JPS609738A - Polyolefin film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to a thermoplastic packaging film. In particular, the present invention provides a single layer of a composition prepared by blending eleven or more ethylene and vinyl acetate copolymers with a linear low density polyethylene material.
! ! For thermoplastic packaging films consisting of one or two surface layers, this blend significantly improves the resistance of the film to attack, breakage and/or degradation resulting from contact with, for example, mineral oil. )
The present invention provides a novel and useful film surface layer formulation which, when used for packaging food products in general and, in particular, meat products containing fat, comes into contact with mineral oil and other oils. and regarding combinations of film layers.

In one embodiment, one film formulation can be heat shrinkable. One distinguishing feature of a shrunken film is its ability to generate shrinkage tension within the film when exposed to a certain degree of shrinkage (or when shrinkage is suppressed).

The production of shrunken films is generally accomplished by extruding a washed resin material heated to its pour or melting point in tubular or flat form through an extrusion die, as is well known in the art. Ru. Rapid cooling after extrusion 1
The extrudate is then reheated to its orientation temperature range and stretched once to orient the molecular configuration of the material and physically stretch it.

The orientation temperature will vary with the different resin polymers and blends thereof that make up one or more layers of the film, generally the orientation temperature of one material is above room temperature and at a humidity below the melting point of the film. It can be stated that

[orientation or "oriented" refers to stretching a polymeric material of nine resins by heating it to an orientation temperature range and immediately cooling it to form a film with a machine by physical alignment and stretching of its molecules. Examples of these properties are contraction tension and oriented release stress. Specific properties of these 6- can be measured according to ASTM-D 2838-69 (Reapproved 1975). Applying a stretching force in one direction will give a -axial orientation. Applying a stretching force in two directions simultaneously will give a biaxial orientation. Orientation is also used interchangeably herein with "heat-shrinkable" or "heat-shrinkable," and these terms refer to a material that is stretched to oriented and fixed by cooling while in the stretched dimension. View ingredients. An oriented -fC, (i.e., 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 producing the film described above, the film, once extruded and initially quenched, is then reheated to its orientation temperature range and oriented by stretching as desired. As will be appreciated, stretching for orientation can be accomplished in a number of ways, such as the S (blown bubble) J technique or the "tenter" technique.
tenterframing) J. These methods are well known in the art and involve various methods of stretching materials in the transverse direction (TD) and/or machine direction (MD). After stretching - the film is Alternatively, rapid cooling is achieved, for example by quenching with cold water, thus fixing the oriented configuration of the molecules in an extended configuration or immobilizing them.

Of course, if you want a film with little or no orientation, e.g., a non-heat shrinkable film,
The film can be hot suction molded. When forming a hot-breathed film, the film is not cooled after extrusion;
Rather, the film is stretched while it is still hot after a short period of extrusion. This method is well known in the art and the resulting films have substantially non-oriented properties. Other methods of forming unoriented films include cast extrusion, one well-known example.
extrusion) te, sru.

After forming, the film can be stored in rolls and then used to tightly package various articles. For example, the product to be packaged can be placed in a bag formed by means well known in the art, or the product can be wrapped in a heat-shrinkable material and then heat-sealed as needed. The wrapped product is then subjected to a vacuum and/or hot water tunnel, for example by passing the product through a vacuum chamber and then through a tunnel of hot air or hot water.
or can be exposed to high temperatures. The high temperature within the tunnel causes the film to shrink around the product when oriented, producing a gap-free package that closely conforms to the product's contours.

9- 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. Nos. 4,274,900 and 4.229.241, 4.1q. o: No. 59, No. 4.18a
No. 445, No. 4.04a428, No. 3,821,
No. 182 and No. 4022,543, the disclosures of these patents are incorporated herein by reference.

Other methods of making films of this type are well known in the art. 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 - then an additional layer is applied to the first tubular layer.
Coating onto the outer surface of the tubular layer or continuous layer. An example of this method is US-1Ro Patent No. 3,741,253, which is also incorporated by reference.

Many other variations are well known in the art.

