JPH0375036B2 - - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to irradiated multilayer films suitable for use in the manufacture of bags for packaging primal and sub-primal, meat cuts and processed meats. The present invention also provides an irradiated multilayer film comprising an irradiated three-layer film in which the outer layer of the film is comprised of an ethylene-vinyl acetate copolymer and the core layer is comprised of a polyvinylidene chloride copolymer or other barrier film. The present invention relates to a film and a method for manufacturing the film. BACKGROUND OF THE INVENTION Primal meat cuts or primals are large cuts of meat that are smaller than, for example, beef flanks, but larger than the final cut sold retail to the consumer. Primal fillets are produced at slaughterhouses and then transported to locations such as retail meat points or restaurants where they are broken down into smaller cuts of meat called sub-primals or sub-primals. Subprimals can also be produced in slaughterhouses. When primals and subprimals are produced in an abattoir, they are usually packaged in a manner that prevents exposure to air during transportation and handling of the meat to minimize spoilage and discoloration. One desirable way to package primals and subprimals to protect them from contact with air is to shrink wrap the primals and subprimals in a packaging material that has good oxygen barrier properties. One such shrink wrap material that has good oxygen barrier properties is polyvinylidene chloride film. However, in actual use, although polyvinylidene chloride itself has excellent oxygen barrier properties, when polyvinylidene chloride is used as a single layer film, it is necessary to ensure that the film has adequate abrasion resistance and ~Ten
It must be plasticized in order to have soft properties at storage temperatures of 20°C. Unfortunately, adding enough plasticizer, e.g. 7-9% by weight of the film, to impart the necessary low temperature properties has a significant negative effect on the oxygen barrier properties of the film. Adjust film thickness from 1.5 to 2.0 mils (0.038 to
For example, the thickness ranges from 5 mils (0.13 mm) to a typical thickness of 0.051 mm
mm) or more will improve the film's oxygen barrier properties;
It is economically undesirable to use a single layer of polyvinylidene chloride or more. Also, with such thick film, bags made from the film are difficult to pull and clip open ends. Provides a film for use in shrink-wrapping primal and sub-primal meat cuts and processed meats that has better oxygen barrier properties than the 1.5-2.0 mil single layer polyvinylidene chloride films conventionally used for that purpose. One approach is to employ a multilayer film, one of which is polyvinylidene chloride with a minimal amount of plasticizer. The other layers of such multilayer films are selected to provide the necessary low temperature properties and abrasion resistance that are lacking in polyvinylidene chloride films containing little or no plasticizer. However, when providing such films, it must be recognized that good oxygen barrier properties, abrasion resistance and low temperature properties are not the only requirements for the film to be used for shrink wrapping primal meat fillets. . The film has sufficient shrinkage characteristics to cause the film to heat shrink in both the longitudinal and transverse directions at about 90° C. within a specified percentage range, such as from about 30 to about 60%. It had to be biaxially stretched.
The film must be heat sealable in order to be able to process bags from the film and to heat seal the open ends of the processed bags. The seams of the heat-sealed bag must not tear during the heat-shrinking operation, and the film must resist puncturing from sharp edges, such as bone ends, during the heat-shrinking operation, and the film must resist puncturing during the heat-shrinking operation. Adequate adhesion between the several layers of the film so that delamination does not occur during exposure of the film to the relatively high temperatures that can be reached during processing or during transportation and storage of the film during the summer months. It must have sex. a multilayer film, one of which is a polyvinylidene chloride copolymer, and at least one of the other layers is a polyvinylidene chloride copolymer;
It has been proposed to make the layer of ethylene-vinyl acetate copolymer. For example, such films include McPhedrees, Giuniar.
(McFedries, Jr.) et al. US Pat. No. 3,600,267; Peterson (Peterson), US Pat. No. 3,524,795;
U.S. patents of Titchenal et al.
