U.S. patent application number 09/796182 was filed with the patent office on 2001-07-19 for polymer bromination process in solution.
Invention is credited to Baade, Wolfgang, Kaszas, Gabor, Konigshofen, Heinrich.
Application Number | 20010008923 09/796182 |
Document ID | / |
Family ID | 25189777 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008923 |
Kind Code |
A1 |
Kaszas, Gabor ; et
al. |
July 19, 2001 |
Polymer bromination process in solution
Abstract
An improved process is provided for the bromination of
isoolefin-conjugated diolefin polymers by brominating said polymer
in solution in selected halogen-containing hydrocarbons as solvent.
There is also provided an improved product of said process wherein
the brominated polymer contains not less than 80 percent of the
bound bromine atoms in a form suitable to participate in the
vulcanization of the polymer and wherein not less than 70 percent
of the bound conjugated diolefin units are similarly so
brominated.
Inventors: |
Kaszas, Gabor; (Corunna,
CA) ; Baade, Wolfgang; (Wildeshausen, DE) ;
Konigshofen, Heinrich; (Bergisch Gladbach, DE) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
25189777 |
Appl. No.: |
09/796182 |
Filed: |
February 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09796182 |
Feb 28, 2001 |
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08804767 |
Feb 24, 1997 |
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6232409 |
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Current U.S.
Class: |
525/332.8 ;
525/333.1; 525/356 |
Current CPC
Class: |
C08F 8/22 20130101; C08F
8/22 20130101; C08F 210/12 20130101 |
Class at
Publication: |
525/332.8 ;
525/333.1; 525/356 |
International
Class: |
C08F 008/22; C08F
136/00 |
Claims
What is claimed is:
1. An improved process for the bromination of a C.sub.4-C.sub.6
isoolefin-C.sub.4-C.sub.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.degree. C. to about
60.degree. 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 comprises an inert
halogen-containing hydrocarbon, said halogen-containing hydrocarbon
comprising a halogenated C.sub.2 to C.sub.6 paraffinic hydrocarbon
or a halogenated aromatic hydrocarbon.
2. An improved process for the bromination of a C.sub.4-C.sub.6
isoolefin-C.sub.4-C.sub.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.degree. C. to about
60.degree. 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 comprises an inert
halogen-containing hydrocarbon selected from the group consisting
of ethyl bromide, propyl chloride, n-butyl chloride and
monochlorobenzene.
3. The process of claim 1 wherein said solvent further contains up
to 20 volume percent of water.
4. The process of claim 2 wherein said solvent further contains up
to 20 volume percent of water.
5. The process of claim 1 wherein the solvent further contains up
to 20 volume percent of an aqueous solution of an oxidizing agent
that is soluble in water and suitable to oxidize the hydrogen
bromide to bromine in the process substantially without oxidizing
the polymeric chain.
6. The process of claim 2 wherein the solvent further contains up
to 20 volume percent of an aqueous solution of an oxidizing agent
that is soluble in water and suitable to oxidize the hydrogen
bromide to bromine in the process substantially without oxidizing
the polymeric chain.
7. The process of claim 1 wherein the solvent further contains up
to 20 volume percent of an oxygen containing oxidizing agent
selected from the group comprising sodium hypochlorite, hydrogen
peroxide, sodium peroxide, sodium chlorate or bromate.
8. The process of claim 2 wherein the solvent further contains up
to 20 volume percent of an oxygen containing oxidizing agent
selected from the group comprising sodium hypochlorite, hydrogen
peroxide, sodium peroxide, sodium chlorate or bromate.
9. The process of claim 1 wherein said solvent further 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.
10. The process of claim 2 wherein said solvent further 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.
11. The process of claim 3 wherein said solvent further 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.
12. The process of claim 4 wherein said solvent further 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.
13. The process of claim 2 wherein the isoolefin-conjugated
diolefin polymer is an isobutylene-isoprene polymer comprising from
about 97 to about 99.5 mole percent of isobutylene and from about
0.5 to about 3 mole percent of isoprene.
14. The process of claim 2 wherein the isoolefin-conjugated
diolefin polymer is an isobutylene-isoprene polymer comprising from
about 97 to about 99.5 mole percent of isobutylene and from about
0.5 to about 3 mole percent of isoprene, the solvent is selected
from the group consisting of ethyl bromide and n-butyl chloride,
the reaction is at a temperature of from about 20.degree. to about
50.degree. C. and the reaction time is from about 1 to about 5
minutes.
