【作者】 于勤；

【导师】 范雪荣；

【作者基本信息】 江南大学 ， 纺织工程， 2016， 博士

【摘要】 目前世界上90%以上的香烟滤嘴采用二醋酸纤维制造,原因是二醋酸纤维通常采用正三角形喷丝孔干法纺丝,纺制的丝束截面呈Y形,形成的香烟滤嘴吸阻小,烟气过滤效率甚佳,可去除卷烟中55%—60%的尼古丁和焦油含量,并且能选择性地吸附卷烟中的酚类等有害成分,同时又保留了一定的烟碱而不失香烟口味。因此,二醋酸纤维当之无愧地成为香烟滤嘴的首选材料。2015年,全球二醋酸纤维丝束产量约85万吨,我国的生产量为28万吨,占世界总产量的32.9%。而我国烟用需求量约35万吨,其他产业用需求量为5万吨,生产量占需求量的70%。显然,我国的二醋酸纤维生产能力还不能满足市场需求,仍需要花费大量外汇进口二醋酸纤维及其丝束。因此,如何提高二醋酸纤维的产量成为重要的研究课题。一般情况下,增加企业生产规模是提高二醋酸纤维丝束产量的通用途径。而本课题通过研究二醋酸纤维纺丝液在正三角形喷丝孔出口处的挤出胀大行为,设计相邻喷丝孔的合理间距,在保持喷丝板尺寸大小不变及纺丝工艺参数不变的前提下,增加喷丝板上喷丝孔的数目,实现提高二醋酸纤维丝束产量之目的。主要研究内容和结论如下:1.研究了二醋酸纤维纺丝液的流变性能本部分以二醋酸纤维纺丝液为例,研究其静态流变性能和动态流变性能。利用Physica MCR101流变测试仪测试了不同质量分数（23.5%、24.5%、25.5%、26.5%和27.5%）、不同温度（55℃、57℃、59℃、61℃和63℃）的二醋酸纤维纺丝液在一定剪切速率范围内(101s^-1102s^-1)的静态流变性能和一定角频率范围内(10-1 rad·s^-1102rad·s^-1)的动态流变性能,得出质量分数、温度对纺丝液流变性能的影响规律。静态流变性能:根据测试的质量分数和温度对二醋酸纤维纺丝液的表观黏度的影响曲线可知,当剪切速率从101s^-1增加到102s^-1时,二醋酸纤维纺丝液的表观黏度呈逐渐减小趋势,即该纺丝液是切力变稀的非线性流体。将质量分数和温度与表观黏度的曲线进行一元线性回归,获得了不同质量分数和不同温度下的二醋酸纤维纺丝液的非牛顿指数。当增加纺丝液质量分数或降低温度时,非牛顿指数呈现下降趋势。动态流变性能:二醋酸纤维纺丝液的动态储能模量和损耗模量是纺丝液动态黏弹性的直接体现,也是挤出胀大程度的直接体现。测试了不同温度、不同质量分数的纺丝液的动态储能模量和损耗模量与角频率之间的关系。结果表明:当角频率增加时,动态储能模量和损耗模量均呈现增加趋势;当纺丝液温度升高时,纺丝液的动态储能模量、损耗模量均有所降低;当纺丝液质量分数增加时,纺丝液的动态储能模量、损耗模量则呈现增加趋势。这些研究结果为二醋酸纤维纺丝液在正三角形喷丝孔出口处挤出胀大比模型的建立提供了基础。2.建立了正三角形喷丝孔挤出胀大比模型应用数学第二型曲面积分和流变学幂律定理等知识建立了正三角形喷丝孔纺丝液压力降模型,以此模型为基础,结合D.L.Mclntosh挤出胀大比式,建立了二醋酸纤维纺丝液在正三角形喷丝孔出口处的挤出胀大比模型23’。该模型不仅推导过程简单,而且直观的描述了挤出胀大比与各参数之间的关系:（1）与纺丝液静态流变参数表观黏度aη、非牛顿指数n之间的关系;（2）与纺丝液动态流变参数储能模量’G、损耗模量G’及其角频率w之间的关系;（3）与纺丝液流量q之间的关系;（4）与喷丝孔的规格参数,即正三角形喷丝孔边长a及喷丝孔的长度L之间的关系。3.验证了正三角形喷丝孔挤出胀大比模型利用压差传感器测试了不同流量（0.577 cm3·min-1⁰.996cm3·min-1）、不同温度（55℃⁶3℃）和不同质量分数（23.5%²7.5%）的二醋酸纤维纺丝液在喷丝孔中的压力降,发现增加纺丝液流量或质量分数,压力降呈现增加趋势;提高纺丝液温度或剪切速率(10¹ s^-110² s^-1),压力降呈现降低趋势。并将试验测试值与压力降模型理论计算值进行比较,结果表明压力降模型的理论计算值和试验测试值之间的偏差最小值为0.05%、最大值为4.99%。采用单个正态总体方差未知时均值的假设检验法分析了两者的偏差,结果表明两者之间无显著性差异,说明压力降模型可靠,为挤出胀大比模型的验证提供了依据。采用激光外径测量仪测试了不同流量、不同温度、不同质量分数的二醋酸纤维纺丝液挤出胀大比,发现增加纺丝液流量或质量分数或角频率,二醋酸纤维纺丝液的挤出胀大比呈现增加趋势;提高纺丝液温度,二醋酸纤维纺丝液的挤出胀大比呈现下降趋势。并将试验测试值与挤出胀大比模型理论计算值进行比较,结果表明挤出胀大比模型的理论计算值和试验测试值之间的偏差最小值为0.01%、最大值为3.52%。采用单个正态总体方差未知时均值的假设检验法分析了两者的偏差,结果表明两者之间无显著性差异,表明正三角形喷丝孔的挤出胀大比模型具有可靠性,从而为喷丝板上喷丝孔的间距设计提供了基础。4.设计了多个喷丝孔密度更高的喷丝板应用验证的挤出胀大比模型,确定了相邻喷丝孔的理论间距2 33mD（29）d（28）a B,并确定了喷丝孔的圈层间距和周向间距的设计依据。以孔边长为57μm的正三角形喷丝孔为例,根据挤出胀大比模型获得挤出胀大比理论计算值,确定了不同流量、不同温度、不同质量分数条件下相邻喷丝孔的理论间距值不小于149.955μm。借鉴南通醋酸纤维有限公司的喷丝孔间距设计的内部控制指标——相邻喷丝孔的实际间距至少为纺丝液挤出胀大直径（md）的9倍,即9A mD3d,从而获得相邻喷丝孔的实际间距,即喷丝孔的实际间距至少为1.350mm,该研究结果为喷丝孔密度分布研究提供了依据。以成功纺制二醋酸纤维丝束的孔数为290孔的喷丝板为基础,以相邻喷丝孔的实际间距为依据,保持喷丝板直径不变及纺丝工艺参数不变的条件下,改变圈层间距和周向间距,增加喷丝孔数,设计了孔数分别为325孔、350孔、370孔的喷丝板。然后对290孔、325孔、350孔和370孔四种喷丝板纺制的二醋酸纤维丝束的单丝性能进行了测试,利用变异系数（均方差系数）检验了同一喷丝板纺制的单丝的均匀性能、单个正态总体方差未知时均值的假设检验法分析了同一喷丝板纺制的丝束单丝强伸性及应用性能的显著性差异、秩和检验法分析了不同喷丝板纺制的丝束单丝强伸性能及应用性能的显著性差异。结果表明:每种喷丝板纺制的二醋酸纤维丝束的单丝均匀性能符合标准,强伸性能及应用性能均无显著性差异;不同喷丝板纺制的丝束单丝的断裂强度及截面异形度无显著性差异,并且370孔喷丝板纺制的丝束单丝质量符合要求。可见,当喷丝孔数从290孔增加到370孔时,丝束产量增加了27.6%,实现了提高二醋酸纤维丝束的产量之目标。目前,该研究成果已在南通醋酸纤维有限公司顺利投入生产。更多还原

