Sound-absorbing material and preparation method therefor, and speaker box using sound-absorbing material

Abstract

The present invention relates to the field of electroacoustics, and more particularly relates to a sound-absorbing material and a preparation method therefor, and a speaker box using the sound-absorbing material. In the present invention, a sound-absorbing slurry is frozen by means of a freezing conveyor belt, and the sound-absorbing slurry is formed by means of a mold, or coated on a film. When the sound-absorbing slurry is pre-cooled by means of a first freezing zone of the conveyor belt, the temperature of the mold and the carrier film is reduced, followed by rapid freezing by means of a second freezing zone, thereby shortening the freezing time of the material. Pre-cooling the mold in advance causes freezing of the sound-absorbing slurry to be uniform, preventing the formation of thick layered ice crystals, and preventing material deformation. The freezing time of the material can be controlled by adjusting the speed of the conveyor belt. In addition, the freezing conveyor belt and the hot air above the conveyor belt form a temperature gradient, causing the sound-absorbing material to freeze from bottom to top, thus making the sound-absorbing material vertically permeable, improving air permeability, yielding better performance, increasing the preparation efficiency of the sound-absorbing material, and facilitating large-scale mass production.

Description

Sound-absorbing material, preparation method thereof, and speaker box using the sound-absorbing material Technical Field

[0001] The present invention relates to the field of acoustics and electronics, and in particular to a sound-absorbing material, a preparation method thereof, and a speaker box using the sound-absorbing material. Background Art

[0002] With the development of lightweight and thin electronic devices, the speaker systems in electronic devices are also getting smaller and smaller. In order to improve the acoustic performance in the limited speaker resonance space, this field will adopt the method of adding sound-absorbing materials therein, and through the adsorption-desorption effect of the sound-absorbing materials on the air, the volume of the resonance cavity is virtually increased. Technical issues

[0003] Sound-absorbing materials are usually made of porous inorganic powders through a special molding method. At present, the preparation process of granular sound-absorbing materials is relatively mature, but when granular materials are used to fill speakers, the static electricity between the particles is large, making it difficult to fill, and the particles collide with each other, causing powder to fall off easily. Sound-absorbing blocks and sound-absorbing sheets can be prepared to match the shape of the cavity, eliminating the filling process, achieving better sound absorption performance, and avoiding static interference. However, during actual preparation, the sound-absorbing slurry often breaks and shatters after being frozen. This is because the sound-absorbing slurry increases in volume when frozen at low temperatures, and becomes lamellar when water crystallizes. After freeze-drying, thicker lamellar pores are left, resulting in poor strength of the block material, no performance, and easy breakage. At present, there is no perfect preparation process for sound-absorbing materials, and sound-absorbing blocks and sound-absorbing sheets are still in small-batch trial production, with complicated processes, low output, and poor reproducibility.

[0004] Therefore, there is an urgent need for a new sound-absorbing material, a preparation method thereof, and a speaker box using the sound-absorbing material to solve the above problems. Technical Solutions

[0005] The purpose of the present invention is to provide a sound-absorbing material, a preparation method thereof, and a speaker box using the sound-absorbing material, aiming to improve the stability and adjustability of the preparation of the sound-absorbing material, improve the preparation efficiency of the sound-absorbing material, and facilitate large-scale mass production.

[0006] In order to achieve the above object, in a first aspect, the present invention provides a method for preparing a sound-absorbing material, the method comprising the following steps:

[0007] S1. Prepare a sound-absorbing slurry, which is prepared by mixing a sound-absorbing powder, an adhesive, a filler, a thickener, and water; wherein the viscosity of the sound-absorbing slurry is 100 cp-10,000 cp; based on the total mass of the sound-absorbing slurry as 100%, the sound-absorbing powder accounts for 30-60% of the sound-absorbing slurry, the adhesive accounts for 3-10% of the sound-absorbing slurry, the filler accounts for 1-10% of the sound-absorbing slurry, the thickener accounts for 1-5% of the sound-absorbing slurry, and the water accounts for 15-65% of the sound-absorbing slurry;

[0008] S2. Coating the sound-absorbing slurry on the surface of the film; or injecting the sound-absorbing slurry into a mold;

[0009] S3, placing the film or the mold at the entrance of a freezing conveyor belt, and sequentially passing the film or the mold through a first freezing zone and a second freezing zone for freezing and crystallization to obtain a film sample or a mold sample; wherein the temperature of the second freezing zone is lower than the temperature of the first freezing zone;

[0010] S4, taking out the film sample or the mold sample at the outlet end of the freezing conveyor and placing it in a low-pressure vacuum environment with a pressure of 0-500 Pa to perform a sublimation treatment to remove ice in the film sample or the mold sample to obtain a de-iced sample;

[0011] S5. Place the de-iced sample in an oven and dry it for a preset time to obtain a sound-absorbing material.

