JP5376783B2 - Single hollow particle, method for producing the same, resin composition, and light diffusion plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single hollow particle having excellent optical diffusibility. <P>SOLUTION: The single hollow particle comprises a vacancy, an inner polymer layer and an outer polymer layer in this order from the center toward the outside. The inner polymer layer has 50,000-400,000 weight average molecular weight (measured by GPC) and comprises a (meth)acrylate-styrene-based copolymer containing 20-70 wt.% (meth)acrylate component. The outer polymer layer comprises a copolymer derived from a monomer mixture of 10-50 wt.% crosslinkable vinyl monomer and 90-50 wt.% hydrophobic (meth)acrylate monomer. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a single hollow particle, a production method thereof, a resin composition, and a light diffusion plate. More specifically, the present invention relates to single hollow particles having excellent light diffusibility, a production method thereof, a resin composition containing the same, and a light diffusion plate. The single hollow particles of the present invention are suitable as a raw material for a light diffusing plate and a light diffusing sheet used for TV screens, lighting covers, liquid crystal backlights and the like.

  Conventionally, polymer particles produced by suspension polymerization have been used as light diffusing agents such as light reflecting materials such as paints and cosmetics, and light diffusing plates for liquid crystal backlights. That is, in paints and cosmetics, the light diffusing agent imparts whiteness by refracting and reflecting light. In the light diffusing plate, the light diffusing agent scatters the incident light so that light incident from the side of the light diffusing plate by a cold cathode tube or the like can be emitted from the surface of the light diffusing plate with uniform brightness. Yes. As such polymer particles, for example, acrylic polymer particles and styrene polymer particles are used. Furthermore, polymer particles are also known that have an effect of reflecting or scattering light by having pores inside.

As a method for producing polymer particles having pores therein, a method described in JP-A-5-12517 (Patent Document 1) is known. In this publication, suspension polymerization is carried out in the presence of a heterogeneous polymer in a monomer mixture composed of a hydrophilic monomer and a crosslinkable monomer. In this polymerization, polymer particles having inner pores can be obtained by using a special polymer that dissolves in the monomer mixture but does not dissolve in the polymer formed by the polymerization of the monomer mixture. It is supposed to be done.
JP-A-5-12517

  However, since the hydrophilic monomer is used in the method described in the above publication, the hydrophilicity of the obtained particles is increased. Therefore, the amount of water in the polymer particles inevitably increases. In the light diffusing plate, the transparent resin and the polymer particles are mixed. However, when the polymer particles described in the above publication are used, the transparent resin may be deteriorated due to moisture.

  The inventors of the present invention, as a result of intensive studies on a method for easily producing resin particles (single hollow particles) having a single pore inside without using a hydrophilic monomer, To find out that the above problem can be solved by suspension polymerization of a mixture of an acrylic ester-styrene copolymer and a (meth) acrylic ester containing a crosslinkable vinyl monomer in the presence of an aqueous medium. Thus, the present invention was completed.

Thus, according to the present invention, the pores, the inner polymer layer, and the outer polymer layer are provided in this order from the center toward the outer side, and the inner polymer layer has a weight in the range of 50,000 to 400,000. A (meth) acrylate-styrene copolymer having an average molecular weight (measured by GPC) and containing 20 to 70% by weight of a (meth) acrylate component, wherein the outer polymer layer is 10 A monomer mixture of ˜50% by weight of a crosslinkable vinyl monomer and 90% to 50% by weight of a hydrophobic (meth) acrylate monomer (provided that the monomer mixture is the crosslinkable vinyl as monomers other than the system monomer includes a copolymer solubility in water of from including no) 0.45 wt% greater than the hydrophilic monomer,
A monomer in which the (meth) acrylic acid ester-styrene copolymer containing the (meth) acrylic acid ester component is selected from styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and t-butylstyrene. Including styrene-based components derived from
The hydrophobic (meth) acrylic acid ester monomer is provided with a single hollow particle characterized by exhibiting hydrophobicity with a water solubility of 0.45% by weight or less.

Further, according to the present invention, 10 to 50 wt% of the crosslinkable vinyl monomer and 90-50 wt% of a hydrophobic (meth) monomer mixture of acrylic acid ester monomer (where the single The monomer mixture does not include a hydrophilic monomer having a solubility in water of more than 0.45% by weight as a monomer other than the crosslinkable vinyl monomer ). 1 to 10 parts by weight of a (meth) acrylate-styrene copolymer having a weight average molecular weight (measured by GPC) in the range of 1,000,000 and containing 20 to 70% by weight of a (meth) acrylate component And 0.01 to 10 parts by weight of a polymerization initiator are dissolved, and the resulting solution is subjected to suspension polymerization in the presence of an aqueous medium, whereby pores and inner polymer layers are formed from the center toward the outside. And an outer polymer layer in this order. It consists in obtaining the sky particles,
A monomer in which the (meth) acrylic acid ester-styrene copolymer containing the (meth) acrylic acid ester component is selected from styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and t-butylstyrene. Including styrene-based components derived from
The hydrophobic (meth) acrylic acid ester monomer has a hydrophobicity with a water solubility of 0.45% by weight or less, and a method for producing single hollow particles is provided.
Furthermore, according to the present invention, there are provided a resin composition containing a mixture of the single hollow particles and the transparent resin, and a light diffusing plate containing the resin composition.

