CA1320934C - Gas dissolving method - Google Patents

Abstract

GAS DISSOLVING METHOD

In a method of charging a flexible container such as a can with non-carbonated liquid, inert gas comprising argon is dissolved in the liquid preferably using a bowl filler to the head space of which nitrogen or argon is supplied. 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

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GAS-DISSOLVING METHOD

This invention rQlates to a gas-dissolving method which is employed in charging a flexible container with liquid.

BACRGROUND OF THE INVENTION
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 ran and glass bottle, when bottling or canning an artificially carbonated be~erage. The pressure of the carbon dioxid~ in the head space of the sealed container is suffiaisnt 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 aninternal 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 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 he 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 , . .
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of several ~ifferent liq~i~ nit~ogen di~p~nsing methcds ~Qr this purpvse, no satisfa~tory solution to the problem of obtaining the dispensing of drops o uniform si2e has yet been achieved.

In US Patènt Specifi~tio~ 4 347 695 ~here is ~isclose~ ~ metho~ of bottling or canning a heverage which is in~ended to l~e use~ ~or non-carbon~te~ ~eve~ages. Prior to its introduction into the bottle or oan, the beverage has dissol.ved in it suf~icient "inert gas" to strip dissolved oxygen from the beverage ~nd ~hen purge air from the head space of the container. Sufficient gas is retained in the beverage to exert a super-atmosphçric pressure internally of tne container af~er i~ is sealed. The only inert gas disc10sed in the Patent Specification for su~h ~se is nitrogen. ~e have dis~overe~
that when ni~ro~en is used in canning to cre~te a super-a~mospheric pressure within a thin-wall~d can it is not pos~ible ~nder ~onventional oper~ting conditions t~ obtain internal pressures that are ~onsistently ade~uate~ In particular, the kind of gas dissolver employed in a conventional ~anning line is normally designed t~ be operated a~ a pressure below 90 psig and some such ~as dissolvers do not tolerate a pressure of ~ore th~n 7S psis. Mo~eover, while conv~ntiona~ b~wl fillers a~e desi~ned to operate up to a maximum pressure of 90 psig, the highest pressure that a thin-w~lled can i5 ~esigned to withstand, it is prefer~ble ~o operate the fille~s at pressures well below 90 psi~ so as to feduce wea~ and the resultant nee~ fo~ frequent maintena~e. I~ is th~se factors which in p~actice make it diEfic~lt to obtain ~dequ~te internal can pressures when operating the method di~closed in US Patent 5pecification 4 347 695 ~t norm~l am~ient te~per~t~re~. An i~provement m~y ~e obtain~d by operatiny at bel~w ambient ~emperature but this practice r~uires refri~ation to be provided and th~refore adds to the cost o the canning ope~ation~ Although ~he ~bove discussion of US P~tent Sp~cification ~ 347 ~95 has been m~de ~i~h regard to canning, similar problems ~rise in ch~rging plasti~ bottles with liquid, particularly if the bv~le has a capacity o 1 lit~e ~ less, and especially when the b~ttle has a GApacity o~ a hal~ a litre ~e les~

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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 by 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 o~
carbon dioxide to the drink is a predetermined value which is not more than 15 : 10,000. However, even in such small ~uantities, 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 wheh the liquid is intended to be still or non-carbonated.

SUMMARY OF THE INVENTION

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 pressur~, charging the container Witll 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 Yolume occupied by the head space of the charged container are so selected that an equilibration there is a super-atmospheric gas pressure in the head space of the container (when measured at ambient temperature).

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~ /8711 1320934 By the term 'iner~ ga~ as u8el~ h~rein is meant a g~s or ~a~ mixtu~e which is ta~teless, colourless and odourles~, and does r~ot re~çt ~heml~ally with ~he aid li~uid.

DE~AILED DE~}~IPIIVN V~' '1~; INV~;N'l'l(JN
___ ~e inert gas com~risi~ argon is preer~bly pure argon. I p~re a~on i9 not U~ the ga& preferably contaln~ a~ lea~t 509~ by volune of ~gon ~nd typi~ally at lea~t 904 by vol~ne o~ ~rgon.
po~sible ~o mix wi~h the argorl One or more o~h~r inert gases, for exalr~le, kryp'con or xenon.

