Method for producing modified conjugated diene polymer, and modified conjugated diene polymer

Abstract

To provide a conjugated diene polymer having excellent toughness and low energy loss and to provide a method for producing the same.SOLUTION: There is provided a method for producing a modified conjugated diene polymer which comprises: an epoxidation step of obtaining an epoxidized conjugated diene polymer by epoxidation of a carbon-carbon double bond of a conjugated diene polymer by reacting the conjugated diene polymer and a peroxide; and a ring-opening step of obtaining a modified conjugated diene polymer which is a conjugated diene polymer having a hydroxyl group in adjacent carbon atoms by reacting the epoxidized conjugated diene polymer and water to ring-open an epoxy ring of the epoxidized conjugated diene polymer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a modified conjugated diene polymer, and a modified conjugated diene polymer. [Background technology]

[0002] 2. Description of the Related Art Modified polybutadienes obtained by modifying polybutadiene are known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-066222 A Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, in various fields, there is a demand for further improvement in toughness of conjugated diene polymer materials such as polybutadiene, and also for low energy loss when used as materials. Under these circumstances, the present inventors produced a conjugated diene polymer with reference to Patent Document 1, but it became clear that the physical properties of the polymer did not necessarily satisfy recent demands.

[0005] In view of the above circumstances, an object of the present invention is to provide a conjugated diene-based polymer having excellent toughness and small energy loss, and a method for producing the same. [Means for solving the problem]

[0006] As a result of intensive investigations into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a modified conjugated diene polymer obtained by epoxidizing and ring-opening a conjugated diene polymer, thereby completing the present invention. Specifically, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) an epoxidation step of reacting a conjugated diene polymer with a peroxide to epoxidize the carbon-carbon double bonds of the conjugated diene polymer to obtain an epoxidized conjugated diene polymer; and a ring-opening step of reacting the epoxidized conjugated diene polymer with water to open epoxy rings of the epoxidized conjugated diene polymer, thereby obtaining a modified conjugated diene polymer, which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms. (2) The method for producing a modified conjugated diene polymer according to the above (1), wherein the modified conjugated diene polymer has a weight average molecular weight of 100,000 or more. (3) The method for producing a modified conjugated diene polymer according to (1) or (2) above, wherein the conjugated diene polymer is a butadiene polymer, an isoprene polymer, or an aromatic vinyl-conjugated diene copolymer. (4) The method for producing a modified conjugated diene polymer according to any one of (1) to (3) above, wherein the ratio of adjacent carbon atoms having hydroxyl groups in the modified conjugated diene polymer to the carbon-carbon double bonds in the conjugated diene polymer is 1 to 50 mol %. (5) an epoxidation step of reacting a conjugated diene polymer with a peroxide to epoxidize the carbon-carbon double bonds of the conjugated diene polymer to obtain an epoxidized conjugated diene polymer; and a ring-opening step of reacting the epoxidized conjugated diene polymer with water to open epoxy rings of the epoxidized conjugated diene polymer, thereby obtaining a modified conjugated diene polymer, which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms. Effect of the Invention

[0008] As will be described below, according to the present invention, it is possible to provide a conjugated diene-based polymer having excellent toughness and small energy loss, and a method for producing the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The modified conjugated diene polymer of the present invention and the method for producing the same will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In addition, each component in the present specification may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified.

[0010] First, the method for producing the modified conjugated diene polymer of the present invention will be described.

[0011] [Method of producing modified conjugated diene polymer of the present invention] The method for producing a modified conjugated diene-based polymer of the present invention (hereinafter also referred to as "the method of the present invention") comprises the following steps. (1) Epoxidation process A step of reacting a conjugated diene polymer with a peroxide to epoxidize the carbon-carbon double bonds of the conjugated diene polymer, thereby obtaining an epoxidized conjugated diene polymer. (2) Ring-opening process A process for obtaining a modified conjugated diene polymer, which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms, by reacting the epoxidized conjugated diene polymer obtained in the epoxidation process with water to open the epoxy rings (oxirane rings) of the epoxidized conjugated diene polymer.

[0012] An embodiment in which 1,4-cis polybutadiene (1,4-cis BR) is used as the conjugated diene polymer will be described below using a structural formula.

[0013] First, 1,4-cis polybutadiene (see below) is reacted with peroxide.

[0014] [ka]

[0015] As a result, at least a portion of the carbon-carbon double bonds of the 1,4-cis polybutadiene are epoxidized to obtain epoxidized 1,4-cis polybutadiene (described below) (epoxidation step).

