Method for recycling rubber product, tire, tire chips, and tire powder

Abstract

The present invention provides a method for recycling a rubber product, the method being capable of preventing degradation in the quality of produced oil. This recycling method is for recycling a rubber product provided with a composite of a rubber member and an organic fiber cord, wherein this recycling method is characterized by comprising: a crushing step of crushing the rubber product to obtain rubber chips containing a crushed product of the rubber member and a crushed product of the organic fiber cord; and a thermal decomposition step of thermally decomposing the rubber chips to obtain produced oil. This recycling method is characterized in that the organic fiber cord includes at least one fiber selected from the group consisting of a polyester fiber, a nylon fiber, and an aramid fiber. This recycling method is also characterized in that the rubber chips thermally decomposed in the thermal decomposition step contain not more than 30g of the crushed product of the organic fiber cord per 1 kg of the crushed product of the rubber member.

Description

Methods for recycling rubber products, tires, tire chips and tire dust

[0001] This invention relates to a method for recycling rubber products, tires, tire chips, and tire powder.

[0002] Polymer materials such as rubber and resins have been produced and consumed in large quantities as useful functional materials in the industrial sector. However, the disposal of the large amount of polymer waste generated is now a significant social issue. To address this social challenge, research is being conducted on methods for recycling polymer waste.

[0003] For example, Patent Document 1 discloses a process for regenerating oil from the thermal decomposition of hydrocarbon-containing materials, such as cut-up vehicle tires.

[0004] Japanese Patent Publication No. 2002-544322

[0005] When regenerating oil by thermally decomposing rubber products, the rubber products are usually crushed to obtain rubber chips before thermal decomposition. However, if the rubber chips contain a lot of moisture, that moisture may mix with the generated oil, potentially degrading its quality.

[0006] This invention has been made in view of the above circumstances, and aims to provide a method for recycling rubber products that can prevent deterioration of the quality of the generated oil. Furthermore, this invention aims to provide a tire that can be used as a rubber product in the above-described method for recycling rubber products, which is durable and easy to recycle. Furthermore, this invention aims to provide tire chips and tire powder, which are intermediate products in the recycling process.

[0007] The gist of the recycling method of the present invention that solves the above problems is as follows.

[0008] [1] A method for recycling a rubber product comprising a composite of a rubber member and an organic fiber cord, comprising: a crushing step of crushing the rubber product to obtain rubber chips containing crushed rubber member material and crushed organic fiber cord material; and a thermal decomposition step of thermally decomposing the rubber chips to obtain a generated oil, wherein the organic fiber cord comprises at least one selected from the group consisting of polyester fiber, nylon fiber, and aramid fiber, and the rubber chips thermally decomposed in the thermal decomposition step contain an amount of crushed organic fiber cord material of 30 g or less per 1 kg of crushed rubber member material.

[0009] [2] The recycling method according to [1], wherein the organic fiber cord includes polyester fibers.

[0010] [3] The recycling method according to [1] or [2], wherein the thermal decomposition step involves continuously thermally decomposing the rubber chips.

[0011] [4] The recycling method according to any one of [1] to [3], wherein the rubber chips have a maximum length of 0.5 to 2.5 inches.

[0012] [5] The recycling method according to [2], wherein the polyester fiber is polyethylene terephthalate fiber and / or polyethylene-2,5-flangecarboxylate fiber.

[0013] [6] The recycling method according to any one of [1] to [5], wherein the rubber chips reach a temperature of 40°C or higher and 200°C or lower.

[0014] [7] The recycling method according to any one of [1] to [6], further comprising a drying step of drying the rubber chips.

[0015] [8] The recycling method according to [7], wherein the rubber chips are dried by blowing air in the drying step.

[0016] [9] The recycling method according to [7] or [8], wherein in the drying step, the rubber chips are heated to 100°C or more and 200°C or less.

[0017]

[10] The recycling method according to [6], wherein the rubber chips reach a temperature of 40°C or higher and 200°C or lower under reduced pressure.

[0018]

[11] The recycling method according to any one of [7] to [9], wherein the drying step is carried out under reduced pressure.

[0019]

[12] The recycling method according to any one of [1] to

[11] , wherein the rubber product is a tire comprising a rubber member and an organic fiber cord, the organic fiber cord contains at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polyethylene-2,5-flangecarboxylate in a content of 80% by mass or more of the total mass of the organic fiber cord, and the twist coefficient R, defined by the following formula R, is 0.20 to 0.50. Formula R: N × (0.139 × D / ρ × 0.9) １／２ ×10 －３ In formula R, N represents the number of twists (twists / 10 cm) of the organic fiber cord, D represents the total dtex number of the organic fiber cord, and ρ represents the specific gravity of the organic fiber cord.

[0020]

[13] The recycling method according to

[12] , wherein the twist coefficient R is 0.30 to 0.40.

[0021]

[14] The recycling method according to

[12] or

[13] , wherein the fineness of the organic fiber cord is 1000 dtex to 7000 dtex.

[0022]

[15] The recycling method according to any one of

[12] to

[14] , wherein the tire comprises a belt layer arranged in the tread portion and a belt reinforcing layer arranged on the radially outer side of the belt layer, and the belt reinforcing layer includes the organic fiber cord.

[0023]

[16] A tire comprising a rubber member and an organic fiber cord, wherein the organic fiber cord contains at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polyethylene-2,5-flangecarboxylate in a content of 80% by mass or more relative to the total mass of the organic fiber cord, and the twist coefficient R, defined by the following formula R, is 0.20 to 0.50. Formula R: N × (0.139 × D / ρ × 0.9) １／２ ×10 －３ In formula R, N represents the number of twists (twists / 10 cm) of the organic fiber cord, D represents the total dtex number of the organic fiber cord, and ρ represents the specific gravity of the organic fiber cord.

[0024]

[17] Tire chips, which are the crushed tire material described in

[16] .

[0025]

[18] Tire powder, which is the crushed tire material described in

[16] .

