Resin powder and method for producing same

Abstract

The resin powder having a median diameter of 20-1000 [mu] m contains a thermoplastic resin (A) and crosslinked resin particles (B). The crosslinked resin particles (B) contain a polyhydroxyalkanoate resin, and have a gel fraction of 50% or more and a volume average particle diameter of 0.1 [mu] m to 10 [mu] m (inclusive). The resin powder can be produced by spray-drying an aqueous dispersion containing a thermoplastic resin (A) and crosslinked resin particles (B).

Description

Technical Field

[0001] The present invention relates to a resin powder containing cross-linked resin particles and a method for producing the same. Background Art

[0002] It is known that introducing a cross-linked structure into a resin can improve its hardness, heat resistance, solvent resistance, etc. Small-sized resin particles formed from resins having such a cross-linked structure are used in various applications such as thermoplastic resin modifiers, spacers, anti-blocking agents, and matting agents.

[0003] Known resin materials for forming such cross-linked resin particles include acrylic resins, acrylic silicon resins, and polystyrene (for example, see Patent Documents 1 and 2).

[0004] On the other hand, plastic waste is burdening the global environment through its impact on ecosystems, the generation of harmful gases during combustion, and global warming due to the large amount of heat from combustion. As a material that can address these issues, the development of biodegradable plastics is gaining momentum.

[0005] Patent Document 3 describes crosslinking poly(3-hydroxyalkanoate), a type of biodegradable plastic, by melt-kneading it in the presence of an organic peroxide. However, this document describes using the crosslinked resin produced by melt-kneading to form films and sheets, but does not describe the production of small-diameter crosslinked resin particles.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-56770

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-82191

[0010] Patent Document 3: International Publication No. 2019 / 022008 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] Until now, there has been no known small-diameter cross-linked resin particles made of biodegradable plastic and showing biodegradability.

[0013] The present inventors have successfully produced crosslinked resin particles made of a biodegradable polyhydroxyalkanoate resin in an aqueous dispersion. These crosslinked resin particles are expected to be useful as environmentally friendly crosslinked resin particles that address the problem of plastic waste.

[0014] However, when attempting to separate the crosslinked resin particles from the aqueous dispersion, as water evaporates, the crosslinked resin particles stick to each other to become rubbery sheets, massive solids, and are difficult to separate in a form that is easy to handle.

[0015] In view of the above, an object of the present application is to provide crosslinked resin particles formed of a polyhydroxyalkanoate-based resin in a form that is easy to handle.

[0016] Method for solving the problem

[0017] The present inventors conducted intensive research and as a result, found that by preparing an aqueous dispersion in which crosslinked resin particles formed of a polyhydroxyalkanoate-based resin are dispersed together with a thermoplastic resin, and spray drying the aqueous dispersion, a resin powder containing crosslinked resin particles in a form that is easy to handle can be obtained, and thus completed the present application.

[0018] That is, the present application relates to a resin powder having a value particle diameter of 20 to 1000 μm, the resin powder containing a thermoplastic resin (A) and crosslinked resin particles (B), the crosslinked resin particles (B) containing a polyhydroxyalkanoate-based resin and having a gel fraction of 50% or more and a volume average particle diameter of 0.1 μm or more and 10 μm or less.

[0019] Further, the present application also relates to a production method for producing the above resin powder, the method including a step of preparing an aqueous dispersion containing a thermoplastic resin (A) and crosslinked resin particles (B), and a step of spray drying the aqueous dispersion.

[0020] Effects of the invention

[0021] According to the present application, crosslinked resin particles formed of a polyhydroxyalkanoate-based resin can be provided in a form that is easy to handle. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present application will be described, but the present application is not limited to the following embodiments.

[0023] The resin powder of the present embodiment contains at least a thermoplastic resin (A) and crosslinked resin particles (B). Since the resin powder is in a form having a particle diameter within a specific range, it is easy to handle.

[0024] First, the crosslinked resin particles (B) will be described.

[0025] < Crosslinked resin particles (B) >

[0026] The crosslinked resin particles (B) are particles formed using a polyhydroxyalkanoate-based resin as a main resin component. Hereinafter, the polyhydroxyalkanoate-based resin will sometimes be referred to simply as "PHA".

[0027] <pha>

[0028] "PHA" is a general term for polymers having hydroxyalkanoic acid as a monomer unit, and is generally biodegradable. The PHA is an aliphatic polyester, preferably a polyester not containing an aromatic ring.

[0029] The PHA is not particularly limited, and examples thereof include, for example, polyglycolic acid, poly(3-hydroxyalkanoate)-based resins, poly(4-hydroxyalkanoate)-based resins, and the like. As the PHA, one kind can be used alone, or two or more kinds can be used in combination. Among them, the poly(3-hydroxyalkanoate)-based resins are preferred. Hereinafter, the poly(3-hydroxyalkanoate)-based resins are sometimes referred to simply as "P3HA".

[0030] The P3HA described above is a polyhydroxyalkanoate containing a 3-hydroxyalkanoic acid repeating unit represented by the formula: [-CHR-CH2-CO-O-] (in the formula, R is a C n H 2n+1 alkyl group represented by the formula: -CH2-CH2-CH2- (n is an integer of 1 or more and 15 or less).) as an essential repeating unit. The P3HA described above preferably contains the 3-hydroxyalkanoic acid repeating unit described above in an amount of 50 mol% or more, more preferably 70 mol% or more, in all monomer repeating units (100 mol%).

[0031] The P3HA is not particularly limited, and can be a homopolymer containing the repeating unit described above, or a copolymer containing the repeating unit described above. As the copolymer described above, examples thereof include, for example, a copolymer of 3-hydroxybutyric acid (hereinafter, sometimes referred to as "3HB") and one or more kinds of monomers selected from the group consisting of 3-hydroxypropionic acid, 3-hydroxyvaleric 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. As other examples of the copolymer described above, a copolymer of 3HB and one or more kinds of monomers selected from the group consisting of 4-hydroxybutyric acid, 4-hydroxyvaleric 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 can be given.

[0032] Specific examples of the homopolymer described above or the copolymer described above are not limited, and examples thereof include poly(3-hydroxybutyrate) (abbreviated as: P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviated as: P3HB3HH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviated as: P3HB4HB), and the like.

[0033] As the P3HA, one kind can be used alone, or two or more kinds can be used in combination.

[0034] In the present specification, "poly(X-co-Y)" means a copolymer containing X repeating units and Y repeating units, and means a copolymer formed by copolymerizing a monomer that is a source of X repeating units and a monomer that is a source of Y repeating units.

[0035] In addition, in the production of P3HA, there is a case where a trace amount (less than 1 mol% level) of a monomer is copolymerized, but in a case where the physical properties of the obtained P3HA are not greatly affected, it is considered that the monomer is not copolymerized, and is referred to by a name not containing the monomer.

[0036] P3HA can be produced by a microorganism. P3HA produced by such a microorganism is usually P3HA formed only of D-body (R-body) hydroxyalkanoic acid repeating units. Among P3HA produced by a microorganism, from the viewpoint of ease of industrial production, P3HB, P3HB3HH, P3HB4HB, more preferably P3HB3HH, P3HB4HB is preferable.

[0037] In a case where the P3HA contains 3-hydroxybutyric acid (3HB) repeating units, from the viewpoint of balance between flexibility and strength, the composition ratio of 3HB repeating units is preferably 60 to 99 mol%, more preferably 61 to 97 mol%, further preferably 62 to 95 mol% in the total monomer repeating units (100 mol%). By making the composition ratio of 3HB repeating units 60 mol% or more, the crosslinked resin particles (B) or the treatment of the resin particles before crosslinking treatment becomes easy. On the other hand, by making the composition ratio of 3HB repeating units 99 mol% or less, there is a tendency to easily ensure the flexibility of the crosslinked resin particles (B). Note that the monomer composition ratio of P3HA can be measured by gas chromatography or the like (for example, refer to International Publication No. 2014 / 020838). As P3HA, two or more kinds of P3HA having different composition ratios of 3HB repeating units can also be used in combination.

