Cross-linked rubber composition for oil recovery by pyrolysis, oil, and producing method of oil

Abstract

To provide a cross-linked rubber composition that is pyrolyzed and used for recovering oil containing a component to be a raw material of an isoprene skeleton rubber.SOLUTION: Provided is a cross-linked rubber composition for oil recovery by pyrolysis, in which the crosslinked rubber composition contains a rubber component and sulfur, the rubber component includes isoprene skeleton rubber, a content of the isoprene-skeleton rubber is 50 pts.mass or more per 100 pts.mass of the rubber component, the content of sulfur is 8 pts.mass or less relative to 100 pts.mass of the rubber component, and a mass ratio of the isoprene skeleton rubber to sulfur (isoprene-based rubber / sulfur) is 12 or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a crosslinked rubber composition for oil recovery by pyrolysis, an oil, and a method for producing the oil. [Background technology]

[0002] Recently, recycling of used rubber products, including used tires, has been promoted from the viewpoint of protecting the global environment. One such recycling method is a technique for pyrolyzing used rubber products and recovering pyrolysis products such as oil and carbon black (carbide). For example, the following Patent Document 1 discloses a method for recovering carbon and a hydrocarbon mixture from waste tires or similar polymer materials by pyrolysis. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2002-523552 Summary of the Invention [Problem to be solved by the invention]

[0004] As described in the above Patent Document 1 and the like, various studies have been conducted on methods for pyrolyzing used tires, but the components in the oil recovered by pyrolysis have not been studied. In addition, since pyrolysis oil from commercially available tires is generally used as fuel, there is no need to consider the components in the pyrolysis oil. On the other hand, in order to pyrolyze used rubber products and return them to isoprene-based rubbers such as natural rubber and isoprene rubber, which are the main components of rubber products, it is necessary to recover isoprene as a monomer. However, since the pyrolysis oil from commercially available tires contains almost no isoprene, recovering isoprene is difficult.

[0005] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a cross-linked rubber composition that can be thermally decomposed to recover oil containing components (monomers such as isoprene, limonene, etc.) that serve as raw materials for isoprene-skeleton rubber. Another object of the present invention is to provide an oil obtained from such a crosslinked rubber composition, and a method for producing an oil from such a crosslinked rubber composition. [Means for solving the problem]

[0006] The outline of the crosslinked rubber composition for oil recovery by thermal decomposition, the oil, and the method for producing the oil according to the present invention, which solves the above problems, are as follows.

[0007] [1] A crosslinked rubber composition for oil recovery by pyrolysis, comprising: The crosslinked rubber composition includes a rubber component and sulfur, The rubber component contains an isoprene skeleton rubber, The content of the isoprene skeleton rubber is 50 parts by mass or more in 100 parts by mass of the rubber component, the sulfur content is 8 parts by mass or less based on 100 parts by mass of the rubber component, A crosslinked rubber composition, characterized in that a mass ratio of the isoprene skeleton rubber content to the sulfur content (isoprene skeleton rubber / sulfur) is 12 or more. The crosslinked rubber composition of the present invention described in [1] above can be thermally decomposed to recover monomers such as isoprene, which are raw materials for isoprene-skeleton rubber, and oils containing limonene and the like.

[0008] [2] Also containing carbon black, The following formula (1): exp(18.977663905+0.0085742124×A-0.003867326×B-0.028534179×C-0. 251024648×D+(C-3.75)×((D-3.948)×0.0118234107)) / 243316566.160943 + exp(17.436413974+0.0140219114×A-0.00394088×B-0.137558684×D-(A-80)×((A-80)×0.000514996)) / 86230236.8833005 ≥ 0.4 ··· (1) [In the formula, A is the content (parts by mass) of the isoprene skeleton rubber in 100 parts by mass of the rubber component, B is the cetyltrimethylammonium bromide (CTAB) adsorption specific surface area (m 2 / g), C is the content (parts by mass) of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine relative to 100 parts by mass of the rubber component, and D is the amount (parts by mass) of the sulfur relative to 100 parts by mass of the rubber component. By thermally decomposing the crosslinked rubber composition described in [2] above, the yield of components that serve as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, is further increased.

[0009] [3] The crosslinked rubber composition according to [1] or [2], wherein the sulfur content is 5 parts by mass or less per 100 parts by mass of the rubber component. By thermally decomposing the crosslinked rubber composition described in [3] above, the yield of components that serve as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, is further increased.

[0010] [4] The cross-linked rubber composition according to any one of [1] to [3], wherein the sulfur content is 3 parts by mass or less per 100 parts by mass of the rubber component. By thermally decomposing the crosslinked rubber composition described in [4] above, the yield of components that serve as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be further increased.

[0011] [5] The cross-linked rubber composition according to any one of [1] to [4], wherein the content of the isoprene skeleton rubber is 70 parts by mass or more per 100 parts by mass of the rubber component. By thermally decomposing the crosslinked rubber composition described in [5] above, the yield of components that are raw materials for isoprene-skeleton rubber, such as isoprene and limonene, is further increased.

[0012] [6] The cross-linked rubber composition according to any one of [1] to [5], wherein the rubber component consists solely of the isoprene skeleton rubber. By thermally decomposing the crosslinked rubber composition described in [6] above, the yield of components that are raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be further increased.

