Polyimide foam composite material containing CIT-1 zeolite molecular sieve, preparation of polyimide foam composite material, loudspeaker and electronic equipment

Abstract

The invention provides a polyimide foam composite material containing a CIT-1 zeolite molecular sieve, preparation of the polyimide foam composite material, a loudspeaker and electronic equipment.The polyimide foam composite material containing the CIT-1 zeolite molecular sieve comprises polyimide polyurethane foam and the CIT-1 zeolite molecular sieve, the polyimide foam is of a polycondensation type, the CIT-1 zeolite molecular sieve is of a CIT-1 zeolite molecular sieve structure, and the CIT-1 zeolite molecular sieve is of a CIT-1 zeolite molecular sieve structure. Framework elements of the CIT-1 zeolite molecular sieve comprise silicon and boron, and the CIT-1 zeolite molecular sieve is distributed in closed pores of the polyimide foam; the total weight of the polyimide foam composite material containing the CIT-1 zeolite molecular sieve is 100%, the content of the polyimide foam is 55-75%, and the content of the CIT-1 zeolite molecular sieve is 25-45%. The CIT-1 zeolite molecular sieve-containing polyimide foam composite material provided by the invention has excellent sound absorption and noise reduction 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 polyimide foam composite material containing CIT-1 zeolite molecular sieve and its preparation, a loudspeaker and electronic equipment, 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] CIT-1 zeolite molecular sieve is an inorganic porous material with three-dimensional 10-membered rings or more channels, and has regular intrinsic micropore channels; by performing special experimental treatment on zeolite molecular sieves, materials with microporous-mesoporous pore structures can be obtained.

[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 novel polyimide foam composite material containing CIT-1 zeolite molecular sieve and its preparation, loudspeaker, and electronic equipment has become a technical problem that needs to be solved urgently in the art. 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 polyimide foam composite material containing CIT-1 zeolite molecular sieve.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned polyimide foam composite material containing CIT-1 zeolite molecular sieve.

[0009] Another object of the present invention is to provide a speaker, wherein at least one of the speaker front cavity, speaker rear cavity, housing and sound-emitting unit is equipped with the above-mentioned polyimide foam composite material containing CIT-1 zeolite molecular sieve.

[0010] Another object of the present invention is to provide an electronic device, wherein the rear cavity of the speaker of the electronic device is equipped with the polyimide foam composite material containing CIT-1 zeolite molecular sieve.

[0011] In order to achieve the above objectives, on the one hand, the present invention provides a polyimide foam composite material containing CIT-1 zeolite molecular sieve, wherein the polyimide foam composite material containing CIT-1 zeolite molecular sieve comprises polyimide foam and CIT-1 zeolite molecular sieve, the polyimide foam is a condensation type, the framework elements of the CIT-1 zeolite molecular sieve include silicon boron, and the CIT-1 zeolite molecular sieve is distributed in the closed pores of the polyimide foam;

[0012] Taking the total weight of the polyimide foam composite material containing CIT-1 zeolite molecular sieve as 100%, the content of the polyimide foam is 55-75%, and the content of the CIT-1 zeolite molecular sieve is 25-45%.

[0013] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above, the CIT-1 zeolite molecular sieve is evenly distributed in the closed-cell pores of the polyimide foam. The collision of the CIT-1 zeolite molecular sieve in the closed-cell pores can consume vibration energy, thereby achieving a better vibration reduction effect.

[0014] The polyimide foam composite material containing CIT-1 zeolite molecular sieve provided by the present invention comprises two porous materials, namely, polyimide foam and CIT-1 zeolite molecular sieve. 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. Moreover, the micropores, mesopores and other structural organizations from the inorganic porous materials can also improve the vibration reduction and noise reduction effect in the low-frequency region of the composite material.

[0015] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above in the present invention, wherein the CIT-1 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 CIT-1 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 CIT-1 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.

