CA1142895A

CA1142895A - Package and method of making same

Info

Publication number: CA1142895A
Application number: CA000277909A
Authority: CA
Inventors: Maurice J. Gifford; Oscar E. Seiferth; Jerome C. Gruber; Eugene D. Serdynsky
Original assignee: Oscar Mayer Foods Corp
Current assignee: Oscar Mayer Foods Corp
Priority date: 1976-05-19
Filing date: 1977-05-06
Publication date: 1983-03-15
Also published as: AU2509977A; JPS538294A; BE854573A; ES458927A1; FR2351877B1; FR2351877A1; ES235697Y; ES235697U; GB1584392A; DE2722412A1; IT1083553B; AU519450B2

Abstract

Abstract of the Disclosure A hermetically sealed package and method of making the package are disclosed, wherein an extruded thermoplastic polyurethane film is extruded, cooled to a temperature of:
from 40°F. to 100°F., placed in overlying relation with a product and bottom package-forming member, and then directly contacted with sealing portions on the bottom package-forming member, forming a hermetic seal therewith without the necessity of an adhesive or conventional heat seal technique. The seal integrity and strength can be selectively controlled and varied to range from entirely fused to readily peelable seals through the selective application of heat, during seal formation, so that the temperature of the seal interface ranges from about 75°F. to 200°F. and preferably is within the range of 90°F. to 175°F.

Description

~ ~Z~15 :

l~ack~rou]ld arld D _crlption of thc Inventio Ihc l)rcsellt invention generally rclates to improvccl ~ ck;l~cs ;111(1 nlctl~ods oC making thc p;l(~k;lgc~ (1, more p~
cularly, to p;lckages having at least one seal-forming surfacc~
composed of a thermoplastic polyurethane film. In this reeard, an important aspect of the present invention involves the extrusion and use Or a thermoplastic polyurethane film as a sealing -film in packages enclosing food products such as wieners,~
bacon, sliced luncheon meats, cheese and the like.
While the use of thermoplastic polyurethane filDls as~
p;lckaging m~ltcr:ials is known, such usc 1nlS not l)rov~ously encolllpassc(l sil~ ltancous extrusion and packa~e rorlnation wherei~n~
the thc~rlllol)lastic polyurethane film is used as thc scalin~ Ellm without thc neccssity of an adhesive or conventional hcat seal.
As used hcrein, the term "heat-seal" is used to designate the~
type of seal wherein at least one of the films at the sea]~
interface is heated to a temperature above its melting p~olnt to incluce fusion thereof to -the other material making up such~seal.
For example, U. S. Patent No. 3,879,330 desc-ribes a food~wrap composed Or a tllermol)lastic urethanc polymer and a vinylidene~
chlor;dc po]ymcr. In describing uses for tl~ese coml)oS;tC Cilms,~
this l)atcnt s~lggests that they can be fahricated into baas by heat sealing one end of a length of a tubular extrusion thereof.
In accordance with an important aspect of the present invention, it has been discovered that thermoplastic polyurethane;
films can be advantageously used in simultaneous film extrusion~
package forming applications to provide packages having hermetic seals which are formed without an adhesive or conventional heat seal techniques. In the packages of this invention, the seal integrity or strength can be selectively controlled and varied to ~ ~42~39~

rangc Eroln cntirely ~used seals (i.e. ~ erein thc seals c~lnnot be separatecl without at least partially destroying at least one~
of the films which make up the seal) to readily peelablF seals.
Adclitionally, these packages are characterized by excellent oxygen barrier properties, durability and flexibility enabling them to be particularly suitable for use in the packaging of food products such as, for example, wieners, bacon, sllced~
luncheon meats, chops, cheese and the like.
I`hereEore, an object of the present invelltion-i~s to~
provide an improved hermetically sealed package and metho~d of making the package wherein the hermetic seai is ~ormed~by~-the~
direct contact of a thermoplastic polyurethane film with~a~n opposed seal-forming material (a thermoplastic or foil) without~
the necessity of an adhesive or conventional heat seal technique~
Another object of the present invention is to provide an improved hermetically sealed package and method l~hich is~
particularly suited for packaging food i.tems.
~ nother object o-f the present invention is to provide~
an improved package having a unique hermetic seal in that~the~
intc~grity and strength of the sc~l can he selectivcly contro~ d~
and variecl to range from an entirely fusecl seal to a re~adlly~
peelable sc~al.
Allother object of the present iilvention is to provlde~
an improved method of making packages wherein a thermoplastic polyurethane film is extruded, cooled and then used as the seal~ng fillll iTI the package being formed.
Another object of the present invention is to provide~
a met]lod wherein simultaneous film extrusion and package form-ation are utilized with a thermoplastic polyurethane film ;~
characterized by improved durability, softness, tackiness ancd flexihility. :
~`

