Cellulose-containing reclaimed rubber

Abstract

To provide a reclaimed rubber which contains cellulose having high dispersibility and is excellent in tensile stress when made into a vulcanized reclaimed rubber.SOLUTION: The reclaimed rubber is obtained by mixing a waste powder rubber having a polymer component content of 40 mass% or more, a carbon black content of 15-35 mass%, a total content of inorganic materials other than carbon black of 15 mass% or less, and an oil content of less than 10 mass% with cellulose and an oil and desulfurizing the waste powder rubber. The reclaimed rubber contains 1-20 pts.mass of the cellulose and 10-100 pts.mass of the oil based on 100 pts.mass of the waste powder rubber.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to cellulose-blended reclaimed rubber and a method for producing the same. [Background technology]

[0002] From the perspective of reducing the environmental impact, used rubber products (waste rubber products) such as waste tires are turned into waste rubber powder, which is then devulcanized and processed into recycled rubber. However, there is an issue that the physical properties of this recycled rubber after vulcanization are inferior to new rubber (virgin rubber).

[0003] In response to this, various studies have been conducted. For example, Patent Document 1 discloses a method in which waste rubber products are crushed and then subjected to desulfurization and functionalization treatments under specified conditions to increase the reactivity of the reclaimed rubber itself and improve the physical properties of the rubber after vulcanization. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-212377 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, even when the reclaimed rubber is subjected to such treatment, the tensile stress is often insufficient when it is vulcanized and reclaimed. In response to this, a method of improving the tensile stress by adding a filler during the production of the reclaimed rubber is considered, but this filler has the problem of being difficult to disperse in the reclaimed rubber, and this problem is particularly significant when cellulose, which has been attracting attention as a filler in recent years, is used.

[0006] Therefore, an object of the present invention is to provide a reclaimed rubber which contains cellulose with high dispersibility and which has excellent tensile stress when made into a vulcanized reclaimed rubber. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors conducted extensive research and discovered that a reclaimed rubber obtained by mixing waste rubber powder having a polymer component content of 40% by mass or more, a carbon black content of 15 to 35% by mass, a total content of inorganic materials other than carbon black of 15% by mass or less, and an oil content of less than 10% by mass with cellulose and oil and devulcanizing the mixture, the reclaimed rubber containing 1 to 20 parts by mass of the cellulose and 10 to 100 parts by mass of the oil per 100 parts by mass of the waste rubber powder, has high dispersibility of the cellulose contained therein and has excellent tensile stress when vulcanized into a reclaimed rubber, thereby completing the present invention.

[0008] That is, the present invention provides the following <1> ~ <6> It is. <1> A reclaimed rubber is obtained by mixing waste rubber powder having a polymer component content of 40% by mass or more, a carbon black content of 15 to 35% by mass, a total content of inorganic materials other than said carbon black of 15% by mass or less, and an oil content of less than 10% by mass with cellulose and oil, and devulcanizing the mixture, the reclaimed rubber containing 1 to 20 parts by mass of said cellulose and 10 to 100 parts by mass of said oil per 100 parts by mass of said waste rubber powder. <2> The cellulose is powdered cellulose. <1> Reclaimed rubber as described in . <3> The cellulose is cellulose nanofibers and / or cellulose nanocrystals; <1> Reclaimed rubber as described in . <4> The oil mixed with the waste rubber powder is a petroleum-derived oil. <1> ~ <3> 2. Reclaimed rubber according to any one of the preceding claims. <5> The oil mixed with the waste rubber powder is a non-petroleum-derived and naturally-derived oil. <1> ~ <3> 2. Reclaimed rubber according to any one of the preceding claims. <6> A method for producing reclaimed rubber, comprising: a devulcanization step of heating and mixing waste rubber powder having a polymer component content of 40% by mass or more, a carbon black content of 15 to 35% by mass, a total content of inorganic materials other than the carbon black of 15% by mass or less, and an oil content of less than 10% by mass, cellulose, oil, and a devulcanizing agent to obtain devulcanized powder rubber; and a reclaimed rubber formation step of forming reclaimed rubber using the devulcanized powder rubber, wherein the amount of the cellulose in the devulcanization step is 1 to 20 parts by mass per 100 parts by mass of the waste rubber powder, and the amount of the oil is 10 to 100 parts by mass per 100 parts by mass of the waste rubber powder. Effect of the Invention

