MXPA99007377A - Pouches for packaging flowable materials - Google Patents

Abstract

An environmentally friendly polymer film pouch made from a polyethylene film structure for the packaging of flowable materials, for example milk, including, for example, a pouch made from a monolayer or multilayer film structure such as a two-layer or a three-layer coextruded film containing at least one layer of a blend of a linear ethylene interpolymer and a high pressure low density polyethylene as a seal layer. Also disclosed is a process for making a pouch for packaging flowable materials using a film structure of a blend of a linear ethylene interpolymer and a high pressure low density polyethylene.

Description

BAGS FOR PACKAGING FLUENT MATERIALS This invention relates to a bag used in consumer packaging, made of certain film structures, useful for packaging flowable materials, for example liquids such as milk. The Patents of E.U.A. Nos. 4,503,102, 4,521,437 and 5,288,531, describe the preparation of a polyethylene film for use in the manufacture of a disposable bag for packaging liquids such as milk. The Patent of E.U.A. No. 4,503,102 discloses bags made from a mixture of a linear copolymer of ethylene copolymerized ethylene and an alpha-olefin on the C to Cio scale and a polymer of ethylene-vinyl acetate acetate, copolymerized of ethylene and vinyl acetate . The linear polyethylene copolymer has a density of 0.916 to 0.930 g / cm3 and a melt index of 0.3 to 2.0 g / 10 minutes. The ethylene-vinyl acetate polymer has a weight ratio of ethylene to vinyl acetate of 2.2: 1 to 24: 1, and a melt index of 0.2 to 10 g / 10 minutes. The mixture described in the Patent of E.U.A. No. 4,503,102, has a weight ratio of low linear density polyethylene, to ethylene-vinyl acetate polymer, from 1.2: 1 to 4: 1, US Pat. No. 4,503,102, also discloses sheets having as a sealing film, the aforementioned mixture. The Patent of E.U.A. No. 4,521,437, discloses bags made of a sealant film, which is from 50 to 100 parts of a linear copolymer of ethylene and octene-1, having a density of 0.916 to 0.930 g / cm3 and a melt index of 0.3 to 2.0 g. / 10 minutes and from 0 to 50 parts by weight of at least one polymer selected from the group consisting of a linear copolymer of ethylene and a C4-Cα-alpha olefin, having a density of 0.916 to 0.930 g / cm3 and a melt index of 0.3 to 2.0 g / 10 minutes, a high pressure polyethylene having a density of 0.916 to 0.924 g / cm3 and a melt index of 1 to 10 g / 10 minutes and mixtures thereof . The sealing film described in the patent of E.U.A. No. 4,521,437, was selected on the basis of providing (a) bags with a substantially smaller M-proof value, in the same film thickness, as in that obtained for film bags from a mixture of 85 parts of a linear ethylene / butene-1 copolymer having a density of 0.919 g / cm 3, and a melt index of 0.75 g / 10 minutes and 15 parts of a high pressure polyethylene having a density of 0.918 g / cm 3 and a melt index of 8.5 g / 10 minutes, or (b) a test value M (2), less than 12%, for bags that have a volume of more than 1.3 to 5 liters. The M, M (2) and M (1.3) tests are defined as bag drop tests in the U.S. Patent. No, 4,521,437. The bags can also be made of mixed films in which the sealing film forms at least one inner layer. The Patent of E.U.A. No. 5,288,531, discloses bags made of a film structure having a mixture of (a) from 10 to 100 weight percent of at least one polymer seal layer of a linear, ultra low density ethylene copolymer. , interpolymerized with ethylene and, at least, an alpha-olefin on the C3-C? o-alpha-olefin scale, having a density of 0.89 g / cm3 and (b) from 0 to 90 weight percent of at least one polymer selected from the group consisting of a linear copolymer of ethylene an a C3-C α-olefin α 8 having a density greater than 0.916 g / cm 3 and a melt index of 0.1 to 10 g / 10 minutes , a high pressure low density polyethylene, having a density of 0.916 to 0.930 g / cm3 and a melt index of 0.1 to 10 g / 10 minutes, or ethylene-vinyl acetate copolymer, having a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melt index of 0.2 to 10g / 10 minutes. The heat seal layer in the U.S. Patent. No. 5,288,531, provides improved hot bond strength and lower heat seal initiation temperature, to a multilayer, co-extruded, two-layer or three-layer film structure, described herein. The polyethylene bags known in the prior art have some deficiencies. The problems associated with films known in the prior art relate to the sealing properties and performance properties of the film for preparing bags. In particular, the prior art films made in bags generally have a high incidence of "leaks", ie, defects in the seal such as holes that develop in or near the seal, through which it escapes the flowable material, for example milk, of the bag. Although the seal and performance properties of the prior art films have generally been satisfactory, there is still a need in the industry to improve seal and performance properties in films for the manufacture of hermetically sealed pouches containing flowable materials. More particularly, there is a need for improved film sealing properties, such as hot adhesion and melt strength, in order to improve the processability of the film and to improve the bags made of the films. For example, the line speed of known packaging equipment, used to manufacture bags such as form, fill and seal machines, is currently limited by the sealing properties of the film used in the machines. Polyethylene films of the prior art have low melt strength. Therefore, the speed at which a form, fill and seal machine can produce a bag is limited, and, therefore, the number of bags produced by a form, fill and seal machine is limited. If the melting strength is increased, then the speed of a form, fill and seal machine can be increased, and, therefore, the number of bags produced can be increased. Until the present invention, several have tried unsuccessfully to improve the sealing properties of the polymer composition used in the film of the bags. It is desired to provide a polyethylene film structure for a bag container having improved melt strength with properties. of performance as good or better than those known in prior art bag films. It is also desired to provide a film structure for a bag container that can be processed through a forming, filling and sealing machine, such as a one layer film. Furthermore, it is desired to provide a bag made of the film structures mentioned above, in such a way that the bag has a reduced failure rate. The present invention provides a bag containing a flowable material, said bag being made of a film structure with at least one seal layer of a polymer composition comprising: (a) from 10 to 100 percent, based on the total weight of said composition, of a mixture of (1) from 5 to 95 weight percent, based on 100 parts by weight of said mixture, of the linear ethylene copolymer interpolymerized from ethylene and, at least, one alpha-olefin on the C3-C18 scale and having a density of 0.916 to 0.940 g / cm3 and a melt index of less than 10g / 10 minutes, and a molecular weight distribution, "Mw / Mn", ratio of more than 4.0, and a peak melting point greater than 100 ° C as measured by a differential scanning colorimeter, and (2) from 5 to 95 weight percent, based on 100 parts by weight of said blend, of density polyethylene low, at high pressure, having a density of 0.916 to 0.930 g / cm3, a lower melt index that 1g / 10 minutes and melt strength greater than 10 cN, as determined using a "Gottfert Rheotens" unit at 190 ° C; and (b) from 0 to 90 percent, based on the total weight of said composition of at least one copolymer selected from the group consisting of an ethylene-vinyl acetate copolymer, having a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melt index of 0.2 to 10g / 10 minutes. One embodiment of the present invention is a bag made of a two-layer co-extruded film, containing an outer layer of linear low density polyethylene, and an inner seal layer of the polymer composition mentioned above. Another embodiment of the present invention is a bag made of a three-layer co-extruded film, containing an outer layer and a polyethylene core layer of low linear density, and an inner seal layer of the polymer composition mentioned above. Another aspect of the present invention is a process for preparing the bag mentioned above. Still another embodiment of the present invention is a bag made of a three-layer coextruded film, which contains an outer layer and a core layer of low density polyethylene, at high pressure, and an inner seal layer of the polymeric composition. mentioned before.

