Resin particle

Abstract

To provide a resin particle that, while maintaining flexibility, suppresses phenomenon in which a plasticizer exudes from resin particle when stored for a long time under high temperature condition.SOLUTION: A master particle containing biodegradable resin and a plasticizer, wherein the biodegradable resin contains at least one kind of natural polymer selected from cellulose acylate, polyester or starch, cellulose, chitin, chitosan, gluten, gelatin, casein, soybean protein, collagen, or keratin, with an amount of at least one metal element selected from Ca, Mg, Al, and Fe, as determined by fluorescent X-ray analysis, being 0.002 mass% or more and 2.0 mass% or less relative to the total resin particles, and of the metal elements, at least 0.002 mass% relative to the total resin particles is forming a cross-linked structure with the biodegradable resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to resin particles. [Background technology]

[0002] Patent Document 1 proposes "a biodegradable resin composition comprising a hardly hydrolyzable biodegradable resin (A), polyglycolic acid (B), and an ester decomposition-accelerating auxiliary (C) consisting of inorganic particles that accelerate the hydrolysis of the polyglycolic acid." Patent Document 2 proposes a method for producing coated particles whose surfaces are coated with a layer made of calcium phosphate, which method comprises dispersing or immersing resin particles having an average particle size of 0.01 μm or more and 1,000 μm or less in an aqueous solution containing Ca ions and phosphate ions at a temperature of 30°C or more for 12 hours or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-077245 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-210848 Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide resin particles that have base particles containing a biodegradable resin and a plasticizer, and that maintain flexibility while suppressing the phenomenon of plasticizer seeping out of the resin particles when stored for a long period of time under high-temperature conditions (hereinafter, the "phenomenon of plasticizer seeping out of resin particles" may be referred to as "bleeding"), compared to when the amount of metal elements that can have an ionic valence of 2 or more, as determined by fluorescent X-ray analysis, relative to the entire resin particle is less than 0.002 mass% or more than 2.0 mass%, when the ratio (Rs / Rp) of the equivalent-circle diameter Rs of the aggregate to the equivalent-circle diameter Rp of the primary particles is 1.5 or more after storage for 3 months under conditions of 50°C and 50% RH. [Means for solving the problem]

[0005] The above problems are solved by the following means: <1> The composition has base particles containing a biodegradable resin and a plasticizer, Resin particles in which the amount of metal elements that can have an ionic valence of 2 or more, as determined by fluorescent X-ray analysis, is 0.002% by mass or more and 2.0% by mass or less relative to the total amount of the resin particles. <2> The metal element capable of having an ionic valence of 2 or more includes at least one selected from the group consisting of Ca, Mg, Al, and Fe. <1> The resin particles according to claim 1. <3> The metal element capable of having an ionic valence of 2 or more contains Ca. <2> The resin particles according to claim 1. <4> The biodegradable resin is cellulose acylate. <1> ~ <3> 10. The resin particles according to any one of the above. <5> The cellulose acylate is at least one selected from the group consisting of cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate. <4> The resin particles according to claim 1. <6> The ratio (B / A) of the content of the plasticizer (B) to the content of the biodegradable resin (A) is 0.1 or more and 0.8 or less. <1> ~ <5> The resin particles according to claim 1. <7> The composition has base particles containing a biodegradable resin and a plasticizer, the ratio (Rs / Rp) of the equivalent circle diameter Rs of the aggregates to the equivalent circle diameter Rp of the primary particles is less than 1.5 after storage for 3 months under conditions of 50°C and 50% RH; Resin particles having a durometer hardness of less than 75. <8> a first layer on the surface of the base particle, the first layer including at least one cationic resin selected from polyalkyleneimine, polyallylamine, and polyvinylamine; a second layer containing an anionic or nonionic hydrophobic compound, <1> ~ <7> 10. The resin particles according to any one of the above. [Effects of the Invention]

[0006] <1> According to the present invention, there is provided a resin particle having a base particle containing a biodegradable resin and a plasticizer, in which the amount of metal elements that can have an ionic valence of 2 or more, as determined by fluorescent X-ray analysis, relative to the entire resin particle is less than 0.002 mass% or more than 2.0 mass%, and which maintains flexibility while suppressing bleeding when stored for a long period of time under high-temperature conditions. <2> According to the present invention, there are provided resin particles that maintain flexibility and suppress bleeding when stored for a long period of time under high temperature conditions, compared to when the metal element that can have an ionic valence of 2 or more includes Ba other than Ca, Mg, Al, and Fe. <3> According to the present invention, there is provided resin particles that maintain flexibility and suppress bleeding when stored for a long period of time under high temperature conditions, compared to when the metal element that can have an ionic valence of 2 or more does not include Ca but includes at least one selected from the group consisting of Mg, Al, and Fe. <4> According to the present invention, resin particles are provided which maintain flexibility compared to when the biodegradable resin is polyester, and which are inhibited from bleeding when stored for a long period of time under high temperature conditions. <5> According to the present invention, resin particles are provided in which cellulose acylate maintains flexibility compared to cellulose triacetate and bleeding is suppressed when stored for a long period of time under high temperature conditions.

[0007] <6> According to the present invention, resin particles are provided which maintain flexibility and suppress bleeding when stored for a long period of time under high temperature conditions, compared to when the ratio (B / A) of the plasticizer content (B) to the biodegradable resin content (A) is less than 0.1 or more than 0.8. <7> According to the invention, there is provided resin particles having base particles containing a biodegradable resin and a plasticizer, which, after storage for three months at 50°C and 50% RH, maintain flexibility while suppressing bleeding when stored for a long period of time under high-temperature conditions, compared to when the ratio of the circle-equivalent diameter Rs of the aggregate to the circle-equivalent diameter Rp of the primary particles (Rs / Rp) is 1.5 or more, or when the durometer hardness is 75 or more. <8> According to the invention, there is provided a resin particle having base particles containing a biodegradable resin and a plasticizer, in which the amount of metal elements that can have an ionic valence of 2 or more, as determined by fluorescent X-ray analysis, is 0.002% by mass or more and 2.0% by mass or less relative to the entire resin particle, or in which the ratio of the circle-equivalent diameter Rs of the aggregate to the circle-equivalent diameter Rp of the primary particles (Rs / Rp) is less than 1.5 after storage for 3 months under conditions of 50°C and 50% RH, and the durometer hardness is less than 75.The resin particle maintains flexibility and is inhibited from bleeding when stored for a long period of time under high-temperature conditions, compared to resin particles that do not have a first layer containing at least one cationic resin selected from polyalkyleneimine, polyallylamine, and polyvinylamine on the surface of the base particle, and a second layer containing an anionic or nonionic hydrophobic compound. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0009] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0010] <Resin particles> The resin particles according to the first embodiment have base particles containing a biodegradable resin and a plasticizer, and the amount of metal elements that can have an ionic valence of 2 or more (hereinafter, "metal elements that can have an ionic valence of 2 or more" will also be referred to as "specific metal elements") determined by fluorescent X-ray analysis is 0.002% by mass or more and 2.0% by mass or less relative to the entire resin particle.

[0011] The resin particles according to the first embodiment, due to the above-described configuration, maintain flexibility and suppress bleeding when stored for a long period of time under high temperature conditions. The reason for this is presumed to be as follows.

[0012] The addition of a plasticizer is effective in improving the flexibility of resin particles containing a biodegradable resin (hereinafter also simply referred to as biodegradable resin particles). However, biodegradable resin particles containing a plasticizer tend to bleed and aggregate when stored for a long period of time under high-temperature conditions.

