CA1062671A - Method of packaging utilizing pressurized containers - Google Patents
Method of packaging utilizing pressurized containersInfo
- Publication number
- CA1062671A CA1062671A CA226,875A CA226875A CA1062671A CA 1062671 A CA1062671 A CA 1062671A CA 226875 A CA226875 A CA 226875A CA 1062671 A CA1062671 A CA 1062671A
- Authority
- CA
- Canada
- Prior art keywords
- container
- paneling
- gas
- room temperature
- psig
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE
Paneling of thin walled metal containers subjected to vacuum conditions after filling is minimized by pressurizing the container at pressures substantially above atmospheric pressure with an inert gas having low absorption in liquids.
By imposing an internal positive pressure in the container of about 5 to about 25 psig with a gas such as nitrogen, metal containers having wall thicknesses of 6 mils or less can be utilized in hot filling operations without encountering paneling after the sealed container and its contents have cooled to room temperature.
Paneling of thin walled metal containers subjected to vacuum conditions after filling is minimized by pressurizing the container at pressures substantially above atmospheric pressure with an inert gas having low absorption in liquids.
By imposing an internal positive pressure in the container of about 5 to about 25 psig with a gas such as nitrogen, metal containers having wall thicknesses of 6 mils or less can be utilized in hot filling operations without encountering paneling after the sealed container and its contents have cooled to room temperature.
Description
106~671 This invention relates to method of packaging and, more particularly, to a method of packaging with metal containers having a body wall thickness less than that conventionally used in the packaging industry.
In the manufacture of containers for use in the packing of a variety of food and non-food products in metal containers, it is desirable, from the standpoint of both economy and convenience, to employ metal plate as thin and as light weight as possible.
Presently, containers formed from metal plate having a thickness o-f 10-15 mils are conventionally used for packaging solid food products, oils and non-carbonated beverages. The major drawback to the extensive use of thinner lighter weight plate, e.g. plate having a thickness of 6 mils or less is that the conventional smooth surfaced cylindrical containers made therefrom do not ordinarily have sufficient wall strength to withstand the substantial vacuum created in the container after the product is packed therein and the container hermetically sealed. For example, food products such as non-carbonated beverages are packaged in metal containers or placed in the container while the product is still heated in order to prevent bacterial contamination. Motor oils are hot when placed in containers as the oil is heated to make it less viscous for filling. As either of these hot liquid products cools in the sealed container, the product is reduced in volume and an internal vacuum, in order of about minus 10 psig, is created in the container, i.e. the pressure inside the container after the .. .
packaged product has cooled to room temperature is about 10 psig less than the pressure outside the container. The result of this condition is a 10 psi external pressure on the container side-walls which tends to force or flex the sidewalls of the '~
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~062671 container inwardly and buckle them. This buckling of the side-walls is referred to in the art as "panellng". When this condi- -tion occurs, the container frequently assumes an undesirably distorted appearance and sometimes deforms to such an extent that it will not support another container that may be stacked on top of it.
In order to reinforce and strengthen the container body against paneling and to maintain its original shape, and yet avoid the use of heavy body plate, the art has devised a number of methods to prevent paneling. These methods however are not without disadvantages. For example, it is common practice in the manufacture of containers used in packaging hot food products to provide the container body with one or more circumferential beads. The use of such beading provides the necessary paneling resistance in containers made from thin light weight metal plate but has a detrimental effect upon the axial strength or resistance of the container to crushing under high container stacking conditions in storage. Because the circumferential beads reduce the axial strength of the container body, the use of metal plate of 10 mils thickness is still required to compensate for the loss in axial strength.
In accordance with the present invention, there is provided a method for the packaging a variety of heated products in containers having wall thicknesses of 6 mils or less wherein paneling of the container after sealing is prevented or sub-stantially retarded which method is accomplished by imposing ; within a hermetically sealed container a superatmospheric pressure in the order of about 5 to about 25 psig with an --inert gas having low absorption in liquids.
According to a broad aspect of the present invention there is provided a process for packaging articles in thin ~- 2 -, walled containers having improved resistance to paneling. The process comprises providing a container having sidewalls which undergo paneling when the container is filled with a product which undergoes a reduction in volume upon cooling. An inert gas forming material is metered into the filled container, -~
; the gas forming material having a coefficient of absorption of less than 0.02. The container is then hermetically sealed and the product packaged therein is allowed to cool and the gas to expand so that a superatmospheric internal pressure in the range of about 5 to about 25 psig is imposed at room temperature upon the sidewalls of the cooled container whereby paneling due to atmospheric pressure is substantially prevented.
By the practice of the present invention containers having a body wall thickness of 4 to 6 mils can be employed , .
for the packaging of hot fill products where 10 mil thickness plate is now presently required.
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The container bodies used in the packaging method of the present invention are preferably made of rigid, gas impermeable .; materials such as metals as steel or aluminum. Containers whose .~ body walls are fabricated from commercially available thermo-plastic resins such as polyethylene or polypropylene are not generally preferred in the practice of the present invention as '`
due~to the relative gas permeability of these materials as compared to metals ~the pressure originally induced in the sealed container '' may~be reduced during the time of storage by the escape of the 0 ~ pressuri~zing gas from the container which will thereafter render the container susceptible to paneling. ;
: It is essential to the practice of the present invention that the gas used to pressurize the container be inert to the ' contcnts~o~the container and~have low absorption in liquids. If th.e~gas is~not inert or has~high absorption in liquids such as do'es~C02, upon storage~, the~chemic:al reaction of the gas or the '.
ab ~ tion of the gas: by liquid;protuct will cause the total : ~ essure:~within tbe contsiner to drop and as a result, the sidewalls :~
of the~container will~panel~:due~to~atmospheric pressure in order to '.
