Halogenated, high molecular weight, gel-free isobutene...

Details Halogenated, high molecular weight, gel-free isobutene... Halogenated, high molecular weight, gel-free isobutene...

2001-12-10

2003-04-08

Lipman, Bernard (Department: 1713)

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

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S355000, C525S356000

Reexamination Certificate

active

06545100

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to halogenated, low-gel, high molecular weight isoolefin multiolefin copolymers, in particular to halogenated, low-gel, high molecular weight butyl rubbers, and halogenated, low-gel, high molecular weight isoolefin multiolefin copolymers synthesized from isobutene, isoprene and optionally further monomers, with a multiolefin content of greater than 2.5 mol %, a molecular weight M
w
of greater than 240 kg/mol and a gel content of less than 1.2 wt. % and a process for their preparation.
BACKGROUND OF THE INVENTION
Butyl rubber is a copolymer of an isoolefin and one or more conjugated multiolefins as comonomers. Commercial butyl comprises a major portion of isoolefin and a minor amount, not more than 2.5 wt %, of a conjugated multiolefin. The preferred isoolefin is isobutylene. Suitable conjugated multiolefins include isoprene, butadiene, dimethyl butadiene, piperylene, etc. of which isoprene is preferred. It is generally prepared in a slurry process using methyl chloride as a vehicle and a Friedel-Crafts catalyst as the polymerization initiator. The methyl chloride offers the advantage that AlCl
3
a relatively inexpensive Friedel-Crafts catalyst is soluble in it, as are the isobutylene and isoprene comonomers. Additionally, the butyl rubber polymer is insoluble in the methyl chloride and precipitates out of solution as fine particles. The polymerization is generally carried out at temperatures of about −90° C. to −100° C. See U.S. Pat. No. 2,356,128 and Ullmanns Encyclopedia of Industrial Chemistry, volume A 23,1993, pages 288-295. The low polymerization temperatures are required in order to achieve molecular weights which are sufficiently high for rubber applications.
Raising the reaction temperature or increasing the quantity of isoprene in the monomer feed results in more poor product properties, in particular, in lower molecular weights. However, a higher degree of unsaturation would be desirable for more efficient crosslinking with other, highly unsaturated diene rubbers (BR, NR or SBR).
The molecular weight depressing effect of diene comonomers may, in principle, be offset by still lower reaction temperatures. However, in this case the secondary reactions, which result in gelation occur to a greater extent. Gelation at reaction temperatures of around −120° C. and possible options for the reduction thereof have been described (c.f. W. A. Thaler, D. J. Buckley Sr., Meeting of the Rubber Division, ACS, Cleveland, Ohio, May 6-9, 1975, published in
Rubber Chemistry
&
Technology
49, 960-966 (1976)). The auxiliary solvents such as CS
2
required for this purpose are not only difficult to handle, but must also be used at relatively high concentrations.
Furthermore, it is furthermore known to perform gel-free copolymerization of isobutene with various comonomers to yield products of a sufficiently high molecular weight for rubber applications at temperatures of around −40° C. using pretreated vanadium tetrachloride (EP-A1-818 476).
It is also possible to use this aged vanadium initiator system at relatively low temperatures and in the presence of an isoprene concentration which is higher than conventional (approx. 2 mol % in the feed), but, as with AlCl
3
-catalyzed copolymerization at −120° C., in the presence of isoprene concentrations of >2.5 mol % this results in gelation even at temperatures of −70° C.
Halogenated butyls are well known in the art, and possess outstanding properties such as oil and ozone resistance and improved impermeability to air. Commercial halobutyl rubber is a halogenated copolymer of isobutylene and up to about 2.5 wt % of isoprene. As higher amounts of isoprene lead to gelation and/or too low molecular weight of the regular butyl being the starting material for halogenated butyl, no gel-free, halogenated butyls with comonomer contents of greater than 2.5 mol %, a molecular weight M
w
of greater than 240 kg/mol and a gel content of less than 1.2 wt. % are known.
SUMMARY OF THE INVENTION
One object of the present invention was to provide halogenated, low-gel, high molecular weight isoolefin multiolefin copolymers, in particular to halogenated, low-gel, high molecular weight butyl rubbers, and halogenated, low-gel, high molecular weight isoolefin multiolefin copolymers synthesized from isobutene, isoprene and optionally further monomers, with a multiolefin content of greater than 2.5 mol %, a molecular weight M
w
of greater than 240 kg/mol and a gel content of less than 1.2 wt. %.
Another object was to provide a process for the production of halogenated low-gel, high molecular weight isoolefin multiolefin copolymers, in particular to halogenated, low-gel, high molecular weight isoolefin diene copolymers, halogenated, low-gel, high molecular weight butyl rubbers, and halogenated, low-gel, high molecular weight isoolefin copolymers synthesized from isobutene, isoprene and optionally further monomers, with a multiolefin content of greater than 2.5 mol %, a molecular weight M
w
of greater than 240 kg/mol and a gel content of less than 1.2 wt. % characterized in that said halogenated copolymers are produced in a process comprising the following steps:
a) polymerizing at least one isoolefin, at least one multiolefin, preferably a diene, and optionally further monomers in presence of a catalyst and a organic nitro compound
b) contacting the resulting copolymer under halogenation conditions with at least one halogenating agent.


REFERENCES:
patent: 2356128 (1944-08-01), Thomas et al.
patent: 2940960 (1960-06-01), Tegge et al.
patent: 3029191 (1962-04-01), King
patent: 3099644 (1963-07-01), Parker et al.
patent: 4634741 (1987-01-01), Gardner et al.
patent: 5569723 (1996-10-01), Baade et al.
patent: 6015841 (2000-01-01), Langstein et al.
patent: 6232409 (2001-05-01), Kaszas et al.
Ullmann's Encyclopedia of Industrial Chemistry, vol. A 23, (month unavailable) 1998, pp. 288-295, Rubber, 3, Synthetic.
W. A. Thaler & D.J. Buckley, Sr., Meeting of the Rubber Division, ACS, Cleveland, Ohio, May 6-9, 1975, published in Rubber Chemistry & Technology 49, (month unavailable) 1976, pp. 960-966.
High-Molecular-Weight, High-Unsaturation Vopolymers of Isobutylene and Conjugated Dienes. I. Synthesis.

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