Composition for metal ion sequestering

Abstract

The present invention provides a metal ion sequestering composition that can improve the calcium ion sequestering ability of condensed phosphates. [Solution] A metal ion sequestering composition characterized by containing at least one of citric acid and a salt thereof, and sodium metaphosphate or sodium ultraphosphate.

Description

[Technical Field]

[0001] This invention relates to a composition for metal ion sequestering. [Background technology]

[0002] Metal ion sequestering (chelation) technology is an extremely important technological field in the food, cosmetics, and detergent sectors from the viewpoints of quality stabilization, discoloration prevention, precipitation prevention, and improved cleaning power. Metal ions such as calcium ions and magnesium ions present in water are known to cause scale formation and quality deterioration, and various chelating agents have been proposed for the purpose of sequestering these metal ions. For example, ethylenediaminetetraacetic acid (EDTA) and its salts have been widely used for the purpose of sequestering polyvalent metal ions such as calcium ions and magnesium ions. However, because EDTA has poor biodegradability, if it remains in the environment, it can leach highly toxic heavy metals and adversely affect ecosystems, raising concerns about environmental impact. Furthermore, in food applications, the use of EDTA is limited to canned and bottled foods, resulting in a lack of versatility in its applications. Against this backdrop, various technologies have been proposed as chelating agents that can replace EDTA. For example, Patent Document 1 discloses a technology for a chelating compound-containing composition using a poly(meth)acrylic acid polymer containing alkali metal atoms or ammonium groups. However, this method is primarily intended for industrial or cosmetic applications, and its application to food products is not straightforward. Furthermore, Patent Documents 2 and 3 disclose hair treatment compositions containing mixtures with DTPA or amodimethicone microemulsions as chelating agents for hair care applications. However, these technologies are limited to hair care applications and have the problem that the chelating power of calcium ions at various pH conditions has not been sufficiently investigated. In addition to these technologies, various technologies using citric acid and its salts, which have excellent versatility, and technologies using phosphates have also been proposed. However, these prior art documents only describe their use in combination as stabilizers or auxiliary agents, and have not been thoroughly investigated from the perspective of synergistically enhancing calcium ion sequestering ability under specific pH conditions. [Prior art documents]

[0003] [Patent Document 1] Japanese Patent Application No. 2014-070108 [Patent Document 2] Special Publication 2019-518064 [Patent Document 3] Japanese Patent Publication No. 2019-069975 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Conventional technologies have problems such as limitations on the amount that can be added, limited applications, or unknown calcium ion sieving capacity under specific pH conditions. In particular, a technology that exhibits high calcium ion sieving capacity while maintaining safety and versatility in a wide range of applications such as food, cosmetics, and detergents has not been sufficiently established. Therefore, the present invention has been made to solve these problems and aims to provide a metal ion sieving composition that improves the calcium ion sieving capacity of condensed phosphates that can be used in general applications. [Overview of the Initiative] [Means for solving the problem]

[0005] The inventors of this invention have diligently investigated the calcium ion sieving capacity of condensed phosphates. As a result, they found that when condensed phosphates are used in an aqueous solution containing at least one of citric acid or a salt thereof, the calcium ion sieving capacity is significantly improved compared to when they are used in other organic acid buffers such as acetate buffer. In particular, they confirmed that the calcium ion sieving capacity of condensed phosphates is remarkably enhanced in an aqueous solution containing citric acid. This invention was completed based on this finding. [Effects of the Invention]

[0006] According to the composition for sequestering metal ions of the present invention, by using condensed phosphates in an aqueous solution containing at least one of citric acid and its salts, the calcium ion sequestering ability can be remarkably improved as compared with the case of using condensed phosphates alone or in an acetic acid buffer solution. In particular, the sequestering ability for calcium ions is remarkably improved, and depending on the conditions, it exhibits a sequestering ability equivalent to or higher than that of EDTA-2Na. Such an effect is presumably due to the fact that the complex formation action of calcium ions by citric acid and the sequestering action by polyvalent coordination by condensed phosphates act complementarily, enhancing the calcium ion sequestering ability more than in the case of using condensed phosphates alone. Therefore, the composition of the present invention is useful as a metal ion sequestering agent in fields such as detergents, food processing applications, cosmetics, etc., and can be applied to a wide range of uses.

