CN112521842B

CN112521842B - Elastic thermal insulation coating for external wall and preparation method thereof

Info

Publication number: CN112521842B
Application number: CN202011252990.XA
Authority: CN
Inventors: 孟运; 孟奎
Original assignee: Hubao New Material Technology Shanghai Co ltd
Current assignee: Hubao New Material Technology Shanghai Co ltd
Priority date: 2020-11-11
Filing date: 2020-11-11
Publication date: 2022-07-05
Anticipated expiration: 2040-11-11
Also published as: CN112521842A

Abstract

The application relates to the field of coatings, and particularly discloses an elastic thermal insulation coating for an external wall and a preparation method thereof, wherein the elastic thermal insulation coating for the external wall comprises the following components in parts by mass: aqueous acrylic emulsion: 35-60 parts; isocyanate: 6-10 parts; hollow glass beads: 10-15 parts; filling: 33-48 parts; defoaming agent: 0.05-0.2 part; leveling agent: 2-4 parts; wetting agent: 0.1-0.3 part; and (3) bactericide: 0.05-0.3 part; deionized water: 3-7 parts. The preparation method comprises the following steps: heating deionized water to 40-50 ℃, adding a leveling agent into the deionized water at the stirring speed of 300-800rpm, and uniformly mixing to obtain a first premix; and (3) adding the wetting agent, the defoaming agent, the water-based acrylic emulsion and the isocyanate into the first premix in sequence, fully and uniformly mixing, filtering and discharging. The elastic thermal-insulation coating for the outer wall can be used for the outer wall of a building, has excellent elasticity and toughness, can reduce the shrinkage rate of a coating film, reduces the generation of shrinkage cavity and cracking phenomena of the coating film, and is favorable for ensuring the heat-insulation and thermal-insulation effects of the coating film.

Description

Elastic thermal insulation coating for external wall and preparation method thereof

Technical Field

The application relates to the technical field of coatings, in particular to an elastic thermal insulation coating for an external wall and a preparation method thereof.

Background

The heat insulation coating is a novel functional coating, can be used for the outer wall of a building to reduce the heat conduction effect indoors and outdoors, keep the comfort of indoor temperature, have good heat insulation effect and contribute to energy saving.

The heat-insulating coating in the related technology is mainly divided into three types, namely a blocking heat-insulating coating, a heat-reflecting heat-insulating coating and a radiation heat-insulating coating, wherein the blocking heat-insulating coating is added with materials such as sepiolite, vermiculite, hollow ceramic powder and the like with low heat conductivity, and a heat-insulating layer is formed by utilizing gaps in the filler to block heat transfer; the heat-reflecting heat-insulating coating realizes the heat-insulating effect by adding the material capable of reflecting sunlight; the radiation heat insulation coating radiates the energy of absorbed sunlight into the air at a certain wavelength, so that the heat insulation effect is realized.

For example, chinese patent application publication No. CN109233521A discloses an exterior wall thermal insulation coating, which is prepared by sequentially weighing: 30-50 parts of pure acrylic emulsion, 15-30 parts of pigment and filler, 2-4 parts of film forming additive, 1-2 parts of dispersing agent, 1-4 parts of hydrophobic agent, 0.5-2.0 parts of thickening agent, 30-40 parts of water and 15-25 parts of modified heat insulation filler, mixing the pure acrylic emulsion and the water in a stirrer, sequentially adding the pigment and filler, the modified heat insulation filler, the hydrophobic agent, the thickening agent, the film forming additive and the dispersing agent into the stirrer, and stirring and mixing for 30-40 min under the conditions that the temperature is 30-45 ℃ and the rotating speed is 300-500 r/min to obtain the exterior wall heat insulation coating.

The external wall heat-insulating coating in the related technology has large shrinkage degree in the processes of film forming, drying and curing, so that the cracking phenomenon appears after the coating is cured, and the heat-insulating effect of the coating is influenced.

