Background Art Currently, the field of composite multi-layered packaging materials such as plastic foils and packaging, as well as related packaging technologies, undergoes intense development. Plastic foils have suitable properties for use as packaging materials and thus are widely used. The plastic material increases the stability of the packaged product, prevents loss of colour, and has further advantages. The popularity of plastic packaging materials results in the need for recycling technologies for these materials.

Composite packaging materials are most commonly used in foodstuff industry. The waste packaging materials are currently disposed of at dumps or are burnt; thus, new technologies for their recycling and further use are necessary. Composite materials typically comprise various combinations of at least two or more plastic foils such as polypropylene, low-density (LD) polyethylene, high-density (HD) polyethylene, polyethylene terephthalate (PET), polyamide, optionally combined with metals, such as aluminium. These components are connected by a binder to form multi-layered foils. Commercial composite packaging material composed of two processed polypropylene layers and used for packaging of products of the company Knoppers may be mentioned as an example. The layers of multi-layered plastic materials must be separated during the recycling process.

Methods of recycling of plastic materials are based on dissolution of the inter-layer binder and separation of individual layers. Several methods are known for the separation of layers, including mechanical treatment of the materials, such as dry treatment or treatment in aqueous suspension. These processes are energetically demanding, complex, and yield substantial amount of waste solvents which cannot be recycled or can be recycled only with difficulties. Multi-step processes stripping one layer in each step are known, but they are time-consuming, complex, and expensive. Methods relying on wet treatment of the composite materials with various solvents are known. The solvents include esters, ethers (EP 0538730), hydrocarbons, ionic liquids (CA 2924589), alcohols, organic acids, water, etc., sometimes with addition of surfactants. These processes often result in decomposition of the composite material components, insufficient separation, long processing times, and insufficient removal of the binders.

Some processes combine mechanical treatment with subsequent extraction (CZ 1997- 3995), however, such processes are time-consuming, complex, and expensive.

Disclosure of the Invention

The disadvantages of the methods described above are overcome by a method for separation of individual components from a composite packaging material, wherein the composite packaging material is crushed, combined with an organic separation agent in weight ratio material: agent 1:5 to 1: 10, the resulting mixture is heated to a temperature in the range of 40 to 100 °C and left to react, the separated components are then isolated from the resulting mixture.

The separation is thus carried out by the action of the liquid organic separation agent under the above-described conditions, and results in separation of the individual components (e.g., layers) for further use.

The mixture is typically left to react at stirring until separation of the individual components is completed, and the individual components are then isolated by any known methods, such as methods based on their different specific weights. Preferably, it is considered that a separation of the components is completed when at least 90% of at least one component is separated.

The composite packaging materials to be subjected to separation contain two or more components, which are the same or different, selected from plastic and metal foil, preferably from polypropylene, polyethylene (low-density (LD) polyethylene, high-density (HD) polyethylene), polyethylene terephthalate (PET), polyamide and metal foil, in particular aluminium foil. The composite packaging materials preferably contain one or more plastics components, or plastic(s) and metal foil. More preferably, the composite packaging materials comprise the components polyethylene/polypropylene, polyethylene/PET, polyethylene/aluminium/polyethylene or polyethylene/aluminium/PET. The components are bound together by a binder. The organic separation agent is a mixture of crude oil fraction with distillation curve from 50 to 200 °C (preferably gasoline) with an organic solvent selected from toluene, xylene, acetone, N-methyl pyrrolidone, N-ethyl pyrrolidone and formic acid. Preferably, the organic separation agent comprises 1 to 4 volume parts of the crude oil fraction with distillation curve from 50 to 200 °C (preferably gasoline) and 1 volume part of the organic solvent. Most preferred organic separation agent is a mixture of gasoline and xylene in volume ratio 3: 1 to 1: 1.

The organic separation agent of the present invention provides advantageous effects over prior art separation agents in that the binder connecting the composite material components is disrupted by the organic solvent component of the organic separation agent, and then it is dissolved in the crude oil distillation fraction at the increased temperature. When the separation is completed and the mixture is cooled down or left to cool down to room temperature, the binder precipitates and the organic separation agent is easily regenerated by removal of the precipitated binder, e.g., by filtration. The prior art separation agents (e.g., esters, chlorinated solvents, acrylic acid) require distillation for regeneration, or cannot be regenerated at all - then they must be disposed of as hazardous waste.

The thus obtained precipitated binder may be isolated and further used, e.g., as an asphalt mixture binder. This further improves the economical and enviromental balance of the process according to the invention.

The organic separation agent of the present invention has a further advantage in that it ensures a complete removal of the binder from the surface of the composite material components, and thus allows further processing and recycling of the components by extrusion. Processing by extrusion is not possible when the binder is not removed completely.