[0026] The present invention provides a method for recycling rubber products that can prevent deterioration of the quality of the generated oil. Furthermore, the present invention provides a tire that can be used as a rubber product in the above-described method for recycling rubber products, which is durable and easy to recycle. Furthermore, the present invention provides tire chips and tire powder, which are intermediate products in the recycling process.

[0027] This is a partial cross-sectional view of a tire relating to an embodiment of the present invention.

[0028] The recycling method of the present invention will be described in detail below, based on its embodiments. 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, and recycled resources.

[0029] In this specification, a numerical range indicated using "~" means a range that includes the numerical values ​​before and after "~" as the lower and upper limits, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0030] In this specification, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, it refers to the total amount of all substances present in the composition unless otherwise specified.

[0031] In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, the molecular weight of a compound having a molecular weight distribution is the weight-average molecular weight (Mw; the same applies hereinafter) unless otherwise specified.

[0032] In this specification, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as their intended function is achieved.

[0033] A recycling method according to one embodiment of the present invention (hereinafter sometimes referred to as "the recycling method of this embodiment") is a method for recycling a rubber product comprising a composite of a rubber member and an organic fiber cord, comprising at least a crushing step of crushing the rubber product to obtain rubber chips containing crushed rubber member material and crushed organic fiber cord material, and a thermal decomposition step of thermally decomposing the rubber chips to obtain generated oil. The recycling method of this embodiment is characterized in that the organic fiber cord comprises at least one selected from the group consisting of polyester fiber, nylon fiber, and aramid fiber, and the rubber chips thermally decomposed in the thermal decomposition step contain an amount of crushed organic fiber cord material of 30 g or less per 1 kg of crushed rubber member material.

[0034] As a result of diligent research by the inventors, it was found that organic fiber cords contained in rubber products such as tires have high water absorption and can contain a large amount of moisture. Furthermore, it was found that this can lead to a large amount of moisture in the rubber chips, which can then be mixed into the generated oil, causing a deterioration in the quality of the generated oil. It was also found that polyester fibers, nylon fibers, and aramid fibers have lower water absorption compared to other fibers, and that using these as tire reinforcement materials can reduce the amount of moisture contained in the rubber chips. As a result of further diligent research by the inventors, it was found that the organic fiber cords include at least one selected from the group consisting of polyester fibers, nylon fibers, and aramid fibers, and that the amount of crushed organic fiber cords in the rubber chips thermally decomposed in the thermal decomposition process is 30 g or less per 1 kg of crushed rubber material, thereby reducing the amount of moisture contained in the rubber chips and thus reducing the amount of moisture contained in the generated oil, and as a result, preventing a deterioration in the quality of the generated oil. Therefore, the recycling method of this embodiment can prevent a deterioration in the quality of the generated oil.

[0035] Furthermore, according to the recycling method of this embodiment, the amount of moisture contained in the rubber chips that are to be thermally decomposed is reduced, which has the effect of preventing deterioration of the furnace used during thermal decomposition.

[0036] <Rubber Products> The rubber products in the recycling method of this embodiment comprise a composite of a rubber member and an organic fiber cord. Such rubber products are, for example, rubber products that have been used once, or collected or discarded without being used.

[0037] The rubber product may consist of a composite of a rubber component and an organic fiber cord, and may also include metals such as steel cords or wires.

[0038] Examples of rubber products include, for example, tires, vibration-damping rubber, seismic isolation rubber, belts such as conveyor belts, rubber tracks, and various hoses. Among these, in the recycling method of this embodiment, it is preferable to use tires, especially used tires, as the rubber product.

[0039] The rubber member contains a rubber component. The rubber component is not particularly limited and can be appropriately selected according to the purpose. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), etc. can be mentioned. The rubber component may be used alone or in combination of two or more.

[0040] The organic fiber cord contains at least one selected from the group consisting of polyester fiber, nylon fiber and aramid fiber. Polyester fiber, nylon fiber and aramid fiber have low water absorption compared with other organic fibers. Therefore, the amount of moisture contained in the rubber chips thermally decomposed in the thermal decomposition process can be reduced, and the amount of moisture contained in the produced oil can be reduced. In addition, since the amount of moisture contained in the rubber chips to be thermally decomposed is reduced, the effect of preventing deterioration of the furnace used in the thermal decomposition can also be achieved. Note that the fibers contained in the tire chips used as the raw material for tire thermal decomposition can be used as the raw material in a state containing moisture by spraying cooling water during crushing or storing outdoors after crushing into chips. Therefore, as the above fibers, fibers with low water absorption are advantageous.

[0041] Examples of the polyester fiber include polyethylene terephthalate (PET) fiber, polyethylene-2,5-furandicarboxylate (PEF) fiber, polyethylene naphthalate (PEN) fiber, polytrimethylene terephthalate (PTT) fiber, polybutylene terephthalate (PBT) fiber, polybutylene naphthalate (PBN) fiber, polyethylene succinate fiber, etc.

[0042] Examples of nylon fibers include nylon 6 fiber, nylon 11 fiber, nylon 12 fiber, nylon 66 fiber, nylon 610 fiber, nylon 612 fiber, nylon 46 fiber, nylon 6T fiber, nylon 6I fiber, nylon 9T fiber, nylon 410 fiber, and the like.

[0043] Examples of aramid fibers include poly(p-phenylene terephthalamide) fiber, poly(m-phenylene isophthalamide) fiber, and the like.

[0044] From the viewpoint of further reducing the amount of moisture contained in the rubber chips and more effectively reducing the amount of moisture contained in the produced oil, the organic fiber cord preferably contains polyester fiber. Also, from the same viewpoint, the above polyester fiber is preferably polyethylene terephthalate fiber and / or polyethylene-2,5-furandicarboxylate fiber.

[0045] In the rubber product, the amount of the organic fiber cord with respect to 100 parts by mass of the rubber member may be 5 to 20 parts by mass.

[0046] The rubber member may further appropriately contain a filler, a crosslinking agent, an antioxidant, a softening agent, and the like.

