A modified expanded vermiculite filler and a protective coating prepared therefrom

Abstract

The application belongs to the field of inorganic functional materials, and discloses a modified expanded vermiculite filler and a protective coating prepared from the same. The preparation method of the modified expanded vermiculite filler comprises the following steps: soaking expanded vermiculite in a siloxane precursor solution, an acidic solution, an alkaline solution, a mixed solution of silane and n-hexane, a mixed solution of diisocyanate and n-hexane in sequence, and finally drying to obtain a low-thermal-conductivity modified expanded vermiculite filler. In the application, silica aerogel is generated in situ between the peripheral layers of expanded vermiculite, the excellent heat insulation performance of the silica aerogel is utilized to improve the heat insulation performance of the expanded vermiculite, and the protective effect of the lamellar interlayer structure of the expanded vermiculite is utilized to reduce the fragmentation tendency of the silica aerogel, so that an expanded vermiculite type heat insulation filler with excellent heat insulation performance and mechanical performance is obtained, and the expanded vermiculite type heat insulation filler is used to prepare a low-thermal-conductivity coating material for ultra-deep well drilling.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inorganic functional materials, in particular to an expanded vermiculite type thermal insulation filler with excellent thermal insulation and mechanical properties, and a low thermal conductivity coating material for ultra-deep wells obtained therefrom, and further relates to a low thermal conductivity modified expanded vermiculite filler for the field of ultra-deep wells. BACKGROUND

[0002] With the extension of oil and gas exploration to deep and ultra-deep (>8000m) and high temperature strata (>300℃), drill pipes face severe challenges in extreme working conditions of high temperature, high pressure and strong corrosion. The rapid rise of drilling fluid temperature caused by the high thermal conductivity of traditional drill pipes seriously reduces the service life of drill pipes, affects the performance of electronic devices such as logging instruments, and even causes damage, and increases the risk of wellbore instability. The existing low thermal conductivity or thermal insulation drill pipe technology has many deficiencies. Some technologies use inner liner or vacuum annulus design (such as CN202011038749.7 patent), which reduces the thermal conductivity coefficient by filling phenolic resin or sand particles, but this structure reduces the inner diameter of the drill pipe by 20%-30%, significantly increases the pumping resistance, and affects the passability of logging tools. At the same time, the welding process is prone to cracks, and the risk of liner falling off is high (the casing loss rate is more than 30%). The traditional phenolic epoxy resin coating material and ceramic coating material have high thermal conductivity, which cannot achieve effective thermal insulation.

[0003] Therefore, actively developing high-performance low thermal conductivity materials for ultra-deep well drilling has become an important research goal in recent years. In coating materials, thermal insulation functional fillers with low thermal conductivity, light weight, high temperature resistance, and good chemical stability are key, among which the most notable are expanded vermiculite, aerogels (such as silica aerogel, carbon aerogel), and hollow microspheres (such as glass beads, ceramic beads).

[0004] Vermiculite is a natural, inorganic, non-toxic mineral that expands under high temperature. It is a relatively rare silicate mineral. Its structural unit layer is composed of two layers of silicon (part of the silicon is replaced by aluminum) oxygen tetrahedral framework sandwiching an octahedral layer filled with Mg 2+ , Fe 3+ , etc. between the layers. There are Mg 2+ , Na + , Ca 2+The interlayer spacing of vermiculite is about 1.4 nm, and there are a large number of interlayer ions, as well as adsorbed water, interlayer water and structural water. The main characteristics of vermiculite: the interlayer of vermiculite is negatively charged and the interlayer ions are exchangeable; vermiculite expands when heated to obtain expanded vermiculite, and the volume of vermiculite will expand by 6-20 times after high-temperature calcination. The specific surface area and porosity of expanded vermiculite will be significantly improved. The ordered and stable layered silicate structure makes vermiculite easy to modify, expand and exfoliate. These characteristics of vermiculite make it widely used in various functional materials. Its unique porous layered structure greatly reduces the solid-phase thermal conductivity. Therefore, expanded vermiculite is an excellent thermal insulation functional filler. At the same time, the chemical stability and high temperature resistance of expanded vermiculite make it suitable for harsh environments, and the mechanical properties of expanded vermiculite are excellent, with excellent toughness.

[0005] Silica aerogel is a new type of lightweight nanoporous amorphous solid material formed by chemical bonds between colloidal particles to form a main skeleton. Silica aerogel is prepared by a relatively common wet chemical synthesis method (sol-gel method). The preparation of silica aerogel generally includes three main steps: sol-gel stage, aging stage and drying stage. The synthesis of silica aerogel usually adopts acid-base two-step catalysis method. Under acid catalysis conditions, the hydrolysis rate of silicon source is greater than the condensation rate, and a large number of oligomers or polymers will be produced in the solution; while under alkaline catalysis conditions, the reaction rate of polymeric hydrolysis and condensation is higher than that of oligomers, and the chain structure of the polymer will preferentially grow in all directions, and the cluster particles in the solution will crosslink with each other to form a gel. In practical applications, silica aerogel has excellent performance such as extremely low thermal conductivity (0.005-0.1 W·(mK) -1 ), high specific surface area (500-1200 m 2 ·g -1 ), high porosity (80-99.8%), low density (0.003-0.5 g·cm -3 ), etc. It has wide application potential in the fields of thermal insulation systems in aerospace, pipeline and wall thermal insulation, etc. However, silica aerogel as a thermal insulation material has the disadvantages of high cost and high brittleness, and there is still room for improvement in dispersion, stability and mechanical strength when used to prepare composite thermal insulation materials.

