JPH0686563B2 - Laminated phenol resin varnish - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a phenol resin varnish having excellent impregnability into a base material for a cellulosic laminate such as kraft paper, linter paper, and mixed paper thereof. is there.

[Prior Art] Generally, a phenolic resin for laminated boards is a modified material, that is, a shoe oil or a refined product thereof, tung oil, linseed oil, castor oil, nonylphenol, aniline, polybutadiene and the like and phenols such as cresol and paratoluenesulfonic acid. React under acidic catalyst such as, and after neutralization add formaldehyde and basic catalyst to perform the resolization reaction,
After obtaining the modified phenolic resin, it is dehydrated and concentrated under reduced pressure and diluted with a solvent such as methanol, ethanol or toluene to obtain a varnish for impregnation.

Next, this varnish is impregnated into a cellulosic laminate base material such as kraft paper, linter paper, or a mixed paper of these papers and dried to obtain a prepreg for a laminate.

However, the conventional varnish has a poor impregnating property of the resin component into the laminate base material, and the obtained laminate has poor electrical performance such as insulation resistance, inductivity, dielectric loss tangent and the like after boiling, and is practically used. It could not be used for.

As a countermeasure for this, a method of making a prepreg for a laminated plate is generally carried out by performing a primary impregnation treatment with a low molecular weight water-soluble phenolic resin or a melamine resin, and then a secondary impregnation treatment with a phenolic resin varnish as described above. However, the resin to be impregnated first is hard and there is a problem in the punchability of the laminated plate, and since it is impregnated twice, there is also a problem in productivity.

It has been attempted to use a conventional varnish and prolong the impregnation treatment time by only one impregnation, but there is a drawback in that the impregnation rate is significantly reduced and the productivity is reduced.

[Object of the Invention] An object of the present invention is to provide a phenol resin varnish having a good impregnating property, which can sufficiently impregnate a substrate with only one impregnation treatment.

[Structure of the Invention] The present invention relates to a phenol resin varnish for a laminate, wherein the phenol resin is a resol type phenol resin, the resin content in the varnish is 45 to 75% by weight, and the solvent is 25 to 55% by weight, and The solvent is a gist of a phenol resin varnish for a laminated board, which is characterized by comprising 20 to 80% by weight of a C _{1 to} C ₃ alcohol, 10 to 70% by weight of toluene or xylene, and 5 to 40% by weight of water. is there.

Here, the resol type phenol resin is a modifier, that is, cashew oil or a refined product thereof, tung oil, linseed oil, castor oil, nonylphenol, aniline, polybutadiene and the like and phenols such as cresol and paratoluenesulfonic acid and the like. It is obtained by reacting under an acidic catalyst, neutralizing, adding formaldehyde and a basic catalyst to carry out a resolization reaction, obtaining a modified phenol resin, and then dehydrating and concentrating under reduced pressure.

In the present invention, it is preferable to use a tung oil-modified resol type phenol resin as the phenol resin.

The phenol resin is diluted with the solvent. Among the solvents, C _{1 to} C ₃ alcohols (hereinafter referred to as lower alcohols) refer to aliphatic monoalcohols having 1 to 3 carbon atoms, such as methanol, ethanol, 1-propanol, and 2-propanol. Methanol and 1-propanol are preferable.

The main feature of the present invention is the use of water with a lower alcohol and toluene or xylene.

The ratio of the above solvent and phenolic resin in the varnish is the solvent
It is 45 to 75% by weight of phenol resin to 25 to 55% by weight (hereinafter referred to as "%").

The ratio of lower alcohol to toluene or xylene to water in the solvent is lower alcohol 20 to 80%, toluene or xylene 10 to 70%, and water 5 to 40%, but lower alcohol 30 to
60%, toluene or xylene 20-60%, and water 10-30% are preferred.

When the phenol resin is a tung oil-modified resol type phenol resin, methanol / toluene = 2/1 to 1/2 is particularly preferable.

That is, the present invention makes it possible to increase the proportion of water by adding toluene or xylene as a solvent in addition to a lower alcohol, and thus the impregnability of the resol-type phenol resin into the cellulose-based laminate substrate. Is improved.

Regarding water, a case where a part or all of the water present in the final varnish is left in the resin during dehydration after production of the phenol resin is also included in the present invention.

The present invention also includes the case where 10% or less of another solvent such as acetone or butanol is added to such a solvent.

[Effects of the Invention] The phenol resin varnish of the present invention has excellent impregnating ability to the substrate for laminates, and therefore the properties of the laminate obtained using this varnish, particularly the electrical properties such as insulation resistance after boiling. It has excellent punchability and water absorption.

Furthermore, it is not necessary to impregnate twice, unlike the conventional varnish.

[Example] Production Example of Phenol Resin Varnish 40 parts of tung oil (parts by weight, the same applies hereinafter), 60 parts of phenol and 0.5 part of paratoluenesulfonic acid were charged in a reaction kettle and reacted at 100 ° C for 2 hours to give 0.6 part of ammonia. Neutralized.

Then, 40 parts of 37% formalin and 6 parts of triethylamine were added and reacted at 100 ° C. for 3 hours. Then, dehydration under reduced pressure was performed at 500 mmHg to obtain a tung oil-modified phenol resin (hereinafter referred to as phenol resin A).

Example 1 100 parts of Phenol Resin A is methanol: toluene: water = 4:
A phenol resin varnish was obtained by diluting with 100 parts of a 4: 2 mixed solvent.

Example 2 100 parts of phenol resin A was diluted with 100 parts of a mixed solvent of 1-propanol: xylene: water = 8: 1: 1 to obtain a phenol resin varnish.

Comparative Example 1 100 parts of phenol resin A was diluted with 100 parts of methanol to obtain a phenol resin varnish.

Comparative Example 2 100 parts of phenol resin A was diluted with 100 parts of a mixed solvent of methanol: water = 8: 2 to obtain a phenol resin varnish.

The resin content and solvent component ratio of the phenol resin varnish obtained in each example are shown in Table 1.

Kraft paper was impregnated with each phenol resin varnish and dried.

Eight sheets of this phenol resin-impregnated paper are piled up at 170 ℃, 1
A phenol resin laminate was obtained by heating and pressurizing at 40 kg / cm ^{2 for} 100 minutes.

The properties shown in Table 2 were measured for the obtained laminate.

The measuring method of each characteristic is as follows.

Insulation resistance, dielectric constant and water absorption after boiling: according to JIS K 6911.

Punching workability: Using a punching die, punch 200 holes at 60 ° C at the same time and check the number of delaminations around the holes.

As described above, the laminated plate of the example is
It can be seen that it is excellent in insulation resistance, dielectric constant, punching workability and water absorption after boiling.

Claims (1)

[Claims] 1. A phenolic resin varnish for a laminate, comprising:
Phenolic resin is a resole phenolic resin, the resin content in the varnish is 45 to 75 wt%, the solvent is 25 to 55 wt%, the solvent is an alcohol 20 to 80 wt% toluene or xylene C ₁ -C ₃ 10-70% by weight Water 5-40% by weight Phenolic resin varnish for laminated boards, characterized in that