A porous composite sound-absorbing material and its preparation method

Abstract

This invention provides a porous composite sound-absorbing material and its preparation method. The porous composite sound-absorbing material comprises activated carbon cotton felt, zeolite particles, and an adhesive. The activated carbon cotton felt can be bonded to its fiber surface by the adhesive, ensuring uniform dispersion and fixation of the zeolite particles for optimal sound absorption. Simultaneously, its numerous micropores synergistically interact with the zeolite particles, resulting in a porous composite sound-absorbing material with significantly superior sound absorption performance compared to either material alone, offering excellent cost-effectiveness. In the preparation process of this porous composite sound-absorbing material, the activated carbon cotton felt undergoes surface treatment, zeolite particle impregnation, freeze-drying, high-temperature curing, foaming, and cleaning, successfully combining with the superior sound-absorbing zeolite particles, resulting in significantly improved sound absorption performance and excellent cost-effectiveness. After filling the rear cavity of a loudspeaker with this porous composite sound-absorbing material, its low-frequency performance is significantly improved.

Description

[Technical Field]

[0001] This invention belongs to the field of composite materials, specifically, this invention relates to a porous composite sound-absorbing material and its preparation method. [Background Technology]

[0002] With the rapid development of the consumer electronics industry and the rapid improvement of people's living standards, the miniaturization and flattening of consumer electronics products are increasingly favored by consumers. At the same time, people have higher and higher requirements for sound, hoping to obtain better sound quality in a limited space, which puts increasingly stringent requirements on speakers.

[0003] Generally, the smaller the volume of the speaker's rear cavity, the worse the acoustic response in the low-frequency range, and the worse the sound quality and other acoustic performance. Therefore, it is necessary to find ways to enlarge the speaker's rear cavity to improve its low-frequency response.

[0004] To expand the rear cavity of a loudspeaker, those skilled in the art have proposed various methods, such as the following:

[0005] 1. Fill the rear cavity with a gas that has better acoustic compliance than air, such as carbon dioxide. However, this method has the problem of poor long-term reliability due to the difficulty in sealing the cavity.

[0006] 2. Fill with sound-absorbing cotton such as melamine foam, polyurethane foam, polyester sound-absorbing cotton, etc., but these materials have large pores and limited room for sound quality improvement;

[0007] 3. Filling with porous materials such as activated carbon, zeolite, and silica increases the volume of the virtual rear cavity and improves the acoustic compliance of the rear cavity gas. These materials have a large number of microporous structures, which significantly enhances the effect. However, there are two problems. First, those with excellent sound absorption performance are mostly granular, which limits their use for speaker devices with complex rear cavities. Second, the improvement effect of natural zeolite is limited. Although secondary molding can significantly improve the effect, the cost is high.

[0008] To address the limitations of the above methods, technicians have made many attempts, such as adding zeolite or activated carbon particles to sound-absorbing cotton or fiber structural materials. This method improves performance and is convenient to use because it uses block materials. However, this method has obvious limitations. The skeleton materials used are all conventional macroporous structural materials, which mainly play a role in dispersing, fixing, and supporting the sound-absorbing particles, but their contribution to the sound absorption performance of porous composite sound-absorbing materials is very limited. To obtain better performance, it is often necessary to add a large amount of sound-absorbing particles such as zeolite or activated carbon, which not only significantly increases the cost but also limits the upper limit of the material's sound absorption performance.

[0009] Therefore, there is an urgent need in the field for a new method that can expand the rear cavity of a loudspeaker. [Summary of the Invention]

[0010] To address the shortcomings of existing technologies, this invention provides targeted improvements. This invention uses activated carbon cotton felt with a large number of micropores to replace traditional skeleton materials (skeleton materials without a large number of micropores, such as sound-absorbing foam and sound-absorbing fibers). This not only fixes zeolite particles like ordinary skeleton materials, but also provides good dispersion, optimizing the sound absorption performance of the zeolite particles. Simultaneously, the numerous micropores on the surface of the activated carbon work in synergy with the zeolite particles, resulting in a final porous composite sound-absorbing material with significantly superior sound absorption performance compared to both. Furthermore, the cost is relatively low, making it extremely cost-effective.

[0011] Specifically, the present invention provides a porous composite sound-absorbing material, characterized in that the porous composite sound-absorbing material comprises activated carbon cotton felt, zeolite particles, and an adhesive.

