JP2000226486A - Light diffusible acrylic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light diffusible acrylic resin compsn. inhibiting reduction of light transmittance, showing high light diffusivity, excellent in its molding's impact resistance, and having an uniform emission light strength. SOLUTION: This light diffusible acrylic resin compsn. comprises 100 pts.wt. acrylic polymer and 0.005-50 pts.wt. composite silicone powder which is a silicone rubber spherical minute particles coated with a polyorganosilsesquioxane resin, and the composite silicone powder comprises 100 pts.wt. silicone rubber spherical minute particle having an average particle diameter of 0.1-100 μm coated with 1-500 pts.wt. polyorganosilsesquioxane. And the composite silicone powder is prepared by adding an alkaline material or an alkaline solution, and an organotrialkoxysilane to an aq. dispersion of the silicone rubber spherical minute particles having an average particles diameter of 0.1-100 μm, and hydrolyzing and condensation polymerizing to coat the surface of the silicone rubber spherical minute particles with the polyorganosilsesquioxane resin, and drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic resin composition suitable as a raw material for a member for scattering light, such as a lighting cover, a lighting signboard, a backlight light guide plate of a liquid crystal display, and a transmission screen.

[0002]

2. Description of the Related Art Conventionally, in order to produce a light-diffusing acrylic resin, an inorganic fine powder such as calcium carbonate, barium sulfate, aluminum hydroxide, talc, silica, a fluororesin, an epoxy resin or the like has been used in a base resin. A method has been used in which a light diffusing agent of fine powder of a synthetic resin such as polyethylene, acrylic resin, polystyrene, nylon resin, and phenol resin is blended. However, although light diffusivity can be obtained by blending these light diffusing agents, on the other hand, light transmissivity is greatly reduced, and there is a problem in terms of effective use of light.
Here, the effective use of light means transmitting light emitted from a light source as much as possible. In order to increase the light transmittance, the amount of the light diffusing agent must be reduced, and as a result, the light diffusing property is reduced.

[0003] To solve these problems, a method of blending a silicone resin has been proposed. For example, a method of blending a polyorganosilsesquioxane resin fine powder (Japanese Patent Application Laid-Open Nos. 1-172801, 1-269902, 2-94058, 2-207743, 3-207743, and 3-294348, JP-A-4-78841, JP-A-4-
No. 95914, JP-A-5-39401, JP-A-6-107881
JP-A-8-82714, JP-A-8-262230, JP-A-9-306217, JP-A-10-73726, JP-A-10-81829, JP-A-10-88008 However, these methods do not sufficiently solve the above-mentioned problems, and there is also a problem that the impact resistance of a molded article of these resin compositions is reduced. Further, a method of blending silicone rubber fine powder (see JP-A-9-306217, JP-A-10-81829, JP-A-10-88008), R
Method of blending silicone resin fine powder, which is a copolymer of ₂ SiO _2/2 unit and RSiO _3/2 unit (R represents an organic group) (see JP-A-6-299035), blending silicone oil Although methods have been proposed (see Japanese Patent Application Laid-Open No. 8-82714), these methods do not sufficiently solve the above problems, and it is difficult to uniformly disperse these compounds in a base resin. There is also a problem.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have solved the above-mentioned problems by suppressing a decrease in light transmittance, exhibiting a high light diffusion property, and exhibiting excellent impact resistance and uniformity of the molded article. It is an object of the present invention to provide a light-diffusing acrylic resin composition having a high emission light intensity.

[0005]

That is, the present invention relates to a method comprising 100 parts by weight of an acrylic polymer and 0.005 to 50 parts by weight of a composite silicone powder comprising silicone rubber spherical fine particles coated with a polyorganosilsesquioxane resin. This is a characteristic light-diffusing acrylic resin composition.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The acrylic polymer used in the present invention is a methacrylate or acrylate homopolymer or a copolymer of these with another vinyl monomer.
Examples of methacrylates include, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate,
As acrylates such as butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc. Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate,
Benzyl acrylate, 2-ethylhexyl acrylate,
Examples thereof include 2-hydroxyethyl acrylate, glycidyl acrylate, dimethylaminoethyl acrylate, and diethylaminoethyl acrylate. Other vinyl monomers include methacrylic acid, unsaturated acids such as acrylic acid, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylol propane trimethacrylate, pentaerythritol tetramethacrylate, ethylene glycol dimethacrylate,
Polyfunctional (meth) acrylates such as 1,3-butylene glycol diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, and cyclohexylmaleimide Etc. are exemplified. Further, it may contain a glutaric anhydride unit and a glutarimide unit. In addition, the above-mentioned polymer, copolymer,
Blends of elastomer components such as polybutadiene, butadiene / butyl acrylate copolymer, and butadiene / polybutyl acrylate copolymer can also be used.

