mole.gif (1741 bytes) Optical Whitener For Paper

SPECIFICATION OF RANIPAL BOP

Our material is an optical whitening agent, with a very good yield, which has been developed specifically to meet the requirements of the paper industry and it is paritcularly effective in the following applications:
Applications:                OPTICAL WHITENING IN THE BEATER:
                                       -of unsized papers
                                       -of talc loaded papers
                                       -of china clay loaded papers(up to 5% ash contgent)
                                       -with the pH above 5.5 in the white or backwater.
                                     SURFACE WHITENING:
                                       -with CMC, starch and gelatine coatings.
                                       -with pigmented coatings with a starch/latex base
                                       -by treating with aqueous solutions, possibly combined-
                                        with CMC.
Appearance/Solubility:
Our material is a pale yellow powder with a bulking value of about 1000 gm/l. solutions of upto 200 gm/l can be obtained by pouring on hot (80-90°C) distilled water. In cold water (20°C) Our material has a solubility of 50gm/l. Strock solutions (upto a maximum of 40gm/l) may be kept for several days in closed, rustless containers away from light.Solution of 1gm/l Our material have a pH about 8.
Storage:
Our material may be kept almost indefinitely in a cool, dry place.
Affinity:
Our material exhausts in the pH range 5.5-11 on to both bleached cellulose and sizes and binders such as CMC, starch and vegatable gums to give neutral whites. The most marked affinity is at pH 8-9.
Fastness/Stability:
Our material has good fastness to light and alkali, when considering that all OBAs have moderate fastness to light and alkali. The resistance of our material to alum is good in white or backwater down to pH 5.5.

Solutions of our material are practically insenstive to chemicals causing hardness in water.

As our material solutions are sensitive to iron and light, whenever posible they should be kept away form light in stainless metal or plastic containers. When no such containers are available the solutions must be used immediately.

As cationic compounds may affect the white effect to some extent, depending on their constitution, their compatibility with our material in each case should be ascertained by preliminary trials.
Application:
The degree of white attainable depends to a great extent on the original whiteness of the bleached cellulose and the white pigment and binder used. Titanium dioxide is an exception as its high refractive index(Rutile 2.7, Anatase2.55) is known to cause a marked reduction in the effect of all optical whiteners.

Papers optically whitened with our material may be shaded with Acid or Direct dyes or with Pigments.
1. Optical Whitening in the Beater:
Addition: generally between 0.02-0.2% our material on weight of dry pulp.

Our material solutions may be added to the beater or hydropupler or to the stock chest. Our material is very substantive and to avoid motting, the hot material solutions should be diluted first with cold water always added to the pulp slowly before the alum.

The maximum white effect is obtained with an addition of 0.4% our material.

With very large additions of titanium dioxide it should be borne in mind that although these will give a higher base white, the optical whitening effect is considerably weaker than that obtained by using silicates.

To obtain a good yield from the optical whitener it is advisable to make
the additions in the following order:
bleached cellulose
  loading
  size
  Our material
shading dyes eventually

alum (if possible 15 minutes after the addition of material or immediately before running off the stock)
2. Surface Whitening by:
Addition: generally in between 0.5-3 gm our material per liter size solution.
   (a) Optical whitening of size coatings:
To improve the printing properties of paper, the surface is treated in the size press or any other coating device either in/or outside the paper machine with a size solution (degraded strach, CMC, etc.) in these cases it is most economical to carry out the optical whitening with the size coating.

Our material exhausts substantively on to the normal sizing agents and guarantees a uniform optical whitening of the size coating. If the solution is made slightly alkaline (pH 8-9) with ammonia, the white effect is strengthened considerably, in addition to making the paper more suitable for subsequent printing.

High white papers should be optically whitened in two stages: initially 0.025%-0.2%(maximum) our material is added to the beater and later the paper surface is given a size coating containing optical whitening agent. The maximum white effect is reached with an addition of 4gm/l.
   (b) Optical whitening of pigmented coatings:
Addition:generally in between 0.5-3 gm. our material per liter pigment coating slurry.

With this method of application also, the degree of white depends on the original whiteness of the white pigments and binders used. The higher the white of the constituents, the small the addition of our material required for a given white effect.

Our material has good compatibility with the normal ingredients, used in pigmented coatings. As with size coatings, a slight alkalinity in these pigment coating slurries has a positive effect on the optical white.

It is preferable to add the our material solution last to the prepared coating slurry.
   (c) Optical whitening with aqueous solutions:
Addition:generally in between 0.2-3gm/l our material

In certain cases the paper surface may be treated with aqueous our material solutions on the size press or water doctor or with devices for sprinkling or spraying. To avoid weakening the bath and uneven whitening through the strong affinity of our material; optical whitening in the acid pH range should be carried out at as low a temperature as possible. Even better effects are obtained by incorporating 2-10 gm/l CMC in a weakly ammoniacal medium (pH 8-9).