Modified hollow glass bead, acoustic matching layer material and preparation method thereof

Abstract

The invention relates to the technical field of ultrasonic sensors, and discloses a hollow glass bead, a sound matching layer material and a preparation method thereof, and the modified hollow glass bead comprises a surface hydroxylated bead, and a first coating layer and a second coating layer which sequentially coat the surface of the surface hydroxylated bead; the surface hydroxylated microbeads are prepared by performing oxygen plasma activation treatment on hollow glass microbeads, and the first coating layer and the second coating layer are formed by sequentially grafting a silane coupling agent and an acrylic acid maleic anhydride copolymer on the surfaces of the surface hydroxylated microbeads. According to the invention, a double interface layer of'chemical bond anchoring-macromolecular chain winding 'is constructed on the surface of the hollow glass bead, so that the bonding strength and shear strength of the modified hollow glass bead-resin interface can be effectively improved, and the modified hollow glass bead can reduce the addition amount of filler, improve the dispersity of the filler and improve the mechanical property of the filler. Furthermore, the agglomeration phenomenon of the hollow glass beads is reduced, and the sensitivity of the acoustic matching layer material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic sensors, in particular to a modified hollow glass microbead, an acoustic matching layer material and a preparation method thereof. Background Art

[0002] As the core component of ultrasonic gas meters, the ultrasonic transducer relies on the efficient conversion of acoustic energy between piezoelectric ceramic materials (such as lead zirconate titanate piezoelectric ceramics, whose acoustic impedance is approximately 30 MRayl) and gas media (such as air, whose acoustic impedance is approximately 400 Rayl). However, the huge difference in acoustic impedance between the two (nearly 5 orders of magnitude) results in an interfacial acoustic energy transmittance of less than 1.3%, which seriously restricts detection sensitivity. The current mainstream acoustic impedance matching layer uses a hollow glass microsphere (3-5 MRayl) / epoxy resin composite system, which reduces the overall acoustic impedance to 1-3 MRayl by adjusting the filler ratio to 30-50%. However, in actual applications, the following problems are faced: First, the sodium ions remaining in the traditional hollow glass microsphere surface modification process (sodium hydroxide etching + silane coupling) will undergo saponification reactions with acidic components such as CO2 and H2S in the fuel gas, resulting in the breakage of the Si-O-Si bond at the interface. In an environment containing 50ppm H2S, the interface debonding rate increases by 12% annually; hydrogen-induced stress cracking caused by hydrogen molecule penetration in a hydrogen-doped environment further reduces the interface shear strength by 34%. Second, a high proportion of filler loading easily leads to the agglomeration of hollow glass microspheres (>50μm), causing a sharp increase in ultrasonic scattering loss to 2.3dB / cm and a 60% attenuation of sensitivity. Therefore, how to improve the bonding strength, interface shear strength, and sensitivity of the acoustic matching layer material is an urgent problem that needs to be solved. Summary of the Invention

[0003] In view of this, the present invention provides a hollow glass microsphere, an acoustic matching layer material and a preparation method thereof to solve the problem that the hollow glass microspheres obtained by the existing surface modification process easily lead to a decrease in the adhesion performance or shear strength of the interface of the acoustic matching layer material, and the high proportion of filler loading easily leads to a low sensitivity of the acoustic matching layer material.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a modified hollow glass microsphere, comprising surface hydroxylated microspheres, and a first coating layer and a second coating layer sequentially coated on the surface of the surface hydroxylated microspheres; the surface hydroxylated microspheres are prepared by treating hollow glass microspheres with oxygen plasma activation, and the first coating layer and the second coating layer are formed by sequentially grafting a silane coupling agent and an acrylic acid-maleic anhydride copolymer onto the surface of the surface hydroxylated microspheres.

[0006] Preferably, the thickness of the first coating layer is 1-5 nm.

[0007] Preferably, the thickness of the second coating layer is 200-800 nm.

[0008] Preferably, the silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane.

[0009] Preferably, the acrylic acid-maleic anhydride copolymer is polymerized from acrylic acid and maleic anhydride in a molar ratio of 3-7:1.

[0010] Preferably, the surface hydroxyl density of the modified hollow glass microspheres is 4.0-4.5 per nm. 2 , with a specific surface area of ​​8-10m 2 / g, surface roughness is 0.25-0.35μm, and surface contact angle is 40-50°.

[0011] In a second aspect, the present invention provides a method for preparing the modified hollow glass microspheres described in any one of the above, comprising the following steps:

[0012] (1) treating hollow glass microspheres with oxygen plasma activation to obtain surface hydroxylated microspheres;

[0013] (2) immersing the surface hydroxylated microbeads in a silane coupling agent solution to carry out a condensation grafting reaction to obtain silanized microbeads; (3) mixing the silanized microbeads with an acrylic acid maleic anhydride copolymer in a first organic solvent to carry out a graft polymerization reaction to obtain modified hollow glass microbeads.

[0014] Preferably, the conditions for the oxygen plasma activation treatment are as follows: vacuum degree of 15-20 Pa, oxygen flow rate of 75-85 sccm, power of 90-110 W, and treatment time of 10-20 min.

[0015] Preferably, the silane coupling agent solution is obtained by dissolving a silane coupling agent in a second organic solvent, wherein the mass concentration of the silane coupling agent is 1.5-2.5%.

[0016] Preferably, the second organic solvent includes one or more of ethanol solution, isopropanol solution, and n-butanol solution.

[0017] Preferably, the condensation grafting reaction is carried out at a pH of 4-5, a reaction temperature of 55-65° C., and a reaction time of 1.5-2.5 h.

[0018] Preferably, the mass ratio of the silylated microbeads to the acrylic acid-maleic anhydride copolymer is 1:7-9.

[0019] Preferably, the reaction temperature of the graft polymerization reaction is 40-60° C., and the reaction time is 2-4 hours.

[0020] Preferably, the first organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

[0021] In a third aspect, the present invention provides an acoustic matching layer material, comprising the following raw materials, in parts by mass: 100 parts of epoxy resin, 15-40 parts of curing agent, 40-60 parts of modified hollow glass microspheres, 3-5 parts of diluent, 2-6 parts of toughening agent, and 2-5 parts of thixotropy imparting agent;

[0022] The modified hollow glass microspheres are any of the modified hollow glass microspheres described above or the modified hollow glass microspheres prepared by any of the methods described above.

[0023] In a fourth aspect, the present invention further provides a method for preparing an acoustic matching layer material, comprising the following steps:

[0024] (1) mixing epoxy resin, curing agent, diluent and toughening agent to obtain a uniform colloid;

[0025] (2) mixing the uniform colloid, the modified hollow glass microspheres and the thixotropy imparting agent to obtain a mixture;

[0026] (3) The mixture is subjected to a stepwise temperature-raising curing process to obtain an acoustic matching layer material.

[0027] Preferably, the molar ratio of the curing agent to the anhydride groups in the acrylic acid-maleic anhydride copolymer is 1.2-1.4:1.

