Titanium dioxide is an excellent filler material for paper mill industries. In spite of its all advantages, the uses of titanium dioxide are limited due to its exclusive price and high abrasive. It is used in such good quality papers that need high opacity, higher brightness and whiteness such as offset papers and bible papers. The molecular formula of Titanium dioxide is TiO2.
Mainly three mineral form of titanium dioxide, these are anatase, rutile and brookite. But only rutile and anatase are used in paper mill industries. Both are tetragonal crystalline system. Rutile has higher refractive index than anatase. The particle size of Titanium dioxide is range 0.25 to 0.45 micrometers.
Benefits of Titanium dioxide
Titanium dioxide has highest light scattering coefficient and refractive index among the paper filler. The light scattering coefficient is about 1035m2/kg and refractive index is 2.55-2.75. Hence it proposes highest opacity among the paper filler. Light scattering are depends on their orientation into paper sheet. Titanium dioxide has excellent brightness about 98-100 ISO. The small particle of titanium dioxide has very high brightness. In addition it has good optical density and it is improving whiteness of the paper.
Titanium dioxide has some disadvantages; it is highly expensive and relatively high abrasive. Moreover it is absorb ultraviolet light.
Since the Light scattering are depends on their orientation (how the particles are separated) into paper sheet. So it must be well dispersed before and after it is added. Titanium dioxide paper filler is anionic. Hence to protect from agglomeration, it should be avoid from cationic materials during premature mixing.
Specification of titanium dioxide
- Physical appearance: odorless white powder
- Density: 4.23 gm/cm2
- Solubility in water: 0.5% max.
- pH value: 6.5-8.5
- Volatile at 105°C: 0.5% max
- Titanium dioxide content (base on dry basis): 98%
- Brightness (ISO): 98% min.