TWI647113B - Sound absorbing material - Google Patents

Abstract

The disclosure provides a sound absorbing material including a polymer body having a first end and a second end opposite to each other, and a plurality of dendritic channels, wherein the plurality of dendritic channels are connected to the first end and face the second end. Extending, the average distance between the plurality of dendritic channels is 5 micrometers to 50 micrometers, and the average width of the plurality of dendritic channels is 5 micrometers to 50 micrometers.

Description

Sound-absorbing material

This disclosure relates to an open-cell type sound absorbing material.

In order to improve echo interference in life, sound-absorbing materials are usually installed on the wall or on the car body to absorb sound waves and reduce the amount of reflection. However, polymer porous materials are often used as sound-absorbing materials, but the traditional manufacturing method is made by a foaming process, which is a closed-cell pore structure. It is less likely for incident sound waves to have multiple reflection effects inside the sound-absorbing material, so that the sound-absorbing effect is limited . In addition, the traditional foaming process requires the use of gases such as foaming agents or carbon dioxide, which is likely to cause environmental pollution.

Therefore, the development of an open-cell sound-absorbing material is an urgent problem to be solved at present.

The disclosure provides an open-cell sound-absorbing material, which can effectively improve the sound-absorbing effect, and does not need to use a foaming agent or a gas to make the hole structure.

The sound-absorbing material provided by an embodiment of the present disclosure includes a polymer body having a first end and a second end opposite to each other, and a plurality of dendritic channels. The plurality of dendritic channels are connected to the first end and extend toward the second end. The average distance between the plurality of dendritic channels is 5 micrometers to 50 micrometers, the average width of the plurality of dendritic channels is 5 micrometers to 50 micrometers.

In order to make the above-mentioned objects, features, and advantages of this disclosure more comprehensible, a preferred embodiment is given below, and the accompanying drawings are described in detail below.

10‧‧‧ Sound-absorbing material

100‧‧‧ polymer body

101‧‧‧ the first end

102‧‧‧ the second end

103, 103 ’, 103’’‧‧‧ dendritic channels

1031‧‧‧Main channel

1032‧‧‧ side access

20‧‧‧freeze casting system

201‧‧‧ Teflon mould (PTFE mould)

202‧‧‧copper cold finger

203‧‧‧liquid nitrogen bath

204‧‧‧sample area

205‧‧‧temperature controller

206‧‧‧Heating coil

A, B‧‧‧central axis

E1, E2‧‧‧location

S‧‧‧Pitch

W‧‧‧Width

X‧‧‧pore-growth direction

Y‧‧‧thickness

θ‧‧‧ angle

FIG. 1 is a schematic diagram of a sound absorbing material according to an embodiment of the disclosure.

Figure 2 is a schematic diagram of a freeze casting system.

FIG. 3 is a cross-sectional SEM image of the sound absorbing material prepared in Example 1 of the present disclosure.

FIG. 4 is a partially enlarged view of FIG. 3.

FIG. 5 is a comparison diagram of sound absorption coefficients for different frequencies of the sound absorbing material prepared in Example 1 of the present disclosure and the sound absorption cotton of Comparative Example 1. FIG.

FIG. 6 is a comparison diagram of sound absorption coefficients for different frequencies of the sound absorbing material prepared in Example 2 of the present disclosure and the sound absorption cotton of Comparative Example 1. FIG.

This disclosure provides a sound-absorbing material with an open-cell structure. Compared with traditional foaming technology, the sound-absorbing material of this disclosure uses the freeze-casting method to make holes. The water solvent in the polymer solution forms ice crystals at low temperatures, and then lowers through the low temperature. The ice crystals are removed by pressing to obtain a sound absorbing material with continuous openings, which can cause incident sound waves to be reflected multiple times inside the material, which greatly improves the sound absorption characteristics.

FIG. 1 is a schematic diagram of a sound absorbing material according to an embodiment of the disclosure. As shown in FIG. 1, the present disclosure provides a sound absorbing material 10 including a polymer substrate. The body 100 and the polymer body 100 have a first end 101 and a second end 102 opposite to each other, and a plurality of dendritic channels 103, 103 ', 103' '. These dendritic channels 103, 103 ', 103' 'are formed inside the polymer body 100, and are connected to the first end 101 and extend in the direction of the second end 102 to form a continuous open-cell structure with directivity between each other. The first end 101 of the polymer body 100 mentioned in this disclosure refers to the incident end or absorption surface for sound waves to enter; the second end 102 of the polymer body 100 mentioned in this disclosure refers to a clear distance from the first end 101 The surface may be parallel or non-parallel to the first end 101; the connection of the dendritic channels 103 to the first end 101 mentioned in the present disclosure means that a plurality of openings are formed in the first end 101 of the polymer body 100 for the sound waves to enter .

