Abstract:
A multiple layer film useful in moisture barrier packaging applications has at least one layer comprising a blend of propylene polymer or copolymer, and a hydrocarbon resin; and two additional layers comprising a propylene polymer or copolymer, ethylene alpha olefin copolymer, ionomer, polybutene, or blends thereof. A core layer of ethylene vinyl alcohol copolymer or other oxygen barrier material, or high density polyethylene, can be included in some embodiments. A preferred embodiment of the multi-layer film exhibits excellent moisture barrier and optical properties, and shrink properties as well if the film has been oriented. High oxygen barrier is also a feature in embodiments including EVOH or other oxygen barrier materials.

Description:
This application is a File Wrapper Continuation of application Ser. No. 08/433,279 filed Apr. 28, 1995, now abandoned, which is a Divisional application of application Ser. No. 08/431,225, filed on Apr. 28, 1995 now U.S. Pat No. 5,910,374, which is a Divisional application of application Ser. No. 08/430,632, filed Apr. 28, 1995 abandoned, which is a Divisional application of application Ser. No. 08/358,121, filed on Dec. 16, 1994, issued as U.S. Pat. No. 5,543,223 on Aug. 6, 1996, which is a Divisional application of application Ser. No. 08/116,798, filed Sep. 10, 1993, issued as U.S. Pat. No. 5,482,771 on Jan. 9, 1996, which is a Continuation-In-Part of application Ser. No. 07/947,244, filed Sep. 18, 1992, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to thermoplastic films for packaging; and more particularly, this invention relates to a multi-layer film having high moisture barrier characteristics. 
     BACKGROUND OF THE INVENTION 
     Thermoplastic film, and in particular polyolefin materials, have been used for some time in connection with packaging of various articles including food products which require protection from the environment, an attractive appearance, and resistance to abuse during the storage and distribution cycle. Suitable optical properties are also desirable in order to provide for inspection of the packaged product after packaging, in the distribution chain, and ultimately at point of sale. Optical properties such as high gloss, high clarity, and low haze characteristics contribute to an aesthetically attractive packaging material and packaged product to enhance the consumer appeal of the product. 
     Various polymeric materials have been used to provide lower moisture permeability in order to reduce the transmission of moisture through the packaging film and thereby extend the shelf life of products such as food, medical, electronic, and other items which are sensitive to moisture gain or loss. For some products, maintenance of a high moisture content is desirable, and the film ideally minimizes loss of moisture from the package to the environment. For other products, maintenance of a low moisture content is desirable, and the film ideally minimizes gain of moisture from the environment through the packaging material. 
     It is also often desirable to include in a packaging film a shrink feature, i.e, the propensity of the film upon exposure to heat to shrink or, if restrained, create shrink tension within the packaging film. This property is imparted to the film by orientation of the film during its manufacture. Typically, the manufactured film is heated to its orientation temperature and stretched in either a longitudinal (machine) or transverse direction (i.e. monoaxial orientation), or both directions (i.e. biaxial orientation), in varying degrees to impart a certain degree of shrinkability in the film upon subsequent heating. When biaxial orientation is done, it can be simultaneous or sequential; that is, the orientation can be done in each of the directions in turn, or else both the longitudinal and transverse orientation can be done at the same time. Any suitable technique, such as blown bubble or tenterframing, can be used to achieve orientation of the film. After being so stretched, the film is rapidly cooled to provide this latent shrinkability to the resulting film. One advantage of shrinkable film is the tight, smooth appearance of the wrapped product that results, providing an aesthetic package as well as protecting the packaged product from environmental abuse. Various food and non-food items may be and have been packaged in shrinkable films. 
     It is sometimes also desirable to orient a packaging film and thereafter heat set the film by bringing the film to a temperature near its orientation temperature. This produces a film with substantially less shrinkability, while retaining much of the advantages of orientation, including improved tensile strength, modulus and optical properties. 
     It is an object of the present invention to provide a thermoplastic multilayer film characterized by good moisture barrier properties. 
     It is a further object of the present invention to provide a thermoplastic multilayer film having an aesthetic appearance with good clarity, and other desirable optical properties. 
     It is another object of the present invention to provide a thin thermoplastic multilayer film having toughness and abrasion resistance. 
     It is still another object of the present invention to provide a thermoplastic multilayer film which may be totally coextruded, oriented, and have good moisture barrier and, in some cases, both moisture barrier and oxygen barrier properties. 
     Of interest are U.S. Pat. Nos. 4,921,749 (Bcssaert et al); 5,085,943 (Crighton et al); 5,091,237 (Schloegel et al); 5,128,183 (Buzio); and 5,212,009 (Peiffer et al) disclosing the use of hydrocarbon resins. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a thermoplastic multi-layer film comprising a core layer comprising a blend of propylene polymer or copolymer, or ethylene alpha olefin copolymer, and a hydrocarbon resin; and two outer layers comprising a propylene polymer or copolymer, ethylene alpha olefin copolymer, polybutene, or blends thereof. 
     In another aspect, the present invention relates to a thermoplastic multi-layer film comprising a core layer comprising a blend of propylene polymer or copolymer, and a hydrocarbon resin; two intermediate layers, on opposite surfaces of the core layer, comprising propylene polymer or copolymer, or a polymeric adhesive; and two outer layers comprising a propylene polymer or copolymer, ethylene alpha olefin copolymer, ionomer, polybutene, or blends thereof. 
     The present invention also relates to a thermoplastic multi-layer film comprising a core layer comprising an ethylene alpha olefin copolymer, ethylene propylene copolymer, rubber modified ethylene propylene copolymer, or ethyene propylene butene terpolymer; two intermediate layers, on opposite surfaces of the core layer, comprising a blend of propylene polymer or copolymer, and a hydrocarbon resin; and two outer layers comprising a propylene polymer or copolymer, ethylene alpha olefin copolymer, ionomer, polybutene, or blends thereof. 
     A film with oxygen barrier as well as moisture barrier properties comprises a core layer comprising an oxygen barrier material; two intermediate layers, on opposite surfaces of the core layer, comprising a polymeric adhesive; two outer layers comprising a blend of propylene polymer or copolymer, or polybutene, and a hydrocarbon resin; and a polymeric sealant layer adhered to at least one of the outer layers. 
