JP6313974B2 - Crosslinked acrylic resin particles and method for producing the same, resin composition and packaging article - Google Patents

Description

  The present invention relates to a crosslinked acrylic resin particle, a method for producing the same, a resin composition, and a packaging article.

  Resin particles produced by suspension polymerization and seed polymerization methods are used in a wide range of fields in place of inorganic particles as paint matting agents, cosmetic lubricants, additives for improving resin properties, light diffusing agents, etc. It is used in.

  In general, when resin particles obtained by suspension polymerization or seed polymerization are used in paints, the resin particles form irregularities on the surface of the coating film, resulting in a matte coating surface. Light diffusibility is imparted to the effect or coating.

  In particular, crosslinked acrylic resin particles are widely used because of excellent weather resistance and transparency. At that time, if the particles are extremely larger than the average diameter, that is, if there are coarse particles, it causes blisters on the coated surface, causes a decrease in appearance, and easily spills from the coated surface. The scratch resistance of the coated surface may be inferior.

  Also, the presence of a large amount of volatile matter in the particles, i.e. moisture or residual monomer, makes it unfamiliar with the coating resin or solvent and causes aggregation, or volatilizes when drying in the coating process. As a result of the occurrence of unevenness on the surface, there is a problem in that the performance of scratches on the surface of the coating film is reduced.

  In Patent Document 1, a drying temperature is set to 60 to 90 ° C. while washing and stirring a wet cake obtained by dehydrating a suspension obtained by dispersing synthetic resin particles in an aqueous dispersion medium. The wet cake is dried and is primarily dried until the moisture content of the wet cake becomes 0.2 to 5.0% by weight, and then the drying temperature is set to 100 to 140 ° C. under a reduced pressure of 1 to 7 kPa. Thus, a method for producing synthetic resin particles that is subjected to secondary drying while adjusting the temperature of the synthetic resin particles to be 3 ° C. lower than the drying temperature is disclosed.

  Patent Document 2 discloses a coating liquid containing an ultraviolet curable resin, a solvent, and translucent fine particles having a weight average particle diameter of 1 μm or more, and the water content of the translucent fine particles is 0.1 to 0. A coating solution of 8 mass% is disclosed.

JP 2006-077047 A JP 2012-215867 A

  However, although the synthetic resin particles can reduce moisture and residual monomers during drying, the moisture in the atmosphere is absorbed and the volatile matter increases in the process of reducing coarse particles, and the resin particles are contained. When a resin composition and a coating solution are applied onto a substrate to form a coating film, resin particles aggregate in the coating film, or unevenness occurs due to volatile components in the drying process, resulting in scratch resistance of the coating film. It has the problem of being lowered.

  The present invention relates to a crosslinked acrylic resin particle which can be used in a paint and can form a coating film having excellent appearance and scratch resistance, a method for producing the same, a resin composition using the crosslinked acrylic resin particle, and Provide packaging items.

  The crosslinked acrylic resin particles of the present invention contain an acrylic resin and have a large particle size that is 1.5% or less after heating for 1.5 hours at 120 ° C. and has a particle size that is at least twice the volume average particle size. The content of the diameter particles is 1.0% by volume or less.

  The acrylic resin contained in the crosslinked acrylic resin particles of the present invention is obtained by polymerizing a raw material monomer containing an acrylic monomer, and polymerizing a raw material monomer containing an acrylic monomer and a polyfunctional monomer. preferable. The acrylic resin contained in the crosslinked acrylic resin particles is preferably crosslinked with a polyfunctional monomer. The acrylic monomer is not particularly limited. For example, acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, dodecyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate Methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, etc. From this, it is possible to obtain crosslinked acrylic resin particles with a small variation in particle strength. Chill methacrylate is preferable. In addition, an acrylic monomer may be used independently or 2 or more types may be used together.

  Examples of the multifunctional monomer include trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, decaethylene glycol di (meth) acrylate , Pentadecaethylene glycol di (meth) acrylate, pentacontactor ethylene glycol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, 1,3-butylene di (meth) acrylate, allyl (meth) acrylate, etc. Examples include functional monomers, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene or their derivatives, and cross-linked acrylics with small variations in particle strength within the particle size distribution. Since it is possible to obtain a system resin particles, preferably an acrylic polyfunctional monomer, acrylic polyfunctional monomer having a plurality of (meth) acryloyl group is preferred. In addition, a polyfunctional monomer may be used independently or 2 or more types may be used together. In the present invention, (meth) acrylate means acrylate or methacrylate. In the present invention, the (meth) acryloyl group means an acryloyl group or a methacryloyl group.

  The production method of the acrylic polyfunctional monomer is not particularly limited. For example, the acrylic polyfunctional monomer produced by the dehydration esterification method (A) and the acrylic type produced by the transesterification method (B) A polyfunctional monomer is mentioned, The acrylic polyfunctional monomer produced | generated by the dehydration esterification method (A) is preferable.

  In the dehydration esterification method (A), raw material alcohol, (meth) acrylic acid and an acidic catalyst are supplied into a solvent, the raw material alcohol and (meth) acrylic acid are ester-reacted, neutralized, washed with water, A method for producing an acrylic polyfunctional monomer by removing the solvent from the system. In addition, (meth) acrylic acid means acrylic acid or methacrylic acid.

  Examples of the raw material alcohol include trimethylolpropane, ethylene glycol, diethylene glycol, triethylene glycol, decaethylene glycol, pentadecaethylene glycol, pentacontactor ethylene glycol, pentaerythritol, 1,3-butanediol, and allyl alcohol. Ethylene glycol is preferred.

  Examples of the acidic catalyst include sulfonic acid catalysts such as concentrated sulfuric acid and paratoluenesulfonic acid. Examples of the solvent include aromatic hydrocarbon solvents such as benzene, toluene, and xylene.

  The transesterification method (B) refers to a method for producing an acrylic polyfunctional monomer by reacting a raw alcohol with a lower (meth) acrylic ester using a neutral catalyst. The alcohol produced is removed out of the system. In addition, since raw alcohol can use the alcohol similar to the dehydration esterification method (A), description is abbreviate | omitted. The neutral catalyst is not particularly limited, and examples thereof include lithium hydroxide, lithium hydroxide monohydrate, lithium methoxide, lithium hydride, lithium acetate, and lithium amide.

  In the transesterification method (B), the transesterification reaction between the raw material alcohol and the lower (meth) acrylic acid ester is an equilibrium reaction, so that an unreacted raw material alcohol is obtained under normal synthesis conditions. About 1 to 3% by weight may remain. Further, since the boiling point of the unreacted raw material alcohol is close to the boiling point of the obtained acrylic polyfunctional monomer, it may be difficult to remove only the unreacted raw material alcohol out of the system.