[0013] [7] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the carbon black is 180 m 2 / g or less of the crosslinked rubber composition according to any one of [2] to [6]. By thermally decomposing the crosslinked rubber composition described in [7] above, the yield of components that serve as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be further increased.

[0014] [8] The crosslinked rubber composition according to any one of [1] to [7], which does not contain an antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. By thermally decomposing the crosslinked rubber composition described in [8] above, the yield of components that serve as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be further increased.

[0015] [9] The crosslinked rubber composition according to any one of [1] to [8], wherein the oil is an oil for producing a rubber composition for tires. According to the crosslinked rubber composition described in [9] above, the crosslinked rubber composition can be chemically recycled.

[0016]

[10] An oil obtained by thermally decomposing the crosslinked rubber composition according to any one of [1] to [9] and recovering the oil. The oil of the present invention described in

[10] above contains a large amount of monomers such as isoprene, which is a raw material for isoprene-based rubber, and limonene.

[0017]

[11] A method for producing an oil, comprising thermally decomposing the crosslinked rubber composition according to any one of [1] to [9]. According to the method for producing oil of the present invention described in

[11] above, it is possible to obtain oil that is rich in monomers such as isoprene, which are raw materials for isoprene-skeleton rubber, and limonene. Effect of the Invention

[0018] According to the present invention, it is possible to provide a crosslinked rubber composition which is used for recovering oil containing components that are raw materials for isoprene skeleton rubber through thermal decomposition. Furthermore, according to the present invention, it is possible to provide an oil obtained from such a crosslinked rubber composition and a method for producing an oil from such a crosslinked rubber composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The crosslinked rubber composition for oil recovery by thermal decomposition, the oil, and the method for producing the oil of the present invention will be illustrated in detail below based on the embodiments.

[0020] <Definition> The compounds described herein may be derived in whole or in part from fossil sources, from biological sources such as plant sources, from recycled sources such as used tires, or from a mixture of two or more of fossil sources, biological sources, and / or renewable sources.

[0021] In this specification, used tires refer to tire products that have been used once or have not been used and are then collected or discarded.

[0022] In this specification, the crosslinked rubber composition refers to a rubber composition after crosslinking a rubber composition, and may be called "crosslinked rubber". The crosslinked rubber composition also includes rubber members, rubber fragments, etc. collected from used rubber products such as used tires.

[0023] <Crosslinked Rubber Composition> The crosslinked rubber composition of the present embodiment is a crosslinked rubber composition for oil recovery by thermal decomposition. The crosslinked rubber composition of the present embodiment is characterized in that it contains a rubber component and sulfur, the rubber component contains an isoprene skeleton rubber, the content of the isoprene skeleton rubber is 50 parts by mass or more per 100 parts by mass of the rubber component, the content of the sulfur is 8 parts by mass or less per 100 parts by mass of the rubber component, and the mass ratio of the content of the isoprene skeleton rubber to the content of the sulfur (isoprene skeleton rubber / sulfur) is 12 or more.

[0024] As described above, conventionally, no study has been made on the components in oil recovered by pyrolysis of used rubber products such as used tires. In response to this, the present inventors have conducted intensive studies with the aim of recovering monomers such as isoprene, which are raw materials for isoprene-skeleton rubber, and have found that when a crosslinked rubber composition containing a rubber component and sulfur, the rubber component contains an isoprene-skeleton rubber, the content of the isoprene-skeleton rubber is 50 parts by mass or more per 100 parts by mass of the rubber component, the content of the sulfur is 8 parts by mass or less per 100 parts by mass of the rubber component, and the mass ratio of the content of the isoprene-skeleton rubber to the content of the sulfur (isoprene-skeleton rubber / sulfur) is 12 or more, oil containing a large amount of monomers such as isoprene and components such as limonene, which are raw materials for isoprene-skeleton rubber, can be recovered. Limonene is a compound consisting of two isoprene units and is a type of isoprene dimer, so it can be used as a raw material for isoprene-skeleton rubber.

[0025] Here, the components that are raw materials for the isoprene skeleton rubber, such as isoprene and limonene, are mainly derived from the isoprene skeleton rubber contained in the crosslinked rubber composition. Therefore, by making the content of the isoprene skeleton rubber 50 parts by mass or more per 100 parts by mass of the rubber component, the yield of the components that are raw materials for the isoprene skeleton rubber, such as isoprene and limonene, is increased. In addition, because sulfur plays a role in crosslinking the rubber component, if there is too much sulfur, the crosslinked rubber composition becomes difficult to thermally decompose, and the amount of complex decomposition products increases, resulting in a decrease in the yield of components (components having an isoprene skeleton) that serve as raw materials for isoprene-skeleton rubber, such as isoprene and limonene. In contrast, by making the sulfur content 8 parts by mass or less per 100 parts by mass of the rubber component, the amount of complex decomposition products produced can be reduced, and the yield of components that serve as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be increased. Also, if the sulfur content is too high relative to the isoprene skeleton rubber content, the crosslinked rubber composition becomes difficult to thermally decompose and the amount of complex decomposition products increases, resulting in a decrease in the yield of components that serve as raw materials for isoprene skeleton rubber, such as isoprene and limonene. On the other hand, by making the mass ratio of the isoprene skeleton rubber content to the sulfur content (isoprene skeleton rubber / sulfur) 12 or more (i.e., by increasing the isoprene skeleton rubber content relatively), the amount of complex decomposition products produced can be reduced and the yield of components that serve as raw materials for isoprene skeleton rubber, such as isoprene and limonene, can be increased. Therefore, by thermally decomposing the crosslinked rubber composition of the present embodiment, monomers such as isoprene, which are raw materials for isoprene-skeleton rubber, and oils rich in limonene and the like can be efficiently recovered.

