Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
  • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
  • B29C55/06—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C53/00—Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
  • B29C53/02—Bending or folding
  • B29C53/04—Bending or folding of plates or sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
  • B29K2023/04—Polymers of ethylene
  • B29K2023/06—PE, i.e. polyethylene
  • B29K2023/0608—PE, i.e. polyethylene characterised by its density
  • B29K2023/0625—LLDPE, i.e. linear low density polyethylene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D2571/00—Bundles of articles held together by packaging elements for convenience of storage or transport, e.g. portable segregating carrier for plural receptacles such as beer cans, pop bottles; Bales of material
  • B65D2571/00006—Palletisable loads, i.e. loads intended to be transported by means of a fork-lift truck
  • B65D2571/00012—Bundles surrounded by a film
  • B65D2571/00018—Bundles surrounded by a film under tension
  • B65D2571/0003—Mechanical characteristics of the stretch film

Definitions

• the object of the invention is a device for producing stretch film intermediates and a stretch film with increased tensile strength.
• Stretch films are mainly made of polyethylene, the consumption of which for this type of film constitutes more than 50% of polyethylene consumption for the production of polyethylene films.
• Stretch films are produced by extrusion blow moulding as so- called sleeve films or by slit-head extrusion moulding as so-called flat films. Due to its much higher efficiency, the slit-head extrusion moulding method provides, despite the use of much more complex and expensive equipment constituting the process line, a more competitive film when used on a large scale, for example for pallet wrapping.
• stretch film technology has been dominated by multilayer materials composed of several to dozens of layers made from different types of polyethylene copolymers, for example: linear low-density polyethylene, linear very low-density polyethylene, metallocene linear low-density polyethylene and the like. This ensures that the product retains a better mechanical strength despite the reduced film thickness.
• the method for producing a five-layer biaxially-oriented polyethylene stretch film comprises extruding metallocene linear low-density polyethylene heated to about 250°C, through a web-forming flat head, composed of five layers of film, cooling the web of film on a cooling roll at a temperature of 20-40°C, and then subjecting the web of film to a sequential orientation process.
• a method for producing a multilayer polyethylene film which consists in the fact that individual layers of film consisting of a mixture of linear low-density polyethylene (LLDPE) with a density in the range of 915-935 kg/m 3 and low-density polyethylene (LDPE) in the amount of 8-40% by weight in relation to LLDPE are co-extruded through a slit head, and then the film web is directed to a first cooling roll at a temperature of 10-25°C and in turn to a second cooling roll at the same temperature as the first one or in the range of 10-20°C, the rotation speed of the second roll being 10-40% higher than the rotation speed of the first cooling roll.
• LLDPE linear low-density polyethylene
• LDPE low-density polyethylene
• each film layer being made of the same ther moplastic material selected from the following materials: polyethylene, polypropylene, polybutadiene, linear low- and medium-density polyethylene, polypropylene-ethylene interpolymer.
• Patent specification US6153702 (A) discloses a composition composed of 85-99% by weight of polyethylene having a density not exceeding 0.94 g/cm 3 and 1-15% by weight of a copolymer derived from 60-80% by weight of propylene and 20-40% by weight of olefinic comonomers, which composition can be used to produce multilayer stretch films.
• a polyolefin five-layer stretch film which is composed of five layers joined together.
• the first layer representing 10 to 12% of the film thickness, is made of an ethylene-n-hexene copolymer with a melt flow rate (MFR) of 1.0 to 6.0 g/10 min.
• MFR melt flow rate
• the second layer representing 28 to 32% of the film thickness is made of a mixture of an ethylene-n-hexene copolymer with a melt flow rate (MFR) of 1.0 to 6.0 g/10 min with a percentage of 20 to 80% by weight, preferably 50% by weight, the ethylene-n-hexene copolymer being obtained with the use of metallocene catalysts, with a melt flow rate (MFR) of 1.0 to 6.0 g/10 min.
• MFR melt flow rate
• the third layer, representing 14 to 18% of the film thickness is made of an ethylene- n-hexene copolymer with a melt flow rate (MFR) of 1.0 to 6.0 g/10 min, preferably 4.0 g/10 min.
• the fourth layer representing 28 to 32% of the film thickness is made from a mixture of ethylene-n-hexene copolymer having a melt flow rate (MFR) of 1.0 to 6.0 g/10 min, in an amount of 20 to 80% by weight, preferably 60% by weight, with polypropylene having a melt flow rate (MFR) of 2.0 to 6.0 g/10 min in an amount of 80 to 20% by weight, preferably 40% by weight.
• MFR melt flow rate
• the fifth layer representing 10 to 12% of the film thickness is made of a mixture of an ethylene-n-hexene copolymer with a melt flow rate (MFR) of 1.0 to 6.0 g/10 min with a percentage of 40 to 95% by weight, preferably 80% by weight, the ethylene-n-hexene copolymer being obtained with the use of metallocene catalysts, with a melt flow rate (MFR) of 1.0 to 6.0 g/10 min and with a percentage of 60 to 5% by weight, preferably 20% by weight.
• MFR melt flow rate
• the reinforcement members contain parallel, longitudinal reinforcing strips defining elongated spaces between them.
