Flame-retardant rubber waterstop for tunnel and preparation method thereof

Abstract

This invention belongs to the field of polymer materials technology, specifically to a flame-retardant rubber waterstop for tunnels and its preparation method. By using modified EPDM rubber, dopamine-modified sepiolite, and modified magnesium oxide as primary materials, the flame-retardant rubber waterstop for tunnels is produced, effectively improving tensile strength, increasing tear strength, and achieving excellent flame retardancy.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a flame-retardant rubber waterstop for tunnels and a preparation method thereof. Background Art

[0002] Shield tunnels, which have experienced rapid development in recent years, utilize prefabricated, assembled segments. The numerous longitudinal and circumferential joints make tunnel leakage nearly ubiquitous. Frequent tunnel leakage can have a significant psychological impact on drivers and pedestrians, and even pose a serious threat to the safety of the tunnel structure, leading to serious accidents. Furthermore, once leakage occurs, it is difficult to completely resolve. Waterstops are shaped, waterproof, and sealing materials for expansion and construction joints in underground structures. Rubber waterstops leverage the high elasticity and compression properties of rubber materials, deforming elastically under various loads to effectively tighten and seal, prevent leakage and seepage, and provide vibration dampening and cushioning.

[0003] A Chinese patent (publication number CN117143402A) discloses a flame-retardant natural rubber waterstop and its preparation method. This invention uses natural rubber as the base material for the flame-retardant rubber waterstop and incorporates a composite flame retardant consisting of ammonium polyphosphate, melamine borate, and zinc borate into the base. The three ingredients synergistically flame-retardant the waterstop, significantly improving its flame retardancy and mechanical properties. Polymethyl methacrylate is also added and coated on the surface of the composite flame retardant, further enhancing its flame retardancy and mechanical properties. However, existing flame-retardant rubber waterstops for tunnels still suffer from low tensile strength, low tear strength, and poor flame retardancy, which seriously hinder their practical use.

[0004] Therefore, how to functionally modify the main components of rubber waterstop to prepare flame-retardant rubber waterstop for tunnels, effectively improve tensile strength, increase tear strength, and obtain good flame retardancy has become a direction that needs to be focused on. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a flame-retardant rubber waterstop for tunnels and a preparation method thereof, aiming to solve the problems of low tensile strength, low tear strength and poor flame retardant performance of the flame-retardant rubber waterstop for tunnels in the existing technology.

[0006] The present invention selects modified EPDM rubber, dopamine-modified sepiolite and modified magnesium oxide as main materials to prepare a flame-retardant rubber waterstop for tunnels, which effectively improves tensile strength, increases tear strength and obtains good flame retardancy.

[0007] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0008] The first aspect of the present invention provides a flame retardant rubber waterstop for tunnels.

[0009] The invention comprises the following components in parts by weight: 56-60 parts of polyisobutylene, 40-44 parts of modified ethylene-propylene rubber, 22-26 parts of carbon black, 18-22 parts of sepiolite, 10-14 parts of magnesium oxide, 6-8 parts of plasticizer, 4-6 parts of zinc oxide, 3-5 parts of stearic acid, 2.2-2.4 parts of dicumyl peroxide and 1.2-1.6 parts of 2-mercaptobenzimidazole;

[0010] The preparation method of the modified EPDM rubber comprises: mixing 30-40 parts of montmorillonite, 40-50 parts of methyltrichlorosilane and 100-120 parts of anhydrous ethanol, stirring the mixture, adding 100-120 parts of tetrahydrofuran and dispersing the mixture evenly, adding 10-16 parts of 4-hydroxyphthalic anhydride and 2-4 parts of sodium hydride to carry out anhydride reaction to obtain anhydride-treated montmorillonite; and kneading 60-70 parts of EPDM rubber and 8-12 parts of the anhydride-treated montmorillonite to obtain the modified EPDM rubber.

