A method for preparing a sound-absorbing composite material

Abstract

This invention provides a method for preparing a sound-absorbing composite material, comprising: Step 1: cleaning a support layer to remove surface contaminants; Step 2: forming a molecular sieve seed layer or a molecular sieve transition layer on the surface of the cleaned support layer, or sequentially forming a molecular sieve seed layer and a molecular sieve transition layer; Step 3: placing the product obtained in Step 2 in the growth solution of a third molecular sieve, followed by crystallization, drying, and calcination (with or without calcination) to form a molecular sieve outer layer. Compared with the prior art, the method for preparing the sound-absorbing composite material provided by this invention does not add a binder, but instead directly deposits a film on the inner wall of the rear cavity material of the loudspeaker, i.e., the support layer, through in-situ molding. The bond between the molecular sieve outer layer and the support layer is stronger, and the performance of the molecular sieve can be more fully and effectively utilized.

Description

Technical Field

[0001] This invention relates to a method for preparing a sound-absorbing composite material, belonging to the field of materials technology, particularly the field of electroacoustic materials technology. Background Technology

[0002] The prosperity of the social economy and the improvement of consumption levels have led people to have higher and higher requirements for the quality of life. As the most important electronic consumer product, mobile phones play a very important role in life, and the quality of the speaker, an important component of mobile phones, is also receiving more and more attention.

[0003] As smartphones evolve towards miniaturization, thinness, and intelligence, the requirements for their electronic components are becoming increasingly stringent. Smartphone speakers are also becoming smaller and smaller. Maintaining or improving the sound quality of speakers while reducing their volume, including the rear cavity, presents a new challenge in the field of materials science.

[0004] Adding sound-absorbing materials, such as sound insulation cotton, activated carbon, and zeolite, to the rear cavity of a speaker to increase its virtual volume is a primary method used by mainstream speaker suppliers, such as AAC Technologies and Goertek, to enhance speaker sound quality. While the addition of these sound-absorbing materials, especially zeolite, significantly improves speaker sound quality, some problems also exist. For example, the zeolite material filling the rear cavity is prone to crumbling into powder over long-term use, and the zeolite particles are difficult to fix within the cavity, easily shifting and affecting sound quality.

[0005] The rear cavity of a loudspeaker is typically made of plastic or stainless steel, serving only as a structural support. CN 112866881A discloses a method for spraying an active coating onto the rear cavity material of a loudspeaker, wherein the active coating contains an adsorbent (such as zeolite) and a binder. While this method reduces the resonant frequency of the loudspeaker to some extent, the active coating sprayed by this method is difficult to bond tightly with the cavity material. Furthermore, loudspeakers are often made of stainless steel or plastic, while molecular sieves are generally made of silicon-aluminum materials; the two can only be connected using a binder, but the addition of the binder will block the pores of the molecular sieve, reducing its sound absorption effect.

[0006] Therefore, providing a method for preparing a sound-absorbing composite material to obtain a sound-absorbing composite material that can be used as at least one surface of a loudspeaker rear cavity has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the aforementioned shortcomings and deficiencies, the present invention aims to provide a method for preparing a sound-absorbing composite material.

[0008] To achieve the above objectives, the present invention provides a method for preparing a sound-absorbing composite material, wherein the method for preparing the sound-absorbing composite material includes:

[0009] Step 1: Clean the support layer to remove surface stains;

[0010] Step 2: Form a molecular sieve seed layer or a molecular sieve transition layer on the surface of the cleaned support layer, or form a molecular sieve seed layer and a molecular sieve transition layer in sequence.

[0011] Step 3: The product obtained in Step 2 is placed in the growth solution of the third molecular sieve, crystallized, dried, and calcined (or not) to form the outer layer of the molecular sieve.

[0012] In one specific embodiment of the preparation method described above, step one specifically includes: placing the support layer in a hydrochloric acid solution with a temperature of 40-50°C, preferably 50°C, and a concentration of 0.5-1.5 mol / L, preferably 1 mol / L, and using ultrasonic cleaning to remove surface stains. The present invention does not specify the number of cleaning cycles and can adjust them reasonably according to the actual needs of on-site operations. For example, in some embodiments of the present invention, the number of cleaning cycles may be three.

[0013] As a specific embodiment of the preparation method described above in this invention, the material of the support layer includes at least one of porous ceramic, plastic or metal materials.

[0014] As a specific embodiment of the preparation method described above in this invention, the metal material includes at least one of stainless steel, aluminum alloy, magnesium alloy, etc.

[0015] As a specific embodiment of the preparation method described above in this invention, the plastic includes at least one of PC, PET, PU, ​​PP, etc.

[0016] As a specific embodiment of the preparation method described above in this invention, when the material of the support layer is a metal material, step two further includes first forming a metal oxide film on the surface of the cleaned support layer by anodizing, that is, using anodizing to perform surface treatment on the cleaned support layer to electroplate a metal oxide film on its surface, and then forming a molecular sieve seed layer or a molecular sieve transition layer on the metal oxide film, or forming a molecular sieve seed layer and a molecular sieve transition layer in sequence.

