JPS59217664A - Manufacture of artificial marble - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing artificial marble, which comprises injecting an acrylic composition mixed with an inorganic powder having a refractive index similar to that of an acrylic polymer into a molding chamber, and then polymerizing it within the mold. This is related to.

The purpose is to propose a method for manufacturing artificial marble with almost no local differences in mechanical properties, thermal properties, etc., because the inorganic powder is uniformly dispersed.

Acrylic resin molded articles filled with inorganic powder are widely used as artificial marble because appropriate transparency can be obtained by matching the refractive index of the inorganic powder to the refractive index of the acrylic resin.

Inorganic powder-filled acrylic resin molded products with an astronomical appearance are made by adding an inorganic powder having a refractive index similar to that of the acrylic resin, such as hydroxide, to an acrylic monomer or an acrylic monomer in which an acrylic polymer is dissolved. It was obtained by injecting a composition containing aluminum and a polymerization initiator into a mold and then polymerizing it. When artificial marble is manufactured using this method, the inorganic powder settles during polymerization, resulting in uneven distribution of the inorganic powder in the molded product, which may affect the appearance, mechanical properties, thermal properties, etc. of the molded product. Partial differences may occur, causing problems such as warping and twisting.

Generally, polymerizable monomer composition and inorganic powder 1
It is difficult to completely eliminate sedimentation of inorganic powder because its specific gravity is quite different from powder, but conventionally, in order to reduce sedimentation of inorganic powder, a large amount of acrylic polymer is dissolved in the monomer composition. Methods such as using a composition with a high viscosity by increasing the viscosity of the inorganic powder, and methods of reducing sedimentation by reducing the particle size of the inorganic powder have been used, but these methods also do not completely prevent the sedimentation of the inorganic powder. If this cannot be prevented and polymerization occurs with the surface of the molded product placed horizontally, a slight difference in the concentration of the inorganic powder will be observed between the upper and lower surfaces, and this will explain the difference in the coefficient of thermal expansion. This has caused problems such as warping and twisting due to heating.

As a result of intensive studies to solve these problems, the present inventors discovered that by changing the placement of the mold during polymerization, a molded product with a uniform distribution of inorganic powder could be obtained, and the present invention was achieved. did.

That is, the present invention provides at least 50% by weight of an acrylic acid alkyl ester or a methacrylic acid alkyl ester.
A polymerizable monomer containing the above-mentioned polymerizable monomers, or a polymerizable monomer mixture obtained by dissolving a polymer mainly consisting of an acrylic acid alkyl ester or a methacrylic acid alkyl ester in the above monomer), the refractive index is 1. A method for manufacturing artificial marble by injecting a composition consisting of an inorganic powder (B) and a polymerization initiator (C) in the range of 45 to 1.60 into a mold and polymerizing it, which becomes the surface of the artificial marble. The method is characterized by fixing the mold so that the parts are vertical, polymerizing in the mold at a polymerization temperature of 90°C or less, and cutting off the upper and lower end parts of the obtained artificial marble molded product. This is a method of manufacturing artificial marble.

Examples of the acrylic acid alkyl ester and methacrylic acid alkyl ester used in the present invention include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, and methacrylate. n-propyl acid, n-methacrylate
Butyl, 2-ethylhexyl methacrylate, etc.
Styrene, 2-hydroxyethyl methacrylate, acrylonitrile, vinyl acetate, etc., which are copolymerized with this, can be used as a mixed monomer.

In addition, inorganic powders include aluminum hydroxide, magnesium hydroxide, quartz, cristobalite, fused silica,
Glass powder, aluminum silicate, magnesium silicate,
Do it with talc etc.

As the polymerization initiator, azo- or peroxide-containing compounds such as 2,2'-azobisisobutyronitrile, benzoyl peroxide, etc. can be used, but in order to more effectively prevent sedimentation of inorganic powder, It is preferable to use a low-temperature-active polymerization initiator that does not reduce the viscosity of the polymerizable monomer composition and is capable of polymerization at lower temperatures.

The low-temperature-active polymerization initiator refers to a polymerization initiator whose decomposition temperature at which the half-life is 10 hours is 50°C or lower, such as diisopropyl peroxydicarbonate, di-2-
Ethylhexyl peroxydicarbonate, di-n-propyl peroxydicarbonate, cimilistyl peroxydicarbonate, bis-(4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, Dimethoxyisopropyl peroxydicarbonate, di(3-methyl-3-
methoxybutyl) peroxydicarbonate, cumyl peroxy neodecanoate, t-butyl peroxy neodecanoate, t-amyl peroxy neodecanoate, t-hexyl peroxy neodecanoate, 2.2 −
7j zobis(4-methoxy-2,4-dimethoxylvaleronitrile) and the like.

