Preparation method of water-based high-permeability reinforced acrylic emulsion

Abstract

The application relates to a preparation method of a water-based high-permeability reinforced acrylic emulsion, which comprises the following steps: uniformly mixing emulsifier I, water, a soft monomer, a hard monomer, a crosslinking monomer and a functional monomer to obtain a monomer pre-emulsion for standby; uniformly mixing emulsifier II and water to obtain a reactor bottom liquid, then the temperature is increased to 84-85 DEG C, 2-4% of the monomer pre-emulsion is added, initiator I is added, and seed emulsion is prepared after reaction for 10-12 minutes; after the seed emulsion is prepared, the remaining monomer pre-emulsion and initiator II are simultaneously added into the reactor for reaction, when the monomer pre-emulsion is 25-35%, the functional monomer is added into the monomer pre-emulsion, the adding is continuously carried out until the reaction is completed, and the reaction is carried out after heat preservation; after the heat preservation is completed, post-treatment is carried out on the obtained emulsion, and a finished product is obtained. The latex prepared by the method has good wetting, permeation and wrapping properties, and can be used for the wetting, permeation, wrapping and reinforcing of a base material.

Description

Technical Field

[0001] This invention relates to the field of acrylic emulsion technology, and in particular to a method for preparing a water-based, high-penetration, reinforced acrylic emulsion. Background Technology

[0002] Compared to solvent-based oil-based emulsions, water-based emulsions offer superior environmental friendliness in manufacturing and application. Using water as both a solvent and diluent, water-based emulsions are not only cost-effective but also non-toxic and odorless, posing no risk of explosion and harming human health. Water-based acrylic emulsions, using acrylic monomers as the main raw material, offer advantages such as good water resistance and weather resistance, making them a functional product marketed by water-based paint manufacturers.

[0003] In architectural coatings, such as those applied to exterior or interior walls, most are cement-based materials. Cement is prone to efflorescence, leading to poor adhesion between the coating and the substrate, resulting in easy peeling and cracking. This significantly reduces the material's waterproof, protective, and adhesion properties. Emulsions, in particular, have a decisive impact on coating performance. Therefore, improving the penetration and encapsulation of water-based emulsions into the substrate to enhance its protective performance is a key issue that the industry needs to focus on and resolve. Existing technologies mainly meet adhesion and reinforcement requirements by increasing the hardness of the emulsion film and increasing the application amount, without addressing improvements to the emulsion product itself. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a water-based, high-penetration, reinforcing acrylic emulsion in order to solve the above-mentioned problems. By improving the particle size of the emulsion and enhancing its penetration and encapsulation of the substrate, the method effectively reinforces the interior of the substrate, thereby greatly improving the protection of the substrate and the wall under the same construction conditions.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing an aqueous, highly permeable, reinforced acrylic emulsion includes the following steps:

[0007] (1) Mix emulsifier I, water, soft monomer, hard monomer, crosslinking monomer and functional monomer evenly to prepare monomer pre-emulsion for later use;

[0008] (2) Mix emulsifier II and water evenly to prepare the bottom liquid of the reaction vessel, then heat it to 84-85℃, then add 2-4% of monomer pre-emulsion, then add initiator I, react for 10-12 minutes to prepare seed emulsion;

[0009] (3) After preparing the seed emulsion, the remaining monomer pre-emulsion and initiator II are simultaneously added dropwise to the reaction vessel for reaction. When the monomer pre-emulsion is 25-35% remaining, the added functional monomer is added to the monomer pre-emulsion and the addition continues until the reaction is completed. After the reaction is completed, the vessel is kept warm.

[0010] (4) After the heat preservation is completed, the resulting emulsion is post-processed to obtain the finished product.

[0011] As a preferred technical solution of the present invention, the monomer pre-emulsion in step (1) is composed of the following raw material components in parts by weight: emulsifier 1-1.5 parts, water 15-25 parts, soft monomer 5-7 parts, hard monomer 13-17 parts, crosslinking monomer 4-6 parts, and functional monomer 3-4 parts.

[0012] More preferably, the monomer pre-emulsion in step (1) is composed of the following raw material components in parts by weight: 1.3 parts emulsifier, 18-21 parts water, 6 parts soft monomer, 15 parts hard monomer, 5 parts crosslinking monomer, and 3.5 parts functional monomer.

