Guide To Converting And Handling Soft Or Heavy Coat Weight

Transcript

3 Guide to Converting and Handling Soft or Heavy Coat Weight Performance Label Materials Technical Bulletin September, 2007 Scope: The purpose of this guide is to provide special considerations for successfully converting label materials with adhesives that present a challenge in converting due either to their soft nature or coat weights in excess of 1.2 mils. Adhesive ooze commonly appears in roll material as label pick to the liner backside and dispensing issues. Refer to the bullet points below when attempting to eliminate adhesive ooze in the converting and end use processes. Die Cutting: • Always use a sharpened die that has been properly tooled to the liner on the specific material being converted. • If die cutting film facestocks be sure you are using dies that are tooled to cut films and not paper. Dies designed to cut paper facestocks will not adequately die cut film facestock materials. • During material start-up, be sure to verify the depth of the die cut. The die must completely cut through the adhesive without cutting through the silicone layer of the liner. Deep die cuts can lead to liner breakage, stripping defects (adhesive snap back), and dispensing issues. Shallow die cuts can lead to labels coming up with the matrix and adhesive snap back. Ultimately, both die cutting insufficiencies will result in exposed adhesive that can leave adhesive residue in a variable printer and cause label transfer to the liner backside. • When tooling to material, be sure to send at least a 6" x 300', for a through press evaluation, to your die manufacturers. We have 300 standard products in sample rolls that are available for shipment to your die manufacturer. • If the application allows, request that the die design be for hand application rather than automatic. This allows for a slightly deeper cut through the adhesive. This works best when used in conjunction with a film and not a paper liner. -1- Technical Bulletin Guide to Converting and Handling Soft or Heavy Coat Weight Performance Label Materials Label Orientation: • Use rounded corners rather than sharp corners. • Orient labels so that the longest direction runs down web. • Whenever possible, butt cut labels to minimize the handling and exposure of the adhesive. • Maintain a minimum distance between labels of 1/8". The minimum recommended label size is 1/2" x 1". Labels smaller than this require the distance between labels to at least equal if not exceed the width of the labels. The lower the ratio of perimeter to area for a label, the less concern for ooze. • Recognize that circular labels are the most challenging label configuration to convert on heavy adhesives. This is because significant pressure is placed on the adhesive at the leading and trailing edges of the circle and the adhesive is squeezed out. Use an extremely loose wind when handling circular labels. Press Settings: • Roll tensions issues is the leading cause of adhesive ooze. Excessive tension may cause the adhesive to squeeze out from beneath the label face in an effort to relieve the tension placed on the rolls. To avoid this issue, be sure to run shorter rolls and maintain minimal winding tensions for both on press and rewind steps. Be sure not to go to the other extreme or the rolls will begin to telescope to winding that is too loose. • Line speed can have an affect on handling of heavy coat weights. Try running at faster speeds to improve the quality of the stripping step. Be sure that both increased and decreased speeds are evaluated to determine the most optimal speed to produce a quality product. • Try to keep the press as cool as possible. This can be done by turning off stations that are not in use, cooling the press with a stream of compressed air, and/or conducting the converting process in a controlled environment. The warmer the material, the greater the tendency for the adhesive to flow. • It is helpful if your press is set to strip the matrix as soon as the material has been die cut. Even a delay of several feet can allow for soft adhesive to flow and knit back together. Material Options: • If a heavier coat weight is not necessary for a particular application a lower coat weight alternative should be considered. Consult with your ADS on available options. • Utilize C2S (coated two side) and film liners. Both liners offer a backside coat that will prevent label pick/blocking to the liner backside. Consult with your ADS on available options. • Always target die cutting heavier adhesives when the facestock is thicker than the adhesive thickness. Thin caliper facestocks will only make die cutting heavy coat weights more challenging. -2- Technical Bulletin Guide to Converting and