RU2187448C2 - Film bag for flowing material (versions), film structure and method of bag making (versions) - Google Patents

Abstract

FIELD: packing. SUBSTANCE: invention relates to ecologically clean polymeric film bags designed for packing flowing materials, for instance, milk. Bag can be made of one-layer or multiplayer film structure such as two- layer or three-layer coextruded film with at least one layer of mixture linear copolymer of ethylene and low- density polyethylene as sealing layer. Invention presents process of bag making for packing flowing materials with use of film structure of mixture of linear copolymer of ethylene and lowdensity polyethylene. Film structures for bags feature improved characteristics of strength limit at melting thermoweld strength limit, especially final thermoweld strength limit. EFFECT: increased speed of automatic packing machine as compared with that when standard commercial film is used for packing. 27 cl, 14 tbl, 6 dwg, 6 ex

Description

 The invention relates to a bag that is used in consumer packaging and is made from certain film structures used for packaging fluid substances, such as a liquid, such as milk.

US Pat. Nos. 4,503,102, 4,521,437, and 5,288,531 disclose a process for producing a polyethylene film that is used in the manufacture of disposable bags for packaging liquids such as milk. US Pat. No. 4,503,102 discloses bags made from a mixture of a linear ethylene copolymer copolymerized from ethylene and an alpha olefin in the range of C ₄ -C ₁₀ and an ethylene vinyl acetate polymer copolymerized from ethylene and vinyl acetate. The linear copolymer of polyethylene has a density of 0.916-0.930 g / cm ³ and a melting index of 0.3-2.0 g / 10 min. The ethylene vinyl acetate polymer has a weight ratio of ethylene to vinyl acetate of 2.2: 1 to 24: 1 and a melting point of 0.2-10 g / 10 min. The mixture disclosed in US Pat. No. 4,503,102 has a weight ratio of linear low density polyethylene to ethylene vinyl acetate polymer from 1.2: 1 to 4: 1. U.S. Patent 4,503,102 also discloses laminates having the aforementioned mixture as a sealing film.

US Pat. No. 4,521,437 describes bags made of a sealing film that has 50 to 100 parts of a linear ethylene-octene-1 copolymer having a density of 0.916-0.930 g / cm ³ and a melting index of 0.3-2.0 g / 10 min. , and from 0 to 50 wt. including at least one polymer selected from the group consisting of a linear copolymer of ethylene and a C ₄ -C ₁₀ alpha-olefin having a density of 0.916-0.930 g / cm ³ and a melting index of 0.3-2.0 g / 10 min, high pressure polyethylene having a density of 0.916-0.924 g / cm ³ and a melting index of 1-10 g / 10 min and mixtures thereof. The sealing film disclosed in US Pat. No. 4,521,437 was selected based on the preparation of (a) packets with an M-test value substantially less than the value, at the same film thickness as that obtained for packets made using a film of a mixture consisting of 85 parts of a linear ethylene / butene-1 copolymer having a density of 0.919 g / cm ³ and a melting index of 0.75 g / 10 min and 15 parts of high pressure polyethylene having a density of 0.918 g / cm ³ and a melting index of 8.5 g / 10 minutes , or (b) with an M (2) test value of less than 12% for packets having a volume of m more than 1.3 to 5 liters, or (c) with a value M (1.3) -test less than 5% for a package having a volume of 0.1-1.3 liters. US Pat. No. 4,521,437 to M, M (2), and M (1.3) tests show the results of packet drop tests. The bags can also be made of multilayer films in which the sealing film forms at least an inner layer. However, US Pat. No. 4,521,437 does not disclose that high pressure polyethylene has a high melting strength and that all high pressure polyethylene resins used in the examples have a melting index of more than 1 g / 10 min. In addition, US Pat. No. 4,521,437 discloses that for ethylene polymer mixtures, the melting strength is not related to the thermal bonding strength or leakage characteristics.

US Pat. No. 5,288,531 discloses bags made of a film with a structure having a mixture of (a) from 10 to 100 weight percent ("wt%") of at least one polymer sealing layer of an ultra low density linear ethylene copolymer copolymerized from ethylene and at least one alpha olefin in the range of C ₃ -C ₁₀ with a density of from 0.89 g / cm ³ to less than 0.915 g / cm ³ , and (b) from 0 to 90 wt.%, at least at least one polymer selected from the group consisting of a linear copolymer of ethylene and a C ₃ -C ₁₈ alpha-olefin having a density of more than 0.91 6 g / cm ³ and a melting index of 0.1-10 g / 10 min, high-density low-density polyethylene having a density of 0.916-0.930 g / cm ³ and a melting index of 0.1-10 g / 10 min, or a copolymer of ethylene vinyl acetate having a mass ratio of ethylene to vinyl acetate of 2.2: 1 to 24: 1 and a melting index of 0.2-10 g / 10 min. In US Pat. No. 5,288,531, a heat seal layer provides an increased tensile strength with heat bonding and lower temperature when a heat seal is formed in a two-layer or three-layer structure of a coextruded multilayer film described therein.

 Plastic bags known in the prior art have some disadvantages. The problems associated with films that are known from the prior art relate to welding properties and film performance in the bag manufacturing process. In particular, prior art films made in the form of bags typically have a high percentage of “leakage”, that is, defects in the heat seal, such as microchannels that form at or near the heat seal, through which fluid substances, such as milk, flow from package. Although the heat seal and the performance of the prior art films were generally satisfactory, the industry still feels the need for better welding and performance of the films for the manufacture of hermetically sealed bags containing fluid substances. More specifically, there is a need to improve film welding properties, such as thermal bonding and melting strength, to improve film processability and the quality of bags made from these films.