According to the present invention, single hollow particles having excellent light diffusibility can be provided.
Moreover, according to the present invention, the single hollow particles can be easily produced without using a hydrophilic monomer.
Further, by melt-kneading the single hollow particles of the present invention with a transparent resin, it is possible to obtain a resin composition for producing a light diffusion plate or the like having an excellent light diffusion effect derived from the unique shape of the single hollow particles. it can.

  The “single hollow particle” in the present invention refers to a substantially spherical particle having a single pore inside. Moreover, the single hollow particle of this invention is equipped with the void | hole a, the inner side polymer layer b, and the outer side polymer layer c in this order toward the outer side from the center, as shown in FIG. In FIG. 1, reference numeral 1 means a single hollow particle. The size of the single hollow particles is not particularly limited, and can be set as appropriate according to the application. For example, in the case of the use of a light diffusion plate, it is preferable to have an average particle diameter of 2 to 50 μm. Within this range, sufficient light diffusibility can be ensured without using a large amount of single hollow particles. A more preferable average particle diameter is 3 to 30 μm.

The inner polymer layer contains a (meth) acrylic acid ester-styrene copolymer. On the other hand, the outer polymer layer contains a copolymer derived from a monomer mixture of a crosslinkable vinyl monomer and a hydrophobic (meth) acrylate monomer. Here, (meth) acryl means acryl or methacryl.
In the copolymer, examples of the styrene monomer (styrene component) include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and t-butylstyrene. These monomers can be used alone or in combination.

Moreover, as a (meth) acrylic acid ester monomer ((meth) acrylic acid ester component), ethyl acrylate, methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, acrylonitrile, ethyl methacrylate, methyl methacrylate , Butyl methacrylate, 2-ethylhexyl methacrylate and the like. These monomers can be used alone or in combination.
In addition to these monomers, diene components such as an acrylic acid component, a methacrylic acid component, 1,3-butadiene, and 2-methyl-1,3-butadiene (isoprene) may be contained.

  As the (meth) acrylic acid ester-styrene copolymer, phase separation is likely to occur, and since it is inexpensive, methyl methacrylate-styrene copolymer, butyl methacrylate-styrene copolymer, butyl acrylate -Styrene copolymers are preferred.

  The (meth) acrylic acid ester-styrene copolymer has a weight average molecular weight of 50,000 to 400,000 (GPC: measured by gel permeation chromatography). If the weight average molecular weight is lower than 50,000, phase separation from the monomer mixture may not be successful, and desired voided particles may not be obtained. If it is larger than 400,000, it may be difficult to dissolve in the monomer mixture, and particles having desired pores may not be obtained. In addition, an oily substance such as toluene is required to promote dissolution. Furthermore, when an oily substance is not used, it may take a long time to dissolve, which may be impractical in production. A more preferable range is 70,000 to 200,000 in view of good solubility in the monomer mixture. The definition of the weight average molecular weight is described below.

  In this specification, dissolution refers to adding a (meth) acrylic acid-styrene copolymer to a monomer mixture of a (meth) acrylic acid ester monomer and a crosslinkable vinyl monomer, and a propeller blade type stirrer. As a result of visually confirming the solution after stirring for 24 hours at room temperature (about 25 ° C.), it means that the solution is in a homogeneous state without floating matter.

Content of the (meth) acrylic acid ester component which occupies for a copolymer is 20 to 70 weight%. When the amount is less than 20% by weight, the phase separation may be insufficient. When the amount is more than 70% by weight, the phase separation may proceed excessively. As a result, the desired single hollow particles may not be obtained. The preferable content is 25 to 65% by weight from the viewpoint of sufficiently promoting the phase separation.
The inner polymer layer may contain a polymer other than the copolymer as long as the effects of the present invention are not impaired. Examples of the other polymer include high impact polystyrene and thermoplastic elastomer.

  Hydrophobic (meth) acrylic acid ester monomers in the monomer mixture include n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, dodecyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, Tetrahydrofurfuryl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, etc. Is mentioned. These monomers can be used alone or in combination.

  Among these hydrophobic (meth) acrylic acid ester monomers, it is preferable to use a monomer having a solubility in water of 0.45% by weight or less from the viewpoint of suppressing resin deterioration due to moisture. Examples of the monomer having such solubility include the hydrophobic (meth) acrylic acid ester monomer. In particular, it is more preferable to use the hydrophobic (meth) acrylic acid ester monomer having a solubility of 0.4% by weight or less.

In the present specification, the solubility in water is measured, for example, by the following method.
(Measurement method of water solubility)
Water and a (meth) acrylic acid ester monomer are mixed at a weight ratio of 1: 1 and stirred at 25 ° C. for 30 minutes. Using a separatory funnel, the aqueous phase and the oil phase are separated, and the amount (% by weight) of the (meth) acrylic acid ester monomer dissolved in the aqueous phase is measured by high performance liquid chromatography (HPLC).

