TWI529184B - Crosslinked acrylic resin particle and manufacturing method thereof, resin composition, optical film and packaged article - Google Patents

Description

Crosslinked acrylic resin particles and a method for producing the same, a resin composition, an optical film, and a packaged article

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

Resin particles produced by a suspension polymerization method or a seed polymerization method are used as a matting agent for paints, a lubricant for cosmetics, an additive for improving physical properties of a resin, a light diffusing agent, and the like in place of inorganic particles, and are used in a wide range of fields.

In general, when the resin particles obtained by the suspension polymerization method or the seed polymerization method are used in a coating material, the resin particles form irregularities on the surface of the coating film, impart a matting effect on the surface of the coating film, or impart light diffusibility to the coating film.

In particular, since the crosslinked acrylic resin particles are excellent in weather resistance and transparency, they are widely used. At this time, when there are particles having a particle diameter much larger than the average particle diameter, that is, coarse particles, the cause of the spots on the coated surface causes a decrease in appearance, and sometimes becomes easy to fall off from the coated surface, and thus the coated surface Poor damage resistance.

In addition, there is a problem in that a volatile component in the particles, that is, moisture or a residual monomer is present in a large amount, and the fusion property with the coating resin or the solvent is deteriorated to cause aggregation, or volatilization occurs during drying of the coating process. Therefore, unevenness or the like is generated on the surface, resulting in a decrease in the damage performance of the surface of the coating film.

Patent Document 1 discloses a method for producing synthetic resin pellets in which a wet cake obtained by dehydrating a suspension obtained by dispersing synthetic resin pellets in an aqueous dispersion medium is washed, and then a drying temperature of 60 is set while stirring. The wet cake is dried at ~90 ° C, and dried once until the moisture content of the wet cake is 0.2 to 5.0% by weight, and then the drying temperature is set to 100 to 140 ° C, and the mixture is adjusted under a reduced pressure of 1 to 7 kPa to synthesize The temperature of the resin pellets is twice as low as the drying temperature by 3 ° C or more.

Further, Patent Document 2 discloses a coating liquid comprising an ultraviolet curable resin, a solvent, and translucent fine particles having a weight average particle diameter of 1 μm or more, and the water-transmitting fine particles have a water content of 0.1 to 0.8% by mass.

Prior art literature

Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2006-077047

Patent Document 2: Japanese Patent Laid-Open Publication No. 2012-215867

However, although the above synthetic resin particles can reduce moisture and residual monomers during drying, in the process of reducing coarse particles, moisture in the atmosphere is absorbed, and volatile components are increased, and the resin composition containing the resin particles and the coating are coated. When the cloth liquid is applied to the substrate to form a coating film, there is a tree The problem that the fat particles are aggregated in the coating film or is uneven due to the volatile component in the drying process, and the damage resistance of the coating film is lowered.

The present invention provides crosslinked acrylic resin particles which are used in a coating material and which can form a coating film excellent in appearance and scratch resistance, a method for producing the same, a resin composition using crosslinked acrylic resin particles, and a packaged article.

The crosslinked acrylic resin particle of the present invention is characterized in that it contains an acrylic resin and has a heating weight loss of 1.5% or less after heating at 120 ° C for 1.5 hours, and a large diameter of a particle diameter of twice or more the volume average particle diameter. The content of the 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 preferably polymerizing a raw material monomer containing an acrylic monomer and a polyfunctional monomer. Made. The acrylic resin contained in the crosslinked acrylic resin particles is preferably formed by crosslinking a polyfunctional monomer. The acrylic monomer is not particularly limited, and examples thereof include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, dodecyl acrylate, and stearyl acrylate. , 2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate Ester, tert-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, etc., can be obtained from the particle size distribution Starting from the crosslinked acrylic resin particles having a small variation in particle strength, methyl methacrylate is preferred. In addition, the acrylic monomers may be used singly or in combination of two or more.

As the polyfunctional monomer, for example, trimethylolpropane tri(methyl) propylene is exemplified Acid ester, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, decaethylene glycol di(meth)acrylate, Pentaethylene glycol (meth)acrylate, pentacontahecta ethylene glycol dimethacrylate, pentaerythritol tetra(meth)acrylate, 1,3-butadiene An acrylic difunctional monomer such as (meth) acrylate or allyl (meth) acrylate, an aromatic divinyl compound such as divinyl benzene, divinyl naphthalene or a derivative thereof, or the like can be obtained. In the case of the crosslinked acrylic resin particles having a small variation in particle strength in the particle size distribution, an acrylic polyfunctional monomer is preferable, and an acrylic polyfunctional monomer having a plurality of (meth)acrylonyl groups is preferable. In addition, a polyfunctional monomer can be used individually or in combination of 2 or more types. In the present invention, (meth) acrylate means acrylate or methacrylate. In the present invention, the (meth)acryl fluorenyl group means an acryl fluorenyl group or a methacryl fluorenyl group.

The method for producing the acrylic polyfunctional monomer is not particularly limited, and examples thereof include an acrylic polyfunctional monomer produced by the dehydration esterification method (A) and an acrylic acid produced by the transesterification method (B). The polyfunctional monomer is preferably an acrylic polyfunctional monomer produced by the dehydration esterification method (A).

The dehydration esterification method (A) is a method in which a raw material alcohol, (meth)acrylic acid, and an acidic catalyst are supplied to a solvent, and an ester reaction between the raw material alcohol and (meth)acrylic acid is carried out, and the water is neutralized and washed with water. The solvent is removed to the outside of the system to produce an acrylic polyfunctional monomer. It should be noted that (meth)acrylic acid means acrylic acid or methacrylic acid.

Examples of the raw material alcohol include trimethylolpropane, ethylene glycol, diethylene glycol, triethylene glycol, ten ethylene glycol, fifteen ethylene glycol, one hundred and fifty ethylene glycol, pentaerythritol, and 1, 3-butanediol, allyl alcohol and the like are preferably ethylene glycol.

Examples of the acidic catalyst include a sulfonic acid catalyst such as concentrated sulfuric acid or p-toluenesulfonic acid. The solvent is, for example, an aromatic hydrocarbon solvent such as benzene, toluene or xylene.

The transesterification method (B) is a method of producing an acrylic polyfunctional monomer by reacting a raw material alcohol with a lower (meth) acrylate using a neutral catalyst. The resulting alcohol is removed to the outside of the system. In addition, since the same alcohol as the dehydration esterification method (A) can be used as a raw material alcohol, it abbreviate|omits description. 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) acrylate is an equilibrium reaction, and therefore, under the usual synthesis conditions, sometimes the unreacted starting alcohol is obtained in the obtained acrylic acid. The polyfunctional monomer remains in an amount of about 1 to 3% by weight. 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 to the outside of the system.

