Preparation method of nitrile rubber elastic layer and product

Abstract

The invention relates to a preparation method of a nitrile rubber elastic layer and a product. The method comprises the following steps: proportionally weighing nitrile rubber, an accelerant, stearic acid, an active agent zinc oxide, an anti-aging agent, sulfur, fumed silica and dioctyl phthalate for later use; uniformly mixing nitrile rubber with a plasticizer sizing material, and hanging and airing in a sheet shape to obtain a nitrile rubber sheet; and sequentially adding stearic acid, an active agent zinc oxide, an anti-aging agent, gas-phase white carbon black, an accelerant and sulfur, rolling the rubber sheet, discharging to obtain a nitrile rubber mixed rubber sheet green sheet, heating and pressurizing, preserving heat and pressure, immersing into concentrated sulfuric acid for treatment, taking out after treatment, cleaning until the surface is neutral, and finally drying to obtain the nitrile rubber elastic layer. The nitrile rubber elastic layer prepared by the method provided by the invention can provide good surface quality, solves the problems of bubbles, pores, uneven surface, low mechanical properties and the like of the nitrile rubber for the traditional missile engine shell, and has unchanged good processing characteristics.

Description

Technical Field

[0001] This invention relates to the elastic layer of a solid rocket winding engine casing, specifically to the preparation method and product of the nitrile rubber elastic layer. Background Technology

[0002] The connecting structure is a crucial component of solid rockets, primarily bearing the combined effects of various external loads such as tension, bending, and lateral shear, resulting in a complex stress state. The elastic layer, acting as an intermediate transition layer in the composite material connection, plays a vital role in coordinating deformation during load-bearing processes.

[0003] Currently popular methods for preparing elastic layers have encountered significant obstacles in practical applications due to their poor uniformity, instability, and the tendency to generate penetrating bubbles on the surface. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a nitrile rubber elastic layer. The elastic layer prepared by this method can effectively solve the above problems.

[0005] The technical solution adopted to achieve the purpose of this invention is a method for preparing a nitrile rubber elastic layer, comprising the following steps: Weigh out each component according to the following ratio: Nitrile rubber 1704: Accelerator TMTM: Stearic acid SA: Activator Zinc oxide ZnO: Antioxidant D: Sulfur S: Fumed silica: Dioctyl phthalate DOP = (18~22): 1: 5: 4: 2: (0.95~1.05): 15: 8. When passing the 1704 nitrile rubber compound through the roll wrapping rollers, dioctyl phthalate (DOP) is added. After the addition is complete, the nitrile rubber compound mixed with plasticizer is passed through the open mill until it is evenly mixed. After the end, the compound is sheeted and the sheet is hung to dry to obtain nitrile rubber sheet. The nitrile rubber sheet is repeatedly passed through a two-roll mill until it is evenly mixed. Then, stearic acid (SA), zinc oxide (ZnO), antioxidant (D), fumed silica, accelerator (TMTM), and sulfur (S) are added in sequence. The roller gap is adjusted according to the sheet thickness requirements, and the speed is adjusted by frequency conversion. After the sheet is wrapped around the roller, the raw nitrile rubber mixed sheet is obtained. The raw nitrile rubber mixed sheet is placed into a flat mold, heated and pressurized, and then kept warm and pressurized. After the molding time is over, the nitrile rubber elastic layer pre-vulcanized sheet is taken out from the hot mold. The pre-cured nitrile rubber elastic layer sheet is immersed in concentrated sulfuric acid. After the sulfuric acid treatment, the nitrile rubber elastic layer sheet is taken out, cleaned until the surface is neutral, and dried to obtain the nitrile rubber elastic layer.

[0006] The roles of each component used in this invention in this patent are as follows: Accelerator TMTM: It is a super-accelerator that, when combined with rubber compounds, provides good scorch resistance, fast vulcanization speed, and excellent vulcanization performance.

[0007] Stearic acid (SA): It has a softening and plasticizing effect on rubber, which can reduce the direct contact between the rubber compound and the equipment and play an external lubricating role.

[0008] Zinc oxide (ZnO), an active agent, reacts with stearic acid to form zinc stearate, which can improve the tear resistance of rubber and delay the thermal degradation process of rubber.

[0009] Antioxidant D: can inhibit the oxidation and aging of rubber.

[0010] Sulfur (S): It improves the mechanical properties of rubber through cross-linking reaction and acts as a vulcanizing agent to change the molecular structure of rubber and form a three-dimensional network structure.

