JP2755902B2 - Injection molding method of phenolic resin molding material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for a phenolic resin molding material having excellent thermal stability and curability, and more particularly to an injection molding method capable of obtaining a molded article which can be molded at a low pressure and has less burrs. It is.

[0002]

2. Description of the Related Art Phenolic resin molding materials are well-balanced in heat resistance, electrical properties, mechanical properties, dimensional stability and the like, and are used in a wide range of fields including electric parts. Generally, these are molded by injection molding,
In the molten state plasticized to 90 to 120 ° C. in the cylinder of the injection molding machine, the resin has a property that the viscosity increases due to the progress of the curing reaction of the resin and the fluidity is lost, and the thermal stability of the molten resin is low. . For this reason, it is necessary to minimize the heat generation of the resin in the cylinder of the injection molding machine, and if the screw for plasticizing and melting is generally used with a compression ratio for plasticizing the thermoplastic resin, the heat generation is large, The curing reaction of the resin is injected and hardened in the injection cylinder, and cannot be injected.

Therefore, in order to mold a phenolic resin molding material, a mechanism for minimizing heat generation during plasticization is provided, for example, by using a full flight screw having no compression ratio and providing a water-cooled jacket on an injection cylinder. It is necessary to use an injection molding machine. Further, a general phenol resin molding material has a relatively high viscosity even in a state of being plasticized at 90 to 120 ° C. in a cylinder, and is hardened by curing.
At the stage of injection into a mold at about 60 to 180 ° C., the viscosity rapidly rises with curing, so that the time during which fluidity is maintained is extremely short. Therefore, in order to obtain a good molded product, it must be injected at a high pressure in a short period of time and injected into a mold. As a result, the molded product is likely to be distorted due to generation of burrs and internal stress.

[0004]

The present invention has been made as a result of various studies to solve these problems. The purpose of the present invention is to provide a plasticized molten state in a cylinder during injection molding. An injection molding machine having a plasticizing mechanism generally used for molding a thermoplastic resin molding material by using a phenol resin molding material having extremely excellent thermal stability and extremely low melt viscosity in a plasticized state. It is another object of the present invention to provide a method for injection-molding a phenolic resin molding material, and a method for obtaining a molded product with less burrs.

[0005]

According to the present invention, there is provided a method for injection molding a phenolic resin, wherein the compression ratio of the screw is 1.
With an injection molding machine having 5 or more plasticizing mechanisms, 100
The present invention relates to an injection molding method characterized by injection-molding a phenol resin molding material having a melt viscosity at 10 ° C. of 10 ³ Pa · s or less.

In the present invention, the phenolic resin molding material having a melt viscosity at 100 ° C. of 10 ³ Pa · s or less is obtained by mixing a normal phenolic resin with a crystalline phenolic compound having a low viscosity at the time of melting. The molding material is generally used, but preferably, a resin component consisting of a binuclear or higher crystalline phenol compound and a phenol resin, hexamethylenetetramine and a filler are blended as essential components, and this mixture is kneaded. A low-viscosity phenolic resin molding material obtained by blending a compound containing two hydroxyl groups on a benzene ring with the above compound and kneading the mixture.

In the present invention, the crystalline phenol compound having two or more nuclei includes bisphenol compounds such as bisphenol A, bisphenol F, bisphenol AD, bisphenol Z, bisphenol S and derivatives thereof, biphenol and its derivatives, and trinuclear phenol compounds. Alternatively, there are tetranuclear phenol compounds and the like, and one or more of these can be used. Such a binuclear or higher crystalline phenol compound is used to impart the property that the phenolic resin molding material is solid at room temperature, melts more quickly by plasticization during injection molding to have a low viscosity, and can be molded under low pressure. Can be In addition, as the phenol resin, a normal novolak-type phenol resin obtained by a reaction between a phenol and formaldehyde can be used.

The compound having two or more hydroxyl groups on the benzene ring is used for imparting the property of improving the curing rate while maintaining a low viscosity without impairing the above properties of the binuclear or higher crystalline phenol compound. Can be As such a compound, one or more of resorcin, hydroquinone, catechol, phloroglucinol, pyrogallol, and derivatives thereof can be used, but resorcin is particularly preferred for accelerating curing.

Therefore, in the present invention, the mixing ratio of the binuclear or higher crystalline phenol compound (A) and the phenol resin (B) can be arbitrarily selected, but preferably A / B = 80/20 to 80/20. 30/70. If the amount of component A is small, the above-mentioned characteristics of crystallinity cannot be sufficiently exhibited, and if it is large, curing is slow. Also, as the mixing ratio of the component B increases, the viscosity of the molten resin increases and the curability improves,
It can be appropriately compounded within the above range depending on the purpose. Further, a compound (C) having two or more hydroxyl groups on a benzene ring
Is used for accelerating the curing, but the preferred compounding ratio is the total amount of the above components A and B / C component = 9
7/3 to 90/10. If the amount of the component C is less than this range, the effect of accelerating the curing becomes small, and if the amount is too large, the curability decreases.

