Processes for synthesis of polymer compositions

Details Processes for synthesis of polymer compositions Processes for synthesis of polymer compositions

2000-11-13

2003-08-26

Zalukaeva, Tatyana (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S145000, C526S146000, C526S147000, C526S319000, C526S318400, C526S328000

Reexamination Certificate

active

06610801

ABSTRACT:

The invention relates to processes for synthesis of polymer compositions, wherein ethylenically unsaturated monomers are polymerized by means of initiators containing a transferable group of atoms 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 the use of these polymer compositions as well as to processes for isolation of polymers from such a polymer solution.
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 98/20050, 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 monomers, transition metal catalysts, ligands and initiators are chosen on the basis of the polymer solution desired. It is assumed that a high rate constant of the reaction between the transition metal/ligand complex and the transferable group of atoms, plus a low equilibrium concentration of free radicals, is essential for a narrow molecular weight distribution. If the free radical concentration is too high, typical termination reactions, which are responsible for a broad molecular weight distribution, will occur. The exchange rate depends, for example, on the transferable group of atoms, on the transition metal, on the ligands and on the anion of the transition metal compound. The person skilled in the art will find valuable advice on selection of these compounds in, for example, International Patent WO 98/40415.
The advantages of known ATRP 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.
The same document also discloses the possibility of polymerizing polar monomers such as methyl methacrylate or styrene by means of metallic copper, but the molecular weight distribution is much more unfavorable than in the use of a mixture of Cu
0
/CuBr or Cu
0
/CuBr
2
.
In Pol. Preprint (ACS, Div. Pol. Chem)., 1999, 40(2), 432, M. J. Ziegler et al. state among other facts that the polymerization of t-butyl methacrylate is difficult to control if the said process takes place in bulk. Both the molecular weight and the polydispersity can be improved by using approximately 20 to 25 wt % of polar solvents. Of course, because of the limited solubility in polar solvents of ethylenically unsaturated ester compounds containing alkyl or heteroalkyl groups with at least 8 carbon atoms, it is difficult by means of the known ATRP processes to polymerize ethylenically unsaturated monomer mixtures that contain at least 50 wt % of ethylenically unsaturated ester compounds containing alkyl or heteroalkyl chains with at least 8 carbon atoms. Furthermore, depending on use, these large volumes of polar solvents must be separated from the composition after synthesis of the polymers.
In view of the prior art, it is now an object of the present invention to provide processes for synthesis of a polymer composition, wherein the polymers contained in the composition are intended to comprise at least 50 wt % of (meth)acrylates containing alkyl or heteroalkyl chains with at least 8 carbon atoms.
Furthermore, the polymers contained in the composition are intended to have a narrow molecular weight distribution. In particular, it is intended that the use of relatively complex processes such as anionic polymerization for synthesis of the polymer mixture will be avoided.
Another object of the present invention was to provide a polymerization process by which polymers with relatively high or high molecular weights can be obtained.
Yet another 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.
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 process for synthesis of polymers, the independent process claim specifies how to achieve the underlying object, while the claim in the use category protects a preferred use of a polymer solution synthesized according to the present process.
By polymerizing ethylenically unsaturated monomers containing 50 to 100 wt %, relative to the total weight of ethylenically unsaturated monomers, of one or more ethylenically unsaturated ester compounds of formula (I)
wherein R denotes hydrogen or methyl, R
1
denotes a straight-chain or branched alkyl group with 8 to 40, preferably 10 to 40 carbon atoms, R
2
and R
3
independently denote hydrogen or a group of the formula —COOR′, wherein R′ denotes hydrogen or a straight-chain or branched alkyl group with 8 to 40, preferably 10 to 40 carbon atoms, in the presence of copper, the concentration of copper of oxidation numbers (I) and (II) in the composition being ≦200 ppm relative to the total weight of the composition, less the weight of copper of oxidation number (0) in the composition, it has become possible in a manner that is not directly foreseeable to achieve a process for synthesis of a polymer composition having a narrow distribution of the polymers.
For this purpose ethylenically unsaturated monomers are polymerized by means of initiators containing a transferable group of atoms 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. This type of synthesis can be achieved particularly inexpensively and in this respect is industrially interesting.
At the same time, several other advantages can be achieved by the inventive process. They include among others:
A narrow distribution of the polymers in the polymer compo

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