A sealant for PCCP pipe joint and a method for preparing and applying the same

Abstract

The application discloses a PCCP pipeline interface sealant and a preparation and application method thereof, and belongs to the technical field of sealants. The application aims to solve the problems of poor flowability, insufficient elastic recovery, weak interface adhesion, poor low-temperature construction adaptability and poor hydrolysis resistance of the existing PCCP pipeline interface sealant, and overcome the defects of the existing deep water pipeline repair glue, such as two-component construction complexity and unsuitability for PCCP interface filling requirements. The sealant is a single-component polyurethane system, the core component contains DL-2000D polyether, EP-330NG polyether, 330 polyether and the like, and a defoaming agent is added once to simplify the process. The sealant has an elastic recovery rate of greater than or equal to 90%, an elongation at break of greater than or equal to 500%, and a tensile strength of greater than or equal to 5.4 MPa, can be constructed at a temperature of-10 to 50 DEG C, has excellent hydrolysis resistance and corrosion resistance, can fully fill irregular gaps at the interface, and has strong adhesion to concrete and steel cylinder base materials. The preparation process is simple, the sealant is suitable for PCCP pipeline interface sealing in the fields of water conservancy and hydropower, municipal water supply and drainage and the like, and industrial production and on-site construction are convenient.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology, specifically the field of sealant synthesis and preparation technology, and relates to a PCCP pipe interface sealant and its preparation and application method. Background Technology

[0002] PCCP pipes, as composite pipes combining the high strength of concrete and the impermeability of steel cylinders, have become core pipe materials in major infrastructure construction. Their joint sealing performance directly determines the operational stability of the pipeline system. PCCP pipe joints must meet multiple stringent requirements: they must adapt to slight displacements caused by temperature changes and foundation settlement, possessing excellent elastic recovery capabilities; they must withstand pipeline pressure, ensuring sufficient tensile strength; they must adapt to different climatic environments, especially the low-temperature flexibility requirements of winter construction in northern regions; they must also withstand long-term immersion in water, possessing good hydrolysis resistance; and they must be able to fully fill irregular gaps at the joint, avoiding dead sealing corners.

[0003] Existing sealants have many shortcomings in pipeline sealing and repair technology. Chinese patent application CN104927731B discloses a sealant for repairing deep-water pipelines. This sealant adopts a two-component design (components A and B), and achieves complete underwater curing, good elasticity, and high bonding strength through the compounding of elastic epoxy resin and hydrophobic curing agent. It can effectively resist the impact of ocean waves and is suitable for repairing damage to the outer skin of deep-water marine pipelines. However, this technology differs fundamentally from the core requirements of PCCP pipe interface sealing: First, this technology targets the bonding and repair of localized damage to the pipe's outer surface, eliminating the need to fill irregular gaps. Its fluidity design is not adapted to the filling requirements of PCCP interfaces, which have minute gaps and irregular structures, requiring the sealant to have good fluidity for full filling. Second, this technology is a two-component system, requiring precise mixing during construction, increasing the difficulty of on-site construction and the risk of human error. PCCP pipe installations are mostly batch constructions, requiring single-component, easy-to-use sealing materials. Third, the elastic design of this technology is designed to adapt to the deformation of the pipe surface under wave impact, rather than the interface displacement caused by temperature changes and foundation settlement during PCCP pipe operation. Its elastic recovery rate and deformation compensation capacity cannot meet the long-term stability requirements of interface sealing. In addition, this technology does not address low-temperature construction adaptability design, failing to meet the installation needs of PCCP pipes in low-temperature environments such as northern winters.

[0004] Current sealants specifically designed for PCCP pipe joints have several shortcomings: their elastic recovery rate is less than 60%, making them prone to cracking and detachment under slight pipe displacement; their tensile strength and elongation at break are unbalanced, making it difficult to simultaneously meet the requirements for pressure resistance and deformation adaptability; their flexibility decreases at low temperatures (≤0℃), making them prone to brittleness and limiting construction in northern winters; their hydrolysis resistance is poor, and their performance degrades rapidly after long-term immersion in water; their interfacial adhesion to concrete and steel cylinder substrates is insufficient, making them prone to peeling under high pressure; their flowability is poor, failing to fully fill tiny gaps in the joint and creating sealing blind spots; and some products require multiple additions of defoamer, increasing the complexity of the preparation process and hindering industrial mass production. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention discloses a sealant for PCCP pipe joint installation and its preparation and application methods.

