Paper making and fiber liberation – Processes and products – Plural fiber containing
Reexamination Certificate
1999-12-03
2002-04-09
Fiorilla, Christopher A. (Department: 1751)
Paper making and fiber liberation
Processes and products
Plural fiber containing
C162S157100, C162S158000, C162S164600, C162S164700, C162S175000, C162S183000, C008S108100, C008S116100, C008S120000, C536S056000, C536S111000
Reexamination Certificate
active
06368456
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to paper comprising aldehyde modified cellulose pulp or fiber prepared using defined oxidation conditions and which further contains selected additives to provide paper products with significantly improved wet and dry strength properties. More particularly, this invention involves paper made from celullose pulp modified by nitroxyl radical mediated oxidiation and containing additives comprising polymers containing functionality capable of reacting with aldehyde or aldehyde functional polymers. This invention also involves paper made from aldehyde modified cellulose pulp where an hydroxyl group containing material is added to the papermaking operation to provide unexpected additional wet strength, dry strength, and/or wet strength/dry strength ratio properties in resulting paper product.
The term “paper” as used herein, includes sheet-like masses and molded products made from pulp or fibrous cellulosic material which may be derived from natural sources. Paper may also be made from synthetic cellulosic fibers and regenerated cellulose as well as recycled waste paper. In addition, paper made from combinations of cellulosic and synthetic materials are applicable herein. Paperboard is included within the broad term “paper”.
Papermaking, as it is conventionally known, is a process of introducing an aqueous slurry of pulp or wood cellulosic fibers (which have been beaten or refined to achieve a level of fiber hydration and to which a variety of functional additives can be added) onto a screen or similar device in such a manner that water is removed, thereby forming a sheet of the consolidated fibers, which upon pressing and drying can be processed into dry roll or sheet form. Typically in papermaking, the feed or inlet to a papermaking machine is an aqueous slurry or water suspension of pulp fibers which is provided from what is called the “wet end” system. In the wet end, the pulp along with other additives are mixed in an aqueous slurry and subjected to mechanical and other operations such as beating and refining. Various additives are commonly added to help provide different properties in the paper product.
The use of aldehyde functional additives in the paper industry as wet and dry strength agents is well known. For example, both oxidative and non-oxidative methods are known for introducing aldehyde groups into starch. Use of these products in papermaking to provide wet and dry strength properties involves the addition of this separate starch additive component.
U.S. Pat. No. 5,698,688 issued to D. J. Smith et al. on Dec. 16, 1997 discloses aldehyde modified cellulose fibers formed from esterified 1,2-disubstituted alkenes and which are useful in providing paper products with wet strength properties.
In copending application Ser. No. 09/374,939 filed Aug. 17, 1999, the preparation of aldehyde modified cellulose pulp using selected oxidation conditions was described. In that application, the aldehyde modified cellulose pulp products were disclosed as being useful in preparing paper products having improved wet strength and dry strength properties.
While the known methods of preparing paper as described have provided products with good wet and dry strength properties, there is always the need for paper products having further significantly improved strength properties.
SUMMARY OF THE INVENTION
Now it has been found that paper comprising aldehyde modified cellulose pulp prepared using defined nitroxyl oxidation conditions and which further contains selected additives comprising polymers containing functionality capable of reacting with aldehyde or aldehyde functional polymers surprisingly have significantly improved wet and dry strength properties.
More particularly, this invention relates to aldheyde modified cellulose pulp with improved wet and dry strength properties wherein the pulp is prepared in an aqueous solution with an oxidant having an equivalent oxidizing power of up to 5.0 g of active chlorine per 100 g of cellulose and an effective mediating amount of nitroxyl radical, the reaction being carried out at a pH of about 8.0 to 10.5 and a temperature of from about 5 to 50° C. and further contains an effective amount of at least one additive polymer selected from the group consisting of an aldehyde functional polymer and a polymer containing functional groups capable of reacting with aldehyde groups.
In another embodiment, this invention relates to paper made from aldehyde modified cellulose pulp where an hydroxyl group containing material is added to the papermaking operation to provide significantly improved wet strength, dry strength, and/or wet strength/dry strength ratio properties in the resulting paper product.
DETAILED DESCRIPTION OF THE INVENTION
The paper product of this invention involves aldehyde modified cellulose pulp prepared using defined nitroxyl mediated oxidation conditions and which further contains selected additives to further improve wet strength, dry strength, and/or wet strength/dry strength ratio properties comprising polymers containing functionality capable of reacting with aldehyde or aldehyde functional polymers.
The additives used in this invention may be polymers containing functionality capable of reacting with aldehyde and will contain at least two aldehyde reactive functional groups, particularly more than two aldehyde reactive functionalities per polymer chain or molecule. More particularly, the polymer with aldehyde reactive functionality will be selected from the group consisting of hydroxyl, amino, amido, thiol, imido and carboxylic acid groups or the alkali, alkaline earth or ammonium salts thereof, or combinations thereof. Hydroxyl groups are most particularly suitable.
Additive polymers with hydroxyl groups include carbohydrates or polysaccharides such as starch, cellulose, gums and derivatives thereof. Illustrative additive polymers with hydroxyl groups include carbohydrate or polysaccharide polymers or modified carbohydrate polymers such as starch or starch derivatives; guar gum or guar gum derivatives such as Hydroxypropyl Guar Hydroxypropyltrimonium Chloride, hydroxyethyl cellulose, Polyquaternium-4, Polyquaternium-10, dextran or dextran derivatives, pullulan or pullulan derivatives, corn fiber gum or derivatives of corn fiber gum, arabinogalactan or derivatives of arabinogalactan and locust bean gum; poly(vinly alcohol) or copolymers of vinyl alcohol with other monomers, which are typically prepared by hydroysis of copolymers of vinyl acetate with other monomers; and copolymers of hydroxyl alkyl esters of acrylic or methacrylic acid such as 2-hydroxyethyl methacrylate with other copolymerizable monomers. Useful carbohydrate derivatives include cationic, anionic, amphoteric, ester and ether derivatives with cationic and amphoteric derivatives being particularly suitable. It is further noted that the hydroxyl group containing polymers may contain other substituent groups.
Polymers with amino groups are illustrated by poly(vinyl amine) or vinyl amine copolymers, which are typically made by hydrolysis of copolymers of vinyl formamide and other copolymerizable monomers, poly(ethylene imine) and derivatives of poly(ethylene imine), and chitosan.
Examples of polymers with amido groups include poly(acrylamide) or acrylamide copolymers with other copolymerizable monomers, poly(vinyl formamide) or vinyl formamide copolymers and poly(vinyl acetamide) or vinyl acetamide copolymers.
Illustrative imido containing polymers include poly(maleimide) and copolymers of maleimide with other copolymerizable monomers.
The polymers containing carboxylic acid functionality or the alkali, alkaline earth or ammonium salts thereof, include homopolymers or copolymers with other copolymerizable monomers of (meth)acrylic acid and the alkali, alkaline earth or ammonium salts thereof, crotonic acid, dicarboxylic acid containing monomers such as maleic, fumaric and itaconic acids and anhydrides, the half esters of unsaturated dicarboxylic acids such as methyl hydrogen fumarate, butyl hydrogen fumarate, ethyl h
Cimecioglu A. Levent
Luczak Kraig A.
Rossi Robert D.
Thomaides John S.
Duncan Laurelee A.
Fiorilla Christopher A.
Halpern Mark
National Starch and Chemical Investment Holding Corporation
Zajarlla, Esq. Eugene
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