For example, a multilayer can be first coextruded with additional layers and then extrusion coated thereon. Or 2
The actual multilayer tube can be coextruded with additional tubes and then extrusion coated sequentially 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 to coextrude the entire film; in such cases, vinylidene chloride and This is the case when attempting to irradiate one or more layers of a film containing an oxygen barrier layer composed of one or more copolymers with vinyl chloride. It is generally recognized in the art that irradiation is detrimental to the structure of such oxygen barrier layers. Thus, by extrusion coating, one or more layers of a stripe are extruded or co-extruded, said layers are exposed to the action of radiation, and then an oxygen barrier layer is extrusion coated and one or more layers for that matter are extruded. can be extrusion coated onto the outside surface of the tube.

As a result, crosslinking of one or more irradiations of the first layer is possible without exposing the oxygen barrier layer to the deleterious effects of the irradiation.

Irradiation of the film layer is desired in order to attempt to improve the abuse resistance and/or puncture resistance and other properties of the film. 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, such as electrons, x-rays, gamma to beta rays, etc. Preferably, electrons with an energy of at least 104 electron volts are used. The irradiation source is a van de Graaff electron accelerator, for example a 2.000.
000 volts can be used. Or to General Electric (General
Electrlc) 2,000. Other high energy electron sources can be used, such as an OOQ Porto resonant transformer or a corresponding 1,000,000 Gault, 4KW resonant transformer. The voltage is to, o o o or 2
．． 00+1. ODD or 6,000.000 & rut or higher. Many other devices for irradiating film are well known in the art. Irradiation is usually carried out at a temperature of 1 to 75 megarads, preferably 8 to 20 megarads. Although irradiation can conveniently be carried out at room temperature, this
- High and low temperatures such as %D°C to 60°C can be used. Also, one-crosslinking can be achieved chemically by the use of peroxides, as is well known.

The polyolefin family of shrink films, especially the polyethylene family, has a wide range of physical and performance properties, e.g.
"shrinkage force" (the amount of force that a film exerts per unit cross-sectional area when it shrinks), "free shrinkage" (the decrease in linear dimension in a specific direction that a material exhibits when exposed to high temperatures without restraining the material) ) 1 "Tensile strength" (the highest force that can be applied to a unit area of the film before it tears) 1 "
sealability J (% ability of a given material to seal to itself or to other surfaces);
"Shrinkage curve" (shrinkage vs. temperature), "tear initiation and resistance" (forces at which the film begins to tear and continues to tear), "optics" (gloss, haze and transparency of materials 14-). ), 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. )
It is a resistance against Since such degradation of the film substantially reduces the effectiveness of the film to perform its function, there continues to be a search for films with improved resistance to such attacks.

The search for films with improved oil paper resistance has focused on at least one area. especially,
Many of the films utilized for the packaging of fresh red meat and other fatty substances include a surface layer that is a copolymer of ethylene and vinyl acetate or a blend of one or more such copolymers. An undesirable disadvantage heretofore associated with such materials is the fact that these materials are easily attacked and degraded upon 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. Thus, in the past, prior art films having a surface layer of ethylene vinyl acetate copolymer were used in connection with packaging machines that were cleaned and maintained in many cases by utilizing mineral oil. Result 1 has been exposed 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 film having a surface layer with greatly increased resistance to attack and/or degradation on 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 heat shrinkable film having an outer surface layer consisting of a blend of one or more ethylene vinyl acetate copolymers and 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 sets forth some preferred embodiments of the invention, so that various modifications and changes within the scope of the invention will be apparent to those skilled in the art upon viewing the following detailed description. It should be understood that this is for illustrative purposes only.

Such modifications and variations are intended to be encompassed within the scope of the claims, unless specifically stated and defined or otherwise limited; as used herein, "polymer" or "polymer resin" refers to Polymer 1 Copolymer 1 Terpolymer 1
Block and graft polymers 1 Random and alternating polymers
mer).

