JPH0450903B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates generally to thermoplastic packaging films. In particular, the present invention comprises one or two surface layers of a composition prepared by blending one or more copolymers of ethylene and vinyl acetate with a linear low density polyethylene material. , relates to a heat-shrinkable thermoplastic film. This blend greatly improves the resistance of the film to attack, fracture and/or degradation caused by contact with mineral oil, for example. Such films commonly come into contact with mineral oil and other oils when used to package food products and, in particular, meat products containing fats. The present invention relates to novel and useful film surface layer formulations and film layer combinations.
One distinguishing characteristic of a shrunken film is its ability to generate shrinkage tension within the film when it shrinks or is inhibited from shrinking when exposed to a certain temperature. The production of shrunken films is generally accomplished by extruding a resin material heated to its pour or melting point through an extrusion die in tubular or flat form, as is well known in the art. . After extrusion, the extrudate is quenched and then reheated to its orientation temperature range and stretched to orient the molecular configuration of the material and physically stretch it. The orientation temperature is 1
or will vary with the polymers of different resins and blends thereof making up the two or more layers. Generally, the orientation temperature of the material can be stated to be above room temperature and below the melting point of the film. "Orientation" or "oriented" refers to stretching a resinous polymeric material heated to an orientation temperature range and then immediately cooled so that the physical alignment and elongation of its molecules results in a certain mechanical alignment of the film. Used herein to describe the properties of the process and the resulting products obtained by improving their properties. Examples of these properties are contraction tension and oriented release stress. These specific properties can be determined according to ASTM-D 2838-69 (Reapproved 1975). Applying a stretching force in one direction results in uniaxial orientation. Biaxial orientation is obtained when stretching forces are applied in two directions simultaneously. Orientation is also referred to herein as "heat shrinkable" or "heat shrinkable"
and used interchangeably, these terms refer to a material that has been stretched, oriented, and fixed by cooling while in the stretched dimension. An oriented (ie, heat-shrinkable) material will tend to return to its original unstretched (unstretched) dimensions when heated to a suitable temperature below its melting point range. Returning to the basic method of manufacturing the aforementioned film, it is understood that once the film is extruded and first quenched, it is then reheated to its orientation temperature range and oriented by stretching as desired. It will be possible. Stretching for orientation can be done in many ways, for example (blown bubble
``bubble'' technology or ``tenter''
This can be achieved by ``framing''. These methods are well known in this field;
and relates to various methods of stretching materials in the transverse direction (TD) and/or machine direction (MD). After stretching the film, e.g.
Rapid cooling is achieved by quenching with cold water, thus fixing the oriented configuration of the molecules in an extended configuration or immobilizing them. Of course, if a film with little or no orientation is desired, such as a non-heat shrinkable film, the film can be heat blow molded. When forming a hot blown film, the film is not cooled after extrusion, but rather the film is stretched immediately after extrusion while the film is still hot. This method is well known in the art and the resulting films have substantially non-oriented properties. Other methods of forming non-oriented films are well known. An example is cast extrusion. After forming, the film can be stored in rolls and then used for tight packaging of various articles. For example, the product to be packaged can be placed into a bag formed by means well known in the art, or the product can be wrapped in a heat-shrinkable material and then optionally heat-sealed to itself. and surround the product. The wrapped product can then be exposed to vacuum and/or high temperatures, for example, by passing the product through a vacuum chamber and then through a tunnel of hot air or hot water. The high temperature within the tunnel causes the film to shrink around the product when oriented, creating a gap-free package that closely conforms to the product's contours. The above overview of producing films and subsequently using them to package products is intended to encompass all of the various methods as these are well known in the art. do not have. For example, U.S. Patent No. 42749000;
4229241, 4194039, 4188443, 4048428, 3821182 and 3022543
See issue. The disclosures of these patents are incorporated herein by reference. Another way to make this type of film is
Well known in this field. One well-known alternative method is to form multilayer films by extrusion coating rather than coextrusion. In extrusion coating, a first tubular layer is extruded and then additional layers are coated onto the outer surface of the first tubular layer or successive layers. An example of this method is US Pat. No. 3,741,253. This patent, as well
Add by citation. Many other variations are well known in the art. For example, multiple layers can be first coextruded with additional layers and then extrusion coated thereon. Alternatively, two multilayer tubes can be coextruded with an additional tube and then sequentially extrusion coated onto the other. When one or more layers of a film are to be subjected to a treatment that may be detrimental to other layers, extrusion coating methods of film formation are preferred for coextruding the entire film. Such is the case when it is desired to irradiate one or more layers of the film containing an oxygen barrier layer composed of one or more copolymers of vinylidene chloride and vinyl chloride. It is generally recognized in the art that irradiation is detrimental to the structure of such oxygen barrier layers. Therefore, by extrusion coating, the first
extruding or coextruding one or more of the layers, exposing said layers to the action of radiation, then extrusion coating the oxygen barrier layer and, for that matter, extrusion coating the other layers onto the outer surface of the extruded tube. can do. As a result, 1 of the first layer
Alternatively, cross-linking of two or more irradiations is possible without exposing the oxygen barrier layer to the deleterious effects of the irradiation. Irradiation of the film layer increases the abuse resistance and/or puncture of the film.
