CN110804205A

CN110804205A - Water-soluble resin heat-insulating material with nano porous structure and preparation method thereof

Info

Publication number: CN110804205A
Application number: CN201911260976.1A
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: 2020-02-18
Anticipated expiration: 2039-12-10
Also published as: CN110898688B; CN110898681B; CN110938271A; CN110898689B; CN110951106A; CN110894167A; CN110898681A; CN110804205B; CN110951106B; CN110898689A; CN110938271B; CN110898688A

Abstract

The invention discloses a water-soluble resin heat-insulating material with a nano porous structure and a preparation method thereof. The preparation method of the water-soluble resin heat insulation material with the nano porous structure comprises the steps of heating a prefabricated body which takes water-soluble resin as a framework and is uniformly dispersed with a proper amount of water so as to vaporize molten resin water and maintain the shape of the molten resin water unchanged; then increasing the volume by bulking until the required porosity is reached; cooling to obtain the water-soluble resin heat-insulating material with the nano-porous polymer skeleton structure.

Description

Water-soluble resin heat-insulating material with nano porous structure and preparation method thereof

Technical Field

The invention belongs to the field of processing and application of heat insulation materials, and mainly relates to a water-soluble resin heat insulation material with a nano porous structure and a preparation method thereof.

Background

The existing heat insulation and preservation material is generally a special gel which replaces liquid in the gel with gas and does not change the network structure or volume of the gel per se, and is a product after hydrogel or 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.

In the preparation process, patent CN107034678B proposes that polyurethane sol is obtained by partial cross-linking of polyurethane prepolymer, then gel formed after silica sol is soaked in glass fiber felt is soaked in the polyurethane sol to convert the polyurethane sol into gel, and composite gel of the glass fiber felt silica gel and polyurethane is obtainedAnd finally, drying under normal pressure or supercritical drying to prepare the polyurethane and silicon dioxide composite heat-insulating material. Mixing chitosan, acid, filler, phenols and aldehydes in water or water/anhydrous ethanol mixed solution, performing hydrothermal reaction to obtain phenolic resin organogel, soaking the phenolic resin organogel in organic solvent for replacement, and performing supercritical CO extraction₂And drying to obtain the phenolic resin heat insulation material. Firstly, a silica sol system is prepared by CN105859320A, melamine foam is put into a mould, the silica sol system is poured, kept stand and aged, and then cleaned, replaced, dried and thermally treated to obtain the light melamine aerogel felt.

The existing heat insulation material processes are all improved aiming at the sol-gel preparation process of the heat insulation material, no innovation is provided on the drying method, and aiming at the problems existing in the processes, the inventor actively researches and innovates on the basis of long-term practical experience and abundant professional knowledge, and finally invents a method for preparing the heat insulation material by high-temperature swelling of an adhesive, so as to solve the defects in the prior art.

Disclosure of Invention

The invention aims to provide a water-soluble resin heat-insulating material with a nano porous structure and a preparation method thereof.

In a first aspect, the invention provides a method for preparing a water-soluble resin heat insulation material with a nano porous structure, which comprises heating a preform with a water-soluble resin as a framework and uniformly dispersed with a proper amount of water to vaporize molten resin water and maintain the shape of the molten resin water unchanged; then increasing the volume by bulking until the required porosity is reached; cooling to obtain the water-soluble resin heat-insulating material with the nano-porous polymer skeleton structure. The thermal insulation material with the nanoscale pore diameter prepared by the method disclosed by the invention has the porosity of 80-99.8%. The aperture size is adjustable within the range of 0.5-999 nm.

The preform is allowed to contain a suitable amount of water which vaporizes at a temperature to cause the preform to expand to form a hole. Too high water content easily causes too large pore diameter or uneven pore diameter distribution, too low water content easily causes insufficient puffing degree or unsuccessful puffing, so that the water content is controlled within a certain range, which is beneficial to the uniform distribution of the pore diameter of the material and the control of the pore diameter, and the heat insulation performance of the material is improved. The material volume is kept unchanged, namely, the material is not expanded when water is vaporized, and the pore size distribution can be controlled. The maintenance of its form means that the water is vaporized without puffing. Maintaining the morphology can be accomplished by controlling the volume of the material constant during the vaporization of the solvent by the heating.

In one scheme, a water-soluble resin raw material is dissolved in water to form a prefabricated body with the water content accounting for 5-40 wt% of the total amount; heating the preform to vaporize the water and maintain its form substantially unchanged; the volume of the material is increased by bulking until the required porosity is reached, and the heat insulation material with the nano porous skeleton structure is obtained.

In a preferred embodiment, the preform having the water-soluble resin as a skeleton and an appropriate amount of water uniformly dispersed therein may be prepared by dissolving the water-soluble resin with an excess amount of water to obtain a solution in which water is uniformly dispersed in the water-soluble resin; finally, the water content of the solution is reduced until the water content reaches the required content. The excessive solvent is used for dissolving the raw materials, so that the raw materials can be fully dissolved, the water can be uniformly dispersed in the raw materials, and the swelling of the product is facilitated to form more uniform pore size distribution. The resin may be dissolved in water in an amount of 0.2 to 10 times the weight of the resin. The amount of the water 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 water. It is understood that the resin should be completely dissolved in water. In some embodiments, the water content of the resulting solution is reduced by heating to a temperature below the glass transition temperature of the water-soluble resin. In some embodiments, the heating temperature is 25-200 ℃. The manner and apparatus of heating are not limited as long as the content of water is reduced to a desired content. The rate of water reduction is slower at lower heating temperatures, but the heating temperature is not too high to avoid premature puffing of the resin.

In order to further improve the properties of the material, in some embodiments, the preform has a water-soluble resin as a skeleton in which an appropriate amount of water and a curing agent are uniformly dispersed. The preparation process of the prefabricated body comprises the steps of dissolving the water-soluble resin by using water, and uniformly mixing the water-soluble resin with the curing agent in a certain proportion to obtain a solution in which the water and the curing agent are uniformly dispersed in the water-soluble resin; finally, the water content of the solution is reduced until the water content reaches the required content. Wherein, the addition amount of the curing agent can be 1-40% of the water-soluble resin. The addition of the curing agent can promote the water-soluble resin to have no fluidity (the viscosity of the material is increased) at the glass transition temperature so as to prevent the influence of the good fluidity on the pore size and the pore size distribution after the material is expanded and increase the strength and the waterproof performance of the material. Preferably, the mass of the curing agent is 1-40 wt% of the water-soluble resin aqueous solution.

The heating temperature for heating the preform to vaporize the molten water of the resin is preferably in excess of the boiling point of water. More preferably, the heating temperature is 140 to 400 ℃. It should be understood that during the heating process (before puffing), the water is ensured to be vaporized under the condition of the water content at the moment, so that the pore-forming of the material by puffing is facilitated at the later stage to form the nano-porous material with uniform pore size distribution. The heating time can be reduced when the heating temperature is high. The control of the addition amount of the curing agent and the water content of the preform can ensure that the preform can keep a skeleton structure in the heating process.

