CN113306238B

CN113306238B - Processing technology of environment-friendly sound insulation pad

Info

Publication number: CN113306238B
Application number: CN202011518903.0A
Authority: CN
Inventors: 何红胜
Original assignee: Wuhu Shangwei Auto Accessories Co ltd
Current assignee: Wuhu Shangwei Auto Accessories Co ltd
Priority date: 2020-12-21
Filing date: 2020-12-21
Publication date: 2022-09-30
Anticipated expiration: 2040-12-21
Also published as: CN113306238A

Abstract

The invention discloses a processing technology of an environment-friendly sound insulation pad, which comprises the steps of porous PET fiber spinning film forming, mesoporous fiber film spinning film forming and multilayer film compounding, wherein the PET fibers are enabled to be in a porous shape by changing condition parameters during electrostatic spinning, and a two-stage pore mechanism is formed by nanometer micropores in the PET fibers and micron-scale pores formed by fiber interweaving, so that the sound absorption capacity of the material is effectively improved under the condition of not increasing the thickness of the material. Adding SiO into colloid ₂ Aerogel, effective againstThe glue stopper is filled in the pores in the fiber membrane in a solid manner, and meanwhile, the air holes in the glue stopper can also be used for assisting in noise elimination. The mesoporous material with the porous structure is added in a proper proportion, so that the fiber density is reduced, the noise reduction effect is improved, the mechanical strength of the fiber can be maintained, and the porous PET fiber is reinforced after compounding, so that the composite membrane is not easy to break when in use. The noise reduction performance of the compounded membrane material is stronger than that of a single PET fiber membrane or a single mesoporous fiber membrane.

Description

Processing technology of environment-friendly sound insulation pad

Technical Field

The invention relates to the field of sound insulation non-woven fabrics, in particular to a processing technology of an environment-friendly sound insulation pad.

Background

Electrostatic spinning is a technology for charging and deforming polymer solution or melt by means of a high-voltage electrostatic field, forming a suspended conical liquid drop at the tail end of a spray head, forming jet flows on the surface of the liquid drop when the charge repulsion force on the surface of the liquid drop exceeds the surface tension of the liquid drop, and finally depositing the liquid drop on a receiving polar plate to form polymer nano fibers after the jet flows are subjected to high-speed stretching of electric field force, solvent volatilization and solidification in a short distance. The method mainly comprises solution spinning and melt spinning, wherein the melt spinning is limited due to the development of a series of problems that a high-temperature environment is needed in the manufacturing process, the diameter of the spun fiber is thick and the like; solution spinning has been used for research in various fields because of its environmental friendliness, simple equipment, wide range of spinnable materials, etc., and as of 2010, more than 200 polymers have been used for solution spinning. In addition, the diameter, the pore diameter, the porosity, the thickness, the surface morphology of the fiber and the like of the nanofiber membrane can be controllably adjusted by changing environmental parameters, processing parameters and the properties of the polymer solution.

The existing sound insulation or absorption materials mostly adopt methods of increasing the thickness or reducing the surface density to increase the number of micro holes in the materials, and the like to reduce noise and absorb sound, and the micro holes or cavities in the materials enable sound waves to vibrate air in the micro holes when passing through the sound absorption materials, so that the sound energy is converted into heat energy, and the purpose of sound absorption is achieved. But lightweight soundproof cloth requires that sound absorbing material's thickness can not too big, otherwise is unfavorable for subsequent shop to paste and use, and reduces areal density and makes sound absorbing material hole grow, and the density reduces, and too big aperture and the density of undersize can lead to sound absorption effect to reduce by a wide margin, and consequently areal density's adjustment range is minimum, is unfavorable for lightweight improvement. The existing sound insulation pad mostly pastes sound insulation materials on the surface of a fabric or is clamped in the fabric, glue or colloid is needed to be used in a pasting method, but the pores are easily and compactly filled in the process of coating the colloid, so that the sound attenuation function of the micropore sound absorption material is lost. Meanwhile, when a micropore silencing strategy is adopted, if micropores exist in the fiber, the mechanical strength of the fiber can be greatly reduced although the fiber can effectively absorb sound, so that the fiber membrane is very easy to break in the application process and is inconvenient to apply.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: the problems and the defects of the existing porous sound insulation material in the application process.

