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
2003-03-31
2004-03-23
Sergent, Rabon (Department: 1711)
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...
C524S839000, C524S840000, C528S049000, C528S071000, C528S075000, C528S085000, C525S123000, C525S131000
Reexamination Certificate
active
06710120
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to aqueous polyurethane dispersions based on fatty acid dialkanolamides, to a process for preparing them and to use as coating compositions.
With the aim of lowering the emissions of organic solvents, aqueous coating compositions are increasingly being used in place of solvent-borne systems. An important class of aqueous film-forming binders are the polyurethane dispersions. An overview is given by D. Dieterich, Prog. Org. Coatings 9, 281 (1981). Polyurethane dispersions unite the important properties of resistance to chemicals and to mechanical loads. Especially in the field of the coating of surfaces under high mechanical stress, therefore, the use of polyurethane dispersions is of advantage.
Of particular interest is the resistance to damage caused by the heels of shoes on flooring coatings (heelmark resistance). Particularly in the case of coatings with pronounced thermoplasticity, such heelmarks lead to permanent damage. The resistance to such damage can be improved by crosslinking the floor coating.
One way of achieving such an improvement in the profile of properties is to use hydrophilicized polyisocyanates, as described, for example, in EP-A 0 540 985. Aqueous two-component (2K) polyurethane coating materials attain a very high level of properties. Owing to the comparatively complicated application technique of 2K coating systems, their field of use is limited, particularly in the case of manual application.
A simple, prior-art route to the production of crosslinked coatings from polyurethane dispersions is the incorporation of unsaturated units into the binder (Advances in Urethane Science and Technology, K. C. Frisch, D. Klempner (eds.) Vol. 10, pp. 121-162 (1987)). Coatings comprising such binders crosslink through reaction with atmospheric oxygen (autoxidative crosslinking). In comparison to the combination of a polyurethane dispersion with a hydrophilicized polyisocyanate, the application, in particular, of these binders, which are processed as a single component, is simplified.
Dispersions comprising urethane groups and air-drying components are also described in EP-A 0 017 199, EP-A 0 379 007, WO-A 97/19120, DE-A 4 004 651, DE-A 4 416 336 and JP-A 6 340 842. A disadvantage of the autoxidatively crosslinkable polyurethane dispersions known to date, however, is that the mechanical properties of the coating film do not match the high level of the purely physically drying polyurethane dispersions. This is evident, for example, in a poorer abrasion resistance.
U.S. Pat. No. 5,039,732 describes oxidatively drying polyurethane dispersions which comprise fatty acid diethanolamides, prepared from diethanolamine and fatty acids or fatty acid derivatives of semi-drying and/or drying oils such as linseed oil or soya oil as the diol component. The preparation of these products leads, via intermediates of very high viscosity, to dispersions which are in turn of high viscosity, and which at solids contents greater than 30% by weight are no longer fluid at room temperature and therefore cannot be applied as a thin, homogeneous film to a substrate.
Another process for preparing polyurethane dispersions comprising unsaturated units is described in EP-A 0 709 414. Through the use of dehydrated castor oil as the sole OH component or as part of the polyol mixture in the preparation of a polyurethane dispersion, products having a defined C═C double bond content are obtained.
In the dehydration of castor oil (see, for example, K. T. Achaya, J. Am. Oil Chem. Soc. 48, p. 758 [1971]) the elimination of each molecule of water produces one C═C double bond. Accordingly, the process described in EP-A 0 709 414 is limited to the effect that dehydration of castor oil having a defined OH group content and double bond content gives products having always the same total number of hydroxyl groups and double bonds. Thus it is not possible by this process, for example, to prepare products having a high double bond content and a high OH group content at the same time.
DE-A 199 30 961 describes coatings of good heelmark resistance which comprise transesterification products of castor oil and drying/semi-drying oils. Nevertheless, for certain applications, where (König) pendulum hardnesses of more than 90 sec are called for, the products have inadequate gloss and/or relatively poor film-forming properties.
It was an object of the present invention to provide polyurethane dispersions which are easy to pigment and possess good film forming properties. At the same time, the intention was that the coatings produced from these dispersions should have sufficient pendulum hardness, preferably above 90 sec, and also good heelmark resistance and high gloss.
DESCRIPTION OF THE INVENTION
Surprisingly it has been possible to achieve the above-noted object by the provision of polyurethane dispersions which contain saturated fatty acid dialkanolamides incorporated into the polymer chains. These dispersions can be processed to particularly high-grade floor coatings if unsaturated, oxidatively drying fatty acids are also included. Besides high resistance to water-ethanol mixtures and good heelmark resistance, such products can have pendulum hardnesses of at least 90 sec (according to König).
The present invention provides aqueous polyurethane dispersions prepared by dispersing a polymer product with water, where the polymer product is prepared by reacting a reaction mixture comprising:
A) at least one condensation product of (i) an oxidatively non-drying fatty acid and (ii) a dialkanolamine and having a number average molecular weight of <500,
B) one or more polyisocyanates,
C) one or more hydrophobic, water immiscible polyols having a number average molar weight of from 500 to 6000 and containing no functional groups being capable of oxidative drying,
D) one or more compounds which contain an ionic group or a group capable of forming an ionic group, and
E) one or more polyols and/or polyamines having a number average molecular weight of <500.
Where appropriate, the reaction mixture may also include monoalcohols and/or monoamines (F) and/or OH- or NH-functional, nonionically hydrophilic polyoxyalkylene ethers (G).
In one preferred embodiment the reaction mixture includes a further component (H) which, in addition to at least one group capable of oxidative drying, contains at least one group which is reactive towards isocyanates.
The reaction mixture comprises from 0.5 to 30% by weight, preferably from 1 to 25% by weight and with particular preference from 2 to 20% by weight of component (A), from 5 to 60% by weight, preferably from 15 to 57% by weight and with particular preference from 25 to 55% by weight of component (B), from 0.5 to 65% by weight, preferably from 2 to 55% by weight and with particular preference from 5 to 50% by weight of component (C), from 0.5 to 15% by weight, preferably from 2 to 14% by weight and with particular preference from 4 to 12% by weight of component (D), from 0.5 to 18% by weight, preferably from 2 to 12% by weight and with particular preference from 4 to 10% by weight of component (E), and from 0 to 10% by weight, preferably from 0 to 7% by weight and with particular preference from 0 to 2% by weight of component (F) and/or from 0 to 10% by weight, preferably from 0 to 7% by weight and with particular preference from 0 to 2% by weight of component (G), the percentages being based on the weight of the resin solids and adding up to 100% by weight.
In the case where component (H) is also included in the reaction mixture, the reaction mixture comprises from 0.5 to 20% by weight, preferably from 1 to 15% by weight and with particular preference from 1.5 to 10% by weight of component (A), from 5 to 60% by weight, preferably from 20 to 57% by weight and with particular preference from 30 to 55% by weight of component (B), from 0.5 to 20% by weight, preferably from 2 to 18% by weight and with particular preference from 3 to 15% by weight of component (C), from 0.5 to 10% by weight, preferably from 2 to 8% by weigh
Gertzmann Rolf
Irle Christoph
Lühmann Erhard
Roschu Rolf
Weikard Jan
Bayer Aktiengesellschaft
Gil Joseph C.
Roy Thomas W.
Sergent Rabon
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