In a preferred embodiment, the preform may be simultaneously pressurized while heating the preform to vaporize the molten resin water. Pressurization is not necessary because pressure is generated by vaporization of water during heating. The pressurization pressure is adjusted according to the water content, the temperature of heating and the desired pore size. The water is vaporized by heating and pressurizing, and the volume of the material is kept unchanged. The material is then slowly depressurized (puffed), i.e., the pressure is reduced, increasing its volume to a specified porosity. The range of pressurization is preferably higher than the saturated vapor pressure of water used for dispersing the resin under the heating condition. The decompression time is controlled to complete the expansion and to form a specified porosity and pore size distribution. Too rapid a pressure reduction tends to result in too large a pore size and a non-uniform pore size distribution. Too slow a pressure reduction tends to result in expansion failure or too low porosity. Preferably, the pressurizing pressure is 0.01-20 MPa. In one embodiment, the pressure reduction time is preferably 0.5 to 10 seconds in order to achieve a pore diameter of 100nm or less and a porosity of 80% or more.

In a preferred embodiment, the swelling temperature is higher than the curing temperature of the water-soluble resin with the added curing agent. Thus, after the swelling is finished, the curing agent and the resin are subjected to chemical reaction, and the curing agent can cure the resin, so that the formation of a polymer framework is promoted, the strength of the resin is improved, and the heat resistance, the water resistance and the corrosion resistance of the resin are enhanced.

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 method can ensure that the porosity of the prepared heat insulation material with the nano-scale aperture is 80-99.8%. And the volume increasing process of the materials in the puffing process is a gradual change process under a controllable state. The material expansion process is preferably achieved by passing the material under controlled conditions through a die having a gradual design of volume. Also, puffing may be accomplished by puffing the material in a die, and by controllably moving the upper and/or lower dies. Alternatively, bulking can be achieved by controlling the speed of rotation of the rollers to move the material controllably by maintaining the gap between the rollers (or heated roller and pressure belt) constant so that the material is compressed and then pulled off the rollers (or heated roller and pressure belt) during movement. The pressure during puffing is gradually reduced from 20-0 MPa.

In a preferred embodiment, the preform heating process and the preform expanding process are performed using a system for preparing a material having a nanoporous structure including a hot press roll. The preform is preferably fed into the manufacturing system at a predetermined rate as a sheet, heated between two rolls and subjected to some compression and water vaporization. The preform is compressed between the rolls to substantially prevent puffing (and to the extent that it is within a closed space) when the preform contacts the rolls on both sides, and puffing does not occur until the preform is subsequently released from the rolls and the pressure is released. The increase in expanded volume occurs as the sheet exits the twin roll gap 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 sheet thickness is preferably made to be well above the twin roll gap by 10-40% so that it is somewhat squeezed as it enters between the rolls. The time for evaporation of the solvent as the material is heated in the nip between the rolls can be controlled by controlling the roll speed, and the rate at which the material exits the rolls (i.e. controlling the puffing process) can also be controlled. In a preferable scheme, the thickness of the sheet is preferably 0.5-5 mm, and the temperature of the double-roller hot press is preferably 230-300 ℃; the speed of the double rollers is preferably 0.4-10 m/min; the twin roll gap is preferably 0.5-6mm (in the case where no particular mention is made, the twin roll gap means the minimum distance between the twin rolls).

In a preferred embodiment, the preform is fed into a system for producing a material having a nanoporous structure comprising a screw extrusion section, heated to vaporize water, then fed into a conveying section while maintaining its morphology, and then fed into a bulking unit of increasing volume to bulk the material to achieve a desired porosity. And the volume increasing process of the materials in the puffing process is a gradual change process under a controllable state. The bulking unit can be a fixed-size die with gradually changed die volume, so that the bulking process of the material is changed into a gradual change process.

In a preferred embodiment, the preform is fed into a molding press having a variable volume container, and the expansion process is controlled by controlling the volume change of the container to achieve the desired porosity. The puffing unit can be a die consisting of an upper die and a lower die with fixed sizes, and the upper die and/or the lower die can move relatively in a controllable way to realize puffing. Specifically, the pressure relief speed can be controlled by controlling the demolding speed, so that the pressure during puffing is controlled to be slowly reduced, the material is uniformly puffed under the condition of pressure, and the porosity can be controlled. The pressure during puffing is gradually reduced from 20-0 MPa.

In a preferred embodiment, the preform is fed into an injection molding machine having a variable volume container, and the expansion process is controlled by controlling the volume change of the container to achieve the desired porosity. The puffing unit can be a die consisting of an upper die and a lower die with fixed sizes, and the upper die and/or the lower die can move relatively in a controllable way to realize puffing.

Preferably, the pore size, pore size uniformity, and/or porosity is controlled by controlling at least one of water content, heating temperature, pressurization pressure, and depressurization (expansion) rate.

According to the preparation method, water is uniformly dispersed in the resin framework, so that the resin is conveniently expanded to form holes after the water is heated and vaporized in the later period. And the pore size, the uniform pore diameter and/or the porosity of the material can be controlled by controlling the temperature and the puffing, and compared with the freeze drying and supercritical drying preparation process, the method is more convenient, quicker and more economic and has adjustable pore diameter.

In a second aspect, the invention further provides the water-soluble resin heat-insulating material with the nano-porous structure, which is obtained by the preparation method, and comprises a porous polymer skeleton formed by taking water-soluble resin as a raw material, wherein nano-scale pores are uniformly distributed in the porous polymer skeleton, and the pore size is adjustable within the range of 0.5-999 nm.

The water-soluble resin heat-insulating material with the nano-porous structure has excellent mechanical property and heat-insulating property.

Drawings

FIG. 1 is a drawing of a polyurethane preform obtained according to an embodiment of the present invention;

FIG. 2 is a diagram of a polyurethane thermal insulation material according to an embodiment of the present invention;

FIG. 3 is a photograph of the polyurethane thermal insulation material obtained in example 6;

FIG. 4 is a photograph of the polyurethane thermal insulation material obtained in example 7;

FIG. 5 is a photograph of the polyurethane thermal insulation material obtained in comparative example 1;

FIG. 6 is a photograph of the polyurethane thermal insulation material obtained in comparative example 2.

Detailed Description

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

The following shows a preparation method of the water-soluble resin heat insulation material with a nano-porous structure.

For some water-soluble resins, water is uniformly dispersed in the water-soluble resin to give a preform having the water-soluble resin as a skeleton in which an appropriate amount of water is uniformly dispersed. Regarding the preparation of the preform, in one embodiment, the water-soluble resin is dissolved in water and directly mixed to prepare the preform. In another embodiment, the preparation of the preform may comprise the following two steps: (1) the water-soluble resin is first dissolved with excess water to obtain a solution. (2) Then, the water of the resulting solution is reduced and the water is uniformly dispersed in the water-soluble resin. The mixing may be performed by a mixing device such as a mixer or a blender. The resin and water 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.

