CA1200643A

CA1200643A - Ionomeric polyethylene heat seal blends

Info

Publication number: CA1200643A
Application number: CA000403902A
Authority: CA
Inventors: George L. Hoh; Donald A. Vassallo
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1980-09-10
Filing date: 1982-05-27
Publication date: 1986-02-11
Also published as: AU8404782A; AU550550B2; US4346196A; EP0094991A1; EP0094991B1

Abstract

Abstract of the Disclosure Heat seal compositions and articles including the compositions are disclosed. The compositions exhibit a broad tempeature range for making heat seals of variable strengths and are useful as the sole heat seal composition in making flexible packages requiring both permanent and peelable seals. The compositions, which are sub-stantially homogeneous blends of polymeric materials comprise (a) 20 to 80 percent, by weight, of a terpolymer having as monomeric components, i) 65 to 95 percent, by weight, ethylene, ii) 4 to 30 percent, by weight, vinyl alkanoate or an ester selected from the group consisting of alkyl acrylate, and alkyl methacrylate wherein the alkanoic acid moiety of the alkanoate and the alkyl group have one to four carbon atoms, and iii) 0.5 to 20 percent, by weight ethylenically unsaturated monocarboxylic acid selected from the group consisting of acrylic acid and methacrylic acid; and (b) 20 to 80 percent, by weight of an ionomer having, as monomeric components, i) 75 to 99 percent, by weight, ethylene, ii) 1 to 25 percent, by weight, ethyleni-cally unsaturated monocarboxylic acid selected from the group consisting of acrylic acid and methacrylic acid wherein the sum of the weight percentages of comono-mers ii and iii in the terpolymer is at least eight percentage points higher than the weight percentage of comonomer ii in the ionomer, wherein 5 to 75 percent of the carboxylic acid groups in the ionomer is neutralized by zinc ions, and wherein 5 to 40 percent of all of the carboxylic acid groups in the blend is neutralized by zinc ions.

Description

BACKGRQUND 0~ TEIE INVENTION
Field o~ the Invention In ~he marlufacture o:E flexible :eilm packages by means of heat s*al methods, there has long been a n~ed ~or heat seal compositions ~xhibiting a broad enough hea~ sealing ~emperature range ~ha~ bo~h p~rmanent and peel~ble seals can ~e made reproducibly in th~ same packages with a variety of ~ilm m~erials.. The permanent ~eals in ~uch package~ are 10 preferably so strong that s~al failure wlll occur by ~ arirlg the packaging f ilm; and th~ peela~le seals are preferably strong enough to hold content~ o~ the package but weak enough to permi separation of the package walls with a moderate ~OrGe. ~up~ure o~ th~
15 peelable seal~ i~ pre~e~ably a cohesive ~ailuxe in the heat ~eal composition itself; and the rupture i~
pr*f~r bly clean witbou~ a loo~e debris of the hea~
seal C:ol~pO8itiO~l. A bxoad ltemperature range b~tween fQrmation of the peelable seals a~d t:he permanent ~als is ilapoxt~nt be::ause~ with a broad temper~ure range, a singl~ heat ~eaïing device can be used to make peelable and perrQan~nt ~eals without need for highly sen~itive th~rmo~ta~ic~ ontrols to be built into th~ device.
De~ription of the Prior Art U,. S~ 4 ,188, 441, issued ~ebruary 12, 1980, di~clo~es a blend o~ polymers useful with high density polyethylene film to make pe~lable heat seal~. The blerld of that pa~nt is disclosed to be of an ethylene vinyl acetate or acrylic ester two~comporlent copolymer and a sodium~neutralized ionomer. The dis~losed ob~ect is tQ mak~ peelable seals only and permanent seals are avoided as undes.irable .
AD-508g 35 ~L2~

