WO2015087269A1 - Multilayer removable self-adhesive film for masking and/or protection during painting operations - Google Patents

Abstract

The self-adhesive film for masking and/or protecting surfaces, in particular those subject to high temperature operations such as painting cycles, is formed of a support having a surface covered by a self-adhesive mass of the "removable type". This support is a multilayer formed from at least two layers assembled together by means of a bonding process. These layers include a layer having one surface covered by the said self-adhesive mass and a backing layer, which are of plastics or metal materials having melting points > 150°C, such as homopolymers and copolymers of polyesters, polypropylene, polyamide and polyurethane, aluminium and its alloys.

Description

Multilayer removable self-adhesive film for masking and/or protection during painting operations

It is known that masking tapes and protective films are used especially during painting operations and in general they comprise a flexible film support onto which an adhesive mass is applied, enabling them to be used in operations even at the high temperatures required for curing paints (usually over 100°C).

The main feature of these supports with applied adhesives is that one side or surface has a coating or a deposit or a spread of a self-adhesive mass which is normally described in the technical literature and in the terminology of those skilled in the art as being of the "removable type", that is firstly one which can be easily and quickly removed after temporary use on the surface in question (low peel strength) and secondly one in which the support and the adhesive mass do not lose their mutual cohesion, so that no obvious traces of the adhesive mass are left on the object protected when the masking is removed.

This property of "removable self-adhesion" is fundamental because it identifies the technical field of this invention, that is that of self-adhesive tapes for removable use functionally intended for temporary use, such as for example the well-known masking tapes, protective films, application tapes, etc., in contrast to the other large and diverse range of supports or self-adhesive tapes for permanent application, which are functionally intended to remain permanently attached to the object or surface to which they have been applied, such as for example the well-known packaging tapes, scotch tape and electrically insulating tapes for the refrigeration, decorative, etc., industries, and therefore provided specifically with self-adhesive masses normally described in the technical literature and in the terminology of those skilled in the art as being of the "permanent type".

If used conventionally without further specification in the technical field of application, as in this description, the terms adhesive and self-adhesive refer without distinction and with the same meaning to adhesive films and tapes known as "pressure sensitive" or the corresponding adhesive masses which are capable of adhering to the objects to which they are applied as a result of only the pressure which may be applied to them and not through a provision dependent on other factors, such as temperature, water, etc.

The terms "adhesive side" and "backing" of a self-adhesive film are essential for the identification of their corresponding characteristics, in particular in the technical field of the invention, because apart from the adhesive side, where adhesion (peel) strength, cohesion of the adhesive mass (no release of adhesive) and resistance to temperature (> 100°C) are essential, the properties of the backing being able to hold oversprayed paint spray (paintability), lesser strength while attached to or unwound from the inner core on which they are wound (peeling of the backing), and in this connection also maintaining a flat profile for the film itself (flatness), that is without a curling effect as they are unwound, are equally essential.

In the present state of the art the removable self-adhesive tapes used in the sector of masking or protecting surfaces undergoing application procedures at a high temperature have supports which are usually of a paper base. The adhesive mass coated onto the adhesive-coatable surface of the support instead normally comprises solutions based on rubber or normally acrylic resins, which are in any event dissolved in synthetic solvents. In the description below the term solvent will unless specified otherwise refer in general to those of an organic nature or in any event synthetic ones. The pair of paper-type backing and the solvent-based self-adhesive mass develop a functional synergy which does not always meet application requirements, that is it suffers from significant limitations and problems which have hitherto not been solved in the operations of masking and protecting surfaces, in particular when these are painted at high temperature. Above all, because of their nature supports of a paper nature have unstable cohesion with self-adhesive masses; thus in order to assist cohesion between the paper support and the self-adhesive mass coated onto one side thereof and to render it stable a preliminary process of making it suitable for adhesion must always be performed on the adhesive- coatable surface. This process comprises depositing special adhesion-promoting polymer mixtures on the said side or surface of the paper film and subsequently drying them in a stove. Deposition or impregnation on the backing of the paper support, that is the side opposite that with adhesive, using the same technological process is also necessary. In this case special anti-adhesive resins are applied to prevent the adhesive film from adhering to the backing through its own adhesive mass when wound in a roll, so that it is consequently impossible to unwind it. This process is commonly referred to as deposition or impregnation with "release", which therefore makes it easier to release or unwind the adhesive film during use, thanks to impregnation of the backing of the support through the said anti-adhesion resins. The technological process itself of impregnating both sides of the paper support is wholly similar to that which is required for making it suitable for adhesive coating, and therefore this type of paper support requires three similar processes at three separate times in order to eventually convert it into self-adhesive film; thus three operations of depositing different substances - adhesion promoters, release resins, and finally a self-adhesive mass proper.

Paper supports further suffer of the limitation that they are incompatible with water-based adhesive masses; in fact they are conventionally coated with solvent-based self-adhesive masses. However, even the conjunction between solvent-based self-adhesive masses and supports of a paper nature has critical problems - when in contact with the paper support the solvent-based adhesive mass in fact develops a synergy which is particularly reactive to thermal stress, such as that experienced during paint curing cycles. This particular reactivity results in weakening the cohesive bond between the paper support and the adhesive mass and also gives rise to a kind of yielding or kind of "curing" effect on the paper support because of the thermal stress.

The undesired effects of this reactivity are apparent during the cooling stage, that is when the masking is removed. During this stage of the process, with the return to ambient temperature, the paper/solvent-based self-adhesive complex suffers rigidification of the self-adhesive mass because of the typically thermo-hardening behaviour of rubbers or resins dissolved in solvent, with a consequent increase in adhesive strength when the masking is removed, or an increase in the peel strength adhesion of the masking to the object; this not infrequently brings about undesired transfer or release of some traces of adhesive onto the article masked, and a subsequent need to clean it.

Additionally, embrittlement of the paper support often occurs during the temperature cycle because, as mentioned, a kind of "curing" of the paper support, which again not infrequently breaks or tears when the masking is removed, leaving pieces attached to the object, thus causing the operator to carry out several individual removal procedures.

The use of solvent-based self-adhesive masses obviously also gives rise to production disadvantages because of the need for post-combustion or recovery of the solvents, the onerous nature of rigid safety standards for workers' health, for environment impact in general, including outside the production site - disposal of processing wastes, etc.

Furthermore, because in the technology of producing any adhesive coated support a particular proportional relationship must always be guaranteed between the thickness of the support and the quantity of adhesive mass, paper self-adhesive films usually have an overall thickness of not less than approximately 140-150 μηι, of which the adhesive mass coating accounts for a dry thickness of up to approximately 40 μιη; thus ultimately such self-adhesive supports have a corresponding overall mass of constituent materials that is in any event never less than approximately 100-120 g/m².

Conventional paper adhesive films also have a rather critical stability as regards their useful storage life, because over time the rubber or resin-based adhesive mass tends to increase its adhesion and become even more attached to the backing of the film, even if that backing is impregnated with release products.

Once again this limitation is related to the special reactivity which the paper/solvent-based self-adhesive mass pair develops in relation to thermal and humidity changes in the environments in which it is kept; because of this, manufacturers are not usually disposed to extend a warranty for more than one year.

At the present time there are therefore no paper or protective film masking tapes that are capable of ensuring that the set of limitations and difficulties just described can be overcome.

The object of this invention is therefore that of providing a new adhesive film which combines several characteristics and performance not available to an ordinary adhesive support of conventional paper, and which therefore overcomes at least one of the disadvantages mentioned above in a significantly advantageous way.

The abovementioned object is achieved through a self-adhesive film for masking and/or protecting surfaces, in particular those undergoing operations at high temperature, such as painting procedures, in which the film is formed of a support having a surface coated with a self-adhesive mass of the "removable type", the said film being characterised by the fact that the said support is a multilayer formed of layers assembled together through a bonding process and that the said layers include a layer having a surface coated with the said self- adhesive mass and a backing layer, which are of plastics or metal materials having a melting point > 150°C selected from the group consisting of homopolymers and copolymers of polyesters, polypropylene, polyamide and polyurethane, aluminium and its alloys. The specific feature of the film according to the invention is therefore that it comprises the use of a multilayer support produced by bonding, whose outer layers - namely the one coated with the self-adhesive mass, referred to briefly as "adhesive- coatable", and the backing - are made of materials selected from those indicated above.

One or more intermediate layers of materials which are the same or different from the materials of the adhesive-coatable layer and the backing layer may also be present, provided that they are compatible with use in the bonding process. Likewise it is possible that the support may not include intermediate layers and comprises only the two outer layers.

Further advantages and features of this invention will be apparent from the following detailed description provided by way of a non-limiting example with reference to the appended drawings in which Figure 1 illustrates the typical general structure of a self- adhesive film according to the invention and Figures 10, 20, 30, 40, 50, 60 and 70 illustrate respective specific structures of films according to the invention. Figure 1 illustrates the component layers of the multilayer adhesive film diagrammatically in cross-section. The first layer, which remains visible and is never adhesive, is conventionally known as backing (1.1) of the support. This layer is assembled to a second film layer which has a surface or layer (1.3) on which adhesive may be coated through a bonding process, normally through the interposition of a layer of adhesive (1.2) so as to firmly join the layers together into a single non-delaminatable film support. A coating of self-adhesive mass (1.4) is applied to the aforesaid adhesive-coatable surface or layer (1.3) and thus definitively converts the multilayer support into a true self-adhesive film. Possible quantitative variants of this typical general arrangement of the support according to the invention are provided (Figure 1), in the meaning that it is possible to add other film layers between the layer acting as a backing (1.1) and the layer having the adhesive- coatable surface (1.3). In this respect it is possible to produce multilayer supports with more than two film layers, but which are assembled together by means of bonding technologies regardless of the nature of the film materials used, including generic materials such as for example: rubber, felt, kraft paper, etc., but which may only be present as internal layers of the multilayer support, that is they will never be used as the adhesive- coatable layer or the backing for the multistructural adhesive film. In this context it is also possible and functional to form a type of multilayer support in accordance with the principles of the invention described hitherto in which the said support comprises at least one layer placed between the said layer having a surface coated with the said self-adhesive mass and the said backing layer, the at least one layer placed in between being of a material which is the same as or different from the materials of the layer having a surface coated with the said self-adhesive mass and the backing layer.

All types of film materials forming the multilayer supporting layers can be easily obtained by acquiring them on the market in the form of films, that is in a physical form (coextruded, woven-non-woven, metallised, films, etc.) which is suitable for forming a flexible multilayer support after assembly.

Average data characteristic of the first group of film materials which can be used in construction of the support for the film according to the invention are provided below.