Disclosure of Invention

In order to solve the problems that a coating film is large in shrinkage rate during drying and curing and is easy to cause shrinkage cavity and cracking in the related technology, the application provides the elastic thermal insulation coating for the outer wall and the preparation method thereof, which can effectively improve the elasticity and toughness of the coating film, reduce the shrinkage rate of the coating film, reduce the probability of shrinkage cavity cracking of the coating film and improve the thermal insulation effect of the coating film.

In a first aspect, the application provides an elastic thermal insulation coating for an external wall, which adopts the following technical scheme:

an elastic thermal insulation coating for an external wall comprises the following components in parts by mass:

aqueous acrylic emulsion: 35-60 parts;

isocyanate: 6-10 parts;

hollow glass beads: 10-15 parts;

filling: 33-48 parts;

defoaming agent: 0.05-0.2 part;

leveling agent: 2-4 parts;

wetting agent: 0.1-0.3 part;

and (3) bactericide: 0.05-0.3 part;

deionized water: 3-7 parts.

By adopting the technical scheme, as the water-based acrylic emulsion and the isocyanate are adopted, the hydroxyl of the water-based acrylate can be crosslinked and solidified with the isocyanate group of the isocyanate to form a crosslinked coating film with a three-dimensional network structure, so that the toughness of the coating film is increased, and the elasticity and the anti-cracking performance of the coating film are improved; meanwhile, the crosslinking and curing of the water-based acrylate and the isocyanate are fast, the drying time is short, so that the shrinkage of the coating film cannot be generated in time, the phenomenon of shrinkage cavity cracking of the coating film is obviously reduced, and the heat insulation and heat preservation effects of the exterior wall coating are ensured.

Preferably, the aqueous acrylic emulsion is prepared according to the following steps:

s101, mixing hydroxyethyl methacrylate, acrylic acid and methyl methacrylate with the mass ratio of 3-5:5-8:70-84:8-15 with styrene to obtain a raw material monomer, adding the raw material monomer into deionized water, adding an emulsifier accounting for 5-9% of the mass of the raw material monomer, and stirring for 15-30min to obtain a pre-emulsified monomer;

s102, taking NH with the mass concentration of 10 percent₄S₂O₈Solution for later use, NH₄S₂O₈The mass of the solution is 8-12% of the mass of the raw material monomer, and an initiator solution is obtained;

s103, heating the sodium bicarbonate buffer solution to 76-88 ℃, and putting 25% -40% of initiator solution and 10% -20% of pre-emulsified monomer into the sodium bicarbonate buffer solution to obtain a first emulsion;

and S104, dropwise adding the residual initiator solution and the pre-emulsified monomer into the first emulsion at a constant speed for 1.5-3h, keeping the temperature at 70-95 ℃ for reaction for 0.5-1.5h after dropwise adding is finished, cooling the emulsion to 25-30 ℃, adjusting the temperature to 7-8 by using a pH regulator, filtering and discharging to obtain the water-based acrylic emulsion.

By adopting the technical scheme, under the action of the initiator, the hydroxyethyl methacrylate, the acrylic acid, the methyl methacrylate and the styrene are polymerized to form the water-based acrylic emulsion containing more hydroxyl groups, which is beneficial to improving the crosslinking density of the water-based acrylic emulsion and the isocyanate, further improving the toughness and the adhesiveness of the coating and reducing the cracking phenomenon of the coating.

The initiator has the function of promoting the raw material monomer to polymerize to generate the water-based acrylic emulsion, the dosage of the initiator is small, the conversion rate of the raw material monomer is small, the prepared water-based acrylic emulsion is insufficient, and the strength of a coating film is not improved; the initiator dosage is large, so that the particle size of the prepared water-based acrylic emulsion is easy to increase, and the phenomenon of non-uniformity appears after the coating is formed into a film.

Preferably, the mass ratio of the hydroxyethyl methacrylate, the acrylic acid, the methyl methacrylate and the styrene in the step S101 is 5:6:81: 10.