[0047] Examples of the filler include carbon black, silica, aluminum hydroxide, clay, alumina, talc, mica, kaolin, glass balloon, glass beads, calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium oxide, titanium oxide, potassium titanate, barium sulfate, and the like. These fillers may be used alone or in combination of two or more.

[0048] The silica mentioned above is not particularly limited, and examples include wet silica (hydrated silica), dry silica (anhydrous silica), calcium silicate, aluminum silicate, etc., with wet silica being preferred among these. These silicas may be used individually or in combination of two or more. Furthermore, in the present invention, the physical properties of the silica used, such as the BET specific surface area and the cetyltrimethylammonium bromide specific surface area (CTAB), are not particularly limited and can be appropriately selected according to the performance of the tire obtained from the rubber composition.

[0049] When the rubber component contains a filler, the amount of filler in the rubber component is preferably 10 to 150 parts by mass per 100 parts by mass of rubber component.

[0050] In particular, from the viewpoint of more reliably obtaining the effects of the recycling method of this embodiment, the amount of silica in the rubber member per 100 parts by mass of rubber component is preferably 0 to 120 parts by mass, more preferably 0 to 50 parts by mass, 0 to 30 parts by mass, 0 to 20 parts by mass, or 0 to 10 parts by mass, and more preferably 0 to 5 parts by mass. Similarly, from the same viewpoint, the amount of aluminum hydroxide in the rubber member per 100 parts by mass of rubber component is more preferably 0 to 50 parts by mass, 0 to 30 parts by mass, 0 to 20 parts by mass, or 0 to 10 parts by mass, and more preferably 0 to 5 parts by mass. This is because silica and aluminum hydroxide tend to retain moisture, which is preferable from the viewpoint of balancing the required performance of the tire with the amount of moisture.

[0051] Examples of crosslinking agents include sulfur-based crosslinking agents (sulfurizing agents) such as sulfur, organic peroxide-based crosslinking agents, inorganic crosslinking agents, polyamine crosslinking agents, resin crosslinking agents, oxime-nitrosamine-based crosslinking agents, and the like.

[0052] When the rubber component contains a crosslinking agent, the amount of the crosslinking agent per 100 parts by mass of the rubber component is preferably 0.1 to 20 parts by mass.

[0053] If the rubber component contains the above-mentioned sulfur-based crosslinking agent (vulcanizing agent), it may further contain a vulcanization accelerator. Examples of the above-mentioned vulcanization accelerator include compounds such as guanidine, aldehyde-amine, aldehyde-ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, and xantate compounds.

[0054] Examples of anti-aging agents include amine-ketone compounds, imidazole compounds, amine compounds, phenolic compounds, sulfur compounds, and phosphorus compounds.

[0055] When the rubber component contains an anti-aging agent, the amount of the anti-aging agent per 100 parts by mass of the rubber component is preferably 0.1 to 5 parts by mass.

[0056] <Crushing Process> In the recycling method of this embodiment, the crushing process involves crushing the rubber product to obtain rubber chips containing crushed rubber material (hereinafter sometimes referred to as "crushed rubber material") and crushed organic fiber cord (hereinafter sometimes simply referred to as "crushed fiber material").

[0057] There are no particular limitations on the operation for crushing rubber products, but examples include crushing with a single-shaft or twin-shaft shredder, crushing with a water jet, and laser crushing.

[0058] In the crushing process, a portion of the organic fiber cord or crushed organic fiber cord may be separated from the rubber chips. To further reduce the content of crushed fibers in the rubber chips, it is preferable to remove the separated organic fiber cord or crushed organic fiber cord from the rubber chips in the crushing process. There are no particular limitations on the operation for removing the separated organic fiber cord or crushed organic fiber cord from the rubber chips, but examples include specific gravity separation and sieving.

[0059] The rubber chips preferably have a maximum length of 0.5 to 2.5 inches. By crushing the rubber chips so that their maximum length falls within the above range, it is possible to efficiently increase the amount of organic fiber cord or crushed organic fiber cord that can be separated from the rubber chips. Furthermore, a maximum length of 0.5 to 2.5 inches is preferable when the rubber chips are continuously thermally decomposed, as will be described later.

[0060] If rubber products contain metals, the rubber chips may also contain metals. Therefore, if rubber products contain metals, the metals may be removed from the rubber chips during the crushing process. There are no particular limitations on the operation for removing metals from rubber chips, but examples include magnetic separation and sieving.

[0061] During the crushing process, heat may be generated due to frictional heat and other factors when crushing rubber products. If the rubber products and / or rubber chips become hot due to the heat generated during crushing, there is a risk that the rubber products and / or rubber chips may ignite. In addition, if heat is generated during crushing, the rubber material may soften, which may reduce the crushing efficiency. For this reason, it is preferable to crush rubber products in a way that suppresses the heat generated during crushing. Specifically, in order to suppress the heat generated during crushing, it is preferable to crush the rubber products and / or rubber chips (the materials to be processed in the crushing process) while they are in contact with water.

[0062] In the recycling method of this embodiment, it is preferable that the rubber chips reach a temperature of 40°C to 200°C. The rubber chips may reach a temperature of 40°C to 200°C at any time in the recycling method of this embodiment, for example, in the drying process described later. In the recycling method of this embodiment, when the rubber chips reach a temperature of 40°C to 200°C, a drying effect occurs on the rubber chips, and the effects of the recycling method of this embodiment can be obtained more reliably. Also, from a similar viewpoint, it is more preferable that the rubber chips reach a temperature of 45°C to 50°C to 60°C to 70°C to 80°C to 10

[0063] In the recycling method of this embodiment, it is more preferable that the rubber chips reach a temperature of 40°C to 200°C under reduced pressure. In the recycling method of this embodiment, when the rubber chips reach a temperature of 40°C to 200°C under reduced pressure, a more effective drying action occurs on the rubber chips, and the effects of the recycling method of this embodiment can be obtained more reliably. Also, from a similar viewpoint, it is preferable that the rubber chips reach a temperature of 45°C or higher, 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, or 100°C or higher under reduced pressure. When the rubber chips reach the above temperatures under reduced pressure, the degree of reduced pressure can be appropriately selected without particular limitations, but for example, it is preferable to have a pressure of 1000 Pa or less, 100 Pa or less, or 10 Pa or less.