[0006] Both silica aerogel and expanded vermiculite are important thermal insulation fillers in industrial applications, and have excellent performance and certain complementarity, so they are used together in practical applications, but the current method is to physically blend the above thermal insulation materials. For example, CN104763063A discloses a nano-porous silica aerogel thermal insulation board, which comprises an infrared reflecting screen, and a porous base material is arranged between the infrared reflecting screen, and nano-silica aerogel particles, nano-porous silicon fibers and nano-antimony oxide are uniformly dispersed in the porous base material; according to the weight fraction, the porous base material is 30-70 parts, the nano-silica aerogel particles are 2-3 parts; the nano-porous silicon fibers are 10-20 parts, and the nano-antimony oxide is 5-30 parts; the porous base material is expanded vermiculite; the particle size of the nano-silica aerogel particles is less than 70 nanometers. The specific preparation method of the material is to place the expanded vermiculite in a blender and stir. Then the nano-silica aerogel particles, nano-porous silicon fibers and nano-antimony oxide are added to the expanded vermiculite and mixed and stirred. Finally, the mixed material formed in the above step is placed into the infrared reflecting screen for molding, and the pressure is maintained for 40 minutes when the mold is extruded.

[0007] The direct blending modification of silica aerogel and expanded vermiculite has the following problems: (1) large density difference, easy to separate; aerogel is extremely light (density 0.003-0.1 g / cm 3 ), vermiculite is relatively heavy (density 0.1-0.3 g / cm 3 ), and the dispersion process needs to be optimized; (2) aerogel is easy to break; the hard particles of vermiculite may damage the porous structure of aerogel during stirring and molding, reducing its thermal insulation performance; (3) water absorption contradiction; aerogel (hydrophobic modified) is hydrophobic, while vermiculite is hydrophilic, and mixing may cause interface compatibility problems, even if silane coupling agent is added, the compatibility improvement is also limited; (4) nonlinear superposition of thermal conductivity performance, simple physical mixing may not achieve the theoretical optimization of thermal conductivity coefficient. Therefore, the purpose of the present application is to obtain an expanded vermiculite type thermal insulation filler with excellent thermal insulation and mechanical properties, for preparing a low thermal conductivity coating material for ultra-deep well drilling. SUMMARY

[0008] To solve the above problems, the application discloses a modified expanded vermiculite filler, and a preparation method of the modified expanded vermiculite filler, which comprises the following steps: pre-impregnating expanded vermiculite in a siloxane precursor solution containing methyltrimethoxysilane, tetraethyl orthosilicate and gamma-aminopropyl triethoxysilane, and filtering to obtain pre-impregnated vermiculite; soaking the pre-impregnated vermiculite in an acidic solution with a pH value of 2-4, and filtering to obtain hydrolyzed modified expanded vermiculite; mixing the hydrolyzed modified expanded vermiculite with an alkaline solution with a pH value of 7-9 and standing, and filtering to obtain gelled modified expanded vermiculite; soaking the gelled modified expanded vermiculite in a silane and n-hexane solution for hydrophobic aging treatment; and performing normal pressure drying on the modified expanded vermiculite after the hydrophobic aging treatment to obtain the modified expanded vermiculite filler, wherein the thermal conductivity of the modified expanded vermiculite filler is 0.015-0.035 W·(mK) -1 .

[0009] Further, the expanded vermiculite is pre-impregnated in a siloxane precursor solution containing methyltrimethoxysilane, tetraethyl orthosilicate and gamma-aminopropyl triethoxysilane, comprising:

[0010] selecting expanded vermiculite;

[0011] configuring a siloxane precursor solution;

[0012] impregnating the expanded vermiculite in the siloxane precursor solution for 0.5-2 hours;

[0013] filtering to obtain pre-impregnated vermiculite.

[0014] Further, the thermal conductivity of the expanded vermiculite is 0.05-0.09 W·(mK) -1 , and the particle size is 80-325 mesh.

[0015] Further, in the siloxane precursor solution, the molar ratio of methyltrimethoxysilane: tetraethyl orthosilicate: gamma-aminopropyl triethoxysilane: ethanol: water is (0.3-0.5):(0.3-0.5):(0.1-0.3):(3-5):(3-5).

[0016] Further, the expanded vermiculite is pre-impregnated in a siloxane precursor solution containing methyltrimethoxysilane, tetraethyl orthosilicate and gamma-aminopropyl triethoxysilane, comprising:

[0017] selecting expanded vermiculite;

[0018] respectively configuring a siloxane precursor solution A and a siloxane precursor solution B;

[0019] impregnating the expanded vermiculite in the siloxane precursor solution A and the siloxane precursor solution B in sequence;

[0020] The ratio of methyltrimethoxysilane: ethyl orthosilicate: ethanol: water in the siloxane precursor solution A is (0.3-0.5):(0.3-0.5):(2-3):(2-3) by mole ratio, and the ratio of gamma-aminopropyltriethoxysilane: ethanol: water in the siloxane precursor solution B is (0.1-0.3):(1-2):(1-2).

[0021] Further, the mass ratio of the pre-impregnation treated vermiculite and the acidic solution is 1:(2-15).

[0022] Further, the mass ratio of the hydrolysis treated modified expanded vermiculite and the alkaline solution is 1:(2-15).

[0023] Further, the temperature of the hydrophobic aging treatment is 30-50 DEG C, and the time is 16-48h; the volume ratio of silane and n-hexane is 1:(8-12).

[0024] Further, before the hydrophobic aging treatment, solvent replacement treatment is performed, and the gelatinized modified expanded vermiculite is placed in a solvent for solvent replacement, and the time is 12-18 days, and the solvent is methanol or cyclohexane or ethanol.

[0025] Further, after the hydrophobic aging treatment, the obtained modified expanded vermiculite after the hydrophobic aging treatment is soaked in a diisocyanate and n-hexane solution for 2-4 hours, and the modified expanded vermiculite after the aging treatment is obtained by filtration.

[0026] The modified expanded vermiculite after the aging treatment is subjected to normal pressure drying to obtain the modified expanded vermiculite filler.

