JPH0140841B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for neutralizing alkaline galactomannans, and more particularly to a method for neutralizing alkaline galactomannans in a so-called slurry method.

Galactomannan is a neutral polysaccharide composed of a main chain consisting of mannose as a constituent unit and galactose units as side chains.In nature, it is mainly contained in large amounts in the seeds of leguminous plants, especially guar beans. Guar gum is a raw material, and locust bean gum is a vegetable gum whose main ingredient is galactomannan.
These plant gums are plant mucilages and have the property of exhibiting extremely high viscosity when dissolved in water. Galactomannan aqueous solution is nonionic, has a stable aqueous viscosity at a pH of 12 or below, and has the characteristics of being able to maintain high aqueous viscosity even in the presence of high concentrations of various salts containing multivalent ions. Because of these properties, it is widely used as a thickening agent in the food field and industrial fields such as paper manufacturing, textile industry, cosmetics, paints, civil engineering and construction, oil mining, and explosives. However, these galactomannans tend to cause agglomeration of powder particles called ``mamako'' when preparing their aqueous solutions, and aqueous solutions of galactomannans are susceptible to attack by bacteria, which causes them to rot over time and cause a decrease in viscosity. It has shortcomings.

In recent years, various modified forms of galactomannan have been proposed to correct the drawbacks of galactomannan. For example, U.S. Patent No. 3,326,890 discloses hydroxyalkyl ethers of galactomannan, U.S. Pat. Various esterified modified products of galactomannan, including mannan nitrate ester, have been published in Japanese Patent Application Laid-open No. 1983-
No. 38039 exemplifies various viscosity-lowering galactomannan modified products obtained by performing operations to lower the molecular weight of galactomannan. Such modified galactomannans have various performances added to the inherent properties of galactomannan, and are used depending on the purpose of various industrial applications.

Conventionally, when producing various modified galactomannans, a method has generally been used in which a modifying agent is reacted with galactomannan in a basic atmosphere. The key point above was how to uniformly neutralize the denatured alkaline galactomannan.

Conventionally, methods for producing modified galactomannan can be roughly divided into two methods: the so-called aqueous method using water as the reaction medium, and the so-called slurry method using an aqueous organic solvent solution as the reaction medium.

The aqueous method is a method in which the reaction is carried out with galactomannan dissolved in water under basic conditions, and the reaction must proceed in an extremely highly viscous state, and the reaction tends to be non-uniform. When neutralizing a product, it is extremely difficult to uniformly add acid to a highly viscous substance, resulting in a locally strong acidic atmosphere, resulting in unexpected acid hydrolysis and a decrease in the viscosity of the product. The drawback was that unneutralized portions were produced during the process, leading to non-uniformity of the product. On the other hand, the slurry method can reduce the viscosity of the reaction system. In the conventional method, acid is added to the slurry after the reaction to neutralize it, but when a dilute acid is used as the acid, the proportion of hydrophilic organic solvent in the slurry medium decreases during the neutralization process. As a result, the neutralized galactomannan-modified product swells or dissolves due to excess water in the slurry medium, resulting in a slurry with poor mobility, making stirring of the slurry difficult and, in turn, inducing non-uniform neutralization. Processes such as purification, filtration, and washing proceed in the state of a liquid containing swollen or dissolved modified galactomannan, resulting in complicated processes and extremely difficult individual unit operations. On the other hand, in order to avoid the above-mentioned disadvantages, there is a method in which a concentrated acid is used in the neutralization operation, but such a method involves adding a concentrated acid to a slurry of modified galactomannan that has extremely poor mobility, so that the neutralization is carried out uniformly. Because it is difficult to perform neutralization and there is a tendency for excessive acid to be added locally, modified galactomannan is exposed to a locally strong acidic atmosphere, and the resulting modified galactomannan causes acid hydrolysis. However, it becomes difficult to obtain modified galactomannan with desired performance.

In view of these circumstances, the present inventors have completed the present invention as a result of intensive studies to find a method for uniformly and easily neutralizing alkaline galactomannans.

