Modified polymer cement waterproof mortar and preparation method thereof

Abstract

The application discloses a modified polymer cement waterproof mortar and a preparation method thereof, and relates to the technical field of waterproof mortar.The application mixes deionized water, sodium dodecyl sulfate, octylphenol polyoxyethylene ether, methyl methacrylate, butyl acrylate, lauryl methacrylate, acrylic acid and N-hydroxymethyl acrylamide, initiates polymerization by using potassium persulfate, and prepares an acrylic emulsion; the acrylic emulsion and a polyvinyl alcohol solution are mixed and dried to prepare a redispersible acrylic latex powder; a silane hydrolysis solution, polyvinylpyrrolidone and nano cellulose are mixed and sprayed on the surface of pre-modified polypropylene fibers to prepare modified polypropylene fibers; dry powder mixture is mixed with tap water to prepare the modified polymer cement waterproof mortar.The modified polymer cement waterproof mortar prepared by the application has excellent waterproof and anti-seepage performance and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of waterproof mortar technology, specifically to a modified polymer cement waterproof mortar and its preparation method. Background Technology

[0002] Compared to traditional ordinary cement mortar, polymer-modified cement waterproof mortar offers the synergistic advantages of a rigid cement matrix and a flexible polymer network. It boasts reliable bonding, convenient construction, and good compatibility with concrete substrates. Furthermore, because the polymer components can fill cement hydration capillaries and bridge micro-cracks, it significantly improves the mortar's impermeability, tensile bond strength, and deformation adaptability, thereby addressing the inherent defects of ordinary mortar such as high brittleness, drying shrinkage cracking, easy interface detachment, and poor long-term water resistance. Currently, polymer-modified cement waterproof mortar mainly comes in two types: two-component emulsion type and one-component dry-mix powder type. The dry-mix type is more suitable for industrial prefabrication and standardized on-site construction requirements due to its stable storage, on-site water addition for application, and strong quality control.

[0003] However, existing products generally use VAE redispersible polymer powder, which has weak resistance to alkali hydrolysis. After long-term immersion in water, the polymer film is damaged, resulting in an increase in interconnected pores inside the mortar and a significant reduction in its impermeability. At the same time, during cement hydration and water evaporation, the mortar generates drying shrinkage and thermal shrinkage microcracks. Conventional unreinforced systems lack an effective crack bridging mechanism. Under conditions of temperature alternation, freeze-thaw cycles, and slight structural deformation, the microcracks continue to expand, forming seepage channels and significantly shortening the service life of the waterproof structure.

[0004] Therefore, there is an urgent need to develop a waterproof, seepage-resistant, durable, and stable single-component dry-mix modified polymer cement waterproof mortar that can solve the problems of leakage, cracking, and peeling failure in the engineering applications of existing products. Summary of the Invention

[0005] The purpose of this invention is to provide a modified polymer cement waterproof mortar and its preparation method to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following solution: A modified polymer cement waterproof mortar is prepared by mixing deionized water, sodium dodecyl sulfate, octylphenol polyoxyethylene ether, methyl methacrylate, butyl acrylate, lauryl methacrylate, acrylic acid, and N-hydroxymethylacrylamide, and polymerizing with potassium persulfate to obtain an acrylic emulsion; mixing and drying the acrylic emulsion with a polyvinyl alcohol solution to obtain a redispersible acrylic latex powder; spraying a mixture of silane hydrolysate, polyvinylpyrrolidone, and nanocellulose onto the surface of pre-modified polypropylene fibers to obtain modified polypropylene fibers; and mixing the dry powder mixture with tap water at a water-cement ratio of 0.42~0.44. The polyvinyl alcohol solution is prepared by mixing polyvinyl alcohol with deionized water; The silane hydrolysate is prepared by hydrolyzing γ-glycidoxypropyltrimethoxysilane. The pre-modified polypropylene fiber is obtained by alkali etching of the polypropylene fiber surface with sodium hydroxide; The dry powder mixture is prepared by mixing 50-60 parts of cement, 2-3 parts of fly ash, 2-4 parts of mineral powder, 2-3 parts of silica fume, 30-40 parts of quartz sand, 4-8 parts of redispersible acrylic latex powder, 0.1-0.3 parts of hydroxypropyl methylcellulose ether, 0.2-0.4 parts of water-reducing agent, 0.15-0.25 parts of defoamer, 0.15-0.25 parts of water-repellent agent, and 0.5-1.5 parts of modified polypropylene fiber.