U~S. Patent No. 3,707,393 issued December 26 197~ on the applicatlon of McDonald disclose~ heat seal use of a combination o~ an ionomer and, in a special instance, a ~rpolymer. The combination o~
materials is merely a physical mixture and not a bl~nd with par~ial neutraliza~ion of both polymers~
U.S. Patent No. 3,789,035 is3ued ~anuary 29, 1974 on th~ application of Iwami et ~1~ discloses a proces~ wh~in carboxyllc acid groups in one pol~me~ic material can be neutra}ized by reaction contact with neutralized c~rbsxylic acid groups in anoth~r pol~meric mater~al. The pate~t also discloses ~epara~ion of the polym~rs ~o neutralized~
~. S~ Pat~nt ~o. 3,~6,061 i~sued ~ebruary 17, 1970 on the appl cation of ~reshour et al. disclo~es h~a~ sealed packages m~de using at lea~t two diferent mat~rial~ so that at least one ~eal will exhibit a peel strength of more than 4û0 gra~ er irlch.
lJ.~. Patent No. 4,189,519 issued ~ebrua~y 19 9 1980 on the application clf Tis::knor di sc:los~s a blend of polymerlc mat~r.ial~ which serves a~ a heat seal ~omposi~ion whe`rein one required ~ompourla i~ an isotacti~ polybutylene.
Summary of the Inventioll The pre~ nt im7ention embra~es a heat seal ~osition which exhibits a broad effective temperatuxe range to achieve heat seals o controlled strength on a variety of sub~trate materialsO The compo~itiorl is a blend of a terpol~ner with a partially r~eutralized ionomer includillg about 20-80 weigh'c parts of the terpolyaner and 2U-80 weight parts of the ionomer. Both polymers contain, as a ~Z~ 3 monomeric component, an un~aturated monocarboxylic acid. The total carboxylic acid in the blend is neutralized 5-40 percent.
The heat seal composition o~ ~his inven~ion exhibits a broad ~emperature range for making heat seals of variablQ s~rengths. The composition of thi~
invention permi~s the manufacture of film, foil or paper packAges wi~h permanent ~ide or bo~om s~als and peelable top ~eals.
~e~cription of ~he Invention ~ eat seal comp~si~ion~ have long been used ~o make package~ fxom films, ~oils and paper 4 The packaging ma~erial substra~e i~ usually co~ed on one ~ide with ~e heat seal eomposition, coated sid~ are ~hen mated ~ace~to-face, and mated ma~erials are heat~d a~ i~tended se~m ar~as ~o melt t~ hea~ seal compositi~n and yield package seam~O
- AGcording to ~his invention th~re i~
pro~ided~ as a ~eat ~eal composition, a substantially homogeneous blend o~ polymeric ma~erials comprlsing~
a terpolymer having ~thylene, vinyl alkanoate or unsa~ura~ed alkyl ~st~r, and a par~ially neukralized, un~a~urated, carboxylic acid as m~nomeric componen~s;
~nd an ionomer having ethylene and a partially-neutralized, unsaturate~, ~arbo~yli~ acid as mono~ric componen~s.
Th~ terpolymer has about 65 ~o 95 percen~, by weigh~, ethylene~ about 4 to 30 percen~, by weight, vinyl alkanoate or unsatllrated alkyl ester~
and about 0.5 to 20 perc~nt, ~y weigh~; unsa~urated carboxylic acid. The vinyl alkanoa~e or unsatura~ed alkyl ester monomeri~ componen~ is present in the ~erpolymer to provid~ a compon~nt for increasi.ng a3 adhesion to f ilm, foil, and paper substra~es and to provide inc:rP~sed flexibili ty to the ::omposition and ~o broad~n the effective hea~ sealing temperatwre range. The un~aturated alkyl e~ers include alkyl 5 acryla~e and alkyl methacrylate wb~rein the alkyl group has one to four carbon atoms. Example~ include znethyl acryla~e, ethyl acryLate, methyl methacryla'ce 9 ethyl methacrylate, isobu~yl acryla~ce, arld the lik~.
The vlnyl alkanoates include vinyl acet~te, vinyl 10 p~9pionate, vinyl butyrat~ and the like whereîrl ~he alkanooc acid moiety of ~he alkanoate has one to fs: ur carbon a~orns. Vinyl ace~ate, 10 o 30 percen~, by weigh~, is pr~f~rred for paper and foil substr~s and isobu~yl acrylai:e, 5 to 25 pe~o~n~, by wei~h l~
15 prefe~red for pol~meric film substra~es~, A
terpol~ner with 'eoo littl~ vinyl al kanoate or unæa~ura~ed ester component exhibits gen~rally poor adhesion and narrow heat sealing ~cemperature range while an @xc~5~ of that csmpollen~ cau~e~ exce~sive 20 tackine~s of th~ heat ~eal composition.
The t~rpolymer can have more ~han three monomeric componellt~ sc~ long as tAe additional c~mponents do not irlterfere wit~i the func~ic;n of tho~e three components which are nece~sary for 25 operaton of t;hi~ invention~
Th~ arboxylic acid monomeric comE~onen~ is present in ~he terpolymer l:o provide a componerl~
similar to the acid compon~nt in ~he io~omerO It is believed tha~ r by th~ presenc:e o carboxylic acid 30 comporlsnt3 in each o ~he hlend ps~l~ners, a cooperation i5 realized betw~en th~ polymers., Although the mechanism i~ not entirely und~rstood, i is believed that the presencia of carboxylic ac:id components in each o~ the ~lend polymers causes a degree QE compatabili~y be~w~en the p~lymers which i5 evidenced: ~irst, by a broadening of ~he temperature ran~e within which peelable h~at seal~ carl be made;
and, second, by a substantial inc:rea~e in ~he Illaximum heat seal strengkh wllich could be obtained by blend~
~f similar materials but without the mutual carboxylic acid compon~nt.
The ellgible carboxylic acids include acrylic acid and metha~rylic ac:id. Those componen s can be usQd in amounts of 0 . S to 20 percent t by weigh of the terpolymer composition, and 0 . 8 to 15 percer~ y weig~t, of ei~h~r ac:id is preferred. Alt acid conterlts which are too low~ the compatib~lizin~
efectq de~cribed aboYe are lo~t and a~ acid corlten~s wh:lch are ~oo high t the terpolymer exhibit~ an undesirably high modulus.
Terpolylaers which incllade the carboxylic acid comp~n~t and which are eligible for use in 2û practice o~ thie invention are described in ~. S., Patent ~3O. 3,264,~7~
The ;onomer has abou~ 75 to 99 percen~ t by weight, ethylene, and abo~t 1`~o 25 percent, by weight, un~atura~ed earboxylic acid. For use in thi~
inverltion, it is preferred that the ionomer hould have 3 to 20 perc~n~ ~ by w~ight, unsaturated caEboxy~ ic a id. From about 5 to about 75 percemt o~
~he carboxyLic acid groups in the ionomer should be r~eutrali2ed ~y zii~c me~al ions.
3û Ionomers which ar~ eligible fox use ir~
pr~ctice of this irlvention are described in ~3 s.
Patent No, 3 ~ 355 9 319 .