Therefore, the acrylic polyfunctional monomer is preferably an acrylic polyfunctional monomer produced by a dehydration esterification method (A) having a small content of a volatile substance such as a raw material alcohol, and more preferably removed by distillation ( An acrylic polyfunctional monomer which has been purified by a methyl methacrylate, an acidic catalyst or the like. The crosslinked acrylic resin particles obtained by polymerizing a raw material monomer containing an acrylic polyfunctional monomer having a small content of a volatile substance and an impurity in this manner have a small content of volatile substances and impurities. For example, when a resin composition comprising crosslinked acrylic resin particles and a binder resin is coated on a coated surface to form a coating film, and the coating film is dried to form a coating film, substantially no cross-linked acrylic acid is produced. The bubbles caused by the volatile substances and impurities contained in the resin-like particles are also excellent in compatibility with the solvent, and therefore, a coating film excellent in adhesion to the coated surface, appearance, and scratch resistance can be obtained.

The content of the polyfunctional monomer in the raw material monomer is preferably from 1 to 100 by weight based on 100 parts by weight of the acrylic monomer, from the crosslinked acrylic resin particles having a small variation in particle strength within the particle size distribution. The portion is more preferably 5 to 80 parts by weight, particularly preferably 20 to 50 parts by weight.

The raw material monomer may further contain a monomer copolymerizable with the acrylic monomer. The monomer is not particularly limited, and examples thereof include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, vinyl chloride, ethyl acetate, and acrylonitrile. , acrylamide, methacrylamide, N-vinylpyrrolidone, and the like. These monomers may be used singly or in combination of two or more.

The crosslinked acrylic resin particles of the present invention are mixed with a binder resin to form a resin composition, and the resin composition can be applied to any coated surface of a substrate or the like and dried to form a coating film.

The inventors have conducted intensive studies on the damage resistance of the obtained coating film, and found that when the amount of the volatile component such as residual monomers and moisture contained in the crosslinked acrylic resin particles is large, the binder in the resin composition is used. The fusion property of the resin and the solvent mixed as needed is lowered, and aggregation occurs between the crosslinked acrylic resin particles, and the dispersibility in the binder resin is lowered.

Furthermore, the inventors have found that after the resin composition is applied to the coated surface, in the drying step of drying the coated film, the volatile components such as residual monomers and moisture contained in the crosslinked acrylic resin particles are The crosslinked acrylic resin particles are released, and the released residual monomers and volatile components such as moisture cause bubbles in the coating film, and the amount of the binder resin in the portion where the bubbles are present is small and the binder resin and the crosslinked acrylic acid The adhesion of the resin particles is lowered, so the damage resistance of the coating film is lowered, and the crosslinked acrylic resin particles are promoted due to the presence of bubbles. The gathering between.

In other words, the weight loss of heating (hereinafter, simply referred to as "heat loss on weight") after heating the crosslinked acrylic resin particles of the present invention at 120 ° C for 1.5 hours is limited to 1.5% or less, preferably 1.0% or less. The total amount of the volatile components such as residual monomers and moisture contained in the crosslinked acrylic resin particles is reduced. By reducing the total amount of volatile components such as residual monomers and water, the fusion property with the binder resin and the solvent is improved, the dispersibility of the crosslinked acrylic resin particles in the binder resin is improved, and the crosslinked acrylic acid is suppressed. The amount of residual monomers and volatile components such as moisture released into the coating film by the resin particles substantially prevents generation of bubbles in the coating film, improves adhesion between the binder resin and the crosslinked acrylic resin particles, and substantially prevents The aggregation between the crosslinked acrylic resin particles, whereby the acrylic resin particles according to the present invention can form a coating film having excellent scratch resistance.

In addition, the weight loss of heating of an acryl resin particle is a value measured by the following points. 9 to 10 g of acrylic resin particles were weighed in a 100 cm ³ beaker (W ₃ ) which had been set to a constant amount, and the weight (W ₁ ) of the sample and the beaker was read to 0.1 mg. After the beaker containing the sample taken was allowed to stand at 120 ° C for 1.5 hours, the beaker was taken out, and the weight (W ₂ ) after standing for 30 minutes in a drier to which the silicone was added was measured. The measurement was carried out in an environment where the temperature of the test chamber was 23 ° C to 27 ° C, and the weight loss on heating of the acrylic resin particles was 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 : the weight of the beaker (g)

Further, the crosslinked acrylic resin particles of the present invention have a volume average particle diameter of 2 The content of the particles (large diameter particles) having a particle diameter of a multiple or more is 1.0% by volume or less. In the crosslinked acrylic resin particles of the present invention, the content of the particles (large diameter particles) having a particle diameter of twice or more the volume average particle diameter is limited to 1.0% by volume or less, preferably 0.5% by volume or less. .

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 substantially suppress the surface of the coating film formed of the resin composition containing the crosslinked acrylic resin particles. Prominent so that the appearance of the coating film is good. Further, the large-diameter particles are prevented from falling off from the surface of the coating film, and the damage resistance of the coating film is improved.

The volume average particle diameter of the crosslinked acrylic resin particles is preferably 50 μm or less from the viewpoint of improving the appearance of the coating film formed of the resin composition containing the crosslinked acrylic resin particles and the scratch resistance of the coating film, thereby further preventing the crosslinking. The aggregation of the acryl-based resin particles further improves the appearance and damage resistance of the coating film. Therefore, it is more preferably 3 to 30 μm, and particularly preferably 5 to 20 μm.

The volume average particle diameter of the acrylic resin particles was measured by Coulter multisizer III (measurement apparatus manufactured by Beckman Coulter, Inc.). The measurement was carried out using an aperture corrected in accordance with the MultisizerTM 3 User's Manual by Beckman Coulter, Inc.

It should be noted that the selection of the pores for measurement is appropriately performed as follows: When the assumed volume average particle diameter of the resin particles is 1 μm or more and 10 μm or less, pores having a size of 50 μm are selected; when the measured volume average particle diameter of the resin particles is more than 10 μm and 30 μm or less, pores having a size of 100 μm are selected; When the assumed volume average particle diameter of the particles is more than 30 μm and not more than 90 μm, a hole having a size of 280 μm or the like is selected. When the volume average particle diameter after the measurement differs from the assumed volume average particle diameter, the hole is changed to a hole having an appropriate size, and the measurement is performed again. set.

In addition, when a hole having a size of 50 μm is selected, Current (hole current) is set to -800, Gain (gain) is set to 4; when a hole having a size of 100 μm is selected, Current is set to -1600, Gain (gain) Set to 2; when selecting a hole having a size of 280 μm and 400 μm, Current is set to -3200 and Gain is set to 1.

