Thermoresponsive basic aluminum lactate solution

Abstract

The challenge is to develop a basic aluminum lactate solution with novel properties. [Solution] The solution is a basic aluminum lactate solution that satisfies the following requirements (1) and (2) and is thermally responsive. Specifically, (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 2.0.

Description

Technical Field

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

Background Art

[0002] Techniques related to basic aluminum lactate solutions have been disclosed in a number of known documents, including, for example, Patent Document 1. Taking advantage of its properties, it has been used as an additive for alkaline refractories to improve air permeability, to suppress the digestion of basic aggregates, etc., or as an aluminum dopant in the raw materials of composite oxides.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to develop a basic aluminum lactate solution having new properties.

Means for Solving the Problems

[0005] As a result of intensive studies on the above problems, the present inventors have found, quite surprisingly, that by containing L-lactic acid (L-lactic acid) and D-lactic acid (D-lactic acid), which are optical isomers of lactic acid, in a predetermined ratio as lactic acid, and further setting the ratio of lactic acid to aluminum within a specific range, a basic aluminum lactate solution having a new property of thermoresponsiveness can be obtained. Based on this finding, the present invention has been completed.

[0006] The present invention is as follows. [1] A basic aluminum lactate solution having thermoresponsiveness and satisfying 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 2.0. [2] The basic aluminum lactate solution described in [1] above, wherein in the following thermal response test, the total light transmittance A is in the range of 80 to 100%, the total light transmittance B is in the range of 0 to 30%, and the absolute value of ΔAC is in the range of 0 to 10%. [Thermal response test] The Al2O3 concentration of the basic aluminum lactate solution was adjusted to 6% by mass to prepare the test solution. For the thermal response test, the test solution, placed in a sealed container, is kept at 100°C for 1 hour, and then kept at 25°C for 1 week. The total light transmittance of the test solution is measured as follows. • Before subjecting the test to thermal response testing, the total light transmittance is measured and defined as total light transmittance A. After holding the sample in a 100°C environment for 1 hour as described above, allow it to cool in a 25°C environment. One hour after the start of cooling, measure the total light transmittance at a liquid temperature of 25°C and define this as total light transmittance B. After being kept in a 25°C environment for one week as described above, the total light transmittance is measured and defined as the total light transmittance C. ΔAC is calculated from the following formula. ΔAC=Total light transmittance A-Total light transmittance C [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]

[0007] 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".

[0008] The present invention relates to a basic aluminum lactate solution that satisfies the following requirements (1) to (2) and is thermally responsive. (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 2.0.

[0009] (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.

[0010] 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%.

[0011] 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 lactic acid used as a 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 a raw material can be obtained.

[0012] (Requirement 2) The basic aluminum lactate solution of the present invention has a range of total lactic acid / Al2O3 (molar ratio) = 1.0 to 2.0. 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 2.0, it becomes difficult to obtain thermoresponsiveness.

[0013] Regarding the Al2O3 concentration of the basic aluminum lactate solution of the present invention, it is preferably in the range of 1 to 20% by mass. The lower limit value is more preferably 3% by mass, still more preferably 5% by mass, from the economic viewpoints of production and transportation. The upper limit value is more preferably 15% by mass.

[0014] (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 the sulfuric acid component. Here, being substantially free of the 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, more preferably less than 0.008.

[0015] 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 molar ratio of CaO / Al2O3 is less than 0.01, more preferably less than 0.008.

[0016] (Thermal responsiveness) The thermal responsiveness of the basic aluminum lactate solution of the present invention is a phenomenon in which a highly transparent solution becomes turbid due to a heat load, the turbidity decreases when the heat load disappears, and finally returns to almost the original transparency. The turbidity start temperature is approximately around 50 °C. For example, when a solution stored at room temperature (15 - 25 °C) is stored at 50 °C, turbidity gradually progresses, and it becomes turbid after several days (for example, about 5 - 8 days) from the start of storage at 50 °C. Also, in the region at a temperature higher than 50 °C, the progress of turbidity tends to be faster. Particularly, at 65 - 70 °C, the turbidity tends to progress rapidly. When a turbid solution in a heat load environment is switched to, for example, room temperature storage, the turbidity gradually decreases and returns to almost the original transparency over several days.

