CA1304550C - Thermoplastic multi-layer packaging film and bags made therefrom - Google Patents

Abstract

ABSTRACT

Disclosed is a heat-shrinkable film suitable for making bags and pouches. The film has at least one layer comprising a copolymer of ethylene and an alpha-olefin with six or more carbon atoms per molecule, said copolymer having a density of about 0.910 g/cc or less and a melt index of about 2 or less.

Description

13~

THERMOPLASTIC MLLTI-LAYER PACKAGING FILM
A~D BAGS MADE THEREFRDM

me invention relates to thermoplastic, nLlti-layer, heat-shrinkable (i.e. oriented), packaging films and bags or pouches nade therefrom. In particular this invention relates to films and bags having excellent heat-shrinkability properties, orientation speed properties, and abuse-resistance pro-perties.

Heat-shrinkable thermoplastic films are being used in packaging of non-food and food products l~ke meat, cheese, poultry and the like. Many attempts have been made to co~bine good abuse-resistance or strength at all temperatures with good shrink properties and also to orient the films at a faster speed; however, there is still rw m for improvement.

BA~KGROUND OF THE INVENTION

A filn known from U. S. Patent No. 3,741,253 to Brax comprises a core layer of a vinylidene chloride copolymer (saran) between a layer of ethylene-vinyl acetate copolymer and layer of a cross-linked ethylene-vinyl acetate copolymer. Ethylene-vinyl acetate co-polymer (EVA~ has some improved properties over the 130~5~0 previously used polyethylene. Vinylidene chloride copolymers are known barrier materials to fLuids such as oxygen.

As disclosed in U. S. Patent No. 4,064,296 to Bornstein the core layer may also be a hydrolized ethylene-vinyl acetate copolymer (EVOH). It has similar oxygen barrier properties as vinylidene chloride copolymers and offers the advantage that it may be irradiated without discoloration, which is further dis-cussed below.

Blends of linear low density polyethylene andethylene vinyl acetate copolymer in oriented barrier films are disclosed in U. S. Patent 4,457,960 to Newsome, which claims an oriented multiple layer poly-meric fi~m, c~rising (a) a first barrier layer, saidfirst layer having two opposing surfaces; (b) a second layer adhered to one said surface, said second layer being 10% to 90% linear low density polyethylene and 90%
to 10% ethylene vinyl acetate; and (c) a third layer adhered to the other said surface, the composition of said third layer being selected from the group consist-ing of (i) ethylene vinyl acetate, and (ii) blends of 10% to 90% linear low density polyethylene with 90% to 10% ethylene vinyl acetate.

The so called linear low density polyethylenes are copolymers of ethylene and varying amounts of higher alpha-olefins with e.g. 5 to 10 carbon atoms per mole-cule (U. S. Patent No. 4,076,698) or 3 to 8 carbon atoms per molecule (Published European Patent A~plication 30 120503 published October 3, 1984, assigned to Union Carbide), for example copol~mers of ethylene and butene-l, copolymers of ethylene and octene-l, and the like. Depending on their density these materials are referred to as linear low density polyethylene (LLDPE) , . . .

13~45C,O
6~536-649 or very low density llnear polyethylene (VLDPE~, the separatlon line belng at a densi~y of about 0.910 g/cc.
Some properties of VLDPE have been descrlbed in Plastlcs Technology, September 1984, page 113. In October 1984, on page 13 of Plastics Technology, was another article describing VLDP~ entitled "New Klnd of Polyethylene Comblnes Flexibility, Toughness, Heat Resistance". The article lists a number of the propertles of YLDPE and compares them with EVA. VLDPE ls also descrlbed ln a company brochure publlshed ln February 1984 by DSM ln the Netherlands and eneitled "Stamylex PE". Thelr pro-percles are sald to be a unlque comblnntion between those of standard polyetllylene and polyoleflnlc rubbers. Thelr sealablllty and thelr com~atlblllty wlth other polymers has been mentioned.

European Patent Appllcatlon No. 0217252 publlshed on Aprll 8, 1987, commonly asslgned to W. R. Grace, discloses a thermoplastlc, multllnyer, packing fllm havlng superlor heat shrlnk and cold seal propertles.
Optlonally, the fllm has a barrler layer. The seallng layer of the fllm comprlses a copolymer of ethylene and higher alpha-olefln sald copolymer havlng a density less than about 0.920g/cm3. Speciflcally, when uslng a co-polymer of ethylene and butene, the comonomer contentshould be between about 10 and 20X by welght, based on the copolymer. Such copolymers have a denslty of less than about 0.915 g/cm3. When employing a copolymer of ethylene and octene, the comonomer content should pre-ferably be lncreased to between about 12 and 25X bywelght, based on the copolymer. Such copolymers ha~e a denslty of less thnn 0.920 g/cc. It 18 also posslble to blend the ethylene/alpha-olefln copolymer with up to 50%
by weight, based on the seallng layer composltlon, of a polymer whlch 15 compatlble wlth sald ethylene/alpha-olefln copolymer. Such further polymer mny preferably ~ A

13~45~0 6q536-649 be selected from llnear low denslty polyethylene (LLDPE) with a ~ensity nbove 0.920 g/cc, llnear hlgh denYlty polyethylene (LHDPE), low density polyethylene (LDPE), ethylene vinyl acetate (EVA), acid modified EVA, poly-propylene, ethylene/propylene copolymers, ionomericpolymers, and ethylene/alkyl-acrylate (EAA) copolymers wherein the alkyl molety has l to 8 C atoms, in particul~r ethylene/methyl-acrylate (EMA), ethylene/
ethyl-acrylate (EEA) and ethylene/butyl-acrylate ~E~A).
The ethylene/alkyl-acrylate copolymer which can be blended with the ethylene/alpha-olefln in the heat seallng layer can comprise about 3 to 30X by weigl-t of alkyl acrylate. In order to achleve optim~l results as per E.P. 0217252 , the comonomer content must increase when golng from the C4 alpha-olefln (bùtene(l)) to the C8 alpha-olefln (octene(l)).

U. S, Patent 4,640,856 to Ferguson et al, commonly asslgned to W. R. Grace, dlscloses a multl-layer, thermoplastic barrler fllm havlng at least three layers comprlslng: (a) a layer conslstlng essentlally of very low denslty polyethylene havlng a denslty of less than 0.9lO gms/cc; (b) a barrler layer comprlsing a materlal selected from the group consistlng of: (1) copolymers of vlnylldene chloride and t2) hydrolyzed ethylene-vlnyl acetate copolymers; (c) a thermoplastlc polymeric layer, sald layer being on the slde of the barrier layer opposlte to thst of layer (a); and (d) the shrinkage of layer (8) controlllng the shrlnkage of the entlre multl-layer barrler fllm, sald multi-layer fllm havlng been orlented and rendered heat shrlnkable at a temperature below l00C. (212F.), said orlentatlon temperature belng about 40F. or more below the melt temperature of sald very low density polyethylene.

U. S. Patent 4,597,920 to Golike, assignor to du Pont, (July, l986) dlscloses a process for maklng a 404/8703lll9/4 A

.

