DE2164515C2 - Process for the production of polybutadiene with predominantly cis-1,4-structure and controllable molecular weight - Google Patents

Description

(A) at least one nickel compound, with

(B) a hydroquinone of the general formula

HO

OH

in which Ri, R2, R3 and Rt are identical or different and denote hydrogen or halogen atoms or Ri and R2 or R3 and R4 each together form a fused aromatic ring, while any remaining substituents that may still be present are hydrogen or halogen atoms, and
an organoaluminum compound

has been prepared, the component (A) mixed with the component (C) in the presence of a small amount of 1,3-butadiene, isoprene or dimethylbutadiene and then the component (B) was added and the catalyst system then at temperatures from 0 to 100 ⁰ C was aged, characterized in that the polymerization is carried out in the presence of a catalyst system which, using a dialkyl aluminum monofluoride with 1 to 6 carbon atoms in the alkyl radicals as component (C), maintains a molar ratio of the nickel compound to dialkyl aluminum monofluoride in the range from 0.001: 1 to 2: 1 and the nickel compound to the hydroquinone in the range of 0.01: 1 to 100: 1 has been prepared that the catalyst system is used in such amounts that component (A) makes up 0.001 to 2 millimoles per mole of the monomer and that the polymerization is carried out in the presence of water, the molar ratio of water to dialkylaluminum monofluoride is from 0.05: 1 to 1.5: 1.

2. The method according to claim 1, characterized in that the polymerization is carried out in the presence furthermore at least one alcohol, a carboxylic acid and / or a phenol in an amount from 0.01 to 0.5 moles per mole of the component (C).

3. The method according to claim 1, characterized in that the polymerization is carried out at molar ratios from water to dialkyl aluminum monofluoride from 0.1: 1 to 1.2: 1

4. The method according to claim 1 to 3, characterized in that the polymerization with 0.01 to 1 mmol of the nickel compound per mole of the 1,3-butadiene used as the starting material.

For the production of polybutadiene with a cis-1,4 structure a large number of catalyst systems have already been described. Typical examples such known catalyst systems are:

(1) A combination of a halogenated Titanium compound and a trialkylaluminum compound; (2) a combination of a halogenated Cobalt compound and an alkyl aluminum halide; and (3) a combination of a nickel or

ίο cobalt compound, a trialkylaluminum compound and a Lewis acid, such as an inorganic halogenated compound or its derivative (see GB 9 06 334 or "Progress in Polymer Science", Vol. 1 (1967); Pp. 130/131).

Of these known catalyst systems, the ternary system (3) has a nickel or cobalt compound contains, due to the high catalytic activity and various advantages in the practical Application received the greatest attention.

From DE-AS 11 43 333 there is also a method known for the production of cis-1,4-polybutadiene. Here, 1,3-butadiene is in the liquid phase by means of a Polymerized catalyst system by mixing one or more cobalt and / or Nickel compounds, an organoaluminum compound, which is preferably an alkyl aluminum halide and water has been prepared in a hydrocarbon solvent

However, this known process leaves something to be desired in terms of yields and leads when using Nickel compounds also form polymers with molecular weights that are too low. In particular, These known processes reduce the rate of polymerization, especially at higher water concentrations adversely affected.

Furthermore, DE-OS 20 24 345 describes that the polymerization of 13-butadiene with Advantageously, be carried out in the presence of a catalyst system of the following composition can:

(A) At least one nickel and cobalt compound;

(B) a trialkylaluminum compound;

(C) a benzotrifluoride represented by the following formula

R-,

in which Ri, R2, R3, R4 and R5 are independent of one another Denotes hydrogen, a halogen atom, an alkyl group or a fluoroalkyl group, and

(D) a hydroquinone represented by the general formula below

Ri

in which Ri ', R2', R3 'and R ₄ ' each independently represent hydrogen or a halogen atom, or Ri 'and R ₂ ' or R3 'and R ₄ ' each

together form an aromatic fused ring, while the optionally still any remaining substituents present are hydrogen or a halogen atom.

In the polymerization reactions carried out using these known catalyst systems, the molecular weight of the polybutadiene can be determined adjust in a manner known per se, for example by checking the composition accordingly the polymerization approach, by controlling the process conditions and the concentration of Catalyst system, by setting the monomer concentration and the polymerization temperature accordingly. For the implementation of such control and control measures, however, special technical experience and care is required. Compliance certain molecular weight ranges is therefore associated with difficulties even for the person skilled in the art, and the measures taken to this end sometimes have an unfavorable effect on other properties of the Catalyst system, e.g. B. the activity.

