Emulsion-resistant rubber sealing material and mixing process thereof

Abstract

The invention discloses a rubber sealing material for emulsion resistance. The rubber sealing material is prepared from the following raw materials in parts by mass: 80-90 parts of nitrile butadiene rubber (NBR) raw rubber; 10 to 20 parts of nylon 6 (PA6) powder; 5-10 parts of indirect method zinc oxide; 3-5 parts of a calcium-zinc composite stabilizer; 10 to 20 parts of carbon black N550; 1 part of polyethylene wax; 2 parts of a carbon black dispersant; 5 parts of a plasticizer DOP; 1 to 1.5 parts of sulfur; 2 parts of an accelerant CZ; 2 parts of an accelerant TMTD; wherein the acrylonitrile content of the nitrile rubber is 19%, the particle size of nylon 6 (PA6) powder is 300-400 meshes, the nylon 6 (PA6) powder is dispersed in the rubber matrix in a physical mixing mode to form a multiphase composite material system, the calcium-zinc composite stabilizer comprises a compound of calcium stearate and zinc stearate, the mass ratio of the calcium stearate to the zinc stearate is (2-3): 1, the nitrile rubber is JSR250S type rubber, the Mooney viscosity ML (1 + 4) 100 DEG C of the nitrile rubber is 45-55, and the nylon 6 (PA6) powder is 5-10%. The specific surface area of the carbon black N550 is 35-45 m < 2 > / g, the DBP absorption value is 110-130 cm < 3 > / 100 g, and the carbon black N550 is low in swelling rate in emulsion and free of local reaction.

Description

Technical Field

[0001] The present invention relates to the field of rubber and plastic sealing, in particular to an emulsion-resistant rubber sealing material. Background Art

[0002] Rolling oil emulsions are a mixture of water and oil, forming an unstable two-phase equilibrium system through vigorous stirring. If the dispersed phase is oil and the continuous phase is water, an O / W (oil-in-water) emulsion is formed; conversely, a W / O (water-in-oil) emulsion is formed. While the strip and rolls are in motion, the emulsion is sprayed onto the workpiece surface, partially disrupting the equilibrium and forming an oil film on the strip and roll surfaces. This film lubricates and prevents rust. Furthermore, the circulating emulsion cools and cleans the strip and rolls. Current rolling oil emulsions used in steel mills are typically O / W, with an oil concentration of 2% to 3%. The oil is composed of a base lubricant, surfactants, rust inhibitors, oiliness enhancers, antioxidants, viscosity reducers, and extreme pressure agents, and is generally weakly acidic or neutral.

[0003] To prevent roll emulsion, iron oxide scale, dust, and other harmful impurities from entering the bearings and causing bearing failure, a layer of rolling oil emulsion-resistant rubber seal must be added to the outside of the bearing oil seal. Due to the temperature rise of the bearing and the friction between the seal and the dynamic seal, heat conduction from the hot rolls, the operating temperature of the seal reaches 70-100°C. In this environment, the seal is highly susceptible to oxygen and ozone, causing it to age and lose its sealing effectiveness. Therefore, the seal must have excellent emulsion resistance.

[0004] Ordinary rubber materials swell or locally react in emulsions to form dot-shaped protrusions, which reduces the wear resistance of the rubber and causes sealing failure. The emulsion-resistant rubber formula of the present invention has a low swelling rate in the emulsion and no local reaction. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an emulsion-resistant rubber sealing material, which has a low swelling rate in the emulsion and has no local reaction.

[0006] The present invention adopts the following technical solutions to achieve the invention objectives:

[0007] An emulsion-resistant rubber sealing material is composed of the following raw materials in parts by mass:

[0008] 80-90 parts of nitrile rubber (NBR) raw rubber;

[0009] 10-20 parts of nylon 6 (PA6) powder;

[0010] 5-10 parts of indirect zinc oxide;

[0011] 3-5 parts of calcium zinc composite stabilizer;

[0012] Carbon black N550 10-20 parts;

[0013] 1 part polyethylene wax;

[0014] 2 parts of carbon black dispersant;

[0015] Plasticizer DOP 5 parts;

[0016] 1-1.5 parts of sulfur;

[0017] 2 parts of accelerator CZ;

[0018] 2 parts of accelerator TMTD;

[0019] The acrylonitrile content of the nitrile rubber is 19%.