13~4S~iO

shrlnk film by scretchlng biaxlally, wlthout prlor crosslinklng, a fllm made of a copolymer of ethylene wlth at least one C8-C18 alpha-olefln, whlch copolymer ha~ two dlstlnct crystalllte meltlng polnts bel~w S 128C., the dlfference between these meltlng polnts be-lng at least 10C., and stretchlng being carrled at a temperature wlthln the ran8e deflned by these meltlng polnts.

The present invention seeks to pro-vlde a packaglng fllm and bags made therefrom whlch haveexcellent or lmproved orlentatlon characterlstlcs over those of the materlals used ln the past. Thls means that the orlentatlon speed durlng processlng should be faster.

lS This invention alsD seeks to provlde 8 packaglng fllm and bags made therefrom whlch have excellent heat-shrlnkablllty characterlstlcs compared to those of materlals used ln the past.

l~lis inventi<~n also seeks to pr~
vlde a packaglng fllm and bags made therefrom havlng the above two characterlstlcs and also havlng excellent abuse reslstance or strength, as compared to materlals used ln the past and thereby provlde a mlnlmal rlsk of breakages when bags made of the fllm material are utillzed ln automated loadlng processes.

Flnally; and most lmportantly this invention seYks to provlde a msterlnl for fllms nnd bags co~blnlng the three above advantage6, l.e. excellent shrlnkablllty characterlstlcs, excellent orlentation chflracterlstlcs, and excellent abuse reslstsnce.

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1 3 ~4 s ~ o 64536-649 SUMMARY OF THE INVENTION
Therefore, the present invention provides a thermo-plastic, multi-layer, heat-shrinkable packaging film comprising at least one layer of a copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule, said ethylene/alpha-olefin copolymer having a density of about 0.910 g/cc or less and a melt index of about 2 or less.
The invention also provides a thermoplastic, multi-layer, heat-shrinkable packaging film having excellent abuse resistance, shrink and orientation properties comprising an out-side polymer layer, a heat sealing layer and an interior layer between said sealing and said outside layers, wherein said inter-ior layer comprises a copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule, said ethylene/alpha-; olefin copolymer having a density of about 0.910 g/cc or less and a melt index of about 2 or less.
The invention also provides a process for manufacturingthermoplastic, multi-layer, heat-shrinkable packaging film com-prising ~I) extruding at least one layer of a copolymer of ethy-lene and an alpha-olefin with 6 or more carbon atoms per molecule, said ethylene/alpha-olefin copolymer having a density of about 0.910 g/cc or less and a melt index of about 2 or less, (II) orienting the extruded polymer in at least one direction, and -~ (III) recovering a heat shrinkable polymeric film.
The invention further provides a thermoplastic, multi-layer, heat-shrinkable packaging film comprising at least one 3~4 5 ~o 64536-649 layer of a copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule, said ethylene/alpha-olefin copoly-mer having a density of about 0.910 g/cc or less and a melt index of about 2 or less, wherein said film exhibits excellent abuse resistance characteristics, excellent shrink characteristics, and excellent orientation characteristics.
In another aspect the invention also provides side seal-ed and/or end sealed bags made from the above-mentioned inventive ~ film.

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DETAILED DESCRIPTION OF THE INVENTION

Suitable ethylene/alpha-olefln copolymers, for use in at least one layer of the multilayer, heat-shrinkable films of the invention, belong to the class of polymers known as very low density linear polyethylene (VLDPE).
VLDPE is further discussed below. The VLDPE's suitable for use in the films of the invention have a density of about 0.910 g/cc or less, a melt index of about 2 or less, and an alpha-olefin comonomer with 6 or more carbon atoms. Such comonomers include, but are not limited to 4-methyl-pentene-1, hexene-l, and octene-1.
Some of the commercially available suitable VLDPE's are the XPR0545 æeries of resins supplied by Dow, XU61512.08L resin supplied by Dow, and DEFD 1629 resin supplied by Union Carbide. This VLDPE- preferably is present in an interior layer of the multilayer film.
Optionally, the films of the invention have a barrier layer such as a layer of EVOH or saran.

Typically, in the manufacture of films, a suitable polymer usually in the form of pellets or the like, is brought into a heated area where the polymer feed is melted and heated to its extrusion temperature and ex-truded as a tubular "blown bubble" through an annular dle. Other methods, such as "slot die" extrusion whereln the resultant. extrudate is in planar, as opposed to tubular, form are also well known. If heat - shrlnkable ~ilm is desired, then after extrusion, the film is typically cooled and stretched, i.e. oriented by "tenter framing" or by inflating with a "trapped bubble", to impart the heat-shrinkable property to the film, as i8 further described below. If desired, ; irradlatlon, typlcally vla an electron beam, may take place after but preferably takes place prior to the stretchlng for orienting the film. However, for the :' ~
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404/~70311/9/7 ' , 13~4SSO
.
present invention, such irradiation is not necessary since a very sultable packaging film i9 obtained without irradlation. Below, flrst is descrlbed in detail the general process for making and orienting film. Then irradiation is described in detail.

More particularly, the manufacture of shrink, l.e.
oriented, films may be generally accompllshed by ex-truslon (single layer fllms) or coextrusion (multl-layer fllms) of thermoplastic reslnous materials which have been heated to or above thelr flow or melting point from an extruslon or coextruslon die in, for example, elther tubular or planar (sheet) form, followed by a post ex-trusion cooling. The stretching for orle~ntlng the film may be conducted at some polnt during the cool down while ~h~ Ellm is still hot and at a temperature within its orientation temperature range, followed by complet-ing the cooling. Alternatively, after the post extrusion cooling, the relatively thick "tape" extrudate is then reheated to a temperature within its orientation temperature range and stretched to orient or align the crystallites and/or molecules of the material,-and then cooled again. The orlentation temperature range for a glven material or materials will vary with the different re~lnous polymers and/or blends thereof which comprise the material. However, the orientat$on temperature range for a given thermoplastic material may generally be stated to be below the crystalline melting point of the material but above the second order transltion temperature (sometimes referred to as the glass transi-tion point) thereof. Within this temperature range, thematerial may be effectively stretched to provide a heat-shrinkable film.
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The terms "orienting" or "oriented" are used hereln to tescribe generally the process steps and re-sultant product characteristics obtained by stretching,tran6versely, longitudinally, or both (whether during ' .

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the post extrusion cool down or during reheatinK after the post extrusion cool down as described in the para-graph above) and substantially immediately cooling a resinous thermoplastic polymeric material which has been heated to a temperature within its orientation temperature range so as to revise the intermolecular configuration of the material by physical alignment of the crystallites and/or molecules of the material to improve certain mechanical properties of the film such as, for example, shrink tension and release stress.
Both of these properties may be measured in accordance with ASTM D 2838-81. When the stretching force is applied in one direction, monoaxial orientating results.
When the stretching force is applied in two directions, biaxial orientating results. The term oriented is also herein used interchangeably with the term "heat-shrinkable" with these terms designating a material which has been stretched and set by cooling while sub-stantially retaining its stretched dimensions. An orieh.~d (i.e. heat-shrinkable) material will tend to return to its original unstretched (unextended) dimenslons when heated to an appropriate elevated temperature. However, by "orientation characteristics or properties" as that term is used herein, it is specifically intended to mean the orientation speed during processing in making the oriented film. When it is intended to refer to the percent shrink of the film and bags made therefrom, then the term "heat-shrinkability characteristics or properties" or the term "shrink ch~racteristics or properties" is employed herein.

