A low-shrinkage high-adhesion water-based polymer repair paste and a preparation method thereof

Abstract

The application relates to the technical field of building decoration materials, in particular to a water-based high-molecular repair paste with low shrinkage and high adhesion and a preparation method thereof. The repair paste comprises the following components in parts by weight: 25-40 parts of water-based acrylic emulsion; 8-15 parts of titanium white powder; 10-20 parts of heavy calcium carbonate; 5-12 parts of talcum powder; 0.8-2.5 parts of silane coupling agent; 1.5-4.0 parts of ethylene glycol; 2.0-5.0 parts of plasticizer; 0.3-0.8 parts of wetting agent; 0.2-0.6 parts of defoaming agent; 0.1-0.3 parts of bactericide; 0.1-0.3 parts of preservative; and 0-3.0 parts of color paste. Through the synergistic effect of the silane-ethylene glycol-plasticizer ternary system and the specific particle size filler grading, the dry shrinkage rate is extremely low while the excellent adhesion is maintained, and the problems of cracking and peeling of the repair layer are effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of building decoration materials technology, specifically to a low-shrinkage, high-adhesion water-based polymer repair paste and its preparation method. Background Technology

[0002] Over long-term use, building walls and floors inevitably develop defects such as cracks, holes, peeling, and detachment due to factors such as building stress, temperature changes, humidity fluctuations, substrate aging, and other installation issues. To restore their functionality and aesthetics, repair materials are usually required.

[0003] Currently, the main types of materials available on the market for wall or floor repair include the following:

[0004] (1) Cement-based repair materials: Cement is the main binder. Although it is inexpensive and widely available, it has problems such as large drying shrinkage, easy cracking, poor flexibility, and weak adhesion to organic substrates. Especially in environments with frequent temperature changes, cement-based materials are prone to secondary cracking because their coefficient of thermal expansion and contraction does not match that of the substrate.

[0005] (2) Solvent-based polymer repair materials: mainly composed of epoxy resin, polyurethane, etc. Although they have good mechanical properties, they contain a large amount of organic solvents, have high VOC emissions, which are harmful to construction workers and the environment. Moreover, they are hazardous chemicals, and their production, transportation and storage are strictly restricted.

[0006] (3) Water-based acrylic repair paste: It uses water-based acrylic emulsion as a base material and has the advantages of being environmentally friendly, low VOC, and easy to apply. It is currently a more ideal repair material.

[0007] However, existing water-based acrylic repair pastes still present a contradiction between shrinkage cracking and insufficient adhesion when actually applied to wall or floor repairs:

[0008] On the one hand, during the drying and film-forming process of water-based acrylic repair paste, the evaporation of water causes the system volume to shrink. If the filler content in the formula is too high to reduce shrinkage, the flexibility of the coating film will decrease and the elastic modulus will increase. When the wall or floor deforms due to temperature changes, the repair layer cannot effectively follow the deformation of the substrate, resulting in stress concentration and cracking inside the repair layer. At the same time, a high filler content will also reduce the wetting and penetration ability of the repair paste to the substrate, weaken the interfacial adhesion, and cause the repair layer to peel off from the substrate surface.

[0009] On the other hand, if the amount of plasticizer is increased to improve the flexibility of the coating film to adapt to the deformation of the substrate, the mechanical strength and water resistance of the coating film will decrease significantly. Moreover, the plasticizer is prone to migration and precipitation, resulting in stickiness and contamination on the coating surface. After long-term use, the flexibility will actually be lost. In addition, increasing the amount of plasticizer does not effectively solve the drying shrinkage problem. Instead, it may exacerbate the sedimentation and separation of fillers by reducing the viscosity of the system.

[0010] In existing technologies, some solutions attempt to improve the adhesion of repair pastes to inorganic substrates by adding silane coupling agents. One end of the silane coupling agent molecule can react with hydroxyl groups on the surface of the inorganic substrate to form a chemical bond, while the other end can bind to organic polymers, theoretically acting as a "molecular bridge" at the organic-inorganic interface. However, in practical applications, silane coupling agents exhibit poor dispersion stability in aqueous systems and are prone to hydrolysis and condensation, leading to self-polymerization. This not only reduces the effective utilization rate but also allows the self-polymerization products to form hard particles, weakening the flexibility and continuity of the coating film. Furthermore, the addition of silane coupling agents does not directly solve the problem of large drying shrinkage in repair pastes; its effect on improving the shrinkage rate is very limited.

[0011] Chinese patent CN114685093B discloses a wall repair paste that improves waterproof performance by adding molecular sieve-loaded lotus leaf water-repellent agent. However, it mainly addresses the issues of efflorescence and waterproofing, without making targeted improvements to the shrinkage, cracking, and adhesion problems of the repair paste. Summary of the Invention

[0012] The purpose of this invention is to provide a water-based polymer repair paste with low shrinkage and high adhesion, so as to solve the contradiction between shrinkage cracking and insufficient adhesion of existing water-based acrylic repair pastes when used for wall or floor repair.

