Figure 1 - Effect of Kybreak Repulping Technology on Glue-Fiber Bond Surface 

Urea-formaldehyde, melamine-formaldehyde, and polyamide resins are commonly used to impart wet strength in paper.  These resins provide wet strength by binding the paper fibers and fines together with additional bonds that are not easily destroyed by water.  While these bonds provide the paper with added tensile strength, they make it difficult to later repulp the paper.  Consequently, a repulping chemical must be used during repulping to weaken the glue-fiber bonds imparted by the wet strength resin.

Traditionally, sodium hypochlorite has been the product of choice to bleach and repulp wet strength paper.  While sodium hypochlorite is an effective repulping agent, it has some serious drawbacks:

It can form chlorinated compounds, which can contaminate a mill’s wastewater stream
Residual chlorine can interfere with the wet end chemistry (e.g., dyes
and cationic material)
It can form free chlorine or chloroform, which are two hazardous air contaminants
It attacks the cellulosic bonds in fiber and darkens mechanical grades
It can not be used on natural kraft paper because it extracts lignin
It can be highly corrosive and damage mill equipment

Because of these factors, paper mills have been looking for an alternative repulping agent.

Kybreak® Repulping Technology is an effective alternative to sodium hypochlorite in repulping wet strength paper.  Unlike chlorine-based repulping agents, this free-flowing peroxygen powder product does not produce AOX or other chlorinated compounds and does not interfere with the wet end chemistry.  Additionally, the product does not degrade fiber or darken mechanical pulp and does not require any additional storage or delivery equipment.

Under optimum conditions, Kybreak® Repulping Technology reacts rapidly with the wet strength resin, thereby reducing the repulping time and increasing the productivity of the pulper.  The technology has been demonstrated on a variety of sanitary, food, packaging, and specialty papers made from a array of furnishes, including bleached kraft, sulfite, CTMP, recycled paper, and unbleached kraft.  Additionally, because of its dye destruction capability, the product can also be used to bleach certain colored papers.

Kybreak® Repulping Technology is generally available in the United States, Europe, Asia-Pacific, and Latin America.

Mode of Action

Kybreak® Repulping Technology oxidises the amine groups in the wet strength resin, weakening the glue-fiber bond (see Figure 1).  Na0H, used along with the product, delaminates and flushes away the oxidized resin debris from the fiber.

Method of Application

Kybreak® Repulping Technology is available in 5 kg, 12 kg, and 20 lb repulpable bags.  The bags are simply thrown on top of the pulper once pulp has been added and the proper pH and temperature conditions have been reached.

Kybreak® has been successfully applied to both dry- and wet-end pulpers.

Recorded Benefits

The following benefits have been recorded from practical applications of Kybreak® Repulping Technology (not all benefits are realized for all applications):

No chlorinated compounds
Easier, safer handling
Lower degradation of fibers
Reduced corrosion
No residual carryover
No yellowing effects