Method for manufacturing laminated metal sheets for packaging and laminated metal sheets for packaging manufactured thereby

Abstract

The present invention relates to a method for producing a laminated metal sheet for packaging and to a laminated metal sheet for packaging produced thereby.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing laminated metal sheets for packaging and to laminated metal sheets for packaging manufactured thereby. [Background technology]

[0002] Laminated metal sheets for packaging include a metal sheet and a laminate layer covering at least one side of the metal sheet. Such laminated metal sheets are manufactured by laminating a laminate layer onto a metal sheet. If the laminate layer contains at least partially polyester, the laminate layer is applied to the metal sheet by i) heat-bonding the laminate layer to the metal sheet, ii) using an adhesion promoter between the laminate layer and the metal sheet, or iii) using a laminate layer that includes an adhesive layer. The laminate layer may be manufactured in-line and laminated to the metal sheet in an integrated laminating process, or a pre-manufactured laminate layer may be laminated to the metal sheet in a separate laminating process.

[0003] Before laminating the laminate layer onto a metal sheet, the method of manufacturing the laminate layer, if not all, involves stretching a thick cast film into a thin laminate layer, often followed by an annealing (heat-setting) step to prevent shrinkage of the laminate layer during lamination to the metal sheet. In most stretched laminate layers, the polymer molecules will be either biaxially or uniaxially oriented, depending on whether the film was biaxially or uniaxially oriented. Heat-setting is particularly important when the laminate layer is stretched in the transverse direction.

[0004] The most commonly used laminate layers are biaxially stretched (or biaxially oriented (BO)), and the laminate layer has a similar degree of orientation in the mechanical direction (MD) and in the direction perpendicular to the mechanical direction (width direction or transverse direction (TD)). Examples of BO laminate layers laminated onto steel substrates based on semicrystalline polyesters, e.g., polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) and their blends are disclosed in EP0312304. In most cases, the BO laminate layer is stretched to the same degree in the mechanical direction (MD) and transverse direction. This generally results in a material with greater in-plane uniformity of polymer chain orientation.

[0005] Another type of stretching of a laminate layer is uniaxial stretching, disclosed in U.S. Patent No. 9,346,254,B2. A mechanically oriented (MDO) laminate layer is provided on one or both sides of a metal substrate. Without heat setting, this uniaxial stretching results in a laminate layer that maintains a strong orientation of polymer chains in the stretching direction. The laminate layer may also be uniaxially stretched in the transverse direction (TDO), resulting in a strong orientation of polymer chains in the transverse direction. In both MDO and TDO laminate layers, the properties of the laminate layer in both in-plane directions (MD and TD) are different.

[0006] The disadvantage of using an MDO laminate layer without heat fixation is that the stability of the MDO laminate layer with respect to wrinkles and shrinkage during lamination is lower than that of a heat-fixed uniaxial or BO laminate layer. On the other hand, heat-fixed laminate layers are more expensive and are only available as pre-prepared films. Therefore, in this case, integrating the lamination process with the manufacture of the laminate layer is not practical. Furthermore, the equipment for manufacturing heat-fixed BO laminate layers based on polyesters, such as PET and PBT, and their blends, requires significant expense and lacks flexibility in changing the composition or recipe of the laminate.

[0007] Thermal bonding of a laminate layer to a heated metal sheet reduces or eliminates residual orientation caused by remelting of the laminate layer, at least on the surface of the metal substrate. It is known that insufficient reduction of residual orientation results in poor formability, corrosion resistance, and appearance of the laminated metal sheet. Therefore, evaluating the residual orientation of the laminate layer in a laminated metal sheet is crucial to guaranteeing customers high-quality laminated metal sheets.

[0008] Conventional procedures for confirming residual orientation in a laminate layer include tensile strength measurement (WO1997030841), birefringence (US5753328), and wide-angle X-ray scattering (WAXS) (JP2011008170), but these are only suitable for analyzing the laminate layer after it has been removed from the laminated metal sheet by dissolving the metal sheet.

[0009] Therefore, these methods are not suitable for the analysis of laminated metal sheets as manufactured products. Furthermore, birefringence is only suitable for evaluating transparent films due to its sensitivity to the size of polymer microcrystals, which can lead to reproducibility problems. Polarized Raman spectroscopy can be used to evaluate semicrystalline polymers in laminated metal sheets (US20160257099). However, using polarized Raman light on semicrystalline polymers is only suitable for quality control of transparent (uncolored) polymer films / coatings due to scattering problems (Technical Note AN-922, 2001, WM Doyle, Axiom Analytical). Moreover, these methods are very time-consuming, taking days or weeks to complete, and require considerable effort to prepare the samples. Since the evaluation results are only available some time after the completion of the manufacturing process of the laminated metal sheet, these timeframes and preparations are incompatible with continuous production lines. Therefore, a rapid response is not possible if undesirable residual orientations are identified, which can lead to a significant amount of rejected material. [Overview of the project] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide a method for producing a laminated metal sheet in which the residual orientation of the laminate layer is controlled to a low degree or is absent.

[0011] Another object of the present invention is to provide a method for producing laminated metal sheets in which there is little or no residual orientation of the laminate layer and a small amount of unacceptable material.

[0012] Another objective of the present invention is to provide a method for rapidly determining the degree of residual orientation in order to reduce the amount of unacceptable material.

