Hot air vulcanization low-pressure-change hydrogenated butadiene-acrylonitrile rubber O-shaped sealing strip

Abstract

The invention discloses a hot air vulcanized low-pressure-change hydrogenated butadiene-acrylonitrile rubber O-shaped sealing strip which is characterized by comprising the following raw materials in parts by mass: 100 parts of HNBR (Dow 3416, the acrylonitrile content is 34%, and the Mooney viscosity is 60); 1 part of stearic acid; 5-10 parts of indirect zinc oxide; 10 to 15 parts of a plasticizer TP759; 50 to 70 parts of carbon black N550; 2 parts of polyethylene wax; 2 parts of a carbon black dispersant; 1.5 parts of an anti-aging agent 445; 5 to 8 parts of a cross-linking agent XL (modified BIPB); the invention discloses peroxide hydrogen sulfide nitrile rubber applicable to a hot air vulcanization process, which is characterized in that the peroxide hydrogen sulfide nitrile rubber comprises the following components in parts by weight: 5-10 parts of peroxide, 3-5 parts of a crosslinking agent TAIC (triallyl isocyanurate) and 3-5 parts of a bridging agent TAIC (triallyl isocyanurate), and the crosslinking agent XL is modified 1, 4-bis (tert-butylperoxy isopropyl) benzene and reacts with oxygen for inerting in the hot air vulcanization process, and solves the problem of large compression deformation rate.

Description

Technical Field

[0001] The invention relates to the field of rubber and plastic sealing, in particular to a hot air vulcanized low-pressure hydrogenated nitrile rubber O-shaped sealing strip. Background Art

[0002] O-type rubber sealing strips are produced using an extrusion process and vulcanized using a microwave or hot air vulcanization process. They have the characteristics of high production efficiency, a wide range of applicable lengths, and no need for vulcanization mold investment. Therefore, they are widely used in metallurgical seals, especially for ultra-large groove seals, solving the problem of large vulcanization molds and excessive investment in vulcanizers.

[0003] O-type rubber sealing strips have high requirements for the compression set of rubber materials because they use a compression seal. Traditional extrusion processes cannot use peroxide vulcanization because the oxygen in the air consumes the peroxide vulcanizing agent faster, resulting in insufficient performance, poor appearance, or damaged service life of the product after vulcanization. The compression set rate of ordinary sulfur or sulfur-carrier vulcanization systems is difficult to reach a better level, which is a major drawback of hydrogenated nitrile rubber extruded sealing strips. The present invention develops a peroxide-vulcanized hydrogenated nitrile rubber that can be used in a hot air vulcanization process, which solves the problem of a large compression set rate. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a hot air vulcanized low-pressure hydrogenated nitrile rubber O-shaped sealing strip, which solves the problem of large compression deformation rate of extruded HNBR strips. The hot air vulcanized strip compression permanent deformation rate can reach 8.5%.

[0005] The present invention adopts the following technical solutions to achieve the invention objectives:

[0006] A hot air vulcanized low-pressure hydrogenated nitrile rubber O-ring sealing strip is composed of the following raw materials in parts by weight: 100 parts of HNBR raw rubber (Dawn 3416, acrylonitrile content 34%, Mooney viscosity 60);

[0007] Stearic acid: 1 part;

[0008] Indirect zinc oxide: 5-10 parts;

[0009] Plasticizer TP759: 10-15 parts;

[0010] Carbon black N550: 50-70 parts;

[0011] Polyethylene wax: 2 parts;

[0012] Carbon black dispersant: 2 parts;

[0013] Antioxidant 445: 1.5 parts;

[0014] Crosslinking agent XL (modified BIPB): 5-8 parts;

[0015] Bridging agent TAIC: 3 to 5 parts.

[0016] As a further limitation of the present technical solution, the crosslinking agent XL is modified 1,4-bis(tert-butylperoxyisopropyl)benzene, which reacts with oxygen to become inert during the hot air vulcanization process.

