Oil-resistant sealing element and preparation method thereof

Abstract

The invention discloses an oil-resistant sealing element and a preparation method thereof, and belongs to the technical field of rubber sealing elements, and the oil-resistant sealing element is prepared from the following components in parts by weight: 80-100 parts of nitrile rubber, 40-50 parts of modified white carbon black, 5-7 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of an accelerant and 1-3 parts of a vulcanizing agent. Wherein the modified white carbon black is prepared by reacting white carbon black with toluene diisocynate to prepare white carbon black grafted with toluene diisocynate and then reacting the white carbon black grafted with toluene diisocynate with 4-aminodiphenylamine. According to the oil-resistant sealing element disclosed by the invention, the aging resistance of the nitrile rubber can be enhanced, and meanwhile, the mechanical property of the nitrile rubber is improved.

Description

Technical Field

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

[0002] Seals are widely used in various mechanical equipment, pipelines, valves, automobiles, aerospace and other fields. Their main function is to prevent fluids or solid particles from leaking from adjacent joint surfaces and to prevent external impurities such as dust and moisture from invading the interior of machinery and equipment or parts.

[0003] Nitrile rubber is a random copolymer obtained by copolymerization of butadiene and acrylonitrile. It is a carbon chain unsaturated polar non-crystalline rubber with good oil resistance, wear resistance and heat resistance. Its oil resistance comes from the large amount of cyanide in the molecular chain. It is widely used in oil-resistant seals.

[0004] Because nitrile rubber contains a large number of unsaturated olefin segments in its molecular structure, it has poor aging resistance and usually requires the addition of antioxidants. However, the synthesis process of antioxidants is complicated, the yield is low, and the cost is high. In addition, the cross-linking reaction between the antioxidant and the double bonds of the rubber changes the network structure of the rubber and reduces the original physical and mechanical properties of the rubber.

[0005] In industry, nitrile rubber often needs to add reinforcing fillers to improve its strength. Common inorganic reinforcing fillers include carbon black, white carbon black, silicates, carbonates, short fibers, etc. Among them, white carbon black has a better reinforcing effect. However, white carbon black has the disadvantage that nanomaterials are easy to aggregate themselves, and white carbon black also has a large number of hydrogen bonds generated by surface hydroxyl groups, which makes it difficult to disperse into the rubber matrix. Summary of the invention

[0006] In view of the above situation, in order to overcome at least part of the defects of the above-mentioned prior art, the present invention provides an oil-resistant seal and a preparation method thereof.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides an oil-resistant seal, which is prepared by comprising the following components in parts by weight: 80-100 parts of nitrile rubber, 40-50 parts of modified white carbon black, 5-7 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of an accelerator and 1-3 parts of a vulcanizing agent; The modified silica is first prepared by reacting silica with toluene diisocyanate to obtain silica grafted with toluene diisocyanate, and then prepared by reacting silica grafted with toluene diisocyanate with 4-aminodiphenylamine.

[0008] In some embodiments, the mass fraction of bound acrylonitrile in the nitrile rubber is 30%-35%.

[0009] In some embodiments, the accelerator is a mixture of one or more of accelerator DM, accelerator CZ, and accelerator TMTD.

[0010] In some embodiments, the vulcanizing agent is one of sulfur, dimethyl disulfide, and dicumyl peroxide.

[0011] The present invention also provides a method for preparing an oil-resistant seal, comprising: The nitrile rubber is placed in an internal mixer for plasticization, and then modified white carbon black, zinc oxide, stearic acid and accelerator are added in sequence for mixing. After mixing, a vulcanizing agent is added, and the mixture is placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal is obtained.

[0012] In some embodiments, the mixing time is 10 min-15 min, and the temperature is 80°C-100°C.

[0013] In some embodiments, the vulcanization time is 15 min-20 min, and the temperature is 120°C-140°C.

