JP2001270913A - Effective hydrogenation method of conjugated diene polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogenation method of a conjugated diene polymer capable of obtaining a high rate of the hydrogenation with less amount of a catalyst for a short time. SOLUTION: The improved hydrogenation method of the conjugated diene polymer polymerized using an organic alkali metal compound as a polymerization initiator is provided, in which a metalocene hydrogenation catalyst is divided and added at least two times and addition time of an additional catalyst is determined from a hydrogen absorption rate for obtaining the hydrogenated polymer with hydrogenation ratio being >=98%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conjugated diene-based polymer obtained by polymerizing an organic alkali metal compound as a polymerization initiator, by contacting the conjugated diene-based polymer with hydrogen using a metallocene-based hydrogenation catalyst to form a double bond of the conjugated diene. In the hydrogenation method, the present invention relates to a hydrogenation method in which the amount of a catalyst is reduced and the hydrogenation reaction is completed in a short time. More specifically, when a hydrogenation catalyst is added in several orders to obtain a conjugated diene polymer having a hydrogenation rate of 98% or more, the optimal addition time of the hydrogenation catalyst to be added is adjusted to the hydrogen absorption rate. And a method for stably and economically hydrogenating in a short time.

[0002]

2. Description of the Related Art When a metallocene catalyst is used for hydrogenation (hereinafter abbreviated as hydrogenation) of a polymer, a smaller amount of hydrogenation under the milder conditions is used as compared with a nickel catalyst. It has the characteristic that it can be achieved.Therefore, after hydrogenation, no special treatment for removing the catalyst residue is required, and even if it is performed, the treatment for removing the catalyst residue can be lightened. It has come to be. However, metallocene-based catalysts are problematic in that they are expensive and easily lose their activity, and various hydrogenation catalysts having higher activity, easier handling, and better long-term storage stability have been studied and proposed. Was. For example, a method of hydrogenating an olefin compound by combining a specific titanocene compound and an alkyl lithium (JP-A-63-1313)
No. 2, JP-A-1-53851), a method of hydrogenating an olefinically unsaturated (co) polymer by combining a metallocene compound with an organic aluminum, zinc, or magnesium (JP-A-61-28507, 62-209103) ), A method of hydrogenating an olefinically unsaturated group-containing living polymer with a combination of a specific titanocene compound and an alkyl lithium (JP-A-61-47706, JP-A-63-540)
No. 2), a method of hydrogenating an olefinic double bond in an olefinically unsaturated double bond-containing polymer with a Tebebe reagent which is a metallacycle compound of a titanocene compound and trimethylaluminum (JP-A-11-71426).
), A method of combining a titanocene compound with a specified amount of lithium alkoxide and hydrogenating the olefinic double bond in the olefinically unsaturated double bond-containing polymer (JP-A-1-275605). ing

[0003]

However, in any of these methods, various problems occur when an attempt is made to obtain a conjugated diene polymer having a high degree of hydrogenation of 98% or more on an industrial scale. The hydrogenation reaction is a violently exothermic reaction.If the temperature rises in the course of the reaction and the hydrogenation catalyst is deactivated, troubles may occur.If the amount of catalyst used is reduced to pursue economic efficiency, the hydrogenation time will increase. However, troubles such as the inability to obtain the desired polymer having a high hydrogenation ratio occurred. For this reason, there has been a demand for an improved hydrogenation method for stably achieving a high hydrogenation rate industrially in a short time with a minimum amount of catalyst used.

[0004]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems of the prior art. As a result, when hydrogenation is performed on an industrial scale, the hydrogenation catalyst is divided into several orders. It is important to add the hydrogenation catalyst, and it has been found that the optimal addition time of the hydrogenation catalyst to be added can be determined by measuring the hydrogen absorption rate. The present invention has been accomplished.

According to the present invention, a conjugated diene-based polymer obtained by polymerizing an organic alkali metal compound as a polymerization initiator is added in two or more portions to a metallocene-based hydrogenation catalyst to obtain a conjugated diene-based polymer having a high hydrogenation rate. The method for hydrogenating a conjugated diene-based polymer is characterized in that the time of addition of the hydrogenation catalyst is determined by measuring the rate of absorption of hydrogen.

