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WO2018184911A1 - Procédé permettant de produire un substrat de métal revêtu de polymère et substrat de bande de métal pourvu d'un revêtement de polymère - Google Patents

Procédé permettant de produire un substrat de métal revêtu de polymère et substrat de bande de métal pourvu d'un revêtement de polymère Download PDF

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Publication number
WO2018184911A1
WO2018184911A1 PCT/EP2018/057758 EP2018057758W WO2018184911A1 WO 2018184911 A1 WO2018184911 A1 WO 2018184911A1 EP 2018057758 W EP2018057758 W EP 2018057758W WO 2018184911 A1 WO2018184911 A1 WO 2018184911A1
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WO
WIPO (PCT)
Prior art keywords
film
polymer film
polymer
stretched
substrate
Prior art date
Application number
PCT/EP2018/057758
Other languages
English (en)
Inventor
Jan Paul Penning
Johannes Willem PATTIASINA
Original Assignee
Tata Steel Ijmuiden B.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tata Steel Ijmuiden B.V. filed Critical Tata Steel Ijmuiden B.V.
Publication of WO2018184911A1 publication Critical patent/WO2018184911A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/18—Handling of layers or the laminate
    • B32B38/1825—Handling of layers or the laminate characterised by the control or constructional features of devices for tensioning, stretching or registration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0011—Combinations of extrusion moulding with other shaping operations combined with compression moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0021—Combinations of extrusion moulding with other shaping operations combined with joining, lining or laminating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets

Definitions

  • This invention relates to a process for producing a polymer coated metal substrate and a metal strip substrate provided with a polymer coating.
  • the polymer coated substrate can be produced by extruding a molten polymer film directly onto the metallic substrate or by producing a thermoplastic polymer film that is subsequently laminated, as a solid film, onto a metallic substrate in an integrated or separate lamination process step.
  • Extrusion coating of a metal substrate is disclosed in for instance EP0067060 and US5919517.
  • Several problems are associated with this technique, in particular the tendency of a molten polymer web to decrease in width after leaving the die ('neck-in'), thickening of the film edges, waviness of film edges, which result in unstable processing behaviour and unsatisfactory properties of the coated product.
  • An improvement of the above direct extrusion coating process involves the use of an intermediate roll to support the molten web while leaving the die, and to stabilise the extruded film, remove its thick edges, etc. The extruded film is then brought into contact with the metal substrate without intermediate winding and/or unwinding of the film (see, for instance, EP1019248).
  • the extrusion coating process is not preferred.
  • the coating operation has to be performed in a continuous, reel-to-reel process.
  • Handling of the metal substrate at high speed in such a process requires a processing line equipped with multiple uncoilers, recoilers, cutters, bridles, looper towers, welding machine and the like, requiring a very high capital investment.
  • Process interruption, product change-over and maintenance stops associated with the extrusion process also stop the metal processing line and severely limit its utilisation rate. Therefore running an efficient and high-speed coating operation based on an extrusion process is very difficult.
  • a film lamination process rather than an extrusion coating process.
  • a film-laminating process a pre-manufactured polymer film is supplied, unwound and passed through a pair of laminating rolls together with the strip of metal substrate and optionally a second film, simultaneously laminated to the opposite side of the strip.
  • This process can be conducted efficiently, at high speed with maximised utilisation of the metal processing line.
  • the quality of the polymer film can be checked prior to the lamination stage, thus avoiding the manufacture of defective product due to insufficient film quality.
  • Well-known examples of film lamination process are based on the use of biaxially stretched polyester films (see, for instance, EP0312303, EP0312304 Bl and EP901899).
  • a separate film lamination process allows higher processing speeds, but processability and success of the lamination step is strongly dependent on the mechanical and physical properties of the film.
  • the extruded films from thermoplastic polyesters such as PET are mechanically very weak and cannot be used in a film lamination process at a commercially viable speed.