[0028] Preferably, the step-by-step temperature curing comprises: first curing at a constant temperature of 35-50° C. for 2-3 hours, and then curing at a constant temperature of 65-80° C. for 4-5 hours.

[0029] The present invention provides a modified hollow glass microsphere, an acoustic matching layer material and a preparation method thereof. Compared with the prior art, the present invention has the following advantages:

[0030] The invention first performs oxygen plasma activation treatment on hollow glass microspheres, and then sequentially grafts a silane coupling agent and an acrylic acid maleic anhydride copolymer on the surface of the hollow glass microspheres to form a first coating layer and a second coating layer to prepare modified hollow glass microspheres; oxygen free radicals (·O) in the oxygen plasma directly oxidize and break Si-O-Si bonds on the surface of the hollow glass microspheres to generate high-density isolated hydroxyl groups (≡Si-OH), while forming a rough surface, thereby increasing the specific surface area of ​​the microspheres and the hydroxyl group density, and providing high-activity sites for the grafting of the silane coupling agent; after the silane coupling agent is grafted on the surface of the hollow glass microspheres, the hollow glass microspheres are Double bond (-CH=CH2) active sites are formed on the surface of the glass microspheres to obtain hollow glass microspheres modified with silane double bonds; then, acrylic acid maleic anhydride copolymer is grafted onto the surface of the silane double bond modified hollow glass microspheres. At this time, the maleic anhydride groups (-CO-O-CO-) of the acrylic acid maleic anhydride copolymer are bonded to the silane double bonds through the Diels-Alder cycloaddition reaction to form a polymer coating layer. Finally, a "chemical bond anchoring-polymer chain entanglement" double interface layer is constructed on the surface of the hollow glass microspheres, thereby improving the bonding strength and shear strength of the modified hollow glass microsphere-resin interface.

[0031] In addition, in the acoustic matching layer material, by replacing the hollow glass microspheres treated by the traditional alkali etching process with the modified hollow glass microspheres of the present invention, the addition amount of fillers such as curing agents, diluents, toughening agents, and thixotropy imparting agents can be reduced, the dispersion of the fillers can be improved, and the agglomeration of the hollow glass microspheres can be reduced, thereby improving the sensitivity of the acoustic matching layer material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0033] Figure 1 This is an electron microscope image of the surface of hollow glass microspheres after treatment with sodium hydroxide;

[0034] Figure 2 This is an electron microscope image of the surface of hollow glass microspheres after oxygen plasma treatment;

[0035] Figure 3 This is an electron microscope image of the cross section of the acoustic matching layer material. DETAILED DESCRIPTION

[0036] The present invention will be described below by specific embodiment, and it will be appreciated by those skilled in the art that the specific embodiment below is only for illustrative purposes, and does not limit the scope of the present invention in any way. In addition, in the following examples, unless otherwise stated, the reagent and equipment used are all commercially available. If in the following examples, concrete treatment conditions and treatment process are not clearly described, then conditions and methods well known in the art can be adopted to process.

[0037] In one aspect of the present invention, a modified hollow glass microsphere is provided, comprising surface hydroxylated microspheres, and a first coating layer and a second coating layer sequentially coated on the surface of the surface hydroxylated microspheres; the surface hydroxylated microspheres are prepared by treating hollow glass microspheres with oxygen plasma activation, and the first coating layer and the second coating layer are formed by sequentially grafting a silane coupling agent and an acrylic acid-maleic anhydride copolymer onto the surface of the surface hydroxylated microspheres.

[0038] In the present invention, oxygen free radicals (·O) in oxygen plasma directly oxidize and break the Si-O-Si bonds on the surface of hollow glass microspheres, generating high-density isolated hydroxyl groups (≡Si-OH), while forming a rough surface, increasing the specific surface area of ​​the microspheres, and increasing the hydroxyl density, providing highly active sites for silane coupling agent grafting; after the silane coupling agent is grafted on the surface of the hollow glass microspheres, double bond (-CH=CH2) active sites are formed on the surface of the hollow glass microspheres, obtaining silane double bond-modified hollow glass microspheres, and then An acrylic acid-maleic anhydride copolymer is grafted onto the surface of hollow glass microspheres modified with silane double bonds. At this time, the maleic anhydride groups (-CO-O-CO-) of the acrylic acid-maleic anhydride copolymer are bonded to the silane double bonds through a Diels-Alder cycloaddition reaction to form a polymer coating layer. Ultimately, the modified hollow glass microspheres of the present invention have a double interface layer of "silane chemical bond anchoring-polymer chain entanglement", thereby improving the bonding strength and shear strength of the modified hollow glass microsphere-resin interface.

[0039] In some embodiments of the present invention, a first coating layer is formed after a silane coupling agent is grafted onto the surface of the surface hydroxylated microbeads. The thickness of the first coating layer is 1-5 nm, specifically 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, etc.; and a second coating layer is formed after acrylic acid maleic anhydride copolymer is grafted. The thickness of the second coating layer is 200-800 nm.

[0040] In some embodiments of the present invention, the silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane.

[0041] In some embodiments of the present invention, the acrylic acid-maleic anhydride copolymer is formed by polymerizing acrylic acid and maleic anhydride in a molar ratio of 3-7:1. When the acrylic acid content is relatively high, the hydrophilicity of the copolymer is enhanced, which is beneficial for the infiltration and bonding with the subsequent epoxy resin system. When the maleic anhydride content is relatively increased, it can provide more anhydride groups, facilitates reaction with curing agents, and enhances the degree of interfacial crosslinking. The molar ratio of the two monomers can be adjusted according to actual conditions and is not particularly limited.

[0042] Specifically, acrylic acid maleic anhydride copolymer can be purchased commercially. Common manufacturers include Sigma-Aldrich. The acrylic acid maleic anhydride copolymer products produced by Sigma-Aldrich have different specifications and parameters, which can be selected according to needs. Alternatively, acrylic acid maleic anhydride copolymer is prepared by free radical polymerization. For example, in the presence of initiators such as potassium persulfate and azobisisobutyronitrile, acrylic acid and maleic anhydride are polymerized in a reaction solvent such as toluene or xylene. The reaction temperature can be controlled between 80-120°C and the reaction time is 3-6 hours. During the preparation process, the molecular weight and molecular weight distribution of the copolymer can be adjusted by controlling the amount of initiator, reaction temperature, and reaction time. Specifically, the molecular weight of the acrylic acid maleic anhydride copolymer can be 5000-20000, and the molecular weight distribution index (PDI) is 1.5-3.0. The moderate molecular weight is conducive to the copolymer forming a coating layer of suitable thickness on the surface of the hollow glass microspheres and can ensure good dispersibility in the epoxy resin system.

