Low-temperature sealing rubber product and preparation method thereof

Abstract

The invention provides a low-temperature sealing rubber product and a preparation method thereof. The low-temperature sealed rubber product is prepared from the following raw materials in parts by mass: 30 to 50 parts of nitrile rubber, 10 to 30 parts of modified ethylene propylene diene monomer, 1 to 5 parts of zinc oxide, 1 to 5 parts of stearic acid, 1 to 5 parts of auxiliaries and 20 to 40 parts of carbon black, the modified ethylene propylene diene monomer is used in the rubber product, so that the crosslinking degree of the rubber product can be increased, and the sealing performance of the rubber is enhanced; by controlling the molar ratio of the three, good mechanical properties at low temperature are maintained, and the application field is widened; through synergistic use of the modified ethylene propylene diene monomer and the nitrile rubber, the sealing performance, the oil resistance and the mechanical property of the rubber product at low temperature are compounded and enhanced, and the application range of the rubber product is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a rubber product with low-temperature sealing performance and a preparation method thereof. Background Art

[0002] In many industrial and daily application scenarios, rubber materials are widely used due to their excellent elasticity, sealing performance, and aging resistance. However, the use of rubber in low-temperature environments faces many challenges, such as hardening, brittle cracking, and decreased sealing performance. Therefore, it is crucial to select a rubber material suitable for low-temperature environments.

[0003] The low-temperature performance of rubber is mainly affected by the glass transition temperature (Tg). When the temperature drops below the Tg of the rubber, the movement of its molecular chains is restricted, and the material becomes hard or even brittle, resulting in a decrease in its elasticity and flexibility. Therefore, it is particularly important to select a rubber with a lower Tg that can still maintain flexibility in low-temperature environments. Currently, the rubbers commonly used in low-temperature environments mainly include the following: Silicone rubber (VMQ): It has excellent cold resistance and can remain soft at -60°C or even lower temperatures. At the same time, it has excellent heat resistance and chemical stability. However, its mechanical strength is relatively low, and the cost is relatively high. Therefore, it is mainly used in special applications with extremely high cold resistance requirements, such as aerospace and medical device fields. Nitrile rubber (NBR): It is mainly used in oil-resistant environments. Although its low-temperature performance can be improved by using plasticizers or modification methods, its overall low-temperature flexibility is relatively poor, and it is prone to hardening in extremely cold environments. Chloroprene rubber (CR): It has good weather resistance and ozone resistance, but its low-temperature performance is average, and it is prone to becoming brittle in cold environments. Therefore, it is not suitable for extremely cold application scenarios. Ethylene propylene diene monomer rubber (EPDM): Due to its excellent low-temperature performance, weather resistance, and good sealing performance, it has been widely used in many fields such as low-temperature industry, automotive, and construction.

[0004] Ethylene propylene diene monomer rubber (EPDM) is a synthetic rubber copolymerized from ethylene, propylene, and a small amount of non-conjugated diene monomers. Its unique molecular structure endows it with good weather resistance, ozone resistance, and a relatively low Tg, enabling it to maintain excellent elastic and sealing properties in low-temperature environments. Although EPDM performs excellently under low-temperature conditions, there are still some limitations and challenges that need to be weighed or optimized in specific applications: For example, although the Tg of EPDM is relatively low, in extremely low-temperature (such as below -50°C) environments, its flexibility may still decrease, affecting the sealing performance. Therefore, in extremely low-temperature environments, it may be necessary to enhance the low-temperature performance of EPDM through blending modification or composite materials. At the same time, compared with some high-performance synthetic rubbers, such as fluororubber (FKM) or polyurethane rubber (PU), the mechanical strength of EPDM is relatively low, and cracks or damage may occur under low-temperature and high-load conditions. It is necessary to strengthen the material formulation design or use reinforcing fillers to improve its mechanical properties.

[0005] Overall, due to its excellent low-temperature flexibility, weather resistance, and good sealing performance, ethylene propylene diene monomer (EPDM) has been widely used in low-temperature environments, especially in the automotive, construction, low-temperature industrial equipment, and aerospace industries. However, under extreme low-temperature or high mechanical stress conditions, material modification or combination with other materials is still required to improve its comprehensive performance. With the continuous progress of materials science, the low-temperature performance of EPDM is expected to be further optimized in the future to meet more stringent industrial requirements. Summary of the Invention

[0006] Object of the Invention: The object of the present invention is to provide a rubber product for low-temperature sealing and its preparation method, to provide a hybrid rubber product of ethylene propylene diene monomer (EPDM) suitable for use at low temperatures, which has excellent elasticity and sealing performance at low temperatures, enhances the elasticity and sealing performance of EPDM in low-temperature environments, and has excellent oil resistance, and is suitable for use in the automotive industry, construction industry, and low-temperature industrial equipment.