As used herein, "melt flow" or "melt flow index" refers to a thermoplastic material that can be forced through a given orifice within 10 minutes at a specified pressure and temperature, as described in A8TM-D123B. The amount of resin (f).

18- “Barrier” or “barrier layer” as used herein means:
Refers to the layer of a multilayer film that acts as a physical barrier to gaseous oxygen molecules. Typically, the barrier layer material is S 1 atm, 22.8°C (73°F) and 0
These values should be obtained according to ASTM standard D1434, which will reduce the oxygen permeability of the film to less than 70 cc/m2 within 24 hours at a relative lake temperature of

As used herein, "intermediate" or "interlayer" refers to the layer of the multilayer film located between the barrier layer and the surface layer.

"Surface" or "surface layer" as used herein means a layer of a multilayer film that constitutes one surface of the film;
I! This is a copolymer of ethylene and one or more comonomers selected from 04-01G alpha olefins, such as butene-IS octene, whose molecules have long chains with almost no side chains or crosslinking structures. means. The side chains present are shorter than in non-linear polyethylene, linear low density polyethylene typically has a
940 f/c (with: and) preferably 1 density [L816~α928t
/cc. Density is ASTM-D7
92. The melt flow index of linear low density polyethylene is approximately 0.1 to i,of
710 minutes, preferably within the range of about α5 to about '5.0 f/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.

“Ethylene vinyl acetate copolymer J (E
VA) means a copolymer formed from ethylene and vinyl acetate, in which the ethylene-derived units in the copolymer are present in a major amount and the vinyl acetate-derived units are present in a minor amount.

"Oriented" or "heat-shrinkable" materials, when heated to a suitable temperature (e.g. 96°C) above room temperature,
Defined herein as a material having a free shrinkage of 5% or more in at least one direction. Free contraction is ASTll,D
2732.

All composition percentages used herein are calculated on a 1 weight basis.

One rad is the amount of ionizing radiation that results in the absorption of 100 ergs of energy per f of irradiated material, ignoring one irradiation source. 1 megarad equals 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 comprises one or more It has been discovered that an ethylene vinyl acetate copolymer can be obtained by providing a film with a surface layer composed of a blend with a colored linear low density polyethylene material. In particular, it has been determined that resistance to mineral oil attack by such surface materials is additively improved when the percentage of vinyl acetate within a blend is about 11.5 times less by weight. Preferably, the single layer film is stretched and oriented to be heat shrinkable in at least one direction.

One preferred embodiment of the film of the present invention comprises approximately 90% by weight of an ethylene vinyl acetate copolymer having vinyl acetate derived units of approximately 9% by weight and a linear low density polyethylene material in the order listed. a first surface layer formulated by blending approximately 10% by weight with (
b) Oxygen barrier layer 1 (C) consisting of a blend of two different vinyl chloride 22-lydene copolymers 1 m vinyl copolymer approximately 60% by weight of a primary ethylene vinyl acetate copolymer with approximately 20% by weight vinyl acetate derived units and (d) approximately 40% by weight of a secondary ethylene vinyl acetate copolymer having approximately 9% by weight vinyl acetate-derived units; and (d) approximately 6.2% by weight vinyl acetate-derived units. It is a four-layer polyolefin film structure consisting of a second surface layer consisting of an ethylene vinyl acetate copolymer having units.

Preferably the third and fourth layers are approximately 4.5 MH
It is bridged by the application of irradiation.

Other preferred total film structure embodiments are shown in Table 1 below.
Examples are shown with the formulated surface layer disclosed therein.

Of course, one additional layer 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 demonstrating the principles of the invention, 127 samples were prepared and analyzed as described below. The complete layer-to-layer structure of each of these samples is shown in Table 1 below.

