Metal rubber composite sealing material resistant to strong acid corrosion and strong alkali corrosion and preparation method of metal rubber composite sealing material

Abstract

The invention relates to a strong acid and alkali corrosion resistant metal rubber composite sealing material and a preparation method thereof, and belongs to the technical field of sealing materials, the strong acid and alkali corrosion resistant metal rubber composite sealing material comprises a metal framework layer, a high-performance corrosion resistant bonding layer coated on the metal framework layer, and a corrosion resistant rubber sealing layer firmly combined with the bonding layer through chemical bonding, the corrosion-resistant rubber sealing layer is prepared from a composite elastomer of fluororubber and perfluoroether rubber, and is compounded with a nanoscale corrosion-resistant filler, and the preparation method mainly comprises the steps of cleaning and microporous treatment of a metal framework, preparation and coating of a corrosion-resistant adhesive, mixing and forming of a corrosion-resistant rubber composite, and preparation of the corrosion-resistant rubber sealing layer. And performing final hot-pressing vulcanization and secondary curing. In the invention, through optimization of a material system and collaborative design of a multi-layer composite structure and an interface strengthening process, the tolerance, permeability resistance and structural integrity of the material to media such as concentrated acid, concentrated alkali and the like under wide temperature range and high pressure difference are remarkably improved, and the material has excellent long-term sealing reliability and long service life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sealing materials, in particular to a metal-rubber composite sealing material resistant to strong acid and strong base corrosion and a preparation method thereof. BACKGROUND

[0002] In the industrial fields of chemical industry, petroleum, pharmaceutical industry, hydrometallurgy, etc., a large number of equipment, pipelines and valves need to operate in extreme corrosive media environments such as strong acid and strong base. Sealing components are key components for preventing medium leakage, ensuring system safety and environmental protection. Traditional single-material sealing components, such as pure rubber sealing components (such as nitrile rubber, ordinary fluororubber) or pure polytetrafluoroethylene sealing components, often have obvious shortcomings when facing alternating acid and alkali media and high temperature and high pressure working conditions: rubber materials are prone to chemical swelling, brittleness or strength reduction; pure polytetrafluoroethylene has the problems of cold flow, poor resilience and easy creep.

[0003] To improve performance, metal-rubber composite sealing materials have emerged, which combine the rigidity of metal and the elasticity of rubber and have been widely used in many harsh working conditions. However, such composite materials in the prior art still face challenges when dealing with strong corrosive media: 1. The interface between metal and rubber is prone to debonding and delamination under long-term penetration of corrosive media, leading to sealing failure; 2. The rubber formula has insufficient corrosion resistance, especially strong dependence on high-cost special rubber such as perfluoroether rubber, and its resistance to some strong alkali media still has room for improvement; 3. There is a lack of systematic material and interface coordination design scheme for extreme corrosion environments.

[0004] For example, the prior art uses polysulfide rubber sealant and an outer anti-diffusion polymer layer (such as chlorinated polyvinyl chloride) to protect equipment. However, the heat oxidation resistance and strong acid resistance of polysulfide rubber itself are limited, and the bonding strength of the outer layer to the substrate may decrease under thermal cycling. Some patents mention using a specific plating layer (such as a copper-zinc-nickel ternary alloy) on the metal surface or using a rubber formula containing cobalt salt and a specific accelerator to improve the bonding strength and durability, but the specificity and long-term stability under alternating strong acid and alkali impact of these schemes need to be verified.

[0005] Therefore, there is an urgent need and important industrial value to develop a metal-rubber composite sealing material that has excellent resistance to strong acid and strong base corrosion, high interface bonding strength, long service life, and reasonable cost controllability. SUMMARY

[0006] The application provides a metal-rubber composite sealing material resistant to strong acid and strong base corrosion and a preparation method thereof, and solves the problems of interface failure, insufficient corrosion resistance of a rubber matrix and limited service life of a metal-rubber composite sealing material in the prior art in an extremely corrosive medium environment, and through innovative material system design, interface structure reinforcement and preparation process optimization, the reliability and durability of the composite material in a concentrated acid or concentrated alkali medium for long-term service are significantly improved.

