JP7843015B2 - Method for producing calcium hydroxide solution - Google Patents

Description

This invention relates to a method for producing an aqueous solution of calcium hydroxide.

Aqueous solutions of calcium hydroxide, a type of reducing solution, are known to be useful in inhibiting and inactivating microbial growth, and the demand for various antibacterial agents, or their raw materials, has been increasing in recent years.

Conventionally, a manufacturing method for producing reducing solutions such as aqueous calcium hydroxide solutions has been widely used, which involves a step of generating hydroxide ions ( ^OH⁻ ) by electrolysis (see Patent Document 1).

Furthermore, other methods for producing reducing solutions include a method involving dissolving hydrogen gas in raw water using a pressurized device (see Patent Document 2), or a method involving eluting calcium and other substances from natural materials such as seashells using contact solid materials such as activated carbon or medicinal stones (see Patent Document 3).

In the manufacturing method disclosed in Patent Document 1, electrolysis is an essential step. Therefore, implementing this manufacturing method requires the installation of a large-scale electrolysis apparatus. Furthermore, implementing the manufacturing method disclosed in Patent Document 2 requires the installation of a hydrogen pressurization apparatus and other ancillary equipment. In other words, in either of the above manufacturing methods, the initial investment in manufacturing equipment and the operating costs tended to be excessively burdensome.

On the other hand, implementing the manufacturing method disclosed in Patent Document 3 requires securing large quantities of natural raw materials such as activated carbon, medicinal stones, and seashells. Furthermore, the low solubility of seashells, a time-consuming and labor-intensive filtration process, is unavoidable, making the method economically disadvantageous. Therefore, it has been difficult to stably mass-produce reducing solutions using this manufacturing method.

The present inventor has already developed a method for producing a reducing solution that can solve the problems of the manufacturing methods disclosed in the above-mentioned Patent Documents 1 to 3. Specifically, this method involves dissolving a mixture of calcium chloride dihydrate and sugars, etc., in water in a container. This process allows for the production of a reducing solution through a purely chemical reaction, without requiring large-scale industrial equipment such as electrolytic devices or hydrogen pressurization devices (see Patent Document 4).

However, in particular, when producing an aqueous calcium hydroxide solution, the low solubility of calcium hydroxide (Ca(OH) _₂ ) in water becomes the rate-limiting factor. Therefore, even if the production method disclosed in Patent Document 4, which assumes the dissolution of a raw material mixture in water in a single container, is directly applied to the production of calcium hydroxide, it remains difficult to stably mass-produce an aqueous calcium hydroxide solution.

Japanese Patent Application Publication No. 8-187492 Japanese Patent Publication No. 2004-351399 Japanese Patent Publication No. 2006-68640 Patent No. 6455689

The present invention aims to provide a method for producing an aqueous calcium hydroxide solution that allows for low-cost, stable, and large-scale production of the solution through a process that proceeds solely through pure chemical reactions.

The inventors of the present invention have significantly improved the method for producing a reducing solution disclosed in Patent Document 4, which they themselves developed. They conceived that the above problem could be solved by performing the steps of "dissolving a calcium salt in water" and "dissolving a hydroxide in water" separately and independently, and then mixing the two aqueous solutions obtained from each step. This led to the completion of the present invention. Specifically, the present invention provides the following:

(1) A method for producing an aqueous calcium hydroxide solution, comprising: a first step of dissolving a calcium salt and sugars in water to obtain an aqueous calcium ion solution as a first aqueous solution; a second step of dissolving an alkali metal hydroxide in water in a mass ratio of 25% to 100% relative to the calcium salt dissolved in water in the first step to obtain an aqueous hydroxide ion solution as a second aqueous solution; and a third step of mixing the first aqueous solution and the second aqueous solution to obtain an aqueous calcium hydroxide solution.

According to the method for producing an aqueous calcium hydroxide solution in (1), the aqueous calcium hydroxide solution can be mass-produced stably and at low cost through a process that allows the reaction to proceed solely through pure chemical reactions.