[0013] Another object of the present invention is to provide laminated metal sheets with a low degree of orientation. [Means for solving the problem]

[0014] In a first embodiment of the present invention, one or more objects are a method for producing a laminated metal sheet (9) for packaging, The laminated metal sheet comprises a metal sheet (1) and a laminate layer (3a) that covers at least one side of the metal sheet. The laminate layer (3a) comprises a single layer containing 50% by mass or more of polyester, or a plurality of layers (3a', 3a'', 3a'''') each containing 50% by mass or more of polyester. The laminate layer (3a) before being laminated to the metal sheet (1) has a preferred molecular orientation in one direction, and the value of the Euclidean distance matrix D between the first and second ATR-FTIR spectra of the laminate layer (3a) before being laminated to the metal sheet (1) is at least 0.20 (i.e., 0.20 or greater). The D value between the first and second ATR-FTIR spectra of the laminate layer after lamination to the metal sheet is 0.10 or less. The first spectrum is measured using an ATR-FTIR spectrometer with an incident IR beam parallel or perpendicular to the mechanical direction of the laminated metal sheet. The second spectrum is measured with the spectrometer after rotating the laminated metal sheet at an angle α selected from 70 to 110° within the same plane as the laminate layer. The ATR-FTIR spectrum is 1160-1520 cm⁻¹. -1 This is achieved by the method described above, which is measured in a spectral range including .

[0015] WO2017102143 discloses a method for laminating a polyester film onto the main surface of a metal strip in a coating line, with an emphasis on preventing creases and wrinkles in the polyester film during lamination by selecting an appropriate combination of film tension, line speed, and yield strength of the polyester film.

[0016] WO2019110616 discloses a method for producing polymer-coated steel sheets for three-piece cans by laminating multiple thin polymer strips onto tinplate.

[0017] Both WO2017102143 and WO2019110616 disclose the use of a post-lamination heating process intended to achieve low-crystallinity or amorphous polymer films after lamination, but neither discloses a method for rapidly determining the level of crystallinity. Only time-consuming offline methods, such as X-ray diffraction, density measurement, and DSC methods, are described in general terms.

[0018] The Euclidean distance matrix D between the first and second ATR-FTIR spectra depends on the selection of the angle α. Therefore, the angle α needs to be selected within the range described in the claims, and the same angle needs to be used when comparing the first and second ATR-FTIR spectra of the laminate layer in order to obtain comparable and clear results.

[0019] The machine direction (MD) of the laminated metal sheet is the same as the rolling direction (RD) of the metal sheet and the moving direction of the metal sheet in the lamination process.

[0020] Preferably, the first spectrum is measured in an orientation in the machine direction, and the second spectrum is measured after being rotated at an angle selected between 70° and 110°. Alternatively, the first spectrum is measured in an orientation perpendicular to the machine direction, and the second spectrum is measured after being rotated at an angle selected between 70° and 110°.

[0021] That the value of D is zero means that the first and second spectra coincide in the observed range region and there is no difference in the orientation of the polymer coating in the two directions. A value of D>0 indicates the presence of residual orientation in the laminate layer. The allowable level of D, which is at most 0.10 (i.e., 0.10 or less), is determined based on a reference sample. When the value of D is 0.20, there is a large difference between the two spectra, which means that the orientation of the polymer chains in the laminate layer is different in the two directions. At a value of D of at least 0.30 or at least 0.40, the difference becomes more significant, and thus the difference in the degree of orientation also becomes more significant.

[0022] The present invention is applicable when the laminate layer before being laminated to the metal sheet has a clear difference in orientation in the rolling direction and the transverse direction (TD). If the orientation in both directions before lamination is the same, the D before lamination may be low. This is the case of a biaxially oriented laminate layer stretched to the same extent in RD and TD and an extrusion laminate layer laminated directly to the metal without intermediate solidification and stretching.

[0023] The present invention is particularly applicable when the laminate layer is stretched only in the machine direction or only in the transverse direction.

[0024] Preferred embodiments are provided by dependent claims 2 to 14. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 is a schematic diagram showing an industrial continuous coating line. [Figure 2] Figure 2 is a schematic diagram showing the distance between the two spectra. [Figure 3] Figure 3 shows the spectrum of a defective sample on CS1-. [Figure 4] Figure 4 shows the spectrum of a good sample on TS1-. [Figure 5] Figure 5 shows the spectrum of a defective sample on CS2-. [Figure 6] Figure 6 shows the spectrum of a good sample on TS2-. [Figure 7] Figure 7 shows the spectrum of a defective sample for CS2-lower. [Figure 8] Figure 8 shows the spectrum of a good sample for TS2-lower. [Figure 9] Figure 9 shows the spectrum of the mechanically oriented film PET5 before lamination. [Figure 10] Figure 10 shows the spectrum of a good sample on TS3-. [Figure 11] Figure 11 shows the structure of a laminated metal sheet. [Figure 12] Figure 12 shows a schematic interpretation of the method according to the present invention. [Modes for carrying out the invention]

[0026] The present invention relates to a method for manufacturing a laminated metal sheet in a continuous coating line, comprising the following steps: The process of preparing a metal sheet; A step of preparing a laminate layer (3a) for coating at least one side of a metal sheet, wherein the Euclidean distance matrix D between the first and second ATR-FTIR spectra is 0.20 or greater; A process of laminating a laminate layer (3a) onto a metal sheet (1) to produce a laminated metal sheet (9); A step of post-heating the laminated metal sheet (9) to a temperature high enough to melt the laminate layer (3a); A process to produce a laminated metal sheet (9) in which the post-heated laminated metal sheet (9) is cooled, preferably rapidly cooled, and the Euclidean distance matrix D between the first and second ATR-FTIR spectra of the laminate layer (3a) is 0.10 or less. This is embodied in a method that includes [this].

