MXPA99003939A - Rf-sealable pillow pouch - Google Patents

Abstract

A pillow pouch of a thermoplastic material, comprising an RF sealable outer layer of ethylene-vinyl acetate copolymer containing from about 14 to about 28 wt.%VA, and a layer of PVDC and a method of packaging a flowable product in a vertical form-fill-seal machine using said RF sealable thermoplastic material.

Description

"PILLOW SEALABLE BAG FOR RADIO FREQUENCY" The present invention relates to a radiofrequency sealable pillow bag of a thermoplastic material, particularly suitable for packaging flowable products and to a method for packaging that product into a vertical seal filling machine using a thermoplastic material sealable by radiofrequency. . Fluent products, such as powders, liquid and pasty materials e.g. detergents, liquid soaps, household cleaning products, bleaches, etc., are currently packaged in so-called pillow bags made of PVC. These pillow bags are typically used as mono-dose packs or as filler cartridges that are opened and emptied into a rigid or semi-rigid container re-usable as desired. The machine that produces and fills the packages in a single operation is called a vertical form-fill-seal machine (ÍVFFS). This machine forms the pouches of a flat flexible continuous film tape, while filling them with the product. The film is fed from a roll to a device that is formed in a tube of appropriate diameter around the product filling tube. The two edges of the movie then They are sealed together longitudinally either as an overlap seal or with a fin seal. As the tube moves down the machine, two horizontal sealing bars come together to form a transverse seal that becomes the bottom of the bag. At that point, a due amount of the product is allowed to flow through the product filling tube and into a precisely formed bag. When the filling time is complete, the upper part of the bag has marched downward from the location of the sealing bar where the bar once again joins together to create simultaneously the upper seal and the lower seal of the next bag that is above. Alternatively, it is also possible to manufacture pillow bags in two separate steps wherein the first step is the production of the bags by any conventional system and the second is the filling of the bag in a vertical machine followed by the sealing of the mouth of the bag. The pillow bags are characterized in that at least one of the transverse seal is a seal that is cut by fusion. The seal that is cut by melting is a seal carried out by heating while at the same time the film is pressed and cut. The sealing bars are therefore equipped with a blade that cuts through the seal to separate the bag filled with the machine. To provide the appearance of a pillow, as the name suggests, once the bag is filled with the regulated supply volume and the fluent product, generally the liquid or pasty product is injected with air or an appropriate gas before the bars Cross sealing are pressed together. When working with ~ PVC, at least the transverse sealing system in these VFFS machines is based on dielectric heating or radiofrequency heating. In this system the high frequency electric current is passed through the film by means of the sealing bars. When the film contains polar molecules as in the case of PVC, these molecules oscillate under the influence of the current and this molecular agitation becomes sufficient heat to melt the film in the area of the seal. The advantages of "pillow bags" are obvious: reduced volume, reduced consumption and plastic material waste, lower cost, etc. However, the use of PVC, which until now has been considered as the selection polymer for this application, presents many inconveniences. First, PVC does not have gas barrier and moisture barrier characteristics. The components volatile, e.g. perfumes, aromas, etc. they tend to escape easily through the packaging material, thereby reducing the content thereof in the packaged product and, when these components have an unpleasant odor e.g. in the case of bleachers, imparting this odor to the entire package. The water can also be evaporated through the PVC layer reducing, therefore, the volume of the packaged product and increasing the concentration of the non-volatile components in it. Second, PVC usually contains a high level of plasticizers. Plasticizers are easily migrated to the packaged product with a consistent package integrity problem. The mechanical properties of PVC films are in fact determined by the level of plasticizers: a decrease in the amount of plasticizers due to their migration to the product or packaging will increase the rigidity and fragility of the PVC thereby reducing its resistance mechanical (perforations, mistreatment). A third disadvantage of the use of thick PVC films is the amount of chlorine-containing polymer that needs to be discarded. The replacement of PVC in the manufacture of pillow bags for the packaging of flowable products has been widely described in the patent literature.

