Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-01-19
2003-04-01
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S151000, C522S152000, C522S153000, C522S154000, C522S155000, C522S156000, C526S245000, C526S273000, C526S317100, C526S318200, C526S318400, C526S328000, C526S328500, C526S329000, C526S329100, C526S329200
Reexamination Certificate
active
06541537
ABSTRACT:
FIELD OF THE INVENTION
The invention is directed to a compound and a method of forming a photopolymerizable acrylated glycidyl acrylic terpolymer resin compound.
BACKGROUND OF THE INVENTION
Acrylate polymers may be used as pressure sensitive adhesives, coatings, and surface application materials for numerous products. For example, acrylic polymers are used to coat the surfaces of printing plates, door jambs, and many other items which require a hard weather resistant coating. Such coatings have many applications for surfaces of items that are particularly heat sensitive such as paper, plastics, and wood.
Many acrylate resin coatings are cured using ultraviolet light. Such coatings may be cured by the impact of ultraviolet light upon the surface of the coating, which results in curing of the composition. In other applications, such compounds may be cured by a cationic curing process.
Radiation curing involves the use of ultraviolet light as a cause of free radical formation. For example, polyester clear coatings which are stored in untinted glass bottles may polymerize in a few days or weeks. In some cases, hardening of such a coating may be achieved by only a few seconds of exposure to ultraviolet light, because of the very efficient conversion of ultraviolet light energy to free radicals.
In general, acrylate resins comprise a class of thermoplastic or thermoset polymers or copolymers. These oligomers polymerize readily in the presence of light, heat or catalysts. In general, acrylate resins must be stored or shipped with inhibitors present in the composition to avoid spontaneous and explosive polymerization. Acrylate resins vary in physical properties from very hard brittle solids to fibrous elastomeric structures to viscous liquids, depending upon the monomer used and the method of polymerization employed.
In some cases, acrylate resins are “bulk” polymerized. For example, in U.S. Pat. No. 3,974,303 to Iwase et al., (see Example #4, column 5, lines 20-42) a method of forming a coating film using “bulk” polymerization is disclosed. In this patent, a method for forming coating films is disclosed which is stated to provide a coating film having impact resistance, adhesion to a substrate article, flexibility and chemical resistance. The method includes a coating having a powdery composition. In the patent a curing agent, a pigment and other additives are provided into a powdery resin. The resin is applied to an article to be coated using electrostatic coating or fluidized bed coating. Then, the coating is heated to a relatively high temperature to effect melting and curing simultaneously. One disadvantage of the process disclosed in U.S. Pat. No. 3,974,303 is that the process typically shows an excess of acrylic acid in the final product. In most cases, that results because the goal in that process is to react all of the epoxide groups. However, under such conditions, there often is no epoxy remaining for a cationic curing process. Therefore, overall curing is limited in such a process because without a light or UV source, curing will undesirably cease.
One significant problem encountered in employing the teachings of the prior art is the fact that many such coatings are not capable of providing both good weathering characteristics and a fast cure speed. Epoxy acrylates are relatively fast curing, but are hard and brittle when cured, and therefore do not weather well due to either the aromatic ring structure or the weak backbone of the aliphatic compounds. Urethane acrylates and polyester acrylates both suffer these problems. For example, polyester acrylates, which comprise a polyester backbone, transesterify upon long term exposure, and the film therefore decomposes after a certain amount of time. Such compounds also are susceptible to degradation from moisture. In general, this class of products cures slower than other types of products.
Another significant problem occurs if the radiation source, during curing, does not hit all of the surface of a coated substrate. Currently known compositions leave the surface of the coated article uncured and tacky in most instances, which is highly undesirable.
What is needed in the industry is an acrylate resin composition and method of forming an acrylate resin composition that produces a resin having desirable physical characteristics. Furthermore, an acrylate resin that is capable of being effectively cured to a hard finish both by radiation curing (i.e., ultraviolet light or visible light) and also by cationic polymerization would be very useful. In general, acrylate resin compositions showing an increased resistance to yellowing and discoloration are very desirable. Compositions which exhibit a relatively low polydispersity value and a low glass transition temperature also are desirable. Furthermore, acrylate resins that are stable at higher temperatures are useful.
SUMMARY OF THE INVENTION
A non-aromatic photopolymerizable acrylate polymer is provided in the invention. In a first step, the polymer may be formed by polymerizing a reactive source of epoxide ions, a source of unsaturated monomers in the presence of a catalyst to form a glycidyl acrylic terpolymer. Then in a second step, the glycidyl acrylic terpolymer is reacted with an epoxy ring opening catalyst and a source of unsaturated acid or anhydride to form the acrylate polymer of the invention. The polymer is formed using a minimum molar amount of acid such that epoxide groups are left upon the polymer backbone (not completely reacted via the second stage carboxy ring opening reaction) and remaining epoxide groups are rendered reactive during polymerization, so that the epoxide groups are available to react cationically.
In another aspect of the invention, the polymer is capable of being cured cationically. The polymer may include many different kinds of unsaturated monomer, and is selected from the group consisting of: methyl methacrylate, butyl acrylate, hydroxyethylacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, s-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, 3,3,5-trimethycyclohexyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, acrylonitrile, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, isobornyl methacrylate, bromoethyl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, diethyl methyleneglutarate, isocyanatoethyl methacrylate, methacrylic acid, methacrylonitrile, 2-(diethylphosphato)ethyl methacrylate, 1-diethylphosphonoethyl methacrylate, ethylene, butadiene, vinylidene chloride, and n-vinylpyrrolidinone.
In one embodiment of the invention, the polymer is capable of polymerizing by: (1) photopolymerization, (2) cationic polymerization, or both photopolymerization and cationic polymerization.
The catalyst employed in the first step may be a peroctoate or any other free radical initiator with a 30-minute half-life at less than 120° C. In the second step of reaction, the catalyst may be a phosphonium or onium salt compound, such as ethyl triphenyl phosphonium bromide, for example.
In one embodiment of the invention, a method is provided that includes forming a photopolymerizable acrylated glycidyl acrylic terpolymer resin in a two-step reaction. First, the method includes providing a source of epoxide ions having an epoxide ring structure, and providing a source of unsaturated monomer. A catalyst is also provided. In the first step, the reactants form a terpolymer chain having epoxide groups along the length of the terpolymer chain. Then, in a second step, the terpolymer chain reacts with acrylic acid, thereby opening the rings of epoxide groups along the terpolymer chain and forming a photopolym
Berman Susan W.
Dority & Manning P.A.
Renaissance Technology LLC
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