[0027] In a preferred embodiment, the laminate layer for coating the metal sheet consists of one or more layers and comprises the following steps: A step of melting thermoplastic polymer granules in one or more extruders in order to form one or more layers; A process of forming a thermoplastic polymer film consisting of two or more layers by passing one or more molten polymers through a flat (co)extrusion die and / or two or three or more calender rolls; Depending on the circumstances, A process of cooling a thermoplastic polymer film to form a solid thermoplastic polymer film; Depending on the circumstances, a step of trimming the edges of the thermoplastic polymer film; A process of stretching a solid polymer film within a stretching unit by applying a stretching force only in the longitudinal direction, thereby reducing the thickness of the solid thermoplastic polymer film; Depending on the circumstances, a process of trimming the edges of the stretched thermoplastic polymer film may be performed. It is manufactured by [company name].

[0028] In one embodiment, the method according to the present invention is used to adjust process parameters in a continuous coating line, such as the post-heat set-point (T2) and line speed (v) of the continuous coating line, or one or both, when the Euclidean distance matrix D of the laminate layer after post-heating and cooling exceeds 0.10. As soon as D exceeds this threshold, the degree of orientation becomes excessively large, which is likely to degrade the performance of the product and lead to material rejection or declassification to a lower-value product. The speed of the method according to the present invention compared to the prior art ensures that the amount of rejection can be significantly reduced.

[0029] In one embodiment, the metal sheet is a steel sheet, preferably an uncoated cold-rolled steel, tinplate, ECCS (also known as TFS), TCCT, galvanized steel, or aluminum-plated steel, and preferably the thermoplastic polymer film is a single-layer or multi-layer polyester or polyolefin polymer film.

[0030] In one embodiment, one or more thermoplastic polymer films are biaxially oriented polymer films.

[0031] In one embodiment, one or more thermoplastic polymer films are uniaxially oriented polymer films.

[0032] In a preferred embodiment, the laminate layer is laminated to the metal sheet to produce a laminated metal sheet without interrupting the continuous lamination process.

[0033] A method for monitoring the residual orientation in the polymer coating of a laminated metal sheet obtained by laminating a uniaxial or biaxially oriented polyester film in line (at-line) is as follows: a. The process of obtaining a sample of a laminated metal sheet; b. The step of positioning the sample in the ATR detector of the ATR-FTIR spectrometer such that the rolling direction of the laminated metal sheet is parallel to the plane of incidence of infrared light from the spectrometer's infrared light source to the ATR crystal; c. At least a frequency range of 1160-1520 cm -1 A process of recording a reflectance profile over a certain period; d. The step of generating a first ATR-FTIR spectrum of the sample in this frequency range using the Fourier transform; e. A step of generating a second ATR-FTIR spectrum by rotating a laminated metal sheet sample at an angle α selected from 70 to 110° in a plane perpendicular to the normal to the sample surface, and repeating steps c and d; f. By calculating the spectral distance represented by the Euclidean distance matrix D between two spectra, we can determine at least 1160–1520 cm⁻¹ -1 A process of mathematically comparing the correlation between the first and second spectra in the frequency range. Includes.

[0034] A value of zero for D means that the first and second spectra coincide in the observed range, indicating no difference in the orientation of the polymer coating in the two directions. A value of D > 0 indicates the presence of residual orientation in the laminate layer. The acceptable level of D, up to 0.10, is determined based on the reference sample. A value of D of 0.20 indicates a large difference between the two spectra, meaning that the orientation of the polymer chains in the laminate layer differs in the two directions.

[0035] In total internal reflection infrared spectroscopy (ATR-FTIR), a low refractive index material (sample) is brought into contact with a high refractive index material, such as a germanium or diamond crystal. Mid-infrared light irradiated through the high refractive index material undergoes total internal reflection at the interface between the two materials. The reflected IR light is then collected by an IR detector and mathematically processed by a Fourier transform to obtain an ATR-FTIR spectrum. The ATR-FTIR spectrum contains reproducible bands with strong characteristics that can be directly assigned to a specific chemical composition (e.g., using an FTIR library database), thus providing information about the chemical composition of the surface layer (typically 1-2 μm) of the material. The IR light before entering the sample is at least partially polarized (either by using an additional polarizer or simply after passing through the high refractive index material). Due to the polarization of the IR light, the interaction with the molecular dipoles of the polymer depends on the orientation of the polymer molecules. If residual orientation exists in the laminate layer, the spectrum depends on the angle between the ATR crystal and the sample. If the sample does not have residual orientation, the ATR-FTIR spectrum is independent of the angle between the ATR crystal and the sample.

