A porosity gradient type porous material and a preparation method and application thereof

Abstract

The application provides a porosity gradient type porous material and a preparation method and application thereof, and the porosity gradient type porous material comprises microspheres and an organic resin adhesive. The porous material uses a low content of organic resin adhesive as an adhesive to form a point connection structure between the microspheres, and the density of the porous material is far lower than that of the same type of porous material prepared by a traditional method while the mechanical strength is maintained; the porous material of the application can realize porosity gradient, effectively improve the material impedance matching problem, solve the shortcomings of the traditional filling type porous material such as high density and poor sound absorption performance, and in addition, the porosity gradient type porous material can maintain the characteristics of high strength and processable cutting.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of porous materials, and particularly relates to a porosity gradient type porous material and a preparation method and application thereof. BACKGROUND

[0002] Sound-absorbing materials have gradually become a new research hotspot, which can not only solve the noise problem in life, but also provide reliable guarantee for underwater equipment with excellent stealth performance. Commonly used materials such as fiber materials, foam materials and porous ceramic materials are widely used as sound-absorbing materials due to their small density and simple forming. According to the sound absorption loss principle of porous materials, the sound absorption effect mainly depends on the consumption of sound waves in the material during transmission, and thus the sound absorption effect depends on the thickness of the material. In order to achieve good sound absorption effect, the thickness of the material needs to be increased, which not only increases the cost, but also reduces the space utilization. The impedance gradient type composite porous material can obtain a thin, light and efficient sound-absorbing material by constructing a gradient sound absorption function structure and improving the sound absorption efficiency. However, the conventional impedance gradient type composite porous material is prepared by bonding and curing of composite porous materials with different densities. The density of the adhesive used for bonding is much higher than that of the composite porous material, which forms a high-density interface layer at the bonding surface, thereby affecting the sound absorption performance of the composite porous material. SUMMARY

[0003] In order to overcome the above problems, the present application provides a porosity gradient type porous material and a preparation method and application thereof. The porous material has the characteristic of porosity gradient, and there is no obvious interface layer in the porous material. The preparation method can solve the problems of non-gradual porosity and interlayer bubble (obvious bubble between two connected layers) of the existing porous material.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0005] A composite porous material has n layers of porous material layers, n is an integer greater than or equal to 2, and the n layers of porous material layers have a porosity gradient.

[0006] Each layer of porous material layer comprises the following components:

[0007] Microspheres: 75-99wt%;

[0008] Organic resin adhesive: 1-25wt%;

[0009] The porosity gradient of the n layers of porous material layers means that the porosity gradually increases or gradually decreases from the first layer to the nth layer.

[0010] According to the present application, the porosity refers to the ratio of the pores between the microspheres to the volume of the porous material layer, i.e. the open porosity, which is related to the packing of the microspheres and the amount of the binder, and is irrelevant to whether the microspheres are hollow structures.

[0011] When the amount of the binder is constant, the microspheres are packed to reach a dense packing, and the porosity can be designed to be sequentially larger or smaller according to the dense packing coefficient, as shown in the following table. Figure 1 The larger the dense packing coefficient of the microspheres in the porous material layer is, the smaller the porosity of the prepared porous material layer is, and the smaller the dense packing coefficient of the microspheres in the porous material layer is, the larger the porosity of the prepared porous material layer is.

[0012] According to the present application, if the layer-to-layer bonding is used, an obvious interface will appear. The present application uses multiple pouring co-forming, and the self-resin curing will be connected together without the need for bonding, and therefore, there is no macroscopic interface between the porous materials of each layer.

[0013] According to the present application, the added mass M1 of the microspheres in each layer of the porous material layer is V x ξ x ρ1; wherein M1 is the mass of the microspheres, V is the volume of each layer of the porous material layer, ρ1 is the true density of the microspheres, and ξ is the dense packing coefficient of the microspheres.