[0007] The application solves the above technical problems in the following manner: a metal-rubber composite sealing material resistant to strong acid and strong base corrosion and a preparation method thereof, comprising a metal framework layer, a corrosion-resistant adhesive layer formed on the surface of the metal framework layer, and a corrosion-resistant rubber sealing layer chemically bonded and firmly combined with the metal framework layer through the corrosion-resistant adhesive layer. The base material of the corrosion-resistant rubber sealing layer is a blended composite elastomer of fluororubber (FKM) and perfluoroether rubber (FFKM).

[0008] On the basis of the above technical solution, the application can also be improved as follows.

[0009] Further, the material of the metal framework layer is 316L stainless steel, Hastelloy C-276 or titanium alloy, and the surface combined with the rubber is subjected to micro-arc oxidation or electrochemical etching treatment to form a roughened structure with a micro-nano aperture. The micro-arc oxidation or electrochemical etching treatment on the surface can construct a ceramicized or roughened structure with a micro-nano aperture on the metal surface. This structure greatly increases the surface area of the metal and provides a strong mechanical interlocking (anchoring) effect for subsequent adhesion, which is a basic physical guarantee for realizing high-strength and durable combination between the metal and the rubber.

[0010] Further, the corrosion-resistant adhesive layer is a composite adhesive system containing a silane coupling agent and a phenolic resin. The silane coupling agent is vinyltriethoxysilane or gamma-glycidoxypropyltrimethoxysilane. One end of the silane coupling agent molecule can form a chemical bond with the hydroxyl group on the metal surface, and the other end (vinyl or epoxy group) can chemically react with the vulcanization system of the rubber, thereby forming a firm chemical bridge at the interface. The phenolic resin, as a high-temperature-resistant and medium-resistant adhesive, can further enhance the overall cohesive strength of the adhesive layer and the stability in harsh environments. The system jointly ensures the durability and reliability of the adhesive layer in a corrosive working condition.

[0011] Further, the corrosion-resistant rubber sealing layer comprises, by weight parts, 70-90 parts of fluororubber (FKM), 10-30 parts of perfluoroether rubber (FFKM), 5-15 parts of nano-sized polytetrafluoroethylene (PTFE) powder, 3-8 parts of fumed silica, and 1-3 parts of vulcanizing agent, so that the FKM as the main body ensures the basic oil resistance, high temperature resistance and resistance to most chemicals; the introduction of the FKM greatly improves the resistance to extreme chemicals (such as concentrated acid, strong base and strong oxidant). The addition of the nano-PTFE powder can significantly reduce the friction coefficient of the composite rubber, improve the wear resistance and medium swelling resistance. The fumed silica as a high-efficiency reinforcing filler can improve the mechanical strength, tear resistance and permanent deformation resistance of the rubber compound. The final blended composite system endows the sealing layer with excellent comprehensive corrosion resistance, elasticity and durability.

[0012] Further, the nano-sized polytetrafluoroethylene (PTFE) powder has a particle size of 50-200 nanometers. The use of the nano-sized PTFE powder can ensure its highly uniform dispersion in the rubber matrix and avoid performance defects caused by agglomeration. The nano-sized dispersion can maximize the surface effect, more effectively improve the self-lubricity and chemical medium permeability of the composite material, and more controllably affect the mechanical properties such as the elastic modulus of the rubber, which is beneficial to maintaining the flexibility and resilience required by the sealing material.

