DK147976B - MATERIAL FOR USE IN MELTUS EXTRACTION OF FILM OF A COPOLYMER OF VINYLIDENCHLORIDE AND AT LEAST ANOTHER ETHYLENIC UNLAMATED MONOMER - Google Patents

Description

o 147976

The present invention relates to a material for use in the melt extrusion of film of a copolymer of vinylidene chloride and at least one other ethylenically unsaturated monomer. In particular, foils which can be included in laminates for use as packaging material are obtained.

For many purposes, packaging materials require high abrasion resistance, e.g. manifests itself at high tensile strength and high tear strength, to survive from outside caused by violence and wear during packaging transport and handling. When the products in the packaging are not soft or compliant, wear can also occur from the inside of the packaging during transport and handling. An example of items that are particularly prone to induce wear from the inside is bone in meat, ie. a piece of meat containing bone. In this way, puncture of the packaging material can be punctured with the relatively hard bone, which of course will adversely affect the meat. Many other consumables also require to be packaged in a material of high abrasion resistance and especially high resistance to violence.

.20 Another important requirement for many packaging materials is that they must have low permeability or permeability to oxygen, especially when food is packaged therein.

A polymeric material which is excellent for this purpose because of its low oxygen permeability is a 25 copolymer of vinylidene chloride with at least one other ethylenically unsaturated monomer, which copolymer contains at least 50% by weight of vinylidene chloride-derived units.

Desirably, it is a copolymer of vinylidene chloride with vinyl chloride. It can e.g. contain 70-85 wt% vinylene chloride derived units and 30-15 wt% vinyl chloride derived units. Other suitable monomers for polymerization with vinylidene chloride so as to obtain a low oxygen permeability polymer are numerous and well known and therefore do not need to be enumerated here.

35 However, the above vinylidene chloride copolymers do not have 2 147976

ISLAND

sufficient wear resistance and. especially resistance to violence for many purposes. Therefore, as packaging, it is proposed to use a laminate comprising a first layer of high resistance to violence and abrasion, a second intermediate layer of vinylidene chloride copolymer and a third layer of high resistance to violence. Such a laminate provides protection against packaging damage, both applied from the inside and from the outside. The vinylidene chloride copolymer layer is usually referred to as a "barrier layer" as it acts as a barrier to the passage or passage of molecular oxygen.

A convenient way to prepare a laminate of the above type would be to melt extrude a wear-resistant or abrasion-resistant substrate, upon which a barrier (after solidification) is melt-extruded a barrier of the vinylidene chloride copolymer layer which solidifies, and on top of the barrier layer a melt extruder is then melted. so as to form a laminate which is then biaxially stretched. However, in this technique there has been a problem with melt extrusion of the vinylidene chloride copolymer. It is convenient and economical to prepare the vinylidene chloride copolymer by emulsion polymerization. However, it has been found that the emulsion polymerized product, herein briefly referred to as "emulsion polymer", sometimes deposited or adhered to the extrusion apparatus.

That is, it does not flow sufficiently well in the molten state. This problem is solved with the present invention.

The material of the invention is characterized in that it consists essentially of a mixture of 5-40 wt% 30 suspension polymerized vinylidene chloride copolymer and 60-95 wt% emulsion polymerized vinylidene chloride copolymer and each of the two copolymers has a content of at least 50 wt. % from vinylidene chloride derived units.

It is completely unexpected that the mixture of emulsion and suspension resins from vinylidene polymer can

ISLAND

melt-extruded and formed into good quality biaxially oriented film. Normally, suspension polymerized resin should be expected to cause gels to form in the emulsion resin during extrusion. However, in the present case 5, the suspension polymer appears to act as a stabilizer rather than to effect gels in the emulsion polymer film. However, without adhering to the following theory, it is believed that the suspension polymer melts more slowly in the extrusion chamber and acts as a rinse or lubricant during the passage of the mixture through the extrusion apparatus, thus impeding the deposition of the polymer on the surface of the extrusion chamber, thereby hindering its disintegration or degradation. In other words, the emulsion polymer tends to adhere as it melts, and the suspension polymer acts as a kind of slide bearing on which it moves. Of course, the entire mixture of copolymers melts and extrudes as such.

