JPH0116245B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a casting composition, more specifically a heat resistant composition,
The present invention relates to a casting composition for obtaining methyl methacrylate resin molded articles having good surface hardness, chemical resistance, and transparency. Over the past few years, the theme of reducing the weight of various industrial materials has been given with the goal of saving energy and resources, and the use of resin for metal and inorganic parts has been considered, but inorganic glass has traditionally been used. The use of resin is also being considered for lighter weight and safety reasons, even in applications such as Among these, molded products made from methyl methacrylate resin by casting and extrusion methods have excellent transparency that is said to surpass that of glass, as well as excellent weather resistance, mechanical strength, and
It is mainly being studied because it has excellent electrical insulation properties. However, although this methyl methacrylate resin molded product has the excellent characteristics mentioned above, it has the disadvantage of insufficient heat resistance and
Heating above ℃ may cause thermal decomposition or
Thermal deformation occurs even at low temperatures such as 110℃,
It has been pointed out that the surface hardness is low and it is easily scratched, and that the chemical resistance is insufficient and the surface is easily attacked by organic solvents such as acetone, causing loss of gloss and transparency. As a method to improve these drawbacks, a polyfunctional acrylic ester compound such as ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate or a polyfunctional allyl compound such as diallyl phthalate is mixed and dissolved in methyl methacrylate, and the mixture is dissolved. Although it is widely known to obtain molded products by casting and polymerizing, even with this method, it is not possible to obtain products with sufficiently improved heat resistance and surface hardness. In particular, when a polyfunctional allyl compound is used, the transparency of the methyl methacrylate resin is likely to be impaired. Due to these drawbacks, the applications in which methyl methacrylate resin compositions can be used are limited. The present invention solves these drawbacks of methyl methacrylate resin and provides a casting composition for obtaining molded products with good heat resistance, surface hardness, chemical resistance, and transparency. That is, the present invention contains (a) 5 to 25% by weight of an ester compound of acrylic acid or methacrylic acid of tris(hydroxyalkyl)isocyanurate, and (b) 95 to 75% by weight of a monomer whose main component is methyl methacrylate. This invention relates to a casting composition. The ester compound of acrylic acid or methacrylic acid of tris(hydroxyalkyl)isocyanurate used in the present invention can be easily obtained by subjecting tris(hydroxyalkyl)isocyanurate and acrylic acid or methacrylic acid to an esterification reaction using a conventional method. can be obtained. Examples of the above tris(hydroxyalkyl)isocyanurate include tris(2-hydroxyethyl)isocyanurate, tris(2-hydroxypropyl)isocyanurate, tris(3-hydroxypropyl)isocyanurate, among others, tris( Preference is given to using 2-hydroxyethyl) isocyanurate. Tris(hydroxyalkyl)isocyanurate has three hydroxyl groups in one molecule, and it is preferable that an average of 1.8 or more of these hydroxyl groups are esterified.
If the number is less than 1.8, the effect of improving heat resistance and chemical resistance may not be sufficient. Furthermore, from the viewpoint of compatibility with methyl methacrylate, weather resistance of the obtained molded product, etc., ester compounds of methacrylic acid are particularly preferable compared to esters of acrylic acid. Tris(hydroxyalkyl) used in the present invention
The amount of the acrylic acid or methacrylic acid ester compound of isocyanurate used is 5 to 25% by weight, particularly preferably 10 to 20% by weight. If the amount used is less than 5% by weight, the surface hardness is slightly improved, but the heat resistance and chemical resistance are not sufficiently improved. In addition, if the amount exceeds 25% by weight, the heat resistance, chemical resistance, surface hardness, etc. of the resin obtained will be sufficiently improved, but the resin will become cloudy and the transparency, which is a characteristic of methyl methacrylate resin molded products, will be obtained. is damaged. Heat resistance, surface hardness, and chemical resistance are particularly improved when the amount used is 10% by weight or more. Further, in order to obtain a molded product with excellent transparency, it is particularly preferable that the amount of the ester compound used is 20% by weight or less. The monomer mainly composed of methyl methacrylate used in the present invention is a methyl methacrylate monomer alone or a mixture with other monomers.
