JPH0925390A - Phenol resin molding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition excellent in injection moldability and curability by using a high-ortho novolak phenol resin as the phenol resin in a composition comprising a blend of a phenol resin with other components. SOLUTION: A high-ortho novolak phenol resin (A) having a number-average molecular weight of 350 to 500 and an ortho/para linkage ratio of 1.5 to 2.5 is blended with a crystalline phenol compound (B) composed of at least two nuclei, hexamethylenetetramine (C), a low-molecular polyolefin compound (D) and a filler (E) to produce a phenol resin molding material. The component B preferably comprises a bisphenol compound, especially bisphenol F. It is desirable to also blend a cure accelerator comprising, e.g. resorcylene. The component D preferably comprises a polyethylene with a molecular weight of 500 to 1,500. The blend is kneaded and ground to give a molding material. This molding material is excellent in melt flow characteristics and curability and permits low-pressure injection molding with little occurrence of flash.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phenol resin molding material which is excellent in heat stability and curability, can be molded under low pressure, and can be used to obtain a molded product with less burrs.

[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.
It is used in a wide range of fields including electrical parts.
Generally, these are molded by injection molding, but in a molten state plasticized at 90 to 120 ° C. in the cylinder of an injection molding machine, the viscosity increases due to the progress of the curing reaction of the resin and the fluidity is lost. Therefore, the thermal stability of the molten resin becomes low. Therefore, when a conventional phenol resin molding material is injection-molded, there is a problem that the molding material melted in the cylinder of the injection molding machine has poor thermal stability and the appropriate molding condition range is extremely narrow.

Further, a general phenol resin molding material has a relatively high viscosity even in a plasticized state in a cylinder at 90 to 120 ° C., and is cured at the stage of being injected into a mold at 160 to 180 ° C. for curing. With this, the viscosity rises sharply, and the fluidity is maintained for a short time. Therefore, in order to obtain a good molded product, it has to be injected at high pressure in a short time and injected into the mold, and residual stress occurs in the molded product shaped in the mold, and After taking out, when the stress diffuses in the cooling process, the molded product is apt to warp or deform. Further, when the resin is injected and injected into the mold at a high pressure, a gap is likely to be formed between the molds, and burrs are unavoidable.

Conventionally, in order to solve these problems, the melt viscosity of the molding material, that is, the fluidity is increased and the injection pressure is decreased to perform molding, but the occurrence of burrs is reduced. Although it is possible, since the curing is slow, the molding cycle becomes long and it is difficult to put it into practical use.

[0005]

The present invention has been made as a result of various studies in order to solve these problems, and an object of the present invention is to achieve thermal stability in a molten state in a cylinder during injection molding. The purpose of the present invention is to provide a phenol resin molding material having excellent properties, a melt viscosity that is extremely low, and excellent curability.

[0006]

The present invention provides (a) a phenol resin, (b) a binuclear or higher crystalline phenolic compound, (c) hexamethylenetetramine, (d) a low molecular weight polyolefin compound, and (e). ) A phenol resin molding material containing a filler, wherein the phenol resin has a number average molecular weight of 350 to 500 and an ortho / para bond ratio (O / P ratio, the same applies hereinafter) of 1.5 to 2.5. The present invention relates to a phenol resin molding material characterized by being a novolac type phenol resin, and a phenol resin molding material obtained by kneading (f) a compound having two or more hydroxyl groups in a benzene ring with the above compound.

Generally, the molecular weight of the novolac type phenolic resin (number average molecular weight, the same applies hereinafter) is 600 to 1000, but by making the number average molecular weight relatively small at 350 to 500, the thermal stability in the molten state is improved, In addition, the low melt viscosity results in good fluidity in the mold. The molecular weight may be 350 or less, but the resin does not easily solidify and the workability in the production of the molding material deteriorates. Further, when the molecular weight is 500 or more, the thermal stability and the fluidity are low, and the application to the present invention may be difficult. A more preferable range is 380 to 450.

In the present invention, the O / P ratio of the novolac type phenolic resin is 1.5 to 2.5, so that the activation energy of the resin becomes high and the curability in the mold becomes good. . When the O / P ratio is 1.5 or less, the curing in the mold is insufficient and the molding cycle becomes long,
If it is 2.5 or more, it is difficult to manufacture the resin. More preferably, it is in the range of 1.8 to 2.3.

