JPH0520442B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention has high hardness, high modulus, rebound properties,
The present invention relates to a selectively partially hydrogenated polymer having excellent heat generation properties and improved heat aging resistance. More specifically, the present invention relates to a selectively partially hydrogenated polymer having a specific structure obtained by selectively partially hydrogenating a butadiene polymer or a styrene-butadiene copolymer having a specific structure. [Prior art and its problems] Polymers obtained by partially hydrogenating styrene-butadiene copolymers have been known for a long time, and they are blended with other diene elastomers or ethylene-propylene copolymer rubber. A proposal to obtain a composition with improved green strength by
No. 35497) has been made. In addition, a proposal regarding a composition with excellent breaking strength and rubber-like elasticity consisting of this and a specific inorganic filler (Japanese Patent Publication No. 47-8928), and a proposal regarding a method for manufacturing oil-extended rubber with excellent heat aging resistance and rebound resilience (Japanese Patent Publication No. 47-8928) Publication No. 46-29020) etc. have been made. However, with conventional catalysts mainly composed of organic compounds of iron, nickel, and cobalt, it is difficult to preferentially select vinyl bonds for partial hydrogenation. , 4 bonds (there are cis bonds and trans bonds) also needed to be increased and hydrogenated. Furthermore, although this method generates a crystalline copolymer and improves the intended impact resilience and heat aging resistance, it only results in an undesirable significant increase in hardness or a decrease in heat generation. On the other hand, a method of selectively hydrogenating only the side chain components of a diene polymer (vinyl bonding portion in the case of a butadiene polymer) has also been proposed, and a method for obtaining a selectively hydrogenated diene polymer having ozone resistance and oxidation stability. It is also known (Japanese Unexamined Patent Publication No. 52-41690). However, although it is true that the polymer produced by this method has some improvement in heat aging resistance or rebound resilience, it is insufficient and there is no significant improvement in hardness or modulus. [Means for Solving the Problems] The present invention proposes a novel polymer that solves the above-mentioned problems all at once. That is, the present invention provides (1) a bound styrene content [S] of 0 to 40% by weight, and (2) a vinyl bond content [V] of the butadiene moiety of 1 to 40% by weight.
80% (3) Weight average molecular weight (Mw) of 1 to 1 million (4) Butadiene polymer or styrene-butadiene copolymer with molecular weight distribution (Mw/Mn) of 1.2 to 5.0 (5) Organometallic compound of titanium (6) The hydrogenation rate [A] of the entire butadiene part is 3 to 60% (7) Water in the vinyl bond part of the butadiene part. Addition rate [B]
is 30% or more, and [A], [B], [S], and [V] are (8) [A] / ([S] + [V]) ^1/2 is 2 to 8 (9) [ The present invention provides a method for producing a selectively partially hydrogenated polymer in which B].[V] ^1/2 /[A] satisfies the relationship of 10 to 16. By the way, as hydrogenation catalysts for butadiene polymers and styrene-butadiene copolymers, in addition to the aforementioned catalysts mainly composed of iron, nickel, and cobalt organic compounds and organometallic compounds, nickel, cobalt, platinum, palladium, rutinium, etc. Catalysts in which metals supported on carriers such as carbon, silica, alumina, diatomaceous earth, etc. are also known, but their activity is low and hydrogenation at low temperatures and pressures has been industrially impossible. Moreover, the vinyl bond of the butadiene moiety was not partially hydrogenated more selectively. Recently, a highly active hydrogenation method using an organometallic compound of titanium as the main component has become known (Japanese Patent Application Laid-open No. 59-133203
No., JP-A No. 60-220147), industrially easily low temperature,
It became possible to hydrogenate only the butadiene portion under mild conditions at low pressure. The present invention applies this to the partial hydrogenation of a butadiene polymer or a styrene-butadiene polymer with a specific structure to obtain a selectively hydrogenated polymer with a specific structure, thereby solving the problems of the prior art at once. . The butadiene polymer and styrene-butadiene copolymer, which are the base polymers of the selectively hydrogenated polymer of the present invention, are required to have a specific structure. That is, (1) the bound styrene content [S] is 0 to 40% by weight (2) the vinyl bond content [V] of the butadiene moiety is 1 to 40% by weight.
