Waterproof sealing gasket material for shield tunnel and preparation method thereof

Abstract

The invention relates to a waterproof sealing gasket material for a shield tunnel and a preparation method of the waterproof sealing gasket material. The preparation method comprises the following steps: plastifying raw rubber to obtain plastified raw rubber; the preparation method comprises the following steps: stirring and mixing plasticated raw rubber, carbon black N550, calcium carbonate, paraffin oil, zinc oxide, stearic acid, calcium oxide, an anti-aging agent and an organic magnesium compound, mixing in a mixing mill, and cooling to room temperature to obtain a mixture I; stirring and mixing the mixture I, modified NPE particles and an accelerant, mixing, and cooling to room temperature to obtain a mixture II; uniformly mixing the mixture II and sulfur in a mixing mill, vulcanizing at high temperature, and standing at room temperature for 24 hours to obtain the waterproof sealing gasket material. According to the waterproof sealing gasket material, the modified NPE particles of the core-shell structure are added, the compatibility of a water-swelling material and non-polar rubber is improved, the organic magnesium compound is added as a multifunctional auxiliary agent, the interface bonding, vulcanization network and flame retardant performance are synergistically improved, and the waterproof sealing gasket material has good waterproof performance. The prepared sealing gasket material has excellent mechanical properties, heat aging resistance, compression set resistance and flame retardance.

Description

Technical Field

[0001] This invention belongs to the field of waterproofing technology for shield tunnel segment joints, specifically relating to a waterproof sealing gasket material for shield tunnels and its preparation method. Background Technology

[0002] Shield tunneling is a key technology for the construction of major infrastructure projects such as urban subways, cross-river and cross-sea tunnels, and municipal utility tunnels. Tunnel segments are precisely spliced ​​to form the tunnel lining ring, but the joints connecting these segments are the weakest points in the tunnel structure's waterproofing. Waterproof sealing gaskets, as crucial elastic sealing elements pre-embedded in the sealing grooves of the tunnel segments, directly determine the tunnel's waterproofing reliability, structural safety, and durability under complex water pressure, geological loads, and long-term service conditions.

[0003] Waterproof sealing gaskets for shield tunnels primarily utilize rubber-based elastic sealing materials. EPDM (ethylene propylene diene monomer) rubber composite water-swellable materials are currently the mainstream choice for shield tunnel waterproof sealing gaskets. EPDM rubber, as the matrix, possesses unparalleled resistance to aging, ozone, heat, and chemical corrosion, as well as excellent physical and mechanical properties and low stress relaxation performance. Water-swellable materials provide crucial self-healing capabilities. Generally, water-swellable materials are uniformly dispersed into EPDM rubber during the mixing process as functional fillers. However, the significant polarity difference between water-swellable materials (such as sodium polyacrylate) and EPDM leads to poor compatibility, resulting in weak interfacial bonding and creating stress weak points that may affect the long-term aging resistance and physical strength of the EPDM matrix. Furthermore, most waterproof sealing gaskets for shield tunnels only consider mechanical properties and aging resistance, neglecting flame retardancy.

[0004] Therefore, in order to address the problems of composite interface defects and lack of flame retardant properties caused by polarity differences in existing technologies, there is an urgent need for a waterproof sealing gasket material with excellent mechanical properties and flame retardancy. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a waterproof sealing gasket material for shield tunnels. By modifying NPE particles with a core-shell structure, the compatibility between the water-swellable material and non-polar rubber is improved. Furthermore, by introducing an organic magnesium compound as a multifunctional additive, the interfacial bonding, vulcanization network, and flame retardant properties are synergistically enhanced. The prepared waterproof sealing gasket material for shield tunnels has excellent mechanical properties, heat aging resistance, compression set resistance, and flame retardancy.

[0006] The technical solution adopted by this invention to solve the above problems is: a method for preparing a waterproof sealing gasket material for shield tunnels, comprising the following steps: (1) Put the raw rubber into a plasticizer and plasticize it to obtain plasticized raw rubber; (2) Mix plasticized raw rubber, carbon black N550, calcium carbonate, paraffin oil, zinc oxide, stearic acid, calcium oxide, antioxidant and organic magnesium compound, mix them in a mixer and then cool them to room temperature to obtain mixture one; (3) Mix the mixture one, the modified NPE particles and the accelerator, mix them in a mixer and then cool them to room temperature to obtain the mixture two; (4) Mix the mixture with sulfur on a mixer, then vulcanize it at high temperature on a vulcanizing machine, and then leave it at room temperature for 24 hours to obtain a waterproof sealing gasket material.