In order to solve the technical problems, the invention provides the following technical scheme:

a processing technology of an environment-friendly sound insulation pad comprises the following specific steps:

(1) preparing a mesoporous fiber membrane: adding a mesoporous material with the particle size of 50-100 nm into a polyacrylonitrile spinning solution, fully and uniformly stirring, and then carrying out spinning film formation on a mesoporous fiber film by adopting an electrostatic spinning method, wherein the solvent of the polyacrylonitrile solution is dimethylformamide, the content of polyacrylonitrile is 13wt%, the addition amount of the mesoporous material is 0.1-0.4 wt% of the polyacrylonitrile spinning solution, the environmental humidity during spinning is controlled to be below 10%, the temperature is 20 +/-5 ℃, and the prepared fiber film is treated in a vacuum oven at 80 ℃ for 2.5 hours to remove residual solvent to obtain the mesoporous fiber film;

(2) preparing a PET nanofiber membrane: firstly, preparing a PET spinning solution, wherein a solvent is dimethylformamide, spinning polyester fibers by using an electrostatic spinning machine, controlling the environmental humidity in the spinning process to be 20-50% and the temperature to be 20 +/-5 ℃, and treating the prepared fiber membrane in a vacuum oven at 80 ℃ for 2.5 hours to remove the residual solvent to obtain a single-layer PET nanofiber membrane; the PET nanofiber membrane consists of loose and porous PET fibers, and the average pore diameter of the PET nanofiber membrane is 4.1-4.5 mu m;

(3) coating colloid on the mesoporous fiber film, then paving and pasting a layer of PET nanometer fiber film, then coating colloid on the PET nanometer fiber film, paving and pasting a layer of mesoporous fiber film, repeating the steps, alternately paving and pasting a plurality of layers of mesoporous fiber films and PET nanometer fiber films, drying the paved and pasted composite film at 50 ℃, and then pasting the composite film on the base fabric to obtain the sound insulation pad.

Preferably, the colloid is prepared from absolute ethyl alcohol, polyvinyl butyral and SiO ₂ Aerogel composition of said polyThe vinyl butyral accounts for 0.6 percent of the total weight of the colloid, and the SiO is ₂ The aerogel accounts for 0.1-0.5% of the total weight of the colloid, and the SiO is ₂ The grain diameter of the aerogel is larger than the average pore diameter of the PET nano fiber membrane or the mesoporous fiber membrane.

Preferably, the SiO ₂ The particle size of the aerogel is 10-30 mu m.

Preferably, the concentration of the PET spinning solution is 18%, and the preparation process comprises the following steps: weighing 41g of DMF solution, putting the solution into a wide-mouth bottle, and stirring the solution on a magnetic stirrer; and weighing 9g of PET particles, respectively pouring the PET particles into the DMF solution, slowly pouring the PET particles under rapid stirring, and after the PET particles are stable, adjusting the speed to a proper speed and stirring the mixture for 12 hours to obtain the PET particles.

Preferably, the processing parameters of the electrostatic spinning machine for processing the PET nanofiber membrane in the step (2) are as follows: the voltage is 30kV, the sliding table speed is 100cm/min, the rotating speed of the roller is 50rpm, the perfusion speed is 3mL/h, the receiving distance is 20cm, the temperature is 20 +/-5 ℃, and the time is 3 h.

Preferably, the mesoporous material is one of mesoporous carbon or mesoporous silicon, and the process parameters of the electrostatic spinning machine for processing the mesoporous fiber membrane in the step (1) are as follows: the voltage is 30kV, the sliding table speed is 100cm/min, the rotating speed of the roller is 90rpm, the perfusion speed is 10mL/h, the receiving distance is 15cm, the temperature is 20 +/-5 ℃, and the time is 3 h.

The invention has the following beneficial effects:

the PET fibers are in a porous shape by changing condition parameters during electrostatic spinning, the nano-scale micropores in the PET fibers and the micron-scale pores formed by fiber interweaving form a two-stage pore mechanism, the structure is similar to a sound-absorbing wedge structure, when sound waves pass through the two-stage pore mechanism, the sound wave capacity is greatly reduced, and the sound absorption capacity of the material is effectively improved under the condition that the thickness of the material is not increased. Adding SiO into colloid ₂ The aerogel can effectively prevent the glue solution from closely filling the pores in the fiber membrane, and meanwhile, the inner pores can also assist in noise elimination. The mesoporous material with the porous structure is added in a proper proportion, so that the fiber density is reduced, the noise reduction effect is improved, the mechanical strength of the fiber can be maintained, and the porous PET fiber is reinforced after compounding, so that the composite membrane is not easy to break when in use. After compoundingThe sound attenuation performance of the membrane material is stronger than that of a single PET fiber membrane or a single mesoporous fiber membrane.