~2~

These ancl other objects o:f the present invention Wllbe apl)arent frolll the following cletailed descril~tion takell in conjunction with the accompanying drawings:i.n which 'L.ike nume~als~
indica-te like elements and wherein~
Figure 1 is a diagrammatic illustration of a proceclure which can be followed in the formation of a laminated film ;~
package embodying princi.ples of the present invention;
Figure 2 i s a schematic top plan view of a wiener package embodying principles of the present inventio Figure 3 is a bottom plan view of the package shown~

in l:igure 2; :~
I:i.gure 4 is a fragmentary sectional view ol' the package~
S ]lO WIl i ll l:igure 2 taken along the 'line 4-4;
Figure 5 is a schematic top plan view of a bacon package embodying principles of the present invention;~
Figure 6 is a fragmentary sectional view of the package shown in Figure 5 taken along the line 6-6;
I'igure 7 is a perspecti~e view, partically broken away, of a sliced luncheon meat package embodying principles of the pre~ent inventionj and I.i.gure 8 is a rragmentary sect:ion.ll view ol' the l)ackaqe~
shown in Figure 7 taken al.ong the line 8-8.
In accordance with the p~esent invention, a thermo;~
plastic polyurethane film is extruded from a suitable resin supply and immediately cooled to a temperature of from approxi~
rnately 40F. to 100F., preferably about 60F., such as, for ::
examl)le, by passing the film through a l~ater bath. While the ~ ~
~ ;:
thermoplastic polyurethane film may be used alone as a single ; ~ :

ply non-laminated packaging film, preferably this film is : :

- 3 - :

~Z13~35 combined with one or more additional thermoplastic films whlch impart advantageous properties to the resultant lamination.
These additional films can be extruded with the thermoplastic polyurethane or furnished from a supply roll.
The thermoplastic polyurethane film is then supplied to a package-forming apparatus such as the apparatus descrlbed in U.S. Patent Nos. 3,083,106 and 3,129,545. While in the package-forming apparatus, the thermoplastic polyurethane film is placed in overlying relation with a product to be packaged which, in turn, is in overlying relation wlth a bottom package-forming member having seal-forming portions which usually are located to peripherally surround the~
product in the finished package. The thermoplastic poly~
urethane film is then placed in direct contact wlth the seal~
forming portions, that is, without the use of an adheslve ;
interface. `
As previously noted, an important aspect of the present invention is that seal integrity and strength can be~
selectively varied by regulating the temperature~of the seal interface at the time the thermoplastic polyurethane film~
is placed in direct contact with the seal-forming portions of~
the bottom package-forming member. Typically, this regulatlcn~
of seal interface temperature can be achieved by employing sealer bars equipped with heating means, examples of which a~re hot water, hot oil and infrared lamps. In the practice of this~
invention, the seal interface temperature will generally~be regulated through the selective application of heat within the range of about 75F. to about 200F., with the temperature~
range of about 90F. to about 175F. being preferred.

- 4 ~

~` :