  Therefore, the acrylic polyfunctional monomer is preferably an acrylic polyfunctional monomer produced by the dehydration esterification method (A) with a low content of volatile substances such as raw material alcohol, and further remains by distillation. An acrylic polyfunctional monomer purified by removing (meth) acrylic acid and acidic catalyst is more preferable. Thus, the cross-linked acrylic resin particles obtained by polymerizing the raw material monomer containing the acrylic polyfunctional monomer having a low content of volatile substances and impurities have a low content of volatile substances and impurities. For example, in the case where a resin composition containing crosslinked acrylic resin particles and a binder resin is applied onto a coated surface to form a coated film, and the coated film is dried to form a coated film, the crosslinked acrylic Air bubbles caused by volatile substances and impurities contained in the resin particles are rarely generated in the coating film, and since the familiarity with the solvent is good, adhesion to the coated surface, appearance and scratch resistance A coating film excellent in adhesion can be obtained.

  The content of the polyfunctional monomer in the raw material monomer is 1 to 100 parts by weight with respect to 100 parts by weight of the acrylic monomer because it is possible to obtain crosslinked acrylic resin particles having a small variation in particle strength within the particle size distribution. Is preferable, 5 to 80 parts by weight is more preferable, and 20 to 50 parts by weight is particularly preferable.

  The raw material monomer may contain a monomer copolymerizable with the acrylic monomer. Such a monomer is not particularly limited. For example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, vinyl chloride, vinyl acetate, acrylonitrile, acrylamide, methacrylamide, N -Vinylpyrrolidone etc. are mentioned. These monomers may be used alone or in combination of two or more.

  The crosslinked acrylic resin particles of the present invention constitute a resin composition by mixing with a binder resin, and a coating film is formed by applying this resin composition to an arbitrary coating surface such as a substrate and drying it. be able to.

  The inventors of the present invention have intensively investigated the scratch resistance of the obtained coating film. When the amount of volatile components such as residual monomer and moisture contained in the crosslinked acrylic resin particles is large, the resin composition contains It has been found that the compatibility with the binder resin and the solvent mixed as necessary decreases, the crosslinked acrylic resin particles aggregate, and the dispersibility in the binder resin decreases.

  Furthermore, the inventors, after applying the resin composition to the coated surface, in the drying step of drying the coated film, residual monomers and volatile components such as moisture contained in the crosslinked acrylic resin particles are present. Air bubbles are generated in the coating film due to the released residual monomer and volatile components such as moisture released from the cross-linked acrylic resin particles, and the amount of the binder resin is small in the portion where the air bubbles are present. As the adhesiveness between the binder resin and the crosslinked acrylic resin particles decreases, the scratch resistance of the coating film decreases and the presence of bubbles promotes the aggregation of the crosslinked acrylic resin particles. .

  That is, the crosslinked acrylic resin particles of the present invention have a heat loss after heating at 120 ° C. for 1.5 hours (hereinafter sometimes simply referred to as “heat loss”) limited to 1.5% or less, preferably 1 By setting the content to 0.0% or less, the total amount of volatile components such as residual monomers and moisture contained in the crosslinked acrylic resin particles can be reduced. By reducing the total amount of volatile components such as residual monomer and moisture, the compatibility with the binder resin and the solvent is improved, and the dispersibility of the crosslinked acrylic resin particles in the binder resin is improved. Suppresses the amount of volatile components such as residual monomer and moisture released from the resin particles into the coating film, substantially prevents bubbles from forming in the coating film, and adheres the binder resin and crosslinked acrylic resin particles to each other. And the aggregation of the cross-linked acrylic resin particles is substantially prevented. Therefore, according to the acrylic resin particles of the present invention, a coating film having excellent scratch resistance can be formed.

In addition, the heat loss of acrylic resin particles refers to the value measured in the following manner. 9 to 10 g is weighed into a 100 cm ³ beaker (W ₃ ) having a constant weight of acrylic resin particles, and the weight of the sample and the beaker (W ₁ ) is read to the order of 0.1 mg. The sampled beaker containing the sample is allowed to stand at 120 ° C. for 1.5 hours, and then the beaker is taken out and the weight (W ₂ ) after standing for 30 minutes in a desiccator containing silica gel is measured. The measurement is performed in an environment of a test room temperature of 23 ° C. to 27 ° C., and the heating loss of the acrylic resin particles is calculated based on the following formula.
Loss on heating (%) = 100 × (W ₁ −W ₂ ) / (W ₁ −W ₃ )
W ₁ : Total weight of sample and beaker before heating (g)
W ₂ : Total weight of sample and beaker after heating (g)
W ₃ : Weight of beaker (g)

  In the crosslinked acrylic resin particles of the present invention, the content of particles having a particle size that is twice or more the volume average particle size (large particle) is 1.0% by volume or less. Thus, in the crosslinked acrylic resin particles of the present invention, the content of particles having a particle size that is twice or more the volume average particle size (large particle) is limited to 1.0% by volume or less, preferably 0. .5% by volume or less.

  Thus, the surface of the coating film formed from the resin composition containing the crosslinked acrylic resin particles by limiting the content of the large-diameter particles contained in the crosslinked acrylic resin particles to a predetermined amount or less. It is possible to improve the appearance of the coating film by generally preventing the large-diameter particles from protruding. Furthermore, the large-diameter particles are prevented from falling off from the surface of the coating film, thereby improving the scratch resistance of the coating film.

  The volume average particle diameter of the crosslinked acrylic resin particles is preferably 50 μm or less because the appearance of the coating film formed from the resin composition containing the crosslinked acrylic resin particles and the scratch resistance of the coating film are improved. Aggregation of the resin particles can be further prevented, and the appearance and scratch resistance of the coating film are further improved. Therefore, 3 to 30 μm is more preferable, and 5 to 20 μm is particularly preferable.

The volume average particle diameter of the acrylic resin particles is measured by Coulter Multisizer III (measurement device manufactured by Beckman Coulter, Inc.). The measurement shall be performed using an aperture calibrated according to the Multisizer ^™ 3 User's Manual published by Beckman Coulter.

  The aperture used for the measurement is selected by selecting an aperture having a size of 50 μm when the assumed volume average particle size of the resin particles to be measured is 1 μm or more and 10 μm or less, and assuming the volume average particle size of the resin particles to be measured. When the particle size is larger than 10 μm and not larger than 30 μm, an aperture having a size of 100 μm is selected. When the assumed volume average particle size of the resin particles is larger than 30 μm and not larger than 90 μm, an aperture having a size of 280 μm is selected as appropriate. . When the volume average particle diameter after measurement is different from the assumed volume average particle diameter, the aperture is changed to an aperture having an appropriate size, and measurement is performed again.

  When an aperture having a size of 50 μm is selected, Current (aperture current) is set to −800, Gain (gain) is set to 4, and when an aperture having a size of 100 μm is selected, Current (aperture current) is − 1600, Gain (gain) is set to 2, and when apertures having sizes of 280 μm and 400 μm are selected, Current (aperture current) is set to −3200 and Gain (gain) is set to 1.

  As a sample for measurement, 0.1 g of crosslinked acrylic resin particles in 10 mL of a 0.1 wt% nonionic surfactant aqueous solution (touch mixer (manufactured by Yamato Kagaku Co., Ltd., “TOUCHMIXER MT-31”)) and ultrasonic cleaner ( A dispersion liquid is used by using “ULTRASONIC CLEANER VS-150” manufactured by Vervo Crea. Set a beaker filled with ISOTON (registered trademark) II (manufactured by Beckman Coulter, Inc .: electrolyte for measurement) in the measurement part of Coulter Multisizer III, and drop the dispersion while stirring the beaker gently. The measurement is started after the concentration meter reading on the Coulter Multisizer III main body screen is adjusted to 5 to 10%. During the measurement, the beaker is gently stirred to the extent that bubbles do not enter, and the measurement ends when 100,000 particles are measured. The volume average particle diameter of the crosslinked acrylic resin particles is an arithmetic average in a volume-based particle size distribution of 100,000 particles.