In the present invention, (b) the crystalline phenol compound having two or more nuclides is a solid at room temperature, has a clear melting point, and becomes a low-viscosity liquid when melted, and a phenol resin such as hexamethylenetetramine. A phenol compound of a binuclear or higher body that is hardened by reacting with the curing agent. As such a crystalline phenol compound having two or more nuclear bodies,
There are bisphenol compounds such as bisphenol A, bisphenol F, bisphenol AD, bisphenol Z, and bisphenol S, and derivatives thereof, biphenol and its derivatives, trinuclear or tetranuclear phenol compounds such as trisphenol AP, and one of these or Two or more kinds can be used. Such a binuclear or higher crystalline phenolic compound is a solid at room temperature and quickly melts to a low viscosity by heating during injection molding.
It is used to give a phenolic resin molding material the property of being molded at a pressure lower than usual. As the phenol resin, it is possible to use a normal novolac resin, but it is possible to further reduce the melt viscosity by using a lower molecular weight novolac resin, while reducing the blending amount of the expensive crystalline phenol compound. You can also Preferred as such crystalline phenol compounds are bisphenol F and bisphenol A, particularly bisphenol F.

(F) The compound having two or more hydroxyl groups on the benzene ring is used for improving the curing rate while maintaining the low viscosity without impairing the above-mentioned characteristics of the crystalline phenol compound having two or more nuclides. To be Such compounds include resorcin, hydroquinone, catechol,
One or more of phloroglucinol, pyrogallol and derivatives thereof can be used,
Resorcin is particularly desirable for accelerated cure.

In the present invention, the blending ratio of (a) the phenol resin and (b) the crystalline phenolic compound having two or more nuclei can be arbitrarily selected, but preferably (a) /
(B) = 20/80 to 90/10. When the amount of the component (b) is small, the above-mentioned characteristics of crystallinity cannot be sufficiently exhibited, and when the amount is large, curing becomes slow. Further, as the ratio of the component (a) increases, the viscosity of the molten resin increases and the curability improves, so that it can be appropriately blended within the above range depending on the purpose. Further, (f) the compound having two or more hydroxyl groups in the benzene ring is used for promoting the curing, and the preferable mixing ratio is the total amount of the above-mentioned components (a) and (b) / (f). Component = 99/1 to 90/10.
If the amount of the component (f) is less than this range, the curing that accelerates the curing becomes small, and if the amount of the component (f) is too large, the curability decreases.

As the hexamethylenetetramine (c) of the present invention, a powdery one used as a curing agent for an ordinary phenol resin is used.
7 to 30 parts by weight, preferably 12 to 20 parts by weight
It is used by blending parts by weight.

Examples of the low molecular weight polyolefin compound (d) of the present invention include low molecular weight polypropylene and low molecular weight polyethylene. Such compounds have a molecular weight of from 300 to 30,000. These compounds reduce heat generation due to shearing that is received from the screw and the cylinder wall when plasticizing and measuring the molding material in the cylinder of the injection molding machine, and suppress the progress of curing to improve the thermal stability. It also has the effect of reducing the viscosity in the molten state at 80 to 120 ° C. The molecular weight of these compounds is preferably between 300 and 3000. In the present invention, it is more preferable that the molecular weight is 500 as a substance that greatly reduces the viscosity.
~ 1500 polyethylene. These compounds are added in an amount of 0.1 to the total amount of the above-mentioned components (a) and (b).
It is used by mixing 10 to 10 parts by weight. If the amount is less than 0.1 part by weight, the above-mentioned action is small, and if the amount is more than 10 parts by weight, plasticization and weighing by an injection molding machine becomes difficult.

Examples of the filler (e) used in the phenol resin molding material of the present invention include wood powder, pulp powder, pulverized products of various fabrics, phenol resin laminates, organic substances such as pulverized products, silica, Alumina, aluminum hydroxide, glass, talc, clay, mica, calcium carbonate, carbon and other inorganic powders, glass fiber,
One or more types of inorganic fibers such as carbon fibers can be used. The blending ratio in the phenol resin molding material of the present invention is 20 to 70% by weight of the resin component containing hexamethylenetetramine and 80 to 30% by weight of the filler.
Further, various additives such as a lubricant, a colorant, 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.

[0016]

In the phenol resin molding material of the present invention, a low molecular weight high ortho novolac type phenol resin having an O / P ratio of 1.5 to 2.5 and a molecular weight of 350 to 500 is used as the phenol resin. It contains a phenol compound of two or more nuclear bodies. Therefore, the activation energy of the phenol resin is high, the curability is excellent, the melt viscosity is small, the fluidity is good in the molten state at 80 to 120 ° C., and the thermal stability is excellent. And 2 on the benzene ring
When it contains a compound having one or more hydroxyl groups, the curability is further improved. Since it contains a low molecular weight polyolefin compound, the melt viscosity is further reduced and the fluidity,
Thermal stability is improved. Therefore, by arbitrarily selecting the compounding ratio of the above resin component and the compounding ratio of the low molecular weight polyolefin compound, more preferably the compound having two or more hydroxyl groups in the benzene ring, excellent curability and low melting in a wide range are obtained. A phenol resin molding material having both viscosity and high thermal stability can be obtained. Such a phenol resin molding material has a melt viscosity of 10 ^{3 at} 100 ° C.
Pa · s or less, and further 1 depending on the compounding ratio of the crystalline phenol compound and the low molecular weight polyolefin compound.
The viscosity is 0 ² Pa · s or less, and the viscosity in the molten state in the cylinder of the injection molding machine is extremely low.

