BASF Aktiengesellschaft 67056 Ludwigshafen Phone: +49 621 60 – 0 Germany http://www.basf.de

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Waldemar Oldenburger Tel.: +49 (6 21) 60-4 69 10 Fax: +49 (6 21) 60-4 94 97 E-Mail: Waldemar.Oldenburger@basf-ag.de

Trade press conference K 2004 on June 22 and 23, 2004, in Ludwigshafen

Efficient production of transparent thin films New applications for S/B polymer: The second generation Styroflex

Report by Robert Huber,

Marketing Styroflex

Communication plastics www.basf.de/plastics

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Styroflex® is a styrene/butadiene and the only thermoplastic elastomer

among BASF’s styrenic plastics (figure 1). Characterized by a combina-

tion of high resilience and toughness, optical clarity and processing sta-

bility as well as gas and water-vapour transmission, Styroflex is mainly

used for transparent, stretchable packaging film. Following further im-

provements to the Styroflex production process, BASF’s researchers

can now offer an even better product - Styroflex 2G 66, which launches

Styroflex into its second generation.

The improvement work was pursued in several directions. A way was

sought to produce extremely thin film, while retaining mechanical be-

haviour (e.g., resilience and puncture resistance) and optical properties.

The presence of gel particles is a major cause of film tear, especially at

very low gauges. BASF has optimized the manufacturing process in a

way that makes Styroflex 2G 66 extraordinarily low in gel particles,

enabling film thicknesses of just 10 microns to be achieved without

problem.

Styroflex 2G 66 – greater stretch stretches costs

Styroflex offers the potential for significant cost reduction in the area of

stretch packaging, a common method of wrapping food and protecting

palletized goods.

Stretch packaging uses the property of certain polymer films to remain

strong when stretched and at the same time exert a squeezing force as

they try to return to their unstretched condition. This allows objects of

different size and shape - palletized goods for example - to be secured.

The Styroflex film clings closely to the packaged goods without tearing

on sharp edges (figure 2). A new type of stretch packaging - stretch

hood technology - involves a hood that is stretched over the object.

Stretch hood technology is ideal for keeping loads clean and dry, and

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P 249e represents a quick and cheap alternative to shrink wrap and stretch

winding techniques.

Styroflex film is far superior to common polyethylene film thanks to its

great elasticity and resilience. For instance, when stretched to 500% of

its original length, a special polyethylene (PE) will at best recover to

only 400%; Styrolux film on the other hand will recovery to 100% when

the tension is released (figure 3). Styrolux's higher resilience means the

size and weight of the wrapper can be halved.

Advantages of stretch hood technology

The use of low-elasticity tubular film usually limits the packer to one size

of pallet. On the other hand, the stretchability of Styrolux allows him to

use a single diameter of wrap to package objects of various size. That

not only reduces downtime - by not having to change the film - it also

saves on inventory costs since only one size of film has to be stored

(figure 4).

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Styroflex 2G 66 as high-performance additive for PE film

Apart from its use in stretch film, Styroflex can also be employed as a

high-performance additive to increase the toughness properties of vari-

ous other types of film. Makers of food-wrapping film in particular can

profit from Styroflex 2G 66. PE in combination with the new Styroflex

offers a cheap alternative to PVC film. The reason: when conventional

PE film is coextruded with the elastomeric Styroflex 2G 66, it acquires

the same high-level of resilience as PVC film - a property that, along

with high oxygen transmission, is especially important for food-wrapping

film (figure 5).

Styroflex 2G 66 can also be used to improve the mechanical properties

of PE film, especially biaxial toughness. By finely distributing nano-sized

particles of Styroflex in the polyethylene matrix, the puncture resistance

of PE film can be increased by up to 60% with negligible loss in stiff-

ness (figure 6). Such an effect gives film extruders numerous possibili-

ties to optimize their systems.

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Styroflex 2G 66 addition rates as low as 3 to 5% allow thinner films to

be extruded while retaining the processing properties of PE-LD (low

density) or PE-LLD (linear low density) film. Or the other way round: If

PE films of a given thickness contain 4% of Styroflex 2G 66, their resis-

tance to tearing is clearly increased (figure 7).