Method for bonding flexible films and apparatus for carrying out the same

Abstract

The present invention relates to a method for bonding flexible films by softening the surface of a first film and then contacting the softened surface with a second film, an apparatus for carrying out the method of the present invention, and a composite obtained by the method or the apparatus of the present invention.

Description

[Technical field]

[0001] The present invention relates to a method for bonding flexible films by converting the surface of a first film into a softened state and then contacting the softened surface with a second film, to an apparatus for carrying out the method of the invention, and to composites obtainable by the method of the invention or by the apparatus of the invention. [Background technology]

[0002] Methods for bonding flexible films are known to those skilled in the art and cover a wide variety of different embodiments and adhesives. In most cases, bonding the films together requires a significant amount of adhesive to fully bond the films together and avoid delamination. However, due to sustainability and resource conservation considerations, attempts are being made to reduce the amount of adhesive required when laminating flexible films.

[0003] US 5,250,610 discloses a composite produced by a process which comprises applying an aqueous polyurethane dispersion based on a high molecular weight polyhydroxyl component containing carboxylic acid groups and an organic polyisocyanate to the surface of a material or workpiece and contacting said surface with the surface of another material or workpiece. By using a special aqueous polyurethane dispersion, the amount of adhesive can be increased to 1.5 g / m2. 2 can be reduced to

[0004] WO 97 / 03821 describes a method for producing a laminate in which a fluid adhesive, the hardening of which is accelerated by a catalyst, is applied to a first solid film, which is then contacted with a second solid or fluid film, composed wholly or partly of a plastic material, the latter film containing a catalyst which accelerates the hardening of the adhesive. The applied amount of adhesive is 1.5 g / m 2 It is.

[0005] However, reducing the amount of adhesive increases the risk of delamination as well as the risk of introducing air bubbles during processing. Such trapped air bubbles can be visually noticeable in the resulting composite, especially when transparent films are used, and can adversely affect the optical and mechanical performance of the resulting product. Furthermore, in most cases, the adhesive not only acts as a bond between the substrates, but also compensates for surface irregularities in the substrates to be bonded. Therefore, if the amount of adhesive is reduced, another method is required to smooth the substrate surface before bonding. One way to smooth the substrate surface is to heat its surface to smooth out any irregularities.

[0006] US2015 / 0140307 discloses a method for bonding two substrates, which comprises applying an adhesive onto a first substrate, combining the first substrate with the applied adhesive with a second substrate made of thermoplastic plastic, transforming the surface of the second substrate into a softened state by heating, and bonding the substrates together by pressure before, during and / or immediately after heating. The adhesive is applied at a coating weight of 2 g / m 2 It is applied as follows:

[0007] Bob Pasquale's article "Lamination system application and design considerations" summarizes several different methods of laminating multiple webs, including thermal bond lamination, where two or more webs are bonded together using heat and pressure. In this case, a primary web that is preheated about the main heat roll and a secondary web, which may be preheated prior to lamination, are introduced to the primary web at the nip point. The article emphasizes the importance of preheating the web as close to the lamination point as possible, and of cooling the product as quickly as possible after lamination and after it leaves the main heat roll.

[0008] DE 102005028661 refers to a method for producing a bilayer film in which two thermoplastic films of different thicknesses are brought to a source of heat radiation and softened or melted before the two films are brought together, the softening or melting being carried out using an infrared radiator.

[0009] US2011 / 0086237 discloses a joining apparatus for joining a thermoplastic first material to a second material, the apparatus including a heater arrangement for heating a joining surface of the first material to melt the joining surfaces, and a moving means for moving the first and second materials together into a joined state.

[0010] However, although the surface is smooth, heating is usually accompanied by deformation, particularly stretching, of the heated substrate, resulting in kinks and distortions in the resulting composite.

