JPS60158138A - Preparation of disodium dl-malate hudrate - Google Patents

Abstract

PURPOSE:To crystallize the titled compound useful as a food additive easily from an aqueous mixture solution of disodium dl-malate with sodium carbonate in obtaining the titled compound, by keeping the concentration and temperature of the above-mentioned aqueous mixture solution under specific conditions. CONSTITUTION:The concentration of an aqueous mixture solution of disodium dl-malate with sodium carbonate is adjusted to establish the following relation between the concentration (y)% of the disodium dl-malate and the concentration (x)% of the sodium carbonate; y=b (1-x/100) (b is 42-55), and the aqueous mixture solution is kept at 15-40 deg.C to crystallize and obtain the aimed disodium dl-malate. The sodium carbonate is preferably dissolved in the aqueous solution of disodium dl-malate, at 30-50 deg.C, preferably 40-45 deg.C under stirring. The pH of the aqueous solution of disodium dl-malate after dissolution of the sodium carbonate is adjusted to 10.5-12.0, preferably 11.0-11.5.

Description

DETAILED DESCRIPTION OF THE INVENTION The object of the present invention is to provide dl-disodium malate in an industrially advantageous manner. That is, the object of the present invention is to provide a method for easily separating low concentration dp-disodium malate as crystals of dl-disodium malate hydrate in the presence of sulfur-IJium carbonate.

Disodium malate is used as a food processing additive and buffering agent, and the demand for it is increasing year by year.

Disodium monomalate can be easily synthesized by reacting an aqueous solution of dl-malic acid with a solid or aqueous solution of sodium hydroxide or sodium carbonate.

However, obtaining this salt as crystals from an aqueous solution is difficult due to the extremely high solubility of disodium malate, which makes it difficult to crystallize, and the formation of several types of hydrate crystals from an aqueous solution. There are many problems.

For example, according to Japanese Patent Publication No. 43-9530, d, 71-
V of crystallizing apple bud sodium as monohydrate
There are examples in which the product is heated to evaporate to 110 to 130°C and allowed to stand until it crystallizes below 30°C, but since it takes a long time for crystallization to stand still, the crystals that crystallize tend to form solid lumps as a whole. However, it has the disadvantage that subsequent handling is extremely laborious, making it unsuitable for mass production.

According to JP-A-52-77010, there is an example in which the concentration of an aqueous disodium malate solution is set to 65% to 75% and then cooling is performed with stirring to crystallize a monohydrate in a fluid state. It will be done. Furthermore, JP-A No. 52-14721 describes an example in which an aqueous solution of disodium malate is concentrated to a concentration of 50 to 65% and then cooled with stirring to crystallize the three water products in a fluid state. Can be seen.

All of these methods are characterized in that an aqueous solution of disodium malate is adjusted to a high concentration and then cooled to perform crystallization. Furthermore, according to the above-mentioned Japanese Patent Application Laid-Open No. 52-14721, at a concentration of 45%, the amount of crystallization is small even when cooled with water.
It is stated that at concentrations below 50%, cooling to below 5°C is required for crystallization, which indicates that disodium malate has a very high solubility and is difficult to crystallize. Therefore, in order to industrially produce disodium malate hydroxide, a highly concentrated aqueous solution is required for crystallization, which requires a large amount of disodium malate, and the mother liquor from which the crystals are separated contains A large amount of disodium malate remains.

