采用H2O2溶液对落叶松表面进行活化处理的研究

为提高用水性高分子异氰酸酯胶粘剂(API)胶接的落叶松木材的胶接性能,采用H2O2溶液对落叶松表面进行活化处理.试验结果表明采用H2O2溶液处理落叶松木材表面可以提高其胶接强度,用H2O2溶液处理过的落叶松表面比未处理过的落叶松素材的常态压缩剪切强度提高15%.文中还讨论了采用H2O2溶液对落叶松表面进行活化处理可以提高其胶接强度的主要机理.通过傅立叶红外吸收光谱(FTIR)证明用H2O2溶液处理落叶松木材表面可以提高其常态压缩剪切强度的机理主要是氧化作用,即用H2O2溶液处理落叶松木材表面后,其表面或获得活性基团羰基.通过对其表面接触角的测定可以看出,H2O2溶液处理过的落叶松表面润湿性增加,这对胶接有利.     

Durability of isocyanate resin adhesives for wood IV: degradation under constant steam heating

The durability of isocyanate resins consisting of emulsion-type polymeric diphenylmethane diisocyanate (EMDI) was investigated under constant steam heating. Two kinds of resin, water only-added resin and polyol/water-added resin, were used in this study. The degradation of the resins under steam heating was observed using Fourier transform infrared spectroscopy (FT-IR), weight changes, and thermogravimetric analysis (TGA). FT-IR analysis showed that the degradation reaction of the resins scarcely proceeded for a few hours and then increased significantly. The weights of the resins decreased linearly during steam heating. The thermal stability of steam-treated resins was made clear by TGA. The bond strength reductions of the specimens bonded with the resins were also observed. The best fitting regression function for the behavior of bond strength reduction was determined statistically. The apparent activation energy of each resin was calculated from the regression function, for the half-life period. Considering the calculated values, the adhesion durability of using polyol-added resin was superior to that of using water only-added resin. It was clarified that the durability of the isocyanate resins under steam heating was markedly inferior to that under dry heating.Part of this paper was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, 2000     

用酚化木材制备酚醛树脂的研究

本文研究了用酚化木材制备酚醛树脂的技术,并对其性能进行分析。在硫酸催化作用下,用苯酚对中国人工林杨树木粉进行液化。待液化产物冷却后,加入一定量的碱性催化剂和福尔马林,在(60?2)C下1小时,然后升温至(85?2)C继续反应1小时,冷却。同时观察了甲醛与苯酚的配比对树脂性能的影响。结果表明当甲醛与苯酚的摩尔比超过1.8时,用酚化木材制备的酚醛树脂具备较高的胶合强度和很强的胶合耐久性,并具有极低的醛类释放量。图4参13。     

Effect of polyol on thermo-oxidative degradation of isocyanate resin for wood adhesives

The thermo-oxidative degradation of various polyol-added isocyanate resins for wood adhesives was studied using differential scanning calorimetry and thermogravimetry. The degradation of the resin cured with water began at 150°C. When a certain polyol was added to the resin at an NCO/OH ratio of 25 in addition to water, the cured resin began to degrade at 200°C. To clarify the cause of the good thermal stability in polyol-added resins, the effect of various polyols on the reactivity of isocyanate was investigated. It was found that the reactivity of isocyanate was enhanced by the addition of a dipropylene glycol and glycerin-type polyols. In addition, the effect of the NCO/ polyol-OH ratio was investigated using dipropylene glycoltype polyol. The reactivity of isocyanate increased with increasing polyol content. The thermal stability of the resin was improved to a certain degree by addition of a small amount of the polyol but deteriorated when a large amount of the polyol was added.Part of this paper was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998     

摩尔比对脲醛树脂胶中甲醛含量的影响

降低人造板甲醛释放量的关键在于使用低游离甲醛树脂胶。在制胶过程中，进行了3种摩尔比试验，结果表明，摩尔比对脲醛树脂中甲醛含量影响极大，低摩尔比的脲醛树脂其游离甲醛含量低，用其生产的人造板产品，甲醛释放量也低，符合环保产品的标准。降低甲醛和尿素的摩尔比及改进制胶工艺的反应过程．是制成环保胶的主要途径。     

淀粉基聚酯型耐水性木材胶粘剂(英)

