Laminates of ethylene vinyl acetate polymers and polymers of vinylidene chloride

(54) Name: Composition of vinylidene chloride polymers

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The present invention relates to a composition of vinylidene chloride polymers as well as films and laminates containing them, and in particular to laminates for use as packaging materials.

For many purposes, packaging materials are required to have good strength against unmatched treatment and to withstand shocks and blows from the outside during transport and handling of the packaging.

When the goods inside the package are not soft or flexible, tearing can also occur from inside the package during transport and handling. An example of goods that often tear the packaging from insides is meat containing bone. The packaging material may be punctured by the relatively hard bone, which of course would have an adverse effect on the meat. Also many other goods require packaging in a material with good resistance to tearing.

Another essential requirement for many packaging materials is that they should have low oxygen permeability, especially in food packaging. A polymeric material superior in this respect due to its low oxygen permeability is a copolymer of vinylidene chloride with at least one other ethylenically unsaturated monomer, the copolymer containing at least 50% by weight of vinylidene chloride derived units.

The copolymers are preferably a copolymer of vinylidene chloride with vinyl chloride. It can, for example, contain 70-85 wt% vinylidene chloride derived units and 30-15 wt% vinyl chloride derived units. However, there are many other well known monomers which are suitable for polymerization with vinylidene chloride to form a low oxygen permeability polymer, which monomers need not be enumerated in this context.

However, the above-mentioned vinylidene chloride copolymers do not have sufficient resistance to tear wear for certain special uses. Therefore, it has been proposed to use a laminate for packaging, which comprises a first layer of high resistance to shredding, a second intermediate layer of vinylidene chloride copolymer, and a third layer of high resistance to shredding. Such a laminate provides protection against damage from the inside and outside of the package. The vinylidene chloride copolymer layer is referred to as barrier layer or barrier layer, since it acts as a barrier for the passage of molecular oxygen.

A suitable way of making a laminate of the above type would be to melt extrude a tear-resistant substrate film, to cool the film to solidify it, to melt extrude a barrier layer over the vinylidene chloride copolymer laminate, to spread the barrier layer to stiffen the laminate and to solidify the barrier layer to solidify to form a laminate and biaxially stretch the laminate. However, problems have arisen in connection with the melt extrusion of the vinylidene chloride copolymer. It is convenient and economically advantageous to prepare the vinylidene chloride polymer by emulsion polymerization.

It has now been found that the emulsion polymerized product, herein referred to as emulsion polymer, is sometimes deposited in the extruder, i.e., it does not flow sufficiently in the molten state. The present invention solves this problem.

Thus, according to the present invention, there is provided a composition comprising 5-50% by weight of suspension polymerized and 95-60% by weight emulsion polymerized copolymers of vinylidene chloride having at least one other ethylenically unsaturated monomer, the copolymers having at least 50% by weight vinylidene chloride derived units.

Surprisingly, it has been found that the above-mentioned composition of emulsion and suspension resins can be melt extruded and formed into a biaxially oriented film of good quality. Normally, the suspension resin would be expected to cause the formation of gels in the emulsion resin during extrusion. In the present case, however, the suspension polymer appears to act as a stabilizer rather than causing gel formation in the emulsion polymer film. Although the invention is by no means limited to the following theory, it is assumed that the suspension polymer melts more slowly in the cylinder of the spraying machine and acts as a polish when the mixture passes through the spraying machine, which prevents the build-up of polymer on the surface of the spraying machine cylinder. In other words, the emulsion polymer tends to stick as it melts and the suspension polymer acts to some extent as ball bearings, which move it forward. The whole mixture of copolymers, of course, eventually melts and extrudes.

It has been found that when the suspension polymer content in the polymer blend exceeds 20%, orientation of the film becomes difficult. Only with very careful handling is it possible to use a mixture containing a suspension polymer content up to 40%. The reason for the difficulty of orienting lies in the fact 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 far too quickly in order to achieve sufficient reduction (film thickness reduction) during the orientation step.

It has been found possible to operate at injection temperatures between the normal process conditions of the emulsion and suspension polymerized polymer, i.e., usually from 158-171 ° C for the particularly preferred compositions. Initially, it was not believed that the blended materials would be compatible in the molten polymer stage because of the differences in melt rate of these two polymerases.