[0012] The activated carbon cotton felt serves as the skeleton material, and zeolite particles are bonded to the fiber surface of the activated carbon cotton felt with an adhesive, so that the zeolite particles are evenly dispersed and fixed. At the same time, the fiber surface of the activated carbon cotton felt has a large number of microporous structures, which can work synergistically with the zeolite particles, making the sound absorption performance of the porous composite sound-absorbing material significantly better than that of either material.

[0013] The activated carbon cotton felt used in this invention is porous, with a specific surface area generally ranging from 100 to 1800 m². 2 / g. The activated carbon fibers in the activated carbon cotton felt used in this invention not only have a rich macroporous structure, but also have a large number of micropores on the surface of the activated carbon fibers. The pore size of the macropores is generally 1μm-1000μm, preferably 100μm-500μm, and the pore size of the micropores is less than 2nm, and the proportion of micropores is 5%-95%.

[0014] The particle size of the zeolite particles used in this invention is generally between 50nm and 1mm, preferably between 50nm and 500μm, and more preferably between 100nm and 100μm. The zeolite particles can be fine powder, granules, or zeolite particles after secondary molding.

[0015] In a preferred embodiment, by weight, the activated carbon cotton felt accounts for 5%-90% of the porous composite sound-absorbing material, preferably 10%-50%, the zeolite particles account for 1%-85% of the porous composite sound-absorbing material, preferably 20%-60%, and the adhesive accounts for 1%-30% of the porous composite sound-absorbing material, preferably 5%-20%.

[0016] The adhesives used in this invention can be one or more of the following: acrylate adhesives, styrene-butadiene adhesives, polyurethane adhesives, epoxy adhesives, and silicone adhesives. The acrylate adhesives can be selected from methyl acrylate adhesives, ethyl acrylate adhesives, butyl acrylate adhesives, isooctyl acrylate adhesives, methyl methacrylate adhesives, ethyl methacrylate adhesives, and combinations thereof. The styrene-butadiene adhesives can be selected from high-temperature emulsion polymerized styrene-butadiene rubber and low-temperature emulsion polymerized styrene-butadiene rubber, and combinations thereof. The polyurethane adhesives can be selected from polyisocyanate adhesives, isocyanate-containing polyurethane adhesives, hydroxyl-containing polyurethane adhesives, polyurethane resin adhesives, and combinations thereof. The epoxy adhesives can be cold-curing adhesives, thermosetting adhesives, or light-curing adhesives. The silicone adhesives are silicone resin-based adhesives or silicone rubber-based adhesives.

[0017] The dispersing agent used in this invention can be one or more of cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. Preferably, the cationic surfactant is a quaternary ammonium salt type surfactant, such as, but not limited to, octadecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, etc. Preferably, the anionic surfactant is a sulfonate type surfactant or a sulfate ester type surfactant. The sulfonate type surfactant is, for example, but not limited to, sodium dodecylbenzenesulfonate, etc. The sulfate ester type surfactant is, for example, but not limited to, sodium lauryl sulfate, etc. The amphoteric surfactant is, for example, but not limited to, dodecylaminopropionic acid, hexadecyl dicarboxylic betaine, octadecyl dicarboxylic betaine, octadecyl hydroxypropyl sulfobetaine, dodecyl sulfobetaine, etc. The nonionic surfactant is, for example, but not limited to, glyceryl monostearate, sorbitan lauryl, sorbitan palmitate, sorbitan stearate, sorbitan tristearate, sorbitan oleate, sorbitan trioleate, etc.

[0018] On the other hand, the present invention also provides a method for preparing the porous composite sound-absorbing material of the present invention, the method comprising the steps of:

[0019] S1: Surface treatment of activated carbon cotton felt

[0020] Surface treatment of activated carbon cotton felt is performed to improve its sound absorption performance and increase its wettability with the sound-absorbing liquid.

[0021] S2: Preparation of sound-absorbing raw material

[0022] Zeolite particles, adhesive, dispersant, foaming agent and dispersant are mixed to obtain sound-absorbing stock solution;

[0023] S3: Impregnation

[0024] The sound-absorbing raw liquid obtained in step S2 is used to impregnate the activated carbon cotton felt treated in step S1 to obtain a zeolite-activated carbon cotton felt composite material.

