JPS63134048A - Production of microcapsule - Google Patents

Abstract

PURPOSE:To uniformize the particle diameter of the title capsule by microcapsulizing a hydrophobic difficult-to-volatilize org. compd. with a urea- formaldehyde copolymer, a melamine-formaldehyde copolymer, etc., as the membrane forming material. CONSTITUTION:The hydrophobic difficult-to-volatilze org. compd. is emulsified in an aq. soln. of a acrylate-methacrylate copolymer. Urea and/or melamine and formaldehyde are added to the emulsion, the materials are polymerized at 2.5-6.0 pH to form the mixture of a urea-formaldehyde copolymer, a melamine-formaldehyde copolymer, or a urea-melamine-formaldehyde copolymer around the hydrophobic difficult-to-volatilize org. compd., and a microcapsule is produced. n-Octyl alcohol, lauryl caproate, cyclohexanone, etc., are exemplified as the hydrophobic difficult-to-volatilize org. compd.

Description

DETAILED DESCRIPTION OF THE INVENTION (11) Purpose of the Invention The present invention relates to a method for producing microcapsules. In particular, the present invention relates to a method for producing capsules used as a coloring agent for thermochromic ink or carbonless paper ink that changes color when the temperature is raised or lowered from room temperature to a specific temperature.

Furthermore, the present invention can also be applied to a method for manufacturing capsules for fragrances, agricultural chemicals, hardening agents for adhesives, and the like.

Conventionally, there are many methods for manufacturing capsules used in thermochromic inks or carbonless paper inks, but in particular, ethylene-maleic anhydride copolymer is used as a system modifier, and urea-formaldehyde copolymer is used. Alternatively, a method using a melamine-formaldehyde copolymer as a film forming material (Japanese Patent Publication No. 16949/1983) has been widely used.

However, when the microcapsules obtained by this method were applied to thermochromic ink, a considerable temperature difference was observed in the sharpness of the color change, the color change when the temperature was raised, and the color restoration when the temperature was lowered.

The present invention aims to improve the above-mentioned drawbacks, shorten the capsule manufacturing process, obtain capsules with a uniform particle size, and provide a method for manufacturing capsules that does not cause deterioration of the dye.

8. Structure of the Invention This invention microencapsulates a hydrophobic refractory organic compound using a urea-formaldehyde copolymer, a melamine-formaldehyde copolymer, or a urea-melamine-formaldehyde copolymer as a film forming material. However, after dissolving or dispersing leuco dyes, fragrances, pesticides, curing agents, etc. in this hydrophobic, hardly volatile organic compound, they are made into microcapsules and are stably stored to produce thermochromic inks, carbonless inks, pesticides, and adhesives. It is applied as a.

Examples of hydrophobic, hardly volatile organic compounds that can be used in the present invention are listed below, and an appropriate one may be selected and used depending on the purpose of use of the microcapsules and the solubility of the solute dissolved in the compound.

Alcohols: n-octyl alcohol, n
-nonyl alcohol, n-f syl alcohol, n-lauryl alcohol, n-myristyl alcohol, n-cetyl alcohol, n-stearyl alcohol, n-icosyl alcohol, n-tocosyl alcohol, oleyl alcohol, cyclohexanol, benzyl alcohol etc.

Esters: Urinope caproate, octyl caproate, butyl laurate, dodecyl laurate, hexyl myristate, myristyl myristate, octyl palmitate, stearyl palmitate, butyl stearate, cetyl stearate.

lauryl behenate, cetyl oleate, butyl benzoate, phenyl benzoate, dibutyl sepatate, etc.

Ketones: cyclohexanone, acetophenone, benzophenone, similistyl ketone, etc.

Ethers: dilauryl ether, dicetyl ether, diphenyl ether, ethylene glycol monostearyl ether, etc.

Fatty acids: caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, araxic acid, behenic acid, lignoceric acid, cerotic acid, partoleic acid, oleic acid, ricinoleic acid , linoleic acid, lylunic acid, eleostearic acid, erucic acid, etc.

Acid amides: capric acid amide, caprylic acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, benzamide, etc.

Hydrocarbons: aliphatic hydrocarbons such as decane, dodecane, and undecane, aromatic hydrocarbons such as naphthalene, asthracene, and diphenylmethane, alicyclic hydrocarbons such as decalin, pinene, and bicyclohexyl, and light oil. , a mixed solvent of the above sold as kerosene.

The copolymer of acrylic acid and methacrylic acid that can be used in this invention has a molar ratio of acrylic acid and methacrylic acid of 1:0.
．． 5 to B with an average molecular weight of 10,000 to 500.00
0.