[0038] As a microorganism that produces P3HA, any microorganism having the ability to produce P3HA can be used without particular limitation. For example, as a P3HB-producing bacterium, the earliest Bacillus megaterium discovered in 1925, and other natural microorganisms such as Cupriavidus necator (old classification: Alcaligenes eutrophus, Ralstonia eutropha), Alcaligenes latus are known. These microorganisms accumulate P3HB in the bacterial cells.

[0039] Further, as a production strain of a copolymer of 3HB and other hydroxyalkanoate, Aeromonas caviae as a P3HB3HH production strain, Alcaligenes eutrophus as a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) production strain, and the like are known. In particular, in order to improve the productivity of P3HB3HH, Alcaligenes eutrophus AC32 strain (Alcaligenes eutrophus AC32, FERM BP-6038) into which a gene of a P3HA synthase group is introduced is preferred (T. Fukui, Y. Doi, J. Bacteriol., 179, p4821-4830 (1997)). A microbial cell is used in which P3HA is accumulated in the cell by culturing such a microorganism under suitable conditions. Further, in addition to the above, a genetically recombined microorganism into which various P3HA synthesis-related genes are introduced depending on the P3HA desired to be produced can be used, provided that the culture conditions including the kind of the substrate are optimized.

[0040] The molecular weight of the PHA is not particularly limited, and the weight average molecular weight is preferably from 50,000 to 3,000,000, preferably from 100,000 to 2,000,000, and more preferably from 150,000 to 1,500,000. By setting the weight average molecular weight to 50,000 or more, the tendency of the strength of the crosslinked resin particles (B) to decrease or the tendency of the tackiness due to a low molecular weight component can be avoided. On the other hand, by setting the weight average molecular weight to 3,000,000 or less, the production and handling of the PHA can be made easy. The value of the weight average molecular weight is a value measured before the crosslinking treatment of the PHA.

[0041] The method for measuring the weight average molecular weight described above can use gel permeation chromatography (GPC) ("High Performance Liquid Chromatograph 20A System" manufactured by Shimadzu Corporation), and a polystyrene gel ("K-G 4A", "K-806M", and the like manufactured by Showa Denko K.K.) is used as the column, with chloroform as the mobile phase, and the molecular weight after conversion to polystyrene is calculated. At this time, the standard curve can be prepared using polystyrene having a weight average molecular weight of 31,400, 197,000, 668,000, and 1,920,000. As the column for this GPC, a suitable column for measuring the molecular weight described above can be used.

[0042] <gel fraction>

[0043] The crosslinked resin particles (B) have a crosslinked structure in which the molecular chains of the PHA are bonded to each other. Due to having such a crosslinked structure in an amount of 50% or more, the crosslinked resin particles (B) exhibit a high gel fraction, specifically a gel fraction of 50% or more. Due to exhibiting such a high gel fraction, the hardness, heat resistance, solvent resistance, and the like of the resin particles containing the PHA can be improved.

[0044] The value of the above-mentioned gel fraction is preferably 60% or more, more preferably 70% or more, further preferably 75% or more, and particularly preferably 80% or more. In addition, it can be 85% or more, and can be 90% or more. The upper limit of the above-mentioned gel fraction is not particularly limited, and can be 100% or less, but from the viewpoint of production efficiency of the crosslinked resin particles (B), it is preferably 99.5% or less, and more preferably 99% or less. In addition, it can be 98% or less, can be 97% or less, and can be 96% or less.

[0045] The above-mentioned gel fraction is a value determined as described below. A dry substance of the crosslinked resin particles (B) is added to chloroform at a concentration of 0.7% by weight, and is dissolved at 60°C for 30 minutes to obtain a chloroform solution. Thereafter, after standing at room temperature for 3 hours, the above-mentioned chloroform solution is filtered with a membrane filter having a pore size of 0.45 μm. The gel remaining on the filter is dried, and the weight of the filter together with the gel is determined, and the gel fraction is calculated using the following formula.

[0046] Formula: Gel fraction = (weight of filter including dried gel - weight of filter alone) / weight of crosslinked resin particles used in the determination x 100 (%)

[0047] <Average particle diameter>

[0048] The volume average particle diameter of the crosslinked resin particles (B) is in the range of 0.1 μm or more and 10 μm or less. By having such a particle diameter, the resin powder of the present embodiment having a particle diameter in a specific range can be formed, and can be used for various uses as described later. From the viewpoint of practical use opportunities, the lower limit value of the above-mentioned particle diameter is preferably 0.1 μm or more, more preferably 0.3 μm or more, and further preferably 0.5 μm or more. In addition, from the viewpoint of productivity (PHA production, crosslinking treatment, etc.), the upper limit value of the above-mentioned particle diameter is preferably 8 μm or less, and more preferably 5 μm or less.

[0049] The above-mentioned volume average particle diameter is a value determined in a state where the crosslinked resin particles (B) are dispersed in a water-based solvent. As a measuring device, a general measuring device can be used, and as an example of such a device, Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd. can be given.

[0050] <Peroxide>

[0051] The crosslinked form of the crosslinked resin particles (B) is not particularly limited, and crosslinked resin particles crosslinked using a peroxide are preferably used. When a peroxide is used, radicals generated due to decomposition of the peroxide act on the molecules of PHA, and the molecular chains of PHA are directly bonded to each other, and thus the above-mentioned crosslinked structure can be formed.

[0052] The above peroxide can be an organic peroxide or an inorganic peroxide. An organic peroxide is preferred because it can more efficiently increase the gel fraction.

[0053] As the above organic peroxide, at least one selected from the group consisting of diacyl peroxides, alkylperoxy esters, dialkyl peroxides, hydroperoxides, peroxyketals, peroxy carbonates, and peroxydicarbonates is preferably used in consideration of the heating temperature, time, and the like during crosslinking treatment.