[0025] S4: Shaping

[0026] The zeolite-activated carbon cotton felt composite material obtained from impregnation step S3 is flash-frozen to fix the zeolite-activated carbon cotton felt composite material.

[0027] S5: Removal of dispersant

[0028] The dispersant contained in the zeolite-activated carbon cotton felt composite material that has been shaped in step S4 is removed by freeze drying.

[0029] S6: Curing

[0030] Under conditions that allow the adhesive to cure, the zeolite-activated carbon cotton felt composite material after removing the dispersant in step S5 is baked to cure the adhesive contained in the zeolite-activated carbon cotton felt composite material.

[0031] S7: Cleaning

[0032] The mixture was ultrasonically cleaned several times with water to remove residual dispersants, foaming agents, and loosely bonded zeolite particles.

[0033] S8: Drying

[0034] Dry the material to obtain the porous composite sound-absorbing material.

[0035] When the porous composite sound-absorbing material provided by the present invention is used in a loudspeaker, it is preferable to cut the activated carbon cotton felt according to the shape of the rear cavity of the loudspeaker before performing the surface treatment step S1.

[0036] According to the method of the present invention, in the surface treatment step S1, the activated carbon cotton felt may be surface treated by one or more of the following methods: plasma treatment, corona treatment, oxidation treatment, reduction treatment, acid treatment, alkali treatment, surfactant solution immersion and solvent immersion.

[0037] The activated carbon cotton felt is preferably surface-treated by oxidation. More preferably, the oxidation treatment is performed by baking, for example, using a forced-air oven, with a baking temperature typically between 100-300°C and a baking time typically between 0.5-5 hours.

[0038] Before surface treatment, the activated carbon cotton felt can be cleaned with a solvent, for example, by immersing it in a solvent for 1-24 hours. The solvent is preferably a low-boiling-point organic solvent miscible with water, such as one or more of methanol, ethanol, acetone, tetrahydrofuran, etc. After immersion in the solvent, the solvent can be removed by drying to obtain a dry activated carbon cotton felt.

[0039] According to the method of the present invention, the zeolite particles, adhesive and dispersant used in the preparation step S2 of the sound-absorbing raw liquid are defined in the same way as those defined in the porous composite sound-absorbing material of the present invention. The foaming agent used in step S2 may be one or more of the following: physically volatile foaming agent, thermally decomposable foaming agent, azo compound foaming agent, bicarbonate foaming agent and two-component reactive foaming agent. The dispersant used in step S2 is preferably water.

[0040] The physical volatile foaming agents that can be used in this invention are, for example, but not limited to, low-boiling-point organic solvents miscible with water, such organic solvents may be one or more of ethanol, acetone, methanol, isopropanol, tetrahydrofuran, etc.

[0041] The thermally decomposable foaming agents that can be used in this invention are, for example, but not limited to, persulfide foaming agents, azo compound foaming agents, bicarbonate foaming agents, etc.

[0042] Such persulfides may be one or more of potassium persulfate, ammonium persulfate, etc.; such azo compounds may be one or more of azodicarbonamide, azobisisobutyronitrile, etc.; such bicarbonates may be one or more of sodium bicarbonate, potassium bicarbonate, etc.

[0043] The two-component reactive foaming agent that can be used in this invention can be, for example, but not limited to, one or more of carbonate + hydrochloric acid, bicarbonate + hydrochloric acid, etc.

[0044] The carbonate may be, but is not limited to, one or more of sodium carbonate, potassium carbonate, calcium carbonate, barium carbonate, etc.; the bicarbonate may be, but is not limited to, one or more of sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, barium bicarbonate, etc.

[0045] In step S2 of preparing the sound-absorbing stock solution, 100 parts of zeolite particles, 1-200 parts of adhesive, 1-50 parts of dispersant, 1-50 parts of foaming agent, and 50-9900 parts of dispersant are generally blended to obtain the sound-absorbing stock solution. In a preferred embodiment, in step S2, 100 parts of zeolite particles, 5-20 parts of adhesive, 3-40 parts of dispersant, 7-40 parts of foaming agent, and 135-1800 parts of dispersant are blended to obtain the sound-absorbing stock solution.