(2) The method for producing an aqueous calcium hydroxide solution according to (1), wherein sucrose is used as the sugar in the first step.

The method for producing an aqueous calcium hydroxide solution in (2) particularly promotes the dissolution of calcium ions during the first step in the production method in (1). Furthermore, it can prevent the browning of the first solution that occurs when monosaccharides such as glucose or galactose are used.

(3) The method for producing an aqueous calcium hydroxide solution according to (1) or (2), wherein in the first step, an amino acid is further dissolved in water to obtain the first aqueous solution.

The method for producing an aqueous calcium hydroxide solution in (3) significantly increases the antioxidant (reducing) properties of the aqueous calcium hydroxide solution obtained by the method in (1) or (2).

(4) The method for producing an aqueous calcium hydroxide solution as described in (3), wherein cysteine is used as the amino acid in the first step.

The method for producing the calcium hydroxide aqueous solution in (4) can significantly increase the antioxidant (reducing) properties of the calcium hydroxide aqueous solution obtained by the method in (3). This allows for the inactivation of a wider range of bacteria and viruses, contributing to the stable supply of superior antibacterial agents at a lower cost. Furthermore, while cysteine is sometimes included alone in antibacterial agents, the action of calcium ions lowers the oxidation-reduction potential, resulting in improved antibacterial activity compared to when it is used alone.

(5) A method for producing an aqueous calcium hydroxide solution according to any one of (1) to (4), wherein in the first step, 4.5% to 10.0% by mass of calcium chloride dihydrate is dissolved in water as the calcium salt, and 7% to 10% by mass of sucrose is dissolved in water as the sugar, to obtain the first aqueous solution; and in the second step, potassium hydroxide is used as the alkali metal hydroxide.

According to the method for producing the calcium hydroxide aqueous solution in (5), the effects described above, which are achieved by any of the production methods (1) to (4), can be reliably and with greater precision.

(6) A raw material combination set for a two-component calcium hydroxide aqueous solution, comprising: a first aqueous solution which is a calcium ion aqueous solution containing a calcium salt and sugars; and a second aqueous solution which is a calcium hydroxide aqueous solution containing an alkali metal hydroxide in a mass ratio of 25% to 100% relative to the calcium salt contained in the first aqueous solution;

According to the raw material combination set for the calcium hydroxide aqueous solution in (6), the calcium hydroxide aqueous solution can be mass-produced stably at low cost by a process that allows the calcium hydroxide aqueous solution to proceed solely through pure chemical reactions.
(7) A set of raw material combinations for the calcium hydroxide aqueous solution described in (6), wherein the sugar contained in the first aqueous solution is sucrose.

According to the raw material combination set for the calcium hydroxide aqueous solution of (7), the dissolution of calcium ions in the first aqueous solution of the calcium hydroxide aqueous solution of (6) is particularly well promoted. Furthermore, it is possible to prevent the browning of the first solution that occurs when monosaccharides such as glucose or galactose are used.

(8) A set of raw material combinations for the calcium hydroxide aqueous solution described in (6) or (7), further comprising an amino acid in the first aqueous solution.

The combination of raw materials for the calcium hydroxide aqueous solution in (8) can significantly increase the antioxidant (reducing) properties of the calcium hydroxide aqueous solution obtained using the raw material combination of (6) or (7).

(9) The method for producing an aqueous calcium hydroxide solution according to (8), wherein the amino acid contained in the first aqueous solution is cysteine.

The raw material combination set for the calcium hydroxide aqueous solution in (9) can significantly increase the antioxidant (reducing) properties of the calcium hydroxide aqueous solution obtained using the raw material combination set in (8). This allows for the inactivation of a wider range of bacteria and viruses, enabling the stable supply of superior antibacterial agents at a lower cost.