For some water-soluble resins, water and a curing agent are uniformly dispersed in the water-soluble resin to give a preform having the water-soluble resin as a skeleton in which an appropriate amount of water and the curing agent are uniformly dispersed. The water is used for making holes and can be vaporized at a certain temperature to enable the prefabricated body to be expanded and formed into holes. Curing agents are a class of substances or mixtures that enhance or control the curing reaction. The curing agent can cure the resin, improve the strength of the resin and enhance the heat resistance, water resistance and corrosion resistance of the resin. The curing agent is capable of chemically reacting with the resin to cure the resin. The curing agent can enable the resin to be cured after being expanded, so that the resin has no flowability at the glass transition temperature, and the influence on the pore diameter and the pore size distribution caused by the good flowability of the resin after being expanded is prevented. The water content in the preform can be 5-40% of the water-soluble resin. When the water is in the content range, the later-stage puffing control is facilitated. Too high water content easily causes too large pore diameter or uneven pore diameter distribution, and too low water content easily causes unsuccessful puffing, so that the water content is controlled within a certain range, which is beneficial to uniform pore diameter distribution and pore diameter control of the material, and the heat insulation performance of the material is improved.

With respect to the preparation of the above preform including the curing agent, in one embodiment, a water-soluble resin is dissolved with water and directly mixed with an appropriate amount of the curing agent to prepare a preform. In another embodiment, the preparation of the preform may comprise the following two steps: (1) the water-soluble resin is dissolved by using excessive water and is uniformly mixed with the curing agent to obtain solution. (2) Then, the water of the resulting solution is reduced, and the water and the curing agent are uniformly dispersed in the water-soluble resin. The mixing may be performed by a mixing device such as a mixer or a blender. The resin and water 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. A large dose of water can dissolve the resin relatively quickly and uniformly. The resin may be dissolved in water in an amount of 0.2 to 10 times the weight of the resin. The amount of the water 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 water. The water is then reduced to an appropriate amount. The addition mass of the curing agent can be 1-40% of the water-soluble resin aqueous solution. If the addition quality of the curing agent is too low, the curing effect may be poor or the curing may be uneven; if the added quality of the curing agent is too high, the resin may be allowed to cure before it is expanded or when the expansion is insufficient.

The preform includes a suitable amount of water which can be vaporized by heating to promote the subsequent expansion of the material to form a nanoporous material (with a porosity of greater than 80%). The water needs to be capable of fully dissolving the resin and uniformly dispersing the water in the resin, thereby being beneficial to the uniformity of the later-stage expanded pore size distribution. Furthermore, the water-soluble resin is not necessarily water-soluble, and may be water-free, and needs to be dissolved by adding water. Drying and setting sol materials with high solvent content directly can have an effect on the pore size of the material (e.g., collapse, deformation) and pore size is difficult to control. The method disclosed by the invention can regulate the pore size, pore uniformity and/or porosity of the material by heating the preform with a certain solvent content, controlling the heating vaporization temperature of the preform with a certain solvent content and the subsequent speed of pressure release in the puffing process, and the prepared nano-porous material has the porosity of more than 80%. Compared with the process for preparing the nano porous material with the porosity of more than 80% by freeze drying and supercritical drying, the method disclosed by the invention is more convenient, quicker, more economical and has adjustable pore diameter.

In the step (2) of the preparation of the above preform, in one embodiment, water may be reduced by applying a certain temperature to the resulting solution. The temperature may be set so that the water in the resin is partially evaporated (vaporized) without melting the resin, and the water content may be within a specific range. In order to ensure that the resin does not swell in advance, the temperature in the step (2) of the preparation of the preform should be lower than the glass transition temperature (or curing temperature) of the resin, so that the resin does not flow and premature swelling is avoided. The heating temperature can be selected within 25-200 ℃ according to different resin types. It should be understood that while the boiling point of water is 100 ℃, the water will not be completely evaporated as long as the time is short enough to reach a specific water content range. The heating temperature is too low, the water is slowly reduced, and the industrial chain time is prolonged; if the heating temperature is too high, the water in the preform is vaporized and expanded in advance, and the pore diameter distribution of the product cannot be controlled to be uneven.

In the step (2) of the preparation of the above preform, any apparatus capable of reducing the water content to effect drying may be used. In another embodiment, the water content can be reduced by an apparatus with high temperature capability, such as a twin screw extruder, which can increase the temperature of the material but can be controlled so that the material does not expand. The resulting solution was reduced in water. The apparatus used for controlling the moisture content may be a parallel twin-screw extruder, a conical twin-screw extruder, an open mill, an internal mixer, a drying cabinet, a microwave oven, a freeze dryer, a pressure sprayer, an impinging stream dryer, or the like. Methods used to reduce water content include, but are not limited to, atmospheric drying, reduced pressure drying, spray drying, fluidized drying, freeze drying, infrared drying, microwave drying, moisture absorption drying, impingement drying, sonic drying, displacement drying, steam drying, ice slurry drying, airless drying, pulse combustion drying, and the like. The industrial mass production can be realized by using the instrument, so that the limitation of the production quantity is avoided.

The source of the water-soluble resin is not particularly limited, and the water-soluble resin can be prepared by the existing method or can be obtained by commercial purchase.

"Water-soluble resin" refers to a resin that is water-soluble. The resin is selected from water-soluble phenolic resin, water-soluble epoxy resin, water-soluble melamine formaldehyde resin, water-soluble urea formaldehyde resin, water-soluble unsaturated polyester resin, water-soluble polyurethane resin, water-soluble acrylic resin, polyacrylamide, sodium polyacrylate, polyethylene glycol, polyvinyl alcohol, polymaleic anhydride, polyethyleneimine, polyethylene oxide, polyvinyl chloride, starch, water-soluble natural gum, methyl cellulose, hydroxyethyl cellulose and sodium carboxymethyl cellulose.

The invention can select proper curing agent according to different requirements and resin types. In some embodiments, suitable curing agents for the water-soluble phenolic resin can be inorganic and organic medium-strong acids, and can also be sodium carbonate, sodium bicarbonate, paraformaldehyde, hexamethylenetetramine, isocyanate, propylene carbonate, methyl methacrylate, vinyl acetate, triethanolamine, butyl acrylate, ammonium chloride, petroleum ether, trimethyl phosphate, benzenesulfonic acid, and the like; suitable curing agents for water-soluble epoxy resins include aliphatic diamines, aliphatic polyamines, aromatic polyamines, nitrogen-containing compounds, modified aliphatic amines, organic acids, acid anhydrides, boron trifluoride and complexes thereof; suitable curing agents for the water-soluble melamine-formaldehyde resin include sulfuric acid, hydrochloric acid, formic acid, ammonium chloride, ammonium sulfate, and the like; suitable curing agents for the water-soluble urea-formaldehyde resin include sulfuric acid, hydrochloric acid, formic acid, ammonium chloride, ammonium sulfate, and the like; suitable curing agents for the water-soluble unsaturated polyester resin include cyclohexanone peroxide, dibenzoyl peroxide, methyl ethyl ketone peroxide, and the like; suitable curing agents for the water-soluble polyurethane resin include toluene diisocyanate, trimethylolpropane, biuret polyisocyanate, and the like; suitable curing agents for water-soluble acrylic resins include isocyanates, pyridine, amino resins, resins with epoxy groups, titanium tetraisopropoxide, and the like.

