An acrylic flame-retardant emulsion and a preparation method thereof

Abstract

This invention discloses an acrylic flame-retardant emulsion and its preparation method, belonging to the technical field of acrylic flame-retardant emulsions. The acrylic flame-retardant emulsion, by weight, comprises the following raw materials: 100 parts water, 35-45 parts hard monomers, 20-25 parts soft monomers, 8-12 parts phosphate ester monomers, 2.8-4.2 parts crosslinking agent, 3-5.4 parts emulsifier, 3-5 parts acrylic functional monomers, 2-3 parts pH adjuster, and 0.6-0.8 parts initiator. The acrylic flame-retardant emulsion uses water as its base component, making it more environmentally friendly than traditional non-aqueous flame-retardant emulsions and coatings. Furthermore, the combined use of soft and hard monomers prevents the glass transition temperature of the acrylic flame-retardant emulsion system from becoming excessively high due to the introduction of hard monomers. This allows the emulsion coating film to resist daily friction while also possessing a certain degree of flexibility. When wood undergoes micro-deformation due to temperature and humidity changes, the emulsion coating film is less prone to cracking, thus maintaining good flame-retardant and fire-resistant properties.

Description

Technical Field

[0001] This invention relates to the field of acrylic flame retardant emulsion technology, and more particularly to an acrylic flame retardant emulsion and its preparation method. Background Technology

[0002] Acrylic flame-retardant emulsions, with their excellent water resistance, adhesion, film-forming properties, weather resistance, gloss and color retention, and mechanical properties, have been widely used as latex paint base materials in textiles, leather, paper, building exteriors, and wood. However, because they are organic substances, they are prone to combustion after film formation, producing dense smoke and large amounts of toxic organic gases. This not only limits their application in scenarios requiring flame retardancy but also poses serious safety hazards and environmental risks. Therefore, flame-retardant modification of acrylic emulsions to improve their flame-retardant properties, expand their application scenarios, and ensure safety is of significant practical importance and necessity. To improve the flame-retardant properties of acrylic flame-retardant emulsions, existing technologies introduce phosphate monomers with flame-retardant properties during the synthesis process. However, these emulsions, after film formation, have poor flexibility, resulting in brittle and cracked films that cannot adapt to the micro-deformations of wood caused by temperature and humidity changes.

[0003] It is evident that existing technologies need improvement and enhancement. Summary of the Invention

[0004] The purpose of this invention is to provide an acrylic flame-retardant emulsion and its preparation method, aiming to solve the problem that existing acrylic flame-retardant emulsions with flame-retardant properties have poor film flexibility after film formation, and the coating film is brittle, hard, and prone to cracking, and cannot adapt to the micro-deformation of wood caused by changes in temperature and humidity.

[0005] The first aspect of this invention provides an acrylic flame-retardant emulsion, the raw materials for which, by weight, are: 100 parts water, 35-45 parts hard monomer, 20-25 parts soft monomer, 8-12 parts phosphate ester monomer, 2.8-4.2 parts crosslinking agent, 3-5.4 parts emulsifier, 3-5 parts acrylic functional monomer, 2-3 parts pH adjuster, and 0.6-0.8 parts initiator.

[0006] Optionally, the hard monomer is methyl methacrylate and n-butyl methacrylate; the ratio of methyl methacrylate and n-butyl methacrylate by weight is (2.5-3):(1-1.5).

[0007] Optionally, the soft monomer is butyl acrylate.

[0008] Optionally, the acrylic functional monomer is a mixture of acrylic acid and methacrylic acid.

[0009] Optionally, the crosslinking agent includes diacetone acrylamide and adipic acid dihydrazide; the ratio of diacetone acrylamide and adipic acid dihydrazide by weight is (2-3):(0.8-1.2).

[0010] Optionally, the emulsifier is a mixture of sodium dodecyl sulfate and dodecylphenol polyoxyethylene ether; the ratio of sodium dodecyl sulfate and dodecylphenol polyoxyethylene ether by weight is (0.6-1):(0.5-0.8).

[0011] Optionally, the initiator is ammonium persulfate; the pH adjuster is ammonia.

