GB1604849A - Containers for and containing carbonated beverages - Google Patents

Description

(54) IMPROVEMENTS RELATING TO CONTAINER FOR AND CONTAINING CARBONATED BEVERAGES (71) We, PLASTONA (JOHN WADDING- TON) LIMITED, a British Company, of Wakefield Road, Leeds Us 10 2TP, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to containers for and containing carbonated beverages. The containers to which the invention relates are those for holding small quantities of beverage for individual consumption, as opposed to bulk containers or storage tanks for holding large quantities of beverage subsequently to be dispensed in or divided into quantities for individual consumption.

Large quantites of carbonated beverages such as beer and soft drinks, are sold in containers throughout the world, and traditionally, such containers have been of glass because it is strong, and has good gas barrier properties which prevent loss of carbonation of the drink before opening of the container.

The trouble with glass is of course that it breaks easily, it is not easy to dispose of, and glass containers are space consuming. Moreover, in the hands of hooligans, empty glass containers become lethal throwing weapons.

Because of the problems associates with the use of glass, there have been developed metal containers, or cannisters, for holding carbonated beverages, such cannisters comprising essentially a metal sleeve with metal ends sealingly crimped thereto, one of such ends having an easy opening device whereby access to the cannister contents may be achieved. Such containers have had considerable success to such an extent that approximately equal numbers of metal cannisters and glass containers are now in use today throughout the world.

These metal cannisters have disadvantages, for example they can also be used as throwing weapons in the hands of unthinking people, they are difficult to dispense of, and they are expensive.

A further type of known container which is used for containing carbonated beverage is a plastic container which is blow moulded.

This container is less dangerous when used as a throwing weapon, but is must be made relatively thick and is expensive to produce, as it requires the provision of expensive machinery, and only a relatively slow production rate is possible.

We have been of the view, since as long ago as 1969, that it would be desireable to provide a container for carbonated beverage which is thermoformed by conventional techniques from extruded sheet plastics material.

The advantages of such a container are in our view considerable. Firstly, the container will be of relatively thin material (comparable with the metal sleeve of the metal cannister), which in turn will make it easier to dispose of and will make it less dangerous, in the hands of hooligans, as it will be light in weight when empty, and secondly, it will be capable of being produced inexpensively and quickly.

We have continuously worked to achieve the production of a plastic container which is for holding carbonated beverage and which is thermoformed from extruded sheet material for the last eight years and we have obtained the grant of a number of British Patents and have other applications pending with this objective in view. In prosecuting these patents and applications, and equivalent patents and/or applications in other countries, we are aware that a number of other parties throughout the world are also seeking to achieve the production of a satisfactory container as outlined above, but at the present time to our knowledge a commercially satisfactory product usable on a large scale has not resulted.

In our earlier attempts to produce a thermoformed plastics material container from extruded plastics sheet, a laminate of polystyrene sheet and a layer of high barrier acrylonitrile polymer were thermoformed in to the container shape by conventional thermoforming techniques. The high barrier acrylonitrile polymer used as BAREX (Registered Trade Mark) of a thickness of 0.003", and the high impact polystyrene was of a thickness 0.045". Basically, the barex layer provided the gas barrier function of the container, whilst the polystyrene outer case provided the strength requirement of the container. After formation, the container was sealed using a metal and having an easy opening device, the metal end being crimped to a top peripheral flange of the plastics material container.

Tests on containers manufactured as indicated above, then filled with carbonated beverage, and then sealed as indicated above revealed a number of technical problems.

Firstly, some of the containers developed hair-line fractures as a result of the sealing operation, indicating a lack of strength of the plastics material used for the containers, in particular the polystyrene. Secondly, with the passage of time, there was a loss of carbonation in the beverage in the case of some of the containers and this was traced to be due to imperfections in the BAREX layer which were not or scarcely detectable with the naked eye. The problem of gas leakage may have been soluble by the obvious method of increasing the thickness of both the BAREX layer and the high impact polystyrene, but increasing of thickness of the layers mitigates against being able to apply a metal lid by rim rolling and the object of producing a satisfactory thermoplastics container at a reasonable cost.