ll~Z895 ~ caL intcgrity and strerlgth can alco be co~]ltrollcd by selectio?l Or the material which is l~laccd in contact wi~th the thermoplastic l~oly~lrethane filln. I:or cxample, ~ der similar scal-forming conditions, rigid polyvillyl cilk)riclc, acrylonitrile-butadiene-styrene copolymers and polycarbonate~
materials will form a more tenacious seal with a thermoplastic~
polyurethane film than will polystyrene, polyamide materials,~
polyacrylonitrile and polyethylene.
Seal strength is also affected by (a) the time~
duration between extrusion of the thermoplastic polyurethane~f and contact thercof with the seal-formlng portions of the~bo package-forming member and (b) the dwell time (i.e., the time~
period during ~hich the sealer bars are in contact with the thermoplastic pQlyurethane film and opposed seal-formi~ng~portlons~
during secLl formation). Generally, in the practice of~the pr~esent~
invention, seal formation should occur wi~hin 30 mlnut.es~from~
time the thermoplastic polyurethane ilm is extruded, with time~
durations of about 30-60 seconds being preferred. Typlcall~
dwell times of a few seconds (e.g., 2 to 10 seconds) are employed to provide highly satisfactory hermetlc seals.
Thermoplastic urethane polymers useful in the~p~rcs-ent~
invelltion can L~e, as is well known in the art, I)roduced~hy reacting essenticllly equivalent amounts oL d cl~ol wlth;an~
or~anic clii~ocyanate. The dioI component contains at l~east~one relatively h:igh molecular weight diol, and may also contaln a~
low molecular weight or monomeric diol. Organic diisocyanates~
which are usefu:L in the prepartion of these thermoplastic urethane polymers include tolylene diisocyanate, b~is (4-isocy~
anatopheny]) methane ("MDI"), and other organic diisocyanate~s that are known in the art. MDI is a preferred organic diisocyanate ~or the preparation of thermoplastic urethane polymers.
~5 ~Z8~

Thc cliol or diol mixture th~t can be employe~l ln preparing the-rmoplastic urethane polymers inclu~les at least OllC relativcly hi~h molecular wci~ht diol. ~uch ~liols can be the reactioll pro(lucts of an excess o~ a ~3ihydric alcohol with a~
dicarboxylic acid, such as those polyester diols prepared by reactin~ an excess of ethylene glycol, propylene glycol, or diethylene glycol, witll adipic acid or terephthalic acid.
~no~her type of high molecular weight diol that can be employed~
is tlle polylactanediols, such as tllose preparcd by the reactlon~
of epsilon-caprolactone with a difunctional initator such~as a dihydric alcohol, a diamine, or an amino alcohol. Bxamples of useful difunctional initiators include ethylene glycol, dietllylcnc ~lycol, 1,4-butalle diol, hexametllyle]le glycol, ethanolamine, ethylene diamine? and 1,3-propanediamine. Still~
another type of relatively high molec~ilar weight diol than can~
he employed in the preparation of thermoplastic urethane polymers~
are the polyether diols. Polyether diols can be prepared, for~
example, by reacting an alkylene oxide such as ethylene oxlde, propylene oxide, butylene oxide, or mixtures thereof wlth a difunctional initiator such as ethylene glycol or diethylene ;~
glycol.
In most instances, the polyester type aromatic iso~
cyanate polyuretllanes are preferred in the practice oC the present invention. I-lowever, the polyether type aromatic isocyanate polyurethanes, the polyester type aliphatic isocyanate~
polyurethanes, and the polyether type aliphatic isocyanate ;
polyurethanes can also be used. Especially preferre(l poly~
urethanes are those sold commercially under the trademark Estane ;~
by B. F. Goodrich Company and under the trademark Rucothane~;by llooker Chemical ~1 Plastics Corp.
:: ~
: :: : ::;

~:
[ll accoldancc witll the prcserlt -invent:ion, the e.Ytrll~lcd .In~l coolccl tl-ermoplastic poly~ircth~ e fi]ln is used as a sealing film with a wide variety of other materlals, such~
as films an(l bases (i.e., relatively rigid product-sllpporting tr~lys) llSeCI in the packaging of food and other products.
~xamples of these other materials include rigid polyvinyl chloride;,~
flexible polyvillyl chloride, saran, polycarhonates, acry-lonitrile-styrene copolymers, polyethy~enetcrel)hthalate, poly-~styrenc, polyl)ropyleTIe, polyethylene, nylon, acrvlol~itrilc-methylacrylate copolymers and non-thernloplastic nl.ltcrLals~sucl as aluminum foil.
Referring now to the drawings, an~l with p.lrtic-llar ~
referellce to F:igure 1, the numeral 21 schem,ltica]ly des~ignates a continuous film-forming and packaging apparatus which can be employed in the practice of the present invention. As is shown,~
apparatus 21 generally includes an upper film lamination extrud~r~
assembly component 22, a cooling bath 23, bottom package member~
supllly component 24, a package -forming component 25, and a heater 26. E`or purposes of illustration, apparatlls 21 will be generally ~escribed in connection with the forming o a package~
ll.lvin~ an u~ cr three-ply film lamination which is scaled to a preformed and product loaded tray-like bottom package member.
~ s is shown, upper film lamination extruder assembly~
component 22 includes three separate extruders 27, 28 and 29 which extrude f:ilms 30, 31 and 32, respectively. Film extruder ;~
27 is supplied witll a resin which produces a thermoplastic poly-urethane film 30, while ex-truders 28 and 29 are supplied wlth resins which produce films 31 and 32 having properties and characteristics which are specifically adapted to rneet the requirements of the package to be ultimately formed. For example, in packaging food products which are subject to deterioration by contact with oxygen, film extruder 28 can be ~;