Polypropylene (PP) is a polymer have a mean specific gravity of 0.90 kg/dm³, a breaking strength of Kr = 33 N/mm² and a melting point of 160°C, normally produced in the form of an extruded film and as a non-woven fabric; the molecular orientation may be linear (OPP) or bi-orientated (BOPP). Polyester (PET) is a polymer having a mean specific gravity of 1.38 kg/dm³, a breaking strength of Kr = 40 N/mm² and a melting point of 230°C, normally produced in the form of an extruded film and as a non-woven fabric. Polyamide or nylon (PA) is a polymer having a mean specific gravity of 1.14 kg/dm³, a breaking strength of Kr = 70 N/mm² and a melting point of 215°C, normally produced in the form of an extruded film and as a non-woven fabric. Polyurethane (PUR) is a polymer having a mean specific gravity of 1.15 kg/dm³, a breaking strength of Kr= 38 N/mm², and a melting point of 170°C. It is further specified that the polymers listed above can be used according to the invention and are normally also available on the market in the form of "non-woven fabric" (nwf), also known as "non- woven". The said nwf flexible polymer films are produced not by the extrusion process but by agglomeration of their fibres and then compacted into flexible films through various agglomeration and interlacing processes. Of the best known types of nwf polymers, which are mentioned purely by way of example and not in any limiting way, mention may be made of those of the "Air-laid" type - essentially films obtained by impregnating polymer fibres with cross-linkable resins which are subsequently dried or consolidated into a single body through the application of heat, a particularly rigid film which can easily be cut up and produced even in particularly small thicknesses; the "Spunlaced" type: the fibres are joined together by high pressure water jets, the end product being particularly soft, and longitudinally elastic/resilient; sometimes the fibres are hydro-entangled and impregnated with synthetic lattices to increase their abrasion resistance; and the "Spunbonded" type: the fibres are assembled or interlaced together by means of a fusion process. One essential in the production of a "spun" is the control of four almost simultaneous operations: extrusion, stretching, coating the sheets and their consolidation. The first two are similar to those for the manufacture of synthetic fibres and constitute the spun material, the other two form the bonded material, hence the English term "Spunbond"; "Thermobond": the polymer fibres are thermally bonded, or pressed in a roller under the action of heat at approximately 170°C.

In the embodiments described by way of a non-limiting example, the "Spunlaced" type has been used for the purposes of constructing the multilayer support according to the invention.

Another film component used is aluminium (AL), a metal with a melting point of 660°C, Kr 65 N/mm, specific gravity 2.7 kg/dm³. It is produced as annealed or unworked alloys and subsequently rolled as a flexible film; in the embodiments illustrated below annealed 1200 aluminium alloy has been selected by way of a non-limiting example, but unworked rolled sheets or any other type of annealed aluminium alloy which can be rolled could be used as an alternative. In the context of the application according to the invention, the thermal performance of the first group of materials described above - polypropylene (PP), polyester (PET), polyamide (PA), polyurethane (PUR) and aluminium (AL) - can be considered to be very high to the extent that it is possible to use these materials to assemble multilayer supports which are capable of withstanding working cycles at temperatures of between 150°C-220°C for a period of approximately half an hour (sufficient time for the cross-linking of any paints, including powder paints, in a stove) without any appreciable changes taking place in their physical/chemical structure.

However for masking and protection applications at lower temperature procedures, that is between 100°C-150°C, it is sufficient to assemble at least one of the polymer film materials belonging to a second group or series having lesser thermal performance or lower melting points belonging to the family of polyolefins, such as the series linear low density polyethylene (LLDPE) having a melting point of 115°C, low density polyethylene (LDPE) having a melting point of 120°C, medium density polyethylene (MDPE) having a melting point of 124°C, high density polyethylene (HDPE) having a melting point of 135°C and again polymers such as polystyrene (PS) with a melting point of 100°C, ethyl vinyl acetate (EVA) with a melting point of 110°C, cellulose acetate (CA) with a melting point of 140°C, including their respective copolymers in the abovementioned series of materials, together with at least one material from the group of materials having high thermal performance between 150°C and 220°C mentioned above. It is thus possible and functional to manufacture a type of adhesive-coatable multilayer support, similarly to the principles of the invention described hitherto, which in addition to comprising at least one material from the group mentioned - PP, PET, PA, PUR, AL - also comprises at least one layer of material having a melting point below 150°C selected from the group comprising homopolymers and copolymers of low density polyethylene (LDPE), high density polyethylene (HDPE), medium density polyethylene (MDPE), linear low density polyethylene (LLDPE), ethyl vinyl acetate (EVA), and polystyrene (PS). It goes without saying that even this type of support will necessarily comprise two outer layers, that is a backing layer and a layer having one surface coated with self-adhesive mass. Also in this case one or more intermediate layers may be present between the two outer layers, or the latter may be the only layers making up the support.

Manufacture of the support according to the invention through assembling various film layers through bonding is the simplest and most reliable technology; this may be achieved in two ways - adhesive bonding or coating one material upon the other. These technologies are well known to those skilled in the art of plastic films and are described here only to indicate unequivocally what is meant by a bonded multilayer film. These bonded multilayer films have been known for a very long time and used for example as films for packaging for food use, industrial bags and vapour-barrier films. The fact of having selected bonding technology for manufacture of the multilayer support according to the invention does not mean that individual polymer layers which will then be assembled together by means of the bonding technology cannot be extruded; on the contrary, individual polymer layers, whether monoextruded or coextruded, can be used without distinction in manufacture of the support according to the invention.

It is thus also possible and functional to manufacture a type of multilayer support according to the principles of the invention described hitherto in which at least one layer of the said support is produced by extrusion. It is likewise possible that all the layers in the said support are produced by extrusion.

In the first form or manner of bonding, the various film layers are assembled by adhesive bonding, using polymer adhesives of various types, which are also normally available on the market and intended specifically for this purpose; these adhesives are well known to those skilled in the art, such as for example monocomponent acrylic adhesives, solventless polyurethane adhesives, UVR cross-linkable acrylate adhesives, hot melt adhesives, etc. One example of a bonding adhesive is a polyurethane system from Rohm and Haas: "MOR-FREE 696A+C-83", which has been used in manufacture of the embodiments illustrated below as examples.

This polyurethane adhesive is therefore mentioned here only by way of a non-limiting example of any type of adhesive which could be used to bond together flexible films under the normal application conditions known to those skilled in the art.

This assembly is performed with the help of machines known as "flexible film bonding machines" which bond together the different layers of film through placing a layer of adhesive between them, such as one of the types just mentioned. The normally bonded widths of the film on a coil usually vary between 1000 and 1500 mm.

The support which is formed in this way will comprise successive layers bonded together into a single non-delaminatable multilayer support.

In particular the preference for this technology for producing a multilayer adhesive- coatable support is due to the fact that, when layers of polymer are assembled together in the case of the multilayer support, the layer of adhesive which binds them makes it possible to compensate for/take up the different plastic-elastic expansions of the various polymer layers in the manner of a joint, especially if they are subjected to thermal stresses.

This is an essential reason for choosing to produce multilayer polymer supports by bonding and not other technologies such as, for example, coextrusion.

In fact polymer coextrusion technology, unlike bonding, produces different layers of polymer film in direct contact with each other, without any intermediate layer, these being in fact directly assembled together at the time when they are produced through the coextrusion process.

When they are subjected to thermal stresses the various plastic-elastic behaviours of the coextruded polymer layers set in motion expansion or microslipping between them, which is not held back or compensated for or mediated in any way, with corresponding risks of dimensional distortions of the support.

The thermal stresses referred to are essentially those to which the multilayer support first experiences during the stage in which it is coated with adhesive (or during polymerisation or drying of the adhesive mass coated onto it in the stove), and secondly during the stage of application proper of the masking/protection for painted articles (or during their stoving).

A first possible consequence deriving from these different plastic-elastic behaviours of the coextruded polymer layers and their consequent microslipping is that when they start to be applied, or when they are being unwound, a "memory" of the different expansions experienced under thermal stress comes back to the coextruded film; this can give rise to dimensional distortion which makes placing of the adhesive film on the surface which has to be masked or protected more problematical; more specifically the multilayer adhesive support tends to suffer a so-called "curling" or "cupping" effect along its longitudinal axis, which should not occur to its planar profile.

That a film should be flat while it is being unwound is in fact essential for any adhesive tape which can be used for masking, because if it is not the operator will have to take very difficult care when applying the curled edges of the tape to the object which has to be protected.

As regards definition of the flatness of self-adhesive masking tapes and films, or its measurement, there is no specific standardised test protocol because at the present time the supports for these masking tapes, which are generally paper supports, do not in any way give rise to the problem of lack of flatness when they are being unwound. In any event the flatness of an adhesive roll which has been wound can easily be checked by examining this adhesive tape in one of the normal widths, that is 50 mm, taken in the form of a piece 500 mm long; placing the back of this piece on a flat surface without any restraint, it can be seen whether any of its edges rise and whether it rolls upon itself, in which case the curling effect is present; if this is not the case, that is if there is continuous contact between the back of the adhesive tape and the flat surface, the property which we can call the flatness of the support is confirmed.

A second possible consequence due to thermal stress experienced by the multilayer adhesive support if it is manufactured by coextrusion is that it remains on painted surfaces at the temperatures necessary for the process of curing the paints themselves (passage through a curing stove); more specifically in this case the "microslipping" of interest is that brought about by uncontrolled linear expansion forces operating on the coextruded support, as we have just seen, and the resistance force which anchors the adhesive film to the protected object, that is the strength of its adhesive mass. In other words it is the self- adhesive mass applied to the coextruded support which is exposed to the pulling forces along the lines of expansion of the layers constituting the support onto which it is coated.

As a result of this forced lateral movement of the adhesive mass on the surface of the masked object there occurs a loosening of cohesion between the adhesive mass and the multilayer support on which it is coated. It is easy to understand how this will not infrequently give rise to the release of obvious traces of the self-adhesive mass on the masked/protected object at the time when it is removed, and that these releases will be obvious in the form of stripes or spots and marks on the object which has been unmasked. Another particular possible manner of bonding, other than that just described by adhesive bonding, which is useful, is coating; in greater detail, in the case of materials such as paper and aluminium there is the possibility of forming bonds with polymer materials by technologies in which one material is coated on the other - by hot coating or even by sublimation - with the result that a single non-delaminatable multilayer support is formed between the different materials. One instance of a multilayer support obtained by bonding by coating is polyethylenated papers in which a layer of polyethylene of thickness between normally 9 μηι and 12 μιη is deposited on a paper film by hot coating.

Metallisation may also be regarded as another particular way of bonding by coating, in that this is also the junction of several materials together in order to obtain a single non- delaminatable multilayer film - typically some of the most widespread are aluminised plastics films, that is those coated with aluminium.

In fact, in addition to being available in the form of a flexible laminate (minimum available thicknesses are around 6-7 μηι) and, as has already been seen, being capable of being bonded to other polymer films by means of adhesive, aluminium can also be made available in very thin layers (0.0070-0.030 μηι) deposited under vacuum in the form of vapours (sublimation) on one or both surfaces of various polymer film materials; this process is known as the "metallisation" of plastics films.