[0017] As a specific embodiment of the preparation method described above in this invention, when the material of the support layer is a metal material, step two includes forming a metal oxide film on the surface of the cleaned support layer by anodizing, without forming a molecular sieve seed layer or a molecular sieve transition layer on the metal oxide film, and without sequentially forming a molecular sieve seed layer and a molecular sieve transition layer on the metal oxide film.

[0018] As a specific embodiment of the preparation method described above in this invention, in step two, when the support layer is a metal material, a sulfuric acid solution with a mass concentration of 5-15%, preferably 10%, is used as the electrolyte. Under the action of a voltage of 5-10V, the cleaned metal material is surface-treated by anodizing to electroplate a metal oxide film on its surface.

[0019] In this invention, the metal oxide in the metal oxide film is the same metal material used in the corresponding support layer. For example, when the metal material is stainless steel, aluminum alloy, and magnesium alloy, the metal oxide is iron oxide, aluminum oxide, and magnesium oxide, respectively.

[0020] As a specific embodiment of the preparation method described above in this invention, step two, forming a molecular sieve seed layer, includes: uniformly coating the seed solution of the first molecular sieve onto the surface of the cleaned support layer and then drying it to form a molecular sieve seed layer.

[0021] In one specific embodiment of the preparation method described above in this invention, in step two, the first molecular sieve includes at least one of NaA molecular sieve, T-type molecular sieve, titanium silicate molecular sieve, and MFI-type molecular sieve. In some embodiments of this invention, the MFI-type molecular sieve may be, for example, ZSM-5 molecular sieve.

[0022] As a specific embodiment of the preparation method described above in this invention, in step two, forming a molecular sieve transition layer includes: first, uniformly coating the seed solution of the second molecular sieve onto the surface of the cleaned support layer or the molecular sieve seed layer and then drying it; then, placing the dried support layer in the growth solution of the second molecular sieve and crystallizing, drying, and calcining (or not calcining) to form a molecular sieve transition layer.

[0023] In one specific embodiment of the preparation method described above in this invention, in step two, the second molecular sieve includes a nano-4A molecular sieve or an MFI-type molecular sieve, etc. In some embodiments of this invention, the MFI-type molecular sieve may be, for example, a ZSM-5 molecular sieve.

[0024] In one specific embodiment of the preparation method described above in this invention, in step two, the seed crystal size of the second molecular sieve is <500nm.

[0025] In one specific embodiment of the preparation method described above in this invention, in steps two and three, the crystallization is carried out at 80-160°C for 4-36 hours.

[0026] In a specific embodiment of the preparation method described above in this invention, during steps two and three, the calcination is carried out at 500-600℃ for 2-6 hours.

[0027] As a specific embodiment of the preparation method described above in this invention, in step two, when the second molecular sieve is a nano 4A molecular sieve, the growth solution of the nano 4A molecular sieve contains sodium hydroxide, sodium aluminate and water, and the mass ratio of the three is 15-25:180:30-50:400-600, preferably 20-30:200:400:500;

[0028] The crystallization is performed at 90-110℃ for 4-6 hours, preferably at 80-120℃ for 4-6 hours.

[0029] In one specific embodiment of the preparation method described above in this invention, in step three, the third molecular sieve includes at least one of NaA molecular sieve, T-type molecular sieve, titanium silicate molecular sieve, and MFI-type molecular sieve. In some embodiments of this invention, the MFI-type molecular sieve may be, for example, ZSM-5 molecular sieve.

[0030] As a specific embodiment of the preparation method described above in this invention, in step three, when the third molecular sieve is a ZSM-5 molecular sieve, the growth solution of the ZSM-5 molecular sieve contains 30-40 wt% silica sol, aluminum sulfate octadecyl water, 25-30 wt% tetrapropylammonium hydroxide aqueous solution and water, and the mass ratio of the four components is 200-500:0.5:30-50:20-30;

[0031] Preferably, the growth solution of the ZSM-5 molecular sieve further comprises ZSM-5 molecular sieve seed crystals, 30 wt% silica sol, aluminum sulfate octadecyl water, 25 wt% tetrapropylammonium hydroxide aqueous solution, and water and ZSM-5 molecular sieve seed crystals in a mass ratio of 200-500:0.5:30-50:20-30:1-5.

[0032] The crystallization process involves crystallizing at 120-160℃ for 12-36 hours.

[0033] As a specific embodiment of the preparation method described above in this invention, in step three, when the third molecular sieve is a NaA molecular sieve, the growth solution of the NaA molecular sieve contains sodium hydroxide, sodium aluminate, sodium silicate and water, and the mass ratio of the four is 15-25:180:30-50:400-600, preferably 22.8:180:42.0:500;

[0034] The crystallization is performed at 90-110℃ for 4-6 hours, preferably at 100℃ for 5 hours.

[0035] In a specific embodiment of the preparation method described above in this invention, in step three, the thickness of the outer layer of the molecular sieve is 3-100 μm, preferably 5-100 μm.

[0036] As a specific embodiment of the preparation method described above in this invention, step three further includes: after crystallization, taking out the product and washing the product with deionized water until the conductivity of the washing water is <300μS / cm.

[0037] In one specific embodiment of the preparation method described above, the drying in steps two and three is a conventional operation, and the drying temperature and time can be reasonably adjusted according to the actual needs of the on-site operation. For example, in some embodiments of the present invention, the drying is performed at 100-120℃ for 12 hours.

