Acrylate emulsion for repairing mortar and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and discloses an acrylate emulsion for repairing mortar and a preparation method thereof, the acrylate emulsion is mainly prepared from the following raw materials by weight: 246-410 parts of a monomer for preparing an acrylate core, 103.5-246 parts of a monomer for preparing an acrylate shell, 2-10 parts of an anionic emulsifier, 2-10 parts of a reactive nonionic emulsifier, 2-5 parts of an initiator, 1-5 parts of a buffer agent, and 400-600 parts of water. A neutralizer is added, so that the pH value of the acrylate emulsion is 7-9; monomers for preparing the acrylate core are prepared from 235 to 400 parts of acrylate monomers, 9 to 11.9 parts of functional monomers and 0 to 1.5 parts of organic silicon monomers; monomers for preparing the acrylate shell are prepared from 100 to 235 parts of acrylate monomers, 2 to 9.5 parts of functional monomers and 0.3 to 1.5 parts of organic silicon monomers. According to the acrylate emulsion with the core-shell structure, the reactive nonionic emulsifier is firmly embedded into the shell structure of emulsion particles, and the mortar performance is improved in application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to an acrylic ester emulsion for repairing mortar and a preparation method thereof. Background Art

[0002] As one of the most commonly used building materials, cement-based materials are widely used in concrete, mortar and other projects. However, traditional cement-based materials also have some inherent defects, such as low bonding strength, high brittleness, poor impermeability, insufficient crack resistance and frost resistance. Polymer modification technology incorporates polymer emulsions into cement-based materials. As the cement hydration and polymer film formation processes proceed, the polymer forms a continuous or discontinuous network structure in the material. This network structure works together with the cement hydration products to greatly improve the microstructural density, interfacial adhesion and overall toughness of the material. This composite effect makes the mechanical properties and durability of polymer-modified materials significantly improved compared to ordinary cement-based materials.

[0003] Polymer cement-based waterproof coatings are a typical application of polymer modification technology. Research on the polymer emulsions used has been relatively extensive, and a wide range of products has been developed. However, research and application in the field of polymer-modified cement mortars is relatively weak, with a limited variety of available polymer emulsions, primarily from international companies such as BASF and Dow. Cement-based polymer emulsions are widely used in mortar and concrete modification. Commonly used types include styrene-butadiene emulsions, acrylate emulsions, and ethylene-vinyl acetate emulsions. Styrene-butadiene emulsions offer good adhesion and flexibility, but due to their unsaturated double bonds, they exhibit poor weathering resistance and are susceptible to aging. Ethylene-vinyl acetate emulsions are susceptible to hydrolysis in alkaline conditions, resulting in relatively poor water resistance. Overall, acrylate emulsions, due to their excellent weathering and water resistance and wide applicability, are the polymer of choice for modifying cement repair mortars.

[0004] The amount of cement and sand in polymer modified mortar is large, but the amount of emulsion is only 1% to 20% of the cement mass. Therefore, in such a system, cement will release a large amount of calcium ions (Ca 2+ ), sulfate ion (SO4 2- ) and other counterions, as well as high shear forces during mixing, can significantly impact the stability of acrylic emulsions, severely affecting the workability and quality of modified mortars. While adding large amounts of emulsifiers can enhance the stability of acrylic emulsions in cement mortar systems, these emulsifiers, while improving the workability of modified cement mortars, also tend to generate significant foam, increasing the mortar's porosity and thus reducing its mechanical strength and durability. Therefore, fundamentally improving the stability of acrylic emulsions in cement mortar systems has become a key challenge in their application. Summary of the Invention

[0005] In view of the problems and shortcomings in the prior art, the present invention aims to provide an acrylic emulsion for repair mortar and a preparation method thereof.

[0006] In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is as follows:

[0007] A first aspect of the present invention provides an acrylate emulsion for repair mortar, wherein the acrylate is mainly prepared from the following raw materials in parts by weight: 246-410 parts of a monomer for preparing an acrylate core, 103.5-246 parts of a monomer for preparing an acrylate shell, 2-10 parts of an anionic emulsifier, 2-10 parts of a reactive nonionic emulsifier, 2-5 parts of an initiator, 1-5 parts of a buffer, and 400-600 parts of water. A neutralizer is also added to keep the pH of the acrylate emulsion between 7 and 9.

[0008] The monomers for preparing the acrylic ester core are composed of 235 to 400 parts of acrylic ester monomers, 9 to 11.9 parts of functional monomers, and 0 to 1.5 parts of organosilicon monomers, in parts by weight;

[0009] The monomers for preparing the acrylic shell are composed of 100 to 235 parts of acrylic acid ester monomers, 2 to 9.5 parts of functional monomers, and 0.3 to 1.5 parts of organosilicon monomers, in parts by weight;

[0010] The anionic emulsifier is sodium fatty alcohol ether sulfate;

[0011] The reactive nonionic emulsifier is allyl alcohol polyoxyethylene ether.

[0012] Preferably, the acrylic ester monomer is two or more of methyl methacrylate, styrene, butyl acrylate, and isooctyl acrylate.

[0013] Preferably, the functional monomer is one or more of acrylic acid, methacrylic acid, acrylamide, N-hydroxymethyl acrylamide, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate.

[0014] Preferably, the organosilicon monomer is one or more of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0015] Preferably, the hydrophilic EO number of the anionic emulsifier is 5-20, and the hydrophilic EO number of the reactive nonionic emulsifier is 10-40.

[0016] Preferably, the initiator is any one of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0017] Preferably, the neutralizing agent is sodium hydroxide or potassium hydroxide.

[0018] Preferably, the buffer is sodium bicarbonate.

