Self-sealing rubber for tires and method for preparing same

Abstract

The application relates to the technical field of adhesives, and discloses a self-sealing adhesive for tires and a preparation method thereof. The self-sealing adhesive is prepared through a closed mixing and extrusion process by taking terpolymer ethylene-propylene rubber as a base material and taking a functional crosslinking agent, an initiator, a plasticizer and modified reinforcing material as auxiliary materials. The functional crosslinking agent contains a disulfide bond-maleimide block alternating connection structure, can realize crosslinking modification of the terpolymer ethylene-propylene rubber, and can convert the terpolymer ethylene-propylene rubber from a straight-chain structure into a three-dimensional crosslinking network structure. The structure has high cohesive energy, and therefore can exhibit higher bonding performance. The disulfide bond contained in the structure of the functional crosslinking agent can endow the three-dimensional network with self-repairing performance. The unsaturated alkenyl functional groups contained on the surface of the modified reinforcing material can participate in the subsequent crosslinking process, so that the kaolin can efficiently play its own advantages and the strength of the sealing adhesive layer can be improved.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a self-sealing adhesive for tires and its preparation method. Background Technology

[0002] In today's rapidly developing automotive industry, tires, as the only component of a vehicle in direct contact with the ground, are of paramount importance for safety. A puncture to a tire by a sharp object not only renders the vehicle inoperable but can also lead to serious traffic accidents. To address this issue, self-sealing tire sealants have been developed. These sealants are formed by coating a layer of sealant on the inside of the tire. They function instantly upon puncture, automatically sealing the wound, preventing air leakage, and avoiding a rapid drop in tire pressure, allowing the vehicle to continue driving for a short distance and giving the driver valuable time to react.

[0003] Currently, tire self-sealing adhesives are generally divided into hot melt adhesive systems and rubber systems. Hot melt adhesive systems are relatively simple in formulation and processing, but their drawback lies in the need for high-temperature spraying. This spraying method makes it difficult to achieve a uniform coating effect inside the rounded structure of a tire, resulting in uneven self-sealing layer thickness and ineffective protection. Rubber systems, compared to hot melt adhesive systems, have a simpler coating process, but their problems include lower cross-linking degree, poor high-temperature dimensional stability, and lack of self-healing properties. If a tire experiences repeated punctures in the same area, there is still a significant risk of accidents. Therefore, this invention provides a self-sealing adhesive that can be directly applied to tires, solving the problems existing in the prior art. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a self-sealing adhesive for tires and its preparation method.

[0006] (II) Technical Solution

[0007] A self-sealing adhesive for tires, comprising the following raw materials by weight:

[0008] 70-85 parts of EPDM rubber, 2-5 parts of functional crosslinking agent, 0.3-0.5 parts of initiator, 10-20 parts of plasticizer, and 5-10 parts of modified reinforcing material;

[0009] The modified reinforcing material is kaolin with unsaturated alkenyl functional groups on its surface.

[0010] As a further aspect of the present invention, the preparation method of the functional crosslinking agent includes the following steps:

[0011] Step 1: Preparation of intermediate materials

[0012] Nitrogen gas is introduced into the reactor to purge air. Then, 3-maleimide propionic acid and acetone are added to the reactor and stirred until homogeneous. Next, a composite catalyst is added to the reactor. After the addition is complete, the mixture is stirred at 30-40°C for 1-2 hours. Then, 1,3-diepoxyglycerol ether glycerol is added to the reactor. After the addition is complete, the mixture is stirred at room temperature for 3-6 hours. The solvent is evaporated and the product is collected to obtain the intermediate material.

[0013] Step 2: Preparation of functional crosslinking agent

[0014] Add intermediate material, 3,3'-dithiodipropionic acid and N,N-dimethylformamide to a nitrogen-filled polymerization reactor. After the addition is complete, start stirring until a homogeneous solution is formed. Then add the phase transfer catalyst to the polymerization reactor. After the addition is complete, start heating and control the temperature at 70-80℃. Continue stirring and maintaining the temperature for 12-18 hours. Then stop heating, cool down and discharge the material to obtain the functional crosslinking agent.

[0015] As a further aspect of the present invention, in step one, the molar ratio of 3-maleimide propionic acid and 1,3-diepoxyglycerol ether glycerol is 1:1.