[0011] Fumed silica: It is an excellent reinforcing agent for rubber, which can increase the strength of rubber by 40 times, the yield modulus by 10 times, and also significantly improve the elongation and creep properties.

[0012] Dioctyl phthalate (DOP): A rubber softener that makes rubber less prone to breakage during stretching and bending.

[0013] The nitrile rubber elastic layer obtained by the preparation method provided by the present invention has good surface quality and mechanical properties (such as Shore hardness, tensile breaking strength, toughness) and weather resistance (heat aging resistance, salt spray resistance, oil stain aging resistance) due to the addition of accelerator, activator, dioctyl phthalate and uniform dispersion with nitrile rubber in proportion. It solves the problems of bubbles, pores, uneven surface and low mechanical properties of nitrile rubber used in traditional missile engine casings, while maintaining good processing characteristics. Attached Figure Description

[0014] Figure 1 This is a flowchart of the method for preparing the nitrile rubber elastic layer of the present invention. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] like Figure 1 As shown, the method for preparing the nitrile rubber elastic layer in this embodiment includes the following steps: S1. Weigh the raw materials of each component: Nitrile rubber 1704: Accelerator TMTM: Stearic acid SA: Activator Zinc oxide ZnO: Antioxidant D: Sulfur S: Fumed silica: Dioctyl phthalate DOP=20:1:5:4:2:1:15:8. Weigh each component for later use.

[0017] S2. Raw material processing: Cut the nitrile rubber 1704 into blocks, each weighing 0.1kg to 0.2kg. Set the open mill roll gap to (2 to 3)mm, the frequency converter speed to (20 to 30)Hz, and the roll temperature not exceeding 50℃. Then, feed the cut nitrile rubber blocks into the open mill for breaking up the rubber. The nitrile rubber blocks are repeatedly passed through the open mill 2 to 3 times.

[0018] S3. Plasticizing: Adjust the roll gap to (1-2) mm. When the nitrile rubber compound passes through the rolls, add 1 / 3 of the plasticizer, dioctyl phthalate (DOP), in three additions over approximately ten minutes. After addition, adjust the roll gap to (0.5-1) mm, set the frequency converter speed to (35-45) Hz, and, with the roll temperature not exceeding 50°C, pass the nitrile rubber compound mixed with plasticizer through the open mill 2-3 times. After completion, unload the sheet and hang it to dry until the temperature does not exceed 30°C to obtain the plasticized nitrile rubber sheet.

[0019] S4. Mixing: Adjust the roller gap of the open mill to (0.5~1)mm and the frequency converter speed to (35~40)Hz. Pass the nitrile rubber plasticized sheet through the mill 2~3 times until it is mixed evenly.

[0020] Add stearic acid according to the component ratio, adjust the roller gap to (2.5~3)mm, adjust the frequency conversion speed to (40~50)Hz, so that the nitrile rubber compound wraps around the roller and passes through twice repeatedly, and control the roller temperature to not exceed 50℃.

[0021] Add zinc oxide according to the component ratio, with a roller gap of (3-3.5) mm and a variable frequency speed of (50-60) Hz. Make the nitrile rubber compound wrap around the roller and pass through it repeatedly 3 times, controlling the roller temperature to not exceed 50℃.

[0022] Add antioxidant D according to the component ratio, with a roller gap of (2-3) mm and a variable frequency speed of (40-50) Hz. Make the nitrile rubber compound wrap around the roller and pass through it repeatedly 2-3 times, controlling the roller temperature to not exceed 50℃.

[0023] Add silica according to the component ratio, adjust the roller gap to (2.5~3.5)mm, adjust the frequency converter speed to (50~60)Hz, so that the nitrile rubber compound wraps around the roller and passes through repeatedly 2-3 times, and control the roller temperature to not exceed 50℃.

[0024] Add accelerator TMTM according to the component ratio, adjust the roller gap to (2.5~3.5)mm, adjust the frequency converter speed to (50~60)Hz, so that the nitrile rubber compound wraps around the roller and passes through repeatedly 2-3 times, and control the roller temperature to not exceed 50℃.

[0025] Add sulfur (S) according to the component ratio, adjust the roller gap to (2.5~3.5) mm, adjust the frequency conversion speed to (50~60) Hz, and make the nitrile rubber compound wrap around the roller, passing through it repeatedly 2-3 times, controlling the roller temperature to not exceed 50℃.

[0026] Adjust the roller gap to (0.5~1)mm, set the frequency converter speed to (35~40)Hz, pass through the thin roller 2-3 times, and control the roller temperature to not exceed 50℃.