.7_ ~2895 ; ~

supplied Wit}l a sui-tal)le oxygen barrier Eilm--forming resln such as, for cxample, a polyvinylidene chlor:i(le-vinyL chl~:oride~
copolylller having a contcnt of about 70 to 90 wcight ilcrcent vlny~
lidcne chlolidc ~n(l about 10 to 30 wci.ght percent vinyl chlori~e.
Similarly, :Eilm extruder 29 can be suppl.icd with a f].exible r~LI:m`~
forming res:i.n such as, for example, a flexible polyvlnyl chlorld~e~
Iilms 30, 31 and 32, upon being extruded, are immc~
diately introduced into the controlled temperature water:~bath~
23 which, as previously noted, is maintained at a temp~erature of Erom approximately 40F. to 100F. and which prefera~bly ~is~
maintained at a temperature of about 60F. The polyvinylidene~
chloride-vinyl chloride Eilm 31, when reduced to this temperaturc,~
w:ill become "s~ crcooled" and exhibit desiral)le pro~erties and~
charllcteris-tics well kno~n to those skilled in this art and~
:Eully descrihed i.n U. S. Patent Nos. 3,083,106; 3,18:6,~505 and~

As is shown, films 30, 31 a~d 32 immediately u~on be introduced in the cooling bath 23 are formed into a film~ lc~mln~
ation 33 by contacting such :Eilms between a palr of combinlnn rollers 34. ~ilm lamination 33 is then directed around~guid~e~
rollers 35 and 36 into the package-:forming component 25.
1ll the illustrated embo~iment, bottom package:member~
supply component 24 feeds a plurality of pre-formed and product;~
loaded tray-like bottom package members 37 into package-forming~
component 25 via conveyor 38 and guide roller 39. While the tray-like bottom package member 37 can bc composed of a wide variety o:E materials, highly satisfactory hermetical].y sealed packages can be Eormed when such tray-like member 37 is composed of a rigid polyvinyl chloride.

Whi:le cntering package-forming conIponent 25, the thermoplastic urethane lami.na 30 of ri:Lm lami.n.Ition 33 is in ;~
overlying rclation with thc product loa(Ic(l tray-.like bottom package meIlll)crs 37. Packagc-forming comr)onent 25 is constructed;~
and opcrates in a knowIl manner to hring fi]m laIlli.nation 33, and in yarticular the thermoplastic urethane lamina 30 thereo-f, into~
direct contact wi.th seal forming portions on the tray-like bottom package member 37 while simultaneously evacuating the interior of the package so formed. Such evacuation can be in the manner more fully described in the aforementioned lI. S.; ;~
Patents 3 083,106 and 3,129,545. Upon l)eing d:ischarged rc.m;
the p<IcIca~c-orllling componcnt 25, the tI-Ius rorme(l ~)a( ka~e~; 40~
can l)e Ileated hy a suitable heLIter 2() to produce the previo~Isly descr:ibed a~lvantageous hermetic seal inte~rity and strength control achievable with this inventio Thc packages 40 IlpOII being thus ormed can be received~
in a combination labeling and trimming uni.t (not shown) whereln~
labels are applied. The packages 40 are separated from the fi.].m lamination web which is received upon a suitablc collectlng;~
roll 41. Ihe separate packages (not S}IOWIl) arc theIl collected {0l Ih~tllCI h~ d~ g~ storage shi~ ing, etc.
Ircs 2-4 generally i~lustratc nnc FO I DI 0 1` I)a C k a ~ e 40 maIlufacture(I in accordance with the previously (Iescri.bcd method. ~s shown, package 40 includes a bottom tray-like member 37 having a plurality of product-shape con-forming cavities 42 therein (which in the illustrated embodiment are shaped and sized to receive miniature or cocktail ~rieners 43). A periphernl:
product-surrounding flange portion 44 has a top surface 44a which is in direct contact with ~he bottom surface 30a of the thermo- ~ :~
plastic polyurethane film lamina 30 and forms a hermetic seal ~ ~ :
therewith without the presence of an ad}lesive or heat seal. : .

