JPH10158301A - Carboxymethylcellulose ether alkali salt excellent in chemical resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carboxymethylcellulose ether alkali salt excellent in chemical resistance. SOLUTION: This carboxymethylcellulose ether alkali salt has a viscosity of 100-10,000cps in a 1% aqueous solution and a degree of etherification of 0.60-1.00mol/c6 . Further, in the carboxymethylcellulose ether alkali salt, (A) the viscosity (η1 ) of a 1% aqueous solution and the viscosity (η2 ) of the solution after the addition of 3wt.% calcium chloride to the 1% aqueous solution satisfy the relation η2 /η1 =0.8-1.2, and (B) the viscosity (η1 ) of a 1% aqueous solution and the viscosity (η3 ) of a 1% solution in a 4% sodium chloride aqueous solution satisfy the relation η3 /η1 =0.8-1.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkali salt of carboxymethyl cellulose ether having excellent chemical resistance.

[0002]

2. Description of the Related Art Conventionally, in civil engineering work, underground continuous wall construction work uses a stable liquid to prevent collapse of a pit wall, and muddy water is used for underground tunnel excavation work, especially excavation work using a muddy water shield method. ing.

[0003] The stabilizing solution and muddy water used in these methods have been obtained by dissolving mineral components such as bentonite and polymer components such as carboxymethylcellulose alkali salt (hereinafter abbreviated as "CMC") in fresh water. However, in construction sites such as artificial offshore islands and undersea tunnels, fresh water required for the preparation of stabilizers is not always sufficient, and the use of seawater instead of fresh water for dissolution of stabilizers is increasing. Have been doing.

When seawater is used for dissolving a stabilizing solution,
The viscosity of CMC, which is a polymer component, was liable to change due to the presence of sodium ions and calcium ions contained in seawater. Even so, sufficient performance could not be demonstrated.

[0005] Further, in the case of performing excavation work such as ground excavation in shield wall construction work or shield cutting of ground with improved ground, cement is inevitably mixed into the stabilizing solution. CMC loses its performance due to calcium ions in it and weakens the mud film, possibly causing serious troubles such as collapse of the groove wall or eruption accident. It has been required to exhibit sufficient viscosity-imparting action and wall-forming performance even in the presence of calcium ions. In other words, CMC, which is a polymer component, is required to have a small change in viscosity even through the presence of sodium ions or calcium ions.

Therefore, as a method of solving the effect of calcium ions among the above-mentioned problems, Japanese Patent Laid-Open Publication No. Hei.
No. 5 has been proposed. That is, the degree of ether substitution is 1.2
This is a method using the following carboxymethylcellulose sodium salt. According to this, the degree to which the cement hydrate containing calcium ions inhibits the viscosity-imparting action of CMC depends on the degree of ether substitution of CMC, and the greater the degree of ether substitution, the greater the degree. The degree of substitution must be less than 1.2. In this method, the change in viscosity with respect to calcium ions is reduced, and the viscosity-imparting effect is improved. However, a substantially satisfactory viscosity-imparting effect is expected when the degree of etherification of CMC is 0.90 or less.

On the other hand, Japanese Patent Publication No. 4-69641 has been proposed as a method for solving the effect of sodium ions.
That is, it is effective to increase DS for the salt water resistance, which is the degree of viscosity of the presence of sodium ions, and epichlorohydrin acts during the CMC reaction process to produce a highly substituted and highly viscous CMC excellent in salt water resistance. It is something to offer. In this method, the change in viscosity with respect to sodium ions was small, but the degree of etherification of CMC required substantially 1.00 or more.