[0064] <Thermal Decomposition Process> In the recycling method of this embodiment, the rubber chips obtained in the crushing process are thermally decomposed in the thermal decomposition process to obtain the generated oil. In the thermal decomposition process, for example, by thermally decomposing the rubber chips, a thermal decomposition gas is generated, and the generated oil can be obtained as an oil by cooling the thermal decomposition gas.

[0065] The temperature in the thermal decomposition process is not particularly limited as long as the rubber chips can be thermally decomposed, and may be, for example, 300°C to 800°C. Furthermore, the temperature in the thermal decomposition process is preferably 350°C or higher, more preferably 390°C or higher, preferably 750°C or lower, and more preferably 710°C or lower.

[0066] The pyrolysis process is preferably carried out in an atmosphere that is substantially free of oxygen (i.e., under an oxygen-free gas). The oxygen-free gas is not particularly limited, but examples include inert gases such as nitrogen, argon, and helium; hydrogen; and hydrocarbons having 1 to 4 carbon atoms.

[0067] The pyrolysis process may be carried out in the presence of a pyrolysis catalyst. The pyrolysis catalyst is not particularly limited, but examples include zeolites, montmorillonite, carbonates such as sodium carbonate, and the like.

[0068] In the pyrolysis process, the rubber chips may be pyrolyzed continuously (continuous method) or in batches (batch method). From the viewpoint of productivity of the produced oil, it is preferable to pyrolyze the rubber chips continuously in the pyrolysis process.

[0069] The pyrolysis process may be carried out in an apparatus having a furnace. The furnace is not particularly limited, but examples include a kettle-type pyrolysis furnace, a fluidized bed-type pyrolysis furnace, a kiln-type pyrolysis furnace, an auger furnace, etc.

[0070] In the thermal decomposition process, the rubber chips that are thermally decomposed have a fiber fragment content of 30 g or less per 1 kg of rubber fragments. From the viewpoint of reducing the amount of water contained in the generated oil and preventing a deterioration in the quality of the generated oil, it is preferable that the above-mentioned fiber fragment content be low. However, in composites of rubber members and organic fiber cords, the rubber member and the organic fiber cord are typically strongly bonded, and the operation of removing the organic fiber cord or organic fiber cord fragments separated from the rubber chips is time-consuming and costly. Furthermore, if the fiber fragment content of the rubber fragments exceeds 30 g per 1 kg of rubber fragments, it may not be possible to sufficiently reduce the amount of water contained in the rubber chips that are thermally decomposed in the thermal decomposition process, and thus may not be possible to reduce the amount of water contained in the generated oil. Therefore, taking into account the balance between the quality of the generated oil and the time and cost of the operation of removing the organic fiber cord or organic fiber cord fragments separated from the rubber chips, in the recycling method of this embodiment, the fiber fragment content of the rubber chips that are thermally decomposed in the thermal decomposition process is set to 30 g or less per 1 kg of rubber fragments. Furthermore, by keeping the fiber shredder content at 30g or less per 1kg of rubber shredder, the amount of moisture contained in the rubber chips, which are the target of thermal decomposition, is reduced, thus preventing the deterioration of the furnace.

[0071] The amount of fiber fragments in rubber chips that are thermally decomposed in the thermal decomposition process can be calculated by determining the "total amount of fiber fragments in rubber chips (g)" by subtracting the "total amount of organic fiber cords and organic fiber cord fragments removed in the crushing process (g)" from the "total amount of organic fiber cords contained in the composite of rubber material and organic fiber cords (g)", and then dividing the "total amount of fiber fragments in rubber chips (g)" by the "total amount of rubber fragments in rubber chips (kg)".

[0072] From the viewpoint of the cost and effort involved in the operation of removing organic fiber cords or crushed organic fiber cords separated from rubber chips, it is preferable that the content of crushed fiber material in the rubber chips thermally decomposed in the thermal decomposition process is 10 g or more per 1 kg of crushed rubber material.

[0073] In this embodiment, since rubber chips with a low fiber crushing content are thermally decomposed, the amount of water in the resulting oil obtained in the thermal decomposition process is reduced. From the viewpoint of the quality of the resulting oil, it is preferable that the amount of water contained in the resulting oil is 5% by mass or less of the total amount of the resulting oil.

[0074] <Drying Process> The recycling method of this embodiment preferably further comprises a drying process for drying the rubber chips. More specifically, the recycling method of this embodiment preferably further comprises a drying process for drying the rubber chips obtained in the crushing process prior to the thermal decomposition process. By performing such a drying process, the amount of moisture contained in the rubber chips can be further reduced, and the amount of moisture contained in the generated oil can be reduced more effectively.

[0075] From the viewpoint of further reducing the amount of moisture contained in the rubber chips and more effectively reducing the amount of moisture contained in the generated oil, it is preferable to dry the rubber chips by blowing air during the drying process.

[0076] From the viewpoint of further reducing the amount of moisture contained in the rubber chips and more effectively reducing the amount of moisture contained in the generated oil, it is preferable to heat the rubber chips to 100°C or higher and 200°C or lower during the drying process.

[0077] From the viewpoint of further reducing the amount of moisture contained in the rubber chips and more effectively reducing the amount of moisture contained in the generated oil, it is preferable that the drying process be carried out under reduced pressure.

[0078] When the drying process is carried out under reduced pressure, the degree of reduced pressure can be selected as appropriate without any particular restrictions, but it is preferable to have a pressure of 1000 Pa or less, 100 Pa or less, or 10 Pa or less.

[0079] The drying process is preferably carried out immediately before the thermal decomposition process. In this case, the effect of preventing the re-adhesion of moisture can be obtained.

