EA045643B1 - METHOD FOR OBTAINING ADDITIVE FOR BITUMEN CONGLOMERATES WITH HIGH MECHANICAL CHARACTERISTICS AND COMPOSITION OF ADDITIVE - Google Patents

Description

Field of technology

The invention relates to the technical field of producing additives for bitumen conglomerates, in other words, to a mixture of polymers and additives that can be used to modify bitumen conglomerates, bitumen and bitumen products such as bitumen membranes, with the aim of imparting elasticity to bitumen compositions suitable for providing road surfaces .

In particular, the present invention relates to a method for preparing an additive composition for bitumen conglomerates from reclaimed and/or recycled plastic material.

In particular, the present invention also relates to the additive composition thus obtained, which makes it possible to improve the mechanical characteristics of a bitumen conglomerate containing said additive, as well as to extend the service life of a road surface made using such a bitumen conglomerate.

State of the art

The need to develop technologies and products that are as environmentally friendly as possible is still a pressing challenge, especially in the production of bitumen, asphalt and bitumen conglomerates, in particular through the use of renewable or environmentally friendly raw materials.

In addition, in this type of technology, the need to optimize methods for obtaining both bitumen conglomerates and the components necessary for their preparation has become very important, thereby reducing the overall extraction of raw materials and, thus, the carbon footprint associated with these processes.

For example, a desirable goal is to develop formulations suitable for modifying virgin bitumen due to its increasingly poor quality.

In addition, the use of additives to improve the properties of bitumen conglomerates, bitumen, bitumen products and asphalts in general is well known in the art, for example, such additives can be compositions containing thermoplastic polymers or elastomers used to improve the mechanical properties of bitumen conglomerate, bitumen and bituminous products containing such additives, such as, in general, fracture resistance or resilience, and to reduce the deterioration of the bitumen conglomerate commonly used as a road surface.

An asphalt composition containing aggregates, granular or powdered material derived from waste rubber, such as waste tires, and a mixture of thermoplastic polymers and copolymers, as well as additional additives and fillers, is described in international patent application WO 2015179553.

Application US 2009/016325 relates to a high quality bitumen mixture containing mineral aggregates coated with a thermoplastic polymer composition mainly containing polyvinyl butyral.

In particular, such a composition may comprise a recyclable or recyclable thermoplastic polymer, including recycled polyvinyl butyral, obtained from the recycling of glass panels used in the construction industry and automotive windshields.

The simple possibility of including polyolefins in such a polymer composition is considered; however, information on specific combinations of materials in the thermoplastic polymer composition is not provided.

CN 103509356 A refers to a modified asphalt mixture material containing the following components in parts by weight: from 150 to 200 parts of polyethylene, from 60 to 90 parts of polystyrene-polybutadiene-polystyrene block copolymer, from 16 to 30 parts of polyethylene terephthalate, from 50 to 80 parts of polyvinyl butyral and from 20 to 40 parts of filler.

The method for producing a modified asphalt mixture material includes the steps of providing the above-mentioned raw material, producing a mixture of polyethylene and polystyrene-polybutadiene-polystyrene block copolymer by melting and granulating them, then mixing the thus mixed granules with the remaining raw material by melting and co-extruding the thus obtained mixture.

In any case, although additives to improve the chemical and mechanical properties of commercially available asphalts, as well as the asphalts that can be made with them, are usually obtained with environmental impact, for example, using scrap from other industrial processes or recycled materials, methods for producing such materials are still unable to best combine the need to significantly reduce the environmental impact of the production of these additives with the mechanical properties of a road surface made using bitumen conglomerates obtained by adding these additives.

Another disadvantage of the prior art is the difficulty of obtaining additives of the above-mentioned type using technologies that make it possible to obtain a homogeneous mixture of constant quality,

- 1 045643 which can be easily dosed.

An additional disadvantage of the prior art is the difficulty of obtaining additives of the above type that can guarantee consistent quality of the finished additive.

Indeed, the need to discover an effective way to recover and reuse scrap or plastic waste, whether recyclable or not, becomes extremely important.

Particularly in Europe, and not only there, the need to find an alternative end-user for waste of the above-mentioned type is of paramount importance, since, on the one hand, in many areas of the continent there is not a sufficient number of installations for the disposal of such waste and/or installations for generating energy using the said waste, while on the other hand, there is a search for the possibility of their reuse, which has less impact on the environment compared to incineration or disposal in a landfill.

In addition, it should be taken into account that the percentage of recycled plastic compared to virgin plastic used in consumer goods is not proportional to the increase in the volume of plastic recycled and collected through increasingly efficient collection systems based on waste sorting.

Accordingly, plastics remaining from such recycling processes or the like, as well as a certain amount of unrecycled plastic, must be disposed of through waste-to-energy processes, landfill delivery, or, less commonly, used in the production of alternative fuels.

In light of the prior art described above, the problem underlying the present invention was to develop a method for producing an additive composition for bitumen conglomerates starting from plastic waste, which allows for the reuse of a wide range of waste and which is more environmentally sustainable, and also allows for the production of a composition with high added value, particularly suitable for use as an additive for the preparation of high-quality bitumen conglomerate mixtures.

The essence of the invention

This problem has been solved by providing a process for preparing an additive composition for mixing with bitumen conglomerate, bitumen or other bituminous paving products, comprising the following steps:

a) providing mixed waste containing a mixture of plastic materials containing at least one plastic material based on a polyolefin thermoplastic polymer;

b) grinding said mixed waste to achieve a particle size of from 40 to 80 mm, a particle size preferably equal to about 60 mm;

c) washing the thus shredded mixed waste and separating in a controlled manner a portion of the plastic material having a characteristic medium density from said mixed waste, said portion of the plastic material comprising said at least one polyolefin thermoplastic polymer-based plastic material;

d) grinding said portion of the plastic material having a characteristic medium density to a particle size of 10 to 20 mm, preferably a particle size of 12 to 15 mm; And

e) mixing at room temperature the thus crushed portion of the plastic material having a characteristic medium density with a material based on polyvinyl butyral (PVB), and grinding the mixture thus obtained to obtain a ready-to-use granular additive composition with a particle size of 4 to 6 mm , with a particle size preferably equal to about 4 mm, wherein said washing and separating step c) is carried out using a density separation method, thereby allowing a predetermined density limit to be selected and a specified portion of the plastic material to be separated from said mixed waste, having a characteristic average density less than or equal to a specified specified limit value, wherein said characteristic average density is less than or equal to 1.0 kg/m ³ as determined according to the procedure of DIN 55990.