Therefore, it has been difficult for the conventional CMC to have good resistance (small change in viscosity) to both calcium and sodium ions.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a CMC which is hardly affected by calcium ions and sodium ions and has excellent chemical resistance.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies on CMC which is hardly affected by calcium ions and sodium ions and has excellent chemical resistance.
% Aqueous solution of carboxymethyl cellulose having a viscosity of 100 to 10000 cps and a degree of etherification of 0.60 to 1.00 mol / c ₆ , wherein (A) the viscosity η _{1 of a} 1% aqueous solution and 3% by weight of the aqueous solution And the viscosity η ₂ after adding calcium chloride is expressed by the following equation: η ₂ / η ₁ = 0.8
(B) the viscosity η ₁ of a 1% aqueous solution and the 1% viscosity η of a 4% aqueous sodium chloride solution
_The intended purpose is attained by carboxymethylcellulose alkali salt which satisfies the relational expression η ₃ / η ₁ = 0.8 to 1.0 (hereinafter referred to as an index of sodium resistance or chemical resistance (B)). I found what I could do.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a 1% aqueous solution has a viscosity of 10%.
The reason why the viscosity is set to 0 to 10000 cps is that the viscosity is 100 cps.
Although CMC satisfying the index (A) and (B) of the chemical resistance of the present invention was obtained even when the viscosity was less than 1, the viscosity imparting property and the wall-building performance were obtained because the viscosity was originally low, or when a stable liquid was used. This is because it is economically disadvantageous, for example, the addition amount must be increased. If it exceeds 10,000 cps, it is not possible to stably obtain those which suitably match the indexes (A) and (B) of the chemical resistance of the present invention.

The degree of etherification is 0.60 to 1.00.
mol / of c in the range of ₆ were considered necessary, chemical resistance index is less than the degree of etherification is 0.60 mol / c ₆ or 1.00 mol / c ₆ than (A) and (B) This is because a CMC satisfying any of the above conditions was not obtained.

Further, the chemical resistance index (A) is a relational expression η ₂ / η ₁ = 0.1 between the viscosity η ₁ of a 1% aqueous solution and the viscosity η ₂ after adding 3% by weight of calcium chloride to the aqueous solution. 8-1.
2 and (B) the viscosity η ₁ of a 1% aqueous solution and the 1% viscosity η ₃ of a 4% aqueous sodium chloride solution are represented by the relational expression η ₃
/ Η ₁ = 0.8 to 1.0 is required to be satisfied because the indexes (A) and (B) of the chemical resistance are 0.8
If it is less than 3, the viscosity decrease in the presence of sodium ions or calcium ions is larger than in the case of a pure aqueous solution. When the index (A) of chemical resistance exceeds 1.2 or the index (B) of chemical resistance exceeds 1.0, the increase in viscosity becomes too large. Viscosity of the stable liquid when using seawater containing water or when digging such as ground excavation in ground wall construction where cement hydrate containing calcium is mixed or shield cutting of ground with ground improvement This is because the change is a major drawback in performing the construction stably.
The upper limit of the chemical resistance index (B) may be any value of 1.2, but it is 1.0 because it can be obtained stably in the production method.

The CMC of the present invention can be obtained by the method disclosed in Japanese Patent Application No. 8-19748 filed by the present inventors. That is, in the production of an alkali salt of carboxymethyl cellulose ether obtained by etherifying a cellulosic material in a water-containing organic solvent, the weight ratio of the organic solvent to water is 80:20 to 93: 7. The relationship between the total mole number A1 of the alkali used and the mole number A2 of the alkali consumed in the neutralization of the etherifying agent and the mole number E of the etherifying agent is 0.85 ≦ (A1-
A2) / E <1.

[0015] In the method of the present invention for suitably obtaining CMC, the cellulosic raw material may be any linter pulp, wood pulp, or the like that is usually used for the production of CMC, and is not particularly limited. .

The hydrated organic solvent is not particularly limited as long as it is one usually used in the production of CMC for etherifying a cellulosic raw material. Specifically, for example, hydrophilic organic solvents such as alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol (IPA), and butyl alcohol; ketones such as acetone and methyl ethyl ketone; A mixture of at least one of a mixture of aromatic hydrocarbons such as toluene and water is exemplified. In the present production method, a mixture of isopropyl alcohol, methyl alcohol and water is preferable. The weight ratio of isopropyl alcohol to methyl alcohol is 80:20 to 9
It may be appropriately selected from the range of 8: 2 according to the required quality of CMC.

As the alkali, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide and the like can be used, but sodium hydroxide is preferred for economic reasons.

As the etherifying agent, monochloroacetic acid or a partially neutralized product thereof, sodium monochloroacetate and the like can be used.