[0007] Among them, the modified NPE particles are core-shell structured masterbatches with SEBS as the shell and SAP as the core.

[0008] Preferably, the modified NPE particles are prepared by the following method: SAP particles treated with silane coupling agent are uniformly dispersed in SEBS shell solution, and then the solvent is removed to obtain modified NPE particles.

[0009] More preferably, the modified NPE particles are prepared by the following method: A. The ethanol solution of silane coupling agent is sprayed evenly onto the surface of SAP particles in a stirred state, and heat-treated at 80-100℃ for 30-60 minutes to chemically graft the silane coupling agent onto the SAP surface. After cooling, a hydrophobic SAP is obtained. B. Dissolve SEBS in toluene at a mass ratio of 5%-10%, and stir at 60-80℃ until completely dissolved to obtain a SEBS shell solution. C. Under stirring, the surface-hydrophobic SAP is slowly added to the SEBS shell solution to obtain a suspension; D. Transfer the above suspension to a reactor equipped with a stirring and reflux condenser to evaporate the solvent and obtain the crude product; E. The crude product is dried in a vacuum oven and then pulverized to obtain modified NPE particles.

[0010] Preferably, the weight ratio of the plasticized raw rubber, carbon black N550, calcium carbonate, paraffin oil, zinc oxide, stearic acid, antioxidant, and organomagnesia compound is 100:60-80:15-25:15-25:5:1:1-2:8-12.

[0011] Preferably, the organomagnesium compound is magnesium stearate or magnesium oleate.

[0012] Preferably, the weight ratio of the raw plastic to the modified NPE granules is 100:5-10.

[0013] Preferably, the weight ratio of the raw plastic to the accelerator is 100:2-4.

[0014] Preferably, the specific process parameters for plasticizing in step (1) are: plasticizing temperature of 145-155℃ and plasticizing time of 10-20min.

[0015] Preferably, the specific process parameters for mixing in step (2) are: mixing temperature of 150-160℃ and mixing time of 15-20min.

[0016] Preferably, the specific process parameters for mixing in step (3) are: mixing temperature of 110-130℃ and mixing time of 3-5min.

[0017] Preferably, the high-temperature vulcanization temperature in step (4) is 147-153℃ and the vulcanization time is 8-12min.

[0018] A waterproof sealing gasket material for shield tunnels, wherein the waterproof sealing gasket material is prepared by the above-described method for preparing waterproof sealing gasket materials for shield tunnels.

[0019] Compared with the prior art, the advantages of the present invention are as follows: (1) The method for preparing waterproof sealing gasket material for shield tunnels of the present invention adds an organic magnesium compound, which can serve as an efficient interface modifier and activator. The organic part of the organic magnesium compound has a good affinity with the rubber molecular chain, while the magnesium ions can form strong ionic bonds or coordination with polar groups such as carboxylate groups on the surface of SAP. When added in the early stage of mixing, it can further strengthen the interfacial bonding force between the rubber matrix and the filler and the subsequently added modified NPE particles, and form a multi-layered stable interface in synergy with the SEBS shell. On the other hand, the organic magnesium compound has an activating and promoting effect in the rubber vulcanization system, which helps to form a denser and more stable cross-linked network, which can not only improve the vulcanization efficiency, but also significantly improve the heat aging resistance and compression set resistance of the vulcanized rubber. In addition, when exposed to fire or high temperature, the organic magnesium compound decomposes to generate magnesium oxide, which works synergistically with calcium oxide to form a halogen-free flame retardant system.

[0020] (2) The waterproof sealing gasket material for shield tunnels of the present invention incorporates modified NPE particles. The modified NPE particles are core-shell structure masterbatches with SEBS as the shell and SAP as the core. The non-polar ethylene-butene segments in the SEBS (styrene-ethylene-butene-styrene block copolymer) molecular chain have excellent compatibility with EPDM raw rubber, and can achieve molecular-level entanglement and mutual solubility. Meanwhile, its styrene blocks generate strong physical interactions with the polar groups on the surface of the SAP (sodium polyacrylate) core, so that the SAP particles can be smoothly and firmly embedded and dispersed in the rubber matrix through the "bridge" and "coating" effect of the SEBS shell, fundamentally eliminating the micro-defects and stress concentration points caused by interface debonding. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the embodiments. Example 1

[0022] A method for preparing a waterproof sealing gasket material for shield tunnels includes the following steps: (1) Put the raw rubber into a plasticizer and plasticize it to obtain plasticized raw rubber.

