Method for producing ion-exchanged hydrotalcite

Abstract

The present invention provides a novel method for producing an ion-exchanged hydrotalcite, the method including no complicated steps, needing no massive equipment, and enabling a hydrotalcite to be ion-exchanged while inhibiting the formation of a by-product, etc.　This method for producing an ion-exchanged hydrotalcite (3) is characterized by comprising a first step, in which a powdery or pasty hydrotalcite (1) is mixed and reacted with an aqueous solution of an acid (2) so that the resultant mixture has a water content in the range of 10-60 mass%, and a second step, in which a reaction product obtained in the first step is dried and pulverized without via a cleaning step.

Description

[Technical field]

[0001] The present invention relates to a method for producing ion-exchanged hydrotalcite. [Background technology]

[0002] In general, when mixing two kinds of substances, mixing liquids (slurries) together is easier to disperse uniformly than mixing powders (solids) together, and therefore a more uniform mixture can be obtained. This is also true for ion exchange (intercalation) of hydrotalcite compounds (hereinafter simply referred to as "hydrotalcite"). It is commonly believed that in order to sufficiently exchange ions of hydrotalcite, it is necessary to mix the liquids together and cause a reaction.

[0003] There are three known general methods for ion exchanging hydrotalcite, i.e., general methods for producing ion-exchanged hydrotalcite: a reconstruction method, an ion exchange method, and a coprecipitation method. An appropriate method is selected depending on the combination of hydrotalcite as a host substance and a guest substance (substance to be intercalated), among other factors.

[0004] Here, the reconstruction method is a method in which hydrotalcite is calcined at a high temperature in advance, and a pyrolyzate obtained by desorbing at least a part of carbon dioxide and interlayer water from the hydrotalcite is made to coexist with a guest substance in a solvent such as water, so that the guest substance is incorporated between the layers when the pyrolyzate returns to hydrotalcite. Specifically, the method includes a step of calcining hydrotalcite at a high temperature, a step of making the pyrolyzate of hydrotalcite coexist with the guest substance in a solvent such as water to react with each other, a step of separating the solid reaction product from the reaction liquid, and a step of drying and pulverizing the separated solid reaction product.

[0005] The ion exchange method is a method of intercalating a guest substance between layers of hydrotalcite by mixing the hydrotalcite with an anionic guest substance in a solvent. Specifically, the method includes a step of suspending hydrotalcite in a solvent, a step of reacting the hydrotalcite with a solution containing an anionic guest substance by dropping the solution containing the anionic guest substance into the suspension (slurry) of hydrotalcite, a step of separating a solid reaction product from the reaction solution, and a step of drying and pulverizing the separated solid reaction product. As an example of such an ion exchange method, for example, Patent Document 1 proposes a method in which a carbonate ion-type layered double hydroxide (LDH) is used as a starting material, and a decarbonation reaction is carried out simply and quickly using a small number of types and amounts of reagents, thereby producing an LDH with excellent anion exchange properties while maintaining the crystal shape, crystal structure, and crystallinity.

[0006] The coprecipitation method is a method for synthesizing hydrotalcite containing a guest substance by dropping a solution of a divalent metal ion salt and a solution of a trivalent metal ion salt, which are raw materials for hydrotalcite, into a liquid in which a guest substance is dissolved or suspended in water, thereby synthesizing hydrotalcite containing a guest substance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2012 / 102151 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the conventional reconstruction methods require a step of calcining hydrotalcite at high temperatures, and the ion exchange method and coprecipitation method require a step of mixing a solution or suspension, making the process complicated and requiring large-scale equipment. In addition, in the method of Patent Document 1, which is an example of the ion exchange method, it is necessary to contact carbonate ion-type LDH with an organic solvent containing an acidic compound, and therefore it is necessary to handle the organic solvent and dispose of the waste liquid. As a result, the process becomes complicated and large-scale equipment is required. Furthermore, these conventional methods require an excess amount of guest substance relative to the desired amount of ion exchange, and therefore require a washing step to remove the excess guest substance remaining in the system after the reaction and by-products resulting from the guest substance (hereinafter sometimes simply referred to as "by-products, etc."), necessitating the provision of equipment for the washing step and measures for treating waste liquid, etc.

[0009] Therefore, the present invention aims to provide a novel method for producing ion-exchanged hydrotalcite, which can ion-exchange hydrotalcite while suppressing the production of by-products, etc., without involving complicated steps or requiring large-scale equipment. [Means for solving the problem]

[0010] As a result of intensive research to achieve the above object, the present inventors have found that, when mixing hydrotalcite (host substance) with a guest substance, limiting the amount of water within a specific range to an extent that an opportunity for contact between ions on the host substance side and ions on the guest substance side can be ensured, it is possible to sufficiently ion-exchange the hydrotalcite while suppressing the generation of by-products, etc. The present invention has been completed based on such findings, and includes at least the following aspects.

[0011] One aspect (Aspect 1) of the present invention is a method for producing ion-exchanged hydrotalcite, A first step of mixing and reacting a powdered or pasty hydrotalcite with an acid aqueous solution so that the water content after mixing is within a range of 10 to 60 mass %; A second step of drying and pulverizing the reaction product obtained in the first step without a washing step; The manufacturing method according to the present invention is characterized in that it comprises the steps of:

[0012] The production method of this embodiment 1 includes a first step of mixing and reacting powdered or pasty hydrotalcite with an acid aqueous solution such that the water content after mixing is within the range of 10 to 60 mass %, and therefore does not require complicated steps or large-scale equipment such as a calcination step or a filtration step of the hydrotalcite, or a washing step after the reaction, which are essential in the conventional reconstruction method, ion exchange method, and coprecipitation method, and can sufficiently ion-exchange the hydrotalcite while suppressing the generation of by-products, etc.