[0007] Technical Solution of the Present Invention:

[0008] In a first aspect, the present invention provides a rubber product for low-temperature sealing. By mass fraction, the raw materials of the rubber product for low-temperature sealing include the following components:

[0009]

[0010] Among them, the polymerization monomers of the modified ethylene propylene diene monomer (EPDM) are ethylene, propylene, and a modified monomer shown in Formula 1:

[0011]

[0012] Among them, n represents any integer from 4 to 9.

[0013] Further, n represents any one of 4, 6, and 9.

[0014] In some embodiments, the molar ratio of ethylene, propylene, and the modified monomer shown in Formula 1 in the modified ethylene propylene diene monomer (EPDM) is 12 - 15:9 - 12:2 - 5.

[0015] Further, the molar ratio of ethylene, propylene, and the modified monomer shown in Formula 1 in the modified ethylene propylene diene monomer (EPDM) is 12 - 13:9 - 10:2 - 3.

[0016] In some embodiments, the molecular weight of the modified ethylene propylene diene monomer (EPDM) is 50000 - 150000.

[0017] In some embodiments, the preparation method of the modified monomer includes the following steps:

[0018] S1: Add a silane coupling agent to deionized water and dissolve it; add an acidic catalyst and continuously stir at room temperature for a hydrolysis reaction;

[0019] S2: Dissolve 1,5 - deoxyxylitol in a solution, slowly add the reaction solution of S1 to the 1,5 - deoxyxylitol solution, and continue stirring the reaction under heating;

[0020] S3: After the reaction is completed, filter the reaction solution and vacuum - dry it to obtain the required modified monomer.

[0021] In some embodiments, the silane coupling agent is selected from one or more combinations of 5 - alkenylhexyltrimethoxysilane (CAS: 58751 - 56 - 7), 7 - alkenyloctyltrimethoxysilane (CAS: 52217 - 57 - 9), 10 - alkenylundecyltrimethoxysilane (CAS: 872575 - 06 - 9).

[0022] In some embodiments, the molar ratio of the silane coupling agent to 1,5 - deoxyxylitol is 1:3 - 3.2.

[0023] In some embodiments, for the continuous stirring reaction under heating in S2, the heating temperature is 40 - 60 °C and the heating time is 0.5 - 2 h.

[0024] In some embodiments, the preparation method of the modified ethylene - propylene - diene monomer (EPDM) rubber is as follows:

[0025] S1: Add a solvent to a reaction kettle, then add ethylene, propylene and the modified monomer, and disperse them evenly; add a catalyst;

[0026] S2: Heat and pressurize the reaction kettle for reaction; after the reaction is completed, evaporate the solvent to obtain the modified EPDM rubber.

[0027] In some embodiments, the reaction temperature in S2 is 60 - 100 °C and the reaction pressure is 2 - 4 MPa.

[0028] In some embodiments, the nitrile - butadiene rubber is selected from one or more combinations of Lanzhou Chemical Industry Corporation's nitrile - butadiene rubber grades NBR2865, NBR3304, NBR3305, NBR2907, NBR2905, N21, NBR2707; further, the nitrile - butadiene rubber is selected from one of NBR2905, NBR2907, NBR2865, NBR3304, NBR3305.

[0029] In some embodiments, the additives can be selected from one or more combinations of silane coupling agents, activators, brighteners, anti - aging agents, softening and tackifying agents, plasticizers, co - crosslinking agents and vulcanization accelerators.

[0030] Further, the raw materials of the low-temperature sealing rubber product include the following components:

[0031]

[0032] In a second aspect, the present invention provides a method for preparing the above low-temperature sealing rubber product, which specifically includes the following steps:

[0033] (1) Add the nitrile rubber and the modified ethylene propylene diene monomer rubber to a blender, and gradually add the zinc oxide, stearic acid, auxiliary agent and carbon black and mix and stir evenly. Heat to 80°C - 100°C at a rate of 5 - 30°C / min to obtain a mixed material;

[0034] (2) Put the obtained mixed material into a twin-screw extruder for melting, kneading and extruding. The extrusion temperature is 140°C - 185°C, and then cool to form pellets, thus obtaining the rubber product.

[0035] Beneficial effects:

[0036] 1. Using the modified ethylene propylene diene monomer rubber in the rubber product can increase the crosslinking degree of the rubber product and enhance the sealing performance of the rubber; and by controlling the molar ratio of the three, it can maintain good mechanical properties at low temperatures and broaden the application fields.