According to the present invention, by the expression mixed waste is meant a mixture of coarse solid residues, that is, solid residues with a particle size generally greater than or equal to 60 mm, said mixture containing solid residues, in turn containing one or more plastic materials, in some cases said mixture contains solid residues consisting of composite materials, that is, containing plastic material and solid material of different chemical nature, for example paper, cardboard or metal, for example aluminum.

In particular, said mixed waste may contain solid residues made of plastic material, which are generated from municipal solid waste or as a result of industrial or handicraft production of products made from plastic material, or any combination thereof, wherein said solid residues are not disposed of or can be recycled in the recycling chain of plastic materials, for example, those containing PVB obtained by shredding windshields and double-glazed windows.

In particular, said residual plastic material, i.e. the predominant part of the recycled plastic material, can be obtained from waste containing so-called hard plastics, i.e. hard and rigid plastic materials that are not usually recycled or cannot be recycled in the plastic material recycling chain, such such as toys, pens, markers and writing utensils made of plastic, slippers, bins and baskets made of plastic, fruit and vegetable boxes, pipes, tables and chairs made of plastic, garden furniture, buckets, washbasins and sinks, covers for audio cassettes, CDs, DVDs, video cassettes and similar products. These items are usually collected together with waste that is collected without waste sorting in the municipal solid waste collection system at the gate of the house, or together with bulky waste at urban environmental sites.

According to the present invention, said plastic material residues can be obtained from waste that was previously completely or partially free of residues consisting of polyvinyl chloride and incidental unwanted materials such as paper, cardboard, wood, fabric, metal or glass.

In any case, said mixed waste may contain minor amounts of solid residues consisting of materials other than plastic, such as paper, cardboard, wood, metal or glass.

To summarize, the method of the present invention allows for the recovery and reuse of said mixed waste typically disposed of in a landfill or incinerator, which provides significant benefits from an environmental point of view.

Further, according to the present invention, the expression at least one plastic material containing a thermoplastic polymer/based on a thermoplastic polymer means a plastic material (i.e. plastic) which contains polymer chains linked by intermolecular interactions, i.e. van der Waals forces , forming linear or branched structures; In particular, due to their chemical structure, thermoplastics soften or melt when heated, then they are shaped, molded, welded, and cured when cooled.

According to the present invention, the term room temperature means the temperature of the external environment in which the operation is performed.

In other words, the above-mentioned step e) is carried out without applying additional heat to the material thus mixed, except for the potentially minor heat passively supplied from the external environment.

For example, said room temperature can be from 2 to 45°C, in particular from 15 to 25°C.

Finally, according to the present invention, by the term particle size is meant a range of numerical values including a minimum value and a maximum value of the diameter of the granules/chips that constitute the mixed waste, wherein the plastic material of such part of the plastic material has a characteristic average density, wherein the specified additive composition can be obtained the method according to the present invention.

An advantage is that the method according to the present invention produces an additive composition that can be added to a mixture of bitumen conglomerate, bitumen or other bitumen products.

The method of the present invention advantageously produces an additive composition that can be added to the asphalt conglomerate mixture to produce a high quality asphalt conglomerate mixture.

In fact, when a bitumen conglomerate mixture containing the granular additive composition produced by the method of the present invention is used to make a road surface, the latter has improved mechanical properties compared to a road surface made using a bitumen conglomerate mixture not containing the additive composition of the present invention. .

In particular, the bitumen conglomerate mixture thus obtained has improved chemical-physical characteristics, especially in terms of consistency, compared to similar products that are usually used for the same purpose.

Accordingly, the above granular additive composition is ready for use, which means that it can be easily dispersed in the additional ingredients required to prepare a bitumen conglomerate mixture containing bitumen and aggregates, which provides an advantage in terms of practical application of the additive composition, and also, precisely because its high homogeneity and distribution in the conglomerate mixture, this mixture of additives makes it possible to obtain a road surface with improved mechanical characteristics due to the use of a conglomerate mixture modified in this way.

- 3 045643

In other words, it is not necessary to subject the additive composition of the present invention to heating, melting and extrusion to obtain extruded granules containing a mixture of both said plastic material having a characteristic average density and said polyvinyl butyral material having consistent and uniform quality characteristics.

In particular, the above-mentioned granular additive composition can be directly dispersed in the additional ingredients required for the preparation of the bitumen conglomerate mixture, thanks to the presence of such plastic material, thus selected in said step c) and having said characteristic average density, a property which is also closely related to properties of the transition state of the plastic material itself.

In fact, at least one thermoplastic polyolefin polymer contained in the plastic material of the part thus selected in step c) has a softening point of from 120 to 180°C and can thus be directly added to aggregates and bitumen by means of the so-called dry process (which does not require hot mixing of thermoplastics and other modifiers with bitumen before adding to aggregates) during the production of bitumen conglomerate.

Thus, the mixture of additives obtained using the method proposed in the present invention can advantageously be effectively hot mixed with bitumen and aggregates, therefore already at the stage of preparing the bitumen conglomerate.

Alternatively, according to the traditional wet method, the conventional additives are necessarily first mixed only with the bitumen at a higher temperature, usually at a temperature greater than or equal to 180°C, for example from 180 to 200°C. The bitumen thus mixed with the additive is then usually kept at a certain temperature before being further mixed with aggregates to produce a bitumen conglomerate ready for laying on the road.

At the same time, at least one thermoplastic polyolefin polymer contained in the plastic material of the part thus selected in step c) has a melting point (Tm) of 120 to 165° C., as determined by differential scan temperature (DSC) according to procedure ASTMD3418.

In another case, the average density of the plastics contained in said mixture of plastic materials contained in said mixed waste before separation of said portion of the plastic material during said step c) is generally from 1.5 to 2 kg/m ³ as determined according to procedure DIN 55990.

Accordingly, the melting temperature (Tm) of the plastics contained in said mixture of plastic materials contained in said mixed waste before separation of the above-mentioned portion in said step c) is from 40 to 250°C, as determined by differential scan temperature (DSC) according to ASTM D3418 procedure.

Naturally, according to an alternative application, the above-mentioned granular additive composition can be dispersed in additional ingredients necessary for the preparation of bitumen or other bituminous mixtures, due to the presence of such plastic material, thus selected in said step c) and also having said characteristic average density.