 For example, the linear speed of known packaging equipment used in the manufacture of bags, such as a molding, filling and capping machine, is currently limited by the properties of the formation of adhesions of the film used in machines. Known plastic films have a low tensile strength during melting. Therefore, the speed at which the molding-filling-capping machine can produce a bag is limited, and thus the number of packages produced on the molding-filling-capping machine is reduced. If the tensile strength during melting increases, then the speed of the molding-filling-capping machine can increase, and thus, the number of packages produced can be increased. Prior to the present invention, many researchers unsuccessfully tried to improve the welding properties of the polymer composition used in the film package.

 Therefore, it is necessary to obtain a structure of a polyethylene film for a package that would have an increased tensile strength during melting with operational properties not inferior to or superior to the known films for packages of the prior art.

 It is also necessary to carry out the film structure for batch packaging, which can be used in a molding-filling-capping machine in the form of a single-layer film.

 In addition, it is necessary to make a bag made of the aforementioned film structures so that the bag has a lower frequency of damage.

The present invention provides a package for a current substance made of a film structure with at least one sealing layer of a polymer composition containing: (a) from 10 to 100% of the total weight of said composition, mixture (1) from 5 to 95 wt.% based on 100 wt. including the said mixture, a linear ethylene copolymer copolymerized from ethylene and at least one alpha olefin in the range of C ₃ -C ₁₈ and having a density of 0.916-0.940 g / cm ³ and a melting index less than 10 g / 10 min, and the Nw / Mn ratio for molecular weight distribution is more than 4.0 and the maximum melting point is more than 100 ^o C, which is measured using a differential scanning calorimeter, and (2) from 5 to 95 wt. %, based on 100 parts by weight said mixture, low-density high-pressure polyethylene having a density of 0.916-0.930 g / cm ³ , a melting index of less than 1 g / 10 min and a tensile strength during melting of more than 0.98 kg (10 cN), which is determined using a Gotfert Reotons device ( Gottfert Rheotons) at a temperature of 190 ^{° C.} , and (b) from 0 to 90% by weight, based on the total weight of said composition of at least one copolymer selected from the group consisting of ethylene vinyl acetate copolymer having a weight ratio of ethylene to vinyl acetate from 2.2: 1 to 24: 1 and a melting index of 0.2-10 g / 10 min.

 One embodiment of the present invention is a bag made of a two-layer coextruded film comprising an outer layer of linear low density polyethylene and an inner sealing layer of the aforementioned polymer composition.

 Another embodiment of the present invention provides a bag made of a three-layer coextruded film comprising an outer layer and a middle layer of linear low density polyethylene and an inner sealing layer of the aforementioned polymer composition.

 Another aspect of the present invention provides a method for producing the aforementioned package.

 Another embodiment of the present invention provides a bag made of a three-layer coextruded film comprising an outer layer and a middle layer of low density high pressure polyethylene and an inner sealing layer of the aforementioned polymer composition.

 It was found that the film structures for the bags of the present invention have improved characteristics of the tensile strength during melting and the tensile strength of the heat seal, especially the tensile strength of the final heat seal. The use of films for the manufacture of the bags of the present invention in a molding-filling-capping machine results in higher machine speeds than those currently achieved using a commercially available film.

Brief Description of the Drawings
The invention is illustrated by reference to the accompanying drawings, in which:
figure 1 depicts a General view of the package packaging according to the present invention;
FIG. 2 is a perspective view of another package package according to the present invention;
figure 3 depicts a partial section in an enlarged view of the film structure of the package according to the present invention;
FIG. 4 is another enlarged partial sectional view of the film structure of a bag according to the present invention;
FIG. 5 is another enlarged partial sectional view of the film structure of a bag according to the present invention;
FIG. 6 depicts in graphical form the dependence of the tensile strength of the final weld on the tensile strength during melting.

 A bag according to the present invention, for example, as shown in FIGS. 1 and 2, for packaging fluid materials is obtained from a single-layer film structure of a polymer sealing layer, which consists of a mixture of linear low density polyethylene and low density high pressure polyethylene having a high melting strength. The mixture may also contain a copolymer of ethylene vinyl acetate.

The "melting strength", which is also referred to in the prior art as "tensile melting", characterizes and quantifies here the stress or force (which is applied using a winding drum provided with a tension element), which is required to stretch the molten extrudate with some a certain speed exceeding its melting point, as it passes through the extruder head of a standard plastometer, which is described, for example, in ASTM D1238-E. The values of the tensile strength during melting, which are presented here in kilograms (centi-Newtons (cN)), are determined using a Gotfert Reotens instrument at a temperature of 190 ^o C. In general, for ethylene-α-olefin copolymers and high-pressure ethylene polymers melting tends to increase with increasing molecular weight, or with an expansion of the distribution of molecular weight, and / or with an increase in the yield strengths during melting. The melting strength of low-density high-pressure polyethylene according to the present invention has a value of more than 0.98 kg (10 cN), which is determined using a Gotfert Reotens instrument at a temperature of 190 ^o C, preferably 1.27-3.93 cN (13-40 SN) and most preferably 1.47-2.45 kg (15-25 SN). In addition, the melting strength of the polymer composition of the present invention has a value of more than 0.98 kg (10 cN), which is determined using a Gotfert Reotens instrument at a temperature of 190 ^o C, preferably 1.47-6.88 kg (15-70 cN ) and most preferably 1.47-4.91 (15-50) SN.