The organic alkali metal compound used as a polymerization initiator in the present invention is generally an aliphatic hydrocarbon alkali metal compound or an aromatic hydrocarbon alkali compound which is known to have anionic polymerization activity for a conjugated diene compound. Metal compounds, including organic amino alkali metal compounds,
Examples of the alkali metal include lithium, sodium, and potassium. Preferred organic alkali metal compounds are aliphatic and aromatic hydrocarbon lithium compounds having 1 to 20 carbon atoms, compounds containing one lithium in one molecule, and dilithium compounds containing a plurality of lithium in one molecule. , Trilithium compounds and tetralithium compounds. Specifically, n-propyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, n-pentyl lithium, n-hexyl lithium, benzyl lithium, phenyl lithium, tolyl lithium, diisopropenyl benzene and sec- Reaction product of butyllithium, divinylbenzene and sec-
Reaction products of butyllithium and a small amount of 1,3-butadiene are exemplified.

The conjugated diene-based polymer of the present invention comprises a conjugated diene homopolymer, a conjugated diene copolymer composed of two or more conjugated dienes, and a conjugated diene copolymerizable with another monomer. Copolymers containing 1,4-polymers, 1,2 or 3,4-polymers having an olefin double bond derived from a conjugated diene in the polymer. As the conjugated diene, a conjugated diene having 4 to 20 carbon atoms, specifically 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3
-Pentadiene, 2-methyl-1,3-pentadiene,
Examples thereof include 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, and 3-butyl-1,3-octadiene. 1,3-butadiene and isoprene are preferable from the viewpoint of obtaining an elastic body which can be industrially advantageously developed and has excellent physical properties. Another typical monomer copolymerizable with the conjugated diene is a vinyl aromatic compound. For example, styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene,
N, N-dimethyl-p-aminoethylstyrene, N, N
-Diethyl-p-aminoethylstyrene and the like,
Preferred are styrene and α-methylstyrene. These copolymers are random or block copolymers.

The hydrogenation is usually carried out in an inert hydrocarbon solvent. The inert hydrocarbon solvent is a conjugated diene polymer solvent which does not adversely affect the reaction during hydrogenation. is there. It is further preferred in the present invention that the polymerization be followed by hydrogenation in the same inert hydrocarbon solvent. Suitable solvents are for example n-butane, isobutane, n-pentane, n-hexane, n-heptane, n-butane
Aliphatic hydrocarbons such as octane, cyclohexane,
Cycloheptane, alicyclic hydrocarbons such as methylcycloheptane, and aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene are also used when the aromatic double bond is not hydrogenated under the selected hydrogenation conditions. Can only be used. The concentration of the conjugated diene polymer dissolved in this solvent is 5 to 40%, preferably 10 to 30%. If the concentration is lower than 5%, the load of the subsequent step of separating the conjugated diene polymer and the solvent is undesirably increased, and if the concentration is higher than 40%, the viscosity becomes extremely high, and hydrogen, hydrogenation catalyst, etc. This is not preferable because the mixing property and the heat transfer property of the compound decrease, which eventually affects the hydrogenation reaction.

The metallocene hydrogenation catalyst used in the present invention is an organometallic compound such as titanium, zirconium, hafnium or the like having two (substituted) cyclopentadienyl groups which are the same or different as ligands. It is used with reducing organic metal compounds such as alkyllithium, alkylsodium, alkylpotassium, alkylmagnesium, alkylaluminum, and alkylzinc.