[0007] A method for preparing modified polymer cement waterproof mortar, the method comprising the following preparation steps: (1) Mix 65-75 parts of deionized water, 0.7-0.9 parts of sodium bicarbonate and 0.1-0.3 parts of potassium persulfate evenly, heat to 75-85℃ under nitrogen protection, stir for 5-10 min, add 10% of pre-emulsion, stir for 15-25 min, add the remaining 90% of pre-emulsion and initiator dropwise at a uniform rate over 2-3 h, keep warm and mature for 1-2 h, cool to 30-40℃, adjust the pH of the emulsion to 8.5-9.5 with 5wt% sodium hydroxide aqueous solution, filter, and obtain acrylic emulsion; (2) Mix acrylic emulsion and polyvinyl alcohol solution at a mass ratio of 1:(0.2~0.3) until uniform, stir at room temperature for 10~20 min, send to spray dryer for drying, inlet air 130~150℃, outlet air 70~80℃, atomizing disc speed 20000~22000r / min, collect the adhesive powder through cyclone collector to obtain redispersible acrylic latex powder; (3) Spray the coating liquid evenly on the surface of the pre-modified polypropylene fiber 3 to 5 times, let it stand for 2 to 4 minutes each time, dry it at 65 to 75℃ for 6 to 8 hours, and then heat it to 85 to 95℃ for 3 to 5 hours to obtain the modified polypropylene fiber. (4) By mass, mix 50-60 parts of cement, 2-3 parts of fly ash, 2-4 parts of mineral powder, 2-3 parts of silica fume, and 30-40 parts of quartz sand evenly, stir at room temperature for 2-4 minutes, add 4-8 parts of redispersible acrylic latex powder, 0.1-0.3 parts of hydroxypropyl methylcellulose ether, 0.2-0.4 parts of water-reducing agent, 0.15-0.25 parts of defoamer, and 0.15-0.25 parts of water-repellent agent, continue stirring for 4-6 minutes, add 0.5-1.5 parts of modified polypropylene fiber, continue stirring for 1-3 minutes to obtain dry powder mixture; mix the dry powder mixture and tap water at a water-cement ratio of 0.42-0.44 evenly, stir at room temperature for 3-5 minutes to obtain modified polymer cement waterproof mortar.

[0008] As an optimization, the preparation process of the pre-emulsion in step (1) is as follows: by mass, 65-75 parts of deionized water, 1.1-1.3 parts of sodium dodecyl sulfate, and 0.7-0.9 parts of octylphenol polyoxyethylene ether are mixed evenly and stirred at room temperature for 5-15 minutes. Then, 35-45 parts of methyl methacrylate, 35-45 parts of butyl acrylate, 7-9 parts of lauryl methacrylate, 2.1-2.3 parts of acrylic acid, and 1.7-1.9 parts of N-hydroxymethylacrylamide are added and stirred for another 15-25 minutes to obtain the pre-emulsion.

[0009] As an optimization, the preparation process of the dropwise initiator in step (1) is as follows: dissolve 0.4~0.6 parts of potassium persulfate in 14~16 parts of deionized water, stir at room temperature for 5~7 minutes, and obtain the dropwise initiator.

[0010] As an optimization, the preparation process of the polyvinyl alcohol solution in step (2) is as follows: polyvinyl alcohol and deionized water are mixed evenly at a mass ratio of 1:(8.5~9.5), heated to 55~65℃ and stirred for 10~20 min, and cooled to room temperature to obtain the polyvinyl alcohol solution.

[0011] As an optimization, the polyvinyl alcohol used was model 1788, with a degree of hydrolysis of 87.0 mol% and a viscosity of 25.0 cps, and was purchased from Guangzhou Hehui Chemical Co., Ltd.

[0012] As an optimization, the preparation process of the spraying liquid in step (3) is as follows: γ-glycidyl etheroxypropyltrimethoxysilane, deionized water, glacial acetic acid, and anhydrous ethanol are mixed evenly in a mass ratio of 1:(0.24~0.26):(0.012~0.014):(9~11), and stirred at room temperature for 15~25 min to obtain silane hydrolysate; silane hydrolysate, polyvinylpyrrolidone, and nanocellulose are mixed evenly in a mass ratio of 1:(0.004~0.006):(0.02~0.06), and stirred at room temperature for 20~30 min to obtain spraying liquid.

[0013] As an optimization, the preparation process of the pre-modified polypropylene fiber in step (3) is as follows: Deionized water and sodium hydroxide are mixed evenly at a mass ratio of 1:(0.015~0.035), stirred at room temperature for 3~5 min, 0.09~0.11 times the mass of deionized water is added to 6~18 mm polypropylene fiber, stirred for 10~20 min, heated to 55~65℃ and soaked for 6~8 h, taken out, washed with deionized water 3~5 times, and dried at 65~75℃ for 6~8 h to obtain the pre-modified polypropylene fiber.

[0014] As an optimization, the polypropylene fiber has a diameter of 20 μm, a density of 0.91 g / cm3, and an alkali resistance of ≥96%, and was purchased from Taian Songze Composite Materials Co., Ltd.

