Coated sheet metal band and production method

Abstract

A coated sheet metal strip includes a rolled sheet metal strip having a first flat side and a second flat side. A first layer over the first flat side includes a carrier layer. The carrier layer contains a reaction accelerator for an adhesive and stores the reaction accelerator on a physical basis. A second layer, including the adhesive, is applied over the second flat side. The second layer is free of the reaction accelerator or any reaction accelerator.

Claims

1. A coated sheet metal strip, comprising: a rolled sheet metal strip having a first flat side and a second flat side; a first layer over the first flat side, wherein the first layer includes a carrier layer, the carrier layer applied directly to the sheet metal strip and containing a reaction accelerator embedded in the carrier layer for an adhesive and stores the reaction accelerator on a physical basis, wherein a ratio in volume of carrier layer material of the carrier layer to the reaction accelerator is between 1/1 and 3/1; and a second layer over the second flat side and including the adhesive, wherein the second layer is free of the reaction accelerator or any reaction accelerator.

2. The coated sheet metal strip as claimed in claim 1, wherein the carrier layer includes an organic resin, polyvinyl alcohol, and/or phenoxy resin.

3. The coated sheet metal strip as claimed in claim 1, wherein the reaction accelerator includes a urea or a urea derivative, a Lewis base, a Lewis acid, an imidazole, or modified or heterocyclic amines, the Lewis base includes tertiary amines, the Lewis acid includes BF.sub.3, and the imidazole includes 1-methylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, or other imidazole derivatives or imidazole adducts.

4. The coated sheet metal strip as claimed in claim 1, wherein the second layer is an epoxy resin-based layer and/or a baking lacquer layer, and the baking lacquer layer includes an epoxy resin-based baking lacquer layer.

5. The coated sheet metal strip as claimed in claim 1, wherein the first layer is free of adhesive.

6. The coated sheet metal strip as claimed in claim 1, wherein the first layer includes less than or equal to 20 vol. % adhesive.

7. The coated sheet metal strip as claimed in claim 1, wherein the first layer includes more than or equal to 20 vol. % adhesive.

8. The coated sheet metal strip as claimed in claim 1, wherein the thickness of the first layer is less than or equal to 2 μm.

9. The coated sheet metal strip as claimed in claim 1, wherein the first layer is free of mineral fillers.

10. The coated sheet metal strip as claimed in claim 1, wherein the thickness of the second layer is greater than or equal to 4 μm.

11. The coated sheet metal strip as claimed in claim 1, wherein the sheet metal strip is an electrical sheet strip.

12. The coated sheet metal strip as claimed in claim 1, wherein the coated sheet metal strip is wound into a coil.

13. The coated sheet metal strip as claimed in claim 1, wherein the first layer consists of the carrier layer.

14. A method for producing a coated sheet metal strip, comprising: applying a first layer over a first flat side of a rolled sheet metal strip, wherein the first layer includes a carrier layer, the carrier layer applied directly to the sheet metal strip and containing a reaction accelerator embedded in the carrier layer for an adhesive, and stores the reaction accelerator on a physical basis, wherein a ratio in volume of carrier layer material of the carrier layer to the reaction accelerator is between 1/1 and 3/1; and applying a second layer, which includes the adhesive, over a second flat side of the rolled sheet metal strip, wherein the second layer is free of the reaction accelerator or any reaction accelerator.

15. The method as claimed in claim 14, wherein the carrier layer includes an organic resin, polyvinyl alcohol, and/or phenoxy resin.

16. The method as claimed in claim 14, wherein the first layer is applied by roller application.

17. The method as claimed in claim 14, wherein the second layer is applied by roller application.

18. The method as claimed in claim 14, further comprising: drying the coated sheet metal strip at a drying temperature of less than or equal to 280° C.

19. The method as claimed in claim 14, wherein the first layer consists of the carrier layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an example process of applying a first layer having reaction accelerator and a second layer having adhesive over opposite flat sides of a rolled sheet metal strip.

(2) FIG. 2 is a cross section through a sheet metal strip coated on both sides, as can be produced for example by the process illustrated in FIG. 1.

(3) FIG. 3 is an example process for producing a component from adhesively bonded-together laminations of the sheet metal strip coated on both sides from FIG. 2.

