RadTech Report Mar-Apr 2006

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RadTech Report Mar-Apr 2006 Powered By Docstoc
					          New Market Opportunity

          for UV-Curable Adhesives
          Wet-Wipe Closure Systems
          By Nicole O’Brien

                                                             et wipes and moist           and lose sealing properties. Standard
                                                             towelettes got their start   hot melt adhesives cannot be used
                                                             with baby wipes many         because the raw materials in these
                                               years ago. As the world started to look    adhesives are also sensitive to the
                                               for ways to become more convenient         chemicals in the package, and they will
                                               and disposable, the wet wipe revolution    lose cohesion properties over time.
                                               began. Now consumers can find most             Solvent acrylics were traditionally
                                               of their favorite cleaning, polishing,     used for this application, but this limits
                                               dusting and sterilizing products in the    the manufacturers of these labels to
                                               form of wet-wipe disposable packages.      solvent coaters. And as always, there
                                               This revolution brought a new              are the existing safety and health issues
                                               opportunity to the adhesive world.         with solvent-coating processes. Recent
                                                                                          advances in UV-curable adhesive
                                               Wet-Wipe Application                       technology now offer an environmentally
                                                  These wet-wipe packages have a          friendly solution for this application,
                                               re-sealable label that is used as the      and these advances have also opened
                                               closure system. The adhesive on this       this market to all manufacturers with
                                               label must be resistant to the chemicals   hot melt coating equipment and UV
                                               inside the package, and this can only      lamps. The market for these products is
                                               be achieved with a solvent acrylic or a    large and also technically demanding.
                                               UV-curable acrylic adhesive. The
                                               reason water-based adhesives cannot        Factors in Choosing Adhesive
                                               be used for this application is because       There are many factors that need to
                                               the chemicals in the package will cause    be considered when choosing an
                                               the water-based adhesive to re-emulsify    adhesive for a wet-wipe closure system.
                                                                                          Some of these challenging factors are:
                                                                                          • Chemicals inside the pouches.
                                                                                          • Number of times the package needs
                                                                                            to be opened and re-sealed.
                                                                                          • Construction of the wet-wipe
                                                                                            closure system.
                                                                                          • Type of film used for the label.
                                                                                          • Type of film used for the pouch.
                                                                                          • Desired peeling performance
                                                                                            (smooth, strong, easy, etc.).
                                                                                          • Coating method—direct or
                                                                                            transfer coated.
                               Baby wipes have a re-sealable label that is used as        • Label printing and
                               the closure system.                                          converting process.

                                                                                                        • Possibility for in-line adhesive.
  Figure 1

                                                                                                          application and label production.
   Test results compare new UV acrylic adhesives to                                                     • Consistent residue free removal.
   traditional solvent-based adhesives                                                                  • High-initial tack on a wide range of
                                                                                                          pouch materials.
                       Customer Substrate; Glossy Pouch 60˚C
                                                                                                        • Soft, noiseless opening and good

                                                                                                          resealing properties.
                                                                          Solvent Benchmark
                                                                                                        • Excellent resistance to wet-wipe
                                                                          UV Adhesive 1
                                                                                                          substances allows residue
                                                                                                          free opening.
                                                                          Solvent Benchmark; 7 days
                                                                                                        • Adhesives can be formulated
                                                                          UV Adhesive 1; 7 days
                                                                                                          according to specific end-use
                                                                                                        • Production with UV-curable
           Soft Peel                                         Failure Mode (Adhesion Failure)
                                                                                                          adhesives is safer than using
           Coating: 25 gsm direct coating on white PP
           Curing: 160 W/cm, H-bulb, 1x10 m/min                                                           solvent-based products.
                                                                                                        • Companies with hot melt equipment
                                                                                                          and UV lamps can produce these
                                                                                                          labels and/or label stock. ◗
    Therefore, adhesive formulation                     refers to a range between cohesion
allows the right product selection for                  failure and adhesion failure. For this              —Nicole O’Brien is an account
                                                                                                          manager with Collano, Greenville,
each wet-wipe product, package,                         application, we want adhesion failure
                                                                                                             SC (Collano AG, Switzerland).
manufacturing parameters, and end-                      from the package because we do not
use requirements. Comparative testing                   want any adhesive residue on the
methods have also been developed to                     package. Therefore, cohesion failure is
compare the new UV acrylic adhesives                    not desired. The highest number on
to the traditional solvent-based                        the chart represents complete
adhesives. The closure systems are                      adhesion failure as the failure mode.
assessed in its final packaging by                      The “Soft Peel” evaluation indicates
comparing adhesion, failure mode, and                   whether the peeling of the label from
the zippiness of the closure system.                    the package is smooth and soft or hard
The results are reported in a graph                     and zippery. Different customers
similar to Figure 1.                                    prefer different adhesive and sealing
    The evaluation is always in                         properties for each application, so the
comparison to at least two products.                    desired properties have to be discussed.
The values stated in Figure 1 are                       Figure 1 gives customers a good way
subjective and are shown after                          of comparing different adhesive/
immediate application to the package                    package performances.
and after seven days on the package.
The seven-day time frame gives an                       Summary
opportunity for the adhesive to be                         There is a new application for
exposed to the wet-wipe package                         UV-curable pressure sensitive
contents, and it also gives a better                    adhesives on the market. The market
indication of the adhesion to the                       continues to grow and so do the
package over time.                                      opportunities for hot melt coaters.
    “Adhesion” is evaluated by the                      The advantages of UV-curable
strength it takes to remove the label                   pressure sensitive adhesives for
from the package. The stronger the                      wet-wipe applications are:
peel strength required, the higher the                  • Environmentally friendly alternative
number will be. The “Failure Mode”                        to solvent-based systems.

                                                                                                      MARCH/APRIL 2006 RADTECH REPORT 31