For Bottles with a Special Look, A Color House Blows Its Own.

Some special coloring effects for plastic bottles cannot be evaluated with a standard color chip, but only an actual bottle. It is especially true of effects that are best achieved with a multi-layer structure. That's why Clariant Masterbatches Div., McHenry, Ill., recently installed its own coextrusion blow molding machine. The model BW 1000 EC, a single-station shuttle machine from Uniloy Milacron, Manchester, Mich., helped Clariant develop what is said to be the first multi-layer PE bottle with an anodized-aluminum look that is molded in rather than applied by vacuum plating and lacquering.

With this machine, prototype development that used to take from eight to 24 weeks can be achieved in two days. We had to mix many combinations of material, ship them to a quality molder, and then tie up a production machine," says Len Kulka, personal-care packaging product manager.

He explains how the multi-layer structure helps reduce pigment cost and improve special effects. "In a mono-layer structure you create sort of a 'mud mix' when different colors are blended because you lose reflectivity" Coextrusion improves special effects by putting one color in the outside layer and a different one in the middle layer. This gives Clariant flexibility to change characteristics such as color, clarity, reflectivity, and texture. For example, Clariant can change the levels of reflection and refraction in the thin outer virgin-resin layer. The level of translucency can be changed in the middle layer, composed of trim scrap and post-consumer waste. The machine's stability and repeatability helps Clariant reduce expensive overuse of additives such as uv absorbers. Kulka also notes that good parison and concentricity control allows making small variations in layer structure. The head design permits color and layer changes in just 30 min.