CA1265277A - Polymeric coating for container induction innerseal - Google Patents

Abstract

POLYMERIC COATING FOR CONTAINER INDUCTION INNERSEAL
Abstract A heat-sealable polymeric composition for use in providing an innerseal on the open mouth of containers, such as bottles, comprising a mixture of a microcrystalline wax, a polystyrene or derivative thereof, and a high molecular weight polymeric material selected from ethylene/acrylic acid copolymers, ethylene/vinyl acetate copolymers, ethylene/vinyl acetate/methacrylic acid terpolymers, ethylene/-methacrylate copolymers, and polyethylene.

Description

33517 C~N lA

I'OI,YMl'~LC ('O~'I'LN(. L;~C)~ )N'~'AlNI.I~ :[I`~DUC'I'I(~N INN~ SL,AL.

~rcchnLc~ ieLcl Tt~ nv~rltlo~l relat~s t:o a polymeric coating wt)ich is utili~e(l to prel~are a seal over a eontainer oper~ cJ, ~uch .~s a ho~t:le, convenLlollally haviog a ~crew Cdp or sndp cap ~lo~lre. Mor~ ~peeiflcally, the polymerlc eoatin~J is ~Itill~.ed ln conjunctiorl with other componcnts to provide arl innerseal over the container opc~ning via induetion heat:irlg.

B~lckcJround Art ____ Screw top ancl snap eap containers for the disperlsing of eonsunler produets sueh as medieines, foods, ete. are typieally sealed to prevent tampering therewith prior to ultimate purehase by thè eonsumer.
Over the past few years, and espeeially in the United States, it 1.9 apparent that sueh tamperincJ of goods has oeeurred, resultillg in injury, often severe, and in SOllle eases, everl dea~tl. ~eeordingly, it has beeome obvious t:hat new ancl ereal:ive sy~tems for the sealing of sueh eont:a:in~rs is neeessary.
One system whiell has met: with signifieant c~olrlmereia:L ~eeess ha-; beell traclemclrked as "SafeGard".
W:it:h this sysL~m, a herllletie seal is provided, whieh is suitable for use witll t:Jle forecJoirlcJ eomlllocllties. ~he ~5 scal is pclrt.ieu:Larly eifeetive for produets whieh are t:o he free from eontdlninclt:ion, oxidat:ion, and/or moisture.
The seal mechanisln of the "Safe-Gard" system typieally involves four parts: a pulp board baeking, a wax eoating, aluminulll foil and a heat sealable polymerie film eoating. These materials ean be typieally supplied in strip form as a laminated strueture, and applied to a filled container in eonventional fashion during the filling proeess. After being eapped, the filled paekage passes through an eleetromagnetie field generated by induetion heating equipmen~, whieh provldes for heating of the outer edge ;,~
of tl~e dluminum foil, t.hereby CaUSillg a meltinc3 of the hcat. ~al~le coat.ing. Upon cooling thereof after lcav~ 3 t.he induct.ion fie~.d, a herlnetie seal of the 10:L1 t.o the~ .Lip of thc cont.ainer is effeeted. At the ~janlc~ t:iln~, clurin~J the in~uetion heating step, the wax layer between t:he foi.l and pulp board backing melts, thcreby dest.roying t.hc bond ther~between. While the wax remc-li.ns in a mol~n st.ate for a short periocl oi time, it is wieked up Ol- absorbed by the pulp baeking sueh that the wax bond is perlllanently weakened. ~pon removal of the eap from t.he container, t:he pulp backing thus remains with the eap inner surfaee whieh eontaets and seals the lip of the cont.ainer after the foil liner has been removed by the consumer.
It has been found that ~.he heat sealable polymerie eoat:ing or c~dhesive presently ut:ilized in the inclus~.ry has a re.].cltivel.y weak bond to glass cont:aincrs, espeeially in the presenGe of "lubrieious coat.inc3s", eurrel~ L.y used in high speed cont:ainer-f:ill.incJ inclust.ries, sueh as the ~ood industry.
I;'urtllerlllo:re, .it. has been found that the eomlllclreiall.y avai.lc.lble adhesive in the induetion innerseal syst.em ean b~ ineffeetive for use with various plast.ic eontclirlers. For exampl.e, while the adhesive may be hi(3ll1y c~eetive for polyethylene cont.ainers, it mcly be relat.i.vely ineffeetive w:ith other eonventional plastie containers, such as polys~yrene or polypropylene.
It has now been diseovered that the polymerie material of this invention, when utilized in an induetion-aekivated innerseal system, will provide a strong, heat-sealed bond on all types of glass eontainers, even those having "lubrieious eoatings"
thereon, as well as most popular plastie eontainers, sueh as polysky:rene, polyethylene, polypropylene, polyvinyl chloride~, et:c.