[0015] As an optimization, the cement used in step (4) is P·O 42.5 ordinary Portland cement, purchased from Daye Jianfeng Cement Co., Ltd.; the fly ash is Grade I fly ash, purchased from Hebei Leijiang New Material Technology Co., Ltd.; the mineral powder is S95 mineral powder, purchased from Shijiazhuang Aokai Mineral Products Co., Ltd.; the silica fume is Grade I silica fume, purchased from Shijiazhuang Baijiang Mineral Products Co., Ltd.; the quartz sand is a mixture of 40~70 mesh fine sand and 80~120 mesh coarse sand in a 3:7 ratio, purchased from Lingshou County Jiaxin Mineral Products Processing Plant; the hydroxypropyl methylcellulose ether has a viscosity of 200000 mPa·s, purchased from Jinzhou Xincheng Cellulose Co., Ltd.; the water-reducing agent is 11A polycarboxylate water-reducing agent, purchased from Aohanshengchuan Chemical (Beijing) Co., Ltd.; the defoamer is organosilicon solid defoamer, purchased from Shandong Maofa Chemical Co., Ltd.; and the water-repellent agent is sodium methylsilicate dry powder water-repellent agent, purchased from Shandong Hongquan Chemical Technology Co., Ltd.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are: First, a pre-emulsion is prepared by mixing deionized water, sodium dodecyl sulfate, octylphenol polyoxyethylene ether, methyl methacrylate, butyl acrylate, lauryl methacrylate, acrylic acid, and N-hydroxymethylacrylamide. Emulsion polymerization is initiated by generating free radicals through the thermal decomposition of potassium persulfate. A polyvinyl alcohol solution is prepared by mixing polyvinyl alcohol with deionized water. A polyvinyl alcohol aqueous solution is prepared as a protective colloid, which is then thoroughly mixed with the acrylic emulsion and dried to obtain a core-shell structured redispersible acrylic latex powder. Sodium dodecyl sulfate and octylphenol polyoxyethylene ether are compounded as anionic / nonionic emulsifiers. The system relies on electrostatic repulsion and steric hindrance to ensure the stability of the entire polymerization and dry powder mixing process. Various acrylic monomers synergistically endow the polymer film with strength, toughness, long-term hydrophobicity and inorganic interfacial bonding ability. N-hydroxymethylacrylamide undergoes intermolecular dehydration condensation during the mortar curing stage to form a three-dimensional cross-linked dense network. The polyvinyl alcohol shell ensures the stability of the powder during dry mixing and storage, and the latex particles are redispersed after water is added. Finally, when the latex powder is added to cement mortar, it can fill capillary pores and bridge microcracks, thereby significantly improving the impermeability, crack resistance and long-term water resistance of the modified polymer cement waterproof mortar.

[0017] Secondly, pre-modified polypropylene fibers are prepared by alkali etching of the polypropylene fiber surface with sodium hydroxide; silane hydrolysate is prepared by hydrolyzing γ-glycidyl etheroxypropyltrimethoxysilane; the silane hydrolysate, polyvinylpyrrolidone, and nanocellulose are mixed and sprayed onto the surface of the pre-modified polypropylene fibers to obtain modified polypropylene fibers; polyvinylpyrrolidone can play a role in dispersion and stabilization and enhance interfacial compatibility, while nanocellulose fills surface micro-defects and builds an organic transition layer. The multiple components work together to construct a continuous polar composite coating on the fiber surface, which improves the chemical bonding and mechanical interlocking between the polypropylene fibers and the cement hydration matrix, enhances the fiber pull-out resistance, and thus effectively improves the crack resistance, toughening, impermeability and durability of the modified polymer cement waterproof mortar. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all 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.

[0019] Example 1: A method for preparing modified polymer cement waterproof mortar, the method comprising the following steps: (1) By mass, 65 parts of deionized water, 1.1 parts of sodium dodecyl sulfate, and 0.7 parts of octylphenol polyoxyethylene ether were mixed evenly and stirred at room temperature for 15 min. Then, 35 parts of methyl methacrylate, 35 parts of butyl acrylate, 7 parts of lauryl methacrylate, 2.1 parts of acrylic acid, and 1.7 parts of N-hydroxymethylacrylamide were added, and stirring was continued for 25 min to obtain a pre-emulsion. 0.4 parts of potassium persulfate were dissolved in 14 parts of deionized water and stirred at room temperature for 7 min. The initiator was prepared by mixing 65 parts of deionized water, 0.7 parts of sodium bicarbonate, and 0.1 parts of potassium persulfate. Under nitrogen protection, the mixture was heated to 75°C and stirred for 10 minutes. 10% of the pre-emulsion was added and stirred for 25 minutes. The remaining 90% of the pre-emulsion and the initiator were added dropwise over 3 hours. The mixture was kept warm and matured for 2 hours. The temperature was lowered to 30°C, and the pH of the emulsion was adjusted to 8.5 with 5 wt% sodium hydroxide aqueous solution. The mixture was filtered to obtain an acrylic emulsion. (2) Polyvinyl alcohol and deionized water are mixed evenly at a mass ratio of 1:8.5, heated to 55℃ and stirred for 20 min, and cooled to room temperature to obtain a polyvinyl alcohol solution; acrylic emulsion and polyvinyl alcohol solution are mixed evenly at a mass ratio of 1:0.2, stirred for 20 min at room temperature, and sent to a spray dryer for drying, with an inlet air temperature of 130℃, an outlet air temperature of 70℃, and a misting disc speed of 20000 r / min. The adhesive powder is collected by a cyclone collector to obtain redispersible acrylic latex powder; (3) Mix deionized water and sodium hydroxide at a mass ratio of 1:0.015, stir for 5 min at room temperature, add 12 mm polypropylene fiber at a mass ratio of 0.09 times that of deionized water, continue stirring for 20 min, heat to 55℃ and soak for 8 h, take out, wash with deionized water 3 times, and dry at 65℃ for 8 h to obtain pre-modified polypropylene fiber; mix γ-glycidyl oxypropyltrimethoxysilane, deionized water, glacial acetic acid and anhydrous ethanol at a mass ratio of 1:0.24:0.012:9, stir for 25 min at room temperature to obtain silane hydrolysate; mix silane hydrolysate, polyvinylpyrrolidone and nanocellulose at a mass ratio of 1:0.004:0.02, stir for 30 min at room temperature to obtain spray solution; spray the spray solution evenly on the surface of pre-modified polypropylene fiber 3 to 5 times, let stand for 4 min each time, dry at 65℃ for 8 h, heat to 85℃ and dry for 5 h to obtain modified polypropylene fiber; (4) By mass, mix 50 parts cement, 2 parts fly ash, 2 parts mineral powder, 2 parts silica fume and 30 parts quartz sand evenly, stir at room temperature for 4 minutes, add 6 parts redispersible acrylic latex powder, 0.2 parts hydroxypropyl methylcellulose ether, 0.2 parts water-reducing agent, 0.2 parts defoamer and 0.2 parts water-repellent agent, continue stirring for 6 minutes, add 1 part modified polypropylene fiber, continue stirring for 3 minutes to obtain dry powder mixture; mix dry powder mixture and tap water at a water-cement ratio of 0.42 evenly, stir at room temperature for 5 minutes to obtain modified polymer cement waterproof mortar.