Table ■ Complete structure of sample and p sample of layer before stretching orientation Internal surface layer (1) Intermediate layer (II) A FIV
A (42% VA) I FIVA (18% VA)” 3 mils thick ttS Mils 7” (1ldpe) 12.5 mils thick 5 mils thick OFtVA (a9% VA) Ma KVA ( EL9VA) 5 mil thickness 10 mil shore height D FiVA (a9%■A)' mvA (a9%vA)
z 5 mil thickness 10 mil thickness 205−
VA) 1 Vinyl Copolymer 3 6 mils thick 10% vinylidene chloride/vinyl chloride copolymer 4 3-5 mils thick & 5 mils thick 25- Table 1 (Continued) Barrier Pigeon (1) Outer Surface Layer (Capital) 6 mil thickness 6.5 mil thickness I I- (continued) 7.5 mil thickness 10 mil thickness z 5 mil thickness 10 mil thickness 7.5 mil thickness 10 mil thickness 5 mil thickness 12.5 mil thickness 5 mil thickness 12.5 mil thickness Q 1ldpe' 60%]! 1 VA (a9%Vum) 1
5 mil thickness 40% 1llpe" 5 mil thickness 206- 26- 20% 11 (11) θ5 2 6.5 mil thickness same as A 95%llCN'A (a9%vA) 75%
1ldpe” 6.5mil Thickness Same as A 60%EIVA (a9%VA) 740% 1
ldpe” & 5 mil thickness same as A so%EVA (a9%VA) 720% 1l
dpe'& 5 mil thickness A and 1; 80%]! ! VA(a9%Vmu)'F20
% 1ldpθ6 Same as 6.5 mil thickness 60%l1iVA (a9%VA) 740%
11 (lp13” 6.5 mil thickness 27- Table 1- (Continued) Sample Internal Surface Layer (1) Intermediate Layer (IN) R11 (1
p8' 6o%EVA (EL9%VA)"7.5 mil thickness 40% 1ldpe"10 mil thickness S 1ldpe 11+ipe' Z5 mil thickness 10 mil thickness T 87%BVA (a9%vA )y B7%EvA(
a9%VA) 716% 1lap' 15% 1ld
pe' 7.5 mil thickness 10 mil thickness z 5 mil thickness 10 mil thickness 11.5 mil thickness W Bo%1! ! 'VA(l1%VA)' 80%BV
A(IB%VA)”21% 11dpe8 20% 1
ldpe' 5 mil thickness 12.5 mil thickness Barrier layer (m) Outer surface layer (m) 40% 1lepe8 6.5 mil thickness 6.5 mil thickness 6.5 mil thickness 6.5 mil thickness 6 mil thickness & 5 mil J'J size table! - (Continued) 207- 28- 128'- Lo as 1 ShiQ Yotsushima 4 m 6 &- With the exception of the shaved trout age linear low density polyethylene sample AA and sample processing if possible. 1 All other samples, for example samples A-■ and J, Z, as follows! M was built. 1st
After irradiation of layers I and ■, layers ■ and ■ were coextruded as tubes and then treated by irradiating these two layers to an irradiation level of approximately 4.5 MH. Coextrusion and then extrusion coating the inner surface of layer 1 (with coextruded JA 2) onto the outer surface of layer 2. As a result 1, in the order listed, layer i,
A four-layer tubular film consisting of n, m and ■ was obtained. 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 is approximately 1.5 mm after stretch orientation.
It was 5 mils thick.

Twelve different tests were devised to demonstrate the significantly and additively improved resistance of FiVA to degradation from contact with mineral oil to which linear low density polyethylene material was added. The first test was a visual test performed as follows: (1) A small amount of material oil was applied to the outer surface of the sample (e.g. 1FiV
A/l]4pθ Prene F surface).

(2) The contaminated area was placed over the mouth of a small beaker where the inside of the beaker was contaminated. (3) The film was then secured to the beaker by placing a rubber band over the film at the top lip of the beaker. (4) Next, invert the beaker and heat it to 953°C (200°C).
The surface of the water maintained at a temperature of (lower) was contacted for 1 second.

It was observed that after several attacks with mineral oil, the mineral oil applied surface became cloudy and rough and could even be removed by scratching with a fingernail. Varying degrees of oil attack could be observed depending on the material. In this regard, the following visual standards were constantly used by the same individual in determining the resistance of a sample to oil attack.

