【作者】 张伟；

【导师】 费本华；

【作者基本信息】 中国林业科学研究院 ， 木材科学与技术， 2009， 博士

【摘要】 麦秸刨花板是近年来新型刨花板产品,具有环保、环境友好、资源综合利用等特点,发展潜力巨大。但是,麦秸刨花板施胶技术与木材刨花板有很大差别,如何解决麦秸刨花板施胶关键技术一直是个难题。本文通过对麦秸刨花板施胶中气流式雾化施胶、高压无气式雾化施胶、离心式雾化施胶方法的研究,以及施胶量、胶滴性质、板的强度、吸水厚度膨胀率等工艺参数进行系统研究,得出以下结论:1.综述了国内外刨花板发展现况和我国刨花板产业发展优势,分析了刨花板工业化生产中施胶技术难点,指出施胶量过大是亟待解决的关键技术问题。通过雾化施胶影响因素的理论分析和评价方法的研究,总结出胶滴平均粒径、雾化角、胶滴粒径分布系数三个参数来评价和衡量胶粘剂雾化效果。2.通过气流式雾化施胶方法研究,对两流体内混型、两流体外混型、三流体混合型三种结构的喷嘴进行雾化特性试验,结果表明:(1)两流体内混型喷嘴的胶滴平均粒径较小,雾化角相对较大,胶滴粒径分布系数较小,粒径分布比较均匀,且能量消耗也较小。胶滴平均粒径随着液相压力、液孔直径、气孔直径和混合孔直径的增大而增大,随着气相压力和气液压力比的增大而减小;胶滴平均粒径的范围在20～110μm,变化范围较大,对胶滴平均粒径的影响按大小依次为气相压力、气液压力比和液孔直径;雾化角随着液相压力、气孔直径和混合孔直径的增大而减小,随着液孔直径、气相压力和气液压力比的增大而增大;雾化角的变化范围在33°～41°,变化范围较小,控制参数和结构参数对雾化角的影响比较接近,影响不明显;喷嘴的胶滴粒径分布系数在1.2～1.8。(2)两流体外混型喷嘴的胶滴平均粒径稍大,雾化角相对稍小,胶滴粒径分布系数较大,雾化性能一般,且能量消耗较大。胶滴平均粒径变化规律基本等同两流体内混型喷嘴,胶滴平均粒径的范围在30～120μm,变化范围较大,对胶滴平均粒径的影响按大小依次为气相压力、气液压力比和液孔直径;雾化角变化规律基本等同两流体内混型喷嘴,变化范围在31°～38°,变化范围较小,喷嘴的胶滴粒径分布系数均小于1.4,粒径的分布均匀性较好。(3)三流体混合型气流式喷嘴的雾化效果介于两流体外混型和两流体内混型之间,喷嘴的消耗能量要大。胶滴平均粒径随着液相压力、液孔直径、气孔直径和混合孔直径的增大而增大,随着二次气相压力和二次气液压力比的增大而减小;胶滴平均粒径的范围在15～130μm,变化范围较大,对胶滴平均粒径的影响按大小依次为液孔直径、一次气相压力和两次气液压力比;雾化角随着液相压力、气孔直径和混合孔直径的增大而减小,随着液孔直径、气相压力和气液压力比的增大而增大;雾化角的变化范围在30°～45°,变化范围较大,控制参数和结构参数对雾化角的影响比较接近,影响不明显。喷嘴的胶滴粒径分布系数在1～1.5,粒径的分布均匀性一般。3.通过高压无气式雾化施胶方法研究,对高压无气式和辅助空气式两种结构的喷嘴进行雾化特性试验,结果表明:高压无气式喷嘴雾化的胶滴平均粒径在70～110μm,增加辅助空气后,胶滴平均粒径的变化范围增大,可达到20～110μm。胶滴平均粒径随着液相压力的增大而减小,随着液孔直径的增大而增大。在相同液压条件下,通过辅助空气的二次雾化后,胶滴平均粒径变小,雾化效果更好。4.通过离心式雾化施胶方法研究,对电动离心式雾化喷嘴进行雾化特性试验,结果表明:胶滴平均粒径随着分散盘转速的增加而减小,变化范围在50～120μm,变化范围一般;胶滴平均粒径随着液相压力增大而增大,变化范围在70～100μm ,变化范围较小;分散盘转速对胶滴平均粒径的影响较大,喷嘴雾化面积随着液相压力和分散盘转速的增大而增大,雾化直径的变化范围在1200～1700mm,变化范围较大。5.通过上述三种雾化施胶方法的研究,确定了四组不同胶滴平均粒径,研究了施胶量、胶滴平均粒径等主要工艺参数对麦秸刨花板物理力学性能的影响关系,结果表明:施胶量的变化对麦秸刨花板的静曲强度、弹性模量、内结合强度、吸水厚度膨胀率有显著影响,对内结合强度的影响极其显著;施胶量相同情况下,胶滴平均粒径对内结合强度、弹性模量和吸水厚度膨胀率有显著影响。因此,可以在保证板材物理力学性能满足国家标准的前提下,选取最佳的胶滴平均粒径,优化施胶技术与工艺,进一步降低刨花板的施胶量,减小秸秆刨花板的生产成本。6.通过雾化施胶方法的理论分析和试验研究,在此基础上,开发了农作物秸秆刨花板用异氰酸酯胶施胶试验系统和专用设备。试验结果表明,新开发的MDI施胶系统和专用设备适用于秸秆刨花板的施胶工艺,实验样板达到国家相关标准。更多还原

