Method for producing a complex of a hydrotalcite compound and an amino acid

Abstract

To provide a method for uniformly and efficiently manufacturing a composite of a hydrotalcite compound and an amino acid with the resulting composite having a high aspect ratio.SOLUTION: The present disclosure relates to a method for manufacturing a composite of a hydrotalcite compound and an amino acid. The composite has an aspect ratio of 85 or more. The manufacturing method includes a solution preparation step and a heating step. The solution preparation step is a step of preparing a slurry solution. The slurry solution is obtained by mixing an aqueous solution of the amino acid and a complex metal oxide. The complex metal oxide is obtained by firing a precursor hydrotalcite compound. The heating step is a step of heating the slurry solution. In the solution preparation step, a slurry concentration is less than 30 g / L. The slurry concentration is a concentration of the slurry solution.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a complex of a hydrotalcite compound and an amino acid.

Background Art

[0002] Hydrotalcite compounds, which represent hydrotalcite or its calcined product, have ion exchange ability and are used in various applications such as suppressing the deterioration of resins by blending them with resins. As this type of hydrotalcite compound, a method of using an amino acid to increase the aspect ratio is known (Patent Document 1 and Non-Patent Document 1). By the methods disclosed in Patent Document 1 and Non-Patent Document 1, a complex of a hydrotalcite compound and an amino acid can be obtained.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the methods disclosed in Patent Document 1 and Non-Patent Document 1 described above, when heat-treating a mixture of a composite metal oxide obtained by firing a hydrotalcite compound and an aqueous solution of glycine, which is a kind of amino acid, the mixture may gel and furthermore, coloring may occur. In particular, when the mixture gels, it becomes impossible to produce a complex of a hydrotalcite compound and an amino acid uniformly and efficiently, and in some cases, problems such as unstable quality of the complex of a hydrotalcite compound and an amino acid may occur.

[0006] Therefore, an object of the present invention is to provide a production method capable of uniformly and efficiently producing a complex of a hydrotalcite compound having a high aspect ratio and an amino acid.

Means for Solving the Problems

[0007] As a result of intensive studies to achieve the above object, the present inventors have found that in a method for producing a complex of a hydrotalcite compound and an amino acid, by setting the concentration of a slurry solution (slurry concentration) obtained by mixing an aqueous solution of an amino acid and a composite metal oxide obtained by firing a precursor hydrotalcite compound within a specific range, it is possible to suppress the gelling of the mixture when heat-treating the mixture of the composite metal oxide and the aqueous solution of the amino acid. The present disclosure has been completed based on such findings and includes the following aspects.

[0008] (First Disclosure) The first disclosure is a method for producing a complex of a hydrotalcite compound and an amino acid. The above complex has an aspect ratio of 85 or more. The above production method has a solution adjustment step and a heating step. The above solution adjustment step is a step of preparing a slurry solution. The above slurry solution is a mixture of an aqueous solution of the above amino acid and a composite metal oxide. The above composite metal oxide is obtained by firing a precursor hydrotalcite compound. The above heating step is a step of heating the above slurry solution. The slurry concentration in the above solution preparation step is less than 30 g / L. The above slurry concentration is the concentration of the above slurry solution.

[0009] (Second disclosure) In the second disclosure, in the first disclosure, the above amino acid has a solubility of 10 g / 100 mL H 2 O or more.

[0010] (Third disclosure) In the third disclosure, in the first disclosure or the second disclosure, the amino acid is glycine.

[0011] (Fourth disclosure) In the fourth disclosure, in any one of the first disclosure to the third disclosure, the above hydrotalcite compound 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 formula (1), M 2+ is a divalent metal cation. In formula (1), M 3+ is a trivalent metal cation. In formula (1), A n- is an n-valent anion. In formula (1), X is a number satisfying 0.17 < X < 0.36. In formula (1), n is an integer from 1 to 6, and m is a number satisfying 0 < m < 1.80.)

[0012] (Fifth Disclosure) In any of the First to Fourth Disclosures, the amino acid concentration is less than 0.6 mol / L. The amino acid concentration is the amino acid concentration of the slurry solution.

Advantages of the Invention

[0013] The production method of the present invention can uniformly and efficiently produce a complex of a hydrotalcite compound having a high aspect ratio and an amino acid.

Brief Description of the Drawings

[0014]

Figure 1

Modes for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments of the method for producing a complex of a hydrotalcite compound and an amino acid of the present invention will be described in detail. In this specification, the "method for producing a complex of a hydrotalcite compound and an amino acid" may be simply referred to as the "method for producing a complex". Further, in this specification, the "complex of a hydrotalcite compound and an amino acid" means a state in which an amino acid is chemically modified to a hydrotalcite compound, and hereinafter, it may be simply referred to as a "complex" or the like.