In particular, if the above-mentioned granular additive composition is used in the direct modification of bitumen or in other processes that use bitumen, such as bitumen membranes, it disperses more easily compared to similar already known products due to its lower softening point (and its specific value melt flow index (MFI)).

In particular, in the mixed waste provided in said step a), said thermoplastic polyolefin polymer is selected from polyethylene, polyethylene copolymer, polypropylene, polypropylene copolymer, or any combination of these materials.

More preferably, the polyethylene may be high density polyethylene and/or low density polyethylene.

In the mixed waste provided in said step a), said mixture of plastic materials may include plastic materials containing at least one polymer selected from polyethylene terephthalate, acrylonitrile butadiene styrene (ABS), polycarbonate, polystyrene, polyurethane or any combination thereof.

In summary, the additive mixture produced by the process of the present invention provides greater usability, energy savings, and more consistent and uniform final physicochemical characteristics than conventional additive mixtures.

The mixture of additives obtained according to the method proposed in the present invention also requires reduced melting and mixing times, which allows the materials that make up the bitumen conglomerate to be mixed within a time not exceeding one minute so that it can be immediately laid on the road.

Said mixed waste is preferably subjected to a preliminary separation step, during which possible fractions made from polyvinyl chloride (PVC) and/or fractions made from unwanted materials such as paper, cardboard, wood, fabric, metal or glass are removed.

According to an equally preferred method, in said grinding step b) after grinding, said mixed waste is subjected to a procedure for separating a metal fraction possibly contained therein, more preferably, said procedure for separating a metal fraction from said mixed waste so crushed includes a first separation step with the use of magnetic means (deferrization) and the second stage of separation of the non-ferrous metal fraction.

As stated above, said washing and separating step c) is carried out by a density separation method, selecting a predetermined density limit value, and separating from said mixed waste a specified portion of the plastic material having an average density less than or equal to the specified limit value.

In particular, as will be clear below with reference to the detailed description, during said washing and separating step c) carried out by the density separation method, selected plastic materials from said mixed waste can be separated by decantation using a solution having a density equal to preset value.

In particular, said density separation can be carried out using an aqueous solution having a density equal to a predetermined value, which is in the range between the density value of said at least one polyolefin thermoplastic polymer-based plastic material contained in said part of the plastic material having the characteristic average density of said mixture of plastic materials, and the density values of materials contained in said mixed waste with a density greater than the density of said at least one polyolefin thermoplastic polymer-based plastic material.

Thus, in said washing and separating step c) it is possible to effectively and accurately separate said portion of the plastic material having a characteristic average density from the mixed waste devoid of said portion of the plastic material.

Depending on the application of the desired additive composition, for example, depending on the specific type of bitumen conglomerate that can be obtained using said additive composition, in said washing and separating step c) selecting said predetermined density limit value and separating the portion of the plastic material that has an average density less than or equal to the specified limit value, wherein the specified characteristic average density is from 0.70 to 0.90 kg/m ³ as determined according to the procedure of DIN 55990.

According to a preferred embodiment, said portion of the plastic material having a characteristic average density separated in said washing and separating step c) has at least one plastic material based on a polyolefin thermoplastic polymer selected from the group consisting of polyethylene, polyethylene copolymer, polypropylene, copolymer polypropylene or any mixture thereof.

Said portion of the plastic material having a characteristic average density may comprise said at least one polyolefin thermoplastic polymer-based plastic material in an amount greater than or equal to 75% by weight relative to the total weight of said portion of the plastic material, more preferably in an amount greater than or equal to 80% by weight relative to the total weight of said portion of the plastic material, even more preferably in an amount greater than or equal to 85% by weight relative to the total weight of said portion of the plastic material, most preferably in an amount greater than or equal to 90% by weight relative to the total weight of said portion plastic material.

According to an equally preferred method, said portion of the plastic material having a characteristic average density, thus separated in said washing and separating step c) may contain polystyrene and/or polyurethane in an amount less than or equal to 15% by weight, relative to the total weight of said portion of the plastic material. material having a characteristic average density, preferably in an amount less than or equal to 10% by weight relative to the total weight of the specified portion of the plastic material, more preferably in an amount less than or equal to 5% by weight relative to the total weight of the specified portion of the plastic material.

According to a preferred embodiment, in said washing and separating step c) a second mixture of plastic materials comprising at least one polyolefin thermoplastic polymer plastic material may be added and mixed with said mixed waste, wherein said second mixture preferably comprises said at least one polyolefin thermoplastic polymer plastic material in an amount equal to at least 75% by weight relative to its total weight, more preferably in an amount equal to at least 80% by weight relative to its total weight, even more preferably in an amount equal to at least 85% by weight relative to its total weight.

According to the present invention, said second mixture of plastic materials contains residues made from plastic material which are obtained from recyclable waste, in particular residues from the processing of recyclable waste collected through waste sorting.

In particular, said residues made of plastic material, which are obtained from recyclable waste, are usually removed and disposed of through collection based on plastic sorting and sent to the recycling chain, such as packaging made of plastic, mixed packaging, such as films made from more than one plastic material or composite material, and mixtures thereof.

In said washing and separating step c) said second mixture of plastic materials preferably comprises plastic materials containing at least one polymer selected from polyethylene, polyethylene copolymer, polypropylene, polypropylene copolymer, polyethylene terephthalate, polystyrene, polyethyl acrylate (PEA), polymethyl acrylate (PMA) , polybutyl acrylate (PBA) or any combination thereof.

According to a completely preferred method, said plastic material residues contained in said second plastic material mixture may be scrap from returnable waste recycling processes made of plastic material or composite material, which are removed and disposed of through collection based on sorting of plastic waste.

According to an equally preferred method, said plastic material residues contained in the second plastic material mixture may be shavings from industrial and/or handicraft production of products made from plastic material.

In a completely preferred method, said second mixture of plastic materials is added to said mixed waste in an amount of 5 to 35% by weight relative to the weight of said mixed waste, preferably in an amount of 10 to 30% by weight relative to the weight of said mixed waste.

It is advantageous that the method proposed in the present invention can thus make it possible to add, in said step c), an additional part of the waste, that is, said second mixture of plastic materials, to said mixed waste so as to enable the reuse of the materials which often typically disposed of in a landfill or sent to an incinerator, which provides an additional environmental benefit.