The invention was therefore based on the object of eliminating this disadvantage, which is quite significant in practice to overcome and provide a polymerization process that is easy and simple can be carried out and in particular regulating the molecular weight in a particularly simple manner enables

The subject of the invention is thus the method described in the claims. .

It was surprising and even with knowledge of DE-AS 11 43 333 not to be expected that it would through Appropriate adjustment of the water content of the reaction mixtures is possible, the molecular weight adjust the polybutadiene accordingly, and that the presence of water in the reaction mixture contrary to expectations, the rate of polymerization is not adversely affected, but rather in the Opposite to an increase in the rate of polymerization compared to anhydrous work leads.

The various salts and organic complex compounds of Nickel can be used.

Nickel halides such as nickel chloride, nickel sulfate, the salts of organic acids such as nickel acetate, Nickel naphthenate, nickel octanoate, the nickel salts of organic sulfonic acids, complex compounds of nickel salts, such as the pyridine complex of nickel chloride, tris-idi-pyridylJ-nickel chloride, bis (ethylenediamine) nickel sulfate, organic coordination compounds of nickel or nickel chelates, such as bis (dimethylglyoxymate) nickel, Bis-iäthylacetacetJ-nickel or Bis (acetylacetonate) nickel.

The following can be used as the hydroquinone compound (B):

Tetrachlorohydroquinone,

2,3,5-trichlorohydroquinone,

2,5-dichlorohydroquinone, bo

2-chlorohydroquinone,

Tetrabromohydroquinone,

2,3,5-tribromohydroquinone,

2,5-dibromohydroquinone,

2-bromohydroquinone, tetraiodohydroquinone,

23.5-triiodohydroquinone,

2,5-diiodohydroquinone,

2-iodine hydroquinone,

Hydroquinone,

1,4-dihydroxynaphthalene,

l ^ -dihydroxy ^ -dichloronaphthalene, 5,10-dihydroxyanthracene,

1,4-dihydroxy anthracene and

1,4-dihydroxyphenanthrene.

Suitable dialkyl aluminum monofluorides (C) are

Dimethyla aluminum monofluoride, diethyl aluminum monofluoride, Diisopropyl aluminum monofluoride, di-n-butyl aluminum monofluoride, Diisobutyl aluminum monofluoride and di-n-hexyl aluminum monofluoride.

As the alcohol, saturated and unsaturated aliphatic alcohols, aromatic alcohols, alicyclic Alcohols or halogenated alcohols can be used. In particular, can be used

Methyl alcohol, ethyl alcohol,
Isopropyl alcohol, butyl alcohol, isobutyl alcohol, amyl alcohol,
Isoamyl alcohol, neopentyl alcohol, hexyl alcohol, isohexyl alcohol,
Heptyl alcohol, isoheptyl alcohol, octyl alcohol, isooctyl alcohol,
Nonyl alcohol, isononyl alcohol, decyl alcohol, isodecyl alcohol,
Dodecyl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol,
sec-butyl alcohol, tert-butyl alcohol, sea-amyl alcohol, tert-amyl alcohol, sec-hexyl alcohol, tert-hexyl alcohol, ethylene glycol, propylene glycol,
Trimethylene glycol, tetramethylene glycol, glycerine, allyl alcohol,
Crotyl alcohol, oleyl alcohol,
Butene-2-diol, propargyl alcohol, benzyl alcohol, cyclohexyl alcohol, 2-chloroethyl alcohol, 2-bromoethyl alcohol and glycerol-2-monochlorohydrin.

As a carboxylic acid, saturated and unsaturated aliphatic carboxylic acids, aromatic carboxylic acids, alicyclic carboxylic acids or halogenated carboxylic acids can be used. In particular, can be used acetic acid, propionic acid, valeric acid, isovaleric acid, butyric acid, isobutyric acid, caproic acid, Heptylic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, Palmitic acid, stearic acid, rhodic acid, naphthenic acid, disproportionated rhodic acid, 2-ethylcaproic acid, Benzoic acid, hexahydrobenzoic acid, j3-chloropropionic acid, 2,4-dichlorobenzoic acid and 2,5-dichlorobenzoic acid.