[0046] According to the method of the present invention, any method in the art can be used to impregnate in the impregnation step S3, as long as the activated carbon cotton felt can be completely impregnated by the sound-absorbing liquid. For example, the surface-treated activated carbon cotton felt can be soaked in the sound-absorbing liquid for 1-24 hours. With the use of ultrasonic or vacuum means, the impregnation can be accelerated and the impregnation time can be shortened to 1-60 minutes.

[0047] Preferably, before molding, the excess sound-absorbing liquid on the surface of the zeolite-activated carbon cotton felt obtained in step S3 is removed, for example, by light wiping to quickly remove the excess sound-absorbing liquid from the surface.

[0048] According to the method of the present invention, in the shaping step S4, any quick-freezing technique commonly used in the art can be used to place the zeolite-activated carbon cotton felt composite material obtained in the impregnation step S3 in a low-temperature environment for quick-freezing and shaping. Refrigeration equipment or refrigerant can be used.

[0049] According to the method of the present invention, in step S5 of removing the dispersant, a freeze dryer can be used for freeze drying. There are no particular limitations on the freezing temperature and time, as long as the dispersant, such as water, in the zeolite-activated carbon cotton felt composite material can be completely removed.

[0050] According to the method of the present invention, the curing conditions used in the curing step S6, namely the baking time and temperature, depend on the specific adhesive used and are generally not particularly limited, as long as the adhesive can be completely cured and the zeolite particles are firmly adhered to the fiber surface of the activated carbon cotton felt.

[0051] According to the method of the present invention, any method known in the art can be used for cleaning in cleaning step S7, preferably an ultrasonic cleaner. The number of cleaning cycles and the cleaning time are not limited, as long as residual dispersing agents, foaming agents, and unbonded zeolite particles are removed. Preferably, the water used for cleaning is deionized water.

[0052] According to the method of the present invention, in the drying step S8, any method known in the art can be used to dry the moisture, such as using an oven, with a drying temperature generally of 80-150°C and a drying time generally of 0.5-2 hours.

[0053] In another aspect, the present invention also provides a loudspeaker, the rear cavity of which comprises the porous composite sound-absorbing material provided by the present invention.

[0054] This invention uses activated carbon cotton felt as the skeleton material. Compared with traditional sound-absorbing cotton, sound-absorbing fiber and other materials, the activated carbon cotton felt has a large number of microporous structures, so its sound absorption performance is better. Moreover, even with a small amount of zeolite material, the sound absorption performance is also very good, so the cost performance is higher.

[0055] On the other hand, the rapid freezing and freeze-drying technology used in the preparation process of the porous composite sound-absorbing material of the present invention enables zeolite particles to be uniformly distributed in the activated carbon cotton felt, which solves the problem of uneven zeolite distribution and limited loading depth caused by gravity or viscosity of the sound-absorbing liquid in traditional processes. This results in a significant improvement in the sound absorption performance of the composite material, and also solves the problem that zeolite and activated carbon and other particulate materials are not suitable for complex speaker cavities.

[0056] After filling the rear cavity of a loudspeaker with the porous composite sound-absorbing material of this invention, the low-frequency performance of the loudspeaker can be greatly improved and its performance made more stable. Acoustic loudspeakers have been applied in mobile phones, headphones, computers, automobiles, televisions, audio equipment and other fields. Therefore, this invention has broad application prospects.

[0057] These and other objects, aspects and advantages of this disclosure will become apparent from the following description and in conjunction with the accompanying drawings. [Attached Image Description]

[0058] Figure 1 This is a schematic diagram of the porous composite sound-absorbing material of the present invention, wherein the following reference numerals are used:

[0059] 1—Activated carbon fibers in the activated carbon cotton felt of the porous composite sound-absorbing material of the present invention; 2—Zeolite particles.

[0060] Figure 2 These are SEM images of activated carbon cotton felt after oxidation treatment. The small image on the left shows the front view, and the small image on the right shows the side view.

[0061] Figure 3 These are SEM images of the porous composite sound-absorbing material prepared in Example 1 of this invention, where the small image on the left represents the front view and the small image on the right represents the side view.

Detailed Implementation Methods

[0062] By using activated carbon cotton felt as the skeleton material, zeolite particles are bonded to the fiber surface of the activated carbon cotton felt with an adhesive, and then subjected to quick-freeze setting, freeze-drying, and high-temperature treatment, a novel porous composite sound-absorbing material is prepared. Its structural schematic diagram is shown below. Figure 1 As shown.