[0009] According to the present invention, it is possible to obtain reclaimed rubber which contains cellulose with high dispersibility and has excellent tensile stress when vulcanized into reclaimed rubber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will now be described. The present invention relates to a reclaimed rubber obtained by mixing waste rubber powder having a polymer component content of 40% by mass or more, a carbon black content of 15-35% by mass, a total content of inorganic materials other than carbon black of 15% by mass or less, and an oil content of less than 10% by mass with cellulose and oil and devulcanizing the reclaimed rubber, the reclaimed rubber containing 1-20 parts by mass of the cellulose and 10-100 parts by mass of the oil per 100 parts by mass of the waste rubber powder. The reclaimed rubber further includes a devulcanization step of heating and mixing the waste rubber powder, cellulose, oil, and devulcanizing agent to obtain devulcanized rubber powder, and a reclaimed rubber forming step of forming reclaimed rubber using the devulcanized rubber powder, the amount of cellulose in the devulcanization step being 1-20 parts by mass per 100 parts by mass of the waste rubber powder, and the amount of oil being 10-100 parts by mass per 100 parts by mass of the waste rubber powder. Hereinafter, these are also referred to as "reclaimed rubber of the present invention" and "manufacturing method of reclaimed rubber of the present invention".

[0011] In the present invention, unless otherwise specified, a numerical range expressed using "~" means a numerical range having the numerical value before "~" as the lower limit and the numerical value after "~" as the upper limit.

[0012] The materials and components used in the reclaimed rubber of the present invention, as well as their contents, will be described in detail below.

[0013] [Waste rubber powder] Waste rubber powder is obtained by processing waste rubber products into powder, and examples thereof include waste rubber products such as waste tires, which are crushed, separated from foreign matter, classified, crushed into fine pieces, separated from foreign matter, and classified in this order. In particular, waste rubber powder obtained by processing the tread portions of waste tires for trucks and / or buses into powder is more preferable because it has excellent uniformity of component ratios.

[0014] The waste rubber powder used in the reclaimed rubber of the present invention has a polymer component content of 40% by mass or more, a carbon black content of 15 to 35% by mass, a total inorganic material content other than carbon black of 15% by mass or less, and an oil content of less than 10% by mass. The polymer component contained in this waste rubber powder is mainly rubber components (75% by mass or more of the polymer component, preferably 80% by mass or more, and more preferably 90% by mass or more), but may also contain resin components and the like. The lower limit of the polymer component content of this waste rubber powder is more preferably 42% by mass or more. The upper limit is 80% by mass or less, and more preferably 75% by mass or less. The carbon black content is more preferably 20 to 30% by mass. Furthermore, the upper limit of the total inorganic material content other than carbon black is more preferably 12% by mass or less, and even more preferably 10% by mass or less. Furthermore, the upper limit of the oil content is more preferably 8% by mass or less, and even more preferably 5% by mass or less. In addition, examples of inorganic materials other than carbon black include silica, clay, calcium carbonate, magnesium carbonate, mica, talc, alumina, aluminum hydroxide, titanium oxide, calcium sulfate, barium sulfate, and zinc oxide (zinc oxide). Here, "silica" refers to silicon dioxide (SiO 2 The term "oil" refers to a particulate material that is made of silicon dioxide or contains silicon dioxide as a main component (e.g., 80% by mass or more, or even 90% by mass or more). The term "oil" refers to petroleum-derived oil, which will be described later.

[0015] From the viewpoint of ease of use of reclaimed rubber in tires, etc., it is more preferable that the polymer component contained in this waste rubber powder contains a diene rubber, and more preferably, the polymer component contains 75 mass % or more, and even more preferably 80 mass % or more, of natural rubber (NR). This diene rubber is a rubber component having a double bond in the polymer main chain, and examples thereof include natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), styrene-isoprene copolymer rubber, and isoprene-butadiene copolymer rubber.