By adopting the technical scheme, because the hydroxyethyl methacrylate contains hydroxyl, the dosage of the hydroxyethyl methacrylate is increased, the content of the hydroxyl in the water-based acrylic emulsion can be effectively increased, and the crosslinking density of the water-based acrylic emulsion and isocyanate is favorably improved, so that the toughness and the impact strength of the coating are enhanced. However, as the crosslinking density increases, the shrinkage of the coating film increases, and the coating film tends to crack. Tests show that by adopting the proportion, the shrinkage rate of the coating is small on the premise of ensuring the toughness of the coating, and the phenomenon of shrinkage cavity cracking is not easy to generate.

Preferably, the hollow glass bead is modified according to the following steps:

s201, fully mixing a silane coupling agent, ethanol and water in a mass ratio of (1-3) to 20:10 to prepare a modifier;

s202, mixing the hollow glass beads with the modifier, stirring for 10-30min at the rotation speed of 1500-2000rpm, filtering and drying to obtain the modified hollow glass beads.

By adopting the technical scheme, the surface of the hollow glass microsphere is modified by using the mixed solution of the silane coupling agent and the hydrated ethanol, the mixed solution of the water and the ethanol can promote the modification effect of the silane coupling agent, the self polycondensation of the silane coupling agent is continued, the dispersibility of the hollow glass microsphere and the inorganic filler in a coating film is improved, and the binding property of the hollow glass microsphere and the inorganic filler with an emulsion interface is improved, so that the heat insulation effect is improved.

Preferably, the filler includes at least one of mica powder, wollastonite fiber and glass fiber.

By adopting the technical scheme, the mica powder, the wollastonite fiber and the glass fiber are fillers with needle-shaped or sheet-shaped structures, so that the heat-insulating coating has good heat-insulating effect, has small internal stress, is beneficial to releasing the stress when the coating shrinks, and can improve the adhesive force of the coating while reducing the cracking and falling phenomena of the coating.

Preferably, the leveling agent is at least one of fluorocarbon modified acrylic acid and carboxymethyl cellulose.

By adopting the technical scheme, the leveling agent can enable the surface tension of the coating to be uniform, improve the leveling and spreading properties of the coating, enable the coating to be flat, smooth and uniform, and further reduce the phenomenon of coating shrinkage. The fluorocarbon modified acrylic acid leveling agent has good compatibility with the water-based acrylic acid emulsion, is easy to disperse when being blended with the water-based acrylic acid emulsion and is beneficial to improving the leveling property of a coating film.

Preferably, the wetting agent is at least one of alkylphenol polyoxyethylene ether, acetylenic diol and diol polyoxyethylene ether.

By adopting the technical scheme, the wetting agent can wet the surface of the outer wall, so that the spreading performance of the coating on the surface of the outer wall can be improved, the smoothness and the flatness of the surface of a coating film are enhanced, and the adverse phenomena of shrinkage, adhesion force reduction and the like caused by low surface tension of the outer wall can be prevented.

Preferably, the bactericide includes at least one of nano silver ion and isothiazolinone.

By adopting the technical scheme, the coating is easy to breed microorganisms and mould in a proper temperature and humidity environment, so that the phenomena of coating release layering, demulsification, mildewing, deterioration and the like are caused. The nano silver ions can catalyze water molecules and oxygen to generate hydroxyl radicals and active oxygen ions, so that the multiplication capacity of bacteria is quickly destroyed, and the antibacterial effect is achieved.

In a second aspect, the application provides a preparation method of an elastic thermal insulation coating for an external wall, which adopts the following technical scheme: a preparation method of an elastic thermal insulation coating for an external wall comprises the following steps:

s301, heating deionized water to 40-50 ℃, adding a leveling agent into the deionized water at a stirring speed of 300-800rpm, and uniformly mixing to obtain a first premix;

and S302, adding the wetting agent, the defoaming agent, the water-based acrylic emulsion and the isocyanate into the first premix in sequence, fully and uniformly mixing, filtering and discharging to obtain the elastic thermal insulation coating for the outer wall.

By adopting the technical scheme, the leveling agent is uniformly dispersed by heating and stirring, and the leveling effect of the coating film is improved; the addition of the defoaming agent in advance can reduce the generation of bubbles in the coating and reduce the probability of coating defects such as cracks and pores caused by the bubbles breaking in the coating.

