WO2016009388A1

WO2016009388A1 - Bituminous membrane and method to make a bituminous membrane

Info

Publication number: WO2016009388A1
Application number: PCT/IB2015/055401
Authority: WO
Inventors: Antonio Fornasier; Alessandro Pavan
Original assignee: Euroline S.R.L.
Priority date: 2014-07-16
Filing date: 2015-07-16
Publication date: 2016-01-21
Also published as: DE212015000180U1

Abstract

A method to make a bituminous membrane (1) comprising the steps of performing a membrane (1), which extends along a longitudinal reference axis (A) and comprises a central supporting layer (2) arranged between at least a first (4) and a second bituminous layer (3) opposite to each other, making on the first bituminous layer (4) a first longitudinal portion (7), which extends parallel to the axis (A) and has a first thickness (SI), and a second longitudinal portion (8), which extends parallel to said axis (A) by the side of the first longitudinal portion (8) and has a second thickness (S2) which is smaller than the first thickness (SI), coating the surface of the second portion (8) by means of a granular coating material so as to make a surface coating layer (9) of the membrane (1) which extends by the side of the first longitudinal portion (7) and has a third predetermined thickness (S3).

Description

BITUMINOUS MEMBRANE AND METHOD TO MAKE A BITUMINOUS MEMBRANE

TECHNICAL FIELD

The present invention relates to a bituminous membrane and to a method to make the membrane itself.

In particular, the present invention relates to a ribbon- shaped/laminated sheath or membrane made using a mix or compound based on "modified bitumen", which can be advantageously applied in the building sector for making waterproofing and/or sealing layers preferably, though not necessarily for covering roofs and/or any parts of building structures; to which the description below will explicitly refer without loss of generality.

BACKGROUND ART

It is known that the ribbon-shaped bituminous membranes mentioned above are generally wound in rolls and have a multi^¬ layer structure comprising: a central supporting layer which is made by means of a film of flexible material trapped between an upper bituminous layer and a lower bituminous layer made by means of a modified-bitumen based mix and forming the flat upper face and, respectively, the lower face of the membrane .

The upper face of some mentioned-above bituminous membranes is partially covered by an additional granular layer, i.e. made of mineral granules, and has laterally to the granular layer, an uncovered smooth, i.e. not covered by the granules, rectilinear surface strip or band, commonly indicated with the term "selvedge", which extends longitudinally along the side of the membrane corresponding to the longer side of the roll, and is adapted, in use, to be overlapped on and joined stably with a lateral surface portion of an adjacent membrane.

Generally, the methods to make the aforesaid membrane include, among the different operating steps, one or more lamination steps adapted to reduce the thickness of the membrane to a predetermined final value, and a subsequent finishing step, during which the granular layer is deposited in a controlled manner with a predetermined thickness on the surface of the upper layer of the membrane, by the side of the smooth band forming the selvedge.

The membranes obtained by means of the aforesaid methods have the drawback of not having a uniform thickness along the whole width but have a first thickness at the portion covered by the granular layer, and a second thickness which is smaller than the first, at the smooth uncovered lateral band.

US 2008/220167 Al describes a method for controlling the thickness of the lateral edge of a membrane in which according to an embodiment the granules are applied to the membrane by means of a surfacing applicator.

Therefore, the Applicant has conducted an in-depth study with the aim of identifying a simple and inexpensive solution that makes it possible to make a membrane of the type described above with a uniform thickness along the whole width.

DISCLOSURE OF INVENTION

The subject matter of the present invention is therefore to provide a solution that allows the aforesaid aim to be achieved .

This aim is achieved by the present invention as it relates to a bituminous membrane and to a method to make the membrane itself, as defined in the appended claims. The present invention also concerns a machine to make said membrane as defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting example of embodiment, wherein:

Fig. 1 schematically shows a bituminous membrane made according to the teachings of the present invention;

- Fig. 2 schematically shows the section of the membrane shown in Fig. 1 along the line I-I;

Fig. 3 schematically shows a machinery for making the membrane shown in Fig. 1 ;

- Fig. 4 schematically shows, with parts removed for clarity, a finishing device of the system shown in Fig. 3;

- Fig. 5 is a schematic front elevation view of the finishing device shown in Fig. 4 ;

Fig. 6 schematically shows a machinery for making the membrane shown in Fig. 1 made according to an alternative embodiment of the present invention;

- Fig. 7 schematically shows, with parts removed for clarity, a finishing device of the machinery shown in Fig. 6;

- Fig. 8 is a schematic front elevation view of an insert which can be coupled to a cylinder according to a variant;

- Fig. 9 schematically shows, with parts removed for clarity, a variant of the finishing device of the machinery shown in Fig. 6;

- Fig. 10 is a schematic front elevation view of the finishing device shown in Fig. 9.

