JPS6246211B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for manufacturing microcapsules containing a hydrophobic core material, and more particularly to a method for extremely easily manufacturing capsules with excellent retention of the capsule core material. In recent years, microencapsulation technology has made remarkable progress, and the fields of use of these microencapsulated products are extremely wide and diverse, including pressure-sensitive copying paper. Various methods are known for manufacturing microcapsules, such as coacervation method, interfacial polymerization method, and in-situ polymerization method.Among them, microcapsules having aldehyde polycondensation resin as a wall film are water resistant, Due to its excellent moisture resistance, various encapsulation methods have been proposed, such as U.S. Pat.
No. 57892, JP-A-51-9079, JP-A-52-66878
No., JP-A-53-84881, JP-A-53-84882, JP-A-53-84883, JP-A-54-25277, JP-A-54
-49984, JP-A-54-53679, JP-A-54-
No. 85184, JP-A-54-85185, JP-A-54-107881
No., JP-A-55-8856, JP-A-55-15660, JP-A-55-47139, JP-A-55-51431, JP-A-55
−67329, JP-A-55-92135, JP-A-55-
No. 132631, Japanese Patent Application Publication No. 152546, Japanese Patent Application Publication No. 1983-
No. 51238, JP-A-56-78626, JP-A-56-102934
No., JP-A-56-115634, JP-A-56-155636,
Examples include JP-A-57-110332, JP-A-57-135038, and JP-A-57-147429. 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 ^- ...Fe ⁺³ or P
−S ^- …Fe When enveloping compounds with strong surface activity such as organophosphorus iron () compounds having ⁺³ bonds or hydrophobic core materials containing these, the retention of the core material is insufficient. It has the disadvantage of being. As a result of intensive research into a method for encasing such highly surface-active core substances with good retention in microcapsules using aldehyde polycondensation resin as a wall membrane, the present inventors found that oil-soluble aromatic The present inventors have discovered that extremely excellent effects can be obtained by incorporating a monoamino compound 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, which is characterized by containing an oil-soluble aromatic monoamino compound in a hydrophobic core material. In the present invention, the oil-soluble aromatic monoamino compound used is not necessarily limited to these, but specific examples include aniline,
Unsubstituted aromatic primary amines such as α-naphthylamine and β-naphthylamine; N-methylaniline, N-ethylaniline, N-n-propylaniline, N-n-butylaniline, N-i-amylaniline, diphenylamine , N,N-dimethylaniline, N,N-diethylaniline, N,N-
Unsubstituted aromatic secondary and tertiary amines such as di-i-amylaniline; o-toluidine, m-toluidine, p-toluidine, p-ethylaniline, p
-isopropylaniline, o-nitroaniline,
m-nitroaniline, p-nitroaniline, o
- Chloraniline, m-chloroaniline, p-chloroaniline, p-bromoaniline, p-aminophenol, o-anisidine, p-anisidine,
Substituted aromatic primary amines such as p-phenetidine;
Substituted aromatic secondary and tertiary amines such as N,N-dimethyl-m-toluidine and N-ethyl-o-toluidine; and further examples include methylrolled products or methylol etherified products of the above amines. Among these, aniline in particular can achieve the desired effects of the present invention extremely efficiently;
The most preferred oil-soluble aromatic monoamino compound. In the present invention, even if the oil-soluble aromatic monoamino compound is not completely dissolved in the hydrophobic core substance, it will have the effect of improving retention if it is partially dissolved, but it is not completely dissolved. 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, economic efficiency, and the purpose of use of the capsule, but generally 0.01 weight per weight of the hydrophobic core material. % or more, preferably 0.2% or more by weight. However, in consideration of economical efficiency, it is desirable to limit its use 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 hydrophobic core substances to be encapsulated in microcapsules are particularly suitable for The present invention is not limited to this, and it is also possible to encapsulate a hydrophobic substance as described below with good retention properties, if necessary, containing, for example, a conventional electron-donating color former, electron-accepting color developer, or the like. 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, triarylmethane,
Aromatic hydrocarbons such as diphenylalkanes,
Alcohols such as oleyl alcohol, tridecyl alcohol, benzyl alcohol, 1-phenylethyl alcohol, glycerin, organic acids such as oleic acid, dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, dioctyl phthalate, diethyl adipate, adipine Esters such as di-n-butyl acid and dioctyl adipate, organic phosphorus compounds such as tricresyl phosphate, tributyl phosphate, tributyl phosphite, and tributyl phosphine oxide, phenyl cellosolve, benzyl carbitol, polypropylene glycol, Ethers such as propylene glycol monophenyl ether,
