JPH05320201A - Purification of natural water-soluble organic macromolecular compound - Google Patents

Abstract

PURPOSE:To remove easily trace heavy metal ions from a natural organic macromolecular compound to a very low level. CONSTITUTION:The process comprises adding a water-soluble salt and/or a water-soluble base to a solution of a natural water-soluble organic macromolecular compound and treating the resulting solution with an anion exchange resin to obtain a solution freed from heavy metal ions and having a pH of 9.0 or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying a polymer compound by adsorbing and removing heavy metal ions contained as impurities in a natural polymer. According to the purification method of the present invention, a polymer having an extremely low content of heavy metal impurities can be obtained, and it can be used for the purification of polymer compounds in general chemical industry, especially in polymer chemical industry, photographic chemical industry, and food chemical industry.

[0002]

2. Description of the Related Art If a heavy metal such as iron or manganese is contained as an impurity in an organic natural polymer compound, particularly a protein, various quality deteriorations such as coloration, discoloration or toxicity are caused. Particularly, in the case of gelatin which is a raw material of a photographic light-sensitive material, even if a trace amount (about several ppm) of heavy metal ions such as iron, copper and lead is contained, the sensitivity and gradation are adversely affected. Therefore, in manufacturing gelatin, it is necessary to carefully select raw materials to be used and to thoroughly clean the manufacturing process.

Conventionally, as a method for removing heavy metal ions, a purification method using a cation exchange resin is generally known. However, heavy metal ions contained in a solution of an amphoteric polymer such as a protein cannot be removed by a cation exchange resin because the binding force with the polymer is strong.

There is also a method of using a chelate resin as another method for removing heavy metal ions, but the chelate resin has low strength and its cost is higher than other ion exchange resins.

Furthermore, attention is paid to the fact that metal ions such as iron, cobalt, copper and zinc form complex anions, which are often adsorbed by anion exchange resins, and iron ions contained in concentrated hydrochloric acid (yellow coloring) There is also a report in which the causative substance (of) was changed to a complex anion to remove it. However, in the case of proteins, especially gelatin, significant decomposition occurs in the strongly acidic region, and such a method cannot be used.

An object of the present invention is to provide a method for easily removing and purifying heavy metal ions contained as impurities in natural polymers, particularly proteins and polysaccharides.

[0007]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that proteins such as gelatin,
Alternatively, the inventors have completed the invention with the finding that when a neutral salt or a base is added to an aqueous solution of a polymer such as a polysaccharide, a high removal rate of heavy metal ions can be obtained with an anion exchange resin.

The present invention comprises adding a water-soluble salt and / or a water-soluble base to a water-soluble organic natural polymer solution and then treating the solution with an anion exchange resin to obtain a treatment solution having a pH of 9.0 or more. The present invention provides a method for purifying a water-soluble organic natural polymer compound, which is characterized by removing ions.

Examples of the organic natural polymer compound to which the purification method of the present invention is applied include proteins such as gelatin, glue and casein; various natural polymers such as alginic acid and polysaccharides such as starch, and derivatives thereof. According to the purification method of the present invention, various heavy metal ions such as iron, copper, lead, manganese, and cobalt are removed.

In the purification method of the present invention, an easily soluble salt or base is added to an aqueous solution of an organic natural polymer to convert a cationic heavy metal ion into an anionic complex, and then the ion is exchanged with an anion exchange resin. Are removed by adsorption. The pH range when treated with an ion exchange resin is preferably a neutral range in order to prevent hydrolysis of the polymer compound. On the other hand, when salts are used, the amount used can be small in the alkaline range, so the pH range is selected in consideration of these. Usually, a weakly acidic to neutral or weakly alkaline region having a pH of 5 to 9 is preferable. The salts and bases may be used alone or in combination of two or more.