- Fig. 11 is a schematic front elevation view of the scraper and of the membrane shown in Fig. 9.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be described in detail with reference to the accompanying figures to allow a person skilled in the art to make and use it. Various modifications to the embodiments described will be immediately evident to those skilled in the art and the general principles described can be applied to other embodiments without departing from the scope of protection of the present invention, as defined in the appended claims. Therefore, the present invention must not be considered limited to the embodiments described and illustrated, but the broadest scope of protection must be granted to the principles and to the features described and claimed herein.

The meaning of the terms used hereunder in the present description shall now the established. The term "bituminous membrane" will be intended hereunder as a strip based on a bituminous compound, preferably adapted to be wound so as to form a roll, which is dimensioned/structured so as to be used preferably in the building sector for waterproofing, sealling parts of building structures (dwellings) such as roofs, walls, substrates or the like.

The term "bituminous compound" is intended as a mix or compound based on natural hydrocarbons or residues deriving from oil distillation or refinement and mixed in a known way, and therefore not describe in detail (forming tar, asphalt, or in general a mixture of high viscosity hydrocarbons), to which a given amount of polymeric material is preferably, though not necessarily, added. The polymeric material can comprise: APP (acronym for atactic polypropylene) and/or SBS (acronym of Styrene - Butadiene - Styrene) and/or polyolefin (for example APAO - Amorphous Poly Alpha Olefin and/or TPO Thermoplastic Polyolefin), and/or styrene-butadiene-styrene (SBS), and/or styrene-ethylene-butadiene-styrene (SEBS), and/or resins, or similar substances.

With reference to Fig. 1, number 1 indicates as a whole a bituminous membrane which extends along a longitudinal reference axis A and can, in use, preferably, though not necessarily, be wound around an axis B orthogonal to the axis A so as to form a roll. However, it is understood that the membrane 1 may not be wound in a roll, but be shaped in the form of a flat sheet.

According to a preferred embodiment shown in Figs. 1 and 2, the membrane 1 can comprise: a central supporting layer 2, which is made using a flexible material film and is trapped between a lower bituminous layer 3 and an upper bituminous layer 4 so as to form therewith a sandwich. Preferably, the central supporting layer 2 can comprise a thin film made of flexible material, paper or plastic or fabric or any other similar flexible material.

With reference to Figs. 1 and 2, the lower bituminous layer 3 and the upper bituminous layer 4 are stably fixed on the opposite faces of the central supporting layer 2 so as to cover it for the whole width L (measured orthogonally to the axis A) , and are made by means of the bituminous compound in the manner described in detail hereunder. According to a preferred embodiment shown in Figs. 1 and 2, the upper bituminous layer 4 is shaped so as to have a longitudinal portion 7 having a thickness SI, and a longitudinal portion 8 which extends adjacent to the portion 7, has a thickness S2 which is smaller than the thickness SI, and is covered by a surface coating layer 9 in non bituminous material having, in turn, a thickness S3. The total thickness S4 corresponding to the sum of the thickness S3 of the surface coating layer 9 and the thickness S2 of the portion 8, can be equal to roughly the thickness SI of the portion 7. The thickness SI of portion 7 can be comprised between roughly 0 mm and roughly 10 mm, preferably comprised between 1 and 6 mm. The thickness S2 of portion 8 can be comprised between roughly 0 and roughly 9 mm, preferably between around 1 mm and around 5 mm. The thickness S3 of layer 9 can be comprised between roughly 0.2 mm and roughly 1.5 mm, preferably 1 mm. It is understood that according to a first alternative embodiment (not shown) different from the embodiment shown in Figs. 1 and 2, the total thickness S4 can be smaller than the thickness SI of portion 7. According to a second alternative embodiment different to the embodiment shown in the accompanying figures, the total thickness S4 can be larger than the thickness SI of the portion 7.