In an embodiment, all or part of the dendritic channels 103, 103 ′, 103 ″ may be directly connected between the first end 101 and the second end 102 of the polymer body 100 (not shown); or part of The dendritic channels 103, 103 ′, and 103 ″ form a longer dendritic channel (not shown) connected in series between the first end 101 and the second end 102 of the polymer body 100. In one embodiment, when the dendritic channels 103, 103 ′, and 103 ″ are connected between the first end 101 and the second end 102 of the polymer body 100, the first end 101 and the second end 102 are respectively separated from each other. A plurality of openings are formed. In an embodiment, the extending direction of each of the dendritic channels 103, 103 ′, and 103 ″ extends from the first end 101 to the second end 102, and is the shortest relative to the first end 101 to the second end 102. The direction of the distance has a directional difference below 45 degrees. As long as the sound absorbing material 10 of the present disclosure allows incident sound waves to enter these dendritic channels 103 from the first end 101 of the polymer body 100, 103 ', 103' and can generate internal reflections, but not limited to this.

As shown in FIG. 1, the dendritic channels 103, 103 ′, and 103 ″ have a distance S from each other, wherein each distance S can be independently the same or different, and the average distance S can be 5 μm to 50 μm. Micron, for example, 10 μm to 30 μm, when the distance S is too large, it may cause a decrease in porosity and reduce the sound absorption effect; when the distance S is too small, it may cause visual penetration and insufficient structural strength. In an embodiment, each of the dendritic channels 103, 103 ', and 103 "has a width W, wherein each width W may be independently the same or different, and the average width W may be 5 micrometers to 50 micrometers. For example, 10 micrometers to 30 micrometers, when the width W is too large, visual penetration and structural strength may be insufficient; when the width W is too small, the porosity of the sound-absorbing material may be reduced and the sound-absorbing effect may be reduced. The distance S between the dendritic channels 103, 103 ', 103' 'mentioned in this disclosure refers to the wall thickness or distance between the main channels of these dendritic channels 103, 103', 103 ''. The width W of the dendritic channels 103, 103 ', 103' 'refers to the size or aperture of the main channel in each dendritic channel 103, 103', 103 '' perpendicular to the central axis A of the main channel.

As shown in Fig. 1, each of the dendritic channels 103, 103 ', 103' 'includes a main channel 1031 and a plurality of side channels 1032. The main channel 1031 is connected to the first end 101 of the polymer body 100 and extends toward the second end 102. Each of the main channels 1031 has a nearly consistent direction and is parallel to each other with the adjacent main channel 1031 (the angle error is less than 10). degree). The side channels 1032 are formed around the main channel 1031 and communicate with the main channel 1031. The plurality of side channels 1032 are from the main channel 1031 to the second channel. The direction of the end 102 extends. In an embodiment, the side channels 1032 and the main channel 1031 form an included angle θ, wherein each included angle θ can be the same or different, and the average included angle θ is 10 degrees to 90 degrees, such as 30 degrees to 80 degrees. The included angle θ mentioned in this disclosure refers to the angle between the central axis A of the main channel 1031 and the central axis B of the side channel 1032, as shown in FIG. 1.

In one embodiment, the main channels 1031 have a distance S from each other. Each of the distances S can be different or the same. The average distance S can be 5 μm to 50 μm, such as 10 μm to 30 μm. In one embodiment, each main channel 1031 has a width W, wherein each width W can be different or the same, and the average width W can be 5 to 50 microns, such as 10 to 30 microns. In an embodiment, each side channel 1032 may be a sheet-like structure or a columnar structure, and each side channel 1032 has a thickness Y, wherein each thickness Y may be independently the same or different. The average thickness Y may be 3 to 20 microns, such as 5 to 10 microns. Generally, the thickness Y of the side channel 1032 is less than or equal to the width W of the main channel 1031. The width W of the main channel 1031 mentioned in this disclosure refers to the size or aperture of the main channel perpendicular to the central axis A direction. The thickness Y of the side channel 1032 mentioned in this disclosure refers to the contact height where the side channel 1032 is connected to the main channel 1031, wherein the contact height is a distance parallel to the direction of the central axis A of the main channel 1031.