In addition, low-temperature active polymerization initiation deicing is also possible by using a combination of peroxide and an accelerator, such as a combination of benzoyl peroxide and a 6th class amine as an accelerator.

In a composition consisting of a monomer mixture, an inorganic powder, and a polymerization initiator, when the content of the inorganic powder is small, the distribution of the inorganic powder in the molded article tends to become uneven due to sedimentation even by the method of the present invention. Therefore, it is preferable that the content of the inorganic powder is 40 volumes or more. When the content of the inorganic powder is 40% by volume or more, the inorganic powders interfere with each other and the sedimentation rate becomes slow, resulting in a molded article with a uniform distribution of the inorganic powder.

An effective way to slow down the sedimentation rate is to reduce the particle size of the inorganic powder to be blended, but according to the method of the present invention, slight sedimentation of the inorganic powder is not a problem, so it is extremely There is no need to use small inorganic powder, and by using inorganic powder in which 95% by weight or more of the inorganic powder has a particle size of 60 μm or less, a molded article in which the inorganic powder is uniformly dispersed can be obtained.

In the conventional method, a composition consisting of a monomer or bleaching material mixture, an inorganic powder, and a polymerization initiator is injected into a mold, and then polymerized by placing the composition so that the surface of the molded product is horizontal. Since the mold wall surface has little effect on restraining the settling of the inorganic powder and slowing down its settling speed, the inorganic powder settles according to Systoke's law.

In addition, if there is some settling due to the conventional method using a horizontal mold, a thin layer of only resin will be formed on the top surface of the mold, and the surface and appearance of the layer with a high content of inorganic powder on the bottom surface will be extremely different. However, it cannot be used in applications where the top and bottom surfaces are facing. Furthermore, if there is a difference in the concentration of the inorganic powder, the coefficient of thermal expansion, thermal conductivity, water absorption, etc. will differ between the upper and lower surfaces, which will cause warping and twisting due to heating and water absorption, which will also cause problems in mechanical properties. .

On the other hand, in the method of the present invention, polymerization is carried out with the mold fixed in the direction in which the surface of the artificial marble is perpendicular, so the sedimentation of the inorganic powder is restrained by the influence of the wall surface of the mold, and its speed is slow. A certain effect will emerge. At the same time, even if the inorganic powder settles slightly, only the concentration of the inorganic powder at the upper and lower end portions of the molded article changes, and the concentration of the inorganic powder at the substantially necessary portions remains almost unchanged. Therefore, by slightly cutting off the upper and lower end portions, a molded article in which the inorganic powder is uniformly distributed throughout can be obtained.

Since the faster the polymerization rate, the less sedimentation of the inorganic powder, it is preferable to use a low-temperature polymerization active initiator and complete the polymerization within 2 hours.

Examples are shown below.

Example 1 Average molecular weight 100. 2 in which polymethyl methacrylate 50f of ODO was dissolved in methyl methacrylate 9501
2 Kf of quartz powder with an average particle size of 10 μm was mixed with monomer mixture 1~ having a viscosity of 0.03 ps at 5°C (measured using a B-type viscometer), and bis-(
4-1-Butylcyclohexyl) peroxydicarbonate 5f was added to obtain a composition. The concentration of quartz powder in this composition is about 42 volumes, and the viscosity (B-type viscometer, 25°C
) had a viscosity that could be easily injected into the mold at 50 ps.

The composition was injected into a mold 11 for a thin plate whose surface was vertically oriented and fixed as shown in FIG. A plate-shaped molded article 2 of artificial marble was obtained by after-airing for a period of time.

At the upper end of the obtained molded product, a region 3 with a high polymer concentration as shown in FIG. 4 is formed due to precipitation of crystalline silica, and at the lower end of the molded product, as shown in FIG. A portion 4 with a high powder concentration is formed, but by cutting out these portions 6 and 4, it was possible to obtain a molded product resembling marble with a uniform concentration of quartz powder and depth due to its slightly transparent finish.

Table 1 also shows the quartz powder concentration in each part of the molded product. It was found that the concentration of quartz powder did not change at all in each part of the molded product.

