Environment-friendly sealing glue for water supply network threading joint and preparation process of environment-friendly sealing glue

Abstract

The invention discloses environment-friendly sealing glue for a threading connector of a water supply network and a preparation process of the environment-friendly sealing glue. The glue takes waterborne polyurethane resin as an environment-friendly base material, and is matched with a compound modified filler, a plant extract modified bio-based tackifier, a waterborne isocyanate environment-friendly curing agent, a functional additive and the balance of deionized water, wherein the compound modified filler is prepared from nano silicon dioxide and talcum powder in a mass ratio of (2-5): 1, and the functional additive is prepared by compounding a food-grade preservative, an anti-aging agent and a defoaming agent. The glue is low in VOCs content, environment-friendly, free of pungent smell, excellent in sealing durability, low in connector leakage rate, capable of being constructed under a micro-wet working condition, simple in preparation and application process, free of special equipment, low in cost and suitable for large-scale production, and the glue is low in VOCs content, environment-friendly, free of pungent smell, excellent in sealing durability and low in connector leakage rate and can be used for construction under the micro-wet working condition. And the comprehensive construction cost is low, the method is suitable for sealing of multi-material pipelines in old communities and threading connectors of newly-built water supply pipe networks, the stability of a water supply system is effectively improved, and the later operation and maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of municipal water supply engineering technology, specifically to an environmentally friendly sealant for threaded joints in water supply networks and its preparation process. It is particularly suitable for environmentally friendly sealing construction of threaded joints in multi-material pipe connection scenarios such as plastic-lined steel pipes and PE pipes in old residential areas, and can also be applied to the sealing of threaded joints in newly built water supply network projects. Background Technology

[0002] In the upgrading and renovation of water supply networks in old urban residential areas, threaded joints are the core components of pipe connections, and their sealing performance directly determines the operational stability of the water supply system. Currently, the traditional threaded joint sealants used in these projects have revealed numerous technical defects in practical applications, failing to meet the demands of modern water supply engineering for environmentally friendly construction and long-term quality assurance.

[0003] The primary problem with traditional sealants is their insufficient environmental friendliness. They contain a large amount of volatile organic compounds (VOCs), which release irritating odors during application, harming the health of workers and polluting the construction site and surrounding environment. Furthermore, discarded sealants easily seep into the soil, causing pollution. Secondly, they have poor compatibility with various materials, exhibiting uneven adhesion to pipes of different materials commonly found in older residential areas, such as plastic-lined steel pipes and PE pipes, leading to leaks at joints and affecting the sealing of the water supply system. Thirdly, their sealing durability is lacking. Under the long-term humid environment, temperature fluctuations, and continuous water pressure of water supply pipes, the sealing performance deteriorates rapidly, significantly shortening the overall lifespan of the pipes. In addition, the curing speed of traditional sealants is poorly designed; excessively fast curing can cause cracks, while excessively slow curing severely impacts construction efficiency and prolongs the project duration.

[0004] Taking the Luoding City water supply upgrade and renovation project as an example, this project involves 36 residential communities and more than 30,000 households. It presented comprehensive requirements for the sealing of threaded joints, including environmental friendliness, compatibility with multiple materials, high sealing reliability, and efficient construction. The aforementioned shortcomings of traditional sealants made them unsuitable for the construction requirements of this type of project. Therefore, developing a threaded joint sealant with excellent environmental performance, compatibility with multiple pipe materials, stable sealing, and convenient construction, to solve the industry pain points of traditional products such as high pollution, poor compatibility, and easy leakage, has become an urgent need in the field of municipal water supply engineering. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing an environmentally friendly sealant for threaded joints in water supply networks and its preparation process. The core objectives are to achieve the following technical goals: the sealant is environmentally friendly with low VOC content, has no irritating odor, and releases no toxic or harmful substances after curing, meeting the environmental protection requirements for construction in sensitive urban areas; it improves the sealant's compatibility with various materials, enabling tight sealing of threaded joints made of different materials and reducing the difficulty of material selection during construction; it enhances the sealant's sealing durability, extending the service life of the water supply network; and it optimizes the sealant's application performance, allowing for application in humid environments without complex interface pretreatment, ensuring construction efficiency and reducing overall construction costs.