  Examples of the crosslinkable vinyl monomer include trimethylolpropane triacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, decaethylene glycol dimethacrylate, pentadecaethylene dimethacrylate. Aliphatic divinyl compounds such as glycol, pentamethaethylene glycol dimethacrylate, 1,3-butylene dimethacrylate, allyl methacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, diethylene glycol dimethacrylate; And aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof. These monomers can be used alone or in combination.

  The crosslinkable vinyl monomer is preferably contained in the monomer mixture in the range of 10 to 50% by weight with respect to the hydrophobic (meth) acrylic acid ester monomer. When the amount is less than 10% by weight, phase separation may be insufficient. When the amount exceeds 50% by weight, phase separation may proceed excessively. As a result, desired single hollow particles may not be obtained. The preferable content is 20 to 40% by weight from the viewpoint of sufficiently promoting the phase separation.

In addition, the monomer mixture may contain other monomers copolymerizable with the (meth) acrylic acid ester monomer. Examples of other monomers include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, vinyl chloride, vinyl acetate, acrylonitrile, acrylamide, methacrylamide, N-vinyl pyrrolidone, and the like. Is mentioned. These monomers can be used alone or in combination. Moreover, a hydrophilic monomer can be used in the range which does not inhibit the effect of this invention.
In order to color the particles, metal oxide pigments such as titanium oxide, zinc oxide, magnesium oxide, chromium oxide and zirconium oxide may be added to the monomer mixture.

  The sample ratio of the (meth) acrylic acid ester-styrene copolymer is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the monomer mixture. When the proportion of the copolymer used is less than 1 part by weight, it may be difficult to form pores inside. When the amount is more than 10 parts by weight, pores may not be easily formed inside. A more preferable usage rate is 2 to 8 parts by weight.

  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, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis ( 2,3-dimethylbutyronitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,3,3-trimethylbutyronitrile), 2,2′-azobis (2-Isopropylbutyronitrile ), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2- (carbamoylazo) isobutyronitrile, 4, Examples include 4′-azobis (4-cyanovaleric acid), dimethyl-2,2′-azobisisobutyrate and the like. Among these, 2,2'-azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile) tend to give the desired single hollow particles.

  From the viewpoint of obtaining the intended single hollow particles, the polymerization initiator is used in a monomer mixture (hydrophobic (meth) acrylic acid ester monomer, crosslinkable vinyl monomer and other monomers). The total amount is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight.

  The amount of the aqueous medium used is preferably about 100 to 1000 parts by weight with respect to a total of 100 parts by weight of the monomer mixture and the (meth) acrylic ester-styrene copolymer, and 110 to 500 parts by weight. More preferably, it is about. Examples of the aqueous medium include water alone, a mixed medium of water and a water-soluble solvent (for example, methanol, ethanol, etc.), and the like. In addition, a dispersion stabilizer may be added to the aqueous medium in order to stabilize the suspended particles.

  Dispersion stabilizers include phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, pyrophosphates such as calcium pyrophosphate, magnesium pyrophosphate, aluminum pyrophosphate and zinc pyrophosphate, calcium carbonate, magnesium carbonate And poorly water-soluble inorganic compounds such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate and colloidal silica. Of these, tricalcium phosphate, magnesium pyrophosphate, calcium pyrophosphate, and colloidal silica are particularly preferable in that the desired single hollow particles can be stably obtained.

The aqueous medium can also be used in combination with a dispersion stabilizer and a surfactant such as an anionic surfactant, a cationic surfactant, a zwitterionic surfactant, and a nonionic surfactant.
Examples of anionic surfactants 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 sulfonates. , Alkane sulfonate, dialkyl sulfosuccinate, alkyl phosphate ester salt, naphthalene sulfonate formalin condensate, polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene alkyl sulfate, and the like.

Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride.
Nonionic surfactants include 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, oxyethylene- Examples include oxypropylene block polymers.
Examples of the zwitterionic surfactant include lauryl dimethylamine oxide.

  These dispersion stabilizers and surfactants can be appropriately selected from the above examples in consideration of the size of the single hollow particles obtained, the dispersion stability during polymerization, and the like. In addition, the amount of the dispersion stabilizer added to the monomer mixture is preferably about 0.5 to 15% by weight in that a desired single hollow particle can be stably obtained. Is preferably about 0.001 to 0.1% by weight based on the aqueous medium.

  In addition, in order to suppress the polymerization of the monomer in the aqueous medium and promote the phase separation inside the droplet, about 0.01 to 1% by weight of a water-soluble polymerization inhibitor is added to the aqueous medium. May be. 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.

  During suspension polymerization, a solution of a monomer mixture and a (meth) acrylic ester-styrene copolymer is dispersed in an aqueous medium. Examples of the dispersion method include a method of dispersing the monomer droplets by a stirring force such as a propeller blade, and a method of using a high shear force composed of a rotor and a stator. For the latter method, a disperser such as a homomixer or an ultrasonic disperser can be used.

