Environment-friendly polymer cement waterproof coating with high toughness and high adhesion and preparation method thereof

Abstract

The application discloses a high-toughness and high-adhesion environment-friendly polymer cement waterproof coating and a preparation method thereof, and relates to the technical field of waterproof coating preparation and waterproof coating. The application introduces mercapto-modified nano silicon dioxide and organosilicon-modified silicone-acrylate emulsion to generate thiol-ene click chemistry reaction, and builds a dynamic covalent interpenetrating network, thereby solving the problem that the elongation rate decreases when the strength of traditional coating increases. Meanwhile, the amphiphilic core-shell styrene-acrylate emulsion with a shell rich in silane functional groups is used to realize strong anchoring through chemical bonding on a humid base. In the preparation method, the reaction rate is controlled by low-temperature time sequence dropping, and the active core-shell particles are protected by a delayed addition of ASE60 thickening agent process. The application replaces ortho phenyl plasticizer with tributyl citrate, and has excellent physical properties and environmental protection characteristics, and is particularly suitable for high-humidity and complex working conditions such as basement and kitchen and bathroom.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly waterproof coating preparation technology, specifically, to a high-toughness, high-adhesion environmentally friendly polymer cement waterproof coating and its preparation method. Background Technology

[0002] With the increasing standards for green building and underground engineering waterproofing, polymer cement (JS) waterproofing coatings are widely used due to their environmental friendliness and cold-applied construction advantages. However, existing products still face insurmountable technical bottlenecks in practical applications, severely restricting the improvement of project quality.

[0003] The primary pain point lies in the "inverted relationship between strength and toughness." Traditional JS coatings typically increase tensile strength by increasing cement content or rigid fillers, but this often leads to brittle coatings, a significant decrease in elongation at break, and micro-cracks in the substrate that easily cause coating cracking and leakage. Although Chinese patent CN110256011A attempts to introduce silicone-modified emulsions, its essence is still physical blending, failing to fundamentally solve the problem of "the conflict between rigidity and flexibility," resulting in poor durability under complex deformation conditions.

[0004] Secondly, adhesion failure on damp substrates is another major problem. During the construction of new basements and kitchens / bathrooms, the concrete substrate is typically in a high-humidity state (moisture content >10%). Polymer emulsions in traditional coatings are easily blocked by the water film on the substrate, failing to form effective wetting and anchoring, leading to a sharp decline in adhesion strength. Prolonged immersion in water can easily result in blistering and delamination. Current technologies often use the addition of silane coupling agents to improve this, but in high-humidity environments, silanes are prone to premature hydrolysis and failure, unable to provide long-lasting chemical bonding.

[0005] Furthermore, the limitations in environmental protection and additive selection are obvious. To improve flexibility, some products often use phthalate plasticizers, which pose a migration risk and do not conform to the environmental protection trend of green building materials; while in the thickening system, conventional alkali-swellable thickeners (such as ASE60) can easily encapsulate functional components if used improperly, further weakening the interfacial performance.

[0006] In summary, current technologies have not yet provided a solution that simultaneously satisfies the requirements of high strength and toughness, ultra-strong adhesion to high-humidity substrates, and overall environmental friendliness. How to overcome the mutual constraints between physical properties through precise microstructural design and achieve interfacial chemical bonding is a critical challenge that urgently needs to be addressed in this technical field. Summary of the Invention

[0007] The purpose of this invention is to provide a high-toughness, high-adhesion environmentally friendly polymer cement waterproof coating and its preparation method, which solves the problems of mutual restriction between tensile strength and elongation at break, adhesion failure on damp substrates, and migration of environmentally friendly additives in existing polymer cement waterproof coatings.

[0008] To solve the above problems, the present invention employs the following technical means: A high-toughness, high-adhesion environmentally friendly polymer cement waterproof coating, comprising liquid and powder components; The liquid material comprises, by weight, 30-45 parts deionized water, 180-220 parts modified silicone-acrylic emulsion, 50-80 parts amphiphilic core-shell styrene-acrylic emulsion, 5-12 parts mercapto-modified nano-silica dispersion, 3-6 parts propylene glycol methyl ether, 4-8 parts tributyl citrate, 1-2 parts bactericide, 0.5-1.5 parts pH adjuster, 1.5-3 parts polyurethane thickener, and 1-2 parts ASE60 thickener; The surface grafting density of the thiol-modified nano-silica is 1.2~2.5 μmol / m. 2 It is used to undergo a thiol-olefin click chemistry reaction with the modified silicone-acrylic emulsion to form an interpenetrating network structure; The shell layer of the amphiphilic core-shell styrene-acrylic emulsion contains silane coupling agent functional groups for forming chemical bonds with the wet substrate. The powder is 1.5-1.8 times the weight of the liquid and is made by mixing 42.5 cement and quartz sand in a mass ratio of 1:1.2.