80% (3) Weight average molecular weight (Mw) must be 1 to 1 million (4) Molecular weight distribution (Mw/Mn) must be 1.2 to 5.0. Here, the bound styrene content [S] is defined as the content (wt%) of bound styrene units relative to the total amount of the raw polymer before hydrogenation, but if the bound styrene content exceeds 40 wt% Even if the other requirements of the present invention are met, the improvements in rebound and heat generation that are the objectives of the present invention are insufficient. The bound styrene content is preferably limited to 30% or less. Further, it is preferable that the bonding mode of styrene is random. The bonding mode of the butadiene moiety in the raw polymer before hydrogenation has a structural formula that is based on 1,4 bonds. Cis (c) and structural formula shown as Structural formula that is based on trans (t) and 1,2 bonds shown in There are three types of vinyl (v) shown in . Therefore, the vinyl content of the vinyl part of the butadiene part [V]
is the entire butadiene moiety Vinyl (v) relative to the total amount of cis (c), trans (t) and vinyl (v) above
It is defined as the content (mol%) of The vinyl bond content of this butadiene moiety is limited to 1 to 80%. Outside this range, there will be too many or too few vinyl bonds, and the selective partial hydrogenation of vinyl bonds in the present invention will be meaningless and will not produce any effect. The vinyl bond content is preferably 5
It is limited to ~60%, more preferably 10 to 50%. In addition, the weight molecular weight (Mw) is 1 to 1 million,
The molecular weight distribution needs to be 1.2 to 5.0 expressed as Mw/Mn. If the molecular weight is less than 10,000 or the molecular weight distribution is more than 5, the physical properties of the raw polymer itself to be improved, such as hardness,
The modulus, rebound properties, and heat generation properties are extremely poor, and even by applying the present invention, a sufficient polymer cannot be obtained. On the other hand, the molecular weight is 100
If the molecular weight distribution exceeds 1,000,000 or is less than 1.2, it becomes difficult to process or obtain the polymer as a rubber, and the present invention cannot be applied. The preferred range of molecular weight is 5-
800,000, more preferably 100,000 to 600,000. Further, the preferred range of molecular weight distribution is 1.5 to 3.0. Molecular weight and molecular weight distribution are measured using a gel permeation chromatograph according to a conventional method and defined using this method. a butadiene polymer with the structure specified above;
The styrene-butadiene copolymer can be easily produced by solution polymerization using an organic compound of nickel, cobalt or titanium and an organometallic catalyst or an organolithium alone or a combination thereof with a Lewis base. A part of the butadiene component of the polymer may be replaced with another conjugated diene component copolymerizable therewith, for example, within a range of 30% by weight or less. Other conjugated diene components include isoprene, 2,3 dimethyl-1,3-butadiene, 1,3 pentadiene, and the like. The same goes for the styrene component, and some of it is t-
Vinyl-substituted aromatic hydrocarbons such as butylstyrene, α-methylstyrene, p-methylstyrene, and divinylbenzene may be substituted. The polymer of the present invention is obtained by selectively partially hydrogenating the above-specified butadiene polymer or styrene-butadiene copolymer (5) The hydrogenation rate [A] of the entire butadiene portion is 3 to 60% (6) Hydrogenation rate of vinyl bond part of butadiene part [B]
is 30% or more, and [A], [B], [S], and [V] are (7) [A] / ([S] + [V]) ^1/2 is 2 to 8 (8) [ B].[V] ^1/2 /[A] is a selective partially hydrogenated polymer satisfying the relationship of 10 to 16. When the butadiene moiety is hydrogenated, the butadiene unit due to the 1,4 bond has the structural formula (-CH ₂ -CH ₂ -CH ₂ -
CH ₂ )― becomes tetramethylene (m), and 1,
Structural formula for those with two bonds It becomes butylene (b) shown as Therefore, the hydrogenation rate [A] of the entire butadiene part is:
The entire butadiene moiety, i.e. cis(c), trans
(t), vinyl (v), tetramethylene (m) and butylene (b)
Total content (mol%) of hydrogenated units tetramethylene (m) and butylene (b) relative to the total amount of
is defined as The hydrogenation rate [A] of the entire butadiene portion is 3 to 60%, preferably 5 to 50%, more preferably 8 to 40%, and particularly preferably 10 to 30%.
