【作者】 王莉莉；

【导师】 陆大年；

【作者基本信息】 东华大学 ， 纺织化学与染整工程， 2013， 博士

【摘要】 纺织品印花是一门综合性的技术,衡量着整个印染行业的发展水平。印花的重点就是要使符合原样设计精神的花样图案在纺织品上准确再现,而这与色浆的流变性能有着密切的关系。在丝网印花中,色浆在不断变化的剪切作用下经历流动和变形过程,进而透过丝网网孔转移到织物上,并向织物和纤维内部渗透。糊料是印花色浆中起着很重要作用的组分,调节并决定色浆的流变性能,进而影响印花织物的表面色光、得色均匀性、花型轮廓清晰度及织物手感。糊料的流变性能在丝网印花的质量最优化控制方面起着越来越重要的作用。但是糊料流变性能和印制性能之间存在何种关联,至今还未得到详细解释和具体说明。糊料是一种高分子聚合物,其溶液的流变性能比较复杂,介于弹性固体和粘性液体之间,需要用流变学理论来描述其性质。目前,对于糊料流变性能的研究,主要采用稳态剪切实验,研究糊料表观粘度随剪切速率的变化情况。已有研究表明,良好的糊料应该在低剪切速率下有着高表观粘度,在高剪切速率下有着低表观粘度。但单一用稳态剪切的方法有着局限性,反映不出糊料所具有的粘弹特征和触变特征。因此,需要采用静态法(稳态剪切和瞬态实验)和动态法(动态振荡实验)对糊料的流变性能进行全面研究,寻找能显著影响其印制性能的重要流变参数。同时,具备怎样流变特征的增稠剂适合作为印花糊料也是需要进行深入探寻的问题。除此之外,在活性染料印花中,国内外一直用海藻酸钠作为糊料,但由于价格上涨、来源受限以及自身存在的流变缺陷,研究者都在试图寻找性能更好的糊料替代海藻酸钠。为了解决以上问题,本课题将流变学研究的静态法(稳态剪切和瞬态实验)和动态法(动态振荡实验)相结合,深入探究印花糊料在不同条件下的流变性能,并将流变数据用流变模型拟合得到流变参数。同时将印制工艺参数与印制质量参数、流变参数相对应,探寻糊料流变性能和印制性能之间的关联,分析各种印制现象的流变原因,进而确定出能显著影响糊料印制性能的重要流变参数,以区分具有不同流变性能的糊料,力求从流变学角度对糊料的印制性能进行初步预测和判断,寻找良好印制性能的糊料应具备的流变特征。随后,通过糊料改性和复配的方法来改变糊料的流变性能,研究糊料流变性能对印制性能的影响,进一步说明糊料流变性能与印制性能的关系,并试图寻找可以用于织物印花的新型糊料。首先,研究了七种常见天然印花糊料的流变性能。采用稳态剪切、动态振荡和瞬态实验,深入探讨常见天然印花糊料的稳态流动性能、动态粘弹性能和触变性能,寻找糊料普遍适用的流变模型。并采用分步剪切的方法得到糊料的粘度回复率,来定量表征糊料的触变性能。研究表明,印花糊料都表现出剪切变稀的特征,黄原胶的流动曲线符合Power-law模型,而其他糊料的流动曲线在低剪切速率下符合Cross模型,在剪切变稀区域内符合Power-law模型。糊料的粘弹曲线都符合Friedrich-Braun模型。由Cross模型可以得到糊料的零剪切粘度,由Power-law模型可以得到糊料的流动指数,由Friedrich-Braun模型可以得到糊料的粘弹特征参数(储能模量、损耗模量、损耗角)。从流变结果来看,其他糊料的流变性能都介于海藻酸钠和黄原胶之间。其次,建立了精细花型印制性能的评价体系,研究了七种常见天然印花糊料的印制性能,探讨了糊料流变性能与印制性能的关系,确定出能显著影响糊料印制性能的重要流变参数。选用海藻酸钠和黄原胶作为两种典型糊料,研究其在不同印制条件下的印制性能,同时将印制工艺参数与印制质量参数、流变参数进行对应关联,分析各种印制现象的流变原因,并初步找到良好印制性能的糊料所应具备的流变特征。糊料在外力作用下的剪切变稀特性、粘弹性能和触变性能,决定色浆的透网性能,进而影响表面得色量、渗透性、色泽均匀性及花型轮廓清晰度。研究表明,显著影响糊料印制性能的重要流变参数为低剪切速率下的表观粘度、剪切变稀区域的流动指数、线性粘弹区域内的损耗角和低频下的损耗角、粘度回复率。良好印制性能的糊料应该具备这样的流变特征,包括较好的流动性能(低剪切速率下具有适当的表观粘度以及剪切变稀区域内具有适当的流动指数),相对稳定的粘弹性能且表现出较多的粘性行为(线性粘弹区域内和低频下的损耗角大于45°),较弱的触变性能(较高的粘度回复率)。为了改善黄原胶的流变性能,在900C的碱性条件下对其进行脱乙酰改性处理,控制氢氧化钠用量,成功制备了一系列不同改性程度的黄原胶。通过红外光谱、凝胶渗透色谱和特性粘度,探讨了改性黄原胶的结构变化及氢氧化钠用量对改性程度的影响。并进行流变实验和印花实验,分析对比不同改性程度黄原胶的流变性能及印制性能,将重要流变参数和印制质量参数相对应来探讨糊料流变性能对印制性能的影响,进一步说明糊料流变性能与印制性能的关系。此外,探讨了改性黄原胶在不同织物印花中的应用。研究表明,随着氢氧化钠用量的增加,黄原胶改性程度逐渐增大,且当加入氢氧化钠的摩尔数与黄原胶五糖重复结构单元的摩尔数之比为0.917：1时,黄原胶完全脱去乙酰基,改性程度达到最大。与未改性黄原胶相比,改性黄原胶的特性粘度和表观粘度会发生一定程度的降低,流动性能变好。随着改性程度的增大,改性黄原胶的弹性效应逐渐减弱,粘性效应逐渐增强,结构粘度逐渐减小,粘度回复性逐渐增大,触变性逐渐减弱。与未改性黄原胶相比,改性黄原胶的透网性能、表面得色量和渗透率分别能够提高30～50%,32-57%,5-66%。完全脱乙酰改性黄原胶0.917MXG可以作为印花糊料,用于不同织物不同染料类型的印花中,其印制性能接近海藻酸钠的大块面花型印制性能,甚至优于海藻酸钠的精细花型印制性能。最后,将海藻酸钠和完全脱乙酰改性黄原胶0.917MXG按照不同比例进行拼混,制成不同复配比例的色浆,研究其流变性能及印制性能,寻找适合大块面花型和精细花型印制的最佳复配比。研究表明,加入少量改性黄原胶于海藻酸钠中,复配色浆流动性能优于海藻酸钠色浆。之后,随着改性黄原胶加入量的增多,复配色浆在低剪切速率下的表观粘度会不断提高,且越来越接近假塑性流体,表现出越来越显著的剪切变稀特征。此外,随着改性黄原胶含量的增加,复配色浆的弹性效应逐渐增强,粘弹性能经历了以粘性为主向以弹性为主的转变。海藻酸钠含量较多的复配色浆体系以粘性效应为主,且类液态特征随着黄原胶加入量的增多而越来越弱；而黄原胶含量较多的复配色浆体系以弹性效应为主,且随着黄原胶加入量的增多而表现出越来越显著的类固态特征。当海藻酸钠和改性黄原胶的复配比例为80：20时,复配色浆SAMXG8可以获得最佳的大块面花型印制性能；当海藻酸钠和改性黄原胶的复配比例为20：80时,复配色浆SAMXG2可以获得最佳的精细花型印制性能。更多还原

