JP2019181350A - Manufacturing method of microcapsule - Google Patents

Abstract

To provide a manufacturing method capable of providing a microcapsule having carboxymethyl cellulose as a film wall, excellent in storage stability under dryness without using an organic solvent and regardless of kinds of a core material.SOLUTION: There is provided a manufacturing method of a microcapsule including a process for preparing a solution by mixing carboxymethyl cellulose and/or a sodium salt thereof, and further one or more kinds of other water soluble polymer, a process for preparing an emulsion dispersion by adding a hydrophobic material with viscosity at 25°C by a B-type viscometer of 100 to 10000 mPa s or a hydrophobic composition, or a mixture by melting and mixing a hydrophobic material with viscosity at 25°C by a B-type viscometer of 100 to 10000 mPa s or a hydrophobic composition and a hydrophobic material having melting point of 25 to 80°C to the solution, and a process for adding bi- or higher valent metal salt to the emulsion dispersion.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a microcapsule, and more particularly to a method for producing a microcapsule having carboxymethylcellulose as a membrane wall.

  Microcapsule production methods include chemical methods using condensation polymerization, physicochemical methods such as coacervation, liquid drying, and melt dispersion cooling, as well as pan coating, air suspension, and spray drying. There are mechanical methods such as law.

  The chemical method by condensation polymerization (hereinafter referred to as condensation polymerization method) is, for example, a polyurethane resin or polyurea resin using polyfunctional isocyanate as a raw material, or melamine using methylol melamine as a raw material as disclosed in Patent Document 1. This is a method for producing a microcapsule having a resin wall as a membrane wall. However, this method has a problem that carbon dioxide gas is generated when the polyurethane film wall or polyurea film wall is generated, and formaldehyde is generated when the melamine resin film wall is generated.

  The complex coacervation method uses a combination of a polycation solution and a polyanion solution as a polymer solution, and encapsulates a concentrated colloid layer that is generated by phase separation by electrical interaction when these are mixed. (Non-Patent Document 1). As a method for producing microcapsules having carboxymethyl cellulose and / or a sodium salt thereof as a membrane wall, a method of using gelatin in combination with this complex coacervation method is used. As polyanions other than carboxymethylcellulose used for complex coacervation, polysaccharides such as gum arabic, sodium alginate, carrageenan and agar are known.

  In this complex coacervation method, no gas is generated as in the above condensation polymerization method, but the pH is adjusted to cause phase separation, and an organic solvent (formaldehyde or ethanol is used to cure the concentrated colloid layer. Etc.), and it is necessary to readjust the pH, and the work becomes complicated, and problems such as residual organic solvent and environmental pollution need to be considered.

  In contrast, Patent Documents 2 and 3 describe a microencapsulation method using celluloses, in which an incompatible cellulose aqueous solution and a copolymer aqueous solution are mixed as a method in which neither an organic solvent nor gelatin is used. And the manufacturing method which adds sodium chloride, calcium chloride, magnesium chloride, or sodium sulfate as a separating agent and produces | generates a microcapsule is disclosed.

  However, in the methods shown in Patent Documents 2 and 3, it is necessary to combine specific celluloses and specific copolymers in order to obtain stable microcapsules. For obtaining microcapsules using carboxymethylcellulose, No specific method is disclosed.

  In order to solve such a problem, Patent Document 4 uses carboxymethyl cellulose or a sodium salt thereof, and does not generate a gas as in the above condensation polymerization method and does not use an organic solvent. The manufacturing method obtained is disclosed.

  In Examples of Patent Document 4, it is described that cypress oil is used as a core material, and microcapsules having carboxymethyl cellulose or a sodium salt thereof as a membrane wall are manufactured. In some cases, when the microcapsules are dried, the membrane wall is broken, the fragrance is diffused, the remaining fragrance is lost, and the fat and oil ooze out.