[0013] As a preferred embodiment of the present invention, the bottom liquid of the reaction vessel in step (2) is composed of the following raw material components in parts by weight: 3.5-4 parts of emulsifier II and 14-20 parts of water. More preferably, the monomer pre-emulsion in step (1) is composed of the following raw material components in parts by weight: 3.7 parts of emulsifier II and 15-18 parts of water.

[0014] As a preferred embodiment of the present invention, both emulsifier one and emulsifier two are mixtures composed of anionic surfactants and nonionic surfactants.

[0015] Preferably, the mass ratio of emulsifier one to emulsifier two is 1:2.5-3, wherein the mass ratio of anionic surfactant to nonionic surfactant in emulsifier one is 2-3:1; and the mass ratio of anionic surfactant to nonionic surfactant in emulsifier two is 1-2:1.

[0016] Preferably, the anionic emulsifier is selected from alkylbenzene sulfonates, for example, linear alkylbenzene sulfonate sodium salt, and as a specific embodiment, Solvay DS-4AP.

[0017] The nonionic surfactant is a polyether emulsifier with ethylene oxide and propylene oxide blocks. For example, as a specific implementation method, Youchuang M-64 can be used.

[0018] As a preferred technical solution of the present invention, the post-added functional monomer in step (3) is tert-butyl acrylate, and the weight ratio of the post-added functional monomer to the total amount of pre-emulsified monomer is 1:5-6.

[0019] As a preferred technical solution of the present invention, the post-processing in step (4) specifically involves adding initiator 3 to eliminate residual monomers, keeping the temperature at 85-88℃ for 60-90 minutes, then cooling the temperature to below 40℃, adjusting the pH to 7-9, stirring for more than 15 minutes, and then filtering out the material.

[0020] As a preferred technical solution of the present invention, the total reaction time in steps (2) and (3) is controlled at 3.5-4 hours, and after the addition is completed, the reaction is kept at 86-88℃ for 1.5-2.0 hours.

[0021] As a preferred embodiment of the present invention, the soft monomer is an acrylate soft monomer selected from at least one of isooctyl acrylate, n-butyl acrylate, and ethyl acrylate, preferably isooctyl acrylate.

[0022] As a preferred embodiment of the present invention, the hard monomer includes styrene monomers (styrene, 3-chlorostyrene, 4-chlorostyrene, p-chlorostyrene, etc.), methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and preferably styrene.

[0023] As a preferred embodiment of the present invention, the crosslinking monomer includes one or more of hydroxyethyl methacrylate, hydroxybutyl methacrylate, and acetylacetoxyethyl methacrylate, and preferably, hydroxyethyl methacrylate can be used.

[0024] As a preferred technical solution of the present invention, the functional monomer includes one or more of acrylic acid, methacrylic acid, glycidyl acrylate, and glycidyl methacrylate. Preferably, for example, a mixture of acrylic acid and glycidyl methacrylate in a mass ratio of 3:3-5 can be used.

[0025] As a preferred technical solution of the present invention, the initiator used is ammonium persulfate, potassium persulfate, or sodium persulfate. The initiator is added in the form of an aqueous solution, and the mass of initiator one, initiator two, and initiator three accounts for 40-50%, 45-55%, and 5-15% of the total initiator dosage, respectively.

[0026] The acrylic emulsion provided by this invention exhibits excellent penetration and encapsulation properties on cement and other substrates, as well as superior water resistance, alkali resistance, anti-efflorescence properties, and reinforcing properties, resulting in good adhesion strength to the substrate. The emulsion primarily uses styrene as a hard monomer, compounded with soft monomers, crosslinking monomers containing hydroxyl or methacrylate groups, and functional monomers containing carboxyl, methacrylate, and glycidyl ester groups. The styrene monomer helps improve the hardness and strength of the emulsion, while the hydroxyl, methacrylate, and carboxyl groups undergo coupling reactions to form strong covalent bonds, increasing reactivity and crosslinking degree.

[0027] This invention employs a seed emulsion polymerization method. In the initial stage of the reaction, a small portion of pre-emulsified monomers undergo preliminary polymerization in the emulsifier under the action of an initiator (i.e., seed emulsion polymerization). After forming a certain number of sufficiently small latex particles in the micelles, these particles continue polymerization with a large amount of other monomer raw materials. By controlling the concentration of monomers in the emulsifier and the dropping rate, nanoscale (<90nm) fine-particle latex particles are prepared. These fine-particle latex particles help improve the permeability of the emulsion. The key aspect of this invention is that in the later stage of the reaction, after most of the monomers have polymerized to form a certain number of latex particles, tert-butyl acrylate is introduced as a post-added functional monomer. Tert-butyl acrylate polymerizes again with the latex particles. Tert-butyl acrylate contains acrylic acid groups and tert-butanol groups. Through free radical reaction, these functional groups are introduced outside the latex macromolecules, forming a three-dimensional network structure. This increases the strength and adhesion of the latex, helps improve the wetting, penetration, and encapsulation properties of the latex particles, and thus provides a stronger wetting, penetration, encapsulation, and reinforcement effect on the substrate.