[0012] Preferably, the sound-absorbing powder is zeolite, and the zeolite is at least one of MFI molecular sieve, MEL molecular sieve and FER molecular sieve.

[0013] Preferably, the adhesive is at least one of acrylic emulsion, styrene-acrylic emulsion, styrene-butadiene emulsion and polyethyl vinyl acetate.

[0014] Preferably, the filler is at least one of mica flakes, glass fiber, carbon fiber and graphene.

[0015] Preferably, the thickener is at least one of sodium alginate, polyacrylamide, sodium polyacrylate, gelatin and sodium carboxymethyl cellulose.

[0016] Preferably, the freezing conveyor belt includes a conveyor belt device driven by a roller, a liquid nitrogen tank arranged on the conveyor belt device, and a copper plate fixed to the conveyor belt device, the copper plate is immersed in the liquid nitrogen in the liquid nitrogen tank, the copper plate is used to regulate the temperature of the second freezing area, the liquid nitrogen tank is provided with a liquid inlet at the entrance end of the first freezing area, and the distance between the liquid nitrogen tank and the conveyor belt device is 0.5 cm to 5.0 cm in height.

[0017] Preferably, the temperature of the first freezing zone is -20°C to 0°C, and the temperature of the second freezing zone is -100°C to -20°C.

[0018] Preferably, in step S3, the time for the film or the mold to pass through the first freezing zone and the second freezing zone for freezing crystallization is 1 min to 30 min.

[0019] Preferably, the thickness of the film sample is 0.05 mm to 1.00 mm; the thickness of the mold sample is 1 mm to 5 mm.

[0020] In a second aspect, the present invention further provides a sound-absorbing material, which is made by the method for preparing a sound-absorbing material as described in any one of the above embodiments.

[0021] In a third aspect, the present invention further provides a speaker box, comprising a shell having a receiving space and a speaker unit received in the receiving space, wherein the speaker unit and the shell are arranged to form a rear cavity, and the rear cavity is filled with the sound-absorbing material as described in the above embodiment. Beneficial effects

[0022] Compared with the prior art, the present invention freezes the sound-absorbing slurry through a freezing conveyor belt, and the sound-absorbing slurry is formed by a mold or coated on a film. When the sound-absorbing slurry is pre-cooled by the first freezing zone of the conveyor belt, the temperature of the mold and the carrier film is reduced, and then it is quickly frozen by the second freezing zone, shortening the freezing time of the material. Pre-cooling the mold in advance allows the sound-absorbing slurry to be frozen evenly, avoiding the appearance of thick layers of ice crystals and preventing deformation of the material. In the second freezing zone, a copper plate is tightly attached to the bottom of the conveyor belt, and the copper plate is immersed in liquid nitrogen, so the temperature of the second freezing zone can be controlled at -100 to -20°C, achieving the purpose of rapid freezing and crystallization. The freezing time of the material can be controlled by adjusting the speed of the conveyor belt. At the same time, a temperature gradient is formed between the freezing conveyor belt and the hot air above the conveyor belt, so that the sound-absorbing material is frozen from bottom to top, making the sound-absorbing material transparent from top to bottom, improving air permeability, and having better performance. The preparation process provided by the present invention improves the preparation efficiency of the sound-absorbing material and facilitates large-scale mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0024] FIG1 is a flow chart of a method for preparing a sound-absorbing material according to an embodiment of the present invention;

[0025] FIG2 is a schematic diagram of the structure of a refrigeration conveyor belt provided in an embodiment of the present invention. Modes for Carrying Out the Invention

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] 1 and 2 , the present invention provides a method for preparing a sound-absorbing material, the method comprising the following steps:

