Development of fast-curing, phenolic resin adhesives

定量研究了各种因素对酚醛树脂胶粘剂固化速率的影响。除温度外，影响固化速度的主要因素是树脂的分子大小、树脂浓度、甲醛与苯酚的摩尔比、碱与苯酚的摩尔比和添加剂。固化速率随分子大小和树脂浓度的增加呈线性增加。缩合反应速率随甲醛/苯酚摩尔比的平方成比例地增加。最佳碱酚摩尔比随甲醛酚摩尔比的变化而变化。结果表明，通过提高树脂的分子量、树脂的浓度、甲醛/苯酚的摩尔比以及选择最佳的碱/苯酚摩尔比，可以得到快速固化的酚醛树脂。然而，沿着这条路线进行升级会带来一些问题：粘度大幅增加，油罐寿命极短。为了克服这些问题，设计了一种悬浮型粘接系统。一种由普通酚醛树脂和数平均分子量为2500的粉末状诺瓦拉克配制而成的悬浮型胶粘剂在粘接高含水率单板时效果良好。

The effects of various factors on the curing-rate of phenolic resin adhesives were investigated quantitatively. The main factors affecting the rate of cure, other than temperature, are the molecular sizes of the resin, resin concentrations, formaldehyde to phenol molar ratios, alkali to phenol molar ratios, and additives. The rate of cure increases in a linear fashion with the increases in the molecular size and in the resin concentration. The rate of condensation reaction increases proportionately with the square of the formaldehyde/phenol molar ratio. The optimum alkali/phenol molar ratio changes with the formaldehyde/ phenol molar ratio. These results show that a fast-curing phenolic resin can be obtained by increasing the resin molecular size, the resin concentration, and the formaldehyde/phenol molar ratio and by choosing the optimum alkali/phenol molar ratio. However, upgrading along this line brings about problems: an enormous increase in viscosity and an extremely short pot-life.To overcome these problems a suspension-type adhesive system was designed. A suspension-type adhesive formulated from an ordinary phenolic resin and a powdered novolac with number-averaged molecular weight of 2,500 worked well in bonding high-moisture content veneers.