CN111037940A

CN111037940A - Preparation system of material with nano-porous structure

Info

Publication number: CN111037940A
Application number: CN201911260708.XA
Authority: CN
Inventors: 刘爱林
Original assignee: Shanghai Xidian New Material Technology Co Ltd
Current assignee: Shanghai Xidian New Material Technology Co Ltd
Priority date: 2019-09-26
Filing date: 2019-12-10
Publication date: 2020-04-21
Also published as: CN110884151A; CN111037941A; CN110901092A

Abstract

The invention aims to provide a preparation system of a material with a nano porous structure, which comprises the following components: a heating unit for heating the preform containing the solvent to melt the preform and vaporize the solvent while maintaining the form of the preform; a bulking unit to bulk the heated material from the heating unit to a desired porosity; and a shaping unit that cools the expanded material from the expanding unit to obtain a material having a nanoporous structure. The invention can prepare the material with the nanometer porous structure with excellent performance by a simplified process at lower cost.

Description

Preparation system of material with nano-porous structure

Technical Field

The invention belongs to the field of material processing and application, and mainly relates to a preparation system of a material with a nano porous structure.

Background

Nanoporous materials are generally useful as the materialHeat insulating material or filtering material. For example, the existing thermal insulation material is generally a special gel which uses gas to replace the liquid in the gel without changing the network structure or volume of the gel per se, and is the product after the hydrogel or the organic gel is dried. It has the features of nano level porous structure, high porosity, etc. and is one of the known solid materials with low density. Such insulation was first made in the 30's of the 20 th century by professor Kistler. The preparation process is complicated and long, and the preparation method is expensive and fragile, so that the preparation method does not attract attention for a long time. With the rapid development of sol-gel technology since the 70 s of the 20 th century, extensive attention has been paid to the research and development of inorganic heat insulating materials based on silica and synthetic polymer heat insulating materials represented by resorcin/formaldehyde and melamine/formaldehyde polycondensates. The porous structure with a large number of nanometer sizes in the heat-insulating material endows the material with ultrahigh porosity (80-99.8%) and high specific surface area (100-1600 m)²(0.004-0.500 g/cm) and ultralow density³) And the like, so that the material has wide application prospects in various fields such as optics, electricity, acoustics, heat, catalysis and the like.

Mixing organic silicon, ethanol and deionized water under an acidic condition, adding phenolic resin, adding ammonia water, carrying out sealed aging on the obtained phenolic resin-silicon dioxide composite hydrogel, carrying out solvent replacement by adopting ethanol and n-hexane to obtain phenolic resin-silicon dioxide composite gel containing an n-hexane solvent, and drying by using supercritical carbon dioxide to obtain the phenolic resin-silicon dioxide composite heat insulation material; dissolving cellulose in NaOH/urea/water solution to obtain cellulose solution, adding chitosan for blending, adjusting the pH value to be acidic to obtain chitosan-cellulose mixed sol, then mixing the chitosan-cellulose mixed sol with potassium permanganate solution, converting the chitosan in a sol system into chitosan carbon by a hydrothermal method, uniformly loading manganese dioxide in the chitosan carbon-cellulose sol system, and finally obtaining the manganese dioxide-chitosan carbon-cellulose gel urea-formaldehyde resin adhesive additive by freeze drying; according to patent CN106564235B, melamine, formaldehyde and water are placed in a reactor, a catalyst, a buffering agent, a solubilizer and a stabilizer are sequentially added, an emulsifier and a plasticizer are added after the melamine is completely dissolved, the mixture is placed in a closed container for gel aging to obtain gel, then absolute ethyl alcohol and acetone are used for replacement, the replaced gel material is subjected to solvent replacement by absolute ethyl alcohol solution, and finally, the melamine nano gel particles are obtained after drying.

The existing preparation processes are all improved aiming at the preparation process of sol-gel, no innovation is provided on the drying method, the preparation processes are complex, and the related preparation equipment is bulky, so that the cost is high.

Disclosure of Invention

The present invention is directed to provide a system for preparing a material having a nanoporous structure, which can prepare a material having a nanoporous structure with excellent performance at a low cost and in a simplified process.

The system for preparing a material having a nanoporous structure according to the present invention comprises: a heating unit for heating the preform containing the solvent to melt the preform and vaporize the solvent while maintaining the form of the preform; a bulking unit to bulk the heated material from the heating unit to a desired porosity; and a shaping unit that cools the expanded material from the expanding unit to obtain a material having a nanoporous structure.

