JPS58120603A - Neutralization of alkaline galactomannan - Google Patents

Abstract

PURPOSE:To neutralize alkaline galactomannan, uniformly and easily, by dispersing galactomannan in an alkaline aqueous solution of a hydrophilic organic solvent, and contacting the dispersion with carbon dioxide as a neutralizing agent. CONSTITUTION:Galactomannan is mixed with a hydrophilic organic solvent (a solvent miscible with water and containing >=30wt% water, e.g. methanol) and an alkaline aqueous solution (obtained by dissolving a basic substance such as sodium hydroxide in water), and stirred at room temperature for several hours to obtain a dispersion. Carbon dioxide gas is introduced into the reactor and bubbled at room temperature under atmospheric pressure to effect the neutralization of the dispersion and obtain galactomannan. USE:For food additive and various industrial fields such as paper manufacture industry, textile industry, etc.

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, 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 representative vegetable gums whose main ingredient is galactomannan.
These plant gums are plant mucilages that dissolve in water.
(It has the property of exhibiting extremely high viscosity. Furthermore, galactomannan aqueous solution is nonionic and has a stable aqueous viscosity at a pH of 12 or less, and has a high aqueous viscosity even in the presence of high concentrations of various salts containing multivalent ions. Due to its ability to maintain viscosity, it is also used in the food industry, paper manufacturing, textile industry, and cosmetics.

It is widely used as a thickener in the industrial fields of paint, civil engineering, construction, oil extraction, and gunpowder.

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. There is.

Recently, various modified forms of galactomannan have been proposed to correct the drawbacks of galactomannan. For example, U.S. Patent No. 33268
No. 90 discloses hydroxyalkyl ethers of galactomannan, and U.S. Pat. No. 2,477,544 discloses various etherified modified products of galactomannan including carboxyalkyl ethers of galactomannan.
No. 12220 discloses various esterified modified products of galactomannan including nitrate ester of galactomannan, and JP-A No. 52-38039 discloses various modified galactomannan to reduce viscosity by performing an operation to lower the molecular weight of galactomannan. Examples include the body. These modified galactomannans have various properties added to the inherent properties of galactomannan, and can be used depending on the purpose of various industrial applications.

Conventionally, in producing various modified galactomannans, it has generally been done to react the modifying agent with galactomannan in a basic atmosphere, and the key technical point in producing such modified galactomannans is the modification. The problem was how to uniformly neutralize the alkaline galactomannan. Conventional methods for producing modified galactomannan can be roughly divided into two methods: the so-called water medium method using water as the reaction medium and the so-called slurry method using organic solvent water 6.1 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, resulting in unexpected acid hydrolysis and a reduction in the viscosity of the product. However, there are disadvantages in that unneutralized portions are 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 ratio of the 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 steps after neutralization, such as purification, filtration and washing, proceed in a liquid state containing swollen or dissolved modified galactomannan, making the process complicated. This results in the individual unit operations being 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 subject to acid hydrolysis. It is 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 in an alkaline aqueous solution of a hydrophilic organic solvent. There is a particular thing.

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 in conventional neutralization operations has been the disadvantageous phenomenon of increased swelling and even dissolution of galactomannans in dispersion media. The present inventors discovered that this problem was caused by water, which had conventionally been unavoidably added to the medium when neutralizing galactomannan.The present inventors developed a neutralization method that does not add water. was discovered.

Since the method of the present invention uses carbon dioxide as a neutralizing agent, it is simple and effective without considering the increase in swelling property of galactomannan derived from water in the medium and the deterioration of 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 changes in product properties in localized acid-rich atmospheres. there were.

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. The locally high concentration of neutralizing agent that occurs when a neutralizing agent is added to the gel causes irresponsibility of neutralization, and also causes deterioration of galactomannan due to acid hydrolysis.

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 depends on the rate of dissolution of carbon dioxide into the highly concentrated 18 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 carried out moderately slowly and uniformly by transition at the gas-liquid interface, and it also does not cause undesirable phenomena as a product, such as acid hydrolysis caused by contact with strong acids. It can be prevented.

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 also proceed extremely easily.

The form of the galactomannan used in carrying out the present invention may be in the so-called split state obtained by coarsely pulverizing beans, or in the unrefined form obtained by finely pulverizing it into powder. It may also be a powdered galactomannan purified with ether, benzene, alcohol, etc., and a galactomannan whose molecular weight has been lowered by further operations such as thermal decomposition, oxidative decomposition, enzymatic decomposition, acid hydrolysis, etc. In addition, various modified products having a galactomannan skeleton, 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% water by weight and can be mixed with water without separating from the water, and such organic solvents include galactomannan, basic Furthermore, when neutralizing the modified galactomannan, it is preferable that the material is one that does not easily react with the modifying agent. Specific examples of typical hydrophilic organic solvents include alcohols such as methanol, ethanol, pronophenol and butanol, ketones such as acetone and methyl ethyl ketone, and mixtures thereof.