  • cast polyester films are susceptible to 'physical aging', which tends to further degrade the mechanical properties and handling characteristics when the cast film is stored. For these reasons polyester films for laminating onto metallic substrates are usually biaxially drawn to achieve the necessary level of mechanical strength and stability.
  • the biaxial stretching process generally results in films of high quality and homogeneity
  • the biaxial stretching process is a complex operation, requiring large-scale and complex equipment with high capital investment and high operational cost.
  • biaxial film stretching lines do not easily allow changes in e.g. the polymer film composition and are inflexible in terms of product change-over.
  • EP2701905 which uses a cast film that is stretched in the longitudinal direction (also called machine direction) only. This greatly simplifies the film manufacture process and product flexibility while still producing a film that is suitable for the high-speed film laminating process outlined above.
  • an adhesion layer for promoting the adhesion between the substrate and the polymer film
  • polymer film consisting of one or more layers is produced by:
  • post-heating the polymer-coated substrate to significantly reduce (or remove) the molecular orientation and crystallinity of the polymer film; cooling, preferably fast cooling, of the post-heated polymer-coated substrate, optionally coiling the cooled post-heated polymer-coated substrate
  • TD stretching naturally smoothens out machine direction propagated imperfections, such as die lines, flow lines, and other film defects related to flow instabilities in the casting process.
  • thicker parts will stretch a little bit further than thinner parts as the film will attempt to reach a constant stress over its entire width. As a result, all regions will reach the same final thickness after stretching.
  • TD stretching will increase the width of the film and decrease its thickness, while the film length will remain essentially constant.
  • a cast film of 0.50 m in width and 100 ⁇ in thickness will be converted into a TD- stretched film of about 2.00 m wide and 25 ⁇ in thickness. Therefore, the cast film width and thickness need to be chosen with the desired properties and dimensions of the TD- stretched film in mind.
  • cast films are usually non-oriented and essentially in an amorphous state. A suitable temperature at which such amorphous films can be stretched is around the glass transition temperature (Tg).
  • the stretching temperature is between Tg - 30 and Tg + 30 °C, preferably between Tg - 20 and Tg + 20 °C.
  • the Tg of the cast film can be conveniently determined by various methods, such as dynamic mechanical thermal analysis (DMTA) or differential scanning calorimetry (DSC) as described in ISO 11357-2 :2013 : Determination of glass transition temperature.
  • DMTA dynamic mechanical thermal analysis
  • DSC differential scanning calorimetry
  • the film After stretching, it is necessary to heat-set the film.
  • the film is heated to a suitable temperature for a brief period of time, while being held under tension. This treatment will affect (further) crystallisation of the film while being kept under tension.
  • the stretching process itself which is conducted at around Tg, may already introduce some crystallisation.
  • the time and temperature conditions of heat setting should be sufficient to affect crystallisation of the film and to reduce the thermal shrinkage of the film.
  • the heat-setting step needs to further increase the degree of crystallinity and thus needs to be conducted at a substantially higher temperature than Tg.
  • the temperature where crystallisation is fastest is normally about half way between Tg and the melting point (Tm).
  • Tmid Tg + (Tm - Tg)/2 to be the minimum temperature for heat-setting.
  • higher temperatures up to Tmid + 60°C, may be employed.
  • Optimum heat-setting temperatures are therefore in the range 170 - 230°C.
  • the heat-set time should be short, preferably 2 seconds or less, preferably 1 second or less. Typical conditions are 1 second at 210°C.
  • the heat-setting step is necessary in order to limit the amount of thermal shrinkage in the width direction of the TD-stretched film. If shrinkage in the width direction of the film would occur during laminating, both the thickness and the width of the film would change prior to laminating, resulting in a defective laminated product. Whereas shrinkage of the film in longitudinal direction can be easily suppressed by applying tension to the film in the machine direction, this method cannot be applied to suppress shrinkage in the transverse direction of the film. Therefore, the TD-stretched film should have intrinsically low shrinkage properties and for this, heat-setting is considered to be a necessary step.
