JPS62161874A - Microcapsule composition - Google Patents

Abstract

PURPOSE:To provide the titled composition free from blur and impairment in color-developing sensitivity, outstanding in stability with time, comprising synthetic resin microcapsules, vinyl pyrrolidone-vinyl acetate copolymer as an adhesive, pigment and water-alcohol-based dispersion medium. CONSTITUTION:The objective composition, i.e. printing ink composition comprising (A) synthetic resin microcapsules, (B) as an adhesive, vinyl pyrrolidone-vinyl acetate copolymer, (C) pigment and (D) water-alcohol-based dispersion medium with a weight ratio of the water to the alcohol falling, pref. between 60/40 and 0/100.

Description

Detailed Description of the Invention (A> Industrial Application Field The present invention relates to a microcapsule composition,
More specifically, the present invention relates to a printing ink composition containing microcapsules.

Microcapsules usually have a particle size of several microns to several tens of microns, and contain fragrances, dyes, adhesives, etc. as an internal phase.
It is a product in which chemicals, liquid crystals, etc. are coated with a natural or synthetic polymer film, and it has great advantages in that it can chemically or physically protect internal substances and handle liquids as solids, making it a carbonless copying method. It is used in a wide range of fields including paper.

(B) Conventional technology Various methods for manufacturing microcapsules are known and have been put into practical use, but methods of encapsulation that effectively protect the internal phase oil include interfacial polymerization, coacervation, The in-length in-ditu polymerization method (in 5-itu method) is an effective method. The microcapsules produced in this way are
Specifically, it is used by being coated on a support such as paper, film, or metal, or it is pulverized and used as a powder (solid).

Microcapsules containing fragrances, liquid crystals, dyes, etc. are usually coated with water as a dispersion medium onto a support such as paper 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. Incidentally, in these recent fields, there is often no substantial distinction between smearing and printing.

That is, both coating and blitting are essentially the same thing because they involve providing a liquid substance in a thin layer on the plane of the support.

The means of implementation are also becoming more common.

The method of preparing microcapsules as printing ink has been known for a long time, and its basic structure is as follows:
Consists of microcapsules, adhesive, pigment, and dispersion medium.

Examples of the microencapsulation method include the known microencapsulation method, Zunawara method, coacervation method, and in 5i method.
Methods such as the tu method and interfacial polymerization method are used. A wide variety of pigments are used, including inorganic and organic pigments, and the type and amount added are determined depending on the purpose.

As the dispersion medium, water is usually used, but if necessary, alcohol and other organic solvents may be used alone or in combination.

Many types of adhesives are known, but they can be classified based on their solubility: 1. Water-soluble adhesives 2. Emulsion type adhesives 3. Water-alcohol soluble adhesives 4. Alcohol-soluble adhesives Divided into 4 types.

The water-soluble adhesive No. 1 includes dissolved starch and its modified products;
Common examples include polyvinyl alcohol, gum arabic, gelatin, casein, carboxymethyl cellulose, alginates, and the like.

The emulsion type adhesive in step 2 is styrene.
Common examples include emulsifying and dispersing agents such as butadiene rubber, vinyl acetate resin, acrylic resin, and polyester resin.

Examples of the water-alcohol soluble adhesive of No. 3 include acrylic ester resins and modified polyvinyl acetate resins.

The alcohol-soluble adhesives in No. 4 are those used in normal flexogravure inks, and specifically include various cellulose derivatives, maleic acid resins, alkyd resins, terpene resins, ketone resins, butyral resins, and rubber resins. etc.

These compositions are combined in various ways depending on the purpose and method of use to prepare printing inks.

(C) Problems to be Solved by the Invention The present invention solves the problems that occur when the various adhesives described in section (B) are used as printing inks.

Water-soluble adhesives exhibit their adhesive strength effectively in water-based inks, and are widely used in terms of ease of use and cost. However, the problem with water-based inks using water-soluble adhesives is that: since the adhesive itself has a low solids content and high viscosity, the prepared ink also has a low solids content and high viscosity.

: Since water is used as a dispersion medium, the energy required for drying is large and the drying performance is poor.

: Printing unevenness, patterns, wrinkles are likely to occur, etc., and it cannot fully meet the demands of high-speed printing.

On the other hand, in order to improve drying properties, it is possible to prepare a water-alcohol printing ink by adding an organic solvent such as alcohol to the water-based ink, but the problem is that: In the case of water-based ink, However, sufficient adhesive strength cannot be obtained.

