New barrier technologies enhance packaging films & bottles.

Compression rolling for monoaxial orientation, nano-thin high-barrier coatings of glass-like silica, fine-detailed pattern metalization, oxygen-scavenging coextrusions, and new polyolefin and polyester resins were among the new packaging technologies presented at the recent Future-Pak '95 conference in Chicago, sponsored by George O. Shroeder Associates, Inc., Appleton, Wis. The news was heavily weighted toward flexible packaging, but some of the developments apply to rigid bottles as well.

PUTTING THE SQUEEZE ON FILMS

Tredegar Film Products, Richmond, Va., described its proprietary compression-rolled orientation (CRO) process used to make its new Monax Plus family of moisture-barrier HDPE films. CRO technology reportedly provides greatly improved film performance at reduced thickness.

The newest development is to put CRO in line with extrusion. Blown or cast film passes through a vertical stack of steel mill rolls under controlled temperature, pressure, and tension. The process imparts monodirectional orientation and reduces the film's thickness to a final 12.5 mil. Maximum flat width is currently 48 in. but will be expanded to 66 in.

Tredegar says the CRO process reduces WVTR up to 65% and imparts high clarity approaching that of OPP (410% haze). Monax films also boast high machine-direction modulus (250,000-290,000 psi) and up to 55% higher puncture resistance than ionomer and EVA coextrusions.

'GLASS' COATINGS ON FILM

BOC Coating Technology (the new name of Airco Coating Technology), Concord, Calif., described the commercial scale-up of its silicon-oxide QLF (Quartz-Like Film) barrier-coating process for films of PET, OPP, LDPE, or biaxially oriented nylon (see PT, Dec. '90, p. 53). The clear, colorless silica coatings are only 20-40 nanometers thick but reportedly can improve the oxygen barrier of a 0.5-mil PET film by 120 times and the moisture barrier by 45 times. QLF coatings are said to be insensitive to humidity - unlike EVOH - and to provide better barrier than PVDC coatings.

QLF coatings are applied by a low-temperature, plasma-enhanced chemical vapor deposition process. The technology has been in development for seven years. The first production-scale QLF roll-coating machines, capable of handling 60-in. webs at up to 330 ft/min were built in 1993. One is operating at BOC's facility; the other was shipped to an unnamed customer. Since then, BOC has built an 80-in.-wide coater with speeds up to 1000 ft/min, which will go into commercial operation at BOC in the U.K. next month. Coating systems cost $3.5 million to $4.5 million. Coating cost is no greater than 3-3.5 [cents]/1000 sq in., BOC says.

BOC has made toll-coating contracts with several major film converters - such as Rollprint Packaging Products Inc., Addison, Ill.; Curwood Inc., Oshkosh, Wis.; James River Corp., Richmond, Va.; and Printpack Inc., Grand Prairie, Texas. Converters have made adhesive-laminated and extrusion-laminated films with QLF coatings and obtained excellent bond strength, BOC reports. Extrusion-laminated bond strength is enhanced by lightly corona treating the QLF surface.

The most significant commercial application of QLF coatings to date is 48-oz juice cartons from Chiquita Brands Co., Cincinnati. The cartons are formed from a laminate of PE, paperboard, and QLF-coated PET supplied by Tetra Pak, Inc., Minneapolis. Better preservation of the juices' color, taste, and vitamin C content, as well as reduced bulging and cracking, are claimed in comparison with previous cartons that used an aluminum-foil barrier.

Packages that take advantage of QLF's clarity as well as barrier properties are in development, including snack packages of OPP film as well as PET and nylon films for meat and cheese wraps and lidding stock.

FINE-PATTERN METALIZATION

Evidence that selective or "pattern" metalization has achieved a new level of sophistication was presented by Advanced Deposition Technology (A.D. Tech), Taunton, Mass. The firm's proprietary vacuum-deposition process, called Pattern Metallized Printing (PMP), is a single-step, roll-to-roll method that allows for cost-effective production of selectively metalized patterns that previously could only be made by a three-step demetalizing process. "Print" resolution is reported to be as fine as 133 dots/in. Dots can be as small as 1.5 mils, spaced 7.5 mils apart. Products of the PMP process will be priced 25-50% lower than those that undergo demetalization, says v.p. of technology John McCormick.

The process is applicable to PET, PE, OPP, PVC, and PC films as thin as 5 microns and as thick as 0.012 in. Running speeds can be faster than 300 meters/min and metalized patterns can be wider than 36 in.

