Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-03-29
2004-06-08
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C427S372200, C427S385500, C522S090000, C522S096000, C522S097000, C522S098000, C524S591000, C524S839000, C524S840000, C525S123000, C525S127000, C525S124000, C525S455000, C428S423100
Reexamination Certificate
active
06747088
ABSTRACT:
The invention relates to UV- and heat-curable polyurethane dispersions which have UV-polymerizable C═C double bonds, hydroxyl groups and blocked isocyanate groups in one molecule or the blocked isocyanate groups in admixed compounds, and to processes for their preparation and use.
Radiation-curable polyurethane dispersions are known, for example, from the Applicant's DE-A 4434554 and are prepared from polyisocyanates, hydroxyl-containing polyesters, compounds containing an isocyanate-reactive group and an acid group, and compounds containing an isocyanate-reactive group and C═C double bonds. In terms of their processing properties, however, the products leave a certain amount to be desired. U.S. Pat. No. 5,859,135 describes aqueous coating mixtures comprising a lipophilic polymer containing at least one hydroxyl group, having a molecular weight of up to 100,000, which is connected on one side to a crosslinkable functional group and on the other side, via a polyisocyanate, to a group containing carboxyl groups and to a hydrophilic polyalkylene oxide monoether radical.
A disadvantage is that coatings produced therewith have a relatively high intrinsic hydrophilicity, even after processing. U.S. Pat. No. 5,296,529 describes a self-crosslinking resin containing carboxyl, hydroxyl, and blocked isocyanate groups, which is prepared from a) a copolymer of a vinyl monomer containing free and blocked isocyanate groups with a styrene and/or (meth)acrylate comonomer, and b) a polyester resin containing hydroxyl and carboxyl groups, some hydroxyl groups of the polyester resin being reacted with some free isocyanate groups of the vinyl copolymer, and remaining isocyanate groups then being blocked. It can be seen that a highly reproducible production of the system counters the risk of a premature unwanted crosslinking of the two polymers. Also, the system described contains no UV-curable double bonds, nor is any radiation curing thereof described.
DE-A-198 60 041 describes reaction products of a) polyisocyanates and b) low molecular mass hydroxy compounds containing C═C double bonds, such as hydroxyalkyl(meth)acrylates or hydroxyalkyl vinyl ethers, the majority of which constitute allophanates of the polyisocyanates with the unsaturated alcohols. The low molecular mass reaction products, which are of low viscosity, have a high polymerizable C═C double bond content in the molecule and can be both polymerized with UV radiation and cured thermally, with the participation of the isocyanate groups, or by exposure to water vapor, ammonia, or amines. An application in the form of aqueous dispersions is not described.
It is an object of the present invention to prepare both UV- and heat-curable aqueous polyurethane dispersions which give rise to coatings having good chemical resistance and good mechanical properties, in particular a high scratch resistance, which dry physically after treatment even at unexposed areas, and are suitable for exterior applications such as for an automobile finish.
We have found that this object is achieved with polyurethane dispersions synthesized essentially from
a) aliphatic polyisocyanates having an NCO functionality of from 2 to 4.5,
b) compounds containing at least one isocyanate-reactive group and at least one UV-polymerizable C═C double bond,
c) aliphatic and/or cycloaliphatic compounds containing at least two hydroxyl, mercapto and/or primary and/or secondary amino groups, having a molecular weight of less than 500 g/mol,
d) compounds containing at least one isocyanate-reactive group and also at least one carboxyl group or sulfonic acid group,
e) at least one basic compound for full or partial neutralization of the acid groups of the compounds d),
f) an isocyanate blocking agent (f1) which converts isocyanate groups into blocked isocyanate groups with an unblocking temperature in the range from 70 to 160° C., or addition of a compound (f2) containing blocked isocyanate groups, and
g) if desired, a compound different than compounds b) to f) which contains only one isocyanate-reactive group,
the reaction products of a) with b) and, if appropriate, c), prepared with a stoichiometric excess of NCO groups in relation to the OH groups, having been reacted with compounds d) and e) in amounts sufficient for dispersibility in aqueous medium, isocyanate groups having been converted into blocked isocyanate groups by reaction with isocyanate blocking agents (f1), or compounds containing blocked isocyanate groups (f2) having been added.