[0016] [ka]

[0017] Next, the epoxidized 1,4-cis polybutadiene obtained in the epoxidation step is reacted with water, whereby at least a part of the epoxy rings of the epoxidized 1,4-cis polybutadiene are opened to obtain a 1,4-cis polybutadiene having hydroxyl groups on adjacent carbon atoms (modified 1,4-cis polybutadiene) (described below) (ring-opening step).

[0018] [ka]

[0019] The modified conjugated diene polymer obtained by the method of the present invention has hydroxyl groups on adjacent carbon atoms, so that adjacent hydroxyl groups interact with each other and also between polymers, forming extremely strong interactions. As a result, the modified conjugated diene polymer obtained is considered to exhibit excellent toughness. In addition, as described above, the formation of strong interactions suppresses mobility, and as a result, energy loss is also considered to be suppressed.

[0020] Each step will be described in detail below.

[0021] [Epoxidation step] The epoxidation step is a step in which a conjugated diene polymer is reacted with a peroxide to epoxidize the carbon-carbon double bonds of the conjugated diene polymer, thereby obtaining an epoxidized conjugated diene polymer. An epoxidized conjugated diene polymer is a conjugated diene polymer in which at least a portion of the carbon-carbon double bonds (C=C) of units derived from a conjugated diene (hereinafter also referred to as "conjugated diene units") in the conjugated diene polymer have been epoxidized (become an epoxy ring).

[0022] <Conjugated diene polymer> The conjugated diene polymer used in the epoxidation step is not particularly limited as long as it is a polymer obtained by using a conjugated diene as a monomer. However, the conjugated diene polymer does not have to be a polymer obtained by actually using a conjugated diene as long as it has the same structure as a polymer obtained by using a conjugated diene as a monomer. For example, natural rubber is a conjugated diene polymer because it has the same structure as a polymer obtained by using isoprene as a monomer.

[0023] (Conjugated dienes) The conjugated diene is not particularly limited, but is preferably butadiene (particularly 1,3-butadiene) or isoprene, because the effects of the present invention are more excellent. That is, the conjugated diene is preferably a butadiene-based polymer or an isoprene-based polymer because the effects of the present invention are more excellent.

[0024] (Specific examples) Specific examples of the conjugated diene polymer include polybutadiene (butadiene rubber) (BR), polyisoprene (isoprene rubber) (IR), natural rubber (NR), aromatic vinyl-conjugated diene copolymer, acrylonitrile-butadiene copolymer (nitrile rubber) (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Examples of the aromatic vinyl-conjugated diene copolymer include styrene-butadiene copolymer (styrene-butadiene rubber) (SBR), styrene-isoprene copolymer (styrene-isoprene copolymer rubber), etc.

[0025] (Preferred embodiment) The above-mentioned conjugated diene polymer is preferably a butadiene polymer (particularly, polybutadiene), an isoprene polymer (particularly, polyisoprene, natural rubber), or an aromatic vinyl-conjugated diene copolymer (particularly, styrene-butadiene copolymer) because the effects of the present invention are more excellent.

[0026] The conjugated diene content of the conjugated diene polymer is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 50 mol% or more, particularly preferably 70 mol% or more, and most preferably 90 mol% or more. The upper limit is not particularly limited, and is 100 mol%. The conjugated diene content is the proportion of units derived from a conjugated diene to all monomer units constituting a conjugated diene-based polymer.

[0027] (molecular weight) The number average molecular weight (Mn) of the conjugated diene polymer is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 5,000 to 5,000,000, more preferably 50,000 to 2,000,000, and even more preferably 100,000 to 1,000,000.

[0028] The weight average molecular weight (Mw) of the conjugated diene polymer is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 10,000 to 10,000,000, more preferably 100,000 to 4,000,000, and even more preferably 200,000 to 2,000,000.

[0029] The molecular weight distribution (PDI) of the conjugated diene polymer is not particularly limited, but for reasons of superior effects of the present invention, it is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. The lower limit of the molecular weight distribution is not particularly limited, but is usually 1.0 or more.

[0030] The above Mn and Mw are values ​​calculated in terms of standard polystyrene obtained by gel permeation chromatography (GPC) measurement under the following conditions. Solvent: Tetrahydrofuran Detector: RI detector

[0031] <Peroxide> The peroxide used in the epoxidation step is not particularly limited.