By adopting the preparation system, the preform is melted and the solvent is gasified, namely, the expansion does not occur, by the heating unit under the state of keeping the shape unchanged. The heated material from the heating unit is then expanded by the expansion unit to increase the volume to the desired porosity, whereby the porosity can be controlled by controlling the expansion process performed in the expansion unit to obtain the desired material. The preparation system has simple structure and strong applicability, can greatly simplify the preparation process of the material with the nano porous structure, and reduces the cost. Compared with the existing freeze drying and supercritical drying preparation process, the preparation method is more convenient, quicker and more economical, and the aperture is adjustable, and the existing methods of supercritical carbon dioxide drying and vacuum freeze drying need to form gel before drying and then dry, but the method does not need the step of forming gel. In addition, the existing porous material preparation process generally adopts means such as high-temperature oil bath for puffing, and the puffing process is uncontrollable, so that the preparation system can control the puffing process and further realize the adjustment of porosity. The preparation system can prepare nano porous materials with the porosity of more than 80 percent, and can be suitable for preparing various materials with nano porous structures, such as heat insulation materials with nano porous structures, filter materials with nano porous structures and the like.

Preferably, the device comprises a pair of hot-pressing rollers, the prefabricated body is a sheet and is conveyed to a position between the two hot-pressing rollers from the feed port, the thickness of the prefabricated body is greater than the minimum distance between the two hot-pressing rollers, and the minimum distance refers to the gap distance between the two points which are closest to the two hot-pressing rollers; the heating unit includes a region from the upstream of the minimum distance where the sheet comes into contact with the heat and pressure roller until the minimum distance is reached; the bulking unit comprises an area with gradually increased gap distance between the two hot-pressing rollers from the position away from the minimum distance; the shaping unit comprises an area where the puffed material is no longer in contact with the two hot press rolls.

According to the present invention, it is possible to heat the solvent-containing preform efficiently from the point where the upstream sheet-like preform at the minimum distance comes into contact with the heat and pressure roller to melt it and vaporize the solvent; and maintaining the heated material morphology unchanged at the minimum distance reached; the material is gradually expanded to increase the volume to reach the required porosity by controlling the expansion process; cooling and setting are then started in the area where the expanded material is no longer in contact with the two heated press rolls. The invention can realize the controllability of the puffing process by simple structure.

Preferably, the thickness of the sheet is greater than the minimum distance by 10-40%. The thickness of the sheet needs to be larger than the minimum distance between the two hot pressing rollers, but cannot be too small, and the sheet is suitable for being comprehensively obtained by 10% -40%, so that the sheet can be fully heated.

Preferably, the porosity is controlled by controlling the puffing speed; specifically, the puffing speed is controlled by controlling the solvent content of the preform, the heating temperature of the heating unit, and the rotation speed of the two hot press rolls. The influence factors are mutually influenced and restricted, so that corresponding condition control is realized under different material requirements. Specifically, the higher the solvent content and the higher the temperature, the lower the rotation speed of the hot-press roll should be; conversely, the lower the solvent content, the lower the temperature and the higher the rotation speed of the hot-pressing roll.

Preferably, the heating temperature is 140 to 400 ℃.

Preferably, the rotating speed of the two hot pressing rollers is 0.4-10 m/min. The speed of expansion should not be too fast, and the yield under industrial conditions should not be too low.

Preferably, the minimum distance is 0.5 to 6 mm.

Drawings

FIG. 1 is a schematic structural diagram of a system for preparing a material having a nanoporous structure according to an embodiment of the invention;

FIG. 2 is a schematic control block diagram of a system for preparing a material having a nanoporous structure according to the invention;

reference numerals:

1. 2, hot pressing roller;

3, feeding a material inlet;

4, prefabricating a body;

a is at the minimum distance;

b starting point of heating unit.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

Disclosed herein is a system for preparing a material having a nanoporous structure according to the present invention, comprising: a heating unit for heating the preform containing the solvent to melt the preform and vaporize the solvent while maintaining the form of the preform; a bulking unit to bulk the heated material from the heating unit to a desired porosity; and a shaping unit that cools the expanded material from the expanding unit to obtain a material having a nanoporous structure.

The above preform may be prepared in advance in a preform preparation unit, and for example, a solvent type resin and a solvent may be used for preparation, but the present invention is not limited thereto, and a water-soluble resin, an inorganic sol, a composite of a resin and an inorganic sol, and the like may be used in addition to a solvent type resin. The preform is allowed to contain a suitable amount of solvent, which can be vaporized at a certain temperature to allow the preform to expand and form a hole.