As a sample for measurement, a contact type mixer ("TOUCHMIXER MT-31" manufactured by Yamato Scientific Co., Ltd.) and an ultrasonic cleaner ("ULTRASONIC CLEANER VS-150" manufactured by VELVO-CLEAR Co., Ltd." were used. A dispersion liquid obtained by dispersing 0.1 g of crosslinked acrylic resin particles in 10 mL of a 0.1% by weight aqueous solution of a nonionic surfactant. A beaker filled with ISOTON (registered trademark) II (manufactured by Beckman Coulter, Inc., measuring electrolyte) was attached to the measurement portion of the Coulter multi-sizer III, and the dispersion was slowly added while stirring the beaker, Coulter multi- The sizerIII starts to measure after the concentration meter reading of the main picture reaches 5~10%. In the measurement, the stirring was slowed to the extent that bubbles were not generated in the beaker, and the measurement was terminated when 100,000 particles were measured. The volume average particle diameter of the crosslinked acrylic resin particles is an arithmetic mean in a volume-based particle size distribution of 100,000 particles.

For high matting properties or to improve adhesion to the binder resin, it is preferred to use porous crosslinked acrylic resin particles. Since the porous crosslinked acrylic resin particles have a large specific surface area and have high hygroscopicity and a large amount of volatile components, a good coating film may not be obtained. Therefore, it is preferable to suppress the heating weight loss to a low level.

Next, a method for producing the crosslinked acrylic resin particles of the present invention will be described. The method for producing the crosslinked acrylic resin particles of the present invention is not particularly limited, and it is preferred to produce crosslinked acrylic resin particles by polymerization (polymerization step). The drying process of drying the resin pellets and the classification process of classifying the crosslinked acrylic resin pellets are carried out. The polymerization method is not particularly limited as long as it is a known polymerization method. Examples of the known polymerization method include bulk polymerization, emulsion polymerization, soap-free emulsion polymerization, seed polymerization, and suspension polymerization. From the viewpoint of obtaining a shape-aligned particle having a particle diameter of 1 μm or more, suspension polymerization or seed polymerization is preferred.

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 containing an acrylic monomer and a polyfunctional monomer is subjected to suspension polymerization in the presence of a polymerization initiator in an aqueous medium to obtain a suspension containing crosslinked acrylic resin particles. Suspension polymerization is carried out by dispersing droplets of a mixture (oil phase) containing a raw material monomer and a polymerization initiator into an aqueous medium (aqueous phase) to polymerize the raw material monomers.

The aqueous medium is not particularly limited, and examples thereof include water, water, and water solubility. A mixed medium of a medium (a lower alcohol such as methanol or ethanol (an alcohol having 5 or less carbon atoms)). In order to stabilize the crosslinked acrylic resin particles, the amount of the aqueous medium to be used is preferably 100 to 1000 parts by weight based on 100 parts by weight of the raw material monomers.

A dispersion stabilizer may also be included in the aqueous medium. As a dispersion stabilizer, it can be enumerated Phosphate such as calcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate; pyrophosphate such as calcium pyrophosphate, magnesium pyrophosphate, aluminum pyrophosphate, zinc pyrophosphate; calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, hydrogen A water-insoluble inorganic compound such as alumina, calcium metasilicate, calcium sulfate, barium sulfate or colloidal cerium oxide; a water-soluble polymer such as polyvinylpyrrolidone or polyvinyl alcohol. Among these, when a compound (for example, calcium carbonate, tricalcium phosphate, magnesium hydroxide, magnesium pyrophosphate, or calcium pyrophosphate) dissolved in water by acid decomposition is used, the dispersion stabilizer can be easily removed after the polymerization step, so that the dispersion stabilizer can be easily removed. for Preferably. In addition, the dispersion stabilizer may be used singly or in combination of two or more.

The amount of the dispersion stabilizer to be used is preferably 0.1 to 20 parts by weight, more preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the raw material monomer, from the viewpoint of ensuring the fluidity of the suspension and the dispersibility of the crosslinked acrylic resin particles in the suspension. 0.5 to 10 parts by weight.

The polymerization initiator is not particularly limited as long as it can initiate polymerization of the raw material monomers, and it is preferred to use a polymerization initiator having a 10-hour half-life temperature of 40 to 80 ° C, such as benzamidine peroxide, laurel peroxide, t-butyl peroxide. Organic peroxide such as ethyl 2-hexanoate, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylisobutyronitrile), 2,2'-couple An azo nitrile compound such as nitrogen di(2,4-dimethylvaleronitrile). The polymerization initiator may be used singly or in combination of two or more.

The amount of the polymerization initiator to be used is preferably from 0.01 to 10 parts by weight, more preferably from 0.01 to 7 parts by weight, particularly preferably from 0.01 to 100 parts by weight based on 100 parts by weight of the raw material monomers. 5 parts by weight.

In the suspension polymerization, in order to further stabilize the suspension (reaction liquid), 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, the surfactant may be used singly or in combination of two or more.

Examples of the anionic surfactant include fatty acid oils such as sodium oleate and castor oil; alkylsulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate; and alkylbenzenes such as sodium dodecylbenzenesulfonate. Sulfonate; alkylnaphthalenesulfonate; alkanesulfonate; sodium dioctylsulfosuccinate Dialkylsulfosuccinate; alkenyl succinate (dipotassium salt); alkyl phosphate salt; formalin condensation polymer of naphthalene sulfonate; polyoxyethylene alkyl phenyl ether sulfate salt, poly a polyoxyethylene alkyl ether sulfate such as oxyethylene lauryl ether sulfate; a polyoxyethylene alkyl sulfate or the like.

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

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, and polyoxysorbitol fat. An acid ester, a polyoxyethylene alkylamine, a glycerin fatty acid ester, an oxyethylene-oxypropylene block polymer, or the like.

Examples of the zwitterionic surfactant include lauryl dimethylamine oxide, a phosphate ester surfactant, and a phosphite surfactant.

In order to reduce the amount of monomers remaining in the obtained crosslinked acrylic resin particles, it is preferred that, in the polymerization step, the polymerization temperature of the raw material monomers is divided into a first temperature region and a second higher than the first temperature region. In the temperature zone, the raw material monomers are suspended and polymerized in the first temperature region, and then the raw material monomers are further suspended and polymerized in the second temperature region.

The first temperature region is preferably 30 ° C or more and less than 80 ° C, and more preferably 40 to 70 ° C. As the second temperature region, a higher temperature than the first temperature region is required, and is preferably 60 to 120 ° C, more preferably 80 to 120 ° C, and particularly preferably 90 to 105 ° C.

As described above, the suspension polymerization is carried out by dividing the suspension polymerization temperature of the raw material monomer into the first temperature region and the second temperature region, and the raw material monomer is slowly decomposed while the polymerization initiator is slowly decomposed in the first temperature region at a low temperature. Polymerization, after the polymerization of the raw material monomer proceeds to a certain extent, the polymerization rate of the raw material monomer is increased in a second temperature region higher than the first temperature region, The polymerization of the raw material monomers can be promoted, and as a result, the amount of residual monomers contained in the obtained crosslinked acrylic resin particles can be reduced.

