Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1999-05-28
2001-08-28
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S014000, C528S018000, C528S019000, C528S026000, C528S028000, C528S038000, C528S039000, C106S287110, C106S287150, C427S387000
Reexamination Certificate
active
06281321
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a coating composition capable of being cured at ambient temperature and useful as a protective coating for steel structures and/or as a weather-resistant exterior coating.
BACKGROUND OF THE INVENTION
Curable coating compositions based on a silane or siloxane containing at least two alkoxy groups bonded to silicon by Si—O—C bonds are known for example from U.S. Pat. No. 3,917,648, U.S. Pat. No. 4,113,665, U.S. Pat. No. 3,776,881, U.S. Pat. No. 5,275,645 and U.S. Pat. No. 5,292,799.
U.S. Pat. No. 4,250,074 describes the production of coatings of modified epoxy polymers with improved resistance to solvent, acid and base by forming an interpenetrating polymer network (IPN) of a polymerised epoxy resin network intertwined with a polysiloxane network formed by the hydrolytic polycondensation of silane groups. This is achieved by the simultaneous polymerisation, at substantially balanced reaction rates, of a mixture of epoxy resin and silane groups to form the two intertwined networks extending throughout the coating. An amine curing agent forms the epoxy network, and water distributed throughout the mixture causes the hydrolytic polycondensation of the silane groups. A preferred method for preparing the IPN is to react epoxy resin with an aminosilane capable of both hydrolytic polycondensation of the silane moiety and amine addition of the oxirane rings of the epoxy resin.
WO-A-96/16109 describes a fully cured non-interpenetrating network epoxy-modified polysiloxane coating composition prepared by combining water, a non-aromatic epoxide resin having more than one 1,2-epoxy group per molecule with an epoxide equivalent weight in the range of from 100 to about 500, a polysiloxane , an organo-oxysilane, a hardener component comprising a difunctional amine and/or an aminosilane, and a pigment or aggregate component. U.S. Pat. No. 4,678,835 describes a coating composition containing an ungelled reaction product of (i) at least 2 percent by weight of an amine having in a molecule thereof at least one amino hydrogen atom and at least one silicon atom directly bonded to a hydrolysable group, (ii) at least 4 percent by weight of a material containing at least one epoxide group, and (iii) a material selected from vinyl alkoxysilanes, non-functional organosilanes, organosilicates and partial hydrolysis products thereof.
U.S. Pat. No. 4,698,406 describes a curable silicone composition comprising (i) an amine-functional organopolysiloxane and (ii) an acryl-functional organopolysiloxane selected from acryloxy-, methacryloxy or acrylamide-functional organopolysiloxanes.
U.S. Pat. No. 4,429,082 describes an anhydrous ungelled reaction product characterised in having a non-vinyl addition back-bone being essentially acrylyl-free, having a silicon content of up to about 12 percent, and derived from the reaction of (a) a condensation product having at least 2 amine-reactive acrylyl residues per molecule and (b) an amino silane.
EP-A-725088 describes a process for post-reacting polymers having acetoacetate functional groups comprising polymerising a monomer mixture comprising an acetoacetate-functional monomer and a vinyl monomer, and then after polymerisation post-reacting the acetoacetate-functional polymer product with an amino-functional silane.
SUMMARY OF THE INVENTION
A curable coating composition according to the present invention has a binder comprising a compound or polymer (A) containing at least one primary or secondary amine group and a compound or polymer (B) containing at least one ethylenically unsaturated double bond activated by an adjacent electron-withdrawing group. The compound or polymer (B) contains at least two activated ethylenically unsaturated double bonds if the compound or polymer (A) contains only one primary or secondary amine group. The coating composition is characterised in that either (A) or (B) contains at least one silicon-bonded alkoxy group in its molecule and the composition additionally contains a polymer (C) containing at least two silicon-bonded alkoxy groups.