The composite silicone powder used in the present invention is described in Japanese Patent Application Laid-Open No. Hei 7-96815, which comprises a silicone rubber spherical fine particle having a particle size of 0.1 to 100 μm and a polyorganosilsesquioxane. Is coated. If the average particle diameter of the silicone rubber spherical fine particles used here is less than 0.1 μm, the light diffusion property of the molded article of the acrylic resin composition will be poor, and if it exceeds 100 μm, the light transmittance of the molded article of the acrylic resin composition will be poor. The average particle size is 0.1
To 100 μm, and a more preferable range is
It is 1 to 30 μm.

[0008] The polyorganosilsesquioxane resin of the composite silicone powder of the present invention may uniformly cover the surface of the silicone rubber spherical fine particles, or may cover a part of the surface. If the amount of the polyorganosilsesquioxane resin in the composite silicone powder of the present invention is less than 1 part by weight per 100 parts by weight of the silicone rubber spherical fine particles, the dispersibility of the composite silicone powder in the acrylic polymer is poor. As a result, the uniformity of the light intensity of the acrylic resin composition is deteriorated, and when the amount exceeds 500 parts by weight, the impact resistance and light transmittance of the molded article of the acrylic resin composition are reduced. Parts by weight, more preferably 2 to 100 parts by weight. In addition, in the polyorganosilsesquioxane resin, a small amount of R ₂ SiO _2/2 units and R ₃ SiO _{1/2 in} addition to the organosilsesquioxane units RSiO _3/2 as long as the covering property is not impaired. Unit, SiO ₂
Units (R is a monovalent hydrocarbon group having 1 to 10 carbon atoms) may be contained.

The method for producing the composite silicone powder in the present invention may be performed according to the method described in the above-mentioned Japanese Patent Application Laid-Open No. Hei 7-96815. That is, by adding an alkaline substance or an alkaline aqueous solution and an organotrialkoxysilane to an aqueous dispersion of spherical silicone rubber fine particles having an average particle diameter of 0.1 to 100 μm, and hydrolyzing and condensation-polymerizing the organotrialkoxysilane, a silicone is obtained. The surface of the rubber spherical fine particles is coated with a polyorganosilsesquioxane resin. Then, it is dried to produce the composite silicone powder of the present invention.

The amount of the composite silicone powder used in the present invention varies depending on the use of the acrylic resin composition, and is determined in consideration of the balance between the light diffusivity and the light transmittance of the acrylic resin composition. For applications requiring more light transmission, such as backlight light guide plates for liquid crystal displays and light transmission screens, the compounding amount of the composite silicone powder is 0.005 to 1 part by weight per 100 parts by weight of the acrylic polymer. Preferably, it is more preferably 0.02 to 0.5 part by weight. For applications requiring more light diffusing properties such as lighting covers and lighting signboards, it is necessary to use 1 to 50 parts by weight, preferably 2 to 20 parts by weight, per 100 parts by weight of the acrylic polymer. is there.

The light-diffusing acrylic resin composition of the present invention contains a light-diffusing agent, a colorant, an ultraviolet absorber, a dispersing aid, an antioxidant, a lubricant, a mold release agent, a flame retardant, an antistatic agent and the like. It can be added and blended as long as it does not deviate from the range. In the present invention, the mixing of the composite silicone powder with the acrylic polymer may be performed according to a known method, and the location of each component is determined using a mixer such as a Henschel mixer, a V-type blender, a ribbon blender, or a raiger. What is necessary is just to mix a fixed amount, melt and knead with an extruder. Further, the method for producing the acrylic resin composition of the present invention includes mixing a composite silicone powder with a liquid material containing a monomer constituting an acrylic polymer and a partial polymer thereof, casting the mixture, and performing suspension polymerization and suspension polymerization. It is also possible to make it.

