Organic fine particles and method for producing same

Abstract

To provide a method for producing an organic fine particle capable of highly preventing an odor of a film into which the organic fine particle is blended.SOLUTION: In a method for producing an organic fine particle, a (meth)acrylic monomer and a bifunctional crosslinkable (meth)acrylic monomer are polymerized under the coexistence of a thermal polymerization initiator in the presence of an aqueous solvent. The thermal polymerization initiator contains a polymerization initiator (B) having a 10 hr half-life temperature of 40°C or more and a polymerization initiator (A) having a 10 hr half-life temperature higher than that of the polymerization initiator (B) by 3°C or more at a mass ratio (the polymerization initiator (A) / the polymerization initiator (B)) of 0.1-0.9.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to organic fine particles obtained by copolymerizing a (meth)acrylic monomer and a (meth)acrylic bifunctional crosslinkable monomer. [Background technology]

[0002] Organic fine particles obtained by copolymerizing a (meth)acrylic monomer and a (meth)acrylic bifunctional crosslinkable monomer are blended into resin films as various additives such as light diffusing agents and antiblocking agents (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 195006 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] Depending on the application of the resin film containing the fine particles, there may be a strong demand for the film to be colorless. In particular, in applications where the appearance is important, such as food packaging films, the absence of coloring is considered to be of high quality. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide organic fine particles which are capable of preventing to a high degree the discoloration of a film in which they are incorporated. [Means for solving the problem]

[0005] The present invention is as follows. [1] A method for producing organic fine particles, comprising polymerizing a (meth)acrylic monomer and a (meth)acrylic bifunctional crosslinkable monomer in the presence of an aqueous solvent and a thermal polymerization initiator, The method, characterized in that the thermal polymerization initiator contains a polymerization initiator (B) having a 10-hour half-life temperature of 40°C or higher, and a polymerization initiator (A) having a 10-hour half-life temperature that is 3°C or higher than that of the polymerization initiator (B), in a mass ratio of the polymerization initiator (A) to the polymerization initiator (B) (polymerization initiator (A) / polymerization initiator (B)) in the range of 0.1 to 0.9. [2] The method for producing organic fine particles according to [1], wherein the polymerization initiator (A) and the polymerization initiator (B) are both peroxide-based polymerization initiators. [3] The method for producing organic microparticles according to [1] or [2], wherein the polymerization initiator (A) is an alkyl peroxy ester type initiator having a 10-hour half-life temperature in the range of 55 to 100°C, and the polymerization initiator (B) is a diacyl peroxide type initiator having a 10-hour half-life temperature in the range of 50 to 75°C. [4] The method for producing organic microparticles according to any one of [1] to [3], wherein the total amount of the polymerization initiator (A) and the polymerization initiator (B) is more than 2.0 parts by mass per 100 parts by mass of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinkable monomer. [5] The (meth)acrylic monomer is (meth)acrylic acid C 1-4 The method for producing organic fine particles according to any one of [1] to [4], wherein the (meth)acrylic bifunctional crosslinkable monomer is an alkyl ester, and the (meth)acrylic bifunctional crosslinkable monomer is an alkanediol di(meth)acrylate. [6] Organic fine particles that are copolymers of (meth)acrylic monomers and (meth)acrylic bifunctional crosslinkable monomers, and have an a value of -0.465 or more and 0.465 or less in the Lab color system. [7] The organic fine particles according to [6], having a b value in the Lab color system of -1.175 or more and 1.175 or less. [8] The organic fine particles according to [6] or [7], wherein the residual amount of the (meth)acrylic monomer is less than 500 ppm (by mass). [9] The organic fine particles according to any one of [6] to [8], which have a mass median particle diameter of 0.5 μm or more and 40 μm or less.

[10] A thermoplastic resin film containing the organic fine particles according to any one of [6] to [9]. Effect of the Invention

[0006] According to the present invention, discoloration of organic fine particles can be prevented to a high degree, and therefore discoloration of a film containing organic fine particles can be prevented to a high degree. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The present invention relates to copolymer microparticles (organic microparticles) of a (meth)acrylic monomer and a (meth)acrylic bifunctional crosslinkable monomer, and is characterized in that the a value in the Lab color system is -0.465 or more and 0.465 or less. The smaller the absolute value of the a value, the closer the organic microparticles are to colorlessness, and the more likely it is that the film containing the organic microparticles will be prevented from being colored. The a value is preferably -0.445 or more, more preferably -0.43 or more. It is also preferably 0.00 or less, more preferably -0.30 or less.

[0008] The organic fine particles preferably have a small absolute b value in the Lab color system, for example, -1.20 or more (particularly -1.175 or more), preferably 0.00 or more, more preferably 1.10 or more, and for example, 1.20 or less (particularly 1.175 or less), preferably 1.15 or less, more preferably 1.14 or less.

[0009] In addition, it is also preferable that the organic fine particles have a small amount of monomers used in copolymerization, particularly (meth)acrylic monomers. In particular, in food packaging films, the amount of residual monomers is strictly regulated by law, and by reducing the amount of the monomers, odor can be improved. The amount of residual (meth)acrylic monomers is, for example, 1000 ppm (by mass) or less, preferably less than 500 ppm (by mass).

[0010] The organic fine particles preferably have a mass average particle diameter (Dw) of 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 2.0 μm or more. The Dw is preferably 40 μm or less, more preferably 30 μm or less, even more preferably 15 μm or less, particularly preferably 10 μm or less, and most preferably 8 μm or less.

