【摘要】 介绍了以甲醛和尿素为原料、聚乙烯醇为改性剂合成改性脲醛树脂的方法。考察了尿素加入方式、甲醛与尿素摩尔比、反应液pH、反应温度及聚乙烯醇用量对脲醛树脂性能的影响。结果表明,在尿素分3次投料,甲醛与尿素摩尔比1.6∶1,加成反应阶段温度70℃左右、反应液pH7.5~8.5,缩聚温度85~90℃、反应液pH5.2~5.4,聚乙烯醇用量占甲醛和尿素总量的1.0%条件下,可制得综合性能较好,游离甲醛含量低的低毒脲醛树脂。更多还原

【Abstract】 Modified urea-formaldehyde was synthesized from formaldehyde and urea as raw materials using polyvinyl alcohol as modifier.The effects of reaction conditions such as urea adding ways,molar ratio of formaldehyde to urea,pH of reaction system,reaction temperature,and dosage of polyvinyl alcohol on the behaviors of urea-formaldehyde were examined.The result showed the product prepared under the following conditions had good balanced performances with low content of free formaldehyde: addition of urea into reaction system in 3 portions,molar ratio of formaldehyde to urea 1.6∶1,addition temperature 70 ℃,pH of reaction system 7.5-8.5,condensation temperature 85-90 ℃ and pH of reaction system 5.2-5.4,dosage of polyvinyl alcohol 1.0%(based on the total mass of formaldehyde and urea).更多还原