[0080] <Fiber Recovery Process> In the crushing process, a portion of the organic fiber cord or crushed organic fiber cord may be separated from the rubber chips. Therefore, in the recycling method of this embodiment, it is preferable to perform a process (fiber recovery process) after the crushing process in which the organic fiber cord or crushed organic fiber cord that can be separated by crushing is sorted and the sorted material is recovered. By performing such a fiber recovery process (for example, wind sorting using the difference in specific gravity or vibration sorting, etc.), the organic fiber cord and crushed organic fiber cord can be recovered and recycled.

[0081] <Tire> A tire according to one embodiment of the present invention (hereinafter sometimes referred to as "the tire of this embodiment") is a tire comprising a rubber member and an organic fiber cord, wherein the organic fiber cord contains at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polyethylene-2,5-frangliancarboxylate in a content of 80% by mass or more of the total mass of the organic fiber cord, and the twist coefficient R, defined by the following formula R, is 0.20 to 0.50. Formula R: N × (0.139 × D / ρ × 0.9) １／２ ×10 －３ In formula R, N represents the number of twists (twists / 10 cm) of the organic fiber cord, D represents the total dtex number of the organic fiber cord, and ρ represents the specific gravity of the organic fiber cord.

[0082] In tires, the rubber component and the organic fiber cord are typically strongly bonded together. Therefore, separating the rubber component from the organic fiber cord when recycling used tires is time-consuming and costly, which is one of the reasons why tire recycling is difficult. In this embodiment, the rubber component and the organic fiber cord are bonded with appropriate strength, thus possessing durability and excellent separability between the rubber component and the organic fiber cord (i.e., ease of recycling). As a result of the above configuration, the tire of this embodiment is durable and easy to recycle, which is advantageous in terms of tire design flexibility and manufacturing costs.

[0083] In the recycling method of this embodiment described above, it is preferable that the rubber product is the tire of this embodiment. As described above, the tire of this embodiment has excellent separability between the rubber member and the organic fiber cord. Therefore, in the recycling method of this embodiment, it is possible to more easily reduce the content of crushed organic fiber cord in the tire chips (rubber chips) and tire powder to below a predetermined value.

[0084] Hereinafter, the "organic fiber cord" in the tire of this embodiment may be referred to as the "specific organic fiber cord."

[0085] -Rubber Member- The tire of this embodiment includes a rubber member. The "rubber member" in the tire of this embodiment is the same as the "rubber member" in the rubber product described above.

[0086] -Specific Organic Fiber Cord- The tire of this embodiment comprises an organic fiber cord (specific organic fiber cord) in which the content of at least one selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethylene-2,5-flangecarboxylate (PEF) is 80% by mass or more of the total mass of the organic fiber cord, and the twist coefficient R, defined by the following formula R, is 0.20 to 0.50.

[0087] The specified organic fiber cord has a content of at least one material selected from the group consisting of PET, PEN, and PEF (i.e., a specified resin) of 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more, relative to the total mass of the organic fiber cord. The specified resin may be 100% by mass relative to the total mass of the specified organic fiber cord. A content of 80% by mass or more of the specified resin in the specified organic fiber cord, relative to the total mass of the organic fiber cord, contributes to efficient recycling.

[0088] Methods for determining whether a tire uses an organic fiber cord with a specific resin fiber content of 80% by mass or more include comparing product information with RFID (Radio Frequency Identification), barcodes, QR codes (registered trademarks), etc. It is also possible to determine this by reading the markings on the tire's sidewall.

[0089] The specific resin contained in the specific organic fiber cord may be one selected from PET, PEN, and PEF, or it may be a combination of two or more selected from these.

[0090] The specific resin contained in the specific organic fiber cord is preferably one of PET, PEN, or PEF.

[0091] Preferably, PET, PEN, and PEF each constitute the filaments included in the specific organic fiber cord. In one embodiment, the specific organic fiber cord may be composed of two or more filaments made from one of the resins PET, PEN, or PEF, twisted together. The specific resins constituting each of the two or more filaments may be the same resin or different resins. The specific organic fiber cord may be a combination of the specific resin and other resins. In one embodiment, the specific organic fiber cord may consist of a composite yarn composed of one or more filaments made from one of the resins PET, PEN, or PEF, twisted together with one or more filaments made from other resins. Other resins are not particularly limited and include nylons such as nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 612, nylon 46, nylon 6T, nylon 6I, nylon 9T, and nylon 410; and aramids such as polyparaphenylene terephthalamide and polymetaphenylene isophthalamide.

[0092] If the specified organic fiber cord contains other resins, the content of the other resins shall be less than 20% by mass of the total mass of the specified organic fiber cord.

[0093] The specified organic fiber cord has a twist coefficient R defined by the following formula R, which is between 0.20 and 0.50. Formula R: N × (0.139 × D / ρ × 0.9) １／２ ×10 －３ In formula R, N represents the number of twists (twists / 10 cm) of the organic fiber cord, D represents the total dtex number of the organic fiber cord, and ρ represents the specific gravity of the organic fiber cord.

[0094] A twist coefficient R of 0.50 or less improves the separability between the rubber component and the specific organic fiber cord, making it easier to recycle used tires. Furthermore, a twist coefficient R of 0.20 or higher ensures good practical durability for the tire. A twist coefficient R of 0.30 to 0.40 is preferable.

[0095] From the perspective of the strength design required for the tire, the fineness (total indicated dtex number) of the specific organic fiber cord is preferably 1000 dtex to 7000 dtex, and more preferably 2000 dtex to 5000 dtex.

[0096] The specific organic fiber cord can be obtained, for example, by twisting a raw yarn composed of a specific resin, combining a plurality of these, and then twisting them in the reverse direction.

[0097] The number of twists is preferably 15 turns / 10 cm to 35 turns / 10 cm, and more preferably 20 turns / 10 cm to 30 turns / 10 cm. Here, the number of twists refers to the above-mentioned number of upper twists. By the number of twists being within the above range, while ensuring the tire cord adhesion required for tire durability, the separability between the tire cord and rubber during recycling becomes better.

[0098] - Polyethylene terephthalate (PET) - Polyethylene terephthalate (PET) is not particularly limited as long as it is a PET applicable to the organic fiber cord provided in the tire.

