Super wear-resistant rubber compound and preparation method thereof

Abstract

The invention discloses a super wear-resistant rubber compound and a preparation method thereof, and belongs to the field of rubber compounds. The rubber compound comprises the following raw materials in parts by mass: 100 parts of a rubber phase, 10-20 parts of white carbon black, 10-15 parts of modified silicon dioxide aerogel, 3-8 parts of a coupling agent, 1.5-3 parts of an anti-aging agent, 1-5 parts of sulfur, 1-3 parts of an active agent, 4-6 parts of an accelerant and 1-3 parts of a cross-linking agent, the rubber phase comprises ethylene propylene diene monomer and butadiene styrene rubber in a mass ratio of (30-40): (60-70); styrene butadiene rubber chain segments are grafted on the surface of the modified silicon dioxide aerogel. The silicon dioxide aerogel can improve the mechanical property of the rubber compound, absorb external stress through micro-deformation and reduce the wear rate of the rubber compound, and after modification treatment, not only can the dispersity and compatibility of the silicon dioxide aerogel be improved, but also the interfacial compatibility between rubber phases can be improved, a physical entanglement network is formed, and the wear resistance of the rubber compound is improved. And integration of filler dispersion and rubber compatibilization is realized.

Description

Technical Field

[0001] The invention relates to the field of rubber compounds, in particular to a super wear-resistant rubber compound and a preparation method thereof. Background Art

[0002] The main chain of the EPDM rubber molecule does not contain reactive functional groups, has stable chemical properties, and has excellent resistance to light, heat, and oxygen. It also has certain hydrophobicity, insulation, high filling properties, high mechanical strength, and good compression resistance, and is used in various fields.

[0003] In order to obtain composite rubber materials with better performance, other rubbers are blended with EPDM rubber to obtain a compound rubber. Traditionally, the common blending and modification method to obtain EPDM rubber compound rubber is to use EPDM rubber and natural rubber together. The vulcanization advantage of natural rubber can make up for the vulcanization defects of EPDM rubber during the mixing process and can also improve the mechanical strength.

[0004] Styrene-butadiene rubber (SBR) is widely used due to its excellent heat resistance and aging resistance. However, SBR has low regularity, high hysteresis energy, low elasticity, low mechanical strength, and poor wet-slip resistance. Because SBR has properties similar to natural rubber, blending it with EPDM can improve its properties to a certain extent. In particular, EPDM's high molecular chain saturation and low polarity result in poor wear resistance, making it prone to rapid wear failure in some dynamic friction scenarios. After mixing with SBR, the rigid units in SBR can improve the wear resistance of EPDM to a certain extent.

[0005] However, because EPDM rubber and SBR have poor compatibility and are thermodynamically incompatible, a weak interface is easily formed after mixing, resulting in stress concentration, which will increase the wear of the rubber mix. During the wear process, the filler particles used for reinforcement are easily detached from the interface, thereby further reducing the wear resistance of the rubber mix.

[0006] With the rapid development of industry, wear-resistant and durable rubber materials are needed in some fields, such as the tread and sidewall of rubber tires, sealing strips and shock-absorbing components of car doors, industrial transmission belts and conveyor rollers, shock-absorbing pads of subway or train tracks, etc. Therefore, the development of a rubber compound with super wear-resistant properties plays an irreplaceable and important role in various fields. Summary of the Invention

[0007] The invention provides a super wear-resistant mixed rubber and a preparation method thereof, which can solve the problem of poor wear resistance of EPDM rubber mixed rubber in the prior art.

[0008] In a first aspect, the present invention provides a super wear-resistant mixed gel, comprising the following raw materials in parts by weight: 100 parts of a rubber phase, 10 to 20 parts of white carbon black, 10 to 15 parts of a modified silica aerogel, 3 to 8 parts of a coupling agent, 1.5 to 3 parts of an antioxidant, 1 to 5 parts of sulfur, 1 to 3 parts of an active agent, 4 to 6 parts of an accelerator, and 1 to 3 parts of a cross-linking agent; The rubber phase includes EPDM rubber and styrene-butadiene rubber in a mass ratio of (30-40): (60-70); styrene-butadiene rubber segments are grafted onto the surface of the modified silica aerogel.