The heat insulation material with the nano-porous structure and the filtering material with the nano-porous structure can be prepared into preforms by adopting the same raw materials and processes, and different final products with the nano-porous structure based on different thicknesses of the preforms can be respectively used as the heat insulation material or the filtering material. For example, a preform for preparing a thermal insulation material having a nanoporous structure may be directly subjected to a subsequent preparation process using the preparation system of the present invention. And a thin layer can be coated on the carrier of the same prefabricated body, and then the preparation system is adopted to carry out the subsequent preparation process, so that the filtering material with the nano-porous structure is obtained.

The following description will be given by taking a solvent-based resin as an example of the preform, but the production system of the present invention is also applicable to preforms made of other materials.

The solvent type resin can be dissolved by a solvent to obtain a solution in which the solvent is uniformly dispersed in the solvent type resin, and a preform with the solvent type resin as a framework and a proper amount of the solvent uniformly dispersed in the solvent type resin can be obtained. Preferably, an excess of solvent is used to dissolve the starting material to provide sufficient dissolution of the starting material to ensure uniform dispersion of the solvent in the resin starting material to aid in the expansion of the product to provide a more uniform pore size distribution. The resin can be dissolved in a solvent in an amount of 0.2 to 10 times the weight of the resin. The amount of the solvent is different according to the dissolution performance of the resin. And some resin products are liquid, and can be uniformly mixed by adding a small amount of solvent. It is understood that the resin should be completely dissolved in the solvent. The preform preparation unit may be a conventional apparatus for preparing an aerogel preform, and may be mixed using a mixing device such as a mixer, a blender, or the like, so that the solvent is uniformly dispersed in the solvent-type resin. The resin and solvent may also be mixed by mechanical action under heated conditions. Mixing can be achieved using equipment with high temperature capabilities such as internal mixers, high temperature kneaders, twin-cone extruders, twin-screw extruders, twin-roll presses, and the like.

The solvent is used for making holes and can be gasified at a certain temperature to enable the prefabricated body to be expanded and formed with holes. Any solvent may be used as long as it can completely dissolve the resin. Preferably, a preform having a solvent content of 5 to 40wt% in total is prepared. Too high solvent content easily causes too large pore diameter or uneven pore diameter distribution, and too low solvent content easily causes insufficient puffing degree or unsuccessful puffing, so that the control of the solvent content in a certain range is beneficial to the uniform distribution of the pore diameter of the material and the control of the pore diameter size of the material, and the heat preservation and heat insulation performance of the material is improved. Thus, the solvent in the above-mentioned resulting solution can be reduced until the solvent reaches a desired content. The solvent of the resulting solution can be reduced, for example, by heating at a temperature below the glass transition temperature of the solvent-type resin, e.g., 25 to 200 ℃. The heating manner and apparatus are not limited as long as the content of the solvent is reduced to a desired content. The solvent is reduced at a lower heating temperature at a lower speed, but the heating temperature cannot be too high to avoid the resin from being expanded in advance, and if the solvent in the preform is gasified and expanded in advance at a too high heating temperature, the pore diameter and the pore diameter distribution of the product cannot be controlled to be uneven.

The system for preparing the material having a nanoporous structure according to the present invention is described in further detail below. The following examples are described by taking the preparation of the thermal insulation material having a nanoporous structure as an example, but the present invention is not limited thereto, and is also applicable to the preparation of the filter material having a nanoporous structure.

First, the preform containing the solvent (for example, a preform prepared using a solvent-based resin and a solvent) is heated in a heating unit while maintaining the form thereof, and the molten resin solvent is vaporized by melting the molten resin. The heating temperature for heating the preform to vaporize the molten solvent of the resin is preferably higher than the boiling point of the solvent and higher than the glass transition temperature of the solvent-based resin. More preferably, the heating temperature is 100 to 400 ℃. The heating temperature exceeds the boiling point of the solvent and the glass transition temperature of the resin, and is higher than the boiling point of the solvent and the glass transition temperature of the resin by a part, which is beneficial to the rapid expansion of the resin and shortens the expansion time. It will be appreciated that during heating (prior to expansion), it is ensured that the resin melts while the solvent vaporizes at this point in time, thereby facilitating the subsequent expansion of the material to form a nanoporous material having a uniform pore size distribution. The heating time can be reduced when the heating temperature is high. The heating means is configured to maintain the form of the resin melt solvent in a state where the resin melt solvent is vaporized without swelling. Preferably, maintaining its form can be achieved by controlling its volume to be constant.