In the process for suitably obtaining the CMC of the present invention, in a water-containing organic solvent in which the weight ratio of the organic solvent to water is 80:20 to 93: 7, the total mole number A1 of the alkali used and the etherifying agent Number of moles of alkali consumed for neutralization A2
And the number of moles E of the etherifying agent used is 0.8
It is necessary to satisfy 5 ≦ (A1−A2) / E <1.00 because the organic solvent is less than 80% by weight and water is less than 2% by weight.
If the amount exceeds 0% by weight or the amount of the organic solvent exceeds 93% by weight and the amount of water is less than 7% by weight, the chemical resistance indexes (A) and (B) even when the relational expression of the alkali and the etherifying agent defined in the present invention is satisfied. ) Is not satisfied. Further, even in a water-containing organic solvent in which the weight ratio between the organic solvent and water is 80:20 to 93: 7, the relational expression between the alkali and the etherifying agent is (A1-A).
2) / E <0.85 or (A1-A2) / E ≧ 1.
This is because at 00, neither of the indexes (A) and (B) of the chemical resistance can be satisfied.

In the method for suitably obtaining the CMC of the present invention, the most preferable weight ratio of the water-containing organic solvent to the organic solvent and water is in the range of 85:15 to 91: 9. Further, the amount of the alkali and the etherifying agent is determined by the relational expression (1) as 0.85.
Optimally, it is in the range of ０．９0.95.

The present invention can be applied irrespective of the method of adding an alkali or an etherifying agent. Therefore, a method of adding the whole amount of the used alkali before the addition of the etherifying agent, a method of adding the used alkali in a divided manner before and after the addition of the etherifying agent, or a method of adding the whole amount of the used alkali after the addition of the etherifying agent Further, the method is suitably applied to any addition method such as a method of simultaneously adding the total amount of the used alkali and the etherifying agent.However, a method of adding the entire amount of the used alkali before the addition of the etherifying agent and the method of adding the used alkali to the ether are preferable. It is more suitably applied to a method in which the agent is added separately before and after the addition of the agent.

In the present invention, neutralization with an acid such as acetic acid is not required, and CMC after completion of the reaction such as aqueous methyl alcohol widely used in the production of CMC is purified to remove by-products such as salt. It may be dried.
Since the CMC after completion of the reaction of the present invention shows alkalinity, there is no problem in adjusting the pH using an extremely small amount of acetic acid or the like.

As described above, the CMC of the present invention has a molar ratio of an alkali to an etherifying agent [total moles of alkali used A1, etherification] Even if the molar ratio = (A1-A2) / E] where the number of moles of alkali consumed for neutralization of the agent is A2 and the number of moles of etherifying agent used is E = (A1-A2) / E] is less than 1.00, it is extremely low. CMC obtained only by combining a limited molar ratio and a weight ratio of a specific organic solvent and water.

The method of measuring and evaluating the quality of CMC used in the present invention and the effective utilization of the etherifying agent are as follows.

(1) DS (degree of substitution) 1.0 g of CMC (anhydride) was precisely weighed, placed in a platinum dish, and dried.
Ashing at 50-600 ° C., titration of sodium oxide generated by the incineration with 0.1 N sulfuric acid using phenolphthalein as an indicator, and calculating its titer Aml by the following formula, DS
(Mol / c ₆ ). DS = {162 × A × f} / {10000-80 × A ×
f｝ (where f is the titer of 0.1N sulfuric acid)

(2) Viscosity of 1% aqueous solution 10 g of CMC (anhydride) is precisely weighed, put into a 1000 ml beaker, 990 g of pure water is added, and the mixture is stirred and dissolved using a triangle stir bar, and the solution is brought to 25 ± 0.2 ° C. The temperature was adjusted and the number of rotations was 30 r using a BM type viscometer (manufactured by Tokyo Keiki).
Read the viscosity η ₁ after rotating at pm for 3 minutes.

(3) Calcium ion resistance (index of chemical resistance (A)) Calcium chloride was added to a part of the 1% aqueous solution of (1) above so as to be 3% by weight, and stirred for 2 hours. 25 ± 0.
After adjusting the liquid temperature to 2 ° C. and using a BM type viscometer (manufactured by Tokyo Keiki Co., Ltd.), the viscosity η ₂ after rotating at 30 rpm for 3 minutes is read. Resistant calcium ionic uses the value of the (1) Viscosity eta _1, calculated by the following equation. Calcium ion resistance = η ₂ / η ₁ .