[0032] (Specific examples) The peroxides include inorganic peroxides and organic peroxides. Examples of the inorganic peroxides include aqueous hydrogen peroxide; persulfuric acid, sodium hydrogen persulfate, potassium hydrogen persulfate and other persulfate compounds; and the like. Examples of the organic peroxide include t-butyl hydroperoxide, m-chloroperbenzoic acid (mCPBA), performic acid, peracetic acid, and perpropionic acid.

[0033] (Preferred embodiment) The peroxide is preferably an organic peroxide, and more preferably m-chloroperbenzoic acid (mCPBA), because the effects of the present invention are more excellent.

[0034] (Amount used) The amount of the peroxide used is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 10 to 200 mass % relative to the amount of the conjugated diene polymer used, and more preferably 50 to 100 mass %.

[0035] <Epoxidation process procedure> The procedure for the epoxidation step is not particularly limited, and examples thereof include a method in which a conjugated diene polymer and a peroxide are mixed and stirred, and then the reaction product is recovered.

[0036] <Epoxidized conjugated diene polymer> The epoxidized conjugated diene polymer obtained in the epoxidation step is a polymer in which at least a portion of the carbon-carbon double bonds (C=C) of the units derived from the conjugated diene in the conjugated diene polymer (hereinafter also referred to as "conjugated diene units") have been epoxidized (become an epoxy ring). Specific examples and preferred embodiments of the conjugated diene polymer portion of the epoxidized conjugated diene polymer are the same as those of the conjugated diene polymer in the epoxidation step described above.

[0037] (epoxidation rate) The epoxidation rate of the epoxidized conjugated diene polymer is not particularly limited, but in order to obtain better effects of the present invention, the epoxidation rate is preferably 1 to 99 mol%, more preferably 2 to 50 mol%, even more preferably 3 to 40 mol%, and particularly preferably 5 to 20 mol%. Here, the epoxidation rate is the proportion of the carbon-carbon double bonds of the conjugated diene units (e.g., butadiene units) in the conjugated diene polymer used in the epoxidation step that have been epoxidized (become epoxy rings). For example, if there are 100 carbon-carbon double bonds of the conjugated diene units in the conjugated diene polymer used in the epoxidation step and 10 of them have been epoxidized, the epoxidation rate of the epoxidized conjugated diene polymer is 10 mol%.

[0038] (molecular weight) The molecular weight of the epoxidized conjugated diene polymer is not particularly limited, but the preferred ranges of Mn, Mw and PDI and the reasons why they are preferred are the same as those of the above-mentioned conjugated diene polymer.

[0039] [Ring opening process] The ring-opening step is a step in which the epoxidized conjugated diene polymer obtained in the above-mentioned epoxidation step is reacted with water to open the epoxy rings of the epoxidized conjugated diene polymer, thereby obtaining a modified conjugated diene polymer, which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms. By opening the epoxy ring, hydroxyl groups are introduced to the two carbon atoms (adjacent carbon atoms) that previously constituted the epoxy ring. That is, the modified conjugated diene-based polymer obtained in the ring-opening step is one in which at least a portion of the epoxy rings in the epoxidized conjugated diene-based polymer are opened, and hydroxyl groups are introduced into two carbon atoms (adjacent carbon atoms) that constituted the ring-opened epoxy ring. Incidentally, a group other than a hydroxyl group (for example, an alkoxy group) may be introduced into some of the two carbon atoms (adjacent carbon atoms) that constituted the opened epoxy ring.

[0040] In the ring-opening step, it is preferable to use a catalyst for activating the epoxy ring, because the effect of the present invention is more excellent.

[0041] <Epoxidized conjugated diene polymer> The epoxidized conjugated diene polymer used in the ring-opening step is the epoxidized conjugated diene polymer obtained in the above-mentioned epoxidation step. The epoxidized conjugated diene polymer is as described above.

[0042] <Catalyst> As described above, in the ring-opening step, it is preferable to use a catalyst for activating the epoxy ring, because the effect of the present invention is more excellent.

[0043] (Specific examples) Specific examples of the catalyst include protonic acids (hydrochloric acid and sulfuric acid), Lewis acids (aluminum chloride, etc.), etc. It is preferable to add a base such as a hydroxide together with the catalyst.

[0044] (Preferred embodiment) The catalyst is preferably hydrazinium, and more preferably hydrazinium sulfate, because the effects of the present invention are more excellent.

