JP3007937B2 - Printing ink composition - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a printing ink composition, and more particularly, to a printing ink composition useful for obtaining a large number of high quality prints without causing set-off.

[Conventional technology]

Printing methods are roughly classified into letterpress printing (including dry offset printing), planographic printing, and intaglio printing (including gravure printing). The properties of the ink differ greatly depending on the printing method, but the printing ink is mainly composed of a vehicle and a drying agent combining colorants, synthetic resins, drying oils and solvents, etc., even if the printing method differs. In common.

In general, in any type of printing ink, only a low-viscosity petroleum-based solvent penetrates mainly into the paper after printing, and the synthetic resin component and the dry oil remain on the paper as if the pigment were wrapped. Quick set type inks are used to form a continuous hard film and set quickly.

However, the ink film thickness on paper such as lithographic prints is 1
Even if the thickness is around μm, the ink set after printing is sometimes insufficient, and the stacking of printed matter may cause ink set-off and stain the back surface of the printed matter. For this reason, in many cases, the powder is sprayed on the surface of the printed material by spraying to reduce the adhesive area between the ink and the paper and prevent set-off. Furthermore, in the case of printed materials such as intaglio printed products in which the thickness of the ink film on paper reaches several tens of μm, in order to prevent set-off, brazed interleaf paper is inserted between the printed materials at present.

[Problems to be solved by the invention]

The present invention provides an ink composition capable of continuously obtaining high-quality printed matter without causing set-off even if the above-described powder spraying operation and use of the slip sheet are omitted.

[Means for solving the problem]

The printing ink composition of the present invention is characterized by comprising as a main component a colorant, a solvent mainly composed of an aliphatic hydrocarbon, and a resin which is soluble in the solvent at normal temperature and has reduced compatibility and insolubility at high temperature.

By the way, the present inventors have confirmed that the above problem can be achieved by using a printing ink that uses a resin that is compatible at room temperature but is reduced in insolubility by increasing the temperature and becomes insoluble. . The present invention has been made by this.

 Hereinafter, the present invention will be described in more detail.

As mentioned above, the printing ink composition according to the present invention comprises a colorant and a specific vehicle as main components.

Examples of the colorant that can be used in the present invention include hydrophobic coloring materials used in ordinary printing inks, coloring materials or extenders that exhibit hydrophilicity, and those obtained by subjecting these hydrophilic pigments to a hydrophobic treatment. It can be suitably used, and specifically, carbon black, lamp black, phthalocyanine blue, phthalocyanine green, nigrosine black, zinc oxide, titanium oxide and the like are applied in the range of 1 to 20% by weight based on the total amount of the ink composition. You.

The vehicle which can be used in the present invention is a resin which is soluble in a solvent mainly composed of an aliphatic hydrocarbon (preferably a solvent containing an aliphatic hydrocarbon and a silicone oil) at room temperature and has reduced compatibility and insolubilized at a high temperature. Preferably,-is a combination of polyvinylpyrrolidone and a silicone resin. In a printing ink using such a vehicle, the polyvinylpyrrolidone and the silicone resin, which are compatible at room temperature in an aliphatic hydrocarbon solvent or a solvent containing an aliphatic hydrocarbon and silicone oil, are compatible with each other by increasing the temperature. Is reduced, and the ink cohesion increases before the solvent permeates and evaporates into the paper, so that the ink can be set quickly.

The main solvent is an aliphatic hydrocarbon having a C ₈ -C ₁₄ linear or side chain or a cyclic high-boiling aliphatic hydrocarbon, specifically, Isopar G (boiling point 159 to 177 ° C.), Isopar G H (boiling point 177-183 ° C), Isopar L (boiling point 18
Those having a boiling point of 150 ° C. or more, such as 9 to 208 ° C., are preferably used. As the silicone oil mixed with these, dimethyl silicone oil (KF96 1.0cs, boiling point 153 ° C.),
Dimethyl silicone oil (KF96 1.5cs boiling point 195 ℃),
Those having a boiling point of 150 ° C. or more, such as phenylmethyl silicone oil (KF58 having no boiling point) and cyclic siloxane (KF994 boiling point of 175 ° C.), are suitably used. The mixing ratio of the aliphatic hydrocarbon to the silicone oil is suitably 1/1 to 5/1.

