Auxiliary sealing element material for double-end-face mechanical sealing and preparation method of auxiliary sealing element material

Abstract

The invention belongs to the technical field of fluorine-containing functional materials, and particularly relates to an auxiliary sealing element material for double-end-face mechanical sealing and a preparation method of the auxiliary sealing element material. The invention aims to solve the problems that the existing fluorine-containing sealing material is easy to age and lose efficacy and poor in self-adaptability. According to the invention, oligomeric PEEK is synthesized through terminal group functionalization polymerization, and the oligomeric PEEK and a dianhydride monomer and a diamine monomer in a specific proportion are subjected to block copolymerization to synthesize a PEEK-PI block copolymer; further, carrying out surface modification treatment to obtain a modified copolymer, and dispersing and mixing the modified copolymer with a wear-resistant filler and an anti-aging additive to obtain a wear-resistant copolymer precursor; and respectively carrying out melt blending on the wear-resistant copolymer precursor and perfluoropolyether, and carrying out segmented sintering with polytetrafluoroethylene powder to obtain the auxiliary sealing element material. The auxiliary sealing element material provided by the invention has high wear resistance and creep resistance, and can give full play to the sealing performance under different working conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine-containing functional materials, and in particular relates to an auxiliary sealing material for double-end mechanical seals and a preparation method thereof. Background Art

[0002] The application of fluorine-containing functional materials in the field of seals has an important technical background and broad development prospects. Fluorine-containing materials, such as polytetrafluoroethylene, fluororubber, and perfluoropolyether, have become the preferred materials for the manufacture of high-performance seals due to their excellent chemical stability, high temperature resistance, corrosion resistance, and low friction coefficient. In the industrial field, seals are widely used in aerospace, automobile manufacturing, petrochemicals, semiconductor production and other scenarios, which place extremely high demands on the durability and reliability of materials. Traditional materials such as natural rubber or ordinary plastics are prone to aging, decomposition or failure in extreme environments, while fluorine-containing functional materials can effectively resist the erosion of harsh conditions such as acids and alkalis, organic solvents, high temperatures and high pressures due to the strong electronegativity and stable bond energy of fluorine atoms in their molecular structure.

[0003] The self-lubricating and low surface energy properties of fluorine-containing materials enable them to perform well in dynamic and static sealing applications, reducing friction and wear and extending service life, especially in the sealing of double-end mechanical applications.

[0004] However, despite the great progress made in fluorine-containing sealing materials, they still face many technical challenges in the face of increasingly complex and extreme working conditions. For example, in extreme temperatures, high pressures, high-speed friction and complex media environments, sealing materials are prone to performance degradation, aging failure, wear and leakage, etc., especially in terms of long life, high reliability and self-repairing, the technology of existing fluorine-containing sealing materials still needs to be broken through. How to further improve the long-term stability and reliability of fluorine-containing sealing materials under harsh conditions, reduce friction and wear, and achieve automatic repair and adaptive adjustment is still the key direction of continuous research and tackling in the field of fluorine-containing functional materials.

[0005] At present, the existing fluorine-containing sealing materials are prone to aging and failure and have poor adaptability, which are still major problems facing the industry.

[0006] To this end, an auxiliary sealing material for double-end mechanical seal and a preparation method thereof are proposed. Summary of the invention

[0007] The purpose of the present invention is to provide an auxiliary sealing material for double-end mechanical seals and a preparation method thereof. The present invention synthesizes oligomeric PEEK by end group functional polymerization, and synthesizes PEEK-PI block copolymers by block copolymerization with dianhydride monomers and diamine monomers in a specific ratio; further, a modified copolymer is obtained by surface modification, and dispersed and mixed with wear-resistant fillers and aging-resistant additives to obtain a wear-resistant copolymer precursor; the wear-resistant copolymer precursor is melt-blended with perfluoropolyether and sintered with polytetrafluoroethylene powder in sections to obtain an auxiliary sealing material.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing an auxiliary sealing material for a double-end mechanical seal comprises the following steps:

[0010] Unless otherwise specified, the parts in the present invention refer to parts by mass, and the average molecular weight refers to the number average molecular weight.