[0013] Another object of the present invention is to provide a method for preparing the above-mentioned low-shrinkage, high-adhesion water-based polymer repair paste.

[0014] To achieve the above objectives, the present invention adopts the following technical solution:

[0015] A low-shrinkage, high-adhesion water-based polymer repair paste, comprising the following components by weight:

[0016] 25-40 parts of water-based acrylic emulsion; 8-15 parts of titanium dioxide; 10-20 parts of heavy calcium carbonate; 5-12 parts of talc; 0.8-2.5 parts of silane coupling agent; 1.5-4.0 parts of ethylene glycol; 2.0-5.0 parts of plasticizer; 0.3-0.8 parts of wetting agent; 0.2-0.6 parts of defoamer; 0.1-0.3 parts of antibacterial agent; 0.1-0.3 parts of preservative; 0-3.0 parts of color paste.

[0017] The aqueous acrylic emulsion has a solid content of 45%–55%; the silane coupling agent is at least one of γ-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560), or N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792); the plasticizer is at least one of dibutyl phthalate (DBP), dioctyl phthalate (DOP), or tributyl citrate; the titanium dioxide has a particle size D50 of 0.2–0.4 μm, the heavy calcium carbonate has a particle size D50 of 2–5 μm, and the talc has a particle size D50 of 5–10 μm.

[0018] Preferably, the weight ratio of the silane coupling agent to ethylene glycol is 1:1.5 to 1:2.5.

[0019] Preferably, the weight ratio of the silane coupling agent to the plasticizer is 1:2 to 1:3.

[0020] Preferably, the weight ratio of titanium dioxide, heavy calcium carbonate and talc is 1:1.2-2.0:0.6-1.0.

[0021] Preferably, the aqueous acrylic emulsion is at least one of pure acrylic emulsion, styrene-acrylic emulsion, or silicone-acrylic emulsion.

[0022] Preferably, the wetting agent is a polyether-modified siloxane wetting agent; the defoamer is a mineral oil defoamer or an organosilicon defoamer; the bactericide is an isothiazolinone bactericide; and the preservative is a benzimidazole preservative.

[0023] In the above technical solution, the synergistic effect of the silane coupling agent and the pre-dispersion of ethylene glycol is as follows:

[0024] Ethylene glycol not only acts as a film-forming aid to lower the minimum film-forming temperature of acrylic emulsions, but more importantly, in this invention, it serves as a pre-dispersion medium and stabilizer for the silane coupling agent. The silane coupling agent forms a stable monomolecular dispersion in ethylene glycol, preventing direct hydrolysis and self-polymerization in aqueous systems. When the pre-dispersion is added to the repair paste system, ethylene glycol and the silane coupling agent work together on the surface of the acrylic latex particles. On the one hand, ethylene glycol promotes the aggregation of latex particles into a film; on the other hand, the silane coupling agent gradually migrates to the interface between the coating and the substrate wall and to the surface of inorganic fillers within the coating during film formation, forming chemical bonds. This significantly improves the effective utilization rate of the silane coupling agent, avoids the formation of self-polymerization products, and thus greatly enhances the adhesion of the repair paste to the wall or floor substrate without weakening the flexibility of the coating.

[0025] In the above technical solution, the synergistic toughening effect of silane coupling agent and plasticizer is as follows:

[0026] Plasticizers insert themselves between the acrylic polymer molecular chains, reducing intermolecular forces and improving the flexibility and ductility of the coating film. The chemical cross-linking points formed by the silane coupling agent in the coating film complement the physical plasticizing effect of the plasticizer: the chemical cross-linking points provide the coating film with strength and resilience, preventing excessive plasticizer migration; the plasticizer, in turn, ensures the coating film's flexibility at low temperatures and its ability to follow substrate deformation. This synergistic effect allows the coating film to maintain sufficient mechanical strength while possessing excellent elastic recovery capabilities, effectively absorbing and releasing stress caused by temperature changes in walls or floors, fundamentally preventing cracking.

[0027] In the above technical solution, three fillers with different particle sizes are used: fine-particle titanium dioxide (D50: 0.2–0.4 μm), medium-particle heavy calcium carbonate (D50: 2–5 μm), and coarse-particle talc (D50: 5–10 μm), graded in a specific ratio. This gradation design allows the filler particles to form a densely packed structure in the coating film, reducing the porosity of the coating film, thereby reducing the moisture evaporation channels and inhibiting drying shrinkage. At the same time, the combination of fillers with different particle sizes optimizes the stress distribution of the coating film. The fine-particle filler fills the gaps between large particles, improving the density and strength of the coating film; the lamellar structure of the coarse-particle talc forms a layered barrier in the coating film, hindering crack propagation and further improving the crack resistance of the coating film.