It has been found that the film structures for the bags of the present invention have improved melt strength, and heat seal strength, particularly the ultimate seal strength. The use of the films for making the bags of the present invention, in form, fill and seal machines, leads to the speeds of the machine, higher than those that can currently be obtained with the use of the commercially available film. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a perspective view of a package of bags of the present invention. Figure 2 shows a perspective view of another package of bags of the present invention. Figure 3 shows a partial view, in elongated cross section, of the film structure of a bag of the present invention. Figure 4 shows another partial view, in elongated cross section, of the film structure of a bag of the present invention. Figure 5 shows yet another partial view in elongated cross section of the film structure of a bag of the present invention. Figure 6 is a graphic illustration of the final seal strength against melt strength. DETAILED DESCRIPTION OF THE INVENTION The bag for packaging flowable materials of the present invention, for example as shown in Figures 1 and 2, is manufactured from a one layer film structure, from a polymeric seal layer, which is a mixture of a linear low density polyethylene and a high pressure low density polyethylene, which has a high resistance to melting. The mixture may also contain an ethylene-vinyl acetate copolymer. "Melt strength" which is also referred to in the prior art as "fusion stress", is defined and qualified herein to mean stress or force (as applied by a rope drum equipped with a cell retention) required to extract a molten extrudate at some specific rate above its melting point as it passes through the die of a normal plastometer such as that described in ASTM D1238-E. The melt strength values, which are reported in centi-Ne tons (cN), are determined using a "Gottfert Rheotens" at 190 ° C. In general, for interpolymers of ethylene α-olefin and high-pressure ethylene polymers, melt strength tends to increase with increased molecular weight, or with broadening of the molecular weight distribution and / or with flow ratios of melting. The melt strength of the low density polyethylene at high pressures of the present invention is greater than 10 cN, as determined using a "Gottfert Rheotens" unit at 190 ° C, preferably from 13 to 40 cN, and more preferably from 15 to 25 cN.

In addition, the melt strength of the polymer composition of the present invention is greater than 10 cN as determined using the "Gottfert Rheotens" unit at 190 ° C, preferably 15 to 70 cN, and more preferably 15 to 50 cN A component of the polymer composition of the present invention is a polyethylene referred to below as "linear low density polyethylene" ("LLDPE"). An example of commercially available "LLDPE" is "DOWLEX ™ 2045" (trademark of and commercially available from "The Dow Chemical Company"). The "LLDPE" is generally a linear copolymer of ethylene and a minor amount of an α-olefin having from 3 to 18 carbon atoms, preferably from 4 to 10 carbon atoms and more preferably from 8 carbon atoms. The "LLDPE" for the polymer composition of the present invention has a density greater than 0.916 g / cm3, more preferably from 0.916 to 0.940 g / cm3, more preferably from 0.918 to 0.926 g / cm3; generally has a melt index of less than 10 g / 10 minutes, preferably 0.1 to 10 g / 10 minutes, more preferably from 0.5 to 2g / 10 minutes, and generally has a ratio of O / L2, from 0.1 to 20, preferably from 5 to 20, and more preferably from 7 to 20. The "LLDPE" can be prepared by continuous solution , in batches, and in semi-batches, slurry or gas phase polymerization of ethylene and no or more optional α-olefin co-monomers in the presence of a Ziegler Natta catalyst. such as by the process described in the U.S. Patent. No. 4,076,698 to Anderson et al., Incorporated herein by reference. The α-olefins suitable for the "LLDPE" of the present invention are represented by the following formula: CH 2 = CHR wherein R is a hydrocarbyl radical having from one to twenty carbon atoms. The interpolymerization process can be a solution, slurry or gas phase technique, or combinations thereof. The α-olefin suitable for use as comonomers include 1-propylene, 1-butene, 1-isobutylene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene, as well as other types of monomers such as styrene, styrenes substituted by halogens or alkyl, tetrafluoroethylene, vinyl benzocyclobutane, 1,4-hexadiene, 1,7-octadiene, and cycloalkanes, e.g., cyclopentene, cyclohexene and cyclo-octene . Preferably, the α-olefin will be 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, or mixtures thereof. More preferably, the α-olefin will be 1-hexene, 1-heptene, 1-octene, or mixtures thereof, such as coatings, profiles and films made with the resulting extrusion composition, will have especially improved abuse properties, wherein said Higher α-olefins are used as comonomers. However, more preferably, the α-olefin will be 1-octene and the polymerization process will be a continuous process of solution.