Returning to the basic process for manufacturing film as discussed above, it can be seen that the film, once extruded (or coextruded if it is a multi-layer film), is then oriented by stretching within its orientation temperature range. The stretching to ~3~45~;0 orient may be accomplished in many ways such as, for example~ by "trapped bubble" technique~ or "tenter framing". These processes are well known to those in the art and refer to orienting procedures whereby the material is stretched in the cross or transverse direction (TD) and/or in the longitudinal or machine direction (MD). After being stretched, the film is quickly cooled while substantially retaining its stretched dimensions to cool the film rapidly and thus set or lock-in the oriented molecular configuration.

The film which has been made may then be stored in -~ rolls and utilized to package a wide variety of items.
If the material was manufactured by "trapped bubble"
techniques the material may still be in tubular form or it may have been slit and opened up to form a sheet of film material. In this regard, a product to be packaged may first be enclosed in the material by heat sealing ; the film to itself where necessary and appropriate to form a pouch or bag and then inserting the product thereln. Alternatively, a sheet of the material may be utillzed to overwrap the product. These packaging ~ methods are all well known to those of skill in the art.
:, When a material is of the heat-shrinkable (i.e.
orlented) type, then after wrapping, the enclosed pro-duct may be sub~ected to elevated temperatures, for ex-ample, by passing the enclosed product through a hot air tunnel or by placing the enclosed product in hot water.
This causes the enclosing heat shrinkable film to shrink around the product to produce a tight wrapping that closely conforms to the contour of the product. As stated above, the film sheet or tube may be formed into bags or pouches and thereafter utilized to package a product. In this caffe, if the film has been formed as a tube it may be preferable first to slit the tubular fllm to form a film sheet and thereafter form the sheet into bags or pouches. Such bags or pouches forming methods, likewi~e, are well known to those of skill in the art.
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The above general outllne for manufacturinR of films ls not meant to be all lnclusive since such pro-cesses are well known to those in the art. For ex-ample, see U.S. Pat. Nos. 4,274,900; 4,299,24l;
S 4,194,039; 4,188,443; 4,048,428, 3,821,182 and 3,022,543. The dlsclosures of these patents are generally representatlve of such processes.

Alternatlve methods of produclng fllms of thls type are known to those ln the art. One well-known alternative ls the method of forming 8 multi-layer fllm by an extruslon coatlng in combination wlth an ex-truslon or coextruslon process as wa3 discussed above.
In extruslon coatlng a flrst tubular layer or layers is extruded and thereafter an additional layer or layers is slmultaneously or sequentlally coated onto the outer surface of the flrst tubular layer or a successlve layer. Exemplary of thls method is U.S. Pat. No.
3,741,253. Thls patent ls generally representative of an extruslon coatlng process.

Many other process varlatlons for formlng fllms sre well known to those ln the art. For example, con-ventlonal thermoformlng or laminating techniques may be employed. For lnstance, multiple substrate luyers may be flrst coextruded vla a blown bubble tube wlth addltlonal layers thereafter being extruslon coated or lamlnated thereon, or two multl-layer tubes may be co-extruded wltll one of the tubcs thereafter belng ex-truslon coated or lsmlnated onto the other.

In the preferred embodlments a8 lllustrated ln theexsmples below, the multl-layer fllm of the lnventlon contalns à barrler layer. The layer is a barrler to flulds such as gas. The barrier layer may be composed 404l~703ll/9/ll ~3~S~
of a layer comprising vinylidene chloride copolymer (commonly known as saran), or composed of a l~yer com-prising hydrolyzed ethylene~vinyl acetate copolymer (EVOH), preferably hydrolyzed to at lease about 50%, most preferably to greater than about 99%, or composed of both a layer comprising vinylidene chloride copolymer and a layer comprising EVOH. When the barrier layer is composed of a layer comprising EVOH, the mole percent of vinyl acetate prlor to hydrolysis should be at least about 29%, since for lesser amounts the effectiveness of the hydrolyzed copolymer as a barrier to fluids such as gas is substantially diminished. It is further pre-ferred that the barrier copolymer have a melt flow being generally compatible wlth that of the other components of the multi-layer film, preferably in the range of about 3-10 (melt flow being determined generally in accordance with ASTM D1238). The gas of main concern is oxygen and transmission is considered to be sufficiently low, i.e. the barrier material is relatively gas im-permeable, when the transmission rate is below 70cc/m2/mil thickness/24 hours/atms, as measured according to the procedures of ASTM Method D-1434. The barrier layer of the multi-layer barrier shrink film according to the barrier film embodiment of the present invention has a trans~ission rate below this value. EVOH csn be advantageously utilized in the film of the invention since irradiative high energy electron treatment of the fully coextruded film does not degrade an EVOH barrier layer, as could be the case for a vinylidene chloride copolymer barrier layer.

When, as further discussed below, a vinyliden~
chloride copolymer (PVDC) is employed instead of or together with EVOH as the barrier layer, then the irradiation preferably should take place prior to application of the saran layer to avoid degradation thereof. This application may be achieved by well ' 404/870311/9112 . .

~3~45~i;0 _:

known extrusion coating methods, as discussed above.
More particularly, the extrusion coating method of film formation is preferable to coextruding the entire film when it is desired to subject one or more layers of the film to a treatment which may be harmful to one or more of the other layers. Exemplary of such a situation is a case where it is desired to irradiate with high energy electrons one or more layers of a film containing a barrier layer comprised of one or more copolymers of vinylidene chloride (i.e. saran), such as of vinylidene chloride and acrylonitrile or such as of vinylidene chloride and vinyl chloride or such as of vinylidene chloride and methyl acrylate. In other words, the barrier layer includes a saran layer in addition to or instead of an EVOH layer. Those of skill in the art generally recognize that irradiation with high energy electrons is generally harmful to such saran barrier layer compositions, as irradiation may degrade and dis-color saran, making it turn brownish. Thus, if full coextrusion and orientation followed by high energy electron irradiation of the multi-layer structure is carried out on a film having a saran layer, the irradiation should be done at low levels with care.
Alternatively, this situation may be avoided by using extrusion coating. Accordingly, by means of extrusion coating, one may first extrude or coextrude a first layer or layers, sub;ect that layer or layers to high energy electron irradiation and thereafter extrusion coat the saran barrier layer and, for that matter, simultaneou~ly or sequentially extrusion coat other later layers (which may or may not have been irradiated) onto the outer surface of the extruded previously irradiated tube and then orient the resultant. This sequence allows for the irradiative treatment of the first and later layer or layers without sub~ecting the saran barrier layer to the harmful discoloration effects thereof.

