Vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material, preparation method thereof, loudspeaker and electronic equipment

Abstract

The invention provides a vibration attenuation, buffering, sound absorption and noise reduction flexible composite material and a preparation method thereof, a loudspeaker and electronic equipment, the vibration attenuation, buffering, sound absorption and noise reduction flexible composite material comprises polyimide foam and zeolite molecular sieves, and the zeolite molecular sieves are distributed in closed pores of the polyimide foam; the total weight of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material is 100%, the content of the polyimide foam is 50-80%, and the content of the zeolite molecular sieve is 20-50%. The vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material provided by the invention has excellent sound-absorbing and noise-reducing performance at low frequency and medium-high frequency, and also has excellent vibration-damping and buffering performance.

Description

Technical Field

[0001] The invention relates to a vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material and a preparation method thereof, a loudspeaker and an electronic device, belonging to the technical field of materials, in particular to the technical field of electronic acoustic materials. Background Art

[0002] In daily use of portable electronic devices (such as mobile phones, headphones, tablets, etc.), the vibrations generated by the speakers, receivers or motors at work will cause coordinated vibrations and separated vibrations of different components inside the electronic device, and even friction between different parts in the same component. Therefore, introducing vibration-damping and sound-absorbing materials into the gaps inside the electronic device can effectively reduce the vibration and noise caused by falling and device operation, reduce the friction loss of components, provide stable working performance, and extend the life cycle of the device.

[0003] Polyimide foam is a type of polymer material containing a large number of gas micropores, mesopores and nanopores. It not only has the common characteristics of foam plastics such as heat insulation, shock absorption and noise reduction, but also has the characteristics and advantages of high temperature resistance, low temperature resistance, intrinsic flame retardancy, radiation resistance and low smoke rate. Polyimide foam is divided into two categories according to the pore structure: soft open-cell foam and hard closed-cell foam. The former is usually prepared from thermoplastic polyimide resin, while the latter is prepared from thermosetting polyimide resin. Soft open-cell polyimide foam is mainly used in the fields of sound insulation, noise reduction, heat protection, and earthquake resistance. It has excellent sound absorption and noise reduction performance above 2000Hz.

[0004] Zeolite molecular sieve is an inorganic porous material with regular pores and regular intrinsic micropores. By subjecting zeolite molecular sieve to special experimental treatment, a material with a microporous-mesoporous pore structure can be obtained. Because the skeleton elements of its structure are adjustable, different heteroatoms can be introduced to modify the chemical and physical properties of the structure. At present, zeolite molecular sieve has important applications in the fields of adsorption separation, sound absorption and volume increase, catalysis, heavy metal capture, biomedicine, etc. For example, CN105013436A uses zeolite molecular sieve in micro speakers to improve their low-frequency acoustic performance.

[0005] For traditional foam materials, their porous structure is large pores, and they are widely used in vibration and noise reduction in medium and high frequencies, but the vibration and noise reduction effect in low frequencies is poor.

[0006] Therefore, providing a new type of vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material and its preparation method, loudspeaker, and electronic equipment has become a technical problem that urgently needs to be solved in the field. Summary of the invention

[0007] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide a vibration-damping, sound-absorbing and noise-reducing flexible composite material.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned vibration-damping, sound-absorbing and noise-reducing flexible composite material.

[0009] Another object of the present invention is to provide a speaker, wherein at least one of the speaker front cavity, speaker rear cavity, shell and sound-emitting unit is equipped with the above-mentioned vibration-damping, sound-absorbing and noise-reducing flexible composite material.

[0010] Another object of the present invention is to provide an electronic device, in which the rear cavity of the speaker is equipped with the above-mentioned vibration-damping, sound-absorbing and noise-reducing flexible composite material.

[0011] In order to achieve the above objectives, on the one hand, the present invention provides a vibration-damping, buffering, sound-absorbing, and noise-reducing flexible composite material, wherein the vibration-damping, buffering, sound-absorbing, and noise-reducing flexible composite material comprises polyimide foam and zeolite molecular sieve, and the zeolite molecular sieve is distributed in the closed-cell pores of the polyimide foam;

[0012] Taking the total weight of the vibration-damping, sound-absorbing and noise-reducing flexible composite material as 100%, the content of the polyimide foam is 50-80%, and the content of the zeolite molecular sieve is 20-50%.

[0013] As a specific embodiment of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material of the present invention, the zeolite molecular sieve is evenly distributed in the closed pores of the polyimide foam. The collision of the zeolite molecular sieve in the closed pores can consume vibration energy, thereby achieving a better vibration damping effect.

[0014] As a specific embodiment of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material of the present invention, the flexible composite material further comprises a non-molecular sieve porous filler distributed in the closed pores of the polyimide foam;

[0015] Taking the total weight of the vibration-damping, sound-absorbing and noise-reducing flexible composite material as 100%, the content of the polyimide foam is 50-80%, and the total content of the zeolite molecular sieve and the non-molecular sieve porous filler is 20-50%.

