In this age of modern technology almost anything is possible. We can design products and processes that produce the cleanest, toughest, lowest off gassing, purest, and highest barrier properties. It is easy for a packaging engineer to envision a product or process that perfectly addresses a set of technical requirements, and to totally absorb oneself in the details of what I call a “technical vacuum.” A “technical vacuum” is an engineering state of mind that focuses only on technical requirements and avoids reality, approaching technical challenges without anticipating market and cost considerations.
The real story of successful packaging engineers is their ability to scrutinize technical requirements, challenge those requirements, and finally condense them into products and processes that are affordable, marketable, and realistic. It is important for you to understand that initial technical requirements presented for packaging applications rarely perfectly match the actual end product of successful development efforts.
This case study is written to provide you some insight in how your packaging suppliers approach your product development needs. Before reading the case study, review the general outline, just below, of how a flexible packaging development team approaches a project.
* Find out what is desired in as much detail as possible. This includes:
* Physical properties and specifications. If specifications are not completely known, explore the customer’s process and help develop preliminary specifications.
* Determine a cost window needed by customer.
* Prioritize the customer’s needs with the customer and determine what is absolutely required.
* Every desired attribute that is not absolutely required should be addressed later in the process.
* Determine if the volume potential is worth the effort/cost involved.
* Determine if there is a skills and technology match. If you do not have the skills and technology to overcome the challenges involved, recognize it immediately and determine if those skills and technology are available elsewhere and their cost. If there is no match, end the project.
* Outline the best theoretical process and product that can provide solutions in the most cost effective way. Check and see if there are existing structures and processes that meet the need. If so, consider a patent search.
* Estimate costs of Step 4 and match them against the cost window needed. If there is not a match, review the goals with the customer. If the customer’s expectations and requirements do not meet their cost window, end the project.
* Develop and test substrates and processes for required attributes. Make sure you remain in the customer’s cost window. If after testing you are outside the cost window, regroup and communicate with the customer about the path forward.
* Test through customer’s process.
* After successful testing, review costs and determine if the nonessential but desired properties are viable and go back to 4.
Our case study occurred several years ago when Fisher Container Corporation had several pharmaceutical industry steam sterilizing operations approach us looking for solutions to problems they were having with available packaging formats. These operations, although in different companies, and making different products, all had very similar process layouts. They were all clean room operations, secondary processing facilities,1 and sterilized with steam autoclave at temperatures of 121C. For those unfamiliar with steam autoclave sterilization, high temperature steam is pulsed through a permeable substrate with a pore size of 0.22 micron or less, that surrounds the item being sterilized. The steam is transferred through the substrate by differentiating the air pressure in an autoclave chamber. As the air pressure inside the permeable package and the surrounding chamber are different, increasing and decreasing in a cycle, steam transfers in and out of the permeable package, sterilizing the item inside. The item is finally dried, using sustained dry heat, to remove moisture left from the steam sterilization cycle.
In brief, their operations were taking items such as vials, containers, stoppers, plungers, etc., sterilizing them in permeable pouches, and then holding them in inventory for use in other final fill operations. Their concern was with the pouches during this process.
The challenges they listed were inconsistent cleanliness, the need for stronger seals, and a desire to reduce the amount of time taken to dry the items after the steam cycle. They desired permeable packaging certified to surface cleanliness Level 100 Mil Spec 1246C. The packaging currently available to them was manufactured with materials certified by the FDA, but was not certified to a specific surface cleanliness level. They needed to tighten surface cleanliness specifications due to anticipated changes in industry cleanliness and processing standards. The high differential pressures used during the autoclave cycles caused great stress on the seals of the permeable packaging currently available in the market. The sterilizing operations averaged 2% seal failures. The items in these packages had to be cleaned and sterilized again at great cost. Seal failures also left open the possibility that contamination could inadvertently occur. The sterilizing operations also wanted to reduce drying times to increase the efficient use of their autoclaves.
We began the development program with a series of justification meetings with potential customers, designed to determine exact specifications, volume potential, and cost window for a new package. The volume potential justified a research effort and we also determined a cost window for the potential package. Next, over a period of several weeks, we gathered a preliminary set of specifications for a new pouch. The following desired specifications were drawn up by the customers in order of priority:
* Surface cleanliness Level 100 Mil Spec 1246C. Substrates had to withstand temperatures up to 125C for 5 minutes and 121C for 45 minutes.
* Substrates used had to have low off gassing and leachables properties. In other words films that would not contaminate the items inside the pouch when autoclaved.
* The permeable substrates had to have a pore size 0.22 micron or smaller. (Microbial barrier had to be <0.22>
* Seal strengths should be as strong as possible. Data was not available on exactly what seal strength was required. We tested their current packaging and found seal strengths ranging from 3-4 lbs. per linear inch. Seals also had to be hermetic.
* There should be as large a permeable surface area as possible to reduce drying times.
* A clear window or face was necessary to allow visual inspection.
* A peelable seal format was needed to allow the pouch to be pulled open easily when the part inside was needed for primary processing.
We then took this priority list and began analyzing potential substrates and process technologies. We checked market sources for existing pouch formats that could fulfill the requirements and found none. Next we partnered with one of the sterilizing plants and did further seal testing in their autoclave to tighten the seal strength specification. Seal strength requirements had to be addressed before we could complete a theoretical product model. The reason we needed to do this is that seal strength requirements can exclude certain substrates being used together, and also determine what seal types and seal equipment can potentially be used. After eight seal test trials taken over a two month period we determined a minimum seal strength requirement of 5.5 lbs. per linear inch in the first autoclave trials.
