Thermoresponsive basic aluminum lactate solution

Abstract

The development of a basic aluminum lactate solution with new characteristics is an issue. 【Solution means】The solution means is a basic aluminum lactate solution that satisfies the following requirements (1) to (2) and has thermoresponsiveness. That is, (1) it contains L-lactic acid, which is an optical isomer of lactic acid, and D-lactic acid, which is a D-isomer, and the ratio of D-lactic acid in total lactic acid (L-lactic acid + D-lactic acid) is in the range of 3 to 99 mol%; and (2) the range of total lactic acid / Al2O3 (molar ratio) = 1.0 to 2.0.

Description

Technical Field

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

Background Art

[0002] Techniques related to basic aluminum lactate solutions have been disclosed in a number of known documents such as Patent Document 1, for example. Taking advantage of its properties, it has been used as an additive for alkaline refractories to improve air permeability and suppress the digestion of basic aggregates, or as an aluminum dopant for 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 heat responsiveness 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 heat responsiveness and satisfying the following requirements (1) to (2). (1) It contains L-lactic acid, which is an optical isomer of lactic acid and is the L-form, and D-lactic acid, which is the D-form, and the proportion of D-lactic acid in total lactic acid (L-lactic acid + D-lactic acid) is in the range of 3 to 99 mol%. (2) The range is total lactic acid / Al2O3 (molar ratio) = 1.0 to 2.0. [2] In the following heat responsiveness test, the basic aluminum lactate solution described in [1] above, wherein 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%. 〔Heat Responsiveness Test〕 Adjust the Al2O3 concentration of the basic aluminum lactate solution to 6% by mass to obtain a test solution. As a heat responsiveness test, the test solution placed in a sealed container is held in a 100°C environment for 1 hour and then held in a 25°C environment for 1 week. For the test solution, measure the total light transmittance as follows. · Measure the total light transmittance before subjecting to the heat responsiveness test, and set it as the total light transmittance A. · After holding in the above-mentioned "100°C environment for 1 hour", cool it in a 25°C environment, and measure the total light transmittance at a liquid temperature of 25°C 1 hour after the start of cooling, and set it as the total light transmittance B. · Measure the total light transmittance after holding in the above-mentioned "25°C environment for 1 week", and set it as the total light transmittance C. Calculate ΔAC 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, including the step of mixing alumina hydrate and lactic acid. [4] A powder obtained by drying the basic aluminum lactate solution according to [1] or [2] above.

Embodiments for Carrying out the Invention

[0007] Hereinafter, the present invention will be described in detail based on preferred embodiments, but the present invention is not limited to the following embodiments, and various modifications can be made within the scope shown in the claims. In the present invention, the notation "numerical value 1 to numerical value 2" regarding a numerical range means a numerical range including both numerical values 1 and 2 with numerical value 1 as the lower limit value and numerical value 2 as the upper limit value, and is synonymous with "numerical value 1 or more and numerical value 2 or less".

[0008] The present invention relates to a basic aluminum lactate solution that satisfies the following requirements (1) to (2) and has thermoresponsiveness. (1) It contains L-lactic acid which is an optical isomer of lactic acid and D-lactic acid which is the D-form, and the proportion of D-lactic acid in total lactic acid (L-lactic acid + D-lactic acid) is in the range of 3 to 99 mol%. (2) The range of total lactic acid / Al2O3 (molar ratio) = 1.0 to 2.0.

[0009] (Requirement 1) Lactic acid has L-form and D-form as optical isomers, which are called L-lactic acid and D-lactic acid respectively. In the literature, if it is simply described as "lactic acid", it is common technical knowledge that it is intended to be L-lactic acid. Generally, when it is described as "L-lactic acid", it is often the case when it is 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 total lactic acid, that is, [L-lactic acid + D-lactic acid] (hereinafter referred to as "D-form ratio") is in the range of 3 to 99 mol%. When the D-form ratio is less than 3 mol% or more than 99 mol%, precipitation is likely to occur. The lower limit value of the above range is preferably 5 mol%, more preferably 7 mol%, still more preferably 8 mol%, and particularly preferably 10 mol%. Therefore, preferred ranges of the D-form ratio include 5 to 99 mol%, 7 to 99 mol%, 8 to 99 mol%, and 10 to 99 mol%.

[0011] In the present invention, the measurement method for obtaining the D-form ratio is as follows. (Treatment of basic aluminum lactate solution) In order to measure the specific rotation of lactic acid in the basic aluminum lactate solution to be measured, a treatment is performed to dissolve aluminum in the solution in hydrochloric acid. Specifically, concentrated hydrochloric acid is added to the basic aluminum lactate solution in the range of Cl in concentrated hydrochloric acid / Al2O3 in the basic aluminum lactate solution (molar ratio) = 3 to 10, and then it is boiled for 10 minutes. Then, the cooled one is used as a sample for measurement. In the above boiling, it is gently boiled so as not to evaporate to dryness. (Calibration curve creation) The lactic acids used to obtain the calibration curve are DL-lactic acid (a mixture of 50 mol% each of L-lactic acid and D-lactic acid) and L-lactic acid. As DL-lactic acid, "DL-Lactic Acid Special Grade" (product code: 000-43525) manufactured by Kishida Chemical Co., Ltd. is used. As L-lactic acid, "L-Lactic Acid Special Grade" (product code: 129-02666) manufactured by Fujifilm Wako Pure Chemical Corporation is used. Approximately 0.5 g each of the above DL-lactic acid and L-lactic acid are precisely weighed with an analytical balance as a guide and placed in a 100 mL volumetric flask. After adding about 20 mL of distilled water and 2 mL of concentrated hydrochloric acid, it is boiled for 10 minutes, cooled, and then made up to the mark with distilled water to prepare a standard solution. In the above boiling, it is gently boiled so as not to evaporate to dryness. The discrimination of optical isomers (L-form, D-form) is performed by measuring the specific rotation. As the measuring device, a polarimeter P-2200 manufactured by JASCO Corporation is used. If a measurement value equivalent to the said measuring device can be obtained, another measuring device may be used. Using the standard solutions of DL-lactic acid and L-lactic acid prepared as above, the specific rotations are measured with the above measuring device to create a calibration curve. Next, the specific rotation of the sample is measured, and the D-form ratio of the sample is determined from the calibration curve. For the blank measurement, distilled water is used. In this measurement method, since a standard solution consisting only of D-lactic acid is not used, depending on the calibration curve, for example, when measuring D-lactic acid, the D-form ratio may exceed 100 mol%, but even if it does, there is no problem, and the value exceeding 100 mol% may be adopted as it is. Incidentally, 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 not necessary. 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 total lactic acid / Al2O3 (molar ratio) in the range of 1.0 to 2.0. When the total lactic acid / Al2O3 (molar ratio) is less than 1.0, the 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 thermal responsiveness.

[0013] The Al2O3 concentration of the basic aluminum lactate solution of the present invention is preferably in the range of 1 to 20% by mass. The lower limit is more preferably 3% by mass, and even more preferably 5% by mass, from the viewpoint of economic efficiency in production and transportation. The upper limit 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 the SO4 / Al2O3 (molar ratio) is less than 0.01, and 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, except for 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 generally 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 several days after the start of storage at 50°C (for example, about 5 - 8 days later). Also, in the region at a temperature higher than 50°C, the progress of turbidity tends to be faster. In particular, at 65 - 70°C, the turbidity tends to progress rapidly. When a turbid solution under 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-isomer 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-isomer 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 is to occur in addition to turbidity. Incidentally, 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, for example, by the following thermal responsiveness test. If the following total light transmittance A is in the range of 80 to 100%, 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%, the basic aluminum lactate solution can be regarded as having thermal responsiveness.

[0019] 〔Thermal Responsiveness Test〕 Adjust the Al2O3 concentration of the basic aluminum lactate solution to 6% by mass to obtain a test solution. As a thermal responsiveness test, the test solution placed in a sealed container is held at 100 °C for 1 hour and then held at 25 °C for 1 week. Measure the total light transmittance of the test solution as follows. · Measure the total light transmittance before subjecting to the thermal responsiveness test and designate it as total light transmittance A. · After holding at 100 °C for 1 hour, cool it at 25 °C and measure the total light transmittance at a liquid temperature of 25 °C 1 hour after the start of cooling, and designate it as total light transmittance B. · Measure the total light transmittance after holding at 25 °C for 1 week and designate it as total light transmittance C. Calculate ΔAC from the following formula. ΔAC = total light transmittance A - total light transmittance C

[0020] When the total light transmittance A is in the range of 80 to 100%, it can be said that the transparency is high. When the total light transmittance B is in the range of 0 to 30%, it can be said that it is sufficiently turbid. When the absolute value of ΔAC is in the range of 0 to 10%, it can be said that it has almost the same total light transmittance as before subjecting to the thermal responsiveness test. Therefore, a basic aluminum lactate solution that satisfies these three conditions can be evaluated as having thermal responsiveness.

[0021] The method for adjusting the Al2O3 concentration of the basic aluminum lactate solution to 6% by mass is to dilute with distilled water when it is higher than 6% by mass. When it is lower than 6% by mass, concentrate it using an evaporator or the like and then subject it to the thermal responsiveness test when it returns to the solution properties before concentration. Note that those that do not return to the solution properties before concentration are judged not to have thermal responsiveness. As the sealed container used for the heat response test, the I-Boy PP wide-mouth bottle 50 mL sold by AS ONE Corporation is preferable. When using this container, the amount of the test solution is set to 20 g. In order to set the environment to 100 °C and 25 °C, for example, it is preferable to use a ventilation dryer, a thermostat, or the like. The total light transmittance is measured using a haze meter "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd. under the conditions of a wavelength of 400 to 700 nm (at 10 nm intervals) and an optical path length of 10 mm for the test solution to be measured. Note that if a measurement value equivalent to that of the said measuring device can be obtained, another measuring device may be used. In the measurement of the total light transmittance B, after holding at 100 °C for 1 hour, the liquid temperature is lowered to 25 °C by cooling for 1 hour. However, visually, almost no decrease in turbidity due to this cooling can be recognized. Therefore, it is considered that the change in the total light transmittance due to cooling for about 1 hour is small. Therefore, the value of the total light transmittance measured as the total light transmittance B can be said to be appropriate for evaluating the turbidity level.

[0022] (Powder) The basic aluminum lactate solution of the present invention may be made into a powder by drying it. The powder can be used as it is or dispersed in water. As the drying method, commonly used methods such as spray drying, static drying, and fluidized bed drying can be adopted. Regarding the drying temperature, 300 °C or lower is preferable.

[0023] (Manufacturing method) A preferred manufacturing method of the basic aluminum lactate solution of the present invention includes a step of mixing an aluminum hydrate and lactic acid. The manufacturing method is a method that substantially does not contain metal elements other than aluminum and substantially does not contain acids other than lactic acid. Here, substantially not containing 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. Also, substantially not containing 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 the alumina hydrate include generally commercially available aluminum hydroxide, hydrates of aluminum oxide, and alumina hydrate gels obtained by neutralization of aluminum salts, etc. Among these, those with high solubility are particularly preferred. A production example of the above alumina hydrate gel is, for example, a production method in which aluminum chloride is reacted with a carbonate or bicarbonate of an alkali metal or ammonium, and the precipitated alumina hydrate is separated and washed.

[0025] As the lactic acid, those containing L-lactic acid and D-lactic acid and having a D-isomer ratio in the range of 3 to 99 mol% are used.

[0026] The mixing ratio of the 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 basic aluminum lactate solution of the present invention obtained thereby is generally in the range of 3 to 6.

[0027] Furthermore, if necessary, a heating step, a filtration step, a concentration adjustment step, a concentration step, etc. may be carried out. The heating temperature in the heating step is preferably, for example, 50 to 100°C. The heating time may be appropriately set according to the heating temperature, but is preferably, for example, 0 to 12 hours. In the above, a heating time of 0 hours means stopping the heating when the predetermined heating temperature is reached after starting the heating.

Examples

[0028] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[0029] (Type 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 described in the test report issued by the company: 91.8 mass%) · L-Lactic acid: "L-Lactic acid, Special Grade" manufactured by FUJIFILM Wako Pure Chemical Corporation (Product Code: 129-02666) (Lactic acid concentration described in the inspection certificate issued by the company: 88.3% by mass) · D-Lactic acid: "D-Lactic acid" manufactured by Corbion (Lactic acid concentration described in the analysis certificate issued by the company: 92.3% by mass)

[0030] (Preparation of alumina hydrate) 1086 parts by mass of distilled water was added to 53.9 parts by mass of aluminum chloride hexahydrate of the normal salt to prepare an aluminum chloride aqueous solution (Al2O3: 1% by mass). 1139.9 parts by mass of the above aluminum chloride aqueous solution was 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 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.

[0031] [Examples 1 to 5 and Comparative Examples 1 to 4] Common to Examples 1 to 5 and Comparative Examples 1 to 4, 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 premixing those described in Table 1 among the above DL-lactic acid, L-lactic acid, and D-lactic acid.

[0032] [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. Stirring was performed from the above mixing to the end of heating.

[0033] Here, in the case of Example 1, the above production method 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 was 10:90) to prepare a lactic acid solution with a D-form rate of 10 mol% as the raw material charging 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 to 70 °C for 30 minutes with 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-isomer ratio> For each of the basic aluminum lactate solutions obtained in Examples 1 to 5 and Comparative Examples 1 to 4, the D-isomer 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 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 on 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 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 = 0.3271x - 16.317 when the D-isomer ratio was x and the specific rotation was y. Next, the specific rotation of Sample A was measured, and the D-isomer 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 weighed 0.5 g each of the above DL-lactic acid and L-lactic acid using an analytical balance, placed them in a 100 mL volumetric flask, added approximately 20 mL of distilled water and 2 mL of concentrated hydrochloric acid, gently boiled them for 10 minutes without a lid, allowed them to cool, and then made 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 DL-lactic acid standard solution and the L-lactic acid standard solution 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. Note that 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> Measured with the portable pH meter LAQUAact manufactured by Horiba, Ltd. <ec> It was measured with a conductivity meter CM-42X manufactured by Toa DKK Corporation. <Total light transmittance> Using a haze meter "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd., it was measured under the conditions of a wavelength of 400 to 700 nm (at 10 nm intervals) and an optical path length of 10 mm. · Thermal response test The total light transmittance of the basic aluminum lactate solution immediately after production was measured and designated as the total light transmittance A. The thermal response test was carried out by the following method. 20 g of the basic aluminum lactate solution was put into a 50 mL I-Boy PP wide-mouth bottle sold by AS ONE Corporation and sealed. This was placed in a ventilation dryer and heated at 100 °C for 1 hour. Next, it was kept in a 25 °C environment for 1 week. After heating at 100 °C for 1 hour, it was allowed to cool in a 25 °C environment, and the total light transmittance was measured at a liquid temperature of 25 °C 1 hour after the start of cooling (total light transmittance B). After keeping in the 25 °C environment for 1 week, the total light transmittance was measured (total light transmittance C). ΔAC was calculated from the following formula. · ΔAC = Total light transmittance A - Total light transmittance C

[0037] Regarding the D-form ratio of each basic aluminum lactate solution obtained in Examples 1 to 5 and Comparative Examples 1 to 4, since the values of (1) the raw material charged value, (2) the lactic acid solution analysis value, and (3) the basic aluminum lactate solution analysis value showed almost the same values, the analysis method was considered to be appropriate.

[0038] The properties of each basic aluminum lactate solution obtained in Examples 1 to 5 were initially transparent, but became turbid upon heating at 100 °C for 1 hour in the thermoresponsive test, and further increased in viscosity and gelled. However, by maintaining it at 25 °C for one week, the transparency and viscosity returned to almost the same as the initial state. Therefore, each basic aluminum lactate solution obtained in Examples 1 to 5 had thermoresponsiveness. To confirm this, each basic aluminum lactate solution obtained in Examples 1 to 5 satisfied a total light transmittance A of 80 to 100%, a total light transmittance B of 0 to 30%, and an absolute value of ΔAC of 0 to 10%. Further, for each basic aluminum lactate solution obtained in Examples 1 and 2, the operation of {heating at 100 °C for 1 hour and then maintaining at 25 °C for one week} was repeated twice, and thermoresponsiveness could be confirmed both times. On the other hand, each basic aluminum lactate solution obtained in Comparative Examples 1, 2, and 4 maintained a high transparency even upon heating at 100 °C for 1 hour and did not show thermoresponsiveness. To confirm this, the values of the total light transmittance A and the total light transmittance B were of the same degree.

[0039] For each basic aluminum lactate solution obtained in Examples 1 to 5 and Comparative Examples 1 to 4, calcium components and sulfuric acid components were detected in all cases, but these were considered to be derived from impurities in the raw materials.

[0040] (Powder) The basic aluminum lactate solution obtained in Example 2 was statically dried at 100 °C with a ventilating dryer to obtain a powder. When ion-exchanged water was added to this powder to make it the same concentration as before drying and dissolved, a solution was obtained. 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 in the same manner as the above thermoresponsive test, it became turbid and gelation was also observed. Thereafter, when it was maintained at 25 °C for one week, it returned to its original transparency.< / ec> < / ph>

Claims

1. A basic aluminum lactate solution having heat responsiveness and satisfying the following requirements (1) to (2). (1) It contains L-lactic acid, which is an optical isomer of lactic acid, and D-lactic acid, which is the D-isomer, and the proportion of D-lactic acid in 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 (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 heat responsiveness 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%. 〔Heat Responsiveness Test〕 Al in basic aluminum lactate solution 2 O 3 The concentration is adjusted to 6% by mass to prepare a test solution. As the heat responsiveness test, a test solution placed in a sealed container is held in a 100°C environment for 1 hour and then held in a 25°C environment for 1 week. For the test solution, the total light transmittance is measured as follows. ・Measure the total light transmittance before subjecting it to the heat responsiveness test, and define it as the total light transmittance A. ・After holding at 100°C for 1 hour, cool it in a 25°C environment, and measure the total light transmittance at a liquid temperature of 25°C 1 hour after the start of cooling, and define it as the total light transmittance B. ・Measure the total light transmittance after holding at 25°C for 1 week, and define it as the total light transmittance C. Calculate ΔAC from the following formula. ΔAC = total light transmittance A - total light transmittance C

3. A step of mixing alumina hydrate and lactic acid A method for producing a basic aluminum lactate solution according to Claim 1 or 2, comprising the step.

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

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