[0043] In some embodiments of the present invention, the surface hydroxyl density of the hollow glass microspheres is 1.2-1.5 per nm. 2 , with a specific surface area of ​​2-3m 2 / g, a surface roughness of 0.1-0.2 μm, a surface contact angle of 80-90°, a surface hydroxyl density of 4.0-4.5 / nm2, and a specific surface area of ​​8-10m 2 / g, surface roughness of 0.25-0.35μm, and surface contact angle of 40-50°. Compared with unmodified hollow glass microspheres, the properties of the modified hollow glass microspheres of the present invention are significantly improved.

[0044] In some embodiments of the present invention, the main chemical composition of the hollow glass microspheres is as follows: SiO2 60-70%, Al2O3 20-30%, B2O3 5-10%; the particle size of the hollow glass microspheres is 60-100 μm, and the density is 0.3-0.6 g / cm 3 , compressive strength is 8-15MPa, thermal expansion coefficient is 5×10 -6-8×10 -6 / ℃.

[0045] In another aspect of the present invention, the present invention provides a method for preparing the modified hollow glass microspheres described in any one of the above, comprising the following steps:

[0046] (1) treating hollow glass microspheres with oxygen plasma activation to obtain surface hydroxylated microspheres;

[0047] (2) immersing the surface hydroxylated microbeads in a silane coupling agent solution to carry out a condensation grafting reaction to obtain silanized microbeads; (3) mixing the silanized microbeads with an acrylic acid maleic anhydride copolymer in a first organic solvent to carry out a graft polymerization reaction to obtain modified hollow glass microbeads.

[0048] In the present invention, hollow glass microspheres are firstly subjected to oxygen plasma activation treatment to obtain surface hydroxylated microspheres.

[0049] In some embodiments of the present invention, the oxygen plasma activation adopts a radio frequency plasma reactor, and the conditions of the oxygen plasma activation treatment are as follows: the vacuum degree is 15-20Pa, specifically 15Pa, 16Pa, 17Pa, 18Pa, 19Pa, 20Pa, etc.; the oxygen flow rate is 75-85sccm, specifically 75sccm, 78sccm, 80sccm, 82sccm, 85sccm, etc.; the power is 90-110W, specifically 90W, 95W, 100W, 105W, 110W, etc.; the treatment time is 10-20min, specifically 10min, 15min, 20min, etc.

[0050] The present invention adopts oxygen plasma treatment process to replace the traditional sodium hydroxide etching. The oxygen free radicals (·O) in the plasma directly oxidize and break the Si-O-Si bonds on the surface of the hollow glass microspheres, generating high-density isolated hydroxyl groups (≡Si-OH, with a density of 4.0-4.5 / nm 2 ), while forming a 50-200nm-level surface roughness structure, which increases the specific surface area of ​​the microbeads by 3-5 times; and using oxygen plasma treatment technology to replace traditional sodium hydroxide etching, avoiding the pollution of high-alkaline wastewater from the source, and eliminating the high-temperature drying (120℃, 24h) link, the comprehensive energy consumption can be reduced by more than 60%. Figure 1 and Figure 2 As shown, compared with the traditional alkaline etching method, the oxygen plasma process of the present invention can completely avoid sodium ion residue, and the hydroxyl density can be increased by 70-85%, providing highly active sites for subsequent silane coupling agent grafting.

[0051] In the present invention, after surface hydroxylated microbeads are obtained, the surface hydroxylated microbeads are immersed in a silane coupling agent solution to carry out a condensation grafting reaction to obtain silanized microbeads.

[0052] The principle of the condensation grafting reaction is as follows: the silanol groups (Si-OH) of the silane coupling agent solution react with the surface hydroxyl groups (≡Si-OH) of the surface hydroxylated microbeads to form Si-O-Si covalent bonds, anchoring the silane molecules on the surface of the hydroxylated microbeads and releasing water molecules at the same time to obtain silanized microbeads.

[0053] In some embodiments of the present invention, the condensation grafting reaction is carried out at a pH of 4-5, specifically 4, 4.2, 4.5, 4.8, 5, etc., and the pH can be adjusted using conventional acetic acid, sodium hydroxide, etc. By adjusting the pH value, the hydrolysis and condensation reaction rates of the silane coupling agent can be controlled, thereby ensuring that the silane coupling agent can be effectively grafted onto the surface of the hollow glass microspheres to form a stable chemical bond.

[0054] Specifically, by adjusting the pH value, on the one hand, excessive hydrolysis of the silane coupling agent can be suppressed: Silane coupling agents undergo hydrolysis in water to generate silanols. If the hydrolysis reaction is too rapid, the silanols will self-polymerize to form siloxane polymer precipitation, thereby reducing the opportunity for the silane coupling agent to react with the hydroxyl groups on the surface of the hollow glass microspheres and reducing the grafting efficiency. Under acidic conditions, the hydrolysis rate of the silane coupling agent can be suppressed, making the hydrolysis reaction slower and more controllable, ensuring that the silane coupling agent can fully react with the hydroxyl groups on the surface of the hollow glass microspheres. On the other hand, it can promote the condensation reaction: the condensation reaction between the silanols generated by the hydrolysis of the silane coupling agent and the hydroxyl groups on the surface of the hollow glass microspheres requires a certain acidic environment to catalyze. Suitable acidic conditions can provide sufficient hydrogen ions to promote the condensation reaction, facilitate the formation of Si-O-Si covalent bonds, and enable the silane coupling agent to be stably grafted to the surface of the hollow glass microspheres.

[0055] In some embodiments of the present invention, the silane coupling agent solution is obtained by dissolving a silane coupling agent in a second organic solvent, wherein the mass concentration of the silane coupling agent is 1.5-2.5%, specifically 1.5%, 1.8%, 2%, 2.2%, 2.5%, etc. The second organic solvent includes one or more of an ethanol solution, an isopropanol solution, and an n-butanol solution, for example, an ethanol solution made of ethanol and water in a volume ratio of 7-9:3-1. The silane coupling agent is hydrolyzed in the second organic solvent, such as the ethanol solution, to generate silanol (Si-OH).

[0056] Specifically, limiting the mass concentration of the silane coupling agent to 1.5-2.5% has better effects in the following aspects:

[0057] (1) Ensure that the grafting reaction is sufficient and uniform: This concentration range can make the silane coupling agent molecules have an appropriate distribution density in the solution. If the concentration is too low (<1.5%), the number of silane coupling agent molecules is small, and the chance of collision and contact with the hydroxyl groups on the surface of the hollow glass microspheres is reduced, resulting in a slow and insufficient grafting reaction, making it difficult to form a complete and dense silanization layer on the surface of the microspheres; while if the concentration is too high (>2.5%), the probability of collision and polymerization between silane coupling agent molecules increases, and self-polymerization reaction is likely to occur to form polymer precipitation, which not only wastes raw materials, but also reduces the silane coupling agent in the solution that effectively participates in the grafting reaction, which is also not conducive to uniform grafting on the surface of the hollow glass microspheres. In addition, within the concentration range of 1.5-2.5%, the silane coupling agent can adsorb and react on the surface of the microbeads at an appropriate rate, thereby forming a relatively uniform silanization layer on the surface of the microbeads. This is crucial for the subsequent grafting of acrylic acid maleic anhydride copolymer and the stability of the performance of the final modified hollow glass microbeads. If the silanization layer is uneven, it will lead to uneven distribution of the subsequent grafted copolymer, affecting the overall performance of the modified microbeads. For example, in the acoustic matching layer material, it will cause uneven acoustic impedance, affecting the acoustic performance.