[0028] Meanwhile, because this invention contains crosslinking monomers, functional monomers, and post-added functional monomers with various functional groups, the polymerization process suffers from low reactivity and emulsion instability, especially during the later introduction of tert-butyl acrylate. To improve the reactivity of the mixed monomers, this invention introduces a mixture of anionic and nonionic surfactants into both the monomer pre-emulsion and the reaction vessel bottom liquid. Furthermore, a higher proportion of emulsifier is added to the reaction vessel bottom liquid to provide a better polymerization environment. The anionic emulsifier, as the main emulsifier, increases the contact area between the monomer and the aqueous phase, promoting monomer dispersion and uniform distribution, which helps form small-diameter micelles. The addition of a nonionic emulsifier stabilizes the small-diameter micelle particles, improves steric hindrance and electrolyte stability, and makes the particles more compact, which is beneficial for forming small-diameter latex particles. Detailed Implementation

[0029] The present invention will now be described in detail with reference to specific embodiments, but these are by no means limitations on the present invention.

[0030] Example 1

[0031] Prepare materials according to the formula in Table 1.

[0032] Table 1. Emulsion Raw Material Formulation for Example 1

[0033]

[0034] A method for preparing a water-based, high-penetration, reinforced acrylic emulsion includes the following steps:

[0035] (1) Emulsifier I, water, isooctyl acrylate, styrene, hydroxyethyl methacrylate, acrylic acid, and glycidyl methacrylate are stirred and mixed to obtain the bottom liquid of the reaction vessel;

[0036] (2) Put emulsifier II and water into the reaction vessel and stir to obtain the bottom liquid of the reaction vessel. Then, heat it to 84-85℃, take about 3% of the monomer pre-emulsion, and then add about 45% of the initiator. React for 10-12 minutes, and then start to add the remaining monomer pre-emulsion and about 50% of the initiator dropwise.

[0037] (3) Control the temperature at 86-88℃. When the monomer pre-emulsion is 30% remaining at this temperature, pour tert-butyl acrylate into the monomer pre-emulsion and continue to add it dropwise. The total dropwise time in steps (2) and (3) is controlled at 3.5-4 hours. After the dropwise addition is completed, keep the temperature at 86-88℃ for 1.5-2.0 hours.

[0038] (4) After the heat preservation is completed, add the remaining initiator to eliminate residual monomers, and heat preservation at 85-88℃ for another 60-90 minutes;

[0039] (5) Cool down to below 40°C, neutralize the pH of the obtained polymer emulsion with caustic soda to 7-9, stir for more than 15 minutes, filter the material through a 200-mesh filter cloth, and obtain the product.

[0040] Example 2

[0041] Prepare materials according to the formula in Table 2.

[0042] Table 2. Emulsion Raw Material Formulation for Example 2

[0043]

[0044] A method for preparing a water-based, high-penetration, reinforced acrylic emulsion includes the following steps:

[0045] (1) Emulsifier I, water, isooctyl acrylate, styrene, hydroxybutyl methacrylate, acrylic acid, and glycidyl acrylate are stirred and mixed to obtain the bottom liquid of the reaction vessel;

[0046] (2) Put emulsifier II and water into the reaction vessel and stir to obtain the bottom liquid of the reaction vessel. Then, heat it to 84-85℃, take about 4% of the monomer pre-emulsion, and then add about 40% of the initiator. React for 10-12 minutes, and then start to add the remaining monomer pre-emulsion and about 50% of the initiator dropwise.

[0047] (3) Control the temperature at 86-88℃. At this temperature, when the monomer pre-emulsion is 35% remaining, pour tert-butyl acrylate into the monomer pre-emulsion and continue to add it dropwise. The entire dropwise addition time is controlled at 3.5-4 hours. After the dropwise addition is completed, keep the temperature at 86-88℃ for 1.5-2.0 hours for reaction.

[0048] (4) After the heat preservation is completed, add the remaining initiator to eliminate residual monomers, and heat preservation at 85-88℃ for another 60-90 minutes;

[0049] (5) Cool down to below 40°C, neutralize the pH of the obtained polymer emulsion with caustic soda to 7-9, stir for more than 15 minutes, filter the material through a 200-mesh filter cloth, and obtain the product.

