JP2000107590A - Production of microcapsule and capsule ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microcapsule producing method capable of preparing capsule ink by producing microcapsules to mix them with an ink component without requiring a process for drying and re-dispersing a microcapsule dispersion. SOLUTION: A protective colloid soln. obtained by dissolving at least one of polyvinylpyrrolidone, polymethyl vinyl ether and derivatives of them in a hydrophilic liquid not substantially containing water and a hydrophobia soln. containing a core substance are mixed and emulsified to produce microcapsules. An electron donating color forming material can be incorporated in microcapsules by adding this color forming material to the hydrophobia soln. A microcapsule dispersion is dispersed in an ink component to obtain capsule ink for a pressure-sensitive recording sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing microcapsules and a capsule ink using the capsules obtained by this method, and more particularly to a pressure-sensitive copying capsule in which microcapsules containing an electron-donating color former are made into ink. The present invention relates to a method for producing microcapsules suitable for use in ink, and a capsule ink using capsules obtained by this method.

[0002]

2. Description of the Related Art Microencapsulation technology has been widely applied as one of the means for encapsulating substances such as dyes, fragrances, liquid crystals, enzymes, catalysts, adhesives, and the like. The function of the substance can be maintained for a long time. As such a microcapsule, for example, a microcapsule containing an electron-donating color forming agent such as crystal violet lactone or benzoyl leucomethylene blue is used, and this electron-donating color forming agent, activated clay, phenol-formaldehyde condensate, aromatic Pressure-sensitive copying sheets utilizing the principle of developing color by reaction with an electron-accepting developer such as a polyvalent metal salt of a carboxylic acid are well known.

In general, such a pressure-sensitive copying sheet is prepared by coating a support with microcapsules containing an electron-donating color former prepared by a method such as a phase separation method, an interfacial polymerization method, or an in-situ method. Lower paper, coated with a support, an electron-accepting developer that forms a color by reacting with a paper,
The middle paper having the color former microcapsules and the color developer applied to different surfaces of a support is appropriately combined and used as a set.

There is also a so-called self-coloring type pressure-sensitive copying sheet in which a coloring agent microcapsule and a color developing agent are coated on the same surface of a support as a laminated or mixed layer. There is a set of a self-coloring type pressure-sensitive copying sheet in which a capsule layer is provided on the back surface of the sheet, and lower paper or middle paper is appropriately combined.

Usually, all the microcapsules used in these pressure-sensitive copying sheets are prepared by removing water from the aqueous dispersion to form a dry powder, and mixing the resulting powder with an ink containing linseed oil or the like as a main component to form a dry powder. Of the capsule ink.
Therefore, to obtain a dry powder of microcapsules,
It is necessary to evaporate a large amount of water, so that there is a problem that the production cost is high, and there is also a problem that the capsule particles after drying are aggregated.

When the capsule particles are agglomerated, when the powdered microcapsules are used as a capsule ink, the agglomerated capsule particles remain in the ink, so that a good printed matter cannot be obtained. Since it is difficult to disperse in an ink solvent and cannot be easily formed into an ink, a method of redispersing powdered microcapsules may be employed, but the effect is not sufficiently improved.

[0007]

The first object of the present invention is to
An object of the present invention is to provide a method for producing microcapsules which can be mixed with an ink component at an arbitrary ratio without going through a step of drying and redispersing a microcapsule dispersion liquid after preparing microcapsules. A second object of the present invention is to provide a capsule ink using the microcapsules obtained by the above method.

[0008]

SUMMARY OF THE INVENTION The first object described above is intended to provide:
Mixing and emulsifying a protective colloid solution obtained by dissolving at least one of polyvinylpyrrolidone, polymethylvinylether or a derivative thereof in a hydrophilic liquid substantially free of water, and a hydrophobic solution containing a core substance. This is achieved by a method for producing microcapsules characterized by the following. A microcapsule containing an electron-donating coloring material as a core substance is suitable as a microcapsule used for a pressure-sensitive recording sheet. Further, when an electron-donating color-forming material and a polyvalent isocyanate are added to the hydrophobic liquid, the wall film of the microcapsules is formed of polyurea and polyurethane, and the heat-resistant microcapsules used in the pressure-sensitive recording sheet are provided. can do. The above-mentioned second object is achieved by a capsule ink characterized in that a dispersion of microcapsules obtained by the above-mentioned production method is dispersed in an ink component.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. In the method for producing microcapsules of the present invention, the protective colloid solution used contains at least one of polyvinylpyrrolidone, polymethylvinylether or a derivative thereof (hereinafter, these compounds are also referred to as solutes) substantially free of water. Obtained by dissolving in a hydrophilic liquid. Examples of the derivatives of polyvinylpyrrolidone include vinylpyrrolidone acrylic acid copolymer, vinylpyrrolidone vinyl acetate copolymer and the like. Examples of the derivatives of polymethyl vinyl ether include polymethyl vinyl ether maleic acid, polymethyl vinyl ether maleic acid monoethyl ester, and polymethyl vinyl ether maleic acid monoisopropyl ester. Polyvinyl pyrrolidone, polymethyl vinyl ether or their derivatives (solutes) may be used alone or in combination of two or more.

