CPAM用量对填料絮聚体稳定性和成纸性能的影响

填料经预絮聚后以絮聚体的形式加填纸张中,絮聚体在湿部的尺寸及稳定性对纸张性能有着重要影响。采用不同用量的阳离子聚丙烯酰胺(CPAM)对沉淀碳酸钙(PCC)进行预絮聚,通过絮聚体粒径的变化,研究了不同剪切条件下PCC絮聚体抗剪切与再絮聚效果,并考查了所得絮聚体对成纸性能的影响。结果表明,随着CPAM用量从1%增加至7%,絮聚体粒径由23.37μm增大至31.92μm。与常规PCC加填方法相比,当CPAM用量为3%~7%且加填量55%时,预絮聚加填纸张留着率均可提高约3个百分点左右。当CPAM用量为3%,填料含量为30%时,预絮聚加填比常规加填纸张抗张指数提升了约16%,而CPAM用量高于3%时所得的大粒径絮聚体对成纸抗张指数反而不利,且纸张白度有所降低。     

碳酸钙预絮聚加填技术研究

造纸湿部预絮聚加填技术完全不同于直接加填技术,实验表明在预絮聚条件下成纸强度性能增大,填料留着增加,达到90％以上;本实验研究过程中的第二组工艺（PCC＋CS＋CP3＋CPAM＋AKD）制备的预絮聚体稳定性好,粒径大小合适。在制备絮聚体时药品的添加顺序,添加量以及剪切李率是主要影响因素,主要影响絮聚体的粒径大小和抗剪切能力。     

GCC预絮聚工艺参数对絮聚体和纸张性能的影响

以重质碳酸钙（GCC）和阳离子聚丙烯酰胺（CPAM）为对象,研究了絮聚剂CPAM溶液质量分数、搅拌转速及GCC悬浮液固含量对絮聚过程的影响。利用Mastersizer分析了未处理GCC和絮聚GCC的中值粒径和粒径分布,同时,探讨了GCC絮聚体颗粒大小和灰分对成纸抗张强度和光学性能的影响。添加高质量分数CPAM溶液可以提高中值粒径。采用1000～3000 r/min的搅拌转速模拟了不同的湍流环境。结果显示,高速搅拌明显降低GCC絮聚体颗粒的大小。纸张成形前进行稀释和低速搅拌GCC悬浮液可以使GCC絮聚体颗粒不被破坏。添加尺寸较大的GCC絮聚体的浆料成纸具有更好的强度性能。     

PCC预絮聚体形成机理探讨

通过对沉淀碳酸钙（PCC）絮聚体形成过程及在纸张中的留着进行观察,比较了PCC预絮聚和实际加填的差异,研究了PCC絮聚体粒径及Zeta电位的变化情况,探讨了用静电场理论解释PCC+CS（阳离子淀粉）+CP3（阴离子有机微聚物）絮聚体的形成机理。将絮聚体理想化为中空的球体,由静电场理论分析可知,在垂直于由PCC粒子和CS形成的絮聚体微小平面空隙的方向上存在电场梯度,在电场力的作用下,CP3可进入絮聚体的类球体内并对外球面产生相互吸引作用而可能产生收缩,这种电场作用力可使絮聚体结合更牢固,抗剪切能力增强。     

双助留体系下预絮聚加填对纸张性能的影响

采用阳离子聚丙烯酰胺(CPAM)、皂土双组分助留体系预絮聚烷基烯酮二聚体(AKD)和沉淀碳酸钙(PCC),探究各组分添加顺序对纸张施胶效果、填料留着率及纸张物理性能的影响。对比传统加填工艺发现,采用[PCC+CPAM+皂土+CS+AKD]的预絮聚加填工艺时,纸张的物理性能提高最为明显,纸张抗张指数提高22.4%,耐破指数提高52.0%,同时,纸张的匀度指数从111.9降低至69.0,匀度显著改善。将AKD提前加入浆料中,然后采用[PCC+CS+CPAM+皂土]的预絮聚加填工艺时,纸张的施胶度和填料留着率明显提高,相比传统纸张加填工艺,Cobb_(60)值降低了24.8%,填料留着率提高了3.7%。但所有预絮聚加填工艺由于增大了PCC的颗粒大小,使得纸张白度、不透明度、透气度都有所降低。     

阳离子聚丙烯酰胺与膨润土对细小纤维-碳酸钙共絮聚的影响

以杨木P-RC APMP浆为原料进行筛分,将细小纤维与碳酸钙进行共絮聚,研究在CPAM/膨润土微粒助留体系中,不同CPAM添加量对细小纤维-碳酸钙共絮聚团和浆料的电性、共絮聚团大小、细小组分留着性能以及膨润土添加量对共絮聚团大小、分布及细小组分留着的影响。结果表明:随着CPAM用量的增加,细小纤维-碳酸钙絮聚团的表面负电荷与浆料的Zeta电位绝对值都在不断减小,细小组分的留着率在不断提高;随着膨润土用量的增加,共絮聚团的平均弦长在不断增大,细小组分的留着在不断增大。     