One component of the polymer composition of the present invention is polyethylene, hereinafter referred to as "linear low density polyethylene" (LDL). An example of a commercially available LDL is a product called DOWLEX ^™ 2045 (a trademark of a product commercially available from the Dow Chemical Company). LDL is usually a linear copolymer of ethylene and a small amount of α-olefin having from 3 to 18 carbon atoms, preferably from 4 to 10 carbon atoms and most preferably 8 carbon atoms. LDL for the polymer composition of the present invention has a density of more than 0.916 g / cm ³ , more preferably 0.916-0.940 g / cm ³ , most preferably 0.918-0.926 g / cm ³ , usually has a melting point less than 10 g / 10 min, preferably 0.1 -10 g / 10 min, most preferably 0.5-2 g / 10 min, and usually has a ratio of 1 _{10/1 2} are 0.1-20, preferably 5-20 and most preferably 7-20.

 LDL can be obtained using a continuous, dosed or semi-continuous solution, polymerization from a suspension or gaseous phase of ethylene and one or more additional α-olefin comonomers not present in the main composition in the presence of a Ziegler Natta catalyst, for example, using the process disclosed US Pat. No. 4,076,698 to Andersen on others, incorporated herein by reference.

Suitable α-olefin for LDL of the present invention is presented in the form of the following formula:
CH ₂ = CHR,
where R is a hydrocarbyl radical having from one to twenty carbon atoms. The copolymerization process can proceed using one method or combinations of methods in solution, suspended state or gas phase. Suitable α-olefin, which is used as comonomers, includes 1-propylene, 1-butene, 1-isobutylene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptane and 1-octene, as well as other types of monomers, such as styrene, halo- or alkyl substituted styrenes, tetrafluoroethylene, vinylbenzocyclobutane, 1,4-hexadiene, 1,7-octadiene, and cycloalkenes, for example cyclopentene, cyclohexene and cyclooctene. 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 these mixtures, since coatings, profiles, and films made using the resulting extrusion composition will especially improve performance where such higher α- olefins are used as comonomers. However, it is most preferred that the α-olefin is 1-octene and the polymerization process is a continuous process in solution.

. Растворитель представляет собой 1,2,4-трихлорбензол, из которого 0,3 массовых процента растворов проб подготавливают для ввода. Скорость потока составляет 1,0 мл/мин, прибор работает при температуре 140^oС, и размер ввода равен 100 микролитрам.The molecular weight distribution of ethylene-α-olefin copolymer compositions and high-pressure ethylene polymer compositions is determined using gel permeation chromatography (GPC) on a Waters 150 high-temperature chromatographic device equipped with a differential refractometer and three columns of mixed porosity. The columns are equipped with "polymer laboratories" and are usually filled with particles with pore sizes of 10 ³ , 10 ⁴ , 10 ⁵ and 10 ⁶

. The solvent is 1,2,4-trichlorobenzene, of which 0.3 weight percent sample solutions are prepared for injection. The flow rate is 1.0 ml / min, the device operates at a temperature of 140 ^o C, and the input size is 100 microliters.

The determination of the molecular weight in relation to the polymer backbone is carried out using standard polystyrene with a narrow molecular weight distribution (from the "polymer laboratories") along with their elution volumes. Equivalent molecular weights of polyethylene are determined using the appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described in an article by Williams and Ward, Journal of Polymers, sections Polymers, v. 6, p. 621, 1968 (Williams and Ward in Journal of Polymer Science. Polymer Letters, Vol. 6, p. 621, 1968)) in order to obtain the following equation:
^M Polyethylene = a * ( ^M Polystyrene) ^b
In this equation, a = 0.4316 and b = 1.0. The mass of the average molecular weight M _{w is} calculated in the usual way in accordance with the formula M _w = Σw _i × M _i , where w _i and M _i are the mass part and molecular weight, respectively, of the i-th part, eluting from the GPC column.

 For LDL, the Nw / Mn ratio is preferably 2-7, especially 4.

 It is assumed that the use of LDL with a high tensile strength during melting in the film structure for the bags of the present invention, which (1) provides a bag that can be made at a higher speed using a molding-filling-capping machine, and (2) provides a batch packaging having slightly fewer flow channels, in particular when the bag of the present invention is compared with bags made using linear low density polyethylene, low density polyethylene or combinations thereof.

 Figures 3-5 show that the film structure of the bag of the present invention also includes a multilayer or composite film structure 30, preferably containing the above-described polymer sealing layer, which is the inner layer of the bag.

It will be clear to those skilled in the art that the multilayer film structure for the bag of the present invention may contain a different combination of film layers, since the sealing layer forms part of the final film structure. The multilayer film structure for the bag of the present invention may be a coextruded film that serves as a coating, or a multilayer film. The film structure also includes a sealant layer in combination with a protective film such as polyester, nylon, EVOH, polyvinylidene dichloride (DCDC), such as SARAN ^™ (trademark and supplied by Dow Chemical Company) , and metallized films. The final destination of the bag determines to a large extent the choice of another material or materials used in combination with the film for the sealing layer. The bags described herein will be considered with sealing layers that are used at least within the bag.