British Patent 1,102,576 discloses a composition based on a mixture of (i) a suspension polymerized copolymer of 75-85% by weight vinylidene chloride and 25-15% by weight vinyl chloride and (ii) 0.05-5% by weight on the weight of the composition, of a vinylidene chloride 50 homopolymer. The purpose of the British patent is to reduce the time it takes for the copolymer to crystallize from an extruded melt. The purpose of reducing the time of crystallization is to provide a hollow extruded material, such as a bottle or hose which exhibits rigidity, by crystallization, sufficiently fast so as not to lose its shape. This is a completely different and practically opposite idea from the idea underlying the present invention, which seeks to avoid too rapid crystallization of the molten polymer, and whose main purpose is to improve the flowability of the vinylidene chloride 40 copolymer in the present invention. extruder cylinder. This object is achieved by using a composition wherein the main polymeric component

7509006-8 (60-95 wt%) is an emulsion polymerized copolymer, which is something quite different from British Patent Specification No. 1,162,576, wherein the polymeric main constituent (95^_99.95% by weight) is a suspension polymerized copolymer, and further, by using a mixture of two copolymers of vinylidene chloride, which is contrary to the requirement of the above-mentioned British patent to incorporate only one copolymer and a certain proportion of a rapidly crystallizable homopolymer .

The present invention will now be further described in the form of preferred embodiments.

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

The preferred proportions of emulsion and suspension polymer in the compositions of the invention are 5-15% suspension polymer and 85-95% emulsion polymer. The composition preferably also comprises 2-10% by weight, more preferably 4-6% by weight, epoxy resin. Thus, the preferred barrier layer composition is based on a copolymer of vinylidene chloride with vinyl chloride having 5-40% vinyl chloride derived units mixed with 2-10% epoxy resin, the copolymer itself being a blend of from 5-40% suspension polymer and 60-95% emulsion polymer. A particularly preferred barrier layer composition comprises (a) a vinylidene chloride / vinyl chloride copolymer having 15-50% 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 refer to weight percent, unless otherwise stated. ___ _______ _____

By epoxy resin is meant an epoxy-containing heat-curable resin of high viscosity, which must not be confused with epoxidized oils, which are the usual epoxy plasticizers and which are normally formed by expoxidized natural oils and which are much less viscous.

The invention comprises a film comprising the above composition of emulsion and suspension copolymers of vinylidene chloride. In addition to a simple film, the invention also includes laminates containing such film.

In one embodiment, the invention comprises a flexible laminate comprising a film of the invention carrying at least one other layer of a polymeric material. The invention is particularly useful for providing the barrier layer in a laminate having at least three layers, namely, tear-resistant layer, barrier layer and another probe wear-resistant layer in said order, and the preparation of such a laminate will be described below. However, it dares

7509006-8, it is observed that the composition of emulsion and suspension polymer can be used to prepare a laminate having only two layers, one of the tear-resistant layers being omitted.

Some laminates with two tear-resistant layers and with a barrier layer therebetween are described in Swedish patent application 4163/72. For use in heat shrink packaging, the polymer films are given a molecular orientation by stretching.

A preferred class of polymers for one or both of the tear-resistant layers are copolymers of ethylene and vinyl acetate containing 5-20% by weight units derived from vinyl acetate. The ethylene / vinyl acetate copolymers referred to herein comprise (consist wholly or contain only as part thereof) polymerized ethylene and vinyl acetate units. Thus, other components may be present; the polymer may be a terpolymer or any other polymer than a copolymer as long as the dominant moieties are derived from ethylene and vinyl acetate. In order to orient such polymers, it is appropriate to first crosslink them. The ways in which such cross-networking is achieved are known per se, e.g. irradiation.

The preferred polymeric material of the first layer (substrate) of the laminate is a copolymer of ethylene and vinyl acetate with

5-20 wt.%, Most preferably 8-12 wt.% Units of vinyl acetate with the required molecular weight distribution. The third, destruction-resistant layer is preferably made of the same copolymer and, if desired, may consist of exactly the polymer used in the substrate.

Embodiments of the invention are described with reference to the accompanying drawings, in which Fig. 1 is a schematic diagram of a device used in a preferred method of laminate manufacture according to the invention; 3 is a view along the line

3-3 in Fig. 2 and Fig. 4 are a sectional view through a laminate of the present invention.

