Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-05-14
2001-10-23
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S318000, C526S318410, C526S320000, C526S326000, C526S329700, C526S332000
Reexamination Certificate
active
06306994
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polymer dispersants having a polymerized monomer including a primary amine functionality, inks comprising such polymer dispersants, and processes of making the same.
BACKGROUND OF THE INVENTION
Ink jet printers are relatively inexpensive machines using non-impact methods to print. Print quality refers to characteristics, such as print sharpness, and is dependent, in part, on the mechanical design of ink jet printers and inks used during printing processes. The physical and chemical characteristics of inks, which affect print quality, may be altered by factors such as solvents, colorants and/or other ink additives. Colorants provide tints to inks and refer to dyes, dispersed dyes, or pigments. Dyes refer to colorants that are soluble during ink formation and printing. Pigments refer to colorants that are insoluble during ink formation and printing. Dispersed dyes refer to colorants that are insoluble during ink formation but become soluble some point during a printing process. Print quality is enhanced when colorants, such as pigments, are well dispersed in inks.
Dispersants attached to insoluble particles enhance the dispersion of insoluble particles in liquids and are sometimes characterized as one or more blocks of polymerized monomers. Hydrophobic blocks, which include polymerized monomers hydrophobic in nature, are involved in the binding of polymer dispersants to insoluble particles. Group transfer polymerization (GTP), can not be used to prepare block copolymers when monomers containing active hydrogens of the type present in primary amines are used as starting materials. Consequently, U.S. Pat. No. 5,272,201 (Ma et al.) discloses the use of a specific initiator for placing a monomer including an amine group at the beginning of a hydrophobic block and a method that forms a hydrophobic block with one or more tertiary amine groups placed within the ends of the hydrophobic block. Polymer dispersants disclosed in U.S. Pat. No. 5,272,201, have in addition to a hydrophobic block, a hydrophilic block that facilitates polymer dispersants' interactions with surrounding liquids. Consequently, a hydrophobic and a hydrophilic block each provide unique characteristics to a polymer dispersant. Modifications made to a hydrophobic block may affect the characteristics of a polymer dispersant differently than modifications made to a hydrophilic block, with each block playing a different role in the dispersion of insoluble particles (attachment versus liquid interaction).
Having a well dispersed ink prevents agglomeration, and settling to the bottom of a pigment, during the printing process. Other ink characteristics include the ability of an ink to bind to paper. Inks that bind well to paper are especially suited for specific applications such as use in high speed ink jet printers because they prevent smearing especially when the printed ink is touched by subsequent printed pages. The ability of an ink to bind to a substrate may be measured by a waterfastness test. An ink drop is applied to a substrate (such as paper) to form a spot. After a specific period of time, the substrate and ink are placed in contact with water. The substrate and ink are visually inspected to determine if the spot, formed by the drop of ink, smears in the presence of water. Another test for measuring the strength of ink binding to a substrate is called the mechanical smear test that requires rubbing the surface of a printed ink with a highlighter.
SUMMARY OF THE INVENTION
The present invention provides aqueous dispersions, preferably smear-resistant inks, having enhanced substrate binding characteristics. These aqueous dispersions comprise a block copolymer dispersant including a polymerized monomer that has a primary amine functionality. Such a block copolymer dispersant includes a hydrophobic block and a hydrophilic block. The hydrophilic block preferably comprises at least one polymerized monomer including a primary amine functionality, preferably aminoalkyl acrylates, aminoalkyl methacrylates, or combinations thereof, and at least one polymerized monomer including a carboxylic acid functionality. Inks of the present invention are preferably aqueous and for use in ink jet printers, and comprise in addition to a polymer dispersant, an aqueous carrier and a colorant.
The present invention also provides an article comprising a substrate, having a first and second major outer surface. Attached to the substrate is a layer of an aqueous dispersion, preferably an aqueous ink, comprising a colorant and a polymer dispersant of the present invention.
The present invention also provides for a monomer having a protected primary amine functionality, N-(2-methyacryloxyethyl)-2,2,5,5-tetramethyl-2,5-disilapyrrolidone. This monomer having a protected primary amine functionality is preferably used in a group transfer polymerization method to produce block copolymer dispersants, which have one or more polymerized monomers including a primary amine functionality.
DETAILED DESCRIPTION OF THE INVENTION
Inventive block copolymer dispersants preferably have a diblock or a triblock structure with one or more monomers having a primary amine functionality, preferably associated with the hydrophilic block. Aqueous dispersions such as inks comprising such polymer dispersants are observed to have enhanced binding to a substrate, such as paper, as illustrated in the examples hereinafter, and may be used in ink jet printers, preferably thermal ink jet printers. The aqueous dispersions of the present invention may also be suitable for other applications such as paints or protective coatings. Aqueous dispersions used as inks may be adapted to the requirements of a particular ink jet printer, such as to provide a balance of light stability, smear resistance, viscosity, surface tension, optical density, and pluggage resistance as desired for the particular application.
Polymer Dispersants
Block copolymer dispersants of the present invention include a hydrophobic block and a hydrophilic block.
Hydrophilic Block
The hydrophilic blocks in the polymeric dispersants of this invention preferably comprise at least one polymerized monomer including a primary amine functionality and at least one polymerized monomer including a carboxylic acid functionality.
Monomers suitable for incorporating a primary amino group into the hydrophilic block of a block copolymer dispersant, utilizing GTP or ionic polymerization, may best be prepared from primary aminoalky acrylates or salts thereof, primary aminoalkyl methacrylates or salts thereof, or combinations therof. The preferred acrylate used for this application is 2-aminoethyl methacrylate hydrochloride. The active hydrogens of the primary amino group are first masked (using a silyl protecting group such as 1,2 bis chlorodimethylsilyl ethane), as described herein, to prevent interference with the polymerization process. An example of a novel monomer prepared from 2-aminoethyl methacrylate hydrochloride with the primary amino suitably masked so that there are no active hydrogens is N-(2-methacryloxyethyl)-2,2,5,5-tetramethyl-2,5-disilapyrrolidone. After the block copolymer is prepared by GTP or anionic polymerization, the silyl protecting group is removed by methanolysis or hydrolysis to form a hydrophilic block, which now contains one or more primary amine groups randomly distributed within that hydrophilic block.
A polymerized monomer including an amine functionality may be prepared from monomer(s) free of a primary amine functionality that include a reactive functionality capable of being converted into a primary amine functionality after the hydrophilic block is formed. It is preferred that one or more polymerized monomer(s) including an amine functionality are located between the ends of a hydrophilic block. Alternatively a polymerized monomer including an amine functionality may be located exclusively at one or both ends of a hydrophilic block with the rest of the hydrophilic block including polymerized monomers free of a primary amine functiona
Donald Dennis Scott
Hertler Walter Raymond
Ma Sheau-Hwa
E. I. Du Pont de Nemours and Company
Harlan R.
Tessari Joseph A.
Wu David W.
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