[0011] As a preferred technical solution of the present invention, the stirring treatment conditions include: a stirring speed of 100-120 rpm, a temperature of 30-40° C., and a time of 12-16 h.

[0012] As a preferred technical solution of the present invention, the conditions of the anhydride reaction include: reaction temperature of 26-30° C., and reaction time of 26-28 h.

[0013] As a preferred technical solution of the present invention, the mixing treatment conditions include: mixing treatment temperature of 100-110° C., and mixing treatment time of 12-16 minutes.

[0014] The modified EPDM rubber contains anhydride-treated montmorillonite. After the anhydride treatment, the spacing between the montmorillonite layers increases, and the EPDM rubber molecular chains are more easily inserted into the montmorillonite layers, forming an intercalated structure, which enhances the interfacial bonding force between the montmorillonite and the rubber matrix. At the same time, the montmorillonite layers, as nano-scale fillers, can effectively limit the slippage of the rubber molecular chains, thereby improving the tensile strength of the material.

[0015] As a preferred technical solution of the present invention, the sepiolite is dopamine-modified sepiolite; the preparation method of the dopamine-modified sepiolite comprises: dispersing 1 to 3 parts of sepiolite and 1 to 3 parts of dopamine in 400 to 500 parts of tris(hydroxymethyl)aminomethane by weight for heating reaction, vacuum drying after the reaction is completed, grinding and crushing to obtain dopamine-modified sepiolite.

[0016] As a preferred technical solution of the present invention, the conditions of the heating reaction include: pH 8.2-8.6, temperature 70-80°C, and time 20-24h.

[0017] Dopamine in dopamine-modified sepiolite has strong adhesion and reactivity, and can form a polydopamine coating on the surface of sepiolite, thereby improving the interfacial bonding between sepiolite and the rubber matrix. A stronger interfacial bonding force is formed between the dopamine-modified sepiolite and the rubber matrix, which can more effectively transmit stress and dissipate energy when subjected to force, reduce local stress concentration, and improve the tear strength of the rubber waterstop.

[0018] As a preferred technical solution of the present invention, the magnesium oxide is modified magnesium oxide; the preparation method of the modified magnesium oxide comprises: adding 10 to 20 parts of magnesium oxide and 2 to 6 parts of γ-glycidyloxypropyltrimethoxysilane to 120 to 140 parts of anhydrous ethanol for coupling treatment to obtain modified magnesium oxide.

[0019] As a preferred technical solution of the present invention, the coupling treatment conditions include: stirring for 2 to 4 hours, then centrifuging at a speed of 7000 to 8000 r / min for 6 to 10 minutes, and vacuum drying the lower precipitate.

[0020] The modified magnesium oxide is treated with the silane coupling agent γ-glycidyloxypropyltrimethoxysilane to avoid uneven distribution caused by agglomeration. The evenly dispersed modified magnesium oxide can better decompose and absorb heat at high temperatures, reduce the surface temperature of the material, and release inert gas to dilute oxygen and combustible gases, thereby inhibiting combustion and improving the flame retardant properties of the material.

[0021] As a preferred technical solution of the present invention, the plasticizer is selected from at least one of triphenyl phosphate, tricresyl phosphate, and toluene diphenyl phosphate.

[0022] A second aspect of the present invention provides a method for preparing a flame-retardant rubber waterstop for a tunnel as described in the first aspect, comprising the following steps:

