Finer, more uniform cell structure of new chemical foaming agents from Clariant help reduce weight and save raw materials

Muttenz, November 4, 2010 - Plastics products and packaging manufacturers trying to reach sustainability goals and reduce costs are expressing keen interest in the newest chemical foaming agents (CFAs) from Clariant’s Masterbatches Business Unit. The finer and more durable foam-cell structures made possible by the latest generation of HYDROCEROL® masterbatches, in combination with processing advances, are opening new applications in
• polyester (PET) plastic sheets used for food trays
• automotive parts and other durable goods
• injection molded and blow molded plastics packaging, caps and closures
Savings on resin use and reduction of part weight – without significant loss in mechanical properties – are being reported.

Clariant Masterbatches is presenting this and other color and performance innovations for the plastics industry in the Hall 8A, Booth J11 at the K2010 plastics exhibition being held in Dusseldorf, Germany, October 27 to November 3.

Added to plastics during processing, HYDROCEROL chemical foaming agents decompose to produce carbon dioxide that forms bubbles in the polymer matrix when pressure is reduced as the resin enters the injection mold or exits the extrusion die. Because the gas displaces the polymer, it takes less plastic to make a given part or package. Material-use reductions of 7% are common in injection molding, and some converters have reported savings of 25% in certain extrusion applications. At the same time, the CFA plasticizes the resin in the processing machine, so less heat needs to be added to melt it (energy savings); less heat has to be removed during cooling, so cycle times are also reduced, often by 10 to 15%.

“Even relatively small reductions in material consumption and cycle time can be very important,” says Hendrik Kammler, Head of Global Marketing – Additives, Clariant Masterbatches. “When you are processing thousands or even millions of plastic parts over the course of a year, it is very easy to save significant amounts of raw material. The increased productivity and reduced material and energy consumption also increase the sustainability credentials of the product in a documented manner. Less tangible, but no less important, are the ‘green’ benefits that arise from reducing shipping weight for both raw materials and finished products.”

IMPROVED FOAM TECHNOLOGY

Foaming is not new. It is used extensively in construction components, home and garden furniture and luggage and more recently in automotive interior parts, to reduce weight and raw material use. But acceptance has been limited by a relatively coarse and non-uniform cell structure that affects appearance and mechanical strength, especially in thinner wall sections. The improved CFA technology used in the new HYDROCEROL masterbatches now makes it possible to achieve a highly uniform structure of cells as small as 20-100 micrometers in diameter. This compares very favorably to the 400 micrometers typical of first-generation foams and even the 200 micrometers, which was considered “fine” until recently.

This means there is no significant appearance or performance difference between structures produced with CFA versus those made without it. Yet the benefits of reduced part weight and lower production costs are undeniable.

NEW TREND: FOAMED PET FOOD TRAYS

Favorable virgin PET prices compared to polyolefins or styrenics and the recyclability of the material have created growing demand for polyester plastic sheets that are formed into food trays. However, until recently polyester’s hydrolytic sensitivity made it difficult to process with endothermic CFAs and the coarse cell structure produced a rough, unattractive surface.

All that has changed now that Clariant Masterbatches has proven that the latest generation of HYDROCEROL CFAs, used in combination with its CESA®-extend chain extending additive masterbatches, results in higher melt strength, a finer, more regular cell structure and significantly smoother surface. A homogeneous and stable foam structure leads to higher production rates, while foaming reduces material usage and costs.

“Increased use of PET has become a priority in Europe,” explains Jan-Erik Wegner, Technical Marketing, Additives/CFA for Clariant Masterbatches (Deutschland) GmbH. “It is considered the greenest of the non-biodegradable polymers due to its outstanding recyclability. Supermarkets and other retailers want to capitalize on the positive environmental profile of foamed PET and so converters of foamed PS and foamed PP are now installing PET lines. The change can be made with only a short learning curve.”

IMPROVED FOAMS HELP AUTOMOBILE MAKERS LOSE WEIGHT

In the pursuit of lower CO2 emissions, the automotive industry is investing heavily in lightweight design, so the latest generation of HYDROCEROL® CFAs is getting special attention. CFAs have been widely used in automotive applications to improve processability, eliminate sink marks, reduce warpage, optimize cycle time and reduce weight. Now smaller cells sizes, improved foam uniformity and surface quality are prompting major players to investigate their use for both structural and appearance parts.

Weight reduction in thin parts is usually limited to 5 to 10%. However, in combination with core-back expansion, much higher foaming rates can be achieved. This technology was adopted by BMW to produce the dashboard carrier of the BMW 3 Series. Clariant offers tailor-made CFAs that can be used in combination with core-back expansion for materials like PP, PPE/PS, PC/ABS, and TPE.

The Clariant CFAs are also being used in under-hood applications. Material reductions of 7 to 10% and cycle-time reductions of 10 to 15% have been observed in 33% glass-filled polyamide parts.

PACKAGING BENEFITS

Historically, poor aesthetic results limited the use of foaming in personal-care packaging, unless packaging designers liked the frosty appearance that came along with the coarse cell structures achievable with previous technology. Today, however, the finer, more uniform structure achievable with HYDROCEROL CFAs has opened new opportunities for packaging converters to save money while working to meet environmental sustainability mandates.

Although actual results can vary, internal trials at Clariant showed, for a typical 20 gram HDPE bottle, a weight reduction of 10%. Applying this to 2000 tons of parts could generate a net raw material saving of more than 200,000 EUR. In addition, optimized processing can significantly reduce cycle time with corresponding processing cost savings possible. Other “green” benefits arise from reduced shipping weight for both raw materials and finished products.

Clariant Masterbatches products are marketed under the following global brand names: REMAFIN® olefinic masterbatches and compounds; RENOL® masterbatches and compounds based on engineering resins, styrenics and PVC; CESA® additive masterbatches; HYDROCEROL® chemical foaming and nucleating agents; OMNICOLOR® universal color masterbatches; MEVOPUR® color and performance masterbatches and compounds for medical and pharmaceutical applications. These brand names are registered trademarks of Clariant.

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