Theoretically it is possible to bond a multilayer even by directly rolling films which are already adhesive, where an adhesive film is bonded by pressure onto the back of another film which is also already adhesive, or one which may be subsequently rendered adhesive, by rolling. This method has proved unreliable in practice, in that it is not capable of ensuring a stable union between the component layers of the multilayer support.

In this respect, it is readily found that these pressure rolled adhesive films delaminate during the operations of removing masking, that is there is a separation between their various layers, with part of the self-adhesive multilayer support still attached to the protected object and part delaminated in the hands of the operator engaged in removing the masking. The subject of the invention is a film with a new type of self-adhesive multilayer support through which surfaces can be masked and temporarily protected. In this respect, and in principle, any type of removable self-adhesive mass, whether water- or solvent-based, or even solventless, already normally used in the production of conventional masking tapes and protective films and therefore wholly well known to those skilled in the art may be coated onto such a support.

However, among all the various types of adhesives available, polymer adhesive masses in aqueous solution are preferred in order to achieve the full characteristics of the self- adhesive multilayer support.

Unlike what is the case with regard to paper supports, adhesive polymer masses in aqueous solution have no contraindication to being coated onto any materials in the groups or series of film supports mentioned above.

Firstly, by using water-based self-adhesive masses with suitable modulation of the cross- linking agents it is possible to obtain optimum removability from the protected supports, that is low values of the force necessary for both application and removal, in addition to suitable adhesion strengths between the film and the object protected; all of this always in comparison to relative typical values for paper supports onto which solvent-based self- adhesive masses have been coated.

Polymer adhesive masses in aqueous solution are normally aqueous dispersions of around 50% of polymer resins (acrylic, styrene-butadiene, acrylonitrile, polyurethane resins, etc.), which can be activated by the addition of suitable cross-linking agents (isocyanates, polyaziridine, etc.), which are capable of completing their polymerisation and altering their adhesive properties.

In all circumstances, once they have been coated onto the support by means of suitable coating machines, the polymer adhesive masses in aqueous solution pass through a stove in order to evaporate off the vehicle, with consequent termination of the cross-linking of the adhesive mass. Times, temperatures, the pull of the drawing rollers and all the other production variables in the coating and drying process and consequent cross-linking are well known to those skilled in the art who normally coat protective films.

Non-limiting formulations of water-based polymer adhesive masses which, in addition to being of a known type and prepared by those skilled in the art, are also normally available on the market already formulated and ready for use are described below.

ADHESIVE MASS FORMULATION NO. 1 - ACRYLIC-BASED RESIN

ADHESIVE MASS FORMULATION NO. 1

CROSS-LINKING AGENT FOR ACRYLIC-BASED RESIN

Polyaziridine % SUPPLIERS

1 XAMA/7(tris trimethylolpropane) 100.00 ICHEMCO

ADHESIVE MASS FORMULATION NO. 2 - ACRYLIC-BASED RESIN

WATER-BASED ACRYLIC EMULSION % SUPPLIERS

1 Acronal 50D (50% DRY) 81.73 BASF 2 Acronal 7D (50% DRY) 18.27 BASF

TOTAL 100.00

ADHESIVE MASS FORMULATION NO. 2

CROSS-LINKING AGENT FOR ACRYLIC-BASED RESIN

In both the formulations the cross-linking agent promoting catalysis is added as a percentage by weight to the weight of adhesive mass. In the case of isocyanates the normal dose lies between 1 and 5%, for polyaziridine between 0.3 and 1%. Another particularly useful type of removable self-adhesive mass which is indicated here by way of a non-limiting example comprises solventless self-adhesives (that is 100% of the polymer without any vehicle) which can be cross-linked by UV rays. This technology well- known to those skilled in the art comprises coating a polymer containing photoinitiators, very frequently in the form of a hot melt, and immediately cross-linking it by exposing it to UV lamps; with this technology costly passages through a stove at high temperature which are necessary in order to cross-link water-based or solvent-based self-adhesive masses are therefore eliminated.

The independent variable in this process is the required quantity of UV rays in the frequency band selected; in the case in point the preferred choice is the use of UV-c rays [200-280 nm] in order to achieve the desired degree of cross-linking. Those skilled in the art will readily identify exposure times and the number of lamps required in this connection; by way of a non-limiting example, a possible commercial formulation of UVR cross-linkable adhesive which can be used for this type of process - BASF polyacrylate resin "ac-Resin DS 3532" - is described below. ADHESIVE MASS FORMULATION NO. 3 - cross-linkable by UV

Other types of removable self-adhesive masses similar to the UVR cross-linkable solventless polyacrylate mentioned above which can therefore be used in the scope of the invention have been used for a long time and are well known to those skilled in the art who can normally obtain supplies on the market.

On the basis of all this, in order to fully implement all the potential advantages of the film according to the invention, a self-adhesive mass which coats one side, in which the said self-adhesive mass is of the aqueous solution, hot melt or solventless type which can be cross-linked by exposure to UV rays, is preferably used.

Thanks to the superior nominal mechanical strength properties of its component layers in comparison with conventional paper supports the multilayer film according to the invention may be of substantially lesser thickness in comparison with those for the same application as far as the support alone is concerned, that is without the adhesive mass deposited on it, and the quantity and type of this may vary depending upon the nature of the specific use.

Thus only a few non-limiting embodiments of the film according to the invention are mentioned below on the basis of actual experience, with corresponding indications of preferred thicknesses relating to particular applications, in connection with only the multilayer support not including the adhesive mass coated onto it.

In order to mask the bodywork of a vehicle during painting, the preferred thicknesses of the multilayer support alone vary around 80 μηι for general use, typically resistant to cycle temperatures of between 120°C and 150°C; this offers optimum conformability of the film and particular ease for the operator when following curved surfaces and the underside of the body shell which has to be painted.

When masking the bodywork of a vehicle and in general any article undergoing painting cycles with very high temperatures from 160°C up to a maximum of 220°C, as in the case of powder paints, the preferred thicknesses for the multilayer support alone may also lie between 36 and 37 μηι.

For masking bodywork when edging and separating different colours on the bodywork minimum possible thicknesses of around 12 μιη make it possible to paint the body shell with two paints of different colour, minimising the thickness of the colour separation line (fine-line use), but they also provide a sharp and aesthetically pleasing separation when writing is applied to the bodywork (application tape use); in this case, because of the need to make the support more robust, its thickness net of the adhesive mass may be suitably around 32 μιη.

In order to protect articles against abrasive action during sandblasting processes, a process sometimes carried out before painting, the multilayer support may count on the use of particularly anti-abrasive materials having a high breaking strength such, for example, polyamide (PA); although a certain thickness is obviously necessary for this application, when a multilayer support is used it is possible not to exceed 100 μηι net of the adhesive mass, which in any event provides a sufficient degree of protection for the sandblasted surface. For the protection of structures, panels or other structures, including during painting cycles and therefore also when subjected to temperatures and "overspraying" mists, multilayer films of different composition and thickness will be necessary depending upon the applications, especially multilayer films which are also capable of withstanding wear in the case of films protecting the floor of stoves; in this respect sufficient thicknesses of the multilayer support around 120 μιη, that is without the self-adhesive mass deposited on them, have already proved to be satisfactory when at least one layer of polyamide is also used. On the basis therefore of the abovementioned experiments it is preferable to use an adhesive multilayer film in which the said corresponding support has a thickness of between 12 and 120 μπι.

As far as aluminium-coated layers in particular are concerned, use of the preferred thicknesses mentioned below significantly improves the performance of the film according to the invention. If associated with other film layers in a multilayer support a layer of aluminium having a thickness > 20 μηι will give rise to a reduced overall ability of the film to conform to the often irregular surfaces which it is required to mask, in proportion to the increase in its own thickness. On the basis of experiments carried out to safely overcome this limitation, the thickness of the single aluminium film layer which should be used must not be greater than 10 μηι.

These very small thicknesses cannot however always completely satisfy some performance required from the film - for example that of temperature resistance, robustness, etc.; there is therefore the problem of combining a relatively small thickness of the aluminium layer with the particular performance required from the multilayer film.

The possible solution identified below by means of experiments comprises manufacturing multilayer supports with several layers of aluminium film, each of which has a thickness not exceeding 10 μιη.

In this case, even when the multilayer support reaches an overall thickness > 20 μιη, two or more layers of aluminium will no longer give rise to the abovementioned problems of excessive rigidity of the support or inadequate conformability, but on the contrary ensure conformability.

The reasons why this performance is ensured are associated primarily with the nature of the aluminium itself, which because of ductility shows very different behaviour to mechanical stresses, not only on the basis of the thicknesses used, but also the number of individual layers through which these thicknesses are achieved in the multilayer support.

Secondly, using several layers of aluminium also proportionately increases the layers of adhesive with which these layers are assembled by bonding; this significantly increases the plastic properties of the support, because as already described the bonding adhesive lies between the bonded layers in the form of a plastic-elastic joint and can thus impart greater and sufficient fidelity to the film as a whole when conforming to masked surfaces. Thus, consistently with what has been described so far, it is preferable to use an adhesive multilayer film in which, if it comprises one or more layers of aluminium, each of these do not individually exceed a thickness of 10 μιη.

On the other hand the use of aluminium as a component material of the multilayer support readily gives rise to another problem in one specific case; in fact in the case in point it is only the situation where solvent-based adhesive masses are coated onto the said support, even regardless of the thickness used for the aluminium, that there is a lack of flatness in the film during unwinding, or longitudinal curling, such as to render application more difficult at least as regards the aim of masking and protecting surfaces, as already described above.

In general the said curling behaviour which always occurs in multilayer adhesive tapes if coated with solvent-based adhesive masses when one or more layers of aluminium is present in the support is due to the relatively high force required when unwinding the film itself (peel strength based on AFERA standard 4001) in order to overcome the strong attachment which solvent-based adhesive masses progressively develop over time to the surfaces to which they adhere (in this case the adhesive side of the film to its own backing). On the contrary, when water-based or solventless self-adhesive masses, which can be adjusted much more readily as regards their peeling values, are used, very low forces for unwinding the adhesive film in comparison with what is required for unwinding an identical film with solvent-based adhesive masses are possible.

Thus in connection with what has been said it will be readily understood how this curling effect derives from the opposition between the force unwinding the tape and the opposing resistance of the solvent-based self-adhesive mass which causes the film to adhere to its own backing. In this connection it will be understood how, as the said adhesive film is being unwound, because of its ductility the aluminium layer will respond to the longitudinal elongation stress first with a kind of micro-contraction of its cross-section and then during the subsequent release stage (once unrolled) by stabilising the plastic deformation undergone by longitudinal resilient lifting of the edges of the film, which converge in this way towards the central axis of the film. The occurrence of this longitudinal curling of the edges of the film is what is commonly meant by the curling effect. Thus in accordance with what has been described hitherto it is preferable to provide the film according to the invention with a multilayer support for a solvent-free adhesive mass, so that the self-adhesive mass is of the aqueous solution, hot melt or solventless type which can be cross-linked by exposure to UV rays, in order to avoid curling effects of the adhesive film as it is being unwound.

