Microcapsule Manufacture

This invention is related to a process for manufacturing microcapsules, which are particularly useful for thermo-changeable color ink changing color when raising or lowering temperatures from room to specified temperature or for color ink for carbonless paper.

Further, this invention can be applied to a process for manufacturing capsules of perfumes, agricultural chemicals, and curing agents for adhesives.

Up to now, there has been many processes for manufacturing capsules for thermo-changeable color ink or carbonless paper ink. Particularly, a process for forming film from urea- or melamine-formaldehyde copolymer using ethylenemaleic anhydride copolymer as a system modifier (patent announcement No. Showa 54-16949) has been widely used.

However, when applying the microcapsules manufactured by the above-mentioned process to thermo-changeable color ink, the marked differences in temperature were observed between the brightness of changed color, the color change in raising temperature, and the color return in lowering temperature.

The present invention provides a process for manufacturing capsules wherein the above-mentioned defects are improved, the manufacturing process is shortened, the capsules of uniform particle size are gained, and no deterioration of dyestuff occurs.

This invention is the encapsulation of hydrophobic, substantially involatile organic compounds in the film of urea-, melamine-, or urea-melamine-formaldehyde copolymer. After dissolving or dispersing leuko dyestuffs, perfumes, agricultural chemicals, and curing agents in the hydrophobic, substantially involatile organic compounds, they are enmicrocapsulated, and the capsules have good preservation stability, and are applied as thermo-changeable color ink, carbonless ink, agricultural chemicals, and adhesives.

The hydrophobic, substantially involatile organic compounds usable in the invention are indicated as examples in the following. According to the use objects of microcapsules and to the solubility or dispersibility of the solutes dissolved or dispersed in the compounds, the compounds are appropriately selected.

Alcohols: n-octyl-alcohol, n-nonyl-alcohol, n-decyl-alcohol, n-lauryl-alcohol, n-myristyl-alcohol, n-cetyl-alcohol, n-stearyl-alcohol, n-eicosyl-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, cetyl-oleate, butyl-benzoate, phenyl-benzoate, dibutyl-sebatate, etc.

Ketones: cyclohexanone, acetophenone, benzophenone, dimyristyl-ketone, etc.

Ethers: dilauryl-ether, dicetyl-ether, diphenyl-ether, ethyleneglycol-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, palmitoleic-acid, oleic-acid, ricinoleic-acid, linoleic-acid, linolenic-acid, eleostearic-acid, erucic-acid, etc.

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

Hydrocarbons: aliphatic hydrocarbons such as decane, dodecane, undecane, etc. aromatic hydrocarbons such as naphthalene, anthracene, diphenylmethane, etc. alicyclic hydrocarbons such as decalin, pinene, bicyclohexyl, etc. mixed solvents of above hydrocarbons being on sale as light oil or kerosene.

Acrylic acid-methacrylic acid copolymer usable in this invention is 1:0.5.about.3 in the mole ratio of acrylic acid to methacrylic acid, and 10,000.about.500,000 in the average molecular weight.

And, acrylic acid-itaconic acid copolymer usable in the invention is 1:0.5.about.3 in the mole ratio of acrylic acid to itaconic acid, and 10,000.about.500,000 in the average molecular weight, and for actual use, Jurimer-50P or 10P-2 mass produced in Nihon Junyaku Co. Ltd. is conveniently used.

When using urea-formaldehyde copolymer as a film forming agent in the invention, it is preferable to use polyoxy phenol as a encapsulation accelerating agent. As the polyoxy phenols, dioxy phenols such as catechol, resorcin, hydroquinone, orcin, etc. or the derivatives and trioxy phenols such as pyrogallol, furoroglucin, gallic acid, etc. or the derivatives are indicated as examples, preferably resorcin, orcin, gallic acid.

In the invention, polyanionic macro-molecules can be added at need as microcapsules stabilizing agents, in which sodium salt of carboxymethylcellulose, sulfonated polyvinyl-alcohol, carboxylated polyvinyl-alcohol, maleic anhydride series resin, sodium alginate, etc. are indicated as examples.

In the invention, a variety of solutes is dissolved or dispersed in the hydrophobic, substantially involatile organic compounds in microcapsules according to the object, wherein leuko dyestuffs are used as solutes when the capsules are used for thermo-changeable color ink or the coloring agents for carbonless paper ink.

Leuko dyestuffs usable in the invention are indicated as examples in the following.

Triphenylmethane phthalides: Crystal-violet-lactone, malachite-green-lactone, etc.

Fluoranes: 3,6-diethoxy-fluorane, 3-dimethylamino-6-methyl-7-chlor-fluorane, 1,2-benz-6-diethylamino-fluoran e, 3-diethylamino-7-methoxy-fluorane, etc.

