Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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.
3- 60557-2858
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`~ ~
--7--
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.
EXAMPLE 1
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.