,~ ~ 20~co~mpensate~for this~internal pressure drop.:~
.~ ~ '~ G~enerally~,~a~gas~having~an~absorption coefficient t~ ) , ~ at;~atmospheric~.pressure'~and~room~temperature (70F) of less than ;.
'0~02~is~sui~table fo:r use~in~the practice of the present invention.
'~` ~ itr ~ n-which is~ the pre~ferred inert gas for use in the practice '"
'of~thé p'résent; invention~has an ~ value of 0.01475.
In~pressurizing;~tho:~container,~the gas may be introduced o: ~ '.container~in~.any~convenient~-anner.~ For example, the . ~ gaseo~us~mat~rial~can:.~.~be:~charged as~a~gas into the vapor space of ' the~o ~ ner~throug~:a~holo in the~closure l~id of the container . ~ ~ ~using~a~press~re~syringe.~'Thereafter the~hole is sealed with a rubber p~lug~or~;spot~wélded to~hermetically seal the cdntainer.
Gases~which -ay liquify or solidify at low temperaturcs and '' ': - 3 -1~6Z67~
thereafter vaporize and expand at room temperature are pre-ferred because of their ease of handling. When such liquid gaseous materials are used, droplets of the liquid gaseous material are metered into the container onto the exposed surface of the packaged product and sealing of the container is carried out rapidly and soon as possible after the liquid gaseous material has been introduced into the container. Liquid nitrogen has been found to perform very satisfactorily under normal conditions and is an excellent example of a liquid gaseous material which is preferred in the practice of the present invention.
The containers used in the practice of the present invention can be formed from metal plate ranging in thickness from about 0.004 inches (4 mils) to about 0.006 inches (6 mils).
The container walls are preferably smooth surfaced and free of any structural reinforcement such as beading.
In packaging heated products in containers in accordance with the practice of the present invention, the heated product is first dispensed into the container and a gas producing material such as liquid nitrogen is metered into the product filled container, The container is then sealed with minimum delay to entrap the gas producing medium in the vapor space or headspace of the container and prevent any appreciable loss of gaseous material.
The amount of gas which is metered into the container ; 25 prior to hermetic sealing of the container is determined by the amount of vapor space remaining in the container after the heated product has cooled to room temperature and the internal pressure required after cooling. For example 0.071 grams of liquid nitrogen when vaporized at 70F exerts a pressure of 7 psig per cubic inch (cu. in.) of volume. The vapor space remaining in a container after a heated product has cooled can be readily ascertained.
For example, the vapor space remaining in a 48 ounce 404 (4 4/16") :. . . . ~ . - :, ~
diameter fruit drink container after filling at 90F is about 6.5 cu. in. Thus, a charge of 0.46 grams of liquid nitrogen confined in such a container filled with fruit drink heated to 190F is sufficient to produce the necessary pressure to pressurize the container between 5 psig and 25 psig after the fruit drink has cooled to room temperature.
After the gas has been metered into the product filled container and the container hermetically sealed, the container is ready for storage. The gas producing material metered into the container expands to fill the headspace area created by the product as it cools and thereafter pressurizes the container sidewalls against buckling from the external atmospheric pressure.
It is critical to the practice of the present invention that sufficient gas be metered into the vapor space of the container to create an internal pressure of about 5 to about 25 psig at room temperature. If the container is pressurized to a pressure less than about 5 psig the sidewalls are spongy and lack paneling resistance and if the internal pressure of the container is raised to substantially more than about 25 psig, during filling, conventional r' 20 end closure units may be permanently deformed at the higher pressures encountered when the hot filled container is initially sealed.
The practice of the present invention is illustrated by the following Examples:
EXAMPLE I
Several 211 (2 11/16") x 413 (4 13/16") 2 piece, drawn and wall ironed steel containers having unbeaded sidewalls of 4 mil thickness were filled with 12 ounces of water heated to 200F.
The containers were hermetically sealed by double flanging with a steel lid equipped with a self-sealing gas valve. The headspace in the container was pressurized immediately to 70 psig with nitrogen which was injected into the container by means of a hypodermic needle inserted through the valve. The needle was - .
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iO~ '71 withdrawn and the valve sealed. Immediately after the pressurized nitrogen gas addition, the container and its contents were allowed to cool to room temperature. The internal pressure of the container at room temperature (75F) was determined to be approxi-mately 25 psig with a Beckman Head Space Sampler. An axial load of 730 pounds was applied to the pressurized container on an Instron Universal Testing Machine with little or no paneling observed in the container sidewalls. In addition to this resistance to paneling, the container sidewalls returned to their original condition after the axial load was removed.
Substantially the same results were observed when by following the above procedure, equivalent containers were pressurized to an internal pressure of 10 psig and 15 psig at room temperature with nitrogen.
By way of contrast when the procedure of Example I was repeated with the exception that nitrogen was metered into the containers in amounts sufficient to raise the internal pressure of the sealed, cooled (75F) containers to 1 psig and 2 psig, the sidewalls of the container could be easily hand deformed and they collapsed under an axial load of 600 pounds.
By way of further contrast when the procedure of Example I was repeated with the exception that no nitrogen was metered into the container after sealing, a vacuum ranging from minus 1 psig to minus 2 psig was measured in the containers and modest to severe paneling of the sealed containers was observed when the containers had cooled to room temperature.