[0023] (2) Mix the plasticized raw rubber, carbon black N550, calcium carbonate, 300# paraffin oil, zinc oxide, stearic acid, calcium oxide, antioxidant and magnesium oleate. After mixing in a mixer and cooling to room temperature, obtain mixture one; the weight ratio of plasticized raw rubber, carbon black N550, calcium carbonate, 300# paraffin oil, zinc oxide, stearic acid, antioxidant and magnesium oleate is 100:70:20:20:5:1:2:10.

[0024] (3) Mix the mixture one, modified NPE granules and accelerator, mix them in a mixer and cool them to room temperature to obtain mixture two; the weight ratio of raw plastic to modified NPE granules is 100:7 and the weight ratio of raw plastic to accelerator is 100:2, wherein the accelerator is a compound of accelerator CZ and accelerator TMTD with a mass ratio of 1.5:0.5.

[0025] (4) Mix the mixture with sulfur on a mixer, then vulcanize it at high temperature on a vulcanizing machine, and then leave it at room temperature for 24 hours to obtain a waterproof sealing gasket material.

[0026] The modified NPE particles are core-shell structured masterbatches with SEB as the shell and SAP as the core. The modified NPE particles are prepared by the following method: A. A 2% silane coupling agent ethanol solution is sprayed evenly onto the surface of SAP particles (100μm) under stirring. The mixture is then heat-treated at 90℃ for 50min to allow the silane coupling agent to be chemically grafted onto the SAP surface. After cooling, a hydrophobic SAP is obtained. B. Dissolve SEBS in toluene at a mass ratio of 7%, and stir at 70°C until completely dissolved to obtain a SEBS shell solution. C. Under stirring, the surface hydrophobic SAP is slowly added to the SEBS shell solution to obtain a suspension, wherein the mass ratio of surface hydrophobic SAP to SEBS shell solution is 1:5. D. The above suspension is transferred to a reactor equipped with a stirrer and a reflux condenser, and distilled under reduced pressure at a temperature of 110°C to obtain the crude product. E. The crude product was dried in a vacuum oven at 70°C for 20 hours, then pulverized and sieved to obtain modified NPE particles (150 μm).

[0027] The specific process parameters for plasticizing in step (1) are: plasticizing temperature of 150℃ and plasticizing time of 15min.

[0028] The specific process parameters for mixing in step (2) are: mixing temperature of 155℃ and mixing time of 15min.

[0029] The specific process parameters for mixing in step (3) are: mixing temperature of 120℃ and mixing time of 4min.

[0030] The high-temperature vulcanization temperature in step (4) is 150°C and the vulcanization time is 12 min. Example 2

[0031] A method for preparing a waterproof sealing gasket material for shield tunnels includes the following steps: (1) Put the raw rubber into a plasticizer and plasticize it to obtain plasticized raw rubber.

[0032] (2) Mix the plasticized raw rubber, carbon black N550, calcium carbonate, 300# paraffin oil, zinc oxide, stearic acid, calcium oxide, antioxidant and magnesium oleate. After mixing in a mixer and cooling to room temperature, obtain mixture one; the weight ratio of plasticized raw rubber, carbon black N550, calcium carbonate, 300# paraffin oil, zinc oxide, stearic acid, antioxidant and magnesium oleate is 100:60:25:25:5:1:2:12.

[0033] (3) Mix the mixture one, modified NPE granules and accelerator, mix them in a mixer and cool them to room temperature to obtain mixture two; the weight ratio of raw plastic to modified NPE granules is 100:10 and the weight ratio of raw plastic to accelerator is 100:2, wherein the accelerator is a compound of accelerator CZ and accelerator TMTD with a mass ratio of 1.5:0.5.

[0034] (4) Mix the mixture with sulfur on a mixer, then vulcanize it at high temperature on a vulcanizing machine, and then leave it at room temperature for 24 hours to obtain a waterproof sealing gasket material.

[0035] The modified NPE particles are core-shell structured masterbatches with SEB as the shell and SAP as the core. The modified NPE particles are prepared by the following method: A. A 2% silane coupling agent ethanol solution is sprayed evenly onto the surface of SAP particles (100μm) under stirring. The mixture is then heat-treated at 90℃ for 50min to allow the silane coupling agent to be chemically grafted onto the SAP surface. After cooling, a hydrophobic SAP is obtained. B. Dissolve SEBS in toluene at a mass ratio of 7%, and stir at 70°C until completely dissolved to obtain a SEBS shell solution. C. Under stirring, the surface hydrophobic SAP is slowly added to the SEBS shell solution to obtain a suspension, wherein the mass ratio of surface hydrophobic SAP to SEBS shell solution is 1:5. D. The above suspension is transferred to a reactor equipped with a stirrer and a reflux condenser, and distilled under reduced pressure at a temperature of 110°C to obtain the crude product. E. The crude product was dried in a vacuum oven at 70°C for 20 hours, then pulverized and sieved to obtain modified NPE particles (150 μm).

