JPS5941645B2 - Method for producing hydroxyalkylated starch or dextrin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for producing hydroxyalkylated starch or dextrin from starch or dextrin.

Generally, when water is added to starch and heated, the starch granules swell or dissolve and become gelatinized.

However, an aqueous solution of dextrin easily gels, and becomes a gel even when the temperature is slightly lowered. Moreover, once it becomes a gel, it does not easily return to its original sol even if it is reheated. Therefore, attempts have been made to make starch and dextrin easier to dissolve in water and to stabilize the resulting aqueous solution. Hydroxyalkylation by reacting starch and dextrin with alkylene oxide is
The purpose of this invention is to obtain starch and dextrin derivatives that improve the aging resistance of starch solutions dissolved in water. The hydroxyalkylated starch and dextrin thus obtained have the property that they gelatinize in cold water while retaining the good properties of starch and dextrin, and that the gelatinized liquid is resistant to aging. Therefore, hydroxyalkylated starches or dextrins are widely used as emulsifying thickeners, printing pastes, textile finishing pastes, sizing agents, and the like. Starch or dextrin (hereinafter both are collectively referred to as starches) is reacted with alkylene oxide to produce hydroxyalkylated starch or hydroxyalkylated dextrin (hereinafter both are referred to as starch) that is soluble in cold water while retaining its granule form. There are two known methods for making derivatives (collectively referred to as derivatives).

One is an organic solvent method and the other is a dry method. The organic solvent method is a method that mainly uses an organic solvent as a solvent, and is a method in which starch is dispersed in an organic solvent to form a slurry, and a reaction is carried out in the slurry state. The dry method is a method in which a solvent is not used at all, or even if it is used, only a very small amount is used, and the reaction is carried out in powder form. Organic solvent methods are described, for example, in U.S. Pat. No. 2,845,417.
It is stated in the specification of the No. This method uses caustic soda as a catalyst and ethanol as a solvent, and the reaction is carried out in the form of a slurry. Therefore, relatively large amounts of organic solvent are required. For this reason, a large reaction vessel is required, and the solvent must be removed and dried after the reaction, side reactions are also likely to occur, and the reaction efficiency remains at 30 to 40%. Therefore, depending on the organic solvent method,
Derivatives cannot be manufactured at low cost. On the other hand, the dry method is described in JP-A-53-39386.

This method uses an organic amine as a catalyst and proceeds with the reaction without using a solvent, so it requires only a small reactor, does not require any effort to remove the solvent after the reaction, and has the additional advantages of high reaction efficiency. There is. However, on the other hand, the dry method
It was found that it has the disadvantage that it is difficult to obtain a product with a high degree of substitution by hydroxyalkyl groups. That is, when trying to obtain a derivative with a degree of substitution of 0.5 or more, it was confirmed that side reactions tend to occur and the reaction efficiency decreases.
Therefore, it was necessary to develop a new method to easily obtain derivatives made from starches, which retain their granule shape, are soluble in cold water, and have a high degree of substitution.

This invention was born in response to this need. The inventor intended to advance the reaction between starch and alkylene oxide in powder form, and attempted to reduce the amount of organic solvent used in the above-mentioned organic solvent method.

Specifically, in order to uniformly disperse the caustic soda, first dissolve the caustic soda in a small amount of water to make an aqueous solution of caustic soda, add a small amount of ethanol to this aqueous solution to make a mixed solution, and add a small amount of this mixed solution. In addition to starch, the starch was first swollen. After that, an alkylene oxide was added to the starch to attempt a hydroxyalkylation reaction. However, in this method, the starch partially gelatinized and could not be uniformly reacted. This is presumed to be based on the relationship that, since the solubility of caustic soda in organic solvents is low, a large amount of organic solvent is required in order to proceed with the reaction smoothly. In any case, it has been found that in the organic solvent method, reducing the amount of organic solvent used to approximate the dry method does not bring about good results. Next, the inventor added caustic soda as a solid to starch, stirred well in the presence of a small amount of water and a small amount of an organic solvent, and then added alkylene oxide to the starch to form an almost dry powder. Attempts were made to allow the reaction to proceed.

