JP3461638B2 - Artificial granular material and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an artificial granule obtained from polyaspartic acid, which has an internal phase and an external phase, and can contain a useful substance in the internal phase, and a method for producing the same. The present invention includes, for example, granular foods (artificial fish eggs, spherical foods, etc.), granular medicines (capsule oral medicines, emulsion intravenous medicines, clinical test agents, etc.), industrial granules (encapsulated catalysts, etc.), feeds. The present invention relates to an artificial granule having a thin and tough outer phase suitable for (animal feed, etc.) and excellent in water retention and texture (outer phase strength) controllability.

[0002]

[Prior art]

[Artificial Granules] Many methods have conventionally been proposed for obtaining artificial granules. For example, at least the following problems are often found in the artificial particles according to the related art. (1) When the artificial granules are left to stand, water is separated from the granules, and the shape and the appearance of the granules are significantly changed with the change of the particle shape, resulting in a decrease in commercial value. (2) The outer phase film of the artificial particles is required to be thin and tough, but in the conventional method, when the film thickness is thin, the practical strength is reduced, and when the strength is increased, the film thickness is also increased.
Particularly in the case of foods, it has a contradictory physical property that the texture is inferior, so that it is difficult to obtain a thin and tough outer phase film.

[Polyaspartic acid] polyamino acid is
It is a polymer consisting of amino acids widely existing in nature,
It has biodegradability and is expected to have high safety and high biocompatibility for living organisms. Among the polyamino acids, polyaspartic acid, in particular, can be easily produced by heating aspartic acid, and therefore is expected to be widely applied to medical applications such as detergent builders and the like, cosmetics and the like. Many techniques are known for the efficient production method of polyaspartic acid. Polyaspartic acid is usually obtained by alkaline hydrolysis of polysuccinimide (PSI). If this manufacturing method is adopted,
The product is usually obtained in the form of an alkali metal salt such as sodium polyaspartate.

[Polysuccinimide (PSI)] PSI
Is a polymer represented by the following formula (1) (formula 1).

[0005]

[Chemical 1] Many techniques are known for the efficient manufacturing method of PSI. For example, Journal of American
Chemical Society (J. Amer. Chem. S
oc. 80, p. 3361 (1958), aspartic acid was heated and condensed at 200 ° C. for 2 to 3 hours to give PS.
A method of obtaining I is disclosed. US Patent No. 5,05
No. 7,597 discloses a method of heat-condensing aspartic acid in a fluidized bed to obtain PSI. Hereinafter, in the present specification, a method of thermally condensing such aspartic acid to obtain PSI is referred to as "heat condensation method".
Say. Japanese Patent Publication No. 48-20638 discloses a method of obtaining a high molecular weight PSI by carrying out a reaction in a thin film form using a rotary evaporator with 85% phosphoric acid as a catalyst. Hereinafter, in the present specification, a method for obtaining PSI using such a catalyst or solvent is referred to as a "catalytic method". Although various applications of polyaspartic acid and its alkali metal salts have been studied as described above,
Probably because it is water-soluble in nature, almost no studies have been made so far on capsule-shaped artificial particles mainly composed of polyaspartic acid. Examples of conventional techniques for encapsulating water-soluble polyaspartic acid include a method of chemically crosslinking. In such a case, the process is complicated, the cost is increased, and the original biodegradability of aspartic acid is impaired, which is not preferable.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides an artificial granular material containing polyaspartic acid as a main component, which is a polymer having biodegradability and expected to be highly safe for the living body and the natural world, and a method for producing the same. To do.

[0007]

