Method for dissolving conjugated diene-based polymer, rubber composition, method for producing same, adhesive, and laminated body using same

Abstract

Provided is a method that is for recovering a rubber composition containing a conjugated diene-based polymer and that favorably and easily dissolves the rubber composition in a solvent.　A method for dissolving a conjugated diene-based polymer according to the present invention comprises: a first step for preparing a rubber composition by mixing a conjugated diene-based polymer (A) which has a functional group with a metal salt (C) which generates bivalent metal ions; a second step for immersing the rubber composition in a solvent (S) to swell the rubber composition; and a third step for adding a compound (B), which is soluble in the solvent (S), to the liquid obtained in the second step, wherein when δA (cal / cm3)0.5 is defined as the solubility parameter of the functional group in the conjugated diene-based polymer (A), δS (cal / cm3)0.5 is defined as the solubility parameter of the solvent (S), and δB (cal / cm3)0.5 is defined as the solubility parameter of the compound (B) which is soluble in the solvent (S), the values of the solubility parameters satisfy the relationship represented by the following formula (1).　(1): δS<δA≤δB

Description

Method for dissolving conjugated diene polymer, rubber composition and method for producing the same, adhesive and laminate using the same

[0001] The present invention relates to a method for dissolving a conjugated diene polymer, a rubber composition and a method for producing the same, an adhesive and a laminate using the same.

[0002] Conjugated diene polymers obtained by polymerization using conjugated diene compounds have various excellent properties such as heat resistance, abrasion resistance, mechanical strength, and moldability, and are therefore widely used in various industrial products such as pneumatic tires, vibration-proof rubber, hoses, and adhesives. Generally, sulfur, peroxides, organic compounds, etc. are used for crosslinking conjugated diene polymers. Since the crosslinking of such conjugated diene polymers forms covalent bonds, crosslinking / decrosslinking is irreversible, making it difficult to recover or reuse the conjugated diene polymers. Meanwhile, dynamic crosslinking using hydrogen bonds or ionic bonds is known, but decrosslinking may occur at high temperatures of around 100°C, or conversely, decrosslinking may not be permanently achieved, which presents practical problems.

[0003] Recovery and reuse of conjugated diene polymers requires a technique for dissolving the conjugated diene polymer in a solvent to prepare a polymer solution and then regenerating the conjugated diene polymer from this polymer solution. For example, Patent Documents 1 and 2 describe a method for swelling or dissolving ethylene-propylene-diene copolymer rubber (EPDM) as a technique for dissolving a conjugated diene polymer in a solvent. Patent Documents 1 and 2 describe that EPDM can be swelled or dissolved by contacting EPDM with an ionic liquid comprising benzoate ions and quaternary ammonium ions.

[0004] JP 2015-074705 A JP 2015-096593 A

[0005] However, in the conventional methods for dissolving a conjugated diene polymer, it was not possible to recover and reuse the conjugated diene polymer after dissolving the conjugated diene polymer in a solvent, and it was also difficult to prevent decrosslinking of the conjugated diene polymer at high temperatures or to artificially control crosslinking / decrosslinking.

[0006] Some aspects of the present invention provide a method for dissolving a conjugated diene polymer in a solvent easily and simply. Also, some aspects of the present invention provide a rubber composition that prevents decrosslinking at high temperatures and allows crosslinking / decrosslinking to be artificially controlled. Furthermore, some aspects of the present invention provide a method for recovering and reusing a rubber composition from a solution of a rubber composition containing a conjugated diene polymer, and a laminate having easy dismantling properties using the dissolving method.

[0007] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized as any of the following aspects.

[0008] One aspect of the method for dissolving a conjugated diene polymer according to the present invention comprises: a first step of preparing a rubber composition by mixing a conjugated diene polymer (A) having a functional group with a metal salt (C) that generates a divalent metal ion; a second step of immersing the rubber composition in a solvent (S) to cause it to swell; and a third step of adding a compound (B) soluble in the solvent (S) to the liquid obtained in the second step, wherein the solubility parameter of the functional group contained in the conjugated diene polymer (A) having a functional group is δ Ａ (cal / cm ３ ) ０．５ , the solubility parameter of the solvent (S) is δ Ｓ (cal / cm ３ ) ０．５ The solubility parameter of the compound (B) soluble in the solvent (S) is δ Ｂ (cal / cm ３ ) ０．５ When δ is set, the values ​​of the solubility parameters satisfy the relationship of the following formula (1): Ｓ <δ Ａ ≦δ Ｂ (1)

[0009] In one embodiment of the method for dissolving a conjugated diene-based polymer, the functional group may be at least one group selected from the group consisting of a pyridyl group, a morpholino group, an imidazole group, and an amino group.

[0010] In any one of the above-mentioned embodiments of the method for dissolving a conjugated diene-based polymer, the metal salt (C) that generates a divalent metal ion has a solubility parameter δ of 9.0 or more and 9.5 or less. Ｓ The metal salt may be soluble in the solvent (S) having the formula:

[0011] In any embodiment of the method for dissolving a conjugated diene-based polymer, the metal salt (C) that generates a divalent metal ion may be at least one metal salt selected from the group consisting of zinc, cobalt, nickel, iron, copper, and manganese.

[0012] In any one embodiment of the method for dissolving a conjugated diene polymer, the content of structural units derived from monomers having a functional group in the conjugated diene polymer (A) having a functional group may be 2 mol % to 30 mol % when the total amount of all structural units is 100 mol %.

[0013] In any embodiment of the method for dissolving a conjugated diene polymer, the compound (B) soluble in the solvent (S) may be at least one compound selected from the group consisting of pyridines, morpholines, imidazoles, and amines.

[0014] In any embodiment of the method for dissolving a conjugated diene polymer, the conjugated diene polymer (A) having a functional group may be obtained by polymerizing a conjugated diene compound, an aromatic vinyl compound, and a monomer having a functional group in an aqueous solvent.

[0015] One embodiment of the method for producing a rubber composition according to the present invention includes a first step of mixing a conjugated diene-based polymer (A) having a functional group with a metal salt (C) that generates a divalent metal ion to prepare a rubber composition.

[0016] In one embodiment of the method for producing the rubber composition, the method may further include a second step of immersing the rubber composition in a solvent (S) to swell it, a third step of adding a compound (B) soluble in the solvent (S) to the liquid obtained in the second step, and a fourth step of removing a part or all of the solvent (S).

[0017] In any one of the above-mentioned embodiments of the method for producing a rubber composition, the solubility parameter of the functional group contained in the conjugated diene polymer (A) having a functional group is set to δ Ａ (cal / cm ３ ) ０．５ , the solubility parameter of the solvent (S) is δ Ｓ (cal / cm ３ ) ０．５ The solubility parameter of the compound (B) soluble in the solvent (S) is δ Ｂ (cal / cm ３ ) ０．５ When δ is set as δ, the values ​​of the solubility parameters may satisfy the relationship of the following formula (1): Ｓ <δ Ａ ≦δ Ｂ (1)

[0018] One embodiment of the rubber composition according to the present invention contains a conjugated diene polymer (A) having a functional group and a metal salt (C) that generates a divalent metal ion.