[0027] Further, the diisocyanate is toluene diisocyanate, isophorone diisocyanate and / or diphenylmethane diisocyanate.

[0028] The application further discloses a protective coating, which has an A component and a B component, and the A component comprises bisphenol A type epoxy resin 20-50 parts, phenolic epoxy resin 10-20 parts, reinforcing fiber 2-8 parts, modified expanded vermiculite filler 6-15 parts, silica aerogel 2-6 parts, hollow glass microsphere 4-8 parts, solvent and additive, and the B component comprises polyamide 10-15, polyether amine 4-8 and solvent, wherein the modified expanded vermiculite filler is the modified expanded vermiculite filler described above.

[0029] The technical effects and advantages of the application are as follows:

[0030] The application in-situ synthesizes silica aerogel in the peripheral layer of expanded vermiculite, and the obtained modified expanded vermiculite is used as the silica aerogel modified expanded vermiculite filler, which has the following excellent performances.

[0031] (1) greatly improve the thermal insulation performance of expanded vermiculite, most of the thermal conductivity coefficient in the market is generally in 0.05-0.09W / (m·K) -1 The present application improves the thermal insulation performance of expanded vermiculite by generating silica aerogel in situ in the interlayer of the peripheral layer of silica, and utilizing the excellent thermal insulation performance of silica aerogel. This is because the interlayer space size of expanded vermiculite is slightly larger, much larger than the average free path of air molecules, and air molecules can move freely and expand in the interlayer space, and the efficiency of heat conduction through air is very high. The air size of silica aerogel is in the nanometer level, which is smaller than the average free path of air molecules, and the air molecules are locked in the small gap, and the probability of collision is low, so it is difficult for heat to be transferred by air convection and conduction. The formation of silica aerogel in the interlayer of the peripheral layer of expanded vermiculite changes the open interlayer space of expanded vermiculite into a closed interlayer space, and the peripheral blocked silica aerogel has excellent thermal insulation performance, thereby effectively improving the thermal insulation performance of expanded vermiculite.

[0032] (2) improve the strength of silica aerogel

[0033] Expanded vermiculite has stable structure and certain toughness. Due to the protection of the interlayer structure of the sheet-like vermiculite, the fragmentation tendency of the silica gel is reduced, and the fragmentation of the silica aerogel caused by high-speed stirring during the preparation of the thermal insulation material is avoided, thereby improving the processing performance of the thermal insulation material containing silica aerogel.

[0034] (3) improve the hydrophobicity of expanded vermiculite

[0035] Expanded vermiculite has certain hydrophilicity, which leads to the adsorption of water during use, thereby causing the decline of the thermal insulation performance. In the preparation of modified expanded vermiculite, the gelled modified expanded vermiculite is soaked in a silane / n-hexane solution for hydrophobic treatment. The silane such as trimethylchlorosilane converts the hydroxyl groups on the surface of the silica aerogel and the expanded vermiculite into hydrophobic silicon methyl groups, thereby improving the hydrophobicity of the composite material and avoiding the influence of water adsorption on the thermal insulation performance of the material.

[0036] (4) In the aging process, the hydrophobic treated modified expanded vermiculite is soaked in a diisocyanate / n-hexane solution. The diisocyanate reacts with the amine groups on the surface of the aerogel to improve the strength of the silica aerogel framework. In addition, when the expanded vermiculite is immersed in the above siloxane precursor solution, it can be predicted that a small part of the siloxane will also be adsorbed on the surface of the expanded vermiculite. Therefore, whether it is the hydrophobic modification of silane or the reaction of diisocyanate with amino and hydroxyl groups, the hydrophobicity is further improved.

[0037] (5) Further, when the expanded vermiculite of the present application is immersed in the above-mentioned siloxane precursor solution, a two-step immersion method can also be used, in which a siloxane precursor solution A containing MTMS, TEOS, ethanol, and water, and a siloxane precursor solution B containing KH550, ethanol, and water are prepared, and the expanded vermiculite is then immersed in the above-mentioned siloxane precursor solution A and the siloxane precursor solution B in sequence. This can make the concentration of the peripheral γ-aminopropyltriethoxysilane in the precursor adsorbed between the layers of the expanded vermiculite slightly higher, so that the concentration of the amino functional group on the outside of the expanded vermiculite is slightly higher, the probability of reaction with diisocyanate is increased, and the crosslinking density on the outside is greatly increased. This can not only improve the toughness but also improve the sealing property and thus the thermal insulation property.

[0038] (6) The present application also conducts in-depth research on the formulation and process of the protective coating containing the above-mentioned modified expanded vermiculite. In terms of the formulation, the addition of the phenolic epoxy resin improves the crosslinking density and significantly improves the glass transition temperature of the protective coating. Meanwhile, the addition of the inorganic filler with good dispersibility also further improves the performance of the protective coating at high temperatures. The present application also adds KH-560 (epoxy silane), which has good compatibility with the epoxy resin and high stability and is not easy to interfere with the curing reaction. The modified effect of the modified expanded vermiculite, glass fiber, and glass microbeads is significant, and the compatibility of the above-mentioned fillers with the epoxy resin is improved, which can significantly improve the adhesion and the bonding strength and mechanical strength of the fillers and the resin. The present application also attempts to use a polyamide and polyether amine composite curing system. The polar amide group (-CONH-) in the polyamide molecule can form a hydrogen bond with the substrate (such as metal and concrete), significantly improving the adhesion, and the wettability of the high-surface-energy fillers (such as glass fiber) is better, reducing the interface defects, and the crosslinking density after curing is higher, which is more suitable for high-temperature environments and has excellent chemical corrosion resistance. The addition of polyether amine (such as D230) enables the system to slowly cure at a low temperature of 5-15℃, solving the problem of winter construction. The long-chain polyether structure of the polyether amine endows the coating with elasticity, and the elongation at break is improved by 30-50%, avoiding brittle fracture caused by high filler content of the vermiculite / aerogel. The low viscosity characteristics of the polyether amine (such as the viscosity of D230 is only 15 mPa·s) also help to penetrate into the porous fillers such as aerogel / vermiculite, reducing the interface defects. Through the synergistic effect of the polyamide (rigidity) and the polyether amine (flexibility), the tensile strength (≥40 MPa) and toughness are balanced, and the adhesion, chemical corrosion resistance, and corrosion resistance of the protective coating at high temperatures are improved.

