Лако-красочные материалы — производство

A typical formulation for a modified acrylic topcoat6 is given below :

FORMULATION 3-7:
MODIFIED ACRYLIC TOPCOAT

Specification

Solids content 27.5%

Viscosity DIN 4/20°C 85 secs

Adhesion 100% on HIPS

100% on ABS

Neocryl B-811 is a 100 % nvc MMA homopolyer of Mw 40,000, soluble in ketones, esters and aromatic solvents at room temperatures. Vinylite VYHH is a vinyl chloride/ vinyl acetate copolymer (86:16), Mn 20,000. It is not very compatible with polymeric plasticisers. Sparkle Silver 3000AR is a coarse grade, acid resistant, non-leafing aluminium pigment. Byk 301 is added to improve the mar resistance.

TPA’s are generally applied at 10-15% weight solids, an extremely “environmentally unfriendly” coating system. Thinners are a blend of true solvents and diluents. The true solvents for the acrylic resin should be kept to a minimum level, giving borderline solubility for the TPA and, ideally, little or no solvent action on the sensitive substrate. Furthermore, they must be fast evaporating solvents, such as toluene. This reduced solubility means that coatings may need to be blended, with twice their own volume of thinner, to achieve a satisfactory application viscosity and flow out on the component. Thinner blends are generally classified as fast evaporating and, as such, are prone to blushing. This is the formation of a milky opalescence caused by moisture condensing onto the surface of the component from the atmosphere. A small percentage of retarder thinner such as diacetone alcohol or butyl lactate is added to overcome this problem.

A ‘mild’ thinner blend for Acrylic finishes could be formulated from the ‘starting point’ formulation below.

FORMULATION 3-8:

‘MILD’ THINNER BLEND FOR ACRYLIC FINISHES

Application

Thin to application viscosity with Butyl Acetate. Overcoatable with two component acrylic urethane system.

Specification

Solids 31.5%

Viscosity DIN 4/20°C 19 1 secs

Adhesion 100% on PA

Neocryl B-723 is a BMA/MMA copolymer of Tg 40°C and Mw 200,000, with good adhesion, colour retention and heat resistance properties. SS 5500AR is a medium grade non-acid resistant aluminium pigment which can produce ‘white’ sparkling silver colour with high gloss. Vinylite VROH is a highly soluble, low molecular weight vinyl chloride (80 %)/ vinyl acetate copolymer with 2 % hydroxyl groups to improve adhesion. It is added to increase the solids and reduce solvent costs.

FORMULATION 3-10:
FORMULATION FOR CLEAR LACQUER

This lacquer is suitable for use as a protective lacquer for vacuum deposited metals. The more resistant types of TPA should be used.

For coating ABS and acrylic plastics(2) a basic formulation might be :

FORMULATION 3-11:

ABS AND ACRYLICS FORMULATION

nvc content 20%

Viscosity 45 mPa. s

CAB 553 and 381 are different grades of cellulose acetate. Slow evaporating cosolvents are added to improve flow.

FORMULATION 3-12:
EMI/RFI SHIELDING PAINT

Specification:

(20°C Rotothinner) 4-5 poise 1.7

<1C2/linear cm 50 microns Noryl or ABS

Thin 1:1 with MEK/Toluene/DAA (45/45/10 ratio).

Neocryl B725 is a methyl methacrylate/butyl methacrylate copolymer purely used to bind to the nickel. The nickel is a flake type material, resulting in a conductive coating shielding EMI/RFI radiation from the outside in and vice versa in electronic equipment. PVC is critical as the CPVC is approached the conductivity improves at a much faster rate with a higher proportion of flakes in direct contact.

Alternative metals are also suitable such as copper, silver and silver plated copper, depending on the degree of conductivity required. Bentone SD-2 induces some thixotropy into the coating to aid stability and application.

FORMULATION 3-13:

SOFT TEXTURE BLACK TV/AUDIO COATING

Specification:

Viscosity/Ford 4/ 20°C 12-17 sec

Dry film thickness 15-30 micron

Substrate ABS or Polystyrene

Thinner Ethyl Acetate/Butyl Acetate/MIBK/n-Butanol/Ethyl Lactate/Cyclohexanone (20/20/10/20/20/10 ratio)

Dianal LR-163 is an acrylic resin. The soft texture feeling is obtained with the Techpolymer MBX-20, an acrylic bead, alternative beads are available from Negami Chemical (Siber Hegner (UK)). The feel is dependent upon film thickness, generally as film thickness increases the soft feel improves. Perenol F40 is a levelling agent improving application and preventing patchiness.

FORMULATION 3-14:

MATT BLACK FINISH FOR AUTOMOTIVE PLASTIC COMPONENTS

Specification:

Viscosity BSB5/20°C 65-70 secs.

Density 0.84-0.92

Substrate ABS

Adhesion 100%

Thinner Xylene/DAA/Acetone/MIBK/Butyl Acetate (34/20/20/20/6 ratio)

Neocryl B805 (ex Zeneca) is a methyl methacrylate polymer well suited to the demands of the automotive sector. The 1/1 blend of acrylic and CAB is often used for automotive exterior and interior requirements, having excellent durability and abrasion resistance. The two grades of CAB have different viscosity profiles and the blend is purely to achieve an application viscosity and solids. The MPP 611 is a polyethylene wax, this improves the product’s performance under crockmeter or taper abrasion testing. SAIB or sucrose acetate isobutyrate is an extremely useful plasticiser for plastic coatings, having excellent migration resistance. The talc/silica blend is an effective means to control gloss and maintain stability in a low solids and low application viscosity system (thinned material is likely to remain standing overnight).

Suitable resins for the formulation of plastics coatings include: Resins for Coatings for Plastic