JPH04275314A - Production of acrylic artifical 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]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing acrylic artificial marble.

0002

[Prior art and problems to be solved] Acrylic artificial marble, which is made by filling acrylic resin with inorganic powder, has a beautiful appearance and excellent properties, and can be used for kitchen countertops, various countertops, bathroom vanities, shower trays, waterproof pans, etc. ,
It is used for flooring, wall materials, partition boards, etc., and depending on the manufacturing method, it is a compression or extrusion molded product of acrylic thermoplastic resin filled with inorganic powder, and an inorganic powder in acrylic unsaturated monomer. It is broadly divided into cast-molded products made of slurry filled with Although the former has excellent productivity, it has poor heat resistance and stain resistance, which limits its uses, whereas the latter has excellent heat resistance, stain resistance, and strength.
It is used for a wide range of purposes. However, in this cast molding, there is no problem if the mold surface is held vertically, but
If the mold surface is not vertical but particularly horizontal, the inorganic powder will settle during polymerization and hardening, so the properties of the front and back surfaces of the cast molded product will not be the same, which may cause warping, for example, due to temperature changes. There is a problem with this. If it is a simple flat plate shape, this can be solved by holding the mold surface vertically, but if this is not possible due to the equipment, or if it is a molded product with a complex shape, so-called irregularly cast molded products, all It is impossible to maintain the surface vertically, and various methods have been proposed to prevent sedimentation. One known method is to use high-viscosity syrup to increase the viscosity of the slurry.
Not only does the high viscosity make it difficult to mix syrup and inorganic powder, but in the case of heat curing, the viscosity decreases as the temperature rises, so there are problems such as not being able to sufficiently prevent the inorganic powder from settling during curing. . A method of imparting thixotropy by adding fine silica particles is also known, but in this case there is a problem that workability is very poor because the fine silica particles are bulky and difficult to handle.

Therefore, an object of the present invention is to provide a method for producing acrylic artificial marble with good workability, which prevents sedimentation and separation of inorganic powder and eliminates various inconveniences caused by it. An object of the present invention is to provide a method for producing acrylic artificial marble having excellent hot water resistance.

0004

[Means for Solving the Problems] The above object is to prepare a slurry consisting of 20 to 80% by weight of an unsaturated monomer mainly composed of methyl methacrylate and 80 to 20% by weight of an inorganic powder to 100 parts by weight of the slurry. On the other hand, it is achieved by polymerization curing in the coexistence of 0.01 to 1 part by weight of water, preferably from 0.01 to 1 part by weight of water and 0.01 to 1 part by weight of acid instead of water. This is achieved by using an acid aqueous solution.

The unsaturated monomer mainly composed of methyl methacrylate as used in the present invention refers to methyl methacrylate alone or methyl methacrylate of 50% by weight or more, preferably 60% by weight or more.
It is a monomer mixture of at least 75% by weight, more preferably at least 75% by weight, of other unsaturated monomers. If the proportion of methyl methacrylate is less than 50% by weight, the weather resistance performance and luxury appearance of the acrylic artificial marble will deteriorate, which is not preferable.

Other unsaturated monomers that can be used in combination with methyl methacrylate include those that can be polymerized alone or copolymerized with other components in the unsaturated monomer mainly composed of methyl methacrylate. There are no particular restrictions. For example, the number of carbon atoms in one molecule is 2 to 18.
Esters of monohydric alcohols or monohydric phenols and acrylic acid or methacrylic acid, monoesters of dihydric alcohols with 2 to 4 carbon atoms per molecule and acrylic acid or methacrylic acid, acrylic acid, methacrylic acid, acrylic methyl acid, acrylonitrile, methacrylonitrile, acrylamide, styrene, α-methylstyrene, vinyl acetate, vinyl chloride, vinylidene fluoride, vinylidene chloride, ethylene, maleic anhydride, maleic acid, fumaric acid, butadiene, glycidyl methacrylate, etc. monofunctional unsaturated monomers, acrylic acid and/or methacrylic acid and ethylene glycol, polyethylene glycol,
propylene glycol, polypropylene glycol, 1
, 3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, tetramethylolmethane, dimethylolethane, trimethylolethane, dimethylolpropane, trimethylolpropane, pentaerythritol, dipentaerythritol Examples include polyhydric esters with polyhydric alcohols, such as divinylbenzene, and polyfunctional unsaturated monomers such as triallyl isocyanurate. It is also possible to use two or more types of other unsaturated monomers used together with methyl methacrylate.