[0058] (2) Controlling reaction rate and cost: This concentration range can keep the hydrolysis of the silane coupling agent and the condensation reaction rate with the hydroxyl groups on the surface of the hollow glass microspheres at an appropriate level. When the concentration is appropriate, the silanols produced by the hydrolysis of the silane coupling agent can promptly undergo condensation reactions with the hydroxyl groups on the surface of the microspheres to form stable Si-O-Si bonds. If the concentration is too high, the hydrolysis and condensation reaction rates will be too fast, which may make the reaction difficult to control and produce too many side reactions. If the concentration is too low, the reaction rate will be too slow, and production efficiency will be reduced. In addition, from a cost perspective, too high a concentration will increase the amount of silane coupling agent used and increase production costs. Although too low a concentration will save raw materials, it may require repeated treatment due to insufficient reaction, which will increase the overall cost. The concentration range of 1.5-2.5% achieves a good balance between raw material cost and production efficiency while ensuring the grafting effect.

[0059] (3) Ensure solution stability: When the concentration of silane coupling agent is 1.5-2.5%, the solution is relatively stable and is not prone to turbidity, precipitation, etc. If the concentration is too high, the silane coupling agent is prone to self-polymerization or excessive hydrolysis, producing insoluble substances that make the solution turbid or even precipitate, affecting the reaction and product quality; if the concentration is too low, although the solution stability is good, the reaction effect is not good. The appropriate concentration can maintain the good state of the solution and ensure the smooth progress of the reaction.

[0060] In some embodiments of the present invention, the reaction temperature of the condensation grafting reaction is 55-65°C, specifically 55°C, 60°C, 65°C, etc.; the reaction time is 1.5-2.5h, specifically 1.5h, 2h, 2.5h, etc., and the impregnation process can be stirred. Impregnation under limited conditions can obtain better cross-linking effect.

[0061] In some embodiments of the present invention, after the impregnation is completed, the microbeads are removed and sequentially filtered under reduced pressure, washed, and dried to obtain silanized microbeads. The washing may be performed 1-5 times with ethanol, and the drying may be performed under vacuum at 70-90°C for 3-5 hours. It should be noted that the reduced pressure filtration, washing, and drying processes are conventional operations and are not particularly limited thereto.

[0062] In the present invention, after obtaining the silylated microbeads, the silylated microbeads are mixed with an acrylic acid-maleic anhydride copolymer in a first organic solvent to carry out a graft polymerization reaction to obtain modified hollow glass microbeads.

[0063] The graft polymerization reaction undergoes a Diels-Alder cycloaddition reaction (double bond addition) and an imidization reaction (crosslinking of anhydride and amino groups). The reaction principle is as follows:

[0064] (1) Diels-Alder cycloaddition reaction: The double bond (-CH=CH2) of the silane coupling agent undergoes a cycloaddition reaction with the anhydride group (-CO-O-CO-) of the acrylic acid maleic anhydride copolymer to form a six-membered ring structure, and the acrylic acid maleic anhydride copolymer molecules are grafted onto the surface of the silanized microbeads: double bond microbead surface + PAMA anhydride → cycloaddition product (grafting point). This reaction is a reversible exothermic reaction and can proceed in the forward direction under heating conditions to form a stable covalent bond.

[0065] (2) Imidization reaction: The anhydride group (-CO-O-CO-) of the acrylic acid maleic anhydride copolymer reacts with the amino group (-NH2) of the curing agent to form an imide bond (-CO-NH-CO-), while releasing water molecules: PAMA anhydride + NH2-curing agent → imide bond + H2O. This reaction further occurs in the subsequent epoxy resin curing stage, allowing the acrylic acid maleic anhydride molecules to form a chemical cross-linking network with the epoxy resin matrix, thereby enhancing the interfacial bonding strength.

[0066] In some embodiments of the present invention, the mass ratio of the silanized microbeads to the acrylic acid-maleic anhydride copolymer is 1:7-9, specifically 1:7, 1:8, 1:9, etc. Limiting the mass ratio of the silanized microbeads to the acrylic acid-maleic anhydride copolymer to this range ensures sufficient grafting and interface layer construction. Specifically, within this range, a sufficient amount of the acrylic acid-maleic anhydride copolymer is guaranteed to fully react with the active sites on the surface of the silanized microbeads, forming a complete and uniform coating layer. Through reaction with the silane coupling agent, the acrylic acid-maleic anhydride copolymer forms a composite interface layer of "chemical bonds-polymer chain entanglements" on the surface of the hollow glass microbeads, enhancing the bonding strength between the microbeads and the subsequent epoxy resin matrix. For example, at this ratio, the acrylic acid-maleic anhydride copolymer can effectively connect with active groups such as double bonds or amino groups on the surface of the silanized microbeads through methods such as a Diels-Alder cycloaddition reaction, resulting in an interface layer thickness within a suitable range (e.g., 200-500 nm), thereby improving the performance of the modified microbeads in the acoustic matching layer material.

[0067] Furthermore, if the mass ratio is less than 1:7, the amount of acrylic acid-maleic anhydride copolymer used is too small to fully cover the active sites on the surface of the silanized microbeads, resulting in insufficient grafting and an incomplete and uneven interface layer. This weakens the bonding between the microbeads and the epoxy resin matrix. In practical applications, the microbeads may fall off the matrix, affecting the overall performance of the material. For example, in the acoustic matching layer of an ultrasonic gas meter transducer, this can lead to unstable acoustic impedance, increased ultrasonic attenuation coefficient, and reduced acoustic energy conversion efficiency. If the mass ratio is greater than 1:9, the amount of acrylic acid-maleic anhydride copolymer used is too high, which not only increases cost but also causes excessive acrylic acid-maleic anhydride copolymer to agglomerate in the system, preventing uniform dispersion and effective bonding with the microbeads. Furthermore, excessive acrylic acid-maleic anhydride copolymer may make the interface layer too thick, leading to reduced mechanical properties of the material, such as poor flexibility and susceptibility to cracking. It may also affect the acoustic properties of the material, such as deviation of the acoustic impedance from the optimal value.

[0068] In some embodiments of the present invention, the first organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

[0069] In some embodiments of the present invention, the reaction temperature of the graft polymerization reaction is 40-60°C, specifically 40°C, 50°C, 60°C, etc.; the reaction time is 2-4 hours, specifically 2 hours, 3 hours, 4 hours, etc. After the reaction is completed, the residual monomers are removed by filtration 1-5 times with the first organic solvent, and then dried at 50-70°C for 8-12 hours to obtain modified glass microbeads with a polymer coating layer on the surface.

