JP5281781B2 - Monodispersed polymer particles, method for producing the same, light diffusible molded article, and light diffusible coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide monodispersed polymer particles with reduced discoloration, having high light diffusibility. <P>SOLUTION: The method for producing a monodispersed polymer particles comprises mixing an emulsion obtained by absorbing a vinyl monomer containing a polymerization initiator to seed particles in an aqueous medium with zirconia sol having pH of 8 or more, and heating the resulting mixture to polymerize the vinyl monomer, thereby obtaining the monodispersed polymer particles. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to monodisperse polymer particles, a method for producing the same, a light diffusible molded article, and a light diffusible coating. The monodisperse polymer particles of the present invention are suitably used as, for example, a display, a rear projection screen for viewing a film, a light diffusing agent used in various lighting devices, a spacer for liquid crystal display, a column filler, a carrier for a diagnostic agent, and the like. it can.

  Various methods for producing monodisperse polymer particles have been reported. For example, in JP-A-5-140204 (Patent Document 1), a droplet having a desired size is obtained using a polymerizable monomer and an aqueous dispersion containing an organic polymerization inhibitor and hardly water-soluble inorganic particles. A technique is described in which polymer particles are obtained by preparing a suspension having the following, and then completing the polymerization of the polymerizable monomer in the suspension.

  According to this technique, since it is possible to prevent the formation of emulsified particles of 1 μm or less in the suspension, it is said that polymer particles containing no fine particles can be obtained. In addition, since micron-order small particles can be obtained without containing emulsified particles of 1 μm or less, it is expected to be used as highly functional particles in various fields including electrophotographic toners.

In JP-A-2002-293809 (Patent Document 2), a polymerizable monomer and a polymerization initiator are dispersed in a medium containing a water-soluble organic dispersant (polyvinyl alcohol) to form a water-soluble organic dispersant. On the other hand, a technique for obtaining monodisperse polymer particles by adding 3 to 30 parts by weight of boric acid to polymerize and washing the resulting polymerization product with a nonionic surfactant aqueous solution is described.
According to this technique, polymer particles that do not change color even when exposed to high temperatures are obtained.

Japanese Patent Laid-Open No. 5-140204 JP 2002-293809 A

In the method described in JP-A-5-140204, polymer particles having a sharp molecular weight distribution (highly monodispersed) can be obtained, but it is desired to further improve the monodispersibility. .
In the method described in Japanese Patent Application Laid-Open No. 2002-293809, it is said that by using polyvinyl alcohol as a water-soluble organic dispersant and boric acid in combination, polymer particles that do not change color even when heated are obtained. Yes. However, since organic substances such as polyvinyl alcohol are more discolored by heat than inorganic substances, it is desired to further suppress discoloration.

  The production method of zirconia sol is known, for example, in JP-A-2-167826 and used as a binder, surface treatment agent, abrasive, filler, etc. in the field of refractory, coating agent, fiber, mold, etc. Has been. The inventor of the present invention, as a result of intensive studies, uses a zirconia sol having a specific pH as a dispersant for a seed polymerization method that has not been reported so far. The present inventors have unexpectedly found that dispersed polymer particles can be obtained, and have reached the present invention.

  Thus, according to the present invention, an emulsion obtained by allowing a vinyl monomer containing a polymerization initiator to be absorbed in seed particles in an aqueous medium was mixed with a zirconia sol having a pH of 8 or more. There is provided a method for producing monodisperse polymer particles, wherein the vinyl monomer is polymerized by heating the mixture to obtain monodisperse polymer particles.

Further, according to the present invention, monodisperse polymer particles having a CV value of 3 to 15% and an average particle diameter of 1 to 20 μm obtained by the above production method, wherein the zirconia component is present in the particles or on the particle surfaces. exist, the zirconia component, monodisperse polymer particles is provided, wherein Rukoto contains 0.1 to 10 wt%.
Moreover, according to this invention, the light diffusable molded object or light diffusable coating material characterized by including the said monodispersed polymer particle and transparent base resin is provided.

  According to the present invention, it is possible to obtain monodisperse polymer particles that are inhibited from discoloration and have high light diffusibility. Moreover, if the monodisperse polymer particle of this invention is used, a high light-diffusion property can be provided to a molded object and a coated material.

