How to use multi-layer barrier technology to release the potential of PET packaging?

Since the early days of PET in the packaging industry, people have realized the excellent properties of this material. It can replace glass and aluminum packaging in many food, beverage, home and personal care products. In addition to having the ability to contain and distribute products and deliver marketing information to consumers, packaging must also provide the necessary protection for its contents, such as at least during the planned warranty period. Some examples of simple applications include preventing the escape of carbon dioxide contained in carbonated beverages, preventing oxygen from contacting sensitive juices and sauce products, and limiting the exposure of dairy products to light (including visible light, ultraviolet light, or infrared light). Although PET has better barrier properties than many other packaging polymers, it is still breathable and the packaged contents undergo a certain degree of gas exchange with the environment, which has often been a factor limiting the product's shelf life.

With the reduction of packaging size, how to provide adequate protection for products has become an increasingly serious challenge. The rate of gas entry (or loss) is directly proportional to the surface area of ​​the package, and the total amount of gas allowed into or out of the package is determined by the product volume. As the volume of the package decreases, the ratio of surface area to volume will inevitably increase, which requires that the necessary product shelf life requirements be met by improving the barrier properties of the package. With the increasing consumer demand for small packages (content control and consumption anytime, anywhere) and the growing need for brand owners to differentiate products on shelves, small-capacity packaging will become more common. Small-capacity packaging also allows brand owners to launch products to emerging markets at a price point that is acceptable to a wide range of potential consumers without eroding value.

The traditional method of improving the barrier properties of PET packaging

There are several ways to extend the barrier properties of PET packaging, and which technology will ultimately be selected will depend on a number of factors. These factors include the extent to which the barrier properties need to be improved, the need to maintain production flexibility, the limitations of the logistics chain, and of course, the total cost of production.

Comparison of CO2 Loss - Comparison of Single-Layer, Single-Layer and Multi-Layer Barrier Technologies

According to Coating Online, the simplest solution to improve the barrier properties of conventional PET packaging is to mix PET with a commercially available barrier material on an extruder in an injection molding system. The resistance to gas permeability (passive barrier) of the mixed product is improved and it is even possible to actively capture oxygen molecules (reactive oxygen scavenger) in the polymer matrix. This method, in addition to polymer metering and mixing aids, does not require any equipment replacement, which may in some cases be a suitable solution. But the simplest solution will often have serious limitations and even bring harm. The barrier improvement factor is directly proportional to the amount of barrier material added to the mixture. As the level of additives increases, the clarity and clarity of PET bottles generally decreases, which limits the degree of improvement that can be achieved while maintaining the desired appearance of the package. More importantly, hybrid solutions increase the cost of barrier materials and have a potential impact on recyclability compared to multilayer packaging.

Coating the bottle is another alternative to improve the gas permeation resistance of single-layer PET packages. Applying a thin layer of glassy coating on the inner surface of the bottle can form an efficient gas-permeable passive barrier. The coating can be performed during the plasma treatment after the blow molding process. The silicon oxide coating is clear and transparent, while the amorphous carbon coating adds a pale yellow color to the transparent package. The effect of such a coating may be limited by the deformation of the bottle, destroy the integrity of the bottle, and reduce the net effect of improved barrier properties. In contrast, multi-layer co-injection barrier solutions provide greater freedom of packaging design because the degree of deformation of the package is less important or even irrelevant to the barrier properties. It is also possible to add active oxygen scavenger material to prevent the ingress of oxygen to reduce the oxygen content in the headspace. When required by the application, it is also possible to create a multilayer structure that can provide light blocking.

At the operational level, coating solutions are attractive due to the low cost of consumables. At the same time, because the plasma coating system is an additional process step between blowing and filling, it is a challenge for preform injection molding companies to supply multiple blow molding production points. The choice of system supplier, among other things, also considers the type of coating chosen. Barrier coating quality control is accomplished by monitoring process parameters. The silicon oxide coating itself can only be tested using laboratory-grade instruments such as scanning electron microscopes. The quality of the barrier layer distribution in multilayer preforms can be confirmed by nondestructive and destructive inspections.

Multilayer preforms are achieved by sequential injection or simultaneous coinjection processes. The preforms obtained using both processes described above contain a unique layer of barrier material sandwiched between the inner and outer layers of PET. Although barrier materials are often approved in the food and beverage industry, another benefit is that only PET can be in direct contact with the contents. Blow-molding and filling steps after injection molding do not require changes to the existing production lines, which means that when needed, manufacturers can maintain the flexibility to supply multiple blowing and canning locations by operating a central injection molding plant. demand.