No. 3,625,348, Shearmer US Pat. Nos. 3,567,539 and 3,607,505. Radiation crosslinking has also been used in the prior art to enhance the properties of films used in packaging operations. For example, U.S. Pat. No. 3,741,253 to Brax et al. teaches a multilayer laminate having a first layer of ethylene-vinyl acetate crosslinked by radiation. The second and third layers of the laminate were not irradiated. The laminate thus produced can then be biaxially stretched. U.S. Pat. Nos. 3,821,182 and 4,112,181 to Byrd et al. teach a combination of three layer films that are irradiated prior to stretching. In addition, Kremak US Pat. No. 4,044,187 irradiates a substrate to form a film laminate with the substrate;
It is then taught to irradiate the entire laminate. Additionally, Bernstein et al., U.S. Pat. Discloses stretching multilayer films. Still further, US Pat. No. 4,318,763 to Bieler et al. teaches that multilayer films can be strengthened by biaxial stretching followed by irradiation to crosslink one of the layers. However, the prior art does not teach the concept of simply biaxially stretching the multilayer film and then irradiating all of the layers of the multilayer film. The present invention relates to a multilayer film having an outer layer of ethylene-vinyl acetate copolymer and a core layer of barrier film, which is biaxially stretched and then irradiated to crosslink the ethylene-vinyl acetate layer. The present invention is based on the discovery that the invention (described herein) can be used to shrink wrap primal and subprimal meat cuts and processed meats with good results. Accordingly, the present invention provides a multilayer film that can be used to fabricate bags useful for shrink-wrapping primal and subprimal meat cuts and processed meats. SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a heat-shrinkable multilayer film having an outer layer of ethylene-vinyl acetate copolymer and a core layer of barrier film that is biaxially stretched and then at a dose level of from about 1 to about 5 megarads. irradiated to provide bags with improved physical properties when used to make bags for packaging primal and sub-primal meat cuts and processed meats, so that the bags have better resistance when sealed. The film was found to have the ability to withstand higher sealing temperatures than similar bags that were not so irradiated.

[Detailed description of the invention]

In accordance with the present invention, a first ethylene-vinyl acetate copolymer has a melt index of about 0.1 to about 1.0 decigrams per minute and a melt index of about 9 decigrams per minute based on the weight of the first ethylene-vinyl acetate copolymer. a first outer layer comprising a vinyl acetate content of from about 15% by weight; a core layer comprising a barrier film; a second ethylene-vinyl acetate copolymer comprising: (a) from about 0.1 to about 1.0 decigrams; /
based on the melt index of minutes and the weight of the second ethylene-vinyl acetate copolymer.
an ethylene-vinyl acetate copolymer having a vinyl acetate content of up to about 18% by weight, preferably from about 10 to about 15% by weight; and (b) a blend of at least two ethylene-vinyl acetate copolymers, comprising: One of the ethylene-vinyl acetate copolymers has a melt index of about 0.1 to about 1.0 decigrams per minute and based on the weight of the copolymer.
having a vinyl acetate content of 10 to about 18% by weight;
and other ethylene-vinyl acetate copolymers have a melt index of about 0.1 to about 1.0 decigrams per minute and about 2 to about 10 decigrams per minute, based on the weight of the copolymer.
A heat shrinkable multilayer film is provided having a second outer layer comprising one selected from the group consisting of one having a vinyl acetate content of % by weight. at least 2
Blend (b) of ethylene-vinyl acetate copolymers of type (b) is about 9% by weight of the copolymer.
It has a vinyl acetate content of up to about 18% by weight, preferably about 10 to about 15% by weight. The first ethylene-vinyl acetate copolymer is a single ethylene-vinyl acetate copolymer or a blend of at least two ethylene-vinyl acetate copolymers having different melt indexes and different vinyl acetate contents. It can be done. The heat-shrinkable multilayer film of the present invention can be made by a known technique, for example, by co-extruding multiple layers to form a primary tube, and then biaxially stretching the tube by a known technique to heat-shrink it. Make it into a sex film. The "double bubble" disclosed in Pahlke U.S. Patent No. 3,456,044
The technique can be used to make the films of the invention. Alternatively, the film can be a slot cast coextruded multilayer film that is biaxially oriented by tentering. After the multilayer film is biaxially stretched, the multilayer film is then irradiated to a dose level of about 1 to about 5 megarads, such as by passing it through an electron beam irradiation unit. The multilayer film can then be used to produce heat shrinkable bags useful for packaging primal and subprimal meat cuts and processed meats. According to a preferred embodiment of the invention, the first outer layer of the multilayer film is an ethylene-vinyl acetate copolymer containing from about 9 to about 15 weight percent vinyl acetate content, based on the weight of the copolymer. and has a melt index of about 0.1 to about 1.0 decigrams/minute, and the copolymer:
It may be selected from the group consisting of (a) a single ethylene-vinyl acetate copolymer and (b) a blend of ethylene-vinyl acetate copolymers having different melt indexes and different vinyl acetate contents. Furthermore, in a preferred embodiment of the invention, the core layer of the multilayer film of the invention is a polyvinylidene chloride copolymer comprising at least 65% by weight, based on the weight of the polyvinylidene chloride copolymer, of vinylidene chloride and Contains up to 5% by weight of plasticizer. The remainder of the polyvinylidene chloride copolymer is preferably vinyl chloride, but may also include acrylonitrile, acrylate esters such as methyl methacrylate, and the like. More preferably, the polyvinylidene chloride copolymer has at least about 70
By weight, the polyvinylidene chloride copolymer contains about 70% by weight or less of polymerized vinylidene chloride.
