Hybrid coating compositions

Details Hybrid coating compositions Hybrid coating compositions

1999-11-24

2001-09-11

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S025000, C528S038000, C528S039000, C528S044000, C428S447000, C428S423100, C106S287110

Reexamination Certificate

active

06288198

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to coating compositions containing aliphatic polyisocyanate-aminosilane adducts and hydrolyzable silanes, and to substrates coated with these compositions.
2. Description of the Prior Art
The paint industry requires sophisticated coatings, e.g., in the automobile industry, which possess an ideal combination of very good mechanical properties, such as very high hardness and abrasion resistance, and also excellent flexibility and very good chemical properties, such as solvent and chemical resistance.
It is known that purely inorganic coating compositions based on a siloxanes, which have been produced by reacting hydrolyzable silane groups with water or dehydrating agents, are distinguished by high scratch resistance and chemical resistance. A generally known process for producing these purely inorganic coatings is the sol-gel Eprocess, which is described in detail by C.J. Brinker and W. Scherer in “Sol-gel science: The Physics and Chemistry of Sol-gel Processing”, Academic Press, New York (1990). A severe disadvantage of these purely inorganic coatings is that they are brittle and prone to stress cracks. Therefore, purely inorganic coatings are not suitable for flexible substrates.
Various attempts are known from the literature for combining the positive properties of purely inorganic coatings with the properties of organic coatings. An overview of the so-called inorganic-organic hybrid coating compositions is found in J. Mater. Chem. 6 (1996) 511. Specific combinations are disclosed in U.S. Pat. No. 5,378,790, U.S. Pat. No. 5,344,712, U.S. Pat. No. 5,316,855, EP-A 565,044, EP-A 505,737 and in DE-A 4,020,316. However, none of these prior art coating compositions provides to the full extent the combination of properties required by the paint industry.
It is an object of the present invention to provide a coating composition that exhibits an improved balance between high hardness, abrasion resistance and chemical resistance on the one hand and high flexibility on the other.
Reaction products of aminosilanes with polyisocyanates are known (see e.g. “Adhesives Age”, 5/1995, p. 30 ff.). Such moisture curing, alkoxy-silane-terminated polyurethanes are used increasingly in flexible sealing and adhesive materials curing at room temperature U.S. Pat. No. 5,700,868, U.S. Pat. No. 4,625,012, U.S. Pat. No. 4,474,933, U.S. Pat. No. 3,979,344, DE-A 4,234,325, DE-A 2,155,259). However, none of these literature references describe condensation products of aliphatic polyisocyanate-aminosilane adducts with hydrolyzable silanes and their use in sol-gel paints.
Surprisingly, it has now been found that condensation products of aliphatic polyisocvanate-aminosilane adducts with hydrolyzable silanes exhibit in sol-gel paint preparations an improved balance between high hardness, abrasion resistance and chemical resistance on the one hand and high flexibility on the other. The polyisocyanateaminosilane adducts react with the hydrolyzable silanes via polycondensation to form flexible inorganic-organic hybrid coatings having high hardness and very good solvent resistance.
SUMMARY OF THE INVENTION
The present invention relates to hybrid coating compositions containing
A) 5 to 80 wt %, based on the weight of A) and B), of an aliphatic polyisocyanate-aminosilane adduct that is the reaction product of
A1) a polyisocyanate component having an average NCO functionality of 2.5 to 5.5 and an isocyanate content, based on solids, of 9 to 50 wt % and containing aliphatic polyisocyanates with
A2) at least 0.7 amino equivalents, based on the NCO equivalents of A1), of an aminosilane corresponding to formula (I)
(RO)
n
Y
3−n
Si—CH
2
CH
2
CH2-NHZ  (I),
wherein
R represents methyl and/or ethyl,
Y represents methyl and/or ethyl,
Z represents H, C
1
-C
12
alky, CH
2
CH
2
CH
2
—Si(OR)
2
Y
3−n
and
n has a value of 1, 2 or 3 and