从高光效的谷物作物玉米中很容易分离出的淀粉适合作为绿色化学工业的可再牛原料.该文介绍一种聚酯型耐水性无甲醛玉米淀粉基木材胶粘剂制作工艺.该工艺包括了4个步骤:1)玉米淀粉硫酸固相氧化制备氧化淀粉;2)氧化淀粉常压快速液化制备高反应活性淀粉基多元醇;3)高活性淀粉基多元醇与等当鼍多兀酸(酸酐)混合和部分酯化交联;4)经过预酯化的产物用无水乙醇稀释使之成为可喷雾施胶的聚酯型木材胶粘剂.使用该新型木材胶粘剂所制备的杨木胶合板的胶合强度和耐水性能可以达到国标Ⅰ类板的要求.该文报道了硫酸的质量分数、氧化反应温度和时间;液化剂与氧化淀粉质量比、液化反应温度和时间、交联剂的羧基与多元醇羟基的当量比等加工工艺参数以及施胶量、热压温度、压力、热压时间等使用技术参数对用该种聚酯型木材胶粘剂制备的杨木胶合板的胶合强度和耐水性的影响.     

大豆基木材胶粘剂的制备及热压工艺研究

应用环氧大豆油(ESO)、硼酸溶液对大豆分离蛋白(SPI)进行改性,制备了环保的大豆基木材胶粘剂.考察了ESO用量、硼酸浓度对蛋白胶粘剂胶合强度和耐水性能的影响,研究了热压工艺对胶粘剂性能的影响.结果表明:最佳反应条件为反应温度为65℃,SPI和ESO用量分别为10g和12 g,硼酸浓度为1.0％,水为100 mL;在热压温度为150℃,压力1.5 MPa,热压时间1.5 min/mm条件下,对杨木的拉伸剪切拉伸强度达到2.2 MPa,耐湿拉伸强度达到1.86 MPa,符合木材胶粘剂的要求;红外光谱证明ESO与SPI发生了改性反应.     

基于改性大豆蛋白胶黏剂的竹刨花板性能

为了开发生物质胶黏剂及环境友好型竹刨花板,研究了基于十二烷基硫酸钠改性的大豆蛋白胶黏剂施胶量对竹刨花板物理力学性能的影响,结果表明,大豆蛋白胶黏剂的较佳施胶量为13%。通过响应曲面设计研究了热压温度、热压时间和板坯含水率对竹刨花板的力学性能及耐水性的影响,得到最优工艺参数条件为:热压温度175℃,热压时间8.5min,板坯含水率26.0%,在此条件下,静曲强度达16.8MPa,内结合强度达0.65MPa,吸水厚度膨胀率达6.7%。实验室测得竹刨花板物理力学性能指标均达到国家标准。     

核桃壳苯酚液化及其产物树脂化制备木材胶黏剂的研究

采用硫酸催化剂,考察了苯酚与核桃壳质量比等条件对核桃壳液化的影响。结果表明相同液化条件下,随着苯酚与核桃壳质量比从2∶1升至5∶1,残渣率从26.49%降至6.60%;随着浓硫酸加入量从2%增至4%、反应时间从5 min延至120 min、反应温度从100℃增至150℃,残渣率则分别从20.79%降至10.48%、48.84%降至15.62%、28.86%降至9.39%,游离酚含量分别从17.32%降至12.67%、41.71%降至10.25%、21.94%降至14.33%。同时,液化产物重均相对分子质量(MW)可降至706~1 030、分散度可降至1.04~1.25;液化产物中高相对分子质量部分随着苯酚与核桃壳质量比的增加有所降低,但随着浓硫酸加入量、液化反应时间和温度的增加而有所增加;核桃壳液化产物/苯酚/甲醛共缩聚树脂胶黏剂(WPF)与传统酚醛树脂胶黏剂(PF)的对比表明,WPF的胶接强度可达1.33 MPa,可作为胶合板用胶黏剂。     

萜烯树脂乳液在水基复膜胶中的应用

用乙烯-醋酸乙烯共聚物(EVA)乳液、萜烯树脂乳液和阳离子型苯乙烯-丙烯酰胺共聚物研制了系列水基复膜胶,并考察了萜烯树脂乳液中乳化剂结构对复膜胶性能的影响。研究结果表明,作为交联剂的阳离子型苯乙烯-丙烯酰胺共聚物可大幅提高EVA乳液的黏度和剥离强度,其最佳加入量为0.5%(以EVA乳液的固形物为基准)。萜烯树脂乳液与EVA乳液的质量比值为0.3时,复膜胶的剥离强度最大。由高分子表面活性剂(HS-2)制得的萜烯树脂乳液增加复膜胶剥离强度的效果最好。