One embodiment of the film structure 30 for the bag of the present invention (FIG. 3) comprises a sealing layer 31 of a mixture of LDL and the high melting LDL of the present invention and at least one polymer outer layer 32. The polymer outer layer 32 is preferably a plastic film layer , more preferably LDL. An example of a commercially available LDL is DOWLEX ^™ 2045 (trademarked by the Dow Chemical Company). The thickness of the outer layer 32 can be of any value since the sealing layer 31 has a minimum thickness of 2.5 microns (0.1 mil).

 Another embodiment of the film structure 30 for the bag of the present invention (FIG. 4) comprises a polymer layer 32 located between two polymer sealing layers 31.

Another embodiment of the film structure 30 for the bag of the present invention (FIG. 5) comprises at least one polymer middle layer 33 located between at least one polymer outer layer 32 and at least one polymer sealing layer 31 The polymer layer 33 can be the same LDL film layer as the outer layer 32, or preferably another LDL, and more preferably LDL, for example DOWLEX ^TM 204S (trademark and supplied by Dow Chemical Company), which has a higher density than the outer layer 32. The thickness of the middle layer 33 can be of any value since the sealing layer 31 has a minimum thickness of 2.5 microns (0.1 mil).

 The final film thickness of the final film product that is used to manufacture the bags of the present invention is from 12.7 microns (0.5 mil) to 254 microns (10 mils), preferably from 25.4 microns (1 mil) to 127 microns (5 mils), more preferably from 50.8 microns (2 mils) to 100 microns (4 mils).

 Additives known to those skilled in the art, such as adhesion inhibitors, glidants, UV stabilizers, dyes and processing aids can be added to the polymers from which the bags of the present invention are made.

 As can be seen from various embodiments of the present invention (FIGS. 3-5), the film structure for the bags of the present invention has structural flexibility. To optimize the specific properties of the films, such as film strength, various LDLs can be used in the outer and middle layers. Thus, the film can be optimized for specific applications, for example for a molding-filling-capping machine operating with a vertical container.

 The structure of the polyethylene film that is used to make the bag of the present invention is obtained using a blown pipe extrusion method or a cast extrusion method, since these methods are well known in the art. The blown pipe extrusion method is described, for example, in the encyclopedic publication "Modern Plastics" mid-October 1989, vol. 66, 11, p. 264-266 (Modern Plastics Mid-October 1989 Encyclopedia Issue, Volume 66, Number 11, pages 264 to 266). The method of extrusion molding is described, for example, in the encyclopedic publication "Modern Plastics" mid-October 1989, v. 66, 11, p. 256-257 (Modern Plastics Mid-October 1989 Encyclopedia Issue, Volume 66, Number 11, pages 256 to 257).

 Embodiments of the bags of the present invention (FIGS. 1 and 2) are hermetically sealed containers filled with “fluid substances”. By "fluid substances" is meant substances that exhibit their fluidity under the influence of gravity or which can be pumped. The term "fluid" does not include gaseous substances. Fluids include liquids, for example, milk, water, fruit juice, vegetable oil, emulsions, for example, ice cream mix, soft margarine, pastes, such as meat pastes, peanut butter; canned food, for example, jams, marmalade for filling pies; jelly; dough, animal meat, for example sausage meat; powders, for example gelatin powders, detergents; granular food products, for example, nuts, sugar and the like. The package of the present invention is particularly suitable for liquid foods such as milk. Fluid substances may also include liquid oils, for example cooking oil or motor oil.

 After obtaining the film structure for the bag of the present invention, the film structure is cut to the required width for use in standard bag forming machines. Embodiments of the package of the present invention (FIGS. 1 and 2) are obtained in the so-called molding-filling-capping machines, well known in the art. 1 shows a bag 10, which is a tubular element 11 having a longitudinal weld bead 12 and a transverse weld 13 so that when filling the bag with fluid, the bag takes the form of a pillow.

 Figure 2 shows a package 20, which is a tubular element 21 having a peripheral weld seam 22 in the form of an edge extending along the three sides of the tubular element 21, for example, the upper weld 22a and the longitudinal side welds 22b and 22c, and having essentially a concave bottom or a "spherical" element 23, which is welded to the bottom of the tubular element 21 so that when viewed in cross section in the longitudinal direction, a substantially semicircular or "arcuate" bottom is formed when filling the bag with a fluid substance. The bag shown in FIG. 2 is an example of the so-called Enviro-Pak) known in the art.

 The bag made according to the present invention is preferably a bag (FIG. 1) made on the so-called vertical molding-filling-capping (WFU) machines, well known in the art. Examples of commercially available WFBU vending machines include those manufactured by Hayssen, Thimonnier, Tetra Pak or Prepac. The WBFU vending machine is described in the following link: F. S. Lewis. Packing-Capping ", Encyclopedia of Packaging, p. 180, 1980 (G.S. Lewis," Form-Fill-Seal ", Packaging Encyclopedia, 180, 1980).