According to conventional wisdom, if caustic soda was added as a solid and a small amount of water and an organic solvent were added thereto, the starch would locally gelatinize and only a non-uniform derivative would be obtained. However, contrary to expectations, it was discovered that the reaction proceeded uniformly and a cold water-soluble derivative with a high degree of substitution was obtained. Motivated by this discovery, we conducted further experiments and found that in order to carry out the reaction in a dry manner, in addition to adding caustic alkali in a solid state, the amount of caustic alkali should be adjusted to 100 parts by weight of starch. It was found that the amount should be 3 to 10 parts by weight. In addition, since water is naturally always included in starches, there is no need to add water, but if you add water, it is necessary to add water to 100 parts by weight of starches, including the water originally contained in starches. It was found that the amount should be 3 to 20 parts by weight. Furthermore, it has been found that the amount of organic solvent should be 3 to 40 parts by weight per 100 parts by weight of starch. This result was based on these findings. This invention involves adjusting the amount of water to 3 to 20 parts by weight, including the water originally contained in the starch, and adding 3 to 40 parts by weight of an organic solvent. , further adding 3 to 10 parts by weight of caustic alkali in solid form, and adding alkylene oxide thereto and continuing stirring to react the alkylene oxide with starch or dextrin. Or it relates to a method for producing dextrin.

The starches used in the method of this invention are starch and dextrin, which is a decomposition product thereof.

All of them have granules with a size of about 1 to 100 microns. Starch includes various types such as corn starch, potato starch, and wheat starch. The method of the invention requires that the caustic alkali be added to the starch in solid state.

As the caustic alkali, caustic soda and caustic potash are used. Solid state refers to a state that has not turned into a solution. Therefore, caustic alkali may be one that has absorbed water, or may be one that has absorbed water and still remains in a solid state. It may be an undissolved mixture that settles as a solid. The amount of caustic alkali to be added is within the range of 3 to 10 parts by weight per 100 parts by weight of starch.

The reason for this is that if the amount of caustic alkali is less than 3 parts by weight, this reaction will be carried out in a dry manner, and the movement of the caustic alkali will not occur quickly, resulting in a non-uniform reaction. Moreover, if the amount exceeds 10 parts by weight, the starch will locally gelatinize, making the reaction uneven. The use of solid caustic alkali in the method of the present invention brings about unexpected results as described above, and the reason is thought to be as follows.

When the solution of caustic alkali comes into contact with starch, the system in the contact area becomes the same as adding a large amount of caustic alkaline solution to a small amount of starch, and non-uniformity occurs between the part that did not come in contact with the system. . As a result, the starch swells only in the contact areas and does not swell in the non-contact areas, resulting in non-uniform reaction. However, if the starch is in a solid state, even when the caustic alkali comes into contact with the starch surface, the starch does not partially swell and forms an alkaline adduct after being dissolved in the water and organic solvent contained in the system. do. By stirring the reaction system, the caustic alkali is rubbed against the starch and pulverized into fine powder, and the small amount of water contained in the system forms alkali adducts one after another. The reaction then proceeds. It is believed that the reaction can be carried out uniformly in this way. To carry out the method of this invention, it is necessary to add an organic solvent.

The amount thereof is within the range of 3 to 40 parts by weight per 100 parts by weight of starch. Among them, 10 are preferable.
It is between 20 and 20. Suitable organic solvents include those compatible with water, particularly lower alcohols such as methanol, ethanol, and isopropanol. others,
Butanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, etc. can be used. Suitable organic solvents are those that have the effect of moistening starches and slightly dissolving caustic alkali. The reason why the amount of organic solvent is limited within the above range is that if it is less than 3 parts by weight, alkali adducts will not be uniformly formed on the surface of starch, whereas if it exceeds 40 parts by weight, starch This is because it locally gelatinates or turns into a slurry, making the entire system in a state different from a slightly damp state. Water is also used in the method of the invention.