Desired to try to improve resistance and other properties. It is generally well known in the art that irradiation of a material cross-links the polymer chains contained therein, and that such effects generally result in materials having improved abuse resistance. When cross-linking is achieved, it is accomplished through the use of high-energy radiation using electrons, x-rays, gamma rays, beta rays, and the like.
Preferably, electrons with an energy of at least 10 <sup>4</sup> electron volts are used. The irradiation source is a van de Graff electron accelerator, for example, 2000000 with an output of 500 watts.
A bolt-operated device can be used. Or General Electric (General
Electric) 2000000 volt resonant transformer or corresponding 1000000
Other high energy electron sources can be used, such as a volt, 4 kilowatt resonant transformer. The voltage can be 10000 or 2000000 or 6000000 volts or higher. Many other devices for irradiating film are well known in the art. Irradiation is usually carried out at a dose of between 1 and 75 megarads, preferably between 8 and 20 megarads. Irradiation can conveniently be carried out at room temperature, although higher and lower temperatures can be used, for example from 0<0>C to 60<0>C. Also,
Crosslinking can be achieved scientifically by the use of peroxides, as is well known. The polyolefin family of shrink films, particularly the polyethylene family, exhibits a wide range of physical and performance properties, such as "shrink force" (the amount of force a film exerts per unit of its cross-sectional area during shrinkage), "free shrinkage" ( When the material is exposed to high temperatures without restraint,
"tensile strength" (the highest force that can be applied to a unit area of the film before the film tears); ``shrinkage temperature curve'' (shrinkage vs. temperature); ``tear initiation and resistance'' (forces at which the film begins to tear and continues to tear); ``optics'' (the ability to seal to itself or to other surfaces); gloss, haze and transparency of the material), and dimensional stability (the ability of the film to retain its original dimensions under various storage conditions). One particularly desirable property that films used in connection with meat products should exhibit is resistance to attack (e.g., decomposition and/or breakage) from mineral oils or other oily substances that may come into contact with the film during the packaging process. ). Since such degradation of the film substantially reduces the effectiveness of the film in performing its function, there continues to be a search for films with improved resistance to such attacks. The search for films with improved oil resistance has focused on at least one area. In particular, many of the films utilized for the packaging of fresh red meat and other fatty substances contain a surface layer that is a copolymer of ethylene and vinyl acetate or a blend of one or more such copolymers. . An unsuitable drawback traditionally associated with such materials is the fact that these materials are easily attacked and degraded on contact with mineral oil. This fact is inappropriate. This is because many meat packaging machines use mineral oil as their cleaning and maintenance fluid. Therefore, it is difficult, if not impossible, to prevent the film from coming into contact with mineral oil during the packaging process.
Have difficulty. Thus, in the past, prior art films having a surface layer of ethylene vinyl acetate copolymer were often used in conjunction with packaging machines that were cleaned and/or maintained by utilizing mineral oil, resulting in It has been subjected to decomposition. It is therefore a general object of the present invention to provide polyolefin films that are improved over films already used in the prior art. A particular object of the present invention is to provide a polyolefin-in-film having a surface layer with greatly increased resistance to attack and/or degradation upon contact with mineral oil. Another object of the present invention is to provide a surface layer composition comprising a blend of one or more ethylene vinyl acetate copolymers and a linear low density polyethylene material. A further object of the present invention is to provide a multilayer shrinkable film having an outer surface layer consisting of a blend of one or more ethylene vinyl acetate copolymers with a linear low density polyethylene material. Further objects and wide range of applicability of the present invention will become apparent from the detailed description hereinafter disclosed. However, the following detailed description of some preferred embodiments of the invention:
Various modifications and changes within the scope of the invention will be apparent to those skilled in the art upon reviewing the following detailed description.