[0020] Example 2: A method for preparing modified polymer cement waterproof mortar, the method comprising the following steps: (1) By mass, 70 parts of deionized water, 1.2 parts of sodium dodecyl sulfate, and 0.8 parts of octylphenol polyoxyethylene ether were mixed evenly and stirred at room temperature for 10 min. Then, 40 parts of methyl methacrylate, 40 parts of butyl acrylate, 8 parts of lauryl methacrylate, 2.2 parts of acrylic acid, and 1.8 parts of N-hydroxymethylacrylamide were added and stirred for another 20 min to obtain a pre-emulsion. 0.5 parts of potassium persulfate were dissolved in 15 parts of deionized water and stirred at room temperature for 6 min. n. Prepare the dropwise initiator; mix 70 parts deionized water, 0.8 parts sodium bicarbonate and 0.2 parts potassium persulfate evenly, heat to 80℃ under nitrogen protection, stir for 7.5 min, add 10% pre-emulsion, stir and react for 20 min, add the remaining 90% pre-emulsion and dropwise initiator at a uniform rate over 2.5 h, keep warm and mature for 1.5 h, cool to 35℃, adjust the pH of the emulsion to 9 with 5 wt% sodium hydroxide aqueous solution, filter, and obtain acrylic emulsion; (2) Polyvinyl alcohol and deionized water are mixed evenly at a mass ratio of 1:9, heated to 60℃ and stirred for 15 min, and cooled to room temperature to obtain a polyvinyl alcohol solution; acrylic emulsion and polyvinyl alcohol solution are mixed evenly at a mass ratio of 1:0.25, stirred for 15 min at room temperature, and sent to a spray dryer for drying, with an inlet air temperature of 130℃, an outlet air temperature of 75℃, and a misting disc speed of 21000 r / min. The adhesive powder is collected by a cyclone collector to obtain redispersible acrylic latex powder; (3) Mix deionized water and sodium hydroxide at a mass ratio of 1:0.025, stir at room temperature for 4 min, add 12 mm polypropylene fiber with a mass ratio of 0.1 times that of deionized water, continue stirring for 15 min, heat to 60℃ and soak for 7 h, take out, wash with deionized water 4 times, and dry at 70℃ for 7 h to obtain pre-modified polypropylene fiber; mix γ-glycidyl etheroxypropyltrimethoxysilane, deionized water, glacial acetic acid and anhydrous ethanol at a mass ratio of 1:0.25:0.013:10, stir at room temperature for 20 min to obtain silane hydrolysate; mix silane hydrolysate, polyvinylpyrrolidone and nanocellulose at a mass ratio of 1:0.005:0.04, stir at room temperature for 25 min to obtain spray solution; spray the spray solution evenly on the surface of pre-modified polypropylene fiber 4 times, let stand for 3 min each time, dry at 70℃ for 7 h, heat to 90℃ and dry for 4 h to obtain modified polypropylene fiber; (4) By mass, mix 55 parts cement, 2.5 parts fly ash, 3 parts mineral powder, 2.5 parts silica fume and 35 parts quartz sand evenly, stir at room temperature for 3 minutes, add 6 parts redispersible acrylic latex powder, 0.2 parts hydroxypropyl methylcellulose ether, 0.3 parts water-reducing agent, 0.2 parts defoamer and 0.2 parts water-repellent agent, continue stirring for 5 minutes, add 1 part modified polypropylene fiber, continue stirring for 2 minutes to obtain dry powder mixture; mix dry powder mixture and tap water at a water-cement ratio of 0.43 evenly, stir at room temperature for 4 minutes to obtain modified polymer cement waterproof mortar.

