A host of applications makes rigid packaging more flexible.

Stiff, unyielding and inflexible — that’s the definition of rigid. But rigid packaging for today’s dairy products is anything but.

Rigid packaging ranges from blow-molded gallons to plastic single-serve bottles to retort and aseptic cartons. The similarities among all of these examples are a move toward lighter, smaller, ergonomic containers with greater portability.

Some of the trends in rigid packaging include manufacturing at higher speeds and processing product at higher temperatures for UHT and aseptic products. Other trends include extended product life and shelf stability, barrier capabilities, shrink labeling, reclosability, unique shapes and thinner wall sections with equal performance.

“Less material addresses the customer’s concern on cost, weight and sustainability,” says John Theis, market manager, Sonoco, Hartsville, S.C. The company produces blow-molded and thermoformed packaging suitable for aseptic and retort applications.

Richard Smith, commercial director, Uniloy Milacron, Tecumseh, Mich., speaks of the demand for lighter containers without sacrificing package performance. “Ergonomically friendlier containers, for example,” he says. “Smaller sizes along with pourability improvement brought about by offset container necks and larger pour openings [are in demand].” Uniloy produces blow-molding equipment and molds for production of lightweight plastic containers.

Some consumer demands haven’t changed in that they still want packaging that is easy to handle and pour, Smith says. Rigid packaging has to be able to stand up in the car’s cup holder and be durable enough to travel from the store to home into the refrigerator and finally into the recycling bin without breaking or leaking.

“A fairly recent change is a result of a renewed emphasis on health and nutrition through all age groups,” Smith says. “It has caused an upward sales trend for single-serve fluid milk and other dairy products in institutional, vending and convenience stores, resulting in myriad portable single-serve container sizes.”  

Consumers expect rigid plastics to be convenient and easy to open and reclose, says Kurt Weiss, manager of rigid plastics R&D at Sonoco. “They also want the lighter-weight package,” he says. “Consumers also focus on new shapes, designs, and features that give shelf appeal.”  

In turn, dairy processors want single-serve and shelf-stable packaging. “Processors are looking for shelf life through barrier properties which can be accomplished with aseptic-filled and retort applications,” Theis says.

SIG Combibloc’s combishape sleeve, base and lid are manufactured from standard compostive material consisting of cardboard, polyethylene and aluminum. In several food segments, carton packs have long advanced form being a practical alternative and have become a preferred option in many cases, says Oliver Bittner, vice president of marketing for North and Central America at SIG Combibloc, Chester, Pa.

The aseptic carton pack combines the positive properties of cardboard, polyethylene and aluminum. Compared to conventional sterilization methods, SIG Combibloc’s product and package are not sterilized together, but separately. Spouts or straws are applied depending on the requirements. As these are applied only after the carton has been sealed, this process does not affect the sterility.

Processors want high package performance, offering a reduced-weight container with the same durability, Smith says. “They also are starting to demand some innovation, for example, new sizes and new ideas pertaining to container geometry,” he says. “Also going forward they will demand technology for their suppliers which enable them to extend the shelf life of their products. This will be driven by two factors: extending their market reach and soaring distribution costs.”

To answer that need, Uniloy developed a blow-molding machine system that produced in the blowing cycle a sealed container with a bacteria-free internal environment. This technology can be used with or without the company’s three-layer technology, which produces a container with three layers, the middle layer designed to be a barrier to light.

Wilmington Machinery, Wilmington, N.C., has designed a new system for producing small bottles that utilize a single parison and individual cavities, instead of tandem, in order to produce the highest-quality bottles with the least variation in material distribution bottle-to-bottle and with the smallest weight variation. This resulted in faster processing, efficiency and cost savings.  Wilmington Machinery focuses on high-output applications requiring a minimum of 250,000 bottles per day or 75 million per year. The company aimed to eliminate problems associated with high-speed bottle handling and make its new system simple to set up, operate and maintain, says Jeff Newman, vice president of sales and marketing.The Wilmington High Speed Small Bottle rotary blow-molding wheel system blow-molds small bottles in a single-cavity mold and guides the containers from under the blow-molder through the trimmer at high speeds. The system is designed specifically for high-speed, high-volume single-serve dairy, food, juice and liquid yogurt applications for 200- to 500-milliliter containers. A smaller clamp has been added to handle bottles as small as 80 milliliters.

“Technical breakthroughs such as Wilmington Machinery’s High Speed Small Bottle Series now give processors the ability to blow each bottle in individual molds while totally eliminating the need for high-maintenance bottle knockout systems, complicated bottle takeout devices and cut-off knives or shear steels,” Newman says. “Customers have reported they were amazed at the easy-start up and operating of Wilmington’s 24-station demonstration wheel at speeds up 240 bottles per minute. Bottles literally fall out of the molds on their own, and because Wilmington Machinery developed the technique to blow 100 percent of the entire parison, bottles and flash never stick together. This process works as well for polypropylene, including multilayer, as it does for HDPE.”  

“One trend is becoming more and more apparent in the beverage sector: Consumers are opting either for inexpensive drinks or premium products,” Bittner says. “Packaging plays a vital role in positioning the individual products. Most purchasing decisions are made directly at the point of sale. The attractiveness of a package is becoming a decisive factor.”

Bittner says smoothies and drinkable yogurts are winning a bigger global market share, and aseptic carton packaging is perfectly suited for filling smoothies because they retain a high-product quality while ensuring a long shelf life without refrigeration.

“If we look at the global packaging mix for UHT milk products, aseptic carton packs constitute the most in-demand packaging form, with around 80 percent of the market,” Bittner says. SIG Combibloc manufactures aseptic carton packaging for long-life beverages and liquid food products and supplies complete systems, including both packaging materials and corresponding filling machines.

Carton packs for UHT milk and dairy products will continue to enjoy positive growth, at a rate of around 3 percent annually, Bittner says. “This popularity is due in large part to the special properties of carton packs, including in particular the protective function that the carton packs offer for the product inside. Dairy products are protected from light, which means the natural flavor is retained,” he says.

Consumers view carton packs as convenient and environmentally friendly, Bittner says, because they are easy to transport and store. “Even in categories in which consumers have hitherto favored plastic bottles, such as the convenience of small-format packages,” he says, “the practical features of carton packaging — including, for example, reclosable screw caps even on the small-size carton packs — have garnered consumer plaudits.”  

Rigid packaging offers more opportunities for size flexibility, resealability, convenience and strength and durability, Smith contends.

Manufacturers are making more cost-competitive packages using thinner walls with equivalent performance, Theis adds.

“Retort and aseptic filled packaging provides longer shelf life than other packaging,” Weiss says. “It also offers convenience because they’re easy to hold, have less weight and a shelf-stable package.”

And there have been improvements along the way, including, Smith says, light-weighting or source reduction, improved performance, improved aesthetics, barrier to light and waste reduction or recycled plastic material.