JPH0723417B2 - Method for producing completely random styrene-butadiene copolymer rubber - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel completely random styrene-butadiene copolymer rubber, that is, a styrene-butadiene copolymer rubber having a structure in which styrene is uniformly distributed in an isolated state or a short chain block state in the molecule. The present invention relates to a manufacturing method of.

[0002]

BACKGROUND OF THE INVENTION Styrene-butadiene copolymer rubber obtained by solution polymerization using a lithium-based catalyst has good impact resilience, abrasion resistance, and exothermic properties, and therefore it can be used alone or blended with synthetic rubber or natural rubber. It is widely used as a material for tire parts, automobile window frames, and other molded products, but due to the difference in the polymerization rate of styrene and butadiene under polymerization conditions, styrene is continuously bonded in the polymer molecular chain. In addition, there is a problem that so-called block styrene is produced, and the well-balanced physical properties of the copolymer are not sufficiently exhibited.

In order to solve such a problem, many attempts have been made to obtain a random styrene-butadiene copolymer rubber in which styrene is distributed in the molecular chain as much as possible. For example, in a polymerization reaction system. A method in which a polar organic compound or an organic salt or complex compound of a metal such as sodium or potassium is allowed to coexist, a method in which a monomer is added to a polymerization reaction system according to the progress of polymerization, and the polymer and an inert diluent are mixed. The method of advancing polymerization while separating it has been proposed so far.

However, according to these methods, although block styrene is reduced to some extent, it is still insufficient as a completely random copolymer, and in general, vinyl bonds of butadiene are increased, resulting in impact resilience and abrasion resistance. It is accompanied by the drawback that the physical properties such as properties deteriorate.

Relatively recently, it was possible to measure the chain distribution of styrene in a styrene-butadiene copolymer rubber by means of an NMR spectrum, and the concept of short-chain block styrene and long-chain block styrene was introduced by this analysis method. Proposals have been made regarding random styrene-butadiene copolymer rubbers and methods for producing the same (JP-A-49-67986 and JP-A-53-69288). However, although the analysis method by NMR can qualitatively measure the chain distribution of styrene to some extent, it may be analyzed by a curve resolver, which is not sufficient for quantitative analysis, and it is not possible to analyze isolated styrene. However, it is not possible to obtain a completely random styrene-butadiene copolymer rubber.

The molecular weight distribution Mw / Mn obtained by solution polymerization using a lithium-based catalyst is 3 to 8, the Mooney viscosity is 30 to 150, and the total bound styrene is 10 to 40% by weight.
A styrene-butadiene copolymer rubber having an expanded molecular weight distribution and a composition distribution of 10% by weight or less of block styrene is also known (JP-A-55-40712),
This product has a high proportion of long-chain block styrene in the total bound styrene and is far from the completely random styrene-butadiene copolymer rubber.

[0007]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of improving the drawbacks of conventional styrene-butadiene copolymer rubbers, particularly the deterioration of physical properties due to the presence of long-chain block styrene.

[0008]

Means for Solving the Problems As a result of intensive studies on the method for producing a styrene-butadiene copolymer rubber, the present inventors have used a catalyst system composed of an organolithium compound and a Lewis base as a catalyst and stirred vigorously. On the other hand, it was found that a novel completely random styrene-butadiene copolymer rubber having a large amount of isolated styrene and a small amount of long-chain block styrene can be obtained when solution polymerization of styrene and butadiene is carried out. The present invention has been completed.

That is, in the present invention, in the presence of an organolithium compound, a catalyst comprising at least one Lewis base selected from ether compounds, thioether compounds, tertiary amines and phosphine compounds, and an inert diluent, When copolymerizing styrene and butadiene, a raw material mixture containing a raw material monomer, a catalyst and an inert diluent,
A Mooney viscosity of 30 which is controlled at a temperature of 80 ° C. or higher and is continuously introduced into a polymerization zone which is vigorously stirred at a stirring efficiency of 5 × 10 ⁻² or more in the vicinity of the introduction port to carry out polymerization. To 150, total bound styrene 10 to 40% by weight, butadiene portion 1,2-vinyl bond 60% or less, ratio Mw of weight average molecular weight and number average molecular weight
/ Mn has a molecular weight distribution of 1.2 to 3.5, the isolated styrene analyzed by gel permeation chromatograph of the ozone decomposition product is 50% by weight or more of the total bound styrene, and the long-chain block styrene is the total bound styrene. 5% by weight
A method for producing a solution-polymerized completely random styrene-butadiene copolymer rubber characterized by the following:

