JPH0360861B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a phenolic resin-based laminate. Prior Art In the manufacturing process of laminates, the most important step is to impregnate and coat the base material with resin varnish. The quality of impregnation affects the performance of the laminate, especially the along-line withstand voltage, and the coating speed greatly affects the efficiency of manufacturing the laminate. To improve impregnation, lower the viscosity of the resin varnish. Increase the time the substrate is immersed in the resin varnish. Increases the hydrophilicity of the resin varnish and increases the hydrophilicity of the cellulose that makes up the base material. Defoaming the base material. Apply physical means (such as pushing with a roll). Possible methods include: Conventionally, methods used include increasing the solvent content of the varnish or raising the varnish temperature; This method involves increasing the immersion distance or lowering the coating speed. In this way, a prepreg is obtained by impregnating and coating a base material with a resin varnish and drying it, and the prepreg is laminated and molded to produce a laminate. Problems to be Solved by the Invention Among conventional methods, increasing the solvent content increases the gas concentration of the solvent that evaporates during the drying process, which is not only undesirable from a safety and hygiene perspective, but also increases cost. It is also disadvantageous. The method of increasing the varnish temperature alters the quality of the varnish, thus shortening and limiting the time during which the varnish can be used. Further, the method of increasing the immersion distance requires larger equipment, and the method of lowering the coating speed is undesirable because it reduces work efficiency. In view of the above points, an object of the present invention is to enable efficient production of laminates with excellent properties in a safe environment in the production of phenolic resin-based laminates. . Means for Solving the Problems In order to achieve the above object, the present invention is characterized in that a cellulose base material is impregnated and coated with a mixed varnish in which a water-soluble low molecular weight resol type phenol resin is mixed with a resol type cresol resin. has. A required number of prepregs obtained by impregnation coating and drying are stacked together, and then heated and pressed to form a laminate. Function In the present invention, a resol type cresol resin, which is generally oil-soluble, is mixed with a low molecular weight resol type phenolic resin which is compatible with the cresol resin and is water-soluble. The presence of this low molecular weight resol type phenolic resin increases the affinity with the cellulose base material and improves the impregnation of the resin varnish into the base material without particularly increasing the solvent content. Examples Cresol used as a raw material for the resol-type cresol resin used in the present invention is generally a mixture of meta-cresol and para-cresol, but it may also be one in which a part of the mixture is replaced with phenol.
The raw material for water-soluble low molecular weight resol type phenolic resin is generally phenol, but alkylphenol may also be mixed therein. The mixing ratio of the water-soluble low molecular weight resol type phenol resin to the resol type cresol resin is preferably 5 to 20% by weight in order to ensure sufficient impregnability. If it exceeds 20% by weight, it is undesirable because the hardness of the resin increases when hot and pressure molded, resulting in poor workability of the laminate. In addition, when impregnating and coating a cellulose base material with a mixed varnish, heating the varnish to 30 to 50°C will lower the viscosity of the varnish and improve its impregnating properties, making it possible to further reduce the amount of solvent used. I can do it. It should be noted that heating above 50°C is even more undesirable because the solvent volatilizes more vigorously. Example 1 37% formalin 90 in 100 parts by weight of metacresol
Add 4 parts by weight of 25% aqueous ammonia into a reaction vessel, and react at 100°C for 60 minutes. Thereafter, the reaction was concentrated under reduced pressure to complete the reaction at a predetermined gel time of the reaction product, and diluted with methanol to a predetermined viscosity to obtain a resol type cresol resin. On the other hand, 60 parts by weight of phenol, 100 parts by weight of 37% formalin, and 6 parts by weight of trimethylamine were charged into a reaction vessel, and after reacting at 75°C for 3 hours, the reaction was concentrated under reduced pressure. A water-soluble low molecular weight resol type phenol resin was obtained by diluting it to a viscosity. The above varnish is mixed at a solid weight ratio of resol type cresol resin/water-soluble low molecular weight resol type phenol resin = 10/1, and this mixed varnish is heated to 35
℃, viscosity 100cps, basis weight 135g/ ^m2 kraft paper
It was impregnated for 15 seconds and then dried at a speed of 20 m/min to obtain a prepreg with a resin content of 51% and a resin flow of 5%. 80 sheets of this prepreg were stacked at 160℃−
Heated at 100Kg/ ^m2 for 45 minutes to obtain a 15mm thick laminate. Comparative Example 1 A laminate with a thickness of 15 mm was obtained using only the same resol type cresol resin as in the example and otherwise under the same conditions as in the example 1. Conventional example 1 Using only the same resol type cresol resin as in Example 1, varnish temperature 20℃, viscosity 30cps, basis weight 135
g/ ^m2 kraft paper for 25 seconds, then 12
Drying was carried out at a speed of m/min to obtain a prepreg with a resin content of 51% and a resin flow of 5%. Using this prepreg, a laminate with a thickness of 15 mm was obtained under the same conditions as in Example 1. Conventional Example 2 Using only the same resol type cresol resin as in the example, the varnish temperature was 20℃, the viscosity was 30cps, and the basis weight was 135.
A prepreg having the same properties as Conventional Example 1 was obtained by impregnating kraft paper at a concentration of g/m ² for 15 seconds and drying at a speed of 20 m/min. Using this prepreg, Example 1
A laminate with a thickness of 15 mm was obtained under the same conditions. Table 1 shows the characteristics of each laminate obtained above.

[Table] Effects of the Invention According to the present invention, as is clear from the comparison between the examples, comparative examples, and conventional examples, it is possible to suppress the amount of solvent used, achieve high viscosity, and perform coating at high speed. , it is possible to produce an excellent laminate that is comparable in properties to a laminate made by heating and press-molding a prepreg obtained by conventional low-viscosity, low-speed coating. Its industrial value is extremely great in that it can efficiently produce laminates with excellent properties without any safety or hygiene problems by using less solvent.

Claims (1)

[Claims] 1. A resol type cresol resin is mixed with a water-soluble low molecular weight resol type phenol resin, the mixed varnish is impregnated and coated on a cellulose base material, and the prepreg is obtained by heating and drying, and the required number of sheets of this prepreg is determined. A method for producing a phenolic resin-based laminate, which is characterized by stacking and heat-pressing molding. 2. The method for producing a phenolic resin laminate according to claim 1, wherein the mixing ratio of the water-soluble low molecular weight resol type phenolic resin is 5 to 20% by weight. 3. The method for producing a phenolic resin laminate according to claim 1, wherein the temperature of the mixed varnish during impregnation coating is 30 to 50°C.