The fillers used in the phenolic resin molding material of the present invention include organic materials such as wood powder, pulp powder, various crushed fabrics, phenolic resin laminates and crushed molded products, silica, alumina, water and the like. One or more of inorganic powders such as aluminum oxide, glass, talc, clay, mica, calcium carbonate, and carbon, and inorganic fibers such as glass fiber and carbon fiber can be used. The mixing ratio in the phenolic resin molding material of the present invention is such that the resin component containing hexamethylenetetramine is 20 to
70% by weight and 80 to 30% by weight of filler. Also,
Various additives such as a lubricant, a coloring agent, a curing accelerator, and a flame retardant can be appropriately added to the phenolic resin molding material of the present invention.

The phenolic resin molding material of the present invention is obtained by mixing a resin component with hexamethylenetetramine, a filler, and other additives, and kneading the mixture with a roll mill, a twin-screw kneader or the like.
It can be manufactured by grinding. In addition, 2
When a compound having two or more hydroxyl groups is blended, the compound may be melt-mixed with the resin component and hexamethylenetetramine in advance, or may be kneaded with a filler or the like in the next step. The compounding of such a compound is preferable in order to maintain good fast curability and low pressure molding.

[0012]

The phenolic resin molding material of the present invention has, for example, a remarkably low viscosity in a molten state at 90 to 120 ° C., excellent thermal stability, and excellent curability at about 160 to 200 ° C. The reason for this is not clear enough, but 9
At 0 to 120 ° C., the binuclear or higher crystalline phenol compound having a relatively small molecular weight melts quickly and extremely low in viscosity, and the shearing heat generated by the screw is small, so that the curing acceleration is suppressed. The decomposition of tetramine proceeds, and the compound having two or more hydroxyl groups on the benzene ring promotes this decomposition,
It is thought to act on the reaction between the crystalline phenolic compound and the phenolic resin to accelerate the curing reaction.

Therefore, in the phenolic resin molding material of the present invention, the acceleration of the curing reaction in the cylinder of the injection molding machine is suppressed, and the plasticization can be easily performed even with a screw having a large compression ratio because of its excellent thermal stability. On the other hand, it can be quickly cured in a high-temperature mold.

[0014]

EXAMPLES The present invention will be described below with reference to examples. In the formulations, "parts" are parts by weight. [Example 1] An injection molding machine having a plasticizing mechanism using a screw having a compression ratio of 2.0, 25 parts of a novolak type phenol resin (average molecular weight: 800), bisphenol F15
Parts, 7 parts of hexamethylenetetramine, 4 parts of calcium hydroxide, 32 parts of wood flour, 12 parts of calcium carbonate, and 3 parts of a release agent, melt-kneaded by a two-roll mill, cooled and pulverized to obtain a low melt viscosity phenol. A resin molding material was obtained. When a test piece of 60 mm x 8 mm was injection-molded (injection temperature 90 ° C, mold temperature 180 ° C) using this molding material, continuous moldability was good. Also, the injection pressure was low, and the occurrence of burrs was small. Example 2 The same method as in Example 1 was carried out except that 3 parts of resorcin was further added. As in Example 1, the continuous formability was good, and the occurrence of burrs was small.

Comparative Example 1 Using an injection molding machine having the same plasticizing mechanism as in Example 1, 44 parts of a novolak type phenol resin (average molecular weight 800), 7 parts of hexamethylenetetramine, 3 parts of calcium hydroxide, wood powder 32 parts, 11 parts of calcium carbonate and 3 parts of a release agent were mixed, and injection molding of a commonly used phenol resin molding material having a high melt viscosity obtained in the same manner as in Example 1 was performed. Since the heat generation was large and the curing was accelerated, the resin was cured in the cylinder at the fifth shot and could not be injected. In addition, a high pressure is required for injection, and the occurrence of burrs is large. Comparative Example 2 Injection molding was performed in the same manner as in Comparative Example 1 using an injection molding machine having a plasticizing mechanism using a screw having a compression ratio of 1.0. The continuous formability was good. However, high pressure is required for injection, and burrs are generated.

In Table 1, the melt viscosities are those measured by a Shimadzu flow tester (CFT-500C, Shimadzu Corporation). The state of occurrence of burrs is determined by visually observing burrs generated on a molded article.

[0017]

[Table 1]

In the above Examples and Comparative Examples, an injection molding machine having a screw having a compression ratio of 2.0 is generally used for molding a thermoplastic resin molding material. An injection molding machine having a screw of 0.0 is used for molding a thermosetting resin molding material such as a phenol resin.

[0019]

By using a phenolic resin molding material having a low viscosity at the time of melting, continuous injection molding can be performed with an injection molding machine having a high compression ratio used for a thermoplastic resin.
Further, since injection molding can be performed at a relatively low pressure, generation of burrs can be suppressed.

Claims (3)

(57) [Claims] 1. A phenol resin injection molding method, wherein the melt viscosity at 100 ° C. is 10 ³ by an injection molding machine having a plasticizing mechanism with a screw compression ratio of 1.5 or more.
An injection molding method characterized by injection molding a phenolic resin molding material having a Pa · s or less. 2. A phenolic resin molding material comprising a component comprising a crystalline phenol compound having two or more nuclei and a phenolic resin, hexamethylenetetramine and a filler as essential components. Injection molding method for phenolic resin molding material. 3. The injection molding method according to claim 1, wherein the phenolic resin molding material contains a compound having two or more hydroxyl groups on a benzene ring.