As the salt, an appropriate water-soluble salt is used, but it is usually preferable to use an alkali metal salt such as hydrochloric acid or sulfuric acid, an alkaline earth metal salt or an ammonium salt. Specifically, it is preferable to use sodium chloride, calcium chloride, potassium sulfate or the like. The amount of salt added depends on the type of polymer to be treated and the concentration of salt that already exists, but the p of the solution after passing through the anion exchange resin column is
Adjust so that the H value is 9 or more. For example, it is preferable to adjust the anion concentration contained in the sample solution before the anion exchange resin treatment to be 2000 ppm or more.

The base may be an inorganic base that dissociates in an aqueous solution to generate a hydroxide ion, and specifically, an alkali metal such as sodium hydroxide, potassium hydroxide or calcium hydroxide or an alkaline earth metal. It is preferable to use the above hydroxide, ammonia, or the like. The amount of alkali added depends on the type of the sample solution and the salt concentration, but the pH of the sample solution before the anion exchange resin treatment is adjusted to 8 or more in order to adjust the pH after the anion exchange treatment to 9 or more. It is good to use that as a guide.

The polymer solution thus treated with salt and / or base is then treated with an ion exchange resin. Such anion exchange resin is a strongly basic anion exchange resin having a three-dimensionally polycondensed polymer as a base and having a quaternary ammonium group as an exchange group, a weakly basic anion exchange resin having a primary to tertiary ammonium group. Any anion exchange resin is used. The treatment conditions using these are not particularly limited, and a normal ion exchange treatment method can be used as it is, and the amount of ion exchange resin is adjusted according to the amount of salts in the sample solution, pH, the treatment rate, and the like.

The polymer solution treated with the anion exchange resin is neutralized with an acid such as sulfuric acid, base or nitric acid.
Then, it is dried by a known method to obtain a polymer compound.
For example, in the case of gelatin, it is cooled and solidified, and then dried by a known method such as drying under reduced pressure. The thus obtained polymer compound can remove heavy metals, which was conventionally insufficient, and the content of heavy metals is extremely low.

[0015]

EXAMPLES Next, the present invention will be described more specifically based on examples.

Example 1 To 100 g of gelatin powder obtained by treating ossein with alkali, 900 mL of pure water was added. This was left standing for 30 minutes and then stirred at 50 ° C. for 30 minutes to obtain a gelatin solution. The pH value of this solution was 6.0. Four similar solutions were prepared, one of which was used as a comparison sample as it was, and the other three were added with a NaOH solution (concentration 2% (weight%, the same below)) to adjust the pH of the gelatin solution to 7.0, respectively. Adjusted to 8.0 and 9.0. Each of these four samples was treated with an anion exchange resin as follows to remove heavy metal ions.

Strong cation anion exchange resin (DIAION PA-) regenerated into OH ^- type with 5% NaOH solution.
316, Mitsubishi Kasei Kogyo Co., Ltd.) resin tower (diameter 3 cm)
To 100 mL. The total amount of the gelatin solution was supplied to each resin tower at a liquid flow rate of 100 mL / hour. Samples with different pH values obtained from each resin tower were adjusted to pH value 6 with sulfuric acid.
After being neutralized into water, it is solidified at 5 ° C and dried under reduced pressure to contain water 8
% Gelatin was obtained. Jelly strength, viscosity, Fe content and Cu content of these gelatins were measured. The jelly strength and viscosity were measured by the Pagui method, and the Fe and Cu contents were measured by the atomic absorption method. The results of these measurements are shown in Table 1 together with the pH values before and after passing through the anion exchange resin.

