FI62121B - VINYLIDENCHLORIDE COPOLYMER COMPOSITION ANVAENDBAR FOER FORMNING AV EN FILM - Google Patents

Description

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Patent- and register-registration Antektn utisgd och uti.tkrffun pubifcured 30.07.82 (32) (33) (31) Pyy «**« y utuolkuu * - Bvgird prlorltut 30.03. 71 USA (US) 129501 (71) W.R. Grace & Co., Grace Plaza, llli * Avenue of the Americas, New York, N.Y. IOO36, USA (72) Harri Jouna Brax, Spartanburg, South Carolina, Joseph Frederick Porinchak, Spartanburg, South Carolina, Alan Stuart Weinberg,

Greenville, South Carolina, USA (US) (7M Berggren Oy Ab (5h) Vinylidene chloride copolymer blend suitable for film production / 72 (Patent 50975) This invention relates to a vinylidene polymer blend and films and laminates containing the same, and in particular to laminates for use in packaging materials.

For many uses, packaging materials must be highly tolerant of violence in order to tolerate external violence during transport and handling. Where the goods contained in the package are not soft or flexible, violence may be applied to the packaging material from inside the package during transport and handling. One example of a commodity that is particularly susceptible to internal violence is meat packed with bones, i.e. a piece of meat containing bone. The packaging material may burst against a relatively hard bone, which of course has a detrimental effect on the meat. Many other consumer products also require packaging in a substance with a high resistance to violence.

Another important requirement for many packaging materials is that they must have low oxygen permeability, especially when food is packaged. A polymeric material which, due to its low oxygen permeability, is excellently copolymer of vinylidene chloride with at least one other ethylenically unsaturated monomer containing at least 50% by weight of molecules derived from vinylidene chloride.

Preferably it is a copolymer of vinylidene chloride with vinyl chloride. For example, it may contain 70-85% by weight of molecules derived from vinylidene chloride and 30-15% by weight of molecules derived from vinyl chloride. Other monomers suitable for polymerization with vinylidene chloride to form a polymer with low oxygen permeability are many and well known, so they are not listed here.

The above-mentioned vinylidene chloride copolymers do not have good enough resistance to violence for some purposes. Therefore, it has been proposed to use a laminate comprising a first layer having good resistance to violence, a second, intermediate layer, vinylidene chloride copolymer, and a third layer having good resistance to violence. Such a laminate provides good protection against damage both inside and outside the package. The vinylidene chloride copolymer layer is called the "barrier layer" because it acts as a barrier to the passage of molecular oxygen.

A convenient way to make a laminate of the above type is to melt extruding a non-violent substrate, cooling the film to solidify it, melt extruding the vinylidene chloride copolymer barrier layer into the laminate, forming a barrier layer over the substrate, solidifying the barrier layer, .

However, there has been a problem in the art with melt extrusion of a vinylidene chloride copolymer. It is convenient and economical to prepare a vinylidene chloride polymer by emulsion polymerization. It has been found that an emulsion polymerized product, referred to herein as an emulsion polymer, is sometimes deposited on an extruder. So. it is not flowing enough in the molten state. The present invention solves this problem.

According to the present invention, there is provided a composition useful in forming a film based on (i) a suspension copolymerized copolymer having at least 50% by weight vinylidene chloride and the remainder at least one copolymerizable ethylenically unsaturated monomer, and (ii) an emulsion polymerized polymer based on vinylidene chloride, characterized in that said emulsion polymerized polymer is a copolymer of at least 50% by weight of vinylidene chloride and the remainder of at least one other copolymerizable copolymeric copolymer and monomer copolymer. the relative amounts are 5-40% and 60-95% by weight, respectively.

It has now unexpectedly been found that a mixture of emulsion resins and suspension resins as defined above can be melt-extruded and formed into a benign, biaxially oriented film. Normally, the suspension resin would be expected to form gels in the emulsion resin during extrusion. In the present case, however, the suspension polymer appears to have a stabilizing effect rather than causing gels in the emulsion polymer. Although the applicant does not wish to be bound by the following assumptions, it is assumed that the suspension polymer melts more slowly in the extruder tube and acts as an abrasive as the mixture passes through the extruder, preventing polymer accumulation on the surface of the extruder housing. In other words, the emulsion polymer tends to stick as it melts, and the suspension polymer acts as if it were a ball bearing, carrying it forward. Of course, the entire copolymer blend eventually melts and extrudes.

