Additive for muddying agent and muddying agent

Abstract

To provide a muddying agent capable of immediately imparting plastic fluidity to excavated soil immediately after preparation of the muddying agent and capable of maintaining the plastic fluidity imparted to the excavated soil for a long period of time.SOLUTION: An additive for a muddying agent contains crosslinked polymer particles (A) containing an unsaturated carboxylic acid (a1) and / or a salt thereof (a2) as an essential constituent monomer, and at least one inorganic compound (D) selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides. The muddying agent contains a clay mineral and the additive for a muddying agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an additive used in a muddying agent for improving the quality of soil excavated during excavation of earth and sand ground. [Background technology]

[0002] In shield tunneling, a method for excavating soil such as sandy ground, an additive for excavation called a mud additive is injected into the excavated soil in the chamber of the shield excavator to give the excavated soil plastic fluidity. The excavated soil with plastic fluidity serves to stabilize the face of the shield excavator, and is then transported to the rear of the shield excavator by pumps and conveyors to be treated as construction sludge.

[0003] A method is known in which a muddying agent containing a polyacrylic crosslinked polymer and bentonite is used as a muddying agent for imparting plastic fluidity to excavated soil (Patent Document 1).

[0004] However, the mud-adding agent described in Patent Document 1 has issues such as the tendency for water to separate over time, and because the composition of the treated excavated soil changes over time as water separates from it, the period over which plastic fluidity can be maintained is short, and the shield excavator loses its plastic fluidity while it is stopped, causing defects at the face when it is restarted. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-171101 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a muddying agent that can immediately impart plastic fluidity to excavated soil immediately after preparation, that does not separate water or the like from the muddying agent over time, and that can maintain the plastic fluidity imparted to the excavated soil for a long period of time. [Means for solving the problem]

[0007] The present inventors have conducted research to achieve the above object and have arrived at the present invention.

[0008] That is, the present invention relates to an additive for a muddying agent, which comprises crosslinked polymer particles (A) having an unsaturated carboxylic acid (a1) and / or a salt thereof (a2) as an essential constituent monomer, and at least one inorganic compound (D) selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides; and a muddying agent comprising a clay mineral and the additive for a muddying agent. [Effects of the Invention]

[0009] The muddy agent using the additive for muddy agents of the present invention can immediately impart plastic fluidity to the excavated soil immediately after preparation, and has the effect of preventing separation of water and other substances from the muddy agent over time, thereby maintaining the plastic fluidity imparted to the excavated soil for a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0010] The additive for a muddying agent of the present invention comprises crosslinked polymer particles (A) having an unsaturated carboxylic acid (a1) and / or a salt thereof (a2) as an essential constituent monomer, and at least one inorganic compound (D) selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides.

[0011] The crosslinked polymer particles (A) contained in the additive for a muddying agent of the present invention are particles made of a crosslinked polymer having an unsaturated carboxylic acid (a1) and / or a salt thereof (a2) as an essential constituent monomer.

[0012] Preferable examples of the unsaturated carboxylic acid (a1) include radically polymerizable unsaturated aliphatic monocarboxylic acids having 3 to 9 carbon atoms.

[0013] Examples of the radically polymerizable unsaturated aliphatic monocarboxylic acid having 3 to 9 carbon atoms include (meth)acrylic acid, butanoic acid (including substituted butanoic acids such as 2-methylbutanoic acid and 3-methylbutanoic acid), pentenoic acid (including substituted pentenoic acids such as 2-methylpentenoic acid and 3-methylpentenoic acid), hexenoic acid (including substituted hexenoic acids such as 2-methylhexenoic acid and 3-methylhexenoic acid), heptenoic acid (including substituted heptenoic acids such as 2-methylheptenoic acid and 3-methylheptenoic acid), and octenoic acid (including substituted octenoic acids such as 2-methyloctenoic acid and 3-methyloctenoic acid).

[0014] The unsaturated carboxylic acid salt (a2) is a salt consisting of a conjugate base of the unsaturated carboxylic acid (a1) and a cation, and examples of the cation include alkali metal ions and (N-substituted) ammonium ions. Examples of the alkali metal ions include lithium ions, sodium ions, and potassium ions, and examples of the (N-substituted) ammonium ions include ammonium ions, primary ammonium ions, secondary ammonium ions, tertiary ammonium ions, and quaternary ammonium ions.

[0015] The ammonium ion is an onium ion (NH4 + )

[0016] The primary ammonium ion refers to an onium ion formed by protonating a primary amine in which one of the hydrogen atoms of ammonia is substituted with an alkyl group, and the alkyl group preferably has 1 to 4 carbon atoms, and examples thereof include a methylammonium ion and a butylammonium ion.

[0017] The secondary ammonium ion refers to an onium ion formed by protonating a secondary amine in which two of the hydrogen atoms of ammonia are substituted with alkyl groups, and the alkyl group preferably has 1 to 4 carbon atoms, and examples thereof include a dimethylammonium ion and a dibutylammonium ion.

[0018] The tertiary ammonium ion refers to an onium ion formed by protonating a tertiary amine in which three of the hydrogen atoms of ammonia are substituted with alkyl groups, and the alkyl group preferably has 1 to 4 carbon atoms, and examples thereof include a trimethylammonium ion and a tributylammonium ion.