EXAMPLE II
Several 211 x 413 3 piece steel containers having unbeaded sidewalls of 6 mil thickness were filled with 12 ounces of water heated to 190F. To the surface of the heated water in the container was added 1.0 gram of liquid nitrogen. The con-tainer was hermetically sealed by double flanging with a steel ~ 06Z671 lid immediately after the liquid nitrogen addition and the con-tainer and its contents were allowed to cool to room temperature.
The internal pressure of the container was determined to be approximately 25 psig ~75F) with a Beckman Head Space Sampler.
An axial load of 1,200 pounds was applied to the pressurized container on an Instron Universal Testing Machine with no paneling observed in the container sidewalls.
EXAMPLE III
Several 404 ~4 4/6") x 700 t7") 3 piece steel containers having unbeaded sidewalls of 6 mil thickness were filled with 46 ounces of water heated to 190F. To the surface of the heated water in the container was added 2.5 grams of liquid nitrogen. The con-tainer was hermetically sealed by double flanging with a steel lid immediately after the liquid nitrogen addition and the container and its contents were allowed to cool to room temperature. The internal pressure of the container was determined to be approxi-mately 11 psig (75F) with a Beckman Head Space Sampler.
An axial load of approximately 1,140 pounds was applied to the pressurized container on an Instron Universal Testing Machine with no paneling observed in the container sidewalls.
- By way of contrast when the procedure of Example III was repeated with the exception that liquid nitrogen was added to the containers in amounts sufficient to raise the internal pressure of the sealed, cooled containers to 1 psig and 2 psig at room temperature, the sidewalls of the container could be easily hand deformed and they collapsed under an axial load of 900 pounds.
By way of further contrast when the procedure of Example III was repeated with the exception that no nitrogen was added to the container after sealing, a vacuum of approximately minus 10 psig was created in the container (at 75F) and severe paneling of the sealed containers was observed when the containers had cooled to room temperature.
' EXAMPLE IV
. .
Several 404 x 700 3 piece, steel containers having unbeaded sidewalls of 6 mil thickness were filled with 46 ounces of water heated to l90~F. The containers were hermetically sealed by double flanging with a steel lid equipped with a self-sealing gas valve. The headspace in the container was pressurized immediately to 25 psig with nitrogen which was injected into the container by means of a hypodermic needle inserted through the valve. The needle was withdrawn and the valve sealed. Immediately after the pressurized nitrogen gas addition, the container and its contents were allowed to cool to room temperature. The internal pressure of the container at room temperature t75F) was determined to be approximately 10 psig with a Beckman Head Space Sampler. An axial load of 1,140 pounds was applied to the pressurized containers on an Instron Universal Testing Machine with little or no paneling observed in the container sidewalls.
By way of contrast when the procedure o~ Example IV was repeated with the exception that nitrogen was metered into the containers in amounts sufficient to raise the internal pressure of the sealed, cooled (75F) containers to 1 psig and 2 psig, the sidewalls of the container could be easily hand deformed.
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~06Z67~
SUPPLEME~TARY DISCLOSURE
The process for packaging articles in thin walled containers of the Supplementary Disclosure is concerned with filling the container with a product heated to above room temperature and which undergoes a reduction in volume upon cooling to room temperature. Also, the inert gas forming material is filled in a container in an amount sufficient to cause an increase in the internal pressure of the container of at least 3 psi.
; 10 According to a broad aspect of the present invention there is provided a process for packaging article~ in thin walled containers having improved resistance to paneling.
The process comprises the steps of providing a container having sidewalls which undergo paneling when the container is filled with a product heated to above roo~ temperature which undergoes a reduction in volume upon cooling to room temperature. The container is filled with the heated product and an inert gas forming material is metered into the filled container in an amount sufficient to cause an increase in the internal pressure of the container of at least 3 psi. The gas forming material has a coefficient of absorption of less than 0.02. The con-tainer is then hermetically sealed and the product packaged therein is allowed to cool to room temperature and the gas to expand so that the internal pressure of the container increases by at least 3 psi at room temperature and imposes a sufficient force upon the sidewalls of the cooled container whereby pànel-ing due to atmospheric pressure is substantially prevented.
By the practice of the present invention containers ' having a body wall thickness of 4 to 6 mils can be employed for 30 the packaging of hot fill products where 10 mil thickness plate is now presently utilized.
1~3 9 .. . . . . . .
lO~iZ671 In pressurizing the container, the g~s may be intro-duced into the container in any convenient manner, and for example, the gaseous material can be charged as a gas into the vapor space of the container. The containers used in the practice of the present invention can be formed from metal plate ranging in thickness from about 0.004 inches (4 mils) to about 0.006 inches (6 mils). The container walls are preferably smooth surfaced and free of any structural reinforce-ment such as beading.
Generally, to prevent paneling in metal containers having a wall thickness of 4 to 8 mils which are used to pack-age liquid products which are at elevated temperatures at the time of filling and particularly at temperatures above pasteurization temperatures (e.g. 140 - 160F) a sufficient amount of gaseous material, is metered into the container to increase the internal pressure in the container when at room temperature in the order of at least 3 psi. Hereinafter, this increase in internal pressure in the container at room temper-ature (70F) will be referred to as ~P.
