Bleaching and dyeing; fluid treatment and chemical modification – Chemical modification of textiles or fibers or products thereof – Cellulose fibers
Reexamination Certificate
1995-02-27
2001-06-05
Diamond, Alan (Department: 1753)
Bleaching and dyeing; fluid treatment and chemical modification
Chemical modification of textiles or fibers or products thereof
Cellulose fibers
C008S194000, C008S196000, C008S119000, C008S120000, C008S127100, C162S164100, C162S168100, C252S008610, C252S008860
Reexamination Certificate
active
06241780
ABSTRACT:
BACKGROUND OF THE INVENTION
Substrates composed predominantly of cellulosic materials are frequently advantageously strengthened by treatment with a polymeric composition. The treatment with a polymeric composition may also provide reduced sensitivity to moisture vapor or water or solvents in addition to reinforcement of the substrate. Furthermore, the polymeric composition should not substantially detract from essential substrate characteristics, as might be the case, for example, if the cured composition were too rigid or brittle or became sticky under processing conditions. Additionally, the polymeric composition should wet out and penetrate preformed cellulosic webs and mats.
There is a need for a method for strengthening cellulosic substrates by treating with a curable aqueous composition which is free from formaldehyde, because of existing and proposed legislation directed to the lowering or elimination of formaldehyde.
DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 5,042,986 discloses an aqueous treating solution for cellulosic textiles, the treating solution containing a cyclic aliphatic hydrocarbon of 4 to 6 carbon atoms having 4 or more carboxyl groups wherein at least two adjacent carboxyl groups are in the trans configuration relative to each other. The treating solution includes a suitable curing agent which is the alkali metal dihydrogen phosphate or the alkali metal salt of phosphorous, hypophosphorous, and polyphosphoric acid. The treating process is disclosed to be advantageously used with textiles containing 30-100% cellulosic materials.
U.S. Pat. Nos. 4,820,307; 4,936,865; and 4,975,209 disclose catalysts for the rapid formaldehyde-free esterification and crosslinking of fibrous cellulose in textile form by polycarboxylic acids including saturated, unsaturated, and aromatic acids as well as alpha-hydroxyacids. The catalysts disclosed are acidic or weakly basic salts selected from the alkali metal dihydrogen phosphates and alkali metal salts of phosphorous, hypophosphorous, and polyphosphoric acids.
U.S. Pat. No. 4,795,533 discloses a solid electrolyte membrane which contains a three component blend prepared by admixing an organic polymer, such as polyvinyl alcohol, with an inorganic compound and a polyorganic acid, such as polyacrylic acid. The inorganic compound is disclosed to be selected from a group consisting of phosphoric acid, sulphuric acid, heteropoly acids, or salts of heteropoly acids. Examples of phosphoric acids which may be employed include hypophosphorous acid, metaphosphoric acid, orthophosphoric acid, pyrophosphoric acid, and polyphosphoric acid.
U.S. Pat. No. 4.076,917 discloses &bgr;-hydroxyalkylamides and certain polymers thereof as curing agents for polymers containing one or more carboxy or anhydride functions. The &bgr;-hydroxyamides are disclosed to be effective in solution, aqueous emulsion, and powder coating form.
None of the references disclose treating a cellulosic substrate with the formaldehyde-free curable aqueous composition of this invention. The composition contains (a) a polyacid containing at least two carboxylic acid groups, anhydride groups, or the salts thereof; (b) optionally, an active hydrogen compound containing at least two active hydrogen groups selected from the group consisting of hydroxyl, primary amino, secondary amino, and mixtures thereof; and (c) a phosphorous-containing accelerator, wherein the ratio of the number of equivalents of said carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of said active hydrogen groups is from about 1/0.01 to about 1/3, and wherein the carboxyl groups, anhydride groups, or salts thereof are neutralized to an extent of less than about 35% with a fixed base.
STATEMENTS OF THE INVENTION
According to a first aspect of this invention there is provided a method for strengthening a cellulosic substrate by treating the substrate with a formaldehyde-free curable aqueous composition and curing the composition.
According to a second aspect of this invention there is provided a method for increasing the solvent- and water-wet strength and dry strength of a cellulosic nonwoven wipe by treating the substrate with a formaldehyde-free curable aqueous composition and curing the composition.
According to a third aspect of this invention there is provided a method for increasing the solvent- and water-wet strength and dry strength of paper oil- and air-filter stock by treating the substrate with a formaldehyde-free curable aqueous composition and curing the composition.
According to a fourth aspect of this invention there is provided a method for increasing the delamination resistance of cellulosic foils or laminates by treating the cellulosic laminating stock with a formaldehyde-free curable aqueous composition and curing the composition. And a method for forming multi-ply laminates which are bonded together and are capable of forming moldable, B-stageable laminates.
According to a fifth aspect of this invention there is provided a method for improving the permanent-press performance of cellulosic woven fabrics by treating the substrate with a formaldehyde-free curable aqueous composition and curing the composition.
According to a sixth aspect of this invention there is provided a method for improving the water resistance of a consolidated wood product by treating the wood components such as, for example, fibers and flakes, prior to consolidation, with a formaldehyde-free curable aqueous composition and curing the composition.
DETAILED DESCRIPTION OF THE INVENTION
A method for strengthening a cellulosic substrate by treating the substrate with a formaldehyde-free curable aqueous composition and curing the composition is provided. The curable composition contains (a) a polyacid containing at least two carboxylic acid groups, anhydride groups, or the salts thereof; (b) optionally, an active hydrogen compound containing at least two active hydrogen groups selected from the group consisting of hydroxyl, primary amino, secondary amino, and mixtures thereof; and (c) a phosphorous-containing accelerator, wherein the ratio of the number of equivalents of said carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of said active hydrogen groups is from about 1/0.01 to about 1/3, and wherein the carboxyl groups, anhydride groups, or salts thereof are neutralized to an extent of less than about 35% with a fixed base. The composition is applied to a substrate composed predominantly of cellulosic components. Such substrates include, for example, paper oil- and air-filter stock, rayon nonwoven wipes, polyester/cotton woven fabrics, cellulosic laminating stock, and wood fibers and flakes consolidated into or suitable to be consolidated into fiberboard, hardboard, particle board, and oriented strand board. By “strengthening a cellulosic substrate” herein is meant that at least one of the mechanical properties such as, for example, dry tensile strength and wet tensile strength of the substrate treated and cured according to the method of this invention is increased over the same property of the untreated substrate.
The formaldehyde-free curable aqueous composition of this invention is a substantially thermoplastic, or substantially uncrosslinked, composition when it is applied to the substrate, although low levels of deliberate or adventitious crosslinking may be present. On heating the binder, the binder is dried and curing is effected by heating, either sequentially or concurrently. By curing is meant herein that a chemical and/or physical change has occured, for example, covalent chemical reaction, ionic interaction or clustering, improved adhesion to the substrate, phase transformation or inversion, hydrogen bonding, and the like.
This invention is directed to a formaldehyde-free curable aqueous composition. By “formaldehyde-free composition” herein is meant that the composition is substantially free from formaldehyde, nor does it liberate substantial formaldehyde as a result of drying and/or curing. In order to minimize the formaldehyde
Arkens Charles Thomas
Egolf Scott Lind
Gleim Robert David
Hsu Oscar Hsien-Hsiang
Wiesinger Kenneth John
Bakule Ronald D.
Diamond Alan
Rohm and Haas Company
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