A mutual interface dual-network modified rubber material and a preparation method thereof

Abstract

The application discloses an interlinked double-network modified rubber material and a preparation method thereof. Based on diene materials and styrene polymer macromolecular materials, by introducing a dynamic covalent bond of dioxaborolane ester, an interlinked double-network is designed and prepared at a molecular level, and a high-performance modified rubber material is obtained. The interlinked double-network modified rubber material has the abilities of rapid self-repair, repeated thermal processing and good toughness, and has impact resistance matching that of high-impact styrene. In addition, the interlinked double-network modified rubber material can be blended with carbon black, silicon dioxide, sulfur, vulcanization accelerators, reactive agents, rubber additives and the like to prepare a rubber compound, so that the mechanical indexes of the material, including tensile strength, impact strength, tear strength, tensile toughness and impact toughness, are further enhanced.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and in particular to an interconnected dual-network modified rubber material and its preparation method. Background Technology

[0002] Rubber is a thermosetting elastomer polymer material with important applications in tires, vibration damping, and sealing. With the expansion of rubber material applications, higher demands are being placed on its service performance, especially its comprehensive performance. For example, tires require materials with high strength, ultra-toughness, high impact resistance, low heat generation, and high wear resistance; sealing rubber materials require high elasticity at low temperatures, flexibility, oil resistance, tear resistance, and aging resistance; and vibration damping rubber materials require good damping and energy dissipation properties. To achieve the target performance of the products, the industry currently mainly uses a multi-component blending method, such as blending multiple synthetic rubbers, including styrene-butadiene rubber, butyl rubber, isoprene rubber, and natural rubber. This method is simple and economical, but most rubbers are difficult to be compatible at the molecular level, and there are even significant phase separation problems, leading to processing difficulties and insufficient stability of the product performance. Chemical methods for directly preparing modified rubber materials from multi-component monomers can achieve molecular-level compatibility and facilitate the control of processing and service properties, enabling customized performance targeting. For example, biomimetic synthetic isoprene rubber prepared by grafting proteins and phospholipids exhibits strength and toughness levels approaching those of high-performance natural rubber. Styrene-butadiene rubber (SBR) is a prime example of copolymerization, and its properties can be controlled by adjusting component ratios and polymerization methods. Chemical modification is an effective and economical approach, particularly for specialized rubber materials used in small quantities.

[0003] On the other hand, once synthetic and natural rubber undergo vulcanization and cross-linking, they form thermosetting polymers. These polymers are difficult to re-process and recycle, making them difficult to degrade and reuse. For example, the large quantities of discarded tires and rubber products have caused serious environmental problems, drawing increasing global attention. The preparation of recyclable, recyclable, and self-healing rubber materials through molecular design has become a research hotspot in recent years, offering a feasible solution to the environmental problems caused by thermosetting rubbers. The preparation of environmentally friendly rubber materials can be achieved through the development of reversible catalysts, the introduction of dynamic covalent bonds, or chemical methods such as pyrolysis. Summary of the Invention

[0004] In view of the problems existing in the prior art, this invention provides an interlocking dual-network modified rubber material and its preparation method. Based on diene materials such as isoprene and butadiene, as well as styrene-based polymer macromolecules, an interlocking dual network is designed and prepared at the molecular level by introducing dynamic covalent bonds of diboroxypentane ester, thus developing a high-performance modified rubber material. The flexible and rigid networks in the modified rubber material form an interlocking dual-network structure composed of reversible chemical crosslinks at the dispersion interface through dynamic covalent bonds, endowing the system with high impact resistance while improving the balance between the material's hardness, strength, and toughness.

[0005] The first technical solution of this invention to solve the above-mentioned technical problems is to provide an interconnected dual-network modified rubber material, comprising a flexible network and a rigid network; the flexible network is a diene copolymer containing diboroxypentane ester dynamic covalent bonds in its chain, wherein the molar ratio of diboroxypentane ester to the double bonds in the diene copolymer is 0.8~3.0; the rigid network is a styrene copolymer containing diboroxypentane ester dynamic covalent bonds in its chain, wherein the molar ratio of diboroxypentane ester to the double bonds in the styrene copolymer is 0.8~3.0; wherein the flexible network and the rigid network are physically and chemically crosslinked.