[0026] (Application) The crosslinked rubber composition of the present embodiment is a crosslinked rubber composition for oil recovery by thermal decomposition, in other words, a crosslinked rubber composition used for recovering oil by thermal decomposition. As described above, the crosslinked rubber composition of the present embodiment is particularly suitable for recovering oil by thermal decomposition because it can efficiently recover monomers such as isoprene, which are raw materials for isoprene-skeleton rubber, and oils containing a large amount of limonene, etc.

[0027] In addition, the oil recovered by pyrolyzing the crosslinked rubber composition is preferably oil for producing a rubber composition for tires. Here, the oil for producing a rubber composition for tires refers to oil that can be a raw material for isoprene-skeleton rubber that is a rubber component of the rubber composition for tires. By using the oil recovered by pyrolyzing the crosslinked rubber composition as a raw material for isoprene-skeleton rubber that is a rubber component of the rubber composition for tires, chemical recycling of the crosslinked rubber composition becomes possible. In addition, when the crosslinked rubber composition is collected from used tires, it can be recycled into tires.

[0028] (Rubber component) The crosslinked rubber composition of the present embodiment contains a rubber component, and the rubber component provides rubber elasticity to the crosslinked rubber composition.

[0029] --Isoprene-based rubber-- The rubber component includes an isoprene-skeleton rubber. The isoprene-skeleton rubber is a rubber whose main skeleton is an isoprene unit, and specific examples thereof include natural rubber (NR) and synthetic isoprene rubber (IR). By pyrolyzing a crosslinked rubber composition containing an isoprene-skeleton rubber as a rubber component, monomers such as isoprene, which are raw materials for the isoprene-skeleton rubber, and oils containing limonene and the like can be recovered.

[0030] The content of the isoprene skeleton rubber is 50 parts by mass or more, and preferably 70 parts by mass or more, per 100 parts by mass of the rubber component. It is more preferable that the rubber component is composed only of the isoprene skeleton rubber. If the content of the isoprene skeleton rubber is less than 50 parts by mass per 100 parts by mass of the rubber component, the yield of raw materials for the isoprene skeleton rubber, such as isoprene and limonene, is reduced. On the other hand, if the content of the isoprene skeleton rubber is 70 parts by mass or more per 100 parts by mass of the rubber component, the yield of raw materials for the isoprene skeleton rubber, such as isoprene and limonene, is further increased. If the rubber component is composed only of the isoprene skeleton rubber, the yield of raw materials for the isoprene skeleton rubber, such as isoprene and limonene, is further increased.

[0031] --Other rubber components-- The rubber component may contain a rubber component other than the isoprene skeleton rubber. The rubber component other than the isoprene skeleton rubber is preferably a diene rubber. The diene rubber is a rubber containing units derived from a diene monomer (diene units), and may further contain units derived from a copolymerizable comonomer. The diene monomer-derived unit enables the diene rubber to be crosslinked (vulcanized), and can exhibit rubber-like elongation and strength. In the crosslinked rubber, the diene rubber is usually present in a crosslinked state, but a part of the diene rubber may not be crosslinked. Specific examples of diene monomers (diene compounds) include 1,3-butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. On the other hand, examples of the copolymerizable comonomer include aromatic vinyl compounds, etc. Specific examples of the aromatic vinyl compounds include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, and p-ethylstyrene. Examples of the diene rubber other than the isoprene skeleton rubber include styrene-butadiene rubber (SBR), butadiene rubber (BR), and chloroprene rubber (CR). Among these, the diene rubber other than the isoprene skeleton rubber is preferably butadiene rubber. When the diene rubber contains butadiene rubber, diene monomers such as butadiene that are easy to reuse can be obtained.

[0032] The amount of the rubber component other than the isoprene skeleton rubber is 50 parts by mass or less, preferably 30 parts by mass or less, and may be 0 part by mass, per 100 parts by mass of the rubber component.

[0033] (sulfur) The cross-linked rubber composition of the present embodiment contains sulfur, which has the effect of cross-linking (vulcanizing) the rubber component, thereby improving the strength of the cross-linked rubber composition. As the sulfur, various types of sulfur can be used, such as ordinary sulfur (soluble sulfur (powdered sulfur) and the like) and insoluble sulfur, and oil treat sulfur and the like can also be used.

[0034] The sulfur content is 8 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and more preferably 1.4 parts by mass or more, relative to 100 parts by mass of the rubber component. If the sulfur content exceeds 8 parts by mass relative to 100 parts by mass of the rubber component, the amount of complex decomposition products produced increases when the crosslinked rubber composition is thermally decomposed, and the yield of components (components having an isoprene skeleton) that serve as raw materials for isoprene skeleton rubber, such as isoprene and limonene, decreases. On the other hand, if the sulfur content is 5 parts by mass or less relative to 100 parts by mass of the rubber component, the yield of components that serve as raw materials for isoprene skeleton rubber, such as isoprene and limonene, further increases. Also, if the sulfur content is 3 parts by mass or less relative to 100 parts by mass of the rubber component, the yield of components that serve as raw materials for isoprene skeleton rubber, such as isoprene and limonene, further increases. Furthermore, when the sulfur content is 1.4 parts by mass or more per 100 parts by mass of the rubber component, the crosslinked rubber composition is sufficiently crosslinked, and various rubber products have excellent strength.