[0013] The resin particles according to the first embodiment have a specific metal element content of 0.002% by mass or more and 2.0% by mass or less, as determined by X-ray fluorescence analysis, relative to the total mass of the resin particles. The specific metal element is likely to bond with functional groups (e.g., hydroxyl groups, carboxyl groups, etc.) possessed by biodegradable resins. Therefore, the specific metal element is likely to form a crosslinked structure with the biodegradable resin. This suppresses bleeding of the plasticizer contained in the resin particles. Furthermore, by setting the amount of the specific metal element within the above numerical range, the crosslinked structure is likely to be present in a large amount, without impairing the flexibility of the resin particles.

[0014] From the above, it is presumed that the resin particles according to the first embodiment maintain flexibility and suppress bleeding when stored for a long period of time under high temperature conditions.

[0015] The resin particles according to the second embodiment have base particles containing a biodegradable resin and a plasticizer. Furthermore, after storage for 3 months under conditions of 50°C and 50% RH, the ratio (Rs / Rp) of the equivalent circle diameter Rs of the aggregates to the equivalent circle diameter Rp of the primary particles is less than 1.5. and a durometer hardness of less than 75. Here, the term "aggregate" refers to a secondary particle formed by aggregating two or more resin particles, which are primary particles.

[0016] The resin particles according to the second embodiment, due to the above-described configuration, maintain flexibility and suppress bleeding when stored for a long period of time under high temperature conditions. The reason for this is presumed to be as follows.

[0017] The resin particles according to the second embodiment have a ratio (Rs / Rp) of the equivalent circle diameter Rs of the aggregates to the equivalent circle diameter Rp of the primary particles of less than 1.5 after storage for three months at 50°C and 50% RH. A ratio (Rs / Rp) of less than 1.5 indicates that aggregation of primary particles is unlikely to occur even when stored for a long period of time under high-temperature conditions. Aggregation of primary particles when resin particles containing a plasticizer are stored for a long period of time under high-temperature conditions tends to be caused by the seepage of the plasticizer from the resin particles. In other words, a ratio (Rs / Rp) of less than 1.5 means that bleeding is suppressed even when stored for a long period of time under high-temperature conditions. Furthermore, the resin particles according to the second embodiment have a durometer hardness of less than 75, which means that they have flexibility.

[0018] From the above, it is presumed that the resin particles according to the second embodiment maintain flexibility and suppress bleeding when stored for a long period of time under high temperature conditions.

[0019] Hereinafter, resin particles corresponding to either the resin particles according to the first or second embodiment will be described in detail, however, an example of the resin particles of the present invention may be any one of the resin particles according to the first or second embodiment.

[0020] (base particle) -Biodegradable resin- The base particles include a biodegradable resin. Examples of the base particles include particles containing a biodegradable resin as a main component, and specifically, examples include particles containing 90 mass%, 95 mass%, 98 mass%, or 100 mass% of biodegradable resin relative to the entire base particle. Here, biodegradable resin is a resin that can be decomposed into water and carbon dioxide by microorganisms. Specifically, biodegradable resin means a resin whose aerobic biodegradation rate measured according to ISO-14855-2 (2018) is 50% or more within one month.

[0021] Examples of biodegradable resins include cellulose acylate, polyester, and natural polymers.

[0022] Cellulose acylate is a cellulose derivative in which at least some of the hydroxyl groups in cellulose are substituted with acyl groups (acylation). AC (R AC represents a hydrogen atom or a hydrocarbon group.) Examples of cellulose acylate include cellulose derivatives represented by the following general formula (CA).

[0023] Examples of polyesters include aliphatic polyesters and aliphatic aromatic polyesters. Examples of aliphatic polyesters include polylactic acid (PLA), polyglycolic acid (PGA), polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polycaprolactone, polybutylene succinate (PBS), polybutylene succinate / adipate (PBSA), and polyethylene succinate (PBA), among other polyhydroxyalkanoates. Examples of the aliphatic aromatic polyester include polybutylene adipate / terephthalate copolymer resin (PBAH) and polytetramethylene adipate / terephthalate copolymer resin.

[0024] Examples of natural polymers include starch, cellulose, chitin, chitosan, gluten, gelatin, zein, soy protein, collagen, and keratin.

[0025] The biodegradable resin is preferably cellulose acylate. Since cellulose acylate has hydroxyl groups in the main chain, it has many sites that can form bonds with the specific metal element, which makes it easier to form crosslinked structures with the specific metal element, thereby further suppressing the bleeding of the plasticizer.

[0026] Cellulose acylate Cellulose acylate is, for example, a cellulose derivative represented by the following general formula (CA).

[0027] [ka]

[0028] In general formula (CA), A1, A2, and A3 each independently represent a hydrogen atom or an acyl group, and n represents an integer of 2 or greater. However, at least some of the n A1s, n A2s, and n A3s represent acyl groups. The n A1s in a molecule may be all identical, some identical, or different from one another. Similarly, the n A2s and n A3s in a molecule may be all identical, some identical, or different from one another.

[0029] The hydrocarbon group in the acyl group represented by A1, A2, and A3 may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear.

[0030] The hydrocarbon group in the acyl group represented by A1, A2 and A3 may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, but is more preferably a saturated hydrocarbon group.

[0031] The acyl group represented by A1, A2 and A3 is preferably an acyl group having a carbon number of 1 to 6. That is, the cellulose acylate is preferably an acyl group having a carbon number of 1 to 6.

[0032] The acyl group represented by A1, A2, and A3 may be a group in which a hydrogen atom in the acyl group is substituted with a halogen atom (e.g., a fluorine atom, a bromine atom, an iodine atom), an oxygen atom, a nitrogen atom, or the like, but is preferably unsubstituted.

[0033] Examples of the acyl group represented by A1, A2, and A3 include a formyl group, an acetyl group, a propionyl group, a butyryl group (butanoyl group), a propenoyl group, a hexanoyl group, etc. Among these, from the viewpoint of improving the biodegradation rate of the resin particles, the acyl group is more preferably an acyl group having from 2 to 4 carbon atoms, and even more preferably an acyl group having 2 or 3 carbon atoms.

[0034] Examples of cellulose acylate include cellulose acetate (cellulose monoacetate, cellulose diacetate (DAC), cellulose triacetate), cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB).

[0035] From the viewpoint of improving the biodegradation rate of the resin particles, the cellulose acylate is preferably a cellulose acylate having two or more types of acyl groups. Specifically, from the viewpoint of improving the biodegradation rate of the resin particles, the cellulose acylate is preferably cellulose diacetate, cellulose acetate propionate (CAP), or cellulose acetate butyrate (CAB), and more preferably cellulose acetate propionate (CAP).

[0036] At least one cellulose acylate selected from the group consisting of cellulose diacetate, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB) has a more appropriate number of hydroxyl groups in the main chain, and is more likely to form resin particles having a crosslinked structure within a range that does not impair the flexibility of the resin particles.As a result, the resin particles are more likely to maintain flexibility and suppress bleeding when stored for long periods under high-temperature conditions.

[0037] The cellulose acylate may be used alone or in combination of two or more kinds.

[0038] The weight average degree of polymerization of the cellulose acylate is preferably 200 or more and 1,000 or less, more preferably 500 or more and 1,000 or less, and even more preferably 600 or more and 1,000 or less.

[0039] The weight-average degree of polymerization of cellulose acylate is determined from the weight-average molecular weight (Mw) by the following procedure. First, the weight average molecular weight (Mw) of cellulose acylate is measured in polystyrene equivalent using tetrahydrofuran with a gel permeation chromatography device (GPC device: HLC-8320GPC manufactured by Tosoh Corporation, column: TSKgel α-M). Next, the degree of polymerization of cellulose acylate is calculated by dividing the molecular weight by the molecular weight of the constituent unit of cellulose acylate. For example, when the substituent of cellulose acylate is an acetyl group, the molecular weight of the constituent unit is 263 when the substitution degree is 2.4, and 284 when the substitution degree is 2.9.

