The invention relates to a multi-layered structure intended for producing a packaging product for storage purposes in ambient conditions, and to a method for producing the structure.
The prior art discloses solutions for a multi-layered packaging product, which consist of layers of cardboard (mandatory layer), polyethylene (mandatory layers) and aluminum foil (optional layer) and produced mainly by means of extrusion lamination. These solutions includes packaging products developed by ELOPAK corporate group (see http://www.elopak.com/products-and-services/board)
and packaging products developed by Tetra Pak corporate group (see https://www.tetrapak.com/en/packaging/materials). The disadvantages of these types of packaging materials are as follows: the impossibility of re-using packaging wastes in the same packaging products; the complexity of recycling packaging products due to the mandatory layers of polyethylene comprised therein; the complexity of recycling packaging products comprising a layer of aluminum—it is usually incineration; the long natural decomposition of recycled packaging products due to the mandatory layers of polyethylene or polyethylene copolymers comprised therein; the use of cardboard results in destroying the world's global forest resources.
RU 2183557 discloses a packaging product made of a multi-layered composition. According to RU 2183557, a material intended for producing beverage and food containers includes a substantially amorphous expanded sheet made of copolyethylene terephthalate, comprising 2-20 mol. % of units formed by isophthalic acid and/or naphthalenedicarboxylic acids, having a density of less than 700 kg/m3, a thickness of 0.2-3 mm and such a crystallization rate that, when it is heated at 120° C. for 5 minutes, a degree of crystallinity does not reach values higher than 15%. The disadvantages of this material include its low quality, and the complexity of its production due to the impossibility of uniform expansion of both primary and secondary polyethylene terephthalate and polyethylene terephthalate copolymers, since a recycling method disclosed in RU 2183557—i.e. solid-state polycondensation of polyethylene terephthalate and polyethylene terephthalate copolymers—does not result in a stable intrinsic bulk viscosity (with a spread of values of more than 0.01 dl/g) and makes the whole expansion process unstable at subsequent recycling steps. More specifically, during the expansion process, different-sized bubbles having different thicknesses of partitions and different strength characteristics are obtained, and the resulting material becomes heterogeneous in terms of physical and mechanical properties, which does not provide the possibility of its use in industrial recycling.
The objective set by the author of a novel multi-layered composition based on expanded recycled polyethylene terephthalate is to eliminate the disadvantages of the prior art analogues. The technical result lies in the creation of an easy-to-use and utilizable multi-layered composition based on expanded recycled (obtained from a polyethylene terephthalate waste) polyethylene terephthalate. This technical result is achieved by the whole set of essential features.
The essence of the invention is that a multi-layered composition based on expanded recycled polyethylene terephthalate comprises a printed layer, a layer of expanded recycled polyethylene terephthalate having a density ranging from 100 kg/m3 to 900 kg/m3 and an intrinsic viscosity ranging from 0.5 dl/g to 1.0 dl/g, as well as a layer of polyethylene or polyethylene copolymer, or polyethylene terephthalate copolymer. The layer of expanded recycled polyethylene terephthalate has a thickness ranging from 200 μm to 1000 μm. The layer of polyethylene or polyethylene copolymer, or polyethylene terephthalate copolymer has a thickness ranging from 10 μm to 40 μm. At the same time, instead of the layer of expanded recycled polyethylene terephthalate, a coextrusion or extrusion-cast layer of non-expanded recycled polyethylene terephthalate in combination with the layer of expanded recycled polyethylene terephthalate may be used. Furthermore, such a layer has a thickness ranging from 20 μm to 100 μm. At the same time, a layer of polyethylene or polyethylene copolymer is added between the printed layer and the layer of expanded recycled polyethylene terephthalate. Such an added layer has a thickness ranging from 5 μm to 15 μm. Additionally, a layer of aluminum foil is added after the layer of expanded recycled polyethylene terephthalate. Moreover, the added layer of aluminum foil has a thickness ranging from 4 μm to 9 μm. A method for producing the multi-layered composition based on expanded recycled polyethylene terephthalate is performed as follows. A polyethylene terephthalate waste is washed and purified, then crushed into fractions having a size ranging from 