[0007] In order to improve the heat resistance, stain resistance, etc. of acrylic artificial marble, it is desirable to use a polyfunctional unsaturated monomer in combination. As the type of polyfunctional unsaturated monomer, those mentioned above can be used, but among them, ethylene glycol dimethacrylate, 1,3 butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethymer propane trimethacrylate, etc. preferable. The amount of polyfunctional unsaturated monomer used is 0.2 to 2 of the unsaturated monomer mainly composed of methyl methacrylate.
5% by weight, preferably 2-10% by weight. If the amount of polyfunctional unsaturated monomer used is less than 0.2% by weight, the effect of improving heat resistance performance, stain resistance performance, etc. will be poor;
Exceeding this percentage by weight is not preferable because the acrylic artificial marble becomes brittle.

[0008] The unsaturated monomer mainly composed of methyl methacrylate is desirably used as a syrup containing a portion thereof as a polymer in order to impart viscosity to the slurry and prevent sedimentation of the inorganic powder. The viscosity of syrup depends on the type of inorganic powder and the amount filled, but it is usually 0.1 to 3 poise, preferably 0.5 to 3 poise. There are no particular restrictions on the method for producing syrup, but an example of a general production method is to polymerize a portion of unsaturated monomers, mainly methyl methacrylate, and then convert the remaining unsaturated monomers into A method of partially polymerizing an unsaturated monomer mainly composed of methyl methacrylate, a method of partially polymerizing an unsaturated monomer mainly composed of methyl methacrylate, and the remaining unsaturated monomer Examples include a method of dissolving it in

The inorganic powder used in the present invention is not particularly limited as long as it is insoluble in the unsaturated monomer mainly composed of methyl methacrylate and does not interfere with its polymerization and curing, and aluminum hydroxide, aluminum oxide, calcium carbonate,
Examples include, but are not limited to, powders of calcium silicate, calcium aluminate, calcium sulfate, magnesium hydroxide, silica, talc, clay, and the like. However, due to the high quality, stain resistance, and processing performance of acrylic artificial marble, aluminum hydroxide,
Magnesium hydroxide, silica, and especially aluminum hydroxide are preferably used. It is also possible to use two or more types of these inorganic powders in combination.

[0010] The particle size of the inorganic powder is usually 0.1 to 100μ.
m, preferably 0.5 to 50 μm, more preferably 1 to 30 μm. If the particle size exceeds 100 μm, it may appear as indistinct and minute spots on the acrylic artificial marble, spoiling its aesthetic appearance. If the particle size is less than 0.1 μm, it will be expensive and the amount of filling may be restricted. Therefore, it is not desirable.

[0011] The amount of inorganic powder to be filled is determined by the performance required of the acrylic artificial marble, but it is usually 20% based on the total amount of the unsaturated monomer, mainly methyl methacrylate, and the inorganic powder. -80% by weight, preferably 40-70% by weight. If the filling amount of the inorganic powder is less than 20% by weight, the heat resistance performance and hardness of the acrylic artificial marble may deteriorate, and the marble-like appearance may be impaired, which is not preferable. On the other hand, if the filling amount exceeds 80% by weight, filling becomes difficult and the strength decreases, which is not preferable.

The amount of water used in the present invention is 0.01 to 1 part by weight per 100 parts by weight of the slurry consisting of an unsaturated monomer mainly composed of methyl methacrylate and inorganic powder.
Preferably 0.02 to 0.5 parts by weight, more preferably 0
．． 03 to 0.2 parts by weight. If the amount of water is less than 0.01 part by weight, the addition effect will be poor, and if it exceeds 1 part by weight, the slurry will lose fluidity and workability will deteriorate, and it will also affect the chemical resistance and stain resistance of acrylic artificial marble. This is not preferable because it reduces the

[0013] When polymerizing and curing the slurry, if the system is alkaline and water is present, the molded product may be colored yellow and its commercial value may be reduced. Therefore, in the present invention, it is more convenient to use an aqueous acid solution than water alone in order to acidify the system and prevent yellowing. The amount of acid itself used depends on the type and amount of inorganic powder, the type and amount of various additives, etc.
Although it cannot be generalized, 0.01 to 1 part by weight, preferably 0.02 parts by weight, per 100 parts by weight of a slurry consisting of an unsaturated monomer mainly composed of methyl methacrylate and inorganic powder.
It is desirable that the amount is 0.5 parts by weight.