[0028] The synergistic effect of the above three aspects enables the repair paste of the present invention to significantly reduce the shrinkage rate during the drying process (the linear shrinkage rate can be controlled below 0.5%), while the adhesion to the concrete substrate reaches more than 1.5MPa and the elongation at break reaches more than 150%, thus achieving a balance between low shrinkage and high adhesion.

[0029] This invention also provides a method for preparing the above-mentioned low-shrinkage, high-adhesion water-based polymer repair paste, comprising the following steps:

[0030] (1) Preparation of pre-dispersion: The silane coupling agent and ethylene glycol are mixed in a weight ratio and stirred at room temperature for 10-20 minutes to fully dissolve the silane coupling agent and obtain the pre-dispersion;

[0031] (2) Preparation of slurry: Add deionized water, wetting agent, defoamer, preservative and sterilizing agent to the dispersion tank and stir at 300-500 rpm for 5-10 minutes; then add titanium dioxide, heavy calcium carbonate and talc in sequence, increase the speed to 1500-2000 rpm and disperse at high speed for 20-30 minutes to obtain a uniform slurry;

[0032] (3) Emulsion mixing: Add the water-based acrylic emulsion to the above slurry and stir at a speed of 500-800 rpm for 10-15 minutes to fully mix the emulsion and the slurry to obtain a mixture;

[0033] (4) Addition of functional additives: Under stirring, slowly add the pre-dispersion liquid prepared in step (1) to the above mixture and continue stirring for 15 to 20 minutes; then add the plasticizer and stir for 10 to 15 minutes;

[0034] (5) Color adjustment and homogenization: Adjust the color as needed, add color paste, and stir at 300-500 rpm for 5-10 minutes; finally, homogenize the mixture by passing it through a colloid mill or a three-roll mill to obtain the low-shrinkage, high-adhesion water-based polymer repair paste.

[0035] This invention also provides a water-based polymer repair paste, which is suitable for both walls and floors. It is further optimized and improved based on the aforementioned water-based polymer repair paste, with improvements including the following:

[0036] The acrylic emulsion is a modified core-shell structured acrylic emulsion;

[0037] The core-shell structured acrylic emulsion has a core glass transition temperature (Tg) of -20℃ to -10℃, a shell glass transition temperature (Tg) of 20℃ to 30℃, a core-to-shell weight ratio of 60:40 to 70:30, and an emulsion solid content of 45% to 55%.

[0038] Preferably, the silane coupling agent is a compound of γ-glycidoxypropyltrimethoxysilane (KH-560) and vinyltrimethoxysilane (A-171) in a weight ratio of 6:4.

[0039] Preferably, the plasticizer includes a reactive plasticizer and an auxiliary plasticizer, wherein the reactive plasticizer is polypropylene glycol diacrylate (PPGDA) with a molecular weight of 400-1000; and the auxiliary plasticizer is tributyl citrate.

[0040] Preferably, the core layer of the core-shell structured acrylic emulsion is formed by copolymerizing at least one soft monomer selected from butyl acrylate and ethyl acrylate with a small amount of methyl methacrylate; the shell layer is formed by copolymerizing at least one hard monomer selected from methyl methacrylate and styrene with a small amount of butyl acrylate.

[0041] Preferably, the weight ratio of the silane coupling agent to ethylene glycol is 1:2 to 1:3.5.

[0042] Preferably, the weight ratio of the reactive plasticizer to the auxiliary plasticizer is 2:1 to 4:1.

[0043] However, after long-term research and extensive engineering practice, the inventors discovered that the aforementioned water-based acrylic repair paste could not simultaneously meet the performance requirements of both wall and floor applications:

[0044] Wall repair requires repair pastes to have excellent flexibility and elongation at break (usually ≥150%) to accommodate the expansion / contraction deformation of the wall caused by temperature changes and prevent cracking of the repair layer. To this end, existing technologies typically use soft acrylic emulsions with low glass transition temperatures (Tg) and a high amount of plasticizer to give the coating high elasticity. However, this highly flexible coating has extremely low surface hardness (pencil hardness usually ≤HB) and poor abrasion resistance. When used for floor repair, it is easily scratched, dented, and worn by foot traffic, furniture dragging, and abrasion from sand particles. Furthermore, its compressive strength is insufficient (usually only 8–12 MPa), making it unable to withstand concentrated loads, causing the repair layer to lose its functionality within a short period.

[0045] Floor repair requires repair pastes to possess high hardness (pencil hardness ≥2H), high abrasion resistance (Taber abrasion ≤0.15g / 1000r), and high compressive strength (≥20MPa) to withstand foot traffic and mechanical wear. To this end, existing technologies typically employ high-Tg hard acrylic emulsions and reduce the amount of plasticizer to increase the hardness of the coating. However, such hard coatings have extremely low elongation at break (typically ≤30%) and poor flexibility. When used for wall repair, they cannot adapt to the temperature deformation of the wall. Under cyclic temperature stress ranging from -20℃ to 50℃, stress concentration occurs within the repair layer, making it highly susceptible to penetrating cracks and even detachment from the substrate.