• the stretch film is made of linear low-density polyethylene LLDPE and is composed of a sheet of basic film on which parallel film strips are applied.
• the thickness of the base film sheet is 0.023 mm and the thickness of the film strip is 0.03 mm.
• perforation holes are provided on the surface between the film strips.
• the application also includes a device for producing the stretch film, which comprises a first unwinding shaft onto which a roll of base film is placed and a second unwinding shaft onto which a roll of overlay film is placed.
• the set of backing rollers and a pressure roller combines the base film and film strips.
• Behind the set of backing rollers and the pressure roller there is a winding roller mounted on a mechanism that induces oscillatory motion in the direction of its axis.
• the pressure roller is mounted on servomotors allowing its pressure force to be adjusted.
• the object of the application is also a method for producing a stretch film which consists in the fact that a base film is unwounded from a first unwinding shaft and an overlay film is simultaneously unwounded from a second unwinding shaft, the overlay film being then cut into strips, after which the strips are rolled with the base film and the combined film is wound onto a winding roller which is set in oscillatory motion towards its axis.
• thermoplastic film which comprises: a base film, wherein the base film comprises a stretchable polyolefin material comprising one or more layers and a plurality of extruded fibrous elements, wherein the extruded fibrous elements are positioned on at least one surface of the base film.
• the extruded fibres form one or more projections in relation to the plane of the base film.
• the domain of the material mixture comprising the base film material and the fibrous material is located between the domain of the pure base film material and the domain of the pure fibrous material.
• the average thickness of the base film is smaller than the average thickness of the projection.
• a reinforced plastic film which comprises a section of plastic film and a reinforcing strip of plastic film which is connected to the former and extends along the length of the film and is spaced from opposite side edges thereof.
• the strip is designed to prevent propagation.
• a non-perforated reinforced stretch film which comprises: a base film which has a thickness in the range of 3 pm to 18 pm, and 5 to 100 reinforcing strips attached to at least one surface of said base film, each reinforcing strip having a width independently ranging from 1 mm to 17 mm.
• a viscous stretchable polyolefin film which is suitable for flexible packaging, comprising a base film containing a stretchable polymeric material, having a plurality of perforations covering at least 25% of the total surface area of the base film and arranged in a series of columns along the longitudinal direction of the film, wherein the columns of perforations are separated by columns without perforations along the longitudinal direction of the film, and the per forations are shifted in a transverse direction across the film. It also has a plurality of reinforcing elements comprising a stretchable polymeric material, wherein the elements are fixed on the base film parallel to the longitudinal direction and at least one element is arranged in a column without perforations.
• a stretch film for packaging goods is known, in particular for packaging goods stacked on a pallet. It consists of a pre stretched main film.
• the main film is reinforced with reinforcing strips extending in the longitudinal direction.
• Reinforcement tapes are made from strips of pre-stretched film that have been repeatedly bent in the longitudinal direction.
• the film strips are symmetrically folded preferably twice, and especially four times in the longitudinal direction.
• the aim of the invention is to increase the strength of the stretch film with a minimum increase in its dimensions, especially with the use of recycled raw materials.
• An additional problem to be solved is to quickly determine the degree of tension in the film when wrapping it around the package.
• An object of the invention is a device for producing stretch film intermediates, having a base and rolls. Its essence lies in the fact that it consists of multiple sets, preferably nine sets placed on strip guiding lines. The lines of every film strip passes over the base with the rolls attached thereto. The axes of these rolls are parallel to each other and perpendicular to the film strip guiding line. Between the rolls in the base, there are pairs of holes, preferably four pairs of holes. Each pair of holes is arranged on a single line perpendicular to the strip line and the holes of each pair are arranged sym metrically on both sides of the strip guiding line. The distances between successive pairs of holes decrease on the side of film insertion. In the pairs of holes, pins are placed which wrap the strips asymmetrically. The pins are located on the side of the strips.
• Another object of the invention is a stretch film made of linear low-density polyethylene - LLDPE, comprising a base film sheet on which parallel film strips are rolled, made using the device according to the invention.
• the essence of the film according to the invention is that asymmetrically over its thickness, the multilayer film strips have a thickness ranging from 44 to 90 pm, and the width of the film strips ranges from 41.67 to 49.07 mm.
• the film strips are made of a material containing LLDPE regranulate.
• the film strips are made of LLDPE, doped with a dye which may be: phthalocyanine blue BN, phthalocyanine green G, aniline black, monoase pigments, anthroquinone derivatives, isoindoline derivatives, di-azo pigments, perthenotete- tracuronic acid derivatives, isoindotizine derivatives, bicinchona violet, thioindigo derivatives, dioxazine pigments.
