CN110884151A

CN110884151A - Preparation system of material with nano-porous structure

Info

Publication number: CN110884151A
Application number: CN201911261974.4A
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: 2020-03-17
Also published as: CN111037941A; CN111037940A; CN110901092A

Abstract

The invention relates to a system for preparing a material with a nano-porous structure, which 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. 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 thermal insulationThermal insulation material or filter material, etc. 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 heating device comprises a heating roller and a pressure belt, wherein the pressure belt is arranged around the heating roller, a gap is formed between the pressure belt and the heating roller, and the gap is formed into a structure that the interval is kept unchanged firstly and then gradually increases; the preform is a sheet, which is conveyed into the gap between the heating roller and the pressure belt; the heating unit includes a gap area where a distance between the heating roller and the pressure belt is kept constant; the bulking unit comprises a gap area with gradually increased distance between the heating roller and the pressure belt; the sizing unit includes an area downstream of the bulking unit and no longer in contact with the heated roller and pressure belt.

According to the present invention, it is possible to efficiently heat the preform containing the solvent through the gap region where the distance between the heating roller and the pressure belt is kept constant to melt and vaporize the solvent while maintaining the heated material form constant; the bulking process is controlled through a gap area with the gradually increased distance between the heating roller and the pressure belt, so that the material is gradually bulked to increase the volume until the required porosity is reached; and then cooling and shaping are carried out in the area where the material is not contacted with the heating roller and the pressure belt any more. The invention can realize the controllability of the puffing process by a simple structure.

Preferably, the device further comprises a metal sheet which covers the pressure belt and is driven by the conveying roller to rotate.

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 shows a schematic control block diagram of a system for preparing the material having a nanoporous structure according to the invention;

reference numerals:

1. a heating roller;

2. a pressure belt;

3. a feed inlet;

4. a discharge port;

5, 6, 7, conveying rollers;

8. a metal sheet;

A. a gap region in which the pitch is kept constant;

B. a gap region with gradually increasing spacing.

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 performances of heat preservation, heat insulation and the like of the material are 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, bulking may be accomplished by causing the material to be compressed in an area where the gap between the heated roller and the pressure belt remains constant, and then the material enters an area where the gap between the heated roller and the pressure belt gradually increases during movement, by controlling the speed of rotation of the rollers to cause the material to move controllably. The pressure during puffing may be gradually reduced from 20 to 0MPa, for example. That is, the preform may be heated and pressurized in a region where the gap between the heating roller and the pressure belt is kept constant, to vaporize the solvent. In this region, since the gap distance is kept constant, the heated material maintains a state in which the shape is constant, and swelling does not occur. The material then continues to be conveyed to the increasingly spaced gap regions (i.e., the expansion units) where the material expands as the regions are spaced apart. In some embodiments, the temperature of the heating roller is 140-400 ℃, and the rotation speed of the heating roller is 0.4-10 m/min.

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 structural 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, the present embodiment includes a heating roller 1 and a pressure belt 2. The pressure belt 2 is disposed around the heating roller 1 with a gap formed therebetween. The gap is formed in a structure in which the pitch is first kept constant and then gradually increased.

Wherein the heating unit includes a gap area a where the interval between the heating roller 1 and the pressure belt 2 is maintained constant. The swelling unit includes a gap region B where the interval between the heating roller 1 and the pressure belt 2 is gradually increased. The two regions A, B are partitioned by a broken line as shown in fig. 1. The fixing unit comprises an area downstream of the expansion unit and no longer in contact with both the heated roller 1 and the pressure belt 2.

In the present embodiment, the preform is preferably a sheet, and the sheet is conveyed to the gap between the heating roller 1 and the pressure belt 2. And the thickness of the sheet may be equal to the size of the gap at the gap area a where the interval between the heating roller 1 and the pressure belt 2 is kept constant as described above.