As was st:ated, the combination o ~inyl alkanoate or alkyl ac.rylate or me~hacrylate wi th acrylic or methacrylic acid in the terpolymer and acrylic or methacrylic acid in the ionomer results in a balance of improved adhesion, improved polymer compatibility, and broadened heat seal temperature range. To obtain the full benefit of that halance, it has been found necessary to provide terpolymer material wherein the combined weight percentage of vinyl alkonate or unsaturated alkyl ester with acrylic or methacrylic acid components is at least eight percentage points greater than the weight percentage of unsaturated acid in the ionomer.
Because these benefits relate, in large part, to alternation of the softening or melting temperature of the blend, it is believed that the component ratio requirements are substantially independent of the amount of terpolymer and ionomer used within the overall requirement that not less than 20 nor more than 80 weight percent of each material must be present in the blend.
The various components of the heat seal composition are combined to form a molecular mixture of materials. The combination can be made by any of the common methods for blending materials. For example, solutions of the materials can be mixed and the solvent subseqeuntly removed; the materials can be mixed together in melt form such as by melt blending in an extruder; or the materials can be milled together such as on a two-roll mill or a Banbury blender. The major requirements of the blending are that the resul-tant blending mu~-t be substantially homogen00us and that the blending must cause mixing of the materials which is intimate enough to permit an equalizing of the neutralization betweerl ~he carboxylic acid groups of the terpolymer and the tonomer. Ex~ru~;ion bl~nding has been found adequa~e and is pre~errad ~or making the blends o thi~ invantion.
It is under3tood ~hat, in ~he blends 9 l~he ~expolymer conl:ains carboxyli.- acid groups which are partially neu~cralized; ~n~ tha~ the ~erpolymer cs:~ald, ~herefQr~, be ~dentif iad as an ion~mer .. In fac~ he ~lend~ of this inven~ion ~:an, also9 be prepared from 10 two ionc~ers or from i3 three-co~ponerst ionoJDer and an unneutrali2ed copolymer, or if desiredg rom appropriate ~ombinati~ns e~f suc:h c omponent~O
Additi~snally, t:he blesids c:as~ be prepi~red Iby melt blerldlng unneutralized c:opoly;~er and ~erpolysr~er and 15 then n~u~raliz~ng th~ blended mix~ure. Suitab~ ~
processes for conducting such a neu~ralizat~on are diSG3.0$~d in t~.80 Pa'cent ~o. 3,404,134 and 3~969,43d~ ofa3: as th~ c:arboxylic a::id grollp~ are Ct3nCerrl~d7 it i5 only nec~ssary ~ha . h~ fini3hed 20 blerld ~DUSt include carboxyl;c acid grouI?~ in ~ach polymer cc;~apor~en~ n~utralized ~o th~ re,quired ~x~ent.
~ t has been found that the bellefit~ 3~ this in~ren~ion ar~ obtai~ed wh~n ~7e degree of n~utralization csf all .arbo~ylic acid groiaps in th 25 Ibler~d :~s f rom 5 to 4û percen~ erpolym~r and ions~mer materials are ~elect*d ~u~h t~at, ~h~n h~
degree of n~u~ralization o ~he unblendedO
n~ul:ralized,~ material ls averaged with th~
unneutralized material during blending, ~he re~lllting, overall ~ ne~atr~lization will be irl the necessary range.
Th~ heat ~eal composil:ion o~ this inv~n~ior c2m be us~d in the ways that heat seal ~- ,~sitions a3 ar~ usually used. It can be used as a self-supporking structure such as in the ~orm of sheets, s~rips or webs; it can be coated onto a substrate packaging ~aterial as a solution or S emulsion, it can be coextruded with a subs~rate packaging film material; and it can be lamina~ed ~o a substratQ material usiny an adhesive.
The heat seal composi~ion of this invention ~an be u~ed with a varie~y of sub~rate packaging mat~rials. A~ earlier described, monomeric omponents o the ~erpolymer and the ionomer can be ~specially selee~ed to increase adhesion of ~he heat ~al ~ompo~ition to ~he substra~e packaging materialO Addlti~nally~ when high densi~y polyethy~en~ polypropylene, polye~ters~ polyamides, or the lik~, are ~o be used as ~he subs~rate packaging material7 i~ has b~en ~ound importan~ to use a metal ion having a valence greater than o~e ~o neu~ralize th~ carboxylic acid group~ of ~he heat seal compositionO Zinc is ~he metal ion preferred and most usually used in such cas~s because zinc ha~
been found to pr~vid~ he required broad hea~ sea~ ing temperature range. `~
~n making peelable heat seals for flexible packag~ is usually desirable and of~en re~u~red tha~ ruptures of th~ seals should occur within the heat seal composition. It is, therefore, impo~tant that the heat seal composition should be more stro~gly adhered to the substrate material than the heat s~al composition layers adhere to themselves when a peelable heat seal i~ made. ~hen permanen~ or fu~ed heat seals are made, it i~ desirable that the heat seal composition should be fused together a~d ~2~1U~ ,3 that i~ should be so strongly adhered to the substrate material tha~ tearing of the substrate m teEial occ~urs before rupture of the heat seal and 'chat, in any everlt, the ~eal doe~ not rupture by separation of the fused hea~ seal composition., Use of zinc as a neu~ra~ g metal ion arld use of appropriate vinyl alkanoa~e or un~aturaked es~er in the terpolymer, particularly vinyl acetat~ or isobutyl acrylate, are 1~elieved ~o be importan~ in lû obtaining a maacimum fu~ed heat seal strength with a varlety of sub~trate packaging materials.
One impo~tant feature of the heat ~eal composition of ~his inverl~ion is the broad heat sealing temperature range ext~nding from ~hak temperature nececsary to achieYe a low strength, pe~lable, he~ al ~.o ~1;2a~ ~emperature required for a ma~im~ treng~h ,, p~rm~nellt, heat seal wherein the heat seal collsposition from mated materials has comple~ly ~used together.
The broad ~mperature range for h at seals made usir:g the heat seal compositions of this invention cara be evLdenced by a s~andædi zed heat sealing t~st in which seiL~supported films of the heat ~eal composition are prepared and ~hen a series o heat ~eals are made with tho~e Eilm~ at a series of temperatures,. The heat qeals ~o made are te~tad a~ to peel tren~th and 'che emperatures are noted which result in peel stren~ths of 118 grams per ~entimeter (300 grams per înch), 275 gram~ per centimeter 17aO gram~ per inch), and tear ~eal~ A
tear seal repre~nts the maximum seal which can be obtained w~ th a given substrate material bec~usa that seal s rerlgth actually represen~s the tear strength g ~ ~ l~