[0011] The ratio (Dn / Dw) of the number average particle size (Dn) to the mass average particle size (Dw) of the organic fine particles is, for example, 0.3 or more, preferably 0.4 or more, and may be as high as 0.6 or more. Dn / Dw is an index of the monodispersity of particle size, and the higher the value, the lower the proportion of fine particles, and the closer to 1, the more monodispersed the particles are. By making Dn / Dw closer to 1, the physical properties of the film containing the organic fine particles can be made more uniform.

[0012] The coefficient of variation (CV value) of the particle size of the organic microparticles is a value determined from the particle size distribution based on mass, and is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less, and is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more.

[0013] The particle size can be measured by a precision particle size distribution measuring device using the Coulter principle (e.g., the Coulter Multisizer III manufactured by Beckman Coulter, Inc.). The particle size is measured as the mass average particle size (Dw) and the number average particle size (Dn), and the coefficient of variation (CV value) of the mass average particle size can be calculated according to the following formula. Coefficient of variation of average particle size (Dw) (%) = (standard deviation of average particle size (Dw) σ / average particle size (Dw)) × 100

[0014] The organic fine particles can be produced by polymerizing a (meth)acrylic monomer and a (meth)acrylic bifunctional crosslinkable monomer in the presence of an aqueous solvent and a thermal polymerization initiator. In particular, organic fine particles having a small absolute value of the above-mentioned a value can be produced by using, as the thermal polymerization initiator, a polymerization initiator (B) having a 10-hour half-life temperature of 40°C or higher and a polymerization initiator (A) having a 10-hour half-life temperature that is 3°C or higher than that of the polymerization initiator (B), in a mass ratio of the polymerization initiator (A) to the polymerization initiator (B) (polymerization initiator (A) / polymerization initiator (B)) in the range of 0.1 to 0.9.

[0015] The (meth)acrylic monomer may be used alone or in combination with another. Examples of the (meth)acrylic monomer include (meth)acrylic acid; monoalkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate; and monocyclic ether-containing acrylates such as tetrahydrofurfuryl (meth)acrylate. As the (meth)acrylic monomer, monoalkyl (meth)acrylates are preferred, and esters of methacrylic acid and alkyl alcohols having about 1 to 4 carbon atoms (i.e., (meth)acrylic acid C 1-4 (Alkyl ester) is more preferred, and methyl (meth)acrylate is particularly preferred. The (meth)acrylic monomer may be either an acrylic monomer or a methacrylic monomer, but is preferably a methacrylic monomer.

[0016] The (meth)acrylic bifunctional crosslinking monomer may be any monomer having two polymerizable functional groups copolymerizable with the (meth)acrylic monomer, and examples of such polymerizable functional groups include vinyl groups and (meth)acryloyl groups, with (meth)acryloyl groups being preferred and methacryloyl groups being particularly preferred, provided that at least one of the polymerizable functional groups is a (meth)acryloyl group.

[0017] The (meth)acrylic bifunctional crosslinkable monomer may be used alone or in combination with another. Examples of the (meth)acrylic bifunctional crosslinkable monomer include alkane diol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and the like; alkene di(meth)acrylates such as 1,3-butylene di(meth)acrylate, and the like; polyalkylene glycol di(meth)acrylates such as polyethylene glycol di(meth)acrylate, and the like. The number of repeating alkylene glycol units in the polyalkylene glycol di(meth)acrylate is, for example, preferably 2 to 150, more preferably 2 to 23, further preferably 2 to 5, and most preferably 2 or 3. The smaller the number of repeating alkylene glycol units, the lower the melting point becomes, and the polyalkylene glycol di(meth)acrylate becomes liquid even at room temperature, improving handleability. Among these, as the (meth)acrylic bifunctional crosslinkable monomer, alkanediol di(meth)acrylate is preferable, alkanediol di(meth)acrylate composed of two (meth)acrylic acids and one alkanediol having about 2 to 4 carbon atoms is more preferable, and ethylene glycol di(meth)acrylate is particularly preferable.

[0018] The (meth)acrylic bifunctional crosslinking monomer is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and, for example, 35 parts by mass or less, preferably 30 parts by mass or less, more preferably 25 parts by mass or less, based on 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinking monomer. When the (meth)acrylic bifunctional crosslinking monomer is used in a predetermined amount or more, the hardness of the organic fine particles can be ensured, and the usefulness as an antiblocking agent can be improved. The quantitative relationship between these monomers is also maintained in the quantitative relationship between the constituent units derived from each monomer in the copolymer after copolymerization (hereinafter the same).

[0019] The total amount of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinkable monomer is, for example, 60 parts by mass or more, preferably 80 parts by mass or more, more preferably 90 parts by mass or more, relative to 100 parts by mass of all monomer components constituting the organic fine particles (copolymer), and may be 100 parts by mass.

[0020] In the present invention, the above-mentioned (meth)acrylic monomer may be copolymerized with another monofunctional monomer. The other monofunctional monomers may be one or more, and may include, for example, one or more of styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and ethylvinylbenzene; aromatic divinyl compounds such as m-divinylbenzene, p-divinylbenzene, divinylnaphthalene, and derivatives thereof; crosslinking agents such as N,N-divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfonic acid; polybutadiene, and reactive polymers described in JP-B-56507-1982, JP-A-59-221304-1984, JP-A-59-221305, JP-A-59-221306, and JP-A-59-221307, etc.

[0021] Furthermore, in the present invention, a monomer other than the above-mentioned (meth)acrylic bifunctional crosslinking monomer may be used as the crosslinking monomer. As such a crosslinking monomer, one or more types may be used, and examples thereof include tetrafunctional (meth)acrylic monomers such as pentaerythritol tetra(meth)acrylate, and hexafunctional (meth)acrylic monomers such as dipentaerythritol hexa(meth)acrylate.