1 mm to 20 mm and separated according to polymer types and color. The polyethylene terephthalate is further melted, and a polyethylene terephthalate melt is subsequently extruded. The solid-state polycondensation of the polyethylene terephthalate is then performed under vacuum to obtain granular polyethylene terephthalate having an intrinsic viscosity ranging from 0.5 dl/g to 1.0 dl/g. The granular polyethylene terephthalate is then extruded, while simultaneously supplying nitrogen and/or carbon dioxide. The polyethylene terephthalate melt is subsequently expanded, whereupon the expanded recycled polyethylene terephthalate is cooled, calendered to a thickness ranging from 200 μm to 1000 μm and wound into a roll. Next, by using an extrusion lamination line, the roll of the layer of expanded recycled polyethylene terephthalate or the roll of the layer of expanded recycled polyethylene terephthalate in combination with the coextrusion or extrusion-cast layer of non-expanded recycled polyethylene terephthalate is installed on a primary unwinding station. Furthermore, at least one roll of the layer of polyethylene or polyethylene copolymer and the layer of aluminum foil are installed on additional unwinding stations. Then, the layer of polyethylene or polyethylene copolymer and the layer of aluminum foil are applied on the layer of expanded recycled polyethylene terephthalate layer or on the layer of expanded recycled polyethylene terephthalate in combination with the coextrusion layer of non-expanded recycled polyethylene terephthalate. After that, the resulting material is temperature-controlled on calender rolls, whereupon the printed layer is applied on its outer surface, and the material is then scored and cut into individual sheets. At the same time, the printed layer is applied by means of rotogravure or offset or flexographic printing, or any combination thereof. In the meantime, bottles, fibers, filaments, sprues, flakes are used as the polyethylene terephthalate waste.
The invention is explained by means of the drawings, in which:
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A method for producing the multi-layered composition based on polyethylene terephthalate is performed using a conventional extrusion lamination line that comprises: an unwinding station; a melt casting station; an extrusion lamination station; a printing station; a quality control station; a winding station. The method is performed as follows. At first, the layer 2 of expanded recycled polyethylene terephthalate is prepared. For this purpose, a polyethylene terephthalate waste 9 (bottles, fibers, filaments, sprues, polyethylene terephthalate flakes) are washed and purified from debris, labels, glue. Then, the polyethylene terephthalate waste is crushed to obtain fractions having a size from 1 mm to 20 mm and separated according to polymer types and color. Next, the separated polyethylene terephthalate waste is loaded into a hopper 10 and melted, and the polyethylene terephthalate melt is extruded on the extrusion line by using an extruder 10, while removing excess contaminants and moisture by means of vacuum pumps 11. After that, the liquid-state polycondensation of polyethylene terephthalate is performed in a reactor 12 under the action of vacuum pumps 13. The condensation leads to an increase in the intrinsic viscosity. High-efficiency vacuum effectively removes harmful chemical impurities from the material, making it possible for the recycled material to be used for 100% safe contact with food products. As the PET melt enters the vertical portion of the P:REACT (LSP reactor) 12, filaments are produced, which form a corresponding surface in volumetric relation. The material is then collected in a horizontal drum and slowly moved forward. The condensation process begins immediately after the production of the filaments and continues until the PET leaves the LSP reactor. An increase in the intrinsic viscosity is controlled by the residence time of the PET melt in the LSP reactor and the degree of vacuum in the LSP reactor and, therefore, may be set to a required level. Parameter settings allow a control unit to maintain a predetermined intrinsic viscosity level within a narrow tolerance range. The process of removing impurities is very effective as it is performed in the liquid state of polyethylene terephthalate. Not only the purification efficiency of the material that exceeds the limits set by food industry standards is provided, but also lubricants are effectively removed from the fibers during the purification process. An increase in the intrinsic viscosity may be measured at a level of about 0.01 dl/g per minute. The continuous operation of the LSP reactor provides a narrow intrinsic viscosity range of a granulate, which is suitable for high-end applications, such as fiber spinning or the production of sheets by extrusion. Fluctuations