[0016] As a further embodiment of the present invention, in step one, the composite catalyst is a mixture of N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in a mass ratio of 0.3-0.4:1.

[0017] As a further aspect of the present invention, in step two, the molar ratio of the intermediate material and 3,3'-dithiodipropionic acid is 1:0.8-1.

[0018] As a further aspect of the present invention, in step two, the phase transfer catalyst is any one of tetrabutylammonium hydrogen sulfate, tetramethylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium chloride, or N,N-dimethylbenzylamine.

[0019] In the above technical solution, 3-maleimide propionic acid and 1,3-diepoxyglycerol ether glycerol are first used as reactants. Under the catalysis of a composite catalyst, the active carboxyl substituents and hydroxyl substituents in their structures can undergo esterification condensation reaction at room temperature to obtain a maleimide derivative containing two equivalent epoxy substituents, i.e., an intermediate. Then, under the action of a phase transfer catalyst, 3,3'-dithiodipropionic acid is used as a chain extender to carry out a continuous ring-opening esterification reaction with the epoxy substituents in the intermediate structure to obtain a macromolecular functional crosslinking agent with ester bond linkage and a disulfide bond-maleimide block alternating linkage structure.

[0020] As a further embodiment of the present invention, the initiator is benzoyl peroxide or dicumyl peroxide; the plasticizer is at least one of polyisoprene, polybutadiene, polybutene or styrene-butadiene copolymer.

[0021] As a further aspect of the present invention, the preparation method of the modified reinforcing material is as follows:

[0022] Kaolin is ultrasonically dispersed in toluene to form a uniform dispersion. Then, functionalizing reagents and organotin catalysts are added to the dispersion. After the addition is complete, the temperature is raised to 80-90℃ and stirred continuously for 6-9 hours. After cooling, the material is discharged and purified through post-processing to obtain the modified reinforcing material.

[0023] As a further embodiment of the present invention, the functionalizing agent is any one of ethyl isocyanate acrylate, isocyanoethyl methacrylate, or 3-isopropyl-dimethylbenzyl isocyanate; the organotin catalyst is any one of dibutyltin dilaurate, dioctyltin dilaurate, methyl thiotin, or octyl thiotin.

[0024] In the above technical solution, under the action of organotin catalyst, the isocyanate group in the functionalized reagent structure can undergo an amino esterification reaction with the hydroxyl group on the surface of kaolin, thereby modifying the unsaturated alkenyl functional group in the functionalized reagent onto the surface of kaolin to obtain a modified reinforcing material.

[0025] A method for preparing a self-sealing adhesive for tires includes the following steps:

[0026] Step 1: Weigh out each ingredient according to the specified weight proportions and set aside.

[0027] The second step involves adding EPDM rubber, functional crosslinking agent, initiator, and modified reinforcing material into an internal mixer for mixing to form a mixture.

[0028] The third step is to add plasticizer to the mixture, mix it thoroughly, and then feed it into a twin-screw extruder for melt extrusion.

[0029] (III) Beneficial Technical Effects

[0030] This invention prepares a macromolecular functional crosslinking agent containing a disulfide-maleimide block alternating linkage structure as a crosslinking agent for EPDM rubber. During subsequent melt extrusion, the presence of this functional crosslinking agent modifies the crosslinking of EPDM rubber, transforming it from a linear structure to a three-dimensional crosslinked network structure. This structure possesses higher cohesive energy, thus exhibiting superior adhesion performance. Furthermore, the presence of numerous hydroxyl functional groups generated by ring-opening esterification in the functional crosslinking agent structure allows for the creation of more hydrogen bond sites with the tire, further enhancing the sealant's adhesion and enabling better bonding to the inner side of the tire. In addition, the disulfide bonds in the functional crosslinking agent structure impart self-healing properties to the three-dimensional network. After a tire is punctured, heating can facilitate self-repair of the sealant, preventing repeated punctures in the same area and significantly reducing the risk of accidents.