Other monomers include, for example, acrylic ester compounds such as ethyl acrylate, ethylene glycol diacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, trimethylolpropane triacrylate, glycerin diacrylate, similar methacrylic ester compounds, styrene, and acetic acid. Vinyl, etc. may be used in an amount of 50% by weight or less based on the total amount of methyl methacrylate and other monomers. However, the above-mentioned component (a) is excluded from such monomers.
If it exceeds 50% by weight, the properties of the methyl methacrylate resin will deteriorate. Particularly preferably 30% by weight
Used below. In addition, polymers soluble in methyl methacrylate, such as polystyrene, polyvinyl chloride, acrylic rubber, etc., may be used, but these should not exceed 30% by weight of the monomer whose main component is methyl methacrylate. is preferred. Hydroquinone, hydroquinone monomethyl ether, benzoquinone, catechol, and the like may be used as polymerization inhibitors in the casting composition of the present invention, but those that cause coloration during the curing process are not preferred. There are no particular limitations on the method of curing the casting composition in the present invention, including radiation irradiation, light irradiation,
Although a heating method, a catalytic method, etc. can be applied, the catalytic method commonly used for curing methyl methacrylate is particularly preferred since it is easy to operate. In this case, the catalyst used is, for example, a radical polymerization catalyst such as benzoyl peroxide, azobisisobutyronitrile, or lauryl peroxide. The amount of catalyst used is usually 0.01% to 1% by weight based on the composition.
It is. If the amount is less than this, the time required for polymerization becomes too long. In addition, if the amount is too large, the polymerization reaction may become intense, resulting in cloudy or foamy phenomena and a decrease in transparency. Furthermore, the mechanical strength, electrical insulation properties, etc. of the resulting molded product may be adversely affected. The curing temperature in this case varies depending on the type and amount of catalyst, but is in the range of room temperature to 150°C. In particular, if the polymer is polymerized at room temperature to 80°C for 1 to 20 hours and then held at 80 to 150°C for 1 to 20 hours to ensure complete curing, a resin molded product with high surface hardness can be obtained. easy. A molded article can be obtained by casting and curing a mixture of the casting composition of the present invention and a curing catalyst. If prepolymerization is carried out at ~100°C for about 10 minutes to 1 hour, then cast and cured, the shrinkage rate can be reduced and the appearance of the molded product will be good. Casting involves adding a curing catalyst if necessary to the casting mixture, or injecting the prepolymerized mixture into a molding frame made of glass, metal, etc., taking care not to introduce air bubbles. This is done by If necessary, after casting, the entire casting frame may be degassed in a reduced pressure atmosphere. Moreover, if necessary, various mold release agents may be applied to the inside of the casting frame. Depending on the shape of the casting frame, the shape of the molded product obtained by curing can be made into a desired shape. Various other additives may be added if necessary, but additives that impair transparency are not preferred. The molded product obtained from the casting composition of the present invention has good heat resistance, surface hardness, chemical resistance, and transparency, whereas conventional methyl methacrylate resin molded products lack heat resistance, surface hardness, etc. It can also be used in applications where glass products are used, such as Fresnel lenses used in overhead projectors, optical disk memory materials, liquid crystal display covers, watch dial covers, and optical lenses. be. Next, examples of the present invention will be shown. Production example Synthesis of tris(2-hydroxyethyl)isocyanurate trimethacrylate ester Tris(2-hydroxyethyl)isocyanurate 261g, methacrylic acid 284g, p-toluenesulfonic acid 26g, phenothiazine 0.12g, toluene
600 g was charged into a flask equipped with a stirrer, a thermometer, a water separator, and an air inlet tube, and the reaction was carried out under reflux while blowing a small amount of air, while separating the produced water from the system. After 8 hours, almost the theoretical amount of water had flowed out, so the reaction system was cooled, washed with an aqueous solution containing 2% by weight of ammonia and 20% by weight of ammonium sulfate, and then with an aqueous solution containing 20% by weight of ammonium sulfate, and then washed with an aqueous solution containing 20% by weight of ammonium sulfate. Toluenesulfonic acid and unreacted methacrylic acid were removed. Toluene was distilled off to obtain 420 g of tris(2-hydroxyethyl)isocyanurate methacrylate. This was heated and dissolved in 500 ml of methanol, and after decolorizing by adding activated carbon, the activated carbon was removed by hot filtration and cooled, and tris (2-hydroxyethyl) isocyanurate methacrylate was recrystallized and purified from the methanol solution. . When this was analyzed by gel chromatography, it was found that Tris(2-
Contains more than 97% by weight of (hydroxyethyl) isocyanurate trimethacrylic acid ester, and has a melting point of 83
It was ~84℃. Examples 1 to 5 Tris(2-hydroxyethyl)isocyanurate trimethacrylate synthesized in Production Example was added to methyl methacrylate in the amount shown in Table 1.