[0019] The quaternary ammonium ion refers to an onium ion formed by further bonding an alkyl group to a tertiary amine, and the alkyl group preferably has 1 to 4 carbon atoms, and examples thereof include a tetramethylammonium ion and a tetrabutylammonium ion.

[0020] As the unsaturated carboxylic acid (a1) and its salt (a2), which are essential constituent monomers of the crosslinked polymer particles (A), (meth)acrylic acid, sodium (meth)acrylic acid salt, and potassium (meth)acrylic acid salt are preferred, and (meth)acrylic acid and sodium (meth)acrylic acid salt are more preferred.

[0021] The unsaturated carboxylic acid (a1) and its salt (a2) may be used singly or in combination of two or more, and preferably contain the unsaturated carboxylic acid (a1) and its salt (a2) as essential constituent monomers. From the viewpoint of the plastic fluidity of the soil excavation product, the ratio of the number of moles of the unsaturated carboxylic acid salt (a2) to the total number of moles of the unsaturated carboxylic acid (a1) and its salt (a2) is preferably 50 to 90 mol %, more preferably 60 to 80 mol %.

[0022] The crosslinked polymer particles (A) may contain, as a constituent monomer, another vinyl monomer (b) copolymerizable with the unsaturated carboxylic acid and its salt.

[0023] As the vinyl monomer (b), known hydrophobic vinyl monomers (for example, the hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553, the vinyl monomers disclosed in paragraph 0025 of Japanese Patent Laid-Open No. 2003-165883 and paragraph 0058 of Japanese Patent Laid-Open No. 2005-75982, etc.) can be used, and the following vinyl monomers (i) to (iii) can be used: (i) Examples of aromatic ethylenic monomers having 8 to 30 carbon atoms include styrene, styrene derivatives (α-methylstyrene, vinyltoluene, hydroxystyrene, etc.), vinylnaphthalene, and halogen-substituted styrene (for example, chlorostyrene, etc.). (ii) Examples of aliphatic ethylenic monomers having 2 to 20 carbon atoms include alkenes (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, and octadecene); and alkadienes (butadiene and isoprene). (iii) Examples of alicyclic ethylenic monomers having 5 to 15 carbon atoms include monoethylenically unsaturated monomers (pinene, limonene, indene, etc.); and polyethylenic vinyl monomers (cyclopentadiene, bicyclopentadiene, ethylidenenorbornene, etc.).

[0024] In the crosslinked polymer particles (A), the ratio of the number of moles of the vinyl monomer (b) to the total number of moles of the unsaturated carboxylic acid (a1), the unsaturated carboxylate (a2), and the vinyl monomer (b) is preferably 0 to 5 mol%, more preferably 0 to 3 mol%, even more preferably 0 to 1.5 mol%, and even more preferably 0 mol%, from the viewpoint of the strength of the mud after treatment.

[0025] The crosslinked polymer particles (A) preferably contain an internal crosslinking agent (c) as a constituent monomer. The internal crosslinking agent (c) is a polyfunctional compound that reacts with an unsaturated carboxylic acid (a1) and its salt (a2) and an optional vinyl monomer (b) to form a crosslinked polymer.

[0026] As the internal crosslinking agent (c), known crosslinking agents can be used (for example, crosslinking agents having two or more ethylenically unsaturated groups disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553, crosslinking agents having at least one functional group reactive with a water-soluble substituent and at least one ethylenically unsaturated group, and crosslinking agents having at least two functional groups reactive with a water-soluble substituent, crosslinking agents having two or more ethylenically unsaturated groups disclosed in paragraphs 0028 to 0031 of Japanese Patent Laid-Open No. 2003-165883, crosslinking agents having an ethylenically unsaturated group and a reactive functional group, and crosslinking agents having two or more reactive substituents, crosslinkable vinyl monomers disclosed in paragraph 0059 of Japanese Patent Laid-Open No. 2005-75982, and crosslinkable vinyl monomers disclosed in paragraphs 0015 to 0016 of Japanese Patent Laid-Open No. 2005-95759).

[0027] As the internal crosslinking agent (c), a crosslinking agent having two or more ethylenically unsaturated groups is preferred, and from the viewpoint of reactivity with the monomer and water absorption properties, poly(meth)allyl ethers of polyhydric alcohols such as alkylene glycol, trimethylolpropane, glycerin, pentaerythritol and sorbitol, polyhydric (meth)allyl compounds such as tetraallyloxyethane and triallyl isocyanurate, and methylenebisacrylamide are preferred.

[0028] The internal crosslinking agent (c) may be used alone or in combination of two or more kinds.

[0029] The crosslinked polymer particles (A) containing an unsaturated carboxylic acid (a1) and / or a salt thereof (a2) as an essential constituent monomer can be obtained by polymerizing a monomer composition containing the unsaturated carboxylic acid (a1) and / or the unsaturated carboxylic acid salt (a2), and optionally a vinyl monomer (b) and an internal crosslinking agent (c) by a known method such as aqueous solution polymerization, bulk polymerization, reversed-phase suspension polymerization, or emulsion polymerization.

[0030] Of these polymerization methods, aqueous solution polymerization and reversed-phase suspension polymerization are preferred from the viewpoint of the strength of the mud after treatment.

