山东轻工业学院硕士学位论文

 

 

I

ABSTRACT 

The primary particle size of nano-TiO

2

 is about 25 nm and the mean size of its 

aggregate is approximately 260 nm when nano-TiO

2

 particles are dispersed in water. 

The isoelectic point of nano-TiO

2

 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-TiO

2

 as solid particle emulsifier. The prepared AKD and 

industry-specific ASA emulsions stabilized by nano-TiO

2

 are applied in internal sizing 

and their sizing performance is exploited. The results show that the AKD emulsion can 

hardly stabilized by nano-TiO

2

 particle alone or by chitosan with a lower dosage. 

However, the mixture of chitosan and nano-TiO

2

 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-TiO

2

 is lower than 2.2 wt%, the mean size 

of droplets decrease with the increase of the concentration of nano-TiO

2

; 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-TiO

2

 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-TiO

2

 concentration. 

Nano-TiO

2

 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-TiO

2

 concentration and reaches 

the minmum at 2.0 wt% of nano-TiO

2

 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-TiO

2

 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-TiO

2

 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,