If the amount is less, the oxygen barrier properties of the copolymer will not be satisfactory. If the vinylidene chloride content is greater than 90% by weight, the polyvinylidene chloride copolymer usually cannot be extruded. The polyvinylidene chloride copolymer preferably contains less than 5% by weight plasticizer, more preferably less than 4% by weight plasticizer (percentages are based on the weight of the copolymer) to maximize the barrier properties of the thin film. ). Conventional plasticizers can be used, such as dibutyl sebacate, epoxidized soybean oil. The second outer layer of the multilayer film of the present invention is (a) an ethylene-vinyl acetate copolymer of about 0.1
having a melt index of ~1.0 decigrams per minute and a vinyl acetate content of from about 9 to about 18%, preferably from about 10 to about 15% by weight, based on the weight of the second ethylene-vinyl acetate copolymer. and (b) a blend of at least two ethylene-vinyl acetate copolymers, wherein one of the ethylene-vinyl acetate copolymers has a melt index of about 0.1 to about 1.0 decigrams per minute. and about 10 to about 18 based on the weight of the copolymer.
% vinyl acetate content, and other ethylene-vinyl acetate copolymers have a vinyl acetate content of about 0.1 to
from about 2 to about 10% by weight, based on a melt index of about 1.0 decigrams/minute and the weight of the copolymer.
ethylene-vinyl acetate copolymers selected from the group consisting of those having a vinyl acetate content of . Blend (b) of the at least two ethylene-vinyl acetate copolymers is about 9 to about 18% by weight, based on the weight of the copolymers, preferably about
It has a vinyl acetate content of 10 to about 15% by weight. The multilayer film of the present invention typically has a thickness of about 1.75 to about 3.0.
Mil (about 0.044 to about 0.076mm), preferably about 2.0 to
having a total thickness of about 3.0 mils (0.051 to about 0.076 mm), because if the thickness of the multilayer film exceeds 3.0 mils (0.076 mm), it is difficult to assemble the open ends of bags made from the film. This is because the problem of clipping is encountered at the point where The multilayer film thickness is 1.75 mil (0.044
mm), the fracture resistance of the bag decreases. The first outer layer is typically about 1.1 to about 1.6 mil (about 0.028 to
approximately 0.041mm), and the core layer is typically approximately
having a thickness of 0.25 to about 0.45 mil (about 0.0064 to about 0.011 mm), with the second outer layer typically having a thickness of about 0.4 to about 1.0 mil (about
0.010 to about 0.025 mm). After biaxially stretching the multilayer film of the present invention by any suitable method well known in the art,
Irradiation is performed by any suitable method, such as by using an electron beam, to a dose level of about 1 to about 5 megarads, preferably about 2 to about 3 megarads.
According to the present invention, it has been found that the irradiation energy applied to the multilayer film is important in the present invention. That is, if the energy level is lower than the above range, sufficient crosslinking will not be obtained to improve the heat sealing properties of the multilayer film or to have a significant effect on the toughness of the film. If the energy level is higher than the above-mentioned range, the deterioration of the polyvinylidene chloride copolymer core layer will cause discoloration of the film, the degree of film shrinkage will be significantly reduced, and no further improvement of the heat-sealing properties and toughness of the film will be achieved. . In another aspect of the invention there is provided a bag suitable for shrink wrapping primal and subprimal meat cuts and processed meats from the multilayer film described above. Bags can be made from the multilayer film of the present invention by any suitable method such as heat sealing. For example, when the film of the present invention is made in the form of a tubular film, the bag is made by heat-sealing one end of a certain length of tubular film, or by sealing both ends of the tube and then slitting one wire. It can be made by forming a mouth. When the film of the invention is made in flat sheet form, the bag can be formed by sealing the three edges of two layers of film.
When performing a heat sealing operation, the surfaces that are heat sealed together to form a seam are the first outer layer of the inventive film. Thus, for example, when heat sealing one edge of a length of tubular film to form a bag, the inner surface of the tube,
That is, the surface that heat seals to itself will be the first outer layer of the film. The invention is further illustrated by the examples that appear below. In the example, the following materials were used: Ethylene-vinyl acetate (“EVA”) copolymer EVA copolymer U-vinyl acetate 12% by weight, melt index 0.25 EVA copolymer F-vinyl acetate 15% by weight melt Index 0.5 EVA Copolymer R - 12% by weight vinyl acetate Melt Index 0.5 EVA Copolymer G - (a) 75% by weight EVA with 12% by weight vinyl acetate and melt index 0.35 and (b) 4.5% by weight vinyl acetate Weight% and melt index
Polyvinylidene chloride copolymer (“PVDC”) blended with 25% by weight of EVA with 0.25 PVDC Copolymer D - 84-87% by weight of vinylidene chloride and 13-16% by weight of vinyl chloride, reduced viscosity at 30°C in cyclohexanone
0.055-0.059 PVDC Copolymer K-vinylidene chloride 71% by weight
and vinyl chloride 29% by weight. The following test methods were used in determining the properties of the resins and films used in the examples. Melt index value is ASTM method D-1238, condition E.