[0031] This invention prepares kaolin with unsaturated alkenyl functional groups on its surface as a modified reinforcing material. Since the unsaturated alkenyl functional groups can participate in the subsequent crosslinking process, the interface problem between kaolin and EPDM rubber can be effectively improved, and kaolin exists in the crosslinking network in the form of crosslinking cores, so as to give full play to its advantages and improve the puncture resistance of the sealant layer. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more complete description will be provided below. Preferred embodiments of the invention are given below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0033] Example 1

[0034] A self-sealing adhesive for tires, comprising the following raw materials by weight:

[0035] 70 parts EPDM rubber, 2 parts functional crosslinking agent, 0.3 parts benzoyl peroxide, 10 parts polyisoprene, and 5 parts modified reinforcing material;

[0036] The preparation method of the self-sealing adhesive includes the following steps:

[0037] Step 1: Weigh out each ingredient according to the specified weight proportions and set aside.

[0038] The second step involves adding EPDM rubber, functional crosslinking agent, benzoyl peroxide, and modified reinforcing material into an internal mixer for mixing to form a mixture.

[0039] The third step is to add polyisoprene to the mixture, mix it thoroughly, and then feed it into a twin-screw extruder. Set the temperature of all three zones to 150°C and the screw length-to-diameter ratio to 60 for melt extrusion.

[0040] The preparation method of the functional crosslinking agent includes the following steps:

[0041] Step 1: Preparation of intermediate materials

[0042] Nitrogen gas was introduced into the reactor to purge air. Then, 0.4 g of 3-maleimide propionic acid and acetone were added to the reactor and stirred until homogeneous. Next, 0.1 g of N-hydroxysuccinimide and 0.3 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added to the reactor. After the addition was complete, the mixture was stirred at 40°C for 1 h. Then, 0.48 g of 1,3-diepoxyglycerol ether glycerol was added to the reactor. After the addition was complete, the mixture was stirred at room temperature for 4 h. The solvent was evaporated to remove the solvent, and the product was collected to obtain the intermediate material.

[0043] Step 2: Preparation of functional crosslinking agent

[0044] Add 0.8g of intermediate material, 0.4g of 3,3'-dithiodipropionic acid, and N,N-dimethylformamide to a nitrogen-filled polymerization reactor. After the addition is complete, start stirring until a homogeneous solution is formed. Then add 0.01g of tetrabutylammonium bromide to the polymerization reactor. After the addition is complete, start heating and control the temperature at 75℃. Continue stirring and maintaining the temperature for 16 hours. Then stop heating, cool down, and discharge the material to obtain the functional crosslinking agent.

[0045] The preparation method of the modified reinforcing material is as follows:

[0046] 1.5g of kaolin was ultrasonically dispersed in toluene to form a uniform dispersion. Then, 0.4g of ethyl isocyanate acrylate and 0.01g of dibutyltin dilaurate were added to the dispersion. After the addition was complete, the temperature was raised to 85℃ and stirred continuously for 8 hours. The material was then cooled and discharged. After post-processing purification, the modified reinforcing material was obtained.

[0047] Example 2

[0048] A self-sealing adhesive for tires, comprising the following raw materials by weight:

[0049] 75 parts of EPDM rubber, 4.5 parts of functional crosslinking agent, 0.4 parts of dicumyl peroxide, 15 parts of polybutadiene, and 8.5 parts of modified reinforcing material;

[0050] The preparation method of the self-sealing adhesive includes the following steps:

[0051] Step 1: Weigh out each ingredient according to the specified weight proportions and set aside.

[0052] The second step involves adding EPDM rubber, functional crosslinking agent, dicumyl peroxide, and modified reinforcing material into a mixer for mixing to form a compound.

[0053] The third step is to add polybutadiene to the mixture, mix it thoroughly, and then feed it into a twin-screw extruder. Set the temperature of all three zones to 150°C and the screw length-to-diameter ratio to 60 for melt extrusion.

[0054] The preparation methods of the functional crosslinking agent and the modified reinforcing material are the same as in Example 1.

[0055] Example 3

[0056] A self-sealing adhesive for tires, comprising the following raw materials by weight:

[0057] 85 parts of EPDM rubber, 5 parts of functional crosslinking agent, 0.5 parts of dicumyl peroxide, 20 parts of polyisoprene, and 10 parts of modified reinforcing material;

[0058] The preparation method of the self-sealing adhesive includes the following steps:

[0059] Step 1: Weigh out each ingredient according to the specified weight proportions and set aside.