  • the TD-stretched polymer film can be produced in a two-step process (film casting and stretching done separately) or in an integrated process (film casting combined with stretching).
  • the solid polymer film is preferably wound onto a reel or coil prior to being fed to the stretching unit. There may be a considerable amount of time between the production of the solid polymer film and the stretching step in the two-step process.
  • the alternative is that the solid polymer film is fed directly into the stretching unit to produce the TD-stretched polymer film.
  • a molten polymer film consisting of one or more layers is produced by melting a suitable mixture of polymers, e.g. in the form of granules, in one or more extruders and passing the molten polymer through an extrusion die, usually a flat die.
  • the molten polymer film is solidified, e.g. by casting it onto a cooled roll, or in case of a calendar process, between two or more rolls. The film is then essentially amorphous and non-oriented.
  • one of the outer layers will function as a so-called adhesion layer, having a composition such that it will create a better bond to the metal substrate than the other layers.
  • thick edges of the film resulting from 'neck in' can optionally be trimmed off. Any trimmed-off material may be fed back into one of the extruders, optionally after intermediate reprocessing, to limit material losses and to optimise cost efficiency.
  • the cast and trimmed film is either coiled onto a reel or passed on directly to the stretching unit.
  • the solid polymer film is fed through an appropriate stretching unit.
  • the TD-stretching process can be performed by different methods, which are well-known in the art.
  • the technology dates back from the time when biaxial stretching of polymer films was developed (see, for instance, US2779684).
  • the most common method uses a so-called tenter frame.
  • the film is directed between parallel rows of tenter clips.
  • the tenter clips grasp the edges of the film and move outward to stretch the film transversely.
  • a TD stretching unit is divided into four zones, including a preheating zone, a stretching zone, a heat-setting zone and a cooling zone.
  • the first zone or pre-heating zone is represented by the entry of the stretching unit until the transverse stretching begins.
  • the second zone is the section between the beginning and the end of the transverse stretching.
  • the third zone is the heat-setting zone where the film is subjected to an elevated temperature, as described above, while the film is held under transverse tension.
  • the fourth zone is usually open to the environment and serves to cool down the film.
  • the film edges may be trimmed to ensure proper winding and further processing of the drawn film.
  • the amount of material that needs to be trimmed off is usually very small.
  • This trimmed-off material can be recycled.
  • the film is coiled on a reel. Between stretching and coiling, one or more of defect inspection, gauge measurement, surface treatment (corona, flame, spraying of (liquid) additives or agents, etc.) and/or slitting into multiple widths may be performed.
  • defect inspection, gauge measurement, surface treatment corona, flame, spraying of (liquid) additives or agents, etc.
  • a disadvantage of the non-oriented solid polymer film is that it is mechanically weak and possibly brittle.
  • the inventors found that it can be processed excellently in the transverse stretching process because the film is still relatively thick at that stage of the process.
  • the above-mentioned physical aging process does not severely limit the processability of the cast film, provided that it is sufficiently thick.
  • the inventors found that a suitable minimum thickness of the solid polymer film prior to stretching is in the order of 50 micron.
  • the stretched films have a thickness that corresponds to the desired final thickness of the polymer coating on the metal substrate. In other words, laminating the stretched film onto the metal substrate produces directly the desired coating thickness.
  • the thickness of the stretched film is between 5 and 50 microns.
  • the TD-stretched polymer film may be highly crystalline and/or oriented. Therefore the metal substrate, after laminating with the film, is heated to a post heat temperature designed to remove all orientation and crystallinity present in the coating. A subsequent rapid cooling step creates a polymer coated metal strip with a highly amorphous (i.e. largely non-crystalline) and essentially non-oriented polymer coating.
  • This material is suited to create a very good formable material, with excellent adhesion and barrier properties, and thus very suitable for making e.g. deep drawn cans.
