A waterproof and heat-insulating coating

Abstract

The invention discloses a waterproof and heat-insulating coating, and relates to the technical field of coatings. The invention performs microwave acid hydrolysis on straw, performs four-stage heating, and sprays a modifier into the heating process to obtain hydrophobic high-purity silica, thereby improving the waterproof effect of the coating, and then uses this as a raw material to form a hydrogel prefabricated solution of different concentrations, and then uses a high-concentration hydrogel as a skeleton, organically combines with a low-concentration hydrogel, and obtains a gradient silica hydrogel, which is freeze-dried and ball-milled to form a nano-scale powder, giving the coating better wear resistance and heat insulation effect; after carbonizing the phenolic resin hollow microspheres, amino silicone oil is used for modification, so that it is chemically bonded with the water-based acrylic resin, and by stirring, the gradient nano-silica aerogel is attached and embedded in the modified micron carbon hollow microspheres, further improving the wear resistance and hydrophobic effect of the coating. The coating prepared by the present invention has waterproof, heat-insulating and wear-resistant effects.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, in particular to a waterproof and heat-insulating coating. Background Art

[0002] Paint is an important invisible presence around people. In addition to some effects on the human body, the performance of the paint itself can also affect the quality of life or the life of the building. A paint with excellent performance can take into account multiple functions at the same time, such as waterproof, heat-insulating, wear-resistant, etc., which can not only make the building environment safer and more hygienic, but also provide certain protection for the building itself. However, in the prior art, the insulation effect of the paint needs to be improved, because the addition of organic heat-resistant agents weakens the waterproof performance of the paint, and we cannot have both.

[0003] Silica aerogel is a hot nanomaterial studied in the field of new materials. It is mainly composed of more than 90% air and less than 10% solid skeleton. It has excellent properties such as low density, low thermal conductivity, and high porosity. Recycling recycled straw and expanding the development of biomass materials to new fields can turn straw resources into treasure and reduce the pollution caused by burning straw to the environment. Using straw to make high-purity silica aerogel is a research direction, and its excellent properties can be used to modify coatings. The present invention combines silica aerogel, carbon hollow microspheres and water-based acrylic resin to prepare a waterproof, heat-insulating, and wear-resistant coating. Summary of the invention

[0004] The purpose of the present invention is to provide a waterproof thermal insulation coating and a preparation method thereof to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a waterproof and thermal insulation coating, which is prepared with gradient nano-silica aerogel and modified micron-carbon hollow microspheres as fillers and water-based acrylic resin as a base material.

[0006] Furthermore, the gradient nano-silica aerogel uses hydrophobic silica produced by four-stage heating as a raw material to prepare two silica hydrogels with different concentrations, and then uses the high-concentration silica hydrogel as a skeleton to chemically combine with the low-concentration silica hydrogel to obtain the aerogel.

[0007] Furthermore, the four-stage heating includes: first heating for a period of time, then cooling and introducing nitrogen doped with chlorine and water vapor, and reacting for a period of time; second heating using vacuum negative pressure auxiliary heating; third heating for high-temperature calcination; fourth heating cooling and spraying polydimethylsiloxane and urea, and continuing to react for a period of time

[0008] Furthermore, a method for preparing a waterproof thermal insulation coating comprises the following preparation steps:

[0009] (1) Soak 2-3 parts of straw in 20 parts of 6% by mass dilute hydrochloric acid, heat at 60-70°C and microwave power of 300-700W for 1-2h, filter, wash the filtrate with deionized water for 3 times, dry in an oven at 105°C for 2-3h, and then put it into a grinder to process it into straw chips;

[0010] (2) 10-20 portions of straw fragments are placed in a four-stage heating furnace for heating; the first stage is heated at a temperature of 500-600°C for calcination for 5-7 hours, then cooled to 50-60°C, and a catalytic gas containing 20% ​​chlorine, 20% water vapor and 60% nitrogen is introduced at a gas pressure of 0.5-0.8 MPa for 80-100 minutes; the second stage is heated at a temperature of 600-750°C for calcination in a negative pressure vacuum of -0.096 MPa for 5-10 hours; the third stage is heated at 750-900°C for calcination for 4-6 hours; the fourth stage is heated at 163-167°C for 6-8 hours to obtain hydrophobic silica;

