Method for producing amino acid-containing hydrotalcite

Abstract

The present invention provides a novel production method which is for amino acid-containing hydrotalcite and by which the amount of an alkaline solution used can be reduced, and amino acid-containing hydrotalcite having stable quality can be obtained even when a reused amino acid aqueous solution is used as a raw material.　The present disclosure is a production method for amino acid-containing hydrotalcite. The production method comprises step (A), a solution preparation step, and a generation step.　Step (A) is a step for separating a slurry containing first amino acid-containing hydrotalcite and a dissolved amino acid into first amino acid-containing hydrotalcite and a dissolved amino acid-containing solution.　The solution preparation step is a step for preparing a slurry solution by mixing a composite metal oxide with an amino acid aqueous solution derived from the dissolved amino acid-containing solution separated from the slurry after step (A).　The generation step is a step for generating second amino acid-containing hydrotalcite by heating the slurry solution.

Description

[Technical Field]

[0001] This invention relates to a method for producing amino acid-containing hydrotalcite. [Background technology]

[0002] Hydrotalcite compounds, including hydrotalcite or its calcined products, possess ion exchange capabilities and are used in various applications, such as suppressing resin degradation when incorporated into resins. Methods for increasing the aspect ratio of this type of hydrotalcite compound using amino acids are known (Patent Document 1 and Non-Patent Document 1).

[0003] In this conventional method, an amino acid-containing hydrotalcite, which is a complex of hydrotalcite compounds and amino acids, can be obtained by heat-treating a mixture of hydrotalcite compounds and an aqueous amino acid solution. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2019 / 092453 [Non-patent literature]

[0005] [Non-Patent Document 1] NATURE COMMUNICATIONS(2019)10:2398, High gas barrier coating using non-toxic nanosheet dispersions for flexible food packaging film. [Overview of the project] [Problems that the invention aims to solve]

[0006] Amino acid-containing hydrotalcite, obtained by heat-treating a mixture of hydrotalcite compounds and an aqueous amino acid solution, is obtained in the form of a slurry containing amino acid-containing hydrotalcite and dissolved amino acids. In Non-Patent Literature 1, purified amino acid-containing hydrotalcite was obtained by adding an alkaline solution to this slurry to precipitate the amino acid-containing hydrotalcite. In this case, the subsequent use of the amino acids used in the production of the amino acid-containing hydrotalcite was not considered.

[0007] Incidentally, with the SDGs (Sustainable Development Goals) adopted at the UN Summit being widely discussed these days, there is a need to utilize raw materials more efficiently and effectively. However, it is not known how to utilize the amino acid aqueous solution remaining after precipitation of amino acid-containing hydrotalcite.

[0008] The present invention aims to provide a novel method for producing amino acid-containing hydrotalcite using an aqueous amino acid solution as a raw material. [Means for solving the problem]

[0009] This disclosure includes the following aspects:

[0010] (First Disclosure) This first disclosure is a method for producing amino acid-containing hydrotalcite. The production method is characterized by comprising the following steps: (A), a solution preparation step, and a production step. Step (A) is a step of separating a slurry containing a first amino acid-containing hydrotalcite and dissolved amino acids into the first amino acid-containing hydrotalcite and a solution containing the dissolved amino acids. The solution preparation step is a step, performed after step (A) above, in which an aqueous amino acid solution derived from the solution containing the dissolved amino acids separated from the slurry is mixed with a composite metal oxide obtained by calcining a precursor hydrotalcite compound to prepare a slurry solution. The production step is a step of heating the slurry solution to produce a second amino acid-containing hydrotalcite.

[0011] (Second Disclosure) In this second disclosure, in the first disclosure, the step (A) is characterized in that water is added to the slurry and separated into the first amino acid-containing hydrotalcite and a solution containing the dissolved amino acid.

[0012] (Third Disclosure) In this third disclosure, in the first disclosure, the step (A) separates the slurry without adding water into a slurry containing the first amino acid-containing hydrotalcite and a part of the dissolved amino acid and a solution containing the remaining part of the dissolved amino acid. Then, water is added to the slurry containing the first amino acid-containing hydrotalcite and a part of the dissolved amino acid, and separated into the first amino acid-containing hydrotalcite and a solution containing the dissolved amino acid, which is characterized in that.

[0013] (Fourth Disclosure) In this fourth disclosure, in the first disclosure, the step (A) has the following steps (a1) and (a2), and is characterized in that the step (a2) is performed once or more times. Step (a1) is a step of separating the slurry without adding water into a slurry containing the first amino acid-containing hydrotalcite and a part of the dissolved amino acid and a solution containing the remaining part of the dissolved amino acid. Step (a2) is a step of, after the step (a1), adding water to the slurry containing the first amino acid-containing hydrotalcite and a part of the dissolved amino acid, and separating it into a slurry containing the first amino acid-containing hydrotalcite and containing a part of the dissolved amino acid or not containing the dissolved amino acid and a solution containing the remaining part of the dissolved amino acid.

[0014] (Fifth Disclosure) In this fifth disclosure, in any one of the first disclosure to the fourth disclosure, it is characterized by further having the following solution preparation step and production step before the step (A). The solution preparation step involves mixing an aqueous amino acid solution with a composite metal oxide obtained by calcining a precursor hydrotalcite compound to prepare a slurry solution. The production process involves heating the slurry solution to produce the first amino acid-containing hydrotalcite.

[0015] (Disclosure 6) This sixth disclosure is characterized in that any of the first to fifth disclosures further comprises a step (B) after step (A) above, in which the amino acids are reduced from the first amino acid-containing hydrotalcite using an alkaline solution.

[0016] (Disclosure No. 7) In this seventh disclosure, in the sixth disclosure, step (B) is characterized by adding the alkaline solution while stirring the first amino acid-containing hydrotalcite.

[0017] (Disclosure No. 8) This eighth disclosure is characterized in that, in any of the first to seventh disclosures, the above-mentioned amino acid is an amino acid with a solubility of 10 g / 100 mL H2O or more.

[0018] (Disclosure 9) This ninth disclosure is characterized in that, in any of the first to eighth disclosures, the above-mentioned amino acid is a glycine compound.

[0019] (Disclosure No. 10) This tenth disclosure is characterized in that, in any of the first to ninth disclosures, the hydrotalcite compounds contained in the first amino acid-containing hydrotalcite are represented by the following formula (1). (M 2+ ) 1-X (M 3+ ) X (OH)2(A n- ) X / n ·mH2O···(1) (In equation (1), M 2+is a divalent metal cation. M 3+ is a trivalent metal cation. A n- is an n-valent anion. X is a number satisfying 0.17 < X < 0.36. n is an integer from 1 to 6. m is a number satisfying 0 < m < 1.80.)

[0020] (Disclosure No. 11) In this 11th disclosure, in any one of the 1st to 10th disclosures, the amino acid concentration of the above slurry is less than 0.6 mol / L, which is a feature. [Advantages of the Invention]

[0021] The present invention can provide a novel method for producing an amino acid-containing hydrotalcite using an aqueous amino acid solution as a raw material. [Brief Description of the Drawings]

[0022] [Figure 1] Figure 1 is a flowchart showing an example of the first embodiment of the present invention. The dashed line in Figure 1 indicates the content of Claim 1. [Figure 2] Figure 2 is a flowchart showing an example of the second embodiment of the present invention. [Figure 3] Figure 3 is a flowchart showing an example of the third embodiment of the present invention. [Figure 4] Figure 4 is a flowchart showing an example of the fourth embodiment of the present invention. [Modes for Carrying Out the Invention]

[0023] Hereinafter, preferred embodiments of the method for producing an amino acid-containing hydrotalcite of the present invention will be described in detail. In this specification, "amino acid-containing hydrotalcite" means a hydrotalcite compound chemically modified with an amino acid.

