CS239429B1 - Process for preparing telechelic polymers of isobutylene - Google Patents

Abstract

Method for preparing telechelic polymers of isobutylene. Method for preparing telechelic polymers of isobutylene with the structure CH, CH, Cl-C-CH, - PIB - CH--C-C1 I I. CH3 CH3 in which PIB denotes a polyisobutylene chain, the essence of which lies in the fact that isobutylene is polymerized in the presence of 2,5 dimethyl-2,5-dichlorohexane as a bifunctional transfer agent in halogen solvents under the catalytic action of ferric chloride, aluminum chloride, aluminum bromide, titanium chloride, ethanediyl chloride or boron trifluoride. The molecular weight of the polymer can be controlled by the content of 2,5-dimethyl-2,5-dichlorohexane added to the polymerization mixture in an amount of 0.3 to 5 wt. % by weight of monomer in the range from Bn = 800 to Bjj = 100,000 at temperatures of -10 to -78 °C.

Description

The invention relates to a process for the preparation of telechelic polymers of isobutylene.

In the cationic polymerization of olefins, the preparation of telechelic isobutylene polymers having reactive chlorine bonded to tertiary carbon at both ends of the polymer chain has been developed in recent years, which can then advantageously be used for further chemical reactions. Dicumyl chloride is exclusively used to prepare these isobutylene-based polymers (J.P. Kennedy, E. Marechal: Carbocationic Polymerization, and Wiley-Intersciences Publieation, 1982).

which participates in both the initiation and transfer reactions of the polymer chain and is therefore also referred to as the so-called INIFER (inltiation-transfer). However, dicumyl chloride is demanding for its synthesis and difficult to access. As a result, they are looking for new analogues that are more readily available.

We have now found that 2,5-dimethyl-2,5-dichloro-hexane can also be advantageously used for the preparation of telechelic polymers of isobutylene.

The present invention provides a process for the preparation of telechelic isobutylene polymers having a structure

CH, CH,

I ¹

C1-C-CH ₂ - PIB - CH ₂ -C-C1

CH ₃ CH ₃ in which PIB denotes a polyisobutylene chain, characterized in that isobutylene is polymerized in the presence of 2,5-dimethyl-2,5-dichlorohexane as a bifunctional transfer agent in halogenated solvents under the catalytic action of ferric chloride, aluminum chloride, aluminum bromide, titanium tetrachloride, vanadium chloride or boron trifluoride.

Another feature of the invention is that the molecular weight of the polymer can be controlled by content

2,5-dimethyl-2,5-dichlorohexane added to the polymerization mixture in an amount of 0.3 to 5 wt. % to the weight of the monomer in the range of = 800 to M _n = 100,000 at temperatures of -10 to -78 ° C.

2,5-Dimethyl-2,5-dichlorohexane is readily prepared against dicumyl chloride. In the polymerization of isobutylene, it is used as a bifunctional, highly efficient transfer agent, thereby obtaining polymers with molecules terminated at both ends of the polymer chain with chlorine bonded to tertiary carbon.

The polymerization can be used as catalyst aluminum chloride (AlClj), aluminum bromide (AlBr _3), titanium tetrachloride (TiCl ^), vanadium tetrachloride (VCl ^) or boron trifluoride (BP _3). Most preferred, however, is ferric chloride (PeCl ₃ ), which utilizes 2,5-dimethyl-2,5-dichlorohexane transfer alongside aluminum chloride (AlCl ₃ ), the largest and many times over the monomer transfer, which must be suppressed in the preparation of telechelic polymers to a minimum.

The polymerization can be carried out not only directly in the halogenated solvent solution, but also by adding to the solution of the metal halide in the respective solvent in the presence of

The 2,5-dimethyl-2,5-dichlorohexane feeds the β-butylene either in the gaseous state or in a solution at a rate such that the temperature of the reaction mixture heated by exothermic polymerization does not exceed the desired limit. It is also suitable to carry out the polymerization by introducing into the solution of the catalyst itself in a halogenated solvent a solution of isobutylene with the required amount of

2,5-dimethyl-2,5-dichlorohexane, thereby maintaining a constant monomer to transfer ratio in the reaction medium during polyiperation. The continuous introduction of the monomer into solution or mixture thereof with transfer to the polymerization environment is advantageous in particular because the concentration of the monomer is kept at a low value in the reaction medium during polymerization.

The stationary concentration in the polymerization medium should not exceed values greater than 9% by weight. % of the monomer during polymerization and should be as low as possible. When the solution polymerization of isobutylene is carried out in the presence of 2,5-dimethyl-2,5-dichlorohexane, the catalyst solution is added gradually to the reaction mixture so that the heat of reaction can be removed by cooling and the process is preferably isothermal.