[0046] The above-mentioned solution employs a modified acrylic emulsion with a specific core-shell structure. The core layer is composed of a soft monomer copolymer with a low Tg (-20℃ to -10℃), providing excellent flexibility and elongation at break, allowing the coating film to fully adapt to the temperature deformation of the wall without cracking. The shell layer is composed of a hard monomer copolymer with a high Tg (20℃ to 30℃), providing high surface hardness and abrasion resistance, enabling the coating film to withstand the wear and tear from flooring. The weight ratio of the core layer to the shell layer is controlled at 60:40 to 70:30 to ensure that the volume of the soft phase in the core layer is sufficient to provide overall flexibility, while the thickness of the hard phase in the shell layer is sufficient to form a continuous high-hardness surface.

[0047] The above-mentioned scheme also preferably uses polypropylene glycol diacrylate (PPGDA) as a reactive plasticizer. During film formation, the acrylate double bonds at both ends of its molecule can undergo free radical copolymerization with the unsaturated groups on the acrylic emulsion polymer chain, permanently grafting the plasticizer molecules into the polymer network. Unlike traditional physical plasticizers (such as DBP and DOP), PPGDA does not migrate or precipitate, maintaining the flexibility of the coating film for a long time. Simultaneously, the polypropylene glycol segments of PPGDA provide molecular chain mobility, while its double bond crosslinking reaction introduces chemical crosslinking points, enabling the coating film to maintain high elongation at break while possessing sufficient resilience and resistance to permanent deformation, preventing dents caused by heavy objects falling onto the floor.

[0048] Compared with the prior art, the present invention has the following significant advantages:

[0049] This invention utilizes the synergistic effect of a silane-ethylene glycol-plasticizer ternary synergistic system and a specific particle size filler gradation to maintain excellent adhesion while exhibiting extremely low drying shrinkage, effectively avoiding cracking and peeling of the repair layer.

[0050] This invention, through the design of a core-shell structured emulsion and the plasticizing effect of a reactive plasticizer, enables the repair paste to simultaneously meet the requirements of high flexibility for walls and high hardness / high abrasion resistance for floors, thereby reducing production and inventory costs and improving ease of application.

[0051] The repair paste of this invention has a film elongation at break of over 150%, which can fully adapt to the deformation of walls or floors; after 1000 freeze-thaw cycles, the repair layer shows no cracking or peeling, and has excellent durability. Detailed Implementation

[0052] The present invention will be further described in detail below through specific embodiments. The following embodiments are for illustrative purposes only.

[0053] This invention is intended to be purported to be applicable, but not to limit the scope of the invention.

[0054] Example 1

[0055] A water-based polymer repair paste, by weight, comprises the following components: 32 parts of water-based acrylic emulsion (pure acrylic emulsion, Tg=-5℃, solid content 50%), 10 parts of titanium dioxide (rutile type, D50=0.3μm), 15 parts of heavy calcium carbonate (D50=3μm), 8 parts of talc (D50=8μm), 1.5 parts of γ-aminopropyltriethoxysilane (KH-550), 3.0 parts of ethylene glycol, 3.5 parts of dibutyl phthalate (DBP), 0.5 parts of polyether-modified siloxane wetting agent, 0.4 parts of mineral oil defoamer, 0.2 parts of isothiazolinone antibacterial agent, 0.2 parts of benzimidazole preservative, 1.5 parts of color paste (white), and the balance of deionized water (to bring the total to 100 parts).

[0056] Prepared according to the following method:

[0057] (1) Mix KH-550 with ethylene glycol and stir at room temperature for 15 minutes to obtain a pre-dispersion;

[0058] (2) Add deionized water, wetting agent, defoamer, preservative and sterilizing agent to the dispersion vessel and stir at 400 rpm for 8 minutes; add titanium dioxide, heavy calcium carbonate and talc in sequence and disperse at 1800 rpm for 25 minutes.

[0059] (3) Add water-based acrylic emulsion and stir at 600 rpm for 12 minutes;

[0060] (4) Slowly add the pre-dispersion liquid and stir for 18 minutes; add DBP and stir for 12 minutes;

[0061] (5) Add color paste, stir at 500 rpm for 8 minutes, and homogenize by colloid mill to obtain repair paste.

