JP3156341B2 - Methacrylic resin composition for injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methacrylic resin composition having excellent processability. In particular, the present invention relates to a methacrylic resin composition having excellent releasability during molding using a mold.

[0002]

2. Description of the Related Art Methacrylic resins make use of transparency, weather resistance, and good mechanical properties, which are excellent in their inherent properties, such as automobile parts such as meter covers, optical parts such as optical disks and lenses, and electric light covers. It is used for lighting parts etc. These molded products are generally obtained by injection molding, injection compression molding, etc., but in precision mold molding such as optical lenses and optical disks, the adhesion between the molded product and the mold surface is extremely high. As a result, mold release failure occurs, resulting in a decrease in productivity.

[0003] Therefore, it has been proposed to include various release agents in a methacrylic resin. For example, JP-A-61-737
No. 54 proposes a resin composition obtained by adding a polyhydric alcohol, a higher fatty acid ester, a higher alcohol, a higher fatty acid, a higher fatty acid amide, and a higher fatty acid metal salt to a methacrylic resin.

[0004]

However, when injection molding is performed with these resin compositions, a certain degree of mold release performance is recognized, but not yet sufficient. In addition, the added release agent and other additives migrate to the surface of the resin, thereby contaminating the surface of the mold or the surface of the molded product or causing coloring of the molded product, thereby significantly lowering the commercial value of the molded product.

[0005] The present invention provides a methacrylic resin composition which overcomes the drawbacks of the conventional release agents and exhibits an excellent release effect with a smaller amount.

[0006]

According to the present invention, a glycerin monoester of a higher fatty acid having 10 to 22 carbon atoms and a glycerin monoester of a higher fatty acid having 10 to 22 carbon atoms are added to 100 parts by weight of a methyl methacrylate polymer. 10/90 to 90/10
And a methacrylic resin composition for injection molding comprising 0.02 to 0.5 parts by weight.

The methyl methacrylate polymer referred to in the present invention is a homopolymer of methyl methacrylate, or methyl methacrylate and 20% by weight or less of an acrylate or methacrylate, acrylic acid, methacryl It refers to a copolymer with an acid, styrene, acrylonitrile, or a diene rubber, glutaric anhydride, glutarimide, or the like. Note that acrylates include methyl acrylate, ethyl acrylate, butyl acrylate, and the like, and methacrylates include ethyl methacrylate, butyl methacrylate, and cyclohexyl methacrylate.

The higher fatty acid amide having 10 to 22 carbon atoms of the present invention includes, for example, lauric amide, palmitic amide, stearic amide, oleic amide, erucic amide, N-oleyl stearamide and the like.

If the higher fatty acid amide has less than 10 carbon atoms, it has high volatility and volatilizes during molding, and a sufficient releasing effect cannot be obtained. On the other hand, those having more than 22 carbon atoms are not preferable because they have a low compatibility with the methyl methacrylate-based polymer and thus easily appear on the resin surface, causing mold stains and molded article stains.

The glycerin monoester of a higher fatty acid having 10 to 22 carbon atoms according to the present invention includes, for example, monoglyceride laurate, monoglyceride palmitate, monoglyceride stearate, monoglyceride oleate and monoglyceride behenate.

The higher fatty acid glycerin monoester having a higher fatty acid having less than 10 carbon atoms has a high volatility and volatilizes during molding, so that a sufficient releasing effect cannot be obtained. On the other hand, those having more than 22 carbon atoms are not preferable because they have a low compatibility with the methyl methacrylate-based polymer and thus easily appear on the resin surface, causing mold stains and molded article stains.

In the present invention, the higher fatty acid amide and the glycerin monoester of the higher fatty acid are 10/10
90-90 / 10, preferably 25 / 75-75 / 2
By using at a ratio of 5, a remarkable synergistic effect appears. The ratio is selected within the range according to the composition, molecular weight, fluidity and the like of the methyl methacrylate polymer used. If the amount of the higher fatty acid amide is too large, the molded article is undesirably colored.

