The Mission:
Formulate and apply a pressure sensitive adhesive (PSA) to a customer supplied woven polypropylene (PP) fabric to produce a wide tape reinforcement for large polyethylene (PE) container liners used in the shipping industry.  The tape would be applied manually by operators during the fabrication of a patented shipping container liner that holds dry-slurry chemicals that are shipped all over the world. 

Background Information:
The customer approached Shawsheen after they had successfully launched a unique, patented product. They had encountered manufacturing problems as they ramped up their production to meet demand.  The original assembly for the container liner required operators to spray a solvent-solution adhesive to bond the woven PP to the PE film. The sprayed adhesive the customer was using contained methyl ethyl ketone (MEK) which was dangerous to work with and unacceptable to OSHA for operator health & safety.  In addition to the health & safety issues, spray application of the adhesive was inconsistent and led to bond failures in the field due to uneven application of the adhesive between the woven PP and the PE film.  Spray application of the adhesive also created delays in the manufacturing process as the operators had to wait for the sprayed adhesive to dry before they could begin the next assembly step. A solution was needed to eliminate the use of MEK in the plant, improve the consistency of the adhesive bond, and speed the manufacturing fabrication in order to meet the customer’s goals for efficient cost per unit.      

The Challenges:

• The woven PP fabric exhibited significant gauge bands and was not manufactured to quality standards common to other wide web tape substrates making it a difficult material to adhesive coat.
• The PE film contained a slip agent making it easy to handle but difficult for PSA to adhere to.
• The PSA coated woven PP fabric had to release easily from its protective release liner for operators to handle in a large size; 48” wide by 15 feet long.
• The PSA had to be initially “repositionable” onto the PE film to allow operators to locate it properly and smooth out any wrinkles.
• The PSA had to form a permanent bond within 24 hours to allow the final assembly to meet the end-user performance requirements.
• The cost release of the liner had to be as low as possible as it was discarded.

    To meet the challenges, SC&C’s design work included a number of key activities:

• Create & Formulate a rubber-based PSA in solvent solution that would bond permanently to the PE film within 12 hours at room temperature and withstand the extreme temperatures of international transportation.
• Qualify & Select a lightweight paper release liner with a precision tuned release coating that was strong enough to withstand operator handling and yet inexpensive enough to meet the customer’s cost goals.
• Implement a variety of tension control systems to handle the woven PP fabric at high line speeds to produce a uniform coated tape product.
• Create & Validate a series of in-house test methods to test and confirm the consistency of the design.

The Process:
SC&C’s Technical Director led the design process to formulate, select, and test a series of PSA’s submitted by our adhesive suppliers.  Once promising candidates were identified in the lab, bench testing confirmed that a production trial was appropriate.  A series of production trials were produced to fine tune all of the properties and characteristics of the tape to ensure all of the challenges were met.

The Results:
A high performance yet cost effective adhesive coating and process was developed to commission coat the woven PP fabric for the customer.  In addition to developing a successful design, SC&C’s efficient material processing ensured that 99% of the woven PP material supplied was coated and returned to the customer keeping the total cost as low as possible.