[0013] Furthermore, while conventional methods required an excess amount of guest substance relative to the desired amount of ion exchange, the production method of the present embodiment 1 allows sufficient ion exchange with an equal amount of guest substance relative to the desired amount of ion exchange (i.e., the amount of guest substance required is equal to the desired amount of ion exchange), making it easy to control the amount of ion exchange and reducing the likelihood of excess guest substance or organic solvent residues being generated. As a result, there are advantages in that the environmental burden can be reduced and production costs are also excellent.

[0014] The production method of this embodiment 1 also has the advantage that it is possible to carry out ion exchange of water-insoluble anions, and therefore possible to produce a variety of specialized products for various applications.

[0015] In another aspect (Aspect 2) of the present invention, in the production method of Aspect 1 above, the powdered or pasty hydrotalcite is a hydrotalcite represented by the following formula (1). M 2+ 1-x M 3+ x (OH)2A n- x / n mH2O (1) (In the formula, M 2+ is a divalent metal ion, M 3+ is a trivalent metal ion, A n- represents an n-valent anion, x represents a number satisfying 0.18≦x≦0.4, n represents an integer of 1 to 4, and m represents a number satisfying 0≦m≦5.

[0016] In the manufacturing method of this embodiment 2, even if the powdered or paste-like hydrotalcite is the highly versatile hydrotalcite represented by the above formula (1), it is possible to sufficiently perform ion exchange while suppressing the production of by-products, etc., and therefore it is possible to realize a wide range of product designs according to various applications, etc.

[0017] In still another embodiment (embodiment 3) of the present invention, in the production method of embodiment 2, M in formula (1) 2+ Mg 2+ and Zn 2+ At least one metal ion selected from the group consisting of M 3+ Al 3+ It is characterized in that:

[0018] In the production method of the present embodiment 3, since the powdery or pasty hydrotalcite is the above-mentioned specific hydrotalcite, the effect of the above-mentioned embodiment 2 can be more reliably achieved.

[0019] In still another embodiment (embodiment 4) of the present invention, in the production method of embodiment 2 or 3, A n- CO3 2- It is characterized in that:

[0020] In the manufacturing method of this embodiment 4, the powdered or paste-like hydrotalcite is the above-mentioned specific hydrotalcite, and the anions contained between the layers of the hydrotalcite can be gasified (as carbon dioxide) and removed after ion exchange. This makes it easier to prevent the generation of by-products, etc., and more reliably eliminates the need for cleaning steps, etc.

[0021] In still another aspect (Aspect 5) of the present invention, in the production method of any one of Aspects 1 to 4 above, the water content of the powdery or paste-like hydrotalcite is within the range of 0 to 60 mass %.

[0022] In the manufacturing method of this embodiment 5, the water content of the powdered or paste-like hydrotalcite is within the range of 0 to 60 mass %, so that the mixture is less likely to become a slurry and lose viscosity, and the mixing in the first step can be carried out more smoothly.

[0023] In still another aspect (Aspect 6) of the present invention, in the manufacturing method of any one of Aspects 1 to 5 above, the acid contained in the acid aqueous solution is at least one acid selected from the group consisting of inorganic acids, inorganic acid salts, organic acids, and organic acid salts.

[0024] In the production method of the sixth embodiment, since the acid contained in the acid aqueous solution serving as the guest substance is the above-mentioned specific acid, the hydrotalcite can be ion-exchanged sufficiently while suppressing the generation of by-products and the like more reliably.

[0025] A further aspect (aspect 7) of the present invention is characterized in that in the production method of any one of the aspects 1 to 6 above, the water content of the aqueous acid solution is within the range of 10 to 70 mass %.

[0026] In the manufacturing method of the seventh embodiment, the water content of the acid aqueous solution is 10% by mass or more, so that the reactivity can be suppressed to a certain level and the surface reaction with the particles can be prevented from occurring preferentially, so that the occurrence of salt by-products, particle aggregation, etc. can be more suppressed. In addition, the water content of the acid aqueous solution is 70% by mass or less, so that a certain level of reactivity can be secured, and the ion exchange reaction can be more reliably carried out.

[0027] In yet another aspect (Aspect 8) of the present invention, in the manufacturing method of any one of Aspects 1 to 7 above, the first step further includes a step of adding the acid aqueous solution to the powdered or pasty hydrotalcite, and the rate of addition of the acid aqueous solution is 0.5 to 710 mass% / min with respect to the mass of the hydrotalcite.

[0028] In the production method of the present embodiment 8, by adding the aqueous acid solution at a rate within the above-mentioned specific range in the first step, it is possible to ensure a certain level of productivity while preventing the surface reaction with the particles from occurring preferentially, thereby making it even more difficult for by-production of salts and aggregation of particles to occur. Effect of the Invention

[0029] According to the production method of the present invention, it is possible to sufficiently ion-exchange hydrotalcite while suppressing the production of by-products, etc., without requiring the complicated steps and large-scale equipment that were essential in conventional methods. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic diagram for illustrating the ion exchange reaction between hydrotalcite as a host substance and an acid as a guest substance in the first step of the production method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The method for producing ion-exchanged hydrotalcite of the present invention (hereinafter sometimes simply referred to as the "production method of the present invention") will be described in detail below.