[0022] These various monomers are polymerized using the above-mentioned two types of polymerization initiators (A) and (B). The polymerization initiator (A) and the polymerization initiator (B) can be appropriately selected from various polymerization initiators and used in combination as long as the following conditions are satisfied: the 10-hour half-life temperatures of the two differ by 3° C. or more (preferably 15° C. or less, more preferably 10° C. or less), and the 10-hour half-life temperature of the initiator having the lower 10-hour half-life temperature (i.e., initiator (B)) is 40° C. or more.

[0023] The 10-hour half-life temperature means the temperature at which it takes 10 hours for the polymerization initiator to decompose and become 1 / 2 its amount, and can be determined by examining the decomposition rate at a given temperature in a solution of the polymerization initiator dissolved in an inert solvent (e.g., benzene) at a concentration of 0.10 mol / L. If the polymerization initiator is not soluble in benzene at a concentration of 0.10 mol / L, the concentration may be 0.05 mol / L. If the polymerization initiator is not soluble in benzene at a concentration of 0.05 mol / L, the solvent may be toluene. If the measurement cannot be performed at these concentrations and solvents, an appropriate solvent may be selected as appropriate. Specifically, a large number of samples for measuring the decomposition rate are prepared in glass tubes that have been substituted with nitrogen, the glass tubes are kept at a predetermined temperature for measuring the half-life, and the contents are taken out at predetermined intervals to measure the polymerization initiator concentration in the contents, and the half-life at the measurement temperature is determined. The polymerization initiator concentration can be determined using high performance liquid chromatography (HPLC). When HPLC is inappropriate as a concentration measurement system, for example, when the separation between the decomposition product peak and the measurement product peak is insufficient, gas chromatography (GC) may be used. For peroxide-based polymerization initiators when HPLC and GC are inappropriate, the half-life may be determined by recording the change in active oxygen concentration over time. Iodine titration may be used to determine the active oxygen concentration. The 10-hour half-life temperature can be determined by plotting the results of measuring the half-life at multiple (e.g., three or more) half-life measurement temperatures (where each half-life measurement temperature is in increments of approximately 5°C, and the 10-hour half-life temperature is included between the upper and lower limits) on a semi-logarithmic graph.

[0024] The polymerization initiator (A) and the polymerization initiator (B) can be appropriately selected from peroxide-based polymerization initiators, azo compound-based polymerization initiators, etc., and are preferably peroxide-based polymerization initiators. peroxides having a -C(O)OOC(O)- structure, such as diacyl peroxide type initiators such as benzoyl peroxide (10-hour half-life temperature 74°C), dilauroyl peroxide (10-hour half-life temperature 62°C), dioctanoyl peroxide, bis(orthochlorobenzoyl) peroxide, and bis(orthomethoxybenzoyl) peroxide, and peroxydicarbonate type initiators such as diisopropyl peroxydicarbonate; peroxides having an -OO-C-OO- structure or an -OOC(=O)- structure, such as dimerized ketone type initiators such as methyl ethyl ketone peroxide, peroxyacetal type initiators such as cyclohexanone peroxide, peroxyketal type initiators such as 1,1-di(t-hexylperoxy)cyclohexane (trade name: Perhexa HC (registered trademark)), and alkyl peroxy ester type initiators such as t-hexylperoxy-2-ethylhexanoate (trade name: Perhexyl O (registered trademark)) (10-hour half-life temperature: 70°C) and 1,1,3,3-tetramethylbutoxyperoxy-2-ethylhexanoate (trade name: Perocta O (registered trademark)) (10-hour half-life temperature: 65°C); Examples of the initiator include peroxides having a -COOH structure (hydroperoxide type initiators), such as cumene hydroperoxide (10-hour half-life temperature 158°C), t-butyl hydroperoxide, and diisopropylbenzene hydroperoxide.

[0025] Examples of the azo compound polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,3-dimethylbutyronitrile), 2,2'-azobis-(2-methylbutyronitrile), 2,2'-azobis(2,3,3-trimethylbutyronitrile), 2,2'-azobis(2-isopropylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-4-methoxy-2,4-dimethylvaleronitrile), 2-(carbamoylazo)isobutyronitrile, 4,4'-azobis(4-cyanovaleric acid), and dimethyl-2,2'-azobisisobutyrate.

[0026] The 10-hour half-life temperature of the polymerization initiator (A) is preferably 55° C. or higher, more preferably 60° C. or higher, particularly preferably 63° C. or higher, and is preferably 100° C. or lower, more preferably 85° C. or lower, particularly preferably 75° C. or lower. The polymerization initiator (A) is preferably a peroxide having a -OO-C-OO- structure or a -OOC(═O)- structure, particularly an alkylperoxyester type initiator.

[0027] The 10-hour half-life temperature of the polymerization initiator (B) is preferably 50° C. or higher, more preferably 55° C. or higher, and is preferably 75° C. or lower, more preferably 70° C. or lower, particularly preferably 65° C. or lower. The polymerization initiator (B) is preferably a peroxide having a —C(O)OOC(O)— structure, particularly preferably a diacyl peroxide type initiator.

[0028] The mass ratio of the polymerization initiator (A) to the polymerization initiator (B) (polymerization initiator (A) / polymerization initiator (B)) is preferably 0.2 or more, more preferably 0.3 or more, and particularly preferably 0.35 or more, and is preferably 0.85 or less, more preferably 0.75 or less, and particularly preferably 0.65 or less.