The hydrophilic liquid containing substantially no water may be any as long as it dissolves polyvinylpyrrolidone, polymethylvinylether or a derivative thereof, and particularly has two or more hydroxyl groups in the molecule. Glycerin and its derivatives, ethylene glycol and its derivatives are preferred. Glycerin derivatives include glycerol monooleate and glycerol monoacetate. Ethylene glycol derivatives include ethylene glycol bis (propylene glycol ethylene glycol) ether.

The amount of solute dissolved in the substantially water-free hydrophilic liquid is 2% to 20% by weight, preferably 5% to 15% by weight, more preferably 8% by weight.
Desirably, it is 10 to 10% by weight. If the amount of the solute in the hydrophilic liquid is less than 2% by weight, poor emulsification that cannot be emulsified to a desired particle size occurs. If the amount exceeds 20% by weight, the viscosity of the hydrophilic liquid is high and generates heat during emulsification. Is not preferred. In the protective colloid solution,
In addition to the above components, for example, a low molecular surfactant component may be added as necessary.

Next, a hydrophobic solution containing a core substance is mixed and emulsified in the above-mentioned protective colloid solution in a continuous phase to obtain a microcapsule dispersion. The core substance in the microcapsule is arbitrarily selected depending on the use of the microcapsule. However, when producing a microcapsule for pressure-sensitive recording, an electron-donating color-forming material is used as the core substance, A hydrophobic solution in which materials, a hydrophobic liquid, a capsule wall film forming substance and the like are dissolved is mixed and emulsified in the continuous phase of the protective colloid solution.

Examples of the electron-donating color-forming material include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone, hereinafter referred to as CVL) as a triallylmethane compound. , 3-Bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindole-
3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis- (1,2-dimethylindole-3
-Yl) -6-dimethylaminophthalide, 3,3-bis- (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis- (2-phenylindol-3-yl ) -5-Dimethylaminophthalide, 3
-P-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

As the diphenylmethane compound, 4,
4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenylleuco auramine, N-2,
4,5-trichlorophenylleuco auramine and the like. Xanthene compounds include rhodamine-B-anilinolactam and rhodamine- (p-nitroanilino)
Lactam, rhodamine B (p-chloroanilino) lactam, 3-dimethylamino-6-methoxyfluoran, 3
-Diethylamino-7-methoxyfluoran, 3-diethylamino-7-chloro-6-methylfluoran, 3-
Diethylamino-7- (acetyllomethylamino) fluoran, 3-diethylamino-7- (dibenzylamino) fluoran, 3-diethylamino-7- (methylbenzylamino) fluoran, 3-diethylamino-7-
(Chloroethylmethylamino) fluoran, 3-diethylamino-7- (diethylamino) fluoran, and the like. Thiazine compounds include benzoyl leucomethylene blue, p-nitrobenzyl leucomethylene blue and the like. Examples of spiro compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3′-dichloro-spiro-dinaphthopyran,
3-benzyl-spiro-dinaphthopyran, 3-methyl-
Naphtho- (3-methoxy-benzo) -spiropyran, 3
-Propyl-spiro-dibenzodipyran and the like.

The hydrophobic liquid dissolves an electron-donating color-forming material, and specifically includes, for example, hydrogenated terphenyl (JP-B-49-2125) and alkylnaphthalene (JP-B-49-2124). A), aromatic oily liquids such as alkylated diphenylalkane (JP-B-49-2126), alkylated triphenyldimethane (JP-B-49-8289), and alkylated diphenyl (Belgian Patent 771661). (COOB) _n (where A, B
Is an ester-based oily liquid represented by a chain or cyclic alkyl group having 1 to 12 carbon atoms or an allyl group)
No. 31414), kerosene, chlorinated diphenyl, chlorinated paraffin, cottonseed oil, linseed oil, soybean oil and the like.

Various materials such as gelatin, alginate, celluloses, polyurea, polyurethane, melamine resin and nylon can be used as the wall film forming material.
Polyurea and polyurethane are preferred. In this case, a polyvalent isocyanate compound is used.

