Packaging technology

Published: 1-11-2011, 13:06

Shrink bands

INTRODUCTION

Shrink labels, bands, and sleeves provide today’s packaging companies with a unique and versatile method for labeling their products. Developed in Japan during the 1960s, shrink bands became popular in the United States in the early 1980s, mainly as unprinted or one-color tamper-evident neckbands. Today, the shrink band is used as a primary label, as a decoration, for multipack applications, and as a traditional tamper-evident feature. The high-quality printing and gloss inherent in shrink labels ensure packagers that their product will generate tremendous visual shelf appeal.

MANUFACTURING

Shrink bands are generally produced using special poly (vinyl chloride) (PVC) films, although PETG films, oriented polystyrene films, and poly(lactic acid) are also used (1). Film thicknesses generally run from 1.25 to 3.0 mils, with 1.50 and 2.0 mils the most prevalent. Material is available in two varieties: seamed film, and tubing. Seamed film is converted by bonding a flat sheet of printed or unprinted material into a sleeve configuration. This is achieved through a process of solvent seaming into the desired dimension or flat width. Tubing is extruded into the desired flat width before printing. Seamed film can be reverse printed with 3601 graphics and generally provides more consistent dimensions in both flat width and gauge profile. Tubing is generally less expensive, and it is used for unprinted or one-color work.

Important dimensional measurements associated with shrink bands are (a) flat width, which represents the dimension relating to the diameter or circumference of the container, and (b) cut height or impression height, which represents the length of the container or the length of the section of the container to which the shrink band will be applied. These dimensions are usually expressed in millimeters.

The inherent shrink is imparted into the material in a heated stretching process. With tubing, this is achieved during the initial extrusion process. With seamed film, a process known as tentering is used. A tenter frame is a modified oven that uses a combination of airflow and temperature zones to orient the material. For example, a 30-in.-wide roll of 5.0-mil material will be converted into a 60-in. roll of 2.0- or 2.5-mil film. Shrink ratios of 50–70% can be achieved by adjusting the process. Various ratios are used, depending on the contour of the container being labeled.

Shrink bands are generally processed using the gravure printing method. Reverse rotogravure allows the image or copy to be printed on the back side of the film, which results in a glossy look to the package as well as protection of the image from scratching or scuffing that may occur in final packaging or distribution. Gravure printing provides excellent color reproduction consistency, high speed, and productivity, and it is an excellent method for printing smooth film surfaces. Flexo printing has made inroads into this market as the technology improves, but gravure is still dominant.

After printing, several other features can be added to the shrink band. Vertical and horizontal perforations, as well as tear tape strips, can be added to make the band removable for the consumer. Some packagers use a horizontal perforation to make part of the label removable, the tamper-evident feature is removed, and the primary label stays on the container. Some examples of this are toothpaste pumps, lip balms, syrups, and salad dressings. Bands can be provided in continuous roll-fed form, or in individual cut pieces for manual application.

APPLICATION

Bands can be applied manually or by automatic machinery. Machinery on the market today is capable of applying bands at speeds of 500 per minute or more, depending on container size, container contour, and label dimensions. For example, a lip-balm label of approximately 27-mm flat width and 60-mm length can be applied faster than a 190-mm-flat width, 40-mm length band for a large dairy container, due to both the label size and the container size. Machinery is dominant in the dairy, packaged-food, and pharmaceutical markets. Most machinery applies shrink bands in a horizontal method, but recent developments have allowed for vertical application of pen barrels, lip balms, and other small cylindrical objects. Most machinery requires material of 2.0 mils or more for processing, and the use of a wedge or other device to open the material before application is common. After application, the container is sent through a heat tunnel, which uses a combination of airflow and heat to shrink the band securely onto the container. A dwell time of 3 s at roughly 3001F is used for most applications, although some products require an elaborate system of varying temperatures and product rotation to achieve the desired effect.

