Epoxy polysiloxane coating compositions with polyurethane-metal or organic based curing systems
Disclosed herein are epoxy-polysiloxane polymer coating compositions suitable for coating surfaces that provide excellent chemical, corrosion, or weather resistance. The epoxy-polysiloxane polymer coating compositions include polysiloxane and non-aromatic epoxide resins, and a cure system, wherein the combined composition reacts to form a cross-linked epoxy-polysiloxane polymer structure. The cure system can include at least a blend of metal or organic catalyst(s) and alkoxy functional aminosilane(s), and may further include a polyurethane, such as a silane terminated polyurethane. The metal catalyst may be coordinated with, or in close proximity to, the polyurethane, thus providing excellent hardening results at very low metal concentrations.
1 . An epoxy-polysiloxane polymer coating composition comprising:
(a) a polysiloxane;
(b) a non-aromatic epoxide resin; and
(c) a cure system comprising (i) a polyurethane coordinated with a metal catalyst or an organic catalyst, and (ii) an alkoxy functional aminosilane,
wherein the polyurethane comprises a silane terminated polyurethane.
2 . The composition according to claim 1 , wherein the metal catalyst comprises a zinc, manganese, zirconium, titanium, cobalt, iron, lead, bismuth, or tin catalyst.
3 . The composition according to claim 1 , wherein the metal catalyst comprises zinc amidine or dibutyltin dilaurate.
4 . The composition according to claim 1 , wherein the silane terminated polyurethane is an aminosilane capped polyurethane.
5 . The composition according to claim 1 , wherein the polyurethane coordinated with the metal catalyst (i) comprises a polyurethane prepolymer that is a reaction product of reactants comprising an aliphatic polyisocyanate, a diol, and the metal catalyst, wherein the metal catalyst comprises a zinc catalyst, a manganese catalyst, a zirconium catalyst, a titanium catalyst, a cobalt catalyst, an iron catalyst, a lead catalyst, a bismuth catalyst, a tin catalyst, or a combination thereof.
6 . The composition according to claim 5 , wherein the polyurethane coordinated with the metal catalyst (i) comprises the polyurethane prepolymer further reacted with an alkoxy functional silane different from the alkoxy functional aminosilane (ii) of the cure system.
7 . The composition according to claim 6 , wherein the alkoxy functional silane different from the alkoxy functional aminosilane (ii) of the cure system comprises an alkoxy functional amino silane or alkoxy functional silanol.
8 . The composition according to claim 1 , wherein the polysiloxane has the formula:
wherein
each R 1 is independently selected from a hydroxy group or an alkyl, aryl, or alkoxy group having up to six carbon atoms,
each R 2 is independently selected from hydrogen, or an alkyl or aryl group having up to six carbon atoms, and
n is selected so that the weight average molecular weight for the polysiloxane is 400 to 10,000 g/mol.
9 . The composition according to claim 1 , wherein the polysiloxane and non-aromatic epoxy resin are supplied in a ratio of 20:80 to 80:20.
10 . The composition according to claim 1 , wherein the non-aromatic epoxide resin has more than one 1,2-epoxide group per molecule and an epoxide equivalent weight of 100 to 5,000 g/mol.
11 . The composition according to claim 1 , wherein the alkoxy functional aminosilane of the cure system comprises a general formula
wherein
R 3 is a difunctional organic radical comprising an aryl, alkyl, dialkylaryl, alkoxyalkyl, alkylaminoalkyl, or cycloalkyl radical, and
each R 4 is independently selected from an alkyl, hydroxyalkyl, alkoxyalkyl, or hydroxyalkoxyalkyl group comprising less than six carbon atoms.
12 . The composition according to claim 1 , wherein the alkoxy functional aminosilane of the cure system comprises aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropyltripropoxysilane, aminoneohexyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltriethoxysilane, N-phenylaminopropyl trimethoxysilane, trimethoxysilylpropyl diethylene triamine, 3-(3-aminophenoxy) propyl trimethoxysilane, aminoethyl aminomethyl phenyl trimethoxysilane, 2-aminoethyl-3-aminopropyl-tris-2-ethylhexoxysilane, N-aminohexyl aminopropyl trimethoxysilane, or trisaminopropyl trismethoxyethoxysilane.
13 . The composition according to claim 1 , wherein the organic catalyst is selected from bicycloguanidine, an imidazole, an acid catalyst, an aliphatic or cyclic amine, a phosphonium salt, a phenolic acid or salt, a sulphonic acid or salt, a tertiary amine and a quaternary ammonium salt.
14 . The composition according to claim 1 , wherein the organic catalyst comprises tetrabutylammonium fluoride and/or 1,8-diazabicyclo[5.4.0]undec-7-ene.
15 . A coated substrate comprising a surface coated with the coating composition according to claim 1 , wherein the dry hard times for the coating composition on the substrate measured according to ASTM-D5895 at 21° C. are essentially the same at 20% and 60% relative humidity.
16 . The composition according to claim 1 , wherein the cure system comprises (a) a silane-terminated polyurethane and (b) an alkoxy functional aminosilane, wherein the silane-terminated polyurethane (a) comprises the reaction product of reactants comprising:
(i) a polyurethane prepolymer component comprising a reaction product of reactants comprising a polyisocyanate, a polyol, and a metal catalyst or an organic catalyst, and
(ii) an alkoxy functional silane different from the alkoxy functional aminosilane (b), wherein the metal catalyst is coordinated with the silane-terminated polyurethane.
17 . The composition according to claim 1 , wherein the polysiloxane (a) has the formula
wherein
each R 1 is independently selected from a hydroxy group or an alkyl, aryl, or alkoxy group having up to six carbon atoms,
each R 2 is independently selected from hydrogen, or an alkyl or aryl group having up to six carbon atoms, and
n is selected so that the molecular weight for the polysiloxane is 400 to 10,000 g/mol;
the non-aromatic epoxide resin (b) has more than one 1,2-epoxide group per molecule with an epoxide equivalent weight of 100 to 5,000 g/mol; and
the cure system (c) comprises 1,8-diazabicyclo[5.4.0]undec-7-ene and an alkoxy functional aminosilane.
18 . A method for coating a surface with a coating composition, the method comprising:
preparing a resin component comprising:
a polysiloxane having the formula
wherein,
each R 1 is independently selected from a hydroxy group or an alkyl, aryl, or alkoxy group having up to six carbon atoms,
each R 2 is independently selected from hydrogen or an alkyl or aryl group having up to six carbon atoms, and
where n is selected so that the molecular weight for the polysiloxane is 400 to 10,000 g/mol; and
a non-aromatic epoxide resin having more than one 1,2-epoxide group per molecule and an epoxide equivalent weight of 100 to 5,000 g/mol;
adding a cure system to the resin component to form a fully cured epoxy-modified polysiloxane coating composition, the cure system comprising (i) a polyurethane coordinated with a metal catalyst, and (ii) an alkoxy functional aminosilane; and
applying the coating composition to a surface of a substrate to be protected before the coating composition becomes fully cured.
19 . The composition according to claim 1 , wherein the metal catalyst or the organic catalyst is included in the composition at from 1 ppm to 1000 ppm.