[0054] Specific examples of such organic peroxides include butyl peroxyneododecanoate, octanoyl peroxide, dilauroyl peroxide, succinic acid 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, butyl peroxybenzoate, butyl bis(butylperoxy)valerate, diisopropylphenyl peroxide, di-tert-hexyl peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyisobutyrate, tert-butyl peroxypivalate, tert-hexyl peroxide, Pivalate, tert-Butylperoxymethylmonocarbonate, tert-Amylperoxymethylmonocarbonate, tert-Hexylperoxymethylmonocarbonate, tert-Heptylperoxymethylmonocarbonate, tert-Octylperoxymethylmonocarbonate, 1,1,3,3-Tetramethylbutylperoxymethylmonocarbonate, tert-Butylperoxyethylmonocarbonate, tert-Amylperoxyethylmonocarbonate, tert-Hexylperoxyethylmonocarbonate, tert-Heptylperoxyethylmonocarbonate, tert-Octylperoxyethylmonocarbonate, 1,1,3,3-Tetramethylbutylperoxyethylmonocarbonate, tert-Butylperoxy-n-propylmonocarbonate, tert-Amylperoxy-n-propylmonocarbonate, tert-Hexylperoxy-n-propylmonocarbonate, tert-Heptylperoxy-n-propylmonocarbonate, tert-Octylperoxy 1,1,3,3-tetramethylbutyl peroxy-n-propyl monocarbonate, tert-butyl peroxy-isopropyl monocarbonate, tert-amyl peroxy-isopropyl monocarbonate, tert-hexyl peroxy-isopropyl monocarbonate, tert-heptyl peroxy-isopropyl monocarbonate, tert-octyl peroxy-isopropyl monocarbonate, 1,1,3,3-tetramethylbutyl peroxy-n-butyl monocarbonate, tert-amyl peroxy-n-butyl monocarbonate, tert-hexyl peroxy-n-butyl monocarbonate, tert-heptyl peroxy-n-butyl monocarbonate, tert-octyl peroxy-n-butyl monocarbonate, 1,1,3,3-tetramethylbutyl peroxy-n-butyl monocarbonate, tert-butyl peroxy-isobutyl monocarbonate, tert-amyl peroxy-isobutyl monocarbonate Butyl monocarbonate, tert-hexyl peroxyisobutyl monocarbonate, tert-heptyl peroxyisobutyl monocarbonate, tert-octyl peroxyisobutyl monocarbonate, 1,1,3,3-tetramethylbutyl peroxyisobutyl monocarbonate, tert-butyl peroxysec-butyl monocarbonate, tert-amyl peroxysec-butyl monocarbonate, tert-hexyl peroxysec-butyl monocarbonate, tert-heptyl peroxysec-butyl monocarbonate, tert-octyl peroxysec-butyl monocarbonate, 1,1,3,3-tetramethylbutyl peroxysec-butyl monocarbonate, tert-butyl peroxytert-butyl monocarbonate, tert-amyl peroxytert-butyl monocarbonate, tert-hexyl peroxytert-butyl monocarbonate, tert-heptyl peroxytert-butyl monocarbonate, tert-octyl peroxytert-butyl monocarbonate, 1,1,3,3-tetramethylbutyl peroxysec-butyl monocarbonate3-tetramethylbutyl peroxy-tert-butyl monocarbonate, tert-butyl peroxy-2-ethylhexyl monocarbonate, tert-amyl peroxy-2-ethylhexyl monocarbonate, tert-hexyl peroxy-2-ethylhexyl monocarbonate, tert-heptyl peroxy-2-ethylhexyl monocarbonate, tert-octyl peroxy-2-ethylhexyl monocarbonate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexyl monocarbonate, diisobutyl peroxide, cumyl peroxy-neodecanate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxy-neodecanate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, tert-hexyl peroxy-neodecanate, tert-butyl peroxy-neodecanate, tert-butyl peroxy-neohexanoate, tert-hexyl peroxy-neopentanoate, tert-butyl peroxy-neopentanoate, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5-dimethyl-2,5-bis(2-ethylhexanoyl peroxy)hexane, tert-hexyl peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, tert-butyl peroxy-2-ethylhexyl carbonate, tert-butyl peroxy-isopropyl carbonate, 1,6-bis(tert-butyl peroxy carbonyloxy)hexane, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, tert-amyl peroxy-3,5,5-trimethylhexanoate, 2,2-bis(4,4-di-tert-butyl peroxy cyclohexyl)propane, 2,2-di-tert-butyl peroxy butane, and the like. The organic peroxide can be used alone or in combination of two or more.

[0055] Among them, the organic peroxide is preferably tert-butyl peroxy-isopropyl monocarbonate, tert-amyl peroxy-isopropyl monocarbonate, tert-hexyl peroxy-isopropyl monocarbonate, tert-butyl peroxy-2-ethylhexyl monocarbonate, tert-amyl peroxy-2-ethylhexyl monocarbonate, tert-hexyl peroxy-2-ethylhexyl monocarbonate, tert-amyl peroxy-isopropyl monocarbonate, di-tert-hexyl peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-isobutanoate, tert-hexyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, tert-butyl peroxy-neopentanoate, tert-hexyl peroxy-neopentanoate, tert-butyl peroxy-neodecanoate, tert-hexyl peroxy-neodecanoate, and 1,1,3,3-tetramethylbutyl peroxy-neodecanoate, because they can efficiently perform crosslinking of PHA.

[0056] Since the heating temperature at the time of the above peroxide crosslinking treatment can be set low, a compound showing a 1-hour half-life temperature of 200°C or lower, more preferably 170°C or lower, and further preferably 140°C or lower is preferred. The lower limit can be 50°C or higher, 60°C or higher, or 70°C or higher.

[0057] As the organic peroxide showing a 1-hour half-life temperature like this, tert-butyl peroxy isopropyl monocarbonate, tert-butyl peroxy 2-ethylhexyl monocarbonate, di-sec-butyl peroxy dicarbonate, tert-butyl peroxy 2-ethylhexanoate, tert-butyl peroxy isobutyrate, tert-hexyl peroxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate, tert-butyl peroxy pivalate, tert-hexyl peroxy pivalate, tert-butyl peroxy neodecanoate, tert-hexyl peroxy neodecanoate, and 1,1,3,3-tetramethylbutyl peroxy neodecanoate are particularly preferred.

[0058] In the case where the above peroxide is an inorganic peroxide, as the inorganic peroxide, hydrogen peroxide, potassium peroxide, calcium peroxide, sodium peroxide, magnesium peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, and the like can be exemplified in consideration of the heating temperature and time at the time of the crosslinking treatment. Among them, from the viewpoints of ease of handling and having a decomposition temperature suitable for the heating temperature at the time of the crosslinking treatment, hydrogen peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate are preferred. The inorganic peroxide can be used alone as one kind or in combination with two or more kinds. In addition, an organic peroxide and an inorganic peroxide can be used in combination.

[0059] <Multi-functional compound>

[0060] The crosslinking structure in the crosslinked resin particles (B) can be introduced using only a peroxide or using both a peroxide and a multi-functional compound. The latter can increase the gel fraction of the crosslinked resin particles (B) with a small amount of peroxide.

[0061] The above multi-functional compound refers to a compound having two or more functional groups capable of crosslinking PHA in one molecule. There is no particular limitation, and a compound having reactivity with radicals generated by a peroxide is preferred, and a compound having two or more radical-reactive groups in one molecule is particularly preferred. As the radical-reactive group, at least one selected from a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group is preferred.

[0062] The multifunctional compound such as this is not particularly limited, and examples thereof include: allyl (meth)acrylate; allyl alkyl (meth)acrylate; allyloxyalkyl (meth)acrylate; 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, pentaerythritol (meth)acrylate, and the like having two or more (meth)acryl groups; divinylbenzene, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, divinylbenzene, and the like. The allyl (meth)acrylate, triallyl isocyanurate, butanediol di(meth)acrylate, and divinylbenzene are preferable, and the allyl (meth)acrylate and triallyl isocyanurate are particularly preferable.

[0063] When a crosslinked structure is formed in the presence of a multifunctional compound, a structure derived from the multifunctional compound can be generally included in the obtained crosslinked resin particle (B). At this time, the molecular chains of the PHA are bonded to each other through the structure derived from the multifunctional compound.

[0064] The crosslinked resin particle (B) can be formed only of the PHA having a crosslinked structure, or can further include a component other than the PHA having a crosslinked structure. As the component other than the PHA having a crosslinked structure, examples thereof include: a resin other than the PHA, an antioxidant, a hydrolysis inhibitor, an antiblocking agent, a crystallization nucleating agent, and a UV absorber.

[0065] The proportion of the PHA in the crosslinked resin particle (B) is not particularly limited, and can be 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. It can also be 99% by mass or more. The upper limit is not particularly limited, and can be 100% by mass or less.

[0066] As the resin other than PHA, for example, polycaprolactone (PCL), polylactic acid (PLA), aliphatic polyester formed by polycondensation of aliphatic diol and aliphatic dicarboxylic acid, aliphatic-aromatic polyester using both aliphatic compound and aromatic compound as monomers, and the like can be given. As examples of the above aliphatic polyester, polyethylene succinate, polybutylene succinate (PBS), polyhexamethylene succinate, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polybutylene succinate-adipate (PBSA), polyethylene sebacate, polybutylene sebacate, and the like can be given. As examples of the above aliphatic-aromatic polyester, poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene sebacate-co-terephthalate), poly(butylene azelate-co-terephthalate), poly(butylene succinate-co-terephthalate) (PBST), and the like can be given. The above other resin can be used alone as one kind, or two or more kinds can be used in combination.

[0067] Unlike the foamed resin particles disclosed in International Publication No. 2007 / 049694 and International Publication No. 2019 / 146555, the crosslinked resin particles (B) are not foamed, i.e., preferably substantially do not contain bubbles inside the particles.