[0016] [Method for Producing Complex] In one embodiment of the present invention, the method for producing the composite is a method for producing a composite of a hydrotalcite compound having an aspect ratio of 85 or more and an amino acid. The method for producing the composite of the present embodiment includes a solution preparation step of mixing an aqueous solution of an amino acid and a composite metal oxide obtained by firing a precursor hydrotalcite compound to prepare a slurry solution; and a heating step of heating the slurry solution. And, in the method for producing the composite of the present embodiment, the slurry concentration of the slurry solution in the solution preparation step is less than 30 g / L.

[0017] In the method for producing the composite of the present embodiment, in the above-described solution preparation step, the concentration (slurry concentration) of the slurry solution obtained by mixing an aqueous solution of an amino acid (for example, glycine, etc.), which is a release agent, and a composite metal oxide obtained by firing a precursor hydrotalcite compound, is within a specific range of less than 30 g / L. Thereby, the method for producing the composite of the present embodiment can suppress the gelation of the mixture in the heating step of heating the mixture of the composite metal oxide and the glycine aqueous solution. As a result, the method for producing the composite of the present embodiment can uniformly and efficiently produce a composite of a hydrotalcite compound having a high aspect ratio and an amino acid.

[0018] In addition, in the method for producing the composite of the present embodiment, in the above-described solution preparation step, the composite metal oxide obtained by firing the precursor hydrotalcite compound is hydrated using an aqueous solution of an amino acid. Examples of the aqueous solution of an amino acid include an aqueous solution of glycine. During hydration, amino acid molecules in the solution are incorporated as anions between the layers of the hydrotalcite compound, causing the layers of the hydrotalcite compound to exfoliate. The exfoliation of the layers of the hydrotalcite compound forms thin particles. The thin particles are heated in the heating step, and a composite is formed as a hydrotalcite compound in which particle growth in the width direction is promoted. In other words, particles with a high aspect ratio are formed. The composite obtained in this way has a high aspect ratio, and when it is blended with a polymer or the like into a coating solution to form a coating layer on a substrate, a plurality of composites are arranged parallel to the plane direction of the coating layer within the coating layer, and excellent gas barrier properties can be exhibited.

[0019] Hereinafter, each step in the method for producing the composite of the present embodiment will be described.

[0020] (Solution Preparation Step) In the solution preparation step, first, a precursor hydrotalcite compound is fired to obtain a composite metal oxide. The firing time when firing this precursor hydrotalcite compound is not particularly limited. For example, when firing using a firing furnace, the time is 0.1 hour or more and 24 hours or less. Similarly, the firing temperature is not particularly limited. For example, when firing using a firing furnace, the temperature is 300°C or more and 700°C or less. The firing time when firing the precursor hydrotalcite compound is, for example, 1 minute or more and 12 hours or less when firing using microwaves. When firing using microwaves, for example, the temperature can also be 300°C or more and 700°C or less.

[0021] Next, an amino acid aqueous solution with a predetermined concentration is added to and mixed with the composite metal oxide powder obtained by firing the precursor hydrotalcite-like compound to obtain a slurry solution. At this time, the slurry concentration of the slurry solution is less than 30 g / L. Usually, since the thickness of the primary particles of the hydrotalcite-like compound obtained using such a releasing agent is as thin as several nm, if the slurry concentration is high, it may gel during the peeling process and become a heterogeneous sample. Therefore, in the production method of the present embodiment, by setting the slurry concentration in the solution preparation step to less than 30 g / L, the interparticle interaction of the hydrotalcite-like compound can be reduced, and gelation during the peeling process can be suppressed. As a result, the above production method can maintain the slurry state of the slurry solution, so that the composite can be produced uniformly and efficiently.

[0022] Note that, from the viewpoint of productivity and the like, the slurry concentration in the solution preparation step is more preferably in the range of 10 g / L to 28 g / L. Here, the slurry concentration can be obtained by the following formula. Slurry concentration (g / L) = weight of composite metal oxide (g) / volume of slurry (L)

[0023] (Hydrotalcite-like compound) The precursor hydrotalcite-like compound used in the production method of the composite of the present embodiment is not particularly limited, and examples thereof include hydrotalcite-like compounds represented by the following formula (1). (M 2+ ) 1-X (M 3+ ) X (OH) 2 (A n- ) X / n ·mH 2 O ···(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, and m is a number satisfying 0 < m < 1.80.)

[0024] In the above formula (1), preferred M 2+ is Mg 2+ and preferred M 3+ is Al 3+ These hydrotalcite compounds have high safety for living bodies, and also have the advantage that it is easy to maintain transparency when a coating layer is formed on a substrate made of such a resin because their refractive indices are close to those of resins such as polypropylene and polyethylene. Furthermore, the molar ratio of Mg / Al 2 is preferably in the range of 4 to 8 from the viewpoint that a hydrotalcite structure can be obtained more reliably.

[0025] Also, in the above formula (1), the type of anion of A n- is not particularly limited, and examples include carbonate ions (CO 3 2- ) and hydroxide ions (OH - ). From the viewpoint that corrosive gases such as chlorine gas and nitrogen dioxide gas are not generated during the firing of the precursor hydrotalcite compounds, that is, the hydrotalcite compounds before firing, carbonate ions are preferred.

[0026] Note that the above-mentioned hydrotalcite compounds are precursor hydrotalcite compounds as raw materials used in the method for producing the composite of the present embodiment, and the same applies to the hydrotalcite compounds contained in the composite obtained by the production method. From the viewpoint of obtaining a composite with a high aspect ratio, preferably hydroxide ions and the like can be mentioned.

[0027] (Amino acid) The amino acids used in the method for producing the composite of the present embodiment are not particularly limited, and examples thereof include various amino acids such as α-amino acids, β-amino acids, and γ-amino acids. More specifically, for example, aspartic acid, glutamic acid, asparagine, serine, glycine, β-alanine, β-aminobutyric acid, γ-aminobutyric acid, β-leucine, and the like can be mentioned. These amino acids may be used alone or in combination of two or more.

[0028] Among the above various amino acids, the amino acids used in the method for producing the composite of the present embodiment are preferably amino acids with a solubility of 10 g / 100 mL H 2 O or more, and glycine is particularly preferred. Such amino acids, especially glycine, are advantageous in that a composite with a thin primary particle thickness can be obtained because they have a high dielectric constant. Furthermore, glycine has a bacteriostatic effect and is also used in supplements, coloring agents, fragrances, etc., and is also advantageous from the viewpoint of biosafety.

[0029] In this specification, "solubility of 10 g / 100 mL H 2 O or more" means a solubility in which the mass of the object to be dissolved (i.e., amino acid) in 100 g of water at 25°C is 10 g or more.

[0030] In addition, the above-mentioned amino acids are amino acids as raw materials used in the method for producing the composite of the present embodiment, and the same applies to the amino acids contained in the composite obtained by the production method. However, the amino acids contained in the composite may contain multimers (i.e., peptides) formed by the binding of a plurality of amino acids that can be generated during the production process. In this specification, a substance containing such an amino acid and a multimer of an amino acid may be referred to as an "amino acid compound". For example, a substance containing glycine and polyglycine may be referred to as a "glycine compound".

[0031] 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 such a range, not only is the aspect ratio 85 or more, but a composite having a Y.I. value indicating the yellowness of the composite within the range of 0 to 5 is easily obtained. When such a composite is blended into a coating solution together with a polymer or the like to form a coating layer on a substrate, it not only has high gas barrier properties, but also can form a highly transparent coating layer without coloring such as yellowish brown. In addition, the amino acid concentration of the slurry solution is more preferably within the range of 0.2 mol / L to 0.5 mol / L.

[0032] In the solution preparation step, the molar ratio of the amino acid in the slurry solution to the trivalent metal cation of the hydrotalcite compound, that is, amino acid / (M 3+ ) 2 The molar ratio of is preferably within the range of 2 to 6. For example, when the amino acid is glycine and the trivalent metal cation of the hydrotalcite compound is Al 3+ , the molar ratio of glycine / Al 2 is preferably within the range of 2 to 6. When such a molar ratio is within such a range, not only is the aspect ratio 85 or more, but a composite having a Y.I. value indicating the yellowness of the composite within the range of 0 to 5 is easily obtained. When such a composite is blended into a coating solution together with a polymer or the like to form a coating layer on a substrate, it not only has high gas barrier properties, but also can form a highly transparent coating layer without coloring such as yellowish brown.

[0033] (Heating step) In the heating step, by heating the slurry solution obtained in the above-described solution preparation step, the particle growth of the hydrotalcite compound is promoted. At this time, the amino acid molecules in the solution are incorporated as anions into the interlayer of the hydrotalcite compound, whereby the interlayer of the hydrotalcite compound is exfoliated, and a composite of the hydrotalcite compound and the amino acid is formed as thin particles (that is, particles having a high aspect ratio).

[0034] In the heating step, it is preferable to heat the slurry solution while stirring. The stirring means is not particularly limited, but those that can stir uniformly while maintaining the fluidity of the slurry solution are preferable.

[0035] In the heating step, the heating temperature is not particularly limited, but it is preferably a temperature within the range of 20°C to 250°C, and the upper limit of the particularly preferred heating temperature is 170°C. This can more reliably suppress the denaturation of amino acids. The heating time is not particularly limited, but it is preferably a time within the range of 1 minute to 100 hours. Also, from the viewpoint that the concentration of the slurry solution is less likely to fluctuate, etc., the heating step is preferably carried out in a closed system.

[0036] (Other steps) The steps after the heating step are not particularly limited as long as they do not inhibit the effects of the present invention. Examples of the steps after the heating step include a washing step of washing the slurry solution after the heating step with an alkaline solution (for example, a sodium hydroxide solution), a solid-liquid separation step of performing a solid-liquid separation treatment after the washing step to obtain a solid, a drying step of drying the solid obtained in the solid-liquid separation step to obtain a composite powder, a surface treatment step of treating the surface of the composite particles with various surface treatment agents, and the like.