[0029] The total amount of the polymerization initiator (A) and the polymerization initiator (B) is preferably 1.5 parts by mass or more, more preferably 1.7 parts by mass or more, based on 100 parts by mass of the total amount of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinkable monomer. By making the total amount of the polymerization initiator (A) and the polymerization initiator (B) 1.5 parts by mass or more, the amount of the remaining (meth)acrylic monomer can be reduced. It is also preferable that the total amount of the polymerization initiator (A) and the polymerization initiator (B) is more than 2.0 parts by mass based on 100 parts by mass of the total amount of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinkable monomer. The more the total amount of these is increased beyond 2.0 parts by mass, the more the coloring of the organic fine particles can be reduced. Note that even if it is about 2.0 parts by mass, the amount of the remaining (meth)acrylic monomer can be reduced, and there is no advantage in further increasing the total amount of the polymerization initiator (A) and the polymerization initiator (B) beyond 2.0 parts by mass from the viewpoint of the remaining monomer. Therefore, it can be said that the total amount of the initiators exceeds 2.0 parts by mass only when the prevention of coloring is the problem. The total amount of the polymerization initiator (A) and the polymerization initiator (B) is more preferably 2.1 parts by mass or more, even more preferably 2.3 parts by mass or more, particularly preferably 2.6 parts by mass or more, and may even exceed 2.9 parts by mass, and is preferably 4 parts by mass or less, more preferably 3.5 parts by mass or less, and particularly preferably 3.3 parts by mass or less, relative to 100 parts by mass of the total amount of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinkable monomer.

[0030] In one preferred embodiment, the mass ratio (A / B) of the polymerization initiator (A) to the polymerization initiator (B) is 0.35 to 0.55, and the total amount of the polymerization initiator (A) and the polymerization initiator (B) (per 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinkable monomer) is 2.55 parts by mass or more. In this case, the absolute value of the b value can be minimized. In another preferred embodiment, the mass ratio (A / B) of the polymerization initiator (A) to the polymerization initiator (B) is 0.45 to 0.65, and the total amount of the polymerization initiator (A) and the polymerization initiator (B) (per 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinkable monomer) is 2.55 parts by mass or more. In this case, the absolute value of the a value can be minimized. In another preferred embodiment, the mass ratio (A / B) of the polymerization initiator (A) to the polymerization initiator (B) is 0.45 to 0.55, and the total amount of the polymerization initiator (A) and the polymerization initiator (B) (per 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic bifunctional crosslinkable monomer) is 2.55 parts by mass or more. In this case, the absolute values ​​of both the a value and the b value can be significantly reduced.

[0031] Polymerization of the monomer is usually carried out in an aqueous solvent in the presence of a dispersion stabilizer, and the particles are prepared, for example, by suspension polymerization, emulsion polymerization, etc. (preferably suspension polymerization). These polymerization methods can make the organic fine particles spherical, and can obtain organic heavy fine particles with a uniform particle size. For example, in the suspension polymerization method, a monomer suspension can be obtained by dispersing and suspending a monomer for forming organic fine particles, a polymerization initiator, a surfactant, and an aqueous solvent. A suspension of organic fine particles can be obtained by polymerizing the monomer in the obtained monomer suspension.

[0032] The dispersion stabilizer may be either an organic dispersion stabilizer or an inorganic dispersion stabilizer. Examples of the organic dispersion stabilizer include a water-soluble polymer, an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, an alginate, zein, and casein. Examples of the inorganic dispersion stabilizer include barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc, clay, diatomaceous earth, bentonite, titanium hydroxide, sodium hydroxide, and metal oxide powder.

[0033] Examples of the water-soluble polymer include polyvinyl alcohol, gelatin, tragacanth, starch, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium polyacrylate, and sodium polymethacrylate.

[0034] Examples of the anionic surfactant include fatty acid salts such as sodium oleate and potassium castor oil; alkyl sulfate ester salts such as sodium lauryl sulfate and ammonium lauryl sulfate; alkyl benzene sulfonates such as sodium dodecylbenzene sulfonate; alkyl naphthalene sulfonates; alkanesulfonates; dialkyl sulfosuccinates; alkyl phosphate ester salts; naphthalene sulfonate-formaldehyde condensates; polyoxyalkylene alkyl ether sulfates such as polyoxyethylene alkyl ether sulfates; polyoxyalkylene aryl ether sulfate salts such as polyoxyethylene phenyl ether sulfate salts; polyoxyalkylene alkyl sulfate salts such as polyoxyethylene alkyl sulfate salts; and the like.

[0035] Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate; and quaternary ammonium salts such as lauryltrimethylalkylammonium chloride.

[0036] Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene sorbitan fatty acid esters, sorbitan fatty acid esters, polyoxysorbitan fatty acid esters, polyoxyethylene alkylamines, glycerin fatty acid esters, and oxyethylene-oxypropylene block copolymers. An example of the zwitterionic surfactant is lauryl dimethylamine oxide. Among these, from the viewpoint of good polymerization stability and suspension stability, anionic surfactants are preferred, and polyoxyalkylene aryl ether sulfates are more preferred.

[0037] The amount of the dispersion stabilizer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, relative to 100 parts by mass of the total amount of monomers.

[0038] The aqueous solvent may contain at least water, and may be, for example, water alone or a combination of water and a water-soluble solvent. By using a water-soluble organic solvent, the particle size of the resulting particles can be controlled. The amount of water is, for example, 80 parts by mass or more, preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and particularly preferably 99 parts by mass or more, per 100 parts by mass of the aqueous solvent. It is preferable to include a sufficient amount of water from the viewpoint of suspension stability.