[0014] The added mass M2 of the organic resin-based bonding agent in each layer of the porous material layer is M1 / ρ1 / λ x ρ2; wherein M1 is the mass of the microspheres, ρ1 is the true density of the microspheres, ρ2 is the density of the organic resin-based bonding agent, and λ is the volume ratio of the microspheres to the organic resin-based bonding agent, which is 100:1 to 9:1, for example, 100:1, 99:1, 95:1, 90:1, 85:1, 80:1, 75:1, 70:1, 65:1, 60:1, 55:1, 50:1, 45:1, 40:1, 35:1, 30:1, 25:1, 20:1, 15:1, 10:1, or 9:1.

[0015] According to the present application, the volume of each layer of the porous material layer is the same or different, which can be adjusted according to specific application occasions.

[0016] According to the present application, the types of the organic resin-based bonding agent in each layer of the porous material layer are the same or different, and are preferably the same.

[0017] According to the present application, the volume ratio of the microspheres to the organic resin-based bonding agent in each layer of the porous material layer is the same or different, and is preferably the same or close, wherein the close means that the volume deviation is less than 10%, so that there is no large fluctuation in density or porosity due to the high proportion of the bonding agent at the interface.

[0018] According to the present application, the porous material layer further comprises a diluent, and the amount of the diluent added is 10-100 times the mass of the organic resin-based adhesive, such as 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90 or 100 times.

[0019] According to the present application, the diluent in each porous material layer is the same or different, preferably the same.

[0020] According to the present application, the mass ratio of the diluent and the organic resin-based adhesive in each porous material layer is the same or different, preferably the same.

[0021] According to the present application, the microspheres are selected from glass microspheres, polymer microspheres, rubber microspheres, ceramic microspheres, carbon microspheres or metal microspheres, and further preferably, the microspheres can be the above-mentioned microspheres with a hollow structure, i.e. hollow glass microspheres, hollow polymer microspheres, hollow rubber microspheres, hollow ceramic microspheres, hollow carbon microspheres or hollow metal microspheres.

[0022] According to the present application, the diameter of the microspheres is 1-300 μm.

[0023] According to the present application, the organic resin-based adhesive comprises an organic resin and optionally an auxiliary agent; the organic resin is selected from at least one of an epoxy resin, a phenolic resin and a polyurethane resin. The auxiliary agent is for example selected from a crosslinking agent, a curing agent and the like.

[0024] In the present application, the organic resin-based adhesive can be cured at room temperature or high temperature, and after curing, the microspheres can be bonded.

[0025] According to the present application, the organic resin-based adhesive is selected from at least one of an epoxy resin-based adhesive, a phenolic resin-based adhesive and a polyurethane resin-based adhesive.

[0026] Exemplarily, the epoxy resin-based adhesive is for example a market product with the trade name HY-914 (Tianjin Haiyan) and JW-1 (Shanghai Huayi), the phenolic resin-based adhesive is for example a market product with the trade name PR-50232 and PR-23 (Jiayou Electrical Wood Co., Ltd.), and the polyurethane resin-based adhesive is for example a market product with the trade name UK8103 (Germany Hanqiao) and SA724A (China Wanhua); other types of products of different models and manufacturers can also be selected.

[0027] According to the present application, the composite porous material is a porosity-gradually-changing porous material.

[0028] According to the present application, the apparent density of the composite porous material is 0.1-0.9 g / cm 3 , such as 0.1-0.5 g / cm​3 .

[0029] According to the application, the porosity of the composite porous material is in the range of 20-60%, which is increased or decreased.

[0030] According to the application, the difference of the porosity of the two layers of porous material is 0.1-20%.

[0031] According to the application, the porosity of each layer of porous material is calculated by the following method:

[0032] Δ=(1 / ρ3-1 / ρ4) / (1 / ρ3);

[0033] Wherein, ρ4 is the true density of each layer of porous material, and ρ3 is the apparent density of each layer of porous material.

[0034] Wherein, the test method of the true density of each layer of porous material refers to the standard GB / T 5071-2013, and the test method of the apparent density of each layer of porous material refers to the standard GB / T 6343-2009.