As the hydrogenation method, any known method can be employed as long as it is a hydrogenation method using a metallocene compound. Preferably, a hydrogenation method in which the hydrogenation catalyst is a titanocene-based catalyst. For example, a method of hydrogenating an olefin compound by combining a specific titanocene compound and an alkyl lithium (Japanese Patent Application Laid-Open No.
No. 53851), a method of hydrogenating an olefinically unsaturated (co) polymer in combination with a metallocene compound and an organoaluminum, zinc or magnesium (JP-A-61-285).
No. 07, 62-209103), a method of hydrogenating an olefinically unsaturated group-containing living polymer with a combination of a specific titanocene compound and an alkyl lithium (Japanese Patent Application Laid-Open No.
A method of hydrogenating an olefinic double bond in an olefinically unsaturated double bond-containing polymer with a Tebbe reagent which is a metallacycle compound of a titanocene compound and trimethylaluminum (JP-A-47706 / 1988). JP-A-11-71426, a method of combining a titanocene compound with a specified amount of lithium alkoxide and hydrogenating the olefinic double bond in the olefinically unsaturated double bond-containing polymer (JP-A-1-27575)
605) or any other method. As for the hydrogenation conditions, the methods described in the respective specifications can be used in accordance with such a hydrogenation catalyst.

The hydrogenation reaction is a typical exothermic reaction. When a large amount of a hydrogenation catalyst is first added, the reaction proceeds violently and the reaction temperature rises. When the reaction temperature becomes high, side reactions such as decomposition and dimerization of the hydrogenation catalyst become remarkable, and the hydrogenation reaction rate decreases. Further, in extreme cases, the reaction is stopped halfway, and a polymer having a high degree of hydrogenation cannot be obtained. Particularly in an industrial large reactor, heat removal is difficult, and this tendency is remarkable.

In order to solve this problem, a hydrogenation catalyst is used.
Rather than adding the whole amount at once, it is to be added in small portions in multiple stages, and is added in two or more times, including the initial one, preferably in 2 to 10 times, more preferably in 2 to 5 times. To be added. By dividing the hydrogenation catalyst into small portions and adding it in multiple stages, a rapid exothermic reaction is suppressed,
The hydrogenation reaction is stabilized, the amount of the hydrogenation catalyst used can be reduced, and the time required for the hydrogenation reaction can be shortened, so that efficient hydrogenation is possible.

The amount of the hydrogenation catalyst to be added first does not need to be the usual amount required to complete the hydrogenation reaction by one addition of the catalyst, but is preferably smaller than that amount. Preferably, the hydrogenation rate is 50% or more and less than 90%. If the specific amount of addition is shown, 70
%, More preferably 50% or less. In the case of such a small amount of the catalyst, the hydrogenation reaction is stopped halfway, but the reaction is continued with the additional catalyst, and as a result, the hydrogenation reaction is performed in a short time with a small amount of the hydrogenation catalyst. Can be completed.

The time for adding the hydrogenation catalyst is determined from the hydrogen absorption rate. The rate of absorption of hydrogen is determined, for example, by measuring the amount of hydrogen added to the reactor.If the pressure and temperature of the reactor fluctuate, the pressure and temperature are corrected to determine the amount of hydrogen remaining in the reactor. It is calculated and calculated from the amount of hydrogen added to the reactor. Further, although it is somewhat difficult to control the hydrogenation reaction, it is also possible to prepare a required amount of hydrogen in the reactor in advance and measure the decrease in the pressure of the reactor.

When the hydrogenation reaction starts, hydrogen is rapidly absorbed, and usually shows a stable hydrogen absorption rate in a short time of about several minutes. This stable hydrogen absorption rate is the hydrogen absorption rate at the start of the reaction referred to in the present invention.

The addition time of the desirable catalyst of the present invention is determined from the hydrogen absorption rate, and a specific example is that the point in time when the hydrogen absorption rate at the start of the reaction decreases to 80% or less. Desirably, more desirably, at the time when it is reduced to 60% or less. At this point, if an additional catalyst is added, the amount of the catalyst to be added can be suppressed to a small value, and efficient hydrogenation in which the time required for hydrogenation is short can be achieved. If the hydrogenation rate exceeds a predetermined value, it is not necessary to add a hydrogenation catalyst even if the hydrogen absorption rate is low, but in order to obtain a high hydrogenation rate, a smaller amount of the hydrogenation catalyst is required. It may be added.