[0032] [Manufacturing method] The production method of the present invention includes a first step of mixing and reacting powdered or pasty hydrotalcite with an acid aqueous solution such that the water content after mixing is within the range of 10 to 60 mass %, and a second step of drying and pulverizing the reaction product obtained in the first step without a washing step.

[0033] In the production method of the present invention, in the first step, powdered or pasty hydrotalcite is mixed with an acid aqueous solution and reacted such that the water content after mixing is within the range of 10 to 60 mass %, thereby making it possible to sufficiently ion exchange the hydrotalcite while suppressing the generation of by-products, etc., without the need for complicated steps or large-scale equipment such as a calcination step or a filtration step of the hydrotalcite, or a washing step after the reaction, which are essential in the conventional reconstruction method, ion exchange method, and coprecipitation method.

[0034] Furthermore, while conventional methods required an excess amount of guest substance relative to the desired amount of ion exchange, the production method of the present invention allows sufficient ion exchange with an equal amount of guest substance relative to the desired amount of ion exchange (i.e., the amount of guest substance required is equal to the desired amount of ion exchange), making it easy to control the amount of ion exchange and reducing the likelihood of excess guest substance or organic solvent residues being generated. As a result, the method has the advantages of reducing the environmental burden and being superior in production costs.

[0035] The production method of the present invention also has the advantage that it is possible to carry out ion exchange of water-insoluble anions, making it possible to produce a variety of specialized products for various applications.

[0036] Each step of the production method of the present invention will be described below.

[0037] [1st step] In the production method of the present invention, the first step is a step of mixing and reacting powdery or pasty hydrotalcite with an aqueous acid solution so that the water content after mixing is within the range of 10 to 60 mass %.

[0038] Specifically, the first step is carried out in the following procedure. That is, a predetermined amount of powdered or pasty hydrotalcite is supplied into a reaction vessel equipped with any stirring means, and a predetermined amount of an aqueous acid solution is added thereto while stirring, and the contents in the reaction vessel are mixed for a predetermined time, thereby causing an ion exchange reaction between the hydrotalcite as a host substance and the acid as a guest substance. In this first step, it is necessary to adjust the water content and supply amount of the hydrotalcite, the water concentration (i.e., the amount of water) and the amount of the aqueous acid solution, and the amount of additional water as necessary, so that the water content of the mixture of the hydrotalcite and the aqueous acid solution is within the range of 10 to 60 mass% with respect to the total mass (100 mass%) of the mixture. The water content after mixing the powdered or pasty hydrotalcite and the aqueous acid solution is preferably within the range of 20 to 60 mass%.

[0039] In this specification, "the moisture content after mixing is within the range of 10 to 60 mass%" means "the moisture content contained in the mixture is within the range of 10 to 60 mass% with respect to the total mass of the mixture (100 mass%)."

[0040] Here, Fig. 1 is a schematic diagram for explaining an ion exchange reaction between hydrotalcite as a host substance and an acid as a guest substance in the first step of the production method of the present invention. Note that the ion exchange reaction shown in Fig. 1 is merely one example of the first step in the production method of the present invention, and the types of hydrotalcite and the acid aqueous solution used in the present invention are not limited to those shown in Fig. 1.

[0041] As shown in FIG. 1, in the first step, the anions (carbonate ions; CO3 2- ) and the anion (X -As a result, ion-exchanged hydrotalcite 3 can be obtained. In the example shown in FIG. 1, the carbonate ions (CO3 2- ) is removed as carbon dioxide (CO2 gas) after ion exchange.

[0042] In this way, in the first step, the production method of the present invention mixes and reacts powdered or pasty hydrotalcite with an acid aqueous solution in the presence of a specific water content of 10 to 60 mass%, and does not require complicated steps or large-scale equipment such as a calcination step or a filtration step of the hydrotalcite or a washing step after the reaction, which were indispensable in the conventional reconstruction method, ion exchange method, and coprecipitation method, and can sufficiently ion-exchange the hydrotalcite while suppressing the generation of by-products, etc. Furthermore, in the production method of the present invention, since sufficient ion exchange can be performed with an equal amount of guest substance to the desired ion exchange amount, it is easy to control the ion exchange amount, and excess amounts of guest substance and organic solvent residues are unlikely to be generated, resulting in the advantages of reduced environmental load and excellent production costs.

[0043] (powder or paste hydrotalcite) In the production method of the present invention, the hydrotalcite that can be used as a host substance as a raw material is not particularly limited as long as it is a powder or paste-like hydrotalcite, and any known hydrotalcite can be used. Note that paste-like hydrotalcite is usually a hydrotalcite having a water content of 60 mass% or less and having a predetermined viscosity and fluidity, and is clearly distinguished from slurry-like hydrotalcite having a water content of more than 60 mass% at least by its water content.

[0044] In the production method of the present invention, the powdered or pasty hydrotalcite used as a raw material is preferably a hydrotalcite represented by the following formula (1). M 2+ 1-x M 3+ x(OH)2A n- x / n mH2O (1) (In the formula, M 2+ is a divalent metal ion, M 3+ is a trivalent metal ion, A n- represents an n-valent anion, x represents a number satisfying 0.18≦x≦0.4, n represents an integer of 1 to 4, and m represents a number satisfying 0≦m≦5.

[0045] The manufacturing method of the present invention can sufficiently exchange ions while suppressing the production of by-products, etc., even if the powdered or paste-like hydrotalcite used as a raw material is a highly versatile hydrotalcite such as that represented by the above formula (1), and therefore can realize a wide range of product designs according to various applications, etc.

