Polymer bromination process

Details Polymer bromination process Polymer bromination process

1998-11-19

2001-03-20

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...

C525S356000

Reexamination Certificate

active

06204338

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an improved process for the bromination of isoolefin polymers and to the product produced by such an improved process.
BACKGROUND OF THE INVENTION
Isoolefin polymers have been known for many years and are commercially available as polymers of an isoolefin and a conjugated diolefin, especially of isobutylene and isoprene. While such polymers have a wide range of desired properties they are not readily covulcanizable with highly unsaturated polymers, such as polymers containing high proportions of one or more conjugated diolefin. In order to overcome such a problem, isoolefin-conjugated diolefin polymers, and especially isobutylene-isoprene polymers which are also known as butyl polymers, have been halogenated. The halogenation, especially chlorination or bromination, is achieved by treating the butyl polymer in solution in an inert organic solvent with controlled quantities of chlorine or bromine. The resulting halogenated butyl polymer has the inherent satisfactory properties of the butyl polymers while also being covulcanizable with the highly unsaturated polymers.
The halogenation process is well known to be rather inefficient. One reason for the inefficiency is that for every atom of chlorine or bromine that is incorporated into the polymer a molecule of hydrogen chloride or hydrogen bromide is formed. Another reason is that some of the hydrogen chloride or hydrogen bromide may add to the polymer forming a chemically undesirable group. A further reason is that the actual efficiency of utilization of the chlorine or bromine is quite low, generally being of the order of about 25 to about 40 percent by weight.
DESCRIPTION OF THE PRIOR ART
The preparation of butyl polymers is well known wherein a mixture of an isoolefin, preferably isobutylene, and a conjugated diolefin, preferably isoprene, in an inert diluent, preferably methyl chloride, is reacted at a temperature of from about −80° C. to about −120° C. in the presence of a Friedel-Crafts catalyst, preferably aluminum chloride. The butyl polymer so produced contains about 95 to about 99.5 mole percent of isobutylene and from about 0.5 to about 5 mole percent of isoprene. Such a polymer is dissolved in an organic solvent and reacted, at about 10° C. to about 60° C., with, preferably, chlorine or bromine for sufficient time to yield a polymer containing not more than 1 atom of combined chlorine per double bond in the polymer or not more than 3, and preferably not more than 1, atoms of combined bromine per double bond in the polymer—see for example U.S. Pat. Nos. 2,944,578 and 3,011,996. U.S. Pat. No. 3,018,275 describes a process for the halogenation of butyl polymers wherein an oxidizing agent, including a material selected from hydrogen peroxide, sodium peroxide, sodium chlorate or bromate and sodium hypochlorite, is present during the halogenation process to increase the utilization of the halogenating agent in the process.
SUMMARY OF THE INVENTION
It is an objective of this invention to provide an improved process for the bromination of isobutylene polymers by increasing the utilization of the bromine in the process.
It is another objective of this invention to provide an improved brominated butyl polymer by use of the improved process.
Accordingly, one aspect of the invention provides an improved process for the bromination of a C
4
-C
6
isoolefin-C
4
-C
6
conjugated diolefin polymer which comprises preparing a solution of said polymer in a solvent, adding to said solution bromine and reacting said bromine with said polymer at a temperature of from about 10° C. to about 60° C. and separating the brominated isoolefin-conjugated diolefin polymer, the amount of bromine being from about 0.30 to about 1.0 moles per mole of conjugated diolefin in said polymer, the improvement being that said solvent is a mixture comprising an inert saturated paraffinic hydrocarbon and an inert halogen-containing hydrocarbon in a volume ratio of from about 90/10 to about 10/90 of said paraffinic hydrocarbon to said halogen-containing hydrocarbon, wherein said halogen-containing hydrocarbon is a mono-, di- or tri-halogenated C
1
to C
6
paraffinic hydrocarbon or a halogenated aromatic hydrocarbon.
In another aspect of the invention, the inert mixture has a dielectric constant of at least about 2.5, and preferably greater than about 3.0.
In a further aspect of the invention, the inert saturated paraffinic hydrocarbon and the inert halogen-containing hydrocarbon are present in a ratio of from about 90/10 to about 50/50, and more preferably in a ratio of from about 90/10 to about 70/30.
In one aspect, the present invention provides an improved process for the bromination of a C
4
-C
6
isoolefin-C
4
-C
6
conjugated diolefin polymer which comprises preparing a solution of said polymer in a solvent, adding to said solution bromine and reacting said bromine with said polymer at a temperature of from about 10° to about 60° C. and separating the brominated isoolefin-conjugated diolefin polymer, the amount of bromine being from about 0.3 to about 1.0 moles per mole of conjugated diolefin in said polymer, the improvement being that said solvent is a mixture comprising an inert saturated paraffinic hydrocarbon and an inert halogen-containing hydrocarbon in a volume ratio of from about 90/10 to about 10/90 of said paraffinic hydrocarbon to said halogen-containing hydrocarbon, wherein said halogen-containing hydrocarbon is selected from the group consisting of methyl chloride, methylene chloride, ethyl chloride, ethyl bromide, dichioroethane, n-butyl chloride and monochloro-benzene.
In particular aspects, the ratio of saturated paraffinic hydrocarbon to halogen-containing hydrocarbon is preferably from about 90/10 to about 50/50, and more preferably from about 90/10 to about 70/30.
In another aspect, the solvent further contains up to 20 volume percent of water.
One aspect of the invention provides for the process wherein the solvent further contains up to 20 volume percent of an aqueous solution of an oxidizing agent. The oxidizing agent is soluble in water and is suitable to oxidize the hydrogen bromide to bromine in the process substantially without oxidizing the polymeric chain. In a particular aspect, the oxidizing agent is an oxygen containing oxidizing agent selected from the group comprising sodium hypochlorite, hydrogen peroxide, sodium peroxide, sodium chlorate, bromate, or other suitable oxidizing agents.
In one aspect, the solvent contains up to 20 volume percent of an aqueous solution of sodium hypochlorite, the amount of sodium hypochlorite being equivalent to not more than about 200 percent of the moles of bromine added.
In a further aspect, this invention provides an improved brominated isoolefin-conjugated diolefin polymer produced by the aforesaid process wherein the brominated polymer contains from about 1 to about 4 weight percent of bromine based on the brominated polymer and not less than about 80 percent of the bound bromine atoms are present in a form suitable to participate in the vulcanization of said polymer and not less than about 70 percent of the 1,4-isoprene units in the original isoolefin-conjugated diolefin polymer are converted in the brominated polymer into a form suitable to participate in the vulcanization of said polymer.
DETAILED DESCRIPTION OF THE INVENTION
Isoolefin-conjugated diolefin polymers are well known in the art as also is the process for the manufacture of such polymers. Isoolefins are selected from the C
4
to C
6
isoolefins with isobutylene being the preferred isoolefin. Conjugated diolefins are selected from the C
4
to C
6
conjugated diolefins with isoprene being the preferred conjugated diolefin. Such polymers comprise from about 95 to about 99.5 mole percent of the isoolefin, preferably from about 97 to about 99.5 mole percent of isobutylene, and from about 0.5 to about 5 mole percent of conjugated diolefin, preferably from about 0.5 to about 3 mole percent of isoprene. The polymer is prepared by the cationic polymerization of the isoole

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