Salt-tolerant bentonite-based composite water swelling strip and preparation method thereof

Abstract

The invention provides a salt-tolerant bentonite-based composite water-swelling sealing rod and a preparation method thereof, and the sealing rod comprises the following raw materials by weight: 100 parts of amino modified bentonite, 8-10 parts of an ethylene-butyl acrylate-glycidyl methacrylate copolymer, 20-30 parts of composite rubber, 30-40 parts of a water-absorbent resin, and 15-20 parts of a tackifying resin. The composite rubber is formed by compounding rubber and graft modified ethylene propylene diene monomer rubber according to the mass ratio of 4: (1-2); the graft modified ethylene propylene diene monomer is prepared by a method comprising the following steps: carrying out transesterification on an acrylate derivative and N-hydroxyethyl imine diacetic acid to prepare a tertiary amino acrylate derivative; the preparation method comprises the following steps: in an inert atmosphere, dissolving ethylene propylene diene monomer, a tertiary amino acrylate derivative and an initiator in an organic solvent, heating, carrying out graft polymerization reaction, adding a precipitator until no precipitate is generated, filtering, washing, and drying, so as to obtain the graft modified ethylene propylene diene monomer. The expansion performance of the water stop strip in saline water is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of waterproof sealing materials, and particularly relates to a salt-resistant bentonite-based composite water-swelling waterstop strip and a preparation method thereof. Background Art

[0002] In recent years, with the continuous increase of underground waterproof projects and the complexity of structural forms, higher requirements have been put forward for the performance and adaptability of waterproof sealing materials. The water-swelling waterstop strip is a kind of material that can absorb water and swell after contacting water, block the possible capillary pores or gaps, make its contact with the gap interface closer, thus generating a large water resistance and forming an impermeable plastic colloid. The water-swelling waterstop strip has been widely used in the deformation joints, construction joints, dam caulking, pipeline joint sealing of infrastructure projects, and waterproof plugging between concrete slabs or blocks of residential roofs. According to the composition, the water-swelling waterstop strip is mainly divided into bentonite water-swelling waterstop strip and rubber water-swelling waterstop strip. Among them, the raw material cost of the bentonite water-swelling waterstop strip is relatively low, its production process is relatively simple, and its application range is wider than that of the rubber water-swelling waterstop strip.

[0003] The bentonite water-swellable waterstop strip is made by processing materials such as rubber, bentonite, and highly viscous resin, and is a rubbery, plastic, solid with a certain elasticity. The working principle of the bentonite water-swellable waterstop strip is mainly based on the water absorption and swelling characteristics of bentonite: when the waterstop strip encounters moisture, the bentonite will absorb the moisture and swell, thereby blocking the seepage gap, cutting off the seepage channel, and preventing leakage. This material not only has good swelling performance, but also remains intact as a whole after swelling, has elasticity, and is resistant to aging and corrosion. Therefore, the bentonite water-swellable waterstop strip has attracted much attention from researchers in this field. For example, a bentonite-based composite waterstop strip disclosed in Patent CN107868375B is composed of modified bentonite, water-absorbing resin, polyallylamine, rubber compound, tackifying resin, plasticizer, and anti-aging agent. During preparation, the rubber is first plasticized to obtain plasticized rubber, and then the plasticized rubber, modified bentonite, water-absorbing resin, plasticizer, anti-aging agent, tackifying resin, and polyallylamine are mixed and kneaded, and then extruded and formed to obtain the bentonite-based composite waterstop strip, and the modified bentonite therein is obtained by mixing and ball-milling bentonite with isocyanate and coupling agent. A self-adhesive reactive water-swellable waterproof sealing material and its production method disclosed in Patent CN104745123B, wherein the self-adhesive reactive water-swellable waterproof sealing material uses butyl rubber as the matrix, and other raw materials include polyisobutylene, amorphous α-olefin copolymer. By weight, the proportions of the above components are as follows: butyl rubber (IIR) 50-100 parts, polyisobutylene 50-120 parts, amorphous α-olefin copolymer 5-10 parts, desulfurized gypsum 100-180 parts, bentonite 80-120 parts, tackifying resin 12-25 parts, lithium chloride 0.1-2 parts, calcium chloride 1-10 parts, calcium stearate 0.08-1.2 parts, cross-linking agent 0.5-3 parts.

