JPS59203634A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To obtain a microcapsule with good quality having a uniform particle size, by emulsifying or dispersing a hydrophobic core substance into a medium containing a water soluble high-molecular substance having a hydroxyl group while adding a liquid mixture consisting of an anionic high-molecular compound having no hydroxyl group and an aldehyde resin precondensate to the resulting emulsion or dispersion. CONSTITUTION:A hydrophilic aldehyde resin precondensate is subjected to polycondensation in water or a hydrophilic medium and a hydrophobic core substance is encapsulated to prepare a microcapsule. In this micro-encapsulating method, the hydrophobic core substance is emulsified or dispersed in a medium containing a water soluble high-molecular substance having a hydroxyl group and a liquid mixture consisting of an anionic high-molecular substance having no hydroxyl group and an aldehyde resin precondensate is added to the obtained emulsion or dispersion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing microcapsules containing a hydrophobic core substance, and in particular, a method for easily producing high-quality microcapsules with extremely uniform particle sizes. It is related to.

As is well known, microcapsules are suitable for keeping unstable substances, reactive substances, liquid or gaseous substances stable, and therefore the field of use of these microcapsules is also sensitive. It is used in a wide variety of fields, including pressure copying paper, pharmaceuticals, agricultural chemicals, adhesives, and fragrances.

Various methods are known for manufacturing microcapsules, such as the coacelhesion method, interfacial polymerization method, and 1n-situ method, and the membrane materials used for this method include gelatin, nylon resin, polyester resin, epoxy resin, Many are known, such as styrene resin, polyurekne resin, polyurea resin, urea or melamine resin. Among them, microcapsules having aldehyde polycondensation resin as a wall membrane are generally excellent in water resistance, solvent resistance, etc., and are capsules that can be applied to a wide range of fields.

In this way, microcapsules can store various substances in various amounts.
However, since the particle size is an important factor in determining capsule quality, it is desirable to stably obtain capsules with a uniform particle size when manufacturing microcapsules. There is.

For example, in the case of pressure-sensitive copying paper, there is generally a tendency for recording color development when making multiple copies to be at odds with stain resistance against color stains caused by static pressure and friction during storage and handling; If recording color development is improved, stain resistance becomes insufficient, and if stain resistance is emphasized, the purpose of copying multiple sheets cannot be completely achieved.

If we look at this problem from the particle size distribution of capsules, we can generally solve this problem under certain conditions by adjusting the various properties of the base paper, the concentration of the coloring material in the oily liquid, the volume ratio of the wall film material and the oily liquid, and the volume ratio of each material in the capsule coating liquid. In this case, the more uniform the particle size, that is, the narrower the particle size distribution, the more excellent the pressure-sensitive copying paper will tend to be, which is excellent in both recording color development and stain resistance. The reason for this is that the main cause of colored stains is the presence of large particle size capsules that are easily destroyed, while capsules that are extremely smaller than the average particle size are not destroyed during recording and do not contribute to recorded color development. It is. Therefore, in producing good pressure-sensitive copying paper, it is an important technical issue to obtain capsules with a desired particle size and a narrow particle size distribution.

Several techniques for producing microcapsules with uniform particle sizes have been reported so far, such as JP-A-53-94273, JP-A-54-32178;
No. 54-74282 discloses that in the coacelation method, the force of the particles trying to stick to each other on the core cells deposited around the minute droplets of the oily substance is appropriately balanced by the separation force of the stirring flow. describes a method for producing polynuclear capsules having a desired particle size and uniform particle size. However, since the capsule membrane material used in these methods is gelatin, the resulting capsules have extremely poor water resistance and moisture resistance, and when applied to single pressure-sensitive copying paper, coloration occurs during the coating or application stage. There is a drawback.