【Abstract】 A series of researches have been engaged in gluing method and technology of wheat straw particleboard. And many results and conclusions have been obtained.1. After describing and analyzing the current development of wheat straw particleboard at home and aboard and advantages in domestic particleboard industry, some technical difficulties in its gluing step of production have been pointed out, which says over-gluing is the vital as well as urgent technical problem. At the same time, researches on theoryanalysis and assessed method about the influential factors in resin spray contributes that resin spray can be assessed by three parameters—the average resin droplet diameter,atomizationangle and the resin droplet distribution.2. After the researches on air-atomizing gluing, including the atomizing characteristic tests on three types of nozzles, which are external mixed two-fluid nozzle,internal mixedtwo-fluid nozzle and mixed triple-fluid nozzle, following conclusions havebeen drawn.(1) The average resin droplet diameter of internal mixed two-fluid nozzle increases with growing of liquid pressure and enlarging of the diameter of liquid, gas outlet, and mixed outlet but decreases with the increasing of the ratio of gas pressure to liquid pressure.The average resin droplet diameters has a wide range , from 20 to 110μm, which is greatlyinfluenced by liquid pressure, then liquid-gas pressure and then diameterof liquid outlet. While atomization angle will becomes lower if liquid pressure,air outletdiameter and mixed outlet diameter increases, but becomes higher if the diameter of liquid outlet, liquid pressureand the pressure ratio of liquid to gas increases. However, it has a narrow range just between 33 degree to 41 degree, and the parameters of controls and structural have the similar but not obvious effects on it. The resin droplet distribution of this nozzle is between 1.2 and 1.8. All in all, the External mixed two-fluidnozzle has its resin droplets in comparatively small diameter, with comparatively atomizing angle, little coefficient of resin distribution, good atomizing effect, little consumption of energy, and well-distributed.(2) The feature of the average droplet diameter of external mixed two-fluid nozzle is basically similar to that of external mixed two-fold nozzle, which means that its averagediameter also has a large fluctuated size between 30 and 120μm, and is influenced in turnby gas pressure, the ratio of gas to liquid pressure and the diameter of liquid outlet. The atomization angle changes similarly as that of external mixed two-fluid nozzle does and the former has a narrow range between 31 degree and 38 degree. This nozzle has its droplet well-distributed, because its distribution coefficients are no more than 1.4. In total, Internal mixed two-fluid nozzle has comparatively large diameter atomizing droplet with a small angle degree, large coefficient in distribution. Ithas an ordinary atomizing effect but relatively high energy consumption.(3) The average resin droplet diameter made by mixed triple-fluid nozzle increases as liquid pressure, the diameter of outlet of liquid, gas and mixed one increase, but decreases as the ratio of twice gas pressure to twice liquid pressure increases, which changes from 15μm to 130μm. This wide range is mainly influenced by the diameter of liquid outlet, once liquid pressure and the ratio of twice liquid pressure to gas pressure in the decreasingorder. The atomization angle decreases when liquid pressure, gas outletdiameter and mixeddiameter increase, but decreases when liquid outlet diameter, gas pressure and the ratio ofgas to liquid pressure increase. The range of atomizing angle is wide, between 30 degree and 45 degree, which is influenced by the parameters of controls and structural similarly but not obviously. The droplet distribution is ordinary with the coefficient of this nozzlefrom 1 to 1.5. Totally speaking, the atomizing effect of Mixed triple-fluid nozzle is betweenthe two above but the energy consumption is the highest of those three types.3. After carrying more researches on the gluing method which uses high pressure and airless, and atomizing characteristic tests on airless nozzle and airless with air-aidednozzle, brief conclusions are as follows: As for airless spray type, it can spray resin intodroplets with the diameter of 70～110μm, whose size can be increased to 20～110μm by adding air-aided. Meanwhile the average droplets diameter will decrease with increasing liquid pressure but will increase because of enlarging the diameter of liquid outlet. Furthermore, in the same liquid pressure, if it can be atomized by air-aided again, the diameter of dropletwill be smaller. Therefore an excellent effect will be achieved.4. After doing researches on the centrifugal atomizing method and atomizing characteristic tests on electric-centrifugal atomizing nozzles, the results are as follows: The average resin droplets ordinarily ranging from 50μm to 120μm, becomes smaller as the increasing of the centrifugal speed, while becomes larger as the increasing of liquid pressure, which has a narrow diameter from 70μm to 100μm. However, the centrifugal speed contributes more. As for the diameter of nozzle’s atomizing circle, which ranges widely from 1,200mm to 1,700mm, can be increased by increasing the liquid pressure or the centrifugal speed.5. After researches on the method of resin spray all above, four groups with different average diameters of droplets are classified and relations between major technological parameters like resin content, the average diameter of droplets and the physical functionof strawboard are analyzed. They all show that using different resin content will makes a big difference to the bending strength, elastic modulus, internal bond strength and determinationof thickness swelling rate of water absorption of strawboard, especially to internal bond strength. Therefore, after satisfying national standards, choosing the best average diameter and optimizing gluing technology can decrease the amount of glueusingin particleboardproduction as well as the cost of it.6. Based on the analysis in theory and researches on tests, an experimental system and a set of particular instruments that uses the glue consisting of isocyanate for strawboardgluing are finally exploited. And the result shows that the MDI gluing system and the setof particular instruments are well fitted for strawboard gluing technology, as the sample has meet national standards.更多还原