According to a preferred embodiment shown in Figs. 1 and 2, the surface coating layer 9 can be made of a coating material corresponding preferably to grit, i.e. mineral fragments /granules, such as slate, or comminuted/ fragmented sand. It is understood that the surface coating material is not limited to grit, but could comprise other types of non-bituminous material, capable of performing a coating function similar to grit, such as fabrics/backings/laminates of various materials and thicknesses.

According to a preferred embodiment shown in Figs. 1 and 2, the portion 7 is arranged adjacent to the longitudinal edge/ side la of membrane 1 so as to extend parallel to axis A by the side of surface coating layer 9 so as to form the "selvedge" or longitudinal lateral band for overlapping of the membrane 1. In other words, portion 7 comprises a rectilinear surface strip or band having a smooth and uncovered upper surface, i.e. not coated/covered by granules, which is commonly indicated with the term "selvedge", which extends longitudinally along the side of the membrane (corresponding to the longer side of the roll), and is adapted, in use, to be overlapped on and stably joined with its smooth surface to the smooth surface of a lateral portion of an adjacent membrane. According to a preferred example of embodiment shown in Figs. 1 and 2, the longitudinal portion 7 has a substantially rectangular section transverse to axis A and is dimensioned so as to have a width LI measured transversely to axis A which is smaller than the width L2 of the portion 8. The width LI of portion 8 can be comprised between roughly 10 mm and roughly 250 mm, preferably 100 mm. The width L2 of portion 7 can be comprised between roughly 750 mm and roughly 1200 mm, preferably 900 mm. The width L of membrane 1 can instead be comprised between roughly 1000 and roughly 1300 mm preferably roughly 1100 mm.

With reference to Figs. 3, 4 and 5, there will be described below a machinery 10 that performs a process/method to make the membrane 1 described above. According to a preferred embodiment shown in Fig. 3, machinery 10 can comprise a forming station 11 adapted to preform the membrane, a coating station 12 adapted to superficially coat/cover the preformed membrane 1, and feeding means, for example motorized rollers (not shown) , to feed the membrane along a preferably horizontal direction K through stations 11 and 12.

Preferably, the forming station 11 of membrane 1 is structured to perform the following operating steps: unwind the central supporting layer 2 from a reel, and plunge, in a controlled manner, the central supporting layer 2 in an impregnation tank 14 containing the bituminous compound in a viscous semi-liquid state, so as to make the bituminous compound adhere/attach to the opposite faces of the central supporting layer 2 and thus form the lower 3 and upper 4 bituminous layers. The forming station 11 can also be structured to perform preferably, though not necessarily, an additional application of bitumen on the two opposite faces of the central supporting layer 2 by means of bitumen distribution apparatus 18, so as to thicken the layers 3 and 4, and at least one lamination of the membrane 1 by means of one or more calenders 15 provided with preferably smooth, rotating cylinders that, during feeding of membrane 1, compress the lower bituminous layer 3 and/or the upper bituminous layer 4 according to predetermined thicknesses. According to the exemplifying embodiment shown in Fig. 3, the forming station 11 provides at the outlet the membrane 1 having the upper bituminous layer 4 having a uniform thickness along the whole width L of the membrane 1 itself. According to a preferred exemplifying embodiment shown in Fig. 4, the uniform thickness of membrane 1 provided at the outlet of forming station 11 is approximately equal to the thickness S2.

With reference to Figs. 3, 4 and 5, the coating station 12 comprises a finishing device 16 adapted to make on the upper bituminous layer 4 the two portions 7 and 8 having the thicknesses SI and respectively S2. The coating station 12 also comprises an apparatus 13 adapted to apply the surface coating layer 9 to the longitudinal portion 8 so as to coat it. According to a preferred embodiment shown in Fig. 3, the apparatus 13 to apply the surface coating layer 9 can comprise a container, for example, a hopper 19 containing the coating material, and a distributor member 20 which is arranged above the membrane 1 in a position adjacent to the face of the upper bituminous layer 4, and is structured so as to deposit, selectively and in a controlled manner, the coating material, for example the granules, only on the portion 8, so as to make the surface coating layer 9 having the thickness S3. In particular the distributor member 20 is structured so that the surface coating layer 9 only covers the portion 8 and is laterally delimited by portion 7 without protruding over this portion, so as to leave it completely exposed.

