【作者】 李翾；

【导师】 沈一丁；

【作者基本信息】 陕西科技大学 ， 应用化学， 2012， 博士

【摘要】 脲醛树脂胶黏剂因为其具有工艺简单、价格低廉等优点，所以在目前市面上所使用的各种木材胶黏剂中仍是使用量最多的一种胶黏剂。但是随着人们环境保护意识的不断加强和胶黏剂技术的不断发展，对于脲醛胶的使用也将会受到更多的限制。因此开发无甲醛系胶黏剂、环保型胶黏剂已成为木材胶黏剂的重要发展方向。本课题的目的在于制备一种不含甲醛且对环境无污染的新型木材胶粘剂，其既能够避免脲醛胶的甲醛释放问题，又能解决目前无甲醛胶粘剂存在的成本较高、强度差、工艺复杂等问题。异氰酸酯由于具有高反应活性且固化速率快等优点，已成为制备环保型胶黏剂的一种重要原料。目前在木材胶黏剂行业中对异氰酸酯的运用，多数集中于用小分子的异氰酸酯与多元醇反应制得异氰酸酯预聚体，然后对其进行乳化制得无醛胶黏剂。这种方法所制得的胶黏剂I中活性异氰酸酯基的含量较小，且不易有效的保留其活性，从而影响了胶黏剂的应用性能。本实验直接以异氰酸酯三聚体作为交联剂为基础，采用多种自身具有较好粘结性或耐水性的聚合物与其进行复配，力求制备出综合性能优越的无醛木材胶黏剂，并研究了复合体系的结构与性能，探讨它们协同作用机理，并用此胶黏剂进行应用研究。本课题的主要任务如下：1.以聚乙烯醇（PVA）为高分子分散剂，丙烯酸（AA）、N-羟甲基丙烯酰胺（NMA）、苯乙烯（St）丙烯酸丁酯（BA）为单体，采用无皂种子乳液聚合法制备了稳定且性能优异的自交联丙烯酸树脂乳液。并用此丙烯酸树脂乳液作为主剂，硅溶胶和六亚甲基二异氰酸酯三聚体（HDI）作为外加交联剂复合制得一种性能优异的无醛人造板胶黏剂。实验讨论了其合成影响因素，并优化了合成工艺条件。研究表明：当ω(PVA)=8%，ω(AA)=6%，ω(NMA)=4%，n(BA)/n(St)=2:1，ω(硅溶胶)=6%，ω(HDI)=8%时，此胶黏剂具有优异的应用效果。用此最佳比例所制得的丙烯酸树脂乳液的粒径为168.5nm，乳胶膜的拉伸强度为7.5Mpa，断裂伸长率为862.19%，吸水率为16%。由胶黏剂的FT-IR分析可看出，在波长2270 cm-1附近未出现吸收峰，说明异氰酸酯基已经发生了反应，体系中没有游离的-NCO。由胶黏剂膜的热分解曲线可看出：此聚合物存在两个明显的分解阶段。由乳液的表观黏度-剪切速率曲线可看出：此胶黏剂乳液是一种假塑性流体，并随着硅溶胶和异氰酸酯用量的增加，乳液黏度随剪切速率增加而降低的趋势更加明显，乳液的假塑性行为增强。同时随着硅溶胶和异氰酸酯用量的增加，体系的黏度增大。乳胶膜的动态力学性能分析看出：外加交联剂硅溶胶和异氰酸酯三聚体的加入，使得乳胶膜的储能模量增大，但当硅溶胶用量超过6%，HDI用量超过8%时，储能模量降低。这说明硅溶胶和异氰酸酯的加入可在一定程度上提高乳胶膜的刚性。用此无醛胶黏剂在细木工板上进行应用实验。结果表明：在ω(硅溶胶)=6%，ω(HDI)=8%，施胶量为250g/m2进行施胶时，细木工板的胶合强度达0.82Mpa，横向静曲强度达20.5 Mpa，耐水性为12h，均符合国家标准。由此可见：此木材胶黏剂具有较佳的实际应用价值。2.在N,N-二甲基甲酰胺（DMF）做助溶剂的作用下，以甲基丙烯酸甲酯、丙烯酸丁酯为主要原料，DMC为功能单体，以偶氮二异丁腈为引发剂，十二硫醇为分子量调节剂，通过乳液聚合合成丙烯酸树脂，然后用此丙烯酸树脂乳化异氰酸酯三聚体制得交联剂乳液，最后将交联剂乳液和羧基丁苯胶乳液复配制得木材胶黏剂。实验讨论了其合成影响因素，并优化了合成工艺条件。研究表明：当DMC含量为单体总质量的30%，BA/MMA=1/1，十二硫醇含量为总固体的0.4%时，制得的丙烯酸树脂性能较佳，此丙烯酸树脂乳胶膜的吸水率为16%，拉伸强度为6.5MPa。当m(丙烯酸树脂)/m(HDI)=2/1时，水性异氰酸酯交联剂的性能最佳，其胶膜的吸水率为14.5%，拉伸强度为7.2MPa。并且从红外光谱分析可知，此交联剂有效的保留了异氰酸酯基的反应活性。水性异氰酸酯交联剂/羧基丁苯胶复合木材胶黏剂的最佳制备工艺条件：当m(异氰酸酯交联剂)/m(羧基丁苯胶)=10%时，制得的胶黏剂性能较佳，其膜的吸水率为12%，拉伸强度为7.6 MPa。红外光谱分析表明：此胶黏剂虽然有效的保留了异氰酸酯基的反应活性，但是还是有一部分发生了反应。热重分析表明：异氰酸酯交联剂的加入，提高了聚合物的热稳定性，并且随着异氰酸酯交联剂加入量的增大，提高幅度越大。乳液流变性分析表明：此胶黏剂乳液是一种假塑性流体，并且随着异氰酸酯交联剂用量的增大，乳液的假塑性行为增强。动态力学分析表明：随着异氰酸酯交联剂用量从0%增加到10%时，乳胶膜的储能模量增加，但当异氰酸酯交联剂用量超过10%达到15%时，储能模量又有所降低，乳胶膜的刚性减弱。胶黏剂乳胶膜的接触角分析表明：不加交联剂的羧基丁苯胶乳胶膜的接触角为68.5°，加入10%的异氰酸酯交联剂后所制得的胶黏剂胶膜的接触角为88°，由此可知，异氰酸酯交联剂的加入能有效的提高乳胶膜的疏水性。胶黏剂在细木工板上的应用实验表明：在热压温度为120℃，施胶量为300g/m2时。所制得的细木工板的胶合强度为0.80MPa，静曲强度为21.4 MPa，耐水性为10小时，符合国家标准。3.在EVA和异氰酸酯三聚体的体系中引入聚乙烯醇，并用EVAIII和聚乙烯醇复配作为主剂，用此主剂乳化六亚甲基二异氰酸酯三聚体（HDI），从而得到EVA-聚乙烯醇/异氰酸酯无醛木材胶黏剂。实验讨论了其合成影响因素，并优化了合成工艺条件。研究表明：当m(PVA)/ m(EVA)=1/3（其中PVA的型号选用1788），六亚甲基二异氰酸酯三聚体用量为10%时，所制得的乳胶膜的拉伸强度达7.8Mpa，断裂伸长率为763.2%，吸水率为23%。由胶黏剂乳液的TEM图可看出：用EVA和PVA作主剂对异氰酸酯三聚体进行乳化所得到的胶黏剂乳液，乳液的粒子呈圆形，且尺寸较为均一，分布较为均匀。胶黏剂乳胶膜的热重分析可看出：由于异氰酸酯三聚体能与聚合物体系中的羟基发生交联反应，使得聚合物结构中出现体型分子，从而提高了乳胶膜的热稳定性。乳胶膜的动态力学性能可看出：体系中随着m(PVA)/ m(EVA)比例的增大，在一定程度上能提高乳胶膜的刚性，但当m(PVA)/ m(EVA)超过1/3时，反而使得乳胶膜的刚性降低；异氰酸酯三聚体的加入量在0%～10%范围内随着其用量的增大，乳胶膜的刚性增大。在热压温度为120℃，热压时间为10min，施胶量为260 g/m2时，细木工板的胶合强度为0.78Mpa，静曲强度为19.5Mpa，耐水性为6.5h。符合国家标准。胶黏剂在中密度纤维板上的应用实验表明：在施胶量为120Kg/m3，热压温度为160℃时。所制得的中密度纤维板的吸水厚度膨胀率为14.5%，内结合强度为2.02Mpa，静曲强度为40.2Mpa。均大于标准值，符合国家标准。更多还原

