JPH08302158A - Phenol resin molding material - Google Patents

Abstract

PURPOSE: To obtain a phenol resin molding material which can be molded under a pressure lower than that for molding a commercially available phenol resin molding material and which enables both a satisfactory mold filling in the molding step and prevention of molding flash. CONSTITUTION: This molding material essentially comprises a novolak phenol resin having an ortho-para ratio of 1.0-2.5 and a soln. viscosity (in the 50% ethanolic soln. by the Ostwald method at 25 deg.C) of (20-70)×10<-6> m<2> /sec, hexamethylenetetramine, and a filler.

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a phenol resin molding material which is excellent in low-pressure moldability and curability and has very few burrs during molding.

[0002]

2. Description of the Related Art Conventionally, phenol resin molding materials have been used for various purposes because they are excellent in various properties such as heat resistance, electrical characteristics and mechanical strength, have good moldability and can be obtained at low cost. There is.

Generally, a phenol resin molding material is injection-molded, and the molding material is injected into the mold cavity at a high pressure, and is cured by applying pressure for a certain period of time to perform shaping. Therefore, residual stress occurs in the molded product shaped in the mold, and in the cooling process after being removed from the mold,
When the residual stress diffuses, the molded product may be warped or deformed. Further, since the molding material is injected into the mold cavity at a high pressure, a minute deformation of the mold creates a gap between the molds, which causes a lot of burrs.

Conventionally, as a method for solving these problems, the melt viscosity of the molding material is lowered, that is, the fluidity is improved and the injection pressure is lowered (for example, described in JP-A-5-156120). However, since the curing of the molding material is delayed, the molding cycle becomes long and it is difficult to put it into practical use.

[0005]

SUMMARY OF THE INVENTION The present invention has been completed as a result of various studies in order to obtain a phenol resin molding material capable of low-pressure molding and having a fast curing,
It is an object of the invention to provide a phenol resin molding material which is excellent in mold filling property and curability in low-pressure molding and has very few burrs during molding.

[0006]

According to the present invention, the ortho-para ratio is in the range of 1.0 to 2.5, and the solution viscosity (50% ethanol solution, Ostwald method (25 ° C), the same measurement method hereinafter). Is a (20 to 70) × 10 ⁻⁶ m ² / sec novolac type phenolic resin, hexamethylenetetramine (hereinafter referred to as “hexamine”) and a filler as essential components. .

The phenolic resin used in the present invention is used for imparting to the phenolic resin molding material the characteristic that it is rapidly melted to have a low viscosity during plasticization during injection molding and can be molded at a low pressure. Since this phenolic resin cures rapidly at high temperatures, it makes it possible to shorten the molding cycle. The conventional novolak resin has a solution viscosity of (80 to 300) × 10 ^-6 m ² / sec, and the molding material has the property of low viscosity sufficient to enable low-pressure molding by plasticization during injection molding. Cannot be granted.

The solution viscosity of the novolac type phenol resin used in the present invention is (20 to 70) × 10 ^-6 m ² / sec. If it is less than 20, the resin tends to liquefy at room temperature,
There are difficulties in storing the resin and manufacturing the molding material. When it is more than 70, the molding material cannot be provided with a property that the viscosity is low enough to enable molding at low pressure due to plasticization during injection molding.

In the phenol resin molding material of the present invention, the compounding ratio of hexamine as a curing agent is 7 to 25% by weight, preferably 10 to 20% by weight based on the phenol resin component.
% By weight. If it is less than 7% by weight, curing will not be sufficiently performed, and if it is more than 25% by weight, curability will not be improved.
On the contrary, the characteristics of the molded product (for example, mechanical strength) are deteriorated.

The filler used in the phenol resin molding material of the present invention includes wood powder, pulp powder, various pulverized woven materials, organic materials such as pulverized powder of phenol resin laminated plates and molded products, silica, alumina. One or more of inorganic powders such as aluminum hydroxide, glass, talc, clay, mica, calcium carbonate and carbon, and inorganic fibers such as glass fiber, garbon fiber and asbestos can be used.

