METHOD OF MAKING ADHESIVE CABLE-WRAP TAPE

Abstract

The invention relates to a method for producing an adhesive tape, in particular a wrapping tape for wrapping around cables in automobiles. A strip-shaped carrier (2) is provided with a UV cross-linkable adhesive coating (5). In addition to an acrylate-based pressure-sensitive adhesive with embedded photoinitiators, the adhesive coating (5) comprises at least one additive. The photoinitiators are activated for cross-linking by irradiation with a UV light source (6) emitting in the range of its activation wavelength. According to the invention, the activation wavelength of the photoinitiators is above 280 nm, in particular above 315 nm.

Claims

1. A method of making a tape for wrapping cables in automobiles, the method comprising the step of: providing an opaque substrate strip having a UV-cross-linkable adhesive coating comprised of: an acrylate-based pressure-sensitive adhesive with embedded photoinitiators cross-linkable by UV light of wavelength in a predetermined activation range, and at least one additive formed of a resin admixture for increasing adhesion to the substrate strip and having no or hardly any absorbency in the range of the activation wavelength of the photoinitiators, activating the photoinitiators are activated for cross-linking through irradiation with a UV light source that emits in the predetermined activation range, and helically wrapping the tape around the cables of a cable set to be sheathed with the substrate strip facing outward.

2. The method according to claim 1, wherein the UV light source irradiates the adhesive coating with a UV dose of at least 15 mJ/cm.sup.2.

3. The method according to claim 1, wherein an LED-based UV light source is used.

4. The method according to claim 3, wherein the LED-BASED UV light source is a UVA LED light source.

5. The method according to claim 1, wherein the photoinitiators are in to the adhesive coating in a grammage of at least 0.05 wt %.

6. The method according claim 1, further comprising the step of: applying the adhesive coating to the substrate strip at an application weight of greater than 15 g/cm.sup.2.

7. (canceled)

8. The method according to claim 1, wherein the substrate strip is a textile fabric with a weight per unit area of between 50 g/m.sup.2 and 250 g/m.sup.2.

9. The method according to claim 8, wherein the textile fabric is dyed.

Description

[0026] The invention is described in further detail below with reference to a schematic drawing showing only one embodiment:

[0027] FIG. 1 is a schematic view of an apparatus for carrying out the method according to the invention,

[0028] FIG. 2 is a graph of an absorption spectrum of the acrylate-based pressure-sensitive adhesive with incorporated photoinitiators and two variants with different additives, and

[0029] FIG. 3 is a graph of the absorption spectrum of the photoinitiators used according to the invention.

[0030] FIG. 1 shows an apparatus for making an adhesive tape 1. For this purpose, a substrate strip 2 is fed to a coater 3 for hot-melt adhesive. In the coater 3 for the hot-melt adhesive, the hot-melt adhesive is at a temperature of about 100 C. to 150 C. and can be applied to the substrate strip 2 being moved past the nozzle 4 via an output-side nozzle 4 of the coater 3, thereby coating the substrate strip 2.

[0031] The substrate strip 2 is a substrate strip 2 formed of a textile fabric and has a weight per unit area of between 50 g/m.sup.2 and 250 g/m.sup.2. After coating of the substrate strip 2 with an adhesive coating 5 in this manner, the adhesive coating 5 is cross-linked by a UV light source 6 that is above the continuously coated substrate strip 2. As will readily be understood, the adhesive coating 5 faces the UV light source 6 during this process. The light source 6 is an LED-based light source. In fact, a large number of LED's are used here. In principle, however, the UV light source 6 can also for example use a mercury vapor lamp. That is not shown, however.

[0032] The substrate strip 2 that has been provided with the adhesive coating 5 moves beneath the UV light source 6 at a speed of from 10 m/min to 100 m/min or more. The adhesive coating 5 is irradiated by the UV light source 6 at a UV dose of at least 15 mJ/cm.sup.2. According to the embodiment, a UV dose in the range of from 150 mJ/cm.sup.2 to 500 mJ/cm.sup.2 is used. The UV light source 6 emits, inter alia, in the range of the activation wavelength for the photoinitiators incorporated in the adhesive coating 5, that is, primarily in a range above 280 nm.

[0033] The adhesive coating 5 has at least one additive in addition to an acrylate-based pressure-sensitive adhesive with incorporated photoinitiators. As an additive, the invention makes use of a resin admixture based on a merely partially hydrogenated abietic acid ester. After the substrate strip 2 has been provided with the adhesive coating 5, the adhesive tape 1 made in this manner can for example be wound up or cut in the longitudinal direction if a fabric web is being fed to the coater 3 here as the substrate strip 2. This is known in detail.