(4) Sodium ion resistance (index of chemical resistance (B)) 10 g of CMC (anhydride) is precisely weighed, put into a 1000 ml beaker, 990 g of 4% saline solution is added, and a triangle stirring bar is used. After stirring and dissolving, adjusting the liquid temperature to 25 ± 0.2 ° C., and using a BM type viscometer (manufactured by Tokyo Keiki Co., Ltd.), read the viscosity η ₃ after rotating at 30 rpm for 3 minutes. Resistant sodium ionic uses the value of the (1) Viscosity eta _1, determined from the following equation. Sodium ion resistance =
η ₃ / η ₁ .

[0029]

EXAMPLES The present invention will be described in more detail below, but the present invention is not limited thereto.

Example 1 To a twin screw kneader having a capacity of 5 L, 1562 g of IPA and 136 g of methyl alcohol were charged. Next, a solution obtained by dissolving 122.0 g of sodium hydroxide in 174 g of water was charged.
While maintaining the temperature at 20 ° C., a linter pulp having a moisture content of 7% (trade names: Buckeye HVE, Buckeye Cellulous Corporat)
215 g). While maintaining this temperature 6
Stir and mix for 0 minutes. Then, monochloroacetic acid 15
A solution prepared by dissolving 1.7 g in a mixed solution of 214 g of IPA and 22 g of water was added, and the mixture was stirred and mixed for 30 minutes, and then heated to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction product was purified twice with 10 L of 65% methyl alcohol, drained, and dried to obtain CMC.

Example 2 1779 g of IPA and 155 g of methyl alcohol were put into a biaxial kneader having a capacity of 5 L. Next, a solution prepared by dissolving 117.3 g of sodium hydroxide in 227 g of water was added.
7% moisture in a nitrogen gas atmosphere while maintaining the temperature at 20 ° C
Linter pulp (trade names: Buckeye HVE, Buckeye Ce)
215 g of llulous Corporation). After stirring and mixing for 60 minutes while maintaining this temperature, a solution prepared by dissolving 145.8 g of monochloroacetic acid in a mixed solution of 203 g of IPA and 24 g of water was added, followed by stirring and mixing for 30 minutes.
C. and maintained at this temperature for 60 minutes. After cooling, the reaction product was purified twice with 10 L of 65% methyl alcohol, and liquified and dried to obtain CMC.

Example 3 1025 g of IPA and 89 g of methyl alcohol were charged into a biaxial kneader having a capacity of 5 L. Then, sodium hydroxide 8
A solution prepared by dissolving 4.4 in 138 g of water was added. While keeping the temperature at 20 ° C, wood pulp with 7% moisture (trade name: N
-DPS, manufactured by Nippon Paper Industries Co., Ltd.). While maintaining this temperature, the mixture was stirred and mixed for 60 minutes. Next, a solution prepared by dissolving 105.0 g of monochloroacetic acid in a mixed solution of 145 g of IPA and 18 g of water was added, stirred and mixed for 30 minutes, and then heated to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction was cooled to 2 with 10 L of 65% methyl alcohol.
The product was purified once, drained and dried to obtain CMC.

Comparative Example 1 IPA (1727 g) and methyl alcohol (150 g) were charged into a 5-liter biaxial kneader. Next, a solution prepared by dissolving 134.8 g of sodium hydroxide in 193 g of water was added.
While maintaining the temperature at 20 ° C., a linter pulp having a moisture content of 7% (trade names: Buckeye HVE, Buckeye Cellulous Corporat)
215 g). While maintaining this temperature 6
Stir and mix for 0 minutes. Then, monochloroacetic acid 15
A solution prepared by dissolving 1.7 g in a mixed solution of 214 g of IPA and 22 g of water was added, and the mixture was stirred and mixed for 30 minutes, and then heated to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction product was purified twice with 10 L of 65% methyl alcohol, drained, and dried to obtain CMC.

Comparative Example 2 1504 g of IPA and 131 g of methyl alcohol were charged into a biaxial kneader having a capacity of 5 L. Next, a solution prepared by dissolving 117.5 g of sodium hydroxide in 168 g of water was added.
While maintaining the temperature at 20 ° C., a linter pulp having a moisture content of 7% (trade names: Buckeye HVE, Buckeye Cellulous Corporat)
215 g). While maintaining this temperature 6
Stir and mix for 0 minutes. Then, monochloroacetic acid 15
A solution prepared by dissolving 1.7 g in a mixed solution of 214 g of IPA and 22 g of water was added, and the mixture was stirred and mixed for 30 minutes, and then heated to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction product was purified twice with 10 L of 65% methyl alcohol, drained, and dried to obtain CMC.