[0016] Furthermore, the weight average molecular weight of the diene rubber contained in this polymer component is preferably 50,000 to 3,000,000, and more preferably 100,000 to 2,000,000. In the present invention, the "weight average molecular weight" refers to a value measured in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent. The GPC measurement is performed at 40°C using a column (MIXED-B, manufactured by Polymer Laboratories) as a measuring instrument.

[0017] In addition, the carbon black contained in the waste rubber powder used in the reclaimed rubber of the present invention is not particularly limited, and may contain any known carbon black compounded in rubber products. For example, specific examples of carbon black include SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, SRF, FT, MT, and other grades. The carbon black may contain one type alone or two or more types. In the case of containing two or more types, the total of the carbon blacks may be the above-mentioned content. Here, the term "carbon black" refers to fine carbon particles made of primary particles having a diameter of about 3 to 500 nm that are manufactured under industrial quality control.

[0018] Furthermore, the waste rubber powder used in the reclaimed rubber of the present invention may contain various additives generally used in rubber products, such as stearic acid, lecithin, silane coupling agent, antioxidant, plasticizer, curing agent, vulcanizing agent (e.g., sulfur, etc.), vulcanization accelerator, vulcanization accelerator assistant, etc., as long as the above-mentioned composition is satisfied. However, the waste rubber powder used in the reclaimed rubber of the present invention does not substantially contain cellulose. In other words, this waste rubber powder does not substantially contain cellulose. Here, "substantially free of cellulose (substantially free of cellulose)" means that the content of cellulose in the waste rubber powder is less than 0.1% by mass.

[0019] [cellulose] The cellulose blended in the reclaimed rubber of the present invention (mixed with the waste rubber powder described above) may be, for example, powdered cellulose. This allows for a relatively inexpensive cellulose-blended reclaimed rubber. Here, this powdered cellulose does not include nanocellulose powder (e.g., cellulose nanocrystal powder, etc.) described below. Examples of this powdered cellulose include Viscopal (a product of Rengo Co., Ltd.) as a roughly spherical (uncontrolled shape) powdered cellulose, and KC Flock (a product of Nippon Paper Industries Co., Ltd.) as a fibrous powdered cellulose, but are not limited thereto. The average particle diameter of this powdered cellulose (D 50 ) is not limited, but is preferably 1000 μm or less, more preferably 800 μm or less, even more preferably 600 μm or less, even more preferably 400 μm or less, even more preferably 250 μm or less, and even more preferably 100 μm or less. The lower limit may be 5 μm or more, and may further be 10 μm or more. Here, this "average particle diameter (D 50 "The volume-based average particle diameter (50% volume cumulative distribution diameter (D 50 )).

[0020] The cellulose to be blended in the reclaimed rubber of the present invention (mixed with the waste rubber powder described above) is preferably cellulose nanofibers and / or cellulose nanocrystals. These are even more difficult to disperse in the reclaimed rubber than the powdered cellulose described above, but the reclaimed rubber of the present invention can also enhance the dispersibility of these. The reclaimed rubber of the present invention containing these tends to have better tensile stress when vulcanized and reclaimed. These are collectively called "nanocellulose", and nanocellulose containing amorphous with an average fiber diameter of 1 to 1000 nm and an average fiber length of 0.5 to 5 μm is cellulose nanofiber (CNF, for example, Cellenpia manufactured by Nippon Paper Industries Co., Ltd.), which is also called microfibrillated cellulose. In addition, crystalline (for example, needle-shaped crystals or spherical crystals) nanocellulose with an average fiber diameter of 1 to 1000 nm and an average fiber length of 0.1 to 0.5 μm is cellulose nanocrystal (CNC, for example, Cellulose Nanocrystal manufactured by Filler Bank Co., Ltd.).

[0021] As described above, the average fiber diameter of the cellulose nanofibers and cellulose nanocrystals is 1 to 1000 nm, but it is preferably 1 to 200 nm. The average aspect ratio (average fiber length / average fiber diameter) is preferably 10 to 1000, more preferably 50 to 500. If the average fiber diameter is less than the above range and / or the average aspect ratio exceeds the above range, the dispersibility in the reclaimed rubber tends to be easily reduced. If the average fiber diameter exceeds the above range and / or the average aspect ratio is less than the above range, the reinforcing performance tends to be easily reduced.