【Abstract】 Textile printing, a comprehensive technology, weighs the development level of the printing and dyeing industry. The emphasis of printing is laid on making the exact reproduction of the patterns on the textiles according to the original design spirits, which is closely related with the rheological properties of the printing pastes. During the screen printing process, the printing pastes experience the flow and deformation under ever-changing shears to pass through the screening openings onto the fabrics, and penetrate into the fabrics and fibers. And the paste, an important component in the printing paste, adjusts and determines the rheological properties of the printing paste, affecting the surface color, levelness, sharp definition as well as handle of the fabric. Paste rheology has been obtaining more and more importance in the quality optimization and control in the screen printing. However, what relations exist between rheology and printability of the pastes has not gotten the detailed explanation and concrete illustration up to now.Paste is a high molecular polymer. The rheological properties of its solution are quite complex between elastic solid and viscous liquid, needing the rheological theory to describe the properties. So far, the studies of paste rheology have mainly adopted steady shear tests to investigate the change of apparent viscosity with shear rate. Previous researches had shown that the excellent pastes should have low apparent viscosity at low shear rates and high apparent viscosity at high shear rates. However, only using the steady-shear method has certain limitations, not depicting the viscoelastic and thixotropic features of the pastes. Consequently, it needs to use the static method (steady shear and transient tests) and dynamic method (dynamic oscillatory tests) together to study the rheological properties of the pastes comprehensively, and find the vital rheological parameters that significantly affect the printing performances. Meanwhile, what kind of rheological thickener can be used as printing paste has also become a problem to be intensively explored. What’s more, sodium alginate is the most widely used thickener in reactive printing at home and abroad. But the relatively high cost, limited supply as well as the undesirable rheological drawbacks, have spurred efforts for researchers to find better alternatives instead of sodium alginate.With the purpose of solving the above-mentioned problems, the research intensively investigated the rheological properties of printing pastes under different conditions by means of the static method (steady shear and transient tests) and dynamic method (dynamic oscillatory tests). And the rheological parameters were obtained by fitting data with rheological models. Meantime, the printing process parameters were correlated with the printing quality parameters and rheological parameters, the relationships between rheology and printability of the pastes were explored, and the rheological reasons for various kinds of printing phenomena were analyzed. Furthermore, the vital rheological parameters were determined to predict and judge the printing performances of pastes from the perspective of rheology tentatively. And the rheological characteristics of pastes with excellent printing performances were found. Subsequently, the influence of rheological properties on printing performances was studied through modification and mixture so as to further illustrate the relationships between rheology and printability of the pastes, and attempt to find a new paste in the textile printing.Firstly, the rheological properties of seven common natural printing pastes were investigated. The steady