JP2003012733A - Styrene fine particle assembly having excellent light resistance, light diffusing agent using the same assembly and method for producing the same assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve light diffusivity of polymer fine particles utilizable as a light diffusing agent and to impart excellent light resistance without deterioration with time to the fine particles. SOLUTION: The styrene fine particle assembly is obtained by polymerizing monomer components consisting essentially of one or more kinds of styrene monomers, one or more kinds of specific ultraviolet stable monomers and one or more kinds of monomers each having >=2 radically polymerizable double bonds and connecting a plurality of the resultant styrene fine particles having 0.01-1 μm average particle diameter into the assembly. The styrene fine particle assembly has 2-200 μm average particle diameter and the excellent light resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrene-based crosslinked fine particle aggregate having excellent light resistance and a method for producing such a fine particle aggregate, and further to a light useful for a liquid crystal display device, a lighting fixture and the like. The present invention relates to a light diffusing agent having a function of diffusing light.

[0002]

2. Description of the Related Art Fine particles of crosslinked polymers have been used as a light diffusing agent. For example, JP-A-5-302
No. 006 discloses a methacrylic resin plate using substantially spherical crosslinked fine particles composed of divinylbenzene and styrene as a light diffusing agent. However, the crosslinked fine particles obtained from aromatic monomers such as styrene and divinylbenzene gradually turn yellow due to the presence of an aromatic ring having poor light resistance, and the light transmittance and the light transmittance are gradually lowered. It is regarded as a problem to lose it.

From the above point of view, in JP-A-8-109272, the light resistance of the methacrylic resin plate is improved by incorporating an ultraviolet absorber in the crosslinked fine particles. However, low molecular weight UV absorbers gradually bleed out to the surface of the plate, and peel off / fall off from the surface of the plate. In addition, there is an inconvenience that the appearance of the plate surface deteriorates with time.

Further, all of the above-mentioned crosslinked fine particles are substantially spherical primary fine particles, and it is necessary to carry out classification for equalizing the particle size after emulsion polymerization, and the light diffusivity is limited. there were.

[0005]

Therefore, in the present invention, it is an object to further improve the light diffusivity of the fine particles and to impart excellent light resistance without deterioration over time.

[0006]

Means for Solving the Problems The styrene-based fine particle aggregate of the present invention, which is capable of solving the above-mentioned problems, has at least one styrene-based monomer and the following general formula (1) or (2). A plurality of styrenic fine particles obtained by polymerization of a monomer component essentially containing one or more kinds of UV stable monomers represented and one or more kinds of monomers having two or more radically polymerizable double bonds are linked together. Average particle size 2-20
It has a gist in that it is an aggregate of 0 μm.

[0007]

[Chemical 3]

(Wherein R ¹ represents a hydrogen atom or a cyano group, R ² and R ³ each independently represent a hydrogen atom or a methyl group, R ⁴ represents a hydrogen atom or a hydrocarbon group,
R ^4's each independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and X represents an oxygen atom or an imino group. )

[0009]

[Chemical 4]

(In the formula, R ¹ represents a hydrogen atom or a cyano group, R ² , R ³ , R ^{2 ′} and R ^{3 ′} each independently represent a hydrogen atom or a methyl group, and R ^{4 ′} are each independently. Represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and X represents an oxygen atom or an imino group.) An ultraviolet stable group is introduced into the skeleton of the crosslinked fine particles by copolymerization of the above ultraviolet stable monomer. Therefore, it exhibits good light resistance. Also,
Secondary particles in which a plurality of fine particles are strongly connected, that is, fine particle aggregates, exhibit excellent light diffusibility, rather than the fine particles themselves.

At this time, the average particle diameter of the fine particles is 0.01 to
1 μm, and the average particle size of the fine particle aggregate is 2 to 200 μm.
When it is m, it shows very excellent light diffusivity. Further, it is preferable that the fine particles are connected to each other by a polymer binder because the fine particles are further strongly connected and the heat resistance and the solvent resistance are improved. The present invention includes a light diffusing agent containing the styrene-based fine particle aggregate.

As a production method for producing the styrene-based fine particle aggregate, an emulsion liquid containing styrene-based fine particles is obtained by emulsion-polymerizing the monomer component according to claim 1, and then the emulsion liquid is sprayed. A method of connecting the styrene fine particles to each other by drying is simple.

