JPS59162943A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To easily obtain a microcapsule excellent in the holdability of a core substance, by a method wherein an oil soluble aromatic monoamine compound is contained in a hydrophobic core substance and the resulting mixture is encapsulated with an aldehyde polycondensed resin. CONSTITUTION:Water or a hydrophilic medium containing an emulsifier such as anion modified polyvinyl alcohol is prepared. A hydrophobic core substance comprising diethyl adipate in which an oil soluble aromatic amino compound such as anilin is emulsified and dispersed in the above mentined medium. An aqueous solution of a prepolymer comprising formaldehyde and melamine or urea is dripped in this system and an aldehyde polycondensed resin is formed to enclose the hydrophobic core substance to obtain a dispersion for a microcapsule. The microcapsule prepared by using said dispersion is excellent in the holdability of the core substance and can be used in various fields such as pressure sensitive copy paper.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for manufacturing microcapsules containing a hydrophobic core material, and in particular to a method for extremely easily manufacturing capsules with excellent retention of a capsule core material. It is.

In recent years, microcapsule technology has made remarkable progress, and the fields of use of these microcapsules are extremely wide and diverse, including pressure-sensitive duplexes and I'i' papers.

Various methods are known for manufacturing microcapsules, such as coacervation, interfacial polymerization, and 1n-situ polymerization, but among them, microcapsules with aldehyde polycondensation resin as a wall film are water resistant and moisture resistant. Various encapsulation methods have been proposed, such as U.S. Patent No. 3016308 and Japanese Patent Publication No. 47
(2) = No. 51714, Japanese Patent Application Publication No. 1972-57892, Japanese Patent Application Publication No. 1973
No. 1-9079, JP-A-52-66878, JP-A-Sho 5
3-84881, JP 53-84882, JP 53-84883, JP 54-25277, JP 5.1-49984, JP 54-53679,
JP-A-54-85184, JP-A-54-85185, JP-A-54-107881, JP-A-55-8856
No., JP-A-55-15660, JP-A-55-4713
No. 9, JP-A-55-51431, JP-A-55-673
No. 29, JP-A-55-92135, JP-A-55-13
No. 2631, JP-A-55-152546, JP-A-56
-51238, JP-A-56-78626, JP-A-5
6-102934, JP 56-115634, JP 56-155636, JP 57-110332
No., JP-A-57-135038, JP-A-57-147
No. 429, etc.

However, although many encapsulation methods have been developed and proposed, aromatic carboxylic acids and their polyvalent metal salts, ligand compounds having a phenolic hydroxyl group, or p-o- ...Fewa or P-8
-... When covering a compound with strong surface activity such as a till iron (Tll) compound having an "Fe" bond, or a hydrophobic core material containing these, the retention of the core material is The disadvantage is that it is insufficient.

As a result of intensive research into a method for encapsulating such highly surface-active core substances with good retention in microcapsules using aldehyde polycondensation resin as a wall film, the present inventors discovered that oil-soluble aromatic monoamino compounds The present inventors have discovered that extremely excellent effects can be obtained by incorporating this into a hydrophobic core material, and have achieved the present invention.

The present invention provides a method for forming a reactant with an aldehyde compound in a microencapsulation method in which a hydrophobic core material is encapsulated by polycondensing an aldehyde polycondensation resin in water or a hydrophilic medium containing an emulsifier. This is a method for producing microcapsules characterized by containing an oil-soluble aromatic monoamino compound in a hydrophobic core material.

(4) In the present invention, the oil-soluble aromatic monoamino compound used is not necessarily limited to these, but specific examples include aniline, α-naphthylamine,
Unsubstituted aromatic-grade amines such as β-naphthylamine;
N-methylaniline, N-ethylaniline, N-n-propylaniline, N-n-butylaniline, N-4-amylaniline, diphenylamine, N,N-dimethylaniline, N,N-dimethylaniline, N,N -G1-
Unsubstituted aromatic secondary and tertiary amines such as amylaniline; o-toluidine, m-1-luidine, p-)luidine, p-ethylaniline, p-isopropylaniline,
0-nitroaniline, m-nitroaniline, p-nitroaniline, o-chloroaniline, m-chloroaniline,
Substituted aromatic-grade amines such as p-chloroaniline, p-bromoaniline, p-aminophenol, O-anisidine, p-anisidine, and p-phenetidine i1"J, N-
Substituted aromatic secondary and tertiary amines such as dimedyl-m-)luidine and N-ethyl-o-toluidine; (5) Furthermore, examples include methylolated products or methylol etherified products of the amines listed below.

Among these, aniline is the most preferred oil-soluble aromatic monoamino compound because it can extremely efficiently achieve the desired effects of the present invention.