[0016] The vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material provided by the present invention includes inorganic porous materials such as polyimide foam, zeolite molecular sieves, and non-molecular sieve porous fillers. Although the introduction of inorganic porous materials will inevitably increase the density of the overall material, it can also improve the rebound performance and compression recovery of the composite material; and the micropores, mesopores and other structural organizations from the inorganic porous materials can also improve the vibration-damping and noise-reducing effect of the composite material in the low-frequency area.

[0017] As a specific embodiment of the vibration-damping, sound-absorbing and noise-reducing flexible composite material described above, the mass ratio of the non-molecular sieve porous filler to the zeolite molecular sieve is 1:1-1:100.

[0018] As a specific embodiment of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material described above in the present invention, the zeolite molecular sieve has an intrinsic cross-pore structure, and the intrinsic cross-pore structure includes a combination of micropore-micropore, micropore-mesopore and mesopore-mesopore, etc. or a combination of several. The mesopores in the zeolite molecular sieve can be obtained by subsequent experimental treatment (such as acid and alkali etching, etc., both of which use acidic etching solution and alkaline etching solution respectively), and can also be introduced in the process of preparing the zeolite molecular sieve. The present invention does not make specific requirements on the concentration of the etching solution used for acid and alkali etching, the temperature, pressure and time of the acid and alkali etching process, and can be reasonably adjusted according to the actual needs of the on-site operation.

[0019] As a specific embodiment of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material described above in the present invention, the framework elements or element combinations of the zeolite molecular sieve include but are not limited to silicon, silicon aluminum, silicon boron, aluminum phosphorus, silicon aluminum phosphorus, silicon germanium, silicon zinc or gallium phosphorus, etc.

[0020] As a specific embodiment of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material described above in the present invention, the structural pores of the zeolite molecular sieve contain pores with more than 8-membered rings but no more than 32-membered rings, wherein the 8-membered rings and 32-membered rings refer to pores consisting of 8 skeleton elements and 32 skeleton elements, respectively.

[0021] As a specific embodiment of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material described above in the present invention, the zeolite molecular sieve includes one or a combination of ZSM-5, X-type molecular sieve, Y-type molecular sieve, beta, ZSM-11, UTD-1F, CIT-5, EMC-2, EMM-23, EMM-25, ITQ-7, ITQ-24, ITQ-34, ITQ-43, ITQ-52 and IM-5, etc.;

[0022] Preferably, the zeolite molecular sieve has a molecular weight not higher than 0.8 g / cm 3 The packing density is high and has micro-meso composite pores;

[0023] More preferably, the zeolite molecular sieve is EMM-25, ZSM-5, X-type molecular sieve, Y-type molecular sieve, beta and ITQ-43.

[0024] As a specific embodiment of the vibration-damping, sound-absorbing and noise-reducing flexible composite material described above in the present invention, the silicon-to-aluminum ratio of the ZSM-5 is greater than 10.

[0025] As a specific embodiment of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material described above in the present invention, the extra-framework elements of the zeolite molecular sieve include but are not limited to one or a combination of several of sodium, potassium, hydrogen, lithium, cesium, magnesium and calcium.

[0026] The zeolite molecular sieve used in the present invention should have good acid-base stability.

[0027] As a specific embodiment of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material described above in the present invention, the non-molecular sieve porous filler is a crystalline material or an amorphous material.

[0028] As a specific embodiment of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material described above in the present invention, the non-molecular sieve porous filler includes but is not limited to silicon-containing materials and the like.

[0029] As a specific embodiment of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material described above in the present invention, the non-molecular sieve porous filler is mainly composed of low-density materials, for example: it includes one or a combination of metal organic framework compounds (MOF), covalent organic compounds (COF), porous aromatic framework materials (PAF), white carbon black, sepiolite, diatomaceous earth, halloysite, kaolin, expanded vermiculite, expanded pearl powder, expanded perlite, hollow glass microspheres, activated carbon and carbon fiber.

[0030] When the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material also contains non-molecular sieve porous fillers, at this time, two inorganic porous materials, zeolite molecular sieve and non-molecular sieve porous fillers, exist at the same time, so that the inorganic porous material has a micropore-mesopore-macroporous multi-level pore structure, thereby further improving the sound absorption and noise reduction performance of the composite material.

[0031] As a specific embodiment of the above-mentioned vibration-damping, sound-absorbing and noise-reducing flexible composite material of the present invention, the polyimide foam is prepared by using aromatic dianhydride and isocyanate as raw materials.

[0032] The foaming multiple of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material provided by the present invention is more than 1.5 times; by introducing different amounts and different ratios of inorganic porous materials, the foaming volume and sound-absorbing and noise-reducing effect of the composite material can be effectively regulated.

[0033] As a specific embodiment of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material of the present invention, the overall density of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material is not more than 400 kg / m 3 , resilience is not less than 42%, compression recovery is not less than 75% and the average sound absorption coefficient is not less than 0.5.