The average maximum particle size (average particle size) of the single hollow particles can be adjusted by the mixing conditions of the monomer mixture and water, the addition amount of a dispersion stabilizer and the like, the stirring conditions, the dispersion conditions, and the like. This average maximum particle size can be appropriately adjusted according to the use of the single hollow particles.
In order to make the diameters of the single hollow particles uniform, a method using a high-pressure disperser utilizing collision between droplets such as a microfluidizer or nanomizer or collision force against the machine wall may be used.

Suspension polymerization may be performed by heating an aqueous medium in which a solution of a monomer mixture and a (meth) acrylic acid ester-styrene copolymer is dispersed, if necessary. As for heating temperature, 30-100 degreeC is preferable normally, More preferably, it is 40-80 degreeC. The polymerization time while maintaining the polymerization temperature is generally about 0.1 to 10 hours. When the boiling point of the (meth) acrylate monomer and the crosslinkable vinyl monomer is near or above the polymerization temperature, the (meth) acrylate monomer and the crosslinkable vinyl monomer Polymerization is preferably performed in a sealed state or under pressure using a pressure-resistant polymerization facility such as an autoclave so that the monomer does not volatilize.
During the polymerization, it is preferable to perform gentle stirring to such an extent that the monomer droplets are prevented from floating and the single hollow particles after the polymerization are prevented from settling.

  After polymerization, the single hollow particles are separated as a hydrous cake by a method such as suction filtration, centrifugal dehydration, centrifugal separation, pressure dehydration, and the obtained hydrous cake is washed with water and dried to obtain the desired single hollow particles. be able to. Here, the adjustment of the average particle size of the single hollow particles is performed by adjusting the mixing condition of the monomer-containing solution and water, the addition amount of the suspension stabilizer, the surfactant and the like, the stirring condition of the above stirrer, and the dispersion condition. Is possible.

  In the single hollow particles of the present invention, since there are pores inside, complicated refraction of light occurs. Therefore, higher light diffusivity can be expected compared to solid particles without voids. For example, a light diffusing plate containing single hollow particles in a transparent resin exhibits excellent optical characteristics even if the amount of single hollow particles added is small. Moreover, since single hollow particles are manufactured from a hydrophobic monomer, there is little deterioration of the transparent resin due to moisture when melt-kneading with the transparent resin. Therefore, the moldability of the molded body can be improved.

The ratio of the pores to the single hollow particles is preferably 1 to 30% from the viewpoint of providing more excellent light diffusibility. The ratio of holes can be measured, for example, by the following method.
(Measurement method of the percentage of vacancies)
The ratio (%) of pores of single hollow particles is calculated by the following equation by measuring the particle specific gravity according to JIS K5201-11-1 and comparing the specific gravity of single hollow particles with the specific gravity of solid particles.
Percentage of vacancies (%) = 100 × (solid particle specific gravity−single hollow particle specific gravity) / solid particle specific gravity When the proportion of vacancies is smaller than 1%, light diffusibility may be lowered. In addition, when the ratio of the pores is larger than 30%, the strength of the single hollow particles becomes low, and the particles may be crushed when kneaded into a transparent resin. A more desirable ratio is 2 to 20%.

  The single hollow particles of the present invention can be used for any application as long as it is desired to diffuse light. As such an application, there is a light diffusion plate. As illustrated in FIG. 2, the light diffusing plate has a configuration in which the light diffusing particles 1 are blended with the transparent resin 2. 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.

  As the transparent resin, a thermoplastic resin is usually used. Examples of the thermoplastic resin include (meth) acrylic resin, (meth) acrylic acid alkyl-styrene copolymer, polycarbonate, polyester, polyethylene, polypropylene, polystyrene, and the like. Is mentioned.

  Among these, when excellent transparency is required, (meth) acrylic resin, (meth) acrylic acid acrylic-styrene copolymer, polycarbonate, polyester, and polystyrene are preferable. These thermoplastic resins can be used alone or in combination of two or more.

  The addition ratio of the single hollow particles to the transparent resin is preferably 0.1 to 15 parts by weight with respect to 100 parts by weight of the transparent resin. If it is less than 0.1 part by weight, it may be difficult to give light diffusibility. When the amount is more than 15 parts by weight, light diffusibility can be obtained, but light transmittance may be lowered. A more preferable addition ratio is 0.5 to 10 parts by weight.