[0006] This invention aims to achieve the following objectives: 1. Based on the original formula of triether synergistic compounding, it solves the problem of imbalance between tensile strength and elongation at break of traditional sealants; 2. It enhances elastic recovery ability to adapt to slight pipeline displacement; 3. It optimizes low-temperature construction performance to meet the construction requirements of environments above -10℃; 4. It enhances hydrolysis and corrosion resistance and extends service life; 5. It adopts a one-time defoamer addition design to simplify the preparation process and adapt to industrial mass production; 6. It optimizes fluidity to fully fill irregular gaps in PCCP interfaces and eliminate sealing dead corners.

[0007] This invention first discloses a PCCP pipe joint sealant, characterized in that it is made of the following components A and B in parts by weight:

[0008] Component A: DL-2000D polyether polyol 230-280 parts, EP-330NG polyether polyol 260-320 parts, DINP 18-23 parts, TDI 75-85 parts;

[0009] Component B: 4-5 parts diethylene glycol, 150-180 parts auxiliary polyether, 150-200 parts fine calcium powder, 260-300 parts trihydroxy polyoxypropylene ether, 2-4 parts defoamer, 0.5-1 part color paste, 30-35 parts coupling agent, and 0.5-1 part catalyst.

[0010] Furthermore, the polyether polyol DL-2000D is a bifunctional polyether polyol with a hydroxyl value of 54.5–57.5 mgKOH / g, a viscosity of 270–370 mPa·s at 25°C, and a moisture content of ≤0.02%; the polyether polyol EP-330NG is a trifunctional highly active polyether polyol with a hydroxyl value of 32.5–35.5 mgKOH / g, a viscosity of 800–1000 mPa·s at 25°C, and a moisture content of ≤0.05%.

[0011] Furthermore, the trihydroxy polyoxypropylene ether is a trifunctional high-resilience polyether with a heat resistance temperature of -40 to 90°C; the auxiliary polyether is a polyoxypropylene glycol or polyoxypropylene triol with a molecular weight of 400 to 4000.

[0012] Furthermore, the defoamer is an organosilicon defoamer.

[0013] Furthermore, the coupling agent is a silane coupling agent KH550 or KH560; the catalyst is an organotin catalyst; the particle size of the fine calcium powder is 600-800 mesh, and the fine calcium powder is surface treated with dibutylamine to further improve its compatibility with the polyether matrix.

[0014] Furthermore, the DINP is diisononyl phthalate with a purity ≥99%; the TDI is toluene diisocyanate with a 2,4-isomer content ≥80%.

[0015] The present invention further discloses a method for preparing a PCCP pipe joint sealant, characterized by comprising the following steps:

[0016] (1) Preparation of mixture A: Weigh out polyether polyol DL-2000D, polyether polyol EP-330NG, DINP and TDI according to the mass fractions, add them to the reactor, heat to 80-85℃ while stirring, keep warm and stir for 2 hours, stirring rate 300-500r / min; then continue to heat to 90-95℃, keep warm and stir for 1 hour to obtain a uniform prepolymer mixture A;

[0017] (2) Preparation of mixture B: Weigh trihydroxy polyoxypropylene ether, auxiliary polyether, fine calcium powder and color paste according to the mass parts, add them to another reaction vessel, heat to 110-120°C while stirring, turn on the vacuum system to dehydrate for 30 minutes; after the vacuum is released, add diethylene glycol and defoamer, keep the speed at 300-500 r / min and stir for 30 minutes, cool down to 70°C; add catalyst and coupling agent, continue to disperse for 20 minutes, and cool naturally to room temperature to obtain mixture B;

[0018] (3) Preparation of finished product: Slowly add mixture A to mixture B, stir at 300-500 r / min for 60 minutes at 25-30℃, and then remove bubbles for 30 minutes under vacuum of -0.08--0.1MPa. After passing the inspection, it is the sealant for PCCP pipe joint installation.

