by Ron Schultz
In-mold labeling in North America has come a long way over the last 25 years. Once limited to extrusion blow in-mold labeling (EB-IML) of bottles for liquid consumer products, new injection molded in-mold labeling (IM-IML) applications are appearing in retail outlets in increasing numbers. These applications include anything from baby wipes, spreadable butter and soft cheeses to prepared salads and ice cream.
Successful development of new IML applications depends upon close collaboration among end users/brand owners, molders, label printers and substrate suppliers. The difficulties inherent in achieving this goal were the topic discussed at a meeting of industry leaders during the 1994 International In-mold Labeling Conference in Chicago. Those attending the meeting agreed that a lack of communication along the supply chain often resulted in unresolved problems and system failures during and after the package development process.
They decided to form an industry organization that would facilitate communications through commonality of terms and testing procedures. Led by Ron Schultz, president of RBS Technologies, Inc., they formed the IML Industry Standards Group. The group’s first undertaking was a survey of the industry to identify major concerns about the IML process along the supply chain. Four supply chain links were studied: label raw materials, label printing and diecutting, blow molding, and the end user. A statistical analysis of the survey results isolated the top four concerns for each link.
In late 1995, the Group began development of useful test methods called IML Procedural Guidelines. Up until this time, it was not uncommon for the printer, blow molder and end user to each have his own test method and terminology for measuring attributes of labels and containers. This often caused a great deal of confusion and miscommunication.
The Guidelines, loosely patterned after ASTM and TAPPI standards, were offered to the industry as common test procedures that could be used by all parties, a sort of “neutral ground” approach. The Guidelines are a “how to” guide to arrive at the actual package and label specifications set by the customer, usually the end user. They are not themselves specifications.
Over the course of several years and a lot of hard volunteer work, the IML Industry Standards Group developed seventeen IML Procedural Guidelines as well as a glossary of IML terms. All of them are in PDF format and are freely available for download from www.rbstechnologies.com/standards. The following is a brief explanation of the Guidelines:
Activation Temperature: Measures the temperature at which the adhesive on the back of an in-mold label will become tacky and bond to the container during the blow molding operation.
Adhesive Uniformity: Uniformity of the adhesive coating on the back of the label is an important attribute in defect-free labeled blow molded containers.
Applied Adhesive Coating Weight: Measures the adhesive coating weight on the back of the label for blow mold applications.
Bottle Weight: A standardized technique for measuring the weight of an in-mold labeled bottle.
Coefficient of Friction: COF or “slip” is a critical property that must be controlled for reliable label handling during both the printing operation and the molding process.
Label Blocking: Measures the tendency of a stack of labels to stick together under adverse environmental conditions. Blocked labels will not feed reliably during molding.
Label Curl: Measures the tendency of the corners or edges of a label to curl. Non-flat labels do not feed reliably during the molding operation.
Label Packaging: Recommendations for proper packaging of in-mold labels.
Measuring IML Label Placement: A procedure for measuring the critical positioning of the label on the container.
Print-to-Die Cut Registration: This is a critical label attribute for reliable feeding from label magazines at the molder.
Print-to-Print Registration: This is a method for measuring the tolerance between colors on a label.
Product Resistance: A method for determining how well the printed label resists the product contained in the package.
Scuff Resistance: A procedure for measuring the printed label’s resistance to scuffing.
Solvent Retention: This procedure measures the amount of solvents retained in either the label’s adhesive or print side. Retained solvents can cause label blocking and affect COF.
Static: Measures the effects of static on the in-mold labeling process.
Storage & Handling Conditions for In-mold Labels: Recommendations for optimum storage, handling, and shipping conditions for labels in all forms.
Wall Thickness: A standard procedure for measuring the wall thickness of a bottle.
Although these Procedural Guidelines were developed for EB-IML, most of them are either directly applicable or can be adapted for IM-IML. Suggestions or requests for new Guidelines specific to IM-IML can be forwarded to ronschultz@rbstechnologies.com.
Ron Schultz is president of RBS Technologies, Inc., the organizer of the International In-Mold Labeling Conference, IMLCON2004, and producer of the ABC’s of IML: A Basic Course (see “Inside the Industry,” p. 37). RBS also acts as the administrator for the IML Industry Standards Group and hosts the Group’s webpage on one of its two websites: www.rbstechnologies.com or www.sourceiml.com.