When the fine particles are linked to each other using a polymer binder, an emulsion liquid containing crosslinked fine particles is obtained by emulsion polymerization of the monomer component according to claim 1, and then the emulsion liquid and the polymer binder are used. It is preferable to employ a method in which the styrene-based fine particles are linked to each other by a polymer binder by spray-drying a mixture with an emulsion liquid containing

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The styrene-based fine particle aggregate of the present invention comprises at least one styrene-based monomer, and at least one UV-stable monomer represented by the general formula (1) or (2).
It is an aggregate of styrene-based fine particles obtained by radical polymerization of a monomer component that essentially contains at least one monomer having two or more radically polymerizable double bonds.

In obtaining the fine particles, the styrene-based monomer is used as an essential component because it has a high refractive index with respect to light, and thus a good light diffusing performance can be obtained. Styrene-based monomers include styrene, α-methylstyrene,
Chlorostyrene, vinyltoluene, and the like can be used, and these can be used alone or in combination of two or more, but styrene is most preferable because it is inexpensive and does not contain halogen.

The UV-stable monomer is a piperidine compound represented by the above formula (1) or (2) and has no ability to absorb UV rays, but has an excellent UV stability by an action different from that of the UV absorber. Exert. Although this UV-stabilizing action has not been fully clarified yet, it is considered that the N-oxyl radical produced by the oxidation of the N-substituent of the piperidine skeleton traps the radical generated by UV. . In the present invention, in order to introduce a UV-stabilizing group in the polymer skeleton constituting the styrenic fine particles using a UV-stable monomer, when mixing a low-molecular UV stabilizer or UV absorber that is easy to bleed out In comparison, the deterioration of light resistance with time is suppressed as much as possible. Further, when a large amount of low molecular weight UV stabilizers or the like is used, after the production of the fine particle aggregate targeted by the present invention, the UV stabilizers or the like may bleed out to weaken the fine particle connecting force, Such inconvenience cannot occur if the above monomers are used.

In the general formula (1) or (2), R
^The substituent represented by ⁴ is a hydrogen atom or a hydrocarbon group, and the hydrocarbon group preferably has 1 to 18 carbon atoms. Specifically, it may be any of an alkyl group such as a methyl group and an ethyl group, an alicyclic hydrocarbon group such as a cyclopentyl group and a cyclohexyl group, an aromatic hydrocarbon group such as a phenyl group and a phenethyl group. Further, R ^{4 ′} each independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.

Specific examples of the UV stable monomer represented by the general formula (1) include 4- (meth).
Acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-2,2
6,6-Tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino-1,2,
2,6,6-pentamethylpiperidine, 4-cyano-4
-(Meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,
2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine and the like can be mentioned.

Examples of the UV stable monomer represented by the general formula (2) include 1- (meth) acryloyl-
4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4
-Cyano-4- (meth) acryloylamino-2,2,
6,6-Tetramethylpiperidine, 1-crotonoyl-
4-crotoyloxy-2,2,6,6-tetramethylpiperidine and the like can be mentioned.

As the UV-stable monomer, only one of the compounds represented by the above general formula (1) or (2) may be used, or two or more thereof may be appropriately mixed and used. Good.

A monomer having two or more radically polymerizable double bonds (the above-mentioned UV-stable monomer (2)) is essential for the synthesis of styrene-based fine particles together with the styrene-based monomer and the UV-stable monomer. except for)
Is. The monomer having two or more radically polymerizable double bonds (hereinafter referred to as a polyfunctional monomer) crosslinks the polymer constituting the styrene-based fine particles during polymerization to form a three-dimensional network structure skeleton. As a result, heat resistance, solvent resistance, strength and other characteristics are imparted to the fine particles.

Specific examples of polyfunctional monomers include divinylbenzene and its derivatives; trimethylolpropane tri (meth) acrylate and mono (di, tri or poly) ethylene glycol di (meth) acrylate.
Examples thereof include esters of a polyhydric alcohol having a valence of 2 or more and two or more molecules of (meth) acrylic acid.