 During the WBFU packaging process, the sheet of plastic film structure described herein is introduced into the WBFU machine, where the sheet is shaped into a continuous pipe in a portion for forming the pipe. The tubular element is obtained by welding the longitudinal edges of the film together or by lap jointing the plastic film and welding the film using the inner / outer seam or by welding in the form of a rib of the plastic film using the inner / inner seam. The welded bar then seals the pipe in the transverse direction at one end, which is the bottom of the “bag”, and then a filling substance, such as milk, is poured into the “bag”. Then, the upper end of the bag is sealed with a welded bar and the plastic film is burned or cut, thereby separating the bag finally formed from the tube. The manufacturing process of the bag using a WFUF machine is described generally in US Pat. Nos. 4,503,102 and 4,521,437, which are incorporated herein by reference.

 The capacity of the packets of the present invention may be different. In general, bags may contain from 5 ml to 10 l, preferably from 1 ml to 8 l, and more preferably from 1 ml to 5 l of a flowable substance.

 The film structure for the bag according to the present invention has precisely adjustable strength. The use of the film structure described in the present invention for the manufacture of the bag results in a more durable bag, and therefore it is more preferable that the bag in use contains slightly fewer leakage channels. The use of a mixture of LDL and PNP in the sealing layer of the present invention in a two or three layer coextruded film product will provide a film structure that can be used to make bags at a higher speed in WFCF, and such produced bags will contain slightly less leakage.

 Given the development trend of the industry of modern consumer packaging and its focus on providing consumers with more environmentally friendly packaging, a plastic bag of the present invention is a good alternative. The use of a plastic bag for packaging consumer liquids such as milk has its advantages over the packaging used in the past: a glass bottle, paper cardboard, and high-density polyethylene containers. For previously used containers, a large amount of natural resources was required in its production, significant areas for waste disposal, a large number of storage areas and a large amount of energy for temperature control of the product (due to the heat-conducting properties of the container).

 The plastic bag of the present invention made from a thin plastic film used for packaging liquids has more advantages compared to the packaging used in the past. A plastic bag (1) consumes slightly less natural resources, (2) requires less space when disposing of waste, (3) can be reused during recycling, (4) can be easily processed, (5) requires less storage space, (6) consumes less energy during storage (thermal conductivity of the bag), (7) can be safely burned and (8) can be reused, for example, an empty bag can be used for other applications, for example, as bags for frozen foods, bags for sandwiches and a bag to the storage of general purpose.

 The polymer resins described in table 1 were used to prepare samples of inflatable films, which are shown in the examples and comparative examples.

 The composition of various mixtures of HDPE and LDL and their melting strength are shown in table 2.

 A sample calculated for a weight of 5 kg of each mixture shown in Table 2 was obtained using a Leistritz twin screw extruder. The tensile strength in melting mixtures was determined using a Gottfert Rheotoens instrument.

Erukamide is a glidant, SiO ₂ is an anti-stick additive, and the process additive was added to each polymer described in Table 1, so that the final concentrations of the additives were as follows: 1200 parts per thousand of erucamide and 2500 parts per thousand of SiO ₂ .

The resulting film structures were subjected to physical testing to determine various properties, including:
(1) a puncture test using the ASTM method D3763,
(2) an instant impact test using ASTM method D1709, method A,
(3) Elmendorf tensile test using the ASTM method D1922,
(4) tensile test using method ASTN D882,
(5) 1% and 2% secant module test using ASTM method 0882,
(6) a thermal bond tensile test using the method described below, and
(7) tensile test of heat seal using the method described below.

 The thermal bonding strength of reference films is measured using the “DTC thermal bonding test method”, which measures the force required to separate the heat seal before the weld is completely cooled (crystallized). This simulates the process of filling a substance into a bag before cooling the weld.

The “DTC Thermal Bonding Strength Test Method” is a test method using the DTC Model 52D Thermal Bonding Test Tool in accordance with the following conditions:
Copy Width - 25.4 mm
Welding time - 0.5 s
Welding pressure - 0.27 N / mm ²
Delay Time - 0.5 s
Peeling speed - 150 mm / s
The number of samples / temperature - 5
Temperature increments - 5 ^o C
The temperature range is 75-150 ^o C.

The heat-seal joint strength of the sample films was measured using the "DTC heat-seal joint test method", which is a measure of the force required to separate the weld joint after cooling the substance to a temperature of 23 ^o C. Before testing, the film samples were exposed at a relative humidity of 50% and at a temperature of 23 ^o C for at least 24 hours.

The "DTC heat seal weld strength test method" uses a DTC heat seal test device, Model 52D, which uses a portion of a heat seal weld of a test apparatus, in accordance with the following conditions:
Copy Width - 25.4 mm
Welding time - 0.5 s
Welding pressure - 0.27 N / mm ²
The number of samples / temperature - 5
Temperature increments - 5 ^o C
Temperature range - 80-150 ^o C
The seam strength of the film samples was determined using a test device using a tensile testing machine brand "Instron", model 1122, in accordance with the following test conditions:
Direction of stretching - 90 ^o in relation to the seam
Traverse speed - 500 mm / min
Full load - 5 kg
The number of samples / temperature - 1% FSL
Break criterion - 80%
Basic sample length - 50.8 mm
Sample Width - 25.4 mm
The physical properties of the films shown in table 3 are presented below in table 4, and the results of the values of the tensile strength during heat bonding and heat-weld are presented in table 5 and 6.

 The present invention is illustrated by the following examples, but not limited to.