[0006] The two networks in the modified rubber material interact through physical entanglement and chemical bonding at the dispersion interface via dynamic covalent bonds, giving the system high impact resistance and improving the balance between the material's hardness, strength, and toughness. Since the boron oxide chemical bond energy of diboroxypentane ester is relatively low, currently considered to be between 38-55 kJ / mol, the proportion of dynamic covalent bonds can be controlled by adjusting the amount of crosslinking agent added. The dynamic covalent bonds introduced by the crosslinking agent can undergo exchange reactions between dynamic chemical bonds at 60-100℃, causing the system to exhibit glass-like flow, thus achieving secondary molding and self-healing of the modified rubber material and its vulcanizates.

[0007] Preferably, the mass fraction of the flexible network is 30-70%. The interlocking dual-network modified rubber material with this composition possesses rapid self-healing, repeated heat processing capabilities, and good elasticity and toughness.

[0008] Preferably, the rigid network has a mass fraction of 50-80%. This composition results in an interlocking dual-network modified rubber material with impact resistance comparable to high-impact styrene.

[0009] Furthermore, the diene block copolymer containing diboroxypentane ester dynamic covalent bonds in the chain is obtained by modifying one or more diene polymers with a weight average molecular weight between 15,000 and 300,000 g / mol.

[0010] Preferably, the diene block copolymer containing diboroxypentane ester dynamic covalent bonds in its chain is a polyisoprene block copolymer containing diboroxypentane ester dynamic covalent bonds, or a polybutadiene block copolymer containing diboroxypentane ester dynamic covalent bonds, or a polybutadiene-isoprene block copolymer containing diboroxypentane ester dynamic covalent bonds. Diene polyolefin materials with a weight-average molecular weight of 15,000 to 300,000 g / mol can also be used. Other diene polyolefin materials, such as polyprene and natural rubber, have similar double bonds in their main chain, which can also yield the flexible network described above.

[0011] The second technical solution of the present invention to solve the above-mentioned technical problem is to provide a method for preparing the interconnected dual-network modified rubber material, comprising the following steps: crushing, mixing and hot-pressing the flexible network and the rigid network respectively to obtain the interconnected dual-network modified rubber material.

[0012] Preferably, between or after the blending and hot pressing steps, the method further includes the step of vulcanizing the mixture of the flexible network and the rigid network.

[0013] Furthermore, the method for fabricating the flexible network includes the following steps: S11. An epoxy diene polymer is subjected to an acyl chloride reaction with hydrochloric acid in tetrahydrofuran solvent to obtain the first random copolymer; S12. The first random copolymer is subjected to an acylation reaction with acryloyl chloride to obtain the second random copolymer; S13. The second random copolymer is reacted and blended with the crosslinking agent 2,2'-(1,4-phenyl)-bis[4-thiol-1,3,2-diboroxypentane ester] by click chemistry to form the flexible network.

[0014] Furthermore, the acylation reaction conditions described in step S12 are: stirring at room temperature after feeding, and reacting for more than 10 hours.

[0015] Furthermore, the preparation method of the epoxy diene polymer includes the following steps: using a catalyst, performing an epoxidation reaction on some of the double bonds on the diene polymer to obtain a partially epoxy polydiene, i.e., the epoxy diene polymer. The degree of epoxidation of the partially epoxy polydiene is 0.1-99.9%.

[0016] It is worth noting that the epoxy diene polymer can be partially or completely replaced by a commercially available epoxy diene polymer, preferably with a weight-average molecular weight of 50,000 to 300,000 g / mol, such as epoxidized polyisoprene rubber or epoxidized natural rubber. The diene polymer is one or more diene polymers with a weight-average molecular weight between 15,000 and 300,000 g / mol.