[0021] Example 3: A method for preparing modified polymer cement waterproof mortar, the method comprising the following steps: (1) By mass, 75 parts of deionized water, 1.3 parts of sodium dodecyl sulfate, and 0.9 parts of octylphenol polyoxyethylene ether were mixed evenly and stirred at room temperature for 5 min. Then, 45 parts of methyl methacrylate, 45 parts of butyl acrylate, 9 parts of lauryl methacrylate, 2.3 parts of acrylic acid, and 1.9 parts of N-hydroxymethylacrylamide were added, and stirring was continued for 15 min to obtain a pre-emulsion. 0.6 parts of potassium persulfate were dissolved in 16 parts of deionized water and stirred at room temperature for 5 min. The initiator was prepared by mixing 75 parts of deionized water, 0.9 parts of sodium bicarbonate, and 0.3 parts of potassium persulfate. Under nitrogen protection, the mixture was heated to 85°C and stirred for 5 minutes. 10% of the pre-emulsion was added and stirred for 15 minutes. The remaining 90% of the pre-emulsion and the initiator were added dropwise over 2 hours. The mixture was kept warm and matured for 2 hours. The temperature was lowered to 40°C, and the pH of the emulsion was adjusted to 8.5 with 5 wt% sodium hydroxide aqueous solution. The mixture was filtered to obtain an acrylic emulsion. (2) Polyvinyl alcohol and deionized water are mixed evenly at a mass ratio of 1:9.5, heated to 65℃ and stirred for 10 min, and cooled to room temperature to obtain a polyvinyl alcohol solution; acrylic emulsion and polyvinyl alcohol solution are mixed evenly at a mass ratio of 1:0.3, stirred for 10 min at room temperature, and sent to a spray dryer for drying, with an inlet air temperature of 130℃, an outlet air temperature of 80℃, and a misting disc rotation speed of 22000 r / min. The adhesive powder is collected by a cyclone collector to obtain redispersible acrylic latex powder; (3) Mix deionized water and sodium hydroxide at a mass ratio of 1:0.035, stir for 3 min at room temperature, add 12 mm polypropylene fiber at a mass ratio of 0.11 times that of deionized water, continue stirring for 10 min, heat to 65℃ and soak for 6 h, take out, wash with deionized water 5 times, and dry at 75℃ for 6 h to obtain pre-modified polypropylene fiber; mix γ-glycidyl oxypropyltrimethoxysilane, deionized water, glacial acetic acid and anhydrous ethanol at a mass ratio of 1:0.26:0.014:11, stir for 15 min at room temperature to obtain silane hydrolysate; mix silane hydrolysate, polyvinylpyrrolidone and nanocellulose at a mass ratio of 1:0.006:0.06, stir for 20-30 min at room temperature to obtain spray solution; spray the spray solution evenly on the surface of pre-modified polypropylene fiber 5 times, let stand for 2 min each time, dry at 75℃ for 6 h, heat to 95℃ and dry for 3 h to obtain modified polypropylene fiber; (4) By mass, mix 60 parts cement, 3 parts fly ash, 4 parts mineral powder, 3 parts silica fume and 40 parts quartz sand evenly, stir at room temperature for 2 minutes, add 6 parts redispersible acrylic latex powder, 0.2 parts hydroxypropyl methylcellulose ether, 0.4 parts water-reducing agent, 0.2 parts defoamer and 0.2 parts water-repellent agent, continue stirring for 4 minutes, add 1 part modified polypropylene fiber, continue stirring for 1 minute to obtain dry powder mixture; mix dry powder mixture and tap water at a water-cement ratio of 0.44 evenly, stir at room temperature for 3 minutes to obtain modified polymer cement waterproof mortar.

[0022] Comparative Example 1: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 1 differs from that in Example 2 only in that the air inlet temperature obtained by the spray dryer in step (2) is changed to 140°C. The remaining steps are the same as in Example 2.

[0023] Comparative Example 2: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 2 differs from that in Example 2 only in that the air inlet temperature obtained by the spray dryer in step (2) is changed to 150°C. The remaining steps are the same as in Example 2.

[0024] Comparative Example 3: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 3 differs from that in Example 2 in that steps (1) and (2) are omitted, and redispersible acrylic latex powder is not added in step (4). The remaining steps are the same as in Example 2.

[0025] Comparative Example 4: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 4 differs from that in Example 2 only in that the amount of redispersible acrylic latex powder added in step (4) is changed to 4 parts. The remaining steps are the same as in Example 2.

[0026] Comparative Example 5: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 5 differs from that in Example 2 only in that the amount of redispersible acrylic latex powder added in step (4) is changed to 8 parts. The remaining steps are the same as in Example 2.

[0027] Comparative Example 6: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 6 differs from that in Example 2 only in that the length of the polypropylene fiber in step (3) is changed to 6 mm. The remaining steps are the same as in Example 2.

[0028] Comparative Example 7: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 7 differs from that in Example 2 only in that the length of the polypropylene fiber in step (3) is changed to 9 mm. The remaining steps are the same as in Example 2.

[0029] Comparative Example 8: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 8 differs from that in Example 2 only in that the length of the polypropylene fiber in step (3) is changed to 18 mm. The remaining steps are the same as in Example 2.

[0030] Comparative Example 9: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 9 differs from that in Example 2 in that step (3) is omitted, and modified polypropylene fibers are not added in step (4). The remaining steps are the same as in Example 2.

[0031] Comparative Example 10: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 10 differs from that in Example 2 only in that the amount of modified polypropylene fiber added in step (4) is changed to 0.5 parts. The remaining steps are the same as in Example 2.

[0032] Comparative Example 11: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 11 differs from that in Example 2 only in that the amount of modified polypropylene fiber added in step (4) is changed to 1.5 parts. The remaining steps are the same as in Example 2.

[0033] Comparative Example 12: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 12 differs from that in Example 2 only in that the amount of hydroxypropyl methylcellulose ether added in step (4) is changed to 0.1 parts. The remaining steps are the same as in Example 2.

