Paper making and fiber liberation – Processes and products – Synthetic fiber
Patent
1997-10-14
2000-06-27
Wilson, James O.
Paper making and fiber liberation
Processes and products
Synthetic fiber
1621641, 162 9, 1621643, 1621577, 162182, 536 56, D21H 348
Patent
active
060802774
DESCRIPTION:
BRIEF SUMMARY
This invention relates to cellulose particles and to a method for producing the same. It further deals with applications of the cellulose particles.
Due to various measures such as circuit concentration, increased use of deinking pulps and high-yield pulps such as wood pulp and TMP (thermomechanic pulp), and neutral processing, there has been a rise in the load of interfering substances (trash) in the water circuits of the paper industry.
Interfering substances were first defined as all those substances which reduce the efficacy of cationic retention aids in the paper stock, i.e. those substances added in order to improve the retention of the fiber/filler mixture on the wire. Recently this definition has been more precisely stated. Interfering substances are thus dissolved or colloidally dissolved anionic oligomers or polymers and nonionic hydrocolloids.
These interfering substances have different effects. They impair the action of retention aids, dry- and wet-strength agents, i.e. substances increasing the strength of the paper, and furthermore lead to deposits in the paper machine circuit, forming and drainage disturbances and a loss of paper strength, whiteness and opacity.
In order to eliminate the adverse effects of these interfering substances on papermaking one uses alum, polyaluminum chloride, low- and high-molecular fixers, cationic starch and inorganic adsorbents. All these substances become attached to the anionic trash with the aid of electrostatic interactions and form complexes therewith. Through binding of these complexes to the fibers or through filtration effects on the wire these aggregates are removed from the paper machine system.
However all these products have their own disadvantages. For example aluminum salts can only be used to a limited extent in neutral processing, which is gaining importance due to the increasing use of calcium carbonate as a filler, since they are not cationically charged and thus not very effective in this pH range.
The use of highly charged, cationic polyelectrolytes in turn involves the problem of exact metering. Otherwise an overcationization of the paper machine circuit and thus cationic dispersion can occur. This means that there can be poor fine-substance retention and reduced sizing.
The problem of the invention is to provide new cellulose particles characterized by special properties and possible applications. The problem of the invention is further to provide cellulose particles which permit interfering substances in the paper circuit, machine circuit or water circuit to be bound in the paper in the greatest possible quantity and thus removed from the circuit without the above-described problems occurring.
The problem of the invention is also to state further possible applications of the cellulose particles.
The invention is based on the finding that this problem can be solved by cellulose particles which have cationic groups even in the interior of the particles.
At least 10%, preferably at least 50%, in particular at least 90%, of the cationic groups are thereby generally present in the interior of the particles. As a result cellulose particles are thus provided which have cationic groups bound to the cellulose distributed over the total cross section of the particles.
So that the particles have sufficient cationicity, at least one cationic group should be present per 100, preferably per 50, anhydroglucose units of the cellulose.
For producing the inventive cellulose particles one reacts the cellulose with a cationizing agent.
The cellulose used can be unsubstituted pulp but also substituted celluloses, in particular cellulose ester or ether such as methyl cellulose, carboxymethylcellulose, cellulose sulfate, cellulose acetate or chitosan. The degree of substitution (DS) should be smaller than 1, that is, no more than one of the three OH groups of the anhydroglucose units of the cellulose should be substituted on the average. The DS must not be too great so that a sufficient number of hydroxyl groups are available for reaction with the cationizing a
REFERENCES:
patent: 4624743 (1986-11-01), Gess
Chem. Abstract 104:20914v ("Water-Soluble Cellulose Derivatives"; Daicel Chemical Industries, Ltd.; 43-Wood Products, vol. 104, p. 77; .COPYRGT.1986).
Chem. Abstract 92:43522p ("Quaternary Ammonium Derivatives of Cellulose"; Fuji Chemical Co., Ltd.) 43-Wood Products, vol. 92, p. 83; .COPYRGT.1980).
"Effects of Retention and Drainage Aids on Paper Machine Drainage: A Review" (Tappi Journal; L. H. Allen et al.; pp. 79-84; Jul., 1991).
"Cellulose: Structure, Modification, and Hydrolysis" (R. A. Young et al.; Wiley-Interscience Publication; pp. 102-110; .COPYRGT.1986).
Moser Thomas
Oberkofler Jorg
Schmalhofer Anton
Spedding Jeffrey F.
Owens Howard
TFM Handels-Aktiengesellschaft
Wilson James O.
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