[0011] Under nitrogen protection, 22 parts of the hydroquinone are dissolved in 200 parts of N-methylpyrrolidone, 30 parts of potassium carbonate and 50-58 parts of 4,4'-difluorobenzophenone are added at a rotation speed of 500 rpm, and the temperature is increased to 180-200°C at a heating rate of 5°C / min. After the reaction is continued for 12 hours, the reaction solution is cooled to 25°C, 500 parts of methanol are added, and the precipitated solid product is washed and dried to obtain oligomeric PEEK.

[0012] Under nitrogen protection, 14 parts of diaminodiphenyl ether and 11 parts of diaminodiphenylmethane are added to 70 parts of N-methylpyrrolidone, and stirred at 400 rpm at 50°C until completely dissolved to obtain a diamine solution; 10 parts of the oxydiphenyl dianhydride and 18 parts of pyromellitic dianhydride are dissolved in 85 parts of N-methylpyrrolidone to obtain a dianhydride solution; in an ice water bath, 50 parts of the dianhydride solution are slowly added dropwise to 60-74 parts of the diamine solution, and the stirring speed is maintained at 2000 rpm. After the dropwise addition is completed, the reaction system is heated to 25°C, stirred at a speed of 800-1000 rpm for 6 hours, 50 parts of oligomeric PEEK are slowly added, and the reaction is continued for 4 hours, 100 parts of acetic anhydride and 20 parts of triethylamine are added to react at 40°C for 4 hours, 400 parts of methanol are added to obtain a precipitate, and the obtained precipitate is washed and dried to obtain a PEEK-PI block copolymer.

[0013] The PEEK-PI block copolymer is surface modified to obtain a modified copolymer.

[0014] The modified copolymer is dispersed and mixed with the wear-resistant filler and the anti-aging additive to obtain the wear-resistant copolymer precursor.

[0015] The wear-resistant filler includes carbon fiber and silicon dioxide; the anti-aging additive includes N,N'-diphenyl-p-phenylenediamine and magnesium oxide.

[0016] The wear-resistant copolymer precursor is melt-blended with perfluoropolyether to obtain a ternary wear-resistant copolymer.

[0017] The auxiliary sealing material is obtained by sintering the ternary wear-resistant copolymer and polytetrafluoroethylene powder in sections.

[0018] The molecular weight of perfluoropolyether is 3200-5500; the polytetrafluoroethylene powder is a dispersed powder with a molecular weight of 2×10 5 -3.5×10 5 .

[0019] Preferably, the surface modification process is: at an operating pressure of 10-50 Pa, the PEEK-PI block copolymer is subjected to plasma treatment using oxygen with a flow rate of 10-50 sccm, a radio frequency power of 240-260 W, and a treatment time of 15 minutes to obtain the modified copolymer.

[0020] Preferably, the dispersion mixing process is: grinding and mixing 100 parts of the modified copolymer with 2 parts of carbon fiber, 3.5 parts of silica, 1.7 parts of N,N'-diphenyl-p-phenylenediamine and 1.3 parts of magnesium oxide in a ball mill, wherein the mixing speed is 2000 rpm, the mixing time is 2 hours, and the wear-resistant copolymer precursor is obtained after mixing.

[0021] Preferably, the melt blending process is: 20 parts of the wear-resistant copolymer precursor and 35 parts of perfluoropolyether are mixed evenly, and then blended in an internal mixer at a temperature of 320-380°C, 10 parts of the wear-resistant copolymer precursor are added again after 20 minutes, and 40 parts of the wear-resistant copolymer precursor are added after continuing to mix for 30 minutes, the screw speed is maintained at 500 rpm, and mixing is continued for 1 hour to obtain a ternary wear-resistant copolymer.

