Process for the decoration of the surface of a film of fluorinated polymer

Abstract

 The process for decorating the surface of a film of fluorinated polymer comprises the steps of: printing, with resins, a three-dimensional decorative pattern on one face of a second polymer film; bringing in contact the decorated face of the second film and at least one surface of the film of fluorinated polymer and supplying thermal energy to them; and detaching the second film from the film of fluorinated polymer, onto whose surface the decorative pattern has been transferred.

Description

[0001] The present invention relates to a process for decorating the surface of a substrate consisting of a film of fluorinated polymer, in particular ETFE (ethylene tetrafluoroethylene).

[0002] ETFE is a thermoplastic polymer that has high mechanical strength and corrosion resistance over a wide temperature range. ETFE has a melting point of 260°C, excellent chemical and dielectric properties, high resistance to chemical attack, and is fast against solar and ultraviolet radiation. Its structural formula is as follows:

[0003] A layer of ETFE has a weight equal to only 60/70% of that of a glass plate of equal volume. Moreover, since it permits the use of more efficient application solutions, the unit weight per m² of a coating of ETFE may be only approx. 5% of that of a similar coating formed from glass and the associated carrying structure. Moreover, this material is self-cleaning owing to its anti-adhesive surface, flame-retardant and incombustible, as well as recyclable at the end of its useful life. ETFE has a wide range of service temperatures (from -200 to +150°C), low flammability, excellent electrical and mechanical properties, excellent resistance to solvents and to chemicals, extremely high resistance to external atmospheric agents, high transmission of light in the visible and UV, anti-adhesion properties, excellent tearing strength, low permeability and good resistance to radiation.

[0004] Its typical applications are architectural membranes, films, coatings, insulation for electric cables, tubes, in particular hoses for fuels, and valves.

[0005] ETFE can be processed using flat head extrusion technology, by means of which films can be produced in widths ranging from 500 to 2000 mm and thicknesses ranging from 13 to 300 µm, with tolerances on thickness not above 4%.

[0006] The raw material in the form of granules is fed by gravity into the feed throat of an extruder, consisting of a thermostatically-controlled barrel, within which a screw of a suitable profile causes, by means of rotation, melting of the granules by friction, homogenizing the melt and increasing its pressure so as to drive it through a filter, for the purpose of separating extraneous and incompletely melted particles.

[0007] Downstream of the filter, the melt enters a gear pump, having the purpose of generating a continuous flow free from pressure fluctuations, which allows uniform distribution of the flow of molten material inside channels of the extruder head, thus avoiding preferential paths that would involve non-uniformity of thicknesses.

[0008] The head is characterized by a linear die head (slit for discharge of the molten material), the opening of which can be varied manually and roughly according to the thickness of film to be produced. The precise, fine regulation of the opening is performed during extrusion by a device that detects the film thickness continuously in real time and, as a function of the error detected relative to a predetermined set-point, sends correcting signals to a series of thermal bolts positioned corresponding to the die head, which by thermal expansion punctually alter the opening of the die head i.e. the slit for discharge of the molten polymer.

[0009] Once it leaves the die head, the film of plastic material is supported on cooling rolls with gradually decreasing temperature, so that it is cooled and stabilized with respect to its dimensional characteristics.

[0010] The films thus produced are of chemically inert material and therefore are not susceptible to chemical attack. They transmit sunlight in a percentage above 90% and are light, having a density of 1.72-1.78 kg/dm³. The characteristics of mechanical strength permit applications with ability to withstand loads and external stresses.

[0011] In the field of architecture, ETFE offers designers, owing to its special properties, notable opportunities for developing modern solutions that combine lightness, durability, design and ecology.

[0012] An ETFE film can also be coloured, by adding suitable pigments in the bulk (master batch) in the form of granules, which are supplied to the extruder in a suitable percentage relative to the base polymer. Moreover, the final film can retain a certain translucency, varying the colour of the light transmitted and extending the range of aesthetic and design possibilities.

[0013] Currently, few companies throughout the world print the surface of ETFE films, an operation that must however be preceded by a corona treatment for surface activation to make the surface wettable by inks or paints.

[0014] The results obtained so far are decorations with monochromatic patterns - silvery, white, black or grey, very simple and repetitive, such as dots or various geometric shapes, in positive or in negative and of various dimensions. These decorations are guaranteed for a resistance of 5 years to solar radiation.

[0015] Generally, these screen-printed films are used as the external and/or internal surface of cushions inflated with air, which function as a coating element for the purpose of limiting insolation inside buildings, reflecting the luminous and solar radiation to the exterior.

[0016] Solutions are known that make it possible to control the amount of radiation that enters a building simply by moving two screen-printed films with complementary patterns closer together or farther apart: there will not be any irradiation when the two films are perfectly in contact, but there will be maximum irradiation when the two films are the maximum possible distance apart. The relative movement of the films inside the cushion is controlled by the air pressure in the various compartments of the latter.

