The HPC group (...) was formed in 2018 to work together in establishing the specific requirements for finishes in this sector. It became clear that to meet the needs and suit the products of the HPC market a new design of weight-optimised finishes would be required.
Through cooperation between the group members including manufacturers of machines, caps, preforms and moulds, the brands and users of this type of bottle and resin suppliers, two new families of designs were achieved: snap-on and screw finishes. Now the HPC group is fully established, with several of its finishes approved and published at Cetie and an ambitious agenda for the future. Its Chair until the end of 2020, Christian Gerlach of Procter & Gamble, has succeeded in cultivating a strong momentum and in establishing an effective working method.
Several screw finishes have been defined in succession, starting with the most widespread: the 27 mm diameter finish (Cetie data sheet GME33.01 “PET Neck 27/22-13.5/1/4.24-1.5 turns”), then the 32 mm version. The dimensions currently being studied are the 43 mm finish, then 24 mm and the 20 mm finish. Together, these finishes form a range of products based on a shared structure: the same shaped threads, index marks, the same finish height across several formats. This range also aims to save weight where possible, such as would constitute a real economy in the material used, all while ensuring that they remain sufficiently safe to use, in particular where aggressive contents are concerned. This is why one of the working group’s aims for 2021 is to expand on the approval process for these finishes by introducing digital simulation, despite the fact that the method used to design the finishes is itself dependable, being based on both pre-existing geometric elements and the experience and expertise of all the businesses involved.
The other approach, the snap-on finish, has followed a different path: Cetie included a finish that was already available on the market in a data sheet with the details of its design drawing and specification (Cetie data sheet GME33.50 “PET Snap Neck Finish 27/22-6.3”). This finish is highly optimised in terms of weight saving and particularly well suited to a single product, few-format changing or moderate speed production lines. In addition to this high level of optimisation, the group decided to work on a more polyvalent but heavier version that can be used on high-speed production lines.
In the context of European Directive 2019/904, the European Commission mandated the CEN (European Committee for Standardisation) to draft a standard to establish the specifications for attached caps of single-use plastic bottles (see L&C404). Since this Directive has significant ramifications for bottle closing systems, the drafting of this standard has proved to be a sensitive topic for the various leaders in this sector, entailing intense discussion within both the CEN group WG25 and at Cetie.
Indeed, the products on the market are highly diverse, from PEHD milk bottles to premium PET bottles, or from drink flasks to drink cartons. Adapting to an attached cap does not represent the same technical challenge across this wide range of products. For this reason, and due to the subject’s novelty, from the end of 2018, it took no less than 15 meetings at Cetie to specify the requirements of the attached cap. The first project for the standard has now been written and registered at CEN, and the enquiry phase can now begin on the basis of this text, following two key requirements:
- The connection of the cap with the bottle (or flask or carton) must resist a force of at least 25 Newtons. This specification is significantly higher than that of the Directive, but those involved in drafting this standard, themselves also manufacturers and brands affected by this development, intended for this force to be enough by itself to let consumers realise that the connection between the cap and the container is intentional.
- The connection must withstand 10 openings/closing cycles without breaking, so as to be dependable throughout punctual use of the product.
In order to respect the application period required by the European Commission (July 2024) and to anticipate the modifications required to products and production lines, manufacturers in the sector are already introducing attached cap solutions.
To avoid a situation in which each industry player creates its own specific finish, Cetie members immediately saw the need to create a standardised PET finish, adapted to highly carbonated beverages with up to 10g/l CO2 (5.2 Vol% CO2) and volumes of up to 3 litres. Developed within Cetie’s PET Plenary group, and championed by the Coca-Cola Company, this finish has its weight reduced to a minimum, which required tests to be performed on the various technical options in coordination with cap suppliers, preform manufacturers, and soda brands until the best compromise was ultimately identified: a finish 15.11 mm high, with a thread diameter of 26.44 (24.2 mm diameter at thread root), and a unique thread that performs almost two turns on a pitch of 2.30 mm. This finish, GME30.40, allows for space above and below the Pilfer Proof ring for the tamper-evident band and for the cap tethering system. It can be fitted for various diameters of support ledges, from 29 to 33 mm according to the type of bottles, and weighs 2.73 g in its widest version (33 mm support ledge). Note that there is also a derivative version without the attaching system to respond to demand from countries outside the European Union. This version, the GME30.41, has the same general characteristics as the first, but with a height of only 13.42 mm.
So while the Directive had called for an attached cap by 2024, as early as 2021 it will get a technically validated high-performance finish standardised within Cetie.
Josquin Peyceré for french Magazine Liquides & Conditionement N°410