【作者】 陈奶荣；

【导师】 林巧佳；

【作者基本信息】 福建农林大学 ， 木材科学与技术， 2014， 博士

【摘要】 用大豆脱脂豆粉(DSF)制备环保型木材胶黏剂,对其中的大豆蛋白进行各种改性以提高豆胶的耐水性已有许多研究,但豆粉中还含有约40%的碳水化合物,影响豆胶的耐水性和使用性能,该组分的改性和利用尚未见报道。本论文先分析了大豆基胶黏剂中大豆蛋白、碳水化合物、蔗糖和葡萄糖含量与其耐水性的关系；再通过半纤维素酶酶解DSF中碳水化合物,并联合酸、盐、碱对DSF中大豆蛋白进行结构修饰,暴露其内部活性基团；接着进行环氧化接枝改性与苯乙烯接枝共聚改性,制备耐沸水大豆基胶黏剂。结果表明：(1)大豆基胶黏剂固化后的羟基含量随碳水化合物减少或蔗糖和葡萄糖成分增加而下降；葡萄糖和蔗糖均通过与蛋白质发生美拉德反应提高大豆基胶黏剂固化后的交联度和疏水性,但葡萄糖效果更好。大豆分离蛋白制备的大豆基胶黏剂吸水率最低,为6.26%；大豆基胶黏剂中碳水化合物的葡萄糖含量为71%和100%时,对应杨木和马尾松胶合板胶合强度最高,分别为0.73MPa和0.76MPa; DSF制备的大豆基胶黏剂固化后吸水率最高,胶合强度最低。降低碳水化合物含量或增加其蔗糖和葡萄糖组分的比例,均可降低大豆基胶黏剂固化后的亲水性,提高胶合强度。(2)较好的半纤维素酶酶解DSF中碳水化合物制备大豆基胶黏剂条件为pH值5.2、酶解温度50℃、时间20min,酶用量可根据实际需要做调整。酶解制备的大豆基胶黏剂p-木糖(64.65ppm)、p-D-葡萄糖(64.70ppm)和α-来苏糖(65.08ppm)的1HNMR谱氢化学位移信号增强,65.29ppm处阿拉伯半乳聚糖的氢化学位移信号减弱；还原糖、葡萄糖含量上升,蔗糖、粗纤维含量下降。导致胶黏剂不溶物含量均低于空白组,固化后的耐水性均高于空白组。(3)大豆基胶黏剂还原糖含量与胶合强度呈显著的正相关关系；半纤维素酶酶解温度和pH值对胶合强度有显著影响,对还原糖含量的影响不显著,酶解时间的影响最小；优化得到的最佳工艺为：酶解温度54℃、酶解时间20min、pH值5.1,获得的大豆基胶黏剂还原糖、葡萄糖、蔗糖、粗纤维含量和胶合强度分别为2.93%、1.020%、0.42%、1.15%和0.62MPa。XRD和1H NMR分析表明,DSF在半纤维素酶与酸盐碱联合处理后,碳水化合物与大豆蛋白均有水解,大豆蛋白有序度下降,但有序结构未改变；制备的大豆基胶黏剂有较多活性官能,固化后耐水性提高,但胶合强度未达到GB/T9846-2004中I类胶合板的要求。(4)较合适的ECH接枝工艺为胶液pH值6.2、接枝温度70℃、接枝时间30min。ECH对改性豆胶粘度影响较大,其添加量为DSF用量25%,粘度提高2889.5%；环氧树脂对改性大豆基胶黏剂的粘度影响较小,添加量为DSF用量50%,粘度提高12.6%。ECH和环氧树脂用量增加,改性豆胶固含量和胶合强度提高,其用量分别为10%和30%时,制作的胶合板可达到GB/T9846-2004中I类胶合板的要求。FTIR、1HMNR、TG和DSC分析表明,ECH接枝大豆基胶黏剂被接枝上环氧基,胶黏剂固化后羧酸酯和醚结构的FTIR吸收峰强度上升,羟基吸收峰强度下降；环氧树脂与大豆基胶黏剂混合后就有环氧基开环反应发生,固化过程中环氧基主要与羟基发生反应；固化后的改性大豆基胶黏剂耐热性能提局。(5)N-羟甲基丙烯酰胺(NMAM)较合适的接枝工艺和用量是：接枝pH值5.2、温度70℃和时间30min,NMAM添加量为DSF用量的15%。苯乙烯用量增加,大豆基胶黏剂粘度、固含量和单体转化率提高；苯乙烯用量为DSF的30%时,胶黏剂粘度为4.939Pa·s,固含量为22.6%,单体转化率为72.3%,pH值为7.53,甲醛含量为零,残留单体为0.28%,适用期4.6h,贮存期47天,制作的马尾松和巨尾桉胶合板胶合强度均达到国家标准GB/T98462004中对耐气候型胶合板的要求。FTIR、1HMNR、TG和DSC分析表明,NMAM在大豆基胶黏剂组分中形成有效接枝,苯乙烯单体与NMAM形成有效共聚；苯乙烯改性大豆基胶黏剂与PMDI混合后进一步消除了亲水性基团,固化后羟基含量下降、乙烯基消失、苯环结构比例增加,进一步提高耐水性。(6)将苯乙烯共聚改性大豆基胶黏剂制作成马尾松和巨尾桉胶合板,并进行加速、自然暴露和土埋老化试验。加速老化2160h,马尾松与巨尾桉胶合板的干状和湿状胶合强度下降范围分别为51.2%-69.0%、67.0%-70.9%与26.9%-55.0%、37.6%-39.1%,木破率趋近于零；自然暴露老化225天,马尾松与巨尾桉胶合板的干状和湿状胶合强度下降范围分别为3.5%-19.9%、10.0%-16.1%与3.8%-24.6%、9.8%-12.9%,相应的干状木破率变化较小,湿状木破率略有下降；土埋老化225天,马尾松与巨尾桉胶合板的干状和湿状胶合强度下降范围分别为37.4%..41.8%、48.2%-53.6%与57.7%-61.1%、59.1%-69.6%；相应的马尾松胶合板干状木破率为95%-100%,湿状木破率为零；巨尾桉胶合板木破率接近100%。马尾松胶合板加速老化比自然暴露或土埋老化的性能损失大,自然暴露老化比土埋老化的性能损失小；巨尾桉胶合板自然暴露老化比加速或土埋老化的性能损失小,土埋和加速老化时间45天的性能相近；加速老化和土埋老化对大豆基胶黏剂粘接性能的影响均剧烈于自然暴露老化；试验范围内3种老化方式对大豆基胶黏剂粘接性能的影响无明确相关性。SEM观测表明,未老化胶合板的单板结合较紧密,且见不到明显的胶接层；加速老化后,胶合板胶接层几乎被破坏,单板间出现分离；自然暴露老化后,胶合板无明显单板分离现象,但可观测到单板间的胶接层；土埋老化后,胶合板也看不到明显的单板分离,但单板腐朽较严重。更多还原

【Abstract】 Preparing environmentally friendly soy-based adhesives using defatted soy flour and improving its water resistance via different types of modification techniques of soy protein were extensively investigated. However, in addition to protein, defatted soy flour also consists of40%(w/w) carbohydrate, which negatively affects the properties of soy-based adhesives. Modification and utilization of these components were rarely reported previously. In this Dessertation, the relationship between contents of soy protein, carbohydrate, sucrose and glucose in soy-based adhesives and its water resistance were determined. Viscozyme L enzymolysis conditions of carbohydrate in defatted soy flour (DSF) were investigated, and combination of acid, salt and alkali was then apply to modify the structure of soy protein in the DSF to expose its active functional groups. Then the epoxides or styrene were grafted into components of DSF to obtain boiling-water-resistant soy-based adhesives. The results showed that:(1) The amount of hydrophilic groups (e.g., hydroxyl groups) in