DE1770212B2 - Isoprene polymer mixtures and process for their preparation - Google Patents

Description

GB-PS 9 43 939 discloses a process for the solution polymerization of isoprene using lithium hydrocarbons known as a catalyst. In this process, the catalyst is used up to the start added continuously to the polymerization, resulting in faster purification of the reaction mixture The accompanying substances contained and reacting with the catalyst result in a faster polymerization rate (shorter initiation time) is achieved. In this known method, individual shares of catalyst can also be added after the start of the polymerization. This is done around the part of the to replace active catalyst, which is deactivated during the polymerization by such impurities which react with the active catalyst too slowly to be able to during the continuous Addition of catalyst before the start of the polymerization ίο would have been removed, and thereby a uniform To obtain polymerization rate.

The isopy polymers produced by this process however, leave something to be desired with regard to their molecular weight distribution and their processability η left.

It is also already known the molecular weight of by Solution polymerization of isoprene in the presence of a lithium-based catalyst isoprene polymers produced controlled by adding an active chain terminator containing 2i) hydrogen atoms, when the isoprene conversion is between 20 and 80% by weight, in an amount that is at least sufficient to maintain the activity of the active lithium catalyst, which is present during the polymerization to> destroy and then add further catalyst in at least one of the added amount of the chain terminator equivalent amount.

Since this process of chain termination and re-initiation prevents growth of the polymer chains up to their maximum length, the growth also being greater with a smaller amount of catalyst, this polymerization process gives polymers with improved processability. Since, in addition, the presence of smaller amounts of the active catalyst generally leads to elastomers with a higher cis-1,4 content, polymers with a high cis-1,4 content and obtained any desired viscosity number. However, this procedure is time-consuming, and the viscosity number of the polymers should not be too low if vulcanizable compositions with a relatively high tensile strength are desired. Therefore, the 4 ^r i processability of Polymerisatgeinisches obtained by this process can be, despite some improvement still to be desired. The process described in FR 13 85 062, in which the isoprene polymer mixture contains a certain proportion of polymer with a much lower viscosity number, brings an improvement. This polymer mixture, which therefore has better processability, is obtained by solution polymerizing isoprene in two stages with different catalyst concentrations. In the first stage, in which the polymers with higher molecular weights are formed, a relatively low catalyst concentration is used until at least 75% of the monomer has reacted. In the second stage, the polymerisation is then continued at a much higher catalyst concentration, thereby forming the polymer content with a low molecular weight.

In this procedure, however, cJas has during the period of working with lower catalysts Concentration obtained polymers generally have such a high intrinsic viscosity that that in the following The lower molecular weight polymers obtained in the stage are difficult to achieve sufficient improvement in the

Processability of the polymer mixture obtained as the end product brings with it.

In the method described in FR 13 85 062, the first stage through the is therefore preferred already mentioned time-consuming technique of chain termination and re-initiation carried out so that the average viscosity number of the polymer mixture is kept below a certain limit. Use of this chain termination and re-initiation procedure during the first stage with a low catalyst concentration results in a polymer mixture which is generally excellent is processable, but which has a rather low tensile strength in the vulcanized state

The object of the invention was therefore to develop a method that would also work without repeated chain termination and renewed initiation leads to isoprene polymer mixtures which not only have a high cis-1,4-content and have good processability, but also result in products after vulcanization that have a fairly have high tensile strength.

The invention thus relates to the isoprene polymer mixtures and the process for their production as described in the claims.

The process according to the invention is usually allowed to run until the isoprene conversion is at least 70%, preferably at least 90%

The concentration of the active lithium compound is according to the invention by adding in portions Catalyst compound increases The increase in the concentration of the active catalyst can be immediate after the start of the polymerization or after a certain percentage of monomer conversion has been achieved has been to begin. The servings can be made gradually or intermittently and with different degrees Speed of addition can be added.

As a rule, the isoprene concentration of the solution to be polymerized is selected so that it between 15 and 22% by weight.