【Abstract】 Morn than 90% of the cigarette filter in the world are currently produced by cellulose diacetate fibers because the cross-setion of the cellulose diacetate tows appears Y-shape owing to acetone solvent evaporation in the spinning column and the filter efficiency of the cigarette tow can reach the maximum value. Meanwhile, not only 55%—60% of the nicotine and tar content can be removed and the harmful ingredients such as phenolics can be selectively absorbed on to the tows, but the nicotine and the taste of cigarettes can be reserved. Therefore, cellulose diacetate fibers are worthy of becoming the first choice of cigarette filter. In 2015, the tows production of cellulose diacetate fibers reached about 850,000 tons, and the production in China was 280,000 tons, accounted for 32.9% of the total world production. However, the demand in China was about 350,000 tons, and the demand in other industry was 50,000 tons, accounted for 70% in our country. Apparently, the production capcity of cellulose diacetate fibers in China can not meet the market demand, and need to pay a large number of foreign exchange to import cellulose diacetate fibers and tows. Consequently, how to improve the production of the cellulose diacetate fibers becomes an impotant subject. Under normal circumstances, increasing the scale of production enterprises is a general way to improve the production of the cellulose diacetate fibers. This study focses on researching the die swell behavior of cellulose diacetate spinning dopes at the exit of the spinneret orifice, ascertaining the reseaonble distance of the adjacent orifices, and increasing the number of spinneret orifices, then achieving the purpose of improving the production of cellulose diacetate fibers. The research contents and conclusions were as follows: 1. Study on the rheological property of cellulose diacetate spinning dopesThe rheological property of spinning dopes has an important influence on die swell behavior. Consequently, the static rheological property and dynamic rheological property of cellulose diacetate as an example were studied.The static rheological properties at shear rate from 101 to 102s^-1 and the dynamic rheological properties at angular frequency from 10^-1 to 10²s^-1 of cellulose diacetate spinning dopes with different mass concentrations from 23.5%to 27.5% and various temperatures from 55℃ to 63℃ were determined using a Physica MCR101 rheoviscometer. So the effect of mass concentrations and temperatures on the rheological property was obtained.Static rheological properties: The variable curves of the mass concentrations and temperatures to apparent viscosity of cellulose diacetate spinning dopes were drawn. From the curves, it was found that apparent viscosity reduced when shear rate increased, that is, cellulose diacetate spinning dope was a non-newtotian fluid of shearing thinning. Then non-newtotian indexes of the spinning dopes with different mass concentrations and various temperatures were acquired.When dope temperatures were higher, non-newtonian index increased and as the dope mass concentrations increased, non-newtonian index reduced.Dynamic rheological properties: The storage modulus and loss modulus of