In the method of hydrogenating a conjugated diene polymer using the metallocene catalyst of the present invention, the rate of the hydrogenation reaction does not depend on the progress of the hydrogenation reaction and changes at a substantially constant rate. Rather, they tend to accelerate. Therefore, by observing the hydrogen absorption rate, the degree of deterioration of the hydrogenation catalyst can be estimated,
The necessity and time of addition of a catalyst can be accurately determined.

In the present invention, the addition timing of the hydrogenation catalyst is determined from the hydrogen absorption rate. Usually, the addition timing is reproducible under the same conditions. In such a case, the addition timing of the hydrogenation catalyst is measured once or several times by this method, and if an accurate addition time is confirmed, the addition timing is determined by another control index such as time, water, or the like. The substitution may be performed depending on the addition rate or the reaction temperature.

The amount of the hydrogenation catalyst to be added in the present invention may be appropriately selected depending on the remaining amount of double bonds. If the amount of the residual double bond is large at the time of adding the catalyst, it may be added in a large amount, and if it is small, it may be added in a small amount. Specifically, it is equal to or less than the amount of the catalyst added first, preferably 70%
The following is good. If a large amount of catalyst is added at one time, rapid heat generation is caused, and the catalyst deactivation reaction becomes remarkable, which is not desirable. By adding in small portions, a stable hydrogenation reaction with reduced heat generation can be achieved.

The number of times of addition of the hydrogenation catalyst of the present invention is not particularly limited, and it is desirable to add the hydrogenation catalyst in small increments. Specifically, the number of additions is from 2 to 20 including the initial one.
Times, more specifically in the range of 2 to 5 times.
The finer the division, the less heat is generated, and a stable hydrogenation reaction can be achieved. However, the finer the division, the more complicated the operation, which is not desirable. It is also a desirable method to continuously add a small amount of an additional catalyst.

The hydrogenation catalyst may be activated after the first addition is mixed with the conjugated diene polymer.
It is preferable to add at least the catalyst to be added after the hydrogenation activity is developed or immediately activated in a hydrogen atmosphere. Regarding the hydrogenation catalyst to be added, the catalyst to be added initially and the catalyst to be added later do not have to be the same, but the same catalyst is more preferable in terms of simplicity of operation.

The present invention provides a high degree of hydrogenation of 96% or more, preferably 98% or more, more preferably 99% of hydrogenation.
This is how to achieve the above. If the degree of hydrogenation is low, the resulting hydrogenated conjugated diene-based polymer will have poor weather resistance and heat stability.

The method of the present invention may be applied to a batch type hydrogenation reaction or may be applied to a continuous type hydrogenation reaction. The method is preferably a batch method. If it is used for a continuous hydrogenation reaction, one or more reactors may be provided with a plurality of locations for adding the hydrogenation catalyst, or a tube-type reactor or a combination thereof may be used. May be implemented. In the case of the continuous type, the hydrogenation rate of the first-stage reactor may be monitored, and the amount of the hydrogenation catalyst added to the second-stage and subsequent reactors may be increased or decreased. The hydrogenation ratio in the present invention means the hydrogenation ratio of the conjugated diene unit contained in the polymer.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. The following production examples show synthesis examples of each living polymer (A polymer and B polymer), hydrogenation catalyst (TPM / Li), and (Tebbe reagent) used in Examples and Comparative Examples.

Production Example 1 Cyclohexane 4.3 was placed in a 16 m ³ reactor equipped with a stirrer.
Ton, 0.20 ton of styrene monomer, n-
4.8 kg of a butyllithium solution and 0.62 kg of tetramethylethylenediamine were added, and the initial temperature was set to 70 ° C., and polymerization was carried out for 40 minutes with stirring. Next, a cyclohexane solution containing 0.924 tons of 1,3 butadiene monomer was added, and polymerization was performed for 1 hour. Further, a cyclohexane solution containing 0.20 ton of styrene monomer was added and added.
Polymerized for minutes. The obtained living polymer (A polymer) has a bound styrene content of 30%, a block styrene content of 30%, a 1,2-vinyl bond content of butadiene unit of 37%, and a number average molecular weight of about 230,000. It was a styrene-butadiene-styrene type block polymer.