In order for the polymerization to proceed in a satisfactory manner, the reaction mixture should be sufficient be homogeneous, which is achieved, for example, by intensively working stirrers

Lithium hydrocarbon compounds that can be used as a catalyst include:
Ethyllithium, isopropyllithium,
n-butyllithium, sec-butyllithium,
tert-butyllithium, isobutyllithium,
Amyllithium and octyllithium.

Also suitable are aromatic or cycloaliphatic lithium compounds such as phenyllithium or cyclohexyllithium, furthermore compounds which contain two or more lithium atoms per molecule, such as
Dilithiomethane, 1,10-dilithiodecane,
1 J5 Dilithionaph Thalin,
1,2-diithio-1,3-diphenylpropane,
13,5-TViIithiopentane and
13,5-trilithiobenzene.

Preferred are branched alkyl lithium compounds having 4 to 8 carbon atoms, in particular secButyllithium and tert-butyllithium are used.

The solvents in which the polymerization is carried out include n-heptane, n-pentane, isopentanes, Amylenes, cyclohexane, and mixtures composed primarily of two or more of these hydrocarbons consist, in particular a hydrocarbon mixture, which mainly consists of amvlenen or amvlenen and pentanes

The inventive method of solution polymerization leads to within a short period of time a polymer mixture with a certain molecular weight distribution, the mixture not only having a relatively high content of cis-1,4-polymer and has good processability, but also vulcanizates with high tensile strength results in the new Isoprene polymer mixtures can be filled with fillers,

ίο stabilizers, plasticizers, vulcanizing agents and mixed with other polymers, vulcanized and processed into moldings.

The intrinsic viscosity (LV.) Of the products mentioned below was determined in toluene at 30 ° C., the cis-1,4 content by infrared absorption according to GJ van Amerongen in "Advances in Chemistry Series (American Chemical Society)" No. 52 , Pages 137-138 and the Hoekstra plasticity according to the method of EW Duck and JA Waterman in "Rubber and Plastics Age" Volume 42 (1961), pages 1079-83 by means of the in "Proceedings Rubber Technology Conference". London, 1938, page 362.
The isoprene polymer mixtures have a viscosity distribution according to the table below. The fractions indicated are obtained and determined by means of G «oil permeation chromatography. The sum of the percentages of all fractions a to g inclusive is 100. At least four fractions

in each make at least 5 wt .-%, based on the total mixture and the sum of the percentages of fractions b to f, inclusive, is at least 30th

J 5 fraction I. V., Jl / g Wt .-% of Total polymer mixed 4 (1 a 14-20 0-40 b 10-14 0-45 C. 8-10 0-50 d 6- 8 0-50 e 4- 6 0-50 45 r 2-4 0-45 G 0-2 0-40

The fraction with an intrinsic viscosity below 0.9 dl / g was determined as such as follows:

0.2 g of the polymer mixture composed of isoprene were dissolved in 50 ml of CHCl _3. 19.1 ml of isopropanol (purity at least 99% by volume, less than 0.1% by volume of water) were added to 15 ml of this solution. The mixture was warmed to a thermostatically controlled bath for 5 minutes at 60 ⁰ C and then cooled again with a thermostatically controlled bath at 25 ° C At this temperature, then the precipitated high molecular weight fraction was removed by centrifugation of the still dissolved low molecular weight fraction. Then 10 ml of the dissolved phase were evaporated, first by means of infrared radiation for 20 minutes and then in vacuo for 10 minutes at 100 ° C. The content of the low molecular weight fraction was obtained in the same way as the difference between the weight of the solvent-free residue and the weight of the solvent-free residue Comparative determination determined without isoprene polymer.

The viscosity distribution, expressed by the content of fractions a to g inclusive, was determined by means of gel penetration chromatography (GPQ according to "Polymer Fractionation" (Academic Press, New York and London, 1967, publisher HJR Cantow), Chapter B 4, pages 123-179 , determined by IC H. Altgelt and J. C Moore using a conventional GPC device, e.g. from Waters, Framinham, Mass, USA. Tetrahydrofuran was used as the solvent, stabilized with 0.2% by weight of an antioxidant such as Tris ( nonylphenyl) phosphite, wherein the temperature of 30 ⁰ C, the flow rate about 1 ml / min and the upper Dunchlässigkeitsgrenze the column ΙΟ ^5, 10 ^4, 10 * and \ (Pnm was. the calibration was conducted by means of linear Isoprenpolymerisate which had a narrow molecular weight distribution .