[0012] A second aspect of this invention provides a method for preparing an acrylic flame-retardant emulsion, comprising the following steps:

[0013] S001. Add emulsifier, hard monomer, soft monomer, acrylic functional monomer, phosphate monomer and crosslinking agent dropwise to a pre-emulsification kettle containing water, and stir to mix evenly to form a stable pre-emulsion.

[0014] S002. Heat the inside of the water-filled reactor to 80-85°C, then add the initiator and 10% by weight of pre-emulsion into the reactor. After observing blue light in the reactor, keep it warm.

[0015] S003. After the heat preservation in step S002 is completed, add the initiator and the remaining pre-emulsion into the reactor. After the addition is completed, raise the temperature inside the reactor to 88-90°C and keep it warm.

[0016] S004. After the heat preservation in step S003 is completed, cool the inside of the reactor to below 40°C, and then add pH adjuster to the reactor.

[0017] S005. After the pH value of the material in the reactor is adjusted to 7-8, a crosslinking agent is added to the reactor. After stirring and mixing evenly, the material in the reactor is filtered to obtain the acrylic flame retardant emulsion.

[0018] Furthermore, in step S001, the stirring speed is 300-400 r / min, and the stirring time is 30 min.

[0019] Furthermore, in step S001, the crosslinking agent is diacetone acrylamide; in step S005, the crosslinking agent is adipic acid dihydrazide.

[0020] The beneficial effects of this invention are:

[0021] The first aspect of this invention provides an acrylic flame-retardant emulsion, which uses water as a base component and is more environmentally friendly than traditional non-aqueous flame-retardant emulsions and coatings. At the same time, by using a combination of soft and hard monomers, the glass transition temperature of the acrylic flame-retardant emulsion system is not too high due to the introduction of hard monomers. This allows the emulsion coating film to resist daily friction while also having a certain degree of flexibility. When the wood undergoes micro-deformation due to changes in temperature and humidity, the emulsion coating film is not prone to cracking, thereby maintaining good flame-retardant and fire-resistant performance.

[0022] The second aspect of this invention provides a method for preparing an acrylic flame-retardant emulsion. By employing a semi-continuous pre-emulsification method to control the dispersion particle size of monomers in the pre-emulsion, it is possible to ensure that the latex particles are of uniform size after polymerization. This allows the latex particles to be tightly packed when the emulsion forms a film, thereby reducing the porosity of the coating film. As a result, the acrylic flame-retardant emulsion provided by this invention has excellent water resistance and high transparency, and does not obscure the wood grain. Attached Figure Description

[0023] Figure 1 This is a flowchart of the preparation method of the acrylic flame-retardant emulsion provided by the present invention.

[0024] Figure 2 This is a comparison chart of Example 1 and Comparative Example 1 after a 1-day water resistance test.

[0025] Figure 3 This is a comparison chart of Example 1 and Comparative Example 1 after the wet heat boiling water test. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The first aspect of this invention provides an acrylic flame-retardant emulsion, the raw materials for which, by weight, are: 100 parts water, 35-45 parts hard monomer, 20-25 parts soft monomer, 8-12 parts phosphate ester monomer, 2.8-4.2 parts crosslinking agent, 3-5.4 parts emulsifier, 3-5 parts acrylic functional monomer, 2-3 parts pH adjuster, and 0.6-0.8 parts initiator.

[0028] In the above composition, the phosphate monomer can be 2-hydroxyethyl methacrylate phosphate. During the synthesis of acrylic flame-retardant emulsions, it can undergo copolymerization with propylene monomers instead of physical mixing, thereby anchoring phosphorus elements in the polymer molecular chain. Therefore, during combustion, it can promote the carbonization of the film-forming material, thereby forming a dense carbon layer that blocks oxygen and heat transfer, giving the acrylic flame-retardant emulsion flame-retardant properties. The hard monomer has a high glass transition temperature, which can impart hardness and good wear resistance to the coating film. When the acrylic flame-retardant emulsion is applied to wood and other fields, the coating film formed by the emulsion can resist daily friction, thus protecting the wood. The soft monomer has a lower glass transition temperature than the hard monomer. When it is used in combination with the hard monomer, it can prevent the glass transition temperature of the acrylic flame-retardant emulsion system from becoming too high due to the introduction of the hard monomer. This allows the emulsion coating film to resist daily friction while also having a certain degree of flexibility. When the wood undergoes micro-deformation due to temperature and humidity changes, the emulsion coating film is not prone to cracking, thus maintaining good flame-retardant and fire-resistant properties.