[0039] Examples of the water-soluble organic solvent include alcohol solvents such as methanol, ethanol, propanol, butanol, 2-methylpropyl alcohol, and 2-methyl-2-propanol; ketone solvents such as acetone and methyl ethyl ketone; ester solvents such as ethyl acetate; and ether solvents such as dioxane, diethyl ether, and tetrahydrofuran.

[0040] The aqueous solvent is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, and even more preferably 300 parts by mass or more, relative to 100 parts by mass of the non-aqueous solvent components (components excluding the aqueous solvent from the monomer reaction liquid), and is preferably 1000 parts by mass or less, more preferably 700 parts by mass or less, and even more preferably 500 parts by mass or less.

[0041] When reacting the monomer in an aqueous solvent, it is preferable to use an antioxidant. By using an antioxidant, the heat resistance of the resulting organic fine particles can be improved. Examples of the antioxidant include hindered phenol-based antioxidants, phosphorus-based antioxidants, lactone-based antioxidants, hydroxylamine-based antioxidants, and vitamin E-based antioxidants, and the hindered phenol-based antioxidants are preferable.

[0042] Specific examples of the hindered phenol-based antioxidant include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox (registered trademark) 1010), octadecyl-3-(3,5-di-tert-butyl-1-hydroxyphenyl)propionate, N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], and benzene Propanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy, C7-C9 side chain alkyl ester, 3,3',3”,5,5',5”-hexa-tert-butyl-a,a',a”-(mesitylene-2,4,6-tolyl)tri-p-cresol, calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-t Hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, N-phenylbenzyl reaction products of benzeneamine and 2,4,4-trimethylbenzene, diethyl [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 2,4-dimethyl-6-(1-methylpentadecyl)phenol, octadecyl-3-(3,5-tert-butyl-4-hydroxyphenyl)propionate, 2',3-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]propionohydrazide, and the like.

[0043] Examples of phosphorus-based antioxidants include tris(2,4-di-tert-butylphenyl)phosphite, tris[2-[[2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphen-6-yl]oxy]ethyl]amine, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl ester phosphorous acid, and tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4'-diylbisphosphonite. Examples of lactone antioxidants include the reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene (CAS No. 181314-48-7), and examples of hydroxyamine antioxidants include the oxidation product of alkylamines made from reduced beef tallow, and examples of vitamin E antioxidants include 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-benzopyran-6-ol.

[0044] The amount of the antioxidant is, for example, 0.2 parts by mass or more, preferably 0.3 parts by mass or more, and more preferably 0.4 parts by mass or more, relative to 100 parts by mass of the total of the monomers, and for example, 5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2 parts by mass or less.

[0045] When suspending or emulsifying the monomer, polymerization initiator (A) (B), antioxidant, dispersion stabilizer, and aqueous solvent, an emulsification and dispersion device can be used. Examples of the emulsification and dispersion device include high-speed shear turbine type dispersers such as Milder (manufactured by Ebara Corporation) and TK Homomixer (manufactured by Primix Corporation); high-pressure jet homogenizers such as piston-type high-pressure homogenizer (manufactured by Gaolin Co., Ltd.) and Microfluidizer (manufactured by Microfluidics Co., Ltd.); ultrasonic type emulsification and dispersion devices such as ultrasonic homogenizer (manufactured by Nippon Seiki Co., Ltd.); medium stirring and dispersion devices such as Attritor (manufactured by Mitsui Mining Co., Ltd.); and forced gap passing type dispersion devices such as Colloid Mill (manufactured by Nippon Seiki Co., Ltd.). In addition, before processing with the emulsification and dispersion device, pre-stirring may be performed with a normal paddle blade or the like.

[0046] The polymerization temperature is preferably 40 to 100° C., more preferably 50 to 90° C. The upper limit of the polymerization temperature T R max (℃) is the 10-hour half-life temperature of the polymerization initiator (A), T A (℃), T R max <T A +40°C is preferable, T R max <T A +30°C is more preferable, T R max <T A The lower limit of the polymerization temperature (polymerization initiation temperature, etc.) T R min (℃) is the 10-hour half-life temperature of the polymerization initiator (B). B (℃), T B -10℃ <T R min Preferably, T B -5℃ <T R min More preferably, T B <T R min It is particularly preferred that:

[0047] The polymerization time is preferably 5 to 600 minutes, more preferably 60 to 400 minutes. When the polymerization time is within the above range, the polymerization degree can be appropriately increased, and the mechanical properties of the particles can be improved. The polymerization atmosphere is preferably an inert atmosphere such as a nitrogen atmosphere or a rare gas atmosphere.

[0048] The obtained polymerization reaction liquid is cooled to 50°C or less, and solid-liquid separation is performed without adding a flocculant, so that organic fine particles can be recovered. If necessary, a flocculant may be added and solid-liquid separation is performed to recover organic fine particles. When substantially no flocculant is added, the flocculant is preferably 0.005 parts by mass or less, more preferably 0.001 parts by mass or less, and most preferably 0 parts by mass, relative to 100 parts by mass of the monomer used. When a flocculant is added, the amount of the flocculant added is preferably more than 0.005 parts by mass, more preferably 0.05 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, relative to 100 parts by mass of the monomer used.

[0049] As the flocculant, one or more types can be used, and examples thereof include metal salts such as sodium chloride, magnesium chloride, calcium chloride, sodium sulfate, aluminum sulfate, zinc sulfate, magnesium sulfate, sodium bicarbonate, sodium carbonate, ammonium chloride, and potassium alum; acids such as sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, carbonic acid, and acetic acid; and alcohols such as methanol and ethanol.