The ratio of various monomers in the monomer component for obtaining the styrene-based fine particles is styrene-based monomer: 3 when the total amount of the monomer components is 100% by mass.
0-97.5 mass%, UV stable monomer: 0.5-
50 mass% and polyfunctional monomer: 2 to 20 mass% is preferable. If the amount of the UV stable monomer is less than 0.5% by mass, the yellowing resistance-improving effect may be insufficient, and if the amount of the polyfunctional monomer is less than 2% by mass, the styrene fine particles are plasticized in a high temperature environment. It is difficult to maintain a fine particle state because it becomes solid or melts in the presence of a solvent. On the other hand, when the amount of the styrene-based monomer is more than 97.5% by mass, as a result, the amount of the UV-stable monomer and the polyfunctional monomer are decreased, and the above-mentioned inconvenience may occur. Also,
If there are too many UV stable monomers or polyfunctional monomers,
As a result, the amount of styrene-based monomer decreases, which is not preferable in terms of refractive index.

In order to obtain the styrene-based fine particles, known radical-polymerizable monomers other than the above-mentioned monomer components can be used without particular limitation as long as they do not impair the light diffusibility. Specifically, alkyl esters of (meth) acrylic acid such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate and cyclohexyl (meth) acrylate; vinyl esters such as vinyl acetate and propion vinyl. And vinyl cyan compounds such as (meth) acrylonitrile; halogen-containing monomers such as vinyl chloride and vinylidene chloride; conjugated dienes such as butadiene. These monomers should be used by replacing a part of the styrene-based monomer, that is, the above-mentioned usage of the styrene-based monomer should be reduced by the usage of these monomers. However, it is preferable to use these monomers in a range of 10% by mass or less based on 100% by mass of the total monomer components in terms of maintaining a high refractive index.

Among the above-mentioned monomers, cycloalkyl group-containing (meth) acrylates such as cyclohexyl (meth) acrylate can be incorporated into various resins which may be deteriorated by the use of UV stable monomers and UV absorbing monomers described later. While exerting the effect of increasing the dispersibility of
Since it also contributes to the improvement of light resistance, it can be preferably used when the light diffusing agent of the present invention is dispersed in a resin plate and applied to the field of use.

When the polymer binder for linking fine particles, which will be described later, has a functional group, a functional group capable of reacting with the functional group of the polymer binder is introduced into the polymer constituting the styrene fine particles. You can leave it. Specifically, a monomer having such a functional group may be copolymerized. For example, a carboxyl group-containing unsaturated monomer such as (meth) acrylic acid; a hydroxyl group-containing monomer such as hydroxyethyl (meth) acrylate; glycidyl (meth) ) It is possible to use an epoxy group-containing monomer such as acrylate. These functional group-containing monomers are also used by replacing a part of the styrene-based monomer, and it is preferable to use them in a range of 10% by mass or less in 100% by mass of the total monomer components in terms of maintaining a high refractive index. .

Further, an ultraviolet absorbing monomer can be used in place of a part of the ultraviolet stable monomer. The ultraviolet ray absorbing monomer refers to a monomer capable of absorbing ultraviolet rays and re-radiating the energy thereof mainly as harmless heat energy and having radical polymerizability. By using these monomers as a copolymerization component, the styrene-based fine particles to be obtained are provided with an ultraviolet absorbing ability.

Examples of the UV absorbing monomer include benzotriazole type monomers represented by the following general formula (3).

[0029]

[Chemical 5]

(In the formula, R ⁵ represents a hydrogen atom or a carbon number of 1 to
8 represents a hydrocarbon group, R ⁶ represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group or a nitro group, and R ⁷ has 1 to 1 carbon atoms. A linear or branched alkylene group having 12 or —O—R ⁹ — (R ⁹ represents a linear or branched alkylene group having 2 or 3 carbon atoms); ⁸ represents a hydrogen atom or a methyl group) can be used.

Further, a benzophenone type monomer represented by the following general formula (4) can also be used.

[0032]

[Chemical 6]

(In the formula, R^Five, R⁸Means the same as above
And R^TenIs a linear or branched chain having 1 to 12 carbon atoms
Represents an alkylene group of R¹¹Is a hydrogen atom or a hydroxyl group
Represent, R ¹²Is a hydrogen atom or alkoxy having 1 to 6 carbon atoms
Represents a group).

Further, a triazine-based monomer represented by the following general formula (5) may be used.

[0035]

[Chemical 7]

(In the formula, R ⁸ has the same meaning as described above, and R ¹³
Bond _{directly, - (CH 2 CH 2 O} ) n - or -CH ₂ CH
(OH) -CH ₂ O- and represents, n is an integer of 1-5. R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹
Each independently represent a hydrogen atom, an alkoxy group having 1 to 10 carbon atoms, an alkenyl group, or an alkyl group).