[0004] The above is a water-swellable waterstop strip with bentonite as the main water-absorbing material, and the bentonite water-swellable waterstop strip exhibits excellent water absorption and swelling performance and mechanical properties. However, with the development of coastal engineering and coastal projects in the country, it is inevitable to face a saline environment. Since the main component of bentonite is montmorillonite with ion exchange ability, the cations in the salt water will enter the interlayer structure of bentonite, change the interlayer charge environment of bentonite, and reduce the opportunity for water molecules to enter the interlayer, resulting in a decrease in the swelling ratio of the bentonite water-swellable waterstop strip in salt water, which will cause gaps between the waterstop strip and the wall surface of the gap, unable to form a tight seal, leading to seawater leakage and posing a serious threat to the durability and safety of coastal buildings or engineering structures.

[0005] Therefore, it is necessary to further improve the water-swellable materials of expansive soil to improve their swelling performance in salt water to ensure the waterproof requirements of the project. Summary of the Invention

[0006] To improve the swelling performance of the swelling waterstop strip containing bentonite in salt water, the present invention provides a salt-resistant bentonite-based composite water-swellable waterstop strip and a preparation method thereof. First, a tertiary amino acrylate derivative is prepared from an acrylate derivative and N-hydroxyethyliminodiacetic acid through an ester exchange reaction, and then the graft modification of ethylene propylene diene monomer (EPDM) is carried out with it to obtain a graft-modified EPDM with chelating functional groups. The graft-modified EPDM can form a barrier for cations in salt water in the swelling waterstop strip, reducing the influence of cations on the swelling property of bentonite. In addition, the amino groups on the surface of amino-modified bentonite can react with the epoxy groups on the ethylene-butyl acrylate-glycidyl methacrylate copolymer to form new chemical bonds, preventing the bentonite from losing its swelling ability due to excessive water absorption, or the structure from collapsing and particle agglomeration due to excessive water loss. Under the action of chemical bonds, the structural integrity of bentonite is maintained, ensuring that it has enough space to absorb and store water.

[0007] To achieve the above object, the following technical solutions are adopted:

[0008] A salt-resistant bentonite-based composite water-swellable waterstop strip, comprising the following raw materials in parts by weight: 100 parts of amino-modified bentonite, 8-10 parts of ethylene-butyl acrylate-glycidyl methacrylate copolymer, 20-30 parts of composite rubber, 30-40 parts of water-absorbing resin, 15-20 parts of tackifying resin, wherein the composite rubber is compounded from rubber and graft-modified EPDM according to a mass ratio of 4:1-2;

[0009] The graft-modified EPDM is prepared by a method including the following steps:

[0010] 1) An acrylate derivative and N-hydroxyethyliminodiacetic acid undergo an ester exchange reaction to obtain a tertiary amino acrylate derivative;

[0011] 2) Under an inert atmosphere, EPDM, the tertiary amino acrylate derivative, and an initiator are dissolved in an organic solvent and heated for graft polymerization reaction. After the reaction is completed, a precipitant is added until no precipitation occurs, and then filtered, washed, and dried to obtain the graft-modified EPDM.

[0012] The mass ratio of rubber to graft-modified EPDM in the composite rubber needs to be strictly controlled. Too much graft-modified EPDM will reduce the low-temperature resistance of the water-swellable waterstop strip, and too little will result in poor improvement of the swelling performance of the water-swellable waterstop strip in salt water.