(10) The first aqueous solution contains, with respect to water, 4.5% to 10.0% by mass of calcium chloride dihydrate as the calcium salt and 7% to 10% by mass of sucrose as the sugars, and the second aqueous solution contains potassium hydroxide as the alkali metal hydroxide, a raw material combination set for the calcium hydroxide aqueous solution according to any one of (6) to (9).

According to the raw material combination set for the calcium hydroxide aqueous solution in (10), any of the raw material combination sets from (6) to (9) can reliably and with greater precision achieve the respective effects described above.

According to the present invention, a calcium hydroxide aqueous solution can be mass-produced stably and at low cost through a process that allows the reaction to proceed solely through pure chemical reactions.

This is a flowchart showing the procedure for producing the calcium hydroxide aqueous solution of the present invention.

The best mode for carrying out the present invention will be described in detail below, with reference to drawings and other relevant materials as appropriate.

<Method for producing calcium hydroxide aqueous solution>
The present invention provides a method for producing an aqueous calcium hydroxide solution, which is described in detail below, by a combination of steps that can be carried out solely by pure chemical reactions. In this specification, "carrying out solely by pure chemical reactions" specifically means carrying out the necessary chemical reactions without using processes that supply a large amount of energy from the outside, such as electrolysis apparatuses or pressurizing devices disclosed in Patent Documents 1 or 2.

[Overall structure]
Figure 1 is a flowchart showing the procedure for producing the calcium hydroxide aqueous solution of the present invention. The method for producing the calcium hydroxide aqueous solution is a process consisting of three steps, from the first to the third. The first step S1 is a step of dissolving a calcium salt and sugars in water to obtain a first aqueous solution (calcium ion aqueous solution) L1. The second step S2 is a step of dissolving an alkali metal hydroxide in water in an amount that is relative to the calcium salt dissolved in water in the first step S1, in a predetermined amount, to obtain a second aqueous solution (hydroxide ion aqueous solution) L2. The third step is a step of mixing the first aqueous solution (calcium ion aqueous solution) L1 and the second aqueous solution (hydroxide ion aqueous solution) L2.

Furthermore, in the first step S1 of the method for producing an aqueous calcium hydroxide solution of the present invention, it is more preferable to dissolve amino acids in water in addition to the calcium salts and sugars mentioned above.

The method for producing an aqueous calcium hydroxide solution of the present invention can be carried out using the "raw material combination set for aqueous calcium hydroxide solution" described later. Of course, as long as the process includes the three steps described above (steps 1 to 3), it falls within the technical scope of the present invention, regardless of whether the "raw material combination set for aqueous calcium hydroxide solution" is used.

[First step]
In the first step S1, a calcium salt, sugars, and preferably an additive such as an amino acid are dissolved in water to obtain a first aqueous solution (calcium ion aqueous solution) L1.

(Calcium salt)
As the calcium salt, various calcium compounds that dissolve in water as calcium ions ( ^Ca²⁺ ) can be used. However, it is preferable to use calcium chloride (CaCl₂), calcium bromide ( _CaBr₂ ), calcium acetate, calcium lactate, or calcium gluconate _, which have superior solubility in water compared to calcium oxide and calcium carbonate ( _CaCO₃ ). Among these, it is even more preferable to use calcium chloride ( _CaCl₂ ) (or calcium chloride dihydrate ( _CaCl₂・_2H₂O )) as the calcium salt.

By using calcium chloride ( _CaCl₂ ), more preferably calcium chloride dihydrate ( _CaCl₂ · _2H₂O ), as the calcium salt, the water molecule clusters are reorganized into even smaller water molecule clusters. This enhances the reducing properties of the calcium hydroxide aqueous solution produced by the present invention, allowing for easy and highly accurate impartation of excellent antioxidant (reducing) properties. Furthermore, from an economic standpoint, it is preferable to select calcium chloride dihydrate ( _CaCl₂ · _2H₂O ), which is the least expensive of the various calcium sources mentioned above.

