Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Patent
1993-09-22
1994-11-08
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
525539, 528392, 528497, 528498, C08G 6702
Patent
active
053628500
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with the removal of palladium from polyketones.
It is known from EP 121864 and many subsequent patent applications that polyketones, which are linear polymers comprised of alternating units of (1) --CO-- and (2) one or more divalent units derived from one or more corresponding olefins, can be prepared by polymerising carbon monoxide with one or more olefins in an appropriate solvent in the presence of a catalyst prepared from a source of palladium, a diphosphine and a source of the conjugate base (anion) of certain acids having a pKa of less than 2. The process, which can be carried out either batchwise or continuously is typically effected at elevated temperature and pressure. A preferred solvent is a lower aliphatic alcohol such as methanol in which the polyketone is insoluble.
The synthesis of polyketones using the above-mentioned or similar palladium catalysts suffers from the disadvantage that significant levels of palladium are incorporated into the polymer mass during its preparation. This is a two-fold problem because firstly palladium is an expensive metal and secondly the incorporated palladium tends to adversely affect the subsequent processability of the polyketone. It would be desirable therefore to identify a method of recovering the palladium from the polyketone particularly if it can be recovered in a form in which it can be re-used without further treatment. Ideally such a method should also be easy to operate on a large scale and not add undue complexity to the polymerisation process.
A number of ways of solving this problem have been published in the art. For example, EP 224304 shows that under conditions where 95% of the palladium used was retained in the polymer, treatment with carbon monoxide followed by a washing step reduced the residual level of palladium to 29%. Similarily in EP 227135, treatment with a phosphine reduced the residual level to 37%.
In EP 283092, treatment of an ethylene/carbon monoxide copolymer with triethylamine reduced catalyst levels from 81 to 42% whilst treatment of an ethylene/propylene/carbon monoxide with triphenylphosphine reduced levels from 67 to 20%. For the same polymer, sodium acetate reduced catalyst levels from 67 to 27%.
Finally, EP 285218 teaches phosphine and amine terminating agents with the additional point that the temperature must be raised after the additional reagent is introduced, giving improvements in catalyst losses of e.g. 67 to 5% and 86 to 6%.
All these approaches to solving the problem have disadvantages. Phosphines, amines and acetates are reagents which cannot be directly recycled to the polymerisation reactor because under certain circumstances they adversely affect the catalyst. Carbon monoxide, on the other hand, is more easily vented from an olefin/CO mixture; consequently the complexity of the polymerisation process can be reduced if the carbon monoxide is removed in preference to the olefin or olefins.
A method of treatment has now been found which gives good catalyst recovery.
According to the present invention there is provided a process for removing palladium from a contaminated polyketone containing palladium which comprises contacting the contaminated polyketone with an olefin in the substantial absence of carbon monoxide at a temperature above the temperature at which the polyketone was formed and in a solvent in which the contaminated polyketone is insoluble.
The present invention solves the problem defined above by contacting the contaminated polyketone with an olefin e.g. ethylene in the substantial absence of carbon monoxide in a solvent, e.g. methanol, in which it is insoluble at a temperature above the temperature at which the polyketone was prepared. This causes the palladium to be extracted out of the polyketone into the solvent. Thereafter the polyketone and the solvent containing the palladium can be separated by filtration or other techniques which will be readily apparent to one of ordinary skill.
It is preferred that the process of the present invention is carried out in
REFERENCES:
patent: 4791190 (1988-12-01), Van Broekhoven
patent: 5070184 (1991-12-01), Wong
Cooper Jeremy B.
Lucy Andrew R.
Smith Kevin G.
BP Chemicals Limited
Foelak Morton
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