In one embodiment, each of the dendritic channels 103, 103 ', 103' 'can be a layered structure, a columnar structure, or a combination thereof. The layered structure or columnar structure mentioned in this disclosure refers to the structure formed by ice crystals in the freeze casting method, and the structure can be adjusted by controlling the cooling temperature or the cooling rate. In one implementation In the example, these dendritic channels 103, 103 ', 103' 'are formed by a freeze casting method. The layered structure or sheet structure mentioned in this disclosure means that the size of the object in the thickness direction is smaller than that of the other two dimensions, such as less than 5 times, 10 times, or 50 times.

In one embodiment, the polymer body 100 is formed of a water-soluble polymer. In another embodiment, the polymer body 100 comprises more than 90% by weight of a water-soluble polymer, and the water-soluble polymer may be exemplified by Polyvinyl Alcohol (PVA) or Polyethylene glycol (PEG). The weight average molecular weight (Mw) of polyvinyl alcohol may be 3000 to 25000, and the weight average molecular weight (Mw) of polyethylene glycol may be 300 to 6000. The water-soluble polymer mentioned in this disclosure refers to a polymer material that is compatible with water. The polymer material itself has a large number of hydrophilic groups, such as cationic groups (tertiary or quaternary amine groups, etc.), anionic groups (Carboxylic acid group, sulfonic acid group, phosphate group or sulfuric acid group, etc.) or polar nonionic group (hydroxyl, ether, amine or amido group, etc.).

In one embodiment, in addition to the water-soluble polymer, the polymer body 100 may also include an inorganic material of less than 10% by weight. The inorganic material may be a porous material having a high specific surface area. For example, diatomite or active carbon can generate more holes, which makes the sound-absorbing material of the present disclosure better in sound absorption. When the specific gravity of the inorganic material is too large, it may cause the number of dendritic channels to decrease, and the porosity may be poor to reduce the sound absorption effect; when the specific gravity of the inorganic material is too small, the sound absorption effect may not be effectively improved. In one embodiment, the polymer body 100 may be composed of more than 94% by weight of a water-soluble polymer and less than 6% by weight of an inorganic material. In one embodiment, the average of the inorganic materials The particle size is 5 to 40 microns. In one embodiment, in addition to being present in the polymer body, a portion of the inorganic material may be exposed on the surface of the dendritic channels to create more pores.

In one embodiment, the density of the sound-absorbing material disclosed in this disclosure is 300kg / m ³ to 400kg / m ^3. When the density is too large, it may cause excessive weight and poor sound absorption effect; when the density is too small, it may cause insufficient structural strength of the sound-absorbing material . The density mentioned in this disclosure refers to the overall density of the polymer body (including a plurality of dendritic channels). In one embodiment, the porosity of the sound-absorbing material disclosed herein is 60% to 80%. When the porosity is too large, the sound-absorbing material may easily collapse or visually penetrate; when the porosity is too small, the sound-absorbing effect may be poor. . The porosity mentioned in this disclosure refers to the porosity measured by the density difference ratio method.

In one embodiment, the sound absorbing material disclosed in this disclosure is measured according to the JIS A1405 method to have a sound absorption coefficient at 500 Hz of 0.6 or more, a sound absorption coefficient at 1000 Hz of 0.55 or more, and a sound absorption coefficient at 2000 Hz of 0.5 or more. In one embodiment, the sound absorbing material of the present disclosure measured in accordance with JIS A1405 method has a sound absorption coefficient of 0.85 or more at 500 Hz, a sound absorption coefficient of 1000 or more at 0.8, and a sound absorption coefficient of 2000 or more at 0.7. The JIS A1405 method mentioned in this disclosure refers to a method of measuring the sound absorption rate of vertical incidence by the in-tube method.