Furthermore, Japanese Patent Application Laid-Open No. 57-84740 discloses a method in which an oily liquid and a solution containing a water-soluble monomer or polymer are mixed, and the mixed liquid is introduced into a passage by a stationary liquid shearing means or by a moving liquid by the passing liquid itself. A method is described in which microcapsules are manufactured by forming an oil-in-water emulsion by force-feeding it through a tubular member provided with a shearing means, and then subjecting it to a wall film forming treatment. However, although it is possible to obtain capsules using this method with excellent moisture resistance, water resistance, solvent resistance, and uniform particle size by carefully selecting the membrane material, it is necessary to use a very special emulsifying machine. It has the disadvantage that the emulsification process is long because the shearing force applied to the oil droplets is weak. Furthermore, in JP-A-56-81131, a wall film consisting of a polycondensate is basically formed on the surface of urea and/or melamine and formaldehyde in the presence of an anionic polymer electrolyte or a nonionic polymer and an organic anion. In the method for manufacturing microcapsules consisting of,
It has been described that capsules with uniform particle sizes can be obtained by using a stirred reaction apparatus consisting of a reaction tank equipped with a baffle that satisfies certain conditions and a stirrer, but this encapsulation method requires a special stirrer. t4≧This method has disadvantages in that it requires a reaction device and that the average particle diameter tends to fluctuate due to subtle differences in P&agitation conditions, making it difficult to control. Furthermore, in JP-A No. 56-58536, a melamine-; Although it is described that capsules having a uniform particle size can be obtained by polymerization, the resulting capsules have a drawback of poor solvent resistance despite the use of melamine-formaldehyde resin.

As a result of intensive research in view of the current situation, the present inventors have developed microcapsules with extremely uniform particle sizes and extremely good performance in terms of moisture resistance, water resistance, solvent resistance, etc. We succeeded in developing a method that allows easy production using a stirred reactor.

The present invention is a microencapsulation method in which a hydrophilic aldehyde resin initial condensate is polycondensed in water or a hydrophilic medium to encapsulate a hydrophobic core material, and a water-soluble polymer containing a hydroxyl group is used. A hydrophobic core material is emulsified or dispersed in a medium, and a mixture of an anionic polymer having no hydroxyl group and an aldehyde resin initial condensate is added to the resulting emulsion or dispersion. This is a method for manufacturing capsules.

The hydrophilic aldehyde resin initial condensate used in the present invention includes, for example, a phenol formaldehyde resin initial condensate, an aminoaldehyde resin initial condensate, and the like. Examples of the phenol-formaldehyde resin initial condensate include initial condensates obtained by condensing formaldehyde with at least one phenol such as phenol, furesol, xylenol, resorcinol, hydroquinone, pyrocatechol, and pyrogallol. As the aminoaldehyde resin initial condensate,
For example, urea, thiourea, alkyl urea, ethylene urea,
At least one amine such as acetoguanamine, henzoguanamine, melamine, guanidine, dicyandiamide, biuret, cyanamide and at least one aldehyde such as formaldehyde, acetaldehyde, parapolmaldehyde, hexamethylenetetramine, geltaraldehyde, glyoxal, and furfural. Initial condensates obtained by condensing or alkylated products such as methylated products thereof, and hydrophilic products such as anionic, cationic or nonionic modified products thereof are used alone or in combination. Examples of anionic modifiers include sulfamic acid, sulfanilic acid, glycolic acid, glycine, acidic sulfite, phenol sulfonate, and glycine. Examples of cationic modifiers include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and dimethylamino. Nonionic modifiers such as ethanol include ethylene glycol, diethylene glycol, and the like. As the initial condensate in the present invention, as long as it is hydrophilic, various types can be used as described above, but aminoaldehyde resin initial condensates are preferred, among which melamine-bormaldehyde initial condensates, urea- The melamine-formaldehyde initial condensate and the urea-formaldehyde initial condensate are preferred because they yield a dense film, and the anion-modified melamine-formaldehyde resin initial condensate is particularly preferred because they yield particles with extremely uniform particle size.

The amount of the hydrophilic aldehyde resin initial condensate is as follows:
It varies depending on the type of hydrophobic core material and aldehyde resin used, the particle size of the capsule, its intended use, etc., and it cannot be determined by -NB, but it is calculated as an amino compound or phenol compound based on 100 parts by weight of the hydrophobic core material. It is preferably 2 parts by weight or more and 50 parts by weight or less, particularly 4 parts by weight or more.
Parts by weight or less are more preferable.