As the polymerization solvent, methylene chloride, methyl chloride, ethyl chloride, 1,2-dichloroethane and others can be used.

The polymerizations were carried out in a glass reactor equipped with a magnetic stirrer and a three-way cock to dispense the catalyst, monomer and transfer agent solution. The reactions were carried out under an inert argon atmosphere and excluding external moisture. The moisture present in the solvents and monomer did not exceed 10 ppm. 2,5-Dimethyl-2,5-dichlorohexane was prepared by adding HCl gas to dimethallyl (2,5-dimethyl-1,5-hexadiene) and recrystallized from heptane solution. The product had a melting point of 67.2 ° C.

He did

In 40 g of methylene chloride 11 g of isobutylene and 0.1 g were dissolved at -78 ° C

2,5-dimethyl-2,5-dichlorohexane. While stirring and cooling, 0.1 ml of a solution of FeCl 2 in nitromethane C (1.5 mol / L) was added to the reaction mixture. The catalyst is gradually added three times in succession, so that the reaction temperature did not exceed -60 C. ^e

After half an hour of polymerization, 2 ml of ethanol was added to the reaction mixture, shaken to ice temperature and warmed to room temperature while warming to room temperature. After evaporation of the volatiles at 40 ° C under reduced pressure, 9.3 g of a polymer having H _n = 6,300 and M _w = 8600 were obtained. The polymer contained 1.4% bound chlorine.

Example 2

In a polymerization reactor, 0.3 g of 2,5-dimethyl-2,5-dichlorohexane was dissolved in 40 g of methylene chloride and 1 ml of a 0.1 mol / l solution of aluminum chloride (AlCl3) in ethyl chloride (Co) was added. While stirring, the isobutylene in the gaseous state was reacted at a rate such that the temperature in the reactor from the heat of reaction did not exceed -60 ° C with external cooling of -70 ° C. A total of 12.4 g of isobutylene was gradually condensed into the reactor. After completion of the polymerization by the addition of alcohol, the product was treated as in Example 1. 8.6 g of polymer were obtained, which after precipitation with acetone had 8 _n = 15,600. From the chlorine content of the polymer, 1 molecule of polymer was calculated to bind 1.8 moles. chlorine.

Example}

20 g of 1,2-dichloroethane, 1 g of 2,5-dimethyl-2,9-dichlorohexane and 800 µm of titanium tetrachloride (TiCl 4) in heptane solution were metered into the reactor. The reaction mixture was cooled to -90 ° C and a 30% solution of isobutylene in 1,2-dichloroethane was added in small portions (2 mL) with stirring at intervals of about 2 min. A total of 20 mL of isobutylene solution was added, followed by polymerization for an additional 10 min. quenched with ethanol. The polymer was isolated as in Example 1. The polymer obtained had a mass H _n = 8 300, the polymerization being carried out to a conversion of 89% by weight.

Example 4

The polymer was prepared as in Example 1 except that a solution of aluminum bromide (AlBr 4) in heptane was added as a catalyst. A total of 90 jumoles were added

ΑΙΒγ ^ at a polymerization temperature of -78 ° C. The polymer obtained after precipitation from acetone had a molecular weight of viscosimetric B n = 69,000 and B n = 38,000.

η n

Example 1 and d 9

The polymer was prepared at -30 ° C as in Example 1 except that

2,5-dimethyl-2,9-dichlorohexane was present in an amount of 2 g. The polymer obtained had a molecular weight B _r = 1860 and a chlorine content of 3.1% by weight.

Claims (2)

SUBJECT OF THE INVENTION A process for the preparation of telechelic isobutylene polymers having a structure CH, CH, I I Cl-C-CH - PIB - CH - C-C-1 '1' OH in which _3% of PIB represents a polyisobutylene chain wherein ieobutylen is polymerized in the presence of 2,9-dimethyl-2,9-dichloro hexane as a difunctional chain transfer agent in halogenated solvents under the catalytic action of ferric chloride, aluminum chloride, aluminum bromide, titanium chloride, vanadium chloride or boron trifluoride. 2. A process according to claim 1, wherein the molecular weight of the polymer is 2,9-dimethyl-2,9-dichlorohexane added to the polymerization mixture in an amount of 0.3 to 9 wt. % by weight of the monomer controlled in the range of B _ft = 800 to B _n = 100,000 at temperatures of -10 to -78 ° C.