[0024] [Method for Producing Amino Acid-Containing Hydrotalcite] In one embodiment of the present invention, a method for producing amino acid-containing hydrotalcite includes the following steps. The production method first includes a step (A) of separating a slurry containing a first amino acid-containing hydrotalcite and dissolved amino acids into the first amino acid-containing hydrotalcite and a solution containing dissolved amino acids. Furthermore, the production method includes a solution preparation step after step (A) of mixing an aqueous amino acid solution derived from the solution containing dissolved amino acids separated from the slurry with a composite metal oxide obtained by calcining a precursor hydrotalcite compound to prepare a slurry solution. The production method then includes a production step of heating the slurry solution to produce a second amino acid-containing hydrotalcite.

[0025] In the manufacturing method of this embodiment, step (A) is a step of separating a slurry containing the first amino acid-containing hydrotalcite and dissolved amino acids into the first amino acid-containing hydrotalcite and a solution containing dissolved amino acids. In step (A), the slurry is the slurry after the production step of the first amino acid-containing hydrotalcite, and is a slurry containing the first amino acid-containing hydrotalcite and dissolved amino acids. This slurry has not been washed with an alkaline solution after the production step of the first amino acid-containing hydrotalcite, and therefore no additional alkaline solution has been added. Here, the additional alkaline solution is an alkaline solution intended to remove amino acids contained in the slurry. In step (A), such a slurry is separated into the first amino acid-containing hydrotalcite and a solution containing dissolved amino acids.

[0026] The first amino acid-containing hydrotalcite production step involves heating a slurry solution, which is a mixture of an aqueous amino acid solution and a composite metal oxide obtained by calcining a precursor hydrotalcite compound, to produce the first amino acid-containing hydrotalcite. In this specification, this production step may be referred to as the heating step. This production step will be explained in detail in the descriptions of each step described later.

[0027] Under conditions where a large amount of dissolved amino acids are present in the slurry, it is necessary to use a certain amount or more of alkaline solution to sufficiently reduce the amount of amino acids contained in amino acid-containing hydrotalcite, which leaves room for improvement in terms of resource conservation and production costs. Furthermore, even when attempting to reuse dissolved amino acids separated by solid-liquid separation after using an alkaline solution for amino acid removal as an aqueous amino acid raw material, variations tend to occur in the amount of metal ions in the aqueous solution, and the amount of amino acids in the slurry is affected by the amount of OH - We found that because the amount is relatively small compared to other sources, it is difficult to obtain hydrotalcite containing amino acids of stable quality.

[0028] The inventors have discovered that the amount of alkaline solution used can be reduced by separating the slurry after the heating process into amino acid-containing hydrotalcite and a solution containing dissolved amino acids, without treating the slurry with an alkaline solution. In this method, after separating the slurry into amino acid-containing hydrotalcite and a solution containing dissolved amino acids, the amino acid-containing hydrotalcite is treated with an alkaline solution. Furthermore, the inventors have found that this method allows for the production of amino acid-containing hydrotalcite with stable quality even when using a recycled amino acid solution as a raw material.

[0029] The present invention was completed based on these findings, and as described above, in the manufacturing method of one embodiment of the present invention, the slurry after the production step is not treated with an alkaline solution, but is separated in step (A) into the first amino acid-containing hydrotalcite and a solution containing dissolved amino acids. Therefore, in the manufacturing method of this embodiment, the separated first amino acid-containing hydrotalcite can be treated with an alkaline solution at any time after step (A). At this time, since the separated first amino acid-containing hydrotalcite contains almost no dissolved amino acids, the amount of alkaline solution required during alkaline treatment can be minimized. In other words, the manufacturing method of this embodiment can reduce the amount of alkaline solution used.

[0030] Furthermore, as described above, the manufacturing method of this embodiment includes a step after step (A) in which the solution containing dissolved amino acids separated from the slurry is reused and used as the raw material aqueous solution for the production of the next amino acid-containing hydrotalcite. That is, this manufacturing method includes a solution preparation step in which an amino acid aqueous solution derived from the separated solution containing dissolved amino acids is mixed with a complex metal oxide to prepare a slurry solution, and a production step in which the slurry solution is heated to produce the next second amino acid-containing hydrotalcite.

[0031] In the manufacturing method of this embodiment, since the solution containing dissolved amino acids separated in step (A) is not treated with an alkaline solution, even if such a solution is reused as the raw material aqueous solution in the next manufacturing process, variations in the amount of metal ions in the aqueous solution are less likely to occur, and the amount of amino acid ions in the slurry is OH - This results in a relatively higher amount. Therefore, the manufacturing method of this embodiment makes it easier to obtain amino acid-containing hydrotalcite of stable quality even when recycled amino acid aqueous solution is used as a manufacturing raw material. Furthermore, the manufacturing method of this embodiment has the advantage of being highly recyclable, which can contribute to achieving the SDGs (Sustainable Development Goals) adopted at the UN Summit.

[0032] Here, "amino acid aqueous solution derived from a solution containing dissolved amino acids" includes not only the solution containing dissolved amino acids itself, but also amino acid aqueous solutions obtained by adjusting the amino acid concentration by subjecting the solution containing dissolved amino acids to various treatments such as concentration, dilution, or adsorption.

[0033] In this embodiment, the slurry before separation in step (A) may be obtained by the same process as the solution preparation step and the production step described above. That is, the manufacturing method of this embodiment may further include a solution preparation step and a production step before step (A). Here, the solution preparation step is a step of preparing a slurry solution by mixing an aqueous amino acid solution with a composite metal oxide obtained by calcining a precursor hydrotalcite compound. The production step is a step of heating the slurry solution to produce the first amino acid-containing hydrotalcite.

[0034] Having such a solution preparation step and production step before step (A) allows for adjustment of various manufacturing conditions in these steps, making it possible to obtain the desired first amino acid-containing hydrotalcite and slurry containing dissolved amino acids with greater precision. This makes it possible to more reliably obtain the effects of the above-described embodiment.

[0035] In addition, the manufacturing method of this embodiment may further include a cooling step to cool the slurry after the above-described generation step and before step (A). This cooling step will be explained in detail in the description of each step below.

[0036] The steps that may be included in the method for producing amino acid-containing hydrotalcite of this embodiment will be described in more detail below, using the first to fourth embodiments shown as examples. In the following descriptions of each step, hydrotalcite may be abbreviated as "HT".

[0037] [First Embodiment] Figure 1 is a flow chart showing an example of a first embodiment of the present invention. As shown in Figure 1, the first embodiment of the present invention includes a solution preparation step, a production step, a cooling step, a separation step (A), and an alkali treatment step (B). In this first embodiment, a purified product of the first amino acid-containing hydrotalcite (purified amino acid-containing HT) is obtained through these steps.

[0038] Furthermore, in the first embodiment, after step (A), there is a step (C) in which the solution containing dissolved amino acids, which is the liquid component separated in step (A), is treated and reused so that it can be used as part of the raw material for the next amino acid-containing hydrotalcite.

[0039] Step (C) of this first embodiment includes a step of treating the solution containing dissolved amino acids separated from the slurry in step (A) in a concentration step to obtain a concentrated amino acid aqueous solution. The concentrated amino acid aqueous solution is an example of an "amino acid aqueous solution derived from a solution containing dissolved amino acids". The concentrated amino acid aqueous solution obtained here is reused as part of the raw material for the production of the next amino acid-containing hydrotalcite (second amino acid-containing hydrotalcite). That is, the concentrated amino acid aqueous solution is used in the solution preparation step when producing the second amino acid-containing hydrotalcite and is mixed with a composite metal oxide obtained by calcining a precursor hydrotalcite compound.

