JP2000281702A - Thixotropic alkali salt of carboxymethylcellulose and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high degree of substitution and high thixotropic properties by preparing an alkali salt of carboxymethylcellulose which has a degree of substitution of carboxymethyl groups above a specified value and whose aqueous solution prepared so as to provide a specified viscosity gives viscosities at specified spindle revolutions at a ratio below a specified value. SOLUTION: An alkali such as potassium hydroxide is dissolved in a water- containing organic solvent comprising a hydrophilic organic solvent, such as methyl alcohol, and water at a weight ratio of (80:20) to (95:5) to prepare a solution having a concentration of 40-49 wt.%. This alkali solution is mixed under agitation at 10-50 deg.C with a cellulose raw material such as linter pulp to effect mercerization, an etherifying agent comprising e.g. monochloroacetate is added in small quantities thereto, and the temperature of this mixture is then raised to 60-80 deg.C to etherify. A thixotropic alkali salt of carboxymethylcellulose is thus obtained which has a degree of substitution of carboxymethyl groups of at least 1.0 and whose aqueous solution prepared so as to provide a viscosity measured with a Brookfield viscometer (at 25 deg.C, at a spindle revolution of 30 rpm) of 10,000 mPa.s gives viscosities at spindle revolutions of 60 rpm and 6 rpm at a ratio of at most 0.6:1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkali salt of carboxymethylcellulose (hereinafter abbreviated as CMC) having a degree of carboxymethyl substitution of 1.0 or more and having a high thixotropic property (thixotropic).

[0002]

2. Description of the Related Art CMC is a cellulose ether obtained by reacting a cellulose raw material such as wood pulp or linter pulp with an etherifying agent such as monochloroacetic acid in the presence of an alkali such as sodium hydroxide. It is widely used in thickeners, dispersants, protective colloids, adhesives, mud regulators for petroleum drilling, binders for feed, printing pastes, and the like.

[0003] In the above applications, CMC is used as an aqueous solution, and its quality is greatly affected by the degree of substitution of carboxymethyl groups (hereinafter abbreviated as DS), viscosity and thixotropy. In general, the lower the DS of CMC, the higher the thixotropic property of the aqueous solution, and conversely, the higher the DS, the lower the thixotropic property of the aqueous solution. That is, in CMC having a low DS, the number of carboxymethyl groups with respect to the hydroxyl groups of cellulose is small, and the distribution of substituents becomes non-uniform. growing. On the other hand, CM with high DS
In C, the number of carboxymethyl groups with respect to the hydroxyl groups of cellulose is large and the distribution of the substituents is uniform, so that the thixotropic property of the aqueous solution is small.

[0004] With the development of applications of CMC and the demand for CMC having various rheological properties, various methods for improving the thixotropic property of CMC have been developed.
Many methods for improving the thixotropy of CMC have been developed mainly for the purpose of reducing the thixotropy of CMC having a low DS. For example, a method of producing a CMC having a uniform carboxymethyl group substituent distribution is produced. Method (Japanese Patent Publication No. 60-42241, Japanese Patent Publication No. 60-3536)
1, JP-B-63-55523) and a method of blending CMC with low thixotropy (JP-B-60-5173).
2, Japanese Patent Publication No. 04-80148).

On the other hand, as a method for increasing the thixotropy of CMC having high DS, a method of blending CMC having high thixotropy (Japanese Patent Laid-Open No. 05-214162)
Is disclosed. However, in such a method of blending CMC, there is a limit to the blending ratio, and therefore, there is a limit in preparing CMC having a target DS and viscosity. In particular, CMC having a DS of 1.0 or more has a very low thixotropy, so that the compounding ratio of CMC having a low DS and a large thixotropy is high, and the DS of the obtained CMC compound is 1.0 or less.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a CMC having a high DS and a high thixotropy. More specifically, DS is 1.0 or more, and a B-type viscometer (25 ° C., spindle rotation speed 30 rp)
An object of the present invention is to provide a CMC characterized in that the viscosity ratio between the spindle rotation speed of 60 rpm and 6 rpm of the aqueous solution prepared so that the viscosity measured in m) is 10,000 mPa · s is 0.6 or less.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have completed the novel thixotropic CMC of the present invention. That is, in the present invention, the spindle rotation speed of an aqueous solution prepared so that the DS is 1.0 or more and the viscosity measured by a B-type viscometer (25 ° C., spindle rotation speed 30 rpm) is 10,000 mPa · s is 60 rpm. And a thixotropic CMC having a viscosity ratio at 6 rpm of 0.6 or less.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, DS needs to be 1.0 or more. When the DS is lower than 1.0, functions of the CMC such as dispersibility and emulsifying property become insufficient.

Further, the spindle rotation speed of a CMC aqueous solution prepared so that the viscosity measured by a B-type viscometer (25 ° C., spindle rotation speed 30 rpm) is 10,000 mPa · s is 60 rpm.
It is necessary that the viscosity ratio between rpm and 6 rpm is 0.6 or less. When the viscosity ratio exceeds 0.6, the thixotropic property of the CMC aqueous solution becomes small, which is not preferable when used as a paint additive, a gelling agent, a shape retaining agent, and the like.