[0037] Furthermore, before the above washing step, a dilution step of diluting the slurry after the heating step with ion-exchanged water may be performed, and instead of the above drying step, a coating liquid preparation step of preparing a coating liquid by mixing with a polymer solution or the like may be performed.

[0038] The composite obtained by the production method of the present embodiment as described above can be used to prepare a coating liquid by mixing with a polymer solution or the like. Furthermore, such a coating liquid can form a coating layer having high gas barrier properties by coating and drying on a substrate.

[0039] Hereinafter, the composite obtained by the production method of the present embodiment will be described.

[0040] [Composite] The composite obtained by the production method of the present embodiment is a composite of a hydrotalcite compound and an amino acid having an aspect ratio of 85 or more. Further, the composite preferably has a Y.I. value indicating yellowness of 0 to 5 and an amino acid content of more than 0% by mass and 10.0% by mass or less with respect to the total mass of the composite by adjusting the amino acid concentration of the slurry solution during production. Regarding the amino acid content, from the viewpoint of easily forming a coating layer having high gas barrier properties and transparency, it is more preferably 1.0% by mass or more and 8.0% by mass or less, and still more preferably 1.5% by mass or more and 6.0% by mass or less.

[0041] When the Y.I. value of the composite is within a specific range of 5 or less and the amino acid content is within a specific range of 10.0% by mass or less, a highly transparent coating layer without coloring such as yellow-brown can be formed when the composite is used as a coating liquid to form a coating layer. Regarding the mechanism of action for obtaining such a highly transparent coating layer, although not restricted by any theory, it is considered as follows.

[0042] First, the production method of the composite of the present embodiment is advantageous in obtaining a hydrotalcite compound with a thin primary particle thickness because the interlayer peeling of the hydrotalcite compound occurs by using an amino acid as a release agent. However, in the heating step for peeling the hydrotalcite compound, the peptide bond between amino acids is promoted under alkaline conditions to generate a polyamino acid (for example, a peptide such as polyglycine). It is known that peptides such as polyglycine turn yellow when they form long chains, and the yellowness increases as the molecular chain becomes longer. Therefore, if a composite of a hydrotalcite compound and an amino acid containing such a long-chain peptide (polypeptide) is blended into a coating liquid together with a polymer or the like, the transparency and appearance of the resulting coating layer may be impaired.

[0043] Therefore, in the above-described solution preparation step, by setting the slurry concentration of the slurry solution to less than 30 g / L and the amino acid concentration within a specific range of less than 0.6 mol / L, the formation of peptide bonds between amino acids can be suppressed even under alkaline conditions, and the production of polyamino acids (peptides) can be inhibited. As a result, it is considered that yellowing of the obtained composite can be suppressed. By adjusting the slurry concentration and amino acid concentration of the slurry solution in this way, a composite having a high aspect ratio of 85 or more, a Y.I. value indicating yellowness of 0 to 5, and an amino acid content greater than 0 mass% and less than or equal to 10.0 mass% can be obtained. And when such a composite is blended into a coating solution together with a polymer or the like to form a coating layer, a coating layer having both high gas barrier properties and transparency can be formed. Thus, the composite obtained by the production method of the present embodiment can be used in a variety of applications that require gas barrier properties without impairing transparency or aesthetics. For example, when a coating solution containing such a composite is applied to a film, high gas barrier properties can be imparted to the film without impairing transparency.

[0044] As described above, it is preferable that the composite has a Y.I. value indicating yellowness of 0 to 5. This Y.I. value serves as an index of the "polyamino acid content" that affects coloring such as yellowing. If this Y.I. value exceeds 5, coloring such as tan occurs, and if such a colored composite is used as a component of a coating solution to form a coating layer, there is a risk of impairing transparency and aesthetics. A more preferable range of the Y.I. value is 4 or less, and more preferably 3 or less. When the Y.I. value is within such a range, a coating layer with higher transparency can be formed.

[0045] In addition, since the composite obtained by the production method of the present embodiment has a high aspect ratio of 85 or more, when it is blended with a polymer or the like in a coating liquid to form a coating layer on a substrate, excellent gas barrier properties can be exhibited. From the viewpoint of obtaining higher gas barrier properties and the like, the aspect ratio of such a composite is preferably 90 or more, and more preferably 100 or more. The upper limit of the aspect ratio of the composite is not particularly limited, but is, for example, 500 or less.

[0046] In the present specification, the aspect ratio of the composite is the ratio of the width (diameter) to the thickness of the primary particles of the composite having a layered structure, and can be obtained by dividing the width of the primary particles of the composite by the thickness.

[0047] As long as the composite obtained by the production method of the present embodiment has an aspect ratio of 85 or more, the thickness of the primary particles is not particularly limited, and examples thereof include a thickness of 20 nm or less. When the composite is blended with a polymer or the like in a coating liquid to form a coating layer on a substrate, it is preferable that the thickness of the primary particles of the composite is 20 nm or less and the aspect ratio is 100 or more from the viewpoint of obtaining more excellent gas barrier properties.

[0048] Furthermore, it is more preferable that the thickness of the primary particles of the composite is in the range of 0.7 nm to 10 nm. When the thickness of the primary particles of the composite is within such a range, the hydrotalcite-like compound is in a sufficiently exfoliated state, and when it is blended with a polymer or the like in a coating liquid to form a coating layer on a substrate, higher gas barrier properties can be exhibited.

[0049] [Coating liquid] A coating liquid containing the composite obtained by the production method of the present embodiment and a polymer can form a coating layer by coating and drying it on a substrate described later. The concentration of the composite contained in the coating liquid is not particularly limited, but from the viewpoint of coatability on the substrate and the like, a concentration of 20% by mass or less is preferable, and a concentration of 10% by mass or less is more preferable.

[0050] (Polymer) The polymer contained in the coating liquid is used in the form of a solution dissolved in a solvent such as water or alcohol. Although the polymer concentration in the solution is not particularly limited, from the viewpoint of coatability on the substrate, etc., a concentration of 20% by mass or less is preferable, and a concentration of 10% by mass or less is more preferable.

[0051] The type of the polymer contained in the coating liquid is not particularly limited, and any polymer can be adopted according to the use of the coating layer or film to be formed, etc. Examples of such polymers include water-soluble polymers. More specifically, polyvinyl alcohol, copolymers containing vinyl alcohol (for example, polyethylene vinyl alcohol, etc.), carboxymethyl cellulose, polyacrylic acid, polyacrylamide, etc. can be mentioned. These water-soluble polymers may be used alone or in combination of two or more. By using a water-soluble polymer, it is easy to separate the substrate and the coating layer, and the recyclability is improved, so it can contribute to the achievement of the SDGs (Sustainable Development Goals) adopted at the United Nations Summit.

[0052] Among these water-soluble polymers, it is preferable to use polyvinyl alcohol from the viewpoints of gas barrier properties, transparency, coatability, etc.

[0053] (Other components) In addition to the above-mentioned composite and polymer, the coating liquid may contain other additive components. Such additive components are not particularly limited, and examples include antioxidants, reinforcing agents, ultraviolet absorbers, pigments, crosslinking agents, flame retardants, etc. These additive components may be used alone or in combination of two or more.

[0054] [Film] The coating liquid containing the composite obtained by the production method of the present embodiment and a polymer can form a coating layer by coating it on a substrate and drying it. The drying conditions can be appropriately set, for example, within a temperature range from room temperature to 160°C for a period from 1 second to 24 hours. Here, when a film-shaped substrate (hereinafter sometimes referred to as "film-shaped substrate") is used as the substrate, a film having a multilayer structure in which the film-shaped substrate is covered with the coating layer can be obtained. Further, by peeling the coating layer on the substrate, a film having a single-layer structure composed of the coating layer may be obtained. The film having a multilayer structure or a single-layer structure thus obtained can be suitably used, for example, as various packaging films.

[0055] (Substrate) The substrate used for forming the film is not particularly limited, and any substrate according to the use of the film to be formed or the like can be used. Such substrates include, for example, the above-mentioned film-shaped substrates, and more specifically, resin films such as polyolefin films such as polyethylene and polypropylene, and polyester films such as polyethylene terephthalate; paper; fiber sheets such as woven fabrics, non-woven fabrics, and knitted fabrics.

[0056] When a film-shaped substrate is used as the substrate, its thickness is not particularly limited, but for example, 0.01 μm to 250 μm is preferable, and a thickness within the range of 1 μm to 100 μm is more preferable. Note that the thickness of the coating layer formed by the above-mentioned coating liquid is also not particularly limited, but is, for example, within the range of 0.01 μm to 100 μm.

[0057] The film using the composite obtained by the production method of the present invention can be used in 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.

[0058] Note that the present invention is not limited to the above-described embodiments, examples described later, etc., and combinations, substitutions, changes, etc. can be made as appropriate without departing from the object and gist of the present invention.

Example

[0059] Hereinafter, the present invention will be described more specifically by way of examples and comparative examples, but the present invention is not limited only to these examples.

[0060] Example 1 (Production of precursor hydrotalcite compounds) Ion-exchanged water was placed in a 1 L reaction vessel, and while stirring, 160 mL of a 1.5 mol / L magnesium chloride aqueous solution, 120 mL of a 1 mol / L aluminum chloride aqueous solution, a mixed solution of 90 mL of an 8 mol / L sodium hydroxide aqueous solution and 60 mL of a 1 mol / L sodium carbonate aqueous solution were simultaneously dropped therein to obtain a reaction product. The pH during the reaction was 9.5. After washing the obtained reaction product with water, ion-exchanged water was added to obtain 700 mL of a re-emulsified slurry. The obtained re-emulsified slurry was hydrothermally treated at 170 °C for 13 hours. Thereafter, the obtained solid was washed with water, dried at 105 °C for 16 hours, and pulverized. The chemical formula of the obtained powder was Mg 0.67 Al 0.33 (OH) 2 (CO 3 ) 0.17 ·0.50H 2 O, which was a hydrotalcite compound. This hydrotalcite compound was used as a precursor hydrotalcite compound for the production of the composite.

