JPS6036201B2 - Process for producing carboxymethylcellulose sodium salt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing carboxymethyl cellulose sodium salt having excellent water dispersibility.

Specifically, the present invention relates to a method for producing carboxymethylcellulose sodium salt having excellent water dispersibility by thermally crosslinking carboxymethylcellulose sodium salt at high temperature. In general, carboxymethyl cellulose sodium salt (hereinafter abbreviated as Na-CMC) has poor dispersibility in water and tends to form so-called "mamako", so it must be added little by little while thoroughly stirring when dissolved in water, and it is necessary to completely It has the disadvantage that it takes a long time to melt. For this reason, there is a method of making Na-CMC into neck grains as a method of preventing the mamako phenomenon, but this is partially due to the mamako phenomenon and is not necessarily sufficient.

Furthermore, a method of treating with glyoxal or the like is known, but it requires time and effort for treatment and pH adjustment, and is also subject to restrictions in terms of purity for addition of a third component. As a result of intensive research into a method for producing Na-CMC without adding any third component as described above, the present inventors discovered and completed a method for producing Na-CMC with extremely excellent water dispersibility. It is.

The reason why Na-CMC turns into a lump when it dissolves in water is because Na-
Because CMC has a very high affinity and dissolving power for water, the surface of Na-CMC particles that come into contact with water immediately dissolves and at the same time binds and retains water molecules, which prevents water from penetrating and diffusing inside the Na-CMC particles. There is a particular thing.

Therefore, the present invention prevents mako by promoting the penetration of water into the inside of Na-CMC particles by partially introducing water-insoluble ester crosslinks into the Na-CMC molecular chains through heat treatment. That's what I was thinking of doing.

The present invention involves a crosslinking reaction with an unsubstituted hydroxyl group (Cell-OH) of the Na-CMC molecular chain by heating a small amount of free carboxylic acid group (Cell-○-CH2COOH) in Na-CMC at high temperature. (Ester bond Cell
-○-CH2COO-Cell).

Na-CMC, which is the starting material of the present invention, can be produced using either an aqueous method or a solvent method.

Regarding the degree of substitution (hereinafter abbreviated as DS) of Na-CMC,
Those having a molecular weight of 0.3 or more and less than 3 can be used. DSO. A CMC of less than 3 is insoluble in water, and since the CMC of DS3 has no unsubstituted water-substituted hydroxyl group, ester crosslinking is impossible. The degree of polymerization or viscosity of Na-CMC is related to the heat treatment conditions, but it is necessary that the Na-CMC has a major concentration of 100 centipoise or more in a 1% aqueous solution.
Since Na-CMC with a low viscosity of 100 centipoise or less has a short molecular chain, it is difficult to exhibit a heating prevention effect even if it is thermally crosslinked.

As a guideline for the viscosity and heating conditions of Na-CMC, if the viscosity of a 1% aqueous solution is 100 to 1000 centipoise,
40oo or more for several hours, if it is 1000 to 3000 centipoise, it will take around 14q○ for 1 to 2 hours, if it is 3000 centipoise or more, it will take several hours at 100 to 130qo.
The desired product can be obtained by heat treatment between two steps. The heating temperature is suitably 100 to 200 qC, more preferably 120 to 180 qC. Although it is possible to use less than 100 qC, it requires a very long treatment time, and above 200 qC, the coloring and decomposition of Na-CMC will become severe, so it is not suitable.

