The bag-in-bottle system consists of a strong bottle made from crystal-clear copolyester and an inner bag of highly transparent DuPont Surlyn with an additional oxygen barrier layer. This novel design is the fruit of a joint development between DuPont Packaging & Industrial Polymers and Gaplast, Saulgrub/Germany, a company which has successfully specialized in plastics packaging for pharmaceuticals and cosmetic products for over 40 years.
Bag-in-bottle systems, developed in the 1990s, have long proved their worth when it comes to reliable storage of highly sensitive ingredients. The innovation in the version now used by La Roche-Posay is the transparency of all the materials used. This means the contents can be checked at any time, keeping a consumer fully informed about the state and amount of the product remaining in the container. In addition, this innovative type of packaging allows the bag to be almost completely emptied, avoiding any unwanted product wastage while the external shape of the bottle remains unchanged.
Bag-in-bottle systems are produced by coextrusion blow molding. In the case of the packaging for Toleriane Ultra, Gaplast first extrudes a four-layer tube with a polyester outer layer to provide rigidity and a highly flexible, chemical-resistant inner layer with a Surlyn/EVOH/Surlyn structure. While still hot, the tube is directly transferred into a mold and pressed against the walls of mold cavity with compressed air. This creates the desired container shape and, at the same time, the bottom of the container is closed. Using deliberately created holes in the container bottom, Gaplast then blows compressed air between the outer container wall and the inner bag. Because the level of adhesion between the selected grade of polyester and Surlyn is very low, the two components can be particularly easily and gently separated.
Gaplast’s special, patented manufacturing technology involves fixing the inner bag to the container bottom during the blow molding operation. The inner bag is then fixed at the top when the dispenser is fitted. This means that the bag remains stretched to its full length as the container is emptied. As the container gets emptier, the bag can thus fold almost completely flat without any inflowing air reaching the contents. As Leonie Kneer, Gaplast’s sales manager says, “Fixing at both ends and the transparency of the bottle mean that a consumer can very easily make sure that the 40 ml contents have actually been completely used up before the bottle is thrown away.
This is exactly the result La Roche-Posay wanted to achieve because it further builds consumer trust.”
Stephan Kneer, research and development manager at Gaplast, explains: “We manufacture under clean room-like conditions and test every single one of these airless systems for tightness. As a result, our packaging meets stringent hygiene requirements. Surlyn has particular advantages over conventional plastics. Thanks to its softness and flexibility, the inner bag folds flat very well. This means that this kind of packaging can be completely emptied. Its excellent extensibility ensures the greatest possible design freedom, while its very good processing characteristics are particularly advantageous. For instance, its low hot tack temperature assists reliable closure of the container bottom during blow molding and the wide processing window of Surlyn facilitates coextrusion with numerous other thermoplastics which are used as the outer envelope and, in certain applications, also in the form of additional functional layers.”
DuPont Packaging & Industrial Polymers manufactures an extensive mix of adhesive, barrier, peelable lidding and sealant resins and provides a globally networked development team to work with customers on packaging programs that help protect the product, environment; improve shelf appeal, convenience; and reduce cost in the food, cosmetics, medical products and other consumer goods and industrial packaging industries.