Method for preparing high-ortho thermoplastic phenolic resin

Abstract

The invention discloses a method for preparing high-ortho thermoplastic phenolic resin. The method comprises the following steps of: (1) feeding phenol and formaldehyde into a reaction kettle in a proportion of 1:0.6-0.8, and uniformly stirring; (2) adding a weak acid salt catalyst with divalent metal ions into the reaction kettle, and then adding a weak acid catalyst, wherein the weak acid salt catalyst with divalent metal ions accounts for 0.5%-1% of the weight of the phenol, and the weight of the weak acid catalyst accounts for 0.2-0.4% of the weight of the phenol; raising temperature to 60 DEG C - 80 DEG C, and stirring to react for 0.5-2 hours; (3) heating, and boiling to reflux for 3-5 hours; and (4) dewatering, and removing excessive phenol. By adopting the composite catalyst system of zinc acetate and oxalic acid, the invention is difficult to gel and cure in the reaction process, and has no need of high-pressure condition, and the yield of the resin achieves more than 95%. The high-ortho thermoplastic phenolic resin prepared by the method has good flowability, high gelling and curing speed, and great application value in the coated sand and injection moulding process.

Description

technical field [0001] The invention relates to the field of phenolic resins, in particular to a preparation method of high ortho-position thermoplastic phenolic resins. Background technique [0002] The biggest feature of high ortho phenolic resin is its fast polymerization speed, which can make the resin cure faster under the condition of adding appropriate hexamethylenetetramine. At the same time, the high-ortho resin also has the characteristics of a relatively low softening point, so it has good coating performance in the application of coated sand, and can make the coated sand reach an appropriate room temperature tensile strength with a relatively low amount of resin added. And higher thermal tensile strength, and significantly reduce the gas generation of coated sand, which is unmatched by ordinary phenolic resin coated sand. In addition, in terms of phenolic resin injection molding process, the ideal injection molding material should have good fluidity in the machi...

AI Technical Summary

Problems solved by technology

The normal pressure reaction has the disadvantages of long time consumption, easy gel solidification and difficult control in the later stage; there are reports in the literature that high-ortho thermoplastic phenolic resins are produced using high-pressure reactors, and the use of high-pressure reactors can enable the reaction to be carried out at a higher temperature. The high temperature of 180°C is conducive to the breakage of ether bonds and prevents the resin gel from curing. However, high pressure conditions require high equipment conditions and increase production costs, which is not conducive to the industrial production of thermoplastic high-ortho phenolic resins.

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