In the original proposal, it was suggested that the base of the container described should be hemispherical in order to make the container creep resistant, it being believed that a hemispherical shape for the base was the most suitable from a strength point of view. The invention was that the inner containers would be filled with carbonated beverage whilst chilled, sealed and then placed in outer cups to which the containers would frictionally adhere in due course as a result of the chilled beverage reaching ambient temperature and release some carbonating gas from solution to increase the internal pressure inside the container and to expand the inner container into frictional engagement with the outer container.Packages containing containers and cups as above described were produced and tested, and showed themselves to be acceptable to the public, but the hair-line fracture and gas retention problems outlined above were not completely solved although the inner containers did satisfactorily adhere frictionally to the outer cups until the inner containers were opened, relieving the internal pressure, and the containers and cups could subsequently be separated, the cup being used as a drinking vessel.

The outer cup and inner container were made of high impact polystyrene, but the quadrupling of the price of oil in the early seventies made the package too expensive, and we immediately started to look at what we referred to as a "one-piece" container comprising basically a plastic container and metal lid. In looking in this direction, it was obvious that the hemispherical end of the original design would have to be modified to make the container free standing. The initial one-piece containers which were investigated also comprised high impact polystyrene BA REX laminates, but these containers still possess the disadvantages of hair-line fracturing and gas retention.In the next stage of the development, we experimented with onepiece containers made entirely of BAREX, of the appropriate thickness, and it was found that the problem of gas retention had been overcome, because BAREX has much better gas retention properties than high impact polystyrene.

The use of 100% barex brought its own problems because BAREX "creeps" under load, and according the BAREX containers which were filled and sealed, with the passage of time, tended to swell in the wall region to an unacceptable extent and/or evert in the base region to such an extent as to make them "rockers" which are containers, which, although able to stand freely, tend to rock between different equilibrium positions if displaced, or indeed the containers become incapable of standing freely.

Certain developments in the design of base of the BAREX containers were made in order to prevent excessive eversion of the base as mentioned above, and we reached the stage of arranging for the test marketing of 25,000 one-piece BAREX containers filled with beer. Because the content was beer, it was necessary that the containers after filling and sealing had to be pasteurised. As the pasteurising process involved the application of heat, and the consequent further release of carbon dioxide from the beverage, with the consequent increase in internal pressure in the containers during pasteurisation, it was necessary to pasteurise the containers whilst the containers were held securely in metal jigs.

The test marketing of the 25,000 containers referred to above was satisfactory from the customer point of view, but the containers themselves were still not completely satisfactory. Thus, a small amount of the containers cracked or developed hair-line fractures at the top during the sealing stage, and the burst strength of the containers was not high enough in that some of the containers burst under pressure as low as 55 p.s.i. We were aware that the burst problem could be cured by thickening the container, but this would have aggravated the problem of cracking during sealing, because during the sealing process the container flange and the flange of the lid are rim rolled, and the container must be of sufficient fleixibility to rim roll without cracking.

We experimented with two other forms of high acrylonitrile containing polymers, namely the material sold under the names CYCOPAC 920 and CYCOPAC 930 made by Borg Warner, but these materials proved themselves to be worse from the point of view of cracking during sealing than the BAREX, and like the BAREX containers they had to be held in metal jigs during pasteurization. CYCOPAC is also a Registered Trade Mark.

Although our development programme was frustrated somewhat by the difficulties, we still believed in the commercial viability of a thermoformed container for holding carbonated beverage, and we decided to investigate a material which is not conventionally thermoformed from extruded sheet, and the material is question was polyester.

We were aware that polyester had been used as film for flexible packages and upon testing its fitness as regards providing a gas barrier for gas retention, initial tests were encouraging. We carred out tests with the two main polyester materials namely Polyethylene Terephthalate and Polybutylene Terephthalate. Polyethylene Terephthalate showed itself to have better gas barrier properties, and we experimented with a number of commercially available grades of polyester, not in themselves sold as materials for extruding into sheet, and these comprised the following:1. Vestadur 2271 sold by Huls of Germany 2. APV 4000 supplied by Hoechet of Germany 3. Low viscosity polyestered grades types 42 and 49 supplied by Hoechst of Germany 4. Polyesters types 5 and 0 supplied by I.C.I.

of the United Kingdom 5. Polyester grade A200 supplied by Akzo in Holland in particular the member of the group identified by Akzo by reference A04/ 102/307.

The material Vestadur 2271 referred to above extruded satisfactorily in to sheet, but in attempts subsequently to thermoform the material into containers, the material did not flow sufficiently evenly to enable us to achieve satisfactory thermoforming.

