Tire, method for manufacturing tire, and method for regenerating tire

Abstract

To provide a tire capable of easily separating a tread portion and a base tire portion when regenerating the tire, a method for manufacturing the tire, and a method for regenerating the tire.SOLUTION: A tire 1 includes a tread rubber layer 7, a cushion rubber layer 6, and a tire case 5 in order from an outer side in a tire radial direction, where the cushion rubber layer 6 contains thermally expandable particles, expansion start temperature of the thermally expandable particles is 110 to 135°C, and an average of expansion ratio of the thermally expandable particles per 10°C from the expansion start temperature to 160°C is 1.25 times / 10°C or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire, a method for manufacturing the tire, and a method for retreading the tire. [Background technology]

[0002] Currently, the recycling of materials and the reuse of components are becoming important in building a sustainable society. The same is true for automobile tires, and retreading technology is particularly superior in terms of reusing components. One of the retreading technologies is the precure method. In the precure method of retreading, the tread portion of a tire that has finished running on the market is scraped off, and a new precure tread is attached to the base tire. Cushion rubber, an unvulcanized rubber that also functions as an adhesive, is used to bond the precure tread to the base tire. The adhesive performance is good, and retreaded tires are not inferior in performance to new tires. On the other hand, the process of scraping off the tread in the retreading process involves the generation and scattering of rubber powder, and this work also consumes electricity, so a technology that allows the tread to be easily peeled off is desired.

[0003] Dismantlable adhesive technology exists as a technique for easily peeling bonded components together. With this technology, a mechanism for later dismantling is built into the adhesive (adhesive layer). There are several methods for dismantlable adhesive technology. Among these is a technique in which a heat-expanding material is mixed into the adhesive, and after use of the product, the expandable material is expanded by heating to distort the adhesive layer or weaken the adhesive force, making it possible to easily peel the components apart. As materials that expand with heat, thermal expansion microcapsules and expandable graphite are preferably used.

[0004] For example, Patent Document 1 discloses a tire having an annular tire frame member formed of a resin material, a tire-constituting rubber member provided radially outside the tire frame member, and an unfoamed rubber member provided between the tire frame member and the tire-constituting rubber member, bonded to the tire frame member and the tire steel member, respectively, and containing an unfoamed foaming agent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-116222 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, there is still a need for a technology that allows the tread portion and the tire base portion to be easily separated when retreading a tire.

[0007] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a tire in which the tread portion and the base tire portion can be easily separated when the tire is retreaded, a method for manufacturing such a tire, and a method for retreading such a tire. [Means for solving the problem]

[0008] The tire, the manufacturing method of the tire, and the retreading method of the tire according to the present invention, which solve the above problems, are outlined as follows.

[0009] [1] A tire comprising, in order from the outside in the tire radial direction, a tread rubber layer, a cushion rubber layer, and a tire case, The cushion rubber layer contains thermally expandable particles, The thermally expandable particles have an expansion starting temperature of 110 to 135° C., The tire, wherein the thermally expandable particles have an average expansion ratio per 10°C from the expansion starting temperature to 160°C of 1.25 times / 10°C or more. With the tire described in [1] above, the tread portion and the tire base portion can be easily separated when the tire is retreaded.

[0010] [2] The tire according to [1], wherein the thermally expandable particles have an expansion ratio of 5 times or more at 140°C. With the tire described in [2] above, the tread portion and the tire base portion can be separated more easily when the tire is retreaded.

[0011] [3] The tire according to [1] or [2], wherein the thermally expandable particles have an expansion ratio of 6 times or more at 150°C to 160°C. With the tire described in [3] above, the tread portion and the tire base portion can be separated more easily when the tire is retreaded.

[0012] [4] The tire according to any one of [1] to [3], wherein the thermally expandable particles have an average particle size of 10 to 50 μm. The tire described in [4] above can prevent cracks from occurring in the cushion rubber layer during use of the tire, while sufficiently reducing the peel resistance of the cushion rubber layer when the thermally expandable particles expand.

