Method for decomposing liquid polymer and method for decomposing organic material

Abstract

The present invention addresses the problem of providing a method for decomposing a liquid polymer, with which it becomes possible to obtain a monomer with high yield. The solution to the problem is a method for decomposing a liquid polymer, the method being characterized by comprising a step for decomposing a liquid polymer in a decomposition furnace, and being also characterized in that: the temperature in the decomposition furnace is 450-800°C; the liquid polymer is dissolved in an organic solvent; and the concentration of the liquid polymer in the organic solvent is 0.5-1000 mg / mL.

Description

Method for decomposing liquid polymers, and method for decomposing organic materials

[0001] The present invention relates to a method for decomposing liquid polymers and a method for decomposing organic materials.

[0002] Traditionally, rubber products primarily made from cross-linked rubber, such as vulcanized rubber, have been difficult to recycle. After their lifespan, they are often reused as fuel, particularly in cement factories. However, with the growing environmental concerns, there is a growing demand for the development of methods to reuse materials obtained by decomposing rubber products, rather than burning them as fuel. Furthermore, uncross-linked rubber materials are sometimes discarded as scraps during the rubber product manufacturing process, and there is a need for the development of methods to reuse such uncross-linked rubber. Various methods exist for decomposing cross-linked and uncross-linked rubber. For example, a technology for thermal decomposition of cross-linked and uncross-linked rubber at high temperatures is known. In addition, Patent Document 1 below discloses a method for decomposing polyisoprene rubber using microorganisms.

[0003] Japanese Patent Publication No. 2009-247241

[0004] As described above, there are various methods for decomposing crosslinked rubber and uncrosslinked rubber, but from the viewpoint of improving the recyclability of crosslinked rubber and uncrosslinked rubber, it is important to increase the yield of chemicals obtained by decomposition, especially monomers. However, as described above, when crosslinked rubber and uncrosslinked rubber are thermally decomposed at high temperatures, the decomposition products tend to gasify or become aromatized, and the yield of monomers cannot be sufficiently increased. Furthermore, when decomposing crosslinked rubber using microorganisms, as in the technology disclosed in Patent Document 1, there are problems such as the fact that decomposition takes a long time and the yield of monomers is low.

[0005] In response to this, the inventors have found that by decomposing crosslinked rubber and uncrosslinked rubber at a lower temperature than conventional thermal decomposition, a liquid polymer (i.e., a partially decomposed rubber product) can be obtained, and by further thermal decomposition of this liquid polymer, monomers can be obtained. However, even with this method, there is still room for improvement in terms of monomer yield.

[0006] Therefore, the present invention aims to solve the problems of the above-mentioned prior art and provide a method for decomposing liquid polymers that can obtain monomers in high yield. Furthermore, the present invention aims to provide a method for decomposing organic materials that can obtain monomers in high yield by applying such a liquid polymer decomposition method.

[0007] The gist of the present invention's method for decomposing liquid polymers and organic materials, which solves the above problems, is as follows.

[0008] [1] A method for decomposing a liquid polymer, comprising the step of decomposing the liquid polymer in a decomposition furnace, wherein the temperature in the decomposition furnace is 450°C or higher and 800°C or lower, the liquid polymer is dissolved or dispersed in an organic solvent, and the concentration of the liquid polymer in the organic solvent is 0.5 to 1000 mg / mL.

[0009] [2] The method for decomposing a liquid polymer according to [1], wherein the organic solvent has a boiling point of 80 to 220°C.

[0010] [3] The method for decomposing a liquid polymer according to [1] or [2], wherein the liquid polymer is dissolved or dispersed in the organic solvent and then sprayed in the decomposition furnace to form a mist.

[0011] [4] The liquid polymer has a weight-average molecular weight (Mw) of 100,000 or less, a method for decomposing a liquid polymer according to any one of [1] to [3].

[0012] [5] A method for decomposing a liquid polymer according to any one of [1] to [4], further comprising the step of lowering the temperature of the decomposition product after the step of decomposing the liquid polymer.

[0013] [6] The method for decomposing a liquid polymer according to [3], wherein the liquid polymer is heated from 100°C to 450°C at a heating rate of 800°C / min or more.

[0014] [7] The method for decomposing a liquid polymer according to [3], wherein the liquid polymer is heated from 100°C to 500°C at a heating rate of 800°C / min or more.

[0015] [8] The method for decomposing a liquid polymer according to [3], wherein the liquid polymer is heated from 100°C to 450°C at a heating rate of 2000°C / min or more.

[0016] [9] The method for decomposing a liquid polymer according to [3], wherein the liquid polymer is heated from 100°C to 500°C at a heating rate of 2000°C / min or more.

[0017]

[10] The method for decomposing a liquid polymer according to any one of [1] to [9], wherein the liquid polymer is a diene polymer.

[0018]

[11] A method for decomposing an organic material, comprising: a step of preparing a liquid polymer by decomposing an organic material selected from crosslinked rubber and uncrosslinked rubber; and a step of decomposing the liquid polymer using the liquid polymer decomposition method described in any one of [1] to

[10] .

[0019] According to the present invention, a method for decomposing a liquid polymer that can obtain monomers in high yield can be provided. Furthermore, according to the present invention, a method for decomposing an organic material that can obtain monomers in high yield can be provided by applying such a liquid polymer decomposition method.

[0020] The following describes in detail, based on embodiments, the method for decomposing liquid polymers and organic materials according to the present invention.

[0021] <Definitions> The compounds described herein may be derived in part or in whole from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires. They may also be derived from a mixture of two or more of fossil resources, biological resources, or recycled resources.

[0022] <Method for Decomposing Liquid Polymers> The method for decomposing liquid polymers according to this embodiment includes the step of decomposing the liquid polymer in a decomposition furnace. The method for decomposing liquid polymers according to this embodiment is characterized in that the temperature inside the decomposition furnace is 450°C or higher and 800°C or lower, the liquid polymer is dissolved or dispersed in an organic solvent, and the concentration of the liquid polymer in the organic solvent is 0.5 to 1000 mg / mL. In this specification, when numerical values ​​A and B are written as "A to B", unless otherwise specified, it means "A or higher and B or lower".

[0023] In the liquid polymer decomposition method of this embodiment, the liquid polymer is dissolved or dispersed in an organic solvent at a predetermined concentration and then decomposed in a decomposition furnace. As a result, the liquid polymer particles are spaced at a certain distance from each other, and thermal decomposition (depolymerization) occurs in this state. Because the liquid polymer particles are spaced at a certain distance from each other, heat is quickly conducted to the liquid polymer particles, reducing the proportion of liquid polymer that is decomposed before reaching a sufficient temperature, and suppressing the generation of high molecular weight decomposition products (oligomers, etc.) from the liquid polymer. Furthermore, in the liquid polymer decomposition method of this embodiment, by performing decomposition at a temperature of 450°C or higher in the decomposition furnace, the decomposition of the liquid polymer can be accelerated and the yield of monomers can be improved. In addition, in the liquid polymer decomposition method of this embodiment, by setting the temperature of the decomposition furnace to 800°C or lower, gasification and aromatization of decomposition products can be suppressed, and the retention rate (selectivity) of the skeleton of the constituent monomers of the liquid polymer after decomposition is improved, resulting in an improved yield of the monomers finally obtained. Therefore, according to the liquid polymer decomposition method of this embodiment, monomers can be obtained in high yield.

[0024] "Decomposition Step" The method for decomposing a liquid polymer in this embodiment includes a step of decomposing the liquid polymer in a decomposition furnace (decomposition step). The decomposition furnace is not particularly limited and examples include batch-type pyrolysis furnaces, flow-type pyrolysis furnaces, etc.

[0025] (Decomposition Conditions) In the liquid polymer decomposition method of this embodiment, the temperature inside the decomposition furnace is 450°C or higher and 800°C or lower. Setting the temperature inside the decomposition furnace to 450°C or higher improves the rate of the liquid polymer decomposition reaction and improves the monomer yield. Setting the temperature inside the decomposition furnace to 800°C or lower suppresses the gasification and aromatization of the decomposition products, and also improves the retention rate (selectivity) of the skeleton of the constituent monomers of the liquid polymer after decomposition, thereby improving the yield of the monomer obtained in the end. The temperature inside the decomposition furnace is preferably 500°C or higher, and preferably 700°C or lower. Setting the temperature inside the decomposition furnace to 500°C or higher further improves the rate of the liquid polymer decomposition reaction and further improves the monomer yield. Furthermore, by keeping the temperature inside the decomposition furnace below 700°C, the gasification and aromatization of decomposition products can be further suppressed. In addition, the retention rate (selectivity) of the skeleton of the constituent monomers of the liquid polymer after decomposition is further improved, resulting in an even higher yield of the monomers ultimately obtained.