Next, in the expansion unit, the heated material from the heating unit is expanded to increase the volume to achieve the desired porosity. The porosity is related to the degree of puffing, i.e. by controlling the puffing process in the puffing unit, the porosity of the material can be adjusted to achieve a specified level. The expansion may be such that the volume of the material expands in any one, two or three directions of XYZ. The requirements, operation processes, equipment or molds are different. The preparation system can ensure that the porosity of the prepared heat insulation material with the nano-scale aperture is 80-99%. And the volume increasing process of the materials in the puffing process is a gradual change process under a controllable state.

In some embodiments, the material may be extruded while the gap between the two heated press rolls is maintained, and then gradually separated from the heated press rolls during the movement, and puffing may be initiated as the gap distance between the two heated press rolls is gradually increased, and puffing may be accomplished by controllably moving the material by controlling the rotational speed of the rolls. The pressure during puffing is gradually reduced from 20-0 MPa.

That is, the preform may be fed into the production system at a predetermined speed, heated and subjected to a certain compression (i.e., heating and pressurizing) between two hot press rolls, and the solvent may be vaporized. When the prefabricated body contacts the rollers on two sides between the two hot-pressing rollers, the material is extruded and basically cannot be puffed (and is equivalent to be in a closed space), and the material is puffed only in the pressure relief process of gradually separating from the two hot-pressing rollers. As the sheet gradually separates from (i.e., is separated from the minimum distance between) the two heated press rolls, bulking occurs as the distance between the two heated press rolls gradually increases (i.e., slowly decompresses) and the volume increases to achieve the desired porosity. At this time, the volume of the material is further increased to 10 times, 20 times or even 50 times of the original volume. The pressurizing pressure can be controlled by controlling the gap between the two hot-pressing rollers, and the decompression speed and the appearance of the air holes are controlled by controlling the rotating speed of the hot-pressing rollers, so that the size of the hole diameter and the uniformity of the hole diameter distribution are controlled. Wherein, slow release pressure is realized through two hot-pressing roller clearance grow gradually, and its pressure is littleer as two hot-pressing roller clearance grow. It will be appreciated that the higher the solvent content and the higher the temperature, the lower the rotation speed of the heated press roll. Because the higher the temperature, the higher the content of the solvent and the higher the fluidity of the material, the lower the rotation speed of the hot-pressing roller can avoid the formation of large bubbles in the heat-insulating material.

Preferably, the thickness of the sheet is 10 to 40% higher than the gap between the two hot press rolls, so that the sheet is pressed to some extent when entering between the two hot press rolls. The vaporization time of the solvent when the material is heated in the gap between the two hot press rolls can be controlled by controlling the roll speed, and the speed of the material separating from the two hot press rolls (i.e. the bulking process) can also be controlled. In a preferred embodiment, the content of the solvent in the preform is preferably 20 to 25% of the resin. The thickness of the sheet is preferably 0.5-5 mm, and the temperature of the two hot press rollers is preferably 230-300 ℃; the speed of the two hot pressing rollers can be less than 40m/min, preferably 0.4-10 m/min, and more preferably 1.5-3 m/min; the gap between the two heat press rolls is preferably 0.5 to 6mm, more preferably 2 to 4mm (in the case where no particular description is given, the two heat press roll gaps are the minimum distance between the two heat press rolls). Under the condition of ensuring that the material can contact the hot-pressing roller, the larger the gap between the two rollers is, the higher the puffing rate is, the larger the porosity is, the better the heat insulation performance is, and the lower the heat conductivity is.

And finally, cooling the expanded material from the expansion unit in the shaping unit to obtain the heat insulation material with the nano porous structure. The volume of the material is no longer changed in the shaping unit, so that the shape of the material that has been subjected to the expansion process in the preceding expansion unit can be determined. In the shaping unit, for example, natural cooling means can be used.

Specifically, fig. 1 is a schematic diagram of a system for preparing a material having a nanoporous structure according to an embodiment of the present invention.

As shown in fig. 1, in the present embodiment, the pair of hot press rolls 1 and 2 are provided, and the preform 4, which is a sheet and is conveyed from the feed opening 3 to between the two hot press rolls, has a thickness larger than the minimum distance between the two hot press rolls (i.e., the gap distance between the two closest hot press rolls). Fig. 1 shows this minimum distance a. Preferably, the thickness of the sheet is greater than the minimum distance by 10-40%. The minimum distance is preferably 0.5 to 6 mm. Fig. 1 shows two heat and pressure rollers arranged in parallel in the horizontal direction, but the present invention is not limited thereto, and two heat and pressure rollers arranged in parallel in the vertical direction may be used.