[0099] Since it is normal for the PET used in the tire not to contain impurities such as isophthalic acid and dyes, PET suitable for recycling can be taken out from the used tire.

[0100] In one aspect, the PET is preferably a PET containing a polymer (hereinafter also referred to as "polymer A") in which 90 mol% or more of all the constituent units constituting the molecular chain are composed of polyethylene terephthalate units, and the intrinsic viscosity calculated from the value measured at 25 °C using o-chlorophenol is 0.8 or more, preferably 0.9 or more. From the perspective of ensuring the strength during dip heat treatment, the content of diethylene glycol, which is a side reaction product contained in the main chain, in polymer A is preferably 1.5 mass% or less. From the perspective of heat resistance, the terminal carboxyl group content in polymer A is 15 equivalents / 10 ６ g polymer or less, preferably 10 equivalents / 10 ６ g polymer or less.

[0101] For polymer A and methods for producing the same, refer to, for example, the information described in Japanese Patent Publication No. 64-14334.

[0102] - Polyethylene naphthalate (PEN) - The polyethylene naphthalate (PEN) is not particularly limited as long as it is a PEN that can be applied to the organic fiber cords that make up the tire.

[0103] The polyethylene naphthalate is preferably polyethylene-2,6-naphthalate. In one embodiment, as polyethylene-2,6-naphthalate, a polymer consisting of 85 mol% or more polyethylene-2,6-naphthalate (hereinafter also referred to as "polymer B") can be used. Polymer B can be synthesized by known methods, for example, according to paragraphs

[0006] to

[0009] of Japanese Patent Application Publication No. 5-163612, and the raw yarn can be produced according to paragraphs

[0015] to

[0020] of the same publication. Polymer B can be synthesized by either conventional melt polymerization or solid-phase polymerization.

[0104] -Polyethylene-2,5-flangecarboxylate (PEF)- The polyethylene-2,5-flangecarboxylate (PEF) is not particularly limited as long as it is a PEF that can be applied to the organic fiber cords that make up the tire.

[0105] PEF is a polymer (hereinafter also referred to as "polymer C") that contains a structural unit represented by the following structural formula, which can be obtained by polycondensing monomer components containing at least furan-2,5-dicarboxylic acid and ethylene glycol in the presence of a polymerization catalyst.

[0106]

[0107] Polymer C may be produced by, for example, a first step of reacting monomer components containing furan-2,5-dicarboxylic acid and ethylene glycol to obtain an ester compound, and a second step of polycondensing the ester compound in the presence of a polymerization catalyst. From the viewpoint of increasing the reaction rate of polycondensation of PEF, the second step is preferably carried out under reduced pressure of 5 Pa to 700 Pa.

[0108] Examples of furan-2,5-dicarboxylic acids that can be used as raw materials for polymer C include furan-2,5-dicarboxylic acids produced by known methods from plant raw materials (biomass) such as cellulose and glucose. Alternatively, the furan-2,5-dicarboxylic acid used in this reaction may be a furan-2,5-diester compound esterified with methanol or ethanol. Examples of ethylene glycol that can be used as a raw material for polymer C include ethylene glycol produced by known methods from bioethanol. The monomer components used in the synthesis of polymer C may further include terephthalic acid, 2,6-naphthalenedicarboxylic acid, propanediol, butanediol, etc. The intrinsic viscosity of polymer C is preferably 0.50 to 1.50 dl / g, and more preferably 0.70 to 1.10 dl / g. The weight-average molecular weight (Mw) of polymer C is preferably 55,000 to 200,000. The amount of terminal carboxylic acid in polymer C is preferably 1 to 100 mmol / kg, and more preferably 20 to 100 mmol / kg.

[0109] For other components that serve as raw materials for polymer C, and for methods of obtaining PEF from a composition containing polymer C, please refer to the description in Japanese Patent Application Publication No. 2017-53060.

[0110] In the used tire recycling method described later, used tires may be mechanically crushed, and the resulting cotton-like specific organic fiber cords (crushed organic fiber cords) may be recovered by dust collection (i.e., the "fiber recovery process" described above may be performed). In this case, since a lower proportion of rubber in the recovered material is more suitable for recycling, the specific organic fiber cords may be treated with a process that reduces the adhesive strength between the rubber component and the specific organic fiber cords by the heat generated during mechanical crushing. As an example, the specific organic fiber cords may be coated with a thermoplastic material (also called "dip treatment"). As the thermoplastic material, for example, any one or a mixture of polyvalent phenolic polysulfide, novolac-type resorcinol formalin resin, or a compound containing an acrylamide structure having a cationic group and / or carboxyl group can be used. The thermoplastic material may also be an adhesive. As for the dip treatment, for example, one can refer to the matter described as dip heat treatment in Japanese Patent Publication No. 64-14334.

[0111] In the tire of this embodiment, the specific organic fiber cord can be used in the carcass layer, the bead reinforcement layer, and the reinforcement belt layer.

[0112] Specifically, the tire of this embodiment comprises a belt layer arranged in the tread portion and a belt reinforcing layer arranged on the radially outer side of the belt layer, wherein the belt reinforcing layer preferably contains a specific organic fiber cord.

[0113] Figure 1 is a partial cross-sectional view showing one embodiment of the tire of this embodiment. In Figure 1, the tire 10 comprises a carcass 14 that is folded back and locked around a bead core 12 from the inside to the outside of the tire, a tread portion 16 located on the crown portion of the carcass 14, a sidewall portion 18 of the carcass 14, at least two belt layers 20 arranged on the inside of the tread portion 16, and a single belt reinforcing layer 22 arranged on the outer circumference of the belt layers 20 and covering the entire tread portion, wherein the belt reinforcing layer 22 contains a specific organic fiber cord.

[0114] The tires of this embodiment, after being used, can be processed into tire chips (rubber chips) or tire powder and used for recycling.