[0009] In this way, a dynamic covalent network is formed through the thiol-olefin click reaction between mercapto-SiO2 and silicone-acrylic emulsion, resulting in both high strength and high elongation. At the same time, the silane groups of the core-shell emulsion form Si-O-Ca bonds with the substrate, thereby solving the problem of adhesion failure on moist substrates; and a specific liquid-to-powder ratio ensures a balance between the inorganic rigid framework and the organic flexible network.

[0010] This results in a finished material that combines high tensile strength and high elongation at break, exhibiting both rigidity and flexibility, while also demonstrating high bonding strength on a substrate with a 15% moisture content.

[0011] Preferably, the mercapto-modified nano silica has a particle size of 20-50 nm, is surface-grafted with γ-methacryloxypropyltrimethoxysilane or 3-mercaptopropyltrimethoxysilane, and is dispersed in propylene glycol methyl ether in a 40% solids content.

[0012] By limiting the particle size and grafting density, it is ensured that the nanoparticles participate in the reaction only during film formation, preventing premature reaction and gelation during storage. Specifically, if the density is too low, network formation is impossible, while if it is too high, brittleness occurs; a 40% solids content dispersion provides steric hindrance to prevent nanoparticle aggregation.

[0013] Furthermore, the core layer of the amphiphilic core-shell styrene-acrylic emulsion is copolymerized from butyl acrylate and styrene, with a glass transition temperature of -25°C to -15°C; the shell layer is copolymerized from acrylic acid, acrylamide and γ-methacryloyloxypropyltrimethoxysilane, with the silane coupling agent accounting for 1.5% to 3.0% of the total monomers.

[0014] The core layer provides low-temperature flexibility and rubbery elasticity to absorb base layer stress, while the shell layer provides chemical anchoring points. The limited silane content is designed to balance reactivity and storage stability.

[0015] This ensures that a continuous film can still be formed at temperatures above 5°C and in humid environments, and that it will not fall off even after prolonged immersion in water.

[0016] Furthermore, the modified silicone-acrylic emulsion is an organosilicon-modified highly crosslinked silicone-acrylic emulsion with a pH value of 7.5-8.5 and a minimum film-forming temperature of 10-15℃.

[0017] Furthermore, the liquid material also includes 0.5 to 1.0 parts of ethyl acetoacetate modified titanate coupling agent, which is mixed into the liquid material before the thickener is added during the preparation process.

[0018] This allows the use of ethyl acetoacetate-modified titanate coupling agents to form a "chelate ring" structure between inorganic powders and organic polymers. This prevents the coating from peeling off at the interface due to thermal expansion and contraction under alternating hot and cold conditions. Compared to single-bond connections, chelate rings offer better flexibility and hydrolysis resistance, acting as molecular springs.

[0019] In addition, a method for preparing the aforementioned environmentally friendly polymer cement waterproof coating includes the following steps: (1) Preparation of thiol phase dispersion: Deionized water, propylene glycol methyl ether and pH adjuster are mixed and thiol-modified nano silica dispersion is added. The mixture is then sheared at 800-1000 r / min for 15 minutes at 25±2℃ to form thiol phase dispersion. (2) Preparation of emulsion phase: Mix the remaining deionized water and tributyl citrate, add amphiphilic core-shell structure styrene-acrylic emulsion and modified silicone-acrylic emulsion, control the pH of the system to 8.5-9.0, and premix by stirring at a low speed of 200-300 r / min to form an emulsion phase; (3) Low-temperature sequential droplet polymerization: The mercapto phase dispersion obtained in step (1) is added to the emulsion phase obtained in step (2) by droplet addition. The droplet addition time is ≥15 minutes, the temperature is controlled ≤35℃ throughout the process, and the stirring rate is 400-500r / min to form a mixture. (4) Delayed thickening: Within 5 minutes before mixing the powder, add polyurethane thickener and ASE60 thickener to the mixture in step (3) and adjust the viscosity by stirring at 600-800r / min. (5) Powder mixing: Add the powder slowly to the liquid obtained in step (4) while stirring, continue stirring until there are no powder lumps, let stand to defoam, and obtain the finished product.