The advantage is that by adding in said step c) said second mixture of plastic materials, it is possible to obtain an additive composition enriched in plastic materials possibly not contained in said mixed waste. Thus, depending on the need of the application, for example, depending on the required mechanical properties of the bitumen conglomerate mixture to which said composition can be added, a second mixture of plastic materials with a certain composition can be added in said step c).

Said step d) of crushing a portion of the plastic material is preferably carried out by granulation in water, possibly using a water mill.

In said grinding and mixing step e) said polyvinyl butyral material with which said portion of the plastic material is mixed preferably has a particle size of 10 to 20 mm, more preferably 12 to 15 mm.

According to a preferred embodiment, said polyvinyl butyral material added in said step e) to said portion of the plastic material having a characteristic average density may comprise polyvinyl butyral (PVB) in an amount greater than or equal to 80% by weight, relative to the total weight of said polyvinyl butyral material. polyvinyl butyral, preferably in an amount greater than or equal to 90% by weight relative to the total weight of said polyvinyl butyral material, more preferably in an amount greater than or equal to 95% by weight relative to the total weight of said polyvinyl butyral material.

According to an equally preferred method, in said grinding and mixing step e) said polyvinyl butyral material with which said portion of the plastic material is mixed is a polyvinyl butyral recyclable material.

Said polyvinyl butyral-based recyclable material is preferably derived from post-consumer waste materials including automobile windshields, insulating glass units, heat-resistant glass window panes, safety glass window panes, and/or is derived from chips (or scraps) from industrial production for the manufacture of the above items, more preferably, it is obtained from automobile windshields.

More preferably, said polyvinyl butyral recyclable material may also contain elastomers, including natural rubber, butadiene and styrene foam, ethylene propylene diene monomer rubber (EPDM), nitrile rubber (nitrile butadiene rubber, NBR ) or any combination thereof.

Alternatively, in said grinding and mixing step e) said polyvinyl butyral material is virgin polyvinyl butyral or a mixture of the above reclaimed material and virgin polyvinyl butyral.

It is advantageous that the method according to the present invention thus makes it possible to recover scrap generated from the above-mentioned waste from glass recycling or replacement of automobile windshields, which are usually sent to waste energy generation processes, since the presence of a significant percentage of glass makes them difficult to dispose of, which provides an advantage not only from an economic point of view compared to disposal through waste-to-energy processes, but also from an environmental point of view.

In addition, the method proposed in the present invention makes it possible to obtain an additive composition of the above type with high performance characteristics, capable of imparting noticeable elastic properties to the bitumen conglomerate to which it is added in use, due to the direct action of polyvinyl butyral.

In addition, similar to the plastic material contained in such a portion of the plastic material, polyvinyl butyral makes it possible to increase the elasticity values of a road surface constructed using the above-mentioned bitumen conglomerate.

According to one embodiment of the method proposed in the present invention, before mixing with the specified part of the plastic material having a characteristic density, in the specified stage e) of crushing and mixing, the specified recyclable polyvinyl butyral-based material is subjected to the following stages:

carrying out preliminary grinding of consumer waste or industrial shavings containing polyvinyl butyral (PVB) to ensure a particle size less than or equal to 30 mm;

separating the glass residues from said shredded wastes to obtain a polyvinyl butyral (PVB)-based recyclable material containing glass in an amount less than or equal to 10% by weight relative to the weight of said recyclable material, preferably less than or equal to 7% by weight relative to the weight of said recyclable material, more preferably less than or equal to 5% by weight relative to the weight of said recyclable material;

grinding said recyclable material to a particle size of 10 to 20 mm, preferably a particle size of 12 to 15 mm; and in an equally preferred method, said polyvinyl butyral material is added to said medium density plastic material portion in an amount equal to 5 to 25% by weight relative to the weight of said medium density plastic material portion, preferably in an amount equal to from 10 to 20% by weight relative to the weight of the specified part of the plastic material having a characteristic average density.

Thus, the method according to the present invention makes it possible to recycle said polyvinyl butyral (PVB) based recyclable material to obtain a high quality additive composition of the above type, ultimately containing a minimum amount of glass which does not impair either the workability of the asphalt conglomerate mixture or other bituminous products to which it is added the actual composition of the additive, nor the mechanical characteristics of the road surface obtained using such a mixture of bitumen conglomerate.

The method of the present invention preferably includes the additional step of drying the additive composition described above.

According to a preferred embodiment, the method of the present invention further comprises the step of mixing said additive composition with a modifier, wherein said modifier is preferably selected from graphene, an adhesion promoter, a regenerating agent, a plasticizer, lignin, or any combination thereof.

According to the most preferred embodiment, said modifier may be a compound of synthetic, mineral or plant origin.

According to the present invention, the term graphene means a carbon material with a two-dimensional structure of carbon monatomic layers with a hexagonal matrix, in which each carbon atom is bonded to the other three carbon atoms through a covalent bond and is connected to the atoms of adjacent layers through van der Waals forces, and also implies any functionalized derivative of such carbon material, for example graphene oxide, i.e. graphene partially functionalized with oxygen-containing groups.

The graphene used according to the method of the present invention preferably has an apparent density of 2 to 100 g/dm ³ , more preferably 10 to 70 g/dm ³ ; in the same time

- 7 045643 the surface area of graphene used in the additive composition according to the present invention ranges from 10 to 300 m ² /g.

The specified surface area is measured using the Bruner-Emmett-Teller (BET) inert gas (nitrogen) absorption method, in particular according to the procedure described in ISO 9277:2010.

In addition, the horizontal dimensions of the graphene layers used according to the method proposed in the present invention are less than 200 μm, preferably less than 100 μm, more preferably less than 50 μm.

In a preferred embodiment, the graphene according to the method of the present invention is recycled graphene, virgin graphene, or a mixture of recycled graphene and virgin graphene.

According to a completely suitable method, by adding graphene to the above additive composition obtained by the method according to the present invention, an additive composition with even higher performance properties is obtained. In particular, graphene makes it possible to increase the elasticity values and, more generally, the mechanical properties of a road surface constructed using bitumen conglomerate to which such a graphene-containing additive composition has been added.

According to a preferred embodiment of the present invention, the proposed method includes the following additional steps:

feeding the granular additive composition described above into an extruder, preferably a twin screw extruder;

heating said additive composition to a predetermined temperature;

extruding and cooling said additive composition to obtain the additive composition in the form of extruded granules with a particle size of from 1.85 to 4.5 mm, preferably from 2 to 4 mm.