32- Numerical Grade Resistance Required Show no evidence.

Indicates shi.

pickpocket I rubbed it lightly with my finger It doesn't peel off.

35- In order to provide an objective means of assessing the damage caused to a given specimen by mineral oil attack and to eliminate the subjectivity associated with visual grades, the following test was devised and some of the specimens We carried out the following. The evaluation was done using a Hunter color difference meter.
Co1or DifferenceMθtθr)D2
This was carried out using Type 5D2. This instrument is capable of measuring changes in color or brightness (in cm), where 0# equals pure black and 100 equals pure white. I can do it,
Various levels of whitening or haze associated with film deterioration can then be expressed and thus 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 procedures.

(2) An unattached section of the sample to be tested was placed on a black standard attached to the machine and located below the inspection port of the instrument, and the material was made flat with the black standard.

All foreign material was wiped away from the sample. (3) The machine was placed on the "L" scale - and the "L" value drawn on the dial of the machine was read and recorded.

(4) A small amount of mineral oil “Lubinol M, F,’ (1?
urepaa Pharmaceutical Oom
Pany.

(obtained from Elizabeth, New Jersey) was applied to the surface of the ETA/1ldpe blend or EVA comparison material on the outside of the sample. Two or three drops were sufficient to cover a sample area a 9 cm (5.5 inches) in diameter. Mineral oil was spread over the sample area with a cotton swab.

(5) Set the sample area to a diameter of 1α2 to 12.7c1n (4 to
The mineral oil was placed on top of the open end of a 5 inch 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 93.6° C. (below 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) Separate the film from the beaker, being careful not to disturb the attacked sample area of the film, and
(Hunter) D 25 Placed inside the D 2 type'
fC,.

Point the attacked surface at the light source of D25D2, and
A reading of the ``L'' value was obtained.

(8) Subtracting the initial unattacked “L#” value from the final unattacked “L” value of the processed film, the resulting 1 delta L# value is the brightness of the film from unattacked to attacked. is a measure of the change in mineral oil and is believed to represent the extent to which a sample is attacked by mineral oil.

Table ■ below indicates the film samples alphabetically, identifies the composition of the fC surface layer under attack with mineral oil, and lists the percentage of vinyl acetate in the sample of the attacked surface layer, and indicates the percentage of vinyl acetate in the sample of the attacked surface layer. List the visual grades you have given, and for the samples you have given data on, state the "delta L" value of the instrument for grading the sample. 39- 211- 11111111 do do - -be do - 38- Figures 1, 2 and 3 graphically represent the data listed in Tables ■ and Table ■. The visual rating of a given material's resistance to attack is plotted 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 different Class 31i EvA materials plotted in Figure 1, with the bottom dashed curve demonstrating a very rapid resistance to mineral oil attack. , reflects the resistance of an EVA material with an initial unblended vinyl acetate derived unit (monomer) of approximately 42% to attack by mineral oil. The dot/dash line in the center shows the FtV, where the initial unblended vinyl acetate derived unit (monomer) percentage is approximately 89%.
Reveal the varying degree of mineral oil attack on A materials. The solid line above shows the varying resistance to mineral oil attack of a PTA material with an initial unblended vinyl acetate derived unit (monomer) percentage of about 12%; data point 2 is
In its original unblended form, 1 was assembled for an EVA material consisting of approximately 18 weight-grams of vinyl acetate-derived units.

Looking at Figure 1 ~ Standard (non-blended) comparative sample A ~
It is clear that all of the plants had inferior resistance to mineral oil attack. ET with a very small proportion of linear low density polyethylene approximately 6.2% vinyl acetate derived units
When added to the A copolymer, mineral oil resistance was very significantly improved. (For example, see point J for 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 FIG. , the use of an ethylene vinyl acetate copolymer with approximately 9% by weight vinyl acetate-derived units in the blend results in 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 light, OlK
Finally, as is also evident from Figure 1, the resistance of such materials to mineral oil attack is very good (grade 2
) to excellent (grade i), an even higher amount of linear low density polyethylene must be added to an ethylene vinyl acetate copolymer having a vinyl acetate percentage of approximately 12%. I have to.