The molecular weight distribution of the ethylene-to-olefin interpolymer compositions and the high pressure ethylene polymer compositions is determined by gel permeation chromatography ("GPC") in a high temperature chromatographic unit "Waters 150", equipped with differential refractometer and three columns of mixed porosity. Columns are supplied by "Polymer Laboratories" and are commonly packaged with pore sizes of 103, 104, 105 and 106A. The solvent is 1,2,4-trichlorobenzene, from which 0.3 percent by weight of the solutions of the samples are prepared by injection. The flow rate is 1.0 milliliter / minute, the operating temperature is 140 ° C and the injection size is 100 microliters. The determination of molecular weight with respect to the structure of the polymer base is deduced using the normal polystyrene of narrow molecular weight distribution (from "Polymer Laboratories") along with its elution volumes. Equivalent polyethylene molecular weights are determined using appropriate "Mark-Houwink" coefficients for polyethylene and polystyrene (as described by Williams and Ward in Journal of Polymer Science, Polymer Letters, Vol. 6, page 621, 1968) for Derive the following equation: Mpolyethylene = a * (Mpolystyrene).

In this equation, a = 0.4316 and b = 1.0. The weight-average molecular weight, MW =? W1XM1, where w, and M, are the fraction by weight and molecular weight, respectively, of the ith fraction eluting from the GPC column. For "LLDPE, preferably the" Mw / Mn "is from 2 to 7, especially 4. The use of" LDPE "having high melt strength in a film structure for bags of the present invention is thought (1) provided a bag that can be manufactured at a faster rate through a form, fill and seal machine, and (2) provides a bag packet that has few leaks, particularly when the bag of the present invention is compared to bags made with linear low density polyethylene, low density polyethylene or a combination thereof With reference to Figures 3 to 5, the film structure of the bag of the present invention also includes a multilayer film structure or mixed 30, preferably containing the polymer seal layer described above, the inner layer of the bag being, as will be understood by those skilled in the art, the multilayer film structure for the bag The present invention can contain various combinations of film layers while the seal layer forms part of the last film structure. The multi-layer film structure for the bag of the present invention can be a co-extruded film, a coated film or a laminated film. The film structure also includes the seal layer in combination with a barrier film such as polyester, nylon, "EVOH", polyvinylidene dichloride ("PVDC") such as "SARAN ™" (Trademark of "The Dow Chemical Company ") and metallic films. The final use for the bags tends to dictate, to a greater degree, the selection of the material or materials used in combination with the seal layer film. The bags described herein will refer to seal layers used at least on the inner side of the bag. One embodiment of the film structure 30, for the bag of the present invention, shown in Figure 3, comprises the. seal layer 31, of a mixture of "LLDPE" and "LDPE" with high melt strength of this invention, and at least one polymeric outer layer 32. The polymeric outer layer 32, preferably is a layer of polyethylene film , more preferably an "LLDPE". An example of a commercially available "LLDPE" is "DOWLEX ™ 2045" (commercially available commercially from "The Dow Chemical Company"). The thickness of the outer layer 32 can be any thickness while the seal layer 31 has a minimum thickness of 2.5 microns. Another embodiment of the film structure 30, for the bag of the present invention, shown in Figure 4, comprises the polymeric layer 32 sandwiched between two layers of polymeric seal 31.

