Prill form masterbatch offers PVC powder blend users enhanced quality and reduced processing costs

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High volume PVC processors such, as pipe and profile extruders, have always preferred to use powder blends rather than granular compounds because they are more cost effective and optimize plant efficiency. However, output performance and colour consistency have always been affected by the type of colourant used and to some extent by how they are introduced to the process. Fully compounded Vynacol PVCu masterbatch in prill form overcomes these problems and enables any PVCu processor using powder blends to benefit from improved quality and throughput.

Prill comprises spherical beads - typically 1.2 to 1.5mm diameter - that present a high surface area to give better distributive mixing. As such it offers significantly better homogenization compared with granular materials.

Distribution in powder blends is even; it wets out quickly and results in improved dispersion and more consistent colour. As mixing is more efficient output is optimized.

Prill is not ideal for blending with granular materials because its particle size tends to separate more easily, although modern dosing systems help to overcome this problem by dosing directly into the polymer flow.

Masterbatch development
Developed by Colour Tone Masterbatch in the UK, Vynacol PVCu masterbatch is based on patented PVC colouring technology that makes it as easy to colour PVC as any other plastic material.

Universal and polymer specific masterbatches for flexible PVC have been available for many years but they have never worked reliably in rigid PVC because of its inherent processing difficulties. PVC is an extremely versatile polymer but it is very heat sensitive and highly resistant to flow in its melt phase.

PVC processors have always had to find just the right grade for their particular plant and application. Consequently there are literally thousands of PVC formulations on the market with varying amounts of additives and different levels of compounding; all developed to meet specific performance and processing requirements, or both.

Polymer specific masterbatches for flexible PVC contain plasticisers. Although this does not present compatibility problems when used in rigid PVC, users are, in effect, adding plasticisers to a polymer chosen specifically for its unplasticised characteristics. This can lead to application failures due to plasticizer migration or changes in the physical properties of the final product. 

Vynacol PVCu polymer specific masterbatch is different because it is plasticizer free and works well both in rigid and flexible grades without any compatibility or homogenisation problems. It overcomes all the traditional difficulties associated with adding colour to rigid PVC via the masterbatch route.

Until recently PVCu polymer specific masterbatches containing large quantities of pigment have not been available in prill format and now the product is available in Poland through Chemiz P.H., Colour Tone’s official distributor.

Benefits
PVC masterbatch offers many benefits to processors including:

• Faster colour changes.
• No loss in production rates - colours run as fast as clear material.
• Better optical properties.
• No compatibility problems.
• No homogenisation problems.
• Reduced stockholding.
• Lower polymer costs.
• Enhanced physical properties including colour ageing.
• Easily dispersed at a dosage of 1-2% for unfilled and up to 5% for filled grades.  
• Overdosing up to 10% with no effect on material properties.
• Contains no plasticisers

Formulation
Not surprisingly the formulation and manufacturing techniques used to produce Vynacol masterbatch are closely guarded secrets but they are based on existing polymer technology and involve specially modified manufacturing plant. The basic ingredients are selected for good weatherability and excellent colour ageing characteristics. Further enhancements to outdoor performance are possible by adding UV stabilisers and absorbers while suitable approved pigments allow the masterbatch to meet all relevant European directives.

Vynacol differs from traditional thermoplastic masterbatches in that as well as combining and dispersing the active ingredients [usually coloured pigments] the polymeric part of the masterbatch it is also compounded from basic ingredients at the same time. This construction of the carrier component is one of the great advantages of the material over other PVC colouring systems because it allows the masterbatch to be tailored to the processors application.

Internal lubrication levels can be varied to take into account subsequent processing; external lubricant levels can be adjusted and reduced for example if surface adhesion is a factor. Ingredient types and levels can also be varied to meet a wide range of processes and applications. The carrier formulation is also varied depending on the type of functional additive [e.g. organic or inorganic pigments], the level of additive[s] or even the dosing level it is to be used at.

As compatibility is not an issue these masterbatches can be formulated for dosing at a level suitable for the process and application rather than using the minimum amount of colourant to avoid “contaminating” the PVC more than necessary. 

Generally the masterbatch is easily dispersed at a recommended dosage of 1-2% and can be used in filled as well as unfilled grades. Depending on thickness and opacity required, dosing in of excess of 10% is possible with no affects on processing or physical properties. Indeed, the product contains additives that improve and enhance the characteristics of the base PVC, for example: ease of processing, improved weld strength, increased ductility, impact strength (especially at low temperatures), and high gloss finish.

Vynacol is manufactured on a Leistritz ZSE 50MAXX extruder fitted with specially designed GALA pelletizer, plate heat exchanger water system and dryer to Colour Tone’s specifications installed at the company’s Caerphilly, Wales, factory. The 50 mm 36D twin screw Leistritz has ‘state of the art’ segmented barrels and screws that facilitate maximum flexibility for machine configurations and the sequencing of process tasks.

Over the past seven years Vynacol colouring technology has established a £multimillion market for adding colour to PVCu via the masterbatch route. Processors in Europe, USA and Australasia use it to produce many products including packaging, toys, profile extrusions, rainwater goods, roofline mouldings, bottles and glazing components.

Contact :
Tony Gaukroger
ColourTone Masterbatch Limited
Pant Glas Farm Industrial Estate
Newport Road
Bedwas
Gwent
NP1 8BJ
Telephone: 01222 888910
Fax: 01222 868487

Press enquiries:
Ian McMath
Copylines
Telephone: 01428 723211
Fax: 01428 722371
Email: ian.mcmath@btopenworld.com