of the substrate material or the cohesive strength of the fused heat seal composition. ~hen performing peel strength tests using films of the heat seal composition, the tear seal occurs at the temperature where the composition is fully fused. In determining temperatures at which hea-t seals have been made, it is improtant to determine the temperature at the interface between the heat seal composition layers rather than heat seal jaw or bar temperatures. Due to calibration errors in the heat sealing devices or variations in heat transfer~ ssaling jaw temper~tures can be higher or lower than the actual interfacial temperature by unpredictable amounts.

For purposes of this invention, it has been determined that a temperature range of at least 7, and preferably more than 8, Celsius degrees is acceptable for the peel seal zone (118 -to 275 grams per centimeter). It has been found desirable although not nscessaryt to have a temperature range of at least ~ and preferably more than 10 Celsius degrees for the tear seal zone (275 grams per centimeter to tear).
Conventional additives, such as fillers, dyes, antioxidants, antistick agentsr and the like can be added to the heat seal compositions of this invention; --the only requirement being that ths presence of the additive does not adversely affect ~he performance of the compositionO Antiblocking additives such as silica and slip agents such as substituted fatty amides are examples of additives which can be added in usual amounts. Additives are conveniently and customarily added to the heat seal compositions during blending and are not usual]y ].0 present in amounts exceedIn~ ~iVe weight perce~t of the total composition.
Description of the Pre~ferred Embodiments In examples of the invention which follow, component materials of heat seal compositions were blended together by flrst mixing the materials in particulate form in the amounts indicated in the Table below; and then melt blending and devolatilizing the mixture in an extruder such as a 28 millimeter Werner & Pfleiderer* twin-screw extruderO The extruded blend was pelletized and, to make film for testing, the pellets were converted into blown film in a 1.9 cm (0.75 inch~
Brabender* extruder fitted with a 2.5 cm (1.0 inch~ die.
The film was generally of a 0O05 mm (2 mil) thickness with a 2.5 blow-up ratio and was cast at a melt temperature of 190-210C.
The film was cut into 2.5 cm (1 inch) wide samples for testing; and pairs of the samples were heat sealed together to provide a 2.5 cm (1 inch) peel length. The seals were made on a device having two heated jaws 2.5 cm (1 inch) wide and the heat seals were made at a clamping pressure of about 275 kPascals (40 psi) for about 3 seconds. The interfacial sealing temp-eratures were determined by locating the thermocouple between film samples being sealed and calibrating the sealing device therefrom for those samples.
Peel strenyths were determined by pulling sealed samples at 23 degrees Celsius and 50% relative humidity in a tensile testing device at the rate of 12.7 cm/min (5 inches/min.). Peel strengths were evaluated as a function of the interfacial sealing *denotes trade mark 11 ~emperature and the peel seal zon~ ~nd the tear seal zone were determined ~herefrom. ~hose determinakions are recorded in the Ta~le ~elow.
Table ~xampl~ Terpolymer Wt % in blend Composition neukO
1 50 ~10 IBA/10 ~AA 0 21 23 E/28 ~A/l MAA O
32 30 ~tlO IBA~10 M~A
43 28 do 0 51 23 do 0 63 ~3 73 33 do 7~ 32 73 29 ~o 82 3n do 0 15 92 ~ ~o 1~ 32 73 32 do O