Disclosure of the Invention In accordance with the invention there is provided a hea-t sealable polymeric composi-tion for use in conjunction with other elements to provide an innerseal on the open mouth of containers. The composition comprises from about 5 to about 50 percent by weight of a microcrystalline wax; from about 5 to about 50 percent by weight of a polystyrene or derivative thereof having a softening temperature, determined by a Ring and Ball Tes-t/ of between about 50C and about 13SC; and from about 25 to about 90 percent by weight of at least one high molecular wei~ht polymeric material selected from the group consisting oE ethylene/acrylic acid copolymers, ethylene/vinyl acetate copolymers, ethylene/vinyl acetate/methacrylic acid terpolymers, polyethylene, and ethylene/methacrylate copolymers.
Detailed Description As aEorementioned, the basic elements oE an innerseal system for containers based on inductlon heating lnclude a pulp board back;ng, a wax coating thereover, aluminum Eoil over -the wax, and a polymeric Ellm over the foil capable of providing a heat sealable bond. In addition, there may be other layers of materials, such as polyethylene terephthalate, polyvinylidene chloride, ethylene/vinyl acetate, and the like, interposed between the heat sealable polymeric coating and the metal foil to heighten particular characteristics, such as a vapor barrier, for example.
Also, there may be a film of, e.g., paper interposed between the heat sealable film or coating and the metallic foil to provide for increased adhesion, to increase the ability to detect ~-3a- 60557-2858 ta~pering, to increase web rigidity for ease of handling during coa-ting operations, etc.
In some instances, a pulp board material may already be included within the container cap to conform -to irregularities in the container opening. In this instance, the wax coating and the pulp board backing q~

nlcly b~ unlleces~ary. ~urt~hcrmoce, if resealability is urln.~-c~ .Jry, as ~or exalllE)l~ wi.th a snap cap closure, t.i-)cs(~ c~nt.~i rl~dil~ Illay be omittcd. ~lowcver, th~
ri~ lity of tllc wel. mu~t: be maintai.ned sufi-iclent:ly 5 h.igh f~r (Jis(~ In.lnch:in~, w~b han~llr)cJ, and relat.ed m.lnllLclctur:i.rlg operat.lorls.
The basic cor~structlon of a web for induction sealing of eont.a.illers typic,llly first comprises a paper pulpbo~lrd which rleed not be greater than about. 1500 micromcLers thick, and lS preferably bet.ween about 125 alld about 1000 micrometers thick. An example thereof is 875 rnicromete.r whit.e li.ned pulpboard.
I~he second component, applied over the pulpboard, is a wax layer, typically less than about 100 micromet.ers t:hick, ancl preferably about 25 miero-meters thiclc. An eXclltlpl.C~ t.hereof :is Victory Amber microcrysl:al.~i.ne wax.
Th~ L.hircl component: is a metallie foil, L~re:Eercll)ly cllum.Lnum. ~rh~ foil neecl not. b~ greater than about 75 mi.erolllete~rs t.h:Lek, and preEerably is from about 5 t.o a~ollt. 3/.5 mlcrom~t.ers t:hiek. An example t.hc~reo~ is Aleoa'i 1.14'j-0 a:Lum:irlum Eoi.l.
'L'h~ last: colllponent :i.s of course th~ heat seal.clb.Le polymeric coat.ing of my invention which need not be ~Jreater than about: 150 rnicrometers t.hick, and is pr~ferably from about: 12.5 to about 62.5 micrometers thick.
As discussed earlier, . other layers of mat:erials can be added t:o enhance desired properties, and if resealability of the eon~ainer is not necessary, the pulpboard and wax layers are not rcquired.
The first eomponent necessary for preparation of the polymerie eoating eomposition of my invention is mierocrystalline wax. Other waxes, sueh as paraffin, deerease the adhesive strength of the polymerie eoating and reduee flexibilit.y thereof. The melting point of the mieroeryst.alline wax, det:ermi.ned pursuant ASTM
D-127, should be between about 65C to 100C, and preferably between about 75 C and about 90C. At less t;~