[0031] In these polymerizations, known polymerization initiators, chain transfer agents and / or solvents can be used.

[0032] The polymerization method by aqueous solution polymerization, reverse phase suspension polymerization, and emulsion polymerization may be a known method, for example, a method of polymerization using a radical polymerization initiator, or a method of irradiating with active energy rays such as radiation, ultraviolet rays, or electron beams, and among these, a method of polymerization using a radical polymerization initiator is preferred.

[0033] Examples of radical polymerization initiators used in polymerization include azo compounds (azobisisovaleronitrile, azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis (2-methyl-N-(2-hydroxyethyl)propionamide, 2,2'-azobis(2-amidinopropane) hydrochloride, etc.), inorganic peroxides (hydrogen peroxide, potassium persulfate, ammonium persulfate, sodium persulfate, etc.), organic peroxides (di-t-butyl peroxide, cumene hydroperoxide, etc.), and redox initiators (combinations of reducing agents such as alkali metal sulfites or bisulfites, ammonium sulfite, ammonium bisulfite, and L-ascorbic acid with peroxides such as alkali metal persulfates, ammonium persulfate, and aqueous hydrogen peroxide). These may be used alone or in combination.

[0034] The polymerization temperature varies depending on the type of initiator used, but is preferably from -10°C to 100°C, more preferably from -10°C to 80°C, from the viewpoint of increasing the degree of polymerization of the polymer.

[0035] The amount of the initiator is preferably 0.000001 to 3.0% by weight, and more preferably 0.000001 to 0.5% by weight, based on the total weight of the monomer composition, from the viewpoint of increasing the degree of polymerization of the polymer.

[0036] Aqueous solution polymerization is a polymerization method in which an aqueous solution of a monomer composition is polymerized. The concentration of the monomer composition in the aqueous solution used for aqueous solution polymerization (polymerization concentration) is preferably 10 to 40% by weight, more preferably 10 to 30% by weight, from the viewpoint of the degree of polymerization of the crosslinked polymer.

[0037] When a crosslinked polymer containing an unsaturated carboxylate (a2) as an essential constituent monomer is obtained by aqueous solution polymerization, it is preferable, from the viewpoint of the degree of polymerization of the crosslinked polymer, to obtain a crosslinked polymer containing an unsaturated carboxylate (a2) as an essential constituent monomer by neutralizing a reaction product obtained by polymerization using a monomer composition containing an unsaturated carboxylic acid (a1) with an alkali metal hydroxide or the like.

[0038] Inverse phase suspension polymerization is a polymerization method in which an aqueous solution of a monomer composition is suspended and dispersed in a hydrophobic organic solvent, such as hexane, toluene, or xylene, in the presence of a dispersant, and polymerized. The total weight concentration of the monomer composition in the aqueous solution is preferably 10 to 40% by weight, more preferably 10 to 30% by weight. Within this range, a crosslinked polymer with a high degree of polymerization can be produced.

[0039] Dispersants used in reverse suspension polymerization include surfactants having an HLB (Hydrophile-Lipophile Balance) value of 3 to 8 {sorbitan fatty acid esters (sorbitan monostearate, etc.), glycerin fatty acid esters (glycerin monostearate, etc.), and sucrose fatty acid esters (sucrose distearate, etc.)}, and polymeric dispersants (hydrophilic group content of 0.1 to 20 wt %, weight average molecular weight of 1,000 to 1,000,000) that have hydrophilic groups in the molecule (for example, hydroxyl groups, carboxyl groups, sulfonic acid groups, etc.) and are soluble in the solvent used to disperse the aqueous monomer solution {maleic acid products of ethylene / acrylic acid copolymers, maleic acid products of ethylene / vinyl acetate copolymers, styrenesulfonic acid (salt) / styrene copolymers, etc.}.

[0040] Among these, from the viewpoint of adjusting the particle size of the crosslinked polymer, a polymer dispersant that is soluble in the solvent used to disperse the aqueous monomer solution is preferred.

[0041] The HLB used in the present invention is calculated by the following formula, which is described on page 142 of Takehiko Fujimoto's Introduction to Surfactants (published by Sanyo Chemical Industries, Ltd.).

[0042] HLB = 20 x {molecular weight of hydrophilic group / molecular weight of surfactant} From the viewpoint of solidification properties in the treatment of surplus soil, the amount of dispersant used is preferably 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, based on the weight of the hydrophobic organic solvent.

[0043] In the reversed-phase suspension polymerization, the weight ratio (W / O ratio) of the aqueous solution of the monomer composition to the hydrophobic organic solvent is preferably 0.1 / 1.0 to 2.0 / 1.0, more preferably 0.3 / 1.0 to 1.0 / 1.0. Within these ranges, the crosslinked polymer can be easily adjusted to a particulate crosslinked polymer having a preferred particle size described below.

[0044] The crosslinked polymer obtained by the aqueous solution polymerization or reversed phase suspension polymerization is obtained as a gel containing water (hydrogel).

[0045] The dried product obtained by drying the hydrogel is optionally pulverized and classified to obtain crosslinked polymer particles.