(4) FIG. 4 is a cross section through a further sheet metal strip having a first layer with reaction accelerator and a third layer with insulating lacquer.

(5) FIG. 5 is an example component which is produced from adhesively bonded-together laminations of the further sheet metal strip from FIG. 4 and of an adhesive-coated sheet metal strip.

(6) FIG. 6 illustrates in an example manner the roller peel resistance (in N/mm) of specimens including two adhesively bonded sheet metal strips directly after the adhesive bonding and also after aging.

DETAILED DESCRIPTION

(7) Terms such as “application” or “applying” and other similar terms (e.g. “applied”) in the description should not be understood to mean that the applied layers must be in direct contact with the surface upon which they are applied. Intervening elements or layers may be present between the “applied” elements or layers and the underlying surface. However, the abovementioned or similar terms in this disclosure can also have the specific meaning that the elements or layers are in direct contact with the underlying surface, that is to say that there are no intervening elements or layers.

(8) The term “over”, which is used in relation to an element or a material layer which is formed or applied “over” a surface, may be used here in the sense that the element or the material layer is applied “indirectly onto” the surface, with intervening elements or layers between the surface and the element or the material layer possibly being present. However, the term “over” may also have the specific meaning that the element or the material layer which is applied “over” a surface is applied “directly onto”, that is to say in direct contact with, the relevant surface. The same applies analogously to similar terms such as for example “overlying”, “below”, “underlying”, etc.

(9) FIG. 1 shows, in an example manner, a method 100 for producing a coated sheet metal strip 200 in accordance with one aspect of the disclosure. The starting product of the method 100 is a rolled sheet metal strip 110. The sheet metal strip 110 can for example include steel. The sheet metal strip 110 can for example be an electrical sheet strip which is provided for the construction of electrical cores. The rolled sheet metal strip 110 can be in the form of a virtually endless sheet metal strip 110 in a continuous belt run (see arrow P), for example in a steelworks.

(10) The sheet metal strip 110 can be for example a cold-rolled sheet metal strip or electrical sheet strip in the finally annealed state. Other sheet metal strips, for example non-finally annealed sheet metal strips or electrical sheet strips are likewise possible.

(11) The sheet metal strip 110 is supplied to a coating system 150. In the example illustrated here, the coating system 150 is illustrated as a double-sided coating system 150. However, it is also possible for the top-side and bottom-side coatings to be applied in different coating systems which each coat just one flat side of the rolled sheet metal strip. In addition, it is possible for one or both coatings to be performed by means of a multiple coating system, that is to say to apply these respectively in multiple coating steps.

(12) In FIG. 1, a first layer 120 is applied over a first flat side 110A of the rolled sheet metal strip 110, and a second layer 130 is applied over a second flat side 1106, lying opposite the first flat side 110A, of the rolled sheet metal strip 110.

(13) The first layer 120 is a so-called depot coating which contains a reaction accelerator for an adhesive. The first layer can be largely or completely adhesive-free with respect to that adhesive for which the reaction accelerator is intended, that is to say that it is not present or is only present to a minor extent (for example less than or equal to 20 vol. % or 10 vol. %) in the first layer 120. The same can apply for any adhesive which interacts with the reaction accelerator. The first layer 120 can also be completely adhesive-free in the sense that no adhesive at all is present in the first layer 120.

(14) On the other hand, it is also possible for the first layer 120 to include a higher proportion of adhesive, for example more than 30 vol. %, 40 vol. %, 50 vol. %, 60 vol. % or 70 vol. % adhesive, which results in better homogeneity of the entire coating system after the adhesive bonding of the coated sheet metal strip 110 or of the sheet metal laminations (sheet metal plates) 320 produced from the coated metal strip (see FIG. 3). This higher proportion of adhesive has proven advantageous in particular for low molecular weight reaction accelerators such as imidazole.

(15) The reaction accelerator can be an activator or catalyst for the adhesive (not present in the first layer 120). That means that the reaction accelerator is capable, upon contact with the adhesive and thermal activation, of shortening the time required for the complete reaction of the chemical adhesive for example by more than or equal to a factor of 2, 3, 4, 5, 6, 7, 8, 9 or 10 compared to the time that would be required without a reaction accelerator.

