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Getting rid of the undesirables

 Process helps eliminate adsorbable organic halogens from resins

The U.S. Patent and Trademark Office has issued patent No. 7,932,349 to Richard Riehle, research fellow, and Stephen Vinciguerra, senior group leader, Ashland Water Technologies.

What is it?
Titled "Membrane separation process for removing residuals polyamine-epihalohydrin resins," the patent is a process for creating resins with reduced levels of potentially toxic and performance-deteriorating residuals. Polyamine-epihalohydrin resins are used for wet strength, dry strength, creping adhesives, and curing agents we formulate.

Applications
Wet strength resins, such as Kymene™, are added to paper, particleboard and paperboard during manufacturing. By using these resins, wet paper can retain at least 10 to 50 percent of its strength. Without the resins, paper only retains 3 to 5 percent of its strength when wet. Wet strength properties are a must for towels, milk cartons, paper bags and liner board.

Wet strength also enhances dry strength properties in paper. Dry strength from highly refined wood pulps can be expensive for formulators; however, using a lower-cost option can reduce their effectiveness. (Click here to learn more about our Hercobond™ dry strength additives.)

Similar resins are also used as creping adhesives. Creping gives paper such as facial tissue and toilet paper textural characteristics, such as softness and bulk. In the creping process, a cellulose web is added to a Yankee dryer cylinder blade that scrapes the dry paper off the cylinder, and in doing so, crinkles it. A good creping adhesive, such as our Crepetrol™ products, will adhere the sheet of paper tightly enough to the drum and impart absorbancy and softness, without losing strength. It's a delicate balance.

The resins can also be used as curing agents for adhesives in engineered wood products, such as particleboard and fiberboard. The technology in our Soyad™ adhesives uses a resin to combine with a protein source such as soy flour.

Despite their many uses, polyamine-epihalohydrin resins often contain undesirable ingredients, known as adsorbable organic halogen (AOX) species. In addition to being environmentally undesirable, AOX and chloride salts in polyamine-epihalohydrin resins make the resin corrosive and lose functionality. 

Benefits
Vinciguerra and Riehle's patent is a cost-effective process to remove AOX and chloride salts from these resins, with minimal loss of the active component, resulting in improved effectiveness and lower levels of residuals. The result? Paper products can be formulated with improved performance that enables packaging and tissue and towel manufacturers to meet their strength and productivity needs.