[0046] The drying process of the hydrogel in the case of aqueous solution polymerization includes a step of shredding the hydrogel with a meat chopper or a cutter-type coarse crusher (for example, by dividing the gel into pieces of 0.5 to 20 mm square) or by cutting the gel into strips of 0.5 to 20 mm width, and neutralizing the hydrogel by adding an aqueous alkali metal hydroxide solution or the like as necessary, and a drying step by static aeration drying (e.g., drying by passing hot air at 50 to 150°C through a material layer prepared by stacking hydrogels that have been divided, etc. on a punched metal or a screen), fluidized aeration drying (e.g., passing and / or circulating hot air through a container containing the divided hydrogel, and drying the gel while further dividing it, etc., with a machine such as a rotary kiln), and / or contact drying (drying the hydrogel by compressing and stretching it on a drum dryer).

[0047] The drying step of the hydrogel in the case of reversed-phase suspension polymerization includes a step of performing solid-liquid separation of the polymerized hydrogel and the organic solvent by a method such as decantation, and a step of performing drying under reduced pressure (preferably a reduced pressure of 100 to 50,000 Pa) or drying by ventilation.

[0048] In the drying step, it is preferable to add a surface cross-linking agent. By adding a surface cross-linking agent, cross-linked polymer particles having a cross-linked structure on the particle surface can be obtained, which is preferable because it improves the plastic flow properties of the excavated soil.

[0049] As the surface crosslinking agent, known organic surface crosslinking agents can be used (such as polyvalent glycidyl compounds, polyvalent amines, polyvalent aziridine compounds, and polyvalent isocyanate compounds described in JP-A-59-189103, polyhydric alcohols described in JP-A-58-180233 and JP-A-61-16903, silane coupling agents described in JP-A-61-211305 and JP-A-61-252212, alkylene carbonates described in JP-A-5-508425, and polyvalent oxazoline compounds described in JP-A-11-240959).

[0050] Among these surface cross-linking agents, polyhydric glycidyl compounds, polyhydric alcohols and polyhydric amines are preferred, polyhydric glycidyl compounds and polyhydric alcohols are more preferred, polyhydric glycidyl compounds are particularly preferred, and ethylene glycol diglycidyl ether is most preferred. The surface cross-linking agents may be used alone or in combination of two or more.

[0051] The amount (wt%) of the surface cross-linking agent used can be adjusted depending on the type, cross-linking conditions, target performance, etc., and from the viewpoint of the plastic fluidity of the soil excavation material, it is preferably 0.001 to 3 wt%, more preferably 0.005 to 2 wt%, and even more preferably 0.01 to 1.5 wt%, based on the total weight of the cross-linked polymer particles.

[0052] The dried crosslinked polymer obtained by drying the hydrogel can be pulverized to form crosslinked polymer particles, if necessary. The pulverization method may be a known method, such as an impact pulverizer (e.g., a pin mill, a cutter mill, a skillel mill, or an ACM pulverizer) or an air pulverizer (e.g., a jet pulverizer).

[0053] The crosslinked polymer particles obtained by pulverization, if necessary, can be adjusted to a desired particle size using a sieving machine (such as a vibrating sieving machine or a centrifugal sieving machine) equipped with a screen, if necessary.

[0054] The volume average particle diameter of the crosslinked polymer particles (A) contained in the additive for a muddying agent of the present invention is preferably 100 to 800 μm, more preferably 200 to 700 μm, and particularly preferably 300 to 500 μm. When the volume average particle diameter is within this range, the crosslinked polymer particles and the muddying agent can be easily handled in the soil treatment process, and the soil treatment process can be simplified.

[0055] The volume average particle size of the crosslinked polymer particles (A) is measured in accordance with dynamic image analysis (JIS Z8827-2 Particle size analysis - Image analysis method Part 2) using, for example, a laser diffraction particle size distribution analyzer [Microtrac (manufactured by Nikkiso Co., Ltd.)].

[0056] The crosslinked polymer particles (A) contained in the additive for a muddying agent of the present invention can also be commercially available water-absorbent resin particles such as the Aquacube series (manufactured by Sumitomo Seika Chemicals Co., Ltd.), the Sunwet series (manufactured by Sanyo Chemical Industries, Ltd.), the Sunfresh series (manufactured by Sanyo Chemical Industries, Ltd.), and the Aqualic series (manufactured by Nippon Shokubai Co., Ltd.).

[0057] In the present invention, the crosslinked polymer particles (A) preferably have two or more peaks in the particle size distribution measured in accordance with dynamic image analysis (JIS Z8827-2 Particle size analysis - Image analysis method, Part 2). Having two or more peaks facilitates achieving both a high absorption rate immediately after preparation of the muddying agent and long-term plastic fluidity (thickening effect) of the muddying agent, which is preferable.

[0058] As a method for making the crosslinked polymer particles (A) have two or more peaks, a method of mixing a plurality of types of crosslinked polymer particles (A) having different average particle sizes can be mentioned.

[0059] From the viewpoint of the plastic fluidity of the excavated soil, it is more preferable that the particle size distribution measured in accordance with the dynamic image analysis method has peaks at 10 to 100 μm and 300 to 500 μm.

[0060] An example of a method for producing a particle having peaks at 10 to 100 μm and 300 to 500 μm is to mix crosslinked polymer particles (A1) having a volume average particle diameter of 10 to 100 μm with crosslinked polymer particles (A2) having a volume average particle diameter of 300 to 500 μm.