The acid used in the present invention may be any acid that can be dissolved and contained in the above-mentioned amount of water, and examples of such acids include phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, etc. inorganic acids, aliphatic saturated carboxylic acids such as formic acid, acetic acid, chloroacetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, glutaric acid, and adipic acid, and oxycarboxylic acids such as glycolic acid, lactic acid, tartaric acid, citric acid, and malic acid. acids,
Examples include p-toluenesulfonic acid, p-toluenesulfinic acid, benzenesulfonic acid, etc.
It is not limited to these. Among these acids, phosphoric acid, oxalic acid, chloroacetic acid, malonic acid, glutaric acid, glycolic acid, lactic acid, tartaric acid, citric acid, malic acid, acetic acid, p
-Toluenesulfonic acid and benzenesulfonic acid are preferred, with phosphoric acid, acetic acid and p-toluenesulfonic acid being particularly preferred. Furthermore, phosphoric acid is most preferred since it also has the effect of improving the hot water resistance performance of acrylic artificial marble. The acid is usually added to the slurry as an aqueous acid solution, but it can also be added separately from the water.

[0015] There is no particular restriction on the order of addition of water, acid or acid aqueous solution, but if they are added, the viscosity of the slurry may increase and it may become difficult to stir. It is appropriate to add water or an aqueous acid solution last.

[0016] Molding methods for producing acrylic artificial marble include cast molding, compression molding, etc., and cast molding is preferably employed.

There are no particular restrictions on the mold that can be used in the present invention, but the effects of the present invention are better exhibited when the mold surface is nearly horizontal than when the mold surface is held vertically. There are no particular restrictions on the material of the mold surface, and any material such as metal, glass, ceramics, resin, etc. can be used. There are no particular restrictions on the structure of the mold, including closed cell devices, open cell devices, open molds, compression molds,
Any device can be used, such as continuous casting equipment.

In the present invention, the method of polymerizing and curing the slurry is not particularly limited, and examples thereof include heating in the presence or absence of a radical polymerization initiator, and a method using a so-called redox system comprising a radical polymerization initiator and an accelerator. , methods of irradiating with ultraviolet rays or radiation.

[0019] If necessary, dyes and pigments, reinforcing agents, modifiers, stabilizers, ultraviolet absorbers, mold release agents, flame retardants, polymerization regulators, etc. may be added to the acrylic artificial marble of the present invention. It is possible.

[0020]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way. Examples 1 to 6 Methacrylic resin (Parabeads HR, manufactured by Kuraray Co., Ltd.) 6
．． 8 parts by weight were dissolved in 31.2 parts by weight of methyl methacrylate and 2 parts by weight of trimethylolpropane trimethacrylate. The resulting syrup had a viscosity of 1 poise at 25°C. To this was added 0.02 parts by weight of stearic acid, 2-
(2'-hydroxy-5'-methylphenyl)benzotriazole 0.1 part by weight, 2,2'-azobisisobutyronitrile 0.02 part by weight, 2,2'-bis(t-butylperoxy) 0.1 parts by weight of butane and 60 parts by weight of aluminum hydroxide powder (Hygilite H310, manufactured by Showa Denko K.K.) were added, stirred at high speed for 30 minutes, and then the amount of water or 50% by weight phosphoric acid aqueous solution shown in Table 1 was added. was added and stirred. Table 1 shows the viscosity (25°C) of the obtained slurry.

A mold was assembled by placing two glass plates of approximately 1.5 m x 2 m in size facing each other and inserting an annular soft gasket along the periphery thereof. The slurry was injected into the mold through the gap where the gasket was partially removed. Return the gasket to its original position and hold the glass surface horizontally.
It was polymerized and cured by heating in water at 0° C. for 4 hours and then in a hot air oven at 120° C. for 2 hours to obtain an acrylic artificial marble flat plate measuring 1.5 m x 2 m and 10 mm thick.