Drawings

FIG. 1 is a schematic structural view of an electrospinning device;

FIG. 2 is an SEM topography of PET nanofibers spun at 45 + -5% humidity.

Detailed Description

The following examples are included to provide further detailed description of the present invention and to provide those skilled in the art with a more complete, concise, and exact understanding of the principles and spirit of the invention.

Example 1: the electrostatic spinning device used in the invention mainly comprises a high-voltage power supply (the voltage regulation range is 0-30kV, 10 nozzles can be installed on a micro-injection pump, the diameter of the used syringe needle is 0.4mm, the roller receiving device (the rotation speed regulation range is 0-200r/min, the length of the roller is 60cm, and the reciprocating sliding table device (the moving speed range is 0-20 ℃ m/min)) is shown in figure 1.

The invention selects Polyacrylonitrile (PAN) or polyethylene terephthalate (PET) with a mature electrostatic spinning process as a solute and DMF as a solvent to spin and prepare the polyester fiber so as to obtain a PET nano fiber film or a mesoporous fiber film with good shape, thereby obtaining the nano fiber material with good sound absorption performance. The method comprises the following specific steps:

(1) preparation of PET nanofiber membrane under different humidities

The humidity can influence the surface appearance and bulkiness of the fiber, so that the spinning is carried out by adjusting different environmental humidities during spinning, the process parameters are shown in table 1, and the specific preparation process is as follows:

TABLE 1 Process parameters for processing PET nanofiber membrane by electrostatic spinning machine

Respectively weighing 3 parts of 41g of DMF solution, putting the solution into a wide-mouth bottle with the capacity of 50mL, and stirring the solution on a magnetic stirrer; respectively weighing 3 parts of 9g of PET particles, respectively pouring the PET particles into a DMF solution, slowly pouring the PET particles under rapid stirring, adjusting the speed to be proper after the PET particles are stable, stirring the mixture for 12 hours, spinning the mixture under different humidity conditions after the PET particles are dissolved, (10 +/-5%, 20 +/-5%, 35 +/-5%, 45 +/-5%, 55 +/-5%, 65 +/-5% and 95 +/-5% of the mixture are spun under different humidity conditions, respectively, treating the formed fiber membrane in a vacuum oven at 80 ℃ for 2.5 hours to remove residual solvent to obtain a single-layer PET nanofiber membrane, wherein the fiber membrane spun by using an electrostatic spinning technology has a fluffy structure, and the PET fibers are provided with a large number of micropores (shown in figure 2).

(2) Preparing a mesoporous fiber membrane: adding mesoporous carbon or mesoporous silicon with the particle size of 50-100 nm into polyacrylonitrile spinning solution, fully and uniformly stirring, and then carrying out spinning film formation on a mesoporous fiber film by adopting an electrostatic spinning method, wherein the solvent of the polyacrylonitrile solution is dimethylformamide, the content of Polyacrylonitrile (PAN) is 13wt%, the addition amount of the mesoporous material is 0.4wt% of the polyacrylonitrile spinning solution, the environmental humidity during spinning is controlled to be below 10%, the temperature is 20 +/-5 ℃, and the prepared fiber film is treated in a vacuum oven at the temperature of 80 ℃ for 2.5 hours to remove residual solvent to obtain the mesoporous fiber film; the technological parameters of the electrostatic spinning machine for processing the mesoporous fiber membrane are as follows: the voltage is 30kV, the sliding table speed is 100cm/min, the rotating speed of the roller is 90rpm, the perfusion speed is 10mL/h, the receiving distance is 15cm, the temperature is 20 +/-5 ℃, and the time is 3 h. Too much humidity can also cause too many micropores in the PAN fiber, and the mechanical strength of the fiber is affected, so the environmental humidity should be reduced as much as possible during the production and processing of the mesoporous fiber membrane.