[0036] The specific process parameters for plasticizing in step (1) are: plasticizing temperature of 155℃ and plasticizing time of 12min.

[0037] The specific process parameters for mixing in step (2) are: mixing temperature of 150℃ and mixing time of 20min.

[0038] The specific process parameters for mixing in step (3) are: mixing temperature of 110℃ and mixing time of 5min.

[0039] The high-temperature vulcanization temperature in step (4) is 147°C and the vulcanization time is 12 min. Example 3

[0040] A method for preparing a waterproof sealing gasket material for shield tunnels includes the following steps: (1) Put the raw rubber into a plasticizer and plasticize it to obtain plasticized raw rubber.

[0041] (2) Mix the plasticized raw rubber, carbon black N550, calcium carbonate, 300# paraffin oil, zinc oxide, stearic acid, calcium oxide, antioxidant and magnesium stearate. After mixing in a mixer and cooling to room temperature, obtain mixture one; the weight ratio of plasticized raw rubber, carbon black N550, calcium carbonate, 300# paraffin oil, zinc oxide, stearic acid, antioxidant and magnesium stearate is 100: 80:15:15:5:1:2:8.

[0042] (3) Mix the mixture one, modified NPE granules and accelerator, mix them in a mixer and cool them to room temperature to obtain mixture two; the weight ratio of raw plastic to modified NPE granules is 100:5, the weight ratio of raw plastic to accelerator is 100:2, and the accelerator is a compound of accelerator CZ and accelerator TMTD with a mass ratio of 1.5:0.5.

[0043] (4) Mix the mixture with sulfur on a mixer, then vulcanize it at high temperature on a vulcanizing machine, and then leave it at room temperature for 24 hours to obtain a waterproof sealing gasket material.

[0044] The modified NPE particles are core-shell structured masterbatches with SEB as the shell and SAP as the core. The modified NPE particles are prepared by the following method: A. A 2% silane coupling agent ethanol solution is sprayed evenly onto the surface of SAP particles (100μm) under stirring. The mixture is then heat-treated at 90℃ for 50min to allow the silane coupling agent to be chemically grafted onto the SAP surface. After cooling, a hydrophobic SAP is obtained. B. Dissolve SEBS in toluene at a mass ratio of 7%, and stir at 70°C until completely dissolved to obtain a SEBS shell solution. C. Under stirring, the surface hydrophobic SAP is slowly added to the SEBS shell solution to obtain a suspension, wherein the mass ratio of surface hydrophobic SAP to SEBS shell solution is 1:5. D. The above suspension is transferred to a reactor equipped with a stirrer and a reflux condenser, and distilled under reduced pressure at a temperature of 110°C to obtain the crude product. E. The crude product was dried in a vacuum oven at 70°C for 20 hours, then pulverized and sieved to obtain modified NPE particles (150 μm).

[0045] The specific process parameters for plasticizing in step (1) are: plasticizing temperature of 145℃ and plasticizing time of 20min.

[0046] The specific process parameters for mixing in step (2) are: mixing temperature of 60℃ and mixing time of 15min.

[0047] The specific process parameters for mixing in step (3) are: mixing temperature of 120℃ and mixing time of 5min.

[0048] The high-temperature vulcanization temperature in step (4) is 153°C and the vulcanization time is 8 min.

[0049] Comparative Example 1 The only difference from Example 1 is that magnesium oleate is not added.

[0050] Comparative Example 2 The only difference from Example 1 is that no modified NPE particles are added.

[0051] Comparative Example 3 The only difference from Example 1 is that the modified NPE particles are replaced with unmodified NPE particles, that is, 100μm SAP particles are directly added.

[0052] The samples from Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests, as detailed below: Mechanical property testing: The hardness, tensile strength, and elongation at break of the specimens were tested according to GB / T531.1-2008 and GB / T528-2009, respectively. Three specimens were tested, and the average value was taken as the final result. The specimens were cut into type II dumbbell-shaped specimens (75×4×2mm3, L×W×H) using a type II cutter. The hardness was measured using a Shore hardness tester, and the tensile strength and elongation at break were measured using a universal tensile testing machine at a tensile rate of 500mm / min.