Phenothiazines: benzoyl-leukomethylene-blue, methyl-leukomethylene-blue, ethyl-leukomethylene-blue, methoxybenzoyl-leukomethylene-blue, etc.

Indolyl phthalides: 2-(phenyliminoethanezylidene)-3,3-dimethyl-indoline, etc.

Spiropyrans: 1,3,3-trimethyl-indolyno-7'-chlor-.beta.-naphtho-spiropyran, di-.beta.-naphtho-spiropyran, benzo-.beta.-naphtho-isospiropyran, xantho-.beta.-naphtho-spiropyran, etc.

Leuko-auramines: N-acetyl-auramine, N-phenyl-auramine, etc.

Rhodamine lactams: Rhodamine B lactam, etc.

In using microcapsules as perfumes, not only dissolving or dispersing perfume ingredients in the hydrophobic, substantially involatile organic compounds but also encapsulating perfume ingredients as the hydrophobic, substantially involatile organic compounds is possible. In manufacturing microcapsules by the invention, capsule contents is prepared from the hydrophobic, substantially involatile organic compounds to be encapsulated, or by dissolving or dispersing solutes such as leuko dye-stuffs in the said compounds according to the objects.

When the film material is a urea-formaldehyde copolymer, per capsule contents 100 weight parts (hereafter, weight parts are simply described as parts.), 3.about.20% , preferably 3.about.10%, aqueous solution of acrylic acid-methacrylic acid copolymer and/or acrylic acid-itaconic acid copolymer 1.about.40 parts, preferably 3.about.20 parts, is prepared, and urea 3.about.10 parts and, if necessary, polyoxy phenol 0.1.about.2 parts as an encapsulation accelerating agent are added, and after warming to 50.degree. C., the solution is adjusted to pH 2.5.about.6.0 with alkali to prepare A solution.

With warming A solution at ca 50.degree. C., capsule contents is added, and the contents is emulsified in A solution by stirring with a homomixer at 2,000.about.10,000 r.p.m. for 5.about.10 min. Under this condition the particle diameter of contents becomes 2.about.8.mu.. Then, formalin (4.5.about.90 parts as 37% formalin) is added, and the solution is stirred under the condition similar with when emulsifying, and slowly stirred with a fan at 60.degree..about.80.degree. C. for 2 hr, and cooled to 20.degree..about.30.degree. C. to complete encapsulation. If necessary, by removing moisture with spray drying, solid capsules may be prepared.

When film material is a urea-melamine-formaldehyde copolymer, melamine 10 g or less is added with the formalin addition mentioned above.

When the film material is a melamine-formaldehyde copolymer, 3.about.20%, preferably 3.about.10%, aqueous solution of acrylic acid-methacrylic acid copolymer and/or acrylic acid-itaconic acid copolymer 1.about.40 parts, preferably 3.about.20 parts, is prepared, and after warming to 50.degree. C., the solution is adjusted to pH 2.5.about.6.0 with alkali to prepare A solution.

With warming A solution at ca 50.degree. C., capsule contents are added, and the contents are emulsified in A solution by stirring with a homomixer at 2,000.about.10,000 r.p.m. for 5.about.10 min. Then, 37% formalin 4.about.60, preferably 5.about.25, parts, and melamine 2.about.20, preferably 3.about.7, parts are added, and the solution is stirred under the condition similar with when emulsifying, and slowly stirred at 60.degree..about.80.degree. C. for 2 hr, and cooled to 20.degree..about.30.degree. C. to complete encapsulation.

In the above-mentioned cases, the mole ratio of urea-polyoxyphenol-formaldehyde in urea-formaldehyde, of melamine-formaldehyde, and of urea-melamine-formaldehyde is respectively 1:0.01.about.0.2:1.about.3 mol, 1:2.about.6 mol, and 1:0.1.about.1:1.5.about.6 mol.

The excess of acrylic acid-methacrylic acid copolymer and/or acrylic acid-itaconic acid copolymer to the capsule contents causes the poor stability of capsule preservation and results in the capsule aggregation due to high viscosity. If it is too little, the capsule contents is unstable for emulsifying, being difficult to be encapsulated. The excess of film forming material to the capsule contents results in the capsule aggregation due to high viscosity. If it is too little, the formed capsule film is brittle. The addition of urea and/or melamine, polyoxy phenol, and alkali to A solution in the beginning indicates the similar effects with the addition in the aqueous solution of acrylic acid-methacrylic acid copolymer or acrylic acid-itaconic acid copolymer after emulsifying the capsule contents.

The preferred embodiments are indicated in the following for further clarification of the invention. The invention is not restricted by these embodiments.

Acrylic-acid-methacrylic acid copolymer (average molecular weight ca 80,000) 5 g, urea 6 g, and resorcin 0.7 g are added to water 95 g and warmed to 50.degree. C. to dissolve, and pH is adjusted to 3.7 with 20% caustic soda aqueous solution to prepare A solution.

