Basic aluminum lactate solution

Abstract

The objective is to develop a basic aluminum lactate solution with excellent storage stability. [Solution] The solution is a basic aluminum lactate solution that satisfies the following requirements (1) to (2): (1) It contains L-lactic acid and D-lactic acid, which are optical isomers of lactic acid, and the proportion of D-lactic acid in the total lactic acid (L-lactic acid + D-lactic acid) is in the range of 3 to 99 mol%; and (2) The total lactic acid / Al2O3 (molar ratio) is in the range of 1.0 to 4.0.

Description

Technical Field

[0001] The present invention relates to a basic aluminum lactate solution.

Background Art

[0002] Basic aluminum lactate solutions have been used, for example, as additives for alkaline refractories to improve air permeability and to suppress the digestion of basic aggregates, or as aluminum dopants in the raw materials of composite oxides.

[0003] There are numerous known documents regarding basic aluminum lactate solutions, including Patent Document 1. Although not specified in most documents, basic aluminum lactate solutions have some difficulty in storage stability and tend to precipitate when stored for a long time.

[0004] In order to maintain long-term stability, Patent Document 2 discloses an invention regarding a basic aluminum lactate solution added with malic acid.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to develop a basic aluminum lactate solution having excellent storage stability by a method different from that of Patent Document 2.

Means for Solving the Problems

[0007] As a result of diligent research into the above-mentioned problems, the inventors of this invention have, to their surprise, discovered that a basic aluminum lactate solution with long-term stability can be obtained by including L-lactic acid (L-lactic acid) and D-lactic acid (D-lactic acid), which are optical isomers of lactic acid, in predetermined proportions. Based on this finding, the inventors have completed the present invention.

[0008] The present invention is as follows: [1] A basic aluminum lactate solution that satisfies the following requirements (1) to (2). (1) The lactic acid contains L-lactic acid and D-lactic acid, which are optical isomers, and the proportion of D-lactic acid in the total lactic acid (L-lactic acid + D-lactic acid) is in the range of 3 to 99 mol%. (2) The molar ratio of total lactic acid to Al2O3 is in the range of 1.0 to 4.0. [2] The basic aluminum lactate solution described in [1] above, wherein the aluminum index is in the range of 0.90 to 1.10 in the storage test described below. [Storage Test] As the Al2O3 concentration before testing, the Al2O3 concentration of the basic aluminum lactate solution described above is measured before being subjected to the storage test. Measure 20 g of the above basic aluminum lactate solution into a 50 mL iBoy PP wide-mouth bottle sold by AS ONE Corporation, seal it tightly, and leave it standing in a constant temperature bath set to 50°C for 3 weeks. Then measure the Al2O3 concentration in the portion from the top to a depth of 5 mm and record this as the Al2O3 concentration after the test. The aluminum index is calculated using the following formula. Aluminum index = Al2O3 concentration after testing ÷ Al2O3 concentration before testing [3] A method for producing the basic aluminum lactate solution according to [1] or [2] above, comprising the step of mixing alumina hydrate with lactic acid. [4] A powder obtained by drying the basic aluminum lactate solution described in [1] or [2] above. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below based on preferred embodiments, but the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the claims. In this invention, the notation "value 1 to value 2" in relation to a numerical range means a numerical range that includes both values ​​1 and 2, with value 1 as the lower limit and value 2 as the upper limit, and is synonymous with "value 1 or greater and value 2 or less".

[0010] The present invention relates to a basic aluminum lactate solution that satisfies the following requirements (1) to (2). (1) The lactic acid contains L-lactic acid and D-lactic acid, which are optical isomers, and the proportion of D-lactic acid in the total lactic acid (L-lactic acid + D-lactic acid) is in the range of 3 to 99 mol%. (2) The molar ratio of total lactic acid to Al2O3 is in the range of 1.0 to 4.0.

[0011] (Requirement 1) Lactic acid has two optical isomers, L-lactic acid and D-lactic acid, which are called L-lactic acid and D-lactic acid, respectively. In literature, it is common technical knowledge to assume that simply "lactic acid" refers to L-lactic acid. Generally, when "L-lactic acid" is specified, it is often necessary to distinguish it from D-lactic acid.