[0034] On the other hand, the present invention also provides a method for preparing the above-mentioned vibration-damping, sound-absorbing and noise-reducing flexible composite material, wherein the preparation method comprises:

[0035] Step (1): adding a low molecular weight saturated alcohol, an aromatic dianhydride, a zeolite molecular sieve, a uniform foaming agent and a catalyst to a highly polar aprotic solvent, mixing them uniformly and performing an esterification reaction to obtain a mixed slurry;

[0036] Step (2): adding isocyanate to the mixed slurry and mixing them evenly, and then pressurizing the obtained mixed solution and then slowly releasing the pressure to normal pressure to obtain a precursor;

[0037] Step (3): after removing the solvent from the precursor, perform imidization treatment to obtain the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material in foam form, that is, the foam body is prepared by foaming the precursor powder obtained after removing the solvent using a foaming method.

[0038] As a specific embodiment of the preparation method described above, step (1) comprises: adding a low molecular weight saturated alcohol, an aromatic dianhydride, a zeolite molecular sieve and a non-molecular sieve porous filler, a foaming agent and a catalyst into a strongly polar aprotic solvent to mix them evenly and react to obtain a mixed slurry.

[0039] In the present invention, deionized water may be added in step (1) of the above-mentioned preparation method to improve the solubility of the catalyst. Preferably, deionized water is added after the catalyst is added. In addition, the present invention does not make specific requirements on the amount of deionized water added in step (1), and it can be reasonably adjusted according to the actual operation conditions on site.

[0040] In step (1) of the preparation method described above, due to the presence of the micropore-mesopore-macroporous multi-level pore structure, the zeolite molecular sieve and non-molecular sieve porous fillers can adsorb molecules such as low molecular weight saturated alcohols and aromatic dianhydrides.

[0041] As a specific embodiment of the above preparation method of the present invention, in step (2), the isocyanate can be, for example, an aromatic isocyanate.

[0042] As a specific embodiment of the preparation method described above, in step (3), the precursor is placed in a vacuum device for evacuation to remove the solvent.

[0043] The non-molecular sieve porous filler has a microporous structure, which results in a large specific surface area, so that the non-molecular sieve porous filler will adsorb small molecules in the air, such as water molecules, CO2 and small molecular VOCs. Therefore, as a specific embodiment of the preparation method described above in the present invention, the preparation method also includes: performing low-pressure and high-temperature heat treatment on the non-molecular sieve porous filler to remove the adsorbed small molecules through low-pressure and high-temperature heat treatment. The present invention does not make specific requirements on the parameters such as temperature, pressure and time of low-pressure and high-temperature heat treatment, and can be reasonably adjusted according to the actual needs of on-site operations.

[0044] The low molecular weight saturated alcohol, aromatic dianhydride, strong polar aprotic solvent, foam leveling agent, catalyst and isocyanate used in the preparation method of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material described above in the present invention are all conventional substances. The present invention does not make specific requirements for their dosage and specific substances. The specific substances used in the present invention can be reasonably selected and adjusted according to the actual needs of the on-site operation, as long as the purpose of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material prepared by the present invention can be achieved. For example, in some embodiments of the present invention, the low molecular weight saturated alcohol can be methanol, the aromatic dianhydride can be 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, the strong polar aprotic solvent can be N-methylpyrrolidone, dimethyl sulfoxide, the isocyanate can be polymethylene polyphenyl polyisocyanate, diphenylmethane-4,4'-diisocyanate, the foam leveling agent can be foam leveling agent DC6070, the catalyst can be triethylamine, triethanolamine, etc. In addition, the present invention does not make any specific requirements on the reaction conditions involved in the preparation method. Those skilled in the art can also reasonably adjust the reaction conditions according to the actual needs of on-site operations, as long as the purpose of obtaining the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material of the present invention can be achieved.

[0045] On the other hand, the present invention also provides a speaker, comprising one or more sound-emitting units and one or more shells, wherein the one or more sound-emitting units are combined with the one or more shells to form a speaker back cavity, wherein at least one of the speaker front cavity, speaker back cavity, shell and sound-emitting unit is equipped with the above-mentioned vibration-damping, sound-absorbing and noise-reducing flexible composite material.

[0046] As a specific implementation of the loudspeaker described above in the present invention, the sound-emitting unit is an acoustic sensor or the like.

[0047] As a specific embodiment of the loudspeaker described above in the present invention, the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material can be loaded inside the rear cavity of the loudspeaker or adhered to the inner wall of the rear cavity of the loudspeaker; the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material can also be adhered to the inner wall of the front cavity of the loudspeaker, the outer surface of the shell and the back of the magnetic bowl of the sound unit and other positions.

[0048] In yet another aspect, the present invention further provides an electronic device, wherein the electronic device comprises the above-mentioned speaker.

[0049] As a specific embodiment of the electronic device described above in the present invention, the electronic device includes a smart phone, TWS earphones, headphones, smart glasses, smart watches, VR devices, AR devices, tablet computers or thin and light laptops, etc.

[0050] Compared with the prior art, the beneficial technical effects that can be achieved by the present invention include:

[0051] The vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material provided by the present invention comprises polyimide foam and zeolite molecular sieve. The zeolite molecular sieve can not only play a role in structural reinforcement, but also play a role in sound absorption and noise reduction due to its pore structure. Due to the presence of polyimide foam, the composite material also has excellent vibration-damping and buffering performance.