According to a possible exemplifying embodiment shown in Fig. 3, the distributor member 20 can comprise, for example, a grooved cylinder adapted to rotate about a horizontal axis, and having a plurality of surface grooves dimensioned so as to be able to receive the granules from hopper 19 and deposit said granules in a controlled manner on portion 8, during rotation of the cylinder, simultaneously leaving the upper surface of portion 7 uncovered.

The distributor member 20 is known and will not be further described except to specify that the grooved cylinder can be interposed between the discharge gate of hopper 19 and the membrane 1 below in a position facing portion 8, can be dimensioned so as to have a width roughly equal to width L2 and can be rotated by a drive unit (not shown) , for example an electric motor controlled, in turn, by an electronic control unit 22. It is understood that electronic control unit 22 can be configured to control the flow of granules fed from hopper 19 to the grooved cylinder, by means of a known dosing system coupled for example to the discharge gate of hopper 19, and simultaneously controls the rotation speed of the grooved cylinder as a function of the thickness S3 of the coating layer 9 to be made.

According to a preferred embodiment shown in Figs. 3, 4 and 5, the finishing device 16 comprises an extrusion head 23 which is arranged preferably above the membrane 1 at the side thereof, in a position adjacent to and facing the portion of the surface of the upper layer 4 on which the longitudinal bituminous portion 7 is to be made. The extrusion head 23 is adapted to form, on surface of upper layer 4 intended to have the longitudinal portion 7, an additional bituminous layer 5 (shown in Fig. 2) corresponding to the lateral selvedge. Preferably, the dosing head 23 is structured to make, on the side of membrane 1, an additional bituminous layer 5 having a width LI and a thickness S5. Preferably, the thickness S5 can be approximately equal to the thickness S3. It is understood that according to an alternative embodiment the thickness S5 can be smaller than or, alternatively, larger than the thickness S3.

It is understood that the positioning of the extrusion head 23 is not limited to the one described above but can have other configurations. For example, according to a not shown, different embodiment, the extrusion head 23 is arranged above the rotating cylinder of the calender 15 present at the output of the forming station. Preferably, the extrusion head 23 is arranged so as to continuously deposit the sheet forming the additional bituminous layer 5 on the outer surface of the upper roller, which rotating preferably in a direction opposite to the feed direction K of membrane 1, in turn deposits the bituminous strip on surface of the upper layer 4 intended to have the longitudinal portion 7, so as to form an additional bituminous layer 5 (shown in Fig. 2) corresponding to the lateral selvedge. Tests performed by the Applicant have shown that this variant is particularly advantageous as it allows a reduction in formation of smears of bitumen on the upper bituminous layer 4.

According to a preferred embodiment shown in Fig. 4, the extrusion head 23 can comprise a frame or casing 21 which is preferably, though not necessarily, parallelepiped in shape or similar and has, at an end, a thin opening or slit 24 that faces the upper bituminous layer 4 of membrane 1 and is shaped so as to extrude/e ect, in use, the additional bituminous layer 5 having substantially the shape of a continuous sheet or strip of bitumen. According to a preferred exemplifying embodiment shown in Fig. 4, the extrusion head 23 comprises an inlet duct 23a receiving the pressurized hot semi-liquid bituminous compound, and an inner chamber 23b communicating on one side with the inlet duct 23a and on the other with the slit 24 with the interposition of a perforated dosing comb 25. The dosing comb 25 extends substantially horizontally while the corresponding holes are distributed horizontally along the body of the comb 25, preferably equidistant from one another, and are dimensioned to dose the bituminous compound and evenly distribute it along the width of slit 24. The slit 24 is instead dimensioned to perform an extrusion of the bituminous compound supplied by the comb 25 so as to deliver a continuous sheet of bitumen having the predetermined thickness, preferably thickness S5, which is deposited on the membrane 1 below and forms thereon the additional layer 5.