[0062] Example 2

[0063] A water-based polymer repair paste, by weight, comprises the following components: 35 parts of water-based acrylic emulsion (styrene-acrylic emulsion, Tg=0℃, solid content 48%), 12 parts of titanium dioxide (rutile type, D50=0.25μm), 18 parts of heavy calcium carbonate (D50=4μm), 10 parts of talc (D50=6μm), 2.0 parts of γ-glycidyl etheroxypropyltrimethoxysilane (KH-560), 4.0 parts of ethylene glycol, 4.5 parts of dioctyl phthalate (DOP), 0.6 parts of polyether-modified siloxane wetting agent, 0.5 parts of organosilicon defoamer, 0.2 parts of isothiazolinone antibacterial agent, 0.2 parts of benzimidazole preservative, 1.5 parts of color paste (white), and the balance of deionized water (to bring the total to 100 parts).

[0064] The preparation method is the same as in Example 1.

[0065] Example 3

[0066] A water-based polymer repair paste, by weight, comprises the following components: 28 parts water-based acrylic emulsion (silicone-acrylic emulsion, Tg=-10℃, solid content 52%), 8 parts titanium dioxide (rutile type, D50=0.35μm), 12 parts heavy calcium carbonate (D50=2.5μm), 6 parts talc (D50=10μm), 1.0 part N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), 2.0 parts ethylene glycol, 2.5 parts tributyl citrate, 0.4 parts polyether-modified siloxane wetting agent, 0.3 parts mineral oil defoamer, 0.1 parts isothiazolinone antibacterial agent, 0.1 parts benzimidazole preservative, 1.5 parts color paste (white), and the balance of deionized water (to bring the total to 100 parts).

[0067] The preparation method is the same as in Example 1.

[0068] Example 4

[0069] A water-based polymer repair paste suitable for both walls and floors, comprising the following components by weight: 32 parts of core-shell structured acrylic emulsion (core Tg=-15℃, shell Tg=25℃, core-shell ratio 65:35, solid content 50%), 10 parts of titanium dioxide (rutile type, D50=0.3μm), 12 parts of heavy calcium carbonate (D50=3μm), 6 parts of talc (D50=8μm), and γ-glycidyl etheroxypropyltrimethoxysilane (KH-5). 60) 1.2 parts, vinyltrimethoxysilane (A-171) 0.8 parts, ethylene glycol 3.0 parts, polypropylene glycol diacrylate (PPGDA, molecular weight 600) 3.0 parts, tributyl citrate 1.5 parts, polyether modified siloxane wetting agent 0.5 parts, mineral oil defoamer 0.4 parts, isothiazolinone antibacterial agent 0.2 parts, benzimidazole preservative 0.2 parts, color paste (white) 2.0 parts, deionized water balance (to bring to 100 parts).

[0070] The preparation method of the core-shell structured acrylic emulsion is as follows:

[0071] (a) Preparation of the core layer preemulsion: 80 parts deionized water, 1.2 parts sodium dodecyl sulfate (SDS),

[0072] 1.8 parts of polyoxyethylene octylphenol ether-10 (OP-10) were added to a reaction vessel, stirred at 300 rpm, and heated to 75°C. 28 parts of butyl acrylate, 8 parts of ethyl acrylate, 4 parts of methyl methacrylate, and 1.5 parts of acrylic acid were mixed, and 10% of this mixture was added to the reaction vessel as a seed monomer. At the same time, 0.3 parts of ammonium persulfate (APS) (dissolved in 5 parts of deionized water) were added. The temperature was raised to 80°C and maintained for 15 minutes. After the system showed blue light, the remaining monomer mixture was added dropwise over a period of 2.5 hours. Simultaneously, APS solution (0.5 parts of APS dissolved in 20 parts of deionized water) was added dropwise. After the addition was complete, the reaction was maintained at this temperature for 1 hour to obtain a core layer pre-emulsion.

[0073] (b) Preparation of shell monomers: Mix 22 parts of methyl methacrylate, 10 parts of styrene, 3 parts of butyl acrylate and 2 parts of methacrylic acid evenly and set aside.

[0074] (c) Synthesis of core-shell emulsion: The core pre-emulsion prepared in step (a) was cooled to 78°C and APS was added.

[0075] 0.2 parts (dissolved in 5 parts deionized water), then begin adding the shell monomer mixture prepared in step (b) dropwise.

[0076] The dropping time was controlled at 1.5 hours, and APS solution (0.3 parts APS dissolved in 15 parts deionized water) was added dropwise simultaneously. After the dropping was completed, the temperature was raised to 85°C and the reaction was maintained at this temperature for 2 hours.

[0077] (d) Post-treatment: Cool the reaction system to 40°C, adjust the pH to 7.5-8.5 with ammonia, add 0.1 parts of isothiazolinone preservative, stir for 30 minutes, filter and discharge to obtain the core-shell structured acrylic emulsion;

[0078] The core-shell structured acrylic emulsion has a core glass transition temperature (Tg) of -15°C, a shell glass transition temperature (Tg) of 25°C, a core-to-shell weight ratio of 65:35, an emulsion solid content of 50%, and an emulsion particle size of 180–220 nm.