[0060] The second step involves adding EPDM rubber, functional crosslinking agent, dicumyl peroxide, and modified reinforcing material into a mixer for mixing to form a compound.

[0061] The third step is to add polyisoprene to the mixture, mix it thoroughly, and then feed it into a twin-screw extruder. Set the temperature of all three zones to 150°C and the screw length-to-diameter ratio to 60 for melt extrusion.

[0062] The preparation methods of the functional crosslinking agent and the modified reinforcing material are the same as in Example 1.

[0063] Comparative Example 1

[0064] A self-sealing adhesive for tires, comprising the following raw materials by weight:

[0065] 75 parts EPDM rubber, 4.5 parts functional crosslinking agent, 0.4 parts dicumyl peroxide, 15 parts polybutadiene, and 8.5 parts kaolin;

[0066] The preparation method of the self-sealing adhesive includes the following steps:

[0067] Step 1: Weigh out each ingredient according to the specified weight proportions and set aside.

[0068] The second step involves adding EPDM rubber, functional crosslinking agent, dicumyl peroxide, and kaolin into an internal mixer for mixing to form a mixture.

[0069] The third step is to add polybutadiene to the mixture, mix it thoroughly, and then feed it into a twin-screw extruder. Set the temperature of all three zones to 150°C and the screw length-to-diameter ratio to 60 for melt extrusion.

[0070] The preparation method of the functional crosslinking agent is the same as that in Example 1.

[0071] Comparative Example 2

[0072] A self-sealing adhesive for tires, comprising the following raw materials by weight:

[0073] 75 parts of EPDM rubber, 4.5 parts of functional crosslinking agent, 0.4 parts of dicumyl peroxide, and 15 parts of polybutadiene;

[0074] The preparation method of the self-sealing adhesive includes the following steps:

[0075] Step 1: Weigh out each ingredient according to the specified weight proportions and set aside.

[0076] The second step involves adding EPDM rubber, functional crosslinking agent, and dicumyl peroxide into an internal mixer for mixing to form a mixture.

[0077] The third step is to add polybutadiene to the mixture, mix it thoroughly, and then feed it into a twin-screw extruder. Set the temperature of all three zones to 150°C and the screw length-to-diameter ratio to 60 for melt extrusion.

[0078] The preparation method of the functional crosslinking agent is the same as that in Example 1.

[0079] Comparative Example 3

[0080] A self-sealing adhesive for tires, comprising the following raw materials by weight:

[0081] 75 parts of ethylene propylene diene monomer (EPDM) rubber, 0.4 parts of dicumyl peroxide, 15 parts of polybutadiene, and 8.5 parts of modified reinforcing material;

[0082] The preparation method of the self-sealing adhesive includes the following steps:

[0083] Step 1: Weigh out each ingredient according to the specified weight proportions and set aside.

[0084] The second step involves adding EPDM rubber, dicumyl peroxide, and modified reinforcing material into a mixer for mixing to form a compound.

[0085] The third step is to add polybutadiene to the mixture, mix it thoroughly, and then feed it into a twin-screw extruder. Set the temperature of all three zones to 150°C and the screw length-to-diameter ratio to 60 for melt extrusion.

[0086] The preparation method of the modified reinforcing material is the same as that in Example 1.

[0087] Performance testing

[0088] The self-sealing adhesives prepared in the examples and comparative examples were made into various film test samples that met the specifications, and various performance tests were conducted. The results are recorded in Table 1:

[0089] Table 1 - Test Results

[0090] 180° peel strength (N / 25mm) Puncture resistance (N / mm) Self-repair rate (%) Example 1 6.8 259 100 Example 2 7.1 265 100 Example 3 7.0 263 100 Comparative Example 1 6.5 218 100 Comparative Example 2 6.6 178 100 Comparative Example 3 5.5 241 20

[0091] The 180° peel strength was tested according to standard GB / T 2792-2014; the puncture resistance was tested according to standard GB / T37841-2019; the self-healing rate test method was as follows: using a scraper, a 5mm deep indentation was scraped on the surface of a 1cm thick film sample, and then the film sample was placed in a temperature environment of 80℃. After 4 hours, it was taken out, the indentation depth was measured, and the repair rate was calculated.