[0029] In the above composition, the crosslinking agent can improve the degree of crosslinking of the polymer, making the coating film dense after the emulsion forms, which is beneficial to improving the water resistance of the coating film. The acrylic functional monomer can introduce carboxyl groups into the acrylic flame retardant emulsion, which can form hydrogen bonds with the hydroxyl groups on the wood surface, thereby improving the adhesion of the acrylic flame retardant emulsion coating film to the wood.

[0030] In an optional embodiment, the hard monomer is methyl methacrylate and n-butyl methacrylate; the weight ratio of methyl methacrylate and n-butyl methacrylate is (2.5-3):(1-1.5). When methyl methacrylate and n-butyl methacrylate are compounded as hard monomers in a weight ratio of (2.5-3):(1-1.5), the high glass transition temperature of methyl methacrylate can be used to impart sufficient hardness and excellent wear resistance to the acrylic flame retardant emulsion film, ensuring that the coating film can withstand daily friction and effectively protect substrates such as wood. At the same time, the introduction of an appropriate amount of n-butyl methacrylate can balance the high rigidity brought by methyl methacrylate, preventing the coating film from becoming brittle due to excessive hardness. In addition, the use of soft monomers further optimizes the glass transition temperature of the emulsion system, so that the coating film retains good flexibility while having protective strength, which can adapt to the micro-deformation of wood caused by temperature and humidity changes, reduce the risk of cracking, and thus ensure the long-term stable flame retardant and fireproof performance of the coating film.

[0031] In an optional embodiment, the soft monomer is butyl acrylate. Butyl acrylate has a glass transition temperature of approximately -56°C. Its introduction into an acrylic flame-retardant emulsion system can maintain the overall glass transition temperature of the emulsion within the range of 20–30°C, ensuring that the emulsion coating is not prone to brittleness at low temperatures and can adapt to the micro-deformation of wood (e.g., expansion or contraction due to changes in wood moisture content).

[0032] In an optional embodiment, the acrylic functional monomer is a mixture of acrylic acid and methacrylic acid. Acrylic acid and methacrylic acid provide carboxyl groups, which form hydrogen bonds with the hydroxyl groups on the surface of substrates such as wood. Simultaneously, the carboxyl groups enhance the interfacial bonding between the emulsion particles and the substrate, significantly improving the adhesion of the emulsion film and preventing coating peeling due to insufficient adhesion. Furthermore, as polar groups, carboxyl groups can enhance the charge density on the surface of the emulsion particles. Combined with the use of emulsifiers, this further optimizes the dispersion stability of the emulsion and reduces the risk of emulsion stratification and flocculation during storage.

[0033] In an optional embodiment, the crosslinking agent includes diacetone acrylamide and adipate dihydrazide. When diacetone acrylamide is used as a crosslinking agent, it can copolymerize into the polymer molecular chain. During the film-forming stage of the emulsion, the ketone groups on diacetone acrylamide can undergo a condensation reaction with the hydrazine groups on adipate dihydrazide to form a three-dimensional crosslinking network. This three-dimensional crosslinking network can significantly reduce the molecular fluidity of the coating film and reduce the permeation channels of water molecules, thereby improving the water resistance of the acrylic flame-retardant emulsion coating film.