In summary, the present application has the following beneficial effects:

1. in the application, the water-based acrylic emulsion and the isocyanate are matched together, and the water-based acrylic emulsion and the isocyanate can be quickly crosslinked to form a three-dimensional network structure, so that the prepared coating has the characteristics of good toughness and small shrinkage rate. Under the same test conditions, the linear shrinkage of the coating prepared from the water-based acrylic emulsion and isocyanate is reduced from 0.33% to 0.12%, the cracking phenomenon of the coating after curing is also obviously reduced, and the impact strength is improved.

2. The hollow glass beads are preferably adopted in the coating, and the hollow glass beads are good in dispersibility in the coating and high in adhesion, so that the thermal conductivity of the coating is reduced from 0.043W/(m.K) to 0.028W/(m.K), and the coating has a more excellent heat preservation and insulation effect.

3. According to the method, the amount of the initiator and the ratio of the raw material monomers are reasonably controlled, so that the coating has good impact resistance and small linear shrinkage.

Detailed Description

The present application will be described in further detail below with reference to examples.

Preparation example

Preparation example 1, an aqueous acrylic emulsion, was prepared as follows:

s101, mixing hydroxyethyl methacrylate, acrylic acid and methyl methacrylate with the mass ratio of 5:6:79:10 with styrene to obtain a raw material monomer, adding the raw material monomer into deionized water, wherein the mass of the deionized water is 60% of that of the raw material monomer, adding sodium dodecyl benzene sulfonate (emulsifier) accounting for 6% of that of the raw material monomer, and stirring for 30min to obtain a pre-emulsified monomer;

s102, taking NH with the concentration of 10 percent₄S₂O₈Solution for later use, NH₄S₂O₈The mass of the solution is 10 percent of the mass of the raw material monomer, and an initiator solution is obtained;

s103, heating a sodium bicarbonate buffer solution with the concentration of 0.2% to 85 ℃, wherein the mass of the sodium bicarbonate buffer solution is 100% of the mass of the raw material monomer to obtain a buffer solution, and adding 30% of an initiator solution and 20% of a pre-emulsified monomer into the buffer solution to obtain a first emulsion;

and S104, dropwise adding the residual initiator solution and the pre-emulsified monomer into the first emulsion at a constant speed for 2 hours, after dropwise adding, carrying out heat preservation reaction at the temperature of 85 ℃ for 1.5 hours, then cooling the emulsion to 25 ℃, adjusting the pH of the emulsion to 8 by using ammonia water, filtering and discharging to obtain the aqueous acrylic emulsion.

Preparation example 2, an aqueous acrylic emulsion, was different from preparation example 1 in that the mass ratio of hydroxyethyl methacrylate, acrylic acid, methyl methacrylate and styrene was 3:6:81:10 in step S101.

Preparation example 3, an aqueous acrylic emulsion, was different from preparation example 1 in that in step S103, the mass ratio of hydroxyethyl methacrylate, acrylic acid, methyl methacrylate and styrene was 7:6:77: 10.

Preparation example 4, an aqueous acrylic emulsion, was different from preparation example 1 in that, in step S102, NH was added₄S₂O₈The mass of the solution was 8% of the mass of the raw material monomer.

Preparation example 5, an aqueous acrylic emulsion, was different from preparation example 1 in that, in step S102, NH was added₄S₂O₈The mass of the solution was 13% of the mass of the raw material monomer.

Preparation example 6, a hollow glass microsphere, modified according to the following procedure:

s201, mixing a silane coupling agent, ethanol and water in a mass ratio of 3:50:50 to prepare a modifier;

s202, immersing the hollow glass beads in the modifier, stirring for 10min at the rotating speed of 1500rpm, filtering and drying to obtain the modified hollow glass beads.

Preparation example 7, a hollow glass bead, was different from preparation example 7 in that the ratio of the silane coupling agent, ethanol and water in step S201 was 1:20: 10.

Preparation example 8, a hollow glass bead, was different from preparation example 7 in that the ratio of the silane coupling agent, ethanol and water in step S201 was 1:10: 10.