Examples 1-3 and comparative examples A
The film samples shown in table 3 were made in the form of a monolayer using a line for the production of films by extrusion with a bloated company Macro. The extruder diameter was 6.4 cm and had a total length to extruder diameter L / D ratio of 24: 1 and a barrier screw with a Maddock mixing head. An extruder head with a diameter of 15.2 cm and a slit size of 1.524 microns was used to obtain test films. The conditions for the manufacture of a film directly obtained by blown extrusion are a blow ratio of 2.5 and a melting point of 220 ^o C.

Examples 4-6 and Comparative Example B
The films shown in Table 3 were cut and had a width of 38.1 cm, suitable for receiving 2 liter milk bags using a prepac IS6 (Prepac IS6) vertical packaging molding and capping machine located at a dairy factory. The module packaged milk in 2-liter packets at a speed of 30 packets per minute under normal operating conditions of the filling head. For each test film, approximately 16–20 bags filled with milk were selected. They were checked for the integrity of the initial seams. 6-8 packages were tested on site for the strength of the heat seal, after which milk was poured out of 10 packages, then they were washed and dried for further testing.

The tensile strength of heat-welded seams was determined using an Instron brand tensile testing machine, model 1122. Before testing, the sample was exposed at a relative humidity of 50% and a temperature of 23 ^o C for 24-48 hours. The test conditions for the Instron brand tensile testing machine were as follows:
Direction of stretching - 90 ^o in relation to the seam
Traverse speed - 500 mm / min
Full load - 5 kg
Threshold - 1% of FSL
Break criterion - 80%
Basic sample length - 50.8 mm
Sample Width - 25.4 mm
The initial verification of the integrity of the final seam included three stages:
1) determination of permanent leaks,
2) subjective testing of the strength of the seam,
3) visual inspection of the final seams.

Persistent leaks
Permanent leaks were only seen in bags made of DOWLEX 2045 brand material. No leaks were found in other films.

Subjective seam strength test
A subjective test of the strength of the seam included compressing the bag from one end until the bag was leaking or the weld was damaged. Table 7 shows that weld damage was not seen in bags made with 20% 1351 or XU 60021.62.

Visual inspection of final welds
Significant thinning of the weld and the appearance of veins in the final welds were found in the films of DOWLEX 2045, as shown in Table 8. In packages made with 20% 609C, some thinning of the weld and some appearance of veins in the final welds were found. Thinning of welds or the appearance of veins was not detected in films made with 20% 1351 and XU 60021.62.

Final weld strength
Ten 2-liter milk bags were tested for the strength of the final heat seal using an Instron brand tensile testing machine, Model 4206, under the same conditions described above, together with the determination of the tensile strength of a heat seal.

 The values of the tensile strength of the heat seal are shown in table 9. It was found that the strength increases, since the strength during melting of the mixture increases. This is graphically depicted in FIG. 6, where 80 wt.% LDL and 20 wt.% HDPE are used, with the exception of the first data point at which the melting strength is 0.62 kg (6.4 cN) without any HDPE. . It is seen that there is no connection between the melting rate of the PNP and the tensile strength of the heat-welded seam.

Microscopic inspection of final welds
The areas of veins and the areas of the edges of the packets were subjected to cryogenic cooling in the entire cross section and were studied using optical microscopy methods. Table 10 presents the final results.

 Films made with 20% 1351 and XU 60021.62 showed very little thinning of the welds and no veins in the final welds (thin polymer filaments extending from the weld area), while films made with 100% DOWLEX 2045 had significant refinement of the weld and vein.

Thin film in the weld area
The weakest part with a good weld is usually the place of the film, located in front of the edge of the weld. Any thinning of this film results in lower values of the tensile strength of the heat seal, since this place is the area that is damaged when the weld is under load. When comparing the tensile strength during melting of resin mixtures (Table 10) with the value of the thinning of the film, which is noticeable in packages made using a commercial automatic machine WFFU (Table 10), it is clear that since the melting strength of the resin mixture increases, the thinning of the film decreases. The relationship between the thinning of the film (table 10) and the melting rate of the PNP in resin mixtures (table 1) was not found.

Seam edge
When comparing the edge thickness of the weld (table 10) with the tensile strength during melting of the resin mixture (table 2) and the melting index of the PNP (table 1), it is clear that there is a strong relationship between the tensile strength at melting and the thickness of the edge, and the relationship between the melting index of the PNP and there is no weld edge thickness. Mixtures with a higher tensile strength during melting lead to thicker edges of the weld.

 The following polymer resin blends shown in Table 11 are used to further illustrate the advantages of the present invention.

Resin mixtures (Table 11) were used to produce 71 micron films using the MACRO ^B blown film production line with a 63.5 mm diameter auger, L / D ratio of 24: 1, and Maddock mixing head . An extruder head with a diameter of 15.2 cm and a slit size of the extruder head of 1524 microns was used. For the supply of chilled air, an annular Macro double-toed air gap was used. Each resin was mixed with a target of 1200 particles per million erucamide, which serves to impart glide, and 2500 particles per million SiO ₂ , which prevents adhesion. Each film was tested for tensile strength during heat bonding of a heat-welded seam, the values of which are presented in table 12 and table 13, respectively.

The thermal bonding tensile strength was determined using a PTC thermal bonding tester, Model D52D, under the conditions described above. Test films were welded at high temperature using a DTC thermal bonding tester, model D52D, under the conditions described above. The tensile strength of a heat-welded seam was determined using an Instron brand tensile testing machine, model 1122. Before testing, the test samples were exposed at a relative humidity of 50% and a temperature of 23 ^o C for 24-48 hours. Testing conditions using an Instron tensile testing machine coincided with the conditions described above.