(Sugars)
Herein, in this specification, "sugars" added as essential components to the first aqueous solution refer to monosaccharides or disaccharides. These sugars promote the dissolution of calcium salts in aqueous solutions. Monosaccharides such as glucose and galactose, as well as sucrose and commercially available disaccharides such as granulated sugar, refined sugar, and medium-white sugar, contribute to improved solubility. Among these, it is particularly preferable to use sucrose, which contributes most significantly to improving solubility.

However, in implementing the present invention, it is not excluded that, in addition to "sugars" in the sense described above—that is, monosaccharides and disaccharides exemplified above—"polysaccharides" may be added to the calcium hydroxide aqueous solution, for example, to impart a moisturizing effect. Even a process of adding polysaccharides within a range that does not hinder the effects of the present invention is naturally within the scope of the present invention.

(amino acid)
The reducing properties can be improved by adding amino acids to the first aqueous solution. Cysteine is a preferred amino acid. Cysteine can be used in various forms, such as L-form, D-form, DL-form, or cysteine hydrochloride monohydrate, without any particular restrictions, but from an economic standpoint, it is preferable to use L-cysteine or L-cysteine hydrochloride monohydrate.

(Other additives)
In addition to the first aqueous solution, other alkaline and stable reducing compounds may be added as needed. Examples of other additives include polyphenols, tannic acid, gallic acid, and the like.

[Second step]
In the second step S2, an alkali metal hydroxide is dissolved in water to obtain a second aqueous solution (hydroxide ion aqueous solution) L2.

The amount of alkali metal hydroxide added to the second aqueous solution (hydroxide ion aqueous solution) L2 is 25% to 100% by mass, more preferably 30% to 100% by mass, and most preferably 60% to 100% by mass, relative to the calcium salt dissolved in water in the first step. Alternatively, the amount of alkali metal hydroxide added may be adjusted so that the hydroxide ions in the first aqueous solution L1 are 60 mol% to 270 mol% in molar ratio to the calcium ions.

(Alkali metal hydroxides)
Potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), and the like can be preferably used as the alkali metal hydroxide in the second step S2.

[Third step]
In the third step S3, a calcium hydroxide aqueous solution can be obtained by mixing the first aqueous solution (calcium ion aqueous solution) L1 and the second aqueous solution (hydroxide ion aqueous solution) L2 obtained in each of the above steps. Specifically, a calcium hydroxide aqueous solution can be produced by adding the second aqueous solution (hydroxide ion aqueous solution) L2 to a container containing the first aqueous solution (calcium ion aqueous solution) L1 at an appropriate rate and mixing them to dissolve both in the aqueous solution.

Furthermore, in the third step S3, the container for mixing the two liquids is preferably made of resin. By using a resin container, it is possible to avoid the erosion of the glass surface that can occur when using a glass bottle.

[Calcium hydroxide aqueous solution raw material combination set]
To carry out the method for producing an aqueous calcium solution of the present invention, the "raw material combination set for aqueous calcium hydroxide solution" of the present invention can be preferably used. This raw material combination set is a two-liquid mixed type raw material combination set comprising a first aqueous solution L1 and a second aqueous solution L2, which are described in detail above, and is intended for use in the production of an aqueous calcium hydroxide solution.

The "raw material combination set for calcium hydroxide aqueous solution" of the present invention, which comprises a first aqueous solution L1 and a second aqueous solution L2, is an optimal combination of chemical substances that can be reliably obtained in large quantities. By using this set as a material for the "method for producing calcium hydroxide aqueous solution" of the present invention, economic problems such as high equipment costs and high operating costs during manufacturing can be solved. Furthermore, this eliminates the need for the time and expense required to secure and prepare natural materials such as seashells. Therefore, by using the "raw material combination set for calcium hydroxide aqueous solution" of the present invention, it becomes possible to mass-produce extremely low-cost reducing solutions and rapidly and inexpensively distribute them to the market.

The present invention will be further described in detail below with reference to examples relating to the "method for producing an aqueous calcium hydroxide solution" of the present invention, but the present invention is not limited to the following examples.