[0022] Preferably, the process of segmented sintering is as follows: 400 parts of the ternary wear-resistant copolymer are ground into 200-mesh powder, mixed evenly with 100 parts of 200-mesh polytetrafluoroethylene powder, 12 parts of polyvinyl alcohol are added, and pre-pressed at an operating pressure of 5 MPa. After maintaining the pressure for 30 minutes, the temperature is increased to 120-150°C at a heating rate of 3°C / min, and kept warm for 2 hours under nitrogen protection, and then the temperature is increased to 330-350°C at a heating rate of 5°C / min. After keeping warm for 2 hours, the temperature is cooled to 25°C at a cooling rate of 2°C / min, and the auxiliary sealing material is obtained after demolding.

[0023] An auxiliary sealing material for double-end mechanical seals comprises: PEEK-PI block copolymer, perfluoropolyether, polytetrafluoroethylene, wear-resistant filler and anti-aging additive.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. Active sites are constructed through end-group functional polymerization, and the feed ratio of hydroquinone to 4,4'-difluorobenzophenone is controlled to generate oligomeric PEEK containing terminal phenolic hydroxyl groups. Further, by adjusting the types and ratios of dianhydride monomers and diamine monomers, a covalently bridged diblock structure is formed, which greatly improves the polymer cross-linking degree and strength of the auxiliary sealing material product, thereby ensuring the excellent creep resistance and wear resistance of the auxiliary sealing material product.

[0026] 2. Based on the synthesis of PEEK-PI block copolymers through block copolymerization and the construction of a molecular-level synergistic framework, the antioxidant N,N'-diphenyl-p-phenylenediamine and the thermal stabilizer magnesium oxide are fixed to the polymer chain network through a dispersed mixing process, and the cross-scale polymer interpenetrating network is realized with the help of a segmented sintering process, achieving a synergistic anti-aging effect and effectively improving the durability of the auxiliary seal in a high temperature environment.

[0027] 3. Carbonyl functional groups are formed on the surface of PEEK-PI block copolymers through surface modification process, which provides a large number of active sites for subsequent filler bonding, and introduces carbon fiber and silica in the wear-resistant filler into the organic network to jointly construct an organic-inorganic hybrid network. Through melt blending and segmented sintering processes, the distribution of wear-resistant fillers, perfluoropolyether and polytetrafluoroethylene in auxiliary sealing material products presents a high gradient, and a multi-scale lubrication network and enhanced interface are successfully constructed, which synergistically achieves the low friction coefficient and high wear resistance of the auxiliary sealing material products.

[0028] 4. PEEK-PI block copolymer is combined with perfluoropolyether and polytetrafluoroethylene through a step-by-step process to construct a reversible microphase separation structure; under high-speed conditions, the PEEK segment will undergo semi-crystalline region dissociation under the action of high-speed friction heat, releasing the perfluoropolyether structure to the outer layer of the polymer network, achieving low friction coefficient and high temperature resistance at high temperatures; at the same time, under low-speed conditions, the three-dimensional cross-linked network constructed by carbon fiber and silica optimizes the internal structure through segmented sintering, which can effectively block the penetration of oily media and has high creep resistance. Under different working conditions, the sealing material provided by the present invention can have good application value in a variety of mechanical sealing scenarios through good adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The figure is a process flow chart of the preparation of the auxiliary sealing material in the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below through some embodiments and experimental examples. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Reference Figure 1 As shown in the process flow chart, the present invention provides a preparation method and application of auxiliary sealing material for double-end mechanical seals, and the technical solution is as follows:

[0032] Example 1

[0033] Under nitrogen protection, 22 parts of the hydroquinone were dissolved in 200 parts of N-methylpyrrolidone, 30 parts of potassium carbonate and 50 parts of 4,4'-difluorobenzophenone were added at a rotation speed of 500 rpm, and the temperature was raised to 180°C at a heating rate of 5°C / min. After the reaction was continued for 12 hours, the reaction solution was cooled to 25°C, 500 parts of methanol were added, and the precipitated solid product was washed and dried to obtain oligomeric PEEK.