Production example 9, a hollow glass bead, differs from production example 7 in that the ethanol in step S201 is replaced with an equal amount of water.

Production example 10, a hollow glass bead, differs from production example 7 in that the water in step S201 is replaced with an equal amount of ethanol.

Examples

Embodiment 1, an elastic thermal insulation coating for exterior walls is prepared according to the following steps:

s301, heating deionized water to 40 ℃, adding a leveling agent into the deionized water at a stirring speed of 500rpm, and uniformly mixing to obtain a first premix;

Wherein the water-based acrylic emulsion is prepared from the water-based acrylic emulsion prepared in preparation example 1, and the hollow glass beads are prepared from the hollow glass beads prepared in preparation example 6, and the average particle size of the hollow glass beads is 120 microns; the filler adopts mica powder with the average grain diameter of 10 mu m and glass fiber with the average grain diameter of 40 mu m; the flatting agent is fluorocarbon modified acrylic acid; the wetting agent adopts dodecyl phenol polyoxyethylene ether; the bactericide adopts nano silver ions.

Examples 2 to 3, an exterior wall elastic thermal insulation coating, are different from example 1 in that the components and their respective contents are shown in table 1.

TABLE 1 compositions and their respective levels (kilograms) of examples 1-3

Example 4, an exterior wall elastic thermal insulation coating, different from example 1, in that the aqueous acrylic emulsion is a badfu MT188 aqueous acrylic emulsion purchased from the chemical company of engender, mountain; the hollow glass microspheres obtained in preparation example 7 were used.

Example 5, an exterior wall elastic thermal insulation coating, differs from example 1 in that the hollow glass beads prepared in preparation example 8 were used.

Example 6, an exterior wall elastic thermal insulation coating, differs from example 1 in that the hollow glass beads prepared in preparation example 9 are used.

Example 7, an exterior wall elastic thermal insulation coating, was different from example 1 in that hollow glass beads prepared in preparation example 10 were used.

Example 8, an exterior wall elastic thermal insulation coating, differs from example 1 in that the aqueous acrylic emulsion prepared in preparation example 2 was used.

Example 9, an exterior wall elastic thermal insulation coating, differs from example 1 in that the aqueous acrylic emulsion prepared in preparation example 3 was used.

Example 10, an exterior wall elastic thermal insulation coating, differs from example 1 in that the aqueous acrylic emulsion prepared in preparation example 4 was used.

Example 11, an exterior wall elastic thermal insulation coating, differs from example 1 in that the aqueous acrylic emulsion prepared in preparation example 5 was used.

Example 12 is an exterior wall elastic thermal insulation coating, which is different from example 1 in that heavy calcium carbonate with the particle size distribution D90 being less than or equal to 10 mu m is adopted as the filler.

Example 13, an exterior wall elastic thermal insulation coating, different from example 1, is that carboxymethyl cellulose with equal mass is used to replace fluorocarbon modified acrylic acid.

Example 14, an exterior wall elastic thermal insulation coating, differs from example 1 in that an equal mass of acetylenic diol is used instead of dodecylphenol polyoxyethylene ether.

Example 15, an exterior wall elastic thermal insulation coating, differs from example 1 in that isothiazolinone of equal mass is used instead of nano silver ion.

Comparative example

Comparative example 1, an exterior wall thermal insulation coating, prepared according to the following steps:

step 1: mixing glucose and water in a mass ratio of 1:25 in a flask, adding potassium iodate with the mass of 0.2 time that of the glucose into the flask, and stirring and mixing for 180min under the conditions that the temperature is 65 ℃ and the rotating speed is 350r/min to obtain a glucose mixed solution;

step 2: mixing the glucose mixed solution with a barium chloride solution with the mass fraction of 20% according to the mass ratio of 1: 5, mixing, stirring and mixing for 40min at the temperature of 45 ℃ and the rotating speed of 400r/min, and filtering to obtain filtrate;