[0011] US6,599,387 relates to a method for producing flat composites from plastic parts, which comprises thermally bonding the surfaces of two plastic parts heated on one side, the surfaces being heated on the bonding side to a surface temperature 10-100K higher than the Vicat softening point, provided that the plastic parts retain their original shape during the preheating stage, and are pressed between a pair of rolls at a forward speed of 5-200mm / sec and with a pressing force of 10-500N applied to the rolls. To heat the bonding surfaces of the plastic parts, there are indirect physical methods such as high-frequency electromagnetic fields and ultrasound, and direct heat irradiation methods such as hot air blowers and infrared ray irradiators. Preferably, the plastic parts are preheated in an oven to avoid thermal stress.

[0012] US2017 / 0203543 addresses the above problems by providing a method for adhesively bonding two substrates, the method comprising the steps of: (i) conveying a first film-like substrate comprising at least one thermoplastic on at least one supporting conveyor belt through a heating zone, where the substrate is heated so that the surface of the first substrate changes to a softened state; and (ii) combining the first substrate with a second substrate, where the surface of the second substrate has a viscosity of 0.01-4 g / m. 2with an adhesive at a coating weight of about 1000 ppm, and during and / or immediately after heating, (iii) adhesively bonding the two substrates together by pressure.

[0013] Prior art methods using a supporting conveyor belt to minimize deformation of the heated substrate film have the disadvantage that special attention must be paid to the conveyor belt operating speed, and although the longitudinal deformation is reduced, the problem of transverse deformation is not solved. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] U.S. Patent No. 5,250,610 [Patent Document 2] WO 97 / 03821 [Patent Document 3] US Patent Application Publication No. 2015 / 0140307 [Patent Document 4] German Patent No. 102005028661 [Patent Document 5] US Patent Application Publication No. 2011 / 0086237 [Patent Document 6] U.S. Patent No. 6,599,387 [Patent Document 7] US Patent Application Publication No. 2017 / 0203543 [Non-patent literature]

[0015] [Non-Patent Document 1] Bob Pasquale, "Lamination system application and design considerations" Summary of the Invention [Problem to be solved by the invention]

[0016] It is therefore an object of the present invention to provide a method by which flexible films can be laminated without the risk of the film deforming during lamination.

[0017] Surprisingly, it has been found that the above mentioned objects are achieved by a method in which the heating of the film is performed by means of an assembly of heatable rollers. [Means for solving the problem]

[0018] A first object of the present invention is therefore a method for bonding flexible films, comprising: i) providing a first film having a thermoplastic surface; ii) providing a second film; iii) pressing the first film and the second film together with pressure; Here, the thermoplastic surface of the first film is heated to soften it and then merge with the second film; The heating of the surface of the first film is characterised by an assembly of heatable rollers (1, 2). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A softened state according to the present invention refers to a state of the substrate in which the surface of the substrate can be plastically deformed while the substrate remains dimensionally stable without losing its original shape.

[0020] In a preferred embodiment, the surface of the second film is coated with an adhesive.

[0021] By heating the surface of the film with an assembly of heatable rollers, complicated heating with radiators or hot air can be avoided. Moreover, it was surprisingly found that the heating efficiency is significantly improved by directly contacting the thermoplastic surface of the film with the heated rollers. Furthermore, an additional smoothness of the surface was observed, which is probably due to the direct contact of the thermoplastic film with the surface of the rollers. Moreover, by including a means for heating the surface in the film transport system, it was possible to increase the transport speed of the film without the risk of deformation of the film in the longitudinal or transverse direction.