[0028] S1. Prepare a sound-absorbing slurry, which is prepared by mixing a sound-absorbing powder, an adhesive, a filler, a thickener, and water; wherein the viscosity of the sound-absorbing slurry is 100 cp-10,000 cp; based on the total mass of the sound-absorbing slurry as 100%, the sound-absorbing powder accounts for 30-60% of the sound-absorbing slurry, the adhesive accounts for 3-10% of the sound-absorbing slurry, the filler accounts for 1-10% of the sound-absorbing slurry, the thickener accounts for 1-5% of the sound-absorbing slurry, and the water accounts for 15-65% of the sound-absorbing slurry;

[0029] S2. Coating the sound-absorbing slurry on the surface of the film; or injecting the sound-absorbing slurry into a mold;

[0030] S3, placing the film or the mold at the entrance of a freezing conveyor belt, and sequentially passing the film or the mold through a first freezing zone a and a second freezing zone b for freezing and crystallization to obtain a film sample or a mold sample; wherein the temperature of the second freezing zone is lower than the temperature of the first freezing zone;

[0031] S4, taking out the film sample or the mold sample at the outlet end of the freezing conveyor and placing it in a low-pressure vacuum environment with a pressure of 0-500 Pa to perform a sublimation treatment to remove ice in the film sample or the mold sample to obtain a de-iced sample;

[0032] S5. Place the de-iced sample in an oven and dry it for a preset time to obtain a sound-absorbing material.

[0033] In this embodiment, the sound-absorbing powder is zeolite, and the zeolite is at least one of MFI molecular sieve, MEL molecular sieve and FER molecular sieve.

[0034] In this embodiment, the adhesive is at least one of acrylic emulsion, styrene acrylic emulsion, styrene butadiene emulsion and polyethyl vinyl acetate.

[0035] In this embodiment, the filler is at least one of mica flakes, glass fiber, carbon fiber and graphene.

[0036] In this embodiment, the thickener is at least one of sodium alginate, polyacrylamide, sodium polyacrylate, gelatin and sodium carboxymethyl cellulose.

[0037] In this embodiment, the freezing conveyor belt includes a conveyor belt device driven by a roller, a liquid nitrogen tank arranged on the conveyor belt device, and a copper plate fixed to the conveyor belt device, the copper plate is immersed in the liquid nitrogen in the liquid nitrogen tank, and the copper plate is used to regulate the temperature of the second freezing area. The liquid nitrogen tank is provided with a liquid inlet at the entrance end of the first freezing area, and the distance between the liquid nitrogen tank and the conveyor belt device is 0.5 cm to 5.0 cm in height.

[0038] In this embodiment, the temperature of the first freezing zone a is -20°C to 0°C, and the temperature of the second freezing zone b is -100°C to -20°C.

[0039] In this embodiment, in step S3, the time for the film or the mold to be frozen and crystallized in the first freezing area a and the second freezing area b is 1 min to 30 min.

[0040] In this embodiment, the thickness of the film sample is 0.05 mm-1.00 mm.

[0041] In this embodiment, the thickness of the mold sample is 1 mm to 5 mm.

[0042] Compared with the prior art, the present invention freezes the sound-absorbing slurry through a freezing conveyor belt, and the sound-absorbing slurry is formed by a mold or coated on a film. When the sound-absorbing slurry is pre-cooled by the first freezing zone of the conveyor belt, the temperature of the mold and the carrier film is reduced, and then it is quickly frozen by the second freezing zone, shortening the freezing time of the material. Pre-cooling the mold in advance allows the sound-absorbing slurry to be frozen evenly, avoiding the appearance of thick layers of ice crystals and preventing deformation of the material. In the second freezing zone, a copper plate is tightly attached to the bottom of the conveyor belt, and the copper plate is immersed in liquid nitrogen, so the temperature of the second freezing zone can be controlled at -100 to -20°C, achieving the purpose of rapid freezing and crystallization. The freezing time of the material can be controlled by adjusting the speed of the conveyor belt. At the same time, a temperature gradient is formed between the freezing conveyor belt and the hot air above the conveyor belt, so that the sound-absorbing material is frozen from bottom to top, making the sound-absorbing material transparent from top to bottom, improving air permeability, and having better performance. The preparation process provided by the present invention improves the efficiency of block material preparation and facilitates large-scale mass production.