[0009] Preferably, the coupling agent includes a combination of one or more of silane coupling agent Si-69, silane coupling agent Si-75, titanate coupling agent NDZ-201 and titanate coupling agent GR-105.

[0010] Preferably, the accelerator includes one or more combinations of dimethylacetamide, dicumyl peroxide, tripropylene glycol and accelerator CBS.

[0011] Preferably, the active agent comprises one or a combination of zinc oxide and stearic acid.

[0012] Preferably, the antioxidant includes one or more combinations of antioxidant 4010NA, antioxidant DNP, antioxidant DPPD, antioxidant ODA and antioxidant RD.

[0013] By adopting the above technical solution, modified silica aerogel is added to the rubber mixture system of EPDM rubber and styrene-butadiene rubber. Compared with other reinforcing wear-resistant fillers, silica aerogel has a high specific surface area and a unique three-dimensional nanoporous network structure. This network structure can help the silica aerogel deeply penetrate into the rubber phase, forming physical anchor points, which can increase the contact area between the rubber phase and the filler, namely white carbon black, thereby inhibiting the slippage of the rubber molecular chains; the high pore volume of the silica aerogel can establish a three-dimensional physical cross-linking network between the molecular chains of the rubber phase through van der Waals forces, thereby improving the mechanical strength and wear resistance of the resulting rubber mixture.

[0014] Furthermore, silica aerogel forms fractal clusters within the rubber phase, effectively dispersing external stress. When the rubber mix is ​​subjected to friction, it absorbs energy through micro-deformation, reducing the wear rate of the mix. Silica aerogel also synergizes with coupling agents to enhance bond strength within the rubber mix, helping to strengthen the binding force of silica filler particles during friction, preventing them from falling out of the rubber phase and thus improving wear resistance.

[0015] At the same time, because the surface of silica aerogel is rich in silanol groups, the interfacial bonding strength between the silica aerogel and the rubber camera body is poor during the mixing process. The silica aerogel has poor dispersibility and is prone to self-agglomeration, and the reinforcement effect is significantly reduced.

[0016] To further address this issue, silica aerogels were modified. Specifically, styrene-butadiene rubber (SBR) segments were grafted onto the surface of the silica aerogels. The SBR segments have long molecular chains and high steric hindrance, forming a flexible polymer layer on the surface of the silica aerogels. This prevents agglomeration of the silica aerogels and improves their dispersibility. Furthermore, the grafted SBR segments have a polarity match with the rubber phase, creating good interfacial compatibility. This further improves the dispersibility of the silica aerogels in the rubber phase and enhances the silica aerogel's reinforcing properties.

[0017] On the other hand, the introduction of styrene-butadiene rubber segments helps form covalent bonds between the silica aerogel and the rubber phase. This allows frictional stress to be efficiently transferred from the rubber phase to the rigid silica aerogel, thereby improving overall wear resistance. At the same time, the styrene-butadiene rubber segments form an interpenetrating structure with the nanopores of the silica aerogel, which enhances the silica aerogel's reinforcing effect on the rubber phase.

[0018] Moreover, due to the thermodynamic incompatibility of EPDM rubber and SBR in the rubber phase, phase separation is easily caused, and the resulting interfacial bonding force is weak. However, the modified silica aerogel contains styrene units in the SBR segments that can match the polarity of SBR in the rubber phase, and butadiene units that can match the polarity of EPDM rubber. The grafted SBR segments can be interspersed between EPDM rubber and SBR to form a physical entanglement network, thereby improving the interfacial bonding force between the rubber phases.

[0019] The super-wear-resistant rubber compound provided by the present invention can not only improve the dispersibility of silica aerogel in the rubber phase, but also improve the interfacial compatibility between EPDM rubber and styrene-butadiene rubber, coordinate the structure of the rubber phase, integrate filler dispersion and rubber volume expansion, greatly reduce the process steps, and enhance the mechanical properties and wear resistance of the rubber compound.