[0012] The basic aluminum lactate solution of the present invention contains L-lactic acid and D-lactic acid as lactic acid, and the proportion of D-lactic acid in the total lactic acid, i.e., [L-lactic acid + D-lactic acid] (hereinafter referred to as "D-part percentage") is in the range of 3 to 99 mol%. If the D-part percentage is less than 3 mol% or greater than 99 mol%, precipitation is likely to occur. The lower limit of the above range is preferably 5 mol%, more preferably 7 mol%, even more preferably 8 mol%, and particularly preferably 10 mol%. Therefore, preferred ranges for the D-part percentage include 5 to 99 mol%, 7 to 99 mol%, 8 to 99 mol%, and 10 to 99 mol%.

[0013] In this invention, the measurement method for determining the D content is as follows. (Treatment with basic aluminum lactate solution) To enable measurement of the optical rotation of lactic acid in the basic aluminum lactate solution, the aluminum in the solution is dissolved in hydrochloric acid. Specifically, concentrated hydrochloric acid is added to the basic aluminum lactate solution in a molar ratio of Cl in the concentrated hydrochloric acid to Al2O3 in the basic aluminum lactate solution (molar ratio) of 3 to 10, and then the solution is boiled for 10 minutes. After cooling, the solution is used as the sample for measurement. Note that the boiling should be done gently to prevent evaporation to dryness. (Creating a calibration curve) The lactic acid used to determine the calibration curve is DL-lactic acid (a mixture of 50 mol% each of L-lactic acid and D-lactic acid) and L-lactic acid. For DL-lactic acid, we use "DL-lactic acid, special grade" (product code: 000-43525) manufactured by Kishida Chemical Co., Ltd. For L-lactic acid, we use "L-lactic acid, special grade" (product code: 129-02666) manufactured by Fujifilm Wako Pure Chemical Corporation. Precisely weigh approximately 0.5g each of DL-lactic acid and L-lactic acid using a precision balance, place them in a 100mL volumetric flask, add approximately 20mL of distilled water and 2mL of concentrated hydrochloric acid, boil for 10 minutes, allow to cool, and then make up with distilled water to prepare the standard solution. Note that the boiling should be done gently to prevent evaporation to dryness. The optical isomers (L-form and D-form) are identified by optical rotation measurement. A polarimeter P-2200 manufactured by JASCO Corporation is used as the measuring instrument. However, other measuring instruments may be used if they can obtain equivalent measurement values. Using the DL-lactic acid standard solution and L-lactic acid standard solution prepared as described above, measure the optical rotation of each using the measuring device described above and create a calibration curve. Next, measure the optical rotation of the sample and determine the D-isomer fraction of the sample from the calibration curve. Distilled water is used for the blank measurement. In this measurement method, since a standard solution consisting solely of D-lactic acid is not used, depending on the calibration curve, the D-part percentage may exceed 100 mol% when measuring D-lactic acid. However, this does not cause any problems, and the value exceeding 100 mol% can be used as is. By the way, when determining the D-isomer ratio using the lactic acid used as the raw material as a sample, addition of concentrated hydrochloric acid and heat treatment for the sample and the standard solution are unnecessary. On the other hand, when using the basic aluminum lactate solution as a sample as described above, by performing addition of concentrated hydrochloric acid and heat treatment on the standard solution as well as on the sample, a D-isomer ratio value consistent with the D-isomer ratio of the lactic acid used as the raw material can be obtained.

[0014] (Requirement 2) The basic aluminum lactate solution of the present invention has a range of total lactic acid / Al2O3 (molar ratio) = 1.0 to 4.0. When the total lactic acid / Al2O3 (molar ratio) is less than 1.0, solution stability tends to be impaired, such as precipitation being likely to occur. On the other hand, when it exceeds 4.0, a stable basic aluminum lactate solution can be obtained regardless of the ratio of the optical isomers of lactic acid, but it is not economical to contain a large amount of lactic acid.

[0015] The Al2O3 concentration of the basic aluminum lactate solution of the present invention is preferably in the range of 1 to 20% by mass. From the viewpoints of economy in production and transportation, the lower limit is more preferably 3% by mass, and even more preferably 5% by mass. The upper limit is more preferably 15% by mass.

[0016] (Other components) The basic aluminum lactate solution of the present invention allows the inclusion of a sulfuric acid component, but is preferably substantially free of a sulfuric acid component. Here, substantially free of a sulfuric acid component means that, excluding the sulfuric acid component derived from impurities in the raw materials, no sulfuric acid component is contained. When the basic aluminum lactate solution of the present invention contains a sulfuric acid component, the content of the sulfuric acid component in the solution is preferably such that SO4 / Al2O3 (molar ratio) is less than 0.01, and more preferably less than 0.008.

