JPS6241535B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides an acrylic resin plate, particularly a lighting cover,
This invention relates to an acrylic resin board suitable for signboards, display displays, etc. Methyl methacrylate polymers are used as plate-like products for signboards, displays, lighting covers, etc. Among them, so-called milky semi-transparent plate-shaped products are often used for lighting covers after undergoing secondary heat processing such as press processing and vacuum processing to increase lighting efficiency and anti-glare effects in interiors and cars. Its use has become widespread recently. The following three main features are important for a lighting cover made of an acrylic resin milky translucent plate. 1. High total light transmittance and energy efficient performance. 2. Parallel light transmittance is low, making it difficult to see the light source through the cover. (Anti-glare effect) 3. The surface must be beautiful. In particular, with the recent trend towards energy conservation, there is a strong demand for improvements in the above characteristics. Conventionally, in order to satisfy the conflicting requirements 1 and 2 above, barium sulfate and the like have been used as a diffusing agent, and improvements have been made by devising various purification methods, particle sizes, etc. The drawback was that the light transmittance was significantly reduced, resulting in poor energy efficiency.
In addition, in order to improve these improvements, the surface is made matte by using a matte roll or the like in the molding equipment to create special minute irregularities on the surface, but press processing, vacuum processing, etc. When secondary thermal processing such as machining is required, the fine irregularities on the surface disappear due to the heat, and the matting effect disappears, so it is hardly used industrially. In addition, as a technology to improve the disappearance of matte surfaces due to thermoforming, for example, we have developed a matte board made by mixing and extruding talc powder (Japanese Patent Laid-Open Publication No.
53-147748), but for example, if the amount of talc added is increased to reduce the parallel light transmittance in order to reduce the "see-through" of the light source through a lighting cover, etc., the total light transmittance will drop significantly and the energy There were drawbacks such as poor efficiency, increased yellowness in color tone, decreased whiteness, and a loss of beauty in appearance. Therefore, the inventors of the present invention have conducted intensive research into a technology that suppresses the decrease in total light transmittance as much as possible even when the parallel light transmittance is lowered, and also improves whiteness. The present invention was completed by discovering that this is possible by blending the body. That is, the present invention uses methyl methacrylate polymer 100
1.0 to 5.0 parts of fine talc powder and 0.1 to 1.0 parts of fine barium sulfate powder are mixed and extruded to produce a beautiful acrylic resin board with a matte surface and excellent anti-glare effect. . The methyl methacrylate polymer referred to in the present invention is
There is no problem with it containing a copolymer or homopolymer containing 85% or more of methyl methacrylate, and containing trace amounts of additives such as ultraviolet absorbers, fluorescent whitening agents, and heat stabilizers. Although the molecular weight is not particularly limited in the present invention, it is generally 50,000 to 50,000 from the viewpoint of ease of kneading and physical properties.
70,000, preferably 70,000 to 300,000. The fine talc powder used in the present invention is a fine powder obtained by mechanically crushing a plate-shaped crystalline talc raw stone whose main component is naturally occurring magnesium silicate.
Its particle size is 1-10μ, preferably 3-7μ. The blending amount varies depending on the intended use, but in order to obtain good optical properties, 1.0 to 5.0 parts is required. If it is less than 1.0 parts, there will be no matte effect, and if it is more than 5.0 parts, the yellow color will become darker and the beauty will be lost. Further, the particle size of the barium sulfate fine powder used in the present invention is usually 1 to 6μ, preferably 2 to 6μ.
It is 4μ. The amount to be blended must be 0.1 to 1.0 parts. If it is 1.0 or more, the total light transmittance decreases and energy efficiency deteriorates, and if it is less than 0.1 part, the decrease in the total light transmittance cannot be prevented. The conditions for kneading and extrusion are not essential components of the present invention, but in general, a single screw type extruder with a kneading mechanism is used, and fine talc powder and barium sulfate are mixed at a resin temperature of about 200 to 300°C. A compound is manufactured by kneading and simultaneously extruding the fine powder, and then this compound is processed into a plate of uniform thickness using a finishing roll, and then cooled to form a plate-shaped product. The present invention will be explained in more detail below using Examples. Example For 100 parts of beads of methyl methacrylate copolymer (molecular weight 180,000) containing 5% methyl acrylate, 2 parts, 3 parts of fine talc powder with an average particle size of 4 μ,
4 parts and 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, and 1.0 parts of barium sulfate fine powder with an average particle size of 3 μm were mixed in each with a Henschel mixer, and then a single screw with a kneading mechanism ( 90
The mixture was kneaded using a T-shaped die with a width of 1000 mm at a resin temperature of 260°C, and processed into a plate with a thickness of 2 mm using three rolls (smooth mirror finish). The optical properties of the cooled plate were measured and evaluated using an HTR meter with an integrating sphere in accordance with JIS-K6717. In addition, the surface whiteness was determined by placing a 50 mm x 50 mm sample on a white paper and looking at the naked eye under a straight cylindrical fluorescent light. : A>B>C>D>E) Grades were classified and evaluated. The results are shown in Table 1. Comparative Example A plate was processed and evaluated in the same manner as in Example 1, except that talc fine powder and barium sulfate fine powder were individually blended. The second result is
Shown in the table.

【table】

【table】

[Table] As is clear from Table 1, Table 2, and Figure 1, a plate-shaped product made by blending, kneading, and extruding both talc fine powder and barium sulfate fine powder has a matte surface and is resistant to parallel light. Even if the transmittance is low, it has a high total light transmittance and has a beautiful appearance. Furthermore, this plate-like product maintains its matte surface even after being heat-treated, so it has useful performance as a lighting cover.

[Brief explanation of the drawing]

The drawing shows a master curve plotted with the vertical and horizontal axes representing the total light transmittance and the parallel light transmittance in Examples and Comparative Examples of the present invention.

Claims (1)

[Claims] 1 For 100 parts of methyl methacrylate polymer,
An acrylic resin board with a matte surface and excellent anti-glare effect, which is made by mixing and extruding 1.0 to 5.0 parts of fine talc powder and 0.1 to 1.0 parts of fine barium sulfate powder.