13~45~
Irradiation may be accomplished by the use of high energy electrons, ultra violet radiation, X-rays, gamma rays, beta particles, etc. Preferably, electrons are employed up to about 20 megarads (MR) dosage level.
The irradiation source can be any electron beam generator operating in a range of about 150 kilovolts to about 6 megavolts with a power output capable of supplying the desired dosage. The voltage can be ad-justed to appropriate levels which may be for example 1,000,000 or 2,000,000 or 3,000,000 or 6,000,000 or hlgher or lower. Many apparatus for irradiating films are known to those of skill in the art. The irradiation is usually carried out at a dosage up to about 20 MR, typically between about 1 MR and about ~20 MR, with a preferred dosage range of about 2 MR to about 12 MR.
Irradiation can be carried out conveniently at room temperature, although higher and lower te~peratures, for example, 0C to 60C may be employed.

In the Examples below the multi-layer films were made by a conventional method of manufacturing, combining tubutar coextrusion (colloquially called the hot blown bubble technique) with extrusion coating to achieve an oriented (heat-shrinkable) film. A tubular process was utilized wherein a coextruded tube of a multi-layer substrate core was extrusion coated with saran and another layer simultaneously, then the re-sultant structure was cooled and collapsed, and then reheated and biaxially stretched in the transverse direction and in the longitudinal machine direction via inflating the tube with a bubble. Then the stretc~hed bubble was cooled and collapsed, and the deflated oriented film wound up as flattened, seamless, tubular film to be used later to make bags, overwrap, et cetera.
Prior to the coating of the saran layer and the addltlonal layer, the substrate core was gulded through an ionlzing radiation field; for example, through the beam of an electron accelerator to receiva a radiation dosage in the range of about 4 to 6 megarads (MR).

13~45~;0 The VL~PE having a comonomer with 6 or more carbon atoms, a density of about 0.910 g/cc or less and a MI of about 2 or less may be blended with one or more various other polymers, said one or more other polymers belng present ln a welght amount up to about 50%, more preferably about 35X, most preferably about 25%. These varlous other polymers fllso may be employed for the lnner heat seallng layer of the preferred multl-layer barrler fllms of the present lnvention. Many of these other polymers are also sultable for use ln nny other layers of the fllms of the present inventlon, whether or not the fllms are bnrrier films. Suitable other poly-mers include, but are not limited to, ethylene acetate (EVA) copolymers, LLDPE, LDPE, HDPE, LM~PE, LHDPE, MDPE, polypropylene, ethylene/propylene oopolymers, ethylene/
alkyl-acrylate copolymers (EAA) [such as ethylene/
methyl-acrylate (EMA), ethylene/ethyl-acrylate (EEA), and ethylene/butyl-acrylate (EBA)], acld modlfled EVA, copolymers of (1) and (11) where (1) 18 an alpha-olefin of the formula RHC~CH2 whereln R 19 H or Cl to C8 alkyl and (11) 18 an alpha,beta-ethylenically unsaturated carboxyllc flcld, and the llke and mlxtures thereof.
Preferably, in the RHC-CH2 copolymer of an olefln and a carboxyllc acld, the olefln 18 ethylene and the car-boxyllc acld 18 acryllc acld or methacryllc acld.Materlals, whlch are the copolymer of an alpha-olefln havlng the formula RHC~CH2 whereln R ls H or C1 to C8 alkyl and an alpha,bets-ethylenlcally unsaturated car-boxyllc acld, representatlvely may be one of the Prlmacor (~t) polymers, supplled by Dow Chemlcal Company, Mldland, Mlchlgan. Prlmacor ls produced by the free radlcal copolymerlzatlon of ethylene and a car-boxyllc acld comonomer therefor ~uch as acryllc acid or methacryllc acld. Al~o, the copolymer of an alpha-olefln havlng the formula RHC-Ctl2 wherein R la H or Cl to C8 alkyl and an alpha,beta-ethylenlcally unsaturated carboxyllc acld may be metal salt neutrallzed such a8 .... .
404/870311~9/15 ,j A

~3~45~0 wlth sodium, Na. Thus, the copolymer may be an ionomer.
Representatively, such an ionomeric material is commercially available as Surlyn (TM) from the E. I.
du Pont de Nemours Company of Wilmington, Delaware, and is d~sc~ibed in detail in U.S. Patent 3,355,319 and U.S.
Patent 3,845,163.

In general, these polymers mentioned in the para-graph above may be blended with each other, and are many of the materials whlch as per published EP 0217252 mentioned above may be blended in a weight amount up to 50X, based on the sealing layer, with the copolymer of ethylene and higher alpha-olefin having a density less than 0.920 g/cc.

DEFINITIONS

The term "saran" or "PVDC", as used herein, refers to a vinylidene chloride copolymer wherein a major amount of the copolymer comprises vinylidene-chloride ant a minor amount of the copolymer comprises one or more unsaturated monomers copolymerizable therewith.
Examples of unsaturated monomers copolymerizable with the vlnylidene chloride are vinyl chloride, acrylonitrile, and alkyl acrylates having 1 to 18 carbon atoms in the alkyl group.

As uset herein the term "extrusion" or the term ` 25 "extrudlng" is intended to include coextrusion, ex-trusion coating, or combinations thereof, whether by tubular methods, planar methods, or combinations thereof An "oriented" or "heat shrinkable" material is de-fined hereln as a material which, when heated to an approprlate temperature above room temperature (for example 96C), wlll have a free shrink of about 5% or greater in at lea6t one linear direction.

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Unless specifically set forth and defined or otherwise limited, the terms "polymer" or "polymer resin" as used herein generally include, but are not limited to, homopolymers, copolymers, such as, for ex-S ample block, graft, random and alternating copolymers,terpolymers, etc. and blends and modifications thereof.
Furthermore, unless otherwise specifically limited the term "polymer" or "polymer resin" shall include all possible molecular configurations of the material.
These structures include, but are not limited to, isotactic, syndiotactic and random molecular con-figurations.

The term "polyethylene" as used ~herein, which "polyethylene'' is employed in the film of the in-vention, refers to families of resins obtained by sub-stantially polymerizing the gas ethylene, C2H4. By varying the comonomers, catalysts and methods of poly-merization, properties such as density, melt index, crystallinity, degree of branching, molecular weight and molecular weight distribution can be regulated over wide ranges. Further modifications are obtained by other processes, such as halogenation, and compounding additives. Low molecular weight polymers of ethylene are fluids used as lubricants; medium weight polymers are waxes miscible with paraffin; and the high mole-cular weight polymers are resins generally used in the plastics industry. Polyethylenes having densities ranging from about 0.900 g/cc to about 0.935 g/cc are called low ~denslty polyethylenes (LDPE) while those having densities from about 0.935 g/cc to about 0.940 g/cc are called medium density polyethylenes (MDPE), and those having densities from about 0.941 g/cc to about 0.965 g/cc and over are called high density polyethylenes (HDPE). The older, classic low density types of polyethylenes are usually polymerized at high pressures and temperatures whereas the older, classic high density types are usually polymerized at re-latively low temperatures and pressures.