[0040] From the viewpoint of improving the biodegradation rate of the resin particles, the substitution degree of cellulose acylate is preferably 2.1 to 2.9, more preferably 2.2 to 2.9, even more preferably 2.3 to 2.9, and particularly preferably 2.6 to 2.9.

[0041] In cellulose acetate propionate (CAP), the ratio of the substitution degree of acetyl groups to propionyl groups (acetyl groups / propionyl groups) is preferably 0.01 or more and 1 or less, more preferably 0.05 or more and 0.1 or less, from the viewpoint of improving the biodegradation rate of the resin particles.

[0042] In cellulose acetate butyrate (CAB), the ratio of the degree of substitution of acetyl groups to butyryl groups (acetyl groups / butyryl groups) is preferably 0.05 to 3.5, more preferably 0.5 to 3.0, from the viewpoint of improving the biodegradation rate of the resin particles.

[0043] The degree of substitution of cellulose acylate is an index showing the degree to which hydroxyl groups in cellulose are substituted with acyl groups. In other words, the degree of substitution is an index showing the degree of acylation of cellulose acylate. Specifically, the degree of substitution means the intramolecular average number of acyl groups replacing three hydroxyl groups in the D-glucopyranose unit of cellulose acylate. The degree of substitution is determined by the integral ratio of the peaks of cellulose-derived hydrogen and acyl group-derived hydrogen using 1H-NMR (JMN-ECA / JEOL RESONANCE).

[0044] These biodegradable resins may be used alone or in combination of two or more.

[0045] -Plasticizer- The base particles contain a plasticizer.

[0046] Examples of plasticizers include ester compounds, cardanol compounds, camphor, metal soaps, polyols, and polyalkylene oxides. From the viewpoint of improving the mechanical properties of the resin particles, the plasticizer is preferably at least one of an ester compound and a cardanol compound. One type of plasticizer may be used alone, or two or more types may be used in combination.

[0047] Examples of ester compounds include fatty acid esters (adipic acid esters, citrate esters, sebacate esters, azelaate esters, phthalate esters, and acetate esters), phosphate esters, condensed phosphate esters, glycol esters (e.g., glycol benzoate esters), and modified fatty acid esters (e.g., epoxidized fatty acid esters). Examples of the esters include monoesters, diesters, triesters, and polyesters. Among these, dicarboxylic acid diesters (e.g., adipic acid diesters, sebacic acid diesters, azelaic acid diesters, and phthalic acid diesters) are preferred.

[0048] The plasticizer is preferably at least one selected from the group consisting of an adipic acid ester, a citrate ester, and a sebacate ester. The adipic acid ester, the citrate ester, and the sebacate ester have high affinity with cellulose acylate and disperse almost uniformly in the cellulose acylate, thereby improving the thermal fluidity more than other plasticizers.

[0049] The adipic acid ester may be a mixture of an adipic acid ester and other components, and examples of commercially available products of such mixtures include Daifatty 101 manufactured by Daihachi Chemical Industry Co., Ltd.

[0050] Examples of fatty acid esters such as citrate esters, sebacate esters, azelaate esters, phthalate esters, and acetate esters include esters of fatty acids and alcohols. Examples of the alcohols include monohydric alcohols such as methanol, ethanol, propanol, butanol, and 2-ethylhexanol; and polyhydric alcohols such as glycerin, polyglycerin (diglycerin, etc.), pentaerythritol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, trimethylolpropane, trimethylolethane, and sugar alcohols.

[0051] Examples of the glycol in the glycol benzoate include ethylene glycol, diethylene glycol, and propylene glycol.

[0052] Epoxidized fatty acid esters are ester compounds having a structure in which the carbon-carbon unsaturated bonds of an unsaturated fatty acid ester have been epoxidized (i.e., oxacyclopropane). Examples of epoxidized fatty acid esters include esters of alcohols with fatty acids in which some or all of the carbon-carbon unsaturated bonds in unsaturated fatty acids (e.g., oleic acid, palmitoleic acid, vaccenic acid, linoleic acid, linolenic acid, nervonic acid, etc.) have been epoxidized. Examples of the alcohols include monohydric alcohols such as methanol, ethanol, propanol, butanol, and 2-ethylhexanol; and polyhydric alcohols such as glycerin, polyglycerin (e.g., diglycerin), pentaerythritol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, trimethylolpropane, trimethylolethane, and sugar alcohols.

[0053] The molecular weight (or weight average molecular weight) of the ester compound as a plasticizer is preferably from 200 to 2000, more preferably from 250 to 1500, and even more preferably from 280 to 1000. Unless otherwise specified, the weight average molecular weight of the ester compound is a value measured in accordance with the method for measuring the weight average molecular weight of cellulose acylate.

[0054] It is also preferable to use a cardanol compound as the plasticizer. Cardanol compounds refer to components contained in naturally occurring compounds made from cashews (for example, compounds represented by the following structural formulas (b-1) to (b-4)) or derivatives of the above components.

[0055] [ka]

[0056] The cardanol compound may be a mixture of naturally occurring compounds made from cashews (hereinafter also referred to as a "cashew-derived mixture").

[0057] The cardanol compound may be a derivative of a cashew-derived mixture. Examples of the derivative of a cashew-derived mixture include the following mixtures and simple substances:

[0058] A mixture of cashew-derived ingredients with adjusted composition ratios A single substance isolated from a mixture of cashew-derived ingredients -Mixtures containing modified components of cashew-derived mixtures A mixture containing a polymer obtained by polymerizing components of a cashew-derived mixture A mixture containing a modified polymer obtained by modifying and polymerizing components in a cashew-derived mixture A mixture containing a modified substance obtained by further modifying the components in the mixture with the adjusted composition ratio. A mixture containing a polymer obtained by further polymerizing the components in the mixture with the adjusted composition ratio. A mixture containing a modified polymer obtained by further modifying and polymerizing the components in the mixture whose composition ratio has been adjusted. A denatured product obtained by further denaturing the isolated monomer A polymer obtained by further polymerizing the isolated monomer A modified polymer obtained by further modifying and polymerizing the isolated monomer. Here, the term "monomer" also includes multimers such as dimers and trimers.

[0059] From the viewpoint of improving the biodegradation rate of the resin particles, the cardanol compound is preferably at least one compound selected from the group consisting of compounds represented by general formula (CDN1) and polymers obtained by polymerizing compounds represented by general formula (CDN1).

[0060] [ka]

[0061] In the general formula (CDN1), R 1 R represents an alkyl group which may have a substituent, or an unsaturated aliphatic group which has a double bond and may have a substituent. 2represents a hydroxy group, a carboxy group, an alkyl group which may have a substituent, or an unsaturated aliphatic group which has a double bond and may have a substituent. P2 represents an integer of 0 to 4. When P2 is 2 or more, a plurality of R 2 may be the same group or different groups.

[0062] In general formula (CDN1), R 1 The alkyl group represented by the formula (I) which may have a substituent is preferably an alkyl group having 3 to 30 carbon atoms, more preferably an alkyl group having 5 to 25 carbon atoms, and even more preferably an alkyl group having 8 to 20 carbon atoms. Examples of the substituent include a hydroxy group; a substituent containing an ether bond such as an epoxy group or a methoxy group; and a substituent containing an ester bond such as an acetyl group or a propionyl group. Examples of the alkyl group which may have a substituent include a pentadecane-1-yl group, a heptan-1-yl group, an octan-1-yl group, a nonan-1-yl group, a decan-1-yl group, an undecane-1-yl group, a dodecane-1-yl group, and a tetradecane-1-yl group.