The blending ratio of the phenol resin molding material of the present invention is such that the phenol resin containing hexamine is 20 to 70.
% By weight and 80 to 30% by weight of filler. Further, various additives such as a lubricant, a solvent, a colorant, a curing accelerator, and a flame retardant can be appropriately added to the phenol resin molding material of the present invention.

[0012]

In the present invention, since the novolac type phenolic resin has a low viscosity when melted, the phenolic resin molding material melts very quickly in the plasticizing step at the time of molding to have a low viscosity,
By having good fluidity, it is possible to fill the cavity of the mold at low pressure without applying extra pressure, and it is possible to extremely reduce the occurrence of burrs during molding due to rapid curing. Also, a molded product having good characteristics can be obtained. Furthermore, shortening the molding cycle,
It is possible to reduce die wear due to less burr, improve die life, and reduce die weight by low-pressure molding.

[0013]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples. Here, "parts" represent parts by weight.

Example 1 A novolac type phenol resin having an ortho-para ratio of 1.5 (solution viscosity 30 × 10 ^-6
m ² / sec, weight average molecular weight 500) 45 parts, hexamine 7 parts, calcium hydroxide 3 parts, wood powder 30 parts, calcium carbonate 10 parts, mold release agent, and pigment 5 parts are mixed and a two-roll mill is used. The mixture was heated and kneaded, cooled, and pulverized to obtain a phenol resin molding material.

Example 2 A novolac type phenol resin having an ortho-para ratio of 2.0 (solution viscosity 50 × 10 ^-6
m ² / sec, weight average molecular weight 750) 45 parts, hexamine 7 parts, calcium hydroxide 3 parts, wood powder 30 parts, calcium carbonate 10 parts, a release agent, a pigment and a solvent 5 parts were mixed. A phenol resin molding material was obtained in the same manner as in Example 1 except for the above.

Comparative Examples 1 and 2 The ortho-para ratio is 1.
Novolak type phenolic resin of 5 (solution viscosity 100
× 10 ^-6 m ² / sec, weight average molecular weight 2000) 45 parts,
Hexamine 7 parts, calcium hydroxide 3 parts, wood flour 30 parts,
5 parts of the release agent and the pigment were mixed. A phenol resin molding material was obtained in the same manner as in Example 1 except for the above.

Table 1 shows the viscosity of the phenol resin used in the examples and comparative examples, the characteristics of the phenol resin molding material, and the amount of burr remaining in the molded product after deburring. In Comparative Examples, Comparative Example 1 is a case of molding with the same gauge pressure of 50 kg / cm ² , and Comparative Example 2 is a case of increasing the gauge pressure to 110 kg / cm ² . As is clear from the results in Table 1, the phenolic resin molding materials obtained in the respective examples have low viscosity and excellent curability. It can be seen that the filling property is good and the occurrence of burrs during molding is extremely small.

[0018]

[Table 1]

The method of measuring the characteristics in Table 1 is as follows. 1. Flowability of molding material: The melt viscosity measured by a Koka type flow tester (CFT-500C manufactured by Shimadzu Corporation) is shown. 2. Curability: The molding material preheated to 100 ° C. was charged into a mold at 175 ° C. by a transfer molding machine, the molded product was taken out after 30 seconds, and the Barcol hardness after 10 seconds was shown. 3. Moldability: Disc by injection molding machine (50φ x thickness 3mm)
Was molded, and the filling property into the cavity and the occurrence of burrs in the air vent were visually determined.

[0020]

EFFECTS OF THE INVENTION The phenol resin molding material of the present invention has a low viscosity when melted and is excellent in curability at the mold temperature, so that low pressure molding is possible, and the mold filling property during molding is improved. It is possible to achieve both suppression of burr generation. Therefore,
It can be widely used as a phenolic resin molding material with excellent moldability, shortening the molding cycle and improving the mold life.

Claims (1)

[Claims] 1. The ortho-para ratio is in the range of 1.0 to 2.5, and the solution viscosity (50% ethanol solution, Ostwald method (25 ° C.)) is (20 to 70) × 10 ⁻⁶ m ² / A phenol resin molding material comprising a novolac-type phenol resin having a sec, hexamethylenetetramine, and a filler as essential components.