[0040] Furthermore, in this first embodiment, any additional steps, such as a drying step or a surface treatment step, may be performed on the purified amino acid-containing HT obtained after step (B).

[0041] The following describes in detail each step of the manufacturing method according to the first embodiment.

[0042] <Solution preparation process> The solution preparation step involves mixing an amino acid aqueous solution with a complex metal oxide obtained by calcining a precursor hydrotalcite compound to prepare a slurry solution. This solution preparation step is common not only when producing the first amino acid-containing hydrotalcite, but also when producing the second amino acid-containing hydrotalcite and subsequent amino acid-containing hydrotalcite. However, at least a portion of the amino acid aqueous solution used as raw material is derived from a solution containing dissolved amino acids that was separated and recovered when producing the previous amino acid-containing hydrotalcite. For example, at least a portion of the amino acid aqueous solution used when producing the second amino acid-containing hydrotalcite is derived from a solution containing dissolved amino acids that was separated and recovered when producing the first amino acid-containing hydrotalcite.

[0043] In the solution preparation step, a precursor hydrotalcite compound is first calcined to obtain a composite metal oxide. The calcination conditions for the precursor hydrotalcite compound are not particularly limited, and any calcination conditions can be adopted depending on the calcination method, etc. For example, when calcining using a calcination furnace, the calcination temperature can be 300°C to 800°C. Furthermore, the calcination time in this case can be 0.1 hours to 24 hours. Similarly, for example, when calcining using microwaves, the calcination temperature can be 300°C to 800°C. Furthermore, the calcination time in this case can be 1 minute to 12 hours.

[0044] Next, a slurry solution is obtained by adding and mixing an aqueous amino acid solution of a predetermined concentration to the powder of a composite metal oxide obtained by calcining the precursor hydrotalcite compounds. At this time, at least a portion of the aqueous amino acid solution is derived from the solution containing dissolved amino acids that was separated and recovered during the previous production of amino acid-containing hydrotalcite, as described above.

[0045] In the solution preparation step, the slurry concentration of the slurry solution obtained by mixing the complex metal oxide and the amino acid aqueous solution is preferably less than 30 g / L. When the slurry concentration is less than 30 g / L, the interparticle interactions of the hydrotalcite compounds are reduced, making it less likely for gelation to occur during the exfoliation process of the hydrotalcite compounds. As a result, the slurry state of the slurry solution is easier to maintain, and the desired amino acid-containing hydrotalcite can be produced more stably.

[0046] Furthermore, from the standpoint of productivity, the slurry concentration in the solution preparation process is more preferably within the range of 1 g / L to 28 g / L. Here, the slurry concentration can be calculated using the following formula. Slurry concentration (g / L) = Weight of composite metal oxide (g) / Volume of slurry (L)

[0047] In the solution preparation step, the above-mentioned composite metal oxide is hydrated using an aqueous solution of an amino acid that functions as a releasing agent. During this hydration, amino acid molecules in the solution are incorporated as anions into the interlayer of the hydrotalcite-like compound. Further, by heating in the next production step, the interlayer of the hydrotalcite is exfoliated, and a thin amino acid-containing hydrotalcite is formed. At this time, the amino acid-containing hydrotalcite promotes particle growth in the width direction. In other words, amino acid-containing hydrotalcite particles with a high aspect ratio are formed.

[0048] (Hydrotalcite-like compound) The precursor hydrotalcite-like compound that can be used in the present embodiment is not particularly limited. For example, a hydrotalcite-like compound represented by the following formula (1) can be mentioned. (M 2+ ) 1-X (M 3+ ) X (OH)2(A n- ) X / n ·mH2O ···(1) In formula (1), M 2+ is a divalent metal cation. M 3+ is a trivalent metal cation. A n- is an n-valent anion. X is a number satisfying 0.17 < X < 0.36. n is an integer from 1 to 6. m is a number satisfying 0 < m < 1.80.

[0049] In the above formula (1), preferable M 2+ is Mg 2+ In the above formula (1), preferable M 3+ is Al 3+ These hydrotalcite-like compounds have the advantage of high safety to the living body. Further, these hydrotalcite-like compounds have an advantage that their refractive index is close to that of resins such as polypropylene and polyethylene, and it is easy to maintain the transparency of a composition with such resins. Furthermore, the molar ratio of Mg / Al2 is preferably within the range of 4 to 8 from the viewpoint that a hydrotalcite structure can be more surely obtained.

[0050] In the above equation (1), A n- The type of anion is not particularly limited; for example, carbonate ion (CO3 2- ), hydroxide ion (OH - ) are examples of such substances. For instance, carbonate ions are preferred because they do not easily generate corrosive gases such as chlorine gas or nitrogen dioxide gas during the calcination of precursor hydrotalcite compounds.

[0051] The hydrotalcite compounds described above are precursor hydrotalcite compounds that are raw materials for the production of amino acid-containing hydrotalcite, and the same applies to the hydrotalcite compounds contained in the final amino acid-containing hydrotalcite. In other words, the hydrotalcite compounds contained in the final amino acid-containing hydrotalcite may be the hydrotalcite compounds represented by formula (1) above. Here, the final amino acid-containing hydrotalcite may be the first amino acid-containing hydrotalcite, the second amino acid-containing hydrotalcite produced next, or even amino acid-containing hydrotalcite produced after that.

[0052] (amino acid) The amino acids that can be used in this embodiment are not particularly limited, and examples include various amino acids such as α-amino acids, β-amino acids, and γ-amino acids. More specifically, examples include aspartic acid, glutamic acid, asparagine, serine, glycine, β-alanine, β-aminobutyric acid, γ-aminobutyric acid, and β-leucine. These amino acids may be used individually or in combination of two or more types.

[0053] Among the above amino acids, amino acids with a solubility of 10 g / 100 mL H2O or higher are preferred, and glycine compounds are even more preferred. Such amino acids, especially glycine compounds, have a high dielectric constant, making it easy to obtain amino acid-containing hydrotalcite with a thin primary particle thickness. Furthermore, glycine has bacteriostatic properties and is used in supplements, colorants, and fragrances, which is advantageous from the standpoint of biosafety.

[0054] In this specification, "solubility of 10 g / 100 mL H2O or higher" means that the mass of the substance that dissolves in 100 g of water at 25°C is 10 g or more. In this case, the substance is an amino acid.

[0055] The amino acids mentioned above are those used as raw materials for the production of amino acid-containing hydrotalcite, and the same applies to the amino acids contained in the final amino acid-containing hydrotalcite. In other words, the amino acids contained in the final amino acid-containing hydrotalcite may be any of the above-mentioned amino acids. However, the amino acids contained in the amino acid-containing hydrotalcite may also include polymers formed by the bonding of multiple amino acids, which can be produced during the manufacturing process. Here, the polymer is a peptide. In this specification, substances containing such amino acids and amino acid polymers are sometimes referred to as "amino acid compounds." For example, a substance containing glycine and polyglycine is referred to as a "glycine compound."

[0056] In the solution preparation step, the amino acid concentration of the slurry solution is not particularly limited, but it is preferably less than 0.6 mol / L. When the amino acid concentration of the slurry solution is within this range, it is easier to obtain amino acid-containing hydrotalcite with an aspect ratio of 85 or higher and less discoloration when forming the resin composition. Resin compositions containing such amino acid-containing hydrotalcite have advantages such as high gas barrier properties and the ability to form a highly transparent coating layer with little discoloration. Furthermore, it is even more preferable that the amino acid concentration of the slurry solution is in the range of 0.02 mol / L to 0.5 mol / L.

