A foamed sound-absorbing material with high open porosity, its preparation method and application

Abstract

The application relates to the technical field of sound-absorbing materials, in particular to a foamed sound-absorbing material with a high open porosity structure, a preparation method and application of the foamed sound-absorbing material, wherein the raw materials of the foamed sound-absorbing material include one or more of polylactic acid, polybutylene adipate terephthalate and polyhydroxyalkanoate, the density of the foamed sound-absorbing material is 0.04-0.08 g / cm 3 , and the open porosity of the foamed sound-absorbing material is higher than 60%. The foamed sound-absorbing material with high open porosity can be prepared without adding other fillers and auxiliaries, the foamed sound-absorbing material has the characteristics of high open porosity and small density, and the foamed sound-absorbing material can realize efficient absorption of sound waves within the thickness range of 10 mm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sound-absorbing materials, in particular to a foamed sound-absorbing material with high open porosity, a preparation method and application thereof. BACKGROUND

[0002] The existing sound-absorbing materials mainly consist of two categories of resonant sound-absorbing materials and foamed sound-absorbing materials. The foamed sound-absorbing materials have great development potential due to low cost, mature processing technology, light weight, and wide application range. When sound waves hit a porous material, sound energy will be reflected, absorbed, and transmitted. After the sound waves enter the foamed material, the air in the bubble cavity vibrates. Due to the complex and tortuous pore wall, the air vibration rubs and adheres to the pore wall, causing part of the sound energy to be converted into heat energy and dissipated, resulting in energy loss. The thickness of the material also has a great influence on the sound-absorbing performance. The greater the thickness of the material, the higher the cost of its application.

[0003] In the prior art, for example, patent CN115966192A provides a cavity resonant sound-absorbing structure performance improvement method based on lattice reflection. This method is based on the basic principle of band gap generated by phononic crystal local resonance. By increasing the lattice outer frame, changing the volume ratio of the lattice outer frame to the cavity resonant sound-absorbing structure, and adjusting the structure geometric parameters of the lattice outer frame, a double-resonance system is generated, and then an acoustic lattice with double sound-absorbing peak values in a certain working frequency range is obtained, thereby improving the sound-absorbing performance of the original cavity resonant sound-absorbing structure. However, the process of establishing the lattice outer frame and the operation are complex, and the requirements for each parameter are strict. For example, CN118725238A provides a polyurethane flexible foamed sound-absorbing material, a sandwich structure sound-absorbing material, and a preparation method. The foamed sound-absorbing material prepared by this method has good waterproofness and pressure resistance and has lower density and thickness. However, this method uses polytetrahydrofuran as raw material, which has low toxicity. In the high-temperature processing process, polytetrahydrofuran may decompose and release tetrahydrofuran monomer or other low-molecular-weight compounds, which may have a stimulating effect on the respiratory tract. SUMMARY

[0004] The present application is carried out to solve the above problems, and aims to provide a foamed sound-absorbing material with high open porosity, a preparation method and application thereof.

[0005] In a first aspect of the present application, a foamed sound-absorbing material with high open porosity is provided, characterized in that,

[0006] The raw material of the foamed sound-absorbing material includes one or more of polylactic acid, polybutylene adipate / terephthalate, and polyhydroxyalkanoate. The density of the foamed sound-absorbing material is 0.04-0.08 g / cm 3 The open porosity of the foamed sound-absorbing material is higher than 60%.

[0007] The present application uses biobased degradable polymers such as polylactic acid, polybutylene adipate / terephthalate and polyhydroxyalkanoate as raw materials to prepare a foamed sound-absorbing material, which has the advantages of environmental protection, biodegradability, carbon emission reduction, excellent sound-absorbing performance, processing friendliness, good mechanical properties and sustainability, etc. The present application can use a supercritical carbon dioxide physical foaming method to prepare a polymer foamed sound-absorbing material with high open porosity without adding other fillers and additives. The foamed sound-absorbing material has the advantages of simple preparation process, environmental protection, non-toxicity, high open porosity, small density, etc. Due to the high open porosity structure of the foamed sound-absorbing material, sound waves can more effectively enter the interior of the foamed sound-absorbing material, promoting the conversion and dissipation of sound energy, thereby improving the overall sound absorption coefficient. Therefore, the foamed sound-absorbing material can achieve efficient absorption of sound waves within a thickness range of 10 mm.

