JPH03247677A - Printing ink for offset and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject ink, preservable for a long period without regard to the kind of a thickener and excellent ink receiving properties by adding a specific water-in-oil type emulsion in which the phosphoric acid in the aforementioned emulsion is reacted with a specific compound on the waterdrop surfaces to a paste containing a pigment dispersed therein. CONSTITUTION:The objective ink obtained by mixing and emulsifying an aqueous plate surface cleaning liquid (pH1-5) containing a phosphoric acid such as orthophosphoric acid dissolved therein in an amount of 30-70% (based on the total amount of the emulsion), adding 2-20% compound expressed by the formula (R is alkyl) to the resultant water-in-oil type emulsion, reacting the aforementioned compound with phosphoric acid on the surfaces of waterdrops, mixing and blending the above-mentioned emulsion with a paste prepared by blending a pigment with a vehicle, diluent, etc., and containing the pigment dispersed therein.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an offset printing ink and a method for producing the same.

``Prior art'' The principle of Oracet printing is that the non-image area (
A plate consisting of a hydrophilic area) and an image area that is difficult to wet with water (oleophilic area) is used, and then during printing, the non-image area is selectively wetted with dampening water, so that the non-image area and the image Normal printing is achieved by increasing the difference in surface chemical properties between the non-image areas, that is, imparting ink repellency to the non-image areas, and increasing ink receptivity to the image areas.

In this field, faster printing speeds are becoming commonplace due to shorter printing delivery times and improved printing productivity.
In order to perform normal printing, it is important to maintain the cleanliness of the non-image area, that is, to maintain a hydrophilic surface that is easily wetted by water. For this reason, if the lipophilic substance adhering to the surface of the hydrophilic aluminum oxide that constitutes the non-image area is left as is, this area may become ink receptive and reduce image reproducibility. If the lipophilic film is not removed as soon as possible using a plate cleaning solution made of a phosphoric acid aqueous solution, it will completely turn into an image area and form an irreparable stain (hereinafter referred to as background stain). This will cause a decrease in image reproducibility.

For this reason, in Japanese Patent Publication No. 48-90, a printing ink was prepared by mixing a water-in-oil emulsion in which an aqueous plate cleaning liquid containing phosphoric acid was emulsified with an alkyd resin into a pigment paste, so that it could be constantly applied to the plate surface. It is known to elute an aqueous plate surface cleaning liquid from printing ink to maintain the cleanliness of non-image areas and perform normal printing.

However, in recent years, printing speeds have become even faster in the field of off-wheel printing for newspaper printing and commercial printing. The viscosity of the printing ink used for this purpose is generally low, so due to the low viscosity of the ink that is the outer phase,
The protective film layer on the surface of the aqueous phase tends to become weaker. For this reason, during storage of printing ink, phosphoric acid in the aqueous phase dissolves into the vehicle, which is the oil phase, and reacts with the ink's thickener calcium carbonate to precipitate water-insoluble calcium phosphate crystals. Not only does it reduce its function as a cleaning liquid and cause poor image reproducibility, but the coarse particles formed by agglomeration of crystals may damage the plate surface or adhere to the image area and impede ink receptivity, resulting in poor transfer properties. This will cause trouble.

"Problems to be Solved by the Invention" The present inventors have conducted research with the aim of eliminating the adverse effects caused by phosphoric acid in an aqueous plate cleaning solution leaching into the oil phase, and as a result, they have arrived at the present invention. .

[Means for Solving the Problems] The present invention provides an offset printing ink containing an aqueous plate surface cleaning liquid in which phosphoric acid is dissolved as a water-in-oil emulsion, in which phosphoric acid and the general formula ( This invention relates to an offset printing ink characterized by reacting with N-alkyl N-polyoxyethylene N'-polyoxyethylated propyldiamine represented by I).

- Formula (I) C However, in the formula, R represents an alkyl group. Furthermore, in the present invention, a water-in-oil emulsion is prepared by dispersing an aqueous plate cleaning liquid in which phosphoric acid is dissolved in an alkyd resin, and N-alkyl N-polyoxyethylene N'~ is added to the oil phase of the emulsion. Polyoxyethylenated propyl diamine is added to react the phosphoric acid with the N-alkyl N-polyoxyethylene N'-polyoxyethylenated propyl diamine at the surface of the water droplets, and the emulsion is then mixed with pigments, vehicles, diluents and other additives. The present invention relates to a method for producing offset printing ink, which is characterized in that it is mixed into a pigment-dispersed paste consisting of additives.