[0050] As the method for solid-liquid separation, an optimal method can be selected from filtration, centrifugation, or a combination thereof. The collected organic fine particles may be dried appropriately as necessary. The drying temperature is, for example, 60° C. or higher, preferably 70° C. or higher, and, for example, 90° C. or lower. The drying is preferably carried out until the moisture content of the organic fine particles is, for example, 5% by mass or lower, preferably 3% by mass or lower, and more preferably 1% by mass or lower. The drying time is, for example, 10 hours or higher, preferably 12 hours or higher, and, for example, 20 hours or lower, preferably 18 hours or lower.

[0051] In order to set the particle size (Dw, Dn), the ratio (Dn / Dw), the coefficient of variation (CV), etc. of the organic fine particles within a predetermined range, classification may be performed as necessary. As classification, either wet classification or dry classification can be used. Wet classification can be performed, for example, by passing the polymerization liquid after polymerization through a metal mesh, and dry classification can be performed by using an appropriate classification device for particles that have been further dried and pulverized after polymerization.

[0052] The organic fine particles of the present invention produced as described above are useful as antiblocking agents and light diffusing agents, and are particularly important as antiblocking agents to be incorporated into food packaging films, since they are suppressed from being colored. When organic fine particles are used as antiblocking agents and light diffusing agents, the organic fine particles are used by being incorporated into, for example, a thermoplastic resin film. The organic fine particle-containing resin film can be produced, for example, by preparing a master batch containing organic fine particles, kneading the master batch with a thermoplastic resin, and then forming the resulting film. By processing the organic fine particles into a master batch, it becomes easy to adjust the amount of organic fine particles incorporated in the thermoplastic resin film, and the dispersion state of the organic fine particles can be made more uniform, thereby suppressing segregation of the organic fine particles.

[0053] Examples of the thermoplastic resin used in the thermoplastic resin film or master batch include polyester resin, polyolefin resin, polyamide resin, polyurethane resin, (meth)acrylic resin, polycarbonate resin, polystyrene resin, and the like. Among these, polyolefin resin is preferred. Examples of the polyolefin resin include polyethylene, polypropylene, poly(4-methylpentene), and the like, with polypropylene being preferred. Polypropylene resins include mainly homopolymers consisting of polypropylene alone, and random polymers obtained by copolymerizing polypropylene (preferably 95% by mass or more) with a small amount (preferably 5% by mass or less) of ethylene. The polypropylene resin in this specification includes the two types of homopolymer and random polymer, and further includes polypropylene resins whose physical properties have been improved by copolymerization with other monomers. Among these, polypropylene resins in which the ratio of units derived from propylene is preferably 90% by mass or more, more preferably 95% by mass or more, are preferred.

[0054] The thermoplastic resin is preferably present in the masterbatch at 50 mass% or more, more preferably at 70 mass% or more, even more preferably at 80 mass% or more, and particularly preferably at 85 mass% or more; it is preferably present at 99 mass% or less, and more preferably at 95 mass% or less.

[0055] The content of organic fine particles in the masterbatch is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of the resin in the masterbatch, and is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less.

[0056] The master batch preferably further contains an antioxidant. The antioxidant can be selected from the ranges exemplified above, and a hindered phenol-based antioxidant or a phosphorus-based antioxidant is preferable. The antioxidant is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 0.8 parts by mass or more, and preferably 7 parts by mass or less, more preferably 4 parts by mass or less, even more preferably 2 parts by mass or less, and particularly preferably 1.5 parts by mass or less, relative to 100 parts by mass of the resin in the master batch.

[0057] The master batch is mixed with a thermoplastic resin and extruded from an extruder to form an organic fine particle-containing resin film. The organic fine particles in the organic fine particle-containing resin film are, for example, 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and, for example, 10% by mass or less, preferably 5% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% by mass or less.

[0058] The thickness of the organic fine particle-containing resin film is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 0.7 μm or more, and even more preferably 1 μm or more, and is preferably 1 mm or less, more preferably 500 μm or less, and even more preferably 400 μm or less.

[0059] In addition, the ratio of the mass average particle diameter of the organic microparticles to the thickness of the resin film layer containing the organic microparticles (organic microparticle diameter / thickness of resin film containing organic microparticles) is preferably 1.5 or more, more preferably 2 or more, and even more preferably 2.5 or more, and is preferably 10 or less, more preferably 7 or less, and even more preferably 5.5 or less.

[0060] The organic fine particle-containing resin film may be further laminated with a base film. For example, the organic fine particle-containing resin film may be laminated on both sides or one side of the base film, and it is preferable to laminate the organic fine particle-containing resin film on both sides of the base film. EXAMPLES

[0061] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is possible to carry out the present invention by making appropriate modifications within the scope of the above and below-mentioned aims, and all of these modifications are included in the technical scope of the present invention.

[0062] The characteristics of the organic fine particles obtained in each of the Examples and Comparative Examples were evaluated as follows.

