METAL STRIP WITH TRANSPORTATION PROTECTION

Abstract

The invention relates to a method for provision of a metal strip (1) with a protection for transportation, wherein the metal strip (1), in a Step i), is coated with a plastic, and, in a Step ii), is wound up in multiple layers, wherein in Step i), the plastic is applied to the metal strip in liquid or paste form, and solidified, wherein in Step i), a strippable varnish based on an organic solvent is applied as a plastic.

Claims

1. A method for provision of a metal strip (1) with a protection for transportation, wherein the metal strip (1), in a Step i), is coated with a plastic, and, in a Step ii), is wound up in multiple layers, wherein in Step i), the plastic is applied to the metal strip in liquid or paste form, and solidified, characterized in that in Step i), a strippable varnish based on an organic solvent is applied as the plastic.

2. The method according to claim 1, wherein the strippable varnish applied in Step i) is dried, and in a subsequent step, it is varnished again with at least one layer of a cover varnish, in particular one based on an organic solvent.

3. The method according to claim 1, wherein the strippable varnish and the cover varnish are sprayed on.

4. The method according to claim 1, wherein the strippable varnish applied in Step i) has a solvent proportion between 30 and 60 percent by weight, wherein toluene and/or acetone, in particular, is/are used as the solvent.

5. The method according to claim 1, wherein the strippable varnish applied in Step i) has a plastic proportion between 30 and 60 percent by weight.

6. A metal strip, wherein it is provided with a protection for transportation in accordance with the method according to claim 1, and has a solvent-based strippable varnish that adheres directly to the metal strip (1).

7. The metal strip according to claim 6, wherein the metal strip has a surface polished to a high shine, which is coated with the strippable varnish over its full area.

8. The metal strip according to claim 7, wherein the strippable varnish has a layer thickness between 50 m and 100 m.

9. The metal strip according to claim 6 or 7, wherein it has at least one layer composed of a cover varnish, applied directly to the strippable varnish, wherein a total thickness of a protective layer (3, 4) comprising strippable varnish and cover varnish amounts to between 100 m and 200 m.

10. (canceled)

Description

[0023] For a better understanding of the invention, it will be explained in greater detail using the following figures.

[0024] These show, each in a greatly simplified, schematic representation:

[0025] FIG. 1 a metal strip wound onto a core in spiral shape, with layers that lie one on top of the other;

[0026] FIG. 2 a metal strip wound up in spiral shape, with layers that are spaced apart from one another;

[0027] FIG. 3 a metal strip coated on one side, in a detail view;

[0028] FIG. 4 a metal strip coated on both sides, in a detail view;

[0029] FIG. 5 an endless metal strip before the winding-up process;

[0030] FIG. 6 the endless metal strip from FIG. 5 after the winding-up process;

[0031] FIG. 7 an exemplary spray device for spraying liquid plastic on;

[0032] FIG. 8 a schematic representation of a pull-off process of the protective layer.

[0033] As an introduction, it should be stated that in the different embodiments described, the same parts are provided with the same reference symbols or the same component designations, wherein disclosures contained in the description as a whole can be applied analogously to the same parts having the same reference symbols or component designations. Also, the position information selected in the description, such as at the top, at the bottom, at the side, etc., for example, relates only to the figure being directly described and shown, and this position information must be applied analogously to a new position in the case of a change in position.

[0034] FIG. 1 shows a first possibility for winding up a metal strip 1. In this case, this strip is wound in spiral shape around a core 2, wherein the individual layers lie one on top of the other.

[0035] In FIG. 2, the metal strip 1 is also wound in spiral shape, but the individual layers are spaced apart from one another here.

[0036] FIG. 3 shows an exemplary protective layer 3, which in this case adheres to the metal strip 1 only on one side.

[0037] In FIG. 4, in contrast, a metal strip 1 is shown that is equipped with protective layers 3 and 4 on both sides.

[0038] The winding techniques shown in FIGS. 1 and 2 are suitable for winding up/reeling up a finite metal strip 1. In FIGS. 5 and 6, in contrast, a winding technique for winding up an endless metal strip 1 is shown. In this regard, the metal strip is laid around a first and a second core 5 and 6. Now a third core 7 is laid onto the metal strip 1 from the outside. While the first and the third core 5 and 7 are held in place (for example, they can be screwed to one another by way of rails), the second core 6 is moved around the cores 5 and 7 in the direction of the arrow, and thereby the metal strip 1 is wound up. Then an arrangement as shown in FIG. 6 occurs. For stabilization of the resulting composite, the second core 6 can also be screwed to the first and third core 5 and 7 by way of rails.