13~45~0 .
The term "l1near low density polyethylene" (LLDPE) as used herein, refers to the newer copolymers of a ma~or amount of ethylene with a minor amount of one or more comonomers selected from C3 to about C10 or higher alpha-olefins such as butene-l, pentene-l, hexene-l, octene-l, etc. in which the molecules thereof comprise long chains with few side chains or branched structures achieved by low pressure polymerization. The side branching which is present will be short as co~pared to non-linear polyethylenes. The molecular chains of a linear polymer may be intertwined, but the forces tend-ing to hold the molecules together are physical rather than chemical and thus may be weakened by energy applied in the form of heat. Linear low densi~y polyethylene has a density preferably in the range from about 0.911 g/cc to about 0.935 g/cc, more preferabIy in the range of from about 0.912 g/cc to about 0.928 g/cc for film making purposes. The melt flow index of linear low density polyethylene generally ranges from between about 0.1 to about 10 grams pe~r ten minutes and preferably between from about 0.5 to about 3.0 grams per ten minutes. LLDPE resins of this type are commercially avallable and are manufactured in low pressure vapor phase and liquid phase processes using transition metal catalysts. The very low density linear low density polyethylenes (VLDPE) have a density from about 0.910 ~ g/cc to about 0.860 g/cc, or even lower.
,~ .
The term "ethylene vinyl acetate copolymer" (EVA) as used herein refers to a copolymer formed from ethy-lene and vinyl acetate monomers wherein the ethylenederlved units in the copolymer are present in major amounts and the vinyl acetate (VA) derived units in the copolymer are present in minor amounts. For film form-ing purposes, it ls desirable that th~ VA content of the EVA be from about 3% to about 25%.

. . . .

13~45~;0 The term "ethylene/alkyl-acrylate copolymer" (EAA) as used herein refers to a copolymer formsd from ethy-lene and alkyl acrylate wherein the alkyl moiety has 1 to 8 carbon atoms and the ethylene derived units in the copolymer are present in major amounts and the alkyl-acrylate derived units in the copolymer are present in minor amounts. Thus, the term "ethylene/methyl acrylate copolymer" (EMA) as used herein for a type of poly-ethylene, refers to a copolymer formed from ethylene and methyl acrylate monomers. The term "ethylene/ethyl acrylate copolymer" (EEA) as used herein for a type of polyethylene, refers to a copolymer fonmed from ethylene and ethyl acrylate monomers. The term "ethylene/butyl acrylate copolymer" (EBA) as used herein for a type of polyethylene, refers to a copolymer formed from ethylene and butyl acrylate monomers. Many suitable EBA's are commercially available and these have a butyl acrylate content from about 3% up to about 18% by weight. USI is a commercial supplier of Resin No. 4895, which is an EBA
having about 3% by weight butyl acrylate and a melt in-dex of 3 and a melting point of about 106~ to 107C.

The following Examples are intended to illustrate the preferred embodiments of the invention and comparisons thereto. It is not intended to limit the invention thereby.

MATERIALS EMPLOYED IN THE EXAMPLES

A suitable adhesive type of polymer employed in the films of the invention is commercially available as A Bynel~CXA 3101. It is an ethylene-based adhesive with a combination of ester and acid comonomer functionally, (i.e. an acid-modified EVA) and is supplied by du Pont.
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Some of the LLDPE employed in the example~ was Dowlex~2045.03 having a melt index of 1.1 and a density of 0.920. It was supplied by Dow Chemical. The co-monomer i9 octene.

Some of the LLDPE employed in the examples was Dowlex 4002 LLDPE having a melt index of 3.3 and a density of 0.912, and some was Dowlex 4001 LLDPE having a melt index of 1 and a density of 0.912. Both were supplied by Dow Chemical. For both, the comonomer i9 octene.

Some of the LLDPE employed in the Examples was Dowlex XU 61502.36 LLDPE having a melt index of 1 and a tensity of 0.917. It was supplied by Dow Chemical. The comonomer is octene.

Some of the LLDPE employed in the Examples was HS
7028 having a melt index of 1.0 and a density of 0.918.
It was supplied by Union Carbide. The comonomer is hexene-1.

Some of the LLDPE employed in the Examples was LL3001.CR1 having a melt index of 1.0 and a density of 0.918. It was supplied by Exxon. The comonomer is hexene-1.

; The HDPE employed in the Examples was Alathon~7850, having melt index of 18 and a density of 0.960. It was supplied by du Pont.

Some of the VLDPE employed in the Examples was XPR0545-36568-5N having a melt index of 0.8 and a density of 0.901. The comonomer is octene-1. It was supplied by Dow Chemical.

.. . . . . . . .
~ 404/870311/9/20 - ~3~S~O

Some of the VLDPE employed in the Examples was XP~0545-36568~6A, having a melt lndex of 0.8 and a density of 0.905. The comonomer is octene-1. It was supplied by Dow Chemical.

Some of the VLDPE employed in the Examples was XPR0545-36568-6E, having a melt index of 0.8 and a density of 0.910. The comonomer is octene-1. It was supplied by Dow Chemical.

Dow XU 61512.08L is a VLDPE supplied by Dow Chemical. It has octene as the comonomer. The density = 0.905 and MI = 0.80.

Some of the VLDPE employed in thè Examples was DEFD 1491, having melt index of 1.0, and a density of 0.900. The comonomer is butene-l. It was supplied by Union Carbide.

Some of the VLDPE employed in the Examples was XPR0545-36568-12D having a melt index of 0.8 and a tensity of 0.900. The comonomer is octene-1. It was supplled by Dow Chemlcal.

Some o~f the VLDPE employed in the Examples was XPR0545-36568-12E, having a melt index of 0.8 and a den~ity of 0.905. The comonomer is octene-1. It was supplied by Dow Chemical.

Some of the VLDPE employed in the Examples was XPR0545-36568-12F, having a melt index of 0.8 and a dens1ty of 0.910. The comonomer is octene-l. It was supplied by Dow Chemical~

Some of the VLDPE was XPR0545-36568-12G. It was supplied by Dow Chemical. It has octene as the comonomer. The density = 0.900 and MI = 0.60.

404/870311/9/~1 ,:
: ~ ` ' ' ' . . .

l3a~s~-~

Some of the VLDPE employed in the examples w~s XPR-0545-33260-46L having a melt index of 3.3 and a density of 0.907 - 0.908. The comonomer is octene-1.
It is supplied by Dow Chemical.

Some of the LLDPE and VLDPE employed was of the A Stamylex~ resins supplied by Dutch State Mines. The comonomer is octene. Each has a me]t index and density as follows: Stamylex 1016, MI = 1.1, density = 0.920;
Stamylex 1026, MI = 2.2, density = 0.920; Stamylex 08-026, MI = 2.2, density = 0.911; Stamylex 2H287, MI =

2.2, density = 0.906; Stamylex 2H286, MI = 2.2, density = 0.902.