[0027] Adjust the roller gap according to the required sheet thickness, and set the frequency converter speed to (20~30) Hz. After the film is wrapped around the roller, the sheet is produced as a raw nitrile rubber mixed film.

[0028] S5, Molding Mold preheating: Start the flat vulcanizing machine, place the flat mold into the heating platform of the vulcanizing machine, so that the flat mold is in contact with the upper and lower heating plates of the vulcanizing machine, and the temperature rises to (110±10)℃ as the equipment heats up.

[0029] Compression molding: Place the raw nitrile rubber mixed sheet into the mold, heat to (110±10)℃, pressurize (20-22)MPa, degas 4-6 times, and keep warm and pressurized for 50-60 minutes.

[0030] Demolding: After the molding time is over, remove the pre-cured nitrile rubber elastic layer from the hot mold. To avoid tearing the elastic part, place it on a clean and flat surface and cover it with a clean release film or cotton cloth.

[0031] S6, sulfonation treatment Wipe the pre-cured nitrile rubber elastic layer with ethyl acetate and let it air dry for 5-10 minutes. Acid treatment: Immerse the pre-vulcanized sheet of nitrile rubber elastic layer in 95% to 98% concentrated sulfuric acid for 80 ± 5 seconds. Cleaning: After sulfuric acid treatment, remove the nitrile rubber elastic layer gel sheet, rinse with pure water, wipe the rubber surface with degreased cotton until the surface is neutral (the pH value is 7 when tested with pH test paper), and finally wipe the surface dry with degreased cotton or cotton cloth. Drying: Set the oven temperature to 50℃ and the time to 90min; lay a plastic film on the oven trolley and place the acid-treated elastic layer on the surface of the film; Drying: close the oven door, start the oven, keep it at 50±5℃ for 90min, and then remove the elastic layer.

[0032] The performance tests of the samples prepared according to steps S1-S6 above are as follows: Elongation at break ≥300% GB / T528-2009 Tensile strength ≥10MPa GB / T528-2009 Density ≤ 1.05 g / cm³ QJ917A-1997 Shore hardness ≤ 50 GB / T531.1-2008 The above performance tests show that the nitrile rubber elastic layer prepared by the method of the present invention can provide good surface quality, solve the problems of bubbles, pores, uneven surface, and low mechanical properties of nitrile rubber used in traditional missile engine casings, and at the same time has good processing characteristics without change.

Claims

1. A method for preparing a nitrile rubber elastic layer, comprising the following steps: Weigh out each component according to the following ratio: Nitrile rubber 1704: Accelerator TMTM: Stearic acid SA: Activator Zinc oxide ZnO: Antioxidant D: Sulfur S: Fumed silica: Dioctyl phthalate DOP = (18~22):1:5:4:2:(0.95~1.05):15:

8. When passing the 1704 nitrile rubber compound through the roll wrapping rollers, dioctyl phthalate (DOP) is added. After the addition is complete, the nitrile rubber compound mixed with plasticizer is passed through the open mill until it is evenly mixed. After the end, the compound is sheeted and the sheet is hung to dry to obtain nitrile rubber sheet. The nitrile rubber sheet is repeatedly passed through a two-roll mill until it is evenly mixed. Then, stearic acid (SA), zinc oxide (ZnO), antioxidant (D), fumed silica, accelerator (TMTM), and sulfur (S) are added in sequence. The roller gap is adjusted according to the sheet thickness requirements, and the speed is adjusted by frequency conversion. After the sheet is wrapped around the roller, the raw nitrile rubber mixed sheet is obtained. The raw nitrile rubber mixed sheet is placed into a flat mold, heated and pressurized, and then kept warm and pressurized. After the molding time is over, the nitrile rubber elastic layer pre-vulcanized sheet is taken out from the hot mold. The pre-cured nitrile rubber elastic layer sheet is immersed in concentrated sulfuric acid. After the sulfuric acid treatment, the nitrile rubber elastic layer sheet is taken out, cleaned until the surface is neutral, and dried to obtain the nitrile rubber elastic layer.

2. The method for preparing the nitrile rubber elastic layer according to claim 1, characterized in that: Nitrile rubber 1704 is cut into blocks, each weighing 0.1kg to 0.2kg. The open mill roll gap is set to 2 to 3mm, the frequency converter speed is set to 20 to 30Hz, and the roll temperature does not exceed 50℃. The cut nitrile rubber blocks are then fed into the open mill for breaking down. The nitrile rubber blocks are repeatedly passed through the open mill to obtain nitrile rubber 1704 compound.