"Method for producing monodisperse polymer particles"
In the present invention, an emulsion obtained by absorbing a vinyl monomer containing a polymerization initiator in seed media in an aqueous medium and a zirconia sol having a pH of 8 or more are mixed, and the resulting mixture is heated. Thus, monodisperse polymer particles can be obtained by polymerizing the vinyl monomer.

(Zirconia sol)
The zirconia sol used in the present invention is not particularly limited as long as it has a pH of 8 or more, and any known zirconia sol can be used. When the pH is less than 8, the resulting polymer particles aggregate to form aggregated particles, so that monodisperse polymer particles cannot be obtained. A more preferred pH is 8-12.

  The zirconia concentration in the zirconia sol is preferably 1 to 60% by weight. Within this range, the generation of fine particles derived from only the vinyl monomer can be suppressed while promoting the absorption of the vinyl monomer into the seed particles. A more preferable zirconia concentration is 5 to 40% by weight.

Zirconia sol usually contains an aqueous medium. Examples of the aqueous medium include water, a mixed medium of water and a water-soluble solvent (for example, a lower alcohol having up to 4 carbon atoms), and the like.
In addition, other oxides such as yttrium oxide, magnesium oxide, and calcium oxide may be added to the zirconia sol.
Further, a known alkali and / or acid may be added to the zirconia sol or diluted with water to adjust the pH to a desired range.

The zirconia sol is preferably used in an amount of 100 to 1000 parts by weight with respect to 100 parts by weight of the vinyl monomer. Within this range, the monodispersity of the polymer particles can be further improved. A more preferable usage amount is 200 to 500 parts by weight. Furthermore, the amount of zirconia in the zirconia sol is particularly preferably in the range of 1 to 600 parts by weight with respect to 100 parts by weight of the vinyl monomer. Within this range, in addition to the effect of the amount of zirconia sol used, the light diffusibility of the resulting polymer particles can be further improved. A more preferable amount of zirconia is 5 to 400 parts by weight.
Specific examples of the zirconia sol include a nano-use series (for example, ZR-40BL, ZR-30BS) manufactured by Nissan Chemical Industries, Ltd.

The zirconia sol is, for example, at least one compound selected from a water-soluble organic acid having a hydroxyl group and a water-soluble organic compound having at least two hydroxyl groups as a dispersion stabilizer in an acidic aqueous zirconia sol. Can be obtained by adding a basic compound.
Examples of the acidic zirconia sol include an acidic zirconia sol obtained by heating and hydrolyzing an aqueous solution of zirconium oxychloride. The zirconia concentration in the acidic zirconia sol is preferably 5 to 50% by weight, more preferably 10 to 30% by weight.

Examples of the dispersion stabilizer include lactic acid, malic acid, citric acid, tartaric acid, salicylic acid, sulfosalicylic acid, and the like, and examples of water-soluble organic compounds having at least two hydroxyl groups include ethylene glycol, propylene glycol, tyrone, Examples include glycerin, polyvinyl alcohol, and hydroquinone. The addition amount of the dispersion stabilizer is preferably 5% by weight, more preferably 10 to 30% by weight with respect to zirconia (ZrO ₂ ).

  Examples of the basic substance include water-soluble inorganic salts such as sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonia, amines such as n-propylamine, monoethanolamine and triethanolamine, monomethyltriethylammonium hydroxide, trimethyl Examples thereof include water-soluble organic bases such as quaternary ammonium hydroxides such as benzoammonium hydroxide or guanidine hydroxides. The addition amount of the basic substance is such an amount that the pH of the zirconia sol after the addition becomes 8 or more.

(Seed particles)
The seed particles that can be used in the present invention are not particularly limited, and examples thereof include vinyl resin particles such as acrylic particles and styrene particles. The seed particles are preferably non-crosslinked or low-crosslinked resin particles in that they readily absorb vinyl monomers.

  Examples of the acrylic particles include particles derived from (meth) acrylic monomers. (Meth) acryl means acryl or methacryl. Examples of (meth) acrylic monomers include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, dodecyl acrylate, stearyl acrylate, 2-acrylic acid 2- Ethylhexyl, tetrahydrofurfuryl acrylate, diethylaminoethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, methacryl Examples include dodecyl acid, 2-ethylhexyl methacrylate, stearyl methacrylate, and diethylaminoethyl methacrylate. These monomers may be used alone or in combination of two or more.

