ADHESIVE TAPE THAT CAN BE WOUND AND STAMPED FOR SELECTIVE UV ACTIVATION

Abstract

An adhesive tape 10 that can be wound and stamped for selective UV activation, comprising at least a first UV activatable adhesive compound 1 on an epoxide basis and a carrier 2, the carrier being UV intransparent, for providing selective UV activatability of the adhesive tape 10.

Claims

1. An adhesive tape adapted to be wound and stamped for selective UV activation, comprising at least a first UV activatable adhesive compound on an epoxide basis and an UV intransparent carrier adapted to provide a selective UV activation of the adhesive tape.

2. The adhesive tape of claim 1, wherein the UV intransparent carrier has a first surface and a second surface; the first UV activatable adhesive compound is arranged on the side of the first surface of the UV intransparent carrier; and a second adhesive compounds is arranged on the side of the second surface of the UV intransparent carrier.

3. The adhesive tape of claim 2, wherein the second adhesive compound is identical to the first UV activatable adhesive compound.

4. The adhesive tape of claim 2, wherein the second adhesive compound is different from the first UV activatable adhesive compound, and the second adhesive compound is UV activatable.

5. The adhesive tape of claim 1, wherein the carrier is a UV intransparent adhesive compound.

6. The adhesive tape of claim 1, wherein the adhesive tape has an adhesive strength between 6 and 20 MPa.

7. The adhesive tape of claim 1, wherein the first UV activatable adhesive compound comprises: a. 2-40 percent by weight of film former, b. 10-70 percent by weight of aromatic epoxy resins, c. cyclo-aliphatic epoxy resins, the cyclo-aliphatic epoxy resins not exceeding 35 percent by weight, d. 0.5-7 percent by weight of cationic initiators, e. 0-50 percent by weight of epoxy-enhanced polyether compounds, and f. 0-20 percent by weight of polyol, the proportions adding up to 100%.

8. The adhesive tape of claim 2, wherein the second adhesive compound is different from the first UV activatable adhesive compound, and the second adhesive compound is non-UV activatable.

9. A method for adhesive joining of two join partners by means of an adhesive tape adapted to be wound and stamped of claim 2, the method comprising: UV activation of a first UV activatable adhesive compound of the adhesive tape; applying the adhesive tape with the activated first adhesive compound on a first join partner during an open time of the first adhesive compound, storage or transport of the first join partner and the adhesive tape, UV activation of a second UV activatable adhesive compound the adhesive tape, and applying the activated second adhesive compound on a second join partner during an open time of the second adhesive compound.

10. The method for adhesive joining of two join partners of claim 9, wherein only one UV activatable adhesive compound per application is irradiated by means of UV radiation.

11. The method of adhesive joining of two join partners of the join partners comprise a high energy.

12. The method for adhesive joining of two join partners of claim 9, wherein the join partners comprise a low energy.

13. The method for adhesive joining of two join partners of claim 11, wherein the high energy surface comprises a high energy surface selected from the group consisting essentially of: a metal surface, a fibre composite surface, and a glass surface.

14. The method for adhesive joining of two join partners of claim 11, wherein the low energy surface comprises a plastic surface.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0043] embodiments are illustrated in further detail by the subsequent description of the Figures. In this:

[0044] FIG. 1 schematically shows a symmetrical double-sided adhesive tape with a UV intransparent carrier and a UV activatable adhesive compound on both sides;

[0045] FIG. 2 schematically shows an asymmetrical double-sided adhesive tape with a UV intransparent carrier and a UV activatable adhesive compound and a non-UV activatable adhesive compound;

[0046] FIG. 3 schematically shows a transfer film having in a UV activatable adhesive compound and a UV intransparent adhesive compound;

[0047] FIG. 4 schematically shows a one-sided adhesive tape having a UV intransparent carrier and a UV activatable adhesive compound;

[0048] FIG. 5 schematically shows the UV activation of the first adhesive compound of FIG. 1;

[0049] FIG. 6 schematically shows the application of the UV activated first adhesive compound of FIG. 5 on a join partner during the open time;

[0050] FIG. 7 schematically shows the UV activation of the second adhesive compound on the pre-equipped join partner of FIG. 6; and

[0051] FIG. 8 schematically shows the application of the UV activated second adhesive compound of FIG. 7 on a second join partner during the open time.

DETAILED DESCRIPTION OF EMBODIMENTS

[0052] Various embodiments now will be described more fully hereinafter with reference to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific embodiments by which the invention may be practiced. The embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the embodiments to those skilled in the art.

