JPH0325354B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to microcapsule compositions, and more particularly to compositions for printing inks containing microcapsules.

Microcapsules are usually several microns to several
It has a particle size of 10 microns, and the internal phase, such as fragrances, dyes, adhesives, chemicals, liquid crystals, etc., is covered with a natural or synthetic polymer film, and the internal phase is chemically or physically coated. It has many advantages in terms of protection and the ability to handle liquids as solids, and is used in a wide range of fields, including carbonless copying paper.

Various methods for producing microcapsules are known and have been put into practical use, but interfacial polymerization, coacervation, and in situ encapsulation methods that effectively protect the internal phase oil are known. Situ method) is an effective method. Specifically, the microcapsules produced in this way are
It is used by coating it on supports such as paper, film, and metal, but it is often pulverized and used as a powder (solid). Microcapsules containing fragrances, liquid crystals, dyes, etc. are usually coated on a support such as paper with water as a dispersion medium by a known method such as air knife coating, roll coating, or blade coating, or by silk screening or other methods. Printing is performed by a known method such as flexography or gravure.

Compared to smearing the entire surface, in the case of printing, partial smearing is possible, which is useful for various purposes or
Although preferable in terms of resource saving, printing inks using microcapsules have hitherto had many problems and have been difficult to use. Generally, microcapsule emulsions are manufactured using water as a dispersion medium, so they are usually smeared (printed) as is, but water requires a lot of energy to dry due to its specific heat of vaporization and boiling point. use.

Furthermore, when it is smeared on paper, the paper expands and contracts, so "wrinkles" are likely to occur, especially in the case of partial printing. Therefore, it is preferable to use an organic solvent instead of water because drying is easy and "wrinkles" are less likely to occur.

However, as organic solvents, benzene, toluene, xylene, cyclohexane, hexane,
When using ligroin, ethyl acetate, methyl acetate, methyl isobutyl ketone, etc., they do not mix well in dispersion water, so the microcapsules are solidified in powder form and then redispersed in these organic solvents. There is a need. However, since microcapsules are a hydrophilic dispersion system that easily disperses in water, these organic solvent systems do not perform well for this redispersion. It is an organic solvent and also has an affinity for water, and alcohols are preferable.The evaporation rate can also be adjusted by using a combination of methanol, ethanol, (iso)propyl alcohol, higher alcohols, etc. It's good.

However, it is also known that these alcohols, or those that dissolve well in both water and organic solvents, such as acetone, extract hydrophobic substances from the internal phase through the capsule membrane.

Because of this drawback (for example, JP-A No. 48-86612,
As described in JP-A-49-32717, JP-A-49-112711, etc., a specific substance is selected as the hydrophobic substance in the inner phase, that is, a substance that is incompatible with methanol in the outer phase, and the composition of the ink is There is. Although this may be suitable for certain specific applications, it is not preferable because it is limited to the internal phase oil, and the selection of the external phase (methanol) is also inconvenient.

The present invention relates to a printing ink containing microcapsules, which has been difficult to achieve in the past.
The feature is that it enables quick-drying microcapsule ink using organic solvents, especially alcohol-based solvents.

The present inventor investigated various aspects for this microcapsule ink and found that only specific microcapsules can be used in this ink, making it possible to manufacture an excellent microcapsule ink.