the soy-based adhesives decreased as the carbohydrate content decreased or sucrose and glucose content increased. The cross-linking and hydrophobicities of cured soy-based adhesives were enhanced by Maillard reactions between soy protein and sucrose and glucose. Soy-based adhesives prepared with soy protein isolated and DSF had the lowest and highest water absorptions, respectively. The highest bonding strength of poplar and masson pine plywood were0.73MPa and0.76MPa, for a glucose content of carbohydrate in the soy-based adhesive of71wt%and100wt%, respectively. The lowest bonding strength was observed in a cured soy-based adhesive prepared from DSF. A reduced carbohydrate content, or increased sucrose and glucose fractions in the carbohydrate, decreased the hydrophilicity and increased the bonding strength of the cured SBA.(2) The suitable Viscozyme L enzymolysis conditions of carbohydrate in DSF are as follows:pH5.2, temperature50℃, and time20min, the additive amount of Viscozyme L depended on the acturelly needed. Under this conditions, the soy-based adhesives with higher1H NMR chemical shift of β-xylose(δ4.65ppm), β-D-glucose(δ4.70ppm), a-lyxose(δ5.08ppm) and lower1H NMR chemical shift of arabinogalactan (δ5.29ppm). Reducing sugar and glucose content was increase, whereas sucrose and coarse fibre content was decrease. The contents of insoluble substances in soy-based adhesives were lower than control, and its water resistance after curing higher than control.(3) Positive correlationship between reducing sugar content and bonding strength of soy-based adhesives was significance. The effects of treatment temperature and pH on bonding strength were significance, but insignificance on reducing sugar content; the effects of Viscozyme L treatment time were the smallest. The optimized preparation conditions of Viscozyme L treatment soy-based adhsive was treatment temperature54℃, treatment time20min, pH=5.1. Under this condition, the contents of reducing sugar, glucose, sucrose, coarse fibre and bonding strength of soy-based adhesives were2.93%,1.020%,0.42%,1.15%and0.62MPa, respectively. XRD and1NMR indicated that during DSF was treated by Viscozyme L with combination of acid, salt, and alkali, the carbohydrate and soy protein of DSF were hydrolysis; and the order degree of soy protein decrease, but the order structure had no variation. The soy-based adhesives contain more active functional groups and with better water resistance after curing, but bonding strength haven’t met the requirement of GB/T9846-2004for plywood type I.(4) The suitable grafting conditions of Epichlorohydrin (ECH) on the components in DSF were as follows:pH6.2, temperature70℃, and time30min. The effects of additive amounts of ECH on viscosity of soy-based adhesives is significance than epoxy resin, the additive amounts of ECH and epoxy resin were25%and50%, viscosity of soy-based adhesives enhancement were2889.5%and12.6%, respectively. Solid content and bonding strength of soy-based adhesives increase with the additive amounts of ECH and epoxy resin. All bonding strength met the requirement of GB/T9846-2004for plywood type I when the additive amounts of ECH and epoxy resin were10%and30%, respectively. FTIR,1HMNR, TG, and DSC indicated that ECH modified soy-based adhesives were grafted epoxy groups, and FTIR absorption peaks of carboxylic ester and ether structure in ECH modified soy-based adhesives enhancement, meanwhile, the absorption peaks of hydroxyl decrease. During epoxy resin blend with soy-based adhesives, partly epoxy groups react with amino groups immediately; and majority epoxy groups react with hydroxyl in the process of curing. The heat resistance of curing soy-based adhesives was increased.