and step 3: mixing the filtrate with a sodium sulfate solution with the mass fraction of 22% according to the mass ratio of 1: 4, mixing, stirring and mixing for 40min at the temperature of 45 ℃ and the rotating speed of 400r/min, filtering, and removing a filter cake to obtain a modified glucose mixed solution;

and 4, step 4: mixing potassium carbonate and titanium dioxide according to a molar ratio of 1.5: 4.0, mixing the mixture in a grinding machine, and grinding for 2 hours to obtain a pretreated powder blank;

and 5: calcining the pretreated powder blank at 850 ℃ for 13h to obtain pretreated powder, grinding the pretreated powder by a grinder for 80min, calcining the pretreated powder at 850 ℃ for 12h, and discharging to obtain a mixed powder blank;

step 6: washing the mixed powder blank respectively with 15% hydrochloric acid and deionized water for 8 times by mass, drying for 3h at the temperature of 60 ℃ to obtain mixed powder, mixing the mixed powder with 22% hydrochloric acid by mass according to the mass ratio of 1:120, stirring and soaking for 15h at the temperature of 45 ℃ and the rotating speed of 320r/min, filtering, repeatedly mixing, and soaking and filtering for 3 times to obtain a modified powder blank;

and 7: washing the modified powder blank with deionized water for 10 times, drying for 5 hours at the temperature of 65 ℃ to obtain modified powder, and mixing the modified powder with a tetrabutylammonium hydroxide solution with the mass fraction of 28% according to the mass ratio of 1: 18, mixing the mixture in a beaker, soaking the mixture for 13 hours at room temperature, adding water with the mass 40 times that of the modified powder into the beaker, stirring and mixing the mixture for 12 hours at the temperature of 40 ℃ and the rotating speed of 280r/min, centrifugally separating the materials in the beaker for 20 minutes at the rotating speed of 2800r/min, and removing supernatant to obtain modified powder sol;

and 8: mixing the modified powder sol and the polyallylamine hydrochloride solution according to the mass ratio of 5: 3, mixing the mixture in a three-neck flask, adding modified glucose mixed solution which is 0.2 time of the modified powder sol into the three-neck flask under the condition that the rotating speed is 600r/min, and stirring and reacting for 2 hours under the conditions that the temperature is 55 ℃ and the rotating speed is 400r/min to obtain pretreated modified powder sol;

and step 9: mixing the pretreated modified powder sol and sodium borohydride according to a mass ratio of 150: 1, stirring and reacting for 3 hours at the temperature of 38 ℃ and the rotating speed of 320r/min to obtain mixed sol, and mixing the mixed sol and sodium hydrogen phosphate according to the mass ratio of 4: 1, mixing, stirring and reacting for 12 hours at the temperature of 42 ℃ and the rotating speed of 300r/min, centrifugally separating for 20 minutes at the rotating speed of 3000r/min, and removing supernatant to obtain a heat-insulating filler blank; washing the heat-insulating filler blank with deionized water for 10 times, and drying for 3 hours at the temperature of 65 ℃ to obtain the heat-insulating filler;

and step 9: weighing the following components in parts by weight: 50 parts of pure acrylic emulsion, 30 parts of titanium dioxide (pigment and filler), 4 parts of propylene glycol monobutyl ether (film forming additive), 2 parts of dispersant NNO, 4 parts of hydrophobic agent 6600, 2.0 parts of thickener ASE-60, 40 parts of water and 25 parts of heat insulation filler, mixing the pure acrylic emulsion and the water in a stirrer, sequentially adding the pigment and filler, the heat insulation filler, the hydrophobic agent, the thickener, the film forming additive and the dispersant into the stirrer, and stirring and mixing for 40min under the conditions that the temperature is 45 ℃ and the rotating speed is 500r/min to obtain the exterior wall heat insulation coating.

Comparative example 2, an exterior wall elastic thermal insulation coating, differs from example 1 in that the aqueous acrylic emulsion prepared in preparation example 1 was replaced with an equal amount of styrene-acrylic emulsion.

Comparative example 3, an exterior wall elastic thermal insulation coating, differs from example 1 in that an equal amount of styrene-acrylic emulsion is used instead of isocyanate.