[0046] In addition, the powder or paste hydrotalcite is represented by M in the above formula (1). 2+ Mg 2+ and Zn 2+ At least one metal ion selected from the group consisting of M 3+ Al 3+ It is more preferable that the hydrotalcite used as the raw material is such a specific hydrotalcite. When the hydrotalcite is a powder or paste, the above-mentioned effects can be obtained more reliably. In addition, as a more preferable combination of metal species, MgAl, MgAlZn, and ZnAl are listed because of their high versatility in various applications, and among them, MgAl is particularly preferable.

[0047] From another viewpoint, the powdered or pasty hydrotalcite is represented by the formula (1) A n- CO3 2- When the powdered or pasty hydrotalcite used as the raw material is such a specific hydrotalcite, the anions contained between the layers of the hydrotalcite can be gasified (as carbon dioxide gas) after ion exchange and removed as shown in Fig. 1, which makes it easier to prevent the generation of by-products and the like, and more reliably makes it possible to eliminate the need for a cleaning process and the like.

[0048] In the production method of the present invention, the water content (i.e., moisture content) of the powdered or pasty hydrotalcite is not particularly limited as long as the water content after mixing with the acid aqueous solution can be adjusted to a range of 10 to 60 mass%, but an example of an upper limit for the water content contained in the paste-like hydrotalcite is a water content of 60 mass% or less. Note that the water content of the powdered or pasty hydrotalcite means the mass ratio (mass%) of water contained in the powdered or pasty hydrotalcite relative to the total mass (100 mass%) of the powdered or pasty hydrotalcite.

[0049] The water content of the powdered or pasty hydrotalcite is preferably 0% by mass or more, i.e., in the range of 0 to 60% by mass, more preferably in the range of 0 to 50% by mass, and particularly preferably in the range of 0 to 10% by mass. When the water content of the powdered or pasty hydrotalcite is in the range of 0 to 60% by mass, it is difficult for the viscosity to decrease due to the formation of a slurry, and the mixing in the first step can be carried out more smoothly.

[0050] (Aqueous acid solution) In the production method of the present invention, the guest substance acid is used in the form of an acid aqueous solution dissolved in water. The pH of the acid aqueous solution is 6 or less. The type of acid contained in the acid aqueous solution is not particularly limited, and any acid can be used depending on the desired product quality, etc., but it is preferable that the acid is at least one acid selected from the group consisting of inorganic acids, inorganic acid salts, organic acids, and organic acid salts. When the acid contained in the acid aqueous solution serving as the guest substance is such a specific acid, the hydrotalcite can be ion-exchanged sufficiently while suppressing the generation of by-products, etc., more reliably.

[0051] Inorganic acids that can be contained in the acid aqueous solution are not particularly limited, but examples thereof include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, carbonic acid, boric acid, hydroiodic acid, hydrobromic acid, hydrofluoric acid, chloric acid, perchloric acid, phosphonic acid, iodic acid, sulfurous acid, and chlorosulfonic acid. Among these inorganic acids, nitric acid, phosphoric acid, and perchloric acid are preferred. In addition, examples of inorganic acid salts that can be contained in the acid aqueous solution include sodium salts, potassium salts, magnesium salts, zinc salts, calcium salts, and ammonium salts of the above-mentioned inorganic acids.

[0052] The organic acid that can be contained in the acid aqueous solution is not particularly limited, but examples thereof include formic acid, acetic acid, citric acid, oxalic acid, malic acid, succinic acid, butyric acid, propionic acid, gluconic acid, tartaric acid, lactic acid, fumaric acid, anionic surfactants, etc. Among these organic acids, acetic acid, citric acid, oxalic acid, and succinic acid are preferred. In addition, examples of organic acid salts that can be contained in the acid aqueous solution include sodium salts, potassium salts, magnesium salts, zinc salts, calcium salts, and ammonium salts of the above-mentioned organic acids.

[0053] In the production method of the present invention, the water content of the acid aqueous solution is not particularly limited as long as the water content after mixing with the powdered or pasty hydrotalcite can be adjusted to within the range of 10 to 60 mass%, but is preferably within the range of 10 to 70 mass% and more preferably within the range of 20 to 50 mass% relative to the total mass (100 mass%) of the acid aqueous solution. When the water content of the acid aqueous solution is 10 mass% or more, the reactivity can be suppressed to a certain level and the surface reaction with the particles can be prevented from occurring preferentially, so that by-production of salts and aggregation of particles can be more unlikely to occur. In addition, when the water content of the acid aqueous solution is 70 mass% or less, a certain level of reactivity can be ensured, so that the ion exchange reaction can be more reliably carried out.

[0054] (Step of adding aqueous acid solution) In the production method of the present invention, the acid aqueous solution is introduced into a reaction vessel equipped with any stirring means to which a predetermined amount of powdery or pasty hydrotalcite has been supplied. That is, in the production method of the present invention, the first step further includes a step of introducing the acid aqueous solution into the powdery or pasty hydrotalcite while stirring it (hereinafter, this may be simply referred to as a "step of introducing the acid aqueous solution").

[0055] In this acid aqueous solution addition step, the addition rate of the acid aqueous solution is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 0.5 to 710 mass% / min (addition time: 0.06 to 80 minutes) relative to the mass (100 mass%) of the hydrotalcite serving as the host substance, and more preferably 1.0 to 8.5 mass% / min (addition time: 5 to 42 minutes). By adding the acid aqueous solution at a rate within such a specific range in the first step, it is possible to ensure a certain level of productivity while preventing surface reactions with the particles from occurring preferentially, and therefore it is possible to further reduce the occurrence of by-production of salts, aggregation of particles, and the like.