It has been found that when the content of the suspension polymer in the polymer blend exceeds 20%, the orientation of the film 20 becomes difficult, but it is still possible to use a blend containing up to 40% suspension polymer by very careful treatment. The reason for this difficulty, which appears in the orientation, is that crystals are formed more quickly in a suspension polymer film. Thus, the suspension polymer acts as a contaminant in the emulsion polymer in the sense that the suspension polymer crystallizes too quickly to obtain an appropriate extraction (reduction of the film thickness) during the orientation step.

It has now been found possible to operate at extrusion temperatures between the normal treatment conditions for emulsion and suspension polymerized polymers, in other words in the general range 138-171 ° C for the most preferred compositions. Initially, it was not thought that the mixed materials would be compatible in the state of a molten polymer, namely because of the difference in melt rates of these two polymers.

The preferred comonomer for vinylidene chloride in these copolymers is vinyl chloride, and preferably 5-40% by weight of 5 units of the copolymer are derived from vinyl chloride.

The preferred proportions of emulsion and suspension polymer in the material of the invention are 5-15% by weight of suspension polymer and 85-95% by weight of emulsion polymer. Preferably, the material also includes 2-10 and most desirably 4-6 wt% epoxy resin. Thus, the preferred barrier layer composition is based on copolymers of vinylidene chloride and vinyl chloride, with the content of vinyl chloride-derived units being 5-40% by weight mixed with 2-10% epoxy resin. The preferred barrier layer material comprises (a) a vinylidene-chloride / vinyl chloride copolymer with 15-30% vinyl chloride derived units and (b) 4-6% epoxy resin, the copolymer being a mixture of 5-15% suspension polymer and 85-95%. emulsion polymer. All percentages listed here are by weight unless otherwise stated.

20 "Epoxy resin" means a high viscous epoxy-containing thermosettable resin which, however, should not be confused with epoxy-dehydrated oils which are the usual epoxy-containing plasticizers and are usually made from epoxidized natural oils but which are far less viscous.

The material according to the invention can be made into foils, including laminates and especially flexible laminates comprising one layer of polymer material according to the invention as barrier layers and one layer of other polymer material arranged on one or both sides of this barrier layer. It is convenient to provide a laminate structure having at least three layers, namely, a wear layer, a barrier layer and a further wear layer in that order, and the preparation of a foil having such a laminate night structure is described below. However, it will be appreciated that the subject matter of this invention mixed with emulsion and suspension copolymers can also be used to prepare other laminate structures, e.g. with only two layers, one of the abrasion-resistant layers mentioned above can be omitted.

Certain laminates with two abrasion-resistant or abrasion-resistant layers and an interposed barrier layer are also described in the application (no. 1587/72). For use in heat shrink wrapping, the polymer sheets are given molecular orientation by stretching.

A preferred class of polymer for one or both of the abrasion-resistant layers mentioned above are copolymers of ethylene and vinyl acetate containing 5-20% by weight units derived from vinyl acetate. These ethylene / vinyl acetate copolymers comprise (i.e. consist entirely of or include only as part) polymerized ethylene and vinyl acetate units. Thus, other components may be present. The polymer could e.g. be a terpolymer or any other polymer than a copolymer, only the predominant proportions being derived from ethylene and vinyl acetate. For orientation of such polymers, they are most conveniently cross-linked first. Various ways of effecting such a crosslinking are known per se and may e.g. is done by irradiation.

The preferred polymeric material for the first layer (substrate) of the laminate is a copolymer of ethylene and vinyl acetate containing 5-20, but most preferably 8-12, wt% units derived from vinyl acetate and having a narrow molecular weight distribution. The third layer, which is to withstand violent influence, is preferably of the same copolymer and, if desired, can be exactly the same as used for the substrate.

Use of the material according to the invention will now be more fully described with reference to the drawing, in which FIG. 1 is a schematic representation of an apparatus for use in a preferred method of making a laminate containing a layer made of the material of the invention; FIG. 2 is a cross-sectional view of a die head in the forming part of this apparatus;

ISLAND

6 147976 fig. 3 is a view taken along line 3-3 of FIG. 2, FIG. 4 is a cross-sectional view of a laminate containing a layer made of the material of the invention.

