Лако-красочные материалы — производство

The use of thermoplastic acrylics in high build, heavy duty anti-corrosive systems is reported by Steed3 who describes top coat formulations based on thermoplastic acrylic resins, chlorinated rubber, solution vinyl resins as well as blends of two or more of these.

Volume solids of up to 40% at application viscosity may be achieved using a thermoplastic acrylic such as Plexigum® PM685 (a BA/MMA bead copolymer powder) plasticised with a chlorinated paraffin such as Cereclor S52 (4.25:1) This binder combination was used to formulate a finishing coat as shown:

® Plexigum is a trade name of Rohm GmbH

FORMULATION 3-17:

WHITE HIGH BUILD EGGSHELL ACRYLIC

Hydrogenated Castor wax thixotrope (e. g. Thixatrol, Crayvallac MT) is added to the formulation under specific conditions of dispersion and temperature to provide the formulation with sufficient shear thinning behaviour to allow application to vertical surfaces without sagging.

A blend of volatile and less volatile solvents is used. The former to provide rapid evaporation to give initial film “set” whilst the slower one allows sufficient wet edge time to allow overlaps.

A calculated PVC/CPVC (L) value of around 0.55 indicates that this paint will be a low-gloss or eggshell finish.

A typical system using this formulation would be over abrasive blast cleaned steel (SIS 05 59 00 Sa2V2 or SSPC-SP10) which has been primed with 1 x 30 microns dft (dry film thickness) zinc rich epoxy primer. The topcoat may be 2 x 150 microns dft white Eggshell acrylic topcoat.

It shows excellent corrosion resistance and superior exterior durability when compared to a similar scheme based on Chlorinated Rubber. The zinc primer is the main provider of anti-corrosive performance, but sufficient dry film thickness of topcoat must be applied to prevent corrosion of the zinc primer which would result in the breakthrough of zinc corrosion products.