And then, carrying out porosity treatment on the intermediate (preform) to obtain the water-soluble resin heat-insulating material with the nano porous structure. The voiding treatment refers to a treatment of melting a resin while vaporizing water to generate voids in the resin. Specifically, the preform is heated to vaporize the resin molten water and keep the volume or the shape of the resin molten water unchanged, then the volume is increased by expanding and releasing pressure until the required porosity is reached, and the water-soluble resin heat insulation material with the nano porous polymer skeleton structure is obtained by natural cooling.

The preform is heated to ensure sufficient time for the resin to melt and the water to vaporize and maintain a constant volume of material. The pressure is then controllably relieved, i.e., reduced (water vaporization pressure), to increase the volume of the material to a desired porosity. And then cooling to keep the structure stable, and preparing the resin heat-insulating material with the nano porous structure. The heating temperature should be higher than the glass transition temperature of the resin to impart fluidity to the resin. And the volume increases as the water vaporizes causing the resin to swell.

The temperature to be heated during the porosification treatment of the intermediate (preform) may be selected according to the kind of the water-soluble resin. In a preferred embodiment, the temperature of heating exceeds the boiling point of water and exceeds the glass transition temperature of the water-soluble resin. A portion of the thermosetting resin must be cured by the addition of a curing agent. For resins requiring the addition of a curing agent, the preform is required to be heated at a temperature higher than the curing temperature of the water-soluble resin. If the temperature is too low, this can result in too low a material expansion; if the temperature is too high, the pore diameter of the material is too large, thereby affecting the heat insulation performance of the material. In some embodiments, the heating temperature is in the range of 140-400 ℃.

The heating time for the preform porosification treatment is preferably controlled so that water is vaporized at the heating temperature. The lower the water content and the higher the temperature, the shorter the heating time. In this heating process, water may be completely vaporized, but a small amount of water may remain, only having a certain influence on the thermal conductivity of the material, as long as the thermal conductivity is satisfactory.

In some embodiments, the preform may also be pressurized simultaneously with the heating to vaporize the water. The water is vaporized by pressurizing while heating, and the volume of the material is kept constant to regulate the pore structure, such as uniform pore distribution and pore size. The pressure can be controlled to be higher than the saturated vapor pressure of water at this time temperature and the volume of the material is made constant. Then the subsequent pressure release is carried out to realize the expansion. In some embodiments, the pressurization pressure is 0.01 to 20 MPa. In a more preferred embodiment, the pressurization pressure is 0.1 to 10 MPa.

After the water is vaporized, slowly releasing the pressure, namely expanding. In the process, the pressure in the material is gradually reduced, and the volume of the material is gradually increased. It should be understood that the process of increasing the volume of the material during puffing should be controlled to be gradual under a controlled state. The bulking process is performed to increase the volume of the material to achieve a specified porosity. In the pressure relief process, because the water is in a gaseous state at this time and the material still has a certain fluidity, the water vapor pressure causes the volume of the material to increase, thereby causing the material to expand. For the pressure relief time, it is desirable to complete the expansion and to provide a suitable porosity and uniform pore size distribution. The rate of pressure reduction should be such that material expansion is achieved and the desired porosity is achieved. In some embodiments the time for pressure release is not less than 0.4 seconds. Too rapid a pressure reduction tends to result in too large a pore size and a non-uniform pore size distribution. But too slow a pressure reduction tends to cause puffing failure or too low a porosity. It should be understood that small amounts of water may remain at the time of initial pressure release, as long as the thermal conductivity is within the desired range.

The present invention can control the pore structure, such as pore size and/or uniformity of pore size distribution, by controlling at least one of water content, heating temperature, puffing rate.

In some embodiments, the preform is sent to a system for preparing a material having a nanoporous structure comprising a heated press roll for porosification.

When the production system of the material having a nanoporous structure including the hot press roll is used, the intermediate material sent to the production system of the material having a nanoporous structure including the hot press roll is preferably a sheet. The sheet can be processed in any manner, including extrusion through a twin-screw extruder, and can also be formed by a two-roll hot press. The processing temperature for forming the sheet should be lower than the puffing temperature, preferably, the processing temperature for forming the sheet is lower than the boiling point of water, and more preferably, the processing mode for forming the sheet is cold pressing at normal temperature. The thickness of the sheet is preferably 10 to 40% higher than the gap between the twin rolls (the minimum distance between the twin rolls is not particularly specified). Since the sheet thickness is higher than the twin roll nip, when the sheet is fed into a system for preparing a material having a nanoporous structure including a hot press roll until the sheet is separated from the twin roll nip (i.e., the minimum distance of the twin rolls), the sheet is subjected to temperature and twin roll compression (i.e., heat and pressure) so that water is vaporized; and after the sheet exits the nip between the rolls, the volume of material increases as the pressure is released as the distance between the rolls increases (i.e., slowly decreases), allowing for puffing. When the preparation system of the material with the nano-porous structure comprising the hot press roller is adopted, the pressurizing pressure can be controlled by controlling the gap of the double rollers, and the decompression speed and the pore morphology can be controlled by controlling the rotating speed of the double rollers, so that the size of the pore diameter and the uniformity of the pore diameter distribution can be controlled. Wherein, the slow pressure relief is realized by the gradual increase of the double-roller gap, and the pressure is reduced as the double-roller gap is increased. It will be appreciated that the higher the water content and the higher the temperature, the lower the speed of rotation of the twin rolls. Since the higher the temperature, the higher the water content and the higher the fluidity of the material, the lower the speed of rotation of the twin rolls, the formation of large bubbles in the insulating material can be avoided. In a specific embodiment, the water content in the preform is preferably 20 to 25% of the resin. The heating temperature of the preform is preferably 250 to 300 ℃. Moreover, the rotating speed of the double rollers can be less than 40m/min, and preferably, the rotating speed of the double rollers is 0.4-10 m/min; more preferably, the rotation speed of the double rollers is 1.5-3 m/min. The gap between the two rollers can be 0.5-6 mm; preferably 2-4 mm. The larger the gap between the rolls, the higher the expansion, the greater the porosity, the better the thermal insulation and the lower the thermal conductivity, provided that the material is allowed to contact the rolls. The larger the gap between the rolls, the higher the expansion, the greater the porosity, the better the thermal insulation and the lower the thermal conductivity, provided that the material is allowed to contact the rolls.