According to Fig. 1, the tubular material 10 is sprayed downwardly from the nozzle head 11, which head is fed from the extruder 9. The extruded tubing material has a thickness of 250-750 microns, especially 375-625 microns. After cooling or curing with water jet supplied from the cooling ring 12, the tubular material is clamped together by clamping rollers 13 and passed through an irradiation vault 14 surrounded by a protective casing. 15, the material being irradiated with electrons from an accelerator 16 with an iron core transformer. Other accelerators such as a Van der Graff accelerator or resonant transformer may also be used. Radiation is not limited to electrons from one

7509006-8 accelerator, without any ionizing radiation can be used. The unit of radiation used in this specification is made up of rows, defined as the amount of radiation that releases 100 energ energy (measured as adsorbed energy) per gram of irradiated material. MRI is one million (10⁶) row.

In some cases, it may be desirable to provide bridging in the polymer, for example with chemical bridges. However, in the preferred method, radiation is used and preferably in the manner described below. The time for irradiation of the tubular material 10 of the ethylene-vinyl acetate copolymer is not critical, but need only be sufficient to provide the dose required for bridging to occur. In the present embodiment, the material 10 is preferably irradiated with a dose of 2-15 MR and especially with a dose of 2-10 MR.

The tubular material 10 is passed through the irradiation arch 14 of rollers 17. After the irradiation, the material 10 is passed through clamping rollers 18, after which it is inflated somewhat by an enclosed gas bubble 20. The tubular material is not stretched longitudinally to an appreciable degree, since the rollers 18 are driven approximately the same speed as the previous rollers 1J. The tubular material is inflated only sufficiently to provide a substantially circular tubular material without appreciable transverse orientation.

The slightly inflated and irradiated tubular material 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-sprayed from the coating nozzle 22 and applied to and adhered directly to the irradiated tube 10 to form a tubular two-layer laminate 24. The second tubular film 23 is preferably a barrier film. This film is made from a vinylidene chloride polymer containing at least 50% by weight of units derived from a vinylidene chloride monomer and is preferably made from a blend of copolymers of vinylidene chloride and vinyl chloride with 5-40% units of vinyl chloride, especially 15-30%. This mixture consists of 5-40% suspension polymer and 95-60% emulsion polymer.

The spraying machine 25 is preferably operated at a cylinder temperature of 43-150 ° C, especially at 121-149 ° C and the spray nozzle is preferably operated at a temperature of 138-171 ° C and especially at 146-167 ° C. The extruded tubular material has a thickness of 25-125 microns, preferably 50-100 microns.

The spraying machine 25 is of a conventional type, ie a standard machine of size 8.2 cm.

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The details of the nozzle 22 are better illustrated in Figs. 2 and 3. The nozzle 22 is a circular nozzle nozzle having an associated insert 26 to form in its preferred shape an aperture 27 of diameter 8.9 cm for the slightly inflated tubular material 10. The aperture 27 through which the inflated support passes is formed by the core 28, which is attached to the nozzle housing 29. The path of the molten coating material 23 is indicated by the arrows in Figures 2 and 3. The vacuum chamber 21 applies a slight vacuum, for example in the range of from about 1 to about 6.4 cm of water column, to the nozzle 22 to pull or suck in the extruded film 23 as it is still molten against the inflated tubular material 10 to prevent formation of vacuum bladders in laminate 24. Vacuum chamber 21 may simply be a cylindrical housing whose inner diameter closely matches the outside diameter of the inflated hose. A vacuum can be applied via the outlet 3θ by conventional vacuum generating means (not shown).

Preferably, the film 24 consisting of two layers is fed to the coating or lamination nozzle 32 when it is still hot. In a discontinuous process, it would be possible to cool or cure the hose 24 before passing it to the second coating nozzle 32, but this would usually also require a new inflation and reheating of the hose in order to obtain an excellent joint between the second and first layers. The first layer, seen from the outside of the hose, would constitute both an outer layer and the outer layer of the tubular material.

