CA2061198A1 - High abuse ionomer bag - Google Patents

Abstract

ABSTRACT
A heat shrinkable multilayer film having a measure of resistance to abuse, useful for packing products, such as meat cuts in which the bones are retained, which have a tendency to penetrate or puncture packaging, comprises at least three layers, including: (a) a first outside layer selected from the group comprising ethylene-vinyl acetate copolymer (EVA), very low density polyethylene (VLDPE) and blends of EVA and VLDPE; (b) a core or internal layer, comprising an ionomer or a blend thereof with EVA, ethylene-methacrylic acid copolymer (EMAA) or ethylene-acrylic acid copolymer (EAA); and, (c) a second outside layer selected from the group comprising EMAA, EAA and ionomers.

Description

SENT B~:Xerox Telecopier 7020 ; 2-11-92 ;1~:39PM ; 1~034332a31~ 916132328440,# 3 rha p~ant ln~ent~Dn r~lat~s to ~mprov~en~s ~n ~ndlor r~1ating to multllayer.he~t shrin~able pl~stic fll~s, Gontainers (~ bags) o~ packag~s using same and to re7ated medns dnd meth~ds.

M~ dyer heat ihrlnkable ~ilrns ha~ been u~ed ~or some time f~r the shrink wrapp~ng of vQrlous food products including Mo~t p~oducts whl~h ~ill r~quire refr~ dtlon or frr~e2in~. ~e~rdb1~ chdrac~ar~s~lcs ~n such ~ s ~r~
their de~ree o~ shrinkd~ un~er ~odera~ h~t an~ th~lr r~sls~ance to ab~se.

~ urr~ntly ~/a~lable ~n New ~ala~d arQ sever21 ~ilm~ useflll In the ~rapp~ng of prnducts sufh A~ m~at~. Th~s~ include lon4m~r bas~d m~t~riAli, dmptoyad in iono~n ~d9S of tr;gorl Packa~;ng Syst~n~s ~lt) L;~lt~d df Cornar A~ n ~r;v~ ~nd ~or~man Ro~, Hamilton, N~w Zoal~nd ond th~ EYA
~ethylene-vlny~ acetqte copolymor~ ba~ed ~at~rlAl~ of W~ Gr~ce (Pl23 ~;mited of ~rosse~ ~tr~ot~ Elsdon, Poriru~, ~hlch ~re kn~m as the~r SL3 and S~ bags.

~ h~ abu~e resi~t~nce ~ the tllm~ it ~m~rQ~d would make 3uch conta1n~
~ore useful ~n the pa~ka~ns ~ product~ havln~ a yreat~r t~n~nry ~4 penetr~
or puncture th~ packa~ln~, su~h as ~eat cuts ln whtch ~ones are ret~lned. It ls also des~ra~le for ~lms to have ~ood re;ls~nce t~ external abuse.

It is also des;r1~le f~r such ~ lms t~ h~ ~high shrink~ as th lmportant w;th respect tç both pr~s~ntation and çon5u~er appeal.

In this re~ard, Nçw 7ealfln~ P~t~nt ~p~liCAtiQn ~o. ~6 ~3 ~ r~c.e ~N2~ Ll~lted reldte~ ta multilayer fllms hQY;nJ both ~od r~sist~nc~ t~ a~us~
~nd heat shr1nk~b~ y. These fil~s cD~prise at least three l~yers; two outs1de lay~rs, e~ch co~prlsln~ ~LDPE (very ~w dens1ty polyethylen~) ~r a bt~nd of ~LD~E~VA, an~ ~n ~nt~nal layc~ w~1ch 1~ EVA r~r pr1m~rlly EVA, S~E ~:lg8Z~081 -8S~ZL~ Z -~ ' NOS ~ r ~ 35 SENT BY:Xerox Telecopier 702~ ; 2~ 92 ;12:40PM ; 18034332831~ 916132~2~44~:# 4 2 ~

-2.

Thc pre~ent 1nvcnticn is dir~t~d t~ fil~n~, contaln~rc, p~ck~g~ and method~ Or prDducln~ f;ln~s, ~hl~h ~ill go som~ way towar~ m~etln~, ~t 1e~t ln p~rt, the ~bovo ~ntion~d a~ms o~ ~ood abusq r~ol~tanco and he~t shr1n~bll1ty by different ~e~ns, or at l~ast pr~id~ th~ p~llC with ~ u~eful cholr-~.

~ used hercin, the term UVLDPE" r~fers to v~ry low d~nslty polyethy7en~
"~YA" r~ers to Dn ~thylen~vlnyl ~cet~ opYl~ne~ E~AA~ r~f~rs ~ ethyl~n~
meth~rryllc acid c~p~lymer, ~EAAI' to ethyl~ne ~cryllc aeld eopoly~er, "PVDC" tov~nyltdene ~hl~rld~t~ln~t chIoride cop~lymer, ~nd "~I~" to ~lnyllden~ chlorlde met~y~ acrylate cop~1ymer.