[0026] The decomposition time (residence time of the liquid polymer in the heated section of the decomposition furnace) is not particularly limited. For example, the decomposition time is preferably 0.1 seconds to 300 seconds, and more preferably 1 second to 150 seconds. Performing the decomposition for 0.1 seconds or more improves the decomposition rate of the liquid polymer. On the other hand, if the decomposition time is too long, the skeletons (double bonds, etc.) of the constituent monomers of the liquid polymer may be decomposed, or the decomposition products may be gasified or aromatized. However, performing the decomposition for 300 seconds or less suppresses the decomposition of the monomer skeletons and the gasification and aromatization of the decomposition products, and improves the retention rate (selectivity) of the skeletons of the constituent monomers of the liquid polymer after decomposition.

[0027] The decomposition is preferably carried out under an inert gas atmosphere. By carrying out the decomposition under an inert gas atmosphere, oxidation and reduction of the liquid polymer and decomposition products can be suppressed, and in particular, hydrogenation of double bonds in the generated monomers can be suppressed. Examples of inert gases include nitrogen, carbon dioxide, argon, and helium.

[0028] To carry out the aforementioned decomposition under an inert gas atmosphere, for example, when using a batch-type pyrolysis furnace, the atmosphere fed into the decomposition furnace should be an inert gas; when using a flow-through pyrolysis furnace, the atmosphere circulated through the decomposition furnace should be an inert gas. Note that hydrogen may be generated during decomposition, but the generated hydrogen is not taken into consideration when determining the decomposition atmosphere.

[0029] In the liquid polymer decomposition method of this embodiment, it is preferable to heat the liquid polymer from 100°C to 450°C at a heating rate of 800°C / min or more. When the heating rate from 100°C to 450°C is 800°C / min or more, the generation of decomposition products with a molecular weight higher than the monomer, such as oligomers, is further suppressed, and the retention rate (selectivity) of the skeleton of the constituent monomers of the liquid polymer after decomposition is further improved.

[0030] In the liquid polymer decomposition method of this embodiment, it is preferable to heat the liquid polymer from 100°C to 500°C at a heating rate of 800°C / min or more. When the heating rate from 100°C to 500°C is 800°C / min or more, the generation of decomposition products with a molecular weight higher than the monomer, such as oligomers, is further suppressed, and the retention rate (selectivity) of the skeleton of the constituent monomers of the liquid polymer after decomposition is further improved.

[0031] In the liquid polymer decomposition method of this embodiment, it is preferable to heat the liquid polymer from 100°C to 450°C at a heating rate of 2000°C / min or more. When the heating rate from 100°C to 450°C is 2000°C / min or more, the generation of decomposition products with a molecular weight higher than the monomer, such as oligomers, is further suppressed, and the retention rate (selectivity) of the skeleton of the constituent monomers of the liquid polymer after decomposition is further improved.

[0032] In the liquid polymer decomposition method of this embodiment, it is preferable to heat the liquid polymer from 100°C to 500°C at a heating rate of 2000°C / min or more. When the heating rate from 100°C to 500°C is 2000°C / min or more, the generation of decomposition products with a molecular weight higher than the monomer, such as oligomers, is further suppressed, and the retention rate (selectivity) of the skeleton of the constituent monomers of the liquid polymer after decomposition is further improved.

[0033] The aforementioned decomposition can be carried out at any pressure, including under reduced pressure, at atmospheric pressure, or under pressurized pressure, but it is preferable to carry it out under reduced pressure or at atmospheric pressure. As an example, the pressure for the decomposition (pressure inside the decomposition furnace) is preferably 1000 kPa to 65 kPa. By carrying out the decomposition under reduced pressure or at atmospheric pressure, polymerization (repolymerization) of the monomers, which are the decomposition products, can be suppressed.

[0034] The aforementioned decomposition may or may not involve the use of a catalyst, but it is preferable not to use a catalyst. By not using a catalyst for the decomposition, costs can be reduced. If a catalyst is used, any catalyst that promotes the decomposition reaction of the liquid polymer can be used.

[0035] (Liquid Polymer) In the method for decomposing a liquid polymer of this embodiment, the liquid polymer to be decomposed is liquid at room temperature (23°C). The monomer units of the liquid polymer are not particularly limited.

[0036] The liquid polymer is preferably a diene polymer. When the liquid polymer is a diene polymer, a diene monomer is obtained by decomposition, and this diene monomer is easily used in rubber synthesis. In this way, by using a diene polymer as the target of decomposition, a diene monomer useful for rubber synthesis can be obtained. The diene polymer contains units (diene units) derived from the diene monomer. Here, examples of diene monomers (diene compounds) constituting the diene monomer units include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and among these, 1,3-butadiene and isoprene are preferred, and isoprene is particularly preferred.

[0037] In the liquid polymer decomposition method of this embodiment, it is preferable to prepare the liquid polymer by decomposing an organic material selected from crosslinked rubber and uncrosslinked rubber. By using crosslinked rubber and / or uncrosslinked rubber as raw materials, the crosslinked rubber and / or uncrosslinked rubber can be recycled and reused.

[0038] The method for producing the liquid polymer is not particularly limited. For example, liquid polymers can be obtained by (i) decomposing crosslinked rubber or uncrosslinked rubber using a metathesis catalyst (first decomposition method), (ii) thermally decomposing crosslinked rubber or uncrosslinked rubber at 150°C to 400°C (second decomposition method), (iii) decomposing crosslinked rubber or uncrosslinked rubber in a solvent (third decomposition method), etc. These first, second, and third decomposition methods will be described in detail in the section "Steps for preparing liquid polymers" in the <Methods for decomposing organic materials> section below.

[0039] In the liquid polymer decomposition method of this embodiment, the liquid polymer is dissolved or dispersed in an organic solvent. The organic solvent may also contain other particles such as finely atomized impurities and carbon black in addition to the liquid polymer. Furthermore, the liquid polymer does not need to be completely dissolved in the organic solvent; it may be dispersed.

[0040] Examples of organic solvents include aromatic solvents, chlorinated hydrocarbons, aliphatic solvents, alicyclic solvents, ethers, esters, and nitriles. Examples of aromatic solvents include benzene, toluene, xylene, benzonitrile, diethylbenzene, o-dichlorobenzene, p-cymene, and 1,2,4-trimethylbenzene. Specific examples of chlorinated hydrocarbons include chloroform, dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, tetrachloroethene, chlorobenzene, and dichlorobenzene. Examples of aliphatic solvents include pentane, hexane, and heptane. Examples of alicyclic solvents include cyclopentane and cyclohexane. Examples of ethers include tetrahydrofuran (THF), cyclopentyl methyl ether, and 4-methyltetrahydropyran. Examples of esters include ethyl acetate, butyl acetate, and methyl benzoate. Examples of nitriles include benzonitrile and acetonitrile. The organic solvent is preferably at least one selected from the group consisting of toluene, xylene, benzonitrile, diethylbenzene, o-dichlorobenzene, p-cymene, 1,2,4-trimethylbenzene, and cyclohexane. When a liquid polymer is dissolved or dispersed in an organic solvent selected from toluene, xylene, benzonitrile, diethylbenzene, o-dichlorobenzene, p-cymene, 1,2,4-trimethylbenzene, and cyclohexane, the liquid polymer is dispersed in the solvent at a molecular level, the spacing between liquid polymer particles widens, the formation of decomposition products with higher molecular weight than the monomer, such as oligomers, is further suppressed, and the yield of monomers is further improved. The organic solvent is preferably having a boiling point of 80 to 220°C. When a liquid polymer is dissolved or dispersed in an organic solvent with a boiling point of 80 to 220°C, the formation of decomposition products with higher molecular weight than the monomer, such as oligomers, is further suppressed, and the yield of monomers is further improved.

