JPH0414283A - Hygroscopicity-improved laminated board for electricity - Google Patents

Abstract

PURPOSE:To improve the hygroscopic characteristic, etc., of a laminated board for electricity by performing preliminary impregnation treatment with a melamine resin on a paper substrate so that the melamine resin can substantially permeate the paper substrate to cell walls of all paper fibers. CONSTITUTION:Cellulose fibers, such as kraft paper, linter paper, cotton paper, rayon pulp paper, etc., are used for preparing the paper substrate of this laminated board. The melamine resin to be used for preliminary impregnation treatment to the paper substrate includes the precondensate of a triazine compound, such as melamines and guanamines, and formaldehyde and those obtained by etherifying part of or all of the methyrol group of the precondensate with such a lower alkanol as methanol, butanol, etc. The appropriate adhering amount of the melamine resin is 10-30% of the total weight of the paper substrate. When the amount is too small, the melamine resin permeates to part of the paper fibers only and, when too large, the permeating property of an unsaturated polyester resin is lowered. After the impregnation, the wet paper substrate is dried., It is important to control the drying temperature to 50-150 deg.C, desirably to 80-120 deg.C at the time of drying the paper substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION Recently, paper-based unsaturated polyester resin electrical laminates, particularly metal foil-clad laminates for printed circuit boards, have been developed by the present applicant and are widely used. These can be produced in a continuous manner, resulting in high productivity, and they also have excellent electrical properties such as tracking resistance. In this case, the paper base material may be treated with melamine resin in advance for the purpose of increasing the adhesion of the unsaturated polyester resin to the base material and improving the moisture absorption properties of the laminate caused by the hydrophilic cellulose fibers. Proposed. Japanese Patent Publication No. 38-13781゜Applicant's Japanese Patent Publication No. 55-144159. See 56-43329, etc. However, until now, there has been no detailed study of the effects of treatment conditions and penetration conditions of melamine resins on performance such as moisture absorption properties of laminates.

SUMMARY OF THE INVENTION The present invention provides a paper-based unsaturated polyester resin electrical laminate with maximum improved moisture absorption properties. The present invention provides an electrical laminate formed by laminating a plurality of paper base materials impregnated with unsaturated polyester resin (including vinyl ester resin), in which substantially all of the paper fibers of the paper base material are laminated. The present invention relates to an electrical laminate characterized in that it is pre-impregnated with a melamine resin so that the melamine resin penetrates into the inside of the cell wall.

Furthermore, in order to obtain a laminate with excellent adhesion between the base material and the impregnated unsaturated polyester resin, the preliminary impregnation treatment is performed by:
Preferably, the substrate is impregnated with a water/methanol mixture in which a melamine resin is dissolved or dispersed, and dried at a temperature of 80° C. or more and 150″ C or less.

The paper base material used in the present invention refers to paper base materials made from cellulose fibers such as kraft paper, linter paper, cotton paper, and rayon pulp paper.

Melamine resins are initial condensates of formaldehyde and triazine compounds such as melamine and guanamines, and products in which part or all of the methylol groups of these initial condensates are etherified with lower alkanols such as methanol or butanol. include. Trimethylolmelamine, its methyl and butyl ethers are representative examples.

Melamine resin is used by being dissolved or dispersed in a mixture of water and a lower alkanol such as methanol. The water/methanol ratio is preferably in the range of 90/10 to 50,150 from the viewpoint of the hygroscopic properties of the laminate. More preferably 2
5/75 No! -55/45 range. The concentration of melamine resin is related to the amount of melamine resin attached to the paper base material.
The concentration must be such that a coating amount of . The amount of melamine resin attached is 10 to 30% based on the weight of the paper base material.
A range of % is appropriate. This is because if the amount is too small, the melamine resin will penetrate only a portion of the paper fibers, and on the other hand, if the amount is too large, the impregnating property of the unsaturated polyester resin will be reduced. The amount of adhesion may be adjusted by, for example, impregnating the paper base material with the melamine resin liquid by dipping or the like, and then squeezing out the excess liquid. After impregnation, the wet paper substrate is dried by hot air, heated drums, far infrared radiation alone, or a combination thereof. At that time, the temperature of the treated paper itself is 50 to 150℃1
It is important that it is heated preferably to a temperature of 80 to 120°C. Furthermore, in order to help the penetration of the melamine resin into the inside of the paper fibers, in addition to setting the optimal mixing ratio of the water/methanol mixture that helps the paper swell as a solvent as described above, it is necessary to use an auxiliary agent that promotes penetration, such as polyethylene. Addition of surfactants such as glycol higher fatty acid esters and nonylphenol ether, pre-impregnation treatment under reduced pressure, and combinations thereof are also effective. The degree of penetration of the melamine resin into the paper fibers can be observed by creating sections of the product laminate using a microtome and using an ultraviolet microscope. Alternatively, it can be determined from the ultraviolet absorption spectrum within the paper layer. It is also possible to apply the same method as above after embedding a base material pre-impregnated with a melamine resin in a cyanoacrylate instant adhesive.