Other monomers may be added to the acrylic monomer. Other monomers include glycol esters of (meth) acrylic acid such as ethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, vinyl acetate, butyric acid Vinyl esters such as vinyl, N-alkyl-substituted (meth) acrylamides such as N-methylacrylamide, N-ethylacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide, nitriles such as acrylonitrile and methacrylonitrile, divinyl Polyfunctional monomers such as benzene, ethylene glycol di (meth) acrylate, trimethylolpropane triacrylate, styrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene, - it includes styrene monomers such as methylstyrene. These other monomers may be used alone or in combination of two or more.
Examples of the styrene particles include particles derived from styrene monomers such as styrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene, and α-methylstyrene. These styrene monomers may be used alone or in combination of two or more.

  You may add another monomer to the said styrene-type monomer. Other monomers include glycol esters of (meth) acrylic acid such as ethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, vinyl acetate, butyric acid Vinyl esters such as vinyl, N-alkyl-substituted (meth) acrylamides such as N-methylacrylamide, N-ethylacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide, nitriles such as acrylonitrile and methacrylonitrile, divinyl Polyfunctional monomers such as benzene, ethylene glycol di (meth) acrylate, trimethylolpropane triacrylate, acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, acrylic Isobutyl acrylate, t-butyl acrylate, dodecyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate, diethylaminoethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacryl (Meth) acrylic monomers such as n-butyl acid, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate and diethylaminoethyl methacrylate It is done. These other monomers may be used alone or in combination of two or more.

  When the seed particles are acrylic particles, the acrylic resin constituting the seed particles preferably has a weight average molecular weight of 10,000 to 1,000,000. If it is less than 10,000, it may be difficult to obtain polymer particles having excellent monodispersity because the shape of the polymer particles is difficult to be a perfect sphere. In addition, phase separation may occur when the molecular structure of the seed particle and the absorbed monomer is different. In this case, as the polymerization proceeds, internal voids and cracks may be generated, and the mechanical strength of the resulting polymer particles may be reduced. If it is greater than 1 million, the monomer absorption rate may decrease. A more preferred weight average molecular weight is 20,000 to 500,000.

When the seed particles are styrene particles, the weight average molecular weight of the styrene resin constituting the seed particles is preferably 10,000 to 1,000,000 for the same reason as the acrylic particles. A more preferred weight average molecular weight is 20,000 to 500,000.
The seed particles can be obtained by a known method such as an emulsion polymerization method or a suspension polymerization method. The average particle size of the seed particles can be appropriately adjusted depending on conditions such as the amount of vinyl monomer to be absorbed and the desired particle size of the monodisperse particles. The average particle diameter of the seed particles is preferably 0.1 to 10 μm, and the CV value of the seed particles is preferably 15% or less.

(Vinyl monomer)
A vinyl monomer will not be specifically limited if it is a vinyl monomer which can be used for a seed polymerization method, The following monomers are illustrated.
As monomers, styrene monomers such as styrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene, α-methylstyrene, methyl acrylate, ethyl acrylate, butyl acrylate, 2-acrylic acid 2- Acrylic acid esters such as ethylhexyl and diethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid esters such as diethylaminoethyl methacrylate, ethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, etc. Glycol esters of (meth) acrylic acid, alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, vinyl esters such as vinyl acetate and vinyl butyrate, N-methylacrylamide N-alkyl-substituted (meth) acrylamides such as N-ethylacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide, nitriles such as acrylonitrile and methacrylonitrile, divinylbenzene, ethylene glycol di (meth) acrylate, trimethylol A polyfunctional monomer such as propane triacrylate is exemplified. These vinyl monomers may be used alone or in combination of two or more.

  The absorption amount of the vinyl monomer is preferably 500 to 20000 parts by weight with respect to 100 parts by weight of the seed particles. When the amount is less than 500 parts by weight, aggregation tends to occur. If it is larger than 20000 parts by weight, the probability of occurrence of small particles may increase. A more preferable absorption amount is 1000 to 10,000 parts by weight.

