Induction sealing is the process of bonding

thermoplastic A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains as ...

materials by induction heating. This involves controlled heating an electrically conducting object (usually aluminum foil) by

electromagnetic induction Electromagnetic or magnetic induction is the production of an electromotive force, electromotive force (emf) across an electrical conductor in a changing magnetic field. Michael Faraday is generally credited with the discovery of induction in 1 ...

, through heat generated in the object by eddy currents. Induction sealing is used in many types of manufacturing. In

packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a coo ...

, it is used for package fabrication such as forming tubes from flexible materials, attaching plastic closures to package forms, etc. Perhaps the most common use of induction sealing is ''cap sealing'', a non-contact method of heating an ''inner seal'' to hermetically seal the top of

plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

and

glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...

containers. This sealing process takes place after the container has been filled and capped.

Sealing process

AM-250 INDUCTION FOIL SEALING MACHINE BY AUTO-MATE PACKAGING KAPSALL

The closure is supplied to the bottler with an aluminum foil layer liner already inserted. Although there are various liners to choose from, a typical induction liner is multi-layered. The top layer is a

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses, Feces#Other uses, herbivore dung, or other vegetable sources in water. Once the water is dra ...

pulp that is generally spot-glued to the cap. The next layer is wax that is used to bond a layer of aluminum foil to the pulp. The bottom layer is a polymer film laminated to the foil. After the cap or closure is applied, the container passes under an induction coil, which emits an oscillating electromagnetic field. As the container passes under the induction coil (sealing head), the conductive aluminum foil liner begins to heat as a result of the eddy currents being induced. The heat melts the wax, which is absorbed into the pulp backing and releases the foil from the cap. The polymer film also heats and flows onto the lip of the container. When cooled, the polymer creates a bond with the container resulting in a hermetically sealed product. Neither the container nor its contents are negatively affected, and the heat generated does not harm the contents. It is possible to overheat the foil and thereby cause damage to the seal layer and to any protective barriers. This could result in faulty seals, even weeks after the initial sealing process, so proper sizing of the induction sealing is vital to determine the exact system necessary to run a particular product. Sealing can be done with either a handheld unit or on a conveyor system. A more recent development (which better suits a small number of applications) allows for induction sealing to be used to apply a foil seal to a container without the need for a closure. In this case, foil is supplied pre-cut or in a reel. Where supplied in a reel, it is die cut and transferred onto the container neck. When the foil is in place, it is pressed down by the seal head, the induction cycle is activated, and the seal is bonded to the container. This process is known as direct application or sometimes "capless" induction sealing.

Potential uses

There are a variety of reasons companies choose to use induction sealing: * Tamper evidence * Leak prevention * Freshness retention * Protection against package pilferage * Sustainability * Production speed

Tamper evidence

With the U.S. Food and Drug Administration (FDA) regulations concerning tamper-resistant

, pharmaceutical packagers must find ways to comply as outlined in Sec. 450.500 Tamper-Resistant

Packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a coo ...

Requirements for Certain over-the-counter (OTC) Human Drug Products (CPG 7132a.17). Induction sealing systems meet or exceed these government regulations. As stated in section 6 of Packaging Systems:

"...6. CONTAINER MOUTH INNER SEALS. Paper, thermal plastic, plastic film, foil, or a combination thereof, is sealed to the mouth of a container (e.g., bottle) under the cap. The seal must be torn or broken to open the container and remove the product. The seal cannot be removed and reapplied without leaving visible evidence of entry. Seals applied by heat induction to plastic containers appear to offer a higher degree of tamper-resistance than those that depend on an adhesive to create the bond..."

Leak prevention/protection

Some shipping companies require liquid chemical products to be sealed prior to shipping to prevent hazardous chemicals from spilling on other shipments.

Freshness

Induction sealing keeps unwanted pollutants from seeping into food products and may assist in extending shelf life of certain products.

Pilferage protection

Induction-sealed containers help prevent the product from being broken into by leaving a noticeable residue on plastic containers from the liner itself. Pharmaceutical companies purchase liners that will purposely leave liner film/foil residue on bottles. Food companies that use induction seals do not want the liner residue as it could potentially interfere with the product itself upon dispensing. They, in turn, put a notice on the product that it has been induction-sealed for their protection; letting the consumer know it was sealed upon leaving the factory and they should check for an intact seal before using.

Sustainability

In some applications, induction sealing can be considered to contribute towards sustainability goals by allowing lower bottle weights as the pack relies on the presence of an induction foil seal for its security, rather than a mechanically strong bottle neck and closure.

Induction heating analysis

Some manufacturers have produced devices which can monitor the magnetic field strength present at the induction head (either directly or indirectly via such mechanisms as pick up coils), dynamically predicting the heating effect in the foil. Such devices provide quantifiable data post-weld in a production environment where uniformity – particularly in parameters such as foil peel-off strength, is important. Analysers may be portable or designed to work in conjunction with conveyor belt systems. High speed power analysis techniques (voltage and current measurement in near real time) can be used to intercept power delivery from mains to generator or generator to head in order to calculate energy delivered to the foil and the statistical profile of that process. As the thermal capacity of the foil is typically static, such information as true power, apparent power and power factor may be used to predict foil heating with good relevance to final weld parameters and in a dynamic manner. Many other derivative parameters may be calculated for each weld, yielding confidence in a production environment that is notably more difficult to achieve in conduction transfer systems, where analysis, if present is generally post-weld as relatively large thermal mass of heating and conduction elements combined impair rapid temperature change. Inductive heating with quantitative feedback such as that provided by power analysis techniques further allows for the possibility of dynamic adjustments in energy delivery profile to the target. This opens the possibility of feed-forward systems where the induction generator properties are adjusted in near real-time as the heating process proceeds, allowing for a specific heating profile track and subsequent compliance feedback – something that is not generally practical for conduction heating processes.