Specific preferred examples of the benzotriazole-based monomer represented by the general formula (3) include 2
-[2'-hydroxy-5 '-(meth) acryloyloxyphenyl] -2H-benzotriazole, 2-
[2′-hydroxy-5 ′-(meth) acryloyloxyethylphenyl] -2H-benzotriazole, 2-
[2'-hydroxy-5 '-(meth) acryloyloxypropylphenyl] -2H-benzotriazole, 2
-[2'-hydroxy-5 '-(meth) acryloyloxyhexylphenyl] -2H-benzotriazole,
2- [2'-hydroxy-3'-tert-butyl-
5 '-(meth) acryloyloxyethylphenyl]-
2H-benzotriazole, 2- [2'-hydroxy-
5 '-(β- (meth) acryloyloxyethoxy)-
3'-tert-butylphenyl] -5-tert-butyl-2H-benzotriazole and the like.

Specific examples of the benzophenone type monomer represented by the general formula (4) include 2-hydroxy-
4- [2- (meth) acryloyloxy] ethoxybenzophenone, 2-hydroxy-4- [2- (meth) acryloyloxy] butoxybenzophenone, 2,2'-dihydroxy-4- [2- (meth) acryloyloxy] Ethoxybenzophenone, 2-hydroxy-4- [2- (meth) acryloyloxy] ethoxy-4 '-(2-hydroxyethoxy) benzophenone, 2-hydroxy-3-
tert-butyl-4- [2- (meth) acryloyloxy] ethoxybenzophenone, 2-hydroxy-3-t
Examples include ert-butyl-4- [2- (meth) acryloyloxy] butoxybenzophenone.

Specific examples of the triazine-based monomer represented by the general formula (5) include 2,4-diphenyl-6- [2-hydroxy-4- (2-acryloyloxyethoxy)]-s-triazine. , 2,4-bis (2
-Methylphenyl) -6- [2-hydroxy-4- (2-
Acryloyloxyethoxy)]-s-triazine,
2,4-bis (2-methoxyphenyl) -6- [2-hydroxy-4- (2-acryloyloxyethoxy)]-s
-Triazine and the like can be mentioned.

Since the above-mentioned ultraviolet absorbing monomers have their respective unique ultraviolet absorbing characteristics, they may be used in various combinations. This ultraviolet absorbing monomer is preferably used in combination with an ultraviolet stable monomer, and the total of both is
It is preferable to use 5 to 20% by mass in 100% by mass of the monomer component.

The styrene-based fine particles can be obtained by polymerizing the monomer components consisting of the above-mentioned monomers by a known radical polymerization method. The polymerization method is not particularly limited, but emulsion polymerization is preferable because fine particles can be easily obtained. Emulsion polymerization is carried out by using an inorganic peroxide or a redox-based initiator, adjusting the amounts of the monomer component and water so that the final solid content concentration is 5 to 60% by mass, and performing ordinary conditions such as 20 to 100 ° C. You can go in.

The emulsifier is not particularly limited, and a known general-purpose emulsifier (for example, polyoxyethylene alkylphenyl ether sulfonate such as "Hitenol N-08" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)) is used as a monomer component. When used in the range of 0.5 to 10 parts by mass with respect to 100 parts by mass, 0.
The emulsion particles having a size of 01 to 1 μm are obtained. Further, a carboxyl group-containing emulsifier such as a polycarboxylic acid type polymer emulsifier may be used as a reaction point with a functional group-containing polymer binder described later.

After obtaining the styrene fine particles by emulsion polymerization, an aggregate is produced. The method for producing an aggregate is not particularly limited, but the simplest method for producing an aggregate is a spray-type drying method. The spray-type drying method is to obtain dry particles by spraying an aqueous dispersion or the like from a nozzle into a gas stream using a spray dryer or a stream dryer.
According to this method, the particle size and shape of the aggregate can be easily controlled by adjusting the airflow temperature and the solid content concentration of the emulsion.