[0022] Here, the "average fiber diameter" and "average fiber length" refer to the average fiber diameter and fiber length values ​​obtained by obtaining an electron microscope image by TEM or SEM observation at a magnification appropriately set according to the size of the constituent fibers, and measuring at least 50 or more fibers in the image. The average aspect ratio is calculated from the average fiber length and average fiber diameter thus obtained.

[0023] In addition, these celluloses (cellulose as a raw material in the case of nanocellulose) may be derived from wood or non-wood (bacteria, algae, cotton, etc.), and are not particularly limited. In addition, examples of the above-mentioned method for producing nanocellulose include a method in which water is added to the raw cellulose, processed with a mixer, etc. to prepare a slurry in which cellulose is dispersed in water, and this is directly defibrated by applying mechanical shear force using a high-pressure or ultrasonic device, and a method in which this slurry is subjected to chemical treatment such as oxidation treatment, alkali treatment, acid hydrolysis, etc. to modify the cellulose to make it easier to defibrate, and then defibrated by applying mechanical shear force using a disperser, etc. By performing such chemical treatment before defibration, the cellulose can be defibrated more finely and uniformly with low energy, and chemically modified nanocellulose (chemically modified nanocellulose) can be easily obtained. Examples of chemical treatments include treatments with chemical treating agents such as 2,2,6,6-tetramethylpiperidine-1-oxyl (hereinafter referred to as "TEMPO"), 4-acetamido-TEMPO, 4-carboxy-TEMPO, 4-amino-TEMPO, 4-hydroxy-TEMPO, 4-phosphonooxy-TEMPO, phosphoric esters, periodic acid, alkali metal hydroxides, and carbon disulfide. Chemical treatments may also be performed after mechanical defibration of cellulose. In addition to the above-mentioned chemical treatments, cellulase treatment, carboxymethylation, esterification, and treatment with cationic polymers may also be performed after the defibration process.

[0024] The reclaimed rubber of the present invention is produced by blending such cellulose with oil when the waste rubber powder is devulcanized. The cellulose is contained in an amount of 1 to 20 parts by mass per 100 parts by mass of the waste rubber powder. From the viewpoint of dispersibility of the cellulose, the upper limit is more preferably 18 parts by mass or less, even more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less. From the viewpoint of tensile stress when vulcanized reclaimed rubber, the lower limit is more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and even more preferably 8 parts by mass or more.

[0025] [oil] The oil blended in the reclaimed rubber of the present invention (mixed with the above-mentioned waste rubber powder) is a component that enhances the dispersibility of cellulose by blending with the above-mentioned cellulose in the devulcanization process of the waste rubber powder. This oil may be, for example, a petroleum-derived oil. This petroleum-derived oil is an oil obtained from petroleum, and examples thereof include process oils such as TDAE (Treated Distillate Aromatic Extract) oil (a product of Shell Lubricants Japan Co., Ltd.), but is not limited thereto.

[0026] It is more preferable that the oil is a non-petroleum-derived and natural product-derived oil. In other words, it is more preferable that the oil is not derived from petroleum and is obtained from animals, plants, microorganisms, or a part thereof. This is because it has a higher affinity with the above-mentioned cellulose and is easy to increase its dispersibility. In particular, from this viewpoint, wood-derived oils are more preferable among the non-petroleum-derived and natural product-derived oils. As the wood-derived oil, tall oil (crude tall oil obtained during the manufacture of kraft pulp from wood such as pine, tall oil fatty acid, tall rosin, distilled tall oil, etc.) are exemplified as preferred, but are not limited thereto. It is more preferable that the wood-derived oil contains more than 50 mass% of fatty acid and resin acid (for example, one or more selected from the group consisting of abietic acid, neoabietic acid, palustric acid, pimaric acid, isopimaric acid, and dehydroabietic acid) in total, and the mass ratio of resin acid to fatty acid (resin acid / fatty acid) is 0.9 or more, further 1.0 or more, and further 1.1 or more is more preferable. The upper limit is more preferably 2.0 or less, even more preferably 1.8 or less, and even more preferably 1.5 or less.