Husky multilayer barrier technology

Husky's multi-layer technology is a fully integrated system solution based on the company's best-in-class monolayer preform performance and reliability. At the same time, since PET and barrier materials can flow through the sprue at the same time into the mold cavity, co-injection can shorten the injection cycle and have the ability to inject thin-wall preforms. Multi-layer melt streams are formed in nozzles of co-injection hot runners, assuming that the same hot runner nozzle pitch and interface can be maintained, and standard mold cold molds can be interchanged between single and multi-layer systems. Although the co-injection system must be equipped with two injection units and a co-injection hot runner, as well as the necessary auxiliary and control systems, Husky's multi-layer system has full flexibility to run single-layer molds (complete molds and Hot Runners can also produce single-layer preforms without changing molds for changes in demand, seasonality, or target market.

Multilayer barrier technology places the barrier exactly where it's needed. The image on the left is an offset black layer that is away from the surface toward the core. The figure on the right is a fully sealed preform dome.

Passive and active barrier materials are more effective when used in a concentrated layer in a multilayer package than a single layer blend of PET. By using only about 50% or less of the mixed barrier material, the same barrier improvement factor and associated shelf life can be obtained in a multilayer barrier package. The effects of co-injection systems have been reported and confirmed in laboratory studies. Although the mechanism is different, it is applicable to oxygen scavenger applications that must prevent oxygen from contacting the product and passive barrier applications that must maintain carbonation inside the package. In the case of passive barriers, gas permeability is reduced by creating denser "barriers" for gas molecules. In the case of active scavengers, the scavenger material's ability to act is ensured by ensuring that only oxygen molecules that reach the barrier layer react with the scavenger and are trapped.

Although light barrier applications do not involve gas diffusion mechanisms, similar material cost and packaging performance advantages can still be obtained from multilayer technologies. At room temperature, the ability to store dairy products (such as UHT milk) for longer periods of time is constrained by many factors, including the breakdown of riboflavin (vitamin B2) and the oxidation of proteins and fats caused by light, resulting in nutritional value. And the loss of taste. The monolayer preform has a TiO2 masterbatch (titanium oxide is usually used to produce a strongly opaque white) that is hardly significantly higher than 12%, and at some point it is not possible to stretch the blowing bottle, limiting what it can achieve. Light blocking capability. In contrast, because the multilayer preform contains a hidden black PET layer in the white PET, its light transmission is greatly reduced, which can block 99.99% of 650nm wavelength light, while reducing the need for expensive opaque white additives. Demand.

The ability to provide uninterrupted barrier layer coverage through the preformed dome improves the barrier properties of the entire package, which is particularly important for oxygen and light sensitive products. In particular, certain food types, such as spaghetti sauces, are not easily mixed in the package, resulting in localized oxidation of the portion of the package that is not covered by the barrier layer, resulting in spoilage. Husky's hot runner design and control system allows multiple layers of preforms to be molded in a manner that is closed or open at the top of the circle (with or without a barrier layer at the bottom of the bottle). In the former case, excellent end portions are provided. Process (back edge) control or barrier layer.

In 2015, Husky began to selectively cooperate with some early adopters to launch the multi-layer technology in the market. Since then, customers have chosen to rely on this solution to provide packaging for a variety of products, including carbonated soft drinks, mineral water, juices, and sauces, which have now been extended to applications in dairy products, beer, and personal care products. In each case, multi-layer technology allows customers to reach a longer shelf life at the same cost, or achieve the same shelf life at a lower cost, while maintaining complete flexibility in the injection molding solution, not the downstream equipment. Or logistics impose additional restrictions.

An important factor in reducing total production costs is the ability to precisely determine the amount for a specific product and allocate just the right amount of barrier material while maintaining the robust productivity of the Husky HyPET HPP system. As we all know, the raw material cost is the main component of the total packaging cost. Barrier materials, although a relatively small percentage of the package weight (usually 2% to 15%), are much more expensive than PET. This makes it important to ensure that the minimum necessary amount of barrier material is delivered to each cavity and that it is distributed within the preform in the most efficient manner.

This advanced level of control can only be achieved with fully integrated systems using unique, state-of-the-art hot runner designs. The technology on which the hot runner is based can achieve an unprecedented degree of balance even before all control devices have undergone production adjustments. This reduces the number of splits of the molten fluid in the hot runner, which is also one of the most important factors in the hot runner imbalance.