[0039] In the process, BYK-110 (anionic) is used for the dispersion of vermiculite / glass beads, and BYK-111 (non-ionic) is used for the dispersion of aerogel, and the two work together to avoid sedimentation and improve the dispersion of vermiculite, glass beads and aerogel. At the same time, the aerogel is pretreated to improve the dispersion and avoid the damage to the structure of the aerogel. The ultrasonic pretreatment of the aerogel slurry (100W pulse) breaks the soft agglomeration, and the detection shows that the D90 particle size is ≤50μm. DETAILED DESCRIPTION

[0040] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application will be described in detail as follows, but it cannot be understood as a limitation to the scope of the present application.

[0041] The present application relates to a modified expanded vermiculite filler, and a preparation method thereof, which comprises the following steps:

[0042] 1. Pre-impregnation of expanded vermiculite: the expanded vermiculite is pre-impregnated in a siloxane precursor solution containing methyltrimethoxysilane, tetraethyl orthosilicate and γ-aminopropyl triethoxysilane, and filtered; specifically comprising:

[0043] 1.1. Selecting expanded vermiculite;

[0044] 1.2. Preparing a siloxane precursor solution, i.e. preparing a solution containing methyltrimethoxysilane (MTMS), tetraethyl orthosilicate (TEOS) and γ-aminopropyl triethoxysilane (KH550);

[0045] 1.3. Impregnating the expanded vermiculite in the above-mentioned siloxane precursor solution for 0.5-2 hours;

[0046] 1.4. Filtering to obtain pre-impregnated vermiculite.

[0047] The thermal conductivity of the expanded vermiculite is 0.05-0.09 W·(mK) -1 , the particle size can be 80-325 mesh, preferably 120-200 mesh, and it can be prepared by general heating method, microwave heating method, intercalation method or microwave heating method+intercalation method.

[0048] In step 1.2, the molar ratio of MTMS:TEOS:KH550:ethanol:water in the siloxane precursor solution is (0.3-0.5):(0.3-0.5):(0.1-0.3):(3-5):(3-5), and is further preferably 0.4:0.4:0.2:4:4. In step 1.3, the mass ratio of expanded vermiculite to siloxane precursor solution is 1:(2-10), for example 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. In the process of impregnation, ultrasonic or vacuum assisted impregnation can be used. In step 1.3, the impregnation time is preferably 0.5-1 hour. If the time is too short, the amount of precursor entering the interlayer is too small, and the periphery of the interlayer cannot be closed. If the time is too long, a large amount of precursor enters the interior of the interlayer, blocking the interior, not only reducing the thermal insulation performance, but also increasing the cost.

[0049] Another alternative way: step 1.2 respectively configures siloxane precursor solution A and siloxane precursor solution B, wherein the molar ratio of MTMS:TEOS:ethanol:water in the siloxane precursor solution A is (0.3-0.5):(0.3-0.5):(2-3):(2-3), and the molar ratio of KH550:ethanol:water in the siloxane precursor solution B is (0.1-0.3):(1-2):(1-2). In step 1.3, the expanded vermiculite is first immersed in the above-mentioned siloxane precursor solution A and then in the siloxane precursor solution B, with the time being 20-80 minutes and 10-40 minutes respectively. Two-step impregnation can make the concentration of γ-aminopropyltriethoxysilane in the precursor adsorbed in the interlayer of the expanded vermiculite slightly higher, so that the concentration of the amino functional group on the outside of the aerogel produced in the interlayer of the expanded vermiculite is slightly higher, increasing the reaction probability with diisocyanate and greatly increasing the crosslinking density on the outside. This not only improves the toughness but also improves the sealing performance and thus improves the thermal insulation performance.

[0050] 2. Sol-gel:

[0051] 2.1. Hydrolysis

[0052] The pre-impregnated vermiculite obtained in step 1 is placed in an acidic solution with a pH value of 2-4 for a certain period of time, and then filtered to obtain a hydrolysis-treated modified expanded vermiculite. Further, the mass ratio of pre-impregnated vermiculite to acidic solution is 1:(2-15), for example 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, or 1:15.

[0053] The acidic solution is a hydrochloric acid solution, and can also be 0.1 mol·L -1hydrochloric acid, deionized water and ethanol. The soaking time is 1-2 hours, and the temperature is 40-60℃ (for example). In the hydrolysis procedure, MTMS, TEOS and KH550 are fully hydrolyzed to generate Si(OH)4.

[0054] 2.2, Gelation

[0055] Condensation stage: the hydrolysis-treated modified expanded vermiculite obtained in step 2.1 is mixed with an alkaline solution with a pH of 7-9 and left to stand for a period of time, filtered, and the gelated modified expanded vermiculite is obtained. Further, the mass ratio of the hydrolysis-treated modified expanded vermiculite to the alkaline solution is 1: (2-15), for example 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14 or 1:15.

[0056] The alkaline solution is ammonia water, a sodium hydroxide aqueous solution or a mixture of 0.5 mol·L -1 of ammonia water, deionized water and ethanol. The soaking time is 0.2-1 hour. This process promotes the condensation of the silica sol between the layers of the expanded vermiculite to form a gel network.