Obtained according to. Decalin extraction was obtained according to ASTM Method D-2765, Condition A. The tensile strength value is
Obtained according to ASTM Method D-882, Procedure A. The non-ASTM test methods employed are explained in the discussion below. Shrinkage values were obtained by measuring unrestrained contraction for 5 seconds at 90°C. A dynamic puncture-impact test procedure is used to compare the bone fracture resistance of the films.
The procedure measures the energy required to puncture a test specimen with a sharp triangular metal tip made to simulate a sharp bone edge. In this test procedure, a Dynamic Ball Burst Tester, model number 13-8, available from Testing Machines, Inc., Amiciville, Long Island, New York, was used;
And use the aforementioned triangular tip with a diameter of 3/8 inch (9.5 mm) installed on the tester probe arm.
Create six specimens approximately 4 inches (10 cm) square, place the specimen in a specimen holder, and drop the pendulum. Record the energy required to puncture the sample material. The test is repeated to evaluate six materials and the test results are averaged. Results are calculated in cm-Kg per mil of film thickness. A hot water destructive test is carried out as follows. 90± of water
Heat to 1°C. One end of a 3/8 inch (9.5 mm) circular wooden dowel is shaved to give it a circular tip of approximately 1/18 inch (1.6 mm), and the sharpened tip is a wooden block. Leave 1-1/2 inch (3.8 cm) beyond the edge of the tape.
Approximately 3 inches (7.6 cm) horizontal width from the test material
and cut material approximately 10 inches (25 cm) long.
Place one end of the material on the opposite end of the wooden block from the pointy dowel pin. Wrap the material around the sharpened dowel end and place it back on the other side of the wooden block. Measure the thickness of the film in the area of contact with the sharpened dowel pin. Quickly dip the material and pointed dowel into hot water and start the timer. Stops the timer when the tip of the wooden dowel punctures the film material. The test is repeated four times on four film specimens from a given test material. The time required for penetration is recorded and then averaged. A fracture propagation tear test is performed to determine the ability of a plastic film to resist fracture and propagation of that fracture. The test equipment is a Puncture Propagation Tear Tester Model No. 83 available from Testing Machines, Inc., Amiciville, Long Island, New York.
-5. Six specimens are prepared for longitudinal testing. Cut the specimen lengthwise to 10 inches (25
cm) x 8 inches (20 cm) horizontally. Fix the specimen in the holder. Place the carriage in the release mechanism and release it. Tear length to nearest 0.05cm
Read to. Average test results from six specimens. Perform an impulse seal range test to determine the acceptable voltage range for sealing the plastic film. Sentinel Model 12, manufactured by Packaging Industries Group, Inc., Hyannis, Minnesota.
12AS Laboratory Sealer was used. Shock time 1.0
seconds, cooling time 1.3 seconds, jaw pressure 50psi (3.5Kg/cm ² )
The following sealing conditions were used. The minimum voltage was determined as the lowest voltage that would allow the four pieces of film to be sealed together, thereby simulating the fold commonly encountered in field testing. The maximum seal voltage was determined as the voltage at which seal "burn thru" began to occur.
"Burn-through" is defined as a hole or tear in the seal caused by high temperatures and pressures in the seal ribbon. This has an undesirable effect on seal strength, integrity, and final packaging appearance. EXAMPLE The "double bubble" process disclosed in U.S. Pat. A biaxially stretched three-layer film was prepared by irradiation with radiation. The film consisted of the following materials: Second outer layer - EVA copolymer F Core layer - PVDC copolymer K First outer layer - EVA copolymer U The resulting biaxially stretched film had an average thickness of 2.5 mil (0.064mm), and MD44% and TD50%
yielded a satisfactory percent free shrinkage of . The test film was irradiated by passing a portion of the biaxially oriented multilayer film through the electronic curtain of the irradiation unit and immediately rewinding the web. film
Experiments were performed using irradiation at various dose levels between 0.5 and 5.0 megarads. Table 1 summarizes the results of impulse heat sealing studies conducted on these films. The data show that doses as low as 0.5 megarads begin to widen the impulse seal range. 2-3
We show that the megarad irradiation dose significantly increases the upper voltage limit without significantly discoloring the film due to PVDC decomposition. At doses of 4 and 5 megarads, no further increase in upper impulse seal voltage was observed and unacceptable film discoloration occurred. The 5 megarad dose also increased the minimum seal voltage by 2 volts, narrowing the acceptable seal range.

[Table] Example The "double bubble" process disclosed in U.S. Pat. A biaxially oriented three-layer film was prepared. The multilayer film consisted of the following materials: First outer layer - EVA copolymer U Core layer - PVDC copolymer D Second outer layer - EVA copolymer F The resulting stretched multilayer film had an average thickness. difference
It had 2.5 mils (0.064mm). The film is fully biaxially stretched and MD45% and
A satisfactory free contraction of TD 46% occurred. Biaxially stretched film at 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0
Irradiated at megarad doses. Irradiation of the test film was carried out by passing a portion of the biaxially oriented multilayer film through the electronic curtain of the irradiation unit and immediately rewinding the web. Industrial field tests were conducted on bottom-sealed bags made from non-irradiated control material, 2 and 4 megarad irradiated material. Double. The subprimal red meat fillets were packaged using a commercial 8300-18 rotary evacuator-sealer available from Earle, Grace and Company Cryovac Division. Both the 2 and 4 megarad materials experienced no seal burn-through during testing. Non-irradiated control film was reduced by 65% due to high impulse seal voltage in 8300-18 evacuator.
This resulted in a burn through. The physical properties of the irradiated film described above were evaluated. The results of these evaluations are summarized in Table 2 along with the results for the non-irradiated controls.

[Table] Color Pass
Pass Pass Pass

[Table] Color Pass
Fail Fail
*MD/TD means vertical/horizontal direction.
From Table 2, it can be seen that the tensile strength of the film gradually increases as the irradiation dose level is increased from 1.0 Megarads to about 4.0 Megarads, and begins to decrease at the 5.0 Megarads dose level. A slight decrease in film shrinkage occurs at all radiation dose levels between 0.5 and 5.0 megarads. The fracture strength of the film was improved in both dynamic and hot water conditions with irradiation dose levels from 0.5 to 5.0 megarads.
More specifically, the dynamic breakdown value increases at dose levels of 1.0 megarads and above, and increases by approximately
Increased by 40%. Hot water breakdown values increased progressively at all exposure dose levels, with all film specimens surviving a maximum exposure time of 2 minutes (120 seconds) from 2.0 to 5.0 megarads. The tear strength of the irradiated films was improved when processed from 1.0 to 5.0 Megarads, and even more improved when processed from 2.0 to 4.0 Megarads, as evidenced by fracture propagation tear length values. . EXAMPLE A composition was coextruded through a multilayer die and then biaxially stretched to produce a three layer film composition using the "double bubble" process disclosed in US Pat. No. 3,456,044. After biaxial stretching, the multilayer film composition was irradiated to effect crosslinking. Film 1 has a second outer layer made of EVA copolymer F, a core layer made of PVDC copolymer K, and EVA
and a first outer layer made of copolymer U. Film 2 has a second outer layer made of EVA copolymer G, a core layer made of PVDC copolymer D, and EVA.
and a first outer layer made of copolymer U. Film 3 consists of a second outer layer made of EVA copolymer R, a core layer made of PVDC copolymer K, and EVA
and a first outer layer made of copolymer U. Three sections of multilayer film were not irradiated and were used as control materials. Other portions of the three outer films were irradiated as described in Example 1 at dose levels of 2.0 and 3.0 megarads and then evaluated for physical properties. The results of these evaluations are shown in Tables 3, 4, and 5.
summarized in.

【table】

【table】

TABLE The data listed in Tables 3, 4, and 5 show that the impulse seal range was significantly increased at the 2 and 3 Megarad exposure doses. The film color change due to PVDC degradation was minimal for all irradiated materials, making the irradiated films still acceptable for applications in the red meat and processed meat industries. The tensile strength of the films irradiated with 2 Megarads increased by an average of 7% compared to the control, and the tensile strength of the films exposed to 3 Megarads increased by an average of 14% compared to the control. The dynamic fracture strength values of the irradiated films increased by an average of about 20% at the 2 megarad dose level, and
There was an average increase of approximately 30% at megarad dose levels. The hot water fracture strength was also significantly increased. We observed at least a 200% increase in non-destructive time for films irradiated with 2 Megarads, and a 600% increase at the 3 Megarad dose level. In summary, the novel film compositions of the present invention have been shown to possess improved physical properties for use as bags in packaging primal meat cuts, and the bags have the desired heat shrink properties and heat properties in that operation. Has sealing properties. Although preferred embodiments of the invention have been described in detail, modifications may be made and certain preferred features may be adopted, all within the scope of the invention, without departing from the broader spirit and scope of the invention. It is possible that For example, polyvinylidene chloride copolymers are preferred as the film for the barrier layer, although other barrier films may be used, such as copolymers of ethylene and vinyl alcohol. Additionally, although a three layer film is shown in the example, multilayer films having more than three layers are considered within the scope of the invention if at least one of the plurality of core layers includes a barrier film.