【Abstract】 Now, in all kinds of wood adhesive, the urea-formaldehyde resin isstill a widely used adhesive due to the simple production technologyand low price. With the increasing awareness of environmentalprotection, the development of science and technology and thecontinuous appearance of new material, the use of theurea-formaldehyde adhesive will be subject to restricted. So thedevelopment of environment friendly adhesive has become theimportant development direction.The purpose of this task is to get a kind of environment friendlyadhesive. It can not only eliminate the problem of releasingformaldehyde, but also could solve the shortcoming of high cost andcomplex process of the environment friendly adhesive. Becauseisocyanate has high reactivity and curing speed, it has become a kind ofimportant raw materials in the preparation of the environment friendlyadhesive. At present isocyanate adhesive did not retain good reactivityof isocyanate, result in the strength is not good. In this paper, withisocyanate polymers as cross-linking agent, a series of wood adhesivewithout formaldehyde will be synthesized by isocyanate polymers andmany kinds of vinyl polymer. And the author study detailedly thestructure and properties of composite systems to explore the mechanismof their synergy. The main content of this paper is as followings:1. With polyvinyl alcohol (PVA) as polymeric colloid stabilizer, akind of surfactant-free copolystyrene-acrylat latex with good stable andexcellent property is successfully synthesized by reacting styrene (St),butyl acrylate (BA), N-hydroxymethyl Acrylamide (NMA) and acrylicacid (AA). The copolystyrene-acrylat latex as the main agent, silicasoland isocyanate polymers (HDI) as cross-linking agent, a kind of woodadhesive without formaldehyde is synthesized by copolystyrene-acrylatlatex, silicasol and isocyanate polymers. At the same time, the factors affecting its synthetic condition are discussed, and the synthetic processis optimized. The results show that adhesive owns excellent propertywhenω(PVA)=8%，ω(AA)=6%，ω(NMA)=4%，n(BA)/n(St)=2:1，ω(Sil)=6%，ω(HDI)=8%. The particle size of acrylic resin emulsion is168.5nm, the tensile strength, elongation at break and water absorptionof acrylic resin films respectively is 7.5Mpa, 862.19% and 16%.FTIR analysis indicates that–NCO has reacted because theabsorption peaks does not appear in the wavelength 2270 cm-1.TG analysis indicates that the polymer has two decompositionstages. The rheological measurement indicated that the viscositydecreased with increasing shear rate, all emulsions exhibitedshear-thinning behavior, and the phenomena became more pronouncedwith increasing silica sol and HDI concentration.DMA showed that the storage modulus of adhesive films isincreased with silica sol and HDI addition. However, when silica solconcentration was greater than 6 wt. %, HDI concentration was greaterthan 8 wt. %, the storage modulus decreased. It means that the rigidityof adhesive films could be improved with silica sol and HDI addition.When the resin content is 250g/m2on the application experiment,the plank bonding strength reaches 0.82Mpa, the static strength reaches20.5 Mpa and the water resistence reaches 12h. The outcome conformthe national standards.2. With dimethylformamide (DMF) as cosolvent, a kind of acrylicresin latex is successfully synthesized by reacting methyl