One consequence of the substantial reduction in the thickness of the support is the possibility of reducing the diameter of the inner core onto which the adhesive multilayer film is rolled, and this with a view to re-establishing a better geometrical and ergonomic proportion between the size of the diameter of the inner core and the thickness of the circular perimeter of the rolled multilayer film.

The term "format" commonly indicates the size or final measurements (thickness x length) in which adhesive films and tapes are presented on the market, e.g.: 50 mm x 50 1m, 19 mm x 66 lm, etc., as well as indicating both the type and dimensions of the inner core onto which they are wound. From this point of view the multilayer adhesive film according to the invention makes formats of limited size and weight possible, again in comparison with conventional competitors on the market. In this respect a comparison between a conventional paper adhesive tape (TESA 4318 PV2) and an embodiment of the invention (Example 4, illustrated below), both used for masking paints at temperatures between 160°C and 170°C, is immediately significant.

The first difference between the two abovementioned types of adhesive tapes is that for the same number of square metres the weight of the multilayer tape (Example 4) is more than 70% less than that of conventional tape (TESA 4318 PV2) for an equivalent application. In addition to this it will be readily noted from the comparison that the overall thickness is approximately 47 μπί for the multilayer tape (Example 4) while it is 170 μπι for the conventional paper-backed stoving tape (TESA 4318 PV2) - thus even the overall volume Occupied by the multilayer is very much smaller. Faced with such a net reduction in weight and volume, apart from the immediate saving in transport costs, logistical areas occupied, packaging materials, etc., a first comment relates to the increased benefit in terms of disposal of the product after use. As mentioned in respect of the saving in the overall amount of mass of materials needed to produce multilayer in comparison with an identical quantity of square metres of paper adhesive backing, there is the substantial reduction in resources used and the relatively smaller environmental impact.

With regard to the reduced weight and a smaller volume of film wound onto a conventional 3" mandrel (approximately 76 mm), it must also be commented that, for the same format, from an ergonomic point of view there is not much sense in leaving the film according to the invention on a conventional 3 " inner core (approximately 76 mm) because in this format, the circular winding would not even achieve a thickness of one centimetre; there would therefore be an obvious disproportion between the size of the inner core and the thickness of the circle of wound film.

Because of this the size of the core can for example be reduced from 76.2 mm to 50.8 mm or even less, thus further increasing more than a number of logistical advantages, because a reduction in the diameter of the core also further reduces the specific volume of the tape, as a result of which the premises of the manufacturing industry and in the transporting and using industries will be of smaller size, as well as during the stage of disposal of the used product, in addition to very much easier handling of the tape during use; in addition to this there will be an appreciable saving in dispatches and the quantity of packaging used.

As a consequence the preferred format for multilayer film according to the invention is that wound round a core of plastics materials of diameter less than 76.2 mm; in which the said core is of plastics material, typically manufactured from PVC or polyethylene tubes having a thickness of around 4 mm, which is lighter than the paper core usually used for winding conventional adhesive films and tapes.

In this way complete optimisation of the logistical yield is achieved, that is the possibility of obtaining volumes/weights which are less for the same number of square metres of adhesive tape moved, which will apply at all times in the production life cycle of the adhesive film, i.e. the receipt of raw materials, production, transport, use and disposal. The logistical comparison table below shows numerical values for the comparison just described.

LOGISTICAL COMPARISON TABLE

In order to provide an immediate idea of the difference between the volumes occupied by two types of adhesive tape, it should be borne in mind that a roll of multilayer tape, such as that in an embodiment of the invention (Example 4), wound onto a core of 50.8 mm will enter completely within the inner space of the 76.2 mm core of a conventional adhesive tape. In other words the empty space enclosed by the 76.2 mm inner core of conventional adhesive tape is the entire space occupied by the multilayer adhesive tape according to the invention, again for the condition of identical formats.

Reference is made here to the conventionally accepted distinction between self-adhesive tapes and films based on the different type of format in which a film is marketed - in the case of masking applications reference is made here to "adhesive tapes" when these have a format for using the said tape in a width not exceeding 100-150 mm so that it can easily be handled in order to attach other films or small sheets or large sheets for the purpose of properly covering the object being masked.

Instead reference is made hereto "self-adhesive supports", in terms of protective film, if they directly perform the function of being laid upon the object requiring protection: that is directly protecting the article over the entire surface area affected by the process without normally attaching any other material having this function; in this application, protective films are normally rolls in the form of bobbins with a larger tape width, that is normally from 150 mm up to 1500-2000 mm, and almost always applied by operators using devices which make unwinding easier, commonly known as dispensers.

Because thicknesses are substantially smaller in comparison with conventional paper supports and because they are easier to use, in terms of substantially reduced weight and dimensions, multilayer self-adhesive films according to the invention can therefore be provided in the format of masking tape in the form of a roll, or of protective film in the form of a bobbin, where preferably the said film is wound around a core of plastics material of diameter less than three inches.

The multilayer adhesive film may also be in variant formats, such as described hitherto, not only in the form of a roll or bobbin, but manufactured in the form of a flat sheet for better application to surfaces of any geometrical shape of already predetermined design. In the production of multilayer supports use may also be made of processes which ensure that their surfaces have a particular roughness, that is a non-smooth or non-uniform surface, such as for example an embossed or micro-perforated surface, the surface processing of the film being normally known to those skilled in the art of the processing of plastic films.

Embossing of the self-adhesive support generally takes place before the coating stage. This process is carried out by causing the film to pass through a suitable heated roll (90°C- 100°C) with an embossing roll between its rollers which imprints a particular imprinted relief geometry onto the film. The embossing is designed to roughen the surface in order to impart low surface slip to the support, and specifically in the case in point also for the better retention of paint spray.

In addition to this the embossed relief which embossing is capable of imprinting onto the film backing makes it possible for the latter not to adhere strongly to the adhesive mass coated onto the adhesive surface.

Thus also in the case where the backing of the film comprises aluminium or strongly adhering polymers such as polyamide or polyester there is no need for the backing to be impregnated with anti-adhering release substances because the relief impressed onto the backing by embossing always prevents strong continuing contact between the backing and the adhesive mass, thus ensuring that the backing has a low peel strength (fall in peel strength AFERA standard 4001 ). After all, a multilayer adhesive film in which the surface of its support opposite the surface coated with the said adhesive mass has a pattern in relief is included within the scope of this invention.

Microperforation normally takes place after the stage in which the film support is coated, being applied immediately before the stage of winding or rewinding a roll locked on the rewinding machine. Microperforation is carried out in order to assist the escape of air which might be trapped in the form of bubbles during manufacture or during the unwinding of adhesive films at the time of application, when these are of a particular width (>150 mm). A multilayer adhesive film in which the support incorporates microperforations on its surface is specifically included within the scope of this invention.

The abovementioned embossing and microperforation technologies are well known and normally practiced by those skilled in the art, and are mentioned purely by way of example as a clear and unequivocal reference to the surface treatment of flexible films.

The essential principles defining the adhesive film according to the invention are therefore clearly apparent: this multilayer film in fact comprises as constituents a layer which can be coated with adhesive and a backing layer, using high thermo-mechanical performance (>150°C) flexible film materials, such as films of polyester (PET), polypropylene (PP), polyamide (PA), polyurethane (PUR), aluminium (AL) and its alloys.

However for applications with lower cycle temperatures it is possible to form multilayer supports also comprising other polymer film materials belonging to other series of materials, such as for example polyolefins or other already mentioned plastics films having a lower melting point, which can in normal cases develop synergies such as to produce a new class of removable self-adhesive supports which resist temperature cycles between at least 100 and 150°C, in addition to the group of said films of PET, PP, PA, PUR and AL. For such a type of multilayer layer support in which the layer with the adhesive-coatable surface and the backing layer are no longer paper, a self-adhesive mass which according to the terminology in the sector can be classified and understood by those skilled in the art as being of the "removable" type, preferably selected from aqueous emulsion polymer, hot melt or solventless self-adhesive masses which can also be cross-linked by means of UV rays, is normally used first to obtain low peel strengths when the film is unwound from its own backing and low peel strengths during the operations removing masking, to the extent that under these conditions the adhesive film according to the invention is free from disadvantages such as release of the adhesive mass onto the object from which the masking has been removed, breaking of the support, a high unwinding force and an evident "curling effect" on unwinding, in addition to a number of further advantages already illustrated in connection with the absence of problems which the use of solvents brings about in production cycles.

In addition to the efficient synergy which is established between a multilayer support characterised by the presence of polymer and/or metal materials coated with solvent-free adhesive masses, the film according to the invention offers a second fundamental advantage - that of reducing the thicknesses of the support as a result of the nominal mechanical strength values of the polymer and metal films, which are very much higher than those of paper supports.

Because of this, for the same thermal and mechanical performance, average thicknesses of films according to the invention are approximately 30% to 70% smaller than the average thicknesses of paper supports.

These two essential requirements in the support according to the invention - the multistructural synergy between its polymer and/or metal layers and the possible use of relatively small thicknesses - give rise to advantageous characteristics of a functional, production and logistical order, which can be summarised in 21 variables assessed in general comparison tables.

In this way it is easily possible to compare some embodiments of the multilayer film according to the invention among the many possible ones having advantageous characteristics in comparison with the state of the art, and these can be summarised as follows:

• The polymer or aluminium materials used in the multilayer support as an adhesive-coatable surface already have in themselves a high predisposition to adhesion as a result of which it is not necessary to coat the support with impregnating products in order for the water-based or solventless self-adhesive mass to adhere, as is the case with paper supports. In this way there is an objective reduction in the times, materials used and cost of the entire process for production of the adhesive film; these costs and times instead always affect the process of impregnating the adhesion-promoting resins which are necessary for paper supports.

• In the case where the polymers selected as the adhesive-coatable surface of the film are polyethylene, polypropylene or other polymer films having low adhesion, in order to impart sufficient attachment of the adhesive mass to that surface of the film a Corona treatment with values equal to or in excess of 38-40 mN/m is sufficient. This treatment can already be carried out "in line" - immediately before the stages of coating or moulding the plastics films; in this way, there is an objective reduction in the times, materials used and cost of the entire process of adhesive film production; these costs and times instead always affect the process of impregnating the adhesion-promoting resins which are necessary for paper supports.