Can be used as phenol

Phenol, o-cresol,

m-cresol, p-cresol,

^ -XylenoU ^ -Xylenol,

S ^ -XylenoU ^ -Xylenol,

p-tert-butylphenol,

2,6-dimethyl-4-tert-butylphenol, S-methyl-ö-tert-butylphenol,

2-methyl-4,6-di-tert-butylphenol,

2,4-di-terL-butylphenol,
2,6-di-tert-butylphenol,
^ e-Di-tert-butyl-i-methylphenol,
«-Naphthol, ^ -naphthol,
Anthranol, o-chlorophenol,
m-chlorophenol, p-chlorophenol,
p-bromophenol, o-bromophenol,
m-bromophenol, 23-dichlorophenol,
2,4,6-trichlorophenol and
2,4,5-trichlorophenol.

The catalytic activity of the catalyst systems used in the process according to the invention depends on the mixing ratio of the components, on the order in which these components are used are mixed together, from the concentration of each catalyst component, from that used in its manufacture the temperature applied to the catalyst system as well as other factors of this ArL in particular the mixing ratio of the individual catalyst components has a great influence on the Catalyst activity. The polymerization according to the invention should take place at molar ratios of the nickel compound to the dialkyl aluminum monofluoride (i.e. the ratio of components (A): (C)) of preferably 0.01: 1 to 1: 1 can be carried out. The molar ratio the nickel compound to the hydroquinone should preferably be kept in the range from 0.1: 1 to 10: 1 will.

In the polymerization process of the present invention, the nickel compound is used in amounts from 0.001 to 2 mmol, preferably from 0.01 to 1 mmol, based on 1 mole of monomeric 1,3-butadiene used.

If the amount of one of the catalyst components used is too large or too small, then reduced the catalytic activity of the catalyst system increases to an extraordinarily high degree and can almost go to 0 sink. Therefore, in order to ensure a high activity of the catalyst systems according to the invention, should the claimed mixing ratios are adhered to.

The individual catalyst components can be mixed in any order usually takes place in the presence of a diluent. For the production of catalyst systems with very high activity, it is useful to use the nickel compound and the dialkylaluminum monofluoride in the presence of a small amount of 1,3-butadiene, isoprene and dimethylbutadiene, respectively mix. In this way it is possible to prevent the formation of to prevent insoluble material and so reduce the harmful influence to the lowest possible value keep that by contamination of the polymerization batch with a small amount of an impurity can be exercised.

The production of a useful process of the invention catalyst system is carried out at a temperature in the field of instrumentation from - 80 to 100 ° C and preferably in the range from -20 to 5O ⁰ C. To a catalyst system to be obtained with increased catalytic activity, the mixture in question is, after all Catalyst components have been mixed homogeneously with one another, and finally aged at a temperature in the range from 0 to 100 ° C.

The catalyst system used according to the invention can be prepared, for example, as follows: Man if the dialkyl aluminum monofluoride is mixed with a diluent, a small amount is initially set 13-butadiene and then the nickel compound and Finally, the hydroquinone hinza. Finally, the mixture obtained in this way is aged in one of these suitable temperature.

In order to reduce the molecular weight of the polybutadiene to the desired value in the process according to the invention To be able to set a value, a predetermined amount of water or a mixture of water and

ίο at least one alcohol, one carboxylic acid or a phenol is added either to the catalyst system or to the polymerization batch

The molar ratio of water to dialkylaluminum monofluoride should preferably be in the range of 0.1: 1 to 1.2: 1. If together with the water an alcohol, a carboxylic acid and / or a phenol are also used, their molar ratio is too the dialkyl aluminum monofluoride in the range of 0.01: ib to 0.5: 1.

Mixing the water, alcohol, carboxylic acid and / or phenol into the polymerization batch can be done in a variety of ways. Incorporation of water, alcohol, one Carboxylic acid and / or a phenol can be added to the catalyst system in any way prior to preparation this catalyst system take place, d. H. some or all of the compounds concerned can be used in a part or the total amount of the nickel compound, the dialkylaluminum monofluoride compound and / or the hydroquinone. According to another embodiment, the compounds in question can also directly to the Polymerization batch are mixed by either absorbing them in 1,3-butadiene or the Admixing diluent, which is used in the reaction mixture with, or by adding one Premix of the catalyst system, 13-butadiene and a diluent before or during the Polymerization reaction clogs.

