Method for preparing high temperature resistant nitrile rubber material

Abstract

The application discloses a kind of high-temperature-resistant butyronitrile rubber material preparation methods, raw material is with 100 parts acrylonitrile content 37% butyronitrile rubber as matrix, compound precipitated silica, pottery, ternary reinforcing system of modified white carbon black, polyester and TP-95 composite plasticizer, MB / 445 compound antioxidant and multi-component synergistic vulcanization accelerator.Preparation process is divided into four stages: one-stage closed mixing subsection mixing filler and additive after cooling and parking;Second stage low temperature open mill is added vulcanization system;Finally, mold pressing vulcanization molding.The application does not need HNBR, fluorine rubber and other high-cost raw materials, relies on formula and two-stage mixing process to improve the dispersibility of filler, material can be used stably for a long time at 120~125 DEG C, with excellent oil resistance, wear resistance and-30 DEG C low temperature resistance;Composite vulcanization system shortens vulcanization cycle, improves production efficiency, and can be widely used in high-speed bearing, automobile and oilfield sealing products.

Description

Technical Field

[0001] This invention relates to a method for preparing high-temperature resistant nitrile rubber materials. Background Technology

[0002] Nitrile butadiene rubber (NBR), with its excellent resistance to mineral oils and greases, is a core material for bearing seals, automotive power seals, and oilfield seals. Bearing seals operate under alternating temperature conditions ranging from -30℃ to 120℃ for extended periods. The high-speed frictional heating and continuous grease impregnation place stringent requirements on the rubber's resistance to high-temperature aging, wear resistance, low-temperature toughness, and long-term sealing stability. Meanwhile, the temperature resistance and durability requirements of sealing components in automotive turbochargers, drive motors, and downhole oil production equipment are constantly being upgraded, making traditional general-purpose NBR materials unsuitable for these high-end applications.

[0003] In existing technologies, there are two main conventional methods to improve the heat and oil resistance of nitrile rubber: one is to use nitrile rubber with high acrylonitrile content. As the acrylonitrile (ACN) content increases, the oil and heat resistance improves, but the material's low-temperature brittleness increases significantly, the flowability of the compounding process deteriorates, and the raw material procurement cost increases significantly. The other is to modify it by blending with special rubbers such as hydrogenated nitrile rubber (HNBR) and fluororubber (FKM). Although this can improve the high-temperature resistance, the high price of special rubbers significantly increases the production cost of the product, which is not conducive to large-scale industrial promotion. Moreover, the blended system is prone to processing defects such as phase separation, uneven vulcanization, and large fluctuations in the mechanical properties of the finished product.

[0004] Conventional reinforced filler compound systems can only slightly improve wear resistance and have limited improvement in heat aging stability; single plasticizer systems cannot simultaneously balance high-temperature non-migration and low-temperature bending resistance; traditional vulcanization systems have slow cross-linking speed, long vulcanization cycle, low production efficiency, and poor thermal stability of the cross-linked network, which is prone to hardening, cracking, and sealing failure under long-term high temperature. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing high-temperature resistant nitrile rubber materials, enabling long-term stable use at 120–125°C, while also exhibiting excellent oil resistance, abrasion resistance, and low-temperature toughness. The method also features rapid vulcanization and crosslinking, shortening the product molding cycle and reducing raw material costs.

[0006] To achieve the above objectives, the present invention provides a method for preparing high-temperature resistant nitrile rubber material, comprising the following steps: Step 1, Material Proportioning, is made from the following raw materials: nitrile rubber, reinforcing agent, protective agent, plasticizer, and vulcanizing agent. The nitrile rubber consists of 100 parts of nitrile rubber with an acrylonitrile content of 37%, 1.5 parts of stearic acid, and 5 parts of zinc oxide. The reinforcing agent is set as follows: 20-30 parts of precipitated silica, 60-80 parts of kaolin, and 10-30 parts of modified silica. The plasticizer is set as follows: 5-10 parts of polyester plasticizer and 5-10 parts of TP-95 plasticizer. The protective agent is set as follows: 4-7 parts of antioxidant MB / 445 compound. The vulcanizing agent is set as follows: 1-2.5 parts of accelerator DM, 2-3 parts of accelerator CZ, 2-3 parts of accelerator TMTD, and 0.5-1.0 parts of accelerator DTDM. Step 2: First stage of intensive mixing. Nitrile rubber is put into an intensive mixer and plasticized at 60-70℃ for 2-3 minutes. Stearic acid and zinc oxide are added sequentially and mixed for 1 minute. All reinforcing fillers are added in two batches and mixed for 3 minutes each time. Polyester plasticizer and TP-95 plasticizer are added and mixed for 2 minutes. Compound antioxidant is added. After heating to 110-120℃, the rubber is discharged and cooled and left to stand for 24 hours to obtain the first stage of masterbatch. Step 3, two-stage mixing: put the first stage of masterbatch into the open mill, pass it through the mill three times at a roller temperature of 50-60℃, add all the vulcanizing agent, knead for 5-8 minutes and then sheet it out. Let it stand at room temperature for 12 hours to obtain the compound. Step 4: Compression vulcanization molding. The mixed rubber is placed into the mold and compressed at 165-175℃ for 8-12 minutes. After demolding, it is cured at room temperature for 2 hours to obtain the finished rubber product.