[0011] (3) Add 2-4 parts of hydrophobized silica to 8-16 parts of 5% sodium hydroxide solution, heat to 50-80°C, heat to react for 2-3h, cool to 25°C, filter, take the filtrate, add sulfuric acid until the pH of the filtrate is 1-2, and then add 10% sodium hydroxide solution dropwise to prepare two prefabricated solutions of different concentrations, wherein the filtrate in the high-concentration prefabricated solution accounts for 3.5-8.5% of the mass fraction, and the filtrate in the low-concentration prefabricated solution accounts for 0.5-3.5% of the mass fraction; first, let 4 parts of the high-concentration prefabricated solution stand for 12h, then add 1-4 parts of the low-concentration prefabricated solution, let stand for 24h, and then wash with deionized water 3 times to obtain a hydrogel;

[0012] (4) freeze-drying the hydrogel at -30°C and a vacuum degree of 20 Pa for 24 hours to prepare a gradient silica aerogel; placing the gradient silica aerogel in a ball mill, using zirconium beads as grinding balls, grinding at 500 r / min for 5-10 minutes, and the number of cycles is 1, to obtain a gradient nano-silica aerogel with a particle size of 50-120 nm;

[0013] (5) The phenolic resin hollow microspheres are fully immersed in a 0.1 mol / L hydrochloric acid solution, washed for 50-80 min, and then placed in a box furnace, heated to 140-240°C at 0.2°C / min in an air atmosphere, oxidized for 20-40 min, and then carbonized at 800°C for 2-3 h to obtain carbon hollow microspheres;

[0014] (6) Mix 1-2 parts of carbon hollow microspheres, 0.1-0.3 parts of dispersant, 3-5 parts of deionized water and 30 parts of zirconium beads, stir at 300-500 r / min for 3 min, then add 0.3-0.5 parts of amino silicone oil and 2-4 parts of gradient nano-silica aerogel, adjust the speed to 1800 r / min, stir for 20 min, add 16-22 parts of water-based acrylic resin, reduce the speed to 700 r / min, stir for 40 min, and prepare a waterproof and thermal insulation coating.

[0015] Furthermore, in step (1), the size of the straw fragments is 40-60 meshes.

[0016] Furthermore, in the fourth stage heating process of step (2), urea and polydimethylsiloxane are sprayed into the calcination chamber in a mist form, the injection flow rate of polydimethylsiloxane is 2-6 mL / min, and the injection flow rate of urea is 30-50 mL / min.

[0017] Furthermore, the mass fraction of sulfuric acid in step (3) is 8%.

[0018] Furthermore, in step (4), the ball-to-material ratio is 100:1.

[0019] Furthermore, in step (5), the particle size of the phenolic resin hollow microspheres is 20-180 μm.

[0020] Furthermore, in step (6), the dispersant is one of polyethylene oxide, methyl cellulose and carboxymethyl cellulose.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] The invention uses gradient nano-silicon dioxide aerogel and modified micron carbon hollow microspheres produced by four-stage heating as fillers and water-based acrylic resin as a base material to prepare a coating to achieve waterproof, heat-insulating and wear-resistant effects.