[0037] 2. By using the modified ethylene propylene diene monomer rubber and nitrile rubber in cooperation, the composite enhances the sealing performance, oil resistance and mechanical properties of the rubber product at low temperatures, and broadens the application range of the rubber product. Specific embodiments

[0038] The following will illustrate the present invention in conjunction with specific implementation schemes. It should be noted that the following examples are examples of the present invention and are only used to illustrate the present invention, rather than to limit the present invention. Without departing from the gist or scope of the present invention, other combinations and various improvements within the concept of the present invention can be made.

[0039] Unless otherwise specified, the chemical reagents used in the present invention are all ordinary commercially available analytical pure.

[0040] The zinc oxide is nano-zinc oxide purchased from Beijing Decode Island Gold Technology Co., Ltd.

[0041] The stearic acid is purchased from Tongliao Xinghe Technology Co., Ltd. and is 12-hydroxy stearic acid.

[0042] The silane coupling agent is purchased from Shin-Etsu Co., Ltd. of Japan, and the brand is KBM-403.

[0043] The antioxidant is purchased from Shijiazhuang Taisheng Chemical Co., Ltd.

[0044] The plasticizer was purchased from Jiangsu Raymond New Materials Co., Ltd., with the brand name LMFLEX LM40.

[0045] The carbon black was acetylene carbon black purchased from Xinxiang Delong Chemical Co., Ltd.

[0046] The styrene-butadiene rubber was purchased from PetroChina Company Limited, with the model number 1502.

[0047] The chloroprene rubber was purchased from Dongguan Hebao Plastic Co., Ltd., with the model number DCR-12.

[0048] Preparation Example of Modified Monomer

[0049] S1: Add 3.1 mol of 5-alkenylhexyltrimethoxysilane to 100 ml of deionized water and dissolve it; add 1 mol of hydrochloric acid and continuously stir at room temperature for 30 min to carry out the hydrolysis reaction;

[0050] S2: Dissolve 1 mol of 1,5-deoxyxylitol in 50 ml of water, and slowly add the reaction solution of S1 to the 1,5-deoxyxylitol solution, and continue to stir and react at 40 °C for 1 h;

[0051] S3: After the reaction is completed, vacuum-dry the reaction solution to obtain the required modified monomer.

[0052] The modified monomer was analyzed by infrared spectroscopy. According to the infrared spectroscopy analysis, it can be obtained that: at 3450 cm -1 the vibration peak of the alcohol hydroxyl group in 1,5-deoxyxylitol disappears; at 1140 cm -1 an absorption peak generated by the stretching vibration of the silicon-oxygen bond (Si-O) is formed; at 1655 cm -1 the absorption peak generated by C=C (olefin) is present; at 1280 cm -1 the absorption peak generated by Si-C is present. From the above analysis, it can be obtained that the infrared spectroscopy data proves that 5-alkenylhexyltrimethoxysilane is grafted onto the three alcohol hydroxyl groups of 1,5-deoxyxylitol, and the preparation of the modified monomer is successful.

[0053] The structural formula of the modified monomer is shown in Formula 1-1.

[0054]

[0055] Preparation Example of Modified Ethylene Propylene Diene Monomer Rubber

[0056] S1: Add 20 L of cyclohexane to the reaction kettle, introduce 132 mol of ethylene and 99 mol of propylene, add 22 mol of modified monomer 1, and add 0.03 mol of catalyst (the molar ratio of titanocene and triethylaluminum is 1:20);

[0057] S2: Heat the reactor to 80 °C and pressurize it to 3 MPa, and react for 4 h; after the reaction, evaporate the solvent to obtain the modified ethylene-propylene-diene rubber.

[0058] Examples and Comparative Examples

[0059] (1) Add ethylene-propylene-diene rubber and nitrile rubber to a blender, and gradually add the zinc oxide, stearic acid, additives and carbon black and mix and stir evenly, and heat up to 100 °C at a rate of 10 °C / min to obtain a mixed material;

[0060] (2) Put the obtained mixed material into a twin-screw extruder for melt kneading and extrusion, the extrusion temperature is 175 °C, and cool to make pellets, thus obtaining the rubber product.

[0061] The materials used and the parts by mass are shown in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] Note: In the table, S represents an example, for example, "S1" represents "Example 1"; D represents a comparative example, for example, "D1" represents "Comparative Example 1".

[0066] After heating and vulcanizing (175 °C, 15 min) the rubber materials prepared in the examples and comparative examples, make standard test pieces, and after placing them at room temperature for 3 months, carry out the following performance tests.

[0067] 1. Conduct a tensile strength test according to GB / T 528;

[0068] 2. Conduct a hardness test according to GB / T 531.1-2008;

[0069] 3. Conduct a low-temperature retraction performance test according to GB / T7758-2020, and TR10 corresponds to the temperature when the specimen retracts by 10%;

[0070] 4. Conduct a gas permeability coefficient test on the standard test piece according to GB / T 1038. The specimen is a circle with a diameter of 5 cm, and the thickness is averaged by 5-point measurement. The test gas is nitrogen, the test temperature is 40 °C, and the degassing time is 12 h.

