GB2203417A

GB2203417A - Filling containers

Info

Publication number: GB2203417A
Application number: GB08808495A
Authority: GB
Inventors: Nicholas Bernard Fitzpatrick; John Nicholas Stefa Kuzniarski
Original assignee: BOC Group Ltd
Current assignee: BOC Group Ltd
Priority date: 1987-04-16
Filing date: 1988-04-11
Publication date: 1988-10-19
Anticipated expiration: 2008-04-11
Also published as: IE881143L; ZA882295B; GB8808495D0; AU606144B2; IE63384B1; AU1453288A; CA1320934C; GB2203417B; GB8709281D0

Abstract

In a method of charging a flexible container such as a can or plastics bottle with non-carbonated liquid, inert gas comprising argon is dissolved in the liquid. A bowl filler to the head space of which nitrogen or argon is supplied may be used. A closure is then fitted gas-tight to the container. The concentration of dissolved gas in the liquid and the volume occupied by the head space of the charged container are so selected that on equilibration there is a super-atmospheric gas pressure in the head space of the container. The method enables thin-walled cans to be employed.

Description

GAS-DISSOLVING METHOD This invention relates to a gas-dissolving method which is employed in charging a flexible container with liquid.

In the canning and bottling industries there has been a trend in recent years to substitute containers having flexible walls for the traditional rigid steel can and glass bottle, when bottling or canning an artificially carbonated beverage. The pressure of the carbon dioxide in the head space of the sealed container is sufficient and essential in such instances to prevent externally applied pressure deforming the bottle or can during normal handling.

More recently, attempts have been made to extend the range of uses of flexible cans by employing them as containers for non-carbonated beverages. In order to create in the can an internal pressure sufficient to prevent or resist permanent deformation during routine handling and stacking, attempts have been made to introduce a small volume of liquid nitrogen into the head space of the can immediately before the can has its lid fitted and joined thereto. The e liquid nitrogen on vaporisation undergoes a very substantial increase in volume and is able to create a super-atmospheric pressure within the can. Since, in typical industrial practice, a canning line is capable of fitting lids to several hundred cans per minute, it is necessary for each one of these cans to be charged with a drop of liquid nitrogen.Difficulties arise in dispensing drops of uniform size with the result that the internal pressure in the cans tend to vary considerably one from another. Some cans tend thus to be under-pressurised with the result that they are readily deformed permanently during routine handling while other cans are over-pressurised with the result that the internal pressures causes deformation. Notwithstanding the existence in the state of the art of several different liquid nitrogen dispensing methods for this purpose, no satisfactory solution to the problem of obtaining the dispensing of drops of uniform size has yet been achieved.

In US Patent Specification 4 347 695 there is disclosed a method of bottling or canning a beverage which is intended to be used for non-carbonated beverages. Prior to its introduction into the bottle or can, the beverage has dissolved in it sufficient "inert gas" to strip dissolved oxygen from the beverage and then purge air from the head space of the container. Sufficient gas is retained in the beverage to exert -a super-atmospheric pressure internally of the container after it is sealed. The only inert gas disclosed in the Patent Specification for such use is nitrogen. We have discovered that when nitrogen is used in canning to create a super-atmospheric pressure within a thin-walled can it is not possible under conventional operating conditions to obtain internal pressures that are consistently adequate.In particular, the kind of gas dissolver employed in a conventional canning line is normally designed to be operated at a pressure below 90 psig and some such gas dissolvers do not tolerate a pressure of more than 75 psig. Moreover, while conventional bowl fillers are designed to operate up to a maximum pressure of 90 psig, the highest pressure that a thin-walled can is designed to withstand, it is preferable to operate the fillers at pressures well below 90 psig so as to reduce wear and the resultant need for frequent maintenance. It is these factors which in practice make it difficult to obtain adequate internal can pressures when operating the method disclosed in US Patent Specification 4 347 695 at normal ambient temperatures.An improvement may be obtained by operating at below ambient temperature but this practice requires refrigeration to be provided and therefore adds to the cost of the canning operation. Although the above discussion of US Patent Specification 4 347 695 has been made with regard to canning, similar problems arise in charging plastic bottles with liquid, particularly if the bottle has a capacity of 1 litre or less, and especially when the bottle has a capacity of a half a litre or less.

