PETpla.net Insider 06 / 2010

CAPPING / CLOSURES 25 PET planet insider Vol. 11 No. 06/10 www.petpla.net There are technical issues as well. Low threads have a less effective opening performance as the customary opening strength of 15-17in-lbs (approx. 1.9Nm) has to be apportioned over a smaller attachment area and could prove to be problematic for children and the elderly. 1,5l preform with MHT21Light mouth Reduced weight, 1810 systems compatibility MHT and CCT concluded that the market actually required a light thread with a standard height of 21 mm. In achieving its MHT21Light, it first made the ring for the original closure thin- ner and reduced the diameter of the support ledge from 33 to 31mm – a diameter that has been in use on non- carbonated water bottles for many years and is accepted by consum- ers. The thread was then constructed to be somewhat thinner. The PCO 1810 thread pitch was retained, which meant that the new thread family is 100% compatible with the most com- monly used screw caps. Conversion of a PCO 1810 production line to the new thread requires just one batch of new neck rings to be inserted into the existing preform mould. The investment cost for approximately 100 million 1.5l bottle preforms is about €39,000. The conversion achieves material savings of €126,500 €/a (at €1,100/t of PET), as the weight of the pre- form is reduced by 1.15 g. MHT says that MHT21Light can show profitabil- ity after just a few months. The standard MHT21LIGHT mouth has already proved its practi- cal suitability. About 5,000 pieces were blown and filled for test pur- poses at a middle-sized bottling plant. In addition, these were fitted with the royalty-free MHTsaveBase, which achieves a further small weight saving because its stretch- blow ratio allows the bottle base to be more thinly blown. No changes were made to the bottling plant and the MHT21Light bottles were simply distributed between the conven- tional 1810. The plant processed both threads simultaneously, without problem. Family of threads Starting with the standard thread, MHT21Light has been developed into a complete mouth ‘family’. The weight for the ‘Light’ version for non- carbonated drinks has been even further reduced (3.4g). The version for ‘compression-moulded closures’ has, as with the PCO 1881, a slight thickening (0.1g) in the pilfer-proof ring area to facilitate removal of the guarantee strip. The range includes ‘Hot Country’ and ‘Hot Fill’ versions; both are resistant to the high temper- atures that develop during transpor- tation in hot countries and during hot bottling. It has been quite unusual to see the 28 thread in non-carbonated water bottling, particularly in the Middle East and southern Europe. Higher filling speeds have led to a preference for larger diameters, so filling lines are primarily designed on 30/25 threads. As water bottles do not require a CO 2 barrier in the form of stable closures, threads are generally lower. The drive to light- weighting has seen three differ- ent heights establish themselves: ‘High’ (18.5mm and 3.92g), ‘Low’ (16.9mm/3.75g) and ‘Supershort’ (12.6mm/2.43g). 29-25 thread with bottle MHT now offers a thread based on the Supershort, measuring 29/25 (height 12.6mm; weight 2.4g). While the weight reduction of 0.03g com- pared to the 30/25 Supershort seems marginal at first glance, 100 million preforms generate material savings of 3tof PET, even at this small amount. There is a tendency towards even smaller threads in America, where MHT supplies preform moulds with 27 or 26mm thread. The light thread market is on the move and since there is an increasing request from the beverage manufacturers for ‘green’ packaging, there is sure to be further development from MHT in this direc- tion as well. *based on an article by Sabine Kob, MHT MHT21Light has been developed into a mouth family for different applications