[0020] In this way, by premixing in stages, reactive components are isolated to prevent premature reaction; the key to achieving high elongation is to use low-temperature dropwise addition to control reaction kinetics and avoid local overheating that leads to explosive polymerization; and the key to solving wet stickiness is to use delayed thickening to protect the surface activity of core-shell particles.

[0021] This ensures that the dual-network structure formed by the aforementioned materials can be accurately constructed, avoiding side reactions.

[0022] Furthermore, the dropping time in step (3) is 15-20 minutes, and the temperature change of the system is monitored during the dropping process. When the temperature exceeds 35°C, the dropping is paused or the dropping speed is reduced.

[0023] In this step, a dropping time of at least 15 minutes ensures that the thiol groups have sufficient time to fully contact and react uniformly with the emulsion double bonds. If the speed is too fast, it will lead to excessively high local crosslinking density, forming hard spots that become fracture sources under stress. This eliminates stress concentration points within the coating film and prevents the formation of microcracks.

[0024] Furthermore, the polyurethane thickener described in step (4) is pre-diluted at a ratio of 1:4, and the ASE60 thickener is a non-associative anionic alkali-swelling thickener.

[0025] Thus, a 1:4 diluted polyurethane thickener provides high shear viscosity to prevent sagging, while ASE60 provides low shear viscosity to prevent settling. The non-associative formulation is specified to avoid unnecessary association with the core-shell emulsion, shielding the active groups. This prevents coating sagging while ensuring spreadability during application.

[0026] Furthermore, step (6) is also included: the coated coating is first cured at 25°C and 60% relative humidity for 3 days, and then cured at 50°C and 40% relative humidity for 1 day.

[0027] In this way, the 50℃ heat treatment provides additional activation energy for the thiol-alkene reaction, promoting the cross-linking of unreacted thiol groups at room temperature. Simultaneously, it accelerates cement hydration, resulting in a denser interfacial bond.

[0028] Furthermore, the aforementioned environmentally friendly polymer cement waterproof coating is applied to the waterproofing treatment of damp concrete substrates or newly poured, undried substrates with a moisture content of 10% to 15%.

[0029] The present invention has the following beneficial effects during use: This application utilizes a thiol-olefin click chemistry reaction between mercapto-modified nano-silica and the double bonds in silicone-acrylic emulsion to construct a dynamic covalent interpenetrating network at the molecular level. When the coating is subjected to tension, the dynamic covalent bonds can dissipate energy through reversible breakage, thereby increasing tensile strength while maintaining a high level of elongation at break, completely breaking the incompatibility problem of increasing strength and decreasing elongation.

[0030] By introducing an amphiphilic core-shell styrene-acrylic emulsion, the silane groups in its shell hydrolyze to generate silanols under alkaline and humid conditions, which then condense with cement hydration products to form Si-O-Ca chemical bonds. Combined with the plasticizing effect of tributyl citrate, the coating achieves strong adhesion even on substrates with a moisture content of 15%, and maintains high strength retention after immersion in water, thus solving the interfacial delamination problem caused by water film barrier.

[0031] By using tributyl citrate instead of traditional phthalic plasticizers, the migration of harmful substances is eliminated; by delaying the addition of ASE60 thickener, the thickener is prevented from encapsulating the active sites of the core-shell emulsion, ensuring the best balance between construction rheology and interfacial activity. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0033] Therefore, the following detailed description of embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0035] An environmentally friendly polymer cement waterproof coating comprises a liquid component and a powder component. The liquid component, by weight, comprises: 30-45 parts deionized water, 180-220 parts organosilicon-modified highly crosslinked silicone-acrylic emulsion (SF900SH), 50-80 parts amphiphilic core-shell styrene-acrylic emulsion, 5-12 parts mercapto-modified nano-silica dispersion, 3-6 parts propylene glycol methyl ether, 4-8 parts tributyl citrate, 1-2 parts bactericide, 0.5-1.5 parts AMP-95 pH adjuster, 1.5-3 parts polyurethane thickener, and 1-2 parts ASE60 thickener. The surface grafting density of the mercapto-modified nano-silica is 1.2-2.5 μmol / m²; the shell layer of the amphiphilic core-shell styrene-acrylic emulsion contains silane coupling agent functional groups. The powder is made by mixing 42.5 cement and quartz sand in a mass ratio of 1:1.2, which is 1.5-1.8 times the weight of the liquid.