[0019] In one embodiment of the rubber composition, the rubber composition may further contain a filler and a crosslinking agent.

[0020] An adhesive according to one embodiment of the present invention contains the rubber composition according to any one of the above embodiments.

[0021] One aspect of the laminate according to the present invention is formed by interposing the rubber composition of any one of the above aspects or the adhesive of any one of the above aspects between a first substrate and a second substrate.

[0022] One aspect of the method for peeling off a laminate according to the present invention comprises a step of applying or immersing a solution α on the laminate of the above aspect, wherein the solution α contains a solvent (S) and a compound (B) soluble in the solvent (S), and the solubility parameter of the functional group of the conjugated diene-based polymer (A) having a functional group is δ Ａ (cal / cm ３ ) ０．５ , the solubility parameter of the solvent (S) is δ Ｓ (cal / cm ３ ) ０．５ The solubility parameter of the compound (B) soluble in the solvent (S) is δ Ｂ(cal / cm ３ ) ０．５ When δ is set, the values ​​of the solubility parameters satisfy the relationship of the following formula (1): Ｓ <δ Ａ ≦δ Ｂ (1)

[0023] According to the method for dissolving a conjugated diene polymer of the present invention, a rubber composition containing a conjugated diene polymer can be easily and satisfactorily dissolved in a solvent by replacing a "specific functional group-metal ion bond" with a "compound (B)-metal ion" bond. This means that the rubber composition does not easily uncrosslink at high temperatures and that crosslinking / uncrosslinking can be controlled artificially. Therefore, when the rubber composition is used as an adhesive between components, it becomes possible to easily dismantle components by crosslinking / uncrosslinking.

[0024] Fig. 1 is a perspective view schematically showing a laminate 100 according to this embodiment. Fig. 2 is a cross-sectional view taken along line A-A of the laminate 100 shown in Fig. 1. Fig. 3 is a perspective view schematically showing a laminate 200 according to this embodiment. Fig. 4 is a cross-sectional view taken along line B-B of the laminate 200 shown in Fig. 3.

[0025] Preferred embodiments of the present invention will be described in detail below. It should be understood that the present invention is not limited to the embodiments described below, but also includes various modifications that are implemented within the scope of the present invention.

[0026] In this specification, "(meth)acrylic..." means "acrylic..." or "methacrylic...", "...(meth)acrylate" means "...acrylate" or "...methacrylate", and "...(meth)acryloyl..." means "...acryloyl..." or "...methacryloyl...".

[0027] In this specification, the functional group contained in the "conjugated diene polymer (A) having a functional group" may be referred to as a "specific functional group."

[0028] In this specification, the "solubility parameter" is calculated using the Fedors method (R.F. Fedors, Polym. Eng. Sci., 14(2), 147-154 (1974)), and is expressed as "(cal / cm ３ ) ０．５ " is expressed in units of ".

[0029] In this specification, a numerical range described using "X to Y" means that the range includes the numerical value X as the lower limit and the numerical value Y as the upper limit.

[0030] 1. Method for Dissolving Conjugated Diene Polymers A method for dissolving conjugated diene polymers according to one embodiment of the present invention comprises the following steps: a first step of preparing a rubber composition by mixing a conjugated diene polymer (A) having a functional group (hereinafter also referred to simply as "conjugated diene polymer (A)") with a metal salt (C) that generates divalent metal ions (hereinafter also referred to simply as "metal salt (C)"); a second step of immersing the rubber composition in a solvent (S) to cause it to swell; and a third step of adding a compound (B) soluble in the solvent (S) (hereinafter also referred to simply as "compound (B)") to the liquid obtained in the second step. Here, the solubility parameter of the functional group of the conjugated diene polymer (A) is defined as δ Ａ (cal / cm ３ ) ０．５ , the solubility parameter of the solvent (S) is δ Ｓ (cal / cm ３ ) ０．５ , the solubility parameter of the compound (B) is δ Ｂ (cal / cm ３ ) ０．５ When δ is set, the values ​​of the solubility parameters satisfy the relationship of the following formula (1): Ｓ <δ Ａ ≦δ Ｂ (1) Each step of the method for dissolving a conjugated diene polymer according to this embodiment will be described below.

[0031] 1.1. First Step The first step is to prepare a rubber composition by mixing a conjugated diene polymer (A) having a functional group with a metal salt (C) that generates a divalent metal ion. The rubber composition thus obtained does not easily uncrosslink at high temperatures, and crosslinking / uncrosslinking can be artificially controlled. Furthermore, the rubber composition exhibits excellent rubber properties and toughness superior to that of commonly used rubber product components. Furthermore, when the rubber composition contains a filler or crosslinking agent described below, in addition to the reinforcing effect of the filler, the bond between the specific functional group and the metal ion exhibits a sacrificial bonding action, thereby further improving toughness.

[0032] The conjugated diene polymer (A) may be a copolymer of a conjugated diene compound and a monomer having a functional group, but from the viewpoint of increasing strength, it is preferably a copolymer of a conjugated diene compound, an aromatic vinyl compound, and a monomer having a functional group.

[0033] Examples of conjugated diene compounds include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, and 2-chloro-1,3-butadiene. Among these, 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene are preferred. Each of the conjugated diene compounds may be used alone, or two or more may be used in combination.

[0034] Examples of aromatic vinyl compounds include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-tert-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-tert-butylstyrene, 3-tert-butylstyrene, 4-tert-butylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene (e.g., 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene). Among these, styrene and α-methylstyrene are preferred. The aromatic vinyl compounds may be used alone or in combination of two or more.

[0035] The functional group possessed by the functional group-containing monomer is preferably a cationic functional group, and more preferably at least one group selected from the group consisting of a pyridyl group, a morpholino group, an imidazole group, and an amino group. When the conjugated diene polymer (A) has the specific functional group, the "specific functional group-metal ion bond" is replaced with a "compound (B)-metal ion" bond by undergoing the second and third steps described below, and the conjugated diene polymer (A) can be dissolved in a solvent. Each of the monomers having a functional group may be used alone, or two or more may be used in combination.

[0036] Examples of the monomer having a pyridyl group include 2-vinylpyridine, 4-vinylpyridine, 5-methyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine, etc. Among these, 2-vinylpyridine and 4-vinylpyridine are preferred.

[0037] Examples of the monomer having a morpholino group include N-(meth)acryloylmorpholine and morpholinoethyl (meth)acrylate.

[0038] Examples of the monomer having an imidazole group include N-vinylimidazole, 4-vinylimidazole, allylimidazole, 1-benzyl-2-(vinyloxymethyl)imidazole, and 1-benzyl-2-(vinyloxyethyloxymethyl)imidazole.