[0034] Under nitrogen protection, 14 parts of diaminodiphenyl ether and 11 parts of diaminodiphenylmethane were added to 70 parts of N-methylpyrrolidone, and stirred at 400 rpm at 50°C until completely dissolved to obtain a diamine solution; 10 parts of the oxydiphenyl dianhydride and 18 parts of pyromellitic dianhydride were dissolved in 85 parts of N-methylpyrrolidone to obtain a dianhydride solution; 50 parts of the dianhydride solution were slowly added dropwise to 60 parts of the diamine solution under an ice-water bath, and the stirring speed was maintained at 2000 rpm. After the dropwise addition was completed, the reaction system was heated to 25°C, stirred at 800 rpm for 6 hours, 50 parts of oligomeric PEEK were slowly added, and the reaction was continued for 4 hours, 100 parts of acetic anhydride and 20 parts of triethylamine were added to react at 40°C for 4 hours, 400 parts of methanol were added to obtain a precipitate, and the obtained precipitate was washed and dried to obtain a PEEK-PI block copolymer.

[0035] Under an operating pressure of 10 Pa, the PEEK-PI block copolymer was subjected to plasma treatment using oxygen with a flow rate of 10 sccm, a radio frequency power of 240 W, and a treatment time of 15 minutes to obtain the modified copolymer.

[0036] 100 parts of the modified copolymer were ground and mixed with 2 parts of carbon fiber, 3.5 parts of silicon dioxide, 1.7 parts of N,N'-diphenyl-p-phenylenediamine and 1.3 parts of magnesium oxide in a ball mill at a mixing speed of 2000 rpm for 2 hours to obtain a wear-resistant copolymer precursor.

[0037] 20 parts of wear-resistant copolymer precursor and 35 parts of perfluoropolyether were mixed evenly and blended in an internal mixer at 320°C. After 20 minutes, 10 parts of wear-resistant copolymer precursor were added again. After continuing to mix for 30 minutes, 40 parts of wear-resistant copolymer precursor were added. The screw speed was maintained at 500 rpm and mixing was continued for 1 hour to obtain a ternary wear-resistant copolymer.

[0038] 400 parts of the ternary wear-resistant copolymer were ground into 200-mesh powder, mixed evenly with 100 parts of 200-mesh polytetrafluoroethylene powder, added with 12 parts of polyvinyl alcohol, pre-pressed at an operating pressure of 5 MPa, and the temperature was increased to 120°C at a heating rate of 3°C / min after maintaining the pressure for 30 minutes. The mixture was kept warm for 2 hours under nitrogen protection, and then heated to 330°C at a heating rate of 5°C / min. After keeping warm for 2 hours, the mixture was cooled to 25°C at a cooling rate of 2°C / min, and the auxiliary sealing material was obtained after demolding.

[0039] Examples 2-20 differ from Example 1 in operating parameters, and specific parameter changes are summarized in Tables 1 and 2.

[0040] Table 1 Operation parameter changes of Examples 1-20 (I)

[0041]

[0042] Table 2 Operation parameter changes of Examples 1-20 (II)

[0043]

[0044] Comparative Example 1

[0045] The difference from Example 1 is that the addition amount of 4,4'-difluorobenzophenone is changed to 30 parts, and the other process parameters are the same.

[0046] Comparative Example 2

[0047] The difference from Example 1 is that the ice-water bath condition in the block copolymerization process is cancelled and the reaction is carried out at 25° C., and the other process parameters are the same.

[0048] Comparative Example 3

[0049] The difference from Example 1 is that the addition amount of the diamine solution is changed to 120 parts, and the other process parameters are the same.

[0050] Comparative Example 4

[0051] The difference from Example 6 is that N,N'-diphenyl-p-phenylenediamine is not added, and other process parameters are the same.

[0052] Comparative Example 5

[0053] The difference from Example 6 is that only a single-stage sintering at 348° C. is performed during the staged sintering process, and other process parameters are the same.

[0054] Comparative Example 6

[0055] The difference from Example 6 is that the ball mill speed during the dispersion and mixing process is changed to 500 rpm, and the other process parameters are the same.

[0056] Comparative Example 7

[0057] The difference from Example 11 is that no surface modification process is performed, and other process parameters are the same.

[0058] Comparative Example 8

[0059] The difference from Example 11 is that the molecular weight of the added perfluoropolyether is changed to 1500, and the other process parameters are the same.

[0060] Comparative Example 9

[0061] The difference from Example 16 is that only a single feed is carried out during the melt blending process, and other process parameters are the same.