JP-A-11-188257 JP 2000-033259 A JP 2001-205075 A JP 2012-217960 A

"Microcapsules-its production, properties, and applications", Sankyo Publishing, Kondo and Makoto Koishi, October 15, 1977, pp. 49-55.

  The present invention has been made in view of the above, and it is easy to produce a microcapsule having carboxymethyl cellulose as a membrane wall, which is excellent in storage stability under drying regardless of the type of the core material without using an organic solvent. An object of the present invention is to provide a method for producing microcapsules obtained in the above.

  In order to solve the above problems, the method for producing a microcapsule of the present invention further comprises a step of preparing an aqueous solution by further mixing one or more kinds of carboxymethyl cellulose and / or its sodium salt and other water-soluble polymers, In the aqueous solution, a hydrophobic substance or a hydrophobic composition having a viscosity of 100 to 10,000 mPa · s at 25 ° C. by a B-type viscometer, or a hydrophobic substance having a viscosity of 100 to 10,000 mPa · s at 25 ° C. by a B-type viscometer A step of preparing an emulsified suspension by adding a mixture obtained by melting and mixing a functional substance or a hydrophobic composition and a hydrophobic substance having a melting point of 25 to 80 ° C., and adding a divalent or higher metal salt to the emulsified suspension. And a step of adding.

  In the above production method, the carboxymethyl cellulose and / or its sodium salt has an etherification degree of 0.5 to 0.8, a PVI value of 0.5 or less, and a structural viscosity of 50 or more. be able to.

  The carboxymethylcellulose and / or its sodium salt may have a 2% by mass aqueous solution viscosity at 25 ° C. of 1 to 1000 mPa · s as measured by a B-type viscometer.

  The water-soluble polymer is one or a mixture of two or more selected from the group consisting of sodium naphthalenesulfonate formaldehyde condensate, sodium alkylnaphthalenesulfonate formaldehyde condensate, polyvinyl alcohol, polystyrene sulfonic acid, and salts thereof. It can be.

  The divalent or higher metal salt can be one or a mixture of two or more selected from the group consisting of calcium salts, iron salts, silver salts, zinc salts, barium salts, aluminum salts, and copper salts.

  According to the production method of the present invention, microcapsules having carboxymethyl cellulose as a membrane wall, which is excellent in storage stability even under drying, regardless of the type of core substance, can be easily produced without using any organic solvent. Is possible.

  The carboxymethyl cellulose used in the present invention (hereinafter sometimes referred to as CMC) and / or its sodium salt (hereinafter sometimes referred to as CMC-Na) has a degree of etherification of 0.5 to 0.8. It is preferable that If the degree of etherification is less than 0.5, the water solubility is insufficient, the liquid does not become a uniform liquid, and the particle size distribution of the microcapsules becomes non-uniform. On the other hand, if the degree of etherification exceeds 0.8, the strength of the microcapsules may be reduced.

  In addition, CMC and / or CMC-Na is preferably 1 to 1000 mPa · s in viscosity of a 2% by mass aqueous solution measured by a B-type viscometer at a rotor rotation speed of 60 rpm and 25 ° C. s is more preferable, and 4 to 40 mPa · s is even more preferable. The higher the viscosity is, the more gelation occurs during emulsification, which tends to make uniform emulsification difficult. The resulting microcapsule aqueous dispersion also has high viscosity and poor fluidity. Therefore, it becomes disadvantageous practically. On the other hand, when the viscosity is low, the concentration of CMC in the aqueous solution can be increased, and thus the thickness of the CMC film wall can be increased.

  CMC and / or CMC-Na preferably has a PVI value of 0.5 or less, and preferably has a structural viscosity of 50 or more, more preferably 60 or more. When the PVI value is 0.5 or less and the structural viscosity is 50 or more, microcapsules excellent in storage stability under drying are easily obtained.

  In the present specification, the degree of etherification, the PVI value, and the structural viscosity indicate numerical values that are defined and measured in Examples described later.