[0053] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The term “herein” refers to the specification, claims, and drawings associated with the current application. The phrase “in an embodiment” as used herein does not necessarily refer to the same embodiment, though it may. Furthermore, the phrase “in another embodiment,” “in a further embodiment,” “in a further development,” “in another development” and so on as used herein does not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[0054] In addition, as used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references.

[0055] Described hereinafter are embodiments based on the Figures. In this, identical or similar elements or elements with the same effect are referenced with identical reference numerals in the different Figures, and these elements are not repeatedly described so as to avoid redundancies.

[0056] FIG. 1 schematically shows a symmetrical configuration of a double-sided adhesive tape 10 with a UV intransparent carrier 2 and UV activatable adhesive compounds 1, 1′. The UV activatable adhesive compounds 1, 1′ may differ in terms of their composition and their mechanical properties. Any UV intransparent spatial material can be used as carrier 2.

[0057] FIG. 2 schematically shows an asymmetrical configuration of a double-sided adhesive tape 10 with a UV intransparent carrier 2 and a UV activatable adhesive compound 1 and a non-UV activatable adhesive compound 3. In this context, the non-UV activatable adhesive compound 3 may for example be any type of pressure-sensitive adhesive.

[0058] FIG. 3 schematically shows a configuration for a UV intransparent adhesive compound 4 and a UV activatable adhesive compound 1. The adhesive tape can be used as a transfer film. Any pressure-sensitive adhesive compound with UV intransparent properties can be used as the UV intransparent adhesive compound 4.

[0059] FIG. 4 schematically shows a one-sided adhesive tape 10 for a UV intransparent carrier 2 and a UV activatable adhesive compound 1.

[0060] FIG. 5 schematically shows the one-sided, i.e. selective UV activation of the symmetrical double-sided adhesive tape 10 of FIG. 1 by means of a UV radiation source 5. The UV radiation source 5 is arranged such that it irradiates only adhesive compound 1. The UV intransparent carrier prevents the UV rays reaching adhesive compound 1′, as well. Adhesive compound 1′ is thus not activated when the first adhesive compound is activated and can therefore be activated separately at a later point in time.

[0061] FIG. 6 schematically shows the application of the first UV activated adhesive compound 1 of adhesive tape 10 of FIG. 5 on a join partner 6. Joining takes place during the open time of the first UV activated adhesive compound 1. Subsequently, analogously, the pre-equipped join partner 6 can be stored or transported.

[0062] FIG. 7 schematically shows the adhesive tape 10 of FIG. 6 joined to the join partner 6. In particular, the UV activation state of the second UV activatable adhesive compound 1′ is shown there. Accordingly, the UV radiation source 5 is directed at the second UV activatable adhesive compound 1′.

[0063] FIG. 8 schematically shows how the adhesive tape 10 of FIG. 7 is applied on a second join partner 7. In particular, the second UV activatable adhesive compound 1′ is applied on join partner 7. The joining of adhesive compound 1′ and the second join partner 7 is effected during the open time of the second UV activatable adhesive compound 1′. Following curing, the join partners 6, 7 are joined by means of the adhesive tape 10. The first join partner 6 and the second join partner 7 can be similar or different in type.

[0064] The manufacture of the adhesive tapes illustrated in the above Figures and in particular the materials used to this end for example derive from the document WO 2017/174303 A1.

[0065] For the manufacture of an adhesive tape an adhesive compound including solvents (thickness 50 μm) is applied to silicon-enhanced polyester film using a blade. Then it is dried at room temperature for 10 minutes, followed by drying in a convection oven at 80° C. for 10 minutes. The amount to be applied is adjusted such that after drying (removal of the solvent mixture) a layer thickness of 150 μm is obtained.

[0066] A pressure-sensitive adhesive (sticky) film is obtained with a thickness of ca. 150 μm.

[0067] No protective measures against UV light are necessary during handling of the raw materials, the adhesive or for the coating. It is sufficient to work under regular laboratory conditions away from the UV lamp. No further shielding is required.

[0068] Subsequently, the coated adhesive film is laminated onto a UV intransparent carrier or a UV intransparent second adhesive layer.

[0069] The pressure-sensitive adhesive film is applied to a UV intransparent carrier or a UV intransparent second adhesive layer subject to mild contact pressure. This can be achieved at a temperature of 30° C. to 40° C. (e.g. using heatable rollers) to ensure advanced applying and wetting of the pressure-sensitive adhesive UV activatable carrier. Moreover, by way of physical surface pre-treatment (plasma, corona, flame treatment, etc.), improved adhesion to the UV intransparent carrier or the second UV intransparent adhesive layer can be obtained.