The gist of the present invention is characterized in that when neutralizing galactomannans suspended and dispersed in an alkaline aqueous solution of a hydrophilic organic solvent, a mixture of a hydrophilic organic solvent and an acid is added to the composition. A method for neutralizing alkaline galactomannans.

One of the features of the present invention is that it prevents unexpected changes in product properties due to hydrolysis, etc. caused by non-uniform neutralization, which was previously thought to be difficult when neutralizing alkaline galactomannans. Another object of the present invention is to obtain galactomannans having desired properties by a simple neutralization method.

In particular, the method of the present invention can be used as an effective neutralization process for producing not only unmodified alkaline galactomannan but also modified galactomannan.

The form of galactomannan used in carrying out the present invention may be in the form of so-called splits obtained by coarsely pulverizing beans, or in the form of finely pulverized powder. Furthermore, powdered galactomannan purified with ether, benzene, alcohol, etc. may also be used. Further, galactomannan whose molecular weight has been reduced by undergoing operations such as thermal decomposition, oxidative decomposition, oxygen decomposition, acid hydrolysis, etc. can also be used. Furthermore, as galactomannan, not only the above-mentioned unmodified galactomannan but also various modified products having galactomannan as a skeleton can be used. Examples include etherified derivatives, esterified derivatives, and graft copolymers. Furthermore, galactomannan having a higher molecular weight or having a higher viscosity, such as one modified with a crosslinking agent or the like, may also be used.

Hydrophilic organic solvents used in carrying out the present invention include alcohols such as methanol, ethanol, propanol, butanol, acetone,
Examples include ketones such as methyl ethyl ketone and mixtures thereof, and in particular, galactomannan that does not separate from water in a hydrophilic organic solvent containing 30% by weight or more of water and is dispersed in this medium. It is necessary that it has poor reactivity with basic substances and acids.

The alkaline aqueous solution used in carrying out the present invention is one in which a basic substance is dissolved in water. Examples of such basic substances include alkali metal hydroxides, alkaline earth hydroxides, ammonia, amines, quaternary An example is an ammonium compound.

The acid used in carrying out the present invention may be any organic acid or inorganic acid that can be dissolved or dispersed in a hydrophilic organic solvent, but in order to ensure uniformity of the neutralization reaction and to prevent side reactions, It is preferable to use an acid that is soluble in the mixture of the organic solvent and water.

The key point in carrying out the present invention is that when neutralizing galactomannans prepared by the slurry method, the salt is not added directly or in the form of an aqueous solution, but is neutralized using a hydrophilic organic solvent or a hydrophilic organic solvent. The point is that it is added by mixing it into an aqueous solution of a hydrophilic organic solvent. By using such a method, the advantage is that the neutralization step, which was considered to be the biggest difficulty in the slurry method, which is conventionally considered to be superior to the aqueous method, can be carried out extremely easily and uniformly.

As discussed earlier, the previously developed slurry method has disadvantages such as non-uniform neutralization, excessive use of neutralizing agent, and changes in the characteristics of the resulting product. However, according to the method of the present invention, the process passability is good, and non-uniformity of neutralization and accompanying excessive use of neutralizing agent,
This results in the characteristic that the product characteristics do not change even in a localized strong acid atmosphere.