flowability, dynamic viscoelasticity and thixotropy of the common natural printing pastes were intensively discussed via steady shear, dynamic oscillatory and transient tests. The widely applicable rheological models of the pastes were explored. And the viscosity recovery rate of the paste was obtained by step-shear method to quantitatively characterize the thixotropy. The results showed that the printing pastes performed shear-thinning features. The flow curve of xanthan was well fit for the Power-law model. And the flow curves of other pastes were well fit for the Cross model within low shear rates and for the Power-law model within shear-thinning region. The viscoelastic curves of all the pastes were well fit for the Friedrich-Braun model. The zero shear viscosity, flow index and viscoelastic parameters (storage modulus, loss modulus as well as loss angle) of the paste could be obtained by the Cross model, the Power-law model and the Friedrich-Braun model, respectively. From the result of rheology, the rheological properties of other pastes were between sodium alginate and xanthan.Secondly, the evaluation system for fine pattern printing was established. The printing performances of seven common natural printing pastes were studied. The relationships between rheology and printability of the pastes were explored to determine the vital rheological parameters that prominently affect the printing performances. And sodium alginate and xanthan were selected as two typical printing pastes. The printing performances under various printing conditions were studied. Meanwhile, the printing process parameters were correlated with the printing quality parameters and rheological parameters in order to discuss the relationships between rheology and printability of the pastes, analyze the rheological reasons for various kinds of printing phenomena, and find the rheological characteristics of pastes with excellent printing performances preliminarily. The shear-thinning feature, viscoelasticity and thixotropy of the pastes under forces determined the paste add-on, influencing the color yield, penetrability, levelness as well as outline sharpness. The results showed that the rheological parameters that determined the printing performances of pastes were apparent viscosity at low shear rates, flow index in the shear-thinning region, loss angle within the linear viscoelastic region and loss angle in low frequency as well as viscosity recovery rate. The pastes with excellent printing performances should possess excellent rheological properties, including better flowability (proper apparent viscosity at low shear rates and flow index in shear-thinning region), relatively stable viscoelasticity and more viscous behaviors (loss angle larger than45°within the linear viscoelastic region and in low frequency) as well as weaker thixotropy (higher viscosity recovery rate).In order to improve the rheological properties of xanthan, it was modified by deacetylation under alkali condition at90℃. A series of modified xanthan with different degrees of modification were successfully prepared by controlling the alkali. The structural change of xanthan and the effect of alkali on the degree of modification were discussed by FT-IR, GPC and intrinsic