     An alternative film with at least seven layers comprises a core layer comprising high density polyethylene; two intermediate layers, on opposite surfaces of the core layer, comprising a polymeric adhesive, ethylene vinyl acetate copolymer, or ethylene alpha olefin copolymer; two moisture barrier layers comprising a blend of propylene polymer or copolymer, and a hydrocarbon resin; and two outer layers comprising propylene polymer or copolymer, polybutene, or blends thereof. 
     Another alternative is a film comprising a core layer comprising an oxygen barrier material; two intermediate layers, on opposite surfaces of the core layer, comprising polyamide; two tie layers, each disposed on a respective polyamide layer, comprising a polymeric adhesive, ethylene alpha olefin copolymer, or ethylene vinyl acetate copolymer; two moisture barrier layers, adhered to respective adhesive layers, comprising a blend of propylene polymer or copolymer, and a hydrocarbon resin; and two outermost layers comprising a propylene polymer, propylene copolymer, ethylene alpha olefin copolymer, or polybutene. 
     In another aspect of the invention, a method of making a thermoplastic multilayer film comprises the steps of coextruding an interior layer of a blend of propylene polymer or copolymer, and a hydrocarbon resin, and two outer layers comprising a propylene polymer or copolymer, ethylene alpha olefin copolymer, polybutene, or blends thereof; cooling the coextruded multilayer film; and collapsing the cooled film. 
     DEFINITIONS 
     “Hydrocarbon resin” (“HC” herein) and the like as used herein means resins made by the polymerization of monomers composed of carbon and hydrogen only. Thermoplastic resins of low molecular weight made from relatively impure monomers derived from coal-tar fractions, petroleum distillates, etc. are also included. A discussion of HC resins can be found e.g. in U.S. Pat. Nos. 4,921,749 (Bossaert et al); 5,091,237 (Schloegel et al); and 5,128,183 (Buzio). 
     “Ethylene alpha olefin copolymer” (EAO) is used here to include such materials as linear low density polyethylene (LLDPE); very low and ultra low density polyethylene (VLDPE and ULDPE); and metallocene catalyzed polymers such as those supplied by Exxon. Tafmer (tm) materials supplied by Mitsui are also included. These materials generally include copolymers of ethylene with one or more comonomers selected from C 4  to C 20  alphaolefins such as butene-1, hexene-1, octene-1, etc. in which the molecules of the copolymers comprise long chains with relatively few side chain branches or cross-linked structures. This molecular structure is to be contrasted with conventional low or medium density polyethylenes which are more highly branched than their respective counterparts. “LLDPE” as defined here has a density in the range of from about 0.916 grams per cubic centimeter to about 0.940 grams per cubic centimeter. Generally, “EAO” as used here includes both homogeneous and heterogeneous polymers. 
     “Intermediate layer” and the like is used herein to define a layer in a multi-layer film enclosed on both sides by other layers, i.e. disposed between other layers of the film. 
     The term “oriented” and the like is used herein to define a polymeric material in which the molecules have been aligned in the longitudinal and/or transverse direction by a process such as a tenter frame or blown bubble process. 
     “Propylene polymer” and the like is used here to mean polymerized propylene in its homopolymer form, and “propylene copolymers” means copolymers such as ethyene propylene copolymer, where generally small amounts of a comonomer such as ethylene are included in the copolymer. Terpolymers are also included. 
     “Polymeric adhesive” and the like here means polymeric materials, of any suitable composition, which can be used to create or enhance interlaminar bonds in multilayer thermoplastic films. Polyolefins are preferred, especially those which have been modified, e.g. by carboxylic acid or acid anhydride in a graft copolymer. 
     “Rubber modified EPC” and the like here means an EPC which has been modified by the inclusion of other moieties in the polymer structure. Such material may provide improved elasticity or other properties. An example is believed to be Himont KS-052 P, or those available from Rexene (El Paso). 
     “Ethylene propylene butene terpolymer” and the like is used here to mean a terpolymer incorporating these three comonomers in various percentages. An example is KT-021 from Himont, or those available from Sumitomo. 
     “Core layer” as used herein means an intermediate layer of a multilayer film, and the central layer where the film has an odd number of layers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details are given below with reference to the drawing figures wherein FIG. 1 is a schematic cross section of a preferred embodiment of a multi-layer moisture barrier film of the invention, and 
     FIGS. 2 and 3 are alternative embodiments of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring specifically to the drawings, in FIG. 1, a schematic cross section of a preferred embodiment of the multi-layer moisture barrier film of the invention is shown. The multi-layer film  10  has the generalized structure of A/B/A where A is an outer layer, and B is a core layer comprising a moisture barrier material. 
     Core layer  12  preferably comprises a blend of a propylene polymer or copolymer, and a hydrocarbon resin, this blend shown as a spotted/striped layer. A typical example of a propylene homopolymer is Exxon PD 4062 E7, or those available from Fina, or Himont PD 064. A preferred propylene copolymer is ethylene propylene copolymer sold under the designation Fina 8473 or Fina 8473X. This material has an ethylene content of about 4%. A preferred hydrocarbon resin is Regalrez 1128 or 1139 from Hercules. The HC resin preferably comprises between about 30% and 50% by weight of the blend. 
     Outer layers  14  and  16  are preferably ethylene propylene copolymer (EPC), polypropylene (PP), or blends thereof. If only polypropylene resin is used, the film can be difficult to use for packaging applications involving heat sealing. Therefore, it is preferable to use EPC alone, or the blend of the two materials. Commercial resin examples are those discussed above for core layer  12 . An alternative polypropylene for the outer layers  14  and  16  is Himont PDO 64. These blend layers may include from 0-100% EPC and 100%-0% PP, although preferably the blend layers include between about 96% and 85% EPC and between about 4% and 15% PP; even more preferably, the blend layer includes about 92% EPC and 8% PP. EAO and polybutene can also be used in the outer layers. 
     In FIG. 2, a schematic cross section of another embodiment of the multi-layer moisture barrier film of the invention is generally shown. The multi-layer film has the structure of A/B/C/B/A where A is an outer layer, B is an intermediate adhesive layer, and C is a core layer comprising a moisture barrier material. 
     The core layer preferably comprises a blend of a propylene polymer or copolymer, and a hydrocarbon resin. Suitable materials are those described above for core layer  12  of film  10 . 
     The outer layers are preferably the materials discussed above for outer layers  14  and  16  of film  10 . The outer layers also preferably include an HC such as described for core layer  12  of film  10 . 