DISCLOSURE OF THE INVENTION The present invention is an granular material having an internal phase and an external phase, wherein the external phase of the granular material contains a polyvalent metal salt of polyaspartic acid. . The present invention, by contacting a droplet of an aqueous solution of an alkali metal salt of polyaspartic acid with a solution of a polyvalent metal salt, to form an outer phase containing the polyvalent metal salt of polyaspartic acid at the contact interface between them. Characteristic,
This is a method for producing an artificial granular material having an inner phase and an outer phase. In the method for producing an artificial granular material according to the present invention, the concentration of the alkali metal aspartic acid salt in the aqueous solution containing the alkali metal polyaspartic acid salt may be 10% by weight or more. In the method for producing artificial granules according to the present invention, the concentration of the polyvalent metal salt solution may be 10% by weight or more. In the method for producing an artificial granular material according to the present invention, the weight average molecular weight of the polyaspartic acid alkali metal salt may be 10,000 or more. In the method for producing an artificial granular material according to the present invention, the polyaspartic acid alkali metal salt may be polyaspartic acid sodium salt. In the method for producing an artificial granular material according to the present invention, the polyvalent metal salt solution may be an aqueous calcium chloride solution.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies to solve the above problems, the present inventors have found that an aqueous solution containing an alkali metal salt of polyaspartic acid in a specific concentration or more is a polyvalent metal salt solution in a specific concentration or more. It was found that a self-supporting film is formed at the contact interface by the contact with the above, and an artificial particle having an outer phase containing a polyaspartic acid polyvalent metal salt is formed, and the present invention has been completed. That is, the present invention is an artificial granular material having a particle phase having an inner phase and an outer phase, wherein the outer phase of the particle material contains a polyvalent metal salt of polyaspartic acid, and a method for producing the same.

[Concept of the word "polyvalent metal salt"] The concept of the word "polyvalent metal salt" used in the claims and the detailed description of the present application is an organic compound of a divalent or higher polyvalent metal. Alternatively, it includes an inorganic salt. Specific examples of polyvalent metals include
For example, as the divalent metal, calcium, zinc, copper,
Aluminum, trivalent metals such as iron and barium,
Examples of tetravalent metals such as iron include silicon. In the present invention, among polyvalent metals, divalent and trivalent metals are preferably used, and divalent metals are more preferably used. Specific examples of the metal salt include calcium chloride, calcium sulfate, calcium citrate, calcium phosphate, calcium lactate, zinc chloride, copper sulfate, iron chloride, aluminum chloride, aluminum sulfate and the like. Usually, calcium chloride is preferably used.

[Concept of "Metal Salt Solution"] The term "metal salt solution" used in the claims of the present application and the detailed description of the invention refers to a solvent capable of dissolving a metal salt at a certain concentration or more. Includes dissolved solutions. The metal salt solution is usually an aqueous solution of the above metal salt, but is not necessarily limited to the aqueous solution.

[Concept of "Artificial Granule"] The concept of the term "artificial granule" used in the claims of the present application and the detailed description of the invention has an internal phase and an external phase, and an external phase. It is a granular substance containing at least polyvalent metal salt of polyaspartic acid, and the internal phase contains liquid and / or solid.

[Concept of the word "granular material"] "Granular material" used in the claims of the present application and the detailed description of the invention.
The term "comprising" includes "particles", "capsules", and the like, which these terms generally have in polymer chemistry. Regarding the external or scanning electron microscopic (morphology) aspects of the "particulates" used in the claims and detailed description of the invention, for example,
Spherical, raspberry-like or rice-rice sugar (Konpeito, Portuguese confeito) -like form with many protrusions, erythroid-like flat form, rugby ball-like or egg-like spheroid-like form, Escherichia coli-like spindle form Such modes are also included. Regarding the cross-sectional morphology or the internal structure aspect of the "granular material" used in the claims of the present application and the detailed description of the invention, for example, a spherical shell, one void (cavity) inside Embodiments of hollow particles, embodiments of hollow particles having two or more voids (cavities) inside, embodiments of further containing non-hollow particles in hollow particles such as bells, Russian folk art Such as Matryoshka, which has one or more hollow particles inside, and one or more hollow particles having one or more voids inside, which connect the inside and the outside. It also includes a mode having a passage (channel, through hole), and the like. The internal voids (voids, cavities) of the artificial granules according to the present invention may contain contents such as useful substances, but the state of the contents is not particularly limited, and a gas phase, a liquid phase, It may be in the form of solid phase, gel or sol. As used in the claims of this application and in the detailed description of the invention, the concept of "particulate matter" includes, for example, microcapsules, microballoons,
It also includes polymer emulsions, latexes, polymer suspensions, polymer colloids, and microspheres that make up coacervates. Thus, the term "particulates" as used in the claims of the present application and in the detailed description of the invention may not necessarily be equivalent to the concepts that these terms typically have in polymer chemistry. However, it should be used for convenience in frequently referring to the essential “aspect” according to the present invention.

