【作者】 赵伟刚；

【导师】 杜官本；

【作者基本信息】 西南林学院 ， 木材科学与技术， 2009， 硕士

【摘要】 人造板工业是一个先分后合的工艺流程,因此胶粘剂的发展现在已经成为决定人造板发展水平的一个关键环节。随着我国经济的发展,整体消费结构向建筑业倾斜,室外用人造板的市场前景十分广阔,比如说定向刨花板(OSB)、胶合层积木(LVL)以及竹材人造板等,使得酚醛树脂的用量逐渐增加。但是酚醛树脂具有生产成本高、固化速度慢以及胶层颜色深的缺点,因此通过尿素实现对酚醛树脂的共缩聚改性成为酚醛树脂研究的热点。期待合成的PUF树脂能够广泛的用于木质人造板的生产,尤其是室外人造板,且效果理想。以往的文献中虽然也涉及报道了PUF的合成、固化等相关的内容,但受条件限制,研究并不深入,同时缺乏系统性。本文以13C核磁共振分析、MALDI-TOF-MS、热机械性能分析为手段,系统研究了各合成参数对树脂结构和性能的影响,其中13C核磁共振(carbon 13 nuclear magnetic resonance spectroscopy,13C NMR)重点分析合成参数变化对树脂结构的影响, MALDI-TOF-MS ( matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, MALDI-TOF-MS)作为13C核磁共振的有效补充,重点分析PUF树脂中的共缩聚结构及其和PF树脂的不同,而热机械性能分析(Thermo Mechanical Analysis,TMA)重点研究合成参数变化对PUF树脂固化性能的影响。同时通过压制胶合板,进一步评估了合成参数对树脂胶合性能的影响,最终旨在确定合理的共缩聚比例,从而为PUF树脂合成和应用提供理论依据。实验结果表明:1.合理的尿素添加比例与原料用量摩尔比密切相关,在本研究的范围内,根据不同的摩尔比合理的选择和控制尿素的加量,即可使得得到的PUF树脂性能与传统PF树脂相近并略优于传统PF树脂。尿素加量应控制在不超过苯酚重量的50 %。2.在其它条件不变的情况下,随着F/P的摩尔比的增加,PUF树脂干状和湿状胶合强度增加显著。甲醛/苯酚的摩尔比从1.75增加到2.6,干状胶合强度和湿状胶合强度分别增加了24%和17%。3.在尿素/甲醛/苯酚摩尔比不变的条件下,NaOH/P的摩尔比从0.2增加到0.53,干状胶合强度和湿状胶合强度分别增加了20%和12%。NaOH/P的摩尔比继续增加,树脂的性能下降,但是仍在胶合板的标准之内。4.甲醛一次加入时,PUF树脂干状和湿状胶合强度降低显著;尿素分次加入使得PUF树脂干状胶合强度下降,而湿状胶合强度增加;苯酚分两次加入,PUF树脂干状和湿状胶合强度都增加。5. 13C核磁共振和MALDI-TOF-MS两种分析手段相互印证,证明了碱性环境中各合成参数不同,所合成的PUF树脂具有十分相近的化学结构,但结构组分存在差异,或者说,合成参数主要影响结构构成比例;其次也证实了PUF树脂中,苯酚、尿素和甲醛三种原料之间共缩聚反应的存在,且碱性环境中的共缩聚反应,连接方式主要为Ph-CH2-N(CH2-)-,而且通常连接在树脂分子的末端;PUF树脂结构仍然以PF树脂为主体,特别是聚合物的链接方式,因此从结构上解释了PUF树脂的表现与传统PF树脂相似的原因。6.尿素的加入能导致构成比例略有差异,特别是邻、对位的羟甲基数量和亚甲基链接方式,尿素用量的增加,导致对位羟甲基数量的增加和邻位羟甲基数量的减少。与传统酚醛树脂相比,PUF树脂在13C图谱的中化学位移55和70附近分别出现两个分裂的小峰,通常归属为三羟甲基脲及其三羟甲基脲与苯环通过亚甲基桥键链接;NaOH/P摩尔比不同的条件下,碱性的增强会导致对位羟甲基数量的减小和邻位羟甲基数量的增加,同时,初期聚合物中对位链接方式比例也略有增加,这正好和尿素用量对PUF树脂结构的影响是相反的。7.与分次加入甲醛和尿素相比较,分次加入苯酚所获得的初期聚合物具有更高组分的邻羟甲基化合物和更高组分的邻位-对位连接方式。甲醛分次加入可以减少醚类化合物等相关副产物,有利于简化反应过程,反应进程中各类羟甲基酚的形成比例几乎固定不变,树脂化过程的竞争反应中,对位-对位连接处于优势;碱性环境中各种加料方式合成的PUF树脂具有十分相近的化学结构,但结构组分存在差异,或者说,加料方式主要影响结构构成比例;碱性环境中各种加料方式下合成PUF树脂时,最终反应进程基本接近,分次加入苯酚、甲醛、尿素时,其聚合程度接近,依次为1.61、1.55和1.69。8. PUF共缩聚树脂的合成反应包含酚醛树脂、脲醛树脂和共缩聚树脂的形成反应。9.通过对不同的尿素加量条件下PUF树脂固化特性的研究,可以得出:相同甲醛/苯酚摩尔比条件下,适量增加尿素用量对PUF树脂凝胶或固化反应的影响并不显著,而相同甲醛/(苯酚+尿素)摩尔比条件下,随着尿素用量的增加,树脂凝胶化反应显逐渐提前的趋势,但固化速度显下降趋势,这一变化同时与甲醛/苯酚摩尔比的变化密切相关。更多还原