Crystalviolet-lactone 4 g is dissolved in Nisseki Hisol (Nihon Sekiyu Co. Ltd.) 90 g by heating to prepare B solution. B solution is added to A solution kept at 50.degree. C., and stirred with a homomixer at 3,000 r.p.m. for 10 min. to emulsify, the particle diameter becoming average 5.0.mu.. 37% formalin 16 g is added to the solution, and after stirring, the solution is slowly stirred for 3 hr at 60.degree. C., and slowly cooled to gain microcapsules.

The paper applied this microcapsules slurry with air spray can be utilized as carbonless paper developing blue color.

Acrylic acid-methacrylic acid copolymer (average molecular weight ca 100,000) 80 g is dissolved in water 90 g, and pH is adjusted to 4.5 with 20% caustic soda aqueous solution to prepare A solution. 3-diethylamino-6-methyl-7-anilinofluorane 5 g is dissolved in KMC-113 (alkyl naphthalene series compound made of Kureha Kagaku Co. Ltd.) 100 g by heating to prepare B solution. B solution is added to A solution kept at 50.degree. C., and stirred with a homomixer at 5,000 r.p.m. for 5 min. to emulsify. Melamine 5 g in 37% formalin 20 g dissolved by heating at 60.degree. C. is added to the mixed solution kept at 60.degree. C., and after stirring, the solution is slowly stirred for 2 hr to gain microcapsules of average particle diameter 4.mu. utilized as carbonless paper ink developing black color.

By operating similarly with example 1 under the above condition, microcapsules utilized as thermo-changeable color ink, reversible red.rarw..fwdarw.colorless at 27.degree..about.31.degree. C., are gained.

By operating identically with example 1 with the exception that melamine is also added with the addition of 37% formalin, microcapsules utilized as thermo-changeable color, reversible green.rarw..fwdarw.colorless at 46.degree..about.52.degree. C., are gained.

By operating identically with example 4, microcapsules utilized as thermo-changeable color, reversible red.rarw..fwdarw.colorless at 22.degree..about.26.degree. C., are gained.

Jurimer-50P (Nihon Junyaku Co. Ltd., acrylic acid-itaconic acid copolymer, average molecular weight ca 200,000) 5 g, urea 6 g, and resorcin 0.9 g are dissolved in water 95 g to prepare A solution.

Crystalviolet-lactone 3 g is dissolved in KMC-113 (Kureha Kagaku Co. Ltd., naphthalene series solvent) 110 g by heating to prepare B solution.

B solution 80 g is added to A solution kept at 50.degree. C., and stirred with a homomixer at 5,000 r.p.m. for 7 min., the particle diameter in B solution becoming 2.about.5.mu..

Then, 20% caustic soda aqueous solution is dropped to adjust pH to 4.0, and further 37% formalin 16 g is added, and after stirring, the solution is stirred for 2 hr at 55.degree. C. to gain microcapsules. The paper applied this microcapsules slurry with air spraying can be utilized as carbonless paper developing blue color.

Jurimer-10P-2 (Nihon Junyaku Co. Ltd., acrylic acid-itaconic acid copolymer, average molecular weight ca 50,000) 10 g is dissolved in water 90 g to prepare A solution.

3-diethylamino-6-methyl-7-anilinofluorane 5 g is dissolved in Nisseki Hisol SAS-296 (Nihon Sekiyukagaku Co. Ltd., diphenylmethane series compound) 100 g by heating to prepare B solution.

B solution is added to A solution kept at 50.degree. C., and stirred with a homomixer at 7,500 r.p.m. for 5 min., the particle diameter in B solution becoming 4.about.6.mu..

Into the above emulsion, 20% caustic soda aqueous solution is dropped to adjust pH to 3.5, and with keeping 60.degree. C., melamine 5 g and 37% formalin 15 g is added, and after stirring, the solution is stirred for 2 hr at 55.degree. C. to gain microcapsules.

This microcapsules can be utilized as a color developer for carbonless paper developing black.

By operating identically with example 6, micro-capsules utilized as thermo-changeable color, reversible violet.rarw..fwdarw.colorless at 46.degree..about.52.degree. C., are gained.

By operating identically with example 6 with the exception that melamine is added with 37% formalin addition, microcapsules utilized as thermo-changeable color, reversible orange.rarw..fwdarw.colorless at 42.degree..about.46.degree. C., are gained.

By operating identically with example 9, microcapsules utilized as thermo-changeable color, reversible black.rarw..fwdarw.colorless at 16.degree..about.22.degree. C., are gained.

The compositions of B solution containing thermo-changeable colors are indicated as examples in the following Table 1.