[0035] The mass ratio of the isoprene skeleton rubber content to the sulfur content (isoprene skeleton rubber / sulfur) is 12 or more, preferably 20 or more, and preferably 80 or less. If the mass ratio of the isoprene skeleton rubber content to the sulfur content (isoprene skeleton rubber / sulfur) is less than 12, the amount of complex decomposition products produced when the crosslinked rubber composition is pyrolyzed increases, and the yield of components that serve as raw materials for isoprene skeleton rubber, such as isoprene and limonene, decreases. On the other hand, if the mass ratio of the isoprene skeleton rubber content to the sulfur content (isoprene skeleton rubber / sulfur) is 20 or more, the amount of complex decomposition products produced when the crosslinked rubber composition is pyrolyzed can be further reduced, and the yield of components that serve as raw materials for isoprene skeleton rubber, such as isoprene and limonene, can be further increased. In addition, if the mass ratio of the isoprene skeleton rubber content to the sulfur content (isoprene skeleton rubber / sulfur) is 80 or less, the crosslinked rubber composition is sufficiently crosslinked and has sufficient strength as various rubber products.

[0036] (Carbon Black) The cross-linked rubber composition of the present embodiment preferably further contains carbon black, which reinforces the cross-linked rubber composition and can improve the reinforcing properties of the cross-linked rubber composition. The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination of two or more.

[0037] The carbon black content is preferably 30 parts by mass or more, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less, based on 100 parts by mass of the rubber component. When the carbon black content is 30 parts by mass or more based on 100 parts by mass of the rubber component, the reinforcing property of the crosslinked rubber composition can be further improved. When the carbon black content is 90 parts by mass or less based on 100 parts by mass of the rubber component, the content of the isoprene skeleton rubber in the entire crosslinked rubber composition relatively increases, and therefore, when the crosslinked rubber composition is thermally decomposed, the yield of components serving as raw materials for the isoprene skeleton rubber, such as isoprene and limonene, further increases.

[0038] The crosslinked rubber composition of the present embodiment has the following formula (1): exp(18.977663905+0.0085742124×A-0.003867326×B-0.028534179×C-0. 251024648×D+(C-3.75)×((D-3.948)×0.0118234107)) / 243316566.160943 + exp(17.436413974+0.0140219114×A-0.00394088×B-0.137558684×D-(A-80)×((A-80)×0.000514996)) / 86230236.8833005 ≥ 0.4 ··· (1) By thermally decomposing a crosslinked rubber composition that satisfies the relationship of the above formula (1) (i.e., the value of the left side of formula (1) is 0.4 or more), the yield of components that are raw materials for isoprene-skeleton rubber, such as isoprene and limonene, is further increased.

[0039] In the crosslinked rubber composition of this embodiment, the value of the left side of the above formula (1) is more preferably 0.6 or more, and even more preferably 1.0 or more. When the value of the left side of the formula (1) of the crosslinked rubber composition is 0.6 or more, the yield of the components that are raw materials for isoprene skeleton rubber, such as isoprene and limonene, is further increased. In addition, when the value of the left side of the formula (1) of the crosslinked rubber composition is 1.0 or more, the yield of the components that are raw materials for isoprene skeleton rubber, such as isoprene and limonene, is particularly increased.

[0040] In the above formula (1), A is the content (parts by mass) of the isoprene skeleton rubber in 100 parts by mass of the rubber component. When the content of the isoprene skeleton rubber in the crosslinked rubber composition increases, the amounts of isoprene and limonene produced tend to increase.

[0041] In the above formula (1), B is the cetyltrimethylammonium bromide (CTAB) adsorption specific surface area (m 2 / g). Here, when the crosslinked rubber composition contains two or more kinds of carbon black, the CTAB adsorption specific surface area is an average value taking into account the mass ratio of each carbon black. In other words, when the crosslinked rubber composition contains n kinds of carbon black, the nth kind of carbon black is referred to as "CB n " Then, the following equation (2): (Average) CTAB adsorption specific surface area (m 2 / g)=Σ(CB n CTAB adsorption specific surface area × CB n Content of CB n Content of (2) It can be calculated from: When the CTAB adsorption specific surface area of ​​the carbon black contained in the crosslinked rubber composition increases, the amounts of isoprene and limonene produced tend to decrease. In this specification, the cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​carbon black is a value measured in accordance with JIS K6217-3, and is the external surface area of ​​carbon black excluding micropores, expressed as the specific surface area when CTAB (cetyltrimethylammonium bromide) is adsorbed onto carbon black.

[0042] In the above formula (1), C is the content (parts by mass) of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine in the crosslinked rubber composition relative to 100 parts by mass of the rubber component. When the content of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine in the crosslinked rubber composition increases, the amount of limonene produced tends to decrease. In the crosslinked rubber composition of this embodiment, the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine is not an essential component, and the content of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine may be 0 parts by mass. As described later, it is preferable that the crosslinked rubber composition of this embodiment does not contain the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

[0043] In the above formula (1), D is the content (parts by mass) of the sulfur relative to 100 parts by mass of the rubber component. When the content of sulfur in the crosslinked rubber composition increases, the amounts of isoprene and limonene produced tend to decrease.