[0045] (Amount used) The amount of the catalyst used is not particularly limited, but in order to obtain a better effect of the present invention, the amount is preferably 1 to 100 mass % and more preferably 10 to 50 mass % relative to the amount of the epoxidized conjugated diene polymer used.

[0046] <Ring-opening process procedure> The procedure for the ring-opening step is not particularly limited, and examples thereof include a method in which an epoxidized conjugated diene polymer, water, a catalyst, etc. are mixed and stirred, and then the reaction product is recovered.

[0047] <Modified conjugated diene polymer> The modified conjugated diene-based polymer obtained in the ring-opening step is one in which at least a portion of the epoxy rings in the epoxidized conjugated diene-based polymer are opened, and hydroxyl groups are introduced into two carbon atoms (adjacent carbon atoms) that constituted the ring-opened epoxy ring. Specific examples and preferred embodiments of the conjugated diene polymer portion of the modified conjugated diene polymer are the same as those of the conjugated diene polymer in the above-mentioned epoxidation step.

[0048] (Ring opening rate) The ring-opening rate of the modified conjugated diene polymer is not particularly limited, but is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 50 mol% or more, even more preferably 60 mol% or more, particularly preferably 70 mol% or more, and most preferably 90 mol% or more, because the effects of the present invention are more excellent. The upper limit of the ring-opening rate is not particularly limited, and is 100 mol%. Here, the ring-opening ratio is the ratio of opened epoxy rings in the epoxidized conjugated diene polymer used in the ring-opening step. For example, when the epoxidized conjugated diene polymer used in the ring-opening step has 10 epoxy rings and all of them are opened, the ring-opening ratio of the modified conjugated diene polymer is 100 mol%.

[0049] (epoxy ring residual rate) The epoxy ring residual ratio of the modified conjugated diene polymer is not particularly limited, but in order to obtain a better effect of the present invention, it is preferably 90 mol% or less, more preferably 70 mol% or less, even more preferably 50 mol% or less, even more preferably 40 mol% or less, particularly preferably 30 mol% or less, and most preferably 10 mol% or less. The lower limit of the epoxy ring residual ratio is not particularly limited, and is 0%. Here, the epoxy ring residual ratio is the ratio of the epoxy rings in the epoxidized conjugated diene polymer used in the ring-opening step that are not opened. For example, when the epoxidized conjugated diene polymer used in the ring-opening step has 10 epoxy rings and all of them are opened, the epoxy ring residual ratio of the modified conjugated diene polymer is 0 mol%.

[0050] (Diol ratio) The diol ratio of the modified conjugated diene polymer is not particularly limited, but is preferably 1 mol% or more, more preferably 10 mol% or more, even more preferably 30 mol% or more, particularly preferably 60 mol% or more, and most preferably 70 mol% or more, because the effects of the present invention are more excellent. The upper limit of the diol ratio is not particularly limited, and is 100 mol%. Here, the diol conversion rate is the ratio of hydroxyl groups introduced to two carbon atoms (adjacent carbon atoms) that constituted the opened epoxy rings of the epoxidized conjugated diene polymer used in the ring-opening step. For example, if there are 10 epoxy rings in the epoxidized conjugated diene polymer used in the ring-opening step, all of them are ring-opened, and hydroxyl groups are introduced to adjacent carbon atoms (total of 12 carbon atoms) that constituted six of the epoxy rings, the diol conversion rate is 60%.

[0051] (denaturation rate) The modification rate of the modified conjugated diene polymer is not particularly limited, but in order to obtain a more excellent effect of the present invention, the modification rate is preferably 1 to 99 mol%, more preferably 2 to 50 mol%, even more preferably 3 to 50 mol%, and particularly preferably 5 to 20 mol%. Here, the modification rate is the ratio of the carbon-carbon double bonds of the conjugated diene units (e.g., butadiene units) in the conjugated diene polymer used in the epoxidation step that are epoxidized to open the ring and introduce hydroxyl groups. For example, if there are 100 carbon-carbon double bonds of the conjugated diene units in the conjugated diene polymer used in the epoxidation step, 10 of them are epoxidized (resulting in 10 epoxy rings), all of them are ring-opened, and hydroxyl groups are introduced to the adjacent carbon atoms (total of 12 carbon atoms) that constituted 6 of the epoxy rings, the modification rate of the modified conjugated diene polymer is 6 mol%.

