JPH0753815B2 - Bentonite modifier - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

TECHNICAL FIELD The present invention relates to a modifier for stabilizing liquid bentonite used when excavating a formation and an excavation method using the modified bentonite.

[Prior art]

Bentonite suspension containing water-soluble polymer compound such as sodium carboxymethyl cellulose (hereinafter referred to as CMC), so-called bentonite stabilizing solution, is filled in the excavated part to excavate the ground while preventing the wall from collapsing, and then concrete is poured. The stable liquid excavation method that is used to construct underground continuous walls and foundation shafts is currently used on the other side. Since bentonite is sensitive to inorganic electrolytes, bentonite stabilizer tends to agglomerate or gel due to the mixture of sodium chloride accompanying the excavation of ground containing seawater and the mixture of cement during concrete pouring. . The bentonite stabilizing solution deteriorated in this way is inferior in forming a stable film (mud case) on the drilling hole wall as a stabilizing solution on the drilling hole wall, and the wall collapse preventing ability decreases, so that it cannot be used as it is. It must be discarded or recycled. Therefore, if a modified bentonite prepared by blending bentonite with a dispersant is used in advance, it is possible to suppress deterioration due to cement or salt mixing. Inorganic polyphosphates and sodium carbonate are known as dispersants for modifying bentonite, and nitrohumates, lignin sulfonates, low polymerization degree polyacrylates, etc. are known as organic dispersants. The degree of polyacrylate is highly effective as a modifier. However, since this bentonite modifier is powder-mixed, it must be a powder product. The low-polymerization degree polyacrylic acid salt can be produced by a method in which it is dried by heating, reduced pressure, etc., and then crushed or spray-dried. It is difficult to use because it absorbs moisture, becomes sticky, and caking easily occurs during storage, storage management is difficult, and modified bentonite with a low polymerization degree polyacrylic acid salt causes caking during storage. Can not. As a countermeasure against this, a copolymer [salt type] of methacrylic acid, acrylamide, acrylic ester, etc. can be considered.
The hygroscopicity cannot be greatly improved, and on the contrary, the bentonite reforming effect is deteriorated. Inorganic polyphosphates and sodium carbonate can be used as the powdery dispersant, but the peptizability of the dispersion is inferior to that of the polyacrylate, and the sustainability of the effect is also inferior. Organic nitrohumates and lignin sulphonates can also be supplied in powder form, but they are less preferred as modifiers because they are inferior in dispersion peptizability to polyacrylates and have foaming properties.

[Problems to be Solved by the Invention]

The present invention has been made for the purpose of providing a powdery bentonite modifier having excellent peptization resistance, cement resistance, salt resistance and extremely low hygroscopicity.

[Means for Solving the Problems]

The present inventor has arrived at the present invention as a result of earnest research to solve these problems. That is, the degree of polymerization is 20
~ 500 powdery (meth) acrylic acid polymers or copolymers of (meth) acrylic acid with other acrylic monomers [(meth) acrylic acid content of 50 mol% or more is required, and ) Acrylic acid means acrylic acid or methacrylic acid], and one selected from the group consisting of one or more acid types and sodium carbonate, sodium bicarbonate, potassium carbonate, sodium tripolyphosphate and sodium hexametaphosphate. Peptization resistance, cement resistance, containing at least one kind of powdery alkaline substance as an essential component,
It is a powdery bentonite modifier with excellent salt resistance and extremely low hygroscopicity. (Requirements Constituting Means) Other acrylic monomers used in the present invention include water-soluble monomers and water-insoluble monomers.
If the copolymer is water-soluble, it can be used. Examples of typical monomers include esters such as acrylamide, methacrylamide, acrylamidomethylpropanesulfonic acid, methyl (meth) acrylate, ethyl (meth) acrylate, and hydroxyethyl (meth) acrylate. In the case of copolymers with acrylic monomers, (meth)
The content of acrylic acid is more preferably 50 mol% or more.
If the content of (meth) acrylic acid is less than 50 mol%, the peptizability for dispersion is lowered. Further, the degree of polymerization is preferably in the range of 20 to 500, and outside this range, the sufficiently satisfactory dispersion peptizing property of the present invention cannot be achieved. Incidentally, a part of the polymer in the present invention, sodium, potassium, ammonium, can also be used in the form of an amine salt, but since the hygroscopicity increases as the content of the salt type increases,
The salt type content is preferably less than 50 mol%. The method for producing the polymer in the present invention is produced by polymerizing using a commonly used method for polymerizing acrylic monomers, dehydrating by heating drying, reduced pressure drying, etc., and then pulverizing or spray drying. be able to. As the powdery alkaline substance of the present invention, at least one selected from the group consisting of powdery sodium carbonate, sodium bicarbonate, potassium carbonate, sodium tripolyphosphate and sodium hexametaphosphate is used. The mixing ratio of the polymer and the powdery alkaline substance is 90:10 to 10:90.
It is preferable to use the ratio of. The alkaline substance can be used in the form of flakes or particles (coarse particles), but fine powder is preferable because it can be mixed with the polymer. The purpose of combined use with alkaline substances is to reduce the pH fluctuation of the stabilizing solution prepared with modified bentonite. The bentonite modifier of the present invention is added to bentonite in an amount of 0.5 to 20% by weight. If it is less than 0.5%, the modification effect is insufficient, and if it exceeds 20%, the peptizing property of the dispersion is too strong, and when suspended in water, the dispersion stability becomes poor and the supernatant generation and sedimented bentonite increase. . The bentonite modifier of the present invention may be used in combination with another dispersant such as tripolyphosphate, hexametaphosphate, sodium carbonate, sodium bicarbonate, lignin sulfonate, or nitrohumate.

