JPH0632955A - Light-diffusive methyl methacrylate/styrene copolymer resin composition - Google Patents

Abstract

PURPOSE:To obtain a resin composition which is uniform, has excellent light diffusivity and light transmittance, and has a matte surface without detriment to light diffusivity even after fabrication, by incorporating a specified amount of a specified acrylic resin into a methyl methacrylate/styrene copolymer resin. CONSTITUTION:100 pts.wt. non-crosslinking monomer consisting of 80-100wt.% 1-4C alkyl methacrylate, 0-20wt.% 1-8C alkyl acrylate and 0-20wt.% other mono- ethylenically unsaturated monomer, (e.g. methyl methacrylate) is mixed with 0.5-20 pts.wt. crosslinking monomer (e.g. 1,6-hexanediol dimethacrylate), and the mixture is subjected to suspension polymerization to give a beadlike crosslinked acrylic resin having a mean particle diameter of 1-30mum. 1-30 pts.wt. of this acrylic resin is incorporated into 100 pts.wt. methyl methacrylate/styrene copolymer resin to give the objective composition.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a light-diffusing methyl methacrylate-styrene copolymer resin composition having a matte surface, which is suitable for a lighting cover having a high light diffusivity and a high light transmittance. Regarding

[0002]

2. Description of the Related Art Conventionally, as a method of imparting a light diffusing property to a molded article, is it necessary to disperse and mix fine particles of an inorganic compound such as calcium carbonate, barium sulfate, titanium oxide or talc with a base resin such as an acrylic resin. Or, a method in which a resin that melts in a mold having a mold pattern is injection-molded, or an embossing roll is used to impart a concavo-convex pattern to the surface of the molded body by a mechanical method is generally used.

However, even if a light-diffusing extruded plate is obtained by the dispersion of the inorganic compound and the mechanical unevenness pattern, the unevenness of the surface is lost when the light-extruded extruded plate is secondary-processed and formed into various shapes such as a lighting cover, so that sufficient light is emitted. There was a drawback that it did not show a diffusion effect.
There is also an example using a bead-shaped crosslinked acrylic resin (Japanese Patent Laid-Open No. 61-159440), which is considered for a polymethylmethacrylate resin composition, and is used as a non-crosslinked monomer of the beaded crosslinked acrylic resin. 20 styrene
When blended in an amount of -40% by weight, the methyl methacrylate-styrene copolymer resin does not exhibit the expected light diffusivity. Further, the particle size is 30 to 30% disclosed in the above-mentioned publication.
When the thickness is 300 μm, the appearance of the sheet becomes rough, and there is a problem that the appearance after secondary molding is particularly insufficient.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, to have uniform and excellent light diffusivity and high light transmittance, and to obtain light even by secondary processing. It is an object of the present invention to provide a light-diffusing methyl methacrylate-styrene copolymer resin composition having a matte surface that does not reduce the diffusibility.

[0005]

Means for Solving the Problems As a result of earnest studies on the light-diffusing methyl methacrylate-styrene copolymer resin composition, the present inventors have found that the difference between the transparency of the acrylic resin and the refractive index between the copolymers. Focusing attention, it was found that the above problem can be solved by blending a methyl methacrylate-styrene copolymer resin with a beaded acrylic resin having a specific particle diameter having a cross-linking structure, and molding the resin composition, and the present invention Arrived

That is, according to the present invention, 100 parts by weight of a methyl methacrylate-styrene copolymer resin (A) is added to 100 parts by weight of a non-crosslinking monomer (a) consisting of the following components and 0.5 to 5 parts of a crosslinking monomer (b). Light-diffusing methyl methacrylate-styrene copolymer resin obtained by blending 1 to 30 parts by weight of a bead-shaped crosslinked acrylic resin (B) having an average particle diameter of 1 to 30 μm obtained by blending 20 parts by weight and performing suspension polymerization. It relates to a composition. (A) Non-crosslinkable monomer Alkyl methacrylate having 1 to 4 carbon atoms in the alkyl group 80 to 100% by weight Alkyl acrylate having 1 to 8 carbon atoms in the alkyl group 0 to 20% by weight Other monoethylenically unsaturated Monomer 0-20% by weight

The methyl methacrylate-styrene copolymer resin used as the base resin in the present invention is generally a resin obtained by copolymerizing a composition of 20 to 80% by weight of methyl methacrylate and 80 to 20% by weight of styrene. A resin obtained by copolymerizing a composition of 55 to 65% by weight of methyl methacrylate and 45 to 35% by weight of styrene is particularly preferable, and its average molecular weight is 120000 to 2 from the viewpoint of extrusion kneading property and physical properties.
Those of 50,000 are preferable.

[0008] In obtaining the above copolymer, if the methyl methacrylate component exceeds 80% by weight, the specific gravity of the obtained copolymer becomes large, weight reduction cannot be achieved, and moldability is poor. Occurs. On the other hand, when the content of the methyl methacrylate component is less than 20% by weight, the weather resistance is remarkably deteriorated, which makes it unsuitable for use as a proof cover.

