Paper making and fiber liberation – Processes and products – Non-fiber additive
Patent
1988-10-26
1990-10-23
Chin, Peter
Paper making and fiber liberation
Processes and products
Non-fiber additive
1621683, 1621812, 1621816, D21H 1745, D21H 1774
Patent
active
049649540
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the production of paper utilizing an improved retention- and dewatering system. More particularly the invention relates to the use of a combination of a cationic polymeric retention agent, an anionic inorganic colloid and polyaluminum compound as retention- and dewatering system in papermaking.
It is previously known to use combinations of cationic retention agents and inorganic colloids as retention and dewatering agents in the production of paper. The European patent application No. 0218674 discloses the use of polyacrylamide in combination with anionic silica sols as binders and retention agents. It is also previously known to use polymeric cationic retention agents in combination with polyaluminum compounds and this is disclosed in the British patent No. 2015614. The effect of the silica sol on for example cationic starch with regard to retention and dewatering of the fibre web is considerably better than the effect obtained by polyaluminum compounds and cationic starch. It is assumed that one of the reasons for this is that the inorganic anionic colloids have much stronger charges than the polyaluminum compounds which have a complex composition. It is assumed that the colloidal particles with their strong charges produce a cross-linking of the polymeric retention agents. It is further known from the U.S. Pat. No. 4,643,801 to use a combination of a cationic starch, an anionic silica sol and an anionic high molecular weight polymer, particularly an anionic polyacrylamide, as a binder in papermaking. The three component system according to the U.S. patent can be used with additional aluminum compounds, such as alum, sodium aluminate or polyhydroxyaluminum chloride.
According to the present invention it has been found that the retention- and dewatering effect in papermaking is improved if a polyaluminum compound is used in combination with an organic, synthetic, polymeric cationic retention agent and an anionic inorganic colloid. As the dewatering effect is increased the speed of the papermachine can be increased and, further, less water will have to be dried off in the drying section of the paper machine.
The present invention thus relates to a process for the production of paper by forming and dewatering a suspension of papermaking fibres, and optionall fillers, on a wire whereby the forming and dewatering take place at a pH above 5 and in the presence of an anionic inorganic colloid, a polyaluminum compound and a cationic, synthetic polymeric retention agent which is a cationic polyacrylamide or a polyethyleneimine.
The three components can be added to the fibre stock in arbitrary order. The best effect is obtained if the polyaluminum compound is added to the stock first, and then followed by addition of cationic retention agent and anionic inorganic colloid. A considerable improvement, in comparison with known technique, is obtained also when the anionic inorganic colloid is first added to the stock and the cationic polymer and the polyaluminum compound are added subsequently, in any order.
The cationic, synthetic polymeric retention agents used in the three-component system for papermaking according to the present invention are per se conventional cationic polyacrylamide and polyethyleneimine retention agents. The amount of the retention agent should be within the range of from 0.01 to 3 percent by weight, preferably within the range of from 0.03 to 2 percent by weight, based on dry fibres and optional fillers.
The anionic inorganic colloids which are used are also per se previously known for use in papermaking. As examples of such colloids can be mentioned colloidal montmorillonite and bentonite, titanyl sulphate sols, silica sols, aluminum modified silica sols or aluminum silicate sols. Silica based colloids are the preferred anionic inorganic colloids. The amount of anionic colloid should be within the range of from 0.005 to 2 percent by weight, preferably within the range of from 0.01 to 0.4 percent by weight, based on dry cellulose fibres and optio
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Rowland, "The Colloidal Nature of Clay with Reference to Papermaking," TAPPI, Oct. 17, 1940, pp. 207-212.
Chin Peter
Eka Nobel AB
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