Preparation process of high-elasticity fireproof coating

Abstract

The invention relates to the technical field of fireproof coatings, in particular to a preparation process of a high-elasticity fireproof coating. The problems that an existing coating is poor in flame retardant effect and poor in elasticity are solved. The organic phosphonate, the organic silicon micropowder and the organic nitrogen-containing compound are used for preparing the compound flame retardant, and the dosage of the compound flame retardant is changed; the polydopamine coated clay is prepared, so that the flame retardant property of the prepared coating is improved; the soft segment type, the ratio of the hard segment to the soft segment and the molecular weight of the soft segment of the waterborne polyurethane are changed; changing the proportion of the waterborne polyurethane, the acrylic resin and the plasticizer, the heating temperature and the stirring time after heating; the particle size of the pigment filler and the stirring time of the slurry are changed, so that the elasticity of the prepared coating is improved.

Description

Technical Field

[0001] The invention relates to the technical field of fire retardant coatings, in particular to a preparation process of a high-elasticity fire retardant coating. Background Art

[0002] With the continuous improvement of the living standards of our country's people, people will choose various coatings to decorate the exterior of buildings when constructing them. Most buildings are based on concrete, with brick walls inside the concrete. After a certain period of time, due to changes in the external climate, the concrete and bricks will expand and contract, which will cause the coating on the outer layer to have varying degrees of cracks, bubbling and even falling off. If elastic coating is used, when it expands and contracts, the elastic coating will use its own elasticity to deform with the change of temperature to make up for the cracks caused by thermal expansion and contraction, which can effectively prevent the coating from cracking.

[0003] At the same time, with society's growing awareness of safety, the fire-retardant properties of coatings are receiving increasing attention and attention. Fires often cause immeasurable damage to people's lives and property. When a fire occurs, fire-retardant coatings can effectively block the invasion of external fire sources, minimizing the damage and harm caused by the fire. Therefore, imparting excellent fire-retardant properties to exterior wall coatings has become a development trend in the coatings industry.

[0004] Chinese patent CN108264812A proposes a nano-thermal insulation coating. This invention uses acrylic resin and alkyd resin as film-forming materials, giving the coating excellent thermal insulation properties, as well as good mechanical properties and impact resistance. The alkyd resin has a high content of weakly polar structures and good solubility, resulting in a coating with good gloss, brushability, and leveling properties. However, the alkyd resin used in this patent lacks high elasticity and has poor adhesion, making it prone to falling off when squeezed or scratched.

[0005] Chinese patent CN113930111B proposes a water-based flame-retardant, energy-saving, and anticorrosive coating and its preparation method. The coating produced by this invention exhibits excellent thermal insulation, thermal stability, and flame retardancy, as well as reliable anticorrosive and antibacterial properties. The rubber latex dispersion acts as a binder, enhancing the coating's elasticity, adhesion, and strength. However, the acrylic resin used in this invention is viscous when hot and brittle when cold. During high summer temperatures, the surface can become severely viscous and easily contaminated by airborne dust, affecting the coating's aesthetics. In low winter temperatures, the acrylic resin becomes brittle, affecting the coating's elongation and elasticity, and even causing cracking.

[0006] In summary, although the coatings prepared in the prior art have made certain progress, they still have some shortcomings, such as poor flame retardant effect, poor elasticity, and easy expansion and cracking when exposed to water and fire.

[0007] Therefore, a preparation process of high elastic fire retardant coating was proposed. Summary of the Invention

[0008] The present invention aims to provide a process for preparing a highly elastic fire-retardant coating, wherein the highly elastic fire-retardant coating is prepared by mixing pigments, a dispersant, a waterborne polyurethane, an acrylic resin, a plasticizer, a defoamer, a compounded flame retardant, polydopamine-coated clay, and deionized water. The flame retardant is prepared by using an organic phosphonate, organosilicon micropowder, and an organic nitrogen-containing compound and varying the amount of the compounded flame retardant; polydopamine-coated clay is prepared to improve the flame retardancy of the coating; the elasticity of the coating is improved by varying the soft segment type, hard segment to soft segment ratio, and soft segment molecular weight of the waterborne polyurethane; the ratio of the waterborne polyurethane, acrylic resin, and plasticizer, the heating temperature, and the stirring time after heating; and the pigments are prepared, and the particle size of the pigments and fillers and the stirring time of the slurry are varied.