     The intermediate layers preferably comprise a propylene polymer or copolymer,or blends thereof, optionally blended with hydrocarbon resin. 
     An alternative A/B/C/B/A structure is also within the scope of this invention, and specifically shown by the position of the moisture barrier layers in the film of FIG.  2 . 
     In this alternative, core layer  24  preferably comprises an ethylene alpha olefin copolymer, more preferably a linear EAO. Very low density polyethylene (VLDPE), and linear low density polyethyene (LLDPE) are preferred. A suitable LLDPE is Dowlex 2045. The core layer  24  can also comprise EPC, a rubber modified EPC, or an ethylene terpolymer, especially an ethylene propylene butene terpolymer such as KT 021 P from Himont. 
     Outer layers  20  and  28  are preferably the materials discussed above for outer layers  14  and  16  of film  10 . 
     Intermediate layers  22  and  26  preferably comprise a blend of a propylene polymer or copolymer, and a hydrocarbon resin. Suitable materials are those described above for core layer  12  of film  10 . An alternative material for layers  22  and  26  is Exxon 6042, which is believed to be a blend of polypropylene and hydrocarbon resin. 
     In FIG. 3, a schematic cross section of another embodiment of the multi-layer moisture barrier film of the invention is shown. The multi-layer film  30  has the generalized structure of A/B/C/D/C/B/A where A is an outer layer, B is a moisture barrier layer, C is an intermediate adhesive layer, and D is a core layer comprising an oxygen barrier material. 
     Core layer  38  preferably comprises an oxygen barrier material such as ethylene vinyl alcohol copolymer, vinylidene chloride copolymer, polyester, or polyamide. 
     Outer layers  32  and  44  are preferably the materials discussed above for outer layers  14  and  16  of film  10 . 
     Intermediate layers  36  and  40  preferably comprise a propylene polymer or copolymer, such as Exxon PD 4062 E7. Alternative materials are polymeric adhesives, especially carboxylic acid or maleic anhydride-modified polyolefins and more preferably polypropylene-based carboxylic acid or maleic anhydride-modified adhesives. Conventional lamination or other suitable methods may sometimes be necessary, depending on the nature of the respective layers, to ensure adequate interlaminar bond strength. 
     Moisture barrier layers  34  and  42  preferably comprise a blend of a propylene polymer or copolymer, and a hydrocarbon resin. Suitable materials are those described above for core layer  12  of film  10 . An alternative material for layers  34  and  42  is Exxon 6042. 
     An alternative film with at least seven layers comprises a core layer  38  comprising high density polyethylene; two intermediate layers  36  and  40 , on opposite respective surfaces of the core layer, comprising a polymeric adhesive, ethylene vinyl acetate copolymer, or ethylene alpha olefin copolymer; two moisture barrier layers  34  and  42  comprising a blend of propylene polymer or copolymer and a hydrocarbon resin; and two outermost layers  32  and  44  comprising propylene polymer or copolymer. 
     A multilayer film of four or six layers, and/or possessing both moisture barrier and oxygen barrier properties, can also be made in accordance with the present invention. In such alternative constructions, a blend of HC resin with propylene polymer or copolymer can be present in any of the layers of the multilayer film. 
     The core, intermediate, and moisture barrier layers of such a film can be like that of film  30 . A sealant layer is coextruded with, or extrusion coated, extrusion laminated, or adhesive laminated, by means and methods well known in the art, to one of the moisture barrier layers. The sealant layer, which can be disposed on one or both outer surfaces of the film structure, preferably comprises an ethylene alpha olefin copolymer, more preferably a linear EAO. Very low density polyethylene (VLDPE), and linear low density polyethyene (LLDPE) are preferred. A suitable LLDPE is Dowlex 2045. The sealant layer can also comprise EPC, a rubber modified EPC, an ethylene propylene butene terpolymer such as KT 021 P from Himont, an ethylene vinyl acetate copolymer, an ethylene alkyl acrylate copolymer, an ethylene acrylic or methacrylic acid copolymer, or an ionomer. 
     The films of the present invention can be made by coextrusion, extrusion coating, extrusion laminating, and conventional adhesive lamination techniques well known in the art, using annular or slot die extrusion equipment as appropriate. 
     The beneficial low moisture transmission rates (high moisture barrier) and other properties associated with exemplary films of the present invention are demonstrated in the Tables. 
     The resins used in these examples are identified in Table 1, and the films made from these resins are identified in Tables 2 through 8. 
     Physical properties of these films are itemized in the remaining Tables. Values given are typically average values obtained from four replicate measurements; values for MVTR are average obtained from three samples. 
     The terms and abbreviations In the Tables have the following meaning: 
     “PP”=polypropylene. 
     “EPC”=ethylene propylene copolymer. 
     “EAO”=ethylene alpha olefin copolymer. 
     “EPB”=ethylene propylene butene terpolymer. 
     “EVOH”=ethylene vinyl alcohol copolymer. 
     “ADH”=polymeric adhesive; ADH  1  is an ethylene butene—based adhesive from Du Pont; ADH  2  is an EPC-based adhesive from Mitsui. 
     “AB”=antiblock. 
     “MO”=mineral oil. 
     “Tensile”=tensile at break and 73° F., in PSI (ASTM D 882-81). 
     “PSI”=pounds per square inch (ASTM 882-81). 
     “Unshrunk”=a film sample or samples that were not shrunk by exposure to heat at the time of testing for the stated property. 
     “Shrunk”=a film sample or samples that were shrunk by exposure to heat at the time of testing for the stated property. 
     “LD”=longitudinal orientation direction. 
     “TD”=transverse orientation direction. 
     “Modulus”=modulus of elasticity (ASTM 882-81) in PSI at 73° F. 
     “Haze”=haze (ASTM D 1003-61 (reapproved 1977)) in per cent. 
     “Clarity”=total light transmission (ASTM D 1003 Method A) in percent. 
     “Gloss”=gloss measured at 45° angle to film surface (ASTM D 2457-70 (reapproved 1977)). 
     “MVTR  1 ”=moisture (water) vapor transmission rate (ASTM F 372) in grams/24 hours, 100 square inches at 100% relative humidity and 100° F. 
     “MVTR  2 ”=moisture (water) vapor transmission rate (ASTM F 372) in grams/24 hours, 100 square inches at 90% relative humidity and 100° F. 
     “OTR”=oxygen transmission rate (ASTM D 3985-81) in cc at standard temperature and pressure, in 24 hours, per square meter, at one atmosphere, at 0% relative humidity. 
     “Tear” =tear propagation in grams at 73° F. (ASTM D 1938-79). 
     “Film Thickness”=the average thickness (gauge) of the film samples in mils (=0.001 inches). 
     “Tensile”=tensile strength at break (ASTM D 882-81) in psi. 
     “Elongation”=elongation at break (ASTM D 882-81) in percent. 
     “Ball Burst”=ball burst impact in centimeters-kilograms at 73° F. (ASTM D 3420-80). 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 MATERIAL 
                 TRADENAME 
                 SUPPLIER 
               
