JPS58191771A - Flexographic capsule ink - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a flexographic capsule ink.

More specifically, the present invention relates to a flexo-type capsule ink made of L Iter 11 capsules that have excellent durability such as heat resistance, impact resistance, abrasion resistance, bath erosion resistance, and weather resistance.

As is already known, microcapsules are unstable substances, chemically reactive substances, biologically active substances, volatile substances, fluid, adhesive/sticky substances,
A normally normless microscopic container that contains fine particles such as colored substances, and is used in the fields of pressure-sensitive recording materials, fragrances, adhesives or adhesives, fertilizers, pharmaceuticals, agricultural chemicals, foods, etc. or technical studies are being conducted.

These microcapsules may be used as dry solids (powder) or blended products, but they may be used as binders, other auxiliary materials, or additives as necessary to make paper, film, cloth, boards, foils, etc. It is often used by being coated with objects, etc. In this case, the coating may be applied over a wide area over the entire surface of the substrate, or may be applied only to desired areas in a butter-like pattern (vert coat).

In order to perform such partial coating (vert coat) industrially efficiently and with good reproducibility, it is preferable to use various printing methods, such as letterpress printing, intaglio printing, and planographic (offset) printing. , screen printing, etc. may be used, but the difficulty of preparing the printing ink (coating liquid), relatively low printing pressure, tolerance of printing (coating) conditions,
For these reasons, the Clavier offset printing method, especially the so-called flexo printing method, is considered to be suitable for partial coating of microcapsules.

That is, in flexographic printing, an ink (coating liquid) consisting of solid content and a volatile medium is usually applied to a base material (coating liquid) via a fountain roll or anilox roll using a printing plate (Batano) manufactured by Com.
(printed material) and dry.

The present inventors prepared flexo inks containing various microcapsules and actually performed flexographic printing, and found that the following problems may occur.

That is, (1) the microcapsules are broken even with a printing pressure comparable to flexographic printing;

(2) When drying with hot air, infrared rays, high frequency, etc., the microcapsules may be thermally deteriorated.

(3) The volatile medium of flexible ink is alcohol,
In the case of organic solvents such as acetate esters, ketones, and cellosolves, microcapsules may be destroyed or the internal phase (core substance) may be extracted.

(4) Microcapsule printed matter may be destroyed by light impact or friction during handling.

(5) Regarding microcapsule printed matter, when toner printing is performed using an electrophotographic method or an electrostatic recording method (wet development), the microcapsules may be destroyed by the developer (and drying heat).

(6) In order to obtain a flexographic ink using an organic solvent such as alcohol as a medium, the aqueous microcapsule emulsion is, for example, spray-dried to form a dry powder, and an organic solvent-based ink is prepared for flexographic printing. If this is done, the microcapsules may be destroyed under the harsh conditions mentioned above.

It has been found that such differences in the durability of microcapsules depend first of all on the microencapsulation method itself.

That is, various microencapsulation methods are already known, such as a method that utilizes the conoplex coacervation phenomenon between a protein such as gelatin and an anionic polymer such as arabicum or CMC, and a method that applies chemical methods for polymer synthesis. interfacial polymerization method (main raw materials include ino-7 anate compounds and epoxy compounds), in-situ polycondensation method (main raw materials include polyvalent amine compounds such as urea, melamine, and aldehyde compounds such as fort and altehyde), and others. Among them, microcapsules using I/Saijutun condensation are famous, especially microcapsules whose walls are made of melamine resin derived from formaldehyde and a polyvalent amine compound mainly composed of melamine (U, S .

P, 4. loo, xo3, U, 8. P, 4,233,1
78 etc.) was found to have the best durability.

However, even then, the durability may not be sufficient as a flexo-type capsule ink, and as a result of extensive research, we have developed a melamine-based ink whose microcapsule wall membrane is cured in hot water with a temperature of over 80°C. It was discovered that a flexo-type capsule ink that can withstand various harsh conditions can be obtained only when it is made of resin, and this led to the present invention.

That is, in the known in situ polycondensation method, a poorly water-soluble substance is added to an aqueous phase containing an anionic water-soluble polymer to finely emulsify it, and then, for example, an initial condensate of melamine-formaltehyde is added, and several dozen A polycondensation reaction was carried out at a temperature of 10°C to obtain microcapsules having an aminoblast wall.

