Proper handling of laminating adhesives and coatings is essential in several key areas. First it assures that the adhesive or coating when applied will have the best chance to properly perform and have the best appearance. Secondly it will help assure that the product will perform through its stated shelf life (most important when container opened and closed multiple times). And lastly but just as important, it allows for worker safety when handling, mixing and applying the product. The above points are valid whether product is single or dual component, or product is water based, solvent based or solvent less.
Let’s begin with worker safety. Each component is supplied with an MSDS(Material Safety Data Sheet) in addition to certain container label warnings. Any person involved in the handling of the product whether it be mixing, application or disposal should be familiar with these documents and labeling. The MSDS or SDS(Safety Data Sheet) as it is often referred is divided into various sections. While all sections are pertinent, there will be specific sections on Handling and Storage, Exposure and Personal Protective Equipment, as well as Toxicological information. Each container carries a warning label. This label will spell out the hazards of the material, what to do in case of exposure as well as proper storage and disposal. The last document of importance is the actual Technical Data Sheet for the product. Each of these documents has a safety, handling and storage section, in addition to physical properties of the product. Review each thoroughly and when in doubt reach out to the manufacturer.
Next let’s focus on the actual handling and storage of the containers both prior to use and when leaving as a partial container for use later. Again, both the TDS and MSDS as well as the warning label spell out proper storage conditions. Regardless of the product typically keep containers in a cool, dry, well ventilated area. Normally temperatures above 50°F and below 120°F are acceptable. Insure that all lids are secured tightly to prevent evaporation and to keep moisture out. When only using a partial container, it is critical that for any urethane product (moisture sensitive) the headspace be capped with an inert gas or dry air. This will prevent water contamination which will affect the quality of the product. Always look closely at the manufacturing and expiration dates clearly marked on container labels. Do not use expired product and always practice FIFO(First in first out) to insure oldest product is used first before newer lots.
Finally, as you handle and mix the adhesive prior to coating or laminating several steps and precautions should be taken to insure quality. Always refer to the TDS (Technical Data Sheet) for proper mix ratio, application solids, diluting solvent etc. Calculate amount of adhesive needed for job and only mix that amount (plus waste), or only mix amount that can be used in normal 8-hour shift. It is often advisable to premix water based container for 5-15 minutes prior to pulling out material, this is not necessary for solvent based products. Always use urethane grade diluting solvent and insure this remains moisture free with use of inert gas blanket or desiccant tubes. Weigh adhesive using calibrated floor or bench top balances at proper ratio. Mixing should be done in round container, using mixing blade 1/3 the diameter of the container with a mild, off center vortex to insure proper mixing but avoiding trapped air. Addition of co-reactant and diluting solvent should be done while mixing. Once proper viscosity/solids have been achieved mixed/diluted material can be pumped into application pan using low shear type pump. Examples are diaphragm, peristaltic, centrifugal, or positive displacement pumps. Recirculation is advised for longer runs to help minimize possible foaming. Keep return distance short with return below fluid level. Keep return as far from intake as possible. While filtering is not usually needed, it can be used to collect and debris our foam that has been generated and can be as simple as cheese cloth. Solids/viscosity should be monitored throughout run and adjusted as needed to insure consistent coating weight and appearance is maintained during run.
By reading, understanding and following both the supplied documentation and above guidelines the various adhesives and coatings can be used safely and applied accurately. Proper handling insures not only worker safety but will help give high quality, high performing adhesive laminations or coated products. Proper handling and storage also will help insure the products will perform throughout manufactured shelf life and enable reuse of partial containers. Any questions can always be referred to the proper manufacturers technical or regulatory departments for clarification.