Anti-aging rubber and preparation method thereof

Abstract

The invention relates to anti-aging rubber and a preparation method thereof. The anti-aging rubber comprises the following raw materials in parts by weight: 60-90 parts of raw rubber A; the raw rubber A is nitrile rubber; 10-40 parts of raw rubber B; the raw rubber B is ethylene propylene diene monomer and / or ethylene propylene diene monomer; 90 to 120 parts of reinforcing filler; the reinforcing filler is a composition of carbon black and white carbon black; 5-8 parts of a rubber lubricant; 0.1 to 0.2 part of a coupling agent; 3-6 parts of a plasticizer; 5-8 parts of zinc oxide; 0.1 to 2.5 parts of sulfur; 1 to 2 parts of peroxide DCP; 1-3 parts of an accelerant; 1-3 parts of stearic acid; and 2-5 parts of an anti-aging agent. According to the aging-resistant rubber and the preparation method thereof, the design is reasonable, a raw rubber system provides basic performance of rubber, a reinforcing system enhances mechanical properties of the rubber, a vulcanization system ensures a cross-linked structure of the rubber, multiple auxiliaries enhance processability, stability and aging resistance of the rubber, and the aging-resistant rubber with good comprehensive performance is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber, and in particular relates to an aging-resistant rubber and a preparation method thereof. Background Art

[0002] As a highly elastic polymer material that occupies a unique position in the field of materials, nitrile rubber has irreplaceable characteristics. Nitrile rubber has excellent elasticity and can withstand considerable strain. This strain tolerance makes it stand out in many complex engineering application scenarios. Nitrile rubber also has a significant advantage. Through careful formula design, it can flexibly meet a variety of material performance requirements. Whether it is special requirements for hardness, wear resistance, oil resistance, or chemical corrosion resistance, they can be achieved by adjusting the formula. It is precisely because of these excellent properties that nitrile rubber has become an ideal raw material for manufacturing seals.

[0003] At present, the sealing rings made of nitrile rubber have been widely used. In various links of industrial production, such as automobile manufacturing, aerospace, petrochemical and many other fields, nitrile rubber sealing rings play a vital sealing role.

[0004] However, aging is an irreversible phenomenon that all polymer materials cannot escape. From a microscopic perspective, the molecular structure inside polymer materials changes under the long-term effects of external environmental factors, resulting in molecular chain breakage, cross-linking or other chemical changes. This change in microstructure manifests itself as a significant decrease in material performance on a macroscopic level, and in severe cases, the material may even completely lose its original application value.

[0005] When the nitrile rubber used to make the sealing ring ages, various undesirable phenomena will appear on the sealing ring. For example, the sealing ring may become sticky, which will cause the sealing ring to easily absorb dust, impurities, etc. during operation, further affecting its sealing performance. Cracking is also one of the common manifestations of aging. Once cracking occurs, the integrity of the sealing ring is destroyed and the sealing effect is greatly reduced. Hardening will cause the sealing ring to lose its original elasticity and fail to fit the sealing surface tightly, thus causing the risk of leakage. Discoloration may indicate that the chemical structure inside the sealing ring has changed, and its physical and chemical properties will inevitably be affected; becoming brittle means that the sealing ring is more likely to break when subjected to external forces, seriously threatening the safety of the sealing system. And rupture is the most serious result of aging. Once rupture occurs, the sealing system will completely fail. These sealing ring problems caused by the aging of nitrile rubber will undoubtedly seriously affect the normal use of nitrile rubber sealing rings in practical applications, and may have an adverse effect on the operation of the entire equipment or system.

[0006] In view of the wide application of nitrile rubber sealing rings in many fields and the serious impact of aging on their performance, in recent years, the research on nitrile rubber sealing rings and aging of nitrile rubber has been increasing.

