Pressure-resistant heat-insulating paper containing hollow porous silica microspheres and preparation method thereof
Technical Field
The application belongs to the technical field of special paper, and particularly relates to pressure-resistant heat-insulating paper containing hollow porous silica microspheres and a preparation method thereof.
Background
Along with the development of economy, the requirements on low carbon, energy conservation and working environment are higher and higher, and the heat-insulating material is taken as a novel functional material and produced at the same time, and the main reasons are that: the heat insulation material can effectively prevent heat transfer, reduce heat loss, achieve the effects of energy conservation and emission reduction, and simultaneously can maintain a higher or lower temperature working environment and improve the working environment.
At present, inorganic fibers are usually adopted to make heat insulation paper, so that the heat insulation paper is high in temperature resistance, high in porosity and low in heat conductivity coefficient, but in the actual use process, the heat insulation paper needs to be tightly bundled and extruded to cause the porosity of the heat insulation paper to be reduced, so that the heat conductivity coefficient is poor, and the heat insulation requirement under extrusion in the application process cannot be met.
The aerogel is a nano porous material, the porosity of the aerogel can reach 80-99%, the size of a hole is generally 5-50 nm, the size of the aerogel is smaller than the free stroke of the thermal motion of a gas molecule, the convection heat transfer and the thermal motion transfer of the gas molecule can be effectively limited, the heat conduction inside the material can be reduced by adding the aerogel into heat insulation paper, the heat conductivity coefficient of pressure-resistant heat insulation paper is reduced, and the heat insulation purpose is achieved.
At present, the method for preparing the heat insulation paper by compounding the silica aerogel and the fiber material mainly comprises two types:
the first type is that sol composed of a precursor for preparing silica aerogel, a solvent and the like is soaked in inorganic fibers, and then supercritical drying is adopted to obtain silica aerogel heat insulation paper, for example, a patent with the reference number of CN107313297A adopts the method to prepare hydrophobic heat insulation paper; however, the method needs a supercritical process, the doping proportion and the dispersibility of silicon dioxide are difficult to control, so that the thickness of the heat insulation paper is difficult to control, and in addition, dust is generated on the surface of the heat insulation paper prepared by the method and is easy to fall off;
the second type is that silica aerogel powder is prepared, then fiber material and/or inorganic (or organic) binder are added, and finally compression molding is carried out to obtain the heat insulation paper, for example, patent with document number of CN1196035A discloses a composite material containing aerogel particles and binder, the aerogel particles and the binder are mixed, the mixture is molded and cured to obtain the composite material; however, the silica aerogel has a large specific surface area and is hydrophobic and difficult to disperse, that is, the silica aerogel is difficult to be uniformly mixed with fibers and other materials, so that the thermal conductivity coefficient of the thermal insulation paper is poor, and meanwhile, the surface of the thermal insulation paper prepared by the method also has dust and is easy to fall off.
In addition, the two methods for preparing the heat insulation paper have a common problem that the conventional silica aerogel is fragile and low in compressive strength, so that the heat conductivity coefficient of the heat insulation paper can be increased due to external force extrusion in the using process, and the heat insulation requirement can not be met.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: in order to solve the defects that the heat insulation paper prepared by the prior art is poor in heat insulation effect under extrusion and easy to fall off powder, the pressure-resistant heat insulation paper containing the hollow porous silica microspheres and the preparation method thereof are provided.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a preparation method of pressure-resistant heat-insulating paper containing hollow porous silica microspheres comprises the following steps:
adding water into glass fibers and glass cotton fibers for pulping and dispersing, adding a binder for uniformly stirring, standing, adding hollow porous silica microspheres for uniformly stirring, and standing to obtain a slurry mixed solution; the hollow silica microspheres comprise a hollow inner cavity, a honeycomb-shaped inner shell layer surrounding the hollow inner cavity and containing compact micropores, mesopores and macropores, and an outer shell layer which is adjacent to the honeycomb-shaped inner shell layer and only contains mesopores;
and (3) making the slurry mixed solution by using a wet paper sheet, squeezing, dehydrating and drying to obtain the pressure-resistant heat-insulating paper containing the hollow porous silica microspheres.
