JPS5876138A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To easily obtain a microcapsule excellent in holdability of a hydrophobic core substance, in preparing the microcapsule having an aminoaldehyde polycondensation resin as the cell membrane thereof, by incorporating an oil soluble polyhydric phenol compound in hydrophobic core substance. CONSTITUTION:In preparing a microcapsule enclosing a hydrophobic core substance by subjecting an aminoaldehyde resin to polycondensation in a hydrophilic medium containing a colloidal substance, an oil soluble polyhydric phenol compound is contained in the hydrophobic core substance. The oil soluble polyhydric phenol compound is one shown by formulaIwherein R1 is H, OH or alkoxy, R2 is saturated or unsaturated 1-18C alkyl, aryl having a benzene ring and a naphthalene ring as base skeleton or substituents shown by formulae II-IV (wherein R3-R5 are same alkyl or aryl as described above). By this method, a polycondensation resin is deposited on the surface of the capsule core substance in good efficiency and a uniform capsule cell membrane free from stress is formed and the capsule excellent in holdability of the core substance is obtained.

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. 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 copying paper.

Various methods are known for producing microcapsules, such as coacervation, interfacial polymerization, and 1n-sizu polymerization.Among them, microcapsules having aminoaldehyde polycondensation resin as a wall film have water resistance, Various encapsulation methods have been proposed due to their excellent moisture resistance.

For example, U.S. Pat. A method of forming a wall film by reacting a urea-formaldehyde resin prepolymer in a suspension containing no agent has been proposed. However, in this encapsulation method, since the polycondensation resin is not efficiently deposited on the surface of the capsule core material, it is necessary to extremely carefully control the preparation conditions, such as the addition of dilution water. In JP-A-51-9079, in order to improve the efficiency of depositing polycondensation resin on the surface of the capsule core material, a monomer is used as a starting material, a prepolymer is produced in a capsule manufacturing system under acidic conditions, and A method of forming a capsule wall film by continuously proceeding with polycondensation has also been proposed, but only a wall film with insufficient strength against heat or solvents is formed. Incidentally, JP-A No. 51-9079 proposes adding polyhydric phenols such as resorcinol and orcin into a hydrophilic medium for the purpose of modifying the capsule wall membrane. However, the ability of the capsules to retain the core material is not sufficient, and in particular, compounds with strong surface activity such as aromatic carboxylic acids and their polyvalent metal salts, or hydrophobic substances containing them, cannot be encapsulated into microcapsules. If covered by law,
The retention of the core material becomes extremely poor.

In view of the current situation, the present inventors conducted intensive research on a method for easily manufacturing microcapsules having an aminoaldehyde polycondensation resin as a wall membrane, and found that capsules with excellent retention of capsule core substances can be easily manufactured. The inventors have discovered that extremely excellent effects can be obtained by incorporating an oil-soluble polyhydric phenol compound into a hydrophobic core material, and have achieved the present invention.

The present invention involves dispersing a hydrophobic core substance containing an oil-soluble polyhydric phenol compound and polycondensing an aminoaldehyde resin in a hydrophilic medium containing a colloidal substance.
A method for producing microcapsules is characterized in that the hydrophobic core substance is encapsulated.

As a colloidal substance used in the present invention.

are anionic colloid substances, cationic colloid substances,
Examples of anionic colloid substances include natural polymers such as gum arabic, carrageenan, sodium alginate, pectic acid, gum tragacanth, almond gum, and agar, carboxymethyl cellulose, sulfated cellulose, and sulfated Semi-synthetic polymers such as methylcellulose, carboxymethyl starch, phosphorylated starch, acrylic acid, methacrylic acid, crotonic acid,
Examples include various polymers containing anionic monomer units such as itaconic acid, maleic acid, and vinylbenzenesulfonic acid, partial amides or partial esters of such polymers, and synthetic polymers such as anion-modified polyvinyl alcohol. It will be done.

Examples of cationic colloidal substances include cationically modified polyvinyl alcohol, and examples of nonionically modified colloidal substances include polyvinyl alcohol and hydroxyethyl cellulose.

Such a colloidal substance may contain 1 as appropriate depending on the core substance to be encapsulated.
Synthetic anionic colloidal substances having both a hydrophobic and a bulk unit are used, especially when encapsulating a hydrophobic liquid as a core substance in a capsule, because they have excellent stability in the emulsification process. Preferably used.

Among them, hydrophobic monomer units (preferably 5 to 60 mol%
, preferably 10 to 50 mol%) and acrylic acid,
Carboxylic acid monomer units such as methacrylic acid, crotonic acid, itaconic acid, maleic acid (preferably 1 to 95
Particularly preferably used are synthetic anionic colloidal substances having a mol %, preferably 2 to 85 mol %.