[0022] In a preferred embodiment, the assembly of heatable rollers comprises 2 to 10, in particular 2 to 5, heatable rollers, which are preferably arranged in succession horizontally to the process direction. The thermoplastic surface of the first film is converted to a softened state by the heating device. However, care must be taken not to heat the surface, so as not to damage the film. To this end, it is desirable to control the energy input during heating without interrupting the process. Surprisingly, it has been found that the energy input can be controlled by adjusting the distance between the heatable rollers and the first film. In a preferred embodiment, each heatable roller of the assembly is individually controllable, for example by removing one or more of the heatable rollers from contact with the first film, thereby adjusting the distance between the heatable rollers and the first film. It has been surprisingly found that this procedure allows easy individual adjustment of the heating of the thermoplastic surface. The temperature of the heatable rollers of the assembly may be adjusted depending on the softening point of the thermoplastic surface of the first film. The softening point of a thermoplastic material can be measured by various methods, for example by the heat deformation method (ASTM D648) or the ring and ball method (ISO 4625). The softening temperatures of commonly used thermoplastics are summarized in the table. In a preferred embodiment, at least one heatable roller has a temperature of 80-300°C, preferably 110-200°C. Preferably, the temperature of each heatable roller can be controlled individually. In this way, the temperatures of the heatable rollers may differ from each other. Thus, in a preferred embodiment, each of the heatable rollers has the same or different temperatures.

[0023] Furthermore, the diameter of the heatable rollers of the assembly can be selected according to need. In a preferred embodiment, said at least one heatable roller has a diameter of 10 to 250 cm, preferably 50 to 100 cm.

[0024] During the course of the present invention, it has been surprisingly found that deformation of the heated film can be avoided without cooling. Instead, the temperature of each heatable roller can be individually adjusted to control the temperature of the film, improving the energy balance. Furthermore, the speed of the heated rollers can be individually adjusted to provide an additional means of control. In a preferred embodiment, each of the heatable rollers is actively driven. Even more preferred are embodiments in which each of the heatable rollers is actively driven and individually addressed.

[0025] In a preferred embodiment of the method of the present invention, the first film is guided through a series of rollers arranged on either side of the film, each roller being individually adjustable to bring the surface of the roller into contact with the film. Preferably, the set of rollers is operated such that adjacent rollers have opposite rotational directions. At least the roller facing the thermoplastic surface of the first film is a heatable roller to transition the thermoplastic surface of the film to a softened state. It has been found that by individually adjusting the rollers, the contact area between the roller and the film can be adjusted as required, allowing precise adjustment of the energy input of the thermoplastic surface. Preferably, the rollers are linearly and / or non-linearly adjustable.

[0026] The method of the present invention is designed for bonding flexible films, such as those used in food packaging. In a preferred embodiment, the first film comprises or is composed of a material selected from polyolefins, such as polyethylene and polypropylene, polyvinyl chloride, ethylene-vinyl acetate, ethylene-acrylate copolymers, ethylene-methyl methacrylate copolymers and ethylene-acrylic acid copolymers, polyesters, polylactides, polyamides and ionomers. In a particularly preferred embodiment, the first film comprises or is composed of polyethylene, polypropylene or a mixture thereof.

[0027] In a preferred embodiment, the second film comprises or consists of a material selected from metals such as aluminum, iron, zinc, metal alloys such as bronze and aluminum alloys, thermosets or thermoplastics such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylonitrile-butadiene-styrene copolymers, polyesters, polyamides, organic polymers such as cellophane, paper, cardboard, woven fabrics, nonwoven fabrics, and the like.

[0028] In a preferred embodiment of the present invention, the surface of the second film is coated with an adhesive to further increase the bond strength between the first and second films. Heating the first film of the present invention can significantly reduce the amount of adhesive required to bond the films together. In a preferred embodiment, the adhesive is 2 g / m 2 Less than 1 g / m 2 Less than 0.01 to 0.7 g / m 2 The adhesive is applied to the surface of the second film with a coating weight of 0.1%. Surprisingly, no peeling of the product was observed, despite the reduced amount of adhesive used. Meanwhile, the bonded film shows excellent adhesive strength and is suitable for various applications. Any suitable adhesive can be used in the method of the present invention. However, in a preferred embodiment, the adhesive employed in the method of the present invention is selected from thermoplastic adhesives or crosslinkable adhesives in solvent-borne, water-based or solvent-free form. Further preferred are embodiments in which the adhesive is based on thermoplastic polymers such as polyurethane, ethylene-vinyl acetate, solvent-borne adhesives such as acrylate adhesives, one- or two-component polyurethane adhesives, reactive adhesives such as silane crosslinking adhesives, one-component polyurethane adhesives, solvent-free one- or two-component polyurethane adhesives, silane-based or radiation crosslinking systems.