Claims (1)

[Scope of Claims] 1. A heat-shrinkable multilayer film suitable for packaging primal and subprimal meat cuts and processed meat, comprising a first outer layer comprising a first ethylene-vinyl acetate copolymer and a barrier film. A heat shrinkable multilayer film comprising a core layer comprising a second ethylene-vinyl acetate copolymer and a second outer layer comprising a second ethylene-vinyl acetate copolymer, and wherein all layers are substantially equally irradiated to a dose level of 1 Megarad or more. 2. The heat-shrinkable multilayer film according to item 1 above, wherein the dose level of 1 to 5 megarads is 1 to 5 megarads. 3 The first ethylene-vinyl acetate copolymer is
A heat-shrinkable multilayer film according to claim 1 having a melt index of 0.1 to 1.0 decigrams/min and a vinyl acetate content of 9 to 15 weight based on the weight of the first ethylene-vinyl acetate copolymer. . 4 The first ethylene-vinyl acetate copolymer is
(a) Single ethylene-vinyl acetate copolymer and
(b) The heat-shrinkable multilayer film of claim 1 selected from the group consisting of blends of ethylene-vinyl acetate copolymers having different melt indices and different vinyl acetate contents. 5. The heat-shrinkable multilayer film according to claim 1, wherein the barrier film comprises a polyvinylidene chloride copolymer containing at least 65% by weight of polyvinylidene chloride based on the weight of the polyvinylidene chloride copolymer. . 6. A heat-shrinkable multilayer film according to claim 5, wherein the polyvinylidene chloride copolymer contains up to 5% by weight of plasticizer, based on its weight. 7. The heat-shrinkable multilayer film according to claim 5, wherein the remainder of the polyvinylidene chloride copolymer is selected from the group consisting of vinyl chloride, acrylonitrile, and acrylate ester. 8. A second ethylene-vinyl acetate copolymer in which the second outer layer has a melt index of 0.1-1.0 decigrams/min and a vinyl acetate content of 9-18% by weight based on the weight of the second ethylene-vinyl acetate copolymer. Claim 1 including combination
The heat-shrinkable multilayer film described in Section 1. 9. Claim 1, wherein the second outer layer comprises a second ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 15% by weight, based on the weight of the second ethylene-vinyl acetate copolymer. heat-shrinkable multilayer film. 10 The second ethylene-vinyl acetate copolymer comprises a blend of at least two ethylene-vinyl acetate copolymers, in which case the ethylene-vinyl acetate copolymer
one of the vinyl acetate copolymers has a melt index of 0.1 to 1.0 decigrams/min and a vinyl acetate content of 10 to 18% by weight based on the weight of the copolymer, and the ethylene-vinyl acetate copolymer A heat-shrinkable multilayer film according to claim 1, wherein one of the combinations has a melt index of 0.1 to 1.0 decigrams/min and a vinyl acetate content of 2 to 10% by weight, based on the weight of the copolymer. . 11 The second ethylene-vinyl acetate copolymer blend is 9 to 18% by weight based on the weight of the ethylene-vinyl acetate copolymer blend.
11. The heat-shrinkable multilayer film according to claim 10, having a vinyl acetate content of . 12 First outer layer is 0.028~0.041mm (1.1~1.6 mil)
The heat-shrinkable multilayer film according to claim 1, having a thickness of . 13. The heat-shrinkable multilayer film according to claim 1, wherein the core layer has a thickness of 0.0064 to 0.011 mm (0.25 to 0.45 mil). 14 Second outer layer is 0.010~0.025mm (0.4~1.0mil)
The heat-shrinkable multilayer film according to claim 1, having a thickness of . 15. The heat-shrinkable multilayer film of claim 1, wherein the film has a total thickness of 0.044 to 0.076 mm (1.75 to 3.0 mils). 16. A heat-shrinkable multilayer film according to claim 1, wherein the film is biaxially stretched and then irradiated to a dose level of 2 to 3 megarads. 17. The heat-shrinkable multilayer film according to claim 1, which is processed into a bag shape. 18 A heat-shrinkable multilayer film suitable for packaging primal and subprimal meat cuts and processed meats, comprising a first outer layer comprising a first ethylene-vinyl acetate copolymer, a core layer comprising a barrier film, and a first outer layer comprising a first ethylene-vinyl acetate copolymer; a second outer layer comprising 2 ethylene-vinyl acetate copolymer, and is biaxially oriented and then all layers are substantially equally irradiated to a dose level of 1 Megarad or more. 19 The heat-shrinkable multilayer film has the first ethylene-
a first outer layer comprising a vinyl acetate copolymer, the first ethylene-vinyl acetate copolymer having a melt index of 0.1 to 1.0 decigrams/min and a weight of the first ethylene-vinyl acetate copolymer; and the first ethylene-vinyl acetate copolymer comprises (a) a single ethylene-vinyl acetate copolymer and (b) different melt indices and a first outer layer selected from the group consisting of blends of ethylene-vinylacetate copolymers having different vinyl acetate contents; a core layer comprising a polyvinylidene chloride copolymer containing at least 65% by weight vinylidene chloride; and; a second outer layer comprising a second ethylene-vinyl acetate copolymer, the second ethylene-vinyl acetate copolymer having a melt index of (a) 0.1 to 1.0 decigrams/min; an ethylene-vinyl acetate copolymer having a vinyl acetate content of 9 to 18% by weight based on the weight of the vinyl acetate copolymer; One of the ethylene-vinyl acetate copolymers is 0.1
having a melt index of ~1.0 decigrams/min and a vinyl acetate content of 10-18% by weight based on the weight of the copolymer and other ethylene-vinyl acetate copolymers of 0.1-1.0 decigrams/min.