[0079] Preparation method of repair paste:

[0080] (1) KH-560 and A-171 were mixed at a weight ratio of 6:4, added to ethylene glycol, stirred in a water bath at 30°C for 30 minutes, and ultrasonically dispersed for 10 minutes to obtain a pre-dispersion;

[0081] (2) Add deionized water, defoamer, preservative, sterilizing agent and AMP-95 to the dispersion vessel, 400 rpm

[0082] Stir for 8 minutes; then add titanium dioxide, heavy calcium carbonate, and talc in sequence, and disperse at 1800 rpm for 30 minutes.

[0083] (3) Add the core-shell structured acrylic emulsion and stir at 600 rpm for 12 minutes; slowly add the pre-dispersion solution.

[0084] Continue stirring for 25 minutes;

[0085] (4) Add PPGDA and stir for 18 minutes; add tributyl citrate and stir for 12 minutes;

[0086] (5) Homogenize the product by colloid mill; then cure the product at 40°C for 24 hours to obtain the repair paste.

[0087] Example 5

[0088] A water-based polymer repair paste suitable for both walls and floors, comprising the following components by weight: 32 parts of core-shell structured acrylic emulsion (core Tg=-18℃, shell Tg=22℃, core-shell ratio 70:30, solid content 48%), 12 parts of titanium dioxide (rutile type, D50=0.3μm), 15 parts of heavy calcium carbonate (D50=3μm), 4 parts of talc (D50=8μm), and γ-glycidoxypropyltrimethoxysilane (KH-5). 60) 1.5 parts, vinyltrimethoxysilane (A-171) 1.0 part, ethylene glycol 3.0 parts, polypropylene glycol diacrylate (PPGDA, molecular weight 600) 3.0 parts, tributyl citrate 1.5 parts, polyether modified siloxane wetting agent 0.5 parts, mineral oil defoamer 0.4 parts, isothiazolinone antibacterial agent 0.2 parts, benzimidazole preservative 0.2 parts, color paste (white) 2.0 parts, deionized water balance (to bring to 100 parts).

[0089] The preparation method of the core-shell structured acrylic emulsion is as follows:

[0090] (a) Preparation of the core layer preemulsion: 85 parts deionized water, 1.5 parts sodium dodecyl sulfate (SDS),

[0091] 2.0 parts of polyoxyethylene octylphenol ether-10 (OP-10) were added to a reaction vessel and stirred at 300 rpm while the temperature was raised to 75°C. 30 parts of butyl acrylate, 10 parts of ethyl acrylate, 3 parts of methyl methacrylate and 1.8 parts of acrylic acid were mixed, and 10% of the mixture was added to the reaction vessel as a seed monomer. At the same time, 0.35 parts of ammonium persulfate (APS) (dissolved in 5 parts of deionized water) were added. The temperature was raised to 80°C and maintained for 15 minutes. After the system showed blue light, the remaining monomer mixture was added dropwise over a period of 3 hours. Simultaneously, APS solution (0.6 parts of APS dissolved in 25 parts of deionized water) was added dropwise. After the addition was completed, the reaction was kept at this temperature for 1 hour to obtain a core layer pre-emulsion.

[0092] (b) Preparation of shell monomers: Mix 20 parts of methyl methacrylate, 8 parts of styrene, 2 parts of butyl acrylate and 2.5 parts of methacrylic acid evenly and set aside;

[0093] (c) Synthesis of core-shell emulsion: The core pre-emulsion prepared in step (a) was cooled to 78°C and APS was added.

[0094] 0.25 parts (dissolved in 5 parts deionized water), then begin adding the shell monomer mixture prepared in step (b) dropwise.

[0095] The dropping time was controlled at 1.5 hours, and APS solution (0.35 parts APS dissolved in 20 parts deionized water) was added dropwise simultaneously. After the dropping was completed, the temperature was raised to 85°C and the reaction was maintained at this temperature for 2 hours.

[0096] (d) Post-treatment: Cool the reaction system to 40°C, adjust the pH to 7.5-8.5 with ammonia, add 0.1 parts of isothiazolinone preservative, stir for 30 minutes, filter and discharge to obtain the core-shell structured acrylic emulsion;

[0097] The core-shell structured acrylic emulsion has a core glass transition temperature (Tg) of -18°C, a shell glass transition temperature (Tg) of 22°C, a core-to-shell weight ratio of 70:30, an emulsion solid content of 48%, and an emulsion particle size of 160–200 nm.

[0098] The preparation method of the repair paste is the same as in Example 4.

[0099] Comparative Example 1

[0100] The only difference from Example 1 is that γ-aminopropyltriethoxysilane is not added.

[0101] Comparative Example 2.

[0102] The only difference from Example 1 is that ethylene glycol is not added.

