JPH0140842B2 - - 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 consisting of a main chain consisting of mannose as a constituent unit and galactose units as side chains, and is mainly contained in large amounts in the seeds of leguminous plants in nature. In particular, guar gum made from guar beans and locust bean gum made from locust beans are typical plant gums whose main component is galactomannan.These plant gums are plant mucilages that dissolve in water. It has the property of exhibiting extremely high viscosity. Furthermore, the galactomannan aqueous solution is nonionic, has a stable aqueous viscosity at a pH of 12 or less, and can maintain a 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 an aqueous solution, and aqueous galactomannan solutions are easily attacked by bacteria, rotting over time, and causing a decrease in viscosity. I have it too.

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 describes hydroxyalkyl ethers of galactomannan, U.S. Pat. Various esterified modified products of galactomannan, including nitrate ester of galactomannan, have been disclosed 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, in producing various modified galactomannan products, it has generally been done to react the modifying agent with galactomannan in a basic atmosphere, and the following are the technical points in producing such modified galactomannan products. The problem was how to uniformly neutralize 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. In the aqueous method, galactomannan is reacted in a state 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 reaction product, it is extremely difficult to uniformly add acid to a highly viscous material, resulting in a locally strong acidic atmosphere that may cause unexpected acid hydrolysis, which may force a decrease in the viscosity of the product, or The drawback was that unneutralized portions were produced, leading to non-uniformity of the product. On the other hand, the slurry method can reduce the viscosity of the reaction system, but in the conventional method, acid is added to the slurry after the reaction to neutralize it. As a result of the proportion of hydrophilic organic solvent in the slurry medium decreasing during the neutralization process, the neutralized galactomannan modified product swells or dissolves due to excess water in the slurry medium, resulting in a slurry with poor mobility. . This fact makes it difficult to stir the slurry, which in turn causes non-uniform neutralization, and the processes such as purification, filtration and washing after neutralization proceed in a liquid state containing swollen or dissolved modified galactomannan. The result is that the process becomes complicated and individual unit operations become extremely difficult.

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 concentrated slurry of modified galactomannan, which has extremely poor mobility. Therefore, it is difficult to perform completely uniform neutralization, and there is a strong tendency for excessive acid to be added locally. Modified galactomannan is locally exposed to a strong acidic atmosphere, and the resulting modified galactomannan is acid-hydrated. This causes decomposition and makes it difficult to obtain a modified galactomannan with desired properties.

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

The gist of the present invention is to provide a method for neutralizing alkaline galactomannans, which comprises contacting carbon dioxide with a medium in which galactomannan is suspended and dispersed in an alkaline aqueous solution of a hydrophilic organic solvent. be.

The gist of the present invention is to use carbon dioxide, which is a weakly acidic substance and is in a gaseous state at room temperature, as a neutralizing agent. One of the technical problems with conventional neutralization operations
Another disadvantageous phenomenon was increased swelling and even dissolution of galactomannans in the dispersion medium. The present inventors discovered that this problem was caused by water, which had conventionally been unavoidably added to the medium when neutralizing galactomannan, and developed a neutralization method that does not add water. They found out.

Since the method of the present invention uses carbon dioxide as a neutralizing agent, it is simple and easy to use, without increasing the swelling property of galactomannan derived from water in the medium and deteriorating process passability leading to dissolution. Neutralization operations can be performed.

The second problem with the conventional method is the non-uniformity of neutralization caused by the addition of a liquid neutralizing agent to highly concentrated slurry galactomannans with poor mobility, and the problem of poor product properties in a localized acid-rich atmosphere. It was a change.

This problem stems from the fact that conventional neutralization operations use liquid neutralizing agents. That is, when a liquid neutralizing agent is used in such a neutralization operation, the neutralization reaction proceeds at an extremely high speed the moment the neutralizing agent is added to the slurry, resulting in a galactomannan slurry in the form of a highly concentrated slurry with poor mobility. When a neutralizing agent is added to the galactomannan, the locally high concentration of the neutralizing agent occurs in the non-uniformity of the neutralization, and furthermore, the deterioration of the galactomannan due to acid hydrolysis is caused.

The neutralizing agent used in carrying out the present invention is carbon dioxide, which is in a gaseous state at room temperature, dissolves in water, and exhibits weak acidity. Neutralization proceeds from the gas-liquid interface of the slurry, and the actual neutralization rate is It depends on the rate of dissolution of carbon dioxide into the concentrated slurry. When carbon dioxide is added to a highly concentrated slurry, it becomes an acid only after it reacts with the water contained in the highly concentrated slurry and exhibits its performance as a neutralizing agent. Therefore, even if a large amount of carbon dioxide is added to the slurry at once, Even when it is added, neutralization is moderately slow and uniform due to transition at the gas-liquid interface, and furthermore, it does not exhibit undesirable effects as a product, such as acid hydrolysis caused by contact with strong acids. It can also prevent sex.

Therefore, by using the neutralization method of the present invention, it is possible to pass through the neutralization process of alkaline galactomannan, which has been considered difficult in the past, very easily and smoothly. Operations such as drying can be carried out extremely easily.