[0009] To achieve the above object, the present invention provides the following technical solutions: A preparation process for a highly elastic fire-retardant coating comprises the following steps: adding a pigment, a filler, and a dispersant to deionized water and stirring the mixture to obtain a slurry; adding waterborne polyurethane, an acrylic resin, a plasticizer, and a dispersant to the slurry, stirring the mixture, adding a compounded flame retardant, then adding polydopamine-coated clay, continuing to stir the mixture, and adding deionized water to adjust the viscosity to obtain a highly elastic fire-retardant coating; The pigment and filler are prepared from wollastonite mineral fiber, mica powder and vermiculite powder; The compound flame retardant is prepared from organic phosphonate, organic silicon micropowder and organic nitrogen-containing compound.

[0010] Preferably, the mass ratio of the waterborne polyurethane, the acrylic resin and the plasticizer is 10:5-10:0.3-0.6.

[0011] Preferably, the preparation process of the compound flame retardant is as follows: dissolving an organic phosphonate, organosilicon powder and an organic nitrogen-containing compound in dichloromethane in a mass ratio of 2-5:1:1-4 to obtain a mixed solution; placing the mixed solution in a reaction kettle, adding benzoyl peroxide thereto, heating to 120-180° C. under nitrogen conditions, reacting for 2.5-4.5 hours to obtain a polymer; cooling the polymer to room temperature, and removing the solvent by rotary evaporation to obtain a compound flame retardant.

[0012] Preferably, the organic phosphonate is one of ethyl diphenylphosphonate, diphenyl phenylphosphonate and dimethyl phosphonate; and the organic nitrogen-containing compound is melamine.

[0013] Preferably, the preparation process of polydopamine-coated clay is as follows: dispersing clay in deionized water and ultrasonically treating the clay to obtain a dispersion; dissolving dopamine hydrochloride in a methanol solution, adding sodium hydroxide thereto, and stirring until the solid is completely dissolved to obtain hydrolyzed dopamine; adjusting the pH value of the hydrolyzed dopamine to 8-9, adding the dispersion, stirring and mixing, and then adding ferric chloride, and continuing to stir and react at room temperature for 12-18 hours to obtain polydopamine-coated clay.

[0014] Preferably, the clay is one of bentonite, kaolin and montmorillonite.

[0015] Preferably, the hard segment of the waterborne polyurethane is isophorone diisocyanate; the soft segment is one of polypropylene glycol, polytetramethylene ether glycol, polyethylene adipate and polyoxypropylene glycol; the mass ratio of the hard segment to the soft segment is 1.5:1-3.5.

[0016] Preferably, the molecular weight of the soft segment is 1500-2500.

[0017] Preferably, the preparation process of the highly elastic fire-retardant coating is as follows: 8.4 parts of pigments and fillers and 0.5 parts of dispersant sodium oleate are added to 30 parts of deionized water, and stirred at a speed of 800 r / min for 25-35 minutes to obtain a slurry; 60 parts of water-based polyurethane, acrylic resin, plasticizer, 0.8 parts of dispersant sodium oleate and 0.6 parts of defoamer BYK-024 are added to the slurry, heated to 35-50°C, stirred at a speed of 500-600 r / min for 10 minutes, and then 5-10 parts of compound flame retardant are added. After stirring for 40 minutes, polydopamine-coated clay is added thereto, and stirring is continued for 20-50 minutes. Deionized water is added to adjust the viscosity of -4 cups at 25°C to 75s to obtain a highly elastic fire-retardant coating; the plasticizer is a mixture of dibutyl phthalate and dioctyl adipate in a mass ratio of 1:1.

[0018] Preferably, the preparation process of the pigment filler is as follows: wollastonite mineral fiber, mica powder and vermiculite powder are added to a planetary mixer in a mass ratio of 2:1.1:1.5, 0.4 parts of dispersant sodium oleate are added, and the mixture is stirred at a speed of 900-1300 r / min for 15-25 minutes to obtain a mixture; the mixture is crushed using a jet mill to obtain a pigment filler with a particle size of 10-30 μm.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. There is a synergistic flame retardant effect between the organic phosphonate, organosilicon powder, and the organic nitrogen-containing compound melamine. This synergistic effect becomes more significant as the amount of the compound flame retardant increases. The organic phosphonate can promote the formation of a char layer, the organosilicon powder can enhance the stability of the char layer, and the gas released by the organic nitrogen-containing compound melamine can cause the char layer to expand. The three work together to improve the overall flame retardant properties of the coating, increase the oxygen index of the coating, reduce the flame propagation speed, and even achieve self-extinguishing to a certain extent. The present invention can significantly improve the flame retardant properties of the coating by preparing a compound flame retardant using an organic phosphonate, organosilicon powder, and an organic nitrogen-containing compound and varying the amount used.

