Polyimide foam composites containing CIT-1 zeolite molecular sieves, their preparation, and their applications in loudspeakers and electronic devices.

Abstract

This invention provides a polyimide foam composite material containing CIT-1 zeolite molecular sieve, its preparation, and its applications in loudspeakers and electronic devices. The polyimide foam composite material comprises polyimide polyurethane foam and CIT-1 zeolite molecular sieve. The polyimide foam is condensation-type, and the framework element of the CIT-1 zeolite molecular sieve includes silicon boron. The CIT-1 zeolite molecular sieve is distributed within the closed pores of the polyimide foam. Based on the total weight of the polyimide foam composite material containing CIT-1 zeolite molecular sieve (100%), the content of polyimide foam is 55-75%, and the content of CIT-1 zeolite molecular sieve is 25-45%. The polyimide foam composite material containing CIT-1 zeolite molecular sieve provided by this invention exhibits excellent sound absorption and noise reduction performance at low and mid-to-high frequencies, as well as excellent vibration damping and buffering performance.

Description

Technical Field

[0001] This invention relates to a polyimide foam composite material containing CIT-1 zeolite molecular sieve, its preparation, and to loudspeakers and electronic devices, belonging to the field of materials technology, particularly the field of electroacoustic materials technology. Background Technology

[0002] In daily use, portable electronic devices (such as mobile phones, headphones, tablets, etc.) experience vibrations from speakers, receivers, or motors, causing coordinated and isolated vibrations among different components within the device, and even friction between different parts within the same component. Therefore, introducing vibration-damping and sound-absorbing materials into the gaps within electronic devices can effectively reduce vibrations and noise caused by drops and device operation, reduce component frictional losses, provide stable performance, and extend the device's lifespan.

[0003] Polyimide foam is a type of polymer material containing a large number of gas micropores, mesopores, and nanopores. It not only possesses the common characteristics of foam plastics such as heat insulation, shock absorption, and noise reduction, but also exhibits advantages such as high-temperature resistance, low-temperature resistance, intrinsic flame retardancy, radiation resistance, and low smoke emission. Polyimide foam is classified into two main categories based on its cell structure: flexible open-cell foam and rigid closed-cell foam. The former is typically made from thermoplastic polyimide resin, while the latter is made from thermosetting polyimide resin. Flexible open-cell polyimide foam is mainly used in sound insulation, noise reduction, heat protection, and shock absorption, exhibiting 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 and above, and has regular intrinsic micropores. Through special experimental treatment of zeolite molecular sieve, materials with micropore-mesopore pore structures can be obtained.

[0005] Traditional foam materials have a porous structure with large pores, which are widely used in vibration and noise reduction at mid and high frequencies, but their vibration and noise reduction effect at low frequencies is not good.

[0006] Therefore, providing a novel polyimide foam composite material containing CIT-1 zeolite molecular sieve, its preparation, and its application in loudspeakers and electronic devices have become urgent technical problems to be solved in this field. Summary of the Invention

[0007] To address the aforementioned shortcomings and deficiencies, one objective of this 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 polyimide foam composite material containing CIT-1 zeolite molecular sieve described above.

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

[0010] Another object of the present invention is to provide an electronic device in which the above-described polyimide foam composite material containing CIT-1 zeolite molecular sieve is assembled in the rear cavity of the speaker.

[0011] 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 includes polyimide foam and CIT-1 zeolite molecular sieve, the polyimide foam is condensation type, the framework element of the CIT-1 zeolite molecular sieve includes silicon boron, and the CIT-1 zeolite molecular sieve is distributed in the closed pores of the polyimide foam;

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

[0013] In one specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above, the CIT-1 zeolite molecular sieve is uniformly distributed in the closed pores of the polyimide foam. The collision of the CIT-1 zeolite molecular sieve within the closed pores can dissipate vibrational energy, thereby achieving a better vibration damping effect.

[0014] The polyimide foam composite material containing CIT-1 zeolite molecular sieve provided by this invention includes two porous materials: polyimide foam and CIT-1 zeolite molecular sieve. Although the introduction of inorganic porous materials will inevitably increase the overall density of the material, it can also improve the resilience and compression recovery of the composite material. Furthermore, the micropores, mesopores and other structural components 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 this invention, the CIT-1 zeolite molecular sieve has an intrinsic cross-pore structure, which includes one or more combinations of micropore-micropore, micropore-mesopore, and mesopore-mesopore structures. The mesopores in the CIT-1 zeolite molecular sieve can be obtained through subsequent experimental treatments (such as acid and alkali etching, using acidic and alkali etching solutions respectively), or they can be introduced during the preparation of the CIT-1 zeolite molecular sieve. This invention does not specify particular requirements for the concentration of the etching solution used in acid and alkali etching, or for parameters such as temperature, pressure, and time during the acid and alkali etching process; these can be reasonably adjusted according to the actual needs of on-site operations.