  It is preferable to use porous cross-linked acrylic resin particles in order to enhance the high matting property or the adhesiveness with the binder resin. Since porous cross-linked acrylic resin particles have a large specific surface area, they are highly hygroscopic and may have a high volatile content and a good coating film may not be obtained. Therefore, it is preferable to suppress the weight loss by heating to a low level.

  Next, the manufacturing method of the crosslinked acrylic resin particle of this invention is demonstrated. The method for producing the crosslinked acrylic resin particles of the present invention is not particularly limited, but after the crosslinked acrylic resin particles are produced by polymerization (polymerization step), the drying step of drying the crosslinked acrylic resin particles, and the crosslinked acrylic type are performed. It is preferable to manufacture through a classification step of classifying resin particles. The polymerization method is not particularly limited as long as it is a known polymerization method. Examples of known polymerization methods include bulk polymerization, emulsion polymerization, soap-free emulsion polymerization, seed polymerization, and suspension polymerization. Suspension polymerization and seed polymerization are preferred because particles with a particle size of 1 μm or more can be obtained.

  First, a case where suspension polymerization is employed as a polymerization method will be described. The polymerization process will be described. In the polymerization step, a raw material monomer including an acrylic monomer and a polyfunctional monomer is subjected to suspension polymerization in an aqueous medium in the presence of a polymerization initiator to obtain a suspension containing crosslinked acrylic resin particles. Suspension polymerization is performed by dispersing droplets of a mixture (oil phase) containing a raw material monomer and a polymerization initiator in an aqueous medium (aqueous phase) to polymerize the raw material monomer.

  The aqueous medium is not particularly limited, and examples thereof include water and a mixed medium of water and a water-soluble organic medium (lower alcohol (alcohol having 5 or less carbon atoms) such as methanol and ethanol). The amount of the aqueous medium used is preferably 100 to 1000 parts by weight with respect to 100 parts by weight of the raw material monomer in order to stabilize the crosslinked acrylic resin particles.

  A dispersion stabilizer may be contained in the aqueous medium. Dispersion stabilizers include phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, pyrophosphates such as calcium pyrophosphate, magnesium pyrophosphate, aluminum pyrophosphate and zinc pyrophosphate, calcium carbonate, magnesium carbonate , Calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, colloidal silica and other poorly water-soluble inorganic compounds, and water-soluble polymers such as polyvinylpyrrolidone and polyvinyl alcohol. Among these, when those which are decomposed by acid and dissolved in water (for example, calcium carbonate, tricalcium phosphate, magnesium hydroxide, magnesium pyrophosphate, calcium pyrophosphate) are used, the dispersion stabilizer can be easily removed after the polymerization step. This is preferable because it can be performed. In addition, a dispersion stabilizer may be used independently or 2 or more types may be used together.

  The amount of the dispersion stabilizer used is 0.1% with respect to 100 parts by weight of the raw material monomer because the fluidity of the suspension is ensured and the dispersibility of the crosslinked acrylic resin particles in the suspension is excellent. -20 parts by weight is preferable, and 0.5-10 parts by weight is more preferable.

  The polymerization initiator is not particularly limited as long as it can initiate the polymerization of the raw material monomer, but has a 10-hour half-life temperature of 40 to 80 ° C., for example, benzoyl peroxide, lauroyl peroxide, t-butyl per Organic peroxides such as oxy-2-ethylhexanoate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2, It is preferable to use an azo nitrile compound such as 4-dimethylvaleronitrile). A polymerization initiator may be used independently or 2 or more types may be used together.

  The amount of the polymerization initiator used is preferably from 0.01 to 10 parts by weight, preferably from 0.01 to 7 parts by weight, based on 100 parts by weight of the raw material monomer, since suspension polymerization of the raw material monomer can be started smoothly. More preferred is 0.01 to 5 parts by weight.

  In order to further stabilize the suspension (reaction solution) during suspension polymerization, a surfactant may be contained in the aqueous medium. As the surfactant, any of an anionic surfactant, a cationic surfactant, a nonionic surfactant, and a zwitterionic surfactant can be used. In addition, surfactant may be used independently or 2 or more types may be used together.

  Examples of the anionic surfactant include sodium oleate; fatty acid oil such as castor oil potassium; alkyl sulfate ester salts such as sodium lauryl sulfate and ammonium lauryl sulfate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; Acid salt; alkane sulfonate; dialkyl sulfosuccinate such as sodium dioctyl sulfosuccinate; alkenyl succinate (dipotassium salt); alkyl phosphate ester salt; naphthalene sulfonic acid formalin condensate; polyoxyethylene alkylphenyl ether sulfate ester Polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate; Polyoxyethylene alkyl sulfate salts and the like It is.

  Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate; quaternary ammonium salts such as lauryltrimethylammonium chloride.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, oxy Examples include ethylene-oxypropylene block polymers.

  Examples of zwitterionic surfactants include lauryl dimethylamine oxide, phosphate ester surfactants, and phosphite ester surfactants.

  In order to reduce the amount of monomer remaining in the obtained crosslinked acrylic resin particles, in the polymerization step, the polymerization temperature of the raw material monomer is divided into a first temperature region and a second temperature region higher than the first temperature region, After the raw material monomer is suspension-polymerized in the first temperature region, it is preferable that the raw material monomer is further suspension-polymerized in the second temperature region.

  As a 1st temperature range, 30 degreeC or more and less than 80 degreeC are preferable, and 40-70 degreeC is more preferable. As a 2nd temperature range, it is necessary to be a temperature higher than a 1st temperature range, 60-120 degreeC is preferable, 80-120 degreeC is more preferable, 90-105 degreeC is especially preferable.

  As mentioned above, the suspension polymerization temperature of the raw material monomer is divided into the first temperature region and the second temperature region, so that the polymerization initiator is gradually decomposed in the low temperature first temperature region. Polymerization of the monomer, and after the polymerization of the raw material monomer has progressed to some extent, the polymerization rate of the raw material monomer can be promoted by increasing the polymerization rate of the raw material monomer in the second temperature region higher than the first temperature region, As a result, the amount of residual monomers contained in the obtained crosslinked acrylic resin particles can be reduced.

  The time for the suspension polymerization of the raw material monomer in the first temperature region is preferably 0.1 to 15 hours because the polymerization of the raw material monomer can sufficiently proceed. The time for suspension polymerization of the raw material monomer in the second temperature region is preferably 0.5 to 5 hours because the amount of residual monomer in the obtained crosslinked acrylic resin particles can be effectively reduced.

  Next, a case where seed polymerization is employed as a polymerization method will be described. First, seed particles are added to an emulsion (suspension) composed of a raw material monomer and an aqueous medium. The emulsion can be prepared by a known method. For example, an emulsified liquid can be obtained by adding a raw material monomer to an aqueous medium and dispersing with a fine emulsifier such as a homogenizer, an ultrasonic processor, or a nanomizer. Examples of the aqueous medium include water or a mixture of water and an organic solvent (for example, a lower alcohol).