Of interest is Patent Number EP-B-477, 025, which discloses the use of a multilayer film having a barrier layer of a thermoplastic material, preferably, an LLDPE or a composite of a polyethylene layer and a polyamide or EVOH layer, and at least, on one side thereof, a layer of a radiofrequency-sealable polymer eg EVA with a high VA content. According to Patent Number EP-B-477, 025, the problem created by the low radiofrequency sensitivity of the thermoplastic barrier materials is overcome by the use of EVA sealing layers with a high VA content and a low " controlled content of additives, while the problem of sticking that results from the use of this sealing layer is overcome by the use of structures with a matte surface.These structures do not contain chlorine and have moisture barrier properties, without However, they do not overcome the other inconveniences related to the use of PVC such as for example the structures described in Patent Number EP-B-477, 025, do not have odor barrier properties or only to a limited extent. , polyethylene and polyamide do not have any odor barrier properties, either moderate or none, the EVOH is very sensitive to moisture and its odor barrier properties, which are satisfactory under the dry ions, it They reduce drastically after being exposed to a humid environment. In addition, due to the low radiofrequency sensitivity of these barrier materials and depending on their thickness, the seal strength of the radio frequency seal can sometimes be unsatisfactory despite the high VA content of the EVA sealing layer. With these structures an additional step in the manufacturing process of the film is required to provide the mat surface, which is added to the extra cost of the film.Also of interest is Patent Number EP-A-471,607 which describes thermoplastic films RF sealants particularly suitable for the packaging of gas-emitting fluent products These films comprise a core polyethylene layer and EVA sealing layers which are characterized by an oxygen transmission rate (OTR) of at least about 600 centimeters cubic per square meter d atmosphere This high OTR is required, in accordance with Patent Number EP -A-471, 607 because in the packaging of products that emit gas, such as bleaches, "a typically oxygen gas is released from storage and must be allowed to dissipate through the wall of the bag to prevent it from Build up pressure on the bag and break the seal on the bag.

Also, the structure described in Patent Number EP-A-471, 607 does not contain chlorine and has moisture barrier properties but does not have odor barrier properties. Furthermore, also in this case, the presence of a thick core layer of polyolefin material with low radiofrequency sensitivity affects the radiofrequency sealing capability of the overall structure. It is likely that due to the low resistance of the seal, of the radiofrequency seal obtained in this way that this high OTR is needed to prevent seal rupture. It has now been found that it is possible to solve the aforementioned problems in a satisfactory manner by using, as a replacement for PVC in the manufacture of the pillow bags, a film comprising an RF-sealable outer layer of an "ethylene-acetate copolymer". vinyl with from about 14 percent to about 28 percent by weight of VA and a layer of PVDC.The use of this film as a PVC replacement offers many advantages since the RF seal will have good seal strength due to the presence of, a layer of PVDC that improves the sealing capacity of the overall structure, it has also been found that the presence of a layer of PVDC imparts to the bag the desired balance of stiffness and flexibility so that thick films of 75 to 150 phenerometers can be operated on commercial VFFS machines providing better performance than conventional 200 or 250 micron thick PVC films, and drastically reducing the amount of plastic material per package that needs to be discarded after use; the amount of the chlorine-containing polymer is greatly reduced since the PVDC layer will only have a thickness of a few microns whereas the PVC bags usually require a sheet with a thickness of 200 to 250 metrometers. In addition, by appropriately selecting the thickness and / or the composition of the PVDC layer it is possible to "modulate" the gas barrier and odor properties of the final structure, to the desired degree.

DEFINITIONS As used herein, the term "Homopolymer" is used with reference to a polymer resulting from the polymerization of a single monomer, that is, a polymer consisting essentially of a single type of a repeating unit. As used herein, the term "copolymer" of waste or polymers formed by -the polymerization reaction of at least two different monomers. As used herein, the term "polymer" refers to both homo-polymers and co-polymers as defined above. As used herein, the term "ethylene homopolymers" identifies polymers that consist essentially of a repeating unit of ethylene. As used herein, the phrase "ethylene alpha-olefin copolymer" and "ethylene / alpha-olefin copolymer" refers to heterogeneous materials such as a linear low density polyethylene. (LLPDE), linear medium density polyethylene (LMDPE) and very low density polyethylene and works (VLDPE and ULDPE); and homogeneous polymers such as metallocene catalyzed polymers, for example, the EXACT ™ materials supplied by Exxon, the AFFINITY ™ and ENGAGE ™ materials supplied by Dow, the LUFLEXEN ™ materials supplied by BASF and the TAFMER ™ materials supplied by Mitsu Petrochemical Corporation. These materials usually include copolymers of ethylene with one or more comonomers selected from alpha-olefins of 4 to 10 carbon atoms such as buten-1 (ie, 1-butene), hexen-1, octen-1, etc. .

As used herein, the term "ethylene ethylenically unsaturated ethylene ester copolymer" refers to copolymers of ethylene with one or more ester comonomers containing a vinyl group such as ethylene / vinyl acetate copolymers, copolymers ethylene / ethyl acrylate, ethylene / butyl acrylate copolymers, ethylene / methyl acrylate, ethylene / methyl methacrylate copolymers. As used herein, the phrase "modified polymer" as well as more specific phrases such as "ethylene vinyl acetate modified copolymer" refers to those polymers having an acid or preferably an anhydride functionality such as maleic or fumaric ring or an acid, inserted therein and / or copolymerized therewith and / or mixed therewith. Preferably, these modified polymers have the functionality of the anhydride grafted onto or polymerized therewith as opposed to being mixed therewith only.

