Process for the preparation of a polyester

Details Process for the preparation of a polyester Process for the preparation of a polyester

2001-01-30

2002-01-01

Acquah, Samuel A. (Department: 1711)

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

Synthetic resins

From phenol, phenol ether, or inorganic phenolate

C528S219000, C528S397000, C528S425000, C524S081000, C524S167000, C524S424000, C524S425000, C524S436000, C524S442000, C524S709000, C524S755000, C524S765000, C524S779000, C524S781000, C524S785000

Reexamination Certificate

active

06335415

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for the preparation of a polyester. More particularly, the present invention relates to a process for the preparation of a polyester from aromatic dilodide, an alkyl or aryl diol and carbon monoxide. More specifically, the invention is concerned with a process for preparing polyesters by contacting an aryl diiodide and an alkyl or aromatic diol with carbon monoxide in presence of a catalyst, the said catalyst then being recovered and recycled further.
BACKGROUND OF THE INVENTION
Polyesters constitute an important class of polymers with extensive commercial applications. The interests in polyesters as industrial material originates form their excellent heat resistance, high strength and high modulus. Generally, polyesters are prepared by;
1. Direct polyesterification (e.g Dicarboxylic acid+diol)
2. Ester exchange (Dialkyl or diaryl ester+diol)
3. Polycondensation of acid chloride and a diol
4. Lactone ring opening polymerization.
While, there are many other different methods for the polyester preparation, most of such conventional processes are characterized by difficulties in handling of unstable aromatic diacids or dichlorides, expensive starting materials and high reaction temperatures during their preparation.
The prior art has shown, as exemplified by U.S. Pat. Nos. 4,933,419 and 4,948,864 that polyesters may be produced from aromatic diiodides or dibromides and diols by treatment with a carbon monoxide using a palladium catalyst. This method of palladium-catalyzed carbonylation—polycondensation of aromatic dihalides and diol for the polyester manufacture based on Heck reaction, was originally developed by Emai and co-workers and subsequently by Perry and co-workers. The commonly employed solvent is monochlorobenzene. The resultant polyester is soluble in the reaction diluent and may be recovered by precipitating into methanol. Thus, all the reaction components including reacting monomers, catalyst and resultant polymer are soluble in the reaction medium. Until now, only homogeneous catalyst compositions have employed in such process A particular disadvantage, which neglects the commercial use of such homogeneous catalysts, is the difficulties in the efficient separation, recovery and further recycling of the catalyst. The loss of the precious metal during frequent recovery cycles makes any such process uneconomical to operate and overshadows technologically attractive conversion rates obtained with homogeneous catalysts.
Because of the commercial interest in polyesters, increasing academic as well as industrial attention has been paid towards research in developing new methods for their preparation. In view of the advantages and features of the present invention, the process of this invention would be a significant advance in the current state of the art related to the polyester synthesis.
Polyesters constitute an important class of synthetic polymers and have enjoyed great amount of commercial as well as industrial interest because of their high performance properties like superior mechanical strength and heat resistance. Conventional methods of preparation for the polyesters are characterised by high temperatures and handling of unstable and expensive reactants like diacid chlorides and the like. Documented literature reveals that only homogeneous catalysts have been investigated so far. A particular disadvantage of the commercial use of such homogeneous catalysts, is the difficulty in the efficient separation, recovery and further recycling of the catalyst. The loss of the precious metal during frequent recovery cycles makes any such process uneconomical to operate and overshadows technologically attractive conversion rates obtained with homogeneous catalysts.
OBJECTS OF THE INVENTION
It is an object of this invention to provide a process for polyester preparation with the provision for catalyst recovery.
It is a further object of this invention to provide a one step process for the preparation of polyesters utilizing a precious metal catalyst such as a palladium catalyst, which is easily recoverable and reusable in the process.
SUMMARY OF THE INVENTION
Accordingly the present invention provides a process for the preparation of polyester of the general formula (III) [—CO—Ar
1
—CO—O—Ar
2
—O—]
n
wherein Ar
1
is a bivalent aromatic residue and Ar
2
is an aromatic or alkyl residue, said process comprising reacting an aromatic diiodide of the general formula (I) I—Ar—I wherein Ar
1
is a divalent aromatic residue, with a diol of the general formula (II) HO—R—OH wherein Ar
2
is a bivalent aromatic or alkyl radical and carbon monoxide in presence of a catalyst containing a group VIII metal and a heterogeneous carrier or support, a base and a solvent.
In one embodiment of the invention, the aromatic diiodide is selected from the group consisting of m-diiodobenzene, p-diiodobenzene, 4,4′diiodobiphenyl, bis(4-iodophenyl)ether and 2,7-diioddnaphatahlene.
In one embodiment of the invention, wherein the diol is selected from the group consisting of Bisphenol A; 4,4′ dihydroxy biphenyl; 4,4′ biphenol, 4,4′ dihydroxy diphenyl sufone, 4,4′ dihydroxydiphenyl sulfone; 1,4 butane diol, 1,6 hexane diol and 1,3 propane diol.
In a further embodiment of the invention, the group VII metal in the catalyst is selected from the group consisting of Rhodium, Palladium, Platinum, Nickel and Cobalt.
In one embodiment of the invention, wherein the catalyst is a heterogeneous palladium catalyst.
In a further embodiment of the invention, wherein the heterogeneous palladium catalyst is selected from the group consisting of Pd/C; Pd/Al
2
O
3
; Pd/CaCO
3
, Pd/ZSM-5 and Pd/MgCl
2
.
In another embodiment of the invention, the carrier is an inorganic material selected from the group consisting of carbon powder, alumina, silica, carbonates and chlorides of calcium, magnesium and zeolite or an organic carrier selected from the group consisting of polymers such as polystyrene, polyvinyl pyrrolidene, polyaniline and polyethylene glycol.
In another embodiment of the invention, the catalyst preferably includes a phosphine selected from the group consisting of triphenylpbosphine, tri-toluylphosphine and trialkylphosphoine or a diphosphine selected from the group consisting of 1,3-diphenylphosphinepropane, 1,4-diphenylphosphinobutane and 1,3-diethylphosphinopropane.
In another embodiment of the invention, the solvent is selected from the group consisting of dimethylacetamide, dimethylformamide, N-methylpyrolidine, pyrridene, benzene, toluene, monochlorobenzene, xylene and tetrahydrofuran.
In another embodiment of the invention, the base employed is selected from the group consisting of a tertiary amine of the general formula NR
3
wherein each R is independently selected from a group containing alkyl, aryl, cycloalkyl residues which may be substituted or unsubstituted, metal hydroxide and metal carbonates.
In a further embodiment of the invention, the base is selected from the group consisting of DBU, DBN, DABCO, triethylamine, tri-butyl amine, Na
2
CO
3
, KOH, NaOH and sodium acetate.
In a further embodiment of the invention, the base is used in its free state or immobilized on a carrier.
In a further embodiment of the invention, the reaction is conducted at a pressure from 0.1 to 100 bars.
In a further embodiment of the invention, the CO used is pure.
In a further embodiment of the invention, the CO is diluted with other gases selected from the group consisting of argon, nitrogen and helium.
In a further embodiment of the invention, the reaction is conducted at a temperature ranging from 60° C. to 210° C.
In another embodiment of the invention, the heterogeneous catalyst is recycled.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method for the preparation of polyesters by contacting an aromatic diiodide, an alkyl or aryl diol and carbon monoxide in presence of a catalyst, an organic base and preferably, a liquid reaction diluent. The said catalyst is a heterogeneous cata

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