It has been found that when the concentration of the suspension polymer 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 up to 40% of suspension polymer. The reason for the difficulty in orientation is that crystals form more rapidly in the suspension polymer film. In this way, the suspension polymer acts as a "contaminant" in the emulsion polymer in the sense that the suspension polymer crystallizes too quickly to obtain sufficient thinning (reduction in thickness) of the film during the orientation step.

It has been found possible to operate at extrusion temperatures between the normal treatment values of emulsion and suspension polymerized polymers, i.e. generally between .138 and 171 ° C with most primary blends. It was not originally thought that the blenders would be compatible in the molten polymer state due to the differences in the melting rates of the two polymers.

British Patent 1,162,576 discloses a blend based on a blend of (i) a suspension polymerized copolymer having 75-86% by weight of vinylidene chloride and 25-15% by weight of vinyl chloride and (ii) 0.05-5% by weight -%, by weight of the mixture, of a vinylidene chloride homopolymer. The object of the invention according to this patent publication is to reduce the time taken for the copolymer to crystallize from the extruded melt. The purpose of reducing the time required for crystallization is to provide a hollow mouth-caps such as a bottle or tube that acquires rigidity through crystallization so rapidly that it does not lose its shape. This is a different and almost opposite idea compared to the present invention, in which too rapid crystallization of the molten polymer must be avoided, and in which the main purpose is to improve the flow of the vinylidene chloride polymer in the extruder housing. This object is achieved by using a mixture in which the larger component of 60 to 95% by weight is an emulsion-polymerized copolymer, in contrast to the above-mentioned patent publication in which the larger component of 95 to 99.95% by weight is a suspension-polymerized copolymer, and further using a , in contrast to the above-mentioned patent publication, which uses only one copolymer and in addition a rapidly crystallizing homopolymer.

The following describes the preferred features of the present invention.

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 ratios of emulsion polymer to suspension polymer in the compositions of the invention are 5-15% suspension polymer and 85-95% emulsion polymer. The mixture preferably also contains 2-10%, preferably 4-6% by weight of epoxy resin. Thus, the preferred barrier layer blend is based on a copolymer of vinylidene chloride with vinyl chloride having 5-40 units based on vinyl chloride, mixed with 2-10% epoxy resin, the copolymer itself being a blend of 5-40% suspension polymer and 60- 95% emulsion polymer. The preferred barrier layer blend comprises (a) a vinylidene chloride / vinyl chloride copolymer with 15-30% vinyl chloride-derived units, and (b) 4-6% epoxy resin as a plasticizer, wherein the copolymer is a blend of 5-15% suspension polymer and 85-95% emulsion polymer. All percentages herein are by weight unless otherwise indicated.

The "epoxy resin" used primarily as a plasticizer because it has been found to give better results than commonly used plasticizers is a high viscosity, epoxy-containing, thermosetting resin that should not be mixed with epoxidized oils, which are common epoxy plasticizers and are normally formed from epoxy natural oil and are much less viscous.

The invention also encompasses a film consisting of a blend of emulsion and suspension copolymers of vinylidene chloride as defined above.

In addition to a simple film, the invention also encompasses laminates containing such a film. In one embodiment of the invention, the invention comprises a flexible laminate comprising a film according to the invention which supports at least one layer of polymeric material. The invention is particularly useful for forming a barrier layer in a laminate having at least three layers, namely a violent tolerant layer, a barrier layer and a second violent tolerant layer, respectively, and the manufacture of such a laminate is explained below. It should be noted, however, that the mixture of emulsion and suspension polymer can also be used to make a laminate comprising only two layers, with the second non-violent layer being omitted.

Certain laminates with two non-violent layers and a barrier layer between them are described in application No. 879/72. For use in heat shrink packaging, the polymeric films are given a molecular orientation by stretching them.

4 4

The primary polymer group for either or both of the non-violent layers consists of copolymers of ethylene and vinyl acetate containing 5-20% by weight of vinyl acetate-based units. The ethylene / vinyl acetate copolymers in question comprise (consist in whole or in part only) polymerized ethylene and vinyl acetate units. Thus, other ingredients may be present; the polymer may be a ter polymer or a polymer other than a copolymer, as long as the major part is derived from ethylene and vinyl acetate. To orient such polymers, they are preferably first crosslinked. Methods of performing cross-linking 6 62121 are known per se, for example irradiation.