[0062] Comparative Example 10

[0063] The difference from Example 16 is that the polytetrafluoroethylene is replaced by an equal mass fraction of high-density polyethylene, wherein the molecular weight of the high-density polyethylene is 3×10 5 , other process parameters are the same.

[0064] Experimental Example 1

[0065] The creep resistance and wear resistance of the auxiliary sealing materials prepared in Examples 1-5 and Comparative Examples 1-3 were tested, and the results are summarized in Table 3.

[0066] The creep resistance test method is as follows: first, measure the initial height H0 of the seal sample, treat the seal material sample with a compressive stress of 2.5 MPa at 25°C, 100°C, and 300°C for 24 hours, and then let it stand for 24 hours after unloading the stress, and measure the final height H0 of the sample. t , calculate the creep strain ε(t)=(H t -H0) / H0, the smaller ε(t) is, the better the creep resistance of the material is.

[0067] The test method for wear resistance is as follows: refer to the pin-disc wear test method of ASTM G99-17, use bearing steel as the friction pair material, conduct a friction test on the sealing material for 30 minutes under a positive pressure of 50N and a sliding speed of 0.1m / s, record the mass of wear loss, calculate the wear volume V, and calculate the wear rate W=V / (positive pressure F×sliding distance L). The larger W is, the worse the wear resistance is.

[0068] Table 3 Creep resistance and wear resistance of auxiliary seal materials prepared in Examples 1-5 and Comparative Examples 1-3

[0069]

[0070] As shown in the creep resistance and wear resistance data of Table 3, the auxiliary seal materials prepared in Examples 1-5 have good creep resistance in the temperature range of 25-300°C. As the temperature increases, the creep resistance gradually decreases, but it still has good creep resistance at 300°C; at the same time, the auxiliary seal materials prepared in Examples 1-5 have good wear resistance. The amount of 4,4'-difluorobenzophenone in Comparative Example 1 is reduced, the molar ratio of hydroquinone to 4,4'-difluorobenzophenone is changed, the terminal hydroxyl density of oligomeric PEEK is reduced, and the crosslinking degree of the copolymer obtained in the block copolymerization process is reduced, resulting in a decrease in its creep resistance at all temperatures, and a certain degree of loss in wear resistance. Comparative Example 2 cancels the ice-water bath condition in the block copolymerization process, making the reaction process of the initial polymerization reaction difficult to control, the polyimide chain segment grows disorderly, and the copolymerization efficiency with oligomeric PEEK is reduced, which significantly reduces the creep resistance of the auxiliary seal material product. Comparative Example 3 increases the amount of diamine solution used and changes the specific ratio of diamine and dianhydride monomers, resulting in excessive amination, which reduces the cross-linking network density of the copolymer and reduces the creep resistance and wear resistance of the auxiliary sealing material product to a certain extent.

[0071] In summary, controlling the feed ratio of hydroquinone to 4,4'-difluorobenzophenone can ensure that the end group of oligomeric PEEK has a higher hydroxyl density. Further adjusting the types and ratios of dianhydride monomers and diamine monomers can form a covalently bridged diblock structure with oligomeric PEEK, greatly improving the polymer crosslinking degree and strength of the auxiliary sealing material product, thereby ensuring that the auxiliary sealing material product has excellent creep resistance and wear resistance.

[0072] Experimental Example 2

[0073] The high temperature durability of the auxiliary sealing materials prepared in Examples 6-10 and Comparative Examples 4-6 was tested, and the relevant data are summarized in Table 4.

[0074] The specific test method for high-temperature durability is as follows: place the sample sealing material under a positive pressure of 50N, and heat treat it at 200℃, 300℃ and 400℃ for 48 hours respectively. Referring to Experimental Example 1, measure the wear rates W0 and Wt before and after treatment. The greater the increase in Wt compared to W0, the worse the high-temperature durability of the corresponding sample.

