CA2388739A1 - Process for producing long chain branched polymers of isobutene, isoprene and allyl halides - Google Patents

Abstract

This invention relates to a process for producing long chain branched polymers comprising repeating units derived from isoolefins and allyl halide monomers in a single stage process in solution, suspension or in the gas phase.

Description

;~;:rv..i i FIELD OF THE >?JVENTZON
This invention relates to a process for producing long chain branched polymers comprising repeating units derived from at least one isoolefin monomer and at least one allyl halide monomer in a single stage process in solution, suspension or in the gas phase.
!0 BACKGROUND OF THE INVENTION
Polymers made from allyl chlorides are known. M. Marek ("Makromol. Chem.", 187, (1986) 2337-44) synthesized homopolymets of methallyl chloride in methylene chloride with A1C13 or AlBr3 as an initiator. The oily products with Ma of about 400-620 g~mol were obtained and the mechanism of reaction was discussed. Allyl chloride 1S was polymerised with AIBr3 at elevated temperatures (Davideon, E. B., Inr.
Synip.
Macromol. Chem., P~epr., 1969, 1, 3SS; Zil6erman, E. N., Kulikova, A_ E., Pinchuk, N.
M., Slonim, I. Y, Mochalova, O. A., Tr. Khim. Khim. Tekhnot., 1971, l, 159, Chem.
Abstr. 77:165139). Only oligomers weoe t~ceived by this technique.
(Co)-polymers comprising allyl chlorides are known. US-3,299,020 makes a 20 reference that the direct reaction of isobutene with methallyl chloride initiated with aluminum halide catalyst in methyl chloride gave a product with very low molecular weight, e.g. 6000 glmol. Furthermore, a process is disclosed for the copolymerization of isobutene and an allyl halide in methyl chloride using a Ftiedel-Crafts catalyst chosen from a group consisting of aluminum chloride, aluminum bromide, boron 25 chloride and stannic chloride. The procedure involved dissolving each monomer separately in solution, adding catalyst to the allyl chloride solution, and subsequently adnuxing both solutions in a reaction zone. The product contained at least about 0.5 wt. ~ of chlorine with polymer molecular weight between 80,000 and 200,000 ~jmol.
Sadykh-Zade et al. CChem. Abstr. 70, 207$6j) studied the copolymerizstion of 30 isobutene (with and without isoprene in the feed) and methallyl chloride using A1C13 as a catalyst.
EP-A1-0 448 627 discloses a catalyst system for cationic (eo)polymerization of 1-olefins. The most preferred 1-olefin is isobutene or feedstock containing isobutene.