[0068] In the case of not being foamed, the apparent density of the crosslinked resin particles (B) shows a large value, preferably exceeds 0.6 g / cm 3 , more preferably 0.7 g / cm 3 , and further preferably 0.9 g / cm 3 or more. The apparent density of the crosslinked resin particles (B) can be determined according to the method described in JIS K0061 (Method of testing density and specific gravity of chemical products), or JIS Z8807 (Method of testing density and specific gravity of solid).

[0069] The average weight per 1 particle of the crosslinked resin particles (B) is not particularly limited, and the volume average particle diameter of the crosslinked resin particles (B) is small when the particle diameter is 10 μm or less, and thus is a value far lower than 0.1 mg.

[0070] <Method of producing crosslinked resin particles (B)>

[0071] An example of the method of producing the crosslinked resin particles (B) will be specifically described. The crosslinked resin particles (B) can be produced by crosslinking PHA in the presence of a peroxide in an aqueous dispersion liquid containing PHA particles before crosslinking treatment. In order to more efficiently crosslink PHA, it is preferable to heat the aqueous dispersion liquid of PHA particles containing a peroxide at a temperature suitable for the decomposition of the peroxide.

[0072] More specifically, the method for producing the crosslinked resin particles (B) preferably includes: a step (1) of preparing an aqueous dispersion of PHA particles in which PHA particles before crosslinking treatment are dispersed in water; a step (2) of adding a peroxide to the aqueous dispersion of PHA particles to impregnate the PHA particles with the peroxide; and a step (3) of heating the aqueous dispersion of PHA particles impregnated with the peroxide to a heating temperature to crosslink the PHA. Further, it is more preferable to include a step (4) of maintaining the heating temperature after the addition of the entire peroxide.

[0073] In the step (1), the aqueous dispersion of PHA particles is an aqueous dispersion obtained by destroying the microbial cells in the culture solution after the PHA-producing microorganism is cultured to accumulate PHA in the microbial cells, and separating and removing the microbial cell components. Alternatively, the aqueous dispersion can be an aqueous dispersion obtained by concentrating or diluting the aqueous dispersion. By such a method, the period from the production of PHA particles by the culture of the PHA-producing microorganism to the crosslinking treatment can be performed without separating the PHA particles from water.

[0074] In addition, the aqueous dispersion of PHA particles can be produced by dispersing the dried PHA particles in water. In addition to water, the aqueous dispersion can contain an organic solvent that is miscible with water, as described later.

[0075] As for the above aqueous dispersion, the volume average particle diameter of the PHA particles is preferably in the same range as the volume average particle diameter of the above crosslinked resin particles (B). In the case where the PHA particles are PHA particles produced by a PHA-producing microorganism, the volume average particle diameter thereof can generally be in the above range, and thus an aqueous dispersion of PHA particles having a desired volume average particle diameter can be obtained even without a special process for adjusting the particle diameter.

[0076] The concentration of the PHA particles in the aqueous dispersion is not particularly limited and can be appropriately set, and can be, for example, about 1 to 70% by weight, preferably about 5 to 50% by weight.

[0077] In order to improve the dispersibility of the PHA particles and allow the crosslinking reaction to proceed uniformly, the aqueous dispersion of the PHA particles preferably contains a dispersant. As the dispersant, anionic surfactants such as dioctyl sodium sulfosuccinate, sodium dodecyl sulfate, sodium lauryl sulfate, and sodium oleate; cationic surfactants such as lauryltrimethylammonium chloride; nonionic surfactants such as fatty acid glycerides, sorbitan fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene polyoxypropylene glycols; water-soluble polymers such as polyvinyl alcohol, ethylene-modified polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, polymethacrylic acid, and sodium polymethacrylate; and the like can be given. These dispersants can be used alone or in combination with two or more.

[0078] When a dispersant is used, the amount of addition is not particularly limited, and for example, 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, and particularly preferably 0.5 to 3 parts by weight, relative to 100 parts by weight of the PHA particles.

[0079] In the process (2), a peroxide is added to the aqueous dispersion of the PHA particles obtained in the process (1) to impregnate the peroxide into the PHA particles. As the peroxide, the above-described peroxide can be used. The peroxide can be added in various forms such as a solid, a liquid, and the like. Alternatively, a liquid substance diluted with a diluent or the like can be added. The peroxide can be added at once, continuously, or in portions.

[0080] In this process (2), when a peroxide and the above-described multifunctional compound are used in combination, the multifunctional compound is preferably also added to the aqueous dispersion of the PHA particles. As the multifunctional compound, the above-described substance can be used. The multifunctional compound can be added in various forms such as a solid, a liquid, and the like. Alternatively, a liquid substance diluted with a diluent or the like can be added. The multifunctional compound can be added at once, continuously, or in portions.

[0081] In order to impregnate the peroxide and the optional multifunctional compound into the PHA particles, after or simultaneously with the addition of these compounds to the aqueous dispersion of the PHA particles, the temperature of the aqueous dispersion is set to, for example, 0°C or higher and lower than a temperature suitable for the decomposition of the peroxide to be used in the next process (3), and the temperature is maintained while the aqueous dispersion is stirred for, for example, about 1 minute to 5 hours. The temperature of the aqueous dispersion during the impregnation can be, for example, about 10°C to 60°C.

[0082] The amount of peroxide used can be appropriately set in consideration of the gel fraction of the crosslinked resin particles (B), for example, preferably 0.01 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, further preferably 0.3 to 5 parts by weight, particularly preferably 0.5 to 3 parts by weight, relative to 100 parts by weight of the PHA particles.

[0083] According to the production method of crosslinking PHA particles in an aqueous dispersion using peroxide, crosslinking is performed while maintaining the particle diameter (volume) before crosslinking, and crosslinked resin particles are easily obtained. On the other hand, in a method of melt-kneading in the presence of peroxide to crosslink the resin, it is sometimes difficult to achieve this.

[0084] In addition, according to the production method of crosslinking PHA particles in an aqueous dispersion using peroxide, temperature rise due to heat generated in the crosslinking reaction is easily controlled, and crosslinked resin particles having a stable crosslinked structure (quality) are advantageously obtained safely and efficiently.

[0085] In addition, the amount of the multifunctional compound used can also be appropriately set in consideration of the gel fraction of the crosslinked resin particles (B), for example, preferably 0.01 to 20 parts by weight, more preferably 0.05 to 15 parts by weight, further preferably 0.1 to 10 parts by weight, more further preferably 0.2 to 5 parts by weight, particularly preferably 0.3 to 3 parts by weight, relative to 100 parts by weight of the PHA particles.

[0086] In the process (3), the aqueous dispersion containing PHA particles impregnated with peroxide is heated to a temperature suitable for decomposition of the peroxide. The heating temperature is preferably in the range of about 25°C above and below the temperature of 1 hour half-life period shown by the above peroxide. Specifically, the heating temperature is preferably 30 to 140°C, more preferably 50 to 135°C, further preferably 60 to 130°C. According to the present method, PHA can be crosslinked at a lower temperature than the melting temperature of PHA, and thus degradation of PHA due to heating during crosslinking treatment can be avoided.

[0087] In the process (4) of bonding, the above heating temperature is preferably maintained. Thus, the crosslinking reaction using peroxide can be sufficiently performed. The time for which the above heating temperature is maintained is not particularly limited, and is preferably 1 minute to 15 hours, more preferably 1 hour to 10 hours.

[0088] By carrying out the above processes (1) to (4), an aqueous dispersion of crosslinked resin particles (B) can be obtained. Using this aqueous dispersion, the resin powder of the present embodiment can be produced. This will be described in detail later.

[0089] <Thermoplastic Resin (A)>

[0090] The resin powder of the present embodiment contains a thermoplastic resin (A) in addition to the crosslinked resin particles (B). By containing the thermoplastic resin (A), a resin powder that is excellent in handleability can be formed even though the crosslinked resin particles (B) are contained.