In the present invention, even if the oil-soluble aromatic monoamino compound is not completely dissolved in the hydrophobic core substance, if it is partially dissolved, the oil-soluble aromatic monoamino compound will have the effect of improving the retention property. is preferable.

The amount of the oil-soluble aromatic monoamino compound to be used is appropriately adjusted depending on the compound's solubility in the hydrophobic core material, economical efficiency, and the purpose of use of the capsule, but generally it is 0.0000% relative to the hydrophobic core material. 01% by weight or more, preferably 0
．． It is used in an amount of 2% by weight or more.

However, considering economic efficiency and the like, it is desirable to limit the amount to 10% by weight or less.

According to the method of the present invention, even core substances with strong surface activity can be encapsulated with excellent retention as described above, but the hydrophobic core substances to be encapsulated in microcapsules (6) However, the present invention is not particularly limited to these, and it is also possible to encapsulate a hydrophobic substance as described below with a good retention property by containing, for example, a conventional electron-donating color former, electron-accepting color developer, etc., if necessary. In addition, the above-mentioned substances with strong surface activity can also be encapsulated by being dissolved or dispersed in the following hydrophobic substances, if necessary.

Hydrophobic substances used here include vegetable oils such as cottonseed oil, kerosene, paraffin, naphthenic oil, mineral oils such as chlorinated paraffin, alkylated bisphenyl, alkylated terphenyl, alkylated naphthalene, diarylethane, and triaryl. Aromatic hydrocarbons such as methane and diphenylalkane, alcohols such as oleyl alcohol, tridecyl alcohol, benzyl alcohol, 1-phenylethyl alcohol, and chrycerin, organic acids such as oleic acid, dimethyl phthalate 1-, and diethyl phthalate. , di-n-butyl phthalate, dioctyl phthalate, diethyl adipate, di-n-butyl adipate, dioctyl adipate and other esters (7), tricresyl phosphate, tributyl phosphate, tributyl phosphate, tributylphosphine oxide, etc. organic phosphorus compounds, phenyl cellosolve, pendyl carbitol, polypropylene glycol,
Ethers such as propylene glycol monophenyl ether, amines such as trioctylamine, stearyldimethylamine, dilaurylamine, α-ethylhexylamine, N,N-dimethylraumide, N,N-dimethylstearamide, N,N - Amides such as dihexyl octylamide, ketones such as diisobutyl ketone and medylhexyl ketone, and the like are exemplified.

In the present invention, the aldehyde polycondensation resin used to cover the surface of the hydrophobic core substance includes, for example, urea, thiourea, alkyl urea, ethylene urea, acetoguanamine,
One or more (8) compounds belonging to amines such as benzoguanamine, melamine, guanidine, dicyandiamide, biuret, and cyanamide, and phenols such as phenol, resorcinol, orcin, and formaldehyde, acetaldehyde, paraformaldehyde, hexamethylenetetramine,
It refers to a resin obtained by polycondensation or copolycondensation of one or more aldehydes such as butyraldehyde, crotonaldehyde, benzaldehyde, geltaraldehyde, glyoxal, and furfural. Among these, the effects of the present invention are more noticeable in the case of resins containing melamine, urea, and formaldehyde as at least one component. Among these, the effects of the present invention are particularly remarkable when anion-modified melamine-formaldehyde+j()IN as described in JP-A No. 55-67329 is used.

Examples of anionic modifiers include sulfamic acid, sulfanilic acid, glycolic acid, glycine, acidic sulfite, sulfonic acid phenol, and taurine.

These aldehyde resin wall materials are added in the form of monomers or prepolymers to water or a hydrophilic medium (9), and a polycondensation reaction is carried out by adjusting the capsule production system in the acidic, more preferably pH range of 2 to 6. is proceeding. At this time, in order to maintain the capsule production system acidic, aldehydes such as formic acid, acetic acid, citric acid, oxalic acid, para-toluenesulfonic acid, sulfamic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, ammonium sulfate, aluminum hydrochloride, etc. A so-called acid catalyst commonly used in the field of resin production is used. In addition, since the polycondensation reaction of aldehyde resin is promoted by heating the system, the
Preferably, the system is heated to a temperature of .degree. Especially 35-8
A temperature range of 0° C. is more preferable because capsules with stable quality can be formed in a relatively short time.