[0063] In general formula (CDN1), R 1 The unsaturated aliphatic group represented by the formula (I) which has a double bond and which may have a substituent is preferably an unsaturated aliphatic group having 3 to 30 carbon atoms, more preferably an unsaturated aliphatic group having 5 to 25 carbon atoms, and even more preferably an unsaturated aliphatic group having 8 to 20 carbon atoms. The unsaturated aliphatic group preferably has 1 or more and 3 or less double bonds. Examples of the substituent include those listed above as the substituent of the alkyl group. Examples of the unsaturated aliphatic group having a double bond and optionally having a substituent include a pentadec-8-en-1-yl group, a pentadeca-8,11-dien-1-yl group, a pentadeca-8,11,14-trien-1-yl group, a pentadec-7-en-1-yl group, a pentadeca-7,10-dien-1-yl group, and a pentadeca-7,10,14-trien-1-yl group.

[0064] In general formula (CDN1), R 1 As the alkyl group, a pentadec-8-en-1-yl group, a pentadeca-8,11-dien-1-yl group, a pentadeca-8,11,14-trien-1-yl group, a pentadec-7-en-1-yl group, a pentadeca-7,10-dien-1-yl group, and a pentadeca-7,10,14-trien-1-yl group are preferred.

[0065] In general formula (CDN1), R 2 The alkyl group which may have a substituent and the unsaturated aliphatic group which has a double bond and may have a substituent represented by R 1 Similarly, preferred examples include those listed as the alkyl group which may have a substituent and the unsaturated aliphatic group which has a double bond and may have a substituent, represented by the formula (I) below.

[0066] The compound represented by general formula (CDN1) may be further modified, for example, epoxidized, and from the viewpoint of improving the biodegradation rate of the resin particles, it is preferably a compound having a structure in which the hydroxy group of the compound represented by general formula (CDN1) is replaced with the following group (EP), that is, a compound represented by the following general formula (CDN1-e):

[0067] [ka]

[0068] In the group (EP) and general formula (CDN1-e), L EP represents a single bond or a divalent linking group.1 , R 2 and P2 are R in general formula (CDN1), 1 , R 2 and P2.

[0069] In the group (EP) and the general formula (CDN1-e), L EP Examples of the divalent linking group represented by include an alkylene group which may have a substituent (preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 1 carbon atom), a -CH2CH2OCH2CH2- group, and the like. The above-mentioned substituents include R 1 The same can be mentioned as the substituents listed in the above.

[0070] L EP As the alkyl group, a methylene group is preferred.

[0071] The polymer obtained by polymerizing the compound represented by general formula (CDN1) refers to a polymer obtained by polymerizing at least two or more compounds represented by general formula (CDN1) with or without a linking group.

[0072] Examples of polymers obtained by polymerizing the compound represented by general formula (CDN1) include compounds represented by the following general formula (CDN2).

[0073] [ka]

[0074] In the general formula (CDN2), R 11 , R 12 and R 13 R each independently represents an alkyl group which may have a substituent, or an unsaturated aliphatic group which has a double bond and may have a substituent. 21 , R 22 and R 23each independently represents a hydroxy group, a carboxy group, an alkyl group which may have a substituent, or an unsaturated aliphatic group which has a double bond and may have a substituent. P21 and P23 each independently represent an integer of 0 or more and 3 or less, and P22 represents an integer of 0 or more and 2 or less. L 1 and L 2 each independently represents a divalent linking group, and n represents an integer of 0 to 10. When P21 is 2 or more, a plurality of R 21 , when P22 is 2 or more, there are multiple R 22 , and when P23 is 2 or more, there are multiple R 23 may be the same or different groups. When n is 2 or more, a plurality of R 12 , R 22 and L 1 may be the same or different groups, and when n is 2 or greater, the number of P22s present may be the same or different.

[0075] In general formula (CDN2), R 11 , R 12 , R 13 , R 21 , R 22 and R 23 The alkyl group which may have a substituent and the unsaturated aliphatic group which has a double bond and may have a substituent represented by R 1 The following are also preferred examples.

[0076] In general formula (CDN2), L 1 and L 2 Examples of the divalent linking group represented by include an alkylene group which may have a substituent (preferably an alkylene group having 2 to 30 carbon atoms, more preferably an alkylene group having 5 to 20 carbon atoms). The above-mentioned substituents include R 1 The same can be mentioned as the substituents listed in the above.

[0077] In formula (CDN2), n is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less.

[0078] The compound represented by general formula (CDN2) may be further modified, for example, epoxidized, specifically a compound in which the hydroxy group of the compound represented by general formula (CDN2) is replaced with a group (EP), that is, a compound represented by the following general formula (CDN2-e):

[0079] [ka]

[0080] In the general formula (CDN2-e), R 11 , R 12 , R 13 , R 21 , R 22 , R 23 , P21, P22, P23, L 1 , L 2 and n are R in general formula (CDN2), 11 , R 12 , R 13 , R 21 , R 22 , R 23 , P21, P22, P23, L 1 , L 2 and n. In the general formula (CDN2-e), L EP1 , L EP2 and L EP3 each independently represents a single bond or a divalent linking group. When n is 2 or more, a plurality of L EP2 may be the same group or different groups.

[0081] In the general formula (CDN2-e), L EP1 , L EP2 and L EP3 Examples of the divalent linking group represented by include L in general formula (CDN1-e). EPSimilarly, the divalent linking group represented by the formula (I) is preferably the same as the divalent linking group represented by the formula (I).

[0082] The polymer obtained by polymerizing the compound represented by general formula (CDN1) may be, for example, a polymer obtained by three-dimensionally crosslinking polymerizing at least three or more compounds represented by general formula (CDN1) with or without a linking group. Examples of the polymer obtained by three-dimensionally crosslinking polymerizing the compound represented by general formula (CDN1) include compounds represented by the following structural formula:

[0083] [ka]

[0084] In the above structural formula, R 10 , R 20 and P20 are R in general formula (CDN1), 1 , R 2 and P2. 10 represents a single bond or a divalent linking group. 10 , R 20 and L 10 may be the same or different groups. 20 may be the same or different numbers.

[0085] In the above structural formula, L 10 Examples of the divalent linking group represented by include an alkylene group which may have a substituent (preferably an alkylene group having 2 to 30 carbon atoms, more preferably an alkylene group having 5 to 20 carbon atoms). The above-mentioned substituents include R 1 The same can be mentioned as the substituents listed in the above.

[0086] The compound represented by the above structural formula may be further modified, for example, may be epoxidized. Specifically, it may be a compound in which the hydroxy group of the compound represented by the above structural formula is replaced with a group (EP), for example, a compound represented by the following structural formula, that is, a polymer in which the compound represented by general formula (CDN1-e) is three-dimensionally crosslinked and polymerized.

[0087] [ka]

[0088] In the above structural formula, R 10 , R 20 and P20 are R in general formula (CDN1-e), 1 , R 2 and P2. 10 represents a single bond or a divalent linking group. 10 , R 20 and L 10 may be the same or different groups. 20 may be the same or different numbers.

[0089] In the above structural formula, L 10 Examples of the divalent linking group represented by include an alkylene group which may have a substituent (preferably an alkylene group having 2 to 30 carbon atoms, more preferably an alkylene group having 5 to 20 carbon atoms). The above-mentioned substituents include R 1 The same can be mentioned as the substituents listed in the above.

[0090] From the viewpoint of improving the transparency of the resin molded body, the cardanol compound preferably contains a cardanol compound having an epoxy group, and is more preferably a cardanol compound having an epoxy group.