[0016] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above in this invention, the CIT-1 zeolite molecular sieve has a three-dimensional pore structure, including

[001] 12-membered rings,

[100] 10-membered rings, and

[010] directional pores. The 10-membered rings and 12-membered rings refer to pores composed of 10 and 12 framework elements, respectively. Compared to 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 this invention has a three-dimensional pore structure (one-dimensional 12-membered rings and two-dimensional 10-membered ring pores that are interconnected). It has a more open pore structure, which is more conducive to the adsorption and desorption of air molecules by the composite material, increasing the volume of the resonant cavity, thereby achieving a more superior 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 this invention, the CIT-1 zeolite molecular sieve has a silica-to-alumina ratio >10.

[0018] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above in this invention, the extra-skeletal 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 this invention should have good acid and alkali stability.

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

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

[0022] As a specific embodiment of the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above in this invention, the molar ratio of boron to silicon in the framework elements of the CIT-1 zeolite molecular sieve 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 this invention, the overall density of the polyimide foam composite material containing CIT-1 zeolite molecular sieve is not greater than 400 kg / m³. 3 Its resilience is not less than 45%, its compression recovery is not less than 75%, and its 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 polyimide foam composite material containing CIT-1 zeolite molecular sieve described above, wherein the preparation method includes:

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

[0026] Step (2): Add diamine to the mixed solution A described in step (1) and mix evenly to obtain mixed solution B, which is a polyamic acid solution containing CIT-1 zeolite molecular sieve; then add pore-forming agent and stir evenly to obtain mixed solution C; transfer the obtained mixed solution C to a mold, spread it evenly, and seal the mold.

[0027] Step (3): Transfer the sealed mold containing mixed solution C to a vacuum oven for imidization and foaming, i.e., remove the solvent and pore-forming agent at high temperature to obtain the polyimide foam composite material containing CIT-1 zeolite molecular sieve.

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

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

[0030] In the preparation method described above in this invention, due to the presence of a multi-level pore structure of micropores-mesopores-macropores, molecules such as dianhydrides, diamines, and porogens can be completely adsorbed or embedded in the CIT-1 zeolite molecular sieve.

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

[0032] As a specific embodiment of the preparation method described above in this invention, in step (3), a sealed mold containing mixed solution C is placed in a vacuum heating device for vacuuming and heating to remove solvent and pore-forming agent.

[0033] In this invention, the CIT-1 zeolite molecular sieve porous packing material has a microporous structure, resulting in a large specific surface area. Therefore, this CIT-1 zeolite molecular sieve porous packing material adsorbs small molecules from the air, such as water molecules, CO2, and small VOC molecules. Thus, as a specific embodiment of the preparation method described above, the preparation method further includes: subjecting the CIT-1 zeolite molecular sieve porous packing material to low-pressure high-temperature heat treatment to remove the adsorbed small molecules. This invention does not specify particular requirements for the temperature, pressure, and time parameters of the low-pressure high-temperature heat treatment; these can be reasonably adjusted according to the actual needs of on-site operations.

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

[0035] In another aspect, the present invention also provides a loudspeaker, including one or more sound-generating units and one or more housings, wherein the one or more sound-generating units and the one or more housings are combined to form a rear cavity of the loudspeaker, wherein at least one of the front cavity of the loudspeaker, the rear cavity of the loudspeaker, the housing and the sound-generating units is equipped with the polyimide foam composite material containing CIT-1 zeolite molecular sieve described above.

[0036] In one specific embodiment of the loudspeaker described above in this invention, the sound-generating unit is an acoustic sensor or the like.

[0037] As a specific embodiment of the loudspeaker described above in this invention, the polyimide foam composite material containing CIT-1 zeolite molecular sieve can be filled into 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 housing, and the back of the magnetic cup of the sound-generating unit.

[0038] In another aspect, the present invention also provides an electronic device, wherein the electronic device includes the speaker described above.

[0039] As a specific embodiment of the electronic device described above in this invention, the electronic device includes smartphones, TWS earphones, headphones, smart glasses, smartwatches, VR devices, AR devices, tablet computers, or thin and light laptops, etc.