5 Figure 5 is discussed just before Table I below.

Referring now to FIG. 1, wherein a tube 10 is extruded downwardly from a die head 11 which is fed from an extruder 9. The extruded tube is 250-750 µm thick and especially 375-625 µm thick. After cooling or quenching 10 by spraying with water supplied from a cooling ring 12, the tube is collapsed by clamping rollers 13 and passed through an irradiation vault 14 surrounded by a shield 15 in which it is irradiated with electrons from an iron core transformer - accelerator 16. Others accelerators such as a Van de Graaf 15 generator or a resonant transformer may be used. The radiation is not limited to electrons from an accelerator, any ionizing radiation being applicable. The radiation unit used according to the present description is rad, which is defined as the amount of radiation that will emit 10 energies of 20 energy (measured as absorbed energy) per day. grams of irradiated material. The MR unit represents one million (10®) rows.

In particular cases, it may be desirable to crosslink the polymer by other measures such as by chemical crosslinking agents. However, radiation is preferably used as described in more detail below. The irradiation time of the ethylene / vinyl acetate copolymer tube 10 is not critical, but only needs to be sufficient to provide the required dose for crosslinking. In the embodiment described herein, the tube 10 is preferably irradiated with a dose of 2-15 MR and in particular with a dose of 2-10 MR.

The tube 10 is passed through the radiation vault 14 by means of rollers 17. After irradiation, the tube 10 passes through clamping rollers 18, after which it is easily inflated by means of a trapped gas bubble 20.

The pipe is not given any significant stretch in the longitudinal direction before inflation, since the rollers 18 are operated at approximately the same speed as the prior rollers 13.

The tube is inflated only sufficiently to provide a roughly circular cross section, i.e. without significant orientation in the transverse direction.

The lightly inflated and irradiated tube 10 is passed through a vacuum chamber 21 to a laminating or coating nozzle 22 disposed below the chamber 21. A second tubular film 23 is melt extruded from the coating nozzle 22 and 10 and is coated directly to the irradiated tube 10 to form a two-layer tubular laminate 24. This second tubular film 23 is a barrier film made of a material according to the invention.

The extrusion apparatus 25 is preferably operated at a room temperature of 43-160 ° C and most preferably at 121-149 ° C, and the extrusion nozzle is preferably operated at a temperature of 138 to 171 ° C and most preferably from 146 to 157 ° C. The extruded tube is 25-125 µm thick and preferably 50-100 µm thick.

The extrusion apparatus 25 is conventional, e.g.

20 is a standard 8.2 cm diameter extruder.

The details of the draft nozzle 22 will be better understood with reference to FIG. 2 and 3. The pull nozzle 22 is a circular cross head nozzle to which is attached a coupling piece 26 such that in its preferred form, it is provided with an 8.9 cm aperture 27 for the slightly inflated tube 20. The aperture 27 through which the inflated support passages are formed through a pull mandrel 28, which is attached to the housing nozzle 29.

The path along which the molten coating material 23 moves is indicated by arrows in FIG. 2 and 3. The vacuum chamber 21 applies a gentle vacuum, e.g. in the range of 0 to approx. 6.4 cm water column so that the extruded film 23 is pulled or "sucked" while still being melted against the inflated tube 10 to prevent the formation of trapped bubbles in the laminate 24. The vacuum chamber 21 can simply consist of a cylindrical housing whose inner diameter closely fits the outer diameter of the inflated tube. Vacuum can be applied through an outlet 30 by conventional vacuum generating means (not shown).

The two-layer foil 24 is sent to a coating or laminating nozzle 32, preferably while still warm. In a discontinuous process, it will be possible to cool or quench the tube 24 before passing it 10 to the second coating nozzle 32, but this will usually also necessitate a rebuilding and reheating of the tube to achieve excellent bonding between the second layer and the first. layer. Considering the tube from the outside, this first layer will be both an outer layer and the outer layer of the tube.

A third layer is melt extruded from the coating nozzle 32 and coated and adhered directly to the two-layer tube laminate 24 to form a three-layer tube laminate 34.

Preferably, the third layer 33 of this tubular laminate 33 is of a material selected from the above indicated during the review of the tubular film 10. Although it need not have the same composition as the tube film 10, it is suitably the same material. The coating method at the nozzle 32 is the same as reviewed 25 above at the nozzle 22. The vacuum chamber 36 serves the same function as the vacuum chamber 21 and operates in the same manner, applying vacuum through an outlet 37. The tubular film in the third layer 33 is 75-375. yes thick and preferably 100-300 p thick.

