Moulding the future

Increasingly, pharma packaging must be produced to specific standards of cleanliness. Stephan Kneer, technical director at Gaplast, outlines how its injection blow moulding line with contamination control features meets pharma container standards

Figure 1: Uniloy Milacron UMIB 78 production cell with 10-cavity turntable

Only a few suppliers with the capability for injection blow moulding production currently serve the pharmaceuticals market. Hence this niche provides an opportunity for companies such as Gaplast.

The company focuses on the pharma-ceutical, medical and beauty sectors, whose products are usually aqueous solutions and require a suitable container. In developing a container the company aims to offer its customers the best solution rather than merely to “sell” them capacity.

The attraction of injection blow moulding lies in the precision of the process, which for the production of preforms is comparable to injection moulding. In contrast to extrusion blow moulding there is no flash, and therefore no production waste on the ends of the articles. This not only saves material but also enables the production of a level base for the containers.

Gaplast has patented a container with a base that has a slightly protruding cross. In comparison with conventional concave bases, this cross-shaped reinforcement in the base region ensures that when the medium in the containers is pumped off, a much lower residual volume is left behind. In small containers this is very important to both manufacturers and users.

Another advantage is flexibility: the company can react quickly to new orders for small containers. Moulds can be in production within three weeks of starting the design process. Rapid implementation of a product idea is the company’s strength. These are just some of the advantages that will favour this process over others in future.

Alternative processes have their disadvantages. For example, extrusion blow moulding has the problem of parison waste, while thermoforming creates relatively high wall thicknesses. Neither of these processes achieves the economic efficiency of injection blow moulding in the manufacture of small, single-skin containers for aqueous solutions.

For this reason, in addition to its injection moulding and mono- and coextrusion blow moulding activities, Gaplast has chosen to expand its capacity in injection blow moulding.

The company introduced the process in 2005 and ordered two Uniloy Milacron Injection Blow (UMIB) 70 and 78 high-performance machines with locking forces of 566 and 600kN respectively. This was followed in 2008 by a further production cell equipped with a UMIB 78.

The company currently uses the injection blow moulding process to produce pharmaceuticals containers for aqueous solutions in sizes of 10–120ml.

A characteristic feature of the UMIB series is the arrangement of the hydraulic components under the turntable so that the work area can be considered oil-free.

Gaplast additionally ordered nickel-plated surfaces for this work area from Uniloy, so that cleaning can be carried out using a steam jet. This provides protection against contamination of parts and reliably prevents corrosion of components of the mould.

All systems were equipped with a laminar flow compartment to ensure the required cleanroom environment. In this way production can be carried out in a closed loop under cleanroom conditions (Class 100,000).

To ensure the containers remain clean and free of dust contamination they are packed in the production cell in two bags in batch sizes of up to 400 units and should reach the bottler in an airtight condition.

The bottler opens the outer bag in its own cleanroom and fills the containers. This means there is a closed circuit all the way from production to filling.

Another characteristic feature of the UMIB series is a process control system at the injection moulding level. In this way, Gaplast can injection blow mould its patented “cross base”.

Three-phase process

The hydraulic UMIB injection blow moulding machines are distinguished by generous mould mounting dimensions on the turntable. In the case of a UMIB 78 this allows applications involving moulds containing up to 10 parallel cavities depending on bottle size (Fig. 3). Uniloy offers very large radii (up to 571mm) for such horizontal arrangements of cavities. This allows high output volumes.

In step one, the 10 cavities are filled by injection to produce the preforms. Surface quality, control of wall thickness and degrees of freedom in geometry are much the same as for injection moulding. These are positive gains with respect to monoextrusion blow moulding.

At the second station the preforms are inflated in accordance with the desired bottle size (Fig. 4) and initial cooling via the mandrels takes place.

In the third phase the finished containers are cooled further by means of the mandrels and passed on to the automated system. A decisive factor is the functional design and temperature control of the mandrels on which the containers “circulate” from station to station on the turntable. First of all the moulding must be provided with the desired internal contours.

Depending on the type of container inflation is in the ratio of 1:4 with respect to the size of the preform on arrival.

At the third station the mandrels spread apart. On retraction, they release a plunger that demoulds and ejects the containers. Temperature control of the mandrels may make the process even faster.

Quality assurance

A special feature at Gaplast is the downstream QA unit supplied by Apis, of Spechtsbrunn. Using this equipment, pairs of containers – still within the production cell – are discharged to a rotary table for three tests that are carried out one after the other in a test time of 0.8 seconds (Fig. 4).

The first is a leak test, in which the containers are exposed to air pressure of 10mbar for 10msec. The drop in pressure is measured and if this is less than 4mbar the containers are rated as leak-free. The second test is what is known as a crack test. An electrode exposes the base of the containers to 50mW at 30,000 volts. The test is intended to identify small hairline cracks.

Test stage three is an optical test using cameras (Fig. 4). The cameras carry out a surface inspection. In this way the containers are checked for particles and contamination. If no particles above 0.3µm are found on the containers, they are rated as “particle-free”. If parts fail one of the three tests, they are rejected and removed from the rotary table by a separator.

After the separation station, the containers are electrostatically discharged so that they do not attract particles. A counter records the exact number of containers that passed the tests.