[0057] 3, Hydrophobic aging

[0058] 3.1, The gelated modified expanded vermiculite is soaked in a silane / n-hexane solution for hydrophobic aging treatment; further, the temperature of the hydrophobic aging treatment is 30-50℃, and the time is 16-48h. Then the hydrophobic aging-treated modified expanded vermiculite is obtained by filtration;

[0059] The volume ratio of silane to n-hexane is 1: (8-12), for example 1:8, 1:9, 1:10, 1:11 or 1:12. The silane can be trimethylchlorosilane (TMCS), hexamethyldisilazane (HMDS) and / or methyltrimethoxysilane (MTMS), and is preferably trimethylchlorosilane. Through silanization, the pore size of the silica network is increased, the aerogel obtains relatively stable hydrophobic properties, and the surface tension is reduced.

[0060] Before step 3.1, a solvent replacement treatment can also be performed in advance, that is, the gelated modified expanded vermiculite is placed in a solvent for solvent replacement for 12-18 days. The solvent is methanol or cyclohexane or ethanol.

[0061] Further, after step 3.1, step 3.2 can also be performed, that is, the hydrophobic aging-treated modified expanded vermiculite obtained in step 3.1 is soaked in a diisocyanate and n-hexane solution for 2-4 hours, and the aging-treated modified expanded vermiculite is obtained by filtration;

[0062] The volume ratio of the diisocyanate to n-hexane is 1:(8-12), for example 1:8, 1:9, 1:10, 1:11 or 1:12, preferably 1:10.

[0063] The diisocyanate can be toluene diisocyanate, isophorone diisocyanate and / or diphenylmethane diisocyanate. The diisocyanate reacts readily with the amine groups on the surface of the aerogel, thereby improving the strength of the silica skeleton.

[0064] 4. The modified expanded vermiculite filler is obtained by performing normal pressure drying to obtain a silica aerogel modified expanded vermiculite composite material, and the thermal conductivity of the modified expanded vermiculite filler is 0.015-0.035 W·(mK) -1 , and more preferably 0.020-0.025 W·(mK) -1 .

[0065] The drying process is 25-80℃ ventilation drying for 24-72 hours, and vacuum assisted drying can also be used to accelerate solvent removal.

[0066] In addition, the n-hexane of the present application can also be replaced by ethanol and / or acetone, and can also be used in combination.

[0067] The present application also relates to a protective coating prepared by using the modified expanded vermiculite filler, and the protective coating is mainly used for drill pipe protective coating. The protective coating has an A component and a B component, and the A component and the B component are calculated by weight percentage, wherein the A component comprises 20-50 parts of bisphenol A type epoxy resin, 10-20 parts of phenolic epoxy resin, 2-8 parts of reinforcing fiber, 6-15 parts of modified expanded vermiculite filler, 2-6 parts of silica aerogel, 4-8 parts of hollow glass microspheres, solvent and additives; the B component comprises 10-15 parts of polyamide, 4-8 parts of polyether amine and solvent.

[0068] The bisphenol A type epoxy resin can be E-20, E-51, E-44, EPON 828 or TDE-85; the phenolic epoxy resin can be F-51, F-44 or DEN 431, wherein the reinforcing fiber is glass fiber, and specifically can be chopped glass fiber. The solvent in the A component and the B component can be butanol, acetone, butanone, dimethylbenzene, ethyl acetate, propylene glycol methyl ether, 1,4-butanediol diglycidyl ether, propylene glycol methyl ether acetate and / or toluene, etc.

[0069] The auxiliary agent includes dispersant, defoaming agent and / or film forming auxiliary agent, etc. The dispersant can be BYK-180, BYK-181, BYK-110, BYK-111, BYK-W 9010, W 940, BYK-9076, BYK-9077, BYK-2150, BYK-2155. When used, the A component and the B component are mixed in a mass ratio of (3-5):1 to obtain the protective coating. The defoaming agent is a polyether modified silicon defoaming agent; the film forming auxiliary agent is one or more of benzyl alcohol, propylene glycol, ethylene glycol butyl ether, propylene glycol phenyl ether and dodecanol ester.

[0070] The A component is prepared by the following method: taking bisphenol A type epoxy resin and phenolic epoxy resin and placing them in a stirred tank, under slow stirring, adding part of the solvent until uniformly dispersed, adding reinforcing fibers, modified expanded vermiculite filler, silica aerogel, hollow glass microbeads, the remaining solvent, auxiliary agent to the stirred tank while stirring and mixing. The B component is prepared by the following method: polyamide, polyether amine, solvent and auxiliary agent are mixed uniformly using a high-speed mixer.

[0071] Further, in terms of weight parts, the A component: bisphenol A type epoxy resin 35-40 parts, phenolic epoxy resin 12-15 parts, reinforcing fiber 4-5 parts, modified expanded vermiculite 10-12 parts, silica aerogel 3-5 parts, hollow glass microbeads 4-6 parts, solvent 15-20 parts, the solvent is specifically xylene 10-12 parts, butanol 2-4 parts and acetone 2-4 parts, silane coupling agent 0.5-1 part, the silane coupling agent is KH-560, dispersant BYK-110 0.3-0.5 parts, dispersant BYK-111 0.2-0.5 parts.

[0072] The B component: polyamide 10-12 parts, polyether amine 4-6 parts, solvent 8-10 parts, wherein the solvent is specifically propylene glycol methyl ether 4-5 parts, xylene 4-5 parts.

[0073] The A component: bisphenol A type epoxy resin 40 parts, phenolic epoxy resin 15 parts, reinforcing fiber 5 parts, modified expanded vermiculite filler 10 parts, silica aerogel 4 parts, hollow glass microbeads 6 parts, solvent 20 parts, the solvent is specifically xylene 12 parts, butanol 4 parts and acetone 4 parts, silane coupling agent 1 part, the silane coupling agent is KH-560, dispersant BYK-110 0.3 parts, dispersant BYK-111 0.2 parts;

[0074] The B component: polyamide 12 parts, polyether amine 6 parts, solvent 10 parts, wherein the solvent is specifically propylene glycol methyl ether 5 parts, xylene 5 parts.