It is advantageous that, according to this latter embodiment, the method proposed in the present invention makes it possible to obtain an additive composition in the form of granules with a size that is practical for use, in particular from the point of view of the flow properties of the composition and the speed of its delivery when added to the bitumen mixture. conglomerate.

According to an alternative embodiment, the method of the present invention includes the additional step of further grinding the granular additive composition described above to obtain the additive composition in the form of fine granules with a particle size of from 0.85 to 2.5 mm, preferably from 1 to 2 mm.

The advantage is that, according to this latter embodiment, the method proposed in the present invention makes it possible to obtain an additive composition for the preparation of high-quality bitumen conglomerates. This additive composition can be effectively mixed with additional ingredients necessary for the preparation of bitumen conglomerates, such as bitumen and aggregates.

In fact, it has been found that the additive composition described above in the form of fine granules is even more easily dispersed in the additional ingredients needed to prepare a bitumen conglomerate mixture containing bitumen and aggregates.

In addition, the above-mentioned additive composition in the form of fine granules is in any case safe to handle, since it does not contain fine powders that can be inhaled by its operators.

The above-mentioned additional step of grinding the additive composition to obtain the additive composition in the form of fine granules may preferably include a sieving step to remove a fraction of the additive granules having a diameter less than or equal to about 0.85 mm.

According to a preferred embodiment of the invention, after obtaining the above additive composition in the form of extruded granules or in the form of small granules, the method proposed in the present invention may include the additional step of adding a modifier to the additive composition, wherein said modifier is selected from graphene, an adhesion promoter, a regenerating agent, a plasticizer, lignin or any combination thereof.

According to the most preferred embodiment of the invention, said modifier may be a compound of synthetic, mineral or plant origin.

According to a more preferred embodiment of the invention, the method proposed in the present invention includes the following additional steps:

dispensing a predetermined amount of the above-described granular additive composition in the form of small granules and pressing it;

applying to the additive composition thus compressed a film of a plastic material based on a thermoplastic polymer, said plastic material preferably being polyethylene, thereby obtaining a capsule.

The above dosing step preferably includes the step of adding a predetermined amount of a liquid modifier to the additive composition, more preferably the latter being selected from an adhesion promoter, a regenerating agent, a plasticizer, lignin or any combination thereof.

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According to the most preferred embodiment of the invention, said modifier may be a compound of synthetic, mineral or vegetable origin, for example, said plasticizer may be an oil of vegetable origin, more particularly, said vegetable oil may be a fatty acid ester or a mixture of fatty acid esters .

More preferably, during said dosing step, said predetermined amount of the additive composition is from 10 to 20 g.

In other words, according to this preferred embodiment of the method proposed in the present invention, it is possible to obtain a capsule containing the specified additive composition in the form of small granules coated with a film of plastic material.

The advantage is that said additive composition in capsule form is particularly suitable for the preparation of high-quality bitumen conglomerates; in fact, said capsule can be effectively added by mixing with additional ingredients required for the preparation of bitumen conglomerates such as bitumen and aggregates.

In particular, when said additive composition in capsule form is added to heated aggregates and bitumen, said film of plastic material readily melts and decomposes, allowing the additive granules to be effectively dispersed directly into the bitumen conglomerate at the mixing stage.

This procedure of dispersing directly into the conglomerate composition provides a short period of time, typically less than or equal to 60 seconds, compared to methods of dispersing additives in bitumen according to the prior art, which provides a noticeable advantage not only from a practical point of view, but also from the point of view significant energy and cost savings.

Moreover, precisely because of its form in the form of capsules containing a predetermined, properly dosed amount of the additive composition, the latter embodiment makes it possible to provide an additive for bitumen conglomerates, which in turn is easier to dose, for example, using pneumatic dosing devices, compared to supplement compositions in the form of powder or granules, that is, not in capsule form.

The technical problem described above was also solved by an additive composition intended for mixing with bitumen conglomerate for paving and suitable for improving the mechanical properties of said bitumen conglomerate containing at least one polyolefin thermoplastic polymer and polyvinyl butyral (PVB) obtained using the above described way.

The melt flow index (MFI) of the additive composition described above is preferably greater than or equal to 1 g/10 min, as determined in accordance with the ISO 1133 procedure at a temperature of 190°C and a load of 2.16 kg, more preferably between 1.5 g/10 min to 2.5 g/10 min, even more preferably from 2 g/10 min to 2.5 g/10 min.

In particular, also due to the specific melt flow index that characterizes the present additive composition, it has been found that the latter is capable of being effectively dispersed in the additional ingredients required for the preparation of a bitumen conglomerate mixture containing bitumen and aggregates, which provides an advantage from the point of view of practical application of the said composition.

In addition, since high uniformity and distribution of the additive composition in the conglomerate mixture can be achieved, the proposed additive composition makes it possible to obtain a road surface with improved mechanical characteristics by using the conglomerate mixture thus modified.

More specifically, with respect to said step c), it has been found that when said portion of the plastic material is thus separated in the above-described washing and separating step c), it has an average density of 0.70 to 0.90 kg/m ³ as determined According to the DIN 55990 procedure, the melt flow index of the additive thus obtained is between 1.5 g/10 min and 2.5 g/10 min, as determined in accordance with the ISO 1133 procedure at a temperature of 190°C and a load of 2.16 kg.

As previously described in connection with the method according to the present invention, the additive composition described above has the following advantages:

the said composition contains materials obtained from a mixture of plastic materials that are not recycled or can not be recycled in plastic material recycling chains according to current technological standards, which allows the recycling and reuse of waste otherwise intended for disposal in a landfill or for use in production processes energy using waste;

said composition may contain materials derived from a second mixture of plastic materials, which may be residues of plastic materials obtained from returnable waste, in particular residues from the processing of said returnable waste collected through waste sorting;

- 9 045643 said composition may include recyclable polyvinyl butyral, which provides an additional advantage from both an economic and environmental point of view;

said composition contains a mixture of different plastic materials, which can be selected depending on the need for application, for example, depending on the required mechanical properties of the bitumen conglomerate mixture to which such a composition can be added;

said composition contains a mixture of plastic materials, individually having a melting point significantly lower than similar additives according to the prior art, as a result of which such a composition is capable of being mixed with bitumen and aggregates immediately at the time of preparing the mixture of bitumen conglomerate immediately before laying it on the road;

this composition has a particle size that guarantees easy dispersion within the bitumen conglomerate mixture, which, after its distribution and hardening, leads to the formation of a road surface with improved mechanical characteristics precisely due to the uniform distribution of the additive composition in the conglomerate mixture.

