Production process of high-purity novolac epoxy resin with ultralow phenolic hydroxyl group content

Abstract

The invention discloses a production process of high-purity novolac epoxy resin with ultralow phenolic hydroxyl group content, which comprises the following steps: 1) synthesis of epoxy resin: respectively adding phenol, formaldehyde and a part of oxalic acid by weight into a reaction kettle, starting heating, carrying out primary reflux, adding the rest oxalic acid by weight into the reaction kettle, and keeping the temperature unchanged, thereby obtaining the epoxy resin with ultralow phenolic hydroxyl group content; carrying out secondary reflux; after confluence is finished, phenol startsto be recycled, phenolic resin is obtained, and weighing is conducted for the next procedure; (2) ring-opening reaction: putting the synthesized epoxy resin into a reaction kettle, adding epoxy chloropropane into the reaction kettle, uniformly stirring, adding a phase transfer catalyst, preparing to dropwise add liquid caustic soda, adding the liquid caustic soda in two times, maintaining the temperature to be not more than 60 DEG C after the dropwise addition is finished, keeping the temperature for 4-6 hours, and after the reaction is finished, reducing the content of produced phenolic hydroxyl groups to be below 400ppm. The requirements of industries such as high-end composite materials and high-pressure component pouring are met, the product color is lighter, the purity is higher, andthe yellowing resistance of downstream products is better.

Description

technical field [0001] The invention relates to the technical field of fine chemical synthesis, in particular to a production process of high-purity novolac epoxy resin with ultra-low phenolic hydroxyl content. Background technique [0002] Novolac epoxy resin is also called F-type epoxy resin. In acidic medium, phenol, bisphenol A, o-cresol and formaldehyde undergo polycondensation reaction to obtain novolac resin, and then polycondensate with excess epichlorohydrin in the presence of sodium hydroxide. It has high epoxy group content, high viscosity, high cross-linking density after curing, and its fiber-reinforced plastic has good physical and mechanical properties. Heat resistance is higher than E-type epoxy resin. Mainly used in glass fiber, carbon fiber composite materials, circuit printing plates, construction of various structural parts and other industries. [0003] During the synthesis process of the resin, most of the phenolic hydroxyl groups of the phenolic res...

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Problems solved by technology

[0003] During the synthesis process of the resin, most of the phenolic hydroxyl groups of the phenolic resin are replaced by epoxy groups, but due to the influence of the steric hindrance effect and the side reaction of the reaction, the conversion rate of the phenolic hydroxyl group does not reach 100%, that is to say, the phenolic hydroxyl group There are still a small amount of phenolic hydroxyl groups in the molecular structure of epoxy resin, and in the application of composite materials, phenolic hydroxyl groups do not participate in the curing reaction, so there are phenolic hydroxyl groups in the molecular chains of the resin and the crosslinked molecular chains, which are easy to absorb water. Decrease the dielectric properties and mechanical properties of the product; at the same time, the phenolic hydroxyl group is easy to generate quinone and other substances under the action of ultraviolet rays and heat, resulting in darker or uneven color of the product

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