If you add the alcohol, the carboxylic acid and / or the phenol together with water, so can while completely avoiding the formation of insoluble substances during catalyst aging otherwise under certain conditions, for example if the water content is too high, such insoluble ones Substances fail. The catalyst system can therefore be completely soluble in the polymerization batch can be made, whereby the continuous production of the polybutadiene becomes possible.

so the polymerization reaction is carried out under conditions in which there is practically no inhibiting Acting substances are present, as they are otherwise usually in the case of the Ziegler-Natta type catalyst system available. If a conventional Ziegler-Natta type catalyst system is used, the one Contains organoaluminum compound, the polymerization reaction must take place under practically anhydrous Conditions are carried out because the presence of water increases the rate of polymerization reduces or a polymerization practically completely prevented. In contrast, the Process according to the invention using the new catalyst systems, the rate of polymerization by the presence of water despite the simultaneous presence of an organic one Aluminum connection increased. In addition, in the process according to the invention, the molecular weight of the polymer by regulating the water

set the amount to a preselected value.

Suitable as solvents and diluents for the catalyst system and / or the polymerization batch themselves, inter alia. aromatic hydrocarbons, such as benzene, toluene or xylene, and also aliphatic hydrocarbons such as hexane, heptane and gasoline, also alicyclic hydrocarbons such as cyclohexane and Decalin, and also hydrogenated aromatic hydrocarbons such as tetralin.

The polymerization is carried out by bringing the 1,3-butadiene into contact with the catalyst system in question in a liquid medium at a temperature in the range from preferably 0 to 100 ^{° C.} The order in which the catalyst system and monomer are fed in! 1.3-butadiene is not mandatory in the reactor and, moreover, the feed can take place in the presence or absence of the diluent.

The polybutadiene formed can be recovered from the reaction mixture in a manner known per se take place, for example, pouring the reaction mixture into a large amount of an aqueous or alcoholic medium such as methanol, isopropanol, a mixture of methanol and acetone or hot water a. If desired, an antioxidant can be added to this medium beforehand, for example Phenol - /? - naphthylamine or 2,6-di-lert.-butyl-p-cresol. The precipitate is then filtered off and washed out with methanol. That way it gets a practically colorless rubber-like polymer.

The polybutadiene produced in accordance with the present invention is a rubbery solid or a high material Viscosity. An analysis of the microstructure of these types of polybutadiene using infrared absorption confirmed the presence of a predominantly cis-1,4 structure in most of the butadiene units.

In the examples below, the viscosity numbers given for characterization are Polymer has been measured in a toluene solution at 30 ° C. The microstructure of the polymer in question is determined by recording the infrared absorption spectrum according to the method of Morero (cf. D. Morero and co-workers: “Chim. e. Ind. ", Vol. 41, p. 758 (1959).

Examples 1 and 2

A solution of

κι 4 mmol of diethylaluminum monofluoride fed in 20 ml of toluene, and then a solution of 2.4 g of 1,3-butadiene in 74 ml of toluene and a solution of 0.4 mmol of nickel naphthenate in 6 ml of toluene are added. ^{This mixture is heated to 25 °} C. for 30 minutes while stirring. 10 ml are then withdrawn and this portion of the catalyst solution is transferred to a glass reactor with a capacity of 200 ml, which is suitable for pressure polymerization. Is then reacted moist toluene with a water content of 0.0417 percent by weight and a solution of 0.04 mmol of tetrachlorohydroquinone in 8 ml of toluene are added and heated with stirring for 15 minutes at 40 ^G C. then filled with toluene to a total volume of 130 ml on. After the mixture has cooled to a temperature below -20 ^° C., 22 g of 1,3-butadiene are added and the reaction tube is melted. All of the above measures are carried out in a stream of argon. The reaction tube is inserted into a rotating bath which is maintained at a constant temperature of 4O ⁰ C, and then polymerization is carried out for 180 minutes. The reaction mixture is then poured into methanol which contains a small amount of 2,6-di-t-butyl-p-cresol, whereby the polymerization is terminated. The precipitated polymer is separated off and dried in vacuo at room temperature. The yield obtained and the physical properties of the polybutadiene thus obtained are shown in Table I below.