UK Patent Specification 2 134 496 A discloses a method in which a non-carbonated drink is canned in a 'soft' thin-walled can, for example an aluminium can, and a suitable internal pressure is created in the can be pre-dissolving nitrogen and a small amount of carbon dioxide in the liquid, and then allowing nitrogen and carbon dioxide to come out of solution in the sealed can. It is disclosed that the weight ratio of carbon dioxide to the drink is a predetermined value which is not more than 15 : 10,000. However, even in such small quantities, carbon dioxide, which is a polar, acidic gas, can have an appreciable effect on the quality or taste of the beverage.

Accordingly, we believe that the use of carbon dioxide in addition to nitrogen in order to create an internal pressure in a can or bottle is an unacceptable practice when the liquid is intended to be still or non-carbonated.

It is an aim of the present invention to provide a method of charging a flexible container with non-carbonated liquid which enables an adequate pressure to be created internally of the container without the need to charge the container to such a level that the size of the head space becomes unacceptably small.

According to the present invention there is provided a method of charging a flexible container with non-carbonated liquid, comprising dissolving an inert gas comprising argon in the liquid at an elevated pressure, charging the container with the liquid in which said gas has been dissolved, and fitting a closure gas-tight to the container, wherein the concentration of dissolved gas in the liquid and the volume occupied by the head space of the charged container are so selected that on equilibriation there is a super-atmospheric gas pressure in the head space of the container (when measured at ambient temperature).

By the term 'inert gas' as used herein is meant a gas or gas mixture which is tasteless, colourless and odourless, and does not react chemically with the said liquid.

The inert gas comprising argon is preferably pure argon. If pure argon is not used, the gas preferably contains at least 50% by volume of argon and typically at least 90% by volume of argon. It is possible to mix with the argon one or more other inert gases, for example, krypton or xenon.

The method according to the present invention is particularly useful in the canning of non-carbonated beverages and we believe that for the first time it provides a practicable method of such canning in thin-walled cans which does not require a change in the conventional practice in the art so far as the proportion of the container is employed as head space is required while enabling the inert gas comprising argon to be dissolved in the liquid at ambient temperature and the containers to be filled at ambient temperature. Dissolution of an inert gas comprising argon in the liquid under pressure will cause an aliquot of such gas to be dissolved.The can is then charged with such liquid under pressure, typically using a conventional bowl filler and when the can is withdrawn from the bowl filler the pressure on the liquid is released thereby causing dissolved gas to start to come out of solution. On sealing the can, the gas will continue to come out of solution and enter the head space until an equilibrium is reached between the gas in the head space and the dissolved gas in the liquid phase. The pressure at equilibrium at a given temperature increases with decreasing volume of head space. The method according to the present invention enables an adequate internal pressure (at least 15 psig at 160C), which renders the can resilient to normal pressures exerted on it during routine handling, without charging the can to such a level that the proportion of the total internal volume of the sealed can occupied by the gas space at the head of the can (i.e. the head space) is less than that conventionally employed for a can of given aspect ratio (i.e. the ratio of its height to diameter). Typically, the proportion of the volume of the can occupied by the head space is at least 5% of the tOtal: internal volume of the can.

The e method according to the present invention may also be used to charge plastic bottles with non-carbonated liquid. in particular, it enables bottles containing non-carbonated liquids to be formed of the materials and with the wall thicknesses currently employed in the bottling in plastic bottles of carbonated beverages.

Preferably sufficient inert gas comprising argon is dissolved in the liquid to create in the sealed container an equilibrium pressure in the range of 15 to 20 psig at 160C, though if desired higher internal pressures may be created.

The method according to the invention may be used to can or bottle a wide range of different non-carbonated drinks. It may for example be used to can or bottle fruit juices; still wines or other non-carbonated alcoholic beverages; soup; milk and other pourable dairy products; and liquids, e.g. beverages, such as naturally fermented ales, which have relatively low levels of carbonation inadequate on their own to generate the necessary internal pressures.

The method according to the invention may also be used to can foodstuffs in a liquid, syrup or sauce, in which instance the argon is dissolved in the liquid syrup, juice or sauce.

The method according to the present invention may also be employed in charging with liquid containers that, like cans, are generally right-cylindrical in form but which are formed of other flexible material than metal.

The pressure under which the gas is dissolved in the liquid is preferably at least equal to that under which the container is charged with the liquid. Preferably, a small excess pressure is employed so as to enable transfer of the liquid from a gas dissolving vessel to the filler to be effected by pressure transfer without the need to employ a mechanical pump intermediate the dissolver and the filler.