cellulose diacetate spinning dopes had a great influence on die swell. The relationship between storage modulus and loss modulus of spinning dopes with different mass concentrations and at various temperatures and angular frequency was acquired. The results demonstrated that when dope mass concentration or dope temperature was fixed, the storage modulus and loss modulus appeared incremental trends with increasing the angular frequency. In addition, when angular frequency was kept constant, with increasing of dope mass concentration or decreasing of dope temperature, the storage modulus, loss modulus appeared incremental trends. Such a study provided a basis for verifying the calculated model of die swell ratio. 2.Establish the die swell ratio model of regular triangular spinneret orificeThe pressure drop model of spinning dope through regular triangular spinneret orifice was aquired using second-type surface integrals and rheological knowledge. Then, based on the pressure drop model and the expression researched by D. L. Mclntosh, the calculated model of die swell ratio at the exit of the regular triangular orifice was developed. Not only the calculated model was easy, but it intuitively described the relationship between die swell ratio and every parameter:（1） the relationship between die swell ratio and aparament viscosity and non-newtonian index;（2） the relationship between die swell ratio and storage modulus, loss modulus and angular frequency;（3） the relationship between die swell ratio and flow rate of spinning dopes;（4） the relationship between die swell ratio and the length of the regular triangular side and the length of the spinneret orifice.3.Verify the die swell ratio model of regular triangular spinneret orificeThe pressure drop of spinning dopes with different flow rates, various temperatures and different mass concentrations was determined by differential pressure transducer and the experimental data was compared to the value of the model data. The results showed that the pressure drop was upward when increasing flow rates or mass concentrations. However, it appeared a downward trend with increasing dope temperatures. From the compared results between calculated model data and experimental data, the minmum deviation between them was 0.05% and the maximum deviation was 4.99%. Hypothesis test of single normal population for unknown variance was used to analyzed the maximum deviation, the analyzed results indicated that there was no prominent differences between them, which demonstrated the pressure drop model was reliable.The die swell ratio of spinning dopes with different flow rates, mass concentrations and at various temperatures was determined with a travelling microscope. The results demonstrated the die swell ratio increased with increasing flow rates, mass concentrations or angular frequency. But it descended when rasing dope temperatures. From the compared results between calculated model data and experimental data, the minmum deviation between them was 0.01% and the maximum deviation was 3.52%. Hypothesis test of single normal population for unknown variance was used to analyzed the maximum deviation, the analyzed results indicated that there was no prominent differences between them, which demonstrated the die swell ratio model was reliable. Such a study provided a basis for the design of the adjacent orifices distance. 