JPS628312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention belongs to the field of manufacturing technology for laminates, and in particular, technology for manufacturing phenolic resin laminates. [Background technology] An important characteristic of laminates for consumer use is punching workability. Due to the industry's needs for low-temperature punching and high-density punching, laminate resins are increasingly becoming plasticized. Therefore, the phenolic resin in the phenolic laminate for low-temperature punching has a low glass transition point,
I'm holding it down. In addition, free phenol was included in the laminate in an amount of about 1.0% because it has a plasticizing effect and is difficult to remove. In addition, resin paper (prepreg) contains 2.0
% of free phenol was included. As described above, the sufficiently plasticized laminate for low-temperature punching had some aspects that were too soft as a substrate.
Another problem was that the strength was weak when heated. [Object of the Invention] The present invention aims to improve the strength of a laminate as a substrate, which is the problem described above, while maintaining low-temperature punching workability. The purpose is to improve strength. [Disclosure of the Invention] Generally, a method for producing a phenolic resin laminate is to impregnate a paper base material (not limited to this) with a phenolic resin varnish, heat and dry it, and then heat and pressure mold it. The present invention is to reduce the pressure in the process of heating and drying the prepreg impregnated with phenolic resin in order to reduce the free phenol concentration in the laminate. Conventionally, in order to improve the impregnation of resin into the base material,
I have tried reducing the pressure during the impregnation process, but not during the drying process. This is because it has been determined that about 1% of free phenol in the laminated layer is not harmful, although it may have a plasticizing effect. The level of decompression is, but is not limited to,
-500 mmHg to -750 mmHg is good, and the greater the reduced pressure, the more convenient it is. By the above method, the free phenol content in the prepreg is reduced to 1.0% or less. By using the above prepreg, better results can be obtained if the free phenol content in the laminate is set to 0.3% or less. Note that if the free phenol content of the prepreg is 1.0% or less, it will be 0.3 or less in the laminate in the case of large or low. [Effects of the Invention] As described above, the viscoelastic spectra of the laminate resin with reduced free phenol and the laminate resin with no reduction are as shown in FIG. As you can see, the resin with reduced free phenol is
It can be seen that the Young's modulus has improved. The effect is especially great when it's hot. However, there is no difference in glass transition temperature. Furthermore, the low-temperature punching processability of the laminate is
There is no difference. This will be explained below using Examples and Comparative Examples. Example 1 A varnish is prepared by diluting a phenolic resin modified with tung oil with a methanol solvent. Dip-impregnate 10 mils thick kraft paper in varnish. Immediately dry under −700 mmHg and set at 150°C to 160°C. The free phenol content of the resin-impregnated paper (prepreg) thus obtained was determined to be 0.7% by gas chromatography. This prepreg was laminated and molded using a conventional method to obtain a laminate with a thickness of 1.6 mm. Free phenol in the laminate was measured in the same manner as the prepreg and was found to be 0.1%. Example 2 Similar to Example 1, but with the level of vacuum reduced to -
It was set to 600mmHg. Free phenol was 0.9% in the prepreg and 0.3% in the laminate. Comparative Example 1 Same as Example 1, but the resin-impregnated paper was dried under normal pressure. Free phenol was 2.0% in the prepreg and 1.0% in the laminate. The punching workability of the laminates obtained in the above Examples and Comparative Examples and the viscoelastic spectrum of the laminate resins were measured, and the results are shown in the table below. 【table】

[Brief explanation of the drawing]

FIG. 1 is a graph representing a viscoelastic spectrum.

Claims (1)

[Claims] 1. An impregnation step in which a base material is impregnated with a phenolic resin varnish to prepare a resin-impregnated base material, a drying step in which a prepreg is prepared by heating and drying the resin-impregnated base material, and a lamination process in which the prepreg is heated and pressurized. 1. A method for producing a phenolic resin laminate comprising a step of forming a plate into a phenolic resin laminate, the method comprising drying a resin-impregnated base material under reduced pressure. 2. The manufacturing method according to claim 1, wherein the prepreg is dried until the content of free phenol contained in the prepreg is 1.0% or less. 3 Free phenol content in the laminate is 0.3%
The manufacturing method according to claim 1, characterized in that the method is dried until the following.