[0014] In some embodiments, the method for preparing the modified silica comprises: S1. Add toluene diisocyanate and white carbon black into an organic solvent, introduce inert gas, stir for 30-40 minutes, heat to 70-80°C for reaction for 4-6 hours, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add the white carbon black grafted with toluene diisocyanate and 4-aminodiphenylamine into an organic solvent, introduce an inert gas, stir for 30 min-40 min, heat to 50° C.-90° C. for reaction for 10 h-15 h, centrifuge after cooling, wash, and dry to obtain modified white carbon black.

[0015] In some embodiments, in step S1, the mass ratio of the toluene diisocyanate to the white carbon black is 1:0.8-1.2.

[0016] The beneficial effects achieved by the present invention are as follows: By grafting toluene diisocyanate on the surface of silica, a large number of hydroxyl groups on the surface of silica can be consumed, thereby improving the dispersibility of silica in nitrile rubber. By modifying silica with 4-aminodiphenylamine and adding the modified silica into nitrile rubber, the aging resistance of the nitrile rubber can be enhanced and the mechanical properties of the nitrile rubber can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a graph showing the aging resistance test results of Example 1 and Comparative Example 1 of the present invention.

[0018] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention 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 them; based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0020] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the examples of various specific processes and materials provided by the present invention, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.

[0021] In order to solve at least some of the defects of the prior art mentioned in the background technology, the technical solution adopted by the present invention is as follows: The embodiment of the present invention provides an oil-resistant seal, which is prepared by the following components in parts by weight: 80-100 parts of nitrile rubber, 40-50 parts of modified white carbon black, 5-7 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of accelerator and 1-3 parts of vulcanizing agent; The modified silica is firstly prepared by reacting silica with toluene diisocyanate to obtain silica grafted with toluene diisocyanate, and then prepared by reacting silica grafted with toluene diisocyanate with 4-aminodiphenylamine.

[0022] According to the oil-resistant seal of the embodiment of the present invention, by grafting toluene diisocyanate on the surface of silica, a large number of hydroxyl groups on the surface of silica can be consumed, thereby improving the dispersibility of silica in nitrile rubber; By modifying silica with 4-aminodiphenylamine and adding the modified silica into nitrile rubber, the aging resistance of the nitrile rubber can be enhanced and the mechanical properties of the nitrile rubber can be improved.

[0023] In some embodiments, the mass fraction of acrylonitrile in the nitrile rubber is 30%-35%. The higher the content of acrylonitrile in the nitrile rubber, the greater the tensile strength, tear strength and hardness of the nitrile rubber, and the worse the cold resistance, resilience and compression permanent deformation performance. Therefore, the mass fraction of acrylonitrile needs to be controlled at 30%-35%.

[0024] In some embodiments, the accelerator is a mixture of one or more of accelerator DM, accelerator CZ, and accelerator TMTD. The accelerator can significantly reduce the vulcanization temperature, accelerate the vulcanization speed, and form a cross-linked network structure of the rubber molecular chain in a shorter time, thereby improving the strength and hardness of the rubber product.

[0025] In some embodiments, the vulcanizing agent is one of sulfur, dimethyl disulfide, and dicumyl peroxide. The vulcanizing agent can significantly accelerate the vulcanization reaction speed of nitrile rubber under heating conditions, so that the cross-linking structure is formed more quickly between the rubber molecular chains.

[0026] The embodiment of the present invention also provides a method for preparing an oil-resistant seal, comprising: The nitrile rubber is placed in an internal mixer for plasticization, and then modified white carbon black, zinc oxide, stearic acid and accelerator are added in sequence for mixing. After mixing, a vulcanizing agent is added, and the mixture is placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal is obtained.

[0027] Among them, stearic acid can promote the flow of rubber molecules, reduce the hardness and tension of rubber, and improve the plasticity and toughness of rubber.

