New Curing System of Urea-Formaldehyde Resins Under Neutral Condition

UF树脂的传统固化系统已经在一个强酸性国家完成。“土壤的多样性被认为是由于残留的强酸造成的，那么将加速最终产品的羟基化。”从这一点来看，使用中性条件对新的curing系统的开发已在本报告中进行了调查。新的曲线系统是基于一种简单的方法，将UF树脂与周围的多功能氢化化合物混合在一起。结果按以下方式合并：1. The adhesive strengths of the Plywood made using four kinds of dihydrazide compounds as hardner of commercial UF resins were not al all inior to the conventional curing by ammonium chloride both in the normal test and the soaking at 60 C and passed the JAS value.2.使用二氢氮聚合物的固化系统（Hardner，不只是显示出与UF树脂的常规固化相比的粘合剂剪切强度，但也从Plywood的最终产品中减少了形式消除排放。它包含了一个由UF树脂组成的氢化化合物的反应，涉及两个阶段。第一阶段是对自由形式的氢化物组的反应。在较高的温度下，第二阶段将导致与甲基UF树脂组的羟基化合物共吸收，以给予UF树脂和氢化化合物之间的交叉连接网络。从实际观点来看，新的曲线系统具有很大的优势，从最终产品使用urea-Formaldehyde树脂来减少正规废水排放，并在中性条件下治愈UF树脂。

The conventional curing system of UF resins is accomplished in the strong acidic state. The difficulties of the resins are considered to be caused from the residual strong acid, which will accelerate the hydrolysis of the final products. From this point of view, the development of the new curing system using neutral condition was investigated in the present report. The new curing system is based on the simple method to mix UF resins with polyfunctional hydrazide compounds under around neutral conditions. Results were concluded as follows:1. The adhesive strengths of the plywood made using four kinds of dihydrazide compounds as hardner of commercial UF resins were not al all inferior to the conventional curing by ammonium chloride both in the normal test and the soaking at 60 ゜C and passed the JAS value.2. The curing system using dihydrazide polymers as hardner not only showed comparable adhesive shear strengths with the conventional curing of UF resins, but also reduced the formaldehyde emission from the final product of plywood.3. It was concluded that the reaction of hydrazide compounds with UF resins involves two stages. The first stage is the reaction of hydrazide group with free formaldehyde. The second stage at the rather higher temperature is due to the cocondensation of hydrazide groups with methylol group of UF resins to give the crosslinking networks between UF resins and hydrazide compound.From the practical point of view, the new curing system has the great advantage of reducing the formaldehyde emission from the final products using urea-formaldehyde resins and to cure UF resins under the neutral condition.