Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-02-25
2004-05-18
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...
C526S217000, C526S258000, C525S374000, C568S924000, C568S949000
Reexamination Certificate
active
06737488
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the preparation of polymers via controlled “pseudo-living” free-radical polymerization of vinyl monomers using nitrogen monoxide.
SUMMARY OF THE INVENTION
A process for the production of polymers by means of pseudo-living free-radical polymerization is disclosed. The process entails (i) reacting a polymerizable vinyl monomer with nitrogen monoxide and at least one initiator to prepare a free-radical intermediate product, and (ii) polymerizing the intermediate product optionally together with one or more additional monomers and/or with a free-radical initiator.
DESCRIPTION OF THE DRAWINGS
FIG. 1
shows the relationship between number average molecular weight and conversion for polymerizations with and without and activator according to the invention;
FIG. 2
shows the relationship between polydispersity (Mw/Mn) and conversion for polymerizations with and without and activator according to the invention;
FIG. 3
shows the relationship between number average molecular weight and conversion for polymerizations according to the invention;
FIG. 4
shows the relationship between number average molecular weight and conversion for polymerizations according to the invention;
FIG. 5
shows the relationship between number average molecular weight and conversion for polymerizations according to the invention;
FIG. 6
shows the relationship between number average molecular weight and polydispersity versus conversion for polymerizations according to the invention;
FIG. 7
shows the relationship between number average molecular weight and conversion for polymerizations according to the invention;
FIG. 8
shows the relationship between number average molecular weight and conversion for polymerizations according to the invention;
FIG. 9
shows the relationship between number average molecular weight and conversion for polymerizations according to the invention;
FIG. 10
shows the relationship between number average molecular weight and time for polymerizations according to the invention;
FIG. 11
shows the relationship between number average molecular weight and conversion for polymerizations according to the invention; and
FIG. 12
shows the relationship between number average molecular weight and time for polymerizations according to the invention.
BACKGROUND OF THE INVENTION
Nowadays, the demand for homopolymers, random copolymers and block copolymers of a specific molecular weight, a narrow molecular weight distribution and/or well-defined end groups has continuously increased in a number of industries. The controlled structure of these macromolecules provides them with novel properties and allows a tailor-made property profile to be obtained. Thus many new technologies require controlled polymer structures, such as for example in the fields of electronics, computer science, communications, genetic engineering, biotechnology and materials science.
Well-defined polymers can for example be produced by ionic living polymerization processes. However, ionic processes require drastic reaction conditions, such as for example temperatures of about −78° C., extreme dryness and the absence of protic species and only a few monomers can be used.
In contrast to ionic processes, free-radical polymerization can be carried out under mild conditions and a wide range of monomers can be used. Significant progress in the control of free-radical polymerization has been made.
Otsu et al., for example, were the first to report on the possible control of the free-radical polymerization of some vinyl monomers based on the iniferter concept (see: J. Polym. Sci.: Part A: Polym. Chem. 2000, 38, 2121). Meanwhile three main methods of controlled free-radical polymerization, sometimes described as “living” free-radical polymerization, have been developed:
(I) Nitroxide-mediated polymerization (NMP), which is based on the reversible capture of the propagating radicals by nitroxide radicals to form dormant chains. This strategy is disclosed for example in U.S Pat. No. 4,581,429. This process is handicapped by slow polymerization kinetics, a limited range of suitable monomers and the high cost of the required nitroxide radicals.
(II) Atom transfer radical polymerization (ATRP), which involves the reversible trapping of the propagating chains by halogen atoms and is mediated by metallic catalysts, is described extensively in Acc. Chem. Res. 1999, 32, 895. A serious drawback of this method is the use of transition metal catalysts (Fe, Cu) which are potentially toxic, impart colour to the resulting polymers and lead to corrosion problems. Removal of the catalyst from the resulting polymers is possible but relatively costly.
(III) Reversible addition-fragmentation chain transfer (RAFT) using dithio esters as transfer agents, which is disclosed for example in WO 98/01478. This method is limited to specific monomers and uses costly dithio esters which impart an unpleasant smell to the resulting polymers.
Although controlled free-radical polymerization represents an attractive method of obtaining new polymer structures there is still a need for an inexpensive, versatile control method that can be applied to a broad range of monomers.
One method of obtaining alkoxyamine initiators as nitroxide precursors has been described in WO 98/13392 and in EP-A 0 891 986. Conventional free-radical initiators are decomposed thermally in the presence of nitrogen monoxide NO. The resulting NO compounds can be used as initiators for controlling the free-radical polymerization of vinyl monomers. A disadvantage of these initiators is that polymerization appears to be controlled only for short polymer chains with number average molecular weights smaller than 15,000. Most industrially relevant polymers have to possess a number average molecular weight in excess of 50,000 in order to display the desired mechanical properties such as rigidity, elasticity or toughness. In addition, the methods described in the cited prior art still require the synthesis and isolation of the initiators in a step separate from the polymerization.
When added directly during free-radical polymerization nitrogen monoxide is reported (such as for example in DE-A 2 660 230, U.S. Pat. Nos. 4,040,912 and 3,964,979) to be a polymerization inhibitor.
Under appropriate conditions sodium nitrite may be used as a precursor of nitroxide compounds. Since sodium nitrite is inexpensive, this could provide a cheap method of access to nitroxide radicals.
The prior art has already mentioned sodium nitrite as a control agent for free-radical polymerization. For instance, EP-A 1 061 059 mentions sodium nitrite as an inhibitor of the free radical polymerization of butadiene when used in combination with specific phosphorus-containing compounds. The possible control of polymerization under such conditions is not disclosed.
In attempts to reduce gel formation during the polymerization of concentrated solutions of sodium acrylate in water, Bortel et al. (J.M.S.-Pure Appl. Chem. 1998, A35(2), 401) observed that adding sodium nitrite inhibits polymerization up to a polymerization temperature of 60° C. It was found that although the molecular weight of the polymer increases slightly with time, the polydispersity (D={overscore (M)}
w
/{overscore (M)}
n
) is very high (typically D higher than 6), this being a clear indication of “classical” free-radical polymerization. Other monomers than sodium acrylate are not disclosed.
The in-situ formation of NO compounds from free radical initiators and nitroso compounds is reported in Mendeleev Comm. 1999, 6, 250. Similar compounds can also be formed by the reaction of free radical initiators with nitrones as reported in WO 99/03894. These methods still however require the use of preformed reagents which may be toxic.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based on the problem of providing homo- and copolymers of controlled molecular weight and controlled molecular structure by a simple and inexpensive method of controlling the free-radical polymerization
Dètrembleur Christophe
Jerome Robert
Meyer Rolf-Volker
Vanhoorne Pierre
Bayer Aktiengesellschaft
Gil Joseph C.
Matz Gary F.
Preis Aron
Zalukaeva Tatyana
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