Your preferred polymeric layer for the first layer (substrate) of the laminate is a copolymer of ethylene and vinyl acetate with 5-20%, preferably 8-12% by weight of units derived from vinyl acetate and having the required molecular weight distribution. The third, non-violent layer is preferably the same copolymer and, if desired, may be exactly the same as that used as the substrate.

Embodiments of the invention will be described in connection with the accompanying drawing, in which: Figure 1 is a schematic diagram of an apparatus used in a preferred method of making a laminate according to the invention; Figure 2 is a cross-sectional view of a nozzle head forming part of this device; Fig. 3 is a view taken along line 3-3 of Fig. 2; and Figure 4 is a cross-sectional view of a laminate according to the present invention.

With respect to Figure 1, the tube 10 is shown to be extruded downward from the extruder head 11 fed from the extruder 9. The extruded tube is 250-750 microns thick, preferably 35-625 microns thick. After cooling, i.e., wetting with water from the cooling ring 12, the tube is flattened by pinch rollers 13 and fed through a radiant vault 14 surrounded by a cover 15, where it is irradiated with electrons from the iron core converter accelerator 16. Other types of converters such as a Van der Graff or resonant converter accelerator can be used. The radiation is not limited to the electrons leaving the accelerators, but any ionizing radiation can be used. The unit of radiation used in this specification is RAD, which is therefore defined as the amount of radiation capable of consuming 100 erg energy (measured as absorbed £ energy) per gram of irradiated material. MR is one million (10) RAD.

In special cases, it may be desirable to crosslink the polymer in other ways, such as with chemical crosslinking agents. However, radiation is used in the primary procedure, as explained above. The radiant run time of the ethylene / vinyl acetate copolymer tube 10 is not critical, but need only be sufficient to provide the required dosage to the cross-link. In the present embodiment, the tube 10 is preferably irradiated with a dose of 2-15 MR and more preferably with a dose of 2-10 MR.

The tubes 10 are guided through the irradiation vault 14 by coils 17. After irradiation, the tube passes between the pinch rolls 18, after which it is slightly inflated by means of a trapped gas bubble 20. The tube is pulsed only to the extent that the tube is made substantially circular in cross-section without significant cross-orientation.

Slightly bulged, the irradiated tube 10 is led through a vacuum chamber 21 to a lamination or coating nozzle 22 located below the chamber 21. The second tubular film 23 is melt-extruded from the coating die 22 and immediately deposited and adhered to the irradiated tube 10 to form a two-layer tubular laminate 24. This second tubular film 23 is preferably a barrier layer film. It is a vinylidene polymer in which at least 50% by weight is units derived from vinylidene chloride monomer and preferably a mixture consisting of a copolymer of vinylidene chloride and vinyl chloride having 5-40% units derived from vinyl chloride, preferably 15-30%. This blend consists of 5-40% suspension polymer and 95-60% emulsion polymer.

The extruder 25 is preferably operated at a temperature of 43-160 ° C, more preferably * 121-149 ° C, and the extruder is suitably operated at a temperature of 138-171 ° C, preferably 146-157 ° C. The thickness of the extruded tube is 25-125 microns, preferably 50-100 microns.

The extruder 25 is a conventional, for example standard 8.2 cm extruder. (»

The details of the nozzle 22 are better seen in Figures 2 and 3.

«

The nozzle 22 is a circular cross-head nozzle to which 4 adapters 26 are attached, so that in its primary form it forms an 8.9 cm opening 27 for the slightly bulged tube 10. The opening 27 through which the bulged substrate passes is formed by a core 28 attached to the die body 29. The path of the molten coating agent · i 4 β 62121 23 is indicated by arrows in Figures 2 and 3. The vacuum chamber 21 develops a slight vacuum, e.g. 6.4 cm of water, to draw or "suck" the extruded film 23 into the die 22 while it is still molten, against the pulverized tube 10, to prevent the formation of closed bubbles in the laminate 24. The vacuum chamber 22 may simply consist of a cylindrical housing the outer diameter. A vacuum can be applied to it along the suction line 30, with a conventional vacuum generating device, (not shown).