[0070] In another aspect of the present invention, the present invention provides an acoustic matching layer material, comprising the following raw materials, in parts by mass: 100 parts of epoxy resin, 15-40 parts of curing agent, 40-60 parts of modified hollow glass microspheres, 3-5 parts of diluent, 2-6 parts of toughening agent, and 2-5 parts of thixotropy imparting agent; wherein the modified hollow glass microspheres are the modified hollow glass microspheres described in any one of the above items or the modified hollow glass microspheres prepared by the method described in any one of the above items.

[0071] like Figure 3 The figure shows an electron micrograph of a cross-section of the acoustic matching layer material, demonstrating the excellent interface density between the modified hollow glass microspheres and the epoxy resin. In the present invention, the maleic anhydride groups (-CO-O-CO-) of the acrylic acid-maleic anhydride copolymer double-bond with the silane via a Diels-Alder cycloaddition reaction and form an imide crosslinking network with the amino groups of the curing agent, effectively improving the bond strength and shear strength of the modified hollow glass microsphere-resin interface.

[0072] In addition, by replacing the hollow glass microspheres processed by traditional processes with the modified hollow glass microspheres of the present invention, the addition amount of fillers such as curing agents, diluents, toughening agents, and thixotropy imparting agents can be reduced, the dispersion of the fillers can be improved, and the agglomeration of the hollow glass microspheres can be reduced, thereby improving the sensitivity of the acoustic matching layer material. Moreover, by limiting the raw materials to the above-mentioned range, the distribution of the acoustic matching layer material can be ensured to be more uniform, reducing the risk of cracking.

[0073] In some embodiments of the present invention, the acoustic matching layer material includes epoxy resin, the added amount of the epoxy resin is 100 parts, and the epoxy resin includes one or more of bisphenol A epoxy resin, hydrogenated epoxy resin, and alicyclic epoxy resin.

[0074] The acoustic matching layer material includes a curing agent, and the amount of the curing agent added is 15-40 parts, specifically 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, etc. The curing agent includes one or more of a phenalkamine curing agent and a triamine curing agent.

[0075] The acoustic matching layer material includes modified hollow glass microspheres, and the added amount of the modified hollow glass microspheres is 40-60 parts, specifically 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, etc.

[0076] The acoustic matching layer material includes a diluent, and the amount of the diluent added is 3-5 parts, specifically 3 parts, 4 parts, 5 parts

[0077] The diluent includes one or more of butyl glycidyl ether, acetone, and cyclohexanone.

[0078] The acoustic matching layer material includes a toughening agent, the amount of which is 2-6 parts, specifically 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, etc. The toughening agent includes one or more of polyethylene glycol, neopentyl glycol diglycidyl ether, and carboxyl-terminated nitrile rubber.

[0079] The acoustic matching layer material includes a thixotropy imparting agent, the addition amount of which is 2-5 parts, specifically 2 parts, 3 parts, 4 parts, 5 parts, etc. The thixotropy imparting agent includes one or more of fumed silica, organic bentonite, and hydrogenated castor oil.

[0080] It should be noted that the types of epoxy resin, curing agent, diluent, toughening agent and thixotropy imparting agent in the acoustic matching layer material are all conventionally selected in the industry and are not particularly limited.

[0081] In some embodiments of the present invention, when the acoustic matching layer material is used in a standard gas source environment, the thickness of the second coating layer in the modified hollow glass microspheres is preferably 200-500 nm, mainly to achieve acoustic impedance matching between the ultrasonic transducer and the object being measured. Calculated by weight, the acoustic matching layer material includes the following raw materials: 100 parts of epoxy resin, 20-30 parts of curing agent, 45-55 parts of modified hollow glass microspheres, 3-4 parts of diluent, 3-5 parts of toughening agent, and 3-4 parts of thixotropy imparting agent. In some embodiments of the present invention, when the acoustic matching layer material is used in a highly corrosive gas source environment, the thickness of the second coating layer in the modified hollow glass microspheres is preferably 500 nm, mainly to resist H2S corrosion and maintain interface stability. Calculated by weight, the acoustic matching layer material includes the following raw materials: 100 parts of epoxy resin, 30-40 parts of curing agent, 50-60 parts of modified hollow glass microspheres, 3-4 parts of diluent, 4-6 parts of toughening agent, and 3-5 parts of thixotropy imparting agent.

[0082] In some embodiments of the present invention, when the acoustic matching layer material is used in a hydrogen-doped natural gas environment, the thickness of the second coating layer in the modified hollow glass microspheres is preferably 600-800 nm, primarily to improve resistance to hydrogen embrittlement and inhibit hydrogen permeation. The acoustic matching layer material comprises the following ingredients, by weight: 100 parts epoxy resin, 35-40 parts curing agent, 55-60 parts modified hollow glass microspheres, 3-4 parts diluent, 5-6 parts toughening agent, and 4-5 parts thixotropy-imparting agent. The carboxyl groups (-COOH) remaining in the maleic anhydride in the acoustic matching layer of the present invention capture free hydrogen through hydrogen bonds (bond energy 21 kJ / mol). After 1000 hours of hydrogen doping (15%) aging testing, the interfacial hydrogen content significantly decreased, effectively preventing the formation of hydrogen bubble cavities.

[0083] In another aspect of the present invention, the present invention also provides a method for preparing an acoustic matching layer material, comprising the following steps:

[0084] (1) mixing epoxy resin, curing agent, diluent and toughening agent to obtain a uniform colloid;

[0085] (2) mixing the uniform colloid, the modified hollow glass microspheres and the thixotropy imparting agent to obtain a mixture;

[0086] (3) The mixture is subjected to a stepwise temperature-raising curing process to obtain an acoustic matching layer material.

[0087] In the present invention, epoxy resin, curing agent, diluent and toughening agent are firstly mixed to obtain a uniform colloid.

[0088] In some embodiments of the present invention, the epoxy resin, curing agent, diluent and toughening agent are mixed by stirring at 40-60°C for 1-3 minutes, with a stirring speed of 100-200 rpm. The mixing temperature can be 40°C, 45°C, 50°C, 55°C, 60°C, etc. Within this temperature range, the viscosity of the system can be reduced, and uniform mixing of the components can be promoted; and the stirring speed can be 100 rpm, 150 rpm, 200 rpm, etc., and the stirring time can be 1 min, 2 min, 3 min, etc. At this stirring speed and stirring time, not only can uniform mixing be ensured, but also the introduction of bubbles due to excessive stirring can be avoided.

[0089] In some embodiments of the present invention, the molar ratio of the curing agent to the anhydride groups in the acrylic acid-maleic anhydride copolymer is 1.2-1.4:1, specifically 1.2:1, 1.3:1, 1.4:1, etc. This molar ratio ensures sufficient formation of imide bonds during the curing reaction. If the molar ratio is too low, such as 1:1, the anhydride groups may not fully react, resulting in insufficient crosslinking density and reduced properties such as the strength and corrosion resistance of the acoustic matching layer material. If the molar ratio is too high, such as 1.5:1, curing agent residue may result, affecting the stability of the system.