Malic acid is an expensive chemical and the presence of a large amount of salt remaining in the mother liquor is industrially disadvantageous and unsatisfactory. In view of these points, the present inventor has determined that a large amount of crystals can be easily crystallized from a low-concentration aqueous solution of disodium malate even at room temperature in each season without forcibly cooling it below room temperature. As a result of various research into an industrially advantageous manufacturing method with low sodium content, we have arrived at the invention of a method. That is, the present invention provides a method for producing dfl-disodium malate hydrate from a mixed aqueous solution of dl-disodium malate and sodium carbonate, in which the concentration of dfl-disodium malate is y% and the concentration of sodium carbonate is x.
Adjust the concentration so that the relationship between % and % is as follows:
A method for producing d1-IJ resin sodium malate trihydrate, which is characterized in that dQ-disodium malate trihydrate is crystallized by holding in G d 1 required to form dl-disodium malate with sodium hydroxide equivalent to ~90 molt and sodium carbonate equivalent to 10-50%.
- Add IJ malic acid by an appropriate method, add water if necessary, and make sure that the concentration of dl-disodium malate (y%) and the concentration of sodium carbonate (X) satisfy the following relationship: Adjust the concentration of yeast, 15-40℃
The present invention relates to a method for producing a dQ-disodium malate hydrate, which comprises maintaining the dl-disodium malate hydrate at a temperature of 100 to 100 ml.

The reason why sodium carbonate is used to reduce the solubility of dl-sodium malate in the present invention is that among sodium compounds, sodium carbonate is particularly suitable. Baking soda also reduces the solubility of sodium malate (dll-'), but is not effective due to its low solubility. Although sodium hydroxide has a great effect on lowering the solubility of dl-sodium malate, when sodium hydroxide is used, the coloring of the dl-disodium malate solution becomes significant and crystallization becomes difficult to occur. There are drawbacks such as coloring of the crystals obtained, which poses problems in use.

However, when sodium carbonate is used, the aqueous solution of dl-disodium malate is only slightly colored, which lowers the solubility of dl-disodium malate, and as a result, crystallization becomes easy, and the crystals are white without being colored. .

The solubility of sodium carbonate in an aqueous solution of dl-apple diwotrium reaches its maximum at around 35°C and tends to decrease as the temperature rises, so it may be difficult to dissolve at temperatures above 50°C, and preferably at 35 to 50°C. 40-4
Preferably, it is dissolved under stirring at 5°C.

The pH of the dfi-disodium malate aqueous solution after dissolving sodium carbonate is 10.5 to 12.0, preferably 1.
Adjust to 1.0-11.5. When the pH is below 10.5, sodium hydrogen carbonate is formed in the solution, and its solubility is very low, so fine crystals often crystallize out and pure d
Disodium l-malate hydrate cannot be obtained. Also, 1
If it exceeds 2, the amount of hydroxide in the solution will increase, which will significantly increase the coloring of the solution, and the resulting dl-disodium malate hydrate will become colored, which is undesirable.
If the pH is lower than 10.5, add sodium hydroxide, and if it is higher than 12, add dl-malic acid or sodium bicarbonate to adjust the pH to 10.5-120, preferably 1□, 0-11.
Adjust to 5.

In the present invention, the concentrations of dl-disodium malate and sodium carbonate are selected from the range expressed by the above formula y=bc1--) 00 . The concentration (y) of disodium malate is the minimum value given by y=b(1--) 00 (b=42 preferably 45
Even if a large amount of sodium carbonate is dissolved, if the concentration is lower than the concentration calculated from d, Q-malate cina), the amount of IJum crystallized will be small and it will not be used industrially. Also, the maximum value given by (b=55 preferably 50
If the concentration is larger than the concentration calculated from will not be adopted.

When the concentration of sodium carbonate (x) is expressed in relation to the concentration of disodium malate (y), b is 42≦b<46, preferably 45
If the concentration is lower than that which occurs when ≦b≦46 and 46≦b≦55, preferably when 46≦b≦50 (HA-'), the effect of reducing the solubility of disodium malate is small;
2≦b≦55 Preferably 45≦b〈Even if the concentration is higher than 50, no particular effect will be observed; on the other hand, if it is too high, crystallization of sodium carbonate will occur due to the cooling temperature, resulting in pure malic acid cina) I
Since Jium hydrate cannot be obtained, neither method is adopted.

In the present invention, while stirring the disodium malate solution,
Crystallization is performed by cooling to 5-40°C. Seed crystals do not need to be added and may or may not be added. The resulting crystal slurry has good fluidity, is easy to transport by pump, and has good separability from the mother liquor.