In the completely random styrene-butadiene copolymer rubber of the present invention, an L rotor is used and 100
It is necessary that the Mooney viscosity measured under the condition of ° C is in the range of 30 to 150. When the Mooney viscosity is 30 or less, excellent physical properties based on complete randomization do not appear, and when it is 150 or more, the processability such as mixing property with various auxiliary materials or moldability until the final use is obtained. descend. The total bound styrene corresponding to the styrene content in the copolymer rubber is 10 to 40% by weight, preferably 15%.
It is necessary to be in the range of ˜30% by weight. This is 1
If it is less than 0% by weight, the effect due to complete randomization is not sufficiently exhibited, and if it exceeds 40% by weight, bound styrene is unnecessary as a copolymer rubber in terms of its physical properties, and this bound styrene is a completely random copolymer. It's also difficult to get it.

Further, in the completely random copolymer rubber of the present invention, in addition to styrene and butadiene, a small amount of other copolymerizable monomer components such as isoprene, dimethylbutadiene, pentadiene, methylstyrene and ethyl as a copolymer component. Styrene, divinylbenzene, diisopropenylbenzene and the like can be included.

The microstructure of the butadiene portion of the completely random styrene-butadiene copolymer rubber of the present invention must be 60% or less, preferably 40% or less, more preferably 20% or less with respect to 1,2-vinyl bonds. If the number of vinyl bonds is larger than this, impact resilience, abrasion resistance and the like are significantly reduced. Further, the molecular weight distribution Mw / Mn represented by the ratio of the weight average molecular weight and the number average molecular weight needs to be in the range of 1.2 to 3.5, preferably 1.5 to 3.0. If the molecular weight distribution is narrower than this range, the processability is remarkably inferior. On the other hand, if the molecular weight distribution is wider than this range, some properties of the copolymer rubber such as impact resilience and exothermicity are lost. The shape of this distribution may be monomodal or bimodal or more multimodal as long as the molecular weight distribution is within the above range. It is preferable to obtain a bimodal molecular weight distribution obtained by coupling a part of the polymerization end living with a polyfunctional coupling agent such as silicon tetrachloride, tin tetrachloride, carbon tetrachloride or chloroform after the polymerization. It is a copolymer rubber having.

The styrene bond state and styrene chain distribution of the completely random styrene-butadiene copolymer rubber of the present invention can be known by gel permeation chromatograph of a low temperature ozone decomposition product of the copolymer rubber. Conventionally, ¹ H-NMR method was used to analyze the chain distribution of styrene.
A method using ¹³ C-NMR or a method using GC analysis of a metathesis degradation product has been known, but both methods are useful for quantitatively measuring isolated styrene and for obtaining information on a relatively long styrene chain. It wasn't enough.
In the present invention, the method recently developed by Tanaka et al. Is used, and the chain distribution of styrene is analyzed by gel permeation chromatograph (GPC) obtained by decomposing all double bonds of butadiene unit by ozone cleavage. (Proceedings of the Society of Polymer Science, Vol. 29, No. 9, p. 2055). In the copolymer rubber of the present invention, the isolated styrene analyzed by this method is 50% by weight or more of the total bound styrene, and the long chain block styrene is 5% by weight or less of the total bound styrene, preferably 2.5% by weight. It must be: Whether the isolated styrene is less than 50% by weight or the long-chain block styrene is more than 5% by weight, the excellent properties of the completely random styrene-butadiene copolymer rubber of the present invention are excellent. It does not exhibit the features of high impact resilience and wear resistance.

The term "isolated styrene" as used herein means styrene which constitutes a chain composed of one styrene unit present in the polymer molecular chain, and the long-chain block styrene has eight or more styrene units linked together. It is styrene that constitutes the chain.

Examples of the organolithium compound used include methyllithium, ethyllithium, n- (sec-
Or tert) -butyllithium, acyllithium, phenyllithium, cyclohexyllithium and the like. Examples of Lewis bases include ether compounds, thioether compounds, tertiary amine compounds, and phosphine compounds. In the present invention, one or more of these are used for polymerization.

Examples of such compounds include dimethyl ether, diethyl ether, diphenyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane, triethylamine,
N, N, N ', N'-tetramethylethylenediamine,
Examples thereof include dialkylaryl sulfide and hexamethylenephosphoamide. The styrene chain distribution varies somewhat depending on the type and amount of the Lewis base used, and particularly preferred Lewis bases for obtaining the copolymer rubber of the present invention are ethylene glycol dialkyl ethers or tertiary diamines. The amount to be used depends on other factors such as polymerization temperature and stirring conditions, but when the Lewis base is ethylene glycol dialkyl ethers or tertiary diamines, it is 0.3 to 20 times mol relative to the organolithium compound, The molar amount is preferably 0.5 to 5.0 times.