Still another embodiment of the film structure 20 for the bag of the present invention, shown in Figure 5, comprises at least one polymeric core layer 33 between at least one polymeric outer layer 32, and at least, a polymer seal layer 31. The polymeric layer 33 may be the same "LLDPE" film layer as the outer layer 32, or preferably a different "LLDPE", and more preferably an "LLDPE", eg "DOWLEX ™ 204S "(Trade Mark of and commercially available from" The Dow Chemical Company ") having a higher density than outer layer 32. The thickness of core layer 33 may be any thickness as long as seal layer 31 has a minimum thickness of 2.5 microns. The thickness of the last film of the final film product used to produce the bag of the present invention is from 12.7 microns to 254 microns, preferably from 25.4 microns to 127 microns; more preferably from 50.8 microns to 100 microns. The additives, known to those skilled in the art, such as antiblocking agents, slip additives, UV stabilizers, pigments and processing aids, can be added to the polymers of which the bags of the present invention are made. As can be seen from the different embodiments of the present invention shown in Figures 3-5, the film structure for the bags of the present invention have design flexibility. Different "LLDPE" can be used in the outer and core layers to optimize the specific properties of films such as film stiffness. Therefore, the film can be optimized for specific applications such as for a machine in vertical form, film and sealing. The polyethylene film structure used to make a bag of the present invention is made either by the tube blow extrusion method or the cast extrusion method, methods well known in the art. The tube blow extrusion method is disclosed, for example, in the "Modern Plastics Mid" Encyclopedia Publication - October 1989, Volume 65, Number 11, pages 264 to 266. The cast extrusion method is disclosed , for example, in the Publication of the Encyclopedia "Modern Plastícs Mid" - October 1989, Volume 66, Number 11, pages 256 to 257. The embodiments of the bags of the present invention, shown in Figures 1 and 2, are hermetically sealed containers filled with "flowable materials". "Flowable materials" means materials that are flowable under gravity or that can be pumped. The term "flowable materials" does not include gaseous materials. The flowable materials include liquids, for example, milk, water, fruit juice, oil; emulsions eg ice cream mixture, soft margarine; pasta, for example, meat paté, peanut butter, preservatives, for example, jam, stand-up jam; jellies, masses; Ground beef, for example, sausage meat, powders for example, gelatin powder, detergents; granulated solids eg nuts, sugar; and similar materials. The bag of the present invention is particularly useful for liquid foods, for example, milk. The flowable material may also include oleaginous liquids for example, cooking oil, or engine oil. Once the film structure for the bag of the present invention is formed, this film structure is cut to the desired width for use in conventional bag forming machines. The embodiments of the bag of the present invention shown in Figures 1 and 2, are made in form, fill and seal machines, so-called, well known in the art, with respect to Figure 1, a bag 10 is shown. being a tubular member 11 having a flap seal 12 and transverse seals 13, such that a "pillow-shaped" bag is formed when the bag is filled with flowable material. With respect to Figure 2, a bag 20 is shown as a tubular member 21 having a peripheral flap seal 22, a. along three sides of a tubular member 21, for example, the upper seal 22a and the longitudinal side seals 22b and 22c, and having a substantially concave or "bowl-shaped" lower member 23, sealed in the lower portion of the member tubular 21, such as when viewed in cross-section, longitudinally, a semicircular or "curved" lower portion is formed substantially, when the bag is filled with flowable material. The bag shown in Figure 2 is an example of the so-called "Enviro-Pak" bag known in the art. The bag manufactured in accordance with the present invention, preferably is the bag shown in Figure 1, produced in vertical form filling and sealing machines ("VFFS"). so-called, known in the art. Examples of "VFFS" machines include those manufactured by "Hayssen", "Thimonnier", "Tetra Pak", or "Prepac". A "VFFS" machine is described in the following reference: FC Lewís, "Form-Fill-Seal", "Packaging Encyciopedia", page 180, 1980. In a "VFFS" packing process, a sheet of the structure of plastic film described herein, is fed into a "VFFS" machine wherein the sheet is formed in a continuous tube in a tube forming section. The tubular member is formed by sealing the longitudinal edges of the film together with, either overlapping the plastic film and sealing the film using an internal / external seal, or by sealing the plastic film using an internal / internal seal. Then, a sealing bar seals the tube transversely at one end, the bottom part being the "bag", and then the filling material, for example milk, is added to the "bag". The sealing bar then seals the upper end of the bag and burns it through the plastic film, or cuts the film, whereby the finished bag "VFFS" is separated, generally disclosed in US Patents. Nos. 4,503,102 and 4,521,437, incorporated herein by reference. The capacity of the bags of the present invention may vary. Generally, the bags can contain from 5 milliliters to 10 liters, preferably from 1 milliliter to 8 liters, and more preferably from 1 milliliter to 5 liters of flowable material. The structure of the film for the bag of the present invention has precisely controlled resistance, the use of the structure of the film described in the present invention to produce a bag, results in a strong bag, and, therefore, more preferably, the bag contains less leakage related to use. The use of a mixture of "LLDPE" and LDPE "in the seal layer of the present invention in a two or three layer coextruded film product will provide a film structure that can be used to form bags at a faster rate in The "VFFS" and said bags produced will contain fewer leaks, Changing the trend in the current packaging industry for the consumer, to provide the consumer with more environmentally friendly packaging, the polyethylene bag of the present invention is a good alternative. The polyethylene bag for packaging consumer liquids, such as milk, has its advantages over the containers used in the past: the glass bottle, paper carton, and high density polyethylene jars. large quantities of natural resources in their manufacture, they required a significant amount of space on the land, they use a lot of space of storage, and used more energy in controlling the temperature of the product (due to the heat transfer properties of the container). The polyethylene bag of the present invention produced from a thin polyethylene film, used to pack liquids, offers several advantages over containers used in the past. The polyethylene bag (1) consumes less natural resources, (2) it requires less space on the earth, (3) it can be recycled, (4) it can be easily processed, (5) it requires less space to be stored (6) it uses less energy to be stored (heat transfer properties of the package), (7) can be incinerated safely and (8) can be reused, for example, the empty bag can be used for other applications such as freezer bags, bags for sandwiches, and storage bags for general purposes. The polymeric resins described in Table 1 below were used to prepare samples of gas-filled films shown in the Examples and Comparative Examples.

Table I: Properties of Resins The composition of several mixtures of LDPE and LLDPE and their resistance to melting is shown in the following Table II.