Preferably, the diameter of the hollow porous silica microsphere is 10-40 μm, and the specific surface area is preferably 520-800 m2The thickness ratio of the inner shell layer to the outer shell layer of the honeycomb structure is preferably 0.05-0.2.
Preferably, the hollow silica microspheres are prepared by the following method:
s1: dispersing a silane compound containing a hydrophobic group in a mixed solution of tetraalkoxysilane and a hydrophilic polymer containing hydroxyl, adding an organic solvent into the mixed solution to ensure that the mixed solution is transparent, then adjusting the solution to be acidic, heating for reaction, and removing the organic solvent in the solution after the reaction is finished to obtain a prepolymer solution;
s2: under the condition of stirring, adding the prepolymer solution into water to form emulsion, adding an alkaline medium to adjust the emulsion to be alkaline, leading the prepolymer to have hydrolytic condensation reaction, then standing the reacted emulsion, and filtering to obtain a precipitate;
s3: and cleaning the precipitate, and heating and drying the precipitate to obtain the hollow porous silica microspheres.
Preferably, the mass ratio of the hydroxyl group-containing hydrophilic polymer to the tetraalkoxysilane is 0.04 to 0.08:1, and the mass ratio of the hydrophobic group-containing silane compound to the tetraalkoxysilane is preferably 0.3 to 0.5: 1.
Preferably, the reaction temperature of the heating reaction is 60-160 ℃, the precipitate is preferably heated and dried in a stepwise manner from low to high, and the heating temperature range is 40-180 ℃.
Preferably, the glass fiber is chopped fiber, the length is preferably 2-5 mm, and the beating degree of the glass wool fiber is preferably 30-60 DEG SR.
Preferably, the adhesive is added simultaneously with the silane coupling agent, the adhesive is preferably polyamide epichlorohydrin and/or polyacrylamide, and the silane coupling agent is preferably YSiX3X is methoxy or ethoxy, Y contains amino or epoxy.
Preferably, the mass ratio of the glass fibers to the glass cotton fibers is 0.1-0.5: 1, the mass ratio of the hollow porous silica microspheres to the total amount of the glass fibers and the glass cotton fibers is preferably 5-50%, and the mass ratio of the binder to the total amount of the glass fibers and the glass cotton fibers is preferably 0.01-0.1: 1.
Preferably, the net feeding concentration of the wet paper sheet making is 0.1-0.5%, the net feeding pH value is 6.5-8.5, and the basis weight of the paper sheet is 100-3000 g/m2。
Preferably, the wet paper sheet is pressed to a dryness of 30-40% by press dewatering, and the drying temperature is preferably 105-150 ℃.
The invention also provides the pressure-resistant heat-insulating paper containing the hollow porous silica microspheres prepared by the method.
The invention has the beneficial effects that:
the invention adopts the hollow silica microspheres with special structures of hollow inner cavities, honeycomb inner shells and outer shells only containing mesopores, when preparing the heat insulation paper, firstly pulping and dispersing glass fibers and glass wool fibers, then adding a bonding agent (further adding a coupling agent) and the hollow silica microspheres in sequence, and finally making, squeezing and dehydrating the pulp mixed solution by wet paper pages, and drying to obtain the pressure-resistant heat insulation paper, wherein the pressure-resistant heat insulation paper has the following specific beneficial effects:
1) the heat insulation performance of the heat insulation paper under high pressure is remarkably improved, particularly, the advantage of the pressure bearing capacity of the heat insulation paper added with the hollow silica microspheres is reflected under the condition of continuously increasing load pressure, and the heat conductivity coefficient of the heat insulation paper under the load pressure of 40Kpa can still be kept below 0.037W/(m.k), so that the industrial application value of the heat insulation paper is well reflected;
2) the added binder (further adding the coupling agent) has little influence on the heat conductivity coefficient of the heat insulation paper, but can effectively solve the problem of powder falling of the heat insulation paper;
3) the breakdown performance and the dielectric property are obviously improved, the electric strength of the heat insulation paper prepared by the method is as high as 3.25KV/mm, and the dielectric loss is as low as 0.0008%;
4) compared with the prior art, the preparation process of the heat insulation paper can effectively control the thickness and the weight of the pressure-resistant heat insulation paper in unit area;
5) the preparation process of the hollow silica microspheres is simple and low in cost, and the preparation process of the heat insulation paper is easy to industrialize and low in production cost.