[0038] As a specific embodiment of the preparation method described above in this invention, when the material of the support layer is a metal material, the transition layer may be a metal oxide film, or a seed layer of a first molecular sieve, or a second molecular sieve layer, or a metal oxide film and a seed layer of a first molecular sieve arranged in sequence, or a metal oxide film and a second molecular sieve layer arranged in sequence, or a seed layer of a first molecular sieve and a second molecular sieve layer arranged in sequence, or a metal oxide film, a seed layer of a first molecular sieve and a second molecular sieve layer arranged in sequence;

[0039] When the material of the support layer is porous ceramic or plastic, the transition layer may be a seed layer of the first molecular sieve, or a second molecular sieve layer, or a seed layer of the first molecular sieve and a second molecular sieve layer arranged sequentially.

[0040] In some embodiments of the present invention, when the support layer is made of a metal material, anodizing can be used to surface-treat the cleaned support layer to electroplate a metal oxide film on its surface. In this case, the metal oxide film serves as a transition layer. Because the metal oxide can be tightly bonded to the silicon-oxygen or aluminum-oxygen bonds in the molecular sieve, it can be tightly bonded to the support layer. Simultaneously, it can also serve as a growth surface for the molecular sieve layer (including a second molecular sieve layer as a transition layer and an outer molecular sieve layer). Therefore, a seed layer of the first molecular sieve or a second molecular sieve layer can continue to be formed on the metal oxide film. In this case, the metal oxide film and the seed layer of the first molecular sieve, the metal oxide film and the second molecular sieve layer together serve as a transition layer, or the outer molecular sieve layer can be directly formed on the metal oxide film. Alternatively, a seed layer of the first molecular sieve or a second molecular sieve layer can be directly formed on the metal material, or a seed layer of the first molecular sieve and a second molecular sieve layer can be formed sequentially as a transition layer. However, in this case, the connection between the transition layer and the metal material is not as tight.

[0041] When the metal oxide film and the second molecular sieve layer together serve as a transition layer, the preparation can be carried out according to the following steps:

[0042] First, the cleaned support layer is surface-treated by anodizing to electroplate a metal oxide film on its surface. Then, the seed solution of the second molecular sieve is evenly coated on the surface of the cleaned support layer and dried. The dried support layer is then placed in the growth solution of the second molecular sieve and crystallized, dried, and calcined (or not) to form a molecular sieve transition layer.

[0043] When the support layer is made of porous ceramic or plastic, it is not necessary to form a metal oxide film on its surface. Instead, a seed layer of the first molecular sieve or a second molecular sieve layer, or a combination of the seed layer of the first molecular sieve and the second molecular sieve layer arranged sequentially, can be used as a transition layer. For example, when the support layer is made of plastic, an irregular surface can be etched on the plastic surface using physical or chemical methods, such as acid etching or alkali etching. Then, a seed solution of the first molecular sieve can be coated to form a tight bond between the seed layer of the first molecular sieve and the plastic surface. Finally, a molecular sieve outer layer is grown on the surface of the seed layer of the first molecular sieve under hydrothermal conditions, so that the molecular sieve outer layer, the transition layer, and the support layer are tightly connected.

[0044] In one specific embodiment of the preparation method described above in this invention, the thickness of the transition layer is 1-10 μm.

[0045] Compared with the prior art, the beneficial technical effects achieved by the present invention include:

[0046] Existing techniques for spraying molecular sieve active coatings onto the inner wall of loudspeakers typically require the addition of binders. However, binders often clog the pores of the molecular sieves, reducing their sound-improving effect. Furthermore, since the inner wall of the loudspeaker's rear cavity is often made of smooth metal or plastic, bonding the molecular sieve to the rear cavity material presents a significant challenge for the binder. Insufficient binder can cause the molecular sieve to peel off within the rear cavity, while excessive binder can severely impair the pores of the molecular sieve. In contrast to existing technologies, the sound-absorbing composite material preparation method provided by this invention does not involve the addition of binders. Instead, it uses an in-situ molding method to directly coat the inner wall of the loudspeaker's rear cavity material, i.e., the support layer. This results in a stronger bond between the outer layer of the molecular sieve and the support layer, and allows the performance of the molecular sieve to be more fully and effectively utilized.

[0047] The sound-absorbing composite material prepared by the method of the present invention is used as at least one surface of the rear cavity of the loudspeaker. The outer layer of the molecular sieve faces the inside of the rear cavity of the loudspeaker, which increases the virtual volume of the loudspeaker, reduces the resonant frequency ΔF0, improves the sound quality of the loudspeaker, and enhances its acoustic performance. Furthermore, this technology does not conflict with the current practice of filling the loudspeaker with sound-absorbing material. It can be used alone or in combination with sound-absorbing material to synergistically improve the acoustic performance of the loudspeaker. Attached Figure Description

[0048] 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.

[0049] Figure 1 The diagram shows the structure of samples 1-5 provided in Embodiments 1-5 of the present invention.

[0050] Figure 2 The image shows the finished product of sample 4 provided in Example 4 of the present invention, which shows one side of the ZSM-5 molecular sieve layer.