[0017] In addition, the basic aluminum lactate solution of the present invention allows the inclusion of calcium components, but is preferably substantially free of calcium components. Here, being substantially free of calcium components means that, excluding the calcium components derived from impurities in the raw materials, no calcium components are contained. When the basic aluminum lactate solution of the present invention contains calcium components, the content of calcium components in the solution is preferably such that the CaO / Al2O3 (molar ratio) is less than 0.01, more preferably less than 0.008.

[0018] (Aluminum index) A preferred form of the basic aluminum lactate solution of the present invention is such that in the following storage test, the aluminum index is in the range of 0.90 to 1.10. 〔Storage test〕 As the Al2O3 concentration before the test, measure the Al2O3 concentration of the basic aluminum lactate solution before the storage test for the test. Weigh 20 g of the basic aluminum lactate solution into a 50 mL IBOY PP wide-mouth bottle sold by AS ONE Corporation, seal it, and leave it standing in a constant temperature bath set at 50°C for 3 weeks. Then, measure the Al2O3 concentration of the portion from the upper surface to a depth of 5 mm, and use this as the Al2O3 concentration after the test. Calculate the aluminum index from the following formula. Aluminum index = Al2O3 concentration after the test ÷ Al2O3 concentration before the test In addition, in the above, for the measurement of the aluminum concentration of the portion from the upper surface to a depth of 5 mm, it is preferable to collect the portion from the upper surface to a depth of 5 mm. When collecting, it is preferable to collect as gently as possible, that is, to collect carefully in a state where the fluidity is suppressed as much as possible. As the collecting instrument, a pipette, a syringe, etc. are preferable.

[0019] If the aluminum index is in the range of 0.90 to 1.10, the change in Al2O3 concentration of the basic aluminum lactate solution before and after the test is small, indicating high storage stability, and long-term stability can also be expected. The lower limit of this range is preferably 0.95. The upper limit of this range is preferably 1.05. Therefore, examples of preferred ranges include 0.95 to 1.10, 0.90 to 1.05, and 0.95 to 1.05.

[0020] (powder) The basic aluminum lactate solution of the present invention may be dried to obtain a powder. This powder can be used as is or dispersed in water. Commonly used drying methods such as spray drying, static drying, and air-flow drying can be employed. The drying temperature is preferably 300°C or lower.

[0021] (Manufacturing method) A preferred method for producing the basic aluminum lactate solution of the present invention includes the step of mixing alumina hydrate and lactic acid. This production method is substantially free of metal elements other than aluminum and substantially free of acids other than lactic acid. Here, "substantially free of metal elements other than aluminum" means that, excluding metal elements other than aluminum derived from impurities in the raw materials, no metal elements other than aluminum are contained. Furthermore, "substantially free of acids other than lactic acid" means that, excluding acids other than lactic acid derived from impurities and by-components in the raw materials, no acids other than lactic acid are contained.

[0022] Examples of alumina hydrates include commercially available aluminum hydroxide and aluminum oxide hydrates, and alumina hydrate gels obtained by neutralizing aluminum salts. Of these, those that are easily soluble are particularly preferred. An example of the production method for the above alumina hydrate gel is a method in which aluminum chloride is reacted with an alkali metal or ammonium carbonate or bicarbonate, and the resulting precipitated alumina hydrate is separated and washed.

[0023] As for lactic acid, use one that contains L-lactic acid and D-lactic acid, with a D-part content in the range of 3 to 99 mol%.

[0024] The mixing ratio of alumina hydrate and lactic acid is set so that the total lactic acid / Al2O3 (molar ratio) is in the range of 1.0 to 4.0. The pH of the resulting basic aluminum lactate solution of the present invention is generally in the range of 3 to 6.

[0025] Furthermore, heating, filtration, concentration adjustment, and concentration steps may be carried out as needed. The heating temperature in the heating step is preferably, for example, 50 to 100°C. The heating time can be set appropriately according to the heating temperature, but for example, 0 to 12 hours is preferred. In the above, a heating time of 0 hours means that heating is stopped when the predetermined heating temperature is reached after heating has started. [Examples]

[0026] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0027] (Types of lactic acid) The types of lactic acid used are as follows: • DL-Lactic Acid: "DL-Lactic Acid Special Grade" manufactured by Kishida Chemical Co., Ltd. (Product Code: 000-43525) (Lactic acid concentration as stated in the test report issued by the company: 91.8% by mass) • L-Lactic Acid: "L-Lactic Acid, Special Grade" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (Product Code: 129-02666) (Lactic acid concentration as stated in the inspection report issued by the company: 88.3% by mass) • D-Lactic Acid: Corbion's "D-Lactic Acid" (Lactic acid concentration as stated in the analysis certificate issued by the company: 92.3% by mass)