[0007] Therefore, the purpose of the present invention is to develop an aging-resistant rubber for use in sealing rings, and to improve its aging-resistant performance through the formulation design of the aging-resistant rubber and the optimization of its preparation method. Summary of the invention

[0008] Purpose of the invention: In order to overcome the above shortcomings, the purpose of the present invention is to provide an aging-resistant rubber and a preparation method thereof, which has a reasonable design, wherein the raw rubber system provides the basic properties of the rubber, the reinforcement system enhances the mechanical properties of the rubber, the vulcanization system ensures the cross-linking structure of the rubber, and a variety of additives enhance the processing properties, stability, and aging resistance of the rubber, thereby obtaining an aging-resistant rubber with good comprehensive performance, which is applied to sealing rings and has broad application prospects.

[0009] The objective of the present invention is achieved through the following technical solutions: An aging-resistant rubber, comprising the following raw materials in parts by weight: 60-90 parts of raw rubber A; the raw rubber A is nitrile rubber; 10-40 parts of raw rubber B; the raw rubber B is EPDM rubber and / or EPDM rubber; 90-120 parts of reinforcing filler; the reinforcing filler is a composition of carbon black and white carbon black; 5-8 parts of rubber lubricant; Coupling agent 0.1-0.2 parts; 3-6 parts of plasticizer; Zinc oxide 5-8 parts; Sulfur 0.1-2.5 parts; Peroxide DCP 1-2 parts; 1-3 parts of accelerator; 1-3 parts of stearic acid; 2-5 parts of antioxidant.

[0010] The anti-aging rubber of the present invention has a reasonable formula design, and various raw materials cooperate with each other to jointly construct an anti-aging rubber with good comprehensive performance.

[0011] Among them, nitrile rubber, EPDM rubber and / or EPDM rubber constitute the raw rubber system. Nitrile rubber provides a good oil-resistant and wear-resistant foundation for the rubber. The addition of EPDM rubber can greatly improve the aging resistance of the entire rubber system. The addition of EPDM rubber can further improve the flexibility and low-temperature performance of the rubber. Moreover, EPDM rubber has good compatibility with EPDM rubber and nitrile rubber, and can synergistically improve the comprehensive performance of the entire raw rubber system.

[0012] Among them, carbon black and white carbon black form a reinforcement system, forming a complementary structure and performance. Carbon black has good reinforcement properties and can be filled between rubber molecular chains to form physical adsorption and chemical bonding, thereby improving the mechanical properties of rubber such as tensile strength, tear strength and wear resistance. White carbon black has a high specific surface area and can have a strong interaction with rubber molecular chains. White carbon black also has good heat resistance and chemical corrosion resistance. Therefore, the combination of the two can improve rubber in multiple performance aspects. And due to the different structures and properties of carbon black and white carbon black, there are differences in their particle size and surface properties. This difference can make them more evenly dispersed in the rubber matrix, thereby improving the processing performance of the rubber.

[0013] Among them, sulfur, peroxide DCP, and accelerator constitute the vulcanization system. Sulfur is a traditional vulcanizer. During the vulcanization process, sulfur reacts with the double bonds in the rubber molecular chain to form sulfur bridges to connect the rubber molecular chains together. Peroxide DCP is a sulfur-free vulcanizer. It decomposes and produces free radicals during the vulcanization process, which triggers the cross-linking reaction between the rubber molecular chains. The combination of sulfur and peroxide DCP allows the vulcanization system to combine the advantages of both. That is, sulfur vulcanization can form a variety of sulfur bonds (single sulfur bonds, disulfide bonds, and polysulfide bonds, etc.), which can give the rubber better initial strength and elasticity, while peroxide DCP vulcanization can produce carbon-carbon bond crosslinking. This crosslinking method makes the vulcanized rubber have better heat resistance and compression permanent deformation resistance. Therefore, the combination of the two can not only ensure the basic properties of the rubber under different usage requirements, but also improve its performance under special environments. Accelerators are used to control the vulcanization speed, so that the vulcanization reaction proceeds evenly from the surface to the inside of the rubber, and ensure the quality of vulcanization.