[0019] A second aspect of the present invention provides a method for preparing the acrylic emulsion for repair mortar according to any one of the first aspects, comprising the following steps:

[0020] S1: According to any of the acrylic emulsions described in the first aspect, monomers for preparing an acrylic core, monomers for preparing an acrylic shell, an anionic emulsifier, a reactive nonionic emulsifier, an initiator, a buffer, and water are weighed, and the water is divided into four parts;

[0021] S2: adding a portion of anionic emulsifier to the first portion of water, stirring to dissolve, then adding monomers for preparing the acrylate core, stirring and emulsifying to obtain a core monomer pre-emulsion;

[0022] S3: Add a reactive nonionic emulsifier to the second portion of water, stir to dissolve, then add the monomer for preparing the acrylate shell, stir and emulsify to obtain a shell monomer pre-emulsion;

[0023] S4: dissolving the initiator in the third portion of water to obtain an initiator solution;

[0024] S5: adding a buffer and the remaining anionic emulsifier to the fourth portion of water, stirring and dissolving to obtain a mixed solution; heating the mixed solution to 75-90° C., adding a portion of the core monomer pre-emulsion solution and a portion of the initiator solution to the mixed solution, and keeping the mixture warm for 20-40 minutes to obtain a seed emulsion;

[0025] S6: adding a portion of the initiator solution and the remaining core monomer pre-emulsion to the seed emulsion, and after the addition is complete, keeping the temperature to react for 10 to 20 minutes;

[0026] S7: Add the shell monomer pre-emulsion and the remaining initiator solution dropwise to the reaction system obtained in step S6. After the addition is completed, heat the reaction system to 88-90° C. and keep warm for 0.5-2 hours. Then, reduce the temperature of the reaction system to below 40° C., adjust the pH value of the reaction system to 7-9 with a neutralizer, and filter to obtain the acrylic ester emulsion.

[0027] Preferably, in step S2, the amount of the anionic emulsifier used is 80 wt% to 90 wt% of the total weight of the anionic emulsifier in the acrylic emulsion formula.

[0028] Preferably, in step S5, the amount of the core monomer pre-emulsion is 1 wt% to 10 wt% of the total weight of the core monomer pre-emulsion prepared in step S2, and the amount of the initiator solution is 25 wt% to 37 wt% of the total weight of the initiator solution prepared in step S4.

[0029] Preferably, in step S6, the amount of the initiator solution used is 38 wt% to 57 wt% of the total weight of the initiator solution prepared in step S4.

[0030] Preferably, the mass ratio of the first portion of water, the second portion of water, the third portion of water and the fourth portion of water is (4-6):(1-6):(2.5-6):(4.5-15.5).

[0031] Preferably, the theoretical glass transition temperature of the acrylic ester emulsion is -25 to 10°C.

[0032] Preferably, the solid content of the acrylic ester emulsion is 45% to 55%.

[0033] Preferably, the particle size of the acrylic ester emulsion is 150 to 300 nm.

[0034] A third aspect of the present invention provides a use of the acrylic emulsion described in any one of the first aspects in repair mortar.

[0035] A fourth aspect of the present invention provides a repair mortar comprising the acrylic emulsion described in any one of the first aspects.

[0036] Preferably, the repair mortar is mainly made of the following raw materials in parts by weight: 200-260 parts of Portland cement, 280-360 parts of quartz sand, 90-110 parts of calcium carbonate, 1-3 parts of water reducer, 1-3 parts of cellulose ether, 0.5-1.5 parts of sodium gluconate, 0.5-2 parts of defoaming agent, 20-60 parts of the acrylic emulsion described in any one of the first aspects, and 80-120 parts of water.

[0037] More preferably, the quartz sand is divided into two types according to particle size: 40-70 mesh and 70-100 mesh, with a mass ratio of 3:5.

[0038] More preferably, the calcium carbonate particle size is 325 mesh.

[0039] More preferably, the water reducer is a carboxylate water reducer.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] (1) Compared to the VAE emulsion commonly used in traditional repair mortars, the acrylate emulsion of the present invention abandons vinyl acetate and uses acrylate monomers as the main polymerization monomer, making the polymerization reaction easier to carry out. Furthermore, since the acrylate monomers have extremely low water solubility, the water resistance of the polymer is significantly improved and hydrolysis during storage is avoided. Furthermore, in cement repair mortar applications, the emulsion can improve the mechanical strength and bonding properties of the mortar under water curing conditions.

[0042] (2) The present invention synthesizes a core-shell structured acrylic emulsion through a special polymerization process, which firmly embeds the reactive nonionic emulsifier into the shell structure of the latex particles. The polymerization process adopted by the present invention is easy to operate and has good stability. By selecting the EO number of the nonionic emulsifier and the anionic emulsifier in the appropriate range, the present invention can better resist the damage of calcium and magnesium ions, maintain the stability of the latex particles, and does not affect the synthesis process. In the cement repair mortar application system, the anionic emulsifier in the emulsion is easy to react with Ca 2+ The nonionic emulsifier in the outer shell does not migrate due to adsorption by the cement mortar, and remains stably coated on the outside of the latex particles. This design significantly improves the compatibility of the latex with the mortar, solving the problem of easy demulsification of acrylic emulsions in cement mortar systems, while also giving the repair mortar excellent workability, fluidity, adhesion, and mechanical strength.