Accordl~gly, In a ~lrst aspec~ the presen~ lnYen~1~n m~y br~dly ~æ ~a~d to comprtse a he~t-shrlnkabl~ multl1ayer ~ h~ g a m~asure o~ resistdnc~ to abu~, comprlstn~ at le~3t th~e~ layers, lnclud~ng~

a) a flrst ol~t~ide ldyer sele~ed fr~n th~ group ~:u~prisiny EVA, VLDPE and blRn~J.s ~f YLDPE and EYA, b) a core or lnternal l~yer, c~mpr~s~ng an ;qnomer or a blen~ ~h~r~n~ wlt~
EYA, ~ or EAA, and G) d iiccnd ~tsid~ l~yer se1ec~ed frorn the ol^oup co~prl~tng EMAA, EAA ~n~
~ nno~rs .

the core or lnternal l~y~r b~ pr~ferably compl~;s~ o~th~r 1~ sc~1um lono~or p~ly~r ~lone, ~r 10nd of ~od;u~ lon~n1er p~lYrne~ w~th EYA, comp~ n~ up to a~o~t 4091 EYA, or Z~S081 ~ 6Z~ ~b~ Z -~: IYOS ~ r ~:~a l,~S

SENT 3Y:Xerox Telecopier 7~20 ; 2~ 92 ;12:4~PM ; 18034332a31~ 916132328440;# 5 ~) 3 b1end o~ sod~l~m l~nomer p~lyn~r w~th E~AA or EAA, co~prisln~ up to about 25~ of tne ~A~ or ~AA-F~r ex~mpl~, a b1end ot ~bot~t ~3$ s~dlunl ion~er p~ or (~ecl~lc gr~vlty0,9~ ~1th a~out 7~ ~YA ~spe~lflc ~rA~l~y 0.96), or d bl~nd ~f dbout 95~ sodlum lon~mer po1ymer wlth ab~ut 5% EMAA ~r EAA ~Pecific ~r~Yi~y O.g4~ ~ay ~ us~d, Th~ flr~t outsld~ layer a) whtch 1s pre~era~ly the ~ut~r o~use l~y~r, pr~f~rably comprt~s ~lther EVA ~lone or a ~lend o~ VL~P~tEYA ccrprl~tno fro~
abcu~ Ok ~ 70~ EVA, Qg a blond ~f 50~ EVA ~speelfl~ ~rav~ty ~.g~ YL~PE
~pec;f;~ gr~vity O.~l).

The second outslde l~rer c~, i5 proforahly ~ lin~ lay~r, ~hlch ln u~e w~ ont~ct A prqduct ~0 be pack~g~ by t~s fllm, ind co~p~iS~ ~1ther EMAA, EAA or sodium l~nolner polylner, ~ h~ f11ms o~ the pres~nt inYenti~n m~y ~l~o ~lnprl~e ~n ~y~en b~rrlar layer, ~uch as l/lnytld~n~ chlorl~ nyl chl~r~de ~polymer, vinylld~ne chlor~de meth~yl acrylate cnpolymer, ethylene v~nyl alc~hol copo~ym~r or p~lya~ide, located ~Qt~een the ~1rst outslde l~yer a) ~nd the lnt~-n~) layer b~. In addlticn, poly~erlc adheslYe layers ~eg ~MAA) ~ay ~e lne~lId~d, b~t~een the rirst Qutside layer nnd ~h~ lnt~rndl l~y~r, or, l~ a barrl~r layer li included, ketween ~he barrier 1ayen and the first ou~s1~e tayer an~tor b~tween the barrier layer and th~ internal layer h).

In ~ ~urther aspcct the pres~nt ln~eneion co~prises a multllayer f~l~
ha~ting ~ ~Qa~urs of res~!;tanc~ to abuse, compn-~no at ~ea~ t~ lAy~rs, in~luding:

~ J6 Y! 16~Zg6~o8~ Z~ ! Z~-z ~ Vd r ~

SENT BY:Xerox Telecopier 702~: 2~ 92 .12:GlPM; 1~034332~31 ~ 91613232a4~0;# 6 119~
~ 4 -a~ ~ tlrst au~slde layer s~l~ct~d ~rom ~ha g~ Jp cornpr~in~ lJi nPF, EVA a~d blond~ ~ VLUPE an~ EVA; dnd C~ a 5~and outside layQr cQ~p~1sin~ EM~.

Prer~ra~y a cor6~ or int~rn~l ldy~r b~ ;nclud~d, wh1ch ls pre~srab1y as hor~inb~for~ d~cr;bad. Al~arnatjv~ly the cor~ l~yer may con)pl~;sQ ~ross-llnk~d EY~.

~ refer~bly the l~rct ~uts~de layer ~s as h~relnbef~re descr~ed.

9~rriar ~ndfnr Adh~tve layers ~s herelnbe~ore descrlb~d may als~ ~e tnclu~ed 1n thls ~orln of the present tn~lentlon.

In a fllrther a~pect the prcs~nt inY~nt~on comprlses a process ~f mdking h~ shrinkable mu~ y~r fi~ln, comprisln~;
~) co-~x~rudin~ as a mu~ttl2y~l~ filnn preeUr~or l~m~nate, a~ ledst three lay~r~, lnclud~ng:

a) ~ flrst ou~slde layer ~e1ected from the ~roup compr;~;n~
EVA, YLDPE and blends of VLOPE and EVA, b) a care Dr lnternat lay~r,c~mpri~iny ~n iQnon~r ~r ~ bie,ld ~h~reof with EVA, EMAA o~ EAA, ~nd scor.d outslds t~y~r ~ ctQd ~rom 1~ g~oup ~olnpri~;ng EMAA, EAA and lonomer~t ~n~l (il) ~ubs2qu~ntly tr~tin~ tho precurs~r ~o pru~ide th~ multllQyer fllm.

g~ #'lg~ T ~S~L~ ~Z~ Z ~ ! NOS ~ ~ r ~ ~S

.

aE,~T BY:Xerox Teiecopier 702~ ; 2-11-92 ;12:42PM ; 18~34332~31* 9161323~8440;~ 7 2 ~
- 5 ~

Pr~ferably sald proC~rsor lanlnat~ 19 gtn~ch~d by r~cl~ing ond~r blowin~ tQ a dns~rad fi1nl, thickn~s Lo th~reby proride th~ h~ t shrlnka~le fil~.