The ratio of such a solvent to the ink greatly varies depending on the type of the ink, but is applied in the range of 20 to 80% by weight based on the total amount of the ink composition.

The resin that is compatible with the solvent at normal temperature and reduces compatibility at high temperature (insolubilized) preferably includes at least a polyvinylpyrrolidone resin and a silicone-based resin such as acrylic-modified or epoxy-modified silicone or pure silicone varnish, Examples thereof include those in which other oil-modified alkyd resins and rosin-modified phenol resins are added. The mixing ratio of the polyvinylpyrrolidone resin and the silicone resin is in the range of 4/1 to 1/4 with respect to the silicone resin, and the mixed resin is applied at 15 to 50% by weight based on the total amount of the ink.

Here, the silicone resin is very well compatible with the mixed solvent via the silicone oil at normal temperature, but when the temperature is raised, the mechanism of action is not clear, but the action with the polyvinylpyrrolidone resin causes gelation. Only slightly heats the printed matter to cause phase separation with the solvent.
It can be set quickly before the ink solvent permeates or evaporates into the paper.

Thus, according to the use of the printing ink composition of the present invention, a printed matter can be obtained without causing set-off. It should be noted that the printing ink of the present invention may be adapted to be used in any suitable form by determining the ratio of the colorant, the vehicle, the drying agent, the amount of the resin in the vehicle and / or the ratio of the resin component. It can be done by changing.

〔Example〕

Next, examples will be shown, but the present invention is not limited to these examples.

Example 1 As a high-boiling aliphatic hydrocarbon solvent, a 4: 1 mixed solvent of Isopar H and phenylmethyl silicone oil was used.
By mixing 7 parts by weight of the polyvinylpyrrolidone resin and 12 parts by weight of the silicone epoxy-modified silicone resin with respect to parts by weight, and kneading and dispersing the mixture on a three roll while gradually adding 10 parts by weight of carbon black, At room temperature, an ink was obtained which was extremely fluid and heated to 60 ° C. or more to phase-separate the solvent and solidify as a gel. When this ink was used for gravure (intaglio) printing, a high-quality printed matter without set-off was obtained.

Example 2 10 parts by weight of phthalocyanine blue, 10 parts by weight of an alkyd-modified silicone resin, 10 parts by weight of polyvinylpyrrolidone,
5 parts by weight of Isopar L and 2 parts by weight of phenylmethylsilicone oil were kneaded and dispersed with a three-roll mill to obtain an ink which was highly fluid at room temperature and gelled at 63 ° C. When this ink was used for offset (lithographic) printing, a high-quality printed matter without set-off was obtained.

Example 3 9.9 parts by weight of carbon black, 3 parts by weight of alkali blue, 10 parts by weight of silicone epoxy resin, 4.4 parts by weight of oil-modified algite, 5 parts by weight of polyvinylpyrrolidone resin, 4 parts by weight of Isopar H, 2 parts by weight of cyclic silicone oil
The resulting mixture was kneaded and dispersed with three rolls, and an ink which was fluid at room temperature and gelled at 61 ° C. was obtained. When this ink was used for offset (lithographic) printing, a high-quality printed matter without set-off was obtained.

〔The invention's effect〕

The printing ink of the present invention has good on-machine stability and can provide high-quality printed matter with excellent reproducibility. Further, even in an intaglio printed matter having a particularly large ink film thickness formed on paper, there is no set-off and no interleaving paper is required, so that workability is excellent and efficiency can be improved.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 11/00-11/20

Claims (1)

(57) [Claims] 1. A colorant, a solvent mainly composed of an aliphatic hydrocarbon and a resin obtained by using a combination of polyvinylpyrrolidone and a silicone resin, which are soluble at room temperature in the solvent and reduced in compatibility at high temperature to become insoluble. A printing ink composition comprising as a main component.