【Abstract】 The technical process of wood-based panels is need divided first, and then gathered by adhesive. All the process depend on the wood adhesives. So the adhesive technology is always one of the symbols for technology progressive of wood-based panels. In recent years, as the development of economy, the consumptive structure is trend to construction industry, the wood-based panels used in extraventricular have very wide market, such as OSB, LVL and bamboo panels. For this reason, the consumption of PF resins increased gradual. PF resins have the disadvantage of high cost, lower curing rate and the fuscous glue line. Modify the phenolic resin by urea is a hot spot for researcher. The phenol-urea-formaldehyde resins wanted can replace the PF resin and used in wood industry widespread, also have good results.There have been a couple of studies reported in open literature about the synthesis, the curing property of PUF resins, but study is not in-depth and lack systematic characteristic. In this studies, the 13C nuclear magnetic resonance spectroscopy (13C NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), the thermo mechanical analysis (TMA) were used to investigation the influence of synthesize parameter to the structure and performance of the PUF co-condensed resin. The 13C NMR was used to analysis the influence of synthesize parameter to the structure of the PUF resin. MALDI-TOF-MS as a complementarities, was used to analysis the influence of synthesize parameter to the structure of the PUF resin and also the difference of the PUF resin and PF resin. TMA was used to evaluate the influence of synthesize parameter to the curing property of PUF resin. This influence was further evaluated by preparing the PUF-bonded plywood panel. The aim of this research is to find out the academic gist for synthesize and application of PUF resin.The results show:1. Evaluation of laboratory plywood showed that different molar ratio of P: U: F used, the performance of PUF resins changed. So the different amount of phenol and formaldehyde addition, the urea addition level should be different. The appropriate urea addition will make the PUF resin have better or almost the same performance as traditional PF resin. The preferential range of urea addition level should less than 50% of the mass of phenol.2. At the condition of other synthesize parameter invariable, as the molar ratio of F/P increasing, the dry and wet strength of PUF resins are increasing obviously. The molar ratio increased from 1.75 to 2.6, the dry and wet strength increased 24% and 17%, respectively.3. At the condition of the molar ratio of urea/formaldehyde/phenol is constant, the molar ratio of NaOH/P increased from o.2 to 0.53, the dry and wet strength increased 20% and 12%, respectively. Over this amount of NaOH added, will cause the performance of PUF decreased drastically, but can be accepted.4. Once feeding of formaldehyde will result the dry and wet strength are all decrease. Feeding the urea time after time will result the dry strength decrease and the wet strength increase. Twice feeding of phenol will result the dry and wet strength of PUF resins increase.5. The 13C NMR spectroscopy and the MALDI-TOF-MS are all proved that the PUF resins obtained under different synthesize parameter showed similar structure with almost same type of linkage but different in percentage of function groups. The results also confirmed that the materials phenol, urea and formaldehyde co-condensed indeed. During the preparation of PUF resin, the main reaction came from PF resin. The connection of the co-condensed structure are mainly Ph-CH2-N (CH2-)-, and always at the end of the resin structure. This is way the PUF resins and PF resins have the similar performance.6. Different urea addition will result similar structure with almost same type of linkage but different in percentage of function groups, especially the quantity of the p-methylol, o-methylol and methene. With the amount of urea increase, the amount of p-methylol increased and o-methylol decreased. Compared with tradition PF resins, there are two fissions small peaks near the chemical shift of 55 and 70, they should be the three-methylolureas, and the link–CH2- connected the three-methylolureas with benzene ring. With the molar ratio of NaOH/P increase, the amount of p-methylol decreased and o-methylol increased. It is opposite with the influence of urea.7. Compared with feeding formaldehyde and the urea different times, feeding phenol two times will obtain the pre polymer which has more p-methylol and more link of p-p. Feeding formaldehyde within 40mins can decrease the Ether Compounds. Different ways to feeding the material will get similar structure with almost same type of linkage but different in percentage of function Feeding phenol, formaldehyde, urea not once, and the extent of polymerization are 1.61, 1.55, and 1.69 respectively.8. The synthesis reaction of PUF resins contains the PF reaction, UF reaction and the co-condensed reaction.9. The results of TMA showed no significant changing on cure performance when the molar ratio of F/ P was kept as a constant. The cure performance, however, observed to become earlier and the cure rate was decreased with the increasing addition of urea at constant molar ratio of F/ (P+U).更多还原