[0023] First, straw is used as raw material. After microwave acid hydrolysis, it is roughly crushed and then heated in four stages: the first stage of heating carbonizes the straw to form ash, which contains heavy metals and sodium silicate. Then, the temperature is lowered and nitrogen doped with chlorine and water vapor is introduced. The chlorine and water vapor are heated to form Cl, which replaces the heavy metals to form metal chlorides. The second heating volatilizes the metal chlorides, thereby improving the purity of silica. At the same time, the sodium silicate is further decomposed to form silica, and the vacuum negative pressure is used to expand the pores of silica, and the pores are more solid. In the third stage of heating, high-purity silica is calcined at high temperature. In the fourth stage of heating, the temperature is lowered and polydimethylsiloxane and urea are sprayed in. Urea is decomposed into ammonia when heated, realizing ammonia gas phase catalysis. The pores on the surface of silica adsorb and accommodate the mist-like polydimethylsiloxane modifier, giving silica hydrophobicity, thereby improving the waterproof effect of the coating; silica is heated to react with sodium hydroxide solution, cooled and filtered to obtain a water glass solution, and then diluted to obtain two silica hydrogels with different concentrations; high-concentration hydrogel is used as the skeleton and organically combined with low-concentration hydrogel to obtain gradient silica hydrogel, which is then freeze-dried to form a double-layer structure aerogel, which is made into nano-powder by ball milling, and added with water-based acrylic resin as a filler to give the coating better wear resistance and thermal insulation effects.

[0024] Secondly, the phenolic resin hollow microspheres are prepared into micron carbon hollow microspheres and modified with amino silicone oil. Under the action of amino silicone oil, they can be chemically bonded with water-based acrylic resin, so that the micron carbon hollow microspheres are evenly dispersed in the coating, thereby improving the wear resistance and stability of the coating. At the same time, the micron-sized carbon hollow microspheres provide binding sites for nano-silica aerogels. During the stirring process, the nano-silica aerogels are embedded in the porous structure on the surface of the carbon hollow microspheres due to the influence of force, thereby forming a micro-nano rough structure on the coating surface, further improving the wear resistance and hydrophobic effects of the coating. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the test methods of the waterproof thermal insulation coating and silica prepared in the following examples as follows:

[0027] Silica purity test: In the 100,000-class clean room of the test center of Wuxi Zhongcai Technology Co., Ltd., use a FEP beaker to take the powder after three-stage heating, dissolve it with 30 vol% ultra-pure hydrofluoric acid, place it in a 10,000-class clean room at 80°C for 2 hours, and use an inductively coupled plasma mass spectrometer to test the total content of metal impurities in the silica sol.

[0028] The coating was applied on clean tinplate, left to stand naturally for 3 hours, and then dried at 75℃ for 30 minutes to obtain a coating with a thickness of 60μm for thermal insulation, wear resistance and waterproofing effect tests:

[0029] Thermal insulation: Test the thermal conductivity of the coating according to standard ASTM D5470;

[0030] Wear resistance: The wear resistance was tested under the following friction conditions: the grinding material was a 4mm diameter GCr15 steel ball, the motor speed was 500r / min, the motion was reciprocating, the stroke was 5mm, the load was 3N, and the test time was 15min.

[0031] Waterproofness: Based on the sessile drop test technology, the contact angle of the droplet is measured using a surface contact angle meter.

[0032] Example 1

[0033] (1) Soak 2 parts of straw in 20 parts of 6% dilute hydrochloric acid, heat at 60°C and microwave power of 300 W for 1 h, filter, wash the filtrate with deionized water 3 times, dry in an oven at 105°C for 2 h, and then put it into a grinder to process it into 40 mesh straw chips;

[0034] (2) 10 portions of straw fragments were placed in a four-stage heating furnace for heating; the first stage was heated at a temperature of 500°C for calcination for 5 hours, then cooled to 50°C, and a catalytic gas containing 20% ​​chlorine, 20% water vapor, and 60% nitrogen was introduced at a gas pressure of 0.5 MPa for 80 minutes; the second stage was heated at a temperature of 600°C and calcined in a negative pressure vacuum of -0.096 MPa for 5 hours; the third stage was heated at 750°C for 4 hours; the fourth stage was heated at 163°C, and urea and polydimethylsiloxane were sprayed into the calcination chamber at a spray rate of 2 mL / min for polydimethylsiloxane and 30 mL / min for urea for 6 hours to obtain hydrophobic silica;