[0044] In the above formula (1), the term "exp(18.977663905+0.0085742124×A-0.003867326×B-0.028534179×C-0.251024648×D+(C-3.75)×((D-3.948)×0.0118234107)) / 243316566.160943" (the first term on the left side) is a term calculated from the amount of limonene produced when the crosslinked rubber composition is thermally decomposed. The present inventors have found that there is a correlation between the amount of limonene produced when various rubber compositions (specifically, the rubber compositions in the Examples and Comparative Examples described below) are pyrolyzed and A: the content of isoprene-skeleton rubber, B: the CTAB adsorption specific surface area of ​​carbon black, C: the content of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and D: the sulfur content, and have discovered the above relationships from the regression equation of multiple regression analysis. Here, the oil obtained by pyrolyzing the crosslinked rubber composition was analyzed by a gas chromatograph mass spectrometer (GC / MS), and the area value (integral value) of the limonene peak in the GC chromatogram was normalized by the concentration of the oil in the sample to be used as the objective variable. In addition, multiple regression analysis was performed using A: the content of isoprene skeleton rubber, B: the CTAB adsorption specific surface area of ​​carbon black, C: the content of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and D: the content of sulfur as explanatory variables to calculate the above relational equation.

[0045] In addition, in the above formula (1), the term "exp(17.436413974+0.0140219114×A-0.00394088×B-0.137558684×D-(A-80)×((A-80)×0.000514996)) / 86230236.8833005" (the second term on the left side) is a term calculated from the amount of isoprene produced when the crosslinked rubber composition is thermally decomposed. The present inventors have found that there is a correlation between the amount of isoprene produced when various rubber compositions (specifically, the rubber compositions of the Examples and Comparative Examples described below) are thermally decomposed, and A: the content of isoprene skeleton rubber, B: the CTAB adsorption specific surface area of ​​carbon black, and D: the sulfur content, and have found the above relationship from the regression equation of multiple regression analysis. Here, the oil obtained by pyrolyzing the crosslinked rubber composition was analyzed by a gas chromatograph mass spectrometer (GC / MS), and the area value (integral value) of the isoprene peak in the GC chromatogram was normalized by the concentration of the oil in the sample to be used as the objective variable. In addition, multiple regression analysis was performed using A: the content of isoprene skeleton rubber, B: the CTAB adsorption specific surface area of ​​carbon black, and D: the sulfur content as explanatory variables to calculate the above relational equation.

[0046] In addition, when the crosslinked rubber composition is thermally decomposed, the amount of limonene produced is considerably larger than the amount of isoprene produced, and the relational equation is strongly influenced by the amount of isoprene produced if the amount of isoprene produced is left as is. Therefore, in order to reflect the influence of the amount of isoprene produced and the amount of limonene produced almost equally, the equation (1) was derived by standardization.

[0047] Specifically, the term "exp(18.977663905+0.0085742124×A-0.003867326×B-0.028534179×C-0.251024648×D+(C-3.75)×((D-3.948)×0.0118234107)) / 243316566.160943" in the first term on the left side of the formula is A: content of isoprene skeleton rubber, B: CTAB adsorption specific surface area of ​​carbon black, C: antioxidant. The content of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, D: The sulfur content is calculated by dividing the "exp(18.977663905+0.0085742124×A-0.003867326×B-0.028534179×C-0.251024648×D+(C-3.75)×((D-3.948)×0.0118234107))" by "243316566.160943". In addition, the second term on the left side of the formula, "exp(17.436413974+0.0140219114×A-0.00394088×B-0.137558684×D-(A-80)×((A-80)×0.000514996)) / 86230236.8833005", is the sum of A: isoprene-based rubber content, B: carbon-based rubber content, and C: carbon-based rubber content. CTAB adsorption specific surface area of ​​the rack, D: Calculated from the sulfur content, "exp(17.436413974+0.0140219114×A-0.00394088×B-0.137558684×D-(A-80)×((A-80)×0.000514996))" is divided by "86230236.8833005".

[0048] Here, the value "243316566.160943" is equal to the value of "exp(18.977663905+0.0085742124×A-0.003867326×B-0.028534179×C-0.251024648×D+(C-3.75)×((D-3.948)×0.0118234107))" of the sample that produced the most limonene when analyzed by GC / MS. In other words, the value of the first term on the left side of the sample that produced the most limonene is normalized to 1. In addition, the value "86230236.8833005" is equal to the value of "exp(17.436413974+0.0140219114×A-0.00394088×B-0.137558684×D-(A-80)×((A-80)×0.000514996))" of the sample that produced the most isoprene when analyzed by GC / MS. In other words, the value of the second term on the left side of the equation for the sample that produced the most isoprene is normalized to 1.

[0049] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the carbon black is 180 m 2 / g or less, and 2 / g or less is more preferable, 2 / g or less is more preferable, and 2 / g or more. The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the carbon black is preferably 180 m 2 When the carbon black has a specific surface area of ​​90 m2 or less, the yield of components serving as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be further increased when the crosslinked rubber composition is thermally decomposed. 2 When the carbon black has a specific surface area of ​​30 m2 or less, the yield of components serving as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be further increased when the crosslinked rubber composition is thermally decomposed. 2 / g or more, the crosslinked rubber composition has sufficient strength for use in various rubber products.

