Shield tail sealing grease for a shield tunneling machine and a method of manufacturing the same

Abstract

The application provides a shield tail sealing grease for a shield tunneling machine and a preparation method thereof. In the preparation raw material of the shield tail sealing grease, polyurea and silicone fluororubber particles are both elastomer particles, which can be filled into the space of a shield tail brush under the elastic force and extrusion force of the particles, so that the shield tail brush is sealed. The silicone resin has good hydrophobicity, which can enhance the cohesion of the shield tail sealing grease and prevent the shield tail sealing grease from being washed away by high-pressure water. The micro-bead-shaped polyethylene wax has rolling property, which can improve the flowability and pumpability of the shield tail sealing grease. The powdered polytetrafluoroethylene is a free-flowing powder, which can reduce the friction coefficient of the shield tail sealing grease, and further improve the flowability and pumpability of the shield tail sealing grease. The granular polytetrafluoroethylene has a smooth surface and a very small friction coefficient, which can improve the flowability of the shield tail sealing grease and improve the hydrophobicity. The preparation raw material in the application is easy to obtain, safe and environmentally friendly, the preparation method is simple and easy to operate, and the shield tail sealing grease can be produced in large quantities.

Description

Technical Field

[0001] This invention belongs to the field of sealing grease technology, and relates to a sealing grease for the tail of a tunnel boring machine and its preparation method. Background Technology

[0002] A tunnel boring machine (TBM) is a type of tunnel boring machine that uses the shield tunneling method to excavate and lay supporting segments in the tunnel. It is widely used in tunnel projects such as subways, railways, highways, municipal works, and hydropower projects.

[0003] The shield tail is formed by extending the outer steel plates of the tunnel boring machine (TBM) and its function is to protect the tunnel lining assembly work. A tail brush is installed at the end of the shield tail, and a tail sealing grease with sealing and lubricating properties is injected between the brushes to ensure a high degree of water tightness. The tail seal achieves isolation between the tunnel's internal and external environments by balancing the pressure of the tail sealing grease with the grouting pressure and the pressure of groundwater and soil. This prevents water, soil, and synchronous grouting slurry from seeping into the TBM, effectively protecting the tail shield and ensuring smooth tunneling. If the seal fails, the tail shield will gush out, and the synchronous grouting slurry, groundwater, and mud entering the tunnel will pose a significant safety threat. Therefore, the tail sealing grease is a key material for ensuring the tail sealing performance of the TBM during tunneling, and its components need to meet multiple functions, including lubrication, sealing, corrosion prevention, water resistance, pumpability, and adhesion.

[0004] Typically, the tail shield sealing grease is a solid or near-solid grease with poor flowability and pumpability, thus requiring an extrusion device to force it into the tail shield brush. If the tail shield sealing grease cannot fill the entire area of ​​the tail shield brush, sealing failure will occur. Furthermore, if the amount of tail shield sealing grease filling the tail shield brush is insufficient or thin, and if the grease has poor water sealing properties, the abundant and pressurized groundwater flow can wash away the grease, ultimately leading to sealing failure. Summary of the Invention

[0005] The purpose of this invention is to provide a shield tail sealing grease and its preparation method to solve the problem of poor sealing performance of existing shield tail sealing greases.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This application provides a shield tail sealing grease for tunnel boring machines, which contains 5-10% silicone fluororubber particles and 5-8% granular polytetrafluoroethylene by weight percentage.

[0008] Silicone fluororubber granules are pulverized silicone fluororubber. When added to the tail shield sealing grease, the granules, due to their elasticity, elastically contract during the compression process as the grease is forced into the tail shield brush. Upon extrusion and filling into the brush, the granules expand under their own elastic force, restoring their original volume and filling the space within the brush, thus sealing the tail shield and improving the sealing performance of the grease. Furthermore, because silicone fluororubber possesses excellent heat resistance, cold resistance, and weather resistance, the tail shield sealing grease filled into the brush exhibits high-temperature resistance, cold resistance, and wear resistance, extending its service life.

[0009] Granular PTFE has a smooth surface, resulting in an extremely low coefficient of friction. Adding granular PTFE to the tail shield sealing grease improves its fluidity and pumpability, allowing it to fill all areas of the tail shield brush and enhance its sealing performance. Furthermore, granular PTFE is a particulate PTFE with a dense internal structure and ordered molecular chains, resulting in high mechanical strength, high chemical stability, a wide temperature range, and non-stick properties.

[0010] In this application, silicone fluororubber particles with an average particle size of 0.5-2 mm and an elastic modulus of 5-10 are selected; spherical granular polytetrafluoroethylene with a particle size of 1-5 mm is selected to improve the fluidity of the shield tail sealing grease while improving its sealing performance.

[0011] Furthermore, the shield tail sealing grease in this application also contains 2-3% polyurea by mass.

[0012] Polyurea is an elastomeric material formed by the reaction of isocyanates and amino compounds. It possesses excellent antioxidant properties, chemical corrosion resistance, water resistance, impact resistance, and abrasion resistance. After polyurea is formed by spraying isocyanates and amino compounds, it is pulverized into granules, forming elastic particles. Due to the elasticity of polyurea, these particles elastically contract during the extrusion of the shield tail sealing grease into the shield tail brush. When extruded and filled into the shield tail brush, the polyurea particles expand under their own elastic force, restoring their original volume, and work together with the silicone fluororubber particles to fill the space in the shield tail brush, achieving a seal and improving the sealing performance of the shield tail sealing grease.

[0013] Furthermore, the shield tail sealing grease in this application also contains 3-5% synthetic wax by mass. The synthetic wax in this application serves to improve pumpability, water erosion resistance, and deemulsification properties. The synthetic wax in this application includes polyethylene wax and / or powdered polytetrafluoroethylene. When polyethylene wax and powdered polytetrafluoroethylene are mixed, their mass ratio is 1:1.

[0014] Polyethylene wax, a white, microbead-like or flake-like substance, possesses excellent cold resistance, heat resistance, chemical resistance, and corrosion resistance. Its hydrophobicity is superior to natural paraffin wax, and it maintains structural stability of the tail shield sealing grease under high water pressure. The microbead-like polyethylene wax also exhibits rolling properties, improving the flowability and pumpability of the tail shield sealing grease.

[0015] Powdered polytetrafluoroethylene (PTFE) is an ultrafine PTFE powder with a particle size of 0.5-15 μm. This free-flowing powder has a low coefficient of friction, reducing the friction of the tail shield sealing grease and improving its flowability and pumpability, allowing it to fill all areas of the tail shield brush. Furthermore, powdered PTFE exhibits good chemical stability, high-temperature resistance, and chemical corrosion resistance, enhancing the water resistance and durability of the tail shield sealing grease.

[0016] Furthermore, the shield tail sealing grease in this application also contains 3-5% silicone resin by weight. The silicone resin in this application acts as a water-repellent agent, providing resistance to water erosion and emulsification. Silicone resin is a solid or semi-solid siloxane polymer with good hydrophobicity, which enhances the cohesiveness of the shield tail sealing grease and prevents it from being dispersed by high-pressure water. The silicone resin in this application is selected from one of methylphenyl silicone resin, methyl silicone resin, epoxy-modified organosilicon resin, polymethyl silicone resin, and fluorosilicone resin.

[0017] Furthermore, the shield tail sealing grease in this application also contains 8-15% by mass of thickener and 5-10% by mass of tackifier, wherein the thickener is used to form a semi-solid paste structure of the base oil, and the tackifier is used to improve the viscosity, cohesion and structural stability of the shield tail sealing grease.

[0018] The thickener used in this application is selected from one or more of lithium soap, calcium soap, calcium-zinc composite soap, and bentonite. Calcium-zinc composite soap exhibits good compressive strength, water resistance, and corrosion resistance, thus improving the water erosion resistance and compressive strength of the shield tail sealing grease. Bentonite possesses good high-temperature resistance; both are used in combination in this application. The tackifier used in this application includes polyisobutylene, polyethylene wax, butyl rubber, ethylene propylene rubber, hydrogenated rosin resin, and polyamide wax.

[0019] In addition to the components mentioned above, this application also contains base oil, accounting for a certain percentage of the remaining mass. Base oil is the main carrier of the shield tail sealing grease, possessing good fluidity and lubricity. The base oil in this application is selected from mineral oils or synthetic oils, such as paraffinic mineral oils, naphthenic mineral oils, polyalphaolefins, ester oils, etc.