As used herein, "PVDC" refers to a vinylidene chloride copolymer wherein a predominant amount of a copolymer comprises vinylidene chloride and a small amount of a copolymer comprises one or more unsaturated monomers copolymerizable therewith, typically sodium chloride. vinyl and alkyl acrylate (eg methyl acrylate) or a mixture thereof different proportions. This term also includes the copolymer (s) when mixed with additives such as stabilizers, plasticizers, etc. as "is known in the art" As used herein the phrase "directly adhered" as applied to the film layers is defined as the adhesion of the film layer present to the film layer of the object without a Mooring layer, adhesive or another layer between them. As used herein, the term "contiguous" when referring to two layers, is intended to refer to two layers that are directly adhered to each other. In contrast, as used herein, the word "between", as applied to a film layer which is expressed as being between two other specified layers, includes both direct adhesion of the object layer to the other two layers between those that remain, as well as the lack of direct adhesion to either or both of the other two layers between which the object layer remains, that is, one or more additional layers - they can be imposed between the object layer and one or more layers of the object layer is between them. As used herein, the phrases "inner layer" and "inner layer" refer to any layer of film having both of its principal surfaces adhered directly to another layer of the film.

As used herein, the phrase "outer layer" refers to any layer of film having only one of its principal surfaces adhered directly to another layer of the film. As used herein, the term "core" and the "core layer" phase refers to any inner film layer that has a primary function other than to serve as an adhesive or compatibilizer to adhere two layers or one to the other. As used herein, the phrase "bulk layer" refers to any layer that is present for the purpose of improving strength, abuse, tenacity, modulus, etc. of the movie. Bulk layers generally comprise polymers that are economical relative to the other polymers in the film that provide a certain specific object unrelated to the abuse resistance, modulus, etc. As used herein, the phrase "tie layer" refers to any inner layer having the primary purpose of adhering two layers to each other.