(16) The adhesive is present in the second layer 130 which is applied over the second flat side 1106 of the rolled sheet metal strip 110. The adhesive and the reaction accelerator are therefore separated during application and in the further belt run by the intervening sheet metal strip 110.

(17) The first flat side 110A and/or the second flat side 1106 can be coated by means of roller application. For example, FIG. 1 illustrates two rollers 151, 152, which apply the first layer 120 and the second layer 130, respectively, for example wet. However, it is also possible for the layer application of the first and/or the second layer 120, 130 to be carried out by other methods, for example a spray process or a printing method.

(18) The first and second layer 120, 130 can be applied either onto an uncoated, rolled sheet metal strip 110 or onto an already pre-coated sheet metal strip 110. For example, there may be present a pre-coating (not illustrated) in the form of a primer, upon which the first layer 120 and/or the second layer 130 are applied. It is also possible for the sheet metal strip 110 upstream of the coating system 150 in the belt run to already have been provided on one side or on both sides with an insulating lacquer layer, so that the first layer 120 and/or the second layer 130 are applied onto the previously applied insulating lacquer layer. Materials which may for example be used for an insulating lacquer layer are also mentioned hereinafter.

(19) The first layer 120 and/or the second layer 130 may be applied onto the respective flat side 110A or 1106 of the rolled sheet metal strip 110 over the whole surface or only over a part of the surface. The second layer 130 can for example be produced with a degree of coverage of less than or equal to 80%, 60%, 40% or 20% of the area of the flat side 1106 of the sheet metal strip 110. The second layer 130 can for example be applied in a striped pattern. The first layer 120 may be applied onto the first flat side 110A over the whole surface; application over only part of the surface is also optionally possible for this layer, wherein the non-covered (left-open) areas should then also not be covered by the second layer 130.

(20) A drying station 160 can be situated downstream of the coating system 150 in the belt run path. The drying system 160 can for example be designed as a continuous drying oven through which the coated sheet metal strip 110 continuously passes.

(21) For example, the maximum temperature of the sheet metal strip 110 in the drying system 160 can be between 150° C. and 280° C., wherein temperature values of less than or equal to 270° C., 260° C., 250° C., 240° C., 230° C., 220° C., 210° C., 205° C., 195° C., 185° C., 175° C. or 165° C. can be provided.

(22) The duration of the heat treatment in the drying system 160 can for example be between 10 s and 40 s and in particular less than, equal to or greater than 20 s or 30 s. As a result of a suitable choice of drying temperature and/or duration of the heat treatment, it can be ensured that the reaction accelerator remains completely or virtually completely in the first layer 120.

(23) It is also possible to apply the reaction accelerator downstream of the drying system 160 in the belt run, for example in that the roller application by means of the roller 151 does not take place until downstream of the drying system 160, or in that the carrier layer of the first layer 120, as shown in FIG. 1, is applied upstream of the drying system 160 in the belt run but the reaction accelerator is applied by a further application process only downstream of the drying system 160.

(24) In the drying system 160, the second layer 130 and optionally the first layer 120 are dried at least to the extent that these layers 120, 130 are mechanically stable and abrasion-resistant downstream of the drying system 160 in the belt run. This then enables the further handling of the dried, coated sheet metal strip 110, for example by deflection rollers or by winding it up into a coil. During the drying in the drying system 160, the adhesive in the second layer 130 is not yet activated, that is to say the chemical reaction (for example crosslinking) of the adhesive is not initiated or at least the adhesive is not reacted to completion.

(25) FIG. 2 shows by way of example a sheet metal strip 200 coated on both sides and produced by the process conducted in FIG. 1. The first layer 120 can have a thickness D1 which is less than or greater than or equal to 0.5 μm, 1.0 μm or 2.0 μm. The first layer 120 can include a carrier layer to which the reaction accelerator is added. The carrier layer can consist for example of an organic resin, polyvinyl alcohol (PVA) and/or phenoxy resin or include the substances mentioned.

(26) The reaction accelerator can for example include an imidazole, in particular 1-methylimidazole, 2-methylimidazole or 2-ethyl-4-methylimidazole (2E4Mlm) or of one or more other imidazole derivatives or adducts thereof with for example epoxy resin, or include urea or urea derivatives, a Lewis base (e.g. tertiary amines), a Lewis acid (e.g. BF.sub.3) or include one or more of the substances mentioned. Furthermore, modified or heterocyclic amines may also be used as reaction accelerators. All of the substances mentioned may be present individually or as a mixture in the reaction accelerator.