Table 1 Molar ratio of
Water to diethyl
aluminum mono-
fluoride Polymerization
Time
(Min.) Polymerization
yield
(%) product
l "l
(dl / g) Micro structure,
cis-1.4 trans-1.4 ! .2 example
No. 0.7
0.2 180
180 81.3
58.1 2.87
2.26 96.1
96.2 1.7
1.7 2.2
2.3 1
2

Example 3

According to the procedure of Example 1, a catalyst system is prepared, but 0.02 mmol Nickel naphthenate and 0.2 mmol diethyl aluminum monofluoride are applied and the total amount

Table II

the catalyst solution is adjusted to 20 ml. The polymerization is then carried out according to the procedure of Example 1 using 44 g of 1,3-butadiene for 2 hours at 25 ° C results obtained are summarized in Table II below

example Molar ratio of Molar ratio of Polymerization product Micro structure,% 1.2 No. Tetrachlorohydro of water too cis-1.4 trans-1.4 chinone too Diet Hylaiuminium Yield [n] Ninaphthenate Monofluoride (%) (dl / g)

0.6

3.82

96.4

1.6

2.0

Example 4

According to the procedure of Example 1, a catalyst system is prepared, but 0.05 mmol Nickel naphthenate and 0.5 mmol diethyl aluminum monofluoride are used and the total volume the catalyst solution is adjusted to 50 ml. the

Table III

10

subsequent polymerization is also carried out according to the procedure of Example 1 using 10.2 g of 1,3-butadiene carried out in a polymerization tube of 100 ml capacity.

The results obtained are summarized in Table III below.

example
No.

Component (D)
link

Molar ratio to ninaphthenate

Molar ratio of water to diethyl aluminum monofluoride

Polymerization time

(Min.) Polymerization product

Yield [n] micro structure,%

(%) (dl / g) cis-1,4 trans-1,4 1,2

Tetrabromous 5

hydroquinone

0.8

180 82.7 2.43 94.3 2.3

Examples 5-10

All of the operations described below are carried out in a stream of argon. the The starting materials and the solvents are carefully dehydrated and de-oxygenated beforehand.

A solution of 4 mmol of diethylamine monofluoride in 20 ml of toluene is placed in a reaction tube made of glass Filled, and then a solution of 2.43 g of 1,3-butadiene in 10 ml of toluene and a solution of 0.4 mmol of nickel naphthenate in 4 ml of toluene was added. This mixture is for 30 minutes at room temperature stirred and then made up with toluene to a total volume of 100 ml.

A 200 ml glass reactor tube suitable for pressure polymerization is mixed with a solution of 0.08 mmol of alcohol in 4 ml of toluene and 7.5 ml of hydrous toluene (water content: 0.045 percent by weight, determined according to the Karl Fischer method) and further charged with a solution of 0.04 mmol of tetrachlorohydroquinone in 8 ml of toluene. In addition, 10 ml of the catalyst solution described above are added. This mixture is ^{heated to 400 °} C. for 15 minutes and then cooled. Then 70 ml of anhydrous toluene are added. After further cooling to a temperature of - 10 ⁰ C 30 ml (22 g) of liquefied 1,3-butadiene are added. Then, the reactor tube is melted, and is polymerized for 3 hours at 40 ⁰ C. The reaction mixture is mixed with a solution of phenyl-j3-naphthylamine in toluene, and this mixture is poured into a large amount of methanol, which phenyl-j3-naphthylamine contains dissolved. The precipitating rubbery polymer is dried in vacuo at a temperature below 50 ⁰ C.

The resulting yield as well as the physical properties of the polybutadiene are shown below summarized in Table IV.

40

Tabel IV Molar ratio Polymerization product M. Micro structure, % 1.2 example alcohol to ninaphthenate Yield (dl / g) cis-1.4 trans-1,4 1.7 No. link 2.0 (%) 3.48 96.8 1.5 1.2 2.0 60.5. 3.69 97.3 1.5 1.6 5 Isopropyl alcohol 2.0 57.3 4.08 96.9 1.5 1.3 6th n-octyl alcohol 2.0 48.5 3.70 97.4 1.3 1.4 7th Allyl alcohol 2.0 53.5 3.41 97.2 1.4 1.4 8th Ethylene chlorohydrin - 62.1 2.93 97.3 1.3 9 Benzyl alcohol 63.5 10 No addition *)

*) During the production of the catalyst system, insoluble substances are formed.