[0052] In summary, the vibration-damping, sound-absorbing and noise-reducing flexible composite material provided by the present invention has excellent sound-absorbing and noise-reducing performance at both low frequencies and medium and high frequencies, and also has excellent vibration-damping and buffering performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 A schematic diagram of a vibration-damping, sound-absorbing, and noise-reducing flexible composite material provided in an embodiment of the present invention.

[0055] Figure 2 This is a SEM image of the vibration-damping, sound-absorbing, and noise-reducing flexible composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0056] It should be noted that the term "comprises" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0057] "Scope" disclosed in the present invention is given in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, a range of 60-120 and 80-110 is listed, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​listed are 3, 4 and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0058] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the present invention, and "0-5" is just an abbreviation of these numerical combinations.

[0059] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0060] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0061] In the present invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0062] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the attached table, drawings and examples. The following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0063] Preparation Example 1

[0064] In this preparation example, the EMM-25 molecular sieve is etched to expand some of the micropores in the original structure of the EMM-25 molecular sieve to a mesopore size, wherein a 0.5M NaOH solution is used as an etching solution to etch the EMM-25 molecular sieve, and the etching conditions include: etching at 60°C for 2h, solid-liquid ratio = 1g:50mL; after etching, it is immediately centrifuged and washed multiple times, and finally dried at 120°C for 12h, and degassed at -0.1MPa, 200°C for 2h to obtain the EMM-25 molecular sieve after alkali etching.

[0065] Preparation Example 2

[0066] In this preparation example, expanded perlite and expanded vermiculite are subjected to low-pressure and high-temperature heat treatment, respectively, so as to remove small molecules adsorbed in the porous materials of expanded perlite and expanded vermiculite through low-pressure and high-temperature heat treatment, wherein the conditions of low-pressure and high-temperature heat treatment are -0.1MPa and 200°C for 2h.

[0067] Example 1

[0068] This embodiment provides a vibration-damping, sound-absorbing, and noise-reducing flexible composite material, which is prepared by a preparation method comprising the following specific steps:

[0069] 40 g of 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 60 g of N-methylpyrrolidone, 15 g of methanol, and 30 g of the alkaline-etched EMM-25 in Preparation Example 1 were added to a round-bottom flask, stirred at 400 rpm, and stirred at 75° C. for 3 h; then, 1.5 g of a foaming agent DC6070, 0.5 g of triethylamine, 0.5 g of triethanolamine, and 10 g of deionized water were added while maintaining the temperature at 75° C.; after stirring evenly, the mixture was naturally cooled to room temperature to obtain a light yellow viscous mixed slurry A;

[0070] Add mixture B (a mixture of 17.65 g of polymethylene polyphenyl polyisocyanate PAPI and 4.41 g of diphenylmethane-4,4'-diisocyanate (4,4'-MDI)) to mixed slurry A; after mixing mixed slurry A and mixed slurry B evenly, quickly inject into a pressure tank, maintain the pressure of the pressure tank at 0.4 MPa, maintain the pressure for 1 hour, and then slowly reduce it to normal pressure to obtain a precursor slurry;

[0071] The precursor slurry is transferred to a beaker and the beaker is placed in a vacuum oven. The solvent is extracted at a temperature of 80°C and a pressure of -0.2MPa for 0.5h. During this process, the volatilization of the solvent and low molecular weight substances can produce a porous structure. After that, imidization is carried out at a high temperature of 280°C, and the open-cell structure is also closed to obtain a closed-cell foam-shaped vibration-damping, sound-absorbing, and noise-reducing flexible composite material. The obtained vibration-damping, sound-absorbing, and noise-reducing flexible composite material is placed in air or an oxygen-rich atmosphere and calcined at 500°C for 6h. After calcination, it is weighed and calculated that the total weight of the vibration-damping, sound-absorbing, and noise-reducing flexible composite material is 100%, and the content of the zeolite molecular sieve is 29.8%.

[0072] Example 2

[0073] This embodiment provides a vibration-damping, sound-absorbing, and noise-reducing flexible composite material, which is prepared by a preparation method comprising the following specific steps:

[0074] 40g of 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 60g of N-methylpyrrolidone, 15g of methanol, 25g of EMM-25 etched by alkali in Preparation Example 1 and 5g of expanded perlite heat-treated at low pressure and high temperature in Preparation Example 2 were added into a round-bottom flask, stirred at 400rpm and stirred at 75°C for 3h; then, 1.5g of foaming agent DC6070, 0.5g of triethylamine and 0.5g of triethanolamine and 10g of deionized water were added while maintaining the temperature at 75°C; after stirring evenly, the mixture was naturally cooled to room temperature to obtain a light yellow viscous mixed slurry A;