[0017] As a further limitation of this technical solution, the extrusion process uses an extruder with a screw diameter of 75-90mm, a die head temperature of 75°C, and an extrusion speed of 3 meters per minute. After extrusion, the rubber strip enters a hot drying tunnel for vulcanization. As a further limitation of this technical solution, the vulcanization process is as follows: first-stage vulcanization: 270°C hot air treatment for 2 minutes to achieve rapid shaping; second-stage vulcanization: 265°C hot air treatment for 2 minutes to complete crosslinking and aging; third-stage vulcanization: 260°C hot air treatment for 2 minutes to improve overall performance.

[0018] As a further limitation of the present technical solution, the total vulcanization time is 6 minutes, and the vulcanization temperature is distributed in a gradient decreasing manner.

[0019] As a further limitation of the present technical solution, the Mooney viscosity of the HNBR raw rubber is 60±5, taking into account both extrusion fluidity and product physical properties.

[0020] As a further limitation of the present technical solution, the mass ratio of plasticizer TP759 to carbon black N550 is 1:(5-7), which optimizes the processability and reinforcement effect of the rubber compound.

[0021] As a further limitation of this technical solution,

[0022] a) Mix the raw materials except the cross-linking agent XL and the bridging agent TAIC to below 160°C;

[0023] b) Add cross-linking agent XL and bridging agent TAIC, and thin out the sheet at below 110°C;

[0024] c) Extrusion vulcanization is carried out according to claims 3 to 5.

[0025] As a further limitation of the present technical solution, the compression permanent deformation rate at 150°C×70h is ≤9%, the tensile strength is ≥17MPa, and the tear strength is ≥40N / mm.

[0026] As a further limitation of this technical solution, it is applicable to the sealing of ultra-large grooves in metallurgical equipment, with a length range of 1 to 100 meters, without the need for a vulcanization mold.

[0027] Compared with the prior art, the advantages and positive effects of the present invention are:

[0028] Ultra-low compression set: By combining the modified crosslinker XL with the gradient vulcanization process, the compression set is reduced by 20.6% compared to the traditional peroxide system (Example 1 vs. Comparative Example 1) and by 88.2% compared to the sulfur system (Example 1 vs. Comparative Example 2), significantly improving sealing reliability.

[0029] Hot air vulcanization adaptability: The antioxidant inert design of crosslinker XL solves the problems of surface stickiness and insufficient crosslinking during hot air vulcanization of peroxide systems, and the product strength is increased by 47.1% (Example 1 vs. Comparative Example 1).

[0030] Process economy:

[0031] No need for vulcanization molds, equipment investment reduced by more than 60%;

[0032] The efficiency of the continuous extrusion vulcanization process has increased by 3 to 5 times, with a single-line daily production capacity of 2,000 meters;

[0033] The applicable length range is extended to 100 meters, breaking through the size limitations of traditional molds.

[0034] Comprehensive performance optimization:

[0035] Tensile strength retention rate> 90% (after thermal aging at 150°C for 72h);

[0036] The tear strength reaches 47.2 N / mm (Comparative Example 2), which combines the high strength of the peroxide system with the tear resistance of the sulfur system. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Comparison of the vulcanization curves of Example 1 and the comparative example rubber (showing the change of crosslinking density over time).

[0038] Figure 2 This is a relationship diagram between the permanent compression set rate of the sealing strip and the vulcanization process (showing the inhibitory effect of gradient vulcanization on the deformation rate). DETAILED DESCRIPTION

[0039] A specific embodiment of the present invention is described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiment.

[0040] In one embodiment:

[0041] A hot air vulcanized low-pressure hydrogenated nitrile rubber O-ring sealing strip is composed of the following raw materials in parts by weight: 100 parts of HNBR raw rubber (Dawn 3416, acrylonitrile content 34%, Mooney viscosity 60);

[0042] Stearic acid: 1 part;

[0043] Indirect zinc oxide: 5-10 parts;

[0044] Plasticizer TP759: 10-15 parts;

[0045] Carbon black N550: 50-70 parts;

[0046] Polyethylene wax: 2 parts;

[0047] Carbon black dispersant: 2 parts;

[0048] Antioxidant 445: 1.5 parts;

[0049] Crosslinking agent XL (modified BIPB): 5-8 parts;

[0050] Bridging agent TAIC: 3 to 5 parts.

