Paper making and fiber liberation – Processes and products – Non-uniform – irregular or configured web or sheet
Reexamination Certificate
1998-08-17
2001-08-28
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-uniform, irregular or configured web or sheet
C524S414000, C524S608000
Reexamination Certificate
active
06280571
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to stabilizer for creping adhesives and more Particularly it relates to a creping composition comprising water soluble polymer and stabilizer comprising certain acids or salts thereof.
2. Description of the Prior Art
The creping process is commonly practiced in the manufacture of tissue and towel grades of paper. This process involves scraping the dried paper web from a drying cylinder (Yankee dryer) by the use of a creping doctor blade. The creping action imparts a fine, rippled texture to the sheet and also increases the bulk of the sheet, resulting in improved softness and absorbency. An adhesive formulation is often used to control the adherence of the paper sheet to the Yankee dryer. In this regard, fibrous webs, particularly paper webs, are conventionally subjected to the creping process in order to give them desirable textural characteristics, such as softness and bulk. The creping process typically involves applying creping adhesive—generally in the form of an aqueous solution, emulsion or dispersion—to a drying surface for the web; preferably, this surface is the surface of a rotating creping cylinder, such as the apparatus known as a Yankee dryer. The web is then adhered to the indicated surface. It is subsequently dislodged from the surface with a creping device—preferably, a doctor blade. The impact of the web against the creping device ruptures some of the fiber-to-fiber bonds within the web, causing the web to wrinkle or pucker. The creping adhesive solution, emulsion or dispersion can be comprised of one or more adhesive components, typically water-soluble polymers, and may also contain one or more release agent components as well as other desired additives that may affect the creping process. This is known as the creping adhesive package. This adhesive is exposed to high temperatures (on the ordeir of 100° C.) and high mechanical shear at the creping blade. Given these conditions, one could expect the adhesive formulation to undergo thermooxidative degradation in the presence of atmospheric oxygen. In fact, dark gummy deposits are sometimes observed on the creping blade or Yankee dryer. these deposits are probably thermooxidative degradation products of the creping adhesive formulation and can cause disruptions in the papermaking process. The present invention describes additives for the creping adhesive formulation that significantly reduce the degradation of the creping adhesive formulation under its expected use conditions.
Espy & Maslanka, U.S. Pat. No. 5,338,807 and Espy & Giles, Canadian Patent 979,579 disclose polyamidoamine-epichlorohydrin resins (PAE resins) as adhesives in the creping process for producing tissue and towel paper products.
A number of patents disclose the use of hypophosphorous acid and its salts as antioxidant in polymeric formulations. These include Papero, U.S. Pat. No. 3,242,134 closing use as a stabilizer for polyamides, Yoshitomi, Nagakura and Matsunuma, Japanese Patent 12,997 disclosing use as an antioxidant in the preparation of alkyd resins, Schuler, Swiss Patent 326,175 disclosing use as a light stabilizer for poly(vinyl chloride) and French Patent 1,391,335 (Imperial Chemical Industries Ltd.) disclosing use as a stabilizer in the preparation of polyurethane foams.
The polymers described in the prior art as stabilized by hypophosphorous acid and its salts are all water-insoluble materials. There is no indication given in the prior art that these stabilizers would work in an aqueous system with a water-soluble polymer.
Chen U.S. Pat. No. 4,883,564 discloses a ci-eping adhesive comprising water-soluble binder (polyvinyl alcohol) and a phosphate salt in order to reduce the hard film build up on the creping surface of the drum dryer.
There is no disclosure in the above references of additives used to impart thermal stability to the creping adhesive compositions.
There is no mention in the above references of oxidative instability neither of polyamidoamine-epichlorohydrin or polyamine-epichlorohydrin resins nor of the use of hypophosphorous acid and its salts as stabilizers for polyamidoamine-epichlorohydrin or polyamine-epichlorohydrin creping adhesives.