Embodiments for Carrying Out the Invention

[0007] The composition for sequestering metal ions of the present invention is characterized by containing at least one of citric acid and its salts and condensed phosphates, and is characterized in that the pH of its aqueous solution is 4 to 7. At this time, a pH adjuster can be used for pH adjustment, and examples of the pH adjuster include inorganic acids such as phosphoric acid, hydrochloric acid, sodium hydroxide, potassium dihydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, tripotassium phosphate, or their salts, etc. can be used.

[0008] The condensed phosphate contained in the composition for sequestering metal ions of the present invention is Na x H y (PO3) (x+y) (where x, y ≧ 1), sodium ultraphosphate, Na n H2P n O 3n+1 Among sodium metaphosphates represented by, the average degree of polymerization is 14 ≦ n < 20 (hereinafter, sodium metaphosphate with low polymerization degree) or Na n H2P n O 3n+1The sodium metaphosphate represented by [formula] is characterized in that its average degree of polymerization is n ≥ 20 (hereinafter referred to as highly polymerized sodium metaphosphate).

[0009] The concentration of at least one of the citric acid and its salts in an aqueous solution of the metal ion sequestering composition of the present invention is preferably 0.05 mol / L to 0.5 mol / L, more preferably 0.1 mol / L to 0.4 mol / L, and most preferably 0.2 mol / L.

[0010] The metal ion sequestering composition of the present invention can be widely used in various fields such as food, cosmetics, detergents, and industrial applications. Specifically, in the food industry, it can be used as a discoloration inhibitor, quality stabilizer, or shelf-life extender for fruits, vegetables, meat, beverages, etc. In the cosmetics industry, by sequestering metal ions present in cosmetics, it can be used as a quality stabilizer for purposes such as preventing discoloration, assisting in oxidation prevention, and stabilizing preservatives. Furthermore, in the detergent industry, it can be used as a builder for detergents, improving cleaning performance by sequestering metal ions such as calcium ions. In the water treatment industry, it can be used as a water softener by sequestering metal ions in water.

[0011] The present invention will be described in detail below with reference to experimental examples, but the present invention is not limited in any way to these experimental examples. Experimental Examples

[0012] [Comparative Examples 1-28, Examples 1-12] 1.0 g of EDTA-2Na or condensed phosphate (highly polymerized sodium metaphosphate, lowly polymerized sodium metaphosphate, or ultrasodium phosphate) was dissolved in 100 mL of citrate buffer or acetate buffer. The citrate buffer was prepared so that the final concentration of at least one of citric acid and its salt was 0.2 mol / L, and the pH was adjusted to the specified level using sodium hydroxide as needed. The acetate buffer was prepared so that the final concentration of at least one of acetic acid and its salt was 0.2 mol / L, and the pH was adjusted to the specified level using sodium hydroxide as needed. 5 mL of saturated ammonium oxalate aqueous solution was added to the resulting solution to prepare the test solution. A 0.5 mol / L calcium chloride aqueous solution was added dropwise to this test solution, and titration was performed until the solution became slightly cloudy (n=5). From the appropriate amount of calcium chloride aqueous solution, the average value of the calcium ion sieving capacity per 1.0 g of EDTA-2Na or condensed phosphate was calculated using the following formula. Calcium ion sieving capacity (calcium ion chelate value) = (0.5 mol / L calcium chloride solution (mL) × 50) / sample (g)

[0013] [Table 1]

[0014] Table 1 shows the evaluation results of calcium ion sieving capacity when various chelating agents are used. In this study, calcium ion sieving capacity was measured using acetate buffer or citrate buffer under conditions without chelating agent addition, and under conditions with EDTA-2Na and various condensed phosphates added, respectively.

[0015] First, examining the cases without the addition of a chelating agent (Comparative Examples 1-8), the calcium ion chelating value in acetate buffer was extremely low, at approximately 2-3. On the other hand, in citrate buffer, values ​​of approximately 25-340 were observed, confirming a significant improvement in calcium ion sequestering capacity compared to acetate buffer. This is thought to be because citrate itself possesses a certain chelating ability for calcium ions.