It should be understood that this is for illustrative purposes only.
Such modifications and variations are included within the scope of the claims. As used herein, "polymer" unless specifically stated and defined or otherwise limited.
Alternatively, "polymeric resin" includes homopolymers, copolymers, terpolymers, block and graft polymers, random polymers and alternating polymers. As used herein, "melt flow" or "melt flow index" refers to the amount of heat that can be forced through a given orifice within 10 minutes at a specified pressure and temperature, as described in ASTM-D1238. It is the amount (g) of plastic resin. As used herein, "barrier" or "barrier layer" refers to a layer of a multilayer film that acts as a physical barrier to gaseous oxygen molecules. Typically, the barrier layer material is heated to 1 atm and 22.8°C.
(73〓) and 0% relative temperature would reduce the oxygen permeability of the film to less than 70 c.c./m ² within 24 hours. These values are ASTM standard
Should be obtained according to D1434. "Middle" or "middle layer" as used here is:
Refers to the layer of multilayer film located between the surface layer of the barrier layer. “Surface” or “surface layer” as used here means
Refers to the layers of a multilayer film that constitute one surface of the film. "Linear low-density polyethylene" used here
(LLDPE) is a molecule consisting of long chains with few side chains or cross-linking structures, consisting of ethylene and _C4 ~
C ₁₀ Alphaolefin means a copolymer with one or more comonomers selected from, for example, butene-1, octene, and the like. The side chains present are short compared to non-linear polyethylene. Linear low density polyethylene usually has a density of about 0.900 to about 0.940 g/cc and preferably the density should be maintained between 0.816 and 0.928 g/cc for film manufacturing purposes. Density should be measured according to ASTM-D792. The melt flow index of linear low density polyethylene is about 0.1 to 10 g/10 min, preferably about
It should be within the range of 0.5 to about 3.0 g/10 minutes.
This type of linear low density polyethylene is commercially available and is produced by low pressure vapor phase and liquid phase processes using transition metal catalysts. As used herein, "ethylene vinyl acetate copolymer" (EVA) means a copolymer formed from ethylene and vinyl acetate, in which ethylene-derived units are present in a major amount and vinyl acetate-derived units are present in a minor amount. . An "oriented" or "heat-shrinkable" material is defined herein as a material that has a free shrinkage of 5% or more in at least one direction when heated to a suitable temperature above room temperature (e.g., 96° C.). Free shrinkage should be measured according to ASTM-D2732. All composition percentages used herein are by weight. One rad is the amount of ionizing radiation that results in the absorption of 100 ergs of energy per gram of irradiated material, ignoring the irradiation source. One megarad is ¹⁰⁶ rads. (MR is an abbreviation for Megarad). A flexible, preferably heat-shrinkable, thermoplastic packaging film having improved resistance to attack and degradation on contact with mineral oils and other oils is made from one or more ethylene vinyl acetate copolymers. It has been discovered that this can be obtained by providing a film with a surface layer composed of a blend of a linear low density polyethylene material and a linear low density polyethylene material. In particular, it has been determined that the resistance to mineral oil attack by such surface materials is additively improved when the percentage of vinyl acetate within the blend is less than about 11.5% by weight. Preferably, the multilayer filter is stretched and oriented to be heat shrinkable in at least one direction. One preferred embodiment of the film of the present invention comprises, in the order described, (a) approximately 90% by weight of an ethylene vinyl acetate copolymer having approximately 8.9% by weight vinyl acetate derived units and approximately 10% by weight of a linear low density polyethylene material; (b) an oxygen barrier layer consisting of a blend of two different vinylidene chloride copolymers/vinyl chloride copolymers; (c) approximately 20% by weight vinyl acetate; Approximately 60% by weight and approximately 8.9% by weight of primary ethylene vinyl acetate copolymer with derivatized units
and (d) approximately 40% by weight of a secondary ethylene vinyl acetate copolymer having vinyl acetate-derived units of approximately 6.2
The second surface layer consists of an ethylene-vinyl acetate copolymer having % by weight of vinyl acetate-derived units, and is a four-layer polyolefin-in-film structure. Preferably, the third and fourth layers are crosslinked by applying approximately 4.5 MR of radiation. Other preferred total film structure embodiments are shown in the examples with formulated surface layers disclosed in the table below. Of course, additional layers can be added to improve other properties of the film. Naturally, the mineral oil resistant layer should be maintained as an outer surface layer to provide adequate oil resistance. For the purpose of illustrating the principles of the invention, as described below:
27 different samples were prepared and analyzed. The complete layer-to-layer structure of each of these samples is shown in the table below.

