JPS6328925B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin composition for low-pressure injection molding that has excellent thermal rigidity and dimensional stability. [Prior Art] Thermosetting resin molding materials are currently used in many mechanical and structural parts because of their heat resistance, heat creep resistance, and other characteristics. Among them, phenolic resin molding materials are widely used because they have excellent injection moldability and are relatively low cost. However, as the range of use expands, the demands on molding materials are also expanding. One such example is the low-pressure injection molding grade of phenolic resin, and in recent years there has been a demand for a much higher level of phenolic resin compared to the conventionally used encapsulation of plugs in electric heating appliances. I'm getting used to it. For example, in the case of automobile parts containing various sensors, low-pressure molding is required to avoid deformation, and at the same time, high heat resistance and dimensional stability are also required. Conventionally, low-pressure molding materials with excellent dimensional stability have been made using novolak-type phenolic resins or resol-type phenolic resins as curing agents with an equivalent weight of about 0.6 to 1.3.
So-called phenol-cured epoxy resins (resol type, for example, JP-A-59-200443), epoxy resins using amines, acid anhydrides as curing agents, etc.
Epoxy resins include epoxy resins, and among them, phenol-cured epoxy resins have relatively high thermal rigidity, but are unsatisfactory in terms of cost, injection moldability, and high thermal rigidity. Therefore, it is desirable to use phenolic resin, but conventional phenolic resin molding materials for low-pressure molding have a relatively high resin content and have a long flow, so they are not always good in terms of dimensional stability. I was not satisfied either. [Purpose of the Invention] The present invention was developed as a result of extensive research in an effort to obtain a product that simultaneously satisfies low pressure molding, thermal rigidity, and dimensional stability that could not be obtained with conventional phenolic resin molding materials. It was discovered that this objective could be achieved by modifying it with an epoxy resin, leading to the present invention. The purpose is to provide a molding material that has excellent low-pressure injection moldability, thermal rigidity, and dimensional stability. [Structure of the Invention] The present invention has a resin component in which 2 to 50 parts by weight of a novolak type epoxy resin having an epoxy equivalent of 170 to 300 is added to 100 parts by weight of a resol type phenolic resin, and the amount of this resin component is 20 to 300 parts by weight. 40% by weight, and 90% by weight or more of the base material component is an inorganic material mainly composed of glass fibers. The reason why we limited the phenolic resin to the resol type here is that there is a clear difference from the novolak type in terms of heat resistance, and liquid and solid resol resins that are normally used as molding materials can be used. A solid resol resin is more desirable in terms of mold fogging during continuous molding. The epoxy resin needs to be a novolak type epoxy resin with a small epoxy equivalent in order to obtain higher thermal rigidity. The present invention uses a resin modified by adding a small amount of novolac type epoxy resin (ratio of epoxy equivalent/phenolic OH group equivalent is 0.35 or less) to a resol type phenol resin, rather than using a composition of a phenol-cured epoxy resin. Therefore, curing takes place primarily as a phenolic resin with methylene bonds. In the present invention, 2 to 50 parts by weight of a novolak type epoxy resin having an epoxy equivalent of 170 to 300 is used per 100 parts by weight of the resol resin (the ratio of epoxy equivalent/phenolic OH group equivalent is about 0.008 to 0.35). If the amount is less than 2 parts by weight, the effect of adding the epoxy resin will not be sufficiently obtained, resulting in insufficient low-pressure moldability and dimensional stability, and if it is more than 50 parts by weight, it is not desirable in terms of thermal rigidity. In addition, in the composition as a molding material, the amount of resin component is 20
~40% by weight is desirable. If it is less than 20% by weight, it is difficult to obtain a long flow sufficient for low pressure molding, and 40
If it exceeds % by weight, it becomes difficult to obtain sufficient dimensional stability, which is not preferable. The base material used for these resin components should contain at least 90% by weight of inorganic materials, and more preferably all of the material should be inorganic. Since the organic base material has a negative effect on both thermal rigidity and dimensional stability, it is not appropriate to use it in an amount of 10% by weight or more based on the total amount of the base material. In addition to glass fiber, inorganic base materials such as calcium carbonate, silica, clay, and mica can be used as the inorganic base material. Considering the balance of various properties, glass fiber is a very preferable base material. If necessary, curing catalysts such as metal oxides, metal hydroxides, amines, imidazoles, lubricants, colorants, etc. are added to the above components, and the mixture is heated and kneaded to obtain a molding material. [Effects of the Invention] The molding material thus obtained can be injection molded at low pressure and has sufficient thermal rigidity and dimensional stability without the need for after-baking. . Such a molding material is ideal as a material for various parts that are required to encapsulate various sensors, motor coils, circuit elements, etc., and to withstand usage conditions such as being exposed to high temperatures. [Example] In Examples Nos. 1, 2, and 3, materials were prepared by heating and kneading the composition shown in the table with a resin composition in the range of 12.5 to 40 phr of epoxy resin to resol resin, and their characteristics. As shown in Table 1, the material has excellent flow, thermal rigidity, and dimensional change rate. On the other hand, although Comparative Example No. 4 is made of only resol resin, the dimensional change rate is large.
Comparative Example No. 5 is a novolak resin with a large amount of resin to achieve long flow, but both the heat distortion temperature and the dimensional change rate are insufficient. Comparative Example No. 6 uses a combination of novolac type phenolic resin and epoxy resin, but has a low heat distortion temperature. Furthermore, Comparative Example No. 7 and Comparative Example No. 8 are epoxy resins using an equivalent amount of novolac type phenolic resin and an equivalent amount of resosol type phenolic resin as hardening agents, respectively, and these also have low heat distortion temperatures. Thus, it is clear that the present invention is superior. 【table】

Claims (1)

[Claims] 1 A resin component is obtained by adding 2 to 50 parts by weight of a novolac type epoxy resin with an epoxy equivalent of 170 to 300 to 100 parts by weight of a resol type phenolic resin, and this resin component is 20 to 40% by weight, and the base material A phenolic resin molding material characterized in that 90% by weight or more of the ingredients are inorganic substances mainly composed of glass fibers.