Table 1 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Test material Before and after liquid flow Jelly strength Viscosity Fe content Cu content (pH) (pH) (g) (mp) (ppm) (ppm) ──────────────────────────── ──────── Comparative sample 6.0 6.9 293 82 5.1 Sample 2.1 7.0 7.9 291 80 80 4.9 1.6 〃 2 8.0 9.1 292 81 3.8 1.0 〃 3 9.0 9.7 292 80 3.4 3.4 1.1 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━

Example 2 A 10% gelatin solution (pH 6.0) was prepared in the same manner as in Example 1. Four similar sample solutions were prepared, and one was used as a comparison sample as it was. For each of the other three samples, sample 1 contains 0.4 g (400
(0 ppm: same as for gelatin)
8g (8000ppm), sample 3 1.2g (12000ppm) N
aCl was added as a 10% aqueous solution. Table 2 shows the results of the anion exchange treatment performed on these four samples under the same conditions as in Example 1.

Table 2 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Test material Before and after passing Jelly strength Viscosity Fe content Cu content (pH) (pH) (g) (mp) (ppm) (ppm) ──────────────────────────── ──────── Comparative samples 6.0 7.0 293 82 5.0 2.3 Sample 1 6.0 9.4 293 81 1.7 1.7 1.3 〃 2 6.0 10.2 292 82 1.3 1.2 〃 3 6.0 10.8 293 81 1.5 1.5 1.1 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━ As shown in Tables 1 and 2, the amount of Fe and Cu in the polymer is very small when the pH after passing the liquid is higher than 9.

Example 3 A 10% gelatin solution (pH 6.0) was prepared in the same manner as in Example 1. Four similar sample solutions were prepared, and one was used as a comparison sample as it was. NaOH solution was added to the other three samples to adjust the pH of the gelatin solution to 7.0. With respect to these gelatin solutions, 0.1 g (1000 ppm: gelatin, the same applies below) for sample 1 and 0.2 g (2000 ppm) for sample 2, respectively.
Sample 3 contains 0.4 g (4000 ppm) of CaCl ₂ .2H ₂ O.
It was added as a 0% aqueous solution. Table 3 shows the results of the anion exchange treatment performed on these four samples under the same conditions as in Example 1.

Table 3 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Test material Before and after passing Jelly strength Viscosity Fe content Cu content (pH) (pH) (g) (mp) (ppm) (ppm) ──────────────────────────── ──────── Comparative sample 6.0 7.1 292 82 5.0 5.0 2.5 Sample 1 7.0 8.8 81 291 81 4.0 2.0 2.0 〃 2 7.0 9.6 291 81 2.0 1.3 〃 3 7.0 10.3 290 80 1.9 1.2 1.2 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━━

[Example 4] Pure water was added to 50 g of sodium alginate (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a 1% aqueous solution. Two similar solutions were prepared, and one of them was used as a comparative sample. 0.4 g of NaCl (8000 ppm based on sodium alginate) was added to the other aqueous solution as a 10% aqueous solution, and the mixture was stirred. Then, the solution was supplied to a column (diameter 3 cm) packed with 100 mL of anion exchange resin at a liquid flow rate of 1 L / hour. The results are shown in Table 4.

Table 4 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Before passing After passing The amount of Fe (pH) (pH) ( ppm) ────────────────────────────── Comparative sample − − 276 Sample 6.80 11.21 150 ━━━━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━

[0025]

According to the purification method of the present invention, a trace amount of heavy metal ions contained in an organic natural polymer can be easily removed to a very low level.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Watanabe 5-6-1 Takashi, Takarazuka City, Hyogo Prefecture (72) Inventor Norio Yamada 16-22 Takamatsucho, Nishinomiya City, Hyogo

Claims (3)

[Claims] 1. A heavy metal ion obtained by adding a water-soluble salt and / or a water-soluble base to a water-soluble organic natural polymer solution and then treating with an anion exchange resin to obtain a treatment solution having a pH of 9.0 or more. A method for purifying a water-soluble organic natural polymer compound, which comprises removing water. 2. The purification method according to claim 1, wherein the water-soluble organic natural polymer is a protein, a polysaccharide or a derivative thereof. 3. The purification method according to claim 2, wherein the water-soluble organic natural polymer is gelatin, glue, casein, alginic acid, starch or a derivative thereof.