The characteristics and advantages of the present invention will be further demonstrated by means of certain embodiments, which are set forth below by way of illustration and not limitation.

Detailed Description of the Invention

The following describes a route for carrying out the method according to the present invention for preparing an additive composition for high quality bitumen conglomerates, bitumen or bitumen products. In particular, in example 3, the mechanical properties of a bitumen conglomerate obtained using the additive composition according to the present invention were evaluated.

Example 1: obtaining an additive composition according to the method proposed in the present invention.

At a waste collection site, etc. the operator was provided with open-top containers previously filled with waste collected without waste sorting, containing a mixture of plastic materials, mainly containing solid residues derived from products made from plastic materials, which cannot be disposed of in the plastic material recycling chain according to modern technological standards, such as, for example, toys, writing utensils made of plastic, slippers, bins and baskets made of plastic, fruit and vegetable boxes, pipes, tables and chairs made of plastic material, garden furniture, buckets, washbasins and sinks, cases for audio cassettes, etc.

As is known, the above products are mainly made of plastic material based on polyolefin thermoplastic polymers, in particular polyethylene and polypropylene.

The operator selected from the above open-top containers residues made of plastic material, mainly containing hard plastics, avoiding, as far as possible, sampling fractions or items consisting of PVC (cables and laminates), as well as fractions of random, unwanted materials such as wood, fabrics and metals.

The plastic material thus selected was accumulated in an open top container to provide a mixed waste containing a mixture of plastic materials, said mixture comprising at least a polyolefin thermoplastic polymer plastic material.

The mixed waste was loaded onto a conveyor belt to first remove additional fractions consisting of PVC, as well as fractions made from random, unwanted materials.

The mixed waste was then sent to a single-shaft waste shredder for the first stage of comminution, which reduced the material to approximately 60 mm in size.

This first comminution step provided a mixed post-process waste that was easier to handle and had a uniform particle size.

Next, the material crushed in this way was distributed onto a conveyor belt and sent to a magnetically controlled separation station.

Then the iron fraction was separated from these mixed wastes; after this procedure, a weight loss of approximately 3% relative to the total mass of the material was recorded.

The mixed waste, thus stripped of iron, was conveyed via a conveyor belt to an induced current separator capable of separating non-magnetic metals, including aluminum, stainless steel and copper.

After this stage of removing non-ferrous metal residues, an additional weight loss of approximately 2% relative to the total weight of the material was recorded.

A conveyor belt conveyed the metal-free material to the washing and separation section.

Together with the material in question, the mixed waste was supplied to a tank specifically designed for the washing and density separation step along with a second plastic material mixture containing at least one polyolefin thermoplastic polymer based plastic material.

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The second mixture of plastic material was in the form of scrap from returnable waste recycling processes made of plastic material or composite material removed and recovered through collection based sorting of waste plastic material.

The weight of the second mixture of plastic material was 25% by weight relative to the total weight of the mixed waste not containing the metal fraction to which it was added.

The percentage by weight of polyolefins in the plastic material constituting the second mixture, as such and/or possibly reinforced by mineral additives mixed into the plastic material, was greater than 85% by weight relative to the dry weight of the latter.

Thus, the mixed waste was enriched with pure polyolefin materials obtained from and mixed with plastic recycling procedures.

Thus, mixed wastes enriched with polyolefin materials of interest (particularly polyethylene and polypropylene) were separated by density separation from the component with the highest molecular weight, in particular from residues of plastic material, and not only, with a density above 1 .1 kg/m ³ by using an aqueous solution whose density value is higher than the density of the plastic materials of particular interest, i.e. high density polyethylene, low density polyethylene and polypropylene, but lower than the density of the plastic materials contained in these mixed wastes and having a density value higher than the density of the plastic materials of interest.

Together with the materials listed above, the thus obtained part of the plastic material having a characteristic medium density also contained polystyrene and expanded polystyrene.

Inert non-plastic materials and plastic material with a density greater than 1.1 kg/m ³ such as nylon ropes or polyvinyl chloride and/or polyethylene terephthalate residues were allowed to decant by settling to the bottom of the tank.

The weight of the highest density portion of the material thus separated was approximately 21% by weight of the total weight of the mixed waste introduced into the washing and separating tank.

In the upper part of the tank, by moving the comb rostrum, placed slightly away from the water, the remains of the plastic material with a characteristic medium density were easily separated from the remains of the higher density material that may have adhered to them. The comb rostrum also moved floating material into the tank area in accordance with the drain screw located at the outlet.

Then, by means of said screw, a portion of the plastic material having this characteristic average density was sent to a further grinding stage, the size of the material being reduced to about 13 mm using a wet granulator. The material crushed in this way was collected in containers.

Next, the crushed and collected part of the plastic material, having a characteristic average density, was sent to a horizontal centrifuge to dry the material; in particular, the material was introduced into a hopper and then fed into a perforated basket, within which a bladed rotor rotated at a very high speed in order to impart strong acceleration to the material, while residual moisture was expelled from the holes of the perforated basket.

The plastic material, thus deprived of some of the moisture, was then further dried using a fan.

The composition and physical characteristics of the thus dried portion of the plastic material having a characteristic average density are shown in the table below. 1.

Table 1

Content of polyolefins as such and/or reinforced mineral supplements More than 90% relative to total dry weight Contents of other plastics, composite materials also containing aluminum foil <50 µm thick, and other materials. Less than 10% by weight relative to total dry weight Volumetric weight per dry weight More than 100 kg/m ³ Particle size 13 mm Physical form Crumbs and granules of various shapes Humidity Less than 10% by weight

- 11 045643

Accordingly, the thus obtained part of the plastic material having a characteristic medium density had the characteristics required by the UNI 10667-16 standard, so it could potentially be used as crushed material for extrusion processes and/or injection molding.