(Polymerization initiator)
As the polymerization initiator, oil-soluble peroxide-based or azo-based initiators usually used for suspension polymerization can be used. For example, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl hydroperoxide Peroxide initiators such as diisopropylbenzene hydroperoxide, azobisisovaleronitrile, 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-iso Ropybutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2- (carbamoylazo) isobutyro Nitriles, 4,4′-azobis (4-cyanovaleric acid), 2,2-azobis- (2-methylpropionate), dimethyl-2,2′-azobisisobutyrate and the like.

  0.1-5 weight part is preferable with respect to 100 weight part of vinylic monomers, and, as for the usage-amount of a polymerization initiator, 0.1-1 weight part is more preferable. When the amount is less than 0.1 parts by weight, the polymerization efficiency may decrease. When the amount is larger than 5 parts by weight, the reaction proceeds rapidly and aggregation may be induced.

(Aqueous medium)
The aqueous medium is not particularly limited, and examples thereof include water and a mixed medium of water and a water-soluble medium (for example, a lower alcohol having up to 4 carbon atoms). It is preferable that the usage-amount of an aqueous medium is 100-1000 weight part with respect to 100 weight part of vinylic monomers.

(Polymerization of vinyl monomers)
The absorption of the vinyl monomer and the polymerization initiator into the seed particles is not particularly limited, and examples thereof include a method of absorbing in a suspension system.
From the viewpoint of suppressing the generation of small particles, absorption is performed at a temperature at which the vinyl monomer does not polymerize and the seed particles can contain the polymerization initiator together with the vinyl monomer while suppressing decomposition. Is called. As the temperature, it is preferable that it is 40 degrees C or less, and it is more preferable that it is 20-30 degreeC.

  The emulsion obtained by absorbing the vinyl monomer and the polymerization initiator into the seed particles is mixed with the zirconia sol. The mixing conditions are not particularly limited, but it is preferable to select a mixing apparatus and set the mixing conditions so that the emulsion and the sol are as uniform as possible.

  Next, the vinyl monomer in the mixture obtained by mixing the emulsion and sol is polymerized. The polymerization conditions are not particularly limited as long as the vinyl monomer can be polymerized. The polymerization temperature is preferably 40 to 80 ° C. The polymerization time is preferably 0.1 to 10 hours.

  After the polymerization, the polymer particles are separated from the mixture as a water-containing cake by suction filtration, centrifugal dehydration, centrifugal separation, pressure dehydration and the like, and the obtained water-containing cake is washed with water and dried to obtain the desired polymer particles. May be isolated.

(Other)
A surfactant such as an anionic surfactant, a cationic surfactant, an amphoteric ionic surfactant, or a nonionic surfactant may be added to the mixture.
Examples of the anionic surfactant include fatty acid oils such as sodium oleate and castor oil potassium, alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and alkylnaphthalene sulfone. Acid salts, alkane sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene alkyl sulfates and the like.

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

Examples of the zwitterionic surfactant include lauryl dimethylamine oxide and phosphate ester or phosphite ester surfactants.
You may use the said surfactant individually or in combination of 2 or more types. The addition amount of the surfactant is preferably 0.01 to 1 part by weight with respect to 100 parts by weight of the mixture from the viewpoint of suppressing the generation of small particles.

  Further, in order to suppress the polymerization of the vinyl monomer in the aqueous medium in the aqueous medium in the above mixture and promote phase separation inside the droplet, the water-soluble property is about 0.01 to 1% by weight. A polymerization inhibitor may be added. Although it does not specifically limit as a water-soluble polymerization inhibitor, For example, nitrites, hydroquinone, ascorbic acids, water-soluble vitamin B, citric acid, polyphenols etc. can be mentioned.

"Monodisperse polymer particles"
In the present invention, there is provided a monodispersed polymer in which the zirconia component obtained by the above method is present in the particle or on the particle surface.
Since the monodisperse polymer particles of the present invention are produced using a zirconia sol that is an inorganic dispersant as a dispersant, a zirconia component is also contained in the particle or on the particle surface. Since this zirconia component is difficult to discolor when heated, the discoloration of the particles can be suppressed more than when an organic dispersant such as polyvinyl alcohol is used as the dispersant.
Furthermore, when the monodisperse polymer particles are mixed with a transparent base resin to form a light diffusive molded product, it is confirmed that the color of the molded product is improved and the optical properties (haze and dispersion) are improved. . The inventor believes that this is due to the following reason.

