JPH04318011A - Production of phenolic resin for molding material - Google Patents

Abstract

PURPOSE:To provide a phenolic resin good in storage stability and the cylinder stability in its injection molding as a molding material, and capable of shortening its molding cycle. CONSTITUTION:The objective phenolic resin can be obtained by reaction at 80 deg.C for 4hr in the presence of triethylamine between paraformaldehyde and phenol (molar ratio: 1.25) followed by addition of ammonia, and then by further reaction at 85 deg.C for 5hr. The present method will reduce the amount of unreacted phenol component and enable higher molecular weight of said phenolic resin.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a phenolic resin suitable for use as a molding material for electrical parts such as microswitches and automobile parts such as heat insulators.

0002

BACKGROUND OF THE INVENTION Phenol resin molding materials are resol resins that do not generate ammonia, methylamine, etc. when insert molding metal parts in the molding of electrical and automobile parts. This resol resin is made by replacing formaldehyde and phenols with Ca(OH)2, Na
It is obtained by reacting in the presence of an alkali catalyst such as OH, KOH, or ammonia, and is mixed with appropriate fillers and additives as reinforcing or extenders, kneaded, and then ground to form a molding material.

0003

[Problem to be solved by the invention] The above resol resin is
The reaction progresses easily even at room temperature, and storage stability is poor. When used as a molding material and injection molded, reactions tend to proceed, resulting in poor cylinder stability. Furthermore, since it contains a large amount of unreacted phenol component, the molding cycle becomes long. The problem to be solved by the present invention is to improve the storage stability of a phenolic resin and, when used as a molding material, to improve cylinder stability for injection molding and to shorten the molding cycle.

0004

[Means for Solving the Problems] In order to solve the above problems, the phenolic resin for molding materials according to the present invention is produced as follows. First, in the first stage reaction, the molar ratio of formaldehyde/phenols was adjusted to 1.2 to 1.3.
and the reaction is carried out in the presence of a triethylamine catalyst. Thereafter, a second stage reaction is carried out in the presence of an ammonia catalyst.

[0005]

[Operation] By carrying out the reaction as described above, the molecular weight of the phenol resin produced can be increased and the amount of unreacted phenol component can be reduced. It is stable at room temperature due to its low molecular weight phenolic resin and small amount of unreacted phenol components, and when injection molded as a molding material, it is stable without rapid curing reaction within the cylinder, and at high temperatures inside the mold. , it cures quickly and can shorten the molding cycle. The molar ratio of formaldehyde/phenols is 1
．． If it is less than 2, the curability when used as a molding material is insufficient, and if it exceeds 1.3, cylinder stability during injection molding will decrease.

[0006]

EXAMPLES The phenols used in the examples of the present invention are monohydric phenols such as phenol, cresol and xylenol, and polyhydric phenols such as catechol and resorcinol. Formaldehyde includes paraformaldehyde, formalin, and the like. The formaldehyde/phenols molar ratio is preferably 1.25 to 1.3.

The amount of triethylamine used as a catalyst is suitably 0.3 to 1% based on the total weight of phenols and formaldehyde. If it is too small, the reaction rate for producing phenolic resin will be slow and the amount of unreacted phenol will be large. Therefore, the curing speed of the obtained phenol resin tends to be slow, and the molding cycle also tends to be long. On the other hand, if the amount of triethylamide is too large, the reaction for producing phenolic resin will become faster and difficult to control. Also,
The amount of ammonia used is 0 based on the total weight of both of the above.
．． 2 to 1% is appropriate. If the amount is too low, the molecular weight of the produced phenol resin will not be sufficiently increased. Note that even if more than 1% is added, the degree of increase in molecular weight remains unchanged.

[0008] In addition to glass fiber, the above phenolic resins include silica, glass powder, talc, kaolin, clay,
Inorganic fillers such as silica and alumina, coloring agents such as carbon black as additives, and mold release agents such as zinc stearate and stearic acid are appropriately blended, and the mixture is kneaded using a kneading machine such as a Henschel mixer or a roll, and then pulverized. Use as a molding material.

Examples 1-2, Comparative Examples 1-2 Using the formulations shown in Table 1, phenol and paraformaldehyde were reacted at 80°C for 4 hours in the presence of triethylamine, and then ammonia was added and the reaction was carried out at 85°C for 5 hours. A resol resin was obtained.

Comparative Examples 3 to 4 Using the formulations shown in Table 1, phenol and paraformaldehyde were reacted at 80°C for 4 hours in the presence of Ca(OH)2, and then ammonia was added and the mixture was reacted at 85°C for 5 hours. A resol resin was obtained.

[0011]

[Table 1]

The gelation time retention rate (ratio of gelation time to the initial value when left at 40° C. for 10 days) of each of the phenolic resins obtained above was measured to evaluate storage stability. Additionally, the amount of unreacted phenol in each phenol resin was measured. The results are shown in Table 2. Further, each of the above-mentioned phenol resins was mixed and kneaded with glass fiber, glass powder, and additives in a Henschel mixer, and then ground and dried to obtain a molding material. This molding material was injection molded (cylinder temperature: front: 90°C, rear: 50°C, mold temperature: 180°C), and the molding cycle and cylinder stability were evaluated. For the molding cycle, (injection time + pressure holding time) was shortened, and the minimum moldable time was evaluated. The results are also shown in Table 2.

[0013]

[Table 2]

[0014]

Effects of the Invention As is clear from Table 2, the phenol resin produced by the method according to the present invention has a high gelation time retention rate and good storage stability. In addition, since there is little unreacted phenol, it becomes a molding material with a short molding cycle, and has excellent stability because it does not harden at low temperatures inside the cylinder.

Claims (1)

[Claims] Claim 1: The molar ratio of formaldehyde/phenols is 1.2 to 1.3, the first stage reaction is carried out in the presence of a triethylamine catalyst, and then the second stage reaction is carried out in the presence of an ammonia catalyst. A method for producing a phenolic resin for molding materials, characterized by the following steps: