Method for synthesizing phenolic resins by using paraformaldehyde

Abstract

The invention belongs to the technical field of phenolic resin synthesis, and discloses a method for synthesizing phenolic resins by using paraformaldehyde. The method comprises the following steps: opening a reaction kettle stirring mechanism, pumping preheated phenol into a reaction kettle in a reduced pressure state, then pumping recycled phenol containing wastewater into the reaction kettle and carrying out vacuum removal on the reaction kettle, and putting paraformaldehyde into the reaction kettle to uniformly heat at normal pressure so as to heat the obtained mixture to be boiled; after the boiling reaction is completed, cooling the obtained mixture, and adding an oxalic acid solution into the reaction kettle; after the obtained mixture is heated to be boiled and the pressure-reduced dehydration temperature rises to 150 DEG C, carrying out slow vacuum enrichment and then emptying on the obtained product so as to obtain phenolic resins, wherein the proportion of macromolecular weights of the phenolic resins is less than 6%, and the proportion of middle molecular weights of the phenolic resins is more than 80%. The phenolic resins prepared by using the method disclosed by the invention have high fluidity, and have a higher bonding strength when being taken as a binder under the condition that the resin adding amount is less.

Description

technical field [0001] The invention belongs to the technical field of synthesis of phenolic resin, and discloses a method for synthesizing phenolic resin with paraformaldehyde. Background technique [0002] In recent years, more and more research work has shown that the molecular weight of phenolic resin, especially the distribution of molecular weight, affects the performance of phenolic resin. Compared with ordinary phenolic resins, phenolic resins with more middle molecular weight distribution have lower softening point, longer fluidity and more uniform curing behavior. improve. [0003] Common methods to narrow the molecular weight include the method of reacting in organic solvents and removing low molecular weight phenolic resins by steam distillation and solution washing. This method is complicated and produces a large amount of organic solvents and waste water, which greatly pollutes the environment and increased production costs. [0004] Kurimoto et al disclose...

AI Technical Summary

Problems solved by technology

This method uses a large amount of NaOH, and the reaction time is too long, so it is difficult to realize industrial production

Chinese patent 00135829.4 introduces the improved process of the above process route. Although the reaction time is reduced, the process control of the base first and then the acid is difficult, and it is difficult to realize industrial production.

[0007] In Chinese patent 00131050.X, organophosphoric acid is used as a catalyst to prepare phenolic resin with narrow molecular weight distribution. In the reaction, a large amount of catalyst needs to be added, and the catalyst needs to be removed by washing, which not only increases the cost, but also increases the amount of waste water. Washing with water, a large amount of catalyst will remain in the resin, which will reduce the performance of the resin

[0008] What Chinese patent CN200710129851.6 adopts is composite catalyst, and the addition amount of catalyst is larger, and cost is high, and what use in production is liquid formaldehyde, and the waste water that produces is also more

Images