  The light diffusing plate can be obtained by melt-kneading a transparent resin and single hollow particles with a uniaxial or biaxial extruder, and then molding. For example, a resin composition composed of a melt-kneaded transparent resin and single hollow particles may be formed into a plate shape via a T die and a roll unit. Moreover, the resin composition obtained by melt-kneading with a uniaxial or biaxial extruder or the like may be pelletized and molded into a plate shape by injection molding or press molding.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited by these Examples. In addition, the weight average molecular weight of a copolymer, the average particle diameter of a single hollow particle, the total light transmittance of a single hollow particle containing molded object, and haze were measured with the following method.
(Weight average molecular weight of copolymer)
The weight average molecular weight (Mw) is measured using GPC (gel permeation chromatography). The measuring method is as follows. In addition, a weight average molecular weight (Mw) means a polystyrene (PS) conversion weight average molecular weight.
A 50 mg sample is dissolved in 10 ml of tetrahydrofuran (THF), filtered through a non-aqueous 0.45 μm chromatographic disk, and measured using a chromatograph. The chromatographic conditions are as follows.

Liquid chromatograph: manufactured by Tosoh Corporation, trade name “Gel Permeation Chromatograph HLC-8020”
Column: Tosoh Corporation, trade name “TSKgel GMH-XL-L” φ7.8 mm × 30 cm × 2 Column temperature: 40 ° C.
Carrier gas: Tetrahydrofuran (THF)
Carrier gas flow rate: 1 ml / min Injection / pump temperature: 35 ° C
Detection: RI
Injection amount: 100 microliters Standard polystyrene for calibration curve: manufactured by Showa Denko KK, trade name “shodex” weight average molecular weight: 1030000 and manufactured by Tosoh Corporation, weight average molecular weight: 5480000, 3840000, 355000, 102000, 37900, 9100, 2630, 870

(Measurement method of average particle size)
The electrolyte solution is filled in pores having a pore diameter of 50 to 280 μm, the volume is obtained from the change in conductivity of the electrolyte solution when the particles pass through the electrolyte solution, and the average particle diameter is calculated. Specifically, the measured average particle diameter is a volume average particle diameter measured by a Coulter Multisizer II manufactured by Beckman Coulter. In the measurement, calibration is performed using an aperture suitable for the particle diameter of the particle to be measured according to REFERENCE MANUAL FOR THE COULTER MULTISIZER (1987) issued by Coulter Electronics Limited.

  Specifically, 0.1 g of particles and 10 ml of a 0.1% nonionic surfactant solution are put into a commercially available glass 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 seconds using a ULTRASONIC CLEANER VS-150 manufactured by VervoCrea, a commercially available ultrasonic cleaner. In a beaker filled with ISOTON 2 (manufactured by Beckman Coulter, Inc .: electrolyte for measurement) equipped with the dispersion, drop it with a dropper while gently stirring, and adjust the concentration meter reading on the screen to around 10%. . Next, the aperture size, Current, Gain, and Polarity are input to the Multisizer II body according to REFERENCE MANUAL FOR THE MULTILIZER (1987) issued by Coulter Electronics Limited 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.

(Total light transmittance and haze)
The total light transmittance and haze are measured by JISK7361. Specifically, the measurement is performed using NHD-2000 manufactured by Nippon Denshoku Industries Co., Ltd. The case where the haze is 99% or more is evaluated as ○.

(Formability)
Ten sheets are formed continuously, and it is visually evaluated whether a silver strip (silver streak) appears on the surface of the formed plate. When silver strips do not appear on all 10 sheets, the molding is good and the evaluation is ○. If a silver strip appears even on one sheet, it is regarded as a molding failure and evaluated as x.

Example 1
In a polymerization vessel equipped with a stirrer and a thermometer, 500 parts by weight of deionized water in which 0.05 part by weight of sodium lauryl sulfate (surfactant) is dissolved is added, and 50 parts by weight of calcium phosphate (dispersion stabilizer) is added thereto. Dispersed. A monomer mixture of 70 parts by weight of butyl acrylate (hydrophobic (meth) acrylic acid ester monomer) and 30 parts by weight of ethylene glycol dimethacrylate (crosslinkable vinyl monomer) prepared in advance. MS300 (methyl methacrylate-styrene copolymer (methyl methacrylate component 30% by weight) / manufactured by Nippon Steel Chemical Co., Ltd., Mw = 170,000) 5 parts by weight, benzoyl peroxide 0.5 part by weight, azobisisobuty A mixed solution in which 0.5 part by weight of nitrile was dissolved was added. The mixture was stirred at 5000 rpm for 10 minutes with a K homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a droplet diameter of about 5 μm. Next, the polymerization reactor was heated to 65 ° C. and subjected to suspension polymerization while stirring and then cooled. The suspension obtained here was filtered, washed, and dried to obtain particles having an average particle size of 5.1 μm. When the particles were observed with an optical microscope, the particle outline was observed twice, and the particles had pores inside.

Further, the particles were clad with an epoxy resin and divided into two at the surface passing through the center of the particle, and the divided surface was stained with ruthenium tetroxide (RuO ₄ ) and observed with a transmission electron microscope. When dyed with ruthenium tetroxide, the (meth) acrylate-styrene copolymer is a copolymer derived from a monomer mixture of a crosslinkable vinyl monomer and a (meth) acrylate monomer. As a result, the distribution state of each copolymer in the particles is known. A photomicrograph is shown in FIG. From FIG. 3, the obtained particles have a multilayer structure, and from the degree of dyeing, from the center toward the outside, pores, an inner polymer layer derived from a (meth) acrylate-styrene copolymer. And a single hollow particle comprising an outer polymer layer derived from the monomer mixture in this order.

