JPH08143753A - Melamine-phenol resin composition - Google Patents

Abstract

PURPOSE: To obtain a melamine-phenol resin compsn. which gives a molding excellent in electrical characteristics (e.g. arc and tracking resistances) and hardly allowing cracks to occur. CONSTITUTION: This resin compsn. is obtd. by compounding 100 pts.wt. melamine resin having a number-average mol.wt. of 180-400 with 10-50 pts.wt. dimethylene- ether resole resin contg. 20-70mol% dimethylene ether bonds and 10-40-mol% methylol groups and having a number-average mol.wt. of 500-1,000, 30-60 pts.wt. aluminum hydroxide, and 20-50 pts.wt. natural org. fibers.

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 equipment, etc. The object of the present invention is to provide excellent electrical characteristics such as arc resistance and tracking resistance, and to prevent cracks. The present invention provides a melamine / phenol resin composition suitable as a molding material for obtaining a molded product that is less likely to generate.

[0002]

2. Description of the Related Art Melamine resin molding materials are used for wiring equipment and electric appliances due to their excellent electrical properties such as flame resistance, coloring, arc resistance and tracking resistance. Because of its large size and lack of flexibility and toughness, when metal fittings are inserted into a molded product, cracks and cracks tend to occur in the molded product, and there are problems in terms of dimensional stability and insert crack resistance. It was

In order to improve these drawbacks, a resol-type solid or liquid phenol resin containing a conventional methylol group mainly in a melamine resin has not been impaired in arc resistance, tracking resistance and coloring property. It is added to the extent. Although this molding material has a smaller dimensional change rate than the molding material containing only melamine resin, the present situation is that a good dimensional change rate is not obtained as compared with the phenol resin molding material. Further, it has been proposed to add rubber particles or polyvinyl butyral resin (Japanese Patent Application Laid-Open No. 4-65453). However, in these trials, it has been found that electrical characteristics such as arc resistance are impaired in the range of effective addition amount, and the current situation is that sufficient balanced characteristics cannot be obtained.

[0004]

The object of the present invention is to blend the specific phenol resin with aluminum hydroxide and organic natural fiber to obtain electric characteristics such as arc resistance and tracking resistance and other characteristics. It is an object of the present invention to provide a melamine / phenol resin composition suitable for a molding material in which cracks are less likely to occur without deteriorating various properties.

[0005]

The present invention contains 20 to 70 mol% of dimethylene ether bond and 10 to 40 mol% of methylol group to 100 parts by weight of melamine resin having a number average molecular weight of 180 to 400. Number average molecular weight 500-
1000 dimethylene ether type resole resin 10-5
A melamine / phenol resin composition comprising 0 parts by weight, 30 to 60 parts by weight of aluminum hydroxide, and 20 to 50 parts by weight of organic natural fiber.

In the present invention, a melamine resin having a number average molecular weight of 180 to 400 is used in order to obtain good moldability. When it is less than 180, the gelation time is long and the curability is lowered, and when it exceeds 400, the fluidity of the molding material is lowered. The melamine resin preferably has a methylolation degree of 1.0 to 3.0. If it is less than 1.0, the crosslink density does not increase,
Curing tends to be inadequate. If it exceeds 3.0, a large amount of gas is generated at the time of molding, which easily causes defective molding.

The phenolic resin used in the present invention is a resol type phenolic resin which contains 20 to 70 mol% of dimethylene ether bonds in all formaldehyde bonds and is mainly dehydrated and condensed by thermal decomposition. The dimensional stability of melamine / phenol resin molded products is
It is affected by the shrinking action that occurs with the curing of the phenolic resin molding material. Since the melamine resin has 6 functional groups, which is larger than the phenol resin having 3 functional groups, the melamine resin component has a larger 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. The 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 alleviated by blending the dimethylene ether type resole resin having a long bond chain.