and the amount of azobisisobutyronitrile shown in
0.05 part by weight was added and completely dissolved. This was placed in a flask and prepolymerized at 80 to 100℃ for about 20 minutes while stirring, then a silicone rubber round rod was sandwiched between two glass plates and fixed with a clasp. It was poured into a cell and allowed to stand at 50°C for 12 hours to polymerize and harden. Thereafter, the cured product was held at 80°C for 2 hours and then at 120°C for 2 hours to complete polymerization. Table 1 shows the appearance, chemical resistance, heat distortion temperature, Vicat softening point, Barcol hardness, and mechanical strength of the obtained cured product. Comparative Example 1 A cured product was obtained in exactly the same manner as in Example 1, except that 2 parts by weight of tris(2-hydroxyethyl)isocyanurate trimethacrylate obtained in Production Example was used in 98 parts by weight of methyl methacrylate.
Table 1 shows various properties of the cured product. Comparative Example 2 A cured product was obtained in exactly the same manner as in Example 1, except that 30 parts by weight of tris(2-hydroxyethyl)isocyanurate trimethacrylate obtained in Production Example was used in 70 parts by weight of methyl methacrylate. . Table 1 shows the properties of the cured product. Comparative Example 3 10 parts by weight of ethylene glycol dimethacrylate and 0.05 parts by weight of azobisisobetyronitrile were added and dissolved in 90 parts by weight of methyl methacrylate, and a cured product was obtained by the same operation as in Example 1.
Table 1 shows various properties of the cured product. Comparative Example 4 10 parts by weight of trimethylolpropane trimethacrylate and 0.05 parts by weight of azobisisobutyronitrile were added and dissolved in 90 parts by weight of methyl methacrylate, and a cured product was obtained by the same operation as in Example 1. Table 1 shows various properties of the cured product. Comparative Example 5 0.05 parts by weight of azobisisobutyronitrile was added and dissolved in 100 parts by weight of methyl methacrylate, and a cured product was obtained in the same manner as in Example 1. Table 1 shows various properties of the cured product.

【table】

[Table] As is clear from the Examples and Comparative Examples, the resin cured product of the casting composition of the present invention is a cured product of methyl methacrylate alone, and other monomers such as ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate. Compared to the cured resin obtained by blending the resin, it has superior heat resistance, surface hardness, and chemical resistance, and has a similar level of transparency in appearance. Furthermore, as the content of tris(2-hydroxyethyl)isocyanurate trimethacrylate ester increases, the rigidity of the resin tends to increase. When the casting composition according to the present invention is cured, it becomes a cured product with excellent heat resistance, surface hardness, chemical resistance, and transparency in appearance.

Claims (1)

[Scope of Claims] 1 Contains (a) 5 to 25% by weight of an ester compound of acrylic acid or methacrylic acid of tris(hydroxyalkyl)isocyanurate, and (b) 95 to 75% by weight of a monomer whose main component is methyl methacrylate. A composition for casting. 2. The casting composition according to claim 1, comprising 10 to 20% by weight of component (a) and 90 to 80% by weight of component (b). 3 The ester compound of acrylic acid or methacrylic acid of tris(hydroxyalkyl)isocyanurate has an average of 1.8 or more of the three hydroxyl groups in one molecule of tris(hydroxyalkyl)isocyanurate being acrylic acid or methacrylic acid. The casting composition according to claim 1 or 2, which is an esterified ester compound.