Cross-linked resin particles and method for producing same

Abstract

The present invention addresses the problem of providing cross-linked resin particles that make it possible to provide a resin composition capable of providing a molded body which has excellent shock resistance and in which there is little or no bleed-out of a plasticizer, said cross-linked resin particles being biodegradable. Provided are cross-linked resin particles comprising a polyhydroxyalkanoate-based resin and a plasticizer, said cross-linked resin particles having a gel fraction of not less than 50%, a volume-average particle diameter of 0.10-10.00 μm, and a glass transition temperature of not higher than -10°C.

Description

Crosslinked resin particles and method for producing the same

[0001] The present invention relates to crosslinked resin particles and a method for producing the same.

[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] An object of one embodiment of the present invention is to provide novel crosslinked resin particles that can provide a resin composition that can provide a molded article that has excellent impact resistance and that does not or only causes little bleed-out of plasticizer, and that are biodegradable.

[0007] As a result of extensive research into solving the above problems, the present inventors have completed one embodiment of the present invention.

[0008] The crosslinked resin particles according to one embodiment of the present invention contain a polyhydroxyalkanoate resin and a plasticizer, have a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of −10° C. or less.

[0009] A thermoplastic resin modifier according to one embodiment of the present invention comprises crosslinked resin particles, the crosslinked resin particles comprising a polyhydroxyalkanoate resin and a plasticizer, and having a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of −10° C. or less.

[0010] A method for producing crosslinked resin particles according to one embodiment of the present invention includes: a preparation step of preparing an aqueous dispersion containing resin particles containing a polyhydroxyalkanoate resin, a plasticizer, and a peroxide; an impregnation step of impregnating the resin particles with the plasticizer; and a crosslinking step of decomposing the peroxide to crosslink the resin particles, wherein the crosslinked resin particles have a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of −10° C. or less.

[0011] According to one embodiment of the present invention, it is possible to provide novel crosslinked resin particles that are biodegradable and can provide a resin composition that can provide a molded product that has excellent impact resistance and that does not or only causes little bleed-out of plasticizer.

[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. Technical Concept According to One Embodiment of the Invention From the viewpoint of reducing environmental impact, there is a demand for the development of biodegradable materials.

[0014] Furthermore, impact resistance may be required for molded articles obtained by molding a thermoplastic resin. As a result of intensive research, the present inventors independently obtained the novel finding that a resin composition obtained by blending a plasticizer with a thermoplastic resin can provide a molded article having good impact resistance. On the other hand, the present inventors also discovered a problem that a molded article of a resin composition obtained by blending a plasticizer with a thermoplastic resin suffers from bleed-out of the plasticizer (the plasticizer present inside the molded article leaks out to the surface of the molded article) when left in a high-temperature environment or at room temperature for a long period of time.

[0015] Furthermore, through intensive research, the present inventors independently discovered the following novel findings: (i) that a resin composition obtained by blending crosslinked resin particles, which have a crosslinked structure in which the molecular chains of the resin constituting the resin particles are bonded intramolecularly and / or intermolecularly, with a thermoplastic resin can provide a molded article with good impact resistance, and (ii) that the glass transition temperature of the crosslinked resin particles tends to affect the impact resistance of the molded article, and that a resin composition obtained by blending crosslinked resin particles with a thermoplastic resin, which have a low glass transition temperature (e.g., −10°C or lower), can provide a molded article with good impact resistance. The glass transition temperature of the crosslinked resin particles can depend on the composition of the resin components that essentially constitute the crosslinked resin particles. However, it is not easy to obtain crosslinked resin particles with a low glass transition temperature (e.g., −10°C or lower) using a biodegradable resin (biodegradable resin).

[0016] As a result of further intensive research, the present inventors have succeeded in producing crosslinked resin particles containing a plasticizer, and have independently obtained the novel finding that crosslinked resin particles containing a plasticizer have a lower glass transition temperature than crosslinked resin particles not containing a plasticizer.

[0017] As a result of further intensive research conducted by the present inventors by combining these findings, the present inventors independently obtained the following novel finding, which led to the completion of one embodiment of the present invention: crosslinked resin particles containing a polyhydroxyalkanoate resin and a plasticizer and having a glass transition temperature of −10° C. or lower are biodegradable, and by blending the crosslinked resin particles with a thermoplastic resin, it is possible to provide a resin composition which has better impact resistance, i.e., a molded article with excellent impact resistance, and which is capable of providing a molded article in which no or little plasticizer bleed-out occurs when left in a high-temperature environment or at room temperature for a long period of time.

[0018] [2. Crosslinked Resin Particles] The crosslinked resin particles according to one embodiment of the present invention contain a polyhydroxyalkanoate resin and a plasticizer, and have a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of −10° C. or less.

[0019] 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."

[0020] The present crosslinked resin particles have the advantage of being able to provide a resin composition that can provide a molded article having excellent impact resistance. In this specification, the impact resistance of a molded article is defined as "tensile impact strength (kJ / m ２ The tensile impact strength (kJ / m ２ The method for measuring the above will be described in detail in the Examples below.

[0021] Furthermore, the present crosslinked resin particles have the advantage of being able to provide a resin composition capable of providing a molded article in which no plasticizer bleed-out occurs, or in which even if bleed-out of the plasticizer occurs, the bleed-out of the plasticizer from the molded article is small. In this specification, the bleed-out of the plasticizer from the molded article can be evaluated by the method described in detail in the Examples below.

[0022] In a preferred embodiment of the present invention, the crosslinked resin particles have the advantage of being able to provide a resin composition capable of providing a molded article having excellent impact resistance as evaluated by the impact energy (J) at the maximum impact point in a puncture impact test. The puncture impact test can also evaluate the fracture mode. In a preferred embodiment of the present invention, the crosslinked resin particles also have the advantage that the fracture mode is "ductile." Methods for measuring and evaluating the impact energy (J) at the maximum impact point and the fracture mode in a puncture impact test will be described in detail in the Examples below.

[0023] The crosslinked resin particles contain a polyhydroxyalkanoate resin, which is a biodegradable resin, and therefore have the advantage of being biodegradable. Therefore, they are expected to be useful as environmentally friendly crosslinked resin particles that address the problem of plastic waste. The polyhydroxyalkanoate resin is biodegradable in soil and ocean. Because the crosslinked resin particles contain a polyhydroxyalkanoate resin, resin compositions and molded articles containing the crosslinked resin particles can prevent soil and / or marine pollution due to waste disposal. As a result, one embodiment of the present invention is expected to contribute to the achievement of Sustainable Development Goals (SDGs), such as Goal 12 "Ensure sustainable consumption and production patterns" and / or Goal 14 "Conserve and sustainably use the oceans and marine resources for sustainable development."

[0024] <Polyhydroxyalkanoate Resin> The present crosslinked resin particles contain a polyhydroxyalkanoate resin (hereinafter, sometimes referred to as "PHA").