[0091] As the thermoplastic resin (A), any thermoplastic resin that can form a resin powder together with the crosslinked resin particles (B) can be used without particular limitation. Specifically, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, polytetrafluoroethylene, polymethyl methacrylate, AS resin, polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyester resin, cyclic polyolefin, and the like can be given. One of these thermoplastic resins can be used alone, or two or more of them can be used in combination.

[0092] As the thermoplastic resin (A), a polyester resin is particularly preferable from the viewpoint of good compatibility with the crosslinked resin particles (B) formed of a polyhydroxyalkanoate-based resin. As the polyester resin, PHA such as poly(glycolic acid), poly(3-hydroxyalkanoate)-based resin, poly(4-hydroxyalkanoate)-based resin, polylactic acid, aliphatic polyester such as polyester formed of polycondensation of an aliphatic diol and an aliphatic dicarboxylic acid, and aliphatic-aromatic polyester formed of both an aliphatic compound and an aromatic compound as monomers can be given. As examples of the aliphatic polyester other than PHA, polycaprolactone, polyethylene succinate, polybutylene succinate (PBS), polyhexamethylene succinate, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polybutylene succinate adipate (PBSA), polyethylene sebacate, polybutylene sebacate, and the like can be given. As examples of the aliphatic-aromatic polyester, poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene sebacate-co-terephthalate), poly(butylene azelate-co-terephthalate), poly(butylene succinate-co-terephthalate) (PBST), polyethylene furandicarboxylate, and the like can be given. One of these polyester resins can be used alone, or two or more of them can be used in combination.

[0093] Since the crosslinked resin particles (B) are formed of PHA that exhibits biodegradability, the thermoplastic resin (A) also preferably contains a resin that exhibits biodegradability. In this case, the biodegradability of the entire resin powder can be improved.

[0094] In addition, when the crosslinked resin particles (B) are manufactured from a plant-derived raw material, from the viewpoint of resource recycling, the thermoplastic resin (A) is also preferably a resin manufactured from a plant-derived raw material.

[0095] When the thermoplastic resin (A) contains the biodegradable resin, the content ratio in the entire thermoplastic resin (A) is preferably 10 to 100% by mass, more preferably 30% by mass or more, further preferably 50% by mass or more, more further preferably 70% by mass or more, and particularly preferably 90% by mass or more.

[0096] From the viewpoint of easiness in manufacturing and good compatibility with the crosslinking resin particle (B), and good workability of the resin powder, the biodegradable resin used as the thermoplastic resin (A) preferably contains the above-described aliphatic polyester, and particularly preferably contains PHA and / or polylactic acid. Furthermore, the PHA used as the thermoplastic resin (A) preferably does not have a crosslinking structure.

[0097] When the thermoplastic resin (A) contains PHA and / or polylactic acid, the content ratio in the entire thermoplastic resin (A) is preferably 10 to 100% by mass, more preferably 30% by mass or more, further preferably 50% by mass or more, more further preferably 70% by mass or more, and particularly preferably 90% by mass or more.

[0098] The PHA that can be used as the thermoplastic resin (A) is not particularly limited, and examples thereof include polyglycolic acid, P3HA, poly(4-hydroxyalkanoate) resins, and the like. As the PHA, one kind can be used alone, or two or more kinds can be used in combination. Among them, P3HA is particularly preferable.

[0099] The P3HA that can be used as the thermoplastic resin (A) is the same as the P3HA related to the crosslinking resin particle (B), and various P3HAs described above can be used. The P3HA used as the thermoplastic resin (A) is preferably different from the P3HA used in relation to the crosslinking resin particle (B), and more preferably is a resin that is harder than the P3HA used in relation to the crosslinking resin particle (B).

[0100] When the P3HA used as the thermoplastic resin (A) contains 3-hydroxybutyric acid (3HB) repeating units, from the viewpoint of balance between flexibility and strength, the composition ratio of the 3HB repeating units in the total monomer repeating units (100 mol%) is preferably 80 to 99 mol%, and more preferably 82 to 97 mol%. By making the composition ratio of the 3HB repeating units 80 mol% or more, the rigidity of the P3HA can be further improved. On the other hand, by making the composition ratio of the 3HB repeating units 99 mol% or less, the P3HA has a tendency that the flexibility is further improved. As the P3HA, two or more kinds of P3HA having different composition ratios of 3HB repeating units can be used in combination.

[0101] The molecular weight of the PHA used as the thermoplastic resin (A) is not particularly limited, and the weight average molecular weight is preferably 50,000 to 3,000,000, preferably 100,000 to 2,000,000, and more preferably 150,000 to 1,500,000. By setting the weight average molecular weight to 50,000 or more, the resin powder of the present embodiment can achieve good rigidity and strength. On the other hand, by setting the weight average molecular weight to 3,000,000 or less, the production and handling of the PHA can be made easy.

[0102] As the polylactic acid that can be used as the thermoplastic resin (A), a conventionally known polylactic acid can be used, and can be either crystalline or amorphous.

[0103] The polylactic acid can be a homopolymer of lactic acid, or a copolymer of lactic acid and another monomer. In addition, it can be a mixture thereof.

[0104] As the above-mentioned other monomer, aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyols, aliphatic polycarboxylic acids, polyfunctional polysaccharides, and the like can be mentioned.

[0105] The lactic acid raw material used for the production of the polylactic acid is not particularly limited, and L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof, L-lactide, D-lactide, meso-lactide, or a mixture thereof, and the like can be used. Lactic acid obtained by microbial fermentation from a renewable raw material derived from plants such as starch can be appropriately used.

[0106] As the method for producing the polylactic acid, a conventionally known method such as a dehydration condensation method, a ring-opening polymerization method, and the like can be applied, and is not particularly limited.

[0107] The molecular weight of the polylactic acid used as the thermoplastic resin (A) is not particularly limited, and the weight average molecular weight is preferably 50,000 to 1,000,000, preferably 70,000 to 700,000, and more preferably 100,000 to 400,000. By setting the weight average molecular weight to 50,000 or more, the resin powder of the present embodiment can achieve good rigidity and strength. On the other hand, by setting the weight average molecular weight to 1,000,000 or less, the production and handling of the polylactic acid can be made easy.

[0108] <Resin powder>

[0109] As described above, the resin powder of the present embodiment contains a thermoplastic resin (A) and crosslinked resin particles (B).

[0110] In the resin powder, the proportion of the crosslinking resin particles (B) in the total of the thermoplastic resin (A) and the crosslinking resin particles (B) is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more, from the viewpoint of easily achieving the effects brought about by the crosslinking resin particles (B). It can also be 40% by mass or more. In addition, since the handleability of the resin powder can be further improved, the upper limit of the proportion of the crosslinking resin particles (B) is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 70% by mass or less. It can also be 60% by mass or less.

[0111] The resin powder of the present embodiment can be formed substantially only of the thermoplastic resin (A) and the crosslinking resin particles (B), and can also contain one or two or more of a dispersing agent or an emulsifying agent, a pH adjuster, an inorganic filler, a coloring agent such as a pigment or a dye, an odor absorber such as activated carbon or zeolite, a flavoring agent such as vanillin or dextrin, a plasticizer, an oxidation inhibitor, an antioxidant, a weather resistance improver, an ultraviolet absorber, a crystallization nucleating agent, a lubricant, a release agent, a water repellent, an antibacterial agent, a slip property improver, and the like, within a range that does not hinder the effects of the present invention.

[0112] In addition, the resin powder of the present embodiment can also contain various components derived from the process of the manufacturing method, within a range that does not hinder the effects of the present invention.

[0113] In the resin powder of the present embodiment, the thermoplastic resin (A) and the crosslinking resin particles (B) are main forming components. Specifically, the proportion of the total of the thermoplastic resin (A) and the crosslinking resin particles (B) to the entire resin powder can be usually 60 to 100% by mass, can be 80 to 100% by mass, can be 90 to 100% by mass, can be 95 to 100% by mass, and can also be 99 to 100% by mass. In addition, the upper limit can be 99.9% by mass or less, and can also be 99% by mass or less.