Drawings
The technical solution of the present application is further explained below with reference to the drawings and the embodiments.
FIG. 1 is an SEM image of hollow porous silica microspheres prepared in example 1 of the present application;
FIG. 2 is an SEM image of the internal structure of hollow porous silica microspheres prepared in example 1 of the present application;
FIG. 3 is a surface view of a pressure-resistant heat-insulating paper containing hollow porous silica microspheres prepared in example 2 of the present application;
FIG. 4 is an SEM image of a pressure-resistant thermal insulation paper containing hollow porous silica microspheres prepared in example 2 of the present application.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
The technical solutions of the present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
Example 1
The embodiment provides a preparation method of hollow porous silica microspheres, which comprises the following steps:
s1: mixing and stirring isopropyl n-silicate (150g) and polyethylene glycol (9.0g) at the rotating speed of 200 revolutions per minute, adding vinyltrimethoxysilane (60.2g) and ethanol (30.1g) under the stirring condition, and stirring until the solution is transparent; then slowly dripping 8.25g of hydrochloric acid solution with the concentration of 5.0mol/L, after the dripping is finished, heating to 100 ℃, continuously stirring for reaction for 12 hours, and quickly distilling butanol in the system under reduced pressure to obtain prepolymer solution with certain viscosity;
s2: dripping 20g of prepolymer solution into 100g of distilled water, and continuously stirring to form emulsion; adding formic acid to adjust the pH of the emulsion to 10, continuously stirring and reacting for 24 hours to obtain white emulsion, standing and filtering to obtain white precipitate;
s3: washing the precipitate twice with water, putting the precipitate into an oven for stepped drying, wherein the heating sequence is as follows: drying at 40 ℃ for 5h, drying at 120 ℃ for 3h and drying at 180 ℃ for 1h to obtain the hydrophilic hollow porous silica microspheres.
The silicon dioxide prepared by the method has complete microspherical shape and uniform particle size distribution, the particle size is within the range of 10-40 mu m, the wall thickness of a shell layer is 0.2-2 mu m, and the specific surface area is 520-800 m2(ii)/g; the obtained hollow porous silica microsphere comprises a hollow porous inner cavity, a honeycomb-shaped inner shell layer of compact micropores, mesopores and macropores surrounds the hollow porous inner cavity, the outer shell layer only contains the mesopores, and the thickness ratio of the inner shell layer to the outer shell layer is 0.05-0.2; the hollow porous silica microspheres had a wet contact angle (θ) of 28 °, and were hydrophilic.