To produce an offset printing ink according to the present invention, an aqueous plate cleaning solution is prepared by dissolving phosphoric acid in water.

The phosphoric acid used in the present invention includes orthophosphoric acid, metaphosphoric acid,
Examples include polyphosphoric acid, and if necessary, alkali salts with the phosphoric acid, ammonium alum, chromium alum, manganese sulfate, etc. may be used in combination. fR
M, for example, a polysaccharide acid such as arabic acid, alginic acid, cellulose glycolic acid, or a carboxyl group partially converted to an alkali metal salt such as sodium or potassium may be used in combination.

The amount of polysaccharide acid added is preferably 0.01 to 0.1 based on the total weight of the ink.

It is desirable that the pH value of the aqueous plate surface cleaning liquid is finally adjusted to a range of 1 to 5.

Next, the aqueous printing plate cleaning liquid as described above is mixed with an alkyd resin and stirred to emulsify it to prepare a water-in-oil emulsion. If necessary, a small amount of a nonionic surfactant having an HLB value of 10 or less may be used in combination.

The alkyd resin used in the present invention is preferably a long-oil type, for example, a polyhydric alcohol such as glycerin or pentaerythritol is transesterified with a relatively large amount of oil to produce a partial ester of the polyhydric alcohol.
It may be produced by reacting this with a polybasic acid such as phthalic anhydride or isophthalic acid.

As the oil phase component of the water-in-oil emulsion, oils, fats, resins, etc. may be added together with the alkyd resin, and recommended examples include linseed oil, Chinese tung oil, soybean oil, rosin-modified phenolic resin, and ester gum.

The N-alkyl N-polyoxyethylene N'-polyoxyethylenated propyldiamine used in the present invention is a hydrocarbon chain with an alkyl chain of 8 to 24 carbon atoms, and the number of moles of ethylene oxide added is A number of 4 to 8 is desirable. Although it may be added directly during ink production, it is preferably added to the emulsion after the aqueous printing surface cleaning liquid is dispersed in the alkyd resin to prepare a water-in-oil emulsion. The amount added to the water-in-oil emulsion is preferably 2 to 20% based on the weight of the plate cleaning liquid.

The proportion of plate cleaning liquid in the water-in-oil emulsion is
30-70% based on the total weight of the emulsion is suitable. Further, the amount of plate surface cleaning liquid added to the printing ink is desirably 5% or less by weight in the ink.

To produce an offset printing ink according to the present invention, the pigment, vehicle, diluent, and other additives are pre-milled to form a pigment-dispersed paste, aged preferably for several weeks, and then milled on a three-roll mill. A water-in-oil emulsion prepared by dispersing an aqueous plate surface cleaning liquid in an alkyd resin may be mixed into the alkyd resin using a stirrer or the like.

Note that if higher alcohols such as lauryl alcohol, oleyl alcohol, and tridecyl alcohol and polyoxyethylene alkyl ethers such as tetraoxylene lauryl ether and diethylene glycol mono-n-hexyl ether are added to the ink vehicle, the emulsion will be absorbed into the oil during printing. The printing effect can be further enhanced by causing a phase change from a water droplet type to an oil-in-water droplet type.

“Examples” Next, the present invention will be explained by examples. However, these Examples merely illustrate the present invention and do not limit the present invention in any way. Furthermore, all parts referred to below are parts by weight.

Example 1 Prepare an aqueous plate cleaning liquid using the following formulation.

Gum arabic 6.0 parts metaphosphoric acid
2.0 chrome alum
12.0 potassium alum 10.0 water 210.0 go
Total 240.0, cottonseed oil 23
1 part of trimethylolpropane, 28 parts of trimethylolpropane, and 0.25 parts of lithium hydroxide are charged into a reaction vessel, heated to 250°C while stirring in a nitrogen gas atmosphere, and transesterification reaction is carried out at the same temperature for 60 minutes. . Next, the temperature was lowered to 200 DEG C., 50 parts of isophthalic acid was added, the temperature was raised again to 250 DEG C., and the reaction was carried out at the same temperature for 6 hours to prepare 309 parts of alkyd resin.

A water-in-oil emulsion was prepared by gradually adding 140 parts of an aqueous plate cleaning liquid to 55 parts of the alkyd resin at a temperature of 50°C and stirring with a homomixer for 30 minutes. By adding 5 parts of N-polyoxyethylene N'-polyoxyethylenated propyl diamine (number of moles of ethylene oxide added, 6) and stirring for 10 minutes, a water-in-oil emulsion 200
Prepare a portion.