[0020] As a further limitation of the present technical solution, the particle size of the nylon 6 (PA6) powder is 300-400 mesh, and is dispersed in the rubber matrix by physical mixing to form a multiphase composite material system.

[0021] As a further limitation of the present technical solution, the calcium-zinc composite stabilizer comprises a complex of calcium stearate and zinc stearate in a mass ratio of (2-3):1.

[0022] As a further limitation of the present technical solution, the nitrile rubber is JSR250S model rubber, and its Mooney viscosity ML (1+4) at 100°C is 45-55.

[0023] As a further limitation of this technical solution, the specific surface area of the carbon black N550 is 35-45m 2 / g, DBP absorption value is 110-130cm 3 / 100g.

[0024] As a further limitation of the present technical solution, in an emulsion resistance test at 100°C for 70 hours, the volume change rate is ≤4%, and the hardness change is ≤+3 Shore A degrees.

[0025] The mixing process of the emulsion-resistant rubber sealing material comprises the following steps:

[0026] (1) Pre-mixing: Mix the nitrile rubber and nylon 6 powder in an internal mixer at a pressure of 0.5-0.7 MPa for 120-180 seconds;

[0027] (2) Stabilization treatment: Add calcium zinc composite stabilizer and continue mixing until the temperature reaches 115-125℃, then discharge the glue and cool to below 50℃;

[0028] (3) Main mixing: Add indirect zinc oxide and polyethylene wax in sequence and mix for 30 seconds, then add carbon black N550, DOP and dispersant and mix to 130-140°C;

[0029] (4) Final refining: Add the vulcanization system on the open mill and control the roller temperature to 40-60℃.

[0030] As a further limitation of the present technical solution, step (1) adopts a two-stage mixing method, wherein the pressure in the first stage is 0.3-0.5 MPa and the mixing is carried out for 60-90 seconds, and the pressure in the second stage is increased to 0.6-0.8 MPa and the mixing is carried out for 60-90 seconds.

[0031] A sealing product is made of a rubber material through a one-step vulcanization process at 180°C for 3 minutes. The product is a dynamic seal that contacts a rolling oil emulsion.

[0032] As a further limitation of the present technical solution, the operating temperature range of the dynamic seal is 70-100° C., the volume swelling rate in an O / W emulsion environment is ≤5%, and the tensile strength retention rate is ≥85%.

[0033] Compared with the prior art, the advantages and positive effects of the present invention are:

[0034] Through a unique formula design, the material's volume change rate in a 100°C x 70h emulsion immersion test is strictly controlled to ≤4% (+3.5% measured in Example 2), which is more than 40% lower than traditional NBR materials (≥6%). This characteristic is due to two innovative mechanisms:

[0035] Dual-phase barrier effect: The low-acrylonitrile NBR (AN 19%) matrix, with its moderate polarity, forms a physically cross-linked network with 300-400 mesh PA6 powder, effectively blocking the permeation path of the oil phase components (base oil, surfactant) in the emulsion. Electron microscopy analysis shows that the PA6 particles, 5-10 μm in size, are evenly dispersed, forming a labyrinthine barrier structure within the rubber matrix.

[0036] Improved dynamic stability: The calcium-zinc stabilizer forms a metal ion chelate layer at the PA6 / rubber interface (EDS detected Ca and Zn concentrations of 1.2-1.5wt%), inhibiting the erosion of the interface by polar molecules in the emulsion at high temperatures. Comparative experiments show that materials without the stabilizer exhibit 3-5μm interfacial cracks under the same conditions, resulting in a volume swelling ratio of +5.1.

[0037] The material exhibits outstanding mechanical stability in a long-term thermo-mechanical coupling environment:

[0038] Breakthrough strength retention: After aging at 100°C for 70 hours, the tensile strength retention rate is ≥85% (91% in Example 2), an increase of more than 20% over the control example (≤75%). This is due to the PA6's rigidity enhancement and the synergistic protection of the calcium-zinc stabilizer: the zinc stearate in the stabilizer captures free radicals (FTIR detection shows a 62% decrease in the carbonyl index after aging), while the PA6 crystalline region (melting point of 220°C as measured by DSC) effectively inhibits the thermal motion of the rubber molecular chains.

[0039] Enhanced compression set resistance: Dynamic sealing tests show that the material's permanent compression set at 100°C for 24 hours is only 15-18%, 40% lower than that of traditional hydrogenated nitrile rubber (25-30%). This allows the seal to maintain stable contact pressure even under roller vibration conditions (measured lip pressure fluctuation ≤ 5%).

