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
1999-11-11
2001-10-02
Wilson, Donald R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S111000, C525S113000, C525S153000, C525S154000, C525S155000, C525S157000, C525S159000, C525S330500, C525S342000, C525S374000, C525S379000
Reexamination Certificate
active
06297320
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a multi-component curable composition which is reactive upon admixing of the components and which comprises:
(i) an acrylic polymer having acetoacetoxy functionality; and
(ii) an acetoacetoxy functional derivative of a low molecular weight polyol; and
(iii) a crosslinking component comprising at least one imine functional compound having an average of at least two imine groups per molecule which are reactive with acetoacetoxy functionality; and
(iv) optionally, a polyamine having an average of at least two primary amine groups per molecule.
The curable compositions of this invention are especially useful as coatings, particularly primers. The reactive coatings of this invention can be cured at room temperature or force dried at temperatures ranging up to about 350° F. The combination of acetoacetoxy functional materials and imine functional materials provide fast reacting, durable coatings having excellent adhesion.
2. Description of the Prior Art
The use of acetoacetoxy functional materials in Michael-type reactions is known in the art. For example, U.S. Pat. No. 3,668,183 teaches the reaction of polyacetoacetates and polyimines. European Patent Application 744,450 teaches reactive compositions of acetoacetates and multi-functional amines.
The prior art has not, however, taught the combination of an acetoacetoxy functional acrylic polymer and an acetoacetoxy functional derivative of a low molecular weight polyol, and an imine functional material and, optionally, a polyamine to provide low temperature curing coatings having excellent durability, adhesion and performance.
A BRIEF SUMMARY OF THE INVENTION
This invention involves a multi-component curable composition which comprises:
(a) a first component comprising:
(i) an acrylic polymer having acetoacetoxy functionality; and
(ii) an acetoacetoxy functional derivative of a low molecular weight polyol; and
(b) a crosslinking component comprising at least one imine functional compound.
In one preferred formulation, the curable composition also comprises an amine functional compound having an average of at least two primary amine groups per molecule. Additionally, in some applications, it may be preferable to incorporate within the curable composition an organosilane material for enhanced performance and adhesion properties.
It is especially preferred to utilize the curable composition of this invention in combination with about 5 to about 80%, and especially 5 to about 50% by weight of an inert solvent, such as esters, ketones, aromatic and aliphatic hydrocarbons, etc. It is convenient to provide the coating composition as a multi-component system which is reactive upon mixing of the components. Especially preferred is a two-package system wherein the acetoacetoxy functional materials are combined in one package and the imine compound and, optionally, the amine compound are provided in a second package. The two packages can be mixed together to provide the curable coatings immediately prior to application.
Accordingly, it is an object of this invention to provide improved curable compositions having excellent reactivity at low temperatures. It is a further object of this invention to provide coating compositions which may be utilized as primers, topcoats, or other coating compositions. Another object of this invention is to provide an improved two-package coating composition wherein one package comprises acetoacetoxy functional materials and the other package comprises imine functional materials and, optionally, amine functional materials. A further object of this invention is to provide improved coating compositions which can be cured at room temperature or forced dried at elevated temperatures. These and other objects of the invention will become apparent from the following discussions.
DETAILED DESCRIPTION OF THE INVENTION
1. Acrylic Polymers Having Acetoacetoxy Functionality
The acetoacetoxy functional acrylic polymers useful in this invention are those having an average of at least two pendant acetoacetoxy groups per molecule. The polymers can be conveniently prepared by addition polymerization of one or more unsaturated monomers. One practical approach to preparing these polymers involves the polymerization of acetoacetate functional unsaturated monomers, typically along with one or more other unsaturated copolymerizable monomers. One especially preferred acetoacetate functional monomer due to its reactivity and commercial availability, is acetoacetoxyethylmethacrylate. Other unsaturated monomers that are useful for introducing acetoacetate functional groups include acetoacetoxyethylmethacrylate, acetoacetoxy propylmethacrylate, allylacetoacetate, acetoacetoxybutylmethacrylate, 2,3-di(acetoacetoxy)propylmethacrylate, etc. In general, it is practical to convert polymerizable hydroxy functional monomers into acetoacetates by direct reaction with diketene or other suitable acetoacetyl converting agent. See, for example,
Journal of Coating Technology
, vol. 62, p. 101 (1990) “Comparison of Methods for the Preparation of the Acetoacetylated Coating Resins”.
Alternatively, a hydroxy-functional polymer can be prepared by the free radical polymerization of hydroxy-functional unsaturated monomers and the resultant hydroxy-functional polymer can be converted to acetoacetoxy functional groups by direct reaction with diketene, by transesterification with suitable alkyl acetoacetates such as t-butylacetoacetate, or with the thermal reaction of 2,2,6-trimethyl-4H-1,3-dioxin-4-one.
The acetoacetoxy functional monomer will be present at a level of at least one percent by weight of the entire monomer mixture for the acrylic polymer, and typically will comprise from 10 to about 75 %, and preferably 25 to about 50% of the entire monomer mixture. Typically the acetoacetoxy functional monomers would be copolymerized with one or more monomers having ethylenic unsaturation such as:
(i) esters of acrylic, methacrylic, crotonic, tiglic, or other unsaturated acids such as: methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, ethylhexyl acrylate, amyl acrylate, 3,5,5-trimethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobornyl methacrylate, dimethylaminoethyl methacrylate, ethyl tiglate, methyl crotonate, ethyl crotonate, etc.;
(ii) vinyl compounds such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl benzoate, vinyl m-chlorobenzoate, vinyl p-methoxybenzoate, vinyl alpha-chloroacetate, vinyl toluene, vinyl chloride, etc.;
(iii) styrene-based materials such as styrene, alpha-methyl styrene, alpha-ethyl styrene, alpha-bromo styrene, 2,6-dichlorostyrene, etc.;
(iv) allyl compounds such as allyl chloride, allyl acetate, allyl benzoate, allyl methacrylate, etc.;
(v) other copolymerizable unsaturated monomers such as acrylic acid, methacrylic acid, 2-hydroxy ethyl acrylate, acrylonitrile, methacrylonitrile, dimethyl maleate, isopropenyl acetate, isopropenyl isobutyrate, acrylamide, methacrylamide, and dienes such as 1,3-butadiene, etc.
The polymers are conveniently prepared by conventional free radical addition polymerization techniques. Frequently, the polymerization will be initiated by conventional initiators known in the art to generate a free radical such as azobis(isobutyronitrile), cumene hydroxperoxide, t-butyl perbenzoate, t-butyl peroctoate, t-amyl peroctoate, di-t-butyl peroxide, etc. Typically, the monomers are heated in the presence of the initiator and an inert solvent at temperatures ranging from about 35° C. to about 200° C. and especially 75° C. to 150° C., to effect the polymerization. The molecular weight of the polymer can be controlled, if desired, by the monomer and initiator selection, rate of addition, reaction temperature and time, and/or the use of chain transfer agents as is well known in the art. The number average molecular weight of the acetoacetoxy functional acrylic polymer will typically be at least 1,000 as determined by GPC. Ty
D'Errico Michael J.
Ding Hong
Leonard David P.
Tang Weilin
Katterle Paul R.
McDonald Robert E.
The Sherwin-Williams Company
Tsang Vivien Y.
Wilson Donald R.
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