  Moreover, it does not specifically limit about the manufacturing method of the seed particle produced separately, For example, methods, such as emulsion polymerization, soap free emulsion polymerization, or suspension polymerization, can be used. Considering the uniformity of the seed particle size and the simplicity of the production method, emulsion polymerization or soap-free emulsion polymerization is preferred. You may adjust the weight average molecular weight of a seed particle with the usage-amount of a polymerization initiator, or the addition amount of a molecular weight modifier.

  The raw material monomer may contain a polymerization initiator as necessary. The polymerization initiator may be preliminarily mixed with the monomer and then dispersed in an aqueous medium, or those obtained by separately dispersing both in an aqueous medium may be mixed. The particle diameter of the raw material monomer droplets present in the obtained emulsion is preferably smaller than the seed particles because the monomer is efficiently absorbed by the seed particles.

  The seed particles may be added directly to the emulsion, or may be added in a form in which the seed particles are dispersed in an aqueous medium (hereinafter referred to as seed particle dispersion). After the seed particles are added to the emulsion, the raw material monomer is absorbed by the seed particles. This absorption can usually be performed by stirring the emulsion after addition of seed particles at room temperature (20 ° C.) for 1 to 12 hours. Moreover, in order to accelerate | stimulate absorption of a monomer, an emulsion may be heated at about 30-50 degreeC.

  The seed particles swell by absorbing the monomer. The mixing ratio of the monomer and the seed particles is preferably 5 to 300 parts by weight, more preferably 100 to 250 parts by weight, based on 1 part by weight of the seed particles. When the mixing ratio of raw material monomers decreases, the increase in particle size due to polymerization decreases, and when the mixing ratio of raw material monomers increases, the raw material monomers are not completely absorbed by the seed particles, and are independently subjected to suspension polymerization in an aqueous medium. Abnormal particles may be generated. In addition, the completion | finish of the raw material monomer absorption by a seed particle can be determined by confirming expansion of a particle size by observation with an optical microscope.

  The polymerization initiator added as necessary is not particularly limited, and examples thereof include benzoyl peroxide, lauroyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide. , T-butylperoxy-2-ethylhexanoate, organic peroxides such as di-t-butyl peroxide; 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-carboni) Ryl), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile, (2-carbamoylazo) isobutyronitrile, 4,4′-azobis (4-cyanovaleric acid), dimethyl-2, Examples thereof include azo compounds such as 2′-azobisisobutyrate, etc. The polymerization initiator is preferably used in the range of 0.1 to 1.0 part by weight with respect to 100 parts by weight of the raw material monomer.

  Next, acrylic resin particles are obtained by polymerizing the raw material monomer absorbed in the seed particles. The polymerization temperature can be appropriately selected according to the type of raw material monomer and polymerization initiator, but in order to reduce the amount of monomer remaining in the resulting crosslinked acrylic resin particles, as in the suspension polymerization described above. In the polymerization step, the polymerization temperature of the raw material monomer is divided into a first temperature region and a second temperature region higher than the first temperature region, and after the raw material monomer is polymerized in the first temperature region, the raw material monomer is Further polymerization is preferably performed in a two-temperature region. Specifically, the first temperature region is preferably 30 ° C. or higher and lower than 80 ° C., and more preferably 40 to 70 ° C. As a 2nd temperature range, it is necessary to be a temperature higher than a 1st temperature range, 60-120 degreeC is preferable, 80-120 degreeC is more preferable, 90-105 degreeC is especially preferable. The polymerization may be performed in an inert gas atmosphere inert to the polymerization, such as a nitrogen atmosphere. The polymerization reaction is preferably performed by raising the temperature after the raw material monomer and the optional polymerization initiator are completely absorbed in the seed particles.

  In the polymerization step, a polymer dispersion stabilizer may be added in order to improve the dispersion stability of the resin particles. Examples of the polymer dispersion stabilizer include polyvinyl alcohol, polycarboxylic acid, celluloses (such as hydroxyethyl cellulose and carboxymethyl cellulose), and polyvinylpyrrolidone. An inorganic water-soluble polymer compound such as sodium tripolyphosphate may be used in combination. Of these polymer dispersion stabilizers, polyvinyl alcohol and polyvinyl pyrrolidone are preferred. The addition amount of the polymer dispersion stabilizer is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the raw material monomer.

  In order to suppress the generation of emulsified particles in the aqueous system in the polymerization step, water-soluble polymerization inhibitors such as nitrites, sulfites, hydroquinones, ascorbic acids, water-soluble vitamin Bs, citric acid, polyphenols, etc. May be used.

  The crosslinked acrylic resin particles are obtained by separating the crosslinked acrylic resin particles from the suspension obtained in the polymerization step by filtration and washing with water or the like.

  Next, the crosslinked acrylic resin particles obtained as described above are preferably subjected to a drying step. By subjecting the crosslinked acrylic resin particles to a drying process, the residual monomer and water content contained in the crosslinked acrylic resin particles can be further reduced, and the heating loss of the resulting crosslinked acrylic resin particles can be further reduced. This is preferable.

  The drying temperature of the crosslinked acrylic resin particles is preferably 30 to 90 ° C., and preferably 60 to 80 ° C., because the amount of residual monomer and moisture contained in the crosslinked acrylic resin particles can be effectively reduced. More preferred.

  The drying of the cross-linked acrylic resin particles is preferably performed under reduced pressure because the amount of residual monomer and moisture contained in the cross-linked acrylic resin particles can be effectively reduced. The degree of vacuum during drying of the crosslinked acrylic resin particles is preferably 0.03 to 0.09 MPa, and more preferably 0.05 to 0.08 MPa. “Vacuum degree” refers to an absolute value of a pressure difference from atmospheric pressure, which is a pressure equal to or lower than atmospheric pressure.

  The drying time of the crosslinked acrylic resin particles is preferably 3 to 24 hours, and preferably 5 to 20 hours, since the amount of residual monomer and moisture contained in the crosslinked acrylic resin particles can be effectively reduced. More preferred.

  Next, in the obtained cross-linked acrylic resin particles, the particle size is large so that the content of particles having a particle size that is twice or more the volume average particle size (large particle) is 1.0% by volume or less. Particles are removed by classification.

  The classification method of the crosslinked acrylic resin particles is not particularly limited as long as particles having a large particle diameter can be removed by classification, and examples thereof include wind classification, screen classification, and the like. Since the resin particles can be classified without causing clogging, air classification is preferable. Wind classification refers to a method of classifying particles using air flow. Screen classification is a method of classifying crosslinked acrylic resin particles on the screen into particles that pass through the screen mesh and particles that do not pass through by supplying the crosslinked acrylic resin particles onto the screen and vibrating the screen. Say.