[0013] [5] The tire according to any one of [1] to [4], wherein the thermally expandable particles have an expansion starting temperature of 120 to 135° C. In the tire described in [5] above, even if the heating temperature during tire production is high, the thermally expandable particles can be contained in the cushion rubber layer of the tire without expanding.

[0014] [6] A method for producing a tire according to any one of [1] to [5], A method for producing a tire, wherein a vulcanization temperature is equal to or lower than the expansion initiation temperature of the thermally expandable particles. According to the tire manufacturing method described in [6] above, a tire can be manufactured in which the tread portion and the tire base portion can be easily separated when the tire is retreaded.

[0015] [7] A method for retreading a tire according to any one of [1] to [5], Heating the tire to 120 to 160°C to expand the thermally expandable particles; and removing the tread rubber layer of the tire. According to the tire retreading method described in [7] above, when retreading a tire, the tread portion and the tire base portion can be easily separated to retread the tire. Effect of the Invention

[0016] According to the present invention, it is possible to provide a tire in which the tread portion and the tire base portion can be easily separated when retreading, a method for manufacturing such a tire, and a method for retreading such a tire. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view taken along the tire width direction of an example of a tire of the present invention. [Diagram 2] 1 is a cross-sectional view taken along the tire width direction, showing the periphery of a cushion rubber layer of an example of a tire of the present invention. [Diagram 3] FIG. 2 is a cross-sectional view taken along the tire width direction, showing the periphery of a cushion rubber layer of an example of a tire of the present invention after the thermally expandable particles in the cushion rubber layer have been expanded. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire, a method for manufacturing the tire, and a method for retreading the tire according to the present invention will be described in detail below with reference to examples based on embodiments.

[0019] <Definition> The compounds described herein may be derived in whole or in part from fossil sources, from biological sources such as plant sources, from recycled sources such as used tires, or from a mixture of two or more of fossil sources, biological sources, and / or renewable sources.

[0020] In this specification, the term "tire width direction" refers to a direction parallel to the tire's axis of rotation, the term "tire radial direction" refers to a direction perpendicular to the tire's axis of rotation, and the term "tire circumferential direction" refers to a direction in which the tire rotates around its axis of rotation.

[0021] In this specification, the term "tread portion" refers to the portion including the tread layer that is removed when a tire is retreaded (e.g., the tread rubber layer and a part of the cushion rubber layer), while the term "base tire portion" refers to the portion that is not removed when a tire is retreaded, that is, the portion including the tire case other than the tread portion (e.g., the tire case and a part of the cushion rubber layer).

[0022] In this specification, the expression "a to b" in the explanation of a numerical range means that the range is from a to b, unless otherwise specified.

[0023] <Tires> The tire of the present embodiment is a tire including, in order from the outer side in the tire radial direction, a tread rubber layer, a cushion rubber layer, and a tire case, The cushion rubber layer contains thermally expandable particles, The thermally expandable particles have an expansion starting temperature of 110 to 135° C., The thermally expandable particles are characterized in that the average expansion ratio per 10° C. from the expansion starting temperature to 160° C. is 1.25 times / 10° C. or more. As described above, the tire of this embodiment contains thermally expandable particles in the cushion rubber layer. The thermally expandable particles expand due to heat, thereby reducing the peel resistance of the cushion rubber layer, which is an adhesive layer, and therefore the tread portion and the base tire portion become more likely to peel off. Therefore, when the tire is retreaded, the tread portion and the base tire portion can be easily separated. Furthermore, because the tread portion and the base tire portion become more likely to peel off in this manner, the generation of rubber powder and the consumption of electricity can be reduced when the tire is retreaded.

[0024] Next, one embodiment of the tire of the present invention will be described in detail with reference to the drawings.

[0025] Fig. 1 is a cross-sectional view along the tire width direction of one example of a tire of the present invention. As shown in Fig. 1, the tire 1 includes an annular tire case 5 including a pair of bead portions 2, a side portion 3 extending radially outward from the bead portions 2, and a crown portion 4 connecting an outer end in the tire radial direction of one side portion 3 to an outer end in the tire radial direction of the other side portion 3. A cushion rubber layer 6 is provided on an outer peripheral surface of the tire case 5 on the outer side in the tire radial direction, and a tread rubber layer 7 is provided on an outer peripheral surface of the cushion rubber layer 6 on the outer side in the tire radial direction.