The liquid is preferably saturated with the inert gas comprising argon at the chosen pressure. Any conventional means of dissolving the gas in the liquid may be employed. For example, the dissolver may comprise a pressure tank adapted to be charged with the liquid to a chosen level and being fitted with means for introducing gas into the liquid, the arrangement being such that undissolved gas enters the head space of the tank. The tank may be provided with one or more diffusers at or near its bottom which are placed in communication with a source under pressure of the inert gas comprising argon so as to enable the gas to be introduced into the liquid in the form of fine bubbles.

The pressure under which the container is filled in accordance with the invention is typically not greater than that which would cause permanent deformation of the container. In the instance of thin-walled cans currently in use in the canning industry, this pressure should not be in excess of 90 psig. Preferably, the filling pressure is in the range 45 to 75 psig, and hence the pressure under which the inert gas comprising argon is dissolved is in this range.

Typically, a conventional bowl filler is employed to charge the cans or bottles with liquid. The e gas that is dissolved in the liquid is preferably supplied directly to the ullage space of the bowl filler.

Surprisingly, we have found it possible to use nitrogen instead of inert gas comprising argon for this purpose while still obtaining adequate internal pressures, Typically, once a can or bottle has been charged with liquid under pressure, it is released from the filling apparatus and is transferred to a sealing station. This procedure involves release of the pressure exerted on the liquid in the filler and thus gas starts to come out of the solution in the liquid in the can or bottle. In the example of canning, we prefer to blow or direct into the head space of the can inert gas comprising argon or, more preferably, nitrogen immediately prior to the sealing of the lid to the top of the can (which operation is preferably performed by a conventional seamer).

It is advantageous to use nitrogen rather than argon for performing such a head space purge. On a qualitative basis, this can be understood by considering the equilibrium of the gas between the liquid phase and the gas phase in the can once it has been sealed.

Suppose, immediately upon sealing of the can the composition of the gas in the head space is 100% argon at a pressure of 1 atmosphere absolute, Suppose also that at the filler the liquid is saturated with argon at a pressure of atmospheres. The argon thus comes out of the solution and continues to do so until equilibrium is established between the partial pressure of argon in the gas phase and the partial pressure of argon in the liquid phase. Suppose now that at sealing of the can, the atmosphere in the head space consists of nitrogen at 1 atmosphere. In this instance there is no partial pressure of argon in the head space immediately upon sealing.

Accordingly, more argon needs to come out of the solution from the liquid and enter the head space of the can before equilibrium is established. Accordingly, the use of nitrogen instead of argon to purge the head space of the can immediately prior to seaming enables a higher internal pressure to be achieved at equilibrium.

The method according to the present invention will now be described in the following examples with reference to the accompanying drawing which is a schematic diagram of a canning plant.

Gas was passed from a pipeline 4 into a volume of water in a gas dissolver 2 of conventional kind and the water saturated with the gas at ambient temperature. The water containing the dissolved gas was then passed from the dissolver 2 via a pipeline 8 to a bowl filler 6 having a single head and being adapted for laboratory use. A pipeline 10 was provided for supplying gas to the headspace of the bowl filler 6. Cans each nominally of 440 ml capacity, were filled one at a time with the water at ambient temperature. In each experiment sufficient water was saturated with gas to enable four cans to be filled. Once filled, each can was immediately transferred manually to a conventional seamer 12 adapted for laboratory use.

Gas was supplied from pipeline 14 across the mouth of each can at ambient temperature before fitting and 'seaming' a lid to each respective can (this practice being known as 'under cover gassing').

The cans were allowed to stand for 24 hours so that the pressure internally thereof would be able to equilibriate and then the internal pressure of the can, and the temperature and volume of the water therein were measured. The results obtained are set out below in Tables 1 and 2.