The three-ply laminate 34 is cooled or quenched by spraying with water from a cooling ring 39. The water usually has a temperature of approx. 7 ° C. By means of clamping rollers 40, the three-layer tubular film is then wound onto a coil 41. Alternatively, in a continuous process, the laminate will not be wound at this location on the coil 41, but 147976

ISLAND

9 will be delivered directly to the next step in the proc e s sequence (stretch).

Thus, as shown in FIG. 1, a dispensing coil 42 which is already manufactured as the winding coil 41 is used which is wound over a guide roller 43. The laminate 34 is practically unstretched and unoriented as it passes over the guide roller 43. The film passes from the lead roller 43 into a hot water bath 44 containing water 45. The preferred reheat temperature or hot water temperature is 70-100 ° C and most preferably 82-96 ° C. The combined three-layer tube film is immersed in the warm water for at least approx. 5 sec ..

This period is usually necessary to bring the film's temperature up to the level required for orientation. A typical residence time in the water bath is approx.

Lead rolls 46 and 47 guide the collapsed tube through the water bath 45.

After obtaining an appropriate orientation temperature, a bubble 54 is blown into the film as it emerges from the water, and the film is stretched in both transverse and longitudinal directions in a stretch ratio of preferably 1: 1.5-1: 6 and preferably 1. : 2-1: 4, which corresponds to a total biaxial orientation of 1: 2.25-: 1: 36 and preferably 1: 4-1: 16. The thickness of the layers is reduced in virtually equal proportions. The bubble 54 is held by clamping rollers 48 and 49. The tube 25 is collapsed by rollers 50, and the laminate passing between clamping rollers 49, over a guide roll 51 and under a free flowing roll 53, is wound on a coil 52.

In the drawing FIG. 4, a cross-section of the oriented laminate 34. is illustrated. The first layer, which makes up the inner layer of the tube, is the layer 10, which preferably has a thickness of 12-125 µ and most preferably 25-50 µ. The barrier layer of the material of the invention is indicated at 23 and preferably has a thickness of 1.25-50 µm and most preferably of 2.5-6 µm. The third layer 33, which constitutes the outer protective layer of the tube, is preferably 2.5-100 µm thick and most preferably 6-25 µm thick. These three layers or 147976 can be directly joined without intermediate or interposed layers. The laminate has a shrinkage stress of usually 2 to 14-35 kg / cm and preferably of 14-28 kg / cm and a free shrinkage of at least 40% and most preferably of at least 50% at 96 ° C and a free shrinkage of at least 20% and preferably at least 30% at 85 ° C.

In an alternative method of preparing the laminate, the second and third applied coatings can be co-extruded onto the preformed tube from a coextruding nozzle. This will produce the same final product as the laminate reviewed above, but is a somewhat more difficult method.

The tubular film produced by this method and as a barrier layer containing a layer of the material of the invention constitutes an excellent material for 15 carrier bags, the layer 10 adhering very nicely to itself at temperatures between 93 and 107 ° C, practically without distortion when this film heat sealed by means of a thermal impulse sealing device.

Layer 10 also gives the bag excellent puncture strength. The thin barrier layer provides the necessary barrier properties at minimum thickness and at minimal cost. 'The coating of unirradiated copolymer gives the bag a high degree of resistance to violence at low temperatures and improved tear strength. The use of the material of the invention for bags is disclosed in U.S. Patent No. 3,552,090. After the bags are evacuated, they are closed by attachment as shown in U.S. Patent No. 3,383,746. A suitable evacuation means is disclosed in U.S. Patent No. 3,628,576.

Articles, especially foodstuffs, may be packed in an oriented film of the material of the invention, or this may constitute a layer in a laminate which then serves as packaging material, after which the film or laminate is heat shrunk.

The above packaging material is particularly suitable for wrapping cut fresh or red meat with exposed legs. This is especially true of the three-layer laminate, whose manufacture is described above. A laminate having a different and inferior barrier layer therefrom will damage the laminate manufacture and impair the quality of the laminate. Said three-layer laminate is non-toxic and is generally suitable for food packaging. It will be appreciated that when a bag is used to wrap a piece of fresh red meat which is not frozen and which is not to be frozen but packaged and kept at refrigerator temperatures, e.g. from 0 to 7 ° C, the laminate encloses the cut or carved piece of meat and is thus exposed to bone or bone splinters penetrating the inner layer of the bag.