[0026] The tire of the present embodiment may be a new tire, or a retreaded tire that has been used one or more times and retreaded.

[0027] (Cushion rubber layer) The tire 1 of this embodiment includes a cushion rubber layer 6 between the tread rubber layer 7 and the tire case 5. The cushion rubber layer 6 serves to bond the tread rubber layer 7 and the tire case 5 together.

[0028] The cushion rubber layer 6 contains heat-expandable particles that expand due to heat. The heat-expandable particles expand due to heat, thereby reducing the peel resistance of the cushion rubber layer 6, so that the tread portion can be easily separated from the base tire when the tire is retreaded.

[0029] The cushion rubber layer 6 is made of a rubber composition. The composition of the rubber composition is not particularly limited as long as it does not impede the effects of the present invention. The rubber composition includes, for example, a rubber component, thermally expandable particles, and any compounding agent.

[0030] Fig. 2 is a cross-sectional view along the tire width direction showing the periphery of the cushion rubber layer of an example of a tire according to the present embodiment. Fig. 3 is a cross-sectional view along the tire width direction showing the periphery of the cushion rubber layer of an example of a tire according to the present embodiment after the thermally expandable particles of the cushion rubber layer are expanded. The thermally expandable particles A contained in the cushion rubber layer 6 of Fig. 2 expand due to heat to become the expanded thermally expandable particles B shown in Fig. 3, which increases the voids in the cushion rubber layer 6 and reduces the peel resistance, making it possible to easily separate the tread portion of the tire from the base tire portion.

[0031] -Thermal expansion particles- As described above, the thermally expandable particles contained in the cushion rubber layer 6 are particles that expand due to heat.

[0032] The thermally expandable particles have an expansion start temperature of 110 to 135°C. Here, the "expansion start temperature" refers to the temperature at which the thermoplastic resin constituting the shell starts to soften, the encapsulated hydrocarbon starts to gasify, the internal pressure increases, and the microcapsules expand. In general, the heating temperature during tire production is lower than 110°C, so if the expansion start temperature of the thermally expandable particles is in the above range, the thermally expandable particles can be included in the tire without expanding during tire production. In addition, since the thermally expandable particles can be included in the tire without expanding even when heated at a higher temperature, the expansion start temperature of the thermally expandable particles is more preferably 120 to 130°C. The expansion starting temperature of the thermally expandable particles is measured by a thermomechanical analyzer.

[0033] The heat-expandable particles have an average expansion ratio per 10°C from the expansion start temperature to 160°C of 1.25 times / 10°C or more. This temperature range is preferable because the heat-expandable particles quickly reach the desired expansion ratio, improving the efficiency of tire retreading. From the viewpoint of retreading efficiency, it is preferable for the heat-expandable particles to expand more quickly, so the average expansion ratio per 10°C is more preferably 2 times / 10°C or more. The "average expansion ratio per 10°C" can be calculated using the following formula. Average expansion rate per 10°C = expansion rate at 160°C / (160°C - expansion start temperature) x 10

[0034] In addition, the thermally expandable particles preferably have an expansion ratio of 5 times or more at 140°C. When the thermally expandable particles have an expansion ratio of 5 times or more at 140°C, the peel resistance of the cushion rubber layer becomes sufficiently small, making it possible to more easily separate the tread portion and the base tire portion. The smaller the peel resistance, the easier it is to separate the tread portion and the base tire portion, so a smaller peel resistance is preferable. In addition, the peel resistance becomes smaller as the expansion ratio of the thermally expandable particles becomes larger. Therefore, from the viewpoint of further reducing the peel resistance of the cushion rubber layer, the thermally expandable particles preferably have an expansion ratio of 6 times or more at 140°C. Here, the "expansion ratio" refers to the size of a particle expanded by heat relative to the size of the particle not expanded when not heated. The expansion ratio at a certain temperature T can be calculated as follows. (Expansion ratio) = (particle diameter of thermally expandable particles at a certain temperature T) / (particle diameter of thermally expandable particles when not heated) The expansion ratio of the thermally expandable particles was determined by mixing the thermally expandable particles with an EVA emulsion, heating the emulsion at each temperature for 2 minutes, and measuring the expansion ratio of the coating film.