[0041] In the liquid polymer decomposition method of this embodiment, the concentration of the liquid polymer in the organic solvent is 0.5 to 1000 mg / mL. When the concentration of the liquid polymer in the organic solvent exceeds 1000 mg / mL, the spacing between liquid polymer particles becomes narrower, making it easier to generate decomposition products with higher molecular weight than monomers, such as oligomers. On the other hand, when the concentration of the liquid polymer in the organic solvent is less than 0.5 mg / mL, the amount of liquid polymer that can be decomposed decreases. From the viewpoint of increasing the amount of liquid polymer that can be decomposed, the concentration of the liquid polymer in the organic solvent is preferably 1.0 mg / mL or higher, and from the viewpoint of suppressing the generation of high molecular weight decomposition products, it is preferably 500 mg / mL or less, and more preferably 250 mg / mL or less.

[0042] In the liquid polymer decomposition method of this embodiment, it is preferable to dissolve or disperse the liquid polymer in the organic solvent and then spray it in the decomposition furnace to form a mist. By dissolving or dispersing the liquid polymer in the organic solvent and then spraying it in the decomposition furnace to form a mist, the liquid polymer particles become sufficiently small, the spacing between the liquid polymer particles widens, the generation of decomposition products with a molecular weight higher than the monomer, such as oligomers, is further suppressed, and the monomer yield is further improved.

[0043] The liquid polymer preferably has a weight-average molecular weight (Mw) of 100,000 or less. When the weight-average molecular weight (Mw) of the liquid polymer is 100,000 or less, the particles of the liquid polymer become sufficiently small, the spacing between the liquid polymer particles widens, the generation of decomposition products with a molecular weight higher than the monomer, such as oligomers, is further suppressed, and the monomer yield is further improved. From the viewpoint of improving the monomer yield, the weight-average molecular weight (Mw) of the liquid polymer is more preferably 50,000 or less, even more preferably 30,000 or less, even more preferably 20,000 or less, and particularly preferably 10,000 or less. Furthermore, the liquid polymer preferably has a weight-average molecular weight (Mw) of 500 or more, and even more preferably 1,000 or more. A liquid polymer with a weight-average molecular weight (Mw) of 500 or more, even when prepared by decomposing crosslinked rubber or uncrosslinked rubber, does not decompose too much, so the retention rate of the monomer skeleton is high, and the monomer yield can be improved by decomposing such a liquid polymer. Here, the weight-average molecular weight (Mw) of the liquid polymer is determined using gel permeation chromatography (GPC) with monodisperse standard polystyrene as the reference.

[0044] "Decomposition Products" In the liquid polymer decomposition method of this embodiment, monomers and the like are obtained as decomposition products by the decomposition.

[0045] In the liquid polymer decomposition method of this embodiment, the decomposition product obtained by the decomposition preferably contains 30% by mass or more of monomers, more preferably 50% by mass or more, and even more preferably 60% by mass or more. By improving the yield and quantity of monomers, the economic and environmental value of the decomposition method is further enhanced. The monomers as decomposition products vary depending on the type of constituent monomer of the liquid polymer to be decomposed, but examples include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc., with 1,3-butadiene and isoprene being preferred. The proportion of monomers in the decomposition product can be controlled, for example, by reaction conditions such as the concentration of the liquid polymer in the organic solvent, the temperature in the decomposition furnace, and the residence time.

[0046] "Cooling Step" The liquid polymer decomposition method of this embodiment preferably further includes a step of lowering the temperature of the decomposition product (cooling step) after the step of decomposing the liquid polymer. By lowering the temperature of the decomposition product, further decomposition of monomers in the decomposition product can be prevented, and the yield of monomers can be further improved. Here, after the decomposition of the liquid polymer, it is preferable to lower the temperature of the decomposition product to 400°C or below, and more preferably to 300°C or below.

[0047] "Other" The liquid polymer decomposition method of this embodiment may include other steps in addition to the decomposition step and cooling step described above. Examples of such steps include a separation and purification step of the decomposition products. For example, by distilling the decomposition products, the target monomer can be separated from other by-products, and the target monomer can be reused as a raw material for polymer (rubber) synthesis.

[0048] <Method for Decomposing Organic Materials> The method for decomposing organic materials according to this embodiment is characterized by comprising the steps of: preparing a liquid polymer by decomposing an organic material selected from crosslinked rubber and uncrosslinked rubber; and decomposing the liquid polymer using the liquid polymer decomposition method described above. According to the method for decomposing organic materials according to this embodiment, since the liquid polymer is decomposed using the liquid polymer decomposition method of this embodiment described above, it is possible to obtain monomers in high yield.

[0049] "Step to prepare liquid polymer" The organic material decomposition method of this embodiment includes a step of preparing a liquid polymer by decomposing an organic material selected from crosslinked rubber and uncrosslinked rubber (also referred to as the "liquid polymer preparation step").

[0050] (Organic materials) The organic materials to be decomposed in the decomposition method of this embodiment are selected from crosslinked rubber and uncrosslinked rubber. These organic materials may be one type or a mixture of two or more types.

[0051] The aforementioned crosslinked rubber and uncrosslinked rubber preferably contain diene rubber as a rubber component, and may further contain compounding agents such as carbon black and sulfur.

[0052] The crosslinked and uncrosslinked rubbers used for decomposition may be grouped beforehand based on the type of diene rubber they contain, and then thermal decomposition may be carried out separately for each group. Alternatively, they may be grouped based on the type of filler they contain (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then thermal decomposition may be carried out separately for each group. Furthermore, both the grouping by diene rubber type and the grouping by filler type may be performed, and then thermal decomposition may be carried out separately for each group. When thermal decomposition is carried out separately for each group in this way, recycled carbon black, recycled silica, etc. with more uniform physical properties can be obtained, resulting in a rubber composition with better performance when they are re-combined into the rubber composition.

[0053] Furthermore, if the cross-linked rubber used for decomposition is derived from tires, it may be grouped beforehand by tire type (for example, passenger car tires, truck and bus tires, heavy off-road vehicle tires, aircraft tires, agricultural vehicle tires, etc.) and then thermal decomposition may be carried out for each group. Alternatively, it may be grouped beforehand by tire component (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 carried out for each group. In addition, it may be possible to group by tire type and by tire component and then thermal decomposition may be carried out for each group. When thermal decomposition is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again blended into a rubber composition, a rubber composition with better performance can be obtained.

[0054] The form of the crosslinked rubber is not particularly limited and may be, for example, powdered rubber. This powdered rubber can be obtained by cutting and crushing used rubber products such as waste tires. The crushing process may include multiple steps such as a preliminary crushing process and a fine crushing process, and the particle size of the powdered rubber to be used may be adjusted by a classification process after the crushing process.

[0055] The form of the uncrosslinked rubber is not particularly limited, and examples include scraps of unvulcanized rubber sheets discarded during the manufacturing process of rubber products.

[0056] The aforementioned cross-linked rubber may be recycled waste rubber, used rubber products, etc. Waste rubber refers to all discarded rubber, including not only rubber generated from rubber products, but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeling rubber. Buffing powder is, for example, fine rubber generated in the buffing process of retreading tires, where the tread portion remaining on the base tire is scraped off. Peeling rubber is, for example, long pieces of rubber, 1 to 2 cm wide, that are peeled off from the surface of rubber products such as tires. Peeling rubber is generated by scraping the surface of rubber products such as tires using a U-shaped or V-shaped knife like a peeler. Rubber products include, for example, final products such as tires and rubber hoses, and rubber parts or components at the manufacturing stage of final products. Used tires may be, for example, retreaded tires, or tires that have been discarded for any reason, such as tire replacements, scrapped vehicles, or End-of-Life Tires (ELTs) that have reached the end of their lifespan as tires.

[0057] -Diene-based rubber- The diene-based rubber is a rubber containing units derived from diene monomers (diene units), and may further contain units derived from copolymerizable comonomers. The units derived from diene monomers enable crosslinking (vulcanization) of the diene-based rubber and can exhibit rubber-like elongation and strength. In crosslinked rubber, the diene-based rubber usually exists in a crosslinked state, but some parts may not be crosslinked. Specific examples of diene monomers (diene compounds) include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and among these, 1,3-butadiene and isoprene are preferred, with isoprene being particularly preferred. On the other hand, examples of copolymerizable comonomers include aromatic vinyl compounds. Examples of the aromatic vinyl compound include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, and p-ethylstyrene.

