Method for producing a multilayer film

Abstract

A method for producing a multilayer film including at least two layers joined by a two-component adhesive includes the following steps: spreading a first component A of a two-component adhesive on a first face of a first layer of film; spreading a second component B of the two-component adhesive on a first face of a second layer of film; bringing the first and second faces of the first and second layers into mutual contact joining the components and to form an adhesive and join the two layers in a multilayer film; and winding the multilayer film obtained.

Claims

1. A method for producing a multilayer film including at least two layers joined by a two-component adhesive, the method comprising: spreading a first liquid component of the two-component adhesive on a face of a first layer of the at least two layers of the film, the first liquid component being spread in a continuous and uniform layer; spreading a second liquid component of the two-component adhesive on a face of a second layer of the at least two layers of the film, the second liquid component being spread in a continuous and uniform layer; bringing the face of the first layer and the face of the second layer into mutual contact joining the first and second liquid components to form the two-component adhesive and join the two layers in the multilayer film; and winding the obtained multilayer film, wherein the spreading the first liquid component and the spreading the second liquid component of the two-component adhesive on the faces of the first and second layers comprises: arranging at least a first metering roller and a second metering roller, mutually facing and spaced by a gap, at least the second metering roller being rotatable with respect to the first metering roller and being in contact with at least one of the first and second liquid components of the two-component adhesive, arranging a regulation device to move at least the first metering roller with respect to the second metering roller, and regulating the gap between the first metering roller and the second metering roller, to regulate the thickness of the respective liquid component of the two-component adhesive spread on the respective layer of film, as a function of one or more of geometric and dimensional parameters of the first metering roller, the regulating the gap comprising: detecting an angular position of the first metering roller, determining the one or more of the geometric and dimensional parameters of an operating zone of the first metering roller as a function of the angular position, and activating the regulation device to move the first metering roller toward or away from the second metering roller, as a function of the one or more of the geometric and dimensional parameters.

2. The method according to claim 1, wherein the winding of the multilayer film is carried out directly after the step of bringing the two layers into contact.

3. The method according to claim 2, wherein the thickness of the layer of the two-component adhesive spread on the first layer of film and on the second layer of film is from 0.3 micron to 0.8 micron.

4. The method according to claim 2, wherein the ratio by weight between the first liquid component and the second liquid component is from 1.5:1 to 1:1.5.

5. The method according to claim 1, wherein the thickness of the layer of the two-component adhesive spread on the first layer of film and on the second layer of film is from 0.3 micron to 0.8 micron.

6. The method according to claim 1, wherein the ratio by weight between the first liquid component and the second liquid component is from 1.5:1 to 1:1.5.

7. The method according to claim 1, further comprising: detecting a temperature parameter correlated to a temperature of the metering rollers; and activating the regulation device to move the first metering roller toward or away from the second metering roller, as a function of said temperature parameter.

8. The method according to claim 1, further comprising: arranging a pair of counter-rotating rollers, of which at least one of said counter-rotating rollers is a heatable calendar; heating the outer surface of the calendar to a temperature from 57° C. to 63° C.; conveying the two layers of film toward a gluing point between said counter-rotating rollers to bring the first and second liquid components of the two-component adhesive into contact.

9. The method according to claim 8, wherein, after the gluing point, the multilayer film is wound on the calendar on an arc of contact with an angle from 18° to 23°.

10. The method according to claim 8, wherein, before the gluing point, the first layer of film is wound on the calendar on an arc of contact with an angle from 68° to 78°.

11. The method according to claim 1, wherein, within 90 minutes from the joining of the two layers, the two-component adhesive has a bonding strength equal to or greater than 1.5 N/15 mm.

12. The method according to claim 1, wherein the material of the first layer of film and the material of the second layer of film is selected from the group consisting of paper, polymers or metal coated polymers, metal sheets, and nonwoven fabric.

13. The method according to claim 1, further comprising cooling the multilayer film, wherein the winding of the multilayer film is carried out after the cooling of the multilayer film.

14. The method according to claim 1, wherein the first liquid component is spread across the face of the first layer, and the second liquid component is spread across the face of the second layer.