viscosity. Moreover, the rheological tests and printing tests were carried out to analyze and compare the rheological properties and printing performances of modified xanthan with different degrees of modification. Else, the vital rheological parameters were correlated with the printing quality parameters to explore the influence of paste rheology on printability, further illustrating the relationships between rheology and printability of the pastes. In addition, the applications of modified xanthan in various textile printing were studied. The results showed that the degree of modification increased with the increase of alkali, and the deacetylation of xanthan was fully completed when the molar ratio of alkali to repeated pentasaccharide units reached0.917:1, indicating the maximum degree of modification. Compared to the native xanthan, the intrinsic viscosity and apparent viscosity of modified xanthan had certain decrease, and the flowability became better. With the degree of modification increasing, the elastic effects of modified xanthan decreased, the viscous effects increased, the structural viscosity decreased, viscosity recovery increased, and thixotropy decreased little by little. In comparison with the native xanthan, the screenability, color yield and penetration of modified xanthan increased by30-50%,32-57%,5-66%, respectively. Furthermore, modified xanthan by full deacetylation0.917MXG could be used as printing paste for different types of fabrics and dyes.-It was able to achieve the excellent printing performances for large patterns as sodium alginate, and even have an advantage over sodium alginate in fine pattern printing.Finally, soudium alginate and modified xanthan by full deacetylation0.917MXG were mixed together in various ratios, and different mixed printing pastes were prepared. The rheology and printability of the mixed printing pastes were studied. Besides, the best ratios for large pattern and fine pattern printing were found. The results showed that with a little addition of modified xanthan to sodium alginate, the flowability of the mixed printing pastes was better than that of sodium alginate. Subsequently, as the addition of modified xanthan increased, the apparent viscosity at low shear rates increased continuously, and the mixed printing pastes performed more and more prominent shear-thinning features of pseudoplastic fluid. Moreover, the elastic effects of the mixed printing pastes were enhanced and the viscoelasticity experienced the transition from viscosity to elasticity with the increase of modified xanthan. The mixed printing pastes with more sodium alginate mainly showed viscous effects, and the liquid-like feature became weaker and weaker with the addition of modified xanthan. While the mixed printing pastes with more modified xanthan mainly had elastic effects, and the solid-like feature became more and more prominent with the addition of modified xanthan. When the ratio of sodium alginate and modified xanthan was80:20, mixed printing paste SAMXG8could obtain the best printing performances for large patterns; and when the ratio of sodium alginate and modified xanthan was20:80, mixed printing paste SAMXG2could obtain the best printing performances for fine patterns.更多还原