In the present embodiment, the heating unit includes a region from where the upstream sheet at the minimum distance a comes into contact with the heat and pressure roller until the minimum distance is reached. Fig. 1 schematically shows a heating unit start point B (i.e., a position where the sheet starts to contact the heat and pressure roller). A medium, which may be, for example, iron flakes, may also be added to the preform during the preparation process. For example, the sheet material may be placed in an iron sheet and then between the hot press rolls 1, 2. Two pieces of release paper of the same specification as the iron sheet may be prepared for better release. The starting point B of the heating unit at this time may also be a position where the gap between the heat and

pressure rollers

1, 2 is equal to the thickness of the preform plus the thickness of the medium.

Since the thickness of the sheet is larger than the minimum distance between the two heat and pressure rollers, the sheet-like preform 4 has been brought into contact with the two heat and

pressure rollers

1, 2 from the heating unit starting point B up to the region where the minimum distance a is reached, before the minimum distance is reached, i.e., upstream of the minimum distance a, and both the heat and

pressure rollers

1, 2 apply heat and pressure, whereby the preform is melted and the resin melt solvent is vaporized. In particular, at this minimum distance a, the material is constrained by this position to maintain its morphology, in which case the solvent evaporates but no expansion, i.e. no foaming, occurs.

The bulking unit comprises a region of increasing gap distance between the two heated press rolls 1, 2 from the minimum distance a. After the minimum distance a, that is, downstream of the two closest points of the two heat and pressure rolls 1 and 2, the gap distance between the two heat and pressure rolls 1 and 2 gradually increases, and thus the material heated and pressurized by the heating means gradually releases the pressure and gradually starts puffing as the gap distance gradually increases. The shaping unit comprises an area where the expanded material is not contacted with the two hot-pressing rollers any more, and the expanded material can be shaped through natural cooling.

The material is mainly heated and extruded to a certain degree between the two hot-

pressing rollers

1 and 2, and the solvent is gasified, and the gasification degree of the solvent is preferably controlled to be 90-100%. The degree of evaporation of the solvent of the material between the two

heated rolls

1, 2 is related to the desired pore size and porosity of the final product. The higher the degree of gasification, the larger the pore size and the higher the porosity. And because the solvent fully dissolves the material and is uniformly distributed in the material, the nano-scale holes left after the solvent is gasified are uniformly distributed in the material. The pressure created by the solvent vapor as the sheet exits the nip of the two

heated rolls

1, 2 causes the material to bulk and increase in volume to achieve the desired porosity. The volume of the material can be further increased to 10 times, 20 times or even 50 times of the original volume. The volume of the material is gradually increased in the puffing process, and the pressure of the material is gradually released. Preferably, the sheet thickness is made to be appropriately larger than the gap between the two hot press rolls 1 and 2 by 10 to 40% so that the sheet is pressed to a certain degree when entering between the two hot press rolls. The time for the vaporization of the solvent when the material is heated between the two heated press rolls can be controlled by controlling the roll speed, as well as the speed at which the material is removed from the two heated press rolls 1, 2 (i.e., controlling the puffing process). In a preferable scheme, when the thickness of the sheet is 0.5-5 mm, the temperature of the two hot

pressing rollers

1 and 2 is preferably 230-300 ℃, and the speed of the hot pressing rollers is preferably 0.4-10 m/min.

In this embodiment, the porosity can be controlled by controlling the puffing rate. Specifically, the puffing speed can be controlled by controlling at least one of the solvent content of the preform, the heating temperature of the heating unit, and the rotational speeds of the two heat and pressure rollers. For example, when the solvent content is high and the heating temperature is high, the mobility of the molten preform is high and the preform is easy to foam, the rotation speed of the hot-pressing roller needs to be slow; on the contrary, when the solvent content is low and the heating temperature is low, the mobility of the molten preform is low and the preform is not easy to foam, so that the rotation speed of the hot-pressing roller needs to be high.

In addition, the two heat and

pressure rollers

1 and 2 may be connected to a driving unit to drive the heat and pressure rollers to rotate. The drive unit may be, for example, a drive motor. The heat and

pressure rollers

1 and 2 may be heated by a heating unit, and the heating unit may be any device capable of heating the heat and pressure rollers, and may be a device that heats by means of heat carrier heating, resistance heating, electric induction heating, or the like.