It has been determined that if the ~P effected by the incorporation of the gaseous material in the vapor space of the container is at least 3 psi containers having sidewalls of reduced thickness can be employed for the packaging of liquids which are introduced into the container at elévated temperatures and shrink in volume when cooled to room temper-ature. A ~P of about 5 to about 35 psi is generally employed , in the practice of the present invention and a ~P of about 8 to about 25 p9i iS preferred. A ~P higher than 35 psi can be employed in the practice of the present invention, but impos-ing such higher pressures does not materially improve the resistance of the container to sidewall paneling. Further, in . , :.
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the case of metal containers sealed with flat metal end closures, the imposition of a QP in excess of 35 psi in the sealed container can cause the end to bulge outwardly from the container creating the false impression that the end has bulged due to a build-up of pressure resulting from the ' deterioration of the packaged product.
The incorporation of the gaseous material in the con-tainer may function to reduce the negative pressure of vacuum within the container to impose a substantial positive pressure, that is, a pressure above atmospheric, within the container.
Thus, within the ~P range of 5 to 35 psi, the actual internal pressure created in the hermetically sealed container at room temperature effected by the addition of the gaseous material may vary, depending on the dimensions of the container, from small negative pressures e.g. -1.0 to -2.0 psig to relatively ' high positive pressures in the order of S to 25 psig. For example, as will hereinafter be illustrated, a 404 (4-4/16") x 700 (7") container having a sidewall thickness of 8 mils ~i filled with 48 ounces of a hot (190 - 200F) liquid can be pressurized with a liquid nitrogen addition and paneling is .; :
avoided at an internal pressure of -1.7 psig, whereas in a 207,5 (2-7,5/16") x 410.5 (4-10.5/16") container having a 6 mil wall thickness, filled with 10 ounces of the same hot liquid, an internal pressure of 12.9 psig is required to avoid paneling.
, By following the practice of the present invention, containers having sidewall thickness in the order of 4 to 8 ,. .~ .
Jj mils can be substituted for containers of identical size having sidewall thickness in the order of 9 to 11 mils in the packag-, 30 ing of hot fill products without undergoing sidewall paneling `', thereby effecting a substantial cost reduction in the price of the container used to package the hot fill item.
- . -- 1 1 --. .,;, : -The practice of the present invention is illustrated by the following additio.~al Examples other than those of the Principal Disclosure.
XAMPLE I
Several hundred 404 (4 4/16") x 700 (7") 3 piece steel containers having unbeaded sid~walls of 8 mils thickness were -filled with 48 ounces of apple juice heated 190F - 200F on a commercial juice packaging line. Liquid nitrogen was added to the surface o~ the heated julce and the container was hermetic-ally sealed by double seaming with a steel lid immediately after the liquid nitrogen addition. ~he container and its con- -tents were allowed to cool to room temperature (70F). The internal pressure of the cooled, juice filled container was determined to be approximately -1.7 psig. No paneling was observed in the sidewalls of any of the containers. The juice had previously b~en packaged in 40~4 x 700 containers having a sidewall thickness of 10 mils. ;
When it was attempted to package hot apple juice in the containers used in Example I without liquid nitrogen addi-tion, severe paneling of the container sidewalls was observed.
It was determined that paneling in the hot juice filled con-tainers used in Example I was initiated at -6.0 to -7.0 psig and that severe paneling occured at vacuums in the order of -9.0 to -10 psig.
EXAMPLE II
Several hundred 207.5 (2-7,5/16") x 410.5 (4-10.5/16") 3 piece steel containers having unbeaded sidewalls of 6 mil thickness were filled with 10 ounces of apple juice heated to 190F - 200F on a commercial juice packaging line. Liquid :', nitrogen was added to the surface of the heated apple juice `~ and the container was hermetically sealed by double seaming - 12 _ 10~;2671 with a steel lid i~ediately after the liquid nitrogen addition and the container and its contents were allowed to cool to room temperature (70F). The internal pressure of the con-tainer was determined to be approximately 12.9 psig. No panel-ing was observe~ in the sidewalls of any of the containers.
reviously 207,5 x 410.5 containers having a wall thickness of 8.9 mils had been used for the packaging of the juice.
When it was attempted to package hot apple juice in the 6 mil containers used in Example II without liquid nitro-gen addition, severe paneling of the container sidewalls wereobserved. It was determined that paneling in the hot juice filled containers used in Example II occurred at a vacuum of about -10.0 psig.
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In the manufacture of containers for use in the packing of a variety of food and non-food products in metal containers, it is desirable, from the standpoint of both economy and convenience, to employ metal plate as thin and as light weight as possible.
Presently, containers formed from metal plate having a thickness o-f 10-15 mils are conventionally used for packaging solid food products, oils and non-carbonated beverages. The major drawback to the extensive use of thinner lighter weight plate, e.g. plate having a thickness of 6 mils or less is that the conventional smooth surfaced cylindrical containers made therefrom do not ordinarily have sufficient wall strength to withstand the substantial vacuum created in the container after the product is packed therein and the container hermetically sealed. For example, food products such as non-carbonated beverages are packaged in metal containers or placed in the container while the product is still heated in order to prevent bacterial contamination. Motor oils are hot when placed in containers as the oil is heated to make it less viscous for filling. As either of these hot liquid products cools in the sealed container, the product is reduced in volume and an internal vacuum, in order of about minus 10 psig, is created in the container, i.e. the pressure inside the container after the .. .
packaged product has cooled to room temperature is about 10 psig less than the pressure outside the container. The result of this condition is a 10 psi external pressure on the container side-walls which tends to force or flex the sidewalls of the '~
.
..
~062671 container inwardly and buckle them. This buckling of the side-walls is referred to in the art as "panellng". When this condi- -tion occurs, the container frequently assumes an undesirably distorted appearance and sometimes deforms to such an extent that it will not support another container that may be stacked on top of it.
In order to reinforce and strengthen the container body against paneling and to maintain its original shape, and yet avoid the use of heavy body plate, the art has devised a number of methods to prevent paneling. These methods however are not without disadvantages. For example, it is common practice in the manufacture of containers used in packaging hot food products to provide the container body with one or more circumferential beads. The use of such beading provides the necessary paneling resistance in containers made from thin light weight metal plate but has a detrimental effect upon the axial strength or resistance of the container to crushing under high container stacking conditions in storage. Because the circumferential beads reduce the axial strength of the container body, the use of metal plate of 10 mils thickness is still required to compensate for the loss in axial strength.
In accordance with the present invention, there is provided a method for the packaging a variety of heated products in containers having wall thicknesses of 6 mils or less wherein paneling of the container after sealing is prevented or sub-stantially retarded which method is accomplished by imposing ; within a hermetically sealed container a superatmospheric pressure in the order of about 5 to about 25 psig with an --inert gas having low absorption in liquids.
According to a broad aspect of the present invention there is provided a process for packaging articles in thin ~- 2 -, walled containers having improved resistance to paneling. The process comprises providing a container having sidewalls which undergo paneling when the container is filled with a product which undergoes a reduction in volume upon cooling. An inert gas forming material is metered into the filled container, -~
; the gas forming material having a coefficient of absorption of less than 0.02. The container is then hermetically sealed and the product packaged therein is allowed to cool and the gas to expand so that a superatmospheric internal pressure in the range of about 5 to about 25 psig is imposed at room temperature upon the sidewalls of the cooled container whereby paneling due to atmospheric pressure is substantially prevented.
By the practice of the present invention containers having a body wall thickness of 4 to 6 mils can be employed , .
for the packaging of hot fill products where 10 mil thickness plate is now presently required.
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The container bodies used in the packaging method of the present invention are preferably made of rigid, gas impermeable .; materials such as metals as steel or aluminum. Containers whose .~ body walls are fabricated from commercially available thermo-plastic resins such as polyethylene or polypropylene are not generally preferred in the practice of the present invention as '`
due~to the relative gas permeability of these materials as compared to metals ~the pressure originally induced in the sealed container '' may~be reduced during the time of storage by the escape of the 0 ~ pressuri~zing gas from the container which will thereafter render the container susceptible to paneling. ;
: It is essential to the practice of the present invention that the gas used to pressurize the container be inert to the ' contcnts~o~the container and~have low absorption in liquids. If th.e~gas is~not inert or has~high absorption in liquids such as do'es~C02, upon storage~, the~chemic:al reaction of the gas or the '.
ab ~ tion of the gas: by liquid;protuct will cause the total : ~ essure:~within tbe contsiner to drop and as a result, the sidewalls :~
of the~container will~panel~:due~to~atmospheric pressure in order to '.
,~ ~ 20~co~mpensate~for this~internal pressure drop.:~
.~ ~ '~ G~enerally~,~a~gas~having~an~absorption coefficient t~ ) , ~ at;~atmospheric~.pressure'~and~room~temperature (70F) of less than ;.
'0~02~is~sui~table fo:r use~in~the practice of the present invention.
'~` ~ itr ~ n-which is~ the pre~ferred inert gas for use in the practice '"
'of~thé p'résent; invention~has an ~ value of 0.01475.
In~pressurizing;~tho:~container,~the gas may be introduced o: ~ '.container~in~.any~convenient~-anner.~ For example, the . ~ gaseo~us~mat~rial~can:.~.~be:~charged as~a~gas into the vapor space of ' the~o ~ ner~throug~:a~holo in the~closure l~id of the container . ~ ~ ~using~a~press~re~syringe.~'Thereafter the~hole is sealed with a rubber p~lug~or~;spot~wélded to~hermetically seal the cdntainer.
Gases~which -ay liquify or solidify at low temperaturcs and '' ': - 3 -1~6Z67~
thereafter vaporize and expand at room temperature are pre-ferred because of their ease of handling. When such liquid gaseous materials are used, droplets of the liquid gaseous material are metered into the container onto the exposed surface of the packaged product and sealing of the container is carried out rapidly and soon as possible after the liquid gaseous material has been introduced into the container. Liquid nitrogen has been found to perform very satisfactorily under normal conditions and is an excellent example of a liquid gaseous material which is preferred in the practice of the present invention.
The containers used in the practice of the present invention can be formed from metal plate ranging in thickness from about 0.004 inches (4 mils) to about 0.006 inches (6 mils).
The container walls are preferably smooth surfaced and free of any structural reinforcement such as beading.
In packaging heated products in containers in accordance with the practice of the present invention, the heated product is first dispensed into the container and a gas producing material such as liquid nitrogen is metered into the product filled container, The container is then sealed with minimum delay to entrap the gas producing medium in the vapor space or headspace of the container and prevent any appreciable loss of gaseous material.
The amount of gas which is metered into the container ; 25 prior to hermetic sealing of the container is determined by the amount of vapor space remaining in the container after the heated product has cooled to room temperature and the internal pressure required after cooling. For example 0.071 grams of liquid nitrogen when vaporized at 70F exerts a pressure of 7 psig per cubic inch (cu. in.) of volume. The vapor space remaining in a container after a heated product has cooled can be readily ascertained.