[0017] Depending on the Al2O3 concentration and D-form ratio of the basic aluminum lactate solution, gelation may occur in addition to turbidity. Regarding the Al2O3 concentration, the higher the concentration, and regarding the D-form ratio, the closer to the center from both end regions of the upper and lower limits of the range (3 - 99 mol%), the more likely gelation occurs in addition to turbidity. In addition, even when gelation occurs, it has thixotropic properties, so the viscosity tends to decrease when a shear stress is applied. When the heat load disappears, the turbidity and viscosity decrease, and finally return to almost the original transparency and viscosity.

[0018] Thermal responsiveness can also be evaluated by the following thermal responsiveness test. If the total light transmittance A is in the range of 80-100%, the total light transmittance B is in the range of 0-30%, and the absolute value of ΔAC is in the range of 0-10%, then the basic aluminum lactate solution can be considered to possess thermal responsiveness.

[0019] [Thermal response test] The Al2O3 concentration of the basic aluminum lactate solution was adjusted to 6% by mass to prepare the test solution. For the thermal response test, the test solution, placed in a sealed container, is kept at 100°C for 1 hour, and then kept at 25°C for 1 week. The total light transmittance of the test solution is measured as follows. • Before subjecting the test to thermal response testing, the total light transmittance is measured and defined as total light transmittance A. After holding the sample in a 100°C environment for 1 hour as described above, allow it to cool in a 25°C environment. One hour after the start of cooling, measure the total light transmittance at a liquid temperature of 25°C and define this as total light transmittance B. After being kept in a 25°C environment for one week as described above, the total light transmittance is measured and defined as the total light transmittance C. ΔAC is calculated from the following formula. ΔAC=Total light transmittance A-Total light transmittance C

[0020] A total light transmittance A in the range of 80-100% indicates high transparency. A total light transmittance B in the range of 0-30% indicates sufficient turbidity. An absolute value of ΔAC in the range of 0-10% indicates that the total light transmittance is approximately the same as before the thermal response test. Therefore, a basic aluminum lactate solution that satisfies these three conditions can be evaluated as possessing thermal responsiveness.

[0021] To adjust the Al2O3 concentration of a basic aluminum lactate solution to 6% by mass, if the concentration is higher than 6% by mass, dilute with distilled water. If the concentration is lower than 6% by mass, concentrate the solution using an evaporator or similar device, and then subject it to a thermal response test once it returns to its pre-concentration solution properties. If the solution does not return to its pre-concentration properties, it is judged to lack thermal responsiveness. For use in the thermal response test, the iBoy PP wide-mouth bottle 50 mL, sold by AS ONE Corporation, is preferred as the sealed container, and when using this container, the amount of test solution should be 20 g. To maintain environments of 100°C and 25°C, it is preferable to use, for example, a forced-air dryer or a constant-temperature oven. The total light transmittance is measured using a haze meter "COH7700" manufactured by Nippon Denshoku Industries, Ltd., under conditions of a wavelength of 400-700 nm (10 nm intervals) and an optical path length of 10 mm. Alternatively, other measuring devices may be used if they can obtain equivalent measurement values. In the measurement of total light transmittance B, the liquid temperature is reduced to 25°C by holding it in a 100°C environment for 1 hour, followed by 1 hour of cooling. However, the decrease in turbidity due to this cooling is hardly noticeable in appearance. Therefore, it is considered that the change in total light transmittance due to cooling for about 1 hour is small. Accordingly, the value of total light transmittance measured as total light transmittance B can be said to be reasonable for evaluating the degree of turbidity.

[0022] (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.

[0023] (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.

[0024] 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.

[0025] 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%.

[0026] 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 2.0. The pH of the resulting basic aluminum lactate solution of the present invention is generally in the range of 3 to 6.

[0027] 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]

[0028] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0029] (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)

[0030] (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. 1139.9 parts by mass of the above aluminum chloride aqueous solution were gradually added to 100 parts by mass of an aqueous ammonium carbonate solution (NH3: 4.7% by mass) under stirring to produce an alumina hydrate containing minor components. This alumina hydrate containing minor components was filtered using a centrifuge and then washed with water to obtain an alumina hydrate with Al2O3: 11.4% by mass, NH3: 0.06% by mass, and Cl: 0.01% by mass.