[0103] Comparative Example 3

[0104] The difference from Example 4 is that the plasticizer only contains polypropylene glycol diacrylate and not tributyl citrate. The amount of tributyl citrate added is supplemented to the amount of polypropylene glycol diacrylate, that is, the amount of polypropylene glycol diacrylate added is 4.5 parts.

[0105] The repair pastes prepared in Examples 1-5 and Comparative Examples 1 and 2 were subjected to the following performance tests:

[0106] (1) Linear shrinkage rate: determined according to the method specified in JC / T 547-2017 "Ceramic Tile Adhesives",

[0107] The specimen dimensions were 40mm×40mm×160mm. The length change was measured after curing under standard curing conditions (temperature 23±2℃, relative humidity 50±5%) for 28 days.

[0108] (2) Tensile bond strength: According to the method specified in JC / T 547-2017, on the surface of the concrete test block...

[0109] Apply repair paste and perform a tensile bond strength test after 28 days of standard curing.

[0110] (3) Elongation at break: as specified in GB / T 16777-2008 "Test Methods for Waterproof Coatings for Buildings".

[0111] The method was used to prepare coated specimens and conduct tensile property tests.

[0112] (4) Crack resistance: Fill the simulated wall crack (crack width 2mm, depth 5mm) with repair paste, and observe whether the repair layer cracks under temperature cycling conditions of -20℃ to 50℃ (12 hours per cycle, 100 cycles in total).

[0113] (5) Freeze-thaw cycle durability: As specified in JG / T 157-2009 "Putty for Building Exterior Walls"

[0114] The method involves conducting freeze-thaw cycle tests (1000 cycles).

[0115] (6) Taber wear resistance: According to GB / T 1768-2006, using a CS-17 grinding wheel with a load of 1000g,

[0116] Rotate 1000 revolutions and measure the wear.

[0117] The test results are shown in Table 1 below:

[0118] Table 1 Test Results

[0119]

[0120] The test results above show that:

[0121] Compared to Comparative Example 1 (without silane coupling agent), Examples 1-3, while maintaining excellent flexibility (elongation at break 152%-185%), showed a reduction in linear shrinkage of approximately 48%-54% (from 0.82% to 0.38%-0.45%), an increase in tensile bond strength of approximately 91%-122% (from 0.88 MPa to 1.68-1.95 MPa), and significant improvements in crack resistance and freeze-thaw cycle durability. This fully demonstrates the crucial role of the silane coupling agent in the system. After pre-dispersion in ethylene glycol, the silane coupling agent can effectively migrate to the coating-substrate interface and the surface of inorganic fillers, forming chemical bonds, thereby significantly improving adhesion and interfacial bonding strength. Simultaneously, through the synergistic toughening effect of chemical crosslinking points and plasticizers, the excellent flexibility of the coating is maintained.

[0122] Compared to Comparative Example 2 (without ethylene glycol), Example 1 showed a reduction in linear shrinkage of approximately 44% (0.42% vs 0.75%), an increase in tensile bond strength of approximately 58% (1.82 MPa vs 1.15 MPa), and an increase in elongation at break of approximately 77% (168% vs 95%). This demonstrates that ethylene glycol plays a dual crucial role in this invention: firstly, as a film-forming aid, it lowers the minimum film-forming temperature of the emulsion, promoting the aggregation of latex particles into a film; secondly, as a pre-dispersion medium and stabilizer for the silane coupling agent, it prevents silane from directly hydrolyzing and condensing in the aqueous system, thus preventing self-polymerization. In Comparative Example 2, due to the lack of pre-dispersion protection from ethylene glycol, the silane coupling agent underwent significant hydrolysis and self-polymerization (the solution was milky white and turbid). The self-polymerized products were dispersed as hard particles in the coating film, which not only reduced the effective utilization rate of silane but also weakened the flexibility of the coating film, resulting in an elongation at break even lower than that of Comparative Example 1 (125%) without silane.

[0123] The difference between Comparative Example 3 and Example 4 is that Comparative Example 3 only added 4.5 parts of polypropylene glycol diacrylate (PPGDA) and did not add tributyl citrate. Although Comparative Example 3 used the reactive plasticizer PPGDA, the low-temperature flexibility and workability of the coating were affected due to the lack of auxiliary plasticizing effect of tributyl citrate. Compared with Comparative Example 3, the elongation at break of Example 4 (138%) was significantly higher than that of Comparative Example 3 (108%). In the impact resistance test, Example 4 passed while Comparative Example 3 failed. In the crack resistance test, Example 4 did not crack while Comparative Example 3 cracked slightly. This shows that tributyl citrate, as an auxiliary plasticizer, can effectively improve the low-temperature flexibility and impact resistance of the coating, forming a synergistic plasticizing effect with PPGDA. PPGDA provides durable bulk flexibility through chemical crosslinking, while tributyl citrate improves low-temperature workability and short-term flexibility through physical plasticizing; both are indispensable.

