HIGH STRENGTH CYANOACRYLATE-BASED TAPES

Abstract

The present invention relates to a curable composition comprising a curable cyanoacrylate component and at least one thermoplastic polyurethane (TPU) component. The compositions of the invention are non-flowable at room temperature (25° C.) and are suitable for use as adhesive compositions, for example in a tape form.

Claims

1. A curable composition comprising: (i) a curable cyanoacrylate component; and (ii) at least one thermoplastic polyurethane (TPU) component; and wherein said at least one TPU component (ii) has a mass average molar mass Mw from 40,000-80,000, and wherein said at least one TPU component (ii) is based on a polyol that is based on at least one diol or dicarboxylic acid wherein said at least one diol or dicarboxylic acid has 6 carbon atoms (C.sub.6) in its main chain and further wherein none of said diols or dicarboxylic acids have greater than 10 carbon atoms (>C.sub.10) in their main chain, and wherein said at least one TPU component (ii) is present in the curable composition in an amount of greater than about 50 wt %, wherein the weight percentage is based on the total weight of the composition.

2. A curable composition according to claim 1, wherein the cyanoacrylate component (i) is a liquid curable cyanoacrylate component.

3. A curable composition according to claim 1, wherein the cyanoacrylate component (i) is selected from the group comprising ethyl cyanoacrylate, butyl cyanoacrylate, β-methoxy cyanoacrylate and combinations thereof.

4. A curable composition according to claim 1, wherein the cyanoacrylate component (i) is present in the curable composition in an amount from about 10 wt % to about 35 wt %, wherein the weight percentage is based on the total weight of the composition.

5. A curable composition according to claim 1, further comprising a solvent selected from the group comprising ethyl acetate, tetrahydrofuran, methyl ethyl ketone, cyclohexanone, and acetone.

6. A curable composition according to claim 5, wherein the solvent used is ethyl acetate.

7. A curable composition according to claim 1, wherein said at least one TPU component (ii) is present in the curable composition in an amount from about 65 wt % to about 85 wt % wherein the weight percentage is based on the total weight of the composition.

8. A curable composition according to claim 1, wherein said at least one TPU component (ii) has a glass transition temperature of from about −60° C. to about −5° C.

9. A curable composition according to claim 1, wherein said at least one TPU component (ii) has a glass transition temperature of from about −55° C. to about −20° C.

10. A curable composition according to claim 1, wherein said at least one TPU component (ii) comprises polyester segments.

11. A curable composition according to claim 1, wherein said at least one TPU component (ii) comprises polyester segments, based on at least one of a C6 diol or a C6 carboxylic acid.

12. A curable composition according to claim 1 wherein said at least one TPU component (ii) is based on a polyester polyol formed from a C6 dicarboxylic acid and one of either 1,6-hexane diol or 1,4-butane diol.

13. A curable composition according to claim 1 wherein said at least one TPU component (ii) is based on a (co)polyester of hexanedioic acid and one of either 1,4-butane diol or 1,6-hexanediol, said (co)polyester having a melting point of about 50-80° C., and with an OH number of less than about 0.5%, for example less than about 0.1% (as measured according to standard procedure DIN 53240-2).

14. A curable composition according to claim 1 further comprising from about 10 ppm to about 200 ppm of a stabiliser of the cyanoacrylate component.

15. A curable composition according to claim 14, wherein the stabiliser is selected from boron trifluoride (BF.sub.3) or sulfur dioxide (SO.sub.2).

16. A curable composition according to claim 14, wherein the stabiliser is sulfur dioxide (SO.sub.2).

17. A curable composition according to claim 1, comprising two TPU components, wherein each of said two TPU components has a mass average molar mass Mw from 40,000-80,000, and wherein each of said two TPU components is based on a polyol that is based on at least one diol or dicarboxylic acid wherein said at least one diol or dicarboxylic acid has 6 carbon atoms (C.sub.6) in its main chain and further wherein none of said diols or dicarboxylic acids have greater than 10 carbon atoms (>C.sub.10) in their main chain, and wherein said two TPU components are present together in the curable composition in a total amount greater than about 50 wt %, wherein the weight percentage is based on the total weight of the composition.

18. A curable composition according to claim 1 provided in tape form.

19. A tape comprising a curable composition according to claims 1 and one or more release liners.

20. A method of preparing a curable composition comprising the steps of: i) combining at least one thermoplastic polyurethane (TPU) component with a curable cyanoacrylate component as set out in claim 1 and a solvent to form a mixture; ii) applying the mixture of step (i) to a substrate, optionally by casting; iii) allowing the solvent to evaporate or actively removing the solvent, thereby forming a solid form curable composition.

21. The method of claim 20 wherein the substrate is a release liner.

22. The method of claim 21, wherein the solvent is ethyl acetate.

23. The composition according to claim 1 in cured form.

24. An assembly comprising two substrates bonded together by the cured form of the composition according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which:

[0074] FIG. 1 depicts the results of tensile shear testing on several substrates using an adhesive tape prepared from a cyanoacrylate composition according to Example 1 of the present invention and provides a comparison of the performance of Example 1 and DURO-TAK 9640.

[0075] FIG. 2 depicts the results of tensile shear testing on several substrates using an adhesive tape prepared from a cyanoacrylate composition according to Example 2 of the present invention and provides a comparison of the performance of Example 2 and DURO-TAK 9640.

