In-Mold Labeling Technology

The application of in-mold labeling (IML) can be extended from technical products to food packaging. In the field of food packaging, the main driving force for the use of IML is more attractive product styles, bar codes and product information related to the law on packaging. Even the use of IML combined with multi-component technology has emerged in the market. The traditional process of decorating products and giving prices and other information is printing or applying stickers. However, in the past few years, great efforts have been made to integrate decorative or other production steps in the injection molding process. Instead of Hot Stamping or laser printing, it is now possible to decorate and distinguish products through IMD (in-mold decoration) or IML, that is, in one process step, in the actual molding process. In the IMD process, a pre-shaped film/sheet is inserted into the mold from the back before the injection begins. On the other hand, for IML, the embedded membrane is amorphous.

The advantages of IML process
Compared with traditional decoration methods, IML offers a lot of advantages:

â—† IML is convincing, of course, with outstanding decorative effects;
â—† The information at the bottom of the container is more and more important. By the IML process, it is possible to decorate all five outer surfaces of the container in one operation;
â—† If a multi-layer label is applied to the entire outer surface of the container, the IML method helps to improve the barrier properties and extend the shelf life of the loaded item;
â—† No pollution to the product due to static electricity;
â—† The film embedded in the IML process improves the hardness of the plastic parts;
â—† The IML implementation produces a decorated and packaged container in one operation. No longer need internal and intermediate storage;
â—† IML can replace container decorations (tags) without interrupting production.

IML technical details
The range of suppliers of system components (molds and processing devices) and the entire IML production system is becoming wider and wider. IML production is currently the most advanced technology and has reached full maturity. Many IML users use prefabricated decorative stickers. In terms of adding labels from the silo to the mold cavity, it is already very mature to control the inlay by the processing equipment while taking out the last product. Some IML users have developed a process that relies on printing rollers. Here, the sticker is immediately penetrated immediately before or at the same time as the injection process.

In order to facilitate handling during printing and production, the film must have a certain hardness. The required thickness is 50 to 80 microns. The use of suitable membranes, correct printing and labeling perforations are essential for the successful application of IML. In order to have better adhesion and prevent any peeling, the material of the label must be the same as the material of the container. In this way, the need for single-component packaging products can also be met. Because of the memory of plastic materials, the direction in which the film is extruded or stretched must be remembered when printing and punching.

Various examples of IML containers and film sizes

IML is suitable for containers of various shapes
In general, IML can be used for items to be decorated. Only the complexity (shape) of the film plays a limiting role. For example, a square container can decorate all five faces or just three faces. The latter style is a low cost option because of the reduced consumption of the film. The full surface decoration of round or oval products by IML requires special production methods. The following are the specific circumstances:

â—† Place the set of labels (sidewall and bottom) in the mold cavity by operating equipment;
â—† The label is rolled onto the dummy core outside the mold. The action of the processing device or integrated into the mold affects the internal transfer of the mold;
â—† With the help of electrostatic charge, the label is directly rolled onto the core.

Via vacuum or electrostatic charge, the label can be placed in the mold. If there is a vacuum, the gap in the mold will generally leave a lower mark on the label. On the other hand, not all membrane labels can rely on electrostatic charges. Label fixing methods must be studied separately for each use.

The cycle time available can vary depending on the method used. Today's IML system operation typically has an embedding/removal time of 0.8-1.5 seconds. Based on the desired production scale and frequency of label changes, the most effective method and system arrangement can be determined.

Different IML production costs
It is virtually impossible to compare the prices of IML and conventional printing in a conventional way. Each condition must be checked and many quantitative factors must be considered. It must be remembered that some products can only be made by the IML process, mainly because of the excellent print quality mentioned initially. In addition to the actual appearance of the product, the use of smaller fonts can reveal much more information on the packaging.

For subsequent printing, the difficult to estimate transport costs are particularly weighty. Repetitive packaging and unpacking, intermediate storage, and internal transportation become apparent. For smaller square containers, complete coverage of all five outer surfaces by the IML is often more expensive than subsequent printing. However, by limiting the IML to three decorative surfaces, the IML is clearly more advantageous.

By properly designing the mold, it is also possible to complete the encapsulation at the gate location. In this case, the gate is not located in the cavity as it is usually, but on the side of the core.

Since polypropylene (PP) is a relatively mature molding material hitherto used for packaging, completion of gates by hot runners or needle-type shutoff valves is increasingly performed. Stacked-mold technology, together with two-color and IML technologies, are technically controlled by people.

Based on IML technology to produce packaging products

IML production system
In order to use IML technology to efficiently produce plastic parts, it is necessary to optimize the various components of the matching system, namely injection molding machines, molds and processing equipment. This is an essential condition for achieving high practicality and productivity. The integration of decoration and higher value-added during the injection molding process requires ensuring the corresponding production capacity. This can be achieved by the high replication of the injection molding machine, precise closed-loop control of the open position, and the shortest cycle time. Netstal's machine layout and control combine high precision with high performance. Parallel motion, high injection capacity and long service life are just a few of the important features.

Related production system
Like in the production of optical discs, PET bottles, or IC cards, the IML is linked to the production system. From a cost perspective, it is attractive to chain together several functions one after the other because various functions, transport and intermediate storage are combined, ignored or eliminated. Thanks to their reliability, flexibility, and speed, Netstal's injection molding machines are particularly suitable for systems assembled in the production line.

IML continues to grow

The IML process is very mature and will continue to occupy a larger application space. Compared with the traditional decoration method, the cost savings and enhanced processing techniques achieved by IML have greatly improved the economic attractiveness of IML. The IML process will continue to be further improved. This also includes improved thin-film technology and specific applications in corresponding applications. Coating type or multi-layer packaging machines with barrier properties 'target=_blank> transparent films are used more and more. With the transparent film, some printing companies can print on both sides. However, the surface to be printed must not be too thick due to the adhesion of the plastic components.

Many uses have become more and more important for packaging products. Packages should be suitable for microwave ovens, dishwashers and freezers. Injection molding allows us to meet the need for greater design freedom and correspondingly better product placement. Plastic parts with labels have flat, non-protruding surfaces, making them suitable for meeting hygienic specifications in the fields of food and medicine.

Extensive systems are often used in IML production

In-Mould Labeling Becomes New Favorite of Condiment Industry
With the increasingly fierce competition in the condiment market, manufacturers are paying more attention to product details. Longmen Hetian and Beijing He Tiankuan... Many companies started to use in-mold labeling technology, and these used companies praised it, and It is believed that with the gradual maturity of this technology, it will become the new darling of the spice industry label.

At the beginning of this year, Beijing Longmen Hetiankuang Food Co., Ltd. adopted the in-mold labeling technology first in its 2.1L “Longmen rice vinegar” because the label often fell off and the paper label was dyed by the product during filling. Dirty things also happen from time to time, and they think it may be the shortcomings of this point, making consumers turn their hands to other products. To this end, Longmen Hetian wide decided to update on the label. According to the person in charge of the company, after adopting the in-mold labeling technology, due to the reduction of labeling links, the workload of the original day can now be completed in two and a half hours, greatly improving the production efficiency; the original products are mostly hand-stitched by workers. The standard is expensive and laborious. Now it is not used anymore. A production line is reduced by 1/3 of the staff. Although the cost of each barrel has increased by a cent, overall, the cost has been reduced. Due to the use of mechanized barrel moulds to complete the labeling method, it is more accurate than manual labeling, and the transport wear after filling is even smaller. The image on the shelf is very beautiful. (Finish)