Method for manufacturing recyclable integrated tire

Abstract

The present invention relates to a method for manufacturing a recyclable integrated tire, the method comprising the steps of: inserting an insert into a mold; injecting a resin composition, in which a molten polymer and a supercritical fluid are mixed, into the mold; foaming the polymer in the mold; and separating the mold.

Description

Method for manufacturing a recyclable integral tire

[0001] The present invention relates to a method for manufacturing a recyclable integral tire and an integral tire manufactured thereby.

[0002] Tires, with their flexibility, heat resistance, and shock absorption, are a key automotive component. However, used tires are increasingly being identified as a major contributor to various environmental problems. In particular, with the increasing demand for automobiles, the waste tires generated when landfilled or incinerated contain cross-linked sulfur compounds, causing secondary environmental pollution.

[0003] Accordingly, various attempts have been made to recycle waste tires, such as removing the tread of waste tires and attaching new treads to manufacture retreaded tires, or manufacturing waste tires in powder form to manufacture urethane flooring for children's playgrounds.

[0004] However, in the case of recycled tires, there is a risk of tire bursting due to the high defect rate, which poses a problem with stability, and in the case of urethane flooring, there are problems such as the detection of harmful substances including lead.

[0005] In addition, even the amount of waste tires recycled as mentioned above is only a very small portion, and most of them are incinerated or landfilled, which still causes serious environmental problems, so recycling waste tires is important from an environmental perspective.

[0006] Therefore, research on manufacturing methods for recyclable tires is necessary.

[0007] The technology behind this application, Republic of Korea Publication Patent No. 10-2021-0113231, relates to a tire recycling method.

[0008] The present invention is intended to solve the problems of the above-mentioned prior art and to provide a method for manufacturing a recyclable integral tire.

[0009] In addition, the purpose is to provide a recyclable integral tire manufactured by the above manufacturing method.

[0010] However, the technical tasks to be achieved by the embodiments of the present invention are not limited to the technical tasks described above, and other technical tasks may exist.

[0011] As a technical means for achieving the above-mentioned technical task, the first aspect of the present invention provides a method for manufacturing a recyclable integral tire, comprising the steps of: inserting an insert into a mold; injecting a resin composition in which a molten polymer and a supercritical fluid are mixed into the mold; foaming the polymer within the mold; and separating the mold.

[0012] According to one embodiment of the present invention, the polymer may include, but is not limited to, a thermoplastic resin.

[0013] According to one embodiment of the present invention, the thermoplastic resin may include, but is not limited to, a resin selected from the group consisting of thermoplastic polyurethane (TPU), polyester elastomer (TPEE), polyolefin elastomer (POE), styrene ethylene butylene styrene copolymer (SEBS), and combinations thereof.

[0014] According to one embodiment of the present invention, the supercritical fluid may include, but is not limited to, a fluid selected from the group consisting of nitrogen, carbon dioxide, air, and combinations thereof.

[0015] According to one embodiment of the present invention, the supercritical fluid may be compressed at a pressure of 150 bar to 250 bar, but is not limited thereto.

[0016] According to one embodiment of the present invention, in the step of inserting the insert into the mold, a cavity may be formed in a space between the periphery of the insert and the mold, and the resin composition may be injected into the cavity, but is not limited thereto.

[0017] According to one embodiment of the present invention, the insert may be inserted in whole or in part onto the mold, but is not limited thereto.

[0018] According to one embodiment of the present invention, in the step of foaming the polymer within the mold, the polymer may be foamed by changing the environment within the mold, but is not limited thereto.

[0019] According to one embodiment of the present invention, the insert and the polymer may be formed as an integral body, but are not limited thereto.

[0020] According to one embodiment of the present invention, the insert may include a resin that is the same as or different from the polymer, but is not limited thereto.

[0021] In addition, the second aspect of the present invention provides a recyclable integral tire comprising an insert and a foam tire integrally bonded to the insert.

[0022] According to one embodiment of the present invention, the foam tire may include, but is not limited to, a polymer physically foamed by a supercritical fluid.

[0023] The above-described problem-solving methods are merely exemplary and should not be construed as limiting the present invention. In addition to the exemplary embodiments described above, additional embodiments may be included in the drawings and detailed description of the invention.