To manufacture a laminate, a paper base material treated as described above is impregnated with an unsaturated polyester resin liquid, and multiple sheets of the same are laminated.
If necessary, it can be manufactured by applying metal foil on one or both sides and then curing it. In this case, it is also possible to dry the resin-impregnated base material once to make a prepreg, and then use a press to carry out the process in a Hanosen style.
Preferably, it is carried out continuously, as described in 13. In the case of a continuous system, the pre-impregnating process for the paper substrate can be incorporated into the line, or the pre-impregnating process can be carried out on a separate line and then rolled up for use in the continuous line. Good too.

Examples of the present invention are shown below. The percentages and parts in the examples are by weight.

Example Commercially available trimethylolmelamine (S-
305) Commercially available kraft paper (ZBS-135, manufactured by Dezumi Kokusaku Pulp) was immersed in a pretreatment solution consisting of 18 parts of nonionic surfactant (Emulgen 905, manufactured by Kao), and 100 parts of 35% methanol water temperature solution. The sample was squeezed to a squeezing rate of 100%, air-dried, and then heated at 100°C for 10 minutes.

This was impregnated with a resin solution containing 100 parts of a commercially available unsaturated polyester resin solution (Polymer 6304 manufactured by Takeda Pharmaceutical Co., Ltd.) and 1 part of an initiator (Perbutyl O manufactured by Nippon Oil & Fats Co., Ltd.), and 6 sheets were laminated. The foil was applied to one side and cured by heating at 100° C. for 30 minutes and then at 120″C for 10 minutes to produce a copper-clad laminate approximately 1.6 mm thick.

The moisture absorption rate of this product was 1.7% at a temperature of 40° C. and a humidity of 90% for a holding time of 96 hours. Furthermore, it was observed from the above-mentioned ultraviolet micrograph that the melamine resin had penetrated evenly into the cell wall of the paper fibers.

Comparative Example I Trimethylolmelamine (S-305) 1.8 parts, 75
The laminates were laminated in the same manner as in the example except that a pretreatment liquid consisting of 100 parts of a hot water solution of methanol was used. The moisture absorption rate of the obtained laminate under the same conditions was 2.6%. Further, from the above-mentioned ultraviolet micrograph, it was observed that the melamine resin was only attached to the surface of the paper fibers and did not penetrate into the inside of the cell wall.

Comparative Example 2 A paper base material pre-impregnated with melamine resin was air-dried at 200″C.
A laminate was produced in the same manner as in Example 1, except that it was heated for 10 minutes. The moisture absorption rate of the obtained laminate under the same conditions is 2
．． It was 9%. Further, by observing the laminate using a scanning electron microscope (SEM), gaps were observed between the paper fibers and the unsaturated polyester resin.

Claims (3)

[Claims] (1) In an electrical laminate made by laminating multiple sheets of paper base material impregnated with unsaturated polyester resin, the melamine resin penetrates into the cell wall of substantially all the paper fibers of the paper base material. An electrical laminate characterized by being pre-impregnated with melamine resin. (2) The preliminary impregnation treatment of the paper base material with the melamine resin is performed by impregnating the paper base material with a water/methanol mixture in which the melamine resin is dissolved or dispersed, and drying at a temperature of 80°C or more and 120°C or less. Electrical laminate according to item 1. (3) The electrical laminate according to item 1 or 2, wherein at least one side is laminated with metal foil.