[0014] Among them, the formula also includes rubber lubricant BR-2, silane coupling agent ST, plasticizer RS735, antioxidant and other additives. Rubber lubricant mainly reduces the friction between rubber molecular chains and reduces the interaction between molecular chains, thereby reducing the stress concentration of rubber during storage and use, improving the processing performance of rubber and improving the dimensional stability of rubber. Silane coupling agent mainly improves the interface bonding between reinforcing filler and rubber matrix. Plasticizer mainly increases the flexibility and plasticity of rubber. Zinc oxide plays the role of activator in the rubber vulcanization process. It can be combined with accelerators to increase the speed and efficiency of vulcanization reaction. Zinc oxide also has a certain anti-aging effect. It can absorb harmful light such as ultraviolet rays and reduce the damage of light to rubber molecular chains. Anti-aging agent is used to prevent the aging of rubber.

[0015] Furthermore, in the above-mentioned aging-resistant rubber, the raw rubber A is one or more combinations of NBR N31, NBR N32, NBR 1052, and NBR3350; the raw rubber B is one or more combinations of EPDM 512E, EPDM 525, EPM V722, and EPM DutralLCO054.

[0016] Furthermore, in the above-mentioned aging-resistant rubber, the raw rubber B is EPDM rubber and EPDM rubber, and the mass ratio of EPDM rubber to EPDM rubber is 50-90:10-40.

[0017] Furthermore, in the above-mentioned aging-resistant rubber, the carbon black is one or a combination of carbon black N220, carbon black N320, carbon black N550, and carbon black N774; in the reinforcing filler, the mass ratio of carbon black to white carbon black is 20-90:10-30.

[0018] Preferably, the carbon black N320, carbon black N550 and white carbon black form a reinforcement system.

[0019] Carbon black N320 has high reinforcing properties and can effectively improve the tensile strength, tear strength and wear resistance of rubber. Carbon black N550 has high structural properties and can give rubber good elasticity and hysteresis properties. Carbon black N550 and carbon black N320 can be used together to reinforce rubber in different aspects. White carbon black has reinforcing properties and transparency. For some rubber products that require a certain degree of transparency, white carbon black can also absorb some small molecular substances in rubber, reduce the migration and volatilization of these substances during the aging process, and play a role in anti-aging performance.

[0020] Furthermore, in the above-mentioned aging-resistant rubber, the rubber lubricant is rubber lubricant BR-2; the coupling agent is silane coupling agent ST-10A; and the plasticizer is plasticizer RS735.

[0021] Furthermore, in the above-mentioned aging-resistant rubber, the accelerator is one or a combination of accelerator MBTS, accelerator DTDC, accelerator ZBEC, accelerator TETD, accelerator CBS, accelerator EZ, accelerator DPTT-6, and accelerator DTDM.

[0022] Preferably, the sulfur, peroxide DCP, accelerator MBTS1 and accelerator DPTT-6 constitute a vulcanization system.

[0023] The above-mentioned vulcanization system adopts a polysulfide method to cooperate. The cross-linked structure formed by sulfur vulcanization and the cross-linked structure formed by peroxide DCP vulcanization can improve the mechanical properties of the vulcanized rubber, such as tensile strength, tear strength and tensile stress, under the regulation of accelerator MBTS1 and accelerator DPTT-6. The sulfur bond network formed by sulfur vulcanization can provide better elasticity and toughness, while the carbon-carbon bond cross-linking formed by peroxide DCP vulcanization can enhance the rigidity and heat resistance of the rubber. Under different usage requirements, it not only guarantees the basic properties of the rubber, but also improves its performance in special environments. In addition, the heat resistance advantage brought by peroxide DCP vulcanization, coupled with the improvement of the heat resistance and aging resistance of the vulcanized rubber by accelerator DPTT-6, can provide aging resistance.

[0024] During the vulcanization process, the accelerator MBTS1 first triggers the vulcanization reaction and starts the reaction, while the accelerator DPTT-6 further adjusts the reaction speed during the reaction to make the vulcanization reaction proceed more smoothly. This design is very helpful for the vulcanization of rubber products of different thicknesses and shapes, making the vulcanization reaction more uniform and improving the quality of the vulcanized rubber.