Comparative example 4, an exterior wall elastic thermal insulation coating, differs from example 1 in that the aqueous acrylic emulsion prepared in preparation example 1 and isocyanate were replaced with an equal amount of styrene-acrylic emulsion.

Performance test

Test 1: determination of coating Heat conductivity

Test subjects: examples 1-12 and comparative examples 1-6.

The test method comprises the following steps: according to a double-plate measuring method in GB/T10294-2008, the outer wall elastic heat-insulating coating is made into 2 coating test plates with the thickness of 150mm x 15mm, a MHY-19714 heat conductivity coefficient tester is used for measuring the heat conductivity coefficient of the outer wall elastic heat-insulating coating, the average value of 10 times of measurement is taken as the heat conductivity coefficient of the outer wall elastic heat-insulating coating, the smaller the heat conductivity coefficient is, the better the heat-insulating effect is, and specific test results are shown in Table 2.

Test 2: paint linear shrinkage test

Test subjects: examples 1-15 and comparative examples 1-4.

The test method comprises the following steps: the test was carried out with reference to the test method and test apparatus of HG/T2625-1994, and the test was carried out at an ambient temperature of 26 ℃. The length of the test mold is 25cm, the radius R1 is 2cm, the radius R1 is 1.5cm., the casting depth is 0.5cm, the thickness of the polytetrafluoroethylene film is 0.025mm, the greater the linear shrinkage rate is measured, the greater the shrinkage rate of the coating is, and the specific test results are shown in Table 2.

Test 3: test objects for impact resistance of coating: paint film test panels were made from the coatings of examples 1-15 and comparative examples 1-4 with reference to GB/T1732-1993.

The test method comprises the following steps: the test is carried out according to the test method and the test device in GB/T1732-1993, the impact height of a heavy hammer is 30cm, a 4-time magnifying lens is used for observing whether the coating has cracks and falling phenomena or not after the test, if the cracks and the falling phenomena exist, the impact resistance strength or the adhesive force of the coating is poor, and the specific test result is shown in Table 2.

Test 4: paint drying test

Test subjects: examples 1-15 and comparative examples 1-4.

The test method comprises the following steps: according to the method of GB/T1727-79, a coating of a sample object is prepared on a tin plate to form a coating film, then the tin plate is placed in an electric heating air blast box to be dried for 90 minutes, and then the tin plate is taken out and placed under the conditions of 25 ℃ and 50% RH humidity for standing for 30 minutes. Observing and measuring the cracking length of the surface of the coating film by using a straight ruler, and recording the cracking length as severe cracking when the cracking length (the length of a straight line between two end points) is more than 5 cm; when the cracking length is between 3 cm and 5cm, recording as medium cracking; when the cracking length is between 1-2cm, recording as slight cracking; when the cracking length is less than 1cm, the steel plate is considered to be not cracked; the specific test results are shown in table 2.

TABLE 2 results of the Performance test of examples 1 to 15 and comparative examples 1 to 4

And (3) analyzing test results:

(1) by combining examples 1-12 and comparative examples 1-4 and table 2, it can be seen that the external wall elastic thermal insulation coating prepared by using the water-based acrylic emulsion, the isocyanate, the hollow glass beads, the leveling agent and the like together has good thermal insulation effect and flexibility, has small linear shrinkage rate during curing, and can effectively avoid or relieve the cracking phenomenon of a coating film caused by shrinkage.

(2) As can be seen by combining examples 1-4 and comparative examples 1-4 and table 2, the linear shrinkage of the elastic thermal insulation coating for exterior walls prepared by using the aqueous acrylic emulsion and the isocyanate in examples 1-4 is between 0.12 and 0.24%, and the linear shrinkage of the aqueous acrylic emulsion and the isocyanate in comparative examples 1-4 are between 0.27 and 0.33%, and the cracking degree of the aqueous acrylic emulsion after drying and curing is obviously improved compared with that of the aqueous acrylic emulsion and the isocyanate in comparative examples 1-4. The water-based acrylic emulsion is matched with isocyanate, so that the shrinkage rate of the coating during curing is obviously reduced, and the cracking phenomenon of the coating is improved.