According to a preferred embodiment shown in Fig. 4, the slit 24 is substantially rectilinear and is arranged transverse to the axis A of membrane 1 during the feeding thereof along direction K. The slit 24 can also be shaped so as to have a width approximately equal to the width LI . According to a preferred embodiment shown in Fig. 3, the finishing device 16 comprises a bitumen feeding system 26 which is connected to the extrusion head 23 for supplying to the latter, in a controlled manner, the amount of bituminous compound required to form the additional layer 5 on membrane 1. According to an exemplifying embodiment shown in Fig. 3, the bitumen feeding system 26 can comprise a tank or container 27 for containing the bituminous compound, and a bituminous- compound suction and injection unit 29 which is connected to container 27 and to the feed-in duct of extrusion head 23, and is adapted to draw the compound from container 27 for supplying it to the dosing head 23 in a controlled manner. Preferably, the bituminous-compound suction and injection unit 29 can comprise a pump coupled to, and driven by, an electric motor (not shown) , preferably controlled by the electronic control unit 22 by means of an inverter (non illustrated) . The electronic control unit 22 can be configured so as to drive the electric motor to adjust, by means of the pump, the pressure and therefore the amount of bitumen fed to the dosing head 23, according to the thickness S5 of the additional layer 5 to be made. According to an exemplifying embodiment shown in Figs. 3 and 4, the apparatus 13 can be advantageously arranged downstream of finishing device 16 with respect to the feeding direction of membrane 1 in station 12, so that the grit of surface coating layer 9 is delimited laterally by the inner longitudinal side of portion 7, i.e. of the additional layer 5 already formed, and therefore does not overflow from the portion 8 to be covered. The method to make the membrane 1 by means of the machinery 10 then provides for the steps of preforming the membrane 1 by means of the forming station 11 as described above, so as to feed into the coating station 12 the membrane 1 in which the upper bituminous layer 4 has a uniform thickness on the width L. Following preforming, the membrane 1 is fed along the direction K, preferably parallel to the axis A, in sequence under the finishing device 16 and the apparatus 13. During feed of the membrane 1, the extrusion head 23 forms/deposits the additional layer on the upper face of the layer 4 at the side la of the membrane 1 according to the thickness S5, so as to form the lateral selvedge, and subsequently the apparatus 13 deposits the grit on the portion 8 by the side of the selvedge itself. The method to make the membrane described above is extremely advantageous as it allows the thickness of the membrane to be made uniform along its whole width by means of a simple and inexpensive solution. The finishing device can in fact be installed simply, rapidly and inexpensively also in existing systems, without requiring relevant changes thereto.

The embodiment shown in Fig. 6 instead relates to a machinery 40 which is similar to the machinery 10, and whose component parts will be marked, where possible, with the same reference numbers that mark corresponding parts of machinery 10. Machinery 40 differs from machinery 10 as the finishing device 16 is adapted to laminate the membrane 1 in the coating station 12 so as to make on the upper layer 4 thereof the portions 7 and 8 having different thicknesses SI and S2. Preferably, the finishing device 16 shown in Fig. 6 comprises a calender formed by two rollers or cylinders 41 and 42 which are parallel and ad acent to each other, and have the opposite distal ends pivoted on a supporting frame 47 so as to be able to rotate about the respective rotation axes C and D transversal to axis A and preferably direction K.

According to the alternative embodiment shown in Figs. 6, 7, 9 and 10, the upper cylinder 42 is shaped so as to have a longitudinal portion 43 (along axis D) having a diameter Dl, and a longitudinal portion 44 adjacent to the portion 43 having a diameter D2 which is smaller than diameter Dl . The difference between the diameters Dl and D2 of portions 43 and 44 is approximately equal to the thickness S5. The Applicant has found that, by performing a lamination of the membrane 1 through the two cylinders 41 and 42, the upper bituminous layer 4 is shaped so as to form the portions 7 and 8. According to the exemplifying embodiment shown in Fig. 7, the length of longitudinal portion 43 (along axis D) is preferably equal to the width L2, while the length of longitudinal portion 44 (along axis D) is preferably equal to the width LI of the lateral selvedge. Preferably, the longitudinal portions 43 and 44 of the upper cylinder 42 delimit with the adjacent outer surface of lower cylinder 41 respective gaps/slits 45 and 46 which are located side by the side to one another, and through which, in use, the membrane 1 passes. According to the exemplifying embodiment shown in Fig. 6, the slit 45 has a height (measured vertically) substantially equal to the thickness of the membrane 1 measured at the longitudinal portion 8, whereas the height of slit 46 (measured vertically) is substantially equal to the thickness of the membrane 1 measured at the longitudinal portion 7. According to exemplifying embodiment shown in Fig. 8, the machinery 40 can also comprise preferably at least one, tubular-shaped cylindrical insert 32 which can be fitted, in a stable though easily removable manner, on the longitudinal portion 44 to advantageously adjust (increase) the outer diameter D2 thereof and cause, in use, a consequent variation of the thickness SI of the selvedge to be made. According to the exemplifying alternative embodiment shown in Figs. 9 and 11, machinery 40 can also comprise a scraper 48 which is arranged downstream of cylinders 41 and 42 along the feeding direction of membrane 1, and is structured to scrape the additional bituminous layer 5 during feeding of membrane 1 so as to reduce its thickness. The scraper 48 can comprise, for example, a blade which is arranged above the membrane 1 in a position horizontal and transversal to axis A at a given height therefrom. The scraper 48 can be associated with a height adjusting device (not shown) which is structured to adjust, when necessary, the height of scraper 48 with respect to the membrane 1 so as to adjust the thickness S5.