  As the air classification, (1) a method in which crosslinked acrylic resin particles are placed in a flow of air and the crosslinked acrylic resin particles collide with the screen to classify the particles into particles that pass through the screen mesh and particles that do not pass through ( 2) Putting the cross-linked acrylic resin particles on the flow of the swirling air flow, the particle size of large and small due to the interaction between the centrifugal force applied to the cross-linked acrylic resin particles by the swirling air flow and the flow of the air flow toward the swirling center of the air flow The method of classifying into groups is mentioned. As an apparatus for performing the air classification in the above (1), for example, the product name “Blower Shifter” is available from Yugrup Co., the product name “Hivolta” from Toyo Hitech Co., and the product name “Micro Shifter” from Makino Sangyo Co., Ltd. Classifiers. Examples of the device for performing the air classification of (2) include a classification device commercially available from Nissin Engineering Co., Ltd. under the trade name “Turbo Classifier” and from Seishin Enterprise Co., Ltd. under the trade name “Sped Classifier”. The above two classification methods can be used properly depending on the properties of the acrylic resin particles to be classified and the target coarse particle removal level. When the adhesion of acrylic resin particles is high and when it is desired to improve the removal accuracy of coarse particles, it is preferable to use the air classifier (2).

  The screen openings used in the air classification of (1) can efficiently classify and remove large particles without causing clogging, so that the cross-linked acrylic resin before classification is removed. It is preferably 2 to 7 times the volume average particle diameter of the particles, more preferably 3 to 5 times.

  The air classification can be performed under an atmosphere of dehumidified air because the heating loss of the crosslinked acrylic resin particles can be kept small. Specifically, the relative humidity of the air is 30% or less. It is preferably performed in an atmosphere, and more preferably in an atmosphere having a relative humidity of air of 20% or less.

After the production, the crosslinked acrylic resin particles obtained in this manner are preferably sealed with a packaging material that hardly permeates moisture and stored as a packaged article so as not to absorb moisture in the air. As a packaging material that hardly permeates moisture, a packaging material having a water vapor permeability of 50 g / m ² · 24 hours or less is preferable. Examples of such packaging materials include bags made of low-density polyethylene having a thickness of 50 to 150 μm, bags made of a vapor-deposited film in which a metal film is vapor-deposited on one surface of a synthetic resin film, and one surface of a synthetic resin film. And a bag made of a laminated film in which a metal film is laminated and integrated. Is preferably not more than 50g / m ² · 24 hours of water vapor transmission as moisture permeability of the packaging material, 30g / m ² · 24 hours or less is more preferable. The water vapor transmission rate was measured using a water vapor transmission rate measurement device (manufactured by MOCON, USA, “Permatran (registered trademark) W3 / 31)” under conditions of a temperature of 40 ° C. and a relative humidity of 90%. It measured based on the B method (infrared sensor method) as described in JIS K7129 (2000 version). Further, each of the two test pieces is measured once, and the arithmetic average value of the two measured values is set as the value of the water vapor transmission rate.

  Next, an example of how to use the crosslinked acrylic resin particles of the present invention will be described. A resin composition is prepared by mixing the crosslinked acrylic resin particles obtained as described above and a binder resin.

  The resin composition may contain a solvent in order to adjust the viscosity. It does not specifically limit as a solvent, For example, toluene, methyl ethyl ketone, ethyl acetate, alcohol, etc. are mentioned. In addition, a solvent may be used independently or 2 or more types may be used together.

  As a method for producing the resin composition, the crosslinked acrylic resin particles and the binder resin may be mixed using a general-purpose mixer. Examples of the mixer include a kneader such as an extruder, a bead mill, and a high-pressure homogenizer.

  The binder resin may be any of ionizing radiation curable resin such as ultraviolet curable resin and electron beam curable resin, thermoplastic resin, or thermosetting resin. Binder resin may be used independently or 2 or more types may be used together. Examples of the thermoplastic resin include the above-described acrylic resins, polycarbonates, polyester resins, polyethylene resins, polyolefin resins such as polypropylene resins, polystyrene resins, and the like. Acrylic resins, polycarbonates, polyester resins, and polystyrene resins are preferred. In addition, a thermoplastic resin may be used independently or 2 or more types may be used together. In the present specification, the “binder resin” is a concept including a monomer which is a raw material of the binder resin and an oligomer obtained by polymerizing the monomer, unless otherwise specified.

  Examples of the thermosetting resin include thermosetting urethane resin composed of acrylic polyol and isocyanate prepolymer, phenol resin, urea melamine resin, epoxy resin, unsaturated polyester resin, and silicone resin.

  As the ionizing radiation curable resin, a polyfunctional (meth) acrylate resin such as a polyhydric alcohol polyfunctional (meth) acrylate; synthesized from a diisocyanate, a polyhydric alcohol, and a (meth) acrylic acid ester having a hydroxy group Such as a polyfunctional urethane acrylate resin. As the ionizing radiation curable resin, a polyfunctional (meth) acrylate resin is preferable, and a polyhydric alcohol polyfunctional (meth) acrylate resin having three or more (meth) acryloyl groups in one molecule is more preferable. Specific examples of the polyhydric alcohol polyfunctional (meth) acrylate resin having three or more (meth) acryloyl groups in one molecule include trimethylolpropane tri (meth) acrylate and trimethylolethane tri (meth) acrylate. 1,2,4-cyclohexanetetra (meth) acrylate, pentaglycerol triacrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol triacrylate, dipentaerythritol pentaacrylate, dipentaerythritol Tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tripentaerythritol triacrylate, tripentaerythritol hexaacrylate, etc. It is below. The ionizing radiation curable resins may be used alone or in combination of two or more.

  As the ionizing radiation curable resin, in addition to the above, a polyether resin having an acrylate functional group, a polyester resin having an acrylate functional group, an epoxy resin having an acrylate functional group, and an acrylate functional group Alkyd resin having acrylate functional group, spiroacetal resin having acrylate functional group, polybutadiene resin having acrylate functional group, polythiol polyene resin having acrylate functional group, and the like.

  When using an ultraviolet curable resin among the ionizing radiation curable resins, a photopolymerization initiator is added to the ultraviolet curable resin to obtain a binder resin. The photopolymerization initiator is not particularly limited. Examples of the photopolymerization initiator include acetophenones, benzoins, benzophenones, phosphine oxides, ketals, α-hydroxyalkylphenones, α-aminoalkylphenones, anthraquinones, thioxanthones, azo compounds, peroxides (Described in JP 2001-139663 A, etc.), 2,3-dialkyldione compounds, disulfide compounds, fluoroamine compounds, aromatic sulfoniums, onium salts, borate salts, active halogen compounds, α-acyloxy And muester.

  Examples of the acetophenones include acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, 1-hydroxydimethylphenyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-4-methylthio-2-morpholinopropio. Phenone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone and the like can be mentioned. Examples of benzoins include benzoin, benzoin benzoate, benzoin benzene sulfonate, benzoin toluene sulfonate, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether. Examples of benzophenones include benzophenone, 2,4-dichlorobenzophenone, 4,4-dichlorobenzophenone, p-chlorobenzophenone, and the like. Examples of phosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide. Examples of ketals include benzylmethyl ketals such as 2,2-dimethoxy-1,2-diphenylethane-1-one. Examples of α-hydroxyalkylphenones include 1-hydroxycyclohexyl phenyl ketone. Examples of α-aminoalkylphenones include 2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) -1-propanone.

