JPH0931288A - Optodiffusive methacrylic resin composition and sheetlike product therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition retaining its optical diffusibility and hiding power even if subjected to melt molding processing, and high in whole light transmittance. SOLUTION: This optodiffusive methacrylic resin composition is obtained by incorporating 100 pts.wt. of a methacrylic resin with 0.2-10 pts.wt. of precipitated calcium carbonate having hexahedral structure and an average particle diameter of 1-15μm. The calcium carbonate is coated with 0.1-5 pts.wt., per 100 pts.wt. of the calcium carbonate, of at least one kind of organic matter selected from fatty acids, resin acids, sulfonic acids, fatty acid esters, resin acid esters, sulfonic esters, phosphoric esters, fatty acid salts, resin acid salts and sulfonic acid salts.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a methacrylic resin composition having excellent heat resistance stability, light diffusivity, and hiding power.
Further, it relates to a light diffusing methacrylic resin sheet material.

[0002]

2. Description of the Related Art Conventionally, as a material for a lighting cover, a light diffusing plate for a transmissive display, a lighting signboard, etc., a light diffusing material containing methacrylic resin mixed with transparent inorganic or organic fine particles having different refractive indexes. Resin materials are widely used.

As the light diffusing resin material, it is required that the image of the light source is hard to see even though the light transmitting property is high (concealing property), and the property of scattering light at a wide angle (light diffusing property). Material that uses calcium carbonate particles, which is an inexpensive material, as a light diffusing agent, because it has an appropriate refractive index difference with respect to the methacrylic resin that is the base material, and therefore has good concealing properties and light diffusing properties. I have a suggestion. Tokkyo 1-22
Japanese Patent No. 861 describes a light diffusing acrylic resin sheet material in which calcium carbonate having an average particle size of 1 μm to 20 μm is dispersed and mixed at a rate of 10 to 200 g / m ² . Japanese Examined Patent Publication No. 3-2188 discloses that the particle shape is substantially hexahedral with respect to a methyl methacrylate polymer, and
A light-diffusing acrylic resin sheet-like product is described in which an appropriate amount of calcium carbonate powder containing 80% by weight or more of particles having a particle diameter of 15μ is blended and which is more excellent in hiding and light diffusing properties.

[0004]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 1-22861
In the resin composition constituting the sheet-like material described in Japanese Patent Publication No. 3-2188 and Japanese Patent Publication No. 3-2188, the calcium carbonate particles are disintegrated by melt molding, and both the hiding property and the light diffusing property are reduced.
Therefore, the present invention provides a light-diffusing methacrylic resin composition in which the light-diffusing property and the hiding property are not deteriorated even when melt molding is performed and the total light transmittance is high.

[0005]

That is, according to the present invention, 100 parts by weight of a methacrylic resin is added to a precipitable calcium carbonate.
In the light-diffusing methacrylic resin composition containing 2 to 10 parts by weight, the precipitating calcium carbonate is a particle having a hexahedral structure and an average particle diameter of 1 to 15 μm, and per 100 parts by weight of the precipitating calcium carbonate. 0.1-5 parts by weight of at least one organic substance selected from fatty acid, resin acid, sulfonic acid, fatty acid ester, resin acid ester, sulfonic acid ester, phosphoric acid ester, fatty acid salt, resin acid salt, and sulfonic acid salt. The light diffusing methacrylic resin composition is characterized in that the surface of the precipitated calcium carbonate particles is coated.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A methacrylic resin containing methyl methacrylate as a main component used in the present invention means a methyl methacrylate homopolymer or 50% by weight or more of methyl methacrylate and another vinyl monomer. It is a copolymer. Examples of the vinyl monomer include methacrylic acid esters such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, and acrylic acid. Methyl,
Acrylic esters such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc., unsaturated acids such as methacrylic acid, acrylic acid, etc. , Styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like. The copolymer may further contain a glutaric anhydride unit and a glutarimide unit. Further, a blend of the above-mentioned polymer or copolymer with a diene rubber or an acrylic rubber may be used.