               
                   
                   
               
             
             
               
                   
                 PP 1 
                 Profax PD-064 
                 Himont 
               
               
                   
                 PP 2* 
                 [see footnote] 
               
               
                   
                 PP 3 
                 PD 4062 
                 Exxon 
               
               
                   
                 PP 4** 
                 Escorene PD 6042 
                 Exxon 
               
               
                   
                   
                 [see footnote] 
               
               
                   
                 EPC 1 
                 Fina 8473 or 
                 Fina 
               
               
                   
                   
                 Fina 8473 X 
               
               
                   
                 EPC 2*** 
                 [see footnote] 
               
               
                   
                 EPC 3 
                 PD 9302 
                 Exxon 
               
               
                   
                 EPB 1 
                 KT-021 
                 Himont 
               
               
                   
                 HC 1 
                 Regalrez 1128 
                 Hercules 
               
               
                   
                 HC 2 
                 Escorez 5340 
                 Exxon 
               
               
                   
                 HC 3 
                 Regalrez 1139 
                 Hercules 
               
               
                   
                 EAO 1 
                 Dowlex 2045.03 
                 Dow 
               
               
                   
                 EAO 2 
                 Dowlex 2045.04 
                 Dow 
               
               
                   
                 ADH 1 
                 Bynel CXA 4104 
                 Du Pont 
               
               
                   
                 ADH 2 
                 Admer QF 551 A 
                 Mitsui 
               
               
                   
                 EVOH 1 
                 EVAL SC H-103 
                 Evalca 
               
               
                   
                 EVOH 2 
                 EVAL LC F-101 A 
                 Evalca 
               
               
                   
                 EVOH 3 
                 EVAL LC H-103 
                 Evalca 
               
               
                   
                 MO 1 
                 Kaydol 
                 Witco 
               
               
                   
                   
               
               
                   
                 *PP 2 is a masterbatch blend of PP 1 with about 4%, by weight of the blend, of a silica-containing anti-blocking agent, about 5% by weight of amide waxes, and about 1% of a lubricating agent. The amide waxes and lubricating agent are well known in the art as slip agents.  
               
               
                   
                 **PP 4 is Escorene PD 6042, believed to be a blend of polypropylene and hydrocarbon resin.  
               
               
                   
                 ***EPC 2 is a blend of EPC 1 blended with about 1.5%, by weight of the blend, of an antiblock agent, and 0.5%, by weight of the blend, of a mineral oil.  
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 (CONTROL) 
               
               
                 Initial efforts to make a moisture barrier material involved the use 
               
               
                 of homopolymer polypropylene in a core layer, with sealant layers of 
               
               
                 propylene copolymer on both surfaces of the core layer. The object was 
               
               
                 to maximize thickness of the core layer to minimize the moisture vapor 
               
               
                 transmission rate (MVTR), while still maintaining adequate free shrink 
               
               
                 and sealability properties of the film. The MVTR did not prove 
               
               
                 adequate for at least some moisture barrier packaging applications. 
               
               
                 An example of this film is given below: 
               
             
          
           
               
                 EXAMPLE 
                 FILM STRUCTURE  
               
               
                   
               
               
                 1. 
                 92% EPC 1 + 8% PP 2/PP 1/92% EPC 1 + 8% PP 2 
               
               
                   
                 The generalized structure of the film of Example 3 was 
               
               
                   
                 A/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 A = 1.0; B = 2.0; A = 1.0.  
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 The films of Table 3 were made in an effort to make a moisture 
               
               
                 barrier material with lower MVTR. This was achieved using hydro- 
               
               
                 carbon resin blended with homopolymer polypropylene. It was found 
               
               
                 that these formulations had much lower moisture vapor transmission 
               
               
                 rate (MVTR) than those of Table 2. However, they could not be 
               
               
                 oriented much over 4.5 × 4.5 racking (orientation) ratio 
               
               
                 because of equipment limitations. On other equipment, e.g. a 
               
               
                 modified bubble process or tenterframing, higher orientation 
               
               
                 (racking) rates can be achieved. They also could not be 
               
               
                 made into heavier gauge films because of relatively poor tear 
               
               
                 properties. Examples of these films are given below: 
               
             
          
           
               
                 EXAMPLE 
                 FILM STRUCTURE  
               
               
                   
               
               
                 2. 
                 
                   90%[92% EPC 1 + 8% PP 2] + 10% HC 1 
                 
               
               
                   
                 
                   PP 3 
                 
               
               
                   
                 
                   84.5% PP 3 + 15% HC 1 + 0.5% MO  1 
                 
               
               
                   
                 
                   PP  3 
                 
               
               
                   
                 
                   90%[92% EPC 1 + 8% PP 2] + 10% HC 1 
                 
               
               
                   
                 The generalized structure of the film of Example 2 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 2.5:0.8:3.7:0.6:2.4. 
               
               
                 3. 
                 92% EPC 1 + 8% PP 2/PP 4/92% EPC 1 + 8% PP 2 
               
               
                   
                 The generalized structure of the film of Example 3 was 
               
               
                   
                 A/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1:2:1 
               
               
                 4. 
                 92% EPC 1 + 8% PP 2/PP 4/92% EPC 1 + 8% PP 2 
               
               
                   
                 The generalized structure of the film of Example 4 was 
               
               
                   
                 A/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1:3:1.  
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Alternative films of Table 4 were made in which, in effect, the core 
               
               
                 layer of the films of Table 3 (i.e. the layer containing the hydrocarbon 
               
               
                 resin) were “split” into two substrate (intermediate) layers. 
               