The polymer mixtures according to the invention can be with or without reinforcing or non-reinforcing black or white fillers, e.g. HAF carbon black or hydrated silica can be processed. By Shaping and vulcanization, objects and moldings can be produced, such as tapes, Plates, shoe soles and car tires or parts therefor.

example 1

Three approaches for the isoprene polymerization (experiments 1 to 3) were each 5 hours at a temperature of 40 ⁰ C (experiments 1 and 2) and 45 ° C (experiment 3) under nitrogen in a 2-1 reaction vessel, which for working pressures was designed up to about 3 bar overpressure. The reaction vessel was equipped with a cooling jacket, belt stirrer and lines with needle valves for introducing catalyst, nitrogen and special reagents. In a further three experiments (Nos. 4 to 6) the polymerization time of experiments 4 and 5 was carried out at 3> 3 ° C and atmospheric pressure was 4 hours, the reaction time in Experiment 6 was 6 hours. This time the 2-1 reaction vessel was equipped with a blade stirrer and a reflux condenser. Finally, an experiment on a larger scale was carried out at 45 ° C. for 5Ά hours in an autoclave with a capacity of 45 m ³ (experiment 7).

In all experiments the feed contained 20.4% by weight isoprene, 32.5% by weight isopentane, 213% by weight 2-methylbutene (2), 133 wt.% 2-methylbutene (1), 7.6 % By weight of n-pentene and 2.7% by weight of 3-methylbutene (1), Remainder small amounts of other hydrocarbons. The catalyst was in each case secButyUithium, dissolved in a Mixture of mainly amylenes and pentenes. the

The catalyst concentration of this solution was 100 mmol / 1. The initial concentration of active lithium compound in the reaction mixture and the program for increasing the catalyst concentration during the polymerization are given in Table I, along with the conversion and total catalyst concentration immediately before each addition of catalyst. Addition of catalyst and total catalyst concentration are in each case given as ppm bound Lt, calculated on the entire batch.

At the end of the reaction time, methanol was added to the reaction mixture to initiate the polymerization cancel and precipitate the polymer mixture. Then a small amount of 2,4,6-tri (3 ', 5'-di-iert.butyl-4'-hydroxybenzyl) benzene as an antioxidant

2ϊ added and the precipitate by steam distillation and drying isolated. The average cis-1,4 content according to the average plasticity Hoekstra, the average intrinsic viscosity, the Polymer content with an intrinsic viscosity below

* i 0.9 dl / g and the distribution of the intrinsic viscosities of the dried polymer mixture were determined as already described. The results are in Table II listed

In addition, the processability of the obtained

r> polymer mixtures determined by their behavior in an open roll mill with two rolls after Schwabenthan For this experiment, which was carried out at 70 ⁰ C, there was used a 30 g sample of polymer mixture and roll spacing 0.5 mm

4 (i and 28 rpm for the faster roller and 20 rpm worked with the slower roller The time until a smooth band was formed (band formation time) measured in seconds and registered the appearance of the tape The results are also in

• r> Table II listed.

Table I.

Ver Li-Kon Polymerization requirements time after Beginning of polvnicrisalions 300 315 360 search 7cntra- min mm min lion at Beginning 60 120 180 240 No. ppm well well now min

0.055 conversion before addition of catalyst,%

Li addition, ppm
Total Li concentration
before addition, ppm

0.055 conversion before addition of catalyst, "/"
Li additionc, ppm
Total Li concentration
before addition, ppm

5.0

12.0

23.3

0.055 ^x ) 0.1 D 0.1 P) 2.2 ^! )
0.055 0.11 0.22 0.33

5.0

9.4

19.6

69 ')

2.53 ') 67')