[0029] Another object of the invention is a device for carrying out the method according to the invention. The device according to the invention comprises: a) a feeding device for feeding a first film having a thermoplastic surface; b) a feeding device for feeding a second film c) a heatable roller assembly for heating the thermoplastic surface of the first film to bring the thermoplastic surface to a softened state; d) a means for contacting the first film with the second film; and e) an output device for dispersing the joined first and second films.

[0030] In the setup of the apparatus of the present invention, the speed at which the film is transported can be adjusted individually. In a preferred embodiment, the rollers are positively driven.

[0031] Surprisingly, it has been found that by carefully controlling the energy input during heating, deformation of the heated film can be avoided. In a preferred embodiment, the heatable rollers included in the device of the invention are therefore individually controllable.

[0032] In a preferred embodiment of the device of the invention, the device consists of a series of rollers arranged on either side of the film, each roller being individually adjustable to bring the surface of the roller into contact with the film. Preferably, the set of rollers is operated such that adjacent rollers have opposite rotational directions. At least the roller facing the thermoplastic surface of the first film is a heatable roller to transition the thermoplastic surface of the film to a softened state. It has been found that by individually adjusting the rollers, the contact area between the roller and the film can be adjusted as required, and the energy input of the thermoplastic surface can be precisely adjusted, without the need for additional cooling. Preferably, the rollers are linearly and / or non-linearly adjustable.

[0033] In a preferred embodiment, the apparatus of the present invention further comprises means for coating a surface of the second film with an adhesive.

[0034] The apparatus of the present invention includes a means for contacting a first film having a thermoplastic surface in a softened state with a second film, In a preferred embodiment, the means for contacting the first and second films includes at least one lamination unit for pressing the second film against the softened surface of the first film.

[0035] The lamination unit is preferably arranged behind the heating device along the process direction. In a particularly preferred embodiment, the lamination unit is arranged in close proximity to at least one heatable roller. In a preferred embodiment, the contact of the first and second film is achieved by directing the film between at least one heatable roller and the lamination unit. The lamination unit is preferably provided in the form of a heatable lamination roller. Surprisingly, it was found that by employing a lamination unit with two rollers, one of which is heatable and the other of which is not heatable, the lamination is improved. In a particularly preferred embodiment, the lamination unit comprises at least two rollers, one of which is preferably a heatable roller. The preferred design of the lamination unit allows a very effective activation of the thermoplastic surface of the first film by heating the areas of the film that are to be bonded by direct contact of the rollers.

[0036] Any component of the apparatus of the present invention can be operated in a manner that ensures rapid and efficient production. In a preferred embodiment, the first film is transported at a speed that is 0.5 to 1.5 times, preferably 0.9 to 1.1 times, that of the second film. Furthermore, the speed of the heatable rollers can be adapted relative to the speed of the first and / or second films as required.

[0037] The method of the invention and the device of the invention are especially designed for laminating flexible films. A further object of the invention is therefore a composite obtained by the method of the invention or the device of the invention. If the method of the invention is carried out with adhesive, the composite of the invention is especially distinguished by a thin layer of adhesive between the films. The adhesive layer preferably has a thickness of less than 5 μm, preferably less than 2 μm, in particular less than 1 μm.