[0008] The present application can control the foaming conditions to adjust and optimize the pore size and open porosity of the foamed material, achieve superior acoustic performance, not only improve the sound absorption effect, but also bring advantages in lightweight and cost-effectiveness, and has a wide application prospect, which can meet the needs of various acoustic applications such as architectural acoustics, automotive interiors and electronic equipment fields.

[0009] In a second aspect, the present application provides a method for preparing a foamed sound-absorbing material with high open porosity as described in the first aspect, characterized in that it comprises the following steps:

[0010] (1) drying the raw materials and then pressing them to obtain a pressed sample;

[0011] (2) using a supercritical carbon dioxide physical foaming method, soaking the pressed sample in a foaming container and then foaming, and then unloading to obtain the foamed sound-absorbing material, wherein the soaking temperature is higher than the foaming temperature.

[0012] In the embodiments, the presence of water can affect the processing performance of the raw materials and the quality of the final product, such as producing bubbles during processing or affecting the melting behavior of the material, so the water in the raw materials is removed by drying the raw materials.

[0013] Further, the dried raw materials are pressed into uniform sheets, which helps to improve the density of the raw materials and provide a better substrate for the foaming process, so as to facilitate the subsequent foaming process.

[0014] Further, the supercritical carbon dioxide physical foaming method is adopted, the pressure and temperature in the foaming container are controlled to be higher than the critical point of carbon dioxide, the foaming process is divided into two steps of high-temperature soaking and low-temperature foaming by adopting the intermittent foaming method, and the soaking temperature is controlled to be higher than the foaming temperature. The flowability of the polymer melt in the soaking process is improved by high-temperature soaking, the diffusion rate of carbon dioxide is accelerated, carbon dioxide is uniformly distributed in the melt, the solubility of carbon dioxide in the polymer melt is increased, the foaming speed is better controlled by low-temperature foaming, more bubble nuclei are formed in the foaming process, and a more uniform foam structure is formed, so that more bubbles are generated during pressure reduction foaming, the foaming efficiency is improved, the soaking time is shortened, the production efficiency is improved, the foaming process and the foam structure are controlled, and the mechanical properties, such as the compressive strength and the elastic modulus, of the foamed sound-absorbing material are improved.

[0015] In some embodiments, the drying temperature in step (1) is 40-60℃, and the drying time is 6-12h.

[0016] In some embodiments, the tabletting process in step (1) is performed by using a flat plate vulcanizing machine.

[0017] In some embodiments, the tabletting conditions in step (1) are as follows: 3-5 MPa of pressure increase, 1-5 min of time; 8-10 MPa of pressure maintenance, 2-5 min of time.

[0018] In the embodiments, 3-5 MPa of pressure increase is used to quickly reach the pressing pressure, and 8-10 MPa of pressure maintenance is used to ensure that the structure of the tablet sample is uniform and defect-free.

[0019] In some embodiments, the soaking temperature in step (2) is 130-160℃.

[0020] In some embodiments, the foaming temperature in step (2) is 100-120℃.

[0021] In some embodiments, step (2) specifically comprises the following steps: after the tablet sample is placed in a foaming container and treated by soaking at the soaking temperature under 11-16 MPa of constant pressure for 30-180 min, the soaking temperature is adjusted to the foaming temperature, the foaming temperature is maintained for 15-180 min to perform foaming, and the foaming is completed to obtain the foamed sound-absorbing material by unloading pressure.

[0022] In the embodiments, the tablet sample is placed in a foaming kettle, the gas in the tablet sample is dissolved under 11-16 MPa of high pressure to prepare for the foaming process, the temperature of the foaming kettle is increased to 130-160℃, the tablet sample is melted at the temperature, and the solubility of the gas in the tablet sample is increased, so that bubbles are formed in the subsequent unloading process.

[0023] Further, the foaming kettle temperature is reduced to 100-120 DEG C and kept for 15-180 min to control the melt viscosity of the tablet sample, so that the bubble structure can be stably formed when the pressure is released. Further, after the holding is completed, the pressure is released, and the pressure is released instantaneously, which causes the gas dissolved in the melt of the tablet sample to expand rapidly, forming bubbles, thereby obtaining the foamed sound-absorbing material.