It is. If the hydrogenation rate [A] is lower than this range, the polymer of the present invention with high hardness and modulus and excellent impact resilience cannot be obtained. On the other hand, if the hydrogenation rate [A] is too high, the polymer will be partially crystalline, giving it too high physical hardness and poor heat generation properties. Furthermore, the hydrogenation rate [B] of the vinyl bonded portion of the butadiene portion is the content of butylene (b), which is a hydrogenated unit, relative to the entire vinyl bonded portion of the butadiene portion, that is, the total amount of vinyl (v) and butylene (b). (mol%), and the hydrogenation rate [B] of the vinyl bonding part of the butadiene part is 30% or more, preferably 30 to 30%.
95%, more preferably 45-95%, even more preferably
Limited to 60-90%. Hydrogenation rate below this [B]
In this case, the effect of improving heat aging resistance and rebound resilience of the present invention is small. In the present invention, the range of the hydrogenation rate [A] of the entire butadiene moiety is determined by the bound styrene content [S] of the butadiene polymer or styrene-butadiene copolymer, which is the original polymer, and the vinyl bond content [V] of the butadiene moiety. ] is determined as a function of That is, it is necessary that [A]/([S]+[V]) ^1/2 be from 2 to 8, preferably from 3 to 7, and more preferably from 4 to 6. If this value is less than 2, the effects of the present invention, especially the increase in hardness and modulus, will not be realized, and if this value is 8 or more, the heat generation property will be poor. Further, the hydrogenation rate [B] of the vinyl bond portion of the butadiene portion is determined as a function of the vinyl bond content [V] of the butadiene portion of the original polymer and the hydrogenation rate of the entire butadiene portion [A]. That is, [B]・[V] ^1/2 / [A] is 10 to 16, preferably
It is limited to 11-15, more preferably 12-14. Outside this range, the polymer will not have the effects of the present invention, which are excellent in hardness, modulus, heat generation properties, rebound resilience, and heat aging resistance. Generally this number is 16
If it exceeds 10, other physical properties may be improved, but the hardness/modulus increases or heat aging resistance is improved.Conversely, if it is less than 10, the physical properties are insufficient in terms of rebound resilience and heat generation, and the overall physical properties deteriorate. The balance is disrupted and becomes undesirable. The butadiene polymer or styrene-butadiene polymer with a specific structure, which is the base polymer of the selectively hydrogenated polymer of the present invention, can be produced by any method as long as it falls under the above-mentioned limited structure. It may be hot. Typical manufacturing methods for obtaining these polymers are as follows. That is, the raw polymer is prepared in an inert solvent such as hexane, cyclohexane, benzene, etc. using n-butyllithium, n-butyllithium, etc. as a polymerization catalyst.
Organolithium or other alkali metal compounds such as sec-butyllithium are used, and representative examples include alkoxides such as potassium butoxide, organic acid salts such as dodecylbenzenesulfonate, and sodium stearate as co-catalyst components if necessary. In addition, if necessary, a polar organic compound such as ether, polyether, tertiary amine, polyamine, thioether, hexamethylphosphortriamide, etc. is used as a compound to adjust the vinyl bond content. butadiene,
Depending on the case, it can be obtained by further copolymerizing styrene alone or in a predetermined ratio. The vinyl bond content can be controlled by the amount of the polar organic compound added and the polymerization temperature. Furthermore, the polymer chain having an active end obtained by the above method is coupled with a polyfunctional compound such as silicon tetrachloride, tin tetrachloride, or a polyepoxy compound, or a branching agent such as divinylbenzene is added. By adding it to the polymerization system, a branched or radial polymer or copolymer can be obtained. Furthermore, in the polymerization method, various polymerization conditions such as adjusting the addition method of the monomer, changing the amount of the compound for adjusting the vinyl bond content, the addition method, and the polymerization temperature in the middle of the polymerization reaction can be used. Polymers or copolymers in which the styrene content or vinyl bond content increases or decreases in the molecular chain, or have a block shape can be obtained. In addition, various compounds such as acetylene, 1,2-butadiene, fluorene, primary amines, and secondary amines can also be used as molecular weight regulators in the polymerization. The polymerization process for obtaining the above polymers can be a batch process, a continuous process, or a combination thereof. In addition, the raw polymer of the present invention can be produced using other polymerization methods other than using a lithium catalyst, such as a Ziegler-based catalyst consisting of an organic compound such as nickel, cobalt, titanium, etc., and an organometallic component such as lithium, magnesium, or