Adhesives are a critical component of paper towel and bath tissue manufacturing operations. Water-soluble adhesives designed for paper towel and bath tissue manufacturing are used for core winding, ply bonding, core start-up, and tail tie applications. These adhesives are unique; they need to have excellent tack when wet to increase bonding efficiency and form a tack-free film when dry to prevent the roll from sticking to unwanted materials. In addition, these adhesives used for tissue and paper towel manufacturing need to be easily separated from pulp and fiber materials during waste processing. These factors play a crucial role in an adhesive formulator's choice of resin for tissue and towel adhesive applications.
POLYOX™ Water Soluble Resins
POLYOX™ Water-Soluble Resins are nontoxic, biodegradable polyethylene oxide polymers with high molecular weights that are ideally suited for use as resins in adhesives for tissue and towel applications. Aqueous solutions of POLYOX™ have a high degree of wet tack that forms tack-free residues when dry. This creates tissue and towel rolls that feel soft and clean where the adhesive is applied. Also, dried POLYOX™ films remain soluble in water and are easily dissolved in the process water during waste treatment. This leads to paper towels and bath tissues that are much easier to decompose. Common grades of POLYOX™ for tissue and toweling adhesives are listed below.
Although POLYOX™ resins are fully water soluble, they must first be dissolved completely. The key to dissolution is making a good initial dispersion. If POLYOX™ resins are not properly dispersed before wetting, the particles will agglomerate and form gels that will not dissolve. High shear mixing must be avoided to prevent POLYOX™ from degrading. Three recommended techniques for good dispersion and dissolution are listed below. More information on these techniques may also be found in this video.
Direct Addition to Water
Direct addition of POLYOX™ resins is recommended for small, lab-scale, and less-than-drum-sized quantities. This method depends mainly on the rate at which the POLYOX™ is added to the water. If POLYOX™ is added too slowly, the viscosity of the solution builds too rapidly. If added too quickly, the particles will clump and not dissolve. A large vortex with only moderate shear can be created using a stirring mechanism like a pitched-blade impeller. This also makes direct addition to water much easier.
Hot Water Method
The hot water method is recommended for small-to-medium-size batch production. POLYOX™ is insoluble in water that is near its boiling point. This inverse solubility allows for another method of dispersion and dissolution. To use the hot water method, the water should be heated to near boiling at 97°C. Then, a vortex should be created by mixing at 500–600 rpm. Next, POLYOX™ is added and allowed to disperse in the hot water. After about one minute, the stir rate should be reduced to 50–60 rpm and the heat source removed until the solution cools and the POLYOX™ is dissolved.
Dispersion in Water-Miscible Non-Solvents
For large-scale batch production, the preferred technique is to disperse in water-miscible nonsolvents. POLYOX™ is insoluble in alcohols and glycols and can be easily dispersed in this medium prior to hydration. First, the nonsolvent is added and stirred in a vessel. The POLYOX™ is then dispersed in the nonsolvent, followed by adding the requisite amount of water. Stirring is then continued until a homogeneous solution is achieved.
Summary
POLYOX™ resins are preferred in paper towel and tissue adhesive applications for several reasons. They are highly soluble in water and have a high degree of wet tack that allows them to bond paper and paper core materials together well. When dry, POLYOX™ resins form tack-free films that preserve the desired feel of paper products. Since they are still soluble in water when dry, they easily wash out during waste treatment. Click below for more information on POLYOX™ and to request a sample for water-soluble adhesive applications.
