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
2001-09-27
2003-05-20
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...
C428S423100, C524S590000, C524S591000, C524S839000, C524S840000
Reexamination Certificate
active
06566444
ABSTRACT:
The invention relates to water-dilutable binder compositions which can advantageously be used as a paste resin for the milling of pigments. The resulting pigment pastes are suitable for incorporation into aqueous coating compositions, especially for incorporation into water-based lacquers and water-based finishing lacquers. The water-dilutable binder compositions can be used in automotive and industrial lacquering for coating plastics and metal substrates.
In the preparation of stable pigmented water lacquers it is necessary to wet the pigments thoroughly, grind them finely in suitable dispersing units and disperse them stably in order to prevent agglomeration or sedimentation of the pigments. When low-solvent water-dilutable dispersions or emulsions are used, the action of the shearing forces may be inadequate owing to the very low viscosities. In addition, it must be taken into account that water-dilutable high molecular weight dispersions or emulsions are not always stable to shear in dispersing units. In those cases it is therefore necessary to replace a portion of the binder that is to be used by a paste resin in which the pigments are milled. The pigment or ground pastes so obtained are subsequently mixed (“lacquered up” or made up) with the main binder.
The mentioned paste resins must meet a number of requirements. For example, the paste binders are to be compatible with the main binder(s) and are not to impair the properties of the lacquer in the required added amount. They are to exhibit a good wetting ability for the pigments in question, are to be stable to storage over a prolonged period and are not to bring about colour changes in the lacquer. For the preparation of repair lacquers from standardised mixed lacquers in particular, it is very important to use lacquer concentrates which are highly reproducible in terms of colouristic and technological properties, in order to produce desired shades of colour economically and without unreasonable outlay in terms of shade.
Various binders which are suitable as a paste resin have already been described, which binders can be used in water-based lacquers or water-based finishing lacquers having various binder compositions. For example, in EP-A-0 260 447, polyester resins, acrylate resins and/or amine-formaldehyde condensation resins are used as the milling resin for the preparation of water-based lacquers. The water-based lacquers contain acrylated polyesters and polyurethane resins as the main binder. The milling resins described therein are not always fully compatible with the main binders, which can lead inter alia to an impairment of the metallic effect in the formulation of metallic lacquers.
EP-A-0 299 148 describes pigment pastes based on water-dilutable polyurethane paste resins, the polyurethane resins being prepared from polyester polyols, the acid component of which contains at least 50 wt. % long-chained carboxylic acids having from 18 to 60 carbon atoms in the molecule.
EP-A-438 090 describes milling resins based on water-dilutable polyester urethanes, which are obtained by reacting carboxyl-group-free polyester polyols and low molecular weight diols, at least some of the low molecular weight diols containing an acid group capable of anion formation, with diisocyanates.
A disadvantage of the mentioned milling pastes is that pigment pastes formulated therefrom, especially white pastes, produce lacquers having an inadequate covering power. It is also very difficult using the known paste formulations to produce a deep black. The formulated pigment pastes are often highly thixotropic, so that the metering ability and pumpability of the pastes are greatly impaired. Furthermore, both the known paste resins and the pigment pastes formulated therewith are not stable to frost, and the resistance to chemicals of the water lacquers prepared using those paste resins or of coatings obtained therefrom is in need of improvement. Occasionally, inadequate solids contents are achieved in the preparation of paste resin dispersions, which inter alia can impair the processability and render it less economical.
Furthermore, EP-A-0 469 389 discloses aqueous two-component polyurethane coating compositions which contain water-dilutable hydroxy-functional polyurethane resins having a total urethane and urea group content of from 9 to 20 wt. %, based on the weight of the polyurethane, and water-dispersible polyisocyanates. The coating compositions may additionally contain as a 3rd component up to 20 wt. % of a polyol having a molar mass of from 62 to 1000, preferably from 62 to 250, which may optionally contain polyether groups. The use of the mentioned polyurethane resins as a paste resin is not mentioned.
Accordingly, the object of the invention was to make available water-dilutable binder compositions which are suitable as a paste resin and which can be used as a pigment paste formulation for incorporation into aqueous coating compositions. Pigment pastes formulated from the binder compositions are to exhibit very good compatibility with a large number of different binder systems as well as a very good pigmenting and wetting ability, and consequently are to enable pigmented lacquers to be prepared in an energy- and time-saving manner. It is to be possible to process and meter, and especially also pump, the pigment pastes readily. The pigment pastes are to yield lacquers having a very good covering power and enable the production of a deep black. The pigment pastes and the aqueous lacquers prepared therefrom are also to be stable to storage and to frost. Coatings having a high gloss, a good metallic effect and also very good hardness and resistance to chemicals are to be obtained.
The object is achieved by a water-dilutable binder composition containing
A) one or more water-dilutable hydroxy-functional polyurethane urea resins having a urea group content (calculated as —NHCONH—) of from 10 to 300, preferably from 20 to 250, mmol in 100 g of solid resin, a urethane group content (calculated as —NHCOO—) of from 20 to 300, preferably from 80 to 250, mmol in 100 g of solid resin, an OH number of from 20 to 250, preferably from 40 to 200, especially from 60 to 150, an acid number of from 15 to 80, preferably from 18 to 65, especially from 19 to 45, and a number-average molar mass Mn of from 1000 to 20,000 g/mol, preferably from 1500 to 15,000 g/mol, which are obtained by
I) preparing an NCO-group-containing polyurethane prepolymer by reacting
a1) one or more hydroxy-functional compounds having a number-average molar mass Mn of from 360 to 8000 g/mol, preferably from 500 to 5000 g/mol, with
a2) one or more polyisocyanates and
a3) at least one compound having at least one group that is able to react with isocyanate and at least one group that is ionic or capable of ion formation,
II) subsequently reacting the NCO-group-containing polyurethane prepolymer with
a4) one or more hydroxy-functional monoamines and optionally with one or more polyols, in such relative amounts that the resulting polyurethane has the desired hydroxyl numbers and urea and urethane group contents,
III) neutralising at least some of the ionic groups of the resulting polyurethane before or after the reaction in step II, and converting the resulting reaction product into the aqueous phase,
and
B) from 2.0 to 25 wt. %, based on the solids content of polyurethane urea resin used, of one or more polyether polyols having a molar mass of from 400 to 5000 g/mol, preferably from 500 to 3000 g/mol.
The binder composition according to the invention contains as component A) one or more water-dilutable hydroxy-functional polyurethane urea resins.
The water-dilutable hydroxy-functional polyurethane urea resins and their preparation will be described hereinbelow.
For the preparation of the water-dilutable polyurethane urea resins, an NCO-functional polyurethane prepolymer is first prepared in a first step (I). The polyurethane prepolymer is obtained by reacting components a1) to a3).
Component a1) for the preparation of the NCO-functional polyurethane prepolymer is hydroxy-functi
Göbel Armin
Schaffer Hermann
Vogt-Birnbrich Bettina
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
Niland Patrick D.
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