[0017] Several ETFE films can be joined together exclusively by heat-sealing. Consequently, the presence of deposits of aluminium on the surface greatly limits the possibility of welding two films together, in fact requiring "scraping" of the graphical patterns from the surfaces corresponding exactly to the welding lines.

[0018] Furthermore, the decorations produced so far are not able to resist the action of external factors throughout the service life envisaged for the associated film. Therefore they must be "protected", in particular by using special embodiments for avoiding their dissolution.

[0019] The purpose of the present invention is therefore to provide a method for decorating the surface of a film of fluorinated polymer, obtaining improved results relative to those of the prior art.

[0020] According to the invention, this purpose is achieved by means of a process for decorating the surface of a film of fluorinated polymer, comprising the steps of:

• printing, with resins, a three-dimensional decorative pattern on one face of a second polymer film,
• bringing in contact the decorated face of said second film and at least one surface of said film of fluorinated polymer and supplying thermal energy to them, and
• detaching the second film from said film of fluorinated polymer, onto the surface of which said decorative pattern has been transferred.

[0021] Using the process of the invention, it is possible to obtain decorated films even with complex and multicoloured patterns, which cannot be removed with solvents or abrasives, and at the same time do not require scraping before carrying out welding.

[0022] Preferably, the aforementioned second film is formed from a layer of extruded polymer material belonging to one of the following classes: polyesters, in particular PET, PBT, PTT, polypropylenes, polyamides, polyurethanes, polyvinyls, celluloses, lignin, or from several co-extruded layers, which may be identical or different, in particular celluloses, and the aforementioned film of fluorinated polymer is of ETFE, FEP, THV, MFA, ECTFE, PFA, PVDF or mixtures thereof, in particular of ETFE homopolymer or copolymer with one or more further, partially or fully fluorinated polymers.

[0023] According to one embodiment of the process of the invention, the printing of the three-dimensional decorative pattern on one face of the second film takes place by a technique of rotogravure, flexography, screen-printing, offset or a combination thereof, which envisages the use of one or more engraved rollers.

[0024] Advantageously, the aforementioned resins of the three-dimensional decorative pattern comprise at least one component selected from: cellulose acetate, cellulose acetobutyrate, cellulose nitrate, cellulose propionate, epoxides, melamine-formaldehyde, polyamides, polyamide-imides, polyacrylonitrile, polybutene-1, polybutyleneterephthalate, polycarbonate, polychlorotrifluoroethylene, polydiallylphthalate, polyethylene, chlorinated polyethylene, polyetherimide, polyetherketone, polyetheretherketone, polyethersulphones, polyethyleneterephthalate, phenolformaldehyde, polyimide, polyisobutylene, polymethacrylimide, polymethylmethacrylate, poly-4-methylpentene-1, polyoxymethylene, polyformaldehyde, polyacetal, polypropylene, polyphenyl ether, polyphenylene oxide, polyphenylene sulphide, polystyrene, polysulphone, polythiophene, polytetrafluoroethylene, polyurethane, polyvinylbutyral, polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl fluoride, regenerated cellulose, silicones, urea-formaldehyde, unsaturated polyester, polydimethylsiloxane.

[0025] Advantageously, the aforementioned resins of the three-dimensional decorative pattern comprise at least one organic pigment belonging to at least one of the classes nitroso, nitro, monoazo, diazo, stilbene, diphenylmethane, triphenylmethane, xanthene, acridine, quinoline, methine, thiazole, indamines, indophenol, azine, oxazine, thiazine, aminoketone, anthraquinone, indigoid, phthalocyanine and derivatives thereof, in particular a pigment of the class of pigments dispersed by sublichromia.

[0026] Preferably, the aforementioned film of fluorinated polymer is provided with additives for increasing the resistance of the aforementioned pigments to electromagnetic radiation.

[0027] According to a further embodiment of the process of the invention, supply of thermal energy takes place by conduction, for example as a result of contact with a heated surface, convection and/or radiation, in such a way that the temperature is between 40 and 300°C. For example, supply of thermal energy can take place in a calender or by direct contact with the heated surface of a press.

[0028] The film of fluorinated polymer, onto the surface of which said decorative pattern has been transferred, preferably displays mechanical and chemical properties substantially corresponding to those of the film without the decorative pattern.

[0029] According to yet another embodiment of the process of the invention, the film of fluorinated polymer, onto the surface of which said decorative pattern has been transferred, is welded to a further film of fluorinated polymer without removing the aforementioned decorative pattern, which is advantageously resistant to the action of rubbing with organic solvents that do not attack the fluorinated polymer per se.