[0027] The reclaimed rubber of the present invention is produced by mixing such oil with cellulose when the waste rubber powder is devulcanized. The oil is contained in an amount of 10 to 100 parts by mass per 100 parts by mass of the waste rubber powder. The upper limit is more preferably 80 parts by mass or less, more preferably 60 parts by mass or less, more preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and more preferably 35 parts by mass or less, from the viewpoint of the dispersibility of cellulose and the tensile stress when the rubber powder is vulcanized and reclaimed. The lower limit is more preferably 12 parts by mass or more, more preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and more preferably 25 parts by mass or more, from the viewpoint of the dispersibility of cellulose. Note that even if the waste rubber powder described above contains oil, the amount of oil derived from the waste rubber powder is not included in the above, and this is the amount (blended amount) of oil blended during devulcanization. However, while this blending amount satisfies the above, the total amount of the amount of oil derived from waste rubber and the amount of the blended oil is more preferably 10 to 100 parts by mass, even more preferably 15 to 80 parts by mass, and even more preferably 20 to 50 parts by mass, per 100 parts by mass of the above-mentioned waste rubber powder (including the amount derived from waste rubber powder).The reclaimed rubber of the present invention is configured such that the amount of the blended oil is greater (has a higher content) than the amount of oil derived from waste rubber powder.

[0028] In addition, although not limited thereto, in the reclaimed rubber of the present invention, from the viewpoint of the dispersibility of cellulose, it is preferable that the ratio of the amount of this oil to the amount of cellulose described above be within a specified range. Specifically, it is preferable that the mass ratio of oil to cellulose (oil / cellulose) is 1 to 10. The lower limit is more preferably 2 or more. The upper limit is more preferably 8 or less, and even more preferably 5 or less. This is also the mass ratio of the blended cellulose and oil, and further, it is more preferable that the mass ratio of the amount of oil derived from waste rubber and the total amount of blended oil to the amount of blended cellulose is within the above range while satisfying this.

[0029] [Other ingredients] The reclaimed rubber of the present invention may contain components other than those mentioned above, provided that the effects of the present invention are not affected. In addition, unreacted devulcanizing agents and the like may also be contained. However, the reclaimed rubber of the present invention does not contain new rubber components (virgin rubber components). In other words, no new rubber components are blended in the process of forming the reclaimed rubber from waste rubber powder. Therefore, all of the rubber components contained in the reclaimed rubber of the present invention are rubber components derived from the waste rubber powder (reclaimed rubber components) described above. Furthermore, the reclaimed rubber of the present invention does not contain a vulcanizing agent. In other words, the reclaimed rubber of the present invention is substantially unvulcanized reclaimed rubber.

[0030] [Manufacturing method] The reclaimed rubber of the present invention is preferably obtained by the following production method (production method of reclaimed rubber of the present invention). Specifically, the method includes a devulcanization step of heating and mixing the waste rubber powder, cellulose, and oil, which have a polymer component content of 40% by mass or more, a carbon black content of 15 to 35% by mass, a total content of inorganic materials other than carbon black of 15% by mass or less, and an oil content of less than 10% by mass, with a devulcanizing agent to obtain devulcanized powder rubber, and a regenerated rubber forming step of forming regenerated rubber using the devulcanized powder rubber, and the amount of cellulose in the devulcanization step is 1 to 20 parts by mass relative to 100 parts by mass of the waste rubber powder, and the amount of oil is 10 to 100 parts by mass relative to 100 parts by mass of the waste rubber powder. These amounts may be the cellulose amount, oil amount, and mass ratio thereof as described above. Furthermore, the cellulose blended in the desulfurization step is preferably powdered cellulose, cellulose nanofiber, or cellulose nanocrystal as described above. Furthermore, the oil blended in the desulfurization step is preferably a petroleum-derived oil or a non-petroleum-derived and natural product-derived oil as described above. Here, the amount of oil in the method for producing reclaimed rubber of the present invention means the amount of oil mixed in the devulcanization step (blended amount), and does not include the amount of oil derived from waste rubber powder.