[0031] [Examples 1-5 and Comparative Examples 1-4] In Examples 1-5 and Comparative Examples 1-4, basic aluminum lactate solutions were prepared using the following manufacturing method. Table 1 shows the amount of each raw material (alumina hydrate, lactic acid solution) added. The lactic acid solution was prepared by pre-mixing the DL-lactic acid, L-lactic acid, and D-lactic acid listed in Table 1.

[0032] <Manufacturing method> Alumina hydrate and lactic acid solution were mixed. The mixture was then heated at 50-70°C for 30 minutes, and then at 90°C for 1 hour to produce a basic aluminum lactate solution. The mixture was stirred throughout the entire heating process.

[0033] Herein, regarding the above manufacturing method, the case of Example 1 is as follows. First, 5.74 g of DL-lactic acid and 23.87 g of L-lactic acid were mixed (with a mixing ratio of D-isomer to L-isomer of 10:90) to prepare a lactic acid solution with a D-isomer content of 10 mol%, which was the same as the raw material's value. 163.5 g of aluminum hydroxide was added with 29.61 g of the above lactic acid solution. This mixture was heated at 50 - 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.

[0034]

Table 1

[0035] <D-form ratio> For each of the basic aluminum lactate solutions obtained in Examples 1 - 5 and Comparative Examples 1 - 4, the D-form ratios in Table 1 are the values determined as follows. (1) Raw material charged value It is a value 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 value <00001`88>The prepared lactic acid solution was used as a sample (hereinafter referred to as "Sample A"). 0.5 g each of the above DL-lactic acid and L-lactic acid were precisely weighed using an analytical balance as a guide and placed in a 100 mL volumetric flask. After dissolving in distilled water, it was made up to the mark to prepare standard solutions of DL-lactic acid and L-lactic acid. For the measurement of specific rotation, a polarimeter P-2200 manufactured by JASCO Corporation was used and measured according to the measurement procedure. Distilled water was used for the blank measurement, and the specific rotations of the standard solutions of DL-lactic acid and L-lactic acid prepared as above were measured to create a calibration curve. The calibration curve was y = 0.3271x - 16.317 when the D-form ratio was x and the specific rotation was y. Next, the specific rotation of Sample A was measured, and the D-form ratio was determined from the above calibration curve. (3) Basic aluminum lactate solution analysis value Concentrated hydrochloric acid was added to the basic aluminum lactate solution at a Cl / Al2O3 (molar ratio) in the concentrated hydrochloric acid to the basic aluminum lactate solution of 6, and then gently boiled for 10 minutes without a lid. After that, the cooled one was used as a sample for measurement (hereinafter referred to as "Sample B"). Precisely weigh 0.5 g each of the above DL-lactic acid and L-lactic acid using an analytical balance as a guide, place them in a 100 mL volumetric flask, add approximately 20 mL of distilled water and 2 mL of concentrated hydrochloric acid, then gently boil for 10 minutes without a lid. After cooling, make up to the mark with distilled water to prepare a standard solution. For the measurement of the specific rotation, a polarimeter P-2200 manufactured by JASCO Corporation was used and measured according to the measurement procedure. Distilled water was used for the blank measurement, and the specific rotations of the standard solutions of DL-lactic acid and L-lactic acid prepared as above were measured to create a calibration curve. The calibration curve was y = -0.0292x + 1.5467 when the D-form ratio was x and the specific rotation was y. Next, the specific rotation of sample B was measured, and the D-form ratio was determined from the above calibration curve.

[0036] Regarding each basic aluminum lactate solution obtained in Examples 1 to 5 and Comparative Examples 1 to 4, 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> A chelometric titration method according to a conventional method was used. The outline is a method of dissolving the basic aluminum lactate solution with hydrochloric acid, chelating aluminum ions with EDTA / 2Na, adjusting the pH with sodium acetate, and then titrating with a zinc solution using xylenol orange as an indicator. <CaO / Al2O3 (Molar Ratio)> The calcium concentration was measured by atomic absorption spectrophotometry according to a conventional method and calculated from the above Al2O3 concentration. <SO4 / Al2O3 (Molar Ratio)> The sulfuric acid concentration was measured by a turbidimetric method using barium chloride according to 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. <Total light transmittance> Measurements were taken using a haze meter "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd., under conditions of wavelength 400-700 nm (10 nm intervals) and optical path length 10 mm. • Thermal response test The total light transmittance of a basic aluminum lactate solution immediately after manufacturing was measured and defined as total light transmittance A. The thermal response test was conducted using the following method. 20 g of basic aluminum lactate solution was placed in a 50 mL iBoy PP wide-mouth bottle sold by AS ONE Corporation and sealed tightly. This was then placed in a ventilated drying oven and heated at 100°C for 1 hour. Next, it was kept at 25°C for 1 week. After heating at 100°C for 1 hour as described above, the sample was allowed to cool in a 25°C environment, and the total light transmittance was measured 1 hour after the start of cooling at a liquid temperature of 25°C (Total Light Transmittance B). The total light transmittance was measured after one week of storage in the 25°C environment described above (total light transmittance C). ΔAC was calculated using the following formula. ·ΔAC=Total light transmittance A-Total light transmittance C

[0037] In Examples 1-5 and Comparative Examples 1-4, 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.

[0038] The properties of each basic aluminum lactate solution obtained in Examples 1-5 were initially transparent, but upon heating at 100°C for 1 hour in the thermal response test, they became cloudy, and their viscosity increased, resulting in gelation. However, after being kept at 25°C for 1 week, the transparency and viscosity returned to almost the same level as the initial state. Therefore, each basic aluminum lactate solution obtained in Examples 1-5 possessed thermal responsiveness. Supporting this, each basic aluminum lactate solution obtained in Examples 1-5 satisfied the following conditions: total light transmittance A was 80-100%, total light transmittance B was 0-30%, and the absolute value of ΔAC was 0-10%. Furthermore, for each basic aluminum lactate solution obtained in Examples 1-2, the operation of {heating at 100°C for 1 hour, followed by keeping at 25°C for 1 week} was repeated twice, and thermal responsiveness was confirmed in both cases. On the other hand, the basic aluminum lactate solutions obtained in Comparative Examples 1, 2, and 4 maintained high transparency even after heating at 100°C for 1 hour and did not exhibit thermal responsiveness. Supporting this, the values ​​of total light transmittance A and total light transmittance B were approximately the same.

[0039] In all of the basic aluminum lactate solutions obtained in Examples 1-5 and Comparative Examples 1-4, calcium and sulfate components were detected, which are thought to be due to impurities in the raw materials.

[0040] (powder) The basic aluminum lactate solution obtained in Example 2 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 4.3 and the EC was 1.2 mS / cm. When this solution was heated at 100°C for 1 hour, as in the thermal response test described above, it became cloudy and gelation was observed. After being kept at 25°C for 1 week, it returned to its original transparency.< / ec> < / ph>

Claims

1. A basic aluminum lactate solution that meets the following requirements (1) to (2) and is thermally responsive. (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 2.

0.

2. The basic aluminum lactate solution according to claim 1, wherein in the following thermal response test, the total light transmittance A is in the range of 80 to 100%, the total light transmittance B is in the range of 0 to 30%, and the absolute value of ΔAC is in the range of 0 to 10%. [Thermal response test] Al in basic aluminum lactate solution 2 O 3 Adjust the concentration to 6% by mass to prepare the test solution. For the thermal response test, the test solution, placed in a sealed container, is kept at 100°C for 1 hour, and then kept at 25°C for 1 week. The total light transmittance of the test solution is measured as follows. - Before subjecting the sample to thermal response testing, the total light transmittance is measured and defined as total light transmittance A. - After holding the sample in a 100°C environment for 1 hour as described above, allow it to cool in a 25°C environment. One hour after the start of cooling, measure the total light transmittance at a liquid temperature of 25°C and define this as total light transmittance B. - After "maintaining in a 25°C environment for one week" as described above, the total light transmittance is measured and defined as the total light transmittance C. ΔAC is calculated from the following formula. ΔAC = Total light transmittance A - Total light transmittance C

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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