[0058] Examples of the diene rubber include isoprene-skeleton rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), and chloroprene rubber (CR). Here, isoprene-skeleton rubber is a rubber whose main skeleton is isoprene units, and specifically includes natural rubber (NR) and synthetic isoprene rubber (IR). Among these, the diene rubber preferably contains at least one selected from the group consisting of isoprene-skeleton rubber, styrene-butadiene rubber, and butadiene rubber, with isoprene-skeleton rubber being particularly preferred. When the diene rubber contains at least one selected from the group consisting of isoprene-skeleton rubber, styrene-butadiene rubber, and butadiene rubber, easily recyclable diene monomers such as isoprene and butadiene can be obtained by decomposition of the crosslinked or uncrosslinked rubber.

[0059] The content of the diene rubber in the crosslinked rubber and uncrosslinked rubber is not particularly limited, but is preferably in the range of 10 to 100% by mass, and more preferably in the range of 30 to 100% by mass from the viewpoint of further improving the yield of the diene monomer. Furthermore, among the diene rubbers, isoprene skeleton rubber is preferred from the viewpoint of further improving the yield of isoprene monomer, and the content of isoprene skeleton rubber in the diene rubber is more preferably in the range of 30 to 100% by mass.

[0060] -Carbon Black- The crosslinked rubber and uncrosslinked rubber may further contain carbon black. The carbon black is not particularly limited, and examples of grades of carbon black include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. In the organic material decomposition method of this embodiment, even when the organic material to be decomposed is crosslinked rubber or uncrosslinked rubber, the diene-based rubber in the crosslinked rubber or uncrosslinked rubber can be decomposed in the thermal decomposition to reduce the molecular weight to, for example, oligomers or monomers. Therefore, even if the crosslinked rubber or uncrosslinked rubber contains carbon black, the carbon black can be easily separated and recovered after thermal decomposition by, for example, centrifugation or filtration, and the recovered carbon black can be reused. The carbon black content in the crosslinked rubber and uncrosslinked rubber is not particularly limited, and is, for example, in the range of 10 to 150 parts by mass per 100 parts by mass of the rubber component (diene rubber), with a preference of 30 to 120 parts by mass. Furthermore, the carbon black content in the crosslinked rubber and uncrosslinked rubber is preferably 20% by mass or more, more preferably 30% by mass or more, preferably 40% by mass or less, and even more preferably 35% by mass or less. When the carbon black content in the crosslinked rubber and uncrosslinked rubber is 20% by mass or more, the amount of carbon black that can be recovered increases.

[0061] -Sulfur- The crosslinked rubber and uncrosslinked rubber may further contain sulfur. In the crosslinked rubber, sulfur usually exists in a crosslinked state of the diene rubber (as a bridge for the diene rubber), but some may be free. The organic material decomposition method of this embodiment allows for the decomposition of the diene rubber in the crosslinked rubber or uncrosslinked rubber to be reduced to a low molecular weight, for example, oligomers or monomers, during the thermal decomposition, even when the organic material to be decomposed is crosslinked rubber or uncrosslinked rubber. Therefore, even if the crosslinked rubber or uncrosslinked rubber contains sulfur, the sulfur can be easily recovered after thermal decomposition by, for example, centrifugation or filtration, and the recovered sulfur can be reused. The sulfur content in the crosslinked rubber and uncrosslinked rubber is not particularly limited, and is, for example, in the range of 0.1 to 10 parts by mass, and preferably in the range of 1 to 5 parts by mass, per 100 parts by mass of the rubber component (diene rubber).

[0062] -Other Components- In addition to the diene-based rubber, carbon black, and sulfur mentioned above, the crosslinked rubber and uncrosslinked rubber may also contain various components commonly used in the rubber industry, such as rubber components other than diene-based rubber, fillers other than carbon black (silica, calcium carbonate, etc.), silane coupling agents, antioxidants, softeners, processing aids, resins, surfactants, organic acids (stearic acid, etc.), zinc oxide (zinc oxide), vulcanization accelerators, crosslinking agents other than sulfur (peroxide, etc.).

[0063] (Decomposition Method) The preparation step for the liquid polymer is not particularly limited, but can be carried out by, for example, (i) decomposing the crosslinked rubber or uncrosslinked rubber using a metathesis catalyst (first decomposition method), (ii) thermally decomposing the crosslinked rubber or uncrosslinked rubber at 150°C to 400°C (second decomposition method), (iii) decomposing the crosslinked rubber or uncrosslinked rubber in a solvent (third decomposition method), etc.

[0064] - First Decomposition Method (Metathesis Decomposition) - In the first decomposition method described above, crosslinked rubber and uncrosslinked rubber are decomposed using a metathesis catalyst. Here, the metathesis catalyst is one of the following general formulas (1), (2), or (3): A catalyst represented by the formula (1), (2), or (3) is preferred. Catalysts of general formulas (1), (2), or (3) are excellent at promoting metathesis decomposition and can decompose diene rubbers easily (under mild conditions) and rapidly.

[0065] In the above general formulas (1), (2), and (3), M is ruthenium (Ru), titanium (Ti), molybdenum (Mo), or tungsten (W). Among these, ruthenium is preferred as M from the viewpoint of promoting the decomposition reaction of diene-based rubber in crosslinked rubber and uncrosslinked rubber.

[0066] In the above general formulas (1) and (2), X １ and X ２ Each of these independently represents a ligand, preferably an anionic ligand. １ and X ２ Examples include hydrogen, halogens, pseudohalogens, linear or branched C1-C30 alkyl groups, C6-C24 aryl groups, C1-C20 alkoxy groups, C6-C24 aryloxy groups, C3-C20 alkyl diketonates, C6-C24 aryl diketonates, C1-C20 carboxylates, C1-C20 alkyl sulfonates, C6-C24 aryl sulfonates, C1-C20 alkylthiol groups, C6-C24 arylthiol groups, C1-C20 alkyl sulfonyl groups, or C1-C20 alkyl sulfinyl groups. １ and X ２ X may be substituted with one or more further groups, for example, halogens (preferably fluorine), C1-C10 alkyl groups, C1-C10 alkoxy groups, or C6-C24 aryl groups, where these groups may also be further substituted with one or more substituents selected from the group consisting of halogens (preferably fluorine), C1-C5 alkyl groups, C1-C5 alkoxy groups, and phenyl groups. In a preferred embodiment, X １ and X ２are the same or different and each is a halogen (especially fluorine, chlorine, bromine or iodine), benzoate, carboxylate having 1 to 5 carbon atoms, alkyl group having 1 to 5 carbon atoms, phenoxy group, alkoxy group having 1 to 5 carbon atoms, alkylthiol group having 1 to 5 carbon atoms, arylthiol group having 6 to 24 carbon atoms, aryl group having 6 to 24 carbon atoms or alkylsulfonate having 1 to 5 carbon atoms. In a particularly preferred embodiment, X １ and X ２ are the same and each is a halogen (especially chlorine), CF ３ COO, CH ３ COO, CFH ２ COO, (CH ３ ) ３ CO, (CF ３ ) ２ (CH ３ )CO, (CF ３ )(CH ３ ) ２ CO, PhO (phenoxy), MeO (methoxy), EtO (ethoxy), tosylate (p-CH ３ -C ６ H ４ -SO ３ ), mesylate (2,4,6-trimethylphenyl) or CF ３ SO ３ (trifluoromethanesulfonate).