[0024] In conventional tire manufacturing methods, injection molding was not possible because the tire was manufactured using a thermosetting resin or rubber, and recycling of the tire was not possible due to the vulcanization process using a chemical crosslinking agent. However, in the tire manufacturing method according to the present invention, injection molding is possible because a thermoplastic resin is used, and since a supercritical fluid is used to physically foam the resin, a vulcanization process using a chemical crosslinking agent is not required, so recycling is possible, and there is an advantage in that it is possible.

[0025] In addition, the method for manufacturing a tire according to the present invention is manufactured through insert injection, and since the wheel and tire are manufactured by being combined as one piece during the manufacturing process, a separate process for combining the wheel and tire is not required, and the problem of separation of the wheel and tire may not occur.

[0026] In addition, the method for manufacturing a tire according to the present invention has the advantage of being able to manufacture a tire with an improved foaming ratio than conventional foam tires because it uses a supercritical fluid to foam a polymer.

[0027] In addition, a tire manufactured through the method according to the present invention exhibits properties comparable to tires manufactured using conventional thermosetting resins, despite using thermoplastic resins, and has advantages in terms of grip and rebound elasticity that are superior to conventional tires.

[0028] However, the effects that can be obtained from this center are not limited to the effects described above, and other effects may exist.

[0029] Figure 1 is a flowchart of a method for manufacturing a recyclable integral tire according to one embodiment of the present invention.

[0030] FIG. 2 is an image of equipment (Gentrex from Tienkang) used in the manufacture of an integral tire according to one embodiment of the present invention.

[0031] Figure 3 is a schematic diagram showing the operation process of equipment used in manufacturing an integral tire according to one embodiment of the present invention.

[0032] FIG. 4 is an image of a mold used in a process for manufacturing an integral tire according to one embodiment of the present invention and an actually manufactured integral tire.

[0033] Below, with reference to the attached drawings, an embodiment of the present invention is described in detail so that a person having ordinary knowledge in the technical field to which the present invention pertains can easily carry out the present invention.

[0034] However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description have been omitted, and similar parts have been designated with similar drawing reference numerals throughout the specification.

[0035] Throughout this specification, when a part is said to be "connected" to another part, this includes not only cases where it is "directly connected" but also cases where it is "electrically connected" with another element in between.

[0036] Throughout this specification, when it is said that a member is located “on,” “above,” “upper,” “lower,” “lower” or “lower” another member, this includes not only cases where the member is in contact with the other member, but also cases where another member exists between the two members.

[0037] Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0038] The terms "about," "substantially," and the like, as used herein, are used to mean at or near the numerical value when manufacturing and material tolerances inherent to the meanings referred to are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that contain precise or absolute numerical values ​​to aid understanding of the present disclosure. Furthermore, throughout the present disclosure, the terms "step of ~" or "step of ~" do not mean "step for ~."

[0039] Throughout this specification, the term "combination thereof" included in the expressions in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expressions in the Makushi format, and means including one or more selected from the group consisting of said components.

[0040] Throughout this specification, references to “A and / or B” mean “A or B, or A and B.”

[0041] Hereinafter, a method for manufacturing a recyclable integral tire according to the present invention will be described in detail with reference to implementation examples, examples, and drawings. However, the present invention is not limited to these implementation examples, examples, and drawings.

[0042]

[0043] As a technical means for achieving the above-mentioned technical task, the first aspect of the present invention provides a method for manufacturing a recyclable integral tire, comprising the steps of: inserting an insert into a mold; injecting a resin composition in which a molten polymer and a supercritical fluid are mixed into the mold; foaming the polymer within the mold; and separating the mold.

[0044] Figure 1 is a flowchart of a method for manufacturing a recyclable integral tire according to one embodiment of the present invention.

[0045] First, insert the insert into the mold. (S100)

[0046] The method for manufacturing a tire according to the present invention is performed using an insert injection process, and a wheel of the tire can be used with the insert, but is not limited thereto.

[0047] According to one embodiment of the present invention, in the step of inserting the insert into the mold, a cavity may be formed in a space between the periphery of the insert and the mold, and the resin composition may be injected into the cavity, but is not limited thereto.

[0048] In conventional tire manufacturing methods, the tire and wheel are manufactured separately and then combined to form a tire. However, in the method according to the present invention, the insert itself can be used as a wheel, and a resin composition is injected around the insert and then foamed to form a tire directly on the insert, so a separate process for combining the tire and wheel is not required.

[0049] In addition, while conventional tires must necessarily have a rim formed on the wheel to combine the tire and the wheel, the tire according to the present invention can be formed by adhering the tire to the wheel when the tire is formed by foaming a polymer around the wheel during the manufacturing process, and thus the rim for fastening the tire to the wheel may not necessarily be included.