[0035] The thermally expandable particles preferably have an expansion ratio of 6 or more at 150 to 160°C. When the thermally expandable particles have an expansion ratio of 6 or more at 150 to 160°C, the peel resistance of the cushion rubber layer is further reduced, so that the tread portion and the base tire portion can be separated more easily. From the viewpoint of further reducing the peel resistance of the cushion rubber layer, the thermally expandable particles more preferably have an expansion ratio of 7 or more at 150 to 160°C, and even more preferably have an expansion ratio of 9 or more.

[0036] The thermally expandable particles preferably have an average particle size of 10 to 50 μm. By setting the average particle size of the thermally expandable particles within the above range, it is possible to prevent cracks from occurring in the cushion rubber layer during use of the tire, while sufficiently reducing the peel resistance of the cushion rubber layer when the thermally expandable particles expand. From the same viewpoint, the average particle size of the thermally expandable particles is more preferably 35 to 45 μm. The average particle size is measured by a laser diffraction / scattering method using a Microtrac particle size analyzer (Microtrac MRB).

[0037] The thermally expandable particles are preferably thermally expandable microcapsules. The thermally expandable microcapsules are configured by encapsulating a thermally expandable substance in a shell material formed of a thermoplastic resin. The shell material of the thermally expandable microcapsules is formed of, for example, a nitrile polymer. The thermally expandable substance encapsulated in the shell material of the thermally expandable microcapsule has the property of vaporizing or expanding due to heat, and is exemplified by at least one selected from the group consisting of hydrocarbons such as isoalkanes and normal alkanes. Examples of the isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, and 2,2,4-trimethylpentane. Examples of the normal alkanes include n-butane, n-propane, n-hexane, n-heptane, and n-octane. These hydrocarbons may be used alone or in combination. A preferred form of the thermally expansive material is one in which a hydrocarbon that is gaseous at room temperature is dissolved in a hydrocarbon that is liquid at room temperature. By using such a mixture of hydrocarbons, sufficient expansive force can be obtained.

[0038] Examples of commercially available thermally expandable particles contained in the cushion rubber layer of the tire of this embodiment include, but are not limited to, Matsumoto Microsphere (registered trademark) FN-105 (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.), Matsumoto Microsphere (registered trademark) FN-100M (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.), and the like.

[0039] The content of the thermally expandable particles is preferably 5 to 40 parts by mass relative to 100 parts by mass of the rubber component of the cushion rubber layer. The content of the thermally expandable particles in the above range is preferable because the physical properties of the rubber before thermal expansion are close to those of unblended rubber. From the same viewpoint, the content of the thermally expandable particles is more preferably 10 to 30 parts by mass relative to 100 parts by mass of the rubber component of the cushion rubber layer.

[0040] -Other ingredients- As described above, the cushion rubber layer 6 is made of a rubber composition, and the rubber composition contains a rubber component. Any known rubber component can be used as the rubber component. The rubber component is not limited to, but may be one or more of natural rubber, polybutadiene rubber, polystyrene butadiene rubber, and the like.

[0041] The rubber composition of the cushion rubber layer 6 may contain known compounding agents, such as, but not limited to, carbon black, silica, a silane coupling agent, a vulcanization compounding agent, an antioxidant, zinc oxide, a softener, and a processing aid.

[0042] (Tread rubber layer) The tire 1 of this embodiment includes a tread rubber layer 7 on the outer peripheral surface on the outer side in the tire radial direction of the cushion rubber layer 6. The tread rubber layer 7 is the portion that comes into contact with the road surface.