15. The process of claim 3 wherein the isoolefin-conjugated
diolefin polymer is an isobutylene-isoprene polymer comprising from
about 97 to about 99.5 mole percent of isobutylene and from about
0.5 to about 3 mole percent of isoprene, the solvent is a
halogen-containing hydrocarbon selected from the group consisting
of ethyl bromide and n-butyl chloride and water forming from about
3 to about 15 volume percent of the solvent, the reaction is at a
temperature from about 20.degree. to about 50.degree. C. and the
reaction time is from about 1 to about 5 minutes.
16. The process of claim 4 wherein the isoolefin-conjugated
diolefin polymer is an isobutylene-isoprene polymer comprising from
about 97 to about 99.5 mole percent of isobutylene and from about
0.5 to about 3 mole percent of isoprene, the solvent is a
halogen-containing hydrocarbon selected from the group consisting
of ethyl bromide and n-butyl chloride and an aqueous solution of
sodium hypochlorite forming from about 3 to about 15 volume percent
of the solvent, the reaction temperature is from about 20.degree.
to about 50.degree. C. and the reaction time is from about 1 to
about 5 minutes.
17. The process of claim 5 wherein the isoolefin-conjugated
diolefin polymer is an isobutylene-isoprene polymer comprising from
about 97 to about 99.5 mole percent of isobutylene and from about
0.5 to about 3 mole percent of isoprene, the solvent is a
halogen-containing hydrocarbon selected from the group consisting
of ethyl bromide and n-butyl chloride and an aqueous solution of
sodium hypochlorite forming from about 3 to about 15 volume percent
of the solvent, the reaction temperature is from about 20.degree.
to about 50.degree. C. and the reaction time is from about 1 to
about 5 minutes.
18. The product of the process of claim 14 wherein the brominated
isobutylene-isoprene 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 isobutylene-isoprene polymer are converted in
the brominated polymer into a form suitable to participate in the
vulcanization of said polymer.
19. The product of the process of claim 15 wherein the brominated
isobutylene-isoprene 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 isobutylene-isoprene polymer are converted in
the brominated polymer into a form suitable to participate in the
vulcanization of said polymer.
20. The product of the process of claim 16 wherein the brominated
isobutylene-isoprene 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 isobutylene-isoprene polymer are converted in
the brominated polymer into a form suitable to participate in the
vulcanization of said polymer.
21. The product of the process of claim 1.
Description
FIELD OF THE INVENTION
[0001] 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
[0002] 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.
[0003] 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
[0004] 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.degree. C. to about -120.degree. 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.degree. C. to about 60.degree. 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
[0005] 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.
[0006] It is another objective of this invention to provide an
improved brominated butyl polymer by use of the improved
process.
[0007] Accordingly, one aspect of the invention provides an
improved process for the bromination of a C.sub.4-C.sub.6
isoolefin-C.sub.4-C.sub.- 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.degree. C. to about
60.degree. 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 comprises an inert
halogen-containing hydrocarbon, said halogen-containing hydrocarbon
comprising a halogenated C.sub.2 to C.sub.6 paraffinic hydrocarbon
or a halogenated aromatic hydrocarbon.
[0008] In one aspect, the present invention provides an improved
process for the bromination of a C.sub.4-C.sub.6
isoolefin-C.sub.4-C.sub.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.degree. to about
60.degree. 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 comprises an inert
halogen-containing hydrocarbon selected from the group consisting
of ethyl bromide, propyl chloride, n-butyl chloride and
monochlorobenzene.
[0009] In another aspect, the solvent further contains up to 20
volume percent of water.
[0010] 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.
[0011] In yet another aspect, the solvent further 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.
[0012] 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
[0013] 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.sub.4 to C.sub.6 isoolefins with
isobutylene being the preferred isoolefin. Conjugated diolefins are
selected from the C.sub.4 to C.sub.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 isoolefin
and conjugated diolefin, in an inert diluent which is preferably
methyl chloride or ethyl chloride, at a temperature of from about
-80.degree. C. to about -120.degree. C. in the presence of a
Friedel-Crafts catalyst which is preferably aluminum chloride.
[0014] For the prior art bromination process, the polymer is
dissolved in an inert hydrocarbon solvent such as pentane, hexane
and heptane and the solution is fed to a halogenation reactor. The
halogenation reactor is typically a vessel equipped with inlet and
outlet lines and an agitator. Bromine is also fed to the
halogenation reactor at a controlled rate in relation to the amount
of polymer and the double bond content of the polymer. The material
from the reactor is treated with an aqueous alkaline solution, such
as sodium hydroxide, to neutralize the hydrogen bromide formed in
the halogenation reaction and to react with residual bromine and
then contacted with hot water and steam to remove the solvent and
produce a slurry of brominated polymer in water which is then
handled in a conventional manner to yield the essentially dry
brominated polymer. Stabilizers for the brominated polymer may be
added during the recovery process.