The ink according to the invention basically consists of pigments,
This ink composition consists of an adhesive, microcapsules, and an alcoholic dispersion medium, and is particularly suitable for gravure or flexographic printing. The pigments mentioned here include general organic and inorganic colored and colorless pigments such as titanium oxide, zinc oxide, calcium carbonate, magnesium carbonate, clays, urea-formalin resin, and starch granules. It is suitable for printing, and has the role of protecting the capsule.
As adhesives, various cellulose derivatives, maleic acid resins, ethylene-acrylics, styrene-modified acrylics, Sierraks, etc. used for general inks can be used. Microcapsules are made of a membrane material containing both melamine-formalin resin and a resin derived from a polyvalent isocyanate compound.
As a manufacturing method, a hydrophobic liquid containing a polyvalent isocyanate compound is emulsified in the form of microdroplets in an aqueous solution containing an emulsifier, and then an initial condensate of melamine-formalin is added from the outer phase (aqueous phase), and the mixture is heated under acidic conditions. Then, a melamine-formalin resin film is formed on the microdroplets of the hydrophobic liquid, the system is made alkaline, and the polyvalent isocyanate compound previously added to the oil phase is mixed with a compound having active hydrogen (polyvalent amine, polyvalent amine, etc.). Polyhydric alcohol, water, etc.) are added from the outer phase to form a polyurethane resin or polyurea resin film. By the above method, microcapsules having two types of resins in their coatings can be obtained. The alcoholic dispersion medium is methanol,
A dispersion medium whose main component is ethanol or (iso)propyl alcohol, but for the purpose of the present invention, the weight percentage of alcohol in the dispersion medium is
It is preferably 40% or less. Furthermore, as the alcohol, ethanol is practical due to the balance between safety and workability.

Examples of the polyvalent isocyanate compound used in the present invention include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,
4-Tolylene diisocyanate, naphthalene-
1,4-diisocyanate, diphenylmethane
4,4-diisocyanate, xylylene-1,4
-diisocyanate, xylylene-1,3-diisocyanate, trimethylene diisocyanate,
Hexamethylene diisocyanate, propylene
1,2-diisocyanate, butylene-1,2-
Diisocyanate, ethyridine diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, etc., and polyvalent isocyanate prepolymers include adducts of hexamethylene diisocyanate and hexane triol, tolylene diisocyanate and Examples include an adduct of hexanetriol, an adduct of tolylene diisocyanate and trimethylolpropane, an adduct of xylene diisocyanate and trimethylolpropane, and the like. These may be used alone or in combination of two or more. Further, the weight ratio of the hydrophobic liquid to the polyvalent isocyanate compound is usually in the range of 100:0.1 to 100:20. Dispersants and emulsifiers used when dispersing and emulsifying hydrophobic liquids in water include gelatin or modified versions thereof, gum arabic, sodium alginate, casein, lecithin, polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, carboxymethylcellulose, and pluronic interfaces. Examples include activators, sucrose fatty acid esters, sorbitan fatty acid esters, alkylbenzene sulfonates, alkylnaphthalene sulfonates, polyoxyethylene sulfates, neat oils, polyoxyethylene alkyl ethers, and particularly preferred examples include maleic anhydride. Examples include acid copolymers. Examples of maleic anhydride copolymers include ethylene maleic anhydride copolymer, propylene maleic anhydride copolymer, (iso)butylene maleic anhydride copolymer, vinyl acetate maleic anhydride copolymer, and styrene maleic anhydride copolymer. Polymers such as vinyl methyl ether maleic anhydride copolymers may be mentioned by way of example. The most preferred among these is ethylene maleic anhydride copolymer. These can be used in combination with known emulsifiers, activators, and polymeric compounds such as polyvinyl alcohol and polyacrylic acid. The aqueous solution containing the maleic anhydride copolymer is prepared so that its pH is usually in the acidic range of 1.0 to 7.0, preferably 3.0 to 6.0. To adjust the pH, sodium hydroxide, ammonia, hydrochloric acid, acetic acid, etc. are usually used, but there are no particular limitations.

The temperature during emulsification is usually 40°C or lower, preferably 30°C or lower. The particle size is desirably less than 20μ, preferably within the range of 3 to 10μ.

The melamine-formalin initial condensate is obtained by adding 1.2 mol or more, preferably 1.5 to 3.5 mol, of formalin to 1 mol of melamine under alkaline conditions, and is generally a mixture of monomethylolmelamine to hexamethylolmelamine and formalin. There are many commercially available products. In addition, modified melamine resins such as methylated and butylated melamine resins are commercially available, and are also modified with phenols, urea, etc., but as long as they are water-soluble, they can be used in the same way as the melamine-formalin initial condensate. be.