[0025] "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%).

[0026] 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).

[0027] 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 %).

[0028] 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).

[0029] Polyglycolic acid can be obtained by known methods such as condensation polymerization of glycolic acid and ring-opening polymerization of glycolide.

[0030] 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＋１where 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 %).

[0031] 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.

[0032] 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"), 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.

[0033] P3HA can be produced by microorganisms. Such microbially produced P3HA is typically composed solely of D-form (R-form) 3-hydroxyalkanoic acid repeating units. Among microbially produced P3HAs, P3HB, P3HB3HH, and P3HB4HB are preferred, with P3HB3HH and P3HB4HB being more preferred, due to ease of industrial production.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The PHA may have a glass transition temperature of 0°C or lower, or may have a glass transition temperature higher than 0°C, or may be a mixture of a PHA having a glass transition temperature of 0°C or lower and a PHA having a glass transition temperature higher than 0°C. From the viewpoint of setting the glass transition temperature of the crosslinked resin particles to -10°C or lower, the PHA contained in the crosslinked resin particles preferably contains a PHA having a glass transition temperature of 0°C or lower. The PHA contained in the crosslinked resin particles preferably contains 60% by weight or more of PHA having a glass transition temperature of 0°C or lower, based on 100% by weight of the total PHA contained in the crosslinked resin particles, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more. The glass transition temperature of the PHA can be easily measured by the method described in the section (Glass Transition Temperature (Tg)) in the [Examples] section below. In other words, the present crosslinked resin particles preferably contain a PHA having a glass transition temperature of 0°C or lower, as determined by the measurement method described below.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] <Plasticizer> The present crosslinked resin particles contain a plasticizer. By containing a plasticizer, the present crosslinked resin particles have a high tensile impact strength (kJ / m ２ ), and exhibits little or no bleed-out of the plasticizer. Furthermore, in a preferred embodiment of the present invention, the crosslinked resin particles contain a plasticizer, thereby enabling the crosslinked resin particles to provide a resin composition capable of providing a molded article having excellent impact resistance as evaluated by the puncture impact test (J) and exhibiting a "ductile" fracture mode. Furthermore, as described above, it is not easy to obtain crosslinked resin particles having a low glass transition temperature (e.g., −10°C or lower) using a biodegradable resin (e.g., PHA). However, by incorporating a plasticizer into the crosslinked resin particles, it is possible to significantly lower the glass transition temperature of the crosslinked resin particles, and as a result, crosslinked resin particles having a low glass transition temperature (e.g., −10°C or lower) can be easily obtained.

[0042] The plasticizer is not particularly limited. Examples of the plasticizer include phthalate ester plasticizers such as di(n-butyl phthalate), di(n-octyl phthalate), di(2-ethylhexyl) phthalate, diisooctyl phthalate, octyldecyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, and di(2-ethylhexyl) isophthalate; and phosphates such as tributyl phosphate, tri(2-ethylhexyl) phosphate, (2-ethylhexyl)diphenyl phosphate, and tricresyl phosphate. Ester-based plasticizers: adipate compounds such as di(2-ethylhexyl) adipate, diisodecyl adipate, (n-octyl)(n-decyl) adipate, and (n-heptyl)(n-nonyl) adipate; sebacate ester-based plasticizers such as dibutyl sebacate, di(2-ethylhexyl) sebacate, dioctyl sebacate, and diisooctyl sebacate; di(2-ethylhexyl) azelaate, dihexyl azelaate, and azelaic acid esters; azelaic acid ester-based plasticizers such as diisooctyl phosphate; citrate ester-based plasticizers such as triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, and tri(2-ethylhexyl) acetyl citrate; glycolic acid ester-based plasticizers such as methylphthalyl ethylglycolate, ethylphthalyl ethylglycolate, and butylphthalyl butylglycolate; trimellitic acid ester-based plasticizers such as tri(2-ethylhexyl) trimellitate, trioctyl trimellitate, di(n-octyl)mono(n-decyl) trimellitate, and diisooctyl monoisodecyl trimellitate; ricinoleic acid ester-based plasticizers such as methylacetyl ricinoleate and butylacetyl ricinoleate; polyether ester-based plasticizers such as polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate;Glycerin-based plasticizers such as acetylated monoglycerides (e.g., glycerin diacetomonolaurate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate), monoglycerides (e.g., glycerin monostearate and glycerin monodistearate), organic acid monoglycerides (e.g., succinic acid fatty acid monoglyceride and citric acid fatty acid monoglyceride), and glycerin fatty acid esters such as medium-chain fatty acid triglycerides; epoxy-based plasticizers such as epoxidized soybean oil, epoxidized linseed oil, and epoxidized tall oil fatty acid (2-ethylhexyl); and adipic acid (1,3-butanediol) (2-ethylhexanol)-based polyesters. Examples of suitable plasticizers include polyester-based plasticizers such as sebacic acid (1,6-hexanediol) (2-ethylhexanol) polyesters and adipic acid (propylene glycol) (coconut oil fatty acid) polyesters; 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.

[0043] In order to achieve good compatibility with polyester-based resins and little bleed-out, the plasticizer preferably contains one or more selected from the group consisting of (i) polyester-based plasticizers, polyether ester-based plasticizers, trimellitic acid-based plasticizers, glycolic acid-based plasticizers, citrate ester-based plasticizers, glycerin-based plasticizers, azelaic acid ester-based plasticizers, sebacic acid ester-based plasticizers, and adipate ester-based compounds, or may consist of only one or more selected from this group; and more preferably contains one or more selected from the group consisting of (ii) polyether ester-based plasticizers, glycolic acid-based plasticizers, glycerin-based plasticizers, citrate ester-based plasticizers, sebacic acid ester-based plasticizers, and adipate ester-based compounds, or may consist of only one or more selected from this group. From the viewpoint of high versatility and a high biomass content, the plasticizer more preferably contains one or more types selected from glycerin-based plasticizers, and particularly preferably contains one or more types selected from glycerin fatty acid esters.

[0044] As the glycerin fatty acid ester (e.g., glycerin diacetomonolaurate and medium-chain fatty acid triglyceride, etc.), commercially available products such as "Biocizer (registered trademark)" manufactured by Riken Vitamin Co., Ltd., "Rikemal (registered trademark)" manufactured by Riken Vitamin Co., Ltd., and "Coconard (registered trademark)" manufactured by Kao Corporation can also be used.

[0045] As the adipic acid ester compound, commercially available products such as "DAIFATTY (registered trademark)-101" manufactured by Daihachi Chemical Industry Co., Ltd. can also be used.