The material APV 4000 was found to extrude and thermoform satisfactorily, but we were advised by Hoechst shortly after the supply of APV 4000 that they were discontinuing the manufacture of this material. The grades 42 and 49 which were supplied by Hoechst were found to be unsatisfactory as regards extrusion into sheet. The polyester types 5 and 0 supplied by I.C.I. again did not extrude satisfactorily in the work carried out by us, but I.C.I. did supply some extruded sheets in materials type 5 and 0, and in subsequent thermoforming of these materials and of testing the containers resulting therefrom, the containers were found to creep to an unsatisfactory degree.

Tests with Akzo material A04/102/307 showed that the material extruded well and thermoformed satisfactorily and a number of containers were made therefrom, filled and sealed and tests on and with these containers as regards gas barrier proportions were encouraging.

Analysis and examination of the various materials tested showed that the material which was eminently suitable for use in containers for carbonated beverage thermoformed from sheet material, as regards thermoforming and gas barrier properties, high molecular weight polyester material.

As regards the problem concerning the seaming of metal lids to the container, this was solved by clamping the sheet material, during thermoforming, at a location spaced from a top part of the mould serving to define an outwardly top flange of the container which is for rim rolling with the metal lid.

Accordingly, the present invention provides a method of producing a circularsectioned open-topped container for holding carbonated beverage, wherein an extruded sheet of high molecular weight, high viscosity polyester material of average molecular weight in the range 37,000 to 55,000 is thermoformed into a circular-sectioned container having an outwardly turned rim at the container top edge to enable the container to be sealed by rim rolling the rim and the edge of a metal lid together, and wherein in the forming of the container its base is shaped so as to provide a means enabling the container to be free standing, and also so as to resist distention of the base due to internal pressure when the container is filled with carbonated beverage and sealed.

The invention also resides in a package produced by the method as aforesaid and such a package when sealed with a metal lid.

The utilisation of high viscosity, high molecular weight polyester achieves the fol lowing: a) a material which can be extruded satisfactorily b) a material which can be thermoformed satisfactorily c) a material to which a metal lid can be applied by rim rolling without hair-line cracks occurring.

d) a material which has only a small degree of creep, if any, after filling with the carbonated beverage and sealing e) a material which has a good gas barrier properties f) a material which has a good strength properties to resist bursting, and all of which is achieved using a material of a thickness comparable with conventional therms formed containers.

Such containers as described above are extremely suitable for containing carbonated beverages which do not require to be pasteurised, but even considering containers of said material which are filled and sealed, and subsequently pasteurised, the heat resistance of the thermoformed containers may be increased by partially crystallising the polyester, which is relatively amorphous, by thermofonning the relatively amorphous sheet in a tool heated by oil or similar means to a temperature between 140"C and 180'C.

The distortion temperature of the containers produced in this way is increased from about 75'C to higher than 200 C giving rise to the possibility of pasteurising and sterilising liquids within the crystallised containers.

Preferably, the container is generally frusto-conical and has a top diameter to depth ratio in the range of 4.8 to 6.8 inclusive.

Additionally, the container has a denesting ring formed at the top end thereof, and the de-nesting ring being of such a height, related to the half cone angle of the container and the thickness of the material, so that the container can be nested one within another before being filled, and can be separated mechanically and accurately.

The container although it has a top flange enabling it to be closed by a metal cap rim rolled thereto, be closed by means of a plastic cap, such as any one of the those disclosed in our British Patent Specification No.

1,477,828, which may be crimped and/or sealed to the container rim.

In the thermoforming of the container, the sheet may be clamped in an annular region surrounding and concentric with a mould cavity and said annular region preferably has an inner diameter which is at least I times the top diameter of the mould cavity and preferably is in the range of 1 + to 2 times said top diameter of the mould cavity.

Creep tests with containers containing carbonated orange drink of carbonation 2.5 volumes by storage at a temperature of 30'C have shown that the containers did not creep objectionably over a period of at least two months. Similar tests at 35'C have shown that there will be no objectionable creep over a period of 48 hours. As regards burst strength capability increasing the internal pressure by injecting air under pressure at ambient temperature has shown that the container can withstand a pressure of 11 > 120 PSI before bursting and the lid blows off rather than the container rupturing.

Because of the advantage outlined above that the containers do not fracture in the rim rolling sealing operation, a wider tolerance can be allowed for in terms of the thickness variation of the rim at the top of the container which is rim rolled with the metal lid. Because of the fact that the material creeps less, the design of the base may be simplified.