(See, for example, point W on the sample.) As is clear from the above description and FIG.
A correlation exists between the resistance of a VA material to attack from mineral oil and the percentage of both vinyl acetate and linear low density polyethylene in the formulated material. Accordingly, FIGS. 2 and 3 plot 42--apparatus (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 figures 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 reciprocal 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 the delta L values obtained by the instrument readings defined above for the three non-blends (e.g. BVA copolymer without linear low density polyethylene) are all very high. it is obvious.

The three non-blends that yielded delta L values were Samples A, E, and B.

43-These materials initially each contained approximately 6.2% vinyl acetate, a9 El vinyl, and 12% vinyl acetate monomer. 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 reveal the points J% 'I', U% V% YSY% and 2 all in one formulation. The delta L values obtained for EVA materials with linear low density polyethylene materials are revealed. These samples were plotted as a percentage of vinyl acetate at the blend point.

In other words, the weight percentage of the vinyl acetate derived component (eg, monomer) of the blend as a whole was calculated and the sample was plotted at that point.

This data specifically reveals that in all cases, the delta L values of Struprene F containing linear low density polyethylene are also improved over those of the ethylene vinyl acetate copolymers.

The negative Z2 reading for point 2 in Figure 2 points out that the unattacked material is likely to be somewhat cloudy in that the application of mineral oil to the surface improves the transparency of the material. want to, therefore 1
The delta L value at point 2 should be ignored, although in our opinion it appears to represent a dramatic improvement. Point 1 AA reveals the delta L value for sample AA and 1 attack here. The exposed surface was entirely linear low density polyethylene material.

Figure 3 shows the visual rating for all mineral oil attacks of the sample versus the weight percent of vinyl acetate derived units in the blend by 7". As can be seen in Figure 3, the unblended comparison All of the materials - samples A, B, 0.D, F,
G, H, and K were visually graded as having poor resistance to mineral oil attack. Therefore, a horizontal line at one vertical axis (grade 5) 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 confidence factor of 95 chi 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 one-phase surplus effect occurs when the weight percent of vinyl acetate in the blend is greater than approximately 11.5%; A visual rating of 2 is found in blends where the weight percentage of vinyl acetate in the blend is less than 8%.

41- From the above data it is very clear that when adding a small amount of linear low density material and the percentage of vinyl acetate derived units in the blend is as low as 11.5% by weight to most preferably 8% by weight When smaller, a compounding effect occurs with respect to the resistance of the ethylene vinyl acetate copolymer to mineral oil attack. This discovery is extremely important 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. Therefore, 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 combines one or more ethylene 4Q-vinyl acetate copolymers with linear low Includes the use of any film material having an outer mineral oil resistant layer comprised of a blend with a density polyethylene material. This surface layer material can be utilized with a number of other layers to obtain a composite film product with desired physical properties.

As mentioned above, a preferred embodiment of the present invention having an overall preferred group of physical properties comprises an ethylene vinyl acetate copolymer having 9% by weight vinyl acetate derived units and 10% linear low density polyethylene material. 4 blends of
for use as the first surface layer of the layer film;
The second layer here is an oxygen barrier layer and constitutes an oxygen barrier blend as defined above in Table i. One preferred embodiment also includes a third layer and a fourth layer, both of which are cross-linked by irradiation to approximately 4.5 MH. The third intermediate layer is comprised of approximately 60% by weight of an ethylene vinyl acetate copolymer having 20% by weight of vinyl acetate-derived units and - approximately 60% by weight of a second ethylene vinyl acetate copolymer having approximately 9% by weight of vinyl acetate-derived units. 40 fL%. The fourth inner surface layer consists of an ethylene vinyl acetate copolymer having approximately 62% vinyl acetate derived units. 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 and their properties are listed in Table ■
, represented by samples J-Z in Tables ■ and Table ■. Many of these samples demonstrate very satisfactory optics.