A very significant advantage is the composition of the organic separation agent which results in synergic effect of individual components in the mixture and in a very high separation activity with very short processing times (of less than 15 minutes, typically). Individual components of the organic separation agent show very little or no effect in separation of the composite material components and rather damage or decompose the individual plastic components. However, when the components of the organic separation agent are used in the claimed combination, preferably in volume ratio of organic solvents to crude oil distillation fraction 1: 1 to 1:4, such mixture shows a high separation activity and allows to easily separate the dissolved and precipitated binder by filtration. The organic separation agent may act selectively on individual components of the composite packaging material. Only pre-determined (e.g., valuable) components (e.g., layers) of the composite material can be selectively separated, and the remaining components (e.g., layers) may remain and be processed in subsequent steps or disposed of. Alternatively, the organic separation agent may separate all individual components of the composite packaging material in one step.

The separation technology for composite materials according to the present invention is highly effective and allows to use continuous processes, thereby facilitating its industrial use.

Examples of carrying out the Invention Example 1.

50 g of composite packaging material having the composition PP/LDPE (polypropylene/low-density polyethylene) in the form of crushed flakes having the size of 0.5 to 1.5 cm was provided in a reactor having the volume of 3 1. 350 g of organic separation agent composed of 4 volume parts of gasoline and 1 volume part of acetone was added. The mixture was heated to 45 °C at stirring for 15 minutes. 100% separation of polyethylene from polypropylene occured. The separated components are isolated from the mixture, and the organic separation agent is recycled for further separation process by filtering off the precipitated binder after cooling down.

Example 2.

50 g of composite packaging material having the composition LDPE/A1/PET (low-density polyethylene/aluminium/polyethylene terephthalate, known as Mill PRF) in the form of crushed flakes having the size of 1 cm was provided in a reactor having the volume of 3 1. 450 g of organic separation agent composed of 3 volume parts of gasoline and 1 volume part of xylene was added. The mixture was heated to 60 °C at stirring for 10 minutes. 97% separation of polyethylene from Al/PET occured. The resulting mixture is processed similarly to Example 1.

Example 3. (polyethylene/aluminium/polyethylene terephthalate) in the form of crushed flakes having the size of 1 cm was provided in a reactor having the volume of 3 1. 450 g of organic separation agent composed of crude oil fraction with a distillation curve from 50 to 200 °C and N-methyl pyrrolidone in the volume ratio 3: 1 was added. The mixture was heated to 45 °C at stirring for 5 minutes. 95% separation of all three components occured. The resulting mixture is processed similarly to Example 1.

Example 4.

50 g of composite packaging material having the composition PE/A1/PP (polyethylene/aluminium/polypropylene) in the form of square flakes having the size of 2 cm was provided in a reactor having the volume of 3 1. 450 g of organic separation agent composed of gasoline and toluene in the volume ratio 3: 1 was added. The mixture was heated to 55 °C and polyethylene was separated from the material. Polypropylene and alumium remained together. The resulting mixture is processed similarly to Example 1.

Example 5. - Comparison of organic separation agents

Comparison of effectiveness of organic separation agents was carried out using three model composite packaging materials at the temperature of 50 °C. The results are shown in the following table:

Composite packaging material

PP/PET PE/PET PE/A1/PET

Organic separation agent separation time min)

gasoline and xylene=4: l 11 12 10

gasoline and xylene =3: 1 10 9 6

gasoline and xylene =2: 1 9 9 6

gasoline and xylene =1: 1 8 7 5 gasoline and toluene =4: 1 15 15 11

gasoline and toluene =3: 1 13 13 10

gasoline and toluene =2: 1 12 11 10

gasoline and toluene =1: 1 9 9 7 gasoline and N-methyl pyrrolidone=4: l 15 15 13

gasoline and N-methyl pyrrolidone =3: 1 14 12 12

gasoline and N-methyl pyrrolidone =2: 1 13 10 9

gasoline and N-methyl pyrrolidone =1: 1 12 10 8 Composite packaging material

PP/PET PE/PET PE/A1/PET

Organic separation agent separation time min)

N-methyl pyrrolidone 68 N N

gasoline N N 120

xylene D D D

toluene D D D

acetone N N N

formic acid 150 450 100

butyl acetate N N N

ethyl acetate N N N

acrylic acid 80 N N

PP = polypropylene; PET = polyethylene terephthalate; PE = polyethylene; Al = aluminium;

separation time = time needed for separation of the material with effectiveness of 90 %;

N = no separation;

D = decomposition of the composite material component.

The results shown in the above table evidence much shorter processing times for organic separation agents according to the present invention, compared to other separation agents, and compared to individual components of the organic separation agents of the invention. The organic separation agents of the invention further do not cause decomposition of the composite material components.

Industrial Applicability

The invention can be used for separation of composite packaging materials into individual components. The separated components of the composite material can be further recycled, e.g., for production of packaging or recycled plastic products.