The bilayer film 24 is preferably applied to the coating or lamination mouthpiece 32 while it is still hot. In a discontinuous process, it is possible to cool, i.e., wet, the tube 24 before it is passed to the second coating nozzle 32, but this usually requires re-bulging and re-rolling of the tube to achieve good bonding between the second layer and my primary layer. The first layer when looking at the outside of the pipe will be both the outer layer and the outer layer of the pipe.

The third layer is melt-extruded from the coating die 32 and deposited and immediately adhered to the bilayer tubular laminate 24 to form a three-layer tubular laminate 34. The composition of the tubular laminate 33 is preferably selected from those shown in the treatment of the tubular film 10 above. Although it need not be the same composition as the tubular film 10, it is suitable that it be the same. The coating process in the nozzle 32 is the same as in the nozzle 22. The vacuum chamber performs the same function as the vacuum chamber 21 and operates in the same manner so as to apply a vacuum down to the suction pipe 37. The thickness of the tubular film or layer 33 is 75-375 microns, preferably 100-300 microns.

The three-layer tubular laminate 34 is cooled, i.e., wetted with a water jet from the cooling ring 39. The water temperature is normally about 7 ° C. The tension rollers 40 then flatten this three-layer tubular film and the film is rolled into a collection roll 41. Alternatively, in a continuous process, the film is not rolled into a collection roll 41 but is immediately delivered to the next step (stretching) of the process.

»9 62121

As shown in Figure 1, the discharge roller 42, previously made on the collection roller 41, is unloaded over the guide roller 43. The laminate 34 is substantially unstretched and unoriented as it passes over the guide roll 43. The film passes from the guide roller 43 to a hot water bath 44 containing water 45. A suitable reheating temperature, i.e. hot water temperature, is 70-100 ° C, preferably 82-96 ° C. The flattened three-layer tubular film is immersed in hot water for at least 5 seconds. This time is usually necessary to raise the temperature of the film to what the orientation stretching requires. A typical residence time in a hot water bath is about 20 seconds. The guide rollers 46 and 47 guide the flattened tube through the water bath 45.

When the appropriate orientation temperature is reached, the bubble 54 is blown into the film while it is above water and the film is stretched in both the transverse and longitudinal directions suitably in a ratio of 1: 1.5 to 1: 6, preferably in a ratio of 1: 2 to 1: 4, which knows biaxial orientation 1: 2.25 to 1:36 and 1: 4 to 1:16, respectively. The thicknesses of the layer then decrease in a substantially equal proportion. The bubble 54 is held between the pinch rollers 48 and 49. The tubes are flattened by rollers 50, and the laminate, as it passes through the pinch rolls 49, over the guide roll 51 and under the idler roll 53, is rolled into a roll 52.

Figure 4 shows a cross-section of an oriented laminate 34. For example, the layer formed, which is the inner layer of the tube, is a layer 10 suitably having a thickness of 12 to 125 microns, preferably 25 to 50 microns. The barrier layer is numbered 23 and suitably has a thickness of 1.25 to 50 microns, preferably 2.5 to 6 microns. The thickness of the third layer 33, which is the outer protective layer of the tube, is suitably 2.5 to 100 microns, preferably 6 to 25 microns. These three layers can join together immediately without intermediate layers. The shrinkage stress of the laminate is usually 14-35 kg / m 2 and preferably 14-28 kg / m 2 and the free shrinkage is at least 40%, preferably at least 50% at 96 ° C and at least 20% and preferably at least 30% at 85 ° C .

According to another preferred method of manufacturing the laminate, the second and third layered coatings can be extruded together into a preformed tube from a co-extrusion die. This gives the same end product laminate, but the procedure is somewhat more difficult.

10,621 21

The tubular film made from the tube according to the invention produces an excellent bag, the layer 10 adhering very well at temperatures of 93-177 ° C without being substantially distorted by heat-sealing with a thermal impulse sealer.

Layer 10 also gives the bag excellent puncture resistance. The thin barrier layer provides the necessary barrier properties with the lowest possible thickness and cost. The outer layer of non-irradiated copolymer provides good resistance to violence at low temperatures and improves the tear strength of the bag.

A preferred method of using bags made of the tube of this invention is disclosed in U.S. Patent No. 3,552,090. After the bags are evacuated, they are suitably closed, for example, by pinching, as disclosed in U.S. Patent No. 3,383,746. A suitable deaeration system is disclosed in U.S. Patent Nos. 3,628,516.