[0050] According to one embodiment of the present invention, the insert may be inserted in whole or in part onto the mold, but is not limited thereto.

[0051] When using a wheel with the above insert, the resin composition is injected and foamed only into the part where the tire is to be formed (i.e., the perimeter of the insert) to form the tire, so the process can proceed by inserting only the perimeter of the insert, not the entire insert, into the mold.

[0052] Next, a resin composition containing a molten polymer and a supercritical fluid is injected into the mold (S200).

[0053] In the resin composition injection step (S200), the temperature of the injector (barrel) can be appropriately controlled depending on the type of polymer used. Specifically, melt processing is possible within a temperature range of 140°C to 230°C for TPU, 200°C to 260°C for TPEE, 120°C to 190°C for POE, and 120°C to 200°C for SEBS. In this way, by appropriately setting the injector temperature according to the melting point of each resin, an optimal melting state can be secured.

[0054] According to one embodiment of the present invention, the polymer may include, but is not limited to, a thermoplastic resin.

[0055] Conventional tires are manufactured using thermosetting resins like rubber or polyurethane. Rubber, as an elastomer, tends to return to its original shape after stretching, making it difficult to completely fill the mold. Furthermore, its long curing time can impact production speed. Thermosetting resins like polyurethane harden upon exposure to heat and cannot be remelted. Therefore, the process temperature must be meticulously controlled to prevent curing before the mold is filled.

[0056] Furthermore, conventional tires made of rubber are manufactured by performing a vulcanization process using a sulfur-containing chemical cross-linking agent to improve the tire's physical properties, such as strength, durability, and elasticity. While vulcanized tires offer the advantage of improved physical properties, they require a desulfurization process for recycling. This process is extremely complex and difficult, and the properties of the raw rubber can be damaged during the desulfurization process. Furthermore, there are problems such as the difficulty in completely removing sulfur.

[0057] Meanwhile, in the case of foam tires made by foaming thermosetting resins such as rubber or polyurethane, they are manufactured using chemical foaming agents to foam the material. However, due to environmental issues, the use of chemical foaming agents is increasingly being restricted worldwide, and when manufactured using chemical foaming agents, there is also the problem that recycling of tires is difficult.

[0058] However, since the method for manufacturing a tire according to the present invention uses a thermoplastic resin, an injection molding process is possible, and since the resin is physically foamed using a supercritical fluid, the use of a chemical crosslinking agent and a foaming agent is not required, so it is an environmentally friendly method and has the advantage of allowing the tire to be recycled.

[0059] According to one embodiment of the present invention, the thermoplastic resin may include, but is not limited to, a resin selected from the group consisting of thermoplastic polyurethane (TPU), polyester elastomer (TPEE), polyolefin elastomer (POE), styrene ethylene butylene styrene copolymer (SEBS), and combinations thereof.

[0060] The thermoplastic resin of the present invention may be thermoplastic polyurethane (TPU), polyester elastomer (TPEE), polyolefin elastomer (POE), styrene ethylene butylene styrene copolymer (SEBS), or the like, used alone or in combination. In the embodiments of the present invention, TPU is used as the main raw material, but this is exemplary and the scope of the present invention is not limited thereto. In fact, the manufacturing method of the present invention can be applied to most thermoplastic resins such as polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), polylactic acid (PLA), polyvinyl alcohol (PVOH), and polycaprolactone (PCL). The reason why various thermoplastic resins can be used in this way is because the present invention adopts a physical foaming method using a supercritical fluid, and this is a feature that differentiates it from conventional technologies that use chemical foaming agents or crosslinking agents.

[0061] According to one embodiment of the present invention, the supercritical fluid may include, but is not limited to, a fluid selected from the group consisting of nitrogen, carbon dioxide, air, and combinations thereof.

[0062] The supercritical fluids used in the present invention may include nitrogen, carbon dioxide, air, and others, either singly or in combination. While nitrogen is used as the supercritical fluid in a particularly preferred embodiment of the present invention, this is merely exemplary and the scope of the present invention is not limited thereto. In actual industrial settings, nitrogen and carbon dioxide are primarily used as supercritical fluids. Considering economic feasibility, air can also be used as a supercritical fluid.

[0063] According to one embodiment of the present invention, the supercritical fluid may be compressed at a pressure of 150 bar to 250 bar, but is not limited thereto.

