Packing pressing cap oil seal and preparation method

Abstract

The invention provides a packing pressing cap oil seal and a preparation method of the packing pressing cap oil seal, and belongs to the technical field of oil seal materials. Comprising the following components: 100 parts of nitrile rubber, 22-24 parts of carbon black, 8-10 parts of acid-etched potassium hexatitanate, 6-8 parts of maleic anhydride modified nano calcium carbonate, 1.2-1.5 parts of an anti-aging agent, 12-13 parts of a plasticizer, 1-2 parts of an accelerant, 1-1.3 parts of sulfur, 6-7 parts of zinc oxide and 2 parts of stearic acid. According to the method, the elongation at break of the prepared packing pressing cap oil seal can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil seal materials, and particularly relates to a packing gland oil seal and a preparation method thereof. Background Art

[0002] The packing gland oil seal has the characteristics of good sealing performance and long service life, and is widely applicable to the petroleum field. The main material of the packing gland oil seal is nitrile rubber because nitrile rubber has excellent oil resistance and wear resistance, and the processability and adhesiveness of nitrile rubber are good, which is convenient for the stable combination of the seal and metal parts.

[0003] When the packing gland oil seal is exposed to sunlight for a long time, due to the poor ultraviolet resistance of nitrile rubber, ultraviolet rays will accelerate the breakage of nitrile rubber molecular chains, resulting in surface cracking and hardening of the packing gland oil seal, and the sealing performance will be significantly reduced, that is, the aging phenomenon is relatively serious. In order to alleviate the defect of poor ultraviolet resistance of nitrile rubber, the existing operation is to add carbon black or titanium dioxide to nitrile rubber. Carbon black or titanium dioxide can absorb or reflect ultraviolet light (200 - 400nm) and reduce the ultraviolet penetration depth.

[0004] However, when the amount of carbon black added is small, the ultraviolet resistance of nitrile rubber cannot be improved well; while adding too much carbon black, although it can further improve the ultraviolet resistance of nitrile rubber, it will increase the brittleness of the prepared packing gland oil seal material, resulting in a decrease in its elongation at break. Summary of the Invention

[0005] To solve the problems in the background art, the present invention provides a packing gland oil seal and a preparation method thereof, which can effectively improve the elongation at break of the prepared packing gland oil seal.

[0006] To achieve the above object, in a first aspect, the present invention provides a packing gland oil seal, which comprises the following components by weight: 100 parts of nitrile rubber, 22 - 24 parts of carbon black, 8 - 10 parts of acid-etched potassium hexatitanate, 6 - 8 parts of maleic anhydride-modified nano calcium carbonate, 1.2 - 1.5 parts of antioxidant, 12 - 13 parts of plasticizer, 1 - 2 parts of accelerator, 1 - 1.3 parts of sulfur, 6 - 7 parts of zinc oxide, and 2 parts of stearic acid.

[0007] Further, the preparation method of the acid-etched potassium hexatitanate is as follows: potassium hexatitanate is ultrasonically cleaned, dried, immersed in an acid solution, stirred and etched for 60 - 80 min, and then rinsed to neutrality to obtain it.

[0008] Further, the acid solution is an oxalic acid solution with a concentration of 7 - 10 wt%.

[0009] Further, the preparation method of the maleic anhydride modified nano calcium carbonate is as follows: Add 1.45 - 1.6 g of sodium stearate to 2 kg of calcium hydroxide suspension with a mass fraction of 3.5% - 4.0% to obtain a first reaction solution; Introduce carbon dioxide gas into the first reaction solution and react for 30 - 35 min to obtain a second reaction solution; Add 2.0 - 2.5 g of maleic anhydride to the second reaction solution and react for 30 - 35 min to obtain a third reaction solution; Perform precipitation, suction filtration and washing on the third reaction solution, and dry the obtained solid to obtain the maleic anhydride modified nano calcium carbonate.

[0010] Further, the flow rate of the carbon dioxide gas is 8 - 10 L / min.

[0011] Further, the drying temperature is 50 - 55 °C and the drying time is 170 - 180 min.