TABLE 1 Gas Gas blown Gas pressure in Gas across can pressure in Gas bowl supplied mouth (at Example dissolver 2 supplied to filler 6/ to bowl 10 in water Number psig dissolver 2 psig filler gauge) Number psig dissolver 2 psig filler gauge) 1 120 N2 60 N2 N2 2 60 Ar 60 Ar Ar 3 90 Ar 90 Ar Ar 4 60 Ar 60 N2 N2 5 90 Ar 90 N2 N2 6 120 Ar 90 N2 N2 7 60 Ar 60 Ar N2 8 90 Ar 90 Ar N2 9 120 Ar 90 Ar N2 10 75 Ar 75 N2 N2 TABLE 2 Equilibriated Temperature of Volume of water Example internal can can controls in can Number psig C cm3 Number psig OC cm3 1 (a) 12 ambient 435 (b) 12 ambient 435 (c) 12 ambient 435 2 (a) 18 15.9 435 (b) -19 15.9 440 (c) 19 15.9 440 (d) 18.5 15.9 438 3 (a) 24 15.8 440 (b) 24 15.8 440 (c) 24 15.8 438 (d) 24 15.8 440 4 (a) 17.5 21 440 (b) 16.5 21 430 (c) 16 21 430 (d) 16.5 21 430 5 (a) 22 20 435 (b) 24.5 20 440 (c) 24 20 440 (d) 24 20 440 Equilibriated Temperature of Volume of water Example internal can can controls in can Number psig C cm3 Number psig OC cm3 6 (a) 25 15.8 440 (b) 25 15.8 440 (c) 25 15.8 440 (d) 25 15.8 440 7 (a) 16 19 435 (b) 16 19 435 (c) 16 19 435 (d) 16 19 435 8 (a) 26 19 435 (b) 26 19 435 (c) 26 19 435 (d) 26 19 435.

9 (a) 26 19 435 (b) 28 19 435 (c) 26. 19 435 (d) 30 19 440 10(a) 18 16.8 435 (b) 18 16.8 435 (c) 16 16.8 435 (d) 20 16.8 434

Claims

CLAIMS 1. A method of charging a flexible container with non-carbonated liquid, comprising dissolving an inert gas comprising argon in the liquid at an elevated pressure, charging the container with the liquid in which said gas has been dissolved, and fitting a closure gas-tight to the container, wherein the concentration of dissolved gas in the liquid and the volume occupied by the head space of the charged container are so selected that on equilibriation there is a super-atmospheric gas pressure in the head space of the container (when measured at ambient temperature).
2. A method as claimed in claim 1, in which the inert gas consists of argon.
3. A method as claimed in claim 1 or claim 2, in which the dissolving of said inert gas comprising argon and the charging of the container. are both performed at ambient temperature.
4. A method as claimed in any one of the preceding claims, in which the inert gas comprising argon is dissolved in the liquid under a pressure in the range 45 to 75 psig.
5. A method as claimed in any one of the preceding claims, in which the container is charged under a gas pressure in the range 45 to 75 psig.
6. A method as claimed in any one of the preceding claims, in which a bowl filler is operated in order to charge the container with the liquid in which said gas has been dissolved.
7. A method as claimed in claim 6, in which inert gas comprising argon is supplied to the head space of the bowl filler.
8. A method as claimed in claim 6, in which nitrogen is supplied to the head space of the bowl filler.
9. A method as claimed in any one of the preceding claims in which the said super-atmospheric gas pressure is at least 15 psig (when measured at 160C).
10. A method as claimed in claim 9, in which the said super-atmospheric gas pressure is in the range 15 to 20 psig 0 (when measured at 16 C).
11. A method as claimed in claim 9, in which the said super-atmospheric gas pressure is greater than 20 psig.
12. A method as claimed in any one of the preceding claims, in which the container is a can.
13. A method as claimed in claim 12, additionally including the step of purging the head space of the charged can with inert gas comprising argon prior to closing and sealing the can.
14. A method as claimed in claim 12, additionally including the step of purging the head space of the charged can with nitrogen prior to closing and sealing the can.
15. A method as claimed in claim 13 or claim 14, in which the can is closed and sealed at ambient temperature.
16. A method as claimed in any one of claims 12 to 15, wherein the head space of the charged can occupies at least 5% of the total internal volume of the can.
17. A method as claimed in any one of claims 1 to 11, in which the container is a plastics bottle.
18. A method as claimed in any one of the preceding claims, in which the liquid is a still beverage.
19. A method as claimed in any one of the preceding claims, in which the liquid is saturated with said inert gas comprising argon prior to being introduced into the container.
20. A method of canning, in which the operating pressures and the gas or gases employed are substantially as set out in any one of Examples 2 to 10 in Table 1.
21. A flexible container when charged with liquid by a method as claimed in any one of the preceding claims.