[0075] Table 4 High temperature durability of auxiliary sealing materials prepared in Examples 6-10 and Comparative Examples 4-6

[0076]

[0077] As shown in the high-temperature durability data in Table 4, after the auxiliary sealing materials prepared in Examples 6-10 were heat-treated at 200°C, 300°C and 400°C, the wear resistance gradually decreased with the increase of the treatment temperature, but the decrease was small. Due to the lack of N,N'-diphenyl-p-phenylenediamine antioxidant, the wear resistance of Comparative Example 4 after high-temperature treatment decreased significantly. Comparative Example 5 changed the multi-stage sintering to a single stage, which increased the stress inside the auxiliary sealing material product, resulting in a decrease in wear resistance. At the same time, the decrease in wear resistance after high-temperature treatment was also large. Comparative Example 6 reduced the ball milling speed, resulting in the difficulty of dispersing the antioxidant and thermal stabilizer in the polymer chain network during the dispersion and mixing process, and then the cross-linking network could not be formed through subsequent processes, which significantly reduced the durability of the auxiliary sealing material product in a high-temperature environment.

[0078] In summary, the block copolymerization process constructs a molecular-level synergistic framework of oligomeric PEEK and PI, and further fixes the antioxidant N,N'-diphenylparaphenylenediamine and the thermal stabilizer magnesium oxide to the polymer chain network through a dispersed mixing process. The segmented sintering process is used to achieve a cross-scale polymer interpenetrating network, achieving a synergistic aging resistance effect and effectively improving the durability of the auxiliary seal in a high temperature environment.

[0079] Experimental Example 3

[0080] The friction coefficient and wear resistance of the auxiliary sealing materials prepared in Examples 11-15 and Comparative Examples 7-8 are summarized in Table 5.

[0081] The test method of wear resistance refers to Experimental Example 1.

[0082] The specific test method for the friction coefficient is as follows: apply a load of 50N positive pressure to the sample sealing material, maintain the relative speed between the sample and the bearing steel interface at 0.1m / s, record the friction force F, and calculate the dynamic friction coefficient μ=F / 50. The larger the dynamic friction coefficient, the greater the friction coefficient of the sample sealing material.

[0083] Table 5 Friction coefficient and wear resistance of auxiliary seal materials prepared in Examples 11-15 and Comparative Examples 7-8

[0084] Dynamic friction factor μ <![CDATA[Wear rate W (10 -5 mm 3 / N·mm)]]> Embodiment 11 0.04 2.3 Example 12 0.04 2.5 Embodiment 13 0.05 2.4 Embodiment 14 0.04 2.6 Embodiment 15 0.05 2.7 Comparative Example 7 0.12 3.9 Comparative Example 8 0.08 4.5

[0085] As shown in the friction coefficient and wear resistance data of Table 5, Examples 11-15 have a lower friction coefficient and higher wear resistance, and the changes with process parameters are not obvious, and have stable performance. Comparative Example 7 cancels the oxygen plasma treatment, resulting in a lack of active sites on the surface of the PEEK-PI block copolymer, which makes it difficult to bond with the filler later, causing the failure of the organic-inorganic hybrid network construction, the overall wear resistance of the auxiliary seal material product is reduced, and the friction coefficient is increased. Comparative Example 8 uses a low molecular weight perfluoropolyether, which is difficult to obtain a uniform polymer network by melt blending with the PEEK-PI block copolymer, resulting in a decrease in lubricity and a decrease in wear resistance.

[0086] In summary, the surface modification process forms a large number of carbonyl functional groups on the surface of PEEK-PI block copolymers to provide active sites, and bonds the fillers involved in the subsequent blending process into the organic-inorganic hybrid network, thereby reducing the impact of additional fillers on the performance of the polymer network. Through the melt blending process and the segmented sintering process, the distribution of wear-resistant fillers and perfluoropolyether and polytetrafluoroethylene presents a high gradient, and a multi-scale lubrication network and enhanced interface are successfully constructed, which synergistically achieves the low friction coefficient and high wear resistance of the auxiliary sealing material products.

[0087] Experimental Example 4

[0088] The friction coefficient of the auxiliary sealing materials prepared in Examples 16-20 and Comparative Examples 9-10 under high-speed and high-temperature conditions, as well as the medium permeability and creep resistance under low-temperature and low-speed conditions were tested. The results are summarized in Table 6.

