Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2002-05-16
2003-06-03
Le, H. Thi (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C430S138000, C525S288000, C525S902000
Reexamination Certificate
active
06572969
ABSTRACT:
FIELD OF INVENTION
This invention concerns cationic core-shell particles having a polymeric core component and a polymeric shell component disposed generally about said core, wherein said shell contains a stabilizer that is covalently bonded to the polymeric shell component. More particularly, the invention concerns the use of these core-shell particles in formulating ink jet receptive coatings.
BACKGROUND OF THE INVENTION
Ink jet printing is widely used to print on a variety of substrates (including paper, textiles, and plastic films). These substrates are often coated with a material that enhances their receptivity for the ink jet ink. Ink jet images are formed by spraying ink formulations, the majority of which are aqueous dye-based ink solutions, onto the ink jet receptive coating. The dyes are molecularly adsorbed on the surface of the coating, where they are subsequently exposed to ambient atmospheric pollutants and light. Over time, photochemical reactions and chemical reactions with oxygen, ozone, nitrogen oxides, and/or sulfur oxides commonly cause the dyes to fade.
A traditional method of attempting to improve the fade resistance of ink jet prints has been to add stabilizers to ink jet ink formulations. For example, U.S. Pat. No. 5,124,723 describes ink formulations, which contain hydroxyphenylbenzotriazole light absorbers produced as water-soluble sulfonate salts. The use of ink formulations containing water-soluble porphines as light absorbers is described in U.S. Pat. No. 5,891,229.
Another approach in the attempt to improve ink jet fade resistance has been to add stabilizers to ink jet coating formulations. U.S. Pat. No. 4,926,190 describes the addition of substituted hydroxyphenylbenzotriazole derivatives to a coating mixture. The use of water-soluble ultraviolet absorbers in a coating formulation is described in U.S. Pat. No. 5,096,781.
The use of water-soluble light stabilizers in ink jet receptive coatings has proven to be somewhat inefficient in that the stabilizers tend to migrate into the fibers of coated fiber-containing substrates. This same migration problem is faced by ink formulations that contain stabilizers as formulation additives; and once the ink is separated from its aqueous polymeric vehicle, the dye is open to interaction with ambient conditions. However, if the stabilizers were not water-soluble, their oleophilic nature would not allow appreciable concentrations of the stabilizers in aqueous based coating systems when employed as formulation additives.
Another problem often experienced with the use of light stabilizers as formulation additives is the tendency of the stabilizers to be extruded out of the substrate (a condition known as “blooming”). Such blooming can cause a lost in effectiveness as well as dust formation problems.
Therefore, an object of this invention is to solve these major problems by disclosing cationic core-shell particles which exhibit properties that make them suitable for formulating ink jet receptive coatings.
Another object of this invention is to disclose cationic core-shell particles.
A further object of this invention is to disclose core-shell particle latexes.
Another object of this invention is to disclose efficient, economical ink jet receptive coatings that are resistant to blooming.
SUMMARY OF THE INVENTION
The objects of this invention are met via the production of cationic core-shell particles having a polymeric core component and a polymeric shell component disposed generally about said core, wherein said shell contains a stabilizer that is covalently bonded to the shell. As used herein the term “stabilizer” means a compound which contains in its molecular chain sites possessing ultraviolet absorbing activity, free radical scavenging activity, antioxidant activity, and/or peroxide decomposing activity.
Due to the core-shell morphology of the particle, only the shell component contains stabilizer (which is covalently bound to the shell polymer). This is an improvement over prior technologies in that the present invention permits placement of the stabilizer where the dye is actually adsorbed into the ink jet receptive coating. Moreover, the core-shell morphology allows one to use smaller quantities of the stabilizer while effecting a greater surface concentration.
The covalent bonding of the stabilizer to the shell component avoids the migration problems often associated with the use of water-soluble light stabilizers as formulation additives to inks or ink jet receptive coatings. Additionally, the binding of the stabilizer into the polymer backbone of the shell component prevents blooming.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The cationic core-shell particles suitable for use in formulating ink jet receptive coatings comprise:
(A) a polymeric core component, said core component comprising the free radical polymerization reaction product of a mixture comprising:
(1) about 80.0% to about 99.5% by total weight of the mixture of a member selected from the group consisting of acrylic esters of alcohols containing from 1 to 22 carbon atoms, methacrylic esters of alcohols containing from 1 to 22 carbon atoms, styrene, substituted styrenes, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl ethers, vinyl esters, N-vinyl amides, acrylamides, methacrylamides, and combinations thereof;
(2) about 0.5% to about 20.0% by total weight of the mixture of a member selected from the group consisting of ethylenically unsaturated monomers containing at least one quaternary ammonium group and combinations thereof; and
(3) a catalytic amount of polymerization initiator; and
(B) a polymeric shell component disposed generally about said core component, said shell component comprising the free radical polymerization reaction product of a mixture comprising:
(1) about 70.0% to about 99.5.0% by total weight of the mixture of a member selected from the group consisting of acrylic esters of alcohols containing from 1 to 22 carbon atoms, methacrylic esters of alcohols containing from 1 to 22 carbon atoms, styrene, substituted styrenes, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl ethers, vinyl esters, N-vinyl amides, acrylamides, methacrylamides, and combinations thereof;
(2) up to about 30.0% by total weight of the mixture of a member selected from the group consisting of ethylenically unsaturated monomers containing at least one quaternary ammonium group and combinations thereof;
(3) about 0.5% to about 30.0% by total weight of the mixture of stabilizer selected from the group consisting of ultraviolet absorbers which contain at least one ethylenically unsaturated group, radical scavengers which contain at least one ethylenically unsaturated group, antioxidants which contain at least one ethylenically unsaturated group, peroxide decomposers which contain at least one ethylenically unsaturated group, and combinations thereof; and
(4) a catalytic amount of polymerization initiator; and wherein said stabilizer is covalently bound to said shell component.
Preferred cationic core-shell particles comprise:
(A) a polymeric core component, said core component comprising the free radical polymerization reaction product of a mixture comprising:
(1) about 85.0% to about 95.0% by total weight of the mixture of a member selected from the group consisting of acrylic esters of alcohols containing from 1 to 22 carbon atoms, methacrylic esters of alcohols containing from 1 to 22 carbon atoms, styrene, substituted styrenes, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, vinyl ethers, vinyl esters, N-vinyl amides, acrylamides, methacrylamides, and combinations thereof;
(2) about 5.0% to about 15.0% by total weight of the mixture of a member selected from the group consisting of ethylenically unsaturated monomers containing at least one quaternary ammonium group and combinations thereof; and
(3) a catalytic amount of polymerization initiator; and
(B) a polymeric shell component disposed generally about said core component, said shell component comprising the free radical
Boshinski Thomas A.
Le H. Thi
McDaniel Terry B.
MeadWestvaco Corporation
Reece IV Daniel B.
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