[0051] Among them, the crosslinking agent XL is modified 1,4-bis(tert-butylperoxyisopropyl)benzene, which reacts with oxygen to become inert during the hot air vulcanization process.

[0052] HNBR raw rubber: Dawn 3416 brand is selected, with an acrylonitrile content of 34% and a Mooney viscosity of 60. It has good comprehensive properties and is suitable as a low-Mooney HNBR raw rubber to meet the requirements of the present invention for the physical properties and extrusion processability of the mixed rubber.

[0053] Stearic acid: Common commercially available stearic acid, as a lubricant, can improve the processing properties of the rubber during the mixing process and prevent the rubber from adhering to the equipment. At the same time, it plays a certain activation role in the vulcanization process and promotes the vulcanization reaction.

[0054] Indirect zinc oxide: Use 5-10 parts by weight of common commercially available indirect zinc oxide. Indirect zinc oxide primarily plays a reinforcing, activating, and vulcanizing role in rubber products, improving the rubber's physical properties such as hardness and tensile strength. It also synergizes with other components in the vulcanization system to promote the vulcanization reaction, resulting in a good vulcanization effect.

[0055] Plasticizer TP759: 10-15 parts by weight of commercially available plasticizer TP759. This plasticizer can reduce the Mooney viscosity of the rubber compound, improve its processing fluidity, and make the mixing process smoother. It also imparts good flexibility and plasticity to the rubber compound, helping to improve its molding properties and the dimensional stability of the finished product.

[0056] Carbon Black N550: 50-70 parts by weight of commercially available carbon black N550. Carbon Black N550 is a semi-reinforcing carbon black with an appropriate particle size and structure. It significantly improves the rubber's physical and mechanical properties, such as tensile strength, wear resistance, and aging resistance, while having minimal effect on the compound's processing properties. It disperses evenly during mixing, enhancing the compound's overall performance.

[0057] Polyethylene wax: 2 parts by weight of common commercially available polyethylene wax. As a lubricant, polyethylene wax can improve the processing properties of the rubber compound, reduce the friction coefficient between the rubber compound and the equipment, and prevent problems such as adhesion and accumulation of the rubber compound during the extrusion process. It also helps to improve the surface smoothness and gloss of the rubber compound, making the surface of the extruded rubber strip more flat and smooth.

[0058] Carbon black dispersant: 2 parts by weight of a common commercially available carbon black dispersant. This carbon black dispersant effectively improves the dispersion of carbon black in the rubber compound, preventing carbon black particles from agglomerating to form large agglomerates. This improves the uniformity and consistency of the rubber compound, ensuring uniform and stable properties across the compound, and contributing to improved appearance and physical properties of the finished product.

[0059] Antioxidant 445: 1.5 parts by weight of common commercially available antioxidant 445. Antioxidant 445 is a multifunctional antioxidant with antioxidant, ozone, and heat aging properties. It can effectively delay the aging of rubber during processing and use, improve the service life and durability of the product, and maintain its good performance.

[0060] Crosslinker XL: 5-8 parts by weight of modified BIPB crosslinker XL, purchased from Shanghai Sendi. This crosslinker is relatively stable to oxygen in the air and does not react with oxygen, meeting the process requirements of microwave + hot air vulcanization. During the vulcanization process, it undergoes an efficient crosslinking reaction with HNBR rubber, forming a stable three-dimensional network structure. This results in an extremely low compression set in the resulting rubber compound, ensuring excellent sealing properties for products such as O-ring seals.

[0061] Bridging Agent TAIC: 3-5 parts by weight of a common commercially available bridging agent TAIC. During the vulcanization process, TAIC works synergistically with the crosslinker XL to further enhance the strength and stability of the crosslinked network, increase the crosslink density of the rubber compound, and improve the compound's physical and mechanical properties, such as tensile strength and tear strength. It also helps enhance the compound's heat resistance and aging resistance.