[0020] Preferably, the raw materials of the modified silica aerogel include silica aerogel and solution-polymerized styrene-butadiene rubber in a mass ratio of 1:(20-30).

[0021] Preferably, the modified silica aerogel is prepared according to the following method: Add solution-polymerized styrene-butadiene rubber to the solvent, stir and dissolve it, then raise the temperature to 40-45° C., add formic acid and stir and mix for 10-20 minutes, then add hydrogen peroxide and stir and react for 1-2 hours, then add silica aerogel, raise the temperature to 50-60° C., continue stirring and reacting for 1-2 hours, and finally filter, wash and dry to obtain the modified silica aerogel.

[0022] Preferably, the molar ratio of solution-polymerized styrene-butadiene rubber, formic acid and hydrogen peroxide is 1:(0.4-0.5):(1.4-1.6).

[0023] More preferably, the solvent includes any one of toluene and cyclohexane.

[0024] By adopting this technical solution, in an acidic environment, formic acid and hydrogen peroxide further react to form peroxyformic acid, which then undergoes an epoxidation reaction with the double bonds in the solution-polymerized styrene-butadiene rubber (SPBR) to form epoxy rings, while preserving the integrity of the SBR's molecular backbone to the greatest extent possible. Silica aerogel is then added, and the silanol groups on the aerogel surface undergo a ring-opening reaction with the formed epoxy groups, forming silicon-oxygen-carbon covalent bonds and thus grafting the SBR segments.

[0025] The modified silica aerogel can greatly improve the dispersion of silica aerogel in the rubber phase and prevent the aerogel particles from agglomerating themselves; and through the styrene-butadiene rubber chain segments, it can improve the compatibility between the silica aerogel and the rubber phase, enhance the interfacial bonding strength between the two, inhibit filler migration, and improve wear resistance.

[0026] In addition, the introduction of styrene-butadiene rubber chain segments can also enhance the compatibility between EPDM rubber and styrene-butadiene rubber. It can serve as a physical cross-linking point, thus penetrating the interface between the two phases, thereby improving the material properties and obtaining a compound rubber with super wear resistance and excellent mechanical properties.

[0027] Preferably, the cross-linking agent includes a combination of one or more of triallyl isocyanurate, triallyl cyanurate and bismaleimide.

[0028] By adopting the above technical solution, a cross-linking agent is also added to the rubber compound. The introduction of the cross-linking agent can form a carbon-carbon bond cross-linking network in the rubber compound, forming a more stable cross-linking structure, which can make up for the defect of the difference in vulcanization rate between EPDM rubber and styrene-butadiene rubber, improve the thermal stability of the rubber phase, and thus improve the processing performance of the rubber compound.

[0029] In addition, the introduction of the cross-linked network can limit the molecular chain movement of the rubber phase, thereby improving the wear resistance of the material, promoting chemical bonding between the filler and the rubber phase, and reducing the problem of easy fall-off of the filler during wear.

[0030] In a second aspect, the present invention provides a method for preparing a super wear-resistant rubber compound, comprising the following steps: S1. The styrene-butadiene rubber is rolled thinly for 4 to 6 times, and the EPDM rubber is added and continued to be rolled thinly for 4 to 6 times to form a rubber phase. Then, the modified silica aerogel is added and the premix is ​​masticated on an open mill to obtain a premix. S2. Adding white carbon black, coupling agent, antioxidant and activator to the premix and mixing them, then adding sulfur, accelerator and cross-linking agent to mix the rubber, and thinly discharging the material to obtain super wear-resistant mixed rubber.

[0031] More preferably, the plasticizing temperature in step S1 is 95-110° C., and the plasticizing time is 15-20 min.

[0032] More preferably, in step S2, the mixing temperature is 40-50° C., and the mixing time is 10-15 min; the mixing temperature is 75-85° C., and the mixing time is 5-10 min.