[0016] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above in the present invention, wherein the structural pores of the CIT-1 zeolite molecular sieve are pores in a three-dimensional direction, including

[001] 12-membered rings,

[100] 10-membered rings and

[010] directional pores. Wherein, the 10-membered ring and the 12-membered ring refer to the pores consisting of 10 skeleton elements and 12 skeleton elements, respectively. Compared with the existing conventional zeolite molecular sieves, such as the one-dimensional 12-membered ring pore structure of MTW zeolite molecular sieve and the one-dimensional 8-membered ring pore structure of BIK zeolite molecular sieve, the CIT-1 zeolite molecular sieve used in the present invention is a three-dimensional pore structure (one-dimensional 12-membered ring and two-dimensional 10-membered ring pores, which are interconnected), which has a more open pore structure, is more conducive to the adsorption and desorption of air molecules by the composite material, increases the volume of the resonance cavity, and thus can achieve a more excellent sound absorption and noise reduction effect.

[0017] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above in the present invention, wherein the silicon-to-aluminum ratio of the CIT-1 zeolite molecular sieve is greater than 10.

[0018] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above, the extra-framework elements of the CIT-1 zeolite molecular sieve include but are not limited to one or a combination of several of sodium, potassium, hydrogen, lithium, cesium, magnesium and calcium.

[0019] The CIT-1 zeolite molecular sieve used in the present invention should have good acid-base stability.

[0020] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above, the polyimide foam is prepared using dianhydride, such as aromatic dianhydride, and diamine, such as aromatic diamine, as raw materials.

[0021] The polyimide foam composite material containing CIT-1 zeolite molecular sieve provided by the present invention has a foaming multiple of more than 1.5 times; by introducing inorganic porous materials in different amounts and different ratios, the foaming volume and sound absorption and noise reduction effect of the composite material can be effectively regulated.

[0022] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above, in the framework elements of the CIT-1 zeolite molecular sieve, the molar ratio of boron element to silicon element is not higher than 1:25.

[0023] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above in the present invention, the overall density of the polyimide foam composite material containing CIT-1 zeolite molecular sieve is not more than 400 kg / m 3 , the rebound resilience is not less than 45%, the compression recovery is not less than 75% and the average sound absorption coefficient is not less than 0.5.

[0024] On the other hand, the present invention also provides a method for preparing the above-mentioned polyimide foam composite material containing CIT-1 zeolite molecular sieve, wherein the preparation method comprises:

[0025] Step (1): mixing dianhydride, CIT-1 zeolite molecular sieve and catalyst in a highly polar aprotic solvent to obtain a mixed solution A;

[0026] Step (2): adding diamine to the mixed solution A in step (1) and mixing evenly to obtain a mixed solution B, i.e., a polyamic acid solution containing CIT-1 zeolite molecular sieve; then adding a porogen and stirring evenly to obtain a mixed solution C; transferring the obtained mixed solution C to a mold, spreading it evenly, and sealing the mold;

[0027] Step (3): transferring the sealed mold containing the mixed solution C to a vacuum oven for imidization and foaming at the same time, that is, removing the solvent and the porogen at high temperature to obtain the polyimide foam composite material containing CIT-1 zeolite molecular sieve.

[0028] In the present invention, the polyimide foam is of condensation type. During the polymerization process, condensation type polyimide will produce small molecules such as H2O, HCl, CO2, etc. These small molecules will increase the pores of the material during the foaming process, which is helpful to obtain a polyimide foam material with more pores.

[0029] As a specific embodiment of the preparation method described above, step (1) comprises: adding dianhydride, CIT-1 zeolite molecular sieve and catalyst into a strongly polar aprotic solvent and mixing them evenly to obtain a mixed solution A.

[0030] In the above-mentioned preparation method of the present invention, due to the existence of the micropore-mesopore-macroporous multi-level pore structure, molecules such as dianhydride, diamine, porogen, etc. can be completely adsorbed or embedded in the CIT-1 zeolite molecular sieve.

[0031] As a specific embodiment of the above preparation method of the present invention, in step (1), the dianhydride can be, for example, an aromatic dianhydride, etc., and in step (2), the diamine can be, for example, an aromatic diamine, etc.

[0032] As a specific embodiment of the preparation method described above, in step (3), the closed mold containing the mixed solution C is placed in a vacuum heating device for evacuation and heating to remove the solvent and the porogen.