  • Essential is the high speed with which this process can be used. Only technical limitations and control issues limit the speed at which the laminating line can be run. The inventors found that the process can be excellently performed at line speeds of from 400 to 700 m/min. Higher speeds of up to 1200 m/min are currently being considered.
  • polymer films such as polyester films, which are perfectly suitable for lamination onto metallic substrates at high speed
  • the polymer film is cast at a relatively high thickness and subsequently drawn and oriented in the transverse direction only.
  • the film becomes wider and thinner, and the desired final thickness of the polymer coating film is thereby achieved.
  • the drawing process is conducted under the proper conditions, the film will achieve a high degree of homogeneity, high mechanical strength, low shrinkage and good handling characteristics for high speed lamination, and is freed from physical aging, thus allowing virtually unlimited storage of the TD-stretched film prior to lamination.
  • a surface treatment of the steel and/or the film prior to the entry in the lamination nip examples are ozone generators, corona treatment or flame treatment. These additional treatments are not essential, but give an improved performance if needed.
  • the metal strip substrate is preferably preheated prior to laminating the TD-stretched polymer film onto the substrate to produce the polymer-coated substrate. If the substrate is preheated, then it is preferably preheated to a temperature between the glass transition temperature and the melting temperature of the TD-stretched polymer film or films, or in case of a multi-layer film, at least to a temperature between the glass transition temperature and the melting temperature of the layer of the TD-stretched polymer film or films that will be adhered to the substrate (the adhesion layer).
  • additional heat treatments can be applied with which the physical structure of the coating (e.g., crystal I in ity) can be further modified.
  • the physical structure of the coating e.g., crystal I in ity
  • Examples for such a treatment are flame treatment, corona treatment, infrared heaters, lasers or hot air furnaces. This treatment can further improve the barrier properties of the film at the expense of some of the formability of the polymer. However, for some particular applications this loss of formability may be justified.
  • the time between the coiling of the TD-stretched film and the lamination onto the metal strip can vary between almost immediately after stretching and coiling, or even inline without intermediate coiling, to very long.
  • the stability of the sufficiently TD-stretched film is such that the film can be stored for up to 5 years or longer. However it is preferable to process the film within 6 months, and even more preferably within 1 month.
  • Lamination of the TD-stretched film onto the metal substrate is preferably accomplished in a process separate from the TD-stretched film production because of the vulnerability for disturbance in the chain of high speed processes.
  • the draw ratio of the solid polymer film is between 2 and 12, preferably at least 3 and/or at most 6. These values are optimised from a technical and commercial point of view.
  • Lamination can be performed in the same line where a metallic coating on the strip is applied, for example a tinplating line. It could also be done in a stand-alone, independent lamination line.
  • the lamination onto the substrate is done using pressing rolls. It can be done on one side or two sides, depending on the application of the coated metal strip. Always a pair of rolls is used for pressing the film against the metal. When coating both sides of the substrate with the TD-stretched film, it can be done simultaneously or in two steps.
  • the polymer films are laminated to the steel strip by a process schematically shown in Figure 1.
  • Figure 2 shows a preferred embodiment of such a process.
  • the metal strip (1) is passed through a first heating device (2) where the temperature of the metal strip is raised to a value suitable for lamination, Tl.
  • a film coil (3a) and (not needed for single side lamination) another film coil (3b) are unwound and passed, together with the pre-heated metal strip, through a pair of laminating rollers (4a, 4b).
  • the laminated product (5) is passed through a second heating device, the post-heat device (6), to remove the orientation and crystallinity within the chosen residence time in the post heat section.
  • the gas atmosphere in the second heating device can be air, or a protective or inert atmosphere such as nitrogen atmosphere containing less than 1000 ppm of oxygen.
  • the method of pre-heating the metal strip in the first heating device is not particularly limited and may include passing the strip over heated rolls, conductive heating, inductive heating, radiative heating etc.
  • the method of post-heating the laminated product in the second heating device is preferably a contactless method, such as heating in a hot gas environment or inductive heating.