[0089] The high-temperature and high-speed working condition refers to: at 300°C, with a positive pressure of 100N and a linear speed of 0.5m / s, the dynamic friction coefficient is tested with reference to Experimental Example 3, and the dynamic friction coefficient after 5 minutes of stable working condition is taken as the reference value.

[0090] Low temperature and low speed conditions refer to: at 50°C, using hydraulic oil as the medium, compressing the sample sealing material at a compression pressure of 2.5 MPa for 12 hours, measuring the penetration amount of the hydraulic oil (μg / min), and testing and calculating the creep strain ε(t) with reference to Experimental Example 1.

[0091] Table 6 Adaptability test data of auxiliary seal materials prepared in Examples 16-20 and Comparative Examples 9-10

[0092]

[0093] As shown in the adaptability test data of Table 6, the sealing materials prepared by Examples 16-20 have a lower friction coefficient under high-speed and high-temperature conditions, and have a lower hydraulic oil permeation and good creep resistance under low-temperature and low-speed conditions, and have good adaptability under different conditions. Comparative Example 9 uses a single feed in the melt blending stage, which cannot form a concentration gradient of perfluoropolyether in the polymer network, resulting in an increase in the dynamic friction coefficient at high temperatures, and the reduction in cross-linking density leads to an increase in the permeation of hydraulic oil at low temperatures. Comparative Example 10 uses high-density polyethylene to replace polytetrafluoroethylene, which causes a significant increase in the friction coefficient and a significant decrease in the barrier performance to hydraulic oil, and does not have adaptability.

[0094] In summary, when the working conditions change, the auxiliary sealing material product undergoes a specific structural transformation as the temperature changes. Under high-speed working conditions, the PEEK segment will undergo semi-crystalline region dissociation under the action of high-speed friction heat, releasing the perfluoropolyether structure to the outer layer of the polymer network, achieving low friction coefficient and high temperature resistance at high temperatures; at the same time, under low-speed working conditions, the three-dimensional cross-linked network constructed by carbon fiber and silica optimizes the internal structure through segmented sintering, which can effectively block the penetration of oily media and has high creep resistance. Under different working conditions, the sealing material provided by the present invention can automatically improve the performance required for the corresponding working conditions through good adaptability, and has good application value in a variety of mechanical sealing use scenarios.

[0095] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an auxiliary sealing material for a double-end mechanical seal, characterized in that: The preparation method is as follows: 4,4'-difluorobenzophenone and hydroquinone were terminally functionalized and polymerized to obtain oligomeric PEEK; Block copolymerizing the oligomeric PEEK with a dianhydride monomer and a diamine monomer to obtain a PEEK-PI block copolymer; Surface-modifying the PEEK-PI block copolymer to obtain a modified copolymer; Dispersing and mixing the modified copolymer with wear-resistant fillers and aging-resistant additives to obtain a wear-resistant copolymer precursor; Wherein, the wear-resistant filler includes carbon fiber and silicon dioxide; the anti-aging additive includes N,N'-diphenyl-p-phenylenediamine and magnesium oxide; Melting and blending the wear-resistant copolymer precursor with perfluoropolyether to obtain a ternary wear-resistant copolymer; Sintering the ternary wear-resistant copolymer and polytetrafluoroethylene powder in sections to obtain the auxiliary sealing material; The molecular weight of the perfluoropolyether is 3200-5500; the polytetrafluoroethylene powder is a dispersed powder with a molecular weight of 2×10 5 -3.5×10 5 .

2. The method for preparing an auxiliary sealing material for a double-end mechanical seal according to claim 1, characterized in that: The process of the end group functionalization polymerization is as follows: by mass, under nitrogen protection, 22 parts of the hydroquinone are dissolved in 200 parts of N-methylpyrrolidone, potassium carbonate and 50-58 parts of the 4,4'-difluorobenzophenone are added at a rotation speed of 500 rpm, the temperature is increased to 180-200°C at a heating rate of 5°C / min, the reaction solution is cooled to 25°C after continuous reaction for 12 hours, 500 parts of methanol are added, and the precipitated solid product is washed and dried to obtain the oligomeric PEEK.