The polyvalent isocyanate compound is a compound having two isocyanate groups in the molecule, m.
-Phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,
4-tolylene diisocyanate, naphthalene-1,4-
Diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxy-biphenyldiisocyanate, 3,3'-dimethyldiphenylmethane-
4,4′-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, 4-chloroxylylene-1,3-diisocyanate, 2-methylxylylene-1,3-diisocyanate, 4,4′-diphenylpropane diisocyanate,
4,4′-diphenylhexafluoropropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1 , 3-Diisocyanate, cyclohexylene-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,4-bis (isocyanatomethyl) cyclohexane and 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate, lysine And diisocyanates. Further, addition products of these bifunctional isocyanate compounds with bifunctional alcohols such as ethylene glycols and bisphenols, and phenols can also be used.

Further, polyfunctional isocyanate compounds can also be used. Examples of such compounds include trimers (buret or isocyanurate) based on the above-mentioned bifunctional isocyanate compounds as main raw materials, polyols such as trimethylolpropane, and polyfunctional as adducts of bifunctional isocyanate compounds. Examples thereof include formalin condensates of benzene isocyanate, polymers of isocyanate compounds having a polymerizable group such as methacryloyloxyethyl isocyanate, and lysine triisocyanate. In particular, xylene diisocyanate and its hydrogenated product, hexamethylene diisocyanate, tolylene diisocyanate and its hydrogenated product as main raw materials, and trimers of these (buret or isocyanurate)
In addition, a polyfunctional adduct with trimethylolpropane is preferred. These compounds are described in "Polyurethane Resin Handbook" (edited by Keiji Iwata, published by Nikkan Kogyo Shimbun (1987)).

If necessary, components such as an ultraviolet curable compound, a photopolymerization initiator, an ultraviolet absorber, an antioxidant and a radical polymerization initiator can be added to the hydrophobic solution containing these core substances. . In this case, the ultraviolet curable compound and the photopolymerization initiator are contained in the microcapsules containing the electron-donating color-forming material.

Examples of the ultraviolet-curable compound include compounds having one or more, preferably two or more vinyl groups or vinylidene groups. Specific examples include acryloyl groups, methacryloyl groups, allyl groups, and unsaturated polyesters. And compounds having a vinyloxyacrylamide group. Examples of the photopolymerization initiator include an aromatic ketone, a quinone compound, an ether compound, and a nitro compound. Examples of the ultraviolet absorber include benzophenone-based, benzotriazole-based, and cyanoacrylate-based ultraviolet absorbers.

Next, the above-mentioned hydrophobic solution in which the core substance is dissolved is mixed and emulsified in the continuous phase of the hydrophilic liquid in which the solute is dissolved, and, for example, a microcapsule dispersion containing an electron-donating color-forming material is formed. can get. At this time, the polyvalent isocyanate in the hydrophobic solution first reacts with the water dissolved in the hydrophilic liquid or the water in the air supplied from the gas-liquid interface, and then reacts with the polyvalent isocyanate in the hydrophobic solution. It is thought that a cross-linking structure is formed by performing the method.

After the dispersion liquid of the obtained microcapsules is subjected to a filtration treatment, the dispersion liquid is directly dispersed in an ink containing an organic medium or the like without requiring a step of evaporating the liquid, thereby producing a capsule ink. A sensitizer, a pigment, a color-desensitizing component, a capsule protective agent, an antioxidant, a fluorescent dye, a plasticizer, and the like for enhancing the efficiency of photopolymerization are added to the capsule ink of the present invention as needed.

The capsule ink containing the electron-donating color former prepared as described above can be applied to a support with a large-sized coating machine to produce a pressure-sensitive recording sheet. Is preferred to be spot printed by a printing machine. In this spot printing, an expensive capsule ink is printed only at a necessary portion of the support, so that a pressure-sensitive recording sheet having a partially different color tone can be obtained, and a pressure-sensitive recording sheet that is economically superior depending on the target product. Becomes

The capsule ink containing the ultraviolet-curable compound and the like together with the electron-donating color-forming material is prepared by using a printing machine equipped with an ultraviolet irradiation device (for example, a letterpress printing machine, offset printing machine, flexographic printing machine, etc.) on a support. Is applied by printing, and the ink is cured by irradiation with ultraviolet rays.

[0025]

Embodiments of the present invention will be described below. [Example 1] 4 g of polyvinylpyrrolidone (polyvinylpyrrolidone K25, manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 36 g of glycerin to obtain a uniform protective colloid solution. 0.44 g of crystal violet lactone (hereinafter abbreviated as CVL) to KM
C113 (Kureha Chemical Co., Ltd., alkyl naphthalene)
To 6 g of the dye solution dissolved in 5.56 g, 2.2 g of Sumidur N3200 (manufactured by Sumitomo Bayer Urethane Co., Ltd.) and 2.2 g of Cosmonate LK (manufactured by Mitsui Toatsu Co., Ltd.) were mixed. A homogeneous solution was obtained. This solution was slowly added to 60 g of the protective colloid solution, and after emulsifying with a homogenizer (manufactured by Nippon Seiki), polyisocyanate was reacted at 75 ° C. for 2 hours with stirring to obtain microcapsules having an average particle size of 1.8 μm. A dispersion was obtained.