t~ali aL~o~lt. ~5 C, thc ,Idhesive rnay tend to block, while a m(~Lt t~ll,per.llurc o~ ~re~tcr th,ln abou~ 100 C will r~duc~ adl)csion. 'r~c InLcrocrystalline waY~ sl~ould be prescnt. d~ froln uboul. 5 pcrcc~nt. to about 50 percent by wei~J~I~ oL t~)e ~o.lylne~:~c colTIE~osit.ion, and more preferdbly bet:wccn about: 10 percent. and about 50 ~ercci-lt by welcJIIt. ~e.Low about 5 perccllt, acdh~sion may b~com~ xce~isivc:Ly reduced, and at. gredt:er than about 50 percerlt, cohesive st:rengt.h may be too low, thereby minirni~ing the abil.it.y to detLct tampering.
Exarnplcs of microcrystallirle waxcs having utility t-lerein include the B Square~series of waxes, such as B -175, 185, 195, etc., and the Victory~Series, such as Victory Alnb~r, both being commercially availabl~ from Bareco. Oth~r microcrystalline waxes fin~ing utili.t:y here:Lrl incl.ude t.he Multiwa ~series from Witco Chemical, cxarnples including W-835, W-445, 180-M, e~:c.
'l`he scconcl componcnt. of my inventlve polymc!r.Lc composi.t:ioll inclucles low molecular weight polystyrctlc OlA pol.yst.yrene cle.r:Lvatives. E.xamples of acc~pt:able cl~riva~.ives inclucle po.Lymerlc materials such as alE~I-a-m~l.hyl s~yrenc and viny:L toluene/dlpha-methyl ~t.yrerlc. Thc~ polyst:yr~rle~ or derivative t.hercoE should havc a softeni.llg tenlpc!rat.ure, as det:ermined by the converltiolldl Rirlg and Ball tcst:, of bct:we~rl abou~ 50C
and about .135C, and preferably between about 70C and about 100C. At a t:~mperature of less t:harl about 50C, the adhesive may tend t:o bloclc, and at greater than about 135C, phas~ separation may occur, thereby r~ducing the adh~sive properties of the composition.
The polyst.yren~ or derivative thereof should be present at from about 5 to about 50 percent by wcight of the polymeric composition, with from about 10 to about 30 pcrcent by weight: being preferred. At less than about 5 percent:, adhesion may be reduced. At ~rcatcr t.h~n about. 50 percent, t.he adhesive may t:end to bloclc ~IICi adhesion is recluced.
- -~ Tr~ ~k $~3X~