[0012] In the second aspect, the present invention provides a preparation method of the above-mentioned packing gland oil seal, including the following steps: S1. Add nitrile rubber, zinc oxide, stearic acid and antioxidant to the internal mixer in sequence and mix to obtain a first mixture; Add carbon black, acid-etched potassium hexatitanate, plasticizer and maleic anhydride modified nano calcium carbonate to the first mixture in sequence and mix until discharging at 135 °C to obtain a first colloid; S2. Add the first colloid obtained in S1 to the open mill, add accelerator, add sulfur, pass thinly 5 times and then take off the sheet, and let it stand for 24 h to obtain the oil seal material; S3. Use the mold pressing method to prepare the above-mentioned packing gland oil seal on a flat vulcanizer at 155 °C and 13 MPa with the oil seal material obtained in S2.

[0013] Further, in S1, the mixing time is 2 - 5 min.

[0014] Further, in S2, the roll temperature in the open mill is 70 - 75 °C.

[0015] This application has the following beneficial effects: In the preparation of the packing gland oil seal of the present invention, the raw material components include carbon black, acid-etched potassium hexatitanate and maleic anhydride modified nano calcium carbonate. On the one hand, in the preparation of acid-etched potassium hexatitanate, acid etching improves the surface roughness of potassium hexatitanate, which is beneficial for the maleic anhydride modified nano calcium carbonate to better fill the gap between carbon black and acid-etched potassium hexatitanate, block the physical interlocking network between the two, and reduce the brittleness of the material; On the other hand, in the preparation of maleic anhydride-modified nano calcium carbonate, the carboxyl group of the introduced maleic anhydride reacts with the -CN group of nitrile rubber to form chemical cross-linking points, which can better buffer the stress of rigid fillers, further block the continuity of the rigid network, and reduce the brittleness of the material; the two aspects of action (physical filling to block the interlocking network + chemical bonding to enhance toughness) work synergistically to synergistically improve the elongation at break of the prepared material. Specific embodiments

[0016] The following further elaborates on the present application in conjunction with embodiments.

[0017] The raw materials of the examples and comparative examples of the present application are all ordinary commercially available products unless otherwise specified.

[0018] Example 1: Preparation of acid-etched potassium hexatitanate: Potassium hexatitanate was ultrasonically cleaned with ethanol (frequency 40 kHz, time 12 minutes) to remove surface oil stains and impurities. After cleaning, it was dried in a vacuum oven at 80 °C for 2 hours to prevent moisture from interfering with the subsequent etching reaction. Then, the dried potassium hexatitanate was immersed in an oxalic acid solution with a concentration of 8 wt%, and magnetic stirring (rotation speed 280 rpm) was used for an etching time of 70 minutes to ensure uniform etching. After the etching was completed, it was immediately rinsed with deionized water until neutral (pH = about 7.0) to block the continued reaction of the residual acid solution, and then low-temperature annealing (300 °C under nitrogen protection, 30 minutes) was carried out to eliminate surface stress microcracks, thus obtaining acid-etched potassium hexatitanate. Potassium hexatitanate was purchased from Wuhan Lana White Pharmaceutical Chemical Co., Ltd.

[0019] Preparation of maleic anhydride-modified nano calcium carbonate: 1.5 g of sodium stearate was added to 2 kg of a calcium hydroxide suspension with a mass fraction of 3.7% to obtain a first reaction solution. Carbon dioxide gas was introduced into the first reaction solution at a flow rate of 9 L / min and reacted for 32 minutes to obtain a second reaction solution. 2.2 g of maleic anhydride was added to the second reaction solution and reacted for 32 minutes to obtain a third reaction solution. The third reaction solution was precipitated, filtered, and washed, and the obtained solid was dried at a drying temperature of 52 °C and a drying time of 175 minutes to obtain maleic anhydride-modified nano calcium carbonate.

[0020] The preparation method of the packing gland oil seal includes the following steps: S1. By weight parts, 100 parts of nitrile rubber, 6.5 parts of zinc oxide (activator), 2 parts of stearic acid (lubricant / activator), and 1.3 parts of antioxidant are successively added into a Banbury mixer and kneaded for 3 min to obtain a first kneaded mixture. 23 parts of carbon black, 9 parts of acid-etched potassium hexatitanate, 12.5 parts of plasticizer, and 7 parts of maleic anhydride-modified nano calcium carbonate are successively added into the first kneaded mixture and kneaded until discharging rubber at 135 °C to obtain a first colloid. Among them, the antioxidant is rubber antioxidant 4020. The plasticizer is dioctyl phthalate. The wear-resistant carbon black (N358) is purchased from Tianjin Yihuachang New Material Technology Co., Ltd.