Example 2
The embodiment provides a preparation method of pressure-resistant heat-insulating paper containing hollow porous silica microspheres, which comprises the following steps:
mixing glass fiber and glass cotton fiber, adding the mixture into a low-speed disperser, adding water, stirring at the rotating speed of 200r/min until the two fibers are fully mixed without flocs, wherein the glass fiber is chopped fiber and has the length of 2mm, the beating degree of the glass cotton fiber is 30 DEG SR, and the mass ratio of the glass fiber to the glass cotton fiber is 0.2: 1;
adding the binder-polyamide epichlorohydrin into the slurry suspension obtained in the step, uniformly stirring, standing for 15min, adding the hollow porous silica microspheres prepared in the embodiment 1, uniformly stirring, and standing for 15min to obtain a slurry mixed solution; the mass ratio of the polyamide epichlorohydrin to the total amount of the glass fiber and the glass cotton fiber is 0.01:1, and the mass ratio of the hollow porous silica microspheres to the total amount of the glass fiber and the glass cotton fiber is 15%;
adding the slurry mixture into a wet paper sheet making system, wherein the net-feeding concentration is 0.2%, the net-feeding pH value is 8.5, and the paper sheet ration is 100g/m2Pressing and dewatering the formed wet paper sheet to 30% dryness, and drying at the drying temperature110℃;
After the paper sheet is dried, cutting the paper sheet according to the requirements of customers, adopting a binder diluent to carry out corner finishing, and drying at the temperature of 110 ℃.
Example 3
Mixing glass fiber and glass cotton fiber, adding the mixture into a low-speed disperser, adding water, stirring at the rotating speed of 300r/min until the two fibers are fully mixed without flocs, wherein the glass fiber is chopped fiber and has the length of 2mm, the beating degree of the glass cotton fiber is 45 DEG SR, and the mass ratio of the glass fiber to the glass cotton fiber is 0.5: 1;
adding a binder-polyacrylamide into the slurry suspension obtained in the above step, uniformly stirring, standing for 15min, adding the hollow porous silica microspheres prepared in example 1, uniformly stirring, and standing for 15min to obtain a slurry mixed solution; the mass ratio of the polyacrylamide to the total amount of the glass fiber and the glass cotton fiber is 0.1:1, and the mass ratio of the hollow porous silica microspheres to the total amount of the glass fiber and the glass cotton fiber is 5%;
adding the slurry mixture into a wet paper sheet making system, wherein the net-feeding concentration is 0.1%, the net-feeding pH value is 6.5, and the paper sheet ration is 1000g/m2Pressing and dehydrating the wet paper sheet after the wet paper sheet is formed, pressing the wet paper sheet to 35% of dryness, and then drying, wherein the drying temperature is 150 ℃;
after the paper sheet is dried, cutting the paper sheet according to the requirements of customers, adopting a binder diluent to carry out corner finishing, and drying at the temperature of 110 ℃.
Example 4
Mixing glass fiber and glass cotton fiber, adding the mixture into a low-speed disperser, adding water, stirring at the rotating speed of 500r/min until the two fibers are fully mixed without flocs, wherein the glass fiber is chopped fiber and has the length of 5mm, the beating degree of the glass cotton fiber is 60 DEG SR, and the mass ratio of the glass fiber to the glass cotton fiber is 0.1: 1;
adding the binder-polyamide epichlorohydrin into the slurry suspension obtained in the step, uniformly stirring, standing for 15min, adding the hollow porous silica microspheres prepared in the embodiment 1, uniformly stirring, and standing for 15min to obtain a slurry mixed solution; the mass ratio of the polyamide epichlorohydrin to the total amount of the glass fiber and the glass cotton fiber is 0.05:1, and the mass ratio of the hollow porous silica microspheres to the total amount of the glass fiber and the glass cotton fiber is 50%;
adding the slurry mixture into a wet paper sheet making system, wherein the net-feeding concentration is 0.5%, the net-feeding pH value is 7.0, and the paper sheet ration is 3000g/m2Pressing and dehydrating the wet paper sheet after the wet paper sheet is formed, pressing the wet paper sheet to 40% dryness, and then drying, wherein the drying temperature is 105 ℃;
after the paper sheet is dried, cutting the paper sheet according to the requirements of customers, adopting a binder diluent to carry out corner finishing, and drying at the temperature of 110 ℃.