[0050] Example 3

[0051] Prepare materials according to the formula in Table 3.

[0052] Table 3. Emulsion Raw Material Formulation for Example 3

[0053]

[0054] A method for preparing a water-based, high-penetration, reinforced acrylic emulsion includes the following steps:

[0055] (1) Emulsifier I, water, n-butyl acrylate, styrene, hydroxyethyl methacrylate, acrylic acid, and glycidyl acrylate are stirred and mixed to obtain the bottom liquid of the reaction vessel;

[0056] (2) Put emulsifier II and water into the reaction vessel and stir to obtain the bottom liquid of the reaction vessel. Then, heat it to 84-85℃, take about 4% of the monomer pre-emulsion, and then add about 45% of the initiator. React for 10-12 minutes, and then start to add the remaining monomer pre-emulsion and about 45% of the initiator dropwise.

[0057] (3) Control the temperature at 86-88℃. At this temperature, when the monomer pre-emulsion is 35% remaining, pour tert-butyl acrylate into the monomer pre-emulsion and continue to add it dropwise. The entire dropwise addition time is controlled at 3.5-4 hours. After the dropwise addition is completed, keep the temperature at 86-88℃ for 1.5-2.0 hours for reaction.

[0058] (4) After the heat preservation is completed, add the remaining initiator to eliminate residual monomers, and heat preservation at 85-88℃ for another 60-90 minutes;

[0059] (5) Cool down to below 40°C, neutralize the pH of the obtained polymer emulsion with caustic soda to 7-9, stir for more than 15 minutes, filter the material through a 200-mesh filter cloth, and obtain the product.

[0060] Comparative Example 1

[0061] Hydroxyethyl methacrylate was replaced with methyl methacrylate, all of emulsifier 2 was added to the monomer pre-emulsion, no emulsifier was added to the bottom liquid of the reaction vessel, and everything else was the same as in Example 1.

[0062] Comparative Example 2

[0063] The formulation is the same as in Example 1, except that the timing of the addition of tert-butyl acrylate is different. Tert-butyl acrylate is added when preparing the pre-emulsified monomer, instead of adding it later. All other aspects are the same as in Example 1.

[0064] Comparative Example 3

[0065] The formulation is the same as in Example 1, except that the amount of emulsifier 1 in Comparative Example 3 is half that in Example 1, and this half of emulsifier 1 is added to the bottom liquid. The rest is the same as in Example 1.

[0066] Comparative Example 4

[0067] The difference from Example 1 is that tert-butyl acrylate was not added in the later stage.

[0068] Comparative Example 5

[0069] The difference from Example 1 is that emulsifier one and emulsifier two use equal amounts of the anionic surfactant Solvay DS-4AP, and the nonionic surfactant U-Chuang M-64 is not added.

[0070] The performance of the above-prepared penetrating and reinforcing emulsion was tested.

[0071] The test methods were conducted according to JG / 210-2018 standard to test water resistance, alkali resistance, efflorescence resistance, and reinforcement performance. Specifically, water resistance was required to be normal for 96 hours, alkali resistance for 48 hours, efflorescence resistance for 120 hours, and reinforcement performance ≥0.2. Test results are shown in Table 4.

[0072] Table 4 Performance Test Results

[0073] Example 1 80nm 82ppm pass pass pass 0.33 Example 2 79nm 95ppm pass pass pass 0.34 Example 3 82nm 80ppm pass pass pass 0.31 Comparative Example 1 110nm 80ppm pass pass Not passed 0.27 Comparative Example 2 93nm 83ppm pass Not passed pass 0.28 Comparative Example 3 75nm 2000ppm (high concentration of residue) pass pass pass 0.34 Comparative Example 4 81nm 80ppm pass pass Not passed 0.22 Comparative Example 5 78nm 300ppm pass pass Not passed 0.21

[0074] As shown in Table 4, the emulsion prepared in the embodiments of the present invention has excellent water resistance, alkali resistance, anti-sodium salt and alkali resistance, and reinforcement properties, which can meet the requirements for use.

[0075] Compared to Example 1, Comparative Example 1 replaced hydroxyethyl methacrylate with methyl methacrylate, and no emulsifier was added to the bottom liquid of the reactor. The product's resistance to efflorescence did not meet the requirements, and its reinforcement was reduced. The possible reasons are that the absence of the crosslinking monomer hydroxyethyl methacrylate affected the degree of crosslinking of the emulsion, and the absence of an emulsifier in the bottom liquid of the reactor had an adverse effect on the emulsion polymerization, resulting in weakened resistance to efflorescence and reduced reinforcement.