[0075] Further, the preferred specific preparation process is: 1, preparation of component A: 40 parts of bisphenol A epoxy resin, 15 parts of phenolic epoxy resin and 10 parts of dimethylbenzene, 4 parts of acetone are stirred at low speed (such as 500 rpm) to transparency. Add 1 part of KH-560 and 0.3 part of BYK-110, stir for 10 minutes. Slowly add 10 parts of modified expanded vermiculite filler, 6 parts of hollow glass microsphere, high speed dispersion (2000 rpm, 30 minutes). The silica aerogel 4 parts and dimethylbenzene 2 parts, 4 parts of butanol and BYK-111 dispersant are pretreated into aerogel slurry, and then the pretreated aerogel slurry is mixed at low speed (300 rpm) to avoid high speed shearing. Finally, 5 parts of reinforcing fiber is added and mixed at low speed (300 rpm) to avoid fiber breakage. 2, preparation of component B: weigh 12 parts of polyamide, 6 parts of polyether amine and 10 parts of solvent and mix uniformly to obtain component B; when used, component A and component B are mixed and coated to form a film.

[0076] Pre-treatment of aerogel slurry preparation process: (1) pre-wetting: mix 4 parts of silica aerogel with 2 parts of dimethylbenzene, 4 parts of butanol and 0.2 parts of BYK-111 dispersant, stand for 10 minutes, and let the solvent slowly penetrate into the pores of the aerogel. (2) low speed initial dispersion: use a magnetic stirrer (300 rpm, 10 minutes) or a low speed stirring blade to form a uniform slurry. The slurry can be subjected to low power ultrasonic (100-300 W, pulse mode: on for 5 seconds / off for 10 seconds, total 2 minutes) to further break the soft agglomeration.

[0077] The protective coating is cured into a film by using a common process, and the dry film thickness is 125 μm-280 μm, and the thermal conductivity of the coating material is ≤0.18 W / (m·K) -1 , further 0.12-0.18 W / (m·K) -1 .

[0078] In order to better illustrate the scheme, the following examples and comparative examples are provided.

[0079] Example 1

[0080] This example provides a modified expanded vermiculite filler A, which is prepared by the following steps:

[0081] 1, pre-impregnation of vermiculite:

[0082] (1) select 200 mesh expanded vermiculite, thermal conductivity is 0.08 W·(mK) -1 ;

[0083] (2) The siloxane precursor solution A and the siloxane precursor solution B are configured, and the molar ratio of MTMS:TEOS:ethanol:water in the siloxane precursor solution A is 0.4:0.4:2.5:2.5, and the molar ratio of KH550:ethanol:water in the siloxane precursor solution B is 0.2:1.5:1.5.

[0084] (3) The expanded vermiculite is immersed in the siloxane precursor solution A and the siloxane precursor solution B in sequence, and the time is 25 minutes and 35 minutes, respectively, and the mass ratio of the expanded vermiculite to the sum of the mass of the siloxane precursor solution A and the mass of the siloxane precursor solution B is 1:6.

[0085] (4) The pre-impregnated vermiculite is obtained by filtration.

[0086] 2. Sol-gel:

[0087] (1) Hydrolysis

[0088] The pre-impregnated vermiculite obtained in step 1 is placed in an acidic solution with a pH value of 3 for a certain period of time, and the hydrolysis-treated modified expanded vermiculite is obtained by filtration. The mass ratio of the pre-impregnated vermiculite to the acidic solution is 1:8. The acidic solution is a hydrochloric acid solution, the time is 1.5 hours, and the temperature is 50°C. In the hydrolysis process, MTMS, TEOS and KH550 are fully hydrolyzed to generate Si(OH)4.

[0089] (2) Gelation

[0090] Condensation stage: The hydrolysis-treated modified expanded vermiculite obtained is mixed with an ammonia solution with a pH value of 8, and is left to stand for a period of time, and is filtered to obtain the gelation-treated modified expanded vermiculite. The mass ratio of the hydrolysis-treated modified expanded vermiculite to the basic solution is 1:8, and the time is 0.5 hours. This process promotes the condensation of the silicic acid sol between the layers of the expanded vermiculite to form a gel network.

[0091] 3. Aging:

[0092] (1) The gelation-treated modified expanded vermiculite is immersed in a trimethylchlorosilane (TMCS) / n-hexane solution for hydrophobic aging treatment, and the temperature is 40°C and the time is 32h. Then the hydrophobic aging-treated modified expanded vermiculite is obtained by filtration; wherein the volume ratio of trimethylchlorosilane (TMCS) to n-hexane is 1:10.

[0093] (2) The hydrophobic aging-treated modified expanded vermiculite obtained is immersed in an isophorone diisocyanate / n-hexane solution for 3 hours, and the aging-treated modified expanded vermiculite is obtained by filtration; wherein the volume ratio of isophorone diisocyanate to n-hexane is 1:10.

[0094] 4. The modified expanded vermiculite treated by aging is dried under normal pressure to obtain a silica aerogel modified expanded vermiculite composite, i.e. modified expanded vermiculite filler A, which has a thermal conductivity of 0.018 W·(mK) -1 , wherein the drying process is: 50°C air drying for 48 hours.

[0095] Example 2

[0096] This example provides a modified expanded vermiculite filler B, which is prepared by the following steps:

[0097] 1. Vermiculite pre-impregnation:

[0098] (1) Select 200 mesh expanded vermiculite, which has a thermal conductivity of 0.08 W·(mK) -1 ;

[0099] (2) Prepare a siloxane precursor solution, i.e. a solution containing methyltrimethoxysilane (MTMS), tetraethyl orthosilicate (TEOS) and γ-aminopropyltriethoxysilane (KH550). The molar ratio of MTMS:TEOS:KH550:ethanol:water is 0.4:0.4:0.2:4:4.

