JPH0564976B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a paper-based phenolic resin laminate for electrical insulation. Prior Art Phenol resin laminates are widely used as insulating substrates for printed circuits, especially in the field of consumer electronics.Especially in recent years, as electronic components have become more densely packaged and more sophisticated, the electrical properties of laminates have improved. and requirements for machinability are becoming stronger. In order to meet the above market needs, undercoating varnishes have traditionally been prepared by diluting methylolphenol resin with organic solvents (methanol, acetone, toluol, etc.) at a concentration of about 10 to 30% by weight.
A two-step impregnation-drying method has been implemented in which paper base material is impregnated and dried, and then a top coat varnish (oil-modified phenolic resin varnish or methylol phenol resin varnish added with a plasticizer) is impregnated and dried. The ability (penetration of the resin into the base material) is low, and the electrical properties and punching workability of the obtained laminate are insufficient, and the market needs cannot be fully met. In order to improve the punching workability, methods such as increasing the amount of oil modification in the top coat varnish or adding a large amount of plasticizer have been adopted, but the interlayer adhesion of the laminate decreases, making it difficult to punch out dense small holes. is inferior. Problems to be Solved by the Invention As described above, in the conventional technology, there is a problem in that the level of interlayer adhesion, electrical properties, moisture resistance, etc. when forming dense small holes is low, especially with regard to punching workability. In order to improve these laminate properties,
It is necessary to improve the permeability of the resin into the paper base material. As a method, it has been proposed to use a large amount of water in the varnish to swell the fibers of the paper base material during impregnation, making it easier for the resin to penetrate, but the methylolphenol resin mentioned above is soluble in water. It separates without being able to be impregnated. To solve this problem, it is possible to use a varnish made of resin emulsion, but this reduces production efficiency due to the drying capacity of the drying process. From these viewpoints, an object of the present invention is to efficiently produce a paper-based phenolic resin laminate having excellent electrical properties, moisture resistance properties, and punching workability. Means for Solving the Problems In order to achieve the above object, the present invention has the following features:
It is characterized in that the prepreg obtained through steps (a) to (c) is molded under heat and pressure. (a) A varnish is prepared by emulsifying an oil-modified phenolic resin, a methylol phenolic resin, and a curing accelerator with a surfactant and using water as a dispersion medium. (b) Impregnating the paper base material with the emulsion varnish and drying it (undercoating step). (c) Furthermore, it is impregnated with oil-modified phenolic resin varnish and dried (top coating process). Function In the present invention, since an emulsion varnish using water as a dispersion medium is used, it is possible to swell the fibers of the paper base material and allow the emulsion resin to penetrate therein. The presence of the oil-modified phenolic resin in the undercoating process increases the affinity with the oil-modified phenolic resin in the topcoating process, contributing to the production of a laminate with excellent properties. In addition, during drying in the undercoating process, the presence of a curing accelerator promotes the curing reaction of the resin to the B stage, leading to increased efficiency. Furthermore, this B-stage curing reaction also promotes the formation of mononuclear phenols and mononuclear methylolphenols into polynuclear bodies, which improves the raw material yield by reducing volatile matter during the drying process. You can also aim for Example An example of the present invention will be described. Example 1 Tung oil modified phenolic resin varnish (solid content 80g)
and methylolphenolic resin varnish (solid content 20
g), and to this mix surfactant 1 (HLB
= 6) 3g, surfactant 2 (HLB = 16) 3g and benzylmethylamine 1g as a curing accelerator,
800 g of water was added and mechanically stirred with a stirrer to prepare a uniformly emulsified and dispersed phenolic resin emulsion varnish (concentration 10% by weight). Apply this emulsion varnish to a paper base (basis weight 135
g/ ^m2 of kraft paper) and dried (resin amount
10% by weight) was then impregnated with tung oil modified phenolic resin varnish (concentration 60% by weight) and dried, resulting in a total resin amount of 48%.
% prepreg by weight was produced. Eight sheets of this prepreg were laminated, copper foil with adhesive was layered on one side, and a copper clad laminate with a thickness of 1.6 mm was produced by heating and pressing at a pressure of 100 Kg/cm ² and a concentration of 160° C. for 90 minutes. Comparative example 1 Tung oil modified phenolic resin varnish (solid content 80g)
and methylolphenolic resin varnish (solid content 20
g) and surfactant 1 (HLB=
6) 3g and surfactant 2 (HLB=16) 3g and water
800 g was added and mechanically stirred with a stirrer to prepare a uniformly emulsified and dispersed phenolic resin emulsion varnish (concentration 10% by weight). This emulsion varnish was used for undercoating, and the same tension laminate was produced in the same manner as in Example 1. Comparative Example 2 A methylolphenol resin varnish (concentration 15% by weight) was prepared by adding 500g of methanol to 100g of solid content of methylolphenol resin and stirring. This varnish was used for undercoating, and a copper-clad laminate was manufactured in the same manner as in Example 1. Table 1 shows the results of characteristic and performance tests on these copper-clad laminates. Table 2 also shows a comparison of raw material yield and efficiency in the impregnating and drying process.

【table】

[Table] Effects of the Invention As described above, according to the present invention, an undercoat varnish is used, which is made by adding a surfactant, a curing accelerator, and water to a combination system of oil-modified phenolic resin and methylol phenolic resin to form an emulsion. This makes it possible to improve the treatment effect of the paper base material and to greatly improve the impregnating properties of the top coat varnish. As a result, as shown in Table 1, the electrical properties, moisture resistance, and punching workability of the phenolic resin laminate were significantly improved compared to conventional products. Furthermore, the efficiency (drying speed) in the impregnating and drying process and the raw material yield can be improved. Furthermore, the use of an emulsion varnish with an aqueous dispersion medium reduces the amount of organic solvent used, which greatly improves work safety.

Claims (1)

[Scope of Claims] 1. A method for producing a phenolic resin laminate, in which prepreg obtained through the following steps (a) to (c) is molded under heat and pressure. (a) Prepare a varnish made by emulsifying an oil-modified phenolic resin, a methylolphenol resin, and a hardening accelerator with a surfactant and using water as a dispersion medium, and (b) impregnate a paper base material with the emulsion varnish and dry it. Step (c) Further, a step of impregnating with an oil-modified phenolic resin varnish and drying is performed.