The method for producing the thixotropic CMC of the present invention includes:
In the process of producing CMC by allowing an alkali to act on a cellulose raw material and then reacting with an etherifying agent in the presence of a water-containing organic solvent, the temperature is lower than the temperature at which the alkali acts by 5%.
A method of reacting an etherifying agent after cooling at a temperature of not less than ° C.

When producing CMC having a DS of 1.0 or more, a high concentration of alkali of 40 to 49% is generally used for preparing mercerized cellulose. The dissolved high-concentration alkaline solution penetrates into the inside of the cellulose raw material by stirring and mixing, and uniform mercerized cellulose is prepared. At this time, by cooling the temperature to 5 ° C. or more before adding the etherifying agent, a part of the high-concentration alkali that has penetrated into the cellulose raw material is insolubilized and precipitated, so that the cellulose raw material is locally immiscible. A uniform mercerization state results. Therefore, the etherification reaction by the etherifying agent proceeds non-uniformly, and CMC in which the distribution of substituents of the carboxymethyl group is locally non-uniform is obtained. Such CMCs exhibit structural viscosity due to hydrogen bonds of unreacted hydroxyl groups and have high thixotropic properties.

In general, CMC by the solvent method is carried out by first preparing a cellulose raw material at 10 ° C. to 50 ° C. with a hydrous organic solvent containing an alkali.
To prepare a mercerized cellulose by stirring and mixing at a temperature of
Subsequently, the etherifying agent dissolved in the water-containing organic solvent was
After adding little by little at a temperature of 0 ° C. and stirring and mixing, 6
It is produced by performing an etherification reaction at a temperature of 0 to 80 ° C.

[0013] In the present invention, the temperature at which the mercerized cellulose is prepared is set by ordinary CMC production.
It may be performed at 0 ° C. to 50 ° C., and there is no particular limitation. The etherifying agent is added after cooling at a temperature of at least 5 ° C., preferably at least 10 ° C. from the temperature at which the mercerized cellulose is prepared. If the cooling temperature is lower than 5 ° C., the mercerization becomes inhomogeneous, and the desired CMC having a large thixotropic property cannot be obtained.

As the cellulose raw material used in the present invention, any linter pulp, wood pulp or the like which is usually used for producing CMC can be used and is not particularly limited.

The hydrated organic solvent is not particularly limited as long as it is a solvent usually used for CMC production. 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 ketone; and aromatic solvents such as benzene and toluene. A mixture of at least one of a mixture of hydrocarbons and water. The weight ratio of the organic solvent to water is preferably in the range of 80:20 to 95: 5.

As the alkali, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide and the like can be used, but sodium hydroxide is preferable for economic reasons. As the method of adding the alkali, the entire amount of the alkali may be added before the addition of the etherifying agent, or the alkali used may be added separately before and after the addition of the etherifying agent. However, the concentration of alkali at the time of mercerization {weight of alkali / (weight of water in water-containing organic solvent + weight of alkali) × 100} indicates that alkali is partially insolubilized and precipitated by cooling after mercerization. It is necessary that the concentration be sufficiently high, and it is desirable that the concentration be 40 to 49%.

As the etherifying agent, monochloroacetic acid or a neutralized product thereof, sodium monochloroacetate and the like can be used. The amount of the etherifying agent to be added is not particularly limited as long as it is an amount necessary for obtaining CMC having a DS of 1.0 or more.

[0018]

The embodiments of the present invention will be described below with reference to examples, but the present invention is not limited to these examples.

The method of evaluating the quality of CMC used in the present invention is as follows. (1) DS (degree of substitution) 1.0 g of CMC (anhydrous) was precisely weighed, placed in a platinum dish and placed in a platinum dish.
Ashing at 50-600 ° C., titration of sodium oxide generated by the incineration with 0.1N 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 0.1 N sulfuric acid) (2) B-type viscosity 10 g of CMC (anhydride) is precisely weighed, put into a 1000 ml beaker, 990 ml of pure water is added, and a triangle stirring rod is used. Stir and dissolve to adjust the liquid temperature to 25 ± 0.2 ° C.
Using a BM viscometer (manufactured by Tokyo Keiki Co., Ltd.), the number of rotations was 30 rp.
Read the viscosity after spinning at m for 3 minutes. (3) Thixotropy (PVI value) The concentration is adjusted according to the viscosity of CMC, and a CMC aqueous solution having an aqueous solution viscosity of 10,000 ± 500 mPa · s measured by a B-type viscosity measurement method is prepared. 25 ± 0.2 of CMC aqueous solution
The liquid temperature was adjusted to ° C., and the respective viscosities at the rotation speeds of 6 rpm and 60 rpm were measured, and the thixotropy was determined by the quotient of the viscosity at the rotation speed of 60 rpm and the viscosity at the rotation speed of 6 rpm as shown in the following formula. The smaller this value, the greater the thixotropic property. Thixotropy = ｛viscosity (60 rpm) / viscosity (6 rp)
m)｝

Example 1 A biaxial kneader having a capacity of 5 L was charged with 1604 g of IPA and 139 g of methyl alcohol. Next, a solution prepared by dissolving 125.2 g of sodium hydroxide in 178 g of water was added. While maintaining the temperature at 30 ° C., 215 g of linter pulp having a water content of 7% was charged. After stirring and mixing for 60 minutes, 15 minutes
° C, and then 151.7 g of monochloroacetic acid was added to IP
A solution dissolved in a mixture of A 214 g and water 22 g was added. After stirring and mixing at 15 ° C. for 30 minutes, the temperature was raised to 70 ° C., and this temperature was maintained for 60 minutes. After cooling, the reaction product was purified twice with 72% methanol, drained, and dried with a blow dryer to produce CMC.