  The zirconia component in the zirconia sol mixed with the emulsion is located between the vinyl monomer absorbed in the seed particles in the mixture and the aqueous medium, so that the seed particles that have absorbed the vinyl monomer are removed. It is considered to be stably dispersed in the mixture. When the vinyl monomer is polymerized, the zirconia component remains in the surface of the polymer particles. Since the zirconia component has a higher refractive index than the polymer particles, the zirconia component remains in the surface of the particles, thereby further increasing the refractive index of the polymer particles. It is a finding that the inventors have unexpectedly found that such a zirconia component increases the refractive index of polymer particles obtained by a seed polymerization method.

The polymer particles preferably contain 0.1 to 10% by weight of the zirconia component. By containing a zirconia component within this range, polymer particles having a higher refractive index are obtained. A more preferable content is 0.1 to 5% by weight.
The degree of monodispersion of the polymer particles can be expressed as a CV value and can be 3 to 15%.
The average particle diameter of the polymer particles is not particularly limited and can be adjusted as desired. For example, the average particle diameter can be in the range of 1 to 20 μm.

The polymer particles of the present invention are also characterized by little yellowing. For example, when the polymer particles are heated in air at 200 ° C. for 1 hour, the b value as the color difference can be set to a range of 0.5 or less. The value in this range is a value improved by 7 or more compared to polymer particles obtained using polyvinyl alcohol as a dispersant, indicating that the polymer particles of the present invention are useful.
The polymer particles can be suitably used as, for example, a display, a rear projection screen for viewing a film, a light diffusing agent used in various lighting fixtures, a liquid crystal display spacer, a column filler, a diagnostic agent carrier, and the like.

"Light diffusive moldings and coatings"
A light diffusable molded article can be provided by mixing the polymer particles with a transparent base resin and molding the resulting mixture. Moreover, the light diffusable coating material obtained by apply | coating the solution which disperse | distributed the said polymer particle and melt | dissolved or disperse | distributed transparent base resin on a base | substrate, and evaporating a solvent can be provided.
The molded body and the coated product have high light diffusibility derived from polymer particles.

  It does not specifically limit as transparent base resin, Any resin well-known in the said field | area can be used. Examples include linear polyesters, acrylic resins, melamine resins, silicon resins, urethane resins, epoxy resins, styrene resins, vinyl acetate resins, and the like.

The mixing ratio of the transparent base resin and the polymer particles can be appropriately set depending on the light diffusibility to be obtained, and is not particularly limited. For example, 0.1 to 10 parts by weight of polymer particles are preferable with respect to 100 parts by weight of the transparent base resin. By including the polymer particles within this range, there is an effect that excellent light diffusibility can be provided. Further, the content of the polymer particles is more preferably 0.5 to 5 parts by weight.
In the present specification, the term “transparent” includes translucent. Further, the term “transparent” means that it is transparent to light having a desired wavelength, and is not necessarily transparent to light having all wavelengths.

  The substrate is not particularly limited, and any substrate known in the art can be used. Examples thereof include resin substrates such as polyethylene terephthalate, polyester, acrylic resin, polycarbonate, and polyamide, and inorganic substrates such as a transparent glass sheet. The thickness is not particularly limited, but is preferably about 10 to 500 μm in consideration of ease of processing and handling properties.

  As a method for forming a coating on the substrate, 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 thickness of the coated material is not particularly limited, but is preferably about 0.1 to 100 μm, more preferably about 1 to 50 μm in consideration of light diffusibility, film strength, and the like.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these Examples. In addition, the measuring method of average particle diameter, CV value, color difference b value, x value and y value, pH of the dispersion, haze, total light transmittance, and degree of dispersion D50 is described below.
(Average particle size of seed particles)
0.1 g of seed particles and 10 ml of a 0.1% nonionic surfactant solution are put into a test tube and mixed for 2 seconds with a touch mixer TOUCHMIXER MT-31 manufactured by Yamato Kagaku. Thereafter, the test tube is predispersed for 10 minutes using a commercially available ultrasonic cleaner, ULTRASONIC CLEANER VS-150, manufactured by Velvo Crea. The average particle size of the seed particles in the dispersion is measured with an LS230 model manufactured by Beckman Coulter, Inc. while irradiating with ultrasonic waves. The optical model at the time of measurement is adjusted to the refractive index of the seed particles.

(Average particle diameter of polymer particles, CV value)
The average particle diameter and the CV value are measured by calibration using a 50 μm aperture according to Reference MANUAL FOR THE COULTER MULTISIZER (1987) published by Coulter Electronics Limited.

  Specifically, 0.1 g of polymer particles are predispersed in 10 ml of 0.1% nonionic surfactant using a touch mixer and ultrasonic waves, and this is provided with ISOTON II (Beckman Coulter, Inc .: for measurement) In a beaker filled with (electrolyte), drop with a dropper while gently stirring, and adjust the reading of the densitometer on the main body screen to about 10%. Next, an aperture size of 50 μm, a current of 800, a gain of 4, and a polarity of + are input to the body of a Coulter Multisizer II (manufactured by Beckman Coulter, Inc .: measuring device) and measured manually. During the measurement, the beaker is stirred gently to the extent that bubbles do not enter, and the measurement is terminated when 100,000 particles are measured. The average particle diameter is an average value of 100,000 particle diameters.

The CV value is a value calculated from the standard deviation (σ) and the mode diameter (x) by the following formula.
CV value (%) = (σ / x) × 100
The mode diameter is the particle diameter (maximum value of the distribution) having the largest appearance ratio when the particle diameter is counted based on the number% distribution.

(Color difference b (b value))
The polymer particles are dehydrated by a suction filtration device and sufficiently dried in a constant temperature bath at 60 ° C. The dried polymer particles are crushed in a mortar, placed in an aluminum container, and heated at 200 ° C. for 1 hour in a thermostatic bath. Next, the polymer particles are further pulverized in a mortar, and the color difference b (b value) of the obtained crushed material is measured with a color difference meter (CR-300 manufactured by Minolta).

(X value and y value)
The chromaticity of the transmitted light is measured according to JISZ8701, and the chromaticity is indicated by the color coordinates of the transmitted light. Specifically, the obtained molded body is placed on a 4 mm cold cathode tube placed at an interval of 40 mm. The chromaticity x and y are measured with a SPECTRORADIOMETER spectral radiance meter (CS-1000A manufactured by Konica Minolta Sensing Co., Ltd.) fixed at a position 30 cm away from the molded body. The chromaticity x and y are yellowish when the numerical value is high, and blue when the numerical value is small.

(PH)
The pH is measured with a glass electrode type hydrogen ion concentration meter HM-11P manufactured by Toa Denpa Kogyo. However, before the measurement, the electrode of the densitometer is calibrated with a standard solution of pH 6.86 and a standard solution of pH 4.01, and after washing the electrode with washing water, the electrode is placed in zirconia sol and the pH is measured.

(Haze and total light transmittance)
The haze is measured according to JIS K7136. Specifically, the measurement is performed using NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. The total light transmittance is measured according to JISK7361. Specifically, the measurement is performed using NHD-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

(Dispersity D50)
Using a 2 mm portion of the plate, the light diffusivity (D50) is determined by the following procedure using an automatic goniophotometer (Goniophotometer GP-1R manufactured by Murakami Color Research Laboratory).
A straight beam from the light source of the automatic goniophotometer is applied from the normal direction of the molded body placed at a distance of 75 cm from the light source. The intensity of light transmitted through the molded body is measured with a movable light receiver. This intensity is converted into transmittance, and the transmittance is plotted on a graph corresponding to the angle from the normal direction. From this graph, the angle at which the transmittance of light in the normal direction (straight light transmittance) is 50% is obtained. This angle is referred to as the degree of dispersion D50, and the unit is “degree”. Moreover, it means that it is excellent in diffusibility, so that dispersion degree D50 is large.

(Production Example 1 of Seed Particles)
Methyl methacrylate (108 g) and octyl mercaptan (11 g) as monomer monomers were charged into a reactor in 630 g of pure water, the reactor was purged with nitrogen, and then the temperature was raised to 55 ° C. Thereafter, a solution obtained by dissolving 0.54 g of potassium persulfate in 100 g of pure water was put into the reactor, and the reactor was purged with nitrogen again. Thereafter, the monomer monomer was polymerized at 55 ° C. for 12 hours to obtain seed particles having an average particle diameter of 0.75 μm in a slurry state.