• In the case where the polymers selected for the film backing are polyethylenes, polypropylenes or other low-adhesion polymer films, in order to impart a sufficient hold for paint mist to that backing (paintability) and at the same time a suitable degree of "release" (reduction in the resistance of the film to unwinding) a Corona treatment with values of between 34 and 36 mN/m can be recommended. This treatment can be already carried out "in line" - immediately before the stages of coating or moulding the plastics films; in this way, there is an objective reduction in times, materials used and cost of the entire process of adhesive film production; these costs and times instead always affect the process of impregnating the adhesion-promoting resins which are necessary for paper supports.

• In the case where the polymers selected as the backing for the film are high- adhesion polymers or aluminium, in order to impart a suitable degree of "release" (reduction in the resistance of the film to unwinding) to that backing an embossing treatment for the surface of the film prior to the coating stage is sufficient; in this way there is an objective reduction in the times, materials used and cost of the entire process of adhesive film production; these costs and times instead always affect the process of impregnating the adhesion-promoting resins which are necessary for paper supports.

· Thanks to the fact that the multilayer support according to the invention has a thickness which is decidedly smaller than that of paper supports it is also possible to apply a proportionately thinner layer of self-adhesive mass and therefore to save substantial quantities of materials used in terms of support and adhesive mass; the saving in the quantity of adhesive mass is also provided by the fact that the multilayer support comprises impermeable materials to the adhesive mass itself as constituent layers; thus, unlike paper supports which absorb part of the adhesive mass, polymer or aluminium supports benefit from all the adhesive mass applied for purposes of adhesion only, without absorbing any part of it.

• A smaller quantity of adhesive mass required to be coated on outer layer supports also has the advantage of increasing the rate of coating or hourly productivity in comparison with paper supports.

· The possibility of not necessarily using solvent-based self-adhesive masses, as is the case for paper supports, ensures that onerous environmental impacts are avoided and that the working environment is better protected when producing film according to the invention.

• The possible and preferable use of water-based or solventless UVR adhesive masses also makes it possible to arrange a more favourable "peel strength" during^' the stage of removing masking, that is a smaller force when removing the adhesive tape, and as a consequence of this, avoiding leaving adhesive mass on the protected objects.

• Thanks also to the fact that the multilayer film according to the invention has a relatively small thickness it is possible to wind it in the form of a roll around a core of smaller diameter than in the case of known tapes. This has evident advantages in logistical terms in respect of spaces occupied and volumes moved, which are reduced by not less than 50% during the entire cycle for the supply of raw materials, production, storage, transport, use and disposal of the product in comparison with those necessary for tapes or films having a paper support, always understood to be for the same amount of square metres of product moved.

In addition to this, there are other added advantages associated with the use of multilayer film, such as:

• greater conformability, that is adhesion to the parts which have to be masked/protected as a result of substantially smaller thicknesses in comparison with paper masking tape;

• superior mechanical and/or thermal performance despite smaller thicknesses, in that the tensile strength values of the polymers and metals used are nominally greater than those which can be sustained by paper supports, as also absolute resistance to temperature, without experiencing deformation or "stoving" of the support, thus avoiding breaks and fractional removal of the self-adhesive tape during the operations of removing masking. · greater ergonomic convenience for the operator as a result of the substantially reduced weight of the thinner adhesive film;

• furthermore, the multilayer film according to the invention has proved to be much more stable and durable over time, given the low chemical/physical reactivity between plastics and/or metal supports and adhesive masses which do not contain synthetic solvents. While conventionally protective tapes with a paper support have a guarantee of not more than 12 months' storage, the multilayer adhesive film according to the invention, in its experimental embodiments illustrated by way of the non-limiting examples illustrated below, has maintained its nominal characteristics and therefore a possible guarantee for up to 20 months from the date of manufacture.

Finally, on the basis of what has been described hitherto concerning the constitution of a multilayer adhesive film, use of the said film for masking and protecting surfaces subject to operations which in particular require exposures to temperatures in the range between 100°C and 220°C, such as painting cycles, can be positively confirmed.

In accordance with this invention, some embodiments are described below purely by way of non-limiting examples illustrated by corresponding cross-sectional drawings of the support for the film according to the invention and by corresponding general comparison tables in which this film is directly compared with products for equivalent uses representing the state of the art in the field of interest.

EXAMPLE 1

In accordance with this invention, Example 1 illustrated by Figure 10 shows in cross- section the multilayer adhesive support comprising a first film layer of polyethylene 9 μπι thick, acting as the backing (11); this layer of film had already been assembled in advance by bonding by coating (polythening process) onto a second single layer of 35 μηι kraft paper having the function of an intermediate layer (12). This layer of kraft paper was in turn assembled by adhesive bonding to the back of a third film layer comprising the self- adhesive film of bi-orientated polypropylene (BOPP) of total thickness 40 μηι functioning as the adhesive surface (14), using 3 g/m (thickness 3 μη ) of Rohm&Haas "MOR-FREE 696A+C-83" polyurethane adhesive (13). This BOPP layer was in fact used in the form of a film which is already self-adhesive (Novacel, "4374P"); this self-adhesive film comprised a BOPP support of 35 μηι (14.a) and a water-based self-adhesive acrylic mass of 5 g/m² (thickness 5 μιη) (14.b). Bonding of a polyolefin film which is already adhesive makes it necessary for the bonding machine to have transfer and bonding rollers which are coated with anti-adhesion materials such as Teflon in thicknesses comprising preferably between 50 and 150 microns. These arrangements for the bonding machine can be easily achieved by those skilled in the art who can find a wide range of anti-adhesion polymer films with which to surface the rollers of the bonding machine on the market in addition to Teflon.

Before being coated with adhesive and/or subsequently during the rewinding stage, in order to impart a sufficient hold for paint spray (paintability) to the backing of the multilayer support and at the same time ensuring an adequate degree of "release" (low resistance to unwinding), the backing (11) was subjected to a Corona treatment with a value of 34-36 mN/m carried out in accordance with the normal application conditions known to those skilled in the art.

The said multilayer support constituted in this way, including the adhesive coating, thus has a total thickness of 87 μηι and is conveniently wound onto an inner core of PVC having a diameter of 50.8 mm and a thickness of approximately 4 mm.

The abovementioned example of a multilayer self-adhesive tape is suitable for application in operations of masking painting for quite general purpose use, with the paints being cured in a stove up to maximum temperatures of 150°C. In the case of the said tape a support which can combine the advantages of the rigidity of a paper layer (12) with the resilience and softness of the two outer polyolefin layers (11 and 14) bonded thereto has been used and assembled. In this way a whole number of advantages typical of the film according to the invention already described previously, primarily better conformability, lower peel strength, greater resistance to temperature, smaller tape volumes and the elimination of solvents during its production have been achieved.

Manufacture and use of the said multilayer adhesive film has led to experiments whose results are illustrated in General Comparison Table No. 1, which are described and which can also therefore be assessed in relation to a direct comparison with a conventional product used for the same application (TESA 4309 PVl), which confirms the improved properties of the film according to the invention in respect of functional values, productive efficiency and logistical optimisation in comparison with the state of the art.

EXAMPLE 2 In accordance with this invention, Example 2 illustrated in Figure 20 shows in cross- section an adhesive multilayer support comprising a first film layer of bi-orientated polypropylene (BOPP) of thickness 12 μιη acting as backing (21), which had already previously been assembled by coating (metallisation process) with a second layer of aluminium of thickness 0.020 μιη (22) which had in turn been assembled to a film layer of low density polyethylene (LDPE) of 18 μηι thickness acting as the adhesive-coatable surface (24) by bonding with 2 g/m² (thickness 2 μηι) of Rohm&Haas "MOR-FREE 696A+C-83" polyurethane adhesive (23); a coating of 8 g/m² (thickness 8 μηι) of acrylic adhesive mass (25) according to the formulation No. 2 already mentioned, catalysed by the addition of a corresponding cross-linking agent in an amount of 3% by weight of the base resin, was coated onto the aforesaid surface intended to be adhesive coated; the said catalysed adhesive mass was coated according to the normal application conditions known to those skilled in the art, with possible coating rates of 60-80 m/min.

Like all those of the type according to the invention, this multilayer support does not need any process for impregnating the adhesive-coatable surface (24) in order to anchor the adhesive mass; in this specific case, as the said surface comprises a layer of low density polyethylene (LDPE), only Corona treatment having a value of 40-42 mN/m which thus makes it possible to anchor the adhesive mass coated upon it is needed for this purpose.

In order to impart a sufficient hold for paint spray to its backing (paintability) and at the same time a suitable level of "release" (low resistance to unwinding), before being coated with adhesive and/or subsequently during the rewinding stage the multilayer support was subjected to Corona treatment of its backing (21) with a value of 34-36 mN/m, carried out in accordance with the normal application conditions known to those skilled in the art.

Net of the adhesive coating the said multilayer support constituted in this way therefore has a thickness of 32.02 μιη and an overall total thickness inclusive of adhesive mass of 40 μηι, and is conveniently wound onto an inner PVC core having a diameter of 50.8 mm and a thickness of approximately 4 mm.

The abovementioned example of multilayer self-adhesive film may find further suitable application: a first use may be as "application tape" masking tape, that is the use in which writing has to be transferred using the technique well known to those skilled in the art of transfer through the use of "application tape". In the case where this transfer of writing takes place on motor vehicle bodywork, with subsequent repainting of the area affected by the writing, the "application tape" must also perform a proper masking function for the bodywork itself during one painting cycle. "Application tape" films with a conventional coextruded polyolefin support (LDPE/HDPE), such as for example Novacel "BN 410" film, are not suitable for the purpose as they are not capable of withstanding the temperatures of the abovementioned cycle. According to the gist of the invention there has instead been obtained for the purpose a multilayer film which provides for assembly of the abovementioned polymers by bonding and not by coextrusion, as just described above.

These temperatures of the painting cycle in question, which are necessary for the specific operation including irradiation by means of IR lamps, normally reach 130°C for not less than 20 minutes; this thermal stress gives rise to serious distortion in the said coextruded polyolefin film with the corresponding very marked release of adhesive mass onto the protected object and with traces of melting, such that it is not possible to achieve peeling when the masking is removed.

The abovementioned multilayer adhesive film according to the invention described above is on the contrary capable of performing a masking function without any distortion of the support or the adhesive mass, even if subjected to this heating cycle. The heat resistance of the said multilayer film is made possible by the presence of the aluminium layer (22) which because of its reflectivity is capable of reflecting most of the thermal energy projected by the IR lamps onto the masked area.

Following measurements with a laser thermometer it has been possible to establish that projected temperatures onto the masked zone around 120-130°C are reduced to only 80-85°C on the side opposite the painted zone of the bodywork, specifically because of the reflectivity of the aluminium layer (22) which, together with a film layer of LDPE such as that of adhesive-coatable surface (24), makes it possible to withstand such a heating cycle.