in the intrinsic viscosity during the mass production are simply ruled out. The separation of harmful impurities, such as lubricants or substances not intended for contact with food products, is performed under the vacuum pumps 13. The high removal rate of the impurities allows the LSP reactor to be utilized in a variety of applications, providing its high operational flexibility. The favorable conditions created in the LSP reactor (temperature/a melt surface-volume ratio/high-efficiency vacuum) allows the PET condensation process to be freely initiated. This leads to an increase in the intrinsic viscosity by about 0.01 dl/g per minute. Faster response times translate into faster achievement of required results and higher profitability. Polyethylene terephthalate granules are produced at the outlet of the LSP reactor. Then, the extrusion of the polyethylene terephthalate granules is performed, while simultaneously supplying nitrogen and/or carbon dioxide. In a connector in front of a die, in the die and at the outlet of the die, the polyethylene terephthalate melt is subjected to temperature- and pressure-controllable extrusion, whereupon the melt is fed from the die to calender rolls where it is cooled (temperature-controlled) and calendered to a thickness of 200 μm to 1000 μm. An additional station for extrusion-casting of either the polyethylene terephthalate melt 5 or the polyethylene or polyethylene copolymer melt 8 may be installed subsequently, and the repeated calendering, temperature control and winding of the film into rolls are performed. Next, the roll of the layer 2 of expanded recycled polyethylene terephthalate or the roll of the layer 2 of expanded recycled polyethylene terephthalate combined with the coextrusion or extrusion-cast layer 5 of non-expanded recycled polyethylene terephthalate or with the additional layer 8 of polyethylene or polyethylene copolymer is installed on the main unwinding station. Further, the roll of the main layer 3 of polyethylene or polyethylene copolymer is installed on additional unwinding stations. If required, the roll of the layer 7 of aluminum foil is also installed on additional unwinding stations. If required, the roll of the additional layer 8 of polyethylene or polyethylene copolymer is also installed on additional unwinding stations. Next, the layer 3 of polyethylene or polyethylene copolymer is applied on the layer 2 of expanded recycled polyethylene terephthalate or the layer 2 of expanded recycled polyethylene terephthalate combined with the coextrusion layer 5 of non-expanded recycled polyethylene terephthalate, and the resulting material is temperature-controlled on the calender rolls. After that, the printed layer is applied on the outer surface of the multi-layered composition based on expanded recycled polyethylene terephthalate by using rotogravure printing or offset printing, or flexographic printing, or any combination thereof. The resulting multi-layered composition is scored and cut into individual sheets.
The claimed invention makes it possible to: recycle a layer of expanded recycled polyethylene terephthalate similarly to cardboard; perform scoring for subsequent folding along a scoring line; perform finishing operations (e.g., printing); perform extrusion lamination with polyethylene terephthalate, polyethylene and polyethylene copolymers and aluminum foil. The claimed invention makes it possible to produce a packaging product consisting of the main carrier layer of recycled polyethylene terephthalate and fully recycle the wasted packaging product based on the multi-layered composition comprising the main carrier layer of expanded polyethylene terephthalate by means of crushing, aluminum filtration (when aluminum is used), and subsequent liquid-state polycondensation of polyethylene terephthalate, thereby restoring the properties of polyethylene terephthalate to those of primary raw materials. The claimed invention makes it possible to recycle multi-layered compositions comprising the main carrier layer of expanded polyethylene terephthalate as many times as one sees fit. In most cases, the claimed invention allows one to produce multi-layered compositions comprising a layer of expanded polyethylene terephthalate having physical and mechanical characteristics better than those of similar multi-layered compositions based on cardboard and/or paper. The claimed invention is 5%-30% cheaper in cost than cardboard or paper, depending on cardboard or paper brands and depending on a required expansion coefficient, and depending on the intrinsic viscosity of polyethylene terephthalate.
Number | Date | Country | Kind |
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2019123943 | Jul 2019 | RU | national |
Filing Document | Filing Date | Country | Kind |
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PCT/RU2019/000644 | 9/17/2019 | WO | 00 |