In some embodiments, the preform heating process and the preform bulking process are performed using a system for preparing a material having a nanoporous structure comprising a heated press roll. The material is heated and extruded to some extent between the two rollers to vaporize water, and the vaporization degree of water is preferably controlled to 90-100%. The degree of vaporization of water in the material between the rolls is related to the desired pore size and porosity of the final product. The higher the degree of vaporization, the larger the pore size and the higher the porosity. And because the water fully dissolves the material and is uniformly distributed in the material, the nano-scale holes left after the water is vaporized are uniformly distributed in the material. The pressure created by the vaporized water as the sheet exits the twin roll gap causes the material to expand 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. The sheet thickness is preferably made to be suitably greater than 10-40% of the twin roll gap so that it is subjected to some squeezing as it enters between the twin rolls. The time for evaporation of the solvent as the material is heated in the nip between the rolls can be controlled by controlling the roll speed, and the rate at which the material exits the rolls (i.e. controlling the puffing process) can also be controlled. In a preferred embodiment, the temperature of the double-roller hot press is preferably 230 to 300 ℃ and the speed of the double rollers is preferably 0.4 to 10m/min when the thickness of the sheet is 0.5 to 5 mm. The sheet material can be placed in iron sheets and between the twin rolls in order to allow sufficient heating. Two pieces of release paper of the same specification as the iron sheet may be prepared for better release.

In some embodiments, the preform is fed into a system for producing a nanoporous material comprising a screw extrusion section, heated to vaporize water, then fed into a conveying section while maintaining its morphology, and then fed into a bulking unit of increasing volume to bulk the material to achieve a desired porosity. And the volume increasing process of the materials in the puffing process is a gradual change process under a controllable state. The bulking unit can be a fixed-size die with gradually changed die volume, so that the bulking process of the material is changed into a gradual change process.

In some embodiments, the intermediate is fed to a molding press for porosification. The intermediate is fed into a closed container placed between an upper die and a lower die of a die press. The shape of the intermediate body can be adjusted according to the shape of the closed container. The puffing unit can be a die consisting of an upper die and a lower die with fixed sizes, and the upper die and/or the lower die can move relatively in a controllable way to realize puffing. The upper part can be driven to move towards the direction far away from the lower part along with the movement of the upper die, so that the volume of the accommodating part is gradually changed. When the molding press is used, the porosity of the material is controlled by controlling the interval between the upper and lower molds, that is, the volume change of the receiving portion.

In some embodiments, the intermediate is fed to an injection molding machine for voiding. The expanding principle of the molding press is basically the same as that of the injection molding machine, and the difference is that the injection molding machine injects materials into a closed container in an injection mode.

In some embodiments, the intermediate is fed to a drum vulcanizer for porosification. The drum vulcanizer works in a similar manner to the two-roll hot press except that the two rolls are replaced by a heated roll and a pressure belt. The preform is heated and pressurized in a region where the gap between the heating roller and the pressure belt is kept constant, to vaporize water. 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 heated roller is 140 ℃ to 400 ℃, and the rotating speed of the heated roller is 0.4-10 m/min.

Compared with the prior art, the preparation method has the beneficial effects that:

1. the puffing and drying technology adopted by the method of the invention provides a brand new idea for drying the heat insulation material. Compared with freeze drying and supercritical drying preparation processes, the method is more convenient, faster, more economical and has adjustable aperture. Both supercritical carbon dioxide drying and vacuum freeze drying require gel formation prior to drying and subsequent drying. The present invention does not require the step of forming a gel.

2. The method is carried out on the basis of the existing equipment without other additional equipment.

3. The method has simple and feasible process and lower cost, and is beneficial to industrial production.

The heat insulation material prepared by the preparation method can be in the forms of plates, films, blocks, powder, particles and the like. Therefore, the material obtained by the preparation method of the invention has the advantages of abundant types, convenient preparation and low cost, and can meet the requirements of various complex geometric shapes, mechanics and thermal properties.

The invention also provides a water-soluble resin heat insulation material with a nano porous structure, which comprises a porous polymer skeleton formed by taking water-soluble resin as a raw material. Wherein the nanopores are uniformly distributed in the porous polymer backbone. And the aperture size is adjustable within the range of 0.5-999 nm.

In some embodiments, the thermal insulation material has a porosity of 80-99.8%. Porosity in the present invention is tested by the following method: p ═ V₀-V)/V₀*100％＝(1-ρ₀ρ) × 100%, wherein: p-porosity of material,%; v₀Volume or apparent volume, cm, of material in its natural state³Or m³；ρ₀Bulk density of the material, g/cm³Or kg/m³(ii) a V-Absolute dense volume of material, cm³Or m³(ii) a Rho-material density, g/cm³Or kg/m³。

In some embodiments, the density of the thermal insulation material is 0.004-0.5 g/cm³. The density in the present invention is measured by the following method: p is m/abt 10⁴Rho-density, kg/m³(ii) a m-dry mass of sample, g; a is the length of the sample, mm; b-width of the sample, mm; t-thickness of the pattern, mm.

In some embodiments, the thermal insulation material has a specific surface area of 100-2000 m²(ii) in terms of/g. The specific surface area of the invention is obtained by testing the specific surface area of V-Sorb 2800P and a pore size analyzer.

In some embodiments, the thermal insulation material has a thermal conductivity of 0.018-0.04W/mk. The thermal conductivity is obtained by testing the thermal conductivity by a transient hot wire method through a thermal conductivity tester.

The water-soluble resin heat insulation material has a nano porous network structure, can effectively inhibit gas heat conduction and solid heat conduction, realizes heat insulation in all aspects, and has good mechanical property and lower density.

In conclusion, the water-soluble resin heat-insulating material provided by the invention is prepared from cheap and easily available water-soluble resin (adhesive) as a raw material by a simple reaction path and a method for controlling pressure release. Moreover, the water-soluble resin heat insulation material has good heat insulation efficiency, low heat conductivity and good high-temperature scour resistance, is mainly used in the technical fields of light heat-proof/high-temperature heat insulation heat protection systems and the like, and has important application value.

The present invention will be described in detail by way of examples. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below. In the case where the present invention is not specifically described, the addition ratio and the content refer to mass.

The water-soluble polyurethanes in the following examples were purchased from shanghai Lingfeng Chemicals, ltd; acrylic emulsion, purchased from Shenzhen Jitian chemical Co., Ltd; water-soluble phenolic resins available from Shanghai Merlin Biotech, Inc.; propylene carbonate, available from Shandong Xin Chemicals, Inc.; water-soluble epoxy resin, purchased from Shenzhen Jitian chemical Co., Ltd; dicyandiamide, available from Shandong Xin Chemicals, Inc.; water-soluble urea-formaldehyde resins, available from enchana industries ltd, Henan; ammonium chloride, available from Shandong triple chemical Co., Ltd; water-soluble unsaturated polyester resins available from Henan Hui energy resins, Inc.; cyclohexanone peroxide, available from Shanghai Yizhen chemical Co., Ltd; isocyanate, available from johnson chemical ltd; polyvinyl alcohol, available from environmental protection technologies, ltd, lonyo, anhui; starch, available from Guangdong Hongxin Biotech, Inc. All other reagents used were analytically pure and were purchased directly without further purification.