~.~-; r r i ~ ~ ii The catalyst system comprised an organo-aluminum compound RrtAIX~, like ethylaluminum dichloride, a methallyl chloride, and SnC4, or SnBr~, or TiCia, or TiBr4.
Two components of the catalyst system were prepared separately and added simultaneously through the two feed lines to the reactor. When methallyl chloride was present in amounts up to 15 wt,°7o with respect to 1-olefin, it could act as a comonomer and isobutene polymers containing halogen atoms could be produced.
Conjugated diolefins bearing an allylic halide moiety were utilized in a direct synthesis of halobutyl-type polymers (US-5,342,908 and US-5,473,029).
It is further known, that benzyt halides can function as both an Inltlator and a monomer ("inime:"), G. Langstein et al_ (IJS 6,156,859) claimed a single stage process for producing branched polyisobutene and butyl rubber using vinylben2yl chloride andfor isoprenylbenzyl chloride as an inimer and methylaluminoxane (MAO) as a co-initiator. However, US 6,156,859 is silent about allyl halides.
The cationic polymerisation of isoolefins is known (set e.g. Ullmanns Encyclopedia of Industrial Chemistry, Vol. A 23, 1993, pages 288-295) and leads to isoolefin-co-polymers, of which isobutene-isoprene co-polymers (butyl rubbers) art the mast important ones. On account of their physical properties, the butyl rubbers and halo-buryl rubbers produced in this manner arc used in industry, particularly for the production of tyre tubes and inner liners for tyres. In this connection, the processing properties of the butyl rubbers produced in this manner during compounding, rolling, extrusion and caiendering are particularly important. The processing properties are associated in particular with a balanced ratio of the green strength of the rubber and to the stress relaxation thereof. This can be achieved, for example, by blending corncsponding polymers with different molecular weights to form products having a custom-made, broad molecular weight distribution. This process is laborious, however.
The direct synthesis of butyl rubbers which exhibit a broad molecular weight distribution and random long-chain branching and which have the desired processing properties can be accomplished, for example, by the copolymerisation of isobutene with isoprene in the presence of bifunctiona! monomers such as divinylbenzene, 2,5-hexadiene or vinylbentyl chloride. However, one significant disadvantage of this copolymerisation is the formation of high proportions of gels in the rubber (see H.-C. Wang, K.W. Powers, ).V. Fusco, ACS Meeting, May 1989 Paper No. 21, for example).
Another method of Introducing long chain branching occurrences was therefore i :a i d"~ 111m: ~ ~~ t introduced, namely the copolymetisation of isobutene and isoprene in the presence of mufti-functional branching agents. The latter are to be understood as soluble polymers which contain functional groups, and which under the process conditions either initiate polymerisation ("grafting from" by tertiary alkyl groups) or react with the cationic end of the growing polymer chain (''grafting onto" by reactive double bonds).
Hydrochlotinated pofy(styrene-co-isoprenes), chlorinated polystyrenes, polyisoprenes or styrene-butadiene block copolymers have been mentioned as mufti-functional branching agents (EP-320 263). The resulting polymer mixtures are termed "star branched butyls". A
disadvantage of this proccdurc is the necessity for scparatc, additional process steps for the polymerisation or halogenation of the branching agents, The simultaneous formntion of linear and branched polymers during polymerisation is a characteristic of Chic procedure.
The production of "mufti-arm star" polyisobutenes by the reaction of active polyisobutene polymers with divinylbenzene is described in Polymer Bull. 31 (1993) 665.
These polyisobutenes arc produced by the "arm-first, core-last" method, which is explained in US-5,458.796.
Another possibility for the production of branched butyl rubbers is the use of mufti-functional initiators, as described in US-5,084,SZZ" This method is also termed the "core-first, arm-last" method. This procedure is also burdened with some disadvantages, on account of the separate process steps for the production of the mufti-functional initiator and for the formation of homopolymers by transfer reactions.

The present invention provides a single-stage process for producing long chain branched polymers comprising repeating units derived from at least one isoolefin monomer and at least one allyl halide, wherein the isololcfin(s), the allyl halides) and optionally further co-monomers ate potymerised in the presence of an initiator selected from the group consisting of alkylalurnoxanes, alkylalutniminium halides RAAIXj.o, with each R being independently a Ct-C4o group and each X being independently a halogen, or mixtures thereof.
DETAILI~D DESCRIPT'iON OF T~ SCION
The present invention provides a single-step process which is understood to be a NI ~ ~t< f t l process that could be accomplished in a single reactor and which does not require any changes in reaction conditions during the process. However, it is understood that in certain polymerisation processes it might be advantageous to transfer the reactor content in another reactor with the same or a different set of reaction conditions.
Those set-ups S arc deemed to be within the present teaching.
The present invention is not limited to a certain type of isoolefins. However, isoolefins which are preferably used ans those of formula CHI--CR6R~
where R6 = Me and R' represents a C'-Cs alkyl such as methyl, ethyl or propyl.
Lcobutene and 2-meehylbutene-1 arc particularly preferred, especially isobutene.
The present invention is not limited to a certain type of ally! halides.
However, preferred are allyl halides of the general formula (I) R'RZG-CR3CXR4R5 (I), in which X denotes for a halide, preferably chloride, and R'-RS are selected independently of each other and each R denotes for hydrogen, a C~-C2o alkyl, a Cs-CZO aryl, a C~-Go a>kylaryl or a C~-Ceo arylatkyl. the following radicals are particularly suitable as C'-Czo alkyl radicals: methyl, ethyl, propyl, butyl, hexyl, octyl, deeyl and eicosyl, preferably methyl, ethyl and propyl, most preferably methyl. Each R may contain hcceroatoms in the chain at long as those heterostoms will not prohibit the polymorieation. Allyl chloride (HzC=CH-CHiCI), 3-chloro-2-methyl-1-propene (methallyl chloride), 1-chloro-2-butene (crotyl chloride) are particularly preferred.
Suitable co-monomers for the present invention are all co-polymerizable monomers lntown to the skilled in the art. Preferred co-monomers are conjugated or non-conjugated dienes and styrene derivatives, such as alkyl styrenes and divinyl benzenes.
Conjugated or non-conjugated dienes which ane suitable for the process according to the invention are those which contain 4 to 20, preferably 4 to 10, most preferably 4 to 6 carbon atoms, such as butadiene, isoprene, piperylene, 2,3-dimethylbutadiene, 2,4 dimethylpentadiene-1,3, cyelopentadiene, methylcyclopentadiene, limonene, 'myrcene andlor 1,3-cyclohcxadicnc, prcfcrably isoprene, piperylene and/or dlmethylbutadlene, _ 4 .. . .. ..~. ,~...p.:~ I I