The building blocks of the polyurethane dispersion:
Component a)
Aliphatic polyisocyanates a) having an NCO functionality of from 2 to 4.5 and preferably from 2.0 to 3.5 include especially, as aliphatic (including cycloaliphatic)diisocyanates, hexamethylene diisocyanate, 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate, and di(isocyanatocyclohexyl)methane. Preference is given to polyisocyanates having a functionality of at least 3, such as polyisocyanates containing isocyanurate groups, biuret groups, uretdione groups or urethane groups and/or allophanate groups. The polyisocyanates containing isocyanurate groups comprise, in particular, simple trisisocyanato isocyanurates, which constitute cyclic trimers of the diisocyanates, or mixtures thereof with their higher homologs containing more than one isocyanurate ring. The isocyanato isocyanurates generally have an NCO content of from 10 to 30, in particular from 15 to 25% by weight, and an average NCO functionality of 3 to 4.5. Polyisocyanates containing biuret groups are adducts of 3 molecules of diisocyanate with 1 molecule of water and have in particular an NCO content from 18 to 22% by weight and an average NCO functionality of from 3 to 4.5. Polyisocyanates containing urethane groups and/or allophanate groups may be obtained, for example, by reacting excess amounts of diisocyanate with simple alcohols such as trimethylolpropane, glycerol, 1,2-dihydroxypropane or mixtures thereof, for example, and generally have an NCO content of from 12 to 20% by weight and an average NCO functionality of from 2.5 to 3. Polyisocyanates having an NCO functionality of more than 2 that may be mentioned also include the adducts of 3 mol of diisocyanates such as isophorone diisocyanate with trihydric alcohols such as trimethylolpropane.
The component a) preferably comprises at least one compound Va) having two free isocyanate groups, at least one allophanate group, and at least one free-radically polymerizable C═C double bond, a carbonyl group or an oxygen atom in ether function being attached directly to the double bond.
The compound Va) is preferably selected from compounds of the formula I
OCN—R
1
&Parenopenst;R
2
—C(O)—R
2
—R
1
&Parenclosest;
n
NCO (I)
where
n is an integer from 1 to 10,
R
1
is a divalent aliphatic or alicyclic C
2
to C
20
hydrocarbon unit or an aromatic C
6
to C
20
hydrocarbon unit,
R
2
in each repeating unit is once —NH— and once
R
3
being a radical derived from an alcohol A by abstracting the hydrogen atom from the alcoholic hydroxyl group, said alcohol A further comprising at least one free-radically polymerizable C═C double bond, and a carbonyl group or an oxygen atom in ether attachment being attached directly to the double bond.
The radicals R
1
preferably comprise those derived by abstracting the isocyanate group from customary aliphatic or aromatic polyisocyanates. The diisocyanates are preferably aliphatic isocyanates having 4 to 20 carbon atoms. Examples of customary diisocyanates are aliphatic diisocyanates such as tetramethylene diisocyanate, hexylmethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, derivatives of lysine diisocyanate, tetramethylxylylene diisocyanate, cycloaliphatic diisocyanates such as 1,4-, 1,3- or 1,2-diisocyanatocyclohexane, 4,4′- or 2,4′-di(isocyanatocyclohexyl)methane, isophorone diisocyanate, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane, 2,4- and 2,6-diisocyan
Beck Erich
Bruchmann Bernd
Meisenburg Uwe
Paulus Wolfgang
Schrof Wolfgang
BASF - Aktiengesellschaft
Niland Patrick D.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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