[0043] The present invention also provides a sound-absorbing material, which is produced by the method for producing a sound-absorbing material as described in any of the above embodiments. Therefore, this sound-absorbing material can achieve the same technical effects as the sound-absorbing material produced by the method described above, and further details are omitted here.

[0044] The present invention also provides a speaker box, which includes a shell having a receiving space and a speaker unit received in the receiving space. The speaker unit and the shell are arranged to form a rear cavity, and the rear cavity is filled with the sound-absorbing material described in the above embodiment.

[0045] In this embodiment, the sound-absorbing sheet can be cut into the same shape as the resonance cavity (back cavity) of the speaker according to actual conditions.

[0046] In this embodiment, the shape of the mold is the same as the resonant cavity (back cavity) of the speaker. The mold can be set to a regular shape or an irregular shape such as a rectangle, a circle, an ellipse, etc. according to actual conditions.

[0047] The speaker box can achieve the technical effects achieved by the sound-absorbing materials described in the above embodiments, which will not be described in detail here.

[0048] In order to better reflect the preparation method of the above-mentioned sound-absorbing material, the following is further described through preparation examples. It should be understood that the specific examples described here are only used to explain the present invention, rather than to limit the present invention.

[0049] Example 1

[0050] In this example, zeolite, acrylic emulsion, glass fiber, sodium alginate, and water were mixed and stirred to produce a mixed slurry with a viscosity of 500 cp. This mixed slurry was then applied to the surface of a PET film to produce a film sample with a thickness of 1 mm. The film sample was then placed at the inlet of a refrigerated conveyor belt. The first freezing zone, a, was set at -20°C, and the second freezing zone, b, was set at -60°C. The conveyor belt was turned on, and the sound-absorbing material was frozen for 1 minute. At the outlet, the frozen film sample was placed in a low-pressure vacuum environment of less than 400 Pa until all water in the sample was sublimated and removed, resulting in a de-iced sample. The de-iced sample was then dried in a 120°C oven for 2 hours. The sample was then cut into sheets with the same shape as the speaker resonant cavity (back cavity), resulting in a sound-absorbing sheet.

[0051] Example 2

[0052] In this embodiment, zeolite, acrylic emulsion, glass fiber, polyacrylamide and water are mixed and stirred to obtain a mixed slurry with a viscosity of 1000cp. The mixed slurry is injected into a mold to obtain a mold sample with a thickness of 2.5mm. The mold sample is then placed at the inlet end of a conveyor belt, the first freezing zone a is -20°C, the second freezing zone b is -80°C, the conveyor belt is turned on, and the sound-absorbing material is frozen for 5 minutes. At the outlet end, the frozen mold sample is placed in a low-pressure vacuum environment of less than 400Pa until the water in the sample is sublimated and removed to obtain a de-iced sample. The de-iced sample is then placed in a 120°C oven and dried for 2 hours to obtain a sound-absorbing block material.

[0053] Comparative Example 1

[0054] Zeolite, acrylic emulsion, glass fiber, polyacrylamide, and water were mixed and stirred to produce a mixed slurry with a viscosity of 3000 cp. This mixed slurry was injected into a mold to produce a mold sample with a thickness of 2.5 mm. The mold sample was then frozen at a constant temperature of -30°C for 20 minutes. The frozen mold sample was placed in a low-pressure vacuum environment of less than 400 Pa until all moisture in the sample was sublimated and removed. The sample was then dried in a 120°C oven for 2 hours to produce the sound-absorbing block.

[0055] In order to compare the performance of the examples and comparative examples, the performance of the sound-absorbing materials was measured using an impedance meter. The results are shown in Table 1. Conventional granular sound-absorbing materials in the field were used for comparison. For ease of comparison, 100 mg of the samples were selected for comparison:

[0056] Table 1: Comparison of samples between different examples

[0057]

[0058] ΔF0 is the change in resonant frequency, which can be used to characterize the improvement effect of the sound-absorbing material on the acoustic performance of the speaker module. The larger the ΔF0 value, the better the optimization and debugging effect of the sound-absorbing material on the acoustic performance of the speaker module; conversely, the smaller the ΔF0 value, the worse the optimization and debugging effect of the sound-absorbing material on the acoustic performance of the speaker module.