[0033] Beneficial effects of the present invention: 1. The super-wear-resistant rubber mix provided by the present invention contains modified silica aerogel, which can greatly increase the mechanical properties of the rubber mix. The cluster aggregates formed in the rubber phase can effectively disperse external stress and absorb external stress through micro-deformation, thereby reducing the wear rate of the rubber mix and improving the wear resistance of the rubber mix.

[0034] 2. The surface of the modified silica aerogel provided by the present invention is also grafted with styrene-butadiene rubber segments, which can, on the one hand, improve the dispersibility and compatibility of the aerogel in the rubber phase and increase the cross-linking network density inside the rubber mix, thereby improving the wear resistance and mechanical properties of the rubber mix; on the other hand, it can match the EPDM rubber and styrene-butadiene rubber in the rubber phase, improve the interfacial compatibility of the rubber phase, form a physical entanglement network, and realize the integration of filler dispersion and rubber volume expansion. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0036] Preparation Example Preparation Example 1: A modified silica aerogel was prepared according to the following method: 25 g of solution-polymerized styrene-butadiene rubber (average molecular weight 2.6×10 5 ), after stirring and dissolving, raise the temperature to 45°C, add formic acid and stir and mix for 15 minutes, then add hydrogen peroxide and stir and react for 1 hour, wherein the molar ratio of solution polymerized styrene-butadiene rubber, formic acid and hydrogen peroxide is 1:0.5:1.5; Then, 1 g of silica aerogel was added, the temperature was raised to 50° C., and the reaction was continued with stirring for 2 h. Finally, the modified silica aerogel was obtained by filtration, washing, and drying.

[0037] Preparation Example 2, a modified silica aerogel, differs from Preparation Example 1 only in that the amount of solution-polymerized styrene-butadiene rubber added is 20 g; and the molar ratio of solution-polymerized styrene-butadiene rubber, formic acid, and hydrogen peroxide is 1:0.4:1.4.

[0038] Preparation Example 3, a modified silica aerogel, differs from Preparation Example 1 only in that the amount of solution-polymerized styrene-butadiene rubber added is 30 g; and the molar ratio of solution-polymerized styrene-butadiene rubber, formic acid, and hydrogen peroxide is 1:0.5:1.6.

[0039] Preparation Example 4, a modified silica aerogel, differs from Preparation Example 1 only in that the amount of solution-polymerized styrene-butadiene rubber added is 10 g.

[0040] Preparation Example 5, a modified silica aerogel, is different from Preparation Example 1 only in that the amount of solution-polymerized styrene-butadiene rubber added is 40 g.

[0041] Preparation Example 6, a modified silica, is different from Preparation Example 1 only in that an equal amount of silica is used to replace the silica aerogel.

[0042] Example Example 1, a super wear-resistant rubber compound, is prepared according to the following process steps: S1. Take 60 parts of styrene-butadiene rubber (type 1502) and roll thinly through it 5 times. Then add 40 parts of ethylene propylene diene monomer (type 4045M) and continue to roll thinly through it 5 times to form a rubber phase. Then, add 12 parts of the modified silica aerogel prepared in Preparation Example 1 and masticate on an open mill to obtain a premix. The mastication temperature is 100°C and the mastication time is 15 minutes. S2. Add 15 parts of white carbon black (average particle size of 40 nm), 6 parts of silane coupling agent Si-69, 2 parts of antioxidant 4010NA and 2 parts of zinc oxide to the premix and mix them at a mixing temperature of 45°C and a mixing time of 10 minutes. Then add 3 parts of sulfur, 5 parts of dimethylacetamide and 2 parts of triallyl isocyanurate and mix them at a mixing temperature of 80°C and a mixing time of 8 minutes. Thinly discharge the material to obtain an ultra-wear-resistant mixed rubber.

[0043] Examples 2 to 4 are super wear-resistant rubber compounds, which differ from Example 1 only in that the raw material ratios of the super wear-resistant rubber compounds are adjusted, as shown in Table 1. Table 1 Raw material ratio table of Example 1 to Example 4 Among them, Examples 2 to 4 all used the modified silica aerogel prepared in Preparation Example 1.