[0039] According to the invention, before the metal strip 1 is wound up or reeled up, it is coated, in a first Step i), with a strippable varnish based on an organic solvent. The liquid strippable varnish can have between 30 and 60 percent by weight organic solvent and between 30 and 60 percent by weight plastic. The plastic can be, for example, polyolefins, for example high-density or low-density polyethylene (PE) or polypropylene (PP). In addition, however, polyvinyl chloride (PVC), polystyrene (PS), various polyesters, as well as polycarbonate (PC) or polyethylene terephthalate (PET) are also suitable. Furthermore, additives can also be added.

[0040] After evaporation of the solvent, the strippable varnish forms a plastic layer in the form of a plastic film that adheres in strippable manner, which film can be pulled off the surface of the metal strip 1 in destruction-free manner. Preferably, the layer thickness of the dried strippable varnish on the metal strip 1 amounts to between 50 m and 100 m.

[0041] FIG. 7 now shows a first possibility, presented schematically, as to how the liquid strippable varnish can be applied to the metal strip 1. In this regard, the metal strip 1 is passed over two rollers 8 and 9 and put into motion, and moved passed a spray device 10 in such a manner that is sprays the liquid strippable varnish onto the metal strip. The spray device 10 is configured as a spray bar that extends over the entire width of the metal strip 1. Furthermore, spraying takes place according to what is called an airless spraying method. Following the spray device 10 in the movement direction of the metal strip, a drying tunnel, not shown here, can be provided, in which the strippable varnish dries.

[0042] After drying of the strippable varnish, in a subsequent step, the strippable varnish is varnished again with a layer of a cover varnish, preferably based on an organic solvent. In this regard, the cover varnish, just like the strippable varnish, can be sprayed on using the spray device 10, wherein multiple cover varnish layers can be sprayed on by means of completely passing the metal strip 1 through under the spray bar 10 multiple times.

[0043] In FIG. 7, coating on only one side is shown, but of course, the metal strip 1 can also be coated on both sides. For example, for this purpose, a second spray device can be provided for this purpose on the inside of the strip, or the metal strip 1 is turned after the first side has been coated. In place of the spray device, an apparatus for brushing on or rolling on the liquid strippable varnish can also be provided, in equivalent manner.

[0044] FIG. 8 shows a further possibility for coating of the metal strip 1. This again is passed over two rollers 8 and 9 and put into motion. In place of a spray device 10, however, an immersion basin 11 with liquid plastic is provided here, through which the metal strip 1 is drawn. Depending on the immersion depth, in this regard, the metal strip 1 can be coated on one side or also on both sides, during one work cycle.

[0045] It is furthermore advantageous if the metal strip 1 is coated on its entire length, because in this way, particularly good protection of the same is provided, in particular also protection in the case of slipping of the layers of the wound-up metal strip 1. Particularly preferably, the metal strip 1 has a highly polished surface, which serves as a process surface used for production of a product, and is coated with the strippable varnish over its full area.

[0046] In general, the methods shown in FIGS. 7 and 8 are not restricted to coating of an endless metal strip 1. Of course, a finite metal strip 1 can also be coated in this manner, in that it is unwound from a roller, coated, and afterward wound up onto another roller, for example.

[0047] After coating, the metal strip 1 is wound up in a subsequent Step ii), for example as shown in FIGS. 5 and 6. As a result, the metal strip 1 is already protected when it is being wound up. Furthermore, in this way the result can be achieved, in relatively simple manner, that the metal strip 1 is covered with a protective layer 3, 4 consisting of strippable varnish and cover layer, over its full area. Checking of the protective layer 3, 4 is also possible in relatively simple manner as a result. Once again, winding up can take place in such a manner that the individual layers lie on top of one another, or in such a manner that they remain at a distance from one another.

[0048] If the individual layers of the wound-up metal strip 1 lie on top of one another, then depending on the coating and the winding technique, either a plastic surface and a metal surface make contact with one another, or two plastic surfaces make contact with one another. If the metal strip 1 is coated on one side, for example, as shown in FIG. 3, and wound up as shown in FIG. 1, then a (solidified) plastic layer 3 makes contact with a metal surface. If it is coated on both sides, then a plastic layer 3 makes contact with another plastic layer 4. For the deliberations below, this latter case is assumed.