A third layer is melt-sprayed from the coating nozzle 32 and applied to and adheres directly to the tubular two-layer laminate 24 in order to form a tubular three-layer laminate 34. The tubular layer 33 preferably has a composition selected from the above in connection with the tubular file. 10 discussed. Although it does not necessarily have the same composition as the tubular film 10, it is appropriate if they are consistent. The coating process at the nozzle 32 is the same as that of the nozzle 22. The vacuum chamber 36 serves the same function as the vacuum chamber 21 and operates in the same manner, vacuum being applied through the outlet 37. The tubular film or layer 33 has a thickness of 75-375 microns and preferably a thickness of IOO-300 microns.

The tubular three-layer laminate 34 is cooled or cured with water jet from the cooling ring 39 · The water usually has a temperature of about 7 ° C. Clamping mills 40 then compress the tubular three-layer file 750-006-8, but then wrap it on a reel roll 4l. Alternatively, in a continuous process, the film is not wound onto the reel roll 4l but delivered directly to the next step of the process (stretching).

As can be seen in Fig. 1, a winding roll 42, which consists of a previously prepared roll-up roll 41, is unwound over the guide roll 45 · The laminate 54 is substantially unstretched and not oriented as it passes over the guide roll 45. The film passes from the guide roll 45 into a hot water bath 44 containing water 45. The preferred reheat temperature or hot water temperature is 70-100 ° C and especially 82-96 ° C. The compressed tubular three-layer film is immersed in the warm water for at least about 5 seconds. This time period is generally required to give the film the temperature required for orientation stretching. A typical residence time in the water is about 20 seconds. The guide rollers 46 and 47 guide the compressed hose through the water bath 44.

When the appropriate orientation temperature is reached, bubble 54 is blown into the film from the water and the film is stretched in both transverse and longitudinal directions in a preferred ratio of 1: 1.5 - 1: 6, especially 1: 2 - 1: 4, corresponding to a biaxial orientation of 1: 2.25 1:56 respectively. 1: 4 - 1:16. The thickness of the layers is reduced substantially in the same proportions. The bubble 54 is held between the clamping rollers 48 and 49. The hose is compressed by the rollers 5θ and the laminate passing through the clamping rollers 49, over the guide roll 51 and under the undrained roll 55, is wound on the roll 52.

Fig. 4 illustrates a cross-section through the oriented laminate 54. The first applied layer, which is the inner layer of the hose, is the layer 10, with a preferred thickness of 12-125 microns and especially 25-50 microns. The barrier layer is denoted by 25 and has a preferred thickness of 1.25 - 50 microns, preferably 2.5-6 microns.

The third layer 53, which constitutes the outer protective layer of the hose, is preferably 2.5-100 microns thick, preferably 6-25 microns. These three layers can be directly joined to each other without intermediate layers.

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The laminate exhibits a shrinkage stress of usually 14-55 kp / cm and preferably 14-28 kp / cm and a free shrinkage of at least 40%, or preferably at least 50% at 9 ° C, and a free shrinkage of at least 20%, especially at least 50%, at 85 ° C.

In another preferred method of preparing the laminate, the second and third applied coatings can be sprayed onto the preformed hose from a syringe nozzle. Thereby, the same final product laminate is obtained but according to a somewhat more difficult process.

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The tubular film, prepared from the tubular material of the invention, gives an excellent bag with barrier and the layer 10 adheres very well to itself at temperatures between 95-177 ° C without turning significantly on heat sealing with a thermal impulse sealer.

The layer 10 also gives the bag excellent strength against puncture.

The thin barrier layer provides the required barrier properties with a minimum of thickness and cost. The outer layer of unirradiated copolymer provides a high degree of resistance to destruction at low temperatures and gives the bag increased resistance to tearing.

An advantageous way of using bags made from the hose material of the present invention is disclosed in U.S. Patent No. 5,552,090. After evacuation of the bags, they are conveniently sealed by the application of clamps, as shown, for example, in US Patent No. 5 · 5θ5 · 746. A suitable evacuation device is disclosed in U.S. Patent No. 5 * 628,576.

According to the invention, a method of packaging a product, in particular a food item, is provided by enclosing the product in a film or laminate according to the invention in molecular oriented form, the film or laminate being in contact with the product, and heat being applied to the film or laminate to Shrinkage should occur.