[0020] In addition, this application also provides a method for preparing a sealing grease for the tail of a tunnel boring machine, the method comprising:

[0021] S01: After pulverizing polyurea into particles, it is mixed with synthetic wax, silicone fluororubber particles, and granular polytetrafluoroethylene to form a solid filler;

[0022] S02: Mix base oil, thickener, tackifier, and silicone resin evenly to form a viscous mixture;

[0023] S03: Mix the solid filler with the viscous mixture to obtain the shield tail sealing grease for the tunnel boring machine.

[0024] The present invention has the following beneficial effects:

[0025] (1) Both polyurea and silicone rubber particles are elastomer particles. During the process of the shield tail sealing grease being squeezed to the shield tail of the tunnel boring machine, both polyurea particles and silicone rubber particles shrink elastically due to the squeeze. When they are squeezed and filled to the shield tail, since they are no longer subjected to pressure, both polyurea particles and silicone rubber particles expand under their own elastic force, restore their original volume, and fill the space of the shield tail brush, thereby achieving the sealing of the shield tail brush and improving the sealing performance of the shield tail sealing grease.

[0026] (2) Microbeaded polyethylene wax and powdered polytetrafluoroethylene have better hydrophobicity than natural paraffin wax, and can maintain the structural stability of the shield tail sealing grease under high water pressure. At the same time, microbeaded polyethylene wax has rolling properties, which can improve the fluidity and pumpability of the shield tail sealing grease; powdered polytetrafluoroethylene is a free-flowing powder, which can reduce the friction coefficient of the shield tail sealing grease, thereby improving the fluidity and pumpability of the shield tail sealing grease.

[0027] (3) Granular polytetrafluoroethylene has a smooth surface and a very small coefficient of friction. Therefore, when it is applied to shield tail sealing grease, it can increase its fluidity and improve its hydrophobicity.

[0028] (4) Silicone resin has good hydrophobicity, which can enhance the cohesion of the shield tail sealing grease and prevent it from being washed away by high pressure water.

[0029] (5) The raw materials for preparation are readily available, safe and environmentally friendly, and the preparation method is simple, easy to operate, and can be mass-produced. Detailed Implementation

[0030] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0031] Example 1

[0032] This application provides a sealing grease for the tail of a tunnel boring machine. The raw materials for its preparation include, by mass percentage, 82% base oil, 10% silicone rubber particles, and 8% granular polytetrafluoroethylene. The base oil is a solid paraffin-based mineral oil, and the particle sizes of the silicone rubber particles and granular polytetrafluoroethylene are 1 mm and 2 mm, respectively.

[0033] The preparation method of the shield tail sealing grease of the tunnel boring machine includes: adding silicone fluororubber particles and granular polytetrafluoroethylene to base oil, stirring evenly, and obtaining the shield tail sealing grease of the tunnel boring machine.

[0034] Example 2

[0035] This application provides a sealing grease for the tail of a tunnel boring machine. The raw materials for its preparation include, by mass percentage, 60% base oil, 8% silicone rubber particles, 7% granular polytetrafluoroethylene, 15% thickener, and 10% tackifier. The base oil is a naphthenic mineral oil, the thickener is lithium soap and bentonite in a mass ratio of 1:1, the tackifier is polyamide wax, and the particle sizes of the silicone rubber particles and granular polytetrafluoroethylene are 0.5 mm and 1 mm, respectively.

[0036] The preparation method of the sealing grease for the shield tail of the tunnel boring machine is as follows:

[0037] S201: Mix silicone fluororubber particles and granular polytetrafluoroethylene to form a solid filler;

[0038] S202: Mix base oil, thickener, and tackifier evenly to form a viscous mixture;

[0039] S203: Mix solid filler with a viscous mixture to obtain shield tail sealing grease for tunnel boring machines.