By way of example, there is shown in the accompanying drawings a circular-sectioned container according to one embodiment of the invention. It will be appreciated that the container is constructed from high viscosity high molecular weight polyester material of average molecular weight in the range 37,000 to 55,000, and in this example is preferably polyethylene terephthalate. The drawings illustrate one constructional form of container suitable for holding carbonated beverage, especially a carbonated beverage such as a soft drink which does not require to be pasteurised.

In the drawings: Fig. 1 is a side elevation of a container thermoformed from extruded plastics sheet material of the nature described above; Fig. 2 is a perspective view of the container shown in Fig. 1 from the underneath; Fig. 3 is a plan view of the container shown in Figs. 1 and 2; Fig. 4 is a sectional elevation of the base and top of the container shown in Figs. 1, 2 and 3 and is shown to an enlarged scale; Figs. 5, 6 and 7 are views similar to Figs. 1, 2 and 3 of the container shown in Figs. 1, 2 and 3 after the top is sealed by means of a metal lid; and Figs. 8 and 9 respectively show two different stages in the process of attachment of the metal lids to the container top edge.

Referring to the drawings the container shown in Figs. 1, 2 and 3 is thermoformed using conventional techniques from extruded sheet material of Polyethylene Terephthalate, except that the sheet is clamped in a circular region of diameter greater than the top diameter of the container, and preferably I i to 2 times the diameter of the container in order that the container will be provided with a rim of material suitable for rim-rolling with the sealing lid. The container may be formed in the region within the clamped portion, by deep drawing, by air pressure moulding, or a combination of these techniques with or without plug assist. The container comprises essentially a frusto-conical wall 10 having at the top thereof a denesting ring 12 and at the top extremity an attachment flange 14 which is outwardly turned. The base region 16 of the container is formed so as to have six downwardly extend ing feet 18 which are petal shaped as shown in the plan view of Fig. 3, and as shown in Fig. 4 these feet 18 essentially project from a part spherical base 20. The feet 18 can either be considered as projecting from the portion 20, or the feet 18 can be considered as separated by curved straps leading to a central region 22. It is to be mentioned that in fact the central region of the curved strap is thicker than the remainder; it is also thicker than the wall of the container. This arises because said central portion is not distended during the thermoforming of the container and also because the central portion strikes a relatively cold portion at the bottom of the mould cavity.In any event, the construction illustrated is designed to resist eversion of the base to such an extent that the region 22 projects downwardly further than the areas of the feet 18 on which the container is adapted to stand. The base can of course be constructed in any other manner with this objective in view, but it is desirable that the base has certain design characteristics from the strength point of view, because the container is specifically for holding carbonated beverage and will be subjected to an internal pressure in use before the contents of the container are consumed.

Figs. 5, 6 and 7 show the container of Figs.

1, 2 and 3 after sealing of the top thereof by means of a metal lid 24 of conventional construction and having a conventionally arranged ring pull device 26, the pulling of which removes the pear shaped portion 28 and permits access to the container interior.

Such metal lids 24 with device 26 and 28 are well known.

It will be appreciated of course that the container is filled with the carbonated beverage before the lid 24 is applied to the top of the container. Conventionally, when such beverages are charged into containers, they are in chilled condition, and sealing takes place as soon as possible after filling in order to maintain the carbonating gas in solution in the beverage. However, when the package comprising the container, its contents and the sealing lid are in transit or storage before consumption of the container contents, the contents will increase in temperature to ambient with a consequent increase in the internal pressure. The level of this internal pressure will depend upon the temperature of the environment in which the package is located, but for the United Kingdom, the containers should be capable of withstanding pressure up to 110/120 p.s.i.We have achieved satisfactory resulsts using containers of the polyester material described of a thickness of 0.055", filled with carbonated organge drink carbonation of 2.5, volumes and sealed with a metal lid. Moreover, such containers have good gas barrier properties to such extent that little carbonation was lost over a 6 months storage period.

The metal lid 24 has a flange 30 as shown in Fig. 8 when it is formed, and the flange 30 is rim rolled with the flange 14 from the position shown in Fig. 8 to the position shown in Fig. 9 in order to complete the seal between the metal lid and the container. The flange 30 as shown in Fig. 8 as contacting the flange 14 directly but it may be desirable to put a sealing washer between the two flanges before they are rim rolled together, and it may also be desirable to pinch the rolled flanges by suitable means as indicated by the arrows X in Fig. 9.

