PRODUCTION OF LAMINATED SHEET

摘要

PURPOSE:To enable the natural curing reaction of a prepreg prepared by impregnating substrates with a tung oil-modified phenolic resin and drying the impregnated substrates to suppress its progress even at ordinary storage temperature (20 deg.C). CONSTITUTION:Tung oil is made to react with p-cresol in the presence of p- toluenesulfonic acid and phenol and paraformaldehyde are added to the resultant reactional product. The reaction is further advanced in the presence of trimethylamine and methanol and toluene are added thereto. The resultant mixture is then cooled. p-Toluenesulfonic acid is added thereto and the obtained mixture is regulated to weak acidity. Paper substrates are then impregnated with the prepared tung oil-modified phenolic resin varnish and dried to produce sheets of prepreg. The resultant sheets of prepreg are subsequently to afford the objective laminated sheet.