[Particle Diameter] The average diameter (particle diameter) of the artificial granules according to the present invention is that the artificial granules according to the present invention, which is a dispersed phase, are substantially uniformly and continuously in a continuous phase such as an aqueous solution. There is no particular limitation as long as it is stable and uniform, and substantially sufficient storage stability and workability are ensured. The particle size of the polymer particles used in the present invention is generally 0.1 to 10 μm.
Is preferred. By setting the particle size to submicron (1 μm or less), it is possible to employ a self-emulsification method in which the particles do not settle in the medium due to the Micro Brownian motion of the particles.

[Preparation Method of Artificial Granules] The preparation method of the artificial granules according to the present invention comprises the desired characteristics of the granules (layer structure, phase structure, solid structure, hollow structure, morphology, particle size, particle size distribution, There is no particular limitation as long as it is a means that can substantially realize (single-modality / multi-modality, etc.).

[Structure of Artificial Granules] The structure of the artificial granules according to the present invention is similar to that disclosed in JP-A-6-246148. That is, the artificial granular material according to the present invention comprises an outer phase and an inner phase adjacent to the outer phase and surrounded by the outer phase. Specific examples of the aspect of the structure of the artificial granular material according to the present invention include (a) to (c) of FIG. FIG. 1 (A) is an artificial granular material in which A is an internal phase and B is an external phase, and each of the internal phase and the external phase is one phase. First
In the figure (b), A is an internal phase, B is an external phase, and O is an oily substance.
It is an artificial granulate containing an oily phase. Figure 1 (c)
Is an artificial granular material in which A is an internal phase, B1B2 is an external phase, the internal phase is one phase, and the external phase is two phases. As described above, the artificial granular material according to the present invention is a granular material having a multi-layer structure or a multi-phase structure having at least one or more inner phase and outer phase.

[Aspect of Method for Producing Artificial Granule] The method for producing an artificial granule according to the present invention is not particularly limited. A method for producing an artificial granular material according to the present invention is disclosed in JP-A-6-2461.
With reference to the technology disclosed in No. 48, the following (1)-
You may employ the aspect like (5). (1) The sol solution as the internal phase is made into droplets by using a nozzle, and depending on the properties of the sol solution, primary particles are prepared by gelling at a low temperature or by gelling with a chemical gelling agent. A method for obtaining artificial particles by further coating the primary particles with an aqueous solution containing at least an alkali metal salt of polyaspartic acid to form an outer phase and treating the particles with a polyvalent metal solution. (2) To the sol solution for the internal phase, at least a polyvalent metal is added to such an extent that the sol solution does not substantially lose fluidity to form droplets, and this is a solution of at least an alkali metal salt of polyaspartic acid. To form particles having an internal phase and an external phase, and treating with at least a polyvalent metal salt solution to obtain artificial particles. (3) In particular, in order to produce artificial granules similar to salmon roe, a substance that is incompatible with the internal phase (usually an oily substance) and a sol solution for the internal phase are used, and the oily substance is used as the internal phase. A method of producing droplets encapsulated with a sol solution for use and obtaining artificial granules having a so-called triple structure, similar to salmon roe, by the same operation as the above (1). (4) Furthermore, in order to obtain an artificial fish egg having a triple structure similar to salmon roe, for example, an external phase containing an oily substance, a sol substance for the internal phase, and at least an aqueous solution of an alkali metal salt of polyaspartic acid from a triple tubular nozzle. A method of releasing artificial sol substances into the air or an oily substance to form liquid droplets, and causing at least a polyvalent metal salt solution to act on the liquid droplets to obtain artificial particles similar to salmon roe. (5) A method of obtaining artificial granules by subjecting the granules of (1) to (4) above to a post-treatment step such as a seasoning step and a drying step and further treating with a polyvalent metal salt solution.

[Polyaspartic acid alkali metal salt] The polyaspartic acid alkali metal salt used as a raw material in the production method of the present invention is represented by the following formula (2) (formula 2) and / or
Alternatively, it is a polymer having a repeating structural unit represented by (3) (Chemical Formula 3).