The styrene fine particles (primary particles) have an average particle diameter of 0.01 to 1 μm. When the primary particles are smaller than 0.01 μm, even if an aggregate (secondary particle) is formed, the light diffusivity is similar to that in the case where the aggregate is one particle, which is not preferable. On the other hand, when it exceeds 1 μm, the number of primary particles constituting the secondary particles decreases, so that it also exhibits a light diffusivity as high as one particle. The aggregate (secondary particles) is 2 to 200 μm. This is because this range exhibits good light diffusibility. If the aggregate is smaller than 2 μm, sufficient light diffusibility cannot be obtained, and if it exceeds 200 μm, the member surface becomes rough when the aggregate is used as a light diffusing member, which is not preferable. The method for measuring the average particle size is not particularly limited, but the average particle size of the primary particles is very small, so it is preferable to measure with a light scattering particle size distribution meter. The average particle size of the secondary particles can be determined by an appropriately known method such as microscopic observation or a method using a Coulter counter.

Specific spray-type drying conditions for obtaining a styrene-based fine particle aggregate having an average particle size of 2 to 200 μm are as follows: solid content concentration of emulsion is 5 to 60% by mass, spray inlet temperature is 100 to 200 ° C. , Powder outlet temperature 30
It is preferable to set the temperature to -100 ° C. Other conditions, such as the supply rate, the spray pressure, the air volume, etc., are appropriately set according to the capability of the spray dryer.

The styrene-based fine particle aggregate can be obtained by simply performing spray drying. This is because the surfaces of the primary particles are plasticized by heating during spray drying, and the particles are fused and connected to each other. It is preferable to use a binder in order to connect more firmly. As the binder, a known polymer used as a coating film forming component in paints and the like can be used without particular limitation. A fine particle aggregate in which styrene fine particles are fixed and connected by the polymer binder is obtained by making the polymer binder into an emulsion state having a solid content concentration of 5 to 60% by mass, mixing it with the styrene fine particle emulsion, and then performing spray drying under the above conditions. Can be obtained. Polymer binder (solid content) to solid content of styrene-based fine particle emulsion
Is used in the range of 2 to 30% by mass, a good coupling force can be obtained. A more preferable amount of polymer binder is 5 to 20% by mass.

In order to connect more strongly, a reactive binder may be used and a means for crosslinking the polymer binder may be employed. In order to crosslink the polymer binder, a method of introducing a functional group into the polymer binder and binding or adsorbing a functional group capable of reacting with the functional group also in the styrene-based fine particles, a self-crosslinkable functional group to the polymer binder Examples thereof include a method of introducing a group, a method of introducing a functional group into a polymer binder, and a method of adding a crosslinking agent capable of reacting with the functional group. If these methods are adopted, a functional group reaction occurs during heating during spray drying, and the polymer binder is crosslinked. The resulting styrene-based fine particle aggregate does not redisperse even when placed in a solvent and stirred, and exhibits an extremely strong connected state.

In order to introduce a functional group into the styrene-based fine particles, the above-mentioned functional group-containing monomer may be used as a copolymerization component. Further, even if the functional group-containing monomer is not particularly copolymerized, since the emulsifier used for emulsion polymerization is adsorbed on the surface of the styrene-based fine particles, when the emulsifier has a functional group such as a carboxyl group, This functional group can also be used as a reaction point.

The functional groups introduced into the polymer binder include oxazoline groups, epoxy groups, aziridinyl groups,
Examples thereof include a carboxyl group and a hydroxyl group. The number of functional groups introduced into the polymer binder is preferably 2 or more per molecule. Specifically, it comprises an oxazoline group-containing polymer containing 2-isopropenyl-2-oxazoline or the like as a constituent unit (for example, "Epocros" series manufactured by Nippon Shokubai Co., Ltd.), various epoxy resins, and monomers having an aziridinyl group or a carboxyl group. Examples thereof include polymers containing units, polyvinyl alcohol, polymers containing hydroxyl group-containing monomers such as hydroxyethyl (meth) acrylate as constituent units, and sugars.

To employ the above method, it is particularly preferable to use a polymer containing an oxazoline group as a polymer binder. This is because the oxazoline group performs self-crosslinking by heating during spray drying even if the styrene-based fine particles have no particular functional group. Therefore, also in this case, a styrene-based fine particle aggregate exhibiting an extremely strong connected state which does not redisperse even when placed in a solvent and stirred is obtained.

