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
2000-06-23
2002-07-16
Sanders, Kriellion A. (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...
C524S555000
Reexamination Certificate
active
06420478
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to binder compositions for aqueous coating compositions, a process for their production, and their use for coating substrates with high mechanical stresses.
2. Description of the Prior Art
Aqueous systems are increasingly being used for coating high mechanically stressed surfaces such as wood, plastics or concrete floors. Demands placed on such coating systems include, in particular, high resistance to chemicals and water, and also to mechanical damage. These demands are largely met by polyurethane dispersions. The possible ways of producing such dispersions have been summarized for example by D. Dieterich in a review article [D. Dieterich, Prog. Org. Coatings 9, 281 (1981)].
As is known from EP-A-0 358 979, the chemical and mechanical resistance of coatings can be improved if crosslinking agents with free isocyanate groups are added to aqueous dispersions containing hydroxyl groups.
The incorporation of such isocyanate-functional crosslinking agents in aqueous dispersions is improved if the polyisocyanates have hydrophilic groups. Hydrophilic polyisocyanates are described, for example, in EP-B 0 540 985. These polyisocyanates also improve the chemical and physical resistance of dispersions free of hydroxyl groups (see, for example, Vaihinger, I-Lack 64 (12), p. 710 [1996]).
The known compositions containing hydrophilic polyisocyanates and polyurethane dispersions have the recurring disadvantage that it is difficult to mix the components.
Thus, in order to produce a shiny, transparent film it is necessary to use a dispersion unit having a high shear action or to pre-dilute the crosslinking agent with water (see for example Carver S.r.I., Technical Leaflet DIVA/S, DIVA/O, rev.04 of 16.02.1998). However, dispersion units are not available for manual coating, which is normally the case when sealing parquet floors. If curing components have to be pre-diluted in an accurately defined amount and time, the application of the two-component coating composition is made considerably more difficult.
It is known from DE-A-19 847 077 and DE-A-19 822 890 that polyisocyanates containing allophanate groups can be incorporated more easily into binders containing hydroxyl groups. However, these binders are not suitable as one-component binders without a curing component.
An object of the present invention is to provide compositions containing polyurethane dispersions and polyisocyanate crosslinking agents that result in coatings having excellent resistance to mechanical and chemical stress and that can also easily be formulated (blended) manually to produce a clear, shiny coating having excellent resistance properties. A further object of the present invention is to provide a coating system that also produces a durable coating without the use of a curing component. The advantage of a simpler application without having to incorporate the curing component can be achieved if correspondingly less stringent requirements have to be satisfied, for example, when coating less highly stressed floors, in which case the maximum achievable resistance does not have to be met.
It has now surprisingly been found that the object can be achieved with the binder compositions of the present invention, which are described in more detail hereinafter.
SUMMARY OF THE INVENTION
The present invention relates to a binder composition containing
A) 70 to 99% of a polyurethane dispersion having an OH number of <10 mg KOH/g of solid resin and
B) 1 to 30% of a water-dispersible polyisocyanate mixture prepared from an aliphatic, cycloaliphatic, araliphatic and/or aromatic diisocyanate, wherein the polyisocyanate mixture has
a) an average isocyanate functionality of at least 2.0,
b) a content of isocyanate groups (calculated as NCO; molecular weight 42) of 5.0 to 25.0 wt. %, and
c) a content of ethylene oxide units of 2 to 50 wt. % (calculated as C
2
H
4
O; molecular weight 44) present within polyether chains containing an average of 5 to 35 ethylene oxide units,
wherein at least 60 mole % of the polyether chains are connected via allophanate groups to two polyisocyanate molecules which are each prepared from at least two diisocyanate molecules and wherein the solids contents of components A) and B) add up to 100%.