[0067] In the above general formulas (1), (2) and (3), L １ , L ２ and L ３ each independently represents a ligand, preferably a neutral (uncharged) electron donor (also referred to as an "electron-donating neutral ligand"). L １ , L ２ and L ３ can be, for example, independently of each other, phosphine, sulfonated phosphine, phosphate, phosphite ester, phosphonit, arsine, stibine, ether, amine, amide, aryloxy, sulfonate, sulfoxide, carboxyl, nitrosyl, pyridine, thioether or imidazolidine ligand. L １ , L ２ and L ３These are, independently of each other, arylphosphine ligands having 6 to 24 carbon atoms, alkylphosphines having 1 to 10 carbon atoms or cycloalkylphosphine ligands having 3 to 20 carbon atoms, sulfonated arylphosphines having 6 to 24 carbon atoms or sulfonated alkylphosphine ligands having 1 to 10 carbon atoms, arylphosphinates having 6 to 24 carbon atoms or alkylphosphinate ligands having 1 to 10 carbon atoms, arylphosphonites having 6 to 24 carbon atoms or alkylphosphonites having 1 to 10 carbon atoms, arylarsines having 6 to 24 carbon atoms or The ligand is preferably a C1-C10 alkylarsine ligand, a C6-C24 arylamine or a C1-C10 alkylamine ligand, a pyridine ligand, a C6-C24 aryl sulfoxide or a C1-C10 alkyl sulfoxide ligand, a C6-C24 aryl ether or a C1-C10 alkyl ether ligand, or a C6-C24 arylamide or a C1-C10 alkylamide ligand, each of which may be substituted with a phenyl group, and the phenyl group may be further optionally substituted with a halogen, a C1-C5 alkyl group or a C1-C5 alkoxy group. The term "phosphine" is, for example, PPh ３ , P(p-Tol) ３ , P(o-Tol) ３ , PPh(CH ３ ) ２ , P(CF ３ ) ３ , P(p-FC ６ H ４ ) ３ , P(p-CF ３ C ６ H ４ ) ３ , P(C ６ H ４ -SO ３ Na) ３ , P(CH ２ C ６ H ４ -SO ３ Na) ３ P (isopropyl) ３ , P(CHCH ３ (CH２ CH ３ )) ３ P (cyclopentyl) ３ P (cyclohexyl) ３ P (Neopentyl) ３ and P (neophenyl) ３ The term "phosphinoate ester" includes, for example, triphenyl phosphinoate, tricyclohexyl phosphinoate, triisopropyl phosphinoate, and methyldiphenyl phosphinoate. The term "phosphite ester" includes, for example, triphenyl phosphite, tricyclohexyl phosphite, tri-tert-butyl phosphite, triisopropyl phosphite, and methyldiphenyl phosphite. The term "styvin" includes, for example, triphenylstyvin, tricyclohexylstyvin, and trimethylstyvin. The term "aryloxy" includes, for example, 2-tert-butyl-4,5-dimethylphenyloxy. The term "sulfonate" includes, for example, trifluoromethanesulfonate, tosylate, and mesylate. The term "sulfoxide" includes, for example, (CH ３ ) ２ S (=O) and (C ６ H ５ ) ２ It includes S=O. The term "thioether" is, for example, CH ３ SCH ３ , C ６ H ５ SCH ３ ,CH ３ OCH ２ CH ２ SCH ３and tetrahydrothiophene are included. The term "pyridine" includes, for example, pyridine, picolines (α-, β-, and γ-picolines), lutidines (2,3-, 2,4-, 2,5-, 2,6-, 3,4-, and 3,5-lutidines), collidine (2,4,6-trimethylpyridine), trifluoromethylpyridine, phenylpyridine, 4-(dimethylamino)pyridine, chloropyridines, bromopyridines, nitropyridines, quinolines, pyrimidines, pyrroles, imidazoles, and phenylimidazoles. In the imidazolidine ligand, the hydrogen atoms bonded to the carbon or nitrogen atoms constituting the imidazolidine ring may be substituted with linear or branched C1-C30 alkyl groups, C3-C20 cycloalkyl groups, C2-C20 alkenyl groups, C2-C20 alkynyl groups, C6-C24 aryl groups, C1-C20 carboxylates, C1-C20 alkoxy groups, C2-C20 alkenyloxy groups, C2-C20 alkynyloxy groups, C6-C20 aryloxy groups, C2-C20 alkoxycarbonyl groups, C1-C20 alkylthio groups, C6-C20 arylthio groups, C1-C20 alkylsulfonyl groups, C1-C20 alkylsulfonates, C6-C20 arylsulfonates, or C1-C20 alkylsulfinyl groups.

[0068] In the above general formulas (1), (2), and (3), R １ , R ２ and R ３Each of these independently represents hydrogen, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, an aralkyl group, a carboxylate group, an alkoxy group, an alkenyloxy group, an alkynyloxy group, an aryloxy group, an alkoxycarbonyl group, an alkylamino group, an alkylthio group, an arylthio group, an alkylsulfonyl group, or an alkylsulfinyl group, where these groups may be substituted with one or more alkyl groups, halogens, alkoxy groups, aryl groups, or heteroaryl groups. Furthermore, the alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, the cycloalkyl group is preferably a cycloalkyl group having 3 to 20 carbon atoms, the alkenyl group is preferably an alkenyl group having 2 to 20 carbon atoms, the alkynyl group is preferably an alkynyl group having 2 to 20 carbon atoms, the aryl group is preferably an aryl group having 6 to 24 carbon atoms, the aralkyl group is preferably an aralkyl group having 7 to 24 carbon atoms, the carboxylate group is preferably a carboxylate group having 1 to 20 carbon atoms, the alkoxy group is preferably an alkoxy group having 1 to 20 carbon atoms, and the alkenyloxy group is preferably an alkenyloxy group having 2 to 20 carbon atoms. As the alkynyloxy group, a C2-C20 alkynyloxy group is preferred; as the aryloxy group, an aryloxy group having C6-C24 is preferred; as the alkoxycarbonyl group, an alkoxycarbonyl group having C2-C20 is preferred; as the alkylamino group, an alkylamino group having C1-C30 is preferred; as the alkylthio group, an alkylthio group having C1-C30 is preferred; as the arylthio group, an arylthio group having C6-C24 is preferred; as the alkylsulfonyl group, an alkylsulfonyl group having C1-C20 is preferred; and as the alkylsulfinyl group, an alkylsulfinyl group having C1-C20 is preferred. In one embodiment, R １ and R ２One of them is hydrogen, and the other is alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 10 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkynyl having 2 to 20 carbon atoms, aryl having 6 to 24 carbon atoms, aralkyl having 7 to 24 carbon atoms, carboxylate having 1 to 20 carbon atoms, alkoxy having 1 to 20 carbon atoms, alkenyloxy having 2 to 20 carbon atoms, alkynyloxy having 2 to 20 carbon atoms, aryloxy having 6 to 24 carbon atoms, alkoxycarbonyl having 2 to 20 carbon atoms, alkylamino having 1 to 30 carbon atoms, alkylthio having 1 to 30 carbon atoms, arylthio having 6 to 24 carbon atoms, alkylsulfonyl having 1 to 20 carbon atoms or alkylsulfinyl having 1 to 20 carbon atoms, and these groups may each be substituted with one or more alkyl groups, halogen, alkoxy groups, aryl groups or heteroaryl groups.

[0069] In the above general formulas (1), (2) and (3), L １ and L ２ may combine with each other to form a ring. L １ and L ２ The ring formed by the combination of may be aliphatic or aromatic, and may be optionally substituted and contain one or more heteroatoms. Examples of the heteroatom include oxygen, sulfur, nitrogen, phosphorus and the like.

[0070] In the above general formulas (1), (2) and (3), R １ and R ２ may combine with each other to form a ring. R １ and R ２ When R １ and R ２ combine with the common carbon atom to which they are attached, the ring formed may be aliphatic or aromatic, and may be optionally substituted and contain one or more heteroatoms.

[0071] In the above general formulas (1), (2) and (3), L １ and R １ may combine with each other to form a ring. L １ and R １The ring formed by the bonding of these elements may be aliphatic or aromatic, and may be optionally substituted to contain one or more heteroatoms. Examples of heteroatoms include oxygen, sulfur, nitrogen, and phosphorus.

[0072] The catalyst represented by the above general formula (1) includes the following structural formulas (1-1) to (1-3): A catalyst represented by any of the following formulas is preferred: [wherein Cy represents a cyclohexyl group and Mes represents a mesityl group (also called a "2,4,6-trimethylphenyl group")]. The catalyst of structural formula (1-1) is called the Grubbs first-generation catalyst, the catalyst of structural formula (1-2) is called the Grubbs second-generation catalyst, and the catalyst of structural formula (1-3) is called the Grubbs-Hovbaida second-generation catalyst. Using a catalyst represented by any of structural formulas (1-1) to (1-3) allows the decomposition reaction (metathesis decomposition) of diene rubbers in crosslinked rubber and uncrosslinked rubber to proceed more rapidly.

[0073] The catalyst represented by the above general formula (2) is shown in structural formula (2-1): A catalyst represented by the formula [wherein Mes represents a mesityl group (also called a "2,4,6-trimethylphenyl group")] is preferred. The catalyst represented by structural formula (2-1) is called the Grubbs third-generation catalyst. When the catalyst represented by structural formula (2-1) is used, the decomposition reaction (metathesis decomposition) of diene rubbers in crosslinked rubber and uncrosslinked rubber proceeds more rapidly.