[0024] In a third aspect, the application provides a use of the foamed sound-absorbing material with high open porosity, characterized in that the foamed sound-absorbing material of the first aspect or the foamed sound-absorbing material prepared by the preparation method of the second aspect is used for noise prevention.

[0025] By implementing the above technical solutions, the application has the following beneficial effects:

[0026] The foamed sound-absorbing material is prepared by using biobased degradable polymers such as polylactic acid, polybutylene adipate / terephthalate, and polyhydroxyalkanoate as raw materials, has the advantages of environmental protection, biodegradability, carbon emission reduction, excellent sound absorption performance, processing friendliness, good mechanical properties, and sustainability, and the like, and can be prepared without adding other fillers and additives to obtain a polymer foamed sound-absorbing material with high open porosity. The foamed sound-absorbing material has the advantages of simple preparation process, environmental protection, and non-toxicity, and the prepared foamed sound-absorbing material has the characteristics of high open porosity and small density. Due to the structure of high open porosity of the foamed sound-absorbing material, the sound wave can enter the inside of the foamed sound-absorbing material more effectively, promoting the conversion and dissipation of sound energy, thereby improving the overall sound absorption coefficient. Therefore, the foamed sound-absorbing material can realize efficient absorption of sound waves in the thickness range of 10 mm.

[0027] The application adjusts and optimizes the pore size and open porosity of the foamed material by controlling the foaming conditions, realizes superior acoustic performance, not only improves the sound absorption effect, but also brings advantages in lightweight and cost-effectiveness, has a wide application prospect, and can meet the needs of various acoustic applications, such as architectural acoustics, automotive interiors, and electronic equipment fields. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Example 1 (left) and Example 4 (right) polymer foamed material electron microscope graph;

[0029] Figure 2 Example 4 high open porosity foamed material pore size;

[0030] Figure 3 Sound absorption test curve of the foamed sound-absorbing material prepared in each example;

[0031] Figure 4 Foamed sound-absorbing material preparation flow chart. DETAILED DESCRIPTION

[0032] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is specifically described below in combination with examples and drawings.

[0033] Example 1

[0034] First, the pure PLA powder was placed in an oven at 40°C and dried for 8 hours to dry the moisture in the raw material. The dried polylactic acid raw material was pressed into a tablet using a flat vulcanizing machine. The conditions were 4 MPa of pressure increase, 1 min of time, 10 MPa of pressure maintenance, and 2 min of time. A polylactic acid tablet sample was obtained. Intermittent foaming was performed using supercritical carbon dioxide foaming. First, the temperature of the foaming kettle was raised to 140°C, and the obtained polylactic acid sample was placed in the foaming kettle. Carbon dioxide was delivered into the foaming kettle by an air compressor, and the pressure in the foaming kettle was 13.8 MPa. The sample was soaked at this temperature and pressure for 60 min. Then, the temperature of the foaming kettle was lowered to 100°C, and the sample was kept at this temperature for 30 min. After the heat preservation was completed, the pressure was released instantaneously, and a polymer foaming sample was obtained.

[0035] Example 2

[0036] First, the pure PLA powder was placed in an oven at 40°C and dried for 8 hours to dry the moisture in the raw material. The dried polylactic acid raw material was pressed into a tablet using a flat vulcanizing machine. The conditions were 4 MPa of pressure increase, 1 min of time, 10 MPa of pressure maintenance, and 2 min of time. A polylactic acid tablet sample was obtained. Intermittent foaming was performed using supercritical carbon dioxide foaming. First, the temperature of the foaming kettle was raised to 140°C, and the obtained polylactic acid sample was placed in the foaming kettle. Carbon dioxide was delivered into the foaming kettle by an air compressor, and the pressure in the foaming kettle was 13.8 MPa. The sample was soaked at this temperature and pressure for 90 min. Then, the temperature of the foaming kettle was lowered to 100°C, and the sample was kept at this temperature for 30 min. After the heat preservation was completed, the pressure was released instantaneously, and a polymer foaming sample was obtained.