[0015] Such prior art processes exhibit poor utilization of the
bromine in the halogenation process, due to the formation of one
molecule of hydrogen bromide for each atom of bromine incorporated
into the polymer, due to the addition of a small amount of the
hydrogen bromide into the polymer and due to the need to use more
bromine than is actually incorporated into the polymer.
[0016] We have now discovered that the halogenation process can be
significantly improved by the use as the solvent for the polymer a
solvent which comprises an inert halogen-containing hydrocarbon,
more specifically a halogenated C.sub.2 to C.sub.6 paraffinic
hydrocarbon or a halogenated aromatic hydrocarbon. Preferably, the
inert halogen-containing hydrocarbon is selected from the group
consisting of ethyl bromide, propyl chloride, n-butyl chloride and
monochlorobenzene. The solvent may also contain up to about 20,
preferably from about 3 to about 15, volume percent, based on the
total solvent, of water. Further, the solvent may also contain up
to about 20, preferably from about 3 to about 15, volume percent of
an aqueous solution of an oxidizing agent such as an oxygen
containing oxidizing agent selected from the group comprising
sodium hypochlorite, hydrogen peroxide, sodium peroxide, sodium
chlorate or bromate. 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. Weak oxidizing
agents at low concentration, such as sodium hypochlorite, are
preferred in order to prevent or minimize oxidation of the polymer.
Preferably, the oxidizing agent will comprise an aqueous solution
of sodium hypochlorite, the amount of sodium hypochlorite being
equivalent to not more than about 200, preferably from about 100 to
about 140, percent of the moles of bromine added to the
process.
[0017] Using such a solvent for the polymer leads to an increase in
the amount of bromine which is incorporated into the polymer to
form chemical structures that participate in the vulcanization of
said polymer. We have found that for a fixed reaction time in the
process of the present invention in excess of about 85 mole percent
of the bromine supplied to the process is incorporated into the
polymer to form chemical structures that participate in the
vulcanization of the polymer. In contrast, in the prior art only
about 60 to 70 mole percent of the bromine is so incorporated. When
the solvent includes water, the improvement in the utilization of
bromine is believed to be due to the hydrogen bromide formed in the
reaction being preferably soluble in the water and thus not so
readily available to form hydrogen bromide addition structures.
When the solvent includes aqueous sodium hypochlorite, the
improvement in the utilization of bromine to form the desired
chemical structures may be as high as about 190 mole percent of the
bromine supplied to the process--this is believed to be due to the
hydrogen bromide formed in the reaction being oxidized by the
sodium hypochlorite to form bromine which may then further react
with the polymer.
[0018] Without intending to limit the scope of the invention, the
bromine utilization improvement is believed to be achieved by the
increase of the dielectric constant of the reaction medium via the
use of select halogen-containing hydrocarbons as solvent for the
isoolefin-conjugated diolefin polymers instead of an inert
hydrocarbon solvent. It is believed that the dielectric constant of
the halogen-containing hydrocarbon could be used as a guide for the
selection of proper reaction medium for the process of this
invention. Table A lists the dielectric constant of some
halogen-containing hydrocarbons and hexane. It is apparent from
Table A that not all the halogen-containing hydrocarbons will be
suitable for the process of this invention. For example, the
dielectric constant of carbon tetrachloride is just slightly higher
than that of hexane, therefore only marginal improvement can be
expected. In contrast use of solvents with high dielectric
constant, such as monochlorobenzene, n-butyl chloride, ethyl
bromide, should lead to exceptional results. To achieve desired
results, the dielectric constant will be greater than that of
carbon tetrachloride.
[0019] In some of the halogenated solvents listed in Table A,
solubility of the polymer may be limited. In such cases addition of
some paraffinic hydrocarbon is recommended to aid dissolution of
the polymer.
1TABLE A Dielectric Constant of Some Solvents Halogenated solvent
Dielectric constant @ 45.degree. C. Hexane 1.85 Carbon
tetrachloride 2.19 Chloroform 4.38 Bromobenzene 5.11 Chlorobenzene
5.30 n-Butyl chloride 6.42 Bromoethane 8.16 Methylene chloride 8.23
Methyl chloride 8.64 Dichloroethane 9.17
[0020] Such a discovery means that the amount of bromine supplied
to the process may be reduced, that the amount of excess bromine
leaving the halogenation reactor with the brominated polymer may be
reduced which in turn reduces the quantity of aqueous alkaline
solution required to react with it, that the amount of bromine
chemically bound in the polymer may be more effectively used in the
subsequent vulcanization process and that the unsaturation level in
the polymer (that is the amount of bound conjugated diolefin) may
be reduced because with the more complete utilization of the
bromine more of the unsaturated double bonds in the polymer are
effectively brominated than in the prior art processes.