[0020] 2. The present invention prepares polydopamine-coated clay so that polydopamine is coated on the surface of the clay. During the combustion process of the coating, the clay can serve as a physical barrier. When the flame contacts the surface of the coating, the polydopamine-coated clay will form a barrier layer on the surface of the coating. In addition, polydopamine has the characteristic of catalytic carbonization at high temperatures. During the combustion process, polydopamine will decompose and release some catalytically active substances, such as nitrogen-containing heterocyclic compounds. These substances can promote the carbonization reaction of organic matter in the coating, thereby improving the flame retardant properties of the coating.

[0021] 3. The present invention can significantly improve the ductility and softness of waterborne polyurethane by changing the type of soft segment and the ratio of hard segment to soft segment, making it more elastic and easy to restore to its original shape, thereby improving the resilience of polyurethane and enabling it to return to its original state more quickly after the external pressure is removed; by appropriately increasing the molecular weight of the soft segment, the molecular chain length can be lengthened, and when the long molecular chain is subjected to external force, more chain segments can participate in deformation and absorb more energy, thereby improving the elasticity of the coating.

[0022] 4. The present invention changes the mass ratio of waterborne polyurethane, acrylic resin and plasticizer, the heating temperature during coating preparation and the stirring time after heating, so that the soft segment and the hard segment are more evenly distributed in the system, and have better interaction with the acrylic resin and the plasticizer. The plasticizer can be better inserted between the molecular chains, reducing the intermolecular force, making the molecular chains easier to move when subjected to force, and the elasticity of the coating is improved, capable of withstanding a certain degree of stretching and bending, and can better recover its original shape after deformation.

[0023] 5. Wollastonite mineral fiber can be evenly dispersed between mica powder and vermiculite powder, and the dispersant sodium oleate can better play its role, so that the surface of each raw material particle can be effectively coated and agglomeration can be reduced. When the coating is subjected to external force, the mineral fiber can play a role similar to reinforcing ribs. The mica powder and vermiculite powder can fill between and around the fibers and deform synergistically, thereby improving the elasticity of the coating, so that the coating can withstand stretching and bending to a certain extent without obvious cracks. The present invention uses wollastonite mineral fiber, mica powder and vermiculite powder to prepare pigments and fillers, and changes the pigment and filler particle size and the slurry stirring time to improve the elasticity of the prepared coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Graph showing the rebound rate test results of Examples 23, 26-34 of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] See also Figure 1 The present invention provides a preparation process of a high elastic fire retardant coating, and the technical solution is as follows: The substance information involved in the present invention is as follows: Sodium oleate CAS No.: 143-19-1; acrylic resin CAS No.: 9003-01-4; dibutyl phthalate CAS No.: 84-74-2; dioctyl adipate CAS No.: 123-79-5; dichloromethane CAS No.: 75-09-2; benzoyl peroxide CAS No.: 94-36-0; ethyl diphenylphosphonate CAS No.: 1733-55-7; diphenyl phenylphosphonate CAS No.: 3848-51-9; dimethyl phosphonate CAS No.: 868-85-9; melamine CAS No.: 108-78-1; dopamine hydrochloride CAS No.: 62-31-7; methanol CAS No.: 67-56-1; sodium hydroxide CAS No.: 1310-73-2; ferric chloride CAS No.: 7705-08-0; bentonite CAS No.: S: 1302-78-9; kaolin CAS: 1332-58-7; montmorillonite CAS: 1318-93-0; isophorone diisocyanate CAS: 4098-71-9; polypropylene glycol CAS: 25322-69-4; polytetramethylene ether glycol CAS: 25190-06-1; polyethylene adipate CAS: 68647-16-5; polyoxypropylene glycol CAS: 25322-69-4; defoamer BYK-024 was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; wollastonite mineral fiber was purchased from Xinyu Southern wollastonite Co., Ltd.; mica powder was purchased from Jinjinle Chemical Co., Ltd.; vermiculite powder was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; and silicone micropowder was purchased from Guangdong Biaomei Silicone Fluorine New Materials Co., Ltd. Example 1