[0025] Furthermore, the above-mentioned aging-resistant rubber is a combination of one or more of the antioxidant 2246, antioxidant MB, antioxidant 445, antioxidant DDA, and antioxidant ZMB2.

[0026] Furthermore, the antioxidant is antioxidant 2246 and antioxidant MB or antioxidant 445 and antioxidant DDA or antioxidant 445 and antioxidant ZMB2.

[0027] Antioxidant 2246 is a phenolic antioxidant with good antioxidant properties. It can capture free radicals generated during the aging process of rubber and prevent the oxidation chain reaction caused by free radicals. Antioxidant MB is a thiocarbamate antioxidant with good ozone resistance and flex crack resistance. Antioxidant 2246 and antioxidant MB are used together, and the effect is better than using them alone.

[0028] Antioxidant 445 is a highly efficient amine antioxidant with excellent resistance to thermal oxidation aging. Antioxidant DDA is a diphenylamine antioxidant that has a good improvement on the weather resistance of rubber. Antioxidant 445 and antioxidant DDA are used together, and the effect is better than using them alone.

[0029] The synergistic effect of antioxidant 445's anti-thermal oxygen aging performance and antioxidant ZMB2 (zinc salt antioxidant) can improve the comprehensive anti-aging performance of rubber. In addition to having certain anti-aging properties, antioxidant ZMB2 can also play a certain role in stabilizing the vulcanization system. The combined use of antioxidant 445 and antioxidant ZMB2 is better than using them alone.

[0030] The present invention also relates to a method for preparing the aging-resistant rubber, comprising the following steps: S1: Add raw rubber A and raw rubber B into an internal mixer, mix for 10-60 seconds, then add rubber lubricant, zinc oxide, stearic acid and antioxidant, continue mixing for 60-180 seconds, then add reinforcing filler, coupling agent and plasticizer, continue mixing for 240-360 seconds, lift the pressure roller and clean for 60-180 seconds, discharge the rubber at 140-150°C to obtain a first-stage mixed rubber; S2 two-stage mixing: add the first-stage mixed rubber to the open mixing mill, then add sulfur, peroxide DCP, and accelerator, pass through 5-10 times, and sheet to obtain the second-stage mixed rubber; S3 vulcanization: After the above-mentioned mixed rubber is left at room temperature for 24 hours, it is vulcanized in a flat vulcanizer at a vulcanization temperature of 140-150°C.

[0031] Furthermore, in the above-mentioned method for preparing aging-resistant rubber, in step S1, the initial temperature of the internal mixer is set to 50-70°C, and the rotor speed is set to 90-100 r·min -1 .

[0032] Compared with the prior art, the present invention has the following beneficial effects: (1) The aging-resistant rubber disclosed in the present invention has a reasonable formula design. The raw rubber system is composed of nitrile rubber, EPDM rubber and / or EPDM rubber, which synergistically improve the basic performance of the entire rubber system. Carbon black and white carbon black form a reinforcement system, which complement each other in structure and performance. It not only has a better reinforcement effect, but also is conducive to uniform dispersion in the rubber matrix. Sulfur, peroxide DCP and accelerator form a vulcanization system, which can ensure the basic performance of the rubber under different usage requirements and improve its performance under special environments, making the vulcanization reaction more uniform and improving the quality of the vulcanized rubber. The addition of multiple additives such as rubber lubricant BR-2, silane coupling agent ST, plasticizer RS735 and antioxidant enhances the processing performance, stability and aging resistance of the rubber. The raw materials cooperate with each other to jointly construct an aging-resistant rubber with good comprehensive performance. (2) The preparation method of the aging-resistant rubber disclosed in the present invention is simple. During the first stage of mixing, raw rubber is first added for preliminary mixing to make the raw rubber preliminarily mixed and uniform; then, additives such as rubber lubricants are added to help disperse the subsequent raw materials; finally, reinforcing fillers are added to make them better dispersed in the rubber matrix that has been mixed with the additives, thereby improving the quality of the mixed rubber; finally, the rubber is discharged at 150°C to complete the first stage of mixing, thereby ensuring that the components are fully mixed and the rubber properties are not damaged; in the second stage of mixing, the first stage of mixed rubber is added to the open mill, and then added Sulfur, vulcanizing agent, accelerator, etc. are passed through the rubber mix multiple times. The passing operation can make the vulcanizing agent, accelerator, etc. evenly dispersed in the rubber mix, further improving the uniformity of the rubber mix. During vulcanization, the rubber mix is ​​left at room temperature for a period of time before vulcanization. Leaving the mixture for a period of time can further stabilize and evenly distribute the components in the rubber mix and reduce internal stress. The vulcanization temperature is designed according to the formula. This temperature can make the vulcanization reaction proceed smoothly, form a stable vulcanization network structure, and increase the crosslinking density of the rubber, thereby enhancing the mechanical properties, stability and aging resistance of the rubber. DETAILED DESCRIPTION