【table】

【table】

[Table] With the exception of linear low-density polyethylene sample AA, and with the possible exception of samples, all of the other samples, e.g. samples A-H and J-
Z was manufactured as follows. First, the layers and were coextruded as tubes. Then these 2
The layer was treated by irradiating it to an irradiation level of approximately 4.5MR. After irradiation of the layers and, the layers and were coextruded as a tube, and then the inner surface of the layer (with the coextruded layer) was extrusion coated onto the outer surface of the layer. This resulted in a four-layer tubular film consisting of, in the order listed, the layers, and. The four-layer tube was then processed according to the blow molding bubble technique to produce a stretch-oriented heat-shrinkable film. The resulting film had a thickness of approximately 2.3 mils after stretch compounding.
The only exception to this statement concerns samples AA and Q. In those cases, the film was approximately 1.5 mils thick after stretch orientation. Added linear low density polyethylene material
To demonstrate the significantly and synergistically improved resistance of EVA to degradation from contact with mineral oil,
Two different tests were devised. The first test was a visual test conducted as follows: (1) A small amount of material oil was applied to the outer surface of the sample (e.g.
(EVA/lldpe blend surface). (2) The contaminated area was placed over the mouth of a small beaker whose inside was contaminated. (3) A rubber band was then placed over the film in the lip above the beaker to secure the film to the beaker. (4) Next, invert the beaker and heat it to 93.3℃ (200〓).
The water was kept in contact with the surface for 1 second at a temperature of . It has been observed that after several attacks with mineral oil, the mineral oil applied surface becomes cloudy and rough and can even be removed by scratching with a fingernail. It was possible to observe varying degrees of oil attack on different materials. In this regard, the following visual standards were constantly used by the same individual in determining the resistance of the samples to oil attack.

[Front] The surface can be lightly scratched with a fingernail.
It can be removed by
In order to create an objective means of evaluating the damage caused to a given sample by mineral oil attack and to eliminate the subjectivity associated with visual grades, the following tests were devised and performed on some of the samples. The evaluation was done using a Hunter Color Difference meter.
The test was carried out using a D25D2 type meter.
This instrument can measure changes in color or brightness (L value), where "0" equals pure black and 100 equals pure white. Changes in brightness or haze can be measured and can represent varying levels of whitening or haze associated with film deterioration and thus can be related to the degree of mineral oil attack to which the sample has been subjected. . This test was conducted in the following manner: (1) The machine was calibrated according to the manufacturer's specified procedure. (2) An unattached section of the sample to be tested was placed on a black standard attached to the machine and located below the viewing port of the instrument. This material was made into a flat shape along with a black standard. All foreign material was wiped away from the sample. (3) Set the machine to the "L" scale and read and record the "L" value drawn on the dial of the machine. (4) A small amount of mineral oil “Lubinol MF” (Purepac
Pharmaceutical Company, Elizabeth, New
(obtained from Jersey) on the outside of the sample.
