Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-08-26
2002-09-24
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S500000, C428S522000, C428S206000
Reexamination Certificate
active
06455134
ABSTRACT:
BACKGROUND OF THE INVENTION
Advances in ink jet technology have placed increased demands on recording papers. To function properly, the recording paper must quickly absorb the ink and ink vehicles directly after printing, maximize the ink optical density, minimize bleeding and wicking of the ink, and provide good water and light fastness. To obtain a paper with the above functions, the paper is usually treated with one or more coatings.
Ink jet paper coatings typically comprise silica pigment for its high absorption power and a polymeric binder, such as poly(vinyl alcohol), for its high binding strength. Non-silica pigments, such as clays, calcium carbonate, titanium dioxide, and aluminum hydrate, are also used. Other known polymeric binders include poly(vinylpyrrolidone), styrene-butadiene copolymers, poly(vinyl acetate), starch, and amine functional polymers such as amine functional poly(vinyl alcohol).
Amine functional poly(vinyl alcohol) is typically produced by the copolymerization of vinyl acetate with amine functional monomers, such as trimethyl-(3-methacrylamido-propyl)ammonium chloride, N-vinylformamide, or acrylamide, followed by saponification to form the poly(vinyl alcohol) derivative. However, there are disadvantages to this approach. The selection of amino comonomers is very limited due to their incompatibility with the saponification conditions to produce poly(vinyl alcohol). Depending on the monomer which is copolymerized with the vinyl acetate, saponification can have a deleterious effect on the comonomer. For example, when 2-(dimethylamino)ethyl methacrylate (DMAEMA) is the comonomer, saponification results in hydrolysis of the ester bond, thus removing the active amine functionality from the polymer backbone. Another disadvantage which limits the number of comonomers that can be used for the preparation of amine functional poly(vinyl alcohol) is the reactivity ratio of the comonomer with vinyl acetate. Depending on these reactivity ratios, there can be severe limitations not only on the level of amine monomer incorporation into the vinyl acetate copolymer, but also on the attainable range of copolymer molecular weights.
Another approach to producing amine functional poly(vinyl alcohol) involves post-reacting poly(vinyl alcohol) with amino synthons. For example, reacting aminobutyraldehyde dimethyl acetal (ABM) with the hydroxyl groups of poly(vinyl alcohol) to form the corresponding poly(vinyl alcohol) acetal or the free radical graft copolymerization of amine functional monomers, such as 2-(dimethylamino)ethylmethacrylate (DMAEMA), with poly(vinyl alcohol). Graft copolymerization provides some advantages over traditional copolymerization with vinyl acetate and subsequent saponification. For example, by using poly(vinyl alcohol) as a reactive synthon to graft polymerize other monomers, the saponification step is circumvented, thereby allowing the use of a much larger number of amine functional monomers and access to a wider range of amine functional poly(vinyl alcohol) compositions. One drawback of graft polymerization reactions is the simultaneous production of homopolymer or copolymers of the monomers being grafted, ultimately resulting in a blend of polymers.
Most of the commercially available amine functional polymers and amine functional poly(vinyl alcohol)s are either economically costly or, in the case of amine functional poly(vinyl alcohol)s, suffer from low levels of amine functionality. Those materials having low levels of amine functionality fail to meet the stringent performance requirements for good ink jet print quality, especially for the high-end, photographic grade ink jet papers. The printed image density and sharpness are inadequate, as is the water resistance. There are, therefore, continuing efforts to produce a high performing polymeric system improved print image density and sharpness and water resistance.
Poly(vinyl alcohol) is commonly used as an emulsion colloid stabilizer for poly(vinyl acetate) homopolymer, poly(vinyl acetate)-co-poly(ethylene) copolymers, and other ethylenically unsaturated polymers and copolymers that are used ink jet coating formulations. The colloid stabilizers are typically incorporated into emulsions at approximately 5 wt % relative to monomers. However, it is known to those practicing the art of ink jet paper coatings that higher levels of poly(vinyl alcohol) are necessary for proper and sufficient binding of pigments to the paper.
Examples of polymers containing amine functionality for use in paper applications are described below:
JP55-125109 (1980) discloses a water soluble high molecular weight composite material which is obtained by polymerizing water soluble ethylene type unsaturated monomers, such as alkylaminoalkyl acrylates or methacrylates, in the presence of a high molecular weight compound, such as starch, poly(ethylene glycol), and poly(vinyl alcohol), having at least one of the following functional groups: ether, hydroxy, and carboxy. The composite material is reported to exhibit good stability and fluidity and to be useful in a variety of areas; e.g., as a dye, paper-treating agent, and viscosity increasing agent.
JP 93-67432 (1993) (abstract) discloses an ink jet recording paper containing a formulation in base paper and/or coat layer and consisting of a copolymer of vinyl alcohol with a cationic monomer such as trimethyl-3-(1-acrylamidopropyl)ammonium chloride and non-colloidal silica powder.
JP 58-185640 and JP 59-030827 (abstracts) disclose the preparation of water dispersible cationic resin powders by emulsion polymerization of vinyl monomers in the presence of cationic poly(vinyl alcohol) emulsifiers or cationic comonomers. The resin powders, when dispersed in water, are reported to have good adherence and film forming property.
U.S. Pat. No. 5,270,103 (Oliver et al., 1993) discloses a receiver sheet which consists of a substrate and a coating containing a pigment and a binder. The binder comprises poly(vinyl alcohol) and an additional binder component; for example, a cationic polyamine, such as poly(2-hdyroxypropyl-1,1-N-dimethyl ammonium chloride), which is relatively insensitive to pH variations compared to other cationic polyamines, or a cationic polyacrylamide. The receiver sheet is particularly useful for printing with aqueous based inks such as in ink jet printing systems.
BRIEF SUMMARY OF THE INVENTION
This invention relates to improved ink jet paper coatings which impart high optical density images and excellent water resistance by the incorporation of an amine functional, colloid-stabilized polymer emulsion into the coating formulation. The improvement resides in the use of amine functional monomers, such as 2-(dimethylamino)ethyl methacrylate (DMAEMA), emulsion copolymerized with other ethylenically unsaturated monomers in a large amount of a colloid stabilizer. The colloid stabilizer is a polymer containing multiple pendent hydroxyl groups; poly(vinyl alcohol) is preferred.
It was found in this invention that emulsion polymerization of ethylenically unsaturated monomers with amine functional monomers, in the presence of a large amount of a colloidal polymer stabilizer having a plurality of pendent hydroxyl groups, such as poly(vinyl alcohol), offers further advantages over homogeneous aqueous graft copolymerization reactions. This invention employs at least 10 wt %, preferably at least 15 wt %, of colloid stabilizer to produce a unique emulsion copolymer system as a polymeric binder. By using large amounts of a hydroxyl containing colloid stabilizer, i.e., at least 10 wt %, more of the stabilizer is available for grafting reactions compared to traditional emulsion systems, thus affording a unique emulsion copolymer and resulting in a single polymeric ink jet paper binding system which provides excellent image quality, complete fixation of ink dyes to the paper under adverse humidity conditions, and high binding power of various pigments. Some advantages of the present emulsion polymerization approach to produce amine functional emulsion polymers are:
the amine functional co
Air Products Polymers, L.P.
Bongiorno Mary E.
Grendzynjk Michael
Hess Bruce H.
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