[0043] The tread rubber layer 7 is made of a rubber composition. The composition of the rubber composition is not particularly limited, and a rubber composition having a known composition can be used. Examples of the rubber composition used in the tread rubber layer 7 include those containing natural rubber, isoprene rubber (IR), butadiene rubber (BR), and styrene-butadiene rubber (SBR).

[0044] (Tire case) The tire 1 of the present embodiment includes a tire case 5. The tire case 5 includes, for example, a bead portion 2, a side portion 3, a crown portion 4, and the like.

[0045] The tire case 5 (for example, the bead portion 2, the side portion 3, the crown portion 4, etc.) may be reinforced with a reinforcing material (polymeric material or metallic fiber, cord, nonwoven fabric, woven fabric, etc.) embedded therein.

[0046] 1, it is preferable that a circular bead core 8 is embedded in the bead portion 2. The bead core 8 can be made of a steel cord, an organic fiber cord, a resin-coated organic fiber cord, a hard resin, or the like.

[0047] A gum chafer 9 may be formed on at least a part of the contact portion of the bead portion 2 of the tire case 5 with a rim (not shown). The gum chafer 9 is preferably made of the same kind of rubber as that used on the outer surface of the bead portion 2 of the tire.

[0048] As shown in Fig. 1, a belt 10 consisting of two belt layers 10A and 10B is preferably disposed on the outer periphery of a tire case 5. Each belt layer 10A, 10B is usually made of a rubberized layer of cords extending at an angle to the tire equatorial plane CL, preferably a rubberized layer of steel cords, and the two belt layers 10A, 10B are laminated so that the cords constituting the belt layers 10A, 10B cross each other with the tire equatorial plane CL in between to constitute the belt 10. Note that the belt 10 in the figure is made of two belt layers 10A, 10B, but the number and structure of the belt layers constituting the belt 10 in the tire 1 of this embodiment are not limited to these.

[0049] <Tire manufacturing method> The method for producing a tire according to the present embodiment is characterized in that the vulcanization temperature is equal to or lower than the expansion start temperature of the thermally expandable particles. In the tire manufacturing method described above, since the vulcanization temperature is equal to or lower than the expansion start temperature of the heat-expandable particles, the heat-expandable particles do not expand during tire manufacturing. Therefore, the heat-expandable particles can be contained in the tire without expanding until the tire is retreaded, and when the tire is retreaded, the heat-expandable particles can be expanded, making it possible to easily separate the tread portion of the tire from the base tire portion.

[0050] Apart from the above, the tire can be manufactured by a known method. Examples of the tire manufacturing method include the following method. The thermally expandable particles are mixed into a cushion rubber disposed between a base tire and a vulcanized tread rubber. The base tire and the vulcanized tread rubber are then attached together via the cushion rubber, and the tire is manufactured by vulcanizing the tire as a whole. In this vulcanization, the vulcanization is performed at a temperature equal to or lower than the expansion start temperature of the thermally expandable particles.

[0051] The gas to be filled in the tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0052] <How to retread tires> The tire retreading method of the present embodiment includes: Heating the tire to 120 to 160°C to expand the thermally expandable particles; and removing the tread rubber layer of the tire. In the tire retreading method, the tire is heated to 120 to 160°C, which causes the heat-expandable particles contained in the tire to expand, making it possible to easily separate the tread portion from the base tire portion.

[0053] In addition to the above, the tire retreading method may include steps necessary for tire retreading, such as a step of arranging a cushion rubber on a base tire, a vulcanization step, etc. These steps can be performed using known methods.

[0054] Moreover, a retreaded tire can be manufactured using the tire retreading method of the present embodiment. EXAMPLES

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0056] Example 1: Evaluation of thermally expandable particles The particle size of the heat-expanding particles was measured by the manufacturer using a Microtrac particle size analyzer (Microtrac MRB) by the laser diffraction / scattering method, and the expansion ratio of the heat-expanding particles was evaluated at intervals of 10°C from 100 to 200°C, from which the expansion ratios in Table 1 below were estimated. The expansion ratio was determined by the supplier by mixing the heat-expanding particles with EVA emulsion and measuring the expansion ratio of the coating film heated for 2 minutes at each temperature. The results are shown in Table 1.