DETAILED DESCRIPTION OF THE INVENTION A first object of the present invention is a pillow bag containing an effluent product, characterized in that the packaging material is a thermoplastic film comprising an outer layer sealed by radiofrequency EVA containing from about 14 percent to -approximately 28 weight percent VA and one layer PVDC. As used herein, the term "an EVA layer" is used to imply that the base thermoplastic material of the layer is essentially EVA. In the EVA layer, the thermoplastic material however, may contain conventional antiblocking and slip agents such as silica, either natural or synthetic silica, calcium stearate, amides or bis-amides, etc., opacifying agents e.g. CaCO3, pigments, e.g. Ti 2, ultraviolet light absorbing agents, etc. as is already known in the art. These additives may be added up to about 30 percent, preferably however they are limited to an amount of about 20 percent and more preferably to a maximum of 15 percent by weight, which is calculated on the weight of the outer layer Sealable by radio frequency. In general, antiblocking and slip agents are added to the sealing layer in an amount of up to about 10 weight percent, typically up to 8 weight percent, while a higher amount of water may be used without problems. agents of opacification and pigments up to about 20 weight percent. As used herein "essentially EVA" does not exclude the presence of small proportions e.g. to less than about 10 percent of other thermoplastic materials, as long as the materials do not impair the RF sealing capability of that outer layer. Examples of thermoplastic materials that could be present in small proportions in another EVA RF sealed external layer are the ethylene-methacrylate, ethylene-ethylacrylate, ethylene-butylacrylate, PVDC and similar polar polymers. In a preferred embodiment, however, the base thermoplastic material of the EVA layer is only EVA. Preferably, the thermoplastic film to be used in the manufacture of the pillow bags according to the present invention has a sealing layer of an ethylene vinyl acetate copolymer containing at least 16 weight percent acetate of vinyl. More preferably, the ethylene vinyl acetate copolymer will contain from about 16 percent to about 22 weight percent VA. Even though ethylene vinyl acetate copolymers with a VA content of less than 14 weight percent are hardly radio-sealable, the Ethylene and vinyl acetate copolymers with more than 22 weight percent VA are sealable by RF, but they are usually very soft and sticky and can create some difficulties when used as external layers in a structure to be operated on a conventional VFFS machine. When applications are used where high odor and gas barrier properties are required, the film will typically have an Oxygen Transmission Rate (OTR) of less than 50 cubic centimeters per square meter. atmosphere, when measured at 23 ° C and from 0 percent to 100 percent relative humidity, and a moisture vapor transmission rate (or MVTR) of <; 25 grams per square meter. d when measured at 38 ° C and 98 percent relative humidity. Even though the OTR is evaluated following the method described in D-3985 of the American Material Testing Society and using a Mocon OX-TRAN instrument, the MVTR is measured by F-1249 of the American Society for the Testing of Materials using a Permatran W-1 instrument from Mocon. This can be easily obtained by using a PVDC with a low plasticizer content. In this case, the PVDC thickness can be as low as 3 micrometers - still providing barrier properties optimum to gas and odor, but preferably at least 5 micrometers and typically consists of between about 5 and about 25 micrometers. These PVDC with low plasticizer content are those conventionally used in the food packaging area to obtain high oxygen barrier properties. On the other hand, when used to package gas emitting products, the film will typically have an OTR of at least about 100 cubic centimeters per square meter. d. atmosphere, and preference for at least 120 cubic centimeters per square meter. d. atmosphere, and still especially preferably at least 150 cubic centimeters per square meter. d. atmosphe This elevated OTR can be obtained in a PVDC that contains a structure reducing the thickness of the PVDC and / or increasing the amount of plasticizers that are mixed therein. It is a widely known fact that the oxygen permeability of PVDC increases with an increased plasticizer content. The additives which can be used satisfactorily to increase the OTR of the PVDC layer comprise the conventionally used pasteurizers, in small amounts, as auxiliaries of. prosecution for PVDC of high barrier properties such as the epoxy compounds, e.g. epoxidized flax seed oil, epoxidized soy bean oil, epoxy resins (such as, for example, Shell EPON 828), alkyl esters such as dibutyl sebacate, acetal tributyl citrate, phosphates such as 2-ethylhexyl diphenylphosphate (sold by Monsanto as Santicizer-141), phenoxypropylene oxide, EVA with a VA weight percentage higher than 15 (such as DuPont's Elvax ™ resins), modified EVA (such as Elvaloy ™ resins sold by DuPont), shock impact modifiers such as chlorinated polyethylene, butyl rubber, chlorobutyl rubber, ethylene-propylene rubber (EPM), elastomeric terpolymer of ethylene, pxopylene and a conjugated diene (EPDM), polyisobutylene, copolymers of styrene- butadiene, etc. The amount of the plasticizer (s) to be added to the PVDC resin depends on the desired OTR and the PVDC thickness in the total structure. Generally, however, it becomes difficult to mix the PVDC resin with the liquid plasticizer (s), such as epoxidized linseed oil, epoxidized soy bean oil, epoxy resins and alkyl esters, when the amount thereof is greater than 15 percent to 20 percent by weight. Typically, therefore, the amount of liquid plasticizer (s) in the PVDC mixture will be up to about 15 weight percent, preferably from about 1 weight percent to about 10 weight percent, most preferably from about 3 weight percent to about 8 weight percent cent in weight. Solid plasticizers, such as EVA, modified EVA, impact modifiers, e.g. those listed above can be mixed with the PVDC up to about 50 weight percent, preferably up to about 40 weight percent and. greater preference up to about 30 weight percent. Solid and liquid plasticizers can also be used in combination. In this case, the PVDC powder is first mixed thoroughly with the solid plasticizer (s), in powder form, and then the liquid plasticizer (s) is mixed therewith. Other additives, such as stabilizers, ultraviolet light absorbing agents, deodorants, anti-oxidants, etc. they can be added in the PVDC resin. These and other additives, in general, are used in small amounts, typically up to about 2 weight percent. To increase_ the OTR of the film, the PVDC thickness can be reduced to approximately 1 micrometer. The conventional thickness e.g. of 3, 5, 10 meters or even more, however, can provide the desired OTR depending on the amount of the type of plasticizers contained therein. Preferably, the film according to the invention has at least three layers, wherein the PVDC layer is a core layer and the other the outer layer, which can be involved in the longitudinal sealing in case of overlap seals is also of an ethylene vinyl acetate copolymer with from about 14 percent to about 28 weight percent VA. The other layers may be present in the film such as tie layers or bulk layers. Suitable bulk layers will comprise copolymers of ethylene and ethylenically unsaturated ester, preferably ethylene vinyl acetate copolymer, ethylene homopolymers or ethylene and alpha-olefin copolymers, as long as the RF sealing capacity of the structure. Suitable tie layers may comprise the modified ethylene and vinyl acetate polymers or modified polyethylenes. In a preferred embodiment, the thermoplastic film to be used in the manufacture of the pillow bags according to the present invention, will comprise at least five layers with minus a core layer of. PVDC, outer layers of ethylene vinyl acetate copolymers with about 14 weight percent VA, preferably about 16 weight percent, VA, to about 28 weight percent VA, and tie layers intermediates optionally comprising copolymers of ethylene and vinyl acetate optionally modified.