[0090] In the present invention, after obtaining the uniform colloid, the uniform colloid, modified hollow glass microspheres and a thixotropy-imparting agent are mixed to obtain a mixture.

[0091] In some embodiments of the present invention, the uniform colloid, modified hollow glass microspheres, and thixotropy-imparting agent are mixed under a vacuum condition of -0.08 to -0.1 MPa and stirred for 3 to 8 minutes at a stirring speed of 150 to 300 rpm. Specifically, the vacuum degree can be -0.08 MPa, -0.09 MPa, -0.1 MPa, etc., the stirring time can be 3 minutes, 5 minutes, 6 minutes, 8 minutes, etc., and the stirring speed can be 150 rpm, 200 rpm, 300 rpm, etc., to eliminate bubble defects.

[0092] In the present invention, after obtaining the mixture, the mixture is subjected to a stepwise temperature curing process to obtain the acoustic matching layer material. In some embodiments of the present invention, the stepwise temperature curing process includes: first curing at a constant temperature of 35-50°C for 2-3 hours, and then curing at a constant temperature of 65-80°C for 4-5 hours.

[0093] The constant temperature curing treatment at 35-50°C for 2-3 hours is the gelation stage. The temperature of the gelation stage can be 35°C, 40°C, 45°C, 50°C, etc., and the time can be 2h, 2.5h, 3h, etc. During the gelation stage, a preliminary reaction between the epoxy resin and the curing agent occurs.

[0094] Specifically, the epoxy resin contains epoxy groups (-CH(CH3)-O-), and the curing agent contains active hydrogen atoms (such as hydrogen on the amino group -NH2). Under the temperature conditions of the gelation stage, the active hydrogen atoms in the curing agent undergo a ring-opening addition reaction with the epoxy groups of the epoxy resin. The hydrogen atoms on the amino group attack the carbon atoms of the epoxy group, causing the epoxy group to open its ring and form new chemical bonds. For example, the primary amine (R-NH2) reacts with the epoxy group to generate a secondary amine group (R-NH-) and a hydroxyl group (-OH). As the reaction proceeds, the molecules in the system begin to connect with each other to form relatively small molecular chains. However, at this time, the degree of reaction is still relatively low, and the degree of cross-linking between the molecular chains is limited. The system begins to transform from a liquid state to a gel state with a certain degree of elasticity. In addition, based on the above-mentioned ring-opening addition reaction, the newly generated active groups such as hydroxyl groups can further react with other epoxy groups or curing agent molecules, causing the molecular chain to continue to grow. As the molecular chains grow, they begin to entangle with each other, further increasing the viscosity of the system and promoting the formation of a gel state. During this process, the fluidity of the system gradually decreases, and it begins to have a certain shape retention ability, but a completely cross-linked three-dimensional network structure has not yet formed.

[0095] The cross-linking stage is a constant temperature curing treatment at 65-80°C for 4-5 hours. The temperature of the cross-linking stage can be 65°C, 70°C, 75°C, 80°C, etc., and the time can be 4h, 4.5h, 5h, etc. In the cross-linking stage, it mainly includes the deep reaction of epoxy resin and curing agent, the formation of three-dimensional network structure, side reaction and group conversion.

[0096] Specifically, the deep reaction between epoxy resin and curing agent: During the gelation stage, the epoxy resin and curing agent have already undergone a preliminary reaction, forming some shorter molecular chains. Entering the crosslinking stage, as the temperature rises, the reaction activity further intensifies, and the epoxy groups in the epoxy resin and the remaining active groups in the curing agent (such as amine groups) continue to undergo ring-opening addition reactions. At this point, the reaction is more complete, and the molecular chains continue to grow and connect with each other. For example, the secondary amine groups formed during the gelation stage can continue to react with epoxy groups, further promoting the extension of the molecular chains.

[0097] Formation of a three-dimensional network structure: As the reaction continues, the molecular chains are connected to each other through cross-linking points, gradually forming a three-dimensional network structure. These cross-linking points are composed of chemical bonds produced by the reaction of epoxy resin and curing agent, which make the originally relatively independent molecular chains intertwined with each other. In this process, the viscosity of the system further increases, and the material gradually changes from a gel state with a certain elasticity to a solid state with high strength and stability. This three-dimensional network structure gives the acoustic matching layer material the required mechanical properties and stability, enabling it to normally perform functions such as acoustic impedance matching in the corresponding environment.

[0098] Side reactions and group transformations: High temperatures can also cause side reactions. For example, a small amount of water in the system may affect the reaction, or some groups may undergo transformations. Overall, however, the core of the crosslinking stage is to build a complete three-dimensional network structure through deep reactions to meet the material's performance requirements.

[0099] The following will be combined with specific embodiments to clearly and completely describe the technical solutions of the present invention. The embodiments of this application are only for example, and all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0100] Example 1

[0101] This embodiment provides a method for preparing modified hollow glass microspheres, and the specific steps are as follows:

[0102] (1) The hollow glass microspheres were subjected to oxygen plasma activation treatment. The conditions of the oxygen plasma activation treatment were as follows: vacuum degree of 20 Pa, oxygen flow rate of 75 sccm, power of 90 W, and treatment time of 10 min to obtain surface hydroxylated microspheres;

[0103] (2) The surface hydroxylated microbeads were immersed in an ethanol solution of a silane coupling agent with a mass concentration of 2% (the volume ratio of ethanol to water was 8:2), the pH was adjusted to 4.5 with acetic acid, stirred at 60°C for 2 hours, filtered under reduced pressure, washed with ethanol three times, and vacuum dried at 80°C for 4 hours to obtain silanized microbeads, wherein the thickness of the first coating layer was 3 nm;

[0104] (3) Silanized microspheres and acrylic acid maleic anhydride copolymer were mixed in N,N-dimethylformamide at a mass ratio of 1:8 at 40°C for 3 h, washed with N,N-dimethylformamide and filtered three times, and dried at 60°C for 10 h to obtain modified hollow glass microspheres, wherein the thickness of the second coating layer was 500 nm.

[0105] Example 2

[0106] This embodiment provides a method for preparing modified hollow glass microspheres, and the specific steps are as follows:

[0107] (1) hollow glass microspheres were subjected to oxygen plasma activation treatment. The conditions of the oxygen plasma activation treatment were as follows: vacuum degree of 18 Pa, oxygen flow rate of 80 sccm, power of 100 W, and treatment time of 15 min to obtain surface hydroxylated microspheres;

[0108] (2) The surface hydroxylated microbeads were immersed in an ethanol solution of a silane coupling agent with a mass concentration of 1.5% (the volume ratio of ethanol to water was 7:3), the pH was adjusted to 4.2 with acetic acid, stirred at 55°C for 2.5 hours, filtered under reduced pressure, washed with ethanol three times, and vacuum dried at 80°C for 4 hours to obtain silanized microbeads, wherein the thickness of the first coating layer was 2 nm;

[0109] (3) The silanized microspheres and acrylic acid maleic anhydride copolymer were mixed in N,N-dimethylformamide at a mass ratio of 1:8 at 50°C for 2 h, washed with N,N-dimethylformamide and filtered three times, and dried at 60°C for 10 h to obtain modified hollow glass microspheres, wherein the thickness of the second coating layer was 400 nm.

