Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-09-17
2003-05-06
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S589000, C524S601000, C524S606000, C524S612000
Reexamination Certificate
active
06559222
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to photoneutralized, pH sensitive, aqueous polymeric dispersions.
2. Description of Related Art
Free radical polymerizable compositions offer a number of advantages over heat or ambient temperature curing, including: rapid curing at ambient temperatures; elimination of solvents and the environmental problems associated with there use; elimination of solvent recovery; elimination of the use of fossil fuels for curing and their polluting effects; and the capability of coating heat sensitive substrates. However, radiation curing at times introduces its own difficulties, such as in connection with formulating compositions having varying degrees of viscosity; use of toxic components and inhibition of curing by air contact. These difficulties may be substantially overcome by selective formulation of the radiation curable composition, and hence, the selection of the components of the radiation curable composition becomes critical.
Radiation curable compositions are well known in the art. Monomers typically used for such purpose include acrylic and methacrylic acid esters of various diols and triols, such as 1,6-hexanediol, diethylene glycol, 1,4 butanediol, trimethoxypropane, pentaerythritol or glycerol, along with alkoxylated monomers, such as ethoxylated and propoxylated derivatives thereof. Typical examples of radiation curable compositions employing some of the above-described monomers have been described in U.S. Pat. Nos. 3,594,410 and 3,380,831, which are concerned with printing and thermal transfer reproductive elements. U.S. Pat. Nos. 3,912,670; 4,025,548; 4,183,796; 4,243,500; 4,360,540; and 4,404,075 teach radiation curable coating and adhesive compositions. It is also well known to prepare radiation curable compositions using specialized polymerizable materials. For example, U.S. Pat. Nos. 4,994,346; 5,308,744; 5,300,380; 5,585,222; and 5,498,765 teach film forming photoreactive polymeric compositions for use in photoresist materials. The polymeric material employed in each case, however, contains cationic polymerizable groups. U.S. Pat. Nos. 5,206,116; 5,296,332; and 5,384,229 describe film forming photoreactive polymers that also contain cationic polymerizable systems for use in electrodeposition or solder masking. In U.S. Pat. Nos. 3,356,461 and 3,342,787, esters of styrene maleic anhydride copolymers are used. U.S. Pat. Nos. 3,862,067 and 3,884,856 disclose styrene maleic anhydride copolymers derived from low molecular weight copolymers of styrene and maleic anhydride. U.S. Pat. Nos. 3,825,430 and 4,401,793 teach the use of polymerizable esters prepared by reacting an anhydride-containing polymer with an excess of hydroxyalkylacrylate or methacrylate wherein the esters are free of unreacted anhydride groups. French Patent 2,253,772 describes the use of styrene-maleic anhydride polymers having free hydroxyl groups. U.S. Pat. No. 4,293,636 teaches a photopolymerizable composition containing polyester, half esterified hydroxyalkylacrylate of polybasic acid and vinyl monomer. However, all of these references teach radiation curable compositions containing organic solvents.
Representing a departure from solvent based radiation curable compositions, European Patent 0 257 554 A2 teaches a radiation curable composition employing a stable aqueous dispersion of polymers produced from a monomer containing ethylenic unsaturation and pendant cationic ethylenic functionalities. The polymers cross-link upon exposure to radiation in the presence of a cationic photoinitiator. U.S. Pat. No. 4,745,138 describes a radiation curable composition comprising low molecular weight partial ester of free anhydride-containing copolymers. These polymers, however, are not water soluble or dispersible due to the free anhydride functionalities.
For the most part, the prior art does not teach aqueous polymer dispersions or solutions wherein in the presence of a cationic photoinitiator, the polymer precipitates out of the dispersion or solution to form a film upon exposure to radiation.
The prior art does not teach aqueous polymer dispersions or solutions wherein in the presence of a cationic photoinitiator, the polymer precipitates out of the dispersion or solution to form and undergo cross-linking upon exposure to radiation.
It is a primary object of the present invention to provide an aqueous polymer dispersion or solution wherein in the presence of a cationic photoinitiator, the polymer does not polymerize but precipitates out of solution to form a film.
It is also an object of the present invention to provide an aqueous polymer dispersion or solution wherein in the presence of a cationic photoinitiator, the polymer does not polymerize but precipitates out of solution to form a free radical cross-linkable film when exposed to radiation.
Another object of the present invention is to prepare simple and inexpensive printing inks and coatings using these aqueous polymer dispersions.
Another object of the present invention is to prepare simple and inexpensive energy curable printing inks and coatings using these aqueous polymer dispersions.
These an other objects, which will become apparent from the following description of the present invention.
SUMMARY OF THE INVENTION
In one aspect the invention is an energy curable basic aqueous polymer dispersion wherein the polymer is substantially free of cationic polymerizable functionalities and capable of being precipitated from the dispersion in the presence of an acid generating photoinitiator upon exposure to radiation.
In another aspect the invention is a water based energy curable coating and ink composition employing these energy curable basic aqueous polymer dispersions.
DETAILED DESCRIPTION OF THE INVENTION
The invention extends the use of radiation curing technology to the vast and economical array of water based polymer systems used in water base printing and coating. Water base polymeric systems typically contain acidic or basic functional resins neutralized to a certain pH by a base or acid, respectively, in order to solubilize the resin or resin system in water. As in the prior art, the polymers of the present invention are neutralized and are soluble or dispersible in aqueous medium. However, unlike prior art polymers, the polymers of the present invention are substantially free of cationic polymerizable functionalities and thereby avoid cross-linking via a cationic mechanism when exposed to radiation. The polymer, may however, optionally contain free radical polymerizable functionalities rendering it capable of cross-linking via a free radical mechanism upon exposure to radiation.
Three essential characteristic features are required of the polymers suitable for use in the present invention: a) the polymer must be substantially free of cationic polymerizable functionalities; b) the polymer must be soluble or dispersible in a basic aqueous solution and an acid generating photoinitiator; and (c) the polymer must precipitate out of such solution upon exposure to radiation. Polymers suitable for use in the present invention, for example, may include polyamide resins, acrylic resins, acrylated acrylic resins, amino resins, polyester resins, urethane resins, starch, polysulfonate resins, phenolic resins and melamine resins. In addition to meeting these requirements the polymer may optionally containing free radical polymerizable functionalities, for example, the class of compounds meeting these requirements would include copolymers of the general structure:
wherein: R
1
and R
2
are independently selected from the group consisting of hydrogen, C
1
-C
20
alkyl, C
6
-C
10
aryl, C
7
-C
14
alkaryl, C
4
-C
12
cycloalkyl and halogen such as chlorine, fluorine and bromine; and preferably are independently selected from hydrogen, methyl, phenyl, benzyl, or C
4
-C
6
cycloalkyl; R
3
, R
4
and R
5
are independently selected from the group consisting of hydrogen and C
1
-C
5
alkyl; and preferably are independently selected from hydrogen and/or methyl; R
6
is selected fro
Chatterjee Subhankar
Laksin Mikhail
Rooney John
Turgis Jean-Dominque
Cain Edward J.
Persley Sidney
Sun Chemical Corporation
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