               
                 A “new” core layer of e.g. LLDPE or EPC is introduced. The practical 
               
               
                 effect of this is to improve tear properties of the film, related to tape 
               
               
                 creasing during the orientation process, so that it can be oriented at e.g. 
               
               
                 6 × 6 ratio. The film was in fact oriented at 4 × 4.5 because 
               
               
                 of the equipment limitations discussed for the Examples of Table 3. 
               
               
                 Examples of these films are given below: 
               
             
          
           
               
                 EXAMPLE 
                 FILM STRUCTURE  
               
               
                   
               
               
                 5. 
                 92% EPC 1 + 8% PP 2/PP 4/EAO 1/PP 4/92% EPC 1 + 8% 
               
               
                   
                 PP 2 
               
               
                   
                 The generalized structure of the film of Example 5 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 6. 
                 92% EPC 1 + 8% PP 2/PP 4/EPC 1/PP 4/92% EPC 1 + 8% 
               
               
                   
                 PP 2 
               
               
                   
                 The generalized structure of the film of Example 6 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5  
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 The inventor took the basic constructions of Table 4, and oriented 
               
               
                 them at generally higher racking ratios of 6 × 6. The result 
               
               
                 was a film showing improvements in (i.e. lower) MVTR. Examples of 
               
               
                 these films are given below: 
               
             
          
           
               
                 EXAM- 
                   
               
               
                 PLE 
                 FILM STRUCTURE  
               
               
                   
               
             
          
           
               
                 7. 
                 92% EPC 1 + 8% PP 2/PP 4/EAO 1/PP 4/92% EPC 1 + 8% 
               
               
                   
                 PP 2 
               
               
                   
                 The generalized structure of the film of Example 7 was 
               
               
                   
                 A/B/C/B/A. This film was like that of Example 5, but with 
               
               
                   
                 both MD and TD racking ratios of about 6 × 6 in the 
               
               
                   
                 longitudinal and transverse directions respectively. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 8. 
                 92% EPC 1 + 8% PP 2/PP 4/EAO 1/PP 4/92% EPC 1 + 8% 
               
               
                   
                 PP 2 
               
               
                   
                 The generalized structure of the film of Example 8 was 
               
               
                   
                 A/B/C/B/A. This film was like that of Example 7, but 
               
               
                   
                 oriented at a higher temperature compared to Example 7. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5 
               
               
                 9. 
                 92% EPC 1 + 8% PP 2/PP 4/EAO 2/PP 4/92% EPC 1 + 8% 
               
               
                   
                 PP 2 
               
               
                   
                 The generalized structure of the film of Example 9 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 10. 
                 92% EPC 1 + 8% PP 2/PP 4/EPB 1/PP 4/92% EPC 1 + 8% 
               
               
                   
                 PP 2 
               
               
                   
                 The generalized structure of the film of Example 10 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 11. 
                 
                   92% EPC 1 + 8% PP  2 
                 
               
               
                   
                 
                   70% PP 3 + 30% HC 2 
                 
               
               
                   
                 
                   EAO 2 
                 
               
               
                   
                 
                   70% PP 3 + 30% HC 2 
                 
               
               
                   
                 
                   92% EPC 1 + 8% PP 2 
                 
               
               
                   
                 The generalized structure of the film of Example 11 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 12. 
                 90% EPC 1 + 10% PP 2/PP 4/EPC 1/PP 4/90% EPC 
               
               
                   
                 1 + 10% PP 2 
               
               
                   
                 The generalized structure of the film of Example 12 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 13. 
                 90% EPC 1 + 10% PP 2/PP 4/EPC 1/PP 4/90% EPC 1 + 10% 
               
               
                   
                 PP 2 
               
               
                   
                 The generalized structure of the film of Example 13 was 
               
               
                   
                 A/B/C/B/A. This film was like that of Example 12, but lower 
               
               
                   
                 racking ratios of 4.5 × 4.5 to produce a film of 132 gauge 
               
               
                   
                 thickness. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 14. 
                 90% EPC 1 + 10% PP 2/PP 4/EPC 1/PP 4/90% EPC 1 + 10% 
               
               
                   
                 PP 2 
               
               
                   
                 The generalized structure of the film of Example 14 was 
               
               
                   
                 A/B/C/B/A. This film was like that of Example 13, but with 
               
               
                   
                 slightly higher racking ratios (4.5 × 5.0) and a final film 
               
               
                   
                 thickness of 155 gauge. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 15. 
                 
                   87.5% EPC  3 +  12.5%  PP 2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   EPC  3 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   87.5% EPC  3  + 12.5%  PP 2 
                 
               
               
                   
                 The generalized structure of the film of Example 15 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 16. 
                 
                   84% EPC 3  +  16%  PP  2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   EPC  3 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   84% EPC  3  + 16%  PP 2 
                 
               
               
                   
                 The generalized structure of the film of Example 16 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5. 
               
               
                 17. 
                 
                   86%  EPC  3  + 14%  PP 2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   EPC  3 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   86%  EPC  3  +  14%  PP  2 
                 
               
               
                   
                 The generalized structure of the film of Example 17 was 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5.  
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 The inventor made a seven layer film (Example 18) as a control, and 
               
               
                 then made two moisture/oxygen barrier seven-layer films (Examples 
               
               
                 19 and 20) with good results. Examples of these films are given below: 
               
             
          
           
               
                 EXAMPLE 
                 FILM STRUCTURE  
               
               
                   
               
               
                 18. 
                 
                   92%  EPC  1  +  8%  PP  2 
                 
               
               
                   
                 
                   PP  3 
                 
               
               
                   
                 
                   ADH  2 
                 
               
               
                   
                 
                   EVOH  1 
                 
               
               
                   
                 
                   ADH  2 
                 
               
               
                   
                 
                   PP  3 
                 
               
               
                   
                 
                   92%  EPC  1  +  8% PP  2 
                 
               
               
                   
                 The generalized structure of the film of Example 18 was 
               
               
                   
                 A/B/C/D/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1:2.5:1:1:1:2.5:1 
               
               
                 19. 
                 