[0022] These flat plates were placed one by one on a horizontally held surface plate in the same orientation as during polymerization and curing, and slowly cooled from 110°C to room temperature, and the magnitude of warpage that occurred was measured. The magnitude of warpage was indicated by the larger value of the distance between the midpoint of each of the two diagonals on the upper surface of the flat plate and the flat plate surface. Also J
The b value of the Lab color coordinates was measured by the method of IS K 7105. Further, the content of aluminum hydroxide powder in a 1 mm surface layer portion of the lower and upper surfaces of the flat plate was measured, and the difference between the lower and upper surfaces was determined. The results of these measurements are shown in Table 1.

[0023] From the results in Table 1, in all of these examples in which water or acid aqueous solution was added, the sedimentation and separation of the inorganic powder was minute, and the acrylic artificial marble board had no warping, or even if it did, it would not pose a practical problem. It can be seen that the coloring is small and that when acid is used, the coloration is small. Comparative Example 1 Examples 1 to 1, except that no water or acid aqueous solution was used.
An acrylic artificial marble board was manufactured by the same method as in 6. As shown in Table 1, this board had significant warpage.

[0024]

[Table 1] Examples 7 and 8 Instead of 40 parts by weight of methacrylic resin-dissolved syrup, 38 parts by weight of syrup with a viscosity of 1 poise obtained by partial polymerization of methyl methacrylate and 2 parts by weight of 1,3-butylene glycol dimethicrylate Acrylic artificial marble plates were obtained by the same operations as in Examples 3 to 6, except that the acid aqueous solution was used as shown in Table 2. As shown in Table 2, the obtained plates had no practical problems with warpage and only slight discoloration.

[0025]

[Table 2] Comparative Example 2 An acrylic artificial marble board was obtained by the same operation as in Examples 7 and 8, except that no acid aqueous solution was used. As shown in Table 2, this board had significant warpage. Example 9 The flat pieces obtained in Examples 2, 6, 7, and 8 and Comparative Examples 1 and 2 were immersed in boiling water for 9 hours. JIS K
Table 3 shows the ΔE values measured by 7105. This shows that the hot water resistance of the material to which phosphoric acid was added is particularly excellent.

[0026]

[Table 3]

[0027]

Effects of the Invention: Acrylic artificial marble produced by cast molding, especially when the slope of the mold surface is close to horizontal, suffers from warping and other problems because the inorganic powder used as a filler settles and separates during cast molding. Prone to defects. To prevent this, fine silica powder is added to impart thixotropy, but this method has the disadvantage of poor workability because the fine silica powder is bulky and very difficult to handle. there were. In contrast, the method of the present invention prevents sedimentation of inorganic powder and makes it possible to produce products without defects such as warping by simply adding water or an aqueous acid solution to the slurry. It has good workability and is useful. Furthermore, the addition of water may cause the product to become discolored; however, in this invention, by using an acid aqueous solution instead of water, this can be prevented.Furthermore, by using phosphoric acid as the acid, the product can be heat resistant. It is also possible and advantageous to improve water performance.

Claims (3)

[Claims] Claim 1: 20-80% by weight of an unsaturated monomer mainly composed of methyl methacrylate and 80-20% by weight of an inorganic powder.
A method for producing acrylic artificial marble, which comprises polymerizing and curing a slurry consisting of the following in the presence of 0.01 to 1 part by weight of water based on 100 parts by weight of the slurry. 2. 20-80% by weight of an unsaturated monomer mainly composed of methyl methacrylate and 80-20% by weight of an inorganic powder.
An acid aqueous solution consisting of 0.01 to 1 part by weight of water, 0.01 to 1 part by weight of water, and 0.01 to 1 part by weight of acid is added to 100 parts by weight of the slurry. A method for producing acrylic artificial marble characterized by polymerization and hardening in coexistence. [Claim 3] Claim 2, wherein the acid aqueous solution is a phosphoric acid aqueous solution.
Manufacturing method described.