[0061] From the viewpoint of the plastic flow properties of the soil excavation material, the crosslinked polymer particles (A) contained in the additive for muddying agents of the present invention preferably contain crosslinked polymer particles (A1) having a volume average particle diameter of 10 to 100 μm and crosslinked polymer particles (A2) having a volume average particle diameter of 300 to 500 μm.

[0062] From the viewpoint of the plastic flow properties of the soil excavation material, the crosslinked polymer particles (A) contained in the additive for muddy soil of the present invention preferably have a weight ratio {(A1) / (A2)} of 0.2 to 2.0 between the crosslinked polymer particles (A1) having a volume average particle diameter of 10 to 100 μm and the crosslinked polymer particles (A2) having a volume average particle diameter of 300 to 500 μm.

[0063] The additive for a muddy agent of the present invention contains at least one inorganic compound (D) selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides. While the crosslinked polymer particles (A) alone would result in a decrease in plastic fluidity due to polymer decomposition, etc., it is presumed that the inclusion of inorganic compound (D) acts on the clay minerals in the muddy agent and / or soil excavation material to fix the clay minerals over time, thereby enabling plastic fluidity to be maintained for a long period of time.

[0064] Examples of the alkali metal oxide contained in the muddying agent additive of the present invention include lithium oxide, sodium oxide, and potassium oxide.

[0065] Examples of the alkali metal hydroxide contained in the muddying agent additive of the present invention include lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0066] Examples of the alkaline earth metal oxide contained in the additive for a muddying agent of the present invention include magnesium oxide, calcium oxide, and barium oxide.

[0067] Examples of the alkaline earth metal hydroxide contained in the additive for a muddying agent of the present invention include magnesium hydroxide, calcium hydroxide, and barium hydroxide.

[0068] From the viewpoint of imparting plastic fluidity to excavated soil, the muddying agent additive of the present invention preferably contains magnesium oxide and / or magnesium hydroxide as at least one inorganic compound (D) selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides.

[0069] The muddying agent additive of the present invention preferably further contains an aqueous organic solvent. The inclusion of an aqueous organic solvent improves the handleability of the muddying agent additive. The aqueous organic solvent refers to an organic solvent that becomes a uniform, transparent liquid when 1 ml of the organic solvent and 1 ml of water are shaken at 20°C for 30 minutes, and preferred examples include methanol, ethylene glycol, and polyethers having polyoxyethylene chains that are liquid at 20°C.

[0070] Among these, from the viewpoint of ease of handling of the muddying agent, polyethers that are liquid at 20° C. are preferred, and polyethylene glycols (PEG200, PEG400, etc.) are particularly preferred.

[0071] The weight ratio of the crosslinked polymer particles (A) to the total weight of the muddy agent additive of the present invention is preferably 10 to 50% by weight, more preferably 15 to 45% by weight, from the viewpoints of the handleability of the muddy agent additive and the plastic fluidity of the soil excavation material.

[0072] The ratio of the total weight of the inorganic compound (D) to the total weight of the muddying additive of the present invention is preferably 1 to 20% by weight, more preferably 5 to 15% by weight, from the viewpoint of the plastic fluidity imparted to the excavated soil.

[0073] In the additive for muddying agents of the present invention, the weight ratio of the total weight of the inorganic compound (D) to the weight of the crosslinked polymer particles (A) is preferably 10 to 40% by weight, more preferably 15 to 35% by weight, from the viewpoint of the plastic fluidity imparted to the excavated soil.

[0074] When the muddy agent additive of the present invention contains an aqueous organic solvent, from the viewpoint of the handleability of the muddy agent additive, the weight ratio of the aqueous organic solvent to the total weight of the muddy agent additive is preferably 30 to 89 wt %, more preferably 45 to 75 wt %.

[0075] The muddy additive of the present invention preferably has an absorption rate (seconds) for ion-exchanged water of 60 or less, more preferably 45 or less. This range is preferable because the muddy additive absorbs water in a short time and can immediately impart plastic fluidity to excavated soil immediately after preparation of the muddy additive.

[0076] The absorption rate for ion-exchanged water can be measured in accordance with JIS K7224-1996. Specifically, the time (unit: seconds) required for 1.0 g of the muddying agent additive to completely absorb 50.0 g of ion-exchanged water stirred at 600 revolutions per minute in a 100 ml tall beaker with a flat bottom as specified in JIS R 3503 is measured.

[0077] The absorption rate for ion-exchanged water can be adjusted, for example, by the amount of crosslinked polymer particles (A) added in the muddying agent additive, the volume average particle diameter of the crosslinked polymer particles (A) (for example, the smaller the volume average particle diameter, the faster the absorption rate), and the apparent density of the crosslinked polymer particles (A).

[0078] The viscosity (mPa·s) of the muddying agent additive of the present invention, when prepared as a water-containing solution containing 2% by weight of the muddying agent additive in ion-exchanged water (24 hours after preparation), is preferably 10 or more, more preferably 25 or more. This range is preferable because the thickening effect is maintained for a long period of time.