~ xample, o:f comlncrclally available poly-st:yrenc o.r deLivLItLves thereof include t.he I'iccolastlc~
ser.ies oi polyst.yrene allcl modl:~ied polystyrene coln~ouncl~j, Sp~ .L.L i.C e:~c~ eS heing A-75, D-75, E-100, et.c. ~`urtl-~er exalf~ les inclucle t.he tlercul.es Krlstalex~
serlcs of Ejoly~ller.ic alpl-la-methyl st.yrene, such as 3085, 1120, ctc.; tne Piccotex~ serics of polymeric vinyl toluene/alpila-nlethyl st:yrene compounds such as 75, LC, 100, etc.; ancl the Piccoclex ~series of styrene/-acrylonitrile copolymeric matcrials such as 100, 110, 1~0, ~tc.
The final component necessary for my polymeric composition includes a high molecular weight polymer or bl.end thereof selected from the group consi.stincJ of ethylene/acrylic acid copolymers, eLhylene/vinyl acetat:.e copolymers, et.hylene/vinyl acetat.c/methclcrylic aci.cl terpolymers, polyethylene and et.hylerlc/mcthacrylal:e copolymers.
Ethylene/;-lcry.l:i.c acicl copolymer~ having ut:i.llty h~-~rc.~.i.tl include t.hosc having an ac:rylic acid collt:elll. of from bet.wee~ll about. 3 t.o about 20 percerlt by we.i~h~ alld pre.Eer.lbly l~.rOlll about. ~ 0 about 13 percent by weigllt; a melt inclex of clt. :Least: about 2.5 grams per 10 millLIte~ alld prcferably a vi.scosity be~weell about 500 t:o about 250,000 cps ~Brookfield 60C). Commercially available examplc?s of suct) ma~-.erials include Allied Chemical's AC-540, AC-580, AC-1120, etc.; and Dow Chemical's EAA-435, EAA-459, etc.
Ethylene/methacrylate copolymers having u~ility herein are those containing approximately 80 percent ethylene and approximately 20 percent rrlethacrylate by weigh~., and having a rnelt index of about 2.4 grams pcr 10 minutes. Commercially available materials include Gulf Oil Chemical's EMA-2205.
Useful polyethylene materials include those having a melt index be~ween about 1.8 and about 600 grams per 10 minut.es, wit:h from about 70 to about 500 grams per 10 minut.es being preferred. An example of a ~ T`~ ~

po.Lycthyl.~rle rndt.~ri.al which has sclt,is~act.ory utili~y h~rei~ .is U.S. :Irldust.Lial Ch~rnlcal's Pe~LO~hen~NA 595.
LLI-Iylc~rle/v.inyl acet atc copolymers inelude t.ho~ wh~relrl t.llc vinyl acc~tdt~e cont.~rlt. is betw~en clbo~lt: ~ arld abou~: 65 perc~nl. by wcight, wit:h from about 15 to about 95 p~.t~~ent by weight bei.ng preferred; a mcLt ind~ o~ grcat~.r t.han about. l.5 grams per lO
mlnutes, and pr~e~ably betweerl about 8 and about 600 grarrls per lO mi.nut~s. Examples of suitable et:hylene/-vinyl ae~t.~t,e copolymers include duPont's Elvax~410, Elvax 210, ~lvax 150, etc.; and U.S. Industrial Cllelllic~al's Ultrathen~ E-632.
Ethylene/vinyl aeetate/me~,haerylie aeid terpolymers hav.ing utility herein inelude those wherein the vinyl aeetate cont:ent is between about 24 and about 30 pere~nt by w~ight.; l.he m~lt index ther~of beinc3 from about 5 to about 600 gralns per lO minu~es with from about. G0 to about. ~70 grallls per lO minutes bcing pre~'orrecl. ~x~mples o.L suitablcn mat~ria.ls lnelude Dupont's Elvax 431,0, ~320, et:e.
If t:he n~ index of t.h~ hic~h molccular w~;ight eomponent: o.r blelld thereof :Ls too low, ineom-pati.b:ilit:y oi' the i.ngredierlt:s m-ly r~sul.t, eausing poor adhesion. Exeess.Lve mel.t inctiees may reduee the Gohesive s~.rcncJt.h of' t.he composition such that minimal talll~.)er indicatinc~ properties may result.
If the vinyl acetate content of the copoly-mers or terpolymers noted above is t.oo low, the adhesiorl of the cornposit:ion t:o thc overlying metallic foil will be reduccd, again reducing the tamper indicating properties thereof. Excessive vinyl acetate content may tend to causc the adhesive to bloclc.
The concelltration of the high molecular weight polymeric component or blend of pol.ymcrs should be from about 25 to abour. gO percent by weight with from about 25 to about 75 percent by weight being preferred. At less than about 25 ~crcent., thc cohesive ~ / r~ ~