[0036] Preparation methods include: (1) Deionized water, propylene glycol methyl ether, pH adjuster and mercapto-modified nano-silica were dispersed by high-speed shearing at 25±2℃ to form a mercapto phase dispersion slurry; (2) Premix the remaining deionized water, tributyl citrate and the two emulsions at low speed, and control the pH to 8.5-9.0; (3) The mercapto phase dispersion is added to the emulsion phase at low temperature within ≥15 minutes, while controlling the temperature to ≤35℃; (4) Add polyurethane thickener and ASE60 thickener 5 minutes before mixing the powder to adjust the viscosity; (5) After mixing the powder, let it stand to defoam.

[0037] The following detailed description is provided in conjunction with specific embodiments. Example

[0038] Formula: Liquid component by weight: 38 parts deionized water, 200 parts SF900SH silicone-acrylic emulsion, 60 parts amphiphilic core-shell styrene-acrylic emulsion (shell layer contains 2% silane), 8 parts mercapto-modified nano-silica dispersion (grafting density 1.8 μmol / m²), 4 parts propylene glycol methyl ether, 6 parts tributyl citrate, 1.5 parts bactericide, 1 part AMP-95, 2 parts polyurethane thickener, 1.5 parts ASE60 thickener. Powder component is 1.6 times the liquid component (42.5 cement: quartz sand = 1:1.2).

[0039] Preparation process: Strictly follow the "low-temperature sequential dropwise addition" and "delayed thickening" process. The thiol phase is prepared at 25°C and added dropwise to the emulsion phase over 15 minutes, with the temperature ≤35°C throughout the process. ASE60 is added 5 minutes before powder mixing.

[0040] Performance testing (standard conditions): Tensile strength: 3.82 MPa Elongation at break: 168% Wet substrate bond strength (moisture content 15%): 1.48 MPa Bond strength retention rate after immersion in water for 168 hours: 93%.

[0041] Comparative Example 1 The formulation differs from Example 1 in that the mercapto-modified nano silica is replaced with an equal amount of unmodified ordinary fumed silica.

[0042] The preparation process is the same as in Example 1.

[0043] Performance testing: Tensile strength: 3.05 MPa Elongation at break: 72% Wet substrate bond strength: 1.35 MPa In this comparative example, due to the lack of thiol groups to undergo click chemical reactions with the emulsion, the nanoparticles exist only as physical fillers, resulting in a brittle coating that cannot dissipate stretching energy. Therefore, the dynamic network formed by thiol-modified nano-silica has a key influence on the high elongation.

[0044] Comparative Example 2 Compared with Example 1, the formulation differs in that the amphiphilic core-shell styrene-acrylic emulsion is removed, and an equal amount of ordinary styrene-acrylic emulsion is used instead, with an additional 0.5 parts of conventional KH-570 silane coupling agent added.

[0045] The preparation process is the same as in Example 1.

[0046] Performance testing: Tensile strength: 3.75 MPa Elongation at break: 160 MPa Wet substrate bond strength: 0.78 MPa In this comparative example, conventional silanes prematurely hydrolyze and fail in the aqueous phase, and cannot displace the water film on the base surface through the hydrophilic shell like a core-shell emulsion. Although silanes are added, chemical anchoring cannot be achieved. Therefore, the core-shell structure with anchoring effect formed in this application has a crucial impact on wet adhesion.

[0047] Comparative Example 3 The same formulation as in Example 1 was used.

[0048] The preparation process adopts the conventional JS coating preparation process. All raw materials (including mercapto slurry, two emulsions, and thickener) are added to the mixing tank at one time and stirred at high speed for 30 minutes, followed by the addition of powder.

[0049] Performance testing: Tensile strength: 2.15 MPa Elongation at break: 95% Wet substrate bond strength: 0.85 MPa In this comparative example, the thickener prematurely encapsulated the core-shell emulsion particles, and the thiol groups and the emulsion under high temperature and high speed shearing caused explosive polymerization (local gelation), resulting in an uneven microstructure and an inability to form an effective interpenetrating network.

[0050] Comparative Example 4 The formula differs from Example 1 in that tributyl citrate is replaced with an equal amount of dibutyl phthalate.

[0051] The preparation process is the same as in Example 1.

[0052] Performance testing: Tensile strength: 3.70 MPa Elongation at break: 155% Wet substrate bond strength: 1.20 MPa In this comparative example, DBP is a small molecule plasticizer. Although its short-term plasticizing effect is acceptable, it poses a risk of migration and has a swelling side effect on wet-tack interfaces, leading to a decrease in wet-tack strength. Therefore, environmentally friendly tributyl citrate plays a crucial role in ensuring interface stability.