(First step)
The "first step," which is an essential step in the method for producing an aqueous calcium hydroxide solution of the present invention, was carried out as follows. Calcium chloride dihydrate (molecular weight 147.01) was used as the calcium salt. Sucrose (molecular weight 342.30) was used as the sugar, and L-cysteine hydrochloride monohydrate (175.63) was used as the amino acid. However, only in Example 3, glucose (molecular weight 180.2) was used instead of sucrose as the sugar. These were then dissolved in purified water to obtain the first aqueous solution. The amount of each agent added per 100 ml of purified water for each example and comparative example is shown in Table 1 below.

(Second step)
Similarly, the "second step" was carried out as follows. Potassium hydroxide (molecular weight 56.11) was used as the alkali metal hydroxide. A second aqueous solution was obtained by dissolving this in purified water. The amount of alkali metal hydroxide added per 100 ml of purified water for each example and comparative example is shown in Table 1 below.

(Third step)
Then, the "third step" was carried out by adding 5,000 ml of the second aqueous solution obtained in the "second step" to a resin reaction vessel containing 5,000 ml of the first aqueous solution obtained in the "first step" above, in a manner in which the entire amount was added dropwise over a period of about 30 minutes.

(Evaluation of calcium hydroxide solution)
The amount of Ca(OH) _₂ produced (%), the oxidation-reduction potential ( mV ), and the presence or absence of precipitate formation when the second aqueous solution was added dropwise were compared and evaluated for the calcium hydroxide solutions of the examples and comparative examples obtained in the "third step" described above.

The amount (%) of Ca(OH) ₂ produced is a theoretical value calculated from the chemical equivalent of each agent. In Examples 1 to 5 , where an appropriate amount of alkali metal hydroxide was added to the second aqueous solution, no precipitate was formed, and a calcium hydroxide solution with sufficient calcium ion concentration was quickly produced.

The oxidation-reduction potential ( mV ) was measured using the ORP simultaneous measurement device attached to the HM50V pH meter manufactured by Toa Denpa Kogyo Co., Ltd.

The presence or absence of precipitate formation was evaluated visually. In Comparative Example 1, the only difference from Example 3, in which no precipitate formed, was that no sugars were added to the first aqueous solution.
The formation of a white precipitate derived from calcium hydroxide was confirmed.

(Evaluation of sugar selection)
In Example 3, when the monosaccharide glucose was used instead of sucrose as the sugar, there was no significant change in the quality (reducing power) of the calcium hydroxide aqueous solution produced in the third step. However, when the sugar was added in the first step, the first aqueous solution temporarily turned brown. It has been confirmed that this phenomenon does not occur when sucrose is used.

Based on the evaluation results above, it is clear that, according to the present invention, it is possible to mass-produce an aqueous calcium hydroxide solution at low cost and stably through a process that allows the reaction to proceed solely through pure chemical reactions.

S1 First step S2 Second step S3 Third step L1 First aqueous solution (calcium ion aqueous solution)
L2 Second aqueous solution (hydroxide ion aqueous solution)

Claims (2)

The first step involves dissolving a calcium salt, sugars, and amino acids in water to obtain a calcium ion aqueous solution as the first aqueous solution.
In the second step, an alkali metal hydroxide in a mass ratio of 25% to 100% of the calcium salt dissolved in water in the first step is dissolved in water in a container separate from the one used in the first step to obtain a second aqueous solution of hydroxide ions.
A third step is performed, in which the first aqueous solution and the second aqueous solution are mixed in the same container to obtain an aqueous calcium hydroxide solution.
A method for producing an aqueous calcium hydroxide solution. A set of raw material combinations for calcium hydroxide aqueous solution,
A first aqueous solution is a calcium ion aqueous solution containing calcium salts, sugars, and amino acids ,
The solution comprises a second aqueous solution, which is an aqueous calcium hydroxide solution containing an alkali metal hydroxide in a mass ratio of 25% to 100% of the calcium salt contained in the first aqueous solution,
A set of raw materials for a two-part calcium hydroxide solution.