~q~

s t r ~ J t ~ . clg.~in r~ c~l bclow d ll a C` C L! p t cl ~ vel, .~nd c~t greatcr than about: 95 percel)t, c~dhesion is un~lccc~ l db I ~ .
My i~C`cl~ ~ic~ll a~le poIym~ric coating cdn be S comL~oun~ by u~ .irlg collverlt.Lonal high pressur~
st.cc~ln he~t~d glas~-lincd or stainlc!ss stcel kettles or oll ~)eatc~ stair~ ss stccl kettles for melting and mixing compollents.
~pplicatLorl of thc polym~rie coating to the metallic foil substratc can be undertaken by convcntional t.cchnlques, including extrusion and other hot m~lt coat.ing techlliqucs. Coat:ing wcights of the polymeric material. should be from about 4.8 grams per square met.er t.o about. 144 grams per square meter.
Prefel'ably, t:hL? COat.:illg weight:s are from about 12 to abo~lt 72 gralns per square rnet:cr.
To prepare a wcb for inncrseal appll.cations, ct p~lp~`L' - b~clccd IllL!t:~lI.iC` foi.l., or t:ll~' foil by itsclf is Ob~ li nL`Cl Liirt.!Ct l.y l:'L'Om venclors. l~ a film, sueh as polyest:cr, I.s clec;Lred, SdmL! Call be converliently applied to t.hc foi.l. V:i.cl COl'lVenl:i.Orlal t.eCI'llliqUeS, e.9., gravure ro.ll C`oat.in~J. `L`I~L pol~ymeric compos:it:ion oE my invenl:ior can t:hc!n be ho~ mcLt: co.lt.ecl OlltO t.he met.all.ie foil (or on~o t.hL? paE)er or film coatin~ t:hereon, iE present) acl.lill us:ing eonverlt:ional t.echniclues.
The inverlti.on w.ill now be more. Eully defined by the followi.ng non~lilnitincJ examples, wherein all pdrts are by weight unless otherwise speeified. In eaeh example, a determinat:ion of the adhesion charae~er-istics t:o speeific containers is made by manual testing, i.e., the foil is attempted to be hand peeled -from t:he edges of t:he cont.ainer opening whcre the seal should be effective.

Int:o a 9 ounce elear g1ass bo~tle were plaeed

2.0 grams of Kristalex 3085, an alph~-methyl styrene polyrn~r from ~Icrcules, 2.0 grarns of B2-175, a miero-_9_ er-y~tdllin~ wa~ tr-oln Bar~co arl~ 1.0 cJram of AC-580, ar.
~tl~ylene/acryllc ~-cld cGpolymer from Al.lied Chemieal.
'rhe bot.t,:Le con~.en~s were heatecl to 176C, ~E't,er Wh.LCtl 7.~ ~3ralll'i C)~ VclX 4320, an et.hylene/vinyl ~CCt.~tejllletllclCryl.iC ~lcid t,er~olylner from duPont. were aclcled and t,l-~e cont.ents h~ated at 176C for 5 n~inutes.
The cont,ent.s w~re t:hcn agit.ated until. a elear molten solut.lon r~sulted.
The molten sol,ution was then poured onto the paper side of a ~0 cm by 20 em paper baeked alurllinum foil. Thi~ sheet was t.herl hot: prexsed at 30 psi for 10 seeonds at 14~C. The coated sheet was then wax bondecl, usincJ Vietory Amber mieroerystc.alline wax from Bareeo, on t:he white line side of 875 mie:rometer pulp board and dic,~ punehed to the desired dise size, and insert~d int.o p:Last.ie eaps. The eaps wer~ then serewed onto the moul:l-)s o:E a polyet:hylerle-eoat.ed gld~s bottle~, all un~.Leclt.e(l gl,.axs bot.tl.e, a polyst,yrene bott.le, a hiyh c.len:.,it:y polyet:l)ylen~! bottl.~!, a polyvinyl ehloride bott::le ancl a polypropy:l.c~rle bot.tle, then sealecl with an induet:ion cJL~neral.or. A:Eter eool.ing, t.he eaps of t.he ~ sea.lecl bot.t.:l.es were :rellloved ancl t.he inrlr!rseals hand peel.ed t:o cleterln.ine t.he decJree o~' tamper .indieation. In all lnxtclne~s exee.l.:l.elll. result:s were obtained.