[0043] (3) The reactive nonionic emulsifier used in the present invention has low foaming. When used in cement repair mortar, it not only maintains good fluidity of the mortar but also controls the air entrainment at a low level, significantly improving the mortar's flexural strength, compressive strength, adhesion, water resistance, and durability, thus comprehensively optimizing the mortar's overall performance. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clear and distinct, the present invention is further described in detail below through examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] Example 1: Acrylate emulsion for repair mortar

[0046] An acrylic emulsion for repairing mortar is prepared from the following raw materials in parts by weight:

[0047] 303 parts of monomers for preparing an acrylate core: 54 parts of methyl methacrylate, 60 parts of styrene, 180 parts of butyl acrylate, 6 parts of acrylic acid, and 3 parts of acrylamide; 202.5 parts of monomers for preparing an acrylate shell: 36 parts of methyl methacrylate, 40 parts of styrene, 120 parts of butyl acrylate, 4 parts of acrylic acid, 2 parts of acrylamide, and 0.5 parts of vinyltrimethoxysilane; 5 parts of sodium fatty alcohol polyether sulfate (12EO), 8 parts of allyl alcohol polyoxyethylene ether (10EO), 2 parts of ammonium persulfate, 1.5 parts of sodium bicarbonate, and 500 parts of water; and a neutralizer is added to adjust the pH of the acrylate emulsion to between 7 and 9.

[0048] The preparation method of the above-mentioned acrylic emulsion comprises the following specific steps:

[0049] (1) 4 parts of sodium fatty alcohol polyether sulfate (12EO) and 120 parts of deionized water were added to a pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. 54 parts of methyl methacrylate, 60 parts of styrene, 180 parts of butyl acrylate, 6 parts of acrylic acid, and 3 parts of acrylamide were slowly added over 30 minutes, and the stirring and emulsification were carried out at a speed of 1500 rpm for 30 minutes to obtain a core monomer pre-emulsion;

[0050] (2) 8 parts of allyl alcohol polyoxyethylene ether (10EO) and 80 parts of deionized water were added to the pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. Within 30 minutes, 36 parts of methyl methacrylate, 40 parts of styrene, 120 parts of butyl acrylate, 4 parts of acrylic acid, 2 parts of acrylamide, and 0.5 parts of vinyltrimethoxysilane were slowly added respectively, and the stirring and emulsification were carried out at a speed of 1500 rpm for 20 minutes to obtain a shell monomer pre-emulsion;

[0051] (3) Weigh 2 parts of ammonium persulfate and dissolve it in 100 parts of deionized water to obtain an initiator solution;

[0052] (4) Add 1 part of sodium fatty alcohol polyether sulfate (12EO), 1.5 parts of sodium bicarbonate and 200 parts of deionized water in a reaction kettle equipped with a stirrer and a reflux condenser, start stirring to dissolve and gradually increase the temperature to set the reaction temperature to 80-82°C;

[0053] (5) Preparation of seed emulsion: Weigh 20 parts of core monomer pre-emulsion and 30 parts of initiator solution into a reactor and keep warm for 30 minutes;

[0054] (6) Add the remaining core monomer emulsion and 43.2 parts of initiator solution to the seed emulsion dropwise over 1.8 hours and keep warm for 10 minutes. Then, add the shell monomer pre-emulsion and the remaining initiator solution dropwise over 1.2 hours. After addition, heat to 90°C and keep warm for 1 hour.

[0055] (7) Cool down to below 40°C and adjust the pH value to 7-9 with the neutralizing agent sodium hydroxide. After filtering, the acrylic emulsion suitable for repair mortar is obtained.

[0056] Example 2: Acrylate emulsion for repair mortar

[0057] An acrylic emulsion for repairing mortar is prepared from the following raw materials in parts by weight:

[0058] 298.2 parts of monomers for preparing an acrylate core: 112 parts of methyl methacrylate, 175 parts of isooctyl acrylate, 10.5 parts of methacrylic acid, and 0.7 parts of vinyltrimethoxysilane; 127.8 parts of monomers for preparing an acrylate shell: 48 parts of methyl methacrylate, 75 parts of isooctyl acrylate, 4.5 parts of methacrylic acid, and 0.3 parts of vinyltrimethoxysilane; 3 parts of sodium fatty alcohol polyether sulfate (5EO), 6 parts of allyl alcohol polyoxyethylene ether (20EO), 2.4 parts of potassium persulfate, 1.6 parts of sodium bicarbonate, and 520 parts of water; and a neutralizer is added to adjust the pH of the acrylate emulsion to between 7 and 9.

[0059] The preparation method of the above-mentioned acrylic emulsion comprises the following specific steps:

[0060] (1) 2.7 parts of sodium fatty alcohol polyether sulfate (5EO) and 120 parts of deionized water were added to a pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. 112 parts of methyl methacrylate, 175 parts of isooctyl acrylate, 10.5 parts of methacrylic acid, and 0.7 parts of vinyltrimethoxysilane were slowly added over 30 minutes, and the stirring and emulsification were carried out at a speed of 1800 rpm for 40 minutes to obtain a core monomer pre-emulsion;

[0061] (2) 6 parts of allyl alcohol polyoxyethylene ether (20EO) and 80 parts of deionized water were added to the pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. 48 parts of methyl methacrylate, 75 parts of isooctyl acrylate, 4.5 parts of methacrylic acid, and 0.3 parts of vinyltrimethoxysilane were slowly added over 30 minutes, and the stirring and emulsification were carried out at a speed of 1800 rpm for 15 minutes to obtain a shell monomer pre-emulsion;

[0062] (3) Weigh 2.4 parts of potassium persulfate and dissolve it in 120 parts of deionized water to obtain an initiator solution;

[0063] (4) In a reaction kettle equipped with a stirrer and a reflux condenser, 0.3 parts of sodium fatty alcohol polyether sulfate (5EO), 1.6 parts of sodium bicarbonate, and 200 parts of deionized water were added in sequence, stirring to dissolve and gradually heating to set the reaction temperature to 86-88°C;

[0064] (5) Preparation of seed emulsion: Weigh 22 parts of core monomer pre-emulsion and 45 parts of initiator solution into a reactor and keep warm for 30 minutes;

[0065] (6) Add the remaining core monomer emulsion and 54.2 parts of initiator solution to the seed emulsion dropwise over 2 hours and keep warm for 15 minutes. Then, add the shell monomer pre-emulsion and the remaining initiator solution dropwise over 0.9 hours. After the addition is complete, heat to 90°C and keep warm for 2 hours.