[0012]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. In addition, the viscosity in an Example is a measured value at 25 degreeC. All percentages in the examples are percentages by weight.

[Preparation Example 1] (Preparation of silicone spherical fine particles) 500 g of methylvinylsiloxane having a viscosity of 600 cSt represented by the following formula (Chemical Formula 1) and methyl hydrogen having a viscosity of 30 cSt represented by the following formula (Chemical Formula 2) After charging 20 g of polysiloxane into a glass beaker having a capacity of 1 liter and stirring the mixture at 2,000 rpm using a homomixer, polyoxyethylene (number of moles added = 9 mol) was added.
Add 5g of octyl phenyl ether and 150g of water and add 6,000r
When the stirring was continued at pm, phase inversion occurred and thickening was observed.
Upon addition of 325 g, an oil-in-water emulsion was obtained.

Embedded image

Embedded image Next, this emulsion was transferred to a glass flask equipped with a stirrer with an anchor-type stirring blade, and a toluene solution of a chloroplatinic acid-olefin complex (with a platinum content of 0.5) was stirred at room temperature.
%) 1 g and polyoxyethylene (addition mole number = 9 mole)
When a mixture of 1 g of octyl phenyl ether was added and reacted for 12 hours, an aqueous dispersion of silicone rubber spherical fine particles (hereinafter abbreviated as aqueous dispersion 1) was obtained. The particle size was measured using Multisizer II (manufactured by Coulter Electronics).
μm.

(Preparation of Composite Silicone Powder) In a 3 liter glass flask, 2,290 g of water, 580 g of the aqueous dispersion 1 obtained above and 60 g of aqueous ammonia (concentration: 28%) were charged, and the water temperature was adjusted to 10 ° C. The mixture was stirred at 200 rpm by an anchor type stirring blade. The pH at this time was 11.2. To this solution, 65 g of methyltrimethoxysilane was added dropwise over 20 minutes. During this time, the temperature of the solution was maintained at 5 to 15 ° C. with stirring, and the mixture was further reacted for 1 hour. After stirring, the obtained liquid was filtered with a pressure filter to obtain a cake having a water content of about 50%. Next, the cake was dried in a hot air circulating drier at a temperature of 105 ° C., and the dried product was crushed by a jet mill. Observation of the obtained silicone powder with an optical microscope confirmed that it was spherical. This powder was dispersed in water using a surfactant, and the average particle size was measured using Multisizer II. The weight of the composite silicone powder was found to be 100 parts by weight of silicone rubber spherical fine particles coated with 10 parts by weight of a polyorganosilsesquioxane resin. The obtained silicone powder is designated as composite silicone powder 1.

Production Example 2 5 g of polyoxyethylene (additional mole number = 9 mol) octyl phenyl ether used in the preparation of the oil-in-water emulsion in Production Example 1
Was changed to 1 g, and a silicone rubber spherical fine particle dispersion (hereinafter referred to as “dispersion 2”) was obtained in the same manner as in Production Example 1 except that the average particle size of the particles in the aqueous dispersion was measured using Multisizer II. It was 15 μm when measured by using. Next, a composite silicone powder was prepared in exactly the same manner as in Production Example 1, except that the aqueous dispersion 2 was used in place of the aqueous dispersion 1. Observation of the obtained composite silicone powder with an optical microscope confirmed that it was spherical. This powder was dispersed in water using a surfactant, and the average particle size was measured using Multisizer II. The result was 15 μm. The weight of the composite silicone powder was found to be 100 parts by weight of silicone rubber spherical fine particles coated with 10 parts by weight of a polyorganosilsesquioxane resin. The obtained composite silicone powder is referred to as composite silicone powder 2.