In such a packaging method, meat containing bone is placed in the biaxially oriented three-layer laminate, which is heat shrinkable. The laminate thus encloses a cut piece of meat containing bone which, depending on the cut or cut of the meat, can always expose the laminate to protruding legs, which may be pointed or sharp after chipping. The bag is evacuated and sealed so that the vacuum is maintained. The bag is then heat shrunk tightly around the meat.

The described three-layer laminate has a number of highly desirable properties, among which typically can be mentioned good shrinkage at moderately elevated temperature, a fracture elongation of at least 50% and preferably 100-125%, an oxygen transmission rate not exceeding 70 cm / m / 24 h / 1 atm at 22.8 ° C and 0% relative humidity (as tested by ASTM-3 2 D1434) and usually not more than 25 cm / m / 24 h / 1 atm at 22.8 ° C and 0 % relative humidity (ASTMD1434). In its 30 preferred form, the foil has a ball breaking strength of at least 25 kg-cm measured on a "Ball Burst Tester No. 13-8" from Testing Machines Inc. using a standard hemispherical head.

The material according to the invention can be formed in the form of 35 independent films. The materials have superior extrude 147976

ISLAND

12 ring properties already enumerated above are either melt-extrusion coated or melt-extruded as self-contained self-supporting foils. Of course, in order to be self-supporting, the extruded vinylidene chloride polymer film must be at least approx. 0.05 to approx. 0.08 mm thick if extruded as a tube using normal, appropriate extrusion technique. In addition, it has been found that the oriented film formed from a mixture consisting essentially of emulsion and suspension polymerized vinylidene copolymers has unexpected tear strength and resistance to puncture compared to the conventional sheets of vinylidene chloride / vinyl chloride polymer.

The material of the invention and various laminate layers produced therefrom can include compatible additives such as stabilizers, pigmentation agents and processing aids such as waxes, deodorizers, antistatic agents and antiblock agents which are intended to counteract that many foil layers are interconnected in a single large block which is difficult to separate.

The following examples serve to further illustrate the present invention and the advantages thereof.

Example 1 The apparatus shown schematically in the drawing is used using the general procedure described above, an ethylene / vinyl acetate copolymer containing 10% vinyl acetate and having a melt index of approx. 2 and a molecular weight distribution as shown by the curve in FIG. 5 (discussed further below), and which are sold by the U.S. Industrial Chemicals Division and National Distillers under trade names "UE 637", are fed to the hopper of the extrusion apparatus 9. The extrusion apparatus has a diameter of 8.9 cm and is operated by the following temperatures, rear zone 121 ° C, center chamber 132 ° C, front chamber 143 ° C, connector 149 ° C and nozzle 166 ° C. Carpenter- 147976

ISLAND

13 speed is 37 rpm. and the pressure is 2,267 kg / cm. The diameter of the nozzle is 8.9 cm and the circumference of the tube produced is 20.3 cm. The water from the cooling ring 12 has a temperature of 7 ° C. The clamping rollers 13 are operated at a speed of 10.7 m per second. and the thickness of the collapsed tube is approx. 460 yes.

The collapsed tube is passed through an irradiation system as depicted in the drawing of FIG. 1, and operated with 500 kg electron volts, 20 MA and a speed of 10.7 m per

10 minutes. Four passes are made and the tube receives a dose of approx. 6 megarad.