Example 2 A protective colloid solution obtained by dissolving 3 g of polyvinylpyrrolidone of Example 1 in 27 g of glycerin was used in the same manner as in Example 1, except that the average particle diameter was 3.6 μm. A microcapsule dispersion was obtained.

Example 3 A microcapsule dispersion having an average particle size of 4.1 μm was obtained in the same manner as in Example 2 except that 8 g of the dye solution of Example 1 was used.

Example 4 An average particle diameter of 6.6 was obtained in the same manner as in Example 2 except that 10 g of the dye solution of Example 1 was used.
A micron microcapsule dispersion was obtained.

Example 5 The same method as in Example 1 was repeated except that polyvinylpyrrolidone used in Example 1 was replaced by polymethylvinyl ether maleic acid (manufactured by Aldrich, molecular weight: 216000). A micron microcapsule dispersion was obtained.

Example 6 Except that glycerol monooleate was used instead of glycerin used in Example 1,
A microcapsule dispersion having an average particle size of 5 μm was obtained in the same manner as in Example 1.

Example 7 Example 1 was repeated except that ethylene glycol was used in place of glycerin used in Example 1.
A microcapsule dispersion having an average particle size of 5 μm was obtained in the same manner as described above.

Preparation of pressure-sensitive recording paper: The microcapsule dispersions of Examples 1 to 4 were coated on a high-quality paper having a basis weight of 40 g so that the coating amount was 3.6 g / m ² , and a white capsule was coated. I got the paper.

Evaluation of pressure-sensitive recording paper: <Evaluation of color development> The coated paper coated with the capsule solution was coated with a color-developing sheet for pressure-sensitive recording (lower paper, manufactured by Fuji Photo Film Co., Ltd.).
N40W) and a static pressure weighted color tester (Shinto Kagaku)
Was used to perform pressure printing at 300 kg / cm ² . The cyan density was measured with a Macbeth densitometer for the density of the color developed on the color developing sheet after printing under pressure. <Evaluation of heat resistance> The coated paper coated with the capsule liquid was 100
After aging for 10 hours in an atmosphere of ° C., the color development was evaluated.
The ratio (%) to the color density before the aging treatment in a 100 ° C. atmosphere was determined. Evaluation of ink suitability: 5 parts by weight of the microcapsule dispersion was mixed with 5 parts by weight of linseed oil, and the compatibility was visually evaluated. In the table, ○ indicates a sufficiently compatible state.

Comparative Example 1 Instead of the glycerin solution of polyvinylpyrrolidone used in Example 1, the average molecular weight was 20.
A microcapsule solution having an average particle size of 5 microns was prepared in the same manner as in Example 1 except that polyethylene glycol 0 was used.

The results are shown in Table 1.

[Table 1]

From the results in Table 1, it can be seen that the microcapsule manufacturing method of the present invention makes it easier to obtain a pressure-sensitive capsule ink without going through the step of drying and redispersing the microcapsule dispersion liquid as compared with the conventional method. It was found that the obtained pressure-sensitive paper had sufficient coloring and heat resistance.

[0037]

As described above, according to the microcapsule production method of the present invention, the microcapsule dispersion is dried and dried.
It can be produced without a re-dispersion step, and can be easily made into microcapsules for capsule ink. Further, according to the capsule ink of the present invention, the obtained pressure-sensitive paper has a sufficient coloring property and heat resistance.

Continued on the front page F-term (reference) 2H085 AA07 BB01 CD09 DD36 DD42 4G005 AA01 AB14 AB27 BA02 BB05 BB12 DB27X DC09X DC18Y DC32X DC32Y DC42X DD02Z DD04Z DD05Z DD07Z DD08Z DD12W DD38Z DD39Z DD56W DD67W0403 BC03 AD03 BC03 BC13 BC14 BC20 BC31 BC33 BC55 BC65 BC68 BC69 BC72 BC73 BC74 BD03 BE22 CA07 GA34

Claims (4)

[Claims] 1. A protective colloid solution obtained by dissolving at least one of polyvinylpyrrolidone, polymethylvinylether or a derivative thereof in a hydrophilic liquid substantially free of water, and a hydrophobic solution containing a core substance. A method for producing microcapsules, comprising mixing and emulsifying. 2. The method for producing microcapsules according to claim 1, wherein the hydrophobic solution contains an electron-donating color-forming material. 3. The method for producing microcapsules according to claim 2, wherein the hydrophobic solution contains an electron-donating color-forming material and a polyvalent isocyanate compound. 4. A capsule ink comprising a dispersion of microcapsules obtained by the method according to claim 1 dispersed in an ink component.