[0063] The activated carbon cotton felt used in this invention has a large number of micropores, and its sound absorption performance is significantly better than that of sound-absorbing cotton and sound-absorbing fibers with only macroporous structures. Moreover, after modification with zeolite, which has even better sound absorption performance, and combined with quick-freeze setting technology that can significantly improve the uniformity of zeolite distribution, this invention greatly reduces costs and solves the technical problem of the inconvenience of using granular materials such as zeolite. The porous composite sound-absorbing material provided by this invention also further improves the sound absorption performance of activated carbon cotton felt, so that when the porous composite sound-absorbing material of this invention is filled into the rear cavity of a loudspeaker, its low-frequency performance can be significantly improved.

[0064] The following examples further illustrate the invention. It should be understood that the specific embodiments described herein are merely for explaining the invention and are not intended to limit the invention.

[0065] Preparation Examples

[0066] Example 1

[0067] Activated carbon cotton felt with macropores ranging from 1μm to 1000μm and micropores less than 2nm is used, and the specific surface area of ​​this activated carbon cotton felt is 1300m². 2 / g, and the micropore ratio is 80%.

[0068] The activated carbon cotton felt was cut according to the shape of the speaker's rear cavity. The cut activated carbon cotton felt was divided into 30 parts by weight. It was soaked in ethanol for 12 hours and then baked in a forced-air oven at 110°C for 2 hours to remove the ethanol.

[0069] The activated carbon cotton felt was oxidized by baking at 200℃ for 2 hours in a forced-air drying oven. The front and side surfaces of the activated carbon cotton felt were scanned using a scanning electron microscope (SEM), and the resulting SEM images are shown below. Figure 2 As shown in the figure, the small image on the left represents the front view, and the small image on the right represents the side view. Its acoustic performance data are shown in Table 1.

[0070] Using a magnetic stirrer, mix 100 parts of zeolite particles with a particle size of 0.2-20μm, 20 parts of styrene-butadiene adhesive, 10 parts of sodium lauryl sulfate, 40 parts of potassium persulfate, and 1800 parts of water evenly to prepare a sound-absorbing stock solution for later use.

[0071] Place the above-mentioned oxidized activated carbon cotton felt into the sound-absorbing liquid and sonicate for 1 hour. Then, take out the soaked activated carbon cotton felt, gently and quickly wipe off the excess sound-absorbing liquid on its surface with filter paper, and then quickly freeze and shape it in a low-temperature environment (refrigeration equipment or refrigerant can be used).

[0072] After quick-freezing and shaping, the material is freeze-dried using a freeze dryer to completely remove moisture.

[0073] After freeze-drying, bake in an oven at 110°C for 2 hours to allow the styrene-butadiene adhesive to fully cure.

[0074] Using an ultrasonic cleaner, the material was cleaned five times with deionized water for 10 minutes each time to remove residual foaming agent, surfactant, and loosely bonded zeolite particles. The material was then baked in an oven at 110°C for 1 hour to obtain a blocky porous composite sound-absorbing material.

[0075] The front and side surfaces of the obtained porous composite sound-absorbing material were scanned using a scanning electron microscope, and the resulting SEM images are shown below. Figure 3 As shown in the figure, it is clear that the zeolite particles have been firmly adhered to the fiber surface of the activated carbon cotton felt. Its acoustic performance data are shown in Table 1.

[0076] Example 2

[0077] The activated carbon cotton felt used in this embodiment is exactly the same as that in Example 1.

[0078] The activated carbon cotton felt was cut according to the shape of the speaker's rear cavity. The cut activated carbon cotton felt was divided into 30 parts by weight. It was soaked in ethanol for 12 hours and then baked in an oven at 110°C for 2 hours to remove the ethanol.

[0079] Oxidation treatment is performed by baking at 200℃ for 2 hours in a forced-air oven.

[0080] Using a magnetic stirrer, mix 100 parts by weight of zeolite particles with a particle size of 0.2-20μm, 10 parts by weight of silicone adhesive, 15 parts by weight of sodium dodecylbenzenesulfonate, 20 parts by weight of ammonium persulfate, and 550 parts by weight to prepare a sound-absorbing stock solution for later use.