PMP packaging applications include "windowing" for see-through metalized packaging, brilliant metalized graphics, and enhanced susceptors for microwave crisping and browning bags. Non-packaging applications include security overlaminates and microtext, flexible circuits, and segmented capacitor film.

Improvements in vacuum-metalizing equipment productivity are claimed by Galileo Vacuum Systems, Inc., East Granby, Conn. Its fifth-generation Mega line of vacuum metalizers reportedly minimizes both pinholes and tramlines while delivering up to 40% higher production rates than earlier models. Enhanced throughput capacity is achieved by cutting idle time with features such as automatic roll loading/unloading, a web-threading device, easier cleaning, and fully computerized process control, including a database of machine settings optimized for different materials.

SOAKING UP OXYGEN

Japan's Toyo Seikan Group described a proprietary oxygen-scavenging material applicable to various types of containers. Coextruded containers made with the Oxyguard material and conventional high-barrier polymers such as PVDC or EVOH reportedly show oxygen-barrier performance similar to metal containers. The oxygen-absorbing layer is a blend of a special reduced iron compound and a thermoplastic matrix. It absorbs both residual oxygen in the headspace air and any that permeates the container during sterilization and storage. Oxyguard can be used in trays, cups, films, pouches, lids, and tubes. Commercial Oxyguard containers in Japan are used for oxygen-sensitive foods or to extend shelf life of foods or intravenous solutions by inhibiting growth of aerobic bacteria.

NEW PACKAGING RESINS

Soon-to-be-launched additions to the Affinity family of specialty metallocene-based resins were discussed by Dow Plastics, Midland, Mich. The two developmental polyolefin plastomers (POPs) are intended as sealants for flexible packaging. One is targeted as a replacement for ULDPE for use in pouches. The other is viewed as an alternative to high-EVA and ionomers for cook-in food packaging. They are said to show low blocking tendencies, low heat-seal initiation temperatures, a broad hot-tack window, strong seal strength, high tear and impact resistance, and high heat resistance.

In PP, Fina Oil & Chemicals, Houston, discussed a newly commercial high-crystallinity (HCPP) grade with high heat resistance and stiffness (flexural modulus is 304,500 psi). Fina says grade EOD-94-08 has potential in injection molding, TPO modification, moisture-barrier films, and as a replacement for HIPS. Even stiffer HCPP grades sporting flex moduli of 348,000-362,500 psi are under development.

A new class of chemically modified PETs with high melt strength for extrusion was introduced by DuPont Packaging & Industrial Polymers, Wilmington, Del. Selar PT HMV (High Melt Viscosity) is a family of three homopolymers and four copolymers that reportedly meet FDA specs for food contact and have a wide range of crystallization rates, melting points (428-491 F), and I.V.s (0.67-0.95).

As commercial use of PEN resins - close cousins of PET - is still in its infancy, industry has yet to explore the potential of various copolymers and blends. Amoco Chemical Co.'s Intermediates Business Group in Chicago (which makes NDC, the key PEN monomer) reported on some novel terpolyesters of PEN, PET, and isophthalic acid. These resins were shown to have a high level of crystallinity and even better oxygen barrier than PEN/PET copolyesters.

R&D on high-barrier alloys of PET with liquid-crystal polyesters (LCPs) was discussed by consulting firm Everest International of Hackettstown, N.J. Most of the work has been carried out at Superex Polymers, Inc., Waltham, Mass. (see Technology Newsfocus section), but a consortium of potential end users is now looking to further develop this approach. Based on a reportedly unique "dual compatibilization" technology, alloys containing only 10% LCP have double the oxygen barrier and two to 5.5 times higher mechanical properties than PET alone. They alloys are said to process very similarly to PET and can be used either in monolayer or coextruded structures.

Mitsui Petrochemicals America, N.Y.C., reported on a new generation of Admer coextrusion adhesive resins. Admer is a modified polyolefin with functional groups that bond to polyolefins, nylon, EVOH, and metals. Developed through a combination of grafting and alloying technologies, the new grades are said to maintain high adhesion after orientation of shrink film or after deep-draw thermoforming.

BASF Corp. Plastic Materials, Mt. Olive, N.J., described a proprietary antiblocking agent that overcomes the drawbacks of nylon 6 in amorphous cast film - namely, the drastic increase in friction and blocking tendency. About 0.1% of the new mineral-based antiblock reportedly achieves an acceptable level of friction even in rapidly quenched film. It is sold as a masterbatch by BASF (Ultramid 119) that is dryblended with nylon.