[0023] In parts by weight, 56-60 parts of polyisobutylene, 40-44 parts of modified ethylene-propylene rubber, 22-26 parts of carbon black, 18-22 parts of sepiolite, 10-14 parts of magnesium oxide, 6-8 parts of plasticizer, 4-6 parts of zinc oxide, 3-5 parts of stearic acid, and 2.2-2.4 parts of dicumyl peroxide are mixed for 10-15 minutes, and then a vulcanizing agent is added and mixed for 3-5 minutes, and the mixture is allowed to stand for 12-24 hours and vulcanized to obtain a flame-retardant rubber waterstop for tunnels.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The modified EPDM rubber of the present invention contains anhydride groups, which can undergo nucleophilic addition reaction with dopamine in dopamine-modified sepiolite, and the epoxy groups introduced into the modified magnesium oxide through the silane coupling agent can not only undergo ring-opening addition reaction with the anhydride groups, but also form new covalent bonds with dopamine (the amine group in dopamine acts as a nucleophilic reagent and preferentially attacks one carbon atom in the epoxy group, causing the epoxy ring to open and form a covalent bond), thereby constructing a high-density interconnected structure in the rubber waterstop, increasing the degree of cross-linking between molecular chains, improving the material's deformation resistance, and effectively improving tensile strength and tear strength; at the same time, the layered montmorillonite in the interconnected structure can form a physical barrier in the matrix, delaying the diffusion of heat and volatile decomposition products, and the nitrogen element in the dopamine-modified sepiolite can capture free radicals during combustion, interrupting the combustion chain reaction and slowing down the combustion rate. Magnesium oxide absorbs a large amount of heat at high temperature, reducing the temperature of the material surface and delaying the thermal decomposition and combustion process. Through the combined action of montmorillonite-dopamine-magnesium oxide, the flame retardant properties are improved.

[0026] (2) The modified EPDM rubber contains anhydride-treated montmorillonite. After the anhydride treatment, the interlayer spacing of the montmorillonite increases, and the EPDM rubber molecular chains are more easily inserted into the montmorillonite interlayers, forming an intercalated structure, which enhances the interfacial bonding force between the montmorillonite and the rubber matrix. At the same time, the montmorillonite layer, as a nano-scale filler, can effectively limit the slippage of the rubber molecular chains, thereby improving the tensile strength of the material.

[0027] (3) Dopamine in dopamine-modified sepiolite has strong adhesion and reactivity, and can form a polydopamine coating on the surface of sepiolite, thereby improving the interfacial bonding between sepiolite and the rubber matrix. A stronger interfacial bonding force is formed between the dopamine-modified sepiolite and the rubber matrix, which can more effectively transmit stress and dissipate energy when subjected to force, reduce local stress concentration, and improve the tear strength of the rubber waterstop.

[0028] (4) The modified magnesium oxide is treated with the silane coupling agent γ-glycidyloxypropyltrimethoxysilane to avoid uneven distribution caused by agglomeration. The evenly dispersed modified magnesium oxide can better decompose and absorb heat at high temperatures, reduce the surface temperature of the material, and release inert gas to dilute oxygen and combustible gases, thereby inhibiting combustion and improving the flame retardant properties of the material. DETAILED DESCRIPTION

[0029] For the convenience of understanding the present invention, the present invention is given below with examples. It should be understood by those skilled in the art that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0030] The sources of some components in the Examples and Comparative Examples are as follows:

[0031] Polyisobutylene, product number P304882, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0032] Ethylene propylene rubber, brand 3092PM, was purchased from Shanghai Sinopec Mitsui Chemicals Co., Ltd.

[0033] Carbon black, product number C124422, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0034] Sepiolite, CAS No. 63800-37-3, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0035] Magnesium oxide, CAS No. 1309-48-4, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0036] Triphenyl phosphate, CAS No. 115-86-6, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0037] Tricresyl phosphate, CAS No. 1330-78-5, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0038] Toluene diphenyl phosphate, CAS No. 26444-49-5, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0039] Zinc oxide, CAS No. 1314-13-2, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0040] Stearic acid, CAS No. 57-11-4, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0041] Dicumyl peroxide, CAS No. 80-43-3, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0042] 2-Mercaptobenzimidazole, CAS No. 583-39-1, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0043] Montmorillonite, product number M141491, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0044] Anhydrous ethanol, CAS No. 64-17-5, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0045] Methyltrichlorosilane, CAS No. 75-79-6, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0046] Tetrahydrofuran, CAS No. 109-99-9, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0047] 4-Hydroxyphthalic anhydride, CAS No. 27550-59-0, was purchased from Jinde Chemical Technology (Shanghai) Co., Ltd.;