[0035] According to the application, the average sound absorption coefficient of the composite porous material is 0.4-0.9 (test environment: air, test frequency band: 200-30 kHz).

[0036] Wherein, the test method of the average sound absorption coefficient refers to the standard GB / T 18696.1-2004.

[0037] The application also provides a preparation method of the composite porous material, which comprises the following steps:

[0038] (1) The microspheres, the organic resin adhesive and optionally the diluent are mixed by the following method to obtain n mixed systems;

[0039] Wherein, the mass of the microspheres in each layer of porous material is obtained according to the following calculation principle:

[0040] M1=V×ξ×ρ1; M1 is the mass of the microspheres, V is the volume of each layer of porous material, ρ1 is the true density of the microspheres, and ξ is the dense packing coefficient of the microspheres;

[0041] Wherein, the mass of the organic resin adhesive in each layer of porous material is obtained according to the following calculation principle:

[0042] M2=M1 / ρ1 / λ×ρ2, wherein M1 is the mass of the microspheres, ρ1 is the true density of the microspheres, ρ2 is the density of the organic resin adhesive, and λ is the volume ratio of the microspheres to the organic resin adhesive, which is 100:1-9:1;

[0043] (2) Pour the n mixtures from step (1) into the mold in the order of layer 1 to layer n and dry them, optionally allowing the diluent to evaporate, then heat and cure them, and demold them.

[0044] According to the present invention, the diluent is selected from volatile organic solvents, and the volatile organic solvent is selected from at least one of ethanol, acetone, and methanol.

[0045] According to the present invention, in step (1), the viscosity of the organic resin adhesive is 20 to 15000 cp (25°C).

[0046] According to the present invention, in step (2), since the viscosity of the n mixed systems in step (1) is relatively high, no penetration will occur when they are poured into the mold in sequence.

[0047] According to the present invention, in step (2), the masses of the n mixed systems poured into the mold in sequence may be the same or different.

[0048] According to the present invention, in step (2), the drying and curing are carried out in an electric thermostatic drying oven.

[0049] According to the present invention, in step (2), drying can be carried out by controlling the drying temperature and the circulating airflow rate. The temperature of the oven is 15 to 200°C, the circulating airflow rate in the oven is 0.5 to 10 m / s, the drying time is, for example, 30 min to 48 h, the curing time is, for example, 30 min to 72 h, and the oven is demolded after cooling to below 30°C.

[0050] For example, the mixture is placed in a forced-air drying oven at a temperature of 50°C and a forced-air circulating airflow speed of 5 m / s for a period of time, such as 4 hours; then the oven temperature is raised to 120°C and cured for a period of time, such as 24 hours, and then cooled to below 30°C for demolding.

[0051] The present invention also provides the use of the above-mentioned composite porous material in the field of sound absorption.

[0052] Preferably, it is used in the fields of building sound absorption and underwater sound absorption.

[0053] According to the present invention, the composite porous material is used to prepare sound-absorbing materials.

[0054] The beneficial effects of this invention are:

[0055] This invention provides a porous material with gradually changing porosity, its preparation method, and its applications. The porous material comprises microspheres and an organic resin binder. Because it uses a low content of organic resin binder, a point-connected structure is formed between the microspheres, resulting in a density significantly lower than that of similar porous materials prepared by traditional methods while maintaining high mechanical strength. This invention employs a solvent evaporation method to prepare the porous material with gradually changing porosity, which not only significantly reduces the amount of binder used while ensuring microsphere adhesion but also forms a relatively uniform bond between the microspheres. There is no obvious transition layer between the layers of the composite porous material with different porosities. The porous material of this invention can achieve a gradual change in porosity, effectively improving the impedance matching problem of the material and solving the shortcomings of traditional filled porous materials, such as high density and poor sound absorption performance. Furthermore, the porous material with gradually changing porosity maintains high strength and machinability. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the structure of the composite porous material according to a preferred embodiment of the present invention.