0.1 P) 0.1P) 2.2 ⁽ )
(1.055 0.055 0.165 0.275 2.475 ')

continuation

Li-Kon- l'polymerisalionsbedingungen point in time after the start of polymerization search center

tion at

Start 60 120 180 240

No. ppm min min min min

300 315 360

min min min

0.055 conversion before catalyst 7.8 17.0 32.0

admission,%

Li addition, ppm

Total Li concentration before addition, ppm

0.11 conversion before catalyst

addedc,%
Li addition, ppm total Li concentration before addition, ppm

0.11 conversion before catalyst

admission,%
Li addition, ppm

Total Li concentration before addition, ppm

0.11 conversion before catalyst

admission,%

Li addition, ppm total Li concentration before addition, ppm

0.055 pre-catalyst conversion 7.8 20.1 39.3

admission,%

Li addition, ppm 0.055 ^x ) 0.11 ") 0.11")

Total Li Concentration 0.055 0.11 0.22

before addition, ppm

") All of a sudden admitted.

^y ) Added continuously over the next 60 minutes.

"') Added continuously over the next (and last) 75 minutes.

^z ) Final value.

Table II

82 ')

0.055 ") 0.11 ") 0.1 Π 2.2 ") - - - 0.055 0.11 0.22 0.33 2.53 ") - - 5.2 12.8 23.3 38.5 62 ^z ) - 0.1 l ^y ) 0.1 l ^y ) 0.22 ^y ) 2.2 ^y ) - _ - 0.11 0.22 0.33 0.55 2.75 ^z ) - - 5.2 12.0 25.1 41.5 61 ^z ) - 0.1 l ^y ) 0.22 ") 0.44 ^y ) 0.22 ^y ) - - - 0.11 0.22 0.44 0.88 l, 10 ^z ) - - 5.2 12.0 23.3 38.5 55.0 75 ² ) 0.1F) 0.1 l ^y ) 0.22 ^y ) 0.55 ^y ) 0.99 ^v ) - - 0.11 0.22 0.33 0.55 1.10 2.09 ^y )

2.75 ^yy )
0.33

87 ^z )

3.08 ^z ) -

Ver cis-1,4- Hoekstra- I.V. Share Distribution of I.V. (dl / g) on fractions such content plastizidl / g with I.V.

No.% tat <0.9 dl / g a b c d e

Wt% 14-20 10-14 8-10 6-8 4-6

Amount of the fraction in% by weight

f
2-4 G
0-2 Behavior on the
Roller mill
Band appearance
formation of the ligaments
after s smooth, transparent
rent, free of holes 7.8 32.0 20th glatL some
Holes 9.5 36.6 30th smooth, transparent
rent, some
Holes 7.0 28.6 25th smooth, transparent
rent, few
Holes 10.5 22.7 25th quite
smooth with
Holes 26.7 45 smooth transparent
rent free of holes 21.7 8.2 15th elatt free of holes _ 29.2 50

91.8 67

91.7 68

91.5 69

91.6

91.7

64

66

6.9 7.2

7.1 6.1

8.3 6th!

5.3 6.2

5.9 0.9

26.5 - 15.5 18.2 30.9 - - 23.0

29.6 16.2 18.6

34.4 20.4

32.1

19.0

12.0

22.2

91.3 56

91.5 59

5.9 5.9 - 36.1 - 21.0 13.0 21.7

8.5 5.4 25.9 16.9 19.5 -

Vulcanization tests

The polymer mixtures of experiments nos. 1, 2, 3, 6 and 7 of example 1 were made without filler vulcanized at 138 "C according to the following recipe:

Weight Parts Polymer mixture 100 Stearic acid 3 sulfur 1.5

10 N-oxydiethylen-2-benzothiazolesulfenamide 0.4

Reaction product of ethylene chloride, formaldehyde and ammonia 0.3
Zinc oxide active 5

2,2-methylenebis (4-methyl-6-tert-butylphenol) 1

The tensile properties of the vulcanized product obtained were determined according to ASTM-D 412-62T (Form head D) determined on test plates of 2 mm thickness. The results are shown in Table III.