[0114] From the viewpoint of making the handleability of the resin powder good, the median particle diameter of the resin powder of the present embodiment can be in the range of 20 μm or more and 1000 μm or less. The lower limit can be 30 μm or more. The upper limit can be 500 μm or less, can be 300 μm or less, can be 200 μm or less, and can also be 100 μm or less.

[0115] The median particle diameter of the resin powder is a value measured by the laser diffraction / scattering method using, for example, LMS-3000 manufactured by Seishin Enterprise Co., Ltd., in a dry method or a wet method. In the case of measurement in a wet method, it is preferable to measure in a state in which the resin powder is added to an aqueous solution to which a small amount of a surfactant as a dispersing agent is added, in a state in which the resin powder is not aggregated.

[0116] The resin powder of the present embodiment preferably has a low water content, and specifically, the water content is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less.

[0117] <Method for producing resin powder>

[0118] The method for producing the resin powder of the present embodiment is not particularly limited. However, it is suitably produced by preparing an aqueous dispersion liquid containing the thermoplastic resin (A) and the crosslinked resin particles (B), and performing spray drying on the aqueous dispersion liquid.

[0119] The aqueous dispersion liquid containing the thermoplastic resin (A) and the crosslinked resin particles (B) can be prepared by adding the thermoplastic resin (A) to the aqueous dispersion liquid of the crosslinked resin particles (B). The aqueous dispersion liquid of the crosslinked resin particles (B) can be produced as described above.

[0120] The thermoplastic resin (A) added to the aqueous dispersion liquid of the crosslinked resin particles (B) can be in a powder form, or can be an aqueous dispersion liquid of the thermoplastic resin (A).

[0121] The volume average particle diameter of the thermoplastic resin (A) in the above-described aqueous dispersion liquid is preferably in the range of 0.1 μm or more and 10 μm or less. By using the thermoplastic resin (A) having such a particle diameter, it is suitably possible to produce the resin powder having the specific range of particle diameters of the present embodiment. The lower limit value of the above-described particle diameter is preferably 0.1 μm or more, more preferably 0.3 μm or more, and further preferably 0.5 μm or more. In addition, the upper limit value of the above-described particle diameter is preferably 8 μm or less, and more preferably 5 μm or less.

[0122] In addition, when the thermoplastic resin (A) in a powder form is added to the aqueous dispersion liquid of the crosslinked resin particles (B), the volume average particle diameter of the thermoplastic resin (A) after the addition is preferably in the range of 0.1 μm or more and 10 μm or less, as described above.

[0123] The above-described aqueous dispersion liquid of the thermoplastic resin (A) can be an emulsion. The method for producing the same is not particularly limited, and it can be produced by, for example: heating and dissolving the resin in a solvent, and then performing crystallization, and further performing pulverization by high-speed stirring with glass beads (for example, refer to paragraph number

[0008] of Japanese Patent Laid-Open No. 9-78494); mixing and kneading the resin in a molten state with an aqueous solution of a surfactant (for example, refer to paragraph number

[0006] of Japanese Patent Laid-Open No. 11-92712, and paragraph number

[0006] of Japanese Patent Laid-Open No. 2001-354841); and pulverizing the resin by freezing, and then dispersing it in water.

[0124] In addition, when the thermoplastic resin (A) is PHA, the aqueous dispersion of the thermoplastic resin (A) can be an aqueous dispersion obtained by destroying the microbial cells in the culture solution after culturing the PHA-producing microorganism to accumulate PHA in the microbial cells, and separating and removing the microbial cell components. Alternatively, the aqueous dispersion can be an aqueous dispersion obtained by concentrating or diluting the aqueous dispersion.

[0125] The aqueous medium contained in the aqueous dispersion of the thermoplastic resin (A) and the crosslinkable resin particles (B) can be water alone, or a mixed solvent of water and an organic solvent that is miscible with water. The concentration of the organic solvent that is miscible with water in the mixed solvent is not particularly limited as long as it is below the solubility of the organic solvent in water.

[0126] The organic solvent is not particularly limited and can be, for example, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, 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; and dimethyl sulfoxide, pyridine, and piperidine. Among these, from the viewpoint of ease of removal, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, acetonitrile, and propionitrile are preferred. From the viewpoint of easy availability, methanol, ethanol, 1-propanol, 2-propanol, butanol, and acetone are more preferred. Further, methanol, ethanol, and acetone are particularly preferred.

[0127] The proportion of water in the entire aqueous medium contained in the aqueous dispersion of the thermoplastic resin (A) and the crosslinkable resin particles (B) is preferably 5% by weight or more, more preferably 10% by weight or more, further preferably 30% by weight or more, particularly preferably 70% by weight or more. It can be 90% by weight or more, or 95% by weight or more. The upper limit is not particularly limited and can be 100% by weight or less.

[0128] The total concentration of the thermoplastic resin (A) and the crosslinkable resin particles (B) in the aqueous dispersion of the thermoplastic resin (A) and the crosslinkable resin particles (B) is not particularly limited. For example, from the viewpoint of practicality in drying, in order to facilitate economy and improve productivity, it is preferably 20% by weight or more, more preferably 30% by weight or more, further preferably 40% by weight or more. In order to ensure the flowability of the aqueous dispersion, the upper limit of the total concentration is preferably 65% by weight or less, more preferably 60% by weight or less. The method of adjusting the total concentration is not particularly limited and can be, for example, a method of adding an aqueous medium and removing a portion of the aqueous medium (for example, by removing the supernatant after centrifugal separation).

[0129] In order to suppress the reduction of the molecular weight of the resin component during the spray drying and post-drying processing steps, the pH of the aqueous dispersion containing the thermoplastic resin (A) and the cross-linked resin particles (B) is preferably adjusted to, for example, 8 or less, preferably 7 or less, and more preferably 6 or less, as needed. In addition, from the perspective of the acid resistance of the container, the lower limit of the above-mentioned pH is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more. The method for adjusting the pH is not particularly limited, and examples thereof include methods such as adding an acid. The acid is not particularly limited and may be an organic acid or an inorganic acid. More specifically, as the acid, for example, sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid, etc. can be used.

[0130] The aqueous dispersion containing the thermoplastic resin (A) and the cross-linked resin particles (B) may further contain one or more of a dispersant or emulsifier, a pH adjuster, an inorganic filler, a colorant such as a pigment or dye, an odor absorbent such as activated carbon or zeolite, a fragrance such as vanillin or dextrin, a plasticizer, an antioxidant, an antioxidant, a weather resistance improver, an ultraviolet absorber, a crystal nucleating agent, a lubricant, a release agent, a water repellent, an antibacterial agent, a slip improver, and the like, within a range not impairing the effects of the invention.

[0131] Furthermore, the aqueous dispersion containing the thermoplastic resin (A) and the crosslinked resin particles (B) may further contain various components derived from the process of the production method, within a range not hindering the effects of the invention.

[0132] In an aqueous dispersion comprising a thermoplastic resin (A) and crosslinked resin particles (B), the thermoplastic resin (A), the crosslinked resin particles (B) and the aqueous medium are the main components. Specifically, the total proportion of the thermoplastic resin (A) and the crosslinked resin particles (B) to the total solid content of the aqueous dispersion may generally be 60 to 100% by weight, 80 to 100% by weight, 90 to 100% by weight, 95 to 100% by weight, or 99 to 100% by weight. Furthermore, the upper limit may be 99% or less by weight, or 95% or less by weight.

[0133] The resin powder of the present embodiment can be preferably produced by spray-drying the aqueous dispersion containing the thermoplastic resin (A) and the cross-linked resin particles (B) as described above.