  Although the manufacturing method of such CMC and CMC-Na is not specifically limited, After performing the alkali cellulose reaction which makes an alkali react with a cellulose, an etherifying agent is added to the obtained alkali cellulose, and an etherification reaction is performed. Can be manufactured.

  Specifically, it is preferable to include the following (Step 1) alkali cellulose reaction step, (Step 2) etherification reaction step, and (Step 3) viscosity reduction step. According to such a production method, the degree of etherification CMC and CMC-Na whose PVI value and structural viscosity are within the above preferred ranges are easily obtained.

(Step 1) Alkal Cellulification Reaction Step The alkali cellulose reaction step is in a water-containing organic solvent (total amount: 100% by mass) containing 10% by mass or more and 15% by mass or less of an alkali metal hydroxide, and is a cellulosic raw material glucose. The reaction can be carried out using 1.0 to 5.0 moles of alkali metal hydroxide per mole of unit. For example, the reaction is carried out at a liquid temperature of 25 to 45 ° C. for 50 to 80 minutes. It can be carried out.

  Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, and the like, and any one kind or a combination of two or more kinds can be used. When the addition amount of the alkali metal hydroxide is 1.0 mol or more, CMC and CMC-Na having a degree of etherification of 0.5 or more are easily obtained. Furthermore, the crystallization region of the cellulosic material is sufficiently destroyed, and the carboxymethyl etherification reaction is easily promoted. On the other hand, when the addition amount of the alkali metal hydroxide is 5 mol or less per mol of glucose unit, the excessive alkali metal salt is prevented from decomposing the etherifying agent in the etherification reaction, and effective use of the etherifying agent is achieved. The rate is improved.

  The water-containing organic solvent is a mixed solvent of a predetermined organic solvent and water. As said organic solvent, the organic solvent generally used for manufacture of CMC and CMC-Na can be used. Although not particularly limited, specifically, alcohol solvents such as ethyl alcohol, methyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol and isobutyl alcohol, ketone solvents such as acetone, diethyl ketone and methyl ethyl ketone, dioxane, diethyl ether Etc. These may be used alone or as a mixture of two or more. Among these, a monohydric alcohol having 1 to 4 carbon atoms is preferable, and a monohydric alcohol having 1 to 3 carbon atoms is more preferable because of excellent compatibility with water.

  Although the content rate of the water with respect to 100 mass parts of organic solvents of the said water-containing organic solvent is not restrict | limited, It is preferable that they are 20 mass parts or more and 60 mass parts or less.

(Step 2) Etherification Reaction Step In the etherification reaction step, the etherifying agent is added at a liquid temperature of 20 ° C. or higher and 40 ° C. or lower for 50 minutes to 80 minutes, and the etherification reaction is performed at 70 ° C. or higher and 100 ° C. It is preferable to carry out at the following liquid temperature for 30 minutes or more and 120 minutes or less.

  Examples of the etherifying agent include monochloroacetic acid.

  The addition amount of the etherifying agent is appropriately set according to the set etherification degree of CMC and CMC-Na.

(Step 3) Viscosity step It is preferable to reduce the viscosity by adding hydrogen peroxide to the carboxymethyl cellulose and / or salt thereof after the etherification step in a reaction system having a pH of 7.0 or more, and the viscosity reduction is particularly limited. However, it can be performed at a liquid temperature of 40 ° C. or higher and 70 ° C. or lower, for example, for 30 minutes or longer and 60 minutes or shorter.

  It is preferable to add 0.1 mass% or more and 10 mass% or less of the hydrogen peroxide addition amount in the said viscosity reduction process with respect to the carboxymethylcellulose sodium salt of a raw material.

  The method for producing the microcapsules of the present invention is carried out by neutralizing excess alkali contained in CMC and CMC-Na after the above-mentioned viscosity-reducing step with an acid, followed by removal of the water-containing organic solvent, washing and drying, followed by pulverization. CMC and CMC-Na which can be suitably used for the production can be produced.