In producing the styrene-based fine particle aggregate,
A desired additive may be added to the emulsion liquid of the styrene-based fine particles and / or the emulsion liquid of the polymer binder. For example, known additives such as cross-linking agents, wetting agents, viscosity modifiers, thickeners, defoamers, modifiers, pigments, colorants, fillers, antioxidants, UV absorbers, UV stabilizers, etc. The amount can be added to such an extent that the object of the present invention is not impaired.

As described above, a styrene-based fine particle aggregate is obtained. The styrene-based fine particle aggregate of the present invention has a shape in which a plurality of styrene-based fine particles are connected while maintaining a spherical shape. For this reason, the surface of the aggregate has irregularities formed by the spherical surfaces of the respective fine particles. It is considered that since the unevenness further increases the light diffusivity, it exhibits good light diffusivity in combination with the high refractive index of the styrene-based fine particles.

Therefore, the styrene-based fine particle aggregate of the present invention can be preferably used as a light diffusing agent, and the light diffusing agent of the present invention is mixed with a resin for forming a light diffusing member (for example, polymethyl methacrylate). Then, the member may be formed by a known method. Alternatively, add it to the coating agent,
A means for forming a light diffusing film on the surface of the light diffusing member may be adopted. Examples of the light diffusing member include a light diffusing layer of a liquid crystal display element, an exterior member of a lighting fixture, and the like, but it can also be used as a matting agent or an ink receiving layer.

[0054]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these. Unless otherwise specified, "part" described in Examples and Comparative Examples means "part by mass".
"%" Means "mass%".

Example 1 433 g of pure water was placed in a 2 liter separable flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet.
And 0.9 g of an emulsifier (“Hitenol N-08”; (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .; polyoxyethylene alkylphenyl ether sulfonate)) were charged and the temperature was raised to 70 ° C. with stirring while performing nitrogen substitution. When the temperature reached 70 ° C., 57 g of styrene was added, and after 5 minutes, 70 g of a 2% aqueous solution of potassium persulfate was added.
To 35 g of divinylbenzene, 60 g of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine (“Adeka Stab LA-82”; manufactured by Asahi Denka Co., Ltd.) and 752 g of pure water, 34 g of Hitenol N-08 was added. And stirred to prepare a pre-emulsion.

20 minutes after the addition of the potassium persulfate, the pre-emulsion was added dropwise at a constant rate over 4 hours while maintaining the temperature at 70 ° C. After the dropping was completed, the temperature was raised to 75 ° C. and the mixture was aged for 2 hours. After aging, cool to 40 ℃,
An emulsion of fine styrene particles was obtained. The average particle size of this emulsion was measured by a light scattering particle size distribution meter (Particle Sizin
It was 0.2 μm when measured with “NICOMP 370” manufactured by g System. Also, the solid content concentration is 37%
Met.

Emulsion 20 of the styrene fine particles
To 0 g, 16 g of an oxazoline group-containing polymer emulsion (“Epocros K-2020E”; manufactured by Nippon Shokubai Co., Ltd .; solid content concentration 46%) was added and mixed well.

This mixture was spray-dried (manufactured by Yamato Chemical Co., Ltd.) at a feed rate of 14 ml / min, a spray pressure of 2.3 kg / cm ² , an air volume of 0.3 m ³ / min, an inlet temperature of 150 ° C. and an outlet. Spray drying at 60 ° C,
A styrene-based fine particle aggregate was produced.

This aggregate was dispersed in water, and the average particle size was measured with a Coulter counter ("Multisizer II type" manufactured by Coulter Co.), and it was 14 μm. Further, when the aggregate was observed with a scanning electron microscope, as shown in FIG. 1, it was confirmed that the styrene fine particles were interconnected while maintaining the spherical shape.

Example 2 In Example 1, 4-methacryloyloxy-2,
3, using 60 g of 2,6,6-tetramethylpiperidine (“Adeka Stab LA-82”; manufactured by Asahi Denka Co., Ltd.)
Example except that the amount was set to 0 g and 30 g of 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole (“RUVA-93”; manufactured by Otsuka Chemical Co., Ltd .; UV absorbing monomer) was used together. A styrene-based fine particle aggregate was produced in the same manner as in 1.

Comparative Example 1 An example was used except that 60 g of an additive type UV stabilizer (“ADEKA STAB LA-77”; manufactured by Asahi Denka Co., Ltd.) which was not a polymerizable monomer was used in place of the UV stable monomer used in Example 1. A styrene-based fine particle aggregate was produced in the same manner as in 1.