The inert diluent used in the present invention is not particularly limited as long as it does not deactivate the catalyst used, but for example, butane, pentane, hexane,
Heptane, octane, cyclohexane, ethylcyclohexane, etc. are used. Particularly preferred is hexane,
It is cyclohexane. Further, in the styrene, butadiene, and inert diluent used, dienes having a molar ratio of 1 or less with respect to the organolithium compound, for example, propadiene, 1,
2-Butadiene, 1,2-pentadiene, 1,2-octadiene and the like may be included.

In the present invention, the temperature of the polymerization zone is 80.
It is necessary that the temperature is not lower than 0 ° C, preferably not lower than 90 ° C. Below this temperature, the long-chain block styrene, which is unfavorable in terms of physical properties, increases, the completely random styrene-butadiene copolymer rubber of the present invention cannot be obtained, and the productivity is also poor. Further, the polymerization zone, particularly the polymerization zone close to the inlet, needs to have high stirring efficiency. The efficiency of stirring is difficult to display because there are many problems that have not yet been solved academically, but the high stirring efficiency in the present invention is defined as follows. That is, it is represented by a value obtained by dividing the linear velocity of stirring (m / sec) near the inlet by the viscosity (poise) of the polymer solution in the polymerization zone,
This value is 5 × 10 ⁻² or more. Stirring below this amount increases long-chain block styrene, which is unfavorable in terms of physical properties.

A particularly preferred method for obtaining the completely random styrene-butadiene copolymer rubber of the present invention is to divide the polymerization zone into two or more sections and also to introduce the monomer into the polymerization zone, in which case In addition, if all the divided monomers to be introduced have the same composition, a very complete and uniform styrene-butadiene copolymer rubber can be obtained.

[0020]

The completely random styrene-butadiene copolymer rubber obtained according to the present invention exhibits extremely excellent tensile strength, impact resilience, abrasion resistance and exothermicity. It can be blended with natural rubber, and can be used for tire applications such as tire treads, carcasses, and sidewalls, or extruded products, automobile window frames, industrial products, etc. after various known blending and vulcanization. Further, it can be used for improving impact resistance by grafting or blending with various plastics.

[0021]

EXAMPLES The effects of the present invention will be described below with reference to examples, but these do not limit the present invention.

The isolated styrene (% by weight) and the long-chain block styrene (% by weight) in each example are measured by the following method.

1) 0.2 g of the rubber from which the stabilizer has been extracted is dissolved in 100 ml of methylene chloride and placed in an air-washing bottle.

2) Oxygen was introduced into a commercially available ozone generator, adjusted to 1.5% ozone / O ₂ , and the oxygen flow rate was 150.
At a rate of ml / min, it is introduced into an air-washing bottle cooled to -30 ° C to be ozonized.

3) The gas discharged from the air bubble bottle outlet is set to 1.5
% Potassium iodide aqueous solution in a second flush bottle.

4) When the initially colorless aqueous potassium iodide solution is slightly yellowed, the ozonation is terminated.

5) 1 g of lithium aluminum hydride and 50 ml of diethyl ether were placed in a flask equipped with a stirrer and a reflux condenser and placed in a nitrogen stream at -20 ° C.
Keep the ozonization liquid (Ozonized S
BR solution in methylene chloride) and add dropwise little by little.

6) After the completion of dropping, while stirring is continued, the temperature is slowly raised, and finally, it is heated to reflux for about 30 minutes in hot water of 40 to 50 ° C.

7) After heating under reflux, the mixture is cooled with cold water while continuing stirring, and about 10 ml of pure water is slowly added drop by drop with a dropping funnel to hydrolyze.

8) Add about 10 g of potassium carbonate, stir, and salt out.

9) The salted-out sample is further filtered, transferred to a flask and concentrated under reduced pressure and heating with a rotary evaporator to about 2 ml.

10) The obtained sample is analyzed by GPC for isolated styrene and long-chain block styrene. GPC conditions may be any method as long as isolated styrene and about 10 or more styrene chains can be sufficiently separated, but chloroform is used as a solvent, a flow rate of 1 ml / min, and a column of shodex KF-803 × 1, KF-8
02 x 1, KF-801 x 2 (8 mmφ each, 30c
m length) It is convenient to measure the styrene chain using a UV detector at room temperature.

11) The area ratio% of the isolated styrene peaks to the cumulative total area of all peaks is defined as the isolated styrene (wt%), and the cumulative area of peaks of styrene chains of 8 or more to the cumulative total area of all peaks is calculated as long chain block styrene ( % By weight).