[0051] Figure 3 The image shows the finished product of sample 5 provided in Example 5 of the present invention, with one side of the NaA molecular sieve layer shown.

[0052] Figure 4 The XRD patterns of samples 1-3 provided in Examples 1-3 of this invention.

[0053] Figure 5 The XRD pattern of sample 4 provided in Example 4 of the present invention.

[0054] Figure 6This is a SEM image of sample 4 provided in Embodiment 4 of the present invention.

[0055] Figure 7 The XRD pattern of sample 5 provided in Example 5 of the present invention.

[0056] Figure 8 This is a SEM image of sample 5 provided in Embodiment 5 of the present invention.

[0057] Figure 9 The molecular sieve pore size distribution diagram of sample 4 provided in Example 4 of the present invention.

[0058] Figure 10 The molecular sieve pore size distribution diagram of sample 5 provided in Embodiment 5 of the present invention.

[0059] Explanation of main icon numbers:

[0060] 1. Support layer;

[0061] 2. Transition layer;

[0062] 3. Outer layer of molecular sieve. Detailed Implementation

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] In this invention, unless otherwise specified, all technical features and preferred technical features mentioned in this invention can be combined with each other to form new technical solutions.

[0068] In this invention, unless otherwise specified, the term "two kinds" as used in this specification means "at least two kinds".

[0069] 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.

[0070] 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 or products that can be prepared by methods known in the art.

[0071] Example 1

[0072] This embodiment provides a stainless steel molecular sieve sound-absorbing composite material, which is prepared by a method including the following specific steps:

[0073] Step (a) Take a stainless steel sheet with a length, width and thickness of 30 mm, 20 mm and 4 mm respectively. First, use 1 mol / L hydrochloric acid to ultrasonically clean it to remove surface impurities. Then, use anodic electroplating with 10% sulfuric acid solution as electrolyte and anodic oxidation for 10 min at 10 V to form a porous continuous metal oxide film on its surface. The main component of the metal oxide film is iron oxide and the thickness of the metal oxide film is 5 μm.

[0074] Step (b) involves first applying a layer of 4A molecular sieve seed solution to the surface of the stainless steel sheet treated in step (a) using a rapid lifting method. The seed crystal size D50 is 458 nm. The sheet is then placed in an oven and dried at 100°C for 12 hours. Next, the treated stainless steel sheet is placed in a 4A molecular sieve growth solution (also known as crystallization mother liquor or casting solution). The 4A molecular sieve growth solution consists of sodium aluminate, sodium hydroxide, and water, with a mass ratio of sodium hydroxide:sodium aluminate:water = 20:200:400. The stainless steel sheet is crystallized in the growth solution at 100°C for 5 hours. After crystallization, the stainless steel sheet is removed and dried at 120°C for 12 hours. At this point, a layer of 4A molecular sieve has grown on the surface of the material, and its thickness is measured to be 4.6 μm using a thickness gauge.

[0075] Step (c) First, the stainless steel sheet with the 4A molecular sieve grown is placed in the ZSM-5 growth solution, which consists of 30wt% silica sol, aluminum sulfate octadecyl water, 25wt% tetrapropylammonium hydroxide aqueous solution, and water, with a mass ratio of 30wt% silica sol: aluminum sulfate octadecyl water: 25wt% tetrapropylammonium hydroxide aqueous solution: water = 220:0.5:30:22. Then, it is crystallized at 160℃ for 18h. After crystallization, the stainless steel sheet is taken out and its surface is rinsed with deionized water until the conductivity of the washing water is less than <300μS / cm. The washing is then stopped. The material is then dried at 120℃ for 12h and finally calcined at 550℃ for 4h to obtain the stainless steel molecular sieve sound-absorbing composite material, which is marked as sample 1.

[0076] The structural schematic diagram of sample 1 is shown below. Figure 1 As shown. From Figure 1 As can be seen from the diagram, it includes a support layer 1, a transition layer 2, and a molecular sieve outer layer 3 arranged sequentially. In this embodiment, the support layer 1 and the molecular sieve outer layer 3 are stainless steel sheets and ZSM-5 molecular sieve layers, respectively, and the transition layer 2 is a combination of iron oxide and nano 4A molecular sieve.

[0077] It should be noted that the stainless steel sheet of a specific size used in this embodiment is merely an example to illustrate the material of the speaker module's rear cavity. In some embodiments, this method can be used to process the entire rear cavity of the speaker module. In other embodiments, this method can be used to process a portion of the speaker module's rear cavity, and then that portion of the structure can be combined with other components of the rear cavity.

[0078] Example 2

[0079] This embodiment provides a ceramic molecular sieve sound-absorbing composite material, which is prepared by a method including the following specific steps:

[0080] Step (a) Take a ceramic sheet with a length, width and thickness of 30 mm, 20 mm and 4 mm respectively, and use 1 mol / L hydrochloric acid to ultrasonically clean it three times to remove surface impurities.