[0013] In another aspect, a preparation method of a metal rubber composite sealing material resistant to strong acid and strong base corrosion comprises the following steps: S1: cleaning the metal skeleton and performing microporous roughening treatment on the surface of the metal skeleton; S2: preparing a corrosion-resistant adhesive and uniformly coating the adhesive on the surface of the treated metal skeleton to form a bonding layer pre-cured film; S3: mixing the components of the corrosion-resistant rubber sealing layer to prepare a rubber compound; S4: bonding the rubber compound on the metal skeleton coated with the bonding layer pre-cured film and placing it in a mold for hot pressing vulcanization to form the rubber layer and realize chemical bonding between the rubber layer and the metal skeleton through the bonding layer; S5: performing secondary high-temperature curing treatment on the vulcanized composite Further, in step S1, the micropore roughening treatment adopts a micro-arc oxidation process, the electrolyte is a silicate system, the treatment voltage is 300-500V, and the treatment time is 10-30 minutes, so that a ceramic oxide layer containing micropores is generated on the metal surface; the micro-arc oxidation process with the specific parameters can in-situ grow a dense, high-hardness ceramic oxide layer on the surface of various selected metals, which is metallurgically combined with the substrate. The layer itself has excellent corrosion resistance and high-temperature resistance. The uniform microporous structure formed by controlling the voltage and time provides an ideal penetration and anchoring space for the adhesive, and is a key process step for obtaining super strong interfacial bonding force.

[0014] Further, in step S4, the heat pressing vulcanization is performed at a temperature of 170-180 DEG C, a pressure of 10-15 MPa, and for 15-20 minutes; and in step S5, the secondary high-temperature curing treatment is performed at 200-230 DEG C for 20-24 hours in an oven. The temperature and pressure of the first heat pressing vulcanization ensure that the rubber is fully crosslinked, densely formed, and closely contacted and initially bonded with the metal framework through the adhesive layer under pressure. The subsequent secondary high-temperature curing treatment can further promote and complete the deep chemical reaction between the silane coupling agent and the rubber, and stabilize the movement of the rubber molecular chain, so as to completely eliminate internal stress and improve crosslinking density. The process combination finally makes the composite material, especially the interface region, have optimal heat resistance, medium resistance and long-term use stability.

[0015] The present application has the following advantages: 1. The present application has excellent and wide corrosion resistance, which is due to the FKM / FFKM blended rubber as the matrix, and the functionalized composite of nano-PTFE and fumed silica. The sealing layer of the present application can resist various extreme chemical media including concentrated sulfuric acid, concentrated nitric acid, strong base and strong oxidant for a long time, has wide medium resistance range, strong anti-swelling and chemical corrosion resistance; 2. The present application has super high strength and stable interfacial bonding, which creates a strengthened interface combining "micro-nano mechanical interlocking" and "multiple chemical bonding". The micro-arc oxidation ceramic layer on the metal surface provides a large anchoring area and physical locking force; the silane coupling agent-phenolic resin composite adhesive system constructs a firm chemical bridging network at the interface. The physical-chemical dual action mechanism ensures the extreme reliability of the interface under the action of heat, chemicals and stress, and effectively prevents the interface from peeling off due to medium penetration; 3. The composite material has excellent comprehensive mechanical properties and durability, and has the structural rigidity of the metal skeleton and the excellent elasticity of the composite rubber layer; the addition of nano PTFE endows the sealing surface with low friction, high wear resistance and anti-adhesion properties; the reinforcing effect of fumed silica improves the strength, tear resistance and compression permanent deformation resistance of the rubber, which makes the sealing element have good sealing performance under high pressure, long-lasting resilience and significantly prolonged service life; 4. The optimized cost and performance balance, through the scientific FKM and FFKM ratio design, the key performance (extreme medium resistance) is close to pure FFKM, while the raw material cost is greatly reduced, at the same time, the surface treatment process such as micro-arc oxidation is mature and controllable, which is beneficial to large-scale production, so that the high-performance composite material has better economic efficiency and market competitiveness.

[0016] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and can be implemented according to the content of the specification, the following is the preferred embodiment of the present application and the detailed description of the drawings. The specific embodiments of the present application are given in detail by the following examples and their drawings. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings: Figure 1 A method flow chart of a metal-rubber composite sealing material resistant to strong acid and strong base corrosion and a preparation method thereof are provided for an embodiment of the present application. DETAILED DESCRIPTION