(27) The carrier layer serves to store the reaction accelerator, that is to say to prevent the reaction accelerator from escaping from the first layer 120 before the coupling with the second layer 130 is effected. The carrier layer material can store the reaction accelerator solely in a physical manner, for which purpose the carrier layer materials are suitable.

(28) In particular for readily evaporable reaction accelerators having a low molar mass, the storage on a physical basis can optionally be improved by adding to the carrier layer material of the first layer 120 a small amount of adhesive, which promotes the storage of the reaction accelerator in the carrier layer via a chemical process. The amount of adhesive in this case is so small (for example, less than or equal to 20 vol. % or 10 vol. % of the first layer 120/the carrier layer) that there is neither a significant consumption of reaction accelerator nor a 3-dimensional crosslinking of the first layer 120/the carrier layer. The adhesive added can for example be the adhesive present in the second layer and/or another adhesive which interacts with the reaction accelerator.

(29) The ratio of carrier layer material of the carrier layer (with or without a small proportion of adhesive) to reaction accelerator may for example be between 1/1 and 3/1 and in particular be approximately 2/1 (in vol. %).

(30) The carrier layer material can additionally also contain further active substances, such as for example a crosslinker (e.g. from the group of the isocyanates).

(31) For the second layer 130, what is known as a baking lacquer can for example be used. Baking lacquer layers are chemically curable, adhesive insulating lacquer layers which have been specially developed for the construction of electrical cores and have high dimensional stability, operational stability and high bonding forces. For example, it is possible to use what is known as Backlack-V®, which enables high bonding forces, a long duration of use due to low aging, an improved long-term behavior and a short baking time at reduced pressure. The second layer 130 can have a thickness D2 which is for example less than or greater than or equal to 4 μm, 6 μm, 8 μm, 10 μm, 12 μm or 15 μm.

(32) The sheet metal strip 110 can for example be manufactured from steel. The thickness D3 of the sheet metal strip 100 can for example be greater than or less than or equal to 0.35 mm, 0.5 mm, 0.75 mm, 1.0 mm, 1.5 mm, 2.0 mm or 2.5 mm.

(33) FIG. 3 illustrates by way of example a method 300 for producing components which are produced for example from the coated sheet metal strip 200. The coated sheet metal strip 200 can for example be in the form of a coil (winding, roll, spool) 310, which has been delivered for example by a steelworks to a customer.

(34) In one method operation, the coated sheet metal strip 200 is separated into individual sheet metal laminations (sheet metal plates) 320. The separation can take place in a separation system 330, for example, by dividing the coated sheet metal strip 200 transversely. The sheet metal laminations 320 can then be cut to their final form.

(35) At least two sheet metal laminations 320_1 and 320_2 are then stacked and adhesively bonded together by means of the adhesive-containing second layer 130. For this, at 340 at least two sheet metal laminations 320_1, 320_2 are stacked such that the second layer 130 of one sheet metal lamination 320_1 is facing the first layer 120 of the other sheet metal lamination 320_2, and are pressed together by applying an areal pressure (F) of from 0.5 to 10 MPa, in particular 2 to 5 MPa with the introduction of energy (by heat, UV radiation, infrared radiation or the like).

(36) The adhesive in the second layer 130 is activated in the process, which may involve a chemical reaction, for example a 3-dimensional crosslinking of the adhesive. During the (thermal) adhesive bonding process, the reaction accelerator diffuses out from the first layer 120 into the adhesive of the second layer 130. The reaction accelerator (activator, catalyst) can bring about an enormous acceleration of the chemical reaction and hence of the adhesive bonding process.

(37) The adhesive bonding at 340 can be effected by heating the compressed sheet metal laminations 320_1, 320_2 for example in an oven or a heatable press (not illustrated) to a temperature T, which is elevated compared to ambient temperature, of for example 100° C. to 250° C., in particular 80° C. to 150° C., as a result of which it is possible to initiate both the diffusion of the reaction accelerator into the second layer 130 and the activation of the adhesive. Other activation processes, which may for example involve the application of radiation energy, are likewise conceivable. After a short adhesive bonding time t, for example less than or equal to 20 min, 15 min, 10 min, 5 min, 1 min, the component is mechanically finalized and can be removed from the adhesive bonding system (e.g. oven or press). It is optionally possible for the adhesive bonding reaction to complete downstream of the press and still to continue outside of the tool.

