In flexible packaging, it is important to control the adhesives used to bond laminates such as films and foils, which requires meticulous accuracy of blending, dispensing and applying adhesives to substrate materials. Yet the adhesive controls required for such accuracy are astonishingly missing from nearly all systems, even in the face of consequences like packaging failure, product loss, and significant downtime.

If not applied in the correct coat weight-too light or heavy-the lamination bonding will fail, causing the overlay to bubble, blister or otherwise delaminate from the base material, a nightmarish scenario that worsens as the packaging travels farther down the distribution chain.

“The ultimate dilemma created by delaminated packaging surfaces when it reaches the store shelf, which is a terrible and costly situation for the product manufacturer and packaging supplier,” says Ray Mayes, a packaging controls specialist for Battle Creek, Mich.-based Cereal City Electric, a firm servicing the Midwestern food industry.

Even when delaminated packaging never leaves the plant, it normally takes adhesives about three days to cure. At that point, if there is a quality problem, the packaging producer has to reprint and relaminate the packaging once again.

“This is a just-in-time world,” Mayes explains. “When you have a lamination error, it is almost impossible to really make up for it. You have to squeeze back in the production queue. The printer may be backed up. The printer or packaging house may be short of materials, and it can take considerable time to replenish them. It’s a very difficult and costly situation.”

An adhesive blending system may eliminate common delamination and other coatings problems typically caused by lack of control with blending, metering and dispensing of adhesive.

The need for controls

Mayes attributes most delamination and other coatings problems to a lack of control with the blending, metering and dispensing of adhesives. Because most adhesive blending and dispensing equipment uses only single gauges to meter adhesive coat weight, the process can slip out of control without the operator or system being aware of it.

“Unless the adhesive’s viscosity and flow rate are validated by a secondary metering system, you have no real control at all,” says Bruce Schuetz, who worked in the metering and blending industry for more than 30 years before ulimately founding InLine Blending Solutions (IBS) in Forest Lake, Ill. “It is shocking to most controls experts that such a situation could exist in the flexible packaging industry, but it does.”

The need for a comprehensive adhesive blending and dispensing feedback and control system led Schuetz and InLine Blending Soltuions to develop a line of solid and solvent-borne adhesive blending and dispensing equipment that focuses on true process control. To provide the required level of control, the equipment is designed to enable accurate, validated metering and dispensing to high-volume inline blending and mixing operations that are completed automatically, on demand.

As the company developed products in collaboration with customers, Schuetz realized that through improved process control he could also incorporate other beneficial adhesive mixing and dispensing systems, including improved system availability, a more healthful working environment, reduced maintenance requirements and enhanced plant appearance.

Unlike the inline system featured here, previous versions of adhesive blending and dispensing equipment used only single gauges to meter adhesive coat weight, allowing the process to slip from the operator's control and generate unsaleable product.

Serving multiple needs

Fundamental to innovating advanced systems, Schuetz' company works closely with prospective customers, collaborating on system analysis and performing a no-commitment site survey to optimize applications and reduce risks. The outcome of this preliminary work can lead to important innovations as well as customer benefits that impact lamination operations in multiple ways.

To that end, Schuetz worked directly with Ray Mayes when he was a controls manager with Cello-Foil, now Exopack, in Battle Creek. Mayes wanted to improve the verification of coat weight on two-component polymer adhesives used in laminating 10-gauge films.

“Before we had the control system, it wasn’t uncommon that we could have a delamination claim from a customer that could be as high as $100,000,” says Mayes. “Once we got the new control system in place, we had complete reliability and never saw any claims.”

Mayes explains that the IBS equipment includes two independent metering technologies, and they are also working on a solid-state polyurethane coat weight analyzer that measures the coat weight. Until recently, such “intelligent” microprocessor-based control of adhesive blending and dispensing has not been available.

“With this unique system it is a simple matter to verify mix ratio and coat weight,” says Mayes. “You would not think this would be unique, especially in the world of controls that we have nowadays. But you can do anything with a microprocessor, and these advanced systems are constantly monitoring and validating flow rates.”

In the collaborative process of designing the equipment, Mayes saw opportunities to improve productivity and ensure that lamination problems were eliminated. He adapted the adhesive unit design so that it became modular, enabling operators to remove a unit containing one type of solid adhesive and simply roll up another unit containing whatever other adhesive was required for the particular job.

“We had each unit built on wheels, so that we could pull it right up to the machine and run one adhesive,” explains Mayes. “If the next order was using a different adhesive, we’d just roll the first unit out of the way and replace it with another machine that was already equipped with the needed adhesive. The benefit, of course, was increased system availability as well as a reduction in the cleanup of the machines.”

Another very significant maintenance and productivity benefit came from the incorporation of PTFE (Teflon) coating on components and sealless pumping cylinders of the blending and dispensing equipment.

Many manufacturers use cylinder rod-type pumps that are exposed to the adhesive. Because the rods eventually get adhesive on them, that adhesive begins to adhere and is cured by the air. On models containing seals, the rods ultimately become sticky enough that they literally tear the seals out of the cylinders, creating a messy situation.

“The way the new system is designed, the cylinder and rod are encapsulated,” explains Mayes. “They are sealless and airless, meaning they never come in contact with the atmosphere. Any parts that might be coated with adhesive are not a problem because the adhesive is not exposed to the atmosphere and never gets the chance to cure. Therefore, we could put the equipment aside for two months and the adhesive would not have sealed, whereas other equipment couldn’t be left for more than two days without having to be cleaned.”

In every plant today the occurrence of VOCs is a major environmental and employee safety concern. Because the solvents used in many adhesive systems are both an OSHA and EPA concern, minimizing the yield of VOCs is another goal of the IBS design.

“With this system, the operator never touches the product,” says Mayes. “We applied it out of a drum that was sealed with a valve on it. You simply bring up the drum on a cart, quick-connect the hose, and turn the valve on. Everything else is automatic. That minimizes the VOCs that can escape from the adhesive and into the plant air.”

Inline Blending Solutions