For example, the vapor space remaining in a 48 ounce 404 (4 4/16") :. . . . ~ . - :, ~
diameter fruit drink container after filling at 90F is about 6.5 cu. in. Thus, a charge of 0.46 grams of liquid nitrogen confined in such a container filled with fruit drink heated to 190F is sufficient to produce the necessary pressure to pressurize the container between 5 psig and 25 psig after the fruit drink has cooled to room temperature.
After the gas has been metered into the product filled container and the container hermetically sealed, the container is ready for storage. The gas producing material metered into the container expands to fill the headspace area created by the product as it cools and thereafter pressurizes the container sidewalls against buckling from the external atmospheric pressure.
It is critical to the practice of the present invention that sufficient gas be metered into the vapor space of the container to create an internal pressure of about 5 to about 25 psig at room temperature. If the container is pressurized to a pressure less than about 5 psig the sidewalls are spongy and lack paneling resistance and if the internal pressure of the container is raised to substantially more than about 25 psig, during filling, conventional r' 20 end closure units may be permanently deformed at the higher pressures encountered when the hot filled container is initially sealed.
The practice of the present invention is illustrated by the following Examples:
EXAMPLE I
Several 211 (2 11/16") x 413 (4 13/16") 2 piece, drawn and wall ironed steel containers having unbeaded sidewalls of 4 mil thickness were filled with 12 ounces of water heated to 200F.
The containers were hermetically sealed by double flanging with a steel lid equipped with a self-sealing gas valve. The headspace in the container was pressurized immediately to 70 psig with nitrogen which was injected into the container by means of a hypodermic needle inserted through the valve. The needle was - .
.
iO~ '71 withdrawn and the valve sealed. Immediately after the pressurized nitrogen gas addition, the container and its contents were allowed to cool to room temperature. The internal pressure of the container at room temperature (75F) was determined to be approxi-mately 25 psig with a Beckman Head Space Sampler. An axial load of 730 pounds was applied to the pressurized container on an Instron Universal Testing Machine with little or no paneling observed in the container sidewalls. In addition to this resistance to paneling, the container sidewalls returned to their original condition after the axial load was removed.
Substantially the same results were observed when by following the above procedure, equivalent containers were pressurized to an internal pressure of 10 psig and 15 psig at room temperature with nitrogen.
By way of contrast when the procedure of Example I was repeated with the exception that nitrogen was metered into the containers in amounts sufficient to raise the internal pressure of the sealed, cooled (75F) containers to 1 psig and 2 psig, the sidewalls of the container could be easily hand deformed and they collapsed under an axial load of 600 pounds.
By way of further contrast when the procedure of Example I was repeated with the exception that no nitrogen was metered into the container after sealing, a vacuum ranging from minus 1 psig to minus 2 psig was measured in the containers and modest to severe paneling of the sealed containers was observed when the containers had cooled to room temperature.
EXAMPLE II
Several 211 x 413 3 piece steel containers having unbeaded sidewalls of 6 mil thickness were filled with 12 ounces of water heated to 190F. To the surface of the heated water in the container was added 1.0 gram of liquid nitrogen. The con-tainer was hermetically sealed by double flanging with a steel ~ 06Z671 lid immediately after the liquid nitrogen addition and the con-tainer and its contents were allowed to cool to room temperature.
The internal pressure of the container was determined to be approximately 25 psig ~75F) with a Beckman Head Space Sampler.
An axial load of 1,200 pounds was applied to the pressurized container on an Instron Universal Testing Machine with no paneling observed in the container sidewalls.
EXAMPLE III
Several 404 ~4 4/6") x 700 t7") 3 piece steel containers having unbeaded sidewalls of 6 mil thickness were filled with 46 ounces of water heated to 190F. To the surface of the heated water in the container was added 2.5 grams of liquid nitrogen. The con-tainer was hermetically sealed by double flanging with a steel lid immediately after the liquid nitrogen addition and the container and its contents were allowed to cool to room temperature. The internal pressure of the container was determined to be approxi-mately 11 psig (75F) with a Beckman Head Space Sampler.
An axial load of approximately 1,140 pounds was applied to the pressurized container on an Instron Universal Testing Machine with no paneling observed in the container sidewalls.
- By way of contrast when the procedure of Example III was repeated with the exception that liquid nitrogen was added to the containers in amounts sufficient to raise the internal pressure of the sealed, cooled containers to 1 psig and 2 psig at room temperature, the sidewalls of the container could be easily hand deformed and they collapsed under an axial load of 900 pounds.
By way of further contrast when the procedure of Example III was repeated with the exception that no nitrogen was added to the container after sealing, a vacuum of approximately minus 10 psig was created in the container (at 75F) and severe paneling of the sealed containers was observed when the containers had cooled to room temperature.
' EXAMPLE IV
. .
Several 404 x 700 3 piece, steel containers having unbeaded sidewalls of 6 mil thickness were filled with 46 ounces of water heated to l90~F. The containers were hermetically sealed by double flanging with a steel lid equipped with a self-sealing gas valve. The headspace in the container was pressurized immediately to 25 psig with nitrogen which was injected into the container by means of a hypodermic needle inserted through the valve. The needle was withdrawn and the valve sealed. Immediately after the pressurized nitrogen gas addition, the container and its contents were allowed to cool to room temperature. The internal pressure of the container at room temperature t75F) was determined to be approximately 10 psig with a Beckman Head Space Sampler. An axial load of 1,140 pounds was applied to the pressurized containers on an Instron Universal Testing Machine with little or no paneling observed in the container sidewalls.
By way of contrast when the procedure o~ Example IV was repeated with the exception that nitrogen was metered into the containers in amounts sufficient to raise the internal pressure of the sealed, cooled (75F) containers to 1 psig and 2 psig, the sidewalls of the container could be easily hand deformed.