[0013] In step 1), the acrylate derivative is selected from one or a combination of two of methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. The specific reaction in step 1) is as follows: Under an inert atmosphere, the acrylate derivative, N-hydroxyethyliminodiacetic acid, p-toluenesulfonic acid, and inhibitor are added to an organic solvent and mixed evenly, then heated to the reflux state for reaction. After the reaction is completed, distillation under reduced pressure is carried out to obtain the tertiary amino acrylate derivative.

[0014] Furthermore, the reaction time is 6 - 12 h. The molar ratio of the acrylate derivative to N-hydroxyethyliminodiacetic acid is 1.3 - 1.5:1. The p-toluenesulfonic acid is 1 - 3 wt% of the total mass of the acrylate derivative and N-hydroxyethyliminodiacetic acid. The inhibitor is selected from one or a combination of two or more of hydroquinone, p-tert-butylcatechol, and 2,5-di-tert-amylhydroquinone. The inhibitor is 0.5 - 1 wt% of the total mass of the acrylate derivative and N-hydroxyethyliminodiacetic acid. The organic solvent is selected from one or a combination of two of DMF and DMSO.

[0015] In step 2), the ethylene content of the ethylene-propylene-diene monomer (EPDM) is 60 - 70 wt%, the Mooney viscosity ML(1+4) at 125 °C is 40 - 60, and the third monomer of the used EPDM is ethylidene norbornene (ENB) with a content of 4.5 - 8 wt%. The initiator is selected from one or a combination of two or more of azobisisobutyronitrile, benzoyl peroxide, and azobisisoheptonitrile. The mass ratio of the EPDM, tertiary amino acrylate derivative, and initiator is 25 - 35:3 - 6:0.3 - 0.5. The organic solvent is selected from one or a combination of two or more of benzene, toluene, and xylene. The temperature is raised to 60 - 80 °C. The graft polymerization reaction time is 2 - 4 h. The precipitant is selected from one or a combination of two or more of acetone, methanol, ethanol, and isopropanol. The washing is carried out by alternately washing with ethanol and benzene 1 - 3 times. The drying is carried out under vacuum at 40 - 60 °C and 0.1 - 0.01 MPa for 1 - 2 h.

[0016] The amino-modified bentonite is obtained by the reaction of an amino-silane coupling agent and bentonite. Its preparation method includes the following steps: The amino-silane coupling agent is added to an aqueous alcohol solution and mixed evenly, then bentonite is added and mixed evenly, and the temperature is raised for reaction. After the reaction is completed, filtration, washing, and drying are carried out.

[0017] The bentonite is sodium-based bentonite with an average particle size of 300 - 500 mesh; the mass ratio of the amino silane coupling agent, bentonite, and the alcohol aqueous solution is 3 - 5:100:360 - 400. The mass ratio of alcohol to water in the alcohol aqueous solution is 90 - 95:5 - 10, and the alcohol is selected from one or a combination of two or more of ethanol, methanol, and isopropanol. The temperature-rising reaction is carried out at 40 - 60°C for 0.5 - 1 h. The drying is carried out at 60 - 80°C until constant weight. The amino silane coupling agent is selected from one or a combination of two or more of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane.

[0018] The melt index of the ethylene-butyl acrylate-glycidyl methacrylate copolymer at 190°C / 2.16 kg is 6 - 12 g / 10 min, and the content of glycidyl methacrylate is 5 - 10 wt%.

[0019] The tackifying resin is selected from one or a combination of two or more of phenolic resin, terpene resin, coumarone resin, rosin resin, and liquid polybutene.

[0020] The rubber is selected from one or a combination of two or more of natural rubber, styrene-butadiene rubber, ethylene-propylene-diene monomer rubber, and nitrile rubber, preferably ethylene-propylene-diene monomer rubber.

[0021] The ethylene content of the ethylene-propylene-diene monomer rubber is 60 - 70 wt%, the Mooney viscosity ML(1+4) at 125°C is 40 - 60, and the third monomer of the used ethylene-propylene-diene monomer rubber is ethylidene norbornene (ENB) with a content of 4 - 8 wt%.