[0033] In the present invention, the CIT-1 zeolite molecular sieve porous filler has a microporous structure, which results in a large specific surface area, so that the CIT-1 zeolite 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: subjecting the CIT-1 zeolite molecular sieve porous filler to low-pressure and high-temperature heat treatment to remove the adsorbed small molecules. The present invention does not make specific requirements on 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.

[0034] The dianhydride, strongly polar aprotic solvent, porogen, catalyst and diamine used in the preparation method of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above are all conventional substances. The present invention does not make specific requirements on their dosage and specific substances. The specific substances used in the present invention can be reasonably selected and their specific dosage can be adjusted according to the actual on-site operation needs, as long as the purpose of the present invention to obtain the polyimide foam composite material containing CIT-1 zeolite molecular sieve can be achieved. For example, in some embodiments of the present invention, the dianhydride is an aromatic dianhydride, specifically 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride, pyromellitic dianhydride and 4,4'-diphenyl ether tetracarboxylic dianhydride, the strongly polar aprotic solvent may be N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide and N,N-dimethylacetamide, the diamine may be 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether and 2,2-bis[4-(4-aminophenoxy)phenyl]-hexafluoropropane, the porogen may be triethylamine, diethylamine, etc., and the catalyst may be, for example, propionic anhydride / pyridine or acetic anhydride / pyridine, 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 the present invention of obtaining the polyimide foam composite material containing CIT-1 zeolite molecular sieve can be achieved.

[0035] 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 polyimide foam composite material containing CIT-1 zeolite molecular sieve.

[0036] As a specific implementation of the loudspeaker described above in the present invention, the sound-emitting unit is an acoustic sensor or the like.

[0037] As a specific embodiment of the loudspeaker described above in the present invention, the polyimide foam composite material containing CIT-1 zeolite molecular sieve can be loaded inside the rear cavity of the loudspeaker or adhered to the inner wall of the rear cavity of the loudspeaker; the polyimide foam composite material containing CIT-1 zeolite molecular sieve 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.

[0038] In yet another aspect, the present invention further provides an electronic device, wherein the electronic device comprises the above-mentioned speaker.

[0039] 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.

[0040] Compared with the prior art, the beneficial technical effects that can be achieved by the present invention include:

[0041] The polyimide foam composite material containing CIT-1 zeolite molecular sieve provided by the present invention is a vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material, which comprises polyimide foam and CIT-1 zeolite molecular sieve. The CIT-1 zeolite molecular sieve can not only play a structural reinforcement role, but also play a role of sound absorption and noise reduction due to its pore structure; and because the CIT-1 zeolite molecular sieve structure contains boron element, it can interact with the branched groups (such as amino, hydroxyl, thiol, ether bond and other residual groups) in the polyimide foam, thereby enhancing the interaction strength between the CIT-1 zeolite molecular sieve and the polyimide foam, so that the foam has higher elastic stiffness, thereby improving the rebound performance of the composite material, thereby avoiding powdering; and due to the presence of the polyimide foam, the composite material also has excellent vibration-damping and buffering performance.

[0042] In summary, the polyimide foam composite material containing CIT-1 zeolite molecular sieve provided by the present invention has excellent sound absorption and noise reduction performance at both low frequencies and medium and high frequencies, and also has excellent vibration reduction and buffering performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 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.

[0044] Figure 1 A schematic diagram of a polyimide foam composite material containing CIT-1 zeolite molecular sieve provided in an embodiment of the present invention.

[0045] Figure 2 This is a SEM image of the polyimide foam composite material containing CIT-1 zeolite molecular sieve prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] 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.

[0047] "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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] Preparation Example 1

[0054] In this preparation example, CIT-1 zeolite molecular sieve (refer to the literature CIT-1: A new molecular sieve with intersecting pores bounded by 10-and 12-rings, J. Am. Chem. Soc., 117, 3766-3779 (1995) for preparing the CIT-1 zeolite molecular sieve) is etched to expand part of the micropores in the original structure of the CIT-1 zeolite molecular sieve to mesopore size, wherein, in this preparation example, a 1.0M NaOH solution is used as an etching solution to etch the CIT-1 zeolite molecular sieve, and the etching conditions include: etching at 60°C for 1h, solid-liquid ratio = 1g:50mL; after etching, it is immediately centrifuged and washed for multiple times, and finally dried at 120°C for 12h, and degassed at -0.1MPa, 200°C for 2h to obtain the CIT-1 zeolite molecular sieve after alkali etching.