In addition, the thus dried portion of the plastic material having a characteristic average density had the physical and rheological characteristics shown in the table below. 2.

table 2

Average density 0.8 g/cm ³ (determined according to DIN 55990 procedure) Melt Flow Index (MFI) 2.5 g/10 min (calculated according to the ISO 1133 procedure at T=190 °C and a load of 2.16 kg)

The dry material was conveyed by pneumatic transport to a 20 cubic meter mixing hopper, in which the said material was homogenized and mixed with recycled material provided in the form of post-consumer polyvinyl butyral-based recyclable material, in particular recycled material containing polyvinyl butyral in an amount equal to 90% by weight of its total weight.

The weight of the added recycled material was 10% by weight relative to the total weight of the thus dried portion of the plastic material having a characteristic average density.

During homogenization and mixing, the materials were ground at room temperature using knife mills to achieve a particle size of approximately 5 mm.

Finally, the material thus obtained was sent to the subsequent fine grinding stage and then fed into a disk grinding chamber in which it was crushed and in which the size of the granules was determined by the distance between the disks. This distance can be adjusted from outside the grinding chamber.

The composition and physical characteristics of the additive mixture thus obtained are shown in the table below. 3.

Table 3

Plastic (and possibly rubber) content, including: - polyolefins, as such and/or reinforced with mineral additives; - polyvinyl butyral; - other plastics 98.6% by weight based on total dry weight 82.7% by weight based on total dry weight 8.2% by weight based on total dry weight 7.7% by weight based on total dry weight Contents of other materials (paper, cardboard, wood, glass, metal, stones, etc.). 1.4% by weight based on total dry weight Apparent bulk mass 0.25 g/cm ³ (calculated according to the UNI EN ISO 61 procedure) Particle size 1.2 mm Physical form Small granules Humidity Less than 10% by weight

Accordingly, the thus obtained part of the plastic material, having a characteristic medium density, had the characteristics provided for in the UNI 10667-14 standard, so that it could be used as a mixture of recycled polymer materials and other materials such as aggregates, in cement mortars, in bitumen and in the asphalt.

Finally, the additive mixture is sent to a mixing hopper equipped with pneumatic recirculation for potential mixing with additional modifying compounds capable of imparting specific properties to the resulting additive mixture containing the additive composition of the present invention and the additional modifying compound. The resulting mixture of additives can be advantageously used as a modifying agent for road bitumen conglomerates.

Example 2: preparation of a mixture of bitumen conglomerate with an additive composition obtained according to the method proposed in the present invention.

This example relates to the evaluation of the characteristics of an additive in a bitumen conglomerate, and not to the production of the additive.

Using the additive composition according to example 1, an appropriate number of bitumen conglomerate briquettes with a diameter of 100 mm and a thickness of approximately 25 mm containing the proposed composition were prepared in the laboratory in accordance with the proportions of the ingredients indicated in the table below. 4.

Table 4

Materials Mass fraction Gravel as an inert component 12/20 25 Gravel as an inert component 6/12 35 Gravel as an inert component 3/6 10 Sand 0/4 25 Filler (CaCO3) 5 Bitumen 70/100 4.5 Additive composition 0.27 Total 104.77

Bitumen conglomerate containing all components according to the recipe given in table. 4 was prepared in the laboratory using the procedure described below using devices that functionally mimic the larger scale production equipment typically used in bitumen conglomerate production plants:

selection of the granulometric composition curve depending on the road surface that needs to be made using bitumen conglomerate, which is currently in the process of preparation;

selection of aggregates in accordance with the above-mentioned particle size distribution curve, in this case aggregates in accordance with table. 4, and heating the aggregates to a temperature of 170 to 180°C inside the mixer;

adding a suitable amount of the additive composition followed by mixing for 40 to 60 seconds to obtain a mixture;

adding a suitable amount of bitumen to the mixture, in this case the amount indicated in the table. 4, followed by stirring for at least 20 to 30 seconds;

adding a suitable amount of filler to the mixture, in this case the amount indicated in the table. 4, followed by mixing for at least 5 minutes (in accordance with EN 12697-35) to obtain a homogeneous mixture of bitumen conglomerate.

In particular, the mixture was maintained at a temperature of from 170 to 180°C during all stages of its processing.

The resulting bitumen conglomerate mixture was a single bitumen-based dispersing phase with a viscous appearance in which the fillers were homogeneously dispersed.

The resulting bitumen conglomerate mixture was then discharged from the mixer, dosed into containers in an amount of approximately 1210 g, and then conditioned in an oven at 150° C. for approximately 3 hours (conditioning was only used to simulate transport conditions).

The bitumen conglomerate thus obtained was then placed, after the oven conditioning step, inside the mold. Next, to ensure a relative void volume of approximately 2.5%, compaction was carried out using a rotary compactor (as an alternative to the rotary compactor, any other type of compactor suitable for this purpose can be used, for example, a Marshall compactor):

pressure created by load: 600 kPa;

rotation angle: 1.25°;

- 13 045643 maximum density: 2400 kg/m ³ .

A suitable number of briquettes were produced for mechanical testing; Finally, these briquettes were placed in climatic chambers for appropriate conditioning for mechanical testing.

Example 3: Carrying out mechanical tests.

This example relates to the evaluation of the characteristics of an additive in a bitumen conglomerate, and not to the production of the additive.

A suitable number of briquettes to obtain a reproducible result were respectively placed in a mechanical press of a special testing basket, then a tensile strength test was carried out in accordance with the UNIEN 12697-23 method.

The mechanical properties were studied by assessing the indirect tensile strength (ITS). ITS simulates the maximum stress generated by traffic that a road surface can withstand. Indirect tensile strength was assessed using the relative ITS parameter.

The average of the individual test results showed that the ITS (MPa) of the asphalt produced using the additive composition of the present invention fully met the requirements, was equal to or higher than that of the bitumen conglomerates produced using conventional additives.

After this, a test was carried out to determine the deformation modulus, which means the ability of bitumen conglomerates to distribute in the surface part of the road surface the load created on the road surface from the vehicle tire rut sections.

A suitable number of briquettes used to obtain a reproducible result were placed on a special stand of a servo-pneumatic dynamic test system, which in turn was located in a climate chamber for temperature control; then a test was carried out to determine the deformation modulus in accordance with the UNI EN 12697-26 method.

The test conditions used to determine the deformation modulus were as follows: temperature: variable;

applied deformation in horizontal direction: 5 µm;

peak time: 124 milliseconds (frequency 2 Hz);

Poisson's ratio: 0.35.