Pref~rably sa;d ~r2~urs~ min~te l~ sl:r~tched ~y ~lrst heatlng ie to sof~enlng point, thon ~xp~ndiltg ;t by blowtn~ ertioal bu~ble to strot~h the lom~n~t~, c~lin~ ~ho ~a~lna~e ~nto ~hln f~lm, ~nd ~11AP3;n9 the bubbl~ onto conver~tllg rolle~s, then w1n~ng ~lR f11 undor ten~lon lnto roll fQ~m.

Preferably 9~1~1 stro~h1n~ ~S ~O ~l~out S to ~ Q~ th~ surPac~
droa ot eh~ tllm precl~rsor.

Preferabl~y ~id pre~urs~r 7el~ te h~s A toee~ thl~kne5s ~f fr about 400 n1lcr~ns t~ ~Ibout 8~0 m;cr~ns. P.ef~rabl~ s~id ~RCQn~
outsldo l~yer c~ of s~ld pre~l~rs~r l~lmlrl~te has Q ~ichn~ss ~ ~bwt 75 t~ ~bout 1~5 mi~r~ns.

Pre~erably sa~d core or lnternal lay~r ~ sald pr~urssr ld~lna~ hdS a cnickness of l'rom a~out Z0~ to a30ut 410 m~crPnS.

Preferably said first ou~side l~yer ~! ~f said precursor 1dmina~
has a thickn~s of from about 125 ~o ob~u~ .5~ mi~rons.

Pre~ara~ly sdld multilaYer Fil~ll h~l5 ~ r~sul~dllt to~l thlckn~
of about 6Q to a~out 120 micrcns.

In a ~ur~har ~p~c:t th~ pr~en~ ;nvont1On ~ompri9~& a prnc~
~aklng a mutt;1~yor f~1TI COI1IPr;S1n~:

SZI' ~'16~66~0~1 8S~ C~ ' W~8Z:~ ' Z6-Z -~ ' NOS ~ ~d P ~ 3S

SENT B~:Xerox Telecopier 702~ . 2~ 92 ;12'42PM ; 18034332331~ 91613232~440;# 8 2 ~ 9 ~

~i~ co.ax~r~djn~ dS a mulLlldyer ~l~m precursnr l~mtn~o at least two layer~, ln~lud~n~:
d~ a ~trst au~ld~ l~y~r ~lect~d ~rom the gr~up c~mpr~sl ~ L~PE, EVA and bl~nds o~ VbQPE ~d FVA, c~ a seccn~ au~gl~ lay~r c~pris~n~ EMAA; ~nd (1t~ ~ubsequ~n~ly traa~lns th~ pr~cllrs~r to prn~7~ ~h~
mult~lay~r fllm.

Pro~erably ~ cor~ layer b~ ig ~Isu ~cx~uded with 1~yers ~) ~nd c ) .

Pr~f~rAbly s~d mut~tl~er f~lm i3 ~5 hereln descrlbed.

The pres~n~ 1nv~ntlon w111 nnw b~ d~scr1~d ln more detail, wlth r~t~rence to ;he acccmpanyin~ dr~wlng6.

Figura I ~how~ ~ ~hr~e l~yer ml.~ltil~y~r helt ~hrlnk~lo T~lm such ~ can ~e producnt by e~trust~n, ~or ~n~ontence ~ ilm thi~kn~3ses b~n9 shown substan~;ally identicQI. ;t will b~ dppre~;4~d th~t it 19 not es~cntlal th~t the film ~f th~ present InY~ntion has ~hreÇ
l~yer~ - ~rom t~ t~ ~our or Inore l~y~rs m~y be used.

F~gur~ 2 i5 ~ dlagramIna~le view of ~ ~hre~ y~r precunsur lamln~t~ ~h~Ying how lt is te ~ hlown ~ n to ~ fil~.

tn one pre~erre~l for~ f tne present inYe~t~n the ~ult~lA?,er ~ilm has th~ee l~yer~. L~yer a) ls preferdbly th~ so-~lled ~utsld~
la,yer, whlCh ~n use ~when ~he fil~ i5 ~sed as a ~r~pplng, ~r to de~ine a contAin~ or p~cka~ will be thd~ surf~ce ~hich ~oes not cnntact S~ 168Z~:P6081 -8g~.L~ : W~ Z ~ r ~:A~

SENT aY:xerox Telecopier 702~ ; 2-11-92 ;12:43P~ : 18~34332~31~ ~1613232844~;~ 9 2 ~ 9 8 ^7-th~ product, Layer c) ts pr~forably the lnn~r sedlln~ ldyer, which in use wlll b~ tha~ surf~ce lik~ly to cont~c~ the foods~f~. Lay~r b) ls th~ ~ore or intern~ yer.