Examples 11-19

A pressure-tight polymerization tube made of glass is charged with a solution of 0.4 mmol of diethylaiuminium monofluoride in 5 ml of toluene, and also a solution of 0.04 to 0.08 mmol of stearyl alcohol in 2 to 5 ml of toluene and a solution of 0.23 g 1,3-butadiene in 3 ml of toluene and a solution of 0.04 mmol of nickel naphthenate in 4 ml of toluene were added The mixture obtained in this way is heated to 25 ° C. for 15 minutes. Then 3 to 6 ml of moist toluene and a solution of 0.04 mmol of tetrachlorohydroquinone in 8 ml of toluene are added. This mixture is aged for 15 minutes at 40 ⁰ C, whereby one transparent, uniform catalyst solution obtained with anhydrous toluene filled up to a total volume of 100 ml and then cooled to -10 ⁰ C. Then add 22 g (30 ml)

Liquefied 1,3-butadiene is added and the polymerization tube melts. The polymerization is carried out ^{at 40 ° C. for 3 hours.} The further work-up takes place as in Example 5. The results obtained are summarized in Table V below.

Table V Molar relation of
Stearyl alcohol too
Ninaphthenate Molverhälinis of
Water to diethyl
aluniinium-mono-
riuorid Polymerization
yield sproduki
1"] Micro structure, % 1.2 No. (%) (dl / g) cis-1.4 trans-1,4 1.4 1.5 0.2 65.9 3.41 97.1 1.5 1.4 11th 2.0 0.2 64.8 3.52 97.3 1.3 1.4 12th 2.5 0.2 57.5 3.78 97.5 1.1 1.5 13th 1.0 0.3 73.2 3.43 97.2 1.3 1.5 14th 1.5 0.3 70.8 3.67 97.0 1.5 1.3 15th 2.0 0.3 70.1 3.82 97.3 1.4 1.4 16 1.0 0.4 68.5 3.62 97.2 1.4 1.3 17th 1.5 0.4 62.8 3.85 97.4 1.3 1.3 18th 2.0 0.4 55.1 4.13 97.3 1.4 19th

Examples 20-25

A catalyst solution is prepared according to the procedure of Example 5, but instead of alcohol phenol is used. Further polymerization of 1,3-butadiene using this catalyst solution is also carried out according to Example 5. The results obtained are summarized in Table VI below.

Tabel Vl Molar ratio Polymerisation product 1"] Micro structure, % 1.2 example phenol to ninaph- Yield 1.4 No. link ihenat (dl / g) cis-1.4 trans-1,4 1.4 2.0 <%) 3.53 97.1 1.5 1.5 2.0 53.5 2.92 97.3 1.3 1.4 20th phenol 2.0 63.2 2.23 97.2 1.3 : ^! 2i p-chlorophenol 2.0 63.8 2.82 97.4 1.2 1.5 22nd 2,4,5-trichlorophenol 70.1 1.3 23 2,6-di-tert-butyl 2.0 3.01 97.0 1.5 4-methylphenol - 61.0 3.08 97.3 1.4 24 / -Naphthol 60.2 25th No addition

Examples 26-29

A Kataiysatoriösung is prepared according to the procedure of Example 5, but one a carboxylic acid is used instead of the alcohol. the

Table VII

Polymerization of 1,3-butadiene using this catalyst solution is also carried out according to Working method of example 5.

The results obtained in this way are identical to iii Table VII summarized.

Example carboxylic acid
^r 'connection

Molar ratio
to ninaphthenate polymerization product
Yield In]

(%) (dl / g)

Micro structure,%

cis-1,4 trans-1,4

26 acetic acid 2.0

27 2-ethylcaproic acid 2.0

28 benzoic acid 3.0

29 No addition -

3.41
3.84
3.23
2.92

96.8
97.2
97.2
97.3

1.5 1.6 1.3 1.2

Claims (1)

Patent claims: 1. A process for the preparation of polybutadiene with predominantly cis - ', 4 structure by polymerizing 13-butadiene in a liquid reaction medium at temperatures of -30 ⁰ C to 150 ° C in the presence of a catalyst system which is produced by mixing