In the method of the present invention, cooling is performed to a temperature selected from 15 to 40°C, and the selection of the cooling temperature is extremely important. That is, in order to obtain pure dl-disodium malate hydrate, the concentration of sodium carbonate in the solution that is crystallized is lower than the concentration of sodium carbonate in the solution at the eutectic point of dl-disodium malate and sodium carbonate at a cold temperature. Sodium carbonate concentration must be low. Conversely, if the concentration of sodium carbonate in the mother liquor increases, crystallization of sodium carbonate will occur, making it impossible to obtain a pure d-trimalate disodium aqueous product.

FIG. 2 shows the solubility curves of disodium d-trimalate and sodium carbonate. 1 to 8 in the figure are 15 and 20, respectively.
, 25, 30, 35, 40.45 and d at 55°C
The solubility of disodium trimalate is shown. 9 to 13 indicate the solubility of sodium carbonate at 15.20.25.30 and 35°C, respectively.

14 to 22 are d disodium trimalate and sodium carbonate, respectively 15 and 20. '23 (dotted line) indicates the eutectic point at 25, 30 and 35°C. As can be seen from FIG. 2, the solubility of sodium carbonate in a K d, Q-disodium malate solution tends to decrease as the temperature decreases.

That is, on the low temperature side, the concentration range of sodium carbonate in which dn-IJ malate dinate IJium trihydrate crystallizes becomes narrower.

Therefore, the cooling temperature must be changed depending on the concentration of sodium carbonate in the disodium malate solution.

In the method of the present invention, the sodium carbonate concentration (x) in the dL-disodium malate solution and the lowest temperature at which it can be cooled are 15°C. When a solution with sodium carbonate concentration (X) is cooled to 15°C, the sodium carbonate concentration in the mother liquor is d! - Since the concentration of sodium carbonate in the aqueous solution containing disodium malate and sodium carbonate is lower than the concentration of sodium carbonate in the solution (approximately 5%) at the eutectic point of 15°C, even if the solution is cooled to 15°C, sodium carbonate aqueous substances will crystallize. There is nothing to do (see Figure 2). For the same reason, the temperature is 20°C and the temperature is 25°C. That is, the lowest temperature at which sodium carbonate can be cooled is 25°C for sodium carbonate, 20°C for sodium carbonate, and 15°C for sodium carbonate. If the cooling temperature is higher than the respective temperature determined by the IJum concentration, pure chu-disodium malate trihydrate can be obtained, but if it is cooled below the respective temperature, sodium carbonate will crystallize. Cooling below this temperature must be avoided as this may occur.

Cooling at different temperatures depending on the concentration of IJium is advantageous because it increases the amount of crystallization, but it is difficult to control the process to avoid contamination with sodium carbonate. During this period, the carbonic acid is
It is desirable to divide the IJium concentration (x') into two and cool the lower concentration side to an intermediate temperature between the two.

Next, a method for reusing the mother liquor after separating and collecting crystals of disodium malate trihydrate from a mixed aqueous solution of Q-disodium malate and sodium carbonate will be explained.

FIG. 1 shows the solubility curve of dL-disodium malate. In the figure, 1 to 6 indicate the solubility at each temperature in solutions where the sodium carbonate concentration in the solution is 0%, 3%, 5%, 7%, 10%, and 12%, respectively. As can be seen from Figure 1, K
Disodium d,9-malate has a very high solubility in water, and the mother liquor after separating and collecting the aforementioned crystals of disodium dL-malate trihydrate usually contains 50 to 5
0q6 d, C-'+) nate cina) Because it contains IJium, the mother liquor is used repeatedly in industry.

According to JP-A-52-14721, when reusing the mother liquor, the mother liquor is reused in the reaction step and the reaction is carried out.

