DE2057160C - Process for the production of 1,4cis-polyisoprene - Google Patents

Description

In the manufacture of 1,4-cis-polyisoprene by Polymerization of isoprene in the presence of one consisting of titanium tetrachloride and an aluminum trialkyl Ziegler-type catalyst is known to be the polymerization reaction by the im general impurities contained in commercially available isoprene, such as cyclopentadiene, to a large extent inhibited, which lowers the yield. In technical polymerization processes in which a Ziegler catalyst is used, must therefore either the impurity of the monomer Isoprene is reduced considerably or a larger proportion of catalyst must be used. In both In cases, however, economic disadvantages must be taken into account in (Cauf.

It is known for example from Belgian patent 543 292 that the formation of 1,4-cis-polyisoprene of isoprene in the presence of one consisting of titanium tetrachloride and an aluminum trialkyl Ziegler catalyst is feasible. However, the activity of this catalyst is determined by the The cyclopentadiene contained in the isoprene used is greatly reduced. The experiments described below show that cyclopentadiene levels of less

jo than 0.01%, i.e. from a few thousandths of a percent that Activity of the conventional Ziegler catalyst e.g. B. to half or a quarter of the initial value humiliate. The commercially available isoprene, which is produced by various processes, contains other

On the other hand, generally a significant amount of cyclopentadiene as an impurity. In the production of JA-cis- polyisoprene, it was therefore necessary to maintain the catalyst activity, to lower the cydopentadiene content of the isoprene to a value of at most a few ten thousandths of a percent before it was used in the polymerization process. In order to achieve such a degree of purity of the isoprene, however, an exact fractionation using a distillation

column with a large number of theoretical trays or special chemical treatment stages necessary. Such methods / ur treatment of the isoprene starting material are, of course, also available Costs associated and affect the economics of an industrial scale procedure to be carried out.

British Patent 870 010 explains a method according to which in the presence one made of a titanium tetrahalide and an organoaluminum compound as a catalyst Isoprene polymerization a non-polymerizable ether as an activator or modifier for the Catalyst is used. Dihalo ethers such as bis (chlorometh > l) ether or bis (/ i-chloroethyl) ether, proposed. However, as shown below, are such dihalo ethers are ineffective even in the presence of low amounts of cyclopentadiene. The object of the invention was therefore to provide a process for the production of high molecular weight 1,4-cis-polyisoprene by polymerizing isoprene in the presence of an improved Ziegler-type catalyst to make available that by the aforementioned impurities of isoprene, in particular cyclopentadiene. is only adversely affected to a small extent and that has a high proportion of 1,4-cis polymer supplies.

This object is achieved by the invention. The invention thus relates to a method for the production of 1,4-cis-polyisoprene by polymerizing isoprene in the presence of a catalyst system from a titanium tetrahalide A, an organoaluminum compound B of the general formula

AlR ¹ R ² R ³

in which R ¹ and R ^{2 are the} same or different and are alkyl, cycloalkyl or aryl radicals and R ^{3 is} a hydrogen atom or an alkyl, cycloalkyl or aryl radical, and a halogen ether C, which is characterized in that one is used as compo -

nente C is a monohalogen ether C of the general formula and / or Ib

RO-C — R '

H H

I I

RO-C — C — R '

I I

H X

A-aluminum trialkyls are preferably used as component B in the process according to the invention of the general formula II

(Ia)

(Ib)

Al (R ⁴ J ₃

(ID

in which R is an alkyl, alkenyl, cycloalkyl or aryl radical, R 'is a hydrogen atom or an alkyl radical and X represents a chlorine, bromine or iodine atom is used.

The ternary catalyst system used in the process of the invention suffers up to a cyclopentadiene switch of the isoprene of about 0.01% there is no clear bullet in activity. It can therefore be considerable Isoprene containing amounts of cyclopentadiene in the process of the invention with good effect as mononu'ies can be used, provided that its cyclopentadiene content has been achieved by a conventional, simple treatment, like a fractional distillation, was lowered to a value below 0.01%. The activity of the Catalyst system used according to the invention only decreases by a few percent if instead of pure isoprene, the cyclopentadiene content of which is almost is zero, an impure isoprene containing 0.004% cyclopentadiene is used. in the In contrast, when using that mentioned in the aforementioned British patent 870010 Dihalo ether already, with a cyclopentadiene content of isoprene of 0.004% hardly any activity of the catalyst with respect to polymerization observed, and at a cyclopentadiene content of 0.006% no polymer was produced at all obtained more (see Comparative Examples 12 to 17). When using halogen-free ethers as a component C, an extremely low yield of polyisoprene was obtained even if a substantially Cyclopentadiene-free isoprene was used as the monomer. As also from the following Comparative experiments shows, the activity of catalysts, in which one of the often called Modifiers of the organoaluminum component of the alcohols used in Ziegler catalysts, such as ethanol or octanol, was also used, even with a cyclopentadiene content of the isoprene decreased from 0.003% to a quarter to a third of the initial value. The one used according to the invention The catalyst system is thus clearly superior to the known catalysts. It can thus be seen that with the aid of the catalyst system used according to the invention due to the contained therein Monohalogenether C can be achieved economically completely satisfactory results, because cheap, impure isoprene can be used as a starting material in the polymerization.