The bead-shaped crosslinked acrylic resin (B) used in the present invention contains 0.5 to 2 parts of the (b) crosslinking monomer in 100 parts by weight of the non-crosslinkable monomer (a) consisting of the following components.
It is obtained by blending 0 parts by weight and carrying out suspension polymerization. Above (a)
The non-crosslinkable monomer has the following components blended as follows. Alkyl methacrylate having 1 to 4 carbon atoms in the alkyl group 80 to 100% by weight Alkyl acrylate having 1 to 8 carbon atoms in the alkyl group 0 to 20% by weight Other monoethylenically unsaturated monomer 0 to 20% by weight

As the alkyl methacrylate having 1 to 4 carbon atoms in the alkyl group, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate or the like can be used alone or in combination, but methyl is used. Methacrylate is preferred, and its proportion is 80 in the non-crosslinking monomer.
~ 100% by weight.

In the present invention, it is possible to use the above alkyl acrylate having 1 to 8 carbon atoms in the non-crosslinking monomer within a range not exceeding 20% by weight, specifically, methyl acrylate, Examples thereof include ethyl acrylate, propyl acrylate, butyl acrylate and 2-ethyl-hexyl acrylate.

Further, the above-mentioned other monoethylenically unsaturated monomers can also be used in the non-crosslinking monomer within a range not exceeding 20% by weight, and specifically, comonomers such as fumaric acid and maleic acid can be used. Polymerizable carboxylic acid and its ester can be illustrated.

As the (b) crosslinkable monomer used in the present invention, a compound having two or more unsaturated bonds in the molecule is used. At least one of the two or more unsaturated bonds is used. It may have an allyl group. Examples of the crosslinkable monomer (b) include allyl methacrylate, triallyl cyanurate, triallyl isocyanate, ethylene glycol dimethacrylate, propylene glycol diallyl ether, divinylbenzene, diethylene glycol dimethacrylate, and 1,6-hexanediol. However, diethylene glycol dimethacrylate and 1,6-hexanediol are preferable.

The amount of the crosslinkable monomer added is 0.5 to 20 per 100 parts by weight of the total amount of the noncrosslinkable monomers.
Parts by weight. If the amount of the crosslinkable monomer added is less than 0.5 parts by weight, a high light transmittance cannot be obtained, and the effect as an unevenness-imparting agent is reduced. If the addition amount of the crosslinkable monomer exceeds 20 parts by weight, thermal coloring is likely to occur, which causes disadvantages such as economical disadvantage.

The bead-shaped crosslinked acrylic resin (B) used in the present invention is produced by a usual suspension polymerization method by blending the above-mentioned (a) non-crosslinked monomer and (b) crosslinked monomer in a fixed ratio. In the present invention, the beaded crosslinked acrylic resin has an average particle size of 1 to 30 μm, preferably 5 to 30 μm.
Is. When the average particle diameter is more than 30 μm, the surface of the molded article obtained from the resin composition of the present invention is inferior in surface property because uniform uneven matte is not obtained. On the other hand, if the average particle diameter is less than 1 μm, a sufficient light diffusion effect cannot be obtained and the matting effect is also insufficient, but 80% or more of the beads-like crosslinked acrylic resin particles have the above 1 to 30 μm. Is particularly desirable.

The bead-shaped crosslinked acrylic resin (B) is blended in a proportion of 1 to 30 parts by weight with respect to 100 parts by weight of the methyl methacrylate-styrene copolymer resin (A) as a base material. If the compounding ratio of the bead-shaped crosslinked acrylic resin is less than 1 part by weight, a sufficient light diffusion effect cannot be obtained,
On the other hand, even if it is blended in an amount of more than 30 parts by weight, it does not particularly improve the light diffusion performance and is not preferable from the viewpoint of light transmittance, appearance, deterioration of physical properties, and economical efficiency.

The light-diffusing resin composition of the present invention contains a flame retardant, a stabilizer, a pigment, and a flame retardant within the range not impairing the object of the present invention.
Various additives such as dyes, lubricants, and fiber reinforcements can be blended. In adjusting the light diffusing resin composition of the present invention, a conventionally known method may be adopted,
A method of kneading with an extruder, a Banbury mixer, a roll or the like is appropriately selected.