纸浆絮聚检测技术在苇浆絮聚特性研究中的应用

利用纸浆絮聚图像分析系统对苇浆在不同助留体系作用下的絮聚状况进行了研究,首先利用动态滤水仪和纤维比容比表面积测定仪分别研究了不同助留体系对苇浆留着和滤水性能的影响,然后利用纸浆絮聚图像检测系统对各种助留体系苇资助的絮聚特性进行检测,通过分析苇浆絮聚体的面积和强度,研究不同助留体系对苇浆的作用规律及絮聚与成纸匀度之间的关系,并与动态滤水和比过滤阻力测定结果加以比较。     

双元体系下细小纤维-碳酸钙共絮聚的研究

以杨木P-RC APMP为原料,对其进行筛分,并对P-RC APMP细小纤维与碳酸钙进行共絮聚,研究了CPAM/膨润土微粒助留体系下,不同的CPAM添加量、膨润土用量及剪切力对细小纤维-碳酸钙共絮聚的影响;结果表明:随着CPAM用量的增加,细小纤维-碳酸钙絮聚团的表面负电荷与浆料的Zeta电位绝对值都在不断减小,细小组分的留着率在不断增大;随着膨润土用量的增加,共絮聚团的平均弦长在不断增大,细小组分的留着在不断增大;随着剪切力的增大,细小纤维-碳酸钙絮聚团的尺寸在不断减小。     

CPAM/膨润土体系中剪切力对细小纤维-碳酸钙共絮聚影响的研究

以杨木P-RC APMP为原料,对其进行筛分,并对P-RC APMP细小纤维与轻质碳酸钙（PCC）进行共絮聚,研究了CPAM/膨润土微粒助留体系下,剪切力对细小纤维-PCC共絮聚团大小、颗粒结构的影响;结果表明：随着剪切力的增大,细小纤维-PCC絮聚团的尺寸不断减小;在高转速下,絮聚团虽然被打碎,但悬浮液中单独的白色颗粒很少（PCC）,体系中还是有许多小的絮聚体.     

用动态滤水仪探讨微粒助留体系絮聚机理

以CaCO3及经100目筛分得到的纤维为实验原料，设计了几种模型，用动态滤水仪(BRITTDDJ)探讨了CPAM／膨润土微粒助留体系的絮聚机理，并与CPAM单元助留体系的留着和抗剪切性能进行了比较。实验发现膨润土的主要作用是与吸附在纤维、细小组分上的CPAM之间产生强的连接键，从而产生絮聚；微粒助留体系比CPAM单元助留体系具有更好的留着和抗剪切性能。     

利用FBRM研究阳离子聚丙烯酰胺对高岭土的动态絮凝过程

利用聚焦光束反射测量仪（FBRM）研究了阳离子聚丙烯酰胺（CPAM）对高岭土颗粒体系的动态絮凝过程,结合浊度仪、激光衍射粒度仪、显微摄像等表征手段,探讨了絮凝剂用量对絮凝性能和絮体结构的影响。同时基于分形理论对絮凝过程中絮体分形维数的变化进行了考察,基于Smoluchowski模型研究了CPAM作用下高岭土粒子的絮凝动力学。结果表明,随着药品用量的增加,体系中粒子的平均弦长和粒径逐渐增大,体系达到稳定的时间延长,浊度不断下降。在絮凝过程中,随着作用时间的延长,絮体结构发生变化,分形维数增加,形成相对致密的絮体。增加絮凝剂的用量,絮凝作用增强,絮体尺寸变大,絮凝速率较快,需较长的絮凝反应时间才能达到平衡。     

The impact of zeta potential on the physical properties of ferric--NOM flocs

The physical properties of natural organic matter (NOM) flocs, such as size, growth rate, and strength, were investigated using a laser diffraction particle sizing device. Conditions were set such that varying carbon coagulant ratio and zeta potential could both be investigated. Results demonstrated a link between zeta potential and coagulation and flocculation performance, with the production of strong flocs and low residual concentrations when the zeta potential was minimized. The overall strength of the connection points within the floc were determined by a combination of steric interactions, polymer bridging, van der Waals forces, and electrostatic forces. Hence, both dose ratio and zeta potential are important in understanding floc properties. Floc growth was dominated by dose ratio, whereas the response to elevated shear was strongly related to zeta potential. The steady-state floc size was a combination of both factors. This allowed the continued development of a qualitative model in order to engineer optimal floc properties when coagulating NOM.     

纤维电荷对阳离子聚电解质吸附性能的影响

以DQP漂白竹浆和麦草浆为原料,以CPAM作为阳离子聚电解质的模型物,以聚电解质滴定技术为研究方法,在测量纤维表面电荷和聚合物电荷密度的基础上,研究CPAM在纤维表面上的吸附量与纤维表面电荷特性的关系.结果发现,在纤维表面电荷一定的情况下聚电解质达到饱和吸附时的吸附量与纤维的表面电荷有很好的对应关系.     