[0017] Furthermore, the method for preparing the rigid network includes the following steps: S21. Styrene, a first RAFT reagent, and a chain initiator are fed into the RAFT polymerization method to obtain a second RAFT reagent; the first RAFT reagent is 1,4-bis(n-butylsulfonylthiocarbonylsulfonylmethyl)benzene; the chain initiator is benzoyl peroxide; S22. A third random copolymer is formed by polymerizing a second RAFT reagent with 4-vinylphenyl-1,3,2-diboroxypentane ester via RAFT polymerization. S23. The third random copolymer is reacted and blended with a crosslinking agent to form the rigid network; the crosslinking agent is 1,4-bis((2-phenyl-1,3,2-dioxaboron-2-yl)methylenethioyl)decane.

[0018] The beneficial effects of this invention are as follows: 1. This invention provides an interconnected dual-network modified rubber material and its preparation method. Through the interaction of physical entanglement and chemical bonding generated at the dispersion interface by dynamic covalent bonds, the system exhibits high impact resistance and simultaneously improves the balance between the material's hardness, strength, and toughness.

[0019] 2. This invention introduces diboroxypentane ester dynamic covalent bonds into rigid and flexible networks. These chemical bonds can break at 50-60℃. At this temperature, the flexible and rigid networks exhibit good plasticity during molding processes such as blending, extrusion, calendering, and compression molding, enabling uniform dispersion at the micro-nano scale. Subsequently, the dynamic bonds are regenerated to obtain an interconnected double network structure, thereby improving the mechanical properties of the system.

[0020] 3. This invention directly prepares modified rubber materials from multiple monomers, achieving molecular-level compatibility. By adjusting the amount of crosslinking agent, the composition of flexible and rigid networks, and the ratio between them, the processing and service properties of the material can be controlled, enabling customization for target performance.

[0021] 4. Traditional thermosetting rubbers, once vulcanized and cross-linked, form thermosetting polymers, which are difficult to re-process once molded, resulting in environmental problems such as difficulty in recycling and degradation. The rubber material provided by this invention is recyclable, recyclable, and self-healing, which helps to solve the environmental problems caused by thermosetting rubbers.

[0022] 5. The interconnected double-network modified rubber material and its preparation method provided by the present invention can be processed on general rubber processing equipment. It can be blended with carbon black, silica, sulfur, vulcanization accelerator, reactive agent, rubber additives, etc. to prepare compound rubber. The olefin double bonds in the modified rubber material can undergo vulcanization reaction to form a sulfur bond chemical cross-linking network, which endows the material with various mechanical strengths and toughnesses, including tensile strength, impact strength, tear strength, tensile toughness and impact toughness. Attached Figure Description

[0023] Figure 1 The tensile property curve is obtained by repeated molding in Example 1 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the molar number of copolymers mentioned below refers to the molar number of double bonds. Example 1

[0026] Example 1 is an interconnected dual-network modified rubber material, comprising a flexible network and a rigid network; the flexible network is an isoprene block copolymer containing diboroxypentane ester dynamic covalent bonds within its chain; the rigid network is a styrene block copolymer containing diboroxypentane ester dynamic covalent bonds within its chain. The flexible and rigid networks are physically and chemically crosslinked.

[0027] The preparation method of epoxy polyisoprene used in Example 1 includes the following steps: 96g of polyisoprene with a weight-average molecular weight of 30,000g / mol and a molecular weight distribution width of 2.60 was taken, 100ml of ethyl acetate and 200ml of distilled water were added, and the mixture was stirred at room temperature until a suspension was formed. The suspension was then placed in an ice-water bath. 0.3g of benzoyl peroxide was added for epoxidation, and the reaction was carried out for 6 hours. The mixture was filtered, washed three times with water, and the product was dried. The degree of epoxidation was detected by nuclear magnetic resonance spectroscopy and found to be approximately 30%.