  Further, 1.0 part by weight of the particles as a transparent resin, 100 parts by weight of polystyrene resin (Toyostyrene GP G200, manufactured by Toyo Styrene Co., Ltd.) was dried in an oven set at 80 ° C. for 3 hours, and then 200 times in an extruder. After melt-kneading at 0 ° C., the mixture was pelletized. The obtained pellets were molded by an injection molding machine (cylinder temperature 230 ° C., residence time 15 minutes) to produce a 2 mm thick, 50 mm × 100 mm molded plate. Table 1 shows the evaluation results (total light transmittance, haze, and moldability) of the resulting molded plate.

Example 2
Instead of MS300, MS600 (methyl methacrylate-styrene copolymer (methyl methacrylate component 60% by weight) / manufactured by Nippon Steel Chemical Co., Ltd., Mw = 160,000) was used in the same manner as in Example 1. Particles having an average particle size of 5.2 μm were obtained. When this particle was observed with an optical microscope, as in Example 1, the outline of the particle was observed twice and it was a single hollow particle having pores inside the particle. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Example 3
(Production of methyl methacrylate-styrene copolymer)
A polymerization vessel equipped with a stirrer and a thermometer was charged with 500 parts by weight of deionized water in which 0.05 part by weight of sodium lauryl sulfate was dissolved, and 50 parts by weight of calcium triphosphate was dispersed therein. A liquid mixture prepared by dissolving 50 parts by weight of a methyl methacrylate and 50 parts by weight of a styrene polymerizable monomer component and 0.5 parts by weight of benzoyl peroxide prepared in advance was added thereto. The resulting dispersion was T.W. The mixture was stirred at 3000 rpm for 10 minutes with a K homomixer (manufactured by Koki Kogyo Co., Ltd.) so that the droplet diameter was approximately 20 μm. Next, the polymerization reactor was heated to 80 ° C. and subjected to suspension polymerization while stirring and then cooled.
The suspension obtained here was filtered, washed, and dried to obtain methyl methacrylate-styrene copolymer particles. When the molecular weight of the obtained particles was measured by GPC, Mw was 90,000.

(Manufacture of molded products)
Particles having an average particle diameter of 4.9 μm were obtained in the same manner as in Example 1 except that the above methyl methacrylate-styrene copolymer (methyl methacrylate component 50% by weight) was used instead of MS300. When this particle was observed with an optical microscope, as in Example 1, the outline of the particle was observed twice and it was a single hollow particle having pores inside the particle. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Example 4
Particles having an average particle diameter of 5.3 μm were obtained in the same manner as in Example 1 except that 60 parts by weight of butyl acrylate and 40 parts by weight of ethylene glycol dimethacrylate were used as the monomer mixture. When this particle was observed with an optical microscope, as in Example 1, the outline of the particle was observed twice and it was a single hollow particle having pores inside the particle. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Example 5
Particles having an average particle size of 5.0 μm were obtained in the same manner as in Example 1 except that 85 parts by weight of butyl methacrylate and 15 parts by weight of ethylene glycol dimethacrylate were used as the monomer mixture. When this particle was observed with an optical microscope, as in Example 1, the outline of the particle was observed twice and it was a single hollow particle having pores inside the particle. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Example 6
Particles having an average particle diameter of 5.1 μm were obtained in the same manner as in Example 1 except that 8 parts by weight of MS300 was used. When this particle was observed with an optical microscope, as in Example 1, the outline of the particle was observed twice and it was a single hollow particle having pores inside the particle. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Example 7
Particles having an average particle size of 5.3 μm were obtained in the same manner as in Example 1 except that 2 parts by weight of MS300 was used. When this particle was observed with an optical microscope, as in Example 1, the outline of the particle was observed twice and it was a single hollow particle having pores inside the particle. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Comparative Example 1
(Production of methyl methacrylate-styrene copolymer)
A polymerization vessel equipped with a stirrer and a thermometer was charged with 500 parts by weight of deionized water in which 0.05 part by weight of sodium lauryl sulfate was dissolved, and 50 parts by weight of calcium triphosphate was dispersed therein. Into this, 50 parts by weight of methyl methacrylate and 50 parts by weight of styrene polymerizable monomer component, 0.5 part by weight of benzoyl peroxide, and 3 parts by weight of n-dodecyl mercaptan were dissolved. The mixture was added. The resulting dispersion was T.W. The mixture was stirred at 3000 rpm for 10 minutes with a K homomixer (manufactured by Koki Kogyo Co., Ltd.) so that the droplet diameter was approximately 20 μm. Next, the polymerization reactor was heated to 80 ° C. and subjected to suspension polymerization while stirring and then cooled.
The suspension obtained here was filtered, washed, and dried to obtain methyl methacrylate-styrene copolymer particles. When the molecular weight of the obtained particles was measured by GPC, Mw was 40,000.