Comparative Example 2 A styrene-based fine particle aggregate was produced in the same manner as in Example 1 except that the UV stable monomer used in Example 1 was not used.

A light resistance test was carried out using the styrene-based fine particle aggregates produced in Examples and Comparative Example 1. Styrene-based fine particle aggregate 1 based on 99% by mass of polyethylene
Add 3.5 mass%, knead and mold with injection molding machine, 3.5c
A test piece having a thickness of mφ × 5 mm was prepared. This test piece was installed in a super light resistance tester (“I Super UV Tester”; manufactured by Iwasaki Denki Co., Ltd.), and 1 hour, 10 hours, and 20 hours passed while irradiating with ultraviolet light having an intensity of 100 mW / cm ^2. The degree of yellowing was evaluated as ◯ for no change, Δ for slightly yellowing, and x for yellowing. The results are shown in Table 1. The styrene-based fine particle aggregate of the present invention did not yellow at all and showed excellent light resistance.

[0064]

[Table 1]

[0065]

The styrene-based fine particle aggregate of the present invention is an aggregate in which a plurality of styrene-based fine particles obtained by radical polymerization of a monomer component containing an ultraviolet-stable monomer having a specific structure are strongly linked. It has excellent diffusivity and light resistance. Further, according to the production method of the present invention, it is possible to easily produce a fine particle aggregate having a strong connecting force. Therefore, the styrene-based fine particle aggregate of the present invention has extremely high performance as a light diffusing agent. It can also be used as a matting agent or as an ink receiving layer.

[Brief description of drawings]

1 is a drawing-substitute photograph of a styrene-based fine particle aggregate obtained in Example 1 by a scanning electron microscope.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C08L 25:08 C08L 25:08 (72) Inventor Yasuhiro Yamamoto, 992, off the coast of Nishihama, Aboshi-ku, Himeji City, Hyogo Prefecture 1 Nippon Shokubai Co., Ltd. (72) Inventor Shuji Shimizu 1 992, Nishi-oki, Akihama, Aboshi-ku, Himeji City, Hyogo Prefecture 1 F-Term (Nippon Shokubai Co., Ltd.) 4F070 AA18 DA34 DC11 4J100 AB02P AB03P AB08P AL08Q AL74Q AM21Q AM23Q BC69 BD14

Claims (5)

[Claims] 1. One or more styrene-based monomers, one or more ultraviolet stable monomers represented by the following general formula (1) or (2), and one monomer having two or more radically polymerizable double bonds. Characterized in that a plurality of styrene-based fine particles having an average particle size of 0.01 to 1 μm obtained by polymerization of a monomer component essentially containing the above are connected to form an aggregate having an average particle size of 2 to 200 μm. A styrene-based fine particle aggregate having excellent light resistance. [Chemical 1] (In the formula, R ¹ represents a hydrogen atom or a cyano group, and R ² , R
³ independently represent a hydrogen atom or a methyl group,
R ⁴ represents a hydrogen atom or a hydrocarbon group, R ^{4 ′} independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and X represents an oxygen atom or an imino group. ) [Chemical 2] (In the formula, R ¹ represents a hydrogen atom or a cyano group, and R ² , R
³ , R ^{2 ′} and R ^{3 ′} each independently represent a hydrogen atom or a methyl group, R ^{4 ′} each independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and X is an oxygen atom or Represents an imino group. ) 2. The styrene-based fine particle aggregate according to claim 1, wherein the fine particles are connected to each other by a polymer binder. 3. A light diffusing agent comprising the styrene-based fine particle aggregate according to claim 1 or 2. 4. The method for producing a styrene-based fine particle aggregate according to claim 1, wherein an emulsion liquid containing styrene-based fine particles is obtained by emulsion-polymerizing the monomer component, and then the emulsion liquid is sprayed. A method for producing a styrene-based fine particle aggregate having excellent light resistance, which comprises connecting styrene-based fine particles to each other by drying. 5. The method for producing a styrene-based fine particle aggregate according to claim 2, wherein an emulsion liquid containing crosslinked fine particles is obtained by emulsion-polymerizing the monomer component, and then the emulsion liquid and the polymer binder. A method for producing a styrene-based fine particle aggregate having excellent light resistance, characterized in that the styrene-based fine particles are connected to each other by a polymer binder by spray-drying a mixture with an emulsion liquid containing the.