Water is kept to the minimum amount necessary to form caustic adducts on the surface of the starch. This is because when the amount of water increases, the starch becomes locally gelatinized, which makes side reactions more likely to occur, and the reaction cannot proceed in a slightly moist state. In addition, water is always contained at least a few percent in the starches used as raw materials.
There's no need to add anything. Therefore, water may not be added. Thus, the amount of water is 3 to 2 parts by weight per 100 parts by weight of starch, including the water originally contained in starch.
It is adjusted within the range of 0 parts by weight. Specifically, when starch contains only a small amount of water, water is added, and when starch contains a large amount of water, it is dried so that the water content is 3 to 20 parts by weight per 100 parts by weight of starch. It is adjusted to the part. In the method of this invention, a sealable container equipped with a stirring mechanism is used as a reaction vessel. First, starch is placed in this container, and then caustic alkali, an organic solvent and, if necessary, water are added. There is no particular restriction on the order in which the caustic alkali, organic solvent, and water are added, but when adding the caustic alkali in a solid state, avoid adding the caustic alkali and water at the same time, and first add the organic solvent and water if necessary. After that, it is preferable to add caustic alkali after stirring well. After adding these materials or before adding water and an organic solvent, the inside of the container is once depressurized to eliminate some of the air inside the container. The reduced pressure may be about 100ml/LH9. Thereafter, alkylene oxide is added to this to cause a reaction. Further, it is preferable that the bottom of the reaction vessel has a jacket structure so that heating and cooling can be freely performed from the outside. Note that the steps up to introducing the alkylene oxide can also be performed in an open container. As the alkylene oxide, ethylene oxide, propylene oxide, butylene oxide, etc. can be used.

The amount added varies depending on the degree of hydroxyalkyl group to be introduced, but is usually in the range of 15 to 50 parts by weight per 100 parts by weight of starch. In this invention method, after adding alkylene oxide, starch is added to
Maintain between 0 and 70°C.

If necessary for this purpose, the reaction vessel is heated externally.
The reason for maintaining this temperature is that if it is below 40°C, the reaction rate is slow and it takes a long time to complete, which is disadvantageous.On the other hand, if it is above 70°C, the starch locally gelatinizes and becomes powdery. This is because the reaction cannot proceed. When starch begins to react with alkylene oxide, the reaction is exothermic and generates heat, which means that it must be cooled from the outside. In this invention method,
The end of the reaction is known by the decrease in pressure within the system.

In other words, the reaction takes place at a temperature above the boiling point of the alkylene oxide, so the pressure in the system is high until the hydroxyalkylation reaction begins, and as the reaction progresses, the alkylene oxide is consumed, so the pressure in the system decreases. . Therefore, when the pressure in the system decreases and becomes constant, it can be considered that the reaction has ended. After the reaction is complete, an acid such as acetic acid is added to the resulting derivative to neutralize the caustic alkali.

Thereafter, in order to remove the added organic solvent or water, the product is dried under reduced pressure to obtain a product. According to the method of this invention, a small amount of solvent is used, and even if combined with water, the amount is less than 60 parts by weight per 100 parts by weight of starch, and half of the solvent is an organic solvent, so starch is Hydroxyalkylation can be carried out in a wet state.

As a result, the method of the present invention does not require a large-capacity reaction vessel, allows easy stirring, suppresses side reactions, and allows efficient reaction. Furthermore, according to the method of this invention, the degree of substitution of the hydroxyalkyl group can be adjusted as desired, and therefore can be increased. moreover,
After the reaction is complete, there are many advantages, such as ease of solvent removal. Moreover, the products obtained by the method of this invention have a quality that is as good as, if not better than, conventional products and can be directly used for the conventional uses of conventional products. Therefore, the method of this invention has high practical value. Next, the details of the method of this invention will be explained with reference to Examples.

Example 1 Corn starch (moisture content 13.5%) was added to a V-type blender.
) After adding 1000 f1, solid state caustic soda 5
09 and methanol 1009 separately, then 30
Stir well for a minute.

Transfer this mixture to a sealable container and reduce the pressure inside the container to 1.
The mixture was degassed under reduced pressure until the pressure reached 00 mmH9. Next, open the valve and inject propylene oxide 2709,
The temperature was raised to ℃ and stirred for 5 hours. During this time, the temperature inside the reaction vessel was maintained at 60°C. Thereafter, it was cooled, neutralized with acetic acid, and dried under reduced pressure for 30 minutes to obtain a product. The product thus obtained passed through all 100 mesh sieves, had a uniform pH of 6.5, and had a degree of substitution by hydroxypropyl groups of 0.53, making it a good product.

Furthermore, the reaction efficiency was 610 it), which was considered to be good. Comparative Example 1 In this comparative example, a product was obtained by processing in exactly the same manner as in Example 1, except that methanol was not used.

When this product 1009 was passed through a 100-mesh sieve, 17.2 g of product did not pass through the sieve.