Example 2 1515 g of IPA and 132 g of methyl alcohol were charged into a twin screw kneader having a capacity of 5 L. Next, a solution prepared by dissolving 119.7 g of sodium hydroxide in 153 g of water was added. While maintaining the temperature at 40 ° C., 215 g of linter pulp having a water content of 7% was charged. After stirring and mixing for 60 minutes, 20
° C, then add 262.5 g of monochloroacetic acid to IP
A solution dissolved in a mixture of A373 g and water 35 g was added. After stirring and mixing at 20 ° C. for 60 minutes, 97.0 g of sodium hydroxide was added in a solid state. After stirring and mixing at 20 ° C. for 60 minutes, the temperature is raised to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction product was purified twice with 72% methanol, drained, dried with a blast drier and CM
C was produced.

Comparative Example 1 IPA (1604 g) and methyl alcohol (139 g) were charged into a 5-liter twin-screw kneader. Next, a solution prepared by dissolving 125.2 g of sodium hydroxide in 178 g of water was added. While maintaining the temperature at 30 ° C., 215 g of linter pulp having a water content of 7% was charged. After stirring and mixing for 60 minutes, a solution prepared by dissolving 151.7 g of monochloroacetic acid in a mixed solution of 214 g of IPA and 22 g of water was added. After stirring and mixing at 30 ° C. for 30 minutes, the temperature was raised to 70 ° C., and this temperature was maintained for 60 minutes. After cooling, the reaction product was purified twice with 72% methanol, drained, and dried with a blow dryer to produce CMC.

Comparative Example 2 1515 g of IPA and 132 g of methyl alcohol were charged into a biaxial kneader having a capacity of 5 L. Next, a solution prepared by dissolving 119.7 g of sodium hydroxide in 153 g of water was added. While maintaining the temperature at 40 ° C., 215 g of linter pulp having a water content of 7% was charged. After stirring and mixing for 60 minutes, a solution prepared by dissolving 262.5 g of monochloroacetic acid in a mixed solution of 373 g of IPA and 35 g of water was added. After stirring and mixing at 40 ° C. for 60 minutes, 97.0 g of sodium hydroxide was added in a solid state. After stirring and mixing at 40 ° C. for 60 minutes, the temperature is raised to 70 ° C. and maintained at this temperature for 60 minutes. After cooling, the reaction product was purified twice with 72% methanol, drained, and dried with a blow dryer to produce CMC.

Table 1 shows the quality of CMC obtained under the manufacturing conditions of Examples 1 and 2 and Comparative Examples 1 and 2. Examples 1-2 are CMCs obtained according to the present invention. Comparative Examples 1 and 2 are CMCs manufactured with the mercerization temperature and the etherification agent addition temperature kept constant as before.

In the examples, the DS of the CMC is 1.0 or more and the DS is high, but the PVI value is significantly lower and the thixotropy is large as compared with the comparative example showing the same DS.

[0026]

[Table 1] Table 1

[0027]

According to the present invention, mercerized cellulose is used
After cooling over ℃, by adding an etherifying agent,
Since the DS is 1.0 or more and the thixotropy is large, it is widely used as a thickener, dispersant, protective colloid, adhesive, mud regulator for petroleum boring, binder for feed, printing paste, etc. Can be used with

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuhiro Hanada 1280, Etsu-cho, Gotsu-shi, Shimane Japan Nippon Paper Industries Co., Ltd. F term in the Chemicals Development Laboratory (reference) 4C090 AA02 AA05 BA29 BB65 BB92 BD08 BD36 CA04 CA33 CA36 DA01 DA03 DA21 4J002 AB031

Claims (2)

[Claims] 1. An aqueous solution prepared so that the degree of substitution of a carboxymethyl group is 1.0 or more and the viscosity measured by a B-type viscometer (25 ° C., spindle rotation speed 30 rpm) is 10,000 mPa · s. Spindle speed of 60rpm and 6rpm
A thixotropic carboxymethylcellulose alkaline salt having a viscosity ratio of 0.6 or less. 2. In the process of producing an alkali salt of carboxymethylcellulose by allowing an alkali to act on cellulose in the presence of a water-containing organic solvent and then reacting with an etherifying agent, the temperature is at least 5 ° C. higher than the temperature at which the alkali acts. 2. The method for producing a thixotropic carboxymethyl cellulose alkali salt according to claim 1, wherein an etherifying agent is allowed to act after cooling.