[0031] For example, the waste rubber powder of the above composition obtained by crushing, separating foreign matter, classifying, crushing, separating foreign matter, and classifying waste rubber products such as waste tires in the crushing step or fine crushing step in this order is used, and a predetermined amount of cellulose, a predetermined amount of oil, and a desulfurizing agent are heated and mixed (150 to 250°C, 3 to 5 hours, etc.) in the desulfurizing step to obtain desulfurized powder rubber, and the desulfurized powder rubber is used to form regenerated rubber by refining (roll), straining, sheeting, etc. in the regenerated rubber forming step. In addition, other additive components can be used within a range that does not affect the effects of the present invention. However, as described above, the method for producing regenerated rubber of the present invention does not include adding and mixing new rubber components and vulcanizing agents. The desulfurizing agent may be, for example, dibenzamide diphenyl disulfide (Noctizer SS, manufactured by Ouchi Shinko Chemical Co., Ltd.), but is not limited thereto.

[0032] The reclaimed rubber of the present invention obtained by the above-mentioned reclaimed rubber manufacturing method of the present invention has improved dispersibility of the cellulose blended in the devulcanization process of the waste rubber powder due to the action of the oil blended at the same time, and when vulcanized into reclaimed rubber, it becomes a reclaimed rubber with excellent tensile stress. In other words, the reclaimed rubber of the present invention is a cellulose-blended reclaimed rubber (cellulose-containing reclaimed rubber) with improved dispersibility of cellulose by adding and mixing the cellulose together with the oil in the devulcanization process.

[0033] Furthermore, even if the reclaimed rubber of the present invention is blended into a rubber composition, the mechanical properties of the resulting rubber composition are unlikely to deteriorate, meaning that the reclaimed rubber can be suitably used as a practical recycled rubber material. In particular, it is more suitable as a blending material for rubber compositions for tires.

[0034] Hereinafter, examples of the present invention will be described, however, the present invention is not limited to the following examples, and various modifications are possible within the technical concept of the present invention. EXAMPLES

[0035] (Preparation and evaluation of reclaimed rubber and vulcanized reclaimed rubber test specimens) Reclaimed rubber and vulcanized reclaimed rubber test pieces shown in Table 1 below were prepared.

[0036] Specifically, first, each component shown in the upper part of Table 1 below and 1 part by mass of a desulfurizing agent (dibenzamide diphenyl disulfide: Noctizer SS, manufactured by Ouchi Shinko Chemical Co., Ltd.) were heated to about 200 ° C in an autoclave and mixed for 4 hours to perform the desulfurization process. After that, the treated product was released from the autoclave and refining (roll), straining, cooling, etc. were performed in a conventional manner to obtain reclaimed rubber. The cellulose nanofiber was made into an aqueous dispersion and then added in the desulfurization process. Furthermore, a 1.7-liter closed Banbury mixer was used to mix and knead each of the reclaimed rubbers obtained above with a predetermined amount of vulcanization accelerator and sulfur, and the mixture was press-vulcanized at 170 ° C for 10 minutes in a predetermined mold to prepare vulcanized reclaimed rubber test pieces.

[0037] The resulting reclaimed rubbers of Reference Example, Comparative Examples 1 to 4, and Examples 1 to 3 were measured and evaluated for dispersibility of the filler (Comparative Examples 1 to 4 and Examples 1 to 3 were filled with cellulose blended in the devulcanization step) in accordance with ISO 11345 (E method). The dispersibility was evaluated on a 10-point scale, with 7 points or more being ◯ and 9 points or more being ◎. Further, for the obtained vulcanized reclaimed rubber test pieces of Reference Example, Comparative Examples 1 to 4, and Examples 1 to 3, a tensile test was performed at a tensile speed of 500 mm / min in accordance with JIS K6251:2010, and the 100% modulus (M100: MPa) was measured at room temperature (20° C.) In Table 1 below, the M100 value of the vulcanized reclaimed rubber test piece of Reference Example is expressed as an index (index%), with the M100 value being 100 for the vulcanized reclaimed rubber test piece of Reference Example.

