“Low-bulk density aggregate of thermoformed composite materials”

DESCRIPTION

Technical field of the invention

The present invention relates to new materials based on highly bio- and eco-compatible low-bulk density aggregates of thermoformed composite material to be used in the packaging field as a valid alternative to expanded polystyrene (EPS) or as an impact energy absorber in applications such as personal protection, sports clothing or other industrial applications needing high energy absorption, as is the case with the automotive industry and transport.

State of the art

In the packaging field, attempts to develop new highly bio- and eco-compatible new materials as a valid alternative to expanded polystyrene (EPS) have been made for a long time.

Materials based on starch are becoming widespread, although they are compostable but not recy clable and also entail the risk their production may deprive agriculture of fertile soil.

To overcome these problems, hydrosoluble materials such as PVA (polyvinyl alcohol) or thermo plastic materials containing polyvinyl alcohol, which are soluble in water but not recyclable, are catch ing on.

In this context, there is still a strong need to implement new highly bio- and eco-compatible materials to be used in the packaging field, suitable to replace expanded polystyrene EPS and having similar, if not improved, mechanical properties compared to the latter or as an impact energy absorber in applications such as personal protection, sports clothing or other industrial applications needing high energy absorption, as is the case with the automotive industry and transport.

Overview of the invention

While carrying on research in the present technical field, the Applicants surprisingly and unexpect edly implemented a low-bulk density aggregate comprising one or more units of thermoformed com posite material definable as a discontinuous heap/discontinuous mass and/or crosslink of said one or more units of thermoformed material according to the present invention, said one or more units being partially aggregated on the surface between portions of it/partially aggregated on the surface between one another, said thermoformed composite material being a thermoformed composite ma terial comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cel lulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and water, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as az ides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydra- zide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said per centage being based on 1 00 parts by weight of the thermoformed composite material,

said one or more units of thermoformed composite material having an average section or average diameter between 1 .5 and 5 mm,

said aggregate having a bulk density, assessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delimited by the aggregate itself, between 0.05 and 0.89 g/cm ³ . Preferably said thermoformed composite material according to the present invention has a density between 0.4 and 1 .2 g/cm ³ .

Preferably said one or more unit of thermoformed composite material according to the present in vention are in the form of:

- filament/filaments having an average section between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm, and bestowing to the aggregate a bulk density, as sessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delim ited by the aggregate itself, preferably between 0.05 and 0.6 g/cm ³ , more preferably between 0.05 g/cm ³ and 0.3 g/cm ³ , said filament/filaments of thermoformed composite material according to the present invention being preferably aggregated to form a cohesive intertwining/mesh, preferably in the form of a ball or swallow's nest, or

- granules/flakes/particulate/spherules having an average diameter between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm, and bestowing to the aggregate a bulk density, assessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delimited by the aggregate itself, between 0.24 g/cm ³ and 0.89 g/cm ³ , preferably between 0.24 g/cm ³ and 0.59 g/cm ³ , even more preferably between 0.24 g/cm ³ and 0.44 g/cm ³ , most prefer ably between 0.27 g/cm ³ and 0.37 g/cm ³ .

A further object of the present invention is the proceeding for preparing a low-bulk density aggregate comprising one or more units of thermoformed composite material in the forms described above.

Brief description of the figures

Figure 1 represents an aggregate implemented with a large number of“short” filaments according to the present invention;

Figure 2 represents an aggregate implemented with three“long” filaments according to the present invention;

Figure 3 represents an aggregate comprising a single filament according to the present invention; Figure 4 shows the stress-strain curve of the aggregate comprising a single filament according to example 1 ;

Figure 5 shows the chart of the energy absorbed during the compression of the aggregate comprising a single filament according to example 1 ;

Figure 6 represents an aggregate according to the present invention comprising the filament accord ing to example 2;

Figure 7 shows the stress-strain curve of the three-dimensional aggregate comprising a single fila ment according to example 2;

Figure 8 shows the chart of the energy absorbed during the compression of the aggregate comprising a single filament according to example 2; Figures 9, 10 and 1 1 represent a kind of device useable in packaging and comprising low-bulk den sity aggregates implemented with filament/filaments of thermoformed composite material according to the present invention;

Figures 12 and 13 show the charts relating to the weight loss of low-bulk density aggregates com prising granules/flakes/particulate/spherules of thermoformed composite material according to the present invention as a result of water evaporation due to drying ;

Figure 14 shows a disk of low-bulk density aggregate comprising granules/flakes/particulate/spher ules of thermoformed composite material 60% (w/w) PVA + 40% (w/w) cellulose obtained without blowing agent;

Figure 15 shows a disk of low-bulk density aggregate comprising granules/flakes/particulate/spher ules of thermoformed composite material 60% (w/w) PVA + 40% (w/w) cellulose obtained with the addition of 2% (w/w) of blowing agent;

Figure 16 shows the chart relating to compression tests on (compacted) low-bulk density aggregates comprising granules/flakes/particulate/spherules of thermoformed composite material containing 50% (w/w) of cellulose compared with two massive samples of material with 50% (w/w) of cellulose fibres;

Figure 1 7 shows the chart relating to compression tests on low-bulk density aggregates comprising granules/flakes/particulate/spherules of thermoformed composite material containing 40% (w/w) of cellulose after several types of drying ;

Figure 1 8 shows the chart relating to compression tests on low-bulk density aggregates comprising granules/flakes/particulate/spherules of thermoformed composite material containing different per centages of cellulose fibres, ranging from 0 to 55% (w/w), after drying (aging) for 30 days at room temperature;

Figures 19 and 20 show the chart relating to compression tests on low-bulk density aggregates com prising granules/flakes/particulate/spherules of thermoformed composite material containing differ ent percentages of cellulose fibres, ranging from 0 to 40% (w/w), obtained from granules manufac tured with or without blowing agent, after drying (aging) for 5 hours at room temperature and 3 hours at 60°C, respectively;

Figures 21 - 24 show the semi-logarithmic and bi-logarithmic charts of the energy absorbed as a function of the stress applied for the low-bulk density aggregates comprising granules/flakes/partic ulate/spherules of thermoformed composite material containing different percentages of cellulose fibres, ranging from 0 to 40% (w/w), obtained from granules manufactured with [2% (w/w) of] or without blowing agent, after drying (aging) for 3 hours at 60°C;

Figure 25 shows low-bulk density aggregates comprising granules/flakes/particulate/spherules of thermoformed composite material consisting of 50% by weight of cellulose and 50% by weight of PVA, submitted to Head Injury Criteria (HIC) method.