[0057] In the solution preparation step, the molar ratio of amino acids to the trivalent metal cations of hydrotalcite compounds in the slurry solution, i.e., amino acid / (M) 3+ The molar ratio of )2 is preferably in the range of 2 to 6. For example, if the amino acid is glycine and the trivalent metal cation of the hydrotalcite compound is Al 3+ In this case, the molar ratio of glycine / Al2 is preferably in the range of 2 to 6. When the molar ratio is within this range, it is easy to obtain amino acid-containing hydrotalcite with an aspect ratio of 85 or more and less discoloration when forming a resin composition. Furthermore, when the molar ratio is within this range, the primary particle thickness of the obtained amino acid-containing hydrotalcite can be, for example, 20 nm or less. In this case, by blending it with a polymer or the like in a coating liquid and forming a coating layer on a resin substrate, high gas barrier properties can be achieved due to the labyrinth effect. Resin compositions containing such amino acid-containing hydrotalcite have advantages such as high gas barrier properties and the ability to form a highly transparent coating layer with little discoloration.

[0058] <Generation process> The slurry solution obtained in the solution preparation step is subjected to the next production step. The production step involves heating the slurry solution to produce amino acid-containing hydrotalcite. In the production step, heating the slurry solution obtained in the solution preparation step promotes the particle growth of hydrotalcite compounds. At this time, amino acid molecules in the solution are incorporated as anions between the layers of the hydrotalcite compounds. As a result, the layers of the hydrotalcite compounds are separated, and thin particles are formed. In addition, the growth of the particles in the width direction is promoted at this time. As a result, amino acid-containing hydrotalcite, which is a complex of hydrotalcite compounds and amino acids, is produced as particles with a high aspect ratio.

[0059] In the production process, it is preferable to heat the slurry solution while stirring it. The stirring means is not particularly limited, but it is preferable to use a means that can stir the slurry solution uniformly while maintaining its fluidity.

[0060] In the production process, the heating temperature is not particularly limited, but it is preferably within the range of 20°C to 250°C. A more preferable upper limit for the heating temperature is 170°C, as this makes it easier to suppress the denaturation of amino acids. In the production process, the heating time is not particularly limited, but it is preferably within the range of 1 minute to 100 hours. Furthermore, it is preferable to carry out the production process in a way that does not cause fluctuations in the concentration of the slurry solution. For example, the production process may be carried out in a closed system, or in an open system where evaporated water is added as appropriate.

[0061] <Cooling process> In this embodiment, the slurry after the production process is subjected to a cooling process, as shown in Figure 1. The cooling process is a process of cooling the slurry containing amino acid-containing hydrotalcite and dissolved amino acids obtained in the production process in order to use it for the next solid-liquid separation process, i.e., process (A). Therefore, the cooling process is performed after the production process and before process (A).

[0062] In the cooling step, the slurry containing amino acid-containing hydrotalcite and dissolved amino acids may be cooled during the transfer process from the production step to step (A). The cooling step may involve cooling the slurry using any cooling device. Alternatively, the cooling step may involve allowing the slurry to cool naturally without using a cooling device.

[0063] In the cooling process, the cooling temperature is not particularly limited, but it is preferably in the range of 10°C to 80°C. From the standpoint of ease of handling, a more preferable cooling temperature is around room temperature. In the cooling process, the cooling time is not particularly limited, but from the standpoint of productivity, it is preferably in the range of 1 minute to 48 hours.

[0064] Furthermore, if the slurry after the generation process can be used directly in the next process (A), such a cooling process may not be necessary. For example, this applies when the equipment and devices used in the subsequent separation process function normally even if the slurry is at a high temperature. On the other hand, if the high temperature of the slurry causes the equipment and devices used in the subsequent separation process to malfunction, it is preferable to perform a cooling process. Examples of cases where a cooling process is preferable include when the separation membrane has poor heat resistance or when the separation equipment malfunctions due to heat.

[0065] <Process (A) / Separation process> The slurry containing amino acid-containing hydrotalcite and dissolved amino acids after the cooling process is subjected to a solid-liquid separation process, which is step (A). Step (A) is a solid-liquid separation process in which the slurry containing amino acid-containing hydrotalcite and dissolved amino acids is separated into amino acid-containing hydrotalcite and a solution containing dissolved amino acids. In this specification, "separation" includes not only cases where the solid and liquid components are completely separated, but also cases where a small amount of unavoidable water is present in the solid component.

[0066] The separation means that can be used in step (A) are not particularly limited and include, for example, membrane separation means, centrifugal separation means, solid-liquid separation means, and natural sedimentation means.

[0067] In this embodiment, step (A) may use the slurry containing amino acid-containing hydrotalcite and dissolved amino acids as is to separate the amino acid-containing hydrotalcite from the solution containing dissolved amino acids, but is not limited to this form. For example, step (A) may add water to the slurry containing amino acid-containing hydrotalcite and dissolved amino acids to separate the amino acid-containing hydrotalcite from the solution containing dissolved amino acids. In this case, step (A) may separate the amino acid-containing hydrotalcite from the solution containing dissolved amino acids after adding water to the slurry. Alternatively, step (A) may separate the amino acid-containing hydrotalcite from the solution containing dissolved amino acids while adding water to the slurry. By adjusting the water content of the slurry before or during separation in this way, the slurry can be separated more accurately into amino acid-containing hydrotalcite and the solution containing dissolved amino acids.

[0068] When adding water to the slurry, the entire amount of water may be added at once, or a predetermined amount of water may be added to the slurry in multiple portions. Furthermore, when separating the amino acid-containing hydrotalcite from the dissolved amino acid solution while adding water to the slurry, the amount of water supplied may be fixed at a constant level, or it may be adjusted to vary as desired. There are no particular restrictions on the type of water added to the slurry, but examples include deionized water.

[0069] In step (A), the slurry containing amino acid-containing hydrotalcite and dissolved amino acids may be separated into amino acid-containing hydrotalcite and a solution containing dissolved amino acids. This separation process may be performed only once, or it may be performed in two or more separate steps. A form of step (A) in which this separation process is performed in multiple steps will be described in a separate embodiment later.

[0070] <Process (B) / Alkali Treatment Process> In this embodiment, the amino acid-containing hydrotalcite solid separated by step (A) described above is subjected to step (B), which is an alkaline treatment step, as shown in Figure 1. Step (B) is a washing step performed after step (A) to reduce amino acids from the amino acid-containing hydrotalcite using an alkaline solution. Through this step (B), amino acids are removed as impurities from the amino acid-containing hydrotalcite, and purified amino acid-containing hydrotalcite (purified amino acid-containing HT) is obtained. It should be noted that the amino acids contained in the solid separated by step (A) are mostly amino acids incorporated between the layers of the hydrotalcite, and may contain some amino acids attached to the surface of the hydrotalcite.

[0071] If such an alkaline treatment process is performed before separating the slurry after the production process into amino acid-containing hydrotalcite and a solution containing dissolved amino acids, a large amount of alkaline solution is required because the slurry contains a large amount of amino acids.

[0072] On the other hand, in this embodiment, the slurry after the production process is separated into amino acid-containing hydrotalcite and a solution containing dissolved amino acids, and then the amino acid-containing hydrotalcite is treated with an alkaline solution. Since the amino acid-containing hydrotalcite after separation has a low amino acid content, in this embodiment, the amount of amino acids contained in the amino acid-containing hydrotalcite can be reduced with a small amount of alkaline solution. In other words, in this embodiment, the amount of alkaline solution used in the alkaline treatment process can be reduced.

