and the gel fraction was calculated using the following formula: Gel fraction = {(weight of filter including dried gel - weight of filter only) / weight of crosslinked resin particles used in measurement} x 100 (%).

[0196] (Solubility in Chloroform) The dried crosslinked resin particles were added to chloroform to a concentration of 0.7 wt % and the solubility was confirmed visually. When the dried particles were not dissolved but were swollen by chloroform and were observed to float, the particles were judged to be insoluble, which was used as an indicator of the completion of gelation.

[0197] (Glass Transition Temperature (Tg)) The temperature determined by measurement using the following method (differential scanning calorimetry (DSC)) was taken as the glass transition temperature of the resin (uncrosslinked resin particles): (1) 2 mg to 3 mg of resin was filled into an aluminum pan; (2) the aluminum pan was placed in a differential scanning calorimeter, and the temperature of the analyzer was raised from -80°C to 180°C at a rate of 10°C / min under a nitrogen stream to completely melt the resin; (3) thereafter, the temperature of the analyzer was lowered from 180°C to -80°C at a rate of 10°C / min; (4) the temperature of the analyzer was again raised from -80°C to 180°C at a rate of 10°C / min; (5) for the DSC curve obtained in (4), the midpoint between the temperature at which a shift (change) from the baseline started and the temperature at which it ended was taken as the glass transition temperature (Tg) of the resin (uncrosslinked resin particles).

[0198] (Tensile Breaking Elongation) A 200 μm thick molded body (film molded body) prepared by the method described below was used as a sample. The sample was aged for 7 days under conditions of 23°C and 50% RH. Thereafter, the tensile breaking elongation of the sample was measured at 23°C at a test speed of 100 mm / min using a tensile tester (Shimadzu Corporation: EZ-LX 1kN) according to JIS K 7127.

[0199] (Tensile Impact Strength) A molded body (sheet molded body) having a thickness of 500 μm, prepared by the method described below, was cured for 7 days under conditions of 23° C. and 50% RH, and then punched out into a shape according to JIS K 71603 to prepare a test specimen. A tensile impact test was carried out on the test specimen according to the method according to JIS K 7160 A.

[0200] [Production of Crosslinked Resin Particles] (Raw Materials for Crosslinked Resin Particles) <Uncrosslinked Resin Particles> Resin particles of the following biodegradable resins were used as uncrosslinked resin particles. Table 1 shows the Tg of each biodegradable resin. PHA-1: (Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), repeating unit composition: (3-hydroxybutyrate) / (3-hydroxyhexanoate)=72 / 28 (mol / mol), weight average molecular weight Mw: 500,000 to 1,500,000) PHA-2: (Poly(3-hydroxybutyrate-co-4-hydroxybutyrate), repeating unit composition: (3-hydroxybutyrate) / (4-hydroxybutyrate)=65 / 35 (mol / mol), weight average molecular weight Mw: 400,000 to 1,500,000) PHA-3: (Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate), weight average molecular weight Mw: 500,000 to 1,500,000) PHA-4: (Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate), weight average molecular weight Mw: 500,000 to 1,500,000) PBAT: Ecoflex (registered trademark) F blend C1200 manufactured by BASF PBSA: FD92 manufactured by Mitsubishi Chemical Corporation PCL: Capa6800 manufactured by Ingevity PHA / PCL: A mixture of 50% by weight of the PHA-1 and 50% by weight of the PCL (total 100% by weight) PBS: Bionolle (registered trademark) manufactured by Showa Denko KK

[0201] <Peroxide> Di(secondary butyl) peroxydicarbonate: "Luperox (registered trademark) 225" manufactured by Arkema Yoshitomi Co., Ltd., 1-hour half-life temperature: 69°C <Polyfunctional compound> Triallyl isocyanurate.

[0202] (Method for Producing Crosslinked Resin Particles) (Examples 1 to 7) Crosslinked resin particles of Examples 1 to 7 were produced according to the procedure described below.

