Plastics bag contg. coffee has pressure relief valve - with zone seal welded esp. with polyethylene to base of valve

摘要

The Parent patent describes an appts. for releasing the pressure from a plastics bag contg. roasted coffee or the like; a multi-layer label covering the hole in the bag comprises a base layer with a central hole, a valve diaphragm above this base layer and having a central strip not bonded to the base layer in the region of the hole but bonded to it on either side. In the patent of addn., the zones on either side of the central strip are sealed or welded to the base layer. Pref., the lower side of the valve diaphragm is coated with sealable or weldable material, esp. polyethylene 10-60 micron thick. The base layer itself may be of rigid polyvinyl chloride 100-200 micron thick. The valve diaphragm is transparent polyester 8-16 micron thick. With this arrangement, improved sealing is obtd.