Next, 200 parts of pre-milled carbon black, 90 parts of alkaline pull torch, 30 parts of Shiraika DD (calcium carbonate), and 53 parts of rosin-modified phenolic resin varnish.
When 100 parts of the above-mentioned water-in-oil type emulsion is added to 900 parts of a pigment dispersion paste consisting of 0 parts and 50 parts of light oil and mixed with a strong dispersion stirrer, the aqueous plate surface cleaning liquid can be easily and evenly mixed into the ink vehicle. to produce the offset printing ink that is the object of the present invention.

The obtained offset printing ink had excellent stability, and the aqueous plate cleaning liquid did not separate from the ink vehicle during storage, and there was no precipitation of calcium phosphate crystals due to metaphosphoric acid and calcium carbonate. . In addition, more than 2,000 copies were printed on newsprint using tap water as dampening water, and printed matter with sharp halftone dots and good image reproducibility could be obtained without causing scumming.

Example 2 231 parts of linseed oil, 24 parts of glycerin, and 0.25 parts of lithium hydroxide were placed in a reaction vessel, heated to 250°C with stirring in a nitrogen gas atmosphere, and transesterified at the same temperature for 30 minutes. After the reaction was carried out and the temperature was lowered to 200°C, 50 parts of isophthalic acid was added, the temperature was raised again to 250°C, and the reaction was carried out at the same temperature for 5 hours to obtain 305 parts of alkyd resin.

Separately, prepare an aqueous plate surface cleaning liquid using the following formulation.

Gum arabic 8.6 parts Orthophosphoric acid 10.2 Ammonium alum 8.0 Water
113.2 total 140
．． A water-in-oil emulsion was prepared by gradually adding 85 parts of an aqueous plate cleaning liquid to 100 parts of an alkyd resin at a temperature of 0 parts and 50°C, and stirring for 30 minutes with a homomixer. 200 parts of a water-in-oil emulsion was prepared by adding 15 parts of N-stearyl N-polyoxyethylene N'-polyoxyethylenated propyldiamine (number of moles of ethylene oxide added, 5) and stirring for 10 minutes. do.

Next, β-phthalocyanine blue 16, which had been kneaded in advance,
110 parts of water-in-oil type emuldigon as described above were added to 900 parts of pigment dispersion paste (pigment dispersion paste consisting of 0 parts, 100 parts of Hosoka DD (calcium carbonate), 570 parts of rosin-modified phenolic resin varnish, and 60 parts of light oil) to make a strong When mixed in a dispersion stirrer, the aqueous plate cleaning liquid is very easily and uniformly dispersed in the ink vehicle to produce the offset printing ink that is the object of the present invention.

The obtained printing ink had the effect of preventing scumming as in Example 1, and furthermore, it was possible to obtain printed matter with sharp halftone dots and good image reproducibility.

``Effects of the invention j Off-line printing ink for Shinkai printing and commercial printing manufactured by applying the water-in-oil emulsion according to the present invention can be stored for a long period of time even if calcium carbonate is used as the ink thickener. Even when printing, the precipitation of calcium phosphate crystals is extremely small, and during printing, the plate cleaning liquid dispersed in the ink vehicle is efficiently eluted into the dampening water on the plate.
Since a hydrophilic coating is formed on the non-image areas on the printing plate, it becomes a printing medium with extremely excellent ink receptivity to the image areas.

Claims (1)

[Scope of Claims] 1. In an offset printing ink containing an aqueous plate cleaning liquid in which phosphoric acid is dissolved as a water-in-oil emulsion, phosphoric acid and a compound represented by the general formula (I) on the surface of the water droplets are provided. An offset printing ink characterized by reacting with N-alkyl N-polyoxyethylene N'-polyoxyethylated propyldiamine. General formula (I) ▲There are numerical formulas, chemical formulas, tables, etc.▼ [However, in the formula, R represents an alkyl group. 2. Prepare a water-in-oil emulsion by dispersing an aqueous plate cleaning liquid in which phosphoric acid is dissolved in an alkyd resin, and add N-alkyl N-polyoxyethylene N'-polyoxyethylene to the oil phase of the emulsion. Propyl diamine is added to react the phosphoric acid with the N-alkyl N-polyoxyethylene N'-polyoxyethylated propyl diamine on the surface of the water droplets, and then the emulsion is made up of pigments, vehicles, diluents and other additives. A method for producing an offset printing ink, which comprises mixing the ink into a pigment-dispersed paste.