[0073] The extent to which the amount of alkaline solution used can be reduced depends on the processing conditions, such as the type and method of alkaline solution used. However, depending on these conditions, it is possible to reduce the amount of alkaline solution used by about 60% compared to performing an alkaline treatment step before the separation step. For example, when glycine is used as the amino acid and sodium hydroxide as the alkali, the total amino acid used is glycine / Al2 = 5.26, and the intercalation amino acid of the exfoliated HT is glycine / Al2 = 2, resulting in an alkali reduction of [1 - (2 / 5.26)] × 100 = 62%. Note that this calculation assumes that all intercalations of hydrotalcite are filled with glycine and that there is no glycine attached to the surface of the hydrotalcite.

[0074] In this embodiment, the type of alkaline component in the alkaline solution that can be used in step (B) is not particularly limited, and any component that can reduce the amount of amino acids from the amino acid-containing hydrotalcite described above is acceptable. Examples of such alkaline components include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, ammonia, and sodium carbonate. Among these alkaline components, sodium hydroxide, potassium hydroxide, and ammonia are preferred, more preferably sodium hydroxide and potassium hydroxide, and even more preferably sodium hydroxide. These alkaline components may be used individually or in combination of two or more alkaline components.

[0075] In step (B), the treatment concentration when treating the amino acid-containing hydrotalcite with an alkaline solution is not particularly limited as long as it is a concentration that can reduce the amount of amino acids in the amino acid-containing hydrotalcite. However, from the viewpoint of suppressing aggregation, conditions that are not too high in concentration are preferred. The treatment concentration refers to the ratio of alkali content to the total volume of the mixture of amino acid-containing hydrotalcite and alkaline solution, i.e., the slurry.

[0076] Furthermore, the concentration of the alkaline solution used in the alkaline treatment is not particularly limited; any concentration within the range that does not cause the slurry of amino acid-containing hydrotalcite with the alkaline solution to thicken is acceptable. For example, the upper limit of the alkaline solution concentration can be 4.0 mol / L or less, preferably 3.0 mol / L or less, and more preferably 2.0 mol / L or less. The lower limit of the alkaline solution concentration is higher than 0 mol / L, preferably 0.1 mol / L or more, and more preferably 0.2 mol / L or more.

[0077] In this embodiment, step (B) can be carried out by stirring a slurry made by adding an alkaline solution to amino acid-containing hydrotalcite. At this time, stirring may be started after adding the alkaline solution to the amino acid-containing hydrotalcite in step (B), or stirring may be performed while adding the alkaline solution to the amino acid-containing hydrotalcite.

[0078] The stirring conditions in step (B) are not particularly limited, but a stirring speed and force sufficient to stir the slurry are preferred. For example, the stirring speed is preferably adjusted so that foaming, splashing, and gelation are suppressed, and the slurry solution becomes uniform. In particular, when adding the alkaline solution, it is preferable to adjust the speed so that local pH imbalances do not occur. The stirring speed can be any speed depending on the type of stirring blade, stirrer, container size and shape, slurry viscosity, slurry concentration, alkaline solution concentration, alkaline solution addition speed, etc., but for example it is 50 to 2000 rpm, preferably 100 to 1500 rpm. The temperature during stirring is not particularly limited, but for example it is room temperature.

[0079] Furthermore, in step (B) of this embodiment, when adding an alkaline solution to the amino acid-containing hydrotalcite, It is preferable to add the alkaline solution while stirring the amino acid-containing hydrotalcite. At this time, it is preferable to gradually add the alkaline solution to the amino acid-containing hydrotalcite while stirring in a way that maintains a slurry state, that is, in a state that can be stirred. By adding the alkaline solution while stirring in this way, local aggregation of the slurry can be suppressed.

[0080] When adding an alkaline solution to amino acid-containing hydrotalcite, it is preferable to adjust the timing, supply amount, temperature, stirring speed, and other conditions as appropriate according to the slurry viscosity so that the slurry does not become thicker.

[0081] <Process (C) / Reuse process> In this embodiment, the solution containing dissolved amino acids, which is the liquid component separated by step (A) described above, is subjected to step (C), which is a reuse step, as shown in Figure 1. Step (C) is a process of treating and reusing the solution containing dissolved amino acids separated by step (A) so that it can be used as part of the raw material for the production of the next amino acid-containing hydrotalcite.

[0082] In step (C), if the solution containing dissolved amino acids can be used directly as a raw material for the production of amino acid-containing hydrotalcite, the solution can be reused without any special treatment. However, it is usually necessary to adjust the amino acid concentration of the solution.

[0083] In this embodiment, as shown in Figure 1, step (C) includes a concentration step to adjust the amino acid concentration of the solution containing dissolved amino acids separated in step (A). In this embodiment, the concentration step is a step to increase the amino acid concentration in the aqueous solution by heating and concentrating the solution containing dissolved amino acids. The concentrated amino acid aqueous solution obtained through this concentration step is reused as part of the raw material for the production of the next amino acid-containing hydrotalcite. For example, the solution containing dissolved amino acids separated and recovered when producing the first amino acid-containing hydrotalcite becomes a concentrated amino acid aqueous solution through the concentration step in step (C), and is used in the solution preparation step when producing the second amino acid-containing hydrotalcite.

[0084] The process of adjusting the amino acid concentration of a solution containing dissolved amino acids is not limited to the concentration process by heating described above. Other examples of processes for adjusting the amino acid concentration include an amino acid addition process, a dilution process by adding deionized water, and an adsorption process by adding a complex metal oxide (calcined HT) to adsorb amino acids. These processes may be employed individually or in combination.

[0085] In step (C), in addition to the step of adjusting the amino acid concentration as described above, there may also be a pH adjustment step and a step of adjusting the amount of metal ions such as magnesium and aluminum eluted from hydrotalcite. In particular, when the production of amino acid-containing hydrotalcite is carried out repeatedly, the amount of metal ions such as magnesium and aluminum in the solution may accumulate, which may have a significant impact on the molar ratio of the raw materials for production. By performing a metal ion adjustment step in step (C) and reducing the amount of metal ions in the solution, amino acid-containing hydrotalcite can be produced repeatedly with greater precision. There are no particular limitations on the metal ion adjustment step, but examples include a step of precipitating and removing the target metal ions as hydroxides, and a step of adsorption removal by adding negatively charged particles.

[0086] <Other processing steps> In this embodiment, any processing step may be performed on the purified amino acid-containing HT obtained after step (B) described above. Examples of such processing steps include a drying step in which the solid obtained in step (B) is dried to obtain a powder of purified amino acid-containing HT, a surface treatment step in which the surface of the particles of purified amino acid-containing HT is treated with various surface treatment agents, and a coating liquid preparation step in which the solid obtained in step (B) is mixed with a polymer solution or the like without drying to prepare a coating liquid.

[0087] According to the manufacturing method of this embodiment described above, an amino acid-containing hydrotalcite with a high aspect ratio can be obtained. Such an amino acid-containing hydrotalcite with a high aspect ratio will be described later.

[0088] Hereinafter, a second to fourth embodiment of the present invention, which differs from the first embodiment described above only in the manner of steps (A) to (C), will be described with reference to the drawings. In the following description, steps other than those that differ from the first embodiment are basically the same as those in the first embodiment described above, and therefore will not be described.

[0089] [Second Embodiment] Figure 2 is a flowchart showing an example of a second embodiment of the present invention. As shown in Figure 2, the second embodiment of the present invention, similar to the first embodiment described above, includes a solution preparation step, a generation step, a cooling step, a separation step (A), an alkali treatment step (B), and a reuse step (C).

[0090] In this second embodiment, only steps (A) and (C) differ from the first embodiment, while all other steps are the same as in the first embodiment described above.