[0050] (Anti-aging agent) The crosslinked rubber composition of the present embodiment preferably further contains an antioxidant. When the crosslinked rubber composition contains an antioxidant, the aging resistance (weather resistance, ozone resistance) is improved, and various rubber products have an excellent life span. Examples of the antioxidant include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, N,N'-diphenyl-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, and N,N'-dicyclohexyl-p-phenylenediamine.

[0051] The crosslinked rubber composition of the present embodiment preferably does not contain the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. When the content of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine in the crosslinked rubber composition increases, the yield of components that are raw materials for isoprene skeleton rubber such as isoprene and limonene tends to decrease when the crosslinked rubber composition is thermally decomposed. Therefore, the content of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine in the crosslinked rubber composition is preferably as low as possible, and it is particularly preferable that the crosslinked rubber composition does not contain the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. By thermally decomposing the crosslinked rubber composition that does not contain the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, the yield of components that are raw materials for isoprene skeleton rubber such as isoprene and limonene can be further increased. In this specification, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine is sometimes referred to as "antioxidant 6PPD."

[0052] The content of the antiaging agent is preferably 6 parts by mass or less per 100 parts by mass of the rubber component. When the content of the antiaging agent is 6 parts by mass or less per 100 parts by mass of the rubber component, the aging resistance of the cross-linked rubber composition is improved, and a decrease in the yield of components serving as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be sufficiently suppressed when the cross-linked rubber composition is thermally decomposed.

[0053] (Other compounded drugs) In addition to the rubber component, sulfur, carbon black, and antioxidant described above, the crosslinked rubber composition of the present embodiment may contain various components commonly used in the rubber industry, such as fillers other than carbon black (inorganic fillers such as silica and calcium carbonate), silane coupling agents, softeners, zinc oxide, stearic acid, vulcanization accelerators, crosslinking agents other than sulfur, which are appropriately selected as necessary within the scope not impairing the object of the present invention. Commercially available products can be suitably used as these compounding agents.

[0054] The content of the zinc white (zinc oxide) is not particularly limited, and is preferably in the range of 0.1 to 10 parts by mass, and more preferably 1 to 8 parts by mass, per 100 parts by mass of the rubber component.

[0055] The content of the stearic acid is not particularly limited, and is preferably in the range of 0.1 to 10 parts by mass, and more preferably 1 to 8 parts by mass, per 100 parts by mass of the rubber component.

[0056] Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators, guanidine vulcanization accelerators, thiazole vulcanization accelerators, thiuram vulcanization accelerators, and dithiocarbamate vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.2 to 4 parts by mass, based on 100 parts by mass of the rubber component.

[0057] (Origin of crosslinked rubber composition) The crosslinked rubber composition of the present embodiment may be derived from various rubber products (used rubber products), for example, from tires, hoses, etc. The crosslinked rubber composition of the present embodiment preferably contains a crosslinked rubber composition derived from tires. When a crosslinked rubber composition derived from tires is contained, it is pyrolyzed to recover oil containing a large amount of monomers such as isoprene, which are raw materials for isoprene-skeleton rubber, and limonene, etc., and synthesize isoprene-skeleton rubber from the monomers such as isoprene and limonene in the oil, and use it again for tires, which makes it possible to recycle tires, and is also preferable from the viewpoint of protecting the global environment.

[0058] The crosslinked rubber composition used for the thermal decomposition may be grouped according to the type of rubber component previously compounded, and then thermally decomposed for each group. Also, the rubber composition may be grouped according to the type of filler previously compounded (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then thermally decomposed for each group. Furthermore, the rubber composition may be grouped according to the type of rubber component and the type of filler, and then thermally decomposed for each group. When thermally decomposing for each group, oils (e.g., including isoprene, limonene, liquid polymers, etc.), regenerated carbon black, regenerated silica, etc., having more uniform physical properties are obtained, and therefore, when compounded again with rubber, a rubber composition with better performance is obtained.

[0059] In addition, when the crosslinked rubber composition used for the thermal decomposition is derived from tires, the tires may be grouped in advance by type (for example, for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for agricultural vehicles, etc.), and then thermal decomposition may be performed for each group. In addition, the tires may be grouped in advance by tire components (for example, tread rubber, sidewall rubber, bead rubber, steel cord coated rubber, organic fiber coated rubber, pad rubber, cushion rubber, etc.), and then thermal decomposition may be performed for each group. Furthermore, the tires may be grouped both by type and by tire components, and then thermal decomposition may be performed for each group. When thermal decomposition is performed for each group in this way, oils (including, for example, isoprene, limonene, liquid polymers, etc.) and recycled carbon black having more uniform physical properties are obtained, so that a rubber composition with better performance can be obtained when it is blended again with rubber.

[0060] (Method of manufacturing crosslinked rubber composition) The method for producing the rubber composition is not particularly limited, but for example, the rubber composition can be produced by blending various components appropriately selected as necessary with the above-mentioned rubber component and sulfur, and kneading, heating, extruding, etc. In addition, the obtained rubber composition can be heated to form a crosslinked rubber composition.