[0030] Further advantages and characteristics of the present invention will become clear from the following non-limiting practical example.

Example

[0031] A cellulose film with a nominal thickness of 20 µm is printed with a three-dimensional decorative pattern by a rotogravure technique that envisages the use of a mixture of organic resins of the class of celluloses. The organic resins contain pigments of the class of those dispersed by sublichromia.

[0032] The decorated cellulose film is then brought in contact with a film of ETFE and heated to a temperature of 220°C using a calender heated with diathermic oil. After intimate contact lasting approximately 25 seconds, the ETFE film has absorbed the pigments of the class of dispersed pigments and displays a decorated appearance, due to transfer of the decorative pattern onto its surface.

[0033] Naturally, without prejudice to the principle of the invention, the details of execution and the embodiments can be varied widely relative to what has been described purely as an example, while remaining within the scope of the invention as defined in the appended claims.

Claims

1. Process for decorating the surface of a film of fluorinated polymer, comprising the steps of:

- printing a three-dimensional decorative pattern on one surface of a second polymer film by using resins,

- placing the decorated surface of said second film and at least one surface of said film of fluorinated polymer in contact and supplying thermal energy thereto, and

- detaching the second film from said film of fluorinated polymer, onto the surface of which the decorative pattern has been transferred.

2. Process according to Claim 1, wherein said second film is formed of a layer of extruded polymer material belonging to one of the following classes: polyesters, in particular PET, PBT, PTT, polypropylenes, polyamides, polyurethanes, polyvinyls, celluloses, lignin or several identical or different co-extruded layers, in particular celluloses.

3. Process according to Claim 1 or 2, wherein said film of fluorinated polymer is of ETFE, FEP, THV, MFA, ECTFE, PFA, PVDF or mixtures thereof, in particular of ETFE homopolymer or copolymer with one or more further partially or fully fluorinated polymers.

4. Process according to any one of the preceding claims, wherein printing of the three-dimensional decorative pattern on one surface of the second film takes place through a rotogravure, flexographic printing, screen printing or offset technique, or a combination thereof, which provides for the use of one or more engraved rollers.

5. Process according to any one of the preceding claims, wherein the resins of the three-dimensional decorative pattern comprise at least one component selected from: cellulose acetate, cellulose acetobutyrate, cellulose nitrate, cellulose propionate, epoxides, melamine-formaldehyde, polyamides, polyamide imide, polyacrylonitrile, polybutene-1, polybutylene terephthalate, polycarbonate, polychlorotrifluoroethylene, polydiallyl phthalate, polyethylene, chlorinated polyethylene, polyether imide, polyetherketone, polyetheretherketone, polyether sulphones, polyethylene terephthalate, phenol formaldehyde, polyimide, polyisobutylene, polymethacrylimide, polymethyl methacrylate, poly-4-methylpentene-1, polyoxymethylene, polyformaldehyde, polyacetal, polypropylene, polyphenyl ether, polyphenylene oxide, polyphenylene sulphide, polystyrene, polysulphone, polythiophene, polytetrafluoroethylene, polyurethane, polyvinyl butyral, polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl fluoride, regenerated cellulose, silicones, urea-formaldehyde, unsaturated polyester, polydimethylsiloxane.

6. Process according to any one of the preceding claims, wherein the resins of the three-dimensional decorative pattern comprise at least one organic pigment belonging to at least one of the classes: nitroso, nitro, monoazo, diazo, stilbene, diphenylmethane, triphenylmethane, xanthene, acridine, quinoline, methine, thiazole, indamine, indophenol, azine, oxazine, thiazine, aminoketone, anthraquinone, indigoid, phthalocyanin and their derivatives, in particular a pigment of the class of dispersed pigments for sublichromia.

7. Process according to Claim 6, wherein said film of fluorinated polymer contains additives for increasing the resistance of said pigments to electromagnetic radiation.

8. Process according to any one of the preceding claims, wherein the thermal energy is provided through conduction, for example following contact with a heated surface, convection and/or irradiation, in such a way that the temperature is between 40 and 300°C.

9. Process according to Claim 8, wherein the provision of thermal energy takes place in a calender or by direct contact with the heated surface of a press.

10. Process according to any one of the preceding claims, wherein the film of fluorinated polymer, onto whose surface said decorative pattern was transferred, has mechanical and chemical properties substantially corresponding to those of the film without the decorative pattern.

11. Process according to any one of the preceding claims, wherein the film of fluorinated polymer, onto whose surface said decorative pattern was transferred, is welded to a further film of fluorinated polymer without removing said decorative pattern.

12. Process according to any one of the preceding claims, wherein said decorative pattern of the film of fluorinated polymer is resistant to rubbing with organic solvents that do not attack the fluorinated polymer per se.