The water-soluble polymer having a hydroxyl group used in the present invention includes anionic, cationic, nonionic, or amphoteric polymers.

Specifically, natural polymers such as starch, gum arabic, characeenan, sodium alginate, 1 to ragacanthus gum, almond gum, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sulfated cellulose, sulfated methylcellulose, carboxydimethyl starch,
Synthetic polymers such as semi-synthetic polymers such as phosphorylated starch, anion-modified polyvinyl alcohol such as polyvinyl alcohol, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, and cation-modified polyvinyl alcohol Among these, preferred are polyvinyl alcohol and anion- or cation-modified polyvinyl alcohol.

In the present invention, water-soluble polymers such as those described above can be used alone or in combination, and if necessary, a low-molecular emulsifier can also be used in combination.

Examples of low-molecular emulsifiers include anionic, cationic, nonionic, and amphoteric ones, but anionic ones are preferred, and among them, organic sulfuric acids having a total carbon number of 1 to 14 are preferred. Or L of organophosphoric acid
t", Na" + K"+ NH♂ salt is preferable, and specifically, sodium vinylsulfonate, sodium Hensensulfonate, sodium Hensensulfinate,
p-toluenesulfonic acid]・lium, p-) Sodium toluenesulfinate, sodium p-vinylbenzenesulfonate, sodium p-1-amylbenzenesulfonate, sodium naphthalene-α-sulfonate, naphthalene-β-sulfonic acid Sodium, sodium 2-methylnaphthalene-6-sulfonate, sodium 2.6-dimethylnaphthalene-8-sulfonate, sodium 2.6-dimethylnaphthalene-3-sulfonate, ■-sodium naphthol-4-sulfonate, Examples include sodium benzene-m-disulfonate, sodium diphenyl phosphate, sodium phenylphosphonate, sodium di-n-butyl phosphate, and sodium di-amyl phosphate.

The above-mentioned polymeric and low-molecular emulsifiers are preferably contained in water or a hydrophilic medium in an amount of 0.5% or more, and from the viewpoint of ease of preparation of the emulsion and stability of the emulsion, the content is preferably 2% or more.
It is more preferable to contain the above amount. The upper limit of the amount used is determined by the viscosity of the system, capsule preparation equipment, etc.
Generally, it is kept at 20% or less.

In the present invention, the anionic polymer having no hydroxyl group and used in combination with the aldehyde resin initial condensate is, for example, a polymer or copolymer consisting of an anionic monomer unit, or an anionic monomer unit and a hydrophobic monomer (UNISO). Specific examples include copolymers of maleic anhydride (including hydrolyzed ones), acrylic acid, methacrylic acid, or crotonic acid polymers and copolymers, and vinylbenzene. Examples include sulfonic acid-based or 2-acrylamido-2-methyl-propanesulfonic acid-based polymers and copolymers, and partial amides or partial esters of such polymers and copolymers.

More specifically, maleic anhydride-based (including hydrolyzed) copolymers include methyl vinyl ether-maleic anhydride copolymer, ethylene, maleic anhydride copolymer, and vinyl acetate-maleic anhydride copolymer. Examples include methacrylamide-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, and the like.

Examples of the acrylic acid copolymer, methacrylic acid copolymer, or crotonic acid copolymer include methyl acrylate-acrylic acid copolymer (hereinafter referred to as "copolymer"), ethyl acrylate-acrylic acid , methyl acrylate-methacrylic acid, methyl methacrylate-acrylic acid, methyl methacrylate-methacrylic acid, methyl acrylate-acrylamide middle acrylic acid, acrylonitrile-acrylic acid,
Acrylonitrile-meccrylic acid, vinyl acetate-acrylic acid, vinyl acetate-methacrylic acid, acrylamide-acrylic acid, acrylamide-methacrylic acid, meccrylamido-acrylic acid, meccrylamido-meccrylic acid, vinyl acetate-crotonic acid, etc. Examples include copolymers.