  • the first technique involves the use of a (liquid) adhesion promoter or primer.
  • the adhesive layer is applied in e.g. liquid form for example by dipping, spraying or roll coating to either the metal substrate or to the polymer film.
  • the second method is known as heat seal lamination.
  • the metal is heated to a temperature which results in softening of the layer of the film which is brought in contact with the metal. This layer is known as the adhesion side or, when a multi-layer film is used, the adhesion layer.
  • the required substrate preheat temperature depends on the polymer to be laminated upon the substrate. For amorphous polymers the temperature is at least 50°C above the Tg.
  • the substrate preheat temperature is between 10 to 50°C below the melting point of the highest melting polymer in the adhesion layer.
  • the exact temperature used is determined using for example viscosity data of the polymers used, the line speed, the lamination pressure, the modulus of the film, the roughness of both the film and the metallic strip, etc. and is a matter of routine experimentation.
  • the preheat temperature is chosen such that the adhesion layer will completely cover the roughness of the metal strip, where the outside of the film, touching the laminating rolls should not exceed the sticking temperatures of the film on the lamination rolls to prevent sticking of the film to these rolls.
  • the lamination pressure in the laminating step to laminate the TD-stretched film onto the substrate is between 0.1 MPa and 10 MPa, preferably at least 0.5 and/or at most 2.5 MPa.
  • the TD-stretched polymer film is brought in contact with the strip using laminating rolls. These rolls are pressed onto the metal strip to generate a good bond.
  • the laminating rolls are usually covered with a relatively thick elastomeric coating which create a laminating nip when pressed together, and which can adopt to thickness variation or thickness profile ("strip crown') of the metal substrate and coating film without damaging either coating or substrate.
  • the rolls can be cooled, at least on the outside, but optionally also on the inside of the roll.
  • the roll diameter, thickness of the elastomeric covering and applied roll pressure may be configured and optimised in such a way that an appropriate laminating nip is created, thus allowing sufficient time for the metal substrate and polymer film to establish a good bond.
  • the tension in the polymer film should be carefully controlled to ensure good web tracking and avoid laminating defects such as creases, folds and wrinkles.
  • the lamination pressure in the laminating step e.g. in the lamination nip between two laminating rolls, is preferably between 0.1 MPa and 10 MPa. Higher values will result in excessive wear of the lamination rolls, lower pressure will result in insufficient adhesion between the coating and the metal and in an increased risk of air entrapment. Preferably the lamination pressure is at least 0.5 MPa and/or at most 2.5 MPa.
  • the coated strip is optionally cooled using e.g. cold air, in order to impart sufficient rigidity, strength and/or toughness for further handling of the semifinished product and to allow contact with additional rolls which may be present in the lamination process (deflector rolls etc.).
  • additional rolls which may be present in the lamination process (deflector rolls etc.).
  • the temperature setting of the post heat is defined by the polymer properties.
  • the TD-stretched film is highly oriented and, if crystallisable polymers are used, highly crystalline.
  • the post heat temperature is chosen such that that the orientation and crystallinity is removed within the chosen residence time in the post heat section.
  • the residence time is preferably at least 0.1 and preferably at most 10 seconds, or preferably at most 5 seconds.
  • the post heat temperature is preferably between Tm and Tm + 50°C.
  • the post heat temperature is preferably between Tg + 50°C and Tg + 150°C and for crystallisable polyaddition polymers, such as polyolefins, the post heat temperature is preferably between Tm + 50°C and Tm + 150°C.
  • the post-heating step may be conducted in an inert or non-oxidising gas atmosphere (see co-pending EP16163683.2). Although it is preferable that all orientation and crystallinity is removed, a small amount of crystallinity and/or orientation is allowable.
  • crystallinity must not exceed more than 50 %, or preferably more than 20% of the crystallinity and/or orientation which existed prior to the post-heat.
  • a method for measuring crystallinity by X-ray diffraction is given in GN 1566422, page 5 line 31-50.
