Definition and composition of high gloss offset ink

2) Dry vegetable oil

In the ink industry, commonly used vegetable oils are dry oils, semi-dry and non-drying oils. In high-gloss inks, dry vegetable oils are mainly used.

Dry oil absorbs oxygen in the air and polymerizes and dries, changing from liquid to solid film. The components of these oils contain more unsaturated fatty acid groups. When these unsaturated fatty acid groups uniformly absorb oxygen in the air, the original straight chain structure will gradually polymerize into a network structure, thereby polymerizing to form a tough solid film. Can dry quickly in the air. In the absence of air, dry oil thickens when heated and increases viscosity, resulting in a rubbery, oil-insoluble colloid.

The commonly used dry vegetable oils such as linseed oil, tung oil and the like have a uniformly distributed three-dimensional structure and contain a conjugated double bond that can undergo polymerization and a group that can form a conjugated double bond under heating conditions. Dry vegetable oils polymerize when heated, producing dimers and trimers; the longer the heating and holding time, the greater the viscosity.

3) High boiling paraffin oil

The mineral oil used in the ink industry is mainly a high-boiling fraction extracted from petroleum. Its main components are various hydrocarbons such as aromatic hydrocarbons, olefins, and paraffin hydrocarbons. Most of these ingredients are inactive materials and have good chemical stability. This part of the mineral oil can be divided into narrow distillate kerosene (distillation range of 250°C-320°C) and mechanical oil (distillation range higher than 320°C) according to the distillation range. These oils are similar in chemical composition and have relatively high boiling points. They can dissolve many kinds of resins to form viscous liquids and can also be mixed with other oils. Therefore, they are used more in printing inks.

The most commonly used high-gloss inks are high-boiling oils obtained by fractional distillation of petroleum at 230 to 320°C. This oil is a low volatility solvent with very low viscosity, which acts as a viscosity-reducing effect on the ink and helps to fix the ink quickly on the paper surface.

4) Resin-oil type material

After the synthesis of synthetic resins, dry vegetable oils and high boiling point mineral oils, resin-oil type binders can be produced. High-gloss ink binders are of this type. The mineral oil solvent is rapidly absorbed by the paper, leaving the ink film of the initially dried resin and oil on the surface of the paper; subsequently, the oil component in the ink film is oxidized and solidified, and the ink film is also cured. Therefore, it is a kind of binder that combines osmotic drying with oxidative conjunctiva drying. The ink has good transfer performance on the printing press, fast fixing speed, high glossiness of the ink film, vivid colors, strong ink film, and clear and complete network of the final printed products.

At present, resin-oil type binders can be classified into three types: high-temperature resin oil, lower-temperature resin oil, and gel resin oil, depending on the refining method.

1 high temperature resin oil

High-temperature resin oil, also known as a dissolving resin binder, is a resin dispersed and dissolved in vegetable oil and mineral oil systems at approximately 250° C., and is retained for a certain period of time to allow the resin to disperse evenly, even when it reacts with the vegetable oil. The inks made from this linking material have high gloss and good stability, but the fixation is relatively slow.

2 lower temperature resin oil

The lower temperature resin oil can also be referred to as a dispersion resin binder. The resin is dispersed in vegetable oil and varnish at a temperature of about 180° C., and is retained for a short period of time or is not kept warm. The ink body made of this kind of linking material has good bone and fast fixation, but its gloss is relatively poor.

3 gel type resin oil

The gel-type resin oil is formed of a gelling agent in a resin oil, an aluminum soap such as aluminum stearate, aluminum octacarbonate, and certain reactive groups in a resin oil to form a cross-linked structure in which an oily substance is surrounded in the structure. , so as to form a gel state. Gel-type resin oil in the ink, can increase the viscosity of the ink, so that the ink has a more body, so that the transfer in the printing press, high ink film gloss, ink penetration, not dirty, the printed dots clear and resistant More water-based, less emulsifiable, more suitable for high-speed printing needs.

(to be continued)