[0028] (Preparation of alumina hydrate) An aqueous solution of aluminum chloride (Al2O3: 1% by mass) was prepared by adding 1086 parts by mass of distilled water to 53.9 parts by mass of normal salt aluminum chloride hexahydrate. 100 parts by mass of an aqueous ammonium carbonate solution (NH₃: 4.7% by mass) under stirring was gradually added with 1139.9 parts by mass of the above aluminum chloride aqueous solution to produce an alumina hydrate containing sub-components. This alumina hydrate containing sub-components was filtered using a centrifuge and further washed with pouring water to obtain an alumina hydrate of Al₂O₃: 11.4% by mass, NH₃: 0.06% by mass, and Cl: 0.01% by mass.

[0029] [Examples 1 to 7 and Comparative Examples 1 to 3] Common to Examples 1 to 7 and Comparative Examples 1 to 3, a basic aluminum lactate solution was prepared by the following production method. Table 1 shows the addition amounts of each raw material (alumina hydrate, lactic acid solution). The lactic acid solution was prepared by previously mixing those described in Table 1 among the above DL-lactic acid, L-lactic acid, and D-lactic acid.

[0030] [Production Method] The alumina hydrate and the lactic acid solution were mixed. Then, it was heated at 50 to 70 °C for 30 minutes and further heated at 90 °C for 1 hour to produce a basic aluminum lactate solution. Note that stirring was performed from the above mixing until the heating was completed.

[0031] Here, for the above production method, in the case of Example 1, it is as follows. First, 5.74 g of DL-lactic acid and 23.87 g of L-lactic acid were mixed (mixing ratio of D-form and L-form is 10:90) to prepare a lactic acid solution with a D-form rate of 10 mol% of the raw material charge value. 29.61 g of the above lactic acid solution was added to 163.5 g of the alumina hydrate. This mixed solution was heated at 50 to 70 °C for 30 minutes under stirring and further heated at 90 °C for 1 hour to produce the basic aluminum lactate solution of Example 1.

[0032] [Table 1]

[0033] [[ID=3I]] [D-form Rate] For each basic aluminum lactate solution obtained in Examples 1 to 7 and Comparative Examples 1 to 3, the D-form rate in Table 1 is the value obtained as follows. (1) Raw material preparation cost This value was calculated from the mixing ratio of DL-lactic acid, L-lactic acid, and D-lactic acid used in the preparation of the raw material lactic acid solution. (2) Lactic acid solution analysis values The prepared lactic acid solution was designated as the sample (hereinafter referred to as "Sample A"). Approximately 0.5 g each of DL-lactic acid and L-lactic acid were accurately weighed using a precision balance, placed in a 100 mL volumetric flask, dissolved in distilled water, and then made up to prepare standard solutions of DL-lactic acid and L-lactic acid. For measuring optical rotation, a polarimeter P-2200 manufactured by JASCO Corporation was used, and measurements were taken according to the measurement procedure. Distilled water was used for blank measurements, and the optical rotations of the DL-lactic acid standard solution and L-lactic acid standard solution prepared as described above were measured to create a calibration curve. The calibration curve was y = 0.3271x - 16.317, where x was the D-part fraction and y was the optical rotation. Next, the optical rotation of sample A was measured, and the D-part fraction was determined from the above calibration curve. (3) Analysis values ​​of basic aluminum lactate solution Concentrated hydrochloric acid was added to a basic aluminum lactate solution at a molar ratio of Cl in the concentrated hydrochloric acid to Al2O3 in the basic aluminum lactate solution of 6. The solution was then gently boiled for 10 minutes without a lid. After cooling, the resulting solution was used as the sample for measurement (hereinafter referred to as "Sample B"). Approximately 0.5g each of DL-lactic acid and L-lactic acid were accurately weighed using a precision balance and placed in a 100mL volumetric flask. Approximately 20mL of distilled water and 2mL of concentrated hydrochloric acid were added, and the flask was gently boiled for 10 minutes without a lid. After cooling, the mixture was diluted with distilled water to prepare the standard solution. For measuring optical rotation, a polarimeter P-2200 manufactured by JASCO Corporation was used, and measurements were taken according to the measurement procedure. Distilled water was used for blank measurements, and the optical rotation of the DL-lactic acid standard solution and L-lactic acid standard solution prepared as described above was measured to create a calibration curve. The calibration curve was y = -0.0292x + 1.5467, where x is the D-part fraction and y is the optical rotation. Next, the optical rotation of sample B was measured, and the D-part fraction was determined from the above calibration curve.