aluminum. or an emulsion polymerization method can be used. The raw polymer obtained by the above method is subjected to the following selective partial hydrogenation. Hydrogenation catalysts that can be suitably used in the present invention include catalysts using organometallic compounds containing titanium as a metal component alone or in combination with organometallic compounds such as lithium, magnesium, and aluminum. -133203 or JP-A-60-220147. The selective partial hydrogenation of the present invention must be carried out using the above-mentioned catalyst under extremely mild reaction conditions. That is, the hydrogen partial pressure in the reaction system needs to be 10 kg/cm ² or less, preferably 6 kg/cm ² or less, more preferably 3 kg/cm ^{2 or} less. The reaction temperature should also be carried out at 0 to 100°C, preferably 20 to 80°C, more preferably 40 to 60°C, and hydrogenation conditions outside this range may result in the hydrogenation of selected parts of the specified structure of the present invention. Hydrogenated polymer cannot be obtained. The hydrogenation reaction is carried out in a solvent in which the raw polymer, which is inactive to the catalyst, is soluble. Suitable solvents include aliphatic hydrocarbons such as n-pentane, n-hexane, and n-octane, alicyclic hydrocarbons such as cyclohexane and cycloheptane, and ethers such as diethyl ether and tetrahydrofuran. It is a mixture whose main components are In the hydrogenation reaction of the present invention, the raw polymer is generally maintained at a predetermined temperature under hydrogen or an inert atmosphere, a hydrogenation catalyst is added with or without stirring, and then hydrogen gas is added. This is carried out by introducing and pressurizing to a predetermined pressure. An inert atmosphere means an atmosphere that does not react with any participants in the hydrogenation reaction, such as helium, neon, argon, and the like. Air and oxygen are not preferred because they oxidize catalyst components and cause catalyst deactivation. Further, nitrogen is not preferred because it acts as a catalyst poison during the hydrogenation reaction and reduces the hydrogenation activity. In particular, it is most preferable to have an atmosphere of hydrogen gas alone in the hydrogenation reactor. Further, when a titanocene diaryl compound is used as a hydrogenation catalyst, it may be added alone to the reaction solution as it is, or may be added as a solution in an inert organic solvent. As the inert organic solvent used when the catalyst is used as a solution, any of the above-mentioned various solvents that do not react with any of the participants in the hydrogenation reaction can be used. Preferably, it is the same solvent as used in the hydrogenation reaction. In addition, the amount of catalyst added is 100% of the original polymer.
0.02-20 mmol/g. The most preferred method for obtaining the polymer of the present invention is to solution polymerize the raw polymer using an organolithium catalyst,
The obtained polymer solution can be used as it is in the next hydrogenation reaction, which is extremely useful industrially. The selectively partially hydrogenated polymer of the present invention can be obtained by removing and drying the solution obtained above. Taking advantage of its properties, the polymer of the present invention can be widely used in applications for which butadiene polymers and styrene-butadiene copolymers are currently used. A particularly preferred application is for automobile tires, where the polymer of the present invention is used alone or blended with natural rubber or other synthetic rubber, and subjected to predetermined "compounding,""molding," and "vulcanization" before being used for final use. . In this case, in order for the polymer of the present invention to exhibit its effects, at least 30% of the raw rubber needs to be the polymer of the present invention. Examples of synthetic rubbers that can be used as a blend include butadiene polymer, styrene-butadiene copolymer, isoprene-butadiene copolymer, acrylonitrile-butadiene copolymer, chloroprene polymer, ethylene-propylene copolymer, and isoprene polymer. -Isobutylene copolymers and the like. Examples of compounds added to the above raw rubber in "compounding" include reinforcing agents, softeners, fillers, vulcanizing agents, vulcanization accelerators, vulcanization accelerators, There are sulfur auxiliaries, colorants, flame retardants, lubricants, blowing agents, and other compounding agents, which are appropriately selected and used depending on the intended use of the composition. Carbon black is a typical reinforcing agent, and various types of reinforcing agents with different particle sizes or structures are used that are obtained by various manufacturing methods, but carbon blacks such as ISAF, HAF, and FEF are used. Suitably used. The amount of carbon black to be added is determined by taking into account the amount of process oil to be added if necessary, but it is 10 to 150 parts by weight, preferably 40 to 100 parts by weight, per 100 parts by weight of raw rubber. section is used. The type and amount of carbon black added are appropriately adjusted depending on the intended use of the rubber composition, and two or more types may be used in combination. Other reinforcing agents added as necessary include inorganic reinforcing agents such as silica and activated calcium carbonate, high styrene resins, and phenol-formaldehyde resins. It is used in an amount of 1 to 100 parts by weight, preferably 5 to 50 parts by weight, per 100 parts by weight of rubber. Typical softeners added as needed include process oils, and various types such as paraffinic, naphthenic, and aromatic softeners are suitably used in rubber compositions, and are added to 100 parts by weight of raw rubber. Against 2