[0057] [Table 1]

[0058] *1 Thermally expandable particle 1: Matsumoto Microsphere (registered trademark) FN-105 (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.), average particle size 35 to 45 μm, expansion start temperature 120 to 135 ° C, maximum expansion temperature 175 to 185 ° C. *2 Thermally expandable particles 2: average particle size 10-20μm, expansion start temperature 120-130℃, maximum expansion temperature 150-160℃ *3 Thermally expandable particle 3: Matsumoto Microsphere (registered trademark) FN-100M (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.), average particle size 20 to 30 μm, expansion start temperature 125 to 135 ° C, maximum expansion temperature 165 to 180 ° C.

[0059] From Table 1, it can be seen that the thermally expandable particles 1 to 3 start to expand at 110 to 135°C.

[0060] <Example 2: Evaluation of peel resistance> Two vulcanized natural rubber sheets (2 mm thick) and one 2 mm thick sheet were prepared using unvulcanized rubber blended with the thermally expandable particles 1 in Example 1. A vulcanized rubber laminate in which the unvulcanized rubber sheet was vulcanized was produced by pressurizing and heating the rubber laminate in which the vulcanized rubber sheet, unvulcanized rubber sheet, and vulcanized rubber sheet were laminated in this order. Thereafter, the prepared rubber laminate was heated to expand the thermally expandable particles, and the vulcanized rubber sheets were peeled from each other, and the peel resistance was evaluated using an Autograph (manufactured by A&D Co., Ltd.). The evaluation results are shown in the following Table 2. The evaluated peel resistance is expressed as the peel resistance at a specific expansion ratio relative to the peel resistance at an expansion ratio of 1 for the thermally expandable particle 1 (peel resistance reduction rate).

[0061] [Table 2]

[0062] From Table 2, it can be seen that the peel resistance decreases as the expansion ratio of the thermally expandable particles 1 increases. Therefore, it can be seen that by increasing the expansion ratio of the thermally expandable particles 1, it becomes easier to separate the tread portion and the base tire portion when retreading a tire. [Industrial Applicability]

[0063] According to the present invention, it is possible to provide a tire in which the tread portion and the tire base portion can be easily separated when retreading, a method for manufacturing such a tire, and a method for retreading such a tire.

[0064] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to "No. 12_Responsible Consumption and Production" and "No. 13_Concrete measures against climate change." [Explanation of symbols]

[0065] 1: Tires 2: Bead section 3: Side section 4: Crown 5: Tire case 6: Cushion rubber layer 7: Tread rubber layer 8: Bead core 9: Gumchafer 10: Belt 10A, 10B: Belt layer A: Thermoexpandable particles B: Expanded thermoexpandable particles CL: Tire equatorial plane

Claims

1. A tire including, in order from the outside in the tire radial direction, a tread rubber layer, a cushion rubber layer, and a tire case, The cushion rubber layer contains thermally expandable particles, The thermally expandable particles have an expansion starting temperature of 110 to 135° C. The tire, wherein the thermally expandable particles have an average expansion ratio per 10° C. from the expansion starting temperature to 160° C. of 1.25 times / 10° C. or more.

2. The tire according to claim 1 , wherein the thermally expandable particles have an expansion ratio of 5 times or more at 140° C.

3. The tire according to claim 1, wherein the thermally expandable particles have an expansion ratio of 6 times or more at 150°C to 160°C.

4. The tire according to claim 1, wherein the thermally expandable particles have an average particle size of 10 to 50 μm.

5. The tire according to claim 1, wherein the thermally expandable particles have an expansion start temperature of 120 to 135°C.

6. 10. A method for manufacturing a tire according to claim 1, comprising the steps of: A method for producing a tire, wherein a vulcanization temperature is equal to or lower than the expansion initiation temperature of the thermally expandable particles.

7. 10. A method for retreading a tire according to claim 1, comprising the steps of: Heating the tire to 120 to 160° C. to expand the thermally expandable particles; and removing the tread rubber layer of the tire.

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