[0019] Furthermore, in step (1), TDI is added in two stages. The first stage adds 60% of the total amount, and the remaining 40% is added after the temperature is raised to 90°C. The above two-stage addition method can improve the uniformity of the prepolymerization reaction and avoid excessive local reaction leading to performance imbalance.

[0020] Furthermore, the vacuum degree of the dehydration process in step (2) remains stable, and the moisture content of the material after moisture removal is ≤0.05%, so as to avoid the moisture affecting the integrity of the polyurethane crosslinking reaction; the defoamer is added after dehydration, which can maximize the elimination of bubbles generated during material mixing and dehydration.

[0021] This invention further provides a method for applying the above-mentioned PCCP pipe joint sealant, characterized in that: the construction temperature is -10 to 50℃, the construction environment can be humid or dry, the sealant is evenly applied to the concrete or steel cylinder contact surface of the PCCP pipe joint, the application thickness is 1 to 5 mm, and the joint can be sealed after natural curing for 12 to 24 hours; it is suitable for sealing PCCP pipe joints with a diameter of 500 to 4000 mm, can withstand complex water quality environments with pH values ​​of 4 to 10, and has a pressure resistance and sealing performance of ≥1.6 MPa after curing.

[0022] This invention provides a sealant for PCCP pipe interfaces suitable for sealing in water conservancy and hydropower projects, municipal water supply and drainage networks, and industrial water transmission networks. This sealant can withstand humid, underwater, and low-temperature environments.

[0023] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0024] Synergistic optimization of core polyethers for balanced performance: Following the formulation of polyether polyol DL-2000D (bifunctional, molecular weight 2000), polyether polyol EP-330NG (trifunctional, molecular weight 5000), and trihydroxy polyoxypropylene ether, the three work synergistically—polyether polyol DL-2000D improves elongation at break and flexibility, polyether polyol EP-330NG enhances tensile strength and resilience, and trihydroxy polyoxypropylene ether ensures low-temperature flexibility and weather resistance. This successfully solves the technical pain point of the imbalance between elasticity and strength in traditional sealants, achieving a precise balance of elasticity recovery rate ≥90%, elongation at break ≥500%, and tensile strength ≥5.4MPa.

[0025] The process is simplified and highly adaptable to industrial applications: the defoamer is optimized from being added in two stages to being added in one stage, and is precisely added after the dehydration of mixture B. This ensures the defoaming effect (eliminating bubbles during material mixing and dehydration), simplifies the preparation process, reduces operational errors in the production process, lowers the difficulty of industrial production, and improves production efficiency.

[0026] It has wide environmental adaptability and is not limited by construction scenarios: it can be constructed in a wide temperature range of -10 to 50℃, does not crack at low temperatures, and does not soften at high temperatures, making it suitable for both northern winters and hot and humid southern environments; it does not rely on a dry construction environment and can still cure normally under humid conditions, solving the problem of outdoor construction being affected by weather, while avoiding the construction complexity of the two-component system in the comparison document.

[0027] Excellent sealing and adhesion performance: The plasticizing system of DINP and diethylene glycol in the formula optimizes the rheological properties, and the flowability is precisely adapted to fill the irregular gaps of the PCCP interface, with no dead corners in the seal; the coupling agent and the surface treatment micro-fine calcium powder work together to greatly improve the interfacial adhesion with concrete and steel cylinder substrates, with a tensile shear strength ≥6.3MPa, and it does not peel or fall off under long-term water pressure.

[0028] High stability and long service life: TDI undergoes a cross-linking reaction with three polyethers to form a stable polyurethane network structure. Combined with the hydrolysis-resistant modification effect of diethylene glycol, the product's performance degradation rate is ≤5% after long-term immersion in water, and its corrosion resistance is significantly better than traditional sealants. At the same time, it avoids the shortcomings of the comparison document, which is only suitable for pipe surface repair and cannot withstand long-term water pressure, and is suitable for the long-term sealing requirements of PCCP interfaces. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. These specific embodiments are further explanations of the principles of the present invention and are not intended to limit the present invention in any way. Any technology that is the same as or similar to the present invention does not exceed the scope of protection of the present invention.