[0055] Example 1

[0056] This embodiment provides a polyimide foam composite material containing CIT-1 zeolite molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0057] Step (1): Add 20.0 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to 45.0 g of N,N-dimethylformamide and stir. After 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is completely dissolved in N,N-dimethylformamide, add 18.0 g of CIT-1 zeolite molecular sieve prepared in Preparation Example 1, and after stirring evenly, add catalyst, i.e., 4.5 g of propionic anhydride and 2.7 g of pyridine, and stir at 500 rpm for 3 h to obtain a mixed solution A.

[0058] Step (2): Add 13.6 g of 4,4'-diaminodiphenyl ether to the mixed solution A, stir evenly to obtain a light yellow viscous mixed solution B, then add 6.7 g of triethylamine to the mixed solution B as a porogen, mix evenly to obtain a mixed solution C, spread the mixed solution C evenly in a rectangular mold (10 cm×10 cm×5 cm), and seal the mold.

[0059] Step (3): The mold is then transferred to a vacuum oven for imidization and foaming, and the conditions are: vacuum degree -1.0MPa, temperature is staged heating, i.e. 220℃ / 2h+280℃ / 2h, wherein 220℃ / 2h is for imidization and foaming, and 280℃ / 2h is for high-temperature closing of the open-cell structure. After the treatment, the polyimide foam composite material containing CIT-1 zeolite molecular sieve is obtained, wherein the polyimide foam is a condensation type.

[0060] The polyimide foam composite material containing CIT-1 zeolite molecular sieve obtained in this embodiment 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 content of CIT-1 zeolite molecular sieve is 34.8%, based on the total weight of the polyimide foam composite material containing CIT-1 zeolite molecular sieve as 100%.

[0061] Example 2

[0062] This embodiment provides a polyimide foam composite material containing CIT-1 zeolite molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0063] Step (1): Add 20.0 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to 45.0 g of N,N-dimethylformamide and stir. After 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is completely dissolved in N,N-dimethylformamide, add 15.0 g of CIT-1 zeolite molecular sieve prepared in Preparation Example 1, and after stirring evenly, add catalyst, i.e., 4.5 g of propionic anhydride and 2.7 g of pyridine, and stir at 500 rpm for 3 h to obtain a mixed solution A.

[0064] Step (2): Add 13.6 g of 4,4'-diaminodiphenyl ether to the mixed solution A, stir evenly to obtain a light yellow viscous mixed solution B, then add 6.7 g of triethylamine to the mixed solution B as a porogen, mix evenly to obtain a mixed solution C, spread the mixed solution C evenly in a rectangular mold (10 cm×10 cm×5 cm), and seal the mold.

[0065] Step (3): The mold is then transferred to a vacuum oven for imidization and foaming, and the conditions are: vacuum degree -1.0MPa, temperature is staged heating, i.e. 220℃ / 2h+280℃ / 2h, wherein 220℃ / 2h is for imidization and foaming, and 280℃ / 2h is for high-temperature closing of the open-cell structure. After the treatment, the polyimide foam composite material containing CIT-1 zeolite molecular sieve is obtained, wherein the polyimide foam is a condensation type.

[0066] The polyimide foam composite material containing CIT-1 zeolite molecular sieve obtained in this embodiment 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 content of CIT-1 zeolite molecular sieve is 30.9%, based on the total weight of the polyimide foam composite material containing CIT-1 zeolite molecular sieve as 100%.

[0067] Example 3

[0068] This embodiment provides a polyimide foam composite material containing CIT-1 zeolite molecular sieve, which is prepared by a preparation method comprising the following specific steps:

[0069] Step (1): Add 20.0 g of pyromellitic anhydride to 45.0 g of N,N-dimethylformamide and stir. After pyromellitic anhydride is completely dissolved in N,N-dimethylformamide, add 18.0 g of CIT-1 zeolite molecular sieve prepared in Preparation Example 1. After stirring evenly, add a catalyst, namely 4.5 g of propionic anhydride and 2.7 g of pyridine. Stir at 500 rpm for 3 hours to obtain a mixed solution A.

