DE69017040T2 - PLASTIC BOTTLE. - Google Patents

Description

Blow-molded bottles made of clear plastic material that is biaxially oriented during its blow-mold step are particularly attractive for packaging food. Such bottles are usually made of PET (polyethylene terephthalate), which has the advantage of being crystal clear so that the potential purchaser of the food can see the food as if it were packaged in a glass container, but when packaged in PET, there is clearer contact than with glass due to its thinner wall. Problems with such containers arise when they are intended to contain food that requires pasteurization, either after it is packaged in such a bottle or when it is, for example, flash pasteurized immediately before being filled into the bottle.

PET has a glass transition temperature of about 70 to 75ºC in its amorphous state, but this increases to 160 to 180ºC once it is biaxially oriented. In a typical blow molded container, the neck region of the container and the center of the bottom are in the amorphous state because this region is not biaxially stretched during the blow molding step, whereas the rest of the container is biaxially oriented as a result of the biaxial stretching during the blow molding step.

Several attempts have been made in the past to produce a PET bottle that can be hot filled with fruit juice immediately after it has been flash pasteurized. Most of these attempts have used a conventional blow molded PET bottle with a neck portion containing an external screw thread and arranged to receive a metal or plastic screw cap. Desirably the closure of such containers has a reasonable diameter of, for example, 38 mm rather than the more common 28 mm neck.

Another attempt has involved a process of crystallizing the neck portion of the bottle, which has the effect of increasing its glass transition temperature to 1600 - 180ºC. This process has some disadvantages:

a. the neck shrinks and its accuracy becomes less predictable;

b. the process step is expensive, energy-intensive and requires a high operating investment; and,

c. the resulting appearance is bulky, opaque and milky and therefore unattractive to the customer.

To date, none of these attempts have been successful. Hot filling of such containers leads to distortion of the neck, which is particularly noticeable in the larger neck sizes, with the result that the screw cap cannot form an effective and reliable closure.

A considerable commercial advantage is that such a PET bottle can be used to package only fresh fruit juice, apart from its use for other food products, since at present fresh fruit juice is packaged either in glass bottles, in laminated containers such as those known under the trade name "TETRABRICK" (registered trademark), or in PET containers into which the product is cold-filled and has a very short shelf life. Glass bottles are heavy and occupy a substantial volume, thus greatly increasing transport and distribution costs, and are also brittle, fragile and easily breakable. On the other hand, laminated box containers are not resealable and when they contain a substantial volume of fruit juice, typically one litre, it is difficult to close the container to keep its contents fresh. Cold filling provides satisfactory packaging, but it has a short shelf life.

Document EP-A-0,237,459 describes a method and apparatus for producing PET containers that can be filled with hot liquids. The method includes the step of heat treating the neck zone of the bottle at a temperature sufficient to crystallize the material of the bottle neck. Document EP-A-0,242,475 discloses an anti-tamper closure arrangement suitable for a plastic bottle in which a film disc forms a primary closure and a snap closure forms a secondary closure.

According to this invention, a plastic bottle filled with contents requiring pasteurization comprises a resealable snap-on cap of plastic material covering an aluminum foil-based primary closure forming a hermetic seal with the upper edge of the bottle neck, and is characterized in that the plastic in the bottle neck zone is in an amorphous state.

We have found that this use of two separate closures solves all the problems of using PET bottles with material to be filled hot. The primary closure formed by the aluminium foil based closure which hermetically seals the neck of the bottle is flexible and can thus adapt itself to a strong distortion of the neck zone of the plastic bottle without risk of breaking its hermetic seal. Secondly, by using a press-on cap type closure instead of a screw cap which has been proposed in the past, a perfectly satisfactory secondary closure is formed which firstly protects the relatively thin foil closure from damage during transport and secondly provides a secondary closure once the hermetic closure has been opened to reseal the bottle. when only a portion of its contents have been consumed by the prospective customer. A snap-on cap type closure provides a perfectly satisfactory secondary closure, although it would probably not be sufficiently reliable to withstand long-term storage if it were the only closure provided. A snap-on cap type closure also has a much greater tolerance than a typical screw thread type closure, and thus this press-on cap also accommodates distortion in the neck portion caused by hot filling.

In addition to these advantages, the aluminum foil-based primary closure provides a greater degree of security against the back-suck of cooling liquid used to cool hot-filled bottles after they have been capped than a conventional screw-type closure, and further, as a result of the semi-vacuum formed within the bottle upon cooling its hot contents, the aluminum foil-based primary closure is drawn downward into the interior of the bottle to at least some extent. By measuring the concavity of the foil closure, the integrity of the hermetic closure formed can be monitored and measured and unsealed bottles can be easily discarded.