[0074] The catalyst represented by the above general formula (3) is shown in structural formula (3-1): Examples of catalysts include those represented by [formula].

[0075] The amount of the catalyst (metathesis catalyst) used is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, more preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component (diene rubber). If the amount of the catalyst used is 0.1 parts by mass or more per 100 parts by mass of the rubber component (diene rubber), the decomposition reaction of the rubber component proceeds further, and if the amount of the catalyst used is 10 parts by mass or less per 100 parts by mass of the rubber component (diene rubber), it is preferable in terms of cost.

[0076] The decomposition by the metathesis catalyst (hereinafter sometimes simply referred to as "metathesis decomposition") is preferably carried out at a temperature of 20°C to 200°C. Carrying out the metathesis decomposition at a temperature of 20°C or higher improves the rate of the decomposition reaction of rubber components in crosslinked rubber and uncrosslinked rubber. Carrying out the metathesis decomposition at a temperature of 200°C or lower suppresses the decomposition of the catalyst represented by the above general formula (1), (2), or (3) (metathesis catalyst), and also improves the retention rate (selectivity) of the monomer skeleton after decomposition. From the viewpoint of improving the rate of decomposition reaction of diene rubber, the metathesis decomposition is more preferably carried out at a temperature of 25°C or higher, and from the viewpoint of suppressing the decomposition of the metathesis catalyst and improving the selectivity of the product that maintains the monomer skeleton, it is more preferably carried out at a temperature of 100°C or lower.

[0077] The metathesis decomposition described above can be carried out at any pressure, including under reduced pressure, at atmospheric pressure, or under increased pressure. For example, the reaction pressure is preferably 1 kPa to 10 MPa, more preferably 10 kPa to 1 MPa, and even more preferably 50 kPa to 500 kPa.

[0078] In the metathesis decomposition described above, the catalyst represented by the general formula (1), (2), or (3) above may be dissolved in a solvent, or the crosslinked rubber or uncrosslinked rubber may be immersed in the solvent. By reacting the crosslinked rubber or uncrosslinked rubber with the catalyst in the solvent, the decomposition reaction of the rubber components in the crosslinked rubber and uncrosslinked rubber proceeds more easily. Here, any solvent that does not inhibit the decomposition reaction can be used as the solvent, for example, ethers, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons (aromatic solvents), etc. More specifically, tetrahydrofuran (THF), hexane, cyclohexane, pentane, cyclopentane, toluene and xylene are preferred as solvents, and toluene and tetrahydrofuran are more preferred. When the solvent is selected from tetrahydrofuran, hexane, cyclohexane, pentane, cyclopentane, toluene and xylene, the decomposition reaction of the diene rubber in the crosslinked rubber proceeds even more easily. The amount of solvent used is preferably 10 mL or more, more preferably 50 mL or more, more preferably 500 mL or less, and more preferably 200 mL or less, per gram of the crosslinked rubber and / or uncrosslinked rubber. If the amount of solvent used is 10 mL or more per gram of the crosslinked rubber and / or uncrosslinked rubber, the decomposition reaction of the diene rubber in the crosslinked rubber and / or uncrosslinked rubber proceeds further, and if the amount of solvent used is 500 mL or less per gram of the crosslinked rubber and / or uncrosslinked rubber, it is preferable in terms of cost.

[0079] The metathesis decomposition may be carried out in the presence of a chain transfer agent (CTA). Examples of chain transfer agents include cis-1,4-diacetoxy-2-butene and cis-1,4-dibenzyloxy-2-butene. The amount of chain transfer agent used is preferably in the range of 1 to 100 mol per mol of catalyst.

[0080] -Second decomposition method (low-temperature thermal decomposition)- In the second decomposition method, the crosslinked rubber and / or uncrosslinked rubber are thermally decomposed at 150°C to 400°C. Performing thermal decomposition at 150°C or higher improves the rate of the decomposition reaction of diene-based rubber in the crosslinked rubber and / or uncrosslinked rubber, and performing thermal decomposition at 400°C or lower suppresses gasification and aromatization of the decomposition products, and also improves the retention rate (selectivity) of the monomer skeleton after decomposition. From the viewpoint of improving the rate of the decomposition reaction of diene-based rubber, the thermal decomposition is preferably 175°C or higher, and more preferably 190°C or higher. Furthermore, from the viewpoint of improving the selectivity of the product that maintains the monomer skeleton, it is preferably 350°C or lower, and more preferably 300°C or lower.

[0081] The second decomposition method described above is preferably carried out under an inert gas atmosphere. By performing thermal decomposition under an inert gas atmosphere, oxidation and reduction of the decomposition products can be suppressed, and in particular, hydrogenation of double bonds in oligomers and monomers in the decomposition products can be suppressed. Oxidation of recycled carbon black can also be suppressed. Examples of inert gases include nitrogen, carbon dioxide, argon, and helium.

[0082] To carry out the aforementioned thermal decomposition under an inert gas atmosphere, for example, if a batch reactor is used, the atmosphere charged into the reactor should be an inert gas; if a flow-through reactor is used, the atmosphere circulating through the reactor should be an inert gas. Although hydrogen may be generated during thermal decomposition, the generated hydrogen is not taken into consideration when determining the atmosphere for thermal decomposition.

[0083] The aforementioned thermal decomposition can be carried out at any pressure, including under reduced pressure, at atmospheric pressure, or under pressure, but it is preferable to carry it out under reduced pressure or at atmospheric pressure. As an example, the reaction pressure for thermal decomposition is preferably 1000 kPa to 65 kPa. By carrying out thermal decomposition under reduced pressure or at atmospheric pressure, polymerization (repolymerization) of oligomers and monomers in the decomposition product can be suppressed.

[0084] The reaction time for the thermal decomposition is not particularly limited. For example, the reaction time for thermal decomposition is preferably 1 to 180 minutes, more preferably 3 to 60 minutes, and even more preferably 5 to 30 minutes.

[0085] The aforementioned thermal decomposition may or may not use a catalyst, but it is preferable not to use a catalyst. By not using a catalyst for thermal decomposition, costs can be reduced. If a catalyst is used, any catalyst that promotes the decomposition reaction of crosslinked rubber can be used.

[0086] -Third Decomposition Method (Solvent Decomposition)- In the third decomposition method described above, the crosslinked rubber and / or uncrosslinked rubber are decomposed in a solvent. When the crosslinked rubber and / or uncrosslinked rubber are decomposed in a solvent, the crosslinked rubber and / or uncrosslinked rubber swell due to the solvent. By decomposing the crosslinked rubber and / or uncrosslinked rubber under solvent swelling, gasification and aromatization of the decomposition products can be suppressed, and decomposition products (liquid polymers) with a higher retention rate of the skeletons (isoprene skeleton, butadiene skeleton, etc.) of the constituent monomers of the diene rubber can be obtained compared to normal high-temperature thermal decomposition.

[0087] Various solvents having the effect of swelling crosslinked rubber and / or uncrosslinked rubber can be used as the solvent, for example, aromatic solvents, aliphatic solvents, alicyclic solvents, ester solvents, etc. Aromatic solvents include benzene, toluene, xylene, etc., aliphatic solvents include pentane, hexane, heptane, etc., alicyclic solvents include cyclopentane, cyclohexane, etc., and ester solvents include ethyl acetate, propyl acetate, butyl acetate, etc. Among these, at least one selected from the group consisting of toluene, xylene, and cyclohexane is preferred as the solvent, and toluene is particularly preferred. When toluene, xylene, or cyclohexane is used as the solvent, a decomposition product (liquid polymer) with a high retention rate of the skeleton (isoprene skeleton, butadiene skeleton, etc.) of the constituent monomer of the diene rubber can be obtained. The amount of solvent used is preferably 1 mL or more, more preferably 5 mL or more, more preferably 500 mL or less, and more preferably 200 mL or less per gram of the crosslinked rubber and / or uncrosslinked rubber. If the amount of solvent used is 10 mL or more per gram of the crosslinked rubber and / or uncrosslinked rubber, the decomposition reaction of the diene rubber in the crosslinked rubber and / or uncrosslinked rubber will proceed further, and if the amount of solvent used is 500 mL or less per gram of the crosslinked rubber and / or uncrosslinked rubber, it is preferable in terms of cost.