[0064] In the present invention, the supercritical fluid is compressed and used at a pressure of 150 to 250 bar, and preferably, it is compressed at a pressure of about 200 bar to create a supercritical state. For example, in the case of nitrogen, in order to become supercritical, the temperature must be -147℃ or higher and the pressure must be 33.9 bar or higher. Therefore, at room temperature, the supercritical state can be realized with only a pressure of 34 bar or higher, and in this case, the ratio of the supercritical fluid injected relative to the raw material shot size can be increased. The reason for increasing the pressure to 200 bar in the present invention is to obtain a more uniform foam structure, dissolve a larger amount of gas, and improve the stability of process control.

[0065] According to one embodiment of the present invention, the insert may include a resin that is the same as or different from the polymer, but is not limited thereto.

[0066] If the above insert is made of the same resin as the above polymer, there is an advantage in that both the wheel and the tire can be recycled.

[0067] Next, the polymer inside the mold is foamed. (S300)

[0068] According to one embodiment of the present invention, in the step of foaming the polymer within the mold, the polymer may be foamed by changing the environment within the mold, but is not limited thereto.

[0069] In the method for manufacturing a tire according to the present invention, the foaming ratio of the tire can be controlled by controlling the mixing ratio of the supercritical fluid in the resin composition, and there is an advantage in that foaming can be performed at a higher foaming ratio than in a foam tire manufactured with a conventional thermosetting resin through the method according to the present invention.

[0070] Specifically, in the present invention, the amount of supercritical fluid injected into the raw resin is determined according to the hardness or specific gravity required for the final product. In a preferred embodiment of the present invention, a relatively small amount of supercritical fluid of 0.3 to 0.5% relative to the raw material shot size (g) may be injected to achieve high hardness of a caster tire. On the other hand, if the critical pressure setting value of the fluid is lowered, a larger amount of supercritical fluid may be injected, and when manufacturing a product requiring high specific gravity, such as shoes, or low hardness, such as a low-hardness tire, a higher ratio of supercritical fluid may be injected.

[0071] Meanwhile, the temperature of the mold can be maintained at 30°C to 50°C, and the internal pressure can be set to 20 bar. The cooling time to ensure dimensional stability of the foamed product is preferably 5 to 20 seconds, but may be longer depending on the product size or operating conditions.

[0072] Finally, separate the mold. (S400)

[0073] According to one embodiment of the present invention, the insert and the polymer may be formed as an integral body, but are not limited thereto.

[0074] As described above, the method for manufacturing a tire according to the present invention is such that the insert and the polymer are formed as an integral body by foaming the polymer around the insert during the manufacturing process, and accordingly, a separate process for combining the wheel and the tire after the manufacturing process is not required, and the problem of separation of the wheel and the tire may not occur.

[0075] In addition, the second aspect of the present invention provides a recyclable integral tire comprising an insert and a foam tire integrally bonded to the insert.

[0076] Regarding the recyclable integral tire according to the second aspect of the present invention, detailed descriptions of overlapping parts with the first aspect of the present invention have been omitted, but even if the descriptions have been omitted, the contents described in the first aspect of the present invention can be equally applied to the second aspect of the present invention.

[0077] According to one embodiment of the present invention, the foam tire may include, but is not limited to, a polymer physically foamed by a supercritical fluid.

[0078] The foam tire according to the present invention, unlike conventional foam tires, is physically foamed using a supercritical fluid such as nitrogen without using a chemical foaming agent, and has the advantage of being recyclable because it is manufactured using a thermoplastic resin instead of a thermosetting resin.

[0079] A tire manufactured by the method according to the present invention exhibits properties comparable to tires manufactured using conventional thermosetting resins, despite using thermoplastic resins, and has advantages in terms of grip and rebound elasticity that are superior to conventional tires.

[0080] The present invention will be described in more detail through the following examples; however, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0081] [Example 1] Integral tire

[0082] FIG. 2 is an image of equipment (Gentrex from Tienkang) used in the manufacture of an integral tire according to one embodiment of the present invention.

[0083] Figure 3 is a schematic diagram showing the operation process of equipment used in manufacturing an integral tire according to one embodiment of the present invention.

[0084] First, the TPU raw material was sufficiently dried at a temperature of 80℃ for 4 hours. The dried TPU raw material was mixed using a stirrer until it was uniform.

[0085] Next, the mold was opened and the insert was mounted at a predetermined position in the mold.