:Depending on the type of adhesive, some may cause aggregation in the liquid due to poor compatibility with organic solvents.

Many emulsion type adhesives themselves have low viscosity and high solids content, and the ink prepared therefrom also has excellent fluidity.

However, since this type of adhesive usually uses water as a dispersion medium, it has poor drying properties and causes wrinkles, as in the case of water-based ink.

On the other hand, addition of an organic solvent such as alcohol leads to destruction of the emulsion form and causes aggregation and dispersion of the resin in the liquid, which is not preferable.

Acrylic acid ester and polyvinyl acetate-based modified resins have been developed as water-alcohol soluble adhesives.
It has become possible to stably prepare water-alcohol based printing inks, and it has also become possible to print at a certain high speed. However, the problem with niacryl ester is that the adhesive contains a considerable amount of water, and the prepared ink also contains a large amount of water, impairing drying properties.

: Polyvinyl acetate-based modified resin has extremely high viscosity, tends to cause uneven matte finish and patterns, and cannot be diluted to a low viscosity, making it difficult to print well. Improvements are required for practical use. It is something.

Regarding alcohol-soluble adhesives, judging from the aspects of solubility in alcohol and adhesive strength, there are those that have high solid content and low viscosity but lack adhesive strength, and those that have excellent adhesive strength but low solid content and high viscosity. It can be divided into 3 types.

The former includes maleic acid resin, terpene resin, alkyd resin, and ketone resin, and the latter includes rubber resin and butyral resin, each of which has its own merits and demerits. Currently, adhesives are used in combination.

However, a major problem with alcohol-soluble adhesives is that they are very unstable when mixed with water.

In other words, when this type of adhesive is used as a water-alcohol-based adhesive for printing ink, the resin precipitates due to poor compatibility with the water present. It is difficult to use it for

The present invention aims to solve the above-mentioned problems using a single adhesive in a printing ink containing alcohol as a main component of the dispersion medium.

(D> Means for Solving Problems The present invention relates to a printing ink containing microcapsules, and the basic 7e of the printing ink in the present invention is
The i″ configuration is: ■Synthetic resin microcapsule.

This is an ink composition particularly suitable for gravure or flexographic printing, consisting of (1) an adhesive, (3) a pigment, and (4) a water-alcoholic dispersion medium.

In the present invention, it is possible to obtain similarly good ink with a so-called water-based ink consisting only of water as a dispersion medium, but in order to improve the drying properties of the ink and eliminate wrinkles and unevenness on the printed surface after drying, The effect can be maximized by setting the ratio (%) of water as a dispersion medium to alcohol at a ratio of 60:40 to 0:'100.

In order to solve the problem shown in section (C) of this specification, the present inventor found that the problem can be solved by using a specific adhesive.

In other words, by using vinylpyrrolidone-vinyl acetate copolymer as an adhesive, it is possible to prepare ink with a low viscosity and high solid content in both water-alcohol mixed systems and 100% alcohol solvent systems, and it is possible to prevent adhesive precipitation, etc. The effect of the present invention was maximized without any problems.

This adhesive can have the desired degree of consistency depending on the characteristics to be designed, and can be synthesized in various states such as solution and emulsion. However, it could be used in the present invention.

The adhesive is used in an amount of 5 parts to 80 parts, preferably 10 parts to 60 parts, based on 100 parts of microcapsules (dry solid content).

Synthetic resin microcapsules form an extremely important skeleton as one of the constituents of the printing ink in the present invention.

That is, since alcohol is used as the dispersion medium of the printing ink in the present invention, microcapsules having a film that can be destroyed or dissolved by alcohol are virtually not used in the present invention.

It goes without saying that if it is assumed that the material will be kneaded for a long time between rolls on a printing press, it will be required to be extremely stable physically and mechanically.

Synthetic resin microcapsules are known to be effective in meeting such requirements.

Examples of methods currently used industrially for producing synthetic resin microcapsules include the in-situ method and the interfacial polymerization method.

As for the in 5 itu method, microcapsules mainly made of aminoplast (amino resin) film have been announced, and specifically, JP-A-51-9079, JP-A-5
Examples include microencapsulation methods using urea-formaldehyde copolymer resins and melamine-formaldehyde resins as described in JP-A No. 2-66878, JP-A-53-84861, and JP-A-54-49984. It will be done.