[0088] The decomposition temperature in the solvent is preferably 150 to 300°C. Performing the decomposition in the solvent at 150°C or higher improves the rate of the decomposition reaction of diene rubber in crosslinked rubber and / or uncrosslinked rubber, and performing the decomposition in the solvent at 300°C or lower suppresses gasification and aromatization of the decomposition products, thereby improving the retention rate (selectivity) of the skeleton of the constituent monomer of the diene rubber in the crosslinked rubber and / or uncrosslinked rubber after decomposition. From the viewpoint of improving the rate of the decomposition reaction of crosslinked rubber and / or uncrosslinked rubber, the decomposition temperature in the solvent is preferably 160°C or higher, and more preferably 180°C or higher. Furthermore, from the viewpoint of improving the selectivity of products that maintain the monomer skeleton, it is preferably 280°C or lower, and more preferably 250°C or lower.

[0089] The decomposition time in the solvent is not particularly limited. For example, the decomposition time in the solvent is preferably 1 to 48 hours, and more preferably 3 to 18 hours. Decomposition in the solvent for 1 hour or more improves the decomposition rate of the crosslinked rubber and / or uncrosslinked rubber. On the other hand, if the reaction time is too long, the skeleton (double bonds, etc.) of the constituent monomers of the diene rubber may be decomposed, or the decomposition products may be gasified or aromatized. However, by decomposing in the solvent for 48 hours or less, the decomposition of the monomer skeleton and the gasification and aromatization of the decomposition products can be suppressed, and the retention rate (selectivity) of the skeleton of the constituent monomers of the diene rubber in the crosslinked rubber and / or uncrosslinked rubber after decomposition is improved.

[0090] The decomposition in the solvent is preferably carried out under an inert gas atmosphere. By carrying out the decomposition in the solvent under an inert gas atmosphere, the amount of active species (oxygen, hydrogen, etc.) dissolved in the solvent can be reduced, thereby suppressing oxidation and reduction of the decomposition products, and in particular, the hydrogenation of double bonds in oligomers and monomers in the decomposition products can be suppressed. Examples of inert gases include nitrogen, carbon dioxide, argon, and helium.

[0091] To carry out the decomposition in the aforementioned solvent under an inert gas atmosphere, for example, when using a batch reactor, the atmosphere supplied to the reactor should be an inert gas, and when using a flow-through reactor, the atmosphere circulating through the reactor should be an inert gas. Although hydrogen may be generated during the decomposition in the solvent, the generated hydrogen is not taken into consideration when determining the atmosphere for the decomposition in the solvent.

[0092] The decomposition in the solvent can be carried out at any pressure, including under reduced pressure, at atmospheric pressure, or under pressure. For example, the reaction pressure is preferably 1 kPa to 10 MPa, more preferably 10 kPa to 5 MPa, and even more preferably 50 kPa to 2 MPa.

[0093] A catalyst may or may not be used for the decomposition in the aforementioned solvent, but it is preferable not to use a catalyst. By not using a catalyst for the decomposition in the aforementioned solvent, costs can be reduced. If a catalyst is used, any catalyst that has the effect of promoting the decomposition reaction of crosslinked rubber and / or uncrosslinked rubber can be used.

[0094] -Other Decomposition Methods- The liquid polymer preparation step in the organic material decomposition method of this embodiment is not limited to the first, second, and third decomposition methods described above. As for the decomposition method in the liquid polymer preparation step, a decomposition method in which 30% or more of the basic structure of the polymer is retained is preferred, a decomposition method in which 50% or more of the polymer structure is retained is more preferred, and a decomposition method in which 70% or more of the polymer structure is even more preferred.

[0095] (Decomposition Products (Intermediate Decomposition Products)) In the organic material decomposition method of this embodiment, a liquid polymer and the like are obtained as decomposition products through the "liquid polymer preparation step" described above. Furthermore, if the crosslinked rubber or uncrosslinked rubber contains carbon black along with the rubber component, the carbon black can be recovered together with the liquid polymer by going through the "liquid polymer preparation step," and the carbon black can be reused.

[0096] "Step of decomposing liquid polymer" The method for decomposing organic materials in this embodiment includes a step of decomposing the liquid polymer using the liquid polymer decomposition method described above. This decomposition step can be carried out according to the method described in the "Method for decomposing liquid polymer" section above.

[0097] (Decomposition Products) In the method for decomposing organic materials of this embodiment, monomers and the like are obtained as decomposition products by the decomposition step. The decomposition products are as described in the section "Method for Decomposing Liquid Polymers" above.

[0098] "Other" The organic material decomposition method of this embodiment can be carried out in either a batch reactor or a flow-through reactor. In addition to the liquid polymer preparation step and liquid polymer decomposition step described above, the organic material decomposition method of this embodiment may also include other steps. Such steps include a pretreatment step for the organic material (e.g., a cutting step, a grinding step) and a separation and purification step for the decomposition products. Furthermore, if the organic material contains carbon black, it is preferable to include a step to recover carbon black from the decomposition products (intermediate decomposition products) after the liquid polymer preparation step. Also, for example, by distilling the decomposition products of the liquid polymer decomposition step, the target monomer and other by-products can be separated, and the target monomer can be reused as a raw material for rubber (polymer) synthesis.

[0099] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0100] <Examples 1-5> Liquid polyisoprene (manufactured by Kuraray Co., Ltd., trade name "LIR-30", weight-average molecular weight (Mw) = 30,000) was dispersed in 10 mL of toluene at concentrations of 1.0 mg / mL, 2.5 mg / mL, 5.0 mg / mL, 10.0 mg / mL, and 20.0 mg / mL to prepare toluene dispersions of liquid polyisoprene.

[0101] A reaction tube (quartz tube, inner diameter = 7 mm, heating section distance = 10 cm) was installed inside a tubular electric furnace. A helium introduction line was provided upstream of the reaction tube, and a cooling trap (60% ethylene glycol aqueous solution, cooled to -20°C) filled with chloroform was provided downstream. The gas that passed through the trap was recovered using a gas bag. Under conditions of a helium flow rate of 50 mL / min, the toluene dispersion of liquid polyisoprene (sample) prepared as described above was sprayed into the reaction tube located in the heating section of the electric furnace heated to 700°C using a syringe pump, and thermal decomposition was carried out. The sample supply rate was 1 mL / min, and the residence time in the heating section was 4.6 seconds. After the reaction was completed, the reaction tube was cooled, and the products precipitated in the reaction tube and trap were recovered, and the gaseous products were also recovered using a gas bag. The mass percentage (yield) of each product is shown in Table 1. Furthermore, the yields of isoprene, limonene, other aliphatic compounds, and aromatic compounds in the liquid product were measured by gas chromatography (GC). The results are summarized in Table 1.

[0102]

[0103] *1 Yield of gaseous products: Calculated from the amount of decomposition products recovered in the gas bag. *2 Yield of liquid products: Calculated from the amount of components that could be qualitatively analyzed by gas chromatography (GC) out of the total amount of (1) decomposition products recovered in the cooling trap and (2) components that dissolved in chloroform among the components adhering to the reaction tube. *3 Yield of oligomers: Calculated from the amount of components that could not be qualitatively analyzed by gas chromatography (GC) out of the total amount of (1) decomposition products recovered in the cooling trap and (2) components that dissolved in chloroform among the components adhering to the reaction tube. *4 Yield of solid products: Calculated from the total amount of (1) residue from the thermal decomposition reaction and (2) components that did not dissolve in chloroform among the components adhering to the reaction tube.

[0104] Table 1 shows that isoprene can be obtained in high yield according to the liquid polymer decomposition method of the present invention.

[0105] <Analysis Method for Liquid Polymers> (1) Analysis Method for Monomer Skeleton Retention Rate Using the "Nuclear Magnetic Resonance Spectrometer JNM-ECA-500" manufactured by JEOL Ltd. as an NMR spectrometer, the decomposition products (liquid polymers) obtained were analyzed to calculate the retention rate of the isoprene skeleton derived from natural rubber contained in the crosslinked rubber sample.