Detailed description of the invention

The purpose of the present invention is therefore:

A low-bulk density aggregate comprising one or more units of thermoformed composite material comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer, wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cel lulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and water, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as az ides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydra- zide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said per centage being based on 1 00 parts by weight of the thermoformed composite material,

said one or more units of thermoformed composite material having an average section or average diameter between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm,

said aggregate having a bulk density, assessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delimited by the aggregate itself, between 0.05 and 0.89 g/cm ³ , preferably between 0.24 g/cm ³ and 0.59 g/cm ³ , even more preferably between 0.24 g/cm ³ and 0.44 g/cm ³ , most preferably between 0.27 g/cm ³ and 0.37 g/cm ³ .

“Low-bulk density aggregate comprising one or more units of thermoformed composite material” ac cording to the present invention is to be intended as a discontinuous cohesive heap/a discontinuous cohesive mass and/or a cohesive crosslink of said one or more units of thermoformed material ac cording to the present invention, said one or more units being partially aggregated in/on the surface between portions of it, in the case of one filament/partially aggregated in/on the surface between one another, in the case of two or more filaments/granules/flakes, said thermoformed composite material being a thermoformed composite material comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cel lulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and water, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as az ides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydra- zide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said per centage being based on 1 00 parts by weight of the thermoformed composite material,

said one or more units of thermoformed composite material having an average section or average diameter between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm.

said aggregate having a bulk density, assessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delimited by the aggregate itself, between 0.05 and 0.89 g/cm ³ , preferably between 0.24 g/cm ³ and 0.59 g/cm ³ , even more preferably between 0.24 g/cm ³ and 0.44 g/cm ³ , most preferably between 0.27 g/cm ³ and 0.37 g/cm ³ .

Preferably said thermoformed composite material according to the present invention has a bulk den sity between 0.4 and 1 .2 g/cm ³ , more preferably between 0.4 g/cm ³ and 0.8 g/cm ³ , even more pref erably between 0.4 g/cm ³ and 0.6 g/cm ³ .

Preferably said one or more unit of thermoformed composite material according to the present in vention are in the form of:

- filament/filaments having an average section between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm, and bestowing to the aggregate a bulk density, as sessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delim ited by the aggregate itself, preferably between 0.05 and 0.6 g/cm ³ , more preferably between 0.05 g/cm ³ and 0.3 g/cm ³ , said filament/filaments of thermoformed composite material according to the present invention being preferably aggregated to form a cohesive intertwining/mesh, preferably in the form of a ball or swallow's nest, or

- granules/flakes/particulate/spherules having an average diameter between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm, and bestowing to the aggregate a bulk density, assessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delimited by the aggregate itself, between 0.24 g/cm ³ and 0.89 g/cm ³ , preferably between 0.24 g/cm ³ and 0.59 g/cm ³ , even more preferably between 0.24 g/cm ³ and 0.44 g/cm ³ , most prefer ably between 0.27 g/cm ³ and 0.37 g/cm ³ .

In a preferred form of embodiment of the low-bulk density aggregate comprising one or more units of thermoformed composite material according to the present invention, as described above, in said thermoformed composite material the thermoplastic material comprising a hydrolisable or hydrosolu ble polyhydroxylated polymer is selected from: a thermoplastic material comprising starch or starch, or else a thermoplastic material comprising a polymer based on polyvinyl alcohol (PVA) or a polymer based on polyvinyl alcohol (PVA), more preferably selected from a thermoplastic material comprising a polymer based on polyvinyl alcohol (PVA) or a polymer based on polyvinyl alcohol (PVA), most preferably a polymer based on polyvinyl alcohol (PVA).

In a preferred form of embodiment of the low-bulk density aggregate comprising one or more units of thermoformed composite material according to the present invention, as described above, in said thermoformed composite material cellulose is in the form of cellulose fibres, preferably of micrometric size, even more preferably the cellulose is in the form of fibres having an average size not exceeding 70 micrometres, preferably not exceeding 45 micrometres.

A further preferred form of embodiment of the present invention is a low-bulk density aggregate comprising one or more units of thermoformed composite material comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cellulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydrox- ylated polymer,

- optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and wa ter, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as azides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydrazide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said percentage being based on 100 parts by weight of the thermoformed composite material, wherein said one or more units of thermoformed composite material according to the present inven tion are in the form of:

filament/filaments having an average section between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm, and bestowing to the aggregate a bulk density, as sessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delim ited by the aggregate itself, preferably between 0.05 and 0.6 g/cm ³ , more preferably between 0.05 g/cm ³ and 0.3 g/cm ³ , said thermoformed composite material according to the present invention hav ing a density preferably between 0.4 and 1 .2 g/cm ³ , more preferably between 0.4 g/cm ³ and 0.8 g/cm ³ , even more preferably between 0.4 g/cm ³ and 0.6 g/cm ³ .

A further preferred form of embodiment of the present invention is a low-bulk density aggregate comprising one or more units of thermoformed composite material comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cellulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydrox ylated polymer,

- optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and wa ter, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as azides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydrazide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said percentage being based on 100 parts by weight of the thermoformed composite material, wherein said one or more units of thermoformed composite material according to the present inven tion are in the form of:

granules/flakes/particulate/spherules having an average diameter between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm, and bestowing to the aggregate a bulk density, assessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delimited by the aggregate itself, between 0.24 g/cm ³ and 0.89 g/cm ³ , preferably between 0.24 g/cm ³ and 0.59 g/cm ³ , even more preferably between 0.24 g/cm ³ and 0.44 g/cm ³ , most prefer ably between 0.27 g/cm ³ and 0.37 g/cm ³ , said thermoformed composite material according to the present invention having a density preferably between 0.4 and 1 .2 g/cm ³ , more preferably between 0.4 g/cm ³ and 0.8 g/cm ³ , even more preferably between 0.4 g/cm ³ and 0.6 g/cm ³ .