L~yer c~, th~ inner ~alin~ 1ayer, may cDmprl~e ~MAA, EAA, or an lonQme~. ~MAA is esp~ciall~ pref~rr~d, i;nc~ us~ of E~A~ ~opolyr4r pro~;des the film with Yery qood ~ea1ab jl j~y pr~pertl~ p~rtdnt ~hen there ~y ~e co~t~mln3~10n o~ th~ material, ~or ~xampl~ by rti~ulatQs, and/or pteats or fcl~s in tha matrridl. A ~ayor c) an ~nomor al~o ~onf~rs ro~onably go~t e~41abillty prop~rt;es cn th~
fil~, 31~h~ugh ~ non-ionis~ fo~n af ENAA 15 pneferned in thts r3spact .

L~r b), tho cor~ ~r lnt~rnAl Idyer, may con~rlsa eith~r an ~onomen (pr~ferably sQdlum ionDmer polytn~r~ or ~ bl~nd th~r~oP wl~h EYA. EMAA ~r EAA. ~i ex~n~1e, tne Intarna7 7ay~r cou1d compr~se a b7end of sod~un) I~n~r polyD~r ~it~ up ta a~out ~/~76 EVA, more pret'erably up to 2W EV~, or a blend ~ wd1um ~onoIner polym~r t~l~h up tt~ dl~OUt 25S EAA or EMAA, ror~ pref~ ly from ~bout l9~ ~Q ~bout 10 b)~ wal~ht of EMAA ~r EA~. The i~nom~r provlde~ th~ fllm i.ith nigh shrink ~nd hlgh clari~y prv~ertto~. it l~ als~ p~ss~ble f~r this l~yer to collpr;se ~ome o~her hs~shrin.k~ble ma~erlAl, ~ h as crost-linked EVA. layers c) ~nd bi aIso ~ he film goad l`~SiSt~lllC~
to internal pun~turln~.

Lay4~ a) tthe "ou~sld~ yar"~, in on~ pr~fQrred for~ ~f the lnvantlon~ Inay ba a b1en~ ~f ~b~ut 50~ ;vlopE wi~h About 5~ of EVA
c~polyms~, ~lthou~h bl~nd~ of Vl~PE ond EYA ~ont~ning up ~ ~bout 7 E~A, o~ ~v~n EYA dlone, n~y ~lso be u~d. Thl3 l~yer pr~id~s th~

~ZJ6 ~!T~8Z6~EOEI ~ W~Z:~ ' Zg-Z ~ N~.~ r ~ a6 S'NT 3Y:Xerox Telecopier ~020 ; 2-11-92 ;12:44PM ; laO34332831~ 9l6l323~Ba4o:#l~
2 ~ 9 8 fllm wlth 9~Od extorn~l ~buse res~stdnce propert~es, while ~t th~ s~me t1me haYlng a ~lossy appearanc~ w,h~n 5hrunk, nnd a s~o~th printable sur~ac~ ~lnlsh.

It ~s als~ p~sslb1~ for there ta b~ ~n additi~nal l~yer, for example dn GXy~ll barrler layen, to en~ure tha~ the Till~ is ~ub~antially i~perneablo to ~s transmls~ion ~a;nly oxy~en)~ Th~
barrler lay~1~ cou1d compr;se ~lly ~f the ~Je~l known re~lns useful in enhancin~ oxygen barrl~r proPer~ies in a film o~ ~a~. 7h~e lnclucle ~Inylidene chloride Yinylchlorl~e copoly~nor, ~nylidene chlDrid~
methyl ~ryl~te ~op~ly~er, eehyl~ne ~nyl alcDhol ~op~lyner and polya~ide .

Adhesl~ lay~ri ~y ~ usad ~ither to adh~r~ ehe out~id~
VL3PEJE~A layer to th~ ra ~pr~fora~ly ionomer) la~r, nnd~or to ~dh~r~ ~n oxyg~n Sarr1~r l~y~r, ~uch a~ PVDC or M~, t~ ehe oth~r rs. App~apr;ata ma~el~ials for ~dhesiYo l~v~r~ wh;ch n~ e us~d inrl-lde E~IA, FM~A, EM ~r lon~lnor. Passl~le ~tru~tu~s whlch ln~ d~
~he uso of ~dhes;v~ l~yer~ ~w;th ~ thul~t d b~rrler l~y~r~ may ~e:
6-1~yer structure:
~Dp~EMA~py~clEMAAllcN~MERJ~M~A
a 3 c d a = outslde layer b ~ adheslv~ lay~r c ~ b~rr~r ldyer d n adhesll~o l~y~r e~ internal lAyer f ~ lnn~r s~aling lay~r or (2l a 4-loyer ~ructu~e:
~LDPE~EMAA~ SûN~lERf E~4A
a b c d a ~ out5id~ r b = cdheslve tay~r c ~ int~rnal ~yer d = lnnQr s~allng lay~r g~ 68zg~g;)9t ~g6Z~ 10~:~: Z4-Z ~ ~,1 r SENT BY:Xerox Telecopier ~20 : 2~ 92 ;12:44PM ; lao34332331~ 916132328~4~;#11 In these ~tructure~, EAA ~y b~ u5~d 1nstead o~ EMAA.