This hot runner technology also provides unprecedented design freedom, optimizes the flow path layout for both material melt delivery systems, and enables high thermal control. Many barrier materials have a lower melting point and are more sensitive to temperature than PET. Excessive heat or excessive residence time can lead to material degradation. This not only affects the quality of preforms and bottles, but also increases the time for hot runner renewal. Using Husky's co-injection hot runner, the transfer system of the two materials is thermally separated and independently controlled by the embedded Altanium control system to ensure that when the two materials are mixed before the gate, the barrier material is only subjected to the PET processing temperature control.

Molders familiar with co-injection will realize that in order to improve the balance of hot runners and to ensure that the flow of melt at multiple gates and the rate of temperature change are as uniform as possible, the heat flow can be adjusted by lowering and raising the temperature of the manifolds and nozzle tips. Road. Husky Hot Runners achieve control flexibility by increasing the number of manifold zones and individually controlled nozzle heads. The traditional pneumatic valve system has been upgraded to an electric servo plate-driven synchronous valve pin system. At the same time, this high degree of balance means that the temperature range required to further adjust the performance is significantly reduced, further reducing the maximum temperature that the barrier material can withstand.

The multi-layer barrier technology is suitable for a variety of applications, including carbonated soft drinks, mineral water, juices, and sauces, and has now expanded into the dairy and beer industries.

Husky's customers evaluated the performance of the hot runner after millions of production cycles in the field. This stability can be achieved without the need for unplanned maintenance. When producing a temperature-sensitive barrier material, it is a good practice to clean the two hot-runner melt-delivery systems with PET during system shut-down and restart, and it has now been automated. Even the best maintenance measures will inevitably lead to accidents such as foreign materials contaminating raw materials. If contaminant particles enter the hot runner, the most likely plugging area is the hot runner nozzle because the melt channel is minimal here. In the past, this site was notoriously difficult to clean and often required removal of the entire hot runner. The HyPET HPP5 barrier system features a front removable nozzle design that allows the nozzle head to be exposed in the injection molding machine by locking the cavity plate to maintain or replace the hot runner nozzle .

Although co-injection is more complex than the traditional single-layer injection molding process, the entire system operates with Husky's intelligence. The support of the preform-centric control system integrates the various aspects of the injection molding process and auxiliary equipment. The process set-up for new product production begins with the development of a single-layer process flow for the preform quality. After the start of barrier material injection, the control system will automatically adjust the PET injection curve based on the content of the barrier material and generate an injection molding curve for the barrier layer, which can be further fine tuned by the operator. Customers who are unfamiliar with the co-injection process find that the Husky system is user-friendly. After a short training period, customers can operate in production with confidence and can be supported quickly and efficiently through the Husky service network. Safeguard all aspects of system operation.

Husky's multi-layer technology provides a complete, integrated solution for the production of food and beverage products that require enhanced barrier properties, with high cost-effectiveness, productivity, and flexibility. It allows brand owners to rely on PET to produce more attractive packaging. These packaging stands out on the shelves of the store and support the replacement of alternative materials, all of which contribute to the growth potential of PET packaging materials.

Witness success

In launching a new multi-layered technology, Husky cooperated with the most famous European manufacturers of preforms and PET bottles to test and validate solutions in this area. Due to the proven track record of cooperating and verifying new technologies, Husky knows that this European customer is well suited as an early partner. The two companies are also working together to develop solutions to advance the PET industry and expand the addressable PET market. This is also a great time for Husky's customers because their existing co-injection barrier system is undergoing maintenance, repair and stability issues and is looking forward to finding upgrade solutions.

The installation and start-up of the first multi-tiered system in this customer's European plant was fully supported by Husky Regional Service Engineers and multi-layered barrier experts from the company's Bolton, Ontario, headquarters. As part of the qualification process, the system successfully completed the uninterrupted production of two batches of multi-layer preforms, one batch of 28-gram soda bottle preforms and the other 14-gram juice bottle preforms.

In fact, if Husky's new multi-layer technology is compared to its existing co-injection barrier system, customers have found no change in performance after running the system for several months. In the past, whenever testing alternatives, they usually saw deterioration in barrier performance in a few weeks, but this time it was different. They also found a significant improvement in the control of the weight of the barrier. When using Husky's new multi-layer barrier layer system, the accuracy and reproducibility of the control of the preform barrier layer content is significantly better than currently attainable. Both applications are produced with a tolerance of +/- 0.5% of the total weight of the preform on the barrier layer, which is achieved while shortening the injection cycle by 40%.

Husky's multi-layer system can run in a more consistent manner for a longer period of time without compromising performance, while reducing the Hot runner maintenance needs. Today, this customer is continuing to cooperate with Husky on the future multi-layered barrier project.

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