[0007] As a further feature of the present invention, the modified silica is silane coupling agent surface-modified fumed silica.

[0008] As a further feature of the present invention, the mass ratio of antioxidant MB to antioxidant 445 is 1:2.

[0009] The beneficial effects of this configuration are as follows: This configuration, using a 37% acrylonitrile butadiene rubber (NBR) compounded with silane-modified silica for reinforcement, ensures a strong bond between the filler and rubber interface. The composite antioxidants provide synergistic antioxidant protection, allowing the finished product to operate continuously in high-temperature environments of 120–125°C without easily hardening or cracking at high temperatures. The mechanical property degradation after thermal aging is significantly lower than that of traditional NBR sealants. The ternary reinforcement system of precipitated silica, kaolin, and modified silica significantly improves the rubber's crosslinking density and surface wear resistance, making it suitable for high-speed friction conditions in bearings. The high acrylonitrile matrix combined with polyester plasticizer results in low swelling rates after long-term immersion in lubricating grease and mineral oil, ensuring long-term sealing stability. The polyester plasticizer, combined with TP-95 low-temperature plasticizer, addresses the low-temperature brittleness defect of high acrylonitrile butadiene rubber, allowing the finished product to withstand bending at -30°C without cracking, making it suitable for alternating hot and cold conditions and applicable to a wider range of scenarios. Furthermore, it uses ordinary NBR single rubber matrix, eliminating the need for expensive specialty rubbers such as HNBR and FKM; the filler is mainly low-cost clay, with only a small amount of modified silica compounded, keeping the total raw material cost under control and offering a significant price advantage compared to hydrogenated nitrile butadiene rubber and fluororubber sealing materials. The multi-component composite vulcanization promoting system works synergistically, resulting in rapid cross-linking reaction, shortening molding vulcanization time, and reducing the molding cycle of single batches, effectively improving the processing efficiency of the sealing product production line. Simultaneously, the graded mixing and two-stage compounding process ensures uniform filler dispersion, eliminating agglomeration and uneven vulcanization issues, resulting in good rubber flowability, no material shortages or air bubbles during molding, and uniform and stable mechanical properties of the finished product. Detailed Implementation

[0010] In the first embodiment of the method for preparing high-temperature resistant nitrile rubber material of the present invention, the following proportions are by mass fraction, and the raw material proportions are as follows: ACN37% Nitrile Rubber: 100 parts Stearic acid: 1.5 parts Zinc oxide: 5 parts Precipitated silica: 20 parts Clay: 60 parts Silane-modified silica: 10 parts Polyester plasticizer: 5 parts TP-95 plasticizer: 5 parts Antioxidant MB: 1.3 parts, Antioxidant 445: 2.7 parts (total 4 parts) Accelerator DM: 1 part Accelerator CZ: 2 parts Accelerator TMTD: 2 parts Accelerator DTDM: 0.5 parts; In the second embodiment of the method for preparing high-temperature resistant nitrile rubber material of the present invention, the following proportions are by mass fraction, and the raw material proportions are as follows: ACN37% Nitrile Rubber: 100 parts Stearic acid: 1.5 parts Zinc oxide: 5 parts Precipitated silica: 25 parts Clay: 70 parts Silane-modified silica: 20 parts Polyester plasticizer: 8 parts TP-95 plasticizer: 8 parts Antioxidant MB: 2 parts, Antioxidant 445: 4 parts (total 6 parts) Accelerator DM: 2 parts Accelerator CZ: 2.5 parts Accelerator TMTD: 2.5 parts Accelerator DTDM: 0.8 parts; The third embodiment of the method for preparing high-temperature resistant nitrile rubber material of the present invention, the following proportions are by mass fraction, and the raw material proportions are as follows: ACN37% Nitrile Rubber: 100 parts Stearic acid: 1.5 parts Zinc oxide: 5 parts Precipitated silica: 30 parts Clay: 80 parts Silane-modified silica: 30 parts Polyester plasticizer: 10 parts TP-95 plasticizer: 10 parts Antioxidant MB: 2.3 parts, Antioxidant 445: 4.7 parts (total 7 parts) Accelerator DM: 2.5 parts Accelerator CZ: 3 parts Accelerator TMTD: 3 parts Accelerator DTDM: 1 part; The preparation process is as follows: plasticize nitrile rubber at 70℃ for 2 minutes, add stearic acid and zinc oxide and mix for 1 minute; add all reinforcing fillers in two batches, mixing for 3 minutes each time; add two plasticizers and mix for 2 minutes; add compound antioxidants; heat to 115℃ to discharge the glue; cool and stand for 24 hours. The masterbatch is fed into the open mill, the roller temperature is 550℃, it is passed through the thin mill 3 times, all the vulcanizing agent is added, and after 5-8 minutes of refining, it is sheeted out and left at room temperature for 12 hours to obtain the compound. Compression vulcanization molding involves loading the compounded rubber into a mold, molding and vulcanizing at 170°C for 10 minutes, demolding, and then curing at room temperature for 2 hours to obtain the bearing sealing compound.