The alkaline bath liquid 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, and alkaline metal hydroxides. Quaternary ammonium compounds are exemplified.

Carbon dioxide used in carrying out the present invention includes:
In addition to dry ice carbon dioxide gas, it also contains carbon dioxide generated from substances that easily generate carbon dioxide when heated or decomposed. 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 to the slurry medium by pulling or dissolving under pressure, but as long as the slurry system is sufficiently stirred, the normal surface contact method at normal pressure is sufficient. This purpose can be achieved. Also, the slurry stirring method used for neutralization is the usual rotating stirring blade method or the blender one-way method.

One-type kneaders are exemplified, but any of these can be used.Also, neutralization can be carried out under normal pressure or under pressure.It is usually better to add carbon dioxide under pressure. Neutralization is carried out better than when carried out under pressure, but neutralization is usually effected sufficiently by addition under 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 1 801 nl of acetone, 50 tnl of water, and 100 g of guar gum powder were placed in a flask with an internal volume of 1 t equipped with a stirring-like dropping funnel condenser.
2 was added to form a slurry with stirring.

Thereafter, a sodium hydroxide solution prepared by dissolving No. 32 sodium hydroxide in a mixture of 20 rnl of water and 20 rnl of acetone was gradually added dropwise from the dropping funnel. After that, at room temperature 8
Stirring was performed for hours. After that, carbon dioxide gas was introduced from the cylinder into the slurry in the flask at room temperature for 1 minute + 100 nm to nl.
Neutralization was performed while bubbling under normal pressure at a rate of cc. This operation was carried out for 20 minutes. This neutralization operation was performed extremely easily and uniformly. Thereafter, the contents were taken out, filtered, washed with an aqueous solution of 80% thiacetone, filtered again, washed with 100% acetone, and then filtered.

Drying and pulverization were performed. The pH of the aqueous solution of guar gum powder obtained in this way was 98 on an absolute dry basis.

Example 2 In a kneader having an internal volume of 1 ton and capable of heating and pressurizing, 100 g of 2proper tool, 40 g of water, and 100 g of locust bean gum powder were charged and stirred to form a slurry. Thereafter, a sodium hydroxide solution prepared by dissolving 32 parts of sodium hydroxide in a mixture of 20 parts of water and 20 parts of propatool was gradually added dropwise.

Thereafter, the mixture was stirred at room temperature for 3 hours. Thereafter, carbon dioxide gas at 20 atm was introduced from the boiler into the kneader for neutralization. The amount of carbon dioxide consumed for neutralization was IL at 2.0 atm. Neutralization proceeded extremely uniformly and easily. After that, filter and add 80% 2propatool aqueous solution 1
50 - Wash in a medium, filter again, and add 2 protons of 100
m7! Locust bean gum powder was obtained by washing, filtering, drying, and pulverizing. Kagaru locust bean gum powder was dispersed in 500 cc of water on an absolute dry basis and dissolved at 80°C. The pH of this aqueous solution is 10.0
Met.

Example 3 In a pressurized and heated kneader similar to that used in Example 2, 100-2 globanol, 20-globanol, and water with a moisture content of 12 were added.
A uniform suspension and dispersion was prepared by adding guar gum powder and stirring. Then add 3f of sodium hydroxide to 307! An aqueous solution of sodium hydroxide dissolved in water was gradually added and stirred. After that, the inside of Nigu was replaced with nitrogen and stirred for 1 hour.
Propylene oxide No. 9 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 below, nitrogen substitution was performed again while stirring, and then 2.5 t of carbon dioxide (calculated at room temperature and pressure) was added. Thereafter, the contents were taken out, filtered, washed with 200 m of 80 2-propamel aqueous solution, filtered, and further washed and filtered with 100 m of 2-gropamel aqueous solution. Thereafter, it was dried and pulverized to obtain a hydroxyglobyl etherified product of guar gum. The pH of a 1% aqueous solution of the hydroxyglobyl etherified product of guar gum was 9.5.

Patent applicant: Mitsubishi Acetate Co., Ltd. (and 1 others)
Name) Agent Patent Attorney 1) Takeshi Mura

Claims (1)

[Claims] 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.