do 121 18 ~28 VA~l MA~ 0 13 30 E~10 IBA/10 MAA 73 do 0 ~o 16 50 do 0 17 70 do 0 ~8~ 3~ . 73 32 do 0 Pa ~ EflO IBA/10 M~A 0 ~ ~
E 30 do 73 do 73 ~o 73 ~o 73 I4 50 do 0 J4 ~0 do 36t~a R 70 d~ 73 Table (continued~
Example Ionom~r wt. ~
blendcompos i ~ ion neu~ .
5 û E/9 MAA 18 21 7~ ~o 18 3~ 69 do 18 43 70 do 18 51 75 ~o 1 63 3;2 13/4 ~
71 37 do 0 82 ~9 E~9 MAA lB
92 77 do 18 11 70 do 0 21 18 Ef4M~ Cl 62 E:/9MAA 18 14 3Q do E/9 ~ 18 16 50 do 18 17 30 do 18 18~ 35 E/4MA~
A :10 0 E/9~IAA 18 B 30 3:/15 M~ ~o C 50 ~/15 ~ 20 D 25 do 20 E 70 E/~ ~ 18 do - 18 G 3 0 ~:/4 ~AA .~ _ . O
E~ 30 do ~4 50 E/12M~ 22~a ;~4 50 ~o Table ( cont i nued ~
peel seal zone tear ~eal zone Overall (118~275 g/cm~ (275 g/cm - tear) Example ~ Neut. C~ C
1 8.5 7.5 17 16~0 9.5 5,5 3 11.8 7~5 9.5 4 11., 6 10 1~
12.3 ~.~ 1505 6 2~.6 7 18.5 7 29.6 ~ 17.5 - ~,0 8 11.8 7.,5 12.5 g 13.3 7.5 11 1~ 29 . 5 6 17., 5 ~1 ~8 0 9 ~ 1 12 ~3 0 9 7 9 13 37.. 8 7 2 14 3L,.2 7~5 1305 1202 7 ~.1 16 8.5 10 1~.5 17 5.0 g ~.~
1~ 2~.~ 7 16.5 1~ 5 11 B 18~,8 5 7 12~0 5.5 7 D 6.7 7 $
E 35.7 7 5.5 ~ ~.,7 60~; 6.. S
~; 6~c3 7 7~5 E~ 62.3 6.5 ~ ~3.5 1;201) ~5 9~5 J 1~4 5 `~
R 52.3 4~,5 8 1 includ~ 2 weight percent, in the blend, o~
one part f inely divided ~ a as an antiblocking agent and two part~ of a 51ip agellt.
includes 0. 6 weigh percent of ~he 30 additives of note 1, above.
3 include~ 1., 2 we ight percent of the additive~ of note 1, above.
4 }onomer was neu~ralized by sodium.