Some of the LLDPE employed was of the DEFD resins supplled by Union Carbide. The comonomer is hexene-l.
Each has a melt index and density as follows:
DEFD1568, MI = 0.50, density = 0.913; DEFD 1569, MI =
1.0, density = 0.912, DEFD 1623, MI = 1.0, density =
0.915; DEFD 1624, MI = 0.5, density = 0.914; DEFD 1626, MI = 0.8, density ~ 0.911; DEFD 1627, MI = 0.8, density e 0.912; DEFD 1628, MI = 0.8, density = 0.915; DEFD
1630, MI = 0.5, density = 0.913; DEFD 1567, MI = 1.0, denslty ~ 0.913; DEFD 1565, MI = 0.5, density = 0.912.

Some of the VLDPE employed was of the DEFD 1629 supplied by Union Carbide. The comonomer of DEFD 1629 ls hexene; MI = 0.5; and density = 0.910.

Some of the VLDPE employed in the Examples was 1137 havlng a melt index of 0.8 and a density of 0.906.
Some was 1491 having a melt index of 1.0 and a density of 0.900. The comonomer of both is butene. Both were supplied by Union Carbide.

USI was the commercial supplier of Resin No. 4895, which was the EBA employed. It has about 3% by weight butyl acrylate (the butyl groups are normal butyl, not tert butyl) and a melt index of 3.

:~ Tr~ ~orl~

130455i0 The saran employed in some of the laboratory ex-amples was Ixan (TM) WV~20 supplied by Solvay Cor-poration. It is a copolymer of vinylidene chloride with vlnyl chlorlde.

5Another saran (denoted in the examples below as Saran-MA) employed in some of the laboratory examples was XU32027.01, supplied by Dow Chemical. It ls a co--polymer of vlnylidene chloride with methyl acrylate.

Some of the EVA employed in the laboratory ex-10amples was LD318.92, which is an EVA containing 9%
vinyl acetate and having a melt index of 2Ø It was supplied by Exxon.

The EVA employed in some of the laboratory ex-amples was LD720.62, which is an EVA containing 18%
vinyl acetate and having a melt index of 1.5. It was supplied by Exxon.

Also employed was Elvax~3165, which is an EVA hav-ing 18% VA, and its MI = 0.7. Some of the EVA employed in the examples was PE3508, which is an EVA having 12%
VA and having a melt lndex of 0.35. Some of the EVA was PE 3507-1, which has 6% VA and a melt index of 2.7.
These were supplied by du Pont.

EXA~PLES

Percentages indicated ln the Examples were calculated as ~ by weight.

The films were made by first hot blowing through an annular dle a two-layer extruded tube of the structure: LAYER l/LAYER 2 as the substrate. Then ~(`o. l Q ~ r ~

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13~14S~
with a two-ply die, a layer of saran (barrier layer 3) and another layer (outside layer 4) were extrusion coated on. The resultant 4-layer structure was then cooled and collapsed. The tube was then reheated and oriented by stretching via a trapped bubble 4:1 in the transverse direction and 3:1 in the longitudinal direction for an overall biaxial orientation of 12:1.
When such films were made into bags, the heat sealing layer 1 was the "inner" or "inside" layer as it was the bag "inside", and "outside" layer 4 was the bag "out-side". The test layer 2 and the barrier layer 3 were "interior" layers of the multi-layer film.

Where irradiation has been indirated in the samples, the two_layer substrate was irradiated at the MR indicated prior to the coating on of saran and the outer layer. Various properties, i.é. orientation speed, abuse resistance (Carson Dart Drop, or ball burst), and ~ shrink, were measured for the films as noted in the Tables below. It is noted that orientation speed, due to the fastest the equipment could be run, could not go any higher than 80 feet/minute. The ball burst and shrink were measured in accordance with pro-cedures set out in ASTM D 3420 and ASTM D 2732, re-spectively.

The Carson Dart Drop is an impact test that measures the impact resistance of film by the free-falllng dart method. The apparatus employed for the free-falling dart impact was as described ln ASTM D
1709. The dart weighed about 41.5 grams. Film samples of about 7 x 7 inches ~17.8 x 17.8 cm) were cut.
Samples and equipment were allowed to equilibrate at room temperature for 36-40 hours prior to testing.
; Three specimens of each kind of film were sequentially placed in the clamp of the apparatus wlth the lnslde (layer 1 of the below films) of the sample up. A
failure height was selected and the dart released. The ~''~ ' .

13~4S~
helght was lowered by 1 inch (2.54 cm) ant testing of another three specimens repeated. The 1 inch lowering was successively repeated until all three samples did not break from the impact of the dart.

EXAMPLE I

Films having 4 layers were made and as indicated below, the polymers for Layer 2 were varied for the various films that were made, whereas the polymers for Layers 1, 3, and 4 were kept the same.

EXTRUSION
SUBSTRATE LAYERS COATED LAYERS

SEALING * BARRIER OUTSIDE

Polymer: EVA EVA or SARAN EVA
(9% VA) LLDPE or ~ (9% VA) 1,~
[LD318.92] VLDPE [LD318.92] -~

Before Orientation Thickness: 3 14.5 3.5 6.5 (mils)**

*When EVA w~s employed (Control Sample 1), layer 2 was lOOX EVA. But when LLDPE or VLDPE was employed (Samples 2-32), layer 2 was a blend of 7% Bynel CXA3101 ant 93% LLDPE by weight or was a blend of 7%
Bynel CXA3101 and 93% VLDPE by weight.
"
**After orientation, the total thickness of the 4-layer ~,~ film was about 2.2 mll~ to about 2.5 mils.
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DISCUSSION OF SAMPLES

Controls 1 (layer 2 was EVA) and 2A-2D (layer 2 was LLDPE): (Below they are compared to samples 10-18, samples illustrating the invention.) As can be seen from EVA sample 1, abuse resistance was poor (17.8 cm for dart drop and 25 cm-kg for ball burst), orientation speed was good (5i feet/minute), and æ shrink was ex-cellent (44% transverse; 27% longitudinal). As for LLDPE (density = 0.920; comonomer = octene) Control Samples 2A-2D, abuse resistance was excellent (38.1 cm and 30.5 cm dart drop for 2A and 2B, respectively) or superior (48.3 cm and 50.8 cm for 2C and 2B, re-spectively), orientation was good (between 46 and 60 feet/minute), and shrink ranged from excellent (34% T, 23% L for 2A and 32% T, 22% L for 2B) to good (28% T, 16% L for 2C and 28% T, 18% L for 2D). For the LLDPE
samples compared with EVA control sample 1, abuse re-sistance was far better, % shrink was not as good, and orientation speed was similar. In summary, with LLDPE
abuse resistance improves and shrink worsens, whereas with EVA shrink improves and abuse resistance worsens.

Samples 3-6: These were other comparative samples wherein layer 2 was LLDPE having octene as the comonomer, like the LLDPE control samples 2A-2D. Samples 3-6 had orientation substantially similar, abuse resistance far worse, and % shrink inconsistent as compared to control samples 2A-2D.