In addition, these colloidal substances are contained in an aqueous medium at a concentration of 0.2% by weight.
The content is preferably 0.5% by weight or more, most preferably 1.5% by weight or more from the viewpoint of ease of capsule preparation and quality of the obtained capsules. The upper limit of the amount to be used is determined depending on economic efficiency, the viscosity of the yarn, the cabbage preparation equipment, etc.; it is generally kept at 20% by weight or less.

In addition, the hydrophilic medium containing the colloidal substance contains polyhydric phenols such as resorcin and orcin described in JP-A No. 51-9079, or m as described in JP-A-56-78626. Microcapsules with even better retention properties can be obtained by containing m-substituted monophenols such as -methoxyphenol.

The method of the present invention has an extremely important feature in that the hydrophobic core substance contains an oil-soluble polyhydric phenol compound. It is a compound represented by the formula.

[In the formula, melon represents a hydrogen atom, a hydroxyl group, or an alkoxy group such as a methquine group or an ethoxy group, and R2 represents a saturated or unsaturated alkyl group having 1 to 18 carbon atoms, a benzene ring, or a naphthalene ring as the basic skeleton. represents an aryl group, or a substituent represented by the following general formulas (a), (b), or (C).

(Rs, R4, and Rs each represent an alkyl group or an aryl group having the same meaning as above.) Among these, gallic acid esters represented by the following general formula are particularly effective in obtaining the desired effects of the present invention extremely efficiently. Therefore, it is the most preferred polyhydric phenol compound.

(In the formula, R4 has the above-mentioned meaning.) In the present invention, even if the oil-soluble polyhydric phenol compound is not completely dissolved in the hydrophobic core substance, it is retained as long as it is partially dissolved. Although it has the effect of improving properties, it is preferable that it is completely dissolved. The amount of the oil-soluble polyhydric phenol compound to be used is appropriately adjusted depending on the solubility of the compound in the hydrophobic core material and economic efficiency, but generally it is 0.01% by weight or more based on the hydrophobic core material. Preferably 0.2
% or more by weight is used. However, in consideration of economic efficiency, etc., it is desirable to limit the amount to 5% by weight or less.

In the present invention, the aminoaldehyde polycondensation resin used to cover the surface of the hydrophobic core substance includes, for example, urea,
Thiourea, alkyl urea, ethylene urea, acetoguanamine, benzoguanamine, melamine, guanidine, dicyandiamide, biuret, cyanamide, and other amines such as formaldehyde, acetaldehyde, parafo V formaldehyde Y1 hexamethylenetetramine, butyraldehyde , refers to a resin obtained by polycondensation or copolycondensation of one or more aldehydes such as crotonaldehyde, benzaldehyde, geltaraldehyde, glyoxal, and furfural.
Among these, the effects of the present invention are particularly noticeable in the case of resins containing melamine and formaldehyde as at least one component.

These aminoaldehyde resin wall materials are added to a hydrophilic medium in the form of monomers or prepolymers, and the polycondensation reaction proceeds by adjusting the capsule manufacturing thread to an acidic pH range, preferably from 2 to 6. It will be done. At that time, in order to maintain the capsule manufacturing system acidic, for example, formic acid, acetic acid, citric acid, oxalic acid, para-toluenesulfonic acid,
So-called acid catalysts commonly used in the field of aminoaldehyde resin production, such as sulfamino acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, ammonium sulfate, and ammonium hydrochloride, are used, but in the present invention, anionic colloidal substances coexisting in the system are used. Of course, it is also possible to utilize the acid groups contained in the . The polycondensation reaction of acetaldehyde resin is promoted by heating the thread, so it is preferable to heat the thread to a temperature of 20 to 100°C, especially in the range of 35 to 70°C, the quality is stable. This is more preferred because the capsules are formed in a relatively short time.

Further, in the capsule manufacturing system of the present invention, ordinary protective colloid agents, surfactants, etc. are used in combination as necessary.

However, the amount used must be kept within a range that does not inhibit the desired effects of the present invention.

Thus, according to the method of the present invention, the polycondensation resin can be efficiently converted to Turnip 7 by simply incorporating an oil-soluble polyhydric phenol compound into the hydrophobic core substance and providing simple polycondensation conditions in the presence of a colloidal substance. It is deposited on the surface of the y-core material, forming a uniform capsule wall film without distortion, and providing capsules with excellent core material retention. Well, aromatic power! This effect is most noticeable when a compound with strong surface activity, such as levonic acid or its polyvalent metal salt, or a hydrophobic substance containing the compound is coated.