2~

I f ~lesire(l, I)a(h,lge ~In ~an l-c l~iov:i~lc(l wit:ll ;l s~ al)le tacil;
xul)l)ol-t recciving aperture 45 whicl~, by reason ol` tllc cnlcllgo~
flarlgc arca, doeS not interfere with tl~c inte-.frity, or seriously ~ICrcct t lle strength, of thc llcrmet:ic se.~
Fi~ure 5 and 6 illustrate a ~ a ckag e embo~l y:i. llg principles of the present invention wilich is particularly suited for packaging bacon strips and s:imilar- elongatcd meat ``~
products. ~s is shown, the package 51 complises ~ baseboard 52 UpOII wilich a product board 53 is mounted. I`lle bacon~l)ro~uct~
54, uxually in the form of a plurality of stackecl el~ongate~
slif_es, extcll(ls alollg the l)roduct hoard 53.~ A lanl~nate(l cover~
55 i; sllown wllicll includes an inner lal1lina ~6 com})oc;ed of a thermoplastic polyurethane :Eilm, an intermediatc lainina 57 composed of a suitable oxygen barrier Eilm such as, for example~
oxygen barrier saran, and an outer lam:ina 55 composed of a suitable flexible film such as, for example, a flexihle pol-y~
vinyl chloride. In accordance with the present inventio~n, inner thermoplastic polyurethane film 56 is in direct contact ~ith the baseboard 52 along a peripheral sea]-forming ma~rginal~
portioll 59 and orms a hermetic seal with mclrgillal portJon 59,~

without the preience of an adhesive.
Figures 7 and 8 illustrate a modified package 60 which is particularly suited-for packaging sliced luncheon meats~
61 such as, for example, bologna, salami, beef loaf, chopped ham loaf, and the like.
As best shown in Figure 8, the package 61 includes a baseboard 62 formed, for example, from rigid polyvinyl chloride,~
and which is provided with a peripheral seal-forming flange portion 63. Baseboard 62 can be formed of other materials which are inherently oxygen impermeable such as, for example, a metal foil-covered paperboard or metal foil-covered thermoplastic ~; ~
material. ~ ~ :

-10- :
.

~4~

[n tl~ erllbodilllent, a cover Inclllber ()~ cludes a outer thermopl~stic oxygen bclrri.cr :f:i.lln lamina 65, -ror cxamp]~e,~
a clyit-;llLizcd l)olyvinyliclcllc chlori(le, wl~ i a~ crc(l to an inller thclmol)lastic l~olyurcthanc ri l", (-6. /~ herllletic scal, ~ree o-L any aclllcs:ivc i~ ormcd l)etween tlle thcrmoplas~tic l)o.i~y~
urethane ~ilm 66 and the product surrounding margin 63 of the ~: ~:; :
baseboard member 62.
While various embodiments of the present invention :~
have been described in detail, it will be appreciated that moclification~i thereto may be made witllaut del)artin~g from:the~
spirit and scope thereof. Accordingly, onlv SUC}I limitations arc to bc ilnl)osc(l Oll this invent:ion ~IS are~ atc~l in thc ~: ~

:~

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A method of packaging a product, wherein said method essentially comprises, in sequential steps:
(a) extruding a thermoplastic polyurethane film;
(b) immediately cooling the extruded film to a tem-perature within the range of 40°F. to 100°F.;
(c) placing the cooled film in overlying relation with a product which, in turn, overlies a bottom package-forming member having generally planar, seal-forming marginal portions which peripherally surround the product, wherein the seal-forming portions are of a thermoplastic or foil material; and (d) directly contacting the film with the seal-forming portions to form, without an adhesive layer or heat seal, a hermetic seal enclosing the product.