~100 parts by weight are used, preferably 5 to 70 parts by weight. It is also possible to use an oil-extended polymer in which process oil is added to the raw rubber in advance. Other softeners include liquid paraffin,
These include coal tar, fatty oil, and sub. As a filler, calcium carbonate, clay,
Examples include talc and aluminum hydroxide. A typical example of the vulcanizing agent is sulfur, which is used in an amount of 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, per 100 parts by weight of raw rubber. Other vulcanizing agents include sulfur compounds such as sulfur chloride, morpholine disulfide, and alkylphenol disulfide, and peroxides, which may be used alone or in combination with sulfur. There are a wide variety of vulcanization accelerators,
These are used in an amount of 0.01 to 5 parts by weight per 100 parts by weight of raw rubber, and two or more types may be used in combination. Typical vulcanization accelerators include guanidine type, aldehyde-amine and aldehyde-ammonia type, thiazole type, imidazoline type, thiourea type, thiuram type, dithiocarbamate type, xanthate type, and mixed accelerators. As a vulcanization aid, metal oxides such as zinc oxide,
There are fatty acid compounds such as stearic acid, amines, etc., and these are 0.1% per 100 parts by weight of raw rubber.
~10 parts by weight are used. Typical anti-aging agents or antioxidants are amine-based, phenol-based, phosphorus-based, sulfur-based, etc. These are added in an amount of 0.001 to 10 parts by weight per 100 parts by weight of raw rubber, and two or more of these are added. It may also be used in combination. Typical scorch inhibitors include phthalic anhydride, salicylic acid, and N-nitroso-diphenylamine. Examples of the tackifier include coumaron-indene resin, terpene-phenol resin, and rosin ester. Furthermore, various other compounding agents may be used as necessary. The rubber composition of the present invention is produced by mixing raw rubber and various compounding agents using various mixing devices generally used for mixing rubber compositions, such as open rolls, Banbury mixers, kneaders, and extruders. Then, after being molded into the desired shape, it is vulcanized. The polymer of the present invention can be suitably used for various automobile tires, belts, hoses, industrial goods such as anti-vibration rubber, footwear, daily necessities, construction materials, and various other uses by taking advantage of its characteristics. Furthermore, the polymer of the present invention is also excellent as a toughening agent for styrenic polymers and is suitably used. [Examples] Hereinafter, the present invention will be specifically explained using Examples and Comparative Examples, but these do not limit the scope of the present invention. Example 1, Comparative Example 3 Butadiene/n-
20% hexane mixture (butadiene concentration 20% by weight)
n-butyllithium/n-hexane solution (concentration 5% by weight) was introduced at a rate of 60 ml/hr, and coupled polymerization of butadiene was carried out at a polymerization temperature of 110°C.
The obtained activated polymer was deactivated with methanol, and the polymer solution 8 was transferred to a reactor with an internal volume of 10 mm and equipped with a stirrer and a jacket, and di-p-tolylbis was added as a hydrogenation catalyst at a temperature of 60°C. (1-cyclopentadienyl)titanium/cyclohexane solution (concentration 1
250 ml of n-butyllithium solution (concentration 5 mmol/) and 50 ml of n-butyllithium solution (concentration 5 mmol/) at 0°C and 2.0
The mixture was added under a hydrogen pressure of Kg/cm ² and reacted for 30 minutes at a hydrogen partial pressure of 2.5 Kg/cm ² . The obtained selective partially hydrogenated polymer solution contains 2,
6-ditertyabutylhydroxytoluene was added at 0.5 parts per polymer and the solvent was removed. Table 1 shows the analytical values of the raw polymer (butadiene polymer of Comparative Example 3) obtained by sampling after methanol deactivation and the analytical values of the selective partially hydrogenated polymer. Table 2 shows the vulcanization properties of a carbon-containing composition of a 75/25 blend of this material and natural rubber. Examples 2 to 8, Comparative Examples 1, 2, 4, 5 and 6 Butadiene polymers and styrene-butadiene obtained by batch polymerization or continuous polymerization using an organolithium catalyst (alone or using tetrahydrofuran as a modifier) The polymer was hydrogenated by changing the reaction conditions (hydrogenation pressure, hydrogenation temperature, time and catalyst amount) of Example 1 to produce Examples 2 to 8 and Comparative Examples 1, 2, and 4.
