JPH0553539B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention The present invention relates to a method for producing microcapsules. In particular, the present invention relates to a method for manufacturing capsules used as a coloring agent for heat-denatured 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.

There have been 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-maleic anhydride copolymer is used as a system modifier.
A method using a formaldehyde copolymer or 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.

B. Structure of the Invention This invention provides a method for converting a hydrophobic refractory organic compound into urea-
Formaldehyde copolymer, melamine-formaldehyde copolymer, or urea-melamine-formaldehyde copolymer is microencapsulated as a film-forming material, and leuco dye, fragrance, After dissolving or dispersing pesticides, curing agents, etc., they are stored stably in the form of microcapsules and used as thermochromic inks, carbonless inks, pesticides, and adhesives.

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-decyl alcohol, n
-Lauryl alcohol, n-myristyl alcohol, n-cetyl alcohol, n-stearyl alcohol, n-icosyl alcohol, n-
Docosyl alcohol, oleyl alcohol, cyclohexanol, benzyl alcohol, etc.

Esters...Lauryl caproate, octyl caprate, butyl laurate, dodecyl laurate, hexyl myristate, myristyl myristate, octyl palmitate, stearyl palmitate, butyl stearate, cetyl stearate, lauryl behenate, oleic acid cetyl, butyl benzoate, phenyl benzoate,
Dibutyl sebatate, etc.

Ketones: cyclohexanone, acetophenone, benzophenone, dimyristyl 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, arachidic acid, behenic acid, lignoceric acid, cerotic acid, partoleic acid, oleic acid, ricinoleic acid, linoleic acid, Linolenic 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, undecane, etc., aromatic hydrocarbons such as naphthalene, asthracene, diphenylmethane, etc.
The above mixed solvents are sold as alicyclic hydrocarbons such as decalin, pinene, and bicyclohexyl, light oil, and kerosene.

The acrylic acid-methacrylic acid copolymer that can be used in this invention has a molar ratio of acrylic acid to methacrylic acid of 1:0.5 to 3 and an average molecular weight of 10,000 to 500,000.

In this invention, when a urea-formaldehyde copolymer is used as a film-forming agent, it is preferable to use polyhydric phenol as an encapsulation accelerator.
Examples of the polyvalent phenols include divalent phenols or derivatives thereof such as catechol, resorcinol, hydroquinone, and orcine, trivalent phenols such as pyrogallur, phloroglucin, or gallic acid, and derivatives thereof, and preferred examples include resorcinol, orcin, and gallic acid. can do.

In addition, in this invention, various solutes are dissolved or dispersed in the hydrophobic refractory organic compound in the microcapsules depending on the purpose. Use leuco dye as Next, leuco dyes that can be used in this invention are illustrated.

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

Fluoranes...3,6-diethoxyfluorane, 3-dimethylamino-6-methyl-7-chlorofluoran, 1,2-benz-6-diethylaminofluorane, 3-diethylamino-7
-Methoxyfluorane etc.

Phenothiazines: bezoyl leucomethylene blue, methyl leuco blue, ethyl leucomethylene blue, methoxybenzoyl leucomethylene blue, etc.

Indolylphthalides...2-(phenyliminoethanedylidene) 3,3-dimethylindoline, etc.

Spiropyrans...1,3,3-trimethyl-indolino-7'-chloro-β-naphthospiropyran, di-β-naphthospiropyran, benzo-β
-naphthoisospiropyran, xantho-β-naphthospiropyran, etc.

Leuco auramines...N-acetyl auramine, N-phenyl auramine, etc.

Rhodamine Rantams...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.

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

Inclusions: 100 parts by weight (hereinafter, parts by weight are simply referred to as parts)
acrylic acid-methacrylic acid copolymer 1~
40 parts, preferably 3 to 20 parts of a 3 to 20% aqueous solution;
It is preferably a 3 to 10% aqueous solution, to which 3 to 10 parts of urea and/or melamine and, if necessary, 0.1 to 2 parts of polyhydric phenol as an encapsulation accelerator are added, and the pH is adjusted to 2.5 to 6.0 with an alkali. Solution A is adjusted to a range of .

While heating liquid A to around 50°C, add the inclusions and stir with a homomixer at a speed of 2000 to 1000 rpm for 5 to 10 minutes to emulsify the inclusions in liquid A. Under these conditions, the particle size of the inclusions becomes 2 to 3 microns. At the same time, formalin (4.5 to 90 parts as 37% formalin) was added and stirred under the same conditions as when emulsifying.
The encapsulation was completed by gently stirring the mixture at ℃ for 2 hours with a splash stirrer.

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

In the above case, the molar ratio of urea-polyphenol formaldehyde, melamine-formaldehyde, and urea-melamine-formaldehyde in urea formaldehyde is 1:0.01 to 0.2:1, respectively.
~3 mol, 1:2-6 mol or 1:0.1~
1:1.5 to 6 moles.