[0066] (7) Cool down to below 40°C and adjust the pH value to 7-9 with the neutralizing agent sodium hydroxide. After filtering, the acrylic emulsion suitable for repair mortar is obtained.

[0067] Example 3: Acrylate emulsion for repair mortar

[0068] An acrylic emulsion for repairing mortar is prepared from the following raw materials in parts by weight:

[0069] 410 parts of monomers for preparing an acrylate core: 160 parts of methyl methacrylate, 120 parts of isooctyl acrylate, 120 parts of butyl acrylate, and 10 parts of acrylamide; 103.5 parts of monomers for preparing an acrylate shell: 40 parts of methyl methacrylate, 30 parts of isooctyl acrylate, 30 parts of butyl acrylate, 2.5 parts of acrylamide, and 1 part of vinyltrimethoxysilane; 7.5 parts of sodium fatty alcohol polyether sulfate (16EO), 5.2 parts of allyl alcohol polyoxyethylene ether (10EO), 4.1 parts of potassium persulfate, 3.1 parts of sodium bicarbonate, and 492 parts of water; and a neutralizer is added to adjust the pH of the acrylate emulsion to between 7 and 9.

[0070] The preparation method of the above-mentioned acrylic emulsion comprises the following specific steps:

[0071] (1) 6 parts of sodium fatty alcohol polyether sulfate (16EO) and 165 parts of deionized water were added to a pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. 160 parts of methyl methacrylate, 120 parts of isooctyl acrylate, 120 parts of butyl acrylate, and 10 parts of acrylamide were slowly added over 30 minutes, and the stirring and emulsification were carried out at a speed of 2000 rpm for 40 minutes to obtain a core monomer pre-emulsion;

[0072] (2) 5.2 parts of allyl alcohol polyoxyethylene ether (10EO) and 40 parts of deionized water were added to the pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. Within 30 minutes, 40 parts of methyl methacrylate, 30 parts of isooctyl acrylate, 30 parts of butyl acrylate, 2.5 parts of acrylamide, and 1 part of vinyltrimethoxysilane were slowly added respectively, and the stirring and emulsification were carried out at a speed of 2000 rpm for 15 minutes to obtain a shell monomer pre-emulsion;

[0073] (3) Weigh 4.1 parts of potassium persulfate and dissolve it in 100 parts of deionized water to obtain an initiator solution;

[0074] (4) In a reaction kettle equipped with a stirrer and a reflux condenser, 1.5 parts of sodium fatty alcohol polyether sulfate (16EO), 3.1 parts of sodium bicarbonate, and 187 parts of deionized water were added in sequence, stirring was started to dissolve, and the temperature was gradually increased to 84-86°C;

[0075] (5) Preparation of seed emulsion: 28 parts of core monomer pre-emulsion and 31 parts of initiator solution were weighed and added into the reactor, and the mixture was kept warm for 20 minutes;

[0076] (6) Add the remaining core monomer emulsion and 58.5 parts of initiator solution to the seed emulsion dropwise over 2.5 hours and keep warm for 10 minutes. Then, add the shell monomer pre-emulsion and the remaining initiator solution dropwise over 0.5 hours. After the addition is complete, heat to 90°C and keep warm for 0.5 hours.

[0077] (7) Cool down to below 40°C and adjust the pH value to 7-9 with potassium hydroxide as a neutralizer. After filtering, the acrylic emulsion suitable for repair mortar is obtained.

[0078] Example 4: Acrylate emulsion for repair mortar

[0079] An acrylic emulsion for repairing mortar is prepared from the following raw materials in parts by weight:

[0080] 246 parts of monomers for preparing an acrylate core: 125 parts of styrene, 110 parts of isooctyl acrylate, 6 parts of acrylic acid, 3.5 parts of N-hydroxymethyl acrylamide, and 1.5 parts of vinyl triethoxysilane; 246 parts of monomers for preparing an acrylate shell: 125 parts of styrene, 110 parts of isooctyl acrylate, 6 parts of acrylic acid, 3.5 parts of N-hydroxymethyl acrylamide, and 1.5 parts of vinyl triethoxysilane; 7.5 parts of sodium fatty alcohol polyether sulfate (20EO), 2.5 parts of allyl alcohol polyoxyethylene ether (10EO), 3 parts of sodium persulfate, 2.5 parts of sodium bicarbonate, and 555 parts of water; and a neutralizer is added to adjust the pH of the acrylate emulsion to between 7 and 9.