(Manufacture of molded products)
Particles having an average particle diameter of 4.9 μm were obtained in the same manner as in Example 1 except that the above methyl methacrylate-styrene copolymer (methyl methacrylate component 50% by weight) was used instead of MS300. When this particle was observed with an optical microscope, the particle contour was not observed twice, and it was a solid particle without voids. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Comparative Example 2
(Production of methyl methacrylate-styrene copolymer)
A polymerization vessel equipped with a stirrer and a thermometer was charged with 500 parts by weight of deionized water in which 0.05 part by weight of sodium lauryl sulfate was dissolved, and 50 parts by weight of calcium triphosphate was dispersed therein. A mixed solution prepared by dissolving 95 parts by weight of a methyl methacrylate and 5 parts by weight of a styrene polymerizable monomer component and 0.5 parts by weight of benzoyl peroxide was prepared. The resulting dispersion was T.W. The mixture was stirred at 3000 rpm for 10 minutes with a K homomixer (manufactured by Koki Kogyo Co., Ltd.) so that the droplet diameter was approximately 20 μm. Next, the polymerization reactor was heated to 80 ° C. and subjected to suspension polymerization while stirring and then cooled.
The suspension obtained here was filtered, washed, and dried to obtain methyl methacrylate-styrene copolymer particles. When the molecular weight of the obtained particles was measured by GPC, Mw was 100,000.

  Particles having an average particle size of 5.1 μm were obtained in the same manner as in Example 1 except that the above-mentioned methyl methacrylate-styrene copolymer (methyl methacrylate component 95% by weight) was used instead of MS300. When this particle was observed with an optical microscope, the particle contour was not observed twice, and it was a solid particle without voids. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Comparative Example 3
(Production of methyl methacrylate-styrene copolymer)
A polymerization vessel equipped with a stirrer and a thermometer was charged with 500 parts by weight of deionized water in which 0.05 part by weight of sodium lauryl sulfate was dissolved, and 50 parts by weight of calcium triphosphate was dispersed therein. A mixed solution prepared by dissolving 30 parts by weight of a methyl methacrylate and 70 parts by weight of a styrene polymerizable monomer component and 0.1 parts by weight of benzoyl peroxide was prepared. The resulting dispersion was T.W. The mixture was stirred at 3000 rpm for 10 minutes with a K homomixer (manufactured by Koki Kogyo Co., Ltd.) so that the droplet diameter was approximately 20 μm. Next, the polymerization reactor was heated to 60 ° C. and subjected to suspension polymerization while stirring and then cooled.
The suspension obtained here was filtered, washed, and dried to obtain methyl methacrylate-styrene copolymer particles. When the molecular weight of the obtained particles was measured by GPC, Mw was 500,000.

  Particles were obtained in the same manner as in Example 1 except that the above methyl methacrylate-styrene copolymer (methyl methacrylate component 30% by weight) was used instead of MS300. Since the methyl methacrylate-styrene copolymer was not dissolved, the subsequent operation was not performed.

Comparative Example 4
Particles having an average particle diameter of 5.2 μm were obtained in the same manner as in Example 1 except that 0.5 part by weight of MS300 was used. When this particle was observed with an optical microscope, the particle contour was not observed twice, and it was a solid particle without voids. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Comparative Example 5
Particles having an average particle diameter of 5.1 μm were obtained in the same manner as in Example 1 except that 20 parts by weight of MS300 was used. When this particle was observed with an optical microscope, the particle contour was not observed twice, and it was a solid particle without voids. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Comparative Example 6
Example 1 except that 20 parts by weight of methyl acrylate (hydrophilic monomer), 50 parts by weight of methyl methacrylate (hydrophilic monomer), and 30 parts by weight of ethylene glycol dimethacrylate were used as the monomer mixture. Thus, particles having an average particle diameter of 5.2 μm were obtained. When the particles were observed with an optical microscope, as in Example 1, the particle outline was observed twice, and the particles had pores inside the particles. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Comparative Example 7
(Production of methyl methacrylate-styrene copolymer)
A polymerization vessel equipped with a stirrer and a thermometer was charged with 500 parts by weight of deionized water in which 0.05 part by weight of sodium lauryl sulfate was dissolved, and 50 parts by weight of calcium triphosphate was dispersed therein. A mixed solution prepared by dissolving 10 parts by weight of methyl methacrylate, 90 parts by weight of a styrene monomer, 0.5 parts by weight of benzoyl peroxide, and 3 parts by weight of n-dodecyl mercaptan prepared in advance. I put it in. The resulting dispersion was T.W. The mixture was stirred at 3000 rpm for 10 minutes with a K homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a droplet diameter of about 20 μm. Next, the polymerization reactor was heated to 80 ° C. and subjected to suspension polymerization while stirring and then cooled.
The suspension obtained here was filtered, washed, and dried to obtain methyl methacrylate-styrene copolymer particles. When the molecular weight of the obtained particles was measured by GPC, Mw was 100,000.