[0075] Add mixture B (a mixture of 17.65 g of polymethylene polyphenyl polyisocyanate PAPI and 4.41 g of diphenylmethane-4,4'-diisocyanate (4,4'-MDI)) to mixed slurry A; after mixing mixed slurry A and mixed slurry B evenly, quickly inject into a pressure tank, maintain the pressure of the pressure tank at 0.4 MPa, maintain the pressure for 1 hour, and then slowly reduce it to normal pressure to obtain a precursor slurry;

[0076] The precursor slurry is transferred to a beaker and the beaker is placed in a vacuum oven. The solvent is extracted at a temperature of 80°C and a pressure of -0.2MPa for 1 hour. During this process, the volatilization of the solvent and low molecular weight substances can produce a porous structure. After that, imidization is carried out at a high temperature of 280°C, and the open-cell structure is also closed to obtain a closed-cell foam-shaped vibration-damping, sound-absorbing, and noise-reducing flexible composite material. The obtained vibration-damping, sound-absorbing, and noise-reducing flexible composite material is placed in air or an oxygen-rich atmosphere and calcined at 500°C for 6 hours. After calcination, it is weighed and calculated that the total weight of the vibration-damping, sound-absorbing, and noise-reducing flexible composite material is 100%, and the content of the zeolite molecular sieve is 30.2%.

[0077] Example 3

[0078] This embodiment provides a vibration-damping, sound-absorbing, and noise-reducing flexible composite material, which is prepared by a preparation method comprising the following specific steps:

[0079] 40g of 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 60g of N-methylpyrrolidone, 15g of methanol, 25g of EMM-25 etched by alkali in Preparation Example 1 and 5g of expanded vermiculite heat-treated at low pressure and high temperature in Preparation Example 2 were added into a round-bottom flask, stirred at a speed of 400rpm, and stirred at a temperature of 75°C for 3h; then, 1.5g of a foaming agent DC6070, 0.5g of triethylamine and 0.5g of triethanolamine and 10g of deionized water were added while maintaining the temperature at 75°C; after stirring evenly, the mixture was naturally cooled to room temperature to obtain a light yellow viscous mixed slurry A;

[0080] Add mixture B (a mixture of 17.65 g of polymethylene polyphenyl polyisocyanate PAPI and 4.41 g of diphenylmethane-4,4'-diisocyanate (4,4'-MDI)) to mixed slurry A; after mixing mixed slurry A and mixed slurry B evenly, quickly inject into a pressure tank, maintain the pressure of the pressure tank at 0.4 MPa, maintain the pressure for 1 hour, and then slowly reduce it to normal pressure to obtain a precursor slurry;

[0081] The precursor slurry is transferred to a beaker and the beaker is placed in a vacuum oven. The solvent is extracted at a temperature of 80°C and a pressure of -0.2MPa for 1 hour. During this process, the volatilization of the solvent and low molecular weight substances can produce a porous structure. After that, imidization is carried out at a high temperature of 280°C, and the open-cell structure is also closed to obtain a closed-cell foam-shaped vibration-damping, sound-absorbing, and noise-reducing flexible composite material. The obtained vibration-damping, sound-absorbing, and noise-reducing flexible composite material is placed in air or an oxygen-rich atmosphere and calcined at 500°C for 6 hours. After calcination, it is weighed and calculated that the total weight of the vibration-damping, sound-absorbing, and noise-reducing flexible composite material is 100%, and the content of the zeolite molecular sieve is 29.7%.

[0082] Comparative Example 1

[0083] This comparative example provides a polyimide foam material, which is prepared by a preparation method comprising the following specific steps:

[0084] 40 g of 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 60 g of N-methylpyrrolidone and 15 g of methanol were added into a round-bottom flask, and stirred at 400 rpm and 75° C. for 3 h; then, 1.5 g of DC6070, 0.5 g of triethylamine and 0.5 g of triethanolamine and 10 g of deionized water were added while maintaining the temperature at 75° C.; after stirring evenly, the mixture was naturally cooled to room temperature to obtain a light yellow viscous mixed slurry A;

[0085] Add mixture B (a mixture of 17.65 g of polymethylene polyphenyl polyisocyanate PAPI and 4.41 g of diphenylmethane-4,4'-diisocyanate (4,4'-MDI)) to mixed slurry A; after mixing mixed slurry A and mixed slurry B evenly, quickly inject into a pressure tank, maintain the pressure of the pressure tank at 0.4 MPa, maintain the pressure for 1 hour, and then slowly reduce it to normal pressure to obtain a precursor slurry;

[0086] The precursor slurry is transferred to a beaker and the beaker is placed in a vacuum oven. The solvent is extracted at a temperature of 80°C and a pressure of -0.2MPa for 1 hour. During this process, the volatilization of the solvent and low molecular weight substances can produce porous tissue. After that, imidization is carried out at a high temperature of 280°C, and the open-pore tissue is also closed to obtain a closed-pore polyimide foam material.

[0087] Test Example 1

[0088] This test example tests the apparent core density of the composite materials provided in Examples 1 to 3 of the present invention and the polyimide foam material provided in Comparative Example 1 respectively according to GB / T 6343-1995 standard;

[0089] The shape of the sample should be convenient for volume calculation. When cutting the sample, it should be ensured that the original cell structure does not deform. At least three samples are tested in each group, and the average value is taken as the apparent core density of the composite material and polyimide foam material.