[0021] The desired chemical structures in the brominated polymer
include the exo allylic bromide structure, the endo allylic bromide
structure and the re-arranged exo allylic bromide structure. In all
of these cases the bromine atom is present attached to a carbon
atom which is in an allylic configuration with a carbon-carbon
double bond (i.e. C.dbd.C--CBr) wherein exo and endo have the
conventional meanings. In these cases, the bromine atom is
chemically very active and participates in the subsequent
vulcanization process. The quantities of these various chemical
structures may be readily determined by 500 MHz HNMR with high
levels of accuracy. The exo allylic bromide structure is the
predominant one and usually forms about 75 to about 85 percent of
the desired chemical structures. The total primary structure thus
refers to the total of the exo allylic bromide, the endo allylic
bromide and the re-arranged exo allylic bromide and the product of
the present process contains not less than about 80 percent of the
bound bromine atoms in these configurations which are the form to
actively participate in the subsequent vulcanization process. The
process of the present invention leads to a high conversion of the
bound 1,4-isoprene units into the primary structure. The present
process leads to such conversions of not less than 70 and up to
about 90 or more percent into the primary structure whereas the
prior art processes lead to such conversions of only about 50 to
about 60 percent. The total primary structure as a percentage of
the bound 1,4-isoprene units clearly shows the above effect.
[0022] The halogenation process may be operated at a temperature of
from about 10.degree. C. to about 60.degree. C., preferably from
about 20.degree. C. to about 50.degree. C. and the reaction time
may be from about 1 to about 10 minutes, preferably from about 1 to
about 5 minutes. The pressure in the halogenation reactor may be
from about 0.8 to about 10 bar.
[0023] The brominated polymer recovered from the halogenation
process typically has a molecular weight, expressed as the Mooney
viscosity (ML 1+8 at 125.degree. C.), of from about 25 to about 55.
Brominated polymer such as bromobutyl polymer contains from about
0.5 to about 3, most preferably from about 1 to about 2, mole
percent of isoprene and from about 97 to about 99.5, most
preferably from about 98 to about 99, mole percent of isobutylene
based on the hydrocarbon content of the polymer, and from about 1
to about 4, preferably from about 1.5 to about 3, weight percent of
bromine based on the bromobutyl polymer. Further, the product of
the present process contains not less than about 80 percent of the
bound halogen atoms in a form suitable to participate in the
vulcanization of the polymer. In the product of the prior art, a
small amount of the bound halogen is present in the polymer as a
result of the addition of a hydrogen bromide molecule across a
carbon-carbon double bond thereby forming a saturated group in
which the bromine atom is essentially inert in the vulcanization
process. In the product of the present process, the amount of bound
bromine present in the polymer as a result of the addition of a
hydrogen bromide molecule across a carbon-carbon double bond is
reduced from that of the prior art. Analysis of the polymer by 500
MHz HNMR was the method used to determine the structural
composition of the brominated polymers. In isobutylene-isoprene
polymers, the isoprene bound in the 1,4-configuration in the HNMR
spectrum exhibits a resonance at about 5.1 ppm. In the brominated
isobutylene-isoprene polymers, the HNMR spectrum exhibits
resonances at about 5.4, 5.05 and 4.35 ppm which correspond to the
exo allylic bromide structure, at about 5.6 ppm which correspond to
the endo allylic bromide structure, at about 4.08 and 4.10 ppm
which correspond to the re-arranged exo allylic bromide structure.
The hydrobrominated structure is calculated from the mass balance.
Also in the product of the present process, the proportion of the
carbon-carbon double bonds that have been reacted with a bromine
atom (to form an unsaturated bromine containing group which is
active in the vulcanization process) is much higher than is the
case for the product of the prior art processes. Hence the product
of the present process contains a higher proportion of the bound
bromine atoms in a form suitable to participate in the
vulcanization process.
[0024] The brominated polymer is used to make vulcanizates. The
vulcanization of polymers is well known. Carbon black is well known
in the art for the reinforcement of vulcanizates and is added to
the polymer during the compounding process. Hydrocarbon extender
oils are also well known materials used in the compounding process.
Generally the carbon black will be selected from the furnace and
channel carbon blacks and may be used in amounts of from about 20
to about 90 parts by weight per 100 parts by weight of polymer.