[0035] (3) Add 2 parts of hydrophobized silica to 8 parts of 5% sodium hydroxide solution, heat to 50°C, heat to react for 2h, cool to 25°C, filter, take the filtrate, add 8% sulfuric acid until the pH of the filtrate is 1, and then add 10% sodium hydroxide solution dropwise to prepare two prefabricated solutions of different concentrations, wherein the filtrate in the high-concentration prefabricated solution accounts for 3.5% of the mass fraction, and the filtrate in the low-concentration prefabricated solution accounts for 0.5% of the mass fraction; first, let 4 parts of the high-concentration prefabricated solution stand for 12h, then add 1 part of the low-concentration prefabricated solution, let stand for 24h, and then wash with deionized water 3 times to obtain a hydrogel;

[0036] (4) freeze-drying the hydrogel at -30°C and 20Pa vacuum for 24h to prepare gradient silica aerogel; placing the gradient silica aerogel in a ball mill, using zirconium beads as grinding balls, with a ball-to-material ratio of 100:1, grinding at 500r / min for 5min, and the number of cycles is 1, to obtain gradient nano-silica aerogel with a particle size of 50nm;

[0037] (5) The phenolic resin hollow microspheres with a particle size of 20 μm were fully immersed in a 0.1 mol / L hydrochloric acid solution, washed for 50 min, and then placed in a box furnace. In an air atmosphere, the temperature was raised to 140 °C at 0.2 °C / min, and after oxidation treatment for 20 min, they were carbonized at 800 °C for 2 h to obtain carbon hollow microspheres;

[0038] (6) Mix 1 part of carbon hollow microspheres, 0.1 part of polyethylene oxide, 3 parts of deionized water and 30 parts of zirconium beads, stir at 300 r / min for 3 min, then add 0.3 parts of amino silicone oil and 2 parts of gradient nano-silica aerogel, adjust the speed to 1800 r / min, stir for 20 min, add 16 parts of water-based acrylic resin, and at the same time reduce the speed to 700 r / min and stir for 40 min to prepare a waterproof and thermal insulation coating.

[0039] Example 2

[0040] (1) Soak 2.5 parts of straw in 20 parts of 6% dilute hydrochloric acid, heat at 65°C and microwave power of 500 W for 1.5 h, filter, wash the filtrate with deionized water three times, dry in an oven at 105°C for 2.5 h, and then put it into a grinder to process it into 50-mesh straw fragments;

[0041] (2) 15 portions of straw fragments were placed in a four-stage heating furnace for heating; the first stage was heated at 550°C for 6 hours, then cooled to 55°C, and a catalytic gas containing 20% ​​chlorine, 20% water vapor, and 60% nitrogen was introduced at a gas pressure of 0.65 MPa for 90 minutes; the second stage was heated at 675°C for 7.5 hours in a negative pressure vacuum of -0.096 MPa; the third stage was heated at 875°C for 5 hours; the fourth stage was heated at 165°C, and urea and polydimethylsiloxane were sprayed into the calcination chamber in a mist form, with the injection flow rate of polydimethylsiloxane being 4 mL / min and the injection flow rate of urea being 40 mL / min, for 7 hours, to obtain hydrophobic silica;

[0042] (3) Add 3 parts of hydrophobic silica to 12 parts of 5% sodium hydroxide solution, heat to 65°C, heat to react for 2.5 hours, cool to 25°C, filter, take the filtrate, add 8% sulfuric acid until the pH of the filtrate is 1.5, and then add 10% sodium hydroxide solution dropwise to prepare two prefabricated solutions of different concentrations, wherein the filtrate in the high-concentration prefabricated solution accounts for 5% by mass and the filtrate in the low-concentration prefabricated solution accounts for 2% by mass; first, let 4 parts of the high-concentration prefabricated solution stand for 12 hours, then add 2.5 parts of the low-concentration prefabricated solution, let stand for 24 hours, and then wash with deionized water 3 times to obtain a hydrogel;