[0057] Figure 2 The value represents the uniaxial compressive strength of the first layer in the composite porous material of Example 1.

[0058] Figure 3 The uniaxial compressive strength is the third layer in the composite porous material of Example 3.

[0059] Figure 4 The uniaxial compressive strength is the first layer in the composite porous material of Example 4.

[0060] Figure 5 The uniaxial compressive strength is the fifth layer in the composite porous material of Example 5.

[0061] Figure 6 The uniaxial compressive strength is the first layer in the composite porous material of Example 6. Detailed Implementation

[0062] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0063] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0064] Example 1:

[0065] A three-layer composite porous material with gradually varying porosity was prepared, with porosities designed to be 36%, 37%, and 38% respectively, from low to high. Each layer of the composite porous material occupied 1000 cm³. 3 .

[0066] The preparation steps are as follows: Hollow glass microspheres and binder HY-914 (density 1.06 g / cm³) are used in the preparation process. 3 The amounts of acetone and diluent are shown in Table 1 below. The components were stirred and mixed evenly according to the mass percentages shown in Table 1 to obtain three mixed systems. Samples were taken for curing and testing of their true density, apparent density, and porosity. The uniaxial compressive strength of the first layer was also tested.

[0067] Table 1

[0068]

[0069] The three mixtures were poured sequentially into a mold, and the mixtures were placed in a forced-air drying oven at 35°C with a circulating airflow rate of 0.5 m / s for 12 hours. The oven temperature was then increased to 85°C for curing for 24 hours. After cooling to below 30°C, the mixture was demolded, yielding a composite porous material with a porosity gradient from 38% to 36%. The apparent density of the composite porous material was measured to be 0.1485 g / cm³. 3 Its average sound absorption coefficient is 0.75, and the uniaxial compressive strength of the first layer is 1.48 MPa (e.g., Figure 2 ).

[0070] Example 2:

[0071] A four-layer composite porous material with gradually varying porosities was prepared, with porosities designed from low to high as 32%, 34%, 36%, and 38%, respectively. Each layer of the composite porous material occupied 1000 cm³. 3 .

[0072] The preparation steps are as follows: Hollow glass microspheres and binder HY-914 (density 1.06 g / cm³) are used in the preparation process. 3 The amounts of acetone and diluent are shown in Table 2 below. The components were stirred and mixed evenly according to the mass percentages shown in Table 2 to obtain four mixed systems. Samples were taken for curing and testing of their true density, apparent density, and porosity. The uniaxial compressive strength of the first layer was also tested.

[0073] Table 2

[0074]

[0075] The four mixtures were sequentially poured into molds, and the mixtures were placed in a forced-air drying oven at 35°C with a circulating airflow rate of 1.5 m / s for 24 hours. Subsequently, the oven temperature was raised to 85°C for curing for 36 hours. After cooling to below 30°C, the mixture was demolded, yielding a composite porous material with a porosity gradient from 38% to 32%. The apparent density of the composite porous material was measured to be 0.2390 g / cm³. 3 The average sound absorption coefficient was measured to be 0.69, and the uniaxial compressive strength of the first layer was 1.48 MPa.

[0076] Example 3:

[0077] A three-layer composite porous material with gradually varying porosity was prepared, with porosities designed to be 34%, 36%, and 38% respectively, from low to high. Each layer of the composite porous material occupied 1000 cm³. 3 .

[0078] The preparation steps are as follows: Hollow glass microspheres and binder UK8103 (density 1.22 g / cm³) are used in the preparation process. 3 The amounts of acetone and diluent are shown in Table 3 below. The components were stirred and mixed evenly according to the mass percentages shown in Table 3 to obtain three mixed systems. Samples were taken for curing and testing of their true density, apparent density, and porosity. The uniaxial compressive strength of the first and third layers was also tested.