e~
T~e accs~panying drawing illu~'crates ~ cor~ing ~o th~
invention and i3 a schematl~ ~lag~m of a c~nlng plant. ~e m~
accoxdlT~ to the pre~nt lnven~ion i~ ~L~tlc~l~rly u eful in the ~annlng of non~arbonated b~ve age~ ~nd we beli~ve Sh~t for the first ~ime i~ pr~vide~ a pr~ctic~ble method of Such canning in thln-walled can3 which does not l ~ulr~ a ch~nge in ~e conventional practlce ln ~e a~ ~o ~ar a~ ~ne proportclon ot ~e ~om mer 1~ employed a~ head 3pace i~ re~uir~d while enablin~ the ir~rt ga~ co~ ing argon to be di5solved ln th~ uid at a~ient te~r~tu~e and the container~ to be ~illed at am~nt ~e~er~ture. Di~olution of an inert ga~
comp~islr~g a~on in l:he liquid ur~r pr~ure will cau~e an ~liquot o ~h 9A~ wl~d ~h4 ran 1~ then ~h~qr~Pf~ wit.h F;l~h llquld un~er pre~ure, typically u~ing ~ conv*nti~ owl filler, and ~n ~ wi~rl f~ wl ~iLL~ t.hk pe~ re on the llq~id 1~ r~lea~ed 'chQ~eby causlnq di~lved gas to st~r~ ~o c~re out of ~olu~ion~ On 8eallng ~h* can, the ~a~ wlll continue to con~e out 0~ 981lltiUrl cu~ hC hc~d ~p~ao ~ntil 3n 8~uilibrium i~
rea~ed b~een ~he g~ in the he~d 3pace ar~ ~he dissolved ~as in the li~sid pha~e. Ih~ pre ~ure at equilibrlum at a given t~mperature ~ rea6e3 with de~reasin~ volun~e of head spaceO Ihe me~od ~ording to ~he p e~nt invention enable~ an adequ~t~ internal pre~ure. ~at .

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least 15 psig at 16C), 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 method according to the present invention may also be u~ed 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 og 15 to 20 pslg at 16C, 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 inadPquate 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.

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- 5a 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.

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The pres~ure und~r which the ga~ 1~ dissolved in ~he li~uid ls preferably at least equal to that under which th~ container i5 charged with the liquid. Preferably, a ~m~11 excess press~re i8 employed 80 a~ to enable ~ransfer of the liquid ~rom a g~s dis501vlng vessel to the iller to be ef~e~ed by pres~ure ~r~n~er without ~he t~ y A Meeh~l9el~ ho dl~ol1J~r 2~1 thQ
filler.

The liquid i~ preferably ~turated with the inert gas comprl~ing a~gon a~ the ~hosen p~e~æUre. Any co~ven~ional mean~ o di~solving th~ 9A# ln ~h~ liquld may he ~ y~. Fhr Px~mpl~l th~ di~olYe~
may ~o~prl~e a pre~sure tan~ ad~pted to be ~h~r~ed with the liquid to a ahosen l~v~l and being fitt0d with mean~ for in~r~ducing ga8 into ~hc liquld, ~ho arr~gomQ~ in~ ~ch that u~dl~901~d ga~ en~er~
~h~ head cpac~ o the tanX~ qhe tank may ~e prsvided wlth on~ or ~e dl~fuser~ ~t or n~a~ its bo~om which are pl~ced in coq~r~ ;ion with ~ ~ource unde~ pre~ure of the lner~ ga~
cwr~ri~ argon ~o ~ ~o ena~le ~h~ ga~ to be in~roduced lnto the li~uid in th~ ~orm of ~ine bubbles.

qhe pressure un~er which the ~ont~inPr i~ ~iLled ln accordance with the invention 1~ ally not graaSer ~an ~hat whlch would cau~e perman~nt defor~tion o~ ~he cont~ine~. In the instan~e of thinowall~d ~an~ ~ur~ently in use ~n thç c~nning indu~t~y, thi~
pre~sure ~hould no~ ~2 in exce~3 of ~0 psig. Preferably, th~ illing p~e~ure i~ in ~h~ range 45 to 75 psig, ~nd hen~e the pre~s~re under ~hioh thE iner~ ~8 comprising ~r~on i~ ~i3solved ~8 in thij range.

Typical~y, a conven~ion~l bowl ille~ i~ employed to ch~rg~ the cans ~L LuLLl~ w~ . Ih~ h~t ia ~ls~ol~cd in ~ho liquid ic pr~erably 3upplied dir~ o the ullage spaCe of the bowl ~lller.
Surp~i~in~ly, we ha~ ou~d it possl~le to u~e ni~ro~en ~n~aad o lner~ g~ pri~ing argon or thi~ purpo~e while still ob~aining Adequate in~nal pre6sur~s, ~ 32033~

Typically, once a can or bottle has been charged with liquid under pressure, it is released ~rom 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 betwe~n the partial pressure of argon in the gas phase and the partial pressura 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 eguilibrium is established. Accordingly, the use of nitrogen instead of argon to purge the head space of the can immediately prior to seaming enables a high internal pressure to be achieved at equilibrium.