and a second outer layer selected from the group consisting of a blend having a vinyl acetate content of 2 to 10% by weight based on the weight of the copolymer, wherein the film is biaxially oriented. 19. The heat-shrinkable multilayer film of claim 18, wherein the heat-shrinkable multilayer film is irradiated to a dose level of 1 to 5 megarads. 20. The heat-shrinkable multilayer film of claim 19, wherein the polyvinylidene chloride copolymer contains up to 5% by weight of plasticizer, based on its weight. 21. The heat-shrinkable multilayer film according to claim 19, wherein the remainder of the polyvinylidene chloride copolymer is selected from the group consisting of vinyl chloride, acrylonitrile, and acrylate ester. 22. Claim 1, wherein the second outer layer comprises a second ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 15% by weight, based on the weight of the second ethylene-vinyl acetate copolymer.
The heat-shrinkable multilayer film according to item 9. 23 The second ethylene-vinyl acetate copolymer blend is 9 to 18% by weight based on the weight of the ethylene-vinyl acetate copolymer blend.
20. The heat-shrinkable multilayer film according to claim 19, having a vinyl acetate content of . 24 First outer layer is 0.028 to 0.041 mm (1.1 to 1.6 mil)
20. The heat-shrinkable multilayer film according to claim 19, having a thickness of . 25. The heat-shrinkable multilayer film of claim 19, wherein the core layer has a thickness of 0.0064 to 0.011 mm (0.25 to 0.45 mil). 26 Second outer layer is 0.010 to 0.025 mm (0.4 to 1.0 mil)
The heat-shrinkable multilayer film according to claim 18, having a thickness of . 27. The heat-shrinkable multilayer film of claim 19, wherein the film has a total thickness of 0.044 to 0.076 mm (1.75 to 3.0 mils). 28. The heat-shrinkable multilayer film of claim 19, wherein the film is biaxially stretched and then irradiated to a dose level of 2 to 3 megarads. 29. The heat-shrinkable multilayer film according to claim 19, which is processed into a bag shape. 30 A method for producing a multilayer film suitable for packaging primal and subprimal meat cuts and processed meat, comprising: (a) a first outer film layer comprising a monomonoethylene-vinyl acetate copolymer; and a barrier film. coextruding a core film layer comprising a core film layer and a second outer film layer comprising a second ethylene-vinyl acetate copolymer; (b) biaxially stretching the multilayer film; A method for producing a multilayer film comprising irradiating the film to a dose level of . 31. The method for producing a multilayer film according to item 30, wherein the dose level of 1 Megarad or more is 1 to 5 Megarad. 32 A claim in which the first ethylene-vinyl acetate copolymer has a melt index of 0.1 to 1.0 decigrams/min and a vinyl acetate content of 9 to 15% by weight based on the weight of the first ethylene-vinyl acetate copolymer. The method according to item 30. 33 The first ethylene-vinyl acetate copolymer is comprised of (a) a single ethylene-vinyl acetate copolymer and (b) a blend of ethylene-vinyl acetate copolymers having different melt indices and different vinyl acetate contents. 31. The method of claim 30, wherein the method is selected from the group consisting of: 34. The method of claim 30, wherein the barrier film comprises a polyvinylidene chloride copolymer containing at least 65% by weight vinylidene chloride, based on the weight of the polyvinylidene chloride copolymer. 35. The method of claim 33, wherein the vinylidene chloride copolymer contains up to 50% by weight of plasticizer, based on its weight. 36. The method of claim 33, wherein the remainder of the polyvinylidene chloride copolymer is selected from the group consisting of vinyl chloride, acrylonitrile, and acrylate esters. 37 A second ethylene-vinyl acetate copolymer in which the second outer layer has a melt index of 0.1-1.0 decigrams/min and a vinyl acetate content of 9-18% by weight based on the weight of the second ethylene-vinyl acetate copolymer. 31. The method of claim 30, comprising coalescence. 38. Claim 3, wherein the second outer layer comprises a second ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 15% by weight, based on the weight of the second ethylene-vinyl acetate copolymer.