The area of ​​application for which the above laminate was specially designed, although obviously other areas also exist, consists of a packaging material for packing pieces of fresh beef or mutton with visible bones. For such application, a three-layer laminate prepared from the above-described preferred materials is used. A laminate with a different and inferior barrier layer would adversely affect the preparation of the laminate and the quality of the laminate. The laminate is non-toxic and is generally suitable for packaging food. It is understood that when a bag is used to package a piece of fresh beef or sheep meat which is not frozen and not to be frozen, but which is packaged and kept at low temperatures, for example at 0-7 ° C, the bony meat piece is enclosed in the laminate , and exposed legs bump into the inside of the bag.

In the preferred packaging method, bony meat is loaded into the three-layer laminate, which is biaxially oriented and shrinks in heat. The laminate thus encloses a piece of meat with bones and, depending on how the meat is cut, there is always a risk that an exposed bone will strike against the laminate. The bag is evacuated and sealed to maintain vacuum. Thereafter, the bag is heat shrunk over the meat.

7509006-8

In the preferred embodiment of the invention, it is important that the radiation dose is within the stated limits to obtain an adhesive coating which exhibits sufficient tensile strength to provide good machining ability, good puncture resistance which may be caused by the meat bone and good orientation ability. The irradiation should be sufficient to increase the tensile strength without, therefore, greatly reducing the elongation, since the material must be able to stretch over the bone when bony pieces of fresh beef or mutton are packed. At the same time, it is desirable for the bag to cling to soft meat and to bones wherever such protrudes from the meat. Fresh beef or sheep meat can be soft and allows the bone to move or float therein. When the film is irradiated too much the elongation is reduced and the bone penetrates the package at impact. The vinyl acetate content above the stated decreases the melting point of the polymer and adversely affects the high temperature properties required for a shrink-wrapping process.

In addition to loss of resistance to destruction occurs at heat shrinkage temperatures, the heat seal is delaminated when the vinyl acetate content exceeds 18% in this particular laminate. As the vinyl lacquer content drops below 5%, the elasticity at low temperatures decreases to the extent that the bag no longer functions as required in an efficient packaging process.

The preferred three-layer laminate exhibits a variety of highly desirable properties, typically including good shrinkage at moderate to elevated temperature, elongation of at least 50%, more preferably 100-125%, oxygen permeation rate not greater than 70 ml / (m / 24 h / l atm) at 22.8 ° C and 0% relative humidity (ASTMD 1434) and usually no more than 25 ml / (m²/ 24 h / l atm) at 22.8 ° C and 0% relative humidity (ASTM

D 143 ^). In its preferred form, the film exhibits a resistance to rupture using a ball of at least 25 cm-kg, measured on a Bali Burst tester No. 13-8 from Testing Machines Inc using a standard spherical head.

Various modifications of the invention may be used independently or in combination, advantage being gained over the materials commonly used. The barrier layer mixture can be formed into independent films. The blends possess the superior spray properties, which prove whether the material is spray-coated or melt-sprayed as independent self-supporting films. To be self-supporting, the vinylidene chloride polymer film must be at least about 50-75 microns thick if ejected as a^! tubular material using the usual suitable spraying technique.

7509006-8

In addition, it has been found that the oriented film formed from a mixture of emulsion and suspension polymerized vinylidene polymer exhibits unexpected resistance to tear and puncture compared to these properties for conventional vinylidene chloride-vinyl chloride polymer films.

In some cases, it may be desirable to use another polymer in the outer layer of the laminate. This layer must be resistant to destruction by wear and tear. Examples of such polymers are polypropylene, polyamides and polyesters as well as copolymers or terpolymers of propylene, amides or esters. Such groups of coating polymers are well known. Of course, in some applications, the outer (third) layer or even the first (inner) layer can be avoided.

The composition of the invention and the various layers of the laminates of the invention may contain compatible additives such as stabilizers, pigments, process aids such as, for example, waxes, air-improving agents, antistatic and anti-blocking agents.

The invention is further illustrated by the following embodiments. Example I.

According to the process, which is schematically illustrated in Figure 1, an ethylene / vinyl acetate copolymer containing 10% vinyl acetate having a melt index of about 2 and marketed as UE 657 by the US Industrial Chemicals Division of National Distillers is fed to the funnel of the sprayer 9. The sprayer has a dimension of 8.9 cm and is operated at the following temperatures: rear zone 121 ° C, center cylinder 152 ° C, front cylinder l45 ° C, insert l49 ° C and nozzle 166 C. The speed of the screw is 57 rpm and the pressure is 267 kp / cm. The diameter of the nozzle is 8.9 and the circumference of the tubular material produced is 20.5. The water from the cooling ring 12 has a temperature of 7 ° C. The clamping rollers 15 are operated at a speed of 10.7 m / min and the thickness of the compressed hose material is about 460 microns.

