Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
1999-10-01
2003-09-09
Fortuna, Jose A. (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S164600, C162S168300, C162S183000
Reexamination Certificate
active
06616807
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to a process for the production of paper, board and cardboard having high dry strength by the addition of cationic, anionic and/or amphoteric starch as a dry strength agent to the paper stock and drainage of the paper stock with sheet formation.
2. Description of The Background
For increasing the dry strength of paper, for example, Ullmanns Encyklopädie der technischen Chemie, 4th edition, Verlag Chemie, Weinheim-New York, 1979, volume 17, page 581, discloses the use of aqueous suspensions of natural starches, which are converted into water-soluble form by heating, as a pulp additive in paper making. However, the retention of the starches dissolved in water by the paper fibers in the paper stock is low. An improvement in the retention of natural products by cellulose fibers in paper making is disclosed, for example, in U.S. Pat. No. 3,734,820. Said publication describes graft copolymers which are prepared by grafting dextran, a naturally occurring polymer having a molecular weight of from 20,000 to 50 million, with cationic monomers, e.g. diallyldimethylammonium chloride, mixtures of diallyldimethylammonium chloride and acrylamide or mixtures of acrylamide and basic methacrylates, such as dimethylaminoethyl methacrylate. The graft polymerization is preferably carried out in the presence of a redox catalyst.
U.S. Pat. No. 4,097,427 discloses a process for the cationization of starch, in which the starch digestion is carried out in an alkaline medium in the presence of water-soluble quaternary ammonium polymers and an oxidizing agent. Suitable quaternary ammonium polymers include quaternized diallyldialkylamino polymers or quaternized polyethyleneimines. Oxidizing agents are, for example, ammonium persulfate, hydrogen peroxide, sodium hypochlorite, ozone or tert-butyl hydroperoxide. The modified cationic starches which can be prepared in this manner are added to the paper stock as dry strength agents in paper making. However, the wastewater has a very high COD (chemical oxygen demand).
U.S. Pat. No. 4,146,515 discloses a process for the preparation of cationic starch which is used for surface sizing and coating of paper and paper products. According to this process, an aqueous suspension of oxidized starch is digested together with a cationic polymer in a continuous digester. Suitable cationic polymers are condensates of epichlorohydrin and dimethylamine, polymers of diallyldimethylammonium chloride, quaternized reaction products of ethylene chloride and ammonia and quaternized polyethyleneimine.
U.S. Pat. No. 3,467,608 discloses a process for the preparation of a cationic starch, in which a suspension of starch in water is heated for from about 0.5 to 5 hours at from about 70 to 110° C. together with a polyalkyleneimine or polyalkylenepolyamine having a molecular weight of at least 50,000. The mixture contains from 0.5 to 40% by weight of polyalkyleneimine or polyalkylenepolyamine and from 99.5 to 60% by weight of starch. According to Example 1, a polyethyleneimine having an average molecular weight of about 200,000 is heated in dilute aqueous solution with potato starch for 2 hours at 90° C. The modified potato starch can be precipitated in a mixture of methanol and diethyl ether. The reaction products of starch and polyethyleneimine or polyalkylenepolyamines, described in U.S. Pat. No. 3,467,608, are used as flocculants.
EP-A-0 282 761 and DE-A-3 719 480 disclose production processes for paper, board and cardboard having high dry strength. In this process [sic], the dry strength agents used are reaction products which are obtainable by heating natural potato starch with cationic polymers, such as polymers or polyethyleneimines containing vinylamine, N-vinylimidazoline or diallyldimethylammonium units in an aqueous medium at temperatures above the glutinization temperature of the starch in the absence of oxidizing agents, polymerization initiators and alkali.
EP-B-0 301 372 discloses just such a process in which appropriately modified enzymatically degraded starches are used. Under the digestion conditions stated there for natural starch, a relatively large amount of degradation products (degradation rates>10%) is also found in addition to incomplete digestion (spectroscopic investigations indicate undissolved, in some cases only partially swollen starch grains).
U.S. Pat. No. 4,880,497 and U.S. Pat. No. 4,978,427 disclose a process for the production of paper having high dry and wet strength, in which a hydrolyzed copolymer which is obtainable by copolymerization of N-vinylformamide and ethylenically unsaturated monomers, for example vinyl acetate, vinyl propionate or alkyl vinyl ethers, and hydrolysis of from 30 to 100 mol % of the formyl groups of the copolymer with formation of amino groups is added as strength agent either to the surface of the paper or the paper stock prior to sheet formation. The hydrolyzed copolymers are used in amounts of from 0.1 to 5% by weight, based on dry fibers.
DE-A-4 127 733 discloses hydrolyzed graft polymers of N-vinylformamide and natural substances containing saccharide structures, which polymers are used as dry and wet strength agents. However, the hydrolysis of the graft polymers under acidic conditions results in a considerable decrease in the molecular weight of the polysaccharides.
WO-A-96/13525 discloses a process for cationic modification of starch by reacting starch with polymers which contain amino and/or ammonium groups in an aqueous medium at from 115 to 180° C. under superatmospheric pressure, not more than 10% by weight of the starch used being degraded.
H. R. Hernandez, describes, in EUCEPA 24
th
Cont. Proc. Pap. Technol., May 1990, pages 186-195, the use of cationic or amphoteric starches together with cationic or anionic retention aids in papermaking. In one paper machine experiment, papermaking is carried out in the alkali pH range being alkenylsuccinic anhydride, Alun, amphoteric waxy starch and an anionic rfetention aid.
If a cationically modified starch is added as a dry strength agent to the paper stock, an undesirable decrease in the drainage rate of the paper stock occurs. At the same time, an increase in the COD of the waste water of the paper machine is observed. This increase in the COD occurs in particular in the case of paper machine waste water having a high salt content.
It is an object of the present invention to provide a process for the production of paper, board and cardboard having high dry strength, higher retention of starch in the paper and hence a lower COD in the paper machine waste water being achieved and moreover an acceleration of the drainage rate being obtained in comparison with the prior art.
SUMMARY OF THE INVENTION
We have found that this object is achieved, according to the invention, by a process for the production of paper, board and cardboard having high dry strength by the addition of cationic, anionic and/or amphoteric starch as a dry strength agent to the paper stock and drainage of the paper stock in the presence of retention aids with sheet formation, if the following are used as a retention aid for starch.
polymers containing vinylamine units
polyethyleneimines
crosslinked polyamidoamines
ethyleneimine-grafted and crosslinked polyamidoamines
polydiallyldimethylammonium chlorides
polymers containing N-vinylimidazoline units
polymers containing dialkylaminoalkyl acrylate or dialkylaminoalkyl methacrylate
polymers containing dialkylaminoalkylacrylamide units or dialkylaminoalkylmethacrylamide units and
polyallylamines.
The present invention furthermore relates to the use of cationic polymeric retention aids from the group consisting of
polymers containing vinylamine units
polyethyleneimines
crosslinked polyamidoamines
ethyleneimine-grafted and crosslinked polyamidoamines
polydiallyldimethylammonium chlorides
polymers containing N-vinylimidazoline units
polymers containing dialkylaminoalkyl acrylate or dialkylaminoalkyl methacrylate
polymers containing dialkylaminoalkylacrylamide units o
Baumann Peter
Dyllick-Brenzinger Rainer
Krüger Ellen
Lorencak Primoz
Meixner Hubert
BASF - Aktiengesellschaft
Fortuna Jos'e A.
LandOfFree
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