Referring specifically to the drawing, yas was passed from a pipeline 4 into a volume of water in a gas dissolver 2 of ~2~3~
- 7a -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 ~,,r ~:'`

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adapted or labora~ory use. A plp~lir,e lO was provided ~or supplying ~a~ to the he~sp~ce of the bo~l filler 6. Cans each nomin~1.1y ~f 44Q ~ apacity, were filled one at a t~lTe with the water at anbient tem,erature. In ~aoh ex~ar~n~; ~uf~icl~nt water wa~ ~atur~tcd wlth gas ~o enable fou~ c~ns to be fllled. O~e filled, ea~h carl was i~nediately ~ran~ferred m~n~aliy 'C4 a conv~ntio~al ~eam~r 12 ad~p~Rd fo~ oratory ll~e.

Gas qa~ ~upplied frorn piFeline l~ across the tnouth of each can at ~ient te~ al;ure before ~it~ing and 'æeaming' a lid to each respectiv@ can ~thi~ practice being known as 'under c~ver g~sln~').
~o ~nc ~r~ ~llow~ f~r ~ hm~rFi ~ that the ~gs~e int~rnally thereof woUld be able ~co equilibrl~e and ~en the lr,ternal pre~u~e of the car" an~ te~nperature ~nd volum~ of the w~ter ~n~reln Were mea~urec~.. ~e ~ull;~ ..LJL~ s~t oul: kelow ~n Table 1 ar~l 2.

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Gas blown Gas ~8 GAS acros~ can p~e~ure in Ga5 pressure ln supplied mouth (~t EKa~ple dlssolver 2 ~upplled to bawl filler to bowl 10 in water ~ber p~ig dlssolvo~ 2 6/p~lq filler gauge) 120 N~ 60 N2 N2 2 60 Ar 60 ~ Ar 3 90 ~ 90 Ar Ar 4 60 A~ 60 N2 N2 Ar 90 N2 N~
6 120 A~ 90 N2 ~:2 7 60 Ar ~0 Ar N2 8 90 Ar ~0 Ar N2 9 120 Ar 90 Ar N2 Ar 7S N~ N2 ~/~i~8711 lO- ~32093~
TA~LE 2 E~uilibrl~ted Ibmperature o~ Volusne o~ water Exarnple ln~ c~ln con~r~l9in alm N~e~ p~ig C c~3 1 (a) 12 ambient 4~5 (b) 12 anJ~ t 435 (c) 12 an~lent 435 2 (a) 1~ 15, 9 43S
~) lg 15 . 9 4~0 (~) 19 15.9 ~0 td) lB.5 15.9 43~

3 la) 24 lS~ 0 (b) ~4 15 . 8 440 ) ~4 15. R 4313 (d) 24 15. ~ 440 (a) 17. 5 21 440 tb) lÇ . 5 21 430 lo) 16 ~ o (d) 16~ 5 21 43û

!~) ' 22 20 435 ~b) 24. 5 20 440 (~ 24 20 44~
(d) 24 20 440 ~ /871~
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E~uilibrlated ~mperature o~ V~ of water ~rrple ~y~ san control in ~an N~ p~ig ~C cm~

6 ~a) ~5 1~ . 8 4~0 (b) ~5 15. 8 441~
~c) 25 15 . 8 440 (d) 25 15. 8 440 7 (a) 16 19 435 (b) 16 1~ 435 tc~ 16 lg 43$
~d) 16 19 435 8 ~a) ~6 19 435 ~b) 26 19 435 6 lg 435 ~d) 26 lg 43S

g ~a) 2~ 19 435 ~ ~b) 2~ 19 435 ~5) Z!6 lS1 43S
(tq) ' 3~ 0 lO(a) 18 16.~ ~35 18 1~. ~ 435 ~) 16 16. ~ 435 ~d) 20 1~. 8 434

Claims (13)

1. A method of charging a flexible container with non-carbonated liquid, comprising dissolving an inert gas comprising argon in the liquid as superatmospheric pressure, passing a liquid containing said dissolved inert gas to a filler vessel, passing nitrogen or inert gas comprising argon into the head space of the vessel to maintain a superatmospheric pressure therein charging the container form the filler vessel with the liquid in which said inert gas comprising argon is 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 is so selected that an equilibration there is a superatmospheric gas pressure in the head space of the container (when measured at 16°C).

2. A method according to claim 1, in which the inert gas consists of argon.

3. A method according to claim 1, 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 according to claim 1, 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 according to claim 1, in which the container is charged under a gas pressure in the range 45 to 75 psig.

6. A method according to claim 1, 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 according to claim 1, in which inert gas comprising at least 50 per cent by volume of argon is supplied to the head space of the bowl filler.

8. A method according to claim 6, in which nitrogen is supplied to the head space of the bowl filler.

9. A method according to claim 1 in which the said superatmospheric gas pressure is at least 15 psig (when measured at 16°C).

10. A method according to claim 1, in which the said superatmospheric gas pressure is in the range 15 to 20 psig (when measured at 16°C).

11. A method according to claim 1, in which the said superatmospheric gas pressure is greater than 20 psig.

12. A method according to claim 1, in which the container is a can.

13. A method according to claim 1, in which the container is a plastics bottle.