  The water-soluble polymer other than CMC and / or CMC-Na used in the present invention is not particularly limited, and may be naturally derived or may be obtained by chemical synthesis. Examples include xanthan gum, gellan gum, polyglutamic acid, gum arabic, guar gum, locust bean gum, carrageenan, starch, chitosan, pectin, and derivatives thereof, and synthetic organic polymers such as polyethylene glycol, polyvinyl alcohol, and polyvinyl pyrrolidone. And polyacrylic acid, polyacrylamide, sodium naphthalene sulfonate or sodium alkyl naphthalene sulfonate formaldehyde condensate or a salt thereof, polystyrene sulfonic acid or a salt thereof, and the like. Moreover, cellulose derivatives other than CMC and CMC-Na, such as hydroxyethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, and ethyl cellulose, can also be used. Among these, formaldehyde condensate of sodium naphthalene sulfonate or sodium alkyl naphthalene sulfonate, polyvinyl alcohol, polystyrene sulfonic acid, and salts thereof are preferable. These water-soluble polymers can be used alone or in combination of two or more.

  The molecular weight of these water-soluble polymers is preferably 3,000 to 1,000,000, more preferably 10,000 to 100,000 in terms of weight average molecular weight (Mw). If the molecular weight is too low, the CMC film wall is hardly formed, and if the molecular weight is too high, the emulsified state tends to be unstable.

  Next, examples of the divalent or higher metal salt used in the present invention include calcium salt, iron salt, silver salt, zinc salt, barium salt, aluminum salt, copper salt and the like. Preferable specific examples include iron chloride, iron sulfate, aluminum sulfate, aluminum acetate, alum, silver nitrate, calcium hydroxide, zinc sulfate, copper sulfate, barium sulfate and the like. One of these divalent or higher metal salts can be used alone, or two or more can be used in combination.

  In the present invention, by using these divalent or higher-valent metal salts, microcapsules having excellent core substance retention of microcapsules and easy release control can be obtained. This is because ion exchange is performed between these divalent or higher metal salts and the hydrogen ion or sodium ion of the carboxyl group of CMC, resulting in cross-linking between the CMC molecules. It is thought that this is because As described above, carbon dioxide gas is generated during the production of microcapsules made of polyurethane film walls or polyurea film walls by the conventional condensation polymerization method, and formaldehyde is generated when microcapsules made of melamine resin are produced. However, in the present invention, since no such gas is generated, it is not necessary to remove gas or unreacted substance, and microencapsulation can be completed in a short time.

  As a core substance used for the capsule of the present invention, a hydrophobic substance or a hydrophobic composition having a viscosity of 100 to 10,000 mPa · s measured by a B-type viscometer at a rotor rotation speed of 60 rpm and 25 ° C., or a B-type viscosity As long as it is a mixture obtained by melting and mixing a hydrophobic substance or a hydrophobic composition having a viscosity of 100 to 10,000 mPa · s measured at 25 ° C. and a hydrophobic substance having a melting point of 25 to 80 ° C. There is no particular limitation (hereinafter, these are collectively referred to as “hydrophobic substances and the like”). Hydrophobic substances include fragrances (natural fragrances, synthetic fragrances, plant essential oils, etc.), agricultural chemicals, physiologically active substances, repellents, deodorants, coloring agents, etc. If the viscosity is not within the specified range, high viscosity Alternatively, it is possible to use a hydrophobic composition adjusted to a viscosity within the predetermined range by mixing with a liquid such as a low-viscosity hydrophobic substance or non-volatile oil. Examples of liquids used for such viscosity adjustment include vegetable oils and fats and the above fragrances. A mixture obtained by melt-mixing a hydrophobic substance or hydrophobic composition having a viscosity of 100 to 10,000 mPa · s measured at 25 ° C. and a hydrophobic substance having a melting point of 25 to 80 ° C. is solid at 25 ° C. However, it is preferable that the viscosity measured with a B-type viscometer at a rotor rotation speed of 60 rpm and a melt-mixed temperature is 100 mPa · s or more. Note that “solid” refers to a state without fluidity.