[0048] Sodium hydride, CAS No. 7646-69-7, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0049] Dopamine, CAS number 51-61-6, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0050] Tris(hydroxymethyl)aminomethane, CAS No. 77-86-1, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0051] γ-Glycidyloxypropyltrimethoxysilane, CAS No. 2530-83-8, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0052] Preparation of dopamine-modified sepiolite: 3 parts by weight of sepiolite and 3 parts of dopamine were dispersed in 500 parts of tris(hydroxymethyl)aminomethane and heated for reaction (pH 8.6, temperature 80°C, time 20 h). After the reaction was completed, the mixture was vacuum dried and ground to obtain dopamine-modified sepiolite.

[0053] Preparation of modified magnesium oxide: In parts by weight, 20 parts of magnesium oxide and 6 parts of γ-glycidyloxypropyltrimethoxysilane were added to 140 parts of anhydrous ethanol for coupling treatment, stirred for 4 hours, and then centrifuged at 8000 r / min for 6 minutes. The lower precipitate was vacuum dried to obtain modified magnesium oxide.

[0054] Example 1

[0055] This embodiment provides a flame retardant rubber waterstop for tunnels.

[0056] The invention comprises the following components in parts by weight: 60 parts of polyisobutylene, 44 parts of modified ethylene propylene rubber, 26 parts of carbon black, 22 parts of dopamine-modified sepiolite, 14 parts of modified magnesium oxide, 8 parts of plasticizer triphenyl phosphate, 6 parts of zinc oxide, 5 parts of stearic acid, 2.4 parts of dicumyl peroxide and 1.6 parts of 2-mercaptobenzimidazole;

[0057] The preparation method of the modified EPDM rubber comprises: mixing 40 parts of montmorillonite, 50 parts of methyltrichlorosilane and 120 parts of anhydrous ethanol, stirring the mixture (stirring speed: 120 rpm, temperature: 40°C, time: 12 hours), then adding 120 parts of tetrahydrofuran and dispersing the mixture evenly, then adding 16 parts of 4-hydroxyphthalic anhydride and 4 parts of sodium hydride and performing an anhydride reaction (reaction temperature: 30°C, reaction time: 26 hours) to obtain anhydride-treated montmorillonite; and kneading 70 parts of EPDM rubber and 12 parts of the anhydride-treated montmorillonite (kneading temperature: 110°C, kneading time: 12 minutes) to obtain the modified EPDM rubber.

[0058] Example 2

[0059] This embodiment provides a flame retardant rubber waterstop for tunnels.

[0060] The invention comprises the following components in parts by weight: 56 parts of polyisobutylene, 40 parts of modified ethylene propylene rubber, 22 parts of carbon black, 18 parts of dopamine-modified sepiolite, 10 parts of modified magnesium oxide, 6 parts of plasticizer tricresyl phosphate, 4 parts of zinc oxide, 3 parts of stearic acid, 2.2 parts of dicumyl peroxide and 1.2 parts of 2-mercaptobenzimidazole;

[0061] The preparation method of the modified EPDM rubber comprises: mixing 30 parts of montmorillonite, 40 parts of methyltrichlorosilane and 100 parts of anhydrous ethanol, stirring the mixture (stirring speed: 100 rpm, temperature: 30°C, time: 16 hours), then adding 100 parts of tetrahydrofuran and dispersing the mixture evenly, then adding 10 parts of 4-hydroxyphthalic anhydride and 2 parts of sodium hydride and performing an anhydride reaction (reaction temperature: 26°C, reaction time: 28 hours) to obtain anhydride-treated montmorillonite; and kneading 60 parts of EPDM rubber and 8 parts of the anhydride-treated montmorillonite (kneading temperature: 100°C, kneading time: 16 minutes) to obtain the modified EPDM rubber.