[0006] To achieve the above objectives, the present invention provides an environmentally friendly sealant for threaded joints in water supply networks, comprising the following components by weight percentage: 40%-50% environmentally friendly base material, 20%-30% modified filler, 5%-10% bio-based tackifier, 3%-8% environmentally friendly curing agent, 2%-5% functional additives, and the balance being deionized water; wherein the environmentally friendly base material is waterborne polyurethane resin, the modified filler is a compound of nano-silica and talc, the bio-based tackifier is modified from plant extracts, and the environmentally friendly curing agent is waterborne isocyanate. After modification, plant extracts introduce hydrophilic active groups such as hydroxyl and carboxyl groups, which can form hydrogen bonds with the amino and ester groups of waterborne polyurethane base materials. They can be uniformly dispersed in aqueous systems with deionized water as the dispersion medium without stratification or agglomeration, ensuring the stability of the adhesive system. The tackifier modified by plant extracts has both polar and non-polar groups. The polar groups can form electrostatic adsorption and hydrogen bond with the metal substrate and plastic lining of the plastic-lined steel pipe, while the non-polar structure can form intermolecular forces with the non-polar molecules of PE pipe, perfectly adapting to the connection needs of various pipe materials such as plastic-lined steel pipes and PE pipes in old residential areas.

[0007] Furthermore, the modified filler has a particle size ≤50nm, and the functional additives are formulated from food-grade preservatives, anti-aging agents, and defoamers. The core active group of the waterborne isocyanate is isocyanate (-NCO), which can undergo an addition reaction with the hydroxyl groups (-OH) in the waterborne polyurethane base material molecules to form a stable polyurethane urea crosslinking network, transforming the adhesive from a linear molecular structure to a three-dimensional network structure, significantly improving the sealing layer's resistance to pressure, flexural stress, and water pressure.

[0008] Furthermore, the mass ratio of nano-silica to talc is 2~5:1. Nano-silica is a nano-sized powder with a large specific surface area and rich in hydroxyl groups. It can form hydrogen bonds and chemical bonds with the amino and ester groups of waterborne polyurethane base materials and the active groups of bio-based tackifiers. At the same time, it can form physical adsorption and chemical bonding with the surface of plastic-lined steel pipes and PE pipes, which is the key to improving the adhesion strength of the adhesive. Talc is a layered silicate powder with a chemically inert surface and weak bonding force with waterborne polyurethane base materials. If the mass ratio is <2:1, it will lead to a significant reduction in the interfacial bonding force between the compound filler and the base material. After the adhesive cures, the filler is prone to peeling off from the base material, resulting in micro-gaps in the sealing layer, which in turn leads to leakage under water pressure. Due to its high surface energy, nano-silica exhibits a strong tendency to agglomerate. If its ratio exceeds 5:1, it is difficult to completely break up the agglomerates under conventional mixing processes in a high-speed disperser. This results in particulate impurities in the adhesive, making it impossible to form a uniform sealing layer during application and easily leaving sealing dead zones at threaded joints. Simultaneously, the agglomerated nanoparticles create pores in the sealing layer, reducing its impermeability. A small amount of talc powder, however, can reduce the internal friction between nano-silica particles, aiding in their dispersion in the base material and preventing agglomeration.

[0009] Furthermore, the bio-based tackifier is one or more of maleic anhydride-modified rosin ester, hydrogenated rosin polyethylene glycol ester, hydroxypropyl methylcellulose ether, propylene oxide-modified lignin, and acetylated modified gum arabic.

