Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1998-09-29
2002-02-19
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S500000, C428S522000
Reexamination Certificate
active
06348256
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
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, such as aminobutyraldehyde dimethyl acetal (ABAA) or free radical graft copolymerization with monomers, such as 2-(dimethylamino)ethyl methacrylate (DMAEMA). Graft copolymerizing amine functional monomers with poly(vinyl alcohol) provides some advantages over the 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. Furthermore, issues that can arise from the monomer reactivity ratios is avoided making it much easier to control the amount of amine functionality introduced on the poly(vinyl alcohol) backbone via a grafted chain. Another advantage of graft polymerizing amine functional monomers onto poly(vinyl alcohol) versus copolymerization with vinyl acetate followed by saponification is the formation of a very different polymer structure. The amine functional poly(vinyl alcohol) produced via copolymerization with vinyl acetate and saponification affords a copolymer with the amine monomer incorporated into the polymer backbone, which can hinder and mask the activity of the amine in some applications. However, the grafted poly(vinyl alcohol) copolymer can contain long chains of polyamine off the poly(vinyl alcohol) backbone which enhances the activity of the amine functionality, since it is more accessible, and provides for a much better balance of properties of the polyamine versus the poly(vinyl alcohol). One potential drawback in graft polymerization reactions is the simultaneous production of homopolymer or copolymers of the monomers being grafted to the poly(vinyl alcohol), ultimately resulting in a blend of polymers.
Most of the commercially available amine functional homo- and copolymers and amine functional poly(vinyl alcohol)s are economically unattractive. The commercially available amine functional poly(vinyl alcohol)s, in addition to being costly, also suffer from low levels of amine functionality. As a result of the low levels of amine functionality, these materials 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 and light resistance. There has, therefore, been a continuing need to produce a higher performing polymeric system that will provide good printed image density and sharpness as well as water and light resistance.
Much of the prior art addresses these performance issues by blending various synthetic amine containing polymers or copolymers into ink jet coating formulations. The ratios of amine containing polymers or copolymers, poly(vinyl alcohol) binder, pigment, and other additives, are then varied to achieve the desired final ink jet paper properties. However, compatibility problems can arise using such blends. For example: 1) when the ink jet coating formulation is prepared and blended together, phase separation, thickening, and/or flocculation can occur resulting in an uncoatable system; 2) the blended polymer system can be incompatible with other reagents which are often used in ink jet coating formulations; and 3) once the paper is coated and dried the incompatibility of the blends can result in a heterogeneous coating surface, which translates into varying degrees of image quality once printed.
Representative examples of polymers containing amine functionality for use in ink jet paper coating and other paper applications are described below:
JP58 186696 (1983) discloses an internal agent used in papermaking comprising a cationated poly(vinyl alcohol) which is produced by graft copolymerization of poly(vinyl alcohol) with an aminoalkyl methacrylate or aminoalkyl acrylate, especially dimethylaminoethyl methacrylate and 3-trimethyl-2-hydroxypropyl methacrylate ammonium chloride. The internal agent is reported to provide filler retention yield, paper strength, and sizing in neutral paper.
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 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 61 230979 (1986) (abstract) discloses an ink jet recording paper having a coated layer containing synthetic amorphous silica and a water soluble polymer binder, preferably, cation-modified poly(vinyl alcohol).
JP 63-149183 (1988) discloses an ink jet recording sheet suitable for high speed recording and multi-color recording. The sheet has an absorption layer containing a graft polymer which is 10 to 60 wt % poly(vinyl alcohol) and 40 to 90 wt % of specified unsaturated compounds, such as acrylamide, methacrylamide, acrylonitrile, and acrylic and methacrylic esters.
JP 63 162276 (1988) (abstract) discloses a silica previously treated with
Boylan John Richard
Klingenberg Eric Howard
Rabasco John Joseph
Bongiorno Mary E.
Celanese International Corporation
Grendzynski Michael E.
Hess Bruce H.
Spiering M. Susan
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