[0061] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of the kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0062] The conditions of the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, heat-in equipment, etc. can be appropriately selected depending on the purpose. Examples of the heat-in equipment include a heat-in roller machine usually used for heat-in of a rubber composition.

[0063] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder that is usually used for extruding a rubber composition. The extrusion temperature can be appropriately determined.

[0064] The crosslinking (vulcanization) device, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. As a device for crosslinking, a molding vulcanizer using a mold used for vulcanizing a rubber composition can usually be mentioned. As a condition for crosslinking, the temperature is, for example, about 100 to 190°C.

[0065] <Oil> The oil of this embodiment is characterized in that it is recovered by pyrolyzing the crosslinked rubber composition of this embodiment described above. Since the oil of this embodiment is recovered by pyrolyzing the crosslinked rubber composition of this embodiment described above, it contains a large amount of monomers such as isoprene, which are raw materials for isoprene-skeleton rubber, and limonene, etc.

[0066] The oil of the present embodiment preferably has an isoprene content of 0.1% by mass or more. The oil of the present embodiment preferably has a limonene content of 1% by mass or more. From oil having an isoprene content of 0.1% by mass or more and / or an limonene content of 1% by mass or more, a large amount of isoprene, which is a raw material for isoprene-skeleton rubber, can be obtained, and therefore the oil can be easily recycled into isoprene-skeleton rubber.

[0067] The oil of the present embodiment is also suitable as an oil for producing a rubber composition for tires. The oil recovered by pyrolyzing the crosslinked rubber composition is used as a raw material for isoprene-skeleton rubber, which is a rubber component of the rubber composition for tires, thereby enabling chemical recycling of the crosslinked rubber composition. In addition, when the crosslinked rubber composition is collected from used tires, it can be recycled into tires.

[0068] The method for producing the oil of this embodiment is not particularly limited, but the oil of this embodiment can be obtained by the method for producing the oil of this embodiment described below.

[0069] <Oil manufacturing method> The method for producing the oil of this embodiment is characterized by pyrolyzing the crosslinked rubber composition of this embodiment described above. Since the method for producing the oil of this embodiment pyrolyzes the crosslinked rubber composition of this embodiment described above, it is possible to obtain an oil that contains a large amount of monomers such as isoprene, which are raw materials for isoprene-skeleton rubber, and limonene.

[0070] The temperature for thermal decomposition of the crosslinked rubber composition is preferably 300° C. or higher, more preferably 350° C. or higher, and is preferably 800° C. or lower, and more preferably 550° C. or lower. When the temperature for thermal decomposition is 350° C. or higher, the decomposition of the crosslinked rubber composition can be sufficiently promoted, and when the temperature is 550° C. or lower, the amount of complex decomposition products produced can be further reduced, and the yield of components serving as raw materials for isoprene-skeleton rubber, such as isoprene and limonene, can be further increased.

[0071] The pyrolysis is preferably carried out under an inert gas atmosphere. By carrying out the pyrolysis under an inert gas atmosphere, oxidation or reduction of the decomposition product can be suppressed. Here, examples of the inert gas include nitrogen, carbon dioxide, argon, and helium.

[0072] The pyrolysis can also be carried out in a solvent. Any solvent that does not inhibit the pyrolysis reaction can be used as the solvent, and examples of the solvent include ethers, aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons (aromatic solvents). More specifically, examples of the solvent include tetrahydrofuran (THF), hexane, cyclohexane, pentane, cyclopentane, toluene, and xylene.

[0073] The method for producing the oil of the present embodiment may further include other steps in addition to the above-mentioned pyrolysis step, such as a pretreatment step of the crosslinked rubber composition (e.g., a cutting step, a pulverization step, etc.).

[0074] The oil production method of the present embodiment can be carried out in either a batch reactor or a flow reactor. In addition, the oil (cracked product) after pyrolysis can be separated and recovered by filtration, distillation, etc., or recovered by precipitation using a poor solvent. EXAMPLES

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0076] <Preparation of Crosslinked Rubber Composition> Rubber compositions were prepared by kneading the compounding recipes shown in Tables 1 and 2. Here, kneading was carried out in two stages, the first kneading stage was carried out at 110°C for 3 minutes 15 seconds, and the second kneading stage was carried out at 80°C for 1 minute. Furthermore, the vulcanization curve of the obtained rubber composition was measured (JIS K 6300-2), and the rubber composition was heated at 145° C. for a time 1.5 times that of T90 to prepare a crosslinked rubber composition.

[0077] <Thermal decomposition of crosslinked rubber composition> 25 g of the crosslinked rubber composition prepared as described above was charged into a tubular reactor at approximately 1 g per 5 minutes, and pyrolysis was carried out under conditions of a temperature of 500° C. and a nitrogen flow rate of 100 mL / min to obtain an oil.