[Action]

The bentonite modifier of the present invention has low hygroscopicity, and thus has good storage stability when mixed with bentonite,
Further, it has a high effect of improving salt resistance and cement resistance, and can be modified into bentonite excellent in cement resistance and salt resistance.

【Example】

Next, the present invention will be specifically described with reference to examples. % And parts are based on weight. Production Example (Production of modifier) 2,2-azobis (2-aminodipropane) as a polymerization catalyst in a mixed solution of 360 g of acrylic acid and 360 g of ion-exchanged water
Dihydrochloride 0.2g was added and polymerized in aqueous solution.
% Aqueous solution was obtained. The aqueous solution was vacuum dried and then pulverized to obtain a polyacrylic acid polymer powder product. The average degree of polymerization of this product was 184. Polymers of various compositions were prepared according to the above, mixed with powdered alkaline substances, and used in the following examples. Example 1 A modified bentonite was obtained by mixing 10 parts of a modifier obtained by mixing a polymer having various compositions and a powdered alkaline substance in a ratio of 1: 1 with 90 parts of bentonite. 10 g of modified bentonite was evenly spread over the entire surface of a petri dish with a diameter of 10 cm and left in an atmosphere with a temperature of 20 ° C. and a relative humidity of 65%, and the moisture absorption rate and powder fluidity were measured to obtain Table 1. It was The moisture absorption rate was judged by measuring the weight increase over time and calculating the water content. The fluidity of the powder was visually determined by tilting the petri dish to see if it fluidized. As is clear from Table 1, the product of the present invention had a low hygroscopicity and maintained sufficient fluidity even after standing for 48 hours. The comparative product absorbed moisture remarkably and caking after 24 hours lost the powder fluidity. Further, even if the acrylate and the alkaline substance were mixed, the hygroscopicity could not be suppressed, and the cake was caked after 48 hours. All modifiers were prepared as 100 mesh sieves and tested. Example 2 A stabilizer was prepared by adding 8 parts of Kunigel V ₁ [bentonite: manufactured by Kunimine Industry Co., Ltd.], which was obtained by adding a modifier to 100 parts of water, and stirring with a propeller-type stirrer for 20 minutes. To 100 parts of this stabilizing solution, 5 parts of ordinary Portland cement was added, and the mixture was stirred for 3 minutes with a juice mixer, and the properties of the stabilizing solution were measured. As is clear from Table 2, in the examples of the present invention, the properties of the stabilizing solution do not change even when cement is mixed, and the good state is maintained. The stabilizing solution of the modified bentonite obtained by adding the powder modifying agent of the comparative example was gelated and lost its fluidity due to the incorporation of cement, so that it could not be used as a stabilizing solution. Example 3 A stabilizing solution was prepared by adding 8 parts of Kunigel V ₁ (bentonite) prepared by adding a modifier to 100 parts of water and stirring the mixture for 20 minutes with a propeller-type stirrer. To 100 parts of this stabilizing solution was added 2 parts of salt, and the mixture was stirred for 3 minutes with a juice mixer to dissolve it, and the properties of the stabilizing solution were measured. As is clear from Table 3, in the examples of the present invention, the properties of the stabilizing solution are not deteriorated even when salt is mixed, and the good state can be maintained. The stabilizing solution of bentonite modified by adding the powder modifier of Comparative Example was deteriorated to a state where it could not be used as a stabilizing solution due to thickening or gelation of the salt or increase of drainage amount due to the inclusion of salt.

【The invention's effect】

The following effects can be obtained by the modifier of the present invention. (1) A modified bentonite having high storage stability can be obtained. (2) The mixing operation is easy. (3) The product value can be improved by modifying it into bentonite with high cement resistance and salt resistance. (4) When a stabilizing solution is prepared with this modified bentonite,
There is little deterioration during drilling, stable liquid management is easy, and safe drilling is possible.

Claims (3)

[Claims] 1. A powdery acrylic acid polymer having a degree of polymerization of 20 to 500, a methacrylic acid polymer, a copolymer of acrylic acid having an acrylic acid content of 50 mol% or more and another acrylic monomer, or methacrylic acid. One or more acid type copolymers of methacrylic acid having an acid content of 50 mol% or more and other acrylic monomers, and sodium carbonate, sodium bicarbonate, potassium carbonate, sodium tripolyphosphate, and A bentonite modifier containing, as an essential component, one or more kinds of powdery alkaline substances selected from the group consisting of sodium hexametaphosphate. 2. A modified bentonite containing the bentonite modifier according to claim 1. 3. A stable liquid excavating method using the modified bentonite according to claim 2.