The total amount of the higher fatty acid amide and the higher fatty acid glycerin monoester is 0.02 to 0.5 part by weight, preferably 0.05 to 0.2 part by weight, per 100 parts by weight of the methyl methacrylate polymer. Parts by weight. If the total amount is less than 0.02 parts by weight, the release performance is insufficient, and the surface layer of the molded product is easily peeled or cracked. On the other hand, when the addition amount exceeds 0.5 parts by weight, the molded article is colored, and an excessive release agent adheres to the mold surface, and the mold is undesirably stained and contaminated. .

In order to make the methyl methacrylate polymer used in the present invention contain the higher fatty acid amide and the glycerin monoester of the higher fatty acid, a well-known method can be used. For example, there is a method in which each component is kneaded in a molten state. The melt kneading is not only a method using a kneading apparatus such as a commonly used single-screw or twin-screw extruder or various kneaders, but also an injection method. There is a method of directly kneading during a melt processing operation such as molding or extrusion molding.

Further, the higher fatty acid amide and the glycerin monoester of the higher fatty acid are added to a monomer or syrup containing methyl methacrylate as a main component, and the mixture is subjected to bulk polymerization, suspension polymerization, or the like. There is a known polymerization method such as an emulsion polymerization method or a solution polymerization method.

The methacrylic resin composition of the present invention contains a known antioxidant such as a hindered phenol antioxidant, a phosphorus antioxidant and a sulfur antioxidant, an ultraviolet absorber and a hindered amine type light. Weathering agents such as stabilizers,
Flame retardants, coloring agents, pigments, and the like can be added, and depending on the purpose, reinforcing fibers such as glass fibers, inorganic fillers, and the like can also be added.

[0017]

The methacrylic resin composition of the present invention is
Compared with a conventional methacrylic resin, it has excellent release properties when molded using a mold, and also has excellent transparency and weather resistance inherent to a methacrylic resin. Therefore,
It is suitable for molding a molded article having a complicated shape such as an automobile part such as a meter cover, an optical part such as a video disk and a lens, a lighting part, and an OA equipment part using a mold.

[0018]

The present invention will be further described with reference to the following examples. The evaluation method used in the examples is as follows.・ Release property: 25 mm × 76.5 mm × 3 in an injection molding machine (M-140SJ type manufactured by each machine) having a capacity of 13 oz.
A 2 mm ASTM test piece mold was attached, and the molding temperature was 260
° C., injection pressure 80 kg / cm ² G, under the conditions of mold temperature 60 ° C., 60 seconds cycle, have created a continuous 40 times the test piece.
At this time, it was represented by the ratio of the number of defective products such as cracks and cracks in the molded product. -Stainability: The state of fogging on the mold surface (mirror surface) immediately after the completion of the above-mentioned molding was visually observed. -Appearance: The stain and coloring of the molded product were visually observed.

Example 1 100 parts of a granular methacrylic resin (SUMIPEX BLO, manufactured by Sumitomo Chemical Co., Ltd.) obtained by suspension polymerization, 0.025 parts of stearamide and 0.025 parts of monoglyceride stearate Was mixed with a Henschel mixer, and then pelletized using a vent-type extruder having a screw diameter of 40 mm. The pellet was evaluated. Table 1 shows the obtained results.

Examples 2 to 5 and Comparative Examples 1 to 4 Example 1 was repeated except that the amounts of stearamide and stearic acid monoglyceride were changed as shown in Table 1.
The same was done. Table 1 shows the obtained results.

Example 6 The procedure of Example 2 was repeated, except that palmitic amide was used instead of stearamide. Table 1 shows the obtained results.

Example 7 The procedure of Example 2 was repeated except that monoglyceride palmitate was used instead of monoglyceride stearate. Table 1 shows the obtained results.

[0023]

[Table 1]

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 33/12 C08K 5/10 C08K 5/20

Claims (1)

(57) [Claims] 1. A higher fatty acid amide having 10 to 22 carbon atoms and 1 carbon atom in 100 parts by weight of a methyl methacrylate polymer.
A methacrylic resin composition for injection molding, comprising 0 to 22 glycerin monoester of higher fatty acid in a weight ratio of 10/90 to 90/10 and containing 0.02 to 0.5 part by weight.