In the examples and the Table, polymer ic component ma~erials ~re iden~if ied as ~ollows: E/10 r~A~10 MA~ is a ~erpolymer with ethylene and having 10 weight percent isobutyl acrylate and 10 weight 5 percent me~hacrylic acid; E/28 V~/l MAA is a terpolymer with ethylene and ha~7ing 28 weigh~ percerlt vinyl acetate and one weight percent methacrylic acid; and E/x MA~ is a copolymer with ethylelle and a weigh~ percen~ o~ me~hacrylic a ::id indica~ed by ~he 0 number ~ubs~itu~ed for "xl' in the Table.
In the examples of the invention which ~ollow, blend~ frol3l previous exaaTples were coextruded with high den~ity polyethylerle to yield a flexible packaging material of a ~ilm of high density 15 polyethylene a~ a ~u~strate packaging material with a ~ilm of one of ~he bl~nd~ adhered thereto as a heat seal compositioR. The coated polyethylelle was then te~t~d for heat ~eal ~trenyth~ as were films of the blends~ previously. Such packaging ma~erial s:)f the 20 blelld coa~ed ola~o a .substrate material is u~ed to laake packages by placing ~wo sheet~ o~ the coat~d mat~rial wil:h h~at seal layer facing heat seal layer and then producing heat seals ;` ~ va~ying or desired str~ngth ~y applyirl~ hea~c ~eal jaws of controlled 25 ~emp~r~ture O
heat seal pe~l ~ealtear ~eal zs: ne compos i t iOllzone ~xample (Example No. )(C~) (C) 6 11.~ 17.5 30 21 7 9 13.
22 8 5.5 3~5 23 9 5,.5 ~0.5 24 10 9 . 5 ~5 .

