EP0500707B1

EP0500707B1 - Plastics bottle

Info

Publication number: EP0500707B1
Application number: EP90917151A
Authority: EP
Inventors: James Butterworth
Original assignee: Lin Pac Plastics International Ltd
Current assignee: Lin Pac Plastics International Ltd
Priority date: 1989-11-23
Filing date: 1990-11-23
Publication date: 1995-02-15
Anticipated expiration: 2010-11-23
Also published as: DK0500707T3; GB8926469D0; DE69017040D1; ZA909428B; DE69017040T2; EP0500707A1; WO1991008146A1; AU6744490A

Abstract

Blow moulded bottles mades of clear plastics material which is bi-axially oriented during its blow moulding step are particularly attractive for packaging foodstuffs but problems arise when they are required to contain a foodstuff which requires pasteurisation either after it is packaged or immediately before it is filled into the bottle. In this case the bottle, especially in its neck region distorts and this leads to sealing problems. These problems are solved by providing a plastics bottle (1) with a re-sealable snap-on cap (8) of plastics material covering a primary aluminium foil based seal (7) which forms an hermetic seal with the top rim (6) of the bottle neck (2). The use of two separate closures solves all of the above problems.

Description

Blow moulded bottles made of clear plastics material which is bi-axially oriented during its blow moulding step are particularly attractive for packaging foodstuffs. Such bottles are usually made of PET (polyethelene terathphalate) which has the advantage of being crystal clear so that the eventual customer of the foodstuffs can see the foodstuff as they can when it is packaged in a glass container but when packaged in PET there is a better contact clarity than glass due to its thinner wall. Problems arise with such containers when they are required to contain a foodstuff which requires pasteurisation either after it is packaged in such a bottle or, for example which is flash-pasteurised immediately before it is filled into the bottle.
PET has a glass transition temperature of around 70 to 75°C in its amorphous state but this increases to between 160 and 180°C once it is bi-axially oriented. In a typical blow moulded container the neck region of the container and the centre of the base panel is in its amorphous state since this region is not bi-axially stretched during the blow moulding step whereas the remainder of the container is bi-axially oriented as a result of being bi-axially stretched during the blow moulding step.
In the past several attempts have been made to produce a PET bottle which is capable of being hot filled with a fruit juice immediately after it has been flash-pasteurised. Most of these attempts have used a conventional blow moulded PET bottle with a neck fitting which includes an external screw thread and which is arranged to take a metal or plastics screw cap. The closure of such containers is desirably of reasonable diameter, say 38mm rather than the more usual 28mm neck. Another attempt has included a method of crystallising the neck portion of the bottle, which has the effect of increasing its glass transition temperature to 160° - 180°C. This method has several disadvantages:

a. the neck shrinks and becomes less predictably accurate;
b. the process step is expensive, energy consuming and requires a large investment in plant; and,
c. the resulting finish is heavy, opaque and milky and thus is unattractive for the consumer. So far none of these attempts have been successful. The hot filling of such containers results in distortion of the neck which is particularly noticeable on the larger neck sizes with the result that the screw cap cannot form an effective and reliable seal.