[0062] In one embodiment, the mixing process includes: 1. Initial mixing: HNBR raw rubber is placed into an internal mixer and preheated to approximately 60-70°C to gradually soften the rubber. Stearic acid and indirect zinc oxide are then added sequentially, and mixing continues for 2-3 minutes to initially disperse these small components within the rubber. During this process, the mixer speed is maintained at 30-40 rpm to ensure thorough mixing without generating excessive shear heat, which could prevent premature vulcanization or performance degradation.

[0063] 2. Plasticization and Reinforcement Stage: Add plasticizer TP759 to the above mixture and mix at low speed for 1-2 minutes to allow the plasticizer to gradually penetrate the rubber compound, reducing its viscosity and improving its processing fluidity. Subsequently, slowly add carbon black N550 while increasing the speed to 40-50 rpm and mix for 3-5 minutes to evenly disperse the carbon black in the rubber compound, forming a good reinforcing network structure and enhancing the physical properties of the rubber compound. During this process, closely monitor the temperature of the rubber compound. If the temperature is too high, cool it down or reduce the speed appropriately to prevent carbon black aggregation and premature vulcanization of the rubber compound.

[0064] 3. Lubrication and Dispersion Stage: Add polyethylene wax and carbon black dispersant and continue mixing at 40-50 r / min for 2-3 minutes. Polyethylene wax further improves the lubricity of the rubber compound, reducing friction between the rubber compound and the equipment, making subsequent processing smoother. Carbon black dispersant effectively prevents carbon black particles from reaggregating, ensuring uniform dispersion of carbon black in the rubber compound and improving the overall performance stability and appearance quality of the rubber compound.

[0065] 4. Anti-aging and cross-linking stage: Add antioxidant 445 to the rubber compound and mix for 1-2 minutes to evenly distribute the antioxidant throughout the compound, providing comprehensive antioxidant, ozone, and thermal aging protection. Next, add cross-linker XL and bridging agent TAIC, reduce the speed to 30-40 rpm, and slowly mix for 3-5 minutes to allow the cross-linker and bridging agent to fully contact and interact with the other components in the rubber compound, preparing for the subsequent vulcanization reaction. During this process, mixing time and temperature must be strictly controlled to prevent premature cross-linking of the cross-linker, which could lead to decreased performance or failure of extrusion molding.

[0066] In one embodiment, the extrusion process includes: 1. Equipment and parameter settings: An extruder with a screw diameter of 75 mm or 90 mm is used, with the specific selection determined based on production scale and product specifications. Prior to extrusion, the extruder is preheated, with the die temperature set to 75°C and the extrusion speed set to 3 m / min to ensure stability during the extrusion process and consistent quality of the rubber strip.

[0067] 2. Rubber Extrusion: The rubber compound obtained through the above mixing process is placed into the extruder hopper. The extruder is turned on. Driven and sheared by the screw, the rubber compound is transported forward along the barrel, gradually heating up. At the die head, the rubber compound is extruded through a specially shaped die at 75°C, forming a rubber strip with the desired cross-sectional shape. During the extrusion process, close attention should be paid to the extrusion pressure, temperature, and appearance of the rubber strip. Equipment parameters should be adjusted promptly to address any issues such as intermittent extrusion and surface roughness, ensuring that the extruded rubber strip is smooth, uniform in size, and free of obvious defects.

[0068] In one embodiment: The vulcanization process includes: 1. Hot air vulcanization stage: The extruded rubber strip is immediately conveyed to the hot drying tunnel, and first undergoes a hot air vulcanization stage. The set temperature is 270°C and the vulcanization time is 2 minutes. During this stage, the high-temperature hot air causes the cross-linking agent XL in the rubber strip to quickly undergo a cross-linking reaction with the HNBR raw rubber. The rubber strip is quickly shaped and initially forms a three-dimensional network structure with a certain strength and hardness, laying the foundation for subsequent maturation and performance improvement. At the same time, it is necessary to ensure that the hot air in the hot drying tunnel circulates evenly so that all parts of the rubber strip are heated evenly to avoid uneven vulcanization due to local temperature differences, which affects product quality.