In this case, in the known method, the reaction temperature is preferably 50 to 80°C, even for microcapsules with melamine resin membranes; at lower temperatures, the reaction rate is slow and the wall membrane is too weak; at higher temperatures, the capsules agglomerate during the reaction. It is unsuitable because it causes many problems such as gelation of the emulsion and destruction of the capsule.

However, the melamine-based resin membrane microcapsules used in the present invention are obtained by first carrying out a sufficient encapsulation reaction at a temperature of 80° C. or lower to obtain microcapsules that do not cause any problems with the ζ normally used. A strong wall film is obtained by curing the film by keeping it at a temperature of 80° C. or higher for a sufficient period of time in a wet state. This made it possible for the first time to produce a flexo-type capsule ink with sufficiently excellent durability.

In this way, it is unknown in conventional microencapsulation technology that the capsules are further heated in water to a high temperature after capsule formation.

In other words, microcapsules produced by coacervation method using gelatin, interfacial polymerization method using isoneanate, etc. are produced at a temperature much lower than 80°C, and furthermore, after microcapsule production, high temperature treatment in water (approximately 70°C) is required. The present inventors have confirmed that the capsule wall is normally destroyed when the above) is carried out.

In other words, microcapsules are generated at a relatively low temperature (80°C or less) and then heat-treated at a temperature exceeding 80°C (it may be cooled once during this period) to produce a product that is sufficient for use as a flexo-type capsule ink. The only microcapsules that can be made are ones with a wall made of aminoplast, and it has been found for the first time that those with a wall made of melamine resin are the best (melamine-based ones can be made by heating in boiling water). (It is possible, and far from being destroyed, it is becoming stronger and stronger.)

The flexographic capsule ink of the present invention usually contains a volatile medium,
It consists of microcapsules, a binder, and other additives (pigments, anti-deterioration agents, etc.) as necessary, and the volatile medium is water and various organic solvents (methanol, ethanol, isopropanol, normal propatool, etc.). Alcohols such as methyl acetate, ethyl acetate, isoprobuterol acetate, φsolv, etc.; ketones such as acetone, methyl ethyl keto 7, etc.; benocene, toluene,
aromatic solvents such as; other petroleum solvents, etc.), or a mixture of these (especially when alconyls are used, the capsules are easily destroyed), and the microcapsules are 80% as described above. Melamine-based resin wall microcapsules heat-treated at temperatures above ℃, and various water-soluble polymer compounds (soluble starch, polyhinyl alcohol, CMC, etc.) are used as binders.

Hydroxy7methylcellulose, acrylic or methacrylic acid (co)polymers, maleic acid copolymers, etc.) and organic solvent-soluble polymer compounds (various vinyl resins, acrylic (or methacrylic) resins, polyesters, polycarbonates, polyamides, etc.) Titanium white, zinc white, finely powdered silica, raw starch powder, etc. are used as pigments.

Normally, the ratio of each component is 1ON100 parts, with the binder being around 50 parts per 100 parts of the microcapsules, and the volatile medium being 100 to 200 parts, but in actual flexographic printing, they should be diluted as appropriate. It is done.

The internal phase (core substance) of microcapsules varies depending on the purpose, but typical examples include various organic solvents, especially high boiling point solvents for pressure-sensitive recording materials (in addition to pressure-sensitive dyes and phenols for pressure-sensitive color developers). resins, salicylic acid derivatives, etc.), fragrances, adhesives or adhesives, agents,
Examples include agricultural chemicals such as insecticides.

The melamine resin referred to in the present invention is an aldehyde polycondensation resin mainly composed of melamine 7, and in addition to melamine, for example, guanamine derivatives, urea, ethylene urea,
It also includes urea derivatives such as thiourea, and resins to which other modifiers have been added.

Next, as an example, the effects of the present invention will be explained in detail by citing a typical example of a flexo-type capsule ink for the purpose of producing a pressure-sensitive recording material.

Example 11 Preparation of color former capsules 15 parts of crystal violet lactone (parts by weight, same hereinafter) was heated and dissolved in 85 parts of Hysol SAS N-296 (manufactured by Nippon Petrochemical Industries, Ltd., a high boiling point solvent for pressure-sensitive recording materials). , 100 parts of internal phase oil (poorly water-soluble substance) was obtained.