[0203] Each resin listed in Table 1 was completely dissolved in chloroform to a concentration of 10%, to obtain raw material 1. Surfactin (manufactured by Kaneka Corporation) and glycerin were mixed in a 6 / 94 wt% ratio and stirred for 5 to 10 minutes to obtain raw material 2. Raw materials 1 and 2 were weighed out to a ratio of 86 / 14 wt%. While stirring raw material 2, raw material 1 was slowly added dropwise to raw material 2. After the entire amount of raw material 1 was added, stirring of the resulting mixture was continued for an additional 30 minutes. Next, 100 wt% deionized water was added to the resulting mixture relative to the total weight of raw materials 1 and 2 (100 wt%) to obtain a resin particle dispersion. The dispersion was then stirred at 65°C for approximately 30 minutes to remove the remaining chloroform from the dispersion, thereby obtaining an aqueous dispersion of uncrosslinked resin particles.

[0204] An aqueous dispersion was prepared by adding to a glass vessel equipped with a stirrer, a baffle, a nitrogen inlet, a nitrogen outlet, and a thermometer an aqueous dispersion in which uncrosslinked resin particles were dispersed in water (100 parts by weight in terms of solids), 200 parts by weight of deionized water, the amount of peroxide shown in Table 1, 2 parts by weight of sodium dioctyl sulfosuccinate, and the amount of polyfunctional compound shown in Table 1. Next, stirring of the obtained aqueous dispersion was started at room temperature, and at the same time, the atmosphere inside the glass vessel was purged with nitrogen.

[0205] The contents of the glass container (aqueous dispersion) were then stirred at room temperature for 1 hour. This operation allowed the peroxide and polyfunctional compound to be impregnated into the interior of the uncrosslinked resin particles. The aqueous dispersion was then heated to the temperature listed in the "Temperature" column of the crosslinking conditions in Table 1. After reaching this temperature, the aqueous dispersion was maintained at this temperature for the time listed in the "Time" column of the crosslinking conditions in Table 1. This operation allowed the crosslinking agent to react, yielding an aqueous dispersion in which crosslinked resin particles were dispersed in water.

[0206] After adjusting the pH of the aqueous dispersion, the aqueous dispersion was dried in an oven. The resulting solid was washed multiple times with ionized water to wash away any glycerin remaining in the solid crosslinked resin particles. The washed crosslinked resin particles were again oven-dried to obtain solidified crosslinked resin particles. The resulting crosslinked resin particles can also be considered a modifier for thermoplastic resins.

[0207] Examples 14 and 15 Crosslinked resin particles of Examples 14 and 15 were produced according to the procedure described below. An aqueous dispersion (100 parts by weight of solids) of uncrosslinked resin particles dispersed in water, 200 parts by weight of deionized water, the amount of peroxide listed in Table 1, 1 part by weight of sodium dioctyl sulfosuccinate, and the amount of polyfunctional compound listed in Table 1 were added to a glass vessel equipped with a stirrer, a baffle, a nitrogen inlet, a nitrogen outlet, and a thermometer to prepare an aqueous dispersion. Stirring of the resulting aqueous dispersion was then started at room temperature (25±5°C), and the atmosphere in the glass vessel was simultaneously purged with nitrogen.

[0208] The contents of the glass container (aqueous dispersion) were then stirred at room temperature for 1 hour. This operation allowed the peroxide and polyfunctional compound to be impregnated into the interior of the uncrosslinked resin particles. The aqueous dispersion was then heated to the temperature listed in the "Temperature" column of the crosslinking conditions in Table 1. After reaching this temperature, the aqueous dispersion was maintained at this temperature for the time listed in the "Time" column of the crosslinking conditions in Table 1. This operation allowed the crosslinking agent to react, yielding an aqueous dispersion in which crosslinked resin particles were dispersed in water.

[0209] After adjusting the pH of the aqueous dispersion, the aqueous dispersion was dried in an oven to obtain solidified crosslinked resin particles, which can also be considered a modifier for thermoplastic resins.

[0210] The median diameter, gel fraction, and solubility in chloroform of the crosslinked resin particles obtained in each Example were measured by the methods described above. The results are shown in Table 1.

[0211] [Production of Thermoplastic Resin Composition] (Raw Materials for Thermoplastic Resin Composition) <Thermoplastic Resin> P3HB3HH (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)): manufactured by Kaneka Corporation, Kaneka Biodegradable Polymer PHBH (registered trademark), repeating unit composition: (3-hydroxybutyrate) / (3-hydroxyhexanoate)=94.4 / 5.6 (mol / mol), weight average molecular weight Mw: 530,000, Tg: 3°C <Crosslinked Resin Particles> Crosslinked resin particles prepared in Examples 1 to 5, 7, 14 and 15 <Crystal Nucleating Agent> Pentaerythritol: Neuizer P manufactured by Nippon Synthetic Chemical Industry Co., Ltd. <Lubricant> Behenamide: BNT22H manufactured by Nippon Fine Chemical Co., Ltd.