[0086] Next, the TPU raw material was melted in an injector set to 200°C. Supercritical nitrogen compressed to 200 bar was mixed into the molten TPU at a ratio of 0.4% relative to TPU. At this time, the injection pressure was set to 100 bar, and the mixed resin composition was injected into a mold whose pressure was reduced to 20 bar.

[0087] Next, the injected resin composition was allowed to spontaneously foam within the reduced pressure environment inside the mold. During this process, supercritical nitrogen formed uniform bubbles within the polymer matrix. The mold temperature was maintained at 40°C during the foaming process, and a cooling time of 15 seconds was applied.

[0088] Finally, after foaming and cooling were complete, the mold was opened and the molded tire was removed. The removed product was allowed to stabilize at room temperature for an additional hour.

[0089] FIG. 4 is an image of a mold used in a process for manufacturing an integral tire according to one embodiment of the present invention and an actually manufactured integral tire.

[0090] [Comparative Example 1] PU Tire

[0091] The W614 product from Taiwan RIANT WHEEL was purchased and used as comparative example 1.

[0092] [Experimental Example 1] Physical property evaluation

[0093] The properties of the integral tire according to Example 1 of the present invention and the PU tire according to Comparative Example 1 were compared and evaluated. The evaluation items were hardness (Shore A), specific gravity, elasticity, and slip, and the results are shown in Table 1.

[0094] Comparative Example 1 Example 1 Hardness (Shore A) 7070 Specific gravity 0.4~0.7 0.45~0.48 Elasticity 30~40 42 Slip 0.5~1.0 1.2

[0095] As can be seen in Table 1, the integral tire according to Example 1 of the present invention exhibited hardness and elasticity at similar levels to the PU tire of Comparative Example 1. In terms of specific gravity, Example 1 exhibited relatively constant properties of 0.45 to 0.48 depending on the ratio of raw materials and supercritical fluid, but Comparative Example 1 showed a significant difference of 0.4 to 0.7. In addition, in terms of elasticity, Example 1 showed a constant property of 42, but Comparative Example 1 showed a significant difference of 30 to 40. Particularly noteworthy is the slip property, where Example 1 showed a value of 1.2, which was higher than Comparative Example 1, which had a slip property of 0.5 to 1.0. This means that the tire manufactured through the method according to the present invention has superior grip. These results demonstrate that the tire of the present invention can secure properties equivalent to or higher than those of a tire using a conventional thermosetting resin, despite using a thermoplastic resin. In particular, the slip characteristics related to the gripping force showed a remarkable improvement compared to the prior art, confirming the superiority of the manufacturing method according to the present invention.

[0096] The above description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0097] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. Step of inserting the insert into the mold; A step of injecting a resin composition mixed with a molten polymer and a supercritical fluid into the mold; a step of foaming the polymer within the mold; and A step of separating the above mold; Including, Method for manufacturing a recyclable integral tire.

2. In paragraph 1, The above polymer comprises a thermoplastic resin, Method for manufacturing a recyclable integral tire.

3. In paragraph 2, The thermoplastic resin is selected from the group consisting of thermoplastic polyurethane (TPU), polyester elastomer (TPEE), polyolefin elastomer (POE), Styrene Ethylene Butylene Styrene copolymer (SEBS), and combinations thereof. Method for manufacturing a recyclable integral tire.

4. In paragraph 1, The supercritical fluid comprises a fluid selected from the group consisting of nitrogen, carbon dioxide, air and combinations thereof. Method for manufacturing a recyclable integral tire.

5. In paragraph 4, The above supercritical fluid is compressed at a pressure of 150 bar to 250 bar. Method for manufacturing a recyclable integral tire.

6. In paragraph 1, At the step of inserting the above insert into the mold, A cavity is formed in the space between the periphery of the insert and the mold, and the resin composition is injected into the cavity. Method for manufacturing a recyclable integral tire.

7. In paragraph 6, The above insert is inserted in whole or in part into the above mold, Method for manufacturing a recyclable integral tire.

8. In paragraph 1, In the step of foaming the polymer within the mold, By changing the environment within the mold, the polymer is foamed. Method for manufacturing a recyclable integral tire.

9. In paragraph 1, The above insert and the above polymer are formed as one piece, Method for manufacturing a recyclable integral tire.

10. In paragraph 9, The above insert comprises a resin identical to or different from the above polymer, Method for manufacturing a recyclable integral tire.

11. A recyclable integral tire comprising an insert and a foam tire integrally bonded to the insert.

12. In paragraph 11, The above foam tire comprises a polymer physically foamed by a supercritical fluid. Recyclable integral tire.

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