[0039] Examples of the monomer having an amino group include 2-aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, monomethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, monoethylaminopropyl (meth)acrylate, and diethylaminopropyl (meth)acrylate.

[0040] The content of the structural units derived from monomers having a functional group in the conjugated diene polymer (A) is preferably 2 mol % to 30 mol %, more preferably 2 mol % to 20 mol %, and particularly preferably 5 mol % to 20 mol %, when the total amount of all structural units is 100 mol %. When the content of the structural units derived from monomers having a functional group is within the above range, the conjugated diene polymer (A) having a functional group has a good balance between strength and solubility in solvents.

[0041] When the conjugated diene polymer (A) is a copolymer of a conjugated diene compound, an aromatic vinyl compound, and a monomer having a functional group, the content of structural units derived from the aromatic vinyl compound in the conjugated diene polymer (A) is preferably 2 mol % to 30 mol %, and more preferably 3 mol % to 25 mol %, when the total amount of all structural units is taken as 100 mol %, from the viewpoint of increasing the strength of the conjugated diene polymer (A). １This is a value measured by H-NMR.

[0042] The polymerization method may be any of bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization, but emulsion polymerization in an aqueous medium is particularly preferred. A known method can be used for this emulsion polymerization. For example, the conjugated diene polymer (A) can be obtained by emulsifying a monomer in an aqueous medium in the presence of an emulsifier, initiating polymerization with a radical polymerization initiator, and terminating the polymerization with a polymerization terminator after a desired polymerization conversion rate is reached.

[0043] When produced by emulsion polymerization, emulsifiers include anionic surfactants, nonionic surfactants, and amphoteric surfactants. These emulsifiers can be used alone or in combination of two or more. To obtain a stable emulsion dispersion, anionic surfactants are typically used, such as salts of long-chain fatty acids having 10 or more carbon atoms, rosinate salts, and linear alkyl group-containing benzenesulfonates. Specific examples include potassium salts and sodium salts of capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, octylbenzenesulfonic acid, dodecylbenzenesulfonic acid, dodecyldiphenyloxidesulfonic acid, and dodecyldiphenyletherdisulfonic acid. Fluorine-based surfactants can also be used.

[0044] The radical polymerization initiator used in the polymerization may be an organic peroxide such as benzoyl peroxide, lauroyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, paramenthane hydroperoxide, trimethylbicycloheptyl hydroperoxide, di-tert-butyl peroxide, or dicumyl peroxide. Also usable are diazo compounds such as azobisisobutyronitrile, inorganic peroxides such as potassium persulfate, and redox catalysts such as combinations of these peroxides with ferrous sulfate. These radical polymerization initiators may be used alone or in combination of two or more.

[0045] A chain transfer agent (molecular weight regulator) can also be used to adjust the molecular weight of the conjugated diene polymer (A). Examples of the chain transfer agent include alkyl mercaptans such as tert-dodecyl mercaptan and n-dodecyl mercaptan, carbon tetrachloride, thioglycols, diterpenes, terpinolene, γ-terpinenes, and α-methylstyrene dimer.

[0046] In the polymerization of the conjugated diene polymer (A) by emulsion polymerization, the respective monomers, emulsifier, radical polymerization initiator, chain transfer agent, etc. may be all charged into a reaction vessel at once to initiate polymerization, or the respective components may be added continuously or intermittently while the reaction is continuing. The polymerization of the conjugated diene polymer (A) can be carried out using a reactor from which oxygen has been removed, usually at a temperature of 0 to 100°C, preferably 0 to 80°C. Operating conditions such as temperature or stirring can also be changed as appropriate during the reaction. The polymerization method may be continuous or batchwise.

[0047] Furthermore, gelation may occur if the polymerization conversion rate becomes too high. Therefore, it is preferable to suppress the polymerization conversion rate to 85% or less, more preferably to 80% or less, and it is particularly preferable to terminate the polymerization when the polymerization conversion rate is in the range of 30 to 70%. The polymerization is terminated by adding a polymerization terminator when the desired polymerization conversion rate is reached. Examples of the polymerization terminator include amine compounds such as hydroxylamine and diethylhydroxylamine, and quinone compounds such as hydroquinone. After the polymerization is terminated, unreacted monomers can be removed from the reaction system as needed by steam distillation or the like to obtain a latex in which the conjugated diene polymer (A) is dispersed.

[0048] In the present invention, the latex may be used as it is as the aqueous dispersion of the conjugated diene polymer (A), or a dispersion thereof as an oil-extended rubber to which a rubber extender oil has been added may be used. The rubber extender oil is not particularly limited, and for example, naphthenic, paraffinic, or aromatic process oils may be used. The amount of rubber extender oil used to prepare the oil-extended rubber is preferably 5 to 100 parts by mass, more preferably 10 to 60 parts by mass, based on 100 parts by mass of the conjugated diene polymer (A) contained in the latex.

[0049] The metal salt (C) that generates divalent metal ions includes at least one metal salt selected from the group consisting of zinc, cobalt, nickel, iron, copper, and manganese.

[0050] Specific examples of the metal salt (C) include zinc salts such as zinc oxide, zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc sulfate, zinc sulfide, zinc nitrate, zinc phosphate, zinc carbonate, zinc thiocyanate, zinc permanganate, zinc chromate, zinc trifluoromethanesulfonate, and zinc dodecylsulfonate; cobalt (II) salts such as cobalt (II) chloride, cobalt (II) sulfide, cobalt (II) sulfate, cobalt (II) nitrate, and cobalt (II) carbonate; nickel (II) salts such as nickel (II) chloride, nickel (II) sulfide, nickel (II) sulfate, nickel (II) nitrate, nickel (II) carbonate, and nickel (II) trifluoromethanesulfonate; iron (II) fluoride, iron (II) chloride, Iron(II) salts such as iron(II) bromide, iron(II) iodide, iron(II) sulfide, iron(II) sulfate, iron(II) selenide, iron(II) nitrate, iron(II) phosphate, iron(II) carbonate, and iron(II) metasilicate; copper(II) salts such as copper(II) fluoride, copper(II) chloride, copper(II) bromide, copper(II) iodide, copper(II) sulfide, copper(II) sulfate, copper(II) nitrate, copper(II) phosphate, copper(II) carbonate, and copper(II) trifluoromethanesulfonate; and manganese salts such as manganese(II) chloride, manganese(II) sulfide, manganese(II) sulfate, manganese(II) nitrate, manganese(II) phosphate, manganese(II) carbonate, manganese(II) metasilicate, and manganese(II) acetate.

[0051] The metal salt (C) has a solubility parameter δ of 9.0 or more and 9.5 or less. Ｓ The metal salt (C) is preferably a metal salt soluble in the solvent (S) having a solubility parameter δ of 9.0 or more and 9.5 or less. Ｓ By using a metal salt that is soluble in the solvent (S) having the formula (I), the "specific functional group-metal ion bond" can be easily replaced by the "compound (B)-metal ion bond" in the second and third steps described below, and the conjugated diene polymer (A) can be easily dissolved in the solvent (S).