The sound absorbing material disclosed in this disclosure can be made by a freeze casting method. FIG. 2 is a schematic diagram of a freeze casting system 20. As shown in FIG. 2, the freeze casting system 20 includes a Teflon mold 201, a cooling copper rod 202, a liquid nitrogen tank 203, a temperature controller 205, and a heating coil 206. Teflon mould 201 A sample area 204 is provided therein for placing the preparation slurry of the sound-absorbing material disclosed herein; a cooling copper rod 202 is connected between the sample area 204 and the liquid nitrogen tank 203; the liquid nitrogen tank 203 is used for liquid nitrogen placement and transmission The cooling copper rod 202 cools the slurry in the sample area 204; the heating coil 206 surrounds the outside of the cooling copper rod 202 and is connected to a temperature controller 205 to control the cooling temperature and the cooling rate. The refrigerated casting system 20 disclosed in the present disclosure is a one-sided temperature control, and a two-sided temperature control may also be adopted, without being limited thereto.

The manufacturing method of the sound-absorbing material disclosed in the present disclosure is as follows. First, a slurry is poured into the sample area 204, wherein the slurry includes at least a water-soluble polymer and water. In some embodiments, the slurry further includes an inorganic material and a water-soluble polymer. The detailed description of the materials and inorganic materials is as described above, in which the proportion of water to the overall slurry is 60wt% to 80wt%; then liquid nitrogen is added to the liquid nitrogen tank 203, and the cooling conditions are controlled through the temperature controller 205 and the heating coil 206 The directional cooling of the water in the slurry to form a directional ice crystal structure; after the slurry in the sample area 204 is solidified into a green body, the ice crystals in the green body are removed by gasification and dried by rapid decompression. Finally, a sound-absorbing material with a continuous opening structure according to the present disclosure is obtained. In one embodiment, after drying, a cross-linking agent can be added to the slurry through heating or added to the paste so that it can generate cross-linking to increase the mechanical strength of the sound-absorbing material. In one embodiment, the completed sound-absorbing material can be further cut to form a plurality of sound-absorbing materials, wherein the cut surface will expose a dendritic channel as a sound-absorbing incident end (the first end of the polymer body). In one embodiment, the sound absorbing material is cut in a direction perpendicular to the extension direction of the dendritic channel. The above manufacturing method is only an example, and the manufacturing method of the sound absorbing material disclosed in this disclosure is not limited to this.

Preparation of sound-absorbing materials Example 1 (100wt% PVA)

First, 2.4 grams of PVA polymer powder (purchased from Polysciences, Mw = 6000, 80% degree of hydrolysis) was mixed with 21.6 grams of water to form a slurry (water 90% by weight), and then the slurry was placed in a freeze-casting In the system's mold (diameter: 2 cm, height: 2 cm), a cooling rate of 10 ° C / min is provided at the bottom of the mold from room temperature 25 ° C to -5 ° C, and the slurry is solidified for 3 minutes, and then at low temperature The low-pressure freeze-drying method (temperature: -80 ° C, pressure: 80mTorr, time: 5 minutes) removes the ice crystals, and then cross-links them at a temperature of 150 ° C to complete. The density of the sound absorbing material obtained in Example 1 was 380 kg / m ³ , and the porosity was 70%.

FIG. 3 is a cross-sectional SEM image of the sound absorbing material prepared in Example 1 of the present disclosure. As shown in Figure 3, position E1 is the first end position adjacent to the polymer body, and position E2 is the second end position adjacent to the polymer body. It can be observed that these dendritic channels are layered to each other, where each branch The hole-forming direction (extending direction) X of the channel is extended from the position E1 to the position E2.

Figure 4 is a partial enlarged view of Figure 3. It can be observed that each dendritic channel includes a main channel and a plurality of side channels, where these main channels and adjacent main channels are arranged in parallel with each other, and they have nearly uniform hole formation Direction X. As can be seen from FIG. 4, the average width W of the main channel is 21 μm, and the average pitch S is 9 μm.

Example 2 (95% wt PVA + 5wt% diatomaceous earth)

First, 2.4 grams of PVA polymer powder (purchased from Polysciences, Mw = 6000, 80% degree of hydrolysis), 0.13 grams of diatomaceous earth (brand, model) and 22.77 grams of water were mixed to form a slurry (water accounts for 90wt%), then put the slurry in the mold (diameter: 2 cm, height: 2 cm) of the freezing casting system, and provide a cooling rate of 10 ° C / min at the bottom of the mold from room temperature 25 ° C to -5 ℃, and maintain for 3 minutes to solidify the slurry, and then use low temperature and low pressure freeze-drying method (temperature: -80 ℃, pressure: 80mTorr, time: 5 minutes) to remove the ice crystals, and then cross-linking at 150 ℃ to complete . The density of the sound absorbing material obtained in Example 2 was 320 kg / m ³ , and the porosity was 75%.