[0034] Preferably, the weight ratio of diacetone acrylamide to adipate dihydrazide is (2-3):(0.8-1.2). When the weight ratio of diacetone acrylamide to adipate dihydrazide is (2-3):(0.8-1.2), the decrease in water resistance of the coating film due to excessive adipate dihydrazide can be avoided. At the same time, the insufficient crosslinking density during the reaction between diacetone acrylamide and adipate dihydrazide due to excessive diacetone acrylamide can also be avoided. Therefore, this ratio can precisely control the degree of crosslinking, so that the density, water resistance and mechanical strength of the emulsion film can be improved through appropriate crosslinking, avoiding the problems of poor adhesion and easy wear of the coating film due to insufficient crosslinking. At the same time, the coating film will not become brittle and lose its flexibility due to excessive crosslinking, ensuring that the coating film can adapt to the micro-deformation of wood caused by changes in temperature and humidity.

[0035] In an optional embodiment, the emulsifier is a mixture of sodium dodecyl sulfate and dodecylphenol polyoxyethylene ether; wherein sodium dodecyl sulfate is an anionic emulsifier, and dodecylphenol polyoxyethylene ether is a nonionic emulsifier. The strong surface activity of the anionic emulsifier rapidly reduces the oil-water interfacial tension, promoting the dispersion of acrylic monomers in the aqueous phase to form a pre-emulsion with uniform particle size; while the nonionic emulsifier forms a three-dimensional protective barrier on the surface of the emulsion particles, reducing the risk of particle aggregation.

[0036] This invention discovers that when the emulsifier is a compound of sodium dodecyl sulfate and dodecylphenol polyoxyethylene ether,

[0037] The optimal weight ratio of sodium lauryl sulfate to dodecylphenol polyoxyethylene ether is (0.6–1):(0.5–0.8). Increasing the amount of sodium lauryl sulfate beyond this ratio leads to a decrease in the water resistance of the emulsion coating, while increasing the amount of dodecylphenol polyoxyethylene ether beyond this ratio results in an increase in gelation during emulsion synthesis, affecting the quality of the emulsion.

[0038] In an optional embodiment, the initiator is ammonium persulfate; the pH adjuster can be ammonia water with a mass concentration of 25%. When ammonia water is used as a pH adjuster, it can neutralize the carboxyl groups in the acrylic functional monomers and produce carboxylates, which can further enhance the adsorption of the coating film to wood.

[0039] A second aspect of this invention provides a method for preparing an acrylic flame-retardant emulsion, comprising the following steps:

[0040] S001. Add emulsifier, hard monomer, soft monomer, acrylic functional monomer, phosphate monomer and crosslinking agent dropwise to a pre-emulsification kettle containing 70 parts of water, and stir to mix evenly to form a stable pre-emulsion.

[0041] Before the polymerization reaction, this step involves mixing the monomers with the emulsifier and water by stirring. This ensures that the monomers are evenly dispersed in the pre-emulsion, preventing uneven polymerization caused by excessively high local monomer concentrations during the polymerization reaction.

[0042] S002. Heat the inside of the reactor containing 25 parts of water to 80-85°C, then add 50% by weight of initiator and 10% by weight of pre-emulsion to the reactor. After observing blue light in the reactor, keep it warm for 10 minutes.

[0043] In this step, the initiator is dissolved in 1 part water before being added to the reactor. By adding a portion of the pre-emulsion and the initiator to the reactor first, seed polymerization can be initiated at a set temperature, thereby forming latex nuclei with uniform particle size (marked by the blue light phenomenon), providing stable growth centers for subsequent polymerization.

[0044] S003. After the heat preservation in step S002 is completed, add the remaining initiator and the remaining pre-emulsion into the reactor within 2-3 hours. After the addition is completed, raise the temperature inside the reactor to 88-90°C and keep it at that temperature for 1 hour to ensure complete polymerization of the monomer.

[0045] In this step, the initiator is also dissolved in 1 part water before being added to the reaction vessel. By controlling the dripping rate of the initiator and the pre-emulsion, local overheating can be avoided, which could lead to emulsion demulsification or molecular weight broadening. This allows the molecular weight of the emulsion to be controlled between 50,000 and 100,000, thereby ensuring the mechanical properties of the coating film.

[0046] S004. After the heat preservation in step S003 is completed, allow the temperature inside the reactor to drop below 40°C, and then add pH adjuster to the reactor.