Examples 1 to 4

The preparation method of the water-soluble resin heat-insulating material with the nano-porous structure takes a polyurethane aqueous solution (with the solid content of 43%) as a raw material, and comprises the following steps:

(1) reducing the water content of the polyurethane aqueous solution to 20% of the polyurethane at 90 ℃ by using an instrumental twin-screw extruder to obtain a preform; the picture of the polyurethane preform is shown in fig. 1;

(2) preparing a sheet material with the thickness of 4mm from the prefabricated body obtained in the step (1) by using an instrument double-roller hot press under the conditions of the temperature of 25 ℃, the double-roller gap of 4mm and the rotating speed of 1.5 m/min;

(3) and (3) conveying the sheet material obtained in the step (2) into a double-roller hot press, and performing puffing to obtain the water-soluble resin heat-insulating material with the nano porous structure.

Examples 1 to 4 differ in the process conditions of step (3). Wherein the content of the first and second substances,

example 1 is: the temperature is 180 ℃, the rotation speed of the double rollers is 1.7m/min, and the gap between the double rollers is 3.5 mm;

example 2 is: the temperature is 200 ℃, the rotation speed of the double rollers is 1.7m/min, and the gap between the double rollers is 3.5 mm;

example 3 is: the temperature is 230 ℃, the rotating speed of the double rollers is 1.7m/min, and the gap between the double rollers is 3.5 mm;

example 4 is: the temperature is 250 ℃, the rotating speed of the double rollers is 1.7m/min, and the gap between the double rollers is 3.5 mm;

in examples 1-4, the thickness of the material was changed from 4mm to 5-7 mm and the volume was 6cm from the two-roll press before the material entered the two-roll press to the exit of the two-roll press³The thickness of the film is 19.5 to 30cm³。

And (3) drying the porous material with the regular shape in an oven at 180 ℃ for 4-6 hours, wherein the weight is marked as m, and the length and the width are marked as a and b. Measuring the height h by using a vernier caliper, wherein the volume V is abh, and the density rho is m/abh;

porous material sample example 1 had a density ρ of 1.80/(5.0 × 3.0 × 0.5) of 0.24g/cm³；

Porous material sample example 2 had a density ρ of 1.73/(5.0 × 3.0 × 0.5) of 0.23g/cm³；

Porous material sample example 3 had a density ρ of 1.89/(5.0 × 3.0 × 0.7) of 0.18g/cm³；

Porous material sample example 4 had a density ρ of 1.79/(5.0 × 3.0 × 0.7) of 0.17g/cm³。

Finding P ═ 1-rho/rho by consulting the data_Polyurethane) X 100% of polyurethane with a density of 1.1g/cm³And then:

example 1 porosity P ═ (1-0.24/1.1) × 100 ═ 78%;

example 2 porosity P ═ (1-0.23/1.1) × 100 ═ 79%;

example 3 porosity P ═ (1-0.18/1.1) × 100 ═ 84%;

example 4 porosity P ═ (1-0.17/1.1) × 100 ═ 85%;

as can be seen from the above examples, the higher the temperature, the higher the porosity of the material.

Examples 5 to 7

Taking a polyurethane aqueous solution (with the solid content of 43%) as a raw material:

(1) reducing the water content of the polyurethane aqueous solution to 12 percent of that of polyurethane at 110 ℃ by using an instrument double-screw extruder to obtain a prefabricated body;

(2) preparing a sheet material with the thickness of 5mm from the prefabricated body obtained in the step (1) by using an instrument double-roller hot press under the conditions of the temperature of 25 ℃, the double-roller gap of 5mm and the rotating speed of 1.5 m/min;

(3) and (3) conveying the flaky material obtained in the step (2) into a double-roller hot press, and performing puffing to obtain the organic-inorganic composite heat insulation material with the nano porous structure.

Examples 5 to 7 differ in the process conditions of step (3). Wherein the content of the first and second substances,

example 5 is: the temperature is 280 ℃, the rotation speed of the double rollers is 1.5m/min, and the gap between the double rollers is 3.5 mm;

example 6 is: the temperature is 280 ℃, the rotating speed of the double rollers is 2.0m/min, and the gap between the double rollers is 3.5 mm;

example 7 is: the temperature was 280 ℃, the twin roll speed 4.0m/min and the twin roll gap 3.5 mm.

The thickness of the obtained heat insulation is changed from 5mm to 6-7 mm, and the volume is changed from 12cm³The thickness of the film becomes 69 to 82.5cm³. FIGS. 3 and 4 are pictures of the polyurethane thermal insulation materials obtained in example 6 and example 7, respectively.

The density of example 5 was measured to be 0.12g/cm³Example 6 density 0.11g/cm³Example 7 Density 0.09g/cm³. Finding P ═ 1-rho/rho by consulting the data_Polyurethane) X 100% of polyurethane with a density of 1.1g/cm³Example 5 porosity P ═ (1-0.12/1.1) × 100 ═ 89%. Example 6 porosity P ═ (1-0.11/1.1) × 100 ═ 90%. Example 7 porosity P ═ (1-0.09/1.1) × 100 ═ 92%. It can be seen from the above example that the porosity is higher the faster the speed of rotation, at the same temperature and with sufficient heat received.

Examples 8 to 9

Examples 8 to 9 differ in the process conditions of step (3). Wherein, the embodiment 8 is: the temperature is 180 ℃, the rotation speed of the double rollers is 1.5m/min, and the gap between the double rollers is 3.5 mm; example 9 is: the temperature is 180 ℃, the rotation speed of the double rollers is 4.0m/min, and the gap between the double rollers is 3.5 mm. The thickness of the material is changed from 4mm to 5.5-6 mm before the material enters the double-roller hot press and the material is separated from the double-roller hot press, and the volume of the material is 8cm³The thickness of the film becomes 19.3 to 17.3cm³。

The density of the material of example 8 was measured to be 0.30g/cm³Example 9 Density 0.33g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_Polyurethane) X 100% of polyurethane with a density of 1.1g/cm³Example 8 porosity P ═ 1-0.30/1.1 × (1-0.30) × 100%73%. Example 9 porosity P ═ (1-0.33/1.1) × 100 ═ 70%. As can be seen from the above example, the faster the rotation speed is, the higher the temperature is not high enough, the higher the porosity is.

Examples 10 to 13

Taking acrylic emulsion (solid content 40%) as a raw material:

(1) reducing the water content of the acrylic emulsion to 15 percent of acrylic acid at 110 ℃ by using an instrumental twin-screw extruder to obtain a preform;

Examples 10 to 13 differ in the process conditions of step (3). Wherein, the temperature of the examples 10-13 is: 200 ℃, 230 ℃, 260 ℃, 300 ℃, the rotation speed of a double roller is 1.8m/min, the gap between the double rollers is 3.5mm, the thickness of the material is changed from 4mm to 4.5-6.5 mm before and after the material is puffed, and the volume is 2.5cm³The thickness of the film becomes 9.5 to 13.3cm³。

The densities of the materials of examples 10-13 were measured to be 0.28g/cm, respectively³、0.20g/cm³、0.18g/cm³、0.14g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_{Acrylic resin}) X 100%, wherein the density of the acrylic resin is 1.1g/cm³The example 10-13 materials had porosities of 75%, 82%, 84%, 87%, respectively. It can be seen that the higher the temperature, the higher the porosity of the material. A picture of the thermal insulation obtained in example 13 is shown in FIG. 2.