[0081] Step (b) involves first applying a layer of 4A molecular sieve seed solution to the surface of the ceramic sheet treated in step (a) using a rapid dip-coating method. The 4A molecular sieve seed crystals have a D50 of 458 nm. The sheet is then dried in an oven at 120°C for 12 hours. Next, the treated ceramic sheet is added to a 4A molecular sieve growth solution (also known as a crystallization mother liquor or casting solution). The 4A molecular sieve growth solution consists of sodium aluminate, sodium hydroxide, and water, with a mass ratio of sodium hydroxide:sodium aluminate:water = 30:200:500. The ceramic sheet is crystallized in the casting solution at 100°C for 4 hours. After crystallization, the ceramic sheet is removed and dried at 120°C for 12 hours. At this point, a layer of 4A molecular sieve has grown on the surface of the ceramic sheet, and its thickness is measured to be 8.2 μm using a thickness gauge.

[0082] Step (c) First, the ceramic sheet with the grown 4A molecular sieve is placed in the ZSM-5 growth solution, which consists of 30wt% silica sol, aluminum sulfate octadecyl water, 25wt% tetrapropylammonium hydroxide aqueous solution, and water, with a mass ratio of 30wt% silica sol: aluminum sulfate octadecyl water: 25wt% tetrapropylammonium hydroxide aqueous solution: water = 490:0.5:50:29. Then, it is crystallized at 130℃ for 36h. After crystallization, the ceramic sheet is taken out and its surface is rinsed with deionized water until the conductivity of the washing water is less than 300μS / cm. The washing is then stopped. The ceramic sheet is then dried at 120℃ for 12h and finally calcined at 550℃ for 4h to obtain the ceramic molecular sieve sound-absorbing composite material, which is marked as sample 2.

[0083] The structural schematic diagram of sample 2 is also as follows Figure 1 As shown. From Figure 1As can be seen from the diagram, it includes a support layer 1, a transition layer 2, and a molecular sieve layer 3 arranged sequentially. In this embodiment, the support layer 1, the transition layer 2, and the outer molecular sieve layer 3 are respectively a ceramic sheet, a nano 4A molecular sieve layer, and a ZSM-5 molecular sieve layer.

[0084] It should be noted that the ceramic sheet of a specific size used in this embodiment is merely an example to illustrate the material of the speaker module's rear cavity. In some embodiments, this method can be used to process the entire rear cavity of the speaker module. In other embodiments, this method can be used to process a portion of the speaker module's rear cavity, and then that portion of the structure can be combined with the other components of the rear cavity.

[0085] Example 3

[0086] This embodiment provides a plastic molecular sieve sound-absorbing composite material, which is prepared by a method including the following specific steps:

[0087] Step (a) Take a piece of plastic with a length, width and thickness of 40mm, 40mm and 10mm respectively. The material of the plastic part is PC. Use a scraper to scratch its surface to form a rough surface. Then use 1mol / L hydrochloric acid to ultrasonically clean it to remove impurities from the surface.

[0088] Step (b) involves first applying a layer of 4A molecular seed aqueous solution to the surface of the plastic part treated in step (a) using a rapid lifting method. The grain size D50 of the 4A molecular seed is 458 nm. Then, the treated plastic part is added to the 4A molecular sieve growth solution (also known as crystallization mother liquor or casting solution) and placed in an oven at 120°C for 10 hours. The 4A molecular sieve growth solution consists of sodium aluminate, sodium hydroxide, and water, with a mass ratio of sodium hydroxide:sodium aluminate:water = 25:200:450. The plastic part crystallizes in the growth solution at 120°C for 5 hours. After crystallization, the plastic part is removed and dried at 120°C for 12 hours. At this point, a layer of 4A molecular sieve has grown on the material surface, and its thickness is measured to be 2.3 μm using a thickness gauge.

[0089] Step (c) involves placing the plastic part with the 4A molecular sieve grown in step (b) into the ZSM-5 growth solution, which consists of 30wt% silica sol, aluminum sulfate octadecyl water, 25wt% tetrapropylammonium hydroxide aqueous solution, and water, in a mass ratio of 30wt% silica sol: aluminum sulfate octadecyl water: 25wt% tetrapropylammonium hydroxide aqueous solution: water = 450:0.5:49:25. Crystallization is carried out at 150℃ for 18 hours. After crystallization, the plastic part is removed and its surface is rinsed with deionized water until the conductivity of the washing water is less than 300 μS / cm. Washing is then stopped, and the plastic part is dried at 120℃ for 12 hours. Finally, it is calcined at 400℃ for 2 hours to obtain the plastic molecular sieve sound-absorbing composite material, labeled as sample 3.

[0090] The structural schematic diagram of sample 3 is also as follows Figure 1 As shown. From Figure 1 As can be seen from the diagram, it includes a support layer 1, a transition layer 2, and a molecular sieve layer 3 arranged sequentially. In this embodiment, the support layer 1, the transition layer 2, and the outer molecular sieve layer 3 are respectively a plastic part, a nano 4A molecular sieve layer, and a ZSM-5 molecular sieve layer.

[0091] It should be noted that the specific size of the plastic part used in this embodiment is only an example to illustrate the material of the speaker module's rear cavity. In some embodiments, this method can be used to process the entire rear cavity of the speaker module. In other embodiments, this method can be used to process a portion of the rear cavity of the speaker module, and then that portion of the structure can be combined with the other components of the rear cavity.

