JPH07207101A - Light dispersing acrylic resin composition and its production - Google Patents

Abstract

PURPOSE:To obtain an acrylic resin composition having excellent light dispersion and flame retardance by dispersing a small amount of liquid polysiloxane in a methyl methacrylate polymer. CONSTITUTION:100 pts.wt. of a component containing mainly methyl methacrylate, optionally, together with a copolymer with ethyl methacrylate, (meth)acrylic acid, styrene, vinyl acetate, etc., is homogeneously mixed with 0.01-1 pts.wt., preferably, 0.05-1 pts.wt. of polysiloxane which is liquid at room temperature and the mixture is subjected to cast polymerization to obtain the objective composition. Further, the polysiloxane in the composition is preferably dispersed as particles of 2-25mum in diameter.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusing acrylic resin composition and a method for producing the same. A light diffusing acrylic resin composition obtained by dispersing a light diffusing agent in an acrylic resin is used for lighting equipment, signboards,
Widely used in glazing and projection screens. Many such light diffusing acrylic resin compositions have been proposed in the past. For example, as a light diffusing agent, one using calcium carbonate (Japanese Patent Publication No. 3-2188) and one using aluminum hydroxide (Japanese Patent Publication No. 4-1184).
No. 2), one using a solid silicone resin (Japanese Patent Application Laid-Open No. 1-172801), and the like. The light-diffusing resin composition shown above has a higher burning rate and a lower flame retardancy than transparent acrylic resins. Therefore, in view of the above problems, the present inventors have considered
As a result of earnest studies to provide a light diffusing resin composition having light diffusibility and less deterioration in flame retardancy, the present invention has been completed. That is, according to the present invention, 0.01 to 1 part by weight of liquid polysiloxane at room temperature is dispersed in 100 parts by weight of a polymer mainly composed of methyl methacrylate. A diffusible acrylic resin composition, and further, 100 parts by weight of a monomer mainly composed of methyl methacrylate or a partial polymer thereof and 0.01 to 1 part by weight of polysiloxane which is liquid at room temperature are uniformly mixed. And a method for producing a light diffusing acrylic resin composition by casting polymerization of the mixture. In the present invention, (A) a polymer mainly composed of methyl methacrylate means a homopolymer or a copolymer of methyl methacrylate, and two or more kinds of polymers which are compatible with these polymers. Although it is a mixture, the proportion of methyl methacrylate is 50% by weight or more, preferably 70% by weight or more. Examples of the unsaturated monomer which serves as a copolymerization component of methyl methacrylate include methacrylic acid esters such as ethyl methacrylate, propyl methacrylate and butyl methacrylate; methyl acrylate, ethyl acrylate, propyl acrylate and butyl. Acrylates such as 2-ethylhexyl acrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid; acid anhydrides such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl acrylate, 2 -Hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, monoglycerol acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, tetrahydrofurfuri Methacrylate, hydroxyl group-containing monomers such as monoglycerol methacrylate;
Nitrogen-containing monomers such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, diacetone acrylamide, and dimethylaminoethyl methacrylate; epoxy group-containing monomers such as allyl glycidyl ether, glycidyl acrylate, and glydicyl methacrylate; Alkylene oxide group-containing monomers such as polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, and polyethylene glycol monoallyl ether; styrene-based monomers such as styrene and α-methylstyrene, vinyl acetate, vinyl chloride,
Other monofunctional monomers such as vinylidene chloride, vinylidene fluoride and ethylene; polyfunctional unsaturated monomers such as allyl acrylate, allyl methacrylate, divinylbenzene, trimethylolpropane triacrylate and polyethylene glycol dimethacrylate Is mentioned. Furthermore, a glutaric anhydride unit, a glutarimide unit, or a diene may be contained as a copolymerization component. The polysiloxane which is liquid at room temperature used in the present invention is a so-called silicone oil.
The viscosity at 25 ° C. is 0.5 to 1,000,000 centistokes. The amount of the polysiloxane is 0.0 per 100 parts by weight of the polymer mainly composed of methyl methacrylate.
It is 1 to 1 part by weight, preferably 0.05 to 1 part by weight.
If it is less than 0.01 parts by weight, the light diffusivity will be poor. Again 1
If the amount is more than parts by weight, the dispersed state deteriorates and the light diffusivity becomes non-uniform, which is not preferable. Further, the polysiloxane in the light diffusing resin composition of the present invention is desired to be dispersed in a particle size of 0.5 μm to 50 μm. Further, a particle size of 2 μm to 25 μm is preferable. When the particle size is 0.5 μm or less, the particle size is smaller than the wavelength of light and it becomes difficult for light to diffuse. Also, 50 μm