[0049] It is now advantageous if a first adhesion friction coefficient between the metal strip 1 and the protective layer 3 that adheres to it, i.e. between the metal strip 1 and the protective layer 4 that adheres to it, is greater than a second adhesion friction coefficient that characterizes the friction between two solidified boundary layers of the protective layers 3 and 4. This means, in other words, that sliding starts between the protective layers 3 and 4, and not between the metal strip 1 and the protective layer 3 or the protective layer 4. In this way, it is advantageously prevented that foreign bodies on the metal surface, which are enclosed by the protective layer 3 or 4, scratch the metal surface if shifting of the layers of the wound-up body takes place. Also, detachment of the protective layers 3 and 4 is prevented in this manner.

[0050] Analogous considerations apply if a protective layer 3 comes to lie on a metal surface 1. In this regard, a distinction must be made between the first boundary surface between metal strip 1 and the protective layer 3, to which the plastic is applied in liquid form, and the second boundary surface between the metal strip 1 and the protective layer 3 that has already solidified. Once again, it is advantageous if the first adhesion friction coefficient at the first boundary surface is greater than a third adhesion friction coefficient at the second boundary surface. This means that sliding is initiated at the second boundary surface, in other words between the solidified plastic layer 3 and metal strip 1, and not between the adhering plastic layer 3 and metal strip 1.

[0051] At this point, it should be noted that not only does friction in the traditional sense occur at the boundary surface between metal strip 1 and the adhering protective layer 3, but rather, shear forces are also in effect because of the adhesion, without a normal force being required for this purpose.

[0052] In the connection described, it is also particularly advantageous if the solidified plastic layers 3 and 4 are block-resistant. Block resistance refers to a property according to which the layers, once they have solidified, no longer adhere to one another if they are pressed onto one another. In this way, it is guaranteed that the protective layers 3 and/or 4 that have been applied to the metal strip 1 do not adhere to one another when the metal strip 1 is wound up.

[0053] It is furthermore advantageous if the solidified plastic layer 3 can be bent upward by at least 180 (see also the angle in FIG. 8) without destruction, in other words at least normal to the metal surface to which it adheres. In this manner, it is made possible that the protective layer 3 can be pulled of easily, i.e. it is guaranteed that it does not break when removed, as is the case for brittle coatings. In an ideal case, the protective layer 3 can generally be removed in one piece.

[0054] In this connection, it is also advantageous if the product of the tensile strength of the solidified plastic and the thickness of the protective layer 3 is greater than its peel resistance, i.e. if the following holds true:

.sub.tension.Math.s>.sub.peeling

[0055] FIG. 8 is supposed to make this clear; it shows a piece of the metal strip 1 with a partially pulled-off protective layer 3. The peel resistance is defined by:

[00001]${}_{\mathrm{peeling}}=\frac{F_A}{b}$

wherein F.sub.A refers to the force that is required for pulling off the protective layer 3, and b is the length of the pull-off edge on which the force F.sub.A acts. The tensile strength is defined as:

[00002]${}_{\mathrm{tension}}=\frac{F_A}{b.Math.s}$

wherein F.sub.A refers to the force that acts within the protective layer, b again is the length of the pull-off edge, and s is the thickness of the protective layer. If the above requirement is met, it is made possible for the protective layer 3 to be pulled off easily, in particular in one piece.

[0056] It is advantageous if the peel resistance of the protective layer 3 amounts to at least 0.1 N/cm and/or maximally 1 N/cm. In this manner, it is guaranteed that the protective layer 3 can still be pulled off by hand. In this regard, it is furthermore advantageous if the tensile strength of the protective layer 3 amounts to at least 0.1 N/cm.sup.2, in particular at least 1 N/cm.sup.2, because in this way it is guaranteed that the protective layer 3 does not tear when it is being pulled off. Furthermore, it is advantageous if the adhesive strength of the protective layer amounts to at least 0.1 N/cm.sup.2 and/or maximally 1 N/cm.sup.2 (see, in this regard, the adhesive strength or adhesion strength F.sub.K with reference to the surface area A in FIG. 8). In this manner, it is guaranteed that the protective layer 3 adheres sufficiently for transport, but can still be pulled off by hand. It is also advantageous if the layer thickness s of the protective layer 3 consisting of strippable varnish and cover varnish amounts to at least 100 m and maximally 200 m. In this range, good protection of the metal strip 1 against damage exists at a reasonable material expenditure for the plastic layer 3.

[0057] For the sake of good order, it should be pointed out, in conclusion, that for a better understanding of the structure, some elements were shown not to scale and/or larger and/or smaller.

REFERENCE SYMBOL LISTING

[0058] 1 metal strip [0059] 2 core [0060] 3 protective layer [0061] 4 protective layer [0062] 5 core [0063] 6 core [0064] 7 core [0065] 8 roller [0066] 9 roller [0067] 10 spray device