[0091] <Step (A) of the second embodiment> In this second embodiment, step (A) is a process of performing a solid-liquid separation of a slurry containing amino acid-containing hydrotalcite and dissolved amino acids into a solution containing amino acid-containing hydrotalcite and dissolved amino acids, in multiple steps. In the example shown in Figure 2, the separation process is performed in two steps.

[0092] Specifically, step (A) of this second embodiment first separates the slurry containing amino acid-containing hydrotalcite and dissolved amino acids into a slurry containing a portion of the amino acid-containing hydrotalcite and dissolved amino acids, and a solution containing the remainder of the dissolved amino acids, without adding water to the slurry. Then, water is added to the slurry containing the amino acid-containing hydrotalcite and a portion of the dissolved amino acids, separating it into amino acid-containing hydrotalcite and a solution containing dissolved amino acids.

[0093] When adding water to the slurry, the entire amount of water may be added at once, or a predetermined amount of water may be added to the slurry in multiple portions. Alternatively, the slurry may be separated into amino acid-containing hydrotalcite and a solution containing dissolved amino acids after adding water, or the separation may be carried out while adding water to the slurry. When separating the amino acid-containing hydrotalcite and a solution containing dissolved amino acids while adding water to the slurry, the amount of water supplied may be fixed at a constant amount, or it may be adjusted to vary as desired. There are no particular restrictions on the water added to the slurry, but examples include deionized water.

[0094] As shown in step (A) of this second embodiment, by dividing the separation process into multiple steps, the amount of amino acids contained in the resulting amino acid-containing hydrotalcite can be reduced. Furthermore, by dividing the separation process into multiple steps, the reuse rate of the amino acids available for reuse can also be improved. In addition, by reducing the amount of amino acids contained in the resulting amino acid-containing hydrotalcite, the amount of alkaline solution used in the subsequent step (B) can be reduced.

[0095] In addition, in step (A) of this second embodiment, all other points not described above are the same as in step (A) of the first embodiment described above.

[0096] <Step (C) of the second embodiment> In this second embodiment, step (C) is a step of processing and reusing a solution containing multiple types of dissolved amino acids separated and recovered by the multiple separation steps of step (A) described above, so that it can be used as part of the raw material for the production of the next amino acid-containing hydrotalcite.

[0097] Specifically, step (C) of this second embodiment first recovers the solution containing the remaining dissolved amino acids separated in the first separation step of step (A) described above. Next, the solution containing the dissolved amino acids separated in the second separation step of step (A) described above is recovered and heated and concentrated in a concentration step to obtain a concentrated amino acid aqueous solution with adjusted amino acid concentration. Then, the solution containing the remaining dissolved amino acids and the concentrated amino acid aqueous solution are mixed to obtain a mixed amino acid aqueous solution. Subsequently, the obtained mixed amino acid aqueous solution is reused as part of the raw material for the production of the next amino acid-containing hydrotalcite.

[0098] As in step (C) of this second embodiment, by using a solution containing multiple types of dissolved amino acids separated and recovered by multiple separation steps as part of the raw material for the production of the next amino acid-containing hydrotalcite, the reuse rate of amino acids for reuse can be improved. Furthermore, as in step (C) of this second embodiment, by individually processing the solutions containing multiple types of dissolved amino acids separated and recovered by multiple separation steps according to the amino acid concentration of each solution, the next amino acid-containing hydrotalcite can be produced with greater precision.

[0099] In step (C), it is not always necessary to perform a concentration step. However, if the amino acid concentration in the solution containing dissolved amino acids decreases as the number of separation steps increases, it is preferable to perform a concentration step on the solution containing dissolved amino acids after the second and subsequent separation steps.

[0100] Furthermore, in step (C) of this second embodiment, all other points not described above are the same as in step (C) of the first embodiment described above.

[0101] [Third Embodiment] Figure 3 is a flowchart showing an example of a third embodiment of the present invention. As shown in Figure 3, the third embodiment of the present invention also includes a solution preparation step, a generation step, a cooling step, a separation step (A), an alkali treatment step (B), and a reuse step (C), similar to the first and second embodiments described above.

[0102] In this third embodiment, only step (C) differs from the second embodiment; all other steps are the same as in the second embodiment described above. That is, all steps other than steps (A) and (C) are the same as in the first embodiment described above.

[0103] <Step (C) of the third embodiment> In this third embodiment, step (C) is a step of processing and reusing a solution containing multiple types of dissolved amino acids separated and recovered by the multiple separation steps of step (A) described above, so that it can be used as part of the raw material for the production of amino acid-containing hydrotalcite. However, step (C) in this third embodiment differs from step (C) in the second embodiment in that, after recovering the solution containing dissolved amino acids separated in the second separation step of step (A) described above, the amino acid concentration is adjusted by an adsorption step and a separation step to form a slurry.

[0104] Specifically, in step (C) of this third embodiment, first, the solution containing the remainder of the dissolved amino acids separated in the first separation step of step (A) above is recovered. Next, the solution containing the dissolved amino acids separated in the second separation step of step (A) above is recovered, and a composite metal oxide, which is a calcined hydrotalcite compound, is added to it to perform an adsorption step to adsorb the amino acids in the solution. Furthermore, a separation step is performed to separate the slurry after the adsorption step into solid components containing hydrotalcite and amino acids and water. Then, the solution containing the remainder of the dissolved amino acids and the solid components after the separation step are mixed to obtain a slurry containing hydrotalcite and amino acids (HT / amino acid slurry). Subsequently, a new amino acid aqueous solution is added to the obtained HT / amino acid slurry and reused as an amino acid raw material in the solution preparation step when producing the next amino acid-containing hydrotalcite.

[0105] In step (C) of this third embodiment, the reuse rate of amino acids for reuse can be improved by using a solution containing multiple types of dissolved amino acids separated and recovered by multiple separation steps as part of the raw material for the next amino acid-containing hydrotalcite. Furthermore, in step (C) of this third embodiment, the next amino acid-containing hydrotalcite can be produced with greater precision by individually processing the solution containing multiple types of dissolved amino acids separated and recovered by multiple separation steps according to the amino acid concentration of each solution.

[0106] Furthermore, as described above, in this third embodiment, in step (C), the solution containing multiple types of dissolved amino acids separated and recovered by the multiple separation steps in step (A) is reused as an amino acid raw material in the solution preparation step when producing the next amino acid-containing hydrotalcite. Therefore, this third embodiment has the advantage of excellent production efficiency when repeatedly producing amino acid-containing hydrotalcite.

[0107] Furthermore, in step (C) of this third embodiment, all other points not described above are the same as in step (C) of the first and second embodiments described above.

[0108] [Fourth Embodiment] Figure 4 is a flowchart showing an example of a fourth embodiment of the present invention. As shown in Figure 4, the fourth embodiment of the present invention also includes a solution preparation step, a generation step, a cooling step, a separation step (A), an alkali treatment step (B), and a reuse step (C), similar to the first embodiment described above.

[0109] In this embodiment, only steps (A) and (C) differ from the first embodiment; all other steps are the same as in the first embodiment described above.

[0110] <Step (A) of the 4th Embodiment> In this fourth embodiment, step (A) is a step in which a slurry containing amino acid-containing hydrotalcite and dissolved amino acids is separated into a solid-liquid solution containing amino acid-containing hydrotalcite and dissolved amino acids, and this is carried out in two or more separate steps.

[0111] Specifically, step (A) of this fourth embodiment has the following steps (a1) and (a2), as shown in Figure 4.

[0112] Step (a1) is a step in which, without adding water to a slurry containing amino acid-containing hydrotalcite and dissolved amino acids, the slurry is separated into a slurry containing a portion of the amino acid-containing hydrotalcite and dissolved amino acids, and a solution containing the remainder of the dissolved amino acids.