The method described in item 0. 39 The second ethylene-vinyl acetate copolymer comprises a blend of at least two ethylene-vinyl acetate copolymers, in which case the ethylene-vinyl acetate copolymer
one of the vinyl acetate copolymers has a melt index of 0.1 to 1.0 decigrams/min and a vinyl acetate content of 10 to 18% by weight based on the weight of the copolymer, and the ethylene-vinyl acetate copolymer 31. The method of claim 30, wherein one of the coalesces has a melt index of 0.1 to 1.0 decigrams/min and a vinyl acetate content of 2 to 10% by weight, based on the weight of the copolymer. 40 The second ethylene-vinyl acetate copolymer blend is 9 to 18% by weight based on the weight of the ethylene-vinyl acetate copolymer blend.
40. The method of claim 39, having a vinyl acetate content of . 41 First outer layer is 0.028-0.041mm (1.1-1.6 mil)
31. The method of claim 30, having a thickness of . 42 First core layer is 0.0064~0.011mm (0.25~
Claim 30 having a thickness of 0.45 mils)
The method described in section. 43 Second outer layer is 0.010~0.025mm (0.4~1.0mil)
31. The method of claim 30, having a thickness of . 44 Multilayer film is 0.044~0.076mm (1.75~3.0
31. The method of claim 30, having a total thickness of 100 mils. 45 Multilayer film is biaxially stretched, then 2~
31. The method of claim 30, irradiated to a dose level of 3 megarads. 46. The method of claim 30, comprising processing the multilayer film into a bag. 47. The method of claim 30, wherein the coextrusion of the film layers produces a multilayer film sheet. 48. The method of claim 30, wherein coextrusion of the film layers produces a multilayer tubular film. 49. A method for producing a multilayer film suitable for packaging primal and subprimal meat cuts and processed meats, comprising: (a) a first outer film layer comprising a monomonoethylene-vinyl acetate copolymer; The first ethylene-vinyl acetate copolymer has a melt index of 0.1-1.0 decigrams/min and a vinyl acetate content of 9-15% by weight based on the weight of the first ethylene-vinyl acetate copolymer. , and the first ethylene-vinyl acetate copolymer comprises (a) a single ethylene-vinyl acetate copolymer and (b) an ethylene-vinyl acetate copolymer having different melt indexes and different vinyl acetate contents. a first outer film layer selected from the group consisting of a blend of; a core film layer comprising a polyvinylidene chloride copolymer containing at least 65% by weight vinylidene chloride; a second ethylene-vinylacetate copolymer; a second outer film layer comprising: (a) a melt index of 0.1 to 1.0 decigrams/min; and a weight of the second ethylene-vinyl acetate copolymer; (b) a blend of at least two ethylene-vinyl acetate copolymers, with a vinyl acetate content of 9 to 18% by weight as a basis; One is based on the melt index of 0.1 to 1.0 decigrams/min and the weight of the copolymer.
~18% by weight vinyl acetate content and other ethylene-vinyl acetate copolymers
coextrusion with a second outer film layer such as selected from the group consisting of a blend having a melt index of 0.1 to 1.0 decigrams/min and a vinyl acetate content of 2 to 10% by weight based on the weight of the copolymer. 31. The method of claim 30, comprising: (b) biaxially stretching said multilayer film; and (c) irradiating said multilayer film to a dose level of 1 to 5 megarads. 50. The method of claim 49, wherein the polyvinylidene chloride copolymer contains up to 5% by weight of plasticizer, based on its weight. 51. The method of claim 49, wherein the remainder of the polyvinylidene chloride copolymer is selected from the group consisting of vinyl chloride, acrylonitrile, and acrylate esters. 52 Claim 4, wherein the second outer layer comprises a second ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 15% by weight, based on the weight of the second ethylene-vinyl acetate copolymer.
The method described in Section 9. 53. The method of claim 49, wherein the second ethylene-vinyl acetate copolymer blend has a vinyl acetate content of 9 to 18% by weight, based on the weight of the ethylene-vinyl acetate copolymer blend. 54 First outer layer is 0.028-0.041mm (1.1-1.6 mil)
50. The method of claim 49, having a thickness of . 55. The method of claim 49, wherein the core layer has a thickness of 0.25 to 0.45 mils. 56 Second outer layer is 0.010~0.025mm (0.4~1.0mil)
50. The method of claim 49, having a thickness of . 57 Multilayer film is 0.044~0.076mm (1.75~3.0
50. The method of claim 49, having a total thickness of 100 mils. 58 Multilayer film is biaxially stretched, then 2~
50. The method of claim 49, wherein the irradiation is to a dose level of 3 megarads. 59. The method of claim 49, comprising processing the multilayer film into a bag. 50. The method of claim 49, wherein coextrusion of 60 film layers produces a multilayer film sheet. 61. The method of claim 49, wherein coextrusion of the film layers produces a multilayer tubular film.