JP3163723B2 - Methacrylic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 at the time of molding using a mold.

[0002]

2. Description of the Related Art A methacrylic resin is used in automobile parts such as meter covers, optical parts such as optical discs and lenses, and electric light covers, etc. by making use of its original properties of excellent transparency, weather resistance and good mechanical properties. Used for lighting parts.
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 that methacrylic resins contain various release agents. For example, JP-A-61-73754
In Japanese Patent Application Publication No. H11-264, a resin composition in which 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 are added to a methacrylic resin is proposed.

[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.

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, 100 parts by weight of a methyl methacrylate-based polymer has the following general formula:

## STR2 ## R ¹ COOR ² (wherein, R ¹ is an aliphatic hydrocarbon group having 10 to 22 carbon atoms,
R ² represents an alkyl group having 1 to 22 carbon atoms) and a glycerin monoester of a higher fatty acid having 10 to 22 carbon atoms in a weight ratio of 10/90 to 90 /
10, 0.02 to 0.5 parts by weight , and if necessary purple
External absorbent, weathering agent, flame retardant, colorant, pigment, reinforced fiber
The present invention also relates to a methacrylic resin composition containing an inorganic filler and containing no other filler .

The methyl methacrylate polymer referred to in the present invention is a homopolymer of methyl methacrylate or methyl methacrylate and not more than 20% by weight of an acrylate or methacrylate, acrylic acid, methacrylic acid, styrene, acrylonitrile. Alternatively, it refers to a copolymer with a diene rubber, glutaric anhydride, glutarimide, and the like. In addition, as the acrylate, methyl acrylate, ethyl acrylate, butyl acrylate, etc.
Examples of the methacrylate include ethyl methacrylate, butyl methacrylate, and cyclohexyl methacrylate.

The higher fatty acid ester represented by the above general formula of the present invention includes, for example, methyl, ethyl, propyl and butyl esters of lauric acid, methyl, ethyl, propyl and butyl esters of palmitic acid, stearic acid Methyl, ethyl, propyl, butyl esters, oleic acid methyl, ethyl, propyl, butyl esters, behenic acid methyl, ethyl, propyl, butyl, behenyl esters, myristate myristyl, stearyl stearate, And the like.

If the fatty acid of the higher fatty acid ester has less than 10 carbon atoms, it has a high volatility and volatilizes during molding, so that a sufficient releasing effect cannot be obtained. On the other hand, fatty acids having more than 22 carbon atoms are not preferred because they have a low compatibility with the methyl methacrylate-based polymer and therefore 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 ester 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.

The total amount of the higher fatty acid ester and the glycerin monoester of the higher fatty acid 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 ester and the glycerin monoester of the higher fatty acid to form a composition, 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 ester and a glycerin monoester of the higher fatty acid are added to a monomer or syrup containing methyl methacrylate as a main component, and mixed.
There is a method of polymerizing this by a known method such as a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, and 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 stabilizer. It is possible to add a weathering agent such as an agent, a flame retardant, a colorant, a pigment and the like, and further, depending on the purpose, a reinforcing fiber such as a glass fiber and an inorganic filler.

[0017]

According to the present invention, the methacrylic resin composition of the present invention has excellent releasability when molded using a mold, and has excellent methacrylic resin inherent properties, as compared with the conventional methacrylic resin. It also has transparency and weather resistance. 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 butyl stearate and 0.025 parts of monoglyceride stearate were used. 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 butyl stearate and monoglyceride stearate 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 stearyl stearate was used instead of butyl stearate. 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]

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08L 33/12 C08K 5/10

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein 100 parts by weight of a methyl methacrylate polymer is represented by the following general formula: R ¹ COOR ² (wherein R ¹ is an aliphatic hydrocarbon group having 10 to 22 carbon atoms,
R ² represents an alkyl group having 1 to 22 carbon atoms) and a glycerin monoester of a higher fatty acid having 10 to 22 carbon atoms in a weight ratio of 10/90 to 90 /
10, 0.02 to 0.5 parts by weight , and if necessary purple
External absorbent, weathering agent, flame retardant, colorant, pigment, reinforced fiber
Or a methacrylic resin composition containing an inorganic filler and no other .