JPH0530364B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a plastic cast molded article containing a filler having a high degree of whiteness and a constant degree of whiteness. (Prior art) Plastic cast-molded products containing fillers obtained by casting a slurry of a curable liquid material containing fillers are used as artificial marble products for various tabletops, countertops, and toiletries. Widely used for tables, sinks, bathtubs, shower trays, waterproof pans, flooring materials, wall materials, partition boards, arts and crafts, etc. However, plastic cast molded products containing fillers may be colored yellow depending on the lot, so the color tone of the product is not uniform, it is difficult to manufacture products with a high degree of whiteness, and the color tone of colored products. The problem is that it is limited. For these, a method of adjusting the color for each lot can be considered, but
In reality, it is rarely used because it is expensive, and adding titanium oxide to increase whiteness deteriorates transparency, resulting in loss of depth and luxury depending on the type. Differences in color tones between lots are especially noticeable when artificial marble products are used together, so as a countermeasure, we try to use products from the same lot, but lot management is complicated and the products are always the same. There is no guarantee that lot products will be available. (Problems to be Solved by the Invention) The present invention prevents yellowing of plastic cast molded products containing fillers and eliminates differences in color tone between lots, and at the same time provides excellent whiteness and coloring. The purpose of the present invention is to provide a method for manufacturing artificial marble easily and inexpensively with a large degree of freedom. (Means for Solving the Problems) The inventors of the present invention have made intensive studies to solve the above problems, and have thus come up with the present invention. That is, when a slurry of a curable liquid material containing a filler is cast-molded to produce a plastic cast-molded article containing a filler, surprisingly,
It was discovered that a simple and inexpensive method of adding 0.001 to 5% by weight of acid can prevent yellowing and eliminate differences in color tone between lots. The reason for this is not clear, but plastic cast molded products contain stabilizers, mold release agents, polymerization initiators,
Contains various additives such as polymerization regulators, and the addition of acid can prevent them from turning yellow due to fillers, impurities contained therein, or alkaline substances in various additives. It is presumed that this can be prevented by neutralizing or acidifying the The plastic cast-molded product containing a filler as used in the present invention is produced by pouring a mixed slurry of a curable liquid material and a filler into a mold, which can be cured by addition polymerization, ring-opening polymerization, introduction of cross-linking, etc. It was introduced and cured. Specific examples of curable liquid materials include:
Esters of monohydric alcohols having 1 to 18 carbon atoms and acrylic acid or methacrylic acid, olefinic nitriles such as acrylonitrile and methacrylonitrile, styrene and α-methylstyrene, P-
Aromatic unsaturated compounds such as methylstyrene and divinylbenzene, vinyl esters such as vinyl acetate and vinyl benzoate, olefinic amides such as acrylamide and methacrylamide, ethylene glycol, polyethylene glycol, polypropylene glycol, 1,3-butanediol, Neobentyl glycol, 1,6-hexanediol,
Polyesters of polyhydric alcohols such as trimethylolethane, trimethylolpropane, tetramethylolmethane, pentaerythritol and dipentaerythritol with acrylic acid and methacrylic acid, allyl compounds such as diallylphthalate and triallylcyanurate, unsaturated polyester resins, Examples include, but are not limited to, vinyl ester resin, liquid epoxy resin, liquid phenolic resin, liquid mixture providing polyurethane, liquid rubber, liquid silicone rubber, and the like. Note that it is also possible to use a mixture of two or more types of curable liquid materials. Further, the curable liquid material can be used as a syrup by partially proceeding with the curing reaction, or by dissolving a polymer. Among various artificial marble products, methacrylic resin-based products have recently been in the spotlight as high-quality products, and the requirements for whiteness and color blurring are also strict. Useful. Note that the methacrylic curable liquid referred to here refers to a curable liquid in which 50% by weight or more is methyl methacrylate, but a portion of methyl methacrylate may be made into a polymer in order to make syrup. . The filler used in the present invention is not particularly limited, and aluminum hydroxide, aluminum oxide, calcium carbonate, calcium silicate, calcium aluminate, calcium sulfate, calcium hydroxide, magnesium hydroxide, and bases are commonly used as fillers. Examples include, but are not limited to, powders of magnesium carbonate, silica, talc, clay, glass, wood, and the like. Two or more types of fillers may be used in combination. The particle size of the filler is suitably 200 μm or less, more preferably 50 μm or less. Among fillers, basic fillers such as aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, calcium hydroxide, and glass often cause yellowing of plastic cast molded products. The technique according to the present invention is particularly effective when used. The amount of filler added is between 20 and 80% by weight, based on the total weight of the plastic casting. If the amount added is less than 20% by weight, the effect of the addition will be small, and if it exceeds 80% by weight, the viscosity of the slurry will become high and it will be difficult to introduce it into the mold, which is not preferable. There are no particular restrictions on the method of mixing the curable liquid material and the filler to obtain the slurry, and any method may be used, such as mixing the two in a tank equipped with a stirrer or in a kneader. The acid used in the present invention is soluble in a curable liquid and has a solubility in water of 1% by weight at 25°C.
The content should preferably be 10% by weight or more. Therefore, stearic acid and the like, which have been conventionally added to curable liquid materials as a mold release agent, have low solubility in water and are therefore not effective in preventing yellowing. Examples of acids that meet the above conditions include formic acid, acetic acid,