Examples of the emulsifier used in the present invention include polymer emulsifiers such as anionic polymer emulsifiers, cationic polymer emulsifiers, and nonionic polymer emulsifiers, and low-molecular emulsifiers. Examples of anionic polymer emulsifiers include gum arabic, carrageenan, sodium alginate, pectic acid, gum tragacanth, (10) natural polymers such as almond gum and agar, carboxymethyl cellulose, sulfated cellulose, sulfated methyl cellulose, carboxymethyl starch, Semi-synthetic polymers such as phosphorylated starch and polymers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, vinylbenzenesulfonic acid and vinylsulfonic acid, as well as anionic monomer units of these and ethylene and propylene , isobutylene, styrene, methyl vinyl ether, vinyl acetate,
Various polymers typified by copolymers with hydrophobic monomer units such as acrylic esters, methacrylic esters, and itaconic esters, and partial amides or partial esters of such polymers, as disclosed in JP-A-55-92135. Examples include synthetic polymers such as anion-modified polyvinyl alcohol as described above.

Examples of cationic polymer emulsifiers include JP-A-57-1
Examples of nonionic polymer emulsifiers include polyvinyl alcohol, (11) starch, hydroxyethylcellulose, methylcellulose, and hydroxypropylmethylcellulose.

In addition, as a low-molecular emulsifier, for example, one having a total carbon number of 1 to 14
Li+ of organic sulfuric acid or organic phosphoric acid.

Examples include Na"+K"+Nuk"salt, specifically,
Sodium vinylsulfonate, sodium benzenesulfonate, sodium benzenesulfinate, sodium p-toluenesulfonate, sodium p-toluenesulfinate, sodium p-vinylbenzenesulfonate,
Sodium p-4-amylbenzenesulfonate, sodium naphthalene-α-sulfonate, sodium naphthalene-β-sulfonate, sodium 2-medylnaphculene-6-sulfonate, 2,6-dimethylnaphthalene-8-sulfone sodium acid, 2,6-dimethylnaphthalene-3-
Sodium sulfonate, sodium 1-naphthol-4-sulfonate, sodium benzene-m-disulfonate, sodium diphenyl phosphate, sodium phenylphosphonate, di-lobe (12), sodium di-amyl phosphate, etc. Can be mentioned.

Among these, the effect of improving inclusion retention caused by adding an oil-soluble aromatic monoamino compound to the hydrophobic core material is due to the fact that the emulsifying agent is anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, polyvinyl alcohol, gum arabic, and carboxymethyl cellulose. When using a polymer emulsifier having a water M group such as
Alternatively, it is noticeable when these polymer emulsifiers having hydroxyl groups and the above low-molecular emulsifiers are used together, and in particular, anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, polyvinyl alcohol is used as the polymer emulsifier, It is effective to use a sulfonate having a total carbon number of 2 to 12.

In addition, these emulsifiers have a concentration of 0.2% in water or a hydrophilic medium.
The content is preferably 0.5% by weight or more in terms of ease of capsule preparation and quality of the capsules obtained.
The content is most preferably 1.5% by weight (13)% or more. The upper limit of the amount used is determined depending on economic efficiency, system viscosity, capsule 11 rill device, etc., but is generally kept at 30% by weight or less.

Thus, according to the method of the present invention, by simply incorporating an oil-soluble aromatic monoamino compound into a hydrophobic core material and providing simple polycondensation conditions in the presence of an emulsifier, the polycondensation resin can efficiently form a capsule core. It is deposited on the material surface to form a uniform capsule wall film without distortion, resulting in capsules with excellent core material retention. In particular, as mentioned above, this effect is remarkable when a compound with strong surface activity covers a hydrophobic substance containing the compound.

Although the reason for such effects is not clear, the amino groups of the oil-soluble aromatic monoamino compound contained in the core material are oriented toward the hydrophilic medium, and the surface of the core material of the aldehyde polycondensation resin is It is thought that the aromatic monoamino compound may increase the deposition efficiency with the aldehyde, or the aromatic monoamino compound may react with the aldehyde to form the inner film.

In order to more specifically explain the method of the present invention (14), examples will be described below regarding the case where it is applied to the field of pressure-sensitive copying paper, but it 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 K.K.) was added to a stirring mixing vessel equipped with a heating device to prepare an aqueous medium for capsule production.

Separately, 15 parts of gallic acid 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 prepare a capsule core material.

This core material was emulsified and dispersed in an aqueous medium so that the average particle size was 5.0 μm, and 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. Thereafter, 1 part of glycine was further added and reacted for 1 minute to prepare a prepolymer aqueous solution tI'liI.

(15) After dropping this prepolymer aqueous solution into the emulsion,
Warm to 70°C with stirring, then 1-ON3
L! Acid was added dropwise to adjust the pH of the system to 4.5, and the mixture was kept warm for an additional 3 hours and then allowed to cool to obtain a milky white capsule dispersion.

Comparative Example 1 A capsule dispersion was obtained in the same manner as in Example 1 except that 2 parts of aniline was not added to the capsule core material.