Specifically, at a gap area a (i.e., a heating unit) where the distance between the above-described heating roller 1 and pressure belt 2 is kept constant, the sheet-like preform conveyed to this area a is brought into contact with both the heating roller 1 and pressure belt 2 and is heated and pressurized, whereby the preform melts and vaporizes the resin melting solvent. In addition, since the gap spacing in the region a is constant, the material is restricted by the gap spacing, and the shape is maintained, and at this time, the solvent is vaporized but the material is not expanded, that is, is not foamed.

Next, in the gap region B (i.e., the expansion unit) where the distance between the heating roller 1 and the pressure belt 2 gradually increases, when the heated and pressurized material is conveyed to the region B, the material is expanded as the distance between the gaps gradually increases. Thus, the factor by which the spacing of the interstices of the bulking unit increases relative to the spacing of the interstices of the heating unit (i.e., the expansion factor) determines the porosity of the final product. Therefore, the pitch size of the bulking units can be set as desired to obtain the desired porosity. If the expansion factor is too small, the porosity of the material is not high, and the heat insulation performance is affected, and if the expansion factor is too large, the pore diameter distribution of the material is uneven. For example, the expansion factor may be from 2 to 50, and correspondingly a porosity of from 50 to 99% may be obtained. Preferably, the expansion factor is 2.5-20, and accordingly 60-95% porosity can be obtained. More preferably, the expansion factor is 5-50, and accordingly, the porosity of 80-99% can be obtained.

The sizing unit comprises an area downstream of the bulking unit and no longer in contact with the heated roller 1 and the pressure belt 2. At this time, the material is not in contact with the heating roller 1 and the pressure belt 2 any more, and the shape of the material in which the swelling process has been completed in the previous swelling unit can be determined by, for example, natural cooling, thereby obtaining the thermal insulation material having a nanoporous structure.

Further, the above preform may be conveyed by a conveying mechanism, which may include a plurality of conveying rollers on which the metal sheet 8 is wound. As shown in fig. 1, in the present embodiment, the conveying mechanism includes three conveying rollers 5 to 7 on which a metal sheet 8 is wound. The conveying mechanism of the present invention is not limited thereto as long as the conveyance of the preform can be achieved. More specifically, in the present embodiment, the conveying

rollers

5, 6 are provided in the vicinity of the heating roller 1, and in particular, the conveying roller 5 is provided near the start of the gap area a where the above-described interval is kept constant, and the conveying roller 6 is provided near the end of the gap area B where the above-described interval is gradually increased.

The conveying roller 5 and the heating roller 1 have a gap therebetween to form the feed opening 3, which corresponds to the pitch size of the above-described gap area a in which the pitch is kept constant. The conveying roller 6 and the heating roller 1 also have a gap therebetween to form the discharge port 4, which gap corresponds to the size of the above-described gap of the end of the gap region B in which the gap gradually increases. That is, as shown in fig. 1, the conveying roller 5 is closer to the heating roller 1 than the conveying roller 6. The feeding of the preform and the discharging of the expanded material can be realized through the feeding port 3 and the discharging port 4 respectively. And at the downstream of the discharge port 4, the expanded material is not contacted with a heating roller and a pressure belt any more, and the expanded material is the shaping unit of the invention.

In addition, the above-mentioned conveying roller, heating roller, etc. may be connected to respective driving units to drive the conveying roller and heating roller to rotate, respectively. The drive unit may be, for example, a drive motor. The heating roller 1 may be heated by a heating section, and the heating section may be any device capable of heating the heating roller 1, and may be a device that heats by means of, for example, heat carrier heating, resistance heating, electric induction heating, or the like.

In addition, the device also comprises a control unit which is connected with each driving unit and the heating unit to control the driving unit and the heating unit, so as to respectively realize the control of the rotating speed and the heating temperature of each roller. The control unit may be, for example, a programmable controller. The control unit may include a control portion that may control the rotation speed and the heating temperature of each roller, and a display portion that may display parameters controlled by the control portion, such as the rotation speed and the heating temperature of each roller.