As indicated above, the thermoplastic films of thickness of 75 to 150 microns could replace the PVC in the current VFFS machines and provide better performance with the conventional PVC film of 250 micron thickness used in these machines. However, thicker films can be used for high demand applications or thinner films for very small bags. Generally, the thickness of the appropriate films can vary from about 50 to about 250 microns, preferably ranging from about 70 to about 200 microns, more preferably from about 75 to about 150 microns. The thickness of the sealing layer is generally at least 10 micrometers, preferably at least 20 micrometers, and even more preferably at least 30 micrometers. Since the polymer used for the sealing layer can also be used to provide the desired thickness of the film, in some cases very thick sealing layers will be present such as in the case of the three-layer structure. The thermoplastic film suitable for use in the manufacture of pillow bags according to the present invention is generally obtained by co-extrusion. The film does not lengthen or guide at least intentionally. A slight orientation, called accidental orientation may be present, depending on the production method used. A preferred method of manufacture thereof is the hot-blow method Alternatively, it is also possible to use an extrusion method of molding, either through a round die, preferably through a flat die. Molding extrusion also allows the film to be obtained by extrusion coating.

In an especially preferred embodiment, the film will be obtained by the bubble-crushing technique which provides the crushing of the bubble obtained by the hot-blow method, when the resin inside is still hot, and pressing it in order to obtain a single continuous tape with the thickness - double that of the film extruded from a number of layers with two layers of PVDC separated. This favorite movie, for example, it may comprise 6, 8 or 10 layers, preferably 6 or 10. To improve the adhesion between the two inner layers of the co-extruded film of the bubble, an ethylene-acetate copolymer is preferably used. vinyl with a high VA content, such as an ethylene vinyl acetate copolymer with from about 16 percent to about 35 weight percent VA, preferably from about 18 percent to about 72 percent by weight VA, more preferably from about 22 percent to about 28 percent by weight VA. The films obtained by this method are particularly suitable as a replacement of PVC in the manufacture of pillow bags. The presence of two separate PVDC layers further improves the desired balance of stiffness and flexibility, while the manufacturing cost is reduced because the layer separation step is avoided. A second object of the present invention therefore is a symmetrical thermoplastic film with an even number of layers, outer layers comprising "a copolymer of styrene and vinyl acetate with from about 14 percent to about 28. Percent by weight of VA, and two internal layers of PVDC separated by at least two contiguous layers comprising a copolymer of ethylene and vinyl acetate. Preferably, the symmetrical structure will have a thickness of at least about 50 micrometers, more preferably at least about 70 micrometers and even more preferably at least about 75 micrometers. In a preferred embodiment, at least two contiguous layers between the two layers of PVDC in the symmetrical structure, comprise an ethylene vinyl acetate copolymer with from about 16 percent to about 15 weight percent VA, preferably from about 18 percent to about 32 percent in percent of. VA, more preferably from about 22 percent to about 8 percent by weight VA. Preferred symmetrical structures will comprise outer layers of a copolymer of ethylene and vinyl acetate with from about 14 percent to about 28 percent. one hundred by weight of VA, and two internal layers of PVDC, separated by at least two contiguous layers of an ethylene vinyl acetate copolymer with from about 22 percent to about 28 weight percent VA.

A third object of the present invention is a symmetric thermoplastic film with an even number of layers, the outer layers comprising a copolymer of ethylene and vinyl acetate with from about 14 percent to about 28 weight percent VA, and two layers internal PVDCs separated by at least two contiguous layers comprising a copolymer of styrene and vinyl acetate, when obtained by the crushed bubble process. In the manufacture of the pillow bags with the thermoplastic material in accordance with the present invention, any VFFS machine that is equipped with a sealing and RF equipment, such as, for example, those commercially available from Thimmonier, can be used. or Sertic. In principle, however, any conventional VFFS machine can be adapted to the manufacture of sealable pillow bags. by RF equipping them simply with a welding apparatus, such as those that can be obtained commercially from v, g. Colpitt, Cosmos or Kiefel. While the longitudinal seal can be obtained either by a conventional thermal seal or by an RF seal, the transverse seal is always obtained by an RF seal. In actual practice, the RF seal is obtained by applying a pressure to both continuous film tapes to be welded together, e.g. by means of a pair of bars, and welding the two continuous tapes together by means of RF at a frequency of approximately 27 MHz, which is the usual frequency that is provided in RF welding equipment. vary from about room temperature to as high as possible as long as the film does not stick to them.In principle, it would be preferable to have heated bars as this would shorten the welding time. At room temperature, since the PVC begins to stick at temperatures just above room temperature, with the thermoplastic films according to the present invention having external layers of EVA, the tempetata of the bars can be appropriately increased up to 70 ° C to 80 ° C. The welding time is - as indicated above - a function of the temperature of the bars, but also of the temperature applied ression, del. thickness of the film, etc. Typically, a welding time of about 0.5 to about 3 seconds, and pressure up to about 6 atmospheres, preferably up to 5 atmospheres, can be used. . Optimal welding conditions, without However, they can be easily adjusted by an expert operator. The film according to the present inventionHowever, it can be used in the manufacture of pillow bags in any type of machine that can be used for this purpose. A fourth object of the present invention is. a method of packaging a flowable product in a pillow bag using an RF weldable film, characterized in that the RF-moldable film is a multilayer thermoplastic film with the RF-sealable external layer of EVA containing from about 14 percent to about 28 percent by weight of VA and one layer of PVDC. In a preferred embodiment of this packaging method, the fluent product is packaged in a pillow bag by means of the VFFS machine. The invention will now be described with reference to the following examples which are intended to be illustrative of some preferred embodiments of thermoplastic films, particularly suitable for the manufacture of pillow bags, for the packaging of flowable products. These examples should not be construed as limiting the scope of the present invention.