DETAILED DESCRIPTION OF THE INVENTION
Polyurethane dispersions A) according to the invention are prepared from
A1) 5 to 70% by weight of polyisocyanates,
A2) 10 to 80% by weight of polymeric polyols having a number average molecular weight of 400 to 6000,
A3) 0 to 10% by weight of monohydric alcohols or monoamines,
A4) 0.5 to 15% by weight of polyols, aminopolyols or polyamines having a number average molecular weight of less than 400 and
A5) 0 to 20% by weight of polyoxyalkylene ethers having with at least one hydroxy or amino group,
wherein the solids contents of components A1) to A5) add up to 100% and preferably at least one of components A3) and/or A4) contains an ionic group or a groups capable of forming an ionic group.
The ionic group may be cationic or anionic, preferably anionic. The phrase “capable of forming an ionic group” refers to the incorporation of compounds with, for example, free acid groups, such as carboxyl groups, into the polyurethane, which can subsequently be converted by neutralization into ionic groups.
Suitable diisocyanates A1) include those having a molecular weight of 140 to 400 and containing aliphatically, cycloaliphatically, araliphatically and/or aromatically bound isocyanate groups. Examples include 1,4-diisocyanatobutane, 1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- and 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1,3- and 1,4-bis-(isocyanatomethyl)-cyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate or IPDI), 4,4′-diisocyanato-dicyclohexylmethane, 1-isocyanato-1-methyl-4(3)isocyanato-methylcyclohexane, bis-(isocyanatomethyl)-norbornane, 1,3- and 1,4-bis-(2-isocyanatoprop-2-yl)-benzene (TMXDI), 2,4- and 2,6-diisocyanato-toluene (TDI), 2,4′- and 4,4′-diisocyanatodiphenyl-methane, 1,5-diisocyanatonaphthalene and mixtures thereof.
Preferred polyisocyanates or polyisocyanate mixtures are those exclusively containing aliphatically and/or cycloaliphatically bound isocyanate groups. Particularly preferred starting components A1) are polyisocyanates or polyisocyanate mixtures containing HDI, IPDI and/or 4,4′-diisocyanatodicyclohexylmethane.
Also suitable as polyisocyanates A1) are lacquer polyisocyanates prepared from at least two aliphatic, cycloaliphatic, araliphatic and/or aromatic diisocyanate molecules and containing a uretdione, isocyanurate, urethane, allophanate, biuret, iminooxadiazine dione and/or oxadiazine trione groups, which are described, for example, in J. Prakt. Chem. 336 (1994) 185-200, DE-A-1 670 666, DE-A-1 954 093, DE-A-2 414 413, DE-A-2 452 532, DE-A-2 641 380, DE-A-3 700 209, DE-A-3 900 053, DE-A-3 928 503, EP-A-0 336 205, EP-A-0 339 396 and EP-A-0 798 299.
Polymeric polyols A2) include the known polyols from polyurethane chemistry, which have an average OH functionality of 1.8 to 4. Examples include polyacrylates, polyesters, polyethers, polycarbonates, polyester carbonates, polyacetals, polyolefins and polysiloxanes. The polyols preferably have a number average molecular weight of 600 to 2500 and an average OH functionality of 2 to 3.
In addition to the use of difunctional OH components, it is also possible, as is known from the literature, to terminate the polyurethane prepolymers with monofunctional alcohols A3). Suitable monohydric alcohols A3) are preferably aliphatic monohydric alcohols with 1 to 18 carbon atoms, such as ethanol, n-butanol, ethylene glycol monobutyl ether, 2-ethylhexanol, 1-octanol, 1-dodecanol and 1-hexadecanol.
The known polyols, aminopolyols and polyamines A4) having a molecular weight of less than 400 may be used as chain extenders to prepare th
Irle Christoph
Kremer Wolfgang
Laas Hans-Josef
Lühmann Erhard
Roschu Rolf
Bayer Aktiengesellschaft
Gil Joseph C.
Roy Thomas W.
Sanders Kriellion A.
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