Benefits of induction vs. conduction sealing

Conduction sealing requires a hard metal plate to make perfect contact with the container being sealed. Conduction sealing systems delay production time because of required system warm-up time. They also have complex temperature sensors and heaters. Unlike conduction sealing systems, induction sealing systems require very little power resources, deliver instant startup time, and have a sealing head which can conform to "out of specification" containers when sealing. Induction sealing also offers advantages when sealing to glass: Using a conduction sealer to seal a simple foil structure to glass gives no tolerance or compressibility to allow for any irregularity in the glass surface finish. With an induction sealer, the contact face can be of a compressible material, ensuring a perfect bond each time.

Real-world applications of induction sealing

Induction sealing is broadly used to preserve the freshness and integrity of various products, such as: *

Sauce In cooking, a sauce is a liquid, cream, or semi- solid food, served on or used in preparing other foods. Most sauces are not normally consumed by themselves; they add flavour, texture, and visual appeal to a dish. ''Sauce'' is a French wor ...

s, jams, and

condiment A condiment is a preparation that is added to food, typically after cooking, to enhance the Flavoring, flavour, to complement the dish or to impart a specific flavor. Such specific flavors generally add sweetness or pungency, or sharp or piquant ...

s *

Dairy product Dairy products or milk products are food products made from (or containing) milk. The most common dairy animals are cow, water buffalo, goat, nanny goat, and Sheep, ewe. Dairy products include common grocery store food around the world such as y ...

s, including

milk Milk is a white liquid food produced by the mammary glands of lactating mammals. It is the primary source of nutrition for young mammals (including breastfeeding, breastfed human infants) before they are able to digestion, digest solid food. ...

and

yogurt Yogurt (; , from , ; also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial Fermentation (food), fermentation of milk. Fermentation of sugars in the milk by these bacteria produces lactic acid, which acts on milk protein to ...

containers *

Beverage A drink or beverage is a liquid intended for human consumption. In addition to their basic function of satisfying thirst, drinks play important roles in human culture. Common types of drinks include plain drinking water, milk, juice, smoothie ...

s, such as

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

coffee Coffee is a beverage brewed from roasted, ground coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content, but decaffeinated coffee is also commercially a ...

, tea, and juices * Nutritional supplements * Ready-to-eat meals,

soup Soup is a primarily liquid food, generally served warm or hot – though it is sometimes served chilled – made by cooking or otherwise combining meat or vegetables with Stock (food), stock, milk, or water. According to ''The Oxford Compan ...

s, and other food products * Pet food and animal care products *

Medication Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmaco ...

s and other pharmeceuticals *

Cosmetics Cosmetics are substances that are intended for application to the body for cleansing, beautifying, promoting attractiveness, or altering appearance. They are mixtures of chemical compounds derived from either Natural product, natural source ...

, such as shampoos and conditioners * Skin care products, such as

lotion Lotion is a low-viscosity topical preparation intended for application to the skin. By contrast, creams and gels have higher viscosity, typically due to lower water content. Lotions are applied to external skin with bare hands, a brush, a clea ...

s, creams, and serums * Various

chemical substance A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be com ...

s, including

cleaning agent Cleaning agents or hard-surface cleaners are substances (usually liquids, powders, sprays, or granules) used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing ...

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

s, and fertilizers * Pastes, adhesives, sealants,

paint Paint is a material or mixture that, when applied to a solid material and allowed to dry, adds a film-like layer. As art, this is used to create an image or images known as a painting. Paint can be made in many colors and types. Most paints are ...

s, and

coating A coating is a covering that is applied to the surface of an object, or substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. powder coatings. Paints ...

s *

Lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, ...

s and greases * Sporting goods supplies

History

*1957–1958 – Original concept and method for induction sealing is conceived and proven by Jack Palmer (a process engineer at that time for the FR Corporation – Bronx, NY) as a means of solving liquid leakage from polyethylene bottles during shipment *1960 – is awarded to Jack Palmer, in which his concept and process of induction sealing is made public *Mid-1960s – Induction sealing is used worldwide *1973 – First solid-state cap sealer introduced *1982 – Chicago Tylenol murders *1983 – First

transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...

ized air-cooled power supply for induction cap sealing *1985 – Universal coil technology debuted *1992 – Water-cooled, IGBT-based sealer introduced *1997 – Waterless cap sealers introduced by Auto-Mate Technologies - The Originator of the Patented "Waterless Cap Sealer (half the size and relatively maintenance-free) *2003
Auto-Mate Technologies SMART-SEAL
Full-Featured "Waterless Cap Sealers" *2004 – 6 kW system introduced, Auto-Mate Technologies adds inspection capabilities to the induction sealing machine; making it a combination inspection machine for inspection of crooked caps, missing foils, checking for sealed caps, conveyor monitoring, rejecting etc.

References

External links

{{packaging Induction heating Packaging machinery