The calcium carbonate in the present invention is a chemically synthesized precipitated calcium carbonate, and has a substantially hexahedral structure among them. The precipitated calcium carbonate is commercially available.

The average particle size of the calcium carbonate is 1 to 15
μm, preferably 2 to 10 μm. When it is less than 1 μm, the light diffusing property and hiding property are deteriorated, and when it exceeds 15 μm, the light diffusing property is insufficient, and the surface smoothness of the molded product is deteriorated.

The content of the calcium carbonate is 0.2 to 10 parts by weight, preferably 1 to 8 parts by weight, based on 100 parts by weight of the methacrylic resin. If the amount is less than 0.2 parts by weight, the light diffusing property and the hiding property are not sufficient, and if the amount is more than 10 parts by weight, the light transmittance is insufficient and the molded product becomes brittle.

The organic substance coating the surface of the calcium carbonate is a fatty acid, a resin acid, a sulfonic acid, a fatty acid ester, a resin acid ester, a sulfonic acid ester, a phosphoric acid ester, a fatty acid salt or a resin acid salt sulfonate.

The fatty acids referred to herein are saturated fatty acids such as caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid and lignoceric acid, undecylenic acid, oleic acid, elaidic acid, It refers to unsaturated fatty acids such as cetoleic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, lenenoic acid, arachidonic acid and stearolic acid. Resin acids include abietic acid, neoabietic acid, d-pimaric acid and iso-
It refers to alicyclic resin acids such as d-pimaric acid, podocarpic acid, and agartendicarboxylic acid, and aromatic resin acids such as benzoic acid, cinnamic acid, and p-oxycinnamic acid. Sulfonic acid refers to alkylsulfonic acid, alkylbenzenesulfonic acid, and the like.

Examples of the fatty acid ester, resin acid ester and sulfonic acid ester include methyl ester, ethyl ester, propyl ester, butyl ester, pentyl ester, hexyl ester, octyl ester and decyl ester of the above-mentioned acids. Examples of the fatty acid salt, resin acid salt, and sulfonic acid salt include alkali metal salts and amine salts of the above-mentioned acids. The phosphoric acid ester is an alkyl or phenyl ester of phosphoric acid, phosphonic acid, phosphorous acid, or the like.

These organic substances are generally called surface treatment agents, and have the function of covering the surface of calcium carbonate and suppressing the agglomeration between particles, as well as increasing the affinity with the resin. Further, it has been found that by covering the surface of the particles with these organic substances, it is possible to significantly suppress the contact destruction of the particles in the base resin.

Among these organic substances, fatty acids, fatty acid esters, and fatty acid salts are preferably used because they have a particularly good compatibility with the methacrylic resin.

The amount of organic matter coated on the calcium carbonate particles is 0.1 to 5 relative to 100 parts by weight of the calcium carbonate.
Parts by weight. If the amount is 0.1 parts by weight or less, the effect of the surface coating is small, and it tends to be broken during melt molding. If it exceeds 5 parts by weight, it may be colored during melt molding.

Means for coating the surface of the calcium carbonate with an organic substance include a dry method and a wet method.
The dry method is a method of stirring the inorganic particles with a Henschel mixer or the like and adding the organic matter under heating conditions to coat the surface of the particles, and the wet method is the method of introducing the organic matter into the water slurry of calcium carbonate, It is a method of adsorbing and coating on the surface.

In order to form the composition by adding the calcium carbonate to the methacrylic resin, a method of mixing both of them with a known thermoplastic resin to form a composition can be used. For example, there is a method of melt-kneading each component, and the melt-kneading is a commonly used uniaxial or biaxial extruder,
There is a method of using a kneading device such as various kneaders. Furthermore, it is also possible to make a molded product in one step by using the molding method described below. Further, there is also a method in which the calcium carbonate is mixed with a syrup containing a monomer constituting the methacrylic resin and a partial polymer thereof, and cast polymerization or continuous cast polymerization is performed to obtain a molded article.