[0092] Example 4

[0093] This embodiment provides a stainless steel molecular sieve sound-absorbing composite material, which is prepared by a method including the following specific steps:

[0094] Step (a) Take a stainless steel sheet with a length, width and thickness of 30 mm, 20 mm and 4 mm respectively. First, use 1 mol / L hydrochloric acid to ultrasonically clean it to remove surface impurities. Then, use anodic electroplating with 10% sulfuric acid solution as electrolyte and anodic oxidation for 10 min at 10 V to form a porous continuous metal oxide film on its surface. The main component of the metal oxide film is iron oxide and the thickness of the metal oxide film is 5 μm.

[0095] Step (b) 30 wt% silica sol, 25 wt% tetrapropylammonium hydroxide aqueous solution, aluminum sulfate octadecyl water, water and seed crystals (pure silicon ZSM-5, the grain size of the seed crystals was detected by a zeta potentiometer, and its D50 was 58 nm) were mixed at 30 °C for 2 h to obtain ZSM-5 growth solution.

[0096] Step (c) The stainless steel sheet treated in step (a) is placed in the ZSM-5 growth solution, and then the whole sheet is transferred to a crystallization vessel and crystallized at 150°C for 24 hours. The stainless steel sheet with the ZSM-5 molecular sieve layer grown on the surface is taken out and washed with deionized water until the conductivity of the washing water is <100μS / cm. The washing is then stopped and the sheet is calcined at 400°C for 4 hours to remove the template agent, thus obtaining the stainless steel molecular sieve sound-absorbing composite material, which is marked as sample 4.

[0097] The structural schematic diagram and finished product diagram of sample 4 are as follows: Figure 1 and Figure 2 As shown. From Figure 1 As can be seen, it includes a support layer 1, a transition layer 2, and a molecular sieve layer 3 arranged sequentially; in this embodiment, the support layer 1, the transition layer 2, and the molecular sieve layer 3 are a stainless steel sheet, an iron oxide layer, and a ZSM-5 molecular sieve layer, respectively. Figure 2 As can be seen, a very thin molecular sieve layer structure, namely the ZSM-5 molecular sieve layer mentioned above, has grown on the surface of sample 4. The thickness of the ZSM-5 molecular sieve layer was measured to be 10 μm using a thickness gauge.

[0098] It should be noted that the stainless steel sheet of a specific size used in this embodiment is merely an example to illustrate the material of the speaker module's rear cavity. In some embodiments, this method can be used to process the entire rear cavity of the speaker module. In other embodiments, this method can be used to process a portion of the speaker module's rear cavity, and then that portion of the structure can be combined with other components of the rear cavity.

[0099] Example 5

[0100] This embodiment provides a plastic NaA molecular sieve sound-absorbing composite material, which is prepared by a method including the following specific steps:

[0101] Step (a) Take a piece of plastic with a length, width and thickness of 40mm, 40mm and 10mm respectively. The material of the plastic part is PC. First, use a scraper to scratch its surface to form a rough surface. Then use 1mol / L hydrochloric acid to ultrasonically clean it to remove impurities from the surface.

[0102] Step (b) The nano 4A molecular sieve seed solution is uniformly coated on the surface of the plastic part treated in step (a), and then placed in an oven and dried at 110°C for 12 hours to dry the nano 4A molecular sieve seed solution. After drying, a transition layer with a thickness of 2μm is formed on the surface of the plastic part. The particle size distribution of the seed crystals is detected using a zeta potentiometer, and its D50 is 89nm.

[0103] Step (c) Sodium hydroxide, sodium aluminate, sodium silicate and deionized water are mixed at 30°C for 2 hours in the mass ratio of sodium hydroxide:sodium aluminate:sodium silicate:deionized water = 22.8:180:42.0:500 to obtain NaA molecular sieve growth solution.

[0104] The plastic part prepared in step (b) was placed in the NaA molecular sieve growth solution, and then the whole part was transferred to a crystallization vessel and crystallized at 100°C for 5 hours. After crystallization, the plastic part with NaA molecular sieve grown on its surface was taken out, washed with deionized water until the conductivity of the washing water was <100μS / cm, and then the washing was stopped. The part was then dried at 110°C for 12 hours to obtain the plastic NaA molecular sieve sound-absorbing composite material, which was marked as sample 5.

[0105] The structural schematic diagram and finished product diagram of sample 5 are as follows: Figure 1 and Figure 3 As shown. From Figure 1 As can be seen, it includes a support layer 1, a transition layer 2, and a molecular sieve layer 3 arranged sequentially; in this embodiment, the support layer 1, the transition layer 2, and the molecular sieve layer 3 are respectively a plastic part, a nano-4A molecular sieve seed layer, and a NaA molecular sieve layer. Figure 3 As can be seen, a very thin molecular sieve layer structure, namely the aforementioned NaA molecular sieve layer, has grown on the surface of sample 5. The thickness of the NaA molecular sieve layer was measured to be 22 μm using a thickness gauge.

[0106] It should be noted that the specific size of the plastic part used in this embodiment is only an example to illustrate the material of the speaker module's rear cavity. In some embodiments, this method can be used to process the entire rear cavity of the speaker module. In other embodiments, this method can be used to process a portion of the rear cavity of the speaker module, and then that portion of the structure can be combined with the other components of the rear cavity.