[0028] In some embodiments, the mixing time is 10 min-15 min, and the temperature is 80°C-100°C. The length of the mixing time directly affects the mixing effect and performance of the nitrile rubber. If the mixing time is too short, the additives of the nitrile rubber may not be fully dispersed evenly, affecting the physical properties and chemical stability of the rubber; if the mixing time is too long, it may cause over-mixing, resulting in the breakage of the rubber molecular chain, reducing the tensile strength and wear resistance of the rubber. At the same time, if the temperature is too low, the dispersion speed of the compounding agent in the rubber will slow down, and the mixing efficiency will be reduced. If the temperature is too high, it may cause the degradation of the rubber molecular chain and even cause scorch, which seriously affects the performance of the rubber.

[0029] In some embodiments, the vulcanization time is 15min-20min, and the temperature is 120℃-140℃. If the vulcanization time is too short, the cross-linking reaction between the rubber molecular chains may not be complete, resulting in the physical properties of the rubber products (such as tensile strength, tear strength, etc.) not meeting the standards. If the vulcanization time is too long, the rubber may be over-vulcanized, scorched, and the rubber products may lose elasticity and plasticity, or even crack. If the vulcanization temperature is too low, the vulcanization reaction rate is slow, and the physical and mechanical properties of the rubber are difficult to meet the requirements. If the vulcanization temperature is too high, the rubber may be over-vulcanized, scorched, and the service life of the rubber may be affected.

[0030] In some embodiments, the method for preparing modified silica includes: S1. Add toluene diisocyanate and white carbon black into an organic solvent, introduce inert gas, stir for 30-40 minutes, heat to 70-80°C for reaction for 4-6 hours, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add the white carbon black grafted with toluene diisocyanate and 4-aminodiphenylamine into an organic solvent, introduce an inert gas, stir for 30 min-40 min, heat to 50° C.-90° C. for reaction for 10 h-15 h, centrifuge after cooling, wash, and dry to obtain modified white carbon black.

[0031] It should be noted that toluene diisocyanate has two isocyanate groups, which can react with the hydroxyl group of silica to obtain silica grafted with toluene diisocyanate. The isocyanate groups introduced on the surface of silica grafted with toluene diisocyanate can also react with the amino group of 4-aminodiphenylamine to obtain modified silica.

[0032] The organic solvent may be acetone, ether, or DMF (N,N-dimethylformamide), and the inert gas may be nitrogen.

[0033] In some embodiments, in step S1, the mass ratio of toluene diisocyanate to white carbon black is 1:0.8-1.2. By controlling the mass ratio of toluene diisocyanate to white carbon black, toluene diisocyanate and white carbon black can be fully combined while avoiding waste.

[0034] In some embodiments, in step S2, the mass ratio of the white carbon black grafted toluene diisocyanate to 4-aminodiphenylamine is 1:1-1.5. By controlling the mass ratio of the white carbon black grafted toluene diisocyanate to 4-aminodiphenylamine, the white carbon black grafted toluene diisocyanate and 4-aminodiphenylamine can be fully combined while avoiding waste.

[0035] The present invention will be further described below by way of specific embodiments.

[0036] The experimental methods in the following examples are conventional methods unless otherwise specified; the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0037] Example 1 Preparation of modified silica: S1. Add 1 g of toluene diisocyanate and 0.8 g of white carbon black into acetone, introduce inert nitrogen gas, stir for 30 min, heat to 70° C. for reaction for 4 h, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add 1 g of white carbon black grafted with toluene diisocyanate and 1 g of 4-aminodiphenylamine into acetone, introduce inert nitrogen gas, stir for 30 min, heat to 50° C. to react for 10 h, cool, centrifuge, wash, and dry to obtain modified white carbon black.

[0038] Preparation of oil-resistant seals: 80 parts of nitrile rubber are placed in an internal mixer for plasticization, and then 40 parts of modified white carbon black, 5 parts of zinc oxide, 1 part of stearic acid, and 1 part of accelerator DM are added in sequence and mixed. After mixing, 1 part of sulfur is added and placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal is obtained.

