JPH07323435A - Method for injection molding of phenol resin forming material - Google Patents

Abstract

PURPOSE:To obtain a molding product which can be molded under low pressure and is lessened in the occurrence of burrs by a method wherein, in a method for injection molding of phenol resin, the molding material of phenol resin having a specific melt viscosity is molded by an injection molding machine having a plasticizing mechanism indicating a specific value of screw compression patio. CONSTITUTION:In the injection molding of phenol resin, the phenol resin molding material having a melt viscosity of at most 10<3>Pa.s at 100 deg.C is molded by an injection molding machine with a plastisizing mechanism having a screw compression ratio of at least 1.5. As for the phenol resin molding material, the molding material is used which contains a crystalline phenol compound low in melt viscosity as a hardenable component in addition to the regular phenol resin and it is preferable to use a low viscous phenol resin molding material formed by kneading the resin component consisting of a crystalline phenol compound of at least two nuclides and phenol resin with a mixture comprising hexamethylenetetramine and filler as essential ingredients.

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 phenol resin molding material having excellent thermal stability and curability, and to an injection molding method capable of low pressure molding and obtaining a molded product with less burrs. Is.

[0002]

2. Description of the Related Art Phenolic resin molding materials have an excellent balance of heat resistance, electrical characteristics, mechanical characteristics, dimensional stability, etc. and are used in a wide range of fields including electric parts. Generally, these are molded by injection molding,
In a molten state plasticized in the cylinder of an injection molding machine at 90 to 120 ° C., the viscosity of the molten resin increases and the fluidity is lost due to the progress of the curing reaction of the resin, and the thermal stability of the molten resin is low. . Therefore, it is necessary to suppress heat generation of the resin in the cylinder of the injection molding machine as much as possible, and the screw for plasticizing and melting generally has a large heat generation when a screw having a compression ratio for plasticizing the thermoplastic resin is used. The curing reaction of the resin is injected and the resin is cured in the injection cylinder and cannot be injected.

Therefore, in order to mold the phenolic resin molding material, a full-flight screw which generally does not have a compression ratio is used, and a mechanism for suppressing heat generation during plasticization is provided, for example, by providing a water-cooled jacket on the injection cylinder. It is necessary to use an injection molding machine. In addition, general phenol resin molding materials have a relatively high viscosity even when they are plasticized in the cylinder at 90 to 120 ° C.
At the stage of injection into a mold at about 60 to 180 ° C., the viscosity rises rapidly with curing, so that the fluidity is maintained for a very short time. Therefore, in order to obtain a good molded product, it must be injected at a high pressure in a short time and injected into the mold, which easily causes the molded product to be distorted due to burrs or internal stress.

[0004]

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

[0005]

According to the present invention, in a method for injection molding a phenol resin, the compression ratio of the screw is 1.
100 by injection molding machine with 5 or more plasticizing mechanism
The present invention relates to an injection molding method, which comprises subjecting a phenol resin molding material having a melt viscosity at 10 ° C. of 10 ³ Pa · s or less to injection molding.

In the present invention, the phenol resin molding material having a melt viscosity at 100 ° C. of 10 ³ Pa · s or less is a curable component prepared by blending an ordinary phenol resin with a crystalline phenol compound having a low viscosity when melted. The molding material is generally used, but preferably, a resin component consisting of a crystalline phenolic compound having a binuclear body or more and a phenol resin, hexamethylenetetramine, and a filler are mixed as essential components, and the mixture is kneaded. A low-viscosity phenol resin molding material obtained by mixing the above compound with a compound having two hydroxyl groups in the benzene ring and kneading the mixture.

In the present invention, examples of the crystalline phenol compound having two or more nuclides include bisphenol compounds such as bisphenol A, bisphenol F, bisphenol AD, bisphenol Z, and bisphenol S, and their derivatives, biphenol and its trinuclear compounds. Alternatively, there are tetranuclear phenol compounds and the like, and one or more of these can be used. The crystalline phenolic compound having two or more nuclides is used in order to impart the property that the phenolic resin molding material is solid at room temperature, melts more quickly and becomes low viscosity by plasticizing at the time of injection molding, and can be molded at low pressure. To be Further, as the phenol resin, a usual novolac type phenol resin obtained by the reaction of phenols 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 the low viscosity without impairing the above-mentioned properties of the crystalline phenol compound having two or more nuclei. To be As such a compound, one or more of resorcin, hydroquinone, catechol, phloroglucinol, pyrogallol and derivatives thereof can be used, and resorcin is particularly preferable for promoting curing.

Therefore, in the present invention, the blending ratio of the crystalline phenolic compound (A) having two or more nuclei and the phenolic resin (B) can be arbitrarily selected, but preferably A / B = 80/20. It is 30/70. If the amount of component A is small, the crystallinity characteristics as described above cannot be sufficiently exhibited, and if the amount is large, curing will be slow. Further, as the blending ratio of the component B increases, the viscosity of the molten resin increases and the curability is improved.
Within the above range, it may be appropriately blended depending on the purpose. Furthermore, a compound (C) having two or more hydroxyl groups on the benzene ring
Is used for accelerating the curing, but the preferable blending ratio is the total amount of the above-mentioned A component and B component / C component = 9.
It is 7/3 to 90/10. If the amount of C component is less than this range, the effect of accelerating the curing becomes small, and if the amount of C component is more than the above range, the curability decreases.