[0056] (Mixing process) In the first step, the powdered or pasty hydrotalcite and the aqueous acid solution in the reaction vessel are mixed for a predetermined time by the stirring means of the reaction vessel. That is, the first step further includes a step of mixing the powdered or pasty hydrotalcite and the aqueous acid solution (hereinafter, sometimes simply referred to as the "mixing step"). Note that, since this mixing step is a step of mixing a predetermined amount of the powdered or pasty hydrotalcite and a predetermined amount of the aqueous acid solution, the stage where the amount of the aqueous acid solution does not reach the predetermined amount (i.e., the above-mentioned step of adding the aqueous acid solution) is not included in the mixing step.

[0057] In this mixing step, the reaction vessel equipped with a stirring means used for mixing the powdered or pasty hydrotalcite and the acid aqueous solution is not particularly limited as long as it can mix the entire mixture by applying a sufficient stress to the mixture, and any mixer known in the art can be used. Examples of such mixers include a batch kneader, a planetary mixer, and a grinding machine.

[0058] Various conditions in the mixing step (e.g., temperature, time, etc.) are not particularly limited as long as the powdered or pasty hydrotalcite and the acid aqueous solution can be sufficiently mixed under the conditions. For example, the mixing temperature (i.e., the reaction temperature of the ion exchange reaction) may be within the range of 20 to 80°C.

[0059] The mixing time (i.e., the reaction time of the ion exchange reaction) can be set, for example, as follows, since the appropriate mixing end point varies depending on the stress of the mixer used. First, 10 g of the mixture is sampled and suspended in 100 mL of ion exchange water. The pH of the resulting suspension is measured, and the time when the pH change becomes pH 0.5 / hour or less is taken as the mixing end point (i.e., the reaction end point). When a general mixer is used, the mixing time is approximately 1 to 300 minutes.

[0060] In the production method of the present invention, the hydrotalcite as the host substance and the acid as the guest substance can be subjected to an ion exchange reaction by such a mixing step in the first step. Then, the reaction product after the ion exchange reaction is provided to the next second step.

[0061] [Second process] In the production method of the present invention, the second step is a step of drying and pulverizing the reaction product obtained in the first step without a washing step.

[0062] Specifically, the second step is carried out in the following manner. That is, the paste-like reaction product obtained in the first step is transported to an arbitrary dryer as it is without going through a washing step, and is dried in the dryer. Next, the dried reaction product is transported to an arbitrary pulverizer, and is pulverized in the pulverizer to obtain ion-exchanged hydrotalcite in a predetermined shape (for example, powder, granules, etc.).

[0063] In the manufacturing method of the present invention, in the above-mentioned first step, powdered or paste-like hydrotalcite is mixed with an acid aqueous solution in the presence of a specific water content of 10 to 60 mass % and reacted, thereby enabling the hydrotalcite to be sufficiently ion-exchanged while suppressing the production of by-products, etc. In particular, sufficient ion-exchange can be performed with an equal amount of guest substance to the desired amount of ion exchange, making it difficult for excess amounts of guest substance or organic solvent residues to be generated. Therefore, in the second step, the paste-like reaction product obtained in the first step can be dried and pulverized as is without going through a washing step.

[0064] (drying process) In the second step, the reaction product obtained in the first step is dried by an arbitrary dryer. That is, the second step further includes a step of drying the reaction product obtained in the first step (hereinafter, sometimes simply referred to as a "drying step").

[0065] The dryer used in this drying step is not particularly limited as long as it can sufficiently dry the reaction product, and any known dryer can be used. Examples of such dryers include flash dryers, band dryers, vacuum dryers, and spray dryers. Note that, as various conditions in the drying step (e.g., temperature, time, etc.), any conditions can be used depending on the type and performance of the dryer used.

[0066] (Crushing process) In the second step, the reaction product after the drying step is pulverized into a predetermined shape by an arbitrary pulverizer. That is, the second step further includes a step of pulverizing the reaction product after the drying step (hereinafter, sometimes simply referred to as a "pulverization step").

[0067] The pulverizer used in this pulverization step is not particularly limited as long as it can pulverize the reaction product after drying into a desired shape (e.g., powder, granules, etc.), and any known pulverizer can be used. Examples of such pulverizers include a hammer mill, a jet mill, and a ball mill. Various conditions (e.g., time, etc.) in the pulverization step can be any conditions depending on the type, performance, etc. of the pulverizer used.

[0068] In the production method of the present invention, ion-exchanged hydrotalcite of a predetermined shape can be obtained through such a pulverization step in the second step.

[0069] The manufacturing method of the present invention may further include any step other than the first and second steps (e.g., a classification step, etc.) within the scope of the object and spirit of the present invention. The manufacturing method of the present invention is not limited to the above-mentioned embodiments or the examples described below, and appropriate combinations, substitutions, modifications, etc. are possible within the scope of the object and spirit of the present invention. EXAMPLES

[0070] 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 these examples. In the following examples, hydrotalcite may be abbreviated as "HT".