Applied to the surface of EVA/lldpe blend or EVA comparison material. 2 or 3 drops are 8.9cm in diameter
(3.5 inches) was sufficient to cover the sample area. Mineral oil was spread over the sample area with a cotton swab. (5) The sample area was placed over the open end of a 4-5 inch diameter beaker with the mineral oil facing the interior of the beaker. The film was secured to the beaker by a rubber band applied tightly just below the lip of the beaker. (6) The beaker with the film attached was inverted, and the film was brought into contact with the surface of water heated to 93.3°C (200°C) for 1 second. Significant mineral oil attack will be manifested by the appearance of dramatic whitening on the surface to which mineral oil has been applied. Depending on the resistance or susceptibility of different materials to oil attack, varying degrees of attack can be observed for those materials. (7) The film was separated from the beaker and placed in a Hunter D25D2, taking care not to disturb the attacked sample area of the film. Point the attacked surface at the light source of D25D2,
A second "L" value reading was then obtained. (8) The initial unattacked "L" value was subtracted from the final unattacked "L" value of the processed film. The resulting "Delta L" value is a measure of the change in lightness of the film from unattacked to attacked, and is believed to represent the degree to which the sample is attacked by the mineral oil. The table below displays the film samples in alpha ablation, identifies the composition of the surface layer attacked by mineral oil, describes the percentage of vinyl acetate in the sample of the attacked surface layer, and describes the percentage of vinyl acetate applied to the sample after oil attack. The visual ratings given are listed and, for the samples for which the data were provided, the "Delta L" value of the instrument used to grade the samples is listed.

【table】

Tables Figures 1, 2 and 3 graphically represent tables and the data contained therein. FIG. 1 plots the visual rating of resistance of a given material to mineral oil attack versus the percentage of linear low density polyethylene material in the attacked surface layer. The three curves represent the varying resistance to mineral oil attack of the three different EVA materials plotted in FIG. The bottom dashed curve demonstrates a very rapid resistance to mineral oil attack for an EVA material with approximately 6.2% initial unblended vinyl acetate derived units (monomer). The central dot/dassel line reflects the varying degree of mineral oil attack on the EVA material, where the initial unblended vinyl acetate derived unit (monomer) percentage is approximately 8.9%. The solid line above is approximately 12
% shows the varying resistance to mineral oil attack of EVA materials with a percentage of initial unblended vinyl acetate derived units (monomer). data point Z
were collected for an EVA material consisting of approximately 18% by weight vinyl acetate derived units in its original unblended form. Looking at FIG. 1, it is clear that all of the standard (unblended) comparative samples A-I had poor resistance to mineral oil attack. Addition of a very small proportion of linear low density polyethylene to an EVA copolymer having approximately 6.2% vinyl acetate derived units improved mineral oil resistance very significantly. (For example, see point J, which is a sample improved to have extremely good mineral oil resistance (grade 1) by adding only 10% by weight of linear low-density polyethylene.) Also, as is clear from Figure 1, , the use of an ethylene vinyl acetate copolymer with approximately 9% by weight vinyl acetate-derived units in the blend to provide resistance to mineral oil attack ranging from very good (grade 2) to excellent (grade 1). It is necessary to increase the addition ratio of linear low density polyethylene. (Sample points L, O,
See K and P. ) Finally, as is also clear from Figure 1, in order to bring the resistance of such materials to mineral oil attack into the range of very good (class 2) to excellent (class 1), approximately Even higher amounts of linear low density polyethylene must be added to the ethylene vinyl acetate copolymer having a percentage of vinyl acetate of 12%.
(See, for example, point W on the sample.) As is clear from the above description and from Figure 1, the resistance of a given EVA material to attack from mineral oil and the resistance of vinyl acetate and linear low density polyethylene in the formulated material. There is a correlation between both percentages. Therefore, FIG. 2 and FIG.
Plot the instrumental (delta L value) grade versus percentage of vinyl acetate in the blend and visual grade versus percentage of vinyl acetate in the blend, respectively. These two drawings demonstrate a clear comparability in the resistance to mineral oil attack of blends of ethylene vinyl acetate copolymer and linear low density polyethylene material compared to ethylene vinyl acetate copolymer containing no linear low density polyethylene material. Prove the improvement graphically. Moreover, FIG. 3 further clearly shows that the additive effect is limited within a certain range of weight percent of vinyl acetate-derived units in the blend. With particular reference to Figure 2, it can be seen that for the three non-blends (e.g. EVA copolymer without linear low density polyethylene), the delta L values obtained by the instrument readings defined above are all very high. it is obvious. Delta L value obtained 3
Types of non-blends are Samples A, E and I.
These materials initially contained approximately 6.2% vinyl acetate, 8.9% vinyl acetate, and 12% vinyl acetate monomer, respectively. The line drawn in Figure 2 is.