[0070] Step (2): Add 18.35 g of 4,4'-diaminodiphenyl ether to the mixed solution A, stir evenly to obtain a light yellow viscous mixed solution B, then add 6.7 g of triethylamine to the mixed solution B as a porogen, mix evenly to obtain a mixed solution C, spread the mixed solution C evenly in a rectangular mold (10 cm×10 cm×5 cm), and seal the mold.

[0071] Step (3): The mold is then transferred to a vacuum oven for imidization and foaming, and the conditions are: vacuum degree -1.0MPa, temperature is staged heating, i.e. 220℃ / 2h+280℃ / 2h, wherein 220℃ / 2h is for imidization and foaming, and 280℃ / 2h is for high-temperature closing of the open-cell structure. After the treatment, the polyimide foam composite material containing CIT-1 zeolite molecular sieve is obtained, wherein the polyimide foam is a condensation type.

[0072] The polyimide foam composite material containing CIT-1 zeolite molecular sieve obtained in this embodiment 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, based on the total weight of the polyimide foam composite material containing CIT-1 zeolite molecular sieve as 100%, the content of CIT-1 zeolite molecular sieve is 35.2%.

[0073] Comparative Example 1

[0074] This comparative example provides a polyimide foam material, which is prepared by a preparation method comprising the following specific steps:

[0075] Step (1): Add 20.0 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to 45.0 g of N,N-dimethylformamide and stir. After 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is completely dissolved in N,N-dimethylformamide, add a catalyst, namely 4.5 g of propionic anhydride and 2.7 g of pyridine, and stir at 500 rpm for 3 hours to obtain a mixed solution A.

[0076] Step (2): Add 13.6 g of 4,4'-diaminodiphenyl ether to the mixed solution A, stir evenly to obtain a light yellow viscous mixed solution B, then add 6.7 g of triethylamine to the mixed solution B as a porogen, mix evenly to obtain a mixed solution C, spread the mixed solution C evenly in a rectangular mold (10 cm×10 cm×5 cm), and seal the mold.

[0077] Step (3): The mold is then transferred to a vacuum oven for imidization and foaming, and the conditions are: vacuum degree -1.0MPa, temperature is staged heating, i.e. 220℃ / 2h+280℃ / 2h, wherein 220℃ / 2h is for imidization and foaming, and 280℃ / 2h is for high-temperature closing of the open-cell structure. After the treatment, the polyimide foam material is obtained, wherein the polyimide foam is a condensation type.

[0078] Comparative Example 2

[0079] This comparative example provides a polyimide foam composite material containing BIK zeolite molecular sieve, which differs from Example 1 only in that the zeolite molecular sieve used is different. The zeolite molecular sieve used in this comparative example is a BIK zeolite molecular sieve after alkali etching, which has a one-dimensional 8-membered ring channel structure and can be prepared by referring to the document The crystal structure of Cs0.35Al0.35Si2.65O6 a cesium-aluminosilicate with the bikitaite framework Z.Kristallogr., 166, 301-306 (1984). The alkali etching method is the same as that in Preparation Example 1, wherein the polyimide foam is a condensation type.

[0080] Test Example 1

[0081] This test example tests the apparent core density of the composite materials provided in Examples 1 to 3 of the present invention, the polyimide foam material provided in Comparative Example 1, and the polyimide foam composite material containing BIK zeolite molecular sieve provided in Comparative Example 2 respectively according to GB / T 6343-1995 standard;

[0082] 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.

[0083] The apparent core density data of the composite materials provided in Examples 1 to 3 of the present invention, the polyimide foam material provided in Comparative Example 1, and the polyimide foam composite material containing BIK zeolite molecular sieve provided in Comparative Example 2 are shown in Table 1 below.