[0090] The apparent core density data of the composite materials provided in Examples 1 to 3 of the present invention and the polyimide foam material provided in Comparative Example 1 are shown in Table 1 below.

[0091] Table 1

[0092] Apparent core density <![CDATA[Sample 1 / (kg / m 3 )]]> <![CDATA[Specimen 2 / (kg / m 3 )]]> <![CDATA[Specimen 3 / (kg / m 3 )]]> <![CDATA[Average value / (kg / m 3 )]]> Example 1 109.2 109.5 109.3 109.33 Example 2 103.7 103.5 103.4 103.53 Example 3 105.2 105.2 105.1 105.17 Comparative Example 1 82.5 82.7 82.6 82.60

[0093] The test results of the apparent core density shown in Table 1 show that the apparent core density of the vibration damping, buffering, sound absorbing and noise reducing flexible composite material prepared by adding zeolite molecular sieve in Example 1 of the present invention and the vibration damping, buffering, sound absorbing and noise reducing flexible composite material prepared by adding zeolite molecular sieve and non-molecular sieve porous fillers in Examples 2 and 3 respectively is higher than the apparent core density of the polyimide foam material prepared in Comparative Example 1 without adding any inorganic porous material; this is mainly because the density of inorganic porous materials such as zeolite molecular sieve and non-molecular sieve porous fillers is higher than that of polyimide foam. The density of expanded perlite and expanded vermiculite is lower than that of zeolite molecular sieve. Therefore, when expanded perlite and expanded vermiculite are introduced into zeolite molecular sieve, the density of the composite materials in Examples 2 and 3 of the present invention is lower than that in Example 1.

[0094] Test Example 2

[0095] This test example tests the steel ball rebound performance of the composite materials provided in Examples 1 to 3 of the present invention and the polyimide foam material provided in Comparative Example 1 according to GB / T 6670-2008 standard, including:

[0096] A steel ball is made to fall freely from the sample surface (the sample surface is 50 cm from the horizontal plane) and the rebound height of the steel ball is measured. Each sample is tested 3 times and the average value is taken as the rebound performance test result of the composite material and the polyimide foam material.

[0097] The test results of the resilience performance of the composite materials provided in Examples 1 to 3 of the present invention and the polyimide foam material provided in Comparative Example 1 are shown in Table 2.

[0098] Table 2

[0099] Rebound rate Sample 1 / (%) Sample 2 / (%) Sample 3 / (%) average value / (%) Example 1 43.6 43.6 43.5 43.57 Example 2 44.7 44.8 44.8 44.77 Example 3 44.2 44.3 44.3 44.26 Comparative Example 1 42.2 42.2 42.3 42.23

[0100] It can be known from the test results of resilience as shown in Table 2 above that the rebound rate of the vibration damping, buffering, sound absorbing and noise reduction flexible composite material prepared by adding zeolite molecular sieve in Example 1 of the present invention and the vibration damping, buffering, sound absorbing and noise reduction flexible composite material prepared by adding zeolite molecular sieve and non-molecular sieve porous fillers in Examples 2-3 is improved compared with the polyimide foam material prepared by not adding any inorganic porous material in Comparative Example 1. This is mainly because after the introduction of zeolite molecular sieve, or zeolite molecular sieve and non-molecular sieve porous fillers, they are evenly dispersed in the system, which enhances the strength of the foam material and makes the foam have higher elastic stiffness, thereby improving the rebound performance of the composite material. Compared with Example 1, Example 2 and Example 3 have higher rebound performance, which is mainly because the expanded perlite and expanded vermiculite have the characteristics of large volume shrinkage deformation. When subjected to external pressure, the internal pores of the expanded perlite and expanded vermiculite shrink and deform, and when the external pressure disappears, the shrinkage deformation recovers.

[0101] Test Example 3

[0102] This test example performs compression recovery tests on the composite materials provided in Examples 1 to 3 of the present invention and the polyimide foam material provided in Comparative Example 1 according to the HG / T 2876-2009 standard, including:

[0103] The samples were divided into rectangular blocks with a length and width of 20 mm and a thickness of 10 mm. The samples were compressed to 50% of the original thickness at room temperature, maintained for 72 h, and then left to stand for 2 h to obtain the recovered thickness. The ratio of the recovered thickness to the original thickness at this time was the compression recovery rate.

[0104] The compression recovery test results of the composite materials provided in Examples 1 to 3 of the present invention and the polyimide foam material samples provided in Comparative Example 1 in three directions are shown in Table 3 below.