[0010] Furthermore, the food-grade preservative is one or more of sodium benzoate, calcium benzoate, potassium sorbate, and sodium sorbate; the anti-aging agent is one or more of antioxidant 264 (BHT), antioxidant 1010, antioxidant 1076, thiodipropionate, and phosphites; and the defoamer is one or more of emulsified silicone oil, polydimethylsiloxane, polyoxypropylene glycerol ether, polyoxypropylene ethylene oxide glycerol ether, and DSA-5.

[0011] On the other hand, the present invention also provides a preparation process for an environmentally friendly sealant for threaded joints in water supply networks as described above, comprising the following steps: S1, pretreatment: drying the modified filler for later use; S2, base material dispersion: adding the environmentally friendly base material to a high-speed disperser in proportion, adding deionized water and stirring to form a uniform dispersion system; S3, component mixing: adding the modified filler and bio-based tackifier sequentially to the dispersion system, increasing the speed and stirring until the filler is uniformly dispersed; S4, curing and optimization: adding an environmentally friendly curing agent and functional additives, adjusting the speed and stirring, and then allowing it to stand to remove bubbles to obtain the finished sealant.

[0012] Furthermore, in step S2, the speed of the high-speed disperser is 600-900 r / min, and the stirring time is 10-30 minutes; in step S3, the speed of the high-speed disperser is increased to 1000-1500 r / min, and the stirring time is 20-50 minutes; in step S4, the speed of the high-speed disperser is adjusted to 400-800 r / min, and the stirring time is 10-30 minutes.

[0013] Furthermore, in step S1, the drying temperature is 50-100℃ and the drying time is 1-5 hours; in step S4, after stirring, the viscosity of the finished sealant is controlled at 5000-8000 mPa·s, and the time for standing to remove bubbles is 5-30 minutes.

[0014] This invention also provides an application process for the environmentally friendly sealant used in the threaded joint of the water supply network as described above, characterized by the following steps: S1, Interface pretreatment: Cleaning impurities from the surface of the threaded joint and the pipe interface, and controlling the interface humidity; S2, Adhesive application: Applying the finished sealant evenly to the inner wall of the threaded joint and the outer surface of the pipe interface, controlling the coating thickness; S3, Connection and curing: Inserting the pipe into the threaded joint and tightening it, allowing it to stand at room temperature to complete the initial curing, and then allowing it to fully cure; S4, Quality inspection: Conducting a water pressure test on the cured joint to determine whether the seal is qualified.

[0015] Furthermore, in step S3, the room temperature standing time is 15-30 minutes to complete the initial curing, and the standing time for complete curing is 24 hours; in step S4, the water pressure test pressure is 1.6MPa, the pressure holding time is 30 minutes, and no leakage means that the seal is qualified.

[0016] The beneficial effects of this invention are: (1) The adhesive uses water-based polyurethane resin as the base material and water-based isocyanate as the curing agent, combined with a bio-based tackifier modified with plant extracts to form a solvent-free water-based system. It has low VOC content and no irritating odor, so it will not harm the health of construction workers during construction, nor will it pollute the construction site and surrounding environment. After curing, no toxic or harmful substances are released, avoiding soil pollution and making it suitable for construction requirements in sensitive urban areas such as old residential areas. At the same time, the functional additives are food-grade preservatives, and the adhesive will not cause secondary pollution when in contact with drinking water, meeting the sanitary and safety standards of municipal water supply.

[0017] (2) After modification, the bio-based adhesive has both polar groups and non-polar structures. The polar groups can form electrostatic adsorption and hydrogen bonding with the metal substrate and plastic lining of the plastic-lined steel pipe. The non-polar structure can form intermolecular forces with the non-polar molecules of the PE pipe. Combined with the interfacial bonding effect of the nano-modified filler, the adhesive has excellent adhesion to various materials such as plastic-lined steel pipe and PE pipe commonly found in old residential areas. This solves the problem of uneven adhesion of traditional adhesives to different materials, greatly reduces the difficulty of material selection during construction, and achieves tight sealing of threaded joints of different materials.