[0040] Example 3

[0041] This application provides a sealing grease for the tail of a tunnel boring machine. The raw materials for its preparation include, by mass percentage, 61% base oil, 9% silicone rubber particles, 7% granular polytetrafluoroethylene, 3% polyurea, 12% thickener, and 8% tackifier. The base oil is paraffinic mineral oil, the thickener is lithium soap, the tackifier is polyethylene wax, and the particle sizes of the silicone rubber particles and granular polytetrafluoroethylene are 2 mm and 5 mm, respectively.

[0042] The preparation method of the sealing grease for the shield tail of the tunnel boring machine is as follows:

[0043] S301: After pulverizing polyurea into granules, it is mixed with silicone fluororubber granules and granular polytetrafluoroethylene to form a solid filler;

[0044] S402: Mix base oil, thickener, and tackifier evenly to form a viscous mixture;

[0045] S403: Mix solid filler with a viscous mixture to obtain shield tail sealing grease for tunnel boring machines.

[0046] Example 4

[0047] This application provides a sealing grease for the tail of a tunnel boring machine. The raw materials for its preparation include, by mass percentage, 56% base oil, 10% silicone rubber particles, 6% granular polytetrafluoroethylene, 3% polyurea, 4% synthetic wax, 12% thickener, and 9% tackifier. The base oil is naphthenic mineral oil, the thickener is calcium-zinc composite soap, the tackifier is ethylene propylene rubber, and the synthetic wax is powdered polytetrafluoroethylene with a particle size of 15 μm. The particle sizes of the silicone rubber particles and the granular polytetrafluoroethylene are 1.5 mm and 2 mm, respectively.

[0048] The preparation method of the sealing grease for the shield tail of the tunnel boring machine is as follows:

[0049] S401: After pulverizing polyurea into granules, it is mixed with synthetic wax, silicone fluororubber granules, and granular polytetrafluoroethylene to form a solid filler;

[0050] S402: Mix base oil, thickener, and tackifier evenly to form a viscous mixture;

[0051] S403: Mix solid filler with a viscous mixture to obtain shield tail sealing grease for tunnel boring machines.

[0052] Example 5

[0053] This application provides a sealing grease for the tail of a tunnel boring machine. The raw materials for its preparation include, by mass percentage, 59% base oil, 8% silicone rubber particles, 6% granular polytetrafluoroethylene, 2% polyurea, 4% synthetic wax, 4% silicone resin, 10% thickener, and 7% tackifier. The base oil is an ester oil, the thickener is calcium soap, the tackifier is butyl rubber, the silicone resin is epoxy-modified organosilicon resin, the synthetic wax is microbeaded polyethylene wax, and the particle sizes of the silicone rubber particles and granular polytetrafluoroethylene are 1 mm and 3 mm, respectively.

[0054] The preparation method of the sealing grease for the shield tail of the tunnel boring machine is as follows:

[0055] S501: After pulverizing polyurea into granules, it is mixed with synthetic wax, silicone fluororubber granules, and granular polytetrafluoroethylene to form a solid filler;

[0056] S502: Mix base oil, thickener, tackifier, and silicone resin evenly to form a viscous mixture;

[0057] S503: Mix solid filler with a viscous mixture to obtain shield tail sealing grease for tunnel boring machines.

[0058] Example 6

[0059] This application provides a sealing grease for the tail of a tunnel boring machine. The raw materials for its preparation include, by mass percentage, 53% base oil, 5% silicone rubber particles, 8% granular polytetrafluoroethylene, 3% polyurea, 3% synthetic wax, 3% silicone resin, 15% thickener, and 10% tackifier. The base oil is a polyalphaolefin or ester oil, the thickener is lithium soap, the tackifier is polyisobutylene, the silicone resin is fluorosilicone resin, the synthetic wax is powdered polytetrafluoroethylene with a particle size of 10 μm, and the particle sizes of the silicone rubber particles and the granular polytetrafluoroethylene are 1 mm and 4 mm, respectively.

[0060] The preparation method of the sealing grease for the shield tail of the tunnel boring machine is the same as in Example 5.

[0061] Example 7

[0062] This application provides a sealing grease for the tail of a tunnel boring machine. The raw materials for its preparation include, by mass percentage, 60% base oil, 10% silicone rubber particles, 5% granular polytetrafluoroethylene, 2% polyurea, 5% synthetic wax, 5% silicone resin, 8% thickener, and 5% tackifier. The base oil is a polyalphaolefin or ester oil, the thickener is lithium soap, the tackifier is polyisobutylene, the silicone resin is fluorosilicone resin, the synthetic wax is powdered polytetrafluoroethylene with a particle size of 10 μm, and the particle sizes of the silicone rubber particles and the granular polytetrafluoroethylene are 1 mm and 4 mm, respectively.