Table II: Resistance to the Fusion of Resin Mixtures (*)% refers to% by weight of LDPE in the mixture A 5 kg sample of each mixture shown in Table II was processed through a double screw extruder "Leistritz". The melt strength of the mixtures were determined using a "Gottfert Rheotoens" unit. Erucamide, a slip agent; Si02, an antiblocking agent; and a processing aid, to each of the resins described in Table I, in such a way that the final concentrations of the additives were as follows: 1200 ppm of Erucamide; 2500 ppm of S02. The produced film structures were subjected to physical tests to determine their different properties, including: (1) Puncture, using the method ASTM D3763; (2) Impact of dart, using ASTM D1709, Method A; (3) Rupture of "Elmendorf", using ASTM D1922; (4) Tensioners, using ASTM D882; (5) 1% and 2% of the drying module, using ASRM D882; (6) Hot Adhesion Resistance, using the method described below; and (7) Heat Seal Resistance, using the method described below; The resistance to hot adhesion of sample films was measured using the "DTC Hot Adhesion Test Method", which measures the force required to separate a seal with heat before the seal has had a chance to cool. (crystallize) completely. This simulates filling the material in a bag before the seal has had a chance to cool. The "DTC Heat Adhesion Test Method" is a test method that uses the DTC # 52D Hot Adhesion Tester Model in accordance with the following conditions: Specimen Width: 25.4 mm Sealing Time: 0.5 seconds Seal Pressure: 0.27 N / mm / mm Delay Time: 0.5 seconds Release Speed: 150 mm / seconds Number of Samples / Temperature: 5 Temperature Increases: 5 ° C Temperature Range: 75 ° C-150 ° C Heat seal resistance of the sample films was measured using the "DC Heat Seal Resistance Test Method", which is a measure designed to measure the force required to separate the seal after the material has been removed. has cooled to a temperature of 23 ° C. Samples of the film were exposed to a relative humidity of 50 percent and at a temperature of 23 ° C for a minimum of 24 hours before the test.

The "DTC Heat Seal Resistance Test Method" utilizes a DTC # 53D Hot Adhesion Tester Model, in which the heat seal portion of the tester is used in accordance with the following conditions: Specimen Width: 25.4 mm Sealing Time: 0.5 seconds Sealing Pressure: 0.27 N / mm / mm Number of Samples / Temperature 5 Temperature Increments 80 ° C-150 ° C The seal resistance of the film samples was determined using an "Instron" Model # 1122 Tension Tester, according to the following conditions: Steering direction: 90 ° towards the seal Crosshead Speed: 500 mm / minute Full Scale Load: 5 kg Number of Samples / Threshold: 1 percent FSL Break Criterion: 80 percent Caliber Length: 50.8 millimeters Sample Width: 25.4 millimeters Table III: Multiple Layer Films (A / B / A) for Physical Properties Tests (*)% refers to weight percent of LDPE in the mixture The physical properties of films shown in Table III are reported in the following Table IV, and the results of hot adhesion strength and heat seal are reported in Table V. Table IV: Physical Properties of Multi-Layered Films - AFF AFF AFF AFF AFF AFF AFFINITY 1880+ 1880+ 1880+ 1880+ 1880 1880 1880 20% 20% 20% 20% XU + 1351 1351 1351 60021.6 20% 20% (80% Id 76.2 mm 2 5031 526I in core) Caliber 63.24 80.7 62.48 63.5 63.5 53.34 64.51 Rupture Elmendorf f M253D Table VI: Resistance to Hot Adhesion / Heat Seal Resistance to Hot Adhesion. N / cm DOWLEX DOWLEX 2045 DOWLEX DOWLEX 2045 + 20% LDPE 2045 + 20% 2045 + 20% 1351 LDPE 609C XU60021.62 TEMPERATURE ° C 90 0. 23 0.14 0.22 0 19 95 0 17 0.21 0 15 0.19 100 0 64 0.62 0.66 0.68 105 1 91 1 91 1 85 1 79 110 47 2.86 2.55 ¿.. Ó 115 > 28 3 47 3.30 3.59 120 - 54 3 04 2 73 3 17 125 2 51 2 96 2 63 3 16 130 2 38 2 86 2 56 3 13 135 2 35 2 73 2 32 2 89 140 2 27 2 48 2 16 262 145 2 17 2 35 2 14 2 39 150 1 96 2 21 2 09 2 12 155 1 99 1 91 1 85 1 89 160 1 65 1 78 1 80 1 84 Table Vi l Heating Resistance with Heat, kg / mm DOWLEX DOWLEX 2045 DOWLEX DOWLEX 2045 + 20% LDPE 2045 + 20% 2045 + 20% 1351 LD P E 609C XU60021 62 TEMPERATURE ° C 100 0 26 0 20 0 19 026 105 0 51 0 72 0 51 0 71 110 4 28 4 88 4 10 4 95 115 4 71 5 76 5 15 6 14 120 5 52 7 09 6 00 783 125 5 71 7 01 6 50 7 79 130 6 02 7 07 6 60 7 82 135 5 33 7 37 5 90 7 70 140 6 11 1 50 6 75 8 00 145 5 56 7 01 6 06 775 150 5.27 7.53 6.33 7.70 155 4.86 7.74 6.48 8.25 160 5.68 7.75 6.50 8.69 The present invention is illustrated by the following examples, but will not be limited by them. Examples 1-3 and Comparative Examples A The film samples described in Table III. were produced as a single layer using blown film line "Macro". The extruder was 6.4 cm in diameter and had a L / D ratio of 24: 1, and a sweeping screw with a "Maddox'L mixing head. A die of 15.2 cm in diameter was used, with a die space of 1,524 microns for the manufacture of the test films The manufacturing conditions for the blowing film exist as there is a blowing radius of 6.4 and a melting temperature of 220 ° C. Examples 4-6 and Comparative example B The films described in Table III were slotted to a width of 38.1 cm to produce bags for 2 liters of milk, using a form machine, Filling and Seal "Prepac 1 S6 Vertical", located in a commercial dairy. Lined with 2 liters of milk, a rate of 30 bags per minute per filling head under normal operating conditions For film tested, approximately 16 to 20 bags filled with milk were collected and inspected for seal integrity. Initial 6 to 8 bags were tested at the site for heat seal resistance and 10 bags were drained, washed and dried for further evaluation Selium resistance was determined using the "instron" Stress Test Model # 1122 Samples were exposed to a relative humidity of 50% and at 23 ° C for 24-48 hours before being tested. The test conditions of "Instron" were the following Direction in which Jala 90 ° of Selio Cruceta Speed 500 mm / minute Full Scale Load 5 kg FSL 1% Threshold Rupture Criterion 80% Caliber Length 50 8 mm Sample Width 25 4 mm The initial examination of the final seal integrity involved three steps i) Online Leak Determination ?? ) SuDjective Seal Resistance Test ni) Visual Examination of Seals finaies Online Leaks Online leaks were seen only with the solids produced from DOWLE? 2045 No leaks were seen with the other films Test of Subjective Subject Resistance The subjective seal resistance test involved squeezing the bag from one end until a bite occurred, or until the seal failed. Table VIII shows that there were no failures with the bags produced with 20% 1351 or XU 60021.62. Visual Examination of Final Seals DOWLEX 2045 films were found to have significant thinning of the seal and stretching of the final seal, as shown in Table IX. It was found that the bags produced with 20% 609C, have some seal thinning and some final seal stretches. In films produced with 20% 1351 and XU 60021.62, neither thinning of the seal nor stretches were found. Final Seal Resistance The 2 liter milk bags were tested for resistance to the final seal using a "Instron" Voltage Tester Model # 4206. under the same conditions described in relation to the determination of resistance to the seal with previous heat. The seal resistances are shown in Table C. It was found that resistance to seal increased as the mixture's melt strength increased. This finding is illustrated graphically in Figure 6. using a mixture of 80 % by weight of LLDPE and 20% by weight of LDPE, except that the first point of the data has resistance to fus i at 64 cN. It does not contain any LDPE. The correlation between LDPE melt index and seal resistance was not evident. Microscopic Examination of Final Seals The stretch regions and edge regions of the bags were cryosected and examined using light microscopy techniques. Table XI summarizes the results. The films produced with 20% 1351 and XU 60021.62, showed very little thinning of the seal and no final seal stretch (fine polymer filaments coming from the selio area), while the films formed with 100% DOWEX 2045, had thinnings and stretches important stamp. Thinning Film in the Seal Region The weakest part of a good seal is usually the film just in front of the stamp flange. Any thinning of this film results in lower seal strengths. since this is the region that fails when the seal is stretched.