[0021] S2. The first colloid obtained in S1 is added into an open mill, the roll temperature in the open mill is about 72 °C, 1.5 parts of accelerator are added to avoid insufficient vulcanization subsequently, and 1.2 parts of sulfur are also added. After passing thinly through 5 times, the sheet is taken off and parked for 24 h to obtain an oil seal material. Among them, the accelerator is a sulfenamide type (N-cyclohexyl-2-benzothiazole sulfenamide).

[0022] S3. The oil seal material obtained in S2 is prepared into a packing gland oil seal by using a mold pressing method at 155 °C and 13 MPa on a flat vulcanizer (vulcanization time 20 min).

[0023] Example 2: The difference between this example and Example 1 lies in the preparation method of the packing gland oil seal, which includes the following steps: S1. By weight parts, 100 parts of nitrile rubber, 6 parts of zinc oxide, 2 parts of stearic acid, and 1.2 parts of antioxidant are successively added into a Banbury mixer and kneaded for 2 min to obtain a first kneaded mixture. 22 parts of carbon black, 8 parts of acid-etched potassium hexatitanate, 12 parts of plasticizer, and 6 parts of maleic anhydride-modified nano calcium carbonate are successively added into the first kneaded mixture and kneaded until discharging rubber at 135 °C to obtain a first colloid.

[0024] S2. The first colloid obtained in S1 is added into an open mill, the roll temperature in the open mill is about 72 °C, 1 part of accelerator is added, and 1 part of sulfur is also added. After passing thinly through 5 times, the sheet is taken off and parked for 24 h to obtain an oil seal material.

[0025] S3. The oil seal material obtained in S2 is prepared into a packing gland oil seal by using a mold pressing method at 155 °C and 13 MPa on a flat vulcanizer.

[0026] Example 3: The difference between this example and Example 1 lies in the preparation method of the packing gland oil seal, which includes the following steps: S1. By weight, 100 parts of nitrile rubber, 7 parts of zinc oxide, 2 parts of stearic acid and 1.5 parts of antioxidant were sequentially added into a mixer and kneaded for 5 min to obtain a first kneaded mixture. Then, 24 parts of carbon black, 10 parts of acid-etched potassium hexatitanate, 13 parts of plasticizer and 8 parts of maleic anhydride-modified nano-calcium carbonate were sequentially added into the first kneaded mixture and kneaded until the rubber was discharged at 135 °C to obtain a first colloid.

[0027] S2. The first colloid obtained in S1 was added into an open mill with the roll temperature of about 72 °C. 2 parts of accelerator and 1.3 parts of sulfur were also added. After passing the rubber sheet thinly through the rolls 5 times, the sheet was taken off and left to stand for 24 h to obtain the oil seal material.

[0028] S3. The oil seal material obtained in S2 was used to prepare the packing gland oil seal on a flat vulcanizer by means of compression molding at 155 °C and 13 MPa.

[0029] Comparative Example 1: The difference between this comparative example and Example 1 is that acid-etched potassium hexatitanate and modified nano-calcium titanate were replaced with carbon black.

[0030] Specifically, the preparation method of the packing gland oil seal includes the following steps: S1. By weight, 100 parts of nitrile rubber, 6.5 parts of zinc oxide, 2 parts of stearic acid and 1.3 parts of antioxidant were sequentially added into a mixer and kneaded for 3 min to obtain a first kneaded mixture. Then, 39 parts of carbon black and 12.5 parts of plasticizer were sequentially added into the first kneaded mixture and kneaded until the rubber was discharged at 135 °C to obtain a first colloid.

[0031] S2. The first colloid obtained in S1 was added into an open mill with the roll temperature of about 72 °C. 1.5 parts of accelerator were also added. After passing the rubber sheet thinly through the rolls 5 times, the sheet was taken off and left to stand for 24 h to obtain the oil seal material.

[0032] S3. The oil seal material obtained in S2 was used to prepare the packing gland oil seal on a flat vulcanizer by means of compression molding at 155 °C and 13 MPa.

