JP6574776B2 - Tail seal composition for shield machine - Google Patents

Description

  The present invention relates to a tail seal composition for a shield machine.

When excavating a tunnel into the ground with a shield machine, the shield machine advances while excavating ground in the direction of travel, and segments behind the shield machine are sequentially assembled as the inner wall of the tunnel. ing. In this case, the outer diameter of the tunnel to be excavated (excavation opening diameter) is the outer diameter of the shield machine, but since the segment is assembled inside the shield machine, the outer diameter of the segment is less than the inner diameter of the shield machine. Become. For this reason, a gap is formed between the outer diameter of the tunnel and the outer diameter of the segment behind the shield machine, and this gap is filled with a backing agent as the shield machine advances.
On the other hand, in the tunnel at the rear end of the shield machine that has not yet been filled with the backfill agent, groundwater or the like has oozed out. A plurality of rows of brush seals for stopping water between the outer circumference of the segment in the shield machine and the inner circumference of the shield machine are provided on the inner circumference of the shield machine. And in order to maintain the water stop, a tail seal composition is filled between these brush seals (see, for example, Patent Document 1). As the shield machine progresses, the tail seal composition of the brush seal diffuses to the ground, so it is necessary to replenish the brush seal with the tail seal composition, and the tail seal composition is pumped through the pipe using a pump. Is done.

  As this tail seal composition, a mixture of mineral oil-based or synthetic-based lubricating base oil and scale-like thickener, other inorganic fillers, organic powder, fiber, etc. is used (patent) Reference 1-5).

Japanese Patent Publication No. 7-6350 Japanese Patent Laid-Open No. 3-197798 JP-A-5-187194 JP-A-7-109893 Japanese Patent Laid-Open No. 9-208943

  Conventionally, tail seal compositions with sufficiently increased water-stopping properties have high viscosities, which may make it difficult to pump and cause problems such as interruption of excavation by a shield machine. On the other hand, a tail seal composition that can be easily pumped has a concern about water-stopping. The present invention solves such problems, and provides a tail seal composition having high water-stopping properties and excellent pumpability.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have surprisingly found that the use of a mixture of a predetermined ratio of mineral oil and polybutene as the lubricating base oil of the tail seal composition makes the fiber moderate. It has been found that the water-stopping property and the pumping property, which are problems that are contradictory to each other, can be remarkably improved at the same time, and that the water-stopping property and the pumping property can be further improved in a balanced manner by using a predetermined combination of fibers. .

The present invention has been made based on such knowledge and is as follows.
(1) Lubricant base oil 15 to 60% by mass, inorganic powder 30 to 70% by mass, and fiber 2 to 10% by mass including short fibers and long fibers, wherein the lubricant base oil is mineral oil and polybutene Is a tail seal composition for a shield machine that contains a mass ratio of 20: 1 to 1: 1.
(2) The average length of the short fibers is 0.8 to 2.4 mm, the average length of the long fibers is 1.5 to 10 times the average length of the short fibers contained, The tail seal composition for a shield machine according to (1) above, wherein the mass ratio is 1: 4 to 4: 1.
(3) The tail seal composition for a shield machine according to the above (1), wherein the mineral oil has a kinematic viscosity at 40 ° C. of 100 to 3000 mm ² / s and the polybutene has a number average molecular weight of 5,000 to 20,000.
(4) The tail seal composition for a shield machine according to the above (1), wherein the inorganic powder contains at least one of talc and calcium carbonate.
(5) The tail seal composition for a shield machine according to (1), wherein the short fibers are natural fibers and the long fibers are synthetic fibers or natural fibers.

  Since the tail seal composition for a shield machine according to the present invention can improve the water-stopping property and the pumping property at the same time, excavation by the shield machine can be efficiently and safely performed.

The tail seal composition for a shield machine according to the present invention contains a lubricating base oil of 15 to 60% by mass, an inorganic powder of 30 to 70% by mass, and a fiber of 2 to 10% by mass. Preferably has a density of 1.1 to 1.8 g / cm ³ at 15 ° C. for ease of pumping, water-stopping, stability when mixed with water, and oil retention at high temperatures. ˜1.5 g / cm ³ is more preferred, and 1.1 to 1.3 g / cm ³ is even more preferred. For the same reason, those having an immiscibility consistency of 150 to 350 are preferred, and 220 to 280 is more preferred. In addition, the measurement of the immiscible penetration referred to in the present invention is based on a method based on JISK2220.
Furthermore, it is preferable that the tail seal composition for a shield machine of the present invention is substantially free of moisture. The fact that it does not substantially contain water means that it does not exclude water inevitably mixed in, but the water content is preferably 5% by mass or less based on the total amount of the tail seal composition, More preferably, it is 1 mass% or less.

[Lubricant base oil]
The lubricating base oil of the present invention contains mineral oil and polybutene in a mass ratio of 20: 1 to 1: 1. It is presumed that the adhesiveness of polybutene to the fiber, the fluidity of mineral oil, and the affinity of both improve the pumpability and water stoppage at the same time. When the content ratio of the mineral oil and polybutene is outside the above range, these effects are lowered. The content ratio of mineral oil and polybutene is preferably 10: 1 to 2: 1 and more preferably 5: 1 to 3: 1.
The physical properties of the lubricating base oil preferably has a kinematic viscosity of 100~3,000mm ² / s at 40 ° C., more preferably 550~1,500mm ² / s. Further, the pour point is preferably −10 ° C. or lower, and the flash point is preferably 150 ° C. or higher from the viewpoint of safety.
The content of the lubricating base oil is 15 to 60% by mass, preferably 25 to 58% by mass, more preferably 35 to 57% by mass, based on the total amount of the tail seal composition.

The mineral oil used as the lubricating base oil can be a commercially available mineral oil-based lubricating oil or a mineral oil-based lubricating base oil that is a base oil. These are usually obtained by subjecting a distillate obtained by subjecting crude oil to atmospheric distillation, or further distilling the distillation residue under reduced pressure, as a base oil as a base oil, Alternatively, it is prepared by blending various additives and the like. The refining process includes hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc., and these are combined in an appropriate order for treatment, thereby providing a mineral oil-based lubrication suitable for the present invention. An oil base oil can be obtained. A mixture of a plurality of refined oils having different properties obtained by using different crude oils or distillate oils by different process combinations and sequences can also be used as suitable mineral oils.
This mineral oil preferably has an aromatic content of 20% or less from the viewpoint of handling safety.

  Polybutene is a copolymer having a long-chain hydrocarbon molecular structure in which normal butene is partially reacted with isobutene as a main component. Those having a number average molecular weight of 2,000 to 50,000, particularly 5,000 to 20,000 are preferably used. The content of polybutene is preferably 2 to 30% by mass, more preferably 5 to 15% by mass, based on the total amount of the tail seal composition.

  As a lubricating base oil other than mineral oil and polybutene, a synthetic base oil or animal and vegetable oil base oil other than polybutene can be contained. Synthetic base oils include, for example, polymer polymers such as poly-α-olefin (PAO) and low molecular weight ethylene / α-olefin copolymers, silicone oils, fatty acid esters, fluorinated oils, alkylnaphthalene, etc. Or in combination. Animal and vegetable oil-based lubricating base oils include milk fat, beef tallow, lard (pig tallow), sheep fat, whale oil, coconut oil, bonito oil, herring oil, coconut oil, soybean oil, rapeseed oil, sunflower Oil, safflower oil, peanut oil, corn oil, cottonseed oil, rice bran oil, sesame oil, olive oil, linseed oil, castor oil, cocoa butter, palm oil, palm oil, hemp seed oil, rice oil, tea seed oil, etc. it can.