[0043] (4) freeze-drying the hydrogel at -30°C and 20Pa vacuum for 24h to prepare gradient silica aerogel; placing the gradient silica aerogel in a ball mill, using zirconium beads as grinding balls, with a ball-to-material ratio of 100:1, grinding at 500r / min for 7.5min, and the number of cycles is 1, to obtain gradient nano-silica aerogel with a particle size of 85nm;

[0044] (5) Phenolic resin hollow microspheres with a particle size of 100 μm were fully immersed in a 0.1 mol / L hydrochloric acid solution, washed for 65 min, and then placed in a box furnace. In an air atmosphere, the temperature was raised to 190 °C at 0.2 °C / min, oxidized for 30 min, and then carbonized at 800 °C for 2.5 h to obtain carbon hollow microspheres.

[0045] (6) 1.5 parts of carbon hollow microspheres, 0.2 parts of methyl cellulose, 4 parts of deionized water and 30 parts of zirconium beads were mixed and stirred at 400 r / min for 3 min. Then, 0.4 parts of amino silicone oil and 3 parts of gradient nano-silica aerogel were added and the speed was adjusted to 1800 r / min. After stirring for 20 min, 19 parts of water-based acrylic resin were added and the speed was reduced to 700 r / min. The mixture was stirred for 40 min to prepare a waterproof and thermal insulation coating.

[0046] Example 3

[0047] (1) Soak 3 parts of straw in 20 parts of 6% dilute hydrochloric acid, heat at 70°C and microwave power of 700 W for 2 h, filter, wash the filtrate with deionized water 3 times, dry in an oven at 105°C for 3 h, and then put it into a grinder to process it into 60-mesh straw fragments;

[0048] (2) 20 portions of straw fragments were placed in a four-stage heating furnace for heating; the first stage was heated at 600°C for 7 hours, then cooled to 60°C, and a catalytic gas containing 20% ​​chlorine, 20% water vapor, and 60% nitrogen was introduced at a gas pressure of 0.8 MPa for 100 minutes; the second stage was heated at 750°C for 10 hours in a negative pressure vacuum of -0.096 MPa; the third stage was heated at 900°C for 6 hours; the fourth stage was heated at 167°C, and urea and polydimethylsiloxane were sprayed into the calcination chamber in a mist form, with the injection flow rate of polydimethylsiloxane being 6 mL / min and the injection flow rate of urea being 50 mL / min, for 8 hours, to obtain hydrophobic silica;

[0049] (3) Add 4 parts of hydrophobized silica to 16 parts of 5% sodium hydroxide solution, heat to 80°C, heat to react for 3 hours, cool to 25°C, filter, take the filtrate, add 8% sulfuric acid until the pH of the filtrate is 2, and then add 10% sodium hydroxide solution dropwise to prepare two prefabricated solutions of different concentrations, wherein the filtrate in the high-concentration prefabricated solution accounts for 8.5% of the mass fraction, and the filtrate in the low-concentration prefabricated solution accounts for 3.5% of the mass fraction; first, let the 4 parts of the high-concentration prefabricated solution stand for 12 hours, then add 4 parts of the low-concentration prefabricated solution, let it stand for 24 hours, and then wash it with deionized water 3 times to obtain a hydrogel;

[0050] (4) freeze-drying the hydrogel at -30°C and 20Pa vacuum for 24h to prepare gradient silica aerogel; placing the gradient silica aerogel in a ball mill, using zirconium beads as grinding balls, with a ball-to-material ratio of 100:1, grinding at 500r / min for 10min, and the number of cycles is 1, to obtain gradient nano-silica aerogel with a particle size of 120nm;

[0051] (5) The phenolic resin hollow microspheres with a particle size of 180 μm were fully immersed in a 0.1 mol / L hydrochloric acid solution, washed for 80 min, and then placed in a box furnace. In an air atmosphere, the temperature was raised to 240 °C at 0.2 °C / min, and after oxidation treatment for 40 min, they were carbonized at 800 °C for 3 h to obtain carbon hollow microspheres.