[0030] Example 1

[0031] The sealant for PCCP pipe joint installation is composed of the following parts by weight: 250 parts of polyether polyol DL-2000D, 290 parts of polyether polyol EP-330NG, 20 parts of DINP, 2 parts of silicone defoamer, 80 parts of TDI, 4.5 parts of diethylene glycol, 165 parts of auxiliary polyether (polyoxypropylene glycol, molecular weight 2000), 175 parts of fine calcium powder (700 mesh, dibutylamine treated), 280 parts of trihydroxy polyoxypropylene ether, 0.8 parts of color paste, 32 parts of silane coupling agent KH560, and 0.7 parts of organotin catalyst.

[0032] Preparation method:

[0033] Preparation of Mixture A: Weigh polyether polyol DL-2000D, polyether polyol EP-330NG, and DINP, add them to a reaction vessel, stir at 400 r / min until homogeneous, and heat to 82℃ while stirring; add 48 parts of TDI (60% of the total amount) for the first time, and keep the temperature and stir for 2 hours; continue to heat to 92℃, add 32 parts of TDI (the remaining 40%), and keep stirring at 400 r / min for 1 hour to obtain a homogeneous mixture A;

[0034] Preparation of Mixture B: Weigh trihydroxy polyoxypropylene ether, auxiliary polyether (165 parts), fine calcium powder, and color paste, add them to another reaction vessel, stir at 400 r / min until homogeneous, and heat to 115℃ while stirring. Turn on the vacuum system (vacuum degree -0.09MPa) to dehydrate for 30 minutes (moisture content after dehydration is 0.03%). After releasing the vacuum, add diethylene glycol and 2 parts of organosilicon defoamer, and stir at 400 r / min for 30 minutes. Cool down to 70℃, add organotin catalyst and silane coupling agent KH560, continue to disperse for 20 minutes, and cool naturally to room temperature to obtain Mixture B.

[0035] Preparation of finished product: Slowly add mixture A to mixture B, stir at 400 r / min for 60 minutes at 28℃, and then remove bubbles for 30 minutes under vacuum of -0.09 MPa. The finished product is obtained after passing the inspection.

[0036] Performance testing: At a construction temperature of 25℃, after curing for 24 hours, the elastic recovery rate is 92%, the elongation at break is 520%, the tensile strength is 5.8MPa, the tensile shear strength (concrete-steel cylinder interface) is 7.6MPa, the pressure resistance and sealing performance is 1.8MPa, and there is no brittleness or delamination at -10℃; after long-term immersion for 30 days (pH=7 water), the performance degradation rate is 3.2%, with no dissolution or peeling; the product has no internal bubble defects and excellent defoaming effect.

[0037] Example 2

[0038] The sealant for PCCP pipe joint installation is composed of the following parts by weight: 230 parts of polyether polyol DL-2000D, 260 parts of polyether polyol EP-330NG, 18 parts of DINP, 2 parts of silicone defoamer, 75 parts of TDI, 4 parts of diethylene glycol, 150 parts of auxiliary polyether (polyoxypropylene triol, molecular weight 1500), 150 parts of fine calcium powder (600 mesh, dibutylamine treated), 260 parts of trihydroxy polyoxypropylene ether, 0.5 parts of color paste, 30 parts of silane coupling agent KH550, and 0.5 parts of organotin catalyst.

[0039] The preparation method is the same as in Example 1, except that the stirring speed is adjusted to 350 r / min. 45 parts of TDI are added for the first time (60% of the total amount), and 30 parts are added for the second time (the remaining 40%). The moisture content after dehydration is 0.04%.

[0040] Performance testing: At an application temperature of -10℃, after curing for 24 hours, the elastic recovery rate is 90%, the elongation at break is 500%, the tensile strength is 5.4MPa, the tensile shear strength is 6.5MPa, and the pressure resistance and sealing performance is 1.6MPa. After long-term immersion for 30 days (in water with pH=4), the performance degradation rate is 4.8%, with no dissolution or peeling. There are no air bubble defects inside the product, and the defoaming effect is stable.