[0124] Example 5 exhibits the best overall performance, with the lowest linear shrinkage (0.32%), the highest tensile bond strength (2.08 MPa), the largest elongation at break (152%), and the lowest Taber wear (0.07 g / 1000 r). This is likely because the core-shell ratio in Example 5 is 70:30, resulting in a larger volume of the soft core phase, which provides superior flexibility; simultaneously, the well-developed network structure of the hard shell phase ensures sufficient surface hardness and wear resistance; and the ratio of PPGDA to tributyl citrate (3.0:1.5, i.e., 2:1) is within the optimal range, achieving the best synergy between reactive plasticizing and assisted plasticizing.

[0125] In summary, the water-based polymer repair paste provided by this invention achieves a balance of low shrinkage, high adhesion, and high flexibility in its basic solution, and further achieves a balance of high hardness, high abrasion resistance, and excellent flexibility in its preferred solution, truly achieving the technical effect of "one paste for two uses," and has significant practical value and market prospects.

Claims

1. A low-shrinkage, high-adhesion water-based polymer repair paste, characterized by, in parts by weight, The product comprises the following components: 25-40 parts of aqueous acrylic emulsion; 8-15 parts of titanium dioxide; 10-20 parts of heavy calcium carbonate; 5-12 parts of talc; 0.8-2.5 parts of silane coupling agent; 1.5-4.0 parts of ethylene glycol; 2.0-5.0 parts of plasticizer; 0.3-0.8 parts of wetting agent; 0.2-0.6 parts of defoamer; 0.1-0.3 parts of antibacterial agent; 0.1-0.3 parts of preservative; and 0-3.0 parts of color paste. The particle size D50 of the titanium dioxide is 0.2-0.4 μm, the particle size D50 of the heavy calcium carbonate is 2-5 μm, and the particle size D50 of the talc is 5-10 μm.

2. The repair paste according to claim 1, characterized in that, The weight ratio of the silane coupling agent to ethylene glycol is 1:1.5 to 1:2.

5.

3. The repair paste according to claim 1, characterized in that, The weight ratio of the silane coupling agent to the plasticizer is 1:2 to 1:

3.

4. The repair paste according to claim 1, characterized in that, The weight ratio of titanium dioxide, heavy calcium carbonate and talc is 1:1.2-2.0:0.6-1.

0.

5. The repair paste according to claim 1, characterized in that, The aqueous acrylic emulsion is a core-shell structured acrylic emulsion. The core layer of the core-shell structured acrylic emulsion has a glass transition temperature (Tg) of -20℃ to -10℃, and the shell layer has a glass transition temperature (Tg) of 20℃ to 30℃. The weight ratio of the core layer to the shell layer is 60:40 to 70:

30.

6. The repair paste according to claim 5, characterized in that, The silane coupling agent is a compound of γ-glycidoxypropyltrimethoxysilane and vinyltrimethoxysilane in a weight ratio of 6:

4.

7. The repair paste according to claim 5, characterized in that, The plasticizer includes a reactive plasticizer and an auxiliary plasticizer. The reactive plasticizer is polypropylene glycol diacrylate with a molecular weight of 400-1000. The auxiliary plasticizer is tributyl citrate.

8. The repair paste according to claim 5, characterized in that, The weight ratio of the silane coupling agent to ethylene glycol is 1:2 to 1:3.

5.

9. The repair paste according to claim 5, characterized in that, The weight ratio of the reactive plasticizer to the auxiliary plasticizer is 2:1 to 4:

1.

10. The method for preparing the repair paste according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Preparation of pre-dispersion: The silane coupling agent and ethylene glycol are mixed in a weight ratio and stirred at room temperature for 10-20 minutes to fully dissolve the silane coupling agent and obtain the pre-dispersion; (2) Preparation of slurry: Add deionized water, wetting agent, defoamer, preservative and sterilizing agent to the dispersion tank and stir at 300-500 rpm for 5-10 minutes; then add titanium dioxide, heavy calcium carbonate and talc in sequence, increase the speed to 1500-2000 rpm and disperse at high speed for 20-30 minutes to obtain a uniform slurry; (3) Emulsion mixing: Add the water-based acrylic emulsion to the above slurry and stir at a speed of 500-800 rpm for 10-15 minutes to fully mix the emulsion and the slurry to obtain a mixture; (4) Addition of functional additives: Under stirring, slowly add the pre-dispersion liquid prepared in step (1) to the above mixture and continue stirring for 15 to 20 minutes; Then add the plasticizer and stir for 10-15 minutes; (5) Color adjustment and homogenization: Adjust the color as needed, add color paste, and stir at 300-500 rpm for 5-10 minutes; finally, homogenize the mixture by passing it through a colloid mill or a three-roll mill to obtain the low-shrinkage, high-adhesion water-based polymer repair paste.

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