[0053] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-toughness, high-adhesion environmentally friendly polymer cement waterproof coating, characterized in that, Including liquid and powder materials; The liquid material comprises, by weight, 30-45 parts deionized water, 180-220 parts modified silicone-acrylic emulsion, 50-80 parts amphiphilic core-shell styrene-acrylic emulsion, 5-12 parts mercapto-modified nano-silica dispersion, 3-6 parts propylene glycol methyl ether, 4-8 parts tributyl citrate, 1-2 parts bactericide, 0.5-1.5 parts pH adjuster, 1.5-3 parts polyurethane thickener, and 1-2 parts ASE60 thickener; The surface grafting density of the thiol-modified nano-silica is 1.2~2.5 μmol / m. 2 It is used to undergo a thiol-olefin click chemistry reaction with the modified silicone-acrylic emulsion to form an interpenetrating network structure; The shell layer of the amphiphilic core-shell styrene-acrylic emulsion contains silane coupling agent functional groups for forming chemical bonds with the wet substrate. The powder is 1.5-1.8 times the weight of the liquid and is made by mixing 42.5 cement and quartz sand in a mass ratio of 1:1.

2.

2. The waterproof coating according to claim 1, characterized in that, The mercapto-modified nano silica has a particle size of 20-50 nm. It is surface-grafted with γ-methacryloxypropyltrimethoxysilane or 3-mercaptopropyltrimethoxysilane and dispersed in propylene glycol methyl ether in a 40% solids content.

3. The waterproof coating according to claim 1, characterized in that, The core layer of the amphiphilic core-shell styrene-acrylic emulsion is copolymerized from butyl acrylate and styrene, with a glass transition temperature of -25°C to -15°C; the shell layer is copolymerized from acrylic acid, acrylamide and γ-methacryloyloxypropyltrimethoxysilane, with the silane coupling agent accounting for 1.5%-3.0% of the total monomers.

4. The waterproof coating according to claim 1, characterized in that, The modified silicone-acrylic emulsion is an organosilicon-modified highly crosslinked silicone-acrylic emulsion with a pH value of 7.5-8.5 and a minimum film-forming temperature of 10-15℃.

5. The waterproof coating according to claim 1, characterized in that, The liquid material also includes 0.5 to 1.0 parts of ethyl acetoacetate modified titanate coupling agent, which is mixed into the liquid material before the thickener is added during the preparation process.

6. A method for preparing the environmentally friendly polymer cement waterproof coating according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Preparation of thiol phase dispersion: Deionized water, propylene glycol methyl ether and pH adjuster are mixed and thiol-modified nano silica dispersion is added. The mixture is then sheared at 800-1000 r / min for 15 minutes at 25±2℃ to form thiol phase dispersion. (2) Preparation of emulsion phase: Mix the remaining deionized water and tributyl citrate, add amphiphilic core-shell structure styrene-acrylic emulsion and modified silicone-acrylic emulsion, control the pH of the system to 8.5-9.0, and premix by stirring at a low speed of 200-300 r / min to form an emulsion phase; (3) Low-temperature sequential droplet polymerization: The mercapto phase dispersion obtained in step (1) is added to the emulsion phase obtained in step (2) by droplet addition. The droplet addition time is ≥15 minutes, the temperature is controlled ≤35℃ throughout the process, and the stirring rate is 400-500r / min to form a mixture. (4) Delayed thickening: Within 5 minutes before mixing the powder, add polyurethane thickener and ASE60 thickener to the mixture in step (3) and adjust the viscosity by stirring at 600-800r / min. (5) Powder mixing: Add the powder slowly to the liquid obtained in step (4) while stirring, continue stirring until there are no powder lumps, let stand to defoam, and obtain the finished product.

7. The preparation method according to claim 6, characterized in that, The dropping time in step (3) is 15-20 minutes, and the temperature change of the system is monitored during the dropping process. When the temperature exceeds 35°C, the dropping is stopped or the dropping speed is reduced.

8. The preparation method according to claim 6, characterized in that, The polyurethane thickener mentioned in step (4) is pre-diluted at a ratio of 1:4, and the ASE60 thickener is a non-associative anionic alkali-swelling thickener.

9. The preparation method according to claim 6, characterized in that, It also includes step (6) gradient temperature curing: the coated coating is first cured at 25°C and 60% relative humidity for 3 days, and then cured at 50°C and 40% relative humidity for 1 day.

10. The environmentally friendly polymer cement waterproof coating according to any one of claims 1 to 5, characterized in that, It is used for waterproofing of damp concrete surfaces or newly poured, undried surfaces with a moisture content of 10% to 15%.