[0079] The viscosity of a water-containing liquid (24 hours after preparation) containing 2% by weight of a muddying agent additive in ion-exchanged water can be measured in accordance with JIS K7117-1: 1999. Specifically, 2.0 g of the muddying agent additive and 98.0 g of ion-exchanged water are stirred and mixed until homogeneous, and then left to stand at 25°C for 24 hours. This mixture is used as a measurement sample, and the viscosity is measured using a digital B-type viscometer (manufactured by Tokimec Corporation) at a measurement temperature of 25°C, a rotor No. 4, and a rotation speed of 6 rpm.

[0080] The viscosity can be adjusted, for example, by the amount of crosslinked polymer particles (A) added in the muddying agent additive, the volume average particle diameter of the crosslinked polymer particles (A) (for example, the larger the volume average particle diameter, the larger the viscosity), and the crosslink density of the crosslinked polymer particles (A).

[0081] The additive for a muddying agent of the present invention can be obtained by mixing the crosslinked polymer particles (A), the inorganic compound (D), and an aqueous organic solvent, which is used as needed, by a known method using a known mixing device.

[0082] When the additive for a muddying agent of the present invention contains an aqueous organic solvent, it is preferable to add the crosslinked polymer particles (A) and the inorganic compound (D) to the aqueous organic solvent and mix them while stirring the aqueous organic solvent in a known stirring and mixing device (such as a container equipped with a stirrer with paddle-type stirring blades).

[0083] The additive for a muddying agent of the present invention is used by adding it to a muddying agent containing clay minerals and the like.

[0084] The muddying agent of the present invention comprises the additive for muddying agents and a clay mineral.

[0085] Examples of clay minerals include single minerals such as sepiolite, attapulgite, ettrinite, kaolin clay, montmorillonite, hectorite, saponite, and beidellite, as well as natural minerals (such as bentonite) containing at least one of these single minerals as the main component. From the viewpoint of the thickening properties of the muddying agent, bentonite (a clay mineral containing montmorillonite as the main component) is preferred. These clay minerals may be used alone or in combination of two or more.

[0086] The weight of the clay mineral contained in the muddying agent of the present invention is preferably 10 to 30 times, more preferably 15 to 25 times, the total weight of the crosslinked polymer particles (A) and the inorganic compound (D).

[0087] The muddying agent of the present invention preferably further contains water from the viewpoint of ease of handling of the muddying agent, etc. When the muddying agent of the present invention contains water, the weight of the water contained is preferably 3 to 75 times, and more preferably 5 to 30 times, the total weight of the clay minerals.

[0088] The muddying agent of the present invention can be obtained by mixing the muddying agent additive, clay mineral, and optionally water using a known mixing device and a known method. When water is used, it is preferable to mix the aqueous dispersion obtained by mixing the clay mineral and water with the muddying agent additive.

[0089] The muddying agent of the present invention can also be obtained by supplying an aqueous dispersion obtained by mixing clay mineral with water and the muddying agent additive described above into an excavating machine and mixing them inside the excavating machine.

[0090] When mixing is performed inside the excavator, a known static mixer such as a static mixer or an in-line mixer can be used. Alternatively, the aqueous dispersion obtained by mixing clay mineral and water and the mud additive may be mixed on the excavation face (also called a cutter) and / or in a chamber (also called a mud chamber) at the front of the excavator.

[0091] When a muddy agent is obtained by mixing the aqueous dispersion obtained by mixing clay minerals with water and the above-mentioned muddy agent additive on the excavation face and / or chamber in front of the excavator, it is possible to obtain the muddy agent and mix it with the excavated soil at the same time.

[0092] The additive for a muddy agent of the present invention can be preferably used in a shield tunneling method or a jacking method which includes a step of mixing the additive for a muddy agent with excavated soil.

[0093] When the muddy agent additive of the present invention is used in a shield tunneling or jacking method, it is preferable to further mix a clay mineral with the muddy agent additive in the step of mixing the muddy agent additive with the excavated soil to form a muddy agent. The clay mineral to be mixed can be the same clay mineral as the clay mineral that can be contained in the muddy agent, and the preferred clay minerals are also the same.

[0094] As an excavator using the additive for a muddy agent and the muddy agent of the present invention, a known excavator used in a shield tunneling method or a jacking method can be used.

[0095] In the shield tunneling or jacking tunneling method using the muddying agent additive and muddying agent of the present invention, the muddying agent additive is sent to the front of the excavator via a specified supply route, mixed with the excavated soil of the shield machine at the excavation face and / or chamber, and then transported to the rear of the excavator using a screw conveyor or the like.

[0096] In the process of mixing the mud additive with the excavated soil, if clay minerals are further mixed to form a mud additive, the mud additive and clay minerals are sent to the excavation surface and / or chamber using separate supply devices and mixed with the excavated soil.

[0097] The clay mineral sent to the excavation surface and / or chamber by a supply device separate from the mud additive additive is preferably in the form of an aqueous dispersion, and the concentration of the clay mineral in the aqueous dispersion is preferably 1 to 25% by weight, more preferably 3 to 17% by weight, from the viewpoint of the handleability of the aqueous dispersion.

[0098] In addition to the step of mixing the muddy agent additive and excavated soil, the shield tunneling or jacking tunneling method using the muddy agent additive of the present invention preferably further includes the steps of excavating the excavation face at the excavation face, sending the excavated soil to a chamber behind the excavation face, sending the excavated soil in the chamber to the rear of the excavation machine using a screw conveyor or the like, and propelling the excavation machine using a propulsion mechanism such as a shield jack.

