Persulfate mixtures for repulping wet strength paper
AssigneeFMC Corporation
InventorsFrank E. Caropreso, Dean S. Thorp, Robert H. Tieckelmann
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Abstract
A method for repulping a wet strength paper is disclosed. Wet strength paper, which contains a wet strength resin, is agitated in water to form an aqueous slurry. An effective amount of a composition that contains a dry mixture of a persulfate and a base in the range of 90:10 to 10:90 is added either before or during agitation, and the slurry heated to produce pulp product for paper manufacture. The persulfate/base combination is capable of breaking down the wet strength resin and adjusting or maintaining the pH at a predetermined level without additional chemical treatment.
Claims25
A method for repulping wet strength broke, comprising:
- combining wet strength broke and water, the wet strength broke comprising wet strength resin and cellulose fiber;
- agitating the wet strength broke and water to form an aqueous slurry;
- adding an effective amount of a composition comprising a dry mixture of a persulfate and a base, said base selected from the group consisting of alkali, alkaline earth or ammonium carbonate, bicarbonate or sesquicarbonate to the aqueous slurry for breaking the resin;
- and
- heating the aqueous slurry to an effective temperature for oxidation of the resin for a period of time sufficient to produce pulp product for paper manufacture, wherein:
- the persulfate and the base have a persulfate to base ratio within the range of 90:10 to 10:90:
- and
- the composition is added prior to, or during, agitation.
A method of repulping wet strength broke, comprising:
- a) preparing an admixture comprising
- i) wet strength broke comprising wet strength resin and cellulose fiber,
- ii) water,
- iii) a base selected from the group consisting of sodium carbonate, sodium sesquicarbonate, and sodium bicarbonate, and
- iv) a persulfate selected from the group consisting of sodium persulfate, potassium persulfate, and ammonium persulfate;
- b) heating the admixture to at least about 50.degree. C.;
- c) agitating the admixture for a sufficient time to oxidize the wet strength resin and repulp the broke to produce at least a Stage 5 pulp according to the TAPPI method T-205-om81;
- wherein:
- the total amount of persulfate and base added 0.5% to 2.50%, based on the weight of the wet strength broke fiber;
- and
- the persulfate and the base have a persulfate to base ratio within the range of 90:10 to 10:90.
Dependencies are inferred from the claim text.