Novacel "BN410" film has also demonstrated limitations in its applicability, because the transfer of writing onto flat supports, which is usually performed through the use of "application tape" with the help of suitable dispensers, is no longer possible when it is a question of transferring these writings onto parts of motor vehicle bodywork; in this case application and laying of the "application tape" with the corresponding writing is carried out in a wholly manual way.

In this instance pronounced curling of the two edges of the said Novacel tape occurred, substantially slowing and complicating its operational use. This limitation must be related to the nature of the assembly of the polyolefin layers in the said Novacel film, which is obtained by coextrusion, while in this embodiment of the multilayer film no curling problem arose because the layers of the support are helped by the cushioning function performed by the bonding adhesive, as previously described in detail.

A second possible application of the said adhesive film may further be that of use as a "fine-line" adhesive tape. In fact for this use the said support will only comprise the first two layers - bi-orientated polypropylene (BOPP) (21) and aluminium coating (22) - so that the overall thickness of the said multilayer support does not exceed 12.02 μιη.

Being then coated with adhesive again with the said adhesive mass in a thickness of 8 μηι (25), the said support, in this case directly laid onto the surface of the aluminium coating (22), achieved a total thickness of 20 μιη.

Thanks to this very small thickness of the adhesive film the "step" which separates the two portions of bodywork of different colour (colour separating masking) will be very much less apparent in comparison with a conventional adhesive tape for the same application. The adhesive tape with which we can make a comparison is, for example, a tape for "fine- line" use such as TESA "4174" (single PVC support), which has a total thickness of 110 μπι. In every case manufacture and use of the said multilayer adhesive film has resulted in experiments whose results are illustrated in General Comparison Table No. 2, which are described and can therefore be assessed in relation to a direct comparison with a conventional product (Novacel, "BN410") for the same application (application tape), which confirms the better properties of the film according to the invention as regards functional values, production efficiency and logistical optimisation in comparison with the state of the art.

EXAMPLE 3 In accordance with this invention, Example 3 illustrated by Figure 30 diagrammatically shows in cross-section a multilayer adhesive support comprising a first film layer of bi- orientated polypropylene (BOPP) of thickness 12 μπι acting as backing (31); this layer was assembled with a second layer comprising an annealed 1200 aluminium laminate of thickness 9 μηι (33) acting as the intermediate layer, through adhesive bonding with 3 g/m (thickness 3 μπι) of Rohm&Haas "MOR-FREE 696A+C-83" polyurethane adhesive, which latter was in turn bonded by means of 3 g/m² (thickness 3 μηι) of Rohm&Haas "MOR-FREE 696A+C-83" polyurethane adhesive (34) to a third layer also comprising an aluminium laminate (annealed 1200 alloy) of thickness 9 μπι acting as the adhesive- coatable surface (35); then a coating of 5 g/m² (thickness 5 μιη) of acrylic adhesive mass (36) according to already mentioned formulation No. 1, catalysed by the addition of a corresponding cross-linking agent in an amount of 0.4% by weight with respect to the base resin, was coated onto the aforesaid surface intended for adhesive coating; this catalysed adhesive mass was applied in accordance with the normal application conditions known to those skilled in the art, with possible coating rates of between 60 and 80 linear metres per minute. Like all those of the type of the present invention, the said multilayer support does not need any impregnation process for the adhesive-coatable surface (35) in order to anchor the adhesive mass because in this specific instance it comprises a layer of annealed 1200 aluminium alloy, and it also requires no Corona treatment because the aluminium layer of which the adhesive-coatable surface is made through its nature guarantees suitable anchorage of the adhesive mass coated upon it.

Before adhesive coating and/or subsequently in the rewinding stage, in order to impart a sufficient hold for paint spray (paintability) to its backing (31) and at the same time a suitable level of "release" (reduced resistance to unwinding), the backing of the abovementioned multilayer support was subjected to Corona treatment at a value of 34- 36 mN/m, as normally known to and carried out by those skilled in the art.

The said multilayer support constituted in this way, net of the adhesive coating, therefore has a thickness of 36 μηι and a total overall thickness inclusive of the adhesive mass of 41 μπι and is conveniently wound on an inner PVC core having a diameter of 50.8 mm and a thickness of approximately 4 mm.

The abovementioned example of a multilayer self-adhesive film finds appropriate application as an adhesive masking tape which is highly resistant up to temperatures of 220°C, typical of powder painting. In these painting cycles it is preferable not to use any polymer layer as the adhesive surface in contact with the surface being masked because these temperatures are close to the melting points of the most resistant polymers such as PET or PA.

In this case aluminium (35) will preferably be used as the adhesive-coatable surface because of its greater thermal resistance. In addition to this, this layer (35) will be bonded to another layer of aluminium (33) in its backing in order to further increase its thermal resistance capacity and the conformability of the adhesive film as a whole.

Manufacture and use of the said multilayer adhesive film has led to experiments whose results are illustrated in General Comparison Table No. 3, which are described and can therefore be assessed on the basis of a direct comparison with a conventional product used for the same application (TESA, 4331), which confirms the improved properties of the film according to the invention in respect of functional values, production efficiency and logistical optimisation in comparison with the state of the art. EXAMPLE 4

In accordance with this invention, Example 4 illustrated by Figure 40 shows diagrammatically in cross-section a multilayer adhesive support comprising a first layer of coextruded polyolefin film of thickness 22 μιη acting as backing (41); in detail it is specified that the layer acting as backing (41) is a coextruded polyolefin comprising three layers in succession respectively: 6 μηι of polypropylene (PP) (41. a), 10 μη of high density polyethylene (HDPE) (41.b), 6 μηι of polypropylene (PP) (41.c).

A coextruded material like that described can be obtained without difficulty on the market for flexible films; in any event if it were to be decided to proceed directly to its production the production parameters normally known to those skilled in the art are summarised below to provide an unequivocal reference.

The said coextruded material can be manufactured using a suitable three-layer "blister" extruder, in which for the first layer (41.a) and the second layer (41.b) (both outer layers of the coextruded material) the corresponding extrusion pumps feed the extrusion head the copolymer mixture comprising 7% by weight of ethylene and 93% of polypropylene with a fluidity index of 0.9 and a specific gravity of 0.915 kg/1. The third intermediate layer, that is the one lying between the two outer layers, is fed by the corresponding extrusion pump to the extrusion head as a copolymer mixture comprising 80% high density polyethylene by weight and 20% low density polyethylene, with a fluidity index of 0.6 and a specific gravity of 0.940 kg/1.

This coextruded material was bonded to a second layer of aluminium film 0.020 μηι thick (43) already previously assembled by contact bonding (metallisation process) to a third 12 μιη layer of polyester film acting as the adhesive-coatable surface (44) through bonding with 3 g/m² (thickness 3 μιη) of Rohm&Haas "MOR-FREE 696A+C-83" polyurethane adhesive (42); then a coating of 10 g/m² (thickness 10 μιη) of acrylic adhesive mass (45) according to already mentioned formulation No. 2, catalysed by the addition of the corresponding cross-linking agent in a quantity of 2% by weight with respect to the base resin, was coated onto the aforesaid surface which is intended to be adhesive coated; the said catalysed adhesive mass was coated in accordance with the normal conditions of application known to those skilled in the art, with possible coating rates of between 60 and 80 linear metres per minute.

Like all those according to the type of this invention, the said multilayer support does not require any process of impregnation of the adhesive-coatable surface (44) for anchoring the adhesive mass; also it requires no Corona treatment because the polyester layer which comprises the adhesive-coatable surface of its nature guarantees a suitable anchorage for the adhesive mass coated upon it. Prior to coating with adhesive and/or subsequently during the rewinding stage, the backing (41) of the multilayer support was subjected to Corona treatment at a value of 34-36 mN/m carried out in accordance with the normal conditions of application known to those skilled in the art in order to impart a sufficient hold for paint spray (paintability) to its backing (41) together with a suitable degree of "release" (reduction in resistance to unwinding).

The said multilayer support constructed in this way, net of the adhesive coating, therefore has a thickness of about 37.02 μκι and an overall total thickness inclusive of adhesive mass of 47 μηι, and is conveniently wound onto an inner PVC core having a diameter of 50.8 mm and a thickness of approximately 4 mm.

The abovementioned example of a multilayer self-adhesive film finds convenient application as an adhesive masking tape during retouching painting operations on motor vehicle bodywork.

In particular it is intended to impart optimum conformability through the use of a coextruded polyolefin layer as backing for the support and high resistance to paint curing temperatures through the use of a metallised polyester support.

Manufacture and use of the said multilayer adhesive film has led to experiments whose results are illustrated in General Comparison Table No. 4, which are described and can also therefore be assessed in connection with a direct comparison with a conventional product used for the same application (TES A, 4318PV2), which confirms the improved properties of the film according to the invention in respect of functional values, production efficiency and logistical optimisation in comparison with the state of the art.

EXAMPLE 5

In accordance with this invention, Example 5 illustrated by Figure 50 shows diagrammatically in cross-section an adhesive multilayer support comprising a first layer of polyamide film (PA) of thickness 16 μπι acting as a backing (51); this layer was assembled by adhesive bonding to a second layer of polyester film in the form of a non- woven fabric of "Spunlaced" polyester (PET-nwf) of thickness 80 μιτι acting as the adhesive-coatable surface (53) by means of 4 g/m (thickness 4 μηι) of Rohm&Haas "MOR-FREE 696A+C-83" polyurethane adhesive (52); then a coating of 16 g/m² (thickness 16 μηι) of acrylic adhesive mass (54) according to already mentioned formulation No. 1, catalysed by addition of the corresponding cross-linking agent in an amount of 0.5% by weight with respect to the base resin, was coated onto the aforesaid surface intended for coating with adhesive; the said catalysed adhesive mass was applied according to the normal application conditions known to those skilled in the art With possible coating rates of between 60 and 80 linear metres per minute.

Like all those of this type according to the invention, the said multilayer support does not require any process for impregnating the adhesive-coatable surface (53) in order to anchor the adhesive mass because in this specific instance it comprises a layer of non-woven polyester fabric; also because of its nature it does not require Corona treatment because the said layer guarantees suitable anchoring of the adhesive mass coated upon it.

Before adhesive coating and/or subsequently during the rewinding stage, the backing (51) of the multilayer support was not subjected to any Corona treatment but to embossing treatment of the entire support carried out in accordance with a specific relief imprint in accordance with the normal application conditions well known to those skilled in the art. This treatment imparts a suitable degree of "release" (reduction in resistance to unwinding) to the adhesive multilayer support and at the same time makes it possible to retain the specific adhesion characteristics of the polyamide, thus also ensuring an optimum hold for paint spray (paintability).

The said multilayer support manufactured in this way therefore has a thickness of 100 μπι, net of the adhesive coating, and a total overall thickness of adhesive mass of 116 μπι. We would point out that the use of a winding core having a diameter of less than 76.2 mm for self-adhesive film thicknesses of 100 μιη or more does not fully offer the logistical advantages already illustrated above, as a result of which the possibility of winding the adhesive film onto a conventional cardboard tube of 76.2 mm is preferred in this embodiment, although in any event the reductions in the weight of adhesive film and occupied volume remain significant with this format.