[0028] The method for fabricating the flexible network in Example 1 includes the following steps: S11. Add 96g of the above epoxy polyisoprene to 100ml of tetrahydrofuran (THF) and stir. Then add 1ml of 10mol / L hydrochloric acid and stir to react, to obtain poly(isoprene-r-3-chloro-2-methyl-2-butanol), i.e., the first random copolymer. S12. The first random copolymer is subjected to an acylation reaction with acryloyl chloride, stirred at room temperature, and reacted for 10 hours to obtain a modified rubber poly(isoprene-r-3-chloro-2-methyl methacrylate) random copolymer, namely the second random copolymer. S13. The second random copolymer was reacted and blended with the crosslinking agent 2,2'-(1,4-phenyl)-bis[4-thiol-1,3,2-diboroxypentane ester] at a molar ratio r = 1:1.5. The system gelled to form the flexible network of Example 1, as shown in the following formula:

[0029]

[0030] The method for preparing the rigid network in Example 1 includes the following steps: S21. By RAFT polymerization, 1,4-bis(n-butylsulfonylthiocarbonylsulfonylmethyl)benzene, a chain transfer agent, is used as the first RAFT agent. Styrene, the above RAFT agent, and benzoyl peroxide, a chain initiator, are added at a molar ratio of 1:0.3:0.002. The mixture is stirred at room temperature and reacted for more than 10 hours to obtain a macromolecular styrene-based RAFT agent with active groups at both ends, i.e., the second RAFT agent. S22. By RAFT polymerization, the second RAFT reagent and 4-vinylphenyl-1,3,2-diboroxypentane ester are polymerized in a molar ratio of 1:1 to form an ABA-type triblock random copolymer, namely the third random copolymer. S23. The third random copolymer was blended with the crosslinking agent 1,4-bis((2-phenyl-1,3,2-dioxaboron-2-yl)methylenethioyl)decane at a molar ratio of 1:2, and the mixture was reacted and blended at 40 rpm for 30 min on an internal mixer to obtain a rigid network. The result is shown in the following formula:

[0031] The above-mentioned flexible network and rigid network were mixed in a mass ratio of 50:50 on a mixer for 15 minutes at a speed of 45 rpm to obtain the interconnected double network modified rubber material Example 1. Example 2

[0032] Example 2 is an interlocking dual-network modified rubber material, comprising a flexible network and a rigid network; the flexible network is a butadiene block copolymer containing diboroxypentane ester dynamic covalent bonds within its chain, with a weight-average molecular weight of 30,000 g / mol; the rigid network is a styrene block copolymer containing diboroxypentane ester dynamic covalent bonds within its chain. The flexible and rigid networks are physically and chemically crosslinked.

[0033] The preparation method of epoxy polybutadiene used in Example 2 includes the following steps: Take 96g of polybutadiene, add 100ml of ethyl acetate and 200ml of distilled water, stir at room temperature to form a suspension, and place in an ice-water bath; add 0.3g of benzoyl peroxide for epoxidation, react for 6 hours, filter, wash three times with water, and dry the product. The degree of epoxidation was detected by NMR spectroscopy to be approximately 30%.

[0034] The method for preparing the flexible network in Example 2 includes the following steps: S11. Add 96g of the above epoxy polybutadiene to 100ml of tetrahydrofuran (THF) and stir. Then add 1ml of 10mol / L hydrochloric acid and stir to induce an acyl chloride reaction to obtain the first random copolymer. S12. The first random copolymer is subjected to an acylation reaction with acryloyl chloride to obtain the second random copolymer; S13. The second random copolymer and the crosslinking agent 2,2'-(1,4-phenyl)-bis[4-thiol-1,3,2-diboroxypentane ester] are hot-pressed at a molar ratio r = 1:1.5, and the system gels to form the flexible network of Example 2.

[0035] The rigid network in Example 2 is the same as that in Example 1.

[0036] The above-mentioned flexible network and rigid network were mixed in a mass ratio of 50:50 on a mixer for 15 minutes at a speed of 45 rpm to obtain the interconnected double network modified rubber material Example 2. Example 3

[0037] Example 3 is an interconnected dual-network modified rubber material, comprising a flexible network and a rigid network; the flexible network is natural rubber containing dynamic covalent bonds of diboroxypentane ester within its chain; the rigid network is a styrene block copolymer containing dynamic covalent bonds of diboroxypentane ester within its chain. The flexible and rigid networks are physically and chemically crosslinked.