[0134] As a method of spray drying, for example, a method in which an aqueous dispersion is supplied to a dryer in a state of fine droplets and dried while being brought into contact with hot air in the dryer can be given. The method of supplying an aqueous dispersion to a dryer in a state of fine droplets (atomizer) is not particularly limited, and known methods such as a method using a rotating disk, a method using a nozzle, and the like can be given. The contact mode of droplets in the dryer with hot air is not particularly limited, and a parallel flow type, a counter flow type, a mode in which they are used in combination, and the like can be given.

[0135] The drying temperature at the time of spray drying is only required to be a temperature at which most of the aqueous medium can be removed from the droplets of the aqueous dispersion. It can be appropriately set under conditions in which it can be dried to a target water content, and quality deterioration (molecular weight decrease, color tone decrease, and the like), melting, and the like are avoided as much as possible. For example, the temperature of hot air blown into a spray dryer can be appropriately selected in the range of 40 to 300°C. In addition, the air volume of hot air in the dryer can be appropriately set, for example, in accordance with the size of the dryer and the like.

[0136] <Use of Resin Powder>

[0137] The use of the resin powder of the present embodiment is not particularly limited, and can be used for a use in which a crosslinked resin particle application conventionally known can be used. Specifically, a resin modifier, a rheology modifier for a paint or an adhesive, a paint pigment, a paper coating agent, a matting agent, an anti-blocking agent, a cosmetic additive, a toner additive, a spacer for liquid crystals, a coating agent, a filler for a tape, a fiber processing agent, a detection particle for medical diagnosis, a filler, and the like can be given, but are not limited thereto.

[0138] The resin powder of the present embodiment can be processed into an article other than the powder. As such an article, for example, a particle, a molded body described later, and the like can be given. Therefore, one embodiment of the present disclosure also relates to a resin composition containing a thermoplastic resin (A) and a crosslinked resin particle (B) containing a polyhydroxyalkanoate-based resin and having a gel fraction of 50% or more. The details of the thermoplastic resin (A) and the crosslinked resin particle (B), and the containing ratio of the two components can be in accordance with the above description.

[0139] The shape of the particle processed from the resin composition of the present disclosure is not particularly limited, and can be, for example, approximately spherical, flat, regular hexahedral (cubic), spindle-shaped, needle-shaped, and the like. The median particle diameter of the particle is not particularly limited, and can be, for example, around 1 mm to 10 mm. The particle can be a granule.

[0140] In the case where the resin powder of the present embodiment is processed into a pellet, the following advantages are obtained: in the case where the other thermoplastic resin described later is in a pellet form, the classification at the time of mixing is prevented; and the adhesion of a screw in a kneader is prevented. As a production method for processing the resin powder of the present embodiment into a pellet, a method in which, for example, the resin powder is melted and extruded using an extruder, and the extrudate is cut using a cutter, or the like, can be given, but the present embodiment is not limited thereto.

[0141] In addition, a molded body can also be produced from the resin powder of the present embodiment. The molded body can expect an improvement in mechanical properties such as impact resistance by containing the crosslinked resin particles (B). The molded body can be produced from the resin powder of the present embodiment alone, or the molded body can be produced after mixing an arbitrary additive and / or other thermoplastic resin. In the case where an arbitrary additive and / or other thermoplastic resin is mixed, it is preferable to produce the molded body after obtaining a thermoplastic resin composition by a melt kneading step.

[0142] The thermoplastic resin composition described above can be produced by a publicly known method. Specifically, a method in which the resin powder of the present embodiment, and an arbitrary additive and / or other thermoplastic resin are melt-kneaded using an extruder, a kneader, a Banbury mixer, a roll, or the like, can be given. In the case of melt-kneading, it is preferable to pay attention to the decrease in molecular weight due to thermal decomposition at the time of mixing. In addition, the thermoplastic resin composition described above can be produced by dissolving each component in a soluble solvent, and removing the solvent.

[0143] As the other thermoplastic resin described above, a resin exemplified for the thermoplastic resin (A) can be used. The same resin as the thermoplastic resin (A) can be used, or a different resin can be used. In addition, as the arbitrary additive described above, the resin powder of the present embodiment can be contained, or the additive described above can be used as the additive.

[0144] In the case of production by melt-kneading, each component can be separately fed to an extruder or the like, or each component can be mixed in advance and then fed to an extruder or the like.

[0145] In the case of melt-kneading by an extruder, the obtained thermoplastic resin composition can be extruded into a strand shape, and then sheared to be processed into a pellet shape such as a rod shape, a cylindrical shape, an elliptical cylindrical shape, a spherical shape, a cubic shape, a rectangular parallelepiped shape, or the like.

[0146] The resin temperature at the time of melt-kneading varies depending on the melting point, the melt viscosity, or the like of the resin used, and cannot be generalized, but from the viewpoint of avoiding thermal decomposition of the thermoplastic resin (A) and the other thermoplastic resin described above, and uniformly dispersing the crosslinked resin particles (B), it is preferable to be in the range of 140 to 250°C, more preferably in the range of 150 to 230°C, and further preferably in the range of 160 to 220°C.

[0147] The molding method is not particularly limited, and a generally used molding method can be applied. Specifically, a blown film molding, an extrusion blow molding, an injection blow molding, an extrusion molding, a calender molding, a vacuum molding, an injection molding, or the like can be mentioned. By these molding methods, for example, a sheet, a film, a blow molded product, an extrusion molded product, a vacuum molded product, an injection molded product can be manufactured.

[0148] The molded body formed from the resin powder of the present embodiment can be suitably used in agriculture, fishery, forestry, horticulture, medicine, sanitary goods, food industry, clothing, non-clothing, packaging, automobile, building material, other fields.

[0149] The following items each list a preferred mode of the present disclosure, but the present invention is not limited to the following items.

[0150] [Item 1]

[0151] A resin powder, wherein the volume average particle diameter is 20 to 1000 μm, wherein

[0152] The resin powder contains a thermoplastic resin (A) and crosslinked resin particles (B),

[0153] The crosslinked resin particles (B) contain a polyhydroxyalkanoate-based resin, and have a gel fraction of 50% or more and a volume average particle diameter of 0.1 μm or more and 10 μm or less.

[0154] [Item 2]

[0155] The resin powder according to item 1, wherein

[0156] The content ratio of the crosslinked resin particles (B) is 10 to 90% by weight in the total of the thermoplastic resin (A) and the crosslinked resin particles (B).

[0157] [Item 3]

[0158] The resin powder according to item 1 or 2, wherein

[0159] The polyhydroxyalkanoate-based resin is a poly(3-hydroxyalkanoate)-based resin.

[0160] [Item 4]

[0161] The resin powder according to any one of items 1 to 3, wherein

[0162] The crosslinked resin particles (B) are crosslinked resin particles crosslinked using a peroxide.

[0163] [Item 5]

[0164] The resin powder according to item 4, wherein

[0165] The crosslinked resin particles (B) are resin particles further crosslinked in the presence of a multifunctional compound.

[0166] [Item 6]

[0167] The resin powder according to any one of Items 1 to 5, wherein

[0168] The proportion of the polyhydroxyalkanoate-based resin in the crosslinked resin particles (B) is 80% by weight or more.

[0169] [Item 7]

[0170] The resin powder according to any one of Items 1 to 6, wherein

[0171] The thermoplastic resin (A) comprises a biodegradable resin.

[0172] [Item 8]

[0173] The resin powder according to Item 7, wherein

[0174] The biodegradable resin is a polyester-based resin.

[0175] [Item 9]

[0176] A production method of the resin powder according to any one of Items 1 to 8, the method comprising:

[0177] a step of preparing an aqueous dispersion liquid containing a thermoplastic resin (A) and crosslinked resin particles (B), and

[0178] a step of spray-drying the aqueous dispersion liquid.

[0179] Examples

[0180] The following examples are shown to specifically describe the present application, but the present application is not limited by any of these examples.

[0181] [1] Measurement conditions

[0182] 1-1. Weight average molecular weight

[0183] The resin to be measured was dissolved in chloroform, heated in a water bath at 60°C for 30 minutes, and filtered using a PTFE-made 0.45-μm pore size disposable filter. The filtrate was used to perform GPC measurement under the following conditions, whereby the weight average molecular weight was calculated.

