人造板中脲醛树脂对其回收制备纤维产品的影响

发布时间：2018-04-28 00:38

本文选题：废弃木材人造板 + 脲醛树脂　；参考：《华南农业大学》2016年硕士论文

【摘要】：废弃木材中所含的胶粘剂杂质一直是废弃木材回收利用中需解决的重点问题,而脲醛树脂由于其廉价、易制备、胶接性能好等特点成为木材中运用最广的胶粘剂。本文选取废弃木材回收中所含的脲醛树脂为对象,通过分析和比较新旧胶粘剂固化体系的界面形态、化学结构、热学性能的差异,了解旧胶粘剂体系对于新胶粘剂体系的物理化学状态的影响。通过测试用含有旧胶粘剂颗粒制备的胶合板的力学性能,确定旧胶粘剂颗粒大小、含量多少对于回收制备新人造板的影响,从而为人造板的回收再造提供理论基础及应用指导。在废弃木材制备纤维素产品的阶段,采用了两种方法分别得到纤维素纳米晶与纤维素纳米纤丝,通过正交实验等方法优化纳米纤维素的制备工艺参数,获得较为经济且效率较高的纳米纤维素的制备方法。通过对比较含有脲醛胶对废弃纤维板和纯净木粉所制备的各阶段产物的产率、成分、热学性质、微观形貌及其他物理化学性质,从而评定脲醛胶在废弃木材制备纳米纤维素时产生的影响。最终利用含有胶粘剂的废弃人造板制备获得高附加值的纳米纤维素产品,提高废弃人造板的利用价值。本文的主要研究结果可以归纳为:(1)旧的胶粘剂粉末在新的胶粘剂体系中未有融合成较为完整的交联体,但是新形成的胶粘剂体系与旧的胶粘剂体系的成分并无变化。通过热分析表明,在脲醛树脂固化时加入粉末杂质会对其固化反应产生多个吸热峰,并使固化反应产生的总焓量增加。脲醛树脂中参入杂质并压制胶合板,通过测定胶合板的胶合强度及浸渍剥离率可知,杂质的混比增大会使得胶合板的胶合强度及浸渍剥离率这些胶合性能显著下降。通过方差分析亦可知,当混比处于较低的2%时增加杂质的粒径对于胶合性能造成的下降,不及当混比上升到较高的6%时增加的杂质粒径对胶合性能造成的下降显著。(2)在利用废弃中纤板提取纤维素的阶段,各阶段产物产率、红外及热重结果表明废弃木材中存在的脲醛树脂胶粘剂会在反应中发生水解,水解主要集中在强碱的处理的阶段,脲醛树脂上的醚键及羟甲基等官能团上的化学键发生断裂,但是水解反应并未进行完全,仍会有一些脲醛胶残留在所制备的纤维素中,并且在中纤板粉末中的脲醛胶杂质的残留要多于直接混入木粉中胶粉的残留。脲醛胶会使纤维素的热解温度开始温度提前到250℃左右,而且热解后的残留物含量增加到20%以上。(3)在硫酸水解制备纳米纤维素阶段,设计的正交实验结果表明,硫酸水解的最佳工艺参数为:硫酸浓度65%、温度60°、反应时间为30min。产率和电导率数据表明了纤维素中残存的胶粘剂会在反应时同时水解,并可降低所制备的纳米纤维素的磺酸化。XRD结果表明了在脲醛胶的影响下,纤维素和其所制备的纳米纤维素的结晶度都有所降低。(4)在TEMPO氧化阶段,不同的NaClO浓度和原料中的胶粘剂对于氧化阶段的产率影响不大,但是从之后的机械研磨阶段的产率可以看出增加NaClO浓度和研磨的时间会增大其机械研磨产率,加入的NaClO为5mmol/g,研磨时间30min为工艺优化和较经济合理的反应条件。而加入胶粘剂杂质则会使其产率降低,增加NaClO浓度会加大纤维素上的羟基氧化成羧基的程度,而胶粘剂会使氧化反应时的羧酸化程度降低。不同方法制备的纳米纤维的微观形貌有较大差异,而在没有胶粘剂杂质影响下的CNC沉淀与CNF的纤维宽度会比杂质影响下制备的纤维宽度略小。
[Abstract]:The adhesive impurity contained in abandoned wood has always been the key problem to be solved in the recycling of abandoned wood. Urea formaldehyde resin has become the most widely used adhesive in wood because of its cheap, easy preparation and good adhesive properties. This paper selects urea formaldehyde resin in waste wood recovery and compares new and old adhesives. The influence of the old adhesive system on the physical and chemical state of the new adhesive system. By testing the mechanical properties of the plywood prepared with the old adhesive particles, the size of the old adhesive particles is determined and the content of the new adhesive is made for the preparation of the newlyweds. It provides theoretical basis and application guidance for the recovery and reengineering of wood-based panels. In the phase of cellulose products prepared by waste wood, two methods are used to obtain cellulose nanocrystalline and cellulose nanofibrils respectively. The preparation parameters of nanoscale are optimized by orthogonal experiment, and the results are more economical and more efficient. By comparing the yield, composition, thermal properties, micromorphology and other physical and chemical properties of the products of each phase prepared by the comparison of urea formaldehyde adhesive to the waste fiberboard and pure wood powder, the effects of urea formaldehyde gum on the preparation of nanofiber in waste wood were evaluated. The main results of this paper can be summarized as follows: (1) the old adhesive powder has not fused into a more complete cross body in the new adhesive system, but the newly formed adhesive system and the old adhesive system There is no change in composition. It is shown by thermal analysis that the