Example 5
This example differs from example 4 only in that: adding a silane coupling agent while adding a binder, wherein the silane coupling agent is NH2(CH2)3Si(OC2H5)3The mass ratio of the silane coupling agent to the binder is 0.5: 1.
Example 6
This example differs from example 4 only in that: adding a silane coupling agent while adding the binder, wherein the silane coupling agent is
The mass ratio of the silane coupling agent to the binder is 0.5: 1.
Comparative example 1
This example differs from example 4 in that: hollow porous silica microspheres were not added.
Comparative example 2
At present, the hollow silica microspheres in the market are expensive, and are not used in the heat insulation paper, and only the silica aerogel crushed powder is used, and the difference between the embodiment and the embodiment 4 is that: the hollow porous silica microspheres were replaced with the pulverized powder of silica aerogel, and the silica aerogel used in this comparative example had a thermal conductivity of about 0.02113W/(m · K) and a porosity of 97.1% before pulverization. The silica aerogel powder had a thermal conductivity of about 0.03089W/(m.K) and a porosity of 87.9%.
Examples of effects
The results of the present embodiment are shown in table 1, in which the thermal conductivity of the thermal insulation paper of examples 2 to 5 and comparative examples 1 to 2 under different load pressures (using NETZSCH HFM 446 Lambda thermal conductivity meter, the test standard is GB/T10295-2008), the thickness of the thermal insulation paper, the weight per unit area, and the electrical strength (using power frequency breakdown voltage tester BDJC-20kV of beijing north broad essence instrument ltd, the test standard is GB/T1408.1-2016), the dielectric loss (using dielectric loss tester BQS-37a of beijing north broad essence instrument ltd, the test standard is GB/T1409-.
Product structure and performance test results of the thermal insulation paper of examples 2 to 5 and comparative examples 1 to 2
It can be seen from the comparison among examples 5, 6 and 4 that the addition of the silane coupling agent while the addition of the binder has little influence on the thermal conductivity, the puncture performance and the dielectric performance of the thermal insulation paper, but no dust is seen on the surface of the thermal insulation paper prepared in practical examples 5 and 6, no powder falling phenomenon occurs even under severe impact, and the powder falling prevention effect of the thermal insulation paper prepared in practical example 4 is better than that of the thermal insulation paper prepared in example 4.
It can be seen from the comparison between comparative example 1 and example 4 that when the thermal insulation paper is prepared without adding the hollow porous silica microspheres, the thermal conductivity of the thermal insulation paper under the load pressure of 0.6Kpa is small due to the slightly large porosity of the thermal insulation paper, but the pressure resistance of the thermal insulation paper without adding the hollow porous silica microspheres is extremely poor, and the thermal conductivity is much higher than that of the thermal insulation paper with adding the hollow porous silica microspheres of example 4 as the load pressure is increased, and in addition, the electrical strength of the thermal insulation paper with the thermal insulation paper is higher and the dielectric loss is smaller due to the adding of the hollow porous silica microspheres of example 4, namely the thermal insulation paper has good puncture resistance and dielectric property.
It can be seen from the comparison between comparative example 2 and example 4 that when the powder of the crushed silica aerogel is added in the preparation of the thermal insulation paper, the thermal conductivity of the thermal insulation paper under different load pressures is larger than that of the thermal insulation paper added with the hollow porous silica microspheres of example 4 due to the poor dispersibility of the silica aerogel powder, especially the thermal insulation effect of the thermal insulation paper of comparative example 2 is poorer under high pressure, and in addition, the electrical strength of the thermal insulation paper of example 4 is higher than that of the thermal insulation paper of comparative example 2, and the dielectric loss is smaller, that is, the thermal insulation paper has better breakdown resistance and dielectric property.
In light of the foregoing description of the preferred embodiments according to the present application, it is to be understood that various changes and modifications may be made without departing from the spirit and scope of the invention. The technical scope of the present application is not limited to the contents of the specification, and must be determined according to the scope of the claims.