Processes and compositions for brightness improvement in paper production
AssigneeEcolab USA Inc.
InventorsPrasad Y. Duggirala, Sergey M. Shevchenko
Life of this patent
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Abstract
Compositions and methods that preserve and enhance the brightness of pulp, and also improve the color of pulp or paper, when applied during different stages of a papermaking process, are disclosed. The compositions and methods maintain or enhance brightness, prevent yellowing, and enhance the performance of paper products. The compositions can include a mixture of reducing agents and can also include optical brighteners, chelants, polycarboxylates, or other additives. The mixture of reducing agents can include a borohydride, such as sodium borohydride, and any other reducing agent, such as a sulfite or bisulfite.
Claims9
A method for preparing a bleached pulp material having enhanced brightness and enhanced resistance to thermal yellowing comprising:
- i) providing bleached kraft pulp material;
- and
- ii) contacting the bleached kraft pulp material with a solution, the solution having a pH of about 10 to about 11 and comprising about 0.25% of a stilbene fluorescent optical brightening agent and about 0.025% of a mixture, the mixture comprising about 12% sodium borohydride and about 39% sodium hydroxide, wherein the solution is added to the bleached pulp in a manner selected from the group consisting of (a) in the press section;
- (b) in the drying section;
- (c) on the calender using a wafer box;
- (d) on paper in an off-machine coater or size press;
- (e) in the curl control unit;
- and (f) any combination thereof, wherein the stilbene fluorescent optical brightening agent is selected from the group consisting of:
- disulfonated stilbenes, disulfonated stilbene derivatives, tetrasulfonated stilbenes, tetrasulfonated stilbene derivatives, hexasulfonated stilbenes, and hexasulfonated stilbene derivatives.
A method for preparing a bleached pulp material having enhanced brightness and enhanced resistance to thermal yellowing, the method consisting of:
- contacting a kraft paper sheet with a solution, the solution consisting of a pH of about 10 to about 11, 0.25% of a stilbene fluorescent optical brightening agent, and 0.025% of a mixture, the mixture consisting of water, 12% sodium borohydride, and 39% sodium hydroxide, wherein the stilbene fluorescent optical brightening agent is selected from the group consisting of:
- disulfonated stilbenes, disulfonated stilbene derivatives, tetrasulfonated stilbenes, tetrasulfonated stilbene derivatives, hexasulfonated stilbenes, and hexasulfonated stilbene derivatives.
Dependencies are inferred from the claim text.