If it exceeds, the light diffusion performance is deteriorated and the light diffusion becomes uneven. The light diffusing resin composition of the present invention contains 0.01 to 100 parts of the polysiloxane per 100 parts of the syrup obtained by previously polymerizing a part of the unsaturated monomer containing methyl methacrylate as a main component or a component thereof. It can be obtained by uniformly mixing 1 part by weight, further adding a well-known polymerization initiator and other additives to the mixture, and then pouring the mixture into a mold having a desired shape for polymerization. In order to adjust the particle size of the polysiloxane in the light diffusing resin composition by the above method, first, it is premised that the syrup and the polysiloxane are thoroughly mixed and uniformly dissolved or dispersed. The larger the amount of the polysiloxane, the larger the particle size, and the higher the viscosity of the polysiloxane, the larger the particle size. Therefore, within the range of the viscosity and the required amount of the polysiloxane, The light diffusing acrylic resin composition in which the polysiloxane having a desired particle size is dispersed can be obtained by selecting the amount and performing the trial several times. As the polymerization initiator, a well-known radical polymerization initiator such as an azo compound or peroxide, or a so-called redox type initiator composed of a radical polymerization initiator and an accelerator can be used. The polymerization reaction is usually from room temperature to 150 ° C., but the temperature conditions may be changed in two stages or more depending on the kind of the polymerization initiator used. The mold is made of a known material such as glass or metal and has a desired shape. For example, when the resin composition is in the form of a plate, a glass cell formed by sealing the periphery of two glass plates facing each other with a gasket, and two endless belts made of metal such as stainless steel sealed with a gasket There is a continuous steel cell. A light-diffusing resin composition may be prepared by adding a predetermined amount of the polysiloxane to a polymer mainly containing methyl methacrylate, melting the mixture, sufficiently kneading and uniformly dispersing the polysiloxane. By this method, the particle size of the polysiloxane in the resin composition is adjusted by selecting the kind and amount of the polysiloxane based on the same idea as the mixing with the syrup described above and conducting the trial several times. This resin composition is formed into a desired shape by injection molding, extrusion molding, or the like,
It is also possible to use by laminating and laminating on the surface of ordinary acrylic resin or the like, or laminating by coextrusion molding. In the light diffusing acrylic resin composition of the present invention, if necessary, other light diffusing agent, colorant, reinforcing agent, filler,
It is also possible to add a release agent, a stabilizer, an ultraviolet absorber, an antioxidant, an antistatic agent, a flame retardant, and the like. The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The evaluation was performed by the following method. Light diffusion property: According to ASTM D1003-61, total light transmittance and haze value were measured using a Poic integrating sphere type haze meter (SEP-HS-30D manufactured by Nippon Seimitsu Optical Co., Ltd.). Particle size of polysiloxane: The obtained plate was observed and measured with an optical microscope. -Flame resistance: The horizontal burning rate was measured according to JIS K6718. Examples 1 to 5 Methyl methacrylate 100 was added to a flask equipped with a stirrer.
Shin-Etsu Silicone KF96 as polysiloxane in parts by weight
The H series having the viscosity (25 ° C centistokes) shown in Table 1 was put in and mixed with stirring for 30 minutes, and 0.10 parts by weight of azobisisobutyronitrile was dissolved. This solution was poured into a polymerization cell composed of a polyvinyl chloride gasket and two glass plates, and heat-polymerized at 70 ° C. for 3 hours and 120 ° C. for 1 hour to obtain an acrylic resin plate having a thickness of 2 mm and a good appearance. It was The evaluation results are shown in Table 1. [Table 1] Comparative Examples 1 to 5 An acrylic resin plate was obtained in the same manner as in Example 1 except that the light diffusing agent shown in Table 2 was added instead of the polysiloxane. The evaluation results are also shown in Table 2. [Table 2] * Tospar 120 Solid Silicone Resin from Toshiba Silicone Co., particle size 2.0 μm * Tospar 145 Solid Silicone Resin from Toshiba Silicone Co., particle size 4.5 μm [Effect of the Invention] Moreover, an acrylic resin composition having excellent flame retardancy is provided.

Claims (1)

Claims: 1. Polysiloxane 0.0, which is liquid at room temperature, is added to 100 parts by weight of a polymer mainly composed of methyl methacrylate.
A light diffusing acrylic resin composition in which 1 to 1 part by weight is dispersed. 2. The polysiloxane is 0.5 μm to 50 μm.
The light-diffusing acrylic resin composition according to claim 1, wherein the light-diffusing acrylic resin composition is dispersed at a particle size of. 3. 100 parts by weight of a monomer mainly composed of methyl methacrylate or a partial polymer thereof and 0.01 to 1 part by weight of polysiloxane which is liquid at room temperature are uniformly mixed, and the mixture is cast. The method for producing the light-diffusing acrylic resin composition according to claim 1, wherein polymerization is performed.