[0018] (3) Nano-silica and talc are compounded at a ratio of 2~5:1 with a particle size ≤50nm. The two form a synergistic effect of enhanced activity and external structural shielding. Nano-silica achieves nano-reinforcement and improves interfacial adhesion, while the layered structure of talc disperses water pressure stress and forms a labyrinthine seepage-proof layer. At the same time, waterborne isocyanate and waterborne polyurethane base material undergo cross-linking reaction to form a dense three-dimensional network structure, which greatly improves the adhesive's compressive strength, water pressure resistance, and temperature change resistance. The adhesive can be used stably for a long time with extremely low interface leakage rate, effectively extending the overall service life of the water supply network and achieving long-term sealing performance.

[0019] (4) The plant extract modified bio-based tackifier introduces hydrophilic active groups, which can form hydrogen bonds with water-based polyurethane base materials. Each component can be uniformly dispersed in deionized water dispersion medium without layering or agglomeration. The modified filler is pre-treated by drying and combined with a gradient speed dispersion stirring process to further ensure the uniformity of the filler in the system. Among the functional additives, the defoamer eliminates bubbles in the preparation process, the preservative prevents the glue from becoming moldy in a humid environment, and the anti-aging agent improves the weather resistance of the glue. The synergistic effect of multiple additives greatly improves the storage stability and use stability of the glue, effectively avoiding sealing defects caused by system instability. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of protection of the present invention.

[0021] I. Core Experimental Conditions Preparation process parameters: modified filler drying 80℃ / 2h; base material dispersion 800r / min / 15min; component mixing 1200r / min / 30min; curing optimization 600r / min / 20min; adhesive viscosity control 5000-8000mPa·s; Application process parameters: interface moisture content 8% (slightly damp conditions), adhesive thickness 0.8mm, application at room temperature (25±5℃); Durability test: After temperature change cycling from -10℃ to 60℃ (1 time / 2h, 1000 times in total), leakage test is performed by holding the water pressure at 1.6MPa for 30 minutes. Workability rating: 10 points, evaluated from three dimensions: smooth application, slightly wet film formation, and no sagging. ≥8 points is excellent, 5-7 points is average, and ≤4 points is poor.

[0022] II. Formulation Design of Examples

[0023] Comparative Example 1 The remaining components are the same as in Example 2, except that the modified filler is a single nano-SiO2 without talc, accounting for 25%.

[0024] Comparative Example 2 The remaining components are the same as in Example 2, except that the modified filler is a single nano-talc powder, without SiO2, accounting for 25%.

[0025] Comparative Example 3 The remaining components are the same as in Example 2, except that the ratio of modified filler nano-SiO2 to talc is 1:1.

[0026] Comparative Example 4 The remaining components are the same as in Example 2, except that the ratio of modified filler nano-SiO2 to talc is 7:1.

[0027] Comparative Example 5 The remaining components are the same as in Example 2, except that a petrochemical-based tackifier (petroleum resin) is used instead of a bio-based tackifier.

[0028] Comparative Example 6 The remaining components are the same as in Example 2, except that solvent-based isocyanate is used instead of aqueous isocyanate.

[0029] III. Experimental Detection Results Table 1. Detection results of the examples