When the coating composition of the invention is coated on a substrate and allowed to cure at ambient (or higher) temperature and humidity (for example 5 to 45° C. and to 90% relative humidity), the binder cures both by Michael-type addition reaction of the amine group of (A) with the activated ethylenically unsaturated double bond of (B) and by hydrolysis and condensation of the Si—O—C bonds of (C) and whichever of (A) and (B) contains a silicon-bonded alkoxy group in its molecule, forming a flexible adherent coating film resistant to heat and weathering. The said component (A) or (B) containing a silicon-bonded alkoxy group as well as either an amine group or an activated double bond can take part in crosslinking reactions with all the components of the binder.
In one preferred coating composition according to the invention the compound or polymer (A) is a silane or siloxane containing at least two alkoxy groups bonded to silicon by Si—O—C bonds and also containing at least one primary or secondary amine group. Such a silane or siloxane (A) can be an aminoalkyl silane containing at least two, preferably three, alkoxy groups bonded to silicon and/or an organopolysiloxane containing both aminoalkyl and Si-bonded alkoxy groups. Most preferably, for finish coatings having high gloss and high weathering resistance, the polymer (C) is a polyorganosiloxane and the silane or siloxane (A) is an aminoalkyl silane containing at least two alkoxy groups bonded to silicon. Such aminoalkyl silanes are commercially available and have good reactivity both in Michael-type reactions and in condensation of alkoxysilyl groups. Aminoalkyl-substituted alkoxy-terminated poly-diorganosiloxanes are also effective but are not generally available commercially.
Thus, according to another aspect of the invention a curable coating composition comprises a polyorganosiloxane (C) containing at least two alkoxy groups bonded to silicon and an aminoalkyl silane (A) containing at least one alkoxy group bonded to silicon and is characterised in that the composition additionally contains a compound or polymer (B) containing at least two ethylenically unsaturated double bonds each activated by an adjacent electron-withdrawing group, whereby the coating is capable of curing at ambient temperature and humidity both by hydrolysis and condensation of the Si—O—C bonds of the polyorganosiloxane (C) and of the aminoalkyl silane (A) and by Michael-type addition reaction of the amine group of the aminoalkyl silane (A) with the activated ethylenically unsaturated double bonds of (B).
DETAILED DESCRIPTION OF THE INVENTION
Examples of preferred aminoalkyl silanes are primary amines such as 3-aminopropyl triethoxy silane,3-aminopropyl trimethoxy silane, 3-aminopropyl methyl dimethoxysilane or 3-aminopropyl methyl diethoxy silane, primary secondary amines such as N-(2-aminoethyl)-3-aminopropyl trimethoxy silane, secondary amines such as N-methyl- or N-phenyl-3-aminopropyl trimethoxy silane, condensed aminoalkyl silanes such as bis(3-aminopropyl) tetramethoxy or tetraethoxy disiloxane NH
2
(CH
2
)
3
—Si(OCH
3
)
2
—O—(CH
3
O)
2
Si—(CH
2
)
3
NH
2
, polyglycolether-modified aminosilanes such as that sold under the Trademark “Dynasylan 121” and triamino functional propyl trimethoxy silanes such as “Dynasylan TRIAMO” available from Hüls AG. Similar silanes having two or three silicon atoms can be used.
The polymer (C) having at least two Si-bonded alkoxy groups used in the first aspect of the invention is preferably a polyorganosiloxane, as is the polymer (C) used in the second aspect, for example of the formula:
where each of the groups R
1
is an alkyl group, preferably having 1 to 6 carbon atoms, each R is an alkyl, aryl or alkoxy group and is preferably an alkyl group having 1 to 6 carbon atoms, or a phenyl group, each R
2
is an alkoxy group, preferably having 1 to 6 carbon atoms, a hydrocarbyl group such as an alkyl (preferably having 1 to 6 carbon atoms) or phenyl group or a branching group of the formula:
Andrews Adrian Ferguson
Birkert Christopher Robin
Kelly Sarah Anne Mackie
Akzo Nobel N.V.
McGillycuddy Joan M.
Moore Margaret G.
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