[0099] The shield tunneling or jacking method using the muddy agent additive and muddy agent of the present invention uses a muddy agent that can maintain the plastic fluidity imparted to the excavated soil for a long period of time, and therefore can prevent defects from occurring at the face when a stopped shield excavator is restarted, and prevent excavated soil transported behind the shield excavator from flowing and contaminating the surrounding area.

[0100] The present specification discloses the following:

[0101] The present disclosure (1) is an additive for a muddying agent, which comprises crosslinked polymer particles (A) having an unsaturated carboxylic acid (a1) and / or a salt thereof (a2) as an essential constituent monomer, and at least one inorganic compound (D) selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides.

[0102] The present disclosure (2) is an additive for a muddying agent according to the present disclosure (1), wherein the crosslinked polymer particles (A) have two or more peaks in a particle size distribution measured in accordance with a dynamic image analysis method.

[0103] The present disclosure (3) is an additive for a muddying agent according to the present disclosure (1) or (2), in which two types of crosslinked polymer particles (A) are used in combination: crosslinked polymer particles (A1) having a volume average particle diameter of 10 to 100 μm and crosslinked polymer particles (A2) having a volume average particle diameter of 300 to 500 μm.

[0104] The present disclosure (4) is the additive for a muddying agent according to any one of the present disclosures (1) to (3), which has an absorption rate (seconds) for ion-exchanged water of 45 or less.

[0105] The present disclosure (5) is a muddying agent additive according to any one of the present disclosures (1) to (4), in which the viscosity (mPa·s) of an aqueous solution (24 hours after preparation) containing 2% by weight of the muddying agent additive in ion-exchanged water is 25 or more.

[0106] The present disclosure (6) is the additive for a muddying agent according to any one of the present disclosures (1) to (5), wherein the inorganic compound (D) is magnesium oxide and / or magnesium hydroxide.

[0107] The present disclosure (7) is a muddying agent containing a clay mineral and the additive for a muddying agent according to any one of the present disclosures (1) to (6).

[0108] The present disclosure (8) is the muddying agent according to the present disclosure (7), in which the clay mineral is bentonite. [Example]

[0109] The present invention will be further explained below with reference to examples, but the present invention is not limited to these examples. <Examples 1 to 11> PEG-200 (19.5 g), an aqueous organic solvent, was placed in a 100 ml glass beaker, and while the contents of the beaker were being stirred using a turbine blade type high-speed stirrer, crosslinked polymer particles (A) shown in Table 1 were gradually added to the beaker using a powder funnel. Furthermore, while continuing to stir, inorganic compound (D) shown in Table 1 was gradually added to the beaker using a powder funnel to prepare the muddying agent additives (1 to 11) of the present invention.

[0110] The obtained additives for muddy agents were added to muddy agents by the following method to prepare muddy agents, and the stability of the prepared muddy agents was evaluated. The results are shown in Table 1.

[0111] <Comparative Example 1> PEG-200 (19.5 g), an aqueous organic solvent, was placed in a 100 ml glass beaker, and while stirring the contents of the beaker with a turbine blade-type high-speed stirrer, the crosslinked polymer particles (A) shown in Table 1 were gradually added to the beaker with a powder funnel to prepare a comparative muddying agent additive (H1). Furthermore, a comparative muddying agent was prepared by adding a comparative muddying agent additive according to the method described below, and the stability of the prepared muddying agent was evaluated. The results are shown in Table 1.

[0112] <Measurement of particle size distribution by dynamic image analysis> The particle size distribution of the crosslinked polymer particles (A) was measured by dispersing the crosslinked polymer particles (A) in methanol and measuring the particle size distribution using a laser diffraction particle size distribution analyzer [Microtrac (manufactured by Nikkiso Co., Ltd.)] in accordance with dynamic image analysis (JIS Z8827-2 Particle size analysis - Image analysis method Part 2). The results are shown in Table 1.

[0113] <Measurement of absorption rate for ion-exchanged water> The absorption rate for ion-exchanged water was measured in accordance with JIS K7224-1996. 1.0 g of muddying additive was added to 50.0 g of ion-exchanged water stirred at 600 rpm in a 100 ml tall beaker with a flat bottom (as specified in JIS R 3503), and the time (unit: seconds) required for the ion-exchanged water to be completely absorbed was measured. An absorption rate of 60 or less is preferable because it allows for the soil excavation to quickly acquire plastic fluidity.

[0114] <Viscosity of a water-containing solution (24 hours after preparation) containing 2% by weight of a muddying agent additive in ion-exchanged water> The viscosity of an aqueous solution (24 hours after preparation) containing 2% by weight of a muddying agent additive in ion-exchanged water was measured in accordance with JIS K7117-1:1999. 2.0 g of the muddying agent additive and 98.0 g of ion-exchanged water were mixed and stirred until homogeneous, and then left to stand at 25°C for 24 hours. This mixture was used as the measurement sample, and the viscosity was measured using a digital B-type viscometer (manufactured by Tokimec) at 25°C, with a No. 4 rotor, and at 6 rpm. A viscosity of 10 mPa·s or higher is preferable, as it provides adequate plastic flowability to the excavated soil.