Since the polymerization of the raw material monomers can be sufficiently performed, the suspension polymerization time of the raw material monomers in the first temperature region is preferably from 0.1 to 15 hours. Since the amount of residual monomers in the obtained crosslinked acrylic resin particles can be effectively reduced, the suspension polymerization time of the raw material monomers in the second temperature region is preferably 0.5 to 5 hours.

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 produced by a known method. For example, the raw material monomer is added to an aqueous medium and dispersed by a fine emulsifier such as a homogenizer, an ultrasonic processor, or a Nanomizer, whereby an emulsion can be obtained. The aqueous medium referred to herein may, for example, be water or a mixture of water and an organic solvent (for example, a lower alcohol).

Further, the method for producing the seed granules to be separately produced is not particularly limited, and for example, a method such as emulsion polymerization, soap-free emulsion polymerization or suspension polymerization can be used. The emulsion polymerization or the soap-free emulsion polymerization method is preferred in consideration of the uniformity of the particle diameter of the seed particles and the simplicity of the production method. The weight average molecular weight of the seed particles can also be adjusted by the amount of the polymerization initiator or the amount of the molecular weight modifier added.

The raw material monomer may further contain a polymerization initiator as needed. The polymerization initiator may be mixed with the monomer in advance and dispersed in an aqueous medium, or may be mixed with a solution in which the two are dispersed in an aqueous medium. It is preferable that the particle diameter of the droplet of the raw material monomer present in the obtained emulsion is smaller than the seed particle, since the monomer can be more efficiently absorbed by the seed particle.

Seed particles can be added directly to the emulsion, or the seed particles can be used in the aqueous medium. The form in which the substance is dispersed (hereinafter referred to as a seed particle dispersion) is added. After the seed particles are added to the emulsion, the raw material monomers are absorbed by the seed particles. This absorption can usually be carried out by stirring the emulsion after adding the seed particles at room temperature (20 ° C) for 1 to 12 hours. In addition, in order to promote the absorption of the monomer, the emulsion can also be heated to about 30 to 50 ° C.

The seed particles swell by absorbing the monomer. The mixing ratio of the monomer to 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 the raw material monomers becomes small, the increase in the particle size based on the polymerization becomes small; when the mixing ratio of the raw material monomers becomes large, the raw material monomers are not completely absorbed by the seed particles, and suspension polymerization is carried out by itself in an aqueous medium, sometimes Generate abnormal particles. In addition, the completion of the absorption of the raw material monomer based on the seed particles can be determined by confirming the particle diameter expansion by observation with an optical microscope.

The polymerization initiator to be added as needed is not particularly limited, and for example, Benzoyl peroxide, laurel, benzoyl peroxide, o-methoxyperoxybenzate, 3,5,5-trimethylhexyl peroxide, t-butyl Organic peroxides such as 2-ethylhexyl oxychloride and di-tert-butyl peroxide; 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethyl Valeronitrile), 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'-azobis(4-methoxy-2,4-dimethylvaleronitrile), (2-carbamidoazo)isobutyronitrile, 4,4'-azobis (4 An azo compound such as -cyanovaleric acid or dimethyl-2,2'-azobisisobutyl ester. The polymerization initiator is preferably used in the range of 0.1 to 1.0 part by weight based on 100 parts by weight of the raw material monomers.

Next, acrylic acid can be obtained by polymerizing a raw material monomer absorbed in the seed particles. Resin particles. The polymerization temperature can be appropriately selected depending on the type of the raw material monomer and the polymerization initiator. However, in the same manner as the above suspension polymerization, in order to reduce the amount of the monomer remaining in the obtained crosslinked acrylic resin particles, it is preferred that in the polymerization step, Dividing the polymerization temperature of the raw material monomer into a first temperature region and a second temperature region higher than the first temperature region, polymerizing the raw material monomers in the first temperature region, and then further polymerizing the raw material monomers in the second 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 the second temperature region, a higher temperature than the first temperature region is required, and is preferably 60 to 120 ° C, more preferably 80 to 120 ° C, and particularly preferably 90 to 105 ° C. The polymerization can also be carried out in an inert gas atmosphere which is inactive to polymerization such as a nitrogen atmosphere. In addition, it is preferable to carry out the polymerization reaction after the raw material monomer and the polymerization initiator of any use are fully absorbed by the seed particle.

In the above 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, cellulose (hydroxyethyl cellulose, carboxymethyl cellulose, etc.), and polyvinylpyrrolidone. Further, an inorganic water-soluble polymer compound such as sodium tripolyphosphate may be used in combination. Among these polymer dispersion stabilizers, polyvinyl alcohol and polyvinylpyrrolidone are preferred. The amount of the polymer dispersion stabilizer added is preferably from 1 to 10 parts by weight based on 100 parts by weight of the raw material monomers.

Further, in the above polymerization step, in order to suppress generation of emulsified particles in the water system, nitrites, sulfites, hydroquinones, ascorbic acid, water-soluble vitamin B, citric acid, polyphenols may also be used. Water-soluble polymerization inhibitors such as a class.

The crosslinked acrylic resin particles are separated from the suspension obtained in the above polymerization step by filtration, and washed with water or the like to obtain crosslinked acrylic resin particles.

Next, for the crosslinked acrylic resin particles obtained as described above, it is preferred that The drying process is carried out. By subjecting the crosslinked acrylic resin particles to a drying step, the residual monomer and water content contained in the crosslinked acrylic resin particles can be further reduced, and the weight loss of heating of the obtained crosslinked acrylic resin particles can be further reduced, which is preferable. of.

Due to the residual monomer and moisture content contained in the crosslinked acrylic resin particles Since it is effectively reduced, the drying temperature of the crosslinked acrylic resin particles is preferably from 30 to 90 ° C, more preferably from 60 to 80 ° C.

Due to the residual monomer and moisture contained in the crosslinked acrylic resin particles The amount is effectively reduced, so drying of the crosslinked acrylic resin particles is preferably carried out under reduced pressure. The degree of vacuum when the crosslinked acrylic resin particles are dried is preferably 0.03 to 0.09 MPa, and more preferably 0.05 to 0.08 MPa. It should be noted that the "vacuum degree" is a pressure below atmospheric pressure and refers to an absolute value of a pressure difference between the pressure and the atmospheric pressure.

Due to the residual monomer and moisture contained in the crosslinked acrylic resin particles The amount is effectively reduced, so the drying time of the crosslinked acrylic resin particles is preferably from 3 to 24 hours, more preferably from 5 to 20 hours.