                    92%  EPC  1  +  8% PP  2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   ADH  1 
                 
               
               
                   
                 
                   EVOH  2 
                 
               
               
                   
                 
                   ADH  1 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   92%  EPC  1  +  8%  PP  2 
                 
               
               
                   
                 The generalized structure of the film of Example 19 was 
               
               
                   
                 A/B/C/D/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:2:1:1:1:2:1.5 
               
               
                 20. 
                 
                   92%  EPC  1  +  8% PP 2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   ADH  2 
                 
               
               
                   
                 
                   EVOH  3 
                 
               
               
                   
                 
                   ADH  2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   92%  EPC  1  + 8%  PP  2 
                 
               
               
                   
                 The generalized structure of the film of Example 20 was 
               
               
                   
                 A/B/C/D/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:2:1:1:1:2:1.5.  
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                 Two alternative films of seven layers have the structure: 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 21. 
                 
                   92%  EPC  1  + 8%  PP 2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   EVA  1 
                 
               
               
                   
                 
                   HDPE  1 
                 
               
               
                   
                 
                   EVA  1 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   92%  EPC  1  +  8%  PP  2 
                 
               
               
                   
                 The generalized structure of the film of Example 21 is 
               
               
                   
                 A/B/C/D/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1:2.5:1:1:1:2.5:1 
               
               
                 22. 
                 
                   92%  EPC  1  +  8% PP  2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   VLDPE  1 
                 
               
               
                   
                 
                   HDPE  1 
                 
               
               
                   
                 
                   VLDPE  1 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   92%  EPC  1  + 8%  PP  2 
                 
               
               
                   
                 The generalized structure of the film of Example 22 is 
               
               
                   
                 A/B/C/D/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1:2.5:1:1:1:2.5:1  
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 8 
               
               
                   
               
               
                 Two additional alternative films of five layers were made, and are 
               
               
                 compared in Table 13 with the film of Example 17. These two 
               
               
                 additional films have the following structures: 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 23. 
                 
                   86%  EPC  3  +  14%  PP  2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   85%  EPC  3  +  15% HC  3 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   86%  EPC  3  +  14%  PP  2 
                 
               
               
                   
                 The generalized structure of the film of Example 23 is 
               
               
                   
                 A/B/C/B/A. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5 
               
               
                 24. 
                 
                   86%  [85%  EPC  3  +  15%  HC  3]  + 14% PP 2 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   85%  EPC  3  +  15%  HC  3 
                 
               
               
                   
                 
                   PP  4 
                 
               
               
                   
                 
                   85%  EPC  3  +  15%  HC 3 
                 
               
               
                   
                 The generalized structure of the film of Example 24 is 
               
               
                   
                 A/B/C/B/C. 
               
               
                   
                 Relative layer thickness ratios: 
               
               
                   
                 1.5:3:1:3:1.5  
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 9 
               
               
                   
                   
               
               
                   
                 Example 1 
                   
                   
                   
               
               
                   
                 (control) 
                 Example 2 
                 Example 3 
                 Example 4 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Modulus 
                   
                   
                   
                   
               
               
                 LD 
                 239,480 
                 279,920 
                 316,030 
                 336,820 
               
               
                 TD 
                 214,690 
                 260,240 
                 298,930 
                 316,820 
               
               
                 Free Shrink/Shrink 
               
               
                 Tension 
               
               
                 at 200° F.: 
               
             
          
           
               
                 LD 
                  7/396 
                  9/321 
                 10/315 
                 11/408 
               
               
                 TD 
                 12/388 
                 14/381 
                 17/528 
                 17/504 
               
               
                 at 220° F.: 
               
               
                 LD 
                 12/435 
                 14/335 
                 14/361 
                 15/439 
               
               
                 TD 
                 18/432 
                 19/383 
                 24/540 
                 25/548 
               
               
                 at 240° F.: 
               
               
                 LD 
                 18/451 
                 20/364 
                 20/443 
                 22/494 
               
               
                 TD 
                 26/469 
                 28/413 
                 33/591 
                 33/516 
               
               
                 at 260° F.: 
               
               
                 LD 
                 31/473 
                 31/397 
                 33/429 
                 33/511 
               
               
                 TD 
                 35/493 
                 39/441 
                 45/538 
                 44/561 
               
               
                 Haze 
               
             
          
           
               
                 Unshrunk 
                 1.2 
                 1.7 
                 1.3 
                 1.3 
               
               
                 Shrunk 
                 1.6 
                 2.3 
                 3.2 
                 2.1 
               
               
                 Clarity 
               
               
                 Unshrunk 
                 81 
                 87 
                 87 
                 88 
               
               
                 Shrunk 
                 80 
                 84 
                 83 
                 87 
               
               
                 Gloss 
                 87 
                 84 
                 87 
                 88 
               
               
                 Film Thickness (mils) 
               
               
                 (related to MVTR data 
               
               
                 given below) 
               
               
                 Unshrunk 
               
               
                 Actual 
                 0.96 
                 0.80 
                 0.77 
                 0.75 
               
               
                 MVTR 1 
               
               
                 Unshrunk 
                 0.60 
                 0.67 
                 0.60 
                 0.55 
               
               
                 Corrected 
                 0.77 
                 0.71 
                 0.62 
                 0.55 
               
               
                 for 75 gauge 
               
               
                 MVTR 2 
               
               
                 Unshrunk 
                 0.49 
                 0.55 
                 0.48 
                 0.45 
               
               
                 Corrected 
                 0.63 
                 0.59 
                 0.49 
                 0.45 
               
               
                 for 75 gauge 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 10 
               
               
                   
                   
               
               
                   
                 Example 7 
                 Example 8 
                 Example 9 
                 Example 10 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Modulus 
                   
                   
                   
                   
               
               
                 LD 
                 271,200 
                 299,200 
                 — 
                 — 
               
               
                 TD 
                 292,100 
                 337,900 
                 — 
                 — 
               
               
                 Free Shrink 
               
               
                 at 220° F.: 
               
             
          
           
               
                 LD 
                 — 
                 — 
                 13 
                 13 
               
               
                 TD 
                 — 
                 — 
                 19 
                 20 
               
               
                 at 240° F.: 
               