Handling Soft or Heavy Coat Weight Performance Label Materials Environmental Conditions: • Avoid exposing the material to high heat during storage or shipping. It is best to keep such materials in a controlled environment (72°F [22°C] and 50% RH) • Store finished labels in sealed polyethylene bags. This will help minimize potential liner growth due to humidity changes. Liner growth can manifest adhesive ooze. • Materials can be refrigerated or freeze to temporarily stiffen the adhesive and minimize oozing. Keep in mind that freezing can affect the fibers in a paper liner. The material should always be placed in a polyethylene bag before any refrigeration. • Whenever possible, complete any additional printing, processing and finishing steps in the same day to minimize roll handling and improper storage. Pattern Coating: • The pattern coating principle is becoming much more widely accepted as a narrow web industry standard. This principle pictured in the diagram below. • Pattern coating can be used for one of three purposes: Problem Resolution • Converting high coat weight and adhesive ooze prone label materials The pattern is set up in such a way that both sides of each slit roll have dry edges. When the material is then run through a flexo press, the adhesive will ooze into part of the dry zone and not out of the roll edge. This keeps the press much cleaner and reduces the times that the web must be stopped for cleaning. It also prevents the sides of the roll from becoming sticky should the adhesive begin to flow during shipment. • Functional dry zone is desired in a label material The pattern is set up so that the dry zone(s) is located to perform a functional purpose in the labels end use such as lift tabs or wrap labels. • Adhesive confusion in double-linered adhesive transfer products. The pattern is set up in such a way that both sides of each slit roll have dry edges. When the material is slit, we are slitting in the patterned zone and this reduces the adhesive contact with the outside of the roll and aids in reducing adhesive confusion. Pattern coating is currently only available on our label materials. For additional details on pattern coating please refer to our Guide for Designing and Converting Pattern Coated Products. -3- Technical Bulletin Guide to Converting and Handling Soft or Heavy Coat Weight Performance Label Materials End User Suggestions: • Education of the end user regarding storage and special handling consideration can be key to the success of an application. Be sure to pass along helpful tips in order to avoid adhesive ooze from manifesting further down in the line at the end use. • If employing a variable print process (laser or thermal transfer) or the use of automated dispensing, the end user should make periodic checks/cleaning of their equipment to prevent adhesive build up. Isopropyl is one such cleaning solvent that can be used. • Note: Follow the manufacturer’s precautions and directions for use for proper handling and storage of solvents. Additional Tips Specific to Handling/Converting 3M™ Tire Tread Adhesive G1120: • Important - Do not store the material banded. Break the steel banking on the pallet upon receipt. • Do not store the material double stacked. • It is best not to ship over a weekend in summer months. Try to specify a ship date that will get the material directly to you during the week in one day or two days max. • Rolls with excessive edge bleed are most likely to be found on the top layer directly under the wooden pallet top. These rolls can be salvaged by rewinding on a table top rewinder and then using Talc powder on the edges. This should be done as soon as possible. • Pattern coating has become a standard practice for 3M™ Tire Tread Adhesive G1120 products. See pattern coating section above for additional details. • Store in a cool area if possible especially during summer months. Recommended storage conditions are 72°F (22°C) and 50% relative humidity. 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Limitation of Liability Except where prohibited by law, 3M and seller will not be liable for any loss or damage arising from the 3M product, whether direct, indirect, special, incidental or consequential, regardless of the legal theory asserted, including warranty, contract, negligence or strict liability. 3 ISO 9001: 2000 This Industrial Adhesives and Tapes Division product was manufactured under a 3M quality system registered to ISO 9001: 2000 standards. Industrial Adhesives and Tapes Division Converter Markets 1030 Lake Road Medina, OH 44256-0428 800-422-8116 • 877-722-5072 (fax) www.3M.com/converter Recycled Paper 40% pre-consumer 10% post-consumer -4- 3M is a trademark of 3M Company. Printed in U.S.A. ©3M 2007 70-0713-4496-7 (9/07)