[Inorganic powder]
As the inorganic powder of the present invention, oxides such as silicon, aluminum, magnesium and calcium, hydroxides, carbonates, sulfates and the like can be used, and a mixture thereof and a naturally produced powder can be used. Ore powders containing these compounds as main components can also be used. Specifically, talc, calcium carbonate, magnesium carbonate, calcium sulfate, aluminum hydroxide, magnesium oxide, calcium oxide, aluminum oxide, silica, bentonite, diatomaceous earth, and the like, particularly talc or calcium carbonate powder are suitable. These inorganic powders may be used alone or as a mixture of a plurality of types.
The inorganic powder preferably has an average particle size of 0.5 to 500 μm, more preferably 5 to 50 μm. The content of the inorganic powder is 30 to 70% by mass, preferably 35 to 60% by mass, based on the total amount of the tail seal composition.

Furthermore, it is necessary to adjust the tail seal composition to a suitable consistency, and it is used as a thickener in grease, etc., as a thickening agent for metal soap, urea thickener, organic polymer. It is preferable to use a thickener in combination.
The content of the thickener is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, based on the total amount of the tail seal composition.

  The metal soap thickener is composed of a metal carboxylate, and the carboxylic acid may be an aliphatic carboxylic acid such as stearic acid or azelaic acid, or an aromatic carboxylic acid such as terephthalic acid. Aliphatic carboxylic acids having 6 to 20 carbon atoms are preferred. The metal may be an alkali metal such as lithium or sodium, an alkaline earth metal such as calcium, or an amphoteric metal such as aluminum, but is preferably an alkali metal, particularly lithium. Such carboxylic acid metal salts may be used singly or in combination.

  As the urea-based thickener, a diurea compound obtained by reaction of diisocyanate and monoamine, a polyurea compound obtained by reaction of diisocyanate and monoamine, diamine, and the like are suitable, and as an organic polymer thickener, PTFE (polytetrafluoroethylene) and the like are suitable. In addition, the thickeners such as metal soap, urea, and organic polymer used in combination with the inorganic powder may be used alone or in combination of two or more.

[Fiber]
The fiber is entangled with a brush that bundles metal nets and metal wires in the tail seal part of the shield machine, and is used to form a filter cloth layer having water-stopper together with a lubricant base oil and a thickener. The fiber content is 2 to 10% by mass, preferably 3 to 8% by mass, based on the total amount of the tail seal composition.
This fiber contains short fibers and long fibers in order to improve the water-stopping property and pumpability in a balanced manner. The average length of the short fibers is 0.8 to 2.4 mm, preferably 1.0 to 2.0 mm. The average length of the long fibers is 1.5 to 10 times the average length of the short fibers used, and preferably 1.6 to 7 times. The mass ratio of the long fiber and the short fiber to be contained is 1: 4 to 4: 1, preferably 1: 2 to 2: 1. The average thickness (diameter) of the short fibers is preferably 5 to 100 μm, more preferably 10 to 50 μm. 10-500 micrometers is preferable and, as for the average thickness (diameter) of a long fiber, 15-200 micrometers is more preferable.

These fibers can be either naturally derived natural fibers or organically synthesized synthetic fibers. For example, naturally occurring natural fibers include cellulose, cotton fibers, and wool fibers. , Polypropylene, polyester and the like. Moreover, although inorganic fibers, such as carbon fiber and glass fiber, can be used, asbestos fiber is not preferable in terms of environmental safety.
In addition, it is preferable that the short fiber is a natural fiber and the long fiber is a synthetic fiber or a natural fiber because the water stoppage and the pumpability can be further improved in a balanced manner.

[D] Other Additives In addition to the above components, the tail seal composition of the present invention contains detergents, dispersants, antiwear agents, oxidation agents, etc., which are generally used in lubricating oils and greases as necessary. Inhibitors, rust inhibitors, corrosion inhibitors, and the like can be added as appropriate. In particular, it is preferable to add 0.2 to 2% by mass of a fatty acid polyol ester or the like as a rust inhibitor, based on the total amount of the tail seal composition.