[0022] The water-absorbing resin is selected from one or a combination of two of polyvinyl alcohol and polyacrylamide.

[0023] The present invention also provides a preparation method of the above-mentioned bentonite-based composite water-swelling waterstop strip, which includes the following steps:

[0024] Adding the ethylene-butyl acrylate-glycidyl methacrylate copolymer and the composite rubber to a plasticator for plasticating, adding the amino-modified bentonite, the water-absorbing resin, and the tackifying resin for mixing, and extruding and molding to obtain the bentonite-based composite water-swelling waterstop strip.

[0025] The plasticating temperature is 60 - 90°C and the time is 10 - 30 min. The mixing temperature is 80 - 120°C and the time is 15 - 60 min.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The swelling water-stop strip based on bentonite composite provided by the present invention contains graft-modified ethylene propylene diene monomer (EPDM) in its raw materials, which can form a barrier for cations in salt water in the swelling water-stop strip, reducing the influence of cations on the swelling property of bentonite. In addition, the amino groups on the surface of amino-modified bentonite can react with the epoxy groups on ethylene-butyl acrylate-glycidyl methacrylate copolymer to form new chemical bonds, preventing the bentonite from losing its swelling ability due to excessive water absorption, or the structure from collapsing and particles from agglomerating due to excessive water loss. Under the action of chemical bonds, the structural integrity of bentonite is maintained, ensuring that it has enough space to absorb and store water. Under the synergistic effect of graft-modified EPDM, amino-modified bentonite, and ethylene-butyl acrylate-glycidyl methacrylate copolymer, the swelling performance of the swelling water-stop strip in salt water is significantly improved. Specific embodiments

[0028] The present invention will be further described below in conjunction with specific embodiments, but it is not limited to the content in the specification. Unless otherwise specified, "parts" in the embodiments of the present invention are all parts by weight. The reagents used are all commercially available reagents in the art.

[0029] Sodium-based bentonite was purchased from Tubawang Bentonite, with an average particle size of 325 mesh.

[0030] The ethylene-butyl acrylate-glycidyl methacrylate copolymer LOTADER AX8900 was purchased from Arkema, with a melt index of 6 g / 10 min at 190 °C / 2.16 kg and a glycidyl methacrylate content of 8 wt%.

[0031] Ethylene propylene diene monomer (EPDM) was purchased from Dongguan Jinshixiang Plastic Raw Material Co., Ltd., Dutral KTER6537 from ENI of Italy, with an ethylene content of 60 wt% and a third monomer content of 8 wt%, and a Mooney viscosity ML(1+4) at 125 °C of 43. Dutral KTER4047, with an ethylene content of 56 wt% and a third monomer content of 4.5 wt%, and a Mooney viscosity ML(1+4) at 125 °C of 55. Dutral KTER4047 from ENI of Italy, with an ethylene content of 56 wt% and a third monomer content of 4.5 wt%, and a Mooney viscosity ML(1+4) at 125 °C of 55.

[0032] Polyvinyl alcohol PVOH122K with a weight average molecular weight of 122,400 was purchased from Shanghai Xibao Biotechnology Co., Ltd.

[0033] Terpene resin T100 with a softening point of 110 °C was purchased from Zhengzhou Cyber Chemical Products Co., Ltd.

[0034] Example 1

[0035] 1) Under a nitrogen atmosphere, 1.3 mol of methyl acrylate, 1 mol of N-hydroxyethyliminodiacetic acid, 2.9 g of p-toluenesulfonic acid, and 1.45 g of hydroquinone were added to a 500 mL DMF reaction kettle and mixed evenly. The temperature was raised to the reflux state and the reaction was carried out for 10 h. After the reaction was completed, impurities were removed by vacuum distillation to obtain a tertiary amino acrylate derivative.