[0033] The following examples 1, 2, and 3 are combined with specific experimental data to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0034] The following examples 1-3 provide an aging-resistant rubber and a preparation method thereof.

[0035] The main raw materials of Examples 1-3 are: NBR N31, a product of PetroChina Lanzhou Petrochemical Company; EPDM 512E, synthesized using a Ziegler-Natta catalyst, having an ethylene content of 68%, an ENB content of 5.0%, and a Mooney viscosity [ML (1+4) 125°C] of 64, a product of Sumitomo Chemical Co., Ltd. of Japan; EPM V722, synthesized using a metallocene catalyst, having an ethylene content of 72%, and a Mooney viscosity [ML (1+4) 125°C] of 18, a product of ExxonMobil Corporation of the United States; the others are all commercially available products.

[0036] The test formulas of the aging-resistant rubbers of Examples 1-3 are shown in Table 1.

[0037] Table 1 Ageing-resistant rubber test formula of Examples 1-3 The preparation method of the aging-resistant rubber of Embodiment 1-3 comprises the following steps: S1 one-stage mixing: NBR N31, EPDM 512E, and EPM V722 are added to the internal mixer, the initial temperature of the internal mixer is set to 65°C, the rotor speed is set to 100 r•min-1, and mixing is performed for 30 seconds. Then, rubber lubricant BR-2, zinc oxide, stearic acid, and antioxidant are added, and mixing is continued for 150 seconds. Then, carbon black N320, carbon black N550, white carbon black, silane coupling agent ST-10A, and plasticizer RS735 are added, and mixing is continued for 300 seconds. The pressure roller is lifted and cleaned for 120 seconds, and the rubber is discharged at 150°C to obtain a first-stage mixed rubber; S2 two-stage mixing: add the first-stage mixed rubber to the open mixing mill, then add sulfur, peroxide DCP, and accelerator MBTS, pass through the mill 6 times, and sheet to obtain the second-stage mixed rubber; S3 vulcanization: After the above-mentioned mixed rubber is left at room temperature for 24 hours, it is vulcanized in a flat vulcanizer at a vulcanization temperature of 150°C.

[0038] The properties of the aging-resistant rubber of Examples 1-3 were tested according to the corresponding national standards. The physical properties are shown in Table 2, the hot air aging resistance properties are shown in Table 3, the high-temperature compression permanent deformation properties (100°C×72 h, compression rate 25%) are shown in Table 4, and the compression heat generation properties (55°C×1 MPa) are shown in Table 5.

[0039] Table 2 Physical properties of aging-resistant rubber of Examples 1-3 Table 3 Hot air aging resistance of aging-resistant rubber of Examples 1-3 Table 4 High temperature compression permanent deformation properties of aging resistant rubber of Examples 1-3 Table 5 Compression heat generation performance of aging-resistant rubber of Examples 1-3 It can be seen from the above that Examples 1-3 prepared by using the aging-resistant rubber formula and preparation method of the present invention all have good comprehensive performance and aging resistance.