Next, for the obtained crosslinked acrylic resin particles, the particle size is removed by classification The particles are such that the content of particles having a volume average particle diameter of 2 times or more (large diameter particles) is 1.0% by volume or less.

The classification method of the crosslinked acrylic resin particles is not particularly limited as long as it can remove particles having a large particle diameter by classification, and examples thereof include wind classification, screen classification, and the like, and can be made smaller without clogging of the mesh. The crosslinked acrylic resin particles having an average particle diameter are classified, and therefore, wind classification is preferred. Wind grading refers to a method of grading particles by the flow of air. Screen grading means that the crosslinked acrylic resin particles are supplied on the screen and the screen is vibrated. A method of classifying crosslinked acrylic resin particles on a screen into particles passing through a mesh of mesh and unpassed particles.

As the wind classification, (1) the crosslinked acrylic resin particles are placed in a gas stream of air, and the crosslinked acrylic resin particles collide with the screen and are classified into particles passing through the mesh of the mesh and failing. a method of granules, (2) placing crosslinked acrylic resin particles in a flow of a swirling gas stream, using a centrifugal force imparted to the crosslinked acrylic resin particles by a swirling gas flow and a flow of a gas stream toward a center of rotation of the gas stream Interactions are graded into a method of sizing two particle sizes. As a device for performing the wind classification of the above (1), for example, the product name "Blower Sifter" commercially available from YOUGROP.CO., LTD, and the product name "HI-BOLTA" commercially available from TOYO HITEC Co., LTD. "Classification device of the product name "MICRO SHIFTER" commercially available from Makino Industry Co., Ltd." The apparatus for performing the wind classification of the above (2) includes a product name "TURBO CLASSIFER" commercially available from Nisshin Engineering Inc., and a classification device commercially available from Seishin Enterprise Co., Ltd. under the trade name "Spedic Classifier". . The above two classification methods can be used depending on the properties of the classified acrylic resin particles and the removal grade of the target coarse particles. When the adhesion of the acrylic resin particles is high and when it is desired to improve the removal precision of the coarse particles, it is preferable to use the air flow classifier of (2).

The mesh size of the screen used in the wind classification of the above (1) is preferably the volume of the crosslinked acrylic resin particles before classification, since the particles having a large particle size can be efficiently classified and removed without causing clogging of the mesh. The average particle diameter is 2 to 7 times, more preferably 3 to 5 times.

Since the heating weight loss of the crosslinked acrylic resin particles can be kept small, the wind classification is preferably performed under a dehumidified air atmosphere, and specifically, it is preferably carried out in an atmosphere having a relative humidity of 30% or less, more preferably The relative humidity of the air is below 20% get on.

The crosslinked acrylic resin particles obtained in this manner are preferably sealed with a packaging material which is hard to pass through moisture and stored as a packaged article in order to prevent absorption of moisture in the air. As a packaging material which is hard to transmit moisture, the water vapor transmission rate is preferably 50 g/m ² . Packaging materials for up to 24 hours. Examples of such a packaging material include a bag made of low-density polyethylene having a thickness of 50 to 150 μm, a bag made of a vapor-deposited film on which a metal film is deposited on one surface of a synthetic resin film, and a synthetic resin film. A bag made of a laminated film in which a metal thin film is integrated is laminated on one surface. As the moisture permeability of the packaging material, the water vapor transmission rate is preferably 50 g/m ² . It is 24 hours or less, more preferably 30 g/m ² . Below 24 hours. Water vapor transmission rate under the conditions of temperature 40 ° C and relative humidity of 90%, water vapor transmission rate measuring device (manufactured by MOCON, Inc., "PERMATRAN (registered trademark) W3/31)") according to JIS K7129 (2000 edition) The B method (infrared sensor method) described in the measurement. Further, the two test pieces were measured once, and the arithmetic mean of the two measured values was taken as the value of the water vapor transmission rate.

Next, an example of the use point of the crosslinked acrylic resin particles of the present invention will be described. The resin composition is produced by mixing the crosslinked acrylic resin particles obtained by the above operation with a binder resin.

In the resin composition, a solvent may be contained in order to adjust the viscosity. The solvent is not particularly limited, and examples thereof include toluene, methyl ethyl ketone, ethyl acetate, and ethanol. In addition, the solvent may be used alone or in combination of two or more.

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

The binder resin may be an ionizing radiation curable resin such as an ultraviolet curable resin or an electron beam curable resin, a thermoplastic resin, or a thermosetting resin. The binder resin may be used singly or in combination of two or more. Examples of the thermoplastic resin include a polyolefin resin such as the above-described acrylic resin, polycarbonate, polyester resin, polyethylene resin, or polypropylene resin, and a polystyrene resin, and are excellent in transparency. From the viewpoint, an acrylic resin, a polycarbonate, a polyester resin, or a polystyrene resin is preferable. In addition, the thermoplastic resin may be used singly or in combination of two or more. In the present specification, the term "adhesive resin" means a concept of including a monomer as a raw material of a binder resin and an oligomer obtained by polymerizing the monomer.

Examples of the thermosetting resin include a thermosetting polyurethane resin formed of an acrylic polyol and an isocyanate prepolymer, a phenol resin, a urea melamine resin, an epoxy resin, an unsaturated polyester resin, and an organic resin.

Examples of the ionizing radiation-curable resin include a polyfunctional (meth)acrylate resin such as a polyol polyfunctional (meth)acrylate; a diisocyanate, a polyhydric alcohol, and a (meth)acrylate having a hydroxyl group. A synthetic polyfunctional urethane acrylate resin or the like. The ionizing radiation curable resin is preferably a polyfunctional (meth) acrylate resin, and more preferably a polyol polyfunctional (meth) acrylate resin having three or more (meth) acryl fluorenyl groups in one molecule. Specific examples of the polyhydric alcohol polyfunctional (meth) acrylate resin having three or more (meth) acrylonitrile groups in one molecule include trimethylolpropane tri(meth)acrylate and trishydroxyl Methyl ethane tri(meth) acrylate, 1,2,4-cyclohexane tetra(meth) acrylate, pentaglyceryl triacrylate, pentaerythritol tetra(meth)acrylate, tris(meth)acrylic acid Pentaerythritol ester, dipentaerythritol triacrylate, dipentaerythritol pentaacrylate, tetra (a) Di) pentaerythritol acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol triacrylate, tripentaerythritol hexaacrylate, and the like. The ionizing radiation curable resin may be used singly or in combination of two or more.

In addition to the above, the ionizing radiation-curable resin may, for example, be a polyether resin having an acrylate functional group, a polyester resin having an acrylate functional group, an epoxy resin having an acrylate functional group, or an acrylate. A functional group-containing alkyd resin, a acetal resin having an acrylate functional group, a polybutadiene resin having an acrylate functional group, a polythiolpolyene resin having an acrylate functional group, and the like.