2. The method of claim 1 wherein said thermoplastic polyurethane film is cooled to a temperature of approximately ;
60°F. immediately after being extruded.

3. The method of claim 1 wherein the seal interface `
formed by contacting said thermoplastic polyurethane film and generally planar marginal portions is at a temperature of about 75°F. to about 200°F.

4. The method of claim 3 wherein the seal interface is at a temperature of about 90°F. to about 175°F.

5. The method of claim 1 wherein said thermoplastic polyurethane film is a polyester type aromatic isocyanate polyurethane.

6. The method of claim 1 wherein said thermoplastic polyurethane film is a polyether type aromatic isocyanate polyurethane.

7. The method of claim 1 wherein said thermoplastic polyurethane film is a polyester type aliphatic isocyanate polyurethane.

8. The method of claim 1 wherein said thermoplastic polyurethane film is a polyether type aliphatic isocyanate polyurethane.

9. The method of claim 1 wherein said bottom package-forming member is composed of a material selected from the group consisting of rigid polyvinyl chloride, flexible poly-vinyl chloride, saran, polycarbonates, acrylonitrilestyrene copolymers, polyethyleneteraphthalate, polystyrene, polypro-pylene, polyethylene, nylon, acrylonitrile-methylacrylate co-polymers and aluminum foil.

10. The method of claim 1 wherein said bottom package-forming member is a rigid polyvinyl chloride.

11. A method of packaging a food product, wherein said method essentially comprises, in sequential steps:
(a) extruding a thermoplastic polyurethane film;
(b) immediately cooling the extruded film to a tempe-rature within the range of 40°F. to 100°F.;
(c) placing the cooled film in overlying relation with a food product which, in turn, overlies a bottom package-forming member having generally planar, seal-forming marginal portions which peripherally surround said food product, where-in the seal-forming portions are of a thermoplastic or foil material; and (d) directly contacting the film with the seal-forming portions to form, without an adhesive layer or heat seal, a hermetic seal enclosing said food product.

12. The method of claim 11 wherein said thermoplastic polyurethane film is cooled to a temperature of approximately 60°F. immediately after being extruded.

13. The method of claim 11 wherein the seal interface formed by contacting said thermoplastic polyurethane film and generally planar marginal portions is at a temperature of about 75°F. to about 200°F.

14. The method of claim 11 wherein the seal interface is at a temperature of about 90°F. to about 175°F.

15. The method of claim 11 wherein said thermoplastic polyurethane film is a polyester type aromatic isocyanate polyurethane.

16. The method of claim 11 wherein said thermoplastic polyurethane film is a polyether type aromatic isocyanate polyurethane.

17. The method of claim 11 wherein said thermoplastic polyurethane film is a polyester type aliphatic isocyanate polyurethane.

18. The method of claim 11 wherein said thermoplastic polyurethane film is a polyether type aliphatic isocyanate polyurethane.

19. The method of claim 11 wherein said bottom package-forming member is composed of a material selected from the group;
consisting of rigid polyvinyl chloride, flexible polyvinyl chloride, saran, polycarbonates, acrylonitrile-styrene copolymers, polyethyleneteraphthalate, polystyrene, polypropylene, poly-ethylene, nylon, acrylonitrile-methylacrylate copolymers and aluminum foil.

20. The method of claim 11 wherein said bottom pack-age-forming member is a rigid polyvinyl chloride.

21. A package comprising a product enclosed between first and second layers of packaging material having respec-tive sealing surfaces which are adhered to each other, with-out an adhesive layer or heat seal, to form a hermetic seal which can be separated when access to the product is desired the sealing surface of one of the layers consisting essen-tially of a thermoplastic polyurethane film, wherein the package has been formed by a method essentially comprising, in sequential steps:
(a) extruding the thermoplastic polyurethane film:
(b) immediately cooling the extruded film to a tem-perature within the range of 40°F. to 100°F.;
(c) placing the cooled film in overlying relation with the product which, in turn, overlies a bottom package-forming member having generally planar, seal-forming, mar-ginal portions which peripherally surround the product, wherein the seal-forming portions are of a thermoplastic or foil material; and (d) directly contacting the film with the seal-form-ing portions to form a hermetic seal enclosing the product.

22. The package of claim 21 wherein said thermoplas-tic polyurethane film is a polyester type aromatic isocyanate polyurethane.