A3) optionally isocyanate-reactive compounds other than A2),
and
B) 20 to 95 wt %, based on the weight of A) and B), of at least one hydrolyzable silane corresponding to formula (II)
QSi(OX)
3
  (II),
wherein
X represents C
1
to C
4
alkyl and
Q represents H, C
1
to C
8
alkyl, phenyl, methoxy, ethoxy, 3-glycidyloxy-propyl, 3-aminopropyl and methacryloxypropyl
and/or hydrolyzates/condensates obtained from these silanes.
The present invention also relates to the use of these coating compositions for coating various substrates, such as paints, plastics, granite, marble, metal, wood, leather and textiles.
DETAILED DESCRIPTION OF THE INVENTION
The hybrid coating compositions according to the invention contain 5 to 80 wt %, preferably 20 to 70 wt %, of aliphatic polyisocyanate-aminosilane adducts A) and 20 to 95 wt %, preferably 30 to 80 wvt %, of silanes B), wherein the preceding percentages are based on the preceding percentages are based on the solids content of components A) and B).
The compositions are prepared by reacting
A) 5 to 80 wt %, based on the weight of A) and B), of an aliphatic polyisocyanate-aminosilane adduct that is the reaction product of
A1) a polyisocyanate component having an average NCO functionality of 2.5 to 5.5 and an isocyanate content of 9 to 50 wt % and containing aliphatic polyisocyanates with
A2) at least 0.7 amino equivalents, based on the NCO equivalents of A1), of an aminosilane corresponding to formula (I) and
A3) optionally isocyanate-reactive compounds other than A2),
with
B) 20 to 95 wt %, preferably 30 to 80 wt %, based on the weight of A) and B), of at least one hydrolyzable silane corresponding to formula (II) and/or hydrolyzates/condensates obtained from these silanes.
The aliphatic polyisocyanate components for the present invention have an average NCO functionality of 2.5 to 5.5, preferably 2.8 to 5.0 and more preferably of 3.0 to 4.5. The NCO content, based on the solids content of polyisocyanate component, is 9 to 50 wt %, preferably 10 to 30 wt % and more preferably 11 to 25 wt %. The content of monomeric diisocyanate in the aliphatic polyisocyanate component is preferably less than 10 wt %, more preferably less than 2 wt % and most preferably less than 0.5 wt %.
Suitable aliphatic polyisocyanates include polyisocyanate adducts containing biuret, isocyanurate, iminooxadiazine dione, uretdione. allophanate and/or urethane groups. The urethane groups are based on the reaction products of monomeric isocyanates with molecular weight polyfunctional alcohols such as trimethylol propane, 1,6-hexanediol, 1,5-pentanediol, diethylene glycol, triethylene glycol, 2,2,4-trimethyl-l, 3-propanediol, neopentyl glycol and mixtures thereof. These polnisocyanate adducts are described, for example, in J. prakt. Chem., 1994, 336. 185-200, and “Lackharze, Chemie, Eigenschaften und Anwendungen”, publ. D. Stoye, W. Freitag, Hanser Verlag, Munich, Vienna 1996.
Particularly preferred are polyisocyanates containing isocyanurate groups (trimers) which have an NCO functionality of 3.0 to 4.5, a monomer content of <2 wt %. They may be prepared by the trimerization process described in EP 330,996.
The aliphatic polyisocyanate adducts are prepared by the oligomerization of monomeric diisocyanates, as described for example in J. prakt. Chem., 336 (1994) 185-200. Examples of suitable monomeric diisocyanates include 1,4-butane diisocyanate, 1,6-hexane diisocyanate (HDI), 3-isocyanatomethyl-3,3,5-trimethylcyclohexylisocyante (isophorone diisocyanate, IPDI), 2-methyl-1,5-pentane diisocyanate, 2,2,4trimethyl-hexamethylene diisocyanate (TMDI), 1,1 2-dodecane diisocyanate, bis(isocyanatomethyl)norbornane and 4,4′-diisocyanato-cyclohexyl methane.
For better handling, the polyisocyanate (mixtures) Al) can be diluted with up to 50 wt % of conventional paint solvents. Suitable paint solvents are those that are not reactive towards NCO groups, such as butyl acetate, ethyl acetate, 1-methoxy-2-propyl acetate, toluene, 2-butanone, xylene, 1,4-dioxane, N-methyl pyrrolidone, dimethyl acetamide, dimethyl formamide and dimethyl sulphoxide. Preferably, N-methyl pyrrolidone is used.

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