[0034] Comparative Example 13: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 13 differs from that in Example 2 only in that the amount of hydroxypropyl methylcellulose ether added in step (4) is changed to 0.3 parts. The remaining steps are the same as in Example 2.

[0035] Comparative Example 14: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 14 differs from that in Example 2 only in that the amount of defoamer added in step (4) is changed to 0.15 parts. The remaining steps are the same as in Example 2.

[0036] Comparative Example 15: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 15 differs from that in Example 2 only in that the amount of defoamer added in step (4) is changed to 0.25 parts. The remaining steps are the same as in Example 2.

[0037] Comparative Example 16: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 16 differs from that in Example 2 only in that the amount of water-repellent agent added in step (4) is changed to 0.15 parts. The remaining steps are the same as in Example 2.

[0038] Comparative Example 17: The preparation method of the modified polymer cement waterproof mortar in Comparative Example 17 differs from that in Example 2 only in that the amount of water-repellent agent added in step (4) is changed to 0.25 parts. The remaining steps are the same as in Example 2.

[0039] Test Example 1 Latex powder performance testing Test Method: Observe the color of the redispersible acrylic latex powder in the examples and comparative examples, whether it is a free-flowing powder, and whether there is any adhesion between the powders. Prepare a 10% redispersible latex powder solution, stir, let it stand, and observe the layering time and situation to evaluate the redispersibility of the redispersible acrylic latex powder. No obvious layering or layering occurring after more than 60 minutes is considered good redispersibility; obvious layering occurring within 10-60 minutes is considered poor redispersibility; obvious layering occurring within less than 10 minutes is considered poor redispersibility. The results are shown in Table 1.

[0040] Table 1

[0041] By comparing Example 2 and Comparative Examples 1-2, it can be found that reducing the inlet temperature of the spray dryer can produce a powder with better flowability. Therefore, the optimal spray drying conditions for redispersible acrylic latex powder are determined to be 130°C.

[0042] Test Example 2 Test on the effect of redispersible acrylic latex powder on the performance of modified polymer cement waterproof mortar Test method: The modified polymer cement waterproof mortar of the examples and comparative examples was filled into a 40mm×40mm×160mm mold in two batches. The test blocks were placed in a standard curing box for 24 hours and then demolded. After demolding, the test blocks were placed in a standard curing box for 28 days to obtain standard specimens, which were used for water absorption rate and impermeability pressure test.

[0043] Water absorption test: According to DLT 5126-2001, the test block was placed in an 80℃ oven to dry for 48 hours and cooled to room temperature. Its mass was weighed and marked as M1. It was then soaked in water at room temperature for 48 hours. The surface water was wiped off with a dry cloth and its mass was weighed and marked as M2. The water absorption rate of the modified polymer cement waterproof mortar was calculated as (M2-M1) / M1×100%.

[0044] Permeability pressure test: According to JGJ / T 70-2009, after the specimen is taken out, it is rinsed clean and the surface is air-dried naturally. The specimen is then wrapped with paraffin wax as a sealant and installed in a permeameter to conduct a water permeability test to test the mortar's permeability pressure.

[0045] Bond strength test: According to JC / T 984-2011, a special rubber mold was placed on a cement-based matrix block. The modified polymer-modified cement waterproof mortar of the examples and comparative examples was poured into the mold and smoothed. After dry curing for 24 hours, the mold was removed. Tensile bond strength tests were conducted on a universal testing machine at a loading speed of 5 mm / min. The results are shown in Table 2.

[0046] Table 2

[0047] A comparison of the experimental data from Examples 1-3 and Comparative Examples 3-5 in Table 2 reveals that when the amount of redispersible acrylic latex powder added is too small, the latex powder cannot form a continuous polymer film inside the waterproof mortar after being dispersed in water, resulting in the anti-seepage pressure and bonding strength of the modified polymer cement waterproof mortar being lower than the standard requirements. When the amount of redispersible acrylic latex powder added is too large, a large amount of polyvinyl alcohol or other highly hydrophilic protective colloids cannot be completely reacted, consumed, or absorbed by the waterproof mortar system. Under prolonged immersion conditions, these free hydrophilic components cause the continuous polymer film and hydrophobic film formed by the redispersible latex powder to redissolve, reducing the water resistance of the modified polymer cement waterproof mortar and leading to a significant increase in water absorption. Therefore, the optimal amount of redispersible acrylic latex powder added is determined to be 6 parts.

[0048] Test Example 3 Test on the Influence of Polypropylene Fiber on the Performance of Modified Polymer Cement Waterproof Mortar Test method: The standard specimen preparation method and the anti-permeability pressure test method are the same as those in Test Example 2.

[0049] Shear strength test: First, the standard specimen was cut in half to make small test blocks of 40mm×40mm×80mm, which were then placed in a curing room for curing. For the shear bond strength test, the cut surface of the small test block was placed in the middle of a triple mold, and then the mortar was molded onto the other half of the triple mold. The specimens were cured to the specified age, and the flexural strength was used to characterize the shear bond strength of the mortar under test. The results are shown in Table 3.