Examples of vinylbenzenesulfonic acid-based or 2-acrylamido-2-methyl-propanesulfonic acid-based copolymers include methyl acrylate-vinylhenzenesulfonic acid (or salt thereof) copolymer, vinyl acetate-vinylbenzenesulfone Acid copolymer, acrylamide-vinylbenzenesulfonic acid copolymer, acryloylmorpholine-vinylbenzenesulfonic acid*', 'M co7M, union, vinylpyrrolidone-vinylhenzenesulfonic acid copolymer, vinylpyrrolidone-2-acrylamide- Examples include 2-methyl-propanesulfonic acid copolymer.

As the anionic polymer having no hydroxyl group, the above compounds are used alone or in combination, but among them, ethylene,
Particularly preferred are copolymers of maleic anhydride and hydrophobic monomer units such as propylene, isobutylene, butadiene, methyl vinyl ether, and vinyl acetate.

Note that the pH of the mixture of the anionic polymer and the aldehyde resin initial condensate should be adjusted except in extreme cases where the initial condensate polymerizes too quickly and cannot be added to the emulsion or dispersion. , any conditions may be used, but preferably P H
The pH is 4.0 or more, more preferably in the range of 5.0 to 12.0.

Further, the mixing ratio of the anionic polymer and the aldehyde resin initial condensate varies depending on the desired particle size distribution, and is not limited to this, but preferably the anionic polymer and the aldehyde resin initial condensate are mixed to 1 part by weight of the aldehyde resin initial condensate. Polymer 0.0
The amount is 5 to 20 parts by weight, more preferably 0.1 to 5 parts by weight.

Incidentally, the reaction conditions in the present invention vary depending on the type of the initial condensate or the degree of requirement for core material retention, and are not limited thereto, but preferably P H
5.0 or less, 50°C or more, particularly preferably P H4,
' 5 or less, 70°C or more, and under those conditions 1
It is preferable to maintain the temperature for at least 3 hours, particularly for at least 3 hours.

In the present invention, in order to maintain the reaction system acidic, for example, formic acid, acetic acid, citric acid, oxalic acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, etc. are used. −.

A so-called acid catalyst commonly used in the field of noaldehyde resin production is used.

In the present invention, the hydrophobic core substance to be encapsulated in the microcapsules is not particularly limited, but the following substances are exemplified.

Animal oils such as fish oil, lard oil, etc., vegetable oils such as olive oil, peanut oil, linseed oil, soybean oil, castor oil, etc., mineral oils such as petroleum, kerosene, xylene, toluene, etc., alkyl-substituted diphenylalkanes, alkyl-substituted naphthalene, biphenylethane, methyl salicylate, diethyl adipate, di-n-propyl adipate,
Synthetic oils such as di-n-butyl adipate, di-methyl phthalate, diethyl phthalate, di-n-propyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate, etc. A solution in which an electron-donating color former, an electron-accepting color developer, a ligand compound, an organic metal salt, etc. are dissolved in an insoluble or substantially water-insoluble liquid or the above-mentioned synthetic oil;
Water-insoluble metal oxides and salts, fibrous materials such as cellulose or asbestos, water-insoluble synthetic polymeric materials, minerals, pigments, glasses, fragrances, flavors, fungicidal compositions, Physiological compositions, fertilizer compositions cheeks.

In the present invention, an oil-soluble aminobomaldehyde resin initial condensate may be added to the core material in order to further enhance the retention of the capsule.

In order to more specifically explain the method of the present invention, examples will be described below in which the method is applied to the field of pressure-sensitive copying paper, but the present invention is of course not limited thereto. Further, unless otherwise specified, parts and % in the examples represent parts by weight and % by weight, respectively.

Example 1 150 parts of a 4% aqueous solution of anion-modified polyvinyl alcohol (trade name Gosenal T-350, manufactured by Nippon Gosei Kagaku KK) was added to a stirring mixing vessel equipped with a heating device to prepare an aqueous medium for capsule production.

Separately, 15 parts of lauryl gallate and 2 parts of aniline were dissolved in a mixed solvent of 50 parts of di-n-butyl adipate and 50 parts of diethyl adipate to obtain a capsule core material.

