Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-05-29
2004-02-10
Wilson, D. R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S381000, C525S379000, C525S330500
Reexamination Certificate
active
06689844
ABSTRACT:
Invention relates to a process for synthesis of polymer compositions with reduced living halogen content, wherein ethylenically unsaturated monomers are first polymerized by means of initiators containing a transferable halogen and of one or more catalysts comprising at least one transition metal in the presence of ligands which can form a coordination compound with the metal catalyst or catalysts. The invention also relates to polymer compositions with reduced living halogen content as well as to the use of these polymer compositions.
Radical polymerization is an important commercial process for synthesis of diverse polymers, such as PMMA and polystyrene. It suffers from the disadvantage that it is relatively difficult to control the composition of the polymers, the molecular weight and the molecular weight distribution.
One solution to this problem is offered by the so-called ATRP process (=Atom Transfer Radical Polymerization). It is assumed that this process comprises “living” radical polymerization, although the description of the mechanism is not to be construed as limitative. In this process a transition metal compound is reacted with a compound containing a transferable group of atoms. Under these conditions the transferable group of atoms is transferred to the transition metal compound, whereby the metal is oxidized. A radical that adds onto ethylenic groups is formed in this reaction. The transfer of the group of atoms to the transition metal compound is reversible, however, and so the group of atoms is transferred back to the growing polymer chain, whereby a controlled polymerization system is formed. Accordingly it is possible to control the composition of the polymer, the molecular weight and the molecular weight distribution.
This reaction procedure is described, for example, by J-S. Wang et al., J. Am. Chem. Soc., Vol. 117, pp. 5614-5615, and by Matyjaszewski, Macromolecules, Vol. 28, pp. 7901-7910 (1995). Furthermore, International Patent Applications WO 96/30421, WO 97/47661, WO 97/18247, WO 98/40415 and WO 99/10387 disclose modifications of the aforesaid ATRP.
The mechanism described hereinabove is not undisputed. WO 97/47661, for example, states that polymerization takes place by insertion, and not by a radical mechanism. Such a differentiation is not pertinent to the present invention, however, since in the reaction procedure disclosed in WO 97/47661 there are used compounds which are also employed for ATRP.
The advantages of known ATRP polymerization processes, however, are largely limited to monomers which are themselves polar or which are readily soluble in polar media. Certainly the occasional use of nonpolar aprotic hydrocarbons such as benzene, toluene, xylene cyclohexane and hexane is also known from the literature, but the polymers synthesized with these solvents exhibit much greater polydispersity. This effect is described in, for example, WO 98/40415.
Usually the polymers obtainable by ATRP processes contain halogen atoms, which as the living chain end permit a narrow molecular weight distribution. Nevertheless, these halogens, which usually are necessarily present at the chain end, are associated with disadvantages. For example, these halogen constituents can be liberated during decomposition of the polymers. Especially upon contact with metals such as are contained in pumps, motors and similar components, liberated halogens cause corrosion, which leads to destruction of the pumps, motors, etc. Furthermore, the halogens lead to problems in reprocessing of the polymers. In particular, combustion can lead to highly toxic dioxins.
The associated problems as well as a process for removal of halogens from polymers obtained by ATRP processes are described in, for example, International Patent Application WO 99/54365. This document describes a process in which the living halogens are transformed to double bonds, by reacting the ATRP polymer containing a halogen atom as the active chain end subsequent to polymerization with a compound containing a double bond capable of limited ATRP polymerization. The compound containing the double bond capable of limited polymerization is added to the living end of the ATRP polymer, and the living halogen atom is eliminated with formation of a double bond. 1,1-Dimethylethylene, 1,1-diphenylethylene, vinyl acetate, isoprenyl acetate, &agr;-methylstyrene, 1,1-dialkoxyolefin, dimethyl itaconate and diiusobutene are explicitly disclosed therein as compounds containing the double bond capable of limited polymerization.
In nonpolar solvents such as mineral oils, however, the use of this process does not lead to the desired elimination of the living halogen atom at the active chain end and to the formation of the terminal double bond. Instead, the living halogen remains unchanged in the polymer.
Nevertheless, processes which can be carried out in nonpolar solvents in order to synthesize ATRP polymer compositions with reduced living halogen content at the active chain end are needed by industry. Such processes would be universally advantageous, especially for synthesis of polymer products such as mineral-oil additives for use in nonpolar solvents, because the otherwise necessary step for changing solvents is obviated. Instead, the desired compositions could be synthesized directly.
The paper by M. Bednarek, T. Biedroni and P. Kubisa entitled “Synthesis of block copolymers by atom transfer radical polymerization of tert-butyl acrylate with poly(oxyethylene) macroinitiators”, Macromol. Rapid Commun., 20, 59-65 (1999), describes the ATRP bulk polymerization of tert-butyl acrylate using a polyoxyethylene macroinitiator. CuBr is used as catalyst and pentamethyldiethylenetriamine (PMDETA) as the ligand. During this polymerization, the living halogen at the active chain end is replaced by hydrogen in a side reaction. In this connection, the authors (page 65, 1st paragraph) do not rule out participation of the PMDETA in the exchange reaction. A process for selective removal of the living halogen at the active chain end of the ATRP polymer and for formation of a polymer with a terminal double bond is not disclosed by this paper.
In view of the prior art, it was now an object of the present invention to provide processes for synthesis of polymer compositions with reduced halogen content, wherein the living halogen atom at the active chain end should be substantially removed.
A further object was to provide a process that can be performed inexpensively and applied on a large industrial scale. Furthermore, the process should be possible easily and simply with commercially available components.
Furthermore, broadening of the molecular-weight distribution of the polymer composition should be prevented by the reaction.
A further object of the present invention was to provide, for synthesis of polymer compositions with reduced halogen content, a process in which decomposition of the polymers contained in the composition is prevented.
A further object was to find polymer compositions which have an excellent spectrum of properties, so that they can be added as an ideal additive to lubricating oils.
This means among other requirements that the polymers contained in the composition have low sensitivity to oxidation and high resistance to shear loads.
In particular, the polymers contained in the polymer composition must have a narrow molecular-weight distribution and be substantially halogen-free.
These objects are achieved by a process for synthesis of a polymer composition having all features of claim 1, as are other objects which are not explicitly cited but which can be obviously derived or inferred from the relationships discussed herein in the introduction. Advantageous modifications of the inventive process are protected in the dependent claims which refer back to claim 1. As regards the polymer compositions, the independent product claim provides a solution to the underlying problem, while the claim from the use category protects a preferred use of a polymer solution synthesized according to the present process.
By the fact that, a
Bollinger Joseph Martin
Roos Sebastian
Scherer Markus
RohMax Additives GmbH
Wilson D. R.
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