[0050] Table 3

[0051] A comparison of the experimental data from Examples 1-3 and Comparative Examples 6-11 in Table 3 reveals that, under the same addition amount, the anti-seepage pressure trend first increases and then decreases; at the same length, with the continuous increase of polypropylene fibers, its shear bond strength gradually increases, reaching its maximum value when 1 part is added; polypropylene fibers mainly act as supporting materials and crack-resistant agents in polymer cement waterproof mortar, reducing the number of cracks, improving the micro-pore structure, improving the interface transition zone between cement stone and aggregate, enhancing density, and improving its anti-seepage ability; however, excessively long and excessive polypropylene fibers can lead to agglomeration, affecting the workability of the mortar and making it difficult to disperse evenly, thus affecting its weak surfaces, generating some harmful voids, reducing density, and reducing its anti-seepage ability; the optimal fiber length within the scope of this experiment is 12 mm and the optimal dosage is 1 part.

[0052] Test Example 3 Test on the effect of additives on the performance of modified polymer cement waterproof mortar Test methods: The preparation method of the standard specimen and the test methods for water absorption and impermeability pressure are the same as those in Test Example 2. The results are shown in Table 4.

[0053] Table 4

[0054] A comparison of the experimental data from Examples 1-3 and Comparative Examples 12-13 in Table 4 reveals that cellulose ether itself has a water-retaining effect, forming water condensation inside the mortar, introducing microbubbles, and disrupting the continuity of microcapillary channels, which helps reduce the water absorption rate of the mortar. Increasing the cellulose ether content reduces the water absorption rate of the modified polymer cement waterproof mortar; at a dosage of 0.3 parts, the downward trend in water absorption begins to slow down. Simultaneously, the water-retaining properties of cellulose ether exhibit a ball-bead effect, which significantly reduces micro-cracks inside the modified polymer cement waterproof mortar, improving its density and flexibility, thereby enhancing its impermeability. Test results show that the modified polymer cement waterproof mortar with 0.2 parts of cellulose ether exhibits the best performance.

[0055] A comparison of the experimental data from Examples 1-3 and Comparative Examples 14-15 in Table 4 reveals that the addition of defoamer significantly reduces the overall air content and improves density, thereby reducing water absorption and enhancing waterproofing performance. Defoamer can improve the microporous structure of the modified polymer cement waterproof mortar, optimize internal porosity, and make the polymer mortar paste more compact, further improving its impermeability. Test results show that the modified polymer cement waterproof mortar with 0.2 parts of defoamer exhibits the best performance.

[0056] A comparison of the experimental data from Examples 1-3 and Comparative Examples 16-17 in Table 4 reveals that the organosilicon water-repellent agent can exist on the surface of cement particles, inhibiting the water absorption of the modified polymer cement waterproof mortar. This allows the silanes linked together through cross-linking to be firmly fixed on the surface of the cement mortar pores. The water-repellent agent can reduce the generation of micro-cracks due to drying shrinkage in the polymer cement waterproof mortar in the later stages, thereby improving its waterproof and impermeable performance. The test results show that the modified polymer cement waterproof mortar with 0.2 parts of water-repellent agent exhibits the best performance.

[0057] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified polymer cement waterproof mortar, characterized in that, The modified polymer cement waterproof mortar is prepared by mixing deionized water, sodium dodecyl sulfate, octylphenol polyoxyethylene ether, methyl methacrylate, butyl acrylate, lauryl methacrylate, acrylic acid, and N-hydroxymethylacrylamide, and polymerizing with potassium persulfate to obtain an acrylic emulsion; mixing and drying the acrylic emulsion and polyvinyl alcohol solution to obtain redispersible acrylic latex powder; spraying a mixture of silane hydrolysate, polyvinylpyrrolidone, and nanocellulose onto the surface of pre-modified polypropylene fibers to obtain modified polypropylene fibers; and mixing the dry powder mixture with tap water at a water-cement ratio of 0.42~0.

44. The polyvinyl alcohol solution is prepared by mixing polyvinyl alcohol with deionized water; The silane hydrolysate is prepared by hydrolyzing γ-glycidoxypropyltrimethoxysilane. The pre-modified polypropylene fiber is obtained by alkali etching of the polypropylene fiber surface with sodium hydroxide; The dry powder mixture is prepared by mixing 50-60 parts of cement, 2-3 parts of fly ash, 2-4 parts of mineral powder, 2-3 parts of silica fume, 30-40 parts of quartz sand, 4-8 parts of redispersible acrylic latex powder, 0.1-0.3 parts of hydroxypropyl methylcellulose ether, 0.2-0.4 parts of water-reducing agent, 0.15-0.25 parts of defoamer, 0.15-0.25 parts of water-repellent agent, and 0.5-1.5 parts of modified polypropylene fiber.