- Samples 7-9: These were samples wherein layer 2 was VLDPE having octene as the comonomer, but having a high MI of 2.2 for samples 8 and 9 and a high MI of 3.3 for samples 7A and 7B. Their performance properties of orientation (49 to 56 feet/minute) and % shrink were also substantially similar to those of LLDPE control ,, .. ..

13~4S~O

samples 2A-2D, excep-t that sample 8 had a better shrink (41~ T, 29~ L). As for their abuse resistance, it was not as high as that of LLDPE control samples 2A-2D. Furthermore, it is noted that these VLDPE samples 7-9, wherein the VLDPE had a high MI, did not exhibit the excellent orientation of the samples of the invention, samples 10-18, discussed in the next 2 paragraphs below.
Samples 10-17: These were samples of the preferred embodiment. They were samples wherein layer 2 was VLDPE having octene as the comonomer and a low MI under about 2Ø For these samples, all of the 3 performance properties, orientation, %
shrink and abuse resistance were consistently excellent. On the other hand as mentioned above, for a particular control sample, one or two of the 3 properties were good or excellent but never were all 3 properties excellent for a particular control sample.
Sample 18: This was another sample of the preferred embodiment. It was a sample wherein layer 2 was VLDPE having hexene as the comonomer and a low MI under about 2. As in samples 10-17, orientation, % shrink and abuse resistance were excellent.
Samples 19-28: These were other comparative samples wherein layer 2 was LLDPE having hexene as the comonomer. Their performance properties of orientation (except for sample 20 which had a poor orientation of 38 feet/minute) and % shrink were substantially similar to those of LLDPE control samples 2A-2D, but their abuse resistance (except for sample 20 which had a Carson Dart Drop of 35.6 cm) was not as high as that of 2A-2D. In fact, for sample 28, abuse resistance was a poor 15.2 cm.

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.
Samples 29-32: These were samples wherein layer 2 was LLDPE or VLDPE havlng butene as the comonomer. Ex-cept for sample 29 which had a poor orientation of only 34 feet/minute, their performance properties of orientation and % shrink were also substantially similar to those of LLDPE control samples 2A-2D. But or all of 29-32, their abuse resistance was not as high as that of controls 2A-2D, and for some of them, namely samples 29 and 32, abuse reslstance was poor, namely Carson Dart Drop of 16.5 cm and 12.7 cm, respectively.

In summary, EVA Control 1 had excellent shrink (44%
transverse; 27% longitudinal), good orientation (57 feet/minute), and poor abuse resistance (7 cm for dart drop and 25 cm-kg for ball burst). On the other hand, the orientation speed of LLDPE Controls 2A-2D was good (46-60 feet/minute), the abuse resistance (Carson Dart Drop was 30.5 to 50.8 cm) of Controls 2A-2D ranged from excellent to superior, and the shrink (for instance, 28%
transverse and 16% longitudinal for 2C) was good. It has be~ll surprisingly discovered that for samples 10-18, wherein the polymer in layer 2 was VLDPE having a MI
below about 2.0, the films exhibited excellent abuse resistance, excellent shrink and excellent orientation speed. Thus, for sample6 10-18, all 3 performance pro-perties were excellent.

EXAMPLE II

., .
Films were mate as in Example I except saran-MA was employed for barrier layer 3, and the polymers were varied ln each of layers 1, 2, and 4. The following films were made:

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TABLE II-A

SAMPLE
NUMBER
AND IRRAD EXTRUSION
OF LAYERS SUBSTRATE LAYERS COATED LAYERS

(MR) LAYER 1 LAYER 2 LAYER 3 LAYER 4 1 LLDPE EVA SARAN-MA 80% LLDPE
(4.5MR) (0.912) (18% VA) (0.912) [Dowlex [LD720.62] [Dowlex 4002] 4001], 20% EBA
2 LLDPE EVA SARAN-MA 40% LLDPE
(4.5MR) (0.912) (18% VA) (0.912) [Dowlex [LD720.62] [Dowlex 4002] 4001];
40% LLDPE
(0.912) [Dowlex 4002];
20% EBA
3 LLDPE EVA SARAN-MA 80~ LLDPE
(4.5MR) (0.912) (18% VA) (0.911) [Dowlex [LD720.62] [Stamylex 4002] 08026];
20% EBA

4 LLDPE EVA SARAN-MA 80% LLDPE
(4.5MR) (0.912) (18% VA) (0.912) [Dowlex [LD720.62] [Dowlex 4002] 4002];
20% EBA
LLDPE EVA SARAN-MA 80% LLDPE
(4.5MR) (0.912) (18~ VA) (0.912) [Dowlex [Elvax 3165] [Dowlex 4002] 4002];
20% EBA
6 LLDPE EVA SARAN-MA 80% VLDPE
(4-5MR) (0.912) (18% VA) (0.908; MI=3.3) [Dowlex [LD720.62] [XPR054-4002] 33260-46L];
20% EBA
7 LLDPE EVA SARAN-MA 80% VLDPE
(4-5MR) (0.912) (18% VA) (0.905; MI=0.8) [Dowlex [LD720.62] [XU61512.08L];
4002] 20% EBA

,.,, .. ,, ..;

13~45SO

SAMPLE
NUMBER
AND IRRAD EXTRUSION
OF LAYERS SUBSTRATE LAYERS COATED LAYERS

(MR) LAYER 1 LAYER 2 LAYER 3 LAYER 4 8 LLDPE 80% VLDPE SARAN-MA 80~ VLDPE
(4.5MR) (0.912) (0.905;MI=0.8) (0.905; MI=0.8) [Dowlex [XU61512.08L]: [XU61512.08L];
4002] 20% EBA 20% EBA
9 LLDPE 80~ VLDPE SARAN-MA 80% VLDPE
(4.5MR) (0.312) (0.905: MI=0.8) (0.908; MI=3.3) [Dowlex [XU61512.08L]; [XPR054-4002] 20~ EBA 33260-46L];
20% EBA

TABLE II-B
ABUSE
RESISTANCE
ORIENTATION CARSON% SHRINK 185F (85C) SPEED DART DROP
SAMPLE FT/MIN INCHES TRANS- LONGI-NUMBER (M/MIN) (CM) VERSE TUDINAL
1* 65 (19.8) 6 tl5.2) 45 35 2~ 55 (16.8) 6 (15.2) 44 34 3* 61 (18.6) 7 (18) 46 35 4* 49 (14.9) 5 (13) 45 34 5* 43 (13.1) 6 (15.2) 44 32 6* 50 (15.2) 6 (15.2) 48 35 7 70 (21.3) 6 (15.2) 49 34 8 71 (21.6) 10 (25.4) 42 26 9 70 (21.3) 8 (20) 40 24 *Comparison Samples 1-6.
As can be seen from Tables IIA-B, the three properties namely orientation, ~ shrink and abuse resistance were consistently excellent for samples 8 and , ~ ..1 ' ~ ' ''' ' r ' ` ~
~' - ~3~4~0 9. These were samples wherein layer 2 comprised a VLDPE
having octene as the comonomer and a low MI under about 2. It is noted that for these samples 8 and 9, the VLDPE of layer 2 was in blend with another polymer compatible therewith, herein EBA. Nevertheless, the three properties of samples 8 and 9 of Table II were all three consistently excellent. From this it can be con-cluded that a film comprising VLDPE having octene as the comonomer and a low MI of about 2 or less will have all 3 properties of orientation speed, abuse resistance and % shrink be excellent even when the VLDPE layer is VLDPE
in blend with another polymer compatible therewith.