The invention provides a method of packaging an article, especially a foodstuff, by enclosing it in a film or laminate in molecularly oriented form according to the invention, the film or laminate being in contact with the article, and applying heat to the film or laminate to shrink it.

The use for which the above-mentioned laminate was specially developed, although it can apparently be used for many other purposes, is a packaging material for packaging fresh, red meat with bare bones. For this purpose, a three-layer laminate made of the primary materials described above is used. A laminate with a different and inferior barrier layer adversely affects the manufacture of the laminate and the quality of the laminate. The laminate is non-toxic and generally suitable for packaging nutrients. It is clear that when the bag is used to package fresh, red meat that has not been chilled and is not intended to be chilled, but to be packed and kept at a low temperature, such as 0-7 ° C, the laminate encloses the piece of meat containing the bone and the bare the bones poke against the inner layer of the bag.

11 62121 In this primary packaging process, bone-containing meat is inserted into a three-layer laminate that is biaxially oriented and heat-shrinkable. The laminate thus encloses a piece of meat containing bone, and depending on the piece of meat, any exposed bone may always collide with the laminate. The bag is deaerated and sealed to maintain a vacuum. The bag is then heat shrunk to tighten the meat.

In a preferred embodiment of the present invention, it is important that the irradiation dosage is within set limits, as this provides a bonding coating with sufficient tensile strength to provide good handling, good bone puncture resistance and good orientation to the laminate. The irradiation must be sufficient to increase the tensile strength without much reduction in elongation, as the substance must stretch over the bone when packing pieces of red fresh meat containing bone. At the same time, it is desirable for the bag to remain attached to the soft flesh, and to the bone at every point where the bone sticks out of the flesh. Fresh, red meat can be soft and allow the bone to move, or “float,” inside. If the film is irradiated too much, its elongation will decrease and the bone will pierce the film when it collides with it. If the vinyl acetate content is higher than that specified above, the melting point of the polymer decreases, adversely affecting the high temperature properties required by the shrink package.

In addition to losing their resistance to violence at heat shrinkage temperatures, heat sealings are delaminated when the vinyl acetate content is well above 18% in this particular laminate. If the vinyl acetate content falls below 5%, the flexibility at low temperatures decreases and the modulus of elasticity increases to the extent that the bag no longer functions as required by efficient packaging delivery.

The primary three-layer laminate has a number of very advantageous properties, characterized by good shrinkage at a reasonably elevated temperature, good elongation, at least 50, preferably 100-125%, oxygen permeation rate not more than 7 ml / m / 24 h / 1 atm 22.8 ° C and 0?. at relative humidity (ASTM D 1434); and most usually not more than 25 ml / m 2/24 h / 1 atm at 22.8 ° C, 0% relative humidity (ASTM D 1434). In its primary form, the film is at least 25 cm. kg ball burst impact resistance, measured with a device called "Ball Burst 12 621 21

Tester No. 13-8 "supplied by Testing Machines Inc. using a standard hemisphere.

The various aspects of the invention may be used alone or in other combinations, preferably compared to substances normally used in the same way. Barrier layer blends can be formed into independent films. The blends have the superior extrusion properties already listed, whether melt-extruded as a coating or as independent, self-supporting films. Of course, in order to be self-supporting, the extruded vinylidene chloride polymer film must be at least about 50-75 microns thick if it is extruded as a tube using normal, appropriate extrusion techniques. In addition, it has been found that a film formed from a blend of emulsion and suspension polymerized vinylidene polymer has unexpected tear and puncture strength compared to the corresponding properties of conventional vinylidene chloride / vinyl chloride polymers.

In certain cases, it may be desirable to use another polymer in the outer layer of the laminate. This is the layer that must be able to withstand abrasion and tearing violence. Examples of such polymers are polypropylene, polyamides and polyesters, and copolymers or terpolymers of propylene, amides or esters. These groups of coating polymers are well known. Of course, in certain applications, the outermost (third) layer or even the first (inner) layer may be omitted.

The composition according to the invention and the different layers of the laminates according to the invention may contain compatible substances such as stabilizers, pigments, process auxiliaries such as waxes, deodorants, static scavengers and anti-seize agents.

