Classification of water-based inks

Date: Oct 03 2024 From: Star Color

Water based ink is a uniform paste like substance composed of binders, pigments, additives, and other substances. Its classification methods are diverse, and the following are some of the main classification methods:

Water based ink classified by type of binder

Water soluble binders: These binders mainly include polyvinyl alcohol, hydroxyethyl cellulose, polyvinylpyrrolidone, etc., which have the property of being permanently dissolved in water. This type of water-based ink is only suitable for situations where it does not come into contact with water.

Alkali soluble binder: This binder is composed of adding an appropriate amount of ammonium hydroxide to an alkaline solution of an acidic resin, and the two can form soluble resin salts through chemical reaction. During the ink drying process, ammonia evaporates and turns the ink into a substance insoluble in water. The performance of this type of ink mainly depends on the type of acidic resin used. Many hydroxylated or acid containing resins can be used as alkali soluble binders, among which acrylic resin has significant advantages in terms of gloss, heat resistance, water resistance, chemical resistance, and pollution resistance.

Diffuse binder: This type of binder is small resin particles suspended in water. Latex is formed by the interaction of resin monomers in water and generally contains propylene, ethylene, or styrene butadiene polymers. Compared with soluble resins, latex binders have the characteristics of high density and low viscosity, and can form high-quality thin film layers after printing. At the same time, latex contains large polymer molecules, which result in higher hardness compared to small molecules, as well as good wear resistance, heat resistance, and adhesion. However, water-based inks using latex as a binder are difficult to print and not easy to clean because once latex solidifies, it becomes an insoluble substance. This type of ink is mainly used as coating ink. If it is mixed with alkali soluble binders, it can achieve better printing results.
Classification of water-based inks

Water based ink classified by plate type

Letterpress ink: used for printing books, newspapers, picture books, documents, account books, etc. The main feature of letterpress printing is that the ink part of the printing plate protrudes from the non ink part. Toppan ink is divided into copperplate water-based ink, rotary water-based ink, and flexographic water-based ink according to the type of printing machine and the purpose of the printed product.

Lithographic ink: Suitable for lithographic printing, the various parts of the lithographic printing plate are basically on the same plane, and the patterned areas are oleophilic while the non patterned areas are hydrophilic. The principle of oil-water repulsion is used for printing, so lithographic ink must have water resistance. According to the process, it can be divided into offset printing ink, roll paper offset printing ink, flat offset printing ink, waterless offset printing ink, iron printing ink, stone printing ink, etc.

Gravure ink: suitable for gravure printing. During printing, ink is applied to the embossed areas of the plate, and the ink on non embossed areas is wiped off or scraped off before printing. There are two types of ink: engraved gravure ink and photographic gravure ink.

Mesh plate ink: Water based ink that is printed by leaking through the mesh holes of the printing plate onto the printing surface. This type of ink has a high viscosity and is currently less commonly used.

Water based inks are classified according to resin systems

1. Waterborne polyurethane resin system
Waterborne polyurethane resin replaces traditional organic solvents by attaching hydrophilic groups to polyurethane molecules, allowing them to disperse in water. This resin system has the advantages of easy use, stable performance, strong adhesion, excellent glossiness, and good heat resistance. It can be suitable for various printing methods, especially for screen printing, plastic packaging, and composite films.

2. Acrylic resin system
Acrylic resin is an efficient wetting and grinding agent that helps with dispersion and coloring, and has good luster. It can reduce pigment usage and is beneficial for environmental protection. In water-based ink, acrylic resin is mainly divided into solution type and lotion type. There are many kinds of lotion acrylic resins. According to the composition, the particles of the lotion formed are different in state and their physical and chemical properties are different. Colloidal dispersion is mainly used in printing ink of corrugated boxes, while conjunctival lotion is widely used because of its good oil resistance, water resistance and gloss.

3. Epoxy resin system
Epoxy resin is a polymer compound with two or more epoxy groups in its molecular structure. The cured epoxy resin has good physical and chemical properties, such as excellent adhesive strength, dielectric properties, small shrinkage rate, good dimensional stability of the product, high hardness, good flexibility, and stability to alkali and most solvents. Epoxy resin, as a connecting material for water-based inks, has the advantages of high mechanical properties, good adhesion, low curing shrinkage, good processability, excellent electrical insulation, as well as good heat resistance and stability.

4. Other resin systems
In addition to the main resin systems mentioned above, water-based inks can also use other resins as binders, such as urethane resin, styrene modified maleic acid resin, water-based amino resin, and carboxymethyl cellulose polymer resin. These resins usually contain hydrophilic groups such as carboxyl, hydroxyl, and amino groups, which can be completely dissolved in water after specific processing and used as connecting materials for water-based inks.

The above is the classification of water-based inks. We hope it is helpful to you. For more knowledge about water-based inks, please follow our website.