(Production example of polymer particles)
Example 1
In a mixed solution consisting of 112 g of methyl methacrylate and 48 g of ethylene glycol dimethacrylate as a monomer, 0.96 g of 2,2-azobis- (2,4-dimethylvaleronitrile) is dissolved to obtain a polymerizable monomer component and did.
Separately, 0.8 g of sodium dodecylbenzenesulfonate was dissolved in 160 g of pure water to obtain an aqueous solution. The polymerizable monomer component was mixed with this aqueous solution and stirred at 8000 rpm for 10 minutes using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). This emulsion was put into a 1 L reactor equipped with a stirrer and a thermometer, and 57 g of the slurry of Production Example 1 was added. The seed particles were swollen by stirring at 120 rpm for 4 hours.

  Next, 0.13 g of sodium nitrite was added to 480 g of zirconia sol (Nanouse ZR-40BL manufactured by Nissan Chemical Industries, Ltd., pH = 9.0, zirconia concentration 30 wt%) to obtain a solution. This solution was added to the slurry after completion of swelling. The steps so far were performed at room temperature (25 ° C.). Next, the temperature of the slurry was raised to 70 ° C., and polymerization was performed at this temperature for 12 hours to obtain polymer particles having an average particle size of 2 μm and a uniform particle size distribution. FIG. 1 shows an electron micrograph of polymer particles. The CV value and b value of the obtained polymer particles were measured.

Example 2
An average particle size of 2 μm was obtained in the same manner as in Example 1 except that the zirconia sol was changed to Nanouse ZR-30BS (pH = 9.0, zirconia concentration 30 wt%), which is another zirconia sol manufactured by Nissan Chemical Industries, Ltd. Polymer particles were obtained. The CV value and b value of the obtained polymer particles were measured.

Comparative Example 1
Polymer particles having an average particle size of 2 μm were obtained in the same manner as in Example 1 except that the zirconia sol was replaced with a 5% polyvinyl alcohol (PVA) aqueous solution (GOHSENOL GM-14 manufactured by Nippon Synthetic Chemical Co., Ltd.). The CV value and b value of the obtained polymer particles were measured.

Comparative Example 2
Polymer particles are obtained in the same manner as in Example 1 except that the zirconia sol is replaced with Nanouse ZR-30AL (pH = 3.1, zirconia concentration 30% by weight) which is another zirconia sol manufactured by Nissan Chemical Industries, Ltd. As a result, the polymer particles aggregated. FIG. 2 shows an electron micrograph of the aggregated particles.

Comparative Example 3
The polymer particles were obtained in the same manner as in Example 1 except that the zirconia sol was changed to one obtained by diluting 480 g of nano-use ZR-30BS (pH = 9.0, zirconia concentration 30 wt%) with 200 g of water. However, the polymer particles aggregated.

Comparative Example 4
Polymer particles having an average particle diameter of 2 μm were obtained in the same manner as in Example 1 except that the zirconia sol was changed to colloidal silica (Snowtex OL: pH 2 to 4 manufactured by Nissan Chemical Industries, Ltd.). The CV value and b value of the obtained polymer particles were measured.
Table 1 summarizes the average particle diameter, CV value, used dispersant type and pH, and b value of the polymer particles obtained in Examples 1-2 and Comparative Examples 1-4.

  From Examples 1 and 2, it can be seen that when an alkaline zirconia sol having a pH of 8 or more is used as a dispersant, polymer particles having high monodispersity can be obtained as shown in FIG. However, from Comparative Examples 2 and 3, when a neutral or acidic zirconia sol having a pH of less than 8 is used as a dispersant, aggregated particles having a wide particle size distribution are obtained as shown in FIG. 2, and a monodisperse polymer is obtained. Particles were not obtained.

(Light diffusive molding)
Example 3
100 parts by weight of styrene-methyl methacrylate copolymer (Estyrene MS-200 manufactured by Nippon Steel Chemical Co., Ltd.) as a transparent base resin, and 1.5 parts by weight of the polymer particles (light diffusing agent) obtained in Example 1 Were melt-kneaded at 230 ° C. in an extruder and pelletized. The obtained pellets were molded by an injection molding machine (cylinder temperature 280 ° C., residence time 15 minutes) to produce a light diffusive molded body having a thickness of 2 mm, a width of 50 mm, and a length of 100 mm. The haze, total light transmittance, dispersity D50, x value and y value of the obtained light diffusable molded product were measured. The obtained results are shown in Table 2.