  Commercially available radical photopolymerization initiators include trade names “Irgacure (registered trademark) 651” (2,2-dimethoxy-1,2-diphenylethane-1-one) manufactured by BASF Japan Ltd., manufactured by BASF Japan Ltd. Trade name “Irgacure (registered trademark) 184”, trade name “Irgacure (registered trademark) 907” (2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1- On) and the like are preferable examples.

  The amount of the photopolymerization initiator used is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, and particularly preferably 1 to 8 parts by weight with respect to 100 parts by weight of the binder resin.

  The content of the binder resin in the resin composition is 25 to 4000 parts by weight with respect to 100 parts by weight of the crosslinked acrylic resin particles because an optical material excellent in both light diffusibility and light transmittance can be produced. Is preferable, and 50 to 2000 parts by weight is more preferable.

  The resin composition is applied to an arbitrary coating surface such as a base material to prepare a coating film, and after drying the coating film, the coating film is cured as necessary to crosslink. A coating film containing acrylic resin particles can be formed. In addition, as a method of coating the resin composition on the coated surface, a known method such as a reverse roll coating method, a gravure coating method, a die coating method, a comma coating method, or a spray coating method can be used.

  An optical film can be obtained by applying the resin composition using a transparent film substrate as a substrate. The optical film can be used as an antiglare film. The material of the transparent film substrate is not particularly limited as long as it has transparency. For example, polyester resin such as polyethylene terephthalate, triacetyl cellulose resin, polystyrene resin, acrylic resin, polycarbonate resin, cyclohexane Examples include olefin resins. The thickness of the transparent film substrate is preferably 5 to 300 μm. When the thickness of the transparent film substrate is thinner than 5 μm, handling of the transparent film substrate during coating, printing, and secondary processing becomes difficult, and workability may be reduced. On the other hand, when the thickness of the transparent film substrate is larger than 300 μm, the visible light transmittance of the transparent film substrate itself may be lowered.

  The resin composition contains cross-linked acrylic resin particles, but the cross-linked acrylic resin particles have a loss on heating of 1.5% or less, and the residual monomer and water content contained in the cross-linked acrylic resin particles Therefore, the cross-linked acrylic resin particles are not aggregated during the application of the resin composition, and the cross-linked acrylic resin particles are good in the thermoplastic resin. To disperse. Therefore, even in the obtained coating film, the crosslinked acrylic resin particles are present in a well dispersed state in the binder resin without agglomeration.

  Furthermore, since the amount of residual monomer and moisture contained in the crosslinked acrylic resin particles is small, the total amount of residual monomer and moisture released from the crosslinked acrylic resin particles during drying of the coating film is extremely small. is there. Therefore, the resulting coating film has almost no bubbles due to residual monomers and moisture released from the crosslinked acrylic resin particles, and the resulting coating film has excellent scratch resistance.

  Moreover, since the content of the large-diameter particles contained in the crosslinked acrylic resin particles is 1.0% by volume or less, the large-diameter particles protrude from the surface of the obtained coating film. The coating film obtained has an excellent appearance because there is almost no large-diameter particles falling off from the coating film surface.

  Since the acrylic resin particles of the present invention have the configuration as described above, when used for forming a coating film by being contained in a resin composition, the resulting coating film has an excellent appearance and scratch resistance. Has a tendency to attach.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

Example 1
An aqueous phase was prepared by adding 5 parts by weight of tribasic calcium phosphate as an inorganic dispersion stabilizer and 0.005 part by weight of sodium lauryl sulfate as an anionic surfactant to 100 parts by weight of deionized water.

  On the other hand, a raw material monomer containing 35 parts by weight of methyl methacrylate and 15 parts by weight of ethylene glycol dimethacrylate, 0.2 parts by weight of benzoyl peroxide and 0.2 parts by weight of 2,2′-azobisisobutyronitrile as a polymerization initiator Was dissolved to obtain an oil phase. Ethylene glycol dimethacrylate was produced by the dehydration esterification method and further purified by distillation. The purity of ethylene glycol dimethacrylate was 98.1% by weight.

  The water phase and the oil phase are stirred and mixed at a rotational speed of 2500 rpm using a disperser (trade name “TK homomixer MODEL S” manufactured by PRIMIX Corporation) to disperse the droplets of the oil phase in the water phase. To obtain a dispersion. The dispersion was supplied to a polymerization vessel equipped with a stirrer and a thermometer, and the dispersion was heated to 55 ° C. (first temperature range) while stirring the dispersion, and the raw material monomer was subjected to suspension polymerization for 3 hours. Subsequently, the dispersion was heated to 100 ° C. (second temperature range), and the raw material monomer was subjected to suspension polymerization for 2 hours to obtain a suspension containing crosslinked acrylic resin particles (polymerization step). During suspension polymerization, the polymerization atmosphere was a nitrogen atmosphere.

  After cooling the obtained suspension to 20 ° C., hydrochloric acid is added to the suspension to decompose tricalcium phosphate, and then the crosslinked acrylic resin particles are separated using a centrifuge (manufactured by Tanabe Wiltech). Then, the obtained crosslinked acrylic resin particles were washed with ion-exchanged water.

  Next, the obtained crosslinked acrylic resin particles were dried for 15 hours under the conditions of 60 ° C. and a vacuum degree of 0.05 MPa (drying step). The obtained crosslinked acrylic resin particles had a volume average particle size of 8.21 μm.

  An air classifier (trade name “HI-VOLTER NR300” manufactured by Toyo Hitec Co., Ltd.) having a screen with a mesh opening of 32 μm was prepared. Using a wind classifier, the crosslinked acrylic resin particles were classified in an air atmosphere having a relative humidity of 20%. Large particles are removed by placing crosslinked acrylic resin particles in an air flow having a relative humidity of 20%, causing the crosslinked acrylic resin particles to collide with the screen and removing particles that do not pass through the screen mesh. As a result, crosslinked acrylic resin particles were obtained.

(Example 2)
Crosslinked acrylic resin particles were obtained in the same manner as in Example 1 except that a raw material monomer containing 47.5 parts by weight of methyl methacrylate and 2.5 parts by weight of ethylene glycol dimethacrylate was used. In addition, ethylene glycol dimethacrylate was produced by a dehydration esterification method and further purified by distillation. The purity of ethylene glycol dimethacrylate was 98.1% by weight.

(Example 3)
An aqueous phase was prepared by adding 5 parts by weight of calcium pyrophosphate as an inorganic dispersion stabilizer and 0.005 parts by weight of sodium lauryl sulfate as an anionic surfactant to 100 parts by weight of deionized water.

  On the other hand, a raw material monomer containing 20 parts by weight of methyl methacrylate and 20 parts by weight of ethylene glycol dimethacrylate, 40 parts by weight of methyl ethyl ketone as an organic solvent and 0.1 part by weight of 2,2′-azobisisobutyronitrile as a polymerization initiator Was dissolved to obtain an oil phase. In addition, ethylene glycol dimethacrylate was produced by a dehydration esterification method and further purified by distillation. The purity of ethylene glycol dimethacrylate was 98.1% by weight.