[0018]

[Chemical 2]

[0019]

[Chemical 3] (In the formula, M is a metal selected from the group consisting of one or more alkali metals.) The ratio of formula (2) to formula (3) in the polyaspartic acid alkali metal salt is not particularly limited. Further, the polyaspartic acid alkali metal salt may be a copolymer having a part of repeating structural units other than those represented by the other formulas (2) and (3), but at least the formula (2) ) Or (3) repeating structural unit is 90 mol% or more. The preferred alkali metal is sodium. Also,
In the formula (2) or (3), M is not necessarily 100
% Does not have to be an alkali metal, and other metal species (such as alkaline earth metal) may be mixed to the extent that water solubility of polyaspartic acid is not significantly impaired. Usually, if the weight average molecular weight of the polyaspartic acid alkali metal salt used is too low, it will be difficult to obtain good artificial granules regardless of the concentration of the metal salt solution. The weight average molecular weight of the alkali metal polyaspartic acid is preferably 1
It is more than 10,000, and more preferably more than 20,000. Generally, the higher the weight average molecular weight, the more preferable the strength of the outer phase of the artificial granular material is. Generally, 2,000,000 or less is suitable in consideration of difficulty in improving the weight average molecular weight and economy.

[Method for producing alkali metal polyaspartate] The method for producing the alkali metal polyaspartate used in the production method of the present invention is not particularly limited.
Preferred is a method by hydrolysis of PSI.
It is preferably obtained by hydrolyzing PSI prepared by the catalytic method with an aqueous solution of an alkali metal hydroxide. PSI obtained by the heat condensation method generally has a low weight average molecular weight, and it is difficult to obtain a high molecular weight (weight average molecular weight of 10,000 or more) polyaspartic acid alkali metal salt used in the method of the present invention. Compared with an alkali metal polyaspartic acid salt of similar weight average molecular weight obtained from PSI prepared by the catalytic method, the formation of an outer phase containing polyaspartic acid polyvalent metal salt is less likely to occur, and the strength of the formed outer phase is also higher. This is because it is often low.

In the method for producing an artificial granular material having an inner phase and an outer phase according to the present invention, a polyvalent metal salt solution is brought into contact with a droplet of an aqueous solution of an alkali metal salt of polyaspartic acid to form a contact interface between the two. It is characterized in that an outer phase containing a polyaspartic acid polyvalent metal salt is formed.

[Aqueous solution containing polyaspartic acid alkali metal salt] The concentration of the polyaspartic acid alkali metal salt in the aqueous solution containing the polyaspartic acid alkali metal salt is preferably a specific concentration or more. Although it varies depending on the weight average molecular weight of the polyaspartic acid alkali metal salt and the concentration of the polyvalent metal salt solution, the concentration of the polyaspartic acid alkali metal salt aqueous solution is preferably about 10% by weight or more. It is more preferably at least 20%, further preferably at least 30%.

[Additives] If desired, additives such as a plasticizer and a reinforcing agent may be added to the aqueous solution containing the alkali metal salt of polyaspartic acid. The reinforcing agent is an additive having a function of reinforcing at least the strength of the outer phase generated by contact with the polyvalent metal salt solution. The reinforcing agent is not particularly limited as long as it can exert the function of reinforcing the strength of the outer phase, and a specific example thereof is a polysaccharide having a carboxyl group. Specific examples of the polysaccharide having a carboxyl group, for example, pectin, sodium alginate, gum arabic, tragacanth gum, xanthan gum,
Examples thereof include karaya gum, gatei gum, okra, sodium starch glycolate, sodium fibrin glycolate and the like. The reinforcing agent can be used alone or as a mixture of several kinds. The reinforcing agent can be used in the sol substance for the outer phase, and depending on the purpose, substances other than the above-mentioned polysaccharide having a carboxyl group can be appropriately combined. The concentration of the reinforcing agent is not particularly limited, but preferably about 0.01-
It is used as an aqueous solution of about 50% by weight, more preferably about 0.1 to about 30% by weight.

[Polyvalent Metal Salt Solution] The polyvalent metal salt solution used in the production method of the present invention preferably has a specific concentration or higher. The polyvalent metal salt solution preferably has a concentration of about 10% or more, although it varies depending on the weight average molecular weight of the polyaspartic acid alkali metal salt used and the concentration of the aqueous solution containing the polyaspartic acid alkali metal salt.
It is more preferably at least 20%, further preferably at least 30%.

[Contact] The contact time between the aqueous solution containing the alkali metal salt of polyaspartic acid and the polyvalent metal salt solution must be at least 30 seconds or more. When the contact time becomes long, the thickness and strength of the outer phase containing the polyaspartic acid polyvalent metal salt produced tends to increase. The contact time is appropriately determined depending on the desired thickness and strength of the outer phase.