The invention is further illustrated by the following examples: Example I

Following the procedure schematically outlined in Figure 1, an ethylene / vinyl acetate copolymer containing 10% vinyl acetate having a melt index of about 2 and sold under the name UE 637 to U.S. Pat. Industrial Chemicals Division of National 13,621 21

Distillers, fed to the hopper of the extruder 9. The extruder is an 8.9 cm extruder and is operated at the following temperatures: stern zone 121 ° C, center housing 132 ° C, front housing 143 ° C, adapter 149 ° C and die 166 ° C. The speed of the coil is 37 rpm and the pressure is 269 kg / m. The diameter of the nozzle is 8.9 cm and the circumferential length of the finished pipe is 20.3 cm. The temperature of the water coming from the cooling ring 12 is 7 ° C. The pinch rollers 13 are driven at a speed of 10.7 meters per minute and the thickness of the flattened tube is approximately 460 microns.

The flattened tube is passed through the irradiation unit shown in Figure 1, which is driven at 500 kilo-electron volts, 20 milliamperes, and at a speed of 10.7 meters per minute. Four passages are made and the tube receives a dosage of about 6 megarads.

The irradiated substrate film is then passed to a coating nozzle 22 where it is coated with a barrier layer material. The barrier layer material contains a lightly plasticized mixture of copolymers of vinylidene chloride and vinyl chloride. The copolymer blend comprises 10% suspension polymerized and 90% emulsion polymerized copolymer. The emulsion copolymerized polymer consists of about 70% units derived from vinylidene chloride and 30% units derived from vinyl chloride, and the suspension polymerized copolymer consists of about 80% units derived from vinylidene chloride and 20% units derived from vinylidene chloride. derived from vinyl chloride. These materials were purchased from Dow Chemical Company and sold under the names "UP 925" (emulsion polymerized resin) and "SP 489" (suspension polymerized resin). The other ingredients in the barrier layer are 5% epichlorohydrin / bisphenol, an epoxy resin sold as "EPON Resin 828" by Shell Chemical Company, and about 0.5% microcrystalline paraffin wax purchased from Sun Chemical Company and sold as "Wax 5512 ". The three resins are mixed in a high-speed, high-intensity Prodex-Henschel mixer and the mixture is fed to a hopper of an extruder 25 which is a 5 cm Prodex extruder driven by a crosshead nozzle of the type shown in Figures 2 and 3. temperatures: stern zone 99 ° C, center housing 127 ° C, front housing 149 ° C, adapter 141 ° C and nozzle 160 ° C. The coil speed o is 34 rpm and the pressure is 390 kg / cm. The diameter of the nozzle is 8.9 cm and the circumferential length of the tube is 20.3 cm. The overhead rolls 18 are driven at a speed of 14,621 21 10.7 meters per minute and the coating thickness is approximately 75 microns.

The third layer is then formed using the same resin as the first layer. The resin is extruded through an extruder 35 which is operated in the same manner as the extruder 9, except that the temperatures are as follows: stern zone 121 ° C, center housing 132 ° C, front housing 193 ° C, adapter 227 ° C and die 232 ° C. The coating nozzle 32 has the same structure as the coating nozzle 22. The lower rollers 40 are driven at a speed of 11.0 meters per minute and the temperature of the water coming from the cooling ring 39 is 7 ° C. The thickness of the coating is approximately 150 microns.

The biaxial orientation is performed by preheating the tube in water at about 88 ° C, as shown in Figure 1, item 44, and passing the thus heated tube between pinch rollers operating at 5.8 meters per minute to drain rolls operating at 21.4 meters per minute and blowing 10 cm a wide tube so that the width of the film is 41 cm, the thickness of the film being approximately 61 microns. This tube is then rolled into a storage roll, which is then converted into bags, sealing the tube transversely, at intervals, to form bottoms in a conventional manner, and cutting the tube into bags of the desired length.

Example II

The procedure described above was repeated except that the barrier layer was changed by adding 2% 2-ethylhexyldiphenylphosphate plasticizer purchased from Monsanto under the name "Santicizer 141" and reducing the epoxy resin content to 3%.

Example m

The procedure of Example I was repeated except that 5% epoxidized soybean oil (not to be mixed with epoxy resin) sold by Swift s Co. called "Epoxol 7-4", was used instead of 5% epoxy resin.

Example IV

The procedure of Example 1 was repeated except that 4% 2-ethylhexyldiphenylphosphate plasticizer and 1% magnesium oxide were used instead of 5% epoxy resin.