[0044] Example 5 is a super wear-resistant rubber compound, which differs from Example 1 only in that the modified silica aerogel prepared in Preparation Example 1 is replaced by an equal amount of the modified silica aerogel prepared in Preparation Example 2.

[0045] Example 6, a super wear-resistant rubber compound, differs from Example 1 only in that the modified silica aerogel prepared in Preparation Example 1 is replaced by an equal amount of the modified silica aerogel prepared in Preparation Example 3.

[0046] Example 7, a super wear-resistant rubber compound, differs from Example 1 only in that the modified silica aerogel prepared in Preparation Example 1 is replaced by an equal amount of the modified silica aerogel prepared in Preparation Example 4.

[0047] Example 8, a super wear-resistant rubber compound, differs from Example 1 only in that the modified silica aerogel prepared in Preparation Example 1 is replaced by an equal amount of the modified silica aerogel prepared in Preparation Example 5.

[0048] Comparative Example Comparative Example 1 is a super wear-resistant rubber compound, which is different from Example 1 only in that the amount of the silica aerogel prepared in Preparation Example 1 added is 5 parts.

[0049] Comparative Example 2 is a super wear-resistant rubber compound, which is different from Example 1 only in that the amount of the silica aerogel prepared in Preparation Example 1 added is 20 parts.

[0050] Comparative Example 3 is a super wear-resistant rubber compound, which differs from Example 1 only in that the modified silica aerogel prepared in Preparation Example 1 is replaced by an equal amount of modified white carbon black prepared in Preparation Example 6.

[0051] Comparative Example 4 is a super wear-resistant rubber compound, which differs from Example 1 only in that the modified silica aerogel prepared in Preparation Example 1 is replaced by an equal amount of white carbon black.

[0052] Comparative Example 5 is a super wear-resistant rubber compound, which differs from Example 1 only in that triallyl isocyanurate is not added.

[0053] Performance testing Preparation of vulcanized samples: The super-wear-resistant rubber mixtures obtained in the examples and comparative examples were first placed at room temperature for 24 hours and then vulcanized at a vulcanization temperature of 165°C, a time of 90 minutes, and a pressure of 10 MPa. The corresponding vulcanized samples were obtained after venting 5 times.

[0054] Performance testing: 1. Mechanical properties test: (1) Tensile property test: According to the relevant records in GB / T 528-2009 “Vulcanized rubber or thermoplastic rubber - Determination of tensile stress-strain properties”, the tensile strength of the vulcanized samples of the examples and comparative examples was tested; (2) Tear strength test: According to the relevant records in GB / T 529-2008 “Vulcanized rubber or thermoplastic rubber — Determination of tear strength (trouser-shaped, right-angled and crescent-shaped test specimens)”, the tear strength of the vulcanized samples of the examples and comparative examples was tested.

[0055] 2. Wear resistance test: According to the relevant records in GB / T 1689-2014 "Determination of wear resistance of vulcanized rubber (using Akron abrasion tester)", the wear resistance of the vulcanized samples of the examples and comparative examples was tested.

[0056] The above test results are shown in Table 2: Table 2 Performance test results According to Table 2, in combination with Example 1, Comparative Examples 1, 2, and 4, it can be seen that compared with Example 1, the tensile strength and tear strength of Comparative Examples 1, 2, and 4 decreased, and the Akron abrasion loss increased, indicating that the mechanical properties and wear resistance of Comparative Examples 1, 2, and 4 decreased compared with Example 1. The reason is that the reduced amount of modified silica aerogel added in Comparative Example 1 not only lacks the reinforcing effect of silica aerogel, but also affects the interfacial compatibility of the rubber phase, resulting in a decrease in various properties. In Comparative Example 4, which uses an equal amount of white carbon black to replace the modified silica aerogel, the performance decreases significantly. In Comparative Example 2, the increased amount of modified silica aerogel added results in excessive rigidity of the rubber mix, loss of elasticity, and a significant decrease in the mechanical properties of the material.