According to the exemplifying alternative embodiment shown in Figs. 6 and 7, the machinery 40 can comprise an apparatus 49 structured for feeding/depositing a given amount of bituminous compound at the slit 46 upstream of cylinders 41 and 42, so as to locally thicken the upper bituminous layer 4 of the membrane, i.e. at the part intended to present the portion 7, before performing the double thickness lamination carried out by cylinders 41 and 42. According to the exemplifying alternative embodiment in Figs. 6 and 7, the apparatus 49 can comprise a tank 50 for containing the bituminous compound arranged immediately upstream of the cylinders 41 and 42, and a system 51 for feeding the bituminous compound in tank 50. Preferably the tank 50 is structured so that, in use, during the feeding of membrane 1 before performing the double thickness lamination, a predetermined amount of bituminous compound contained in tank 50 overflows above the first bituminous layer at the first longitudinal portion of said cylinder, so as to fill the slit 46 provided between the longitudinal portion 44 of the upper cylinder 42 and the lower cylinder 41. According to the embodiment shown in Fig. 7, the tank 50 is structured so as to have a longitudinal lateral wall 51 which is parallel to axis A and extends vertically from the bottom 53 of the tank 50 so as to be adjacent to and facing the lateral side of the portion 43 of cylinder 41, and an opposite longitudinal lateral wall 52 which is parallel to axis A and extends vertically from the bottom of the tank 50 so as to be adjacent to and facing the lateral side of the portion 44 of cylinder 41. Preferably, the lateral wall 52 is dimensioned so as to extend above the lower cylinder 41 for a height larger than the height of slit 46. The Applicant has found that, due to the extended lateral wall 52 of tank 50, the bituminous compound fed in pressure in the same tank by means of a pump 54 overflows from the side of tank 50 corresponding to the same lateral wall 52, above the upper bituminous layer 4, so as to fill up the slit 46 during lamination of the membrane 1 itself.

It has therefore been demonstrated that the present invention allows the aims indicated above to be achieved.

Finally, it is clear that modifications and variants can be made to the method, to the machine and to the machinery described and illustrated herein without however departing from the scope of the present invention defined by the appended claims.

Claims

1. A method to make a bituminous membrane (1), characterized in that it comprises the following steps:

- preforming a membrane (1), which extends along a longitudinal reference axis (A) and comprises a central supporting layer (2) arranged between at least a first bituminous layer (4) and a second bituminous layer (3), which are opposite to each other;

- making, on said first bituminous layer (4), a first longitudinal portion (7), which extends parallel to said axis (A) and has a first thickness (SI), and an upper coupling surface adapted, in use, to be overlapped on and associated stably with a corresponding lateral surface portion of another membrane; and a second bituminous longitudinal portion (8), which extends parallel to said axis (A) by the side of said first bituminous longitudinal portion (8) and has a second thickness (S2) which is smaller than said first thickness (SI) ;

- coating only the upper surface of said second portion (8) by means of a granular coating material so as to simultaneously leave the upper coupling surface of the first longitudinal portion (7) uncovered so as to make a surface coating layer (9) of the membrane (1), which extends by the side of said first longitudinal portion (7) without covering it and has a predetermined third thickness (S3) .

2. A method according to claim 1, wherein said first thickness (SI) is approximately equal to the sum of the second thickness (S2) and third thickness (S3) .