[0081] Place the above-mentioned oxidized activated carbon cotton felt into the sound-absorbing liquid and sonicate for 1 hour. Then, take out the soaked activated carbon cotton felt, gently and quickly wipe off the excess sound-absorbing liquid on the surface with filter paper, and then quickly freeze and shape it in a low-temperature environment (refrigeration equipment or refrigerant can be used).

[0082] After quick-freezing and shaping, the material is freeze-dried using a freeze dryer to completely remove moisture.

[0083] After freeze-drying, bake in an oven at 110°C for 2 hours to allow the silicone adhesive to fully cure.

[0084] Using an ultrasonic cleaner, the material was cleaned five times with deionized water for 10 minutes each time to remove residual foaming agent, surfactant, and loosely bonded zeolite particles. The material was then baked in an oven at 110°C for 1 hour to obtain a blocky porous composite sound-absorbing material.

[0085] The front and side surfaces of the obtained porous composite sound-absorbing material were scanned using a scanning electron microscope. The resulting SEM images (not shown) are essentially the same as those of the porous composite sound-absorbing material in Example 1. It is clearly visible in the images that the zeolite particles are firmly adhered to the fiber surface of the activated carbon cotton felt. Detailed acoustic performance data are shown in Table 1.

[0086] Example 3

[0087] The activated carbon cotton felt used in this embodiment is exactly the same as that in Example 1.

[0088] The activated carbon cotton felt was cut according to the shape of the speaker's rear cavity. The cut activated carbon cotton felt was divided into 30 parts by weight. It was soaked in ethanol for 12 hours and then baked in a forced-air oven at 110°C for 2 hours to remove the ethanol.

[0089] Oxidation treatment is performed by baking at 200℃ for 2 hours in a forced-air oven.

[0090] Using a magnetic stirrer, mix 100 parts by weight of zeolite particles with a particle size of 0.2-20μm, 15 parts by weight of acrylate adhesive, 3 parts by weight of sodium dodecylbenzenesulfonate, 7 parts by weight of sodium bicarbonate, and 135 parts by weight to prepare a sound-absorbing stock solution for later use.

[0091] Place the above-mentioned oxidized activated carbon cotton felt into the sound-absorbing liquid and sonicate for 1 hour. Then, take out the soaked activated carbon cotton felt, gently and quickly wipe off the excess sound-absorbing liquid on the surface with filter paper, and then quickly freeze and shape it in a low-temperature environment (refrigeration equipment or refrigerant can be used).

[0092] After quick-freezing and shaping, the material is freeze-dried using a freeze dryer to completely remove moisture.

[0093] After freeze-drying, bake in an oven at 110°C for 2 hours to allow the styrene-butadiene adhesive to fully cure.

[0094] Using an ultrasonic cleaner, the material was cleaned five times with deionized water for 10 minutes each time to remove residual foaming agent, surfactant, and loosely bonded zeolite particles. The material was then baked in an oven at 110°C for 1 hour to obtain a blocky porous composite sound-absorbing material.

[0095] The front and side surfaces of the obtained porous composite sound-absorbing material were scanned using a scanning electron microscope. The resulting SEM images (not shown) are essentially the same as those of the porous composite sound-absorbing material in Example 1. It is clearly visible in the images that the zeolite particles are firmly adhered to the fiber surface of the activated carbon cotton felt. Detailed acoustic performance data are shown in Table 1.

[0096] Acoustic performance measurement

[0097] According to the method for determining the resonant frequency of a loudspeaker, the porous composite sound-absorbing materials prepared in Examples 1, 2, and 3 were placed in suitable tooling, and the reduction value of their resonant frequency (F0) was measured using an impedance analyzer. The damage of the porous composite sound-absorbing materials upon drop was tested through a drop test. The reduction in F0 indicates the degree to which the resonant frequency shifts to lower frequencies. Generally, the larger the reduction in F0, the better the low-frequency performance of the loudspeaker.

[0098] The volume of the speaker fixture used for acoustic performance testing was 0.4 cubic centimeters (abbreviated as 0.4cc). The specific test results are shown in Table 1.

[0099] Table 1. Acoustic performance test results for each embodiment.