[0040] This solution breaks through the traditional technical route of rubber modification and creatively achieves:

[0041] Process simplification: Using PA6 physical blending instead of chemical grafting, mixing time is shortened from 15-20 minutes in the traditional process to 10-12 minutes (a 30% efficiency improvement), and no pre-activation treatment is required. Internal mixer power monitoring shows that the optimized two-stage mixing process (0.5-0.7MPa partial pressure control) reduces energy consumption by 25%.

[0042] Enhanced quality controllability: By precisely controlling the final temperature of the main mixing process (135±5°C), the PA6 is fully dispersed (image analysis shows a dispersion uniformity of 94.2%) while preventing thermal degradation (TGA analysis shows the onset temperature of PA6 thermal weight loss remains above 220°C). Compared with traditional nano-modification processes, the Mooney viscosity fluctuation range of the finished rubber is reduced from ±5 to ±2.

[0043] Environmental breakthrough: DOP plasticizer dosage is reduced by 30% (only 5 parts are needed), and due to the reinforcement of PA6, the density of the vulcanized rubber is reduced by 8% (1.18→1.09g / cm 3 ), and the raw material cost of a single product decreased by 12%. Industrial application data shows that a production line with an annual output of 100,000 seals can reduce VOC emissions by 1.2 tons / year. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a graph showing the relationship between the acrylonitrile content of different raw rubber materials and their performance changes in oil resistance tests. DETAILED DESCRIPTION

[0045] 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.

[0046] like Figure 1 As shown in Figure 2, the relationship between the acrylonitrile content of different raw rubber materials (JSR250S and JSR220S) and their performance changes in the oil resistance test (100°C × 70 hours emulsion resistance test) includes:

[0047] Material comparison:

[0048] JSR250S: Acrylonitrile content 19% (lower)

[0049] JSR220S: Acrylonitrile content 40% (higher)

[0050] Test indicators:

[0051] Hardness change: Hardness change of the material after being immersed in oil medium (Shore A hardness)

[0052] Volume change: Volume change rate caused by material swelling due to oil absorption (%)

[0053] Base material selection: JSR250S nitrile rubber (19% acrylonitrile, Mooney viscosity ML (1+4) at 100°C = 45-55) is used to balance polarity and processability. DSC testing shows a glass transition temperature (Tg) of -21°C, ensuring performance over a wide temperature range of -30°C to 120°C.

[0054] Modification system:

[0055] Nylon 6 (PA6) powder: Particle size 300-400 mesh (measured by a laser particle size analyzer), physically blended to form an island-in-the-sea structure. When the PA6 content reaches 15 parts per million, the tensile strength increases by 23%, and the elongation at break retention rate exceeds 85%.

[0056] Calcium zinc composite stabilizer: Calcium stearate / zinc stearate mass ratio (2-3): 1, reduces heavy metal pollution compared to traditional lead salt systems, and has a heat aging coefficient of 0.87 at 175°C (ASTM D573 standard).

[0057] Functional additives:

[0058] Carbon black N550: specific surface area 38-42m 2 / g (BET method), DBP absorption value 115-125cm 3 / 100g, building a three-dimensional conductive network, and the volume resistivity is reduced to 2.1×10 8 Ω·cm.

[0059] Polyethylene wax: molecular weight 1500-2000, significantly improves the dispersibility of PA6 and reduces the Mooney viscosity of the compound by 12-15 units.

[0060] Examples 1-3 (basic formula examples)

[0061] Table 1 Composition of Examples 1-3 (parts by mass)

[0062]

[0063]

[0064] Preparation method:

[0065] 1. Pre-mixing: Put NBR raw rubber and PA6 powder into internal mixer, mix for 90 seconds at an initial pressure of 0.5 MPa, then increase the pressure to 0.7 MPa and continue mixing for 90 seconds.

[0066] 2. Stabilization treatment: Add calcium zinc stabilizer, adjust the speed of the internal mixer to 40 rpm, and mix until the material temperature reaches 120°C (about 5 minutes).

[0067] 3. Main mixing: Add zinc oxide and polyethylene wax in sequence and mix for 30 seconds, then add carbon black, DOP and dispersant, mix to 135℃, and clean the mixing chamber wall twice during the process.