[0107] Test Example 1

[0108] In this test example, XRD was used to detect the crystal phase of samples 1-3 provided in Examples 1-3. The results are shown below. Figure 4 .from Figure 4The XRD spectra of the three samples show that, compared with the standard ZSM-5 spectra, all three samples have a standard MFI structure (i.e., all are pure-phase MFI molecular sieves) without any impurities. This indicates that all three samples successfully grew a pure-phase ZSM-5 molecular sieve layer, and the presence of nano-4A molecular sieve layers in the samples did not cause the growth of impurities.

[0109] Test Example 2

[0110] This test example performs XRD and SEM analyses on samples 4-5 provided in Examples 4-5, respectively. The XRD pattern and SEM image of sample 4 are shown below. Figure 5 and Figure 6 As shown, the XRD pattern and SEM image of sample 5 are as follows: Figure 7 and Figure 8 As shown.

[0111] from Figure 5 As can be seen, the molecular sieve grown on the surface of sample 4 is also a pure ZSM-5 molecular sieve, such as... Figure 7 The XRD pattern of sample 5 shown indicates that sample 5 has a pure phase LTA structure and is a NaA molecular sieve.

[0112] Test Example 3

[0113] In this test example, a portion of the molecular sieve from the surface of samples 1-5 was gently scraped off using a scraper, with each scraped portion weighing 0.1-0.2 g. Then, the specific surface area, pore volume, and pore size were measured using a BET analyzer. Before testing, the samples were treated at 300℃ under a nitrogen atmosphere for 3 hours to remove moisture. Nitrogen was used as the adsorption medium for samples 1-4, and CO2 was used as the adsorption medium for sample 5. The specific surface area and pore volume data measured in this test example are shown in Table 1 below. The molecular sieve pore size distribution diagrams for samples 4 and 5 are shown below. Figure 9 and Figure 10 As shown.

[0114] Table 1

[0115] <![CDATA[Specific surface area m 2 / g]]> <![CDATA[Pore volume g / cm 3 <!-- 9 -->]]> Sample 1 455 0.23 Sample 2 443 0.24 Sample 3 512 0.27 Sample 4 385 0.25 Sample 5 484 0.21

[0116] As can be seen from Table 1 above, the specific surface area of ​​the molecular sieve layers in samples 4 and 5 provided in the embodiments of the present invention is both 300-600 m². 2 Within the range of / g, the pore volume is consistently between 0.2 and 0.4 cm³. 3 Within the range of / g; from Figure 9 and Figure 10 As can be seen, the molecular sieves of samples 4 and 5 have obvious microporous features with a pore size of about 0.5 nm, which is consistent with the pore characteristics of MFI and LTA structures.

[0117] Application Example 1

[0118] In this application example, samples 1, 2, 3, 4, and 5 are used as the speaker rear cavity materials of the speaker devices. That is, samples 1, 2, 3, 4, and 5 are used to replace the speaker rear cavity materials of five original speaker devices (denoted as speaker device A, speaker device B, speaker device C, speaker device D, and speaker E, respectively).

[0119] Specifically, samples 1, 2, 3, 4, and 5 are placed on the upper part of the rear cavity of loudspeaker devices A, B, C, D, and E, respectively, with the upper surface material of the rear cavity being samples 1, 2, 3, 4, and 5, respectively. The ZSM-5 molecular sieve layer or NaA molecular sieve layer faces the interior of the rear cavity. Acoustic performance tests are then performed on each device using conventional methods in the art. For example, the "impedance measurement" method described in paragraphs 0049-0054 of Chinese patent application CN105049997A can be used to test the acoustic performance of each loudspeaker device. Specifically, each loudspeaker device is tested according to the "impedance measurement" method to obtain an impedance spectrum. The curve in the impedance spectrum corresponds to the impedance curve, where the frequency corresponding to the highest point of the impedance curve is F0.

[0120] The test environment included: the original speaker unit was a commercially available 1115 model, the rear cavity volume was 0.4cc, the humidity was 40%, and the temperature was room temperature.

[0121] The test results obtained in this application example are shown in Table 2 below.

[0122] Table 2

[0123]

[0124] Note: The sound-absorbing particles in Table 2 are commercially available conventional materials, and their main component is zeolite molecular sieve.

[0125] As can be seen from the test results shown in Table 2 above, after replacing the rear cavity shell of the original speaker device with samples 1-5 provided in Examples 1-5 of this invention, the resonant frequency of the rear cavity of the speaker is significantly reduced. This indicates that the molecular sieve sound-absorbing composite material provided by this invention can effectively increase the acoustic performance of the rear cavity of the speaker and even the speaker device. Moreover, compared with the molecular sieve sound-absorbing composite material provided in Example 5, i.e., sample 5, the molecular sieve sound-absorbing composite material provided in Example 4, i.e., sample 4, has a greater reduction in resonant frequency. This indicates that compared with NaA molecular sieve, ZSM-5 molecular sieve is a better molecular sieve material for reducing the resonant frequency of the rear cavity of the speaker.

[0126] In summary, in the loudspeaker device provided by the embodiments of the present invention, at least one surface of the rear cavity of the loudspeaker is made of a sound-absorbing composite material, which can improve the sound quality of the loudspeaker device and enhance its acoustic performance.