3. The method for preparing an auxiliary sealing material for a double-end mechanical seal according to claim 1, characterized in that: The dianhydride monomer includes pyromellitic dianhydride and oxydiphenyl dianhydride; the diamine monomer includes diaminodiphenylmethane and diaminodiphenyl ether; the process of the block copolymerization is: according to the mass fraction, under the protection of nitrogen, the diaminodiphenyl ether and the diaminodiphenylmethane are added to N-methylpyrrolidone, and stirred at 50°C and 400rpm until completely dissolved to obtain a diamine solution; the oxydiphenyl dianhydride and pyromellitic dianhydride are dissolved in N-methylpyrrolidone to obtain a dianhydride solution; Under a water bath, 50 parts of the dianhydride solution are slowly added dropwise to 60-74 parts of the diamine solution, and the stirring speed is maintained at 2000 rpm. After the addition is completed, the reaction system is heated to 25°C, stirred at a speed of 800-1000 rpm for 6 hours, the oligomeric PEEK is slowly added, and the reaction is continued for 4 hours. Acetic anhydride and triethylamine are added and reacted at 40°C for 4 hours, and 400 parts of methanol are added to obtain a precipitate. The precipitate is washed and dried to obtain the PEEK-PI block copolymer.

4. The method for preparing an auxiliary sealing material for a double-end mechanical seal according to claim 1, characterized in that: The surface modification process is as follows: at an operating pressure of 10-50 Pa, the PEEK-PI block copolymer is subjected to plasma treatment using oxygen with a flow rate of 10-50 sccm, a radio frequency power of 240-260 W, and a treatment time of 15 minutes, to obtain the modified copolymer after treatment.

5. The method for preparing an auxiliary sealing material for a double-end mechanical seal according to claim 1, characterized in that: The dispersion mixing process is as follows: by mass, 100 parts of the modified copolymer are ground and mixed with 2 parts of the carbon fiber, 3.5 parts of the silicon dioxide, 1.7 parts of the N,N'-diphenyl-p-phenylenediamine and 1.3 parts of the magnesium oxide in a ball mill, wherein the mixing speed is 2000 rpm and the mixing time is 2 hours, and the wear-resistant copolymer precursor is obtained after mixing.

6. The method for preparing an auxiliary sealing material for a double-end mechanical seal according to claim 1, characterized in that: The melt blending process is as follows: 20 parts of the wear-resistant copolymer precursor and 35 parts of the perfluoropolyether are mixed uniformly by mass, and then blended in an internal mixer at a temperature of 320-380° C., 10 parts of the wear-resistant copolymer precursor are added again after 20 minutes, and 40 parts of the wear-resistant copolymer precursor are added after continuing to mix for 30 minutes, the screw speed is maintained at 500 rpm, and mixing is continued for 1 hour to obtain the ternary wear-resistant copolymer.

7. The method for preparing an auxiliary sealing material for a double-end mechanical seal according to claim 1, characterized in that: The process of the segmented sintering is as follows: grinding the ternary wear-resistant copolymer into a powder of 200 mesh by mass, mixing it evenly with the polytetrafluoroethylene powder of 200 mesh, adding polyvinyl alcohol, pre-pressing at an operating pressure of 5MPa, maintaining the pressure for 30 minutes, heating the mixture to 120-150°C at a heating rate of 3°C / min, keeping the temperature for 2 hours under nitrogen protection, then heating the mixture to 330-350°C at a heating rate of 5°C / min, keeping the temperature for 2 hours, cooling the mixture to 25°C at a cooling rate of 2°C / min, and demolding the mixture to obtain the auxiliary sealing material.

8. An auxiliary sealing material for double-end mechanical seal, characterized in that: The auxiliary sealing material for double-end mechanical seal is prepared by the preparation method described in any one of claims 1 to 7; the auxiliary sealing material for double-end mechanical seal comprises: PEEK-PI block copolymer, perfluoropolyether, polytetrafluoroethylene, wear-resistant filler and aging-resistant additive.

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