[0039] Example 2 Preparation of modified silica: S1. Add 1 g of toluene diisocyanate and 1.2 g of white carbon black into acetone, introduce inert nitrogen gas, stir for 40 min, heat to 80° C. for reaction for 6 h, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add 1 g of white carbon black grafted with toluene diisocyanate and 1.5 g of 4-aminodiphenylamine into acetone, introduce inert nitrogen gas, stir for 40 min, heat to 90° C. to react for 15 h, cool, centrifuge, wash, and dry to obtain modified white carbon black.

[0040] Preparation of oil-resistant seals: 100 parts of nitrile rubber are placed in an internal mixer for plasticization, and then 50 parts of modified white carbon black, 7 parts of zinc oxide, 2 parts of stearic acid, and 2 parts of accelerator DM are added in sequence and mixed. After mixing, 3 parts of dimethyl disulfide are added and placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal is obtained.

[0041] Example 3 Preparation of modified silica: S1. Add 1 g of toluene diisocyanate and 0.8 g of white carbon black into acetone, introduce inert nitrogen gas, stir for 30 min, heat to 70° C. for reaction for 4 h, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add 1 g of white carbon black grafted with toluene diisocyanate and 1.5 g of 4-aminodiphenylamine into acetone, introduce inert nitrogen gas, stir for 40 min, heat to 90° C. to react for 15 h, cool, centrifuge, wash, and dry to obtain modified white carbon black.

[0042] Preparation of oil-resistant seals: 100 parts of nitrile rubber are placed in an internal mixer for plasticization, and then 50 parts of modified white carbon black, 7 parts of zinc oxide, 2 parts of stearic acid, and 2 parts of accelerator CZ are added in sequence and mixed. After mixing, 3 parts of diisopropylbenzene peroxide are added, and the mixture is placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal is obtained.

[0043] Example 4 Preparation of modified silica: S1. Add 1 g of toluene diisocyanate and 0.8 g of white carbon black into acetone, introduce inert nitrogen gas, stir for 30 min, heat to 70° C. for reaction for 4 h, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add 1 g of white carbon black grafted with toluene diisocyanate and 1.5 g of 4-aminodiphenylamine into acetone, introduce inert nitrogen gas, stir for 40 min, heat to 90° C. to react for 15 h, cool, centrifuge, wash, and dry to obtain modified white carbon black.

[0044] Preparation of oil-resistant seals: 80 parts of nitrile rubber are placed in an internal mixer for plasticization, and then 40 parts of modified white carbon black, 5 parts of zinc oxide, 1 part of stearic acid, and 1 part of accelerator CZ are added in sequence and mixed. After mixing, 1 part of sulfur is added and placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal is obtained.

[0045] Example 5 Preparation of modified silica: S1. Add 1 g of toluene diisocyanate and 1 g of white carbon black into acetone, introduce inert nitrogen gas, stir for 35 min, heat to 75 ° C for reaction for 5 h, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add 1 g of white carbon black grafted with toluene diisocyanate and 1.2 g of 4-aminodiphenylamine into acetone, introduce inert nitrogen gas, stir for 35, heat to 70°C for reaction for 13 h, cool and centrifuge, wash and dry to obtain modified white carbon black.

[0046] Preparation of oil-resistant seals: 90 parts of nitrile rubber are placed in an internal mixer for plasticization, and then 45 parts of modified white carbon black, 6 parts of zinc oxide, 1.5 parts of stearic acid, and 1.5 parts of accelerator TMTD are added in sequence and mixed. After mixing, 2 parts of dimethyl disulfide are added and placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal is obtained.

[0047] Example 6 Preparation of modified silica: S1. Add 1 g of toluene diisocyanate and 1.1 g of white carbon black into acetone, introduce inert nitrogen gas, stir for 35 min, heat to 75 ° C for reaction for 5 h, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add 1 g of white carbon black grafted with toluene diisocyanate and 1.3 g of 4-aminodiphenylamine into acetone, introduce inert nitrogen gas, stir for 35 min, heat to 80° C. to react for 13 h, cool, centrifuge, wash, and dry to obtain modified white carbon black.