[0061] (Firing of precursor hydrotalcite compounds) The obtained precursor hydrotalcite compound was fired in an electric furnace at 450 °C for 12 hours to obtain a fired product (composite metal oxide).

[0062] (Solution preparation step) 17.5 g of the obtained fired product was put into a glass beaker, 175 mL of a 2 mol / L aqueous glycine solution (equivalent to 26.3 g of glycine powder) was added, and the mixture was stirred until it became uniform. At this time, the glycine / Al 2 molar ratio of the obtained slurry solution was 5.26. Then, ion-exchanged water was added to make the total volume 700 mL, and the mixture was stirred again until it became uniform. The slurry concentration at this time was 25 g / L. Also, the glycine concentration at this time was 0.5 mol / L.

[0063] (Heating step) Subsequently, while stirring the slurry solution at 700 rpm, hydrothermal treatment was performed at 100 °C for 48 hours. The obtained sample (slurry solution) was in a slurry state and white, and no particular odor was felt. A photograph of the slurry solution after the heating step is shown in Fig. 1.

[0064] (Washing step - Drying step) Next, ion-exchanged water was added to the obtained slurry solution to make the total volume 1750 mL, and the mixture was stirred at 400 rpm for 16 hours at room temperature using a stirrer. While maintaining the stirring of the slurry solution, 88.4 mL of a 3.96 mol / L aqueous sodium hydroxide solution was gradually added dropwise to the slurry solution. The obtained slurry solution was subjected to solid-liquid separation to obtain a solid. Further, the obtained solid was dried at 60 °C for 16 hours to obtain the sample (composite) of Example 1. The characteristics of the obtained sample are shown in Table 1 below.

[0065] Example 2 A sample of Example 2 was obtained in the same manner as in Example 1, except that 14.0 g of the fired product was used in the solution preparation step and 140 mL of a 2 mol / L aqueous glycine solution (equivalent to 21.0 g of glycine powder) was used. The slurry concentration of the slurry solution in the solution preparation step was 20 g / L, and the glycine concentration was 0.4 mol / L.

[0066] Example 3 In the solution preparation step, a sample of Example 3 was obtained in the same manner as in Example 1, except that 7.0 g of the fired product was used and 70 mL of a 2 mol / L aqueous glycine solution (equivalent to 10.5 g of glycine powder) was used. The slurry concentration of the slurry solution in the solution preparation step was 10 g / L, and the glycine concentration was 0.2 mol / L.

[0067] Comparative Example 1 In the solution preparation step, a sample of Comparative Example 1 was obtained in the same manner as in Example 1, except that 70.0 g of the fired product was used, 700 mL of a 2 mol / L aqueous glycine solution (equivalent to 105.1 g of glycine powder) was used, and stirring was not performed in the heating step. The slurry concentration of the slurry solution in the solution preparation step was 100 g / L, and the glycine concentration was 2 mol / L.

[0068] Comparative Example 2 In the solution preparation step, a sample of Comparative Example 2 was obtained in the same manner as in Example 1, except that 70.0 g of the fired product was used, 266 mL of a 2 mol / L aqueous glycine solution (equivalent to 39.9 g of glycine powder) was used, and stirring was not performed in the heating step. The slurry concentration of the slurry solution in the solution preparation step was 100 g / L, and the glycine concentration was 0.76 mol / L.

[0069] Comparative Example 3 In the solution preparation step, a sample of Comparative Example 3 was obtained in the same manner as in Example 1, except that 70.0 g of the fired product was used, no aqueous glycine solution was used, stirring was not performed in the heating step, and the washing step was not performed. The slurry concentration of the slurry solution in the solution preparation step was 100 g / L, and the glycine concentration was 0 mol / L.

[0070] Comparative Example 4 In the solution preparation step, a sample of Comparative Example 4 was obtained in the same manner as in Example 1, except that 35.0 g of the fired product was used and 350 mL of a 2 mol / L aqueous glycine solution (equivalent to 52.5 g of glycine powder) was used. The slurry concentration of the slurry solution in the solution preparation step was 50 g / L, and the glycine concentration was 1 mol / L.

[0071] Comparative Example 5 In the solution preparation step, a sample of Comparative Example 5 was obtained in the same manner as in Example 1, except that 28.0 g of the fired product was used and 280 mL of a 2 mol / L aqueous glycine solution (equivalent to 42.0 g of glycine powder) was used. The slurry concentration of the slurry solution in the solution preparation step was 40 g / L, and the glycine concentration was 0.8 mol / L.