  The water phase and the oil phase are stirred and mixed at a rotational speed of 3000 rpm using a disperser (trade name “TK homomixer MODEL S” manufactured by PRIMIX Corporation) to disperse the droplets of the oil phase in the water phase. To obtain a dispersion. The dispersion was supplied to a polymerization vessel equipped with a stirrer and a thermometer, and the dispersion was heated to 50 ° C. (first temperature region) while stirring the dispersion to subject the raw material monomer to suspension polymerization for 5 hours. Subsequently, the dispersion was heated to 70 ° C. (second temperature range), and the raw material monomer was subjected to suspension polymerization for 2 hours to obtain a suspension containing crosslinked acrylic resin particles (polymerization step). During suspension polymerization, the polymerization atmosphere was a nitrogen atmosphere. The suspension containing the crosslinked acrylic resin particles was distilled under conditions of 85 ° C. and a vacuum degree of 0.063 MPa to remove methyl ethyl ketone from the suspension.

  After cooling the obtained suspension to 20 ° C., hydrochloric acid was added to the suspension to decompose calcium pyrophosphate, and then the crosslinked acrylic resin particles were separated using a centrifuge (manufactured by Tanabe Wiltech). The obtained crosslinked acrylic resin particles were washed with ion-exchanged water.

Next, the obtained crosslinked acrylic resin particles were dried for 24 hours under the conditions of 90 ° C. and a vacuum degree of 0.07 MPa (drying step). The volume average particle diameter of the obtained crosslinked acrylic resin particles was 10 μm. The crosslinked acrylic resin particle was a porous body having a specific surface area of 91 cm ² / g.

  An air classifier (trade name “HI-VOLTER NR300” manufactured by Toyo Hitec Co., Ltd.) having a screen with a mesh opening of 32 μm was prepared. Using a wind classifier, the crosslinked acrylic resin particles were classified in an air atmosphere having a relative humidity of 20%. Large particles are removed by placing crosslinked acrylic resin particles in an air flow having a relative humidity of 20%, causing the crosslinked acrylic resin particles to collide with the screen and removing particles that do not pass through the screen mesh. As a result, crosslinked acrylic resin particles were obtained. The heat loss of the obtained crosslinked acrylic resin particles was 0.65%.

A bag made of a laminated film (water vapor permeability: 0.7 g / m ² · 24 hours) formed by laminating and integrating a metal film on one surface of a synthetic resin film (produced by Nippon Shokubai Co., Ltd., trade name “Rami Zip AL-14”) ) Was prepared, and 50 g of the crosslinked acrylic resin particles obtained in this bag were accommodated and sealed to prepare a packaged article. The packaged article was left in a thermo-hygrostat (trade name “TBE” manufactured by Espec Corp.) adjusted to 30 ° C. and relative humidity 80% for 24 hours. Thereafter, the packaged article was opened, and the loss on heating of the crosslinked acrylic resin particles stored in the bag was measured and found to be 0.66%.

Example 4
To a separable flask equipped with a stirrer, a thermometer and a reflux condenser, a reaction solution containing 60 parts by weight of ion exchange water, 10 parts by weight of methyl methacrylate and 0.05 parts by weight of n-dodecyl mercaptan as a polymerization regulator was supplied. While stirring the reaction solution, the inside of the flask was purged with nitrogen, and the reaction solution was heated to 70 ° C. While maintaining the reaction solution in the flask at 70 ° C., 0.05 part by weight of potassium persulfate was supplied to the reaction solution as a polymerization initiator, and then the reaction solution was polymerized for 20 hours to obtain an emulsion (A). The resulting emulsion (A) contained 14 wt% solids. The solid content contained spherical particles having a volume average particle size of 0.4 μm.

  A reaction solution containing 55 parts by weight of water, 7 parts by weight of the emulsion (A), 10 parts by weight of methyl methacrylate and 0.05 parts by weight of n-dodecyl mercaptan in a separate separable flask equipped with a stirrer, a thermometer and a reflux condenser. While the reaction solution was stirred, the atmosphere in the flask was replaced with nitrogen, and the reaction solution was heated to 70 ° C. While maintaining the reaction solution in the flask at 70 ° C., 0.05 part by weight of potassium persulfate was supplied to the reaction solution as a polymerization initiator, and then the reaction solution was polymerized for 12 hours to obtain an emulsion (B). The resulting emulsion (B) contained 14 wt% solids. The solid content contained spherical particles (seed particles) having a volume average particle diameter of 1.0 μm.

  In another separable flask equipped with a stirrer, a thermometer, and a reflux condenser, 40 parts by weight of methyl methacrylate as a raw material monomer, 30 parts by weight of ethylene glycol dimethacrylate and 30 parts by weight of styrene, and 2,2′- as a polymerization initiator 6 parts by weight of azobisisobutyronitrile was supplied and mixed uniformly to obtain a mixture. In addition, ethylene glycol dimethacrylate was produced by a dehydration esterification method and further purified by distillation. The purity of ethylene glycol dimethacrylate was 98.1% by weight.

  100 parts by weight of ion-exchanged water containing 1 part by weight of sodium succinate as a surfactant is supplied to the resulting mixture, and a disperser (trade name “TK homomixer MODEL S” manufactured by PRIMIX Co., Ltd.) Was mixed at 20 ° C. for 10 minutes at a rotation speed of 8000 rpm to obtain an aqueous emulsion. To this aqueous emulsion, 8 parts by weight of emulsion (B) was added with stirring to prepare a dispersion.

  After stirring the dispersion for 3 hours at 20 ° C., the dispersion was observed with an optical microscope. As a result, the raw material monomer in the dispersion was absorbed by the seed particles (swelling ratio was about 20 times). Next, 200 parts by weight of an aqueous dispersion stabilizer solution was supplied to the dispersion. The aqueous dispersion stabilizer solution was prepared by dissolving 4 parts by weight of polyvinyl alcohol (trade name “PVA-224E” manufactured by Kuraray Co., Ltd.) as a dispersion stabilizer in 196 parts by weight of ion-exchanged water. While stirring the dispersion, the raw material monomer was polymerized at 60 ° C. (first temperature range) for 6 hours. Subsequently, the dispersion was heated to 100 ° C. (second temperature range) to polymerize the raw material monomer over 3 hours to obtain a suspension containing crosslinked acrylic resin particles (polymerization step). During the polymerization, the polymerization atmosphere was a nitrogen atmosphere.

  After cooling the obtained suspension to 20 ° C., the crosslinked acrylic resin particles were filtered and separated using a pressure filter, and the obtained crosslinked acrylic resin particles were washed with ion-exchanged water.

  Next, the obtained crosslinked acrylic resin particles were dried for 15 hours under the conditions of 60 ° C. and a vacuum degree of 0.05 MPa (drying step). The obtained crosslinked acrylic resin particles had a volume average particle size of 5.01 μm.

Using a wind classifier (trade name “Turbo Classifier TC-15” manufactured by Nissin Engineering Co., Ltd.), the crosslinked acrylic resin particles were classified in an atmosphere having a relative humidity of 25% (classification step). Specifically, the cross-linked acrylic resin particles are placed on a swirling airflow generated under the conditions of a rotor rotation speed of 4500 rpm and an air volume of 2.0 m ³ / min. The large particles were removed by sieving into large particles and small particles by the interaction with the flow of airflow toward the center of rotation to obtain crosslinked acrylic resin particles.