[0036] Some limitations in measuring residual orientation in conventional techniques can be overcome, for example, in the case of total internal reflection-Fourier transform infrared spectrometers (ATR-FTIR), by irradiating a laminated metal sheet with partially polarized infrared light, and then collecting and analyzing the reflected infrared light. This method uses the dichroic IR band in the ATR-FTIR spectrum, which is one of the components used as an orientation marker. The band intensity of the dichroic IR band depends largely on the orientation of the polymer chains to the incident polarized infrared light. For example, the degree of orientation can be evaluated by comparing the intensity of the dichroic IR band in two directions relative to the IR detector of the laminated metal sheet. In the case of an isotropic laminate layer, the band intensity of the dichroic IR band is the same at all positions of the laminated metal sheet sample relative to the IR detector. Typically, the intensity of the dichroic IR band is normalized against the intensity of the non-dichroic IR band to correct for defects on the sample surface, etc. In the case of polymer coatings containing polyethylene terephthalate (PET) and polymer coatings containing blends thereof, the degree of orientation is usually the trans form (1340 cm) of the CH2 portion of PET. -1 , JP2003127307) or Gauch form (1043cm -1 According to the intensity of the dichroic peak assigned to JP2002160721, then at 1410 cm -1The non-dichroic IR band (in-plane bending vibration of the PET benzene ring) is normalized and evaluated. The limitation of this approach is that, in the case of PET, it evaluates the overall surface orientation of a semi-crystalline polymer blend based on the behavior of only one component (orientation marker), rather than the entire polyester blend. Furthermore, this method relies heavily on the presence of a well-resolved dichroic IR band, which is not always the case, as IR bands are often superpositions of several distinct bands. Therefore, the analysis of each new polyester blend may require completely different dichroic IR bands if they are not based on PET or contain little to no PET. Simple analysis of dichroic IR band intensity also ignores changes in the shape or spectral position of the dichroic IR band for samples at different positions relative to the ATR-FTIR spectrometer.

[0037] These problems can be overcome by the method of the present invention, for example, in the case of an ATR-FTIR total internal reflection infrared spectrometer, which involves irradiating and collecting partially polarized infrared light. 。

[0038] The inventors have found that the orientation of a semi-crystalline blend laminated to a metal sheet is measured in a specific frequency range (1160-1520 cm⁻¹) in two different directions of the laminated metal sheet sample rotated at a set angle with respect to the normal of the sample. -1 We found that this can be determined by comparing two ATR-FTIR spectra within a range that encompasses but is not necessarily limited to that range.

[0039] The preferred frequency range is 1160-1520 cm. -1The rotation angle α between the two directions of the sample is preferably about 90°. An advantage of such a method for evaluating residual orientation based on measurements of two ATR-FTIR spectra is that it is feasible for a wide range of PET and / or PBT-based polyester blends, copolyesters, and blends. This approach provides similar information to birefringence measurements but has the advantage that measurements can be performed on laminated metal sheets regardless of the size of the polymer microcrystals. Furthermore, this approach takes into account not only the changes in the intensity of the IR bands of polymer-coated samples placed at different positions, but also the influence of the sample position on the shape or spectral position (shift) of various IR bands.

[0040] The laminated metal sheet according to the present invention may have a laminate layer on one or both sides of the metal sheet. In the latter case, the laminate layers (3a, 3b in Figure 1) may be the same or different in terms of composition, thickness, or structure.

[0041] In one embodiment, the laminated metal sheet according to the present invention has a Euclidean distance matrix D between two ATR-FTIR spectra of the laminate layer, in the range of 0.00 to 0.07. The smaller the value of D, the smaller the difference between the two spectra and the lower the degree of orientation of the laminate layer. In a preferred embodiment, the Euclidean distance matrix D between two ATR-FTIR spectra of the laminate layer is 0.00 to 0.05, and more preferably D is up to 0.03.

[0042] The laminate layer according to the present invention is a thermoplastic single-layer / multilayer semicrystalline oriented film containing at least 50% polyester. Preferably, the laminate layer contains semicrystalline polyester or a blend of polyesters, particularly a blend of semicrystalline polyester or polyesters based on PET, PETg, IPA-PET, CHDM-PET, and PBT (in any proportion). The total amount of polyester in the laminate layer is preferably at least 60%. Preferably, the amount is at least 70%, more preferably at least 80%, and even more preferably at least 90% or at least 95%.

[0043] The metal sheet is selected from the group of metal sheets, such as cold-rolled steel, tinplate, tinplate, ECCS, TCCT®, galvanized steel, aluminum, or aluminum alloys. The metal sheet is preferably supplied in coil form. Laminated metal sheets can also be supplied to customers in the form of metal sheets or blanks, but are preferably supplied in coil form.

[0044] In one embodiment, the laminate layer is applied to at least the metal sheet surface that will be the inside of packaging, such as a container or can, and the polyester in the laminate layer contains at least 70 mol% ethylene terephthalate units. Preferably, the laminate layer contains at least 80 mol% or at least 85 mol% ethylene terephthalate units.

[0045] In one embodiment, the laminate layer is applied to at least the metal sheet surface that will be the inside of packaging, such as a container or can, and the polyester in the laminate layer contains at least 85 mol% butylene terephthalate units.

[0046] In one embodiment, the laminate layer is applied at least to the metal sheet surface that is the inside of the packaging, for example, a container or a can, and the polyester in the laminate layer includes a blend of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), preferably with the ratio of PET to PBT being 60:40 or more. Preferably, the ratio is 70:30.

[0047] In one embodiment, the laminate layer is applied at least to the metal sheet surface that is the inside of the packaging, for example, a container or a can, and the polyester in the laminate layer includes at least 85 mol% of a blend of a polyester containing 85 mol% of ethylene terephthalate units and a polyester containing at least 85 mol% of butylene terephthalate units.

[0048] According to a second aspect of the present invention, a laminated metal sheet for packaging according to the present invention is provided in claim 15.

