PACKAGING: The contenders

Beer is pass. The quest to package beer in PET bottles was last year’s hot topic, but the emphasis of research and product development now seems to have moved to another arena — that of the high-growth beverage categories of New Age, isotonics, sports drinks and others. Tea and sauces also represent a large potential market segment for PET. Packaging manufacturers, machinery companies and resin suppliers are all touting new developments that herald victories in the ongoing contest to convert hot-fill products from glass to plastic containers.

BREAKING THE 185 DEGREE BARRIER

To clarify — over half of all hot-filled containers are already made of plastic. These are filled at 185F or below. The portion of the market that is filled above these temperatures (fruit juices, pasta sauces, teas, tomato juice, baby foods, pet foods, for example) had largely remained out of the reach of plastic containers. But Shelley Steele of container manufacturer Schmalbach Lubeca Plastic Containers USA Inc. says that is changing.

“New developments in container designs have opened up the PET market. Products such as tomato juices, apple sauces, soups, jams and other products are now hot-filled in PET containers at temperatures well above 185 F. For these applications the container design is extremely important.”

Ridges, domes and panels help to counter the vacuum that is created by the cooling of the hot liquids. The panels flex on cooling and take up the vacuum, while the rest of the container remains rigid to counter the top-load, shrink and ovalization, and keep the container within spec.

Graham Packaging Co. has also made inroads to packaging foods and beverages with higher filling and processing temperatures in PET. The company won three AmeriStar Package Competition awards from the Institute of Packaging Professionals last year for hot-fill containers for pasta sauce and jelly, and for single-serve bottles for juices and teas.

The juice bottles use Bariocade oxygen inhibiting barrier coating developed by PPG to protect freshness and extend shelf life.

Mark Leiden, director of commercial development for Graham Packaging, says “This technological advance is one of the important reasons that PET has become such a strong and economical choice over glass.”

The company says its barrier coating is the first high-speed coating application in the U.S. that offers a commercial alternative to multi-layer containers.

SITTING ON A SHELF

The quest to improve the barrier properties of PET and thus improve shelf life of packaged products is another packed battlefield of competing technologies.

Amcor PET Technologies’ Lindsay Mulholland summarized barrier improvement methods at a presentation during Plast-Ex earlier this year. Current methods include:

coating, internal (examples are Sidel’s Actis plasma coating and PPG’s Glaskin)

coating, external ( BestPET, marketed by Krones AG, is an example)

multi-layer, passive (EVAL, nylon)

multi-layer, active (BP Amoco’s Amosorb oxygen scavenger addivite)

monolayer, passive (PEN resin, which Mulholland says is a great barrier but too expensive)

monolayer, active (Amcor’s own AmcoRx)

But shelf life is actually dictacted by many components in the packaging system, not just the material of the bottle. “In the last two years,” says Mulholland, “we have brought the barrier properties of PET to better than that of glass. Now the closure manufacturers need to rethink what they are doing for PET.”

Looking ahead, Mulholland is convinced PET bottles can be pasturized, post-filling, with the right combination of bottle design and resin selection. In fact, a Chinese company plans to bring to market by the end of this year a commercial pasteurizable beer bottle. Zhong Fu Industrial Group has been working with Kortec, an American company, for over 18 months on the project. Kortec has developed a co-injection process for PET bottles that runs at similar speeds to the production of monolayer bottles. Zhong Fu reportedly chose the Kortec process because the multi-layer bottle is best able to survive the rigors of expansion and contraction during the tunnel pasteurization process. A six-month shelf life is achieved through the combination of a barrier layer and an oxygen scavenger in the middle layer of the bottle.

RESIN SOLUTIONS

Eastman has gone one step further to protect the contents of a PET container with its Heatwave CF746 resin for hot-fill packaging. The new resin has the added feature of UV protection.

“Vitamins and flavors in hotfill PET applications, such as isotonics, fruit juices, teas, nutritional and New Age drinks can be adversely affected by exposure to light,” says Bobby Jackson, an Eastman business manager. “Heatwave resin provides the essential UV absorbers to protect these products from UV light.”