[0059] As shown in Table 1, both the sound-absorbing blocks and sheets exhibit superior sound absorption performance compared to conventional sound-absorbing particles in the field. The sample in Comparative Example 1 exhibits poor performance, with large pores visible on the surface of the blocks and a loose structure. Of course, the above descriptions represent only specific examples of the present invention and are not intended to limit the scope of the inventive examples.

[0060] Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

[0061] The above description is only an embodiment of the present invention. It should be pointed out that those skilled in the art can make improvements without departing from the creative concept of the present invention, but these improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a sound-absorbing material, characterized in that: The preparation method comprises the following steps: S1. Prepare a sound-absorbing slurry, which is prepared by mixing a sound-absorbing powder, an adhesive, a filler, a thickener, and water; wherein the viscosity of the sound-absorbing slurry is 100 cp-10,000 cp; based on the total mass of the sound-absorbing slurry as 100%, the sound-absorbing powder accounts for 30-60% of the sound-absorbing slurry, the adhesive accounts for 3-10% of the sound-absorbing slurry, the filler accounts for 1-10% of the sound-absorbing slurry, the thickener accounts for 1-5% of the sound-absorbing slurry, and the water accounts for 15-65% of the sound-absorbing slurry; S2. Coating the sound-absorbing slurry on the surface of the film; or injecting the sound-absorbing slurry into a mold; S3, placing the film or the mold at the entrance of a freezing conveyor belt, and sequentially passing the film or the mold through a first freezing zone and a second freezing zone for freezing and crystallization to obtain a film sample or a mold sample; wherein the temperature of the second freezing zone is lower than the temperature of the first freezing zone; S4, taking out the film sample or the mold sample at the outlet end of the freezing conveyor and placing it in a low-pressure vacuum environment with a pressure of 0-500 Pa to perform a sublimation treatment to remove ice in the film sample or the mold sample to obtain a de-iced sample; S5. Place the de-iced sample in an oven and dry it for a preset time to obtain a sound-absorbing material.

2. The method for preparing the sound-absorbing material according to claim 1, wherein: The sound-absorbing powder is zeolite, and the zeolite is at least one of MFI molecular sieve, MEL molecular sieve and FER molecular sieve.

3. The method for preparing the sound-absorbing material according to claim 1, wherein: The adhesive is at least one of acrylic emulsion, styrene-acrylic emulsion, styrene-butadiene emulsion and polyethyl vinyl acetate.

4. The method for preparing the sound-absorbing material according to claim 1, wherein: The filler is at least one of mica flakes, glass fiber, carbon fiber and graphene.

5. The method for preparing the sound-absorbing material according to claim 1, wherein: The thickener is at least one of sodium alginate, polyacrylamide, sodium polyacrylate, gelatin and sodium carboxymethyl cellulose.

6. The method for preparing the sound-absorbing material according to claim 1, wherein: The freezing conveyor belt includes a conveyor belt device driven by a roller, a liquid nitrogen tank arranged on the conveyor belt device, and a copper plate fixed to the conveyor belt device. The copper plate is immersed in the liquid nitrogen in the liquid nitrogen tank. The copper plate is used to regulate the temperature of the second freezing area. The liquid nitrogen tank is provided with a liquid inlet at the entrance end of the first freezing area. The height difference between the liquid nitrogen tank and the conveyor belt device is 0.5 cm to 5.0 cm.

7. The method for preparing the sound-absorbing material according to claim 1, wherein: The temperature of the first freezing zone is -20°C to 0°C, and the temperature of the second freezing zone is -100°C to -20°C.

8. The method for preparing the sound-absorbing material according to claim 1, wherein: In step S3, the film or the mold passes through the first freezing zone and the second freezing zone for freezing crystallization for a time period of 1 min to 30 min.

9. The method for preparing a sound-absorbing material according to claim 1, wherein: The thickness of the film sample is 0.05 mm to 1.00 mm; the thickness of the mold sample is 1 mm to 5 mm.

10. A sound-absorbing material, characterized in that: The sound-absorbing material is made by the method for preparing the sound-absorbing material according to any one of claims 1 to 9.

11. A speaker box, comprising a housing having a receiving space, and a speaker unit received in the receiving space, wherein the speaker unit and the housing are arranged to form a rear cavity, wherein: The rear cavity is filled with the sound-absorbing material as claimed in claim 10.

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