In order to carry out the esterification crosslinking reaction only by heat treatment, free carboxylic acid groups (Cell
-OCH2COOH) is required. The amount is required to be at least 0.05 per 100 of the sodium carboxylic acid salt in terms of equivalent ratio.
-CMC is possible by adjusting the pH to 7.5 or less in the neutralization step during production. Usually pH 7.5-6.
In the case of 0, as for the amount of free carboxylic acid groups present, the more carboxylic acid groups there are, the more likely esterification crosslinking will occur. Therefore, if it is less than 0.05, there will be too few cross-linking points even when heated, and prevention of macaques cannot be expected. The quantitative determination of free carboxylic acid groups was carried out by the acid-alkali titration method, as in the case of carboxylic acid Na salt. Conversely, if the amount of free carboxylic acid groups exceeds 20 to 100 of the sodium carboxylic acid salt in equivalent ratio, the dispersibility of CMC in water after heating is good, but the water dropability decreases. Undesirable. Therefore, the desirable equivalent ratio of free carboxylic acid group to carboxylic acid Na salt is 0.
05-2 administration is 100. As mentioned above, DS is 0.3
or more, less than 3, free carboxylic acid group and carboxylic acid Na
Na-CMC with a salt equivalent ratio of 0.05 to 2 and a 1% aqueous solution viscosity of 100 centipoise or more is water-dispersed by heating at 100 to 200 centipoise within several tens of minutes to several hours. The inventors discovered that Na-CMC with significantly superior properties could be obtained, leading to the present invention. In addition,
When Na-CMC treated according to the present invention is immersed in water, it quickly diffuses on the water surface and at the same time quickly settles into the water.

This aqueous solution has a lower apparent viscosity than when Na-CMC is dissolved before heat treatment, and if the undissolved content increases, the viscosity can be easily increased by adding an alkaline substance,
Moreover, it is possible to complete the non-melting decomposition.

For example, when Na-CMC treated according to the present invention is put into a weakly alkaline aqueous solution such as sodium carbonate, it will be dispersed and completely dissolved without becoming lumpy. More specifically,
Degree of substitution 0.7, viscosity 150 ps, free carboxylic acid group 0
．． Two nights of Na-CMC of No. 09 (versus 100% of sodium carboxylic acid salt) heat-treated at 140° C. for 2 hours were added to 200% of each aqueous solution whose pH was adjusted to 10 and 11 with sodium carbonate. As a result, a high viscosity solution with a 1% aqueous solution viscosity of 100 ps was obtained, in which the sample particles did not become lumpy, were dispersed quickly, and the sample particles were completely dissolved. The Na-CMC of the present invention can be used in petroleum borings, fiber walls, foods, feeds, iron disintegrators, glues, muddy water conditioners, and the like.

Since there is no established method for evaluating dispersibility in water, the following method was used for convenience. That is, put 200 ml of water in a 300 ml beaker, fix a funnel in the center at a height of 30 ml above the water surface, and put a 0.5 ml sample into the funnel and keep it under static conditions from beginning to end. In addition to observing the dispersion and settling conditions of the sample, we also measured the time it took for all the samples to disperse into the water for 0.5 days, and used this time as a representative value for the dispersibility in water (preventing effect). .
This will be explained below using examples.

Example 1-6 The following various Na-CMCs were heat-treated and their dispersibility in pure water was evaluated.

The evaluation method was to measure the time required for the entire sample to be dispersed in water under static conditions using the above-mentioned simple method. Raw materials used
The a-CMC had a moisture content of 5-10% and a particle size of 80 mesh pass. A hot air circulation dryer was used for heat treatment.
The results are shown in Table 1. Note in Table 1) Marked with *: There was almost no dispersion even after 4 hours of standing, and it was compatible with mamako.

Examples 7 to 10 Four types of CMC with different degrees of substitution and equivalent ratios of free carboxylic acid groups and carboxylic acid sodium salts were heat-treated for *140°C for 1 hour, and their dispersibility in pure water was evaluated in the same manner as in Example 1. did.

The results are shown in Table 2.

Note in Table 2) *Marked: Even after standing for 4 hours, it was hardly dispersed and became sticky.

Claims (1)

[Claims] 1 The degree of substitution per anhydroglucose unit is 0.3 or more and less than 3, the equivalent ratio of free carboxylic acid group to carboxylic acid sodium salt is 0.05 to 20:100, and the viscosity of 1% aqueous solution is 100 centipoise or more A method for producing carboxymethylcellulose sodium salt, which comprises heating carboxymethylcellulose sodium salt at 100 to 200°C.