The average of the indicated individual test results showed that the modulus of deformation (MPa) of the samples at different temperatures (T=5°C, T=2O°C and T=4O°C) in relation to the conglomerate obtained using the additive composition according to the present invention, fully met the requirements, was equal to or higher compared to bitumen conglomerates obtained using conventional additives.

Thus, the tests described above have demonstrated the absolute effectiveness of the additive composition obtained by the method according to the present invention to obtain a mixture of bitumen conglomerate with high mechanical properties; The bitumen conglomerate thus obtained can be used to provide a stable and efficient road surface.

Claims (16)

1. A method for producing an additive composition intended for mixing with bitumen conglomerate, bitumen and bitumen products for road surfaces, including the following stages: a) providing mixed waste containing a mixture of plastic materials containing at least one plastic material based on a polyolefin thermoplastic polymer; b) grinding said mixed waste to achieve a particle size of 40 to 80 mm; c) washing the thus shredded mixed waste and separating in a controlled manner a portion of the plastic material having a characteristic medium density from said mixed waste, said portion of the plastic material comprising said at least one polyolefin thermoplastic polymer-based plastic material; d) grinding said portion of the plastic material having a characteristic average density to achieve a particle size of 10 to 20 mm; And e) mixing at room temperature the thus crushed portion of the plastic material having a characteristic medium density with a material based on polyvinyl butyral, and further grinding the mixture thus obtained to obtain a ready-to-use granular additive composition with a particle size of 4 to 6 mm and index melt flow from 1.0 g/10 min to 2.5 g/10 min, as determined according to the ISO 1133 procedure at a temperature of 190°C and a load of 2.16 kg; wherein said washing and separating step c) is carried out using a density separation method, thereby allowing a predetermined density limit value to be selected and a specified portion of the plastic material having a characteristic average density less than or equal to said predetermined limit value to be separated from said mixed waste value, wherein the indicated characteristic average density is less than or equal to 1.0 kg/m ³ as determined according to the procedure of DIN 55990. 2. Method according to claim 1, characterized in that in said step d) the particle size is from 12 to 15 mm. 3. Method according to claim 1 or 2, characterized in that at said stage e) the melt flow index is from 1.5 g/10 min to 2.5 g/10 min. 4. A method according to any of the previous claims, characterized in that in said step a) of providing mixed waste, said mixed waste contains solid residues made of plastic material, which are generated from municipal solid waste or as a result of industrial or handicraft production of products made from plastic material, or any combination thereof, wherein said solid residues are not recycled or recyclable in the plastic material recycling chain. 5. A method according to any of the previous paragraphs, characterized in that said mixed waste is first subjected to a preliminary separation step, during which possible fractions made from polyvinyl chloride and/or fractions made from unwanted materials such as paper, cardboard, wood are removed , fabrics, metal or glass. 6. A method according to any of the preceding claims, characterized in that in said grinding step b) after grinding, said mixed waste is subjected to a separation procedure for a metal fraction possibly contained therein, said separation procedure preferably comprising a first separation step using magnetic means and the second stage of separation of the metal fraction of non-ferrous metals. 7. Method according to any of the previous claims, characterized in that during said washing and separating step c) said characteristic average density is from 0.70 to 0.90 kg/m ³ as determined according to the DIN 55990 procedure. 8. The method according to any of the previous claims, characterized in that in said portion of the plastic material having a characteristic average density, said at least one plastic material is based on a polyolefin thermoplastic polymer selected from the group consisting of polyethylene, polyethylene copolymer, polypropylene , a polypropylene copolymer, or any mixture thereof, wherein said portion of the plastic material preferably contains said at least one plastic material in an amount greater than or equal to 75% by weight relative to its total weight, more preferably in an amount greater than or equal to 80% by weight relative to its total mass. 9. The method according to any of the previous claims, characterized in that in said washing and separating step c) a second mixture of plastic materials containing at least one plastic material based on a polyolefin thermoplastic polymer is added and mixed with said mixed waste, at wherein said second mixture preferably contains said at least one polyolefin thermoplastic polymer-based plastic material in an amount equal to at least 75% by weight relative to its total weight, more - 15 045643 more preferably in an amount equal to at least 80% by weight relative to its total weight. 10. A method according to any of the preceding claims, characterized in that said polyvinyl butyral material contains polyvinyl butyral in an amount greater than or equal to 80% by weight relative to the total weight of said polyvinyl butyral material. 11. A method as claimed in any one of the preceding claims, wherein said polyvinyl butyral material is a polyvinyl butyral recyclable material, wherein said polyvinyl butyral recyclable material is preferably derived from consumer waste, including automobile windshields, insulating glass units, window glass from heat-resistant glass, safety glass window panes, and/or obtained from industrially produced shavings in the manufacture of these products. 12. The method according to claim 10 or 11, characterized in that said polyvinyl butyral-based material is added to said portion of the plastic material having a characteristic density in an amount equal to 5 to 25% by weight relative to the weight of said portion of the plastic material, preferably equal to from 10 to 20% by weight relative to the weight of the specified part of the plastic material. 13. The method according to any of the previous claims, including the additional step of mixing said additive composition with a modifier, preferably selected from graphene, adhesion promoter, regenerating agent, plasticizer, lignin or any combination thereof, more preferably said modifier is of synthetic, mineral or plant origin. 14. The method according to any of the previous paragraphs, comprising the following additional steps: feeding said additive composition into an extruder, preferably a twin-screw extruder; heating said additive composition to a predetermined temperature; extruding and cooling said additive composition to obtain the additive composition in the form of extruded granules with a particle size of from 1.85 to 4.5 mm, preferably from 2 to 4 mm. 15. The method according to any one of claims 1 to 13, comprising the additional step of further grinding said additive composition to obtain the additive composition in the form of fine granules with a particle size of from 0.85 to 2.5 mm, preferably from 1 to 2 mm. 16. The method according to claim 15, including the following additional steps: dispensing a predetermined amount of said additive composition in the form of small granules and compressing it, wherein said predetermined amount of the additive composition is preferably from 10 to 20 g; applying to the additive composition thus compressed a film of a plastic material based on a thermoplastic polymer, wherein said plastic material is preferably polyethylene, thereby obtaining a capsule, wherein said dosing step preferably includes the step of adding a predetermined amount of a liquid modifier to said additive composition More preferably, said liquid modifier is selected from an adhesion promoter, a regenerating agent, a plasticizer, lignin, or any combination thereof.