Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-05-11
2002-03-19
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S044000, C524S045000, C524S047000, C524S050000, C524S521000, C524S522000, C524S517000, C524S519000, C523S402000
Reexamination Certificate
active
06359040
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions having advantageous Theological properties comprising an ionic polymer and a viscosity promoter. The invention also relates to processes for preparation and use of compositions having advantageous rheological properties, as well as to compositions and methods for treating paper.
BACKGROUND OF THE INVENTION
It is desired by various industries to employ rheology modifiers to achieve thickening, flow control, water retention, and other properties in aqueous systems. A number of rheology modifiers are commercially available such as sodium carboxymethyl cellulose, guar gum, sodium alginate, hydroxyethylcellulose, alkali-soluble latices, xanthan gum, polyacrylamide and so forth.
The hydrophilic groups that these various water-soluble polymers express may be classified as non-ionic, anionic, or cationic. Anionic or cationic water-soluble polymers are most commonly employed in the absence of an oppositely-charged polymeric species, due to problems of incompatibility. For example, in cases where anionic polymers are employed, such as paper coatings, these polymers are traditionally employed without the use of a cationic additive being present, because cationic additives will typically precipitate most anionic water-soluble polymers, and thus reduce their effectiveness. Similarly, the overwhelming majority of the commercial use of either anionic or cationic polymers finds these additives employed with the oppositely-charged species being avoided. It is also known that the presence of polyvalent cationic inorganic salts, such as calcium or aluminum salts, can adversely affect the solubility and effectiveness of anionic polymers.
However, even though the presence of polyvalent cationic solutes is usually avoided in applications in which anionic water-soluble polymers are employed, there have been occasional findings disclosed where an anionic polymer has been used with either cationic water-soluble polymers or cationic inorganic salts. These include the following:
U.S. Pat. No. 3,049,469 presents the use of the anionic water-soluble polymer sodium carboxymethyl cellulose in conjunction with a cationic polymer polyamide-epichlorohydrin copolymer for enhancing the strength of paper.
U.S. Pat. Nos. 5,502,091, 5,318,669, and 5,338,407, describe mixtures of cationic and anionic guar for enhancing the dry strength of paper.
U.S. Pat. No. 5,338,406 and family member EP 0362770 describe mixtures of high molecular weight cationic water-soluble polymers, such as cationic guar or cationic polyacrylamide, with anionic polymers for enhancing the dry strength of paper.
U.S. Pat. No. 3,719,503 describes the formation of water-based gels by means of specific mixtures of anionic water-soluble polymers with aluminum salts.
U.S. Pat. No. 4,035,195 discloses the use of sodium carboxymethyl hydroxyethylcellulose and cross linking cationic additives, such as chromium or aluminum salts, for the purpose of thickening brine solutions for oil field applications.
In most cases, such as in U.S. Pat. Nos. 3,049,469, 3,058,873, 3,719, 503, 5,502,091, 5,318,669, 5,338,407, and 5,338,406, anionic and cationic polymers are mixed in sequence with colloids, such as paper fibers or suspended particulates, in order to facilitate adsorption/flocculation of the colloids with the water-soluble polymers. Therefore, the water-soluble polymers are wholly removed from the aqueous phase and enhanced viscosity of the polymeric solution in solution is not obtained.
SUMMARY OF THE INVENTION
The present invention relates to aqueous compositions having advantageous rheological properties, preferably including any of enhanced yield stress, enhanced viscosity, enhanced water retention, and combinations thereof. The present invention also relates to processes for preparing and using the compositions.
Compositions of the present invention can be prepared with an interactive mixture of ionic water-soluble polymer combined in solution with vicosity promoter for the ionic polymer, the viscosity promoter having a net ionic charge opposite to that of the ionic polymer. Compositions of the present invention optionally comprise moderating agent to prevent or reduce precipitate formation and/or gelation. The aqueous solutions of the present invention exhibit unexpected rheological properties, and are useful in various applications, such as size press surface treatment of paper, and paper coating rheology control.
The process of size press treatment of paper is commonly used to coat paper. In this process, a previously formed sheet is fed through the size press, where a solution of dissolved starch is typically added to one or both sides of the paper, typically adding about 3-5 wt % solids to the paper by dry weight of the untreated paper. Paper sheets are typically very absorbent, leading to a large penetration of the starch solution into the pores of the paper. This penetration is undesirable because the coating is typically needed on the surface of the paper, not in the pores. Thus, penetration of the solution requires addition of more starch to obtain the desired coating, which results in a loss of efficiency.
Although mixtures of anionic guar with cationic guar, as well as mixtures of anionic polyacrylamide copolymers with cationic polyacrylamide copolymers, have been used for various purposes in the papermaking art, these combinations are inoperable in the present invention due to strong precipitate formation. Thus, the present invention differs in kind from prior art compositions with respect to the chemical nature of the combined polymer species. The present invention also differs from the prior art in the ratios and concentrations employed to prepare solutions of a novel rheological mixture. Novelty of the present invention becomes evident with the recognition that the prior art, in most cases, teaches away from successful mixtures of anionic polymers and cationic viscosity promoters.
In the papermaking industry, there is a need for compositions and processes that are better able to keep a coating composition from penetrating deeply into paper pores, thereby increasing the coating efficiency. Such efficiency is desirable because, among other things, it reduces the amount of additives, e.g., strengthening agents and sizing agents, needed.
There is also a need for compositions and processes that are capable of efficiently sealing pores in paper, resulting in paper with reduced porosity.
In one aspect, the present invention provides aqueous compositions comprising at least one first ionic polymer and at least one viscosity promoter, the at least one viscosity promoter comprising at least one second ionic polymer having a net ionic charge opposite to that of said at least one first ionic polymer, the aqueous composition having a yield stress greater than about 5 dynes/cm
2
.
In another aspect, the invention provides an aqueous composition prepared by combining at least one first ionic polymer, at least one viscosity promoter, and an aqueous medium, the at least one viscosity promoter comprising at least one second ionic polymer having a net ionic charge opposite to that of said first ionic polymer, the aqueous composition having a yield stress greater than about 5 dynes/cm
2
.
In another aspect, the invention provides an aqueous composition comprising water, at least one first ionic polymer and at least one viscosity promoter, the at least one viscosity promoter comprising at least one second ionic polymer having a net ionic charge opposite to that of the at least one first ionic polymer, the aqueous composition having a yield stress at least about 10% higher than the yield stress of a composition having about the same viscosity as the aqueous composition, and the same ingredients as said aqueous composition but for the absence of at least one of the at least one first ionic polymer or at least one viscosity promoter.
In another aspect; the invention provides an aqueous composition comprising water, at least one first ionic polymer and at least one viscosity promoter, the at least on
Hercules Incorporated
Rajguru U. K.
Seidleck James J.
Sloan Martin F.
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