A further purpose of the present invention is a proceeding for preparing a low-bulk density aggregate comprising one or more units of thermoformed composite material comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cellulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydrox ylated polymer,

- optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and wa ter, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as azides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydrazide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said percentage being based on 100 parts by weight of the thermoformed composite material, said one or more units of thermoformed composite material having an average section or average diameter between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm,

said aggregate having a bulk density, assessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delimited by the aggregate itself, between 0.05 and 0.89 g/cm ³ , preferably between 0.24 g/cm ³ and 0.59 g/cm ³ , even more preferably between 0.24 g/cm ³ and 0.44 g/cm ³ , most preferably between 0.27 g/cm ³ and 0.37 g/cm ³ ,

said thermoformed composite material according to the present invention having a bulk density pref erably between 0.4 and 1 .2 g/cm ³ , more preferably between 0.4 g/cm ³ and 0.8 g/cm ³ , even more preferably between 0.4 g/cm ³ and 0.6 g/cm ³ ,

said proceeding comprising the steps of:

a) providing said one or more units of thermoformed composite material, preferably said one or more units in the form of filament/filaments or granules/flakes/particulate/spherules;

b) mixing said one or more units of thermoformed composite material with water or with a solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch, said solvent or a hydroxylated solvent or a polar or non polar organic solvent, preferably water, water or said solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch being in an amount between one third and twice the weight of said one or more units of thermoformed composite material, preferably in an amount between half and once the weight of said one or more units of thermoformed composite material, until the surface of said one or more units of thermoformed composite material is wetted/im bibed/at least partially solubilised, thus achieving self-sticking properties to obtain a cohesive heap of said one or more units of thermoformed composite material; c) compacting/pressing/die-forming under atmosphere pressure or under higher-than-atmosphere pressure the cohesive heap of said one of more units of thermoformed composite material as ob tained in step b);

d) drying, also in an oven, to obtain an aggregate such as a discontinuous cohesive heap/a discon tinuous cohesive mass and/or a cohesive crosslink from the cohesive heap of said one or more units of thermoformed composite material as obtained in step c), preferably achieving a maximum volume including the empty spaces delimited by the aggregate itself, which is that delimited by the die.

A further purpose of the present invention is a proceeding for preparing a low-bulk density aggregate comprising one or more units of thermoformed composite material comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cellulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydrox ylated polymer,

- optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and wa ter, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as azides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydrazide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said percentage being based on 100 parts by weight of the thermoformed composite material, wherein said one or more units of thermoformed composite material according to the present inven tion are in the form of:

filament/filaments having an average section between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm, and bestowing to the aggregate a bulk density, as sessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delim ited by the aggregate itself, preferably between 0.05 and 0.6 g/cm ³ , more preferably between 0.05 g/cm ³ and 0.3 g/cm ³ ,

said thermoformed composite material according to the present invention having a density preferably between 0.4 and 1 .2 g/cm ³ , more preferably between 0.4 g/cm ³ and 0.8 g/cm ³ , even more preferably between 0.4 g/cm ³ and 0.6 g/cm ³ ,

said proceeding comprising the steps of:

a) providing said filament/filaments of thermoformed composite material;

b) mixing said filament/filaments of thermoformed composite material with water or with a solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch, said solvent or a hydroxylated solvent or a polar or non polar organic solvent, preferably water, water or said solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch being in an amount between one third and twice the weight of said filament/filaments of thermoformed composite material, preferably in an amount between half and once the weight of said filament/filaments of thermoformed composite ma terial and for a time between 15 minutes and 30 minutes, until the surface of said filament/filaments of thermoformed composite material is wetted/imbibed/at least partially solubilised, thus achieving self-sticking properties to obtain a cohesive heap of said filament/filaments of thermoformed compo site material;

c) compacting/pressing/die-forming under atmosphere pressure or under higher-than-atmosphere pressure the cohesive heap of said filament/filaments of thermoformed composite material as ob tained in step b);

d) drying, also in an oven, to obtain an aggregate such as a discontinuous cohesive heap/a discon tinuous cohesive mass and/or a cohesive crosslink from the cohesive heap of said filament/filaments of thermoformed composite material as obtained in step c), preferably achieving a maximum volume including the empty spaces delimited by the aggregate itself, which is that delimited by the die.

A further purpose of the present invention is a proceeding for preparing a low-bulk density aggregate comprising one or more units of thermoformed composite material comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cellulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydrox ylated polymer,

- optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and wa ter, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as azides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydrazide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said percentage being based on 100 parts by weight of the thermoformed composite material, wherein said one or more units of thermoformed composite material according to the present inven tion are in the form of:

granules/flakes/particulate/spherules having an average diameter between 1 and 5 mm, preferably between 1 .5 and 3 mm, more preferably between 1 .75 and 3 mm, and bestowing to the aggregate a bulk density, assessed as ratio of the mass of the aggregate to its volume, hence including the empty spaces delimited by the aggregate itself, between 0.24 g/cm ³ and 0.89 g/cm ³ , preferably between 0.24 g/cm ³ and 0.59 g/cm ³ , even more preferably between 0.24 g/cm ³ and 0.44 g/cm ³ , most prefer ably between 0.27 g/cm ³ and 0.37 g/cm ³ ,

said thermoformed composite material according to the present invention having a density preferably between 0.4 and 1 .2 g/cm ³ , more preferably between 0.4 g/cm ³ and 0.8 g/cm ³ , even more preferably between 0.4 g/cm ³ and 0.6 g/cm ³ ,

said proceeding comprising the steps of:

a) providing said granules/flakes/particulate/spherules of thermoformed composite material;

b) mixing said granules/flakes/particulate/spherules of thermoformed composite material with water or with a solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch, said solvent or a hydroxylated solvent or a polar or non polar organic solvent, preferably water, water or said solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch being in an amount between one third and twice the weight of said granules/flakes/particulate/spherules of thermoformed composite material, preferably in an amount between half and once the weight of said gran ules/flakes/particulate/spherules of thermoformed composite material until the surface of said gran ules/flakes/particulate/spherules of thermoformed composite material is wetted/imbibed/at least par tially solubilised, thus achieving self-sticking properties to obtain a cohesive heap of said gran ules/flakes/particulate/spherules of thermoformed composite material;

c) compacting/pressing/die-forming under atmosphere pressure or under higher-than-atmosphere pressure the cohesive heap of said granules/flakes/particulate/spherules of thermoformed composite material as obtained in step b);

d) drying, also in an oven, to obtain an aggregate such as a discontinuous cohesive heap/a discon tinuous cohesive mass and/or a cohesive crosslink from the cohesive heap of said gran ules/flakes/particulate/spherules of thermoformed composite material as obtained in step c), prefer ably achieving a maximum volume including the empty spaces delimited by the aggregate itself, which is that delimited by the die.

“Drying” in step d) of the proceedings according to the present invention is to be intended as any proceeding suitable to achieve evaporation of the water or solvent used to wet/imbibe/at least par tially solubilise said one or more units of thermoformed composite material, both at room temperature and at higher temperatures, also in oven or ventilated oven or through infrared radiation by exposition to IR lamps, at variable temperatures and times, such as for example: at room temperature for about 240 hours (about 10 days), at 130°C for about 2 hours, at 170°C for less than one hour. In particular, both filament/filaments and granules/flakes/particulate/spherules of thermoformed composite mate rial according to the present invention are generally heated at temperatures from 60°C to 180°C, preferably from 60°C to 160°C, more preferably from 60°C to 120°C, most preferably from 60°C to 80°C.

The processing times of step c) of compacting/pressing/die-forming under atmosphere pressure or under higher-than-atmosphere pressure of the proceedings according to the present invention de pend on the operating conditions wherein said step is performed: die size, nature of die material, atmosphere pressure or pressure higher than atmosphere pressure, ranging from a few minutes to tens of minutes to one or a few hours.

The low-bulk density aggregate comprising one or more units of thermoformed composite material according to the present invention and as described above is two- or three-dimensional and charac terised by mechanical properties such as:

- high energy absorption, that is high shock absorption, or

- high ability to absorb strain energy and reversible elastic recovery, that is easily adjustable ability to absorb energy (effect of energy dissipation)

representing an excellent alternative to expanded polystyrene in packaging.

In actual fact, the low-bulk density aggregate comprising one or more units of thermoformed compo site material according to the present invention features similar, if not improved, mechanical proper ties such as:

- high energy absorption, that is high shock absorption, or

- high ability to absorb strain energy and reversible elastic recovery, that is easily adjustable ability to absorb energy (effect of energy dissipation)

compared to expanded polystyrene, but, compared to the latter, the low-bulk density aggregate com prising one or more units of thermoformed composite material according to the present invention is totally biocompatible, since it is fully recyclable in the industry of paper/cardboard processing.

The expanded polystyrene used in packaging represents one of the main factors of pollution, partic ularly of the sea. This is because it is often not properly recycled and because it tends to crumble and is hence inevitably dispersed in the environment.

The material covered by the present invention, particularly low-bulk density aggregates implemented with filament/filaments of thermoformed composite material according to the present invention, may be a valid replacement from both an environmental and an economic standpoint.

This entails the exploitation of the elastic properties of the previously described and characterised aggregates based on filaments.

The ability of the thermoformed composite material according to the present invention to become self-sticking if wetted/imbibed/partially solubilised with water or with a solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch, said solvent or a hydroxylated solvent or a polar or non polar organic solvent, makes it possible to obtain aggregates with an absolutely innovative technology.

The technology (wetting/imbibing/partial solubilisation with water or with a solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch, said solvent or a hydroxylated solvent or a polar or non polar organic solvent, of one or more units of thermoformed composite material according to the present invention, followed by compacting in order to achieve the partial self-sticking in/of/on the surface of said one or more units and the following drying, also in an oven, so as to achieve an aggregate such as a discontinuous cohesive heap/a discontinuous cohesive mass and/or a cohesive crosslink of said one or more units of thermoformed composite material) can be used on one or more units of thermoformed composite material according to the present invention, said one or more units in the form of granules providing low-bulk density aggregates having partially compacted, high-en ergy absorbing structures which are suitable for packaging bur hardly able to be elastically deformed, hence tending to transfer forces to the objects they are supposed to protect, without absorbing them. The same technology can however be used also on one or more units of thermoformed composite material according to the present invention in the form of “short” or“long” filaments which, when wetted with water, become easily deformable and self-sticking, thus enabling, after the more or less forced introduction inside dies or receptacles of various shapes and the formation of bonds from several points of the filament as a result of self-adhesion, to obtain aggregates with a programmable low bulk density, once the volume to be filled is known and the weight of the material to be introduced based on the desired density is calculated.

“Short” filaments according to the present invention are to be intended as filaments being shorter than the component/device to be implemented comprising the low-bulk density aggregate of ther moformed composite material according to the present invention ;“long” filament/filament according to the present invention are to be intended as filament/filaments being considerably longer than the component to be implemented comprising the low-bulk density aggregate of thermoformed compo site material according to the present invention.

Both in the case of“short” and in the case of“long” filaments, the filament/filaments according to the present invention is/are not shorter than twice the average diameter of said filament/filaments.

The low-bulk density aggregate comprising one or more units of thermoformed composite material, when said one or more units are in the form of filament/filaments, has further considerable ad vantages:

- the obtained bulk density can be widely varied, for example from 0.05 to 0.30 g/cm ³ in the case of long filaments and from 0.20 to 0.30 g/cm ³ in the case of short filaments,

- the low density is useful not only in that it determines a low weight, but also in that it proportionally decreases the cost of the material,

- a real die is not required for forming, but a simple containing shape, to be implemented with prac tically any material, is sufficient,

- low-bulk density aggregates of filament/filaments of thermoformed composite material according to the present invention, formed in this manner, show a strongly and surprisingly elastic behaviour, which in the case of long filaments makes it possible to deform it through compression even to the extent of 95%, recovering in time most of the deformation without damaging the structure,

- the properties of the low-bulk density aggregate of one or more units of thermoformed composite material according to the present invention are related to the discontinuous and/or crosslinked struc ture of the obtained aggregate, also on account of the intrinsic properties of the thermoformed com posite material according to the present invention, a material which is hydrosoluble and hence self- sticking when contacting water or a solvent suitable to at least partially solubilise the polyvinyl alcohol or the starch, said hydroxylated solvent or a polar or non polar organic solvent, and which on account of said self-sticking property, as a result of its partial solubilisation, enables the partial aggregation in/on the surface of said one or more units between portions thereof in the case of a filament/partial aggregation on the surface between one another in the case of two or more filaments/aggregates, said partial aggregation in/on the surface of said one or more units being required to implement the technology covered by the present invention,

- aggregates implemented in this manner, as will be shown hereinafter, determine a robust structure, however characterised by high possibility of strain and reversible elastic recovery, warranting an easily adjustable ability to absorb energy, combining the length of the filaments and bulk density of the component.

This accounts for the interest in the combination of materials and technology, that is the low-bulk density aggregate and the relevant preparation proceedings, all covered by the present invention, for replacing expanded polystyrene in packaging, also owing to the recyclability of the thermoformed composite material in the paper/cardboard industry.

The developed technology (the proceeding for preparing low-bulk density aggregates of ther moformed composite material according to the present invention, such as for example compacting of filament/filaments or granules/flakes/particulate/spherules of thermoformed composite material according to the present invention after wetting with water) allows manufactured items with low den sity and high energy absorption ability to be produced.

The low-bulk density aggregates of thermoformed composite material according to the present in vention feature several important advantages compares to the eco-compatible materials used in the packaging field in terms of ability to absorb energy, density, cost per volume unit.

The use of a hydrosoluble (PVA) matrix loaded with cellulose fibre has considerable advantages in terms of eco-sustainability:

- it is manufactured by using cellulose fibre obtained from recycled paper, in a circular economy approach,

- it can be used for implementing“single-material” packaging, since it can be recycled with corru gated cardboard, thus solving the problems related to the use of expanded polystyrene.

The possibility to obtain complex shapes of items of the low-bulk density aggregate material accord ing to the present invention, by casting one or more units of thermoformed composite material ac cording to the present invention, such as filament/filaments or granules/flakes/particulate/spherules of thermoformed composite material according to the present invention wetted/imbibed/partially sol ubilised with water or solvent as described above, inside simple shapes (ideally made of cardboard submitted to hydrophobic treatment), as suitable receptacles or dies without the need for complex processing, may find varied applications, without disposal problems.

Particularly, in the case of low-bulk density aggregates comprising granules/flakes/particulate/spher ules of thermoformed composite material according to the present invention, the preparation pro ceeding shows the additional particular advantages briefly outlined below:

- the granules/flakes/particulate/spherules of thermoformed composite material are achieved through extrusion and following pelletisation from a thermoplastic blend or thermoformable compo site material according to the present invention, followed by

- wetting of the granules with an amount of water approximately equal to at least one third of the weight of the granules, followed by

- compacting of the granules (either manually or by filling a die or through casting in a die), for a time of no less than several tens of minutes, lastly followed by

- evaporation of excess water through drying at room temperature, through an aging which may require, also in relation with the thickness of the item, several week at room temperature, several hours at 60°C, several tens of minutes at 130°C or with the use of IR lamps.

SHAPING

A certain amount of granules is mixed with one third by weight of water for 15”, the paste can then be shaped, within about 1 hour since water addition, in a die or manually, acquiring a sufficient firm ness already after the first compacting. After water evaporation the material acquires high shock resistance.

The item obtained in this manner, after the evaporation of the water used to compact it, acquires an absolutely surprising shock resistance. In the case at issue, the item removed from the die and left in the open air for a few days was struck repeatedly and violently with a hammer and no fracture or strain occurred, hence showing high energy absorption ability.

CASTING IN CARDBOARD TEMPLATES

For the implementation of functional objects, for example for the implementation of single-material packagings, the granules, previously wetted with water, can be cast inside appropriate paper or card board templates (which may have been made hydrophobic through a surface treatment).

In this manner, after the evaporation of excess water, the granules steadily bind themselves both with one another and with the cardboard template, forming a single stiff and robust piece, recyclable with the external packaging of corrugated cardboard, solving the environmental problems which are currently connected with the use of expanded polystyrene in packaging. The thermoformed composite material according to the present invention is obtained by applying common hot-forming, or thermoforming, methods for thermoplastic materials, such as extrusion, in jection, drawing, pressure and vacuum moulding, rotational moulding, blow moulding or 3D printing, the thermoplastic composition comprising:

- cellulose, in combination with

- a thermoplastic material comprising a hydrolisable or hydrosoluble polyhydroxylated polymer,

- wherein cellulose is present in an amount between 30 and 60% by weight, preferably between 40 and 50% by weight, said percentage being based on 100 parts by weight of the combination of cellulose with the thermoplastic material comprising a hydrolisable or hydrosoluble polyhydrox ylated polymer,

optionally, a blowing agent selected from the group comprising physical blowing agents such as HCFCs, hydrocarbons such as pentane, isopentane, cyclopentane, liquid CO2, chemical blowing agents such as nitrogen compounds, azides, hydrazides, sodium bicarbonate, isocyanate and water, mixtures of said physical/chemical blowing agents, preferably chemical blowing agents such as az ides, hydrazides, more preferably hydrazides, most preferably p,p’-Oxy bis(Benzene Sulfonyl Hydra- zide), preferably in an amount between 0 and 6% by weight, preferably between 0.5 and 6% by weight, more preferably between 1 and 4% by weight, most preferably of 2% by weight, said per centage being based on 1 00 parts by weight of the thermoplastic composition.

The thermoformed composite material according to the present invention is obtained with or without a blowing agent as described in the present invention.

Both in the thermoformed composite material and in the thermoplastic composition according to the present invention, cellulose is present in an amount between 30 and 60% by weight, preferably be tween 40% and 50% by weight, such as in an amount of 30%, 35%, 40%, 45%, 50%, 55% or 60% by weight and corresponding ranges comprising them as ends, such as the following ranges of % by weight: 30 - 35%, 35 - 40%, 40 - 45%, 45 - 50%, 50 - 55%, 55 - 60%, 30 - 40%, 30- 45%, 30 - 50%, 30 - 55%, 35 - 45%, 35 - 50%, 35 - 55%, 35 - 60%, 40 - 50%, 40 - 55%, 45 - 55%, 45 - 60% or 50 - 60% by weight, particularly in an amount of 40% or 50% by weight, said percentages being based on 100 parts by weight of the combination of cellulose with the thermoplastic material com prising a hydrolisable or hydrosoluble polyhydroxylated polymer.

A thermoplastic material comprising a hydrosoluble polymer based on polyvinyl alcohol according to the present invention is to be intended as a plastic material which is well-known in the art and easily available on the market, such as for example the polyvinyl alcohol PVA marketed as HYDROLENE®, whose possible forms have long been described in patent literature, such as for example the ther moplastic material comprising a hydrosoluble polymer based on polyvinyl alcohol as described in Italian patent No. 1 140 254 and in the corresponding European patent No. EP 122 337 wherein the polyvinyl alcohol, in combination with one or more polyhydroxylated alcohol monomers, preferably selected from those having at least three primary alcohol functional groups per mole, shows the main melting peak, determined through DTA (differential thermal analysis), between 1 60°C and 230°C, and preferably the polyvinyl alcohol has a degree of hydrolysis exceeding 70%, expressed as molar fraction, and a degree of polymerization between 500 and 2500.

A further example of thermoplastic material according to the present invention is the thermoplastic material comprising hydrosoluble polymers based on polyvinyl alcohol as described in Italian patent No. 1 275 860, wherein the material described in Italian patent No. 1 140 254 is characterised by a polyvinyl alcohol with a degree of polymerization exceeding 500 and a degree of hydrolysis of at least 70 and containing a maximum of 20% by weight of one or more low-freezing point liquid aliphatic polyhydroxy alcohols, compared to the polyvinyl alcohol.

A further example of thermoplastic material according to the present invention is the thermoplastic material comprising hydrosoluble polymers based on polyvinyl alcohol as described in patent appli cation WO 2013 /069037, where the thermoplastic material comprises a poly (vinyl alcohol) having a middle-low molecular weight, with a molecular weight preferably between 12000 and 200000Da and more preferably between 15000 and 140000Da, with a dynamic viscosity in 4% aqueous solution of less than 10mPaS (as measured by a viscometer Brookfield) at a temperature of 20 °C (DIN 5301 5), and is characterised by a degree of hydrolysis preferably between 70 and 99% and more preferably between 75 and 90% (even more preferably between 80 and 88%).

Starch according to the present invention is to be intended as both starch originated from food source such as maize, potato, rice, tapioca, wheat or legume starch and any other kind of starch to be found on the market, generally consisting for about 20 - 30% of amylose and for about 70 - 80% of amylo- pectin.

It may also be intended as a starch consisting of a higher percentage up to 90% of amylose, char acterised by improved properties of extrudability and higher dimensional stability compared to tradi tional starch.

Cellulose according to the present invention is to be intended as a polysaccharide whose long linear chains are formed only by units of b-D-glucose, joined to one another by a glycosidic bond b(1 ®4). The average molecular mass is about 500 000 u, but there are chains with higher molecular mass, up to two million.

The term“thermoforming” or“hot-forming”, which are equivalent to each other, are to be intended according to the present invention as all the known methods for forming thermoplastic materials, such as extrusion, injection, drawing, pressure and vacuum moulding, rotational moulding, blow moulding or 3D printing.

The term“thermoformed” or“hot-formed”, which are equivalent to each other, are to be intended according to the present invention as a thermoplastic composite material obtained by submitting the thermoplastic composition according to the present invention to the known methods for forming ther moplastic materials, such as extrusion, injection, drawing, pressure and vacuum moulding, rotational moulding, blow moulding or 3D printing.

“Providing said one or more units of thermoformed composite material” according to the present invention as step a) of the proceedings according to the present invention is to be intended particu larly as the production of said one or more units of thermoformed composite material, as described in the present invention, wherein said one or more units is/are produced for example in the form of filament/filaments or granules/flakes/particulate/spherules, at the time when the thermoformed com posite material as described herein is produced through thermoforming or hot-forming, as described herein, or as described more generally in Italian patent No. IT 102015000028276, also in the name of the Applicants.

Said one or more units of thermoformed composite material according to the present invention, both in the form of filament/filaments and in the form of granules/flakes/particulate/spherules, are obtained through the common methods for hot-forming, or thermoforming, thermoplastic materials, such as: extrusion, injection, drawing, pelletisation of filaments by rotating blade and so on, such as those described in patent application WO 2016/207849.

Particularly, for example in the case of extrusion/injection/drawing of filament/filaments, the average section of the filament/filaments is due to the average value of the diameter of the nozzle of the extruder/injector/drawbench from which the filament/filaments is/are obtained. In the case of gran ules/flakes/particulate/spherules, the size of the diameter is due to the average value of the diameter of the nozzle of the extruder/injector/drawbench and, particularly with the pelletisation, the length is due to the rotational speed of the rotating blade cutting the granules/flakes/particulate/spherules. EXAMPLES

Unless specified otherwise, the percentages (%) are to be intended as % w/w weight by weight

LOW-BULK DENSITY AGGREGATES COMPRISING FILAMENT/FILAMENTS OF THER- MOFORMED COMPOSITE MATERIAL

Preparation of the thermoformed composite material in the form of filament/filaments

A solid thermoplastic composition according to the present invention, comprising micrometric cellu lose fibre combined with an amount of a thermoplastic material comprising a polymer based on pow der polyvinyl alcohol, was prepared so as to obtain a composition comprising the combination cellu lose fibre - polymer based on polyvinyl alcohol containing 40% by weight of cellulose fibre.

The composition was submitted to ordinary blending in order to have a uniform dispersion of the two relevant components.

The solid mixture thus obtained was extruded by a screw extruder to achieve filaments with a diam eter of 1 .75 and 3 mm (operating conditions: Temp.: 140 - 190 °C, throughput 31 g/min, rotations per minute: 150) and variable length.

Preparation of low-bulk density aggregates comprising filament/filaments of thermoformed composite material

Figure 1 shows an aggregate implemented with a large number of“short” filaments having a diameter of 1 .75 mm and being shorter than the implemented aggregate.

The space filling is comparatively high and the aggregate, having a diameter of 125 mm and a height of 25 mm, weighs 85 g, with a consequent bulk density of 0.28 g/cm ³ .

Based on its structure, it may be expected that the aggregate thus obtained is characterised by a comparatively high resistance, but with limited possibility of strain and elastic recovery after com pression.

Figure 2 shows an aggregate implemented with three“long” filaments having a diameter of 1 .75 mm and being longer than the piece to be implemented. The space filling is low and the aggregate, having a diameter of 290 mm and a height of 60 mm, weighs 190 g, with a consequent bulk density of 0.073 g/cm ³ .

Based on its structure, it may be expected that the aggregate thus obtained is characterised by a comparatively low resistance, but with high possibility of strain and elastic recovery after compres sion.

Example 1

A filament of the thermoformed composite material according to the present invention, having a di ameter of 1 .75 mm and an overall weight of 7.1 g, was immersed in water for 30”, removed from water and introduced inside a cylinder with an inner diameter of 41 mm and a height of 20 mm, forming a three-dimensional aggregate structure having a bulk density of 0.27 g/cm ³ . After about 1 minute, the filament shaped in this manner was put in an oven at 60°C for 2 hours. The picture of the aggregate comprising a single filament according to the present invention is shown in Figure 3. Compression tests of the three-dimensional aggregate comprising a single filament of example 1

The three-dimensional aggregate comprising a single filament according to example 1 was submitted to a compression test at a speed of the moving crosspiece of 0.15 mm/second, up to the aggregate thickness of 5 mm (corresponding to a 75% strain).

The movement of the crosspiece was then reversed to bring the crosspiece back to its starting posi tion.

Figure 4 shows the stress-strain curve of the aggregate comprising a single filament according to example 1 , obtained by dividing the force by the rated section of the specimen. Said curve was then integrated to calculate the energy absorbed during the compression of the aggregate comprising a single filament according to example 1 , as shown in Figure 5.

It was observed that during unloading the aggregate comprising a single filament according to ex ample 1 experienced elastic recovery, which continued in time up to the recovery of 58.4% of the strain, with a residual strain of 16.6%.

The aggregate comprising a single filament according to example 1 was then submitted to a new compression test under the same conditions described above and in this case as well the ability of the specimen to absorb strain energy was tested: the strain turned out to be mostly recovered in a spontaneous manner at the end of the test.

Example 2

A filament of the thermoformed composite material according to the present invention, having a di ameter of 1 .75 mm and an overall weight of 16.2 g, was immersed in water for 30”, removed from water and introduced inside a cylinder with an inner diameter of 78 mm and a height of 34 mm, forming a three-dimensional aggregate structure having a bulk density of 0.1 g/cm ³ .

After about 1 minute, the filament shaped in this manner was put in an oven at 60°C for 2 hours. The picture of the aggregate according to the present invention comprising the filament according to ex ample 2 is shown in Figure 6.

Compression tests of the three-dimensional aggregate comprising a single filament of example 2

The three-dimensional aggregate comprising a single filament according to example 2 was submitted to a compression test at a speed of the moving crosspiece of 0.15 mm/second, up to the aggregate thickness of 1 .5 mm (corresponding to a 96% strain).

The movement of the crosspiece was then reversed to bring the crosspiece back to its starting posi tion.

Figure 7 shows the stress-strain curve of the three-dimensional aggregate comprising a single fila ment according to example 2, obtained by dividing the force by the rated section of the specimen. Said curve was then integrated to calculate the energy absorbed during the compression of the ag gregate comprising a single filament according to example 2, as shown in Figure 8.

It was observed that during unloading the three-dimensional aggregate comprising a single filament according to example 2 experienced elastic recovery, which continued in time up to the recovery of 86% of the strain, with a residual strain of 10%.

The three-dimensional aggregate comprising a single filament according to example 2 was then sub mitted to a new compression test under the same conditions described above and in this case as well the ability of the aggregate to absorb strain energy was tested: the deformation turned out to be mostly recovered in a spontaneous manner at the end of the test.

Example 3

A possible, although not the only one, type of device useable in packaging and comprising low-bulk density aggregates implemented with filament/filaments of thermoformed composite material accord ing to the present invention can consist of:

- a low-thickness band implemented with bulk density and distribution of the filaments suitable to be folded up to 180°, having a length comparable to that of the packaging, typically of corrugated cardboard, which is meant to be used therewith

- two high-thickness disks implemented with variable bulk density depending on the forces which are expected to be absorbed,

as shown in Figures 9, 10. For optimal use, the packaging implemented in this manner should be folded 180° and introduced inside the, as shown in Figure 1 1 .

LOW-BULK DENSITY AGGREGATES COMPRISING GRANULES/FLAKES/PARTICULATE/SPHERULES OF THERMOFORMED COMPOSITE MATERIAL

When mentioned, the blowing agent is to be intended as p,p’-Oxy bis(Benzene Sulfonyl Hydrazide).

Preparation of the thermoformed composite material in the form of granules/flakes/particulate/spherules, optionally comprising a blowing agent/optionally expanded by a blowing agent

Various solid thermoplastic compositions according to the present invention, comprising micrometric cellulose fibre, combined, from time to time, with different amounts of powder polyvinyl alcohol (PVA), were prepared so as to obtain compositions comprising the combination cellulose fibre - polyvinyl alcohol containing various percentages by weight of cellulose fibre: 40% or 30% by weight of cellu lose fibre.

In the case of expanded granules, a thermoformed composite material in the form of expanded gran ules was produced before compacting said expanded granules by wetting them with water, in order to decrease weight and cost per volume unit, also assuming to increase the ability to absorb strain energy. To optimise expansion, the starting blend consisted of a powder blend (dry blend) 70% PVA + 30% cellulose microfibres (% by weight); variable percentages of a particular type of blowing agent ranging between 2 and 6% of the blend (PVA + cellulose) were then added.

Obviously other kinds of blowing agents or other expanding technologies might be used. The blends PVA + cellulose + possible blowing agent were extruded into filaments having a rated diameter of 3 mm and granulated into pellets having a length of about 3 mm (operating conditions: Temp.: 140 - 190 °C, throughput 31 g/min, rotations per minute: 150). The granule weight was then measured in a receptacle having a volume of 1 10 cm ³ .

The results are shown in Table 1 . Table 1

It could be concluded that:

- the addition of a blowing agent is most effective at a percentage of 2%, effectiveness decreasing for lower (1 %) and higher (4 and 6%) percentages,

- this apparently unpredictable behaviour can be accounted for in that small percentages of blowing agent tend to form a large number of small-sized air bubbles, whereas higher percentages of blow ing agents tend to form a lower number of large-sized air bubbles.

2% of blowing agent was then used for PVA 100% and a blend 60% PVA + 40% cellulose. A test was also performed with a blend 50% PVA + 50% cellulose, which gave no positive outcome, since in order to extrude said blend it is necessary to increase the extruder’s temperature over 170°C, which is the limit for the stability of the used blowing agent. This problem might be solved by using other blowing agents. Table 2 shows the features of the granules produced for later experimenting. Table 2

EVAPORATION TIMES OF THE ADDED WATER

The water added to wet the granules progressively evaporates, solidifying the material.

Tests of weight loss were performed, whose results are shown in Figure 12.

The tests proved that water evaporation occurs at room temperature in about 240 hours (about 10 days), at 130°C in about 2 hours and at 170°C in less than an hour.

It can also be remarked that in the event of high-temperature drying the weight of the compacted granules decreases compared to the starting weight, because the moisture which is however present in the granules is also removed, to be then slowly recovered at room temperature in about 48 hours (Figure 13).

Alternatively, the granules can be dried through heating by IR lamps.

Figures 14 and 15 show the pictures of disks obtained by compacting after wetting with water and following drying, having a diameter of 101 mm and a height of 36 mm. Figure 14 shows the disk of low-bulk density aggregate comprising granules/flakes/particulate/spher ules of thermoformed composite material 60% PVA + 40% cellulose, obtained without expansion, whereas Figure 15 shows a disk of low-bulk density aggregate comprising granules/flakes/particu late/spherules of thermoformed composite material 60% PVA + 40% cellulose, obtained with the addition of 2% of blowing agent.

COMPRESSION TESTS

As can be seen in Figures 14 and 15, the macrostructure of the low-bulk density aggregate compris ing granules of thermoformed composite material according to the present invention is similar to that of expanded polystyrene, a material which is known to be able to absorb shocks.

The porous structure of the low-bulk density aggregate comprising granules/flakes/particulate/spher ules of thermoformed composite material according to the present invention is actually able to absorb a lot of energy during compression strain on account of a“peak load” effect connected with the aggregate structure (a discontinuous cohesive heap/a discontinuous cohesive mass/a cohesive crosslink), as well as with the granular form. It can be assumed that the structure of the low-bulk density aggregate comprising granules/flakes/particulate/spherules of thermoformed composite ma terial according to the present invention, obtained through compacting and following drying of the wetted granules is close to the mechanical behaviour of expanded foams.

In order to quantitatively assess these assumptions, compression tests were performed on a wide range of disks having a diameter of 15 mm and a height of 10 mm.