[0046] The content of the plasticizer in the present crosslinked resin particles is not particularly limited. From the viewpoint of suppressing bleed-out while exerting a sufficient plasticizing effect, the content of the plasticizer in the present crosslinked resin particles is preferably 0.5 to 30 parts by weight, more preferably 1 to 25 parts by weight, even more preferably 2 to 20 parts by weight, and particularly preferably 3 to 15 parts by weight, relative to 100 parts by weight of the resin component of the crosslinked resin particles. Note that the term "resin component of the crosslinked resin particles" refers to the resin that essentially constitutes the crosslinked resin particles, and does not include components that crosslink molecular chains of the resin (e.g., structures derived from polyfunctional compounds), residues of components used to crosslink molecular chains of the resin (e.g., unreacted peroxides, decomposition products of peroxides, unreacted polyfunctional compounds, etc.), or the plasticizer.

[0047] Among the compounds described above as plasticizers, there are also compounds that can exert effects other than those of a plasticizer (for example, effects as a dispersant, lubricant, antioxidant, hydrolysis inhibitor, ultraviolet absorber, colorant such as a dye or pigment, and antistatic agent). In this specification, even if each of the above-mentioned compounds exerts an effect other than that of a plasticizer, it is considered to be a plasticizer, and its content is considered to be the content of a plasticizer.

[0048] <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 PHA 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.

[0049] 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.

[0050] 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.

[0051] <Volume average particle diameter> The volume average particle diameter of the present crosslinked resin particles is 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 volume average particle diameter is more preferably 0.15 μm or more, and even more preferably 0.20 μm or more. Furthermore, from the viewpoint of productivity (such as PHA production and / or crosslinking treatment), the upper limit of the volume average particle diameter is more preferably 8.00 μm or less, and even more preferably 5.00 μm or less.

[0052] In this specification, the volume average particle diameter (MV) of the crosslinked resin particles is a value obtained by measuring an aqueous dispersion in which the crosslinked resin particles are dispersed in an aqueous medium. More specifically, the volume average particle diameter (MV) of the crosslinked resin particles is a value calculated by the following formula (1), i.e., formula (2), when the particle diameters of the individual crosslinked resin particles contained in a population of k crosslinked resin particles in total are denoted as d1, d2, ..., di... dk in ascending order, and the volumes of these individual crosslinked resin particles are denoted as V1, V2, ..., Vi... Vk (where Vi is the volume of the crosslinked resin particle with particle diameter di):

[0053] A general-purpose measuring device can be used to measure the particle size and volume of crosslinked resin particles in an aqueous dispersion, and an example of such a device is Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd. In this specification, the volume average particle size of uncrosslinked resin particles can be measured by replacing "crosslinked resin particles" with "uncrosslinked resin particles" in the above method.

[0054] <Glass transition temperature> The crosslinked resin particles have a glass transition temperature of -10°C or lower. This configuration has the advantage that a molded article obtained by molding a resin composition containing the crosslinked resin particles and a thermoplastic resin has excellent impact resistance. Furthermore, in a preferred embodiment of the present invention, since the crosslinked resin particles have a glass transition temperature of -10°C or lower, a molded article obtained by molding a resin composition containing the crosslinked resin particles and a thermoplastic resin also has the advantage of excellent impact resistance at low temperatures.

[0055] The glass transition temperature of the present crosslinked resin particles is more preferably −12° C. or lower, and even more preferably −13° C. or lower. The lower limit of the glass transition temperature is not particularly limited, but is, for example, −100° C.

[0056] The method for measuring the glass transition temperature of the crosslinked resin particles will be explained in detail in the Examples below.

[0057] The glass transition temperature of the crosslinked resin particles depends, for example, on the composition (type of resin) of the resin components that substantially constitute the crosslinked resin particles. Furthermore, as described above, crosslinked resin particles containing a plasticizer have a lower glass transition temperature than crosslinked resin particles that do not contain a plasticizer. In other words, the glass transition temperature of the crosslinked resin particles depends on the composition of the resin components of the crosslinked resin particles and the type and content of the plasticizer contained in the crosslinked resin particles. In one embodiment of the present invention, the crosslinked resin particles having a glass transition temperature of −10° C. or lower can be obtained by any method, including, but not limited to, (i) a method of crosslinking resin particles in the presence of a plasticizer to obtain crosslinked resin particles containing a plasticizer, and / or (ii) a method of impregnating crosslinked resin particles with a plasticizer, and (iii) a method of using a polyhydroxyalkanoate resin having a low glass transition temperature (e.g., 0° C. or lower) in addition to the methods (i) and / or (ii).

[0058] <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., PHA) that constitute the resin particles. As a result, molecular chains of the resin that constitute the resin particles are directly bonded to each other, thereby forming a crosslinked structure.

[0059] 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.

[0060] 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.

[0061] 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 crosslinking temperature and / or crosslinking time in the crosslinking step.

[0062] 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.

[0063] 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.

[0064] The peroxide is preferably a compound exhibiting a one-hour half-life temperature of 200° C. or lower, more preferably a compound exhibiting a one-hour half-life temperature of 170° C. or lower, and even more preferably a compound exhibiting a one-hour half-life temperature of 140° C. or lower, because this allows the crosslinking temperature in the crosslinking step to be set low. The lower limit of the one-hour half-life temperature of the peroxide may be 50° C. or higher, 60° C. or higher, or 70° C. or higher.

[0065] 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.

[0066] 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 crosslinking temperature and / or crosslinking time in the crosslinking step. Among these, hydrogen peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate are preferred because of their ease of handling and decomposition temperatures suited to the crosslinking temperature in the crosslinking step. 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.

[0067] <Multifunctional Compound> The crosslinked structure in the present crosslinked resin particles may be introduced using only peroxide, but it is preferable that it is introduced using both peroxide and a multifunctional compound. That is, it is preferable that the present crosslinked resin particles are crosslinked in the presence of peroxide and a multifunctional compound. When both 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 peroxide is used.

[0068] 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., PHA) 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.

[0069] 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.

[0070] 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.

[0071] <Other Components, etc.> The present crosslinked resin particles are crosslinked resin particles containing PHA. Therefore, the present crosslinked resin particles may be crosslinked resin particles containing only PHA, or may be crosslinked resin particles containing other components other than PHA. Examples of the other components include resins other than PHA, antioxidants, hydrolysis inhibitors, antiblocking agents, crystal nucleating agents, lubricants, ultraviolet absorbers, etc.

[0072] The proportion of PHA in the present crosslinked resin particles is not particularly limited. The content of PHA in 100% by weight of the resin component of the present crosslinked resin particles may be 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, particularly preferably 95% by weight or more, and may even be 99% by weight or more. The upper limit of the content of PHA in 100% by weight of the resin component of the present crosslinked resin particles is not particularly limited, and may be 100% by weight or less.