15,621 21

Example V

The procedure of Example I was repeated except that a mixture of 53.3% by weight of isotactic polypropylene (Movamont * F007), 33.3% of polybutylene-1 (Mobil * PB 103) and 13.3% of atactic polypropylene (Novamont * Lot 2030 ) was used to form the third layer. The atactic and isotactic polypropylene is first added in an appropriate ratio to the Banbury mixer and melt blended for approximately 8 minutes at 204 ° C and then extruded into a web which was cut into pellets. These pellets were combined with polybutene-1 pellets in a rotating drum and this mixture was charged to a hopper of an extruder 35. The extruder 35 was operated at the following temperatures: stern zone 196 ° C, center zone 204 ° C, front zone 222 ° C, adapter 204 ° C, and die 218 ° C.

y *

Movamont is a trademark of Movamont Corp., and * Mobil is a trademark of Mobil Oil Co.

Example VI

The mixture used to form the barrier layer in Example II, except that 4% epoxy resin was used and the UP 925 resin content was reduced to 1%, was extruded as a self-supporting single-layer film under the extrusion conditions of Example II. A propylene glycol coating was deposited on the inside of the tube to prevent sticking when the tube was set aside prior to biaxial orientation. The process was continuous, and bubble 54 was formed after the tube had collapsed but not rolled into a roll. In addition, the water bath temperature was maintained 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 when the total orientation-stretch ratio was about 12: 1 biaxially. The film was found to have an unexpectedly good tear and puncture resistance as an oriented film compared to conventional known oriented vinylidene chloride-vinyl chloride copolymer oriented films.

Packaging violence tolerance tests

The following test procedure was performed. All test bags were precoded and preconditioned for 24 hours at 7-10 ° C. Randomly selected bags were used to package whole rib cuts of meat weighing 11.3-13.6 kg, with bone included. The bags were 16,621 21 41 cm wide times 76 or 81 cm deep. The packages were deaerated and the bags were pinched, sealed and shrunk, and dried in a stream of air. The packages were then packed in wax-coated corrugated boxes, 3 pieces in their boxes. The boxes were then sealed with single filament nylon tape.

In the drop test, private boxes were dropped from a height of 0.91 m, from a moving conveyor. In the transport violence test, the boxes were stored at 3 ° C for 24 hours and then shaken for 7.5 minutes in 1 g of L.A.B. In a vibration tester moving in a vibratory motion, - 200 km to simulate road transport.

In both tests, air was pumped into the packages and immersed under water to detect leaks. Leaking packaging was classified as discarded.

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Claims (3)

18 62121 A polymer composition, based on the formation of a film, based on (s) a suspension polymerized with a shampol polymer of at least 50% by weight of vinyl chloride and an intermediate comprising a copolymer of a monomer, and (ii) an emulsion polymer polymer of the emulsion polymer , in which the emulsion polymer polymer is shampooed from a polymer of at least 50% by weight of vinylidene chloride and an ether which gives a copolymer or ethenic monomer, and a suspension polymer of the shampoo polymer. emulsionspolymeriserad sampolymer är 5-40 vikt-% resp. 60-95% by weight. A polymeric composition suitable for film formation, based on (i) a suspension polymerized copolymer of at least 50% by weight of vinylidene chloride and the remainder of at least one other copolymerizable ethylenically unsaturated monomer, and (ii) an emulsion polymerized polymer based thereon of vinylide. that the emulsion polymerized polymer is a copolymer of at least 50% by weight of vinylidene chloride and the rest of the at least one other copolymerizable ethylenically unsaturated monomer, and that the relative amounts of suspension polymerized polymer and emulsion polymerized copolymer are 60-95% and 60% by weight, respectively. 2. A composition according to claim 1, wherein the suspension polymer is shampooed in an amount of 5-15%, and the emulsion polymer is shampooed in an amount of 85-95%. Mixture according to Claim 1, characterized in that the relative amount of suspension-polymerized copolymer is 5 to 15% and that the relative amount of emulsion-polymerized copolymer is 85 to 95%. Mixture according to Claim 1 or 2, characterized in that it also contains 2 to 10%, preferably 4 to 6% by weight, of an epoxy resin as a plasticizer. 3. A composition according to claim 1 or 2, which comprises an amount of 2-10% by weight, 4-6% by weight of epoxy resin.