Specific examples of those suitable as component A of the catalyst system used according to the invention Titanium tetrahalides are titanium tetrachloride, titanium tetrabromide and titanium tetraiodide. Of these In halides, titanium tetrachloride is preferably used.

in which the radicals R ⁴ denote alkyl radicals, is used. Specific examples of ^{alkyl radicals suitable as radicals R 4} are the ethyl, propyl, butyl, isobutyl, amyl, hexyl and octyl groups. Specific examples of aluminum urialkyls of the general formula II are aluminum trimethyl, aluminum triethyl, aluminum tripropyl, aluminum triisobutyl, aluminum trihexyl and aluminum trioctyl.

The most essential component C for the purposes of the invention are the α-halogen ethers in general Formula I a and the / ϊ-halogen ethers of the general Formula Ib. The radical R in the general formulas Ia and Ib generally has 1 to 10 carbon atoms and

preferably 1 to 6 carbon atoms. The radical R 'is preferably a hydrogen atom. Alkyl radicals suitable as radicals R 'generally have up to 4 carbon atoms.
Specific examples of those suitable as component C

Halogen ethers are the following compounds, the monochloroethers being particularly preferred:

Monochloromethyl methyl ether,

Monobromodimethyl ether,

Monoiodine dimethyl ether,

Chloromethyl ethyl ether,

Bromomethyl ethyl ether,

Iodine methyl ethyl ether,

Chloromethyl propyl ether,

Chloromethyl isobutyl ether,

Chloromethyl isoamyl ether,

Chloromethylhexyl ether,

Chloromethyl octyl ether,

/ i-chloroethylphenyl ether,

/ i-bromoethylphenyl ether,

fi-iodoethylphenyl ether,

/ f-chloroethyl vinyl ether,

Iodomethyl propyl ether,

Chloromethyl isopropyl ether

Chloromethyl butyl ether.

and

It is surprising that the monohalogen ethers of the general formula used as component C I a or I b when used together with a titanium tetrahalide A and an organoaluminum compound B have a high catalytic activity for isoprene polymerization and also have the property show that the catalyst activity is due to the cyclopentadiene present as an impurity is not adversely affected. As above

is explained. such an effect can be achieved with ethers of a different type, such as those containing no halogen atoms Ethers or dihalo ethers, cannot be obtained.

The aforementioned three can be used to prepare the catalyst system used in accordance with the invention Components (A, B and C) in a suitable organic solvent, expediently a hydrocarbon, such as benzene, toluene, hexane, heptane or cyclohexane, mix. Though the order the addition when mixing the three catalyst components is not prescribed, the Component A is generally added to a mixture of components B and C.

The molar ratio of component C to component B can in the case of that used according to the invention Kalalysatorsystems 0.01: 1 to 1: 1 and is preferably 0.05: ί to 0.85: 1. If the component C per mole <Jer component B is present in a proportion of less than 0.01 mol, the method of the invention does not give the desired results. With a higher proportion of component C as 1 mole per mole of component B, the catalyst activity is lowered. The Molar ratio of component B to component A in the catalyst system used according to the invention 0.5: 1 to 2: 1 and is preferably 0.9: 1 to 1.5: 1. When used from outside of the aforementioned range, the molar ratios of component B to component A is the Catalyst activity decreased.

The polymerization according to the V process of Invention is carried out either without a solvent or in the presence of a suitable organic solvent carried out, inan either the catalyst components in the presence of the monomer mixed with one another or the monomer is added to a mixture of the catalyst components.

Solvents can advantageously be used as organic solvents in the process of the invention Based on hydrocarbons, such as aliphatic hydrocarbons, e.g. B. pentane, hexane or heptane, acyclic hydrocarbons, e.g. B. Cyclohixane, or aromatic hydrocarbons, such as benzene or toluene, can be used.

The in the process of the invention in the polymerization temperature used is not particularly critical. In general, however, at temperatures worked from -40 to 80'C.

Polyisoprene produced by the process of the invention is a high molecular weight 1,4-cis polymer. its intrinsic viscosity [> /] (dl / g; in toluene at 30 ° C.) is generally 3 to 7, and about 98% has a 1,4-cis structure.

The invention also relates to the catalyst system used in the aforementioned process.

The examples illustrate the invention.