With a firm seal strength specification in hand, and three months into the project, the development group set out to justify a theoretical process and pouch form that met the specification list. We quickly determined that the ideal permeable film type was spun bond high density polyethylene (SBHDPE). We had experience cleaning this film and had attempted to clean other permeable substrates to Mil Spec 1246C level 100 without success in the past. This made SBHDPE the only film type that could meet the cleanliness requirement. SBHDPE also had a pore size less than 0.22 micron, and could withstand 121C for sustained periods of time, and temperature spikes up to 121C. The film had great off gassing and leachables characteristics as well. Hermetic seals were easily achieved with this film type. Although SBHDPE was promising, we had several hurdles related to the use of this film type when matched against other specification requirements:
* The best seal strength that could be achieved in a peelable seal format was 3.5 lbs. per linear inch.
* The best seal strength we had ever achieved in any format with SBHDPE was 5 lbs. per linear inch.
* SBHDPE was expensive and it would not be possible to make a pouch completely with this film type and remain in the cost range needed. We determined that only one side of the pouch could be SBHDPE given the cost window set for the pouch. Also, if SBHDPE was 100% of the pouch, drying times could be reduced; but if the pouch were 50% SBHDPE this could not be achieved.
* We needed to develop another film type that was inexpensive, clean, pure, and had the ability to seal well to SBHDPE at strength levels above 5.5 lbs. per linear inch.
* The plastic resins that could theoretically produce this new film type (noted as film type PCHD from this point) would not produce crystal clear film. This would conflict with the desire for a clear widow or face.
This justification process lasted a month, taking us into the fourth month of the effort. Before proceeding we needed to present our conclusions to our customers and see if any of these findings would be an insurmountable hurdle. After several weeks of discussion we agreed on the following:
* That a clear window or face was not required. The customers had used a clear window in the past as a visual check for contamination. If we provided clean certified film this was no longer necessary. This meant a pouch made of 50% SBHDPE and 50% PCHD was a viable option.
* The minimum seal strength requirement remained 5.5 lbs. per linear inch. This eliminated the possibility of peelable seals, which was acceptable. This also meant we had to improve our seal process or seal technology as the highest seal strength we had ever achieved with SBHDPE was 5 lbs. per linear inch.
* Drying time reduction was not an absolute requirement when weighed against product cost considerations. Again, this made a 50% SBHDPE pouches a viable option.
With this feedback, our group outlined the potential costs associated with the development of the second film type, PCHD, and the development of new seal processes or seal equipment that could achieve seal strengths of 5.5 lbs per linear inch. We weighed this cost estimate against the market potential, and the product cost window, and determined we should still continue with the project.
Now in the sixth month of the project, we began focusing on the development of PCHD. We could not proceed with seal strength improvement efforts until we had our second film type. We had previously chosen a plastic resin base that theoretically could produce a pure, clean film with identical melt temperature characteristics to SBHDPE. Over a three month period we completed a series of justification trials on the PCHD resin base, testing off gassing, leachables and extractables, temperature, and cleanliness characteristics of film produced from the resin. All the tests were successful allowing us to begin seal tests in the ninth month of the project.
We began the seal tests using our current technology. The pouch was to be formed from two sheets of material, unwound from separate rolls that passed through clean processing units, and into a forming area that applied seals on three sides. We varied processing speed, dwell time, dwell pressure, and temperature in every conceivable combination. We were able to obtain seal strengths of over 6 lbs. per linear inch; however our process range of performance still produced pouches with seals below 5.5 lbs. per linear inch. After three months of analysis we determined that we needed to change the angle of attack on the sealing heads that heated and compressed the seal area. This would reduce the shear forces on the edges of the seals and tighten the range of seal strengths produced by the process. This required having new sealing heads designed and manufactured for our equipment. Four months later we received the sealing heads and now in the sixteenth month of the project began seal integrity tests again. The results were satisfying with seal strengths averaging 7 lbs. per linear inch, and a seal range of 6 - 8 lbs. per linear inch.
Over the next two months we ran several complete manufacturing runs testing the final product for purity, cleanliness, and seal strength. Next we arranged justification trials at our customers site, producing separate lots of pouches according to the inspection and justification regimens of each customer. This trial period took us into the twenty third month of the project and successfully concluded the project.
The final pouch format that was adopted by our customers clearly differed from their original specification request, but they were still thrilled with the outcome. This case study highlights again the need for you the customer, and your packaging partner, to clearly communicate about specifications and attributes that are absolutely required, and to work together to challenge your specification requirements. Our challenge in this case was to develop a pouch that met their primary needs in a target cost range, and that clearly required some compromises. The benefits for the customer were an increased level of quality assurance, and a reduction in processing failures. Our customers now knew off gassing, leachables, and cleanliness characteristics of all packaging used in their secondary sterilizing operations. This served them greatly when the FDA and the industry tightened quality assurance regulations several months after we began supplying product. We, as a company, also received several unintended benefits from this effort. We were able to use the new seal technology to manufacture 100% SBHDPE pouches, and other pouch styles with superior seals. We were also able to use the set of comprehensive test data from this project to apply successfully for a process patent for this style pouch under the title “Autoclavable Breather Bag.”
1 A secondary processing facility concentrates on parts and processes that prepare items for internal use. These items would then be used for primary processing. Primary processing is the manufacture of items that would be sold.