[0038] The epoxy natural rubber used in Example 3 was purchased from Shandong Kepler Biotechnology Co., Ltd., with product number DN-803 and ENR50.

[0039] The method for fabricating the flexible network in Example 3 includes the following steps: S11. Add 96g of the above-mentioned epoxy natural rubber to 100ml of tetrahydrofuran (THF) and stir. Then add 1ml of 10mol / L hydrochloric acid and stir to produce an acyl chloride reaction to obtain the first random copolymer. S12. The first random copolymer is subjected to an acylation reaction with acryloyl chloride to obtain the second random copolymer; S13. The second random copolymer and the crosslinking agent 2,2'-(1,4-phenyl)-bis[4-thiol-1,3,2-diboroxypentane ester] are hot-pressed at a molar ratio r = 1:1.5, and the system gels to form the flexible network of Example 3.

[0040] The rigid network in Example 3 is the same as that in Example 1.

[0041] The above-mentioned flexible network and rigid network were mixed in a mass ratio of 50:50 on an internal mixer for 15 minutes at a speed of 45 rpm to obtain the interconnected double network modified rubber material Example 3. Example 4

[0042] Example 4 is an interconnected dual-network modified rubber material, comprising a flexible network and a rigid network; the flexible network is an isoprene block copolymer containing diboroxypentane ester dynamic covalent bonds within its chain; the rigid network is a styrene block copolymer containing diboroxypentane ester dynamic covalent bonds within its chain. The flexible and rigid networks are physically and chemically crosslinked.

[0043] The flexible network and rigid network in Example 4 are the same as in Example 1.

[0044] The difference lies in that the above-mentioned flexible network and rigid network are mixed in a mass ratio of 30:70 on an internal mixer for 15 minutes at a speed of 45 rpm to obtain the interconnected double network modified rubber material Example 4. Example 5

[0045] Example 5 is an interconnected dual-network modified rubber material, comprising a flexible network and a rigid network; the flexible network is an isoprene block copolymer containing dynamic covalent bonds of diboroxypentane ester within its chain; the rigid network is a styrene block copolymer containing dynamic covalent bonds of diboroxypentane ester within its chain. The flexible and rigid networks are physically and chemically crosslinked.

[0046] The flexible network and rigid network in Example 5 are the same as in Example 1.

[0047] The difference lies in that the above-mentioned flexible network and rigid network are mixed in a mass ratio of 60:40 on an internal mixer for 15 minutes at a speed of 45 rpm to obtain the interconnected double network modified rubber material Example 5.

[0048] Comparative Example 1 is a high-grade natural rubber (domestic rubber RSS1).

[0049] Comparative Example 2 is a synthetic styrene-butadiene rubber (in which the mass fraction of styrene units is 23.5%).

[0050] Experimental Example 1 Take 100 parts by weight of each of Examples 1-6 and Comparative Examples 1-2. Add 3 parts of zinc oxide and 2 parts of stearic acid to each, mix for 5 minutes at 45 rpm; after cooling, add 2.5 parts of sulfur and 1.5 parts of vulcanization accelerator, mix for 1 minute at 45 rpm.

[0051] The above blend was molded on a flat vulcanizing machine, heated at 145°C for 20 min, and pressed into a vulcanized sheet with a thickness of 2 mm under a pressure of 30t. The sample strips were cut using a dumbbell-shaped cutter and tested for tensile strength, modulus, elongation at break, toughness and impact strength using a universal testing machine. The results are shown in Table 1.

[0052] Table 1

[0053] Experimental Example 2 Example 1 was directly molded at 100°C to prepare a 1 mm thick sheet, and its mechanical properties were tested. The sheet was then broken up and repeatedly molded 5 times, and its tensile mechanical properties were tested, yielding similar tensile property curves, as shown in the attached figure. Figure 1 .