When an ultraviolet curable resin is used for the ionizing radiation curable resin, A photopolymerization initiator is added to the ultraviolet curable resin to form a binder resin. The photopolymerization initiator is not particularly limited. Examples of the photopolymerization initiator include acetophenones, benzoin, benzophenones, phosphine oxides, ketals, α-hydroxyalkylphenones, and α-aminoalkylphenones. , anthracene, thioxanthone, azo compound, peroxide (described in JP-A-2001-139663, etc.), 2,3-dialkyl glycol compound, disulfide compound And fluoroamine compounds, aromatic guanidines, sulfonium salts, borate salts, active halides, α-mercapto oxime esters, and the like.

Examples of the acetophenones include acetophenone and 2,2-diethoxyacetophenone. O-Dimethylacetophenone, 1-hydroxydimethylphenyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-4-methylthio-2-morpholinopropiophenone, 2- Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone and the like. Examples of the benzoin include benzoin, benzoin benzoate, benzoin benzenesulfonate, benzoin tosylate, benzoin methyl ether, benzoin ethyl ether, and benzene. Affinity isopropyl ether and so on. Examples of the benzophenones include benzophenone, 2,4-dichlorobenzophenone, 4,4-dichlorobenzophenone, and o-chlorobenzophenone. Examples of the phosphine oxides include 2,4,6-trimethylbenzhydrazide. Diphenylphosphine oxide and the like. Examples of the ketal include benzyl methyl ketals such as 2,2-dimethoxy-1,2-diphenylethane-1-one. Examples of the α-hydroxyalkylphenones include 1-hydroxycyclohexyl phenyl ketone and the like. Examples of the α-aminoalkylphenones include 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone.

The commercially available photoradical polymerization initiator is exemplified by the trade name "IRGACURE (registered trademark) 651" (2,2-dimethoxy-1,2-diphenylethane) manufactured by BASF Japan Ltd. 1-ketone), trade name "IRGACURE (registered trademark) 184" manufactured by BASF Japan Ltd., trade name "IRGACURE (registered trademark) 907" manufactured by BASF Japan Ltd. (2-methyl-1-(4-) As a preferred example, thiophenyl)-2-morpholinopropan-1-one) and the like are mentioned.

The photopolymerization initiator is used preferably in an amount of from 0.5 to 20 parts by weight, more preferably from 1 to 10 parts by weight, particularly preferably from 1 to 8 parts by weight, per 100 parts by weight of the binder resin.

The content of the binder resin in the resin composition is preferably 25 to 4000 parts by weight, based on 100 parts by weight of the crosslinked acrylic resin particles, from the viewpoint of producing an optical material excellent in both light diffusibility and light transmittance. It is preferably 50 to 2000 parts by weight.

The resin composition is applied to any coated surface of a substrate or the like to produce a coating film, and after the coating film is dried, the coating film is cured as necessary, whereby a coating containing crosslinked acrylic resin particles can be formed. membrane. 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.

The optical film can be obtained by coating the above resin composition using a transparent film substrate as a substrate. The optical film can be used as an anti-glare film or the like. The material of the transparent film substrate is not particularly limited as long as it has transparency, and for example, polyethylene terephthalate is exemplified. A polyester resin such as an alcohol ester, a triethylene glycol cellulose resin, a polystyrene resin, an acrylic resin, a polycarbonate resin, or a cycloolefin resin. 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 deteriorated. On the other hand, when the thickness of the transparent film substrate is thicker than 300 μm, the visible light transmittance of the transparent film substrate itself may be lowered.

The resin composition contains crosslinked acrylic resin particles, crosslinked acrylic resin particles The weight loss on heating is 1.5% or less, and the residual monomer and water contained in the crosslinked acrylic resin particles are small, so that the fusion property with the binder resin or the solvent is good, and the crosslinked acrylic acid is not coated in the coating of the resin composition. In the case where the resin-like particles are aggregated, the crosslinked acrylic resin particles are well dispersed in the thermoplastic resin. Therefore, among the obtained coating films, the crosslinked acrylic resin particles are also present in a state of being well dispersed in the binder resin without aggregation.

Further, the residual monomer and water contained in the crosslinked acrylic resin particles are small. Therefore, in the drying of the coating film, the total amount of residual monomers and moisture released from the crosslinked acrylic resin particles is extremely small. Therefore, bubbles which are generated by residual monomers and moisture released from the crosslinked acrylic resin particles are substantially absent in the obtained coating film, and the obtained coating film has excellent scratch resistance.

In addition, since the content of large diameter particles contained in the crosslinked acrylic resin particles is Since it is 1.0% by volume or less, it does not substantially become a state in which the large-diameter particles protrude on the surface of the obtained coating film, and the large-diameter particles are not substantially peeled off from the surface of the coating film, and thus the obtained coating film has an excellent appearance.

The acrylic resin particles of the present invention have the constitution as described above, and thus are included in the resin group. When used in the formation of a coating film, the obtained coating film has excellent appearance and scratch resistance.

The invention will be further illustrated in the following examples, but the invention is not limited by the examples.

(Example 1)

To 100 parts by weight of deionized water, 5 parts by weight of tricalcium phosphate as an inorganic dispersion stabilizer and 0.005 parts by weight of sodium lauryl sulfate as an anionic surfactant were added to prepare an aqueous phase.

On the other hand, 0.2 parts by weight of a benzamidine peroxide as a polymerization initiator and 2,2' are dissolved in 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 azobisisobutyronitrile to prepare an oil phase. Ethylene glycol dimethacrylate is produced by a dehydration esterification process and further purified by distillation. The purity of ethylene glycol dimethacrylate was 98.1% by weight.

Using a disperser (manufactured by PRIMIX Corporation, trade name "T.K. HOMOMIXER MODEL S"), the aqueous phase and the oil phase were stirred and mixed at a number of revolutions of 2,500 rpm, and droplets of the oil phase were dispersed in the aqueous phase to obtain a dispersion. The dispersion liquid was supplied to a polymerization vessel equipped with a stirrer and a thermometer, and the dispersion liquid was heated to 55 ° C (first temperature region) while stirring the dispersion liquid, and the raw material monomers were suspended and polymerized over 3 hours. Next, the dispersion liquid was heated to 100 ° C (second temperature region), and the raw material monomers were subjected to suspension polymerization over 2 hours to obtain a suspension containing crosslinked acrylic resin particles (polymerization step). It should be noted that in suspension polymerization, polymerization is achieved. The atmosphere is a nitrogen atmosphere.

After cooling the obtained suspension to 20 ° C, hydrochloric acid is added to the suspension to decompose the phosphoric acid. The tricalcium was then separated into crosslinked acrylic resin particles using a centrifugal separator (manufactured by TANABE WILLTEC INC.), and the obtained crosslinked acrylic resin particles were washed with ion-exchanged water.