[0047] S005. After the pH value of the material in the reactor is adjusted to 7-8, add the crosslinking agent to the reactor, stir and mix evenly (30 min), and then filter the material in the reactor (using a 100-mesh filter) to obtain the acrylic flame retardant emulsion.

[0048] In this step, the crosslinking agent is dissolved in 3 parts of water beforehand, which can react with the crosslinking agent introduced in step S001. Moreover, the reaction temperature is below 40°C, which can avoid the embrittlement of the coating film caused by rapid crosslinking at high temperature.

[0049] This invention uses a semi-continuous pre-emulsification method to control the dispersion particle size of monomers in the pre-emulsion, thereby ensuring that the latex particles are of uniform size after polymerization. This allows the latex particles to be tightly packed when the emulsion forms a film, thereby reducing the porosity of the coating film. As a result, the acrylic flame-retardant emulsion provided by this invention has excellent water resistance and high transparency, and does not obscure the wood grain.

[0050] Furthermore, in step S001, the stirring speed is 300–400 r / min, and the stirring time is 30 min. This stirring speed range ensures thorough mixing of the raw materials such as water, monomers, and emulsifiers in the pre-emulsification vessel. It avoids uneven oil phase dispersion and the formation of coarse, aggregated particles due to excessively low speeds, while also preventing excessive shearing and damage to the emulsion system due to excessively high speeds. The 30 min stirring time ensures complete dispersion of all components, forming a stable pre-emulsion with uniform particle size, laying the foundation for uniformity in the subsequent polymerization reaction.

[0051] Furthermore, in step S001, the crosslinking agent is diacetone acrylamide; in step S005, the crosslinking agent is adipate dihydrazide. By fully copolymerizing diacetone acrylamide with acrylic monomers during the pre-emulsification stage, the ketone groups can be stably bonded to the polymer molecular chain, reserving sufficient active sites for subsequent crosslinking reactions. Adipate dihydrazide, added after cooling and pH adjustment, enables its hydrazine groups to undergo a highly efficient crosslinking reaction with the ketone groups on the polymer chain, thereby improving the water resistance of the coating film formed by the acrylic flame-retardant emulsion.

[0052] The above examples and comparative examples further illustrate the present invention.

[0053] Example 1

[0054] This embodiment provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 25 parts methyl methacrylate, 10 parts n-butyl methacrylate, 20 parts butyl acrylate, 8 parts 2-hydroxyethyl methacrylate phosphate, 2 parts diacetone acrylamide, 0.8 parts adipate dihydrazide, 1 part acrylic acid, 2 parts methacrylic acid, 2 parts ammonia, 0.6 parts ammonium persulfate, 1.5 parts sodium dodecyl sulfate, and 1.5 parts dodecylphenol polyoxyethylene ether.

[0055] This embodiment also provides a method for preparing an acrylic flame-retardant emulsion, comprising the following steps:

[0056] S001. Add emulsifier, hard monomer, soft monomer, acrylic functional monomer, phosphate monomer, and diacetone acrylamide dropwise to a pre-emulsification kettle containing 70 parts of water, and stir at 400 r / min for 30 min to form a stable pre-emulsion.

[0057] S002. Heat the inside of the reactor containing 25 parts of water to 80°C, then add 50% by weight of initiator (the initiator is dissolved in 1 part of water beforehand) and 10% by weight of pre-emulsion to the reactor. After observing blue light in the reactor, keep it warm for 10 minutes.

[0058] S003. After the heat preservation in step S002 is completed, add the remaining initiator (the initiator is dissolved in 1 part of water beforehand) and the remaining pre-emulsion into the reactor within 3 hours. After the addition is completed, raise the temperature inside the reactor to 88°C and keep it at that temperature for 1 hour to ensure that the monomer is completely polymerized.

[0059] S004. After the heat preservation in step S003 is completed, cool the inside of the reactor to 35°C, and then add pH adjuster to the reactor.

[0060] S005. After the pH value of the material in the reactor is adjusted to 7-8, add adipic acid dihydrazide (dissolve adipic acid dihydrazide in 3 parts water beforehand), stir and mix evenly (30 min), then filter the material in the reactor (using a 100-mesh filter) to obtain the acrylic flame retardant emulsion.