[0084] Table 1

[0085] Apparent core density <![CDATA[Sample 1 / (kg / m 3 )]]> <![CDATA[Specimen 2 / (kg / m 3 )]]> <![CDATA[Sample 3 / (kg / m 3 )]]> <![CDATA[Average value / (kg / m 3 )]]> Example 1 103.1 102.9 103.2 103.07 Example 2 102.5 102.4 102.4 102.43 Example 3 103.2 103.3 103.3 103.27 Comparative Example 1 82.6 82.7 82.6 82.63 Comparative Example 2 106.8 107.0 107.0 106.9

[0086] It can be known from the test results of the apparent core density shown in Table 1 that the apparent core density of the polyimide foam composite material containing CIT-1 zeolite molecular sieve obtained by adding CIT-1 zeolite molecular sieve in Examples 1-3 of the present invention is higher than the apparent core density of the polyimide foam material obtained by not adding any inorganic porous material in Comparative Example 1; this is mainly because the density of CIT-1 zeolite molecular sieve is higher than that of polyimide foam. It can also be seen from Table 1 that the apparent core density of the composite material provided in Example 2 of the present invention is slightly lower than that of the composite material provided in Examples 1 and 3, mainly because the addition amount of CIT-1 zeolite molecular sieve in the composite material system provided is slightly lower. BIK zeolite molecular sieve is introduced in Comparative Example 2, because the density of BIK zeolite molecular sieve (which is a silicon aluminum molecular sieve with a density of 2.02g / cc) is higher than that of CIT-1 molecular sieve (density of 1.62g / cc), so compared with Examples 1-3 of the present invention, the apparent core density of the composite material obtained by introducing the same mass of BIK zeolite molecular sieve in Comparative Example 2 is greater.

[0087] Test Example 2

[0088] This test example tests the steel ball rebound performance of the composite materials provided in Examples 1 to 3 of the present invention, the polyimide foam material provided in Comparative Example 1, and the polyimide foam composite material containing BIK zeolite molecular sieve provided in Comparative Example 2 according to GB / T 6670-2008 standard, including:

[0089] 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.

[0090] The rebound performance test results of the composite materials provided in Examples 1 to 3 of the present invention, the polyimide foam material provided in Comparative Example 1, and the polyimide foam composite material containing BIK zeolite molecular sieve provided in Comparative Example 2 are shown in Table 2.

[0091] Table 2

[0092]

[0093]

[0094] From the test results of resilience shown in Table 2 above, it can be known that the rebound rate of the polyimide foam composite material containing CIT-1 zeolite molecular sieve prepared by adding CIT-1 zeolite molecular sieve in Examples 1 to 3 of the present invention is improved compared with the polyimide foam material prepared in Comparative Example 1 without adding any inorganic porous material. This is mainly because after the introduction of CIT-1 zeolite molecular sieve, it is evenly dispersed in the system, thereby enhancing the strength of the foam material, and because the CIT-1 zeolite molecular sieve structure contains boron, it can interact with the branched groups (such as amino, hydroxyl, thiol, ether bond and other residual groups) in the polyimide foam, thereby enhancing the interaction strength between the CIT-1 zeolite molecular sieve and the polyimide foam, so that the foam has a higher elastic stiffness, thereby improving the rebound performance of the composite material, thereby avoiding powdering. The rebound rate of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material prepared by introducing BIK zeolite molecular sieve in Comparative Example 2 is improved to a certain extent compared with the polyimide foam material prepared in Comparative Example 1 without adding any inorganic porous material, but it is still lower than the polyimide foam composite material containing CIT-1 zeolite molecular sieve prepared by adding CIT-1 zeolite molecular sieve in Examples 1 to 3 of the present invention. This is because: BIK zeolite molecular sieve is a conventional silicon-aluminum structure, and the aluminum element in the structure hardly reacts with the side chain group in the polyimide foam, so the introduction of BIK zeolite molecular sieve in Comparative Example 2 has very limited improvement on the rebound performance of the obtained composite material.

[0095] Test Example 3

[0096] This test example performs compression recovery tests on the composite materials provided in Examples 1 to 3 of the present invention, the polyimide foam material provided in Comparative Example 1, and the polyimide foam composite material containing BIK zeolite molecular sieve provided in Comparative Example 2 according to the HG / T 2876-2009 standard, including:

[0097] 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.