Examples

[0049] To illustrate the present invention, a laminated metal sheet was manufactured. In each case, a laminate layer of a thermoplastic polymer was provided on both sides of the metal sheet. The metal sheet is a low-carbon cold-rolled packaging steel generally called electrolytic chromium-coated steel (「ECCS」), and both sides are electrolytically coated with a layer of metallic chromium and chromium oxide, and the total amount of chromium on each side is about 90 mg / m 2 is.

[0050] Comparative samples and test samples were manufactured using the polyester films in Table 1.

[0051]

Table 1

[0052] Films PET1 to PET6 were laminated onto an ECCS strip by a thermal bonding process schematically shown in Figure 1. The metal strip (1) passes through a first heating device (2), where its temperature rises to a preheating temperature T1 suitable for lamination. The film coils (3a, 3b) are simultaneously unwound and pass through a pair of laminating rollers (4a, 4b) together with the preheated metal strip. The laminated product (5) passes through a second heating device (6), where its temperature rises to a post-heating temperature T2. After the second heating device, the laminated product is rapidly cooled to room temperature by passing through a quenching device (7). The method of preheating the metal strip in the first heating device is not particularly limited and may include passing the strip on a heated roll, conductive heating, induction heating, radiant heating, etc. In the second heating apparatus, the method for post-heating the laminated product is preferably a non-contact method, such as heating in a high-temperature gas environment or induction heating. The method of quenching in the quenching apparatus is not particularly limited and may include applying cold air or passing through a cold water bath. The laminated product then passes through drying rollers (8a, 8b), after which the sample is collected to obtain an ATR-FTIR profile of the sample.

[0053] Table 2 identifies the comparative samples ("CS") and test samples ("TS") prepared to demonstrate the applicability of the described ATR-FTIR methodology to measuring residual orientation for a wide range of polyester film compositions. Table 2 also identifies the corresponding processing conditions used to obtain these samples. In the case of the TS3 sample, it was not possible to prepare a corresponding comparative sample that was not postheated or had a low postheating temperature due to delamination during processing. The data obtained from the PET5 film before lamination were compared with the data from the TS3 sample.

[0054] [Table 2]

[0055] After sample preparation, ATR-FTIR spectra were recorded, and spectral distances D were derived for the plane containing the MDO films (PET1, PET3, PET4, PET5). Based on the obtained spectral distances D, the quality of the metal-laminate materials was classified as described below. The classification results obtained by ATR-FTIR of the polymer-coated metal strips were then compared with the results of product performance tests (for polymer-coated metal strip samples) and the results of DSC and tensile strength measurements of the PET5 film or the independent (free-standing) laminate film (after metal removal with hydrochloric acid).

[0056] A laminated metal sheet sample was cut into 7.5 × 7.5 cm panels. ATR-FTIR spectra were recorded using a Bruker Tensor II ATR-FTIR spectrometer equipped with a diamond crystal having a fixed incidence angle of 45°. (1160–1520 cm⁻¹) -1 , resolution 0.4cm -1 The ATR-FTIR signal was recorded using 16 scans. The background signal was recorded before recording the actual ATR-FTIR spectrum. For the TS3 sample, which was to be compared with the PET5 film data (as a corresponding less postheated film was not manufactured), the ATR-FTIR spectrum was recorded using a Thermo Scientific Nicolet 650 iS10 ATR-FTIR spectrometer with a ZnSe crystal having a predetermined fixed incidence angle of 42°. In that case, the same 0.4 cm⁻¹ scan was used. -1 Eight scans were collected at this resolution.

[0057] Two spectra were recorded for each sample. Spectrum 1 was recorded in the sample rolling direction perpendicular to the plane of incidence of infrared light from the spectrometer's infrared light source to the ATR crystal (this is identical to the machine direction (MD) of the continuous coating line), and Spectrum 2 was recorded after rotating the metal laminate sample 90° within the sample plane.

[0058] 1160~1520cm -1 A mathematical comparison of Spectrum 1 and Spectrum 2 was performed by calculating the spectral distance D after vector normalization (to correct for intensity differences due to surface defects) within the spectral range. The calculated spectral distance D is the Euclidean distance matrix between the two spectra. The calculated Euclidean distance matrix can range from 0 (perfect spectral match) to 2 (perfect spectral mismatch). As a threshold, D = 0.10 was identified by comparing the results of known good and bad samples.

[0059] The following formula was used to calculate D.

[0060]

number

[0061] Before determining the spectral distance D, the data needs to be preprocessed. Doing so ensures that the value of D is between 0 (equal spectra) and 2 (maximum inequality between spectra). This preprocessing is a normalization process that first calculates the mean y-value of the spectrum and uses only data points within the selected spectral range. Then, the calculated mean is subtracted from the spectrum. This centers the spectrum around y=0. Following this, the sum of squares of all y-values ​​is calculated, and each spectrum is then divided by this sum of squares. The square root Divide by . The vector norm of the resulting spectrum is 1.

[0062]

number

[0063] If a normalized spectrum is represented in n-dimensional space, where n is the number of selected data points, then all spectra lie on a unit sphere (an n-dimensional sphere with radius 1 around the coordinate origin). The maximum distance between two spectra is the diameter of the unit sphere, i.e., (D=)2. The minimum distance, i.e., D=0, is when all points of the two spectra overlap on the unit sphere.