This core substance was emulsified and dispersed in the above aqueous medium so that the average particle size was 5.0 μm, and then the temperature of the system was raised to 60°C.

Separately, 10 parts of melamine was added to 30 parts of a 37% formaldehyde aqueous solution and reacted at 60°C for 15 minutes, and then 1 part of glycine was added and reacted for 1 minute to prepare a prepolymer aqueous solution, which was then mixed with ethylene whose pH was adjusted to 5.5. -Maleic anhydride copolymer, trade name EMA-31. The mixture was mixed with 100 parts of a 5% aqueous solution (manufactured by Monsando).

This mixed solution was dropped into the emulsion under stirring, and reacted under the same conditions for 3 hours. Then, 1.0-N-hydrochloric acid was added dropwise to adjust the pH of the system to 4.5. The mixture was heated to 70°C and reacted under these conditions for 3 hours, and then allowed to cool to obtain a milky white capsule dispersion.

When the particle size of the capsules thus obtained was measured using a Coulter Counter (Model TA, manufactured by Coalcou Electrox), it was found that the capsules had a very uniform particle size distribution as shown in Figure 1. .

Comparative Example 1 Prepolymer aqueous solution was not mixed with EMA-31 aqueous solution,
In addition to adding prepolymer water/8 liquid alone to the emulsion,
A capsule dispersion liquid was obtained in the same manner as in Example 1.

When the particle size of the capsules thus obtained was measured using a Coulter counter, it was found that the particle size distribution was extremely irregular as shown in Figure 2.Example 2 Polyvinyl alcohol was used as the aqueous medium for capsule production. (
A capsule dispersion was prepared in the same manner as in Example 1, except that 8 parts of sodium styrene sulfonate was dissolved in 150 parts of a 2% aqueous solution of PVA-217-EE (trade name, M), manufactured by Kuraray Corporation.

Further, as a result of measurement, it was found that the obtained capsules had a very uniform particle size distribution.

Examples 3 and 4 Ethylene-maleic anhydride copolymer (trade name EMA=3
Use polyacrylic acid (trade name Aron A-10H) instead of 100 parts of the 5.0% aqueous solution in 1).

manufactured by Toagosei Kagaku Co., Ltd.) or methyl vinyl ether maleic anhydride (trade name Gantrez A N-139,
Except for using 100 parts of a 5.0% aqueous solution (manufactured by GAF),
Capsules were prepared in the same manner as in Example 1.

Further, as a result of measurement, it was found that the two types of capsules obtained had a very uniform particle size distribution.

[Brief explanation of the drawing]

FIGS. 1 and 2 are charts obtained by measuring the particle diameters of capsules obtained in Example 1 and Comparative Example 1 using a Coulter counter, respectively. Patent applicant Kanzaki Paper Co., Ltd.

Claims (5)

[Claims] (1) In the microencapsulation method, in which a hydrophilic aldehyde resin initial condensate is polycondensed in water or a hydrophilic medium to encapsulate a hydrophobic core substance, a water-soluble polymer containing a hydroxyl group is used. A hydrophobic core material is emulsified or dispersed in a medium, and a mixture of an anionic polymer having no hydroxyl group and an aldehyde resin initial condensate is added to the resulting emulsion or dispersion. Method of manufacturing capsules. (2) The method for producing microcapsules according to claim (1), wherein the aldehyde resin initial condensate is an aminoaldehyde resin initial condensate. (3) The method for producing microcapsules according to claim (2), wherein the aminoaldehyde resin initial condensate is an anion-modified melamine-formaldehyde 41 fat M condensate. (4) The method for producing microcapsules according to items (1) to (3), wherein the water-soluble polymer having hydroxyl groups is polyvinyl alcohol or modified polyvinyl alcohol. (5) The anionic polymer having no hydroxyl group is a polymer or copolymer composed of anionic monomer units, or a copolymer of an anionic monomer unit and a hydrophobic monomer unit. 4) The method for producing microcapsules as described in section 4).