[0098] The compression recovery test results of the composite materials provided in Examples 1 to 3 of the present invention, the polyimide foam material provided in Comparative Example 1, and the polyimide foam composite material samples containing BIK zeolite molecular sieve provided in Comparative Example 2 in three directions are shown in Table 3 below.

[0099] Table 3

[0100] Compression recovery rate long / (%) Width / (%) thick / (%) average value / (%) Example 1 81.6 81.5 81.7 81.60 Example 2 81.2 81.1 81.1 81.13 Example 3 81.7 81.9 81.8 81.80 Comparative Example 1 77.2 77 77 77.07 Comparative Example 2 79.1 79.0 79.0 79.03

[0101] From the compression recovery test results shown in Table 3, it can be known that the compression recovery rate of the vibration damping, buffering, sound absorbing and noise reduction flexible composite materials prepared by adding CIT-1 zeolite molecular sieve in Examples 1 to 3 of the present invention and by adding BIK zeolite molecular sieve in Comparative Example 2 is 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 CIT-1 and BIK zeolite molecular sieves, the inorganic porous material particles will gradually undergo slight displacement to absorb the internal stress generated by the compression; after the external pressure disappears, as the bubbles recover, the displaced CIT-1 and BIK zeolite molecular sieve 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, thereby improving the compression recovery of the composite material. At the same time, the compression recovery rate of the vibration-damping, sound-absorbing and noise-reducing flexible composite material prepared by introducing BIK zeolite molecular sieve in Comparative Example 2 is still lower than that of the polyimide foam composite material containing CIT-1 zeolite molecular sieve prepared by adding CIT-1 zeolite molecular sieve in Examples 1 to 3 of the present invention. This is because the material density of BIK zeolite molecular sieve is higher than that of CIT-1 zeolite molecular sieve. Therefore, under the same added mass, CIT-1 zeolite molecular sieve will exhibit a larger filling volume and can withstand more internal stress.

[0102] From the experimental data in Table 2 and Table 3, it can be seen that the resilience (rebound rate) and compression recovery (compression recovery rate) of the polyimide foam composite materials containing CIT-1 zeolite molecular sieve prepared by adding CIT-1 zeolite molecular sieve in Examples 1 to 3 of the present invention are improved compared with the polyimide foam material prepared in Comparative Example 1 without adding any inorganic porous material and the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material prepared by introducing BIK zeolite molecular sieve in Comparative Example 2. 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 and friction of internal components, thereby improving the working stability of the workpiece and extending the service life of the equipment and components.

[0103] Test Example 4

[0104] In this test example, according to the test standard GBJ 88-85 (Standing Wave Tube Method Sound Absorption Coefficient and Acoustic Impedance Measurement Specification), the standing wave tube method is used to test the sound absorption performance of the composite materials provided in Examples 1 to 3 of the present invention, the polyimide foam material provided in Comparative Example 1, and the polyimide foam composite material containing BIK zeolite molecular sieve provided in Comparative Example 2. The instrument used for the test is a dual-channel tester from Shengwang Company, and the sound absorption sample is a Φ100mm cylinder.

[0105] The sound absorption performance test results of the composite materials provided in Examples 1 to 3 of the present invention, the polyimide foam material provided in Comparative Example 1, and the polyimide foam composite material containing BIK zeolite molecular sieve provided in Comparative Example 2 are shown in Table 4 below.

[0106] Table 4

[0107]

[0108] From the test results of the sound absorption performance shown in Table 4, it can be known that the sound absorption performance of the polyimide foam composite material containing CIT-1 zeolite molecular sieve prepared by adding CIT-1 zeolite molecular sieve in Examples 1 to 3 of the present invention is significantly improved in both low-frequency and medium-high frequency bands compared with the polyimide foam material prepared in Comparative Example 1 without adding any inorganic porous material. This is mainly because the CIT-1 zeolite molecular sieve material introduced in the examples of the present invention provides a multi-level pore structure such as micropore-mesopore and mesopore-macroporous, enriches the pore structure of the polyimide foam, 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. It can also be seen from Table 4 that the average sound absorption coefficient of the vibration-damping, buffering, sound-absorbing and noise-reducing flexible composite material prepared by introducing BIK zeolite molecular sieve in Comparative Example 2 is improved to a certain extent compared with the polyimide foam material prepared without adding any inorganic porous material in Comparative Example 1, but is still lower than the polyimide foam composite material containing CIT-1 zeolite molecular sieve prepared by adding CIT-1 zeolite molecular sieve in Examples 1 to 3 of the present invention. This is because: the CIT-1 zeolite molecular sieve used in the embodiments of the present invention has a three-dimensional pore structure (one-dimensional 12-membered ring and two-dimensional 10-membered ring pores, which are interconnected), and has a more open pore structure than the one-dimensional 8-membered ring pore of BIK zeolite molecular sieve, which is more conducive to the adsorption and desorption of air molecules by the composite material, increases the volume of the resonance cavity, and thus can achieve better sound absorption and noise reduction effects.