[0115] In the tire of this embodiment, if the adhesive strength between the organic fiber cord and the rubber member is 9 (N / cord) or more, it can be determined that the composite of the organic fiber cord and the rubber member has practically acceptable durability when used as a tire. Furthermore, if the adhesive strength is between 9 and 16 (N / cord) or less, it can be determined that the recyclability is good. The specific measurement method and measurement conditions for the adhesive strength are shown in the examples described later.

[0116] <Method for recycling used tires> The method for recycling used tires is a method for recycling used tires of this embodiment, and includes crushing and / or pulverizing the used tires.

[0117] More specifically, the above-described method for recycling used tires preferably includes the steps of crushing and / or pulverizing the used tires, separating the pulverized used tires into materials consisting of rubber, fibers, and metal, and recycling each of the separated materials by any method.

[0118] Since the specific organic fiber cord included in the tire of this embodiment exhibits excellent separability from rubber components, a recycled material with a high resin content can be easily obtained by using the used tire recycling method according to this disclosure.

[0119] <Tire Chips> The tire chips of one embodiment of the present invention are the crushed tire material of this embodiment (hereinafter sometimes referred to as "tire chips of this embodiment"). In this specification, the crushed tire material refers to the material obtained by fragmenting a tire using any crushing means. There are no particular restrictions on the crushing means, and examples include "an operation to crush rubber products" in the crushing process.

[0120] The shape of the tire chips in this embodiment is not particularly limited. The size of the tire chips in this embodiment is not particularly limited, but from the viewpoint of ease of application to used tire recycling methods, man-hours and costs for crushing, etc., the maximum length is preferably 0.5 to 3 inches, and more preferably 0.5 to 2.5 inches. 1 inch is 2.54 cm.

[0121] <Tire Powder> The tire powder of one embodiment of the present invention is the pulverized tire of this embodiment. In this specification, the pulverized tire refers to a tire that has been powdered by any pulverizing means.

[0122] The tire powder of this embodiment may be produced by first processing the tire of this embodiment into tire chips and then crushing the resulting tire chips, or by directly crushing the tire. Examples of crushing methods include using a tire crusher or a grinder-like device.

[0123] The particle size of the tire powder in this embodiment is not particularly limited, but from the viewpoint of separation between rubber material and fiber material, and ease of application to the recycling method of used tires, it is preferable that the tire powder has passed through a 200-mesh sieve. In particular, among the tire powder that has passed through a 200-mesh sieve, it is more preferable that the tire powder contains 70% or more particles with a particle size of 75 μm or less when measured with a light scattering particle size analyzer at room temperature (20°C).

[0124] 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.

[0125] First, the water absorption rates of PET, nylon, and aramid organic fibers were measured individually. The results are shown in Table 1. The water absorption rates were calculated using the following procedure: 1. Each of the organic fibers listed in Table 1 was thoroughly dried (drying operation). The mass of the organic fibers after the drying operation was measured. 2. The dried organic fibers were immersed in water for 12 hours, then removed and excess water was wiped off (water absorption operation). The mass of the organic fibers after the water absorption operation was measured. 3. Using each measured value, the water absorption rate was calculated from the following formula: Water absorption rate (mass %) = (mass of organic fibers after water absorption operation - mass of organic fibers after drying operation) × 100 / mass of organic fibers after drying operation

[0126] Here, the proportion of organic fibers in a tire is typically around 10% by mass. Based on this typical example, if the organic fiber (or crushed organic fiber) content in tire chips is 10% by mass, then, based on the water absorption rate of the organic fibers alone, it is estimated that tire chips exposed to water for a long period of time will contain approximately 1.0 to 3.4% by mass of moisture, depending on the proportion of fiber types, as shown in Table 1.

[0127]

[0128] *1: Calculated value of the amount of water contained in tire chips exposed to water for a long period of time, assuming that the organic fiber (or crushed organic fiber) content in the tire chips is 10% by mass.

[0129] On the other hand, in actual practice, the oil produced by thermal decomposition of tire chips typically has a moisture content of 4.2 to 13.2 mass%, and the yield of the produced oil is typically 34%. Here, let's assume that when 1000g of tire chips are thermally decomposed to obtain the produced oil, the yield of the produced oil is 34%, and the moisture content of the produced oil is 4.2 to 13.2 mass%. In this case, the amount of produced oil is calculated to be 340g, and the amount of moisture (g) contained in the produced oil is calculated to be 14 to 45g. Using these calculation results, the amount of moisture (mass%) contained in 1000g of tire chips is calculated to be 1.4 to 4.5 mass%. Comparing this calculation result (1.4 to 4.5 mass%) with the amount of moisture contained in tire chips shown in Table 1 (1.0 to 3.4 mass%), it can be seen that they are about the same. From this, it can be concluded that most of the moisture contained in the produced oil is derived from organic fibers. Based on the above, it is considered that by following the recycling method of this embodiment, the amount of crushed organic fiber cords in rubber chips such as tire chips can be reduced, thereby reducing the amount of water contained in the rubber chips and the amount of water contained in the generated oil.

[0130] [Example 1] (1) Preparation of a specific organic fiber cord A polyethylene naphthalate yarn was prepared by referring to Example 1 of Japanese Patent No. 3555809. Two of these yarns were used and adjusted so that the twist coefficient R was 0.23 to obtain a twisted cord. Next, the obtained twisted cord was subjected to a dipping treatment by applying adhesive and heat treatment as described in paragraph

[0052] of Japanese Patent No. 3555809 to obtain a specific organic fiber cord (1). The specific organic fiber cord (1) had a cord structure of 1100 dtex / 2 [indicated as twist count lower × upper (turns / 10cm) in Table 2], with a lower twist of 16 turns / 10cm, an upper twist of 16 turns / 10cm, and a twist coefficient R of 0.23.

[0131] (2) Evaluation of adhesive strength (2-1) Preparation of organic fiber cord-rubber composite A specific organic fiber cord (1) was embedded in an unvulcanized rubber composition and co-vulcanized at 160°C for 20 minutes to obtain a composite (1) of the organic fiber cord and rubber member. The unvulcanized rubber composition used was a rubber composition containing natural rubber, styrene-butadiene rubber, carbon black, and vulcanizing chemicals.