[0062] Example 3

[0063] This embodiment provides a flame retardant rubber waterstop for tunnels.

[0064] The invention comprises the following components in parts by weight: 58 parts of polyisobutylene, 42 parts of modified ethylene propylene rubber, 24 parts of carbon black, 20 parts of dopamine-modified sepiolite, 12 parts of modified magnesium oxide, 7 parts of plasticizer toluene diphenyl phosphate, 5 parts of zinc oxide, 4 parts of stearic acid, 2.3 parts of dicumyl peroxide and 1.4 parts of 2-mercaptobenzimidazole;

[0065] The preparation method of the modified EPDM rubber comprises: mixing 35 parts of montmorillonite, 45 parts of methyltrichlorosilane and 110 parts of anhydrous ethanol, stirring the mixture (stirring speed: 110 rpm, temperature: 35°C, time: 14 hours), then adding 110 parts of tetrahydrofuran and dispersing the mixture evenly, then adding 14 parts of 4-hydroxyphthalic anhydride and 3 parts of sodium hydride and performing an anhydride reaction (reaction temperature: 28°C, reaction time: 27 hours) to obtain anhydride-treated montmorillonite; and kneading 65 parts of EPDM rubber and 10 parts of the anhydride-treated montmorillonite (kneading temperature: 105°C, kneading time: 14 minutes) to obtain the modified EPDM rubber.

[0066] Comparative Example 1

[0067] The difference between this comparative example and Example 1 is that commercially available EPDM rubber (brand 3092PM) is used instead of the modified EPDM rubber.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that commercially available sepiolite (CAS No. 63800-37-3) is used instead of dopamine-modified sepiolite.

[0070] Comparative Example 3

[0071] The difference between this comparative example and Example 1 is that commercially available magnesium oxide (CAS No. 1309-48-4) was used to modify magnesium oxide.

[0072] The performance of the rubber waterstop provided in the above embodiments and comparative examples was tested, and the test method was as follows:

[0073] (1) Tensile strength test: refer to the requirements of GB / T 18173.2-2014 Polymer waterproof materials Part 2: Waterstop for testing.

[0074] (2) Tear strength test: Test in accordance with the requirements of GB / T 18173.2-2014 Polymer waterproof materials Part 2: Waterstop.

[0075] (3) Oxygen index test: Test in accordance with the requirements of GB / T 10707-2008 Rubber - Determination of combustion performance.

[0076] The above performance test data is shown in Table 1.

[0077] Table 1 Performance test results

[0078]

[0079] From the above content, it can be seen that the present invention uses modified EPDM rubber, dopamine-modified sepiolite and modified magnesium oxide as main materials to prepare flame-retardant rubber waterstop for tunnels (Example 1 to Example 3), which has better comprehensive performance.

[0080] Compared with Example 1, when commercially available EPDM rubber (brand 3092PM) is used instead of the modified EPDM rubber, the tensile strength is reduced, the tear strength is reduced, and the oxygen index is reduced (Comparative Example 1); compared with Example 1, when commercially available sepiolite (CAS No. 63800-37-3) is used instead of dopamine-modified sepiolite, the tensile strength is reduced, the tear strength is reduced, and the oxygen index is reduced (Comparative Example 2); compared with Example 1, when commercially available magnesium oxide (CAS No. 1309-48-4) is used to modify magnesium oxide, the tensile strength is reduced, the tear strength is reduced, and the oxygen index is reduced (Comparative Example 3).

[0081] In summary, the present invention uses modified EPDM rubber, dopamine-modified sepiolite and modified magnesium oxide as main materials to prepare a flame-retardant rubber waterstop for tunnels, which effectively improves tensile strength, increases tear strength, and obtains good flame retardancy.