This was emulsified and dispersed in 100 parts of a 5X aqueous solution having a pH of 5.5 in which a styrene-maleic anhydride copolymer was dissolved together with a small spoonful of sodium hydroxide. Add 7 parts of melamine and 18 parts of 37X formalin to 30 parts of water, adjust the pH to 9.0 with sodium hydroxide, heat for 15 minutes to obtain a melamine-formaldehyde initial condensate, and add this to the emulsified dispersion. The liquid temperature was maintained at 60° C. for 3 hours (Microcapsule 1-A). Average particle size 50 μm.

Half of this amount was further heated to 91° C. and continued to be heated and stirred for 1 hour (Microcapsule 1-B).

Example 2 Preparation of Color Developer Capsule Rose-Phenylphenol-Formaldehyde Resin 4
0 part was heated and dissolved in 60 parts of Hysol 5ASN-296 to obtain 100 parts of internal phase oil. This was encapsulated in the same manner as in Example 1 to obtain developer capsules with an average particle size of 70 μm.

Microcapsules reacted at 60°C for 3 hours...Microcapsules-A Further heated at 95°C for 1 hour...Microcapsules 2-B Example 3. Powderization process These microcapsule dispersions are dried into capsule powder using a centrifugal atomizer and one-way spray dryer.
Got the kind. The powdering conditions were: capsule concentration 30×1 outlet temperature 85°C.

Example 4. Process of Making Ink The obtained powder capsules were made into a flexo-type capsule ink using the following formulation.

Color developer capsules of Example 1: 20 parts (microcapsules 1-A or 1-B) Color developer capsules of Example 2: 80 parts (microcapsules 2-A or 2-B)
) Modified vinyl acetate derivative 50 parts (Cohonyl, manufactured by Nippon Gohsei) Diocnal phosphate ester heptanoethanolamine salt
25 parts special wheat starch powder
40 parts methyl alcohol
Four types of flexographic capsule inks were obtained by uniformly mixing 150 parts or more of the composition.

Example 5. Flexographic printing process The flexographic ink obtained in Example 4 was diluted with methyl alcohol, and flexographic printing was performed on high-quality paper with a basis weight of 50 t/& using a foam printing machine, so that the amount of ink applied was 5 in terms of solid content.
Partially coated carbonless pressure-sensitive transfer paper was prepared in such a manner that the transfer paper was coated with a coating film of 100% by weight.

Looking at the printed surface after drying, microcapsules 1-A and 2
-A combination had a slightly blue color.

On the other hand, the combination of 1-B and 2-B was pure white.

Example 6. Printed matter evaluation test say/rf The transfer paper was stacked so that the capsule printing surface was in contact with the high-quality paper, and a writing test was performed from above with a ballpoint pen.It was found that with the combination of 1-A and 2-A, At this stage, the copied characters were hardly colored, and the paper was already rejected as a partially coated non-carphone pressure-sensitive transfer paper.

The combination of 1-B and 2-A and the combination of 1-A and 2-B somehow passed the test at this stage.

The combination of 1-B and 2-H passed the test perfectly.

The three types of partially coated carbonless pressure-sensitive transfer papers that passed this stage were soaked in a liquid toner (developer) for electrostatic recording and then dried by irradiating them with infrared rays. Afterwards, we tested the ability to transfer color onto high-quality paper using a ballpoint pen.
In both the combinations of 1-B and 2-A and the combination of 1-A and 2-H, the transfer coloring ability was significantly reduced. On the other hand, it was determined that the combination of 1-B and 2-B had transfer coloring ability at a practical level.

Note that the partially coated carbonless pressure-sensitive transfer paper used in this example is a self-contained paper intended for pressure-sensitive copying onto plain paper, unlike ordinary pressure-sensitive recording paper consisting of a clay paper and a base paper. However, if the microcapsules are destroyed and the internal phase oozes out, the subsequent transfer coloring ability is extremely reduced.

Moreover, it is not necessarily limited to only partial coating, and it is also possible to print or coat the entire surface of the substrate to be coated, and of course, the effects of the present invention are also exhibited in that case.

Claims (1)

[Scope of Claims] l In a flexo-type cassisel ink made by dispersing microcapsules containing a poorly water-soluble substance in a volatile medium, the wall membrane of the microcapsules is heat-treated in hot water at a temperature exceeding 80°C. Flexible type capsule ink characterized by being made of melamine-based resin. 2. The flexo-type capsule ink according to claim 1, wherein the volatile medium is mainly a lower alcohol (having 1 to 3 carbon atoms in the chemical structural formula).