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

[0041] The polyimide foam composite material containing CIT-1 zeolite molecular sieve provided by this invention is a flexible composite material for vibration damping, buffering, sound absorption, and noise reduction. It includes polyimide foam and CIT-1 zeolite molecular sieve. CIT-1 zeolite molecular sieve not only plays a role in structural reinforcement, but also plays a role in sound absorption and noise reduction due to its porous structure. Furthermore, since the CIT-1 zeolite molecular sieve structure contains boron, it can interact with the branched groups (such as amino, hydroxyl, mercapto, ether bonds, and other residual groups) in the polyimide foam, enhancing the interaction strength between the CIT-1 zeolite molecular sieve and the polyimide foam, giving the foam higher elastic stiffness, thus improving the resilience of the composite material and preventing powder shedding. At the same time, due to the presence of 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 this invention has excellent sound absorption and noise reduction performance in both low and mid-to-high frequencies, and also has excellent vibration damping and buffering performance. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is 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 Implementation

[0046] It should be noted that the term "comprising" and any variations thereof in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. 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 explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0047] The "range" disclosed in this invention is given in the form of a lower limit and an 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 and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0048] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0049] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0050] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0051] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it 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 it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying tables, drawings, and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified 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 the preparation of this CIT-1 zeolite molecular sieve) was etched to enlarge some of the micropores in the original structure of the CIT-1 zeolite molecular sieve to the mesopore size. In this preparation example, a 1.0 M NaOH solution was used as the etching solution to etch the CIT-1 zeolite molecular sieve. The etching conditions included: etching at 60 °C for 1 h, solid-liquid ratio = 1 g: 50 mL; after etching, it was immediately subjected to multiple centrifugal washings, and finally dried at 120 °C for 12 h, and degassed at -0.1 MPa and 200 °C for 2 h to obtain the alkaline-etched CIT-1 zeolite molecular sieve.

[0055] Example 1

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

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

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

[0059] Step (3): The mold is then transferred to a vacuum oven for imidization and foaming. The conditions are: vacuum degree -1.0MPa, temperature is increased in stages, i.e. 220℃ / 2h+280℃ / 2h, where 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 condensation type.

[0060] The polyimide foam composite material containing CIT-1 zeolite molecular sieve obtained in this embodiment was placed in air or an oxygen-rich atmosphere and calcined at 500°C for 6 hours. After calcination, it was 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 was 34.8%.

[0061] Example 2

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

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

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

[0065] Step (3): The mold is then transferred to a vacuum oven for imidization and foaming. The conditions are: vacuum degree -1.0MPa, temperature is increased in stages, i.e. 220℃ / 2h+280℃ / 2h, where 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 condensation type.

[0066] The polyimide foam composite material containing CIT-1 zeolite molecular sieve obtained in this embodiment was placed in air or an oxygen-rich atmosphere and calcined at 500°C for 6 hours. After calcination, it was 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 was 30.9%.

[0067] Example 3

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

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

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

[0071] Step (3): The mold is then transferred to a vacuum oven for imidization and foaming. The conditions are: vacuum degree -1.0MPa, temperature is increased in stages, i.e. 220℃ / 2h+280℃ / 2h, where 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 condensation type.

[0072] The polyimide foam composite material containing CIT-1 zeolite molecular sieve obtained in this embodiment was placed in air or an oxygen-rich atmosphere and calcined at 500°C for 6 hours. After calcination, it was 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 was 35.2%.

[0073] Comparative Example 1

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

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

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

[0077] Step (3): The mold is then transferred to a vacuum oven for imidization and foaming. The conditions are: vacuum degree -1.0MPa, temperature is increased in stages, i.e. 220℃ / 2h + 280℃ / 2h, where 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. The only difference between this and Example 1 is the zeolite molecular sieve used. The zeolite molecular sieve used in this comparative example is BIK zeolite molecular sieve after alkali etching, which has a one-dimensional 8-membered ring channel structure. It can be prepared with reference to 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 Example 1. In this example, 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 1-3 of this 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 GB / T 6343-1995 standard.