~b1e 1 shows th~ structures ~ 3 ~ erent multll~yer ~three-layer~ films n ~ccordancc ~l~h ~he pr~sent 1nvs71tIon~
TA~LE l: THE Pi4C~;A~iNG STRUCTURES
~-=~J~ ~_~D==~=~~ ~a~tc~ -3~ =~a~s STRUCTURE N0. 1 Z 3 LArER ~ (lnsld~) Resin ~e~ ~o7ow~ A ~ C
Th~knQs$ (mlcron) qo go gO
~olerance ~f-10 ~-10 ~/-1û +~
LAYER b~ ~ore or Intqrnal) Restn ~5ee bolow) A A D
Th~ohn~ mlcron~ 235 235 23~
l'oleran~e-~f-20 ~I-20 ~ 20 ~1-20 LAYER ~ utslde~
Resin (see belo~) ~ B 3 ~h~kn~ss ~mlcron) 145 1~6 146 roleran~e ~-20 I~a~ 2~ 20 __~~ ~~~___~_~__-___~_n_~____~_______-________-___n TOTAL T~rc~HEss ~F
PRECUR50R ~AMINAt~:
~mlcr~n) 470 4~ 470 470 rol~r~n~e ~/-F0 ~ 0 ~/~^50 ~/-S~
~ AA ~ A--~ ~ A '; ~ ~ A a AA ~
BL0~ UP RArlO: 6.76 6A7~ 6.7 RESllLTANT FIlM
THIC,YNESS (m~ct~on~ i ~0 ~0 ~0 roler~nce ~~5 1~^~S t~A5 ~t~5 A~ A_l-- A ~A~ A~A~ A A~.~W~ A~ A~A~
RESINS;
- Sodlum lono~er Polyl~er, speciFic graYity ~Ss) 0.94 8 ~ Pl~nd o~ Su~ by w~t~"t of V~ry Low U~nsity Polye~hylcn~
~EqPE), ~ 0.~1 with 50~ ~f Fthylone Y~ny1 Ace~e~^ ~E~A) ~opoly~er, sg 0.~3.
E~hyl~ne Metha~rylic Acid î,opoly~r~EMAAJ,~g O.g4.
D - 81en~ of 93~ of Sodiu~ Iono~ P~lsner, so OAg4~ wl~h 7~ of E~A C~poly~o~, a~ 0,96.
S~i~J3=_AA~AA~ A~ A~ n--=~ C~rA==~

SZJ11$~ 6~081 ~ Z~ dO~:I,: Z~ r ~ S

SENT 9Y:Xerox Telecopier 702~ ' 2-11-92 ;12:45PM ; laO34332831~ ~161323~4~ 12 ~ha ~n~r~1 properties of th3 fin~l p~ckagln~ structures ~r~, 3. P~rc~nt ~rink at ~CI

longl~udJ~ d~r~ct~on) ~ 35 ~ 45 TD ~tran3v~r~e t;rection) = SO to b. T~n311e Str~n~th in kg/sq C~l;

~ ~ 400 to S50 rD - 4~0 to ~

c. P~rcent El~n9~tion:

LD ~ 120 tO 1 TD l~O to 25û

rhe packa~ng per~ormance ~hari~cteristl~ o~ each tay~r in ~A~h structure ars dependent on th~ r~ h~ing us~d~ T~Q 5har~C~ar1~ttC~
may b~ generallsed as follows:

~tRUCTURE l:

Ltlyer~ c) ~d b) E~sy se~ tv thrnllnh c~nta~lna~n and pl~ts.
Hl~th cl~r~t~ ~nd h1gh 5~ink.
~30d r~s~s~anc~ to 1ntqrnal puncturlny.

S~JZI~!16~ZC~Ca81 -~tl6~ZLg ! ~06:~ ~ Z6~Z ~ ! ,N~6 ~ r V 1~ a~

ScNT BY:Xerox Telecopier 70~ ; 2-11-92 :12:45PM ; laO34332~31~ 91613232a~40;#13 L 9 ~3 I.dyer e~ 3y ~ppeararl~e when shr4nk.
Goo~ resis~anc~ x~ern~l Abus~ punotur;n9.
S~oo~h prln~c~lo ~urf~e finish, ST~CIURE 2l Lcy~r e~ ~ ~ASy s~labi1~ty ~t l~w ta~peratures t~ro~gh c~nt~m~natl~n an~ plea~s.
Htgh clarl~y.
~ood r~tstanc~ to l~rna~ pun~turing.

Laysr b) Hiqh ~l~rity and hi~h shrlnh, Gcod r~slst~n~e to internal punc~ur~n~.

L~e~ a) ~ S~r~ ~3 S~ucture 1.

SrRU~TURE 3:
Layer c) ~ Sa~e dS Struc~u~ z.

Lay2r ~ - s~lne ~S Str~cture 2.

L~y~r ~J ~ Sa~e dS Structure 1.