[0061] Example 2

[0062] This embodiment provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 28 parts methyl methacrylate, 12 parts n-butyl methacrylate, 22 parts butyl acrylate, 10 parts 2-hydroxyethyl methacrylate phosphate, 2.5 parts diacetone acrylamide, 1 part adipate dihydrazide, 2 parts acrylic acid, 2 parts methacrylic acid, 2 parts ammonia, 0.8 parts ammonium persulfate, 2.1 parts sodium dodecyl sulfate, and 1.8 parts dodecylphenol polyoxyethylene ether.

[0063] This embodiment also provides a method for preparing an acrylic flame-retardant emulsion, which is the same as the method provided in Example 1.

[0064] Example 3

[0065] This embodiment provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 30 parts methyl methacrylate, 15 parts n-butyl methacrylate, 25 parts butyl acrylate, 12 parts 2-hydroxyethyl methacrylate phosphate, 3 parts diacetone acrylamide, 1.2 parts adipate dihydrazide, 2 parts acrylic acid, 3 parts methacrylic acid, 3 parts ammonia, 0.6 parts ammonium persulfate, 3 parts sodium dodecyl sulfate, and 2.4 parts dodecylphenol polyoxyethylene ether.

[0066] This embodiment also provides a method for preparing an acrylic flame-retardant emulsion, which is the same as the method provided in Example 1.

[0067] Comparative Example 1

[0068] This comparative example provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 25 parts methyl methacrylate, 10 parts n-butyl methacrylate, 8 parts 2-hydroxyethyl methacrylate phosphate, 2 parts diacetone acrylamide, 0.8 parts adipate dihydrazide, 1 part acrylic acid, 2 parts methacrylic acid, 2 parts ammonia, 0.6 parts ammonium persulfate, 1.5 parts sodium dodecyl sulfate, and 1.5 parts dodecylphenol polyoxyethylene ether.

[0069] This comparative example also provides a method for preparing an acrylic flame-retardant emulsion, which is the same as the method provided in Example 1, but without the addition of butyl acrylate.

[0070] Comparative Example 2

[0071] This comparative example provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 30 parts methyl methacrylate, 5 parts n-butyl methacrylate, 20 parts butyl acrylate, 8 parts 2-hydroxyethyl methacrylate phosphate, 2 parts diacetone acrylamide, 0.8 parts adipate dihydrazide, 1 part acrylic acid, 2 parts methacrylic acid, 2 parts ammonia, 0.6 parts ammonium persulfate, 1.5 parts sodium dodecyl sulfate, and 1.5 parts dodecylphenol polyoxyethylene ether.

[0072] This comparative example also provides a method for preparing an acrylic flame-retardant emulsion, which is the same as the method provided in Example 1.

[0073] Comparative Example 3

[0074] This embodiment provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 20 parts methyl methacrylate, 15 parts n-butyl methacrylate, 20 parts butyl acrylate, 8 parts 2-hydroxyethyl methacrylate phosphate, 2 parts diacetone acrylamide, 0.8 parts adipate dihydrazide, 1 part acrylic acid, 2 parts methacrylic acid, 2 parts ammonia, 0.6 parts ammonium persulfate, 1.5 parts sodium dodecyl sulfate, and 1.5 parts dodecylphenol polyoxyethylene ether.

[0075] This comparative example also provides a method for preparing an acrylic flame-retardant emulsion, which is the same as the method provided in Example 1.

[0076] Comparative Example 4

[0077] This embodiment provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 25 parts methyl methacrylate, 10 parts n-butyl methacrylate, 20 parts butyl acrylate, 8 parts 2-hydroxyethyl methacrylate phosphate, 2.2 parts diacetone acrylamide, 0.6 parts adipate dihydrazide, 1 part acrylic acid, 2 parts methacrylic acid, 2 parts ammonia, 0.6 parts ammonium persulfate, 1.5 parts sodium dodecyl sulfate, and 1.5 parts dodecylphenol polyoxyethylene ether.

[0078] This comparative example also provides a method for preparing an acrylic flame-retardant emulsion, which is the same as the method provided in Example 1.