[0018]

EXAMPLES Next, the present invention will be described more specifically by way of examples. The evaluation of the physical properties in this example was performed according to the methods described below. 1) The total light transmittance, the diffused light transmittance and the haze value were measured with a haze meter manufactured by Nippon Denshoku Industries Co., Ltd. 2) For the surface roughness, a surface roughness measuring instrument manufactured by Kosaka Laboratory Ltd. was used to measure the maximum roughness Rz value of the molded product. 3) The surface roughness residual rate indicates the rate before and after molding. 4) Diffusivity Measured by a transmission method with an automatic goniophotometer manufactured by Murakami Color Research Laboratory Co., Ltd. Diffusivity (%) = (100) x (20 ° brightness value + 70 ° brightness value) / (5
Luminance value x 2) 5) Dispersity Dispersion: When the amount of transmitted light when γ = 0 ° (in the linear direction) is 100 when light is applied to the sample, γ when the transmitted light amount becomes 50 Angle (angle with linear direction)

Example 1 Methyl methacrylate-styrene copolymer resin (manufactured by Nippon Steel Chemical Co., Ltd., obtained from 64 parts by weight of methyl methacrylate and 36 parts by weight of styrene monomer, average molecular weight 1)
50,000 pellets) to 100 parts by weight, as a light diffusing agent and a matting agent, bead-shaped acrylic crosslinked fine particles having an average particle size of 13 μm (95% by weight of methyl methacrylate as a non-crosslinkable monomer, 1,6-as a crosslinking monomer).
5 parts by weight of hexanediol dimethacrylate mixed at a ratio of 5% by weight and produced by usual suspension polymerization) and 1.5 parts by weight of a milk white dry color colorant were mixed and stirred with a mixer, and a vent extruder having a diameter of 65 mm was used. Was extruded through a T-die, and processed into an extruded plate having a thickness of 1.8 mm with a three-roll (embossing roll). Next, this extruded plate was vacuum-formed at 160 ° C. for 3 minutes, and the optical properties before and after the forming were compared and measured. The evaluation results are shown in Table 1.

Example 2 With respect to 100 parts by weight of the methyl methacrylate-styrene copolymer resin used in Example 1, 25 parts by weight of the acrylic crosslinked fine particles used in Example 1 as a light diffusing agent and a matting agent, and an opalescent dry 1.5 parts by weight of the colorant was mixed and stirred to form an extruded sheet, and the optical properties before and after vacuum forming were measured for comparison. The evaluation results are shown in Table 1.

Comparative Example 1 A one-sided mat extruded plate with mechanical processing embossing was formed in the same manner as in Example 1 except that a light diffusing agent was not added, and the physical properties of this extruded plate before and after vacuum forming are shown in Table 1. .

[0022]

[Table 1] Example 1 Example 2 Comparative Example 1 Original plate before molding Total light transmittance (%) 66.6 64.7 68.2 Diffused light transmittance (%) 61.3 59.7 51.2 Diffusivity (%) 58.9 72.2 34.3 Dispersion degree (°) 34.4 41.0 21.2 Haze value (%) 92.1 92.3 75.1 Surface roughness RZ value (μm) 8.0 11.5 7.5 Total light transmittance of molded products (%) 65.7 64.4 67.2 Diffused light transmittance (%) 60.3 59.2 31.7 Diffusivity (%) %) 32.7 37.1 7.9 Dispersion (°) 20.1 22.7 3.8 Haze value (%) 91.8 92.0 42.7 Surface roughness RZ value (μm) 7.3 10.9 2.5 Surface roughness residual rate (%) 91.3 94.8 33.3 ──────── ──────────────────────────

From Examples 1 and 2, the molded product obtained by blending the bead-shaped acrylic crosslinked fine particles with the methyl methacrylate-styrene copolymer resin of the present invention is excellent in the light diffusivity and haze value of the extruded base plate and the diffusion after the molding. It can be seen from Table 1 that the transmittance and the haze value hardly change. In the case of the comparative example containing no light diffusing agent, the diffused light transmittance, haze value and surface roughness after molding were remarkably lowered, and the light diffusing property was lost. Since the surface roughness residual rate of the light-diffusing methyl methacrylate-styrene copolymer resin molded product of the present invention in vacuum molding is very high, fine irregularities are maintained in the appearance of the molded product and a matte appearance is exhibited. Also, when a light source lamp is placed inside the molded product of the present invention and viewed from the outside, it shows a soft bright light emission,
It was also confirmed that the shape of the light source was transparent and that the anti-glare effect was not visible.

[0024]

The extruded plate containing acrylic crosslinked fine particles imparting the light diffusing effect and the matting effect according to the present invention has almost no change in the diffuse transmittance and the haze value before and after vacuum pressure molding, and has a surface roughness after molding. The fine irregularities are maintained and the matte surface of the molded product is retained.

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Claims (1)

[Claims] 1. To 100 parts by weight of a methyl methacrylate-styrene copolymer resin (A), 100 parts by weight of a non-crosslinking monomer (a) consisting of the following components and 0.5 to 20 parts by weight of a crosslinking monomer (b). A light-diffusing methyl methacrylate-styrene copolymer resin composition obtained by blending 1 to 30 parts by weight of a beaded crosslinked acrylic resin (B) having an average particle diameter of 1 to 30 μm obtained by blending and suspension polymerization. (A) Blending ratio of non-crosslinkable monomer 80 to 100% by weight of alkyl methacrylate having 1 to 4 carbon atoms in the alkyl group 0 to 20% by weight of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group Other monoethylenic Unsaturated monomer 0-20% by weight