Production Example 2 Cyclohexane 3.8 was placed in a 16 m ³ reactor equipped with a stirrer.
After putting 8 tons and 0.264 tons of styrene monomer,
17 kg of n-butyllithium solution was added, and 2.1 kg of tetramethylethylenediamine was further added.
It was set at 0 ° C. and polymerized for 30 minutes with stirring. Then, 1,3
A cyclohexane solution containing 1.242 tons of butadiene monomer was added and polymerized for 45 minutes. Further, a cyclohexane solution containing 0.264 tons of styrene monomer was added, and 3
Polymerized for 0 minutes. The obtained living polymer (B polymer) has a bound styrene content of 30%, a block styrene content of 30%, and a 1,2-vinyl bond content of butadiene unit of 51%, and a number average molecular weight of about 61,000. It was a styrene-butadiene-styrene type block polymer.

Production Example 3 (Tebbe reagent) A hydrogenation catalyst was prepared by a method based on the method of JP-A-11-71426. 5 kg of bis (cyclopentadienyl) titanium dichloride (TC) was added to 70.1 kg of cyclohexane, and after stirring, 24.9 kg of a 10% trimethylaluminum (TMAL) solution was added and reacted for 72 hours to obtain a hydrogenation catalyst (Tebbe reagent). ) Prepared as solution.

Production Example 4 (TPM / Li) A hydrogenation catalyst prepared by a method according to the method of JP-A-8-33846 was added. That is, 6 kg of bis (cyclopentadienyl) titanium di-p-tolyl (TPM)
Was dissolved in 526 kg of cyclohexane, 60 kg of liquid 1,2 polybutadiene was added, 7.1 kg of a 15% butyllithium solution was added, and ethanol 0.6 k was further added.
g was added and reacted to prepare a hydrogenation catalyst (TPM / Li).

[0029] As Example 1 pretreatment, the living polymer obtained in Production Example 1 (A polymer), ethyl alcohol was added 0.9 eq mole fraction of n- butyl lithium, followed of the polymer solution 20 m ³ The whole amount was transferred to a reactor equipped with a stirrer. Further, after adding purified and dried cyclohexane to the reactor with the stirrer to adjust the cyclohexane solution to a polymer concentration of 12%, the inside of the reactor was set to an initial temperature of 80 ° C. under stirring, and hydrogen gas was supplied to the inside of the reactor. And further pressurized with 0.7 MPa of hydrogen gas. Production Example 4 was added to this polymer solution.
The catalyst (TPM / Li) obtained in (1) was added to the reaction vessel so as to be 20 ppm based on the weight of the polymer based on the weight of Ti, and hydrogenation was started. Two minutes after the start of the hydrogenation reaction, the hydrogen absorption rate was stabilized, and reached 7.2 Nm ³ / min. When the rate of hydrogen absorption dropped to 70% of the starting rate, an additional 20 ppm of catalyst was added. At this time, the hydrogenation rate of the polymer was 85.4% based on the hydrogen gas consumption. Further, the hydrogenation reaction was continued, and the hydrogenation rate of the polymer became 100% in view of the consumption of hydrogen gas. Since the absorption of hydrogen into the polymer solution was stopped, the hydrogenation was terminated, and the hydrogenation rate of the polymer was measured by NMR. Was 99.7%. The maximum temperature during hydrogenation was 92 ° C., and the time required for the reaction was 42 minutes.