[0079] Comparative Example 5

[0080] This embodiment provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 25 parts methyl methacrylate, 10 parts n-butyl methacrylate, 20 parts butyl acrylate, 8 parts 2-hydroxyethyl methacrylate phosphate, 1.3 parts diacetone acrylamide, 1.5 parts adipic acid dihydrazide, 1 part acrylic acid, 2 parts methacrylic acid, 2 parts ammonia, 0.6 parts ammonium persulfate, 1.5 parts sodium dodecyl sulfate, and 1.5 parts dodecylphenol polyoxyethylene ether.

[0081] This comparative example also provides a method for preparing an acrylic flame-retardant emulsion, which is the same as the method provided in Example 1.

[0082] Comparative Example 6

[0083] This embodiment provides an acrylic flame-retardant emulsion, the raw materials of which, by weight fraction, include: 100 parts water, 25 parts methyl methacrylate, 10 parts n-butyl methacrylate, 20 parts butyl acrylate, 8 parts 2-hydroxyethyl methacrylate phosphate, 2 parts diacetone acrylamide, 0.8 parts adipate dihydrazide, 1 part acrylic acid, 2 parts methacrylic acid, 2 parts ammonia, 0.6 parts ammonium persulfate, 2.2 parts sodium dodecyl sulfate, and 0.8 parts dodecylphenol polyoxyethylene ether.

[0084] This comparative example also provides a method for preparing an acrylic flame-retardant emulsion, which is the same as the method provided in Example 1.

[0085] The emulsions provided in the above examples and comparative examples were formulated into primers according to the following formulas. The primers were then applied to poplar wood samples or other test boards, with the dry film thickness controlled at 30–40 μm, and then tested. The test items included: flame retardancy test, coating water resistance test, pendulum hardness test, and bending performance test.

[0086] The primer formulation by weight is as follows: 80 parts acrylic flame retardant emulsion, 0.2 parts defoamer (BYK-024), 2.5 parts dipropylene glycol methyl ether, 2.5 parts dipropylene glycol butyl ether, 0.3 parts wetting agent (104E), 0.4 parts high shear thickener (RM-2020), 0.3 parts medium shear thickener (80%PUR48), 0.2 parts low shear thickener (80%PUR64), and 13.6 parts water.

[0087] The flame retardancy test was conducted according to the standard GB8624-2012 "Classification of Burning Performance of Building Materials and Products". The water resistance test was divided into two parts: resistance to humid heat boiling water / 30min and water resistance / 1d, conducted according to the standard GB1733-1993 "Determination of Water Resistance of Paint Films". The water resistance performance of the coating was graded, with grade 5 being the best and grade 1 the worst. The pendulum hardness test was conducted according to the standard GBT1730-2023 "Damping Test of Pendulum for Paints and Varnishes". The bending performance test was conducted according to the standard HG-T 4847-2015 "Waterborne Alkyd Resin Coatings".

[0088] The test results are shown in Tables 1 and 2 below.

[0089] Table 1:

[0090]

[0091] Table 2:

[0092]

[0093] Comparing Comparative Example 1 with Example 1, it was found that the flexural performance test of the sample using the acrylic flame-retardant emulsion provided in Comparative Example 1 failed to meet the standard requirements, and the water resistance of the coating film deteriorated (see Comparative Example 1). Figure 2 , Figure 3 This is because the acrylic flame retardant emulsion provided in Comparative Example 1 did not use soft monomers, resulting in poor coating flexibility and high hardness.

[0094] Comparing Comparative Example 2 with Example 1, it was found that the bending performance test of the sample using the acrylic flame retardant emulsion provided by Comparative Example 2 failed to meet the standard requirements, and the water resistance of the coating film deteriorated. This is because the proportion of methyl methacrylate used in the acrylic flame retardant emulsion provided by Comparative Example 2 is too high, and the glass transition temperature of methyl methacrylate is significantly higher than that of n-butyl methacrylate, resulting in a higher overall glass transition temperature of the emulsion, poor coating film flexibility, and high hardness.