Preferably, the aluminium foil based closure 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 heat sealing or ultrasonically welding the aluminium foil based closure to the upper edge of the neck of the bottle. Alternatively, the aluminium foil based closure can be bonded to the upper edge of the neck of the bottle using an adhesive. A The aluminum foil-based closure is substantially impermeable, thus providing a more impermeable closure than many closures made from plastics material. The aluminum foil also acts as a theft detection barrier. Other methods of demonstrating that tampering has occurred are possible, such as the inclusion of a thermal strip indicating secondary heat application. Preferably, the aluminum foil-based closure includes a tab extending outwardly from its closure with the top edge of the bottle neck to allow the closure to be easily grasped and torn open by the consumer.

The plastic snap cap may be a standard press-on cap such as that sold under the trade designation J Cap by Johnson and Jorgensen. The cap may also include a theft detection feature comprising a tear-off collar which must be torn before the snap cap can be removed from the neck of the bottle. Preferably, such a standard snap cap is modified to have a much deeper cap so as to accommodate the depending tab formed on the aluminum foil-based primary closure.

Preferably, the bottle is made of PET, but can instead be made of polystyrene or SAN (styrene acrylonitrile). In any case, it is better if the material is transparent and crystal clear so that the food contained in the bottle can be clearly seen.

A particular example of a bottle according to this invention will now be described with reference to the accompanying drawing which is a radial cross-section through a bottle neck.

A bottle according to this invention comprises a bottle 1 made of PET by a stretch blow molding process and has a neck 2 with a neck support ring 3 and annular projections 4 and 5 to receive a theft detection ring and a press-on cap respectively. Typically the neck is arranged to receive a 38 mm press-on cap. The neck 2 includes a top rim 6 which is heat sealed to a flexible aluminium-PET laminate film closure 7. A cap 8 similar to the conventional Johnson and Jorgensen theft detection J-Cap is mounted on the neck 2 of the bottle 1 on top of the film closure 7. The film closure 7 includes a projecting tab 9 to enable it to be easily grasped and torn off by the potential consumer. To accommodate this, the height of the snap-on lid portion 10 of the cap 8 is increased above that of the conventional cap.

The bottle is first hot filled with, for example, fruit juice, and then the aluminium foil closure 7 is heat sealed onto the upper edge 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 an arrangement arranged to measure the concavity of the foil closure 7 to ensure that a hermetic seal has been formed between the closure and the upper edge of the neck 2 of the bottle 1. Finally, the press-on cap and anti-theft ring 8 assembly is pressed down onto the neck of the bottle.

Once the bottle has been delivered to the potential consumer, the consumer tears off a pull tab 11 of the anti-theft J-Cap 8, opens the cap 10 and then tears a hole in the foil seal 7 or removes it using the tab 9 before some fruit juice is poured out of the neck 2 of the bottle. If some of the contents remain in the bottle, the press-on cap 8 is then used to reseal the bottle 1 to prevent spoilage or spillage of its contents.

The foil closure 7 can be printed with a brand identification or, for example, be used as a voucher in a sales promotion.

Claims (7)

1. A plastic bottle (1) filled with contents requiring pasteurization, comprising a resealable snap cap (8) made of plastic material covering an aluminum foil-based primary closure (7) which forms a hermetic seal with the upper edge (6) of the bottle neck (2), and is characterized in that the plastic in the zone of the bottle neck is in an amorphous state. 2. A plastic bottle according to claim 1, wherein the aluminium foil-based closure (7) is formed by a laminate of aluminium foil and plastic material. 3. A plastic bottle according to claim 2, wherein the plastic material is the same as that from which the bottle is formed. 4. A plastic bottle according to any one of the preceding claims, wherein the aluminium foil-based closure (7) includes a tab (9) projecting outwardly from its closure with the upper edge (6) of the bottle neck (2) to enable the closure (7) to be easily grasped and torn off by the consumer. 5. A plastic bottle according to any one of the preceding claims, wherein the snap cap (8) also includes a theft detection feature comprising a tear collar (11) which must be torn before the snap cap (6) can be removed from the neck (2) of the bottle. 6. A plastic bottle according to any one of the preceding claims, made of plastic material, which is transparent and crystal clear so that the contents of the bottle are clearly visible. 7. A plastic bottle according to claim 6, which is made of PET (polyethylene terephthalate).