(5) The suitable grafting conditions of N-methylol acrylamide (NMAM) on components in DSF were as follows:pH5.2, temperature70℃, and time30min; And the additive amounts of NMAM was15wt%of DSF."Viscosity, solid content, and monomer percent conversion increase with the additive amounts of styrene. The viscosity, solid content, monomer percent conversion, pH value, formaldehyde content, residual monomer, working life, and shelf life of styrene modified soy-based adhesive were4.939Pa.s,22.6%,72.3%,7.53,0,0.28%,4.6h, and47days, respectively, when the additive amounts of styrene was30wt%of DSF. Its bonding strength could meet the requirement of GB/T9846-2004for weathering plywood. FTIR,1HMNR, TG, and DSC indicated that NMAM was grafted into the component of soy-based adhesive, and styrene monomer copolymerization with NMAM. Hydrophilic groups of styrene grafted soy-based adhesives were further removed during blend with PMDI. The curing adhesives with hydroxyl group content decrease, vinyl disappearance, benzene ring percentage increase; finally, its water resistance was improved further.(6) Ageing ability of masson pine and eucalyptus grandis plywood were employed to evaluate the properties of styrene grafted soy-based adhesive. The decreased dry and wet strength of masson pine or eucalyptus grandis plywood were range from51.2%to69%,67%to70.9%,26.9%to55.0%, and37.6%to39.1%, respectively; and wood fail percentage was almost zero when accelerated ageing time was2160h. The decreased dry and wet strength of masson pine or eucalyptus grandis plywood were range from3.5%to19.9%,10.0%to16.1%,3.8%to24.6%, and9.8%to12.9%, respectively; and wood fail percentage of dry samples were no veriation, but wood fail percentage of wet samples were decrease when natural ageing time was 225days. The decreased dry and wet strength of masson pine or eucalyptus grandis plywood were range from37.4%to41.8%,48.2%to53.6%,57.7%to61.1%, and59.1%to69.6%, respectively; and wood fail percentage of dry masson pine samples were range from95%to100%, but wood fail percentage of wet masson pine samples were zero; all the wood fail percentage of eucalyptus grandis samples were almost100%when soil burial time was225days. The properties reduction of masson pine plywood during accelerated ageing test was higher than natural ageing or soil burial test, and soil burial test was higher than natural ageing test. The properties reduction of eucalyptus grandis plywood during natural ageing test was lower than accelerated ageing or soil burial test, and during45days of soil burial and accelerated ageing test, the properties reduction was similarly. The effects of accelerated ageing test or soil burial test on gluability of styrene grafted soy-based adhesive was severer than natural ageing test. Under the experimental scope, there are no significant correlations of the three kinds of ageing methods on gluability of soy-based adhesive. SEM indicated that combination of veneers in control samples were tight and bonding layers not clearly. All bonding layers of samples were almost damaged and veneers were delaminated during accelerated ageing test. There are no veneers of samples were delaminated during natural ageing test, but bonding layers were clearly. Also no veneers of samples were delaminated during soil burial test, but veneers were severe rotten.更多还原