中密度纤维板用超低n(F)∶n(U)比例MUF胶粘剂

MUF adhesives with ultra-low molar ratio of n(F):n(U) for medium density fiberboard

采用"碱-酸-碱"传统合成工艺、n(F)∶n(U)比例降至0.96∶1、尿素分3次投料、调节三聚氰胺的加入量以及加入方式、加入聚乙烯醇(PVA)等其他助剂、控制缩聚温度为90℃和缩聚阶段的pH为4.8左右等,制备MDF(中密度纤维板)用MUF(三聚氰胺-尿素-甲醛共缩聚树脂)胶粘剂。研究结果表明:MUF的游离甲醛含量低于0.2%、固含量约53%,并且其固化时间和黏度等均适用于MDF的制备;当w(总三聚氰胺)=4%、w(前期三聚氰胺)=2%时,选择适宜的热压工艺,所得MDF的性能[如内结合强度(IB)、静曲强度(MOR)、弹性模量(MOE)和吸水厚度膨胀率(TS)等]和甲醛释放量(7.94 mg/100 g)均达到GB/T 11718—2009标准要求。

The MUF （ melamine- urea-formaldehyde copolycondensation resin ） adhesive for MDF （ medium density fiberboard） was prepared by some methods such as ＂alkali-acid-alkali＂ traditional synthesis process, decreasing molar ratio of n（F）：n（U） until 0.96：1 ,adding urea according to three times,regulating melamine contents and feeding order, adding polyvinyl alcohol （PVA） and other additives, eontroling temperature at 90 ℃ and pH about 4.8 in polycondensation phase. The research results showed that the MUF＇s free formaldehyde content was less than 0.2% ,solid content was about 53% ,and its curing time and viscosity were suitable for preparing MDF. Choose suitable hot-pressing process, the MDF＇s properties （such as IB, MOR, MOE and TS） and formaldehyde emission （7.94 mg/100 g） could all reach standard requirement of GB/T 117t8--2009 when mass fractions of total melamines and prophase melamine were 4% and 2% respectively.