[0073] Examples of the resin other than PHA include aliphatic polyesters other than PHA and aliphatic aromatic polyesters. Examples of aliphatic polyesters 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 polyesters 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, polybutylene sebacate, etc. Examples of the aliphatic aromatic polyester include aliphatic aromatic polyesters obtained by copolymerizing both an aliphatic compound and an aromatic compound as monomers (both aliphatic compounds and aromatic compounds are used as monomers). 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"). These resins other than PHA may be used alone or in combination of two or more. In the crosslinked resin particles (B), the resin other than PHA may be crosslinked or uncrosslinked.

[0074] 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.

[0075] 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).

[0076] The average weight per particle of the present crosslinked resin particles is not particularly limited. For example, when the volume average particle size of the present 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.

[0077] 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.

[0078] <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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] <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.

[0084] [3. Thermoplastic Resin Modifier] One embodiment of the present invention provides a thermoplastic resin modifier comprising crosslinked resin particles, the crosslinked resin particles comprising (i) a polyhydroxyalkanoate resin and a plasticizer, (ii) a gel fraction of 50% or more, (iii) a volume average particle diameter of 0.10 μm to 10.00 μm, and (iv) a glass transition temperature of −10° C. or less. 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 and in which there is little or no bleed-out of the plasticizer.

[0085] For each aspect of the thermoplastic resin modifier, the description in the above section [2. Crosslinked Resin Particles] is incorporated herein by reference as appropriate.

[0086] [4. Method for Producing Crosslinked Resin Particles] A method for producing crosslinked resin particles according to one embodiment of the present invention includes: a preparation step of preparing an aqueous dispersion containing resin particles containing a polyhydroxyalkanoate resin, a plasticizer, and a peroxide; an impregnation step of impregnating the resin particles with the plasticizer and the peroxide; and a crosslinking step of decomposing the peroxide to crosslink the resin particles, wherein the crosslinked resin particles have a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of −10° C. or less.

[0087] In this specification, "a method for producing crosslinked resin particles according to one embodiment of the present invention" may be referred to as "the present production method."

[0088] <Preparation Step> The preparation step is not particularly limited as long as it is a step of preparing an aqueous dispersion containing resin particles containing a polyhydroxyalkanoate resin, a plasticizer, and a peroxide. "Resin particles containing a polyhydroxyalkanoate resin" refers to resin particles made of a polyhydroxyalkanoate resin or resin particles made of a resin mixture containing a polyhydroxyalkanoate resin. "Resin particles containing a polyhydroxyalkanoate resin" may also be referred to as "uncrosslinked resin particles" below.

[0089] The preparation step may include, for example, a step of preparing a mixture containing an aqueous medium and uncrosslinked resin particles (hereinafter, sometimes referred to as "aqueous dispersion precursor"), and a step of adding a plasticizer and a peroxide to the mixture (aqueous dispersion precursor). The plasticizer and the peroxide may be added simultaneously (together) or separately. After preparing a mixture containing the plasticizer and the peroxide, the mixture may be added to the aqueous dispersion precursor.

[0090] Alternatively, the preparation step may include a step of preparing a mixture containing an aqueous medium and a peroxide, and a step of adding a mixture containing a plasticizer and an aqueous medium and uncrosslinked resin particles (aqueous dispersion precursor) to the mixture. The plasticizer and the aqueous dispersion precursor may be added simultaneously (together) or separately. After preparing a mixture containing the plasticizer and the aqueous dispersion precursor, the mixture may be added to a mixture containing the aqueous medium and the peroxide.

[0091] Alternatively, the preparation step may include preparing a mixture containing an aqueous medium and a plasticizer, and adding a mixture containing a peroxide, an aqueous medium, and uncrosslinked resin particles (aqueous dispersion precursor) to the mixture. The peroxide and the aqueous dispersion precursor may be added simultaneously (together) or separately. After preparing the mixture containing the peroxide and the aqueous dispersion precursor, the mixture may be added to the mixture containing the aqueous medium and the plasticizer.

[0092] Alternatively, the preparation step may include a step of preparing a mixture containing an aqueous medium, a plasticizer, and a peroxide, and a step of adding a mixture containing an aqueous medium and uncrosslinked resin particles (aqueous dispersion precursor) to the mixture.

[0093] The process for preparing an aqueous dispersion precursor containing an aqueous medium and uncrosslinked resin particles is not particularly limited. A case will be described in which the uncrosslinked resin particles are composed solely of a resin (e.g., PHA) produced within the body of a microorganism. In this case, the process for preparing the aqueous dispersion precursor may include, for example, step (A) of culturing a resin-producing microorganism (e.g., a PHA-producing microorganism) to accumulate the resin within the microorganism, and then disrupting the microorganism in the culture medium to separate and remove the microorganism components, thereby obtaining an aqueous dispersion precursor. The aqueous dispersion precursor obtained by step (A) may be further concentrated or diluted. According to step (A), the process from producing uncrosslinked resin particles by culturing a resin-producing microorganism to the crosslinking step can be carried out without separating the uncrosslinked resin particles from water.

[0094] The process for preparing the aqueous dispersion precursor containing the aqueous medium and the uncrosslinked resin particles may be, for example, a process for obtaining the aqueous dispersion precursor by dispersing dried uncrosslinked resin particles (e.g., powder) in an aqueous medium such as water. The aqueous medium may contain, in addition to water, the above-mentioned water-compatible organic solvent.

[0095] The volume average particle diameter of the uncrosslinked resin particles is preferably within the same range as the volume average particle diameter of the crosslinked resin particles described above.When the uncrosslinked resin particles produced by PHA-producing microorganisms are used as raw materials, the volume average particle diameter of the uncrosslinked resin particles can usually be within the above range.Therefore, when the uncrosslinked resin particles produced by PHA-producing microorganisms are used as raw materials, an aqueous dispersion of uncrosslinked resin particles having a desired volume average particle diameter can be obtained without carrying out a special process for adjusting the particle diameter.

[0096] The concentration of the uncrosslinked 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.

[0097] In the step of adding the plasticizer and the peroxide, the plasticizer and the peroxide can be those described above. In the step of adding the plasticizer and the peroxide, the plasticizer and the peroxide can be added independently in various forms, such as solid or liquid. In this step, the plasticizer and the peroxide may be added independently in liquid form diluted with a diluent or the like. In this step, the entire amount of the plasticizer and the entire amount of the peroxide to be used may be added independently all at once, continuously, or in portions. Furthermore, during the crosslinking step described below, additional peroxide and / or plasticizer may be added. In this case, the entire amount of the peroxide and / or the entire amount of the plasticizer to be used may be added all at once, continuously, or in portions.

[0098] The amount of peroxide used in the present production method is 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, relative to 100 parts by weight of the uncrosslinked resin particles.

[0099] The amount of plasticizer used in this production method is preferably an amount such that the content of plasticizer in the finally obtained crosslinked resin particles falls within the preferred numerical range described above in the section <Plasticizer>. For example, the amount of plasticizer used in this production method is preferably 0.5 to 30 parts by weight, more preferably 1 to 25 parts by weight, even more preferably 2 to 20 parts by weight, and particularly preferably 3 to 15 parts by weight, per 100 parts by weight of uncrosslinked resin particles.