EX_ML~L~S 2-5 The foll.owing eolnposlt.ions were pr~pared, proeessed and test.ed as per Example 1:

Colnporlent ~'arts E~. 2 Ult.rcathene U'E-632, an ethylene/vinyl 16.6 clCCt.atC eopolymer frc~n U.S.I. Ch(?rn.
Elvax 43~0 50.0 B 175 mieroerystalline wax frern Bareeo 16.7 Kristalex 30~5 16.7 100.O

~6~

1~;. 3 I~MA 2205, an etily~cl1e/rn~thacryl~te 33.4 co~)Lym~r from Gu:LL
VLCtOIY ~n~-ior, a micrc)cryst.allirle WCIX 33~3 f:rc~n liar~eo L':iccolex l.C, .1 vinyl toluene/alpha-rr~ts~yl 33.3 styrelle copo.ly~ r l~rom tlercules 100 .0 I x . q Elvax 4310 50 . 0 Pet rot.helle NA-595, a poly~thylene25 . 0 from U.S.I. Csl~m.
~32175 wax 12.5 Piccolastic A-75, a polystyrene from12. 5 Hercules 100 . O

Ex. 5 AC-580, an ets~ylcne/acrylic acid 16 . 6 copolyn~r from Alli~d Chelll.
Elvax 4320 50 . 0 Mult.:iwax 180--M, a mi.crocrystalline wax 16.7 f rom W:i. k t:co Ch~m .
Krisl:al.cx :L1.20, an alptlc.l~lllet:slyl st:yrene 16.7 polymer :Erc~n ~ rcll:Lc.~s __ 100 . O

:Ln cc:lch exasnpl.~, result.s similar to those of Exaln~le 1 were obtai.rl~cl.

Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A heat sealable polymeric composition capable of providing an innerseal for the open mouth of a glass or plastic container, the composition comprising:
from about 5 to about 50 percent by weight of a microcrystalline wax;
from about 5 to about 50 percent by weight of a polystyrene or derivative thereof having a softening temperature, determined by a Ring and Ball Test, of between about 50°C and about 135°C; and from about 25 to about 90 percent by weight of at least one high molecular weight polymeric material selected from the group consisting of ethylene/acrylic acid copolymers, ethylene/vinyl acetate copolymers, ethylene/vinyl acetate/meth-acrylic acid terpolymers, polyethylene, and ethylene/methacrylate copolymers.

2. The composition of claim 1 wherein said microcrystalline wax has a melting point between about 65°C and about 100°C.

3. The composition of claim 1 wherein said polystyrene or derivative thereof has a softening temperature of between about 70° and about 100°.

4. The composition of claim 1 wherein said ethylene/acrylic acid copolymers have an acrylic acid content of from about 3 to 20 percent by weight and a melt index of at least about 2.5 grams per 10 minutes; said ethylene/methacrylate copolymers have about 80 percent by weight ethylene and a melt index of about 2.4 grams per 10 minutes; said polyethylene material has a melt index between about 1.8 and about 600 grams per 10 minutes;
said ethylene/vinyl acetate copolymers have a vinyl acetate content between about 8 and about 65 percent by weight and a melt index greater than about 1.5 grams per 10 minutes; and said ethylene/vinyl acetate/methacrylic acid terpolymers have a vinyl acetate content between about 24 and about 30 percent by weight and a melt index from about 5 to about 600 grams per 10 minutes.