Aliphatic saturated carboxylic acids such as chloroacetic acid, fluoroacetic acid, propionic acid, butyric acid, valeric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, acrylic acid, crotonic acid, methacrylic acid, propiolic acid, maleic acid, fumaric acid,
Aliphatic unsaturated carboxylic acids such as itaconic acid, oxycarboxylic acids such as glycolic acid, lactic acid, tartaric acid, citric acid, malic acid, acid anhydrides such as acetic anhydride and maleic anhydride, inorganic acids such as phosphoric acid and carbonic acid, acidic Phosphate sester, P-trienesulfonic acid, L-
Examples include, but are not limited to, ascorbic acid and phenols. Among these acids, formic acid, acetic acid, chloroacetic acid, fluoroacetic acid, malonic acid, glutaric acid, acrylic acid, methacrylic acid, maleic acid, glycolic acid,
Lactic acid, tartaric acid, citric acid, malic acid, acetic anhydride,
Phosphoric acid, P-toluenesulfonic acid and the like having high solubility in water are preferred, and formic acid, acetic acid, acetic anhydride, acrylic acid, methacrylic acid, P-toluenesulfonic acid and the like are particularly preferred. It is also possible to use two or more types of acids in combination. Note that when an unsaturated carboxylic acid is used, mold releasability may deteriorate, but this can be resolved by appropriately changing the mold material and mold release material. The amount of acid added to the plastic cast molded article containing the filler, i.e., the amount added to the slurry, is the amount necessary to neutralize or acidify the slurry, which is usually 0.001 to 5% by weight of the slurry, preferably It is 0.01 to 2% by weight, more preferably 0.05 to 0.5% by weight. If the amount of acid is less than 0.001% by weight, the effect of preventing yellowing will be poor, and if it exceeds 5% by weight, it will not only be economically disadvantageous but also undesirable because properties such as heat resistance, weather resistance, and strength will deteriorate. . Note that it is often more effective to add the acid to the curable liquid before the filler than the reverse order. The slurry obtained in the present invention is directly injected into a mold and cured, but the mold according to the present invention includes not only closed cell devices, closed cell devices, open molds, etc., but also continuous pour molding devices. It is something that The method for curing the curable liquid material according to the present invention is not particularly limited, and any method suitable for curing the curable liquid material, such as addition polymerization, ring-opening polymerization, and introduction of crosslinking bonds, can be employed. Examples include heating in the presence or absence of a radical polymerization initiator, a method using a so-called redox system consisting of a radical polymerization initiator and an accelerator, and a method of irradiating ultraviolet rays or radiation. It is not limited. Examples of radical polymerization initiators include azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile), diisopropyl peroxydicarbonate, di(methoxy isopropyl) peroxydicarbonate,
t-Butyl peroxyneodecanoate, lauroyl peroxide, benzoyl peroxide, 2,2
Examples include, but are not limited to, peroxides such as -bis(t-butylperoxy)butane. The radical polymerization initiator is used in an amount of 0.005 to 3% by weight, preferably 0.01 to 1% by weight, based on the curable liquid material. It is also possible to use two or more types of radical polymerization initiators in combination. In addition to the above-mentioned components, the plastic cast-molded product containing the filler of the present invention includes a facial cleanser,
It is also possible to include reinforcing agents, modifiers, stabilizers, mold release agents, flame retardants, and the like. Among the various artificial marble products explained above, a methacrylic resin injection filled with aluminum hydroxide powder is obtained from a mixed slurry of a methacrylic hardening liquid containing 50% by weight or more of methyl methacrylate and aluminum hydroxide powder. Since molded products are considered to be of the highest quality and are used in various interior products, there are even more stringent requirements for stable color tone and high whiteness. Therefore, the technology related to the present invention is most effective for methacrylic resin-based artificial marble filled with aluminum hydroxide powder. As described above, the methacrylic curable liquid may be a syrup obtained by replacing a portion of methyl methacrylate with a methacrylic resin. (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 30 ppm of hydroquinone was added to a monomer mixture consisting of 30.4 parts by weight of methyl methacrylate and 2 parts by weight of trimethylolproban trimethacrylate.
7.6 parts by weight of methacrylic resin beads (Parabeads HR, manufactured by Kyowa Gas Kagaku Kogyo Co., Ltd.) were added and dissolved while stirring at a temperature of 0.degree. C. to obtain a syrup. Add 2-(2'-
Hydroxy-5′-methylphenyl)benzotriazole 0.1 part by weight, lauroyl peroxide 0.1
Parts by weight, 1,1-bis(t-butylperoxy)
- Add and dissolve 0.05 parts by weight of 3,3,5-trimethylcyclohexane and the amount of acid shown in Table 1,
Next, aluminum hydroxide powder (Hygilite H
-310, manufactured by Showa Light Metal Co., Ltd.) were mixed to obtain a slurry. The above slurry was injected into a cell assembled by sandwiching a U-shaped flexible polyvinyl chloride gasket between two glass plates, immersed in a 60°C water bath for 5 hours, and then heated to 120°C. Polymerization was completed by heating in a hot air circulating oven for 2 hours, and the mold was released from the cell to obtain an artificial marble plate with a thickness of 12 mm. However, in the case of Examples 4 and 5, vinylon film was pasted on the surface of a glass plate and cast molding was performed. The above operation was performed once a day for 5 days, and the b value of the Lab color coordinate of the artificial marble board obtained for each batch was measured using the method of JIS K 7105. The results are shown in Table 1. Ta. As is clear from Table 1,
The artificial marble obtained by the technology related to the present invention has substantially no yellowing, has high whiteness, and has extremely small variation.