[Production Example 3] In a 3 liter glass flask were charged 2,290 g of water, 350 g of the aqueous dispersion 1 obtained in Production Example 1, and 60 g of aqueous ammonia (concentration: 28%), and the water temperature was 10 ° C.
And the mixture was stirred at 200 rpm by an anchor-type stirring blade. At this time
pH was 11.1. Add methyltrimethoxysilane to this solution
300 g was added dropwise over 100 minutes. During this time, the liquid temperature was kept at 5 to 15 ° C., and the mixture was further reacted for 1 hour with stirring.
And then stirred for 1 hour, and the obtained liquid was filtered with a pressure filter to obtain a cake having a water content of about 50%. Next, the cake is placed in a hot-air circulation dryer.
After drying at 105 ° C., the dried product was crushed by a jet mill. Observation of the obtained composite silicone powder with an optical microscope confirmed that it was spherical. This powder was dispersed in water using a surfactant, and the average particle size was measured using Multisizer II to find that it was 4 μm.
The weight of the composite silicone powder was found to be 100 parts by weight of silicone rubber spherical fine particles coated with 81 parts by weight of a polyorganosilsesquioxane resin. The obtained composite silicone powder is referred to as composite silicone powder 3.

[Preparation Example 4] In Preparation Example 1, 55 g of methyltrimethoxysilane and 6 g of vinyltrimethoxysilane were used.
A composite silicone powder was prepared in exactly the same manner as in Production Example 1 except that the mixture of Example 1 was used as a mixture. Observation of the obtained composite silicone powder with an optical microscope confirmed that it was spherical. This powder was dispersed in water using a surfactant, and the average particle size was measured using Multisizer II. The weight of this composite silicone powder was determined by weight analysis to indicate that a polyorganosilsesquioxane resin
It was found that parts by weight were coated. The obtained composite silicone powder is referred to as composite silicone powder 4.

Production Example 5 A composite silicone powder was prepared in exactly the same manner as in Production Example 1, except that a mixture of 55 g of methyltrimethoxysilane and 5 g of phenyltrimethoxysilane was used. Observation of the obtained composite silicone powder with an optical microscope confirmed that it was spherical. This powder was dispersed in water using a surfactant, and the average particle size was measured using Multisizer II. The weight of this composite silicone powder was determined by weight analysis to indicate that a polyorganosilsesquioxane resin
It was found that parts by weight were coated. The obtained composite silicone powder is designated as composite silicone powder 5.

[Production Example 6] The aqueous dispersion 1 obtained in Production Example 1 was heated to 90 ° C. to destabilize the dispersion of fine particles, and then filtered with a pressure filter to obtain a water content of about 50. % Cake-like product, and further dried at 105 ° C. in a hot air circulating dryer to obtain a silicone rubber powder. Observation of the obtained silicone rubber powder with an optical microscope confirmed that it was spherical. This powder was dispersed in water using a surfactant, and the average particle size was measured using Multisizer II to find that it was 4 μm.

Production Example 7 A 3 liter glass flask was charged with 2,445 g of water and 60 g of aqueous ammonia (concentration: 28%), and the temperature was adjusted to 20 ° C. The pH was 11.6. Stir at 200 rpm with an anchor type stirring blade, methyltrimethoxysilane
495 g was added dropwise over 3 hours.
Keep at 15 ~ 25 ℃, react for another 1 hour, then 55 ~ 60 ℃
The resulting solution was filtered through a pressure filter to obtain a cake having a water content of about 30%. Then, the cake is placed in a hot air circulating dryer for 1 hour.
Dry at a temperature of 05 ℃, crush the dried material with a jet mill,
A polymethylsilsesquioxane resin powder was obtained. Observation of the obtained polymethylsilsesquioxane resin powder with an optical microscope confirmed that it was spherical. This powder was dispersed in water using a surfactant, and the average particle size was measured using Multisizer II.

Examples 1-6, Comparative Examples 1-2 Methacrylic resin / Acrypet VH # 001 (trade name, manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts by weight of the composite silicone powder shown in (Table 1) or The silicone powder was blended in the blending amounts (parts by weight) shown in Table 1 and uniformly mixed. The obtained mixture was fed to a twin-screw co-rotating screw kneading extruder at a rate of 20 kg / hr, extruded at 240 ° C., cooled with water, and then pelletized with an electric cutter. The obtained pellets were molded into a flat plate of 80 × 80 × 2 mm by injection molding, and the dispersibility, total light transmittance, light diffusion and impact resistance were evaluated by the methods described below, and the results are shown in Table 1. .