Of course, good optics is a highly desirable physical property in packaging films. Accordingly, preferred embodiments of the invention are selected from films that demonstrate superior overall optics. As is readily recognized in the field, some optical properties are related to the overall structure of the film (e.g., total transmission), while others are directly related to the materials utilized as the surface layer of the film (e.g., glossiness).

Since high gloss is highly desirable, one preferred embodiment of the surface layer blend of the present invention will have a gloss of greater than 70%, more preferably greater than 80%.

The average optics for the sample are detailed in Table ■ below. >-H TOKYO SHIZHIZU 51- The above data represent average values obtained by collecting measurements of four replicate experiments.

The above detailed description and specific examples showing presently preferred embodiments of the invention are intended to be illustrative only, as various changes and modifications will become apparent to those skilled in the art upon viewing thereof and are within the spirit and scope of the invention. It should be understood that only

[Brief explanation of drawings]

FIG. 1 shows the improved resistance to attack and/or degradation from contact with mineral oil associated with a film layer formulation made from a blend of linear low density polyethylene material and ethylene vinyl acetate copolymer. This is a graph of the data. FIG. 1 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 shows the relative 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 ethyl vinyl acetate copolymer. This is a graph of the data. Figure 2 shows the delta “L” of one film surface layer.
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. 5 shows visual data showing the relative 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 film surface layer's resistance 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. 53- Recurring bonds t & book 9 rie 乎ren fN hundred and present FIG 1 Vinegar flavor in the blend) irl White Cave IG 2,? ,, A, B, (C, D, E, F, Q, Hx忰
X Target 1': 4 e a'' *Y Grade a, 3 %/e @2 Bren's face is in the middle, Yusuke is driving IG from Vinii II- 3

Claims (1)

[Claims] 1. having a surface layer resistant to decomposition by mineral oil;
The surface layer comprises one or more ethylene vinyl acetate copolymers,
and linear low density polyethylene, wherein ff[
A polyolefin film wherein the vinyl monomer comprises less than about 11.5% by weight of the blend. 2. having a surface layer resistant to decomposition by mineral oil ~ said surface layer comprising one or more ethylene vinyl acetate copolymers;
and linear low density polyethylene, wherein the vinyl acetate monomer present in said blend comprises less than about 8% by weight of said blend. 3. A first surface layer consisting of a blend of approximately 90% by weight of an ethylene vinyl acetate copolymer having approximately 89% by weight vinyl acetate-derived units and approximately 10% by weight of linear low density polyethylene ~ two different vinylidene chlorides. Oxygen barrier layer consisting of a blend of vinyl chloride/vinyl chloride copolymers, a first layer having approximately 20% by weight of vinyl acetate derived units, a first layer having approximately 60% by weight of an ethylene vinyl acetate copolymer and a second layer having approximately 8.9% by weight vinyl acetate derived units. an intermediate layer consisting of a crosslinked blend with approximately 40% by weight of a diethylene vinyl acetate copolymer;
and a second surface layer consisting of a cross-linked ethylene vinyl acetate copolymer having approximately 6.2% by weight vinyl acetate-derived units). 4. The film according to claim 1 or 2, wherein the surface layer is crosslinked; 5. The film according to claim 1 or 2, wherein the surface layer has a delta L value of less than 20. film. & The film according to claim 1 or 2, wherein the surface layer has a gloss greater than 70%. 2. The film according to claim 1 or 2, wherein the surface layer has a gloss of more than 80%. 8. The film according to claim 1, 2 or 3, wherein the film is heat-shrinked.
Film according to section 9, wherein the crosslinking layer has a thickness of approximately 4.5 M.
Claim 1 bridged by application of H.
Or the film according to item 2 or 3. 1[lL I+! jClaim 1st or 2nd or 3rd
2. Bags formed from the film described in Section 1 and adapted for packaging products. 11. The film of claim 3, wherein said surface layer has a delta L value less than 20. 12. The film according to claim 6, wherein the surface layer has a gloss greater than 70%. 1 & The film according to claim 3, wherein the surface layer has a gloss greater than 80%.