The compressed material is passed through a radiation unit, such as that shown in Fig. 1, which is operated at 500 kilo-electron volts.

MA and a speed of 10.7 m / min. Pyra passes are performed and the tubular material receives a dose of about 6 mega.

The irradiated substrate film is then fed to a coating nozzle 22 where it is covered with a barrier material. The barrier material contains a slightly plasticized mixture of copolymers between vinylidene chloride and vinyl chloride. The copolymer mixture consists of 10% suspension polymerized and 90% emulsion polymerized copolymer. The emulsion polymerized copolymer consists of about 70% units from vinylidene chloride and 50% units from vinyl chloride, while the suspension polymerized copolymer comprises about 80% units obtained from vinylidene chloride and 20% units from vinyl chloride. These materials were purchased from Dow Chemical Company and sold as UP 925 (the emulsion polymerized plastic) and SP 489 (the suspension polymerized plastic). Other constituents of the barrier layer consist of 5% epichlorohydrin bisphenol A, an epoxy resin sold under the name EPON plastic 828 by Shell Chemical Company and about 0.5% microcrystalline paraffin wax sold by Sun Chemical Company under the name Wax 5512. These three plastics are blended into a high-speed, high-intensity brand Prodex-Henschel mixer, whereupon the mixture is fed to the funnel of the extruder 25, which is a Prodex extruder having a dimension of 5 cm including an angular head type nozzle illustrated in Fig. 2 and 5 · This extruder operates at the following temperatures: rear zone 99 ° C, center cylinder

127 ° C, front cylinder 149 ° C, insert 144 ° C and nozzle 160 ° C. The screw speed is 54 rpm and the pressure is 590 kp / cm. The nozzle diameter is 8.9 cm and the circumference of the tubular material is 20.5 cm. The upper rollers 18 are operated at a speed of 10.7 m / min and the thickness of the coating is about 75 microns.

Then, a third layer is formed using the same plastic as in the first layer. The plastic is sprayed through an extruder 55 which is operated in the same manner as the machine 9 except that the following temperatures are used: rear zone 121 ° C, center cylinder 152 ° C, front cylinder 195 ° C, insert 227 ° C and nozzle 252 ° C. The coating nozzle 52 has the same design as the nozzle 22. The bottom rollers 40 are operated at a speed of 11.0 m / min and the water from the cooling ring 59 has a temperature of 7 ° C. The thickness of the coating is approximately 150 microns.

Biaxial orientation is achieved by preheating the tubular material in water at about 88 ° C as shown at 44 in Fig. 1, after which the heated material is fed through the clamping rollers operated at the speed of 5, θ m / min to the air discharge rollers driven by the velocity is 21.4 m / min, whereby the 10 cm wide tubular material is inflated to give a film width of about 4 cm and a film thickness of about 6 l microns. The tubular material is then wound onto a storage roll, after which bags are formed by the material through transverse sealing at intervals to form bottoms in the usual manner and the tubular material is torn off at desired bag lengths.

7509006-8

Example II.

The above procedure was repeated except that the barrier layer was modified by the addition of 2% 2-ethylhexyl-dimethylphosphate plasticizer, sold by Monsanto under the name Santicizer 144, and the epoxy plastic content was reduced to

Example III.

The procedure of Example I was repeated except that 5% of an epoxidized soybean oil (not to be confused with epoxy resin) from Swift & Co., designated Epoxol 7-4, replaced 5% epoxy resin.

Example IV.

The procedure of Example I was repeated except that 5% epoxy plastic was replaced with 4% 2-ethylhexyl diphenylphosphate plasticizer and 1% magnesium oxide.

Example V.

