Waterproof sealant for underwater pipes and preparation method thereof

Abstract

The present invention relates to the field of sealant technology, and discloses a waterproof sealant for underwater pipes and a preparation method thereof, wherein the sealant of the present invention includes the following components in parts by weight: 100 parts of epoxy resins, 6-10 parts by weight of reactive diluents, 20-36 parts by weight of underwater curing agents, 8-20 parts by weight of hyperbranched polyether amides, etc. The hyperbranched polyether amide of the present invention contains flexible ether bonds, and the amino group contained can participate in the curing reaction of the epoxy resin, thereby playing a good toughening effect on the epoxy resin cured product, improving impact strength and toughness. Simultaneously, the hyperbranched polyether amide contains multiple hydrophobic benzene ring structures, which can keep the epoxy resin at a lower water absorption rate, and is conducive to improving the waterproof performance of the sealant.

Description

Technical Field

[0001] The present invention relates to the technical field of sealants, in particular to a waterproof sealant for underwater pipes and a preparation method thereof. Background Art

[0002] Epoxy resins, due to their excellent bonding, mechanical strength, insulation, waterproofing, and corrosion resistance, can be made into sealants, insulating adhesives, and structural adhesives, finding widespread application in materials such as metal substrates, plastics, asphalt, and concrete. Underwater-curing epoxy resins cure in water and typically consist of a resin matrix, an underwater curing agent, and fillers. Traditional underwater-curing epoxy resins and sealants suffer from prolonged exposure to water, which can affect their adhesion and toughness. Therefore, improvements are needed to improve the waterproofing, flexibility, and bonding properties of epoxy resins.

[0003] Adding polymer modifiers, such as polyphenylene ether, polyaryletherketone, and hyperbranched polymers, to epoxy resins can improve their toughness, heat resistance, and water resistance. Chinese patent CN113717339B discloses a curing agent for reducing adhesive volatility. This hyperbranched polymer-modified curing agent, obtained by chemically modifying a hyperbranched polyamide amine into an amine curing agent, improves the tensile and shear strength of epoxy resin adhesives. However, this patent does not address the poor toughness of epoxy resins and their poor adhesion to plastics and pipes. Summary of the Invention

[0004] (1) Technical problems solved: In response to the shortcomings of the existing technology, the present invention provides a waterproof sealant for underwater pipes and a preparation method thereof, which solves the problems of low peel strength and poor toughness of epoxy resin sealants, while improving the waterproof performance of the sealant.

[0005] (II) Technical Solution: A waterproof sealant for underwater pipes and a preparation method thereof, comprising the following components in parts by weight: 100 parts epoxy resin, 6-10 parts reactive diluent, 20-36 parts underwater curing agent, 8-20 parts hyperbranched polyether amide, 5-20 parts filler, 0.2-1 parts dispersant, and 0.6-1.2 parts defoamer. The preparation method comprises adding the reactive diluent, hyperbranched polyether amide, filler, dispersant, and defoamer to the epoxy resin, shearing and dispersing the mixture, then adding the underwater curing agent and stirring to obtain the waterproof sealant for underwater pipes.

[0006] Furthermore, the filler is titanium dioxide, talc or montmorillonite.

[0007] Furthermore, the active diluent is ethylene glycol diglycidyl ether or 1,4-butanediol diglycidyl ether.

[0008] Furthermore, the preparation method of the hyperbranched polyether amide is:

[0009] (1) Add N-(3-aminopropyl)methyl acrylamide hydrochloride (CAS registration number 72607-53-5) and an inorganic base to ethanol, stir, then add 4,4'-oxybenzaldehyde (CAS registration number 2215-76-1), stir and react, then heat and volatilize, cool in an ice-water bath, and a large amount of precipitate will precipitate. After filtering and washing the precipitate with water, it is then recrystallized in dichloromethane to obtain bisacrylamide monomer. The reaction formula is: .

[0010] (2) Add bisacrylamide monomer to methanol, stir, then dropwise add diethylenetriamine aqueous solution in an ice-water bath, stir, and then carry out polymerization reaction. Then, distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain hyperbranched polyether amide. The reaction formula is:

[0011] .