[0011] Comparative example: 100 parts general-purpose NBR (ACN 28%), single carbon black reinforcement, DOP single plasticizer, single-component vulcanization accelerator, no modified silica, no MB / 445 composite antioxidant.

[0012] Performance test results Standard samples were prepared using the rubber compounds from Examples 1-3 and the comparative examples, and their thermal aging, oil resistance, low temperature, and abrasion resistance properties were tested respectively. 125℃×72h heat aging: The tensile strength of the comparative example decreased by 38%; the tensile strength of Examples 1-3 of the present invention decreased by ≤16%, and the heat aging resistance was greatly improved; Volume swelling rate after immersion in 120℃ grease for 72 hours: Comparative example 12.7%; All embodiments of the present invention ≤5.5%, indicating better oil resistance and sealing performance; -30℃ low temperature bending test: The comparative example showed cracks after 10 bends; the embodiment of the present invention showed no cracks after 100 bends; Wear resistance performance: Akron wear, comparative wear amount 0.92cm³ / 1.61km; wear amount of the embodiment of the present invention ≤0.38cm³ / 1.61km, wear life is more than doubled; Vulcanization cycle: The comparative example vulcanization takes 18 minutes; the present invention only takes 8 to 12 minutes, increasing production efficiency by more than 30%.

[0013] Test results show that the nitrile rubber material prepared by the formula and preparation process of this invention is significantly superior to traditional nitrile sealant in terms of high temperature resistance, oil resistance, wear resistance, low temperature toughness, and production efficiency, and does not require expensive special rubber, thus having a significant cost advantage.

[0014] The above examples are merely one preferred embodiment of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention are all included within the protection scope of the present invention.

Claims

1. A method for preparing a high-temperature resistant nitrile rubber material, characterized in that: Includes the following steps, Step 1, Material Proportioning, is made from the following raw materials: nitrile rubber, reinforcing agent, protective agent, plasticizer, and vulcanizing agent. The nitrile rubber consists of 100 parts of nitrile rubber with an acrylonitrile content of 37%, 1.5 parts of stearic acid, and 5 parts of zinc oxide. The reinforcing agent is set as follows: 20-30 parts of precipitated silica, 60-80 parts of kaolin, and 10-30 parts of modified silica. The plasticizer is set as follows: 5-10 parts of polyester plasticizer and 5-10 parts of TP-95 plasticizer. The protective agent is set as follows: 4-7 parts of antioxidant MB / 445 compound. The vulcanizing agent is set as follows: 1-2.5 parts of accelerator DM, 2-3 parts of accelerator CZ, 2-3 parts of accelerator TMTD, and 0.5-1.0 parts of accelerator DTDM. Step 2: First stage of intensive mixing. Nitrile rubber is put into an intensive mixer and plasticized at 60-70℃ for 2-3 minutes. Stearic acid and zinc oxide are added sequentially and mixed for 1 minute. All reinforcing fillers are added in two batches and mixed for 3 minutes each time. Polyester plasticizer and TP-95 plasticizer are added and mixed for 2 minutes. Compound antioxidant is added. After heating to 110-120℃, the rubber is discharged and cooled and left to stand for 24 hours to obtain the first stage of masterbatch. Step 3, two-stage mixing: put the first stage of masterbatch into the open mill, pass it through the mill three times at a roller temperature of 50-60℃, add all the vulcanizing agent, knead for 5-8 minutes and then sheet it out. Let it stand at room temperature for 12 hours to obtain the compound. Step 4: Compression vulcanization molding. The mixed rubber is placed into the mold and compressed at 165-175℃ for 8-12 minutes. After demolding, it is cured at room temperature for 2 hours to obtain the finished rubber product.

2. The method for preparing high-temperature resistant nitrile rubber material according to claim 1, characterized in that: The modified silica is silane coupling agent surface-modified fumed silica.

3. The method for preparing high-temperature resistant nitrile rubber material according to claim 1, characterized in that: The mass ratio of antioxidant MB to antioxidant 445 is 1:2.