[0027] 20 parts of wollastonite mineral fiber, mica powder and vermiculite powder were added to a planetary mixer in a mass ratio of 2:1.1:1.5, 0.4 parts of sodium oleate as a dispersant were added, and the mixture was stirred at a speed of 900 r / min for 15 minutes to obtain a mixture; the mixture was pulverized using a jet mill to obtain a pigment filler with a particle size of 10 μm; An organic phosphonate, 10 parts of organosilicon powder, and an organic nitrogen-containing compound, melamine, are dissolved in 30 parts of dichloromethane in a mass ratio of 2:1:1 to obtain a mixed solution; the mixed solution is placed in a reaction kettle, 1 part of benzoyl peroxide is added thereto, and the mixture is heated to 120°C under nitrogen conditions and reacted for 2.5 hours to obtain a polymer; the polymer is cooled to room temperature, and the solvent is removed by rotary evaporation to obtain a composite flame retardant; the organic phosphonate is ethyl diphenylphosphonate; 15 parts of clay were dispersed in 35 parts of deionized water, and ultrasonic treatment was performed to obtain a dispersion; 20 parts of dopamine hydrochloride were dissolved in 40 parts of methanol solution, sodium hydroxide was added thereto in a ratio of 1:1, and the mixture was stirred until the solid was completely dissolved to obtain hydrolyzed dopamine; the pH value of the hydrolyzed dopamine was adjusted to 8, the dispersion was added, 0.4 parts of ferric chloride was added after stirring and mixing, and the reaction was continued at room temperature with stirring for 12 hours to obtain polydopamine-coated clay; the clay was bentonite; 8.4 parts of pigments and fillers and 0.5 parts of dispersant sodium oleate were added to 30 parts of deionized water, and stirred at a speed of 800 r / min for 25 minutes to obtain a slurry; 60 parts of waterborne polyurethane, acrylic resin, plasticizer, 0.8 parts of dispersant sodium oleate and 0.6 parts of defoamer BYK-024 were added to the slurry, heated to 35°C, stirred at a speed of 500 r / min for 10 minutes, and then 5 parts of compound flame retardant were added. After stirring for 40 minutes, 8 parts of polydopamine were added thereto. The coated clay was stirred for 20 minutes, and deionized water was added to adjust the viscosity of -4 cups at 25°C to 75s to obtain a highly elastic fire-retardant coating; the mass ratio of waterborne polyurethane, acrylic resin and plasticizer was 10:5:0.3; the hard segment of the waterborne polyurethane was isophorone diisocyanate; the soft segment was polypropylene glycol; the mass ratio of the hard segment to the soft segment was 1.5:1; the molecular weight of the soft segment was 1500; and the plasticizer was a mixture of dibutyl phthalate and dioctyl adipate in a mass ratio of 1:1.

[0028] Examples 2-14 Referring to the preparation method and parameter conditions of Example 1, the specific differences are shown in Table 1; the three substances in Table 1 are organic phosphonate, organosilicon powder and organic nitrogen-containing compound.

[0029] Table 1 Specific preparation parameters of Examples 2-14

[0030] Comparative Example 1 The preparation method and parameter conditions are similar to those of Example 1, except that only organic phosphonate is used as the flame retardant.

[0031] Comparative Example 2 The preparation method and parameter conditions are similar to those of Example 1, except that only organic silicon micropowder is used as the flame retardant.

[0032] Comparative Example 3 The preparation method and parameter conditions are similar to those of Example 1, except that only organic nitrogen-containing compounds are used as flame retardants.

[0033] Example 15 Flame retardant performance test Refer to GB / T 2406.2-2009 standard to test the coating oxygen index; The vertical combustion grade of the coating was tested according to the UL94 standard: V0: the vertical specimen stopped burning within 10 seconds, and no dripping was allowed; V1: the vertical specimen stopped burning within 30 seconds, and no dripping was allowed; V2: the vertical specimen stopped burning within 30 seconds, and dripping of burning materials was allowed (but the dripping burning materials could not ignite the absorbent cotton); the results are shown in Table 2.

[0034] Table 2 Flame retardant performance test of Examples 1-14 and Comparative Examples 1-3