The form of the 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 unrefined particles obtained by finely pulverizing beans. It may also be a powdered galactomannan purified with ether, benzene, alcohol, etc. Galactomannan may be further subjected to thermal decomposition, oxidative decomposition, enzymatic decomposition, acid hydrolysis, etc. to reduce its molecular weight. In addition, various modified products having galactomannan as a backbone, such as various etherified derivatives, esterified derivatives, and graft copolymers of galactomannan, as well as high It also includes galactomannan with increased molecular weight or increased viscosity.

The hydrophilic organic solvent used in carrying out the present invention is an organic solvent that contains at least 30% by weight of water and can be mixed with water without separating from it, and such organic solvents include galactomannan, basic When neutralizing the modified galactomannan, it is preferable that the material be less reactive to the modifying agent. Specific examples of typical hydrophilic organic solvents include alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone and methyl ethyl ketone, and mixtures thereof.

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

In addition to dry ice and carbon dioxide gas, the carbon dioxide used in carrying out the present invention includes carbon dioxide generated from substances that easily generate carbon dioxide upon heating or decomposition. It also includes combustion gases of substances such as hydrocarbons and carbohydrates that can be completely combusted to produce carbon dioxide and water. Although it is possible to add carbon dioxide to the slurry system all at once, it is preferable to add it gradually. Carbon dioxide can be added by methods such as bubbling into the slurry medium and dissolving under pressure, but as long as the slurry system is sufficiently stirred, the usual liquid surface contact method at normal pressure is sufficient to add carbon dioxide. Able to achieve purpose. Examples of the slurry stirring method for neutralization include the usual rotating stirring blade method, blender method, kneader method, etc., and any of these methods can be used. Further, neutralization can be carried out either under normal pressure or under increased pressure. Neutralization is better carried out when carbon dioxide is added under pressure than when it is carried out at normal pressure, but neutralization is usually achieved sufficiently by addition at normal pressure.

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.

This will be explained in more detail below with reference to Examples.

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.
A slurry was formed under 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. After that, carbon dioxide gas was introduced from the cylinder into the slurry in the flask at room temperature.
Neutralization was carried out by bubbling under normal pressure at a rate of 100 c.c. per minute. This operation was carried out for 20 minutes. This neutralization operation was performed extremely easily and uniformly. Afterwards, remove the contents and filter 80%.
Wash with acetone aqueous solution, filter again and then add acetone
After washing with 100 ml, filtration, drying, and pulverization were performed. The absolute dryness of the guar gum powder thus obtained is 1
% aqueous solution was 9.8.

Example 2 100 ml of 2-propanol, 40 ml of water, and 100 g of locust bean gum powder were charged into a kneader having an internal volume of 1 and capable of heating and pressurizing, and a slurry was formed under stirring. Then, add 3g of sodium hydroxide to water.
A solution of sodium hydroxide dissolved in a mixture of 20 ml and 20 ml of 2-propanol was slowly added dropwise. Thereafter, the mixture was stirred at room temperature for 3 hours. Thereafter, carbon dioxide gas at 2.0 atm was introduced from the cylinder into the kneader for neutralization. The amount of carbon dioxide consumed for neutralization was 1 at 2.0 atm. Neutralization proceeded extremely uniformly and easily. After that, it was filtered, washed in 150 ml of an 80% aqueous 2-propanol solution, filtered again, further washed with 100 ml of 2-propanol, filtered, dried,
It was pulverized to obtain locust bean gum powder. This locust bean gum powder is 5.0% on an absolute dry basis.
It was dispersed in 500 c.c. of pure water and dissolved at 80°C.
The pH of this aqueous solution was 10.0.

Example 3 In a pressurized and heatable kneader similar to that used in Example 2, 100 ml of 2-propanol, 20 ml of water, and guar gum powder with a moisture content of 12% were charged and stirred to create a uniform suspension dispersion. . Thereafter, a sodium hydroxide aqueous solution prepared by dissolving 3 g of sodium hydroxide in 30 ml of water was gradually added and stirred. Thereafter, the inside of the kneader was purged with nitrogen, and after stirring for 1 hour, 15 g of propylene oxide was added under pressure using a metering pump, the temperature of the kneader was raised to 80° C., and the reaction was continued for 3 hours. Thereafter, the inside of the kneader was cooled to 35° C. or lower, nitrogen substitution was performed again with stirring, and then 2.5 carbon dioxide (calculated at room temperature and pressure) was added. After that, the contents were taken out, filtered, washed with 200 ml of 80% 2-propanol aqueous solution, filtered, and further washed with 100 ml of 2-propanol aqueous solution.
Filtered. Thereafter, it was dried and pulverized to obtain a hydroxypropyl etherified product of guar gum. The pH of a 1% aqueous solution of the hydroxypropyl etherified guar gum on bone dry basis was 9.5.

Claims (1)

[Claims] 1. A method for neutralizing alkaline galactomannans, which comprises bringing carbon dioxide into contact with a medium in which galactomannan is suspended and dispersed in an alkaline aqueous solution of a hydrophilic organic solvent.