Fusion Flow Indexes (MFI) are measured by Method D-1238 of the American Society for the Testing of Materials, Condition E, 190 ° C / 2.16 kilograms, and are reported in grams for 10 minutes. The densities have been measured by Method D 792 of the American Society for the Testing of Materials.

Melting temperatures, if not stated otherwise, have been determined by DSC following Method D-3418 of the American Society for the Testing of Materials (second heating - 10 ° C per minute). The value is evaluated. OTR at 23 ° C and 0 percent or 100 percent relative humidity according to Method D-3985 of the American Society for Testing Materials using an OX-TRAN instrument from Mocon. - The MVTR is measured by Method F-1249 of the American Society for the Testing of Materials, using a Permatran W-1 instrument from Mocon.

Example 1 A 3-ply film is obtained by hot blowing having the following structure: A / B / A, where A is an ethylene vinyl acetate polymer with 18 weight percent VA, MFI = 0.7 grams / 10 ', melting temperature = 87 ° C (Elvax ™ 3165. can be obtained commercially from DuPOnt) comprising about 0.3 percent silica and about 0.5 percent erucamide, and is about 42 micrometers thick; B is a 3 micron thick layer of PVDC (VDC / VC) containing about 7 weight percent epoxidized soy bean oil, about 1 weight percent hydrocalcite of about 0.3 weight percent of an absorption of ultraviolet light.

Example 2 A 5-ply film is obtained by hot blowing having the following structure: A / C / B / C / A, wherein the resins used for the layers A and B and the additives compressed therein are defined in the Example 1 and C is a copolymer of ethylene and vinyl acetate with about 25 weight percent VA, MFI = 4 grams / 10 ', melting temperature = 72 ° C (Evatane ™ 2803 which is commercially available from Elf Atochem) . The total thickness of the structure was 75 micrometers with a layer ratio of 5/2/1/2/5.

Example 3 A 5-ply film is obtained by hot blowing having the following structure: A / C / B / C / A, where the resins used for layers A and B and C, and the additives contained therein are as is defined in Example 2. The total thickness of the structure was 140 micrometers, with a layer ratio of 5/1/2/1/5.

Example 4 A white and shiny 5-layer film having the following structure: A '/ C / B / C / A, where A, B and C are as defined in Example 2 and A' corresponds to A with the addition of 6 percent by weight of a white pigment masterbatch (60 weight percent TiO2, 40 weight percent of the carrier of ethylene vinyl acetate copolymer) is obtained by hot blowing.

Example 5 A 10-layer film is obtained by coextruding a 5-layer film having the structure A / C / B / C / C, wherein A, B and C are as defined in Example 1 and Example 2, by hot blowing method and then crushing the tube during cooling in the winding machine by means of crushing pressure cylinders. The final film had the following structure: A / C / B / C / C / C / C / B / C / A, with a total thickness of 130 micrometers and a layer ratio of 10/5/1/5/10 / 10/5/1/5/10. The OTR of its structure is 115 cubic centimeters / square meter. d. atmosphere.

Example 6 A 10-layer film having the structure of A '/ C / B / C / C / C / C / B / C / A' is obtained following the procedure of Example 5, but replacing the ream A with A ', as is defined in Example 4.

