【作者】 赵振环；

【导师】 刘温霞；

【作者基本信息】 山东轻工业学院 ， 制浆造纸工程， 2011， 硕士

【摘要】 纳米二氧化钛原生直径约25 nm,分散在水中以平均粒度约260 nm的聚集体形式存在。其等电点为pH 6.4,在水中呈酸性,带有正电荷。本文利用纳米二氧化钛作为固体微粒乳化剂,研究了其对反应型施胶剂AKD和ASA的乳化作用。以AKD和工业级ASA制备的纳米二氧化钛稳定的乳状液用于浆内施胶,研究了乳液的施胶效果。发现,纳米二氧化钛单独使用不能稳定AKD乳液,而壳聚糖在用量较低时也不能有效地稳定AKD乳液。但二者联合使用时,在油水比为1:5、壳聚糖用量为2.0 wt%时,制备了稳定的O/W型AKD乳液,并当二氧化钛用量低于2.2 wt%时,乳液平均粒径随二氧化钛用量的增加而减小;当二氧化钛用量高于2.2 wt%时,继续增加二氧化钛用量,乳液粒径不再变化。经纳米二氧化钛/壳聚糖稳定的AKD乳液具有较高的施胶效率,且纸张施胶度在二氧化钛用量低于2.2 wt%时随二氧化钛用量的增加而提高。纳米二氧化钛单独使用能够稳定工业级ASA乳液。当ASA含量低于50%时,乳液稳定性好,粒径随纳米二氧化钛用量的增加而减小,至二氧化钛颗粒用量达到2.0 wt%时,乳液粒径不再随之减小。所得ASA乳液具有较好的施胶效果,并在施胶剂用量从0.4%增加到0.5%时,纸张施胶度迅速提高。乳液粒径的减小有助于提高其施胶效果,因此,适当提高稳定剂二氧化钛用量,ASA乳液的施胶效果也得到改善。但乳液的水解稳定性较差,在50分钟之内,施胶效果几乎降低50%左右。纳米二氧化钛能有效地稳定试剂级ASA乳液,乳液在3000 rpm下离心15min不破乳、不分层、不沉降。增加水相质量分数,能使纳米二氧化钛稳定的W/O型乳液转变为O/W型乳液,且纳米二氧化钛初始分散方式、乳化速度和颗粒浓度对乳液转相时的水相质量分数有显著影响。当纳米二氧化钛预先分散在ASA中时,乳液转相时的水相质量分数低于纳米二氧化钛预先分散在水中时转相所需的水相质量分数。通过纳米二氧化钛在ASA/水界面的扩散实验和红外光谱分析发现,当纳米二氧化钛分散在水中时,ASA的水解产物烯基琥珀酸在界面上对纳米二氧化钛进行了吸附改性,导致纳米二氧化钛分散在水中时更“疏水”。较高的乳化速度提供更多的能量促使乳液在较低的水相质量分数下从W/O转变为O/W型乳液;而在较高的二氧化钛浓度下,由于分散体系的黏度较高,致使W/O型乳液在较高的水相质量分数下才能转变为O/W型乳液。更多还原

【Abstract】 The primary particle size of nano-TiO₂ is about 25 nm and the mean size of its aggregate is approximately 260 nm when nano-TiO₂ particles are dispersed in water. The isoelectic point of nano-TiO₂ particles in aqueous dispersion is pH 6.4. The pH of particle dispersion is less than 6.4, the particle is thus positively charged. In the present paper the emulsification behaviors of reactive sizing agents AKD and ASA have been investigated using nano-TiO₂ as solid particle emulsifier. The prepared AKD and industry-specific ASA emulsions stabilized by nano-TiO₂ are applied in internal sizing and their sizing performance is exploited. The results show that the AKD emulsion can hardly stabilized by nano-TiO₂ particle alone or by chitosan with a lower dosage. However, the mixture of chitosan and nano-TiO₂ can well stabilize the O/W AKD emulsion when the oil/water ratio is 1:5 and the concentration of chitosan is 2.0 %. Meanwhile when the concentration of nano-TiO₂ is lower than 2.2 wt%, the mean size of droplets decrease with the increase of the concentration of nano-TiO₂; while the mean size of emulsion droplet keep constant when the particle concentration is higher than 2.2 wt%,. The AKD emulsion stabilized by nano-TiO₂ and chitosan has high sizing efficiency. When the particle concentration is lower than 2.2 wt%, the sizing degree of the paper increases with the increase of nano-TiO₂ concentration.Nano-TiO₂ particle can stable industry-specific ASA alone. When the content of ASA is lower than 50%, the prepared ASA emulsion is very stable. The mean diameter of ASA emulsion decreases with the increase of nano-TiO₂ concentration and reaches the minmum at 2.0 wt% of nano-TiO₂ concentration. The emulsion can impart a high sizing degree to handsheet and the sizing degree rises abruptly when the charge level of ASA increases from 0.4% to 0.5%. The emulsions with smaller droplet size perform better in sizing development. Thus the appropriate increase of nano-TiO₂ concentration can ameliorate the sizing efficiency of ASA emulsion. However the stability of the prepared emulsion to hydrolysis is very poor and within 50 min the emulsion loses nearly half of its sizing performance.Nano-TiO₂ particle can effectively stabilize reagent grade ASA. When the prepared emulsions are centrfuged at 3000 rpm for 15 min, the emulsions are stable to deemulsificaiton, creaming and sedimentation. The W/O emulsion can invert to O/W emulsion with increasing the mass fraction of water phase. The particle initial location, homogenization speed and particle concentration show remarkable effects on the required mass fraction of water phase for phase inversion. When the nano-TiO₂ particles are initially located in ASA, the mass fraction of water phase for phase inversion is lower than that when nano-TiO₂ particle initially dispersed in water. The results of diffusion experiment of nano-TiO₂ particle through ASA/water interface and infrared spectral analysis indicate that nano-TiO₂ particle has been modified in situ at ASA/water interface by alkenyl succinic acid which is the hydrolysate of ASA. As a consequence the particles are more“hydrophobical”when they are initially dispersed in water. Higher homogenization speed provides more energy to invert to the emulsion from W/O to O/W at a relative low mass fraction of water phase. While at higher particle concentration, the invertion from W/O to O/W ocurrs at higher mass fraction of water phase due to the relative high viscosity of the system.更多还原