[0105] Table 3

[0106] Compression recovery rate long / (%) Width / (%) thick / (%) average value / (%) Example 1 78.6 78.4 78.5 78.50 Example 2 81.4 81.5 81.3 81.40 Example 3 81.1 81.0 81.1 81.06 Comparative Example 1 77.8 77.7 77.8 77.77

[0107] From the compression recovery test results shown in Table 3, it can be known that the compression recovery rate of the vibration-damping, sound-absorbing, and noise-reducing flexible composite material prepared by adding zeolite molecular sieve in Example 1 of the present invention and the vibration-damping, sound-absorbing, and noise-reducing flexible composite material prepared by adding zeolite molecular sieve and non-molecular sieve porous fillers in Examples 2 and 3 respectively are improved compared with the polyimide foam material prepared in Comparative Example 1 without adding any inorganic porous material. This is mainly because after long-term compression of the introduced zeolite molecular sieve, or inorganic porous materials such as zeolite molecular sieve and non-molecular sieve porous fillers, the inorganic porous material particles will gradually undergo slight displacement to absorb the internal stress generated by compression; after the external pressure disappears, as the bubbles recover, the displaced inorganic porous material particles will release the internal stress generated by the displacement under the restoring force of the bubbles or bubble walls, synergistically promoting the recovery of the bubbles, that is, improving the compression recovery of the composite material.

[0108] From the experimental data in Tables 2 and 3, it can be seen that the resilience (rebound rate) and compression recovery (compression recovery rate) of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material prepared by adding zeolite molecular sieve in Example 1 of the present invention and the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite materials prepared by adding zeolite molecular sieve and non-molecular sieve porous fillers in Examples 2 to 3 respectively are improved compared with the polyimide foam material prepared in Comparative Example 1 without adding any inorganic porous material. The improvement of the resilience and compression recovery of the composite material is beneficial for electronic equipment and internal components to better cope with external impacts and vibration friction of internal components, thereby improving the working stability of the workpiece and extending the service life of the equipment and components.

[0109] Test Example 4

[0110] In this test example, the sound absorption performance of the composite materials provided in Examples 1 to 3 of the present invention and the polyimide foam material provided in Comparative Example 1 was tested using the standing wave tube method according to the test standard GBJ 88-85 (Standing Wave Tube Method Sound Absorption Coefficient and Acoustic Impedance Measurement Specification). The instrument used for the test was a dual-channel tester from Shengwang Company, and the sound absorption specimen was a Φ100mm cylinder.

[0111] The test results of the sound absorption performance of the composite materials provided in Examples 1 to 3 of the present invention and the polyimide foam material provided in Comparative Example 1 are shown in Table 4 below.

[0112] Table 4

[0113]

[0114] From the test results of sound absorption performance shown in Table 4, it can be known that the sound absorption performance of the vibration-damping, sound-absorbing and noise-reducing flexible composite material prepared by adding zeolite molecular sieve in Example 1 of the present invention and the vibration-damping, sound-absorbing and noise-reducing flexible composite material prepared by adding zeolite molecular sieve and non-molecular sieve porous fillers in Examples 2 and 3 respectively are significantly improved in low-frequency and medium-high frequency bands compared with the polyimide foam material prepared without adding any inorganic porous material in Comparative Example 1. This is mainly because the zeolite molecular sieve introduced in the embodiments of the present invention, or inorganic porous materials such as zeolite molecular sieve and non-molecular sieve porous fillers, provide multi-level pore structures such as micropore-mesopore and mesopore-macroporous, enrich the pore structure of the polyimide foam, which is beneficial to the adsorption and desorption of air molecules by the composite material, effectively increases the volume of the resonance cavity, and further matches the impedance of the composite material with the impedance of the air, thereby achieving a more excellent sound absorption and noise reduction effect.

[0115] Test Example 5

[0116] In this test example, the vibration-damping, sound-absorbing, and noise-reducing flexible composite material prepared in Example 1 of the present invention was subjected to SEM analysis. The obtained SEM image is as follows: Figure 2 As shown, the schematic diagrams of the vibration-damping, sound-absorbing and noise-reducing flexible composite materials provided by the embodiments of the present invention are as shown Figure 1 As shown. Figure 1 and Figure 2 It can be seen that the vibration damping, buffering, sound absorbing and noise reducing flexible composite material provided in the embodiments of the present invention includes either polyimide foam and zeolite molecular sieve, or includes polyimide foam, zeolite molecular sieve and non-molecular sieve porous fillers, and the zeolite molecular sieve or the zeolite molecular sieve and non-molecular sieve porous fillers are distributed in the closed pores of the polyimide foam.

[0117] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the protection scope of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other and with each other, and with each other.

Claims

1. A vibration-damping, sound-absorbing, and noise-reducing flexible composite material, characterized in that: The vibration-damping, sound-absorbing and noise-reducing flexible composite material comprises polyimide foam and zeolite molecular sieve, wherein the zeolite molecular sieve is distributed in the closed-cell pores of the polyimide foam; Taking the total weight of the vibration-damping, sound-absorbing and noise-reducing flexible composite material as 100%, the content of the polyimide foam is 50-80%, and the content of the zeolite molecular sieve is 20-50%.