15. The method according to claim 1, wherein the spreading the first liquid component, the spreading the second liquid component, the bringing the face of the first layer and the face of the second layer into mutual contact, and the winding are carried out without an external energy device configured to provide energy to cause mixing of the first liquid component and the second liquid component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of the present invention will become more apparent from the description of an example of a preferred, but not exclusive, embodiment of an apparatus for producing a multilayer film, as illustrated in the accompanying drawings, wherein:

(2) FIG. 1 is a schematic lateral view of an apparatus for producing a multilayer film in accordance with the present invention;

(3) FIG. 2 is a schematic lateral view of a spreading unit of the apparatus of FIG. 1;

(4) FIGS. 3a and 3b are two perspective views of the regulation device of the position of the metering roller in the spreading unit of FIG. 2;

(5) FIG. 3c is a sectional view along a plane perpendicular to the axis of the metering roller;

(6) FIG. 3d is a sectional view along a plane passing through the axis of the metering roller;

(7) FIG. 4 is a schematized representation of a part of the regulation device of FIG. 2;

(8) FIG. 5 is a schematic lateral view of the coupling unit of the apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) With reference to the accompanying FIG. 1, the number 1 indicates as a whole an apparatus for producing a laminated multilayer film.

(10) The apparatus 1 comprises at least a coupling unit 10, a first spreading unit 20 and a second spreading unit 30. Said first and second spreading unit 20, 30 are configured to each spread a component of an adhesive respectively on a first layer of film S1 and on a second layer of film S2.

(11) The two layers of film S1 and S2, are subsequently guided by a plurality of rollers toward the coupling unit in which they are made to adhere to each other to create a coupled multilayer film M.

(12) The first and the second layer of film S1, S2 are unwound from two reels B1, B2 supported and rotated by a first unwinder 40 and by a second unwinder 50 that respectively serve the first spreading unit 20 and the second spreading unit 30.

(13) The multilayer film M is instead wound on a reel BM by a winder 60.

(14) FIG. 2 illustrates in more detail a spreading unit of the apparatus 1. The spreading units 20, 30 are substantially identical; the description below must therefore be understood to refer to both the aforesaid units.

(15) The spreading unit, indicated as a whole with 120, comprises a first metering roller 121 and a second metering roller 122, arranged facing the first. The first metering roller 121 is preferably maintained blocked in rotation during operation of the apparatus. The second metering roller 122 is instead rotated with respect to the first in a direction of rotation indicated by the arrow Rd. The outer surface of the metering rollers 121, 122 is preferably smooth and coated, or made of chromed steel.

(16) In the space between the two metering rollers 121, 122 there is defined a chamber 123 into which there can be transferred a component of a two-component adhesive, typically in fluid form, in contact with the outer surfaces of both rollers. To maintain the viscosity of the components of the adhesive at a desired value, the metering rollers are preferably provided with heating means to heat the outer surface.

(17) The surfaces of the two metering rollers 121, 122 are spaced by a gap of a few hundredths of millimetre so that, following rotation of the second metering roller with respect to the first, the adhesive is laminated through the gap and a thin and uniform layer remains adhering to the surface of the second metering roller 122.

(18) This layer of adhesive, by means of one or more rollers that rotate in contact with the second metering roller 122, is transferred to a moving film S1, S2.

(19) In the variant illustrated, the spreading device comprises a further conveyor roller 124 that rotates in contact with the second metering roller 122 in an opposite direction of rotation Rt. The conveyor roller 124 is preferably coated with a layer of vulcanized rubber. The task of the conveyor roller 124 is to pick up the layer of adhesive from the second metering roller 122 and transfer it to a spreading roller 125 that rotates in contact therewith in an opposite direction of rotation Rs.

(20) The spreading roller 125 is, in turn, placed in contact with the layer of moving film S1, S2, on which the adhesive is spread in a continuous and uniform +layer.

(21) Advantageously, the rotation speed of the spreading roller 125 is greater with respect to that of the conveyor roller 124 which, in turn, is greater with respect to that of the second metering roller 122.

(22) This increase in speed allows a gradual decrease in the thickness of the layer of adhesive deposited on the surface of the rollers and, subsequently, on the layer of film.

(23) The gap, i.e. the minimum distance between surfaces of the metering rollers 121, 122, can be regulated by means of a regulation system so as to vary the thickness of the layer of adhesive picked up by the second metering roller 122 and, consequently, the thickness of the layer of adhesive applied to the film S1, S2.

