Reduce Drip And Sag In Sprayable Adhesives

Up to now formulators have taken several different approaches to solving this problem:

• Focus on only one aspect of the product, allowing the adhesive to clog the nozzle or drip but not do both.
• Formulate with a thickener that thins to exit the nozzle but firmly adheres to the wall.

This last scenario enhances the end user experience while also creating the perception of a higher quality product.

One worthwhile solution is the use of a cellulosic thickener. Cellulosics promote shear thinning through the nozzle avoiding clogging, but then rapidly thicken to spread evenly on the surface without dripping or running. Additionally, cellulosics promote excellent wet tack. Their use allows larger work areas to be treated, speeding installations.

When selecting a cellulosic thickener there are a few key aspects to consider:

• Is my product solvent based or water based?
• To what kind of surface is my product being applied?

Depending on the answers to the questions above, there are a few different choices for thixotropic thickeners:

• One option is the use of METHOCEL™ methylcellulose. METHOCEL™ A grades form strong gels in water based formulations. There are other METHOCEL™ (E, F, J, and K) grades based on hydroxypropyl methylcellulose (HPMC) that will thicken both solvents and water.
• Another option is to use a synthetic POLYOX™, poly(ethylene oxide) polymer. POLYOX™ based adhesives are used to adhere to glass, steel, painted metal, paper, wood and textiles. POLYOX™ is soluble in water and organic solvents and adds lubricity to formulations.
• A third option is for solvent based adhesive formulations. ETHOCEL™ ethylcellulose is solvent soluble, water resistant and is particularly suited to thicken solvent based adhesives.

Cellulosic thickeners are versatile, multi-functional products that support the needs of spray applied adhesives. Formulators no longer need to make the either/or choice, they can now make the ‘and’ choice. Make a spray adhesive that does not clog the nozzle and adheres to the surface.