Using the following lubricating base oil, inorganic powder, thickener, and fiber, the tail seal composition was prepared by mixing at the ratio (mass%) shown in Table 1, and the density (g / Cm ³ ) and immiscible penetration. The results are shown in Table 1.
[Components of tail seal composition]
A. Lubricating base oil Base oil A1: Mineral oil (manufactured by JX Nippon Oil & Energy, solvent refined lubricating base oil, density of 0.90 g / cm ^{3 at} 15 ° C., kinematic viscosity at 40 ° C. of 500 mm ² / s)
Base oil A2: polybutene, average molecular weight; 15,000
The kinematic viscosity (mm ² / s) at 40 ° C. of each base oil is shown in Table 1.
B. Inorganic powder, thickener Inorganic powder B1: Talc, average particle size: 20 μm
Inorganic powder B2: calcium carbonate, average particle size: 10 μm
Thickener B3: Li stearic acid soap (reagent manufactured by Kanto Chemical Co., Inc.)

C. Fiber Fiber C1: Cotton fiber, average length: 1.8 mm, average diameter: 18 μm
Fiber C2: Polystyrene terephthalate fiber, average length: 5 mm, average diameter: 20 μm
Fibrous C3: cellulose fiber, average length: 3.0 mm, average diameter: 43 μm

[Evaluation of Tail Seal Composition 1: Water Resistant]
A water pressure resistance test was performed under the following conditions to measure the presence or absence of effluent water.
A stainless steel pressure vessel having an inner diameter of 52 mm and a total of 16 openings (diameter 3 mm) was used at the center of the bottom part in 4 rows vertically and horizontally with a center interval of 5 mm. A stainless steel mesh (No. 50, thickness 0.85 mm) was placed on the opening, and 50 g of the tail seal composition prepared above was introduced. Water (10 g) was placed on the tail seal composition, pressurized with air at a pressure of 35 kgf / cm ² for 5 minutes, and the water stoppage was evaluated by the presence or absence of water outflow from the bottom opening (no outflow of water; no; ○, slight presence; Δ, considerable presence; x). The results are shown in Table 1.
As a result, it can be seen that Comparative Example 3 with a small amount of inorganic powder does not have water blocking properties.

[Evaluation of Tail Seal Composition 2: Pumpability]
The pumpability was evaluated by an apparent viscosity test defined in JISK2220. 300 g or more of the tail seal composition prepared above is packed in a cylinder, extruded through a capillary tube by hydraulic pressure, and the pressure generated in the system at this time is measured. The apparent viscosity was calculated using the Poiseuille equation and evaluated by the apparent viscosity at a shear rate of 1 sec ⁻¹ (apparent viscosity of 10,000 Pa · s or less; ○, 10,000 to 20,000 Pa · s; Δ, 20 1,000 Pa · s or more; x). The lower the value of the apparent viscosity, the smaller the pressure loss and the better the pumpability. The results are shown in Table 1.
As a result, Examples 1 to 7 containing polybutene at a predetermined ratio satisfy both the pumpability and water-stopping property at the same time, but in particular, Examples 1 to 5 containing short fibers and long fibers at a predetermined ratio. This composition is excellent in balance between pumpability and water stoppage.

  The tail seal composition of the present invention can sufficiently prevent water from entering the brush seal portion of the shield machine tail and can be easily pumped to the brush seal portion. It is useful as a tail seal composition.

Claims (5)

  It contains 15 to 60% by mass of a lubricant base oil, 30 to 70% by mass of inorganic powder, and 2 to 10% by mass of fibers including short fibers and long fibers, and the lubricant base oil masses mineral oil and polybutene. A tail seal composition for a shield machine containing a ratio of 20: 1 to 1: 1.   The average length of the short fibers is 0.8 to 2.4 mm, the average length of the long fibers is 1.5 to 10 times the average length of the short fibers contained, and the mass ratio of the long fibers to the short fibers is The tail seal composition for a shield machine according to claim 1, wherein the tail seal composition is 1: 4 to 4: 1. ^{2. The} tail seal composition for a shield machine according to claim 1, wherein the mineral oil has a kinematic viscosity at 40 ° C. of 100 to 3000 mm ² / s and the polybutene has a number average molecular weight of 5,000 to 20,000.   The tail seal composition for a shield machine according to claim 1, wherein the inorganic powder contains at least one of talc and calcium carbonate.   The tail seal composition for a shield machine according to claim 1, wherein the short fibers are natural fibers and the long fibers are synthetic fibers or natural fibers.