[0037] Example 3

[0038] Firstly, the pure PLA powder was put into an oven at 40 °C and dried for 8 hours to dry the moisture in the raw material; the dried polylactic acid raw material was pressed into a sheet using a flat vulcanizing machine; the conditions were 4 MPa of pressure increase, 1 min of time; 10 MPa of pressure holding, 2 min of time; a polylactic acid sheet sample was obtained; intermittent foaming was used for supercritical carbon dioxide foaming, firstly, the temperature of the foaming kettle was raised to 140 °C, the obtained polylactic acid sample was put into the foaming kettle, carbon dioxide was delivered into the foaming kettle by an air compressor, the pressure in the foaming kettle was 13.8 MPa, soaking was carried out at the temperature and pressure for 120 min, then the temperature of the foaming kettle was reduced to 100 °C and kept for 30 min; after the end of the heat preservation, the pressure was released instantaneously, and a polymer foaming sample was obtained.

[0039] Example 4

[0040] Firstly, the pure PLA powder was put into an oven at 40 °C and dried for 8 hours to dry the moisture in the raw material; the dried polylactic acid raw material was pressed into a sheet using a flat vulcanizing machine; the conditions were 4 MPa of pressure increase, 1 min of time; 10 MPa of pressure holding, 2 min of time; a polylactic acid sheet sample was obtained; intermittent foaming was used for supercritical carbon dioxide foaming, firstly, the temperature of the foaming kettle was raised to 147 °C, the obtained polylactic acid sample was put into the foaming kettle, carbon dioxide was delivered into the foaming kettle by an air compressor, the pressure in the foaming kettle was 13.8 MPa, soaking was carried out at the temperature and pressure for 60 min, then the temperature of the foaming kettle was reduced to 100 °C and kept for 30 min; after the end of the heat preservation, the pressure was released instantaneously, and a polymer foaming sample was obtained.

[0041] Example 5

[0042] Firstly, the pure PLA powder was put into an oven at 40 °C and dried for 8 hours to dry the moisture in the raw material; the dried polylactic acid raw material was pressed into a sheet using a flat vulcanizing machine; the conditions were 4 MPa of pressure increase, 1 min of time; 10 MPa of pressure holding, 2 min of time; a polylactic acid sheet sample was obtained; intermittent foaming was used for supercritical carbon dioxide foaming, firstly, the temperature of the foaming kettle was raised to 147 °C, the obtained polylactic acid sample was put into the foaming kettle, carbon dioxide was delivered into the foaming kettle by an air compressor, the pressure in the foaming kettle was 13.8 MPa, soaking was carried out at the temperature and pressure for 90 min, then the temperature of the foaming kettle was reduced to 100 °C and kept for 30 min; after the end of the heat preservation, the pressure was released instantaneously, and a polymer foaming sample was obtained.

[0043] Example 6

[0044] Firstly, pure PLA powder was put into an oven at 40 °C and dried for 8 hours to dry the moisture in the raw material; the dried polylactic acid raw material was pressed into a sheet using a flat vulcanizing machine; the conditions were 4 MPa pressure increase, 1 min; 10 MPa pressure holding, 2 min; to obtain a polylactic acid sheet sample; using supercritical carbon dioxide intermittent foaming, first, the temperature of the foaming kettle was raised to 147 °C, the obtained polylactic acid sample was put into the foaming kettle, carbon dioxide was delivered into the foaming kettle by an air compressor, the pressure in the foaming kettle was 13.8 MPa, soaked at this temperature and pressure for 120 min, then the temperature of the foaming kettle was reduced to 100 °C and kept for 30 min; after the end of the heat preservation, the pressure was released, the pressure was released instantly, and the polymer foaming sample was obtained.

[0045] Example 7

[0046] Firstly, pure PLA powder was put into an oven at 40 °C and dried for 8 hours to dry the moisture in the raw material; the dried polylactic acid raw material was pressed into a sheet using a flat vulcanizing machine; the conditions were 4 MPa pressure increase, 1 min; 10 MPa pressure holding, 2 min; to obtain a polylactic acid sheet sample; using supercritical carbon dioxide intermittent foaming, first, the temperature of the foaming kettle was raised to 147 °C, the obtained polylactic acid sample was put into the foaming kettle, carbon dioxide was delivered into the foaming kettle by an air compressor, the pressure in the foaming kettle was 13.8 MPa, soaked at this temperature and pressure for 120 min, then the temperature of the foaming kettle was reduced to 120 °C and kept for 30 min; after the end of the heat preservation, the pressure was released, the pressure was released instantly, and the polymer foaming sample was obtained.