methacrylate(MMA), butyl acrylate (BA) and dimethylaminoethylmethacrylate(DMC). The aqueous isocyanate crosslinking agent is got by acrylicresin latex and isocyanate polymers (HDI). Then the wood adhesive wasprepared via compounding carboxyl butyl benzene and the aqueousisocyanate crosslinking agent. At the same time, the factors affecting itssynthetic condition are discussed, and the synthetic process is optimized.The results show that the acrylic resin latex owns excellent propertywhenω(DMC)=30%，n(BA)/n(MMA)=1:1，ω(dodecylmercaptan)=0.4%. The tensile strength and water absorption of acrylic resin films respectively is 6.5Mpa and 16%.When m(acrylic resin)/m(HDI)=2/1, the aqueous isocyanatecrosslinking agent owns excellent property. The tensile strength andwater absorption of isocyanate crosslinking agent films respectively is7.2Mpa and 14.5%. FTIR analysis indicates that–NCO has not reacted.The crosslinking agent retains better reaction activity.TG analysis indicates that the thermal stability of adhesive isincreased with isocyanate crosslinking agent addition. The rheologicalmeasurement indicated that the viscosity decreased with increasingshear rate, all emulsions exhibited shear-thinning behavior, and thephenomena became more pronounced with increasing isocyanatecrosslinking agent concentration.DMA shows that the storage modulus of adhesive films isincreased with isocyanate crosslinking agent concentration increasedfrom 0% to 10%. However, when isocyanate crosslinking agentconcentration is 15%, the storage modulus decreased.The test of contact angle of adhesive films shows that the contactangle of carboxylbutyl benzene reach 68.5°without isocyanatecrosslinking agent addition, the contact angle of adhesive films reach88°when isocyanate crosslinking agent concentration is 10%. It meansthat the water resistance of adhesive films is improved with isocyanatecrosslinking agent addition.The experiment which adhesive is used in blockboard shows thatwhen m(isocyanate crosslinking agent)/m(carboxylbutyl benzene)=10% ,the resin content is 300g/m2and the temperature is 120℃, the plankbonding strength reaches 0.80Mpa, the static strength reaches 21.4 Mpaand the water resistence reaches 10h. The outcome conform the nationalstandards.3. The wood adhesive is prepared via compounding EVA, polyvinylalcohol (PVA) and isocyanate polymers (HDI). The factors affecting itssynthetic condition are discussed, and the synthetic process is optimized.The results show that the tensile strength, elongation at break and waterabsorption of adhesive films respectively is 7.8Mpa, 763.2% and 23%, when m(PVA)/ m(EVA)=1/3 andω(HDI)=10%.TEM photos show that the adhesive emulsion particles are regularsphericity, and the surface of the particles is clean.TG analysis indicates that the thermal stability of adhesive isincreased with HDI addition due to the cross-linking reaction betweenHDI and PVA.DMA shows that the rigidity of adhesive films is increased withm(PVA)/ m(EVA) increased. However, when m(PVA)/ m(EVA) isgreater than 1/3, the rigidity of films decreased. The rigidity ofadhesive films is increased with HDI concentration increased from 0%更多还原