Example 2 11 capsules were prepared in the same manner as in Example 1 except that 8 parts of sodium styrene sulfonate was dissolved in 11,150 parts of 1.3% water of anion-modified polyvinyl alcohol T-350 as the aqueous medium for capsule production. The liquid was obtained.

Example 3 The same procedure as in Example 1 was carried out (16) except that 8 parts of sodium vinyl sulfonate dissolved in 170 parts of a 1.2% aqueous solution of anion-modified polyvinyl alcohol T-350 was used as the aqueous medium for capsule production. A capsule dispersion was obtained.

Example 4 Capsules were dispersed in the same manner as in Example 1, except that 8 parts of sodium phenylphosphonate was dissolved in 150 parts of a 1.3% aqueous solution of anion-modified polyvinyl alcohol T-350 as the aqueous medium for capsule production. I got the liquid.

Example 5 Polyvinyl alcohol (
A capsule dispersion was obtained in the same manner as in Example 1, except that 8 parts of sodium styrene sulfonate was dissolved in 150 parts of a 1.3% aqueous solution of PVA-217 (trade name, manufactured by Kuraray Co., Ltd.).

Example 6 Polyvinyl alcohol (
1.3% of product name PVA-217-EE (manufactured by Kuraray)
A capsule dispersion was obtained in the same manner as in Example 1, except that 8 parts of sodium styrene sulfonate dissolved in 150 parts of an aqueous solution was used.

Example 7 (17) In place of 2 parts of aniline, 2 parts of p-iso-propylaniline
A capsule dispersion liquid was obtained in the same manner as in Example 1, except that 10% of the above-mentioned ingredients were added.

Example 8 A capsule dispersion was obtained in the same manner as in Example 1 except that 2 parts of o-)luidine was added instead of 2 parts of aniline.

An aqueous solution prepared by dissolving 135 parts of ferric chloride in 1000 parts of water to an aqueous solution prepared by adding 250 parts of diphenyl phosphate and 89 parts of tert-butylbenzoic acid to 1200 parts of a 5% aqueous solution of caustic soda. was added under stirring to produce a composite iron salt of diphenyl phosphate and tert-butylbenzoic acid as a precipitate, and after filtration and washing, it was dispersed in water to obtain a pale colored slurry with a concentration of 10 parts. .

Separately, dissolve 1 part of sodium polyacrylate and 1 part of hydroxyethylcellulose in 80 parts of water, and add 3 parts of titanium oxide to this.
After adding 0 parts of calcium carbonate and 60 parts of calcium carbonate and strongly dispersing, add 15 parts of Calhoki (18) silica-modified styrene-butadiene copolymer latex (solid content concentration 50%) to the dispersion liquid to prepare a pigment dispersion liquid. Obtained.

Next, the above iron salt slurry and pigment dispersion were mixed to form a coating liquid just before coating in a two-component injection format, and 40g/-
The following paper was coated with a rod blade coater to give a dry weight of 5 g/+d to obtain a base paper.

To the capsule dispersions obtained in Preparative Examples 1 to 8 and Comparative Example 1, 50 parts of a 10% starch aqueous solution, 10 parts of a 10% polyvinyl alcohol (PVA-217) aqueous solution, 20 parts of wheat starch powder, Add and mix 10 parts of pulp powder and further dilute with water to make a coating liquid with a solid content concentration of 18%.
0 g/rtrO paper was coated with an air knife coater to give a dry weight of 6 g/rd to obtain a top paper.

Next, the upper paper and lower paper obtained as described above were stacked and treated at 100°C for 2 hours, yielding the results shown in the table.

(19) (Note) Judgment criteria: ◎: Hardly clean.

O: Slightly dirty.

×: Not practical.

As is clear from the results in Table 1, all pressure-sensitive copying papers using 1 to 7 microcapsules produced by the method of the present invention had excellent core substance retention.

Patent applicant Kanzaki! i! ! Paper Co., Ltd. (20)

Claims (1)

[Claims] () In a microencapsulation method in which a hydrophobic core material is encapsulated by polycondensing an aldehyde polycondensation resin in water or a hydrophilic medium containing an emulsifier, the aldehyde compound and the reactant are 1. A method for producing microcapsules, which comprises incorporating an oil-soluble aromatic monoamino compound capable of forming into a hydrophobic core material. (2) The method for producing microcapsules according to claim (1), wherein the aldehyde polycondensation resin is a melamine-formaldehyde resin. (3) The method for producing microcapsules according to claim fi1, wherein the aldehyde polycondensation resin is a urea-formaldehyde resin. (4) The method for producing microcapsules according to Items 1 and 1, wherein the aldehyde polycondensation resin is an anion-modified melamine-formaldehyde resin. (1) (5) The method for producing microcapsules as described in Items 1 and 1. The method for producing microcapsules according to items (1) to (4).