Example 4
A light diffusable molded article was produced in the same manner as in Example 3 except that the polymer particles obtained in Example 2 were used. The haze, total light transmittance, dispersity D50, x value and y value of the obtained light diffusable molded product were measured. The obtained results are shown in Table 2.

Comparative Example 5
A light diffusable molded article was produced in the same manner as in Example 3 except that the polymer particles obtained in Comparative Example 1 were used. The haze, total light transmittance, dispersity D50, x value and y value of the obtained light diffusable molded product were measured. The obtained results are shown in Table 2.

Comparative Example 6
Except for using the aggregated particles obtained in Comparative Example 2 in place of the polymer particles, an attempt was made to produce a light diffusive molded article in the same manner as in Example 3, and the aggregated particles were uniform with the transparent base resin. Since it was not possible to knead, the molded body was not produced.

Comparative Example 7
A light diffusable molded article was produced in the same manner as in Example 3 except that the polymer particles obtained in Comparative Example 4 were used. The haze, total light transmittance, dispersity D50, x value and y value of the obtained light diffusable molded product were measured. The obtained results are shown in Table 2.

From Comparative Example 5 and Examples 3 and 4, it can be seen that Examples 3 and 4 have higher haze and dispersity D50. This is presumed that the zirconia component in the polymer particles contributes.
From Comparative Example 6, since the particles of Comparative Example 2 were agglomerated, the agglomerated particles and the transparent base resin could not be uniformly kneaded.
From Comparative Example 7, it can be seen that the polymer particles used (Comparative Example 4) have a low b value, but the haze and dispersity D50 of the light diffusible molded product are lower than those of Examples 3 and 4.
From Table 2 above, it can be seen that polymer particles obtained using a zirconia sol having a pH of 8 or higher as a dispersant give excellent diffusibility and chromaticity to the light diffusable molded article.

(Light diffusion coating)
Example 5
200 parts by weight of the polymer particles of Example 1 and 310 parts by weight of an acrylic binder (trade name: Medium VM (K): manufactured by Dainichi Seika Co., Ltd. (solid content: 32%), transparent base resin-containing binder) are mixed. It was. To the obtained mixture, 240 parts by weight of a mixed solution of toluene and methyl ethyl ketone in a ratio of 1: 1 was added as a solvent. The resulting mixture was stirred for 3 minutes with a centrifugal stirrer and allowed to stand for 3 hours. Thereafter, 30 parts by weight of a curing agent (trade name: Medium VM: manufactured by Dainichi Seika Co., Ltd.) was added to the mixed solution, and the mixture was again stirred with a centrifugal stirrer for 3 minutes. The resulting mixed solution was coated on a PET film using a # 80 bar coater. The obtained coating film was dried for 1 hour with a drier kept at 70 ° C. to obtain a light diffusable coating (coating film). The haze and total light transmittance of the obtained coated product were measured. The results are shown in Table 3.
Example 6
A light diffusable coating was obtained in the same manner as in Example 5 except that the polymer particles of Example 2 were used. The haze and total light transmittance of the obtained coated product were measured. The results are shown in Table 3.

  From Table 3 above, the polymer particles obtained using a zirconia sol having a pH of 8 or more as a dispersant are excellent in diffusibility (haze 95% or more) and excellent permeability (total haze) in the light diffusable coating material. It can be seen that the light transmittance is 80% or more).

2 is an electron micrograph of monodisperse particles of Example 1. FIG. 4 is an electron micrograph of polymer particles of Comparative Example 2.

Claims (4)

An emulsion obtained by absorbing a vinyl monomer containing a polymerization initiator in seed media in an aqueous medium and a zirconia sol having a pH of 8 or more are mixed, and the resulting mixture is heated to produce the vinyl. A method for producing monodisperse polymer particles, comprising polymerizing a monomer to obtain monodisperse polymer particles. A monodisperse polymer particle having a CV value of 3 to 15% and an average particle diameter of 1 to 20 μm obtained by the production method according to claim 1, wherein the zirconia component is present in the particle or on the particle surface , monodisperse polymer particles wherein the zirconia component, characterized in Rukoto contains 0.1 to 10 wt%. A light diffusive molding comprising the monodisperse polymer particles according to claim 2 and a transparent base resin. A light diffusable coating comprising the monodisperse polymer particles according to claim 2 and a transparent base resin.