Лако-красочные материалы — производство

Before proceeding into detailed discussion, it is worth revising the differences between solution (in solvent)and emulsion acrylic polymers. Their typical characteristics are compared in Table 7-5.

The majority of vinyl and acrylic surface coating resins are manufactured by either solution or emulsion polymerisation techniques. It is also worthwhile recapping the distinct types of waterborne resins.

A. Emulsions

The monomers for the resin are polymerised in the presence of water

or

A water insoluble resin is dispersed in water using surfactants, etc.

B. Water Reducible/Dispersed/lnverted Resin

Acid (or amine) functional resin is conventionally polymerised in a water soluble
solvent, neutralised and inverted/dispersed/solubilised in water

or

Acid (or amine) functional emulsion polymerised resin is neutralised and
dispersed/solubilised in water. These are sometimes referred to as alkali thickening
emulsions (in the case of an acid functional emulsion).

C. Water Soluble

These are resins consisting of a water soluble composition with no need for additives, emulsifiers or neutralisers. They are normally of very low molecular weight, otherwise their viscosities would be too high. Some water soluble crosslinkers could possibly belong to this category, but generally truly water soluble resins are not used in surface coating applications, due to their reduced water resistance properties, unless heavily crosslinked.

Any of the above resins may be either

• Thermoplastic

Where films form by evaporation only. The resistance and performance properties must be inherent in the resin or

• Thermoset

Crosslinked either with a crosslinking agent or resin or with itself. This greatly increases the molecular weight, making the film insoluble in water and greatly enhances resistance and mechanical properties of the crosslinked (cured) film.