JPH0827359A - Melamine/phenol resin composition - Google Patents

Abstract

PURPOSE:To obtain a resin composition which can give a molding being excellent in tracking resistance and showing very good dimensional stability even when used at high temperatures. CONSTITUTION:This composition is prepared by mixing 100 pts.wt. melamine resin having a number-average molecular weight of 180-400 with 10-50 pts.wt. dimethylene ether-type resol resin containing 20-70mol% dimethylene ether bonds and having a number-average molecular weight of 500-1000 and 1-15 pts.wt. vinyl acetate resin having a degree of polymerization of 100-5000.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a molding material used for wiring equipment, electric appliances and the like. The object of the present invention is to obtain extremely good dimensional stability even when used at high temperature and to prevent cracks. It is intended to provide a melamine phenol resin composition suitable as a molding material for obtaining a molded product that hardly occurs.

[0002]

2. Description of the Related Art Melamine resin molding materials are used for wiring equipment, electric equipment, etc. due to their excellent tracking resistance, electric insulation, coloring, etc. Since the ratio is high, molded products are liable to crack, crack, warp, etc.
There is a problem in terms of crack resistance. In order to improve such a defect, a conventional melamine resin is usually added with a resol-type solid or liquid phenol resin mainly containing a methylol group to an extent that the tracking resistance and the coloring property are not impaired. . Although this material has a smaller dimensional change rate than a material containing only melamine resin, the present situation is that a sufficient dimensional change rate is not obtained as compared with a phenol resin molding material.

Further, an example in which a conventional polyvinyl butyral resin is added to a melamine / phenol resin composition (Japanese Patent Laid-Open No. Hei 4)
-65453). Although this material also has a smaller molding shrinkage than the material containing only melamine / phenol resin, it cannot be said to be sufficient, and it is the current situation that a sufficient molding shrinkage has not been obtained in comparison with a phenol resin molding material. By adding a large amount of an inorganic filler to the melamine resin, the molding shrinkage rate is improved, but the dimensional change rate after the heat treatment is not sufficient and the specific gravity is large.

Since the dimensional change rate is large as described above, the melamine resin molding material is rarely used for precision moldings which require high dimensional accuracy. Therefore, the melamine resin molding material does not need to have a high degree of dimensional accuracy, and is currently used only for applications in which electrical properties such as foods and foods that are required to have tracking resistance are absolutely necessary.

[0005]

The object of the present invention is to blend a specific phenol resin and a specific vinyl acetate resin at a high temperature without deteriorating tracking resistance and other properties. Another object of the present invention is to provide a melamine / phenolic resin composition which has excellent dimensional stability even when used and is hardly cracked, and which is used as a molding material.

[0006]

According to the present invention, 20 to 70 mol% of dimethylene ether bonds are contained in 100 parts by weight of melamine resin having a methylolation degree of 1.0 to 3.0 and a number average molecular weight of 180 to 400. 10 to 50 parts by weight of a dimethylene ether type resole resin having an average molecular weight of 500 to 1000,
It is a melamine-phenol resin composition characterized by being blended with 1 to 20 parts by weight of a vinyl acetate resin having a degree of polymerization of 100 to 5000.

The phenolic resin used in the present invention is a resol type phenolic resin containing a lot of dimethylene ether bonds and dehydrated and condensed by this thermal decomposition. The dimensional stability of a melamine / phenolic resin molding depends on the shrinkage action that occurs with the curing of the melamine / phenolic resin molding material. Since the melamine resin has 6 functional groups, which is greater than the phenol resin having 3 functional groups, the melamine resin component has a greater shrinkage during crosslinking. The dimethylene ether type resole resin used in the present invention has a longer internuclear distance between the phenol nuclei and the phenol nuclei than the conventionally used phenol resins mainly containing methylene groups and methylol groups, and has a methylene group of 2.8. A dimethylene ether group is 5.0 to 5.8 angstroms with respect to ˜3.0 angstrom, and the curing shrinkage of the melamine resin is moderated by blending the dimethylene ether type resole resin having a long bond complex.

At the same time, the vinyl acetate resin to be blended with the melamine resin is not particularly limited, but a powdery resin having a degree of polymerization of 100 to 5000 is preferable. That is, if the degree of polymerization is less than 100, sufficient flexibility with the melamine / phenol resin cannot be obtained, and if it exceeds 5,000, the compatibility decreases and sufficient effects cannot be obtained.

The amount of the phenol resin blended is preferably 10 to 50 parts by weight with respect to 100 parts by weight of the melamine resin. If it is less than 10 parts by weight, improvement in dimensional stability and insert crack resistance is not observed, and if it exceeds 50 parts by weight, tracking resistance is deteriorated. The vinyl acetate resin content is preferably 1 to 15 parts by weight with respect to 100 parts by weight of the melamine resin. If it is less than 1 part by weight, flexibility, which is one of the properties of the vinyl acetate resin, is not imparted, so that improvement in dimensional stability and insert crack resistance is not observed, and if it exceeds 15 parts by weight, heat resistance becomes poor.

Melamine resin for producing molding materials,
Raw materials used together with the phenol resin and vinyl acetate resin are a filler, a curing agent, a coloring agent, a release agent and the like. The melamine resin used in the present invention may be modified with an epoxy resin, rubber or the like. Further, a part of the melamine resin may be replaced with a urea resin or the like. In the method for producing a molding material using the melamine / phenol resin composition, kneading may be carried out by a usual mixing roll or a twin-screw extrusion kneader, or granulation may be carried out by a high-speed rotary mixer.

The molding method for obtaining a molded product using the molding material from the melamine / phenol resin composition according to the present invention is applicable to any of injection molding, transfer molding, compression molding and the like, and is not limited. .

[0012]

EXAMPLES The raw materials shown in Table 1 were kneaded in a predetermined composition with a mixing roll and pulverized to produce a molding material. Molding shrinkage, post-shrinkage after 24-hour after-baking, tracking resistance (CTI) and flexural modulus according to JIS K 6911 were measured for the obtained molding material.

[0013]

[Table 1] * 1: Methylolation degree 1.70, number average molecular weight 300 * 2: Dimethylene ether group 50 mol%, methylol group 15%, number average molecular weight 750 * 3: Degree of polymerization 5000

When a dimethylamine ether type resole resin and a vinyl acetate resin are blended with a melamine resin as in the examples, flexibility is imparted, and a molded article having excellent dimensional stability even when used at high temperature is obtained. I understand.

[0015]

EFFECTS OF THE INVENTION The resin composition of the present invention is excellent in tracking resistance and can be used to obtain a molded article having excellent dimensional stability even when used at high temperatures. Therefore, it is excellent in tracking resistance, which could not be produced in the past, and a molded product for use especially at high temperatures can be easily manufactured, and thus it is suitable as an industrial melamine / phenol resin molding material.

Claims (1)

[Claims] 1. A dimethylene ether bond is added to 100 parts by weight of a melamine resin having a number average molecular weight of 180 to 400.
Number average molecular weight containing 0 to 70 mol% 500 to 100
0 to 50 parts by weight of dimethylene ether type resole resin of 0 and vinyl acetate resin of 1 to 1 having a polymerization degree of 100 to 5000
A melamine / phenolic resin composition characterized by being mixed with 5 parts by weight.