[0054] It can be seen that the tensile properties of the interconnected dual-network modified rubber material provided by the present invention remain basically unchanged after repeated hot processing, exhibiting good thermal reversibility. It also maintains good mechanical properties after multiple processing, meeting the requirements of recyclability, reprocessability, and repairability.

[0055] The above-described contents can be implemented individually or in various combinations, and these variations are all within the protection scope of this invention.

[0056] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0057] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered within the scope of protection of the present invention.

Claims

1. An interconnected dual-network modified rubber material, characterized in that... The material is obtained by crushing, blending, and hot-pressing a flexible network and a rigid network, respectively. The flexible network is a diene copolymer containing dynamic covalent bonds of diboroxypentane ester within its chain, wherein the molar ratio of double bonds in the diboroxypentane ester to the diene copolymer is 0.8~3.

0. The rigid network is a styrene copolymer containing dynamic covalent bonds of diboroxypentane ester within its chain, wherein the molar ratio of double bonds in the diboroxypentane ester to the styrene copolymer is 0.8~3.

0. The flexible network and the rigid network form an interconnected dual network that is physically and chemically cross-linked in the material.

2. The interconnected dual-network modified rubber material according to claim 1, characterized in that, The quality fraction of the flexible network is 30-70%.

3. The interconnected dual-network modified rubber material according to claim 1, characterized in that, The quality fraction of the rigid network is 50-80%.

4. The interconnected dual-network modified rubber material according to claim 1, characterized in that, The diene copolymer containing diboroxopentane ester dynamic covalent bonds in the chain is obtained by modifying one or more diene polymers with a weight average molecular weight between 15,000 and 300,000 g / mol.

5. The interconnected dual-network modified rubber material according to claim 1, characterized in that, The diene copolymer containing diboroxopentane ester dynamic covalent bonds within the chain is: Polyisoprene copolymers containing diboroxopentane ester dynamic covalent bonds within the chain. Or polybutadiene copolymers containing diboroxypentane ester dynamic covalent bonds within the chain. Or a polybutadiene-isoprene copolymer containing diboroxopentane ester dynamic covalent bonds within the chain.

6. The interconnected dual-network modified rubber material according to claim 1, characterized in that, Between or after the blending and hot pressing steps, the method further includes the following step: vulcanizing the mixture of the flexible network and the rigid network.

7. The interconnected dual-network modified rubber material according to claim 1, characterized in that, The method for fabricating the flexible network includes the following steps: S11. An epoxy diene polymer is subjected to an acyl chloride reaction with hydrochloric acid in tetrahydrofuran solvent to obtain the first random copolymer; S12. The first random copolymer is subjected to an acylation reaction with acryloyl chloride to obtain the second random copolymer; S13. The second random copolymer is reacted and blended with the crosslinking agent 2,2'-(1,4-phenyl)-bis[4-thiol-1,3,2-diboroxypentane ester] by click chemistry to form the flexible network.

8. The interconnected dual-network modified rubber material according to claim 7, characterized in that, The preparation method of the epoxy diene polymer includes the following steps: using a catalyst, performing an epoxidation reaction on some of the double bonds on the diene polymer to obtain a partial epoxy polydiene, namely the epoxy diene polymer.

9. The interconnected dual-network modified rubber material according to claim 1, characterized in that, The method for preparing the rigid network includes the following steps: S21. Styrene, a first RAFT reagent, and a chain initiator are fed into the RAFT polymerization method to obtain a second RAFT reagent; the first RAFT reagent is 1,4-bis(n-butylsulfonylthiocarbonylsulfonylmethyl)benzene, and the chain initiator is benzoyl peroxide; S22. A third random copolymer is formed by polymerizing a second RAFT reagent with 4-vinylphenyl-1,3,2-diboroxypentane ester via RAFT polymerization. S23. The third random copolymer is reacted and blended with a crosslinking agent to form the rigid network; the crosslinking agent is 1,4-bis((2-phenyl-1,3,2-dioxaboron-2-yl)methylenethioyl)decane.

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