[0057] Combining Example 1 and Comparative Example 3, it can be seen that the mechanical properties and wear resistance of Comparative Example 3 are reduced compared with those of Example 1. The reason is that in Comparative Example 3, white carbon black that has undergone the same modification treatment is used to replace the modified silica aerogel. Compared with silica aerogel, the white carbon black filler does not have a porous network structure, the bonding force between the white carbon black filler and the rubber phase is reduced, and the level of dispersed stress is reduced, resulting in a decrease in the mechanical properties and wear resistance of the obtained rubber mix.

[0058] Combining Example 1 and Comparative Example 5, it can be seen that the mechanical properties and wear resistance of Comparative Example 5 are lower than those of Example 1. The reason is that no cross-linking agent is added in Comparative Example 5, the cross-linking density of the rubber mix is ​​reduced, the stability of the cross-linked structure is reduced, and the performance improvement effect of the vulcanized cross-linked network material alone is not good, which leads to a decrease in various properties of the rubber mix.

[0059] The above disclosures are only a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A super wear-resistant rubber compound, characterized in that: The invention comprises the following raw materials in parts by mass: 100 parts of rubber phase, 10-20 parts of white carbon black, 10-15 parts of modified silica aerogel, 3-8 parts of coupling agent, 1.5-3 parts of antioxidant, 1-5 parts of sulfur, 1-3 parts of active agent, 4-6 parts of accelerator and 1-3 parts of cross-linking agent; The rubber phase comprises ethylene propylene diene monomer (EPDM) rubber and styrene butadiene rubber (SBR) in a mass ratio of (30-40): (60-70); and the surface of the modified silica aerogel is grafted with SBR segments.

2. The super wear-resistant rubber compound according to claim 1, characterized in that The raw materials of the modified silica aerogel include silica aerogel and solution-polymerized styrene-butadiene rubber in a mass ratio of 1:(20-30).

3. The super wear-resistant rubber compound according to claim 2, characterized in that: The modified silica aerogel is prepared according to the following method: Add solution-polymerized styrene-butadiene rubber to the solvent, stir and dissolve it, then raise the temperature to 40-45° C., add formic acid and stir and mix for 10-20 minutes, then add hydrogen peroxide and stir and react for 1-2 hours, then add silica aerogel, raise the temperature to 50-60° C., continue stirring and reacting for 1-2 hours, and finally filter, wash and dry to obtain the modified silica aerogel.

4. The super wear-resistant rubber compound according to claim 3, characterized in that: The molar ratio of the solution-polymerized styrene-butadiene rubber, formic acid and hydrogen peroxide is 1: (0.4-0.5): (1.4-1.6).

5. The super wear-resistant rubber compound according to claim 1, characterized in that: The coupling agent includes one or more of a silane coupling agent Si-69, a silane coupling agent Si-75, a titanate coupling agent NDZ-201 and a titanate coupling agent GR-105.

6. The super wear-resistant rubber compound according to claim 1, characterized in that: The cross-linking agent includes one or more of triallyl isocyanurate, triallyl cyanurate and bismaleimide.

7. The super wear-resistant rubber compound according to claim 1, characterized in that: The accelerator includes one or more combinations of dimethylacetamide, dicumyl peroxide, tripropylene glycol and accelerator CBS.

8. The super wear-resistant rubber compound according to claim 1, characterized in that: The active agent includes one or a combination of zinc oxide and stearic acid.

9. The super wear-resistant rubber compound according to claim 1, characterized in that: The antioxidant includes one or more combinations of antioxidant 4010NA, antioxidant DNP, antioxidant DPPD, antioxidant ODA and antioxidant RD.

10. A method for preparing a super wear-resistant rubber compound according to any one of claims 1 to 9, characterized in that: The process steps include: S1. The styrene-butadiene rubber is rolled thinly for 4 to 6 times, and the EPDM rubber is added and continued to be rolled thinly for 4 to 6 times to form a rubber phase. Then, the modified silica aerogel is added and the premix is ​​masticated on an open mill to obtain a premix. S2. Adding white carbon black, coupling agent, antioxidant and activator to the premix and mixing them, then adding sulfur, accelerator and cross-linking agent to mix the rubber, and thinly discharging the material to obtain super wear-resistant mixed rubber.

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