According to the method of the present invention, even when the galactomannan slurry concentration is high, a strong acid can be efficiently added and reacted without significantly reducing the slurry concentration, and the neutralization reaction can be easily and uniformly carried out.
Moreover, it can be carried out with good process passability. In other words, a method is adopted in which a small amount of a hydrophilic organic solvent or an aqueous solution of a hydrophilic organic solvent with a higher proportion of hydrophilic organic solvent than the slurry medium is added to the galactomannan in a state of high slurry concentration under stirring. The slurry of galactomannans, which is in a state of high slurry concentration, becomes highly mobile, and thereafter, the uniform state of a slurry of high concentration of galactomannans can be maintained again. When a hydrophilic organic solvent or a mixture of an acid dissolved in an organic solvent aqueous solution having a higher ratio of hydrophilic organic solvent than the solvent composition of the solvent and the slurry medium is added to galactomannans in a state of high slurry concentration under stirring. The slurry of galactomannans, which is temporarily in a high slurry concentration state and has poor mobility, becomes highly fluid, and neutralization proceeds extremely easily and uniformly. Furthermore, operations such as solid-liquid separation, purification, washing, and drying after neutralization can be carried out extremely easily. The ratio of water to hydrophilic organic solvent in the aqueous solution of hydrophilic organic solvent mixed with acid used for neutralization is preferably 70:30 to 100:0 in terms of volume ratio, and more preferably a high ratio of hydrophilic organic solvent. In addition, good results can be obtained when the ratio of water is smaller than the ratio of the hydrophilic organic solvent to water in the aqueous solution of the hydrophilic organic solvent used as the slurry medium.

On the other hand, it is generally more preferable for the ratio of acid and water to be added to the aqueous solution of hydrophilic organic solvent mixed with acid for neutralization to be as low as possible. Although it is possible to add the mixture of the acid and the hydrophilic organic solvent or the aqueous solution of the hydrophilic organic solvent to the slurry system all at once, it is preferable to add it gradually. Further, during neutralization, it is necessary to stir the substance to be neutralized, and such stirring may be by a conventional stirring blade method, a blender method, or a forced stirring method such as a kneader.

The neutralization method according to the present invention can be used to neutralize basic substances generated when producing not only galactomannan but also various modified forms of galactomannan. It can neutralize mannans.

A more detailed explanation will be given below with reference to Examples.

Comparative Example 1 80 ml of acetone, 50 ml of water, and 100 ml of guar gum powder in a flask with an internal volume of 1 and equipped with a stirrer, dropping funnel, and condenser.
After preparing 3g and forming a slurry with stirring, 3g
A solution of sodium hydroxide dissolved in a mixture of 20 ml of water and 20 ml of acetone was gradually added dropwise from the dropping funnel. Thereafter, the mixture was stirred at room temperature for 8 hours. Thereafter, when 4.3 ml of glacial acetic acid was added dropwise, the area where the drop was added was partially discolored and uniform neutralization was not achieved. Furthermore, the reaction product was filtered, washed with 150 ml of 80% acetone aqueous solution, washed again with 100 ml of acetone, filtered, dried, and pulverized to obtain a powder. A 1% aqueous solution of such guar gum powder on bone dry basis
The pH was 10.4. Further, the viscosity of a 1% aqueous solution of the guar gum powder on an absolute dry basis was measured with a B-type viscometer and was found to be 1800 cps. The liquid temperature at the time of measurement was 25
℃, and the spindle rotation speed was 30 rpm.

Comparative Example 2 80 ml of acetone, 50 ml of water, and 100 ml of guar gum powder in a flask with an inner volume of 1 and equipped with a stirrer, dropping funnel, and condenser.
A slurry was formed under stirring. Then, add 3g of sodium hydroxide to 20ml of water and acetone.
A sodium hydroxide solution dissolved in 10 ml of the mixed liquid was gradually added dropwise from the dropping funnel. Thereafter, the mixture was stirred at room temperature for 8 hours. Then add 4.3ml of glacial acetic acid.
When an aqueous acetic acid solution dissolved in 40 ml of water was gradually added dropwise through a dropping funnel, the guar gum slurry swelled and aggregated, resulting in extremely poor mobility, making it difficult to neutralize well. Furthermore, when an attempt was made to filter the reaction product, the filter paper was blocked by the swollen and aggregated guar gum reaction product, making it impossible to filter.