[0212] (Method for producing thermoplastic resin composition) For each example, the thermoplastic resin, crosslinked resin particles, crystal nucleating agent, and lubricant listed in Table 2 were mixed in the amounts listed in Table 2 to obtain a mixture. The obtained mixture was melt-kneaded for 180 seconds in a small twin-screw kneader (Xplore MC5 manufactured by DSM) with the barrel temperature heated to 175°C and a screw rotation speed of 100 rpm to obtain a melt-kneaded product. The obtained melt-kneaded product was dried in a dryer at 80°C for 4 hours to sufficiently reduce the moisture content, thereby obtaining the thermoplastic resin compositions of Comparative Example 1 and Examples 8 to 13, 16, and 17. The thermoplastic resin compositions of Comparative Example 1 and each example were press-molded to a predetermined thickness at 165°C to produce molded products (film molded products and sheet molded products).

[0213] The tensile elongation at break was measured by the above-mentioned method for the molded articles of Comparative Example 1 and each Example. The tensile impact strength was also measured by the above-mentioned method for the molded articles of Comparative Example 1 and Examples 11, 13, 16, and 17. The results are shown in Table 2.

[0214] From Table 2, it can be seen that the molded bodies of the examples to which crosslinked resin particles were added exhibited better tensile elongation and tensile impact strength than the molded bodies of the comparative examples to which crosslinked resin particles were not added.

[0215] According to one embodiment of the present invention, crosslinked resin particles having biodegradability and excellent impact resistance and tensile properties can be provided, and therefore, one embodiment of the present invention can be suitably used as a modifier for thermoplastic resins, a spacer, an antiblocking agent, a matting agent, etc.

Claims

1. Crosslinked resin particles comprising a biodegradable resin (A) having a glass transition temperature of less than 0°C and having a gel fraction of 50% or more.

2. The crosslinked resin particles according to claim 1, excluding those containing 90% by weight or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) as the biodegradable resin (A).

3. The crosslinked resin particles according to claim 1, wherein the biodegradable resin (A) is at least one selected from the group consisting of (i) poly(3-hydroxybutyrate-co-4-hydroxybutyrate), (ii) poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate), (iii) polycaprolactone, (iv) aliphatic polyesters having a structure obtained by polycondensation of an aliphatic diol and an aliphatic dicarboxylic acid, and (v) aliphatic aromatic polyesters.

4. The crosslinked resin particles according to claim 1, wherein the median diameter of the crosslinked resin particles is 0.10 μm to 10.00 μm.

5. The crosslinked resin particles according to claim 1, wherein the crosslinked resin particles are crosslinked using a peroxide.

6. The crosslinked resin particles according to claim 5, wherein said crosslinked resin particles are crosslinked in the presence of said peroxide and a polyfunctional compound.

7. The crosslinked resin particles according to claim 1, wherein the crosslinked resin particles are not foamed.

8. A thermoplastic resin composition comprising a thermoplastic resin and the crosslinked resin particles according to any one of claims 1 to 7.

9. The thermoplastic resin composition according to claim 8, wherein the thermoplastic resin comprises a biodegradable resin (B).

10. The thermoplastic resin composition according to claim 9, wherein the biodegradable resin (B) comprises a polyester-based resin.

11. The thermoplastic resin composition according to claim 8, further comprising a crystal nucleating agent and / or a lubricant.

12. A molded article obtained by molding the thermoplastic resin composition according to claim 8.

13. The molded product according to claim 12, which is a film molded product, a sheet molded product, a blow molded product, an extrusion molded product, a vacuum molded product, or an injection molded product.

14. A modifier for thermoplastic resins, comprising crosslinked resin particles, the crosslinked resin particles comprising a biodegradable resin (A) having a glass transition temperature of less than 0°C and a gel fraction of 50% or more.

15. The thermoplastic resin modifier according to claim 14, wherein the crosslinked resin particles exclude those containing 90% by weight or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) as the biodegradable resin (A).