  • the crystallinity can be determined from density measurements as described in EP0312304, page 2, line 27-37.
  • Crystallinity can also be determined by differential scanning calorimetry (DSC), e.g. using a Mettler Toledo DSC821e calorimeter operated at a sample heating rate of 10°C/min.
  • the hot metal coated strip is cooled very rapidly after exiting the post heat section. This is preferably done in a cold water bath, but could also be done with cooled rolls or cold gasses, as long as the cooling rate of the polymer film is at least 100°C/s, more preferably at least 400°C/s.
  • the width of the laminating film and the width of the metal substrate may be adjusted to each other by various means, in order to achieve the desired laminated end product.
  • the film may be wider than the metal substrate, and the excess width is trimmed off just before the laminating rolls.
  • the wider film may be laminated to the metal substrate, and trimming off the excess width, together with a small amount of metal strip after laminating, to obtain a metal strip covered with the polymer film over its entire width.
  • the film may also be somewhat narrower than the metal strip, leaving a small bare edge of uncoated metal at the side of the strip.
  • the polymer film produced according to the invention can be used for applications other than cans or containers, it is particularly suitable for those applications where properties like adhesion, barrier properties and formability are essential. This makes it very suitable for the production of cans and containers.
  • the film may also be used in the production of laminated metal substrates for building materials, furniture or materials for transport applications (automotive, aerospace, etc.).
  • Polymer-metal laminates made using this process may be used for cans or containers, more preferably formed cans made using deep drawing and/or stretching and/or wall ironing.
  • the TD-stretched polymer films and polymer coated substrates that can be produced by the process according to the invention are preferably based on polycondensates, such as polyesters, co-polyesters (including PET, PBT, polyethylene furanoate (PEF), poly(lactic acid) (PLA)) or polyamides, polyolefins, elastomers, non-crystallisable vinyl polymers, such as polystyrene, polyacrylate, PVC or PVDC, crystallisable polyaddition polymers, such as polyolefins, or any other polymer that can be formed in a film by extrusion.
  • polycondensates such as polyesters, co-polyesters (including PET, PBT, polyethylene furanoate (PEF), poly(lactic acid) (PLA)) or polyamides
  • the polymer coating may consist of one or more layers.
  • the TD-stretched film comprises or consists of polyethylene terephthalate, IPA-modified polyethylene terephthalate, CHDM- modified polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene furanoate, poly (lactic acid) or copolymers or blends thereof.
  • the process according to the invention has particular advantages when producing polymer films which consist of essentially linear, thermoplastic polymers produced by polycondensation reactions (polyesters, polyamides, polycarbonates, polyimides etc.).
  • This structure limits the speed at which these polymers can be extruded and therefore extrusion coating for these polymers is limited to low speeds.
  • polyolefins such as PE and PP
  • the maximum possible extrusion speeds are much higher due to their molecular architecture (high molecular weight, short-chain branching, long-chain branching, etc.).
  • Extrusion and extrusion coating at > 600 m/min is known for polyolefins.
  • the one or more of the layers of the TD-stretched film contains colour additives such as inorganic pigments or organic dyes, and/or wherein the TD- stretched film is non-transparent or opaque, and/or wherein the TD-stretched film is white. Because of the TD-stretching, any local differences in pigmentation as a result of the casting of the polymer film will have been removed by the TD-stretching.
  • the metallic substrate can be an uncoated metal such as steel or aluminium or aluminium alloys or a metallic-coated metal such as tinplate or galvanised steel, and may contain an additional conversion layer or passivation layer to further enhance the product performance and/or promote adhesion between the metal and the polymer coating.
  • This additional conversion layer or passivation layer can e.g. be based on chromium oxide, chromium/chromium oxide, titanium oxide, zirconium oxide, phosphates.