Table III

Vulcanizate mixture from Example 1

Experiment No. 1

Tensile strength, MPa
Elongation at break,%
Module 300%, MPa
Module 500%, MPa
Modulus 700%, MPa
Fracture deflection,%

29,518 29.910 30.106 28.733 910 921 910 922 1.373 1.373 1.176 1.274 2.648 2.746 2,452 2.746 16.769 16,966 17.064 16.083 16 16 18th 13th

26.478 1000

2,452 4,413

30th

Comparative tests A to C

A) In the first experiment, the procedure for terminating the chain and restarting the polymerization was carried out with an initial catalyst concentration of 0.11 ppm bound lithium, based on the total batch. The polymerization was interrupted and restarted five times , 11 ppm bound lithium, based on the total batch, carried out. The final conversion was 85%. Otherwise, the conditions were fully comparable with those of Experiment 7.
It took at least 8 hours to obtain a polymer mixture with an average intrinsic viscosity of about 8 dl / g, and this mixture, after vulcanization according to the above vulcanization tests, gave a product with approximately the same tensile strength properties as the vulcanizate according to test 7. But the tape formation time of the crude polymer mixture was 120 seconds instead of 50 seconds, and the tape, although smooth, showed holes.

B) The second comparative experiment was carried out under the same conditions as in the first comparative experiment worked until a conversion of 80% was reached. At this point the concentration of the active secButyllithiums bound to 33 ppm Lithium, based on the total batch, increased and the polymerization up to a conversion of 98% continued. It was again a polymer mixture with an average Obtained intrinsic viscosity of about 8 dl / g. This mixture turned out to be very easy to process, but the tensile strength of the vulcanizate was only 21.575MPa.

C) The third comparative experiment was carried out as in comparative experiment B, but without Chain termination and renewed start of polymerization The polymer obtained was almost impossible to process and had an average intrinsic viscosity in excess of 20 dl / g. After a band formation time of Only a bad and uneven belt with many holes was obtained for 600 seconds.

Claims (2)

Patent claims: 1. Isoprene polymer mixtures with an average content of at least 90% of the Monomer units in a cis-1,4 structure, an average plasticity according to Hoekstra from 40 to 85, an average intrinsic viscosity of 4 to 10 dl / g and a maximum content of 10% by weight of polymers with an intrinsic viscosity below 03 dl / g, produced by polymerizing isoprene in a hydrocarbon solvent 30 to 45 ° C, up to a monomer conversion of more than 50%, by adding a portion at a time Lithium hydrocarbon compound, the isoprene content at the beginning of the polymerization between 10 and 25 wt .-% of the total batch and the lithium compound at the beginning of Polymerization is used in an amount corresponding to an active lithium compound concentration between 0.04 and 0.2 parts by weight of bound lithium per million parts by weight of the total batch corresponds, the concentration of active lithium compound then to at least 0.1 and at most 0.45 parts by weight of bound lithium is increased as long as the monomer conversion falls below 25% is further increased to at least 0.2 and at most 0.7 parts by weight of bound lithium, so long the monomer conversion is between 25 and 50% and at least 0.25 and at most 6.0 Parts by weight of bound lithium is increased when the monomer conversion is 50% or higher. 2. Process for the preparation of isoprene polymer mixtures by polymerizing isoprene in a hydrocarbon solvent, at 30 to 45 ° C, to a monomer conversion of more than 50%, by adding a lithium hydrocarbon compound in portions, the isoprene content at the beginning of the polymerization is between JO and 25 wt .-% of the total batch, thereby characterized in that the lithium compound is used in an amount at the start of the polymerization used, which has a concentration of active lithium compound between 0.04 and 0.2 parts by weight bound lithium per million parts by weight of the total batch and the concentration of active lithium compound then to at least 0.1 and at most 0.45 parts by weight Bound lithium increased as long as the monomer conversion is below 25% and further to at least 0.2 and at most 0.7 parts by weight of bound lithium increased as long as the monomer conversion is between 25 and 50% and bound to at least 0.25 and at most 6.0 parts by weight of lithium increased when the monomer conversion is 50% or higher.