[0072] Comparative Example 6 In the solution preparation step, a sample of Comparative Example 6 was obtained in the same manner as in Example 1, except that 21.0 g of the fired product was used and 210 mL of a 2 mol / L aqueous glycine solution (equivalent to 31.5 g of glycine powder) was used. The slurry concentration of the slurry solution in the solution preparation step was 30 g / L, and the glycine concentration was 0.6 mol / L.

[0073] Example 4 (Preparation of Coating Liquid) The solid content concentrations of the sample of Example 1 and an aqueous polyvinyl alcohol (PVA) solution (manufactured by Sigma-Aldrich, Mw 67,000, Mowiol® 8-88) were measured, and ion-exchanged water was added and adjusted so that the composite of the hydrotalcite compound and the glycine compound in Example 1 was 3 wt% and PVA was 2 wt%. A coating liquid was obtained by mixing while stirring.

[0074] (Preparation of Film) First, a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., Lumirror (registered trademark), film thickness 50 μm, product number type #50-U483) cut into a size of 55 mm in length and 105 mm in width, which is a film-shaped substrate, was fixed on a glass plate of an automatic coating apparatus (PI-1210 type, manufactured by Tester Sangyo Co., Ltd.). Next, a baker applicator (YBA type, manufactured by Yoshimitsu Seiki Co., Ltd.) was set on the glass plate of the automatic coating apparatus, and a coating liquid was applied onto the PET film so that the thickness would be uniformly 50 μm. The film of Example 4 was obtained by drying the coating layer formed by the applied coating liquid at room temperature for 16 hours.

[0075] Comparative Example 7 A film of Comparative Example 7 was obtained in the same manner as in Example 4, except that the sample of Comparative Example 1 was used instead of the sample of Example 1.

[0076] Comparative Example 8 A film of Comparative Example 8 was obtained in the same manner as in Example 4, except that the precursor hydrotalcite-like compound obtained in the "Production of precursor hydrotalcite-like compound" step of Example 1 was used instead of the sample of Example 1 (a composite of a hydrotalcite-like compound and a glycine-like compound). That is, the film of Comparative Example 8 uses an unpeeled hydrotalcite-like compound (unpeeled HT) instead of a composite of a hydrotalcite-like compound and a glycine-like compound.

[0077] Comparative Example 9 A film of Comparative Example 9 was obtained in the same manner as in Example 4, except that the coating liquid was not applied. That is, the film of Comparative Example 9 is a single PET film (film-shaped substrate) on which a coating layer by the coating liquid is not formed.

[0078] Comparative Example 10 A film of Comparative Example 10 was obtained in the same manner as in Example 4, except that a coating liquid containing only PVA was used.

[0079] Example 5 (Production of Film) A polypropylene (PP) film (manufactured by Toyobo Co., Ltd., Pyren (registered trademark) Film - OT, film thickness 50 μm, brand P2261) was used as the film - like substrate, and the film of Example 5 was obtained in the same manner as in Example 4, except that the coating liquid was applied so that the thickness was uniformly 25 μm.

[0080] Example 6 The film of Example 6 was obtained in the same manner as in Example 5, except that the coating liquid was applied so that the thickness was uniformly 12.5 μm.

[0081] Comparative Example 11 The film of Comparative Example 11 was obtained in the same manner as in Example 5, except that the coating liquid was not applied. That is, the film of Comparative Example 11 is a single PP film (film - like substrate) on which a coating layer by the coating liquid is not formed.

[0082] Comparative Example 12 The film of Comparative Example 12 was obtained in the same manner as in Example 5, except that a coating liquid containing only PVA was used.

[0083] [Various Measurements] For the samples of Examples 1 to 3 and Comparative Examples 1 to 6, various physical properties and the like shown below were measured. These measurement results are shown in Table 1 below. Also, photographs were taken of the slurry solutions after the heating process for Examples 1 to 3 and Comparative Examples 1 to 3, and of the slurry solutions when the temperature was raised to 100 °C in the heating process for Comparative Examples 4 to 6. This photograph is shown in Figure 1.

[0084] (Viscosity Measurement after Heating Process) After adjusting the temperature of the slurry solution to 25 °C, the viscosity was measured at the same temperature using a B - type viscometer (manufactured by Brookfield, DV2T type).

[0085] (Measurement of Thickness and Aspect Ratio of Primary Particles of Composite) Using a scanning probe microscope (manufactured by Shimadzu Corporation, model SPM-9700HT), the width and thickness of the primary particles were measured. The aspect ratio was determined by the following formula. (Aspect ratio of primary particles) = (Width of primary particles) / (Thickness of primary particles) Note that for 20 arbitrary primary particles, the aspect ratio was calculated for each, and the average value was taken as the aspect ratio of the sample.