[0127] In this embodiment of the invention, at least one surface of the speaker's rear cavity is made of a sound-absorbing composite material, which is equivalent to growing a molecular sieve layer on one or more surfaces of the speaker's rear cavity. Compared with the prior art of spraying active coatings, the molecular sieve layer and the support layer are more firmly bonded, and no adhesive is added, resulting in better acoustic performance of the speaker device.

[0128] The embodiments of the present invention do not conflict with the existing mainstream methods for enhancing the sound quality of loudspeakers, namely, filling the rear cavity of the loudspeaker with sound-absorbing material, and the two can be combined. That is, the present invention can also fill the rear cavity of the loudspeaker, at least one surface of which is made of sound-absorbing composite material, with sound-absorbing material, which can significantly enhance the acoustic performance of the loudspeaker device.

[0129] 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 method for preparing a sound-absorbing composite material, characterized in that, The preparation method includes: Step 1: Clean the support layer to remove surface stains; Step 2: Form a molecular sieve transition layer on the surface of the cleaned support layer, or form a molecular sieve seed layer and a molecular sieve transition layer in sequence; In step two, forming a molecular sieve transition layer includes: first, uniformly coating the seed solution of the second molecular sieve onto the surface of the cleaned support layer or the molecular sieve seed layer and drying it; then, placing the dried support layer in the growth solution of the second molecular sieve and crystallizing, drying, and calcining (or not calcining) to form a molecular sieve transition layer; in step two, the seed crystal size of the second molecular sieve is <500nm. Step 3: The product obtained in Step 2 is placed in the growth solution of the third molecular sieve, crystallized, dried, and calcined (or not) to form the outer layer of the molecular sieve.

2. The preparation method according to claim 1, characterized in that, Step one specifically includes: placing the support layer in a hydrochloric acid solution with a temperature of 40-50℃ and a concentration of 0.5-1.5mol / L, and using ultrasonic cleaning to remove surface stains.

3. The preparation method according to claim 1, characterized in that, The material of the support layer includes at least one of porous ceramic, plastic or metal.

4. The preparation method according to claim 3, characterized in that, The metallic material includes at least one of stainless steel, aluminum alloy, and magnesium alloy.

5. The preparation method according to claim 3, characterized in that, The plastic includes at least one of PC, PET, PU, ​​and PP.

6. The preparation method according to any one of claims 1-4, characterized in that, When the material of the support layer is a metal material, step two further includes first forming a metal oxide film on the surface of the cleaned support layer by anodizing, and then forming a molecular sieve transition layer on the metal oxide film, or forming a molecular sieve seed layer and a molecular sieve transition layer in sequence.

7. The preparation method according to claim 6, characterized in that, In step two, when the support layer is a metal material, a sulfuric acid solution with a mass concentration of 5-15% is used as the electrolyte. Under the action of a voltage of 5-10V, the cleaned metal material is surface-treated by anodizing to electroplate a metal oxide film on its surface.

8. The preparation method according to any one of claims 1-4, characterized in that, In step two, forming a molecular sieve seed layer includes: uniformly applying the seed solution of the first molecular sieve onto the surface of the cleaned support layer and then drying it to form a molecular sieve seed layer.

9. The preparation method according to claim 8, characterized in that, In step two, the first molecular sieve includes at least one of NaA molecular sieve, T-type molecular sieve, titanium silicate molecular sieve, and MFI type molecular sieve.

10. The preparation method according to claim 1, characterized in that, In step two, the second molecular sieve includes nano 4A molecular sieve or MFI type molecular sieve.

11. The preparation method according to claim 1, characterized in that, In steps two and three, the crystallization is carried out at 80-160℃ for 4-36 hours.

12. The preparation method according to claim 1, characterized in that, In steps two and three, the roasting process is carried out at 500-600℃ for 2-6 hours.

13. The preparation method according to claim 1, characterized in that, In step three, the third molecular sieve includes at least one of NaA molecular sieve, T-type molecular sieve, titanium silicate molecular sieve, and MFI type molecular sieve.

14. The preparation method according to claim 1 or 13, characterized in that, In step three, when the third molecular sieve is ZSM-5 molecular sieve, the growth solution of ZSM-5 molecular sieve contains 30-40 wt% silica sol, aluminum sulfate octadecyl water, 25-30 wt% tetrapropylammonium hydroxide aqueous solution and water, and the mass ratio of the four is 200-500:0.5:30-50:20-30. The crystallization process involves crystallizing at 120-160℃ for 12-36 hours.

15. The preparation method according to claim 14, characterized in that, The growth solution of the ZSM-5 molecular sieve also contains ZSM-5 molecular sieve seed crystals, 30wt% silica sol, aluminum sulfate octadecyl water, 25wt% tetrapropylammonium hydroxide aqueous solution, and water and ZSM-5 molecular sieve seed crystals in a mass ratio of 200-500:0.5:30-50:20-30:1-5.

16. The preparation method according to claim 1 or 13, characterized in that, In step three, when the third molecular sieve is a NaA molecular sieve, the growth solution of the NaA molecular sieve contains sodium hydroxide, sodium aluminate, sodium silicate and water, and the mass ratio of the four is 15-25:180:30-50:400-600. The crystallization process involves crystallizing at 90-110℃ for 4-6 hours.

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