Next, the obtained crosslinked acrylic resin particles were at 60 ° C and a vacuum of 0.05 MPa. The drying was carried out for 15 hours under the conditions (drying step). The volume average particle diameter of the obtained crosslinked acrylic resin particles was 8.21 μm.

Prepare a wind classifier with a mesh size of 32 μm (TOYO) Manufactured by HITEC Co., LTD., trade name "HI-BOLTANR300"). The crosslinked acrylic resin particles were classified using an air classifier under an air atmosphere having a relative humidity of 20%. The crosslinked acrylic resin particles are placed in a gas stream of air having a relative humidity of 20%, and the crosslinked acrylic resin particles are struck against the screen to remove particles that have not passed through the mesh of the mesh, thereby removing particles having a large particle size. The crosslinked acrylic resin particles were obtained.

(Example 2)

The crosslinked acrylic resin particles were obtained in the same manner as in Example 1 except that the raw material monomers of 47.5 parts by weight of methyl methacrylate and 2.5 parts by weight of ethylene glycol methacrylate were used.

(Example 3)

To 100 parts by weight of deionized water, 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 were added to prepare an aqueous phase.

On the other hand, 40 parts by weight of methyl ethyl ketone as an organic solvent is dissolved in a raw material monomer containing 20 parts by weight of methyl methacrylate and 20 parts by weight of ethylene glycol methacrylate, and 0.1 part by weight of 2,2'-azobisisobutyronitrile of a polymerization initiator was used to prepare an oil phase.

The dispersion and the oil phase were stirred and mixed at a rotation speed of 3000 rpm using a dispersing machine (manufactured by PRIMIX Corporation, trade name "T.K. HOMOMIXER MODEL S"), and droplets of the oil phase were dispersed in the water phase to obtain a dispersion. The dispersion liquid was supplied to a polymerization vessel equipped with a stirrer and a thermometer, and the dispersion liquid was heated to 50 ° C (first temperature region) while stirring the dispersion liquid, and the raw material monomers were suspension-polymerized over 5 hours. Next, the dispersion liquid was heated to 70 ° C (second temperature region), and the raw material monomers were suspension-polymerized over 2 hours to obtain a suspension containing crosslinked acrylic resin particles (polymerization step). In the suspension polymerization, the polymerization atmosphere was a nitrogen atmosphere. The suspension containing the crosslinked acrylic resin particles was distilled at 85 ° C under a vacuum of 0.063 MPa to remove methyl ethyl ketone from the suspension.

After the obtained suspension was cooled to 20 ° C, hydrochloric acid was added to the suspension to decompose the tricalcium phosphate, and then the crosslinked acrylic resin particles were separated using a centrifugal separator (manufactured by TANABE WILLTEC INC.), and washed with ion-exchanged water. Crosslinked acrylic resin particles.

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

An air classifier (manufactured by TOYO HITEC Co., LTD., trade name "HI-BOLTANR300") having a mesh size of 32 μm was prepared. The crosslinked acrylic resin particles were classified using an air classifier under an air atmosphere having a relative humidity of 20%. The crosslinked acrylic resin particles are placed in an air stream having a relative humidity of 20%, and the crosslinked acrylic resin particles are struck against the screen to remove particles that have not passed through the mesh of the mesh, thereby removing particles having a large particle size. get Crosslinked acrylic resin particles. The obtained crosslinked acrylic resin particles had a heating weight loss of 0.65%.

A bag made of a laminated film (water vapor transmission rate: 0.7 g/m ² .24 hours) in which an integrated metal thin film is laminated on one surface of a synthetic resin film (manufactured by Nippon Co., Ltd., trade name "Lamizip AL-"14"), 50 g of the obtained crosslinked acrylic resin particles were accommodated in the bag and sealed to manufacture a packaged article. The packaged article was placed in a thermo-hygrostat adjusted to 30 ° C and a relative humidity of 80% (manufactured by ESPEC CORP., trade name "TBE") for 24 hours. Then, the packaged article was opened, and the weight loss of heating of the crosslinked acrylic resin particles contained in the bag was measured, and as a result, it was 0.66%.

(Example 4)

To a separable flask equipped with a stirrer, a thermometer, and a reflux condenser, a reaction liquid containing 60 parts by weight of ion-exchanged water, 10 parts by weight of methyl methacrylate, and 0.05 parts by weight of n-dodecylmer as a polymerization regulator was supplied. The inside of the flask was purged with nitrogen while stirring the reaction liquid, and the reaction liquid was heated to 70 °C. The reaction liquid in the flask was kept at 70 ° C, and 0.05 parts by weight of potassium persulfate as a polymerization initiator was supplied to the reaction liquid, and then the reaction liquid was polymerized for 20 hours to obtain an emulsion (A). The obtained emulsion (A) contained 14% by weight of a solid component. The solid component contained spherical particles having a volume average particle diameter of 0.4 μm.

55 parts by weight of water, 7 parts by weight of the above emulsion (A), 10 parts by weight of methyl methacrylate and 0.05 parts by weight of n-dodecyl mercaptan were supplied to another separable flask equipped with a stirrer, a thermometer and a reflux condenser. The reaction liquid was subjected to nitrogen substitution while stirring the reaction liquid, and the reaction liquid was heated to 70 °C. The reaction liquid in the flask was kept at 70 ° C, and 0.05 parts by weight of potassium persulfate as a polymerization initiator was supplied to the reaction liquid, and then the reaction liquid was polymerized for 12 hours to obtain an emulsion (B). The obtained emulsion (B) contained 14% by weight of a solid component. Solid ingredient package A spherical particle (seed particle) having a volume average particle diameter of 1.0 μm.

40 parts by weight of methyl methacrylate, 30 parts by weight of ethylene methacrylate, and 30 parts by weight of styrene as a raw material monomer were supplied to another separable flask equipped with a stirrer, a thermometer, and a reflux condenser, and 6 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was uniformly mixed to obtain a mixture.

To the obtained mixture, 100 parts by weight of ion-exchanged water containing 1 part by weight of sodium succinate as a surfactant was supplied, and a dispersion machine (manufactured by PRIMIX Corporation, trade name "TKHOMOMIXER MODEL S") was used at a speed of 8000 rpm for 10 minutes. The mixture was mixed at 20 ° C to obtain an aqueous emulsion. To the aqueous emulsion, 8 parts by weight of the emulsion (B) was added while stirring to prepare a dispersion.