The irradiated substrate film is then fed to a coating nozzle 22, where it is coated with a barrier material. This barrier material contains a lightly softened mixture of copolymer of vinylidene chloride with vinyl chloride. The copolymer mixture consists of 10% suspension polymerized and 90% emulsion polymerized copolymer. The emulsion polymerized copolymer consists of approx. 70% units derived from vinylidene chloride and 30% units derived from 20 vinyl chloride, and the suspension polymerized copolymer consists of approx. 80% units derived from vinylidene chloride and 20% units derived from vinyl chloride. These materials are available from the Dow Chemical Company under the trade name "U.P. 925" (the emulsion polymerized resin) and "S.P. 489" (the 25 suspension polymerized resin). Other constituents of the barrier layer are 5% of an epichlorohydrin / bisphenol A epoxy resin sold under the designation "EPON resin 828" by Shell Chemical Company, and approx. 0.5% of a microcrystalline paraffin wax available from Sun Chemical Company and sold under the designation "Wax 5512". These three resins (i.e., the two vinylidene chloride copolymers and the epoxy resin) are blended into a fast-running high-intensity Prodex-Henschel blend, and the blend is fed to the hopper of the extrusion device 25, a 5 cm Prodex extrusion device powered by a cross-head nozzle of the embodiment shown in FIG. 2 o 14 147976 and 3 illustrated type. The extruder is operated at the following temperatures: Rear zone 99 ° C, center zone 127 ° C, front zone 149 ° C, adapter or coupler 141 ° C and nozzle 160 ° C. The worm speed is 34 rpm. and the pressure is 390 kg / cm. The diameter of the nozzle is 8.9 cm and the circumference of the tube is 20.3 cm. The top rollers 18 are operated at 10.7 m per and the thickness of the coating is approx. 75 ji.

A third layer is then formed using the same resin as the first layer. The resin is extruded through the extruder 35 which is operated in the same manner as the extruder 9 except that the temperatures are as follows: Rear zone 121 ° C, center zone 132 ° C, front zone 193 ° C, coupler 227 ° C and nozzle 232 ° C.

The coating nozzle 32 is of the same construction as the coating nozzle 22. The bottom rollers 40 are operated at 11.0 m per second. and the water from cooling ring 39 is 7 ° C. The coating thickness is approx. 150 ji.

Biaxial orientation is accomplished by preheating the 20 tube in water to ca. 88 ° C, as shown at 44 in FIG. 1, and the thus heated tube is passed through clamping rollers driven at 5.8 m per. per minute for deflating rollers operated at 21.4 m per minute. minute, with it being approx. 10 cm wide tubes between these two sets of rollers are inflated to produce a film width of approx. 41 cm and a film thickness of approx. 61 ji.

The tube thus produced is then wound onto a bearing roll which is then converted into bags by sealing the tube transversely and at intervals to produce bottoms in the conventional manner and cutting the tube to the desired bag lengths.

Example 2

The procedure of Example 1 is repeated except that the barrier layer is changed by the addition of 2% 2-ethyl-hexyl diphenylphosphate plasticizer obtained from Monsanto 0 15 147976 under the registered trademark "Santicizer 141" and reducing the content of the epoxy resin to 3 %.

Example 3 The procedure of Example 1 is repeated with the exception that instead of the 5% epoxy resin, 5% of an epoxidized soybean oil (which must not be confused with epoxy resin) is used and which is negotiated by Swift and Co. under the designation "Epoxol 7-4".

10

Example 4

The procedure of Example 1 is repeated except that 4% 2-ethylhexyl diphenylphosphate plasticizer and 1% magnesium oxide are used in place of the 5% epoxy resin.

Example 5

The composition used in Example 2 for preparing the barrier layer is used except that it contains 4¾ of the epoxy resin and the content of the "UP 925" resin is reduced by 1%, this composition being extruded as a self-supporting single layer film under extrusion conditions such as listed in Example 2. A coating of propylene glycol is applied to the inside of the tube to prevent adhesion when the tube is folded prior to biaxial orientation. The process is continuous, with bubble 54 being formed after the tube is collapsed, but without intermediate winding of the tube. In addition, the water bath is kept at approx.

38 ° C. The thickness of the extruded film is approx. 125 µ, and the thickness of the biaxially oriented film is approx. 19 µl after a total biaxial orientation tensile ratio of approx. 12: 1. The foil is found to have unexpectedly high tear strength and resistance to puncture for an oriented foil compared to the usual known oriented foil of vinylidene chloride vinyl chloride copolymer.

ISLAND

1A 7 976 16

Testing of Packaging Resistance to Violence The following test method is carried out: All test bags are pre-coded and conditioned for 24 hours at 7-10 ° C.

Randomly selected bags are used for packaging cut-out right-handed meat containing bone with a weight of 11.3-13.6 kg. The bags are 41 cm wide and 76 or 81 cm deep. These packages are evacuated and the bags are closed with metal clips, sealed and shrunk in an air stream.