[0052] The method for preparing the rubber composition by mixing the conjugated diene polymer (A) having a functional group with the metal salt (C) that generates a divalent metal ion is not particularly limited as long as it is a method that allows crosslinking between the specific functional group of the conjugated diene polymer (A) and the divalent metal ion. Examples include the liquid-liquid mixing method and the internal mixing method shown below.

[0053] (Liquid-liquid mixing method) First, a metal salt solution is prepared by dissolving a metal salt (C) in a solvent. Next, a polymer solution is prepared by dissolving a conjugated diene polymer (A) in the same or a different solvent, and the metal salt solution is added to this polymer solution to obtain a mixed solution. Thereafter, the mixed solution is cast in nitrogen, dried under reduced pressure, and pressurized to obtain a rubber composition.

[0054] (Internal Mixing Method) The conjugated diene polymer (A) and the metal salt (C) are thoroughly stirred and mixed using an internal mixer such as a Banbury mixer to obtain a mixture, which is then formed into a sheet using a roll and pressed under pressure to obtain a rubber composition.

[0055] The rubber composition thus obtained may be compounded with the additives shown below for the purpose of further enhancing functionality. Examples of additives include fillers, crosslinking agents, vulcanizing agents, extender oils, etc. When the rubber composition according to this embodiment contains a filler or a crosslinking agent, in addition to the reinforcing effect of the filler, the bond between the specific functional group and the metal ion exhibits a sacrificial bonding action, thereby further improving toughness.

[0056] (Filler) Examples of the filler include silica, as well as reinforcing fillers such as carbon black, clay, and calcium carbonate.

[0057] Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. Among these, wet silica is particularly preferred from the viewpoint of improving fracture properties and achieving both wet grip and low rolling resistance. Highly dispersible silica is also preferred from the viewpoint of improving dispersibility in the rubber composition and improving physical properties and processability. Silica may be used alone or in combination of two or more.

[0058] Examples of carbon black include, but are not limited to, GPF, FEF, HAF, ISAF, SAF, etc. Carbon black may be used alone or in combination of two or more.

[0059] The rubber composition according to the present embodiment preferably contains at least one of silica and carbon. The total amount of silica and carbon black in the rubber composition is preferably 1 to 150 parts by mass, more preferably 5 to 140 parts by mass, and particularly preferably 20 to 130 parts by mass, per 100 parts by mass of the polymer component contained in the rubber composition.

[0060] (Crosslinking Agent) Examples of the crosslinking agent include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyamine compounds, alkylphenol resins having a methylol group, etc., and sulfur is usually used. The amount of sulfur blended is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the total amount of polymer components contained in the rubber composition.

[0061] (Extender Oil) Extender oils include various oils known in the art, such as aromatic oils, paraffinic oils, naphthenic oils, vegetable oils, and oils with a low content of polycyclic aromatic compounds (low PCA oils), such as mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), special residual aromatic extracts (SRAE), and heavy naphthenic oils. Examples of commercially available MES, TDAE, and SRAE include Shell's Catenex SNR (heavy paraffin obtained by solvent dewaxing distillate oil), H&R Wasag AG's Vivatec 500 TDAE, and Japan Energy Corp.'s NC140 SRAE. The extender oil may be blended into the rubber composition by directly adding the oil during rubber compounding, or may be added to an elastomer and then the elastomer may be blended into the rubber composition. The blending amount of the extender oil is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, per 100 parts by mass of the hydrogenated conjugated diene rubber in the rubber composition.

[0062] In addition to the components described above, the rubber composition according to the present embodiment may contain various additives that are generally used in rubber compositions for tires, such as antioxidants, zinc oxide, stearic acid, softeners, vulcanization accelerators, silane coupling agents, compatibilizers, vulcanization aids, processing aids, scorch inhibitors, etc. The blending ratios of these additives may be appropriately selected depending on the various components, as long as the effects of the present disclosure are not impaired.

[0063] The rubber composition according to the present embodiment can be applied to various rubber products as a crosslinked rubber by kneading the above-described rubber composition and other components blended as necessary using a kneader such as an open kneader (e.g., a roll) or an internal kneader (e.g., a Banbury mixer), molding the composition, and then crosslinking (vulcanizing) the resulting mixture. Specific applications include tire applications such as tire treads, undertreads, carcasses, sidewalls, and bead portions; sealants such as packings, gaskets, weatherstrips, and O-rings; interior and exterior skin materials for various vehicles such as automobiles, ships, aircraft, and railways; building materials; vibration-proof rubbers for industrial machinery and equipment; various hoses and hose covers such as diaphragms, rolls, radiator hoses, and air hoses; belts such as power transmission belts; linings; dust boots; medical equipment materials; fenders; insulating materials for electric wires; and other industrial products.

[0064] 1.2. Second Step The second step is a step in which the rubber composition obtained in the first step is immersed in a solvent (S) to cause swelling. It is believed that the second step causes the rubber composition to absorb the solvent (S) and swell, weakening the "specific functional group-metal ion bond" formed in the rubber composition. This facilitates the replacement of the "specific functional group-metal ion bond" with a "compound (B)-metal ion bond" in the third step described below, making it possible to easily dissolve the conjugated diene polymer (A) in the solvent (S).

[0065] In the second step, the rubber composition obtained in the first step is immersed in the solvent (S) and left to stand, for example, at room temperature for 1 to 24 hours.

[0066] Examples of the solvent (S) include aliphatic hydrocarbons such as hexane, heptane, octane, decane, and dodecane; alicyclic hydrocarbons such as cyclohexane, cycloheptane, cyclooctane, and cyclodecane; aromatic hydrocarbons such as toluene, xylene, mesitylene, naphthalene, and tetralin; alcohols such as methanol, ethanol, n-propanol, and isopropanol; ketones such as methylhexyl ketone and dipropyl ketone; esters such as butyl acetate, butyl butyrate, and methyl butanoate; ethers such as dibutyl ether, tetrahydrofuran, and anisole; and lactams such as N-methyl-2-pyrrolidone and 2-pyrrolidone. These solvents (S) can be used alone or in combination of two or more. Among these, toluene, xylene, tetrahydrofuran, methanol, ethanol, and mixed solvents thereof are preferred.

[0067] 1.3. Third Step The third step is a step of adding a compound (B) soluble in the solvent (S) to the liquid obtained in the second step. By going through the third step, the "specific functional group-metal ion bond" formed in the rubber composition is replaced with a "compound (B)-metal ion bond," and the rubber composition can be dissolved in the solvent (S). This means that the rubber composition does not easily decrosslink at high temperatures and that decrosslinking can be artificially controlled.

