Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1997-03-07
2001-04-17
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S094000
Reexamination Certificate
active
06218486
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the use of an organocobalt (III) catalyst to polymerize vinyl chloride monomer. In particular, it relates to the use of an acid activated cationic catalyst having two organic ligands covalently bonded to a cobalt atom and four ligands donating electron pairs to the cobalt atom, where the various ligands can be bridged together.
Commercially, a peroxide initiator is used to produce poly(vinylchloride) (PVC) from vinyl chloride monomer (VCM). Peroxide initiators are difficult to handle because they are unstable and can explode if proper safety precautions are not followed. Since the reaction mixture containing the peroxide initiators must be heated to start the polymerization process, the production of PVC periodically grinds to a halt while reactors are heated to the necessary temperature. In addition, when a peroxide is used it is incorporated, which can destabilize the polymer.
Cationic organocobalt (III) catalysts have been used to polymerize various monomers, including methyl methacrylate (Gridnev A. A., et al.—Dokl. Akad.Nauk SSSR, v.267, N.1, p. 103 (1982)), 1,1,2-trifluoro-1,3-butadiene (Rogova E. V., et al.—Polymer Science, Ser.B, v.37, N.9-10, p.447 (1995)), and styrene Russian Patent SU 1816764 (1993)). However, catalysts used in the addition polymerization of unsaturated monomers tend to be specific to a given monomer. For example, many metallocene catalysts that will readily polymerize ethylene or styrene will not polymerize vinyl chloride.
SUMMARY OF THE INVENTION
We have discovered that certain organocobalt (III) complexes are useful as catalysts for polymerizing VCM. Surprisingly, we have discovered that some of these complexes are very active and convenient to use as polymerization catalysts. Because these catalysts are activated by acids rather than heat, there is no delay in the production of the PVC due to heating the reactor, as there is with peroxide catalysts.
While PVC produced in a suspension process using peroxide catalysts consists of many small particles enclosed in a pericular skin (see
Particulate Nature of PVC
by G. Butters, pages 4,8, and 9; 1982), PVC produced in a suspension process using a catalyst according to this invention is skinless. The absence of this skin is an unexpected phenomenon that is expected to accelerate the removal of unreacted VCM from the particles and the diffusion of plasticizer into the particles.
REFERENCES:
patent: 4694054 (1987-09-01), Jamewicz
patent: 767417 (1957-02-01), None
patent: 1136326 (1968-12-01), None
patent: 1816764 (1993-05-01), None
M. Clark, Particulate Nature of PVC, 1982, pp. 1 to 10.
PCT International Appl. WO9615158 A1.
A. A. Gridnev, et al. Doki. Akad. Nauk SSSR, v. 267, N. 1, p. 103 (1982).
E. V. Rogova et al.—Polymer Science, Ser B, v. 37, N. 9-10, p. 447 (1995).
Nagy Sandor
Tyrell John
Brookes Anne E.
Fuerle Richard D.
Henderson Christopher
Occidental Chemical Corporation
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