[Embodiment of Method for Producing Artificial Granule] An example of a preferred embodiment of the method for producing an artificial granule according to the present invention will be shown. If necessary, a substance to be included is added to an aqueous solution containing an alkali metal salt of polyaspartic acid at a concentration of 10% by weight or more, and the solution is appropriately placed in a metal salt solution at a concentration of 10% by weight or more. The polyaspartic acid polyvalent metal salt phase is quickly formed on the surface (interface with the metal salt solution) of the droplets of the aqueous solution of the alkali metal polyaspartic acid in the metal salt solution to form a capsule. After leaving the droplets in the metal salt solution for a predetermined time, the produced capsules are isolated from the metal salt solution by filtration or the like.

Another example of a preferred embodiment of the method for producing an artificial granular material according to the present invention will be given. The solid polyaspartic acid alkali metal salt aqueous solution is attached to the periphery or the surface of the solid by immersing the solid in an aqueous solution containing the polyaspartic acid alkali metal salt, and the solid is added to the polyvalent metal salt solution. As a result, a granular substance containing the polyaspartic acid polyvalent metal salt in the outer phase and encapsulating the solid substance in the inner phase is obtained.

[Uses and Applications of Artificial Granules] The artificial granules according to the present invention are capsules having an outer phase and an inner phase,
By incorporating a useful substance in the internal phase, various uses and
Application can be expected. For example, by encapsulating a useful substance in a solid phase or a liquid phase as an inclusion, a drug (sustained release drug, etc.), feed (livestock / fish / live feed), food (artificial roe, spherical food) , Industrial granules (encapsulation catalysts, etc.), cell engineering (encapsulation of animal and plant cells / microorganism cells, artificial seedlings encapsulating plant cells / callus, cell fusion, etc.), recording materials (dye and pigment capsules, etc.) , Adhesives (encapsulation of adhesives, etc.), pesticides (encapsulation of pesticides and fertilizers), cosmetics (microencapsulation / encapsulation of perfumes and cosmetics), and the like. In addition, examples of the use of the granular material in which the solid matter is included in the inner phase include seed coating of vegetables and fruits.

[0029]

EXAMPLES The present invention will be described in detail below with reference to examples. The physical properties shown in the examples were measured as follows.

[Weight Average Molecular Weight] The weight average molecular weight (hereinafter referred to as Mw) of the polymer was measured by gel permeation chromatography (hereinafter referred to as GPC) under the following conditions. Solvent: 0.01 M KCl / water / methanol = 8: 2 mixed solvent Standard substance: polyethylene oxide Device: JASCO 880-PU Detector: JASCO 830-RI Column: Shodex OHpak B-804 Concentration: 0.5 wt% Injection volume: 20 μl Flow rate: 1.0 ml / min

Preparation Example 1 <Method for Obtaining Sodium Polyaspartic Acid Salt from PSI by Catalytic Method> 300 g of L-aspartic acid and 128 g of polyphosphoric acid were placed in a 2 L separable flask and heated to 200 ° C. under reduced pressure. The reaction was carried out for 2 hours with dehydration. After completion of the reaction, the product was dissolved in 2 L of dimethylformamide and purified by reprecipitation in about 5 volumes of water. The PSI obtained by recovering and drying was a white powder. Yield 95%. The PSI thus obtained was suspended in water, and an aqueous solution of sodium hydroxide was added dropwise to hydrolyze the PSI. The reaction solution was poured into methanol and reprecipitated to obtain sodium salt of polyaspartic acid. It was By changing the weight average molecular weight of the PSI used and the hydrolysis conditions (temperature, time, concentration, etc.), several types of sodium polyaspartic acid salts having different weight average molecular weights were obtained.

[Preparation Example 2] <Method for obtaining polyaspartic acid sodium salt from PSI by heat condensation method> 200 g of L-aspartic acid was placed in a container and reacted in a 250 ° C. oven under a nitrogen stream for 6 hours to give a brown color. A powdered PSI was obtained. Hydrolysis was performed with an aqueous sodium hydroxide solution in the same manner as in Preparation Example 1 to obtain polyaspartic acid sodium salt. Weight average molecular weight is 97
It was 00.

[Examples 1 to 13] As shown in Table 1 (Table 1), polyaspartic acid sodium salt having various weight average molecular weights obtained in Preparation Example 1 was made into an aqueous solution at various concentrations to prepare various solutions. Was added dropwise to the polyvalent metal salt aqueous solution having the concentration of.
In any of Examples 1 to 13, the sodium polyaspartate aqueous solution droplets form a polyvalent metal salt phase of polyaspartic acid at the interface with the polyvalent metal salt solution, and the polyaspartic acid sodium salt aqueous solution is formed. It became a spherical capsule containing. The contact time between the droplet of the sodium polyaspartate aqueous solution and the metal salt solution was 10 minutes or more.

