by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
FLEXO Magazine : July 2008
TECHNOLOGIES & TECHNIQUES Table 1. Adhesive System Coating Weight (Pounds/ream) 100% Solids Solvent Based Water Based I-part 0.8-1.2 1.25-1.5 1.0-1.25 2-part 0.8-1.2 1.25-1.5 1.0-1.25 High Performance 1.25-1.5 2.0-3.0 - The solventless adhesive also has some cost advantage simply due to applied weight. Solventless adhesive is generally applied at lower weight on average (Table 1). MACHINE REQUIREMENTS Solventless adhesives require a dedicated coating head, consist- ing of three or four smooth application rolls for the adhesive. A conventional gravure, offset gravure, or flexographic coating sys- tem cannot be used effectively. In addition, superior tension con- trol of the substrates is required due to low bond and low shear of the solventless adhesive. Current dedicated solventless machines cost much less than similar laminators dedicated to water- or solvent-based adhesives, or a combination of solventless/water/ solvent-based with interchangeable coating heads (Table 2). ENERGY EFFICIENCY Over the last five years, the cost of natural gas has increased 50 percent and the cost of crude oil has increased by more than 246 percent (U.S. Energy Information Administration). In today's economy, there is more to the cost of an adhesive than just the de- livered cost to the converter or energy consumed to use it. There is also the need to consider the Life Cycle Inventory (LCI). This is an analysis of the energy required to make and use an adhesive, as well as water consumption and carbon dioxide emissions associ- ated with manufacture and use of an adhesive. Table 2. Chart 1 compares the energy LCI of the various adhe- sive types and shows much lower energy consumption for solventless adhesives. Note that energy used for transportation is much lower for solventless because fewer drums are shipped. This also means the converter uses less warehouse space, and has fewer drums to handle/ dispose of/recycle. PRODUCT CATEGORIES Adhesives encompass the categories of general purpose Qow demandflow performance), medium performance (demanding bonds and performance) and high performance (elevated tempera- ture and specialty/aggressive content performance). Current sol- ventless adhesives cover the full range of lamination use, having the capability to be used in place of water-based and solvent-based adhesives. Solventless adhesives can be used across all the current substrates commonly used in packaging (Table 3). Currently, available solventless adhesives cure more quickly than older versions without the need for energy cure assist, extended hot room acceleration cure, special handling and equipment. FDA REGULATIONS For food packaging adhesives, there are very specific regula- tions in Title 21 of the Code of Federal Regulations (CPR) under parts 170 to 199, under the Food and Drug Administration (FDA). Of the many parts, the three that are most pertinent are: · Part 175.105 - Adhesives (for use up to 120 F). . Part 177-1390 - Laminate structures for use at temperatures of 250 F and above. . Part 177.1395 - Laminate structures for use at temperatures between 120 F and 250 F. Table 3. Machine Solventless Solvent Water Characteristic Use existing No - need func- Yes - can use Yes - can use tion specific coating conventional conventional laminator method laminator laminator Coating head 3 or 4 smooth roll Flexo, gravure, Flexo, application offset gravure gravure Drying None Yes Yes Typical Line speed (feet/ 700-1500 300-1000 500-1200 minute) Relative machine Low Medium Medium cost (dedicated) - high - high Tension control Superior Average to Average to good good Factory footprint Low to medium Medium to Medium to high high Meter/mix/pump Needed Not needed Not needed Adhesive waste Low High Medium - high Heated rolls Application rolls, nip Nip nip End Use Solventless Solvent Water Base Base Snack Food ./ ./ ./ Confectionery ./ ./ ./ Meat and ./ ./ ./ Cheese Stand Up ./ ./ +/- Pouch All Plastic ./ ./ ./ Lamination Barrier Plastic ./ ./ ./ Lamination Metal ./ ./ ./ Lamination Fresh Produce ./ ./ ./ Medical ./ ./ ./ Hot Fill and ./ ./ +/- Boilable Retort ./ ./ no Agricultural ./ ./ +/- Chemicals - J U L Y 2008 www.flexography.org FLEXO
Flexo Sustainable Fall 2008