[0091] Commercially available cardanol compounds may be used. Examples of commercially available cardanol compounds include NX-2024, Ultra LITE 2023, NX-2026, GX-2503, NC-510, LITE 2020, NX-9001, NX-9004, NX-9007, NX-9008, NX-9201, and NX-9203 manufactured by Cardolite Corporation, and LB-7000, LB-7250, and CD-5L manufactured by Tohoku Kako Co., Ltd. Commercially available cardanol compounds having an epoxy group include NC-513, NC-514S, NC-547, LITE513E, and Ultra LTE 513 manufactured by Cardolite Corporation.

[0092] From the viewpoint of improving the biodegradation rate of a resin molded article, the hydroxyl value of the cardanol compound is preferably 100 mgKOH / g or more, more preferably 120 mgKOH / g or more, and even more preferably 150 mgKOH / g or more. The hydroxyl value of the cardanol compound is measured in accordance with Method A of ISO 14900.

[0093] When a cardanol compound having an epoxy group is used as the cardanol compound, from the viewpoint of improving the transparency of a resin molded product, the epoxy equivalent is preferably from 300 to 500, more preferably from 350 to 480, and even more preferably from 400 to 470. The epoxy equivalent of the cardanol compound having an epoxy group is measured in accordance with ISO 3001.

[0094] The molecular weight of the cardanol compound is preferably 250 or more and 1000 or less, more preferably 280 or more and 800 or less, and even more preferably 300 or more and 500 or less, from the viewpoint of improving the biodegradation rate of the resin molded article.

[0095] The cardanol compounds may be used alone or in combination of two or more.

[0096] The ratio (B / A) of the plasticizer content (B) to the biodegradable resin content (A) is preferably 0.02 or more and 0.9 or less, more preferably 0.05 or more and 0.85 or less, and even more preferably 0.1 or more and 0.8 or less.

[0097] By setting the content of the plasticizer within the above range, the flexibility of the resin particles is more likely to be improved, which is preferable.

[0098] -Other ingredients- The base particles may contain other components. Examples of other components include flame retardants, compatibilizers, release agents, light resistance agents, weather resistance agents, colorants, pigments, modifiers, anti-drip agents, antistatic agents, hydrolysis inhibitors, fillers, reinforcing agents (glass fiber, carbon fiber, talc, clay, mica, glass flakes, milled glass, glass beads, crystalline silica, alumina, silicon nitride, aluminum nitride, boron nitride, etc.), acid acceptors for preventing acetic acid release (oxides such as magnesium oxide and aluminum oxide; metal hydroxides such as magnesium hydroxide, calcium hydroxide, aluminum hydroxide, and hydrotalcite; calcium carbonate; talc; etc.), and reactive trapping agents (for example, epoxy compounds, acid anhydride compounds, carbodiimides, etc.). The content of each of the other components is preferably 0% by mass or more and 5% by mass or less relative to the total amount of the base particles, where "0% by mass" means that no other components are included.

[0099] The base particles may contain other resins besides the biodegradable resin. However, if other resins are contained, the content of the other resins relative to the total amount of the base particles is preferably 5% by mass or less, and more preferably less than 1% by mass. It is more preferable that the base particles do not contain other resins (i.e., 0% by mass). Examples of other resins include conventionally known thermoplastic resins, specifically, polycarbonate resins; polypropylene resins; polyester resins; polyolefin resins; polyester carbonate resins; polyphenylene ether resins; polyphenylene sulfide resins; polysulfone resins; polyether sulfone resins; polyarylene resins; polyetherimide resins; polyacetal resins; polyvinyl acetal resins; polyketone resins; polyether ketone resins; polyether ether ketone resins; polyaryl ketone resins; polyether nitrile resins; liquid crystal resins; polybenzimidazole resins; polypa Examples of suitable resins include lavanic acid resins, vinyl polymers or copolymers obtained by polymerizing or copolymerizing one or more vinyl monomers selected from the group consisting of aromatic alkenyl compounds, methacrylic acid esters, acrylic acid esters, and vinyl cyanide compounds, diene-aromatic alkenyl compound copolymers, vinyl cyanide-diene-aromatic alkenyl compound copolymers, aromatic alkenyl compound-diene-vinyl cyanide-N-phenylmaleimide copolymers, vinyl cyanide-(ethylene-diene-propylene (EPDM))-aromatic alkenyl compound copolymers, vinyl chloride resins, and chlorinated vinyl chloride resins. These resins may be used alone or in combination of two or more.

[0100] (First and second layers) The resin particles according to this embodiment preferably have, on the surface of the base particle, a first layer containing at least one cationic resin selected from the group consisting of polyalkyleneimine, polyallylamine, and polyvinylamine, and a second layer containing an anionic or nonionic hydrophobic compound, in this order. By having the first and second layers, even if the plasticizer seeps out from the base particles, the plasticizer is easily retained between the base particle surface and the first and second layers, thereby suppressing the seepage of the plasticizer from the resin particles. Therefore, by having the first and second layers, the resin particles are more likely to be those in which bleeding is further suppressed.

[0101] -First layer- The first layer is a resin layer present on the surface of the base particle, and contains at least one cationic resin selected from the group consisting of polyalkyleneimine, polyallylamine, and polyvinylamine.

[0102] The cationic resin may be any of polyalkyleneimine, polyallylamine and polyvinylamine, but polyalkyleneimine is preferred from the viewpoint of improving the rate of biodegradation over time and reducing the initial rate of biodegradation.

[0103] As the polyalkyleneimine, from the viewpoint of improving the biodegradation rate over time and reducing the initial biodegradation rate, a polyalkyleneimine having a structural unit with an alkylene group having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms), is preferred, and polyethyleneimine is more preferred.

[0104] In particular, polyethyleneimine is a compound with high adhesiveness and high water absorption. This is because the amino group of polyethyleneimine forms a hydrogen bond with a hydroxyl group, an ionic bond with a carboxyl group, and a covalent bond with a carbonyl group. Polyethyleneimine has a polar group (amino group) and a hydrophobic group (ethylene group) in its structure, which makes it easy to bond with different substances. Furthermore, polyethyleneimine is a compound with high cationicity, and therefore, polyethyleneimine exists as a polycation in water and neutralizes and adsorbs anionic substances. Furthermore, polyethyleneimine is a highly reactive compound because it contains a highly reactive primary or secondary amino group, which allows it to easily react with a variety of compounds. Therefore, when polyethyleneimine is used as the polyalkyleneimine, the second layer containing the hydrophobic compound is more firmly coated on the base particles, and while the base particles have a biodegradation rate over time, the initial biodegradation rate tends to be slower.

[0105] The number average molecular weight of the cationic resin is preferably 300 or more and 100,000 or less, more preferably 10,000 or more and 85,000 or less, and even more preferably 50,000 or more and 80,000 or less, from the viewpoint of improving the biodegradation rate over time and reducing the initial biodegradation rate. The number average molecular weight of the cationic resin is measured in polystyrene equivalent terms using tetrahydrofuran with a gel permeation chromatography device (GPC device: HLC-8320GPC manufactured by Tosoh Corporation, column: TSKgel α-M).

[0106] -Second layer- The second layer is a compound layer disposed on the first layer, and includes an anionic or nonionic compound or a hydrophobic compound.

[0107] Examples of anionic or nonionic compounds or hydrophobic compounds include hydrophobic compounds having an anionic group (such as -COOH (carboxyl group), -SOH (sulfonic group)), and hydrophobic compounds having no cationic or anionic groups. The hydrophobic compound refers to a compound that imparts hydrophobicity (specifically, water contact angle) to the biodegradable resin particles described below.

[0108] Examples of the hydrophobic compound include a silicone compound, a hydrocarbon compound, a fatty acid compound, an acrylic resin, a polyester resin, and a urethane resin. Among these, from the viewpoint of improving the biodegradation rate over time and reducing the initial biodegradation rate, at least one selected from the group consisting of silicone compounds, hydrocarbon compounds, fatty acid compounds, acrylic resins, polyester resins, and urethane resins is preferred.