 From the results of tests on the tensile strength during heat bonding and heat bonding and heat-sealing seam, shown in table 12 and table 13, it is seen that the maximum tensile strength during heat bonding is achieved using a mixture of 50% DOWLEX 2545/50% XU 60021.62. The highest tensile strength was also achieved with 50% DOWLEX 2045/50% XU 60021.62.

 The calculated values of the tensile strength during thermal bonding are presented in table 14.

 The results of the calculated values of the tensile strength during thermal bonding, depending on the actual values, are shown in Table 14. It can be seen that the actual values of the tensile strength during thermal bonding according to the present invention significantly exceed the level of the calculated values, showing a clearly synergistic effect.

Claims (27)

1. A bag for a fluid substance made of a film structure with at least one sealing layer of a polymer composition, characterized in that the polymer composition contains: (a) from 10 to 100% of the total weight of said composition, a mixture of (1 ) from 5 to 95 wt.% based on 100 wt. including parts of said mixture, a linear ethylene copolymer copolymerized from ethylene and at least one alpha olefin in the range of C ₃ -C ₁₈ and having a density of 0.916-0.940 g / cm ³ and a melting index of less than 10 g / 10 min, and the ratio Nw / Mn for a molecular weight distribution of more than 4.0 and a maximum melting point of more than 100 ^{° C.} , which is measured using a differential scanning calorimeter, and (2) from 5 to 95 wt. %, based on 100 wt. including the above-mentioned mixture, low-density high-density polyethylene having a density of 0.916-0.930 g / cm ³ , a melting index of less than 1 g / 10 min, and a melting strength of more than 0.98 kg (10 cN), which is determined using a Gotfert device Reotens at a temperature of 190 ^o C, and (b) from 0 to 90% of the total weight of the said composition of an ethylene vinyl acetate copolymer having a mass ratio of ethylene and vinyl acetate from 2.2: 1 to 24: 1 and a melting index of 0.2-10 g / 10 minutes. 2. A bag for a fluid substance made of a multilayer film structure, characterized in that the multilayer film structure contains: (I) a layer of a polymer composition consisting of: (a) from 10 to 100% of the total weight of said composition, a mixture of (1 ) from 5 to 95 wt.% based on 100 wt.h. said mixture of a linear ethylene copolymer copolymerized from ethylene and at least one alpha-olefin in the range of C ₃ -C ₁₈ and having a density of 0.916-0.940 g / cm ³ and a melting index of less than 10 g / 10 min, and the ratio Nw / Mn for a molecular weight distribution of more than 4.0 and a maximum melting point of more than 100 ^o C, which is measured using a differential scanning calorimeter, and (2) from 5 to 95 wt.%, Based on 100 wt. including a mixture of low-density high-density polyethylene having a density of 0.916-0.930 g / cm ³ , a melting index of less than 1 g / 10 min and a tensile strength during melting of more than 0.98 kg (10 cN), which is determined using a Gotfert Reotens instrument at a temperature of 190 ^o C, and (b) from 0 to 90% of the total weight of the said composition of an ethylene vinyl acetate copolymer having a mass ratio of ethylene and vinyl acetate from 2.2: 1 to 24: 1 and a melting index of 0.2-10 g / 10 min, and (II) at least one layer of a linear ethylene copolymer copolymerized from ethylene and at least e one alpha-olefin in the range of C ₃ -C ₁₈ and having a density of 0,916-0,940 g / cm ³ and a melt index of 0.1-10 g / 10 min.  3. The bag according to claim 1, characterized in that the film structure has a tubular shape and the bag has heat-welded ends in the transverse direction. 4. The package according to claim 2, characterized in that it contains (III) a layer of high pressure polyethylene, which has a density of 0.916-0.930 g / cm ³ and a melting index of 0.1-10 g / 10 min.  5. The package according to claim 2, characterized in that the layer (I) is a sealing layer.  6. The package according to claim 2, characterized in that the layer (II) is the outer layer, and the layer (I) is a sealing layer.  7. The package according to claim 4, characterized in that the layer (II) is the outer layer, the layer (III) is the middle layer and the layer (I) is a sealing layer.  8. The package according to claim 2, characterized in that the linear ethylene copolymer has a melting index of less than 10 g / 10 min.  9. The bag according to claim 1, characterized in that the bag holds from 5 to 10,000 ml.  10. The package according to claim 1, characterized in that the fluid substance is milk. 11. The package according to claim 1, characterized in that the ethylene copolymer has an indicator of molecular weight distribution (I ₁₀ / I ₂ ) from 0.1 to 20.  12. The package according to claim 1, characterized in that the film structure contains an additive for imparting slip, an additive that prevents adhesion, and an additional technological additive.  13. The package according to claim 1, characterized in that the film structure contains a pigment that makes the film structure opaque.  14. The package according to claim 1, characterized in that the film structure contains an additive that absorbs ultraviolet light.  15. The package according to claim 1, characterized in that the alpha-olefin of the film structure is 1-octene.  16. The package according to claim 1, characterized in that the tensile strength during melting of low-density high-density polyethylene is in the range of 0.98-3.93 kg (10-40 cN).  17. The package according to claim 1, characterized in that the tensile strength during melting of low-density high-density polyethylene is in the range of 1.27-2.45 kg (13-25 cN).  18. The package according to claim 1, characterized in that the tensile strength during melting of the polymer composition has a value in the range of 0.98-6.88 kg (10-70 cN).  19. The package according to claim 1, characterized in that the thickness in the region of the edges is reduced by 25%. 20. The film structure of the polymer composition for packaging, characterized in that the polymer composition contains: (a) from 10 to 100% by weight of the total composition, a mixture of (1) from 5 to 95% by weight, based on 100 parts by weight . said mixture of a linear ethylene copolymer copolymerized from ethylene and at least one alpha-olefin in the range of C ₃ -C ₁₈ and having a density of 0.916-0.940 g / cm ³ and a melting index of less than 10 g / 10 min, and the ratio Nw / Mn for a molecular weight distribution of more than 4.0 and a maximum melting point of more than 100 ^o C, which is measured using a differential scanning calorimeter, and (2) from 5 to 95 wt.%, Based on 100 wt.h. said mixture, low-density high-density polyethylene having a density of 0.916-0.930 g / cm ³ , a melting index of less than 1 g / 10 min and a tensile strength in melting of more than 0.98 kg (10 cN), which is determined using a Gotfert Reotens apparatus at a temperature of 190 ^{° C.} , and (b) from 0 to 90% of the total weight of said composition of an ethylene vinyl acetate copolymer having a weight ratio of ethylene and vinyl acetate of 2.2: 1 to 24: 1 and a melting index of 0.2-10 g / 10 min . 21. The film structure according to claim 20, characterized in that the density of the linear ethylene copolymer is 0.916-0.940 g / cm ³ .  22. The film structure according to claim 20, characterized in that the concentration of the ethylene vinyl acetate copolymer is 5-85% of the total weight of said composition.  23. The film structure according to p. 20, characterized in that the concentration of the ethylene vinyl acetate copolymer is 5-25% of the total weight of said composition.  24. The film structure according to claim 20, characterized in that the tensile strength during melting of the polymer composition has a value in the range of 0.98-6.88 (10-70 cN). 25. A method of obtaining a bag for a fluid substance, in which a film structure is formed by extrusion of a blown pipe or extrusion by injection molding a film structure into a tubular element and heat seal the opposite ends of the tubular element in the transverse direction, while the tubular element contains a film structure for bag capacities with at least one sealing layer of a polymer composition, characterized in that a polymer composition containing (a) from 10 to 100% of the total m ssy said composition a mixture of (1) from 5 to 95 wt. %, based on 100 parts by weight said mixture of a linear ethylene copolymer copolymerized from ethylene and at least one alpha-olefin in the range of C ₃ -C ₁₈ and having a density of 0.916-0.940 g / cm ³ and a melting index of less than 10 g / 10 min, and the ratio Nw / Mn for a molecular weight distribution of more than 4.0 and a maximum melting point of more than 100 ^o C, which is measured using a differential scanning calorimeter, and (2) from 5 to 95 wt.% Based on 100 wt.h. said mixture, low-density high-density polyethylene having a density of 0.916-0.930 g / cm ³ , a melting index of less than 1 g / 10 min and a tensile strength in melting of more than 0.98 kg (10 cN), which is determined using a Gotfert Reotens apparatus at a temperature of 190 ^{° C.} , and (b) from 0 to 90% of the total weight of said composition, at least one copolymer selected from the group consisting of ethylene vinyl acetate copolymer having a weight ratio of ethylene and vinyl acetate of 2.2: 1 to 24 : 1 and a melting index of 0.2-10 g / 10 min. 26. A method of obtaining a bag for a fluid substance, in which a film structure is formed by extrusion of a blown pipe or extrusion by molding, a film structure is formed into a tubular element and heat sealing of the opposite ends of the tubular element in the transverse direction, characterized in that the tubular element is used, containing (I) a layer of a polymer composition comprising: (a) from 10 to 100% by weight of the total composition, a mixture of (1) from 5 to 95% by weight, based on 100 parts by weight said mixture, a linear ethylene copolymer copolymerized from ethylene and at least one alpha olefin in the range of C ₃ -C ₁₈ and having a density of 0.916-0.940 g / cm ³ and a melting index of less than 10 g / 10 min, and the ratio Nw / Mn for a molecular weight distribution of more than 4.0 and a maximum melting point of more than 100 ^o C, which is measured using a differential scanning calorimeter, and (2) from 5 to 95 wt.% Based on 100 wt.h. said mixture, low-density high-density polyethylene having a density of 0.916-0.930 g / cm ³ , a melting index of less than 1 g / 10 min and a tensile strength during melting of more than 0.98 kg (10 cN), which is determined using a Gotfert Reotens apparatus at a temperature of 190 ^{° C.} , and (b) from 0 to 90% of the total weight of said composition, at least one copolymer selected from the group consisting of ethylene vinyl acetate copolymer having a weight ratio of ethylene and vinyl acetate of 2.2: 1 to 24 : 1 and a melting index of 0.2-10 g / 10 min; (II) at least one layer of a linear ethylene copolymer copolymerized from ethylene and at least one alpha olefin in the range of C ₃ -C ₁₈ and having a density of 0.916-0.940 g / cm ³ and a melting index of 0.1- 10 g / 10 min. 27. The method according to p. 26, characterized in that the tubular element further comprises (III) at least a layer of high pressure polyethylene having a density of 0.916-0.930 g / cm ³ and a melting index less than 1 g / 10 min.

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