The abovementioned example of a multilayer self-adhesive film is suitable for application as an adhesive masking tape for sandblasting which, as is known, is a preparatory operation in the painting cycle of manufactured articles which still have old coatings which have to be removed.

With conventional paper self-adhesive tapes the thicknesses of the paper support have to be increased in order to withstand the mechanical action of the abrasive flow applied to the articles in question, which are sometimes also raised to temperatures over 100°C to assist removal of the coating which has to be removed. Using the multilayer technology the abrasive/destructive effect of sandblasting can be withstood by creating a support which relies not only on the thickness of the material making up the support but also on its qualities of abrasion resistance and absorption of the energy of the abrasive flow. For these various functions a polyamide film (PA) (71) having an anti-abrasive function and in any case also guaranteeing the mechanical integrity of the tape as a result of its high breaking strength Kr = 70 N/cm is selected for the backing.

The adhesive-coatable layer is instead of NWF polyester (Spunlaced PETnwf) (53), which is used because of its ability to absorb/attenuate the energy of the abrasive flow.

Manufacture and use of the said multilayer adhesive film has resulted in experiments whose results are also illustrated in General Comparison Table No. 5, and are described and therefore capable of assessment on the basis of a direct comparison with a conventional product used for the same application (TESA 4432), which confirms the improved properties of the film according to the invention in respect of functional values, production efficiency and logistical optimisation in comparison with the state of the art.

EXAMPLE 6 In accordance with this invention, Example 6 illustrated by Figure 60 shows diagrammatically in cross-section an adhesive multilayer support comprising a first layer of bi-orientated polypropylene film (BOPP) having a thickness of 10 μηι acting as backing (61); this layer was assembled by bonding a second layer of high density polyethylene (HDPE) film with a thickness of 18 μηι acting as the adhesive-coatable surface (63) using a layer of 2 g/m² (thickness 2 μιη) of Rohm&Haas "MOR-FREE 696A+C-83" polyurethane adhesive (62); then a coating of 5 g/m² (thickness 5 μηι) of acrylic self- adhesive mass (64) according to already mentioned formulation No. 2, catalysed by the addition of a corresponding cross-linking agent in an amount of 2% by weight with respect to the base resin in accordance with the normal application conditions known to those skilled in the art was coated onto the aforesaid surface for coating with adhesive, with possible coating rates of between 60 and 80 linear metres per minute.

Like all those of the type according to this invention, the said multilayer support does not need any process of impregnating the adhesive-coatable surface (64) in order to anchor the adhesive mass; in this specific case, as the said surface comprises a layer of high density polyethylene (HDPE), only Corona treatment with a value of 40-42 mN/m, which thus makes it possible to anchor the adhesive mass coated on it, is needed for this purpose.

In order to impart a sufficient hold for paint spray (paintability) to the backing (61) of the said multilayer support and at the same time a suitable degree of "release" (reduction in resistance to winding) Corona treatment normally known and carried out by those skilled in the art with a value of 34-36 mN/m was applied to the backing (61) during the rewinding stage.

During the rewinding stage the multilayer adhesive film was subjected to micro- perforation treatment, a process normally known to and carried out by those skilled in the art, to allow microbubbles of air, which would otherwise give rise to swelling of the film on the surface to which it adheres, to escape during application of the film.

The said multilayer support constituted in this way, net of the adhesive coating, therefore has a thickness of 30 μιη with a total overall thickness inclusive of adhesive mass of 35 μιη, and is conveniently wound on an internal PVC core having a diameter of 50.8 mm and a thickness of approximately 4 mm.

The abovementioned example of multilayer self-adhesive film is suitable for application as a protective film within the painting booth/stove area on panels and other vertical parts of the structure, such as pre-painted, zinc-coated and glazed surface panels.

In general, it is noted that transparent protective films are normally coextruded with low melting point polyolefins such as for example LDPE, LLDPE, MDPE, HDPE, etc.; however, if the said polymers are assembled by bonding to a least one polymer having higher technical performance such as for example PP, PET, PA, PUR, a multilayer polymer support having decisively better thermo-mechanical performance can be obtained and will be capable of withstanding temperatures well above 90-95°C, which in general remains the thermal operating limit for polyolefins obtained by coextrusion.

According to the gist of the invention, an adhesive bonded multilayer film which therefore combines two polymers (BOPP)(61) and (HDPE)(63) belonging to classes of polymers having different thermal performance, but which is made suitable in this way in order to withstand temperatures of up to 140°C without distortions of the adhesive film or the release of adhesive when applied to the structure of painting stoves by means of a layer of adhesive, is thus obtained. At the present time, for the said stove areas the conventional protective solution is the application of layers of liquid polybutylene onto the surfaces which have to be protected, and this is periodically removed by washing the sheets, panels and glazing of the stoving booth using organic solvents. Hence it is not possible to make a comparison with other films in the manner of the comparative table below, but it is nevertheless confirmed that there are improvements with respect to the state of the art in the application conditions - such as higher speed, safety and environmental safety, etc. - together with improved performance, such as a longer period of protection, thanks to the greater quantity of paint spray (overspraying) retained on the surface of the adhesive multilayer film in comparison with surfaces protected with polybutylene.

EXAMPLE 7

In accordance with this invention, Example 7 illustrated by Figure 70 shows diagrammatically in cross-section an adhesive multilayer support comprising a first layer of low density polyethylene film (LDPE) in a thickness of 95 μηι acting as backing (71); this layer was assembled with a second layer of polyester film of thickness 23 μπι acting as the adhesive-coatable surface (73) by adhesive bonding using 2 g/m (thickness 2 μπι) of Rohm&Haas "MOR-FREE 696A+C-83" polyurethane adhesive (72); then a coating of adhesive mass (74) according to already mentioned formulation No. 3 - solventless polyacrylic resin cross-linked by exposure to UV-c - was coated onto the said surface intended to be coated with adhesive; the weight selected was 20 g/m² (thickness 20 μηι); in connection with this a passage for the absorption of UV-c may be carried out at a speed of around 100 m/min under irradiation from four UV-c lamps each radiating 30 mJ/cm²; the cycle can also be performed at different speeds by adjusting the number of lamps in proportion. Other secondary variables such as the distance of the lamps from the working plane and the most suitable cone of light for covering the surface which has to be irradiated are wholly within the knowledge and discretion of those skilled in the art.

Like all those of the type according to this invention, the said multilayer support does not need any process for impregnating the adhesive-coatable surface (73) for anchoring the adhesive mass; also because of its nature it does not require any Corona treatment because the polyester layer comprising the adhesive-coatable surface guarantees suitable anchoring for the adhesive mass laid upon it. In order to impart a sufficient hold for paint spray (paintability) and at the same time a suitable level of "release" (reduction in resistance to unwinding) to the backing of the said multilayer support, Corona treatment normally known and carried out by those skilled in the art with a value of 34-36 mN/m was applied to the said backing (71) during the rewinding stage.

The multilayer adhesive film was subjected to microperforation treatment during the rewinding stage, a process normally known to and carried out by those skilled in the art, to allow microbubbles of air, which would otherwise give rise to swelling of the film on the surface to which it adheres, to escape during the stage when the film was being applied.

The said multilayer support manufactured in this way, net of the adhesive coating, therefore has a thickness of 120 μιη and a total overall thickness inclusive of the adhesive mass of 140 μιη. We would point out that the use of a winding core with a diameter of less than 76.2 mm does not fully offer the logistical advantages already illustrated earlier for self-adhesive film thicknesses of 100 μιη or more, as a result of which the possibility of winding the adhesive film onto a conventional paper tube of 76.2 mm is preferred in this embodiment.

The abovementioned example of multilayer self-adhesive film finds suitable application within the painting stove booth as a protective film against paint spray (overspraying) and/or related drips affecting horizontal surfaces such as flooring and passageways above which the conveyors of the body shells which have to be painted move. At the present time these surfaces are coated with flexible non-adhesive aluminium laminates having a thickness of around 100 μηι and a width of around a metre, which are periodically removed during technical maintenance and cleaning operations on the facilities. This solution gives rise to safety problems however, because first of all these aluminium films are rather slippery when trafficked by those involved in technical cleaning, and secondly because the aluminium film alone is very ductile and therefore not infrequently pierced and torn during application. In order to overcome these difficulties a multilayer support comprising a particularly soft film (LLDPE) (71) intended to be the backing for the film was produced and somewhat pronounced embossing (height 1.5 mm) was also imprinted upon it in relief, thus obtaining a layer which is intended to be trafficked with optimum non-slip properties; subsequently the said embossed film (LLDPE) (71) was bonded to polyester film (PET) (73); the desired mechanical resistance to tearing was achieved through provision of the said polyester layer.

It is not possible to make comparisons with other films according to the scheme in the comparative table below because at the present time the film used for the abovementioned application is a non-adhesive aluminium film, but improvement in application conditions in comparison with this state of the art has also been confirmed - that is greater speed in application onto horizontal surfaces, because as the multilayer support is adhesive the use of adhesive tapes for attaching it is avoided - as well as improvement in performance, such as longer life of the protection as a result of the greater quantity of paint spray (overspraying) retained on the backing of the multilayer adhesive film.