(3) Preparing colloid, wherein the solvent of the colloid is absolute ethyl alcohol, and the solute is SiO with the particle size of 10-30 mu m ₂ Aerogel and polyvinyl butyral (PVB), said SiO ₂ Aerogel accounts for 0.5 percent of the total weight of the colloid, PVB accounts for 0.6 percent of the total weight of the colloid, PVB plays a role in bonding, and a certain amount of SiO is firstly prepared ₂ Pouring the aerogel into weighed absolute ethyl alcohol, sealing and stirring for 10min, and then placing into an ultrasonic instrument for treatment for 30min to uniformly disperse the particles; then adding the weighed PVB with the concentration of 0.5 percent, and stirring for 12 hours in a sealed way; wherein SiO is ₂ The grain diameter of the aerogel should be larger than that of the PET nano fiber film or mesoporous fiberThe average pore size of the membrane to prevent the gel from filling the pores tightly.

(4) On the mesoporous fiber membrane according to the ratio of 15g/m ² Painting the prepared colloid, paving and pasting a layer of PET (polyethylene terephthalate) nano fiber film, painting the colloid on the PET nano fiber film, paving and pasting a layer of mesoporous fiber film, repeating the process, alternately paving and pasting 5 layers of mesoporous fiber films and 5 layers of PET nano fiber films to obtain a composite film, drying the paved composite film at 50 ℃, and then covering and pasting the composite film on a basic cotton-flax fabric to obtain the sound insulation pad.

The pore size and other parameters of the monolayer PET nanofiber membrane were determined as follows:

TABLE 2 basic parameters and average pore diameter of PET nanofiber membranes

Table 2 shows that the increase of the ambient humidity significantly increases the average thickness of the fiber membrane, and the fiber diameter gradually increases with the increase of the ambient humidity, and the average diameter of the fiber membrane increases from 1.02 to 2.35 μm. The increase of the fiber diameter macroscopically increases the thickness of the single-layer fiber membrane, but the amplitude is smaller, the area density is reduced along with the increase of the volume of the porous fiber, but the amplitude is smaller, and meanwhile, the environmental humidity hardly influences the pore diameter of micron-sized pores generated by interweaving among the fibers.

Under certain spinning conditions, the humidity influences the property of a medium around the jet flow, particularly the compatibility with a solvent, further influences the volatilization of the solvent, and finally influences the surface appearance of the fiber. From SEM, it can be seen that there are a large number of micropores on the surface of the fiber, which are generated by the volatilization of the solvent during the formation of the jet, and are related to the properties of the solvent and the polymer; in addition, the jet flow is not stretched enough under the external electric field drafting, so that the internal structure of the fiber is not compact, and a large number of holes are formed on the surface of the fiber, and the increase of the humidity inhibits the volatilization of DMF, so that the jet flow is not stretched enough, and the internal structure of the fiber is influenced, thereby forming a larger and more hole structure.

In the actual spinning process, the fiber film formed under the condition that the humidity is more than 65 +/-5 percent has overlarge bulkiness, the fiber is difficult to receive due to low mechanical strength, and the finally formed film has a thinner thickness. Its thickness, areal density, maximum pore size, minimum pore size and average pore size are all poor.

The pore diameter and other parameters of the prepared mesoporous fiber membrane are measured, and the results are as follows:

TABLE 3 pore diameter and other parameters of mesoporous fiber membrane

In the invention, a SW series impedance tube test system of Beijing prestige company is adopted for testing the sound absorption performance of a sample, and the test is carried out according to GBT18696.2-2002, part 2 of measurement of sound absorption coefficient and sound impedance in an acoustic impedance tube, namely a transfer function method, wherein the frequency range corresponding to the SW477 type impedance tube is 1000-6300 Hz, the frequency range corresponding to the SW422 type impedance tube is 63-500 Hz (the position of a microphone is connected with 0-2) and 250-1600 Hz (the position of the microphone is connected with 1-2), each sample is tested for 3 times, the position of the microphone is required to be exchanged to test again to eliminate phase difference during each test, the depth of a cavity is 25mm, and data are output according to 1/3 octave. The relatively sensitive sound frequency range of people in daily life is 250-2000 Hz, so the sound absorption performance of the fiber film in the frequency range of 100-2500 Hz is mainly researched, and the corresponding 1/3 octaves are 100, 200, 400, 500, 630, 800, 1000, 1250, 1600, 2000 and 2500 Hz.

