Multi-Injection Blow Molding

A number of healthcare packaging trends, including demand for better clarity and safety, are creating a need for improvements in traditional monolayer materials such as glass and plastic. In Vitro Diagnosis (IVD) and pharmaceutical applications increasingly require packaging that can withstand autoclave and gamma sterilization methods as well as impact. Also common to both areas of packaging is the need for clarity combined with barrier (moisture or gas/oxygen) protection to facilitate sample collection and drug efficacy. There are other emerging material requirements as well, including low protein binding, advanced hemocompatibility and chemical resistance, which increase the complexity of materials selection.

Due to these trends, increasingly there is no one material that meets the growing set of requirements for specification in today's IVD and pharma packaging. However, uses of Lexan HP polycarbonate (PC) resins from SABIC Innovative Plastics are now being applied to help resolve gaps with current solutions. Lexan polycarbonate is already used in healthcare devices and packaging due to its water-clear transparency and high resistance to breakage. It also delivers excellent chemical and temperature resistance. Lexan HP specialty resins are engineered for the healthcare industry, offering the potential for hemocompatibility, low protein binding and other properties. However, for certain applications, polycarbonate materials have limited ability to provide a moisture or gas barrier.

Layer structure must be carefully controlled throughout the full application from the finish through the body to the bottom.

To help customers overcome the limitations of glass and monolayer thermoplastic solutions by enabling the use of Lexan HP resins in applications requiring oxygen, carbon dioxide and/or water vapor barrier capabilities, SABIC Innovative Plastics turned to a multiinjection blow molding. This process produces a high-performance, multimaterial barrier package. A processing and testing environment was created at SABIC Innovative Plastics' Polymer Process Development Center in Pittsfield, MA, as part of the company's Global Application Technology (GApT) customer support services. This facility is available to customers worldwide for application development through a Virtual Lab that is connected to similar facilities around the world.

Healthcare Packaging

A number of trends are prompting packaging manufacturers to rethink traditional vials, drug containers and sample collection tubes made of monolayer glass and plastics. Cleanliness and sanitation continue to receive strong attention globally, requiring containers to withstand a range of chemicals and sterilization techniques, including autoclaving. For example, the U.S. Food and Drug Administration (FDA) recommends terminal sterilization instead of aseptic filling of pharmaceuticals, including combination products, when possible.

The need to reduce the level of blood or a drug or biopharmaceutical product that may bind to the surface of the container holding it is increasingly important in IVD, pharmaceutical, and biopharmaceutical products. By enabling low-adhesion or non-binding surfaces, more of the contents will be available for use and/or unaffected by contact with the container. Related trends include the need for better chemical resistance as more non-invasive tests are designed using a wide range of samples from the body such as hair, tears, saliva, urine, etc. This property is also becoming more important with the surge in specialized pharmaceuticals and biopharmaceuticals for oncology, rheumatology, diabetes and anemia where the drug composition may vary in pH, demanding more chemicallyresistant containers.

Error reduction and compliance with the patient's designated therapy have created a demand for unit-dose packaging. Individual dose packaging helps to ensure accuracy of delivery, thus aiding both staff and patients in the hospital and home.

Although there are many different plastics, as well as glass, being used for IVD and pharma packaging, each has limitations that make them less than ideal for today's complex requirements. For example, polypropylene (PP) - lacks clarity and is marginally autoclavable. Polyethylene terephthalate (PET) and polyamide (PA) cannot typically be autoclaved. Cyclic olefin copolymers (COC) have limited gas barrier properties and can be cost-prohibitive. And glass, while clear, inexpensive, autoclavable and an excellent water and gas barrier, falls short in ductility (breakage), may experience adhesion of proteins to its surfaces, and has less design freedom than plastic alternatives.