[0110] Example 3

[0111] This embodiment provides a method for preparing modified hollow glass microspheres, and the specific steps are as follows:

[0112] (1) The hollow glass microspheres were subjected to oxygen plasma activation treatment. The conditions of the oxygen plasma activation treatment were as follows: vacuum degree of 20 Pa, oxygen flow rate of 85 sccm, power of 110 W, and treatment time of 20 min to obtain surface hydroxylated microspheres;

[0113] (2) The surface hydroxylated microbeads were immersed in an ethanol solution of a silane coupling agent with a mass concentration of 2.5% (the volume ratio of ethanol to water was 9:1), the pH was adjusted to 4.8 with acetic acid, stirred at 65°C for 2 h, filtered under reduced pressure, washed with ethanol three times, and vacuum dried at 80°C for 4 h to obtain silanized microbeads, wherein the thickness of the first coating layer was 4 nm;

[0114] (3) Silanized microspheres and acrylic acid maleic anhydride copolymer were mixed in N,N-dimethylformamide at a mass ratio of 1:7 at 50°C for 3 h, washed with N,N-dimethylformamide and filtered three times, and dried at 60°C for 10 h to obtain modified hollow glass microspheres, wherein the thickness of the second coating layer was 600 nm.

[0115] Comparative Example 1

[0116] This comparative example is basically the same as Example 1, with the only difference being that there is no oxygen plasma activation treatment step, that is, step (1) is not performed.

[0117] Comparative Example 2

[0118] This comparative example is basically the same as Example 1, except that:

[0119] The conditions of the oxygen plasma activation treatment are as follows: vacuum degree of 20 Pa, oxygen flow rate of 70 sccm, power of 80 W, and treatment time of 5 min.

[0120] The surface properties of the hollow glass microspheres before modification and the prepared modified hollow glass microspheres used in Examples 1-3 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1. The test standard for surface hydroxyl density was "GB / T23260-2009 Method for Determination of Hydroxyl Content of Nanomaterials", the test standard for specific surface area was "GB / T19587-2017 Determination of Specific Surface Area of ​​Solids by Gas Adsorption BET Method", the test standard for surface roughness was "GB / T3505-2009 Product Geometric Technical Specification (GPS) Surface Structure Profile Method Terms, Definitions and Surface Structure Parameters", and the test standard for surface contact angle was "GB / T24368-2009 Contact Angle Measurement Method for Detection of Hydrophobic Contaminants on Glass Surface".

[0121] Table 1

[0122]

[0123] It can be concluded from Table 1 that oxygen plasma activation treatment of hollow glass microspheres can significantly increase the surface hydroxyl density, specific surface area, and surface roughness of the microspheres, and significantly reduce the surface contact angle. The increase in hydroxyl density indicates that more hydroxyl groups have been introduced into the surface of the hollow glass microspheres. The introduction of hydroxyl groups can increase the polarity of the microsphere surface, thereby improving its compatibility and adhesion with the resin, which is beneficial to improving the overall performance of the acoustic matching layer material; the increase in specific surface area indicates that the surface of the hollow glass microspheres is rougher, which can provide more active sites, which is beneficial to the interaction and reaction between the microspheres and other substances; the increase in surface roughness can enhance the mechanical bite between the microspheres and other substances, thereby improving their adhesion; and the reduction in surface contact angle indicates that the surface hydrophilicity of the hollow glass microspheres is enhanced, and the surface of the microspheres is more easily wetted by water or other polar solvents, improving the dispersion and stability of the microspheres in subsequent processing.

[0124] Example 4

[0125] This embodiment provides an acoustic matching layer material, which is composed of the following materials, measured by mass: 100 parts of bisphenol A epoxy resin, 15 parts of phenolic amine curing agent, 50 parts of modified hollow glass microspheres, 4 parts of acetone, 3 parts of carboxyl-terminated nitrile rubber, and 3 parts of fumed silica. The thickness of the first coating layer of the modified hollow glass microspheres is 1-5 nm, and the thickness of the second coating layer is 200-500 nm.

[0126] The preparation method of the acoustic matching layer material is as follows:

[0127] (1) mechanically stirring the epoxy resin, curing agent, diluent, and toughening agent at 50° C. and 150 rpm for 2 min to obtain a uniform colloid, wherein the molar ratio of the curing agent to the anhydride group in the acrylic acid-maleic anhydride copolymer is 1.2:1;

[0128] (2) stirring the uniform colloid, the modified hollow glass microspheres, and the thixotropy-imparting agent at −0.09 MPa and 100 rpm for 5 min to obtain a mixture;

[0129] (3) The mixture was cured at a constant temperature of 40°C for 2 hours, and then cured at a constant temperature of 70°C for 4 hours to obtain an acoustic matching layer material. The acoustic matching layer material of this embodiment was applied to a standard gas source environment. The parameters of the standard gas source environment were as follows: the gas composition was mainly methane, containing a small amount of CO2, N2, etc., and the total sulfur (calculated as sulfur) was ≤100 mg / m 3 , hydrogen sulfide ≤ 20mg / m 3 , carbon dioxide mole fraction ≤ 4%, hydrogen (H2) content < 1%; pressure is constant at 0.1-0.4 MPa; temperature is constant at 20±5°C.

[0130] Example 5

[0131] This embodiment is basically the same as embodiment 4, the only difference being that:

[0132] The acoustic matching layer material is composed of the following materials, measured by mass: 100 parts bisphenol A epoxy resin, 30 parts phenalkamine curing agent, 54 parts modified hollow glass microspheres, 4 parts acetone, 5 parts carboxyl-terminated nitrile rubber, and 4 parts fumed silica. The thickness of the first coating layer of the modified hollow glass microspheres is 1-5 nm, and the thickness of the second coating layer is 500 nm.

[0133] The preparation method of the acoustic matching layer material is as follows:

[0134] (1) mechanically stirring the epoxy resin, curing agent, diluent, and toughening agent at 50° C. and 150 rpm for 2 min to obtain a uniform colloid, wherein the molar ratio of the curing agent to the anhydride group in the acrylic acid-maleic anhydride copolymer is 1.2:1;

[0135] (2) stirring the uniform colloid, the modified hollow glass microspheres, and the thixotropy-imparting agent at −0.09 MPa and 100 rpm for 5 min to obtain a mixture;

[0136] (3) The mixture was cured at a constant temperature of 40° C. for 2.5 h, and then cured at a constant temperature of 70° C. for 4.5 h to obtain an acoustic matching layer material.