[0052] (Preferred embodiment) The modified conjugated diene polymer is preferably a modified conjugated diene polymer having units represented by the following formulas (A1) to (A3), (B1) to (B3), and (C) (hereinafter also referred to as a "specific modified conjugated diene polymer"), because the effects of the present invention are more excellent. Here, the unit represented by formula (A1) is a conjugated diene unit (cis or trans type), the unit represented by formula (A2) is an epoxidized version of formula (A1), and the unit represented by formula (A3) is a ring-opened version of formula (A2). The unit represented by formula (B1) is a conjugated diene unit (vinyl type), the unit represented by formula (B2) is an epoxidized version of formula (B1), and the unit represented by formula (B3) is a ring-opened version of formula (B2). The unit represented by formula (C) is an aromatic vinyl unit.

[0053] [ka]

[0054] In formulae (A1) to (A3), (B1) to (B3) and (C), R represents a hydrogen atom or an aliphatic hydrocarbon group. A plurality of R's may be the same or different. In formula (C), Ar represents an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be linear, branched or cyclic. Specific examples of the aliphatic hydrocarbon group include linear or branched alkyl groups (particularly having 1 to 30 carbon atoms), linear or branched alkenyl groups (particularly having 2 to 30 carbon atoms), linear or branched alkynyl groups (particularly having 2 to 30 carbon atoms), etc. Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups having 6 to 18 carbon atoms, such as a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

[0055] In the formulas (A1) to (A3), (B1) to (B3), and (C), a1 to a3, b1 to b3, and c represent the proportion (mol %) of each unit. In order to obtain better effects of the present invention, a1 is preferably from 1 to 99 mol %, more preferably from 50 to 95 mol %, and even more preferably from 70 to 90 mol %. In order to obtain a better effect of the present invention, b1 is preferably from 1 to 99 mol %, more preferably from 50 to 95 mol %, and further preferably from 70 to 90 mol %. For reasons of superior effects of the present invention, a1+b1 is preferably from 1 to 99 mol %, more preferably from 50 to 95 mol %, and further preferably from 70 to 90 mol %. For reasons of superior effects of the present invention, a2 is preferably 0 to 99 mol %, more preferably 0 to 50 mol %, further preferably 0 to 30 mol %, and particularly preferably 0 to 10 mol %. For reasons of superior effects of the present invention, b2 is preferably 0 to 99 mol %, more preferably 0 to 50 mol %, further preferably 0 to 30 mol %, and particularly preferably 0 to 10 mol %. Because the effects of the present invention are superior, a1+b2 is preferably 0 to 99 mol %, more preferably 0 to 50 mol %, further preferably 0 to 30 mol %, and particularly preferably 0 to 10 mol %. For reasons of superior effects of the present invention, a3 is preferably 0.1 to 99 mol %, more preferably 0.5 to 50 mol %, further preferably 0.8 to 40 mol %, and particularly preferably 1 to 20 mol %. For reasons of better effects of the present invention, b3 is preferably 0.1 to 99 mol %, more preferably 0.5 to 50 mol %, further preferably 0.8 to 40 mol %, and particularly preferably 1 to 20 mol %. Because the effects of the present invention are superior, a3+b3 is preferably 0.1 to 99 mol %, more preferably 0.5 to 50 mol %, even more preferably 0.8 to 40 mol %, and particularly preferably 1 to 20 mol %. Because the effects of the present invention are superior, c is preferably 0 to 90 mol %, more preferably 0 to 50 mol %, further preferably 0 to 30 mol %, and particularly preferably 0 to 25 mol %.

[0056] (molecular weight) The molecular weight of the modified conjugated diene polymer is not particularly limited, but the preferred ranges of Mn, Mw and PDI and the reasons why they are preferred are the same as those of the above-mentioned conjugated diene polymer.

[0057] [Modified conjugated diene polymer] The modified conjugated diene polymer of the present invention (hereinafter also referred to as "the polymer of the present invention") is a modified conjugated diene polymer produced by the above-mentioned method of the present invention. The modified conjugated diene polymer is as described above.

[0058] [Application] The polymer of the present invention is suitably used in rubber compositions (for example, rubber compositions used in tires, conveyor belts, hoses, vibration-proof materials, rubber rolls, outer covers of railway vehicles, etc.). EXAMPLES

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0060] [Production Example] The modified polybutadiene was prepared as follows.