[0079] Table 3

[0080]

[0081] The three mixtures were poured sequentially into a mold, and the mixtures were placed in a forced-air drying oven at 50°C with a circulating airflow rate of 2 m / s for 12 hours. The oven temperature was then increased to 120°C for curing for 24 hours. After cooling to below 30°C, the mixture was demolded, yielding a composite porous material with a porosity gradient from 38% to 34%. Due to the use of a foaming adhesive, the final material porosity is higher than that of the previously described embodiment. The apparent density of the composite porous material was measured to be 0.1839 g / cm³. 3 The average sound absorption coefficient was measured to be 0.77, the uniaxial compressive strength of the first layer was 1.32 MPa, and the uniaxial compressive strength of the third layer was 2.73 MPa (e.g., ...). Figure 3 ).

[0082] Example 4:

[0083] A three-layer composite porous material with gradually varying porosity was prepared, with porosities designed from low to high as 32%, 42%, and 52%, respectively. Each layer of the composite porous material occupied 1000 cm³. 3 .

[0084] The preparation steps are as follows: Hollow glass microspheres and binder PR-50232 (density 1.14 g / cm³) are used in the preparation process. 3 The amounts of ethanol and diluent are shown in Table 4 below. The components were stirred and mixed evenly according to the mass percentages shown in Table 4 to obtain three mixed systems. Samples were taken for curing and testing of their true density, apparent density, and porosity. The uniaxial compressive strength of the first layer was also tested.

[0085] Table 4

[0086]

[0087] The three mixtures were poured sequentially into a mold, and the mixtures were placed in a forced-air drying oven at 45°C with a circulating airflow rate of 0.5 m / s for 12 hours. The oven temperature was then raised to 105°C for curing for 12 hours. After cooling to below 30°C, the mixture was demolded, yielding a composite porous material with a porosity gradient from 52% to 32%. Due to the use of a foaming adhesive, the final material porosity was higher than that of the previously described embodiment. The apparent density of the composite porous material was measured to be 0.1743 g / cm³. 3 The average sound absorption coefficient was measured to be 0.81, and the uniaxial compressive strength of the first layer was 0.94 MPa (e.g., Figure 4 ).

[0088] Example 5:

[0089] Five layers of composite porous material with gradually varying porosities were prepared, with porosities designed from low to high as 30%, 32%, 34%, 36%, and 38%, respectively. Each layer of composite porous material occupied 1000 cm². 3 .

[0090] The preparation steps are as follows: Hollow glass microspheres and binder PR-23 (density 1.10 g / cm³) are used in the preparation process. 3 The amounts of ethanol and diluent are shown in Table 5 below. The components were stirred and mixed evenly according to the mass percentages shown in Table 5 to obtain five mixed systems. Samples were taken for curing and testing of their true density, apparent density, and porosity. The uniaxial compressive strength of the first and fifth layers was also tested.

[0091] Table 5

[0092]

[0093]

[0094] The five mixtures were poured sequentially into a mold, and the mixtures were placed in a forced-air drying oven at 50°C with a circulating airflow rate of 0.5 m / s for 12 hours. Subsequently, the oven temperature was increased to 135°C for curing for 24 hours. After cooling to below 30°C, the mixture was demolded, yielding a composite porous material with a porosity gradient from 38% to 30%. The apparent density of the composite porous material was measured to be 0.2794 g / cm³. 3 The average sound absorption coefficient was measured to be 0.83, the uniaxial compressive strength of the first layer was 1.71 MPa, and the uniaxial compressive strength of the fifth layer was 3.16 MPa (e.g., Figure 5 ).

[0095] Example 6:

[0096] A three-layer composite porous material with gradually varying porosity was prepared, with porosities designed to be 34%, 36%, and 38% respectively, from low to high. Each layer of the composite porous material occupied 250 cm². 3 500cm 3 1000cm 3 .

[0097] The preparation steps are as follows: Hollow glass microspheres and binder UK8103 (density 1.22 g / cm³) are used in the preparation process. 3 The amounts of acetone and diluent are shown in Table 6 below. The components were stirred and mixed evenly according to the mass percentages shown in Table 6 to obtain three mixed systems. Samples were taken for curing and testing of their true density, apparent density, and porosity. The uniaxial compressive strength of the first layer was also tested.