[0063] The preparation method of the sealing grease for the shield tail of the tunnel boring machine is the same as in Example 5.

[0064] Comparative Example 1

[0065] This application provides a comparative example of a shield tail sealing grease for a tunnel boring machine. This comparative example does not contain polyurea or silicone rubber particles, and is otherwise the same as in Example 1.

[0066] Comparative Example 2

[0067] This application provides a comparative example of a shield tail sealing grease for a tunnel boring machine. This comparative example does not contain synthetic wax or granular polytetrafluoroethylene, and is otherwise the same as in Example 1.

[0068] Comparative Example 3

[0069] This application provides a comparative example of a sealing grease for the tail of a tunnel boring machine. This comparative example does not contain polyurea, silicone rubber particles, synthetic wax, or granular polytetrafluoroethylene, and is otherwise the same as in Example 1.

[0070] Comparative Example 4

[0071] This application provides a comparative example of a sealing grease for the tail of a tunnel boring machine. This comparative example does not contain silicone resin, and the rest is the same as in Example 1.

[0072] In this application, the tail seal greases prepared in Examples 1-7 and Comparative Examples 1-4 were tested for pumpability, water pressure sealing performance, cone penetration, water flushing loss, volatility, corrosion resistance, and density. The test results are shown in Table 1. Each performance test was conducted according to existing standards, specifically the indicators in the "Tail Seal Grease for High Water Pressure Shield Tunneling Machines" issued by the State-owned Assets Supervision and Administration Commission of the State Council on May 19, 2021.

[0073] Table 1: Performance Test Results of Tail Shield Sealing Grease

[0074]

[0075] As shown in Table 1, the performance indicators of the shield tail sealing greases prepared in Examples 1-7 of this application all meet the test standard requirements, and they exhibit good pumpability, good water pressure sealing performance, and low water flushing loss; especially the shield tail sealing greases prepared in Examples 5-7. Some performance indicators of the shield tail sealing greases prepared in Comparative Examples 1-4 also meet the test standard requirements.

[0076] Compared with the shield tail sealing greases prepared in Examples 1-7 of this application, the shield tail sealing greases prepared in Comparative Examples 1-4 have poor water sealing performance, low pumpability, and low water flushing loss.

[0077] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A sealing grease for the tail of a tunnel boring machine, characterized in that, According to mass percentage, the shield tail sealing grease of the tunnel boring machine contains 5-10% silicone rubber particles, 5-8% granular polytetrafluoroethylene, 2-3% polyurea, 3-5% synthetic wax, 3-5% silicone resin, 8-15% thickener, 5-10% tackifier, and the remainder is base oil; the average particle size of the silicone rubber particles is 0.5-2mm, and the elastic modulus is 5-10; the granular polytetrafluoroethylene is round in shape and has a particle size of 1-5mm; the synthetic wax includes polyethylene wax and / or powdered polytetrafluoroethylene; the thickener is selected from one or more of lithium soap, calcium soap, calcium-zinc composite soap, and bentonite; the tackifier is selected from polyisobutylene, polyethylene wax, butyl rubber, ethylene propylene rubber, hydrogenated rosin resin, or polyamide wax.

2. The shield tail sealing grease of a tunnel boring machine according to claim 1, characterized in that, The powdered polytetrafluoroethylene has a particle size of 0.5-15 μm, and the polyethylene wax in the synthetic wax is microbead-like polyethylene wax.

3. The method for preparing the shield tail sealing grease of a tunnel boring machine according to claim 1, characterized in that, include: After polyurea is crushed into particles, it is mixed with synthetic wax, silicone fluororubber particles, and granular polytetrafluoroethylene to form a solid filler. The base oil, thickener, tackifier, and silicone resin are mixed evenly to form a viscous mixture; The solid filler is mixed with the viscous mixture to obtain the shield tail sealing grease for the tunnel boring machine.

Images