[0106] (2) Method for Analyzing the Weight-Average Molecular Weight (Mw) of Liquid Polymers The weight-average molecular weight (Mw) of the decomposition products (liquid polymers) in polystyrene equivalent was determined using gel permeation chromatography (hereinafter sometimes referred to as GPC analysis. Liquid delivery unit: Shimadzu LC-20AB, Column: combination of Showa Denko KF-803 and KF-804 or combination of Tosoh G2000HXL and G4000HXL, Detector: Shimadzu differential refractometer RID-10A, Analysis system: Shimadzu LabSolutions, Eluent: Tetrahydrofuran), with monodisperse standard polystyrene as the reference. The measurement temperature was 40°C.

[0107] <Preparation of Crosslinked Rubber Samples> A rubber composition was prepared by blending 100 parts by mass of natural rubber with 50 parts by mass of carbon black, 1.0 part by mass of the antioxidant 6PPD [N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine], 2.0 parts by mass of stearic acid, 2.5 parts by mass of zinc oxide, 1.5 parts by mass of the vulcanization accelerator (N-cyclohexyl-2-benzothiazolyl sulfenamide), and 4.5 parts by mass of sulfur. The rubber composition was then heated and crosslinked to prepare crosslinked rubber. The obtained crosslinked rubber was cut into 3 mm × 3 mm × 2 mm shapes to prepare crosslinked rubber samples.

[0108] <Examples 6-8> (Preparation of Liquid Polymer) 0.4 g of crosslinked rubber sample and 4 mL of toluene were added to a reactor and stirred under an Ar atmosphere at 200°C or 240°C for 6 or 9 hours to carry out the decomposition reaction. After the reaction, the mixture was separated into solvent (toluene) soluble components and solvent-insoluble components. The solvent-soluble components consisted mainly of liquid polymer, while the solvent-insoluble components consisted mainly of carbon black. The obtained solvent-soluble components (liquid polymer) were then subjected to the following treatment: １¹H-NMR analysis was performed to calculate the retention rate of the isoprene skeleton. Furthermore, the weight-average molecular weight (Mw) of the liquid polymer was analyzed using GPC analysis.

[0109] 25 mg of the liquid polymer obtained as described above was dissolved in 10 mL of toluene to prepare a toluene solution of the liquid polymer with a concentration of 2.5 mg / mL.

[0110] (Decomposition of Liquid Polymer) A reaction tube (quartz tube, inner diameter = 7 mm, heating section distance = 10 cm) was placed inside a tubular electric furnace. A helium introduction line was provided upstream of the reaction tube, and a cooling trap (60% ethylene glycol aqueous solution, cooled to -20°C) filled with chloroform was provided downstream, and the gas that passed through the trap was recovered using a gas bag. Under conditions of a helium flow rate of 50 mL / min, the toluene dispersion of the liquid polymer (sample) prepared as described above was sprayed into the reaction tube located in the heating section of the electric furnace heated to 700°C using a syringe pump, and thermal decomposition was carried out. The sample supply rate was 0.5 mL / min, and the residence time in the heating section was 4.6 seconds. After the reaction was completed, the reaction tube was cooled, and the products precipitated in the reaction tube and trap were recovered, and the gaseous products were also recovered using a gas bag. The mass percentage (yield) of each product is shown in Table 2. Furthermore, the yields of isoprene, limonene, other aliphatic compounds, and aromatic compounds in the liquid product were measured by gas chromatography (GC). The results are summarized in Table 2.

[0111]

[0112] *1 Yield of gaseous products: Calculated from the amount of decomposition products recovered in the gas bag. *2 Yield of liquid products: Calculated from the amount of components that could be qualitatively analyzed by gas chromatography (GC) out of the total amount of (1) decomposition products recovered in the cooling trap and (2) components that dissolved in chloroform among the components adhering to the reaction tube. *3 Yield of oligomers: Calculated from the amount of components that could not be qualitatively analyzed by gas chromatography (GC) out of the total amount of (1) decomposition products recovered in the cooling trap and (2) components that dissolved in chloroform among the components adhering to the reaction tube. *4 Yield of solid products: Calculated from the total amount of (1) residue from the thermal decomposition reaction and (2) components that did not dissolve in chloroform among the components adhering to the reaction tube.

[0113] Table 2 shows that isoprene can be obtained in high yield according to the liquid polymer decomposition method (and organic material decomposition method) of the present invention.

[0114] <Comparative Examples 1-3> (Decomposition of Liquid Polymer) 0.1 g of a liquid rubber sample (liquid polyisoprene LIR-30, manufactured by Kuraray Co., Ltd.) wrapped in quartz wool (Fine, manufactured by Tosoh, fiber diameter: 2-6 μm) was packed into a reaction tube, and quartz wool was packed into the upstream and downstream sides. A helium introduction line was provided on the upstream side of the reaction tube, and a cooling trap (60% ethylene glycol aqueous solution, cooled to -20°C) filled with chloroform was provided on the downstream side, and the gas that passed through the trap was recovered in a gas bag. Under the condition of a helium flow rate of 50 mL / min, the liquid rubber sample in the reaction tube was slid into a heating section in an electric furnace heated to 500°C, 600°C, or 700°C, and heated at that temperature for 3 minutes to perform thermal decomposition. At this time, the temperature of the liquid rubber sample was monitored with a thermocouple and the heating rate was determined. After the reaction was complete, the reaction tube was cooled, and the precipitated products in the reaction tube and trap were collected. The gaseous products were also collected using a gas bag. The mass percentage (yield) of each product is shown in Table 3. Furthermore, the yields of isoprene, limonene, toluene, xylene, other aromatic compounds, and other aliphatic compounds in the liquid product were measured by gas chromatography (GC), and the total yield of C4-C10 chemicals was determined.

[0115]

[0116] *1 Yield of gaseous products: Calculated from the amount of decomposition products recovered in the gas bag. *2 Yield of liquid products: Calculated from the amount of components that could be qualitatively analyzed by gas chromatography (GC) out of the total amount of (1) decomposition products recovered in the cooling trap and (2) components that dissolved in chloroform among the components adhering to the reaction tube. *3 Yield of oligomers: Calculated from the amount of components that could not be qualitatively analyzed by gas chromatography (GC) out of the total amount of (1) decomposition products recovered in the cooling trap and (2) components that dissolved in chloroform among the components adhering to the reaction tube. *4 Yield of solid products: Calculated from the sum of (1) the amount obtained by subtracting the carbon black content in the cross-linked rubber sample from the residue of the thermal decomposition reaction and (2) the amount of components that did not dissolve in chloroform among the components adhering to the reaction tube.

[0117] Table 3 shows that when liquid polymers are decomposed without being dissolved in a solvent, the yield of isoprene is low.

Claims

1. A method for decomposing a liquid polymer, comprising the step of decomposing the liquid polymer in a decomposition furnace, wherein the temperature in the decomposition furnace is 450°C or higher and 800°C or lower, the liquid polymer is dissolved or dispersed in an organic solvent, and the concentration of the liquid polymer in the organic solvent is 0.5 to 1000 mg / mL.

2. The method for decomposing a liquid polymer according to claim 1, wherein the organic solvent has a boiling point of 80 to 220°C.

3. The method for decomposing a liquid polymer according to claim 1, wherein the liquid polymer is dissolved or dispersed in the organic solvent and then sprayed in the decomposition furnace to form a mist.

4. The method for decomposing a liquid polymer according to claim 1, wherein the liquid polymer has a weight-average molecular weight (Mw) of 100,000 or less.

5. The method for decomposing a liquid polymer according to claim 1, further comprising the step of lowering the temperature of the decomposition product after the step of decomposing the liquid polymer.

6. The method for decomposing a liquid polymer according to claim 3, wherein the liquid polymer is heated from 100°C to 450°C at a heating rate of 800°C / min or more.

7. The method for decomposing a liquid polymer according to claim 3, wherein the liquid polymer is heated from 100°C to 500°C at a heating rate of 800°C / min or more.

8. The method for decomposing a liquid polymer according to claim 3, wherein the liquid polymer is heated from 100°C to 450°C at a heating rate of 2000°C / min or more.

9. The method for decomposing a liquid polymer according to claim 3, wherein the liquid polymer is heated from 100°C to 500°C at a heating rate of 2000°C / min or more.

10. The method for decomposing a liquid polymer according to claim 1, wherein the liquid polymer is a diene polymer.

11. A method for decomposing an organic material, comprising the steps of: preparing a liquid polymer by decomposing an organic material selected from crosslinked rubber and uncrosslinked rubber; and decomposing the liquid polymer using the liquid polymer decomposition method described in any one of claims 1 to 10.

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