[0012] Furthermore, the reaction temperature in (1) is 40-60°C, and the reaction time is 5-8h.

[0013] Furthermore, the molar ratio of N-(3-aminopropyl)methyl acrylamide hydrochloride, inorganic base, and 4,4'-oxybenzaldehyde in (1) is (2-2.2):(2-2.2):1.

[0014] Furthermore, the inorganic base in (1) is sodium hydroxide or potassium hydroxide.

[0015] Furthermore, the molar ratio of bisacrylamide monomer to diethylenetriamine in (2) is 1:(1.1-1.2);

[0016] Furthermore, the polymerization reaction temperature in (2) is 65-80°C, condensation reflux is performed during the reaction, and the reaction time is 24-36 hours.

[0017] (III) Beneficial technical effects: The present invention utilizes a bisacrylamide monomer containing a flexible ether bond and multiple hydrophobic benzene ring structures to undergo a hyperbranched polymerization reaction with diethylenetriamine to obtain a hyperbranched polyether amide, which is then compounded with an epoxy resin, an active diluent, an underwater curing agent, a filler, etc. to obtain a waterproof sealant for underwater pipes. The hyperbranched polyether amide contains active amino groups and can replace part of the curing agent to undergo a curing reaction with the epoxy resin, thereby increasing the cohesive force of the sealing adhesive and helping to improve the bonding performance.

[0018] The hyperbranched polyetheramide of the present invention contains Schiff base groups that can form coordination properties with stainless steel surfaces, thereby improving the sealing adhesive's adhesion and bonding performance to the stainless steel substrate. Furthermore, the hyperbranched polyetheramide contains amide bonds that can form hydrogen bonds and other interactions with the amide bonds in the nylon 6 matrix, thereby improving the adhesion and bonding performance between the sealant and the nylon substrate. This makes the sealant ideal for bonding and sealing metal pipes such as stainless steel and plastic pipes such as nylon and PVC.

[0019] The hyperbranched polyether amide of the present invention contains flexible ether bonds and amino groups that can participate in the curing reaction of epoxy resin, thereby effectively toughening the epoxy resin cured product and improving its impact strength and toughness. Furthermore, the hyperbranched polyether amide contains multiple hydrophobic benzene ring structures, which can maintain a low water absorption rate of the epoxy resin, thereby improving the waterproof performance of the sealant. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] The epoxy resin model is E44, purchased from Nantong Changchen Chemical Co., Ltd. The underwater curing agent model is JA-IS, with an active ingredient content of 95%, purchased from Sichuan Aopai Epoxy Additive Technology Co., Ltd. The nylon plastic model is Lanxess K224-G7, 35% glass fiber reinforced PA6, purchased from Shanghai Xianshun Plastics Co., Ltd. The dispersant model is BYK W966, purchased from Nanjing Quanxi New Materials Co., Ltd. The defoamer model is TEGO8030, purchased from Xuzhou Yihuiyang New Materials Co., Ltd.

[0022] Example 1:

[0023] (1) Add 100 mmol of N-(3-aminopropyl)methyl acrylamide hydrochloride and 100 mmol of potassium hydroxide to 400 mL of ethanol, stir, then add 50 mmol of 4,4'-oxybenzaldehyde, heat to 60 °C, stir and react for 5 h, heat to evaporate, cool in an ice-water bath, and a large amount of precipitate will precipitate. Filter and wash the precipitate with water, then recrystallize it from dichloromethane to obtain bisacrylamide monomer.

[0024] (2) Add 50 mmol of bisacrylamide monomer to 150 mL of methanol, stir, and then dropwise add 100 mL of an aqueous solution containing 55 mmol of diethylenetriamine in an ice-water bath. Stir and heat to 70 °C. Condensate and reflux for 24 h. Distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain hyperbranched polyether amide.

[0025] (3) Add 7 g of active diluent ethylene glycol diglycidyl ether, 8 g of hyperbranched polyether amide, 14 g of talc, 0.7 g of dispersant, and 0.6 g of defoamer to 100 g of epoxy resin E44, shear and disperse, then add 36 g of underwater curing agent, stir and mix, and obtain a waterproof sealant for underwater pipes.