[0109] Test Example 5

[0110] In this test example, the polyimide foam composite material containing CIT-1 zeolite molecular sieve 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 polyimide foam composite material containing CIT-1 zeolite molecular sieve provided in the embodiments of the present invention are as shown Figure 1 As shown. Figure 1 and Figure 2 It can be seen that the polyimide foam composite material containing CIT-1 zeolite molecular sieve provided in the embodiment of the present invention comprises polyimide foam and CIT-1 zeolite molecular sieve, and the CIT-1 zeolite molecular sieve is distributed in the closed-cell pores of the polyimide foam.

[0111] 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 polyimide foam composite material containing CIT-1 zeolite molecular sieve, characterized in that: The polyimide foam composite material containing CIT-1 zeolite molecular sieve comprises polyimide foam and CIT-1 zeolite molecular sieve, wherein the polyimide foam is of polycondensation type, the framework elements of the CIT-1 zeolite molecular sieve comprise silicon boron, and the CIT-1 zeolite molecular sieve is distributed in the closed pores of the polyimide foam; Taking the total weight of the polyimide foam composite material containing CIT-1 zeolite molecular sieve as 100%, the content of the polyimide foam is 55-75%, and the content of the CIT-1 zeolite molecular sieve is 25-45%.

2. The composite material according to claim 1, characterized in that The CIT-1 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.

3. The composite material according to claim 1 or 2, characterized in that: The structural pores of the CIT-1 zeolite molecular sieve are three-dimensional pores, including [001] 12-membered rings, [100] 10-membered rings and [010] directional pores.

4. The composite material according to claim 1 or 2, characterized in that: The extra-framework elements of the CIT-1 zeolite molecular sieve include, but are not limited to, one or a combination of several of sodium, potassium, hydrogen, lithium, cesium, magnesium and calcium.

5. The composite material according to claim 1 or 2, characterized in that: In the framework elements of the CIT-1 zeolite molecular sieve, the molar ratio of boron to silicon is not higher than 1:

25.

6. The composite material according to claim 1 or 2, characterized in that: The overall density of the polyimide foam composite material containing CIT-1 zeolite molecular sieve is not more than 400 kg / m 3 , the rebound resilience is not less than 45%, the compression recovery is not less than 75% and the average sound absorption coefficient is not less than 0.

5.

7. The method for preparing the polyimide foam composite material containing CIT-1 zeolite molecular sieve according to any one of claims 1 to 6, characterized in that: The preparation method comprises: Step (1): mixing dianhydride, CIT-1 zeolite molecular sieve and catalyst in a highly polar aprotic solvent to obtain a mixed solution A; Step (2): adding diamine to the mixed solution A and mixing evenly to obtain a mixed solution B, i.e., a polyamic acid solution containing CIT-1 zeolite molecular sieve; then adding a porogen and stirring evenly to obtain a mixed solution C; transferring the obtained mixed solution C to a mold, spreading it evenly, and sealing the mold; Step (3): transferring the sealed mold containing the mixed solution C to a vacuum oven for imidization and foaming to obtain the polyimide foam composite material containing CIT-1 zeolite molecular sieve.

8. 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, speaker rear cavity, housing and sound-emitting unit is equipped with the polyimide foam composite material containing CIT-1 zeolite molecular sieve according to any one of claims 1 to 6.

9. An electronic device, characterized in that: The electronic device comprises the speaker according to claim 8.

10. The electronic device according to claim 9, 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.

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