There is a considerable commercial advantage in being able to provide such a PET bottle for packaging fresh fruit juice alone, apart from its use for other foodstuffs because, at present, fresh fruit juice is either packaged into glass bottles , into lined laminated containers such as that known by the trade name of "TETRABRICK" (Registered Trade Mark) or into very short shelf life PET containers where the product is cold filled. Glass bottles are heavy and occupy a substantial volume which greatly adds to the transport and distribution costs as well as being brittle, fragile and easily broken. On the other hand, the lined laminated box containers are not re-sealable and thus, when they contain a substantial volume of fruit juice, typically one litre, it is difficult to close the container to keep their contents fresh. Using cold filling provides a satisfactory package but this has only a short shelf life.
The document EP-A-0,237,459 describes a method and apparatus for the manufacture of PET containers which are capable of being filled with hot liquids. The method includes the step of heat treating the neck region of the bottle at a temperature which is sufficient to crystallise the material of the bottle neck. The document EP-A-0,242,475 discloses a tamper resistant closure arrangement suitable for a plastics bottle in which a foil disc forms a primary seal and a snap fit closure forms a secondary seal.
According to this invention a plastics bottle filled with contents which require pasteurisation includes a resealable snap on cap of plastics material covering a primary aluminium foil based seal which forms a hermetic seal with the top rim of the bottle neck is characterised in that the plastics in the region of the bottle neck is in an amorphous state.
We have found that this use of two separate closures solves all of the problems with using PET bottles with material which has to be hot filled into them. The primary seal formed by the aluminium foil based seal which is hermetically sealed onto the neck of the bottle is flexible and so can accommodate even severe distortion of the neck region of the plastics bottle without any danger of breaking its hermetic seal. Secondly, by using a press on cap type closure rather than a screw cap which has been proposed in the past, forms a perfectly satisfactory secondary seal which, initially, protects the relatively thin foil seal from damage during transport and, secondly, provides a secondary seal once the hermetic seal has been opened to allow the bottle to be re-closed when only part of its contents have been used by the eventual consumer. A snap on cap type closure provides a perfectly satisfactory secondary seal even though it probably would not be sufficiently reliable to withstand long term storage if that was the only seal provided. A snap on type seal also has a very much greater tolerance than a typical screw threaded type closure and thus this press on cap also accommodates distortion in the neck fitting caused by hot filling.
In addition to these advantages the aluminium foil based primary seal provides a greater degree of security against suck back of cooling liquid used to cool hot filled bottles after they have been sealed than does a conventional screw type closure and also, as a result of the semi-vacuum that is formed inside the bottle on cooling of its hot contents the primary aluminium foil based seal is, at least to some extent, pulled downwards into the inside of the bottle. By measuring the concavity of the foil seal the integrity of the hermetic seal formed can be monitored and measured and unsealed bottles readily rejected.
Preferably the aluminium foil based seal is formed by a laminate of aluminium foil and plastics material and preferably the plastics material is the same as that from which the bottle is formed. This facilitates the heat sealing or ultrasonic welding of the aluminium foil based seal to the top rim of the neck of the bottle. Alternatively, the aluminium foil based seal can be adhered to the top rim of the neck of the bottle using an adhesive. An aluminium foil based seal is substantially impermeable and thus provides a more impermeable closure than many closures made from plastics material. Also the aluminium foil also acts a pilfer evident barrier. Further methods of showing that tampering has taken place are possible such as the inclusion of a thermal strip which indicates a secondary heat application. Preferably the aluminium foil based seal includes a tab projecting outwards from its seal with the top rim of the bottle neck to enable the seal to be grasped easily by the user and ripped off.
The snap-on cap of plastics material may be a standard press-on cap such as that sold under the trade name of J Cap made by Johnson and Jorgensen. The cap may also include a pilfer proof feature including a tear off neck band which has to be torn off before the snap-off cap can be removed from the neck of the bottle. Preferably such a standard snap-on cap is modified to have a much deeper cap so that it will accommodate the depending tab formed on the aluminium foil based primary seal.
Preferably the bottle is made from PET but, instead, it may be made from polystyrene, or SAN (styrene acrylonitrile). In any event it is preferred that the material is transparent and crystal clear so that the foodstuff contained within the bottle can be seen clearly.
A particular example of a bottle in accordance with this invention will now be described with reference to the accompanying drawing which is a radial cross-section through a bottle neck.
A bottle in accordance with this invention comprises a bottle 1 made by a stretch blow moulding process from PET having a neck 2 with a neck support ring 3 and annular projections 4 and 5 to receive a pilfer-proof ring and press-on cap, respectively. Typically the neck is arranged to receive a 38mm press-on cap. The neck 2 includes a top rim 6 on which is heat sealed to a flexible aluminium PET laminate foil seal 7. A cap 8 similar to the conventional pilfer-proof J cap made by Johnson and Jorgensen is fitted to the neck 2 of the bottle 1 on top of the foil seal 7. The foil seal 7 includes a projecting tab 9 to enable it easily to be gripped and ripped off by the eventual user. To accommodate this the height of the snap-off lid portion 10 of the cap 8 is increased over the conventional cap.
The bottle is initially hot filled with, for example fruit juice and then the aluminium foil seal 7 is heat sealed onto the top rim 6 of the neck 2. The bottle is then subjected to a post-filling pasteurisation step followed by cooling, typically using water jets to cool the fruit juice to room temperature. The production line may include a device arranged to measure the concavity of the foil seal 7 to ensure that an hermetic seal has been formed between the seal and the top rim of the neck 2 of the bottle 1. Finally, the press-on cap and pilfer-proof ring assembly 8 is pushed downwards onto the neck of the bottle.
Once the bottle has been delivered to the eventual consumer the consumer tears off a pull strip 11 of the pilfer-proof J-cap 8, opens the lid 10 and then punches a hole in or removes the foil seal 7, using the tab 9, before pouring some of the fruit juice from the neck 2 of the bottle. When some contents remain in the bottle the press-on cap 8 is then used to re-close the bottle 1 to prevent spoilage or spillage of its contents.
The foil seal 7 may be overprinted with brand identification or, for example to be used as a token in a sales promotion.

Claims

A plastics bottle (1) filled with contents which require pasteurisation includes a re-sealable snap on cap (8) of plastics material covering a primary aluminium foil based seal (7) which forms an hermetic seal with the top rim (6) of the bottle neck (2) is characterised in that the plastics in the region of the bottle neck is in an amorphous state.
A plastics bottle according to claim 1, in which the aluminium foil based seal (7) is formed by a laminate of aluminium foil and plastics material.
A plastics bottle according to claim 2, in which the plastics material is the same as that from which the bottle is formed.
A plastics bottle according to any one of the preceding claims, in which the aluminium foil based seal (7) includes a tab (9) projecting outwards from its seal with the top rim (6) of the bottle neck (2) to enable the seal (7) to be grasped easily by the user and ripped off.
A plastics bottle according to any one of the preceding claims, in which the snap on cap (8) also includes a pilfer proof feature including a tear off neck band (11) which has to be torn off before the snap off cap (6) can be removed from the neck (2) of the bottle.
A plastics bottle according to any one of the preceding claims, which is made from plastics material which is transparent and crystal clear so that the contents of the bottle are clearly visible.
A plastics bottle according to claim 6, which is made from PET (polyethylene terephthalate).