[0078] <Oil analysis> The oil obtained by pyrolysis was dissolved in chloroform to prepare a measurement sample, which was then analyzed using a gas chromatograph mass spectrometer (GC / MS, Agilent Technology, product name "7890 GC System 5977B MSD", equipped with Agilent Technology's "HP-5MS UI (length 30 m, inner diameter 0.25 mm, film thickness 0.25 um)"). The peak area values ​​(integral values) of isoprene and limonene were normalized by the concentration of oil in the measurement sample, and multiple regression analysis was performed using the peak area values ​​(integral values) of isoprene and limonene as the objective variables and the blending factors as the explanatory variables, to derive the relationship shown in the above formula (1). The peak area values ​​and area ratios of the produced isoprene and limonene are shown in Tables 1 and 2. Also, the left side of equation (1): exp(18.977663905+0.0085742124×A-0.003867326×B-0.028534179×C-0.251024648×D+(C-3.75)×((D-3.948)×0.0118234107)) / 243316566.160943 + exp(17.436413974+0.0140219114×A-0.00394088×B-0.137558684×D-(A-80)×((A-80)×0.000514996)) / 86230236.8833005 = exp(log limonene) / 243316566.160943 + exp(log isoprene) / 86230236.8833005, and the values ​​of "log limonene" and "log isoprene" are shown in Tables 1 and 2.

[0079] [Table 1]

[0080] [Table 2]

[0081] *1 NR: Contains 0.06 parts by mass of "Noctizer SD" (product name) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. per 100 parts by mass of natural rubber. The actual amount of natural rubber is shown in the lower part. *2 BR: Butadiene rubber, manufactured by UBE Elastomers Corporation, product name "UBEPOL BR150L" *3 Carbon black 1: CTAB adsorption specific surface area = 41m 2 / g *4 Carbon black 2: CTAB adsorption specific surface area = 74m 2 / g *5 Carbon black 3: CTAB adsorption specific surface area = 123 m 2 / g *6 Stearic acid: NOF Corporation, product name "Kiri brand stearic acid" *7 Zinc oxide: Manufactured by Hakusui Tech Co., Ltd., product name "Zinc oxide" *8 Antioxidant 6PPD: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C" *9 Vulcanization accelerator CBS: N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Sanshin Chemical Industry Co., Ltd., product name "Suncerer CM-G" *10 Sulfur containing 20% ​​oil: Manufactured by Shikoku Chemical Industry Co., Ltd., product name "Mu-Clon OT-20 EX", contains 20% oil by mass, actual amount of sulfur is shown in the lower part *11 Antioxidant TMQ: 2,2,4-trimethyl-1,2-dihydroquinoline polymer, manufactured by Seiko Chemical Co., Ltd., product name "Nonflex RD"

[0082] From Tables 1 and 2, it is clear that by pyrolyzing the crosslinked rubber compositions of the examples according to the present invention, it is possible to recover oil containing large amounts of components that are raw materials for isoprene-skeleton rubber, such as isoprene and limonene. [Industrial Applicability]

[0083] The crosslinked rubber composition of the present invention can be thermally decomposed and used to recover monomers such as isoprene, which are the raw materials for isoprene-skeleton rubber, and oils rich in limonene and the like.

[0084] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to the achievement of goals such as "No. 9_Let's build a foundation for industry and technological innovation," "No. 12_Responsible consumption and production," and "No. 13_Concrete measures against climate change."

Claims

1. A crosslinked rubber composition for oil recovery by pyrolysis, comprising: The crosslinked rubber composition includes a rubber component and sulfur, The rubber component contains an isoprene skeleton rubber, The content of the isoprene skeleton rubber is 50 parts by mass or more in 100 parts by mass of the rubber component, the sulfur content is 8 parts by mass or less per 100 parts by mass of the rubber component, A crosslinked rubber composition, characterized in that a mass ratio of a content of the isoprene skeleton rubber to a content of the sulfur (isoprene skeleton rubber / sulfur) is 12 or more.

2. Further contains carbon black, The following formula (1): exp(18.977663905+0.0085742124×A-0.003867326×B-0.028534179×C-0. 251024648×D+(C-3.75)×((D-3.948)×0.0118234107)) / 243316566.160943 + exp (17.436413974+0.0140219114×A-0.00394088×B-0.137558684×D-(A-80)×((A-80)×0.000514996)) / 86230236.8833005 ≧ 0.4... (1) [In the formula, A is the content (parts by mass) of the isoprene skeleton rubber in 100 parts by mass of the rubber component, B is the cetyltrimethylammonium bromide (CTAB) adsorption specific surface area (m ２ / g), C is the content (parts by mass) of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine relative to 100 parts by mass of the rubber component, and D is the amount (parts by mass) of the sulfur relative to 100 parts by mass of the rubber component.

3. The crosslinked rubber composition according to claim 1, wherein the sulfur content is 5 parts by mass or less based on 100 parts by mass of the rubber component.

4. The crosslinked rubber composition according to claim 1, wherein the sulfur content is 3 parts by mass or less based on 100 parts by mass of the rubber component.

5. The crosslinked rubber composition according to claim 1, wherein the content of the isoprene skeleton rubber is 70 parts by mass or more per 100 parts by mass of the rubber component.

6. The crosslinked rubber composition according to claim 1 , wherein the rubber component consists solely of the isoprene skeleton rubber.

7. The carbon black has a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​180 m ２ The crosslinked rubber composition according to claim 2, wherein the crosslinked rubber composition has a viscosity of 100:1 or less.

8. 2. The crosslinked rubber composition of claim 1 which is free of the antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

9. The crosslinked rubber composition according to claim 1 , wherein the oil is an oil for producing a rubber composition for tires.

10. An oil recovered by pyrolyzing the crosslinked rubber composition according to any one of claims 1 to 9.

11. A method for producing an oil, comprising pyrolyzing the crosslinked rubber composition according to any one of claims 1 to 9.

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