[0018] The following will be combined with the Figure 1 The principles and characteristics of the present application are described, and the examples are only used to explain the present application, not to limit the scope of the present application. In the following paragraphs, the present application is described in more detail with reference to the drawings. According to the following description, the advantages and characteristics of the present application will be more clear. It should be noted that the drawings are very simplified and use non-precise proportions, only to facilitate and clearly assist the purpose of explaining the embodiments of the present application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0020] As Figure 1As shown, the present application provides a metal rubber composite sealing material resistant to strong acid and strong base corrosion and a preparation method thereof, comprising a metal skeleton layer for providing mechanical support and strength; a corrosion-resistant adhesive layer for realizing high strength and medium-resistant chemical bonding; and a corrosion-resistant rubber sealing layer for providing final elastic sealing function; The metal skeleton layer is preferably a high corrosion-resistant metal such as 316L stainless steel, Hastelloy C-276 or titanium alloy, and the key improvement is that the surface combined with the rubber is treated by micro-arc oxidation or similar electrochemical etching to form a ceramicized rough surface with micro-nano pore size, which greatly increases the specific surface area and provides firm mechanical interlocking anchor points for subsequent bonding; The corrosion-resistant adhesive layer is formed by a specially prepared composite adhesive, which mainly uses corrosion-resistant phenolic resin and is compounded with specific types of silane coupling agents (such as vinyl triethoxysilane or gamma-glycidoxypropyl trimethoxysilane), the silane coupling agent reacts with the hydroxyl group on the metal surface at one end and with the unsaturated bond or functional group in the rubber at the other end, thereby forming a stable "chemical bridge" at the interface; The corrosion-resistant rubber sealing layer uses a blend system of fluororubber (FKM) and perfluoroether rubber (FFKM) as the base, FKM provides excellent comprehensive chemical resistance and cost balance, and FKM contributes extreme high temperature resistance and solvent resistance, the two are complementary to each other, and nano-sized polytetrafluoroethylene (PTFE) powder and fumed silica are added as corrosion-resistant fillers in the rubber matrix to further improve the impermeability and corrosion resistance, nano-PTFE not only improves the chemical resistance, but also improves the wear resistance and low friction characteristics of the material.

[0021] The specific working principle and use method of the present application are as follows: Step one, metal skeleton surface treatment, select a 316L stainless steel O-shaped metal skeleton with an inner diameter of 50mm and a wire diameter of 3mm, clean and dry by ultrasonic cleaning with acetone, alkaline cleaning agent and deionized water in turn, place the metal skeleton in the electrolyte of the micro-arc oxidation equipment (with sodium silicate as the main salt), treat for 20 minutes under 400V direct current voltage, after treatment, a uniform grayish white porous oxide ceramic layer is formed on the metal surface, with an average pore size of about 2-5 microns; Step two, corrosion-resistant adhesive preparation and coating, weigh: phenolic resin (such as TY-501) 100 parts, gamma-glycidoxypropyl trimethoxysilane (KH-560) 15 parts, and an appropriate amount of solvent (methyl ethyl ketone / toluene mixture) to the appropriate viscosity for coating, mix the components uniformly, stand for defoaming, and uniformly coat the adhesive on the treated metal skeleton surface by dip coating, and pre-cure in an 80℃ oven for 15 minutes to form a semi-cured adhesive film; Step three, the preparation of corrosion-resistant rubber compound, the following raw materials are prepared by weight parts: fluorine rubber (FKM, brand GLS2691) 80 parts, perfluoroether rubber (FFKM, brand PFR-94) 20 parts, nano PTFE powder (average particle size 100 nm) 10 parts, fumed silica (Aerosil 200) 5 parts, vulcanizing agent (bisphenol AF) 2 parts, accelerator (benzyl triphenyl phosphonium chloride) 0.5 parts; Mix FKM and FFKM on the open mill, add nano PTFE powder, fumed silica in turn, and finally add vulcanizing agent and accelerator, mix until uniform, and cut into sheets for use; Step four, compounding and vulcanization, cut the rubber compound into rubber strips of appropriate shape, insert them into the peripheral groove of the metal skeleton coated with an adhesive layer, and place the whole into the preheated O-ring mold, and perform one-stage vulcanization on the flat vulcanization machine: temperature 175℃, pressure 12MPa, time 18 minutes, and demold after vulcanization is completed; Step five, secondary curing, place the one-stage vulcanized composite O-ring into a high-temperature oven for two-stage curing: program the temperature to rise to 220℃, and keep at this temperature for 22 hours, then cool down to room temperature with the oven, and the finished product composite sealing ring is obtained.

