PETpla.net Insider 06 / 2017

PREFORM PRODUCTION PET planet Insider Vol. 18 No. 06/17 www.petpla.net 9 contrast, the multi-layer co-injection barrier solution provides a greater package design freedom, since the package creep and deformation levels are less critical or even inconsequen- tial for the barrier performance. It further allows active oxygen scaven- ger materials to be introduced, pre- venting oxygen ingress and lowering oxygen content in the headspace. A multi-layer structure providing a bar- rier to light can also be created when required. On the operational level, coatings are attractive due to a low cost of con- sumable materials. At the same time, a plasma coating system represents an additional process step between bottle blowing and filling, which can pose a challenge to preform moulders supplying multiple blowing sites. Multi-Layer Technology A multi-layer preform is pro- duced in a sequential injection or a simultaneous co-injection process. In both cases, the resulting preform contains a distinct layer of the bar- rier material sandwiched between the inner and outer layers of PET. Even though barrier materials are typically approved for food and beverage applications, as an added benefit this results in only PET being in direct contact with such products. Preform blowing and filling steps subsequent to injection moulding do not require changes to the existing production lines. This means that, when desirable, a producer is able to maintain the flexibility of operating a central injection moulding facility supplying multiple blowing and filling locations. Husky’s Multi-Layer Technology is an integrated system solution build- ing on the monolayer preform perfor- mance of the company’s HyPET HPP5 product line. Simultaneous co-injection results in faster cycle times and the ability to inject thinwall preforms, since both PET and the barrier materials flow into the mould cavity through the gate at the same time. The multi-layer melt flow is formed in the nozzle of the co- injection hot runner, while the standard mould cold half can be interchanged between the monolayer and the multi- layer systems, assuming the same hot runner pitch and nozzle interface is maintained. Both passive and active barrier materials are more effective when used in a concentrated layer in a multi-layer package, compared to a monolayer blend with PET. The same barrier improvement factor can be achieved in a multi-layer barrier pack- age using approximately 50% or less of the blended barrier material. The effect has been reported with co-injec- tion systems and confirmed in labora- tory studies. This holds true for both the oxygen scavenger applications, where oxygen must be prevented from reaching the product, and for passive barrier applications, where carbona- tion must be kept inside the package, although the mechanism differs. In the case of a passive barrier layer, the gas permeation rate is reduced by creating a denser “fence” for gas molecules. In the case of an active scavenger, the useful capacity of the scavenger mate- rial is extended by ensuring only the oxygen molecules that reach the bar- rier layer are reacting with the scaven- ger and are trapped. Even though light barrier appli- cations do not involve gas diffusion mechanisms, similar material cost and package performance advantages are derived from a multi-layer technol- ogy. Shelf life of dairy products (such as UHT milk) processed for long shelf life at ambient temperature is limited, among other factors, by the breakdown of riboflavin (vitamin B2) and oxida- tion of proteins and lipids triggered by exposure to light, leading to a loss in nutritional value and off-flavours. Mon- olayer preforms containing significantly above 12% of a TiO2 master batch (titanium oxide commonly used to produce a strongly opaque white) are difficult and at some point impossible to stretch blow, thus limiting the extent of light barrier that can be achieved. In contrast, multi-layer preforms contain- ing a black PET layer hidden within an opaque white PET achieve signicantly lower light transmission, blocking up to 99.99% of light up to 650nm wave- length, while reducing the amount of expensive opaque white additive that is needed. The ability to provide uninterrupted barrier layer coverage through the pre- form dome improves package barrier performance and is especially important for oxygen and light sensitive applica- tions. In particular, some food types (i.e. pasta sauces) do not readily mix inside the package, creating a potential for local oxidisation of the product in seg- ments of the package not covered by the barrier layer, causing spoilage. The Husky hot runner design and control system allow moulding of the multi-layer preforms with either closed or open dome tips (with or without barrier layer in the bottle base), in the former case providing outstanding control over the termination (trailing edge) or the barrier layer. An important factor to lowering the total cost to produce is the ability to precisely dose and distribute just the Husky’s Multi-Layer Technology combines the benefits of the company’s proven HyPET HPP5 system with a revolutionary new hot runner to enable the most precise and controlled dosing of barrier material.