Comparative Example 3 A silicone resin powder consisting of (CH ₃ ) ₂ SiO _2/2 units and CH ₃ SiO _3/2 units instead of the composite silicone powder [(CH ₃ ) ₂ SiO _2/2 / CH ₃ SiO
_3/2 weight ratio = _20/80 , softening point = 70 ° C.] in the amounts shown in (Table 1), except that Examples 1-6 and Comparative Examples 1-2 were used.
A plate of methacrylic resin was obtained in the same manner as described above, and the characteristics were evaluated. The results are shown in Table 1.

Comparative Example 4 A methacrylic resin, Acrypet VH # 001 (described above) was supplied to a twin-screw co-rotating screw kneading extruder at a rate of 20 kg / hr, and dimethyl silicone oil / KF96 [Shin-Etsu Chemical Industrial Co., Ltd. product, viscosity 10,000cs] is supplied from another supply port at a rate of 0.6 kg / hr (3 parts by weight with respect to 100 parts by weight of methacrylic resin), extruded at 240 ° C., and cooled with water. Pelletized with an electric cutter. The obtained pellets were formed into a flat plate of 80 × 50 × 2 mm by injection molding, and the characteristics were evaluated in the same manner as described above. The results are shown in (Table 1).

Comparative Example 5 A methacrylic resin plate was obtained in the same manner as in Examples 1 to 6 and Comparative Examples 1 and 2, except that the composite silicone powder was not blended, and the properties were evaluated in the same manner as described above. The results are shown in (Table 1).

The characteristics of the flat plates obtained in the examples and comparative examples were evaluated by the following methods. (Dispersibility of silicone) Observed with an optical microscope. ：: Silicone is uniformly dispersed. X: Dispersion of silicone is non-uniform. (Total light transmittance) According to JIS K-7105, UV-Visible spectrophotometer UV with integrating sphere type attachment device FSR260
It was measured by 3100 [manufactured by Shimadzu Corporation]. (Light diffusibility) The transmitted light intensity (I ₀ ) at a transmission angle of 0 degree due to vertically incident light and the transmitted light intensity (I ₇₀ ) at a transmission angle of 70 degrees due to vertically incident light is measured by an automatic goniophotometer GP-1R [(Co., Ltd.). ) Murakami Color Research Laboratory], and I ₇₀ / I ₀ was regarded as light diffusion. (Impact resistance) Using a drop weight graphic impact tester [Toyo Seiki Seisakusho Co., Ltd.], set 10 flat plates, drop a 200g weight from a height of 20cm, and show the impact resistance by the number of pieces broken Was.

[0026]

[Table 1]

[0027]

The light-diffusing acrylic resin composition of the present invention exhibits a high light-diffusing property by suppressing a decrease in light transmittance, has excellent impact resistance, has a uniform intensity of emitted light, and has an illumination cover and an illumination. It is suitable for a raw material of a member for scattering light, such as a signboard, a backlight light guide plate of a liquid crystal display, and a transmission screen.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 BG041 BG051 CP032 FA082 FB262

Claims (3)

[Claims] 1. A light-diffusing acrylic resin composition comprising 100 parts by weight of an acrylic polymer, and 0.005 to 50 parts by weight of a composite silicone powder in which polyorganosilsesquioxane resin is coated on silicone rubber spherical fine particles. object. 2. The composite silicone powder has an average particle size of 0.1 to 1
The light-diffusing acrylic resin composition according to claim 1, wherein 100 parts by weight of silicone rubber spherical fine particles of 100 µm are coated with 1 to 500 parts by weight of a polyorganosilsesquioxane resin. 3. The composite silicone powder has an average particle size of 0.1 to 0.1.
An alkaline substance or an alkaline aqueous solution and an organotrialkoxysilane are added to an aqueous dispersion of 100 μm silicone rubber spherical fine particles, and the resultant is hydrolyzed and condensation-polymerized to form a silicone rubber spherical fine particle surface of a polyorganosilsesquioxane resin. The light-diffusing acrylic resin composition according to claim 1, wherein the composition is dried and coated.