[0036]

[0037] 2) Under a nitrogen atmosphere, 25 g of ethylene propylene diene monomer Dutral KTER6537, 6 g of the tertiary amino acrylate derivative, and 0.3 g of azobisisobutyronitrile were dissolved in 80 mL of xylene. The temperature was raised to 70 °C and the graft polymerization reaction was carried out for 4 h. After the reaction was completed, acetone was added until no precipitation occurred. The product was filtered, washed alternately with ethanol and benzene 3 times, dried at 60 °C and 0.08 MPa for 2 h to obtain a graft-modified ethylene propylene diene monomer; the grafting rate was 18.6 wt%.

[0038] 3) 5 g of 3-aminopropyltrimethoxysilane was added to a mixed solution of 400 g of ethanol and water with a mass ratio of 90:10 and mixed evenly. 100 g of sodium-based bentonite was added and mixed evenly. The temperature was raised to 60 °C and the reaction was carried out for 1 h. After the reaction was completed, the product was filtered, washed with water 3 times, and dried at 80 °C to constant weight to obtain an amino-modified bentonite.

[0039] 4) 10 g of LOTADER AX8900 and 30 g of a composite rubber prepared by compounding Dutral KTER4047 and the graft-modified ethylene propylene diene monomer in a mass ratio of 4:2 were added to a plasticizer and plasticized at 80 °C for 20 min. 100 g of the amino-modified bentonite, 40 g of polyvinyl alcohol PVOH122K, 20 g of terpene resin, and 0.5 g of antioxidant NBC were added and kneaded at 1100 °C for 30 min, and then extruded and molded to obtain a bentonite-based composite water-swellable waterstop strip.

[0040] Example 2

[0041] The rest was the same as in Example 1, except that in step 2), the amount of the tertiary amino acrylate derivative was 3 g; the grafting rate was 10.1 wt%.

[0042] Example 3

[0043] The rest was the same as in Example 1, except that in step 2), Dutral KTER4047 of equal mass was used to replace Dutral KTER6537; the grafting rate was 18.0 wt%.

[0044] Example 4

[0045] The rest is the same as in Example 1, except that in step 4), the composite rubber is prepared by compounding Dutral KTER4047 and graft-modified ethylene propylene diene monomer rubber in a mass ratio of 4:1.

[0046] Example 5

[0047] The rest is the same as in Example 1, except that in step 4), the amount of the composite rubber used is 20 g.

[0048] Example 6

[0049] The rest is the same as in Example 1, except that in step 4), the amount of LOTADER AX8900 used is 8 g.

[0050] Example 7

[0051] 1) Under a nitrogen atmosphere, 1.5 mol of methyl acrylate, 1 mol of N-hydroxyethyliminodiacetic acid, 3.08 g of p-toluenesulfonic acid, and 1.54 g of hydroquinone were added to a 500 mL DMF reaction kettle and mixed evenly. The temperature was raised to the reflux state for reaction for 10 h. After the reaction, impurities were removed by vacuum distillation to obtain a tertiary amino acrylate derivative.

[0052] 2) Under a nitrogen atmosphere, 35 g of ethylene propylene diene monomer rubber Dutral KTER6537, 6 g of the tertiary amino acrylate derivative, and 0.3 g of azobisisobutyronitrile were dissolved in 80 mL of xylene and the temperature was raised to 70 °C for graft polymerization reaction for 4 h. After the reaction, acetone was added until no precipitation occurred, and it was filtered, washed alternately with ethanol and benzene 3 times, dried at 60 °C and 0.08 MPa for 2 h to obtain graft-modified ethylene propylene diene monomer rubber; the grafting rate was 13.5 wt%.

[0053] 3) 5 g of 3-aminopropyltrimethoxysilane was added to a mixed solution of 400 g of ethanol and water in a mass ratio of 90:10 and mixed evenly. 100 g of sodium-based bentonite was added and mixed evenly. The temperature was raised to 60 °C for reaction for 1 h. After the reaction, it was filtered, washed with water 3 times, and dried to constant weight at 80 °C to obtain amino-modified bentonite.