Comparing the melting strength of resin mixtures (Table II) with the amount of film thinning seen with the bags produced with a commercial VFFS unit (Table XI). it is observed that, as the melting strength of the resin mixture increases. decreases the amount of film thinning No correlation is observed between the film thinning (Table XI) and the Melt Index of LDPE in resin mixtures (Table I). Seiio Flange Comparing the thicknesses of the seal flange (Table XI) with the melting strength of the resin mixture (Table II) and the LDPE melt index (Table I), it is observed that there is a strong correlation between the melt strength and flange thicknesses, and there is no correlation between LDPE melt index and seal flange thickness. Higher melt strength blends resulted in thicker seal flanges.

Table VIII: Evaluation of VFFS of "Prepac" of Milk of "Liconsa" Subjective Resistances of Selio Table IX: Evaluation of VFFS of "Prepac" 'of Milk of "Liconsa' Visual Examination of Final Seals Table X: VFFS of "Prepac" End Seal Resistance of the Bags Series # LLDPE Ml LDPE Ml% L D P E Seal strength. kg / m 1 DOWLEX - 0 94.78 2045 2 DOWLEX 609C 20 103.17 2045 3 DOWLEX 135C i 20! 121.2 2045: 4 DOWLEX XU 62: 20 125.12 1 2045 Table XI "Prepac" Summary of Analysis of Microscopy of "VFFS ' * 550μm measured from the seilo ** cross section measured in the thinnest part of the film before the seal The following polymer resin blends shown in Table XII. were used to further illustrate the advantages of this invention: Table XII. Resin mixtures (*)% refers to percent by weight of the amount of LDPE in various mixtures. The resin mixtures of Table XII. They were used to make films with a thickness of 71 microns, using a line of blown films "MACROS". They have a barrier screw with a diameter of 63.5 mm. ratio of L / D 24.1 and mixing head "Maddock" A 15.2 cm die was used. with a die space of 1524 microns. A two-lip air ring "Macro" was used. supplied with cooled air. Each resin was mixed to a point of 1200 ppm of erucamide slider and 2500 ppm of Si02 antiblocker. Each film was tested for hot adhesion strength and heat seal, values were reported respectively in Table XIII and Table XIV.

TABLE XIV RESISTANCE OF HOT DAMAGES (KG / M) OF MIXTURES "DOWLEX 2045 / LDPE XU 60021 62" o 00 The hot adhesion strength was determined using a Hot Density Tester "DTC" Model "D52D, under the conditions described above.The test films were heat sealed using the Hot Adhesion Tester" DTC "Model # D52D, under the conditions described above, The heat seal resistance was determined using an "Instron" Voltage Tester Model # 1122. The test samples were exposed to a relative humidity of 50 percent and 23 ° C for 24 hours. 48 hours before being tested The conditions of the "Instron" test were the same as those described above, based on the results of the heat adhesion and heat seal tests shown in Table XIII and Table XIV It is observed that the maximum hot adhesion strength was reached with the 50 percent blend of "DOWLEX 2045" / 50 percent "XU 600021.62." The highest heat seal strength was also achieved. observed with the mixture of "DOWLEX 2045" / 50 percent of "XU 600021 62".