Examples 1 to 3, Comparative Examples 1 to 3, Comparative Example 7 A reactor having an internal volume of 10 liters equipped with a stirrer was filled with about 5 liters of hexane heated to a predetermined temperature, and an inlet port was provided at the bottom of the reactor. More specified catalyst and styrene 0.45kg / h
r, butadiene 1.35 kg / hr and hexane 7.2
It was continuously introduced at an introduction rate of kg / hr, and after the reaction, the polymer solution discharged from the discharge port at the top of the reactor was
4-di-tert-butyl-p-cresol was added to 0.5 g per 100 g of the copolymer and mixed to obtain styrene-butadiene copolymer rubbers having various styrene chain distributions. Table 1 shows other polymerization conditions and analysis values of the obtained copolymer rubber. The stirring conditions in this reaction were controlled so that the stirring efficiency defined in the text was 5.0 × 10 ^-2 , except for Comparative Example 3 in which stirring was carried out at the other 1/10.

Examples 4 and 5 and Comparative Examples 4 and 8 The same reactor as in Example 1 was used, and other conditions were the same.
The introduction rates of styrene, butadiene and hexane are 0.33 kg / hr, 1.50 kg / hr and 7.2 k, respectively.
In addition to g / hr, the introduction port was introduced not only at the bottom portion but also at another introduction port located just in the middle between the bottom portion and the top portion. The amount introduced into the new inlet was 1/3 weight of the total amount. Table 1 shows other polymerization conditions and analysis values of the obtained copolymer rubber.

Comparative Example 5 Comparative Example 5 was carried out by the so-called batch polymerization without continuously introducing the catalyst, styrene, butadiene and hexane, using the same reactor as in Example 1 and under the same stirring conditions. . In this reaction, the polymerization temperature instantly increased and could not be kept constant and increased to 100 ° C. The obtained polymer solution was discharged from the bottom by nitrogen pressure from the top, and after discharging, Example 1
A copolymer rubber was obtained in the same manner as in. Table 1 shows other polymerization conditions and analytical values of the obtained copolymer rubber.

Comparative Example 6 Comparative Example 6 was carried out under the conditions shown in Table 1 using a tubular reactor having a similar internal volume as used in Example 1 and having a reactor diameter / reactor length of 1/16. . The analytical values of the obtained copolymer rubber are also shown in Table 1.

[0038]

[Table 1]

As is clear from Examples 1 to 5 and Comparative Examples 1 to 8 above, the copolymer rubber obtained by the production method of the present invention is a so-called completely random styrene-butadiene copolymer rubber, and in the conventional method. It is a copolymer rubber having a novel styrene chain distribution that cannot be obtained.

Reference Example Using the copolymer rubbers of Examples 1-5 and Comparative Examples 1-8, vulcanized rubbers were prepared according to the formulations shown in Table 2. Table 3 shows the physical properties of the vulcanized rubber thus obtained.

[0041]

[Table 2]

[0042]

[Table 3]

As is clear from this table, the copolymer rubber of the present invention has substantially the same Mooney viscosity, excellent bonding strength, and excellent tensile strength as compared with the copolymer rubber of Comparative Example having 1,2 bonds in the butadiene portion. It exhibits impact resilience, wear resistance, and heat generation.

Front Page Continuation (56) References Japanese Patent Publication No. 54-44315 (JP, B2) Japanese Patent Publication No. 49-38036 (JP, B1) Japanese Patent Publication No. 55-23568 (JP, B2)

Claims (1)

[Claims] 1. Styrene and butadiene in the presence of an organolithium compound, a catalyst comprising at least one Lewis base selected from ether compounds, thioether compounds, tertiary amines and phosphine compounds, and an inert diluent. In the copolymerization, the raw material mixture containing the raw material monomer, the catalyst and the inert diluent is controlled at a temperature of 80 ° C. or higher and the stirring efficiency in the vicinity of the inlet is 5 × 1.
0 ^-2 polymerization zone which is stirred vigorously at least continuously introduced, characterized in that to perform polymerization, Mooney viscosity 30 to 150, total bound styrene 10 to 40 wt%, 1,2 butadiene portion -Vinyl bond 60% or less, molecular weight distribution 1.2 to 3.5 represented by the ratio Mw / Mn of weight average molecular weight to number average molecular weight, total isolated styrene analyzed by gel permeation chromatography of ozone decomposition products A method for producing a solution-polymerized completely random styrene-butadiene copolymer rubber in which 50% by weight or more of bound styrene and 5% by weight or less of long-chain block styrene are all bound styrene.