If the steps of concentration and cooling are repeated, the mother liquor becomes noticeably colored, and even if it is cooled with stirring, no crystallization occurs immediately. Therefore, after heating and concentrating the reaction solution to a concentration of 65 to 75, the concentrated bath liquid is mixed with the mother liquor to bring the concentration to 50 to 65.
The mother liquor is adjusted to the desired temperature and crystallized in the crystallization process.
Examples of methods used can be found. That is, the aqueous disodium malate solution obtained by the reaction is heated and concentrated to 65~
There is a proposal for a method in which a solution with a high concentration of 75% is formed and the solution heated to a high temperature is mixed with a mother liquor cooled to around room temperature to bring the temperature of the mixed solution close to a temperature suitable for crystallization. being done.

However, the process of heating and concentrating an aqueous solution of disodium malate is not preferred not only for economical reasons due to solution handling and energy consumption (but also from the viewpoint of suppressing by-products) (industrially unsatisfactory).

As a result of further investigation into the development of an industrially advantageous production method, the present inventors found that by returning to the mother liquor reaction step and carrying out the reaction by adding sodium hydroxide, sodium carbonate, and d-malic acid in the mother liquor, (Compared to the case where sodium hydroxide is reacted alone, the temperature rise of the solution due to the reaction is small, and the temperature of the solution is hydroxylated.) By changing the reaction ratio of IJium and sodium carbonate, the temperature of the reaction solution can be arbitrarily selected. case,
If the reaction is carried out with IJum alone (carbonic acid), the viscosity of the mother liquor is high and the bubbles generated by carbon dioxide are difficult to break, so the solution overflows from the container and the reaction cannot proceed. ) When a reaction is carried out using IJum and sodium carbonate at the same time, the carbon dioxide in the bubbles is quickly absorbed by the sodium hydroxide in the solution by stirring, and the bubbles disappear immediately. The present invention was completed by discovering that the so-called bubble removal is very good, and therefore the reaction can be carried out quickly.

Next, the method of the present invention will be explained in more detail.

In the present invention, the mother liquor is returned to the reaction step, and the synthesis of disodium malate by the reaction of malic acid with sodium hydroxide and sodium carbonate is carried out in the mother liquor. The mother liquor obtained when the crystals are separated is purified by adding a decolorizing agent such as activated carbon as necessary.

The amount of sodium hydroxide used in the present invention is selected from 50 to 90 molt of sodium required to neutralize dfi-malic acid, and sodium carbonate (or at least selected from 10 to 50 molt of sodium, an amount to compensate for this). The reaction is carried out by dissolving or dispersing the solution in the mother liquor on a plate where the sodium hydroxide is less than 50 mol. The viscosity of the product is high (which makes subsequent handling difficult. Furthermore, as the amount of sodium carbonate reacts increases, the amount of foaming due to carbon dioxide increases, making it difficult to break the foam, so the reaction takes a long time and is not used. ℃・
.

If the amount is more than 90 molt, the temperature of the solution will rise sharply to a high temperature exceeding 70° C., which is undesirable and is not used.

The hydroxide used in the present invention may be either a solid or aqueous solution. Sodium carbonate is an anhydrous salt (soda ash),
Any hydrate may be used, but a powdery one with fine particles is preferable from the viewpoint of solubility and reactivity. dfi-malic acid may be in the form of a solid, slurry, or aqueous solution, and if it is a solid, it is preferably in the form of a powder that is easily dissolved or reacted, but the concentration in terms of the reaction solution is 65
Adjust the amount of each ingredient and water so that it reaches ~85%, and add more water if necessary.

Water can be added at any time before, during, or after the reaction.
°C) and the concentration in terms of reaction solution (65 to 85 °C). Sodium carbonate (to compensate for the shortage of sodium hydroxide) is dissolved or dispersed in the mother liquor on a plate and the reaction is carried out with stirring.It is stirred to the extent that the generated carbon dioxide bubbles are sufficiently mixed with the solution. The bubbles generated by the reaction are immediately destroyed, and the carbon dioxide inside is released into the air, but the remaining bubbles are mixed with the solution, absorbed by sodium hydroxide, and returned to sodium carbonate, forming bubbles. disappears (that is, carbonic acid is formed as a result). Most of the malic acid that reacted with IJium reacted with sodium hydroxide.