3. The method for preparing the nitrile rubber elastic layer according to claim 1, characterized in that... The process of adding dioctyl phthalate (DOP) is as follows: Adjust the roller gap of the open mill to 1-2 mm, and add DOP in three batches when the nitrile rubber compound passes through the rolls, each batch containing one-third of the compound. After the addition is complete, adjust the roller gap of the open mill to 0.5-1 mm, adjust the frequency converter speed to 35-45 Hz, and ensure the roller temperature does not exceed 50°C. Then, mix the nitrile rubber 1704 compound with DOP on the open mill until the mixture is homogeneous, and finally sheet the compound.

4. The method for preparing the nitrile rubber elastic layer according to claim 3, characterized in that: After completion, remove the film and hang it in a sheet to dry until the temperature does not exceed 30°C.

5. The method for preparing the nitrile rubber elastic layer according to claim 4, characterized in that: The nitrile rubber plasticized sheet is obtained by hanging the sheet to dry. The roller gap of the open mill is adjusted to 0.5-1mm and the frequency converter speed is adjusted to 35-40Hz. The nitrile rubber plasticized sheet is repeatedly passed through the mill until it is evenly mixed.

6. The method for preparing the nitrile rubber elastic layer according to claim 5, characterized in that: The process of sequentially adding stearic acid (SA), activator zinc oxide (ZnO), antioxidant (D), fumed silica, accelerator (TMTM), and sulfur (S) is as follows: Add stearic acid according to the component ratio, adjust the roller gap to 2.5-3mm, and adjust the frequency converter speed to 40-50Hz to make the nitrile rubber mixture wrap around the roller and pass through repeatedly until it is evenly mixed. Add zinc oxide according to the component ratio, adjust the roller gap to 3-3.5mm, and adjust the frequency converter speed to 50-60Hz, so that the nitrile rubber mixture wraps around the roller and passes through repeatedly until it is mixed evenly; Add antioxidant D according to the component ratio, adjust the roller gap to 2-3mm, and adjust the frequency conversion speed to 40-50Hz. Make the nitrile rubber mixture wrap around the roller and pass through repeatedly until it is evenly mixed. Add silica according to the component ratio, adjust the roller gap to 2.5-3.5mm, and adjust the frequency converter speed to 50-60Hz, so that the nitrile rubber mixture wraps around the roller and passes through repeatedly until it is mixed evenly; Add accelerator TMTM according to the component ratio, adjust the roller gap to 2.5-3.5mm, and adjust the frequency converter speed to 50-60Hz. Allow the nitrile rubber mixture to wrap around the rollers repeatedly until it is uniformly mixed, controlling the roller temperature to not exceed 50℃. Add sulfur (S) according to the component ratio, adjust the roller gap to 2.5-3.5mm, and adjust the frequency converter speed to 50-60Hz. Allow the nitrile rubber mixture to wrap around the rollers repeatedly until it is uniformly mixed, controlling the roller temperature to not exceed 50℃. Adjust the roller gap according to the required sheet thickness, and set the frequency converter speed to 20-30Hz. After the film is wrapped around the roller, the sheet is produced as a raw nitrile rubber blend film.

7. The method for preparing the nitrile rubber elastic layer according to claim 6, characterized in that: Before placing the raw nitrile rubber compound into the mold, preheat the mold: Start the flat vulcanizing machine, place the flat mold into the heating platform of the vulcanizing machine, so that the flat mold is in contact with the upper and lower heating plates of the vulcanizing machine, and heat it to (110±10)℃ as the equipment heats up. After the mold is preheated, place the raw nitrile rubber compound into the flat mold, heat it to (110±10)℃, pressurize it to 20-22MPa, exhaust it 4 to 6 times, and keep it at the temperature and pressure for 50 to 60 minutes.

8. The method for preparing the nitrile rubber elastic layer according to claim 7, characterized in that: The pre-vulcanized sheet of nitrile rubber elastic layer is immersed in 95%–98% concentrated sulfuric acid for 80 ± 5 seconds.

9. The method for preparing the nitrile rubber elastic layer according to claim 8, characterized in that: The process involves placing the gelled nitrile rubber elastic layer sheet in an oven for drying; laying a plastic film on the oven trolley and placing the acid-treated elastic layer on the surface of the film; starting the oven and removing the nitrile rubber elastic layer after the heat preservation period is complete.

10. A nitrile rubber elastic layer, characterized in that: The nitrile rubber elastic layer prepared by any one of the preparation methods described in claims 1-9.

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