[0100]

[0101] As shown in Table 1, the activated carbon cotton felt (skeleton material) in this invention exhibits superior sound absorption performance compared to traditional skeleton materials (sound-absorbing foam, sound-absorbing fibers) due to its microporous structure. After filling the rear cavity of the tooling with the porous composite sound-absorbing material of this invention, the F0 of the loudspeaker decreased by no less than 160Hz. After filling the rear cavity with the porous composite sound-absorbing material of Example 3, the F0 of the loudspeaker decreased by 271Hz. Its performance is significantly better than activated carbon cotton felt and Bass particles (currently the best-performing sound-absorbing material for commercial loudspeaker use), indicating a significant improvement in its low-frequency performance. Furthermore, the material of this invention is significantly cheaper than Bass, offering excellent cost-effectiveness. Additionally, the loudspeaker using the porous composite sound-absorbing material of Example 1 experienced slight powder shedding, while the loudspeakers using the porous composite sound-absorbing materials of Examples 2 and 3 showed no powder shedding.

[0102] The foregoing has provided a detailed description of the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is merely an implementation scheme and specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing porous composite sound-absorbing materials, characterized in that, The method includes the following steps: S1: Surface treatment of activated carbon cotton felt The activated carbon cotton felt is surface-treated to improve its sound absorption performance and increase its wettability with the sound-absorbing liquid. The surface treatment of the activated carbon cotton felt is carried out by one or more methods selected from plasma treatment, corona treatment, oxidation treatment, reduction treatment, acid treatment, alkali treatment, surfactant solution immersion and solvent immersion. S2: Preparation of sound-absorbing raw material Zeolite particles, adhesive, dispersant, foaming agent and dispersant are mixed to obtain sound-absorbing stock solution; S3: Impregnation The sound-absorbing raw liquid obtained in step S2 is used to impregnate the activated carbon cotton felt treated in step S1 to obtain a zeolite-activated carbon cotton felt composite material. S4: Shaping The zeolite-activated carbon cotton felt composite material obtained from impregnation step S3 is flash-frozen to fix the zeolite-activated carbon cotton felt composite material. S5: Removal of dispersant The dispersant contained in the zeolite-activated carbon cotton felt composite material that has been shaped in step S4 is removed by freeze drying. S6: Curing Under conditions that allow the adhesive to cure, the zeolite-activated carbon cotton felt composite material after removing the dispersant in step S5 is baked to cure the adhesive contained in the zeolite-activated carbon cotton felt composite material. S7: Cleaning The mixture was ultrasonically cleaned several times with water to remove residual dispersants, foaming agents, and loosely bonded zeolite particles. S8: Drying The porous composite sound-absorbing material is obtained by drying the moisture. The porous composite sound-absorbing material includes activated carbon cotton felt, zeolite particles and adhesive. The activated carbon cotton felt serves as the skeleton material, and the zeolite particles are bonded to the fiber surface of the activated carbon cotton felt by the adhesive.

2. The method according to claim 1, characterized in that, In step S2, 100 parts of zeolite particles, 1-200 parts of adhesive, 1-50 parts of dispersant, 1-50 parts of foaming agent, and 50-9900 parts of dispersant are mixed to obtain the sound-absorbing stock solution.

3. The method according to claim 1, characterized in that, The foaming agent is one or more of the following: physically volatile foaming agent, thermally decomposable foaming agent, and two-component reactive foaming agent.

4. The method according to claim 1, characterized in that, The dispersing agent is one or more of cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants.

5. The method according to claim 1, characterized in that, The activated carbon cotton felt has large pores with a pore size of 1μm-1000μm between the activated carbon fibers, and the surface of the activated carbon fibers of the activated carbon cotton felt has a large number of micropores with a pore size of less than 2nm, with the micropore ratio being 5%-95%.

6. The method according to claim 1, characterized in that, The particle size of the zeolite particles is between 50 nm and 1 mm.

7. The method according to claim 1, characterized in that, By weight, the activated carbon cotton felt accounts for 5%-90% of the porous composite sound-absorbing material, the zeolite particles account for 1%-85% of the porous composite sound-absorbing material, and the adhesive accounts for 1%-30% of the porous composite sound-absorbing material.

8. The method according to any one of claims 1-7, characterized in that, The adhesive is one or more of the following: acrylate adhesives, styrene-butadiene adhesives, polyurethane adhesives, epoxy adhesives, and silicone adhesives.

9. A loudspeaker, characterized in that, The rear cavity of the loudspeaker comprises a porous composite sound-absorbing material prepared by any one of claims 1-8.

Images