[0092] Based on the test results, it can be concluded that the self-sealing adhesive prepared in the embodiments of the present invention has good adhesion, puncture resistance and self-healing effect.

[0093] When the modified reinforcing material is replaced with unmodified kaolin, the interface problem prevents the kaolin from effectively exerting its reinforcing effect, resulting in a significant reduction in puncture resistance.

[0094] After the functional crosslinking agent is removed, the self-sealing adhesive cannot form a crosslinked structure, and the structure does not contain disulfide bonds, so it cannot produce a self-healing effect.

[0095] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0096] Based on the preferred embodiments of the present invention, and through the above description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A self-sealing adhesive for tires, characterized in that, By weight, it includes the following ingredients: 70-85 parts of EPDM rubber, 2-5 parts of functional crosslinking agent, 0.3-0.5 parts of initiator, 10-20 parts of plasticizer, and 5-10 parts of modified reinforcing material; The modified reinforcing material is kaolin with unsaturated alkenyl functional groups on its surface. The preparation method of the functional crosslinking agent includes the following steps: Step 1: Preparation of intermediate materials: Nitrogen gas is introduced into the reactor to purge air. Then, 3-maleimide propionic acid and acetone are added to the reactor and stirred until homogeneous. Next, a composite catalyst is added to the reactor. After the addition is complete, the mixture is stirred at 30-40°C for 1-2 hours. Then, 1,3-diepoxyglycerol ether glycerol is added to the reactor. After the addition is complete, the mixture is stirred at room temperature for 3-6 hours. The solvent is evaporated and the product is collected to obtain the intermediate material. Step 2: Preparation of functional crosslinking agent: Add intermediate material, 3,3'-dithiodipropionic acid and N,N-dimethylformamide to a nitrogen-filled polymerization reactor. After the addition is complete, start stirring until a homogeneous solution is formed. Then add the phase transfer catalyst to the polymerization reactor. After the addition is complete, start heating and control the temperature at 70-80℃. Continue stirring and maintaining the temperature for 12-18 hours. Then stop heating, cool down and discharge the material to obtain the functional crosslinking agent. The preparation method of the modified reinforcing material includes: Kaolin is ultrasonically dispersed in toluene to form a uniform dispersion. Then, functionalizing reagents and organotin catalysts are added to the dispersion. After the addition is complete, the temperature is raised to 80-90℃ and stirred continuously for 6-9 hours. After cooling, the material is discharged and purified through post-processing to obtain the modified reinforcing material.

2. The self-sealing adhesive for tires according to claim 1, characterized in that, In step one, the molar ratio of 3-maleimide propionic acid and 1,3-diepoxyglycerol ether glycerol is 1:

1.

3. The self-sealing adhesive for tires according to claim 1, characterized in that, In step one, the composite catalyst is a mixture of N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in a mass ratio of 0.3-0.4:

1.

4. The self-sealing adhesive for tires according to claim 1, characterized in that, In step two, the molar ratio of the intermediate material to 3,3'-dithiodipropionic acid is 1:0.8-1.

5. The self-sealing adhesive for tires according to claim 1, characterized in that, In step two, the phase transfer catalyst is any one of tetrabutylammonium hydrogen sulfate, tetramethylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium chloride, or N,N-dimethylbenzylamine.

6. The self-sealing adhesive for tires according to claim 1, characterized in that, The initiator is benzoyl peroxide or dicumyl peroxide; the plasticizer is at least one of polyisoprene, polybutadiene, polybutene, or styrene-butadiene copolymer.

7. The self-sealing adhesive for tires according to claim 1, characterized in that, The functionalizing agent is any one of ethyl isocyanate acrylate, isocyanoethyl methacrylate, or 3-isopropyl-dimethylbenzyl isocyanate; the organotin catalyst is any one of dibutyltin dilaurate, dioctyltin dilaurate, methyl thiotin, or octyl thiotin.

8. A method for preparing a self-sealing adhesive for tires as described in claim 1, characterized in that, Includes the following steps: Step 1: Weigh out each ingredient according to the specified weight proportions and set aside. The second step involves adding EPDM rubber, functional crosslinking agent, initiator, and modified reinforcing material into an internal mixer for mixing to form a mixture. The third step is to add plasticizer to the mixture, mix it thoroughly, and then feed it into a twin-screw extruder for melt extrusion.