[0030] As Example 2 pretreatment, the living polymer obtained in Production Example 1 (A polymer), ethyl alcohol was added 0.9 eq mole fraction of n- butyl lithium, followed of the polymer solution 20 m ³ The whole amount was transferred to a reactor equipped with a stirrer. Further, after adding purified and dried cyclohexane to the reactor with the stirrer to adjust the cyclohexane solution to a polymer concentration of 12%, the inside of the reactor is set to an initial temperature of 80 ° C. with stirring, and the inside of the reactor is hydrogenated. The gas was replaced, and the pressure was further increased to 0.7 MPa with hydrogen gas. Production Example 4 was added to this polymer solution.
Was added into the reaction vessel so as to be 15 ppm based on the weight of the polymer based on the weight of Ti, and hydrogenation was started. Two minutes after the start of the hydrogenation reaction, the hydrogen absorption rate became stable and reached 5.8 Nm ³ / min. When the rate of hydrogen absorption dropped to 70% of the starting rate, an additional 10 ppm of catalyst was added. At this time, the hydrogenation rate of the polymer was 80.1% based on the hydrogen consumption. Again the hydrogen absorption rate dropped to 70% of the starting value, so an additional 5 ppm of catalyst was added. At this time, the hydrogenation rate of the polymer was 94.5% as viewed from the hydrogen consumption. Further, the hydrogenation reaction was continued, and the hydrogenation rate of the polymer became 100% in view of the consumption of hydrogen gas. Since the absorption of hydrogen into the polymer solution was stopped, the hydrogenation was terminated, and the hydrogenation rate of the polymer was measured by NMR. Was 99.9%. The maximum temperature during hydrogenation was 90 ° C., and the time required for the reaction was 39 minutes.

Example 3 As a pretreatment, trimethylchlorosilane was added to the living polymer (B polymer) obtained in Production Example 2 in an amount of 0.9 equivalent mol of n-butyllithium, and then the polymer solution was added to 20 m ^3. Was transferred to a reactor equipped with a stirrer.
Further, after adding purified and dried cyclohexane to the reactor with a stirrer to adjust the cyclohexane solution to a polymer concentration of 17%, the inside of the reactor is set to an initial temperature of 80 ° C. with stirring, and then the inside of the reactor is hydrogenated. Replace with gas, then 0.7M
The pressure was set to Pa hydrogen gas pressure. A hydrogenation catalyst (Tebebe) prepared in the same manner as in Production Example 3 was added to this polymer solution.
12 ppm based on the weight of the polymer based on the weight of Ti
It was added into the reaction vessel and hydrogenation was started. Start of hydrogenation reaction 2
After one minute, the absorption rate of hydrogen became stable, reaching 6.3 Nm ³ / minute. When the hydrogen absorption rate has dropped to 50% of the starting rate, 5 pp of additional catalyst (TTebbe reagent) was added.
m was added. At this time, the hydrogenation rate of the polymer was 82.0% based on the consumption of hydrogen gas. When the rate of hydrogen absorption again dropped to 50% of the starting value, 5 ppm of additional catalyst (TC / TMAL) was added. At this time, the hydrogenation rate of the polymer was 91.1%, based on the amount of hydrogen absorbed. Furthermore, the hydrogen absorption rate is 50% of the starting rate.
% Of additional catalyst (TC / TMAL)
ppm was added. At this time, the hydrogenation rate of the polymer was 97.5% based on the amount of hydrogen absorbed. Further, the hydrogenation reaction was continued, and the hydrogenation rate of the polymer became 100% from the viewpoint of the consumption of hydrogen gas. Since the absorption of hydrogen into the polymer solution was stopped, the hydrogenation was terminated. Was 100%. The maximum temperature during hydrogenation was 90 ° C., and the time required for the reaction was 38 minutes.

Comparative Example 1 A living polymer (A) obtained in the same manner as in Production Example 1
After the polymer) solution was pretreated in the same manner as in Example 1, the whole amount was transferred to a 20 m ³ reactor equipped with a stirrer to obtain a 12% polymer solution. The initial temperature of the reactor is 80 with stirring.
° C, the inside of the reactor was replaced with hydrogen gas, and 0.7
The pressure was set at a hydrogen gas pressure of MPa. In this polymer solution,
The catalyst (TPM / Li) obtained in Production Example 4 was added so as to be 40 ppm based on the weight of the polymer based on the weight of Ti, and hydrogenation was started. 52 minutes after the start of hydrogenation, the hydrogenation rate of the polymer was 91.3% from the viewpoint of the consumption of hydrogen gas. However, the hydrogenation was stopped because the absorption of hydrogen into the polymer solution was almost stopped. The degree of hydrogenation of the final polymer determined by NMR was 91.2%. The maximum temperature reached during hydrogenation was 95 ° C. As is clear from Example 1 and Comparative Example 1, when the same amount of hydrogenation catalyst is used, the target hydrogenation rate cannot be obtained by the method of Comparative Example in which all the catalysts are added first. .

