Paper making and fiber liberation – Processes and products – Pore forming in situ
Patent
1996-10-28
2000-08-15
Chin, Peter
Paper making and fiber liberation
Processes and products
Pore forming in situ
162158, 1621643, 1621646, D21H 2108
Patent
active
061030600
DESCRIPTION:
BRIEF SUMMARY
The present invention is directed to a method for manufacturing a paper or non-woven sheet in a foam medium.
The invention applies to the paper industry for making paper or non-woven sheets for domestic, household or sanitary uses. With regard to these applications, the desired properties in the sheet of paper or non-woven are softness, dry or wet strength, absorption, specific volume, and the like. A balancing between these various properties is necessary. Finished products made using known procedures for making paper in a foam medium preclude optimizing all of the desired properties.
The expression "foam medium" as used herein denotes a wet manufacturing method for paper or non-woven sheets wherein the water is replaced by an aqueous solution containing a foam-generating surfactant.
European Patent Application No. 481,746 of James River Corp. of Virginia, U.S.A. describes a manufacturing procedure for foam-medium papermaking. The procedure consists in preparing a fabrication composition in the form of a foaming fiber dispersion by mixing a suspension of fibers in water with a foaming liquid comprising a surfactant. Further described in forming a fiber layer on a papermaking machine, is the recovery of the foaming liquid, recycling part of the foaming liquid to prepare the manufacturing composition, and the treating of a part of the recovered foaming liquid by separating the surfactant from the liquid. Many surfactants can be used. Suitable surfactants include anionic, cationic or nonionic surfactants to form the fiber layer and some amphoteric surfactants. U.S. Pat. Nos. 3,716,449 and 3,871,952 describe anionic, cationic and nonionic surfactants.
Cationic surfactants, such as lauramine oxide, are not used because they are adsorbed on the anionic sites present in the paper pulp used in making household paper.
On the other hand, among the various anionic surfactants, the .alpha.-olefin sulfonates (AOS) have been found to be particularly suitable for evincing optimal industrial performance, namely as being highly foaming, retaining much gas (air), i.e., about 60%-volume for the foam generated by the surfactant, and lacking toxicity.
Other known nonionic surfactants have been found to be less effective than the above anionic surfactant with regard to processing, i.e., recovery rate, surfactant enrichment and the like.
However, major disadvantages are present in using the anionic .alpha.-olefin-sulfonates of the prior art where cationic additives are needed to improve certain paper properties such as softness and tear-strength in the moist or dry state. One problem which arises when a cationic substance is added during a foaming procedure using an anionic surfactant, in this case an AOS, is that the anionic and cationic compounds chemically react with each other and thus lose effectiveness. The added cationic substance loses effectiveness and the surfactant loses gas in the formed foam thereby requiring the addition of substantial quantities of AOS to the foaming liquid. On account of its softening properties, excessive incorporation of AOS results in a product which in the dry state is too weak. In turn this requires more pulp refining or the inclusion of other additives, such as modified starch, to remedy the loss in strength.
An object of the present invention is to palliate the above noted disadvantages encountered when using AOS as a surfactant while retaining its advantageous performance with respect to its method of use and the advantageous properties, mechanical and other, which are provided in the final product made by the method.
Another object of the present invention is to employ cationic additives without incurring chemical incompatibility with the surfactant utilized, i.e., the additives will not react with the surfactant.
Another object of the present invention is to create a method providing improved surfactant consumption and improved recovery of the surfactant in recycling relative to the procedures using a foaming medium of the prior art.
Yet another object of the present invention is to cr
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Awofeso Antony D.
Harper Frank D.
Munerelle Corinne
Ostrowski Henry S.
Schroeder Gary L.
Chin Peter
Fort James France
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