Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Patent
1997-12-15
1999-11-09
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
528 44, 528 61, 528 67, 528 69, 525452, 525453, C08G 1881, C08G 1800
Patent
active
059816848
DESCRIPTION:
BRIEF SUMMARY
The invention relates to highly functional, highly branched poly-urethanes, their preparation, and monomers for the preparation of polyurethanes of this type.
Highly functionalized molecules, ie. dendrimers or arboroles, and highly branched polymers, also called hyperbranched polymers, have recently been attracting interest in chemistry and pharmacy.
Dendrimers are three-dimensional, highly ordered, highly branched oligomeric and polymeric compounds which, starting from small molecules, are formed by a continuously repeating reaction sequence. In this process, higher and higher branchings are formed, at the end of which in each case are functional groups which, in turn, are the starting point for further branchings.
A description of dendrimers is found in D. A. Tomalia, A. M. Naylor, W. A. Goddard III, Angew. Chem., 1990, 102, 119-157.
A highly branched polyurethane is described in R. Spindler, J. M. J. Fr e chet, J. Chem Soc. Perkin Trans. I, 1993, 913.
The monomer used there has the structural formula ##STR1## An isocyanate-terminated, highly branched polyurethane can be prepared from this monomer by a polyaddition reaction.
A problem in this case is the preparation of the monomer. The starting material used is a compound having the following structure: ##STR2## First, the hydroxyl group is blocked with tert-butyldiphenylsilyl chloride, and the nitro groups are converted by hydrogenation and subsequent phosgenation into isocyanate groups, which are blocked with phenol. To carry out the polyaddition reaction, the blocking agents are removed. Owing to the necessity of removing the phenol and the use of the very expensive tert-butyldiphenylsilyl chloride, the described preparation of the highly branched polyurethanes is uneconomical.
A. Kumar and S. Ramachrishnan, J. Chem. Soc., Chem. Commun. 1993, 1453, describe highly branched polyurethanes which are prepared from monomers of the following structure: ##STR3## The acid azide eliminates nitrogen on warming and by rearrangement intermediately forms the isocyanate, which reacts further to give a hydroxyl-terminated polyurethane.
Here too, the starting monomer is difficult to prepare because acid azides decompose easily and in some cases with violent reactions, additionally the urethane group formed from isocyanate and phenolic hydroxyl group is thermally unstable.
It is an object of the present invention to provide highly branched and dendrimeric polyurethanes which can be reproducibly prepared from easily accessible monomers by simple process steps.
We have found that this object is achieved by reaction of monomers containing an NCO group and containing n groups reactive with NCO or a group reactive with NCO and n NCO groups, where groups reactive with NCO are, in particular, mercapto, but preferably amino or hydroxyl groups, and n is in the range from 2 to 5, in particular 2 to 4, and is particularly preferably equal to 2 to 3.
The difference between highly branched and dendrimeric polyurethanes is in that dendrimeric polyurethanes, starting from an initiator core, are built up like a shell in defined reaction stages (generations) and have a defined molar mass, highly branched polyurethanes, however, are built up irregularly and have a molar mass distribution.
These structural differences are intended to be illustrated in the following schematic representations:
Highly branched polyurethanes formed from AB.sub.2 monomers: ##STR4## Polyurethane dendrimers formed from initiator core I and AB.sub.2 monomers: ##STR5## In this context, in the present case, A and B can be a hydroxyl or isocyanate group, BA a urethane group and I the initiator core. Depending on functionality, even more of the dendrimer branches shown can be attached to the initiator core I.
To prepare the compounds according to the invention, it is first necessary to prepare monomers of the type AB.sub.n, where A and B are each an isocyanate group and an H-functional group reactive with it and n is a positive number .gtoreq.2, in particular equal to 2 or 3.
By way of example, the preparation of a
REFERENCES:
patent: 5041516 (1991-08-01), Frechet et al.
Two-step Approach towards the Accelerated Synthesis of Dendritic Macromolecules. Ralph Spindler and Jean M.J. Frechet. J Chem. Soc. Prekin Trans. I, Jan. 1993 (913-918).
Bruchmann Bernd
Graf Hermann
Wingerter Frank
Wolff Stefan
BASF - Aktiengesellschaft
McClendon Sanza L.
Seidleck James J.
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