[0052] (6) Mix 2 parts of carbon hollow microspheres, 0.3 parts of carboxymethyl cellulose, 5 parts of deionized water, and 30 parts of zirconium beads, stir at 500 r / min for 3 min, then add 0.5 parts of amino silicone oil and 4 parts of gradient nano-silica aerogel, adjust the speed to 1800 r / min, stir for 20 min, add 22 parts of water-based acrylic resin, and reduce the speed to 700 r / min. Stir for 40 min to prepare a waterproof and thermal insulation coating.

[0053] Comparative Example 1

[0054] The difference between Comparative Example 1 and Example 2 lies in the difference in step (2), where step (2) is modified as follows: 15 portions of straw fragments are placed in a four-stage heating furnace for heating; the first stage heating is performed at a temperature of 550° C. and calcined for 6 h; the second stage heating is performed at a temperature of 675° C. and calcined for 7.5 h in a negative pressure vacuum of -0.096 MPa; the third stage heating is performed at a temperature of 875° C. and calcined for 5 h; the fourth stage heating is performed at a temperature of 165° C., urea and polydimethylsiloxane are sprayed into the calcination chamber in a mist form, the injection flow rate of polydimethylsiloxane is 4 mL / min, the injection flow rate of urea is 40 mL / min, and the duration is 7 h, to obtain hydrophobic silica; the remaining steps are the same as those in Example 2.

[0055] Comparative Example 2

[0056] The difference between Comparative Example 2 and Example 2 is that step (2) is different, and step (2) is changed to: 15 parts of straw fragments are placed in a three-stage heating furnace for heating; primary heating, the temperature is 550° C., calcined for 6 hours, then cooled to 55° C., and a catalytic gas containing 20% ​​chlorine, 20% water vapor and 60% nitrogen is introduced, the gas pressure is 0.65 MPa, and the time is 90 minutes; the secondary heating temperature is 675° C., and calcined at normal pressure for 7.5 hours; the tertiary heating is 165° C., urea and polydimethylsiloxane are sprayed into the calcination chamber in a mist form, the injection flow rate of polydimethylsiloxane is 4 mL / min, the injection flow rate of urea is 40 mL / min, and the duration is 7 hours to obtain hydrophobic silica; the remaining steps are the same as those in Example 2.

[0057] Comparative Example 3

[0058] The difference between Comparative Example 3 and Example 2 lies in the difference in step (2), whereby step (2) is modified as follows: 15 portions of straw fragments are placed in a three-stage heating furnace for heating; the first stage is heated at a temperature of 550° C. for calcination for 6 h, then cooled to 55° C., and a catalytic gas containing 20% ​​chlorine, 20% water vapor and 60% nitrogen is introduced at a gas pressure of 0.65 MPa for 90 min; the second stage is heated at a temperature of 675° C. for calcination in a negative pressure vacuum of -0.096 MPa for 7.5 h; the third stage is heated at a temperature of 875° C. for calcination for 5 h; the fourth stage is heated at a temperature of 165° C. to obtain silicon dioxide; and the remaining steps are the same as those in Example 2.

[0059] Comparative Example 4

[0060] The difference between Comparative Example 4 and Example 2 is that step (2) is different, and step (2) is changed to: 15 parts of straw fragments are placed in a four-stage heating furnace for heating; the first stage is heated at a temperature of 550° C., calcined for 6 hours, then cooled to 55° C., and a catalytic gas containing 20% ​​chlorine, 20% water vapor, and 60% nitrogen is introduced, the gas pressure is 0.65 MPa, and the time is 90 minutes; the secondary heating temperature is 675° C., and calcined in a negative pressure vacuum of -0.096 MPa for 7.5 hours; the tertiary heating is 875° C., and calcined for 5 hours; the fourth stage heating is 165° C., polydimethylsiloxane is sprayed into the calcination chamber in a mist form, the flow rate is 4 mL / min, and the duration is 7 hours to obtain hydrophobic silica; the remaining steps are the same as Example 2.