[0033] Comparative Example 2: The difference between this comparative example and Example 1 is that modified nano-calcium titanate was replaced with carbon black.

[0034] Specifically, the preparation method of the packing gland oil seal includes the following steps: S1. By weight, 100 parts of nitrile rubber, 6.5 parts of zinc oxide, 2 parts of stearic acid and 1.3 parts of antioxidant were sequentially added into a mixer and kneaded for 3 min to obtain a first kneaded mixture. Then, 30 parts of carbon black, 9 parts of acid-etched potassium hexatitanate and 12.5 parts of plasticizer were sequentially added into the first kneaded mixture and kneaded until the rubber was discharged at 135 °C to obtain a first colloid.

[0035] S2. Add the first colloid obtained in S1 into an open mill. The roll temperature in the open mill is about 72 °C, and add 1.5 parts of accelerator. After thin pass 5 times, take off the sheet and let it stand for 24 h to obtain the oil seal material.

[0036] S3. Use the oil seal material obtained in S2 at 155 °C and 13 MPa by the compression molding method to prepare a packing gland oil seal on a flat vulcanizer.

[0037] Comparative Example 3: The difference between this comparative example and Example 1 is that the acid-etched potassium hexatitanate is replaced with carbon black.

[0038] Specifically as follows: The preparation method of the packing gland oil seal includes the following steps: S1. By weight, add 100 parts of nitrile rubber, 6.5 parts of zinc oxide, 2 parts of stearic acid and 1.3 parts of antioxidant into a mixer and knead for 3 min to obtain the first kneaded product. Add 32 parts of carbon black, 12.5 parts of plasticizer and 7 parts of maleic anhydride modified nano calcium carbonate into the first kneaded product in sequence, and knead until the glue is discharged at 135 °C to obtain the first colloid.

[0039] S2. Add the first colloid obtained in S1 into an open mill. The roll temperature in the open mill is about 72 °C, and add 1.5 parts of accelerator. After thin pass 5 times, take off the sheet and let it stand for 24 h to obtain the oil seal material.

[0040] S3. Use the oil seal material obtained in S2 at 155 °C and 13 MPa by the compression molding method to prepare a packing gland oil seal on a flat vulcanizer.

[0041] Test example: Test object: The packing gland oil seal specimens prepared in Examples 1 - 3 and Comparative Examples 1 - 3. Test item: Elongation at break. Test result: See Table 1.

[0042] Table 1. Test example data Result analysis: Analyze Examples 1 - 3 and combine with the data in Table 1. It can be seen that in the case of high proportion of inorganic fillers (carbon black, acid-etched potassium hexatitanate and maleic anhydride modified nano calcium carbonate) in the present invention (Examples 1 - 3), the elongation at break of the prepared packing gland oil seal specimens is as high as more than 356%.

[0043] Analyze Example 1 and Comparative Examples 1 - 3 and combine with the data in Table 1. By comparing Comparative Example 1 and Comparative Example 2, it can be known that compared with Comparative Example 1, Comparative Example 2 replaces part of the carbon black with acid-etched potassium hexatitanate, and as a result, the elongation at break of the prepared packing gland oil seal specimens decreases from 307% (Comparative Example 1) to 285% (Comparative Example 2); it shows that the introduction of acid-etched potassium hexatitanate will cause the elongation at break of the prepared packing gland oil seal specimens to decrease instead of increase.

[0044] This is because carbon black improves weather resistance by absorbing / scattering ultraviolet light, but its high specific surface area will adsorb rubber molecular chains and limit the movement of chain segments. After introducing acid-etched potassium hexatitanate, the acid etching increases the surface roughness of potassium hexatitanate while maintaining the integrity of its tunnel-like rigid structure. The higher surface roughness enhances the combination of potassium hexatitanate and carbon black, forming a stronger physical interlocking network, which further restricts the movement of nitrile rubber molecular chains, resulting in an increase in the brittleness of the prepared material and a decrease in the elongation at break.

[0045] By comparing Comparative Example 1 and Comparative Example 3, it can be seen that compared with Comparative Example 1, in Comparative Example 3, part of the carbon black was replaced with maleic anhydride-modified nano-calcium titanate, and as a result, the elongation at break of the packing gland oil seal sample prepared increased from 307% (Comparative Example 1) to 338% (Comparative Example 3). This shows that the introduction of maleic anhydride-modified nano-calcium titanate can increase the elongation at break of the prepared packing gland oil seal sample.

