PET Preform Stretch-Blow Moulding with Liquid Injection
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Solution Overview
Problem
Conventional PET bottle manufacturing processes, such as blow moulding and stretch-blow moulding, do not fully optimize the mechanical strength and crystallinity of PET containers, leading to limitations in their lifetime and production efficiency.
Innovation Solution
A method involving the injection of a beverage into a heated preform within a mould to promote expansion, combined with controlled longitudinal displacement of a stretch rod, ensuring a volume of beverage greater than 50% of the predetermined volume during the stretching process, enhances the crystallinity and mechanical strength of the containers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If compressed air is used for blow moulding or stretch-blow moulding, then the manufacturing process is simple and production rate is high, but the mechanical strength and crystallinity of the PET containers are not optimized
Solution Approach 1:
The patent changes the physical state parameter of the expanding medium from gas (compressed air) to liquid (beverage product itself). This parameter change enables the liquid to penetrate and plasticize the PET preform more effectively during stretching, promoting crystallization and enhancing mechanical strength while maintaining the blow moulding process framework
Solution Approach 2:
The beverage liquid acts as an intermediary substance that mediates between the stretching force and the PET preform. The liquid penetrates the preform walls during stretching, providing internal plasticization and promoting crystallization, thereby improving mechanical strength without requiring complex additional equipment
2Duration of action of stationary object
If the preform is stretched using compressed air, then the production process is efficient, but the lifetime of the containers is limited
Solution Approach 1:
Changing the expanding medium from gas to liquid fundamentally alters the physical-chemical interaction with the PET preform. The liquid beverage promotes crystallization during stretching, creating a more stable molecular structure that extends container lifetime while the process remains integrated into the existing blow moulding production line
Solution Approach 2:
The beverage is introduced into the preform before the stretching process completes, allowing the liquid to penetrate and plasticize the material during the forming stage. This preliminary action of liquid infiltration promotes crystallization that strengthens the container structure for extended service life
3Strength
If high crystallinity is achieved by modifying the manufacturing process, then mechanical strength improves, but the process complexity increases
Solution Approach 1:
The beverage liquid serves multiple functions simultaneously: it acts as the expanding medium for blow moulding, as a plasticizer during stretching, and as a crystallization promoter. This multi-functionality achieves high crystallinity and mechanical strength without adding separate process steps or equipment
Solution Approach 2:
The patent merges the expanding medium function with the crystallization promoter function into a single substance (the beverage liquid). This combination eliminates the need for separate gas expansion and chemical treatment steps, reducing process complexity while achieving high crystallinity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in PET bottles with improved mechanical strength and extended lifetime, while also optimizing the industrial production process by minimizing in-line losses and increasing production rates.
Implementation Method 1
a method of delivering a predetermined volume of beverage into a thermoplastic container formed from a heated preform
Implementation Method 2
The preform is heated beforehand so as to be in the mould at a temperature above the glass transition temperature (about 100° C.) so as to enable it to be formed by stretch-blow moulding
Data Source
AI summary
The invention relates to a method of, and a device for delivering a predetermined (1) volume of beverage into a thermoplastic container formed from a heated preform, the preform being positioned in a mold, characterized in that the method includes a step of injecting at least some beverage into a recess in the preform so as to promote expansion of the preform inside the mold, the mold defining the shape of the container, a longitudinal displacement of a stretch rod (10) carried out during a given period ensuring longitudinal elongation of the heated preform, the stretch rod being immobile at the end of the given period, and a volume of beverage greater than a predefined fraction of the predetermined volume, preferably equal to 50%, being present in the recess at said end of the given period.