Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-08-21
2002-11-12
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S063000, C525S426000, C525S430000, C525S434000, C525S449000
Reexamination Certificate
active
06479588
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to a graft copolymer of polyamide and a glycidyl group-containing acrylate copolymer and a process for preparing the graft copolymer. The present invention further relates to a coating composition containing the graft copolymer, particularly a powder coating composition.
B. Description of the Related Art
Over the years, society has greatly benefitted from the development of a wide spectrum of polymeric materials. Polymers have been used in almost every phase of everyday life and have found particular applicability in automotive parts, containers, fibers, filaments, fabric, construction materials, adhesives and coatings. Due to the diverse characteristics of different polymers, some polymers are especially useful in certain environments while others are contraindicated. In an effort to alleviate the less advantageous properties of polymers, attempts have been made to modify polymers by blending additives or even other polymers. In addition, attempts have been made to chemically modify polymers by adding reactive groups, by copolymerization with compatible monomers, by block copolymerization or by graft copolymerization.
In the field of coatings, particularly powdered coatings, polymeric materials have played a prominent role. For instance, U.S. Pat. No. 4,042,645, reissued as Reissue Pat. No. 32,261, describes a thermosetting powder coating composition obtained by mixing a major proportion of a solid copolymer prepared from defined amounts of (A) a (meth)acrylate ester, (B) an &agr;,&bgr;-ethylenically unsaturated carboxylic acid or anhydride or a glycidyl acrylate or methacrylate, optionally (C) a monomer copolymerizable with (A) and (B), and a minor portion of a cross-linking compound or an epoxy resin containing at least two epoxy radicals in the molecule in the presence of a tertiary amine curing accelerator.
To modify the properties of the powder coatings, blends with additives or other polymers have typically been employed. However, one of the drawbacks of blends is that a hazy or opaque coating often is obtained. While such a result might be acceptable if the coating is to be pigmented, it is unacceptable if the haze or opacity adversely affects the aesthetics of the coating or if a clear coat is desired.
Further illustrative of the art relating to powder coatings is U.S. Pat. No. 5,407,706 which describes a powder coating composition that provides low gloss upon curing. The composition comprises (A) a resin comprising from 10 to 90 weight % of an acrylic resin having a viscosity of 100 to 800 poises at 140° C. that is obtained by polymerizing 10 to 50 weight % of glycidyl acrylate or glycidyl methacrylate with 90 to 50 weight % of a copolymerizable monomer and 90 to 10 weight % of a further acrylic resin having a viscosity of 1,000 to 5,000 poises at 140° C. that is prepared from defined comonomers, and (B) a polybasic acid compound having a viscosity of 100 to 2,000 poises at 150° C. The equivalent ratio of the glycidyl groups to the acid groups of the polybasic acid compound may be from 1.5 to 0.5.
U.S. Pat. No. 5,436,311 describes a powder thermosetting composition comprising as binder a mixture of a linear carboxyl group-containing polyester and a glycidyl group containing acrylic copolymer. The polyester has an acid number of 20 to 50 mg KOH/g. The acrylic copolymer has a number average molecular weight of from 4,000 to 10,000 and is obtained from 5 to 30% by weight glycidyl acrylate or glycidyl methacrylate and 70 to 95% by weight of methyl methacrylate whereby up to 25% by weight of the methyl methacrylate can be replaced by another vinyl monomer.
U.S. Pat. No. 5,744,522 relates to a low gloss coating composition containing a glycidyl group-containing acrylic copolymer, an aromatic polyester and a defined isocyanurate curing agent. The background of this patent provides a description of the previously described patents and other documents relating to coating compositions.
In addition to various acrylic polymers, the art has developed certain modified polyamides. Illustrative of such modified polyamides is U.S. Pat. No. 4,973,617 which relates to a water-borne printing ink composition based on acrylic resins and maleated rosin modified polyamides. The modified polyamides are said to provide good adhesion, clean printing, excellent film wetting and superior resolubility and the resulting ink compositions are said to be especially useful for printing onto plastic substrates.
U.S. Pat. No. 5,574,101 describes an acrylic resin composition comprising at least one polyamide elastomer consisting of hard segments and soft segments, an acrylic resin and optionally at least one electrolyte. The composition is said to possess permanent anti-static properties and good transparency which is only slightly deteriorated even when immersed in water. The compositions are disclosed as being useful for parts of electronic products, household appliances, office automation appliances and other devices.
Japanese Unexamined Patent Publication No. 02-060930 relates to graft copolymers which are said to exhibit transparency, flexibility and heat resistance which are useful for the preparation of coatings, adhesives, etc. The graft copolymers are prepared by polycondensing a polyalkyl (meth)acrylate, such as polybutyl acrylate, a dicarboxylic acid and an aromatic diamine.
BRIEF SUMMARY OF THE INVENTION
In one aspect, the present invention provides a graft copolymer comprising a polyamide to which is grafted a glycidyl group-containing acrylate copolymer.
In a further aspect, the present invention provides a process for preparing a graft copolymer comprising a polyamide to which is grafted a glycidyl group-containing acrylate copolymer. The process comprises:
A) dispersing in an organic solvent a polyamide and a material which will react with the polyamide to form the graft copolymer of the polyamide and the glycidyl group-containing acrylate copolymer; and
B) reacting the polyamide and the material so as to form said graft copolymer.
In a still further aspect, the present invention provides coating compositions comprised of the graft copolymer.
DETAILED DESCRIPTION OF THE INVENTION
As noted above, one aspect of the present invention relates to a graft copolymer comprising a polyamide to which is grafted a glycidyl group-containing acrylate copolymer. The polyamide preferably exhibits a relatively low melting point which is less than about 160° C., more preferably less than about 145° C., as determined by a differential scanning calorimeter and ASTM B3418. Polyamides of this type generally have a weight average molecular weight greater than about 100,000 as determined by gel permeation chromatography.
Polyamides which can be used in the present invention are known in the art. For instance, one type of polyamide which can be used is a block copolymer prepared from nylon 12 (polydodecanolactam) and polytetramethylene ether glycol. Such polyamide is commercially available from Elf Atochem under the designations Pebax 2533, 3533 and 5533.
The glycidyl group-containing acrylate copolymer can be grafted to the polyamide in a process which involves sufficiently dispersing the polyamide in an organic solvent selected so that the polyamide can be reacted to form the graft copolymer. The organic solvent is typically a non-polar aromatic solvent such as xylene, toluene or commercially available proprietary solvents, such as Aromatic 100, or mixtures thereof and is preferably selected so that the polyamide can be totally dispersed (i.e., dissolved) in the solvent. The preferred organic solvent is xylene. Although not critical, the polyamide is dispersed in an amount ranging from about 2 to about 25% by weight of the organic solvent.
The material which forms the graft copolymer with the polyamide can be added with the polyamide into the organic solvent, but is preferably added after the polyamide has been dispersed. As used in the present invention, the term “material” means a component or plurality of components that ca
Lu Szu-Ping
Norton Hiram A.
Prucnal Paul J.
Anderson Development Co.
Bissett Melanie
Burns Doane , Swecker, Mathis LLP
Seidleck James J.
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