             
          
           
               
                 LD 
                 20 
                 17 
                 20 
                 18 
               
               
                 TD 
                 28 
                 23 
                 30 
                 27 
               
               
                 at 260° F.: 
               
             
          
           
               
                 LD 
                 — 
                 — 
                 27 
                 28 
               
               
                 TD 
                 — 
                 — 
                 37 
                 38 
               
               
                 Haze 
               
               
                 Unshrunk 
                 — 
                 — 
                 1.7 
                 1.8 
               
               
                 Clarity 
               
               
                 Unshrunk 
                 — 
                 — 
                 82 
                 84 
               
               
                 Gloss 
                 — 
                 — 
                 84 
                 55 
               
               
                 Film Thickness (mils) 
               
               
                 (related to MVTR data 
               
               
                 given below) 
               
             
          
           
               
                 Unshrunk 
                 0.86 
                 0.76 
                 0.86 
                 0.77 
               
             
          
           
               
                 Shrunk 
                 1.00 
                 0.97 
                 — 
                 — 
               
               
                 MVTR 1 
               
               
                 Unshrunk 
                 0.51 
                 0.56 
                 — 
                 — 
               
               
                 Shrunk 
                 0.41 
                 0.46 
                 — 
                 — 
               
               
                 Corrected 
               
               
                 for 75 gauge 
               
               
                 Unshrunk 
                 0.58 
                 0.57 
                 — 
                 — 
               
               
                 Shrunk 
                 0.55 
                 0.59 
                 — 
                 — 
               
               
                 MVTR 2 
               
             
          
           
               
                 Unshrunk 
                 0.45 
                 0.47 
                 0.42 
                 0.43 
               
             
          
           
               
                 Shrunk 
                 0.35 
                 0.38 
                 — 
                 — 
               
               
                 Corrected 
               
               
                 for 75 gauge 
               
             
          
           
               
                 Unshrunk 
                 0.52 
                 0.48 
                 0.48 
                 0.44 
               
             
          
           
               
                 Shrunk 
                 0.47 
                 0.49 
                 — 
                 — 
               
               
                 Tear (grams) 
               
             
          
           
               
                 LD 
                 — 
                 — 
                 8.6 
                 5.0 
               
               
                 TD 
                 — 
                 — 
                 8.4 
                 6.1 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 11 
               
               
                   
                   
               
               
                   
                 Example 11 
                 Example 12 
                 Example 13 
                 Example 14 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Modulus 
                   
                   
                   
                   
               
               
                 LD 
                 345,750 
                 352,880 
                 322,950 
                 320,470 
               
               
                 TD 
                 374,990 
                 392,020 
                 334,660 
                 319,420 
               
               
                 Free Shrink 
               
               
                 at 240° F.: 
               
               
                 LD 
                 20 
                 17 
                 18 
                 14 
               
               
                 TD 
                 29 
                 23 
                 24 
                 25 
               
               
                 Haze 
               
               
                 Unshrunk 
                 48.5 
                 1.3 
                 3.3 
                 5.3 
               
               
                 Clarity 
               
               
                 Unshrunk 
                 21 
                 85 
                 74 
                 64 
               
               
                 Gloss 
                 107 
                 89 
                 73 
                 64 
               
               
                 Film Thickness 
               
               
                 (mils) (related 
               
               
                 to MVTR data 
               
               
                 given below) 
               
               
                 Unshrunk 
                 0.85 
                 0.81 
                 1.40 
                 1.60 
               
               
                 MVTR 2 
               
               
                 Unshrunk 
                 0.36 
                 0.36 
                 0.23 
                 0.19 
               
               
                 Corrected for 
                 0.41 
                 0.39 
                 0.43 
                 0.41 
               
               
                 75 Gauge 
               
               
                 Tear (grams) 
               
             
          
           
               
                 LD 
                 — 
                 — 
                 8.6 
                 5.0 
               
               
                 TD 
                 — 
                 — 
                 8.4 
                 6.1 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 12 
               
               
                   
                   
               
               
                   
                 Example 19 
                 Example 20 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Modulus 
                   
                   
               
               
                 LD 
                 300,890 
                 307,380 
               
               
                 TD 
                 315,460 
                 291,480 
               
               
                 Free Shrink/Shrink Tension 
               
               
                 at 220° F.: 
               
             
          
           
               
                 LD 
                  8/440 
                 14/395 
               
               
                 TD 
                 19/632 
                 20/595 
               
               
                 at 240° F.: 
               
               
                 LD 
                 18/477 
                 21/429 
               
               
                 TD 
                 28/654 
                 27/611 
               
               
                 at 260° F.: 
               
               
                 LD 
                 28/446 
                 29/436 
               
               
                 TD 
                 38/621 
                 35/601 
               
               
                 at 280° F.: 
               
               
                 LD 
                 44/467 
                 43/487 
               
               
                 TD 
                 52/600 
                 46/587 
               
               
                 at 300° F.: 
               
               
                 LD 
                 59/— 
                 60/— 
               
               
                 TD 
                 62/— 
                 61/— 
               
               
                 Haze 
               
               
                 Unshrunk 
                 1.6 
                 1.8 
               
               
                 Clarity 
               
               
                 Unshrunk 
                 76 
                 76 
               
               
                 Gloss 
                 89 
                 86 
               
               
                 Film Thickness (mils) 
               
               
                 (related to MVTR data given below) 
               
               
                 Unshrunk 
                 1.09 
                 1.12 
               
               
                 MVTR 2 
               
               
                 Non-shrunk 
                 0.35 
                 0.33 
               
               
                 Corrected for 
                 0.51 
                 0.49 
               
               
                 75 gauge 
               
               
                 Tear 
               
               
                 LD 
                 6 
                 6 
               
               
                 TD 
                 6 
                 7 
               
               
                 Tensile 
               
               
                 LD 
                 19,415 
                 20,407 
               
               
                 TD 
                 19,296 
                 16,990 
               
               
                 Elongation 
               
               
                 LD 
                 63 
                 62 
               
               
                 TD 
                 71 
                 77 
               
               
                 Ball Burst 
                 12 
                 11 
               
               
                 OTR 
                 3.0 
                 4.5 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 13 
               
               
                   
                   
               
               
                   