• perforation holes are provided on the surface between the film strips.
• the advantageous effect of the produced stretch film according to the invention is that it has a higher strength due to the use of layers with increased thickness and a smaller width pressed onto the film. This combination reduces the amount of material used.
• the pre-stretched film does not need to be stretched during the application process. This film provides three times lower wear than standard stretch film. This ensures less waste and a lower cost of disposal. The use of recycled waste makes this film more environmentally friendly than those produced so far.
• the use of dyed films helps to determine the safe tension of the film when packaging products.
• FIG.4 - a diagram of a technological line for film production.
• the device for increasing the thickness of film strips in the embodiment consists of nine sets placed on strip guiding lines 2a. Five sets are at one height, with four such sets below them.
• the line 2a of each film strip 2 passes over the base 3 with rolls 4a, 4b, 4c, 4d attached thereto.
• the axes of the rolls 4a, 4b, 4c, 4d are parallel to each other and perpendicular to the film strip 2 guiding line 2a.
• the device for producing stretch film intermediates by increasing the thickness of the film strips 2 in the embodiment has been placed in a technological line for film production, the schematic diagram of which is shown in [Fig.4] of the drawing. It comprises a first unwinding shaft 7 onto which a roll of base film 1 is placed and a second unwinding shaft 8 onto which a roll of overlay film is placed. Behind the second unwinding shaft 8 in the overlay film unwinding line, there is a set of knives 9 cutting the overlay film into film strips 2. Behind it, a device for increasing the thickness of film strips is mounted, behind which there is a set of two backing rollers 10a, 10b and a pressure roller 11 between them which has a spiral groove on its surface.
• the set of backing rollers 10a, 10b and pressure roller 11 combines the base film 1 and the film strips 2. Behind the set of backing rollers 10a, 10b and pressure roller 11, there is a film perforating mechanism 12, a film stretching mechanism and an edge alignment mechanism, behind which there is a winding roller 13 mounted on a mechanism that induces an oscillatory motion in the direction of its axis.
• the production of the stretch film in the embodiment consists in unrolling the base film 1 from the first unrolling shaft 7 and in parallel unrolling the overlay film from the second unrolling shaft 8, which is then cut by the set of knives 9 into nine strips 2.
• the film strips 2 are wrapped on the wrapping device, and their width and thickness depend on where the individual pegs 6 are fixed in the holes 5 located in the base 3 of the device.
• the base film 1 and the film strips 2 symmetrically distributed on it are directed to the rollers of the set of backing rollers 10a, 10b and pressure roller 11 and the strips 2 are rolled with the base film 1.
• the pressure roller 11 is pressed against the base film sheet 1 and the strips 2 located on the backing rollers with a force of 1.07 MPa.
• the longitudinally connected film reinforced with the strips 2 is stretched, the edges are aligned and wound onto the winding roller 13 which moves in an oscillatory motion towards its axis.
• the winding speed is 400 m/min.
• a stretch film made using the device according to the invention comprises a sheet of the base film 1 on which there are nine strips 2 evenly distributed over its entire width.
• the sheet of the base film 1 was made from a jumbo transparent stretch film sheet by Star Pak sp. z o.o., which is made of linear low-density polyethylene LLDPE.
• the film has the following parameters: sheet width 500 mm +/- 5 mm, point measured thickness 0.023 mm (tol. +/- 5%), running metre weight - 10.75 g (tol. +/- 5%), weight per square metre 21.50 g (tol. +/- 5%), density 0.921 kg/ m 3 , low-slip value >0.4 and stretchability 300%.
• a sheet of jumbo transparent stretch film from Star Pak sp. z o.o. which was made of linear low-density polyethylene (LLDPE), was used to produce the film strips 2.
• the film has the following parameters: sheet width 250 mm +/- 5 mm, point measured thickness 0.023 mm (tol. +/- 5%), running metre weight 6.92 g (tol. +/- 5%), weight per square metre 27.60 g (tol. +/- 5%), density 0.921 kg/m 3 , low-slip value >0.4 and stretchability 300%.
• the film has the following parameters: sheet width 250 mm +/- 5 mm, point measured thickness 0.023 mm (tol. +/- 5%), running metre weight 10.6 g (tol. +/- 5%), weight per square metre 21.20 g (tol. +/- 5%), density 0.918 kg/m 3 and stretchability 150%.
• stretch film produced by Lood Pack Sp. z o.o. made from linear low-density polyethylene (LLDPE), was used to produce the film strips 2.
• the film has the following parameters: sheet width 250 mm +/- 5 mm, point measured thickness 0.023 mm (tol. +/- 5%), running metre weight 10.6 g (tol. +/- 5%), weight per square metre 21.20 g (tol. +/- 5%), density 0.92 kg/m 3 and stretchability 150%.
• the LLDPE films used have the following dyes in their composition:
• the type of dye additive has no measurable effect on the strength parameters of the sample, therefore separate values are not provided.

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Citations (2)

• 2020
  • 2020-06-23 PL PL434413A patent/PL237815B1/pl unknown
• 2021
  • 2021-06-20 EP EP21752148.3A patent/EP4028238A1/en active Pending
  • 2021-06-20 WO PCT/IB2021/055420 patent/WO2021260513A1/en unknown

Patent Citations (2)

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