[0054] 4) 8 g of LOTADER AX8900 and 30 g of a composite rubber prepared by compounding Dutral KTER4047 and graft-modified ethylene propylene diene monomer rubber in a mass ratio of 4:2 were added to a plasticizer and kneaded at 80 °C for 20 min. 100 g of amino-modified bentonite, 40 g of polyvinyl alcohol PVOH122K, 20 g of terpene resin, and 0.5 g of antioxidant NBC were added and kneaded at 1100 °C for 30 min, and then extrusion molding was carried out to obtain a bentonite-based composite water-swellable waterstop strip.

[0055] Comparative Example 1

[0056] The rest is the same as in Example 1, except that step 3) is cancelled, and in step 4), sodium bentonite with the same mass is used to replace the amino-modified bentonite.

[0057] Comparative Example 2

[0058] The rest is the same as in Example 1, except that in step 4), graft-modified ethylene-propylene-diene monomer rubber with the same mass is used to replace Dutral KTER4047 in the composite rubber, that is, the composite rubber is all Dutral KTER4047.

[0059] The water-swellable waterstops prepared in the above examples and comparative examples were subjected to the following performance tests:

[0060] Volume expansion ratio: Referring to the standard GB / T 18173.3-2002 Polymer waterproofing materials - Part 3: Water-swelling rubber, the waters used were the simulated brine and distilled water shown in Table 1, and the immersion time was 72 h, and the volume expansion ratios ΔV 水 、ΔV 盐水 were tested and calculated, and the retention rate P of the volume expansion ratio of the swelling waterstop in brine relative to its volume expansion ratio in distilled water was calculated according to the following formula:

[0061] P = ΔV 盐水 / ΔV 水 × 100%

[0062] Table 1 Ion composition of simulated brine

[0063]

[0064] High-temperature flowability: Tested referring to the standard GB / T 18173.3-2002 Polymer waterproofing materials - Part 3: Water-swelling rubber.

[0065] Low-temperature test: Tested referring to the standard GB / T 18173.3-2002 Polymer waterproofing materials - Part 3: Water-swelling rubber.

[0066] Table 2 Performance test results

[0067] Project <![CDATA[ΔV 水 %]]> P％ High-temperature fluidity Low-temperature test Example 1 343 90.0 No flow No brittle fracture Example 2 325 89.2 No flow No brittle fracture Example 3 337 92.6 No flow No brittle fracture Example 4 312 88.1 No flow No brittle fracture Example 5 304 87.4 No flow No brittle fracture Example 6 349 88.7 No flow No brittle fracture Example 7 328 88.5 No flow No brittle fracture Comparative Example 1 321 81.3 Flow No brittle fracture Comparative Example 2 330 75.3 Flow No brittle fracture

[0068] As can be seen from Table 1, the bentonite-based composite water-swellable waterstop prepared by the present invention has excellent expansion performance and high and low temperature resistance, and still has a high volume expansion ratio after being immersed in brine, and can be applied to the waterproof sealing of buildings or projects in coastal areas.

[0069] The above detailed description is a specific description of one of the feasible embodiments of the present invention, and this embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification without departing from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A salt-resistant bentonite-based composite water-swellable waterstop, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of amino-modified bentonite, 8-10 parts of ethylene-butyl acrylate-glycidyl methacrylate copolymer, 20-30 parts of composite rubber, 30-40 parts of water-absorbent resin, and 15-20 parts of tackifying resin, wherein the composite rubber is compounded by rubber and graft-modified EPDM rubber in a mass ratio of 4:1-2; The graft-modified EPDM rubber is prepared by a method comprising the following steps: 1) an acrylate derivative and N-hydroxyethyliminodiacetic acid undergo an ester exchange reaction to obtain a tertiary amino acrylate derivative; 2) Under an inert atmosphere, EPDM rubber, tertiary amino acrylate derivatives and initiator are dissolved in an organic solvent and heated to carry out graft polymerization reaction. After the reaction is completed, a precipitant is added until no precipitation is generated, and the reaction is filtered, washed and dried to obtain a graft-modified EPDM rubber.