The number average molecular weight of this resol type phenol resin is 500 to 1,000. If it is less than 500, the softening point is low and handling becomes difficult. If it exceeds 1,000, curing is slow and the fluidity of the molding material is lowered. The amount of the phenol resin compounded is 10 to 100 parts by weight of the melamine resin.
50 parts by weight is preferred. If it is 10 parts by weight or less, dimensional stability and insert crack resistance are not sufficiently improved, and if it is 50 parts by weight or more, tracking resistance is deteriorated.

In the present invention, various inorganic base materials have been studied in order to obtain a molding material in which cracks are less likely to occur without deteriorating electrical characteristics such as arc resistance and tracking resistance. As a result, it has been found that the compounding of aluminum hydroxide has the greatest effect of imparting the most flexibility without impairing flame retardancy and electrical properties. If the added amount is increased, the flexibility is improved, but the specific gravity is increased, which is not practical. Therefore, by combining it with an organic natural fiber which has been conventionally known to be excellent in flexibility, it is balanced with other characteristics without impairing the electrical characteristics such as arc resistance.

Aluminum hydroxide blended in the melamine / phenolic resin composition of the present invention has a central particle size of 10 μm.
It is preferably m or less. That is, when the central particle diameter is 10 μm or more, the specific surface area is small and the adhesion with the resin tends to be poor, so that the mechanical properties may deteriorate. The blending amount of this aluminum hydroxide is 30 with respect to 100 parts by weight of the melamine resin.
-60 parts by weight is preferred. If the amount is 30 parts by weight or less, flexibility, which is one of the features of aluminum hydroxide, is not sufficiently imparted, so that the improvement in insert crack resistance is not recognized, and if it is 60 parts by weight or more, the specific gravity becomes large, which is not practical.

As the organic natural fibers to be blended at the same time, defibrated pulp, powdered pulp, crushed cloth and the like can be used. However, the defibration degree, dispersibility, bulkiness of the material, etc. when formed into a molding material results in fibers. The length is preferably 1 mm or less. The organic natural fiber content is preferably 20 to 50 parts by weight with respect to 100 parts by weight of the melamine resin. If the amount is 20 parts by weight or less, the effect of improving flexibility is not sufficiently obtained, and if the amount is 50 parts by weight or more, the electrical properties such as dimensional stability, arc resistance and tracking resistance, and heat resistance are impaired.

Melamine resin for producing molding materials,
Raw materials used with phenolic resins, aluminum hydroxide, and organic natural fibers are curing agents, colorants, release agents, 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 using 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. Absent.

[0014]

EXAMPLES The raw materials shown in Table 1 were kneaded at a predetermined ratio with a mixing roll and pulverized to produce a molding material. The obtained molding material was molded by transfer molding at 150 ° C. for 3 minutes to obtain a molded product (test piece). Regarding the obtained molded product, electrical characteristics (arc resistance, tracking resistance (CTI)), dimensional stability (molding shrinkage ratio, post-shrinkage ratio (1
After heating at 20 ° C. for 24 hours)), each test of flexibility (flexural strength, flexural modulus, flexural deflection amount) was performed. These tests were performed according to JIS K6911. However, the bending deflection amount was in accordance with JIS K7203.

[0015]

[Table 1]

When a dimethylene ether type resole resin, aluminum hydroxide and organic natural fiber are used as in the examples, dimensional stability and flexibility are imparted without impairing electrical characteristics such as arc resistance and tracking resistance. Thus, a molded product in which cracks are unlikely to occur was obtained.

[0017]

The molding material using the melamine / phenolic resin composition of the present invention is excellent in electric characteristics such as arc resistance and tracking resistance, and a molded product in which cracks hardly occur can be obtained. Therefore, since it is excellent in arc resistance and tracking resistance that could not be manufactured conventionally, and a molded product obtained by insert molding can be easily manufactured, 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.
10 to 50 parts by weight of dimethylene ether type resole resin containing 0 to 70 mol% and 10 to 40 mol% of methylol group and having a number average molecular weight of 500 to 1000, 30 to 60 parts by weight of aluminum hydroxide, and 20 to 20 organic natural fibers. A melamine / phenolic resin composition comprising 50 parts by weight.