The extrapolated delta L values expected for ethylene vinyl acetate copolymers with the indicated percentages of vinyl acetate are determined. Points J, T, U, V, Y,
Y, and Z all account for the delta L values obtained for EVA materials with formulated linear low density polyethylene materials. These samples were plotted as a percentage of vinyl acetate at the blend point. In other words, the percent polymerization of the vinyl acetate-derived components (eg, monomers) of the blend as a whole was calculated and the samples were plotted at that point. This data specifically reveals that in all cases the delta L values of blends containing linear low density polyethylene are improved over the delta L values of ethylene vinyl acetate copolymers. Negative 7.2 for point Z in Figure 2
We would like to point out that this reading seems plausible in that the unattacked material is somewhat hazy and the application of mineral oil to the surface improves the clarity of the material. Therefore, the delta L value at point Z should be ignored, although in our opinion it appears to represent a dramatic improvement. Point AA reveals the delta L value for sample AA, where the surface attacked was entirely linear low density polyethylene material. FIG. 3 plots the visual grade for all mineral oil attack of the sample versus the weight percent of vinyl acetate-derived units in the blend. As can be seen in Figure 3, all of the unblended comparative materials, Samples A, B, C, D, E, F, G, H, and I, have inferior resistance to mineral oil attack. visually graded as Therefore, a horizontal line at OK (grade 5) on the vertical axis was drawn to define the expected visual grade for all ethylene vinyl acetate copolymers. Visual data for all other samples are plotted in FIG. A computer generated quadratic curve using statistical least squares and with a 95% confidence coefficient was plotted for points representing the data for the blend samples. As this curve clearly shows, the resistance to mineral oil attack of the ethylene vinyl acetate copolymer with the addition of linear low density polyethylene material was significantly and additively improved. Also, as Figure 3 clearly shows, no additive effect occurs when the weight percent of vinyl acetate in the blend is greater than approximately 11.5%. Furthermore, very significant improvements, such as a visual rating of 1 or 2, are found in blends where the weight percentage of vinyl acetate in the blend is less than 8%. From the above data, it is very clear that when adding a small amount of linear low density material and when the percentage of vinyl acetate derived units in the blend is less than 11.5% by weight, most preferably less than 8% by weight ,
A compounding effect occurs with respect to the resistance of the ethylene vinyl acetate copolymer to mineral oil attack. This discovery is of critical importance to the meat packaging industry, and for that matter any industry that uses flexible packaging materials with machinery that is cleaned or lubricated using mineral oil. Thus, when the improved formulated material of the present invention is used as the outer layer of a packaging film, the overall resistance of the film to attack and degradation by contact with mineral oil is greatly improved. thus,
In its widest range of applications, the present invention consists of blends of one or more ethylene vinyl acetate copolymers with linear low density polyethylene materials in which ethylene vinyl acetate derived units represent no more than 11.5% by weight of the blend. Includes the use of any film material with an outer mineral oil resistant layer. This surface layer material can be utilized in conjunction with a number of other layers to
Composite film products with desired physical properties can be obtained. As mentioned above, a preferred embodiment of the present invention having an overall preferred group of physical properties is approximately 8.9
It consists of using a blend of ethylene vinyl acetate copolymer having % vinyl acetate-derived units by weight and 10% linear low density polyethylene material as the first surface layer of a four-layer film, where the second layer is an oxygen barrier. layer and constitute an oxygen barrier blend as defined above in the table. Also,
A preferred embodiment includes a third layer and a fourth layer, both of which are cross-linked by irradiation to approximately 4.5 MR. The third intermediate layer comprises approximately 60% by weight of an ethylene vinyl acetate copolymer having approximately 20% by weight of vinyl acetate derived units and approximately 40% by weight of a second ethylene vinyl acetate copolymer having approximately 9% by weight of vinyl acetate derived units. Consisting of a blend with %. The fourth inner surface layer is approximately 6.2%
It consists of an ethylene vinyl acetate copolymer having vinyl acetate-derived units of . This particular preferred embodiment not only demonstrates improved resistance to mineral oil attack as described above, but also demonstrates many other physical properties desired in a flexible packaging film. Other embodiments of the invention and their properties are described in Tables, Tables and Samples J to Z of Tables
It is represented by Many of these samples demonstrate very satisfactory optics. Of course, good optics is a highly desirable physical property in packaging films. Therefore, preferred embodiments of the invention are selected from films that demonstrate better overall optics. As is readily recognized in the field, certain optical properties are related to the overall structure of the film (e.g., total transmission).