  Particles having an average particle diameter of 5.1 μm were obtained in the same manner as in Example 1 except that the above methyl methacrylate-styrene copolymer (methacrylic acid ester component 10% by weight) was used instead of MS300. When the particles were observed with an optical microscope, the outline of the particles was not observed twice and was a solid particle without voids. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

(Comparative Example 8)
Particles having an average particle diameter of 5.2 μm were obtained in the same manner as in Example 1 except that 95 parts by weight of butyl acrylate and 5 parts by weight of ethylene glycol dimethacrylate were used. When the particles were observed with an optical microscope, the outline of the particles was not observed twice and was a solid particle without voids. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

(Comparative Example 9)
Particles having an average particle size of 5.3 μm were obtained in the same manner as in Example 1 except that 40 parts by weight of butyl acrylate and 60 parts by weight of ethylene glycol dimethacrylate were used. When the particles were observed with an optical microscope, the outline of the particles was not observed twice and was a solid particle without voids. Further, a molded plate was produced in the same manner as in Example 1, and the obtained molded plate was evaluated. The results are shown in Table 1.

Table 1 shows the following.
From Examples and Comparative Examples 1 to 5, it can be seen that single hollow particles have higher haze than solid particles and have good light diffusibility.
From Examples and Comparative Examples 1 and 3, it can be seen that particles having a high haze and good light diffusivity can be provided when the weight average molecular weight is in the range of 50,000 to 400,000.
From Examples and Comparative Examples 2 and 7, the proportion of the (meth) acrylic acid component in the copolymer is in the range of 20 to 70% by weight, thus having high haze and good light diffusibility. It can be seen that the particles can be provided.

From Examples and Comparative Examples 4 and 5, it can be seen that particles having a high haze and good light diffusibility can be provided when the addition amount of the copolymer is in the range of 1 to 10 parts by weight.
From Examples and Comparative Examples 8 and 9, when the addition amount of the crosslinkable vinyl monomer is in the range of 10 to 50% by weight, particles having high haze and good light diffusibility are provided. I understand that I can do it.

From Examples 1 and 5, it can be seen that even if the type of the hydrophobic (meth) acrylic acid ester monomer is changed, particles having high haze and good light diffusibility can be provided.
From Comparative Example 6, it can be seen that if a hydrophilic monomer is used instead of the hydrophobic (meth) acrylic acid ester monomer, the moldability is lowered.

It is a schematic sectional drawing of a single hollow particle. It is the schematic of a light diffusing plate. 2 is an electron micrograph of a cross section of a single hollow particle of Example 1. FIG.

Explanation of symbols

a hole b inner polymer layer c outer polymer layer 1 single hollow particle (light diffusing particle)
2 Transparent resin

Claims (4)

From the center to the outside, a pore, an inner polymer layer, and an outer polymer layer are provided in this order, and the inner polymer layer has a weight average molecular weight in the range of 50,000 to 400,000 (measured by GPC). And a (meth) acrylic acid ester-styrene copolymer containing 20 to 70% by weight of a (meth) acrylic acid ester component, and the outer polymer layer has a crosslinkability of 10 to 50% by weight. A monomer mixture of a vinyl monomer and 90 to 50% by weight of a hydrophobic (meth) acrylate monomer (provided that the monomer mixture is a monomer other than the crosslinkable vinyl monomer). as mer comprises a copolymer solubility in water of from including no) 0.45 wt% greater than the hydrophilic monomer,
A monomer in which the (meth) acrylic acid ester-styrene copolymer containing the (meth) acrylic acid ester component is selected from styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and t-butylstyrene. Including styrene-based components derived from
Single hollow particles, wherein the hydrophobic (meth) acrylic acid ester monomer exhibits hydrophobicity with a solubility in water of 0.45% by weight or less. 10 to 50 wt% of the crosslinkable vinyl monomer and 90-50 wt% of a hydrophobic (meth) monomer mixture of acrylic acid ester monomer (provided that the monomer mixture, said crosslinkable As a monomer other than a vinyl monomer, a hydrophilic monomer having a solubility in water of greater than 0.45% by weight is not included. ) In 100 parts by weight, a weight average molecular weight in the range of 50,000 to 400,000 (Measured by GPC) and 20 to 70% by weight of a (meth) acrylic acid ester-styrene copolymer 1 to 10 parts by weight and a polymerization initiator 0.01 to 70% by weight 10 parts by weight are dissolved, and the resulting solution is subjected to suspension polymerization in the presence of an aqueous medium, whereby the pores, the inner polymer layer, and the outer polymer layer are formed in this order from the center toward the outside. From obtaining single hollow particles with Ri,
A monomer in which the (meth) acrylic acid ester-styrene copolymer containing the (meth) acrylic acid ester component is selected from styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and t-butylstyrene. Including styrene-based components derived from
The method for producing single hollow particles, wherein the hydrophobic (meth) acrylic acid ester monomer exhibits hydrophobicity with a water solubility of 0.45% by weight or less.   A resin composition comprising a mixture of the single hollow particles according to claim 1 and a transparent resin.   A light diffusing plate comprising the resin composition according to claim 3.