[0070] The pressure-sensitive adhesive film is activated by means of UV light radiation:

[0071] In the case of an adhesive tape 10 with a symmetrical configuration according to FIG. 1 or the one-sided adhesive tape 10 according to FIG. 4, the UV activatable pressure-sensitive adhesive film (adhesive compound) 1 is activated by means of UV light from a discharging lamp or UV A light (from a UV A LED source) only on one side, i.e. the open adhesive layer. Subsequently, the pressure-sensitive adhesive film of the test-set-up of a size of ca. 312 mm.sup.2 (width: 25 mm, length: 12.5 mm) is glued on to the first substrate 6 (plate made of fibre-reinforced plastic FRE, length: 100 mm, width: 25 mm, thickness: 2 mm) during the open time. In the case of a double-sided adhesive tape 10 according to FIG. 1, the radiation of the second UV activatable adhesive compound 1′ is dissociated from the above process. Hence, the radiation can be performed immediately or during the shelf life of the adhesive tape 10. After radiation of the second side, during the open time and outside of the radiation zone, the second substrate 7 is pressed onto the open adhesive film, i.e. the second adhesive compound 1′ (the adhesive film is still pressure-sensitive adhesive also after radiation) so that the two substrates 6,7 overlap and the adhesive surface amounts to 25 mm×12.5 mm. The two substrates 6,7 are fixed with braces and stored at room temperature. Tensile shear strength tests are then performed on this sample 24 hours after the second substrate 7 was joined, unless specified otherwise.

[0072] In the case of the asymmetrical configuration with the UV intransparent carrier 2 according to FIG. 2 or with the UV intransparent second adhesive layer 4 according to FIG. 3, the UV activatable adhesive compound 1 is irradiated by means of UV light and applied to a first substrate during the open time. The application of a second substrate on the non-UV activatable adhesive compound 3 and the UV intransparent adhesive compound 4, respectively, can also be dissociated from that first process step.

[0073] For UV radiation, unless specified otherwise, the LED spot 100 by the company Hönle is used. The lamp comprises a UV LED (wavelength 365 nm) and a radiation chamber. The samples are irradiated in the radiation chamber for 15 seconds. The radiation dosage, measured using a UV Power Puck II by the company EIT Instrument Market Group, amounts to 5000 mJ/cm.sup.2.

[0074] Tests with a UV C lamp are carried out in a UV lab device by Beltron with a conveyor belt and a UV-C radiator with a radiation maximum at 256 nm. The conveyor belt is operated at 2m/min. The radiation dosage in the UV-C range, measured using a UV Power Puck II by the company EIT Instrument Market Group, amounts to 197 mJ/cm.sup.2.

[0075] Despite the substantially higher wavelength, the adhesive compounds can also be activated using the UV LED device. Similar radiation times as in the UV-C device are feasible and the results regarding open time and adhesion strength are in the same range.

[0076] The open time is considered the maximum feasible period between the removal from the radiation belt (UV-C) or removal from the radiation chamber (UV A), respectively, and the point in time when the joining with the second substrate takes place. During this period, the join partners can be joined. It is defined such that the adhesive layer is still pressure-sensitive adhesive (tacky). The open time is determined by finger-checking the tackiness of the surface of the adhesive films after radiation. Directly after radiation, the adhesive film is still tacky. After a certain time, the degree of tangible tackiness decreases and reduces further until eventually the surface is non-tacky. The open time is determined as the point in time when tackiness tangibly decreases so that afterwards no tack remains. It turns out that as long as the surfaces are still tacky, joining is possible and the subsequent curing results in a homogeneous adhesive bond. As soon as the surfaces lose all tack, the curing process has advanced so much already that no joining is possible any longer. This is reflected in the significantly reduced strength values determined based on the quasi-static tensile shear strength. The adhesive films are joined directly after UV activation.

[0077] Test Methods

[0078] a) Quasi-Static Tensile Shear Test

[0079] In order to determine parameters for the adhesive strength on FRE, tensile shear tests are carried out according to DIN EN 1465 (2009) at 23° C.±2° C. and 50%±5% relative humidity at a testing speed of 2 mm/min. The substrates are cleaned with isopropanol and joined afterwards. The curing is achieved using UV light, and the mechanical check is performed 24 h after activation. The results are indicated in MPa (N/mm.sup.2). The figures stated are the mean value based on five measurements including standard deviation.

[0080] b) Peel Test

[0081] The peel resistance of the cured adhesive tapes on glass is determined according to DIN EN 1939 (1996) at 23° C.±2° C. and 50%±5% relative humidity at a testing speed of 100 mm/min and a peel-off angle of 90°. The samples are cured using UV light and tested 24 h after activation. The results are indicated in N/mm. The figures stated are the mean value based on five tear resistance measurements including standard deviation.