[0061] Comparative Example 5

[0062] The difference between Comparative Example 5 and Example 2 is that step (3) is different. Step (3) is changed to: add 3 parts of hydrophobized silica to 12 parts of 5% sodium hydroxide solution, heat to 65°C, heat to react for 2.5h, cool to 25°C, filter, take the filtrate, add 8% sulfuric acid to the filtrate until the pH of the filtrate is 1.5, and then add 10% sodium hydroxide solution dropwise to make a 3.5% solution. After standing for 24h, wash with deionized water 3 times to obtain a hydrogel; the remaining steps are the same as Example 2.

[0063] Comparative Example 6

[0064] The difference between Comparative Example 6 and Example 2 is that there is no step (5), and step (6) is changed to: 0.2 parts of methyl cellulose, 4 parts of deionized water and 30 parts of zirconium beads are mixed, stirred at 400 r / min for 3 minutes, and then 0.4 parts of amino silicone oil and 3 parts of gradient nano-silica aerogel are added, the rotation speed is adjusted to 1800 r / min, and stirred for 20 minutes, and then 19 parts of water-based acrylic resin are added, and the rotation speed is reduced to 700 r / min, and stirred for 40 minutes to prepare a waterproof and thermal insulation coating; the remaining steps are the same as those in Example 2.

[0065] Comparative Example 7

[0066] The difference between Comparative Example 7 and Example 2 is that step (6) is different. Step (6) is changed to: 1.5 parts of carbon hollow microspheres, 0.2 parts of methyl cellulose, 4 parts of deionized water, and 30 parts of zirconium beads are mixed, stirred at 400 r / min for 3 minutes, and then 3 parts of gradient nano-silica aerogel are added. The rotation speed is adjusted to 1800 r / min. After stirring for 20 minutes, 19 parts of water-based acrylic resin are added, and the rotation speed is reduced to 700 r / min. Stir for 40 minutes to prepare a waterproof and thermal insulation coating; the remaining steps are the same as Example 2.

[0067] Effect example

[0068] Table 1 below shows the performance analysis results of the waterproof and thermal insulation coatings and silicon dioxide of Examples 1 to 3 of the present invention and Comparative Examples 1 to 7.

[0069] Table 1

[0070]

[0071] From the comparison of the experimental data of the purity of silica in the embodiment and the comparative example, it can be found that the present invention uses straw as raw material, and after microwave acid hydrolysis, it is first roughly crushed and then subjected to four-stage heating: the first-stage heating carbonizes the straw to form ash, which contains heavy metals and sodium silicate, and then cools down and introduces nitrogen doped with chlorine and water vapor. The chlorine and water vapor are heated to form HCl, which displaces the heavy metals to form metal chlorides; the second-stage heating volatilizes the metal chloride, thereby improving the purity of silica, and at the same time, the sodium silicate is further decomposed to form silica, and the vacuum negative pressure is used to expand the pores of silica, and the pores are more firm; during the third-stage heating, high-purity silica is calcined at high temperature; from the comparison of the experimental data of the hydrophobicity of the embodiment and the comparative example, it can be found that in the fourth-stage heating of the present invention, polydimethylsiloxane and urea are added, and the urea is decomposed into ammonia by heat, so as to realize the gas phase catalysis of fumigation of ammonia, and give the silica hydrophobicity, and at the same time, the micron-sized carbon hollow microspheres and the nano-sized silica aerogel A micro-nano rough structure is formed to further improve the waterproof effect of the coating; from the comparison of the experimental data of the thermal insulation of the embodiment and the comparative example, it can be found that the present invention uses silica aerogel and carbon hollow microspheres as fillers to effectively improve the thermal insulation of the coating; from the comparison of the experimental data of the wear resistance of the embodiment and the comparative example, it can be found that the present invention uses high-concentration hydrogel as a skeleton and organically combines it with low-concentration hydrogel to prepare a gradient double-layer structure aerogel, which preliminarily improves the wear resistance of the coating; then, the phenolic resin hollow microspheres are prepared into micron carbon hollow microspheres, and modified with amino silicone oil. Under the action of amino silicone oil, they can be chemically bonded with water-based acrylic resin, so that the micron carbon hollow microspheres are uniformly dispersed in the coating, and at the same time, the micron-sized carbon hollow microspheres provide binding sites for the nano-silica aerogel. During the stirring process, they are affected by force, so that the nano-silica aerogel is embedded in the porous structure on the surface of the carbon hollow microspheres, further improving the wear resistance of the coating.

