中文论文文摘

    目前,我国大量使用的造纸原料是草浆、苇浆和再生浆等。这些原料由于纤维短、杂细胞含量高、保水值高等缺点，严重影响纸张的抄造和纸张质量。纸张增强剂作为造纸助剂之一，其应用相当广泛。目前，较常使用的造纸湿强剂有五种：a)脲醛树脂及其改性产品(UF)；b)三聚氰胺甲醛树脂及其改性产品(MF)；c)聚酰胺聚胺环氧氯丙烷树脂(PAE或PPE)及其改性产品聚酰胺聚脲(PAPU)等；d)聚乙烯亚胺(PEI)；e)其他种类。
PEI是一种多支链聚合物，其分子中存在伯、仲、叔三种胺基基团，能与纤维素的羟基产生静电吸引形成次价力交联网络，可作为纸张湿强剂和助留剂。在造纸领域中使用的多为未改性的PEI。
为了发挥PEI的结构性能，可对其进行有效的改性。本文在综述纸张增强剂增强原理和改性PEI研究进展的基础上，分别利用环氧氯丙烷（ECH）、水性双酚A型环氧树脂（BAE）和丙三醇缩水甘油环氧树脂（GE）对PEI进行了改性。通过改性，制备出了具有强阳离子性的改性PEI纸张增强剂，对纸张具有明显的增强作用。重点讨论了增强剂组成、添加量和助留剂（CPAM）等因素对纸张强度的影响；其次，为了提高改性PEI与纸纤维的结合，在浆液中改变了改性PEI与CPAM的添加顺序，研究了不同添加顺序对纸张强度的影响。采用流变仪、Zeta电位仪、FTIR、TG、和SEM对改性PEI的流变性能、浆料电位、分子结构、热稳定性及纸样微观结构进行了表征。
研究结果表明：
（1）使用PEI/ECH湿增强剂对纸张进行浆内增强，较佳的应用工艺为：PEI与ECH等质量比改性、增强剂添加量为1.0%、CMC为0.2％。从而，纸张湿抗张指数从3.23 N•m•g -1增加到6.49 N•m•g -1，湿强度从14.26%增加到26.48%。
（2）使用PEI/BAE湿增强剂对纸张进行浆内增强，较佳的应用工艺为：当m(PEI)/m(BAE)=5：1.5，w(CPAM)=0.2‰，添加量为1%时，纸张湿强度从14.46%提高到了21.65%，纸张环压指数提高40.54%；Zeta电位分析表明，当m(PEI)/m(BAE)=5：1.5，改性物添加量为1%时，浆料电荷趋于零。
（3）使用PEI/GE湿增强剂对纸张进行浆内增强，较佳的应用工艺为：当w(GE)=17%，w(CPAM)=0.2‰，改性PEI添加量为1%时，纸张湿强度达到22.84%，纸张耐折度提高10%以上。Zeta电位分析表明：随着改性PEI加入量的增加，纸浆zeta电位连续上升；当w(GE)=17%，改性PEI添加量为1%时浆料zeta电位趋于零。
（4）先添加CPAM时，既影响了改性PEI的留着，还产生了不同程度的树脂障碍，导致纸张性能下降，故应先添加改性PEI。
（5）FTIR表明：PEI/ECH产物分子结构中出现了季铵基团；PEI/BAE产物分子结构中出现了属于苯环的骨架振动吸收峰以及对位取代苯环的特征吸收峰；PEI/GE产物分子结构中出现了羟基吸收峰、醚键的特征吸收峰、甲基特征吸收峰，和环氧基吸收峰。以上证实了环氧基与PEI发生了反应。
（6）热重（TG）分析结果表明：PEI起始分解温度在197℃以上；PEI/ECH起始分解温度在270℃以上；PEI/BAE起始分解温度在287℃以上；PEI/GE起始分解温度在271℃以上。以上证实了改性物耐热性均有明显提高。
（7）SEM分析表明：纸张断裂是由纤维断裂引起的，为改性PEI可增加纤维间的结合强度提供了依据。

外文论文文摘

    Currently, straw, reed and recycled fiber are largely used for paper making raw materials. Papermaking process and paper quality are seriously affected by short fibers，high content of parenchyma cell and the high water retention value etc. Paper strength agent is widely used as one of papermaking additives. Paper wet-strength aids includes five kinds: a) UF and modified UF; b) MF and modified MF; c) PAE/PPE; d) polyethylene mine (PEI); e) others species.
PEI is a kind of polymer with highly branched chains, primary amine, secondary amine and tertiary amine groups. Crosslinking network is formed between PEI and hydroxyl group on fibers. So it can be used for wet-strength aids and retention agent. Non-modified PEI is mainly applied in papermaking field.
    Bringing structural performance into full play, PEI was effectively modified. The cationic strength agents of paper were prepared through modification of PEI with ECH, bisphenol A epoxy resin emulsion and water-soluble glycerine epoxy resin respectively. The influence of composition, additive amount and retention aid of cationic polyamide on paper strength is discussed. Secondly, improving adhesive strength between PEI and fibers, The effect of adding order of PEI and CPAM on paper strength is studied, and the rheological properties, pulp potential, molecular structure, thermal stability and paper microstructure were characterized by Zeta potential instrument, rheoviscometer, FTIR, TG and SEM, respectively.
The main results show as follows:
（1）Under the optimum conditions of w(modified PEI)1.0%, w(CMC)1.0% and m（PEI）∶m（ECH）1∶1, the wet-tensile index was enhanceed from 3.23 N•m•g -1 to 6.49 N•m•g -1, and the wet strength was increased from 14.26% to 26.48%.
（2）Under the optimum conditions of w(modified PEI)1.0%，w(CPAM)＝0.2‰, and m（PEI）∶m（BAE）1∶1.5, the wet strength was enhanced from 14.46% to 21.65% and the ring crush index improves by 40.54%. Zeta potential analysis showed that the electric charge of slurry system tended to zero when m（PEI）∶m（BAE）was 1∶1.5, w(modified PEI) was 1%, and w(CPAM) was 0.2‰.
（3）Under the optimum conditions of w (modified PEI)1.0%，w (modified PEI)17%, and w (CPAM)0.2‰, wet strength was 22.84% and folding endurance was increased over 10%. Zeta potential analysis showed that the electric charge of slurry system tended to zero when w(GE) was 17%, w(modified PEI) was 1%,
（4）When it was filled earlierly than the modification, CPAM affected the retention rate of the modification of PEI and produced different drgee of resin obstacle,which decreased paper properties.
（5）FT-IR analysis indicates that quaternary ammonium groups are found in the modified PEI/ECH molecular structure. The vibration absorption peak of benzene ring framework and characteristic absorption peak of benzene ring are found in the modified PEI/BAE molecular structure. The vibration absorption peaks of hydroxy, ether bond, methyl and epoxy group are found in the modified PEI/ GE molecular structure.
（6）Thermograbimetry analysis shows that decompositions temperature of PEI, the modified PEI/ECH, the modified PEI/BAE and the modified PEI/ GE respectively start at more than 197℃, 270℃, 287℃, 271℃, Which proved that the heat resistances of the modified PEI were improved obviously.
（7）SEM analysis indicates that paper fracture is caused by fiber breakage, which provides basis for the fact that the modified PEI can increase interfiber-bonding strength.