4. Design the spinneret with the regular trianglur orifice of higer distribution densityAccording to die swell ratio model, the theoretical distance of the adjacent orifices was confirmed as follows: 2 33mD（29）d（28）a B. Meanwhile, the desigh rules of the layers distance and the circumferential disatance were confirmed. Based on the the calculated value of the model, the theoretical distance of the adjacent orifices was 149.955μm when the flow rates were from 0.577 cm3·min-1 to 0.996cm3·min-1, dope temperatures were from 55℃ to 63℃ and dope mass concentrations were from 23.5% to 27.5%. The reference of the internal indicators from Nantong cellulose fibers CO.,LTD. was used to describe the relationship between the practical distance and the die swell diameter, i,e,. the practical distance should be 9 times to the die swell diameter（ 9A mD 3d.）Therefore, the relationship can be converted into the followings,. The paractical distance should be more than 1.350 mm, which could provide a basis for orifices density distribution.Based on the spinneret with 290 orifices, which had been successfully used in tows production, and on the premise of keeping the spinneret diameter and processing parameter, another three kinds of spinnrets including 325 orifices, 350 orifices and 370 orifices were designed by changing the layers distance, the circumferential disatance and increasing the number of orifices. Then, the tows were produced by the above spinnerets, and the physical properties were tested. Because the physical properties appeared large sample data due to lots of filaments, and it was unable to find the corresponding orifices of evey filament, the mean square deviation was used to analyze the linear density of the filaments, the hypothesis test of single normal population for unknown variance was used to analyze the prominent difference of the mechanical properties and application properties, and the rank sum test was used to analyze the prominent difference of the broken tenacity and sectional area profile form of the filaments produced by the spinnerets. The results that the linear density was complied to the criterion and there was no prominent difference about broken tenacity, ectional area profile form and friction coefficient among the filaments. Meanwhile, the quality of the cellulose diacetate tows produced by the spinneret with 370 orifices met the demand of the application. More importantly, tow productions were increased by 27.6% when spinneret orifices was increased from 290 to 370, which demonstrated that the purpose of this study has achieved. Such the study has been currently used in Nantong Cellulose Fibers Co. Ltd.更多还原