[0068] In the third step, after it is confirmed that a swollen aggregate in which the rubber composition has swollen has been obtained in the second step, the compound (B) is added to the solvent (S) and thoroughly stirred. The stirring may be carried out using a magnetic stirrer, a chemical mixer, or the like at room temperature for 1 to 24 hours. The amount of the compound (B) added is preferably 0.8 to 1.2 molar equivalents, and more preferably 0.9 to 1.1 molar equivalents, when the functional group content of the conjugated diene polymer (A) is taken as 1 molar equivalent.

[0069] The compound (B) is preferably a compound having a cationic functional group, and more preferably a compound having a structure similar to the functional group of the conjugated diene polymer (A). That is, the compound (B) is preferably at least one compound having a structure similar to the specific functional group and selected from the group consisting of pyridines, morpholines, imidazoles, and amines. This replaces the "specific functional group-metal ion bond" with a "compound (B)-metal ion bond," allowing the conjugated diene copolymer (A) to be dissolved in the solvent (S).

[0070] Examples of pyridines include pyridine, 2-isobutylpyridine, 3-isobutylpyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 4-propylpyridine, 2-n-hexylpyridine, 3-n-hexylpyridine, 3,5-dimethylpyridine, 3,5-diethylpyridine, 2,6-di-tert-butylpyridine, 2-benzylpyridine, 4-benzylpyridine, 2-phenylpyridine, 3-phenylpyridine, 4-phenylpyridine, 2,6-diphenylpyridine, 2-(3-phenylpropyl)pyridine, 4-(3-phenylpropyl)pyridine, and picoline.

[0071] Examples of morpholines include morpholine, N-methylmorpholine, N-ethylmorpholine, and N-propylmorpholine.

[0072] Examples of imidazoles include imidazole, N-isobutylimidazole, 1-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-n-propylimidazole, 2-isopropylimidazole, 1-butylimidazole, 2-butylimidazole, 2-phenylimidazole, 4-methylimidazole, 4-ethylimidazole, 4-nitroimidazole, 4-phenylimidazole, 2-methyl-4-phenylimidazole, 4,5-dimethylimidazole, 1-isobutyl-2-methylimidazole, 2,4,5-trimethylimidazole, 2,4,5-triphenylimidazole, benzimidazole, 2-methylbenzimidazole, and 2-phenylbenzimidazole.

[0073] Examples of amines include tert-butylamine, tert-pentylamine, tert-hexylamine, tert-octylamine, di-tert-butylamine, di-tert-pentylamine, di-tert-hexylamine, di-tert-octylamine, trimethylamine, triethylamine, ethylenediamine, N,N-diisopropylethylamine, N,N-dimethylaniline, and N,N-diethylaniline.

[0074] 1.4. Fourth Step By going through the first to third steps, a polymer solution in which the conjugated diene polymer (A) is dissolved in the solvent (S) can be obtained. A fourth step may then be provided in which a rubber composition is obtained by removing part or all of the solvent (S) from the obtained polymer solution. This allows the rubber composition to be recovered from the polymer solution, thereby facilitating the recycling and reuse of the conjugated diene polymer (A).

[0075] The method for removing the solvent (S) from the polymer solution is not particularly limited, and examples thereof include a method in which the obtained polymer solution is cast in nitrogen and dried under reduced pressure, and a method in which ethanol is added to the obtained polymer solution and stirred, and then an aggregated precipitate and the solution are separated by filtration, and the aggregated precipitate is dried under reduced pressure.

[0076] The rubber composition recovered as described above does not easily decrosslink at high temperatures, and crosslinking / decrosslinking can be artificially controlled. As a result, when the rubber composition is used as an adhesive between components, it becomes possible to easily dismantle components by crosslinking / decrosslinking.

[0077] The recovered rubber composition can be reused as a rubber composition as it is. The recycled rubber composition exhibits excellent rubber properties and exhibits toughness that surpasses that of commonly used rubber product components.

[0078] The recovered rubber composition may be compounded with the above-mentioned additives for the purpose of further improving the functionality.

[0079] 1.5. Solubility Parameter In the method for dissolving a conjugated diene polymer according to this embodiment, the solubility parameter of the functional group contained in the conjugated diene polymer (A) is δ Ａ (cal / cm ３ ) ０．５ , the solubility parameter of the solvent (S) is δ Ｓ (cal / cm ３ ) ０．５ , the solubility parameter of the compound (B) is δ Ｂ (cal / cm ３ ) ０．５ When δ is set, the values ​​of the solubility parameters satisfy the relationship of the following formula (1): Ｓ <δ Ａ ≦δ Ｂ (1)

[0080] When each solubility parameter satisfies the relationship of the above formula (1), the "specific functional group-metal ion bond" formed in the rubber composition is replaced with a "compound (B)-metal ion bond," and the rubber composition can be dissolved in the solvent (S).

[0081] solubility parameter δ Ｓ (cal / cm ３ ) ０．５ is preferably 7.0 to 15.0 (cal / cm ３ ) ０．５ and more preferably 8.0 to 14.0 (cal / cm ３ ) ０．５and particularly preferably 8.5 to 13.0 (cal / cm ３ ) ０．５ is.

[0082] solubility parameter δ Ａ (cal / cm ３ ) ０．５ is preferably 8.0 to 16.0 (cal / cm ３ ) ０．５ and more preferably 9.0 to 15.0 (cal / cm ３ ) ０．５ and particularly preferably 10.0 to 14.0 (cal / cm ３ ) ０．５ is.

[0083] solubility parameter δ Ｂ (cal / cm ３ ) ０．５ is preferably 8.0 to 16.0 (cal / cm ３ ) ０．５ and more preferably 9.0 to 15.0 (cal / cm ３ ) ０．５ and particularly preferably 10.0 to 14.0 (cal / cm ３ ) ０．５ is.

[0084] 2. Examples Specific examples of the present invention will be described below, but the present invention is not limited to these examples. Note that "%" in the following Production Examples, Examples, and Comparative Examples is based on mass unless otherwise specified.