3. A method according to claims 1 or 2, comprising:

- preforming said membrane (1) so that, before the formation of said first portion (7) and second portion (8), said first bituminous layer (4) has a uniform thickness on the entire width (L) of the membrane (1) approximately equal to said second thickness (S2);

depositing an additional bituminous layer (5) having a fourth thickness (S5) and a width corresponding to the width (LI) of said first longitudinal portion (7) on the surface portion of the first bituminous layer (4) intended to form the first longitudinal portion (7) .

4. A method according to claim 3, wherein the sum of the fourth thickness (S5) and of the second thickness (S2) is equal to the first thickness (SI) .

5. A method according to claims 3 or 4, comprising:

- arranging an extrusion head (23) provided with an ejection slit (24) of said bituminous compound, which faces the surface portion of said first bituminous layer (4) intended not to be coated by said surface coating layer (9) and is dimensioned so as to have a length which is substantially equal to the width (LI) of said first portion (8);

adjusting the amount of bituminous compound fed to said extrusion head (23) according to said fourth thickness (S5) of said additional bituminous layer (5) .

6. A method according to claims 3 or 4, comprising:

laminating said membrane (1) by means of two rotating cylinders (41) (42) which are parallel and face each other, wherein a first cylinder (42) is shaped so as to have a first longitudinal portion (44) having a first diameter (D2) and a second longitudinal portion (43) by the side having a second diameter (Dl) which is greater than said first diameter (D2) .

7. A method according to claim 6, wherein the difference between the second diameter (D2) and the first diameter (Dl) is approximately equal to said fourth thickness (S5) .

8. A method according to claims 6 or 7, wherein the width of the first portion (43) of the first cylinder (44) is equal to the width (LI) of the first portion (8) of said first bituminous layer (4) and the width of the second portion (43) of the first cylinder (42) is equal to the width (L2) of the second portion (8) of the first bituminous layer (4) .

9. A method according to any one of claims 6 to 8, comprising the step of scraping the first portion by means of a scraper (48) so as to adjust said fourth thickness (S5) .

10. A method according to any one of claims 6 to 9, comprising the step of feeding the bituminous compound at said first portion (44) of said first cylinder (42) .

11. A method according to any one of claims 6 to 10, comprising:

- plunging the membrane (1) in a tank (50) containing said bituminous compound so as to make a given amount of bituminous compound flow over the first bituminous layer (4) at the first longitudinal portion (44) of said first cylinder (42) so as to fill the slit (46) arranged between the first longitudinal portion (44) of said first cylinder (42) and the second cylinder (41) ;

laminating said membrane (1) by means of the said first cylinder (42) and second cylinder (41) .

12. A method according to claim 1, wherein the first thickness can be comprised between around 0 mm and around 10 mm, preferably comprised between 1 and 6 mm; and/or the second thickness (S2) can be comprised between around 0 and around 9 mm, preferable between around 1 mm and around 5 mm; and/or the third thickness (S3) can be comprised between around 0.2 mm and around 1.5 mm, preferably 1 mm.

13. A method according to claim 3, wherein said fourth thickness (S4) is smaller than the first thickness (SI) .

14. A method according to claim 3, wherein said fourth thickness (S4) is larger than the first thickness (SI) .

15. A method according to claim 1, wherein said first longitudinal portion (7) has a substantially rectangular section transverse to said axis (A) and is dimensioned so as to have a width (LI) measured transversely to said axis (A) which is smaller than the width (L2) of the second portion (8) .

16. A method according to claim 1, wherein the width (LI) of the second portion (8) can be comprised between around 10 mm and around 250 mm, preferably 100 mm; and/or the width (L2) of the first portion (7) can be comprised between around 750 mm and around 1200 mm, preferably 900 mm; and/or the width (L) of the membrane (1) can instead be comprised between around 1000 and around 1300 mm, preferably around 1100 mm.