[0100] According to a production method in which uncrosslinked resin particles are crosslinked in an aqueous dispersion using a peroxide, crosslinking can be promoted while maintaining the particle size (volume) before crosslinking, and crosslinked resin particles can be easily obtained. On the other hand, it may be difficult to achieve this with a method in which the resin is crosslinked by melt-kneading in the presence of a peroxide.

[0101] Furthermore, the manufacturing method in which uncrosslinked resin particles are crosslinked 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.

[0102] The present production method preferably further includes an addition step of adding a polyfunctional compound to the aqueous dispersion. In other words, the preparation step in the present production method preferably further includes an addition step of adding a polyfunctional compound to the aqueous dispersion. The polyfunctional compound can be any of the compounds described above. In the addition step, the polyfunctional compound can be added in various forms, such as a solid or liquid. In addition, a liquid diluted with a diluent or the like may be added in the addition step. In addition, in the addition step, the entire amount of the polyfunctional compound used may be added all at once, continuously, or in portions. Furthermore, during the crosslinking step described below, additional polyfunctional compounds may be added. In this case, the entire amount of the polyfunctional compound used may be added all at once, continuously, or in portions.

[0103] The timing of the addition step of adding a polyfunctional compound to the aqueous dispersion (in other words, the timing of adding the polyfunctional compound to the aqueous dispersion) is not particularly limited. This addition step may be performed simultaneously with the step of adding a plasticizer and a peroxide to the aqueous dispersion precursor. For example, after preparing an aqueous dispersion precursor containing an aqueous medium and uncrosslinked resin particles, the plasticizer, peroxide, and polyfunctional compound may be added to the obtained aqueous dispersion precursor. The plasticizer, peroxide, and polyfunctional compound may be added simultaneously (together) or separately. After preparing a mixture containing the plasticizer, peroxide, and polyfunctional compound, the mixture may be added to the aqueous dispersion precursor.

[0104] Alternatively, the addition step may be performed between the step of preparing an aqueous dispersion precursor containing an aqueous medium and uncrosslinked resin particles and the step of adding a plasticizer and a peroxide to the aqueous dispersion precursor. For example, after preparing an aqueous dispersion precursor containing an aqueous medium and uncrosslinked resin particles, a polyfunctional compound may be added to the obtained aqueous dispersion precursor, and then a plasticizer and a peroxide may be added to the aqueous dispersion precursor containing an aqueous medium, uncrosslinked resin particles, and a polyfunctional compound. Alternatively, the addition step may be performed after the step of adding a plasticizer and a peroxide to the aqueous dispersion precursor. For example, after preparing an aqueous dispersion containing an aqueous medium, uncrosslinked resin particles, a plasticizer, and a peroxide, a polyfunctional compound may be added to the obtained aqueous dispersion.

[0105] In the present production method, the amount of the polyfunctional compound used is 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 uncrosslinked resin particles.

[0106] <Impregnation step> The impregnation step is not particularly limited as long as it is a step that can impregnate the uncrosslinked resin particles with the plasticizer.The impregnation step is preferably a step that can impregnate the uncrosslinked resin particles with not only the plasticizer but also the peroxide.When a polyfunctional compound is used in the preparation step, the impregnation step is preferably a step that can impregnate the uncrosslinked resin particles with not only the plasticizer but also the polyfunctional compound, and more preferably a step that can impregnate the uncrosslinked resin particles with both the peroxide and the polyfunctional compound.

[0107] In the impregnation step, the plasticizer is preferably at least partially impregnated into the uncrosslinked resin particles, more preferably completely impregnated, and in the impregnation step, the peroxide and / or polyfunctional compound is preferably at least partially impregnated into the uncrosslinked resin particles, more preferably completely impregnated.

[0108] The impregnation step may be, for example, a step of setting (heating) the temperature of the aqueous dispersion precursor to a predetermined temperature (impregnation temperature) while adding a plasticizer, a peroxide, and optionally a polyfunctional compound to the aqueous dispersion precursor containing uncrosslinked resin particles, and optionally maintaining the temperature of the aqueous dispersion precursor at the predetermined temperature (impregnation temperature) for a predetermined time (impregnation time). Alternatively, the impregnation step may be, for example, a step of adding a plasticizer, a peroxide, and optionally a polyfunctional compound to the aqueous dispersion precursor containing uncrosslinked resin particles, and then setting (heating) the temperature of the resulting aqueous dispersion to a predetermined temperature (impregnation temperature), and optionally maintaining the temperature of the aqueous dispersion at the predetermined temperature (impregnation temperature) for a predetermined time (impregnation time). The impregnation step may involve both of these two steps.

[0109] In the impregnation step, the set temperature (heating temperature) of the aqueous dispersion, i.e., the impregnation temperature, is not particularly limited. The impregnation temperature may be, for example, (i) 0°C or higher and lower than a temperature suitable for decomposing the peroxide used in the crosslinking step described later, (ii) 0°C or higher and lower than 80°C, or (iii) 0°C or higher and lower than 60°C.

[0110] In the impregnation step, the time for which the aqueous dispersion is maintained at the impregnation temperature, i.e., the impregnation time, is not particularly limited and may be, for example, 1 minute to 5 hours, 10 minutes to 3 hours, or 30 minutes to 1 hour.

[0111] In the impregnation step, by maintaining the aqueous dispersion at the impregnation temperature and for the impregnation time described above, the uncrosslinked resin particles can be impregnated with not only the plasticizer but also the peroxide and, if used, the polyfunctional compound.

[0112] <Crosslinking Step> The present manufacturing method includes a crosslinking step of decomposing the peroxide and crosslinking the resin particles. As described above, decomposition of the peroxide generates radicals, which directly bond the molecular chains of the resin constituting the resin particles, thereby forming a crosslinked structure. In other words, the resin particles are crosslinked as long as the peroxide is decomposed. Therefore, the crosslinking step is not particularly limited as long as it can decompose the peroxide.

[0113] The crosslinking step may be, for example, a step of heating the aqueous dispersion obtained in the preparation step or the aqueous dispersion obtained through the preparation step and the impregnation step to a temperature suitable for decomposing the peroxide (hereinafter, also referred to as the "crosslinking temperature"). Alternatively, the crosslinking step may be a step of mixing the aqueous dispersion obtained in the preparation step or the aqueous dispersion obtained through the preparation step and the impregnation step with a substance that promotes the decomposition of the peroxide (for example, an acid, an alkali, a reducing agent, etc.).

