Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2002-02-28
2004-01-06
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S164300, C162S164600
Reexamination Certificate
active
06673206
ABSTRACT:
The present invention relates to a process for the production of paper, board and cardboard by draining a paper stock in the presence of polymers.
It is generally known that paper comprises essentially fibers, consisting of wood and/or of cellulose, and, if required, of mineral fillers, in particular calcium carbonate and/or aluminum silicate, and that the essential papermaking process consists of separating these fibers and fillers from a dilute aqueous suspension of these substances by means of one or more movable wires. It is also known that certain chemicals are added to the suspension of fibers and fillers in water, both for improving the separation process and for achieving or improving certain properties of the paper. A very current review of the generally used paper chemicals and their use is to be found, for example, in—
Paper Chemistry
, J. C. Roberts ed., Blackie Academic & Professional, London, Second edition 1996, —and in—
Applications of Wet
-
End Paper Chemistry
, C.O. Au and I. Thorn eds., Blackie Academic & Professional, London, 1995.
As is evident from the literature cited, many of the paper chemicals used are cationic water-soluble polymers or, in other words, cationic polyelectrolytes or polycations having, preferably, an average or high molar mass. These products are added to the very dilute paper fiber slurry before the paper sheet forms therefrom on the wire. Depending on their composition, they result, for example, in more fine material remaining behind on the wire or in the separation of the water on the wire taking place more rapidly or in certain substances being fixed to the paper fibers and hence not entering the white water, and, in the case of the last property, both the cleanliness of the white water and the effect of the fixed substances, e.g. dyes or sizes, on the properties of the finished paper may be important. However, polycations may also increase the strength of the paper or impart improved residual strength to the paper in the wet state. However, this wet strength is generally obtained by using polycations which additionally carry reactive groups which react with the paper components or with themselves with network formation and, owing to the resulting covalent bonds, make the paper more resistant to water.
U.S. Pat. No. 5,556,938 discloses that the thermal polycondensation of amino acids is carried out in the presence of organic or inorganic acids. For example, aspartic acid, alanine, arginine, glycine, lysine and tryptophan are mentioned as amino acids. The condensates thus obtainable are used, for example, in detergents and cleaning agents, as scale inhibitor, as dispersants for pigments and as dispersants in papermaking.
U.S. Pat. No. 3,869,342 discloses cationic, heat-curable resins based on polyamidoamines, which resins can be crosslinked by reaction with epichlorohydrin and can be cured by heating. Resins of this type are used, for example, as wetstrength agents in papermaking.
The polycations used according to the prior art for said purposes are almost exclusively polymers of synthetic origin, i.e. products based on petrochemicals. Important exceptions, however, are the cationic starches, which originate from the reaction of a plant-based raw material with a synthetic cationizing agent. In rare cases, other polysaccharides modified with synthetic cationizing agents are also used in papermaking, for example cationic guar flour. The literature also describes, as the cationic paper assistant, the polysaccharide chitosan, which is obtained by chemical reaction with chitin from crustaceans, but no permanent practical application is known to date.
Regardless of their specific action profiles, products based on vegetable or animal starting materials frequently have the advantage of being more readily biodegradable on reintroduction into the natural cycle. The use of plant-based raw materials also helps to protect fossil resources and to reduce carbon dioxide emission.
The polycations based on renewable raw materials and suitable to date as paper chemicals are exclusively polysaccharides having a very narrow action profile. The principally used cationic starches are employed for increasing the dry strength of the paper and, to a lesser extent, also as retention aids.
It is an object of the present invention to provide further substances which are based on natural raw materials and, for example, fix anionic substances in the paper in papermaking and improve the retention of fillers.
We have found that this object is achieved, according to the invention, by a process for the production of paper, board and cardboard by draining a paper stock in the presence of polymers with sheet formation, if the polymers used are crosslinked condensates which are obtainable by reaction of
(i) homocondensates of basic amino acids, condensates of at least two basic amino acids and/or cocondensates of basic amino acids and cocondensable compounds with
(ii) at least one crosslinking agent having at least two functional groups.
Condensates are derived, for example, from homo- or cocondensates of lysine, arginine, ornithine and/or tryptophan. They are obtainable, for example, by condensing
(a) lysine, arginine, ornithine, tryptophan or mixtures thereof with
(b) at least one compound cocondensable therewith.
The polymers are prepared by condensation of
(a) lysine, arginine, ornithine, tryptophan or mixtures thereof with
(b) at least one compound selected from the group consisting of the monoamines, diamines, triamines, tetraamines, monoaminocarboxylic acids, lactams, aliphatic aminoalcohols, urea, guanidine, melamine, carboxylic acids, carboxylic anhydrides, diketenes, nonproteinogenic amino acids, alcohols, alkoxylated alcohols, alkoxylated amines, amino sugars, sugars and mixtures thereof.
Of particular industrial interest here are cocondensates which are obtainable by condensation of
(a) lysine and
(b) at least one compound selected from the group consisting of the C
6
- to C
18
-alkylamines, lactams having 5 to 13 carbon atoms in the ring, nonproteinogenic amino acids, monocarboxylic acids, polybasic carboxylic acids, carboxylic anhydrides and diketenes.
The compounds of groups (a) and (b) are used, for example, in a molar ratio of from 100:1 to 1:20, preferably from 100:1 to 1:5, in general from 10:1 to 1:2, in the condensation.
Suitable polymers for papermaking are crosslinked condensates of basic amino acids. Such crosslinked condensates are obtainable, for example, by reaction of
(i) homocondensates of basic amino acids and/or condensates of at least two basic amino acids and/or cocondensates of basic amino acids and cocondensable compounds with
(ii) at least one crosslinking agent having at least two functional groups.
The basic amino acids lysine, arginine, ornithine and tryptophan which are suitable in the condensation as compounds of group (a) can be used in the condensation in the form of the free bases, of the hydrates, of the esters with C
1
- to C
4
-alcohols and of the salts, such as sulfates, hydrochlorides or acetates. Lysine hydrate and aqueous solutions of lysine are preferably used. Lysine may also be used in the form of the cyclic lactam, &agr;-amino-&egr;-caprolactam. Lysine mono- or dihydrochlorides or mono- or dihydrochlorides of lysine esters can also be used. If the salts of compounds of group (a) are used, the equivalent amounts of inorganic bases, e.g. sodium hydroxide solution, potassium hydroxide or magnesium oxide, are preferably used in the condensation. The alcohol components of mono- and dihydrochlorides of lysine esters are derived, for example, from low-boiling alcohols, e.g. methanol, ethanol, isopropanol or tert-butanol. Preferably, L-lysine dihydrochloride, DL-lysine monohydrochloride and L-lysine monohydrochloride are used in the condensation.
Examples of cocondensable compounds of group b) are aliphatic or cycloaliphatic amines, preferably methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, stearylamine,
Dirks Bernd
Fehringer Dietrich
Linhart Friedrich
Mohr Bernhard
Tresch Rainer
BASF - Aktiengesellschaft
Chin Peter
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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