It is desirable to use it as an accelerator. Examples of the polyhydric phenol include dihydric phenols or derivatives thereof such as catechol, reso, lucine, hydroquinone, and orcin, octahydric phenols such as birogalur, 70 loglucin, or gallic acid, and derivatives thereof, and preferably resorcinol, orcin, and gallic acid. Examples include acids.

In addition, in this invention, various solutes are dissolved or dispersed in the hydrophobic refractory organic compound in the microcapsules depending on the purpose, but when used as a coloring agent for thermochromic ink or carbonless paper ink, A leuco dye is used as a solute.

Next, leuco dyes that can be used in this invention are illustrated.

Triphenylmethane phthalides: crystal violet lactone, malachite green lactone, etc.

Fluoranes...8,6-dinitoxyfluorane, 8-dimethylamino-6-methyl-7-chlorofluoran, l,2-benz-6-dinithylaminofluorane, 8-diethylamino- 7-methoxyfluorane etc.

Phenothiazines: benzoyl leucomethylene blue, methyl leucomethylene blue, ethyl leucomethylene blue, methoxybenzoyl leucomethylene blue, etc.

Indolylphthalides...2-(phenyliminoethanedylidene)8,8-dimethylindoline, etc.

Spiropyrans...1,8.8-4-limethyl-indolino-7-chloro-β-naphthospiropyran, di-β-naphthospiropyran, benzo-β-naphthoisospiropyran, xantho-β-naphthospiropyran, etc. .

Leucoolanes...N-acetyl auramine, N-phenyl auramine, etc.

Rhodamine lactams: Rhodamine B lactam, etc.

When used as a fragrance, not only can the aromatic component be dissolved or dispersed in a hydrophobic, slightly volatile organic compound, but also the aromatic component can be microencapsulated as a hydrophobic, slightly volatile organic compound.

To produce microcapsules according to the present invention, inclusions are prepared by dissolving or dispersing a hydrophobic, hardly volatile organic compound to be microencapsulated or a solute such as a leuco dye in the compound depending on the purpose.

Per 100 parts by weight of inclusions (hereinafter parts by weight are simply referred to as parts), 1 to 40 parts, preferably 3 to 20 parts, of an acrylic acid-methacrylic acid copolymer is added to an 8 to 20% aqueous solution, preferably 8 to 10%. To this is added 8 to 10 parts of urea and/or melamine, and if necessary 0.1 to 2 parts of polyhydric phenol as an encapsulation accelerator, and purified with an alkali.
Adjust H to a range of 2.5 to 6.0 to obtain liquid A.

While heating liquid A to around 50°C, add the inclusions and stir with a homomixer at a speed of 2,000 to 10,000 r, p, m for 6 to 10 minutes to remove the inclusions in liquid A. Emulsify.

Under these conditions, the particle size of the inclusions becomes 2 to 8 microns. In addition, formalin (4.6 to 90 parts as 87% formalin)
Add and stir under the same conditions as when emulsifying, and then stir at about 65°
The mixture was stirred slowly with a splash for 2 hours at C to complete the encapsulation.

If necessary, water may be removed by spray drying to form a solid capsule.

In the above case, urea-polyphenol-formaldehyde, melamine-pho/L/
The molar ratios of formaldehyde and urea-melamine-formaldehyde are 1:0.01-0.2:1-8 mol and 1, respectively.
:2 to 6 moles or 1:0.1 to 1:1.5 to 6 moles.

If the acrylic acid-methacrylic acid copolymer is in excess of the inclusions, the storage stability of the capsule will be poor and the viscosity will increase, causing capsule aggregation. It is difficult to form capsules. If the film-forming material is in excess of the encapsulated material, the viscosity will increase and cause capsule aggregation, and if it is too little, the formed capsule film will become brittle.

Moreover, the same effect can be obtained whether urea and/or melamine, polyhydric phenol, and alkali are added to liquid A first or after emulsifying the inclusions in an aqueous solution of acrylic acid-methacrylic acid copolymer.

Next, examples will be shown to further clarify the invention.

Example 1 Acrylic acid-methacrylic acid copolymer, average molecular weight approximately 80,000 52 urea
6f resorcinol
0.71 water
959 plus 50°C
Dissolve the mixture by heating to pH 8. with a 20% caustic soda aqueous solution.
Adjust to 7 and use as solution A.

A liquid B is obtained by heating and dissolving crystal violet lactone 4f (diphenylmethane solvent) in Nisseki Hysol 5AS-2969Of manufactured by Nippon Oil Co., Ltd.

While keeping Solution A at 50°C, add Solution B and stir with a homomixer at 8.00 Or, p, m for 10 minutes to emulsify and disperse.

At this time, the average particle size was 5.0 μm.