分散聚合法制阳离子聚丙烯酰胺及其对竹浆废水的絮凝性能

以丙烯酰胺(AM)和丙烯酰氧乙基三甲基氯化铵(DAC)为共聚单体,采用分散聚合法在无机盐水溶液中得到了性能稳定的聚合物乳液。产物的红外光谱及粒径分析表明,这种分散聚合法在制备阳离子聚丙烯酰胺乳液上是成功的。将所得阳离子聚丙烯酰胺乳液(CPAM)与聚硅氯化铝配合使用处理竹浆废水,结果表明自制阳离子聚丙烯酰胺具有良好的絮凝性能。     

Octadecylamine Graft-modified Cellulose Nanofiber and Its Reinforcement to Poly(butylene adipate-co-terephthalate) Composites

Biodegradable polymers such as poly(butylene adipate-co-terephthalate) (PBAT) have attracted great interest as alternatives to traditional petroleum-based polymers. Nonetheless, it is necessary to improve some properties of PBAT, such as mechanical strength. Cellulose nanofiber (CNF) can improve PBAT mechanical strength, but its dispersion and compatibility in the PBAT matrix require further improvement. In this study, octadecylamine (ODA) was utilized to graft-modify CNF to change the fiber-to-fiber interaction and improve its compatibility with the PBAT matrix. PBAT composites with 1 wt% CNF were prepared using a masterbatch premixing method to avoid CNF aggregation during extrusion. The effects of ODA graft modification on CNF properties were studied; varying degrees of CNF modification were investigated for their effect on PBAT properties. ODA-modified CNF (OCNF)/PBAT melt-extruded composites possessing 17.2% higher tensile strength than pure PBAT polymer were obtained without affecting the thermal stability of PBAT. As a result, surface modification of CNF with ODA is an effective strategy for improving CNF-PBAT compatibility.     

Influence of Flocculation on Optical Properties of Emulsions

ABSTRACT: The influence of droplet flocculation on the optical properties of 1 and 10 wt% oil-in-water emulsions with and without dye was investigated. Flocculation was induced by addition of SDS micelles to the aqueous phase of emulsions to increase the depletion attraction between droplets. Droplet flocculation caused the spectral reflectance and L -value (lightness) of emulsions to decrease, and the magnitude of the a - and b - values to increase, but the changes were rather small. Similar trends were observed for emulsions with and without dye. Overall, emulsion optical properties were dominated by light scattering from droplets rather than flocs.     

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

Flocculation is prerequisite for bulk sedimentation of yeast during brewery fermentation. Although single yeast cells gradually sediment in green beer, this sedimentation rate is too slow without formation of large yeast flocs. The present review concerns the major determinants of yeast flocculation and sedimentation in brewery fermentations. Flocculation characteristics of yeast are strongly strain‐dependent and largely defined by which FLO genes are functional in each strain. In addition to the genetic background, several environmental factors affect flocculation. These can be, somewhat arbitrarily, classified as physiological factors, such as the calcium availability, pH, temperature and ethanol and oxygen concentrations in the medium or physical factors, such as cell surface hydrophobicity, cell surface charge and the presence of appropriate hydrodynamic conditions for the formation of large flocs. Once yeast flocs are formed, their size, shape and density and the properties of the surrounding medium affect the rate at which the flocs sediment. Higher gravity worts usually result in green beers with higher viscosity and density, which both retard sedimentation. Moreover, environmental factors during yeast handling before fermentation, e.g., propagation, storage and cropping, influence the flocculation potential of yeast in subsequent fermentation. Premature yeast flocculation (PYF) and the role of PYF factors are discussed. In conclusion, some potential options available to adjust yeast flocculation are described.     

甘蔗汁中絮凝物产生的影响因素

为了解决甘蔗汁絮凝物沉淀引起的饮料浑浊问题,以甘蔗汁为原料,对膜滤后的甘蔗清汁中影响絮凝物生成的因素进行了研究。通过控制温度、pH来研究二者对絮凝物产生的影响,并对絮凝物中蛋白质、总糖、灰分等成分进行分析,利用傅里叶红外光谱和扫描电镜能谱仪观测絮凝物官能团结构和组成元素。研究发现,温度对生成絮凝物的影响较小。絮凝物的产量随pH的升高而增加,推断氢氧根会促进甘蔗汁中絮凝物的产生。傅里叶红外光谱结果表明,絮凝物主要由多糖、蛋白质以及灰分等物质构成。通过能谱分析电子扫描和红外扫描可以看出,絮凝物中含有铁、钙、磷、硅、锰等无机离子。说明在碱性条件下,糖类与蛋白质分子相互作用产生絮凝结构,铁、钙等金属离子生成的氢氧化铁、氢氧化钙与蛋白质和多糖产生的絮凝结构网络在一起,形成饮料中的絮凝沉淀物。