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...
Patent
1997-12-29
1999-09-28
Acquah, Samuel A.
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...
524376, 524377, C08J 510, C08K 506, C08L 7508
Patent
active
059590130
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to auxiliaries for formulating aqueous thickeners, more particularly based on polyurethanes, in liquid form and to aqueous thickener formulations produced with these auxiliaries. The invention also relates to the use of the thickener formulations in systems to be thickened, for example in water-based emulsion paints.
2. Discussion of Related Art
Polyurethane-based thickeners, of which the thickening properties can be described by an associative action mechanism, are suitable as auxiliaries for establishing Theological properties in water-based systems such as, for example, automotive and industrial lacquers, plasters and paints, printing inks and textile dyes, pigment printing pastes, pharmaceutical and cosmetic formulations, plant protection formulations and filler dispersions. The action mechanism of such thickeners is described, for example, in Polymers Paint Colour Journal, 181, 270 (1991). Besides polyurethanes, ethoxylated fatty alcohols additionally reacted in blocks or statistically with a small percentage of long-chain epoxides or nonionic polyacrylates or polyacrylamides partly esterified with long-chain fatty alcohols or even cellulose derivatives etherified with long alkyl chains may be used as associative thickeners in water-based systems. They are increasingly replacing or complementing the cellulose ethers traditionally used as thickeners in paints and lacquers and the traditional alkali-soluble polyacrylates. Associative thickeners have a number of advantages over conventional thickener systems including, for example, to shearing (approaching newtonian flow behavior).
The production and use of such thickeners is described, for example, in U.S. Pat. No. 4,079,028 and in U.S. Pat. No. 4,426,485.
Although polyurethane-based thickeners have a far lower viscosity than polyacrylates or cellulose ethers for the same thickening effect, the formulation of polyurethane-based liquid thickeners still involves difficulties. In the form of aqueous solutions, known polyurethane thickeners have a very high viscosity which makes them very difficult to incorporate in aqueous systems.
Various attempts have been made in the past to reduce the viscosity of polyurethane thickeners. For example, their molecular weight has been reduced although this resulted in a seriously diminished thickening effect.
A standard method for reducing the viscosity of aqueous polyurethane thickener solutions is to add water-soluble low molecular weight solvents such as, for example, water-soluble monohydric or polyhydric alcohols. Serious disadvantages of this method are the deterioration in the performance properties, for example spreadability or stability, and the increased emission of volatile solvents.
The above-mentioned disadvantages of using low molecular weight solvents in thickener formulations can be overcome, for example, by supplying and processing the thickener in solid form. However, the disadvantages of formulating the thickener in solid form lie in additional process steps both during the production and subsequent processing of the thickener. In the first case, the thickener has to be isolated from the reaction medium and converted into powder form whereas, in the second case, the powder first has to be converted into a processable form by dissolution or swelling before or during its intended use so that final application is possible.
The possibility of reducing the viscosity of thickener systems by adding relatively large quantities of water appears uneconomical because it would involve an unwanted production in the concentration of active substance and, hence, an increase in the quantity applied.
Now, according to DE-A-43 10 702, alkoxylated alcohols or phenols may be added to reduce the viscosity of aqueous solutions of polyurethane thickeners, although they have to be used in high concentrations to achieve an adequate reduction in the viscosity of the thickener. The document in question also discloses the use of 2,4,7,9-tetramethyl-5-de
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Conradi Joachim
Gress Wolfgang
Neumann Ralf
Schieferstein Ludwig
Schulte Heinz-Guenther
Acquah Samuel A.
Grandmaison Real J.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Rajguru U. K.
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