(24) FIGS. 3a to 3d illustrate a detail of the spreading device in which the aforesaid regulation system, indicated as a whole with 130, is visible. In accordance with a preferred variant of the invention, said regulation system acts on the first metering roller 121 moving it with respect to the second metering roller 11 whose axis of rotation is fixed.

(25) The first metering roller 121 comprises an operating central portion 121a comprised between two support shafts 121b (FIG. 3d), by means of which the metering roller is supported by the frame of the spreading device (not illustrated in the figure).

(26) Each support shaft 121b is coupled with an eccentric support 131 comprising a fixed portion 131a, integral with the frame of the device, and moving portion 131b, connected to the fixed portion and rotatable with respect to it about an axis of rotation Xe. Said fixed and moving portions are preferably in the form of concentric rings. More in detail, the moving portion 131b, inner ring, is housed in the fixed portion 131a, outer ring.

(27) The support shaft 121b is, in turn, housed rotatingly in a seat produced in the moving portion 131a so that its axis of rotation X is decentred with respect to the axis of rotation Xe of the moving portion. FIG. 4 represents, schematically and in section, the fixed portion 131a, the moving portion 131b and support shaft 121b. In the figure, the letter E indicates the eccentricity between the axis X of the first metering roller 121 and the axis of rotation Xe of the moving portion 131b, which, to make the drawing clearer, is intentionally out of proportion. In actual fact, the value of the eccentricity E is preferably from 0.2 mm to 1 mm.

(28) By observing FIG. 4, the operation of the regulation device 130 can be better understood. When the moving portion 131b is rotated about the axis Xe by an angle α, the axis X of the first metering roller 121 performs a rotation along a circumference with a radius E moving, with respect to an initial position, by a length D. This movement causes the surface of the first metering roller 121 to move toward or away from the surface of the second metering roller 122 and, therefore, increase or decrease of the gap G.

(29) On the outer surface of the moving portion 131b there are produced teeth 132, preferably with a helical profile, meshed on which is a worm screw 133 (FIGS. 3c, 3d).

(30) Rotation of the worm screw 133, in one or in the other direction, causes rotation of the moving portion 131b and therefore, as described above, an increase or decrease of the gap G.

(31) The screw 133 is moved by a motor 134, optionally associated with an encoder 140.

(32) A regulation system of this type allows variations of the gap G to be obtained with a precision up to one micron where the extension of the gap is typically from 50 to 80 micron.

(33) According to the invention, the regulation system is controlled by a control unit (not illustrated in the figure) configured to correct the position of the first metering roller 121 with respect to the second metering roller 122, as a function of the geometric and/or dimensional parameters of the surface of the first metering roller. In fact, as said first metering roller 121 is maintained in a fixed angular position during the spreading process, any defects (geometric and/or dimensional tolerances) cannot be averaged as instead occurs for the second metering roller 122.

(34) For this purpose, according to a preferred aspect of the invention, the control unit is connected to a device for detecting the angular position of the first metering roller 121. By means of this device, the control unit detects which part of the surface of the first metering roller 121 is involved in the spreading process, and in particular the zone close to the gap G where the adhesive is laminated on the surface of the second metering roller 122.

(35) In fact, this operating part is not always the same, but, on the contrary, the first metering roller 121 is used in different angular positions, at times even in the same production batch, for example to utilize a new clean zone or, in any case, to utilize its surface in a uniform manner.

(36) Advantageously, the control unit can be connected to, or can contain, a database in which the aforesaid geometric and/or dimensional parameters of the first metering roller 121 such as eccentricity, cylindricity, rectilinearity, etc., are stored.

(37) These parameters can be detected in advance by means of measurement instruments and stored in the aforesaid database.

(38) As a function of the aforesaid parameters, the control unit can control, in a coordinated manner, operation of the motors 134 of the two eccentric supports 131 to arrange the first metering roller 121 so that the value of the gap G corresponds as closely as possible to the nominal process value constant along the length of the operating part of the metering rollers.

(39) In this way, the regulation device 130 is able to compensate the operating tolerances of the metering rollers, maintaining constant and correct the amounts and hence the thickness of the adhesive picked up by the second metering roller.