5. An article capable of providing an innerseal on the open mouth of plastic or glass containers and comprising a matallic foil having disposed on one surface thereof a heat sealable polymeric composition, said composition comprising:
from about 5 to about 50 percent by weight of a microcrystalline wax;
from about 5 to about 50 percent by weight of a polysty-rene or derivative thereof having a softening temperature, determined by a Ring and Ball Test, of between about 50°C and about 135°C; and from about 25 to about 90 percent by weight of at least one high molecular weight polymeric material selected from the group consisting of ethylene/acrylic acid copolymers, ethylene/vinyl acetate copolymers, ethylene/vinyl acetate/meth-acrylic acid terpolymers, polyethylene, and ethylene/meth-acrylate copolymers.

6. The article of claim 5 wherein said microcrystalline wax has a melting point of between about 65°C and about 100°C.

7. The article of claim 5 wherein said polystyrene or derivative thereof has a softening temperature of between about 70°C and about 100°C.

8. The article of claim 5 wherein said ethylene/acrylic acid copolymers have an acrylic acid content of from about 3 to about 20 percent by weight and a melt index of at least about 2.5 grams per 10 minutes; said ethylene/methacrylate copolymers have about 80 percent by weight ethylene and a melt index of about 2.4 grams per 10 minutes; said polyethylene has a melt index between about 1.8 and about 600 grams per 10 minutes;
said ethylene/vinyl acetate copolymers have a vinyl acetate content between about 8 and about 65 percent by weight and a melt index greater than about 1.5 grams per 10 minutes, and said ethylene/vinyl acetate/methacrylic acid terpolymers have a vinyl acetate content between about 24 and about 30 percent by weight and a melt index from about 5 to about 600 grams per 10 minutes.

9. The article of claim 5 wherein said metallic foil is aluminum foil.

10. The article of claim 9 wherein said aluminum foil has a paper backing thereon and said polymeric composition is disposed on said paper backing.

11. The article of claim 5 further containing a wax layer disposed on the metallic foil on the surface thereof opposite said heat sealable polymeric composition and a paper pulp board disposed over said wax layer.

12. A glass or plastic container having a screw top or snap cap closure associated therewith, the open mouth thereof having a tamper-proof innerseal thereover, said innerseal comprising a metallic foil attached to the edge of said open mouth, attachment thereto being by virtue of a heat sealed polymeric composition, said composition comprising:
from about 5 to about 50 percent by weight of a microcrystalline wax;
from about 5 to about 50 percent by weight of a polystyrene or derivative thereof having a softening temperature, determined by a Ring and Ball Test, of between about 50°C and about 135°C; and from about 25 to about 90 percent by weight of at least one high molecular weight polymeric material selected from the group consisting of ethylene/acrylic acid copolymers, ethylene/vinyl acetate copolymers, ethylene/vinyl acetate/-methacrylic acid terpolymers, polyethylene, and ethylene/-methacrylate copolymers.

13. The container of claim 12 wherein said microcrystalline wax has a melting point of between about 65°C to about 100°C.

14. The container of claim 12 wherein said polystyrene or derivative thereof has a softening temperature of between about 70°C and about 100°C.

15. The container of claim 12 wherein said ethylene/acrylic acid copolymers have an acrylic acid content of from about 3 to about 20 percent by weight and a melt index of at least about 2.5 grams per 10 minutes; said ethylene/methacrylate copolymers have about 80 percent by weight ethylene and a melt index of about 2.4 grams per 10 minutes; said polyethylene has a melt index between about 1.8 and about 600 grams per 10 minutes;
said ethylene/vinyl acetate copolymers have a vinyl acetate content between about 8 and about 65 percent by weight and a melt index greater than about 1.5 grams per 10 minutes, and said ethylene/vinyl acetate/methacrylic acid terpolymers have a vinyl acetate content between about 24 and about 30 percent by weight and a melt index from about 5 to about 600 grams per 10 minutes.