Amines such as trioctylamine, stearyldimethylamine, dilaurylamine, α-ethylhexylamine, N,N-dimethylraumide,
Examples include amides such as N,N-dimethylstearamide and N,N-dihexyl octylamide, and ketones such as diisobutyl ketone and methylhexyl ketone. In the present invention, the aldehyde polycondensation resin used to cover the surface of the hydrophobic core material includes, for example, urea, thiourea, alkyl urea, ethylene urea, acetoguanamine, benzoguanamine, melamine, guanidine, dicyandiamide, biuret, and cyanamide. amines such as phenols, resorcinol, orcin, and one or more compounds belonging to phenols such as phenols, resorcinols, orcines, and formaldehyde, acetaldehyde, paraformaldehyde, hexamethylenetetramine, butyraldehyde, crotonaldehyde, benzaldehyde, glutaraldehyde, glyoxal, furfural, etc. It means a resin obtained by polycondensation or copolycondensation of one or more aldehydes. 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 resins such as those described in JP-A No. 55-67329 are used. Examples of the anion modifier include sulfamic acid, sulfanilic acid, glycolic acid, glycine, acidic sulfites, phenol sulfonate, and taurine. These aldehyde resin wall materials are added in the form of monomers or prepolymers to water or a hydrophilic medium, and the polycondensation reaction is carried out by adjusting the capsule manufacturing system to an acidic pH range, preferably 2 to 6. Proceed. At that time, in order to maintain the capsule production system acidic, for example, 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 aldehyde resin production is used. In addition, since the polycondensation reaction of aldehyde resin is accelerated by heating the system,
Preferably, the system is heated to a temperature of 100°C. In particular, a temperature range of 35 to 80°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 natural polymers such as gum arabic, carrageenan, sodium alginate, pectic acid, gum tragacanth, almond gum, agar, etc.
Semi-synthetic polymers such as carboxymethylcellulose, sulfated cellulose, sulfated methylcellulose, carboxymethyl starch, phosphorylated starch, acrylic acid, methacrylic acid, crotonic acid, itaconic acid,
Polymers of maleic acid, vinylbenzenesulfonic acid, vinylsulfonic acid, etc., as well as these anionic monomer units and ethylene, propylene,
Various polymers represented by copolymers with hydrophobic monomer units such as isobutylene, styrene, methyl vinyl ether, vinyl acetate, acrylic esters, methacrylic esters, itaconic esters, etc., and partial amides or partial esters of such polymers. and synthetic polymers such as anion-modified polyvinyl alcohol as described in JP-A No. 55-92135. As a cationic polymer emulsifier, for example, JP-A-Sho
Examples of nonionic polymer emulsifiers include cationically modified polyvinyl alcohol as described in No. 57-110332, and examples of nonionic polymer emulsifiers include polyvinyl alcohol, starch,
Examples include hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, and the like. In addition, as a low-molecular emulsifier, for example, organic sulfuric acid or organic phosphoric acid having a total carbon number of 1 to 14,
Examples include Li ⁺ , Na ⁺ , K ⁺ , NH ₄ ⁺ salts, and specifically, sodium vinylsulfonate, sodium benzenesulfonate, sodium benzenesulfinate, sodium p-toluenesulfonate, p-
Sodium toluenesulfinate, sodium p-vinylbenzenesulfonate, sodium p-i-amylbenzenesulfonate, naphthalene-α-
Sodium sulfonate, sodium naphthalene-β-sulfonate, sodium 2-methylnaphthalene-6-sulfonate, 2,6-dimethylnaphthalene-
Sodium 8-sulfonate, Sodium 2,6-dimethylnaphthalene-3-sulfonate, Sodium 1-naphthol-4-sulfonate, Sodium benzene-m-disulfonate, Sodium diphenyl phosphate, Sodium phenyl phosphonate,
Examples include sodium di-n-butyl phosphate and sodium di-i-amyl phosphate. 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 emulsifier is anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, polyvinyl alcohol, gum arabic, When using a polymer emulsifier having a hydroxyl group such as carboxymethyl cellulose, or
This is noticeable when these polymeric emulsifiers having hydroxyl groups and the above-mentioned low molecular weight emulsifiers are used together. It is effective to use 2 to 12 sulfonate salts together. It should be noted that these emulsifiers are preferably contained in water or a hydrophilic medium in an amount of 0.2% by weight or more, and from the viewpoint of ease of capsule preparation and quality of the capsules obtained, the content of these emulsifiers is 0.5% by weight or more, most preferably 1.5% by weight.