[0071] 5. Conduct an oil resistance test according to GB / T 1690-2010. The oil is liquid B (30% toluene, 70% isooctane), the thickness of the specimen is 2 mm, and the full immersion mode is adopted. The volume change rate is tested after soaking at 23 °C for 168 h.

[0072] Table 1 Test Results

[0073]

[0074]

[0075] Compared with Comparative Example 3, the gas permeability coefficient of the rubber material in the example can reach 1.2 - 1.5×10 -13 cm 3 ·cm / (cm 2 ·s·Pa), which is significantly better than 3.32×10 -13 cm 3 ·cm / (cm 2 ·s·Pa) of Comparative Example 3, and the oil resistance is maintained at an excellent level. It shows that the rubber material combination provided by the present invention has a higher crosslinking degree due to the addition of modified ethylene propylene diene monomer rubber, has more excellent airtightness, and is compounded with nitrile rubber to achieve an excellent effect of low temperature resistance, oil resistance and sealing. Compared with Comparative Examples 4 / 5 / 6, the tensile strength and hardness of the sealing rubber material in the example are significantly improved, and the lowest TR10 can reach -60.3 °C and the highest only reaches -55.2 °C. It shows that different nitrile rubber models will also affect the overall low temperature resistance and oil resistance of the composition due to different acrylonitrile contents. The data prove that selecting a suitable nitrile rubber can obtain rubber products with excellent low temperature resistance while maintaining oil resistance.

[0076] According to the experimental data of the rubber products in Examples 1 - 3, the rubber product in Example 2 has the best tensile strength, hardness, helium gas permeability and the fastest TR10, indicating that the formula in Example 2 can further synergistically enhance the low temperature resistance of the sealing rubber product and meet the sealing requirements in extremely cold and high temperature environments.

[0077] The present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A rubber product with low-temperature sealing, characterized in that, The raw materials of the rubber product with low-temperature sealing, by mass parts, include the following components: Among them, the polymerization monomers of the modified ethylene-propylene-diene monomer (EPDM) are ethylene, propylene, and a modified monomer shown in Formula 1: Among them, n represents any integer from 4 to 9.

2. The rubber product according to claim 1, characterized in that, The molar ratio of ethylene, propylene, and the modified monomer shown in Formula 1 in the modified EPDM is 12 - 15:9 - 12:2 - 5.

3. The rubber product according to claim 1, characterized in that, The molecular weight of the modified EPDM is 50,000 - 150,000.

4. The rubber product according to claim 1, characterized in that, The preparation method of the modified monomer includes the following steps: S1: Add the silane coupling agent into deionized water and dissolve it; add an acidic catalyst and continuously stir at room temperature for hydrolysis reaction; S2: Dissolve 1,5-deoxyxylitol in the solution, slowly add the reaction solution of S1 into the 1,5-deoxyxylitol solution, and continue stirring the reaction under heating; S3: After the reaction, filter the reaction solution and dry it under vacuum to obtain the required modified monomer.

5. The rubber product according to claim 1, characterized in that, The molar ratio of the silane coupling agent to 1,5-deoxyxylitol is 1:3 - 3.

2.

6. The rubber product according to claim 1, characterized in that, The preparation method of the modified EPDM is specifically as follows: S1: Add a solvent into the reaction kettle, then add ethylene, propylene, and the modified monomer, and disperse them evenly; add a catalyst; S2: Heat and pressurize the reaction kettle for reaction; after the reaction, evaporate the solvent to obtain the modified EPDM.

7. The rubber product according to claim 1, characterized in that, The nitrile rubber is selected from one or a combination of Lanzhou Chemical Industry Corporation nitrile rubber grades NBR2865, NBR3304, NBR3305, NBR2907, NBR2905, N21, NBR2707.

8. The rubber product according to claim 1, characterized in that, The auxiliary agents can be selected from one or a combination of silane coupling agents, activators, brighteners, anti-aging agents, softening and tackifying agents, plasticizers, co-crosslinking agents, and vulcanization accelerators.

9. The rubber product according to claim 1, wherein The raw materials of the rubber product with low-temperature sealing include the following components:

10. The preparation method of the rubber product according to any one of claims 1-9, characterized in that, Include the following steps: (1) Add the modified EPDM and nitrile rubber into a blender, and gradually add the zinc oxide, stearic acid, auxiliary agents, and carbon black, and mix and stir evenly. Heat to 80°C - 100°C at a rate of 5 - 30°C / min to obtain a mixed material; (2) Put the obtained mixed material into a twin-screw extruder for melt kneading and extrusion. The extrusion temperature is 140°C - 185°C, and cool to make pellets, thus obtaining the rubber product.

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