The product that passed through the sieve had a pH of 6.0 and the degree of substitution by hydroxypropyl groups was 0.45, and was in a homogeneous state, but the product that did not pass through the sieve had a pH of 11.9 and the degree of substitution by hydroxypropyl groups was 0.45. was 0.21, it swelled, took on a granular shape, and was non-uniform as a whole. From the comparison between Example 1 and Comparative Example 1,
It has been found that since methanol is used in the method of this invention, a uniform product with a high degree of substitution can be efficiently obtained.

Example 2 Potato starch (moisture content 16%) 1 in a ball mill
After adding 0009, solid caustic soda 8
09 and ethanol 1509 were added separately, followed by stirring for 1 hour.

Transfer this mixture to a sealable container and reduce the pressure inside the container to 1.
The mixture was degassed under reduced pressure until the pressure reached 00 mmH9. Next, open the valve, inject propylene oxide 2709, and heat to 50°C.
and continued stirring for 8 hours. During this time, the temperature inside the reaction vessel was maintained at 50°C. Thereafter, it was cooled, neutralized with acetic acid, and dried under reduced pressure for 30 minutes to obtain a product. The product thus obtained passes through a 100-mesh sieve and has a pH of
It was uniform with a value of 6.5, and the degree of substitution by hydroxypropyl group was 0.50, indicating that it was a good product. Furthermore, the reaction efficiency was 56%, which was considered to be good. Comparative example
2 In this comparative example, a product was obtained by processing in exactly the same manner as in Example 2, except that ethanol was not used.

When this product 1009 was passed through a 100-mesh sieve, 20.39 pieces did not pass through the sieve.

The product that passed through the sieve had a pH of 6.0 and the degree of substitution by hydroxypropyl groups was 0.41, and was in a uniform state, but the product that did not pass through the sieve had a pH of 11.9 and a degree of substitution of 0.41. was 0.19, and it swelled and took on a granular shape and was non-uniform throughout. From a comparison between Example 2 and Comparative Example 2, it was found that because the method of this invention used ethanol, a uniform product with a high degree of substitution could be efficiently obtained.

Example 3 Tapioca starch (moisture content 14
(f)) After adding 10009, solid state caustic soda 609 and methanol 1509 were added simultaneously, and then 1
Stir for hours.

Next, after depressurizing and degassing until the pressure inside the container reached 100 mmH9, the valve was opened and propylene oxide 2
709 was injected, the temperature was raised to 50°C, and stirring was continued for 8 hours. During this time, the temperature inside the reaction vessel was maintained at 50°C.
Thereafter, it was cooled, neutralized with acetic acid, and dried under reduced pressure for 30 minutes to obtain a product. The product thus obtained had a degree of substitution by hydroxypropyl groups of 0.53 and was of good quality.

Moreover, the reaction efficiency was 60%, which was recognized as good.
Comparative Example 3 In this comparative example, the amount of water was brought close to the upper limit of the method of this invention, and the amount of ethanol was much greater than the upper limit, and the reaction was carried out in a slurry state.

Specifically, put corn starch (moisture content 13.5%) 10009 in a sealable container, and add 3 parts of caustic soda to it.
09 and water 609 and etanoichi) L/800f! and stirred for 30 minutes. Then, the pressure inside the container was increased to 100 m
After degassing under reduced pressure to mHg, open the valve and inject propylene oxide 2709, raise the temperature to 40°C and continue stirring for 24 hours.
It was kept at ℃. Thereafter, it was cooled, neutralized with acetic acid, the solvent was filtered off, and then dried under reduced pressure for 2 hours to obtain a product. The product thus obtained had a degree of substitution by hydroxypropyl groups of 0.31, and was found to have a low degree of substitution.

Claims (1)

[Claims] 1. For 100 parts by weight of starch or dextrin, the amount of water is adjusted to 3 to 20 parts by weight, including the water originally contained therein, and 3 to 40 parts by weight of organic Add a solvent, add 3 to 10 parts by weight of caustic alkali in solid form, and add alkylene oxide thereto, continue stirring to react the alkylene oxide with starch or dextrin. A method for producing starch or dextrin. 2. The method according to claim 1, wherein the organic solvent is methanol, ethanol, or propanol. 3. The method according to claim 1 or 2, wherein the caustic alkali is caustic soda or caustic potash.