[0137] The acoustic matching layer material of this embodiment is applied to a highly corrosive gas source environment, wherein the gas components of the highly corrosive gas source environment mainly contain methane, high concentration of H2S (500-1000ppm), SO2 (≤100ppm), and total sulfur (calculated as sulfur) ≥500mg / m 3 , CO2 mole fraction ≤ 5%; pressure is constant at 1.6-6MPa; temperature is constant at 20-50℃.

[0138] Example 6

[0139] This embodiment is basically the same as embodiment 4, the only difference being that:

[0140] The acoustic matching layer material is composed of the following materials, measured by weight: 100 parts bisphenol A epoxy resin, 35 parts phenalkamine curing agent, 45 (55-60) parts modified hollow glass microspheres, 4 parts acetone, 6 parts carboxyl-terminated nitrile rubber, and 5 parts fumed silica. The thickness of the first coating layer of the modified hollow glass microspheres is 1-5 nm, and the thickness of the second coating layer is 600-800 nm.

[0141] The preparation method of the acoustic matching layer material is as follows:

[0142] (1) mechanically stirring the epoxy resin, curing agent, diluent, and toughening agent at 50° C. and 150 rpm for 2 min to obtain a uniform colloid, wherein the molar ratio of the curing agent to the anhydride group in the acrylic acid-maleic anhydride copolymer is 1.2:1;

[0143] (2) stirring the uniform colloid, the modified hollow glass microspheres, and the thixotropy-imparting agent at −0.09 MPa and 100 rpm for 5 min to obtain a mixture;

[0144] (3) The mixture was cured at a constant temperature of 40°C for 3 hours, and then cured at a constant temperature of 70°C for 5 hours to obtain an acoustic matching layer material. The acoustic matching layer material of this embodiment was applied to a hydrogen-doped natural gas environment, where the gas composition of the hydrogen-doped natural gas environment included 15% ± 2% hydrogen, 60% - 75% methane, and a total sulfur content (calculated as sulfur) ≤ 100 mg / m 3 , CO2≤3%; pressure is constant at 0.4-4.0MPa; temperature is constant at 20-60℃.

[0145] Comparative Example 3

[0146] This comparative example is substantially the same as Example 4, with the only difference being that the modified hollow glass microspheres are replaced with unmodified hollow glass microspheres.

[0147] The acoustic matching layer material of this comparative example is applied to a standard air source environment, which is the same as the air source environment of Example 4.

[0148] Comparative Example 4

[0149] This comparative example is substantially the same as Example 4, except that the molar ratio of the curing agent to the anhydride groups in the acrylic acid-maleic anhydride copolymer is 1.1:1.

[0150] The acoustic matching layer material of this comparative example is applied to a highly corrosive gas source environment, which is the same as the gas source environment of Example 5.

[0151] The performance of the acoustic matching materials prepared in Examples 4-6 and Comparative Examples 3-4 was tested. The results are shown in Table 2.

[0152] Table 2

[0153]

[0154]

[0155] It can be seen from Table 2 that the acoustic matching layer material of the present invention is applicable to various air source environments, and various properties of the acoustic matching layer material are significantly improved.

[0156] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A modified hollow glass microsphere, characterized in that: The invention comprises surface hydroxylated microbeads, and a first coating layer and a second coating layer sequentially coated on the surface of the surface hydroxylated microbeads; The surface hydroxylated microbeads are prepared by treating hollow glass microbeads with oxygen plasma activation. The first coating layer and the second coating layer are formed by sequentially grafting a silane coupling agent and an acrylic acid maleic anhydride copolymer onto the surface of the surface hydroxylated microbeads.

2. The modified hollow glass microsphere according to claim 1, characterized in that: The thickness of the first coating layer is 1-5 nm, and the thickness of the second coating layer is 200-800 nm; The silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; the acrylic acid maleic anhydride copolymer is polymerized by acrylic acid and maleic anhydride in a molar ratio of 3-7:

1.

3. The modified hollow glass microsphere according to claim 1 or 2, characterized in that: The surface hydroxyl density of the modified hollow glass microspheres is 4.0-4.5 per nm. 2 , with a specific surface area of ​​8-10m 2 / g, surface roughness is 0.25-0.35μm, and surface contact angle is 40-50°.

4. A method for preparing the modified hollow glass microspheres according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) treating hollow glass microspheres with oxygen plasma activation to obtain surface hydroxylated microspheres; (2) immersing the surface hydroxylated microbeads in a silane coupling agent solution to perform a condensation grafting reaction to obtain silanized microbeads; (3) Mixing the silanized microbeads with acrylic acid maleic anhydride copolymer in a first organic solvent to carry out graft polymerization reaction to obtain modified hollow glass microbeads.

5. The method for preparing the modified hollow glass microspheres according to claim 4, wherein: The conditions of the oxygen plasma activation treatment are as follows: vacuum degree of 15-20 Pa, oxygen flow rate of 75-85 sccm, power of 90-110 W, and treatment time of 10-20 min.

6. The method for preparing modified hollow glass microspheres according to claim 4, wherein: The silane coupling agent solution is obtained by dissolving a silane coupling agent in a second organic solvent, wherein the mass concentration of the silane coupling agent is 1.5-2.5%; The second organic solvent includes one or more of ethanol solution, isopropanol solution, and n-butanol solution; The condensation grafting reaction is carried out at a pH of 4-5, a reaction temperature of 55-65° C., and a reaction time of 1.5-2.5 h.

7. The method for preparing the modified hollow glass microspheres according to any one of claims 4 to 6, characterized in that: The mass ratio of the silanized microbeads to the acrylic acid-maleic anhydride copolymer is 1:7-9; The reaction temperature of the graft polymerization reaction is 40-60°C and the reaction time is 2-4h; The first organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

8. An acoustic matching layer material, characterized in that: The raw materials are as follows, calculated by mass: 100 parts of epoxy resin, 15-40 parts of curing agent, 40-60 parts of modified hollow glass microspheres, 3-5 parts of diluent, 2-6 parts of toughening agent, and 2-5 parts of thixotropy imparting agent; The modified hollow glass microspheres are the modified hollow glass microspheres according to any one of claims 1 to 3 or the modified hollow glass microspheres prepared by the method according to any one of claims 4 to 7.

9. A method for preparing the acoustic matching layer material according to claim 8, characterized in that: The following steps are involved: (1) mixing epoxy resin, curing agent, diluent and toughening agent to obtain a uniform colloid; (2) mixing the uniform colloid, the modified hollow glass microspheres and the thixotropy imparting agent to obtain a mixture; (3) The mixture is subjected to a stepwise temperature-raising curing process to obtain an acoustic matching layer material.

10. The method for preparing the acoustic matching layer material according to claim 9, characterized in that: The molar ratio of the curing agent to the anhydride groups in the acrylic acid-maleic anhydride copolymer is 1.2-1.4:1; The step-by-step temperature curing comprises: first curing at a constant temperature of 35-50° C. for 2-3 hours, and then curing at a constant temperature of 65-80° C. for 4-5 hours.

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