[0072] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A waterproof and heat-insulating coating, characterized in that: The waterproof and heat-insulating coating is prepared with gradient nano-silicon dioxide aerogel and modified micron-carbon hollow microspheres as fillers and water-based acrylic resin as a base material; A method for preparing a waterproof and heat-insulating coating comprises the following preparation steps: (1) Soak 2.5 parts of straw in 20 parts of 6% dilute hydrochloric acid, heat at 65°C and microwave power of 500 W for 1.5 h, filter, wash the filtrate with deionized water three times, dry in an oven at 105°C for 2.5 h, and then put it into a grinder to process it into 50-mesh straw fragments; (2) 15 portions of straw fragments were placed in a four-stage heating furnace for heating; the first stage was heated at 550°C for 6 hours, then cooled to 55°C, and a catalytic gas containing 20% ​​chlorine, 20% water vapor, and 60% nitrogen was introduced at a gas pressure of 0.65 MPa for 90 minutes; the second stage was heated at 675°C for 7.5 hours in a negative pressure vacuum of -0.096 MPa; the third stage was heated at 875°C for 5 hours; the fourth stage was heated at 165°C, and urea and polydimethylsiloxane were sprayed into the calcination chamber in a mist form, with the injection flow rate of polydimethylsiloxane being 4 mL / min and the injection flow rate of urea being 40 mL / min, for 7 hours, to obtain hydrophobic silica; (3) Add 3 parts of hydrophobized silica to 12 parts of 5% sodium hydroxide solution, heat to 65°C, heat to react for 2.5 hours, cool to 25°C, filter, take the filtrate, add 8% sulfuric acid until the pH of the filtrate is 1.5, then add 10% sodium hydroxide solution dropwise to prepare two prefabricated solutions of different concentrations, wherein: The mass fraction of the filtrate in the high-concentration prefabricated solution is 5%, and the mass fraction of the filtrate in the low-concentration prefabricated solution is 2%; first, 4 parts of the high-concentration prefabricated solution are allowed to stand for 12 hours, and then 2.5 parts of the low-concentration prefabricated solution are added, and after standing for 24 hours, the solution is washed with deionized water for 3 times to obtain a hydrogel; (4) freeze-drying the hydrogel at -30°C and 20Pa vacuum for 24h to prepare gradient silica aerogel; placing the gradient silica aerogel in a ball mill, using zirconium beads as grinding balls, with a ball-to-material ratio of 100:1, grinding at 500r / min for 7.5min, and the number of cycles is 1, to obtain gradient nano-silica aerogel with a particle size of 85nm; (5) Phenolic resin hollow microspheres with a particle size of 100 μm were fully immersed in a 0.1 mol / L hydrochloric acid solution, washed for 65 min, and then placed in a box furnace. In an air atmosphere, the temperature was raised to 190 °C at 0.2 °C / min, oxidized for 30 min, and then carbonized at 800 °C for 2.5 h to obtain carbon hollow microspheres. (6) 1.5 parts of carbon hollow microspheres, 0.2 parts of methyl cellulose, 4 parts of deionized water and 30 parts of zirconium beads were mixed and stirred at 400 r / min for 3 min. Then, 0.4 parts of amino silicone oil and 3 parts of gradient nano-silica aerogel were added and the speed was adjusted to 1800 r / min. After stirring for 20 min, 19 parts of water-based acrylic resin were added and the speed was reduced to 700 r / min. The mixture was stirred for 40 min to prepare a waterproof and thermal insulation coating.

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