[0035] As can be seen from Tables 1 and 2, in Examples 1-3, the type of organic phosphonate was changed. Since phenylphosphonate diphenyl ester contains nitrogen in its molecular structure, it produces a synergistic flame retardant effect with phosphorus. Therefore, the flame retardant obtained by using phenylphosphonate diphenyl ester, organosilicon powder, and melamine to prepare a composite flame retardant has the best flame retardant performance. The phosphorus-based flame retardant decomposes to produce phosphoric acid, which promotes carbonization to form a carbon layer; the silicon-based flame retardant forms a silicon dioxide protective film at high temperatures, enhancing the stability of the carbon layer; the nitrogen-based flame retardant decomposes to produce gases such as ammonia, which dilutes the concentration of combustible gases and reacts with the phosphorus-based and silicon-based flame retardants to further promote carbonization. This synergistic effect enables the flame retardant to exert a more excellent flame retardant effect during the combustion process, improving the flame retardant performance of the material. In Examples 2, 4-7, the mass ratio of the organic phosphonate, organosilicon powder, and organic nitrogen-containing compound was changed. When the mass ratio of the three was 3:1:2, the coating with the best flame retardant performance was obtained. In Examples 6, 8-10, as the polymerization reaction temperature increases, the reaction rate accelerates, molecular chain growth, and the degree of crosslinking increases. In Example 9, when the temperature is raised to 160°C, a relatively stable polymer structure is formed, which better exerts its flame retardant effect in both the condensed phase and the gas phase, promoting char formation and releasing flame-retardant gases, effectively inhibiting flame propagation. Further increases in temperature can lead to partial decomposition or structural damage of the polymer, resulting in a decrease in flame retardancy. In Examples 9, 11-12, the polymerization reaction time is too short, and the raw materials do not fully react to form effective flame-retardant structural units, resulting in limited flame retardancy. As the reaction time increases, more raw materials participate in the reaction, the polymer structure gradually improves, and the flame retardancy improves. However, if the reaction time is too long, excessive crosslinking occurs, reducing flame retardancy. In Examples 11, 13-14, the flame retardancy of the resulting coating increases with increasing flame retardant dosage. However, excessive flame retardant dosage can cause agglomeration in the material, resulting in uneven dispersion and affecting the flame retardant effect. In Example 13, when the organic phosphonate was selected as phenylphosphonoamino acid diphenyl ester, the mass ratio of the organic phosphonate, organosilicon powder, and organic nitrogen-containing compound was 3:1:2, the polymer heating temperature was 160°C, and the polymer reaction time was 3.5 hours to prepare the composite flame retardant, and the amount of the flame retardant was 7 parts, the resulting high-elasticity fire-retardant coating had the best flame retardant properties, with an oxygen index of 29 and a vertical combustion rating of V0. In Comparative Examples 1-3, when the flame retardant was only one of the organic phosphonate, organosilicon powder, and organic nitrogen-containing compound, the flame retardant properties of the resulting coatings all decreased.

[0036] Examples 16-24 Referring to the preparation method and parameter conditions of Example 13, the specific differences are shown in Table 3; in Table 3, stirring time 1 is the time for stirring to obtain polydopamine-coated clay, and stirring time 2 is the time for stirring to obtain highly elastic fire retardant coating after adding polydopamine-coated clay.

[0037] Table 3 Specific preparation parameters of Examples 16-24

[0038] Example 25 Flame retardant performance test Refer to GB / T 2406.2-2009 standard to test the coating oxygen index; The vertical combustion grade of the coating was tested according to the UL94 standard: V0: the vertical specimen stopped burning within 10 seconds, and no dripping was allowed; V1: the vertical specimen stopped burning within 30 seconds, and no dripping was allowed; V2: the vertical specimen stopped burning within 30 seconds, and dripping of burning materials was allowed (but the dripping burning materials could not ignite the absorbent cotton); the results are shown in Table 4.

[0039] Table 4 Flame retardant performance test of Examples 13, 16-24

[0040] As can be seen from Tables 3 and 4, in Examples 13, 16-17, the clay type is changed. Since kaolin has high chemical stability and a unique layered structure, its aluminosilicate layer can form a stable carbon layer during combustion, effectively blocking the transfer of heat and oxygen. After being compounded with polydopamine, polydopamine can further enhance the strength and stability of the carbon layer and improve the flame retardant effect. Therefore, when the clay type is kaolin, the flame retardant performance of the prepared material is the best. In Examples 16, 18-19, when the pH value is low, the polymerization reaction rate of dopamine is inhibited. At this time, it is difficult for dopamine molecules to fully polymerize to form an effective polydopamine coating layer, and the coating of the clay surface is incomplete. When applied to flame retardant materials, the flame retardant synergistic effect of polydopamine cannot be effectively exerted; when the pH value is too high, it will lead to excessive polymerization of dopamine, and the structure of the formed polydopamine may change, resulting in agglomeration or excessive cross-linking, which will affect its coating effect on the clay surface and its synergistic effect with the clay. In Examples 18, 20-21, as the stirring time increases, dopamine is gradually and evenly coated on the surface of the clay particles, forming a relatively complete coating layer with a moderate thickness; however, if the stirring time is too long, the already formed polydopamine coating structure will be destroyed, resulting in damage to the integrity of the coating layer. In Examples 20, 22-24, the stirring time is changed to a shorter stirring time, and the polydopamine-coated clay may not be evenly dispersed, forming local agglomeration. When the coating burns, only some areas can exert the flame retardant effect of the polydopamine-coated clay; and excessive stirring may destroy some of the microstructures already formed in the coating, causing the coating layer of the polydopamine-coated clay to be damaged to a certain extent, reducing the synergistic efficiency of the polydopamine and clay. In Example 23, when the clay type is kaolin, the pH value of the desalted dopamine is adjusted to 8.5, the stirring time to obtain the polydopamine-coated clay is 15 hours, and the stirring time to obtain the high-elasticity fire-retardant coating after adding the polydopamine-coated clay is 40 minutes, the highly elastic fire-retardant coating finally prepared has the best flame retardant performance, an oxygen index of 38, and a vertical combustion grade of V0.