[0081] The preparation method of the above-mentioned acrylic emulsion comprises the following specific steps:

[0082] (1) 6.7 parts of sodium fatty alcohol polyether sulfate (20EO) and 100 parts of deionized water were added to a pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. 125 parts of styrene, 110 parts of isooctyl acrylate, 6 parts of acrylic acid, 3.5 parts of N-hydroxymethyl acrylamide, and 1.5 parts of vinyl triethoxysilane were slowly added over 30 minutes, and the mixture was stirred and emulsified at a speed of 1700 rpm for 30 minutes to obtain a core monomer pre-emulsion;

[0083] (2) 2.5 parts of allyl alcohol polyoxyethylene ether (10EO) and 100 parts of deionized water were added to the pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. Within 30 minutes, 125 parts of styrene, 110 parts of isooctyl acrylate, 6 parts of acrylic acid, 3.5 parts of N-hydroxymethyl acrylamide, and 1.5 parts of vinyl triethoxysilane were slowly added respectively, and the speed was stirred and emulsified at 1700 rpm for 30 minutes to obtain a shell monomer pre-emulsion;

[0084] (3) Weigh 2.5 parts of sodium persulfate and dissolve it in 100 parts of deionized water to obtain an initiator solution;

[0085] (4) In a reaction kettle equipped with a stirrer and a reflux condenser, 0.8 parts of sodium fatty alcohol polyether sulfate (16EO), 2.5 parts of sodium bicarbonate, and 255 parts of deionized water were added in sequence, stirring was started to dissolve, and the temperature was gradually increased to 82-84°C;

[0086] (5) Preparation of seed emulsion: 10.5 parts of core monomer pre-emulsion and 25.5 parts of initiator solution were weighed and added to the reactor, and the mixture was kept warm for 25 minutes;

[0087] (6) Add the remaining core monomer emulsion and 38.5 parts of initiator solution to the seed emulsion dropwise over 1.5 hours and keep warm for 15 minutes. Then, add the shell monomer pre-emulsion and the remaining initiator solution dropwise over 1.5 hours. After the addition is complete, heat to 90°C and keep warm for 0.5 hours.

[0088] (7) Cool down to below 40°C and adjust the pH value to 7-9 with potassium hydroxide as a neutralizer. After filtering, the acrylic emulsion suitable for repair mortar is obtained.

[0089] Example 5: Acrylate emulsion for repair mortar

[0090] An acrylic emulsion for repairing mortar is prepared from the following raw materials in parts by weight:

[0091] 351 parts of monomers for preparing an acrylate core: 58.1 parts of methyl methacrylate, 105 parts of styrene, 98 parts of isooctyl acrylate, 77 parts of butyl acrylate, 7 parts of acrylic acid, 4.9 parts of hydroxyethyl methacrylate, and 1 part of vinyl triisopropoxysilane; 150.5 parts of monomers for preparing an acrylate shell: 24.9 parts of methyl methacrylate, 45 parts of styrene, 42 parts of isooctyl acrylate, 33 parts of butyl acrylate, 3 parts of acrylic acid, 2.1 parts of hydroxyethyl methacrylate, and 0.5 part of vinyl triisopropoxysilane; 5 parts of sodium fatty alcohol polyether sulfate (7EO), 3 parts of allyl alcohol polyoxyethylene ether (40EO), 2.5 parts of ammonium persulfate, 2 parts of sodium bicarbonate, and 510 parts of water; and a neutralizer is added to adjust the pH of the acrylate emulsion to between 7 and 9.

[0092] The preparation method of the above-mentioned acrylic emulsion comprises the following specific steps:

[0093] (1) 4 parts of sodium fatty alcohol polyether sulfate (7EO) and 150 parts of deionized water were added to a pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. Then, 58.1 parts of methyl methacrylate, 105 parts of styrene, 98 parts of isooctyl acrylate, 77 parts of butyl acrylate, 7 parts of acrylic acid, 4.9 parts of hydroxyethyl methacrylate, and 1 part of vinyl triisopropoxysilane were slowly added over 30 minutes, and the mixture was stirred and emulsified at a speed of 1500 rpm for 30 minutes to obtain a core monomer pre-emulsion;

[0094] (2) Add 3 parts of allyl alcohol polyoxyethylene ether (40EO) and 75 parts of deionized water to the pre-emulsification kettle in sequence, start stirring to dissolve them completely, and slowly add 24.9 parts of methyl methacrylate, 45 parts of styrene, 42 parts of isooctyl acrylate, 33 parts of butyl acrylate, 3 parts of acrylic acid, 2.1 parts of hydroxyethyl methacrylate, and 0.5 parts of vinyl triisopropoxy silane within 30 minutes, and stir and emulsify at a speed of 1500 rpm for 20 minutes to obtain a shell monomer pre-emulsion.

[0095] (3) Weigh 2.5 parts of ammonium persulfate and dissolve it in 100 parts of deionized water to obtain an initiator solution;

[0096] (4) In a reaction kettle equipped with a stirrer and a reflux condenser, 1 part of fatty alcohol polyether sodium sulfate (7EO), 2 parts of sodium bicarbonate, and 185 parts of deionized water were added in sequence, stirring was started to dissolve, and the temperature was gradually increased to 86-88°C;

[0097] (5) Preparation of seed emulsion: 16 parts of core monomer pre-emulsion and 34 parts of initiator solution were weighed and added to the reactor, and the mixture was kept warm for 20 minutes;

[0098] (6) Add the remaining core monomer emulsion and 48 parts of initiator solution to the seed emulsion dropwise over 2.3 hours and keep warm for 15 minutes. Then, add the shell monomer pre-emulsion and the remaining initiator solution dropwise over 1.1 hours. After the addition is complete, heat to 90°C and keep warm for 0.8 hours.

[0099] (7) Cool down to below 40°C and adjust the pH value to 7-9 with the neutralizing agent sodium hydroxide. After filtering, the acrylic emulsion suitable for repair mortar is obtained.

[0100] Example 6: Repair mortar

[0101] A repair mortar, the raw material composition of which is shown in Table 1, the acrylic emulsion is the acrylic emulsion prepared in Example 1, and the raw materials are mixed and stirred to obtain the repair mortar.

[0102] Table 1 Composition of cement repair mortar

[0103]

[0104]

[0105] Example 7: Repair mortar

[0106] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Example 2.

[0107] Example 8: Repair mortar

[0108] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Example 3.

[0109] Example 9: Repair mortar

[0110] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Example 4.