Carefully add malic acid and carry out the reaction. After the reaction is completed, the pH of the solution is adjusted to 10.5 to 12.0, preferably 1.
Adjust to 1.0 to 11.5 by adding sodium hydroxide, phosphoric acid, or sodium hydrogen carbonate.

If the temperature of the solution exceeds 60°C during the reaction, most of the emitted carbon dioxide will eventually be released into the air, but if it is below 60°C, some will dissolve into the solution and form hydrogen carbonate. It exists as sodium, which lowers the pH. However, in this case, hydroxide) is added to PI(
When adjusted to 1O95 to 12.0, preferably 11.0 to 11.5, IJum changes to sodium carbonate.

The dρ-malic acid used in the present invention is reacted in the mother liquor, the pH is adjusted, and if necessary, sodium carbonate is added to dissolve the solution, and the d, Q
-Use necessary and sufficient amounts of calculation so that the concentrations of disodium malate and sodium carbonate are selected from the range indicated by ia.

According to the present invention, if the mother liquor is returned to the reaction step and reused, by selecting the reaction ratio of sodium hydroxide and sodium carbonate, the reaction can be carried out without heating or cooling in the reaction step, and after the reaction The solution temperature can be adjusted to advantage for the next crystallization step. The reaction time is therefore shortened.

In the present invention, heating and concentration are not performed in all steps. In the present invention, since the mother liquor is used as a solvent for the reaction, the concentration in terms of reaction solution can be made substantially high, and further concentration is not required.

This is extremely advantageous industrially, and by adjusting the reaction temperature and omitting the concentration process, coloration and crystallization of the solution caused by by-products caused by high-temperature heating during the reaction and concentration process are less likely to occur. Things can be avoided.

1. That is, if the reaction is carried out according to the present invention, the reaction time can be shortened, the concentration step can be omitted, and the temperature of the reaction solution can be favorably selected for the crystallization step, and the entire process can be simplified, such as shortening the cooling period during crystallization. be done.

On the other hand, it is very difficult to increase the concentration of the reaction solution to 65-85% without carrying out heating and concentration using the method for producing hydrates proposed in the above-mentioned Japanese Patent Application Laid-Open No. 52-14721. In other words, if the reaction is carried out at such a high concentration, the reaction solution will generate heat and reach a high temperature of over 100°C, and if it is cooled, the reaction solution will have low water content and high viscosity, making it difficult to carry out a sufficiently uniform reaction and making it difficult to handle. Therefore, it is impossible to prepare a highly concentrated solution without heating, cooling, or concentrating.

When the mother liquor is reused in the reaction step according to the method of the present invention and crystallization is repeated, disodium malate trihydrate crystallizes immediately after the 122nd time, and there is no change from the 1st to 12th times. Crystals were obtained. However, no change was observed in the crystals crystallized for the 6th time, but coloration was observed in the mother liquor, so prior to the use of the mother liquor for the 7th time, 1% activated carbon was added for purification treatment, and as a result, no coloration was observed again. ,
Crystals of Q-malic acid cina) IJium trihydrate were obtained.

Various methods can be used to measure the concentration of dfi-disodium malate and sodium carbonate in a solution, but the following method is convenient because it can be measured quickly.

〔sodium carbonate〕

Precisely weigh approximately 52 ml of sample solution into S1? ) of water to dissolve it. Add methyl orange solution as an indicator, titrate with N-Hc4 bleaching solution until the liquid turns orange, and add another 2 to 3 ml (total A# +7, boil gently for 2 to 3 minutes and cool.

From now on, add phenolphthalene solution as an indicator, and
After titration with a NaOH standard solution, the concentration of sodium carbonate is calculated using the following formula.

[Disodium malate]

Accurately weigh approximately 522) of the sample solution and dilute to the marked line in a 250-volume flask. Take that 25- and pass it through the column below, then fill the column with 50#+7! Wash twice with pure water. Combine the effluent and washing liquid, titrate with N/1ONaOH standard solution using phenolphthalene solution as an indicator until the solution turns red (Crn1), and calculate the concentration of disodium malate using the following formula.