[0184] GPC measurement device: High-performance liquid chromatograph 20A system made by Shimadzu Corporation

[0185] Column: K-G 4A (1), K-806M (2) manufactured by Showa Denko K.K.

[0186] Sample concentration: 1 mg / ml

[0187] Eluent: chloroform solution

[0188] Eluent flow rate: 1.0 ml / min

[0189] Sample injection amount: 100 μL

[0190] Analysis time: 30 minutes

[0191] Standard: standard polystyrene

[0192] 1-2. Volume average particle diameter

[0193] The volume average particle diameter of the crosslinked resin particles or the uncrosslinked resin particles was measured in the state of the latex of the resin particles. As the measuring device, Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd. was used.

[0194] 1-3. Gel fraction

[0195] The dry substance of the crosslinked resin particles was added until the concentration thereof was 0.7% by weight with respect to chloroform, and it was allowed to dissolve at 60°C for 30 minutes, and a chloroform solution was obtained. Thereafter, after standing at room temperature for 3 hours, the above chloroform solution was filtered using a micropore filter having a pore diameter of 0.45 μm. The filtration was performed while sufficiently washing the inside of the container and the filter using chloroform several times, thereby preventing loss. The gel remaining on the filter was dried, and the weight of the filter together with the dried gel was measured, and the gel fraction was calculated by the following formula.

[0196] Formula: Gel fraction = (weight of the filter including the dried gel - weight of the filter alone) / weight of the crosslinked resin particles used for the measurement x 100 (%)

[0197] [2] Raw material of the crosslinked resin particles

[0198] 2-1. Uncrosslinked resin particles

[0199] Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate): (3-hydroxybutyrate) / (3-hydroxyhexanoate) = 72 / 28 (mol / mol), weight average molecular weight Mw: 5 to 15 million, volume average particle diameter: 1.7 μm

[0200] 2-2. Peroxide

[0201] Di(sec-butyl)peroxydicarbonate (Luperox 225 manufactured by Arkema K.K., 1-hour half-life temperature: 69°C)

[0202] 2-3. Polyfunctional compound

[0203] Triallyl isocyanurate

[0204] [3] Method for producing aqueous dispersion of crosslinked resin particles (B)

[0205] An aqueous dispersion in which uncrosslinked resin particles were dispersed in water (100 parts by weight of solid content), deionized water (200 parts by weight), a peroxide (2 parts by weight), sodium dioctyl sulfosuccinate (2 parts by weight), and a polyfunctional compound (0.5 parts by weight) were added to an autoclave equipped with a stirrer, a buffer, a nitrogen inlet / outlet, and a thermometer, and stirring was started at room temperature while nitrogen replacement was performed in the autoclave.

[0206] After that, the contents in the autoclave were stirred for 1 hour at room temperature, and the peroxide and the polyfunctional compound were allowed to impregnate into the interior of the uncrosslinked resin particles, and then the temperature was raised to 75°C as the reaction temperature. After the reaction temperature was reached, an aqueous dispersion in which crosslinked resin particles (B) were dispersed in water was obtained by allowing it to react at the reaction temperature for 3.5 hours.

[0207] The volume average particle diameter of the crosslinked resin particles (B) in the aqueous dispersion was measured by the above-described method, and was 1.7 μm.

[0208] In addition, after adjusting the pH of the aqueous dispersion, it was dried by an oven, and thereby solidified crosslinked resin particles (B) were obtained. The particle gel fraction of the particles was measured by the above-described method, and was 95%.

[0209] [4] Method for producing aqueous dispersion for drying

[0210] (a) Aqueous dispersion of thermoplastic resin (A) (solid content concentration 50%)

[0211] Thermoplastic resin (A): poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (manufactured by Kaneka Corporation, Kaneka Biodegradable Polymer PHBH (registered trademark), (3-hydroxybutyrate) / (3-hydroxyhexanoate) = 94.4 / 5.6 (mol / mol), weight average molecular weight Mw: 530,000, volume average particle diameter: 2.2 μm

[0212] An aqueous dispersion of an ethylene oxide / propylene oxide copolymer nonionic dispersant (PLONON 208 manufactured by NOF Corporation, molecular weight of polyethylene oxide: 8,000, molecular weight of polypropylene oxide: 2,000) was added at 1 part by weight with respect to 100 parts by weight of the thermoplastic resin (A)

[0213] (b) an aqueous dispersion of the above crosslinked resin particles (B) (solid content concentration 25%)

[0214] The aqueous dispersion (a) and the aqueous dispersion (b) were mixed in the proportions (weight of solid content basis) described in Table 1, warmed to about 50 to 55°C, and then the pH was adjusted until it stabilized at 3.8, to obtain a mixed aqueous dispersion.

[0215] [5] Spray drying method

[0216] A spray dryer of L-8 type manufactured by Okawara Chemical Machinery Co., Ltd. was used to perform spray drying on the mixed aqueous dispersion obtained as described above, under the conditions described in Table 1, to obtain a resin powder containing the thermoplastic resin (A) and the crosslinked resin particles (B).

[0217] A LMS-3000 manufactured by Seishin Enterprise Co., Ltd. was used to measure the median particle diameter of the resin powder obtained by spray drying, by a dry method of laser diffraction / scattering. The results are shown in Table 1.

[0218] (Oven drying method)

[0219] The mixed aqueous dispersion obtained as described above was placed in an oven at 55°C for 24 hours or more, to sufficiently evaporate the water, to obtain a rubbery sheet that was difficult to handle.

[0220]

[0221] As can be seen from Examples 1 to 3 in Table 1, by performing spray drying on an aqueous dispersion containing the thermoplastic resin (A) and the crosslinked resin particles (B), a resin powder containing the thermoplastic resin (A) and the crosslinked resin particles (B) can be obtained. The resin powder obtained in each of the examples was good in handleability.

[0222] In Comparative Example 1 (not described in the table), although spray drying was attempted on an aqueous dispersion containing only the crosslinked resin particles (B), the resin particles aggregated and adhered to the wall surface inside the spray dryer, making it difficult to recover, and a resin powder as obtained in each of the examples could not be obtained. From this, it can be seen that the crosslinked resin particles (B) have very high adhering and aggregating properties, and are difficult to recover as a single powder.< / pha>

Claims

1. A resin powder having a median particle size of 20 to 1000 μm, wherein: The resin powder contains thermoplastic resin (A) and cross-linked resin particles (B). The crosslinked resin particles (B) are made of a polyhydroxyalkanoate-based resin, have a gel fraction of 50% or more, and have a volume average particle size of 0.1 μm to 10 μm.

2. The resin powder according to claim 1, wherein The content ratio of the cross-linked resin particles (B) in the total of the thermoplastic resin (A) and the cross-linked resin particles (B) is 10 to 90% by weight.

3. The resin powder according to claim 1 or 2, wherein The polyhydroxyalkanoate resin is a poly(3-hydroxyalkanoate) resin.

4. The resin powder according to claim 1 or 2, wherein The crosslinked resin particles (B) are crosslinked resin particles crosslinked using a peroxide.

5. The resin powder according to claim 4, wherein The crosslinked resin particles (B) are resin particles that have been further crosslinked in the presence of a polyfunctional compound.

6. The resin powder according to claim 1 or 2, wherein The ratio of the polyhydroxyalkanoate resin in the cross-linked resin particles (B) is 80% by weight or more.

7. The resin powder according to claim 1 or 2, wherein The thermoplastic resin (A) contains a biodegradable resin.

8. The resin powder according to claim 7, wherein The biodegradable resin is a polyester resin.

9. A method for producing the resin powder according to claim 1 or 2, comprising: a step of preparing an aqueous dispersion containing a thermoplastic resin (A) and crosslinked resin particles (B), and A step of spray-drying the aqueous dispersion.

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