If the acrylic acid-methacrylic acid polymer is in excess of the encapsulated material, the storage stability of the capsule will be poor and the viscosity will increase, causing capsule aggregation. If the amount is too low, the emulsification of inclusions will be unstable and it will be difficult to form capsules. If the film-forming material is in excess of the inclusions, the viscosity will increase, causing capsule aggregation, and if it is too little, the formed capsule film will become brittle. Urea and/or melamine, polyhydric phenol, and alkali have the same effect whether they are added to liquid A first or after emulsifying the inclusions in an aqueous acrylic acid-methacrylic acid copolymer solution.

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

Example 1 Acrylic acid-methacrylic acid copolymer, average molecular weight approximately 80,000 5g, 6g of urea, 0.7g of resorcinol were added to 95g of water, heated to 50°C to dissolve, and the pH was adjusted to 3.7 with a 20% aqueous solution of caustic soda. Make it into a liquid.

Nisseki Hysol SAS-296 manufactured by Nippon Oil Co., Ltd.
Dissolve 4g of crystal violet lactone in 90g of (diphenylmethane solvent) by heating to obtain liquid B.

While keeping Solution A at 50°C, add Solution B and stir with a homomixer at 3000 rpm for 10 minutes to emulsify and disperse.

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

After adding 16 g of 37% formalin and stirring, the mixture was slowly stirred at 60°C for 3 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 of about 100,000 80 g, dissolved in 90 g of water and adjusted to pH 4.5 with 20% aqueous sodium hydroxide solution to prepare solution A.

Solution B is prepared by heating and dissolving 5 g of 3-diethylamino-6-methyl-7-anilinofluorane in 100 g of kmc-113 (alkylnaphthalene compound) manufactured by Kureha Chemical Co., Ltd.

While keeping the A solution at 50°C, add the B solution and stir with a homomixer at 5000 rpm for 5 minutes to emulsify and disperse.

While maintaining this mixture at 60℃, 5g of melamine and 20g of 37% formalin were heated and dissolved at 60℃, stirred, and then slowly stirred for 2 hours.A black color useful for carbonless paper ink developed. Microcapsules with an average particle size of 4μ, which are colorants for coloring, were obtained.

Example 3 Liquid A Acrylic acid-methacrylic acid copolymer, average molecular weight approximately 60,000 6g Urea 6g Resorcinol 0.9g Water 95g B Liquid Lauric acid 55g Myristic acid 25g Palmitic acid 20g Bisphenol A 4g 3-diethylamino-6-methyl -7-Chloroflurane 2g Using 90g of the above B solution Emulsification conditions Homo mixer 4500r.pm PH adjustment for 8 minutes PH3.6 with 20% caustic soda aqueous solution Film forming additive 37% formalin 16g According to Example 1, red←→colorless We obtained microcapsules for printing ink containing thermochromic dyes that reversibly change color.

Example 4 Liquid A acrylic acid-methacrylic acid copolymer, average molecular weight approximately 120,000 3 g Water 97 g B Liquid myristic acid 100 g Bisphenol A 2 g Bisphenol Z 1 g 3-ethylphenylamino-7-methylphenylaminofluorane 1g Using 90g of the above B solution Emulsification conditions Homomixer 6000r.pm for 6 minutes PH adjustment PH4.6 with 20% caustic soda aqueous solution Film forming material Melamine 4g 37% formalin 20g According to Example 1, reversibly changed from green to colorless. Microcapsules of thermochromic dyes that change color were obtained.

Comparative Example 1 Printing ink was produced using exactly the same composition and manufacturing method except that 6 g of acrylic acid-methacrylic acid copolymer in Example 3 was replaced with 6 g of ethylene-phthalic anhydride copolymer (manufactured by Monsanto, EMA-31). microcapsules were obtained.

C. Effects of the Invention 50 g of the capsule slurry obtained in Example 3 and Comparative Example 1 and 50 g of a 5% polyvinyl alcohol aqueous solution were kneaded to prepare an ink for silk screen printing.

Using this ink and a 100 mesh silk plate,
Silk printing on high quality paper and drying at room temperature 20℃
The temperature was raised to 40° C. at a rate of 1° C./min, and the temperature was then lowered, and changes in color from the original printed matter were observed, as shown in FIGS. 1 and 2. Observations were expressed using a color difference meter CR-100 manufactured by Minolta.

Figures 1 and 2 show that the thermochromic ink using the capsule according to the method of the present invention changes color more clearly (size on the y-axis) than the thermochromic ink using the conventional capsule. 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 also 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 time required for spray drying, which is a subsequent process, is shortened.

(3) Since the pH during 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.

[Brief explanation of the drawing]

FIG. 1 shows a temperature-color development curve of a printed matter using the microcapsules obtained in Example 3;
FIG. 2 is a curve showing the change in temperature versus color development of a printed matter using the microcapsules obtained in Comparative Example 1.

Claims (1)

[Claims] 1. Emulsify a hydrophobic, poorly volatile organic compound in an aqueous solution of acrylic acid-methacrylic acid copolymer, then add urea, melamine, and formaldehyde, and polymerize in the pH range of 2.5 to 6.0 to form a hydrophobic, poorly volatile organic compound. 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 an organic compound.