(40) In a preferred variant, said system for detecting the angular position of the first metering roller comprises one or more sensors 138, integral with the frame of the device, adapted to detect references 139 produced on the first metering roller 121 or on a part integral therewith.

(41) In the variant illustrated, the sensor 138 comprises an optical sensor configured to detect the position of a plurality of holes 139 produced on a hub 141 integral with the first metering roller 121. Alternatively, the sensor 138 can comprise an inductive, capacitive or magnetic sensor, or other position sensors with or without contact.

(42) As mentioned above, the first metering roller 121 can be arranged in different angular positions, which are then maintained while the spreading device is operating. According to a preferred variant, these positions are defined by a plurality of seats 137 produced on the hub 141. A positioning mechanism 136 can engage said seats 137 to maintain, during the process, a given selected angular position.

(43) According to a preferred aspect of the invention, the control unit can be connected to sensors adapted to detect a parameter correlated with the temperature of the surface of one or of both the metering rollers 121, 122.

(44) This parameter can comprise, for example, the temperature of a fluid by means of which the surface of the metering rollers is heated.

(45) The control unit, processing the aforesaid temperature values, is able to calculate the thermal expansions of the rollers and, also as a function of the viscosity of the adhesive used, can correct the position of the metering rollers to restore the ideal value of the gap G.

(46) In order to regulate the thickness of the layer of adhesive deposited on the film S1, S2, the control unit can be configured to control the motor means that rotate the second metering roller 122 and the conveyor roller 124 and, in particular, to continuously regulate the rotation speed as a function of the translation speed of the film S and optionally of the temperature parameter of the metering rollers.

(47) FIG. 5 represents the coupling unit 10 of the apparatus. In the coupling unit 10, the first layer of film S1, on the face S if of which the component A of the adhesive is spread, and the second layer of film S2, on the face S2f of which the second component B of the adhesive is spread, converge.

(48) According to a preferred variant, the coupling unit 10 comprises a heated calendar 11 and an opposing roller 12, preferably rubber coated, that rotates in contact with the calendar 11.

(49) The presser roller 12 is mounted on a moving support 13 that, by means of actuators 14, can be rotated around a pivot point Ps to move the presser roller 12 away from the calendar 11 or to regulate the contact pressure.

(50) Between the calendar 11 and the presser roller 12 there is defined a gluing point I, in which the two faces S1f and S2f come into contact to start the chemical reaction of the two components A and B of the adhesive.

(51) The contact pressure exerted by the presser roller is sufficient to mix the two components A and B of the adhesive so that, after the gluing point, the two layers of film S1, S2 are joined and in a multilayer film M.

(52) According to a preferred variant, the first layer of film S1 is partially wound around the surface of the calendar 11 before the contact point I, while the second layer of film S2 is partially wound on the outer surface of the presser roller 12.

(53) According to a preferred variant, the calendar 11 is heatable with the aid of a fluid that circulates under the outer surface, for example in a network of coiled pipes.

(54) The heat released from the calendar 11 can be transferred to the first component A of the adhesive on the first layer of film S1 to improve the efficiency of the cross-linking process.

(55) For this purpose, the first layer of film S1 is conveyed toward the gluing point I so that the winding angle α on the calendar 11 is preferably from 68° to 78° and more preferably from 71° to 75°. An ideal angle is of around 73°.

(56) The second layer of film S2 is instead conveyed toward the gluing point I so that the winding angle β on the presser roller is preferably from 18° to 26° and more preferably from 20° to 24°. An ideal angle is of around 22°.

(57) Again to improve the cross-linking process of the adhesive, after the gluing point I, the coupled multilayer film M is preferably maintained in contact with the calendar 11 for an arc of contact of δ from 18° to 23°.

(58) A plurality of guide rollers 15 convey the coupled film M from the gluing point I toward the winder 60 in which it is wound onto a take-up reel BM.

(59) Preferably, the coupling unit is provided with a further cooled calendar 16, placed between the gluing point and the winder 60.

(60) As a function of the material of the layers of film S1, S1, the multilayer film M can be cooled, winding it partially on said calendar 16 before it is wound.

(61) The invention has been described purely for illustrative and non-limiting purposes, according to some preferred embodiments. Those skilled in the art may find numerous other embodiments and variants, all falling within the scope of protection of the claims below.