  • the present invention is aimed to produce polymer-coated materials at high productivity with relatively low capital expenditure (compact unit operations), relatively low fixed costs whilst maintaining the variable costs (high line speed) and flexible production logistics (integrated drawing or not, variable storage time possible, easy polymer changeover). Enabling high line speed is one of the key benefits of this invention but it will also work at lower line speeds.
  • the process according to the invention provides excellent polymer- coated metals, which can be produced at extremely high speeds having excellent properties to produce a can from the material. Also, the process can be operated using compact unit operations and allows high flexibility in product composition and production logistics.
  • a cast film of poly (ethylene terephthalate) was produced by melting the polymer granules in a lab-scale extruder, passing the molten polymer through a flat die and cooling the extruded polymer film on a chilled casting roll.
  • the as-produced film had a thickness of 400 ⁇ and contained clearly visible surface irregularities in the film casting direction.
  • Stretching of the film was done using a Bruckner Karo IV lab-scale biaxial stretching machine. Samples measuring 9 x 9 cm were cut from the cast film and placed in the stretching machine. The samples were stretched at various ratios as specified in Table 1 at a stretching temperature of 80°C, followed by heat-setting at 200°C during 1 second while keeping the sample under tension. When the samples were stretched in the machine direction (machine direction stretching or MD-stretching), the initially present surface irregularities of the cast film persisted in the stretched sample. When the samples were stretched in the transverse direction (transverse direction stretching or TD-stretching), the initially present surface irregularities were removed and a stretched sample with perfectly homogeneous structure was obtained.
  • Figure 1 shows schematically (from left to right) the steps to arrive to a polymer coated material based on a metal strip and (in this case) two polymer films by lamination.
  • Fig. 2 shows a preferred embodiment of this process for double-sided lamination of polymer films on a steel strip.
  • the polymer film prior to lamination are heat-set TD-stretched polymer film. Obviously, if only one heat- set TD-stretched polymer film would be provided, then the substrate would be coated on one side only.
  • Figure 3 shows a schematic sequence of the various steps, including some optional (dashed) ones. Finally, in figure 4, the difference between TD-stretching, MD- stretching and biaxial stretching is clarified.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
  • Laminated Bodies (AREA)

Abstract

La présente invention a trait à un procédé permettant de produire un substrat de métal revêtu de polymère et à un substrat de bande de métal pourvu d'un revêtement de polymère.
PCT/EP2018/057758 2017-04-03 2018-03-27 Procédé permettant de produire un substrat de métal revêtu de polymère et substrat de bande de métal pourvu d'un revêtement de polymère WO2018184911A1 (fr)

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Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2779684A (en) 1954-06-08 1957-01-29 Du Pont Polyester films and their preparation
US3816584A (en) 1971-03-05 1974-06-11 Kalle Ag Asymmetrical transverse stretching of plastic film
EP0016653A1 (fr) 1979-03-22 1980-10-01 Nippon Petrochemicals Company Limited Procédé et dispositif pour l'étirage latéral d'une pellicule ou d'une bande fibreuse
EP0067060A1 (fr) 1981-06-09 1982-12-15 Taiyo Steel Co., Ltd: Bande métallique revêtue et procédé pour sa fabrication
EP0312304A1 (fr) 1987-10-15 1989-04-19 CMB Foodcan plc Feuille métallique revêtue