[0071] Example 1 Carbonate ion type hydrotalcite (HT) compound Mg 0.667 Al 0.333 (OH)2(CO3) 0.16550 g of 0.5H2O powder was fed to a grinding machine (Ishikawa Factory Co., Ltd., Ishikawa type mixing and crushing machine No. 20), and 53 mL of 4 mol / L nitric acid aqueous solution was added thereto at a rate of 26 mass% / min over about 1 minute while stirring, so as to obtain the compounding ratio shown in Table 1 below. The mixture was then allowed to react for 10 minutes, and a paste-like reaction product was obtained. The resulting paste-like reaction product was evaporated to dryness in a dryer (Yamato Scientific Co., Ltd., Drying Oven DS44), pulverized in a pulverizer (Fuji Paudal Co., Ltd., Sample Mill KIIW-1), and then sieved through a 100-mesh wire screen to obtain a test sample (ion-exchanged hydrotalcite) of Example 1.

[0072] The structure of the test sample of Example 1 obtained in this manner was confirmed by X-ray diffraction using "EMPYRIAN" manufactured by PANalytical, and it was found to be a mixture of nitrate ion type HT compounds and carbonate ion type HT compounds. The amount of ion exchange was calculated from the diffraction intensity ratio a / b, where a is the X-ray diffraction intensity (near 2θ=9.9°) of the nitrate ion type HT compound and b is the X-ray diffraction intensity (near 2θ=11.6°) of the carbonate ion type HT compound. The analysis results of the test sample of Example 1 are shown in Table 1 below.

[0073] Comparative Example 1 Carbonate ion type HT compound Mg 0.667 Al 0.333 (OH)2(CO3) 0.16550 g of .0.5H2O powder was placed in a 1 L beaker, and ion-exchanged water was added to prepare a 6 mass% aqueous slurry. This aqueous slurry was heated to 80°C and stirred. Then, 53 mL of 4 mol / L nitric acid aqueous solution was added to this aqueous slurry at a rate of 26 mass% / min over about 1 minute so as to obtain the compounding ratio shown in Table 1 below. The mixture was then continued for 60 minutes to react, and a slurry-like reaction product was obtained. The obtained slurry-like reaction product was dehydrated using a suction filter, washed with ion-exchanged water in an amount 20 times the solid content, and dehydrated. The obtained dehydrated product was evaporated to dryness using a dryer (Drying Oven DS44, manufactured by Yamato Scientific Co., Ltd.), pulverized using a pulverizer (Sample Mill KIIW-1, manufactured by Fuji Paudal Co., Ltd.), and then sieved through a 100-mesh wire screen to obtain a test sample of Comparative Example 1. The amount of ion exchange was determined in the same manner as in Example 1. The analytical results of the test sample of Comparative Example 1 are shown in Table 1 below.

[0074] [Table 1]

[0075] Example 2 Carbonate ion type HT compound Mg 0.667 Al 0.333 (OH)2(CO3) 0.165 50g of 0.5H2O powder was fed to a grinding machine (Ishikawa Factory Co., Ltd., Ishikawa type mixing and crushing machine No. 20), and 15mL of 4mol / L phosphoric acid aqueous solution was added to the grinding machine at a rate of 47.7 mass% / min over about 1 minute while stirring, so that the mixing ratio was as shown in Table 2 below. The mixture was then allowed to react for 10 minutes, and a paste-like reaction product was obtained. The resulting paste-like reaction product was evaporated to dryness in a dryer (Yamato Scientific Co., Ltd., Drying Oven DS44), pulverized in a grinder (Fuji Paudal Co., Ltd., Sample Mill KIIW-1), and then sieved through a 100-mesh wire screen to obtain a test sample for Example 2.

[0076] The structure of the test sample of Example 2 thus obtained was confirmed by X-ray diffraction using "EMPYRIAN" manufactured by PANalytical, and it was found to be a mixture of phosphate ion type HT compound and carbonate ion type HT compound. The amount of ion exchange was calculated from the diffraction intensity ratio c / b, where c is the X-ray diffraction intensity (at about 2θ=10.6°) of the phosphate ion type HT compound and b is the X-ray diffraction intensity (at about 2θ=11.6°) of the carbonate ion type HT compound. The analysis results of the test sample of Example 2 are shown in Table 2 below.

[0077] Comparative Example 2 Carbonate ion type HT compound Mg 0.667 Al 0.333 (OH)2(CO3) 0.165 50 g of .0.5H2O powder was placed in a 1 L beaker, and ion-exchanged water was added to prepare a 6 mass% aqueous slurry. The aqueous slurry was heated to 80°C and stirred. 15 mL of a 4 mol / L aqueous phosphoric acid solution was added to the aqueous slurry at a rate of 47.7 mass% / min over about 1 minute so that the mixing ratio was as shown in Table 2 below. The mixture was then allowed to react for 60 minutes to obtain a slurry-like reaction product. The obtained slurry-like reaction product was dehydrated using a suction filter, washed with ion-exchanged water in an amount 20 times the solid content, and dehydrated. The obtained dehydrated product was evaporated to dryness using a dryer (Drying Oven DS44, manufactured by Yamato Scientific Co., Ltd.), pulverized using a pulverizer (Sample Mill KIIW-1, manufactured by Fuji Paudal Co., Ltd.), and then sieved through a 100-mesh wire screen to obtain a test sample for Comparative Example 2. The amount of ion exchange was determined in the same manner as in Example 2. The analytical results of the test sample of Comparative Example 2 are shown in Table 2 below.