[0041] Examples 26-34 Referring to the preparation method and parameter conditions of Example 23, the specific differences are shown in Table 5.

[0042] Example 35 Elasticity Test The rebound resilience test was conducted on the coatings of Examples 23, 26-34 on 200 μm thick films with reference to GB / T 1681 Determination of rebound resilience of vulcanized rubber. The results are shown in Tables 5 and Figure 1 shown.

[0043] Table 5 Elasticity test of Examples 23, 26-34

[0044] From Table 5 and Figure 1 As can be seen in Examples 23, 26-28, by changing the type of polyurethane soft segment, when polyoxypropylene glycol is used as the polyurethane soft segment, the molecular chain has better flexibility, which can enable the polyurethane elastomer to maintain good elasticity at low temperatures and is less prone to brittleness. In Examples 28-31, increasing the soft segment ratio can significantly improve the ductility and softness of the polyurethane, making it more elastic and easier to recover its original shape, thereby improving the polyurethane's resilience and allowing it to return to its original state more quickly after the external pressure is removed. When the ratio of polyurethane hard segment to soft segment is 1.5:2.5, the resulting material has the best resilience. In Examples 30, 32-34, by changing the molecular weight of the polyurethane soft segment, higher molecular weight soft segments generally give the polyurethane better elasticity and flexibility. Long-chain soft segment molecules can more effectively expand and contract when subjected to stress, thereby providing greater elastic deformation capacity. As molecular weight increases, the rebound rate of the resulting coating typically changes from small to large and then back to small, forming an inflection point. This is because the change in molecular weight affects the arrangement and interaction of the polyurethane molecular chains, thereby affecting its elastic properties. In Example 33, when the polyurethane soft segment is polyoxypropylene glycol, the hard segment to soft segment ratio is 1.5:2.5, and the soft segment molecular weight is 2100, the resulting coating exhibits optimal elasticity, with a rebound rate of 56.3%.

[0045] Examples 36-43 Referring to the preparation method and parameter conditions of Example 33, the specific differences are shown in Table 6; the mass ratio of the three in Table 6 is the mass ratio of waterborne polyurethane, acrylic resin and plasticizer; the heating temperature and stirring speed are the reaction temperature and stirring speed after adding waterborne polyurethane, acrylic resin, plasticizer, dispersant and defoaming agent to the slurry.

[0046] Comparative Example 4 Refer to the preparation method and parameter conditions of Example 33, except that the mass ratio of waterborne polyurethane, acrylic resin and plasticizer is 10:20:0.4.

[0047] Example 44 Elasticity Test The coatings prepared in Examples 33, 36-43 and Comparative Example 4 were coated on 200 μm thick films and subjected to resilience tests with reference to GB / T 1681 Determination of the Rebound Resilience of Vulcanized Rubber; the results are shown in Table 6.