Example 1 80 ml of acetone, 50 ml of water, and 100 ml of guar gum powder are added to a flask with an internal volume of 1 and equipped with a stirrer, dropping funnel, and condenser.
g to form a slurry while stirring. Then, add 3g of sodium hydroxide to 20ml of water and acetone.
A sodium hydroxide solution dissolved in 20 ml of the mixed liquid was gradually added dropwise from the dropping funnel. Thereafter, the mixture was stirred at room temperature for 8 hours. Thereafter, an acetic acid solution prepared by dissolving 4.3 ml of glacial acetic acid in a mixture of 10 ml of water and 30 ml of acetone was gradually added dropwise through a dropping funnel, and neutralization was performed extremely uniformly and easily. Then filter 80
Wash in 150 ml of % acetone aqueous solution, filter again, wash with 100 ml of acetone, filter, dry,
Grinding was performed to obtain guar gum powder. The pH of a 1% aqueous solution of the guar gum powder on an absolute dry basis was 8.3.
Further, the viscosity of a 1% aqueous solution of the guar gum powder on an absolute dry basis was measured using a B-type viscometer and was found to be 4500 cps. The liquid temperature at the time of measurement was 25° C. and the spindle rotation speed was 30 rpm.

Example 2 In a flask equivalent to that used in Example 1, 2-
Add 80 ml of propanol, 50 ml of water, and 100 g of locust bean powder and form a slurry while stirring.
Afterwards, add 3g of sodium hydroxide to 20ml of water.
- A sodium hydroxide solution dissolved in a mixture of 20 ml of propanol was gradually added dropwise from the dropping funnel.
Thereafter, the mixture was stirred at room temperature for 3 hours. after that
An acetic acid solution prepared by dissolving 4.3 ml of glacial acetic acid in a mixture of 10 ml of water and 30 ml of 2-propanol was gradually added dropwise through a dropping funnel. Neutralization proceeded extremely uniformly and easily. Thereafter, it was filtered, washed in 150 ml of an 80% aqueous 2-propanol solution, filtered again, washed with 100 ml of 2-propanol, filtered, dried, and ground to obtain locust bean gum powder. A 1% aqueous solution of the locust bean gum powder on an absolute dry basis
The pH was 8.5. Further, the viscosity of a 1% aqueous solution of the locust bean gum powder on an absolute dry basis was measured using a B-type viscometer and found to be 5,600 cps. The liquid temperature at the time of measurement was 25° C. and the spindle rotation speed was 30 rpm.

Example 3 In a flask similar to that used in Example 1, 100
ml of 2-propanol, 20 ml of water, and guar gum powder with a moisture content of 12% are charged and stirred to create a uniform suspension and dispersion. Thereafter, an aqueous sodium hydroxide solution prepared by dissolving 3 g of sodium hydroxide in 30 ml of water was gradually added dropwise from the dropping funnel. After stirring at room temperature for 1 hour, 15 g of propylene oxide was added dropwise from the dropping funnel, and the entire flask was heated to 80° C. using a water bath, and the reaction was continued for 7 hours. Then the inside of the flask is 35
The mixture was cooled to below .degree. C., and while stirring, an acetic acid solution prepared by dissolving 4.3 ml of glacial acetic acid in 10 ml of water and 50 ml of 2-propanol was gradually added through a dropping funnel. Such neutralization operation was extremely uniform and easily performed. Afterwards, remove the contents, filter and add 200ml of 80%2-
It was washed with an aqueous propanol solution, filtered, and further washed and filtered with 100 ml of an aqueous 2-propanol solution. Thereafter, it was dried and ground to obtain a hydroxypropyl etherified product of guar gum. The pH of a 1% aqueous solution of hydroxypropyl ether of guar gum is
It was 9.2. The viscosity of a 1% aqueous solution of the hydroxypropyl etherified guar gum on an absolute dry basis was measured with a B-type viscometer and found to be 5200 cps.
The liquid temperature at the time of measurement was 25℃, and the spindle rotation speed was
It was hot at 30 rpm.

Claims (1)

[Claims] 1. A method for neutralizing alkaline galactomannans, which comprises neutralizing galactomannan by adding an acidic solution of a hydrophilic organic solvent to a medium in which galactomannan is suspended in an alkaline aqueous solution of a hydrophilic organic solvent.