[0078] [Table 2]

[0079] Example 3 Carbonate ion type HT compound Mg 0.667 Al 0.333 (OH)2(CO3) 0.1651100g of 0.5H2O powder was fed to a batch kneader (PELLETER EXDF-60, manufactured by Fuji Paudal Co., Ltd.), and 840mL of 5.3mol / L aqueous perchloric acid solution was added thereto at a rate of 19.8 mass% / min over about 5 minutes while stirring, so as to obtain the compounding ratio shown in Table 3 below. The mixture was then allowed to react for 30 minutes, and a paste-like reaction product was obtained. The resulting paste-like reaction product was evaporated to dryness in a dryer (Drying Oven DS44, manufactured by Yamato Scientific Co., Ltd.), pulverized in a pulverizer (Sample Mill KIIW-1, manufactured by Fuji Paudal Co., Ltd.), and then sieved through a 100-mesh wire screen to obtain a test sample for Example 3.

[0080] The structure of the test sample of Example 3 thus obtained was confirmed by X-ray diffraction using "EMPYRIAN" manufactured by PANalytical, and it was found to be a mixture of perchlorate ion type HT compounds and carbonate ion type HT compounds. The amount of ion exchange was calculated from the diffraction intensity ratio d / b, where d is the X-ray diffraction intensity (at about 2θ=19.5°) of the perchlorate ion type HT compound and b is the X-ray diffraction intensity (at about 2θ=11.6°) of the carbonate ion type HT compound. The analysis results of the test sample of Example 3 are shown in Table 3 below.

[0081] Furthermore, the particle size of the test sample of Example 3 was measured as follows. First, 70 mL of 0.2 mass% sodium hexametaphosphate aqueous solution was placed in a 100 mL glass beaker, 0.7 g of the dried test sample powder was placed in it, and ultrasonic treatment was performed for 3 minutes. The volume-based cumulative 50% particle size (d50) and the volume frequency of particle sizes of 5 μm or more (>5 μm) were measured for this aqueous solution using a laser diffraction scattering type particle size distribution device (MT3000, manufactured by Nikkiso Co., Ltd.). The particle size measurement results are shown in Table 3 below.

[0082] Example 4 A test sample of Example 4 was obtained in the same manner as in Example 3, except that 840 mL of a 5.3 mol / L aqueous perchloric acid solution was added at a rate of 9.9 mass% / min over about 10 minutes to obtain the compounding ratio shown in Table 3 below. The ion exchange amount and particle size were measured in the same manner as in Example 3. The results are shown in Table 3 below.

[0083] Example 5 A test sample of Example 5 was obtained in the same manner as in Example 3, except that 840 mL of a 5.3 mol / L aqueous perchloric acid solution was added at a rate of 5.0 mass% / min over about 20 minutes to obtain the compounding ratio shown in Table 3 below. The ion exchange amount and particle size were measured in the same manner as in Example 3. The results are shown in Table 3 below.

[0084] Example 6 Carbonate ion type HT compound Mg with a water content of 48.2 mass% 0.667 Al 0.333 (OH)2(CO3) 0.165 2283 g of 0.5H2O paste was placed in a batch kneader (PELLETER EXDF-60, manufactured by Fuji Paudal Co., Ltd.), and 840 mL of 5.3 mol / L aqueous perchloric acid solution was added at a rate of 19.8 mass% / min over about 5 minutes while stirring, so that the blending ratio was as shown in Table 3 below. The mixture was then allowed to react for 60 minutes to obtain a paste-like reaction product. The obtained paste-like reaction product was evaporated to dryness in a dryer (Drying Oven DS44, manufactured by Yamato Scientific Co., Ltd.), pulverized in a pulverizer (Sample Mill KIIW-1, manufactured by Fuji Paudal Co., Ltd.), and then sieved through a 100-mesh wire mesh to obtain a test sample of Example 6. The ion exchange amount and particle size were measured in the same manner as in Example 3. The results are shown in Table 3 below.

[0085] Comparative Example 3 Carbonate ion type HT compound Mg 0.667 Al 0.333 (OH)2(CO3) 0.16550 g of .0.5H2O powder was placed in a 1 L beaker, and ion-exchanged water was added to prepare a 10 mass% aqueous slurry. The aqueous slurry was heated to 40°C and stirred. 38 mL of a 5.3 mol / L aqueous solution of perchloric acid was added to the aqueous slurry at a rate of 2.5 mass% / min over about 40 minutes so that the mixing ratio was as shown in Table 3 below. The mixture was then allowed to react for 60 minutes to obtain a slurry-like reaction product. The obtained slurry-like reaction product was dehydrated using a suction filter, washed with ion-exchanged water in an amount 20 times the solid content, and dehydrated. The obtained dehydrated product was evaporated to dryness using a dryer (Drying Oven DS44, manufactured by Yamato Scientific Co., Ltd.), pulverized using a pulverizer (Sample Mill KIIW-1, manufactured by Fuji Paudal Co., Ltd.), and then sieved through a 100-mesh wire screen to obtain a test sample for Comparative Example 3. The ion-exchange amount and particle size were measured in the same manner as in Example 3. The results are shown in Table 3 below.

[0086] [Table 3]

[0087] Example 7 Carbonate ion type HT compound Mg 0.502 Zinc 0.165 Al 0.333 (OH)2(CO3) 0.165 50g of 0.5H2O powder was fed to a grinding machine (Ishikawa Factory Co., Ltd., Ishikawa type mixing and crushing machine No. 20), and 53mL of 4mol / L nitric acid aqueous solution was added to it at a rate of 26 mass% / min over about 1 minute while stirring, so that the composition ratio shown in Table 4 below was obtained. The mixture was then allowed to react for 10 minutes, and a paste-like reaction product was obtained. The resulting paste-like reaction product was evaporated to dryness in a dryer (Yamato Scientific Co., Ltd., Drying Oven DS44), pulverized in a grinder (Fuji Paudal Co., Ltd., Sample Mill KIIW-1), and then sieved through a 100-mesh wire screen to obtain a test sample for Example 7.