[0100] (3) The expanded vermiculite is immersed in the above siloxane precursor solution for 1 hour. The expanded vermiculite and the siloxane precursor solution are used in a mass ratio of 1:6.

[0101] (4) Filter to obtain the pre-impregnated vermiculite.

[0102] 2. Sol-gel:

[0103] (1) Hydrolysis

[0104] The pre-impregnated vermiculite obtained in step 1 is placed in an acidic solution with a pH of 3 for a certain period of time, and then filtered to obtain the modified expanded vermiculite treated by hydrolysis. The mass ratio of the pre-impregnated vermiculite to the acidic solution is 1:8. The acidic solution is a hydrochloric acid solution, the time is 1.5 hours, and the temperature is 50°C. In the hydrolysis process, MTMS, TEOS and KH550 are fully hydrolyzed to form Si(OH)4.

[0105] (2) Gelation

[0106] Condensation stage: The modified expanded vermiculite treated by hydrolysis is mixed with an ammonia solution with a pH of 8 and left to stand for a period of time, then filtered to obtain the modified expanded vermiculite treated by gelation. The mass ratio of the modified expanded vermiculite treated by hydrolysis to the basic solution is 1:8, and the time is 0.5 hours. This process promotes the condensation of the silicic sol between the layers of the expanded vermiculite to form a gel network.

[0107] 3. Aging:

[0108] (1) The gelled modified expanded vermiculite is soaked in a trimethylchlorosilane (TMCS) / n-hexane solution for hydrophobic aging treatment at a temperature of 40°C for 32 hours. Then, the modified expanded vermiculite after hydrophobic aging treatment is obtained by filtration; wherein the volume ratio of trimethylchlorosilane (TMCS) to n-hexane is 1:10.

[0109] (2) The modified expanded vermiculite after hydrophobic aging treatment obtained is soaked in an isophorone diisocyanate / n-hexane solution for 3 hours, and the modified expanded vermiculite after aging treatment is obtained by filtration; wherein the volume ratio of isophorone diisocyanate to n-hexane is 1:10.

[0110] 4. The modified expanded vermiculite after aging treatment is subjected to normal pressure drying to obtain a silica aerogel modified expanded vermiculite composite, i.e. modified expanded vermiculite filler B, and the thermal conductivity of the modified expanded vermiculite filler B is 0.025 W·(mK) -1 , wherein the drying process is: 50°C ventilation drying for 48 hours.

[0111] Example 3

[0112] This example provides a modified expanded vermiculite filler C. Compared with Example 2, in the aging process of step 3, a solvent replacement treatment process is added before the hydrophobic aging treatment process of soaking in a silane / n-hexane solution, i.e. the gelled modified expanded vermiculite is placed in cyclohexane for solvent replacement for 15 days, and the rest is completely the same as the preparation process of Example 2. The thermal conductivity of the modified expanded vermiculite filler C obtained is 0.021 W·(mK) -1 .

[0113] Example 4

[0114] This example provides a modified expanded vermiculite filler D. Compared with Example 2, in the aging process of step 3, the obtained modified expanded vermiculite after hydrophobic aging treatment is omitted to be soaked in an isophorone diisocyanate / n-hexane solution, and the rest is completely the same as the preparation process of Example 2. The thermal conductivity of the modified expanded vermiculite filler D obtained is 0.027 W·(mK) -1 .

[0115] Comparative Example 1

[0116] The comparative example provides a modified expanded vermiculite filler E. Compared with example 2, the mixed solution of methyltrimethoxysilane (MTMS), tetraethyl orthosilicate (TEOS) and γ-aminopropyl triethoxysilane (KH550) in example 2 is replaced by methyltrimethoxysilane (MTMS) when configuring the siloxane precursor solution in the vermiculite pre-impregnation process step (2), and the rest is completely the same as the preparation process of example 2. The thermal conductivity of the obtained modified expanded vermiculite filler E is 0.032 W·(mK) -1 .

[0117] Example 5

[0118] The preparation process of protective coating A is as follows: the raw materials of the coating are weighed, and the weight fraction is as follows: component A: bisphenol A type epoxy resin 40 parts, phenolic epoxy resin 15 parts, reinforcing fiber 5 parts, modified expanded vermiculite filler 10 parts, silica aerogel 4 parts, hollow glass microsphere 6 parts, solvent 20 parts, including xylene 12 parts, butanol 4 parts, acetone 4 parts, silane coupling agent 1 part, silane coupling agent is KH-560, dispersant BYK-110 0.3 parts, dispersant BYK-111 0.2 parts; component B: polyamide 12 parts, polyether amine 6 parts, solvent 10 parts, including propylene glycol methyl ether 5 parts, xylene 5 parts. The bisphenol A type epoxy resin and the phenolic epoxy resin are placed in the stirred tank, and under slow stirring, part of the solvent is added until it is uniformly dispersed, and the reinforcing fiber, the modified expanded vermiculite filler, the silica aerogel, the hollow glass microsphere, the remaining solvent, and the additives are added to the stirred tank while stirring and mixing. The B component is prepared by the following method: polyamide, polyether amine and solvent are mixed uniformly by using a high-speed mixer. When used, the A component and the B component are mixed in a mass ratio of 4:1 to obtain the protective coating A, and coating and curing are carried out to form a film. Among them, the modified expanded vermiculite filler is the modified expanded vermiculite filler B prepared in example 2.

[0119] Comparative example 2

[0120] Preparation of protective coating B: replace the modified expanded vermiculite filler of example 5 with conventional 200 mesh unmodified expanded vermiculite with a thermal conductivity of 0.08 W·(mK) -1 .

[0121] Performance test

[0122] The thermal conductivities of the modified expanded vermiculite fillers A-E are tested, and the above modified expanded vermiculite fillers are mixed with ethanol at a mass ratio of 1:3, then high-speed dispersed (1000 rpm, 30 minutes), filtered, dried, and then the corresponding thermal conductivities are detected. The specific data are as follows in table 1.