  The method for producing a microcapsule according to the present invention includes (1) a step of further mixing CMC and / or CMC-Na and one or more other water-soluble polymers to prepare an aqueous solution; A hydrophobic substance or a hydrophobic composition having a viscosity at 100 ° C. of 100 to 10,000 mPa · s, or a hydrophobic substance or a hydrophobic composition having a viscosity of 100 to 10,000 mPa · s measured at 25 ° C. with a B-type viscometer Adding a mixture obtained by melting and mixing a hydrophobic substance having a melting point of 25 to 80 ° C. to prepare an emulsified suspension; and (3) adding a divalent or higher metal salt to the emulsified suspension. Including at least.

  In the step (1) of preparing an aqueous solution such as CMC, the concentration of CMC and / or CMC-Na in the aqueous solution is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass. Moreover, 0.1-10 mass% is preferable and, as for the density | concentration of water-soluble polymers other than CMC and / or CMC-Na in this aqueous solution, 1-5 mass% is more preferable. This aqueous solution can be prepared according to a known method, and may be heated up to about 60 ° C. as necessary to facilitate dissolution in water. When heated to a temperature exceeding 60 ° C., the viscosity of the aqueous solution such as CMC becomes too low, and the particle size of the microcapsules may vary.

  Next, in the step of preparing an emulsified suspension by adding a hydrophobic substance or the like to the aqueous solution, the concentration of the hydrophobic substance or the like is 0. 0 in the microcapsule aqueous dispersion including the finally obtained aqueous medium. It is preferable to adjust so that it may become 1-50 mass%. If the concentration is higher than 50% by mass, emulsification may become difficult and the viscosity of the microcapsule aqueous dispersion may increase. On the other hand, when it is less than 0.1% by mass, the microcapsules can be prepared without any problem, but the concentration of the target core substance becomes too low, which is not practical from an economical viewpoint. The emulsification suspension can be performed by a known method using a homodisper or the like.

  Furthermore, in the step of adding a divalent or higher metal salt to the emulsion suspension, the concentration of the divalent or higher metal salt is preferably 0.0001 to 0.01% by mass in the target aqueous dispersion. 0.001 to 0.005 mass% is more preferable. As the timing of adding the metal salt, it is preferable to add the metal salt in anticipation of a stable emulsified state. If it is visually confirmed that the obtained emulsion suspension is sufficiently uniform, the emulsion suspension operation is terminated.

  After completion of the emulsification suspension operation, aging is preferably performed at about 18 to 80 ° C. for about 1 to 24 hours. By aging in this way, the crosslinking proceeds sufficiently, so that the CMC film wall can be made stronger.

  By the production method of the present invention described above, an aqueous dispersion (including a slurry) in which microcapsules are stably dispersed in water is obtained. The microcapsules obtained by the production method of the present invention are generally spherical particles having an average particle diameter of usually 1 to 1000 μm, and the average particle diameter is appropriately selected depending on the application, and the stirring speed by homodisper or the like during emulsification is adjusted. It can be adjusted by doing.

  The obtained microcapsule aqueous dispersion can be used as it is, and can also be used after diluting with water or the like, if necessary. For example, in the case of a microcapsule aqueous dispersion having a fragrance as a core substance, the microcapsule adheres to the fabric product by appropriately diluting it and applying it to the fabric product by spraying, dipping or the like and drying it. Thus, it is possible to obtain a fabric product that maintains the scent for a long period of time.