Although the reason for such effects is not clear, the hydroxyl groups of the oil-soluble polyhydric phenol compound contained in the core material are oriented toward the hydrophilic medium and reach the surface of the core material of the aminoaldehyde polycondensation resin. It is thought that this does not increase the storage efficiency of the product.

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, vegetable oils such as olive oil, peanut oil, linseed oil, soybean oil, castor oil, petroleum, mineral oils such as kerosene, xylene, toluene, etc., alkyl-substituted diphenylalkanes, alkyl Substituted naphthalene, diphenylethane, methyl salicylate, ethyl adipate, di-n-butyl adipate,
Synthetic oils such as di-octyl adipate, di-methyl phthalate, diethyl phthalate, di-n-butyl phthalate, di-octyl phthalate, benzyl alcohol, etc. liquid insoluble in water,
Water-insoluble metal oxides and salts, fibrous materials such as cellulose or anubest, water-insoluble synthetic polymeric materials, minerals, pigments, glasses, fragrances, flavors, fungicidal compositions, Physiological compositions, fertilizer compositions.

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 to these.

It's not. Further, unless otherwise specified, parts and percentages in the examples represent parts by weight and percentages by weight, respectively.

Example 1 A 3.3% aqueous solution of ethylene/maleic anhydride copolymer (trade name EM4-3.1, manufactured by Monsanto) was added to a stirring mixing vessel equipped with a heating device, and a 20% aqueous solution of caustic soda was added thereto. The pH was adjusted to 4.0 to obtain an aqueous medium for capsule production.

Separately, 100 parts of alkylnaphthalene (trade name: KMC oil, manufactured by Kenbetsu Kagaku Co., Ltd.) was added to
) 15 parts of zinc salicylate and 1 part of lauryl gallate were dissolved to prepare 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 this system was raised to 60°C.

Separately, 10 parts of mewomine was added to 30 parts of a 37% formaldehyde aqueous solution and reacted at 60° C. for 15 minutes to prepare a prepolymer aqueous solution.

After dropping this prepolymer aqueous solution into the emulsion,
The mixture was heated to 70° C. with gentle stirring, kept warm for -3 hours, and then allowed to cool to obtain a capsule dispersion of opalescent males.

Example 2 0.5 amyl gallate instead of 1 part lauryl gallate
A capsule dispersion was obtained in exactly the same manner as in Example 1) except that

Example 3 A capsule dispersion was obtained in exactly the same manner as in Example 1) except that 1.0 part of lauryl protocatechuate was used instead of 1 part of lauryl gallate.

Comparison Example 1 Example 1 except that 1 part of lauryl gallate was not used
A capsule dispersion was obtained in exactly the same manner as above.

Performance comparison tests were conducted on the four types of capsule dispersions thus obtained according to the following method. That is, 20 parts of cellulose powder, -
A capsule coating solution obtained by adding 100 parts of a 2% hydroxymethylcellulose aqueous solution was coated on a 40f/vf base paper to a dry coating amount of 4f/ft and dried to obtain an upper sheet for pressure-sensitive copying paper.

Created a paper.

Separately, carboxy-modified styrene and 20 parts of butadiene copolymer latex (solid content)
The coating solution prepared by adding the above was applied to a 40 f/d base paper to a dry weight of 5 g/g, and dried to prepare a lower sheet for pressure-sensitive copying paper.

Furthermore, on the back side of the above-mentioned bottom paper, the four types of Turnip 7 V mentioned above were added.
The coating liquid was applied and dried to a dry weight of 4 f/r/f to prepare a middle sheet for pressure-sensitive copying paper.

Using the top paper, middle paper, and bottom paper obtained in this way, performance comparison tests were conducted on the following items, and the results were summarized in the first paper.
It is listed in the table.

1. Heat-resistant top paper and bottom paper are stacked so that the coated surfaces are facing each other, and heated to 115℃ with a load of 5 kg/cm2 applied.
The paper was left in a heat treatment machine for 3 hours, and the degree of colored staining on the coated surface of the lower paper was determined.

26 Solvent-resistant middle paper was left in a saturated atmosphere of trichlorethylene at room temperature for 10 hours, and the degree of colored staining on the coated surface of the bottom paper was determined.

Table 1 (Notes) Judgment criteria ○... No practical problems at all ×...
・It is extremely dirty and is not suitable for practical use.

Patent applicant: Kanzaki Paper Co., Ltd. 25

Claims (2)

[Claims] (1) In a microencapsulation method in which a hydrophobic core material is encapsulated by polycondensing an aminoaldehyde resin in a hydrophilic medium containing a colloidal substance, an oil-soluble polyhydric phenol compound is contained in the hydrophobic core material. A method for producing microcapsule V, characterized by: (2) The production method according to claim (1), wherein the oil-soluble polyhydric phenol compound is gallic acid entel.