2. A method for preparing modified polymer cement waterproof mortar, characterized in that, The preparation method of the modified polymer cement waterproof mortar includes the following preparation steps: (1) Mix 65-75 parts of deionized water, 0.7-0.9 parts of sodium bicarbonate and 0.1-0.3 parts of potassium persulfate evenly, heat to 75-85℃ under nitrogen protection, stir for 5-10 min, add 10% of pre-emulsion, stir for 15-25 min, add the remaining 90% of pre-emulsion and initiator dropwise at a uniform rate over 2-3 h, keep warm and mature for 1-2 h, cool to 30-40℃, adjust the pH of the emulsion to 8.5-9.5 with 5wt% sodium hydroxide aqueous solution, filter, and obtain acrylic emulsion; (2) Mix acrylic emulsion and polyvinyl alcohol solution at a mass ratio of 1:(0.2~0.3) until uniform, stir at room temperature for 10~20 min, send to spray dryer for drying, inlet air 130~150℃, outlet air 70~80℃, atomizing disc speed 20000~22000r / min, collect the adhesive powder through cyclone collector to obtain redispersible acrylic latex powder; (3) Spray the coating liquid evenly on the surface of the pre-modified polypropylene fiber 3 to 5 times, let it stand for 2 to 4 minutes each time, dry it at 65 to 75℃ for 6 to 8 hours, and then heat it to 85 to 95℃ for 3 to 5 hours to obtain the modified polypropylene fiber. (4) By mass, mix 50-60 parts of cement, 2-3 parts of fly ash, 2-4 parts of mineral powder, 2-3 parts of silica fume, and 30-40 parts of quartz sand evenly, stir at room temperature for 2-4 minutes, add 4-8 parts of redispersible acrylic latex powder, 0.1-0.3 parts of hydroxypropyl methylcellulose ether, 0.2-0.4 parts of water-reducing agent, 0.15-0.25 parts of defoamer, and 0.15-0.25 parts of water-repellent agent, continue stirring for 4-6 minutes, add 0.5-1.5 parts of modified polypropylene fiber, continue stirring for 1-3 minutes to obtain dry powder mixture; mix the dry powder mixture and tap water at a water-cement ratio of 0.42-0.44 evenly, stir at room temperature for 3-5 minutes to obtain modified polymer cement waterproof mortar.

3. The method for preparing modified polymer cement waterproof mortar according to claim 2, characterized in that, The preparation process of the preemulsion in step (1) is as follows: by mass, 65-75 parts of deionized water, 1.1-1.3 parts of sodium dodecyl sulfate, and 0.7-0.9 parts of octylphenol polyoxyethylene ether are mixed evenly and stirred at room temperature for 5-15 minutes. Then, 35-45 parts of methyl methacrylate, 35-45 parts of butyl acrylate, 7-9 parts of lauryl methacrylate, 2.1-2.3 parts of acrylic acid, and 1.7-1.9 parts of N-hydroxymethylacrylamide are added and stirred for another 15-25 minutes to obtain the preemulsion.

4. The method for preparing modified polymer cement waterproof mortar according to claim 2, characterized in that, The preparation process of the drop initiator in step (1) is as follows: Dissolve 0.4 to 0.6 parts of potassium persulfate in 14 to 16 parts of deionized water and stir at room temperature for 5 to 7 minutes to obtain the drop initiator.

5. The method for preparing modified polymer cement waterproof mortar according to claim 2, characterized in that, The preparation process of the polyvinyl alcohol solution in step (2) is as follows: polyvinyl alcohol and deionized water are mixed evenly at a mass ratio of 1:(8.5~9.5), heated to 55~65℃ and stirred for 10~20min, and cooled to room temperature to obtain the polyvinyl alcohol solution.

6. The method for preparing modified polymer cement waterproof mortar according to claim 5, characterized in that, The polyvinyl alcohol is of type 1788, with a degree of alcoholysis of 87.0 mol% and a viscosity of 25.0 cps.

7. The method for preparing modified polymer cement waterproof mortar according to claim 2, characterized in that, The preparation process of the spraying liquid in step (3) is as follows: γ-glycidyl etheroxypropyltrimethoxysilane, deionized water, glacial acetic acid and anhydrous ethanol are mixed evenly in a mass ratio of 1:(0.24~0.26):(0.012~0.014):(9~11) and stirred at room temperature for 15~25 min to obtain silane hydrolysate; silane hydrolysate, polyvinylpyrrolidone and nanocellulose are mixed evenly in a mass ratio of 1:(0.004~0.006):(0.02~0.06) and stirred at room temperature for 20~30 min to obtain spraying liquid.

8. The method for preparing modified polymer cement waterproof mortar according to claim 2, characterized in that, The preparation process of the pre-modified polypropylene fiber in step (3) is as follows: Deionized water and sodium hydroxide are mixed evenly at a mass ratio of 1:(0.015~0.035), stirred at room temperature for 3~5 min, 0.09~0.11 times the mass of deionized water of 6~18 mm polypropylene fiber is added, stirred for 10~20 min, heated to 55~65℃ and soaked for 6~8 h, taken out, washed with deionized water 3~5 times, and dried at 65~75℃ for 6~8 h to obtain the pre-modified polypropylene fiber.

9. The method for preparing modified polymer cement waterproof mortar according to claim 8, characterized in that, The polypropylene fiber has a length of 12 mm, a diameter of 20 μm, a density of 0.91 g / cm3, and an alkali resistance of ≥96%.

10. The method for preparing modified polymer cement waterproof mortar according to claim 2, characterized in that, The cement used in step (4) is P·O 42.5 ordinary Portland cement; the fly ash is grade 1 fly ash; the mineral powder is S95 mineral powder; the silica fume is grade 1 silica fume; the quartz sand is a mixture of 40~70 mesh fine sand and 80~120 mesh coarse sand in a ratio of 3:7; the viscosity of the hydroxypropyl methylcellulose ether is 200000 mPa·s; the water-reducing agent is 11A polycarboxylate water-reducing agent; the defoamer is an organosilicon solid defoamer; and the water-repellent agent is sodium methylsilicate dry powder water-repellent agent.

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