砂轮片用单宁树脂结合剂的制备与应用基础研究

A novel tannin resin binder for grinding wheel will be prepared using local abundant tannin resource in Yunnan province. The tannin resin binder prepared in previous studies was too dangerous to achieve the mass production because of the unpurified powder of tannin, the self-condensation of furfuryl alcohol in acid condition and long curing molding time of grinding wheel. In this project, firstly, the powder of tannin will be extracted using chemical extraction method. Secondly, the formaldehyde will be used to react with furfuryl alcohol to obtain the hydroxymethyl of furfuryl alcohol for the addition of the active site of furfuryl alcohol and for the decrease of the furfuryl alcohol self-condesation reaction. Thirdly, the“high temperature and high press” method as a fast curing molding process will be used for preparation of grinding wheels to get rid of the “oven” curing process for the production efficiency improvement of tannin resin based grinding wheels. The MALDI-ToF and 13C-NMR will be used to study the chemical structure of tannin, reactivity of tannin and chemical structure of tannin resin in different reaction stages; The heat resistance and curing properties of the tannin resin binder were studied by the DSC, the TMA and the TG; The SEM also will be used to observe the internal structure of grinding wheels; The mechanical strength of grinding wheels will be tested by the universal mechanical testing machine; The wear-resisting performance of grinding wheels will be studied using a abrasion tester and a electric Angle grinder. Moreover, in this study, the types, shapes and sizes of abrasive particles and types of interlayer fibers also will be selected reasonably for the system evaluation of physical properties and mechanical properties of grinding wheels to obtain the oretical guidance for the tannin resin binder synthesis process.

以云南丰富的单宁为原料，制备全新砂轮片用单宁树脂结合剂。针对前期制备中存在的单宁粉末纯度低、糠醇在酸性条件下的自缩聚及砂轮片固化成型时间较长而难以实现规模化生产等问题，首先，本项目采用化学提纯法处理单宁粉末、其次，用甲醛与糠醇制备羟甲基糠醇来增加糠醇的活性位点和减少糠醇的自缩聚、再次，砂轮片制备采用“高温高压”快速固化工艺，摆脱“烘箱式”固化，提高生产效率。用MALDI-ToF 和13C-NMR研究单宁结构、活性及不同反应阶段合成单宁树脂的结构；用DSC、DMA、TG研究合成单宁树脂结合剂的耐热性能及固化性能；用SEM观测单宁树脂砂轮片的内部构造；用万能力学试验机测试砂轮片的力学强度；用耐磨测试仪和电动角磨机研究砂轮片的耐磨性能。研究还对研磨颗粒的种类、形状、尺寸及夹层纤维的种类进行有效选择，系统评估砂轮片的各项物理力学性能, 为单宁树脂结合剂的合成提供理论指导。

砂轮片普遍应用于房屋建造、室内装修等领域，目前，砂轮片用树脂结合剂主要以酚醛（PF）树脂为主，但PF树脂砂轮片原材料来自石油化工且含有毒物质甲醛，严重污染环境；云南是我国单宁资源最丰富的地区之一，在黑荆树、坚木、杨梅树等树皮中单宁含量高且具备较高的应用价值。本项目以云南丰富的黑荆树单宁为原料，制备砂轮片用单宁/糠醇（TF）树脂并拓展其应用制备木材胶黏剂来替代PF树脂。对TF树脂的结构、基本性能、固化性能和热性能进行了分析，针对前期制备中存在的单宁粉末纯度低、糠醇在酸性条件下自缩聚及砂轮片固化成型时间长而难实现工业化等问题采取了改性措施，首先，本项目采用了甲醇抽提处理单宁粉来除去单宁中的杂质，处理后单宁中杂质的质谱吸收峰明显降低；其次，用乙二醛与糠醇反应来提高糠醇与单宁的反应活性和减少糠醇的自缩聚，提高TF树脂的交联度和分子量，乙二醛可与糠醇的羟甲基反应引入新的反应官能团，进一步与单宁反应制备单宁/糠醇/乙二醛（TFG）树脂；再次，采用尿素替代部分和全部糠醇制备出了一款单宁/糠醇/尿素/乙二醛（TFUG）或单宁尿素/乙二醛（TUG）树脂，降低了TF树脂的成本；最后，砂轮片制备采用压机固化工艺，即“高温高压”快速固化工艺，摆脱“烘箱式”固化，提高生产效率，制备砂轮片的时间由原来的两天缩短至1.5小时。用MALDI-TOF、13C-NMR、XRD、ESI-MS研究了黑荆树单宁和坚木单宁的基本结构和黑荆树单宁的活性及不同反应阶段合成单宁树脂的结构，发现黑荆树单宁相对坚木单宁的结构更适用于热固性树脂的制备。用DSC、DMA、TGA研究了合成单宁树脂的耐热性能及固化性能，发现TFG树脂的固化时间较PF树脂短，但前者具备更高的玻璃转化温度和热稳定性。TF、TFG、TFUG、TUG树脂砂轮片的表面光滑无孔隙和裂痕，且与PF树脂砂轮片相比，它们均具有更高的硬度和较好的力学强度和耐磨性能。单宁树脂的天然生物质材料占到 80%以上，采用TF基树脂制备砂轮片或木材胶黏剂替代PF树脂具有重要的现实意义。