2. The vibration-damping, sound-absorbing and noise-reducing flexible composite material according to claim 1, characterized in that: The flexible composite material also includes a non-molecular sieve porous filler distributed in the closed pores of the polyimide foam; Taking the total weight of the vibration-damping, sound-absorbing and noise-reducing flexible composite material as 100%, the content of the polyimide foam is 50-80%, and the total content of the zeolite molecular sieve and the non-molecular sieve porous filler is 20-50%.

3. The vibration-damping, sound-absorbing and noise-reducing flexible composite material according to claim 2 is characterized in that: The mass ratio of the non-molecular sieve porous filler to the zeolite molecular sieve is 1:1-1:

100.

4. The vibration-damping, sound-absorbing, and noise-reducing flexible composite material according to any one of claims 1 to 3, characterized in that: The zeolite molecular sieve has an intrinsic cross-pore structure, which includes a combination of micropore-micropore, micropore-mesopore and mesopore-mesopore or a combination of several of them.

5. The vibration-damping, sound-absorbing and noise-reducing flexible composite material according to any one of claims 1 to 3, characterized in that: The framework element or element combination of the zeolite molecular sieve includes, but is not limited to, silicon, silicon aluminum, silicon boron, aluminum phosphorus, silicon aluminum phosphorus, silicon germanium, silicon zinc or gallium phosphorus.

6. The vibration-damping, sound-absorbing, and noise-reducing flexible composite material according to any one of claims 1 to 3, characterized in that: The structural pores of the zeolite molecular sieve include pores with more than 8-membered rings but no more than 32-membered rings.

7. The vibration-damping, sound-absorbing, and noise-reducing flexible composite material according to any one of claims 1 to 3, characterized in that: The zeolite molecular sieve includes one or a combination of ZSM-5, X-type molecular sieve, Y-type molecular sieve, beta, ZSM-11, UTD-1F, CIT-5, EMC-2, EMM-23, EMM-25, ITQ-7, ITQ-24, ITQ-34, ITQ-43, ITQ-52 and IM-5.

8. The vibration-damping, sound-absorbing, and noise-reducing flexible composite material according to any one of claims 1 to 3, characterized in that: The extra-framework elements of the zeolite molecular sieve include, but are not limited to, one or a combination of several of sodium, potassium, hydrogen, lithium, cesium, magnesium and calcium.

9. The vibration-damping, sound-absorbing, and noise-reducing flexible composite material according to claim 2 or 3, characterized in that: The non-molecular sieve porous filler is a crystalline material or an amorphous material.

10. The vibration-damping, sound-absorbing, and noise-reducing flexible composite material according to claim 2 or 3, characterized in that: The non-molecular sieve porous filler includes but is not limited to silicon-containing materials.

11. The vibration-damping, sound-absorbing, and noise-reducing flexible composite material according to claim 2 or 3, characterized in that: The non-molecular sieve porous filler includes one or a combination of metal organic framework compounds, covalent organic compounds, porous aromatic framework materials, white carbon black, sepiolite, diatomaceous earth, halloysite, kaolin, expanded vermiculite, expanded pearl powder, expanded perlite, hollow glass microspheres, activated carbon and carbon fiber.

12. The vibration-damping, sound-absorbing, and noise-reducing flexible composite material according to any one of claims 1 to 3, characterized in that: The overall density of the vibration-damping, sound-absorbing and noise-reducing flexible composite material is not more than 400 kg / m 3 , resilience is not less than 42%, compression recovery is not less than 75% and the average sound absorption coefficient is not less than 0.

5.

13. The method for preparing the vibration damping, buffering, sound absorbing and noise reducing flexible composite material according to any one of claims 1 to 12, characterized in that: The preparation method comprises: Step (1): adding a low molecular weight saturated alcohol, an aromatic dianhydride, a zeolite molecular sieve, a uniform foaming agent and a catalyst to a highly polar aprotic solvent, mixing them uniformly and performing an esterification reaction to obtain a mixed slurry; Step (2): adding isocyanate to the mixed slurry and mixing them evenly, and then pressurizing the obtained mixed solution and then slowly releasing the pressure to normal pressure to obtain a precursor; Step (3): removing the solvent from the precursor and then performing imidization treatment to obtain the vibration-damping, buffering, sound-absorbing, and noise-reducing flexible composite material.

14. The preparation method according to claim 13, characterized in that: Step (1) comprises: adding low molecular weight saturated alcohol, aromatic dianhydride, zeolite molecular sieve and non-molecular sieve porous filler, foaming agent and catalyst into a strong polar aprotic solvent, mixing them evenly and reacting them to obtain a mixed slurry.

15. A speaker, comprising one or more sound-emitting units and one or more shells, wherein the one or more sound-emitting units and the one or more shells are combined to form a speaker rear cavity, characterized in that: At least one of the speaker front cavity, the speaker rear cavity, the shell and the sound-emitting unit is equipped with the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material according to any one of claims 1 to 12.

16. An electronic device, characterized in that: The electronic device comprises the speaker according to claim 15.

17. The electronic device according to claim 16, characterized in that: The electronic device includes a smart phone, a TWS headset, a head-mounted headset, smart glasses, a smart watch, a VR device, an AR device, a tablet computer or a thin and light laptop computer.

Images