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
2000-05-03
2003-07-15
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...
C525S064000, C525S065000, C525S066000, C525S191000, C525S192000, C525S214000, C525S227000
Reexamination Certificate
active
06593423
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an adhesion promoting agent, to coating compositions utilizing the adhesion promoting agent for coating thermoplastic and thermosetting polymeric materials, and to the coated polymeric materials.
BACKGROUND OF THE INVENTION
Polymeric materials, such as thermoplastic polyolefin (TPO) and reaction injected molding urethane (RIM), are useful in many applications, such as automobile parts and accessories, containers, household appliances and other commercial items. It is often desirable to coat articles made from such polymeric materials with organic coating compositions to decorate or protect them from degradation when exposed to atmospheric weathering conditions such as sunlight, moisture, heat and cold. To achieve longer lasting and more durable parts, it is important for the coatings to be tightly adhered to the surface of the article.
Polymeric substrates made from a variety of thermoplastic and thermosetting materials have widely varying surface properties, including surface tension, roughness and flexibility, which make strong adhesion of organic coatings difficult, particularly after aging or environmental exposure of the coated polymeric materials. To facilitate adhesion of organic coatings to polymeric substrates, the substrate can be pretreated using an adhesion promoter layer or tie coat, e.g., a thin layer about 0.25 mils (6.35 microns) thick, or by flame or corona pretreatment. For automotive applications, it is important that the coating composition and/or adhesion promoter layer is resistant to fuel damage, i.e. maintains good adhesion of the coating to the substrate even if fuel is accidentally spilled onto the coated substrate.
Typically, adhesion promoter layers used on TPO surfaces contain chlorinated polyolefins, some examples of which are described in U.S. Pat. Nos. 4,997,882; 5,319,032; and 5,397,602, herein incorporated by reference. However, chlorinated polyolefins provide some processing limitations. For example, while chlorinated polyolefins are soluble in aromatic solvents, THF, and chlorinated solvents, they are not readily soluble in solvents such as alcohols, ketones, or esters which are preferred for use in coating compositions. Further, conventional chlorinated polyolefins typically have no curing or crosslinking sites and therefore must be used at high molecular weights to have a positive effect on coating strength.
Coating compositions that exhibit acceptable adhesion directly to polymeric materials, such as TPO and RIM, without the use of separate adhesion promoter layers or tie coats have been developed. For example, polyolefin diols have been used in coating compositions to improve adhesion to polymeric substrates without the use of separate adhesion promoter layers or tie coats. For example, U.S. Pat. No. 6,001,469, herein incorporated by reference, discloses a coating composition containing a saturated polyhydroxylated polydiene polymer having terminal hydroxyl groups.
U.S. Pat. No. 5,863,646, herein incorporated by reference, discloses a liquid adhesion promoting coating composition having a blend of a saturated polyhydroxylated polydiene polymer and a chlorinated polyolefin.
Coating compositions having reacted adhesion promoters have also been developed. For example, U.S. Pat. No. 5,135,984 discloses a coating composition having an adhesion promoting material obtained by reacting a chlorinated polyolefin, maleic acid anhydride, acryl or methacryl modified hydrogenated polybutadiene containing at least one acryloyl group or methacryloyl group per unit molecule, and organic peroxide.
JP 6-16746 discloses a resin coating composition having either a polydiene and acryl-based oligomer or a polyester-based oligomer grafted onto a chlorinated polyolefin.
While these known adhesion promoting compositions are generally acceptable for commercial applications, they tend to either have good adhesion to polymeric substrates with poor to moderate fuel resistance; good fuel resistance but with commercially acceptable adhesion to only a narrow range of polymeric substrate types; or good adhesion and good fuel resistance but only at high levels of chlorinated polyolefin resulting in high VOC.
It would be desirable to provide an adhesion promoting agent that could be used either in an adhesion promoter layer or as an ingredient in a coating composition that improves coating adhesion to polymeric substrates and also provides adequate fuel resistance for automotive applications.
SUMMARY OF THE INVENTION
An adhesion promoting agent of the invention comprises a graft copolymer comprising (i) a halogenated polyolefin polymer having at least one reactive functionality, and (ii) a substantially saturated hydrocarbon polymer having more than one reactive functionality, at least one reactive functionality of the hydrocarbon polymer being reactive with the reactive functionality of the halogenated polyolefin.
An adhesion promoting agent for promoting the adhesion of a coating onto a surface of a polymeric substrate comprises a graft copolymer comprising (i) a chlorinated polypropylene polymer having at least one reactive functionality selected from the group consisting of anhydride, carboxylic acid, hydroxyl, epoxy, and isocyanate; and (ii) a substantially saturated polybutadiene polymer having more than one reactive functionality. At least one reactive functionality of the polybutadiene polymer is reactive with the reactive functionality of the chlorinated polypropylene polymer and is selected from the group consisting of hydroxyl, amine, carboxylic acid, epoxy, and isocyanate.
A coating composition of the invention comprises (a) at least one crosslinkable film-forming material and (b) an adhesion promoting agent. The adhesion promoting agent comprises a graft copolymer comprising (i) a halogenated polyolefin polymer having at least one reactive functionality; and (ii) a substantially saturated hydrocarbon polymer having more than one reactive functionality, at least one reactive functionality of the hydrocarbon polymer being reactive with the reactive functionality of the halogenated polyolefin.
A coated article of the invention comprises a polymeric substrate and a coating deposited over at least a portion of the substrate. The coating is formed from a coating composition comprising (a) at least one crosslinkable film-forming material; and (b) an adhesion promoting agent. The adhesion promoting agent comprises a graft copolymer comprising (i) a halogenated polyolefin polymer having at least one reactive functionality; and (ii) a substantially saturated hydrocarbon polymer having more than one reactive functionality, at least one reactive functionality of the hydrocarbon polymer being reactive with the reactive functionality of the halogenated polyolefin.
A method of promoting the adhesion of a coating to a polymeric substrate comprises applying a coating composition to a surface of a polymeric substrate, the coating composition comprising an adhesion promoting agent comprising a graft copolymer comprising (i) a halogenated polyolefin polymer having at least one reactive functionality; and (ii) a substantially saturated hydrocarbon polymer having more than one reactive functionality, at least one reactive functionality of the hydrocarbon polymer being reactive with the reactive functionality of the halogenated polyolefin polymer.
The present invention also provides polymeric articles coated with the coating compositions of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Other than in the operating examples or where otherwise specified, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”.
As used herein, the term “polymer” is meant to refer to oligomers and both homopolymers and copolymers. Any numeric references to amounts, unless otherwise specified, are “by weight”. Molecular weight quantities, whether Mn or Mw, are those determinable from gel permeation ch
Kondos Constantine A.
Martz Jonathan T.
Nakajima Masayuki
Altman Deborah M.
Mullis Jeffrey
PPG Industries Ohio Inc.
Uhl William J.
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