[0085] 2.1. Preparation of Conjugated Diene Polymer (A) Having Functional Groups [Synthesis of SBR1: Emulsion Polymerization Method] 41.1 L of water, 670 g of sodium dodecyldiphenyletherdisulfonate (emulsifier), 7.5 g of potassium chloride (electrolyte), 9.5 g of ethylenediaminetetraacetic acid sodium salt (chelating agent), and 19 g of sodium hydrosulfite (oxygen scavenger) were added to a nitrogen-purged 100 L reactor. Subsequently, 240 mL of water containing 3.99 g of ethylenediamineacetic acid sodium salt, 1.52 g of ferrous sulfate, and 6.27 g of sodium formaldehyde sulfoxylate (activator), 57 g of tert-dodecyl mercaptan (chain transfer agent), 13.5 kg of 1,3-butadiene as monomers, 3.6 kg of styrene, and 900 g of 2-vinylpyridine were charged. The reactor contents were stirred at 330 rpm, and the temperature was adjusted to 10°C. Then, 11.9 g of paramenthane hydroperoxide (polymerization initiator) was added to initiate polymerization. The polymerization was carried out under temperature control conditions (10°C). If the polymerization reaction did not proceed, activator and initiator were added in amounts of 10 to 50% of the initial amounts. After confirming that the polymerization conversion had reached 70%, 900 mL of a 6.3% aqueous solution of N,N-diethylhydroxylamine (polymerization terminator) was added to terminate the polymerization. The pressure was reduced to -0.1 MPa in a stripping tank, and the temperature was raised to 60°C. Stripping was performed for 30 minutes to remove residual monomers and obtain a synthetic rubber latex. Next, calcium chloride (coagulant) was added to warm water at 90°C or higher to a concentration of 0.1% and stirred until dissolved. After confirming sufficient dissolution, the latex obtained by the polymerization was poured into an aqueous calcium chloride solution heated to 50 to 60°C, where it precipitated as a solid rubber. Thereafter, the rubber was washed with water at 70°C, 50°C, and 20°C in that order, and then dried in a hot air dryer adjusted to 90°C, thereby obtaining a pyridyl group-containing conjugated diene polymer SBR1.

[0086] [Synthesis of SBR2 to SBR7: Emulsion Polymerization Method] Polymerization, desolvation, and drying were carried out in the same manner as in the above "Synthesis of SBR1," except that the types and amounts of raw materials used were as shown in Table 1 below, to obtain dispersions of SBR2 to SBR7, respectively. The compositions of SBR1 to SBR7 are shown in Table 1 below.

[0087] [Synthesis of SBR8: Solution Polymerization Method] A nitrogen-purged, 1-liter pressure bottle was charged with 500 parts by mass (200 g) of tetrahydrofuran as a solvent, and 5 parts by mass of styrene, 85 parts by mass of 1,3-butadiene, and 10 parts by mass of 2-vinylpyridine as monomers. The temperature of the reactor contents was adjusted to −78°C, and then 0.064 parts by mass of n-butyllithium (n-BuLi) was added as a polymerization initiator to initiate polymerization. The polymerization was carried out under isothermal conditions, and when the polymerization conversion rate reached 99%, 5 parts by mass of 2-propanol (iPrOH) was added as a polymerization terminator to terminate the reaction after 10 minutes.

[0088] Next, 0.004 parts by mass of 2,6-di-tert-butyl-p-cresol was added to the obtained polymer solution. Next, the solvent was removed by steam stripping using hot water whose pH had been adjusted to 9 with sodium hydroxide, thereby obtaining a conjugated diene-based polymer. Thereafter, the obtained polymer was dried using a heated roll adjusted to 110°C, thereby obtaining SBR8.

[0089]

[0090] 2.2. Evaluation of Solubility of Various Metal Salts in Various Solvents Each metal salt and each solvent shown in Table 2 below were mixed and stirred so that the metal salt concentration was 5% by mass, and the presence or absence of metal salt residue in the solvent was visually confirmed. The evaluation criteria are as follows: (Evaluation criteria) ◯: No metal salt residue was found in the solvent, so it was judged to be soluble. ×: Metal salt residue was found in the solvent, so it was judged to be insoluble.

[0091]

[0092] In Table 2 above, solvents 1 to 4 are the following solvents. <Solvents> Solvent 1: toluene, δ Ｓ =8.9(cal / cm ３ ) ０．５ Solvent 2: tetrahydrofuran, δ Ｓ =9.1(cal / cm ３ ) ０．５ Solvent 3: tetrahydrofuran (95%) + methanol (5%), δ Ｓ =9.3(cal / cm３ ) ０．５ Solvent 4: methanol, δ Ｓ =12.7(cal / cm ３ ) ０．５

[0093] 2.3. Preparation of Rubber Compositions (Examples 1-18, Comparative Examples 1-2) [Liquid-Liquid Mixing Method] A conjugated diene polymer was dissolved in various solvents to a concentration of 10% by mass to prepare a polymer solution. Separately, a solution was prepared in the same solvent by dissolving a certain amount of metal salt in accordance with the metal salt addition concentration ratio, in terms of the amount of metal salt relative to the amount of modifying groups (mol%) of the conjugated diene polymer (A) used. This solution was added to the polymer solution and stirred at room temperature for 10 minutes. The mixed solution was then cast in nitrogen, dried under reduced pressure, and pressed at 80°C for 20 minutes to obtain a sheet (rubber composition). Tensile test specimens were punched out of the sheet in the shape specified in JIS K7139-A25.

[0094] [Internal Mixing Method] The amount of metal salt was determined based on the metal salt addition concentration ratio, as the amount of metal salt relative to the amount (mol%) of modifying groups in the conjugated diene polymer used, relative to 100 parts by mass of the conjugated diene polymer (A). Using a Banbury mixer, an internal mixer, the masses of the conjugated diene polymer (A) and the metal salt were determined so that the volume was approximately 70% of the volume of the mixing and stirring section. The temperature of the mixing and stirring section was set to 50°C, and the stirring section rotor was rotated at a speed of 30 rpm for 5 minutes. After mixing, the mixture was formed into a sheet using a roll and pressed under pressure at 80°C for 20 minutes to obtain a sheet (rubber composition). Samples for tensile testing were prepared by punching out the sheet into the shape specified in JIS K7139-A25.

[0095] [Tensile Test] The sample piece for tensile test obtained above was pulled at a rate of 50 mm / min. The tensile stress M at 100% elongation was １００ (MPa), elongation ratio λ at break Ｂ The tensile tester is recommended to be an Autograph series manufactured by Shimadzu Corporation, but it is sufficient if it is equipped with an appropriate load cell, displacement meter, and sample piece grip.

[0096] [Compositions and Evaluation of Rubber Compositions] Tables 3 and 4 below show the compositions and evaluation results of tensile tests of rubber compositions 1 to 20 produced by the liquid-liquid mixing method or the internal mixing method described above.

[0097]

[0098]

[0099] In Tables 3 and 4, solvents 1 to 4 are the same as those in Table 2. In Table 3, "ESBR" used as the conjugated diene polymer is ENEOS Materials Corporation, product name "ESBR 1502," an emulsion-polymerized styrene-butadiene rubber with a styrene content of 23.5%.

[0100] The results in Tables 3 and 4 above show that the rubber compositions (Examples 1 to 18) obtained by mixing the conjugated diene polymer (A) having a functional group with the metal salt (C) that generates a divalent metal ion exhibit very excellent rubber properties and exhibit toughness that surpasses that of commonly used rubber compositions (Comparative Examples 1 and 2).

