Application of aluminum pigment technology in ink coatings!

Aluminum flakes will undergo the following oxidation reactions in water, resulting in gas generation:

2Al+6H2O－－→2Al(OH)3+3H2

There are two technologies based on different principles to overcome the above problems: one of them is the additive technology, that is, the additive is physically mixed on the surface of the aluminum pigment particles, and a protective layer is formed on the outer layer of the aluminum flake through a barrier layer mechanism.

1.

The most common method of preventing outgassing of aluminum flakes is to treat them with organophosphorus compounds.

One of the product series (STAPAHydrolac series) contains solvent gasoline and another solvent, which can be water (STAPAHydrolacW-series), methoxypropanol (STAPAHydrolacPM-series), or butanediol (STAPAHydrolacBG-series) )

A side effect of stabilization is that some properties of the coating are adversely affected (eg drying time, intercoat adhesion, moisture resistance)

2.

A second technique for developing water-based aluminum flakes is to fully coat the pigment particles for better protection

The first generation of pigments with coating technology used a layer of insoluble chromium(III) compounds (STAPAHydrolux): these pigments do not contain soluble chromium(VI) salts (<1ppm) and are therefore non-toxic

The outgassing of these differently stabilized aluminium pigments in the same paint formulation can be determined

3.

All raw materials, resins, pigments and additives, as well as production techniques, must be taken into account by the formulator in order to optimize the optical, technical and gassing properties of the product

Good mixing of metallic flake pigments and resins: Improper mixing of the two - too high a shear force applied - can negatively affect the optical properties of the product

Preparation of aluminum flake pre-dispersion system: All aluminum powder pastes need to be pre-dispersed in a suitable solvent to obtain pigment paste

Wetting agent: In many cases, it is advisable to add a wetting agent to the metal flake pigment paste to assist the wetting of the flake pigment

pH value and neutralization: If water-soluble resin is used, it is not appropriate to use a neutralizing agent that is too alkaline.

Alignment orientation of metallic flake pigments: This is a very important aspect of metallic effect coatings