TABLE XV- Resistance to DOWLEX 2045 LDPE 1351 DOWLEX DOWLEX 2045 Adherence to 2045+ 20% + 20% LDPE Hot LDPE 1351- 1351 - REAL Predicted against EXPECTED Real Temperature (° C) 95 0.29 0.18 0.24 0.27 100 0.45 0.22 0.33 0.35 105 1.76 0.56 1.16 0.97 110 2.40 0.81 1.60 2.19 115 2.82 0.86 1.84 3.18 120 2.96 0.74 1.85 3.41 125 2.77 0 69 1.73 3.54 130 2.54 0.69 1.62 3.34 135 2.40 0.64 1.52 3.10 140 2.31 0.64 1.47 3.05 145 2.32 0.60 1.46 2.87 150 2 18 0.56 1.37 2.74 The expected hot bond strength, was calculated according to the following. HEAT ADHERENCE = (hot adhesion 0 5 X LLDPE) + (hot adhesion 0 5 + LDPE) The results of resistance to hot adhesion predicted against the real one are shown in Table XV / It can be noted that the resistance to the actual hot adhesion of the present invention, is significantly higher than the predicted level, indicating a clearly synergistic effect.

Claims (27)

1. CLAIMS 1. A bag containing a flowable material, said bag being made of a film structure with at least one seal layer of a polymer composition comprising: (a) from 10 to 100 percent, based on the total weight of said composition, of a mixture of (1) from 5 to 95 weight percent, based on 100 parts by weight of said mixture, of the linear ethylene copolymer interpolymerized from ethylene and, at least, one alpha -olefin on the scale of C3-C18 and having a density of 0.916 to 0.940 g / cm3 and a melt index of less than 10g / 10 minutes, and a molecular weight distribution, "Mw / Mn", ratio of more than 4.0 , and a peak melting point greater than 100 ° C as measured by a differential scanning colorimeter, and (2) from 5 to 95 weight percent, based on 100 parts by weight of said mixture, of low density polyethylene , at high pressures, having a density of 0.916 to 0.930 g / cm3, a melting index of less than 1g / 10 minutes and melt strength greater than 10 cN, as determined using a "Gottfert Rheotens" unit at 190 ° C; and (b) from 0 to 90 percent, based on the total weight of said composition, of at least one copolymer selected from the group consisting of an ethylene-vinyl acetate copolymer, having a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melt index of 0.2 to 10g / 10 minutes.
2. 2. A bag containing a flowable material, said bag being made of a multilayer structure comprising: (I) a layer of polymer composition comprising: (a) from 10 to 100 percent, based on the total weight of said composition, of a mixture of (1) from 5 to 95 percent in Weight, based on 100 parts by weight of said mixture, of the linear ethylene copolymer interpolymerized from ethylene and, at least, an alpha-olefin on the C3-C18 scale and having a density of 0.916 to 0.940 g / cm3 and a melt index of less than 10g / 10 minutes, and a molecular weight distribution, "Mw / Mn", ratio of more than 4.0, and a peak melting point greater than 100 ° C as measured by a colorimeter of differential sweep, and (2) from 5 to 95 weight percent, based on 100 parts by weight of said mixture, of low density polyethylene, at high pressures, having a density of 0.916 to 0.930 g / cm3, an index of fusion less than 1g / 10 minutes and melt strength greater than 10 cN, as determined using a "Gottfert" unit Rheotens "at 190 ° C, and (b) from 0 to 90 percent, based on the total weight of said composition, of at least one copolymer selected from the group consisting of an ethylene-vinyl acetate copolymer, which has a weight ratio of ethylene to vinyl acetate of 2.2: 1 to 24: 1 and a melt index of 0.2 to 10 g / 10 minutes, and (II) at least one layer of linear ethylene copolymer interpolymerized from ethylene and at least one alpha-olefin on the scale of C3-C? 8 and having a density of 0.916 to 0.940 g / cm3 and a melt index of 0.1 to 10 g / 10 minutes 3.
3. The bag of claim 1, in which said film structure has a tubular shape and said bag has ends transversely sealed with heat 4.
4. The bag of claim 2, having (lll) a layer of a high pressure polyethylene, having a density of 0.916 to 0.930 g / cm3 and a melt index of 0.1 to 10 g / 10 minutes 5.
5. The bag of claim 2, in the which layer (I) is a seal layer.
6. The bag of claim 2, wherein the layer (II) is an outer layer and the layer (I) is a seal layer.
7. The bag of claim 4, wherein the layer (II) is an outer layer, the layer (III) is a core layer, and the layer (I) is a seal layer.
8. 8. The bag of claim 2, wherein the linear ethylene copolymer has a melt index of less than 10g / 10 minutes.
9. 9. The bag of claim 1, wherein the bag contains from 5 ml to 10,000 ml.
10. 10. The bag of claim 1, wherein the flowable material is milk.
11. The bag of claim 1, wherein the ethylene copolymer has a molecular weight distribution indicator (l? O / l2) of 0.1 to 20.
12. The bag of claim 1, wherein the structure of film contains a slip agent, an antiblocking agent, and, optionally, a processing aid.
13. 13. The bag of claim 1, wherein the film structure contains a pigment to opaque the film structure.
14. 14. The bag of claim 1, wherein the film structure contains an ultraviolet light absorbing additive.
15. 15. The bag of claim 1, wherein the alpha-olefin of the film structure is 1-octene.
16. 16. The bag of claim 1, wherein the melt strength of high pressure low density polyethylene is in the range of 10 to 40 cN.
17. 17. The bag of claim 1, wherein the melt strength of high density low density polyethylene is in the range of 13 to 25 cN.
18. 18. The bag of claim 1. wherein the melt strength of the polymer composition is in the range of 10 to 70 cN
19. 19. The bag of . Claim 1, wherein the thinning in the edge region is reduced by less than 25 percent.