These packages are then inserted into wax-coated corrugated containers with three in each container. These containers are then closed with nylon monofilament tape.

The individual containers are then subjected to a fall test where they fall from a height of 0.91 m from a moving conveyor belt. The container is subjected to a transport shuttle sample after being stored at 3 ° C for 24 hours, then shaken for 7.5 minutes at 1 g on an L.A.B. testing machine. L.A.B. = Laboratory determined accelerated fracture is performed in a standard commercial shaking machine comprising a platform of ca. 1.5mxlm with side-20 walls on which the packages are loaded as it moves up / down and forward / back (ie moved in two planes) in repeated cycles where the number of cycles / minute is preselected after a known correlation with the number of km transport in truck. In this way, packaging can be subjected to accelerated testing of their strength against violence perpetrated by road transport in lorries.

In both tests, the packaging is then pumped up with air and immersed in water to determine any leakage. A leak packaging is judged as failure.

The results set out in Table I below are obtained with bags made using the laminates prepared as described in Examples 1 and 2, and compared with bags intended for such packaging purposes and with the same dimensions, but made from conventional sheets of related nature. These comparison bags are subjected to exactly the same test conditions. In the table the result is 17 147976

ISLAND

The percentages expressed as percentages of the number of packages surviving the specified sample relative to the total number of tested packages or packages that have been subjected to the sample.

5 In FIG. 5 is a graph expressing the molecular weight distribution of an ethylene / vinyl acetate polymer, wherein the molecular weight distribution is determined using gel permeation chromatography. This curve is analyzed according to standard statistical technique and the following determinations are made: 10 Standard deviation (sd) 3.07

Number average molecular weight (M) 28.96 s <3.

Coefficient of variation 100 x -jj- 10.62

Area under curve -10% of M 64.32

A polymer with a coefficient of variation of not more than 15 13 is considered to have a narrow molecular weight distribution. The average molecular weight number is the weighted average molecular weight, (i.e. the summation of the molecular weight having a given molecular weight according to the abscissa of Fig. 5 times the number of molecules having this given molecular weight divided by summation of the number of molecules with this given molecular weight since both summations are summed from 1 to infinity).

25 30 35 18 147976 ctf \

H

Cr> <U in fig · <*

• H -H

H * P I

U

RJ tji m o in o o (¾ cn · <»-¾1 ro in in

ra \ Η H

fi cm

0 O

1 Ό on Ό H

Ο Ο M

g> φ ap a vo Η OP H OP dP <#> dP - Ο ο cm cm o in vo mg> oo σν co ro Φ <U Π3 H> fi U s. m φ h +>> (¾ to o Ό H 0 fi g φ H ′ +3 »->

(I) O 'dP

Λ Φ * 0 fi n (0> O * H dP dP dP dP -

Eh ©. g h m ro ro in ro H a) r * t "vo cm cm (¾¾ +> Ό fi X H (8 fi Φ +» fi fe M ft m ft] +> "0) 0) +> ω

m H H OV H CO

fid) VO VO in 'i * H, ¾ B M S> PI -Ml' ϋ

i m i -H

ο cu <d cm ακ

tr> tJi &> Φ H Φ 0 <l> M

H H H ιφ Φ +) * 0 Η H 0 θι -01 -01 · ΗΕΦ · τΙΛΉΛ

IH iH m Η> ιΗ O H O U

• Η Η Η> iH HU> iH Φ +) φ fiO-H fi ^ ίΙιΛΌ +) +) +> ri ft-P »3 -H fi: · 0ι · Η ΦΗ φ Φ CM> OM> -H, ¾ Λ

Η Η H U g Φ> H U

HH HH HH ό i φο ό \ <d cd m ΗΦ-ΗΦΗΦ ΗΌΗΦ HtigraU +) (¾ +> & +) (¾ tO-HVHH Φ · η £ ιΟ 10 g Mg MgT3H OtIHH & fi Ο) gφgφgφfi0φ · fi00 0

Μ ΦΜ φ Μ ΦΜ ttSHMOS (0Hft = H

Ο Η Λ! UX M AS +) + 3 0 · +> +3 0 vo fi (¾ (χιΦϋιΦΡ ^ Φωο ais co o o vo &