Injection stretch blow molding process

• Main Author: ETESSE PATRICK JEAN-FRANCOIS
• Format: Patent
• Language: English
• Published: 01.03.2016
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULARARTICLES; INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS; MAKING GRANULES OR PREFORMS; PERFORMING OPERATIONS; PREPARATION OR PRETREATMENT OF THE MATERIAL TO BESHAPED; PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCESIN A PLASTIC STATE; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIALCONTAINING PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

The present invention relates to a process for blow molding a polyethylene container comprising the steps of: a) providing a solid preform made from a polyethylene material having a melt flow index from 0.01 to 10.0 g/10 minutes, wherein the preform comprises a neck region, side walls and a base region, and wherein the side walls between the neck region and the base region have substantially straight and parallel outer walls; b) reheating the preform so that the maximum temperature difference between the hottest and coldest regions of the side walls and the base region of the reheated preform is less than 4° C.; c) transferring the reheated preform to a blow mold; d) stretching the preform at a pressure below 10 bars; and e) increasing the pressure within the reheated preform so as to cause the walls of the stretched preform to expand to the shape and dimensions inside the blow mold. A polyethylene container made according to the present invention preferably has a minimum wall thickness of the container of less than 200 micrometers, and a weight to volume ratio of the empty container of less than 50 grams per liter.