20. 20. A film structure of a polymer composition for a packaging application comprising: (a) from 10 to 100 percent, based on the total weight of said composition, of a mixture of (1) from 5 to 95 percent by weight weight, based on 100 parts by weight of said mixture, of the linear ethylene copolymer interpolymerized from ethylene and, at least, an alpha-olefin on the scale of C3-C? 8 and having a density of 0.916 to 0.940 g / cm3 and a melting index of less than 10g / 10 minutes, and a molecular weight distribution, "Mw / Mn", ratio of more than 4.0, and a peak melting point greater than 100 ° C as measured by a colorimeter of differential scanning, and (2) from 5 to 95 weight percent, based on 100 parts by weight of said mixture, of low density polyethylene, at high pressures, having a density of 0.916 to 0.930 g / cm3, an index of fusion less than 1g / 10 minutes and fusion resistance greater than 10 cN, as determined using a "Gottfert Rheotens "at 190 ° C, and (b) from 0 to 90 percent, based on the total weight of said composition, of at least one copolymer selected from the group consisting of an ethylene-vinyl acetate copolymer, which has a weight ratio of ethylene to vinyl acetate of 2.2: 1 to 24: 1 and a melt index of 0.2 to 10g / 10 minutes 21.
21. The film of claim 20, wherein the density of the ethylene copolymer. linear is from 0.916 to 0.940 g / cm 3.
22. The film of claim 20, wherein the concentration of ethylene-vinyl acetate copolymer, is from 5 to 85 percent based on the total weight of said composition.
23. The film of claim 20, wherein the concentration of ethylene-vinyl acetate copolymer is from 5 to 25 percent based on the total weight of said composition 24.
24. The film of claim 20, wherein the The melt strength of the polymer composition is on a scale of 10 to 70 cN.
25. A process for preparing a bag containing a flowable material, comprising forming a film structure either by extrusion by tube blowing, or by cast extrusion, forming the film structure in a tubular member and heat sealing transversely opposite ends of the tubular member, said tubular member comprising a film structure for a bag container with at least one seal layer of a polymer composition comprising: (a) from 10 to 100 percent, based on the total weight of said composition, of a mixture of (1) from 5 to 95 weight percent, based on 100 parts by weight of said mixture, of the linear ethylene copolymer etherpolymerized from ethylene and, at least, an alpha-olefin on the C3-C18 scale and having a density of 0.916 to 0.940 g / cm3 and a melt index of less than 10g / 10 minutes, and a molecular weight distribution, "Mw / Mn", ratio of more than 4.0, and a peak melting point greater than 100 ° C as measured by a differential scanning colorimeter, and (2) from 5 to 95 percent by weight, based on 100 parts by weight of said mixture, of low density polyethylene, at high pressures, having a density of 0.916 to 0.930 g / cm3, a melt index of less than 1 g / 10 minutes and resistance to fusion greater than 10 cN, as determined using a "Gottfert Rheotens" unit at 190 ° C; and (b) from 0 to 90 percent, based on the total weight of said composition, of at least one copolymer selected from the group consisting of an ethylene vinyl acetate copolymer, having a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melt index of 0.2 to 10g / 10 minutes.
26. 26. A process for preparing a bag containing a flowable material, comprising forming a film structure either by extrusion by tube blowing, or by cast extrusion, forming the film structure in a tubular member and heat sealing transversely the opposite ends of the tubular member, said tubular member comprising: (I) a layer of polymer composition comprising: (a) from 10 to 100 percent, based on the total weight of said composition, of a mixture of (1) of at 95 weight percent, based on 100 parts by weight of said mixture, of the linear ethylene copolymer interpolymerized from ethylene and, at least, an alpha-olefin on the C3-C18 scale and having a density of 0.916. at 0.940 g / cm3 and a melt index of less than 10g / 10 minutes, and a molecular weight distribution, "Mw / Mn", ratio of more than 4.0, and a peak melting point greater than 100 ° C as measured by a different color scanner and (2) from 5 to 95 weight percent, based on 100 parts by weight of said mixture, of low density polyethylene, at high pressures, having a density of 0.916 to 0.930 g / cm3, a melt index less than 1g / 10 minutes and melt strength greater than 10 cN, as determined using a "Gottfert" unit Rheotens "at 190 ° C, and (b) from 0 to 90 percent, based on the total weight of said composition, of at least one copolymer selected from the group consisting of an ethylene-vinyl acetate copolymer, which has a weight ratio of ethylene to vinyl acetate of 2.2: 1 to 24: 1 and a melt index of 0.2 to 10g / 1O minutes, and (II) at least one layer of linear ethylene copolymer interpolymerized from ethylene and at least one alpha-olefin on the scale of C3-C? 8 and having a density of 0.916 to 0.940 g / cm3 and a melt index of 0.1 to 10 g / 10 minutes
27. 27. The claim process 26, in which the film structure includes: (lll) at least one layer of a high pressure polyethylene, having a density of 0.916 to 0.930 g / cm3 and a melt index of 0.1 to 10g / 10 minutes. RESU M IN an environmentally friendly polymer film bag made of a polyethylene film structure for the packing of flowable materials, for example milk, including, for example, a bag made of a single layer film structure. or multilayer, such as a two-layer or three-layer coextruded film, containing at least one layer of a mixture of a linear ethylene interpolymer and a low density polyethylene at high pressures, such as a seal layer. A process for producing a bag for packaging flowable materials using a film structure of a mixture of a linear ethylene interpolymer and a low density polyethylene at high pressures is also described.