Compounds with active hydrogen that react with polyvalent isocyanates to form films include polyvalent amines such as ethylenediamine, hexamethylenediamine, octamethylenediamine, triethylenetetramine, paraphenylenediamine, piperazine, diethylenetriamine, and amine addition to epoxy resins. These may be used alone or in combination of two or more. Examples of polyhydric alcohols include catechol, resorcinol, 3,4-dihydroxytoluene, 2,4-dihydroxyethylbenzene, 1,3-naphthalenediol, 1,
5-naphthalenediol, 0-0′ biphenol,
p-p'biphenol, 1,1-bi-2-naphthol, bisphenol A, ethylene glycol,
1,3-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,
1,1-trimethylolpropane, hexanetriol, penta-erythritol, glycerin,
Examples include sorbitol, which may be used alone or in combination of two or more. These active hydrogen-containing compounds are usually used in a concentration range of less than 50% based on the weight of the polyvalent isocyanate.
Water can also be used as the active hydrogen compound. In the encapsulation step, a hydrophobic liquid containing a polyvalent isocyanate is dispersed and emulsified in an aqueous solution containing a preferably PH-adjusted maleic anhydride copolymer, and an already dissolved melamine-formalin initial condensate is added therein. Temperatures of 60°C or higher, particularly preferably 70°C or higher
By keeping it for 15 minutes or more, a melamine-formalin resin film is formed. After this, the system was tested at the same temperature.
A polyurea resin or a polyurethane resin is formed by making the pH alkaline to 7.0 to 14.0, preferably 8.0 to 11.0, and adding a compound having active hydrogen. To raise the pH, an aqueous sodium hydroxide solution or aqueous ammonia is usually used, but there are no particular limitations. Further, the compound having active hydrogen may be added alone or may be added in combination with the alkaline aqueous solution. The thus prepared microcapsules having two types of coatings were extremely resistant to solvents, especially to alcohol. Furthermore, the microcapsules used in the present invention are formed by forming a polyurea resin or polyurethane resin as a coating resin by reacting a polyvalent isocyanate with a compound having active hydrogen, rather than an inner phase (oil phase), and then forming a polyurea resin or a polyurethane resin as a coating resin in the outer phase. Since it forms a melamine-formalin resin, microcapsules with extremely strong coatings can be obtained. In particular, it has extremely strong resistance not only to chemical destruction (depicting internal phase substances) caused by alcohol, etc., but also to mechanical pressure applied during the printing process, as well as physical pressure on the resulting sheet, especially against friction (rubbing). It is a microcapsule that shows the gender. The proportion of solid content in the ink can be determined appropriately based on the purpose, but it is common to add 10 to 100 parts of the pigment adhesive and 0 to 50 parts of the pigment adhesive to 100 parts of the microcapsules (dry). It is. Here, 0 parts of adhesive means that the microcapsule dispersion liquid itself also contains an adhesive, and the adhesive added later is unnecessary.

The microcapsules of the present invention can contain a hydrophobic substance itself as an internal phase substance or a hydrophobic substance dispersed and dissolved in a suitable solvent. Particularly preferable examples include perfumes, colored dyes, colorless substances for carbonless paper Examples include dyes and color developers for carbonless paper.

The microcapsule composition of the present invention cannot be prepared using gelatin-based microcapsules produced by the so-called complex coacervation method because the substance inside the capsule is easily visualized by alcohol. Furthermore, when microcapsules made by using various polyvalent isocyanate compounds as main membrane precursors are used, the internal phase is less likely to be visualized by alcohol than in the case of microcapsules mainly made of gelatin, but this is unsatisfactory. Microcapsules produced by in situ polymerization, in which the membrane is mainly made of urea-formalin resin, are better than capsules made mainly of gelatin, but they cannot withstand alcohol sufficiently. Furthermore, although microcapsules whose film is mainly made of melamine-formalin resin are extremely resistant to alcohol, the physical properties of the film of the microcapsules according to the present invention were even better. In the end, the alcohol-based microcapsule composition of the present invention became possible only by using microcapsules having both a melamine-formalin resin and a resin derived from a polyvalent isocyanate compound as a film as in the present invention. be.