[0114] The aqueous dispersion obtained in the preparation step and the aqueous dispersion obtained through the preparation step and the impregnation step may each independently be an aqueous dispersion such as the following: (i) an aqueous dispersion containing resin particles impregnated with a plasticizer and a peroxide, and optionally, a plasticizer and a peroxide that are not impregnated into the resin particles; (ii) an aqueous dispersion containing resin particles partially impregnated with a plasticizer and a peroxide, and a plasticizer and a peroxide that are not impregnated into the resin particles; (iii) an aqueous dispersion containing resin particles not impregnated with a plasticizer and a peroxide, and a plasticizer and a peroxide that are not impregnated into the resin particles; (iv) an aqueous dispersion containing resin particles partially impregnated with a plasticizer and a peroxide, resin particles not impregnated with a plasticizer and a peroxide, and a plasticizer and a peroxide that are not impregnated into the resin particles, or; (v) An aqueous dispersion containing resin particles impregnated with a plasticizer and a peroxide, resin particles partially impregnated with a plasticizer and a peroxide, and / or resin particles not impregnated with a plasticizer and a peroxide, and plasticizer and peroxide not impregnated into resin particles.

[0115] The crosslinking temperature is preferably within a range of about 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 crosslinking 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 configuration allows the uncrosslinked resin particles to be crosslinked at a temperature lower than the melting temperature of the resin component that constitutes the uncrosslinked resin particles, thereby preventing deterioration of the uncrosslinked resin particles due to heat. The melting temperature of the PHA is, for example, 50°C to 210°C.

[0116] In the crosslinking step, the aqueous dispersion is preferably maintained at the above-mentioned crosslinking temperature for a predetermined time (crosslinking time). The crosslinking time is not particularly limited, but is preferably 1 minute to 15 hours, and more preferably 1 hour to 10 hours. This configuration allows the crosslinking reaction using the peroxide to proceed sufficiently.

[0117] In the crosslinking step, the pH of the aqueous dispersion is preferably 4 to 13, more preferably 7 to 12. When the pH of the aqueous dispersion is within the above range, there is an advantage that the dispersibility of the crosslinked resin particles in the aqueous dispersion is improved.

[0118] In the crosslinking step, the pressure in the reactor is preferably less than 1 MPa in gauge pressure, more preferably less than 0.8 MPa, even more preferably less than 0.6 MPa, and particularly preferably less than 0.2 MPa. The pressure in the reactor is preferably 0 MPa or more in gauge pressure. When the pressure in the reactor is within the above range, the reaction can be carried out under mild conditions, which has the advantage of increasing the options for reactors.

[0119] In the crosslinking step, it is sufficient that at least a portion of the resin particles is crosslinked. In the crosslinking step, it is preferable that the resin particles are crosslinked to such an extent that crosslinked resin particles having a desired gel fraction (e.g., 50% or more) are obtained.

[0120] The above-described production method can produce crosslinked resin particles containing a plasticizer, more specifically, crosslinked resin particles in which the plasticizer remains and is encapsulated within the crosslinked structure. This makes it possible to provide a resin composition containing crosslinked resin particles and a thermoplastic resin that produces a molded product in which the plasticizer bleeds out little or no.

[0121] 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.

[0122] 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.

[0123] [5. Resin Composition] A thermoplastic resin composition according to one embodiment of the present invention contains a thermoplastic resin and the crosslinked resin particles described in the section [2. Crosslinked Resin Particles] above.

[0124] In this specification, the "thermoplastic resin composition according to one embodiment of the present invention" may be referred to as the "resin composition".

[0125] Because the resin composition has the above-described structure, it can fully utilize the effect of the crosslinked resin particles in improving mechanical strength such as impact strength, etc. As a result, the resin composition has the advantage of being able to provide a resin composition that can provide a molded article that is excellent in impact resistance and that does not or only causes little bleed-out of the plasticizer.

[0126] A molded article can be obtained by molding the thermoplastic resin composition by a known method.

[0127] 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.

[0128] <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.

[0129] 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.

[0130] Specific embodiments of the aliphatic polyester and the aliphatic aromatic polyester are the same as those described in the sections <Polyhydroxyalkanoate resin> and <Other components> in [2. Crosslinked resin particles] above, and therefore, the descriptions therein are incorporated by reference and will not be described here.

[0131] Since the crosslinked resin particles contain biodegradable PHA, it is preferable that the thermoplastic resin also contains a biodegradable resin, i.e., a biodegradable resin. 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.

[0132] The biodegradable resin contained in the thermoplastic resin may be a biodegradable resin having a glass transition temperature of 0° C. or lower, a biodegradable resin having a glass transition temperature of higher than 0° C., or a mixture of a biodegradable resin having a glass transition temperature of 0° C. or lower and a biodegradable resin having a glass transition temperature of higher than 0° C. Since the effects of incorporating crosslinked resin particles (e.g., the effect of improving impact resistance) can be more fully enjoyed, the biodegradable resin contained in the thermoplastic resin preferably includes a biodegradable resin having a glass transition temperature of higher than 0° C.

[0133] The biodegradable resin contained in the thermoplastic resin preferably contains 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 80% by weight or more of a biodegradable resin having a glass transition temperature above 0° C., based on 100% by weight of the biodegradable resin. The biodegradable resin may be composed solely of a biodegradable resin having a glass transition temperature above 0° C.

[0134] 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.

[0135] The case where the thermoplastic resin contains a biodegradable resin will be described below. The thermoplastic resin preferably contains 10% to 100% by weight of the biodegradable resin relative to 100% by weight of the thermoplastic resin. The thermoplastic resin more preferably contains 30% or more by weight of the biodegradable resin relative to 100% by weight of the thermoplastic resin, more preferably 50% or more by weight, even more preferably 70% or more by weight, and particularly preferably 90% or more by weight. The thermoplastic resin may be composed solely of the biodegradable resin.

[0136] 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 contained in the thermoplastic resin preferably contains a polyester-based 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.

[0137] The case where the thermoplastic resin contains PHA and / or polylactic acid as a biodegradable resin 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] Polylactic acid usable as the thermoplastic resin may be any conventionally known polylactic acid, and may be crystalline polylactic acid, amorphous polylactic acid, or a mixture of crystalline polylactic acid and amorphous polylactic acid.

[0143] 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.

[0144] Examples of the other monomers include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polycarboxylic acids, and polyfunctional polysaccharides.

[0145] 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.

[0146] 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.

[0147] The weight-average molecular weight of the polylactic acid used as the thermoplastic resin 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 the polylactic acid 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, 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 can be easily handled to achieve the object of one embodiment of the present invention.

[0148] Regarding the PHA used as the thermoplastic resin, other aspects than those described above are the same as those explained in the section [2. Crosslinked Resin Particles] above, and therefore, the explanation therefor is omitted here by citing the same.

[0149] 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.

[0150] <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.

[0151] 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.

[0152] 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.

[0153] <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.

[0154] 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.

[0155] <Other Components> The present resin composition may contain other components such as 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] <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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] <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.