most preferably isoprene.
The production of butyl rubber, i.e. the copolymerisation of ally! halides, isobutene and isoprene, is quite particularly preferred.
If co-monomers are present, the molar ratio of ally! halides) to the co-monomers used is usually within the range of from 1:104 to 1:10, preferably 1:10'' to 1:50, most preferably 1:10 to 1:24.
When copolymcrizing with isoolefins and dienes, the molar ratio of isoolefins to dienes is usually 1:103 to 1:10, preferably l:IOZ to 1:50.
The process according to the invention can be advantagcouely conducted in the presence of one or more inert organic culvants such as linear or branchod hydnxorbons andJor linear and branched halogenated hydrocarbons, such ar, pentane, hexane and/or methylene chloride. In this rospect, the amount of inert solvent used is not critical. The most suitable amount can easily be determined by appropriate preliminary tests.
As initiators alkylalumoxanes may be used. Suitable, preferred alkylalumoxanes are methyl, ethyl and/or butylalumoxanes, particularly methylalumoxanes, such as those described in Polyhedron, Vol. 7, No. 22123 (1988), page 2375 et seq. Other suitable initiators are compounds of the general formula R"AlX3.e, with each R being independently a CrC4o group and each X being independently a halogen, such as ethylaluminum dichloride. Of course, ii is possible to use a mixture of different initiators to custom tailor the initiation profile. Alkylaiumoxanes and mixtures of alkylalumoxanes with said compounds of the general formula R"AIX~.", with each R
being independently a Ct-Cso group and each X being independently a halogen arc preferred in this respect. In the procxss according to the invention, tha initiators) and the ally! halides are usually used in a molar ratio from 1:104 to 1:10, preferably from 1:103 to 1:3, most preferably from !:!0i to 1:2.
Other suitable additives can also be added for the polymerisation according to the invention. Examples of suitable additives include electron donors such as dimethyl-acetamide and/or dimethyl sulphoxide, or proton acceptors such as di-tert:
butylpyridine (see US 5169 914, for example).
It is important to note that the process of the present invention does not require the presence of metal salts such as Ti- or Sn-salts. This feawre tenders is extremely suitable for solution polymerizations.
The initiator can be addod to the monomer mixturt to be polymerised ~I~IAtV'3~- !