COMPARATIVE EXAMPLE 3 IPA (2510 g) and methyl alcohol (218 g) were charged into a 5 L biaxial kneader. Next, a solution obtained by dissolving 122.0 g of sodium hydroxide in 174 g of water was charged.
While maintaining the temperature at 20 ° C., a linter pulp having a moisture content of 7% (trade names: Buckeye HVE, Buckeye Cellulous Corporat)
215 g). While maintaining this temperature 6
Stir and mix for 0 minutes. Then, monochloroacetic acid 15
A solution prepared by dissolving 1.7 g in a mixed solution of 222 g of IPA and 14 g of water was added, and the mixture was stirred and mixed for 30 minutes. Then, the temperature was raised to 70 ° C., and this temperature was maintained for 60 minutes. After cooling, the reaction product was purified twice with 10 L of 65% methyl alcohol, drained, and dried to obtain CMC.

Comparative Example 4 602 g of IPA and 52 g of methyl alcohol were charged into a biaxial kneader having a capacity of 5 L. Then, sodium hydroxide 12
2.0 was dissolved in 174 g of water. Linter pulp with 7% moisture while keeping the temperature at 20 ° C (trade name: Buckeye HVE, Buckeye Cellulous Corporation)
215 g). While maintaining this temperature, the mixture was stirred and mixed for 60 minutes. Then monochloroacetic acid 151.7
g was dissolved in a mixed solution of 186 g of IPA and 50 g of water, and the mixture was stirred and mixed for 30 minutes, and then heated to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reactants were
Purification was performed twice with 10 L of 5% methyl alcohol, followed by deliquoring and drying to obtain CMC.

Comparative Example 5 1965 g of IPA and 171 g of methyl alcohol were charged into a biaxial kneader having a capacity of 5 L. Next, a solution prepared by dissolving 129.6 g of sodium hydroxide in 251 g of water was charged.
7% moisture in a nitrogen gas atmosphere while maintaining the temperature at 20 ° C
Linter pulp (trade names: Buckeye HVE, Buckeye Ce)
215 g of llulous Corporation). After stirring and mixing for 60 minutes while maintaining this temperature, a solution prepared by dissolving 145.8 g of monochloroacetic acid in a mixed solution of 203 g of IPA and 24 g of water was added, followed by stirring and mixing for 30 minutes.
C. and maintained at this temperature for 60 minutes. After cooling, the reaction product was purified twice with 10 L of 65% methyl alcohol, and liquified and dried to obtain CMC.

Comparative Example 6 IPA (1133 g) and methyl alcohol (99 g) were charged into a 5-liter twin screw kneader. Then, sodium hydroxide 9
A solution obtained by dissolving 3.3 in 152 g of water was charged. While keeping the temperature at 20 ° C, wood pulp with 7% moisture (trade name: N
-DPS, manufactured by Nippon Paper Industries Co., Ltd.). While maintaining this temperature, the mixture was stirred and mixed for 60 minutes. Next, a solution prepared by dissolving 105.0 g of monochloroacetic acid in a mixed solution of 145 g of IPA and 18 g of water was added, stirred and mixed for 30 minutes, and then heated to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction was cooled to 2 with 10 L of 65% methyl alcohol.
The product was purified once, drained and dried to obtain CMC.

Comparative Example 7 1058 g of IPA and 92 g of methyl alcohol were charged into a biaxial kneader having a capacity of 5 L. Then, sodium hydroxide 9
A solution obtained by dissolving 0.4 g in 118 g of water was charged. Linter pulp with a 7% moisture content while maintaining a nitrogen atmosphere at a temperature of 20 ° C. (trade names: Buckeye HVE, Buckeye Cellulous
Corporation) (215 g). Stir and mix for 60 minutes while maintaining this temperature to obtain monochloroacetic acid 19
A solution obtained by dissolving 8.3 g in a mixed solution of 280 g of IPA and 29 g of water was added, and the mixture was further stirred and mixed for 60 minutes. Next, 73.3 g of sodium hydroxide was added in a solid state, stirred and mixed for 60 minutes, and then heated to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction product was purified twice with 13 L of 75% methyl alcohol, drained, dried, and CM
C was obtained.