EP0312303A1 (fr) 1987-10-15 1989-04-19 CMB Foodcan plc Feuille métallique revêtue
EP0901899A1 (fr) 1996-04-10 1999-03-17 TOYO KOHAN Co., Ltd Plaque metallique enduite d'une resine de terephtalate de polyethylene et possedant de grandes capacites de traitement
US5919517A (en) 1993-05-05 1999-07-06 Aluminum Company Of America Method for coating a metal strip
EP1019248A1 (fr) 1997-01-23 2000-07-19 Hoogovens Staal B.V. Procede et dispositif de revetement d'une bande plastique pelable sur un substrat metallique en forme de ruban et ruban ainsi obtenu
JP2002120278A (ja) * 2000-10-13 2002-04-23 Toyo Kohan Co Ltd 金属板被覆用樹脂フィルムの製造方法、金属板被覆用樹脂フィルム、樹脂フィルム被覆金属板の製造方法、樹脂フィルム被覆金属板およびそれを成形してなる缶
US7229271B2 (en) 2001-05-31 2007-06-12 3M Innovative Properties Company Apparatus for making transversely drawn films with substantially uniaxial character
US20110247681A1 (en) * 2009-10-10 2011-10-13 E. I. Du Pont De Nemours And Company Method for manufacturing multilayer films and solar panel backsheets formed thereof
US20120028058A1 (en) * 2010-07-29 2012-02-02 Toray Plastics (America), Inc. High barrier heat sealable film with linear tear properties
WO2012146654A1 (fr) * 2011-04-28 2012-11-01 Tata Steel Ijmuiden Bv Procédé permettant de produire un substrat de métal revêtu de polymère et substrat de bande de métal pourvu d'un revêtement de polymère

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2779684A (en) 1954-06-08 1957-01-29 Du Pont Polyester films and their preparation
US3816584A (en) 1971-03-05 1974-06-11 Kalle Ag Asymmetrical transverse stretching of plastic film
EP0016653A1 (fr) 1979-03-22 1980-10-01 Nippon Petrochemicals Company Limited Procédé et dispositif pour l'étirage latéral d'une pellicule ou d'une bande fibreuse
EP0067060A1 (fr) 1981-06-09 1982-12-15 Taiyo Steel Co., Ltd: Bande métallique revêtue et procédé pour sa fabrication
EP0312304A1 (fr) 1987-10-15 1989-04-19 CMB Foodcan plc Feuille métallique revêtue
EP0312303A1 (fr) 1987-10-15 1989-04-19 CMB Foodcan plc Feuille métallique revêtue
EP0312304B1 (fr) 1987-10-15 1993-03-24 CMB Foodcan plc Feuille métallique revêtue
US5919517A (en) 1993-05-05 1999-07-06 Aluminum Company Of America Method for coating a metal strip
EP0901899A1 (fr) 1996-04-10 1999-03-17 TOYO KOHAN Co., Ltd Plaque metallique enduite d'une resine de terephtalate de polyethylene et possedant de grandes capacites de traitement
EP1019248A1 (fr) 1997-01-23 2000-07-19 Hoogovens Staal B.V. Procede et dispositif de revetement d'une bande plastique pelable sur un substrat metallique en forme de ruban et ruban ainsi obtenu
JP2002120278A (ja) * 2000-10-13 2002-04-23 Toyo Kohan Co Ltd 金属板被覆用樹脂フィルムの製造方法、金属板被覆用樹脂フィルム、樹脂フィルム被覆金属板の製造方法、樹脂フィルム被覆金属板およびそれを成形してなる缶
US7229271B2 (en) 2001-05-31 2007-06-12 3M Innovative Properties Company Apparatus for making transversely drawn films with substantially uniaxial character
US20110247681A1 (en) * 2009-10-10 2011-10-13 E. I. Du Pont De Nemours And Company Method for manufacturing multilayer films and solar panel backsheets formed thereof
US20120028058A1 (en) * 2010-07-29 2012-02-02 Toray Plastics (America), Inc. High barrier heat sealable film with linear tear properties
WO2012146654A1 (fr) * 2011-04-28 2012-11-01 Tata Steel Ijmuiden Bv Procédé permettant de produire un substrat de métal revêtu de polymère et substrat de bande de métal pourvu d'un revêtement de polymère
EP2701905A1 (fr) 2011-04-28 2014-03-05 Tata Steel IJmuiden BV Procédé permettant de produire un substrat de métal revêtu de polymère et substrat de bande de métal pourvu d'un revêtement de polymère

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* Cited by examiner, † Cited by third party
Title
W. J. SCHRENK ET AL., POLYM. ENG. SCI., vol. 18, 1978, pages 620

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