[0113] Step (a2) is performed after step (a1) by adding water to a slurry containing amino acid-containing hydrotalcite and some of the dissolved amino acids, thereby separating it into a slurry containing amino acid-containing hydrotalcite and some or no dissolved amino acids, and a solution containing the remainder of the dissolved amino acids. Step (a2) is performed once or multiple times.

[0114] When adding water to the slurry, the entire amount of water may be added at once, or a predetermined amount of water may be added to the slurry in multiple portions. Alternatively, the slurry may be separated into amino acid-containing hydrotalcite and a solution containing dissolved amino acids after adding water, or the separation may be carried out while adding water to the slurry. When separating the amino acid-containing hydrotalcite and a solution containing dissolved amino acids while adding water to the slurry, the amount of water supplied may be fixed at a constant amount, or it may be adjusted to vary as desired. There are no particular restrictions on the water added to the slurry, but examples include deionized water.

[0115] In step (A) of this fourth embodiment, the amount of amino acids contained in the resulting amino acid-containing hydrotalcite can be reduced by dividing the separation process into multiple steps. Furthermore, dividing the separation process into multiple steps can also improve the reuse rate of the amino acids available for reuse. In addition, by reducing the amount of amino acids contained in the resulting amino acid-containing hydrotalcite, the amount of alkaline solution used in the subsequent step (B) can be reduced.

[0116] Furthermore, in step (A) of this fourth embodiment, all other points not described above are the same as in step (A) of the first and second embodiments described above.

[0117] <Step (C) of the fourth embodiment> In this fourth embodiment, step (C) is a step of processing and reusing a solution containing multiple types of dissolved amino acids separated and recovered by the multiple separation steps of step (A) described above, so that it can be used as part of the raw material for the production of amino acid-containing hydrotalcite. However, step (C) in this fourth embodiment differs from step (C) in the first to third embodiments in that the solutions containing dissolved amino acids separated by the multiple separation steps of step (A) described above are mixed, and a complex metal oxide is added to the resulting mixed amino acid aqueous solution to form a slurry.

[0118] Specifically, step (C) of this fourth embodiment involves recovering a solution containing multiple types of dissolved amino acids separated in the multiple separation steps of step (A) described above, namely step (a1) and one or more steps (a2), and mixing them to obtain a mixed amino acid aqueous solution. Next, a complex metal oxide, which is a calcined product of hydrotalcite compounds, is added to this mixed amino acid aqueous solution to obtain a slurry containing hydrotalcite and amino acids (HT / amino acid slurry). This HT / amino acid slurry is then reused as an amino acid raw material in the solution preparation step during the production of the next amino acid-containing hydrotalcite.

[0119] In this fourth embodiment, step (C) also improves the reuse rate of amino acids by using a solution containing multiple types of dissolved amino acids separated and recovered by multiple separation steps as part of the raw material for the next amino acid-containing hydrotalcite. Furthermore, as described above, in this fourth embodiment, in step (C), the solution containing multiple types of dissolved amino acids separated and recovered by multiple separation steps in step (A) is reused as an amino acid raw material in the solution preparation step when producing the next amino acid-containing hydrotalcite. Therefore, this fourth embodiment also has the advantage of excellent production efficiency when repeatedly producing amino acid-containing hydrotalcite.

[0120] Furthermore, in step (C) of this fourth embodiment, all other points not described above are the same as in step (C) of the first to third embodiments described above.

[0121] According to the manufacturing methods of each embodiment of the present invention described above, interlayer delamination of hydrotalcite compounds occurs by using amino acids as a release agent, making it possible to obtain amino acid-containing hydrotalcite with a thin primary particle thickness, i.e., a high aspect ratio. Next, the amino acid-containing hydrotalcite obtained by the manufacturing methods of each embodiment described above will be explained.

[0122] [Amino acid-containing hydrotalcite] The amino acid-containing hydrotalcite obtained by the manufacturing methods of each embodiment described above is amino acid-containing hydrotalcite having a high aspect ratio of 85 or more.

[0123] Such amino acid-containing hydrotalcite with a high aspect ratio can be mixed with a polymer, such as polyvinyl alcohol, to form a coating solution. When this coating solution is applied to a substrate to form a coating layer, multiple amino acid-containing hydrotalcite particles are arranged within the coating layer parallel to the surface direction of the coating layer, exhibiting excellent gas barrier properties. Therefore, the amino acid-containing hydrotalcite obtained by the manufacturing methods of each embodiment described above can be used in a wide variety of applications requiring gas barrier properties. For example, when a coating solution containing such amino acid-containing hydrotalcite is applied to a film, high gas barrier properties can be imparted to the film.

[0124] In this specification, the aspect ratio of amino acid-containing hydrotalcite is the ratio of the width (diameter) to the thickness of the primary particles of amino acid-containing hydrotalcite having a layered structure. The aspect ratio can be determined by dividing the width of the primary particles of amino acid-containing hydrotalcite by the thickness.

[0125] Furthermore, the coating solution containing the amino acid-containing hydrotalcite and polymer described above may also contain other additives. Such additives are not particularly limited, but examples include antioxidants, reinforcing agents, UV absorbers, pigments, crosslinking agents, and flame retardants. These additives may be used individually or in combination of two or more.

[0126] The films using the aforementioned amino acid-containing hydrotalcite can be applied to a wide range of fields, such as food packaging films, beverage packaging films, beverage bottles, pharmaceutical packaging films, industrial gas barrier films, gas separation films, and paper barrier materials.

[0127] Furthermore, the manufacturing method of the present invention is not limited to the embodiments described above or the examples described later, and can be appropriately combined, substituted, or modified without departing from the purpose and spirit of the present invention. [Examples]

[0128] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to such examples.

[0129] Example 1 (Production of precursor hydrotalcite compounds) Deionized water was placed in a 1 L reaction vessel. To this vessel, 160 mL of 1.5 mol / L magnesium chloride aqueous solution, 120 mL of 1 mol / L aluminum chloride aqueous solution, and a mixed solution of 90 mL of 8 mol / L sodium hydroxide aqueous solution and 60 mL of 1 mol / L sodium carbonate aqueous solution were simultaneously added dropwise while stirring to obtain the reaction product. The pH during the reaction was 9.5. The obtained reaction product was washed with water. Then, deionized water was added to the reaction product to obtain a re-emulsified slurry of 700 mL. The obtained re-emulsified slurry was subjected to hydrothermal treatment at 170°C for 13 hours. The obtained solid was washed with water. The washed solid was dried at 105°C for 16 hours. Furthermore, the dried solid was pulverized. The chemical formula of the obtained powder is Mg 0.67 Al 0.33 (OH)2(CO3) 0.17 The compound was a hydrotalcite compound represented by 0.50H2O. This hydrotalcite compound was used as a precursor hydrotalcite compound in the production of amino acid-containing hydrotalcite.

[0130] (Castration of precursor hydrotalcite compounds) The obtained precursor hydrotalcite compounds were calcined in an electric furnace at 450°C for 12 hours to obtain a calcined product (composite metal oxide).

[0131] (Solution preparation step 1) 14.0 g of the obtained calcined material was placed in a glass beaker. 140 mL of a 2 mol / L glycine aqueous solution (equivalent to 21.0 g of glycine powder) was added to this glass beaker. The slurry solution in the glass beaker was stirred until homogeneous. At this time, the molar ratio of glycine / Al2 in the obtained slurry solution was 5.26. Then, deionized water was added to the slurry solution to make a total volume of 700 mL. The slurry solution was stirred again until homogeneous. The slurry concentration at this time was 20 g / L. The glycine concentration at this time was 0.4 mol / L.