[0088] The structure of the thus obtained test sample of Example 7 was confirmed by X-ray diffraction in the same manner as in Example 1, and it was found to be a nitrate ion type HT compound. The ion exchange amount was determined in the same manner as in Example 1. The analysis results of the test sample of Example 7 are shown in Table 4 below.

[0089] Comparative Example 4 Carbonate ion type HT compound Mg 0.502 Zinc 0.165 Al 0.333 (OH)2(CO3) 0.165 50 g of .0.5H2O powder was placed in a 1 L beaker, and ion-exchanged water was added to prepare a 6 mass% aqueous slurry. This aqueous slurry was heated to 80°C and stirred. Then, 53 mL of 4 mol / L nitric acid aqueous solution was added to this aqueous slurry at a rate of 26 mass% / min over about 1 minute so as to obtain the compounding ratio shown in Table 4 below. The mixture was then continued for 60 minutes to react, and a slurry-like reaction product was obtained. The obtained slurry-like reaction product was dehydrated using a suction filter, washed with ion-exchanged water in an amount 20 times the solid content, and dehydrated. The obtained dehydrated product was evaporated to dryness using a dryer (Drying Oven DS44, manufactured by Yamato Scientific Co., Ltd.), pulverized using a pulverizer (Sample Mill KIIW-1, manufactured by Fuji Paudal Co., Ltd.), and then sieved through a 100-mesh wire screen to obtain a test sample of Comparative Example 4. The amount of ion exchange was determined in the same manner as in Example 1. The analytical results of the test sample of Comparative Example 4 are shown in Table 4 below.

[0090] Example 8 Carbonate ion type HT compound Zn 0.667 Al 0.333 (OH)2(CO3) 0.16550g of 0.5H2O powder was fed to a grinding machine (Ishikawa Factory Co., Ltd., Ishikawa type mixing and crushing machine No. 20), and 53mL of 4mol / L nitric acid aqueous solution was added to it at a rate of 26 mass% / min over about 1 minute while stirring, so that the composition ratio shown in Table 4 below was obtained. The mixture was then allowed to react for 10 minutes, and a paste-like reaction product was obtained. The resulting paste-like reaction product was evaporated to dryness in a dryer (Yamato Scientific Co., Ltd., Drying Oven DS44), pulverized in a grinder (Fuji Paudal Co., Ltd., Sample Mill KIIW-1), and then sieved through a 100-mesh wire screen to obtain a test sample for Example 8.

[0091] The structure of the thus obtained test sample of Example 8 was confirmed by X-ray diffraction in the same manner as in Example 1, and it was found to be a nitrate ion type HT compound. The ion exchange amount was determined in the same manner as in Example 1. The analysis results of the test sample of Example 8 are shown in Table 4 below.

[0092] [Table 4]

[0093] As shown in Tables 1 to 4, the comparison results of Examples 1 to 8 and Comparative Examples 1 to 4 show that by mixing and reacting powdered or pasty hydrotalcite with an acid aqueous solution so that the water content after mixing is within the range of 10 to 60 mass%, it is possible to sufficiently ion-exchange the hydrotalcite while suppressing the generation of by-products, etc., without requiring complicated steps such as a calcination step, a filtration step, or a post-reaction washing step, or large-scale equipment. Also, it was found that in Examples 1 to 8, sufficient ion-exchange was possible with an equal amount of guest substance to the desired ion-exchange amount. [Industrial Applicability]

[0094] The ion-exchanged hydrotalcite obtained by the production method of the present invention can be used in a wide range of applications of hydrotalcite, such as resin additives (e.g., heat stabilizers, color inhibitors, flame retardants, etc.), adsorbents, and pharmaceuticals (e.g., DDS, etc.). [Explanation of symbols]

[0095] 1. Hydrotalcite 2. Acid 3. Ion-exchanged hydrotalcite

Claims

1. A method for producing ion-exchanged hydrotalcite, comprising the steps of: A first step of mixing and reacting a powdered or pasty hydrotalcite with an acid aqueous solution so that the water content after mixing is within a range of 10 to 60 mass %; A second step of drying and pulverizing the reaction product obtained in the first step without a washing step; Including, The water content of the powdered or pasty hydrotalcite is within the range of 0 to 60 mass %, The above-mentioned production method, characterized in that the powdery or pasty hydrotalcite is a hydrotalcite represented by the following formula (1): M 2+ 1-x M 3+ x (OH) 2 A n- x / n ・mH 2 O (1) (In the formula, M 2+ represents a divalent metal ion, M 3+ represents a trivalent metal ion, A n- represents CO 3 2- , x represents a number satisfying 0.18≦x≦0.4, n represents an integer from 1 to 4, and m represents a number satisfying 0≦m≦5.)

2. M in the formula (1) ２＋ Mg ２＋ and Zn ２＋ At least one metal ion selected from the group consisting of M ３＋ Al ３＋ The method according to claim 1 ,

3. 2. The method according to claim 1, wherein the acid contained in the aqueous acid solution is at least one acid selected from the group consisting of inorganic acids, inorganic acid salts, organic acids and organic acid salts.

4. The method according to claim 1, wherein the water content of the aqueous acid solution is within a range of 10 to 70% by mass.

5. 2. The method according to claim 1, wherein the first step further includes a step of adding the acid aqueous solution to the powdery or pasty hydrotalcite, and the rate of addition of the acid aqueous solution is 0.5 to 710 mass% / min with respect to the mass of the hydrotalcite.

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