[0026] Example 2:

[0027] (1) Add 110 mmol of N-(3-aminopropyl)methyl acrylamide hydrochloride and 110 mmol of sodium hydroxide to 400 mL of ethanol, stir, then add 50 mmol of 4,4'-oxybenzaldehyde, heat to 40 °C, stir and react for 8 h, heat to evaporate, cool in an ice-water bath, and a large amount of precipitate will precipitate. Filter and wash the precipitate with water, then recrystallize it from dichloromethane to obtain bisacrylamide monomer.

[0028] (2) Add 50 mmol of bisacrylamide monomer to 200 mL of methanol, stir, and then dropwise add 120 mL of an aqueous solution containing 60 mmol of diethylenetriamine in an ice-water bath. Stir and heat to 65 °C. Condensate and reflux for 36 h. Distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain hyperbranched polyether amide.

[0029] (3) Add 10 g of active diluent 1,4-butanediol diglycidyl ether, 12 g of hyperbranched polyether amide, 5 g of titanium dioxide, 0.2 g of dispersant, and 0.8 g of defoaming agent to 100 g of epoxy resin E44, shear and disperse, then add 25 g of underwater curing agent, stir and mix, and obtain a waterproof sealant for underwater pipes.

[0030] Example 3:

[0031] (1) Add 50 mmol of bisacrylamide monomer to 200 mL of methanol, stir, and then dropwise add 120 mL of an aqueous solution containing 60 mmol of diethylenetriamine in an ice-water bath. Stir and heat to 80 °C. Condensate and reflux for 24 h. Distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain hyperbranched polyether amide.

[0032] (2) Add 6 g of active diluent ethylene glycol diglycidyl ether, 16 g of hyperbranched polyether amide, 20 g of montmorillonite, 1 g of dispersant, and 1.2 g of defoamer to 100 g of epoxy resin E44, shear and disperse, then add 30 g of underwater curing agent, stir and mix, and obtain a waterproof sealant for underwater pipes.

[0033] Example 4:

[0034] (1) Add 50 mmol of bisacrylamide monomer to 150 mL of methanol, stir, and then dropwise add 100 mL of an aqueous solution containing 58 mmol of diethylenetriamine in an ice-water bath. Stir and heat to 70 °C. Condensate and reflux for 30 h. Distill under reduced pressure, wash with water and ethanol in sequence, and dry to obtain hyperbranched polyether amide.

[0035] (2) Add 10 g of active diluent 1,4-butanediol diglycidyl ether, 20 g of hyperbranched polyether amide, 12 g of talc, 0.6 g of dispersant, and 1.2 g of defoamer to 100 g of epoxy resin E44, shear and disperse, then add 20 g of underwater curing agent, stir and mix, and obtain a waterproof sealant for underwater pipes.

[0036] Comparative Example 1:

[0037] (1) Add 7 g of active diluent ethylene glycol diglycidyl ether, 14 g of talc, 0.7 g of dispersant, and 0.6 g of defoamer to 100 g of epoxy resin E44, shear and disperse, then add 36 g of underwater curing agent and stir to obtain a sealant for underwater pipes.

[0038] Comparative Example 2:

[0039] (1) Hyperbranched polyamide was prepared according to the method of the journal Journal of Southwest Petroleum University (Natural Science Edition), Vol. 43, No. 4, August 2021, “Synthesis of Hyperbranched Polymer HP-NH2 and Study on Anti-collapse Mechanism”. 20 mmol N, N-methylenebisacrylamide was added to 100 mL of water, 22 mmol of diethylenetriamine was added dropwise, the mixture was stirred at 60 ° C for 12 h, and water was removed by vacuum distillation to obtain hyperbranched polyamide.

[0040] (2) Add 7 g of active diluent ethylene glycol diglycidyl ether, 8 g of hyperbranched polyamide, 14 g of talc, 0.7 g of dispersant, and 0.6 g of defoamer to 100 g of epoxy resin E44, shear and disperse, then add 36 g of underwater curing agent, stir and mix, and obtain a sealant for underwater pipes.