                 Example 17 
                 Example 23 
                 Example 24 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Modulus 
                   
                   
                   
               
               
                 LD 
                 398,000 
                 420,000 
                 437,000 
               
               
                 TD 
                 442,000 
                 473,000 
                 488,000 
               
               
                 Free Shrink 
               
               
                 at 220° F.: 
               
               
                 LD 
                 15 
                 14 
                 15 
               
               
                 TD 
                 19 
                 19 
                 22 
               
               
                 at 240° F.: 
               
               
                 LD 
                 20 
                 19 
                 19 
               
               
                 TD 
                 26 
                 26 
                 28 
               
               
                 at 260° F.: 
               
               
                 LD 
                 30 
                 30 
                 26 
               
               
                 TD 
                 38 
                 36 
                 38 
               
               
                 at 280° F.: 
               
               
                 LD 
                 44 
                 44 
                 44 
               
               
                 TD 
                 51 
                 51 
                 52 
               
               
                 at 300° F.: 
               
               
                 LD 
                 64 
                 63 
                 62 
               
               
                 TD 
                 68 
                 67 
                 68 
               
               
                 Haze 
               
               
                 Unshrunk 
                 1.8 
                 2.0 
                 1.2 
               
               
                 Clarity 
               
               
                 Unshrunk 
                 82 
                 81 
                 81 
               
               
                 Gloss 
                 86 
                 83 
                 89 
               
               
                 Film Thickness (mils) 
               
               
                 (related to MVTR data given 
               
               
                 below) 
               
               
                 Unshrunk 
                 0.89 
                 0.91 
                 0.82 
               
               
                 MVTR 2 
               
               
                 Unshrunk 
                 0.33 
                 0.36 
                 0.33 
               
               
                 Corrected for 
                 0.39 
                 0.44 
                 0.36 
               
               
                 75 gauge 
               
               
                 Tear 
               
               
                 LD 
                 1 
                 7 
                 4 
               
               
                 TD 
                 5 
                 7 
                 6 
               
               
                 Tensile 
               
               
                 LD 
                 28,000 
                 31,000 
                 25,000 
               
               
                 TD 
                 29,000 
                 33,000 
                 29,000 
               
               
                 Elongation 
               
               
                 LD 
                 80 
                 86 
                 84 
               
               
                 TD 
                 71 
                 52 
                 73 
               
               
                   
               
             
          
         
       
     
     In a typical working example of making the film of the present invention: 
     An ethylene propylene copolymer (Fina 8473) containing about 4% by weight ethylene, was blended with the polypropylene in a blend ratio of about 92% by weight EPC and 8% by weight PP. (The PP percentage includes the additives discussed above). 
     The EPC/PP blend was then blended with a hydrocarbon resin (Regalrez 1128 from Hercules) in a blend ratio of about 90% by weight EPC/PP and 10% by weight HC. 
     A second blend was also prepared, in a blend ratio of about 84.5% by weight PP (Exxon PD 4062 E7), 15% by weight HC (Regalrez 1128), and 0.5% white mineral oil (Kaydol from Witco Chemical). 
     A circular coextrusion die was fed with three extruders to prepare a rive layer shrink film. One extruder was used to feed the blend of EPC or polypropylene, and HC, as a melt to the extrusion die to form the outer layers. Another extruder fed a polypropylene (Exxon PD 4062 E7) to the extrusion die to provide the intermediate layers in the multi-layer film. The third extruder provided, the second blend of PP and HC to the extrusion die. 
     The extruded tape was rapidly cooled to room temperature and collapsed by pinch rolls. The tape was subsequently heated to an orientation temperature. Using a bubble technique well known in the art, internal air pressure stretched the tape to about 4.5 times its unstretched dimensions in the longitudinal (machine) direction and about 4.0 times its unstretched dimensions in the transverse direction to form a bubble which provided biaxial orientation to the resulting film. The bubble was then rapidly cooled by chilled air in order to maintain the oriented state of the film. Finally, the bubble was collapsed and the expanded film gathered on a take-up roll. After orientation, the total wall thickness of the film was about one mil with 50% of the structure being the blend of ethylene propylene copolymer and polypropylene; 15% of the structure being the intermediate layers; and the remainder or 35% of the structure being the core layer. 
     It will be clear to one skilled in the art that the degree of stretching may be varied to obtain the desired degree of film gauge or thickness and to regulate the desired amount of shrink tension, free shrink, and other shrink properties of the final film, depending on the packaging application. Preferred stretching or racking ratios are between about 3.0 and 8.0 in both the machine and transverse directions. 
     The multi-layer film of the present invention is preferably not irradiated. However, the sealant material, if extrusion laminated, extrusion coated, or conventionally laminated to the substrate moisture barrier film, can itself be irradiated or electronically or chemically crosslinked prior to lamination. Irradiation may be accomplished by means well known in the art. 
     The blend ratios of the EPC and PP may be varied according to desired properties or end-use of the multi-layer film. For example, increasing the polypropylene in the blend will add stiffness to the film, but also increase the sealing temperature of the film. Conversely, increasing the EPC in the blend tends to lower the shrink temperature of the oriented film, or to increase shrink at the same temperature, and also lowers the sealing temperature of the film. A preferred blend includes between about 4% and 15% PP and between about 96% and 85% EPC. 
     The multilayer film of the present invention is preferably oriented either monoaxially or biaxially, and preferably used as a shrink film. Optionally, the oriented film may be further processed by reheating the film to a temperature near its orientation temperature, i.e. either somewhat below, at, or somewhat about its orientation temperature, to heat set the film. This future processing step has the advantage of substantially retaining many of the favorable physical characteristics of an oriented film, such as higher tensile strength, modulus and improved optical properties, while providing a substantial shrink-free film in applications where a shrink feature is undesirable. 
     The film of the present invention can utilize hydrocarbon resin in at least one or more, or even all the layers of the film, as long as the HC resin in any given layer is compatible from a process and performance point of view with the resin with which it is blended. 
     Films in accordance with this invention are preferably oriented, and preferably heat shrinkable. Preferred films exhibit a free shrink at 240° F. of at least 10% (LD) and 15% (TD), more preferably at least 15% (LD) and 22% (TD). 
     Obvious modifications to the invention as described may be made by one skilled in the art without departing from the spirit and scope of the claims as presented below.