17. A machinery (10) (40) to make a bituminous membrane (1), characterized in that it comprises:

a forming station (11) structured to preform a membrane (11), which extends along a longitudinal reference axis (A) and comprises a central supporting layer (2) arranged between at least a first bituminous layer (4) and a second bituminous layer (3), which are opposite to each other; and

a coating station (12) comprising in turn:

a finishing device (16) structured for making, on said first bituminous layer (4), a first longitudinal bituminous portion (7) which extends parallel to said axis (A) and has a first thickness (SI) and an upper coupling surface adapted, in use, to be overlapped on and associated stably with a lateral surface portion of an adjacent membrane; and a second longitudinal bituminous portion (8) which extends parallel to said axis (A) by the side of said first longitudinal portion (8) and has a second thickness (S2) which is smaller than said first thickness (SI); and an apparatus (13) structured to cover only the upper surface of said second portion (8) by means of a granular coating material so as to simultaneously leave the upper coupling surface of the first longitudinal portion (7) uncovered so as to make a surface coating layer (9) of the membrane (1), which extends by the side of said first longitudinal portion (7) and has a predetermined third thickness (S3) .

18. A machinery according to claim 17, wherein said finishing device (16) comprises:

- an extrusion head (23) provided with an ejection slit of said bituminous compound which faces the surface portion of said first bituminous layer (4) intended not to be covered by said surface coating layer (9), and is dimensioned so as to have a length which is substantially equal to the width of said first portion (8);

- means for adjusting the amount of bituminous compound fed to said extrusion head (23) according to said fourth thickness (S5) of said additional bituminous layer (5) .

19. A machinery according to claim 17, wherein said finishing device (16) comprises two rotating cylinders which are parallel and faced each other, wherein a first cylinder is shaped so as to have a first longitudinal portion having a first diameter (Dl) and a second longitudinal portion having a second diameter (D2) which is greater than said first diameter (Dl) .

20. A finishing device (16) of a bituminous membrane (1) installable in a machinery (10) (40), comprising a forming station (11) structured to preform a membrane (1) which extends along a longitudinal reference axis (A) and comprises a central supporting layer (2) arranged between at least a first bituminous layer (4) and a second bituminous layer (3), which are opposite to each other, and a coating station (12), comprising, in turn, an apparatus (13) structured to cover only the upper surface of a second bituminous portion (8) of the first bituminous layer (4) by means of a granular coating material so as to make a surface coating layer (9) of the membrane (1), which extends by the side of a first longitudinal bituminous portion (7) of the first bituminous layer (4) itself; said finishing device (16) being structured so as to make, on said first bituminous layer (4), said first longitudinal bituminous portion (7), which extends parallel to said axis (A) and has a first thickness (SI) and an upper coupling surface adapted to be overlapped on and associated stably with a lateral surface portion of an adjacent membrane, and said second longitudinal bituminous portion (8), which extends parallel to said axis (A) by the side of said first longitudinal portion (8) and has a second thickness (S2) which is smaller than said first thickness (SI) .

21. A finishing device (16) according to claim 20, comprising an extrusion head (23) provided with an ejection slit of said bituminous compound which faces the surface portion of said first bituminous layer (4) intended not to be coated by said surface coating layer (9) and is dimensioned so as to have a length which is substantially equal to the width of said first portion (8); and means for adjusting the amount of bituminous compound fed to said extrusion head (23) according to said fourth thickness (S5) of said additional bituminous layer (5) .

22. A finishing device (16) according to claim 20, comprising two rotating cylinders which are parallel and face each other, wherein a first cylinder is shaped so as to have a first longitudinal portion having a first diameter (Dl) and a second longitudinal portion by the side having a second diameter (D2) which is greater than said first diameter (D2) .

23. A bituminous membrane (1) extending along a longitudinal reference axis (A) and comprising a central supporting layer

(2) arranged between at least a first bituminous layer (4) and a second bituminous layer (3) opposite to each other; said membrane being characterized in that said first bituminous layer (4) has a first longitudinal bituminous portion (7), which extends parallel to said axis (A) and has a first thickness (SI) and an upper coupling surface adapted to be overlapped on and associated stably with a lateral surface portion of an adjacent membrane, and a second longitudinal portion (8), which extends parallel to said axis (A) by the side of said first longitudinal portion (8) and has a second thickness (S2) which is smaller than said first thickness (SI) ;

said second portion (8) being coated by means of a granular coating material so as to make a surface coating layer (9) of the membrane (1), which extends by the side of said first longitudinal portion (7) and has a predetermined third thickness (S3);

said first longitudinal portion (7) having the upper surface not coated by said granular coating material.

24. A membrane according to claim 23, wherein the first thickness (SI) is approximately equal to the sum of the second thickness (S2) and the third thickness (S3) .