[0095] Comparing Comparative Example 3 with Example 1, it was found that the coating hardness of Comparative Example 3 was lower. This was because the amount of n-butyl methacrylate used in the acrylic flame retardant emulsion provided by Comparative Example 3 was higher, and the glass transition temperature of n-butyl methacrylate was lower than that of methyl methacrylate, resulting in a lower overall glass transition temperature of the emulsion.

[0096] Comparing Comparative Example 4 with Example 1, it was found that the water resistance of the sample using the acrylic flame retardant emulsion provided by Comparative Example 4 was worse, and the hardness of the coating film decreased. This was because the amount of crosslinking agent diacetone acrylamide in the emulsion provided by Comparative Example 4 was too high, resulting in insufficient crosslinking density.

[0097] Comparing Comparative Example 5 with Example 1, it was found that the water resistance of the sample using the acrylic flame retardant emulsion provided by Comparative Example 5 was worse. This is because the emulsion provided by Comparative Example 5 contained a higher amount of adipic acid dihydrazide, some of which remained in the coating film in a free state.

[0098] Comparing Comparative Example 6 with Example 1, it was found that the water resistance of the sample using the acrylic flame retardant emulsion provided by Comparative Example 6 was worse. This was because the amount of anionic emulsifier (sodium dodecyl sulfate) used in Comparative Example 6 was increased, and some of it remained in the coating in a free state, which was prone to interacting with moisture in the environment.

[0099] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An acrylic flame-retardant emulsion, characterized in that, The raw materials for its preparation, by weight, include: 100 parts water, 35-45 parts hard monomer, 20-25 parts soft monomer, 8-12 parts phosphate ester monomer, 2.8-4.2 parts crosslinking agent, 3-5.4 parts emulsifier, 3-5 parts acrylic functional monomer, 2-3 parts pH adjuster, and 0.6-0.8 parts initiator; the hard monomer is methyl methacrylate and n-butyl methacrylate; the weight ratio of methyl methacrylate and n-butyl methacrylate is (2). 5-3): (1-1.5); the soft monomer is butyl acrylate; the crosslinking agent includes diacetone acrylamide and adipate dihydrazide; the weight ratio of diacetone acrylamide and adipate dihydrazide is (2-3):(0.8-1.2); the emulsifier is a mixture of sodium dodecyl sulfate and dodecylphenol polyoxyethylene ether; the weight ratio of sodium dodecyl sulfate and dodecylphenol polyoxyethylene ether is (0.6-1):(0.5-0.8); The preparation method of the acrylic flame-retardant emulsion includes the following steps: S001. Add emulsifier, hard monomer, soft monomer, acrylic functional monomer, phosphate ester monomer and 2 to 3 parts of crosslinking agent dropwise to a pre-emulsion kettle containing water, stir and mix evenly to form a stable pre-emulsion. S002. Heat the inside of the water-filled reactor to 80-85°C, then add the initiator and 10% by weight of pre-emulsion into the reactor. After observing blue light in the reactor, keep it warm. S003. After the heat preservation in step S002 is completed, add the initiator and the remaining pre-emulsion into the reactor. After the addition is completed, raise the temperature inside the reactor to 88-90°C and keep it warm. S004. After the heat preservation in step S003 is completed, cool the inside of the reactor to below 40°C, and then add pH adjuster to the reactor. S005. After the pH value of the material in the reactor is adjusted to 7-8, add 0.8-1.2 parts of crosslinking agent to the reactor, stir and mix evenly, and then filter the material in the reactor to obtain the acrylic flame retardant emulsion. In step S001, the crosslinking agent is diacetone acrylamide; in step S005, the crosslinking agent is adipic acid dihydrazide.

2. The acrylic flame-retardant emulsion according to claim 1, characterized in that, The acrylic functional monomer is a mixture of acrylic acid and methacrylic acid.

3. The acrylic flame-retardant emulsion according to claim 1, characterized in that, The initiator is ammonium persulfate; the pH adjuster is ammonia.

4. The acrylic flame-retardant emulsion according to claim 1, characterized in that, In step S001, the stirring speed is 300-400 r / min and the stirring time is 30 min.

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