Table 2 shows ex~mples of al~crna~l~e stru~tur~s af nlul~;-layer filn~c 1n aGcardance with the present Inv~ntlurl, ir~ which lay~r a~ ~t.h~ outsld~
layer~ compr~se~ EYA capo1y~er alon~. ln th~se ~tructurss, layer c) ~th~
tnsidQ c2~11ng l~y~r~ c~nlp~isas EMAA or EAA (~p~c7~ ravlty ~ 0~
!ayQr b) ~th~ cora lay~r~ ~en1pri~as ~od~um ionomllr b1~rd~tl w1~h CMAA or sæJ~ szs~sl ~S6~Z~ J~ Y~ 3S

SENT BY:Xerox Tel~copier 7~20 ; 2-11-92 ;12:46PM ; 1~034~32~31 91613232844~;~14 EAA at d rat~o of 5~6 b,y 7~0;9ht of EMM ~r EAA ~ono~r ~pet:Sf;~: ~ravl~y ^
0.~4); and l~yer a) (the outsi~ yer~ comprigg~ E~A ~poly~el~ ~spz~lc gr~tty ~ 0.96).
Table 2 Fur~h,~r,P~c,,k~ging Structures Structure No. 4 5 0 7 _ _ _ _ ~ .. _ . .. ,. ~ .. ,. ~ .. _ _ _ _ _ .. .. ... v .. ~ . c .. _ ~ _ v .
L~yer c) ~ln~tde~
Resi~ (~ee bel3w) C C ~ D
Thlckn~ss ~m~çron~ 90 90 90 90 T~lera~ce ~t-lO
L~y~r b) ~core~
Resln ~Sdd h~low) E G E
Tn~ckness ~icron) ZW 2~0 2nn ~oo ~ol~ranc~ 2Q
Lqyer a) (out~ide) Res~n ~see below~ F F F
~hlcknes~ ron~ 180 .t80 1~0 18 Tolerance +~-20 Total thlckness ~f pr~c~rsor lAmln~te ~ icr~n~ ~70 47~ 470 470 Tolor~nce ~50 Blow Up Ratlo ~76 ~.76 ~.7~ 6.7 Resultant ~11m ~htckn~s~ ~micron~ 8~ 80 B0 80 ~ol~ranco ~f~50 R~SIN5:

C = 'thylene Meth~cryl;c Ac~ Capolymer !EMkA), s~. 0.94 D ~ Ethylene Acryllc ~tcid Copolylnor ~Ah), ~. Q.94 E ~ ~lend of 95~1 s~dlum lonhmer p~7ymer ~Nith 5t~ ~MAA copolymer (lono~ner ~.~. 0.94) F 'Y~ cop~lymer G G Blend of 95~i sodillln l~nolner polym~r wl~:n 5X EAA copaly~n~ J. n.
tne prec~rsor ,~n~ndtes aldy 4~ Infld~ hy USill~J ~ ~hrr~ yen co~xtruSlqn pl~ocess ~ ~x~mples ~ th~ res~ns And p~f~rred lay~r thicknesses 3re spe~ d ~n Ta~les 1 and ~, Th~ thicknesses of the SZ~tz:~68Z~ s~ t~;0 ~ ze~ ,YOS ~ ~fd r S~NT 3~:x~rox Telecopier ~1020; 2~ 2 ;12:47PM; 13~3433Z831~ 9l6l3232a44~;#l5 , ul .~. u ~ u~ .n i ~7;~9~ laO~ s~ 2~ ~

v~rious l~yt?r~ ~re ch~sen ~o as to prov~de an ovQrall ~ult~lay~r ~lm thlckness th~t ;s des;l~d. The tot~i thiekne~3 of ~h~ precurson l~mtna~e ls pref~r~bly ~n th~ rang~ ~ al~3ut 400 to ~20 rnicr~n~.

A,~er the prec4rsor la~ln~t~ ha~ been l'cr~ed, lt 15 ~rlen~ y f;rs~ heating it to sot'tening polnt, t~e~l axpandlng tt by 41D~;n~ a vert~cal bub~le. Th~s stre~oh~s ~lle ldmtn~t2 inco a thln ~ whlch fs ca~led. The bubbl~ is collapsed by conYer~ln~ rollers then ~aund under tens;~n into rol~ for~. ~n this re~ard, Fi~ur~ ~ ~hows hoq th~ precursor la~inac~ is ~o ~e blo~n down ~o ~tlm.

Alternatlyely, ~n~al~ frame str~tching may bo used to s~r~ah the pn~cur~or lamin~e.

~ ha ~rQtch;ng procsss orients~ss t:h~ poly~e~ ~olecul~s ~nto longitudinal and transvqrss dlr~ctions ~a and ~). The a~ount of tch ;s ~ile Blow IJp R~tlo whlch ~s ~p~clfted ln Td~ he preferred 81OW Up Ratlo i3 ~sb~ut ~.76. Th~ ~ot~t ~hkknass c~ tho ~
ftlm ~fter cc~xtrusion and orien~t~on~ i~ pr~f~rabl~ frn~ about 6d to ~20 ~lcrcn~, Other processes kn~wn in th~ ~r~ such ~ ~rus;~n contin~, ~nd con~Qn t~nsl lamlnatlon, m~.y als~ be u5ed tD m~l~e ~h~ prec~lrsor 1 a~l n3t~s Optl~nally, whQn the Inner sealln~ layor c~mpr~ses EMAA br ~AA, ~n~
tha c~r~ l~y~r ls n~t a-l lonomer ~ when the c~re layer ~mpri~ E~A) the ~ca~ing layer, th~ c~r~ lay~r, and an~ ddditional l~yers loc~ted betw~en the cor~ and se~lfng l~y~rs, may be cr~..l1nked, usln~. fDr ex~mpl~, irr~diat~on.