[Comparative Example 1] A polyaspartic acid sodium salt aqueous solution was dropped in the same manner as in Example 1 except that the concentration of the calcium chloride aqueous solution was changed to 5% by weight, but no formation of capsules was observed.

[Comparative Example 2] The same procedure as in Example 1 was carried out except that the concentration of the sodium polyaspartate aqueous solution was changed to 5% by weight, but no capsule formation was observed.

Comparative Example 3 The procedure of Example 13 was repeated except that the polyaspartic acid sodium salt having a weight average molecular weight of 5600 obtained in Preparation Example 1 was used. I was not able to admit.

Comparative Example 4 The procedure of Example 13 was repeated, except that the sodium polyaspartic acid salt obtained in Preparation Example 2 (weight average molecular weight 9700) was used, but capsules were formed. Was not recognized. Except for Comparative Example 4, the catalytic PSI obtained in Preparation Example 1 was used.
Was used, and in Comparative Example 4, the polyaspartic acid sodium salt from the heat condensation method PSI obtained in Preparation Example 2 was used.

[Evaluation of artificial particle (capsule) formation (Table-
1)] Regarding artificial granules (granular capsule-shaped granules), those in which a phase (phase of polyaspartic acid polyvalent metal salt) having a strength capable of continuously maintaining the shape is formed are indicated by "○". What was not formed was marked with "x".

[0039]

[Table 1]

[0040]

Industrial Applicability According to the present invention, an artificial granule obtained from a polyamino acid containing polyaspartic acid as a main component, which is a polymer having high biodegradability and expected to be highly safe for the living body and the natural world, is obtained. Can be provided.
INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an artificial granule obtained from polyaspartic acid, which has an inner phase and an outer phase, and can encapsulate a useful substance in the inner phase, and a method for producing the same. According to the present invention, for example, granular foods (artificial salmon roe, artificial caviar, artificial fish roe, spherical foods, etc.), granular medicines (capsule oral medicine, emulsion intravenous medicine, clinical test medicine, etc.), industrial granules (capsule) It has a thin and tough outer phase, suitable for oxidization catalysts) and feed (livestock feed etc.),
In addition, it is possible to provide an artificial granular material which is excellent in terms of ease of control of water retention / texture (strength of outer phase).

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a typical embodiment of the structure of an artificial granular material according to the present invention. Where (a) ~
(C) is as follows. (A) is an artificial granular material in which A is an internal phase and B is an external phase, and each of the internal phase and the external phase is one phase. (B) is an artificial granular material containing an oily phase in which A is an internal phase, B is an external phase, and O is an oily material.
(C) is an artificial granular material in which A is an internal phase, B1 and B2 are external phases, the internal phase is one phase, and the external phase is two phases.

[Explanation of symbols]

A Internal phase B, B1, B2 Foreign phase O 2 oily phase

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-9-71044 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 3/14

Claims (7)

(57) [Claims] 1. A granular material having an inner phase and an outer phase,
An artificial granule, wherein the outer phase of the granule contains a polyvalent metal salt of polyaspartic acid. 2. A method for bringing a droplet of an aqueous solution of an alkali metal salt of polyaspartic acid into contact with a polyvalent metal salt solution,
A method for producing an artificial granular material having an inner phase and an outer phase, which comprises forming an outer phase containing a polyaspartic acid polyvalent metal salt at a contact interface between the both. 3. The concentration of the alkali metal aspartic acid salt in the aqueous solution containing the polyaspartic acid alkali metal salt is 1.
The method for producing an artificial granular material according to claim 2, wherein the content is 0% by weight or more. 4. The method for producing an artificial granular material according to claim 2, wherein the concentration of the polyvalent metal salt solution is 10% by weight or more. 5. The method for producing an artificial granular material according to claim 2, wherein the weight average molecular weight of the polyaspartic acid alkali metal salt is 10,000 or more. 6. The method for producing an artificial granular material according to claim 2, wherein the alkali metal polyaspartate is sodium polyaspartate. 7. The method for producing artificial granules according to claim 2, wherein the polyvalent metal salt solution is an aqueous calcium chloride solution.