(Comparative Example 1)
Crosslinked acrylic resin particles were obtained in the same manner as in Example 2 except that the polymerization time of the raw material monomer at 55 ° C. (first temperature range) was 8 hours.

(Comparative Example 2)
Crosslinked acrylic resin particles were obtained in the same manner as in Example 3 except that classification of the crosslinked acrylic resin particles was performed in an air atmosphere having a relative humidity of 80%.

(Comparative Example 3)
Crosslinked acrylic resin particles were obtained in the same manner as in Example 1 except that the classification step was not performed.

(Comparative Example 4)
Crosslinked acrylic resin particles were obtained in the same manner as in Example 4 except that the raw material monomer was polymerized at 60 ° C. (first temperature range) for 8 hours and the classification step was not performed. The obtained crosslinked acrylic resin particles had a volume average particle size of 5.03 μm.

  About the obtained cross-linked acrylic resin particles, the amount of heat loss after heating at 120 ° C. for 1.5 hours, the volume average particle size, and the content of particles having a particle size more than twice the volume average particle size (large particle) Was measured as described above, and the results are shown in Table 1. The surface properties of the coating film obtained from the resin composition containing the obtained crosslinked acrylic resin particles were measured in the following manner, and the results are shown in Table 1.

(Surface property of coating film)
0.4 parts by weight of crosslinked acrylic resin particles, 2.5 parts by weight of a polyester resin (trade name “Byron 200” manufactured by Toyobo Co., Ltd.), 5.0 parts by weight of toluene and 1.0 part by weight of methyl ethyl ketone are stirred and defoamed. (Product name “Fabori Netaro” manufactured by Shinky Corporation) was mixed for 3 minutes and then defoamed for 1 minute to prepare a resin composition.

The obtained resin composition was applied on a black ABS plate so as to have a thickness of 100 μm, and the coating film was dried in an oven at 70 ° C. for 3 minutes to prepare a coating film. The obtained coating film surface was visually observed and judged based on the following criteria.
A: No irregularities or irregularities were observed.
B: Slight or unevenness was observed.
C ... Many irregularities or irregularities were observed.

(Preparation of resin composition for antiglare film and production example of antiglare film)
[Production Example 1]
80 parts by weight of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (trade name “Aronix (registered trademark) M-305” manufactured by Toa Gosei Co., Ltd.) as an ultraviolet curable resin, and toluene and cyclopentanone as organic solvents 120 parts by weight of a mixed solution (toluene: cyclopentanone (volume ratio) = 7: 3), 5 parts by weight of the cross-linked acrylic resin particles produced in Example 4, and (2-methyl) as a photopolymerization initiator 1- (4-Methylthiophenyl) -2-morpholinopropan-1-one) (trade name “Irgacure (registered trademark) 907” manufactured by BASF Japan Ltd.) 5 parts by weight is mixed to give a resin composition for an antiglare film. A product was prepared.

A transparent polyethylene terephthalate (PET) film having a thickness of 200 μm was prepared as a transparent film substrate. The resin composition for an antiglare film was applied to one side of a polyethylene terephthalate film using a bar coater to form a coating film. Next, the coating film was dried by heating at 80 ° C. for 1 minute. Thereafter, the coating film was cured by irradiating the coating film with ultraviolet light with an integrated light quantity of 300 mJ / cm ² using a high-pressure mercury lamp to form an antiglare hard coat layer. An antiglare film was obtained in which the antiglare hard coat layer containing the crosslinked acrylic resin particles of Example 4 was laminated and integrated on one side of the polyethylene terephthalate film.

[Comparative Production Example 1]
An antiglare film was obtained in the same manner as in Production Example 1 except that the crosslinked acrylic resin particles of Comparative Example 4 were used instead of the crosslinked acrylic resin particles of Example 4.

  The antiglare property, total light transmittance and haze of the obtained antiglare film were measured as follows, and the results are shown in Table 2.

(Anti-glare property)
The anti-glare film was placed directly under the fluorescent lamp, and the surface of the anti-glare film was visually observed and evaluated based on the following criteria. The fluorescent lamp was disposed at a position 50 cm vertically above the surface of the antiglare film.

A: The outline of the fluorescent lamp appeared blurred.
B: I saw the outline of the fluorescent lamp, and I was a little worried about the outline.
C: The outline of the fluorescent light was clearly visible

(Total light transmittance and haze)
The total light transmittance of the antiglare film was measured according to JISK7361-1, and the haze (haze) of the antiglare film was measured according to JISK7136. Specifically, the total light transmittance and haze of the antiglare film were measured using a haze meter (NDH2000) commercially available from Nippon Denshoku Industries Co., Ltd.

Claims (11)

The content of large-diameter particles containing an acrylic resin and having a heat loss of 1.5% or less after heating at 120 ° C. for 1.5 hours and a volume average particle diameter of twice or more is 1.0 volume. % Cross-linked acrylic resin particles characterized by being less than or equal to%. The cross-linked acrylic resin particles according to claim 1, wherein the volume average particle diameter is 50 μm or less. The crosslinked acrylic resin particles according to claim 1 or 2, wherein the crosslinked acrylic resin particles are porous. The acrylic resin is cross-linked by an acrylic polyfunctional monomer having a plurality of (meth) acryloyl groups, and the acrylic polyfunctional monomer is a product obtained by dehydration esterification and purified by distillation. The crosslinked acrylic resin particles according to any one of claims 1 to 3, wherein the crosslinked acrylic resin particles are used. Polymerization in which a raw material monomer including an acrylic monomer and a polyfunctional monomer is polymerized in a first temperature region and then further polymerized in a second temperature region higher than the first temperature region to produce crosslinked acrylic resin particles. A step of drying, a step of drying the crosslinked acrylic resin particles obtained in the polymerization step at a vacuum degree of 0.03 to 0.08 MPa and 30 to 90 ° C., and a step of drying in the step of drying. The above-mentioned crosslinked acrylic resin particles are classified so that the content of large-diameter particles having a particle size more than twice the volume average particle size by air classification in an atmosphere having a relative humidity of 30% or less is 1.0% by volume or less. A method for producing crosslinked acrylic resin particles, comprising a classification step of classification. The polyfunctional monomer includes an acrylic polyfunctional monomer having a plurality of (meth) acryloyl groups, and the acrylic polyfunctional monomer is a product obtained by a dehydration esterification method and purified by distillation. The method for producing crosslinked acrylic resin particles according to claim 5, wherein: 6. The method for producing crosslinked acrylic resin particles according to claim 5, wherein the first temperature region is 30 ° C. or more and less than 80 ° C., and the second temperature region is 80 to 120 ° C. 6. A resin composition comprising a binder resin and the crosslinked acrylic resin particles according to any one of claims 1 to 4. An optical film obtained by coating the resin composition according to claim 8 on a transparent film substrate. The optical film according to claim 9 , which is used for antiglare. A packaged article, wherein the crosslinked acrylic resin particles according to any one of claims 1 to 4 are sealed with a packaging material having a water vapor permeability of 50 g / m ² · 24 hours or less.