[0040] The present invention has many specific application paths, and the above is only a preferred embodiment of the present invention. It should be pointed out that the above embodiments are only used to illustrate the present invention, and are not used to limit the protection scope of the present invention. For those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. An aging-resistant rubber, characterized in that: The anti-aging rubber comprises the following raw materials in parts by weight: 60-90 parts of raw rubber A; the raw rubber A is nitrile rubber; 10-40 parts of raw rubber B; the raw rubber B is EPDM rubber and / or EPDM rubber; 90-120 parts of reinforcing filler; the reinforcing filler is a composition of carbon black and white carbon black; 5-8 parts of rubber lubricant; Coupling agent 0.1-0.2 parts; 3-6 parts of plasticizer; Zinc oxide 5-8 parts; Sulfur 0.1-2.5 parts; Peroxide DCP 1-2 parts; 1-3 parts of accelerator; 1-3 parts of stearic acid; 2-5 parts of antioxidant.

2. The aging-resistant rubber according to claim 1, characterized in that: The raw rubber A is one or more of NBR N31, NBR N32, NBR1052, and NBR 3350; the raw rubber B is one or more of EPDM 512E, EPDM 525, EPM V722, and EPM Dutral LCO 054.

3. The aging-resistant rubber according to claim 1, characterized in that: The raw rubber B is ethylene propylene diene monomer rubber and ethylene propylene diene monomer rubber, and the mass ratio of the ethylene propylene diene monomer rubber to the ethylene propylene diene monomer rubber is 50-90:10-40.

4. The aging-resistant rubber according to claim 1, characterized in that: The carbon black is one or a combination of carbon black N220, carbon black N320, carbon black N550, and carbon black N774; in the reinforcing filler, the mass ratio of carbon black to white carbon black is 20-90:10-30.

5. The aging-resistant rubber according to claim 1, characterized in that: The rubber lubricant is rubber lubricant BR-2; the coupling agent is silane coupling agent ST-10A; and the plasticizer is plasticizer RS735.

6. The aging-resistant rubber according to claim 1, characterized in that: The accelerator is one or a combination of accelerator MBTS, accelerator DTDC, accelerator ZBEC, accelerator TETD, accelerator CBS, accelerator EZ, accelerator DPTT-6, and accelerator DTDM.

7. The aging-resistant rubber according to claim 1, characterized in that: The antioxidant 2246, antioxidant MB, antioxidant 445, antioxidant DDA, antioxidant ZMB2, or a combination of one or more thereof.

8. The aging-resistant rubber according to claim 7, characterized in that: The antioxidants are antioxidant 2246 and antioxidant MB or antioxidant 445 and antioxidant DDA or antioxidant 445 and antioxidant ZMB2.

9. A method for preparing an aging-resistant rubber according to any one of claims 1 to 8, characterized in that: The steps include: S1: Add raw rubber A and raw rubber B into an internal mixer, mix for 10-60 seconds, then add rubber lubricant, zinc oxide, stearic acid and antioxidant, continue mixing for 60-180 seconds, then add reinforcing filler, coupling agent and plasticizer, continue mixing for 240-360 seconds, lift the pressure roller and clean for 60-180 seconds, discharge the rubber at 140-150°C to obtain a first-stage mixed rubber; S2 two-stage mixing: add the first-stage mixed rubber to the open mixing mill, then add sulfur, peroxide DCP, and accelerator, pass through 5-10 times, and sheet to obtain the second-stage mixed rubber; S3 vulcanization: After the above-mentioned mixed rubber is left at room temperature for 24 hours, it is vulcanized in a flat vulcanizer at a vulcanization temperature of 140-150°C.

10. The method for preparing an aging-resistant rubber according to claim 9, characterized in that: In step S1, the initial temperature of the internal mixer is set to 50-70°C, and the rotor speed is set to 90-100 r·min -1 .

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