[0069] 2. Second-stage hot air vulcanization: After completing the first stage of vulcanization, the strip continues to undergo a second stage of vulcanization in a hot drying tunnel at a temperature of 265°C for 2 minutes. The temperature in this stage is slightly lower than that of the first stage of vulcanization. This allows the strip to undergo further cross-linking reactions based on the initial vulcanization setting, resulting in a more complete and dense cross-linking network. This allows the product to continue to mature, gradually improving various physical properties such as tensile strength and tear strength. Furthermore, temperature control during the second stage of vulcanization is crucial to prevent over-vulcanization of the strip and the generation of unpleasant odors.

[0070] 3. Three-stage hot air vulcanization: Finally, the strip enters the three-stage vulcanization zone of the hot drying tunnel, where the temperature is 260°C and the curing time is 2 minutes. During this stage, the strip undergoes further heat treatment to ensure a more complete and stable cross-linking reaction, further optimizing the strip's performance, such as improving its heat resistance and aging resistance, while also further stabilizing its appearance and dimensions. After three stages of vulcanization, the strip achieves optimal overall performance, meeting the requirements of high-quality sealing strips and other products.

[0071] 4. Strip Cooling: After vulcanization is complete, remove the strip from the hot drying tunnel and immediately cool it. Air or water cooling can be used to quickly lower the strip temperature to near room temperature to prevent performance changes or deformation caused by prolonged exposure to high temperatures. The cooled strip is ready for subsequent inspection, packaging, and storage, pending use as sealing strips and other products.

[0072] In one embodiment, performance testing includes: 1. Hardness testing: Using a Shore A durometer, perform a hardness test on the vulcanized rubber strip in accordance with relevant standards. The rubber strip sample is placed on a flat testing platform, with the indenter of the durometer pressed vertically into the strip surface. The reading is recorded after stabilization. In this embodiment, the rubber strip has a hardness of 70 Shore A, meeting design requirements. Compared to 67 Shore A in Comparative Example 1 and 69 Shore A in Comparative Example 2, this exhibits a moderate hardness, ensuring the sealing performance of the sealing strip without compromising its flexibility and installation performance due to excessive hardness.

[0073] 2. Tensile Strength Test: The rubber strips were subjected to a tensile strength test using a tensile testing machine according to standard methods. The rubber strip samples were cut into standard dumbbell-shaped specimens and clamped between the upper and lower clamps of the tensile testing machine. The specimens were stretched at a certain tensile speed until they broke. The maximum tensile force at break was recorded, and the tensile strength was calculated based on the cross-sectional area of the specimen. The tensile strength of the rubber strips in this example reached 17.8 MPa, which is higher than the 12.1 MPa of Comparative Example 1. Although slightly lower than the 18.4 MPa of Comparative Example 2, after considering other properties, it still meets the actual use requirements and has the significant advantage of a low compression set rate.

[0074] 3. Elongation at Break Test: During the tensile strength test, the elongation at break of the specimen was recorded and compared with the original length to calculate the elongation at break. The elongation at break of the rubber strip of this example was 201%, which is relatively lower than the 281% of Comparative Example 1 and the 279% of Comparative Example 2, but still within an acceptable range. This demonstrates that the rubber strip has a certain degree of elasticity and flexibility, which can adapt to the deformation requirements of the sealing part to a certain extent, and does not cause breakage or seal failure due to excessive elongation.

[0075] 4. Tear Strength Test: Using the trouser-shaped tear test method, the rubber strip samples were cut into trouser-shaped specimens and torn on a tensile testing machine. The maximum force during the tearing process was recorded, and the tear strength was calculated based on parameters such as the specimen thickness. The tear strength of the rubber strip in this example was 41.5 N / mm, higher than the 37.3 N / mm of Comparative Example 1, but slightly lower than the 47.2 N / mm of Comparative Example 2. This demonstrates that the rubber strip has good tear resistance and can withstand the potential tearing caused by sharp objects or stress concentration points during use, ensuring the integrity and sealing performance of the sealing strip.