[0111] Example 10: Repair mortar

[0112] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Example 5.

[0113] (1) Acrylate Emulsion Performance Testing: The basic properties of the acrylate emulsions prepared in the present invention were tested in accordance with GB / T 20623-2006, "Emulsions for Architectural Coatings." For comparison purposes, the present invention also prepared Comparative Examples 1 to 5. The basic performance parameters of the acrylate emulsions prepared in Examples 1 to 5 and Comparative Examples 1 to 5 are shown in Table 2.

[0114] Comparative Example 1

[0115] The content of Comparative Example 1 is basically the same as that of Example 5, except that the anionic emulsifier sodium fatty alcohol polyether sulfate (7EO) in Example 5 is replaced with sodium lauryl sulfate (0EO), and the reaction is performed to prepare an acrylic emulsion suitable for repair mortar.

[0116] Comparative Example 2

[0117] The content of Comparative Example 2 is basically the same as that of Example 5, except that the anionic emulsifier sodium fatty alcohol polyether sulfate (7EO) in Example 5 is replaced with sodium dodecylbenzenesulfonate (0EO), and the nonionic emulsifier allyl alcohol polyoxyethylene ether (40EO) is replaced with fatty alcohol polyoxyethylene ether (7EO), and the reaction is prepared to obtain an acrylic emulsion suitable for repair mortar.

[0118] Comparative Example 3

[0119] The content of Comparative Example 2 is basically the same as that of Example 5, except that the anionic emulsifier sodium fatty alcohol polyether sulfate (7EO) in Example 5 is replaced with sodium fatty alcohol polyoxyethylene ether sulfate (3EO), and the nonionic emulsifier allyl alcohol polyoxyethylene ether (40EO) is replaced with nonylphenol polyoxyethylene ether (10EO), and the reaction is prepared to obtain an acrylic emulsion suitable for repair mortar.

[0120] Comparative Example 4

[0121] An acrylic emulsion is prepared from the following raw materials in parts by weight:

[0122] Prepare 505.5 parts of acrylic acid ester monomers: 90 parts of methyl methacrylate, 100 parts of styrene, 300 parts of butyl acrylate, 10 parts of acrylic acid, 5 parts of acrylamide, 0.5 parts of vinyltrimethoxysilane; 5 parts of sodium fatty alcohol polyether sulfate (12EO), 8 parts of allyl alcohol polyoxyethylene ether (10EO), 2 parts of ammonium persulfate, 1.5 parts of sodium bicarbonate, and 500 parts of water; and add a neutralizer to adjust the pH of the acrylic acid ester emulsion to between 7 and 9.

[0123] The preparation method of the above-mentioned acrylic emulsion comprises the following specific steps:

[0124] (1) 4 parts of sodium fatty alcohol polyether sulfate (12EO), 6.4 parts of allyl alcohol polyoxyethylene ether (10EO) and 200 parts of deionized water were added to a pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. 90 parts of methyl methacrylate, 100 parts of styrene, 300 parts of butyl acrylate, 10 parts of acrylic acid, 5 parts of acrylamide and 0.5 parts of vinyltrimethoxysilane were slowly added over 30 minutes, and the mixture was stirred at a high speed of 1500 rpm for 30 minutes to obtain a monomer pre-emulsion;

[0125] (2) Weigh 2 parts of ammonium persulfate and dissolve it in 100 parts of deionized water to obtain an initiator solution;

[0126] (3) In a reaction kettle equipped with a stirrer and a reflux condenser, 1 part of fatty alcohol polyether sodium sulfate (12EO), 1.6 parts of allyl alcohol polyoxyethylene ether (10EO), 1.5 parts of sodium bicarbonate, and 200 parts of deionized water were added in sequence, and the mixture was stirred and dissolved while gradually heating to a temperature of 80-82°C.

[0127] (4) Preparation of seed emulsion: Weigh 20 parts of core monomer pre-emulsion and 30 parts of initiator solution into a reactor and keep warm for 20 minutes;

[0128] (5) Add the remaining core monomer emulsion and 43.2 parts of initiator solution to the seed emulsion dropwise over 1.8 hours and keep warm for 10 minutes. Then, add the shell monomer pre-emulsion and the remaining initiator solution dropwise over 1.2 hours. After addition, heat to 90°C and keep warm for 1 hour.

[0129] (6) Cooling to below 40°C and adjusting the pH value to 7-9 with a neutralizing agent, sodium hydroxide, and filtering to obtain an acrylic emulsion.

[0130] Comparative Example 5

[0131] An acrylic emulsion for repairing mortar is prepared from the following raw materials in parts by weight:

[0132] Prepare 501.5 parts of acrylic acid ester monomers: 83 parts of methyl methacrylate, 150 parts of styrene, 140 parts of isooctyl acrylate, 110 parts of butyl acrylate, 10 parts of acrylic acid, 7 parts of hydroxyethyl methacrylate, 1.5 parts of vinyl triisopropoxysilane; 5 parts of sodium fatty alcohol polyether sulfate (7EO), 3 parts of allyl alcohol polyoxyethylene ether (40EO), 2.5 parts of ammonium persulfate, 2 parts of sodium bicarbonate, and 510 parts of water; and add a neutralizer to adjust the pH of the acrylic acid ester emulsion to between 7 and 9.