[0038] The present invention will be described in more detail with reference to the following figures, which should not be understood in any way as limiting the scope or spirit of the invention. Preferred aspects of the invention include the following. [1] A method for laminating a flexible film, the method comprising: i) providing a first film (9) having a thermoplastic surface; ii) providing a second film (10); iii) Bringing the first and second films together by pressure. Here, the thermoplastic surface of the first film is heated to soften it and then merge with the second film; wherein the heating of the surface of the first film is performed by an assembly of heatable rollers (1, 2). [2] The method according to [1], characterized in that the surface of the second film (10) is coated with an adhesive. [3] The method according to any one of [1] and [2], characterized in that the heating of the thermoplastic surface of the first film is carried out by an assembly of 2 to 10, preferably 2 to 5, heatable rollers (1, 2). [4] The method according to any of the preceding claims, characterized in that each of the heatable rollers (1, 2) of the assembly is individually controllable. [5] The method according to any of the preceding claims, characterized in that the first film (9) comprises or is made of a material selected from polyolefins, polyvinyl chloride, ethylene copolymers, polyesters, polylactic acid, polyamides and ionomers. [6] The method according to any of the preceding claims, characterized in that the second film (10) comprises or is made of a material selected from metals, metal alloys, thermosetting or thermoplastic plastics, organic polymers, textiles and nonwoven materials. [7] 2g / m 2 Less than 1 g / m 2 Less than 0.01 to 0.7 g / m 2 The method according to claim 2, wherein the adhesive is applied to the second film with a coating weight of [8] An apparatus for carrying out the method according to any one of [1] to [7]. [9] a) a supply device for supplying a first film having a thermoplastic surface; b) a feeding device for feeding a second film; c) a heatable roller assembly for heating the thermoplastic surface of the first film to bring the thermoplastic surface to a softened state; d) a means for contacting the first film with the second film; and e) an output device for discharging the spliced ​​first and second films; The device according to [8], comprising:

[10] An apparatus according to any of the preceding claims, characterized in that each of the heatable rollers (1, 2) of the assembly is individually controllable.

[11] An apparatus according to any of the preceding claims, characterized in that the rollers (1, 2) are individually adjustable, preferably linearly and non-linearly.

[12] An apparatus according to any of the preceding claims, characterized in that each roller (1, 2) is actively driven.

[13] The apparatus according to any of the preceding claims, characterized in that the means for contacting the first and second films preferably includes at least one lamination unit arranged in close proximity to at least one heatable roller (1, 2).

[14] A complex obtained by the method according to any one of [1] to [7] or the device according to any one of [8] to

[13] . [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 shows an embodiment of the invention in which a pair of linearly adjustable rollers are positioned on either side of a first film, with the apparatus of the invention in an idle position. [Diagram 2] FIG. 2 shows an embodiment of the invention in which a pair of linearly adjustable rollers are positioned on either side of a first film, with the apparatus of the invention in an operative state. [Diagram 3] FIG. 3 shows an embodiment of the invention in which a set of rollers is non-linearly adjustable, with the apparatus of the invention in an idle state. [Figure 4] FIG. 4 shows an embodiment of the invention in which a set of rollers is non-linearly adjustable, and in which the device of the invention is in a working state.

[0040] Figures 1 and 2 show an embodiment of the invention in which a set of linearly adjustable rollers is arranged on either side of the first film. Figure 1 shows an embodiment of the invention in the idle state, and Figure 2 shows an embodiment of the invention in the working state. The film (9) with a thermoplastic surface is passed through a series of rollers (1, 2), at least one of which is a heatable roller, to bring the thermoplastic surface of the film into a softened state. The contact of the rollers (1, 2) with the film is established by adjusting the rollers along their axes (5), whereby the contact area between the film and the rollers can be adjusted as required. After being guided through the series of rollers, the first film (9) is brought into contact with the second film (10) in such a way that the surface of the second film (10) is in contact with the thermoplastic surface of the first film (9) in the softened state. The contact is made through a lamination unit (7) to obtain a laminated product (11).