In addition, the device also comprises a control unit which is connected with the driving unit and the heating part and is used for controlling the driving unit and the heating part, so that the control of the rotating speed and the heating temperature of the two hot-pressing rollers is realized respectively. The control unit may be, for example, a programmable controller. The control unit may include a control part that may control the rotation speeds and heating temperatures of the two hot press rolls, and a display part that may display parameters controlled by the control part, such as the rotation speeds and heating temperatures of the two hot press rolls.

Further, the solvent content in the preform may be measured by a measuring unit. The solvent content may be measured after the preform is prepared and before the preform is hot-pressed. The determination unit can determine the solvent content, for example, by means of sampling measurements. The sampling and measuring of the solvent content can be carried out by adopting modes of an oven, a hot press and the like, and the solvent content can be calculated only by ensuring the drying of the solvent content. The measured value of the solvent content can be fed to the control unit or manually input to the control unit.

The operation of the system for preparing a material having a nanoporous structure according to the present invention will be described in detail below with a specific example. In this example, a preform prepared using a solvent-based resin and a solvent is used to prepare a thermal insulation material having a nanoporous structure using the preparation system according to the above embodiment.

First, the solvent content of a preform prepared from a solvent-type resin and a solvent is measured by a measuring unit, and the measured value of the solvent content is sent to a control unit.

Subsequently, the preform is made in sheet form, for example by means of cutting. The sheet is conveyed between two hot press rolls through the feed opening 3. In this example, the minimum distance between the two heat and pressure rollers may be 2mm, and the thickness of the sheet may be 2.5 mm. The preform is heated and pressurized in a region from where the upstream sheet at the minimum distance a comes into contact with the heat and pressure roller (i.e., the heating unit starting point B) until the minimum distance is reached, so that it is melted and the resin melt solvent is vaporized. In this region, the heated material remains in a form-stable state and does not expand.

Then, after the material passes through the minimum distance a, the material is gradually expanded as the gap distance between the two heat and pressure rollers is gradually increased. The control unit may control the rotation speed and heating temperature of the heated press roll based on the aforementioned measured value of the solvent content to control the puffing process to obtain a desired porosity.

Specifically, in example 1, the measured solvent content was 30%, the heating temperature was 300 ℃, the solvent content was high, and the heating temperature was high, and the rotation speed of the hot press roll was controlled to be slightly slow.

In example 2, the measured solvent content was 15%, the heating temperature was 200 ℃, the solvent content was low, and the heating temperature was low, the rotational speed of the hot-press roll was controlled to be a little faster.

And finally, when the puffed material is not in contact with the two hot-pressing rollers, the shape of the puffed material is shaped through natural cooling, so that the solvent type resin heat-insulating material with the nano porous polymer skeleton structure is obtained.

As the present invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiments are therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description herein, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the appended claims.

Claims

1. A system for preparing a material having a nanoporous structure, comprising:

a heating unit for heating the preform containing the solvent to melt the preform and vaporize the solvent while maintaining the form of the preform;

a bulking unit to bulk the heated material from the heating unit to a desired porosity; and

a shaping unit for cooling the expanded material from the expansion unit to obtain the material with nano-porous structure.

2. The production system according to claim 1,

the device comprises a pair of hot pressing rollers, wherein the prefabricated body is a sheet and is conveyed to a position between the two hot pressing rollers from a feed port, the thickness of the prefabricated body is larger than the minimum distance between the two hot pressing rollers, and the minimum distance refers to the gap distance between two points which are closest to the two hot pressing rollers;

the heating unit includes a region from the upstream of the minimum distance where the sheet comes into contact with the heat and pressure roller until the minimum distance is reached;

the bulking unit comprises an area with gradually increased gap distance between the two hot-pressing rollers from the position away from the minimum distance;

the shaping unit comprises an area where the puffed material is no longer in contact with the two hot press rolls.

3. The production system according to claim 2,

the thickness of the sheet is greater than the minimum distance by 10-40%.

4. The production system according to claim 2 or 3,

the porosity is controlled by controlling the puffing speed.

5. The production system according to claim 4,

the puffing speed is controlled by controlling the solvent content of the preform, the heating temperature of the heating unit and the rotating speed of the two hot-pressing rollers.

6. The production system according to claim 5,

the heating temperature is 140-400 ℃.

7. The production system according to claim 5,

the rotating speed of the two hot pressing rollers is 0.4-10 m/min.

8. The production system according to any one of claims 2 to 7,

the minimum distance is 0.5-6 mm.