Claims

1. A flame retardant rubber waterstop for tunnels, characterized in that: The invention comprises the following components in parts by weight: 56-60 parts of polyisobutylene, 40-44 parts of modified ethylene-propylene rubber, 22-26 parts of carbon black, 18-22 parts of dopamine-modified sepiolite, 10-14 parts of modified magnesium oxide, 6-8 parts of plasticizer, 4-6 parts of zinc oxide, 3-5 parts of stearic acid, 2.2-2.4 parts of dicumyl peroxide and 1.2-1.6 parts of 2-mercaptobenzimidazole; The preparation method of the modified EPDM rubber comprises: mixing 30-40 parts by weight of montmorillonite, 40-50 parts of methyltrichlorosilane and 100-120 parts of anhydrous ethanol, stirring the mixture, adding 100-120 parts of tetrahydrofuran and dispersing the mixture evenly, and then adding 10-16 parts of 4-hydroxyphthalic anhydride and 2-4 parts of sodium hydride to carry out anhydride reaction to obtain anhydride-treated montmorillonite; and kneading 60-70 parts of EPDM rubber and 8-12 parts of the anhydride-treated montmorillonite to obtain the modified EPDM rubber. The preparation method of dopamine-modified sepiolite comprises: dispersing 1 to 3 parts of sepiolite and 1 to 3 parts of dopamine in 400 to 500 parts of tris(hydroxymethyl)aminomethane, heating the mixture, vacuum drying the mixture after the reaction is complete, and grinding the mixture to obtain the dopamine-modified sepiolite; The preparation method of the modified magnesium oxide comprises: adding 10 to 20 parts of magnesium oxide and 2 to 6 parts of gamma-glycidyloxypropyltrimethoxysilane to 120 to 140 parts of anhydrous ethanol for coupling treatment to obtain the modified magnesium oxide.

2. The flame-retardant rubber waterstop for tunnels according to claim 1, characterized in that: The stirring conditions include: a stirring speed of 100-120 rpm, a temperature of 30-40° C., and a time of 12-16 h.

3. The flame retardant rubber waterstop for tunnel according to claim 1, characterized in that: The conditions of the anhydride reaction include: a reaction temperature of 26-30° C. and a reaction time of 26-28 h.

4. The flame retardant rubber waterstop for tunnel according to claim 1, characterized in that: The mixing treatment conditions include: mixing treatment temperature of 100-110° C., and mixing treatment time of 12-16 minutes.

5. The flame retardant rubber waterstop for tunnel according to claim 1, characterized in that: The conditions of the heating reaction include: pH 8.2-8.6, temperature 70-80° C., and time 20-24 h.

6. The flame retardant rubber waterstop for tunnel according to claim 1, characterized in that: The coupling treatment conditions include: stirring for 2 to 4 hours, then centrifuging at a speed of 7000 to 8000 r / min for 6 to 10 minutes, and vacuum drying the lower precipitate.

7. The flame-retardant rubber waterstop for tunnels according to claim 1, characterized in that: The plasticizer is selected from at least one of triphenyl phosphate, tricresyl phosphate, and toluene diphenyl phosphate.

8. The method for preparing a flame-retardant rubber waterstop for tunnel according to any one of claims 1 to 7, characterized in that: The following steps are involved: In parts by weight, 56-60 parts of polyisobutylene, 40-44 parts of modified ethylene-propylene rubber, 22-26 parts of carbon black, 18-22 parts of dopamine-modified sepiolite, 10-14 parts of modified magnesium oxide, 6-8 parts of plasticizer, 4-6 parts of zinc oxide, 3-5 parts of stearic acid, and 2.2-2.4 parts of dicumyl peroxide are mixed for 10-15 minutes, and then a vulcanizing agent is added and mixed for 3-5 minutes, and the mixture is allowed to stand for 12-24 hours and vulcanized to obtain a flame-retardant rubber waterstop for tunnels.

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