2. The salt-resistant bentonite-based composite water-swellable waterstop according to claim 1, characterized in that: In step 1), the acrylate derivative is selected from one or a combination of two of methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate.

3. The salt-resistant bentonite-based composite water-swellable waterstop according to claim 1, characterized in that: Step 1) The reaction is as follows: under an inert atmosphere, an acrylate derivative, N-hydroxyethyliminodiacetic acid, p-toluenesulfonic acid, and a polymerization inhibitor are added to an organic solvent and mixed evenly, and the mixture is heated to reflux state for reaction. After the reaction is completed, the mixture is distilled under reduced pressure to obtain a tertiary aminoacrylate derivative.

4. The salt-resistant bentonite-based composite water-swellable waterstop according to claim 3, characterized in that: The molar ratio of the acrylate derivative and N-hydroxyethyliminodiacetic acid is 1.3-1.5:1; the p-toluenesulfonic acid is 1-3wt% of the sum of the mass of the acrylate derivative and N-hydroxyethyliminodiacetic acid.

5. The salt-resistant bentonite-based composite water-swellable waterstop according to claim 1, characterized in that: In step 2), the ethylene content of the EPDM rubber is 60-70wt%, the Mooney viscosity ML (1+4) at 125°C is 40-60, the third monomer of the EPDM rubber is ethylidene norbornene (ENB), and the content is 4.5-8wt%; the mass ratio of the EPDM rubber, tertiary amino acrylate derivative, and initiator is 25-35:3-6:0.3-0.

5.

6. The salt-resistant bentonite-based composite water-swellable waterstop according to claim 1, characterized in that: The amino-modified bentonite is obtained by reacting an aminosilane coupling agent with bentonite. Furthermore, the preparation method of the amino-modified bentonite comprises the following steps: adding the aminosilane coupling agent to an alcohol aqueous solution and mixing evenly, adding bentonite and mixing evenly, heating to react, filtering, washing and drying after the reaction is completed.

7. The salt-resistant bentonite-based composite water-swellable waterstop according to claim 6, characterized in that: The bentonite is sodium bentonite with an average particle size of 300-500 meshes; the mass ratio of aminosilane coupling agent, bentonite and alcohol aqueous solution is 3-5:100:360-400; the mass ratio of alcohol to water in the alcohol aqueous solution is 90-95:5-10; the aminosilane coupling agent is selected from 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, or a combination of two or more thereof.

8. The salt-resistant bentonite-based composite water-swellable waterstop according to claim 1, characterized in that: The tackifying resin is selected from one or a combination of two or more of phenolic resin, terpene resin, coumarone resin, rosin resin, and liquid polybutene; the water-absorbing resin is selected from one or a combination of two of polyvinyl alcohol and polyacrylamide; the melt index of the ethylene-butyl acrylate-glycidyl methacrylate copolymer under 190°C / 2.16kg conditions is 6-12g / 10min, and the glycidyl methacrylate content is 5-10wt%; the rubber is selected from one or a combination of two or more of natural rubber, styrene-butadiene rubber, ethylene-propylene-diene rubber, and nitrile rubber, preferably ethylene-propylene-diene rubber.

9. The salt-resistant bentonite-based composite water-swellable waterstop according to claim 8, characterized in that: The ethylene content of the EPDM rubber is 60-70wt%, the rubber Mooney viscosity ML (1+4) at 125°C is 40-60, and the third monomer of the EPDM rubber is ethylidene norbornene (ENB) with a content of 4-8wt%.

10. The method for preparing the bentonite-based composite water-swellable waterstop strip according to any one of claims 1 to 9, characterized in that: The steps include: Ethylene-butyl acrylate-glycidyl methacrylate copolymer and composite rubber are added to a plasticizer for plasticizing, and amino-modified bentonite, water-absorbing resin and tackifying resin are added for mixing and extrusion molding to obtain a bentonite-based composite water-swellable waterstop.

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