From 1905 to 1909, L.H. Baekeland systematically studied the phenolic resin and its molding process. In 1910, the general phenolic resin company was established at the Rügs factory in Berlin to realize industrial production. In 1911, J.W. Aylesworth proposed the curing of thermoplastic phenolic resin with hexamethylenetetramine, and obtained a good performance plastic product, which has been widely used. In 1969, a fiber made from phenol-formaldehyde resin was developed by the American Emery Company, and then produced by the Japanese company Keno. There are also productions in the United States, the Soviet Union, and China. The production of phenolic resin has not deteriorated. In 1984, the world's total output was about 1946kt, ranking first in thermosetting resins. China began production in the 1940s, with a production of 77.6kt in 1984. Production methods Commonly used raw materials are phenol, resorcinol, m-cresol, xylenol, p-tert-butyl or p-phenylphenol and formaldehyde, furfural and the like. The production process consists of two steps of polycondensation and dehydration. According to the formula, the raw materials are put into the reactor and mixed uniformly, the catalyst is added, stirred, heated to 55-65 ° C, and the reaction is exothermic to automatically raise the material to boiling. Thereafter, the heating is continued to maintain micro-boiling (96 to 98 ° C) to the end point, and the mixture can be discharged after dehydration under reduced pressure. In recent years, a new process for continuous polycondensation of phenolic resins has been developed. The main factors affecting the synthesis and properties of the resin are the chemical structure of the phenol and the aldehyde, the molar ratio and the pH of the reaction medium. When the molar ratio of phenol to aldehyde is greater than or equal to 1, the initial product is monomethylol phenol, and a linear resin is formed during polycondensation; when less than 1, a polyhydroxymethylphenol derivative is formed, and the formed polycondensation resin can be crosslinked and cured. When the pH of the reaction medium is less than 7, the resulting methylol phenol is unstable and easily polycondensed into a linear resin; when it is greater than 7, the polycondensation is slow, which is favorable for the formation of a polymethylol phenol derivative. The production of thermoplastic phenolic resin is usually carried out by using hydrochloric acid, phosphoric acid or oxalic acid as a catalyst (see acid-base catalyst) to make the pH of the medium 0.5 to 1.5. To avoid violent boiling, the catalyst can be added in portions. The boiling reaction time is generally 3 to 6 hours. The dehydration can be carried out under normal pressure or reduced pressure, and the final dehydration temperature is 140 to 160 °C. The molecular weight of the resin is from 500 to 900. The production of thermosetting phenolic resin can be carried out by using sodium hydroxide, barium hydroxide, ammonia water and zinc oxide as a catalyst. The boiling reaction time is 1 to 3 hours, the dehydration temperature is generally not more than 90 ° C, and the molecular weight of the resin is 500 to 1000. The strong base catalyst is advantageous for increasing the methylol content of the resin and its compatibility with water. The ammonia catalyst can directly participate in the resination reaction, and the resin prepared by the same formula has a high molecular weight and poor water solubility. The zinc oxide catalyst can produce a high ortho-structure phenolic resin with good storage stability.