[0171] By carrying out the above-described molding method using the present resin composition, it is possible to provide a molded product with excellent impact resistance and with little or no plasticizer bleed-out, with good productivity. Specifically, by carrying out the above-described molding method using the present resin composition, it is possible to produce 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. In this specification, the term "film molded product" refers to a product conforming to JIS 20108:2012, specifically a thin film-like product having a thickness of less than 0.25 mm. In this specification, the term "sheet molded product" refers to a product conforming to JIS 20108:2012, specifically a thin plate-like product having a thickness of 0.25 mm or more.

[0172] 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.

[0173] An embodiment of the present invention may have the following configuration.

[0174] [1] Crosslinked resin particles comprising a polyhydroxyalkanoate resin and a plasticizer, having a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of −10° C. or lower.

[0175] [2] The crosslinked resin particles according to [1], wherein the polyhydroxyalkanoate resin is a poly(3-hydroxyalkanoate) resin.

[0176] [3] The crosslinked resin particles according to [1] or [2], wherein the crosslinked resin particles are crosslinked using a peroxide.

[0177] [4] The crosslinked resin particles according to [3], wherein the crosslinked resin particles are crosslinked in the presence of the peroxide and a polyfunctional compound.

[0178] [5] The crosslinked resin particles according to any one of [1] to [4], wherein the crosslinked resin particles are not foamed.

[0179] [6] The crosslinked resin particles according to any one of [1] to [5], wherein the content of the polyhydroxyalkanoate resin in 100% by weight of the resin component of the crosslinked resin particles is 80% by weight or more.

[0180] [7] The crosslinked resin particles according to any one of [1] to [6], wherein the gel fraction is 70% to 100%.

[0181] [8] An aqueous dispersion in which the crosslinked resin particles according to any one of [1] to [7] are dispersed in an aqueous medium.

[0182] [9] A thermoplastic resin composition comprising a thermoplastic resin and the crosslinked resin particles according to any one of [1] to [7].

[0183]

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

[0184]

[11] The thermoplastic resin composition according to

[10] , wherein the biodegradable resin includes a polyester resin.

[0185]

[12] The thermoplastic resin composition according to any one of [9] to

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

[0186]

[13] A molded article obtained by molding the thermoplastic resin composition according to any one of [9] to

[12] .

[0187]

[14] The molded article according to

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

[0188]

[15] A modifier for thermoplastic resins, comprising crosslinked resin particles, the crosslinked resin particles comprising a polyhydroxyalkanoate resin and a plasticizer, having a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of −10° C. or less.

[0189]

[16] A method for producing crosslinked resin particles, comprising: a preparation step of preparing an aqueous dispersion containing resin particles containing a polyhydroxyalkanoate resin, a plasticizer, and a peroxide; an impregnation step of impregnating the resin particles with the plasticizer; and a crosslinking step of decomposing the peroxide to crosslink the resin particles, wherein the crosslinked resin particles have a gel fraction of 50% or more, a volume average particle size of 0.10 μm to 10.00 μm, and a glass transition temperature of −10° C. or less.

[0190] 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.

[0191] [Measurement method and evaluation method] (Volume average particle diameter) The volume average particle diameter of the crosslinked resin particles or the uncrosslinked resin particles was measured using an aqueous dispersion of the crosslinked resin particles or the uncrosslinked resin particles as a sample. A Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd. was used as the measuring device. Specifically, the particle diameter and volume of each of the crosslinked resin particles (B) or the uncrosslinked resin particles in the aqueous dispersion of the crosslinked resin particles (B) or the uncrosslinked resin particles were measured using the above-mentioned device, and the volume average particle diameter was calculated from the measurement results based on the above-mentioned formula (1), i.e., formula (2).

[0192] (Gel Fraction) A dried product of crosslinked resin particles or uncrosslinked resin particles was added to chloroform to a concentration of 0.7% by weight, and the mixture was kept 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 its weight was measured 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 or uncrosslinked resin particles used in measurement) x 100 (%).

[0193] (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 (PHA) or crosslinked resin particles: (1) 2 mg to 3 mg of the resin (PHA) or crosslinked resin particles were packed 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 (PHA) or crosslinked resin particles.

[0194] (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.

[0195] (Impact energy (J) and fracture mode during puncture impact test) A 900 μm thick molded body (sheet molded body) prepared by the method described below was cured for 7 days under conditions of 23 ° C. and 50% RH, and then cut into a 60 mm x 60 mm shape to prepare a test piece. The test piece was subjected to a puncture impact test at a test temperature of 0 ° C. and a test speed of 2 m / s according to a method in accordance with ASTM D3763-15, and the impact energy (J) at the maximum impact point was measured. In addition, the fracture mode was evaluated based on the results obtained. Specifically, if the molded body fractured without plastic deformation, the fracture mode was judged to be "brittle", and if the molded body fractured with plastic deformation, the fracture mode was judged to be "ductile".

[0196] (Bleeding out of plasticizer in molded body) A molded body (sheet molded body) having a thickness of 500 μm produced by the method described below was left to stand in an oven at 120° C. for 2 hours and cooled to room temperature. Thereafter, the surface of the molded body was visually observed to determine whether or not bleed-out occurred. Specifically, when precipitation of plasticizer was observed on the surface of the molded body, it was determined that bleed-out was "present," and when precipitation of plasticizer was not observed on the surface of the molded body, it was determined that bleed-out was "absent."

[0197] (Confirmation of Change in Tg Over Time by DMA Measurement (Bleed-Out Test)) Molded bodies (sheet molded bodies) with a thickness of 500 μm, prepared by the method described below, were aged for one week or five weeks under conditions of 23°C and 50% RH. After each aging period, dynamic mechanical analysis (DMA) of the molded bodies was performed under the following conditions using a DVA-200 manufactured by IT Measurement & Control Co., Ltd. The maximum point (peak) of the loss tangent of the obtained results was taken as the Tg of each molded body. In the obtained results, if the plasticizer remains in the crosslinked resin particles, two peaks (maximum points) originating from the crosslinked resin particles (peak 1) and the matrix resin (peak 2) are clearly observed. In the obtained results, if the plasticizer leaks out from the crosslinked resin particles, it is confirmed that the peak (Tg) originating from the crosslinked resin particles is shifted to a higher temperature, and the peak (Tg) originating from the matrix resin is shifted to a lower temperature, compared to the results (peaks) when the plasticizer remains in the crosslinked resin particles. <Conditions> Measurement mode: Tensile Grip spacing: 20 mm Test piece width: 5 mm Measurement temperature: -40°C to +150°C Heating rate: 5°C / min Measurement frequency: 1 Hz.

[0198] [Raw materials for crosslinked resin particles] (1) Uncrosslinked resin particles P3HB3HH (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, Tg: −6.7° C. The weight average molecular weight and glass transition temperature of the resin were measured by the methods described above.