Further, as shown in fig. 1, in the present embodiment, the metal piece 8 is wound around the conveying rollers 5 to 7 and rotates together with the conveying rollers. And the metal sheet 8 wound on the conveying roller 5 is laid over the pressure belt 2 downstream of the feed opening 3 and starts to be wound on the conveying roller 6 at the end of the pressure belt 2. That is, a gap is formed between the metal sheet 8 coated thereon and the heating roller 1 in the extension range of the pressure belt 2, and the gap is formed in a structure in which the gap is first kept constant and then the gap is gradually increased. Specifically, the interval between one end of the metal sheet adjacent to the conveying roller 5 and the heating roller 1 is small, and the interval between the other end of the metal sheet adjacent to the conveying roller 6 and the heating roller 1 is large. The prefabricated body sent from the feeding hole 3 is conveyed by the metal sheet 8, the prefabricated body is conveyed in a gap with constant interval and gradually increased interval along with the rotation of the metal sheet 8, so that the process of heating and pressurizing firstly and then gradually puffing is realized, and finally the puffed material is sent out of the discharging hole 4 by the metal sheet 8.

Further, the degree of gap progression in gap region B, which is a progressively increasing pitch of the bulking units, is related to the feed rate. The feeding rate is controlled to be slower when the pitch of the region B is changed sharply, and is controlled to be faster when the pitch of the region B is changed slowly. The feeding speed is determined by the rotating speed of the heating roller and the conveying speed of the metal sheet, and the rotating speed of the heating roller is the same as the conveying speed of the metal sheet. And the speed of the sheet metal is determined by the speed of the conveying rollers. Preferably, the rotating speed of the heating roller and the rotating speed of the conveying roller are both less than 40m/min, and more preferably, in the range of 0.4-10 m/min.

The heating temperature of the heating roller also needs to be controlled, and can be controlled by the heating part, such as resistance heating, heating medium heating, electric induction heating; the heating temperature of the material in the area A and the area B is the same, and the heating temperature range can be 140-400 ℃.

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 of the first embodiment.

First, a preform prepared using a solvent type resin and a solvent is fed through a feed port 3 to a gap area A (i.e., a heating unit) where the interval is maintained, and the heating temperature of the heating roller is set to 270 ℃ by a control unit, the rotation speed of the conveying roller is 2m/min, and the rotation speed of the heating roller is also 2 m/min. The preform is heated and pressurized in the region a to melt the preform and vaporize the resin melting solvent. In this region a, since the gap distance is kept constant, the heated material maintains a state in which the shape is constant, and swelling does not occur.

The material then continues to be conveyed to the spaced regions B of increasing spacing (i.e., the expansion unit) where the material expands as the spacing of the regions B increases. The expansion factor of the puffing unit (i.e., the increase factor of the pitch of the gap) in this example is set to 5 times.

And finally, the puffed material enters a shaping unit, and the shape of the puffed material is shaped by adopting a natural cooling means, so that the solvent type resin heat insulation material with the nano porous polymer skeleton structure is obtained, and the porosity of the solvent type resin heat insulation material is 80%.

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 heating device is provided with a heating roller and a pressure belt, wherein the pressure belt is arranged around the heating roller, a gap is formed between the pressure belt and the heating roller, and the gap is formed into a structure that the interval is kept unchanged firstly and then gradually increases;

the preform is a sheet, which is conveyed into the gap between the heating roller and the pressure belt;

the heating unit includes a gap area where a distance between the heating roller and the pressure belt is kept constant;

the bulking unit comprises a gap area with gradually increased distance between the heating roller and the pressure belt;

the sizing unit includes an area downstream of the bulking unit and no longer in contact with the heated roller and pressure belt.

3. The production system according to claim 2,

the device also comprises a metal sheet which covers the pressure belt and is driven by the conveying roller to rotate.