[0030] Table 2 Comparative test results

[0031] IV. Experimental Data Analysis The experimental data above shows that in Comparative Example 1, the single nano-SiO2 filler, without talc, met environmental standards, but exhibited slightly reduced adhesion strength, a leakage rate of 0.3%, and a workability score of only 5.6. The core reason is that the high surface energy of nano-SiO2, without the lubricating dispersion aid of talc, easily leads to agglomeration during preparation, resulting in micropores in the sealing layer. After temperature cycling, these pores expand, causing slight leakage. Simultaneously, the agglomerated nanoparticles cause fine particles in the adhesive, resulting in poor application smoothness, uneven spreading, and a significant decrease in workability. This indicates that the addition of talc is a necessary component to solve the agglomeration of nano-SiO2 and improve workability and sealing performance. Comparative Example 2 used a single nano-talc filler, without SiO2, meeting environmental standards, but exhibited extremely low adhesion strength, a leakage rate as high as 18.5%, and a workability score of only 7.8. Talc powder, a layered silicate powder, has a chemically inert surface and extremely weak adhesion to water-based polyurethane base materials. It cannot form effective chemical / hydrogen bonds with the base material or pipe surface, resulting in a sealing layer that relies solely on physical adhesion. Under temperature changes and water pressure, this adhesion rapidly peels off, causing severe leakage. Although the slipperiness of talc powder allows for relatively smooth application, the core adhesion and sealing performance is completely ineffective. This indicates that nano-SiO2 is the core filler for improving the interfacial adhesion strength of the adhesive and ensuring sealing durability. In Comparative Example 3, the filler ratio was 1:1, with excessive talc powder. While environmental compliance was met, the adhesion strength was lower than the patent requirement, the leakage rate was 6.2%, and the workability score was 6.1. Excessive talc powder significantly diluted the active binding sites of nano-SiO2 due to its inert surface, leading to a sharp decrease in the interfacial adhesion between the filler and the base material. After curing, micro-peeling easily occurs between the filler and the base material, forming leakage channels. Simultaneously, excessive talc powder reduces the overall strength of the sealing layer, and micro-peeling expands after temperature cycling, causing significant leakage. In Comparative Example 4, the filler ratio was 7:1, with excessive SiO2, meeting environmental standards, resulting in a leakage rate of 0.5% and a workability score of 5.2. The excessive SiO2 ratio exacerbated agglomeration; even high-speed dispersion could not completely break up the agglomerates, leading to micropores in the sealing layer and slight leakage. Furthermore, the agglomerated nanoparticles slightly increased the adhesive viscosity, making it prone to clumping and uneven spreading during application, resulting in even worse workability than Comparative Example 1. In Comparative Example 5, replacing the bio-based tackifier with a petrochemical-based tackifier caused a sharp increase in VOCs content to 36.2 g / L, resulting in slightly lower adhesion strength, a leakage rate of 1.5%, and a workability score of 7.6. Petrochemical-based petroleum resins are oil-soluble and have poor compatibility with the water-based system of this patent, making them difficult to disperse evenly. Furthermore, they lack the polar / non-polar dual structure of bio-based tackifiers, resulting in reduced adhesion to pipes made of various materials and the presence of micro-gaps in the sealing layer. At the same time, petrochemical-based tackifiers themselves contain volatile organic solvents, leading to a significant increase in VOCs content and compromising the environmental friendliness of the adhesive. This indicates that plant extract-modified bio-based tackifiers are the core component for achieving low VOCs environmental friendliness and high compatibility with multiple materials.In Comparative Example 6, the use of solvent-based isocyanate instead of water-based isocyanate resulted in a VOC content as high as 63.8 g / L, a curing time of only 10 minutes, a leakage rate of 1.0%, blistering of the sealing layer, and a workability score of 3.8. Solvent-based isocyanate releases a large amount of volatile organic solvents, leading to excessive VOCs. Its strong side reaction with water, under slightly damp construction conditions, reacts with moisture at the interface to generate numerous bubbles, causing porosity in the sealing layer. Simultaneously, the excessively rapid curing reaction leaves insufficient time for construction personnel to complete pipe connections, and rapid curing easily induces micro-cracks in the sealing layer. After temperature cycling, these cracks expand, causing leakage and complete failure of workability. This demonstrates that water-based isocyanate is key to achieving environmental friendliness, adaptability to damp construction, and controllable curing speed.