[0048] Table 6 Elasticity test of Examples 33, 36-43 and Comparative Example 4

[0049] Table 6 shows that in Examples 33, 36-39, the mass ratio of waterborne polyurethane, acrylic resin, and plasticizer was varied. When the mass ratio approached 10:5:0.3, the high content of waterborne polyurethane and the presence of isophorone diisocyanate as its hard segment resulted in a relatively rigid overall coating structure. When the mass ratio approached 10:10:0.3, the coating became too soft and, under significant external force, could lose its original shape, resulting in excessive deformation and failure to recover. A mass ratio of 10:8:0.4 yielded the most elastic material. In Examples 38, 40-41, as the heating temperature increases, the molecular chains of the waterborne polyurethane become more active, the soft segments and hard segments can be more evenly distributed in the system, and have better interaction with the acrylic resin and the plasticizer. The plasticizer can be better inserted between the molecular chains, reducing the intermolecular forces, making the molecular chains easier to move when subjected to force, and the elasticity of the coating is improved. It can withstand a certain degree of stretching and bending, and can better recover to its original shape after deformation, with good elastic properties; however, too high a temperature will cause excessive movement of the waterborne polyurethane molecular chains, and may even cause degradation or structural damage of some molecular chains, thereby reducing the elasticity of the coating. In Examples 40, 42, and 43, the stirring speed is too slow, resulting in uneven fusion between the waterborne polyurethane, acrylic resin, and plasticizer, which may lead to local enrichment or uneven dispersion of components. When subjected to stress, due to the uneven distribution of components, the elastic response of different regions varies, which can easily lead to excessive local deformation and damage the overall elastic properties, reducing the elasticity of the coating. Stirring too fast will cause more heat to be generated in the system, causing local temperature increases, affecting the stability of components such as the waterborne polyurethane. Excessive stirring speeds may also disrupt the orderly arrangement between molecular chains, reducing the elasticity of the coating. In Example 42, when the mass ratio of waterborne polyurethane, acrylic resin, and plasticizer was 10:8:0.4, the heating temperature was 45°C, and the stirring speed was 550 r / min, the resulting high-elasticity fire-retardant coating had the best elasticity, with a rebound rate of 62.3%. In Comparative Example 4, when the mass ratio of waterborne polyurethane, acrylic resin, and plasticizer was 10:20:0.4, the resulting coating had reduced elasticity, with a rebound rate of 45.2%.

[0050] Examples 45-55 Referring to the preparation method and parameter conditions of Example 42, the specific differences are shown in Table 7.

[0051] Example 56 Elasticity Test The coatings prepared in Examples 42 and 45-53 were coated on 200 μm thick films and subjected to resilience tests according to GB / T 1681 Determination of the resilience of vulcanized rubber. The results are shown in Table 7.

[0052] Table 7 Elasticity test of Examples 42, 45-53

[0053] In Examples 42, 45-46, when the stirring speed of the mixture is too low, the dispersion between the mineral fibers and the powder is not uniform, and agglomeration may occur. When the coating is stretched or bent by external forces, the agglomerated parts cannot deform well in coordination with the coating matrix material, resulting in stress concentration around the agglomerates, making the coating prone to cracking and reducing elasticity. When the stirring speed is too fast, the mineral fibers will break, reducing the fiber aspect ratio. The reduction in the fiber aspect ratio will reduce its reinforcing effect. In Examples 45, 47-48, as the stirring time of the mixture increases, the mineral raw materials can achieve a better mixing state, the fibers and powder can be evenly distributed, the dispersant can also play an effective role, and the prepared pigment filler can be well matched with the other components of the coating, improving the elasticity of the coating. However, if the stirring time is too long, the mineral fibers will be excessively worn and the particle structure of the mica powder and vermiculite powder will be damaged, thereby affecting the elasticity of the coating. In Examples 47, 49-51, the pigment and filler particle size was varied. When the pigment and filler particle size was moderate, they were able to fully contact the coating matrix without excessive agglomeration due to a small particle size. This allowed the coating to recover well after significant elastic deformation, resulting in stable elastic properties. In Examples 50, 52-53, the slurry stirring time was varied. When the slurry stirring time was moderate, the pigment and filler were well dispersed in water, and the dispersant sodium oleate was effectively coated on the pigment and filler surface, allowing them to be evenly distributed in the slurry. After the slurry was mixed with other ingredients, the evenly dispersed pigment and filler could better interact with waterborne polyurethane, acrylic resin, and other components. When the coating was subjected to external forces, the pigment and filler could evenly share the stress. At the same time, the soft segments of the waterborne polyurethane and acrylic resin could better exert their flexibility, improving the coating's elasticity. In Example 52, when the mixture is stirred at a speed of 1100 r / min and the stirring time is 20 min, the pigment filler is obtained, the wollastonite mineral fiber can be evenly dispersed between the mica powder and the vermiculite powder, and the dispersant sodium oleate can better play its role, so that the surface of each raw material particle can be effectively coated, reducing agglomeration, and when the coating is subjected to external force, the mineral fiber can play a role similar to reinforcing ribs, and the mica powder and vermiculite powder can be filled between and around the fibers and deform synergistically, thereby improving the elasticity of the coating, so that the coating can withstand stretching and bending to a certain extent without obvious cracks; and when the particle size of the pigment filler is 20 μm, the prepared pigment filler is used in the coating, and when the slurry stirring time is 30 min, the prepared coating has the best elasticity and a rebound rate of 66.5%.