In addition, many microencapsulation methods using interfacial polymerization methods have been published, and microencapsulation methods using polyurethane resin and polyurea resin films are published in Japanese Patent Publication No. 42-446@, Publication No. 2882-2882, and Japanese Patent Publication No. 42-2882. 8693
It is stated in the publication.

These synthetic resin microcapsules may be freely designed depending on the composition of the intended printing ink, the purpose of use, and the printing method, and are not particularly limited in the present invention.

The pigment used in the present invention can be organic, inorganic, colored,
Common colorless pigments such as titanium oxide, zinc oxide, silica, calcium carbonate, kaolin, urea-formalin resin particles, melamine particles, starch particles, and various synthetic resin particles can also be used.

The alcohol-based dispersion medium used in the present invention is selected from methanol, ethanol, n-propertool, and iso-propertool as main components, and these are selected at appropriate ratios while controlling the drying rate of the ink. can be mixed with

Further, although it is possible to add other organic solvents, it is necessary to set the addition amount to a range that has good compatibility with the water-alcohol system and that will not cause separation, and also to select a solvent that will not separate.

The solid content in the ink may be appropriately determined depending on the intended use of the ink and the viscosity of the ink, but is preferably in the range of 30 to 70%, more preferably 40 to 60%.

The printing ink according to the present invention has a water-alcohol ratio (%
) O: 100 (i.e., a completely non-aqueous ink) can sufficiently exhibit the effects of the present invention, but in order to do so, it is necessary to dehydrate the water during capsule preparation, and in that case,
Water can be removed by centrifugation, filter press, screw press, spray drying, etc.

(E) Examples Next, examples of the present invention will be specifically described.

Example 1 Hysol 5AS containing 10 parts of CVL (crystal violet lactone) as electron-donating colorless dye 1
-200 parts of N-296 (Nippon Petrochemical Co., Ltd., high-boiling hydrocarbon oil) were mixed with 5 parts of styrene-maleic anhydride copolymer.
% water solubility (pH 4,8>200 parts and emulsified to an average particle size of 3.5μ. Next, 20 parts of melamine and 37
% formaldehyde solution and 15 parts of water pl-19
, 5 to obtain a melamine-formalin initial condensate, which was added to the emulsion and stirred, reacted at 75° C. for 2 hours, and then adjusted to pH 9.5. The above microcapsule 10
To 0 parts (dry solid content), 50 parts of kaolin clay and 40 parts (dry solid content) of Sevian-A (manufactured by Daicel Chemical, vinyl pyrrolidone-vinyl acetate copolymer, solid content 50%, IPA solution *) were added, The solid content of the ink was adjusted to 50% using ethanol and used as an ink for flexo and gravure. The type B viscosity of the ink (measured at 25° C.) was 110 cps, and the water-alcohol ratio in the dispersion medium was 50:50.

When this printing ink was used to print on 82.4 y/m high-quality paper using a 40 μm mesh gravure plate, a no-pressure paper with good color development was obtained. The printed surface had no satin unevenness or wrinkles and had good drying properties.

Example 2 After adding 200 parts of methanol to 100 parts of the microcapsule dispersion (dry solid content) in Example 1 and mixing well, the dispersion medium was separated using a centrifuge at 10,000 GX for 10 minutes. was added to increase the solid content to 4
The microcapsule slurry was redispersed to 0%.

To 100 parts (dry solid content) of this microcapsule dispersion, 40 parts of wheat starch (manufactured by Okumoto Seifun Co., Ltd., floating powder) and 35 parts of Cevian A (dry solid content) as in Example 1 were added as an adhesive. The solid content of the ink was adjusted to 55% using methanol which had been added and well dispersed.

The type B viscosity (25°C) of this ink was 85 CpS, and the water-alcohol ratio was 10:90.

When this ink was used for flexographic printing on 409 copies of high-quality paper using a 60-mesh anilox roll, a no-strength bond paper showing good color development was obtained. In addition, the printing surface has no matte unevenness or wrinkles, and the printing speed is 1007mm.
7? Even when the drying time was increased to ,/min, the drying property was good.

Example 3 The microcapsule dispersion in Example 1 was applied to the mini spray DL-21 spray dryer manufactured by Yamato Scientific Co., Ltd.
After pulverizing it using a mold, it was redispersed to a solid content of 50%. Next, 40 parts of the wheat starch in Example 2 and 30 parts of Cevian A were added, and the mixture was made into a stock with methanol to a solid content of 50% to obtain a printing ink. Flexographic printing was carried out in the same manner as in Example 2, and even at a printing speed of 150 yrt/min, no satin unevenness, wrinkles, etc. were observed, and the drying properties were good.