After adding 87% formalin 169 and stirring, the mixture was slowly stirred at 60°C for 8 hours and slowly cooled to obtain microcapsules.

By applying this microcapsule slurry to paper using air spray, it can be used as carbonless paper that develops a blue color.

Example 2 Acrylic acid-methacrylic acid copolymer, average molecular weight approximately 100,000, 80 g water
909 and adjust the pH to 4.5 with a 20% caustic soda aqueous solution to obtain Solution A.

8-diethylamino-6-methyl-7-anilinofluorane 5f (alkylnaphthalene compound) was heated and dissolved in KMC-118100y manufactured by Kureha Chemical Co., Ltd. to obtain liquid B.

While keeping Solution A at 50°C, add Solution B and stir with a homomixer at 500 Or, 1) and frL for 6 minutes to emulsify and disperse.

While maintaining the mixture at 60°C, melamine 5287% formalin 201 dissolved by heating at 60°C was added and stirred, and then slowly stirred for 2 hours to develop a black color useful for carbonless paper ink. Microcapsules having an average particle diameter of 4 μm were obtained as a coloring agent.

Example 8 Solution A Acrylic acid-methacrylic acid copolymer, average molecular weight approximately 60,000 6y urea
61 resorcinol
0.9f water
959B liquid Lauric acid 55g Myristic acid 251 Palmitic acid
201 Bisphenol A
498-diethylamino-6-methyl-7-chlorofluorane 2g Above liquid 90
1 Emulsification conditions used Homomixer 4500 r, p, m, 8 minutes pH adjustment pH 8 with 20% caustic soda aqueous solution 6 Film forming additive 87% formalin From 16N, according to Example 1, red-colorless paste reversibly changes color Microcapsules of thermochromic pigment for printing ink were obtained.

Example 4 Solution A: Acrylic acid-methacrylic acid copolymer, average molecular weight: approximately 120,000 3000 ml
97FB liquid myristic acid
100g bisphenol A
2g bisphenol 2 1g8-
Ethylferalamino-7-methylphenylaminofluorane 1f Above solution B 90
Emulsification conditions: Homomixer 6000r, p, m, p for 6 minutes
H adjustment pH 4.6 with 20% caustic soda aqueous solution Film forming material Melamine 4F 87% formalin 209 According to Example 1, microcapsules of a thermochromic dye that reversibly changes color from green to colorless were obtained.

Comparative Example 1 The same composition and manufacturing method were used for printing ink except that acrylic acid-methacrylic acid copolymer 61 of Example 8 was replaced with ethylene-phthalic anhydride copolymer 6y (manufactured by Monsanto, HMA-81). Microcapsules were obtained.

Effect of the invention Capsule slurry 5Of obtained in Example 8 and Comparative Example 1
and 6% polyvinyl alcohol 1[50f] to prepare a silk screen printing ink.

Using this ink and a 100-mesh silk plate, silk-print onto high-quality paper and dry the printed matter at a temperature of 40°C from 20°C.
The temperature was raised to C at a rate of 1° C./min and then lowered, and changes in color from the original printed matter were observed and are shown in FIG. 1 and FIG. 2. The observation was expressed using a color difference meter CR-100 manufactured by Minolta.

As can be seen from Figures 1 and 2, the thermochromic ink using capsules according to the method of the present invention changes color more clearly than the thermochromic ink using conventional capsules. It can be seen that the temperature difference (size on the X axis) is small.

In addition to exhibiting the above characteristics when used in thermochromic ink,
It has the following advantages.

It has the following advantages in comparison.

(1) Since the acrylic acid-itaconic acid copolymer has high solubility in water, the working time required for encapsulation is shortened, leading to cost reduction.

(2) Since a microcapsule slurry with high concentration and low viscosity can be obtained, the work time for spray drying, which is a subsequent process, is shortened.

(3) Since the pH at the time of encapsulation is relatively high, no color develops when used as a colorant for carbonless paper.

(4) The particle size of the capsules becomes uniform, and when used in carbon paper, printing ink, etc., uniform coatings can be obtained.

Procedural amendment document May 30, 1986 1985 Patent Application No. 236176 2. Name of the invention Microcapsule manufacturing method 3. Person who makes corrections

Claims (1)

[Claims] A hydrophobic, slightly volatile organic compound is emulsified in an aqueous solution of acrylic acid-methacrylic acid copolymer, and urea and/or melamine and formaldehyde are added to the solution to pH 2.5 to 6.
．． A method for producing microcapsules in which a film of a urea-formaldehyde copolymer, a melamine-formaldehyde copolymer, or a urea-melamine-formaldehyde copolymer is formed around a hydrophobic refractory organic compound.