Further, the light diffusing methacrylic resin composition of the present invention contains a matting agent, a dye / pigment, a light stabilizer, an antioxidant,
Well-known additives such as a filler, a release agent, and a flame retardant may be added.

Further, in order to mold the light-diffusing methacrylic resin composition into a sheet, there are known methods such as extrusion molding, injection molding and press molding. For example, in extrusion molding, after melt-kneading with a uniaxial or biaxial extruder,
It is a method of processing into a plate shape through a die and a roll unit.

Also, is the light diffusing methacrylic resin composition
As a sheet-shaped product made of, a sheet thickness is 0.8 to 5 m.
m is common. The content of the calcium carbonate is
Even if the amount is the same, the light diffusivity varies depending on the sheet thickness.
Therefore, it is desirable to express it by the amount per unit area, and after all 10
~ 200g / m ^TwoIt is preferred that If this amount is too small
The light transmittance is high, but the hiding and light diffusing properties are both high.
Very low, and too much of this amount has high hiding and light diffusing properties
However, the light transmittance becomes too low.

[0021]

The light-diffusing methacrylic resin composition of the present invention is excellent in light-diffusing property and hiding property even when it is subjected to heat-melt molding under shear and pressure, that is, extrusion molding and injection molding. You can get the goods. Therefore, the resin composition is used for a meter panel of an automobile, a lighting cover, a signboard,
It can be suitably used for various molded products such as a light diffusion plate of a transmissive display and a light emitting switch button, and various films.

[0022]

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 method is as follows.・ Average particle size; optical diffraction scattering particle size measuring instrument (Nikkiso Co., Ltd.)
Manufactured by Microtrac Particle Size Analyzer Model 9220 FRA), and the value of D ₅₀ was taken as the average particle diameter.・ Total light transmittance (Tt): Poic integrating sphere type haze meter (SEP-HS manufactured by Nippon Seimitsu Optical Co., Ltd.) in accordance with ASTM D 1003-61
-30D). -Hidden property and light diffusivity; transmitted light intensity (I ₀ ) at a transmission angle of 0 ° by vertical incident light, transmitted light intensity at a transmission angle of 5 ° by vertical incident light (I ₅ ), transmission angle at 70 ° by vertical incident light Transmitted light intensity (I ₇₀ ) of Murakami Color Research Laboratory Co., Ltd., using an automatic goniophotometer GP-1R, I ₅ / I ₀ as a concealing property, I ₇₀ / I ₀ as light Diffusive.

Examples 1 to 6 and Comparative Examples 1 to 6 100 parts by weight of methacrylic resin beads (SUMIPEX-EXA, manufactured by Sumitomo Chemical Co., Ltd.) and an organic substance-coated calcium carbonate of the type shown in Table 1 are shown in Table 2. After mixing with a Henschel mixer, the molten resin was extruded from a T die at a resin temperature of 265 ° C. using a Tanabe Plastics Machinery Co., Ltd. 40 mm uniaxial extruder, and a width of 23 cm was obtained through three polishing rolls with a thickness shown in Table 2. Got the sheet. The results of evaluating the physical properties of the obtained sheet are shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

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Claims (2)

[Claims] 1. A light diffusible methacrylic resin composition comprising 100 parts by weight of methacrylic resin and 0.2 to 10 parts by weight of precipitated calcium carbonate, wherein the precipitated calcium carbonate has a hexahedral structure. 1 to 15 μm particles, and 0.1 to 5 parts by weight of fatty acid, resin acid, sulfonic acid, fatty acid ester, resin acid ester, sulfonate ester, per 100 parts by weight of the precipitated calcium carbonate,
A light diffusing methacrylic resin composition in which the surface of the precipitated calcium carbonate particles is coated with at least one organic substance selected from phosphoric acid ester, fatty acid salt, resin acid salt, and sulfonic acid salt. Stuff. 2. The light-diffusing methacrylic resin composition according to [claim 1], which has a thickness of 0.8 to 5 mm and contains 10 to 200 g / m < ² > of the precipitated calcium carbonate dispersed therein. A light diffusing methacrylic resin sheet material.