〔column〕

Pour the strongly acidic cation exchange resin into a glass tube for an ion exchange resin column with an inner diameter of about 15 mm according to the usual method, and heat it to a height of 2.
Prepare a 0 cm column. The resin is passed through N-HC and then purified water to form an H-form for testing. Passage and washing of the sample solution is carried out at SV, 10-20 (7-13 m1/m1n).
) speed.

Next, the present invention will be explained in more detail with reference to Examples. Note that "chi" and "part" are "parts by weight" unless otherwise specified.
and "parts by weight".

Actual example 1 697 parts (5.2 mol) of malic acid at 6°C in 700 parts of water
of 48% sodium hydroxide solution under stirring.
After carefully adding 50 parts to adjust the pH of the solution to 8.3, the solution was knitted under reduced pressure to obtain 2055 parts of a concentrated solution.

The concentration of dfi-disodium malate in this concentrate is 45
It is Chi. This concentrated liquid was cooled to 50°C, 190 parts of sodium carbonate (soda ash) powder was added and dissolved while stirring, and filtration was performed to remove suspended matter.
Got 45 copies. The concentration in the filtrate was 41.2% du-disodium malate, 8.5% sodium carbonate, and P
It was H11.3. The obtained filtrate was left under stirring overnight.
When the mixture was washed with water and cooled to room temperature (approximately 25°C), du-disodium malate hydrate crystallized to form a slurry. The slurry solution had no lumps or crystals, had good fluidity, and was very easy to stir and separate the mother liquor. The resulting slurry solution was separated from the mother liquor using a centrifuge to obtain hydrate crystals of disodium malate. The pH of this crystal is 10.
It was 2.

0.6% powder d based on the wet crystals obtained
fi-1 malic acid was added and mixed and dried at 50°C to obtain 530 parts of a six-color disodium malate hydrate.

After drying, the crystals have a pH of 8.0 and a moisture content (crystal water) of 23.
．． dfi-disodium malate with 2% needle crystals 3
It is considered to be a hydrate, and no contamination of IJium (carbonate) was observed.

Next, malic acid and sodium hydroxide were reacted, and the concentration of the malic acid cina) IJum solution was varied, and a solution in which sodium carbonate was dissolved in various proportions was cooled with stirring to crystallize. The results are shown in Table 1.

Table 1 Reference Example 1 In the same manner as in Example 1, reaction and concentration were carried out to dissolve sodium carbonate, resulting in 41.5% du-disodium malate.
% and a solution with a sodium carbonate concentration of 8.3% was obtained. The lowest temperature at which this solution can be cooled is from 25°C. This solution was cooled to 18° C. while stirring to effect crystallization, and the crystallized crystals were separated using a centrifuge to obtain hydrate crystals. When the obtained crystals were added to a dilute hydrochloric acid solution, intense foaming occurred, and the contamination of sodium carbonate hydrate was clearly observed.

Example 2 To 1527 parts of mother liquor cooled to around room temperature, 170 parts of 48% hydroxide solution, 7 parts of granular sodium hydroxide
5 parts and 89 parts of sodium carbonate (soda ash, same hereinafter) were added and dissolved, and while stirring the solution, 376 parts of du-malic acid was carefully and gradually added to carry out the reaction. When malic acid was added to the solution, it foamed violently, but the bubbles disappeared quickly, and the reaction was completed in a short time without the liquid overflowing from the container. The liquid temperature at the end of the reaction was 53°C. The pH of the solution was slightly low at approximately 10, so 48% sodium hydroxide solution was added to adjust the pH to 11.3, and then 17 parts of sodium carbonate was added to dissolve the solution.To remove suspended matter, filtration was performed to obtain 2217 parts of a filtrate. Ta. The reaction ratio of sodium hydroxide and sodium carbonate in this reaction is 7:30, and the concentration in terms of reaction solution is 74.1. The concentration of the obtained filtrate was measured and found to be 47.1% dfi-disodium malate and 48% sodium carbonate. The lowest temperature at which this filtrate can be cooled is from 20°C.

