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
2000-08-01
2002-08-13
Michl, Paul R. (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...
Reexamination Certificate
active
06433072
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention provides pigment pastes and resin pastes for incorporating into aqueous surface coating agents, in particular for incorporating into aqueous basecoat lacquers and aqueous topcoat lacquers and also coating agents containing the pigment pastes. The pigment pastes and surface coating agents containing them may advantageously be used in the vehicle and industrial lacquering sector for coating plastics and metal substrates.
When preparing stable pigmented aqueous basecoat lacquers, the pigments have to be well wetted and finely milled and distributed in a stable manner in appropriate dispersing equipment in order to prevent agglomeration or sedimentation of the pigments. When using low-solvent water-dilutable dispersions or emulsions, the shear forces may not act effectively due to the very low viscosities. In addition, the fact that water-dilutable, high molecular weight dispersions or emulsions are not always shear-stable in dispersing equipment has to be taken into account. In this case, therefore, some of the binder being used has to be replaced by a paste resin (pigment paste resin), into which the pigments are rubbed. The pigment pastes or milled pastes obtained in this way are then mixed with the main binder (“lacquered up” or completed).
The paste resins mentioned then have to satisfy a number of requirements. For example, the paste binders should be highly compatible with the main binder(s) and not alter, in a detrimental manner, the properties of the lacquer when added in the requisite amounts. They should exhibit a good wetting capacity for the particular pigments, be storage-stable for a relatively long period and cause no colour changes in the lacquer. In particular for the production of repair lacquers from standardised mixed lacquers, it is very important to use lacquer concentrates with readily reproducible coloristic and technological properties in order to produce the desired shade of colour economically and without unreasonable use of the colorant.
Various binders which are suitable for use as paste resins and which are used in aqueous basecoat or aqueous topcoats have already been described. Thus, in EP-A-0 260 447, polyester resins, acrylate resins and/or amine/forrnaldehyde condensation resins are used as pigment paste resins for preparing aqueous basecoat lacquers. As the main binder, the aqueous basecoat lacquers contain acrylated polyesters and polyurethane resins. The pigment paste resins described here are not always fully compatible with the main binder, which can lead to an impairment of the metallic effect when formulating metallic lacquers.
Pigment pastes based on water-dilutable polyurethane paste resins are described in EP-A-0 299 148, wherein the polyurethane resins are prepared from polyesterpolyols in which the acid component contains at least 50 wt. % of long-chain carboxylic acids with 18-60 carbon atoms in the molecule.
EP-A-0 438 090 describes pigment paste resins based on water-dilutable polyesterurethanes, wherein the polyesterurethanes are obtained by reacting carboxyl group-free polyesterpolyols and low molecular weight diols, wherein at least some of the low molecular weight diols contain acid groups capable of forming anions, with diisocyanates.
The disadvantage of the pigment paste resins mentioned is that pigment pastes formulated with them, in particular white pastes, produce lacquers with defective covering capacity. Also, the known paste formulations pose serious problems when making up a deep black. Furthermore, both the known paste resins and also the pigment pastes formulated therewith are not frost-resistant and the resistance to chemicals of aqueous lacquers formulated with these paste resins and the surface coatings obtained therefrom require some improvement. From time to time, when preparing paste resin dispersions, insufficient solids contents are produced which, inter alia, can impair the processability and make them less economically viable.
Thus, the object of the invention was to provide pigment pastes, for incorporation into aqueous surface coating agents, which are very compatible with a large number of different binder systems and also exhibit very good pigmenting and wetting powers and as a result enable the energy- and time-saving production of pigmented lacquers. The pigment pastes should be readily processable, produce lacquers with very good covering capacity and enable the formulation of a deep black. The pigment pastes and also the aqueous lacquers prepared therefrom should be storage-stable and frost-resistant. Surface coatings with a high gloss, a good metallic effect and very high hardness and resistance to chemicals should be obtained.
SUMMARY OF THE INVENTION
The object is achieved by a pigment paste, containing paste resin and pigments in a pigment to binder ratio by weight of 0.3:1 to 20:1, preferably 0.5:1 to 15:1, particularly preferably 0.8 to 1 to 12:1, and optionally water, organic solvent and/or conventional lacquer additives, which is characterised in that it contains, as a paste resin, one or more water-dilutable hydroxy-functional polyurethaneurea resins with a urea group content (calculated as —NHCONH—) of 10 to 300, preferably 20 to 250 mmol in 100 g of solid resin, a urethane group content (calculated as —NHCOO—) of 20 to 300, preferably 80 to 250 mmol in 100 g of solid resin, an OH value of 20 to 250, preferably 40 to 200, particularly preferably 60 to 150, an acid value of 15 to 80, preferably 18 to 65, particularly preferably 19 to 45 and a number average molecular weight Mn of 1000 to 20000 g/mol, preferably 1500 to 15000 g/mol, which are obtainable by
I) preparing a NCO group-containing polyurethane prepolymer by reacting
a1) one or more hydroxy-functional compounds with a number average molecular weight (Mn) of 360 to 8000, preferably 500 to 5000 g/mol, with
a2) one or more polyisocyanates and
a3) at least one compound with at least one group which can react with isocyanate and at least one group which is ionic or capable of forming ions,
II) subsequent reaction of the NCO group-containing polyurethane prepolymer with
a4) one or more hydroxy-functional monoamines and also optionally with one or more polyols in ratios by weight such that the resulting polyurethane has the required hydroxyl values and proportions of urea and urethane groups,
III) at least partial neutralisation of the ionic groups or groups which can be converted into ionic groups in the polyurethane obtained, before or after reaction in stage II, and transfer of the reaction product obtained to the aqueous phase.
The water-dilutable hydroxy-functional polyurethaneurea resins contained in pigment pastes according to the invention and their preparation will be described in the following.
The invention also provides preparation of the water-dilutable polyurethaneurea paste resins. Here, a NCO-functional polyurethane prepolymer is prepared in a first stage (I). The polyurethane prepolymer is obtained by reacting components a1) to a3).
Component a1) for preparing NCO-functional polyurethane prepolymers consists of hydroxy-functional linear or branched compounds, which preferably have an OH-functionality of 2 to 3, particularly preferably of 2, an OH value of 50 to 250 and a number average molecular weight (Mn) of 360 to 8000 g/mol, preferably 500 to 5000 g/mol.
The invention also relates to the paste resins obtainable by this procedure.
DETAILED DESCRIPTION OF THE INVENTION
The following may be used as component a1): polyesterpolyols, polycarbonatepolyols, polyetherpolyols, polylactonepolyols and/or poly(meth)acrylatepolyols or the corresponding diols. The polyols and diols may each be used separately or in combination with each other.
Polyesterpolyols, e.g. polyesterdiols, are preferably used as component a1). Particularly preferably, they are linear polyesterpolyols, in particular linear polyesterdiols.
The polyesterpolyols may be prepared in a conventional manner known to a person skilled in the art, for example by polycondensation from organic dicarboxylic acids or their anhydr
Göbel Armin
Vogt-Birnbrich Bettina
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
Michl Paul R.
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