[0109] Examples of silicone compounds include dimethylpolysiloxane, methylpolysiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentanesiloxane, methylcyclopolysiloxane, various modified silicone oils (alkyl-modified silicone oil, polyether-modified silicone oil, alcohol-modified silicone oil, fluorine-modified silicone oil, amino-modified silicone oil, etc.), MQ resin, and silicone rubber. Among these, from the viewpoints of improving the biodegradation rate over time and reducing the initial biodegradation rate, at least one silicone compound selected from the group consisting of dimethylpolysiloxane, methylpolysiloxane, MQ resin, and silicone rubber is preferred. Here, MQ resin refers to a silicone resin having M units, which are monofunctional siloxane units [(CH3)3SiO1 / 2], and Q units, which are tetrafunctional siloxane units [SiO4 / 2].

[0110] Commercially available silicone compounds include silicone compounds manufactured by Shin-Etsu Chemical Co., Ltd. (KM-902, KM-903, KM-910, KM-9729, POLON-MN-ST, KM-9737A, KM-9782, KM-9738A, KM-752T, POLON-MF-33, KM-9717, X-51-1302M (MQ Resin), POLON-MF-56, KM-2002-L-1, KM-2002-T, KM-9772, KM-9749, POLON-MF-40, KM-9729, X-52-1133, etc.), and a silicone compound manufactured by Wacker Asahi Kasei Silicone Co., Ltd. (BELSIL DM3112VP).

[0111] Examples of hydrocarbon compounds include petroleum waxes (paraffin wax, microcrystalline wax, petrolatum wax, etc.) and synthetic hydrocarbon waxes (polyethylene wax, polypropylene wax, polybutene wax, Fischer-Tropsch wax, etc.). Among these, from the viewpoint of improving the biodegradation rate over time and reducing the initial biodegradation rate, at least one hydrocarbon compound selected from the group consisting of paraffin wax, microcrystalline wax, polyethylene wax, and polypropylene wax is preferred.

[0112] Commercially available hydrocarbon compounds include microcrystalline wax (EMUSTAR-0001, etc.) manufactured by Nippon Seiro Co., Ltd., paraffin wax (EMUSTAR-0135, etc.) manufactured by Nippon Seiro Co., Ltd., paraffin wax (AQUACER 497, etc.) manufactured by BYK Co., Ltd., polyethylene wax (AQUACER 507, AQUACER 840, AQUACER 1547, AQUACER 272, etc.) manufactured by BYK Co., Ltd., polyethylene wax (Hitec E-2213, Hitec E-6324, etc.) manufactured by Toho Chemical Industry Co., Ltd., polypropylene wax (AQUACER 593, etc.) manufactured by BYK Co., Ltd., and polypropylene (Hitec P-9018, Hitec P-5060P, etc.) manufactured by Toho Chemical Industry Co., Ltd.

[0113] Examples of fatty acid compounds include vegetable oils containing fatty acids (castor oil, tung oil, linseed oil, shortening, corn oil, soybean oil, sesame oil, rapeseed oil, sunflower oil, rice bran oil, camellia oil, coconut oil, palm oil, walnut oil, olive oil, peanut oil, almond oil, jojoba oil, cocoa butter, shea butter, neem oil, safflower oil, Japan wax, candelilla wax, rice wax, carnauba wax, etc.). Among these, from the viewpoint of improving the biodegradation rate over time and reducing the initial biodegradation rate, at least one wax selected from the group consisting of carnauba wax, rice wax, candelilla wax, palm wax, castor oil wax, soybean oil wax, and sunflower oil wax is preferred.

[0114] Commercially available fatty acid compounds include carnauba wax (EMUSTAR-0413 (carnauba wax)) manufactured by Nippon Seiro Co., Ltd., rice wax (AQUASPROUT-7300, etc.) manufactured by Nippon Seiro Co., Ltd., palm wax (AQUASPROUT-7100, etc.) manufactured by Nippon Seiro Co., Ltd., castor oil wax (AQUASPROUT-7500, etc.) manufactured by Nippon Seiro Co., Ltd., soybean oil wax (AQUASPROUT-7200, etc.) manufactured by Nippon Seiro Co., Ltd., sunflower oil wax (AQUASPROUT-7400, etc.) manufactured by Nippon Seiro Co., Ltd., and palm oil wax (Cuckoo Ace TKE, etc.) manufactured by Nippon Seiro Co., Ltd.

[0115] Examples of the acrylic resin include well-known acrylic resins such as polymers of acrylic acid and polymers of alkyl acrylate esters. Commercially available acrylic resins include, for example, acrylic resins manufactured by Taisei Fine Co., Ltd. (3WX-2015, 3MF-320, 3MF-333, 3MF-407, etc.) and acrylic resins manufactured by DIC Corporation (COAT SFC-6440, BONCOAT CE-6270, BONCOAT CE-6400, BONCOAT CF-2800, etc.).

[0116] Examples of polyester resins include well-known polyester resins such as polycondensates of polycarboxylic acids and polyhydric alcohols, and ring-opening polycondensates of cyclic lactams. Commercially available polyester resins include, for example, polyester resins manufactured by Takamatsu Oil & Fat Co., Ltd. (A-110F, A-160P, A-520, A-613D, A-615GE, A-640, A-645GH, A-647GEX, etc.).

[0117] Examples of the urethane resin include well-known urethane resins such as polyester-based polyurethane, polyether-based polyurethane, polycarbonate-based polyurethane, etc. Furthermore, as the urethane resin, a material having a urethane polymer shell layer around an acrylic polymer core may be used. Commercially available urethane resins include, for example, urethane resins manufactured by Taisei Fine Co., Ltd. (WEM-031U, WEM-200U, WEM-321U, WEM-3000, WBR-016U, WBR-2101, etc.).

[0118] -Content of each layer- In the biodegradable resin particles according to this embodiment, from the viewpoint of improving the biodegradation rate over time and reducing the initial biodegradation rate, the mass ratio of the coating amount of the cationic resin in the first layer to the coating amount of the hydrophobic compound in the second layer (coating amount of the cationic resin / coating amount of the hydrophobic compound) is preferably 0.05 or more and 20 or less, more preferably 0.1 or more and 10 or less, and even more preferably 0.1 or more and 3 or less.

[0119] Furthermore, from the viewpoint of improving the biodegradation rate over time and reducing the initial biodegradation rate, the content of the cationic resin relative to the base particles is preferably 0.05% by mass or more and 15% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less. Furthermore, from the viewpoint of improving the biodegradation rate over time and reducing the initial biodegradation rate, the content of the hydrophobic compound relative to the base particles is preferably 0.05% by mass or more and 15% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less.

[0120] Here, the coating amounts of the cationic resin and the hydrophobic compound (i.e., the coating amounts of the first layer and the second layer) are measured as follows. The coating amount of the cationic resin is determined by the difference between the amount of cationic resin treated and the amount of cationic resin obtained by drying the supernatant after treatment. Similarly, the coating amount of the hydrophobic compound is determined by the difference between the amount of hydrophobic compound treated and the amount of hydrophobic compound obtained by drying the supernatant after treatment.

[0121] <Characteristics of resin particles> (particle size) The volume average particle size of the resin particles is preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 70 μm or less, and even more preferably 8 μm or more and 60 μm or less.

[0122] The large diameter particle size distribution index GSDv of the biodegradable resin particles is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.2 or less.