It is further noted in particular f~or sample 9 of Tables IIA and B, that the VLDPE employed in outside layer 4, resin XPR054-33260-46L which had octene as the comonomer but had a high MI = 3.3, was also the same VLDPE employed in interior layer 2 of samples 7A and 7B
of Table I, yet sample 9 had an excellent orientation speed of 70 feet/minute, whereas samples 7A and 7B had only a good orientation speed of only 50 feet/minute.
This is because sample 9 of Tables IIA and B also had a VLDPE layer, namely layer 2, wherein the VLDPE was resin XU61512.08L having octene as the comonomer but having a low MI, i.e. the MI was 0.8. No such layer with VLDPE having a low MI was present in samples 7A and 7B of Table I and that is why they did not exhibit an excell~n~ ~rientation. -As for~sample 7 in Tables IIA-B compared to sample 9 in Table I, it is noted that each had a layer (layer 4 of sample 7 and layer 2 of sample 9) of the same VLDPE
~resin XU61512.08L] having octene as the comonomer and having a low MI - 0.8, and each exhibited comparable excellent orientation speed and % shrink. Sample 7 of Tables IIA-B, however, exhibited a poor abuse resistance (Carson Dart Drop ~ 15.2 cm), whereas sample 9 of Table `" 13~?4S.tiO

I exhibited excellent abuse resistance (Carson Dart Drop 25.4 cm). While it i8 not lntended to be bound to any theory, lt is believed this is due to the VLDPE layer of sample 7 having a before-orientation thickness of only 6.5 mils, whereas the VLDPE layer of sample 9 had a before-orientation thickness of 14.5 mils. It is be-lieved if sample 7 were repeated but with its VLDPE
layer being 14.5 mils thick, then good abuse resistance would be obtained too.

While certain representative embodiments and details have been shown for the purpose of illustration, numerous modifications to the formulations described above can be made without departing from the invention disclosed.

; 404/870311/9/37 ~: .

Claims (17)

1. A thermoplastic, multilayer, heat-shrinkable packaging film comprising at least one layer of a copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule, said ethylene/alpha-olefin copolymer having a density of about 0.910 g/cc or less and a melt index of about 2 or less.

2. The film of claim 1, wherein said copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule is in blend with another polymer up to 50% by weight, based on the layer composition, of a polymer which is compatible with said ethylene/alpha-olefin copolymer and is selected from ethylene/alkylacrylate copolymer, linear low density polyethylene (LLDPE), high density polyethylene (HDPE), linear medium density polyethylene (LMDPE), linear high density polyethylene (LHDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), ethylene/vinyl acetate (EVA), acid-modified EVA, polypropylene, ethylene/propylene copolymers, copolymers of an alpha-olefin having the formula RHC=CH2 wherein R is H or C1 to C8 alkyl and an alpha, beta-ethylinically unsaturated carboxylic acid, and mixtures thereof.

3. The film of claim 1 further including a barrier layer.

4. The film of claim 1 wherein said at least one layer of copolymer of ethylene/alpha-olefin is an interior layer.

5. The film of claim 1 wherein said at least one layer of ethylene alpha-olefin copolymer has been irradiated at a dosage up to about 20 MR.

6. A thermoplastic, multi-layer, heat-shrinkable packaging film having excellent abuse resistance, shrink and orientation properties comprising an outside polymer layer, a heat sealing layer and an interior layer between said sealing and said outside layers, wherein said interior layer comprises a copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule, said ethylene/alpha-olefin copolymer having a density of about 0.910 g/cc or less and a melt index of about 2 or less.

38a

7. The film of claim 6, wherein said interior layer further includes up to 50% by weight, based on the layer composition, of a polymer which is compatible with said ethylene/alpha-olefin copolymer and is selected from ethylene/alkyl-acrylate copolymer, linear low density polyethylene (LLDPE), high density polyethylene (HDPE), linear medium density polyethylene (LMDPE), linear high density polyethylene (LHDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE) ethylene/vinyl acetate (EVA), acid-modified EVA, poly-propylene, ethylene/propylene copolymers, copolymers of an alpha-olefin having the formula RHC=CH2 wherein R is H or C1 to C8 alkyl and an alpha,beta-ethylenically un-saturated carboxylic acid, and mixtures thereof.

8. The film of claim 6 further including a barrier layer between said sealing layer and said outside layer.

9. The film of claim 6 wherein said interior layer has been irradiated at a dosage up to about 20 MR.

10. A process for manufacturing thermoplastic, multi-layer, heat-shrinkable packaging film comprising (I) extruding at least one layer of a copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule, said ethylene/alpha-olefin copolymer having a density of about 0.910 g/cc or less and a melt index less of about 2 or less, (II) orienting the ex-truded polymer in at least one direction, and (III) re-covering a heat-shrinkable polymeric film.

11. The process of claim 10 further including extruding a barrier layer prior to the orienting step.

12, The process of claim 10 wherein said copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule is in blend with another polymer up to 50% by weight, based on the layer composition, of a polymer which is compatible with said ethylene/alpha-olefin copolymer and is selected from ethylene/alkylacrylate copolymer, linear low density polyethylene (LLDPE), high density polyethylene (HDPE), linear medium density polyethylene (LMDPE), linear high density polyethylene (LHDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), ethylene/vinyl acetate (EVA), acid-modified EVA, polypropylene, ethylene/propylene copolymers, copolymers of an alpha-olefin having the formula RHC=CH2 wherein R
is H or C1 to C8 alkyl and an alpha, beta-ethylinically unsaturated carboxylic acid, and mixtures thereof.

39a

13. The process of claim 10 further including irradiating said layer of ethylene/alpha-olefin copolymer at a dosage up to about 20 MR prior to the orienting step.

14. A thermoplastic, multi layer, heat-shrinkable packaging film comprising at least one layer of a copolymer of ethylene and an alpha-olefin with 6 or more carbon atoms per molecule, said ethylene/alpha-olefin copolymer having a density of about 0.910 g/cc or less and a melt index of about 2 or less, wherein said film exhibits excellent abuse resistance characteristics, excellent shrink characteristics, and excellent orientation characteristics.

15. A bag formed from the film of claim 1, said bag having end seal(s), side seal(s), or a combination thereof.

16. The bag of claim 15 further including a barrier layer.

17. The bag of claim 15 wherein at least one layer of copolymer of ethylene/alpha-olefin is an interior layer.