Comparative Example 1

Acoustic cotton (PU) purchased from Anda Industrial Co., Ltd. was used.

Test examples of sound-absorbing materials

The sound absorbing materials of Example 1, Example 2 and Comparative Example 1 were tested for sound absorption in accordance with JIS A1405 method (using 4206-T acoustic impedance tube of Bruel & Kjaer company, 4187 1 / 4-inch microphone and TL software). , Import sound waves with a frequency range from 300Hz to 6000Hz and calculate the sound absorption coefficient at each frequency with TL software. The test results are shown in Figure 5 and Figure 6.

FIG. 5 is a comparison diagram of sound absorption coefficients for different frequencies of the sound absorbing material prepared in Example 1 of the present disclosure and the sound absorption cotton of Comparative Example 1. FIG. As shown in FIG. 5, regarding the sound absorbing material of Comparative Example 1, it can be observed that the sound absorbing characteristics of the sound absorbing material of Example 1 of the present disclosure have better sound absorption characteristics at medium and high frequencies (1000 Hz to 2000 Hz) and low frequencies (500 Hz to 1000 Hz). Sound absorption effect.

FIG. 6 is a sound absorbing material and a comparative example prepared in Example 2 of the present disclosure 1 Comparison chart of sound absorption coefficient of sound absorption cotton for different frequencies. As shown in FIG. 6, it can be observed that the sound absorbing properties of the sound absorbing material of Example 2 in this disclosure in all frequency bands (500 Hz to 4000 Hz) are much higher than the sound absorbing material of Comparative Example 1. Therefore, adding a trace amount of inorganic sound-absorbing material can indeed help improve the overall sound-absorbing effect.

Although the present invention has been disclosed above with several preferred embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make any changes without departing from the spirit and scope of the present invention. And retouching, so the scope of protection of the present invention shall be determined by the scope of the attached patent application.

Claims (14)

A sound absorbing material comprises: a polymer body having a first end and a second end opposite to each other, and a plurality of dendritic channels; wherein the plurality of dendritic channels are connected to the first end and extend toward the second end; The average distance between the plurality of dendritic channels is 5 micrometers to 50 micrometers, and the average width of the plurality of dendritic channels is 5 micrometers to 50 micrometers. For example, the sound absorbing material of the first patent application range, wherein each of the dendritic channels includes a main channel and a plurality of side channels, the main channel is connected to the first end of the polymer body and extends toward the second end, A plurality of side channels are formed around the main channel and communicate with the main channel. For example, the sound-absorbing material of the second patent application range, wherein the plurality of side channels extend from the main channel to the second end. For example, the sound absorbing material of the second patent application range, wherein the main channel and the adjacent main channel of each dendritic channel are arranged in parallel with each other. For example, the sound absorbing material according to the second item of the patent application, wherein the average thickness of the plurality of side channels is 3 micrometers to 20 micrometers. For example, the sound absorbing material of the first scope of the patent application, wherein each of the dendritic channels is a layered structure, a columnar structure, or a combination thereof. For example, the sound absorbing material of the first patent application range, wherein the polymer body comprises a water-soluble polymer of more than 90% by weight. For example, the sound absorbing material according to item 7 of the application, wherein the water-soluble polymer comprises polyvinyl alcohol or polyethylene glycol. For example, the sound absorbing material of the seventh scope of the patent application, wherein the polymer body further comprises an inorganic material of less than 10% by weight. For example, the sound absorbing material according to item 9 of the application, wherein the inorganic material comprises diatomaceous earth or activated carbon. For example, the sound absorbing material of the first scope of the patent application, wherein the density of the sound absorbing material is 300 kg / m ³ to 400 kg / m ³ . For example, the sound absorbing material in the first scope of the patent application, wherein the porosity of the sound absorbing material is 60% to 80%. For example, the sound absorption material of the first patent application range, wherein the sound absorption material measured at 500 Hz according to JIS A1405 method is 0.6 or more, and the sound absorption coefficient at 2000 Hz is 0.5 or more. For example, the sound-absorbing material according to the first patent application range, wherein the plurality of dendritic channels are formed by a freeze casting method.