Claims

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

1. A substantially homogeneous blend of polymeric materials comprising.
a) 20 to 80 percent, by weight, of a terpolymer having, as monomeric components, i) 65 to 95 percent, by weight ethylene, ii) 4 to 30 percent, by weight vinyl alkanoate or an ester selected from the group consisting of alkyl acrylate, and alkyl methacrylate wherein the alkanoic acid moiety of the alkanoate and the alkyl group have one to four carbon atoms, and iii) 0.5 to 20 percent, by weight, ethylenically unsaturated monocarboxylic acid selected from the group consisting of acrylic acid and methacrylic acid; and b) 20 to 80 percent, by weight of an ionomer having, as monomeric components, i) 75 to 99 percent by weight, ethylene, ii) 1 to 25 percent, by weight ethylenically unsaturated monocarboxylic acid selected from the group consisting of acrylic acid and methacrylic acid.
wherein the sum of the weight percentages of comonomers ii) and iii) in the terpolymer is at least eight percentage points higher than the weight percentage of comonomer ii) in the ionomer, wherein 5 to 75 percent of the carboxylic acid groups in the ionomer is neutralized by zinc ions, and wherein 5 to 40 percent of all of the carboxylic acid groups in the blend is neutralized by zinc ions.

2. The blend of Claim 1 wherein the monomer, ii), of the terpolymer is a vinyl alkanoate and the alkanoate is acetate.

3. The blend of Claim 1 wherein the monomer, ii), of the terpolymer is an alkyl acrylate and the alkyl group is isobutyl.

4. The blend of Claim 1 wherein self-supported films of the blend material exhibit a peel seal (118 to 275 grams per centimeter) tempera-ture range of at least 7 Celsius degrees.

5. The blend of Claim 4 wherein self-supported films of the blend material exhibit a tear seal (275 grams per centimeter to tear) tempera-ture range of at least 8 Celsius degrees.

6. A flexible packaging material comprising the blend of Claim 1 coated onto a substrate packaging material.

7. The packaging material of Claim 6 wherein the substrate material is selected from the group con-sisting of polyethylene, polypropylene, polyesters, and polyamides.

8. The packaging material of Claim 7 wherein the substrate material is polyethylene.

9. A flexible packaging comprising a film of the blend of Claim 1 adhered to a substrate packaging material.

10. The packaging material of Claim 9 wherein the substrate material is selected from the group con-sisting of polyethylene, polypropylene, polyesters, and polyamides.

11. The packaging material of Claim 10 wherein the substrate material is polyethylene,