TABLE 4 influence of the spinning environment humidity on the sound absorption coefficient of the fibrous membranes

The results in table 4 show that too low humidity results in poor fiber bulk, few micropores and a significant reduction in the acoustic absorption coefficient at the same frequency. When the humidity is too high, the density of the fiber film is reduced, and the sound absorption coefficient is greatly reduced.

Example 2: the rest is the same as example 1 except that:

setting the environmental humidity in the step (1) to be 50 +/-5%;

setting experimental groups by taking the addition amount of the mesoporous material as 0.05, 0.1, 0.2, 0.4, 0.8 and 1.0 wt% of the polyacrylonitrile spinning solution to respectively prepare mesoporous fiber membranes, and determining the mechanical strength of the mesoporous fiber membranes as follows:

TABLE 5 influence of mesoporous material on sound absorption coefficient and mechanical strength of mesoporous fibrous membrane

The results in table 5 show that the addition of the mesoporous material makes the interior of the PAN fiber present a porous structure, and as the addition amount of the mesoporous material increases, the PAN fiber becomes fluffy, which gradually decreases the mechanical strength of the mesoporous fiber membrane, but the sound absorption coefficient gradually increases, and the addition amount of the mesoporous material should not be too large or too small in order to take account of the mechanical strength and the sound absorption coefficient.

Example 3: the rest is the same as example 1 except that SiO ₂ The aerogel accounts for 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 1.0 percent of the total weight of the colloid, and the humidity is set to be 50 +/-5 percent. The sound absorption coefficient of the composite film was measured, and the results were as follows:

TABLE 6 Effect of aerogels on Sound absorption coefficient in colloids

Table 6 results show that although the addition of aerogel significantly improves the sound absorption coefficient of the composite membrane, since the specific gravity of aerogel is very small, excessive addition of aerogel causes a decrease in the adhesive force between the membrane layers, and the improvement of the sound absorption coefficient is of limited help.

Comparative example 2: the same thickness of 4mm is adopted, and the surface density is 150g/m ² The PET polyester fiber non-woven fabric is used as a control group for subsequent performance test.

The composite film, the PET nanofiber film and the mesoporous fiber film (the processing humidity of the PET nanofiber film is 50 ± 5%) were prepared by the method in the example, and were subjected to sound absorption performance test and characterization with the nonwoven fabric of comparative example 2:

TABLE 7 Sound absorption Properties test and characterization of different film materials

Frequency (Hz)	PET nanofiber membrane	Mesoporous fiber membrane	Composite membrane	Comparative example 2
					800	0.127	0.101	0.557	0.098
1000	0.336	0.281	0.628	0.146
					1250	0.542	0.443	0.743	0.225
1600	0.631	0.471	0.811	0.326
					2000	0.718	0.558	0.847	0.358

The thickness and the surface density are similar, compared with the fiber porous sound absorbing material, the sound absorbing and insulating effect of the common non-woven fabric is the worst, which further indicates that the sound loss is a complicated process, and the fiber structure is an important parameter influencing the performance of the fiber porous sound absorbing material.

The PET nanometer fiber film or the mesoporous fiber film with the same thickness as the composite film is bonded by colloid and then is used for measuring the tensile strength, and the result is as follows:

TABLE 8 measurement results of mechanical strength of different film materials

In conclusion, the PET fibers are in a porous shape by changing the condition parameters during electrostatic spinning, the mesoporous materials, the nano-scale micropores in the PET fibers and the micron-scale holes formed by interweaving the fibers form a two-stage pore mechanism, the structure is similar to a sound-absorbing wedge structure, when sound waves pass through the two-stage pore mechanism, the sound wave capability is greatly reduced, and the sound-absorbing capability of the material is effectively improved under the condition that the thickness of the material is not increased. Adding SiO into colloid ₂ The aerogel can effectively prevent the glue solution from closely filling the pores in the fiber membrane, and meanwhile, the inner pores can also assist in noise elimination. The mesoporous material with the porous structure is added in a proper proportion, so that the fiber density is reduced, the noise reduction effect is improved, the mechanical strength of the fiber can be maintained, and the porous PET fiber is reinforced after compounding, so that the composite membrane is not easy to break when in use. The noise reduction performance of the compounded membrane material is stronger than that of a single PET fiber membrane or a single mesoporous fiber membrane.

