Лако-красочные материалы — производство

The classical deflocculating additive has a typical structure with one or more closely spaced pigment affinic groups and a number of resin-like chain structures extending in the vehicle, as described in Figure 5.2. Such additives are low MW polymers that can be adsor­bed strongly on the pigment surface and provide sufficient steric stabilization to give a deflocculated condition and hence more New­tonian flow. This type of additive is very important for high-gloss top coats and efficient utilization of expensive colored pigments.

Generally the phenomenon of flocculation is considered negative in coatings; however, controlled flocculation may be desirable in certain systems where gloss is not important. In the normal floc­culation state, the pigment particles make direct contact with one another, while in the controlled flocculation state, no direct pig­ment-pigment contact occurs, as the additive molecules are always between the pigment particles.

In controlled flocculating addi­tives, the pigment affinic groups are distributed in a special fashion over the molecule, rather than being confined to a small region therefore, they can function as bridges between various pigment particles (Figure 5.6). As a result, the controlled flocculation state forms a three-dimensional network structure, which is beneficial for thixotropic flow behavior in the coating and leads to less settling — which if it occurs, is less serious — along with reduced flooding and floating because different pigments are bound together in the floccu­lates, and consequently cannot separate to cause flooding or floating.