SENT BY:Xerox Teleco~ler 7020 , 2~ 92 .I2~47FM; laO34332a31 ~ 1~u~491~6Jl32328440.~16 -13~.
I~ lS ~elleY~d tha~ a ~ul~lldyer ~llm ~n accord~nce wlth ~he pr~sent fnvontton wil1 provld~ n mult11~y~r ~llm hav~n~ goad ~b4s2 r~sf~t~nc~
propertidsl both t~ in~erna1 ~nd ox~o~na~ punce~r~ng ~du~ to tho p~eson~
of a la~e~ comprlsin9 ~ blend ~f VL~PE~IEYA or E~A~, whllu at ~h~ same tlme h~vin~ good hsa~ ~hr;nkability, h;gh clar;ty ~nd good s~21abllity.

Claims (66)

1. A heat-shrinkable multilayer film having a measure of resistance to abuse, comprising at least three layers, including:

a) a first outside layer selected from the group comprising EVA, VLDPE and blends of VLDPE and EVA, b) a core or internal layer, comprising an ionomer or a blend thereof with EVA, EMAA or EAA, and c) a second outside layer selected from the group comprising EMAA, EAA, and ionomers.

2. A multilayer film as claimed in claim 1 wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EMAA copolymer, and wherein the blend comprises from about 0%
to 25% EMAA copolymer.

3. A multilayer film as claimed in claim 1 or 2, wherein the core or internal layer b) comprises a blend of about 95% sodium ionomer polymer with about 5% EMAA copolymer.

4. A multilayer film as claimed in claim 1, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EAA copolymer, and wherein the blend comprises from about 0%
to 25% EAA copolymer.

5. A multilayer as claimed in claim 1 or 4 wherein the core or internal layer b) comprises a blend of about 95% sodium ionomer polymer with about 5% EAA copolymer.

6. A multilayer film as claimed in claim 1, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EVA, and wherein the blend comprises from about 0% to 40%
EVA.

7. A multilayer film as claimed in claim 1 or 6, wherein the core or internal layer b) comprises a blend of about 93% sodium ionomer polymer with about 7% EVA copolymer.

8. A multilayer film as claimed in claim 1, wherein the core or internal layer b) comprises sodium ionomer polymer alone.

9. A multilayer film as claimed in any one of claims 2 to 8 wherein said sodium ionomer polymer has a specific gravity of about 0.94, and said EVA has a specific gravity of about 0.96.

10. A multilayer film as claimed in any preceding claim wherein the first outside layer a) comprises a blend of VLDPE and EVA, and wherein said blend comprises from about 0% to 70% EVA.

11. A multilayer film as claimed in claim 10 wherein the first outside layer a) comprises a blend of about 50% by weight VLDPE and about 60% by weight of EVA.

12. A multilayer film as claimed in any one of claims 1 to 9 wherein the first outside layer a) comprises EVA alone.

13. A multilayer film as claimed in any one of claims 1 to 11 wherein said VLDPE has a specific gravity of about 0.91.

14. A multilayer film as claimed in any one of claims 1 to 13 wherein said EVA of said first outside layer has a specific gravity of about 0.93.

15. A multilayer film as claimed in any one of the preceding claims wherein the second outside layer c) is a sealing layer which in use will contact a product to be packaged by the film.

16. A multilayer film as claimed in claim 15 wherein the sealing layer c) comprises EMAA.

17. A multilayer film as claimed in claim 15 wherein the sealing layer c) comprises EAA.

18. A multilayer film as claimed in any one of the preceeding claims wherein the FMAA or EAA has a specific gravity of about 0.94.

19. A multilayer film as claimed in claim 15 wherein the sealing layer comprises a sodium ionomer polymer.

20. A multilayer film as claimed in any preceding claim which further includes an oxygen barrier layer located between the first outside layer a) and the internal layer b).

21. A multilayer film as claimed in claim 20 wherein the barrier layer comprises PVDC or MA.

22. A multilayer film as claimed in any one of claims 1 to 10 which further includes an adhesive layer between the first outside layer a) and the internal layer.

23. A multilayer film as claimed in claim 20 or 21 which further includes one or more adhesive layers between the barrier layer and the first outside layer a), and/or between the barrier layer and the internal layer b).

24. A multilayer film having a measure of resistance to abuse, comprising at least two layers, including:

a) a first outside layer selected from the group comprising VLDPE, EVA and blends of VLDPE and EVA; and c) a second outside layer comprising EMAA.

25. A multilayer film as claimed in claim 24, further including a core or internal layer b).

26. A multilayer film as claimed in claim 25, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EMAA copolymer, and wherein the blend comprises from about 0%
to 25% EMAA copolymer.

27. A multilayer film as claimed in claim 25 or 26, wherein the core or internal layer b) comprises a blend of about 95% sodium ionomer polymer with about 5% EMAA copolymer.

28. A multilayer film as claimed in claim 25, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EAA copolymer, and wherein the blend comprises from about 0%
to 25% EAA copolymer.

29. A multilayer film as claimed in claim 25 or 28, wherein the core or internal layer b) comprises a blend of about 95% sodium ionomer polymer with about 5% EMAA copolymer.

30. A multilayer film as claimed in claim 25, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EVA, and wherein the blend comprises from about 0% to 40%
EVA.

31. A multilayer film as claimed in claim 25 or 30, wherein the core or internal layer b) comprises a blend of about 93% sodium ionomer polymer with about 7% EVA copolymer.

