JPS6327186B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a phenolic resin laminate in which dehydration of phenol varnish is completed at a lower temperature than conventionally. In recent years, laminates use kraft paper instead of conventional linter paper as the paper base material to reduce warping during the processing of printed wiring boards. but,
When kraft paper is used, the fibers contain a large amount of impurities, and since these impurities contain a large amount of electrolyte, the electrical properties deteriorate, which is a practical problem. Therefore, conventional varnishes for low-temperature punching processable laminates are made by mixing 10 to 20 parts of water-soluble phenol varnish that improves electrical properties with tung oil modified phenol varnish, or by pre-impregnating paper base material with water-soluble phenol varnish. A paper base material to which 10 to 15% water-soluble phenol varnish was attached by drying was used, and the paper base material was further impregnated with tung oil-modified phenol varnish and dried to obtain a prepreg. The laminates obtained by these methods have satisfactory electrical properties, but when water-soluble varnish is used, the plasticizer content is relatively reduced, making the laminates hard and poor in punching properties, so the punching temperature must be lowered. It was necessary to raise the punching temperature by 20 to 40°C, and when the punching temperature was increased, the warpage of the printed wiring board increased, causing problems in use. Therefore, there has been a desire for a method that can improve electrical properties without reducing punching workability. In response to such demands, the present inventors increased the water content of the paper base material from the usual 7% to 10 to 15%, or added phenol varnish with 1 to 3% water.
We have found a method for improving the electrical properties by adding % to 50% of the metal without substantially reducing the punching workability. The reason why the presence of water in the phenol varnish improves the electrical properties of the laminate is considered as follows. The water contained in the phenol varnish causes the fibers of the paper base to expand, which makes it easier for the phenol resin to penetrate into the inside of the fibers, improving the adhesion between the fibers of the paper base and the phenol resin. The electrical properties of phenolic resin laminates decrease when the amount of water absorbed increases, but as the adhesion between the fibers of the paper base and the phenolic resin improves, the amount of water absorbed by the laminate decreases, reducing the negative effects of moisture and improving the electrical properties. It is thought that this will improve. From the above facts, it can be seen that it is best to allow water to remain in the phenol varnish, but if the water content increases, it will no longer dissolve in the phenol varnish, and the water and phenol varnish will separate, making it practically unusable. A small amount of water will dissolve in phenol varnish, but
In particular, phenol varnish modified from tung oil is difficult to dissolve in water. Conventionally, the phenol varnish temperature was set at 100℃±5 to avoid separation of water and phenol varnish.
Phenol varnish that has been dehydrated until the temperature rises to a temperature of 0.degree. C., especially phenol varnish modified with tung oil, has been sufficiently dehydrated, but as mentioned above, the more water that can be contained in the phenol varnish, the better. The present invention has been made in view of the above points, and its purpose is to terminate the vacuum dehydration of the produced phenol varnish when water within the solubility limit remains in the phenol varnish. This allows a larger amount of water to remain in the phenol varnish within the solubility limit than before, which can improve the water absorption rate and insulation resistance of the laminate obtained by laminating paper base prepreg impregnated with phenol varnish. The present invention provides a method for producing a phenolic resin laminate. The present invention will be explained in detail below. Tung oil modified phenols are produced by reacting a mixture of phenol or phenols such as cresol with tung oil, water and para-toluene sulfonic acid (PTSA), and then the tung oil modified phenols and formalin are reacted under an alkali catalyst. The reaction produces a resol-type phenol varnish modified with tung oil. The generated phenol varnish was dehydrated under reduced pressure, and once the temperature of the phenol varnish rose to 60 to 90°C, the vacuum dehydration was completed with water dissolved in the phenol varnish, and then the obtained phenol varnish was dissolved in methanol. Afterwards, a water-soluble phenol varnish is mixed with the phenol varnish dissolved in methanol. Next, a paper base material such as kraft paper is impregnated with a phenol varnish mixed with a water-soluble phenol varnish and dried to obtain a paper base prepreg, and then a plurality of stacked paper base prepregs are heated and pressurized to form a phenol resin laminate. Form a board. Using phenol modified with tung oil as the phenol, the resulting phenol varnish is heated to the conventional final dehydration temperature of 100 to 105℃.
