Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-12-22
2002-09-03
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S450000, C524S588000, C524S591000, C524S838000, C524S839000, C106S287110, C106S287130
Reexamination Certificate
active
06444325
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to two-component coating compositions containing adhesion promoters based on aspartate silanes and to their use for preparing coatings having improved adhesion, especially wet adhesion.
2. Description of the Prior Art
Two-component coating compositions containing a polyisocyanate component and an isocyanate-reactive component, preferably a polyhydroxyl compound, are known and can be used to coat a variety of substrates. One of the deficiencies of these coatings is that they do not possess adequate wet adhesion, which is a critical requirement for coatings used underground, e.g., as coatings for oil and gas transmission pipelines.
Coatings previously used for this application have suffered from other problems. Asphaltic coatings are biodegradable and not suitable for long term (20 to 50 years) use. Coal tar coatings are not used because of toxicity. Liquid epoxy coatings require application temperatures of >55° C. and cure too slowly for production use in the field. Polyolefin coatings do not maintain adhesion under cathodic protection.
High performance coatings are needed. Known polyurethane coatings have the ability to be rapidly cured, but do not have the wet adhesion necessary for this application.
Accordingly, it is an object of the present invention to provide coating compositions that are suitable for preparing coatings having improved adhesion, especially wet adhesion.
This object may be achieved with the two-component coating compositions according to the present invention which contain certain silane adhesion promoters. The silane compounds are prepared by the reaction of compounds containing one or more isocyanate groups with aspartate silanes as described hereinafter.
The adhesion promoters used in the compositions of the present invention are described in U.S. Pat. No. 5,908,948. However, the compounds disclosed in the patent are used as coating compositions; their use as adhesion promoters to improve the wet adhesion of two-component coating compositions is not disclosed.
The use of silanes as adhesion promoters has been suggested. A product information bulletin from OSi Specialties discloses the use of several silane compounds as adhesion promotors for various coating resins, including polyurethanes. However, as shown by the comparison examples of the present application, most of the disclosed silane compounds were not very effective for improving the adhesion, especially the wet adhesion, of two-component polyurethane coating compositions. Accordingly, it is apparent that the reference to polyurethanes was a reference to one-component, fully reacted polyurethanes.
It must be regarded as surprising and unexpected that the adhesion promoters according to the present invention provide good adhesion, especially wet adhesion, since they contain less silane per unit weight than the silane compounds disclosed in the OSi bulletin when added in similar amounts. In addition, because they contain less silane the adhesion promoters according to the invention are less costly, thereby reducing the cost of the resulting coating compositions.
SUMMARY OF THE INVENTION
The present invention relates to two-component coating compositions containing
a) a polyisocyanate component,
b) an isocyanate-reactive component and
c) 0.1 to 20 wt. %, based on the weight of components a) and b), of a compound containing alkoxysilane groups and urea groups corresponding to the formula
wherein
X represents identical or different organic groups which are inert to isocyanate groups below 100° C., provided that at least one of these groups is an alkoxy group,
Y represents a linear or branched alkylene group containing 1 to 8 carbon atoms,
R represents the residue obtained by removing the isocyanate groups from a monoisocyanate or a polyisocyanate,
R
1
and R
2
are identical or different and represent organic groups which are inert to isocyanate groups at a temperature of 100° C. or less,
R
3
and R
4
are identical or different and represent hydrogen or organic groups which are inert to isocyanate groups at a temperature of 100° C. or less, and
n has a value of 1 to 6.
The present invention also relates to substrates coated with these coating compositions, in particular metal substrates.
DETAILED DESCRIPTION OF THE INVENTION
The compounds containing alkoxysilane groups that are used as component c) in the compositions according to the present invention are based on the reaction products of compounds containing one or more isocyanate groups and compounds containing alkoxysilane groups and aspartate groups (secondary amino groups) corresponding to formula II)
The compounds of formula II are prepared by reacting aminoalkyl alkoxysilanes corresponding to formula III)
H
2
N—Y—Si—(X)
3
(III)
with maleic or fumaric acid esters corresponding to formula IV)
R
1
OOC—CR
3
═CR
4
—COOR
2
(IV)
In formulas I to IV
X represents identical or different organic groups which are inert to isocyanate groups below 100° C., provided that at least one of these groups is an alkoxy group, preferably alkyl or alkoxy groups having 1 to 4 carbon atoms and more preferably alkoxy groups;
Y represents a linear or branched alkylene group containing 1 to 8 carbon atoms, preferably a linear group containing 2 to 4 carbon atoms or a branched group containing 5 to 6 carbon atoms, more preferably a linear group containing 3 carbon atoms,
R represents the residue obtained by removing the isocyanate groups from a monomeric polyisocyanate, a polyisocyanate adduct or an NCO prepolymer, preferably a monomeric polyisocyanate or a polyisocyanate adduct,
R
1
and R
2
are identical or different and represent organic groups which are inert to isocyanate groups at a temperature of 100° C. or less, preferably alkyl groups having 1 to 9 carbon atoms, more preferably methyl, ethyl or butyl groups,
R
3
and R
4
are identical or different and represent hydrogen or organic groups which are inert towards isocyanate groups at a temperature of 100° C. or less, preferably hydrogen, and
n has a value of 1 to 6, preferably 1 to 4.
With regard to the preceding definitions R
1
and R
2
may be different when the compounds of formula II) are prepared from mixed maleates, such as methylethyl maleate. In addition, one R
1
may be different from another R
1
. For example, when a mixture of compounds containing alkoxysilane groups (e.g. those prepared from dimethyl and diethyl maleate) is used to prepare the compounds of formula I ), one pair of R
1
and R
2
groups will be methyl and the other will be ethyl.
Especially preferred are compounds in which X represents methoxy, ethoxy groups or propoxy groups, more preferably methoxy or ethoxy groups and most preferably methoxy groups, and Y is a propylene group.
Examples of suitable aminoalkyl alkoxysilanes of formula III include 2-aminoethyl-dimethylmethoxysilane; 6-aminohexyl-tributoxysilane; 3-aminopropyl-trimethoxysilane; 3-aminopropyl-triethoxysilane; 3-aminopropyl-methyidiethoxysilane; 5-aminopentyl-trimethoxysilane; 5-aminopentyl-triethoxysilane and 3-aminopropyl-triisopropoxysilane. 3-aminopropyl-trimethoxysilane and 3-aminopropyl-triethoxysilane are particularly preferred.
Examples of optionally substituted maleic or fumaric acid esters suitable for use in the preparation of polyaspartates II) include dimethyl, diethyl, dibutyl (e.g., di-n-butyl), diamyl, di-2-ethylhexyl esters, the previously discussed mixed maleates and fumarates, and the corresponding maleic or fumaric acid esters substituted by methyl in the 2- and/or 3-position. The dimethyl, diethyl and dibutyl esters of maleic acid are preferred and the diethyl and dibutyl esters are especially preferred.
The reaction of primary amines with maleic or fumaric acid esters to form aspartates is disclosed in U.S. Pat. Nos. 5,126,170, 5,236,741 and 5,364,955 (the disclosures of which are herein incorporated by reference). The compounds of formula III are colorless to pale yellow. They may be reacted with polyisocyanates to form the compound
Hergenrother P. Richard
Roesler Richard R.
Bayer Corporation
Dawson Robert
Feely Michael J
Gil Joseph C.
Roy Thomas W.
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