Screw cap
A screw cap is used to hermetically seal containers such as tubes , plastic cans , canning jars and beverage bottles, which are provided with a thread at the opening for this purpose.
production
The screw cap (also known as capsule) consists either of elastic solid material (e.g. PE / PP) or of metal, usually aluminum (for bottles) or sheet steel (for screw-top jars). The thread of the plastic cap is created during its manufacture.
poetry
The seal takes care of a foamed, liquid inserted or used as a film or molding. Various materials are available for the inlay in aluminum caps, such as B. PE , Saranex ( PVdC ) or tin foil are available. Liquid foamed and inserts with plasticizers are now only used for wide-neck bottles and screw-top jars.
Closing
For later closing, the plastic closure is "screwed" onto the thread of the container. In contrast, the metal screw cap is manufactured without a thread. During the closing process, it is first pressed against the sealing surface from above, then the thread is "rolled on" to the side, a copy of the thread from the container being formed into the cap.
- The MCA closure is widespread in Germany. (Metal Closure Aluminum, metal closure made of aluminum)
- The BVS closure (Bague Vin Suisse) has not yet been standardized, a corresponding standard is available as a draft.
The rolling of aluminum caps on bottles with a damaged thread, as well as incorrectly adjusted machines, can loosen splinters from the bottle neck (crunches when opening). Such bottles should be returned to the dealer.
Closures for food bottles
Screw cap for wine
Traditionally, only simple "pints were crying " bottled with screw cap. Due to the accumulation of cork tasters (because of TCA ), more and more high-quality wines are closed with the screw cap. In contrast to the closure with natural corks, there are only minor changes in taste during the subsequent storage. The cheaper versions of the screw cap, however, have increased oxygen permeability and are therefore not very suitable for high-quality wines that can be stored. The so-called long cap and Stelvin cap closures have been introduced to the market in Australia and Switzerland since the early 1970s . These closures have a sealing insert made of polyvinylidene chloride (PVdC), which in the high-quality version is additionally provided with a laminated tin layer and ensures oxygen permeability (0.0002 to 0.0008 cm 3 O 2 per day). This is an important requirement for storage in terms of freshness and shelf life.
A large part of the Australian and New Zealand wine industries now use screw caps. In other wine regions of the world, too, there are increasing changes. In Europe, Switzerland and Germany in particular are pioneers in the use of screw caps for high-quality wines. In Austria, too, an increasing proportion of quality white wines in particular has been bottled in screw-cap bottles since the turn of the millennium. Some winemakers use screw caps in parallel to natural cork for the same wines and offer them as alternatives. An important reason for this is the lack of acceptance of the screw cap in upscale gastronomy, which in some cases does not want to do without opening the bottle in front of the customer with a sommelier knife .
The use of screw caps is the subject of controversial discussion. For example, in Germany, comparisons of wines that have been stored under cork or screw caps for 25 years show that screw caps are superior in terms of freshness and shelf life. In France a similar comparison comes to the exact opposite.
A research project by the Geisenheim research institute on the subject of cork and mustache problems in wine shows that this problem can also apply to wine in bottles with screw caps.
Screw cap for beer
At the end of the 1980s, the resealable swing top for beer bottles came back into fashion. This alternative to crown corks challenged the brewers to achieve the advantages of resealability in terms of convenience with modern, machine-compatible closure systems. Here, too, the screw cap was introduced as the standard cap in the mid-1990s.
Screw cap for soft drinks
Plastic screw caps have become established for lemonade, juice and mineral water bottles. The perforated freshness seal remains hanging on the screw cap after opening. The inside can be used for various collection campaigns or competitions e.g. B. be printed with colored Knibbelbilder or code numbers on the rubber seal. Returnable bottles should always be returned to the beverage company with a cap, as this protects the thread, which is quite sensitive to impact, during return transport.
Screw cap for Tetrapaks
Screw caps are also used with Tetra Paks . With one turn of the screw cap, the freshness seal is severed and at the same time the freshness film of the Tetra-Pak “cover” is pierced and cut.
Rotary cam locks for canning jars
For industrially processed canning jars, mostly jars with cam lids are used. Cam covers are designed in accordance with DIN EN ISO 9100. A part of the standard is published there for each orifice diameter. Cam covers are also known as twist-off screw covers. Compared to screw-on lids, the cams, which are under spring tension after closing, ensure a particularly firm closure of the containers. Twist-off lids or cam lids are usually made from tinplate and printed or painted. For sealing purposes, a sealing compound made of plastic, which is also known as ESBO (epoxidized soybean oil ), is usually injected into the lid opposite the mouth edge of the glass .
Closures for laboratory bottles
The threads of screw caps on laboratory bottles are designed in accordance with the standards DIN 168-1: 1998-04 and ISO 4796-1: 2000-04. Some of the closures have special seals that are far more resistant to chemicals than the material of the screw closures. An example of this are silicone seals to which a thin PTFE film has been applied that points towards the contents of the bottle.
Permeable closures
While most screw caps are designed to seal the lid tightly, there are also those with openings in the lid:
- The salt shaker is probably the best-known example of this.
- The baby bottle has a screw cap that resembles a union nut.
- Sprouts are attracted in jars in which the screw cap contains a sieve , which enables the water to be poured out, but without releasing the sprouts.
Recovery
Screw caps made of PP and HDPE were collected from 2014 to 2019 by the Lid Association and the profits made from this were used to eradicate polio .
Screw lid of a salt shaker
Sprout jar with sieve lid and seedlings
Various modern screw caps for drinking bottles
Safety lock; can only be unscrewed if pressed sideways at the same time
See also
Web links
- FAZ : "Screw cap beats natural cork" Rhein-Main-Zeitung - FAZ.NET
- Thread standard for glass threads
- Lehrerfreund.de thread: screw thread for mineral water bottles etc.
Individual evidence
- ↑ MCA complete.pdf, lwg.bayern.de closure in viticulture PDF
- ↑ The BVS bottle mouthpiece ( Memento of the original from January 5, 2013 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (Bague Vin Suisse) corresponds to the mouthpiece of the European standard GME 30.06 with a few exceptions, e.g. B. the distance to the thread start of 2.8 mm instead of the usual 1.65 mm. BVS mouthpieces are not yet standardized, but are largely based on the CE.TIE GM 30.06 10/01.
- ↑ Beuth Verlag: Draft standard DIN EN 16293: 2011-05
- ↑ Research Institute: cork and wine Mufftonproblematik ( Memento of the original on 26 March 2012 at the Internet Archive ) Info: The archive link is automatically inserted and not yet tested. Please check the original and archive link according to the instructions and then remove this notice.