[0132] (Generation process 1) Next, the slurry solution was subjected to hydrothermal treatment at 100°C for 48 hours while being stirred at 700 rpm. The resulting slurry solution was in a slurry-like state. The resulting slurry solution was white. The resulting slurry solution had no particular odor.

[0133] (Process (A) / Separation process) Next, 650 mL of the obtained slurry solution was mixed with deionized water to make a total volume of 1300 mL. The slurry concentration at this time was 10 g / L. Furthermore, the slurry solution was stirred at room temperature at 400 rpm for 16 hours using a stirrer. The resulting stirred slurry was subjected to solid-liquid separation. The solution obtained after solid-liquid separation was used as the solution containing dissolved glycine compounds. The concentration of glycine compounds in this solution was 0.143 mol / L. The pH of this solution was 8.9.

[0134] (Solution preparation step 2) 0.143 g of the calcined product obtained in the "Catalization of Precursor Hydrotalcite Compounds" described above was placed in a fluororesin container. 20 mL of the solution containing the above 0.143 mol / L dissolved glycine compounds was added to this fluororesin container. The slurry solution in the fluororesin container was stirred until homogeneous. At this time, the molar ratio of glycine compounds / Al2 in the obtained slurry solution was 5.26. The slurry concentration was 7.15 g / L.

[0135] (Generation process 2) Next, the fluororesin container was sealed. The slurry solution inside the sealed fluororesin container was heat-treated at 100°C for 48 hours under non-stirring conditions. The resulting slurry solution was in a slurry-like state. The resulting slurry solution was white.

[0136] (Process (B) / Alkali treatment process) Next, the obtained slurry solution was stirred at room temperature for 16 hours. While maintaining the stirring of the slurry solution, an equivalent amount of 4.00 mol / L aqueous sodium hydroxide solution to the glycine compound was gradually added dropwise to the slurry solution. The obtained slurry solution was subjected to solid-liquid separation to obtain the amino acid-containing hydrotalcite of Example 1.

[0137] The primary particles of amino acid-containing hydrotalcite obtained in Example 1 had an aspect ratio of 93. The thickness of the primary particles of amino acid-containing hydrotalcite obtained in Example 1 was 3.0 nm.

[0138] Comparative Example 1 In the "Solution Preparation Step 1" described above, the amount of calcined material was 17.5 g, 175 ml of a 2 mol / L glycine aqueous solution (equivalent to 26.3 g of glycine powder) was used, before "Step (A) / Separation Step", an amount of 4.00 mol / L sodium hydroxide aqueous solution equivalent to the amount of glycine compounds was added dropwise to the slurry solution, the concentration of the glycine compounds was 0.158 mol / L, and the pH was 12.4, and in "Solution Preparation Step 2", 0.158 g of calcined material was used, and the slurry concentration was 7.90 g / L. In addition, the amino acid-containing hydrotalcite of Comparative Example 1 was obtained in the same manner as in Example 1.

[0139] The primary particles of the amino acid-containing hydrotalcite obtained in Comparative Example 1 had an aspect ratio of 14. The thickness of the primary particles of the amino acid-containing hydrotalcite obtained in Comparative Example 1 was 18 nm.

[0140] As described above, in the manufacturing method of Example 1, in which the slurry solution is treated with an alkaline solution after step (A) / separation step, it was found that stable quality amino acid-containing hydrotalcite can be obtained even when recycled amino acid aqueous solution is used as a raw material, compared to Comparative Example 1, in which the slurry solution is treated with an alkaline solution before step (A) / separation step. [Industrial applicability]

[0141] The present invention's method for producing amino acid-containing hydrotalcite can be suitably used to produce amino acid-containing hydrotalcite that can be applied to a wide range of fields, such as food packaging films, beverage packaging films, beverage bottles, pharmaceutical packaging films, industrial gas barrier films, gas separation films, paper barrier materials, paints, scratch-resistant materials, cosmetics, and additives.

Claims

1. Step (A) of separating a slurry containing a first amino acid-containing hydrotalcite and dissolved amino acids into the first amino acid-containing hydrotalcite and a solution containing the dissolved amino acids, Following step (A), a solution preparation step is performed in which an aqueous amino acid solution derived from the solution containing the dissolved amino acids separated from the slurry and a composite metal oxide obtained by calcining a precursor hydrotalcite compound are mixed to prepare a slurry solution. A production step involves heating the slurry solution to produce a second amino acid-containing hydrotalcite, A method for producing amino acid-containing hydrotalcite, characterized by containing the following:

2. The manufacturing method according to claim 1, characterized in that step (A) involves adding water to the slurry to separate it into the first amino acid-containing hydrotalcite and the solution containing the dissolved amino acid.

3. Step (A) involves separating the slurry without adding water into a slurry containing the first amino acid-containing hydrotalcite and a portion of the dissolved amino acids, and a solution containing the remainder of the dissolved amino acids. The manufacturing method according to claim 1, characterized by adding water to a slurry containing the first amino acid-containing hydrotalcite and a portion of the dissolved amino acids, thereby separating the first amino acid-containing hydrotalcite from the solution containing the dissolved amino acids.

4. Step (A) is a step (a1) of separating the slurry into a slurry containing the first amino acid-containing hydrotalcite and a portion of the dissolved amino acids, and a solution containing the remainder of the dissolved amino acids, without adding water to the slurry. The process is further comprising the step (a2) of adding water to the slurry containing the first amino acid-containing hydrotalcite and a portion of the dissolved amino acids after the above step (a1), thereby separating it into a slurry containing the first amino acid-containing hydrotalcite and a portion of the dissolved amino acids or not containing the dissolved amino acids, and a solution containing the remainder of the dissolved amino acids. The manufacturing method according to claim 1, characterized in that the above step (a2) is performed once or more times.

5. Before step (A), A solution preparation step involves mixing an aqueous amino acid solution with a composite metal oxide obtained by calcining a precursor hydrotalcite compound to prepare a slurry solution. A production step of heating the slurry solution to produce the first amino acid-containing hydrotalcite, The manufacturing method according to claim 1, further comprising the above.

6. The manufacturing method according to claim 1, further comprising a step (B) after step (A) of reducing the amount of amino acids from the first amino acid-containing hydrotalcite with an alkaline solution.

7. The manufacturing method according to claim 6, characterized in that step (B) involves adding the alkaline solution while stirring the first amino acid-containing hydrotalcite.

8. The amino acids contained in the first amino acid-containing hydrotalcite, the amino acids contained in the second amino acid-containing hydrotalcite, the amino acids contained in the dissolved amino acids, and the amino acids contained in the amino acid aqueous solution have a solubility of 10 g / 100 mLH ２ The method for producing amino acids according to claim 1, characterized in that the amino acids are 0 or more.

9. The method for producing the product according to claim 1, characterized in that the amino acid contained in the first amino acid-containing hydrotalcite, the amino acid contained in the second amino acid-containing hydrotalcite, the amino acid contained in the dissolved amino acid, and the amino acid contained in the aqueous amino acid solution are glycine compounds.

10. The method for producing the product according to claim 1, characterized in that the hydrotalcite compound contained in the first amino acid-containing hydrotalcite is represented by the following formula (1). (M ２＋ ) １－Ｘ (M ３＋ ) Ｘ (OH) ２ (A ｎ－ ) Ｘ／ｎ ・mH ２ O・・・(1) (In equation (1), M ２＋ M is a divalent metal cation, ３＋ A is a trivalent metal cation, ｎ－ (where is an n-valent anion, X is a number satisfying 0.17 < X < 0.36, n is an integer from 1 to 6, and m is a number satisfying 0 < m < 1.80.)

11. The manufacturing method according to claim 1, characterized in that the amino acid concentration of the slurry is less than 0.6 mol / L.

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