[0098] Table 6

[0099]

[0100] The three mixtures were poured sequentially into a mold, and the mixtures were placed in a forced-air drying oven at 45°C with a circulating airflow rate of 5 m / s for 5 hours. The oven temperature was then increased to 110°C for curing for 12 hours. After cooling to below 30°C, the mixture was demolded, yielding a composite porous material with a porosity gradient from 38% to 34%. Due to the use of a foaming adhesive, the final material porosity is higher than that of the previously described embodiment. The apparent density of the composite porous material was measured to be 0.1411 g / cm³. 3 The average sound absorption coefficient was measured to be 0.70, and the uniaxial compressive strength of the first layer was 1.52 MPa (e.g., Figure 6 ).

[0101] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite porous material, wherein, The composite porous material has n porous material layers, where n is an integer greater than or equal to 2, and the porosity of the n porous material layers gradually changes. Each porous material layer comprises the following components: Microspheres: 75~99wt% Organic resin adhesives: 1~25wt%; The gradual change in porosity of the n-layer porous material means that the porosity increases or decreases sequentially from the first layer to the nth layer. The composite porous material is prepared by the following method: (1) Mix microspheres and organic resin adhesives as follows to obtain n mixed systems; The mass of the microspheres in each porous material layer is calculated according to the following principles: M1 = V × ξ × ρ1; M1 is the mass of the microsphere, V is the volume of each porous material layer, ρ1 is the true density of the microsphere, and ξ is the compaction coefficient of the microsphere. The mass of the organic resin adhesive in each porous material layer is calculated according to the following principles: M2 = M1 / ρ1 / λ×ρ2, where M1 is the mass of the microspheres; ρ1 is the true density of the microspheres; ρ2 is the density of the organic resin adhesive; and λ is the volume ratio of the microspheres to the organic resin adhesive, which is 100:1-9:

1. (2) Pour the n mixed systems from step (1) into the mold in the order of layer 1 to layer n for drying, then heat and cure, and demold. In step (2), drying is carried out by controlling the drying temperature and the airflow velocity of the circulating air. The temperature of the oven is 15~200℃, the airflow velocity of the circulating air in the oven is 0.5~10m / s, the drying time is 30min~48h, the curing time is 30min~72h, and the mold is removed after cooling to below 30℃.

2. The composite porous material according to claim 1, wherein, Each porous material layer also includes a diluent, the amount of which is 10 to 100 times the mass of the organic resin adhesive.

3. The composite porous material according to claim 1, wherein, The microspheres are selected from glass microspheres, polymer microspheres, rubber microspheres, ceramic microspheres, carbon microspheres, or metal microspheres.

4. The composite porous material according to claim 1, wherein, The microspheres are selected from hollow glass microspheres, hollow polymer microspheres, hollow rubber microspheres, hollow ceramic microspheres, hollow carbon microspheres, or hollow metal microspheres.

5. The composite porous material according to claim 1, wherein, The organic resin adhesive is selected from at least one of epoxy resin adhesives, phenolic resin adhesives, and polyurethane resin adhesives.

6. The composite porous material according to claim 2, wherein, The diluent is selected from volatile organic solvents, and the volatile organic solvent is selected from at least one of ethanol, acetone, and methanol.

7. The composite porous material according to any one of claims 1-6, wherein, The apparent density of the composite porous material is 0.1~0.9 g / cm³. 3 ; And / or, the porosity of the porous material layer is in the range of 20-60%; And / or, the porosity difference between two adjacent porous material layers is 0.1% to 20%; And / or, the average sound absorption coefficient of the composite porous material is 0.4~0.

9.

8. Use of the composite porous material according to any one of claims 1-7, for the purpose of sound absorption.

9. The use according to claim 8, for use in the fields of building sound absorption and underwater sound absorption.

10. The use according to claim 8, wherein the composite porous material is used to prepare a sound-absorbing material.

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