[0133] The preparation method of the above-mentioned acrylic emulsion comprises the following specific steps:

[0134] (1) 4 parts of sodium fatty alcohol polyether sulfate (7EO), 2.4 parts of allyl alcohol polyoxyethylene ether (40EO) and 225 parts of deionized water were added to a pre-emulsification kettle in sequence, and stirring was started to dissolve them completely. Within 30 minutes, 83 parts of methyl methacrylate, 150 parts of styrene, 140 parts of isooctyl acrylate, 110 parts of butyl acrylate, 10 parts of acrylic acid, 7 parts of hydroxyethyl methacrylate and 1.5 parts of vinyl triisopropoxysilane were slowly added respectively, and the mixture was stirred and emulsified at a speed of 1500 rpm for 30 minutes to obtain a monomer pre-emulsion;

[0135] (2) Weigh 2.5 parts of ammonium persulfate and dissolve it in 100 parts of deionized water to obtain an initiator solution;

[0136] (3) In a reaction kettle equipped with a stirrer and a reflux condenser, add 1 part of fatty alcohol polyether sodium sulfate (7EO), 0.6 part of allyl alcohol polyoxyethylene ether (40EO), 2 parts of sodium bicarbonate and 185 parts of deionized water in sequence, start stirring to dissolve and gradually increase the temperature to set the reaction temperature to 86-88°C;

[0137] (4) Preparation of seed emulsion: 16 parts of core monomer pre-emulsion and 34 parts of initiator solution were weighed and added into a reactor, and the mixture was kept warm for 20 minutes;

[0138] (5) Add the remaining core monomer emulsion and 48 parts of initiator solution to the seed emulsion dropwise over 2.3 hours and keep warm for 15 minutes. Then, add the shell monomer pre-emulsion and the remaining initiator solution dropwise over 1.1 hours. After the addition is complete, heat to 90°C and keep warm for 0.8 hours.

[0139] (6) Cool down to below 40°C and adjust the pH value to 7-9 with the neutralizing agent sodium hydroxide. After filtering, the acrylic emulsion suitable for repair mortar is obtained.

[0140] Table 2 Basic properties of acrylic emulsions of Examples 1 to 5 and Comparative Examples 1 to 5

[0141]

[0142] (2) Repair mortar performance test:

[0143] The repair mortars prepared in Examples 6 to 10 were tested for performance. The DL / T 5126-2001 Test Procedure for Polymer-Modified Cement Mortar was used to test the performance of the acrylate emulsion-modified cement repair mortars. The cement repair mortar samples were cured for 28 days. For comparison purposes, the present invention also prepared Comparative Examples 6 to 10.

[0144] Comparative Example 6

[0145] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Comparative Example 1.

[0146] Comparative Example 7

[0147] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Comparative Example 2.

[0148] Comparative Example 8

[0149] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Comparative Example 3.

[0150] Comparative Example 9

[0151] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Comparative Example 4.

[0152] Comparative Example 10

[0153] A repair mortar, whose composition is basically the same as that of Example 6, except that: the acrylic emulsion is the acrylic emulsion prepared in Comparative Example 5.

[0154] (1) Performance analysis of repair mortars in Examples 6 to 10

[0155] The specific properties of the acrylic ester emulsion-modified cement repair mortars prepared in Examples 6 to 10 are shown in Table 3, wherein the comparative sample is a cement repair mortar prepared using commercially available acrylic ester emulsion.

[0156] Table 3 Performance test results of cement repair mortar prepared in Examples 6 to 10 and comparative samples

[0157]

[0158] Analysis of Table 3 shows that the acrylate emulsion-modified cement repair mortars prepared in Examples 6 to 10 of the present invention have an extended initial setting time compared to the control sample. This shows that the acrylate emulsion prepared in the present invention has good compatibility with the mortar, while ensuring mixing uniformity and construction performance. In addition, the compressive, flexural, and bonding strengths of the acrylate emulsion-modified cement repair mortars prepared in Examples 6 to 10 of the present invention are all improved compared to the control sample. Their water-resistant tensile bonding strength and freeze-thaw-resistant tensile bonding strength are excellent, and the strength decrease is small, and the water absorption rate is reduced. Among them, the acrylate emulsion-modified cement repair mortar prepared in Example 10 has the best comprehensive application performance.

[0159] (2) Performance analysis of repair mortars prepared in Comparative Examples 6 to 8

[0160] The performance of the cement repair mortars prepared in Comparative Examples 6 to 8 was tested, and the test results are shown in Table 4.

[0161] Table 4 Performance test results of cement repair mortar prepared in Example 10 and Comparative Examples 6 to 8

[0162]

[0163] As shown in Table 4, compared with the comparative example, the acrylate emulsion prepared in Example 10 using sodium fatty alcohol polyether sulfate (7EO) and allyl polyoxyethylene ether (40EO) emulsifiers meets the requirements of the present invention when used in cement repair mortar. Its initial setting time is significantly prolonged, and the mechanical properties and durability of the cement mortar are significantly improved. This result demonstrates that the emulsification system of the present invention plays a key role in the application of acrylate emulsions in cement mortar.

[0164] (3) Performance analysis of the repair mortar prepared in Comparative Examples 9 and 10

[0165] The performance of the cement repair mortars prepared in Comparative Examples 9 and 10 was tested, and the test results are shown in Table 5.

[0166] Table 5 Performance test results of cement repair mortar prepared in Example 6, Example 9, Comparative Examples 9 to 10

[0167]

[0168] As can be seen from Table 5, compared with Comparative Example 9 and Comparative Example 10, Example 6 and Comparative Example 10, the present invention adopts a special core-shell polymerization process (using an anionic emulsifier to prepare a core monomer pre-emulsion and a nonionic emulsifier to prepare a shell monomer emulsion) to prepare an acrylate emulsion to prepare cement repair mortar. Compared with the cement repair mortar prepared by the traditional polymerization process (using a composite solution of anionic emulsifiers and nonionic emulsifiers to prepare core and shell monomer pre-emulsions), the acrylate emulsion prepared by the traditional polymerization process improves the stability, mechanical strength and durability of the cement repair mortar.