COMPARATIVE EXAMPLE 8 IPA (814 g) and methyl alcohol (71 g) were charged into a 5 L twin screw kneader. Then, sodium hydroxide 7
0.3 was dissolved in 115 g of water. While keeping the temperature at 20 ° C, wood pulp with 7% moisture (trade name: N
-DPS, manufactured by Nippon Paper Industries Co., Ltd.). While maintaining this temperature, the mixture was stirred and mixed for 60 minutes. Next, a solution prepared by dissolving 85.2 g of monochloroacetic acid in a mixed solution of 117 g of IPA and 15 g of water was added, and the mixture was stirred and mixed for 30 minutes, and then heated to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction was cooled to 2 with 10 L of 65% methyl alcohol.
The product was purified once, drained and dried to obtain CMC.

Table 1 shows the quality of CMC obtained under the reaction conditions of Examples 1 to 3 and Comparative Examples 1 to 8 described above. Examples 1 to 3 are CMCs obtained according to the present invention. Both calcium ion resistance and sodium ion resistance, which are indicators of chemical resistance, were good.

On the other hand, Comparative Examples 1, 5, and 6 did not satisfy the relational expression between the alkali and the etherifying agent defined by the production method of the present invention, and (A1-A2) / E was 1.00 or more. 1%
Although the aqueous solution viscosity and the degree of etherification were within the numerical limits of the CMC of the present invention, calcium ion resistance and sodium ion resistance were significantly inferior.

Comparative Example 2 does not satisfy the relational expression between the alkali and the etherifying agent limited by the production method of the present invention (A1-
A2) / E was less than 0.85. 1% aqueous solution viscosity,
Although the degree of etherification was within the numerical limits of the CMC of the present invention,
Calcium ion resistance and sodium ion resistance were significantly inferior. Comparative Example 3 does not satisfy the weight ratio of the solvent and water defined by the method of the present invention, and the solvent is more than 93% by weight and the water is 7% by weight.
Was less than.

Further, Comparative Example 4 did not satisfy the weight ratio of the solvent and water defined in the production method of the present invention, and the solvent contained less than 80% by weight and water contained more than 20% by weight. In both CMCs, the 1% aqueous solution viscosity and the degree of etherification were within the numerical limits of the CMC of the present invention, but the calcium ion resistance and sodium ion resistance were significantly inferior. Comparative Examples 7 and 8 are CMCs obtained by the production method of the present invention.
Was out of numerical limits. Calcium ion resistance and sodium ion resistance were significantly inferior.

[0045]

[Table 1]

[0046]

As described in detail above, the CMC of the present invention is 1
% Aqueous solution viscosity eta ₂ after the addition of calcium chloride viscosity eta ₁ and the aqueous solution 3% by weight of relation η ₂ / η ₁ = 0.
Satisfies 8-1.2, and 1% aqueous solution viscosity η ₁ and 4%
The 1% viscosity η ₃ in an aqueous solution of sodium chloride is related to the equation η ₃
/ Η ₁ = 0.8 to 1.0, the viscosity change in the presence of calcium ions and sodium ions, which has been well known to cause a significant decrease in viscosity as compared with a pure aqueous solution, Low and excellent in chemical resistance.

Therefore, the CMC of the present invention can be used to perform viscosity improvement and formation of a stabilizing liquid or mud for use in performing excavation work such as excavation of ground in ground wall construction or shield shaving of ground with improved ground. It has been found that it can be suitably used as a wall material, as a viscosity imparting agent for seawater kneading at construction sites such as marine artificial islands and submarine tunnels where sufficient stable liquid and fresh water for preparing muddy water cannot be obtained, and as a wall-forming agent. Thus, the present invention has been completed.

Claims (1)

[Claims] 1. The viscosity of a 1% aqueous solution is from 100 to 10,000.
cps, degree of etherification 0.60-1.00 mol / c
A is a carboxymethyl cellulose alkali salt _6, (A) 1% viscosity of aqueous η1 and the 1% aqueous solution 3% by weight of the viscosity eta ₂ after the addition of calcium chloride relation η ₂ / η ₁ = 0.8-1.2 and (B) 1%
Aqueous solution viscosity η ₁ and 1% in 4% sodium chloride solution
An alkali salt of carboxymethyl cellulose having excellent chemical resistance, wherein the viscosity η ₃ satisfies a relational expression η ₃ / η ₁ = 0.8 to 1.0.