[0068] 4. Final refining: Add sulfur and accelerator into the open mill (roller temperature 50℃), pass the mill 5 times, then remove the sheet and leave it for 24 hours.

[0069] 5. Vulcanization process: Place the mixed rubber in a mold and vulcanize it at 180℃ for 3 minutes to produce a standard test piece (thickness 2mm) and a sealing ring sample.

[0070] Example 4 (Process Parameter Example)

[0071] The same formulation as in Example 2 was used, but the mixing process was adjusted:

[0072] 1. Pre-mixing stage: pressurization in three stages (0.3MPa×60s→0.5MPa×60s→0.7MPa×60s); 2. Stabilization endpoint temperature: increased to 125°C, and mixing time extended to 7 minutes; 3. Tests showed: the tensile strength of the material increased to 18.2MPa (originally 17.8MPa), and the volume swelling rate decreased to 3.5%.

[0073] Comparative Examples 1-3 (Comparison of Key Components)

[0074] Table 2 Comparative Example Formula (parts by mass)

[0075]

[0076]

[0077] Performance comparison data:

[0078]

[0079] Example 5 (Extreme Working Condition Verification)

[0080] The sealing ring prepared in Example 2 was installed in the bearing position of the rolling mill for field testing:

[0081] Working conditions: emulsion temperature 85℃, pH 6.2, oil concentration 3.2%

[0082] Run results:

[0083] After 1200 hours of continuous operation, the wear of the sealing lip is ≤0.15mm

[0084] No emulsion leakage, pollutant content in the bearing cavity <50ppm

[0085] Compared with traditional seals (ordinary NBR), the service life is increased by 3.2 times

[0086] Example 6 (Material Microstructure Analysis)

[0087] The cross-sectional morphologies of Example 2 and Comparative Example 2 were observed by scanning electron microscopy (SEM):

[0088] Example 2: PA6 particles (5-10 μm in diameter) are uniformly dispersed in the rubber matrix, and a transition layer formed by calcium zinc stabilizers exists at the interface (EDS detects the enrichment of Ca and Zn elements)

[0089] Comparative Example 2: There are obvious cracks (width 2-5 μm) at the interface between PA6 and rubber, and phase separation occurs in some areas. Experimental Example 7 (Accelerated Aging Test)

[0090] The samples of Examples 1-3 were immersed in an emulsion at 100°C for 168 hours and tested:

[0091]

[0092] Through a unique formula design, the material's volume change rate in a 100°C x 70h emulsion immersion test is strictly controlled to ≤4% (+3.5% measured in Example 2), which is more than 40% lower than traditional NBR materials (≥6%). This characteristic is due to two innovative mechanisms:

[0093] Dual-phase barrier effect: The low-acrylonitrile NBR (AN 19%) matrix, with its moderate polarity, forms a physically cross-linked network with 300-400 mesh PA6 powder, effectively blocking the permeation path of the oil phase components (base oil, surfactant) in the emulsion. Electron microscopy analysis shows that the PA6 particles, 5-10 μm in size, are evenly dispersed, forming a labyrinthine barrier structure within the rubber matrix.

[0094] Improved dynamic stability: The calcium-zinc stabilizer forms a metal ion chelate layer at the PA6 / rubber interface (EDS detected Ca and Zn concentrations of 1.2-1.5wt%), inhibiting the erosion of the interface by polar molecules in the emulsion at high temperatures. Comparative experiments show that materials without the stabilizer exhibit 3-5μm interfacial cracks under the same conditions, resulting in a volume swelling ratio of +5.1.

[0095] The material exhibits outstanding mechanical stability in a long-term thermo-mechanical coupling environment:

[0096] Breakthrough strength retention: After aging at 100°C for 70 hours, the tensile strength retention rate is ≥85% (91% in Example 2), an increase of more than 20% over the control example (≤75%). This is due to the PA6's rigidity enhancement and the synergistic protection of the calcium-zinc stabilizer: the zinc stearate in the stabilizer captures free radicals (FTIR detection shows a 62% decrease in the carbonyl index after aging), while the PA6 crystalline region (melting point of 220°C as measured by DSC) effectively inhibits the thermal motion of the rubber molecular chains.

[0097] Enhanced compression set resistance: Dynamic sealing tests show that the material's permanent compression set at 100°C for 24 hours is only 15-18%, 40% lower than that of traditional hydrogenated nitrile rubber (25-30%). This allows the seal to maintain stable contact pressure even under roller vibration conditions (measured lip pressure fluctuation ≤ 5%).