[0101] 2.4. Dissolution and Regeneration of Rubber Composition (Examples 19-33, Comparative Examples 3-4) After the tensile test, the test specimen was again immersed in the solvent and left for several hours. Next, after confirming the presence of swollen aggregates in the solvent, compound (B) was added in an amount equal to the amount of modifying groups possessed by the rubber composition immersed in the solvent and stirred. Thereafter, it was visually confirmed whether the swollen aggregates had dissolved. The resulting redissolved liquid was cast in nitrogen, dried under reduced pressure, and pressed at 80°C for 20 minutes to obtain a sheet (rubber composition). Sample pieces for tensile tests were prepared by punching out from the sheet in the shape specified in JIS K7139-A25.

[0102] Tables 5 and 6 below show the materials used to dissolve the rubber compositions and the evaluation results of the tensile tests on the recycled rubber compositions.

[0103]

[0104]

[0105] In Tables 5 and 6, solvents 1 to 4 are the same as those in Table 2, and compounds having the same structure as the functional group are as follows: <Compounds having the same structure as the functional group> Modified compound 1: pyridine, δ Ａ =10.7(cal / cm ３ ) ０．５ Modified compound 2: morpholine, δ Ａ =10.8(cal / cm ３ ) ０．５ Modified compound 3: imidazole, δ Ａ =12.1(cal / cm ３ ) ０．５ Modified compound 4: ethylenediamine, δ Ａ =12.3(cal / cm ３ ) ０．５

[0106] The results in Tables 5 and 6 show that the method for dissolving a conjugated diene polymer according to the present invention enables a rubber composition containing a conjugated diene polymer (A) having a functional group to be dissolved in a solvent easily and satisfactorily. Furthermore, the rubber compositions (Examples 19 to 21 and 29 to 33) obtained by reclaiming the polymer solution exhibit excellent rubber properties and toughness superior to that of commonly used rubber compositions (Comparative Examples 1 and 2).

[0107] 2.5. Evaluation of Rubber Compositions Blended with Additives (Example 34, Comparative Examples 5-6) Using a Banbury mixer, an internal mixer, the total weight was determined so that the volume was approximately 70% of the volume of the mixing and stirring section, and various raw materials were weighed according to Table 7 below. However, natural rubber (RSS #3) was previously masticated with a roll for approximately 10 minutes before use. The mixing and stirring section temperature was set to 100°C, and the stirring section rotor rotation speed was set to 45 rpm. First, the rubber material or rubber composition 4 prepared in Example 2 was mixed with the carbon black through the antioxidant for 10 minutes. Next, using an internal mixer, the mixing and stirring section temperature was set to 50°C, the stirring section rotor rotation speed was set to 30 rpm, and the mixture was mixed with sulfur and vulcanization accelerator. The mixture was then formed into a sheet with a roll and pressure-pressed at 160°C for 30 minutes to obtain a sheet. Tensile test specimens were punched out of the sheet in the shape specified in JIS K7139-A25.

[0108] Table 7 below shows the rubber composition and the evaluation results of the tensile test.

[0109]

[0110] The materials listed in Table 7 above are as follows. <Conjugated diene polymer> ESBR: ENEOS Materials Corporation, emulsion polymerization styrene butadiene rubber, styrene content = 23.5%, trade name "ESBR 1502" Natural rubber: RSS#3 <Additives> Carbon Black N339: Mitsubishi Chemical Corporation, "Diablack N339" Zinc oxide: Mitsui Mining & Smelting Co., Ltd., trade name "Zinc Oxide (Zinc White)" Stearic acid: NOF Corporation, trade name "Beads Stearic Acid Tsubaki" Antioxidant 6C: Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac 6C" (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) Oil treatment sulfur: Hosoi Chemical Industry Co., Ltd., trade name "Oil Sulfur" Vulcanization accelerator NS: Sanshin Chemical Industry Co., Ltd., trade name "Suncerer NS-G"

[0111] As can be seen from the results in Table 7 above, the rubber composition (Example 34) obtained by mixing the conjugated diene polymer (A) having a functional group with the metal salt (C) that generates divalent metal ions exhibits even better rubber properties by adding sulfur and a filler, and exhibits toughness that surpasses that of commonly used rubber compositions (Comparative Examples 5 and 6). This is thought to be due to the reinforcing effect of the filler, as well as the sacrificial bonding action of the bond between the specific functional group and the metal ion, which further improves toughness.

[0112] 2.6. Preparation of Laminates and Evaluation of Easy Disassembly Adhesion (Examples 35-38, Comparative Examples 7-10) 2.6.1. Preparation of Laminates 2.6.1.1. Preparation of Vulcanized Rubber Sheets Except for using the types of rubber and the types and amounts of reagents shown in Table 8 below, kneading and vulcanization were carried out in the same manner as in Comparative Example 5 to obtain vulcanized rubber sheets A and B, each measuring 15 mm long x 5 mm wide x 2 mm thick.

[0113]

[0114] 2.6.1.2. Preparation of Laminate 100 The types of vulcanized rubber sheets used were as shown in Table 9 below. An adhesive layer 20 (length 5 mm × width 5 mm × thickness 0.1 mm) made of rubber composition 4 prepared in Example 2 was sandwiched between vulcanized rubber sheets 10 (length 15 mm × width 5 mm × thickness 2 mm) on both sides as shown in Figures 1 and 2, and heat-treated in a pressure press at 100°C for 30 minutes to prepare a laminate 100 having the shape of a test piece for lap-shear adhesion evaluation as shown in Figures 1 and 2.

[0115] 2.6.1.3. Preparation of Laminate 200 The types of vulcanized rubber sheets and rubber compositions used were as shown in Table 10 below. Adhesive layer 20 (length 5 mm × width 5 mm × thickness 0.1 mm) made of rubber composition 4 prepared in Example 2 was sandwiched on both sides with adhesive layer 30 (length 5 mm × width 5 mm × thickness 0.4 mm) made of rubber composition 23 prepared in Example 34, and this was further sandwiched on both sides with vulcanized rubber sheets 10 (length 15 mm × width 5 mm × thickness 2 mm) as shown in Figures 3 and 4. The laminate 200 was then heat-treated in a pressure press at 100°C for 30 minutes to prepare a laminate 200 having the shape of a test piece for lap-shear adhesion evaluation as shown in Figures 3 and 4.

[0116] 2.6.1.4 Modified Examples of Laminates The laminate 100 has a three-layer structure of vulcanized rubber sheet 10 / adhesive layer 20 made of rubber composition 4 / vulcanized rubber sheet 10, and the laminate 200 has a five-layer structure of vulcanized rubber sheet 10 / adhesive layer 30 made of rubber composition 23 / adhesive layer 20 made of rubber composition 4 / adhesive layer 30 made of rubber composition 23 / vulcanized rubber sheet 10. The laminate may have a laminate structure of three or more layers, as long as it has an adhesive layer such as adhesive layer 20 made of rubber composition 4.

[0117] Furthermore, like the laminate 200, the adhesive layer included in the laminate may be one layer or two or more layers.