[0016] Next, when considering the case where EDTA-2Na was added (Comparative Examples 9 to 16), the calcium ion chelating value showed a value of about 9 to 160 in the acetate buffer solution. On the other hand, in the citrate buffer solution, it showed a value of about 40 to 550, and it was confirmed that the calcium ion blocking ability changes depending on the type of buffer solution. From these results, a tendency was recognized that the chelating action of EDTA-2Na was observed as a higher value in the citrate buffer solution.

[0017] Furthermore, when considering condensed phosphates, in the acetate buffer solution, the calcium ion chelating value remained in the range of approximately 50 to 180 for all of sodium polymetaphosphate, sodium metaphosphate of low polymerization degree, and sodium ultraphosphate (Comparative Examples 17 to 28). In contrast, in the citrate buffer solution, the result that the calcium ion blocking ability of these condensed phosphates was significantly improved was obtained (Examples 1 to 12). Specifically, for sodium polymetaphosphate, the calcium ion chelating value showed a value of about 110 to 770, for sodium metaphosphate of low polymerization degree, it showed a value of about 150 to 810, and for sodium ultraphosphate, it showed a value of about 100 to 650. A calcium ion blocking ability several times higher than that in the case of the acetate buffer solution was confirmed.

[0018] From the above results, it was confirmed that by using a condensed phosphate in an aqueous solution containing at least one of citric acid and its salts, the calcium ion blocking ability is significantly improved as compared with the case of using it in an acetate buffer solution. Such an effect is presumed to be due to the synergistic action between citric acid or its salt and the condensed phosphate, indicating that the composition for blocking metal ions of the present invention has an extremely excellent calcium ion blocking ability.

[0019] Also, under the conditions of the present invention, it has been confirmed that the condensed phosphate shows a calcium ion blocking ability equal to or higher than that of conventionally widely used EDTA-2Na, and the composition of the present invention is considered to be useful as an alternative or auxiliary agent to EDTA-based chelating agents.

Industrial Applicability

[0020] The metal ion sequestering composition of the present invention can improve the calcium ion sequestering ability of condensed phosphates in an aqueous solution containing at least one of citric acid and its salts, and can therefore be widely used in applications that reduce the influence of metal ions such as calcium ions and magnesium ions. Specifically, it can be used as a discoloration inhibitor, quality stabilizer, and shelf-life extender in the food industry, a quality stabilizer in the cosmetics industry, a builder in the detergent industry, and a water softener in the water treatment industry, and is useful in various industrial fields such as food, cosmetics, detergents, and water treatment. [Brief explanation of the drawing]

[0021] [Figure 1] This figure shows the calcium ion chelation value of highly polymerized sodium metaphosphate. [Figure 2] This figure shows the calcium ion chelate value of low-polymer sodium metaphosphate. [Figure 3] This is a diagram showing the calcium ion chelation value of sodium ultraphosphate. [Figure 4] This is a diagram showing the calcium ion chelation value of EDTA-2Na.

Claims

1. A metal ion sequestering composition characterized by containing at least one of citric acid and its salts and a condensed phosphate.

2. The metal ion sequestering composition according to claim 1, characterized in that the calcium ion sequestering ability is synergistically enhanced by the combined use of at least one of citric acid and its salts with a condensed phosphate compared to when each component is used alone.

3. Condensed phosphate is Na ｘ H ｙ (PO ３ ) （ｘ＋ｙ） Sodium ultraphosphate, or Na, represented by (x, y≧1). ｎ H ２ P ｎ O ３ｎ＋１ The metal ion sequestering composition according to claims 1 and 2, characterized in that, among the sodium metaphosphate represented by , n ≥ 14.

4. The metal ion sequestering composition according to claims 1 to 3, wherein the pH of the aqueous solution is 4 to 7.

5. The metal ion sequestering composition according to claims 1 to 4, wherein the concentration of at least one of citric acid and its salt is 0.05 to 0.5 mol / L.

6. A metal ion sequestering composition according to claims 1 to 5, used for sequestering calcium ions.

7. A metal ion sequestering composition according to claims 1 to 6, used in food products, cosmetics, detergents, industrial applications, etc.

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