[0063] 1. Residual monomer (methyl methacrylate) rate 0.2 g of organic fine particles and 0.015 g of butylbenzene (internal standard) are mixed with 10 g of acetone and stirred for at least 2 hours to extract the remaining methyl methacrylate. The extract is then filtered through a filter with a pore size of 0.45 μm or less, and the amount of methyl methacrylate in the filtrate is determined by the calibration curve method using gas chromatography, thereby determining the amount of methyl methacrylate in the organic fine particles. The gas chromatography conditions are as follows: Equipment: Shimadzu Corporation "GC-2025" Column: DB-5MS (J&W Scientific) Length: 30 m, column diameter: 0.53 mm, liquid phase film thickness: 1.50 μm Vaporization chamber temperature: 280℃ Detector temperature: 280℃ Injection volume: 1.0μL Split ratio: 10.0 Carrier gas (helium): total flow rate 98.2 mL / min, purge flow rate 4.0 mL / min Column linear velocity: 59.2 cm / sec Column temperature program: 50°C (3 minutes from start) Heat up at 10℃ / min (up to 260℃) Hold at 260℃ (for 15 minutes) Methyl methacrylate retention time: approx. 6.0 min

[0064] 2. Coloring evaluation The color of the organic particles is measured using a spectrophotometer (Nippon Denshoku Industries Co., Ltd., "SE6000"). After standardization using a standard white board, the sample is ground in a mortar and placed in a Unipack A-8 (Japan-made low-density polyethylene bag (dimensions: 70 x 50 mm, thickness: 0.08 mm)) of 10 g, the air inside is removed to make the thickness uniform, a sample press is placed on top of it, and a dark box is placed over it, after which the white balance (WB), L value, a value, and b value are measured. The measurements are performed three times, and the average values ​​are the WB, L value, a value, and b value of the sample.

[0065] 3.Moisture content Approximately 0.5 g of dry organic fine particles are dispersed in a methanol solution, and the amount of water carried into the methanol solution by the organic fine particles is measured using a Karl Fischer volumetric titration device (automatic water content measurement device "AQV-300" manufactured by Hiranuma Sangyo Co., Ltd.). 3 mg of Aquamicron SS-Z (manufactured by Mitsubishi Chemical Co., Ltd.) is used as the titrant, and the titration of the titrant is performed using deionized water.

[0066] 4. Particle size, coefficient of variation Approximately 0.1 g of organic fine particles are thoroughly mixed with 0.5 g of a surfactant ("Neopelex (registered trademark) G15", sodium dodecylbenzenesulfonate, manufactured by Kao Corporation), and then irradiated with ultrasonic waves for 5 minutes. 15 g of deionized water is added to the resulting viscous dispersion liquid, and ultrasonic waves are further irradiated to prepare an organic fine particle dispersion liquid in which the particles are dispersed. Using a precision particle size distribution measuring device ("Coulter Multisizer III" manufactured by Beckman Coulter, Inc., aperture 50 μm), the particle sizes of 30,000 particles and 100,000 particles are measured, and the mass-based average particle size and the coefficient of variation of the particle size are calculated. Coefficient of variation of particle size (%) = (σ / d50) × 100 Here, σ represents the standard deviation of the particle size based on mass, and d50 represents the average particle size based on mass.

[0067] 5. 10-hour half-life temperature of polymerization initiator The 10-hour half-life temperatures of the polymerization initiators used in the examples and comparative examples were determined as follows. (5.1) Lauryl peroxide (LPO) A polymerization initiator (LPO) was weighed out and placed in a specified glass container, and the inside of the container was replaced with nitrogen. Benzene was added to the container to make 0.1 mol / L, and the polymerization initiator solution was prepared by dissolving and sealing the container. The solution was immersed in a thermostatic bath at a specified temperature (55°C, 60°C, 65°C, 70°C) to thermally decompose the polymerization initiator. The concentration of the polymerization initiator, which decreased over time, was measured. By plotting the time and the concentration of the polymerization initiator (LPO) at 55°C, 60°C, 65°C, and 70°C, the half-life (t 1 / 2 ) (unit: time) was calculated. The horizontal axis is the reciprocal of absolute temperature (1 / T) and the vertical axis is lnt 1 / 2 The relationship between these two is plotted, and the temperature at which the half-life is 10 hours is calculated from the straight line obtained from this plot. This is the 10-hour half-life temperature. The concentration of the polymerization initiator (LPO) at the above-mentioned predetermined temperature was measured by using high performance liquid chromatography (HPLC) under the following conditions. Column: CAPCELL PAK C18 (Shiseido Co., Ltd.) Type MG Particle size 5μm Size 4.6mm I.D.×250mm Column temperature: 45℃ Eluent: Acetonitrile Flow rate: 0.5mL / min Detector: UV 230nm The 10-hour half-life temperature of LPO determined by this method was 62°C. (5.2) t-Hexylperoxy-2-ethylhexanoate (PHO) The same procedure as in (5.1) was followed, except that the concentration of the polymerization initiator (PHO) was determined by gas chromatography under the following conditions. Equipment: Shimadzu Corporation "GC-2014" Column: TC-WAX (GL Science), 30 m long, Column diameter: 0.53 mm, liquid phase film thickness: 1.00 μm Vaporization chamber temperature: 120℃ Detector temperature: 200℃ Column temperature: 70℃ Injection volume: 0.5μL Carrier gas (helium): total flow rate 10 mL / min, purge flow rate 3.0 mL / min The 10-hour half-life temperature of PHO determined by this measurement method was 70°C.

