- January 01, 2007, David J. Bentley, Jr., Editor
Providing practical information to the converting and packaging industries…
Non-Polar Process Aids Improve Extrusion Productivity
by Niall Marshall, Sasol Wax
Case studies presented in the paper discuss how the addition of a non-polar process aid to polyolefins allowed achieving higher productivity. The material is a highly crystalline, linear, non-polar Fischer-Tropsch hydrocarbon (FTHC) with a melting point of approximately 240°F. A key advantage in the use of non-polar process aids such as additives primarily intended for use as antistats, antifog additives, acid scavengers, slip additives, etc., at higher than recommended levels may also result in processing benefits to polyolefins.
The use of non-polar process aids such as FTHC allows manufacturers of extruded sheet and cast and blown film to adjust their process parameters to increased outputs, improved run stability, and reduced power consumption resulting in increased productivity. Increased productivity generally leads to increased profitability. Reducing power consumption may result in lower utility costs. Although not discussed here the addition of suitable non-polar processing aids has no significant effect on film mechanical properties, printability. or the sealing or welding performance of a film.
Troubleshooting Corona Treatment Issues
by Rory A. Wolf, Enercon Industries Corporation
Because these costs are frequently understated, having troubleshooting information for component systems on production lines such as corona treaters can help mitigate such costs. A review of corona treater instruction manuals, power supply diagnostics, diagnostic options, and the support structure of the supplier are part of an introductory course for production line operators in preparing for potential treater issues.
Preventative maintenance is key to preempting issues arising with surface treaters. Regular cleaning of bare and covered dielectric ground rolls and cleaning of electrodes and inspection of exhaust airflow and air gaps will ensure peak discharging. Controlling ozone by ensuring blower efficiency through the regular cleaning of the exhaust plenum is also important.
This paper recommends conducting a treater system audit on a basis concurrent with maintenance schedules. System audits include inspections of power supplies, station components, and the high voltage transformer. An outline of system checks is available from a treater manufacturer for integration into maintenance procedure manuals and protocols. A treater company service engineer can also perform on-site audit activities with maintenance staffs to bring treater performance back to standard levels and advise new station components including software and hardware to enhance new treater capabilities.
Electron Beam Curable Gas and Aroma Barrier Technology
by Im Rangwalla, Energy Sciences, Inc.
The initial goal of the laboratory work was to improve the adhesion of vacuum metallized aluminum layers to biaxially oriented polypropylene and polyester by using organofunctional silanes of the vinyl benzyl amine alkoxysilane class. The idea was to apply such silanes at very low coat weights below 0.5 g/m2 on polyolefin films followed by metallization and EB treatment of the entire structure. This would result in EB grafting of the vinyl group to the polyolefin and the formation of a Si-O-Al bond to the aluminum.
This development resulted in substantially increasing the aluminum adhesion to the polyolefin as desired. It also gave a significant improvement in the barrier properties of the metallized polypropylene structure. More importantly, the barrier property of non-metallized polypropylene also improved. This discovery led to the development of an entire class of organofunctional silanes and ethylenically unsaturated carboxylic acids that provided gas barrier property and adhesive properties upon EB treatment. The oxygen barrier properties probably resulted from the high polarity of the salt created by the unsaturated carboxylic acid and the amino organofunctional silane. Si-O-Si cross-linking and EB curing of the unsaturated carboxylic acid helps to maintain the oxygen barrier and adhesion properties under high humidity conditions.
The new family of EB curable materials developed provide oxygen and aroma barrier. Barrier properties occurred when these materials were used as coatings or adhesives with a broad range of films commonly used in flexible packaging. In addition to the results presented in the paper, these EB curable barrier materials were also tested with several different types of inks including solvent-based flexographic inks. Good adhesion occurred between the inks and the barrier materials. Future work in the development of these materials includes development of aqueous or close to 100% solids adhesive and coating systems, reduction of the dose to cure the barrier adhesive without the use of primer, reduction of the sensitivity to humidity without the use of primer or high EB cure dose, and completion of food law migration work.
The Role of Adhesives In The Retort Pouch
by Thomas R. Mueller, Rohm and Haas Co.
The needs of the marketplace are constantly changing, and adhesive suppliers must keep up with such changes. Everyone always wants to improve efficiency, reduce waste, and decrease the environmental impact from adhesives. Some concepts of future adhesives being explored address these concerns. Different reaction mechanisms to achieve polymers of comparable performance to the current polymers used in adhesives are being explored. These mechanisms may lead to faster curing adhesive systems.
Radiation curable adhesives may be a way to improve efficiency because the cure is instantaneous and the potential for waste would be lower. Radiation curable adhesives are also 100% solids systems meaning no solvent discharges to the environment. Aqueous systems with improved performance over the current technology are also undergoing exploration. Solventless adhesives are already finding use for some retort applications. Continual improvement of these adhesive systems may increase their use in retort applications.
Retort packaging constructions are varied and may be proprietary. The chemistry of many adhesives used in retort packaging today is urethane chemistry. Side reactions of the components of urethanes can lead to lower performance of the adhesive. Care is necessary on the part of the converter to ensure that these side reactions do not interfere with adhesive performance. This means checking compatibility of all inks and ensuring that they are dry. Improper mixing of adhesives can also lead to poor performance of an adhesive. Care is necessary to follow curing times and temperatures for retort adhesives. Because many use aliphatic isocyanate chemistry, retort adhesives may take longer to cure, require elevated temperatures to cure, or both. Adhesive suppliers are continually working to improve the chemistry of adhesives to meet the needs of a changing marketplace.
For information about the PLACE Division of TAPPI, access the TAPPI web page at tappi.org. To obtain the complete papers whose expanded summaries appear in this section, go to the TAPPI web site at tappi.org., then click on "the PLACE" in the section designated Journals.
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