[0115] <Method for testing the stability of muddy agents containing additives for muddy agents> A bentonite suspension was prepared by stirring 120.9 g of ion-exchanged water and 9.1 g of bentonite (Kanto Chemical Co., Ltd., Grade 1 Reagent) for 60 minutes using a turbine blade type high-speed stirrer, and then allowed to stand at room temperature (20±3°C) for 24 hours.

[0116] 1.04 g of the muddying agent additives (1 to 11) obtained in Examples 1 to 11 or the comparative muddying agent additive (H1) was weighed and added to 130 g of bentonite suspension that had been left to stand. The mixture was stirred for 5 minutes using a turbine blade type high-speed mixer to prepare a muddying agent, which was then placed in a bag made of 255 mesh (opening: 57 μm) nylon netting.

[0117] The nylon mesh bag containing the mud-adding agent was placed in a zippered polyethylene bag larger than the nylon mesh bag and sealed.The top of the nylon mesh bag and the top of the polyethylene bag were clamped and secured with a clip with a string so that the bottom of the nylon mesh bag did not come into contact with the bottom of the polyethylene bag, and the bag was hung using the string attached to the clip and left to stand in a room at 20°C.

[0118] The weight (g) of water that had accumulated at the bottom of the polyethylene bag was measured 48 hours and 168 hours after the start of standing, and this was recorded as "stability after 48 hours" or "stability after 168 hours." The results are shown in Table 1.

[0119] The less water that accumulates at the bottom of the polyethylene bag, the less likely it is that water will separate from the muddying agent over time, and the less likely the composition of the soil excavated material to change when the muddying agent is added, meaning that the plastic fluidity imparted to the soil excavated material by adding the muddying agent can be maintained for a long period of time.

[0120] [Table 1]

[0121] In Examples 1 to 11 and Comparative Example 1, the following raw materials were used. <Crosslinked polymer particles (A)> Cross-linked polymer particles (A1): Product name: Sunfresh IM-1000MPS (acrylic acid polymer partially sodium salt cross-linked particles manufactured by Sanyo Chemical Industries, Ltd., volume average particle diameter 30 μm) Cross-linked polymer particles (A2): Product name: Sunfresh OK-100 (acrylic acid polymer partially sodium salt cross-linked particles manufactured by Sanyo Chemical Industries, Ltd., volume average particle diameter 400 μm) <Inorganic compounds (D)> Magnesium oxide: Grade 1 reagent manufactured by Kanto Chemical Co., Ltd. Calcium oxide: Grade 1 reagent manufactured by Kanto Chemical Co., Ltd. Magnesium hydroxide: Grade 1 reagent manufactured by Kanto Chemical Co., Ltd. Calcium hydroxide: Grade 1 reagent manufactured by Kanto Chemical Co., Ltd. Sodium hydroxide solution (48% by weight): Special grade reagent manufactured by Kanto Chemical Co., Ltd. Potassium hydroxide aqueous solution (40% by weight): Special grade reagent manufactured by Kanto Chemical Co., Ltd. <Water-based organic solvent> PEG-200: Polyethylene glycol 200 manufactured by Sanyo Chemical Industries, Ltd.

[0122] The muddy additives of Examples 1 to 11 have a high absorption rate of ion-exchanged water, and the viscosity of the aqueous solution containing 2% by weight of the muddy additive in ion-exchanged water is high, which shows that the muddy additive can impart plastic fluidity to excavated soil immediately after preparation. Furthermore, water separation from the muddy additives is unlikely to occur, making the muddy additives highly stable. Furthermore, because the muddy additives are highly stable, the composition of the excavated soil to which they are added is unlikely to change, and it is clear that the plastic fluidity imparted to the excavated soil can be maintained for a long period of time by adding the muddy additive. [Industrial Applicability]

[0123] The muddy agent using the additive for muddy agents of the present invention can instantly impart stable plastic fluidity to soil, and therefore can be used not only in excavation work using methods such as shield tunneling, which involves the removal of excavated soil, but also in land improvement and land development.

Claims

1. The additive for a muddying agent comprises crosslinked polymer particles (A) having an unsaturated carboxylic acid (a1) and / or a salt thereof (a2) as an essential constituent monomer, and at least one inorganic compound (D) selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides.

2. 2. The additive for a muddying agent according to claim 1, wherein the crosslinked polymer particles (A) have two or more peaks in a particle size distribution measured in accordance with dynamic image analysis.

3. The additive for a muddying agent according to claim 1, wherein the crosslinked polymer particles (A) are a combination of two types of crosslinked polymer particles (A1) having a volume average particle diameter of 10 to 100 μm and crosslinked polymer particles (A2) having a volume average particle diameter of 300 to 500 μm.

4. 2. The additive for a muddying agent according to claim 1, which has an absorption rate (seconds) for ion-exchanged water of 45 or less.

5. 2. The additive for a muddying agent according to claim 1, wherein the viscosity (mPa·s) of a water-containing solution (24 hours after preparation) containing 2% by weight of the additive for a muddying agent in ion-exchanged water is 25 or more.

6. 2. The additive for a muddying agent according to claim 1, wherein the inorganic compound (D) is magnesium oxide and / or magnesium hydroxide.

7. A muddying agent comprising a clay mineral and the additive for muddying agents according to any one of claims 1 to 6.

8. 8. The muddying agent according to claim 7, wherein the clay mineral is bentonite.

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