The procedure of Example I was repeated except that a mixture of 53.5% by weight isotactic polypropylene (Novamont F007), 33.3% polybutene-1 (Mobile PB 103) and 13.3% atactic polypropylene (Novamont Lot 2030) was used to form the third layer. Atactic and isotactic polypropylene are first put in proper proportions to a banbury-type mixer and melt blended for about 8 minutes at 204 ° C, after which the mixture is sprayed onto a sheet which is punched into grits. These groats are combined with polybutene-1 groats in a rotating drum, whereupon the mixture is charged to the hopper in the spraying machine 35- The spraying machine 35 is operated at the following temperature: rear zone 196 ° C, middle zone 204 ° C, front zone 232 ° C, insert 204 ° C and nozzle 2l8 ° C.

Example VI.

The composition used in Example II to form the barrier layer except that 4% epoxy plastic was used and the content of the UP 925 plastic was reduced to 1% was sprayed as a self-supporting single layer film under the spray conditions described in Example II. A coating of propylene glycol was applied to the inside of the tubular material to prevent adhesion when the material is compressed before biaxial orientation occurs. The process was continuous, bubble 54 was formed after the tubular material was compressed, but without the tube being unwound. In addition, the water bath was kept at about 38 ° C. The thickness of the extruded film was about 125 microns and the thickness of the biaxially oriented film was about 19 microns after a total orientation ratio of about 12: 1 measured biaxially. The film was found to have an unexpectedly high resistance to tear and puncture to be oriented film compared to previously known oriented films

7509006-8 of copolymers between vinylidene chloride-vinyl chloride.

Attempt to destroy the packaging.

The following experimental procedure was carried out. All sample bags were labeled and conditioned for 24 hrs at 7-10 ° C. Randomly selected bags were used to package whole nut side with the ribs remaining, weighing 11.5 15.6 kg. The bags were 41 cm wide and 76 or 8 cm deep. The packages were evacuated and the bags were provided with clamps, shrunk sealed and dried in a forced pull. The packages were then placed three and three in wax-coated corrugated containers. The containers were then sealed with single-fiber nylon tape.

In a fall trial, the containers were dropped from a height of 0.91 meters from a running conveyor belt. In the attempt to examine destruction during transport, the containers were stored at J ° C for 24 hrs and then shaken 7.5 min at 1 g on a LAB vibration tester for the purpose of simulating transport along a 200 kg long stretch of road.

In both experiments, air was pumped into the packages, which were then submerged under water for the purpose of determining leakage. A leaky package was classified as unsuccessful.

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Etfc or alternatively preferred barrier layer material is a coating material of the type used to deposit a vinylidene chloride polymer coating from a solvent or from an emulsion. Previously, such a copolymer was applied from a solution in a solvent at room temperature and the layer subsequently dried. This liquid coating polymer can be exchanged for the suspension polymerized polymer in the composition of the invention. It is believed that this liquid coating vinylidene chloride copolymer increases the flow of the barrier layer composition in the same way as a lubricant due to its low melt viscosity. Liquid vinylidene chloride polymers for coating have not been believed to be fusible. In other cases, it has been found possible to replace the entire amount of vinylidene chloride copolymer in the composition with the liquid coating vinylidene chloride copolymer and form the barrier layer by melt spraying. It is surprising that it is possible to create or form a good film in this way. Liquid coating vinylidene chloride copolymers are also usually polymerized by emulsion technique but have established a pronounced position in the art. Preferably, this vinylidene chloride copolymer contains from 5 to 15% by weight of vinylidene chloride derived units.

The invention not only encompasses laminates with such a barrier layer but generally relates to a process for forming an article, fc.ex. in the form of a film, which means melting a liquid coating type vinylidene chloride copolymer. In a preferred embodiment, the liquid coating type vinylidene chloride polymer is present in an amount of from 5-100%, the residue (if present) being 2-10% epoxy resin and melt extrusion grade vinylidene chloride polymer.

Example VII.

The procedure of Example I was repeated with the exception that the barrier layer composition was 66% vinylidene chloride / vinyl chloride copolymer resin UP 925, 50% of a liquid coating vinylidene chloride polymer resin sold by Dow Chemical Company as QX 2168, 2% Epon resin

828 and 2% Sanitizer.

Example VIII.

The procedure of Example VII was repeated except that the vinylidene chloride polymer in the barrier layer composition was constituted by QX 2168 alone.

Examples IX and X.

The procedures of Examples VII and VTII were repeated with the exception of a liquid coating vinylidene chloride polymer sold by WR, Grace &amp; Co, which Daran CR 6795-H used instead of QX 2168.

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