[0169] The present invention significantly improves the stability, workability, water resistance and mechanical strength of the acrylic ester emulsion prepared by rationally selecting monomer components and emulsification systems and adopting a special polymerization process in cement repair mortar, effectively overcoming the problem that the existing commercially available products are limited in their application in the field of repair mortar due to insufficient stability.

[0170] The above is an explanation of the embodiments of the present invention. The description of the disclosed embodiments enables those skilled in the art to implement or use the present invention, and is not intended to limit the present invention. It is impossible to fully reflect all aspects of the present invention in the above embodiments. Any equivalent changes or modifications made by any professional skilled in the art without departing from the spirit or scope of the present invention are within the scope of protection and disclosure of the present invention.

Claims

1. An acrylic emulsion for repairing mortar, characterized in that: The acrylic emulsion is mainly made of the following raw materials in parts by weight: 246-410 parts of monomers for preparing an acrylic core, 103.5-246 parts of monomers for preparing an acrylic shell, 2-10 parts of anionic emulsifier, 2-10 parts of reactive nonionic emulsifier, 2-5 parts of initiator, 1-5 parts of buffer, 400-600 parts of water, and a neutralizer is added to keep the pH of the acrylic emulsion between 7 and 9. The monomers for preparing the acrylic ester core are composed of 235 to 400 parts of acrylic ester monomers, 9 to 11.9 parts of functional monomers, and 0 to 1.5 parts of organosilicon monomers, in parts by weight; The monomers for preparing the acrylic shell are composed of 100 to 235 parts of acrylic acid ester monomers, 2 to 9.5 parts of functional monomers, and 0.3 to 1.5 parts of organosilicon monomers, in parts by weight; The anionic emulsifier is sodium fatty alcohol ether sulfate; The reactive nonionic emulsifier is allyl alcohol polyoxyethylene ether.

2. The acrylic emulsion according to claim 1, wherein The acrylic acid ester monomers are two or more of methyl methacrylate, styrene, butyl acrylate and isooctyl acrylate.

3. The acrylic emulsion according to claim 2, characterized in that The functional monomer is one or more of acrylic acid, methacrylic acid, acrylamide, N-hydroxymethyl acrylamide, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate; the silicone monomer is one or more of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane.

4. The acrylic emulsion according to claim 1, characterized in that The hydrophilic EO number of the anionic emulsifier is 5-20, and the hydrophilic EO number of the reactive nonionic emulsifier is 10-40.

5. The acrylic emulsion according to claim 1, characterized in that The initiator is any one of ammonium persulfate, sodium persulfate, and potassium persulfate; the neutralizer is sodium hydroxide or potassium hydroxide; and the buffer is sodium bicarbonate.

6. A method for preparing the acrylic emulsion according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: According to any one of claims 1 to 5, weigh the monomers for preparing the acrylate core, the monomers for preparing the acrylate shell, an anionic emulsifier, a reactive nonionic emulsifier, an initiator, a buffer, and water, and divide the water into four parts; S2: adding a portion of anionic emulsifier to the first portion of water, stirring to dissolve, then adding monomers for preparing the acrylate core, stirring and emulsifying to obtain a core monomer pre-emulsion; S3: Add a reactive nonionic emulsifier to the second portion of water, stir to dissolve, then add the monomer for preparing the acrylate shell, stir and emulsify to obtain a shell monomer pre-emulsion; S4: dissolving the initiator in the third portion of water to obtain an initiator solution; S5: adding a buffer and the remaining anionic emulsifier to the fourth portion of water, stirring and dissolving to obtain a mixed solution; heating the mixed solution to 75-90° C., adding a portion of the core monomer pre-emulsion solution and a portion of the initiator solution to the mixed solution, stirring and dissolving, and keeping the mixture warm for 20-40 minutes to obtain a seed emulsion; S6: adding a portion of the initiator solution and the remaining core monomer pre-emulsion to the seed emulsion, and after the addition is complete, keeping the temperature to react for 10 to 20 minutes; S7: Add the shell monomer pre-emulsion and the remaining initiator solution dropwise to the reaction system obtained in step S6. After the addition is completed, heat the reaction system to 88-95° C. and keep warm for 0.5-2 hours. Then, reduce the temperature of the reaction system to below 40° C., adjust the pH value of the reaction system to 7-9 with a neutralizer, and filter to obtain the acrylic ester emulsion.

7. The preparation method according to claim 6, characterized in that In step S2, the amount of anionic emulsifier used is 80wt% to 90wt% of the total weight of the anionic emulsifier in the acrylate emulsion formula; in step S5, the amount of core monomer pre-emulsion used is 1wt% to 10wt% of the total weight of the core monomer pre-emulsion prepared in step S2, and the amount of initiator solution used is 25wt% to 37wt% of the total weight of the initiator solution prepared in step S4; in step S6, the amount of initiator solution used is 38wt% to 57wt% of the total weight of the initiator solution prepared in step S4.

8. Use of the acrylic emulsion according to any one of claims 1 to 5 in repair mortar.

9. A repair mortar, characterized in that: The invention comprises the acrylic ester emulsion according to any one of claims 1 to 5.

10. The repair mortar according to claim 9, characterized in that: The repair mortar is mainly made of the following raw materials in parts by weight: 200-260 parts of silicate cement, 280-360 parts of quartz sand, 90-110 parts of calcium carbonate, 1-3 parts of water reducer, 1-3 parts of cellulose ether, 0.5-1.5 parts of sodium gluconate, 0.5-2 parts of defoamer, 20-60 parts of the acrylic emulsion according to any one of claims 1 to 5, and 80-120 parts of water.

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