JPH0438772B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing a paper-based phenolic resin laminate that has good heat resistance and electrical insulation properties and exhibits small dimensional changes even after repeated heat treatments. Conventional technology In the production of paper-based phenolic resin laminates that require electrical insulation, impregnated paper is usually used to improve the interlayer adhesion of the laminate and the adhesion when attaching metal foil to the surface. In order to improve the properties and electrical properties, a two-step impregnation drying method is used in which a paper base material is impregnated with a water-soluble phenolic resin and then dried, and then further impregnated and dried with a phenolic resin that becomes a base resin. However, in recent years, electronic devices and consumer devices have become smaller and more dense in order to reduce prices, so the laminates used in these devices have to have stable dimensions when processed by heat treatment. There is now a demand for low shrinkage laminates that do not change much. One way to deal with this is to reduce the dimensional shrinkage of the paper base material itself. To reduce the dimensional shrinkage rate of the phenolic resin itself, which is the base resin. Adding an appropriate amount of inorganic filler to resin to reduce dimensional shrinkage. Such methods have been considered. Problems to be Solved by the Invention However, among these methods, the method for manufacturing the base material is complicated, which increases the price of the base material, and the number of man-hours increases, as well as during the resin varnish manufacturing and resin impregnation processes. If stirring is not performed sufficiently, there is a risk that the inorganic filler will not be sufficiently dispersed and reliability will deteriorate. In addition, a wide variety of ways of thinking are possible, and a wealth of experimental experience and demonstration is required, and it will take many years to solve the problem. On the other hand, since water-soluble phenolic resins conventionally used as undercoat resins are low-molecular compounds, reactions proceed during the lamination process and curing shrinkage during the curing process cannot be avoided. For these reasons, a means for obtaining a laminate with a small dimensional shrinkage rate using conventional manufacturing methods has not yet been completed. In view of these points, the present invention provides a paper-based phenolic resin laminate that does not use water-soluble phenolic resin, has good heat resistance and electrical insulation, and has small dimensional changes even after repeated heat treatments. The purpose is to Means for Solving the Problems In order to achieve the above object, the present invention uses tung oil modified phenol as the undercoat, which has a lower concentration than the topcoat, when impregnating and drying a paper base material with a resin in two stages: undercoat and topcoat. Impregnate with resin varnish and dry. Then, a high-concentration varnish containing a tung oil-modified phenolic resin is applied as a top coat and dried to obtain impregnated paper. This impregnated paper is laminated and molded to obtain a laminate. Effects Since the present invention does not use a water-soluble phenolic resin, it is possible to obtain a laminate with small dimensional shrinkage.
The tung oil-modified phenolic resin varnish used for the undercoat has a low concentration, so it fully penetrates into the paper base material, and it bonds well with the tung oil-modified phenolic resin of the top coat, resulting in a laminated layer that maintains good electrical insulation and heat resistance. You can get a board. Example An example of the present invention will be described. Example 1 (1) 720 g of tung oil, 530 g of meta-cresol, and 0.74 g of para-toluenesulfonic acid were put into a three-necked flask, and after reacting at 80°C for 1 hour, synthetic phenolic acid was added.
500 g of 86% paraform, and 35 g of 25% aqueous ammonia were added, and the mixture was heated and stirred at 80°C to react. (2) Continue the reaction, and when the gel time at 160°C of this reaction product reaches 6 minutes, dehydrate and concentrate.
Add methanol to this dehydrated condensate and
A phenolic resin varnish modified with tung oil of % by weight was obtained. (3) The varnish from (2) above was adjusted to have a resin content of 15% by weight using a solvent with a weight ratio of toluene/methanol = 1/1, and then impregnated into 10 mils kraft paper and heated at 120°C for 15% by weight. By heating and drying for 1 minute, an impregnated paper (2) with a resin content of 15% by weight was obtained (undercoat). (4) Furthermore, the tung oil-modified phenolic resin obtained in the steps (1) and (2) above, a bisphenol-type brominated epoxy resin with an epoxy equivalent of 400, and triphenyl phosphate, respectively, in terms of solid content weight ratio.
Mix the mixture in a ratio of 70/22.5/7.5 to make a varnish, impregnate the impregnated paper () obtained in (3) with it, heat dry it, and make the impregnated paper () with a total resin content of 50% by weight.
(overcoat). (5) 8 sheets of the impregnated paper obtained in (4) above and 1 sheet of adhesive-coated copper foil with a thickness of 35 μm were stacked together and heated and pressed using a conventional method to obtain a single-sided copper-clad laminate with a thickness of 1.6 mm. Ta. Comparative Example 1 (1) Put 548 g of synthetic carbolic acid, 508 g of paraform, and 72 g of triethylamine into a three-necked flask, and
Continue heating and stirring at ℃, and when the gel time of the reaction product at 160℃ reaches 5 minutes, cool it.
Methanol was added to obtain a water-soluble phenolic resin initial condensate having a resin content of 50% by weight. (2) Dissolve 90g of trimethylolmelamine in 600g of water, add 891g of methanol, stir and mix evenly, then add 420g of the water-soluble phenolic resin initial condensate (resin content 50% by weight) obtained in (1) and stir. This was used as an undercoat varnish with a resin content of 15% by weight. (3) This undercoating varnish was impregnated into 10 mils kraft paper and dried in the same manner as in Example 1, item (3) to obtain impregnated paper with a resin content of 15% by weight. Further, using this impregnated paper, a single-sided copper-clad laminate with a thickness of 1.6 mm was obtained through the same steps as in sections (4) and (5) of Example 1. Table 1 shows the characteristics of the single-sided copper-clad laminates obtained in Example 1 and Comparative Example 1.

【table】

[Table] Effects of the Invention As described above, according to the present invention, when producing impregnated paper for paper-based phenolic resin laminates, the undercoat resin is a low-concentration tung oil-modified phenolic resin varnish, so that the undercoat cannot be applied as before. Compared to a laminate in which the resin is a water-soluble phenolic resin initial condensate, the dimensional shrinkage rate during heat treatment can be reduced.
Further, the impregnating property of the resin into the paper base material is also good, and there is an effect that the electrical insulation properties of the laminate can be improved.

Claims (1)

[Claims] 1. In the production of laminates in which paper substrates are laminated with impregnated paper obtained by impregnating and drying resin in two stages: an undercoat and a topcoat, the paper substrate is impregnated with a tung oil-modified phenolic resin varnish, which has a lower concentration than the topcoat, as an undercoat. A method for producing a paper-based phenolic resin laminate, which is dried and further impregnated with a high-concentration varnish containing a tung oil-modified phenolic resin as a top coat and dried.