Comparative Example 2 A living polymer (A) obtained in the same manner as in Production Example 1
After the polymer) solution was pretreated in the same manner as in Example 1, the whole amount was transferred to a 20 m ³ reactor equipped with a stirrer to obtain a 12% polymer solution. The initial temperature of the reactor is 80 with stirring.
° C, the inside of the reactor was replaced with hydrogen gas, and 0.7
The pressure was set at a hydrogen gas pressure of MPa. In this polymer solution,
The catalyst (TPM / Li) obtained in Production Example 4 was added in an amount of 20 ppm based on the weight of the polymer based on the weight of Ti, and hydrogenation was started. Fifteen minutes after the start of hydrogenation, an additional 20 ppm of the catalyst was added. The hydrogenation rate of the polymer was 43.3% from the viewpoint of hydrogen gas consumption. 51 minutes after the start of hydrogenation, the hydrogenation rate of the polymer was 9 based on the hydrogen gas consumption.
Although it was 3.5%, hydrogenation was stopped because absorption of hydrogen into the polymer solution was almost stopped. The hydrogenation rate of the final polymer determined by NMR was 93.4%. The highest temperature reached during hydrogenation was 94 ° C.

As is clear from Example 1 and Comparative Example 2, even when the hydrogenation catalyst is added in two portions, a product having a target hydrogenation rate is obtained if the timing of catalyst addition is inappropriate. I can't do that. By using the method of the present invention to determine the timing of addition while measuring the amount of hydrogen absorbed, the catalyst activity can be accurately determined, the target high hydrogenation rate polymer,
It can be seen that it can be obtained with a low amount of hydrogenation catalyst and in a short time.

[0035]

[Table 1]

[0036]

According to the present invention, when a metallocene-based hydrogenation catalyst is used to obtain a conjugated diene-based polymer having a degree of hydrogenation of 98% or more, the hydrogenation catalyst is added in several steps and added. By determining the time of addition of hydrogen using the rate of absorption of hydrogen, it is possible to provide an industrially extremely advantageous method capable of stably and reliably hydrogenating with a small amount of hydrogenation catalyst in a short time.

Claims (7)

[Claims] When a hydrogenated conjugated diene polymer is obtained by adding a metallocene-based hydrogenation catalyst in two or more portions to a conjugated diene-based polymer obtained by polymerizing an organic alkali metal compound as a polymerization initiator, hydrogen is added. An improved method for hydrogenating a conjugated diene-based polymer, characterized in that the time for adding the added catalyst is determined by measuring the rate of hydrogen absorption. 2. The improved method for hydrogenating a conjugated diene polymer according to claim 1, wherein the hydrogenation reaction is performed in a batch system. 3. The improvement according to claim 1, wherein the addition time of the hydrogenation catalyst is added when the hydrogen absorption rate falls to 80% or less of the hydrogen absorption rate at the start of the reaction. A method for hydrogenating a conjugated diene polymer. 4. The hydrogenation catalyst as claimed in claim 1, wherein the hydrogenation rate is 50% or more and 90% or more.
An improved method for hydrogenating a conjugated diene-based polymer, characterized by adding an amount of less than 2. 5. The improved method for hydrogenating a conjugated diene polymer according to claim 1, wherein the degree of hydrogenation is 98% or more. 6. The improved conjugated diene-based weight according to claim 1, wherein the amount of the added hydrogenation catalyst is equal to or less than the amount of the initially added hydrogenation catalyst. Method of hydrogenation of coalescence. 7. The improved method for hydrogenating a conjugated diene-based polymer according to claim 1, wherein the hydrogenation catalyst is a titanocene-based catalyst.