[0061] <Epoxidation process> A methylene chloride solution (100 mL) of m-chloroperbenzoic acid (mCPBA) (Kanto Chemical, 25% water content, 7.0 g) was added dropwise to a methylene chloride solution (150 mL) of polybutadiene (1,4-cis BR, Mn=199,000, Mw=490,000, PDI=2.5, 10.2 g) and stirred at room temperature for 24 hours. The resulting solution was added dropwise to methanol (Kanto Chemical, 1.5 L) and the solid component was separated. The solid component was dissolved in tetrahydrofuran (THF) (Kanto Chemical, 200 mL) and re-precipitated by adding dropwise to methanol to obtain a white solid (10.4 g). Regarding the obtained white solid 1 H-NMR measurement (CDCl3) revealed that the epoxy ring-derived fluorine atom was detected at 2.9 ppm. 1H signal was observed, and it was found that the carbon-carbon double bonds of polybutadiene were epoxidized to obtain epoxidized polybutadiene (Mn = 205,000, Mw = 495,000, PDI = 2.4) with an epoxidation rate of 16 mol%.

[0062] <Ring opening process> The epoxidized polybutadiene (10.3 g) obtained in the above-mentioned epoxidation step was dissolved in toluene (Kanto Chemical, 150 mL). A solution of hydrazinium sulfate (Kanto Chemical, 5.2 g) in water (80 mL) was added to the obtained solution, and the mixture was stirred under reflux conditions for 48 hours. After that, the insoluble components of the obtained solution were taken out, and water (100 mL) was added to the insoluble components, and the mixture was stirred at room temperature to remove the inorganic components. This operation was repeated twice. The insoluble components were dried to obtain a pale yellow solid component (10.3 g) insoluble in THF. The pale yellow solid component obtained was 13 C-NMR (CPMAS) measurement revealed that the epoxy ring-derived 13 The C signal disappears, and the C signal at 73 ppm is due to the adjacent carbon atom with a hydroxyl group. 13 A C signal was observed (at around 70 ppm, originating from a single carbon atom (not adjacent carbon atoms) with a hydroxyl group). 13 It was found that all epoxy rings of the epoxidized polybutadiene were opened, and a modified polybutadiene having hydroxyl groups on adjacent carbon atoms (ring-opening rate: 100 mol%, diol rate: 50 mol% or more, modification rate: 8 to 16 mol%) (Mn = 205,000, Mw = 495,000, PDI = 2.4) was obtained. The modified polybutadiene obtained corresponds to the above-mentioned specific modified conjugated diene polymer. Here, all R in the formulas (A1) and (A3) are hydrogen, a1 is 84 mol%, and a3 is 8 to 16 mol%.

[0063] 〔evaluation〕 The resulting modified polybutadiene (Examples) and the unmodified polybutadiene (1,4-cis BR, Mn=199,000, Mw=490,000, PDI=2.5) (Comparative Example) were subjected to dynamic viscoelasticity measurement (frequency: 6 cpm (cycles per minute), dynamic strain: 2%, temperature range: 30 to 150°C) to measure the shear modulus and tan δ (loss tangent). The results are shown in Table 1. The shear modulus was expressed as an index with the comparative example being set at 100. A higher shear modulus indicates higher toughness, and a lower tan δ indicates lower energy loss.

[0064] [Table 1]

[0065] As can be seen from Table 1, the modified polybutadiene produced by the method of the present invention (Examples) exhibited superior toughness and small energy loss compared to the polybutadiene before modification (Comparative Examples).

Claims

1. an epoxidation step of reacting a conjugated diene polymer with a peroxide to epoxidize the carbon-carbon double bonds of the conjugated diene polymer to obtain an epoxidized conjugated diene polymer; a ring-opening step of reacting the epoxidized conjugated diene polymer with water without using a carbon solid acid to open epoxy rings of the epoxidized conjugated diene polymer, thereby obtaining a modified conjugated diene polymer, which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms, The modified conjugated diene polymer has a weight average molecular weight of 100,000 or more.

2. 2. The method for producing a modified conjugated diene polymer according to claim 1, wherein the conjugated diene polymer is a butadiene polymer, an isoprene polymer, or an aromatic vinyl-conjugated diene copolymer.

3. The method for producing a modified conjugated diene polymer according to claim 1 or 2, wherein a ratio of adjacent carbon atoms having hydroxyl groups in the modified conjugated diene polymer to carbon-carbon double bonds in the conjugated diene polymer is 1 to 50 mol %.

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