[0034] FIG. 2 shows the absorption or absorbency E relative to the wavelength. Dimensionless absorbency E is known to be a measure of the reduction in the intensity of the light measured in a photometer as it passes through the corresponding sample. The progression of the absorbency or absorption relative to the wavelength for the acrylate-based pressure-sensitive adhesive used in the invention in this case, namely acResin A203UV, is shown by a solid line. The other curves relate to the acrylate-based pressure-sensitive adhesive in question, on the one hand with an additive 1 (dashed line). Additive 1 is a resin admixture based on abietic acid ester that has been partially hydrogenated. The dot-dashed variant with additive 2 also relates to a resin admixture based on abietic acid ester having only slight or virtually no partial hydrogenation. The product YT311 from Yser was used as additive 1. Additive 2 is YT321, also from Yser.

[0035] It can be seen that the adhesive coating 5 produced in this manner increasingly absorbs in the direction of higher UV wavelengths as the hydrogenation of the abietic ester-based resin admixture decreases. Since, according to the invention, the activation wavelength of the photoinitiators is above 280 nm and particularly above 315 nm, such resin admixtures can be used nonetheless, because sufficient light of the UV light source 6 penetrates into the adhesive coating 5 despite these resin admixtures. This is indicated by FIG. 2, which shows the minimum of the activation wavelength of 280 nm as well as the preferred range above 315 nm.

[0036] Finally, FIG. 3 also shows the absorption spectrum of the photoinitiators used according to the invention. In fact, the absorbency E is reproduced over the wavelength in this case as well. It can be seen that the absorption maximum of the photoinitiators used is in the range between about 280 nm and 300 nm, so that the appropriately configured activation wavelength of the UV light source 6 can cross-link the photoinitiators properly.

[0037] Finally, it should also be noted that the substrate strip 2 is opaque. For this purpose, the substrate strip 2 is a dyed textile fabric, for example a black-dyed woven fabric, a black-dyed nonwoven, etc. Incident natural UV light or daylight is thus absorbed by the substrate strip 2 because it faces outward both in the stored state and in the processing state. In fact, it can be seen from the device shown in FIG. 1 that the adhesive tape 1 in question is wound up with the substrate strip 2 facing outward in the roll, so that, when stored, no UV radiation can penetrate to the adhesive coating 5 inside due to the opaque substrate strip 2. The same applies to a case in which the adhesive tape 1 made in this manner is used in the specified manner as a tape for wrapping cables in automobiles.

[0038] After all, the adhesive tape 1 in question is wrapped helically for this purpose around the respective cables that are to be grouped together. In this case as well, the substrate strip 2 faces outward and ensures with its opaque character that any daylight and consequently UV components present in daylight do not or practically do not reach the adhesive coating 5 present on the inside tape face. As a result, the degree of cross-linking set during manufacturing is not or is practically not influenced.

[0039] In particular, the illustration in FIG. 2 in combination with FIG. 3 makes it clear that, in the context of the invention, the wavelength of the photoinitiators used, more particularly the absorption spectrum thereof, is or can be adapted to the UV light source 6. In fact, the photoinitiators are those containing benzoin ethers such as benzoin methyl ethers and are available, inter alia, under the trade name IRGACURE 651. Reference should also be made in this regard to above-cited WO 2016/186877 that describes such photoinitiators. In any case, this enables resin admixtures that are favorable overall in terms of production engineering and have no or hardly any absorbency in the range of the activation wavelength of the photoinitiators to be considered as additives for the purpose of increasing the adhesion to the substrate strip. This can be seen from FIG. 2 and for example from additive 2 whose absorbency E has fallen to values of 1.0 in the range above 280 nm, the activation wavelength of the photoinitiators, whereas absorbencies of 2 and even more are observed below the activation wavelength.

[0040] This circumstance becomes all the more clear if an activation wavelength of 315 nm is assumed. Here, the absorbency E of the additive 2 is less than 0.1, whereas the absorbency in the range below that takes on values that are typically 10 times that or more. In other words, the resin admixture, additive 2 in the example, has no or hardly any absorbency in the range of the activation wavelengths of the photoinitiators and above, which means that the absorbency E is reduced by at least a factor of 5, typically by a factor of 10 or more compared to the absorbency E of the resin admixture (additive 2) below the activation wavelength.