simultaneously, in succession, continuously or batch-wise. The alkylalumoxanes can of course be produced in situ in the lrnown manner, by the hydrolysis of corresponding aluminum alkyls.
The grocess according to the invention usually will be conducted within the S temperature range from +20 to -100°C, preferably within the temperature range from -20 to -90°C, particularly from -40 to -80°C.
The process according to the invention can be conducted in solution, suspension or in the gas phase. It is preferably conducted in solution in a inert hydrocarbon solvent, such ~ hexane. It is also possible to conduct the process 8s n batch, flow or continuous process, where the reaction times or residence times range from 2 seconds to 20 hours, preferably from 60 seconds to 1 hour. particularly from IS to 40 minutes.
As mentioned above, the process according to the invention results in polymers, wherein the degree of branching and the molecular weight are dependent in particular on the reactivity of the allyl halide, on the initiator, on the concentration of the initiator, on the molar ratio of monomer to allyl halide, on the reaction temperature and on the reaction time. It is therefore possible individually to adjust the degree of branching and the molecular weight of the resulting polymer to be produced, by suitably varying the sfommentioned parameters.
For example, ttte process according to the invention can be conducted in a manner such that the reactor, which is cooled to the reaction temperature, is charged with purified solvent and with the monomers, and after adjusting the temperature of the reactor to the decirod reaction temperature the requisite amount of initiator is added end is slimed with the monomer mixture placed therein. The reactor contents are vigorously and thoroughly mixed. All manipulations favourably are carried out under an inert gas. The course of the polymerisation could be followed by monitoring the generation of heat. After the completion of the exothermic reaction, the polymerisation usually is terminated, e.g. with 2,S-di-tart: butyl-4-methoxypheno! dissolved in ethanol. The polymer obtained usually is then worked up in the usual manner, e.g., by coagulation or steam stripping.
The advantages of the process according to the invention are due in particular to the simple single-step reaction procedure, wherein defined, branched co-polymers, preferably butyl rubbers, are obtained, which exhibit superior processing properties.
The invention is further illustrated in the following Examples.

p ilwfi~ t ~ ~ ' EXAMPLES
The polymers were investigated by the gel permeation chromatography with a triple detector for determination of absolute molecular weights. The testing was done using Viscotek, TDA model 300, with Waters Alliance 2690 Separation Module equipped with one GPC linear column. Tetrahydrofuran served as the eluent with the flow race 0.5 mLmin. The composition of polymers was determined by'H 1V1VIR

MHz spectroscopy (Bruker Avance DRX-S00) with TMS as an internal standard for ppm. Tha samples were diasolvcd in deutcratcd chloroform (Aldrich).
Calculations were based on integrated aliphatic, olafinic and inimor pocks.
The n-hexane (Philips 66 Co.) was dried and distilled over CaHz before its ure as a reaction medium for polymerizations.
Methylalumoxane (1v1A0, Aldrich) was used as ready-made 10 wt. °!o solution in toluene.

2S0 mL of dry hexane were placed in a S00 rnL round bottom flask equipped with an overhead stirrer, cooled to - 80 °C, mixed with 106.4 mL of isobutene at - 80 °C followed by adding 3.13 mL of isoprene measured at room temperature. The reaction mixture was cooled down to - 80 °C and 200 I,tL, of ethylaluminum dichlori~
(1.0 M solution in hexanes) was added to start the reaction.
Tha reaction was carried out in MHRAUN~ dry box under the atmosphere of dry nitrogen. The reaction was terminated after 24 minutes by adding 5 mL of ethanol NaOH solution into the reactor.
2S The gravimetrically determined yield was 24.3 g. Characterization of the polymer by GPC-Viscotek gave Me = 117,400, MW = 210,100, and Mi = 360,800.
Isoprene content was 1.81 mole percent.
This example is provided for comparative purposes for Example 2 and Example 3.

The reaction feed was prepared similarly like in Example 1, but in this case 2.52 mL of mcthallyl chloride was also added to the feed (measured at room temperature).

i~,;~ . ~

The reaction mixture was cooled down to - 80 °C and 200 ~tl, of ethylaluminum dichloride (1.0 M solution in hexanes) was added to start the reaction.
The reaction was carried out in MBRAUIVQ° dry box under the atmosphere of dry nitrogen. The reaction was terminated after 24 minutes by adding 5 mL of ethanol NaOH solution into the reactor.
The gravimetrically determined yield was 25.8 g. Characterization of the polymer by GPC-~scotek gave Mn = 99,740, MW = 178,900, and MZ = 320,600.
Isoprene content was 1.85 mol percent and methallyl chloride content was 1.03 mol percent.
~:1~ 3 The reaction feed was prepared exactly like in Example 2.
The reaction mixture was cooled down to - 80 °C. 2.0 mL of 10 wt °~6 solution of methylalumoxane (MAO) in toluene and 400 LtL, of ethylaluminum dichloride (1.0 M
solution in hexanes) was mixed together. The reaction was initiated with 1.80 mL of the above solution.
The reaction was carried out in MHRAIJN~ dry box under the atmosphere of dry nitrogen. The reaction was terminated after 60 minutes by adding 5 mL of ethanol NaOH solution into the reactor.
The gravimetrically determined yield was 35.5 g. Characterization of the polymer by GPC-Viscotek gave Mo = 128,400, Mw = 297,500, and MZ = 747,600.
Isoprene content waa 2.34 mot percent and no allylic chloride was detectable.
The increase of Mt indicates the branched structure of the polymer.