[0046] Combined with the comparison of Example 1, it can be seen that replacing part of the carbon black with acid-etched potassium hexatitanate and maleic anhydride-modified nano-calcium titanate at the same time can produce a synergistic effect and synergistically increase the elongation at break of the prepared packing gland oil seal sample.

[0047] This is because in the preparation of acid-etched potassium hexatitanate, the acid etching increases the surface roughness of potassium hexatitanate, which is beneficial to the better filling of the carbon black-acid-etched potassium hexatitanate gap by maleic anhydride-modified nano-calcium carbonate, blocking their physical interlocking network and reducing the brittleness of the material. In the preparation of maleic anhydride-modified nano-calcium carbonate, the carboxyl group of the introduced maleic anhydride reacts with the -CN group of nitrile rubber to form chemical cross-linking points, which can better buffer the stress of rigid fillers, further block the continuity of the rigid network, and reduce the brittleness of the material. The two effects work synergistically, thus achieving the effect of synergistically increasing the elongation at break of the prepared material.

[0048] In addition, it should be noted that among the various specific technical features described in the above specific embodiments, they can be combined in any appropriate way without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combination methods.

[0049] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. A packing gland oil seal, characterized in that, By weight parts, it includes the following components: 100 parts of nitrile rubber, 22 - 24 parts of carbon black, 8 - 10 parts of acid-etched potassium hexatitanate, 6 - 8 parts of maleic anhydride-modified nano calcium carbonate, 1.2 - 1.5 parts of antioxidant, 12 - 13 parts of plasticizer, 1 - 2 parts of accelerator, 1 - 1.3 parts of sulfur, 6 - 7 parts of zinc oxide, and 2 parts of stearic acid.

2. The packing gland oil seal according to claim 1, wherein The preparation method of the acid-etched potassium hexatitanate is as follows: Ultrasonically clean potassium hexatitanate, dry it, immerse it in acid solution, stir and etch for 60 - 80 min, then rinse until neutral to obtain it.

3. The gland packing oil seal according to claim 2, wherein The acid solution is an oxalic acid solution with a concentration of 7 - 10 wt%.

4. The packing gland oil seal according to claim 1, wherein, The preparation method of the maleic anhydride-modified nano calcium carbonate is as follows: Add 1.45 - 1.6 g of sodium stearate to 2 kg of calcium hydroxide suspension with a mass fraction of 3.5% - 4.0% to obtain a first reaction solution; Pass carbon dioxide gas into the first reaction solution and react for 30 - 35 min to obtain a second reaction solution; Add 2.0 - 2.5 g of maleic anhydride to the second reaction solution and react for 30 - 35 min to obtain a third reaction solution; Precipitate, filter and wash the third reaction solution, and dry the obtained solid to obtain maleic anhydride-modified nano calcium carbonate.

5. The gland packing oil seal according to claim 4, characterized in that, The flow rate of the carbon dioxide gas is 8 - 10 L / min.

6. The gland packing oil seal according to claim 4, characterized in that, The drying temperature is 50 - 55 °C, and the drying time is 170 - 180 min.

7. A preparation method of the packing gland oil seal according to any one of claims 1-6, characterized in that, It includes the following steps: S1. Add nitrile rubber, zinc oxide, stearic acid and antioxidant to the internal mixer in sequence, mix to obtain a first mixture; Add carbon black, acid-etched potassium hexatitanate, plasticizer and maleic anhydride-modified nano calcium carbonate to the first mixture in sequence, mix until discharging rubber at 135 °C to obtain a first colloid; S2. Add the first colloid obtained in S1 to the open mill, add accelerator, add sulfur, thin pass 5 times and then take off the sheet, and let it stand for 24 h to obtain an oil seal material; S3. Use the die pressing method at 155 °C and 13 MPa to prepare the packing gland oil seal on a flat vulcanizer with the oil seal material obtained in S2.

8. The preparation method of the packing gland oil seal according to claim 7, characterized in that, In S1, the mixing time is 2 - 5 min.

9. The preparation method of the packing gland oil seal according to claim 7, characterized in that, In S2, the roll temperature in the open mill is 70 - 75 °C.

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