[0076] 5. Compression Set Test: In accordance with relevant standards, rubber strip samples were cut into circular or sheet-shaped specimens of a specific size and placed on a compression set testing machine. A 25% compression rate was applied to the specimens at 150°C for 70 hours. The specimens were then removed and cooled to room temperature. The permanent deformation of the specimens was measured, and the compression set rate was calculated. The compression set rate of the rubber strip in this example was 8.5%, significantly lower than the 10.7% in Comparative Example 1 and the 72% in Comparative Example 2. This significant advantage enables the rubber strip to maintain good resilience after prolonged compression, effectively preventing seal failure due to excessive compression set, thereby ensuring the sealing reliability and service life of products such as O-ring sealing strips.

[0077] 6. Appearance Inspection: The vulcanized rubber strips were visually inspected to ensure a smooth and even surface, and to check for defects such as bubbles, cracks, and wrinkles. The rubber strips in this example exhibited excellent appearance, with no apparent sticking or wrinkling at bends. This contrasted sharply with the sticking and wrinkling problems in Comparative Example 1, demonstrating that the formulation and process of the present invention can produce rubber strips with excellent appearance quality, meeting the appearance requirements of practical applications.

[0078] In summary, this embodiment is operated strictly in accordance with the formula and preparation process of the present invention, and the peroxide-hydrogenated nitrile rubber compound produced shows excellent results in various performance tests, especially low compression set, which can effectively solve the problem of large compression set of existing extruded HNBR strips. The prepared strip has good sealing performance and comprehensive physical and mechanical properties, can be widely used in fields such as O-type sealing strips, and has significant market application value and promotion prospects.

[0079] like Figure 1 As shown, Figure 1 Comparison of the vulcanization curves for Example 1 (the present invention), Comparative Example 1 (a peroxide system), and Comparative Example 2 (a sulfur system) is shown. The horizontal axis represents the vulcanization time (minutes), and the vertical axis represents the crosslink density (relative value). It can be seen that the gradient vulcanization process of the present invention steadily increases the crosslink density, ultimately reaching 0.95, while the crosslink density of Comparative Examples 1 and 2 increases more slowly or stagnates.

[0080] Figure 2 Illustration: This figure shows the relationship between compression set and vulcanization process. The horizontal axis represents the vulcanization process stage, and the vertical axis represents compression set (%). The three-stage gradient vulcanization process of the present invention controls the set to 8.5%, significantly better than the 10.7% in Comparative Example 1 and the 72% in Comparative Example 2. The figure also shows the gradual suppression of set with each vulcanization stage.

[0081] The quality table of this patent and two comparative examples:

[0082]

[0083]

[0084] HNBR raw rubber: As the main base material, the three solutions use the same amount, which ensures the basic consistency of the experimental comparison. Its characteristics directly affect the main performance of the compound rubber.

[0085] Stearic acid, indirect zinc oxide, plasticizer TP759, carbon black N550, polyethylene wax, carbon black dispersant, antioxidant 445: The dosage of these small ingredients in different schemes is basically the same, and they are used to improve the processing performance, reinforcement, anti-aging and other conventional properties of the rubber compound.

[0086] Cross-linking agent XL: This patent uses a special cross-linking agent that gives the rubber mix stability to oxygen and the ability to meet special vulcanization processes. The dosage is 5-8 parts, while Comparative Examples 1 and 2 do not use it.

[0087] Cross-linking agent BIPB: The cross-linking agent used in Comparative Example 1 was used in an amount of 5-8 parts, but it did not achieve the effect of the cross-linking agent XL in this patent, resulting in poor performance after vulcanization.

[0088] Bridging agent TAIC: This patent and comparative example 2 both use it. This patent uses 3-5 parts to enhance the cross-linked network. However, comparative example 2 combined with its vulcanization system does not achieve the compression deformation performance of this patent.

[0089] Sulfur, TMTD: Comparative Example 2 uses components of a traditional vulcanization system. Although the physical properties and appearance are acceptable, the compression set rate is large.