[0038] [Table 1]

[0039] The details of each component in Table 1 above are as follows: Scrap tire rubber powder: PolyDyne80 (rubber powder with 30% or more by mass passing through a 105 μm mesh, polymer component content of 42% or more by mass, carbon black content of 25 to 30% by mass, total content of inorganic materials other than carbon black of 8% or less by mass, oil content of 5% or less by mass, manufactured by Lehigh Technologies) Powdered cellulose: Viscopal D-30 (average particle size (D 50 ) 20-40μm, manufactured by Rengo Co., Ltd. Cellulose nanofiber: Oxidized cellulose nanofiber (CNF; Nippon Paper Industries, Cellenpia) TDAE: TDAE (Treated Distillate Aromatic Extract) oil (Extract No. 4; petroleum-derived, manufactured by Shell Lubricants Japan) Tall oil: Crude tall oil derived from pine (obtained by neutralizing black liquor obtained during the manufacture of kraft pulp from pine wood (alkali cooking) with an acid, and containing a total of 80% or more by mass of fatty acids and resin acids. The mass ratio of resin acids to fatty acids (resin acid / fatty acid) is approximately 1.2, and the resin acids include at least abietic acid, neoabietic acid, and palustric acid.)

[0040] First, the results of dispersibility showed that by mixing a specified amount of cellulose (powdered cellulose or cellulose nanofiber) and a specified amount of oil (TDAE or crude tall oil) with waste tire rubber in the devulcanization process and mixing them under heat, a reclaimed rubber with high dispersibility of the filler including the mixed cellulose can be obtained (Examples 1 to 3). In particular, Example 3, which used pine-derived crude tall oil as the oil, showed extremely high dispersibility. On the other hand, in Comparative Examples 1 and 2, in which the amount of oil blended was outside the specified range, and in Comparative Example 4, in which the amount of cellulose blended was high, the dispersibility of the filler, including cellulose (especially the dispersibility of the cellulose added in the desulfurization process), was low.

[0041] Furthermore, the test results of the vulcanized reclaimed rubber test pieces revealed that the vulcanized reclaimed rubber test pieces of Examples 1 to 3 obtained from reclaimed rubber with high filler dispersion had superior tensile stress than the vulcanized reclaimed rubber test piece of Reference Example. In particular, Example 3, which used pine-derived crude tall oil as the oil, also had extremely superior tensile stress. On the other hand, the vulcanized reclaimed rubber test pieces of Comparative Examples 1, 2, and 4, which were obtained from reclaimed rubber with low filler dispersibility, had lower tensile stress than the vulcanized reclaimed rubber test piece of the Reference Example. Furthermore, the vulcanized reclaimed rubber test piece of Comparative Example 3, which was obtained from reclaimed rubber with high filler dispersibility but a low amount of cellulose, also had a lower tensile stress than the vulcanized reclaimed rubber test piece of the Reference Example.

Claims

1. A reclaimed rubber obtained by mixing waste rubber powder having a polymer component content of 40% by mass or more, a carbon black content of 15 to 35% by mass, a total content of inorganic materials other than said carbon black of 15% by mass or less, and an oil content of less than 10% by mass with cellulose and oil and devulcanizing the mixture, The reclaimed rubber comprises 1 to 20 parts by mass of the cellulose and 10 to 100 parts by mass of the oil per 100 parts by mass of the waste rubber powder.

2. 2. The reclaimed rubber according to claim 1, wherein the cellulose is powdered cellulose.

3. The reclaimed rubber according to claim 1, wherein the cellulose is cellulose nanofiber and / or cellulose nanocrystal.

4. The reclaimed rubber according to any one of claims 1 to 3, wherein the oil mixed with the waste rubber powder is a petroleum-derived oil.

5. The reclaimed rubber according to any one of claims 1 to 3, wherein the oil mixed with the waste rubber powder is a non-petroleum-derived and naturally-derived oil.

6. The method comprises a devulcanization step of heating and mixing waste rubber powder having a polymer component content of 40% by mass or more, a carbon black content of 15 to 35% by mass, a total content of inorganic materials other than the carbon black of 15% by mass or less, and an oil content of less than 10% by mass, cellulose, oil, and a devulcanization agent to obtain devulcanized rubber powder, and a reclaimed rubber formation step of forming reclaimed rubber using the devulcanized rubber powder, The amount of the cellulose in the desulfurization step is 1 to 20 parts by mass per 100 parts by mass of the waste rubber powder, and the amount of the oil is 10 to 100 parts by mass per 100 parts by mass of the waste rubber powder.

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