[0118] Although the laminate 100 and the laminate 200 use a vulcanized rubber sheet as the substrate, the present invention is not limited to this and various commonly used substrates can be used.

[0119] 2.6.2. Evaluation of Laminate Disassembly Adhesion The laminates 100 and 200 prepared above were fixed at both ends of the test specimen with the tensile test grips, and pulled at a tensile speed of 10 mm / min and a tensile load of 7.5 N to determine whether the adhesive on the test specimen peeled off from the vulcanized rubber sheet. A peeling solution was prepared by adding the same amount of compound (B) as the amount of modifying groups in the rubber composition to solvent (S), and the solution was dripped for 3 minutes to check whether peeling occurred. Disassembly was evaluated by checking whether peeling occurred after the solution was dripped. A tensile tester, such as the Shimadzu Autograph series, is recommended, as long as it is equipped with an appropriate load cell, displacement meter, and sample grip.

[0120]

[0121] As shown in Table 9 (Examples 35 and 36) above, the vulcanized rubber sheet was peeled off by using the stripping solution, demonstrating high ease of dismantling. That is, it can be said that the dissolution method according to the present invention can satisfactorily and easily dissolve the rubber composition containing the conjugated diene polymer (A) having a functional group, and based on the same principle, the adhesive made of the same rubber composition was dissolved by dropping the solution and easily peeled off.

[0122]

[0123] As shown in Table 10 (Examples 37 and 38), even in a laminate 200 with a total of five layers including three adhesive layers using two types of rubber compositions, the vulcanized rubber sheet peeled off when a solution of compound (B) in solvent (S) according to the dissolution method of the present invention was used, demonstrating high ease of dismantling. Note that in Examples 37 and 38, it was found that the adhesive layer 30 did not dissolve, but the adhesive layer 20 dissolves, thereby dismantling the laminate 200.

[0124] The present invention is not limited to the above-described embodiments, and various modifications are possible. The present invention includes configurations that are substantially identical to the configurations described in the embodiments (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect). The present invention also includes configurations in which non-essential parts of the configurations described in the above embodiments are replaced with other configurations. Furthermore, the present invention also includes configurations that achieve the same effects or purposes as the configurations described in the above embodiments. Furthermore, the present invention also includes configurations in which publicly known technology is added to the configurations described in the above embodiments.

[0125] 10... vulcanized rubber sheet, 20... adhesive layer made of rubber composition 4, 30... adhesive layer made of rubber composition 23, 100, 200... laminate

Claims

1. A method for dissolving a conjugated diene polymer in a liquid, comprising: a first step of preparing a rubber composition by mixing a conjugated diene polymer (A) having a functional group with a metal salt (C) that generates divalent metal ions; a second step of immersing the rubber composition in a solvent (S) to cause it to swell; and a third step of adding a compound (B) soluble in the solvent (S) to the liquid obtained in the second step, wherein the solubility parameter of the functional group of the conjugated diene polymer (A) having a functional group is δ Ａ (cal / cm ３ ) ０．５ , the solubility parameter of the solvent (S) is δ Ｓ (cal / cm ３ ) ０．５ The solubility parameter of the compound (B) soluble in the solvent (S) is δ Ｂ (cal / cm ３ ) ０．５ When δ is set as the solubility parameter, the values ​​of the solubility parameters satisfy the relationship of the following formula (1): Ｓ <δ Ａ ≦δ Ｂ (1) 2. The method for dissolving a conjugated diene polymer according to claim 1, wherein the functional group is at least one group selected from the group consisting of a pyridyl group, a morpholino group, an imidazole group, and an amino group.

3. The metal salt (C) that generates the divalent metal ion has a solubility parameter δ of 9.0 or more and 9.5 or less. Ｓ 3. The method for dissolving a conjugated diene polymer according to claim 1 or 2, wherein the metal salt (S) is soluble in the solvent (S) having the formula:

4. A method for dissolving a conjugated diene polymer according to claim 1 or 2, wherein the metal salt (C) that generates the divalent metal ions is at least one metal salt selected from the group consisting of zinc, cobalt, nickel, iron, copper and manganese.

5. A method for dissolving a conjugated diene polymer according to claim 1 or claim 2, wherein the content of structural units derived from monomers having functional groups in the conjugated diene polymer (A) having functional groups is 2 mol % to 30 mol % when the total amount of all structural units is 100 mol %.

6. A method for dissolving a conjugated diene polymer according to claim 1 or 2, wherein the compound (B) soluble in the solvent (S) is at least one compound selected from the group consisting of pyridines, morpholines, imidazoles and amines.

7. A method for dissolving a conjugated diene polymer according to claim 1 or 2, wherein the conjugated diene polymer (A) having a functional group is obtained by polymerizing a conjugated diene compound, an aromatic vinyl compound, and a monomer having a functional group in an aqueous solvent.

8. A method for producing a rubber composition, comprising a first step of mixing a conjugated diene polymer (A) having a functional group with a metal salt (C) that generates a divalent metal ion to prepare a rubber composition.

9. A method for producing a rubber composition according to claim 8, further comprising: a second step of immersing the rubber composition in a solvent (S) to cause it to swell; a third step of adding a compound (B) soluble in the solvent (S) to the liquid obtained in the second step; and a fourth step of removing a part or all of the solvent (S).

10. The solubility parameter of the functional group contained in the conjugated diene polymer (A) having a functional group is δ Ａ (cal / cm ３ ) ０．５ , the solubility parameter of the solvent (S) is δ Ｓ (cal / cm ３ ) ０．５ The solubility parameter of the compound (B) soluble in the solvent (S) is δ Ｂ (cal / cm ３ ) ０．５ The method for producing a rubber composition according to claim 9, wherein the values ​​of the solubility parameters satisfy the relationship of the following formula (1) when δ Ｓ <δ Ａ ≦δ Ｂ (1) 11. A rubber composition comprising (A) a conjugated diene polymer having a functional group and (C) a metal salt that generates a divalent metal ion.

12. The rubber composition according to claim 11, further comprising a filler and a crosslinking agent.

13. An adhesive containing the rubber composition according to claim 11 or 12.

14. A laminate formed by interposing the rubber composition according to claim 11 or claim 12 or the adhesive according to claim 13 between a first substrate and a second substrate.

15. A method for producing a laminate according to claim 14, comprising the steps of applying or immersing a solution α to the laminate, wherein the solution α contains a solvent (S) and a compound (B) soluble in the solvent (S), and the solubility parameter of the functional group of the conjugated diene polymer (A) having a functional group is δ Ａ (cal / cm ３ ) ０．５ , the solubility parameter of the solvent (S) is δ Ｓ (cal / cm ３ ) ０．５ The solubility parameter of the compound (B) soluble in the solvent (S) is δ Ｂ (cal / cm ３ ) ０．５ When δ is set, the values ​​of the solubility parameters satisfy the relationship of the following formula (1): Ｓ <δ Ａ ≦δ Ｂ (1)

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