[0082] The shape of the sample should facilitate volume calculation. When cutting the sample, it should be ensured that the original pore structure does not deform. At least 3 samples should be tested in each group, and the average value should be 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 1-3 of this 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[Specimen 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] The apparent core density test results shown in Table 1 indicate that the apparent core density of the polyimide foam composite materials containing CIT-1 zeolite molecular sieve prepared in Examples 1-3 of this invention is higher than that of the polyimide foam material prepared in Comparative Example 1 without any inorganic porous material. This is mainly because the density of CIT-1 zeolite molecular sieve is higher than that of polyimide foam. Table 1 also shows that the apparent core density of the composite material provided in Example 2 of this invention is slightly lower than that of the composite materials provided in Examples 1 and 3. This is mainly because the amount of CIT-1 zeolite molecular sieve added to its composite material system is slightly lower. Comparative Example 2 introduced BIK zeolite molecular sieve. Because the density of BIK zeolite molecular sieve (which is a silica-alumina molecular sieve with a density of 2.02 g / cc) is higher than that of CIT-1 molecular sieve (density of 1.62 g / cc), the composite material prepared in Comparative Example 2 with the same mass of BIK zeolite molecular sieve has a higher apparent core density compared to Examples 1-3 of this invention.

[0087] Test Example 2

[0088] This test example, according to GB / T 6670-2008 standard, tests the steel ball rebound performance of the composite materials provided in Examples 1-3 of this 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, including:

[0089] A steel ball is dropped freely from the sample surface (50 cm above the horizontal plane), and the rebound height of the steel ball is measured. Each sample is tested three times, and the average value is taken as the test result of the rebound performance of the composite material and polyimide foam material.

[0090] The rebound performance test results of the composite materials provided in Examples 1-3 of this 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] As shown in Table 2 above, the resilience test results indicate that the resilience of the polyimide foam composite materials containing CIT-1 zeolite molecular sieve prepared in Examples 1-3 of this invention is higher than that of the polyimide foam material prepared in Comparative Example 1 without any inorganic porous material. This is mainly because after the introduction of CIT-1 zeolite molecular sieve, it is uniformly dispersed in the system, enhancing the strength of the foam material. Furthermore, since the CIT-1 zeolite molecular sieve contains boron, it can interact with the branched groups (such as amino, hydroxyl, mercapto, ether bonds, and other residual groups) in the polyimide foam, enhancing the interaction strength between the CIT-1 zeolite molecular sieve and the polyimide foam, giving the foam higher elastic stiffness. Therefore, the resilience of the composite material is improved, thus preventing powder shedding. The resilience of the vibration-damping, 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 materials in Comparative Example 1. However, 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 1-3 of this invention. This is because: BIK zeolite molecular sieve has a conventional silicon-aluminum structure, and the aluminum element in the structure hardly interacts with the branched groups in the polyimide foam. Therefore, the improvement of the resilience performance of the composite material obtained by introducing BIK zeolite molecular sieve in Comparative Example 2 is very limited.

[0095] Test Example 3

[0096] This test example, according to HG / T 2876-2009 standard, performs compression recovery tests on the composite materials provided in Examples 1-3 of this 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, including:

[0097] The sample was divided into rectangular blocks with a length and width of 20 mm and a thickness of 10 mm. The sample was compressed to 50% of its original thickness at room temperature and kept for 72 hours. Then it was left to stand for 2 hours to obtain the recovered thickness. The ratio of the recovered thickness to the original thickness is the compression recovery rate.

[0098] The compression recovery test results of the composite materials provided in Examples 1-3 of this 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 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] As shown in Table 3, the compression recovery test results indicate that the compression recovery rate of the vibration-damping, sound-absorbing, and noise-reducing flexible composite materials prepared by adding CIT-1 zeolite molecular sieve in Examples 1-3 and BIK zeolite molecular sieve in Comparative Example 2 is higher than that of the polyimide foam material prepared without any inorganic porous materials in Comparative Example 1. This is mainly because after long-term compression, the inorganic porous material particles of the introduced CIT-1 and BIK zeolite molecular sieves will gradually undergo slight displacement, absorbing the internal stress generated by 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 displacement under the restoring force of the bubbles or bubble walls, synergistically promoting bubble recovery, thus improving the compression recovery of the composite material. Meanwhile, the compression recovery 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 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 1-3 of this 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] Based on the experimental data in Tables 2 and 3, it can be seen that the resilience (resilience rate) and compression recovery (compression recovery rate) of the polyimide foam composite materials containing CIT-1 zeolite molecular sieve prepared in Examples 1-3 of this invention are all improved compared with the polyimide foam material prepared without any inorganic porous materials in Comparative Example 1 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 improved resilience and compression recovery of the composite materials are beneficial for electronic equipment and internal components to better cope with external impacts and vibration friction of internal components, thereby improving the stability of workpiece operation and extending the service life of equipment and components.