Comparative Example 1 The same microcapsule dispersion and pigment as in Example 1 were used, and polyvinyl alcohol GL-05 was used as the adhesive.
(Nippon Gosei Kagaku Kogyo ■Specially low polymerization degree PVA) was added in the same amount as in Example 1 to prepare a water-based printing ink. however,
Since this polyvinyl alcohol is only 20% soluble in water, the solid content of the obtained ink was also limited to 43%.

Comparative Example 2 ゛An ink was formed with the same composition as in Example 2, except that Marquid Nα31 (Higashi Kagaku Kogyo (Tai-made alcohol-soluble maleic acid resin) was used as the adhesive in the printing ink in Example 2, A printing ink was obtained.

Comparative Example 3 As a binder in the printing ink in Example 2,
Water-alcohol soluble adhesive, Cohonyl PK-40
(The ink was made with the same composition as in Example 2 except that Nippon Gosei Kagaku Kogyo (modified vinyl acetate resin manufactured by IQ) was used, but in order to obtain good printed matter on a flexo printing machine,
It was necessary to reduce the viscosity by diluting it with alcohol to a solids concentration of 30%.

Comparative Example 4 The microcapsule dispersion prepared in Example 1 was prepared using Yamato Scientific (II Spray Dryer Mini Spray-DL-2).
After powdering using Type 1, it was redispersed in methanol to a solid content concentration of 50%. Next, 50 parts of kaolin clay and 31.40 parts of Marquid Nα were added, and the mixture was prepared with methanol to a solid content of 50% to obtain a printing ink.

Comparative Example 5 In preparing the ink in Comparative Example 4, S-LEC BL-X (butyral resin manufactured by Sekisui Chemical ■) was used as an adhesive.
A printing ink was obtained in the same manner as in Comparative Example 4 except that . Table 1 shows the properties of the printing inks obtained in Examples 1 to 3 and Comparative Examples 1 to 5.

(*1, Measured using gas chromatography.

*2. Judgment was made based on the peeling state of the printed surface with the cellophane adhesive tape. ) (Hereinafter in the margin) (F) Effects of the Invention The following effects can be obtained by using a specific adhesive for a water-alcohol based printing ink as in the present invention.

1. As a recording paper, there is no decrease in color development sensitivity.

2. Unintended color development, that is, staining is less likely to occur.

3. It is possible to form an ink with a low viscosity, high solids content, and excellent stability over time, which is preferable as a printing ink.

4. Unevenness, patterns, and marginal zones are less likely to occur on the printed surface.

5. Since it is a colorless and odorless adhesive, it does not cause coloring of the printed surface and is very effective as a colorless carbon ink.

6. Since it is freely soluble in water, water can be used to clean the rolls of printing presses, etc., which provides many advantages such as a marked improvement in the working environment compared to when organic solvents are used as cleaning liquid. It is something.

The above effects can be similarly obtained by using the specific adhesive according to the present invention even in the case of 100% alcohol composition, that is, completely alcoholic ink.
It was suitable for high-speed printing.

Tewa “Lne 111 official manuscript (spontaneous) 1. Indication of thing 1!1 1985 Patent application No. 389
No. 8 No. 2, Name of the invention Microcapsule composition 3, Relationship with the person making the amendment Patent applicant address 4-2 Marunouchi Otsu-chome, Chiyo A1-ku, Tokyo Contact address: 125 Higashiganemachi-chome, Katsushika-ku, Tokyo 4-1 Mitsubishi Paper Mills Co., Ltd. Patent Department! (600) 2111 4. Column 1, "Detailed Description of the Invention" in the Specification Subject to Amendment (1) "Not in" in 1h of page 3 for the specification is amended to "does not change to".

(2) Ibid., page 5, No. 7, amend "they" in t-r to "these."

(3) Same, page 7, line 4, U-dispersed snow is corrected to ``direction if j.''

Claims (2)

[Claims] (1) Basically, [1] synthetic resin microcapsules, [
2) A microcapsule composition comprising a printing ink composition comprising an adhesive, [3] a pigment, and [4] a water-alcoholic dispersion medium, wherein the adhesive is a vinylpyrrolidone-vinyl acetate copolymer. (2) The microcapsule composition according to claim 1, wherein the water:alcohol ratio (%) in the water-alcohol dispersion medium is 60:40-0:100.