The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby, and any modification made on the basis of the technical scheme according to the technical idea proposed by the present invention falls within the protection scope of the present invention; the technology not related to the invention can be realized by the prior art.

Claims

1. The processing technology of the environment-friendly sound insulation pad is characterized by comprising the following specific steps of:

(1) preparing a mesoporous fiber membrane: adding a mesoporous material with the particle size of 50-100 nm into a polyacrylonitrile spinning solution, fully and uniformly stirring, and then carrying out spinning film formation on a mesoporous fiber film by adopting an electrostatic spinning method, wherein the solvent of the polyacrylonitrile spinning solution is dimethylformamide, the content of polyacrylonitrile is 13wt%, the addition amount of the mesoporous material is 0.1-0.4 wt% of the polyacrylonitrile spinning solution, the environmental humidity during spinning is controlled to be below 10%, the temperature is 20 +/-5 ℃, and the prepared fiber film is treated in a vacuum oven at 80 ℃ for 2.5 hours to remove residual solvent to obtain the mesoporous fiber film;

(2) preparing a PET nanofiber membrane: firstly, preparing a PET spinning solution, wherein a solvent is dimethylformamide, spinning polyester fibers by using an electrostatic spinning machine, controlling the environmental humidity to be 20-50% and the temperature to be 20 +/-5 ℃ during spinning, and treating the prepared fiber membrane in a vacuum oven at 80 ℃ for 2.5 hours to remove the residual solvent to obtain a single-layer PET nanofiber membrane; the PET nanofiber membrane consists of loose and porous PET fibers;

(3) coating colloid on the mesoporous fiber film, then paving and pasting a layer of PET (polyethylene terephthalate) nano fiber film, coating colloid on the PET nano fiber film, then paving and pasting a layer of mesoporous fiber film, repeating the steps, alternately paving and pasting a plurality of layers of mesoporous fiber films and PET nano fiber films, drying the paved and pasted composite film at 50 ℃, and then covering and pasting the composite film on a base fabric to obtain the sound insulation pad;

the colloid is prepared from absolute ethyl alcohol, polyvinyl butyral and SiO ₂ The aerogel consists of polyvinyl butyral accounting for 0.6 percent of the total weight of the colloid, and SiO ₂ The aerogel accounts for 0.1-0.5% of the total weight of the colloid, and the SiO is ₂ The grain diameter of the aerogel is larger than the average pore diameter of the PET nano fiber membrane or the mesoporous fiber membrane.

2. The process for manufacturing an environment-friendly sound insulation mat as claimed in claim 1, wherein: the SiO ₂ The particle size of the aerogel is 10-30 mu m.

3. The process for manufacturing an environment-friendly sound insulation mat as claimed in claim 1, wherein: the concentration of the PET spinning solution is 18%, and the preparation process comprises the following steps: weighing 41g of DMF solution, putting the solution into a wide-mouth bottle, and stirring the solution on a magnetic stirrer; and weighing 9g of PET particles, respectively pouring the PET particles into the DMF solution, slowly pouring the PET particles into the DMF solution under the condition of rapid stirring, and after the PET particles are stable, adjusting the speed to a proper speed and stirring the mixture for 12 hours to obtain the PET particles.

4. The process for manufacturing an environment-friendly sound insulation mat as claimed in claim 1, wherein: the technological parameters of the electrostatic spinning machine for processing the PET nanofiber membrane in the step (2) are as follows: the voltage is 30kV, the sliding table speed is 100cm/min, the rotating speed of the roller is 50rpm, the perfusion speed is 3mL/h, the receiving distance is 20cm, the temperature is 20 +/-5 ℃, and the time is 3 h.

5. The process for manufacturing an environment-friendly sound insulation mat as claimed in claim 1, wherein: the mesoporous material is one of mesoporous carbon or mesoporous silicon, and the technological parameters of the electrostatic spinning machine for processing the mesoporous fiber membrane in the step (1) are as follows: the voltage is 30kV, the sliding table speed is 100cm/min, the rotating speed of the roller is 90rpm, the perfusion speed is 10mL/h, the receiving distance is 15cm, the temperature is 20 +/-5 ℃, and the time is 3 h.