[0090] Basic performance table of this patent and two comparative examples:

[0091]

[0092] Hardness: The hardness of this patent is moderate, which not only ensures the sealing performance but also has a certain flexibility. It is slightly higher than that of comparative example 1 and close to that of comparative example 2, but it is better in terms of other properties.

[0093] Tensile strength: This patent has a value of 17.8 MPa, which is higher than that of comparative example 1. Although slightly lower than that of comparative example 2, it is still practical when combined with advantages such as low compression deformation.

[0094] Elongation at break: This patented product is 201%, which is within a reasonable range and exhibits a certain degree of elasticity, which can meet the deformation requirements of the sealing strip during use.

[0095] Tear strength: This patent has a tear strength of 41.5 N / mm, which is higher than that of comparative example 1 and lower than that of comparative example 2. However, considering the overall performance, the tear resistance meets the standard.

[0096] Compression permanent deformation rate: This patent is 8.5%, which is much lower than that of comparative examples 1 and 2. This is its core advantage, ensuring the sealing performance of the sealing strip after being under pressure for a long time.

[0097] Appearance: This patent has a good appearance, avoids the adhesion and wrinkle problems of comparative example 1, and meets the product quality requirements.

[0098] The comparison in the above table clearly demonstrates the advantages of this patented formula in terms of material selection and performance compared to the comparative example, especially the significant reduction in compression set, highlighting the practical application value of the innovation.

Claims

1. A hot air vulcanized low pressure hydrogenated nitrile rubber O-shaped sealing strip, characterized in that It is composed of the following raw materials in parts by mass: HNBR raw rubber: 100 parts; Stearic acid: 1 part; Indirect zinc oxide: 5-10 parts; Plasticizer TP759: 10-15 parts; Carbon black N550: 50-70 parts; Polyethylene wax: 2 parts; Carbon black dispersant: 2 parts; Antioxidant 445: 1.5 parts; Cross-linking agent XL: 5-8 parts; Bridging agent TAIC: 3 to 5 parts.

2. The sealing strip according to claim 1, characterized in that: The crosslinking agent XL is modified 1,4-bis(tert-butylperoxyisopropyl)benzene, which reacts with oxygen during hot air vulcanization to become inert.

3. An extrusion process for the sealing strip according to claim 1, characterized in that: An extruder with a screw diameter of 75 to 90 mm, a die head temperature of 75°C, and an extrusion speed of 3 m / min is used. After extrusion, the rubber strip directly enters a hot drying tunnel for vulcanization.

4. A vulcanization process for the sealing strip according to claim 1, characterized in that: One-stage vulcanization: 270℃ hot air treatment for 2 minutes to achieve rapid shaping; Second stage vulcanization: 265℃ hot air treatment for 2 minutes to complete cross-linking and aging; Three-stage vulcanization: 260℃ hot air treatment for 2 minutes to improve overall performance.

5. The vulcanization process according to claim 4, characterized in that: The total vulcanization time is 6 minutes, and the vulcanization temperature is distributed in a gradient decreasing manner.

6. The sealing strip according to claim 1, characterized in that: The Mooney viscosity of the HNBR raw rubber is 60±5, taking into account both extrusion fluidity and product physical properties.

7. The mixing process of the sealing strip according to claim 1, characterized in that The mass ratio of the plasticizer TP759 to the carbon black N550 is 1:(5-7), which optimizes the processability and reinforcement effect of the rubber compound.

8. A method for preparing the sealing strip according to claim 1, characterized in that: a) Mix the raw materials except the cross-linking agent XL and the bridging agent TAIC to below 160°C; b) Add cross-linking agent XL and bridging agent TAIC, and thin out the sheet at below 110°C; c) Extrusion vulcanization is carried out according to claims 3 to 5.

9. The sealing strip according to claim 1, characterized in that: 150℃×70h compression permanent deformation rate ≤9%, tensile strength ≥17MPa, tear strength ≥40N / mm.

10. Use of the sealing strip according to claim 1 in sealing super-large grooves of metallurgical equipment, with an applicable length range of 1 to 100 meters.

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