500 mL of dry hexane were placed in a 2 L reactor equipped with an overhead stirrer, cooled to - 80 °C, mixed with 212.75 mL of isobutene at - 80 °C followed by adding 6.~6 mL of isoprene measured at room temperature. The reaction mixture was cooled down to - 80 °C and 450 IrL, of ethylaluminum dichloride (1.0 M
solution in hexanes) was added to start tho roaction.
The reaction was carried out in MBRAUN'a dry box under the atmosphere of dry nitrogen. The reaction was terminated after 60 minutes by adding 5 mL of ethanol NaOH solution into the reactor.
The gavimetrically determined yield was 78.? g. Characterization of the polymer by GPC-Yacotek gave M" = 87,330, MW = 162,900, and MZ = 286,800.
Isoprene content was 1.87 mol percent.
This example is provided for comparative purposes for Example 5.

The reaction feed was prepared similarly like in Example 4, but in this case 5.04 mL of mathallyl chloride was also added to the feed (measured at room temperature).
The reaction mixture wao cooled down to - 80 °C and 5.0 mL of 10 wt. ~b solution of MAO in toluene was added to start the reaction. The reaction was carried out in MHRACJIV~ dry box under the atmosphere of dry nitrogen. The reaction was terminated after 2 hours by adding 5 mI, of ethanol NaOH solution into the reactor.
The gcavimetrically determined yield was 84.5 g. Characterization of the 1 S polymer by GPC-Viscocek gave M, = 69,570, Mw = 153,600, and M= = 335,200.
Isoprene content was 2.48 mol percent and methallyl chloride content was 0.22 mol percent.
The Mark-Houwink plots for polymers obtained in Example 4 and Example 5 were compared. The plot for Lhe polymer containing methallyl chloride deviated from the line for polymer obtained in reaction 4 (in the high end of molecular weights) indicating ehet the polymer with mcthallyl chloride had a branched structure.

Claims (8)

1. A process for producing polymers comprising repeating units derived from at least one isoolefin monomer and at least one allyl halide, wherein the isoolefin(s), the allyl halide(s) and optionally further co-monomers are polymerised in the presence of at least one initiator selected from the group consisting of alkylalumoxanes, alkylaluminiumhalides R n A1X3o, with each R being independently a C1-C40 group and each X being independently a halogen, or mixtures thereof.

2. A process according to claim 1, wherein dienes sue used at co-monomers.

3. A process according to claim 2, wherein a diene selected from the group consisting of isoprene, piperylene, 2,3-dimethylbutadiene and mixtures thereof are used and isobutene is used as isoolefin.

4. A process according to claim 1, wherein the allyl halide is allyl chloride, methallyl chloride or crotyl chloride.

5. A process according to any of claims 1 to 4, wherein methyl-, ethyl-, butyl-, octylaluminoxane or a mixture of one or more of the mentioned alkylalumoxanes is used as alkylalununoxane.

6. A process according to any of claims 1 to 5, wherein the alkylaluminoxane is taken from a solution in toluene .

7. A process according to any of claims 1-6, wherein a mixture of an alkylaluminoxane and a compound R n A1X3-o, with each R being independently a C1-C40 group and each X being independently a halogen is used.

8. A process according to any of claims 1-7, wherein the ratio of the alkylaluminaxane(s) and/or the alkylaluminium halide(s) to the allyl halide is less than 2.