Example 7 The procedure of Example 5 is repeated replacing B with B 'which is PVDC (VDC-VC) comprising 10 weight percent epoxidized soybean oil, 1 weight percent hydrotalcite, and 0.3 weight percent of an ultraviolet light absorbing agent. The final 10-layer film, 130 micrometer thick, has the following structure A / C / B '/ C / C / C / C / B' / C / A in where the ratio of the thickness between layers is as in Example 5. The OTR of this structure is 141 cubic centimeters / square meter .d. atmosphere. - - Example 8 The procedure of Example 5 is repeated by replacing B with B "which is PVDC (VDC-VC) comprising 4 weight percent epoxidized soy bean oil, 1 weight percent hydrotalcite, 0.3 weight percent an ultraviolet light absorbing agent and about 5 weight percent of a modified EVA (Elvaloy ™ 742, which can be obtained commercially from DuPont). The final 10-layer film, 130 micrometer thick, has the following structure A / C / B "/ C / C / C / C / B" / C / A where the thickness ratio between the layers is as in Example 5. The OTR of this structure is 199 cubic centimeters / square meter. d. atmosphere.

Example 9 The procedure of Example 5 is repeated replacing B with B '' 'which is PVDC (VDC-VC) comprising 4 weight percent of epoxidized soy bean oil, 1 weight percent hydrotalcite, 0.3 weight percent of an ultraviolet light absorbing agent and about 10 weight percent of a modified EVA (Elvaloy ™ 742, that can be obtained commercially from DuPont). The final 10-layer film, 130 micrometer thick, has the following structure A / C / B "'/ C / C / C / C / B"' / C / A where the ratio of the thickness between the layers is as in Example 5. The OTR of this structure is 394 cubic centimeters / square meter. d. atmosphere.

Example 10 A 5-layer film having the structure of A / C '/ B / C' / A was obtained by the following procedure of Example 2 but using C, an polyolefin grafted with anhydride in a copolymer of ethylene and vinyl acetate ( Plexar ™ 107 that can be obtained commercially from Quantum), instead of resin C.

Example 11 A 10-layer film having the structure of A "/ C / B / C / C / C / C / B / C / A" is obtained by following the procedure of Example 5 but replacing A with A "which is a mixture of A and 20 weight percent of a basic mixture comprising 40 weight percent of A as the carrier and the remaining 60 weight percent of a mixture of Ti? 2, CaCO3, silica and erucamide. The thickness of the two layers of PVDC combined is 8 micrometers, that of each of the two outer layers is 40 micrometers, and the thickness of the film of 10 total layers is .130 millimeters.

Example 12 The procedure of Example 9 is repeated increasing the amount of modified EVA from 10 weight percent to 25 weight percent. The OTR of this structure is approximately 1,000 cubic centimeters per square meter. d. atmosphere.

Example 13 A 7-layer film having the structure of A / D / C '/ B / C / D / A where A, B and C are as defined in Examples 1 and 10, and D is a copolymer of ethylene and octene-1, with d = 0.920, MFI of 1 gram / 10 ', and melting temperature = 124 ° C (Dowlex ™ 2045E obtainable commercially available from Dow), is obtained by the hot blowing technique. The total thickness is 120 micrometers and the layer ratio is 9/2/2/2/2/2/9.

Example 14 A 10-layer film having the structure of A "/ C / Blv / C / C / C / C / Blv / C / A'_ 'is obtained following the procedure of Example 5 but replacing A with A" which is a mixture of A and 20 weight percent of a basic mixture comprising 40 weight percent of A as the carrier and the remaining 60 weight percent of a mixture of Ti02, CaC03, silica and erucamide, and B with Bl " which is PVDC (VDC-V) comprising 4 weight percent of epoxidized soy bean oil, 1 weight percent hydrotalcite, and 0.3 weight percent of an ultraviolet light absorbing agent. Two layers of PVDC combined is 20 micrometers, that of each of one of the two outer layers is 30 micrometers, and the thickness of the total 10 layer film is 130 micrometers.The OTR of the structure mentioned above is 0 One hundred and 100 percent of Relative Humidity is 13 and 14 cubic centimeters per square meter, atmosphere, day, respectively.

The MVTR of the aforementioned film at 38 ° C and 98 percent Relative Humidity was 4.7 grams per square meter.

Example 15 Following essentially the same procedure of the previous Example but varying the thickness of the external layers from 30 micrometers to 25 micrometers, and that of the inner layers C to 5 micrometers, each, a film of 10 layers thickness of 100 micrometers is obtained with a layer ratio of 5/1/2/1/1/1/1/2/1/5.

Example 16 Following essentially the same procedure of Example 14 but replacing A "with A as in Example 1, a film with 10 layers of high barrier properties, 130 micrometers thick, is obtained with the following structure A / C / B "/ C / C / C / C / Biv / C / A.