B e i s ρ i e 1 e 1 to 5

The aim is to determine the effect of the cyclopentadiene content of the isoprene used on the polyisoprene yield are shown.

12 ml of a solution of aluminum triethyl in toluene (concentration = 0.5 mol / l) are placed in a flask equipped with a stirrer made of polytetrafluoroethylene in which a nitrogen atmosphere has been generated. This solution at 0 ° C under stirring with a solution of 3.6 ml Monochlordimethyläther (concentration = 0.5 mol / l) was added and the resulting mixture is reacted for 10 minutes at 10 ⁰ C. Subsequently, the reaction solution is - 40 ⁰ C cooled, then 10 ml of a solution of titanium tetrachloride in toluene (concentration = 0.5 mol / l) was added, and finally the total mixture for the preparation of the catalyst is stirred for 1 hour at 10 ° C. It is always worked in a nitrogen atmosphere. Then 160 ml of water and oxygen-free hexane, 40 ml (27.2 g) of isoprene and a certain amount of a solution of cyclopentadiene in hexane (concentration = 0.548 g / l) in a pressure-tight 300 ml glass reactor, in which a Nitrogen atmosphere was generated, and then 2 ml of the catalyst solution prepared in the manner described above (molar ratio isoprene / titanium = 1000: 1) are added. The reactor is then closed and the polymerization is carried out for 5 hours with shaking at a constant temperature of 20 ° C.

After a certain time, the reaction is stopped by adding isopropanol, which contains 2,6-di-tert-butylp-cres oil as an oxidation inhibitor, and the entire mixture is then poured into a large amount of methanol while stirring, and the polymer formed in to transfer the solid state. The product is washed with methanol and ^{dried for about 15 hours at 45 °} C. and under reduced pressure. Table I shows the results.

Table I.

example Cyclopentadiene 6th yield
% of theory till 9 1 0 95 2 0.002 95 3 0.004 93 4th 0.006 86 5 0.008 78 Examples

It should be the influence of the molar ratio of the monochlorodimethyl ether to aluminum triethyl on the catalyst activity and the Grenzvi & kosiüit des Polymer when using the same molar ratio of aluminum triethyl / titanium tetrachloride (component B / component A = 1.2: 1) as shown in example 1.

Into a 5-1 polymerization reactor in which a nitrogen atmosphere has been generated, 2400 ml of water and oxygen-depleted n-hexane and 408 g (6 mol) of isoprene are charged, and the mixture is added with 30.6 ml of a solution of the catalyst , in which the molar ratio of monochlorodimethyl ether to aluminum triethyl according to Example 1 was set to certain values (the molar ratio of isoprene / titanium is 1000: 1). The mixture is then reacted at 10 ^° C. for 5 hours, and the product obtained is converted into the solid state and dried. The results are shown in Table II.

Table II yield
% of theory at 30 ⁰ C (intrinsic viscosity). [- /] *)
(dl / g) example Monochlorodiraethyl
ether / AI (C2H ₅ ) ₃
Mole ratio 98 5.2 6th 0.3: 1 94 5.7 7th 0.5: 1 91 5.4 8th 0.7: 1 72 5.5 9 0.8: 1 *) In toluene

Γ,

ie

nc rdc
1).
cn
• nc
nd
he-

Examples 10 to 15

In these examples, instead of monochlorodimethyl ether from Example 1 different other halogen ethers and instead of aluminum triethyl Aluminum triisobutyl used. The catalyst preparation and the polymerization are carried out according to Example 1 carried out unless otherwise specified. Those obtained in the polymerization Results are shown in Table III.

Table III

Halogen ethers AI (R ⁴ J ₃ temperature Bulging (dl gl example in the
Polymerization % of theory 4.7 Chloromethyl ethyl ether AlAt ₃ *) 100 5.3 10 / i-chloroethylphenyl ether AlAt ₃ 20th 77 - 11th / 3-chloroethyl vinyl ether AlAt ₃ 20th 70 3.8 12th Monochlorodimethyl ether AlO-Bu) ₃ **) 20th 92 4.0 13th Chloromethyl ethyl ether Al (I-Bu) ₃ 50 85 3.7 14th / J-chloroethylphenyl ether AUi-Bu) ₃ 50 88 15th 50

*) At = ethyl.
**) i-Bu = isobutyl.

Comparative Examples 1 to 5

It becomes the resistance of not according to the invention Comparative systems that can be used as catalyst systems versus cyclopentadiene are illustrated. In Comparative Examples 2 to 5, the same procedure is used as in Example 1, Instead of monochlorodimethyl ether, however, acetone, acetoin, ethanol or n-octanol are used. In Comparative Example 1, component C is omitted and an Al / Ti molar ratio of Applied 1: 1 to ensure the highest catalyst activity. The other conditions are with Comparative Example 1 is the same as in Example 1. The results are shown in Table IV.