[0082] c) Tensile Test

[0083] In order to determine parameters for the strength of the adhesive film alone in its cured state, tensile tests are carried out according to DIN EN 527 (2012) at 23° C.±2° C. and 50%±5% relative humidity at a testing speed of 10 mm/min. To this end, strips of a width of 19 mm and of a length of 100 mm are cut out of cured adhesive films. In the results illustrated, the layer thickness amounts to 0.2 mm. The samples are cured using UV light and tested 24 h after activation. The results are indicated in MPa (N/mm.sup.2). The figures stated are the mean value based on five measurements including standard deviation.

[0084] The following table illustrates examples of adhesive tape configurations, whereas K1-K4 represent configurations in accordance with the present disclosure and V1 represents an adhesive transfer film UV intransparent carrier.

TABLE-US-00001 Example: K1 K2 K3 K4 V1 Adhesive Compound (AC); AC 1 AC 1 AC 2 AC 2 AC 2 thickness: 0.15 mm Carrier (C) C 1 C 2 C 1 C 2 — Adhesive Compound (AC); AC 1 AC 1 AC 2 AC 2 AC 2 thickness: 0.15 mm

[0085] The following table summarises the results of the tensile shear, tensile and peel tests.

TABLE-US-00002 Example: K1 K2 K3 K4 V1 Tensile shear 18.6 ± 1.5  9.9 ± 0.7 23.9 ± 1.8  8.6 ± 1.4 21.8 ± 0.8  strength (AF/CSF) (AF) (CSF) (AF) (AF/CSF) [MPa] Resistance to 0.12 ± 0.03 0.71 ± 0.18 0.14 ± 0.04 0.79 ± 0.11 0.11 ± 0.02 peel [N/mm] (AF) (AF) (AF) (AF) (AF) Tensile 34.6 ± 1.2  9.1 ± 1.3 30.6 ± 2.1  10.1 ± 1.1  11.8 ± 2.4  strength [MPa] Key: AF: Adhesion Failure; CF: cohesive join partner failure

[0086] Adhesive films K1 and K2 as well as K3, KV and V1 all feature the same UV activatable adhesive compounds. Only the respective carrier was varied to illustrate differences in the selection of the carrier.

[0087] The adhesive films according to K1, K3 and V1 are not significantly different in terms of tensile shear strength and peel resistance within the range of the standard deviation. Here, the impact of the carrier is not very dominant in comparison to a transfer film. The tensile strength results present differently. There, the carrier has a decisive impact so that in the examples according to K1 and K3 the shear strength measured was much higher compared to V1.

[0088] The tensile shear strength and peel resistance values of examples K2 and K3 are not significantly different within the range of standard deviation. The tensile strength of said examples is at the same level of the transfer film according to V1.

[0089] Thus, it was possible to prove the impact of the different carrier materials. Carrier material 1 in the examples K1 and K3 increases tensile strength in comparison to reference V1, carrier material 2 in the examples K2 and K4 significantly increases peel resistance.

[0090] The following table illustrates the different activations. In example K5, the two adhesive compounds were activated and then joined in direct succession. In example K6, first the first adhesive compound was activated and joined and the second adhesive compound was activated four days later and joined with the second tensile shear substrate.

TABLE-US-00003 Example: K5 K6 Side 1: Adhesive Compound (AC); AC 2 AC 2 thickness: 0.15 mm Carrier (C) C 2 C 2 Side 2: Adhesive Compound (AC); AC 2 AC 2 thickness: 0.15 mm Time between activation of side 15 seconds 4 days 1 and side 2

[0091] The following table summarises the results of the tensile shear tests.

TABLE-US-00004 Example: K5 K6 Tensile shear 8.6 ± 1.4 9.2 ± 1.2 strength (AF) (AF) [MPa] Key: AF: Adhesion failure; CF: cohesive join partner failure

[0092] The tensile shear strengths of the adhesive films according to K5 and K6 show no difference within the range of the standard deviation. Thus, the effectiveness of the UV intransparent carrier and the thus dissociated process chain could be validated and verified.

[0093] Insofar as applicable, all individual features illustrated in the sample embodiments can be combined and/or exchanged without leaving the scope of the present disclosure

LIST OF REFERENCE NUMERALS

[0094] 10 adhesive tape [0095] 1 First UV activatable adhesive compound [0096] 1′ Second UV activatable adhesive compound [0097] 2 UV intransparent carrier [0098] 3 Non-UV activatable adhesive compound [0099] 4 UV intransparent adhesive compound [0100] 5 UV radiation source [0101] 6 First join partner [0102] 7 Second join partner