[0041] Comparative Example 3:

[0042] (1) Add 100 mmol of N-(3-aminopropyl)methacrylamide hydrochloride and 100 mmol of potassium hydroxide to 350 mL of ethanol, stir, then add 50 mmol of terephthalaldehyde, heat to 60°C, stir and react for 5 hours, heat to evaporate, cool in an ice-water bath, and a large amount of precipitate will precipitate. Filter and wash the precipitate with water, then recrystallize it from dichloromethane to obtain bisacrylamide monomer. The structural formula is as follows:

[0043] .

[0044] (2) Add 50 mmol of bisacrylamide monomer to 150 mL of methanol, stir, and then dropwise add 100 mL of an aqueous solution containing 55 mmol of diethylenetriamine in an ice-water bath. Stir and heat to 70 °C. Condensate and reflux for 24 h. Distill under reduced pressure, wash with water and ethanol in turn, and dry to obtain hyperbranched polyamide.

[0045] (3) Add 7 g of active diluent ethylene glycol diglycidyl ether, 8 g of hyperbranched polyamide, 14 g of talc, 0.7 g of dispersant, and 0.6 g of defoamer to 100 g of epoxy resin E44, shear and disperse, then add 36 g of underwater curing agent, stir and mix, and obtain a sealant for underwater pipes.

[0046] The sealant's bonding performance to stainless steel was tested according to standard GB / T 7124-2008. Two stainless steel substrates were ground and polished, then immersed in water before being coated with the sealant and bonded together. The specimens were cured at 25°C for 24 hours, then removed and left at room temperature for 12 hours before being tested for tensile shear strength.

[0047] To test the adhesive properties of sealant on nylon plastic, two test pieces of nylon plastic were molded, the surfaces polished and cleaned, and then soaked in water. The pieces were then coated with glue, bonded, and cured at 25°C for 24 hours. The nylon plastic test pieces were removed and left at room temperature for 12 hours before being tested for tensile shear strength.

[0048] To test the adhesive bond to PVC sheets, polish and clean the surfaces of two PVC sheets, soak them in water, apply the adhesive, and bond them together. Curing at 25°C for 24 hours, remove the PVC bonded specimens, and allow them to stand at room temperature for 12 hours before testing the tensile shear strength.

[0049] Pour the sealant into the mold and cure it at 25°C for 24 hours to make a cured film sample. Test the impact strength according to standard GB / T 2567-2021.

[0050] Prepare a 10cm x 10cm x 0.5cm specimen of the cured film, dry it, and weigh it (denoted as m0). Place it in water and soak it at 70°C for 72 hours. Remove the specimen, wipe off the surface moisture, and weigh it (denoted as m). Calculate the water absorption W: W = (m-m0) / m0 × 100%.

[0051] Table 1 Sealant performance test

[0052]

[0053] Testing revealed that the sealant in Comparative Example 1 exhibited low tensile shear strength and poor adhesion to stainless steel and nylon plastics, as well as low impact strength, high water absorption, and poor toughness and water resistance. The sealants in Examples 1-4 incorporated hyperbranched polyetheramide (HPE) with active amino groups, which can replace some of the curing agent and undergo a curing reaction with the epoxy resin, thereby increasing the sealant's cohesion and improving its adhesion. Furthermore, the HPE contains Schiff base groups (-C=N-), which can form coordination properties with the stainless steel surface, thereby improving the sealant's adhesion and bonding properties to the stainless steel substrate, exhibiting higher tensile shear strength, while also maintaining good adhesion to polyvinyl chloride. Furthermore, the HPE contains amide bonds, which can form hydrogen bonds and other interactions with the amide bonds in the nylon 6 matrix, thereby enhancing the sealant's adhesion and bonding properties to the nylon substrate, exhibiting higher tensile shear strength. Furthermore, the HPE contains flexible ether bonds, and the active amino groups can participate in the curing reaction of the epoxy resin, providing a good toughening effect on the cured product, thereby improving its impact strength and toughness. Hyperbranched polyetheramide contains multiple hydrophobic benzene ring structures, which can keep the epoxy resin at a low water absorption rate, thereby improving the waterproof performance of the sealant.