[0068] Experimental Example 1 (Comparative Example) A flask equipped with a stirrer, an inert gas inlet tube, a reflux condenser, and a thermometer was charged with 519.1 parts by mass of deionized water in which 6 parts by mass of polyoxyethylene distyrylphenyl ether sulfate ester ammonium salt (trade name "Hitenol (registered trademark) NF-08", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) had been dissolved. To the water was added 288 parts by mass of methyl methacrylate (MMA) as a monomer, 72 parts by mass of ethylene glycol dimethacrylate (EGDMA), 6.84 parts by mass (1.9% by mass relative to the monomer mass) of lauryl peroxide (manufactured by NOF Corporation, trade name "Perloyl L") (also known as dilauroyl peroxide) (abbreviation LPO) as a polymerization initiator (B), and t-hexylperoxy-2-ethylhexanoate ( 0.00 part by mass (0.00 mass% based on the mass of the monomer) (abbreviation PHO, product name "Perhexyl O" manufactured by NOF Corporation) and 1.8 parts by mass (0.5 mass% based on the mass of the monomer) of a hindered phenol-based antioxidant (product name "Irganox (registered trademark) 1010" manufactured by BASF Japan, pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]) as an antioxidant were charged, and the mixture was stirred at 5,500 rpm for 8 minutes using a TK homomixer MARK II model 2.5 (manufactured by Primix Corporation) to obtain a uniform suspension. 900 parts by mass of deionized water was added to the suspension, transferred to a polymerization kettle filled with nitrogen gas, and heated to 65°C while blowing in nitrogen gas. The reaction vessel was kept warm at 65°C, and the reaction was started when the liquid temperature reached a peak temperature (about 80°C) due to self-heating. The reaction solution was kept at 75°C and stirred for 1.5 hours (when the amount of polymerization initiator was large, the jacket temperature was appropriately adjusted so that the peak temperature did not exceed 85°C). Thereafter, the polymerization liquid was further heated to 85°C and stirred for 4 hours to complete the polymerization reaction. Thereafter, the reaction liquid (suspension) was cooled to 50°C or less, filtered, and the polymerization product was collected by filtration. This was dried at 85°C for 14 hours using a hot air dryer (manufactured by Yamato Scientific Co., Ltd.) to obtain organic fine particles. The moisture content of the organic fine particles was 1% or less. Table 1 shows the monomer residual rate, coloration (WB, L value, a value, b value), mass average particle size, and variation coefficient of the organic fine particles.

[0069] Experimental Examples 2-10 Except for appropriately changing the amounts of PHO and LPO, the same procedure as in Experimental Example 1 was carried out. The results are shown in Table 1.

[0070] [Table 1]

[0071] As is apparent from Table 1, by adjusting the ratio (A / B) of the polymerization initiators (A) and (B) within an appropriate range, coloring (particularly the absolute value of the a value) can be reduced. [Industrial Applicability]

[0072] The organic fine particles produced by the present invention are useful as an antiblocking agent, a light diffusing agent, and the like.

Claims

1. The method for producing organic fine particles comprises polymerizing a monoalkyl(meth)acrylate and an alkanediol di(meth)acrylate in the presence of an aqueous solvent and a thermal polymerization initiator, the thermal polymerization initiator comprises a polymerization initiator (B) having a 10-hour half-life temperature of 40° C. or more and 75° C. or less, and a polymerization initiator (A) having a 10-hour half-life temperature of 100° C. or less and having a 10-hour half-life temperature 3° C. or more higher than that of the polymerization initiator (B), in such a range that the mass ratio of the polymerization initiator (A) to the polymerization initiator (B) (polymerization initiator (A) / polymerization initiator (B)) is 0.1 to 0.9; the total amount of the polymerization initiator (A) and the polymerization initiator (B) is more than 2.0 parts by mass per 100 parts by mass of the total amount of the monoalkyl(meth)acrylate and the alkanediol di(meth)acrylate, The polymerization initiator (A) is an alkyl peroxy ester type initiator, and the polymerization initiator (B) is a peroxide type polymerization initiator, the amount of the alkanediol di(meth)acrylate is 5 to 35 parts by mass per 100 parts by mass of the total of the monoalkyl (meth)acrylate and the alkanediol di(meth)acrylate, The method according to claim 1, wherein the total amount of the monoalkyl(meth)acrylate and the alkanediol di(meth)acrylate is 80 parts by mass or more per 100 parts by mass of all monomer components constituting the organic fine particles.

2. The method for producing organic fine particles according to claim 1, wherein the polymerization initiator (A) is an alkyl peroxy ester type initiator having a 10-hour half-life temperature in the range of 55 to 100°C, and the polymerization initiator (B) is a diacyl peroxide type initiator having a 10-hour half-life temperature in the range of 50 to 75°C.

3. The monoalkyl (meth)acrylate is (meth)acrylic acid C 1-4 3. The method for producing organic fine particles according to claim 1, wherein the organic fine particles are alkyl esters.

4. It is a copolymer of monoalkyl(meth)acrylate and alkanediol di(meth)acrylate, the amount of the structural units derived from the alkanediol di(meth)acrylate is 5 to 35 parts by mass relative to 100 parts by mass of the structural units derived from the monoalkyl (meth)acrylate and the alkanediol di(meth)acrylate, the total amount of the structural units derived from the monoalkyl(meth)acrylate and the alkanediol di(meth)acrylate is 80 parts by mass or more relative to 100 parts by mass of the structural units derived from all monomers constituting the copolymer, The a value in the Lab color system is −0.465 or more and 0.465 or less, Organic fine particles having a residual amount of monoalkyl (meth)acrylate of 1000 ppm (by mass) or less.

5. 5. The organic fine particles according to claim 4, wherein the b value in the Lab color system is from -1.175 to 1.

175.

6. 6. The organic fine particles according to claim 4, wherein the residual amount of monoalkyl (meth)acrylate is less than 500 ppm (by mass).

7. The organic fine particles according to any one of claims 4 to 6, having a mass average particle size of 0.5 µm or more and 40 µm or less.

8. A thermoplastic resin film comprising the organic fine particles according to any one of claims 4 to 7.

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