Machinery is available to pack two containers together with one band. This process is used in lieu of an overall bundling method, which then may require the application of another printed label for bar coding or to convey the promotional message. Manual applications are used when product volume is small or in market trial introductions.

Since shrink bands adhere using shrink energy, no glue or glue applicating systems is required to apply shrink bands.

USES

Shrink bands are generally used in three ways: as tamperevident neck bands, as primary labels and decorations, or for promotional multipacking (see Figure 1 for examples). Food and pharmaceutical packagers have been using neckbands as a tamper-evident feature ever since the Tylenol incident in Chicago in 1982. They are often used in conjunction with vacuum packaging, inner seals, and breakaway closures for product integrity. One advantage for consumers is that neckbands provide evidence of tampering before the consumer brings the product home, as any attempt at removal is evident on the store shelf. In the food-packaging market, yogurt, sour cream, salad dressing, mayonnaise, syrup, mustard, and jelly are just some examples of products that use neckbands (2). In the pharmaceutical and health–beauty arena, use of neckbands is even more prevalent. Eye care, mouthwash, cough syrup, pain relief, and vitamins as well as many ethical medicines are among the products that utilize this tamper-evident feature (see Tamper-Evident Packaging).

In the primary label and decorating market, shrink bands provide a versatile and unique way to package various products. The reverse printing capability allows graphics to stand out on the store shelf as well as provide durability. Batteries have been labeled using shrink film for years, because the fine copy and metallic look required on these products are achievable with shrink labels. Lipbalm labeling combines a primary and tamper-evident label using a horizontal perforation for easy removal of the tamper-evident feature. Since this product is often sold loose at drug and convenience-store checkout counters, the lip-balm package can be easily displayed without any further packaging. In recent years, writing instruments decorated with multicolor graphics have become popular, especially those with designs targeted to the teenage market. One advantage of shrink labels on this product is that the reverse printing protects the image from the oils and dirt that occur naturally on people’s hands, which can erode an image directly printed on a writing instrument. Other products using shrink bands as primary labels or decorations are Christmas ornaments, Easter egg decorating kits, children’s shampoos and soaps, deodorant sticks, plastic baseball bats, golf clubs, yarn and thread spools, craft paints, and tobacco containers. Seal-it Inc offers holographic labels (3).

Examples of commercial uses of shrink bands
Examples of commercial uses of shrink bands. Figure 1.

Full-body sleeves cover 360° of a product from top to bottom., and they provide the maximum promotional area. Perforations are available that are easily removed, but the label remains on the containers. Up to 10 colors are available (2).

A third use of shrink labels is for multipacking purposes. Two or more products are bundled together using a shrink band. Printing the bands eliminates the need to apply a paper label later in the distribution process. Two products are placed side by side, and the label is applied vertically over the top. It is not uncommon to put two different products together. Examples of this would be 16 oz of shampoo and a trial size of conditioner, or mouthwash and a toothbrush. When three containers are banded, placing the products in a triangle configuration provides for a more secure package, because this prevents the third product from falling out of the middle. Just about any product can be packaged this way; some common uses are for packaging of hair-care products, vitamins, car-care products, lubricants, peanut butter, caulking compounds, and cooking sauces. Three tubs of baby wipes are stacked on top of each other and vertically sleeved using a shrink band. Most multipacks are done manually, and almost any product or container allows for this banding method. Basic uses for multipacks are trial sizes, values, twin packs, buy-one-get-one-free, and seasonal promotions (4).

Shrink bands will continue to provide packaging companies with a unique method of labeling their products. The double benefit of increased tamper evidence and integrity along with attractive graphic impact is beneficial for almost any product. Shrink bands will continue to grow as a labeling method in the beverage, industrial, and toy markets as well as maintaining an important position in the traditional food, health and beauty, and pharmaceutical markets.

DAVID R. KOPSILK

ED FISHER

CMS Gilbreth Packaging Systems, Trevose, Pennsylvania Updated by Staff