This will be explained in detail below using Examples.

Example 1 As an electron-donating coloring agent, 2.0 g of crystal violet lactone and 1.0 g of benzoyl leucomethylene blue were dissolved in 97 g of SAS oil N-296 (Nippon Petrochemical, trade name), and then 2.3 g of polyvalent isocyanate was dissolved. Coronate HL (Nippon Polyurethane Co., Ltd., aliphatic isocyanate) and 30 g of ethyl acetate as an auxiliary solvent were added and dissolved. Hydrophobic liquid: ethylene maleic anhydride copolymer, 5.0 g
100g of emulsifier aqueous solution with pH set to 4.5
with vigorous stirring to form hydrophobic droplets with a diameter of 4-10μ. A melamine-formalin initial condensate aqueous solution containing 5.0 g of melamine and 11.7 g of 37% formaldehyde dissolved at pH 9.0 is added to the emulsion and heated at 70° C. for 1 hour. 20 after this
% aqueous sodium hydroxide solution, the pH was set at 9.5, and heating and stirring at the same temperature was continued for 1 hour to complete the encapsulation.

A mixed and dispersed liquid of 20 parts of kaolin clay, 150 parts of ethanol, and 10 parts of Marquid (manufactured by Arakawa Chemical Co., Ltd., maleic acid resin) was added to 100 parts (solid content) of the above microcapsules to obtain an ink for flexogravure. After adjusting the viscosity of this flexogravure ink with ethanol to an appropriate viscosity, it was printed at 82.4 g/m ² using a 40μ gravure plate manufactured by Miyakoshi Seisakusho Co., Ltd.
When gravure printing was performed on high-quality paper at a speed of 50 m/min, carbonless paper with good color development was produced. When the printed surface was observed with a scanning electron microscope, almost no capsule destruction was observed.

Example 2 Oil Color Scarlet, manufactured by Orient Chemical Co., Ltd., was used as an oil-soluble red dye instead of the electron-donating coloring agent in Example 1.
Capsules were manufactured using the same amount of #308 under the same conditions as in Example 1, and printed in the same manner. This printed paper was useful as a red transfer paper or copy paper, and could also be used in combination with cloth, etc., for patterns such as cotton paper, or for embroidery.

Example 3 The microcapsules produced in Example 1 were dried into powder using a spray drying device (manufactured by Yamato Chemical Co., Ltd.), and 100 parts of the microcapsules were mixed with the following:
Water/isopropyl alcohol (1/1) mixed solvent
A flexogravure ink was prepared by mixing and dispersing 20 parts of Marquid (manufactured by Arakawa Chemical Co., Ltd., maleic acid resin) in 100 parts and 10 parts of titanium oxide.

This ink was applied to commercially available carbonless copy paper (51 g/m ² ) using the printing machine in Example 1.
Although printing was carried out at a speed of 50 m/min, the dye inside the microcapsules was not depicted and a white, carbon-free self-coloring sheet was created.

Claims (1)

[Claims] 1 Basically, a hydrophobic liquid containing a pigment adhesive polyvalent isocyanate compound dissolved therein is emulsified in an aqueous phase containing an emulsifier, and then a melamine-formalin initial condensate is added and the hydrophobic liquid is dissolved under acidic heating. A film that combines a melamine-formalin resin obtained by forming a melamine-formalin resin film on the droplet and then reacting a polyvalent isocyanate compound with a compound having active hydrogen under alkaline conditions and a resin derived from the polyvalent isocyanate compound. A microcapsule composition for printing ink consisting of an alcohol-based dispersant.