Comparative example 1

(1) reducing the water content of the polyurethane aqueous solution to 43 percent of that of polyurethane at 70 ℃ by using an instrument double-screw extruder to obtain a prefabricated body;

(3) and (3) conveying the sheet material obtained in the step (2) into a double-roller hot press, wherein the temperature is 220 ℃, the gap between the double rollers is 2mm, the rotating speed of the double rollers is 1.5m/min, and the porosity of the material prepared by bulking is 82%. In this comparative example, the material was removed from the two roll press before entering the two roll press, but macroscopic macropores were present as shown in fig. 5.

Comparative example 2

(1) reducing the water content of the polyurethane aqueous solution to 4 percent of that of polyurethane at 120 ℃ by using an instrument double-screw extruder to obtain a prefabricated body;

(3) the sheet material obtained in step (2) was sent to a two-roll hot press at a temperature of 220 ℃, a gap between the two rolls of 2mm, a speed of rotation of the two rolls of 1.5m/min, and the porosity of the material obtained by puffing was 53%. In this comparative example, the thickness of the material was changed from 4mm to 4.5mm before entering the two-roll press to exit the two-roll press. Volume is from 3.8cm³It became 5.4cm³. The picture of the material obtained in this comparative example is shown in figure 6, where it can be seen that the material is not fully expanded.

The density of the material of comparative example 2 was measured to be 0.52g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_Polyurethane) X 100% of polyurethane with a density of 1.1g/cm³Comparative example 2 had a porosity P of (1-0.52/1.1) × 100% of 53%.

The data for examples 1-13 and comparative examples 1-2 are set forth in Table 1.

TABLE 1 Performance test Table for solvent type resin thermal insulation materials of examples 1-13 and comparative examples 1-2

Example 14

Taking water-soluble phenolic resin as a raw material:

(1) dissolving water-soluble phenolic resin with water, and uniformly mixing the water-soluble phenolic resin with a curing agent propylene carbonate, wherein the adding proportion of the water to the curing agent is respectively 50% and 5% of the resin, so as to obtain a solution;

(2) reducing the water content of the uniformly mixed solution obtained in the step (1) at 80 ℃ by using an instrument double-screw extruder until the water content reaches 20% of the water-soluble phenolic resin to obtain a prefabricated body;

(3) preparing a sheet material with the thickness of 4mm from the prefabricated body at the temperature of 80 ℃ and the pressure of 2 MPa;

(4) and (4) conveying the sheet material obtained in the step (3) into a double-roller hot press, and puffing at the temperature of 220 ℃, the clearance of 3mm and the double-roller speed of 1.5m/min to obtain the water-soluble phenolic resin heat-insulating material with the nano porous structure. In this example, the thickness of the material was changed from 4mm to 5mm before entering the two roll press to exit the two roll press. Volume from 1.5cm³It became 6.5cm³。

Example 14 density ρ 0.24g/cm³. Tong (Chinese character of 'tong')^{For treating}Looking up the data to get P ═ 1-rho/rho_{Phenolic resin) × 1}00% of phenolic resin with the density of 1.15g/cm³Then, then^{Fruit of Chinese wolfberry}Example 14 porosity P ═ (1-0.24/1.15) × 100 ═ 79%.

Example 15

Taking water-soluble epoxy resin as a raw material:

(1) dissolving water-soluble epoxy resin in water, and uniformly mixing the water-soluble epoxy resin with a curing agent dicyandiamide, wherein the addition ratio of the water to the curing agent is respectively 15% and 20% of the resin, so as to obtain a solution;

(2) uniformly mixing the materials obtained in the step (1) at the temperature of 60 ℃ by using an instrument double-cone extruder through mechanical force to obtain a prefabricated body;

(3) preparing a sheet material with the thickness of 5mm from the prefabricated body at the temperature of 60 ℃ and the pressure of 3 MPa;

(4) and (4) conveying the sheet material obtained in the step (3) into a double-roller hot press, and puffing at the temperature of 170 ℃, the clearance of 4mm and the speed of 1.8m/min to obtain the water-soluble epoxy resin heat insulation material with the nano porous structure. In this example, the thickness of the material was changed from 5mm to 6.5mm before entering the two roll press to exit the two roll press. Volume from 1.9cm³Becomes 8.3cm³。

The density p of example 15 was measured to be 0.37g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_{Epoxy resin}) X 100%, wherein the density of the epoxy resin is 1.85g/cm³Example 15 porosity P ═ (1-0.37/1.85) × 100 ═ 80%.

Example 16

The water-soluble urea-formaldehyde resin is used as a raw material:

(1) dissolving water-soluble urea-formaldehyde resin with water, and uniformly mixing the water-soluble urea-formaldehyde resin with a curing agent ammonium chloride, wherein the adding proportion of the water to the curing agent is respectively 20% and 5% of the resin, so as to obtain a solution;

(2) uniformly mixing the materials in the step (1) at the temperature of 80 ℃ by using an instrument double-cone extruder through mechanical force to obtain a prefabricated body;

(3) preparing a sheet material with the thickness of 5mm from the prefabricated body at the temperature of 80 ℃ and the pressure of 3 MPa;

(4) and (4) conveying the sheet material obtained in the step (3) into a double-roller hot press, and puffing at the temperature of 200 ℃, the clearance of 4mm and the speed of 1.8m/min to obtain the water-soluble urea-formaldehyde resin heat-insulating material with the nano porous structure. In this example, the thickness of the material was changed from 5mm to 6mm before entering the two roll press to exit the two roll press. Volume from 2.0cm³It became 7.5cm³。

The density ρ of example 16 was measured to be 0.27g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_{Urea-formaldehyde resin}) X 100%, wherein the urea-formaldehyde resin density is 1.17g/cm³Example 16, the porosity P is (1-0.27/1.17) and the prepared product is¹00％＝77％。

Example 17

Taking water-soluble unsaturated polyester resin as a raw material:

(1) dissolving water-soluble unsaturated polyester resin with water, and uniformly mixing the water-soluble unsaturated polyester resin with a curing agent cyclohexanone peroxide, wherein the adding proportion of the water to the curing agent is respectively 10% and 3% of the resin, so as to obtain a solution;

(3) preparing a sheet material with the thickness of 5mm from the prefabricated body at the temperature of 60 ℃ and under the pressure of 2 MPa;

(4) and (4) sending the flaky material obtained in the step (4) to a double-roller hot press, and puffing at the temperature of 220 ℃, the clearance of 4mm and the speed of 1.5m/min to obtain the water-soluble unsaturated polyester resin heat insulation material with the nano porous structure. In this example, the thickness of the material was changed from 5mm to 6.3mm before entering the two roll press to exit the two roll press. Volume from 1.6cm³It became 7.8cm³。

The density of example 17 was measured to be 0.31g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_{Unsaturated polyester resin}) X 100%, wherein the unsaturated polyester resin has a density of 1.73g/cm³Example 17 porosity P ═ (1-0.31/1.73) × 100 ═ 82%.

