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
2001-09-27
2003-06-24
Mullis, Jeffrey (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...
C525S09200D, C525S09200D, C525S093000, C525S094000
Reexamination Certificate
active
06583223
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to thermosetting coating compositions containing flow control agents. Particularly, the invention relates to such compositions containing flow control agents that are low surface tension (meth)acrylate containing block (co)polymer compositions prepared in a controlled radical (co)polymerization process.
BACKGROUND OF THE INVENTION
Coating compositions, liquid and powder coatings for example, are used in a wide variety of applications, including for example, the automotive, appliance and industrial markets. Coatings are often used to provide decorative qualities and/or corrosion protection to the substrates over which they are applied. Correspondingly, applied coatings are typically required to have at least a continuous defect free surface. The automotive industry has particularly strict requirements as to the smoothness of the coatings that are used, as is the case with automotive clear topcoat compositions.
Coating compositions typically contain a flow control agent (also referred to as a flow modifier) to improve the appearance of the cured coating. Flow control agents have surface active properties and are thought to improve the appearance of a cured coating by altering the flow and leveling of the applied coating during its cure cycle. Flow control agents containing functional groups, such as carboxylic acid groups and/or hydroxyl groups, are known, and in addition to enhancing appearance, can also improve adhesion of the coating to the substrate over which it is applied, and/or improve the adhesion or compatibility of a subsequently applied coating.
Coating compositions are typically required to provide optimum properties, such as appearance and/or corrosion resistance, at a minimum film thickness. For example, in the automotive industry, clear topcoats are typically required to have cured film thickness of no greater than 50 microns (2 mils). Advantages associated with coatings applied at lower film thickness include, for example, reduced material costs and weight gain of the coated ware, which is particularly desirable in the aircraft industry. However, as the film build of an applied coating composition is decreased, the appearance of the resulting cured coating typically diminishes, for example, as evidence by lower measured gloss values.
In addition to the application of coatings at lower film builds, investigation and development in recent years has been directed toward reducing the environmental impact of coating compositions, in particular, the associated emissions into the air of volatile organics during their use. Accordingly, interest in coatings having lower volatile organic content (VOC), for example powder coatings and high solids coatings, has been increasing. Powder coating compositions are free flowing particulate compositions that are essentially free of solvents. The appearance of powder coatings typically degrades rather precipitously with decreasing film thickness, for example at film thickness less than 75 microns (3 mils), and in particular at film thickness less than 50 microns (2 mils). In the absence of solvents that can enhance the flow and leveling of an applied coating, a flow control agent is a critical component in the majority of powder coating compositions.
A wide variety of radically polymerizable monomers, such as methacrylate and acrylate monomers, are commercially available and can confer to a polymer or copolymer (hereinafter, collectively referred to as (co)polymer) produced therefrom a wide range of properties including, for example, hydrophilic and hydrophobic properties or the ability to interact with crosslinkers or to self crosslink. The use of conventional, i.e., non-living or free-radical (co)polymerization methods to synthesize (co)polymers provides little control over molecular weight, molecular weight distribution and, in particular, (co)polymer chain structure.
U.S. Pat. Nos. 5,807,937, 5,789,487 and 5,763,548, and International Patent Publication Nos. WO 98/40415, WO 98/01480, WO 97/18247 and WO 96/30421 describe a radical polymerization process referred to as atom transfer radical polymerization (ATRP). The ATRP process is described as being a living radical polymerization that results in the formation of polymers having predictable molecular weight and molecular weight distribution. The ATRP process also is described as providing highly uniform products having controlled structure (i.e., controllable topology, composition, etc.). The '937 and '548 patents also describe (co)polymers prepared by ATRP, which are useful in a wide variety of applications including, for example, dispersants and surfactants.
A number of initiators and macroinitiator systems are known to support ATRP polymerization. These initiators are described, for example, in U.S. Pat. Nos. 5,807,937 and 5,986,015. U.S. Pat. No. 5,807,937 discloses a number of initiators, including halide groups attached to a primary carbon. Halides attached to primary carbons are known as efficient initiators in ATRP processes. U.S. Pat. No. 5,986,015 discloses polymer macroinitiators prepared from vinyl chloride and another monomer, and their use in preparing graft (co)polymers with low polydispersity.
It also is desirable to have multiple initiation sites on an initiator in order to create unique branched (co)polymer structures, such as star (co)polymers. Such (co)polymers have a variety of practical applications, including as a resin component of a film-forming coating composition. These unique (co)polymers also will find use in the health care or cosmetics industries for instance, as materials for bioengineering. (Co)polymers of low polydispersity (Mw/Mn) are also desirable not only for their structural regularity and related usefulness in producing defined block and multiblock (co)polymer structures, but for their unique physical characteristics. For instance, a star (co)polymer having low polydispersity is a high molecular weight material having low viscosity in solution.
Fluorocarbon containing copolymers have been used as binding agents, wetting agents, surfactants and coatings in a variety of applications. Fluorocarbon containing copolymers made by conventional free radical polymerization methods have inevitable shortcomings as it is difficult to control their molecular weight distribution and composition in order to optimize the desired physical properties. For example, the common problem of poor control of molecular weight distribution can result in a high molecular weight “tail”, which can give poor flow properties due to the high viscosity that results. Conversely, poor binding properties can result when too much of a low molecular weight “tail” is present.
U.S. Pat. Nos. 5,397,669 and 5,283,148 disclose an electrostatic liquid toner imaging process that uses a liquid toner comprised of a perfluorinated solvent and a polymer containing highly fluorinated units. The polymer was prepared using traditional free radical polymerization techniques and was characterized as having a polydispersity of 4.
U.S. Pat. No. 3,407,247 discloses fluoro olefin block copolymers prepared by traditional fee radical polymerization of a (meth)acrylic monomer to form a prepolymer which is subsequently reacted with a fluoro olefin. While block copolymers were formed to some extent, the resulting block copolymers inherently vary widely in block length and molecular weight leading to a wide compositional variation and distribution as well as a large polydispersity.
U.S. Pat. No. 5,026,621 discloses a toner for electrophotography which includes a block copolymer binder resin comprised of a fluoroalkyl acryl ester block and a fluorine-free vinyl or olefin monomer block. The block copolymers were made using a unique peroxypolyether initiator, which is then used to initiate a first free radical polymerization, forming a peroxypolymer, which initiates a second free radical polymerization. While block copolymers are formed, the resulting block copolymers inherently vary widely in block length and molecular weight leading to a wi
Barkac Karen A.
Coca Simion
Goetz Jonathan D.
Humbert Kurt A.
Schimmel Karl F.
Mullis Jeffrey
PPG Industries Ohio Inc.
Uhl William J.
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