[0064] The thermal properties (Tg, Tm, orientation-induced bulk crystallinity) of the polymer film were determined by DSC. A Mettler Toledo DSC821e instrument was used, operated at a heating rate of 10°C / min, and spectra were recorded. DSC requires the analysis of independent films obtained from laminated metal sheets. Independent polymer films were obtained by dissolving the metal substrate in 18% hydrochloric acid from metal-laminate samples from the line. After dissolving the metal substrate, the polymer films were thoroughly rinsed and dried. Crystalline fractions were determined from the heat of recrystallization and thermal melt recorded during the initial heating run, as described in detail elsewhere. The values ​​of orientation-induced crystallinity were given as a ratio:

number

[0065] The mechanical properties of the polymer film after metal removal were measured using a Shimadzu EZ-LX tensile testing machine with a single column main unit having a stroke length of 920 mm, a pneumatic action grip, and a 500 N load cell. Tensile tests were performed according to ISO 527. In this test, strips with a width of 15 mm and a length of 150 mm were cut from individual polymer films. To measure the tensile properties of the film in the mechanical direction, a single test speed of 50 mm / min was applied from the start to the end of the test (film breakage). To measure the tensile properties of the film in the transverse direction, a dual-speed method was applied, starting with 50 mm / min until an elongation of 60 mm, and then increasing the test speed to 500 mm / min until the break point. This difference in speed methods for the mechanical and transverse directions is because the tensile strain and elongation at breakage in the transverse direction can be much larger than those at breakage in the mechanical direction. All tests were performed 10 times for each polymer film, and then the maximum variation at 10% modulus was obtained by excluding outlier values. The modulus values ​​were then averaged. Orientation was evaluated by comparing the modulus (MPa) in the mechanical and transverse directions of the samples.

[0066] In this test, 7.5 × 7.5 cm panels were cut from a flat sheet. The panels were then placed in an aqueous solution containing Maggi (12 g / L) + plasmal (2 g / L) in a sealed container and sterilized at 121°C for 90 minutes (for samples TS1, TS2, CS1, and CS2). For TS3, the sample was sterilized in water at 121°C for 90 minutes. After sterilization and cooling of the samples, 4 × 5 mm cross-hatching was applied to the flat portion of the panel according to the method described in ISO 2409:1992, 2nd edition, and then adhesive tape was applied. Delamination was then evaluated using a Gitterschnitt scale ranging from 0 (excellent) to 5 (poor) (Table 3). All tests were performed three times for each side of each metal-laminate variant in Table 2. The scores of the three results were then averaged and rounded to the nearest integer.

[0067] [Table 3]

[0068] All characteristic data for the test and comparison samples are summarized in Table 4. Then, the characteristic data for the independent films and the adhesion and sterilization data for the metal-laminate samples are compared with the spectral distance value D derived by comparing the ATR-FTIR spectra 1 and 2 of the corresponding metal-laminate or PET5.

[0069] As shown in Table 4, post-heating of metal laminates TS1 at T2=260°C, TS2 at T2=270°C, and TS3 at T2=275°C yields completely unoriented isotropic polymer coatings. In these coatings, uniaxial orientation and residual orientation (present in PET1, PET3, PET4, and PET5 before lamination) in the mechanical direction are removed. In addition, in the case of PET-based coatings, the coatings are completely amorphous, as evidenced by the low crystallinity values ​​(less than 10% in all cases) derived by DSC. The unoriented isotropy of these polymer films is confirmed by measuring their mechanical properties. In particular, the free polymer films obtained from the top surfaces of TS1 and TS3, and from both sides of TS2, exhibit similar modulus values ​​in the mechanical and transverse directions. The performance of surfaces coated with PET1, PET3, and PET4 during adhesion and sterilization tests (Gitterschnitt) is excellent (less than 5% of the cross-cut area is affected). The Gitterschnitt test data are consistent with the mechanical properties of the free coating film and the fully remelted isotropic and amorphous PET coatings confirmed by DSC. Therefore, samples TS1-TS3 are classified as good quality samples.

[0070] In contrast, if metal-laminate CS1 is postheated at T2=200°C, or if postheating is not performed in the production of metal-laminate CS2, the semi-crystalline polymer coating will not be completely remelted, and in these cases, uniaxial orientation in the mechanical direction (PET1, PET3 before lamination) will not be achieved. and PET 4 The presence of PET5 is retained. When attempting to laminate PET5 at a post-heating temperature below 275°C to prepare CS3, it resulted in complete delamination of the PET5 laminate layer during processing. The high crystallinity of the comparative samples that were not completely remelted is supported by the high crystallinity values ​​derived by DSC (over 30% in all cases). These polymers -The existence of preferential orientation in coated films is supported by measuring their mechanical properties. In particular, the modulus values ​​in the mechanical direction, measured for PET5 films before polymer coating or lamination from CS1 and CS2, are more than 2 times (top surfaces of CS1 and CS2), 2.6 times (bottom surface of CS2), and 1.4 times (PET5) higher than the modulus values ​​in the transverse direction. Films from CS1 (top surface) and CS2 (top and bottom surfaces) coated with PET1, PET3, and PET4 during adhesion and sterilization tests. Sex The performance is insufficient, and the cross-cut areas of 5-15% (TS1 top surface) and 65-100% (TS2) are affected. The Gitterschnitt test data for metal-laminate samples CS1 and CS2 are consistent with the development of crystallinity and residual orientation in the polyester coating of these samples described above. Therefore, samples CS1 and CS2 are classified as samples of poor quality.