Selected partially hydrogenated polymers of 5 and 5 were obtained. In Comparative Example 6, the raw polymer used in Example 6 was used without hydrogenation. Table 1 shows the structural analysis values for each polymer. In addition, Tables 2 and 3 show the vulcanized physical properties of carbon compounded compositions of these polymers alone or blended with natural rubber. Comparative Examples 7 to 11 Butadiene polymers and styrene-butadiene polymers obtained by batch polymerization or continuous polymerization using organolithium catalysts (alone or using tetrahydrofuran as a modifier) under reaction conditions (hydrogenation pressure, hydrogenation pressure, The selected polymers of Comparative Examples 7 to 9 were obtained by hydrogenation at different temperatures (temperature, time, and catalyst amount). Also,
In Comparative Examples 10 and 11, the hydrogenation catalyst was
A partially hydrogenated polymer was obtained using a nickel-based catalyst shown in No. 35497. Table 1 shows the structural analysis values for each polymer. Further, Table 3 shows the vulcanizability of carbon-blended compositions of these polymers alone or blended with natural rubber.

【table】

【table】

【table】

[Table] Examples 9 and 10, Comparative Example 12 The polymers obtained in Examples 1 and 2 and Comparative Example 3 were used as toughening agents to carry out bulk polymerization of styrene as shown below. Six parts by weight of the partially water-applied butadiene polymer rubber was dissolved in 94 parts by weight of styrene and 8 parts by weight of ethylbenzene, and further 0.05 parts by weight of benzoyl peroxide and 0.10 parts by weight of α-methylsulfone dimer were added to the styrene. and polymerization was carried out under stirring at 80°C for 4 hours, at 110°C for 4 hours, and at 150°C for 4 hours. Further, heat treatment was performed at around 230° C. for 30 minutes, and then unreacted styrene and ethylbenzene were removed under vacuum to obtain a styrenic resin. After pulverizing this, it was formed into pellets using an extruder, injection molded, and the physical properties were measured. The results are shown in Table 4.
Table 4 shows that the polymer of the present invention is also excellent as a toughening agent for impact-resistant polystyrene resins. That is, polystyrene made of the polymer of the present invention as a toughening agent has excellent impact strength and flexural modulus.

[Table] is Kg・cm/cm
*2: According to ASTM D-790; unit is Kg/cm ²
[Effects of the Invention] As explained above, the selectively hydrogenated polymer having the specified structure of the present invention has high hardness and modulus, excellent rebound resilience and heat generation property, and also has excellent heat aging resistance. Raw material rubber with well-balanced physical properties and excellent properties was provided. In addition, carbon-blended raw rubber compositions obtained by using this polymer alone or by blending it with other rubbers are suitable for tires, especially tire treads.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the FT-NMR absorption of the raw polymer of Example 1, and FIG. 2 is a diagram showing the FT-NMR absorption of the polymer after selective partial hydrogenation of Example 1.

Claims (1)

[Claims] 1 (1) The bound styrene content [S] is 0 to 40% by weight (2) The vinyl bond content [V] of the butadiene moiety is 1 to 40% by weight
80% (3) A butadiene polymer or styrene-butadiene copolymer with a weight average molecular weight [Mw] of 1 to 1 million (4) A molecular weight distribution [Mw/Mn] of 1.2 to 5.0 (5) An organometallic compound of titanium (6) The hydrogenation rate [A] of the entire butadiene part is 3 to 60% (7) Water in the vinyl bond part of the butadiene part. Addition rate [B]
is 30% or more, and [A], [B], [S], and [V] are (8) [A] / ([S] + [V]) ^1/2 is 2 to 8 (9) [ A method for producing a selective partially hydrogenated polymer in which B].[V] ^1/2 / [A] satisfies the relationship of 10 to 16.