Table IV

even then only a very low yield can be achieved as component C of the catalyst, if the isoprene used does not contain any cyclopentadiene. The monochlorodimethyl ether from Example 1 is replaced here by dimethyl ether and anisole, and a cyclopentadiene-free isoprene is used. The catalyst preparation, the polymerization and the aftertreatment are carried out according to Example 1 carried out. The results are shown in Table V.

Table V ^x

■ "Comparative example

Catalyst system Cyclopentadiene. % 7th 73 0.003 0.004 yield 41 Vcr- 82 D the theory 41 equal 0 75 - 28 example TiCVAlAt ₃ 87 - - TiCl ₄ / AlAt ₃ / acetone 95 ._ - 1 TiCVAlÄt ₃ / acetoin 21 2 TiCVAlÄta / ethanol 32 3 TiCl ₄ / AlEt ₃ / octanol 4th 5

40

45

10

11th

Molar ratio
Ether / triethylaluminum

Dimethyl ether

Dimethyl ether

Dimethyl ether

Anisole

Anisole

Anisole

0.1:
0.3:
0.7:
0.1:
0.3:
0.7:

yield
% the
theory

26th

13th

24
17th

Comparative Examples 6 to 11

From these examples it can be seen that when used an ether containing no halogen atom

table

Comparative Examples 12 to 17

The monochlorodimethyl ether used in Example 1 is replaced here by bis (chloromethyl) ether or bis (/ i-chloroethyl) ether. The influence of the cyclopentadiene content of the isoprene on the polymer yield is shown. Unless otherwise stated, the conditions described in Example 1 are used in the preparation of the catalyst and the polymerization. The results are shown in Table VI.
VI

■ comparison
example Halogen ethers Molar ratio
Halogen ether / Al Cyclopentadiene
% yield
% of theory 12th
13th
14th
15th
16
17th Bis (chloromethyl) ether
Bis (chloromethyl) ether
Bis (chloromethyl) ether
Bis - (/? - chloroethyl) ether
Bis-i / J-chloroethyl ether
Bis- (J? -Chloroethyl) -ether 0.1: 1
0.1: 1
0.2: 1
0.1: 1
0.1: 1
0.2: 1 0.004
0.006
0.004
0.003
0.004
0.004 16
0
0
7th
0
0

209 663,438

10

Examples 16 to 21

To illustrate the influence of the Cyclopentadicngchaltsdes Isoprene on the Pohmerausbcute are different Monochlorälher as a component C of the catalyst fed in.

Tiuintetrachlorid.as component B aluminum triethyl is used as component A. The various monochloroethers listed in Table VII are used as component C. The polymerization is carried out in a similar manner as in Example I or 4, however, a molar ratio (B) Z (A) of 1:15, a molar ratio (C) / (β) of 0.2: 1 and a Molar ratio of isoprene / (A) of 1000: 1 is used, and the polymerization is carried out ^{at 10 ° C. for 5 hours.} The results are shown in Table VII.

Table VII

Monochlorine ethers Polvmerisaiausbcute 0.006%
Cyclo "(i the theory pentadiene example Monochloromethyl no cyclo 85 methyl ether pentadiene 16 Monochloromethyl KX) 85 ethyl ether 17th Monochloromethyl 100 86 n-butyl ether 18th Monochlorous partial 100 87 l-methylprop \ l- 19th ether 100 Monochlorometal 1- 88 2-methylprop \ l- 20th ether 100 Monochloromethyl 88 2-ethylhexyl ether 21 100

Claims (3)

Patent claims: 1. Process for the production of 1,4-cis-polyisoprene by polymerization of isoprene in the presence of a catalyst system from a Titanium tetrahalide A, an organoaluminum compound B of the general formula AlR ¹ R ² R ³ in which R ¹ and R ^{2 are} identical or different and are alkyl, cycloalkyl or aryl radicals and R ^{3 represents} a hydrogen atom or an alkyl, cycloalkyl or aryl radical, and a halogen ether C, characterized in that component C is a Monohalogen ether C of the general formula Ia and / or Ib I.
RO-CR '(la) H H RO-C-C-R '(Ib) H X in which R is an alkyl, alkenyl, cycloalkyl or aryl radical, R 'is a hydrogen atom or an alkyl radical and X represents a chlorine, bromine or iodine atom is used. 2. The method according to claim 1, characterized in that a catalyst system is used that is, a molar ratio of component B to component A of 0.5: 1 to 2: 1, preferably from 0.9: 1 to 1.5: 1. 3. The method according to claim 1 or 2, characterized in that there is a catalyst system used, which has a molar ratio of component C to component B of 0.01: 1 to 1: 1, preferably from 0.05: 1 to 0.85: 1.