  In the production method of the present invention described above, additives such as surfactants, preservatives, pH adjusters, thickeners and the like that are usually used in the production method of microcapsules are added as long as they are within the scope of the invention. It can also be added to the aqueous solution or emulsion suspension.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example. In the following examples, “%” means “mass%” unless otherwise specified. Further, the viscosity of a hydrophobic substance or the like is the viscosity at a rotor rotation speed of 60 rpm and 25 ° C. by a B-type viscometer, and the viscosity of CMC-Na is 2 mass at a rotor rotation speed of 60 rpm and 25 ° C. by a B-type viscometer. % Viscosity of aqueous solution.

[Production of carboxymethylcellulose sodium salt]
[Production Example 1]
100 g of low density pulp pulverized by a home mixer was charged into a 3 L kneader reactor equipped with a biaxial stirring blade. After dissolving 60 g of sodium hydroxide in 500 g of a water-containing organic solvent in which IPA: water is mixed at a mass ratio of 80:20, it is put into the reactor containing the pulp and stirred at 35 ° C. for 60 minutes to make an alkali cellulose. Reaction was performed to obtain alkali cellulose. Next, 55 g of monochloroacetic acid was dissolved in 33 g of the above water-containing organic solvent and adjusted to 25 ° C., then the alkali cellulose was added over 60 minutes while maintaining the temperature at 35 ° C., and then the temperature was raised to 80 ° C. over 30 minutes. The etherification reaction was carried out at 60 ° C. for 60 minutes.

  After the etherification reaction, 5 g of a 20% aqueous hydrogen peroxide solution was added, and a viscosity reduction reaction was performed at 50 ° C. for 60 minutes. After the reaction, unreacted excess sodium hydroxide was neutralized with 50% by mass of acetic acid to adjust the pH to 6.5 to 7.5. The neutralized product in the form of a slurry was taken out from the reactor, and IPA was removed by centrifugation to obtain a crude carboxymethylcellulose sodium salt. This crude carboxymethylcellulose sodium salt was washed with a 70% by mass aqueous methanol solution to remove by-product sodium chloride, sodium glycolate and sodium acetate. This washing operation was repeated twice, followed by drying at 80 ° C. for 4 hours and pulverization to obtain carboxymethylcellulose sodium salt.

  As a result of measuring various physical properties of the obtained carboxymethylcellulose sodium salt by the measuring methods described later, the etherification degree was 0.75, the 2 mass% aqueous solution viscosity was 15 mPa · s, the PVI value was 0.42, and the structural viscosity was 64. Met.

[Production Example 2]
Production was carried out in the same manner as in Production Example 1 except that the amount of monochloroacetic acid charged and the amount of the water-containing organic solvent in which monochloroacetic acid was dissolved were changed as shown in Table 1 below. Thus, carboxymethylcellulose sodium salt of Production Example 2 was obtained.

  As a result of measuring various physical properties of the obtained carboxymethylcellulose sodium salt by the above measurement method, the degree of etherification was 0.66, the 2 mass% aqueous solution viscosity was 80 mPa · s, the PVI value was 0.46, and the structural viscosity was 70. there were.

[Measurement of physical properties of carboxymethylcellulose sodium salt]
<Degree of etherification>
Carboxymethylcellulose sodium salt 0.6 g was dried at 105 ° C. for 4 hours. After precisely weighing the mass of the dried product, it was wrapped in filter paper and incinerated in a magnetic crucible. The ashed product was transferred to a 500 ml beaker, 250 ml of water and 35 ml of 0.05 mol / l sulfuric acid aqueous solution were added and boiled for 30 minutes. After cooling, the excess acid was back titrated with a 0.1 mol / l aqueous potassium hydroxide solution. In addition, phenolphthalein was used as an indicator. The degree of etherification was calculated from the following formula (1) using the measurement results.