[0199] (2) Peroxide Di-sec-butyl peroxydicarbonate: "Luperox 225" manufactured by Arkema Yoshitomi Co., Ltd., 1-hour half-life temperature: 69°C (3) Polyfunctional compound Triallyl isocyanurate (4) Plasticizer Glycerin fatty acid ester: "Biocizer (registered trademark)" manufactured by Riken Vitamin Co., Ltd. Adipate ester compound: "DAIFATTY (registered trademark)-101" manufactured by Daihachi Chemical Industry Co., Ltd. [Method for producing crosslinked resin particles] The types of raw materials listed in Table 1 were used in the amounts listed in Table 1, and crosslinked resin particles of Examples 1 to 4 and 9 were produced according to the procedure described below.

[0200] (Preparation step) A water dispersion in which uncrosslinked resin particles are dispersed in water (100 parts by weight in terms of solid content), 200 parts by weight of deionized water, a predetermined amount of peroxide, 1 part by weight of sodium dioctyl sulfosuccinate, a predetermined amount of a polyfunctional compound, and a predetermined amount of a plasticizer were added to a glass vessel equipped with a stirrer, a baffle, a nitrogen inlet, a nitrogen outlet, and a thermometer to prepare a water dispersion. Next, stirring of the obtained water dispersion was started at room temperature, and simultaneously the atmosphere in the glass vessel was replaced with nitrogen.

[0201] (Impregnation Step) The content (aqueous dispersion) of the glass container was then stirred at room temperature for 1 hour, whereby the peroxide, the polyfunctional compound, and the plasticizer were impregnated into the uncrosslinked resin particles.

[0202] (Crosslinking step) Thereafter, the aqueous dispersion was heated to a temperature shown 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 shown in the time column of the crosslinking conditions in Table 1. By this operation, the crosslinking agent was reacted to obtain an aqueous dispersion in which crosslinked resin particles were dispersed in water.

[0203] 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.

[0204] The volume average particle size, gel fraction and glass transition temperature (Tg) of the crosslinked resin particles obtained in each of the Examples and Reference Examples were measured by the methods described above. The results are shown in Table 1.

[0205] [Raw materials for resin composition] (1) 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 (2) Crosslinked resin particles Crosslinked resin particles prepared in Examples 1 to 4 and 9 (3) Plasticizer Glycerin fatty acid ester: Biosizer manufactured by Riken Vitamin Co., Ltd.): 4.5 parts by weight (4) Nucleating agent Pentaerythritol: Neuizer P manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (5) Lubricant Behenic acid amide: BNT22H manufactured by Nippon Fine Chemical Co., Ltd.

[0206] [Method for producing resin composition] For each example and comparative example, the thermoplastic resin, crosslinked resin particles, plasticizer, 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 in a twin-screw extruder (KZW15TWIN-45WG, manufactured by Technovel Co., Ltd.) with the barrel temperature heated to 140°C to 165°C and a screw rotation speed of 80 rpm to obtain a melt-kneaded product (mixture). The obtained melt-kneaded product was dried in a dryer at 80°C for 4 hours to sufficiently reduce the moisture content, thereby obtaining a thermoplastic resin composition. Furthermore, the obtained thermoplastic resin composition was press-molded to a predetermined thickness at 165°C to produce a molded product (sheet molded product).

[0207] For the molded bodies (sheet molded bodies) of each Example and Comparative Example, the tensile impact strength, the impact energy (J) and fracture mode at the maximum impact point during the puncture impact test, the bleed-out of the plasticizer in the molded body, and the change in Tg over time by DMA measurement (bleed-out test) were measured and evaluated by the methods described above. The results are shown in Table 2.

[0208] It can be seen from Table 2 that the Tg values ​​obtained by DMA measurement did not change significantly between the Tg values ​​after 1 week and the Tg values ​​after 5 weeks for the molded articles of Examples 5 to 8. This means that the plasticizer remained in the crosslinked resin particles and did not bleed out in the molded articles of Examples 5 to 8.

[0209] In Comparative Example 2, a plasticizer was directly added to the thermoplastic resin in an amount approximately equal to the amount of plasticizer (plasticizer contained in the crosslinked resin particles) blended into a total of 100 parts by weight of the thermoplastic resin and crosslinked resin particles in Examples 5 and 7. Therefore, in Comparative Example 2, the Tg of the thermoplastic resin was lowered, and although the tensile impact strength was improved compared to Comparative Example 1, it was still far from the tensile impact strength of Examples 5 to 8. This demonstrates the high impact strength-improving effect of the plasticizer-containing crosslinked resin particles. Furthermore, Example 5 showed ductile fracture in a puncture impact test at 0°C, confirming that impact strength was also improved in low-temperature environments.

[0210] According to one embodiment of the present invention, biodegradable crosslinked resin particles can be provided, which can provide a resin composition capable of producing molded articles having excellent impact resistance and little or no plasticizer bleed-out. 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 polyhydroxyalkanoate resin and a plasticizer, having a gel fraction of 50% or more, a volume average particle size of 0.10 μm to 10.00 μm, and a glass transition temperature of -10°C or lower.

2. The crosslinked resin particles according to claim 1, wherein said polyhydroxyalkanoate resin is a poly(3-hydroxyalkanoate) resin.

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

4. The crosslinked resin particles according to claim 3, wherein said crosslinked resin particles are crosslinked in the presence of said peroxide and a polyfunctional compound.

5. The crosslinked resin particles according to claim 1, wherein said crosslinked resin particles are not foamed.

6. The crosslinked resin particles according to claim 1, wherein the content of said polyhydroxyalkanoate resin in 100% by weight of the resin component of said crosslinked resin particles is 80% by weight or more.

7. The crosslinked resin particles according to claim 1, wherein the gel fraction is 70% to 100%.

8. An aqueous dispersion in which the crosslinked resin particles according to any one of claims 1 to 7 are dispersed in an aqueous medium.

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

10. The thermoplastic resin composition according to claim 9, wherein the thermoplastic resin comprises a biodegradable resin.

11. The thermoplastic resin composition according to claim 10, wherein the biodegradable resin comprises a polyester-based resin.

12. The thermoplastic resin composition according to claim 9, further comprising a crystal nucleating agent and / or a lubricant.

13. A molded article obtained by molding the thermoplastic resin composition according to claim 9.

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

15. A modifier for thermoplastic resins, comprising crosslinked resin particles, the crosslinked resin particles comprising a polyhydroxyalkanoate resin and a plasticizer, the crosslinked resin particles having a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of -10°C or less.

16. A method for producing crosslinked resin particles, comprising: a preparation step of preparing an aqueous dispersion containing resin particles containing a polyhydroxyalkanoate resin, a plasticizer and a peroxide; an impregnation step of impregnating the resin particles with the plasticizer; and a crosslinking step of decomposing the peroxide and crosslinking the resin particles, wherein the crosslinked resin particles have a gel fraction of 50% or more, a volume average particle diameter of 0.10 μm to 10.00 μm, and a glass transition temperature of -10°C or less.