[0054] Compared with Example 1, Comparative Example 2 is polymerized with N,N-methylenebisacrylamide and diethylenetriamine, and the hyperbranched polyamide obtained contains active amino group, can react with epoxy resin to cure, is conducive to improving the cohesion of sealant, thereby improving bonding performance and tensile shear strength. However, this hyperbranched polyamide does not contain Schiff base structure, and its coordination performance with stainless steel surface is weak, resulting in poor bonding and bonding ability of sealant to stainless steel, and low tensile shear strength. And hyperbranched polyamide does not contain flexible ether bond, and is not good for the toughening effect of sealant cured product, resulting in low impact strength, and does not contain hydrophobic benzene ring structure, resulting in large water absorption of cured product, and poor waterproof performance. Comparative Example 3 is raw material with terephthalaldehyde, and the bisacrylamide monomer and hyperbranched polyamide prepared do not contain flexible ether bond, and are not good for the toughening effect of sealant cured product, resulting in low impact strength, and hydrophobic benzene ring structure is significantly less than the hyperbranched polyether amide of Example 1, resulting in slightly higher water absorption of sealant cured product than Example 1, and poor waterproof performance.

[0055] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A waterproof sealant for underwater pipes, characterized in that: The waterproof sealant for underwater pipes comprises the following components in parts by weight: 100 parts of epoxy resin, 6-10 parts by weight of reactive diluent, 20-36 parts by weight of underwater curing agent, 8-20 parts by weight of hyperbranched polyether amide, 5-20 parts by weight of filler, 0.2-1 parts by weight of dispersant, and 0.6-1.2 parts by weight of defoaming agent; The preparation method of the hyperbranched polyether amide comprises: adding bisacrylamide monomer to methanol, stirring, then dropwise adding an aqueous solution of diethylenetriamine in an ice-water bath, stirring, performing a polymerization reaction, performing reduced pressure distillation, washing with water and ethanol in sequence, and drying to obtain the hyperbranched polyether amide; The molar ratio of the bisacrylamide monomer to diethylenetriamine is 1:(1.1-1.2); the structural formula of the bisacrylamide monomer is as follows: ; The polymerization reaction temperature is 65-80° C., and the reaction time is 24-36 hours.

2. The waterproof sealant for underwater pipes according to claim 1, characterized in that: The filler is titanium dioxide, talc or montmorillonite.

3. The waterproof sealant for underwater pipes according to claim 1, characterized in that: The active diluent is ethylene glycol diglycidyl ether or 1,4-butanediol diglycidyl ether.

4. The waterproof sealant for underwater pipes according to claim 1, characterized in that: The preparation method of the bisacrylamide monomer comprises the following steps: adding N-(3-aminopropyl)methacrylamide hydrochloride and an inorganic base to ethanol, stirring, adding 4,4'-oxybenzaldehyde, stirring for reaction, heating for volatilization, cooling in an ice-water bath, filtering, and washing with water; and recrystallizing the product in dichloromethane to obtain the bisacrylamide monomer.

5. The waterproof sealant for underwater pipes according to claim 4, characterized in that: In the preparation method of the bisacrylamide monomer, the reaction temperature is 40-60° C. and the reaction time is 5-8 hours.

6. The waterproof sealant for underwater pipes according to claim 4, characterized in that: The molar ratio of the N-(3-aminopropyl)methacrylamide hydrochloride, the inorganic base, and 4,4'-oxybenzaldehyde is (2-2.2):(2-2.2):

1.

7. The waterproof sealant for underwater pipes according to claim 6, characterized in that: The inorganic base is sodium hydroxide or potassium hydroxide.

8. A method for preparing the waterproof sealant for underwater pipes according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: adding active diluent, hyperbranched polyether amide, filler, dispersant and defoamer to epoxy resin, shearing and dispersing the mixture, then adding underwater curing agent and stirring and mixing the mixture to obtain waterproof sealant for underwater pipes.

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