[0032] The above description is merely a preferred 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. An environmentally friendly sealant for threaded joints in water supply networks, characterized in that, It is composed of the following components by weight percentage: 40%-50% environmentally friendly base material, 20%-30% modified filler, 5%-10% bio-based tackifier, 3%-8% environmentally friendly curing agent, 2%-5% functional additives, and the balance being deionized water; the environmentally friendly base material is water-based polyurethane resin, the modified filler is a compound of nano-silica and talc, the bio-based tackifier is modified from plant extracts, and the environmentally friendly curing agent is water-based isocyanate.

2. The environmentally friendly sealant for threaded joints in water supply networks according to claim 1, characterized in that, The modified filler has a particle size ≤50nm, and the functional additive is a compound of food-grade preservatives, anti-aging agents, and defoamers.

3. The environmentally friendly sealant for threaded joints in water supply networks according to claim 1 or 2, characterized in that, The mass ratio of nano-silica to talc is 2~5:

1.

4. The environmentally friendly sealant for threaded joints in water supply networks according to claim 1 or 2, characterized in that, The bio-based tackifier is one or more of maleic anhydride-modified rosin ester, hydrogenated rosin polyethylene glycol ester, hydroxypropyl methylcellulose ether, propylene oxide-modified lignin, and acetylated modified gum arabic.

5. The environmentally friendly sealant for threaded joints in water supply networks according to claim 2, characterized in that, The food-grade preservative is one or more of sodium benzoate, calcium benzoate, potassium sorbate, and sodium sorbate; the anti-aging agent is one or more of antioxidant 264 (BHT), antioxidant 1010, antioxidant 1076, thiodipropionate, and phosphites; the defoamer is one or more of emulsified silicone oil, polydimethylsiloxane, polyoxypropylene glycerol ether, polyoxypropylene ethylene oxide glycerol ether, and DSA-5.

6. A preparation process for an environmentally friendly sealant for threaded joints in water supply networks as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Pretreatment: Dry the modified filler and set it aside for later use; S2. Base material dispersion: Add the environmentally friendly base material to a high-speed disperser according to the ratio, add deionized water and stir to form a uniform dispersion system; S3. Component mixing: Add the modified filler and bio-based tackifier to the dispersion system in sequence, increase the speed and stir until the filler is uniformly dispersed; S4. Curing and optimization: Add the environmentally friendly curing agent and functional additives, adjust the speed and stir, and let stand to remove bubbles to obtain the finished sealant.

7. The preparation process according to claim 6, characterized in that, In step S2, the speed of the high-speed disperser is 600-900 r / min, and the stirring time is 10-30 minutes; in step S3, the speed of the high-speed disperser is increased to 1000-1500 r / min, and the stirring time is 20-50 minutes; in step S4, the speed of the high-speed disperser is adjusted to 400-800 r / min, and the stirring time is 10-30 minutes.

8. The preparation process according to claim 6, characterized in that, In step S1, the drying temperature is 50-100℃ and the drying time is 1-5 hours; in step S4, after stirring, the viscosity of the finished sealant is controlled at 5000-8000 mPa·s, and the standing time for defoaming is 5-30 minutes.

9. An application process for an environmentally friendly sealant for threaded joints in water supply networks as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Interface Pretreatment: Clean impurities from the surface of the threaded joint and the pipe interface, and control the humidity of the interface; S2. Adhesive Application: Apply the finished sealant evenly to the inner wall of the threaded joint and the outer surface of the pipe interface, and control the thickness of the adhesive application; S3. Connection and Curing: Insert the pipe into the threaded joint and tighten it to fix it. Allow it to stand at room temperature to complete the initial curing, and then let it stand until it is fully cured; S4. Quality Inspection: Conduct a water pressure test on the cured joint to determine whether the seal is qualified.

10. The application process according to claim 9, characterized in that, In step S3, the room temperature standing time is 15-30 minutes to complete the initial curing, and the standing time for complete curing is 24 hours; in step S4, the water pressure test pressure is 1.6MPa, the pressure holding time is 30 minutes, and the seal is qualified if there is no leakage.

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