The Solution

Lexan HP polycarbonate resins for healthcare applications offer a solution for IVD and pharma packaging, as they provide clarity, ductility, and a range of sterilization capabilities, including autoclave and gamma radiation; however, barrier performance is not at the level required for most IVD and pharma applications. Therefore, SABIC Innovative Plastics made a significant investment in an older technology - multi-injection blow molding - to add gas and water barrier performance to the outstanding physical and mechanical capabilities of Lexan HP resins. Implementing a multiinjection blow-molding system supports the development work of its customers in creating new packaging designs that take advantage of Lexan HP resins. This system helps customers in their efforts to transition from glass or monolayer plastics solutions to multi-material technologies.

The goal of the multi-injection blowmolding optimization project was to integrate Lexan HP resins with traditional barrier materials in a "sandwich" construction: two exterior layers of the polycarbonate resin enclosing a core layer of a barrier plastic such as amorphous nylon or COC. This approach leverages the advantages of two materials to deliver superior application performance.

SABIC Innovative Plastics worked with three equipment/tooling companies: Uniloy Milacron for the UMIB 85 injection blow molding machinery; Big 3 Precision Products - Abramo Division for the tooling; and Kortec for co-injection technology and system integration in order to refine the process for improved quality and consistency of core/skin layer distribution, and consistency of the layer structures around the circumference of the package with such equipment. Among the issues were:

• Thickness profiling: Control over the thickness of the core/skin layers along the length of the container, distributing the barrier material where it is most beneficial
• Weld line strength: Ability of the material to maintain mechanical properties such as impact strength in areas where the flow front has been separated and rejoined during injection.
• Gate closure: Creating a core layer that is free from voids in the proximity of the gate.

To effectively manage the barrier performance of the application, the core layer must be continuous from the finish (top) through the gate. The inner and outer skin layers also deliver value to the application, such as impact resistance or autoclave protection provided by Lexan HP resins, thus requiring control of layer distribution as well. An example of the necessary layer control using this multi-injection process is shown in the chart on page 79. The layers are uniformly controlled from the finish through the neck and body of the application (bottle).

Key Process Considerations

SABIC's Global Application Technology (GApT) facility is available to customers worldwide for application development.

To successful ly respond to key trends such as breakage resistance, autoclavability and barrier performance, careful consideration must be given to materials selection, part design and final layer structure.

Through the development of its multiinjection blow-molding system, SABIC Innovative Plastics gained expertise in utilizing a variety of Lexan HP resins combined with commonly used barrier materials to overcome the limitations of existing monolayer plastic materials and glass. The results of the development process demonstrated that several aspects of part design may significantly influence application performance and manufacturability. For example, part design considerations include neck finish diameter, blow ratio, neck length, and nominal wall thickness.

Finally, layer structure also plays an important role in achieving the desirable attributes such as shelf life (barrier capability), breakage resistance and autoclavability. Layer structure must be carefully controlled throughout the full application from the finish (top of bottle) through the body to the bottom (gate area). For example, management of the barrier layer coverage must be continuous and adequate to achieve shelf-life goals for the application. Similarly, the inner and outer skin layers must also be of adequate thickness throughout the application. Important to this process is synchronizing the skin and core layers during the multiinjection blow-molding process.

SABIC Innovative Plastics evaluated multi-injection blow-molding equipment, parameters and other factors to achieve an optimized process for applying Lexan HP resins as the outer and inner skin layers. Based on the characteristics of Lexan HP resin, the team concluded that a one-step process offered the best results, thus enabling the use of materials that do not possess the melt strength required for extrusion blow-molding or twostep blow-molding processes. This expands the processing window of materials such as Lexan HP resins in blow-molded applications.

Resources

Polymers within the Lexan HP resins portfolio offer a selection of performance options for healthcare applications. This portfolio encompasses: Lexan HPS resins that offer enhanced stability to gamma and e-beam sterilization; Lexan HPH resins that enable steam autoclave sterilization at temperatures as high as 134oC; Lexan HPM resins that offer the potential for advanced hemocompatibility and low protein binding; and Lexan HPX resins for enhanced processing.

SABIC Innovative Plastics is extending the availability of this application development line to assist medical and pharmaceutical industries in taking advantage of Lexan HP resins to enhance the system performance of a wide variety of vials, tubes and bottles with increasing functional demands.