Лако-красочные материалы — производство

For Marine and off-shore use, an acrylic/vinyl blend is often favoured. These coatings have lower solids content, but are less prone to plasticiser migration which can occur with the previous formulation in tropical climates.

FORMULATION 3-18:
WHITE ACRYLIC / VINYL ENAMEL

This formulation does not use extenders and with a PVC/CPVC (L) value of 0.33 the coating will be glossy in appearance (>75% / 60°)

A blend of polar and aromatic solvents is used to dissolve the thermoplastic vinyl resin and to promote compatibility between acrylic and vinyl during film formation.

Vinyl Resin VAGH (polyvinyl chloride/polyvinyl acetate copolymer) may be used for a topcoat formulation which is applied over acrylic/vinyl intermediate coats. The carboxyl function VMCH resin is used to promote better adhesion to metal substrates.

This formulation would be used as the topcoat over high build intermediate coats which would use similar resins and solvents, but a pigment package somewhat similar to that shown in the earlier example.

All coatings would typically be applied via Airless Spray to build up a three coat system over abrasive blast cleaned steel (SIS 05 59 00 Sa2*/2 or SSPC-SP10):

2 x 75 microns dft High build Acrylic/Vinyl intermediate 1 x 50 microns dft White Acrylic/Vinyl Topcoat

For better anti-corrosive protection in Marine and Off-shore environments a zinc-rich or epoxy primer would normally be used over abrasive blast cleaned steel. Acrylic/chloro — rubber based formulations are favoured for these thermoplastic applications rather than acrylic/vinyl based systems.

(iv) High Durability Coil Coating Enamels for Metal Cladding Poly Vinylidene Fluoride (PVF2 Coatings)

Kynar(R)500 is a solid polyvinylidene fluoride (PVF2) polymer powder supplied by Atochem. It is used in premium quality coil coating enamels for the exterior protection of metal cladding for buildings. Correctly formulated coatings based on this technology are guaranteed for longer than 20 years.

Due to the insolubility of the PVF2 powder, the coil coating enamel formulation relies upon a thermoplastic acrylic resin to disperse the pigment. To be suitable for this application, the acrylic not only has to be compatible with the PVF2 when the coating is formed by fusion at temperatures around of 200°C, but also it must not adversely affect the overall performance of the coating. Atochem, who only supply Kyner 500 to paint companies licensed to use this technology, recommends the thermoplastic acrylic Paraloid B44 (a MMA copolymer of Tg 60°C in toluene) to be used in a 70/30 PVF2/Acrylic w/w ratio. Higher levels of acrylic have been found to detract from performance.

A typical formulation(9) based on Kynar 500 is shown below:

FORMULATION 3-19:

WHITE HIGH DURABILITY COIL COATING PVF2/ACRYLIC FORMULATION

Total solids content 54.0

Vehicle solids content 47.5

Pigment/binder ratio 0.6/1

Curing to Peak Metal temperature 240-250°C

Titanium Dioxide from Du Pont de Memoirs

Atochem

Rohm + Haas

Isophorone is a slow evaporating solvent. A plasticiser is added to improve flow. The cured film (25 microns applied to primed aluminium) has exceptional flexibility and weathering performance as illustrated below :

Pencil hardness HB

T bend flexibility ОТ

MEK resistance (double rubs) Good

ASTM Salt spray resistance > 2000 hrs

45° South Florida weathering Excellent

An air drying alternative to the above formulation has also been developed which is based on a copolymer of PVF2 with tetrafluoroethylene and hexafluoroprene (Kynar ADS). This is also used in combination with the thermoplastic acrylic Paraloid B44. The air drying formulation (after 1 week) offers the same flexibility and weathering performance as Kynar 500, but is weaker in its solvent resistance.

Commercial thermoplastic acrylic resins recommended for metal coatings include: