WO2004113426A1

WO2004113426A1 - Process for improving the adhesion capacity of a natural and/or synthetic fiber material to a plastic material

Info

Publication number: WO2004113426A1
Application number: PCT/IT2004/000349
Authority: WO
Inventors: Paolo Canonico
Original assignee: M & H S.R.L
Priority date: 2003-06-20
Filing date: 2004-06-17
Publication date: 2004-12-29
Also published as: ITMI20031256A0; ITMI20031256A1

Abstract

A method for improving the adhesion capacity of a material in natural and/or synthetic fibre and a plastic material, in which the fibres are appropriately processed through exposure to cold plasma adapted to modify the surface chemical and physical characteristics of said fibre material.

Description

PROCESS FOR IMPROVING THE ADHESION CAPACITY OF A NATURAL AND/OR SYNTHETIC FIBER MATERIAL TO A PLASTIC MATERIAL

DESCRIPTION

The present invention relates to an industrial method for improving the adhesion capacity of a material in fibre of animal, plant, synthetic or artificial origin to a plastic material .

The traditional processing method adopted to obtain adhesion between two materials is based on the use of adhesives and glues of various natures, that act to attach the bonded parts through the binding and interfacing action performed by the surfaces of the two materials.

The adhesive action efficacy is increased if the surface is more carefully and more adequately prepared, generally demanding surface cleaning and abrasion, sometimes involving long and complex manual work.

Generally the adhesive substances are rich in various types of solvent, that have the dual function of increasing the fluidity of the product and lowering the surface tension to facilitate spreading and wetting of the surface to be glued.

The need for using products with low surface tension is determined by the fact that many materials, especially those of animal origin (wool, cashmere, etc) or synthetic origin such as polyethyleneterphthalate (PET) , polyamides (PA) , polypropylenes

(PP) , polytetrafluoroethylene (PTFE) , etc are characterised by the fact that they are water repellent and therefore not easily wettable by chemical products in liquid form, and subsequently difficult to glue.

Furthermore it is well known that certain adhesives are difficult to use and handle because of the presence of toxic solvents, that are dangerous for the health of the user, as well as being harmful for the environment in which the products are easily diffused because of their extremely volatile nature.

On the other hand water-based adhesives, characterised by higher surface tension, have lower adhesive properties and/or higher costs compared to solvent-based adhesives.

The technical task of the present invention is therefore to realise a method to improve the adhesive capacity of a material in natural and/or synthetic fibres to a plastic material that is able to eliminate the technical problems that arise with known state of the art.

Within the context of this technical task one scope of the invention is to realise a method to improve the adhesive capacity of a material in natural and/or synthetic fibres in order to avoid or limit the use of glues or adhesives in a manner that will eliminate the problems associated with said adhesives.

Another scope of the invention is to realise a method for improving the adhesive capacity of a material in natural and/or synthetic fibre that permits the preparation of the material adhesion surface in a manner so that its characteristics of wettability, hydrophily, and adhesion capacity result as being greatly improved.

The last but by no means least scope of the invention is to realise a method to improve the adhesion capacity of a material in natural and/or synthetic fibre that results as safe for the user and non-polluting for the environment.

The technical task, as well as these and other scopes, according to the present invention are achieved by realising a method for improving the adhesion capacity of a first material in natural and/or synthetic fibre to a second material in plastic, characterised by the fact that said first material in fibre is processed inside a reactor and subject to exposure to cold plasma adapted to modify the chemical-physical characteristics of the surface.

A surface physical modification caused by cold plasma processing consists in increasing the surface roughness of the first material to create a greater contact surface with the second material or with an adhesive applied between the first and second materials.

A chemical surface modification caused by cold plasma processing consists in implanting new chemical groups in the chemical structure of the surface of the first material to create new chemical bonds with the second material or with an adhesive applied between the first and second materials. Other characteristics of the present invention are defined below in the following claims.

Advantageously the method can be employed to realise multilayer structures having improved resistance to delamination, for example to realise at least one portion of a multi-layer conveyor belt, or a multi-layer item of clothing, or yet again, to realise at least a portion of a structure composed of a footwear item having improved adhesion capacity between the various parts.

Further characteristics and advantages of the invention will be made clearer from the description of various embodiments of said method provided for purely indicative but by no means, limitative purposes.

Cold plasma processing is an ecological surface modification process that basically provides an increase in the hydrophily and wettability, as well as an increase in the chemical reactivity of the surface of a first material subject to plasma processing, in order to strongly increase the physical and chemical compatibility with the surface of the second material to which the first material must adhere.

The processing occurs in a reactor under vacuum caused by the effect of an electromagnetic field using a gas and/or a mixture of gases (e.g: air, N_{2 r} 0₂ , Ar, He, NH₃ , C0₂ , etc) .

The material to be subjected to processing is exposed for a variable period of time ranging between a few seconds to several minutes, during which the rarefied gas inside the reaction chamber wherein an adequate vacuum level has been produced, is converted to plasma caused by the effect of the energy supplied by the electromagnetic field excited in a determined manner, that separates the plasma into atoms, electrons, ions, radicals, UV radiation and other strongly excited molecular and atomic species that attack the surface, modifying it, for a depth limited to the first molecular layers, both physically, sometimes with the consequential increase in the surface roughness, as well as chemically, through the insertion of new functional groups in the chemical structure of the processed surface.

Performing cold plasma processing therefore means subjecting the surface of the material for processing to physical attack by particles charged with excited gas, to a series of chemical reactions between the components of the chemical structure of the material to be processed, and the reactive species present in the plasma, as well as to irradiation by visible and ultraviolet rays.

As described above, all this activity generates a change in the surface physical-chemical characteristics of the processed fibre material.

The method is performed by exposing the surface to be processed to cold plasma, and in particular, by moving the surface to be processed inside a reactor wherein the plasma is generated.

Advantageously the functional activation of the processed surface of the first material with the consequential creation of active sites for the insertion of new chemical species inside the surface polymeric structure, is such that it creates new and stronger chemical bonds with the second material in contact with the first material, so that in certain cases the glues and adhesives traditionally employed are no longer necessary, and in other cases, the use of the adhesive is reduced considerably.

Furthermore, the characteristics of the surfaces obtained through cold plasma processing depend on the gas and the processing conditions applied, meaning the time of exposure to plasma, and the pressure and intensity of the electrode charge that generates the electromagnetic fields.

The installation used to activate this method is the "roll to roll" type equipment wherein the fibre material to be processed forms a strip that runs through the installation from one roll to another during processing.

An instalment of this type is formed by a tubular or parallelepiped reactor sized to accommodate the strip type material to be processed, the conveyor system, for example- one or more motor driven rollers adapted to pull the strip through the reactor, a pump to provide the required vacuum level inside the reactor, and a frequency generator to excite an electromagnetic field at high frequency through current charges between electrodes.

Plasma processing can be performed according to the following schematic description.

A strip of material in fibre to be processed is placed in the reactor, positioned on the unwinder roller.

The required vacuum level is generated inside the reactor, and maintained constant using the vacuum pump.

The required quantity of gas is introduced into the reactor.

The current generator is inserted, so that its electrodes excite the high frequency electromagnetic field to split up the gas that activates the physical-chemical processes homogeneously on the surfaces to be processed.

At this point the strip of fibre material is passed between the electrodes and rewound on the rewinder roller.

Once the plasma processing is completed, the current generator is disconnected, the reactor is returned to atmospheric pressure and the following strip of fibre material is introduced into the reactor for processing.

If necessary, the rotation direction of the winder rollers can be inverted one or several times so that the surface of the fibre material is subjected to the plasma processing one or more times.

With reference to the applications that will be described below, this processing can result as particularly advantageous in the^' clothing, footwear and conveyor belt sectors, due to the fact that it satisfies the need for strong long-lasting adhesion on one hand, and the elimination or limiting of the use of adhesives or glues, on the other.

EXAMPLE 1. Bonding of fabrics in the clothing sector.

In the clothing sector the bonding of fabrics with other fabrics or polymeric films of various natures is relatively recent. The polymeric films include polyurethane (PU) , polyethyleneterphtalate (PET) polytetrafluoroethylene (PTFE) , polyamides, (PA) etc. and confer new improved comfort and functionality properties to manufactured clothing items.

One of these examples is fabrics bonded with other fabrics such as wool and cotton, or linen and wool, or wool and polyester, etc.

The example of fabrics bonded with polymeric film are wool and PET , PU or PTFE membrane films, PA bonded with elastic PU film, PET-cotton bonded with PET or PU of PTFE membrane film, etc.

At present these bonded products have two defects that limit the diffusion on the market: low resistance to delamination, that provokes negative results in low duration characteristics, and difficulty in washing the clothing items, plus the rigidity of the fabrics obtained because of the very high adhesive content, that provokes negative results in low comfort and wearability levels, as well as on the appearance of the finished item.

In particular, the optimisation of the method for obtaining better adhesion of a PA fabric to a synthetic resin film, especially PU, will be described below.

The 100% PA cloth fabric, with 200 grams/m² is subject to plasma processing in the following conditions:

Gas : air

Pressure : 100 Pa

Fabric travel speed: 15 meters/minute, equal to an exposure of approximately 30 seconds.

Current discharge: 150 A.

For quantities over 30 meters of fabric, the PA fabric can be subject to dehumidification processing to prevent working pressure oscillation during the plasma processing.

The fabric processed in this manner presents increased surface roughness, easily noted under an atomic force microscope, and a modified surface chemical composition, identified through XPS analysis, as described below:

The increase in oxygen present on the surface that results in an increase in the O/C ratio from 0.17 to 0.24 is obvious, and the increase in nitrogen is also considerable. In particular, the introduction of new oxygen on the surface provokes the elimination of certain bonds (C-C and C-H) typical of the non-oxidised original material, and increases the presence of the oxidised groups, as shown below:

The physical-chemical variation introduced by the plasma processing generates a considerable increase in the PA hydrophily levels.

The initial contact angle of a drop of water with non- processed PA fabric results as 80° and the drop is absorbed very slowly, to the point that after 10 seconds the contact angle is still 30°, while the contact angle with plasma processed ' PA' has an initial value of 65° and descends to 20° after about only one second.

Therefore the hydrophily and wettability of the PA are strongly increased after plasma processing. In fact, a drop of water spreads and is absorbed totally within the fabric weave in a few seconds.

Once the fabric has been prepared as described above, the surface is coated with adhesive according to traditional methods (spotting, impregnation, spreading, transfer, etc) ; when the adhesive finds itself in contact with the surface that has a greater wettability capacity, it spreads immediately and penetrates in a uniform manner without the need for excessive quantities or strong pressure.

The PU film that is normally wrapped in a release agent paper, or that exits directly from the extruder, is bonded with the PA fabric at a certain pressure and temperature that guarantee the creation of bonding action between the adhesive and the surfaces with which they are in contact.

The presence of larger oxidised areas on the processed PA fabric surface guarantees stronger adhesion, greater resistance to washing, and longer life, as well as greater breathability and humidity transport.

In fact it was discovered that the resistance to delamination of the processed PA fabric was increased by approximately 100%, washing resistance increased by 70%, and the quantity- of adhesive necessary was reduced by approximately 50%.

In fabric bonding in the clothing sector, plasma processing can also be used to realise or improve humidity transport in order to create a breathable fabric, or to improve the transpiration levels for liquids or damp vapour, if already present.

In particular, it should be noted that cold plasma processing provides an increase in the properties for transferring liquids or humidity vapours from one surface to another in synthetic fabrics.

In this manner it is possible to realise clothing items with a hydrophily lining for example, even where realised in a partially or totally synthetic fabric.

By no means least, materials that are appropriately activated by cold plasma processing may also demonstrate an improvement in wettability and ink adhesion for printing purposes.

EXAMPLE 2.

Layer bonding in the conveyor belt sector.

Numerous types of conveyor belts exist for a wide variety of uses .

In this example, we will consider a multi-layer belt, composed of layers of materials of different nature, each one performing an appropriate function. The layers are laid on top of each other and are bonded to each other by means of an adhesive.

One of the main characteristics that determines the performance and duration of a conveyor belt is the quality of the adhesion between the various layers. The types of stress to which a conveyor belt must resist during its work life are mechanical and/or thermal, and/or chemical, and are of a level that often separate the various layers, thus terminating the life of the product in question.

The use of adhesive is advantageous thanks to the reduction of the final thickness that can be obtained for the product, and this also determines the reduction of differentiated tension inside^' the conveyor belt due to less inertia, thus providing longer product life.

A multilayer is composed of one or more layers of fabric and/or non-woven fabric, containing fibres of PET, PA, aramidic, para-amidic, PP, PE, cotton, glass etc. bonded with plastic materials of various natures such as PU, polyvinylchloride (PVC) PTFE, PP, PE, etc.

The bonding processes can vary, but they are mainly performed though hot melt, calendaring, transfer, coagulation, impregnation, etc.

It has been demonstrated that plasma processing makes the adhesion of PET and PU based plastic materials possible using hot melt processing without the need for adhesives.

In particular, the optimisation of the method, and that for obtaining improved adhesion of a PET sub-layer to a synthetic resin film, in particular, PU, will be described below.

A 100% PET cloth woven fabric , with 250 grams/m² , is subjected to plasma processing under the following conditions:

Gas : C0₂

Pressure : 100 Pa

Fabric travel speed: 5 meters/minute, equal to an exposure of approximately 80 seconds.

Current discharge: 150 A.

The fabric processed in this manner presents increased surface roughness, easily observed under an atomic force microscope, and a modified surface chemical composition, identified through XPS analysis, as described below:

The increase in oxygen present on the surface that results in an increase in the O/C ratio from 0.32 to 0.49 is obvious, and the increase in nitrogen is also considerable.

In particular, the introduction of new oxygen on the surface provokes the elimination of certain bonds (C-C and C-H) typical of the non-oxidised original material, and increases the presence of the oxidised groups, as shown below:

In particular, the carbon (C4) concentration due to the presence or carboxylic acid or ester groups is increased strongly, providing the material with new and greater hydrophylic and adhesive properties.

Furthermore, new bonds (C3) not present in the un-processed material are not identified. These bonds that produce carbonyls or other groups characterised by the fact that they create double bonds between the carbon and the oxygen, are typical of plasma processed PET using gases containing oxygen, and these are mainly due to a reactive mechanism of rearrangement and lattice cross linking of the polymeric chain surface caused by ionic bombardment and UV radiation.

The PET surface chemical composition is obviously modified after plasma processing.

The chemical-physical variation introduced by plasma processing generates a considerable increase in PET hydrophily.

The delamination resistance of PET fabric bonded with PU film through hot melting is defined as follows:

Delamination resistance without plasma processing or adhesive : 5N/Cm

Delamination resistance without plasma processing but with adhesive : 25N/Cm

Delamination resistance after plasma processing with- 0₂ ' gas and PET fabric travel speed of 10 meters/minute without adhesive : 21 N/Cm

Delamination resistance after plasma processing with 0₂ gas and PET fabric travel speed of 5meters/minute without adhesive : 26 N/Cm

Delamination resistance after plasma processing with C0₂ gas and PET fabric travel speed of 5meters/minute without adhesive : 31 N/Cm.

Results show that it is possible to exceed more than 20% of the reference value without plasma processing, but using a common adhesive, and over 600% of the reference value without plasma processing and the use of common adhesive.

Once more, in reference to conveyor belts, we will now examine a particular type composing the printing matrix of a printing roller adapted to apply printing ink.

The printing matrix has at least one layer composed of a PU based material that is cold plasma processed to obtain various e fects .

First of all, the exposed or external surface of the printing matrix can present a greatly improved wettability level due to the cold plasma processing.

Secondly, the exposed or external and/or the hidden or internal surface of the matrix can present greatly improved adhesion capacity due to the cold plasma processing.

These aspects are useful during the stage where the printing matrix is associated with its support and/or also in the case where the ends of the printing matrix strip wound on the printing roller need to be united.

Advantageously, if necessary the cold plasma processing can be realised so that it generates diversified roughness between the exposed surface and the hidden surface so that these are adapted to their different functions in optimal manner.

The PU based layer of the printing matrix on the printing roller has a thickness between 1 mm and 10 mm , and preferably between 0.5 mm and 0.7 mm, and this can be obtained through cold plasma processing, preferably in 0₂ gas, at a pressure of 60 Pa, current discharge of 180A, and a travel speed between 5 and 20 meters /minute, equal to an exposure rate of approximately 80 and 15 seconds.

EXAMPLE 3.

Adhesion between different footwear components.

Gluing is becoming much more common for attaching footwear components to replace stitching which is tending to disappear.

Whatever the destination sector of the footwear item, there are always various components that need to be glued, such as film, fabric, membrane, supports, reinforcing, soles, uppers, etc.

It is obvious that the problems concerning gluing and its resistance to various types of stress (fatigue, abrasion, damp, water, etc) are of fundamental importance.

In current processing, in order to guarantee good gluing results, very powerful adhesives are used and these require special care during application, as well as often needing long stabilising periods and lengthy work.

In certain cases the surfaces to be bonded require manual mechanical processing such as gauze application that take a good deal of time to create the essential roughness required for attaching the glue or the other product to be bonded.

The bonding of the two parts to be glued is performed by placing the pre-processed components in a mould. A liquid plastic product is then injected into the mould, solidifying as it comes into contact with the surface of the pre-processed element.

In other cases, such as toe puffs and counters/heel socks the textile product is impregnated with resin that provides it with the necessary rigidity and form required.

It has been discovered that, according to the present invention, it is possible to obtain adhesion levels between textile and para-textile products, single or multi-layer structures of various types (PA, PET, PP, PTFE, PE, aramidic, para-aramidic, cotton, etc.) with synthetic resins or another type, that are far higher than those obtained according to traditional methods.

Therefore plasma processing does not simply reduce or eliminate the use of adhesives, but can also increa-se 'the adhesion value.

Plasma ionic bombardment can be activated according to the conditions described in examples 1 and 2.

As well as modifying the surface from the PA and PET chemical point of view to create chemical bonds (ionic, co- valent, Van der Waals) between the parts in contact, the processing also alters the surface roughness of the processed material at nanometric level, creating a greater contact surface between the parts to be glued together, thus helping to provide a more uniform and more solid adhesion.

Naturally the increase in adhesion capacity can be useful in various other situations, for example, for the application on the cold plasma processed footwear component of a label, a membrane with special breathing properties or other characteristics, velcro closing strips, shoe laces or press- buttons, or even for better ink printing on the footwear item, etc.

Furthermore, the hydrophily and humidity transport properties of a footwear material processed using cold plasma, can be modified to obtain a shoe with at least one portion that can breathe, for example, at least the lining component of the shoe, and/or at least one portion of the upper, and/or at least one portion of the sole, and/or the half-sole, and/or the insole, and/or the toe-puff and/or the counter/heel sock of the shoe, even where said components are realised in synthetic material or in any case, originally not hydrophylic or with very little hydrophily.

The method conceived in this manner can be subject to numerous modifications and variants, all of which remain within the context of the inventive concept; furthermore, all details can be replaced with elements that are technically equivalent.

Claims

1. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre with a second material in plastic, characterised by the fact that said first fibre material is processed inside a reactor through exposure to cold plasma adapted to modify the chemical-physical surface characteristics .

2. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre with a second material, characterised by the fact that said first material is moved inside a reactor through exposure to cold plasma adapted to modify the chemical-physical surface characteristics.

3. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre with a ^• second material in plastic, according to one or more of the previous claims, characterised by the fact that a surface physical modification of said first material processed by said cold plasma processing consists in increasing the surface roughness of said first material to create a greater contact surface with said second material or with an adhesive applied between the said first and said second materials.

4. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre with a second material in plastic, according to one or more of the previous claims, characterised by the fact that a surface chemical modification of said first material processed by said cold plasma consists in inserting new chemical groups in the chemical structure of the surface of said first material in order to create new chemical bonds with said second material or with an adhesive applied between the said first and said second materials .

5. A method for improving the adhesion capacity of a first material to a second material according to one or more of the previous claims, characterised by the fact that said cold plasma processing is adapted to modify said surface chemical- physical characteristics of said first material in a manner to increase the wettability, hydrophily, breathability, and humidity transport of said first material.

6. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre according to one or more of the previous claims, characterised by the fact that said reactor inside which the said cold plasma processing occurs, operates under vacuum and the plasma is formed therein by a partially ionised gas, and maintained by the energy supplied by a high frequency electromagnetic field.

7. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre according to one or more of the previous claims, characterised by the fact the surface chemical-physical characteristics of said first material can be controlled by varying the nature of said gas and/or the pressure of said gas and/or the exposure time of said first material to the plasma and/or the discharged current that excites said electromagnetic field.

8. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre according to one or more of the previous claims, characterised by the fact said gas contains oxygen or hydrogen in a manner so that it creates oxidised chemical groups on the surface of the said first material or amino groups .

9. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre according to one or more of the previous claims, characterised by the fact that said gas is composed of air or C0₂ , or N₂ or 0₂ or Ar or He or NH₃ .

10. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre according to one or more of the previous claims, characterised by placing a strip of said fibre material to be processed inside a reactor between an unwinding roller and a rewinding roller, by generating the vacuum level required inside said reactor, by introducing a required quantity of said gas inside said reactor, by introducing a current generator that excites a high frequency electromagnetic field by means of electrodes to split up said gas, by activating the physical and chemical processes homogeneously on the surface to be processed on said strip, and by moving said strip between said electrodes by rewinding it on the said rewinder roller.

11. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre with a second material in plastic, according to claim 9, characterised by the fact that once the plasma processing has been terminated, said current generator is disconnected, said reactor is returned to atmospheric pressure, and the following strip of fibre material to be processed in then introduced into said reactor.

12. A method for improving the adhesion capacity of a first material in natural and/or synthetic fibre with a second material in plastic, according to claim 10, characterised by the fact that if the rotation direction of said rollers is inverted one or more times, the surface of said strip of material in fibre can be subjected to the plasma processing one or more times .

13. Equipment for the execution of a process compliant with one or more of the previous claims to improve the adhesion capacity of. a first material in natural and/or synthetic fibre with a second material in plastic, characterised by the fact that this includes a reactor inside which said first material in strip form is moved to travel between a winding roller and an unwinding roller, driving means for said material strip, a pump to maintain a certain vacuum level inside said reactor, and a current generator to excite said high frequency electromagnetic field able to transform the gas contained inside the said reactor into plasma.

14. Structure characterised by the fact that it is realised through a method adapted to improve the wettability and/or adhesion capacity of a first material in natural and/or synthetic fibre to a second material, said first material being processed inside a reactor through exposure to a cold plasma adapted to modify the surface chemical-physical characteristics.

15. Structure according to claim 14, characterised by the fact that it forms at least one portion of a conveyor belt.

16. Structure according to claim 15, characterised by the fact said conveyor belt is a printing matrix of a printing roller adapted to transfer printing ink, said printing matrix having at least one layer presenting said first material with a PU base.

17. Structure according to claim 16, characterised by the fact that said at least one layer presenting said PU based first material, presents opposite surfaces with diversified roughness to optimise the wettability with said ink on one hand, and on the other hand, the adhesion of said printing matrix with its support and/or with itself.

18. Multilayer structure of at least one portion of a conveyor belt according to claim 14, characterised by the fact that it includes said first material in PET and said second material in synthetic resin.

19. Multilayer structure according to claim 14, characterised by the fact that it forms at least one portion of a clothing item .

20. Multilayer structure according to claim 19, characterised by the fact that said clothing item includes at least a breathing lining presenting said first material.

21. Multilayer structure according to claim 19, characterised by the fact that it includes said first material in PA and said second material in synthetic resin.

22. Multilayer structure according to claim 21, characterised by the fact that said first material is subject to a dehumidifying processing to avoid working pressure oscillation during the plasma processing.

23. Structure according to claim 14 characterised by the fact that it forms at least one portion of a footwear item.

24. Structure according to claim 23, characterised by the fact that said first material is in the form of a textile or para-textile structure, in single or multilayers, and that said second material is in the form of a synthetic resin.

25. Structure according to claim 24, characterised by the fact that said first material is present in at least one breathing portion of a lining of said footwear item, and/or in at least one breathing portion of the upper of said footwear item, and/or in at least one breathing portion of the sole, and/or of the half-sole, and/or the toe-puff, and/or the counter/heel sock of said footwear item.

26. Mehtod and equipment for improving the adhesion capacity of a first material in natural and/or artificial fibre and a second plastic material according to the aforesaid claims and description.