(Degree of etherification) = 162 × A / (10000-80A) (1)
A = (af−bf1) / weight of dried product (g)
A: Amount of 0.05 mol / l sulfuric acid aqueous solution consumed by bound alkali in 1 g of sample (ml)
a: Amount used of 0.05 mol / l sulfuric acid aqueous solution (ml)
f: titer of 0.05 mol / l sulfuric acid aqueous solution b: titration of 0.1 mol / l potassium hydroxide aqueous solution (ml)
f1: titer of 0.1 mol / l potassium hydroxide aqueous solution

<2% by weight aqueous solution viscosity>
Carboxymethylcellulose sodium salt (about 4.4 g) was placed in a 300 ml Erlenmeyer flask with a stopper and precisely weighed. The amount of water calculated by the calculation formula “sample (g) × (99−water content (mass%))” was added thereto, left to stand for 12 hours, and further mixed for 5 minutes. Using the obtained solution, the viscosity at 25 ° C. was measured using a BM type viscometer (single cylinder type rotational viscometer) according to JIS Z8803. At that time, (a) the rotor rotational speed was measured at 60 rpm, (b) when the measured value in (a) above was 8000 mPa · s or more, the rotor rotational speed was changed to 30 rpm, and (c) When the measured value in the above (b) was 16000 mPa · s or more, the rotor rotation speed was changed to 12 rpm and the measurement was performed.

<PVI value>
An aqueous solution having a viscosity of 10000 ± 500 mPa · s was prepared using sodium carboxymethylcellulose and stirred well, then covered with a wrap and allowed to stand overnight in a 25 ° C. incubator. Next, it was taken out from the thermostat and sufficiently stirred with a glass rod. Next, the viscosity was measured using a BH viscometer and rotor No. 5 at 2 rpm (η2). Next, the viscosity was measured at a rotational speed of 20 rpm (η20). From these measured values, the PVI value was calculated by the following formula (2). The closer the PVI value is to 1.0, the stronger the Newtonian property, and the closer to 0, the stronger the non-Newtonian property.
PVI * = η20 / η2 (2)
* P rinting V iscosity I ndex (printing viscosity index)

<Structural viscosity>
An aqueous solution having a viscosity of 10,000 ± 500 mPa · s was prepared using sodium carboxymethylcellulose and stirred well, then covered with a wrap and allowed to stand overnight in a 25 ° C. incubator. Next, it was taken out from the thermostatic chamber, and the viscosity at 20 rpm was measured using a BH viscometer and rotor No. 5 (ηM). Next, after stirring for 10 minutes at 400 rpm using a three-one motor, the viscosity at 20 rpm was measured using a BH viscometer and rotor No. 5 (ηm). The structural viscosity was calculated by the following formula (3) using the measured viscosities.
Structural viscosity (%) = (ηM−ηm) / ηM (3)

<Manufacture of microcapsules>
[Example 1]
Table 2 shows CMC-Na and polyvinyl alcohol (trade name: Gohsenol GL-05, manufactured by Nippon Synthetic Chemical Co., Ltd., saponification degree 88%, 4% viscosity 5.0 mPa · s) obtained in Production Example 1 above. Dispersed in water at the stated blending ratio, heated to 80 ° C. and dissolved to obtain an aqueous solution.

  After dissolution, 60 g of the above aqueous solution cooled to room temperature was placed in a 300 mL tall beaker, and a hydrophobic substance (oil phase) mixed at a ratio shown in Table 2 was added, and homodisper (blade diameter φ 40 mm, stirring) The mixture was emulsified for 10 minutes at a speed of 1000 rpm. Five minutes after the start of emulsification, 5 g of an aqueous solution of calcium chloride prepared to 0.1% was added little by little. The viscosity of the hydrophobic substance and the like was measured using a BM type viscometer (single cylinder type rotational viscometer) in the same manner as the measurement of the viscosity of the 2% by mass aqueous solution of carboxymethyl cellulose sodium salt, and the rotational speed of the rotor was 60 rpm. And measured.