[Table] Comparative Example 1 The same operation as in Example 1 was carried out without adding acid,
The b values of the artificial marble for each batch are shown in Table 2. As is clear from Table 2, some of the artificial marbles that do not use acid are colored yellow, and the color tone is not stable.

[Table] Example 7 Adding 30 ppm of hydroquinone to a monomer mixture consisting of 32.3 parts by weight of methyl methacrylate and 2 parts by weight of 1,3-butylene glycol dimethacrylate,
Heat to 45℃ and add acrylonitrile while stirring.
Styrene copolymer resin pellets (Sevian N,
020SF (manufactured by Daicel Chemical Industries, Ltd.) was added and dissolved to obtain a syrup. 2-(2'-Hydroxy-5'-methylphenyl)benzotriazole was added to the syrup cooled to room temperature while stirring.
Add and dissolve 0.2 parts by weight, 0.02 parts by weight of 2,2'-azobisisobutyronitrile, 0.05 parts by weight of 2,2-bis(t-butylperoxy)butane, and 0.1 parts by weight of acetic acid, and then dissolve aluminum hydroxide. A slurry was obtained by mixing 60 parts by weight of powder (Hygilite H-310, manufactured by Showa Light Metal Co., Ltd.). Using this slurry, an artificial marble plate with a thickness of 12 mm was obtained by the same operation as in Example 1. Repeat the above operations 5 times in the same way as in Example 1.
B-values of the artificial marble plates for each batch are shown in Table 3. As is clear from this, the artificial marble obtained by the technology related to the present invention has virtually no yellowing, has high whiteness, and has extremely small variations.

[Table] Comparative Example 2 The same operation as in Example 7 was carried out without adding acetic acid, and the b value of the artificial marble for each batch is shown in Table 4. As is clear from this, artificial marble that does not use acid may be colored yellow, and the color tone is not stable.

[Table] (Effects) According to the method of the present invention, artificial marble with a high level of constant whiteness can be obtained by a simple and inexpensive method that only requires adding a small amount of acid. Therefore, since there is no difference in color tone between lots, the joints are not noticeable even when the artificial marble products are joined together, and since the base has a high degree of whiteness, it has the great advantage of being able to be colored in any color. Moreover, since the amount of acid used in the present invention is small, it does not impair various performances required of artificial marble, such as mechanical properties, thermal properties, stain resistance, and weather resistance. Methacrylic resin-based artificial marble, which has been attracting attention as a luxury product in recent years, has stricter requirements for whiteness and color blurring, so the technology related to the present invention is particularly effective in this field. This is especially effective when using basic fillers such as powders of magnesium hydroxide, basic magnesium carbonate, glass, and the like.

Claims (1)

[Scope of Claims] 1. Plastic casting containing a filler, characterized in that 0.001 to 5% by weight of acid is added to the slurry when casting a curable liquid slurry containing the filler. Method of manufacturing molded products. 2. A method for producing a plastic cast molded article containing a filler according to claim 1, wherein the filler is aluminum hydroxide powder. 3. A method for producing a plastic cast molded article containing a filler according to claim 1, wherein 50% by weight or more of the curable liquid is methyl methacrylate. 4. A plastic cast molded article containing a filler according to claim 1, wherein the plastic cast molded article containing a filler is a methacrylic resin cast molded article filled with aluminum hydroxide powder. manufacturing method.