The dispersion was stirred for 3 hours at 20 ° C, and then the dispersion was observed with an optical microscope. As a result, the raw material monomers in the dispersion were absorbed by the seed particles (swelling ratio was about 20 times). Next, 200 parts by weight of a dispersion stabilizer aqueous solution was supplied to the dispersion. The dispersion stabilizer aqueous solution was produced by dissolving 4 parts by weight of polyvinyl alcohol (manufactured by KURARAY CO., LTD., trade name "PVA-224E") as a dispersion stabilizer in 196 parts by weight of ion-exchanged water. The raw material monomer was polymerized at 60 ° C (first temperature region) for 6 hours while stirring the above dispersion. Next, the dispersion liquid was heated to 100 ° C (second temperature region), and the raw material monomers were polymerized over 3 hours to obtain a suspension containing crosslinked acrylic resin particles (polymerization step). In addition, in the polymerization, the polymerization atmosphere was made into a nitrogen atmosphere.

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

Next, the obtained crosslinked acrylic resin particles are at 60 ° C and a vacuum of 0.05 MPa. The drying was carried out for 15 hours under the conditions (drying step). The obtained crosslinked acrylic resin particles had a volume average particle diameter of 5.01 μm.

The classification of the crosslinked acrylic resin particles (classification step) was carried out in an atmosphere having a relative humidity of 25% using an air classifier (manufactured by Nisshin Engineering Inc., trade name "TURBO CLASSIFER TC-15"). Specifically, the crosslinked acrylic resin particles are placed in a swirling gas flow generated under the conditions of a rotor rotation speed of 4,500 rpm and an air volume of 2.0 m ³ /min, and the centrifugal force of the particles imparted by the swirling airflow and the airflow toward the center of rotation of the airflow are utilized. The interaction between the flows is classified into particles having a large particle diameter and particles having a small particle diameter, whereby the large particles are removed to obtain crosslinked acrylic resin particles.

(Comparative Example 1)

The 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 region) was 8 hours.

(Comparative Example 2)

The crosslinked acrylic resin particles were obtained in the same manner as in Example 3 except that the crosslinking of the crosslinked acrylic resin particles was carried out 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 carried out.

(Comparative Example 4)

In the same manner as in Example 4, the crosslinked acrylic resin particles were obtained in the same manner as in Example 4 except that the polymerization time of the raw material monomer at 60 ° C (the first temperature range) was 8 hours. The obtained crosslinked acrylic resin particles had a volume average particle diameter of 5.03 μm.

With respect to the obtained crosslinked acrylic resin particles, the weight loss by heating, the volume average particle diameter, and the particles having a particle diameter of twice or more the volume average particle diameter after heating at 120 ° C for 1.5 hours were measured according to the above points (large diameter particles). The content is 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 according to the following points, and the results are shown in Table 1.

(surface properties of the film)

Stirring deaerator (manufactured by THINKY CORPORATION, trade name "Lantaro Stirring Deaerator" "Taro")) 0.4 parts by weight of crosslinked acrylic resin particles, 2.5 parts by weight of a polyester resin (manufactured by TOYOBO CO., LTD., "Byron 200"), 5.0 parts by weight of toluene, and 1.0 part by weight of methyl ethyl ketone. After 3 minutes, defoaming was performed for 1 minute to produce a resin composition.

The obtained resin composition was applied to a black ABS plate so as to have a thickness of 100 μm, and the coated film was dried in an oven at 70 ° C for 3 minutes to prepare a coating film. The surface of the obtained coating film was visually observed and judged according to the following criteria.

A. . . No spots and unevenness were observed.

B. . . A little spot or unevenness was observed.

C. . . A large number of spots or unevenness were observed.

(Preparation of resin composition for anti-glare film and production example of anti-glare film)

[Manufacturing Example 1]

80 parts by weight of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate as an ultraviolet curable resin (manufactured by TOAGOSEI CO., LTD., trade name "Aronix (registered trademark) M-305"), toluene as an organic solvent Mixture of cyclopentanone (toluene: cyclopentane) Ketone (volume ratio) = 7:3) 120 parts by weight, 5 parts by weight of the crosslinked acrylic resin particles produced in Example 4, and 2-methyl-1-(4-methylthio group as a photopolymerization initiator) 5 parts by weight of phenyl)-2-morpholinopropan-1-one (manufactured by BASF Japan Ltd., trade name "IRGACURE (registered trademark) 907") was mixed to prepare a resin composition for an antiglare film.

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

[Comparative Manufacturing Example 1]

An anti-glare 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 according to the following points, and the results are shown in Table 2.

(anti-glare)

The anti-glare film was placed directly under the fluorescent lamp, and the surface of the anti-glare film was visually observed and evaluated according to the following criteria. It should be noted that the fluorescent lamp is disposed at a position 50 cm vertically above the surface of the anti-glare film.

A. . . The outline of the fluorescent light is not clear.

B. . . You can see the outline of the fluorescent light, and the outline is slightly obvious.

C. . . The outline of the fluorescent lamp can be clearly seen.

(total light transmittance and haze)

The total light transmittance of the antiglare film was measured in accordance with JIS K7361-1, and the haze (haze value) of the antiglare film was measured in accordance with JIS K7136. Specifically, the total light transmittance and haze of the anti-glare film were measured using a haze meter (NDH2000) commercially available from Nippon Denshoku Industries Co., Ltd.

Claims (10)

A crosslinked acrylic resin particle comprising an acrylic resin, having a heating weight loss of 1.5% or less after heating at 120 ° C for 1.5 hours, and having a large diameter of a particle diameter of at least twice the volume average particle diameter The content of the particles is 1.0% by volume or less. The crosslinked 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, which are porous. The crosslinked acrylic resin particles according to claim 1 or 2, wherein the acrylic resin is cross-linked by an acrylic polyfunctional monomer having a plurality of (meth)acryl fluorenyl groups. The acrylic polyfunctional monomer is a product of a dehydration esterification process and is purified by distillation. A method for producing crosslinked acrylic resin particles, comprising the steps of: a polymerization step in which a raw material monomer containing an acrylic monomer and a polyfunctional monomer is polymerized in a first temperature region, and then Further polymerizing in a second temperature region higher than the first temperature region to produce crosslinked acrylic resin particles; and a drying step of causing the crosslinked acrylic resin particles obtained in the polymerization step to have a vacuum degree of 0.03 Drying under conditions of ~0.09 MPa and 30 to 90 ° C; and classification step, the crosslinked acrylic resin particles dried in the drying step by air grading in an atmosphere having a relative humidity of 30% or less The classification is carried out so that the content of the large-diameter particles having a particle diameter of twice or more the volume average particle diameter is 1.0% by volume or less. a method for producing crosslinked acrylic resin particles according to claim 5, which The first temperature region is 30 ° C or higher and lower than 80 ° C, and the second temperature region is 80 to 120 ° C. 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 a resin composition as described in claim 7 on a transparent film substrate. The optical film of claim 8, which is used for anti-glare. A packaged article characterized in that the crosslinked acrylic resin particles according to any one of claims 1 to 4 have a water vapor transmission rate of 50 g/m ² . Sealed with packaging materials for less than 24 hours.