Hydrocarbon extender oils may be selected from the paraffinic,
naphthenic and aromatic oils, preferably from the paraffinic and
naphthenic oils, and may be used in amounts from about 5 to about
40 parts by weight per 100 parts by weight of polymer. The
vulcanization systems for use with the present product are those
already known in the art for use with bromobutyl polymers and
generally will include a metal oxide, at least one sulphur based
accelerator and, optionally, elemental sulphur. A suitable metal
oxide is zinc oxide used in an amount of from about 1 to about 7
parts by weight per 100 parts by weight of polymer. Suitable
sulphur based accelerators may be selected from the thiuram
sulphides, the thiocarbamates, the thiazyl compounds and the
benzothiazyl compounds. The amounts of such accelerators may be
from about 0.3 to about 3 parts by weight per 100 parts by weight
of polymer. Elemental sulphur may be present in an amount up to
about 2 parts by weight per 100 parts by weight of polymer. Various
stabilizers, antioxidants, tackifiers, etc. may also be added
during the compounding process. The compounding itself will be by
conventional methods using a rubber mill or an internal mixer,
controlling the temperature to keep it below about 80.degree. C.,
in one or two stages, generally with the cure active components
being added last. The so-formed compounds are then shaped and
vulcanized by heating for from about 5 to about 60 minutes at
temperatures of from about 150.degree. C. to about 200.degree.
C.
EXAMPLE
Example 1
[0025] To a 0.5 L glass reactor, equipped with a stirrer and two
reagent addition ports, was added a solution of 20 g of butyl
polymer (an isobutylene-isoprene polymer containing 1.77 mole
percent of isoprene) in 270 mL of solvent. The solvent used is
shown in Table I. The polymer solution, with the agitator in
operation, was heated to 45.degree. C. following which 18 mL of
water or an aqueous sodium hypochlorite solution was added and
dispersed thoroughly throughout the solution. The reaction mixture
was protected from light to avoid light induced bromination of the
polymer or the solvent. Through one of the reagent addition ports
was added 0.18 mL of bromine and agitation of the mixture was
continued. After a reaction time of two minutes, the reaction was
stopped by the addition, through the second reagent addition port,
of 20 mL of a 6% solution of sodium hydroxide. Stabilizers for the
polymer were added, the solution was washed with distilled water
until neutral and the brominated polymer was recovered by removing
the bulk of the solvent in a rotary evaporator followed by final
drying in a vacuum oven.
[0026] Analysis of the polymers by 500 MHz HNMR gave the results
shown in Table I. Experiment #1 was a control because hexane was
used as the solvent. The improvements in the nature of the product
are clearly seen in the results.
Example 2
[0027] Using the procedures described in Example 1, further
solvents were evaluated as shown in Table II, the Experiments #6
and 7 being controls.
2TABLE I Expt. # 1 2 3 4 5 Solvent - hexane (mL) 270 -- -- -- -- -
ethyl bromide (mL) -- 270 270 -- -- - n-butyl chloride (mL) -- --
-- 270 270 - H.sub.2O (mL) 18 18 -- 18 -- - NaOCl/H.sub.2O (mL) --
-- 18 -- 18 Product Composition Exo structure (mole %) 0.53 0.88
1.32 0.74 1.29 Total primary structure (mole %) 0.61 0.94 1.46 0.79
1.37 Unreacted isoprene (mole %) 1.05 0.66 0.2 0.91 0.29
[0028]
3TABLE II Expt. # 6 7 8 9 Solvent - Carbon tetrachloride (mL) 270
270 -- -- - monochlorobenzene (mL) -- -- 270 270 - H.sub.2O (mL) --
18 -- 18 -NaOCl/H.sub.2O (mL) -- 18 -- 18 Product Composition Exo
structure (mole %) 0.69 1.00 0.89 1.4 Total primary structure (mole
%) 0.78 1.22 0.96 1.53 Unreacted isoprene (mole %) 0.87 0.45 0.66
0.15 Hydrobrominated structure (mole %) 0.12 0.1 0.15 0.09 Bromine
utilization (mole %) 80.2 125.8 98.6 158.6 Total primary structure
as % of total bromine present % 86.6 91.9 86.5 94.7 Total primary
structure as % of bound 1,4-isoprene of 44.1 68.9 54.2 86.4
original polymer %
Definitions
[0029] The term Inert in relation to halogenated solvents means
solvents that are inert with respect to reaction with bromine under
the conditions of bromination.
[0030] It is of course, understood that the above examples are
submitted merely to illustrate the invention and there is no
intention to limit the invention to them. Resort may be had to
various modifications and variations of the present invention
without departing from the spirit of the discovery or the scope of
the appended claims.
[0031] The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
* * * * *