(38) In addition to the reaction acceleration, the use of the reaction accelerator brings about further advantages. Due to the short adhesive bonding time t, an improvement in the leakage behavior can be achieved, meaning that lateral emergence of adhesive at the adhesive gap is minimized. The reaction accelerator also makes it possible to initiate a more aging-resistant reaction mechanism, that is to say that the aging stability of the adhesive bond with reaction accelerator can be increased compared to an adhesive bond without a reaction accelerator (see also FIG. 6).

(39) FIG. 4 shows a cross section through a further sheet metal strip 400 having a first layer 120 with reaction accelerator and an optional third layer 430 which includes or consists of an insulating lacquer.

(40) To avoid repetitions, reference is made to the description above with regard to the sheet metal strip 110 and the first layer 120.

(41) The insulating lacquer of the third layer 430 can for example be a C6 lacquer. In particular, for example, it is possible to use the Remisol EB500FF C6 lacquer. “FF” in this case stands for “formaldehyde-free” (i.e. free of formaldehyde emissions). A C5 lacquer or a C3 lacquer is likewise also employable, for example. The insulating lacquer of the third layer 430 can be adhesive-free.

(42) FIG. 5 shows an example component 500 which is produced from adhesively bonded-together laminations of the further sheet metal strip 400 with depot coating (see FIG. 4) and of an adhesive-coated sheet metal strip 510.

(43) The adhesive-coated sheet metal strip 510 can include a sheet metal strip 110 and a second layer 130 which is arranged over the second flat side 1106 of the sheet metal strip 110, which can be designed in accordance with the description hereinabove. In contrast to the coated sheet metal strip 200, however, the adhesive-coated sheet metal strip 510 does not have a first layer 120 (depot coating). Instead, the first flat side 110A of the sheet metal strip 110 can either be uncoated or possibly can be coated with an insulating lacquer coating 530 corresponding to the third layer 430.

(44) To produce the component 500 shown in FIG. 5, two different sheet metal strips—typically supplied in the form of two coils—are therefore required, one coil (not illustrated) containing the sheet metal strip 400 with the depot coating and the other coil (not illustrated) containing the sheet metal strip 510 with the adhesive coating.

(45) The adhesive bonding is then effected analogously to that which was explained with reference to FIG. 3, where here, too, contact between the reaction accelerator and the adhesive does not take place until during the adhesive bonding process and hence the same features, properties and advantages as described above are present and achieved.

(46) The components illustrated by means of FIGS. 3 and 5 can in all example embodiments contain substantially more than the two adhesively-bonded sheet metal laminations depicted and can for example be produced by a stack of a large number (e.g. greater than or equal to 10, 50, 100, etc.) of sheet metal laminations.

(47) The graph in FIG. 6 illustrates the results of experiments showing the roller peel resistance (in N/mm) of specimens including two adhesively bonded sheet metal strips directly after the adhesive bonding and also after aging. The roller peel resistance is a measure of the tearing force required to tear the two adhesively bonded sheet metal strips apart.

(48) The adhesive bonding temperature T was 150° C. during the experiments, an adhesive bonding time t of 10 min was awaited and a pressing force (F) of 3 MPa was applied. As reaction accelerator, 2E4Mlm was used in the first layer 120, the second layer 130 was a Backlack-V® layer.

(49) The results of the experiments show that with these parameters a high-strength bond of the sheet metal strips, with tearing forces on average above 6 N/mm, was achieved directly after the adhesive bonding (bar 601). After aging for 1 month (bar 602), the strength values lay within the same region (see experimental tolerances), that is to say that a significant deterioration in the adhesive bond as a result of aging could not be detected.

(50) In comparison, without a depot coating (i.e. without the use of the reaction accelerator) it was not possible to achieve any usable adhesive bond with these parameters (see right-hand bar 603).

(51) It can be assumed that the results illustrated by reference to experiments in FIG. 6 represent generally valid statements which are transferable to all example embodiments described within this disclosure.

(52) A description has been provided with reference to embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).