[0132] (2-2) Evaluation of Organic Fiber Cord-Rubber Composite Using composite (1), the specific organic fiber cord (1) was peeled off from the composite (1) by pulling at a speed of 300 mm / min, and the peel resistance per specific organic fiber cord was determined and defined as the adhesive strength (N / cord). When the adhesive strength was within the range of 9 (N / cord) to 16 (N / cord), it was determined that the composite of organic fiber cord and rubber member had sufficient durability for practical use as a tire and was also excellent in terms of ease of recycling. The range of adhesive strength is the range in which both durability due to strong adhesion between the organic fiber cord and rubber member when used as a tire and ease of separation of the organic fiber cord and rubber member when the tire is recycled can be achieved. The greater the adhesive strength exceeds the upper limit, the more difficult it becomes to separate the organic fiber cord and rubber member, and the more difficult recycling tends to be. On the other hand, the greater the adhesive strength exceeds the lower limit, the easier it becomes to separate the organic fiber cord and rubber member, but the less durable the tire tends to be. The results are shown in Table 2.

[0133]

[0134] [Examples 2-3, Comparative Examples 1-2] Except for adjusting the cord structure, number of twists, and twist coefficient R to the values ​​shown in Table 2 in Example 1, the specific organic fiber cords (2) and (3) of Examples 2 and 3, and the organic fiber cords (C1) to (C3) of Comparative Examples 1 and 2 were prepared in the same manner as the specific organic fiber cord (1). Using the obtained specific organic fiber cords (2) and (3) and organic fiber cords (C1) to (C3), the adhesive strength was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0135] The adhesive strength results shown in Table 2 indicate that when composites (1) to (3) of Examples 1 to 3 are applied, the resulting tires have sufficient durability for practical use and are also highly recyclable.

[0136] In the above study, organic fiber cords containing PEN fibers were fabricated and evaluated. However, it can be inferred that tires equipped with specific organic fiber cords using PET and PEF also possess practically acceptable durability and excellent ease of recycling.

[0137] The present invention provides a method for recycling rubber products that can prevent deterioration of the quality of the generated oil. Furthermore, the present invention provides a tire that can be used as a rubber product in the above-described method for recycling rubber products, which is durable and easy to recycle. Furthermore, the present invention provides tire chips and tire powder, which are intermediate products in the recycling process.

[0138] 10 Tire 12 Bead core 14 Carcass 16 Tread section 18 Sidewall section 20 Belt layer 22 Belt reinforcement layer

Claims

1. A method for recycling a rubber product comprising a composite of a rubber member and an organic fiber cord, comprising: a crushing step of crushing the rubber product to obtain rubber chips containing crushed rubber member material and crushed organic fiber cord material; and a thermal decomposition step of thermally decomposing the rubber chips to obtain a generated oil, wherein the organic fiber cord comprises at least one selected from the group consisting of polyester fiber, nylon fiber, and aramid fiber, and the rubber chips thermally decomposed in the thermal decomposition step contain 30 g or less of crushed organic fiber cord material per 1 kg of crushed rubber member material.

2. The recycling method according to claim 1, wherein the organic fiber cord includes polyester fibers.

3. The recycling method according to claim 1 or 2, wherein the thermal decomposition step involves continuously thermally decomposing the rubber chips.

4. The recycling method according to claim 1 or 2, wherein the rubber chips have a maximum length of 0.5 to 2.5 inches.

5. The recycling method according to claim 2, wherein the polyester fiber is polyethylene terephthalate fiber and / or polyethylene-2,5-flangecarboxylate fiber.

6. The recycling method according to claim 1 or 2, wherein the rubber chips reach a temperature of 40°C or higher and 200°C or lower.

7. The recycling method according to claim 1 or 2, further comprising a drying step of drying the rubber chips.

8. The recycling method according to claim 7, wherein the rubber chips are dried by blowing air in the drying step.

9. The recycling method according to claim 7, wherein in the drying step, the rubber chips are heated to a temperature of 100°C or higher and 200°C or lower.

10. The recycling method according to claim 6, wherein the rubber chips reach a temperature of 40°C or higher and 200°C or lower under reduced pressure.

11. The recycling method according to claim 7, wherein the drying step is carried out under reduced pressure.

12. The recycling method according to claim 2, wherein the rubber product is a tire comprising a rubber member and an organic fiber cord, the organic fiber cord contains at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polyethylene-2,5-flangecarboxylate in a content of 80% by mass or more of the total mass of the organic fiber cord, and the twist coefficient R, defined by the following formula R, is 0.20 to 0.

50. Formula R: N × (0.139 × D / ρ × 0.9) １／２ ×10 －３ In formula R, N represents the number of twists (twists / 10 cm) of the organic fiber cord, D represents the total dtex number of the organic fiber cord, and ρ represents the specific gravity of the organic fiber cord.

13. The recycling method according to claim 12, wherein the twist coefficient R is 0.30 to 0.

40.

14. The recycling method according to claim 12, wherein the fineness of the organic fiber cord is 1000 dtex to 7000 dtex.

15. The recycling method according to claim 12, wherein the tire comprises a belt layer disposed on the tread portion and a belt reinforcing layer disposed on the radially outer side of the belt layer, and the belt reinforcing layer includes the organic fiber cord.

16. A tire comprising a rubber member and an organic fiber cord, wherein the organic fiber cord contains at least one material selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polyethylene-2,5-flangecarboxylate in a concentration of 80% by mass or more relative to the total mass of the organic fiber cord, and the twist coefficient R, defined by the following formula R, is 0.20 to 0.

50. Formula R: N × (0.139 × D / ρ × 0.9) １／２ ×10 －３ In formula R, N represents the number of twists (twists / 10 cm) of the organic fiber cord, D represents the total dtex number of the organic fiber cord, and ρ represents the specific gravity of the organic fiber cord.

17. Tire chips, which are the crushed tire material described in claim 16.

18. Tire powder, which is the crushed tire material according to claim 16.

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