Example 18

Taking water-soluble polyurethane resin as a raw material:

(1) dissolving water-soluble polyurethane resin with water, and uniformly mixing the water-soluble polyurethane resin with a curing agent biuret polyisocyanate, wherein the adding proportion of the water to the curing agent is respectively 20% and 20% of the resin, so as to obtain a solution;

(2) uniformly mixing the materials obtained in the step (1) at the temperature of 50 ℃ by using an instrument double-cone extruder through mechanical force to obtain a prefabricated body;

(3) preparing a sheet material with the thickness of 5mm from the prefabricated body at the temperature of 50 ℃ and the pressure of 3 MPa;

(4) and (4) conveying the sheet material obtained in the step (3) into a double-roller hot press, and puffing at the temperature of 180 ℃, the clearance of 4mm and the speed of 1.5m/min to obtain the water-soluble polyurethane resin heat insulation material with the nano porous structure. In this example, the thickness of the material was changed from 5mm to 6.6mm before entering the two roll press to exit the two roll press. Volume ofFrom 1.8cm³Becomes 8.0cm³。

The density of example 18 was measured to be 0.19g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_Polyurethane) X 100% of polyurethane with a density of 1.1g/cm³Example 18 porosity P ═ (1-0.19/1.1) × 100 ═ 83%.

Example 19

Taking water-soluble acrylic resin as a raw material:

(1) dissolving water-soluble acrylic resin with water, and uniformly mixing the water-soluble acrylic resin with curing agent isocyanate, wherein the adding proportion of the water to the curing agent is respectively 15% and 10% of the resin, so as to obtain a solution;

(3) preparing a sheet material with the thickness of 5mm from the prefabricated body at the temperature of 80 ℃ and the pressure of 2 MPa;

(4) and (4) conveying the sheet material obtained in the step (3) into a double-roller hot press, and puffing at the temperature of 200 ℃, the clearance of 4mm and the speed of 1.8m/min to obtain the water-soluble acrylic resin heat-insulating material with the nano porous structure. In this example, the thickness of the material was changed from 5mm to 6mm before entering the two roll press to exit the two roll press. Volume from 1.9cm³It became 7.5cm³。

The density of the material of example 19 was measured to be 0.23g/cm³Looking up the data to get P ═ 1-rho/rho_{Acrylic resin}) X 100%, wherein the density of the acrylic resin is 1.1g/cm³Example 19 porosity P ═ (1-0.23/1.1) × 100 ═ 79%.

Example 20

Polyvinyl alcohol is used as a raw material:

(1) dissolving polyvinyl alcohol in water, and uniformly mixing, wherein the adding proportion of water is 20% of that of the polyvinyl alcohol to obtain a solution;

(4) and (4) conveying the sheet material obtained in the step (3) into a double-roller hot press, and puffing at the temperature of 200 ℃, the clearance of 4mm and the speed of 3m/min to obtain the water-soluble polyvinyl alcohol heat-insulating material with the nano porous structure. In this example, the thickness of the material was changed from 5mm to 6.2mm before entering the two roll press to exit the two roll press. Volume from 1.6cm³It became 7.5cm³。

The density of example 20 was measured to be 0.26g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_{Polyvinyl alcohol}) X 100% of polyvinyl alcohol with a density of 1.28g/cm³Example 20 porosity P ═ (1-0.26/1.28) × 100 ═ 80%.

Example 21

The preparation method of the water-soluble resin heat-insulating material with the nano-porous structure takes starch as a raw material and comprises the following steps:

(1) dissolving starch in water, and uniformly mixing, wherein the adding proportion of water is 25% of that of the starch, so as to obtain a solution;

(4) and (4) conveying the sheet material obtained in the step (3) into a double-roller hot press, and puffing at the temperature of 200 ℃, the clearance of 2mm and the speed of 1.8m/min to obtain the water-soluble starch heat-insulating material with the nano porous structure. In this example, the thickness of the material was changed from 5mm to 6mm before entering the two roll press to exit the two roll press. Volume is from 1.8cm³It became 7.3cm³。

The density of example 21 was measured to be 0.35g/cm³. Obtaining P ═ 1-rho/rho by consulting the data_Starch) X 100% of starch with a density of 1.6g/cm³Example 21 porosity P ═ 1 to 0.35^/1.6)×100％＝78％。

The test data for examples 14-21 are shown in Table 2.

Table 2 examples 14 to 21 table for testing the performance of heat insulating and preserving materials of solvent type resin

It should also be understood that the above examples are for illustrative purposes only and are not to be construed as limiting the scope of the present invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings.

Claims

1. A preparation method of a water-soluble resin heat insulation material with a nano porous structure is characterized in that a preform which takes water-soluble resin as a framework and is uniformly dispersed with a proper amount of water is heated to vaporize molten resin water and maintain the shape of the molten resin water unchanged; then increasing the volume by bulking until the required porosity is reached; cooling to obtain the water-soluble resin heat-insulating material with the nano-porous polymer skeleton structure.

2. The method according to claim 1, wherein the water content is 5 to 40% of the water-soluble resin.

3. The production method according to claim 1 or 2, characterized in that the production of the preform comprises:

dissolving water-soluble resin with water to obtain a solution in which water is uniformly dispersed in the water-soluble resin;

the water of the resulting solution is reduced to the desired level.

4. The production method according to claim 3, wherein the water content of the resulting solution is reduced by heating at a temperature lower than the glass transition temperature of the water-soluble resin.

5. The production method according to any one of claims 1 to 4, wherein the preform is heated at a temperature exceeding the boiling point of water and exceeding the glass transition temperature of the water-soluble resin.

6. The production method according to claim 5, wherein the preform is heated at a temperature of 140 to 400 ℃.

7. The production method according to any one of claims 1 to 6, wherein the preform is heated to vaporize the molten water of the resin while being pressurized at a pressure higher than the saturated vapor pressure of water under the heating condition.

8. The method according to claim 7, wherein the pressure is 0.01 to 20 MPa.

9. The production method according to any one of claims 1 to 8, wherein the pore size and porosity are controlled by controlling at least one of water content, heating temperature, and puffing speed.

10. The water-soluble resin heat-insulating material with the nano-porous structure obtained by the preparation method of any one of claims 1 to 9, which is characterized by comprising a porous polymer skeleton formed by taking water-soluble resin as a raw material, wherein nano-scale pores are uniformly distributed in the porous polymer skeleton, and the pore size is adjustable within the range of 0.5 to 999 nm.