'; -' .
~. . , . : . . .
~06Z67~
SUPPLEME~TARY DISCLOSURE
The process for packaging articles in thin walled containers of the Supplementary Disclosure is concerned with filling the container with a product heated to above room temperature and which undergoes a reduction in volume upon cooling to room temperature. Also, the inert gas forming material is filled in a container in an amount sufficient to cause an increase in the internal pressure of the container of at least 3 psi.
; 10 According to a broad aspect of the present invention there is provided a process for packaging article~ in thin walled containers having improved resistance to paneling.
The process comprises the steps of providing a container having sidewalls which undergo paneling when the container is filled with a product heated to above roo~ temperature which undergoes a reduction in volume upon cooling to room temperature. The container is filled with the heated product and an inert gas forming material is metered into the filled container in an amount sufficient to cause an increase in the internal pressure of the container of at least 3 psi. The gas forming material has a coefficient of absorption of less than 0.02. The con-tainer is then hermetically sealed and the product packaged therein is allowed to cool to room temperature and the gas to expand so that the internal pressure of the container increases by at least 3 psi at room temperature and imposes a sufficient force upon the sidewalls of the cooled container whereby pànel-ing due to atmospheric pressure is substantially prevented.
By the practice of the present invention containers ' having a body wall thickness of 4 to 6 mils can be employed for 30 the packaging of hot fill products where 10 mil thickness plate is now presently utilized.
1~3 9 .. . . . . . .
lO~iZ671 In pressurizing the container, the g~s may be intro-duced into the container in any convenient manner, and for example, the gaseous material can be charged as a gas into the vapor space of the container. The containers used in the practice of the present invention can be formed from metal plate ranging in thickness from about 0.004 inches (4 mils) to about 0.006 inches (6 mils). The container walls are preferably smooth surfaced and free of any structural reinforce-ment such as beading.
Generally, to prevent paneling in metal containers having a wall thickness of 4 to 8 mils which are used to pack-age liquid products which are at elevated temperatures at the time of filling and particularly at temperatures above pasteurization temperatures (e.g. 140 - 160F) a sufficient amount of gaseous material, is metered into the container to increase the internal pressure in the container when at room temperature in the order of at least 3 psi. Hereinafter, this increase in internal pressure in the container at room temper-ature (70F) will be referred to as ~P.
It has been determined that if the ~P effected by the incorporation of the gaseous material in the vapor space of the container is at least 3 psi containers having sidewalls of reduced thickness can be employed for the packaging of liquids which are introduced into the container at elévated temperatures and shrink in volume when cooled to room temper-ature. A ~P of about 5 to about 35 psi is generally employed , in the practice of the present invention and a ~P of about 8 to about 25 p9i iS preferred. A ~P higher than 35 psi can be employed in the practice of the present invention, but impos-ing such higher pressures does not materially improve the resistance of the container to sidewall paneling. Further, in . , :.
. .. ~. : . - ' ~ ' .' . .
, ~. ~ . ~ ., .
the case of metal containers sealed with flat metal end closures, the imposition of a QP in excess of 35 psi in the sealed container can cause the end to bulge outwardly from the container creating the false impression that the end has bulged due to a build-up of pressure resulting from the ' deterioration of the packaged product.
The incorporation of the gaseous material in the con-tainer may function to reduce the negative pressure of vacuum within the container to impose a substantial positive pressure, that is, a pressure above atmospheric, within the container.
Thus, within the ~P range of 5 to 35 psi, the actual internal pressure created in the hermetically sealed container at room temperature effected by the addition of the gaseous material may vary, depending on the dimensions of the container, from small negative pressures e.g. -1.0 to -2.0 psig to relatively ' high positive pressures in the order of S to 25 psig. For example, as will hereinafter be illustrated, a 404 (4-4/16") x 700 (7") container having a sidewall thickness of 8 mils ~i filled with 48 ounces of a hot (190 - 200F) liquid can be pressurized with a liquid nitrogen addition and paneling is .; :
avoided at an internal pressure of -1.7 psig, whereas in a 207,5 (2-7,5/16") x 410.5 (4-10.5/16") container having a 6 mil wall thickness, filled with 10 ounces of the same hot liquid, an internal pressure of 12.9 psig is required to avoid paneling.
, By following the practice of the present invention, containers having sidewall thickness in the order of 4 to 8 ,. .~ .
Jj mils can be substituted for containers of identical size having sidewall thickness in the order of 9 to 11 mils in the packag-, 30 ing of hot fill products without undergoing sidewall paneling `', thereby effecting a substantial cost reduction in the price of the container used to package the hot fill item.
- . -- 1 1 --. .,;, : -The practice of the present invention is illustrated by the following additio.~al Examples other than those of the Principal Disclosure.
XAMPLE I
Several hundred 404 (4 4/16") x 700 (7") 3 piece steel containers having unbeaded sid~walls of 8 mils thickness were -filled with 48 ounces of apple juice heated 190F - 200F on a commercial juice packaging line. Liquid nitrogen was added to the surface o~ the heated julce and the container was hermetic-ally sealed by double seaming with a steel lid immediately after the liquid nitrogen addition. ~he container and its con- -tents were allowed to cool to room temperature (70F). The internal pressure of the cooled, juice filled container was determined to be approximately -1.7 psig. No paneling was observed in the sidewalls of any of the containers. The juice had previously b~en packaged in 40~4 x 700 containers having a sidewall thickness of 10 mils. ;
When it was attempted to package hot apple juice in the containers used in Example I without liquid nitrogen addi-tion, severe paneling of the container sidewalls was observed.
