Pet Peeves

Plastics, whether rigid containers or pliable films, can present challenges during baling. When it comes to rigid plastics, there is the material’s memory to contend with. And even though plastic films are flexible, their slippery nature can make baling difficult.

Despite these challenges, making dense plastic bales is not impossible, as long as recyclers keep a few tips in mind.

BE FORECEFUL. Among the common mistakes that recyclers who are new to baling plastics make is choosing undersized baling equipment that is not heavy-duty enough to stand up to the application, Bob Pfeffer, vice president of sales, western division, Harris Waste Management Group, says.

"The most efficient and versatile baler for a multi-plastics application would be a two-ram baler with a bale separation door," Pfeffer says. "A two-ram will provide consistent bale sizes, bale density, multi-strap capability and normally provides the highest production throughputs."

Harris, based in Peachtree City, Ga., offers a variety of two-ram balers, including the Centurion, Gorilla and Badger lines.

Scott Jable, Midwest regional manager, Van Dyk Baler Corp., based in Stamford, Conn., says that two-ram balers have long been considered the "better type of baler for plastics." However, he adds, the Bollegraaf HBC 120 baler that Van Dyk distributes is "able to compete with the two-ram balers" when it comes to producing dense bales of plastic.

Operations that bale a variety of materials often try to make do with what they have, which can sometimes lead to inefficiencies when baling plastic, David B. Wilhelmy of International Baler Corp., Jacksonville, Fla., says, adding that often times balers employed in these operations are made specifically to bale corrugated containers or paper.

"Plastics have a great deal more memory than paper or OCC," he says. "A machine that is specifically designed to do plastic has more force to give you better compression and has a device to hold the plastics in place while compressing—we call them dogs. We can make those bigger, stronger and more defined to hold the product back when baling plastics," Wilhelmy adds.

Pfeffer also says that a baler that offers "partial baler chamber penetration" can help to remove air space in the plastic material, which can help to improve bale density.

In the past, fewer operations were dedicated solely to sorting and baling plastics, Wilhelmy says. Today, he adds, more companies are specializing in secondary plastics, necessitating the use of more defined equipment to achieve optimal efficiency. "The better the equipment, the better the bale is going to be," he says. A bale that does not have good integrity will be difficult to store because it could fall apart, creating facility cleanliness issues and possible safety hazards for employees.

Jable agrees that the needs of an operation that focuses solely on plastics are very different than one that handles curbside recyclables, as generally 70 percent of the incoming material in such an operation is fiber. In these situations, he recommends finding a baler that does a good job with fiber and also provides good weights on plastics. "There are a lot of balers that do a good job with plastic but have good capacity with fiber," he adds.

For operations that handle a variety of materials, balers other than two-ram machines can still be used to bale plastics. However, one technique in particular can prove useful: perforating.

ERASE MEMORY. Perforating, or slightly shredding, plastic bottles can help to produce a denser bale by removing air from the material prior to baling. Some manufacturers recommend using the technique with some baler styles.

"If the customer is utilizing a vertical, a closed-door horizontal or an open-end auto tie baler, perforating plastic containers is required," Pfeffer says. "A shredded or perforated bottle (or bottles with lids removed) will bale more efficiently, as there is minimal room for air to remain trapped."

Jable says that perforating has few drawbacks. "The only negative of perforating is if you have perforators that require a lot of maintenance that results in a lot of downtime." Which is why Van Dyk offers a perforator that can be mounted in the throat of the baler as opposed to numerous perforators that are used in the sorting process, Jable says. The perforator is operated hydraulically and can be moved out of the way for baling paper or other non-plastics, he adds.

When it comes to using balers other than two-rams to process the material, Jable recommends compacting plastics using the baler’s ram and then backing off the ram to allow some of the memory to come back before tying the bale off. He says this can result in a loss of bale density, but it will reduce popping and improve integrity.

In addition to perforation, Pfeffer says that horizontal closed-door and open-end auto-tie balers may also require a shorter bale length relative to the fiber bales the machine produces. He says this helps to lessen the expansion of the bale and wire tie failures.

TIE ONE ON. The way in which a bale of plastic is tied can contribute to its longevity and durability.

"Bale tying is important, as improper tying can result in broken bales, housekeeping nightmares and safety issues," Pfeffer says.

Wilhelmy says that the material and its memory under pressure will determine the thickness of the wire used. "Untreated PET takes very thick wire," he says.

Wilhelmy recommends using a "quick-lock" when tying a bale manually. With a quick-lock, he says, each end of the wire has a loop that is affixed to the other end, which helps to take the "human-factor" out of manually tying a bale.

"Usually on vertical and closed-door balers, you should double strap the outer ties and possibly all the ties to prevent wire breakage as the plastic expands," Pfeffer suggests.

In addition to the shorter bale length that is typically necessary when using open-end auto-tie balers, Pfeffer also advises using heavier wire, up to 10-gauge, to increase bale longevity.

"Two-ram balers have the ability to multi-strap the bales at adjustable spacing to offer secure containment," he adds.

Jable suggests that the best way to determine the best wire and tying technique for an application is to experiment. "Each plastic grade will be different. Each baler manufacturer and wire manufacturer might be a little different," he says. "Experiment with the gauge of the wire and the number of twists you use around the knot. When it comes to tying off, you need to have a flexible number of twists in the knot you make—too tight, the odds of snapping go up; too loose, it could come unraveled."

Experimentation and experience could be considered the magic words when it comes to choosing baling equipment for plastics in light of the assortment of variables, Wilhelmy says. He suggests talking to a baler manufacturer who has experience with baling plastics as well as to other recyclers who can offer insight into a particular application.