GENERAL COMPARISON TABLE NO. 1, EXAMPLE 1

ADHESIVE FILM

EXAMPLE 1 TESA "4309 PVl " STANDARD CHARACTERISTICS

FUNCTIONAL ADVANTAGES

Support thickness 1 82 μηι 150 μιη

Total thickness 2 87 μηι 170 μπι AFERA 4006

Conformability (*) 3 (++) (+)

Elongation 4 28% 12% AFERA 4005

Removable natural

Type of adhesive mass 5 Removable acrylic

rubber

Adhesive mass vehicle 6 Water Solvent

Temperature resistance 7 150°C 120 °C AFERA 4003

Release of adhesive mass and/or break¬

8 Not possible Possible

up of the support

Peeling on the panel 9 92 cN/cm 350 cN/cm AFERA 4001

Peeling on the article after the Manual

10 155 cN/cm 441 cN/cm

temperature cycle dynamometer

Peeling of the backing (resistance to

1 1 46 cN/cm 263 cN/cm AFERA 4001 unwinding)

Warranty 12 20 months 12 months

Holding of paint on the backing

13 (++) (++)

(paintability) (*)

Flatness when unwound 14 Yes Yes

PRODUCTION AD VANTAGES

Impregnation of the support 15 No Yes

Constituent materials 16 88 g/m² 126 g/m² Coating rate 17 Not specified 30-40 m/min

Management of solvents 18 No Yes

Environment impact of solvents 19 Non-existent Present

LOGISTICAL ADVANTAGES

(multilayer on 2" core)

Weight of 50 mm x 50 m roll 20 223 g 320 g

50 mm x 50 m roll volume 21 0.317 dm³ 0.660 dm³

(*) Evaluation in comparison with the TESA® variety:

(+++) Excellent, (++) very good, (+) good, (o) average, (-) poor

GENERAL COMPARISON TABLE NO. 2, EXAMPLE 2

ADHESIVE FILM

EXAMPLE 2 Novacel "BN410" STANDARD CHARACTERISTICS

FUNCTIONAL ADVANTAGES

Support thickness 1 32.02 μπι 95 μπι

Total thickness 2 40 μηι 105 μιη AFERA 4006

Conformability (*) 3 (++) (++)

Elongation 4 1 10 % 450 % AFERA 4005

Removable Removable acrylic

Type of adhesive mass 5

acrylic

Adhesive mass vehicle 6 Water Water

Temperature resistance 7 130°C 90-95°C AFERA 4003

Release of adhesive mass and/or break-up Obvious traces of

8 Not possible

of the support release

Peeling on the panel 9 121 cN/cm 1 15 cN/cm AFERA 4001

Peeling on the article after the temperature Not detectable; Manual

10 132 cN/cm

cycle molten support Dynamometer

Peeling of the backing (resistance to

1 1 64 cN/cm 57 cN/cm AFERA 4001 unwinding) Warranty 12 20 months 12 months

Holding of paint on the backing

13 (++) (-)

(paintability) (-*)

Flatness when unwound 14 Yes No

PRODUCTION ADVANTAGES

Impregnation of the support 15 No No

Constituent materials 16 47 g m² 1 10 g/m²

Coating rate 17 60-80 m/min 60-80 m/min

Management of solvents 18 No Yes

Environment impact of solvents 19 Non-existent Present

LOGISTICAL ADVANTAGES

(multilayer on 2" core)

Weight of 50 mm x 50 m roll 20 120 g 281 g

50 mm x 50 m roll volume 21 0.198 dm³ 0.490 dm³

(*) Evaluation in comparison with the TESA® variety:

(+++) Excellent, (++) very good, (+) good, (o) average, (■

GENERAL COMPARISON TABLE NO. 3, EXAMPLE 3

ADHESIVE FILM CHARACTERISTICS EXAMPLE 3 TESA 4331 STANDARD

FUNCTIONAL ADVANTAGES

Support thickness 1 36 μηι 100 μήι

Total thickness 2 41 μιη ΠΟ πι AFERA 4006

Conformability (*) 3 (+++) (+)

Elongation 4 65 % 100 % AFERA 4005

Type of adhesive mass 5 Removable acrylic Removable silicone

Adhesive mass vehicle 6 Water Solvent

Temperature resistance 7 220°C 200°C AFERA 4003

Release of adhesive mass and/or break-up of 8 Not possible Not possible the support

Peeling on the panel 9 123 cN/cm 514 cN/cm AFERA 4001

Peeling on the article after the temperature Manual

10 177 cN/cm . 470 cN/cm

cycle Dynamometer

Peeling of the backing (resistance to

1 1 69 cN/cm 273 cN/cm AFERA 4001 unwinding)

Warranty 12 20 months 12 months

Holding of paint on the backing (paintability)

13 (++) (-)

(*)

Flatness when unwound 14 Yes Yes

PRODUCTION ADVANTAGES

Impregnation of the support 15 No Yes

Constituent materials 16 67 g/m² 105 g/m²

Coating rate 17 60-80 m/min 30-40 m/min

Management of solvents 18 No Yes

Environment impact of solvents 19 Non-existent Present

LOGISTICAL ADVANTAGES

(multilayer on 2" core)

Weight of 50 mm x 50 m roll 20 171 g 268 g

50 mm x 50 m roll volume 21 0.200 dm³ 0.501 dm³

(*) Evaluation in comparison with the TESA® variety:

(+++) Excellent, (++) very good, (+) good, (o) average, (-) poor

GENERAL COMPARISON TABLE NO. 4, EXAMPLE 4

ADHESIVE FILM

EXAMPLE 4 TESA 4318 PV2 STANDARD CHARACTERISTICS

FUNCTIONAL ADVANTAGES

Support thickness 1 37.02 150

Total thickness 2 47 μπι 170 μπι AFERA 4006

Conformability (*) 3 (++) (+) Elongation 4 35% 12% AFERA 4005

Removable natural

Type of adhesive mass 5 Removable acrylic

rubber

Adhesive mass vehicle 6 Water Solvent

Temperature resistance 7 170°C 160°C AFERA 4003

Release of adhesive mass and/or break¬

8 Not possible Possible

up of the support

Peeling on the panel 9 139 cN/cm 400 cN/cm AFERA 4001

Peeling on the article after the Manual

10 146 cN/cm 444 cN/cm

temperature cycle dynamometer

Peeling of the backing (resistance to

11 80 cN/cm 290 cN/cm AFERA 4001 unwinding)

Warranty 12 20 months 12 months

Holding of paint on the backing

13 (++) (++)

(paintability) (*)

Flatness when unwound 14 Yes Yes

PRODUCTION ADVANTAGES

Impregnation of the support 15 No Yes

Constituent materials 16 53 g/m² 124 g/m²

Coating rate 17 60-80 m/min 30-40 m/min

Management of solvents 18 No Si

Environment impact of solvents 19 Non-existent Present

LOGISTICAL ADVANTAGES

(multilayer on 2" core)

Weight of 50 mm x 50 m roll 20 135 g 317 g

50 mm x 50 m roll volume 21 0.215 dm³ 0.650 dm³

(*) Evaluation in comparison with the TESA® variety:

(+++) Excellent, (++) very good, (+) good, (o) average, (-) poor

GENERAL COMPARISON TABLE NO. 5, EXAMPLE 5 ADHESIVE FILM

EXAMPLE 5 TESA 4432 STANDARD CHARACTERISTICS

FUNCTIONAL ADVANTAGES

Support thickness 1 100 290

Total thickness 2 116 μηι 330 μιη AFERA 4006

Conformability (*) 3 (+++) (o)

Elongation 4 10% 6% AFERA 4005

Removable natural

Type of adhesive mass 5 Removable acrylic

rubber

Adhesive mass vehicle 6 Water Solvent

Temperature resistance 7 180°C 100°C AFERA 4003

Release of adhesive mass and/or break¬

8 Not possible Possible

up of the support

Peeling on the panel 9 244 cN/cm 800 cN/cm AFERA 4001

Peeling on the article after the Manual

10 283 cN/cm 910 cN/cm

temperature cycle dynamometer

Peeling of the backing (resistance to

1 1 90 cN/cm 420 cN/cm AFERA 4001 unwinding)

Warranty 12 20 months 12 months

Holding of paint on the backing

13 (++) (++)

(paintability) (*)

Flatness when unwound 14 Yes Yes

PRODUCTION ADVANTAGES

Impregnation of the support 15 No Yes

Constituent materials 16 130 g/m² 292 g/m²

Coating rate 17 60-80 m/min 30-40 m/min

Management of solvents 18 No Yes

Environment impact of solvents 19 Non-existent Present

LOGISTICAL AD VANTAGES

(multilayer on 76.2 mm core)

Weight of 50 mm x 50 m roll 20 328 g 737 g 0 mm x 50 m roll volume 21 0.387 dm³ 1.063 dm³

(*) Evaluation in comparison with the TESA® variety:

(+++) Excellent, (++) very good, (+) good, (o) average, (-) poor

Of course, without altering the principle of the invention, details of embodiments and forms of implementation may vary widely in comparison with what has been described purely by way of example without thereby going beyond the scope of the invention as defined by the appended claims.

Claims

1. Self-adhesive film for masking and/or protecting surfaces, in particular subject to high temperature operations, such as painting cycles, which film is formed by a support having a surface covered by a self-adhesive mass of "removable type", said film being characterized in that said support is a multilayer support formed by layers assembled together by a bonding process and in that said layers include a layer having a surface covered by said self-adhesive mass and a backing layer which are of plastics or metallic materials having melting point >150°C, selected from the group consisting of homopolymers and copolymers of polyester, polypropylene, polyamide and polyurethane, aluminium and alloys thereof.

2. Film according to claim 1 , wherein said support also comprises a layer of material having a melting point lower than 150°C selected from the group consisting of homopolymers and copolymers of low density polyethylene (LDPE), high density polyethylene (HDPE), medium density polyethylene (MDPE), linear low density polyethylene (LLDPE), ethylene vinyl acetate (EVA), cellulose acetate (CA), and polystyrene (PS).

3. Self-adhesive film for masking and/or protection of surfaces, the film being formed of a support having a surface covered by a self-adhesive mass of "removable type", the said film being characterised in that the said support is a multilayer formed of layers assembled together by a bonding process and in that the said layers include at least one layer of material selected from the group consisting of homopolymers and copolymers of polyesters, polypropylene, polyamide and polyurethane, aluminium and its alloys, and at least one layer of a material having a melting point below 150°C selected from the group consisting of homopolymers and copolymers of Polyethylene (PE), Ethyl vinyl acetate (EVA), Cellulose acetate (CA) and Polystyrene (PS) and preferably Low density polyethylene (LDPE), High density polyethylene (HDPE), Medium density polyethylene (MDPE) and Linear low density polyethylene (LLDPE).

4. Film according to any one of the preceding claims, in which all the layers of the said support are produced by extrusion.

5. Film according to any one of the previous claims, wherein said self-adhesive mass is of the type in aqueous solution, hot melt or solventless curable by UV rays.

6. Film according to any one of the previous claims, wherein said support has a thickness in the range 12 to 120 μηι.

7. Film according to any one of the previous claims, wherein said support comprises at least one layer interposed between said layer having a face covered by said self-adhesive mass and said backing layer, which at least one interposed layer is of material that is the same as or different from the materials of the layer having a surface covered by said self- adhesive mass and the backing layer.

8. Film according to any one of the previous claims, comprising one or more layers of aluminium, each of which has a thickness not greater than 10 μπι.

9. Film according to any one of the previous claims, wound around a core of plastics material of diameter less than 76.2 mm.

10. Film according to any one of the previous claims 1 to 8, shaped as a flat sheet.

1 1. Film according to any one of the previous claims, wherein the surface of said support opposite to the surface covered by said self-adhesive mass has a relief pattern.

12. Film according to any one of the previous claims, wherein said support has micro- perforations on the surface thereof.

13. Use of a film according to any one of claims 1, 2 and from 4 to 12 when dependent upon claims 1 or 2 for masking and/or protection of surfaces subject to operations which require exposure to temperatures within the range between 100°C and 220°C, such as painting cycles.

14. Use of a film according to claim 3 and from 4 to 12 when dependent upon claim 3 for masking and/or protecting surfaces which are subjected to operations requiring in particular exposure to temperatures in the range 100°C to 150°C, such as painting cycles.