addition of powder impurities in urea formaldehyde resin will produce a number of endothermic peaks and increase the total enthalpy of the curing reaction. The urea formaldehyde resin enters into the plywood with impurities and presses the plywood. It is known that the mixture ratio of the plywood is increased by measuring the adhesive strength of the plywood and the exfoliation rate of impregnation. The adhesive strength of plywood and the exfoliation rate of the plywood decreased significantly. By the analysis of variance, it can be found that when the mixing ratio is at a lower 2%, the particle size of the impurity is reduced to the gluing performance, and it is not as significant as the increase of the particle size to the gluing performance when the mixed ratio rises to a higher 6%. (2) The yield of the products in various stages, infrared and thermogravimetric results show that the urea formaldehyde resin adhesive in the abandoned wood will hydrolyze in the reaction. The hydrolysis is mainly concentrated in the stage of the treatment of strong alkali. The ether bonds on the urea formaldehyde resin and the chemical bonds on the Qiang Jiaji and other functional groups break, but the hydrolysis is hydrolyzed. The reaction is not complete, and some of the urea formaldehyde glue remains in the prepared cellulose, and the residue of urea formaldehyde in the MDF powder is more than that in the direct mixed wood powder. The urea formaldehyde glue will make the temperature of the cellulose pyrolysis temperature start to about 250 C, and the residue content after the pyrolysis is increased to 2. More than 0%. (3) the preparation of nanofibers in the hydrolysis of sulfuric acid. The orthogonal experimental results show that the optimum process parameters for the hydrolysis of sulfuric acid are as follows: the concentration of sulfuric acid 65%, the temperature 60 degree, the reaction time of 30min. yield and electrical conductivity data show that the residual adhesives in the cellulose can hydrolyze at the same time in the reaction and reduce the prepared nanofibers. The results of the sulfonated.XRD showed that the crystallinity of the cellulose and the nanoscale prepared by the UF was reduced. (4) in the TEMPO oxidation stage, the different NaClO concentration and the adhesive in the raw material had little effect on the yield of the oxidation stage, but the yield of the mechanical lapping phase after that was seen. The increase of NaClO concentration and grinding time will increase the mechanical grinding yield, the added NaClO is 5mmol/g, the grinding time 30min is the process optimization and the more economical and reasonable reaction conditions. The addition of the adhesive impurities will reduce the yield, the increase of NaClO concentration will increase the oxidation of the hydroxyl group on the cellulose to the carboxyl group, and the adhesive will make oxygen. The micromorphology of the nanofibers prepared by different methods is greatly different, but the width of CNC precipitation and the fiber width of CNF will be slightly smaller than that of the fibers under the influence of impurities.

【学位授予单位】：华南农业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X705;TQ352

【参考文献】