32. A multilayer film as claimed in claim 25, wherein the core or internal layer b) comprises sodium ionomer polymer alone.

33. A multilayer film as claimed in any one of claims 26 to 32, wherein said sodium ionomer polymer has a specific gravity of about 0.94, and said EVA has a specific gravity of about 0.96.

34. A multilayer film as claimed in claim 25, wherein said internal layer b) comprises cross-linked EVA.

35. A multilayer film as claimed in claim 25, wherein the first outside layer a) comprises a blend of VLDPE and EVA, and wherein said blend comprises from about 0% to 70% EVA.

36. A multilayer film as claimed in claim 35, wherein the first outside layer a) comprises a blend of about 50% by weight VLDPE
and about 50% by weight of EVA.

37. A multilayer film as claimed in any one of claims 25 to 34 wherein the first outside layer a) comprises EVA alone.

38. A multilayer film as claimed in any one of claims 25 to 36 wherein said VLDPE has a specific gravity of about 0.91.

39. A multilayer film as claimed in any one of claims 25 to 38 wherein said EVA of said first outside layer has a specific gravity of about 0.93.

40. A multilayer film as claimed in any one of claims 24 to 39, wherein the second outside layer c) is a sealing layer, which in use will contact a product to be packaged by said film.

41. A multilayer film as claimed in any one of claims 24 to 40, wherein said EMAA has a specific gravity of about 0.94.

42. A multilayer film as claimed in any one of claims 25 to 41 which further includes an oxygen barrier layer located between the first outside layer a) and the internal layer b).

43. A multilayer film as claimed in claim 42 wherein the barrier layer comprises PVDC or MA.

44. A multilayer film as claimed in any one of claims 25 to 41 which further includes an adhesive layer between the first outside layer a) and the internal layer b).

45. A multilayer film as claimed in claim 42 or 43 which further includes one or more adhesive layers between the barrier layer and the first outside layer a), and/or between the barrier layer and the internal layer b).

46. A process of making a heat-shrinkable multilayer film, comprising:
(i) co-extruding as a multilayer film precursor laminate, at a) a first outside layer selected from the group comprising EVA, VLDPE and blends of VLDPE and EVA, b) a core or internal layer, comprising an ionomer or a blend thereof with EVA, EMAA or EAA, and c) a second outside layer selected from the group comprising EMAA, CAA, and ionomers, and (ii) subsequently treating the precursor to provide the multilayer film,

47. A process as claimed in claim 46 wherein said precursor laminate is stretched by racking and/or blowing to a desired film thickness to thereby provide the multilayer film.

48. A process as claimed in claim 47 wherein said stretching is to about 5 to 9 times the surface area of the film precursor.

49. A process as claimed in any one of claims 46 to 48 wherein said precursor laminate has a total thickness of from about 400 to about 820 microns.

50. A process as claimed in any one of claims 45 to 49 wherein said layer c) of said precursor laminate has a thickness of about 75 to about 155 microns.

51. A process as claimed in any one of claims 46 to 50 wherein said layer b) of said precursor laminate has a thickness of about 200 to about 410 microns.

52. A process as claimed in any one of claims 46 to 51 wherein said layer a) of said precursor laminate has a thickness of about 125 to about 255 microns.

53. A process as claimed in any one of claims 46 to 52 wherein said multilayer film has a resultant total thickness of about 60 to about 120 microns.

54. A multilayer film as claimed in any one of claims 1 to 23 when produced by a process as claimed in any one of claims 46 to 53.

55. A process of making a multilayer film comprising:
(i) co-extruding as a multilayer film precursor laminate at least two layers, including:
a) a first outside layer selected from the group comprising VLDPE, EVA and blends of VLDPE and EVA, c) A second outside layer comprising EMAA; and (ii) subsequently treating the precursor to provide the multilayer film.

56. A process as claimed in claim 55 wherein a core or internal layer b) is co-extruded with layers a) and c) to form the multilayer film precursor laminate, said layer b) comprising either cross-linked EVA or an ionomer or a blend thereof with EVA, EMAA
or EAA.

57. A process as claimed in claim 55 or 56 wherein said precursor laminate is stretched by racking and/or blowing to a desired film thickness to thereby provide the heat-shrinkable film.

58. A process as claimed in any one of claims 55 to 57 wherein said stretching is to about 5 to 9 times the surface area of the film precursor.

59. A process as claimed in any one of claims 56 to 58 wherein said precursor laminate has a total thickness of from about 400 to about 820 microns.

60. A process as claimed in any one of claims 55 to 59 wherein said layer c) of said precursor laminate has a thickness of from about 75 to about 155 microns.

61. A process as claimed in any one of claims 56 to 60 wherein said layer b) of said precursor laminate has a thickness of about 200 to about 410 microns.

62. A process as claimed in any one of claims 56 to 61 wherein said layer a) of said precursor laminate has a thickness of about 125 to about 255 microns.

63. A process as claimed in any one of claims 55 to 62 wherein said multilayer film has a resultant total thickness of about 60 to about 120 microns.

64. A multilayer film as claimed in any one of claims 24 to 45 when produced by a process as claimed in any one of claims 55 to 63.

65. A multilayer film substantially as herein described with reference to the examples and/or the accompanying drawings.

66. A process of making a multilayer film substantially as herein described with reference to the examples and/or the accompanying drawings.