Table 1 Comparative example 1 of crystalline silica concentration in each part of a molded product The same composition as in Example 1 was poured into a mold 5 arranged so that the surface of the molded product shown in Fig. 1 was horizontal. Polymerization was carried out under the same conditions as in Example 1 to obtain a plate-shaped molded product 6.

・1 The obtained molded product has the cross section shown in Figure 2, and has a layer 7 with a high polymer concentration on the upper surface layer over the entire molded product.
A layer 8 having a high concentration of quartz powder was formed on the lower surface layer.

Because of this, the quartz powder concentration changes in the thickness direction,
The coefficient of thermal expansion was significantly different between the front and back surfaces, and warping occurred even when heated to 50°C.

In addition, since the surface condition and appearance were different between the front and back sides, there was a problem that only one side could be used as a board separator.

Example 2 Polymethyl methacrylate 240f with an average molecular weight of 3100.000 was dissolved in methyl methacrylate 960f.
A monomer mixture with a viscosity of 1 cps (B type viscometer) at 5°C was mixed with 1.2 parts and 9 parts, aluminum hydroxide with an average particle size of 4 μm was mixed with 2.8 parts and 9 parts, and Similistilper was added as a polymerization initiator. 8 tons of oxydicarbonate was added and mixed uniformly to obtain a composition. The concentration of aluminum hydroxide in this composition was about 48 by volume, and the viscosity (B-type viscometer, 25° C.) was 200 cps, just enough to be injected into a mold.

A molded article was obtained using the composition in the same manner as in Example 1.

The obtained molded product had a deep marble-like appearance due to its transparency, and the concentration of aluminum hydroxide varied in each part of the molded product as shown in Table 2. It was completely unchanged.

Table 2: Aluminum hydroxide concentration in each part of the molded product 1) The aluminum hydroxide concentration was calculated assuming that the sample was completely converted to alumina after being incinerated.

Comparative Example 2 The same composition as in Example 2 was injected into a mold arranged so that the surface of the molded product shown in Figure 1 was horizontal, and polymerized under the same conditions as in Example 1 to produce a molded product. I got it.

The obtained molded article has a cross section shown in FIG. 2, although it is not very clear, and the concentration of aluminum hydroxide changes in the thickness direction throughout the molded article. For this reason, the upper surface with a high polymer concentration has a so-called shiny plastic feel, and the depth of marble cannot be seen at all. -The lower surface, which has a high concentration of aluminum hydroxide,
On the contrary, the molded product had no luster at all, and the depth of the astronomical stone-like appearance could not be obtained on this surface, and the molded product had an appearance completely different from that of the molded product of Example 2.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a mold placed so that the surface of the conventional molded product is horizontal, Figure 2 is an enlarged cross-sectional view of the molded product in section A in Figure 1, and Figure 3 is the actual molded product. Figures 4 and 5 are cross-sectional views of the mold arranged so that the surface of the molded product used in the example is vertical, and are enlarged cross-sectional views of the molded product at portions B and 0 in Figure 3, respectively. be. 1. Molding mold arranged so that the surface of the molded product is vertical, 2. Molded product of the example, 6. Portion with high polymer concentration, 4. Portion with high silica concentration, 5.・Mold placed so that the surface of the molded product is horizontal, 6. Molded product of comparative example, 7. Layer with high polymer concentration, 8. Layer with high silica concentration, 9. Gasket. .

Claims (4)

[Claims] (1) A polymerizable monomer containing 50% by weight or more of an acrylic acid alkyl ester or a methacrylic acid alkyl ester, or a polymer mainly composed of an acrylic acid alkyl ester or a methacrylic acid alkyl ester as the monomer. a polymerizable monomer mixture (A) dissolved in
Inorganic powder CB with a refractive index in the range of 1.45 to 1.60
) and a polymerization initiator (0) are injected into a mold and polymerized within the mold to produce artificial marble, in which the mold is fixed so that the surface of the artificial marble is vertical. A method for producing artificial marble, which comprises polymerizing at a polymerization temperature of 90° C. or lower in a mold, and cutting off the upper and lower end portions of the resulting marble molded product. (2) The inorganic powder CB) is aluminum hydroxide, magnesium hydroxide, quartz, cristobalite, fused silica, glass powder, aluminum silicate, magnesium silicate, or talc. The manufacturing method of artificial marble. (3) At least 95% by weight of the inorganic powder (B) has a particle size of 6
Claim 1 characterized in that it is 0 μm or less
Method for producing artificial marble as described in Section 1. (4) The method for producing artificial marble according to claim 1, characterized in that the inorganic powder CB) accounts for at least 40 volumes of the composition.