[0123] The volume average particle size and the large particle size distribution index GSDp of the biodegradable resin particles are measured as follows. The particle size is measured using an LS particle size distribution analyzer "Beckman Coulter LS13 320 (manufactured by Beckman Coulter)" and the cumulative particle size distribution is plotted from the smallest diameter side on a volume basis. The particle size at 50% of the cumulative distribution is determined as the volume average particle size. On the other hand, the cumulative particle size distribution is plotted from the small diameter side on a volume basis, and the particle size at 50% of the cumulative distribution is defined as the number average particle size D50v, and the particle size at 84% of the cumulative distribution is defined as the number particle size D84v. The large diameter side number particle size distribution index GSDv is calculated using the formula GSDv = (D84v / D50v) 1 / 2 Calculated as follows.

[0124] (Amount of specific elements) The amount of metal elements (specific metal elements) that can have an ionic valence of 2 or more, as determined by fluorescent X-ray analysis, is 0.002% by mass or more and 2.0% by mass or less with respect to the total mass of the resin particles.

[0125] The amount of the specific metal element is measured by the following procedure. Qualitative and quantitative analysis measurements are performed using an X-ray fluorescence analyzer (Shimadzu Corporation, XRF1500) under conditions of an X-ray output of 40 V, 70 mA, a measurement area of ​​10 mmφ, and a measurement time of 15 minutes. Here, the elements analyzed are all elements present in the measurement area. The atomic weights of all elements present in the measurement area and the atomic weight of the specific metal element are then calculated. The atomic weights of all elements present in the measurement area and the atomic weight of the specific metal element are then converted to mass. The percentage of the mass of the specific metal element relative to the mass of all elements present in the measurement area is then calculated, and this is the amount of the specific metal element determined by X-ray fluorescence analysis.

[0126] From the viewpoint of obtaining resin particles that maintain greater flexibility while suppressing bleeding when stored for long periods under high-temperature conditions, the amount of the specific metal element determined by X-ray fluorescence analysis is preferably 0.02% by mass or more and 1.5% by mass or less, more preferably 0.1% by mass or more and 1.2% by mass or less, and even more preferably 0.2% by mass or more and 1.0% by mass or less, relative to the total amount of the resin particles.

[0127] The specific element is not particularly limited as long as it is a metal element that can have an ionic valence of 2 or more, and examples thereof include metal elements in Group 2 of the periodic table, such as Mg and Ca; metal elements in Group 12 of the periodic table, such as zinc; metal elements in Group 13 of the periodic table, such as Al; metal elements in Group 14 of the periodic table, such as Si; and transition metal elements, such as Fe, Ti, and Zr.

[0128] The specific metal element preferably includes at least one selected from the group consisting of Ca, Mg, Al, and Fe, and more preferably includes Ca.

[0129] Among the specific metal elements, Ca, Mg, Al, and Fe are more likely to bond with functional groups in biodegradable resins, making the resin particles more likely to have a crosslinked structure. Among these, Ca has a relatively large ionic radius, making it more likely to bond with functional groups in biodegradable resins. Therefore, the resin particles tend to maintain greater flexibility and suppress bleeding when stored for long periods under high-temperature conditions.

[0130] (Ratio (Rs / Rp)) After storage for 3 months under conditions of 50°C and 50% RH, the ratio (Rs / Rp) of the equivalent circle diameter Rs of the aggregates to the equivalent circle diameter Rp of the primary particles is less than 1.5.

[0131] From the viewpoint of further suppressing bleeding during long-term storage under high-temperature conditions, the ratio (Rs / Rp) is preferably 1.4 or less, more preferably 1.3 or less, and even more preferably 1.2 or less. The lower limit of the ratio (Rs / Rp) is preferably 1.0 or more.

[0132] The equivalent circle diameter Rs of the aggregate and the equivalent circle diameter Rp of the primary particle are calculated as follows. First, the resin particles are stored for three months in a chamber at a temperature of 50°C and a humidity of 50%. After storage, aggregates present in the resin particles are observed and images are taken using a scanning electron microscope (SEM) (Hitachi, Ltd.: S-4100). These images are then imported into an image analyzer (LUZEX III, Nireco Corporation). The area of ​​each aggregate is measured by image analysis, and the equivalent circle diameter is calculated from this area value. This calculation of the equivalent circle diameter of the aggregate is performed for 100 aggregates. The arithmetic mean value of the equivalent circle diameters calculated from the 100 aggregates is then taken as the equivalent circle diameter Rs of the aggregate. The equivalent circle diameter Rp of the primary particles present in the resin particles after storage is also calculated using the same procedure as for the equivalent circle diameter Rs of the aggregate. Here, the determination of whether the resin particles after storage are aggregates or primary particles is made as follows: In an image obtained by observing the resin particles after storage with an SEM device, a single resin particle is considered to be a primary particle, and two or more resin particles that are in contact with each other are considered to be aggregates.

[0133] (Durometer hardness) The durometer hardness is less than 75. From the viewpoint of further improving flexibility, the durometer hardness is preferably 30 or more and 74 or less, more preferably 40 or more and 70 or less, and even more preferably 50 or more and 65 or less.

[0134] Durometer hardness is specified as follows: The resin particles are heated to 200°C and then molded into a 2mm thick disk. The obtained disk is used as the measurement object, and measurements are performed using a Type D durometer under a measurement load of 5000g. The durometer hardness measurement is performed in accordance with JIS K 7215:1986.

[0135] <Method of manufacturing resin particles> The resin particles can be produced, for example, by the following method. (1) A kneading and crushing method in which the components are kneaded, and the resulting kneaded mixture is crushed and classified to obtain granules; (2) A dry manufacturing method in which the shape of granules obtained by the kneading and grinding method is changed by mechanical impact force or thermal energy to obtain granules. (3) A method of agglomeration and coalescence in which particle dispersions of each component are mixed, the particles in the dispersion are agglomerated, and heat-fused to obtain granules. (4) A dissolution suspension method in which an organic solvent in which each component is dissolved is suspended in an aqueous solvent to form granules containing each component. (5) A kneading and dissolving method in which each component and a binder are kneaded and extruded to form pellets, and the resulting pellets are granulated by stirring them in a solvent that dissolves only the binder.

[0136] The resin particles are preferably produced by the method (4) above, from the viewpoint of making the amount of the specific metal element determined by fluorescent X-ray analysis 0.002% by mass or more and 2.0% by mass or less of the total resin particles.

[0137] In producing resin particles by the above method (4), it is preferable to dissolve a metal element source containing a specific metal element in the aqueous solvent before suspending the organic solvent in which each component has been dissolved in the aqueous solvent.

[0138] Examples of the metal element source include carbonates containing specific metal elements and hydroxides containing specific metal elements. Examples of carbonates containing specific metal elements include calcium carbonate, magnesium carbonate, aluminum carbonate, and iron carbonate. Examples of hydroxides containing specific metal elements include calcium hydroxide, magnesium hydroxide, aluminum hydroxide, and iron hydroxide.

[0139] The content of the metal element source in the aqueous solvent is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 15% by mass or less, and even more preferably 3% by mass or more and 10% by mass or less, based on the total amount of the aqueous solvent.

[0140] Examples of methods for producing resin particles having the first and second layers include the following methods.

[0141] -First step- In the first step, base particles are prepared. Examples of methods for producing the base particles include the methods (1) to (5) for producing the resin particles.

[0142] Next, an aqueous dispersion of the obtained base particles is prepared. Before preparing the aqueous dispersion, it is preferable to wash the base particles with an acid.

[0143] Next, the aqueous dispersion, the aqueous dispersion containing the base particles, and an aqueous solution containing a cationic resin are mixed together, whereby, for example, the hydroxyl groups of the resin contained in the base particles react with the amine sites of the cationic resin to form a first layer.

[0144] -Second process- In the second step, the base particles on which the first layer has been formed are removed from the mixed solution. The base particles are removed, for example, by filtering the mixed solution. The removed base particles are preferably washed with water. This allows the unreacted cationic resin to be removed.