Phenol varnish that has been dehydrated under reduced pressure and dissolved in methanol so that the methanol content is 30 to 35% by weight dissolves 3 to 10% water, but the gel time of phenol varnish at this time is 10 to 20 minutes, and the water Solubility is proportional to gel time. In the present invention, dehydration is completed when water within the solubility limit remains in the phenol varnish without adding water to the phenol varnish after dehydration, and when 3 to 10% of water remains in the phenol varnish. In order to terminate the vacuum dehydration of the phenol varnish, the vacuum dehydration may be completed when the temperature of the phenol varnish, which once decreased during dehydration, rises to 60 to 80°C. Note that the above temperatures are for a dehydration time of 20 to 40 minutes, and if the dehydration time is different, the temperature at which vacuum dehydration ends will also change, so it is necessary to investigate the relationship between temperature and amount of dehydration in advance. In addition, cresol varnish modified with tung oil is used as the phenol, and the cresol varnish produced is dehydrated under reduced pressure to the conventional final dehydration temperature of 100 to 105°C, and the cresol varnish is dissolved in methanol to make the methanol content 30 to 35% by weight. 1-3%
When dissolved, the gel time of cresol varnish is 10 to 20 minutes, similar to phenol varnish. 1
To finish the vacuum dehydration of the cresol varnish when ~3% of water remains in the cresol varnish, if the dehydration time is 20 to 40 minutes, the temperature of the cresol varnish, which once decreased during dehydration, must drop to 80 to 90℃. When the temperature rises, the vacuum dehydration may be completed. In the present invention, phenols and formalin are reacted to produce phenol varnish, and the vacuum dehydration of the produced phenol varnish is completed when water within the solubility limit remains in the phenol varnish. Even when phenol or cresol is used, water within the solubility limit can remain in the phenol varnish, and the water does not separate in the phenol varnish. In this way, phenol varnish can be prepared using the condensed water generated by reacting phenols and formalin, and there is no need for dilution with water in a separate process, and it can be prepared through a series of production processes. Phenol varnish can be prepared,
This increases productivity. In addition, since a laminate is formed by laminating paper base prepreg impregnated with phenol varnish that retains moisture after dehydration, the fibers of the paper base material that have absorbed the moisture in the phenol varnish expand and the phenol resin is transferred to the paper. It can penetrate deep into the fibers of the base material, improving the adhesion between the fibers of the paper base material and the phenolic resin, reducing the water absorption rate of the laminate, and making it difficult for the laminate to absorb moisture. Electrical properties such as insulation resistance are improved. That is, the present invention uses condensed water generated during the production of phenol varnish to expand the fibers of the paper base material,
The aim is to manufacture a phenolic resin laminate with good production efficiency and excellent electrical properties. The present invention will be specifically explained below using examples. Example 1 130g of phenol, 65g of tung oil, 8.5g of water and
Add 0.17g of PTSA to 1 flask and heat to 113℃~
The reaction was carried out at 120°C for 30 minutes. After the reaction was completed, the product was cooled, and when the temperature reached approximately 50°C, 140 g of 37% formalin and 6 c.c. of 25% aqueous ammonia were added and heated.
A phenol varnish was produced by reacting at 100° C. for 60 minutes, and then dehydrated by reducing the pressure to 65 cmHg. 3～
The liquid temperature reached 55-60°C in 5 minutes, but as time passed and the amount of water decreased, the liquid temperature gradually rose. When the temperature of the phenol varnish reached 80°C, dehydration was completed, and 100 g of methanol was added to cool it. After mixing 10 parts of water-soluble phenol varnish with 100 parts of the obtained phenol varnish, paper base material (HL-10) was prepared.
The mixture was impregnated with varnish and dried to obtain a prepreg with a resin content of 48-50%. Eight sheets of this prepreg and 35 μm adhesive-coated copper foil were layered and molded in a mold to obtain a laminate. Table 1 shows the properties of the obtained laminate. Example 2 Cresol 130g, tung oil 65g and PTSA 0.10g
was charged into one flask and reacted at 123 to 130°C for 30 minutes. After the reaction is complete, cool the product, add 140 g of 37% formalin and 50 c.c. of 25% aqueous ammonia, and add 100 g of 37% formalin and 50 c.c.
The reaction was carried out at ℃ for 60 minutes. The cresol varnish thus produced was dehydrated as in Example 1, and after the dehydration was completed at a liquid temperature of 90° C., 100 g of methanol was added and cooled. After mixing 10 parts of the obtained cresol varnish with 10 parts of water-soluble phenol varnish, a laminate was obtained in the same manner as in Example 1 using the mixed varnish. Table 1 shows the properties of the obtained laminate. Comparative Example 1 The same procedure as in Example 1 was carried out, except that the final temperature for dehydration of the phenol varnish was 100°C. The dehydration time was 35 minutes. Comparative Example 2 The procedure was carried out in almost the same manner as in Example 2, except that the final temperature for dehydration of the phenol varnish was 100°C.

[Table] As is clear from Table 1, Example 1 of the present invention
The laminates obtained in Example 2 had lower water absorption and improved insulation resistance than those of Comparative Examples.

Claims (1)

[Claims] 1. Generate phenol varnish by reacting phenols and formalin, and terminate vacuum dehydration of the generated phenol varnish when water within the solubility limit remains in the phenol varnish,
A method for manufacturing a phenolic resin laminate, comprising impregnating a paper base material with the phenol varnish in which water remains, and then laminating a paper base prepreg impregnated with the phenol varnish.