[0071] For the corresponding samples TS1 (top), TS2 (top and bottom), CS1 (top), and CS2 (top and bottom), data on DSC and mechanical strength against the free polymer coating film, and data on adhesion and sterilization against the metal-laminate were compared with the corresponding spectral distance value D. Directly recorded for the metal-laminate sample or PET5 before lamination, at 1160–1520 cm⁻¹. -1The value of D was derived by comparing ATR-FTIR spectra 1 and 2 in the spectral region. As shown in Table 4, the D values ​​of the corresponding fully remelted isotropic samples TS1 (top) (0.016), TS2 (top) (0.046), TS2 (bottom) (0.006), and TS3 (top) (0.010) are close to 0, corresponding to well postheated isotropic non-oriented coatings as measured by ATR-FTIR. In contrast, the D values ​​of the mechanically oriented PET5 film (0.424), and the test samples CS1 (top) (0.482), CS2 (top) (0.480), and CS2 (bottom) (0.482), which were not fully remelted, are much greater than 0, corresponding to oriented coatings with preferential orientation in one direction, consistent with the DSC and mechanical property test data for these samples. A D threshold of 0.10 can be used to distinguish between samples of poor quality and samples of good quality.

[0072] Brief explanation of the drawing The present invention is illustrated by the following non-limiting figures.

[0073] Figure 1 shows a schematic diagram of an industrial continuous coating line. Figure 2 shows a schematic diagram of the distance between the two spectra. Figure 3: Spectra of a defective sample for CS1-U. Figure 4: Spectra of a good sample for TS1-U. Figure 5: Spectra of a defective sample for CS2-U. Figure 6: Spectra of a good sample for TS2-U. Figure 7: Spectra of a defective sample for CS2-lower. Figure 8: Spectra of a good sample for TS2-lower. Figure 9: Spectrum of the mechanically oriented film PET5 before lamination. Figure 10: Spectra of a good sample for TS3-U. Figure 11: Structure of a laminated metal sheet. Figure 12: Schematic interpretation of the method according to the present invention.

[0074] The laminate layer is laminated to the metal strip by the method schematically shown in Figure 1. The metal strip (1) passes through a first heating device (2), where the temperature of the metal strip is raised to a preheating temperature T1 suitable for lamination. In this embodiment, T1 was selected to be 200°C for lamination of pure PET film, 220°C for lamination of film containing 25% PBT, and 225°C for lamination of film based on pure PBT. The coils of film PET1, PET3, or PET5 (3a) and PET2, PET4, or PET6 (3b) are unwound simultaneously and pass through a pair of laminating rollers (4a, 4b) together with the preheated metal strip. The laminated metal sheet (5) passes through a second heating device (6), where the temperature of the laminated metal sheet is raised to a postheating set temperature T2. After the second heating device, the laminated metal sheet is rapidly cooled to room temperature by passing through the rapid cooling device (7). The method of preheating the metal strip in the first heating device is not particularly limited and may include passing the strip on a heated roll, conductive heating, induction heating, radiant heating, etc. The method of postheating the laminated metal sheet in the second heating device is preferably a non-contact method, such as heating in a high-temperature gas environment or induction heating. The method of rapid cooling in the rapid cooling device is not particularly limited and may include applying cold air, passing through a cold water bath, etc.

[0075] The spectral distance D is proportional to the area between the two curves. Figure 2 shows the sinusoidal curves of two models. The spectral distance is proportional to the gray area between the two sinusoidal curves.

[0076] Figure 11 shows a diagram of the structure of a laminated metal sheet. The upper figure shows the simplest form of a laminated metal sheet 9, in which a single laminate layer 3a is provided on a metal sheet 1. The lower figure shows a more complex embodiment according to the present invention, in which a multilayer laminate layer 3a is provided on the top of the metal sheet 1, and the multilayer (in this example) comprises three distinct layers 3a', 3a'' and 3a'''', which may function, for example, as a top layer, a bulk layer and an adhesive layer, each having a different composition tailored to the requirements imposed on each distinct layer, and a second laminate layer is provided on the bottom of the metal sheet, the second laminate layer may be the same as the upper laminate layer in terms of composition, structure or thickness in the case of a symmetrical laminated metal sheet, or may be different in the case of an asymmetrical laminated metal sheet.

[0077] Figure 12 shows a schematic interpretation of the preparation of a sample taken from a laminated metal sheet and subsequent measurement using an ATR-FTIR spectrometer. The first spectrum is measured in the direction of the incident IR beam parallel to the machine direction (MD) (same as the rolling direction (RD)), and the second spectrum is measured in the direction of the incident IR beam approximately perpendicular (rotation angle α) to the machine direction. The Euclidean distance matrix D is determined between these two spectra, and after post-heating and cooling, the value of D according to the present invention is a maximum of 0.10.