Heatwave resin is said to offer significant productivity and processing advantages in blow molding. It provides superior reheat consistency for heatset processing, can be processed at reduced blow mold temperatures which results in less downtime for blow mold cleaning, and may offer the possibility of downgauging to a thinner walled container.

KoSa also offers a resin geared specifically for beer and other hotfill applications. The company says its 2201 PET resin will allow beer to be tunnel pasteurized directly in the packaging, as is currently done with glass bottles. This resin “is noted for its dimensionally stability, which prevents shrinkage and expansion of the container,” says Kevin Fogarty, vice-president and general manager of KoSa’s packaging resins business. Its improved heat-set characteristics may also allow for higher production rates, lighter bottles and more storage flexibility than traditional hot-fill materials.

MEAL SOLUTIONS IN THE SPOTLIGHT

While high growth is still anticipated for the home meal replacement (HMR) or “meal solutions” market, prepared food purchases from supermarkets leveled off between 1999 and 2000. According to the Food Marketing Institute’s Trends in the United States –Consumer Attitudes and the Supermarket, 2000 report nearly one in five shoppers said supermarkets are their main source for food consumed but not prepared at home. The report states that at least once a month, 26 percent of shoppers buy pre-cooked meat, poultry and other main dishes. Nearly four in ten buy frozen side dishes. This “meal solutions” market segment is technically demanding for packaging because the package must preserve, protect, sell and cook the contents.

Polyethylene terephthalate (PET) and polypropylene (PP) are the preferred materials for thermoformed trays used in packaging prepared food. According to German Laverde, manager of marketing for Battenfeld Gloucester, some of the coextruded structures used to produce these trays by the thermoforming process are:

APET/CPET/CPET

A combination of amorphous PET and crystalline PET improves the sealing properties of the trays with polyester films, as well as the impact properties. Trays made from this structure are usually used for prepared foods that can go directly into a conventional oven.

PP/Tie/EVOH/Tie/PP

A combination of polypropylene and ethylene vinyl alcohol has an advantage in terms of density and cost compared with PET-based structures. However, a disadvantage is that these trays can only be used in microwave ovens instead of the conventional ones.

PP/Reclaim material/Tie/Reclaim material/PE

A combination of polypropylene, polyethylene, ethylene vinyl alcohol and reclaimed material obtained from the edge trim during sheet production or the thermoforming process itself offers cost savings due to the use of reclaimed material in addition to being a very good barrier.

VEGGIES MOST POPULAR

This year’s Food Marketing Institute Trends survey found strong support for time-saving vegetable preparations. Well over half of all shoppers buy pre-cut, cleaned and ready-to-cook vegetable items. Forty-eight percent buy pre-cut, cleaned and bagged salads.

Common structures for vegetable packaging, according
to Laverde, are:

mLLDPE/coPP/mLLDPE

A copolymer polypropylene film sandwiched between two layers of a metallocene based low density polyethylene films of thicknesses between 50 to 63 microns (2-2.5 mls.). This combination provides good sealability and optimum gas transmission. It also has excellent mechanical properties and good performance on packaging machines.

EVA/ Phillips’ K Resin/EVA

This structure provides high stiffness, good optical properties and high gas transmission rates.

Peakfresh films from Chantler Packaging are also an option for vegetable packaging. Roy Ferguson, CEO of Chantler Packaging Inc., explains that Peakfresh is a mineral-impregnated polyethylene film which prolongs the life, freshness and the color of packaged fruits and vegetables. Most produce releases ethylene gas after harvesting, accelerating the ripening and deterioration process. The presence of the mineral removes the ethylene gas and its anti-fogging properties allow modified atmosphere packaging (MAP), thus minimizing bacterial growth. The presence of the moisture keeps the products fresh, in addition to the advantages of excellent permeability and deodorizing properties.

Ferguson says the company is researching a new development to improve on present levels of clarity of the films and obtain better viewing of the products.