The disks were submitted to compression tests at an imposed speed of 0.15 mm/s, up to a 90% strain, so as to achieve specimens with a final thickness of 1 mm.

The results of the performed tests, grouped as a function of the various purposes of the different tests, are described below.

1. Comparison between massive material and compacted material (aggregate according to the present invention)

Firstly, tests were performed on two massive samples of material with 50% of cellulose fibres and a sample of low-bulk density aggregate according to the present invention of a material with the same percentage of cellulose, obtained by compacting granules after wetting them with water and drying them (aging) for 30 days at room temperature. Massive material is to be intended as a material having the same composition in % by weight of cellulose of PVA, but with a continuous mass, not in the form of an aggregate of granules joined to one another on a portion of their surface, as in the present invention.

The results are shown in the chart of Figure 16.

As can be noted, the mechanical behaviour of the compacted material does not change considerably compared to the massive material, confirming that compacting of the granules by wetting them with water is very effective for the formation of various components.

2. Effect of drying (aging) time

As previously pointed out, after compacting the granules by wetting them with water, the material is at first plasticised on account of the presence of residual water and tends to become stiff in time, as water evaporates owing to aging.

In order to assess the times which bring to the structure stiffening, compression tests were performed on specimens containing 40% of cellulose after several kinds of drying. The results are shown in Figure 17.

As can be observed, stationary conditions are achieved after several days at room temperature or a few hours at 60°C.

It is however obvious that the drying (aging) time depends on the thickness of the material and must be optimised on a case-by-case basis.

3. Effect of the percentage of cellulose

In order to test the effect of the percentage of cellulose, compression tests were performed on spec imens with different percentages of cellulose fibre, ranging from 0 to 55%, after drying (aging) for 30 days at room temperature. The results are shown in Figure 18.

As can be seen from the results shown in Figure 18, the increase of the percentage of cellulose determines a considerable increase of the mechanical compression properties of the material, also in terms of stiffness of the material, with a fivefold increase of the initial inclination of the stress-strain curves.

4. Effect of the addition of a blowing agent

As previously pointed out, the possibility to expand the granules by adding an optimal 2% of a com mercial blowing agent to the blend of starting powders was tested.

Compositions of 100% PVA/0% cellulose, 70% PV A/30% cellulose and 60% PVA/40% cellulose were expanded. Specimens obtained from granules produced with and without blowing agent were submitted to compression tests. The results are shown in Figures 19 and 20.

The addition of a blowing agent, although decreasing the bulk density of the material, determines a significant increase of the mechanical properties of the material.

This occurs both during drying (aging) of the material (5 days at 25°C) and, above all, at the conclu sion of drying (aging) (3 hours at 60°C).

5. Ability to absorb strain energy

The stress-strain curves can be integrated in order to calculate the absorbed energy as a function of the applied stress (i.e., assess the toughness of the materials). This was done on the specimens of the low-bulk density aggregates comprising granules/flakes/particulate/spherules of thermoformed composite material with 0, 30 and 40% of cellulose, without and with the addition of 2% of blowing agent.

The results are shown in Figures 21 , 22, 23 and 24, on both a semi-logarithmic and a bi-logarithmic scale.

It is plain to see that with cellulose percentages of 30 and 40% the ability to absorb energy of the expanded material, compacted with water and dried for 3 hours at 60°C, is significantly higher than that of the corresponding unexpanded materials.

HEAD INJURY CRITERIA TESTS

In order to assess the exceptional ability to absorb energy, expressed in Joule (J), of the material, tests based on the Head Injury Criteria (HIC) method were used, assessing the probability of head injuries resulting from an impact and usable to assess the safety of vehicles, personal protection equipment and sports outfit. Normally the value results from the measurements taken by an accel erometer mounted at the centre of the head of a crash test dummy, when the dummy is exposed to crash forces. The HIC takes into account the effects of the acceleration of the head and the duration of the acceleration. Considerable accelerations may be tolerated for very short times. A HIC of 1000 corresponds to an 18% probability of a serious head trauma, a 55% probability of a serious injury and a 90% probability of a moderate head damage for an average adult. In order to accomplish the tests, granules of thermoformed composite material according to the present invention were aggre gated to form disks having a diameter of 100 mm and a height of 35 mm, in compliance with ASTM 1621 -73 (Standard Test Method for Compressive Properties of Rigid Cellular Plastics). The speci mens were submitted to the following heat treatments: none (25°C), 80°C for 30’, 120°C for 30’, 160°C for 30’. Said disks, all of thermoformed composite material consisting of 50% by weight of cellulose and 50% by weight of PVA, were submitted to the following heat treatments: none (25°C), 80°C for 30’, 120°C for 30’, 160°C for 30’, so as obtain the low-bulk density aggregates comprising granules/flakes/particulate/spherules of thermoformed composite material consisting of 50% by weight of cellulose and 50% by weight of PVA, as shown in Figure 25.

A drop tower obtained from a "chin guard" in compliance with standards BS6658 and SNELLM2000 was used and the transducer was placed at the centre of the support. The low-bulk density aggre gates comprising granules/flakes/particulate/spherules of thermoformed composite material accord ing to the present invention are placed in a shaped compartment having a depth of 4 mm and a hemispherical drop hammer having a radius of 50 mm, with a mass of 5,1 10 g was dropped on each aggregate from a height of 2 metres. The system is able to detect acceleration, the times T1 and T2 (duration in msec o ms (milliseconds) of the time by which acceleration (g) exceeds 150 and 200 g, respectively), the maximum crushing and the permanent crushing experienced by the specimen. Based on the accomplished surveys, the HIC is then calculated in accordance with the following formula:

The results are shown in Table 3.

A specimen of high-density expanded polystyrene (EPS) was also tested for comparison.

Table 3

For the above tested materials, PSAs and various aggregates, the relevant densities, expressed in grams/litre (g/l), are also specified. As can be seen, against an impact speed of about 6 m/s and an energy of nearly 100 Joule, the low-bulk density aggregate comprising granules/flakes/particu late/spherules of thermoformed composite material according to the present invention experiences a considerable acceleration (twice as much as a high-density expanded polystyrene), with a very low permanent deformation (2-3 mm against more than 20 mm for EPS).

The low-bulk density aggregate comprising granules/flakes/particulate/spherules of thermoformed composite material according to the present invention is accordingly able to stand without breaking and with small residual strains a HIC value which is three times that endured by a human head. It can accordingly be applied wherever there is the need to absorb large amounts of energy.

It can also be noted that the solidification achieved as a result of drying at room temperature or at high temperatures do not determine variations in shock resistance.