[0022] It should be noted that in this paper, relationship terms such as first and second are only used to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between the entities or operations. The contents not described in detail in this specification are prior art known to those skilled in the art.

[0023] The above is only a preferred embodiment of the present application, and does not limit the present application in any form; anyone skilled in the art can easily implement the present application according to the drawings and the above description; however, those skilled in the art can make some changes, modifications and equivalent changes within the scope of the technical solutions of the present application, which are equivalent embodiments of the present application; at the same time, any equivalent changes, modifications and evolution of the above embodiments according to the essential technology of the present application are still within the protection scope of the technical solutions of the present application.

Claims

1. A metal-rubber composite sealing material resistant to strong acid and alkali corrosion, characterized in that: It comprises a metal skeleton layer, a corrosion-resistant adhesive layer formed on the surface of the metal skeleton layer, and a corrosion-resistant rubber sealing layer that is chemically bonded and firmly bonded to the metal skeleton layer by the corrosion-resistant adhesive layer; The base material of the corrosion-resistant rubber sealing layer is a blended composite elastomer of fluororubber (FKM) and perfluoroether rubber (FFKM); The preparation method includes the following steps: S1, cleaning the metal skeleton and roughening its surface by microporous treatment; S2, prepare a corrosion-resistant adhesive and apply it evenly to the surface of the treated metal skeleton to form a pre-cured adhesive layer film; S3, the components of the corrosion-resistant rubber sealing layer are mixed to prepare the compound rubber; S4, the compounded rubber is bonded to a metal skeleton coated with a pre-cured adhesive layer, and then placed in a mold for hot-press vulcanization, so that the rubber layer is formed and chemically bonded to the metal skeleton through the adhesive layer. S5 involves subjecting the vulcanized composite to a secondary high-temperature curing process.

2. The metal-rubber composite sealing material resistant to strong acid and alkali corrosion according to claim 1, characterized in that, The metal skeleton layer is made of 316L stainless steel, Hastelloy C-276, or titanium alloy. The surface of the metal skeleton layer bonded to the rubber is treated with micro-arc oxidation or electrochemical etching to form a roughened structure with micro- and nano-scale pores.

3. The metal-rubber composite sealing material resistant to strong acid and alkali corrosion according to claim 1, wherein the corrosion-resistant adhesive layer is a composite adhesive system containing a silane coupling agent and a phenolic resin, wherein the silane coupling agent is vinyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

4. The metal-rubber composite sealing material resistant to strong acid and alkali corrosion according to claim 1, characterized in that, The corrosion-resistant rubber sealing layer comprises, by weight: 70-90 parts of fluororubber (FKM), 10-30 parts of perfluoroether rubber (FFKM), 5-15 parts of nano-grade polytetrafluoroethylene (PTFE) powder, 3-8 parts of fumed silica, and 1-3 parts of vulcanizing agent.

5. The metal-rubber composite sealing material resistant to strong acid and alkali corrosion according to claim 4, characterized in that, The particle size of the nano-sized polytetrafluoroethylene (PTFE) powder is 50-200 nanometers.

6. The method for preparing a metal-rubber composite sealing material resistant to strong acid and alkali corrosion according to claim 1, characterized in that, In step S1, the microporous roughening treatment adopts a micro-arc oxidation process, the electrolyte is a silicate system, the treatment voltage is 300-500V, and the treatment time is 10-30 minutes, to generate a ceramic oxide layer containing micropores on the metal surface.

7. The method for preparing a metal-rubber composite sealing material resistant to strong acid and alkali corrosion according to claim 1, characterized in that, In step S4, the conditions for hot-press vulcanization are: a vulcanization temperature of 170-180℃, a pressure of 10-15MPa, and a time of 15-20 minutes; in step S5, the conditions for the secondary high-temperature curing treatment are: maintaining the temperature at 200-230℃ in an oven for 20-24 hours.

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