Rheologically active urea urethane compounds

Details Rheologically active urea urethane compounds Rheologically active urea urethane compounds

2001-08-16

2003-09-09

Barts, Samuel (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C560S026000

Reexamination Certificate

active

06617468

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a process for preparing a solution which comprises urea urethanes and is effective as a thixotropic agent, which involves reacting monohydroxy compounds with an excess of toluene diisocyanate, removing the unreacted portion of the toluene diisocyanate from the reaction mixture, and further reacting the resultant monoisocyanate adducts with diamines in an aprotic solvent in the presence of a lithium salt to give urea urethanes. The invention additionally relates to the use of the solution to receive thixotropic coating compositions.
BACKGROUND OF THE INVENTION
In order to control the rheology of liquid coating systems, predominantly organically modified bentonites, silicas, hydrogenated castor oil and polyamide waxes are used. A disadvantage of these substances is that they are mostly dry solids which have to be brought into the form of a semi-finished product using solvents and shear forces, and incorporated into the liquid coating system under careful temperature control. Failure to observe such temperatures results in crystallites in the finished coating system, which may lead to defects in the coating.
The general disadvantage of these presently used theological auxiliaries is that they lead to turbidities and haze in clear, transparent coatings. Moreover, handling dry pulverulent products which give rise to dusts in the course of processing is undesirable.
Different solutions for rheology control have been described in European Patent Application EP-A-0 198 519. There, an isocyanate is reacted with an amine in the presence of solutions of film-forming resin to give a urea which forms acicular crystals in very finely disperse form. The film-forming binders thus modified are sold as rheology-controlling and anti-sagging binders, referred to as sag control agents. The disadvantage of these products is that they are always bound to the binders in which they were prepared, and there is no possibility of subsequent, universal correction of finished coating compositions.
European Patent EP-B-0 006 252 describes a process for preparing a thixotropic agent that removes some of the abovementioned disadvantages, describing urea urethanes which are prepared by reaction of isocyanate adducts with polyamines in aprotic solvents in the presence of lithium salts. The products prepared, however, have two significant disadvantages. Firstly, these thixotropic agents are characterized by an undefined structure owing to the preparation process. Although monoisocyanate adducts are described, the actual products are in fact not monoadducts at all, as is clearly evident from the example, but rather mixtures of different adducts. In the process described, one mole of a diisocyanate is first reacted with one mole of a monoalcohol. By this process the desired NCO-functional monoadducts are partially formed, but also non-NCO-functional diadducts, which in the course of subsequent reaction with polyamines in the presence of lithium chloride leads to uncontrolled chain extension of the urea urethane and to polymeric ureas. These products then tend to display precipitation phenomena and are extremely difficult to keep in solution. A further disadvantage of the thixotropic agents prepared by this process can be recognized in the fact that always only monoisocyanate adducts with the same structure are reacted with the diamine. This leads firstly to limited compatibility in the coating systems used, manifested in gel structures or severe turbidities, and secondly to a poorer rheological effectiveness.
It is therefore an object of the present invention to find thixotropic agents which on the one hand have a defined structure and therefore permit relatively high storage stability of the solution thus prepared, over several months, and on the other are characterized by a relatively broad compatibility in binders, thereby permitting reliable use of the products. This is of particular interest in modem coating systems which are relatively polar formulations, such as waterborne coating materials or high-solids systems, for example.
Surprisingly it has been found that this object can be achieved in a process of the type specified at the outset by reacting at least two structurally different monoisocyanate adducts, which differ in their alcohol component, with the diamines to give urea adducts.
SUMMARY OF THE INVENTION
The present invention accordingly provides a process in which at least two structurally different monohydroxy compounds of the general structure R—OH, in which R represents an n-alkyl radical or an iso-alkyl radical having from 4 to 22 carbon atoms, an alkenyl radical having from 3 to 18 carbon atoms, a cycloalkyl radical, an aralkyl radical, or a radical of the formula C
m
H
2m+1
(O—C
n
H
2n
)
x
, C
m
H
2m+1
(OOC—C
v
H
2v
)
x
or Z—C
6
H
4
(O—C
n
H
2n
)
x
, in which m is 1-22, n is 2-4, x is v is 4 or 5 and Z is an alkyl radical having from 1 to 12 carbon atoms, are reacted with a from 1.5- to 5-fold excess of toluene diisocyanate to give monoisocyanate adducts of the general structure (I)
and the unreacted portion of the toluene diisocyanate is removed from the reaction mixture, and the resultant monoisocyanate adducts are reacted with diamines of the formula H
2
N—R
3
—NH
2
, in which R
3
is a radical having the formula —C
i
H
2i
—, where i is from about 2 to about 12;—(C
p
H
2p
—O—C
p
H
2p
)
q
, where p is from about 2 to about 4 and q is from about 1 to about 10;
where R
4
is CH
3
or hydrogen;
or mixtures thereof in an aprotic solvent in the presence of a lithium salt to give urea adducts of the general structure (II)
wherein the radicals R
1
and R
2
satisfy the conditions for the radical R.
In the process of the invention, the abovementioned diamines may be replaced in whole or in part by paraxylylenediamine of the formula
Alkyl, alkoxy, alkylene, etc. denote both straight and branched groups; but reference to an individual radical such as “propyl” embraces only the straight chain radical, a branched chain isomer such as “isopropyl” being specifically referred to. Alkylene denotes a divalent straight or branched alkyl group (e.g., methylene (—CH
2
—) or ethylene (—CH
2
CH
2
—)). When alkyl or alkylene can be partially unsaturated, the alkyl chain may comprise one or more (e.g. 1, 2, 3, or 4) double or triple bonds in the chain.
By the process of the invention, the solution which comprises urea urethanes and is active as a thixotropic agent may be obtained in principle by two different routes:
a) on the one hand, it is possible first to mix at least two structurally different alcohols R—OH (i.e., R
1
—OH and R
2
—OH) and then to react the mixture with a from 1.5-to 5-fold excess of toluene diisocyanate. The unreacted portion of the toluene diisocyanate is subsequently removed from the reaction mixture under gentle conditions, in accordance with the prior art, and the resultant mixture of the structurally different monoisocyanate adducts is then reacted with the diamines in an aprotic solvent in the presence of a lithium salt to give urea urethanes of the general structure (II).
b) on the other hand, it is possible first to react at least two structurally different alcohols R—OH separately from one another with a from 1.5- to 5-fold excess of toluene diisocyanate. The unreacted portion of the toluene diisocyanate is removed from the respective reaction mixture under gentle conditions, in accordance with the prior art, and the resultant, structurally different monoisocyanate adducts are mixed with one another. The resultant mixture of structurally different monoisocyanate adducts is then reacted with the diamines in an aprotic solvent in the presence of a lithium salt to give urea urethanes of the general structure (II).
The molar fraction of the respective monoisocyanate adducts in the mixture of structurally different monoisocyanate adducts is between 20 and 80%, preferably between 35 and 65%, with particular preference between 45 and 55%, the sum of the molar fractions of the monoisocyanate adducts being 100%. The molar exces

Affiliated with

Also associated with

Rating

Rheologically active urea urethane compounds does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Rheologically active urea urethane compounds, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rheologically active urea urethane compounds will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3027843