[0103] Test Example 4

[0104] This test example uses the standing wave tube method to test the sound absorption performance of the composite materials provided in Examples 1-3 of this 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 test standard GBJ 88-85 (Standing Wave Tube Method for Measurement of Sound Absorption Coefficient and Acoustic Impedance). The instrument used for testing is a Shengwang Company dual-channel tester, and the sound absorption sample is a cylinder with a diameter of 100 mm.

[0105] The sound absorption performance test results of the composite materials provided in Examples 1-3 of this 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] As shown in Table 4, the test results of the sound absorption performance show that the sound absorption performance of the polyimide foam composite materials containing CIT-1 zeolite molecular sieve prepared in Examples 1-3 of this invention is significantly improved in both low and mid-high frequency ranges compared with the polyimide foam material prepared in Comparative Example 1 without the addition of any inorganic porous materials. This is mainly because the CIT-1 zeolite molecular sieve material introduced in the embodiments of this invention provides a multi-level pore structure such as micropore-mesopore and mesopore-macropore, which enriches the pore structure of the polyimide foam, facilitates the adsorption and desorption of air molecules by the composite material, effectively increases the volume of the resonant cavity, and further matches the impedance of the composite material with the impedance of the air, thereby achieving a better sound absorption and noise reduction effect. As can be seen from Table 4, 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. However, 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 1-3 of this invention. This is because: the CIT-1 zeolite molecular sieve used in the embodiments of this invention has a three-dimensional pore structure (one-dimensional 12-membered ring and two-dimensional 10-membered ring pores, which are interconnected). Compared with the one-dimensional 8-membered ring pores of BIK zeolite molecular sieve, it has a more open pore structure, which is more conducive to the adsorption and desorption of air molecules by the composite material, increases the volume of the resonant cavity, and thus achieves a better sound absorption and noise reduction effect.

[0109] Test Example 5

[0110] This test example performs SEM analysis on the polyimide foam composite material containing CIT-1 zeolite molecular sieve prepared in Example 1 of this invention. The obtained SEM images are shown below. Figure 2 As shown, schematic diagrams of the polyimide foam composite material containing CIT-1 zeolite molecular sieve provided in other embodiments of the present invention are also shown. Figure 1 As shown. Figure 1 and Figure 2 As can be seen from the above, the polyimide foam composite material containing CIT-1 zeolite molecular sieve provided in the embodiments of the present invention includes polyimide foam and CIT-1 zeolite molecular sieve, and the CIT-1 zeolite molecular sieve is distributed in the closed pores of the polyimide foam.

[0111] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

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 includes polyimide foam and CIT-1 zeolite molecular sieve. The polyimide foam is condensation type, and the framework element of the CIT-1 zeolite molecular sieve includes silicon boron. The CIT-1 zeolite molecular sieve is distributed in the closed pores of the polyimide foam. Based on the total weight of the polyimide foam composite material containing CIT-1 zeolite molecular sieve as 100%, the content of polyimide foam is 55-75%, and the content of 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 one or more combinations of micropore-micropore, micropore-mesopore, and mesopore-mesopore.

3. The composite material according to claim 1 or 2, characterized in that, The CIT-1 zeolite molecular sieve has a three-dimensional structure with channels including [001] 12-membered rings, [100] 10-membered rings, and [010] directional channels.

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 greater than 400 kg / m³. 3 Its resilience is not less than 45%, its compression recovery is not less than 75%, and its 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 1-6, characterized in that, The preparation method includes: Step (1): Mix the dianhydride, CIT-1 zeolite molecular sieve and catalyst evenly in a strongly polar aprotic solvent to obtain mixed solution A; Step (2): Add diamine to the mixed solution A and mix evenly to obtain mixed solution B, which is a polyamic acid solution containing CIT-1 zeolite molecular sieve; then add pore-forming agent and stir evenly to obtain mixed solution C; transfer the obtained mixed solution C to a mold, spread it evenly, and seal the mold. Step (3): Transfer 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 loudspeaker, comprising one or more sound-emitting units and one or more housings, wherein the one or more sound-emitting units and the one or more housings are combined to form a loudspeaker rear cavity, characterized in that, At least one of the speaker front cavity, speaker rear cavity, housing, and sound-generating unit is equipped with the polyimide foam composite material containing CIT-1 zeolite molecular sieve as described in any one of claims 1-6.

9. An electronic device, characterized in that, The electronic device includes the speaker as described in claim 8.

10. The electronic device according to claim 9, characterized in that, The electronic devices include smartphones, TWS earphones, headphones, smart glasses, smartwatches, VR devices, AR devices, tablets, or thin and light laptops.

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