[0048] Preparation of oil-resistant seals: 90 parts of nitrile rubber were placed in an internal mixer for plasticization, and then 45 parts of modified white carbon black, 6 parts of zinc oxide, 1.5 parts of stearic acid, and 1.5 parts of accelerator TMTD were added in sequence and mixed. After mixing, 2 parts of diisopropylbenzene peroxide were added, and the mixture was placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal was obtained.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that white carbon black is used instead of modified white carbon black to prepare an oil-resistant seal.

[0050] Test experiment The aging resistance test was performed on Example 1 of the present invention and Comparative Example 1: According to the test standard GB / T 3512-2014, a special hot air aging box was used, and the specific steps were as follows: the sample was hung in the aging box continuously at high temperature, and the performance of the test sample was taken out after aging for a period of time. The aging resistance was measured by the tensile performance retention rate, that is, the tensile performance retention rate = tensile performance after aging / tensile performance before aging.

[0051] Figure 1 This is a graph showing the results of the aging resistance test. As shown in the figure, the aging resistance of Example 1 is greatly improved compared with that of Comparative Example 1.

[0052] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An oil-resistant seal, characterized in that: The invention comprises the following components in parts by weight: 80-100 parts of nitrile rubber, 40-50 parts of modified white carbon black, 5-7 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of accelerator and 1-3 parts of vulcanizing agent; The modified white carbon black is firstly prepared by reacting white carbon black with toluene diisocyanate to obtain white carbon black grafted with toluene diisocyanate, and then prepared by reacting white carbon black grafted with toluene diisocyanate with 4-aminodiphenylamine.

2. The oil-resistant seal according to claim 1, characterized in that: The mass fraction of combined acrylonitrile in the nitrile rubber is 30%-35%.

3. The oil-resistant seal according to claim 1, characterized in that: The accelerator is a mixture of one or more of accelerator DM, accelerator CZ, and accelerator TMTD.

4. The oil-resistant seal according to claim 1, characterized in that: The vulcanizing agent is one of sulfur, dimethyl disulfide and dicumyl peroxide.

5. The method for preparing an oil-resistant seal according to any one of claims 1 to 4, characterized in that: include: The nitrile rubber is placed in an internal mixer for plasticization, and then modified white carbon black, zinc oxide, stearic acid and accelerator are added in sequence for mixing. After mixing, a vulcanizing agent is added, and the mixture is placed in a vulcanizer for vulcanization. After compression molding, an oil-resistant seal is obtained.

6. The preparation method according to claim 5, characterized in that: The mixing time is 10 min-15 min, and the temperature is 80° C.-100° C.

7. The preparation method according to claim 5, characterized in that: The vulcanization time is 15 min-20 min, and the temperature is 120° C.-140° C.

8. The preparation method according to claim 5, characterized in that: The preparation method of the modified white carbon black comprises: S1. Add toluene diisocyanate and white carbon black into an organic solvent, introduce inert gas, stir for 30-40 minutes, heat to 70-80°C for reaction for 4-6 hours, cool, wash, and dry to obtain white carbon black grafted with toluene diisocyanate; S2. Add the white carbon black grafted with toluene diisocyanate and 4-aminodiphenylamine into an organic solvent, introduce an inert gas, stir for 30 min-40 min, heat to 50° C.-90° C. for reaction for 10 h-15 h, centrifuge after cooling, wash, and dry to obtain modified white carbon black. 9 . The preparation method according to claim 8 , wherein in step S1 , the mass ratio of the toluene diisocyanate to the white carbon black is 1:0.8-1.

2. 10 . The preparation method according to claim 8 , wherein in step S2 , the mass ratio of the white carbon black grafted with toluene diisocyanate to the 4-aminodiphenylamine is 1:1-1.5.

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