SUMMARY OF THE INVENTION
According to the present invention there is provided a composition comprising at least one water soluble polymer selected from the group consisting of polyamidoamine-epichlorohydrin resin, polyamine epichlorohydrin resin, polyacrylamide, polyvinyl alcohol, polyvinylamine, polyethyleneimine, polymethacrylamide, poly(acrylic acid), poly(methacrylic acid), poly(hydroxyethyl acrylate), poly(hydroxyethyl methacrylate), poly(n-vinyl pyrrolidinone), poly(ethylene oxide), hydroxyethyl cellulose, hydroxypropyl cellulose, guar gum, starch, agar, chitosan, alginic acid, carboxymethyl cellulose, highly branched polyamidoamines and silylated polyamidoamines; and at least one stabilizer selected from the group consisting of hypophosphorous acid, phosphorous acid, hypodiphosphoric acid, diphosphorous acid, hypophosphoric acid, pyrophosphorous acid and salts of any of these acids.
Further provided according to the present invention are creping adhesives comprising at least one of the above water soluble polymers and at least one of the above stabilizers.
Provided according to the present invention there are processes of forming creped paper comprising: (a) applying the water soluble polymer and stabilizer of the present invention to a drying surface for fibrous web, (b) pressing a fibrous web against the drying surface to adhere the fibrous web to the drying surface, and (c) dislodging the fibrous web from the drying surface with a creping device to crepe the fibrous web.
DETAILED DESCRIPTION OF THE INVENTION
Surprisingly it has been discovered that certain acids, such as phosphorous acid, hypophosphorous acid etc. and their salts are effective additives in preventing thermal degradation of water soluble polymers, e.g., polyamidoamine-epichlorohydrin and polyamine-epichlorohydrin resins. This type of stabilizer should be useful in the manufacture of tissue papers and paper toweling by providing a more stable creping adhesive coating on the Yankee dryer.
In the context of the present application the term “polymer” is intended to include homopolymers as well as copolymers.
The stabilizers have been shown to be effective in reducing color formation and charring of water soluble polymers, such as polyamidoamine-epichlorohydrin and polyamine-epichlorohydrin resins at levels, of about 1 to 5%.
The water soluble polymer suitable for the present invention can be selected from the group consisting of polyamidoamine-epichlorohydrin resin, polyamine epichlorohydrin resin, polyvinyl alcohol, polyvinylamine, polyethyleneimine, acrylamide polymers, polymethacrylamide, poly(acrylic acid), poly(methacrylic acid), poly(hydroxyethyl acrylate), poly(hydroxyethyl methacrylate), poly(n-vinyl pyrrolidinone), poly(ethylene oxide), hydroxyethyl cellulose, hydroxypropyl cellulose, guar gum, starch, agar, chitosan, alginic acid, carboxymethyl cellulose, highly branched polyamidoamines and their reaction product with epichlorohydrin and silylated polyamidoamines. Preferably the water-soluble polymer is selected from the group consisting of polyamidoamine-epichlorohydrin resin, polyamine-epichlorohydrin resin, highly branched polyamidoamines, silylated polyamidoamines, polyvinyl alcohol, polyvinylamine, polyethyleneimine, acrylamide polymers, poly(N-vinyl pyrrolidinone), hydroxyethylcellulose and carboxymethylc,ellulose, and most preferably they are selected from the group consisting of polyamidoamine-epichlorohydrin resin, polyamine-epichlorohydrin resin, highly branched polyamidoamines, silylated polyamidoamines, polyvinyl alcohol, polyvinylamine and polyethyleneimine.
The stabilizer is selected from the group consisting of hypophosphorous acid, phosphorous acid, hypodiphosphoric acid, diphosphorous acid, hypophosphoric acid, pyrophosphorous acid and salts of any of these acids. Preferably the stabilizer is hypop
Chin Peter
Greenblum & Bernstein P.L.C.
Hercules Incorporated
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