  After the emulsification is completed, the homodisper blade is changed to a bowl-shaped stirring blade and aged at 200 rpm for 1 hour at room temperature to be aged, so that an aqueous microcapsule dispersion (slurry, hereinafter) having the composition shown in Table 2 is obtained. The same).

[Examples 2 to 7, Comparative Examples 1 and 2]
An aqueous solution was prepared in the same manner as in Example 1 except that the hydrophobic substance and the like (oil phase) of Example 1 and CMC-Na were changed to the formulation shown in Table 2, and then emulsified. After the emulsification, the blade is changed to a bowl-shaped stirring blade, further heated to 60 ° C., stirred at that temperature for 1 hour and aged to obtain a microcapsule aqueous dispersion having the composition shown in Table 2. It was.

  In addition, the hydrophobic substance of Example 5 was obtained by heating castor oil and stearic acid to 80 ° C. and melt-mixing them. The viscosity at a rotor rotation speed of 60 rpm and 80 ° C. by a B-type viscometer was 20 mPa · s, but solidified when the temperature dropped to 25 ° C.

  The average particle size of the microcapsules obtained in each of the above Examples and Comparative Examples was measured with a laser diffraction particle size distribution measuring device (SALD-2200, manufactured by Shimadzu Corporation). The results are shown in Table 2.

  As shown in Table 2, in Examples 1 to 7 and Comparative Examples 1 and 2, microcapsules having an average particle size of 20 μm or less were obtained.

<Dry evaluation>
Place one drop of the microcapsule aqueous dispersion obtained above on the scanning electron microscope (SEM) sample stage, air-dry, and observe with a scanning electron microscope to confirm the presence or absence of microcapsule membrane wall cracks. did.

  As shown in Table 2, from the comparison between Examples 1 to 7 and Comparative Examples 1 and 2, when a predetermined hydrophobic material or the like was used as the core material of the microcapsule, no dry crack was observed. .

  The microcapsules obtained by the production method of the present invention can be used for sustaining and controlling the release of fragrances (natural fragrances, synthetic fragrances, plant essential oils, etc.), agricultural chemicals, physiologically active substances, repellents, deodorants, coloring agents, and the like. .

Claims (5)

A step of preparing an aqueous solution by further mixing one or more kinds of carboxymethyl cellulose and / or its sodium salt and other water-soluble polymers;
In the aqueous solution, a hydrophobic substance or a hydrophobic composition having a viscosity at 25 ° C. of 100 to 10,000 mPa · s by a B-type viscometer, or a hydrophobic substance having a viscosity of 100 to 10,000 mPa · s at 25 ° C. by a B-type viscometer A step of preparing an emulsified suspension by adding a mixture obtained by melting and mixing an active substance or a hydrophobic composition and a hydrophobic substance having a melting point of 25 to 80 ° C .;
A step of adding a divalent or higher metal salt to the emulsified suspension.   The carboxymethyl cellulose and / or its sodium salt has an etherification degree of 0.5 to 0.8, a PVI value of 0.5 or less, and a structural viscosity of 50 or more. 2. A method for producing a microcapsule according to 1.   The carboxymethylcellulose and / or sodium salt thereof has a 2% by mass aqueous solution viscosity at 25 ° C measured by a B-type viscometer of 1 to 1000 mPa · s, The microcapsule according to claim 1 or 2, Method.   The water-soluble polymer is one or a mixture of two or more selected from the group consisting of sodium naphthalene sulfonate formaldehyde condensate, sodium alkyl naphthalene sulfonate formaldehyde condensate, polyvinyl alcohol, polystyrene sulfonic acid, and salts thereof. The method for producing a microcapsule according to claim 1, wherein the method is a microcapsule. The divalent or higher metal salt is one or a mixture of two or more selected from the group consisting of calcium salt, iron salt, silver salt, zinc salt, barium salt, aluminum salt and copper salt The manufacturing method of the microcapsule of any one of Claims 1-4.