[0053] Compression set: determined according to GB / T 7759.1-2015 standard, under the following conditions: the sample is compressed to 75% of its original thickness (i.e., compression ratio 25%) and placed in a constant temperature oven at 70℃ for 24 hours.

[0054] Water swelling rate: determined according to GB / T 18173.4-2010 standard, the sample is completely immersed in distilled water or deionized water at a constant temperature of (23 ± 2)°C for 24 hours.

[0055] Heat aging resistance: Tested according to GB / T 3512-2014 standard, the sample was suspended in a hot air aging test chamber at 100°C and continuously exposed for 72 hours.

[0056] Flame retardant performance test: The samples were cut into sizes (150×6.5×3mm3, L×W×H) according to GB / T 10707-2008. The oxygen index of the samples was measured using a vertical flame retardant performance tester. Three samples were tested, and the average value was taken as the final result.

[0057] The test results are shown in Table 1: Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-3

[0058] As can be seen from the table above, the sealing gasket materials of Examples 1-3 all possess excellent mechanical properties, low compression set, high performance retention after heat aging, and flame retardancy. From Examples 1 and Comparative Example 1, it can be seen that the addition of magnesium oleate is beneficial for improving compression set, heat aging resistance, and flame retardancy. This is because magnesium oleate not only acts as an interface agent and activator, helping to form a denser and more stable cross-linked network, but also acts as a flame retardant synergist, forming a halogen-free flame retardant system with calcium oxide. From Examples 1 and Comparative Example 2, it can be seen that without the addition of... Modified NPE particles do not have the function of swelling upon contact with water. As can be seen from Example 1 and Comparative Example 3, although the initial swelling rate of directly adding SAP particles is high (220%), the swelling is uneven and uncontrollable, resulting in local pulverization of the material, a sharp drop in strength, and poor compression deformation. This shows that adding core-shell structure modified NPE particles achieves a moderate and controllable swelling rate upon contact with water (120-180%), and the material remains intact after swelling. The SEBS shell effectively protects the SAP core and its firm bond with the rubber matrix avoids the drawbacks of poor interfacial compatibility.

[0059] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a waterproof sealing mat material for a shield tunnel, characterized by: The method comprises the following steps: (1) plasticize raw rubber in a plasticator to obtain plasticized raw rubber; (2) mix the plasticized raw rubber, carbon black N550, calcium carbonate, paraffin oil, zinc oxide, stearic acid, calcium oxide, antioxidant and organic magnesium compound, mix in a mixer, cool to room temperature, and obtain mixture one; (3) mix mixture one, modified NPE particles and accelerator, mix in a mixer, cool to room temperature, and obtain mixture two; (4) mix mixture two and sulfur in a mixer, high-temperature vulcanize in a vulcanizing machine, and then place at room temperature for 24 hours to obtain the waterproof sealing gasket material. The modified NPE particles are core-shell structure masterbatch with SEB as shell and SAP as core.

2. The method of claim 1, wherein the method further comprises: The modified NPE particles are prepared by the following method: uniformly disperse silane coupling agent treated SAP particles in SEBS shell layer solution, and then remove the solvent to obtain the modified NPE particles.

3. The method of claim 1, wherein the method further comprises: The weight ratio of the plasticized raw rubber, carbon black N550, calcium carbonate, paraffin oil, zinc oxide, stearic acid, antioxidant and organic magnesium compound is 100:60-80:15-25:15-25:5:1:1-2:8-12.

4. The method of claim 1, wherein the waterproofing sealant material for a shield tunnel is prepared by the steps of: The weight ratio of the plastic raw rubber and modified NPE particles is 100:5-10. ​ 5. The method of claim 1, wherein the method further comprises: The weight ratio of the plastic raw rubber and accelerator is 100:2-4.

6. The method of claim 1, wherein the method further comprises: The specific process parameters of the plasticizing in step (1) are as follows: plasticizing temperature is 145-155℃, and plasticizing time is 10-20min.

7. The method of claim 1, wherein the method further comprises: The specific process parameters of the mixing in step (2) are as follows: mixing temperature is 150-160℃, and mixing time is 15-20min.

8. The method of claim 1, wherein the method further comprises: The specific process parameters of the mixing in step (3) are as follows: mixing temperature is 110-130℃, and mixing time is 3-5min.

9. The method of claim 1, wherein the method further comprises: The high-temperature vulcanization temperature in step (4) is 147-153℃, and the vulcanization time is 8-12min.

10. A waterproof gasket material for a shield tunnel, characterized by: The waterproof sealing gasket material is prepared by the method for preparing waterproof sealing gasket material for shield tunnel in any one of claims 1-9.

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