[0078] [Table 4]

Claims

1. A method for manufacturing a laminated metal sheet (9) in a continuous coating line, The laminated metal sheet (9) comprises a laminate layer (3a), The above method comprises the following steps: Steps to prepare the metal sheet (1); A step of preparing a laminate layer (3a) for coating at least one side of the metal sheet, wherein the value of the Euclidean distance matrix D between the first and second ATR-FTIR spectra is 0.20 or greater, where the first and second ATR-FTIR spectra are measured using a sample of the laminate layer, the first ATR-FTIR spectrum is measured with an ATR-FTIR spectrometer using an incident IR beam parallel or perpendicular to the mechanical direction of the sample, the second ATR-FTIR spectrum is measured with the spectrometer after rotating the sample by an angle α selected from 70 to 110° in a plane perpendicular to the normal to the surface of the sample, and the first and second ATR-FTIR spectra are measured between 1160 and 1520 cm⁻¹. －１ It is measured within the spectral range that includes; A step of laminating the laminate layer (3a) onto the metal sheet (1) to produce a laminated metal sheet (9); A step of post-heating the laminated metal sheet (9) to a post-heating set point T2 in which the laminate layer (3a) can be melted; A step of producing a laminated metal sheet (9) in which the value of the Euclidean distance matrix D between the first and second ATR-FTIR spectra of the laminate layer (3a) is 0.10 or less, wherein the first and second ATR-FTIR spectra are measured using a sample of the laminated metal sheet, the first ATR-FTIR spectrum is measured with an ATR-FTIR spectrometer using an incident IR beam parallel or perpendicular to the machine direction of the sample, the second ATR-FTIR spectrum is measured with the spectrometer after rotating the sample by an angle α selected from 70 to 110° in a plane perpendicular to the normal to the surface of the sample, and the first and second ATR-FTIR spectra are measured between 1160 and 1520 cm⁻¹. －１ Measured within the spectral range that includes The method, including the method described above.

2. The laminate layer for coating the metal sheet consists of one or more layers, and the process is as follows: A step of melting thermoplastic polymer granules in one or more extruders in order to form the aforementioned one or more layers; If the laminate layer consists of one layer, a thermoplastic polymer film consisting of one layer is formed by passing one or more of the molten polymer through a flat extrusion die; if the laminate layer consists of two or more layers, a thermoplastic polymer film consisting of two or more layers is formed by passing one or more of the molten polymer through a flat co-extrusion die and / or two or more calender rolls. The method according to claim 1, manufactured by [the specified method].

3. The method according to claim 1, wherein the laminate layer is a thermoplastic polymer film, and the thermoplastic polymer film is a single-layer or multi-layer polyester or polyolefin polymer film.

4. The method according to claim 1, wherein the laminate layer consists of one or more thermoplastic polymer films, and the one or more thermoplastic polymer films are biaxially oriented polymer films.

5. The method according to claim 1, wherein the laminate layer consists of one or more thermoplastic polymer films, and the one or more thermoplastic polymer films are uniaxially oriented polymer films.

6. The method according to any one of claims 1 to 5, wherein if the value of the Euclidean distance matrix D of the laminate layer after post-heating and cooling exceeds 0.10, the post-heating set point (T2) or the line speed (v) of the continuous coating line, or both the post-heating set point and the line speed, is adjusted.

7. The method according to any one of claims 1 to 6, wherein α is selected from 80° to 100°.

8. The method according to any one of claims 1 to 7, wherein the metal sheet is made of steel.

9. The method according to any one of claims 1 to 8, comprising laminating the laminate layer onto the metal sheet to produce a laminated metal sheet without interrupting the continuous coating line.

10. The method according to any one of claims 1 to 9, wherein the laminate layer (3a) is applied to at least the metal sheet surface that is on the inside of the packaging, and the polyester in the laminate layer contains at least 70 mol% ethylene terephthalate units.

11. The method according to any one of claims 1 to 10, wherein the laminate layer (3a) is applied to at least the metal sheet surface that is on the inside of the packaging, and the polyester in the laminate layer contains at least 85 mol% butylene terephthalate units.

12. The method according to any one of claims 1 to 11, wherein the laminate layer is applied to at least a metal sheet surface that is on the inside of the packaging, and the polyester in the laminate layer comprises a blend of polyethylene terephthalate and polybutylene terephthalate.

13. The method according to any one of claims 1 to 12, wherein the laminate layer is applied to at least the metal sheet surface that is the inside of the packaging, and the polyester in the laminate layer comprises at least 85 mol% of a blend of polyester containing 85 mol% ethylene terephthalate units and polyester containing at least 85 mol% butylene terephthalate units.

14. The method according to any one of claims 1 to 13, wherein the laminate layer (3a) comprises a single layer containing 50% by mass or more polyester, or a plurality of layers (3a', 3a'', 3a'''') containing 50% by mass or more polyester, the Euclidean distance matrix D between the first and second ATR-FTIR spectra of the laminate layer before lamination to the metal sheet is 0.20 or more, and the value of D between the first and second ATR-FTIR spectra of the laminate layer after lamination to the metal sheet is 0.10 or less.

15. A laminated metal sheet (9) for packaging, The laminated metal sheet comprises a metal sheet (1) and a laminate layer (3a) that covers at least one side of the metal sheet. The laminate layer (3a) comprises a single layer containing 50% by mass or more polyester, or a plurality of layers (3a', 3a'', 3a'''') containing 50% by mass or more polyester. The value of D between the first and second ATR-FTIR spectra of the laminate layer (3a) after lamination to the metal sheet is a maximum of 0.

10. The first ATR-FTIR spectrum is measured using an ATR-FTIR spectrometer with an incident IR beam parallel or perpendicular to the mechanical direction of the laminated metal sheet. The second ATR-FTIR spectrum is measured with the spectrometer after rotating the laminated metal sheet at an angle α selected from 70 to 110° within the same plane as the laminate layer. The first and second ATR-FTIR spectra were obtained in the range of 1160–1520 cm⁻¹. －１ The laminated metal sheet (9) is measured in a spectral range including the above.

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