[0047] Example 8

[0048] Firstly, pure PBAT and PLA powder were put into an oven at 40 °C and dried for 8 hours to dry the moisture in the raw material, PBAT and PLA were melt blended according to the weight ratio of 4:6 using a Hake torque rheometer to obtain a PBAT / PLA composite material; the PBAT / PLA composite material was pressed into a sheet using a flat vulcanizing machine; the conditions were 4 MPa pressure increase, 1 min; 10 MPa pressure holding, 2 min; to obtain a polylactic acid sheet sample; using supercritical carbon dioxide foaming constant temperature foaming method, the temperature of the foaming kettle was raised to 70 °C, the obtained PBAT / PLA composite material sample was put into the foaming kettle, carbon dioxide was delivered into the foaming kettle by an air compressor, the pressure in the foaming kettle was 13.8 MPa, soaked at this temperature and pressure for 120 min, then the temperature of the foaming kettle was reduced to 100 °C and kept for 30 min; after the end of the heat preservation, the pressure was released, the pressure was released instantly, and the polymer foaming sample was obtained.

[0049] Performance test

[0050] Open cell rate test: vacuum density tester UPYC 1200e, USA, Quantachrome

[0051] Density test: solid-liquid density meter JHY-S300, Jinheyuan

[0052] Table 1: Open cell rate and density test data table in examples

[0053] Openness Density (g / cm 3 )]]> Example 1 63.10% 0.070 Example 2 60.00% 0.058 Example 3 61.09% 0.045 Example 4 61.87% 0.055 Example 5 69.31% 0.045 Example 6 70.87% 0.043 Example 7 63.23% 0.049 Example 8 60.02% 0.103

[0054] According to Table 1, compared with Examples 1-8, the density of the foamed material prepared in Example 8 is larger because the soaking temperature and the foaming temperature are consistent in the constant temperature foaming method.

[0055] The above embodiments are preferred cases of the present application and are not intended to limit the protection scope of the present application.

Claims

1. A foamed sound absorbing material having a high open porosity, characterized in that, The raw material of the foamed sound-absorbing material is one or more of polylactic acid, polybutylene adipate / terephthalate, and polyhydroxyalkanoate, the density of the foamed sound-absorbing material is 0.04-0.08 g / cm 3 , and the open porosity of the foamed sound-absorbing material is higher than 60%; the preparation method of the foamed sound-absorbing material comprises the following steps: (1) drying the raw material and then performing tabletting to obtain a tablet sample; (2) using a supercritical carbon dioxide physical foaming method, immersing the tablet sample in a foaming container for treatment and then foaming to obtain the foamed sound-absorbing material, wherein the immersion temperature is higher than the foaming temperature; In the step (2), the immersion temperature is 130-160 DEG C, and the foaming temperature is 100-120 DEG C. The step (2) specifically comprises: immersing the tablet sample in the foaming container at the immersion temperature for 30-180 min under a constant pressure of 11-16 MPa, adjusting to the foaming temperature, keeping for 15-180 min for foaming, and then releasing the pressure to obtain the foamed sound-absorbing material.

2. The foamed sound absorbing material of claim 1, wherein, In the step (1), the drying temperature is 40-60 DEG C, and the drying time is 6-12 h.

3. The foamed sound absorbing material of claim 1, wherein, In the step (1), a flat plate vulcanizing machine is used for tabletting.

4. The foamed sound absorbing material of claim 3, wherein, In the step (1), the tabletting conditions are: 3-5 MPa for 1-5 min for pressurizing, and 8-10 MPa for 2-5 min for pressure keeping.

5. Use of a foamed sound-absorbing material having a high open porosity, characterized in that The foamed sound-absorbing material according to any one of claims 1-4 is used for noise prevention.

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