Closure (container)

For other uses, seeClosure (disambiguation).

An aluminum bottle with a threaded aluminum screw closure

Aclosureis a device used to close or seal acontainersuch as abottle,jug,jar,tube,orcan.A closure may be acap,cover,lid,plug,liner, or the like.The part of the container to which the closure is applied is called thefinish.

Other types of containers such asboxesanddrumsmay also have closures but are not discussed in this article. Many containers and packages require a means of closing, which can be a separate device or seal or sometimes an integral latch or lock.

Purpose of closures

The closure is often the most critical part of a package, and must fulfill all of thebasic functions of packagingin addition to being easy to open and (if applicable) reclose.

Depending on the contents and container, closures have several functions:

• Keep the container closed and the contents contained for the specifiedshelf lifeuntil time of opening
• Provide a barrier to dirt, oxygen, moisture, etc. Control ofpermeationis critical to many types of products: foods, chemicals, etc.
• Keep the product secure from undesired premature opening
• Provide a means of reclosing or reusing the container
• Assist in dispensing and use of product
• Allow reasonable ease to open the container by the intended user. Difficult to open containers may causewrap rage.Theforceortorquerequired to open a closure is an important consideration forpackaging engineers.

Many types of packaging with their closures are regulated for strength, safety, security, communication, recycling, and environmental requirements plus many others.

Types of closures

Closures need a means of attaching to the container with sufficient security. Threads, lugs, hinges, locks, adhesives, etc. are used. Many plastic closures are made byinjection molding.

Many closures need to have the ability to adjust to slight manufacturing variation in the container and the closure structure. Some closures are made of flexible material such ascork,rubber,or plastic foam. Often ano-ringor a closure liner (gasketmade of pulp or foam cap liner) is used. Linerless closures often use a deformable plastic rim or structure to maintain the seal.

Secondary seals are common with sensitive products that may deteriorate or where extra security is needed. Foil or plastic inner seals are used on some bottles, Heat sealed lidding films are used on some tubs. External shrink bands,labels,and tapes are sometimes used outside the primary closure structure. Additionally, many closures feature ventilation to prevent bloating, collapse or explosion due to unequalized pressure during processing or storage. Venting technologies utilize common materials such asPTFE,PP,etc. These elements are preferred due to their ability to withstand temperatures of 260 °C and water intrusion pressure levels of 770 mbar.

Screw top

Closures

Main articles:Screw capandScrew cap (wine)

A screw closure is a mechanical device which is screwed on and off of a threaded "finish" on a container. Either continuous threads (C-T) or lugs are used. Metal caps can be either preformed or in some instances, rolled on after application. Plastic caps may use several types of molded polymer.

Some screw tops have multiple pieces. For example, amason jaroften has a lid with a built in rubbery seal and a separate threaded ring or band.

Crown cap

Crown caps

Main article:Crown cap

Beverage bottles are frequently closed with crown beverage caps. These are shallow metal caps that are crimped into locking position around the head of the bottle.

Snap on

Some closures snap on. For opening, the top is designed to pry off or, break off, or have a built in dispenser.

Friction fit

Some containers have a loose lid for a closure.Laboratory glasswareoften hasground glass jointsthat allow the pieces to be fitted together easily.

AnInterference fitor friction fit requires some force to close and open, providing additional security. Paint cans often have a friction fit plug.

Tamper-evident

Main article:Tamper resistant

Main article:Tamper-evident

Resistance to tampering is required for some types of products. Container closures can be one of several layers of packaging to deter tampering and to provide evidence of attempts at tampering. *Sometimes tamper resistance is obtained by atamper-evident band;separate or integral with the closure.

Dispensing

Main article:Pump dispenser

A wide variety of convenience dispensing features can be built into closures.Spray bottlesand cans withaerosol spray(valves, actuator) have special closure requirements. Pour spouts, triggers, sprayer cap, measuring attachments, sifting devices, etc. are common caps.

Spray bottle

Main article:Spray bottle

A spray bottle is a bottle that can dispense, squirt, spray or mist fluids. A common use for spray bottles is dispensing cool cleaners, cosmetics, and chemical specialties.

Child-resistant

Main article:Child-resistant packaging

Child-resistant packaging or C-R packaging has special closures designed to reduce the risk of children ingesting dangerous items. This is often accomplished by the use of a special safety cap. It is required by regulation for prescription drugs, over-the-counter medications, pesticides, and household chemicals.

Examples

• 
  Spray bottle cap
• 
  rubber stoppers on flasks
• 
  spray duster with long tube for dispensing
• 
  Closure and roll-on device for deodorant
• 
  Inverted ketchup bottle with innerseal and dispensing closure
• 
  Bottle ofGeritolwith a child-resistant cap
• 
  An openedflip-topbottle closure
• 
  A screw cap capsule is fitted onto a wine bottle and heat shrunk tightly
• 
  Recycled bottle stoppers as art in Vienna
• 
  Aliving hingeon the lid of aTic Tacbox

History

Early pottery and ceramic containers often had lids that fit reasonably snug onto the body of the container. The narrow necks of ancientamphorawere closed with a plug ofcork,wood, or ceramic and sealed with mortar. WoodenBarrelsoften hadbungholesclosed by cork or woodbungs.

Some earlytinplatecans were made with threaded necks for screw top closures.

Beverage bottles started using the Hutter Stopper in 1893. This involved aporcelainplugfitted with a rubber washer, which was then forced down into the lip of the bottle. This technique only works withcarbonated beverages.The Hutter Stopper became standard in beer bottling in the late 1890s / early 1900s. Bail closures on bottles were invented by Henry William Putnam in 1859. These involved heavy wire bail attached to a bottle's neck that swung over the cork to hold it in.

The world's first modern bottle cap, thecrown cork,was invented byWilliam Painterin 1890 inBaltimore. The screw cap usingrustresistantaluminumwas first used inprescription drugbottling in the 1920s. Molded urea based bottle caps were first introduced in the early 1900s.

A history of accidents involving children opening household packaging and ingesting the contents led theUS Congressto pass the Poison Prevention Packaging Act of 1970.

• 
  Greek pottery with lid, 5th century
• 
  An assortment ofwine corks
• 
  bail closure on jam jar
• 
  bunginbungholeof a winebarrel

The manufacture of closures

TheInternational Society of Beverage Technologists (ISBT)is the maintrade associationfor closure manufacturers. It develops voluntary industry standards for its members to use in the manufacture of closures.

See also

• Bottle cap
• Crown cork
• GPI container finish standardswhich includes closures for glass containers
• Hutchinson Patent Stopper
• Lid (container)
• Screw cap
• Stopper (plug)
• Tab (beverage can)
• Tamper resistant
• Tamper-evident

References

Books

• Yam, K.L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009,ISBN978-0-470-08704-6
• Soroka, W, "Fundamentals of Packaging Technology", IoPP, 2002,ISBN1-930268-25-4

External links

• History of Closures from the CCMA website
• Collector's website on history of bottle closures