Contained above. The upper limit of the amount used is determined depending on economics, system viscosity, capsule preparation equipment, 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, forming 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, 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 Anion-modified polyvinyl alcohol (trade name Gosenal T) was placed in a stirring mixing vessel equipped with a heating device.
150 parts of a 4% aqueous solution of Nippon Gosei Kagaku Co., Ltd.) was added to prepare an aqueous medium for capsule production. Separately, add lauryl gallate to a mixed solvent of 50 parts of di-n-butyl adipate and 50 parts of diethyl adipate.
15 parts and 2 parts of aniline were dissolved to form a capsule core material. This core material was added to the above aqueous medium with an average particle size of 5.0.
After emulsifying and dispersing the mixture so as to have a particle size of μ, the temperature of this 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 further added and reacted for 1 minute to prepare an aqueous prepolymer solution. After dropping this prepolymer aqueous solution into the emulsion, it was heated to 70°C while stirring, and then
1.0N hydrochloric 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 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 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 anion-modified polyvinyl alcohol T-350 as the aqueous medium for capsule production. Ta. Example 3 A capsule dispersion was prepared in the same manner as in Example 1, except that 8 parts of sodium vinyl sulfonate was dissolved in 170 parts of a 1.2% aqueous solution of anion-modified polyvinyl alcohol T-350 as the aqueous medium for capsule production. Obtained. Example 4 A capsule dispersion was obtained 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. Ta. Example 5 1.3% polyvinyl alcohol (trade name PVA-217, manufactured by Kuraray) as an aqueous medium for capsule production
8 parts of sodium styrene sulfonate in 150 parts of aqueous solution
A capsule dispersion liquid was obtained in the same manner as in Example 1, except that a solution containing 100% of the total amount of the capsules was used. Example 6 Polyvinyl alcohol (trade name PVA-217-EE, manufactured by Kuraray) as an aqueous medium for capsule production
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 . Example 7 A capsule dispersion was obtained in the same manner as in Example 1, except that 2 parts of p-iso-propylaniline was added instead of 2 parts of aniline. Example 8 A capsule dispersion was obtained in the same manner as in Example 1, except that 2 parts of o-toluidine was added instead of 2 parts of aniline. Creating the bottom sheet: Stir an aqueous solution prepared by dissolving 135 parts of ferric chloride in 1000 parts of water into 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. Add below,
Precipitated diphenyl phosphate and tert-
A complex iron salt of butylbenzoic acid was produced, and after filtration and washing, it was dispersed in water to obtain a pale colored slurry with a concentration of 10%. Separately, 1 part of sodium polyacrylate and 1 part of hydroxyethylcellulose were dissolved in 80 parts of water, and 30 parts of titanium oxide and 60 parts of calcium carbonate were added thereto.
After strong dispersion, 15 parts of carboxy-modified styrene-butadiene copolymer latex (solid content concentration 50%) was added to the dispersion to obtain a pigment dispersion. Next, the above iron salt slurry and pigment dispersion were mixed in a two-component injection format to form a coating solution, and the mixture was rolled onto a 40 g/m ² paper so that the dry weight was 5 g/m ² . A base paper was obtained by smearing with a blade coater. Evaluation 50% of a 10% starch aqueous solution was added to each of the capsule dispersions obtained in Examples 1 to 8 and Comparative Example 1.
part, 10% polyvinyl alcohol (PVA-217)
10 parts aqueous solution, 20 parts wheat starch powder, pulp powder
Add and mix 10 parts and further dilute with water to reach a solid concentration of 18
% coating liquid, 6 g/ ^m2 dry weight on 40 g/m2 paper.
The upper paper was obtained by smearing with an air knife coater so that the thickness was ² m2. 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.

[Table] As is clear from the results in Table 1, all pressure-sensitive copying papers using microcapsules obtained by the method of the present invention were excellent in core substance retention.

Claims (1)

[Scope of Claims] 1. 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, a reactant is formed with the aldehyde compound. 1. A method for producing microcapsules, the method comprising containing an oil-soluble aromatic monoamino compound in 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 1, wherein the aldehyde polycondensation resin is a urea-formaldehyde resin. 4. Claim 1, wherein the aldehyde polycondensation resin is an anion-modified melamine-formaldehyde resin.
2. Method for producing microcapsules as described in Section 1. 5. The method for producing microcapsules according to claims 1 to 4, wherein the aromatic monoamino compound is aniline.