[0034] For each basic aluminum lactate solution obtained in Examples 1 to 7 and Comparative Examples 1 to 3, the measurement methods for each analysis item described in the "Analysis Values of Basic Aluminum Lactate Solution" in Table 1 are as follows. In Comparative Example 3, precipitation occurred in the obtained basic aluminum lactate solution, so some analysis items were not analyzed. <Al2O3 Concentration> Chelometric titration by a conventional method was used. The outline is a method in which the basic aluminum lactate solution is dissolved with hydrochloric acid, aluminum ions are chelated with EDTA / 2Na, the pH is adjusted with sodium acetate, and then titrated with a zinc solution using xylenol orange as an indicator. <CaO / Al2O3 (Molar Ratio)> The calcium concentration was measured by atomic absorption spectrophotometry by a conventional method and calculated from the above Al2O3 concentration. <SO4 / Al2O3 (Molar Ratio)> The sulfuric acid concentration was measured by nephelometry using barium chloride by a conventional method and calculated from the above Al2O3 concentration. <ph> The measurement was taken using a portable pH meter, LAQUAact, manufactured by Horiba, Ltd. <ec> The measurement was taken using a CM-42X electrical conductivity meter manufactured by Toa DKK Corporation. <Aluminum Index> The Al2O3 concentration of the basic aluminum lactate solution was measured before storage testing (pre-test Al2O3 concentration). 20 g of basic aluminum lactate solution was measured into a 50 mL iBoy PP wide-mouth bottle sold by AS ONE Corporation, sealed tightly, and left to stand in a constant temperature bath set to 50°C for 3 weeks. After that, a portion from the top to a depth of 5 mm was carefully collected using a pipette, and the Al2O3 concentration in the collected portion was measured (post-test Al2O3 concentration). The aluminum index was calculated using the following formula. Aluminum index = Al2O3 concentration after testing ÷ Al2O3 concentration before testing

[0035] In Examples 1-7 and Comparative Examples 1-3, the D-part ratios of each basic aluminum lactate solution were found to be approximately the same for (1) raw material preparation, (2) lactic acid solution analysis, and (3) basic aluminum lactate solution analysis. Therefore, the analytical methods were considered to be appropriate.

[0036] The aluminum index of each basic aluminum lactate solution obtained in Examples 1 to 7 was within the range of 0.90 to 1.10, indicating high storage stability.

[0037] In all of the basic aluminum lactate solutions obtained in Examples 1-7 and Comparative Examples 1-3, calcium and sulfuric acid components were detected, which are thought to be due to impurities in the raw materials.

[0038] (powder) The basic aluminum lactate solution obtained in Example 5 was dried statically in a forced-air dryer at 100°C to obtain a powder. This powder was dissolved in deionized water to the same concentration as before drying, yielding a solution. The properties of this solution were the same as those of the basic aluminum lactate solution before drying. The pH of this solution was 4.5 and the EC was 0.6 mS / cm.< / ec> < / ph>

Claims

1. A basic aluminum lactate solution that meets the following requirements (1) to (2). (1) The lactic acid contains L-lactic acid and D-lactic acid, which are optical isomers, and the proportion of D-lactic acid in the total lactic acid (L-lactic acid + D-lactic acid) is in the range of 3 to 99 mol%. (2) Total lactic acid / Al 2 O 3 The molar ratio is in the range of 1.0 to 4.

0.

2. The basic aluminum lactate solution according to claim 1, wherein the aluminum index is in the range of 0.90 to 1.10 in the storage test described below. [Storage Test] Before the exam Al 2 O 3 As for the concentration, the Al of the above basic aluminum lactate solution before storage test. 2 O 3 Measure the concentration. Measure 20 g of the above basic aluminum lactate solution into a 50 mL Ibo PP wide-mouth bottle sold by AS ONE Corporation, seal it, and let it stand in a thermostat set at 50°C for 3 weeks. Then, measure the Al concentration in the part from the upper surface to a depth of 5 mm and use it as the Al concentration after the test. 2 O 3 concentration and use it as the Al concentration after the test. 2 O 3 concentration after the test. The aluminum index is calculated using the following formula. Aluminum index = Al after testing 2 O 3 Concentration ÷ Al before test 2 O 3 concentration

3. The process of mixing alumina hydrate and lactic acid, A method for producing a basic aluminum lactate solution according to claim 1 or 2, comprising:

4. A powder obtained by drying the basic aluminum lactate solution according to claim 1 or 2.

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