[0098] This solution breaks through the traditional technical route of rubber modification and creatively achieves:

[0099] Process simplification: Using PA6 physical blending instead of chemical grafting, mixing time is shortened from 15-20 minutes in the traditional process to 10-12 minutes (a 30% efficiency improvement), and no pre-activation treatment is required. Internal mixer power monitoring shows that the optimized two-stage mixing process (0.5-0.7MPa partial pressure control) reduces energy consumption by 25%.

[0100] Enhanced quality controllability: By precisely controlling the final temperature of the main mixing process (135±5°C), the PA6 is fully dispersed (image analysis shows a dispersion uniformity of 94.2%) while preventing thermal degradation (TGA analysis shows the onset temperature of PA6 thermal weight loss remains above 220°C). Compared with traditional nano-modification processes, the Mooney viscosity fluctuation range of the finished rubber is reduced from ±5 to ±2.

[0101] Environmental breakthrough: DOP plasticizer dosage is reduced by 30% (only 5 parts are needed), and due to the reinforcement of PA6, the density of the vulcanized rubber is reduced by 8% (1.18→1.09g / cm 3 ), and the raw material cost of a single product decreased by 12%. Industrial application data shows that a production line with an annual output of 100,000 seals can reduce VOC emissions by 1.2 tons / year.

Claims

1. An emulsion-resistant rubber sealing material, characterized in that It is composed of the following raw materials in parts by mass: 80-90 parts of raw rubber; 10-20 parts of nylon powder; 5-10 parts of indirect zinc oxide; 3-5 parts of calcium zinc composite stabilizer; Carbon black N550 10-20 parts; 1 part polyethylene wax; 2 parts of carbon black dispersant; Plasticizer DOP 5 parts; 1-1.5 parts of sulfur; 2 parts of accelerator CZ; 2 parts of accelerator TMTD; The acrylonitrile content of the nitrile rubber is 19%.

2. The emulsion-resistant rubber sealing material according to claim 1, characterized in that: The particle size of the nylon powder is 300-400 meshes, and the nylon powder is dispersed in the rubber matrix in a physical mixing manner to form a multiphase composite material system.

3. The emulsion-resistant rubber sealing material according to claim 1, characterized in that: The calcium-zinc composite stabilizer comprises a composite of calcium stearate and zinc stearate in a mass ratio of (2-3):

1.

4. The emulsion-resistant rubber sealing material according to claim 1, characterized in that: The nitrile rubber is a JSR250S rubber, and its Mooney viscosity ML (1+4) at 100° C. is 45-55.

5. The emulsion-resistant rubber sealing material according to claim 1, characterized in that: The specific surface area of the carbon black N550 is 35-45m 2 / g, DBP absorption value is 110-130cm 3 / 100g.

6. The emulsion-resistant rubber sealing material according to claim 1, characterized in that: In the emulsion resistance test at 100℃×70h, the volume change rate is ≤4%, and the hardness change is ≤+3 Shore A degrees.

7. The mixing process of the emulsion-resistant rubber sealing material according to any one of claims 1 to 6, characterized in that The following steps are involved: (1) Pre-mixing: Mix the nitrile rubber and nylon 6 powder in an internal mixer at a pressure of 0.5-0.7 MPa for 120-180 seconds; (2) Stabilization treatment: Add calcium zinc composite stabilizer and continue mixing until the temperature reaches 115-125℃, then discharge the glue and cool to below 50℃; (3) Main mixing: Add indirect zinc oxide and polyethylene wax in sequence and mix for 30 seconds, then add carbon black N550, DOP and dispersant and mix to 130-140°C; (4) Final refining: Add the vulcanization system on the open mill and control the roller temperature to 40-60℃.

8. The mixing process according to claim 7, wherein: In step (1), a two-stage mixing method is adopted, wherein the pressure in the first stage is 0.3-0.5 MPa and the mixing is performed for 60-90 seconds, and the pressure in the second stage is increased to 0.6-0.8 MPa and the mixing is performed for 60-90 seconds.

9. A sealing product, characterized in that The product is made by subjecting the rubber material according to any one of claims 1 to 6 to a single vulcanization process at 180° C. for 3 minutes, and the product is a dynamic seal that contacts a rolling oil emulsion.

10. The sealing product according to claim 9, characterized in that The operating temperature range of the dynamic seal is 70-100°C.

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