The above-mentioned phenol resin molding material has a low melt viscosity (10 ³ Pa · s to 10 ² Pa · s or less), and 9
It has excellent thermal stability at 0 to 120 ° C., but if it is a phenol resin molding material satisfying the above-mentioned melt viscosity as a molding material and having good thermal stability, it has excellent moldability as an object of the present invention. Can be obtained.

Therefore, the phenolic resin molding material of the present invention rapidly melts in the injection molding machine to have a low viscosity and has good fluidity, so that it can be injected at a low pressure without applying extra pressure during injection. Since it can be filled in the mold cavity, it is possible to suppress the occurrence of burrs. Furthermore, since it can be melted at a temperature of 70 to 80 ° C. in the injection molding machine cylinder, heat generation due to shearing is small, acceleration of the curing reaction can be further suppressed, and thermal stability is dramatically improved. Also, 1
It has excellent fluidity and curability in the mold at 60 to 200 ° C. Therefore, in the phenol resin molding material of the present invention,
Wide range of molding conditions in injection molding and excellent continuous moldability.

[0019]

The present invention will be described below with reference to examples. In the formulations, "parts" are parts by weight. The resin and compound shown in Table 1 were kneaded with a heating roll to obtain a phenol resin molding material. Using these molding materials, the melt viscosity was adjusted, and injection molding was performed to evaluate the in-cylinder stability and curability. Table 1 shows the results.

(Measurement method) 1. Melt viscosity: Shimadzu flow tester (CFT, Shimadzu Corporation)
-500C). 2. Thermal stability: Labo Plastomill (C manufactured by Toyo Seiki Seisaku-sho, Ltd.)
(Mold) to measure the time from melting to curing. 3. Cylinder stability: Test piece (60φ x 4m
m, same hereafter) 20 shots continuous molding (cylinder temperature 90 ° C, mold temperature 175 ° C, hereafter, molding under the same conditions))
After that, it is left in a metered state, and after a certain period of time, injection is performed. When molding was performed while changing this standing time, the longest standing time during which the molten material flows and can be sufficiently filled in the mold was determined. 4. Curability: Change the holding time in the mold after injection molding,
The presence or absence of blisters on the test piece surface was observed. 5. Injection pressure: The minimum injection pressure at which the test piece can be continuously molded without causing defects such as insufficient filling is indicated by the hydraulic gauge value of the injection molding machine. 6. Burr generation: Burrs generated on the test piece were visually determined.

[0021]

[Table 1]

[0022]

As is clear from the above examples, the phenolic resin molding material of the present invention is rich in fluidity and thermal stability in a molten state and excellent in curability at high temperature. Therefore, in injection molding, the viscosity increase of the molten molding material in the cylinder of the molding machine is suppressed, and the molding material is rapidly cured in the mold, so that the moldability is excellent. Furthermore, since injection molding can be performed at a low pressure, generation of burrs can be suppressed. The phenol resin molding material of the present invention is 100
Since the melt viscosity at 0 ° C. is 10 ² to 10 ³ Pa · s or less, which is an extremely low viscosity as compared with ordinary phenol resin molding materials (10 ⁴ to 10 ⁵ Pa · s), it is generally a thermoplastic resin molding material. Good injection molding can be performed by using an injection molding machine equipped with a screw having a compression ratio of 1.5 or more, or a screw provided with a backflow prevention ring, which is used for the injection molding of 1.

Claims (3)

[Claims] 1. A phenol resin containing (a) a phenol resin, (b) a binuclear or more crystalline phenol compound, (c) hexamethylenetetramine, (d) a low molecular weight polyolefin compound, and (e) a filler. In the molding material, the number average molecular weight of the phenol resin is 350 to 500.
And a high ortho novolac type phenolic resin having an ortho / para coupling ratio of 1.5 to 2.5. 2. The phenol resin molding material according to claim 1, wherein (f) a compound having two or more hydroxyl groups in the benzene ring is kneaded with the mixture. 3. The phenolic resin molding material according to claim 1, wherein the low molecular weight polyolefin compound (d) is poly (ethylene) having a molecular weight of 500 to 1500.