WHAT WE CLAIM IS: 1. A method of producing a circularsectioned open-topped container for holding carbonated beverage, wherein an extruded sheet of high molecular weight, high viscosity polyester material of average molecular weight in the range 37,000 to 55,000 is thermoformed into a circular-sectioned container having an outwardly turned rim at the container top edge to enable the container to be sealed by rim rolling the rim and the edge of a metal lid together, and wherein in the forming of the container its base is shaped so as to provide a means enabling the container to be free standing, and also so as to resist distention of the base due to internal pressure when the container is filled with carbonated beverage and sealed.

2. A method of producing a circularsectioned, open-topped container for holding carbonated beverages, substantially as hereinbefore described with reference to the accompanying drawings.

3. A container when produced according to the method of Claim 1 or Claim 2.

4. A package comprising a container according to Claim 3 and a metal lid as seamed to the top flange of the container.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. ing feet 18 which are petal shaped as shown in the plan view of Fig. 3, and as shown in Fig. 4 these feet 18 essentially project from a part spherical base 20. The feet 18 can either be considered as projecting from the portion 20, or the feet 18 can be considered as separated by curved straps leading to a central region 22. It is to be mentioned that in fact the central region of the curved strap is thicker than the remainder; it is also thicker than the wall of the container. This arises because said central portion is not distended during the thermoforming of the container and also because the central portion strikes a relatively cold portion at the bottom of the mould cavity.In any event, the construction illustrated is designed to resist eversion of the base to such an extent that the region 22 projects downwardly further than the areas of the feet 18 on which the container is adapted to stand. The base can of course be constructed in any other manner with this objective in view, but it is desirable that the base has certain design characteristics from the strength point of view, because the container is specifically for holding carbonated beverage and will be subjected to an internal pressure in use before the contents of the container are consumed. Figs. 5, 6 and 7 show the container of Figs. 1, 2 and 3 after sealing of the top thereof by means of a metal lid 24 of conventional construction and having a conventionally arranged ring pull device 26, the pulling of which removes the pear shaped portion 28 and permits access to the container interior. Such metal lids 24 with device 26 and 28 are well known. It will be appreciated of course that the container is filled with the carbonated beverage before the lid 24 is applied to the top of the container. Conventionally, when such beverages are charged into containers, they are in chilled condition, and sealing takes place as soon as possible after filling in order to maintain the carbonating gas in solution in the beverage. However, when the package comprising the container, its contents and the sealing lid are in transit or storage before consumption of the container contents, the contents will increase in temperature to ambient with a consequent increase in the internal pressure. The level of this internal pressure will depend upon the temperature of the environment in which the package is located, but for the United Kingdom, the containers should be capable of withstanding pressure up to 110/120 p.s.i.We have achieved satisfactory resulsts using containers of the polyester material described of a thickness of 0.055", filled with carbonated organge drink carbonation of 2.5, volumes and sealed with a metal lid. Moreover, such containers have good gas barrier properties to such extent that little carbonation was lost over a 6 months storage period. The metal lid 24 has a flange 30 as shown in Fig. 8 when it is formed, and the flange 30 is rim rolled with the flange 14 from the position shown in Fig. 8 to the position shown in Fig. 9 in order to complete the seal between the metal lid and the container. The flange 30 as shown in Fig. 8 as contacting the flange 14 directly but it may be desirable to put a sealing washer between the two flanges before they are rim rolled together, and it may also be desirable to pinch the rolled flanges by suitable means as indicated by the arrows X in Fig. 9. WHAT WE CLAIM IS:

1. A method of producing a circularsectioned open-topped container for holding carbonated beverage, wherein an extruded sheet of high molecular weight, high viscosity polyester material of average molecular weight in the range 37,000 to 55,000 is thermoformed into a circular-sectioned container having an outwardly turned rim at the container top edge to enable the container to be sealed by rim rolling the rim and the edge of a metal lid together, and wherein in the forming of the container its base is shaped so as to provide a means enabling the container to be free standing, and also so as to resist distention of the base due to internal pressure when the container is filled with carbonated beverage and sealed.

2. A method of producing a circularsectioned, open-topped container for holding carbonated beverages, substantially as hereinbefore described with reference to the accompanying drawings.

3. A container when produced according to the method of Claim 1 or Claim 2.

4. A package comprising a container according to Claim 3 and a metal lid as seamed to the top flange of the container.