This filtrate was cooled to 20° C. while stirring to perform crystallization. The obtained slurry of malic acid cina) IJium hydrate crystals had fluidity, and the crystals could be easily separated from the mother liquor using a centrifuge. 0.5 malic acid for the obtained crystals
tib was added and mixed, and the result of drying at 508C was PH7.9.
670 parts of dρ-disodium malate hydrate were obtained.

In addition, 1482 parts of mother liquor was obtained. The obtained hydrate crystals had a water content of 23.1% and were trihydrate. Subsequently, a second reaction was carried out in the same manner as described above. That is, the obtained mother liquor 1
To 482 parts, 84 parts of 48 sodium hydroxide solution, 109 parts of granular sodium hydroxide, and 115 parts of sodium carbonate were added, dissolved, and carefully mixed with 37 parts of dρ-malic acid.
6 parts was added to carry out the reaction, and the final pH of the liquid was 114.
Adjusted to. The solution temperature was 54°C. Subsequently, filtration was performed to obtain 2124 parts of filtrate. The concentration of the filtrate is dll-'
) Disodium malate 47.8%, sodium carbonate 5.
It was 3 chi. The filtrate was cooled to 20° C. with stirring to effect crystallization. The resulting crystals [0.6% of IJ malic acid were added and mixed and dried at 50°C to obtain 653 parts of crystals with a pH of 8.0. In addition, 1420 parts of mother liquor was obtained. This mother liquor was further repeatedly used for the next reaction. These results are shown in Table 2.

The water content of the crystals was measured using Karl Fischer reagent.

Table-2

[Brief explanation of drawings]

FIG. 1 shows the dissolution curve of dρ-disodium malate in a constant concentration sodium carbonate solution corresponding to each temperature. FIG. 2 shows the isothermal dissolution curve of dρ-disodium malate. Patent Applicant Taiyo Chemical Co., Ltd. Procedural Amendment Officer (Voluntary Amendment) February 2, 1919 Special Patent No. 1 [Director General Kazuo Sugi (Right) 1.81 Displays Patent Applications 1973-/, 2 and Relationship to Otsuko case Patent applicant address 9-2-7 Kameido, Koto-ku, Tokyo Name Taiyo Kagaku Kogyo Co., Ltd. 4, Agent G Contents of amendment (1) / page 3 / line 3 “jθ~30chi” " is supplemented with "30-5θchi". (2) Correct page 23/line "Height 20 degrees" to [tube size, 2 Q Cttb J. +3), 100% of page 27 line “2chi: 30 section”: 3θ
"Ch," he corrected.

Claims (2)

[Claims] (1) In the method of producing dfi-disodium malate hydrate from a mixed aqueous solution of dfi-disodium malate and sodium carbonate, dll-') Concentration of disodium malate y% and concentration of sodium carbonate X% Adjust the concentration so that the following formula % formula % holds true,
dfi-malate disodium hydrate (dll-malate disodium) IJ
A method for producing umum hydrate. (2) In the method of producing dfi-disodium malate hydrate from a mixed aqueous solution of dρ-disodium malate and sodium carbonate, dl-') concentration of y% of disodium malate and X% of sodium carbonate The concentration was adjusted so that the following formula (% formula %) was established, and the temperature was 15 to 40℃.
dρ-disodium malate hydrate is separated from the mother liquor obtained).
Add dl-IJ malic acid necessary to form sodium hydroxide equivalent to molti and sodium carbonate to dl-disodium malate equivalent to 10 to 50 molti by an appropriate method, and add water as necessary. and the concentration y% of dl-disodium malate and the concentration x% of sodium carbonate are Y
= b(1--) OO However, the relationship b; 42 to 55 is established, and the pH of the mixed solution is set to 10.5.
-12.0, and the temperature of the mixed solution was adjusted to 15-40.
1. A method for producing dl-disodium malate hydrate, which comprises maintaining the hydrate at 0.degree. C. to crystallize disodium malate hydrate.