(3) As can be seen by combining examples 1-3 and examples 8-9 with Table 2, examples 1-3 used hydroxyethyl methacrylate, acrylic acid, methyl methacrylate and styrene in a mass ratio of 5:6:79:10 to produce an aqueous acrylic emulsion, while example 8 used hydroxyethyl methacrylate, acrylic acid, methyl methacrylate and styrene in a mass ratio of 3:6:81:10 to produce an aqueous acrylic emulsion, and example 9 used hydroxyethyl methacrylate, acrylic acid, methyl methacrylate and styrene in a mass ratio of 7:6:77:10 to produce an aqueous acrylic emulsion; compared with the elastic thermal insulation coating prepared in the embodiment 1-3, the elastic thermal insulation coating for the outer wall prepared in the embodiment 8 has cracks after an impact resistance test, which shows that the crosslinking density is small, and the toughness and the impact resistance of a coating film are reduced; while the linear shrinkage of the coating film in example 9 is increased to 0.2, and a medium cracking phenomenon occurs, which shows that the crosslinking density of the coating film is too high and the coating film is easy to crack due to the adoption of the formula in example 9.

Comprehensively, monomers such as hydroxyethyl methacrylate, acrylic acid, methyl methacrylate and styrene in a mass ratio of 5:6:79:10 are adopted to prepare the aqueous acrylic emulsion, the crosslinking density of the aqueous acrylic emulsion and isocyanate is proper, and the coating film has small shrinkage and is not easy to crack under the condition of ensuring the toughness and the impact strength of the coating film.

(4) As can be seen by combining examples 1-3 and examples 10-11 with Table 2, the mass of the initiator used in examples 1-3 was 10% of the mass of the raw material monomer, the mass of the initiator used in example 10 was 8% of the mass of the raw material monomer, and the mass of the initiator used in example 11 was 10% of the mass of the raw material monomer; compared with the examples 1-3, the elastic thermal insulation coating for the external wall prepared in the example 10 has cracks after an impact resistance test, which shows that the content of the prepared water-based acrylic emulsion is low and the film forming strength of the coating is reduced due to the low initiator consumption. The elastic thermal insulation coating for the external wall prepared in the embodiment 11 has the phenomena of cracks and medium cracks, which shows that the use amount of the initiator is too large, so that the uniformity of the formed film is poor, and the performances such as impact resistance and shrinkage resistance are reduced.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The elastic thermal insulation coating for the outer wall is characterized by comprising the following components in parts by mass:

aqueous acrylic emulsion: 35-60 parts;

isocyanate: 6-10 parts;

hollow glass beads: 10-15 parts;

filling: 33-48 parts;

defoaming agent: 0.05-0.2 part;

leveling agent: 2-4 parts;

wetting agent: 0.1-0.3 part;

and (3) bactericide: 0.05-0.3 part;

deionized water: 3-7 parts;

the flatting agent comprises a fluorocarbon modified acrylic flatting agent;

the wetting agent comprises at least one of alkylphenol polyoxyethylene, acetylenic diol and diol polyoxyethylene;

the filler comprises at least one of mica powder, wollastonite fiber and glass fiber;

the water-based acrylic emulsion is prepared by the following steps:

s101, mixing hydroxyethyl methacrylate, acrylic acid and methyl methacrylate with the mass ratio of 5:6:79:10 with styrene to obtain a raw material monomer, adding the raw material monomer into deionized water, adding an emulsifier accounting for 5-9% of the mass of the raw material monomer, and stirring for 15-30min to obtain a pre-emulsified monomer;

2. The elastic thermal insulation coating for the external wall according to claim 1, wherein the hollow glass beads are modified according to the following steps:

s202, mixing the hollow glass beads with the modifier, stirring for 10-30min at the rotating speed of 1500-2000rpm, filtering and drying to obtain the modified hollow glass beads.

3. The elastic thermal insulation coating for external walls according to claim 1, wherein the bactericide comprises at least one of nano silver ions and isothiazolinone.