[0123] Table 1 Thermal conductivity of expanded vermiculite filler

[0124]

[0125] From the above thermal conductivity comparison, it can be seen that the pre and post impregnation of precursor solution, the reasonable configuration of silane precursor monomer, the replacement of hydrophobic solvent in aging process and the modification of isocyanate can improve the thermal conductivity and enhance the anti-crushing effect to a certain extent, and then reduce the adverse effect on the heat insulation performance under the later high-speed dispersion.

[0126] According to SY / T 0544-2016 and SY / T 6717(2016) Technical Conditions for Inner Coating of Oil Drill Pipe, protective coating A and protective coating B were detected, and the thermal conductivity was also detected, as shown in Table 2.

[0127] As shown in Table 2, by modifying the expanded vermiculite filler, the heat insulation performance of the protective coating is greatly improved, and the adhesion is also improved accordingly. This may be because the expanded vermiculite is modified to improve the compatibility with the epoxy resin system, thereby facilitating the improvement of adhesion.

[0128] Table 2 Performance of protective coating

[0129]

Claims

1. A modified expanded vermiculite filler, characterized by: The preparation method of the modified expanded vermiculite filler comprises the following steps: pre-impregnating expanded vermiculite in a siloxane precursor solution containing methyltrimethoxysilane, ethyl silicate and gamma-aminopropyl triethoxysilane, and filtering to obtain pre-impregnated treated vermiculite; soaking the pre-impregnated treated vermiculite in an acidic solution with a pH value of 2-4, and filtering to obtain hydrolyzed modified expanded vermiculite; mixing the hydrolyzed modified expanded vermiculite with an alkaline solution with a pH value of 7-9 and standing, and filtering to obtain gelled modified expanded vermiculite; soaking the gelled modified expanded vermiculite in a silane and n-hexane solution for hydrophobic aging treatment; and performing normal pressure drying on the modified expanded vermiculite after the hydrophobic aging treatment to obtain the modified expanded vermiculite filler, and the thermal conductivity of the modified expanded vermiculite filler is .

2. The modified expanded vermiculite filler according to claim 1, characterized in that, The pre-impregnation of the expanded vermiculite in the siloxane precursor solution containing methyltrimethoxysilane, tetraethyl orthosilicate and gamma-aminopropyl triethoxysilane comprises: selecting expanded vermiculite; preparing the siloxane precursor solution; impregnating the expanded vermiculite in the siloxane precursor solution for 0.5-2 hours; and filtering to obtain the pre-impregnated vermiculite.

3. The modified expanded vermiculite filler of claim 1, wherein, The thermal conductivity of the expanded vermiculite is 80-325 mesh.

4. The modified expanded vermiculite filler of claim 2, wherein, In the siloxane precursor solution, the molar ratio of methyltrimethoxysilane: tetraethyl orthosilicate: gamma-aminopropyl triethoxysilane: ethanol: water is (0.3-0.5):(0.3-0.5):(0.1-0.3):(3-5):(3-5).

5. The modified expanded vermiculite filler of claim 1, wherein, The pre-impregnation of the expanded vermiculite in the siloxane precursor solution containing methyltrimethoxysilane, tetraethyl orthosilicate and gamma-aminopropyl triethoxysilane comprises: selecting expanded vermiculite; respectively preparing siloxane precursor solution A and siloxane precursor solution B; impregnating the expanded vermiculite in siloxane precursor solution A and siloxane precursor solution B in sequence; wherein the molar ratio of methyltrimethoxysilane: tetraethyl orthosilicate: ethanol: water in siloxane precursor solution A is (0.3-0.5):(0.3-0.5):(2-3):(2-3), and the molar ratio of gamma-aminopropyl triethoxysilane: ethanol: water in siloxane precursor solution B is (0.1-0.3):(1-2):(1-2).

6. The modified expanded vermiculite filler of claim 1, wherein, The mass ratio of the pre-impregnated vermiculite to the acidic solution is 1:(2-15).

7. The modified expanded vermiculite filler of claim 1, wherein, The mass ratio of the hydrolysis-treated modified expanded vermiculite to the alkaline solution is 1:(2-15).

8. The modified expanded vermiculite filler of claim 1, wherein, The temperature of the hydrophobic aging treatment is 30-50℃, and the time is 16-48h; the volume ratio of silane to n-hexane is 1:(8-12).

9. The modified expanded vermiculite filler of claim 1, wherein, Before the hydrophobic aging treatment, a solvent replacement treatment is performed, in which the gelled modified expanded vermiculite is placed in a solvent for solvent replacement for 12-18 days, and the solvent is methanol or cyclohexane or ethanol.

10. The modified expanded vermiculite filler of claim 1, wherein, After the hydrophobic aging treatment, the obtained modified expanded vermiculite after the hydrophobic aging treatment is soaked in a diisocyanate and n-hexane solution for 2-4 hours, and then filtered to obtain the aging-treated modified expanded vermiculite; The aging-treated modified expanded vermiculite is subjected to normal pressure drying to obtain the modified expanded vermiculite filler.

11. The modified expanded vermiculite filler according to claim 10, characterized in that, The diisocyanate is toluene diisocyanate, isophorone diisocyanate and / or diphenylmethane diisocyanate.

12. A protective coating, characterized in that The protective coating has an A component and a B component, wherein the A component comprises bisphenol A type epoxy resin 20-50 parts, phenolic epoxy resin 10-20 parts, reinforcing fiber 2-8 parts, modified expanded vermiculite filler 6-15 parts, silica aerogel 2-6 parts, hollow glass microsphere 4-8 parts, solvent, and auxiliary agent; and the B component comprises polyamide 10-15, polyether amine 4-8, and solvent, wherein the modified expanded vermiculite filler is the modified expanded vermiculite filler according to any one of claims 1-11.

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