[0041] Example 3

[0042] The sealant for PCCP pipe joint installation is composed of the following parts by weight: 280 parts of polyether polyol DL-2000D, 320 parts of polyether polyol EP-330NG, 23 parts of DINP, 4 parts of silicone defoamer, 85 parts of TDI, 5 parts of diethylene glycol, 180 parts of auxiliary polyether (polyoxypropylene glycol, molecular weight 2500), 200 parts of fine calcium powder (800 mesh, dibutylamine treated), 300 parts of trihydroxy polyoxypropylene ether, 1 part of color paste, 35 parts of silane coupling agent KH560, and 1 part of organotin catalyst.

[0043] The preparation method is the same as in Example 1. The stirring speed is adjusted to 450 r / min. 51 parts of TDI are added for the first time (60% of the total amount), and 34 parts are added for the second time (the remaining 40%). The moisture content after dehydration is 0.02%.

[0044] Performance testing: At an application temperature of 50℃, after curing for 12 hours, the elastic recovery rate is 93%, the elongation at break is 530%, the tensile strength is 6.2MPa, the tensile shear strength is 7.8MPa, and the pressure resistance and sealing performance is 2.0MPa. After long-term immersion in water at pH=10 for 30 days, the performance degradation rate is 2.9%, with no dissolution or peeling. There are no air bubble defects inside the product, and the defoaming effect is significant.

[0045] Comparative Example 1 (Traditional PCCP Interface Sealant)

[0046] A single polyether (molecular weight 3000) was used as the matrix. No polyether polyol DL-2000D, polyether polyol EP-330NG and trihydroxy polyoxypropylene ether were added. The defoamer was added in two parts (1 part each). Other components were in the same proportions as the non-core components in Example 1.

[0047] Performance testing: The product exhibits the following characteristics: construction temperature range of 10–35℃; brittle fracture at -10℃; elastic recovery rate of 65%; elongation at break of 320%; tensile strength of 4.2 MPa; tensile shear strength of 4.5 MPa; pressure resistance and sealing performance of 1.0 MPa; performance degradation rate of 15.6% after 30 days of long-term immersion; slight peeling occurs; a small number of microbubbles are present inside the product, and the defoaming effect is generally poor; the manufacturing process involves multiple steps, resulting in a production efficiency 20% lower than that of this invention.

[0048] Comparative Example 2 (Comparison document CN104927731B product)

[0049] The two-component sealant disclosed in this patent is used, with component A (85 parts of MS-1086T elastic epoxy resin, 5 parts of polysulfide rubber, 10 parts of nano alumina, and 0.1 parts of E8 defoamer) and component B (20 parts of 810 curing agent, 35 parts of JA-IS curing agent, and 0.2 parts of accelerator), and the mass ratio of component A to component B is 1:0.55.

[0050] Performance testing: When used for sealing PCCP interfaces, it has insufficient fluidity and cannot fill tiny gaps in the interface; the construction window after mixing the two components is short (only 2 hours), making batch construction difficult; it cannot cure at -10℃; the tensile shear strength at the concrete interface is 5.1 MPa, and it peels off after 30 days under long-term water pressure (1.6 MPa); the elastic recovery rate is 82% and the elongation at break is 95.6%, which cannot meet the displacement requirements of PCCP pipelines; the amount of defoamer added is small (0.1 parts), and the defoaming effect is insufficient for PCCP interface filling scenarios.

[0051] The comparison shows that the present invention strictly follows the original formula of the tri-ether compound system and adopts the process optimization of adding defoamer in one step. It is significantly superior to traditional sealants and comparative products in terms of elastic recovery rate, tensile strength, low temperature adaptability, hydrolysis resistance, defoaming effect and construction convenience, and fully meets the complex usage requirements of PCCP pipe interface installation.