Some, on the other hand, are directly related to the material utilized as the surface layer of the film (eg, gloss). Since high gloss is highly desirable, preferred embodiments of the surface layer blends of the present invention will have a gloss of greater than 70%, more preferably greater than 80%. The average optics for the samples are detailed in the table below:

TABLE The data above represent average values obtained by collecting measurements from four replicate experiments. The above detailed description and specific examples depicting presently preferred embodiments of the invention are intended to be illustrative, as various changes and modifications will become apparent to those skilled in the art upon viewing thereof and within the spirit and scope of the invention. It should be understood that this is only for the purpose of

[Brief explanation of the drawing]

FIG. 1 provides visual data showing improved resistance to attack and/or degradation from contact with mineral oil associated with a film layer formulation consisting of a blend of linear low density polyethylene material and ethylene vinyl acetate copolymer. This is a graph of Figure 1 shows
Figure 2 is a plot of the visual rating of the resistance of a film surface layer to mineral oil attack versus the percentage of linear low density polyethylene in the surface layer. FIG. 2 is a set of instrumental data showing the complementary resistance to attack and/or degradation from contact with mineral oil associated with a film layer formulation consisting of a blend of linear low density polyethylene material and ethylene vinyl acetate copolymer. It is a graph. Figure 2 shows the delta “L” of the film surface layer.
Figure 2 is a plot of value grade versus percentage of linear low density polyethylene in the surface layer. A comparison is made of the unblended ethylene vinyl acetate standard and the blend. FIG. 3 provides visual data showing the complementary resistance to attack and/or degradation from contact with mineral oil associated with a film layer formulation consisting of a blend of linear low density polyethylene material and ethylene vinyl acetate copolymer. It is a graph. FIG. 3 is a plot of the visual rating of the resistance of a film surface layer to mineral oil attack versus the percentage of linear low density polyethylene in the surface layer. A comparison is made of the unblended ethylene vinyl acetate standard and the blend.

Claims (1)

[Claims] 1. A surface layer resistant to degradation by mineral oil, said surface layer consisting of a blend of: one or more ethylene vinyl acetate copolymers; and linear low density polyethylene. , the vinyl acetate monomer present in the blend is 11.5% by weight of the blend.
1. A polyolefin in-film comprising: a polyolefin film having a polyolefin structure, and being heat-shrinkable. 2 having a surface layer resistant to degradation by mineral oil, said surface layer consisting of a blend of one or more ethylene vinyl acetate copolymers, and linear low density polyethylene, present in said blend; A polyolefin-in-film characterized in that the vinyl acetate monomer comprises less than 8% by weight of said blend and is heat shrinkable. 3 Approximately 90% by weight of ethylene vinyl acetate copolymer with approximately 8.9% by weight vinyl acetate derived units
an oxygen barrier layer consisting of a blend of two different vinylidene chloride/vinyl chloride copolymers, having approximately 20% by weight vinyl acetate-derived units. Approximately 60% by weight of primary ethylene vinyl acetate copolymer
and approximately 40% by weight of a secondary ethylene vinyl acetate copolymer having approximately 8.9% by weight vinyl acetate-derived units; and a cross-linked ethylene vinyl acetate copolymer having approximately 6.2% by weight vinyl acetate-derived units. A four-layer polyolefin in-film comprising: a second surface layer comprising a copolymer; and being heat-shrinkable. 4. The film according to claim 1 or 2, wherein the surface layer is crosslinked. 5. The film of claim 1 or 2, wherein the surface layer has a delta L value of less than 20. 6. The film according to claim 1 or 2, wherein the surface layer has a gloss of greater than 70%. 7. The film according to claim 1 or 2, wherein the surface layer has a gloss of greater than 80%. 8. A film according to any one of claims 1, 2 and 3, wherein the crosslinking layer is crosslinked by applying approximately 4.5MR. 9. A bag formed from the film according to any one of claims 1, 2 and 3 and adapted for packaging a product. 10. The film of claim 3, wherein said surface layer has a delta L value of less than 20. 11. The film according to claim 3, wherein the surface layer has a gloss of greater than 70%. 12. The film according to claim 3, wherein the surface layer has a gloss of greater than 80%.