[0076] Compared to Example 1, Comparative Example 2 had the functional monomer tert-butyl acrylate added at the beginning, which caused changes in the distribution and structural position of the functional monomer in the polymer chain segments, ultimately having an adverse effect on the alkali resistance and reinforcement of the substrate.

[0077] Compared with Example 1, the amount of emulsifier added to the reactor in Comparative Example 3 was adjusted, which affected the distribution of the emulsifier and had an adverse effect on the initial emulsion particle size. This resulted in insufficient emulsifier distribution and coating, which affected the polymerization of monomers and led to an increase in the final gelation rate.

[0078] Compared to Example 1, Comparative Example 4 did not add functional monomers in the later stage, and the polymer chain segments lost their umbrella-like steric hindrance effect, which could not effectively block external erosion of the paint film, resulting in a decline in performance.

[0079] Compared to Example 1, Comparative Example 5 did not include a nonionic emulsifier, which caused changes in the distribution of the emulsifier in the latex particles, increased the gelation rate, and reduced its antiionic stability. This resulted in poorer effective wetting and penetration of the emulsion into the substrate, leading to reduced reinforcement.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a water-based, high-permeability reinforced acrylic emulsion, characterized in that, Includes the following steps: (1) Mix emulsifier one, water, soft monomer, hard monomer, crosslinking monomer and functional monomer evenly to prepare a monomer pre-emulsion for later use. The emulsifier one is 1-1.5 parts, water is 15-25 parts, soft monomer is 5-7 parts, hard monomer is 13-17 parts, crosslinking monomer is 4-6 parts and functional monomer is 3-4 parts. The soft monomer is at least one of isooctyl acrylate, n-butyl acrylate, and ethyl acrylate; The hard monomer is a styrene monomer, methyl methacrylate, ethyl methacrylate, or n-butyl methacrylate; The crosslinking monomers include one or more of hydroxyethyl methacrylate, hydroxybutyl methacrylate, and acetylacetoxyethyl methacrylate; The functional monomers include one or more of acrylic acid, methacrylic acid, glycidyl acrylate, and glycidyl methacrylate; (2) Mix 3.5-4 parts of emulsifier II and 14-20 parts of water evenly to prepare the bottom liquid of the reaction vessel, then heat it to 84-85℃, then add 2-4% of monomer pre-emulsion, then add initiator I, react for 10-12 minutes to prepare seed emulsion; (3) After preparing the seed emulsion, the remaining monomer pre-emulsion and initiator II are simultaneously added dropwise to the reaction vessel to carry out the reaction. When the monomer pre-emulsion is 25-35% remaining, the added functional monomer is added to the monomer pre-emulsion and the addition continues until the reaction is completed. After the reaction is completed, the temperature is maintained. The added functional monomer in step (3) is tert-butyl acrylate, and the weight ratio of the added functional monomer to the total amount of pre-emulsion monomer is 1:5-6. (4) After the heat preservation is completed, the resulting emulsion is post-processed to obtain the finished product; both emulsifier one and emulsifier two are mixtures composed of anionic surfactants and nonionic surfactants, and the mass ratio of emulsifier one to emulsifier two is 1:2.5-3. The anionic emulsifier is an alkylbenzene sulfonate, and the nonionic surfactant is a polyether emulsifier with ethylene oxide and propylene oxide blocks.

2. The method for preparing an aqueous high-permeability reinforced acrylic emulsion according to claim 1, characterized in that, The total reaction time for steps (2) and (3) should be controlled at 3.5-4 hours. After the addition is completed, keep the temperature at 86-88℃ for 1.5-2.0 hours.

3. The method for preparing an aqueous high-permeability reinforced acrylic emulsion according to claim 1, characterized in that, The post-processing described in step (4) specifically involves adding initiator 3 to eliminate residual monomers, keeping the temperature at 85-88℃ for 60-90 minutes, then cooling the temperature to below 40℃, adjusting the pH to 7-9, stirring for more than 15 minutes, and then filtering out the material.

4. The method for preparing an aqueous high-permeability reinforced acrylic emulsion according to claim 1, characterized in that, The initiators used are ammonium persulfate, potassium persulfate, and sodium persulfate, which are added in the form of an aqueous solution.

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