Fillers used in the phenol resin molding material of the present invention include organic materials such as wood powder, pulp powder, crushed products of various fabrics, phenol resin laminated plates and crushed products, silica, alumina and water. One or more kinds 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 blending ratio in the phenol resin molding material of the present invention is such that the resin component containing hexamethylenetetramine is 20 to 20%.
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 phenol resin molding material of the present invention.

The phenol resin molding material of the present invention comprises a resin component, hexamethylenetetramine, a filler, and other additives, which are kneaded with a roll mill, a twin-screw kneader, or the like,
It can be crushed and manufactured. In addition, it is 2
When a compound having one or more hydroxyl groups is blended, the resin component and hexamethylenetetramine may be melt-mixed in advance, or may be kneaded with a filler in the next step. The compounding of such a compound is preferable in order to maintain good fast curing property and low pressure molding.

[0012]

The phenol resin molding material of the present invention has, for example, a remarkably low viscosity in the 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 crystalline phenolic compound having a relatively small molecular weight of a dinuclear or more melts quickly and at an extremely low viscosity, and the shearing heat generated by the screw is small, so that the curing acceleration is suppressed, but at 160 ° C or higher, hexamethylene is used. The decomposition of tetramine proceeds, and the compound having two or more hydroxyl groups on the benzene ring accelerates this decomposition,
It is considered to act on the reaction of the crystalline phenolic compound and the phenolic resin to accelerate the curing reaction.

Therefore, in the phenol resin molding material of the present invention, the acceleration of the curing reaction in the cylinder of the injection molding machine is suppressed, and since it is excellent in thermal stability, it can be easily plasticized even by a screw having a large compression ratio, On the other hand, it can be quickly cured in a high temperature mold.

[0014]

The present invention will be described with reference to the following examples. In the formulation, “part” is part by weight. Example 1 An injection molding machine having a plasticizing mechanism with a screw having a compression ratio of 2.0, 25 parts of novolac type phenol resin (average molecular weight 800), bisphenol F15
Part, 7 parts of hexamethylenetetramine, 4 parts of calcium hydroxide, 32 parts of wood powder, 12 parts of calcium carbonate, and 3 parts of release agent are mixed, melt-kneaded by a two-roll mill, cooled and pulverized to obtain a phenol having a low melt viscosity. A resin molding material was obtained. When a 60φ × 8 mm test piece was injection-molded (injection temperature 90 ° C., mold temperature 180 ° C.) using this molding material, the continuous moldability was good. Moreover, 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. Similar to Example 1, the continuous moldability was good, and the occurrence of burrs was small.

Comparative Example 1 An injection molding machine having the same plasticizing mechanism as in Example 1 was used, and 44 parts of a novolac type phenol resin (average molecular weight 800), 7 parts of hexamethylenetetramine, 3 parts of calcium hydroxide and wood flour were used. When 32 parts, 11 parts of calcium carbonate, and 3 parts of a release agent were mixed, a commonly used phenol resin molding material having a high melt viscosity obtained in the same manner as in Example 1 was injection-molded. Since the heat generation was large and the curing was promoted, it was cured in the cylinder at the fifth shot and could not be injected. In addition, high pressure is required for injection, and burrs are 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 with a screw having a compression ratio of 1.0. The continuous moldability was good. However, high pressure is required for injection, and burrs are also generated.

In Table 1, the melt viscosity is measured by a Shimadzu flow tester (CFT-500C manufactured by Shimadzu Corporation). Further, the state of occurrence of burrs is determined by visually observing burrs generated in the molded product.

[0017]

[Table 1]

In the above examples and comparative examples, the injection molding machine having a screw having a compression ratio of 2.0 is generally used for molding a thermoplastic resin molding material, and the compression ratio 1 shown in the comparative example is used. An injection molding machine having a 0.0 screw is used for molding thermosetting resin molding materials such as phenol resin.

[0019]

EFFECTS OF THE INVENTION By using a phenol resin molding material having a low viscosity when melted, continuous injection molding can be performed with an injection molding machine having a high compression ratio used for a thermoplastic resin.
Further, since the injection molding can be performed with a relatively low pressure, it is possible to suppress the generation of burrs.

Claims (3)

[Claims] 1. In the injection molding method of a phenol resin, 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 in that a phenol resin molding material of Pa · s or less is injection-molded. 2. The phenolic resin molding material is a mixture of a crystalline phenolic compound having two or more nuclear bodies and a phenolic resin, hexamethylenetetramine and a filler as essential components. Injection molding method for phenolic resin molding materials. 3. The injection molding method according to claim 1, wherein the phenol resin molding material contains a compound having two or more hydroxyl groups in the benzene ring.