[0086] (Measurement of glycine compound content) 0.5 g of a powder sample dried at 60 °C for 16 hours, 5 g of potassium sulfate, and 2 g of copper(II) sulfate pentahydrate were thoroughly mixed and placed in a sample tube, and 15 ml of concentrated sulfuric acid was added. Subsequently, using a Kjeldahl analysis system (manufactured by Buchi, model KjelFlex K-360 / K-425 SpeedDigester), it was treated at 470 °C for 90 minutes. Furthermore, steam distillation was carried out for 240 seconds using 10 mL of ion-exchanged water, an aqueous sodium hydroxide solution of 30%, and 40 mL of a 2% boric acid aqueous solution. 3 drops of a mixed indicator of methyl red and methylene blue were added to the obtained distillate, and titration was carried out using a 0.1 mol / L hydrochloric acid aqueous solution until the distillate turned purple. Titration was also carried out in the same manner for a blank without using the powder sample, and the glycine compound content was calculated from the following formulas (I) and (II). (Nitrogen N content) [wt%] = ((Factor of 0.1 mol / L hydrochloric acid aqueous solution) × (Drop volume [ml] - Blank [ml]) × 1.401 [mg / ml]) × 100 / Powder sample amount [mg] ··· (I) (Glycine compound content) [wt%] = (Nitrogen N content) [wt%] × (75.07 [g / mol] / 14.01 [g / mol]) ··· (II)

[0087] (Measurement of yellowness (Y.I. value)) The powdered sample dried at 60 °C for 16 hours was pulverized, sieved through a sieve with an opening size of 150 μm, and then 0.2 g of it was placed in a glass reagent bottle. Subsequently, using a 10Φ viewing port and sample stage, measurements were carried out with a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., Color meter ZE6000 type) that had been calibrated in advance with a standard white plate. A total of 3 measurements were performed, and before each measurement, the reagent bottle was shaken 10 times. The average value was calculated from the 3 measurement values obtained, and the Yellow Index value (Y.I. value) was obtained.

[0088] [Evaluation of Film] For the films of Examples 4 to 6 and Examples 7 to 12 of the Comparative Examples, various physical properties and the like shown below were measured. These measurement results are shown in Tables 2 to 3 below.

[0089] (Measurement of Total Light Transmittance and Haze) 20 mm was cut from the end point of film coating, and with the coated surface on the incident light side, measurements were carried out with a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH4000 type) to obtain the total light transmittance and Haze.

[0090] (Measurement of Oxygen Gas Permeability) The film was cut into a circle with a diameter of about 55 mm, and the gas permeability was measured using a gas permeability measuring device (manufactured by GTR Tech Co., Ltd., GTR-11AET type). The measurement method was in accordance with JIS K 7126-1 Part 1 (differential pressure method), and the measurements were carried out under the following conditions. · Measurement temperature: 23.0 °C · Relative humidity: zero · Permeation area: 15.2 cm 2 · Measurement gas: oxygen gas The oxygen gas permeating through the film was analyzed with a capillary gas chromatograph system (manufactured by Shimadzu Corporation, GC-2014 type) to obtain the oxygen gas permeability. In the measurement of oxygen gas permeability, the measurement and analysis time can be appropriately adjusted according to the gas permeability of the film.

[0091]

Table 1

[0092]

Table 2

[0093]

Table 3

[0094] As shown in Table 1 to Table 3 and FIG. 1, in the examples of the present invention, in the heating step, uniform stirring can be performed, and a composite of a hydrotalcite compound having a high aspect ratio and a glycine (amino acid) compound can be obtained without gelation. Therefore, it was found that the production method of the examples can uniformly and efficiently produce a composite having a high aspect ratio. Furthermore, it was found that the composite obtained by the production method of the present invention can form a film (coating layer) having high gas barrier properties and transparency. On the other hand, in the comparative examples, uniform stirring could not be performed in the heating step, gelation occurred, or the aspect ratio of the obtained composite decreased, and a composite having a high aspect ratio as in the present invention could not be uniformly and efficiently produced.

Industrial Applicability

[0095] The method for producing the composite of the present invention can be suitably used for the production of products in 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, additives, and the like.

Claims

1. A method for producing a composite of a hydrotalcite compound and an amino acid, wherein the aspect ratio is 85 or more, comprising: a solution preparation step of preparing a slurry solution by mixing an aqueous solution of the amino acid and a composite metal oxide obtained by firing a precursor hydrotalcite compound; a heating step of heating the slurry solution; and having a production method, characterized in that the slurry concentration of the slurry solution in the solution preparation step is less than 30 g / L and the amino acid is glycine.

2. The amino acid is glycine having a solubility of 10 g / 100 mL H ２ O or more, and the production method according to claim 1, characterized in that it is said glycine.

3. The production method according to claim 1, characterized in that the slurry concentration is in the range of 10 g / L to 28 g / L.

4. The production method according to claim 1, characterized in that the hydrotalcite compound 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 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, and m is a number satisfying 0 < m < 1.80.)

5. The production method according to claim 1, characterized in that the amino acid concentration of the slurry solution in the solution preparation step is less than 0.6 mol / L.

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