[0145] Next, after preparing an aqueous dispersion in which the base particles are dispersed, the aqueous dispersion is mixed with an emulsion solution of an anionic or nonionic hydrophobic compound, so that the emulsion of the hydrophobic compound is adsorbed onto the first layer of the base particles. The mixture is then dried, breaking up the emulsion of the hydrophobic compound and coating the hydrophobic compound on the first layer, thereby forming a second layer.

[0146] Through the above steps, the resin particles according to this embodiment are obtained.

[0147] <Application> Applications of the resin particles according to this embodiment include granular materials such as cosmetic base materials, rolling agents, abrasives, scrubbing agents, display spacers, materials for forming beads, light diffusing particles, resin reinforcing agents, refractive index control agents, biodegradation accelerators, fertilizers, water-absorbing particles, toner particles, and anti-blocking particles. [Example]

[0148] Examples will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are by mass.

[0149] <Preparing each ingredient> The following materials were prepared:

[0150] [Biodegradable resin] CAB: Eastman Chemical "CAB381-20", cellulose acetate butyrate, weight average degree of polymerization 890, acetyl substitution degree 1.05, butyryl substitution degree 1.74. CAP: Eastman Chemical "CAP482-20", cellulose acetate propionate, weight average degree of polymerization 716, acetyl substitution degree 0.18, propionyl substitution degree 2.49 PLA: Polylactic acid, weight average molecular weight 180,000 PBS: Polybutylene succinate, weight average molecular weight 200,000 DAC: Daicel Corporation "L-50", cellulose diacetate, weight average degree of polymerization 570 TAC: Daicel Corporation "LT-35", cellulose triacetate, weight average degree of polymerization 385

[0151] [Plasticizer] DIBA: Diisobutyl adipate ATBC: Tributyl O-acetylcitrate CDN: Cardolite "NX-2503", hydroxyethylated cardanol, molecular weight 296-320

[0152] [First layer cationic resin] PEI: Polyethyleneimine, number average molecular weight 70,000 PAA: Polyallylamine, number average molecular weight 25,000 PVAM: Polyvinylamine, number average molecular weight 100,000

[0153] [Anionic or nonionic hydrophobic compound of the second layer] EMUSTAR-0413: Carnauba wax, anionic, manufactured by Nippon Seiro Co., Ltd. EMUSTAR-0136: Paraffin wax, non-ionic, manufactured by Nippon Seiro Co., Ltd.

[0154] [Examples 1 to 11, 14 to 21, Comparative Examples 1, 2, 4 to 6] (Production of resin pellets) The cylinder temperature was adjusted according to the charged composition ratio shown in Table 1, and kneading was carried out using a twin-screw kneader (TEX41SS, manufactured by Toshiba Machine Co., Ltd.) to obtain a resin composition in the form of pellets (hereinafter referred to as resin pellets).

[0155] (Preparation of resin particles) 300 g of resin pellets were completely dissolved in 700 g of methyl ethyl ketone. 50 g of the metal element source shown in Table 1 was added to an aqueous solution prepared by dispersing it in 500 g of pure water, and the mixture was stirred for 3 hours. Next, 4 g of carboxymethyl cellulose and 200 g of methyl ethyl ketone were added to an aqueous solution prepared by dispersing it in 600 g of pure water, and the mixture was stirred for 5 minutes using a high-speed emulsifier. 10 g of sodium hydroxide was added to the mixture, which was then heated to 80°C and stirred for 3 hours to remove the methyl ethyl ketone. Next, 10 g of dilute hydrochloric acid was added to dissolve the metal element source. The residue was filtered, and the solid was freeze-dried to obtain resin particles.

[0156] [Examples 12, 13, 22 to 24, Comparative Example 3] (Production of resin pellets) The cylinder temperature was adjusted according to the charged composition ratio shown in Table 1, and kneading was carried out using a twin-screw kneader (TEX41SS, manufactured by Toshiba Machine Co., Ltd.) to obtain a resin composition in the form of pellets (hereinafter referred to as resin pellets).

[0157] (Preparation of mother particles) 300 g of resin pellets were completely dissolved in 700 g of methyl ethyl ketone. 50 g of the metal element source shown in Table 1 was added to an aqueous solution prepared by dispersing it in 500 g of pure water, and the mixture was stirred for 3 hours. Next, 4 g of carboxymethyl cellulose and 200 g of methyl ethyl ketone were added to an aqueous solution prepared by dispersing it in 600 g of pure water, and the mixture was stirred for 5 minutes using a high-speed emulsifier. 10 g of sodium hydroxide was added to the mixture, and the mixture was heated to 80°C and stirred for 3 hours to remove the methyl ethyl ketone. Next, 10 g of dilute hydrochloric acid was added to dissolve the metal element source. The residue was filtered and then dispersed again in pure water to obtain a base particle slurry.

[0158] (Preparation of resin particles) Using the materials for the first and second layers shown in Table 1, biodegradable resin particles were obtained as follows. 500 parts of a base particle slurry adjusted to a solids content of 20% was prepared. To the solids content (100 parts) of this slurry, the amount of cationic resin solution shown in Table 1 in terms of pure content was added, and the mixture was stirred at 25°C for 1 hour. After stirring, the residue was filtered and re-dispersed in pure water to prepare 500 parts of a mixture adjusted to a solids content of 20%. To the solids content (100 parts) of this slurry, the amount of hydrophobic compound shown in Table 1 in terms of pure content was added, and the mixture was stirred at 25°C for 1 hour. After stirring, the residue was filtered, and the solids were freeze-dried to obtain biodegradable resin particles. Through the above steps, biodegradable resin particles were obtained.

[0159] <Evaluation> The amount of metal elements with ionic valences of 2 or more ("metal element amount" in the table), the number-average particle diameter D50v, the durometer hardness, and the ratio of the equivalent circle diameter Rs of the aggregates to the equivalent circle diameter Rp of the primary particles (Rs / Rp) after storage for 3 months at 50°C and 50% RH were measured for the resulting resin particles according to the described method. The results are shown in Table 2.

[0160] (Flexibility Assessment) The flexibility of the resin particles was evaluated using the measured durometer hardness values ​​according to the following evaluation criteria. The results are shown in Table 2. -Evaluation criteria- G1(〇): Durometer hardness ≦65 G2(△):65<Durometer hardness<75 G3(×):75≦Durometer hardness

[0161] (Long-term heat storage evaluation) The calculated ratio (Rs / Rp) was used to evaluate the long-term heat storage stability of the resin particles according to the following evaluation criteria. The results are shown in Table 2. -Evaluation criteria- G1(〇): Ratio (Rs / Rp)≦1.2 G2(△):1.2<Ratio(Rs / Rp)<1.5 G3(×):1.5≦Ratio (Rs / Rp)

[0162] [Table 1]

[0163] [Table 2]

[0164] From the above results, it is clear that the resin particles of this example are resin particles that maintain flexibility and are suppressed from bleeding when stored for a long period of time under high temperature conditions.

Claims

1. The present invention has base particles containing a biodegradable resin containing cellulose acylate, polyester, or at least one natural polymer selected from starch, cellulose, chitin, chitosan, gluten, gelatin, casein, soy protein, collagen, and keratin, and a plasticizer, Resin particles having an amount of at least one metal element selected from Ca, Mg, Al, and Fe of 0.002% by mass or more and 2.0% by mass or less based on the total mass of the resin particles, as determined by fluorescent X-ray analysis.

2. The resin particles according to claim 1 , wherein the metal elements form a crosslinked structure with the biodegradable resin in an amount of 0.002% by mass or more and 2.0% by mass or less based on the total mass of the resin particles.

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