It was determined that paneling in the hot juice filled con-tainers used in Example I was initiated at -6.0 to -7.0 psig and that severe paneling occured at vacuums in the order of -9.0 to -10 psig.
EXAMPLE II
Several hundred 207.5 (2-7,5/16") x 410.5 (4-10.5/16") 3 piece steel containers having unbeaded sidewalls of 6 mil thickness were filled with 10 ounces of apple juice heated to 190F - 200F on a commercial juice packaging line. Liquid :', nitrogen was added to the surface of the heated apple juice `~ and the container was hermetically sealed by double seaming - 12 _ 10~;2671 with a steel lid i~ediately after the liquid nitrogen addition and the container and its contents were allowed to cool to room temperature (70F). The internal pressure of the con-tainer was determined to be approximately 12.9 psig. No panel-ing was observe~ in the sidewalls of any of the containers.
reviously 207,5 x 410.5 containers having a wall thickness of 8.9 mils had been used for the packaging of the juice.
When it was attempted to package hot apple juice in the 6 mil containers used in Example II without liquid nitro-gen addition, severe paneling of the container sidewalls wereobserved. It was determined that paneling in the hot juice filled containers used in Example II occurred at a vacuum of about -10.0 psig.
, ;, ~ ' : ., .g , .
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.
Claims (11)
1. A process for packaging articles in thin walled con-tainers having improved resistance to paneling which comprises providing a container having sidewalls which undergo paneling when the container is filled with a product which undergoes a reduction in volume upon cooling, metering an inert gas forming material into the filled container, the gas forming material having a coefficient of absorption of less than 0.02, and then hermetically sealing the container and allowing the product packaged therein to cool and the gas to expand so that a superatmospheric internal pressure in the range of about 5 to about 25 psig is imposed at room temperature upon the side-walls of the cooled container whereby paneling due to atmos-pheric pressure is substantially prevented.
2. The method of claim 1 wherein the gas is nitrogen.
3. The method of claim 1 wherein the gas forming material is liquid nitrogen.
4. The method of claim 1 wherein the container is formed from metal plate having a thickness of 3 to 6 mils.
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
5. A process for packaging articles in thin walled containers having improved resistance to paneling which com-prises, providing a container having sidewalls which undergo paneling when the container is filled with a product heated to above room temperature which undergoes a reduction in volume upon cooling to room temperature, filling the container with the heated product, metering an inert gas forming material into the filled container in an amount sufficient to cause an increase in the internal pressure of the container of at least 3 psi, the gas forming material having a coefficient of absorption of less than 0.02, and then hermetically sealing the container and allowing the product packaged therein to cool to room temperature and the gas to expand so that the internal pressure of the container increased by at least 3 psi at room temperature imposes a sufficient force upon the sidewalls of the cooled container whereby paneling due to atmospheric pressure is substantially prevented.
6. The process of claim 5 wherein the increase in internal pressure of the container is in the range of about 5 to about 35 psi.
7. The process of claim 5 wherein the sidewall thickness of the container is in the range of 4 to 8 mils.
8. The process of claim 7 wherein the internal pressure in the cool container is reduced to within 1 to 2 psig of atmospheric pressure by the addition of the inert gas to the filled container.
9. The process of claim 7 wherein the internal pressure in the cool container is increased to range between about 5 and 25 psig.
10. The process of claim 5 wherein the gas is nitrogen.
11. The process of claim 10 wherein the gas forming material is liquid nitrogen.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US53111374A | 1974-09-12 | 1974-09-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1062671A true CA1062671A (en) | 1979-09-18 |
Family
ID=24116288
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA226,875A Expired CA1062671A (en) | 1974-09-12 | 1975-05-14 | Method of packaging utilizing pressurized containers |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5168382A (en) |
| CA (1) | CA1062671A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4588000A (en) * | 1982-08-26 | 1986-05-13 | Metal Box Public Limited Company | Method and apparatus for metering and dispensing volatile liquids |
| US5251424A (en) * | 1991-01-11 | 1993-10-12 | American National Can Company | Method of packaging products in plastic containers |
| US5884792A (en) * | 1990-03-15 | 1999-03-23 | Continental Pet Technologies, Inc. | Preform for a hot fill pressure container |
| US10302252B2 (en) | 2014-04-14 | 2019-05-28 | United Technologies Corporation | Container having an internal structure with minimum surfaces |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57142869A (en) * | 1981-02-23 | 1982-09-03 | Toyo Seikan Kaisha Ltd | Canned provision |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4026131Y1 (en) * | 1965-03-08 | 1965-09-06 |
-
1975
- 1975-05-14 CA CA226,875A patent/CA1062671A/en not_active Expired
- 1975-09-26 JP JP11570475A patent/JPS5168382A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4588000A (en) * | 1982-08-26 | 1986-05-13 | Metal Box Public Limited Company | Method and apparatus for metering and dispensing volatile liquids |
| US5884792A (en) * | 1990-03-15 | 1999-03-23 | Continental Pet Technologies, Inc. | Preform for a hot fill pressure container |
| US5251424A (en) * | 1991-01-11 | 1993-10-12 | American National Can Company | Method of packaging products in plastic containers |
| US10302252B2 (en) | 2014-04-14 | 2019-05-28 | United Technologies Corporation | Container having an internal structure with minimum surfaces |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5168382A (en) | 1976-06-12 |
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