Claims

1. A PCCP pipe joint sealant, characterized in that: It is made from the following parts by weight of component A and component B: Component A: DL-2000D polyether polyol 230-280 parts, EP-330NG polyether polyol 260-320 parts, DINP 18-23 parts, TDI 75-85 parts; Component B: 4-5 parts diethylene glycol, 150-180 parts auxiliary polyether, 150-200 parts fine calcium powder, 260-300 parts trihydroxy polyoxypropylene ether, 2-4 parts defoamer, 0.5-1 part color paste, 30-35 parts coupling agent, and 0.5-1 part catalyst.

2. The PCCP pipe joint sealant according to claim 1, characterized in that: The polyether polyol DL-2000D is a bifunctional polyether polyol with a hydroxyl value of 54.5–57.5 mgKOH / g, a viscosity of 270–370 mPa·s at 25°C, and a moisture content of ≤0.02%. The polyether polyol EP-330NG is a trifunctional, highly active polyether polyol with a hydroxyl value of 32.5–35.5 mgKOH / g, a viscosity of 800–1000 mPa·s at 25°C, and a moisture content of ≤0.05%.

3. The PCCP pipe joint sealant according to claim 1, characterized in that: The trihydroxy polyoxypropylene ether is a trifunctional high-resilience polyether with a heat resistance temperature of -40 to 90°C; the auxiliary polyether is a polyoxypropylene glycol or polyoxypropylene triol with a molecular weight of 400 to 4000.

4. The PCCP pipe joint sealant according to claim 1, characterized in that: The defoamer is an organosilicon defoamer.

5. The PCCP pipe joint sealant according to claim 1, characterized in that: The coupling agent is a silane coupling agent KH550 or KH560; the catalyst is an organotin catalyst; the fine calcium powder has a particle size of 600-800 mesh and is surface treated with dibutylamine.

6. The PCCP pipe joint sealant according to claim 1, characterized in that: The DINP is diisononyl phthalate with a purity ≥99%; the TDI is toluene diisocyanate with a 2,4-isomer content ≥80%.

7. A method for preparing a PCCP pipe interface sealant as described in any one of claims 1 to 6, characterized in that... Includes the following steps: (1) Preparation of mixture A: Weigh out polyether polyol DL-2000D, polyether polyol EP-330NG, DINP and TDI according to the mass fractions, add them to the reactor, heat to 80-85℃ while stirring, keep warm and stir for 2 hours, stirring rate 300-500r / min; then continue to heat to 90-95℃, keep warm and stir for 1 hour to obtain a uniform prepolymer mixture A; (2) Preparation of mixture B: Weigh trihydroxy polyoxypropylene ether, auxiliary polyether, fine calcium powder and color paste according to the mass parts, add them to another reaction vessel, heat to 110-120°C while stirring, turn on the vacuum system to dehydrate for 30 minutes; after the vacuum is released, add diethylene glycol and defoamer, keep the speed at 300-500 r / min and stir for 30 minutes, cool down to 70°C; add catalyst and coupling agent, continue to disperse for 20 minutes, and cool naturally to room temperature to obtain mixture B; (3) Preparation of finished product: Slowly add mixture A to mixture B, stir at 300-500 r / min for 60 minutes at 25-30℃, and then remove bubbles for 30 minutes under vacuum of -0.08--0.1MPa. After passing the inspection, it is the PCCP pipe joint installation sealant.

8. The method for preparing a PCCP pipe joint sealant according to claim 7, characterized in that: In step (1), TDI is added in two parts: 60% of the total amount is added first, and the remaining 40% is added after the temperature is raised to 90°C.

9. The method for preparing a PCCP pipe joint sealant according to claim 7, characterized in that: The vacuum degree in the dehydration process in step (2) remains stable, and the moisture content of the material after water removal is ≤0.05%.

10. A method for applying the PCCP pipe joint sealant as described in any one of claims 1 to 6, characterized in that: The construction temperature is -10 to 50℃, and the construction environment can be humid or dry. Apply the sealant evenly to the concrete or steel cylinder contact surface of the PCCP pipe joint, with a thickness of 1 to 5 mm. After natural curing for 12 to 24 hours, the joint will be sealed. It is suitable for sealing PCCP pipe joints with a diameter of 500 to 4000 mm, and can withstand complex water quality environments with a pH value of 4 to 10. After curing, the pressure resistance and sealing performance is ≥1.6 MPa.