[0054] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A preparation process for a highly elastic fire retardant coating, characterized by: The preparation process of the highly elastic fire retardant coating is as follows: Adding pigments, fillers and dispersants to deionized water and stirring to obtain a slurry; adding waterborne polyurethane, acrylic resin, plasticizer and the dispersant to the slurry, stirring and adding a compound flame retardant, then adding polydopamine-coated clay and continuing to stir, adding the deionized water to adjust the viscosity, and obtaining the highly elastic fire retardant coating; The pigment filler is prepared from wollastonite mineral fiber, mica powder and vermiculite powder; The compound flame retardant is prepared from organic phosphonate, organic silicon micropowder and organic nitrogen-containing compound.

2. The preparation process of a highly elastic fire retardant coating according to claim 1, characterized in that: The mass ratio of the waterborne polyurethane, the acrylic resin and the plasticizer is 10:5-10:0.3-0.

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3. The preparation process of a highly elastic fire retardant coating according to claim 1, characterized in that: The preparation process of the compound flame retardant is as follows: dissolving the organic phosphonate, the organosilicon powder and the organic nitrogen-containing compound in dichloromethane in a mass ratio of 2-5:1:1-4 to obtain a mixed liquid; placing the mixed liquid in a reaction kettle, adding benzoyl peroxide thereto, heating to 120-180° C. under nitrogen conditions, reacting for 2.5-4.5 hours to obtain a polymer; cooling the polymer to room temperature, and rotary evaporating to obtain the compound flame retardant.

4. The preparation process of a highly elastic fire retardant coating according to claim 3, characterized in that: The organic phosphonate is one of ethyl diphenylphosphonate, diphenyl phenylphosphonate and dimethyl phosphonate; and the organic nitrogen-containing compound is melamine.

5. The preparation process of a highly elastic fire retardant coating according to claim 1, characterized in that: The preparation process of the polydopamine-coated clay is as follows: dispersing clay in deionized water and ultrasonically treating the clay to obtain a dispersion; dissolving dopamine hydrochloride in a methanol solution, adding sodium hydroxide thereto, and stirring to obtain hydrolyzed dopamine; adjusting the pH value of the hydrolyzed dopamine to 8-9, adding the dispersion, stirring and mixing, and then adding ferric chloride, and continuing to stir and react for 12-18 hours to obtain the polydopamine-coated clay.

6. The process for preparing a highly elastic fire retardant coating according to claim 5, characterized in that: The clay is one of bentonite, kaolin and montmorillonite.

7. The process for preparing a highly elastic fire retardant coating according to claim 1, characterized in that: The hard segment of the waterborne polyurethane is isophorone diisocyanate; the soft segment is one of polypropylene glycol, polytetramethylene ether glycol, polyethylene adipate and polyoxypropylene glycol; the mass ratio of the hard segment to the soft segment is 1.5:1-3.

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8. The process for preparing a highly elastic fire retardant coating according to claim 7, wherein: The soft segment molecular weight is 1500-2500.

9. The process for preparing a highly elastic fire retardant coating according to claim 1, characterized in that: The preparation process of the highly elastic fire-retardant coating is as follows: adding the pigment and the dispersant to the deionized water and stirring for 25-35 minutes to obtain the slurry; adding 60 parts of the aqueous polyurethane, the acrylic resin, the plasticizer and 0.8 parts of the dispersant to the slurry, heating to 35-50° C., stirring at a speed of 500-600 r / min, and then adding 5-10 parts of the compound flame retardant; after stirring, adding 8 parts of the polydopamine-coated clay, continuing to stir for 20-50 minutes, and adding the deionized water to adjust the viscosity to obtain the highly elastic fire-retardant coating.

10. The preparation process of a highly elastic fire retardant coating according to claim 1, characterized in that: The preparation process of the pigment and filler is as follows: mixing the wollastonite mineral fiber, the mica powder and the vermiculite powder, adding the dispersant, stirring at a speed of 900-1300 r / min for 15-25 minutes to obtain a mixture; using a jet mill to crush the mixture to obtain the pigment and filler with a particle size of 10-30 μm.

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