Example 17 The film of Example 14 (160 mm wide) was used in a _VFFS Thimmonier machine for the manufacture of bags of 250 cubic centimeters filled with a softener. Both the longitudinal seal (an overlap seal of a width of approximately 8 millimeters) and the transverse seals were manufactured by means of an RF sealer operating at 27.12 Mhz. The line was running at approximately 45 bags per minute. The seal strength of the bags obtained in this way was evaluated by placing the bag between two parallel horizontal stainless steel plates and increasing the pressure applied to the upper one until the bag breaks. This test was carried out in the bags two hours after its manufacture and the bags showed that they resisted the applied pressure up to 250 kilograms. The same test, repeated after storage of the bags for 3 months at room temperature, shows no statistically significant difference, thus confirming that unlike PVC, with the structures according to the present invention there is no deterioration of the mechanical properties of the packaging material with the passage of time. The appearance of the bags after 3 months of storage is almost identical to that of the original bags. PVC pillow bags are currently used for the packaging of non-flowing food products, usually liquid or paste-like, such as products for personal hygiene, for example, soaps, shampoos, creams, lotions, etc. and household products such as detergents, chemical solutions, etc. The use of PVC in the manufacture of pillow bags for food products, due to the migration of plasticizers to the product, in fact, would be unacceptable. On the contrary, with the films described in the present application, it is possible to employ the scale of products that can be packaged including also food products, such as cold or hot sauces, creams, soups and similar products. The high and medium gas and odor barrier properties could be achieved by modifying the PVDC layer (s).

Claims (15)

R E I V I N D I C A C I O N E S:

1. A pillow bag containing a product, fluent characterized in that the packaged material is a thermoplastic multilayer film comprising an RF sealable outer layer of an ethylene vinyl acetate copolymer with from about 14 percent to about 28 percent by weight of VA and one layer of PVDC.

2. The pillow bag of claim 1, wherein the thermoplastic multilayer film is from about 50 microns to about 250 microns, preferably from about 70 microns to about 200 microns, and of greater 15 preferably from about 75 microns to about 150 microns thick.

3. The pillow bag of claim 1, wherein the copolymer of ethylene and ethyl acetate contains from about 16 percent to about 20 22 percent by weight of VA.

4. The pillow bag of claim 2, wherein the outer layer sealable by RF is at least of a thickness of about 10 microns, preferably of. a thickness of at least about 20 micrometers and more preferably of a thickness of at least about 30 micrometers.

5. The pillow bag of claim 1, wherein the film has an OTR menort of 50 cubic centimeters per square meter. d. atmosphere when measured at 23 ° C and from 0 percent to 100 percent relative humidity, and an MVTR less than or equal to 25 grams per square meter. d when measured at 38 ° C and 98 percent relative humidity.

The pillow bag of claim 5, wherein the thickness of the PVDC layer or if more than one layer of PVDC is present, the sum of the thickness of the PVDC layers is from about 3 to about 25 microns.

The pillow bag of claim 1, wherein the packaging material has OTR of at least about 1000 cubic centimeters per square meter, d. atmosphere, preferably at least 120 cubic centimeters per square meter. . atmosphere, and still especially preferably at least 150 cubic centimeters per square meter. d. atmosphere.

The pillow bag of claim 7, wherein the thickness of the PVDC layer, or if more than one layer of PVDC is present, the sum of the thickness of the layers of PVDC is from about 1 to about 10 microns.

9. A symmetrical thermoplastic film with an even number of outer layer layers comprising an ethylene vinyl acetate copolymer with from about 14 percent to about 28 weight percent VA, and two internal layers of PVDC separated by at least two contiguous layers comprising copolymers of ethylene and vinyl acetate.

10. The symmetric thermoplastic film of claim 9, which is from about 50 microns to about 250 microns, of ~. preferably from about 70 microns to about 200 microns, and most preferably from about 75 microns to about 150 microns thick.

11. A symmetrical thermoplastic film with outer layers comprising an ethylene vinyl acetate copolymer with from about 14 percent to about 28 weight percent VA and two internal layers of PVDC, when obtained by the crushed bubble process. The symmetrical thermoplastic film of claim 9, comprising two outer layers of an ethylene vinyl acetate copolymer containing about 16 percent to about 22 percent by weight. VA weight percent, two layers of internal PVDC separated by at least two contiguous layers comprising a copolymer of ethylene and vinyl acetate containing from about 16 percent to about 32 percent by weight VA. 13. The symmetric film of claim 12, wherein the inner layers of PVDC are separated by at least two contiguous layers comprising an ethylene vinyl acetate copolymer containing from about 22 percent to about 28 weight percent VA. 14. In a method for packaging a fluent product in a pillow bag wherein the method includes an RF sealing step, the improvement comprising using a multilayer thermoplastic film with an RF sealable outer layer comprising the copolymer- of ethylene and vinyl acetate containing from about 14 percent to about 28 weight percent VA, and a layer of PVDC, such as the packaging layer. 15. The method of claim 14, wherein the fluent product is packaged by means of a VFFS machine.