Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-11-27
2004-02-24
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S449000, C524S451000, C524S492000, C524S493000, C524S494000, C524S556000, C524S565000, C524S566000, C524S571000, C524S573000, C524S575000, C524S821000, C524S836000, C524S561000, C524S562000, C525S329300, C525S331900, C526S091000, C526S093000, C528S487000, C528S488000, C528S499000
Reexamination Certificate
active
06696518
ABSTRACT:
The present invention relates to a process for hydrogenating ethylenically unsaturated double bonds in polymers P by reacting an aqueous dispersion of at least one polymer P with hydrogen in the presence of at least one hydrogenation catalyst.
The hydrogenation of ethylenically unsaturated double bonds is an important method of derivatizing polymers containing such bonds. A range of polymers of this kind are produced on the industrial scale, examples being butadiene- and/or isoprene-based polymers. Therefore, hydrogenation makes it possible to provide classes of polymer which are new or which can otherwise be prepared only by a very much more complex method.
In developing hydrogenation processes for polymers a consideration is that the polymers for hydrogenation may contain not only the ethylenically unsaturated double bonds but also other hydrogenation-reactive functionalities. A feature of the hydrogenation process must therefore be, in general, a high level of selectivity toward the target double bonds. Further, an intrinsic risk of hydrogenation is that there may be generated on the polymer reactive intermediates which have the capacity to react with remaining double bonds and so cause crosslinking.
Techniques for hydrogenating polymers that contain ethylenically unsaturated double bonds are fundamentally known. An overview of such techniques is given by N. T. McManus et al. (J. Macromol. Sci., Rev. Macromol. Chem. Phys. (C 35(2), 1995, 239-285). A common feature of all of the techniques described is that the reaction is conducted in an organic medium. This includes the homogeneous reaction of the dissolved polymer in the presence of a homogeneously dissolved catalyst in an organic solvent, and heterogeneous reactions of polymers in suspension in an organic solvent in the presence of homogeneously dissolved catalysts, and also the hydrogenation of polymer solutions and/or polymer melts in the presence of heterogeneous catalysts. However, gelling is generally observed in the course of the hydrogenation, which points to crosslinking reactions.
EP-A 588097 discloses the hydrogenation of polymers based on butadiene/acrylonitrile (NBR). In these processes the polymers are reacted in the form of aqueous dispersions in at least five times the amount, based on the dispersion, of an organic solvent and in the presence of ruthenium catalysts. Special additives are added to extensively suppress the formation of crosslinked polymers. A disadvantage of this process is the large quantities of solvent that are employed.
Fundamentally there is great interest in the transfer of the catalytic hydrogenation of polymers containing ethylenically unsaturated double bonds to aqueous reaction systems. For instance, some industrially important butadiene polymers are available commercially as aqueous polymer dispersions. Furthermore, the use of solvents in the course of production is a not insignificant cost factor. Solvent avoidance also appears desirable on the grounds of workplace safety and environmental protection.
Singha et al. (Rubber Chemistry and Technology, Vol. 68, 1995 pp. 281-86) describe the hydrogenation of an aqueous NBR dispersion in the presence of water-soluble catalysts of the Wilkinson type. Despite comparatively high catalyst quantities, the conversions achieved are low.
The older German Patent Application P 197 53 302.7 describes the hydrogenation of aqueous polymer dispersions containing butadiene in the presence of a transition metal catalyst comprising rhodium and/or ruthenium and at least one phosphorus compound. In this case a solution of the hydrogenation catalyst is prepared first of all, from a salt or complex compound of the respective transition metal and a phosphorus compound in an organic solvent, under a hydrogen atmosphere, and this solution is subsequently added to the aqueous polymer dispersion to be hydrogenated. This method leads to satisfactory hydrogenation conversions and avoids the use of relatively large amounts of solvent. A disadvantage, however, is that with the catalyst an organic solvent is incorporated into the polymer dispersion. Furthermore, the separate preparation of the catalyst entails additional effort.
It is an object of the present invention to provide a process for hydrogenating ethylenically unsaturated double bonds in polymers which can be conducted in an aqueous dispersion of the polymers P and ensures high selectivity of the hydrogenation of the ethylenic double bond over the hydrogenation of other functionalities and over crosslinking reactions.
We have found that this object is achieved, surprisingly, by a process in which an aqueous dispersion of a polymer P having ethylenically unsaturated double bonds is hydrogenated in the presence of a hydrogenating catalyst which comprises at least one transition metal selected from rhodium and/or ruthenium and at least one nonionic phosphorus compound capable of forming a coordinative compound with the transition metal and is incorporated in the aqueous dispersion of the polymer P without addition of a solvent.
The present invention therefore provides a process for hydrogenating ethylenically unsaturated double bonds in polymers P by reacting an aqueous dispersion of at least one polymer P with hydrogen in the presence of at least one hydrogenation catalyst comprising at least one transition metal selected from rhodium and/or ruthenium and at least one nonionic phosphorus compound capable of forming a coordinative compound with the transition metal, which comprises incorporating the hydrogenation catalyst into the aqueous dispersion of the polymer P without adding a solvent.
In the present case an ethylenically unsaturated double bond is a singly, doubly or triply substituted C═C double bond which is not part of an aromatic &pgr;-electron system. It is preferably not conjugated with other double bonds.
In accordance with the invention, the hydrogenation catalyst is incorporated into the dispersion of the polymer P to be hydrogenated without addition of an organic solvent. For this purpose the hydrogenation catalyst can be incorporated as it is, i.e., in the form of a complex compound containing the respective transition metal and at least one phosphorus compound as ligand, into the dispersion. In this case the catalyst is generally incorporated by adding the complex compound comprising transition metal and phosphorus compound to the aqueous dispersion of the polymer P to be hydrogenated. The complex compound comprising transition metal and phosphorus compound can be added as a solid, as an aqueous solution, or as a solution in a dilute aqueous mineral acid, e.g., in dilute hydrochloric acid.
The transition metal and the phosphorus compound can also be incorporated separately into the dispersion of the polymer P to be hydrogenated. For this purpose, the transition metal is incorporated in the form of a salt or complex compound containing no phosphorus compound into the dispersion of the polymer P. In this case the phosphorus compound is incorporated separately into the dispersion of the polymer P.
For incorporating the transition metal into the dispersion of the polymer P it is possible, for example, to add a salt or an appropriate complex compound of the transition metal as a solid, aqueous solution or solution in a dilute mineral acid to the dispersion of the polymer P. The transition metal can also be incorporated by dissolving a salt or complex compound of the transition metal in the monomers M to be polymerized, prior to the preparation of the dispersion of the polymer P, and subsequently preparing the polymer P by polymerizing the monomers M in the presence of the transition metal. This method is particularly appropriate when the aqueous dispersion of the polymer P is prepared by free-radical aqueous emulsion polymerization of the monomers M constituting the polymer P. Where the aqueous dispersion of the polymer P is a secondary dispersion, the transition metal can be dissolved in appropriate form in a solution or melt of the polymer, which is then converted to the actual aqueous
Dersch Rolf
Maas Heiko
Schädler Volker
BASF - Aktiengesellschaft
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Reddick Judy M.
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