Types and Applications of Liquid Digital Printing Inks (Part 2)

2. Composition and properties of solvent ink

(1) Colorant

The colorant in the solvent type ink may use a pigment or a dye, and its type and name are the same as the water-based ink.

(2) Solvent

Solvent-based inks generally use organic solvent as the main solvent, and add the appropriate amount of water. Commonly used organic solvents are diethylene glycol compounds and dipropylene glycol compounds that are liquid at normal temperature and pressure, and diethylene glycol compounds may be diethylene glycol ethers (especially alkyl ethers) such as diethylene glycol monomethyl ether; Diethylene glycol esters such as diethylene glycol monoethyl ether acetate; may also contain polyethylene glycol monoether compounds and other polar organic solvents such as alcohols (methanol, ethanol, propanol, etc.), ketones Classes (acetone, methyl ethyl ketone, cyclohexanone, etc.) and carboxylic esters.

The mixing ratio (weight ratio) of the diethylene glycol compound and the dipropylene glycol compound is from 20:80 to 80:20, and the content is preferably from 85% to 95% with respect to the total weight of the ink.

(3) Dispersing agent

When a pigment is used as a colorant, a polyester polymer compound is added as a dispersant to the ink mixture. It is preferably used in an amount of 30% to 120% by weight of the colorant (especially pigment).

(4) Other additives

Other additives include stabilizers (such as antioxidants or UV absorbers), surfactants, binder resins, and wetting agents. Antioxidants can use BHA (2,3-butyl-4-oxyanisole) or BHT (2,6-di-tert-butyl-p-cresol); UV absorbers can use benzophenones or benzotriazole Azo compounds; Surfactants can be any of anionic, cationic, amphoteric or nonionic surfactants; adhesive resins are acrylic resin, styrene acrylic resin, rosin modified resin, polyester resin, polyamide Resin, epoxy resin, polyethylene vinyl acetate copolymer, cellulose resin, etc. In addition, the use of a wetting agent helps prevent the ink from drying or crusting within the spray head. Commonly used wetting agents include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, tetraethylene glycol, poly Ethylene glycol, glycerol and the like are used in an amount of 5.0% to 6.0% of the total weight of the ink mixture.
The composition of the liquid solvent type ink is as follows:

Formula 1:

Pigments 4.0%

Polyester polymer compound (dispersant) 2.4%

Polycyclic ethylene derivatives 0.5%

Mixed organic solvents 93.1%

Formula 2:

Oil dye 1.0% oil 30.0%

Propyl alcohol 29.0% Formamide 40.0%

3. Thermal imaging ink

Thermal transfer imaging technology is widely used in digital printing, and it is mainly sublimation technology. Thermal imaging inks can be either water-based inks or solvent-based inks. The main difference between the two types of inks is the colorant. Here is a description of the composition of a dye-sublimation ink whose main components include dye-sublimation dyes and pigments, solvents (transfer agents, water-based or alcohol-based emulsions), surfactants, water-based adhesives, lubricants, dispersants, defoamers. Agent. Percentage by weight, dye-sublimation dyes and pigment dispersion blue (or magenta, yellow, cyan, black) account for 10% to 35%, waterborne preservatives 1.0% to 6.0%, surfactants 1.5% to 6.0%, water-based adhesives 1.0% to 7.0%, lubricant 1.0% to 4.5%, dispersant 0.5% to 4.0%, defoamer 1.0% to 6.5%, and the balance being water or a mixture of water and alcohol. The specific formula is as follows:

Disperse Blue AC-E 10% Chloroform 2.5%

Ethylenediamine tetraacetic acid 3.0% Sodium carboxymethylcellulose 3.3%

Polyol 2.0% Potassium pyrophosphate 1.0%

Emulsified silicone oil 2.2% distilled water

It is also possible to change the proportion of the formulation component according to the characteristics of the specific printed material.

(3) Surfactants

Surfactants commonly used are benzene sulfonates, alkylamine oxides and amine salts, acetylenic diols, and fluorosurfactants, typically 0.1% to 1.0% by weight of the ink, preferably 0.5%.



Source: Printing Technology

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