[0041] Figures 3 and 4 show an embodiment of the invention in which a set of rollers can be adjusted non-linearly, with Figure 3 showing the device in an idle state and Figure 4 showing the device in a working state. A film (9) with a thermoplastic surface is passed through a series of rollers (1, 2), at least one of which is a heatable roller, to bring the thermoplastic surface of the film into a softened state. The contact of the rollers (1, 2) with the film is established by adjusting the rollers along the axis (5), thereby maximizing the contact area between the film and the rollers and achieving high efficiency. After being guided through the series of rollers, the first film (9) is brought into contact with a second film (10) such that the surface of the second film (10) is in contact with the thermoplastic surface of the first film (9) in a softened state. The contact is made through a lamination unit (7) to obtain a laminated product (11). [Explanation of symbols]

[0042] List of reference numbers: 1 Upper Roller 2 Lower Rollers 3. Contact Area 4 Rotation Direction 5-axis movement 6 Front pulley 7 Lamination Unit 8-axis 9. First Film 10. Second Film 11 Lamination

Claims

1. 1. A method for laminating a flexible film, the method comprising: 0) Providing a conveying system including a lamination roller and a heating device, where the lamination roller is disposed behind the heating device along the process direction. i) providing a first film (9) having a thermoplastic surface; ii) providing a second film (10); iii) pressing the first and second films together, where the thermoplastic surface of the first film is heated to soften it and then merge with the second film; Including, Heating of the surface of the first film is achieved by an assembly of heatable rollers (1, 2). the means for contacting the first and second films includes a lamination roller; and Coating the surface of the second film (10) with an adhesive, wherein the adhesive is 2 g / m ２ Applying adhesive to the second film with a coating weight of less than A method comprising:

2. 2. The method according to claim 1, characterized in that the heating of the thermoplastic surface of the first film is performed by an assembly of 2 to 10 heatable rollers (1, 2).

3. 3. The method according to claim 2, characterized in that the heating of the thermoplastic surface of the first film is performed by an assembly of 2 to 5 heatable rollers (1, 2).

4. The method according to any of claims 1 to 3, characterized in that each of the heatable rollers (1, 2) is individually controllable by adjusting the distance between the first film and each roller.

5. The method according to any of the preceding claims, characterized in that the first film (9) comprises or is made of a material selected from polyolefins, polyvinyl chloride, ethylene copolymers, polyesters, polylactic acid, polyamides and ionomers.

6. The method according to any of the preceding claims, characterized in that the second film (10) comprises or is made of a material selected from metals, metal alloys, thermoset or thermoplastics, organic polymers, textiles and nonwoven materials.

7. 1 g / m ２ The method according to any one of claims 1 to 6, characterized in that the adhesive is applied to the second film with a coat weight of less than 1000g.

8. 0.01~0.7g / m ２ 8. The method of claim 7, wherein the adhesive is applied to the second film with a coat weight of

9. a) a feeding device for feeding a first film (9) having a thermoplastic surface; b) a feeding device for feeding a second film (10), where the surface of the second film (10) is coated with adhesive, the adhesive being 2 g / m ２ applied to the second film with a coat weight of less than c) a heating device for heating the thermoplastic surface of the first film (9) to bring the thermoplastic surface into a softened state; d) a lamination roller for contacting the first film (9) and the second film (10); and e) an output device for discharging the spliced ​​first and second films; wherein the heating of the surface of the first film is performed by an assembly of heatable rollers (1, 2), each of the heatable rollers (1, 2) being individually controllable; An apparatus comprising a conveying system comprising: the heatable rollers (1, 2) are individually controllable by adjusting the contact area of ​​each roller with the first film; and The lamination roller is located behind the heating device along the process direction An apparatus comprising:

10. 10. Device according to claim 9, characterized in that the rollers (1, 2) are linearly and non-linearly adjustable.

11. Device according to any of claims 9 to 10, characterized in that each roller (1, 2) is actively driven.

12. Apparatus according to any of claims 9 to 11, characterised in that at least one lamination roller is arranged in close proximity to said at least one heatable roller (1, 2).

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