[0076] FIG. 3 depicts the results of tensile shear testing on several substrates using an adhesive tape prepared from a cyanoacrylate composition according to Example 3 of the present invention and provides a comparison of the performance of Example 3 and DURO-TAK 9640.

[0077] FIG. 4 depicts the results of T-peel testing obtained using adhesive tapes prepared with cyanoacrylate compositions according to the present invention and provides a comparison of their performance with that of DURO-TAK 9640.

[0078] FIG. 5 depicts the results of side impact tests obtained using compositions according to the present invention and provides a comparison of their performance with that of DURO-TAK 9640.

EXAMPLES

[0079] Example compositions 1-3, suitable for practising the present invention, were prepared as detailed below.

[0080] The ethyl acetate solvent was placed in a suitable vessel and TPU component Pearlbond 106 was added. The mixture was stirred and brought to a temperature of about 65° C. Full dissolution of the TPU component occurred under high shear mixing at 1330 rpm with a dissolver blade in approximately 1-2 hours. A boron trifluoride stabiliser was then added, followed by the relevant cyanoacrylate monomer.

[0081] Table 1 provided below summarises the compositions of Examples 1-3.

TABLE-US-00001 TABLE 1 Mass/g Component Example 1 Example 2 Example 3 Pearlbond 106 300.0 300.0 250.0 Ethyl acetate 300.0 300.0 250.0 Butyl cyanoacrylate 162.0 0 0 β-methoxy cyanoacrylate 0 162.0 60.8 Boron trifluoride (1000 24.3 24.3 16.4 ppm solution in ethyl cyanoacrylate)

[0082] The compositions of Examples 1-3 were used to prepare adhesive tapes suitable for practising the present invention.

[0083] Each adhesive formulation was coated onto a siliconized polyester film available from PPI films (SRF 122/75 μm). A wet coating thickness of 150 microns was used. The film was dried for 5 minutes at 60° C. to facilitate the removal of the ethyl acetate solvent, after which film thickness was approximately 60 μm. Once dried the adhesive tape was transferred under mild finger pressure to the substrate to be tested. This ease of transfer (instant tack) is achieved due to the presence of the liquid monomer.

[0084] Table 2 provided below shows the weight percentages of each component in the compositions of Examples 1-3 after removal of the solvent. Weight percentages are based on the total weight of the composition.

TABLE-US-00002 TABLE 2 Percentage by weight Component Example 1 Example 2 Example 3 Pearlbond 106 62% 62% 76% Butyl cyanoacrylate 33%  0%  0% β-methoxy cyanoacrylate  0% 32% 19% Boron trifluoride (1000 5% (50 ppm 5% (50 ppm 5% (50 ppm ppm solution in ethyl BF.sub.3) BF.sub.3) BF.sub.3) cyanoacrylate)

[0085] The adhesive tapes prepared from the compositions of Examples 1-3 were subjected to several comparative tests to assess their performance compared to control composition DURO-TAK9640. DURO-TAK9640 is a cyanoacrylate tape based on a solid cyanoacrylate monomer and a polyethylene/polyvinylacetate film former. Tensile shear (across various substrates), T-peel (grit blasted mild steel (GBMS)), and side impact testing was carried out.

[0086] The results of tensile shear testing with an adhesive tape of the invention according to the composition of Example 1, based on butyl cyanoacrylate, are shown in FIG. 1. Tensile shear tests were performed in accordance with ASTM D 1002 (2000). The tensile strength of the tape was measured across various substrates and compared to that of DURO-TAK 9640. Bonds were assembled at room temperature (25° C.), and testing was carried out after a further 24 h at room temperature. In FIGS. 1-3, ‘SF’ is used to report substrate failure, which occurs when the bond is stronger than the substrate causing the substrate to break before the bond. Each tensile shear test was carried out 5 times so 20% substrate failure, for example, is reported when substrate failure was observed in one of the 5 experiments.

[0087] The adhesive tape prepared with the composition of Example 1 showed significantly improved performance over DURO-TAK9640 across all substrates tested. The greatest tensile shear values measured for the composition of Example 1 were on PC (polycarbonate) and teak substrates.

[0088] The results of tensile shear testing with an adhesive tape of the invention according to the composition of Example 2, based on β-methoxy cyanoacrylate, are shown in FIG. 2. The tensile strength of the tape was measured across various substrates and compared to that of DURO-TAK9640. Bonds were assembled at room temperature (25° C.), and testing was carried out after a further 24 h at room temperature.

[0089] The adhesive tape prepared with composition Example 2 showed significantly improved performance over DURO-TAK9640 across almost all substrates tested, being outperformed only when tested on aluminium. The greatest tensile shear value was measured on a teak substrate. The results of tensile shear testing with an adhesive tape of the invention according to the composition of Example 3 are shown in FIG. 3. Example 3 is also based on 8-methoxy cyanoacrylate but the cyanoacrylate component is present in a lower proportion than in Example 2. The tensile strength of the tape was measured across various substrates and compared to that of DURO-TAK9640. Bonds were assembled at room temperature (25° C.), and testing was carried out after a further 24 h at room temperature.

[0090] The adhesive tape prepared with the composition of Example 3 showed improved performance over DURO-TAK9640 across all substrates tested. Again, the highest tensile shear value was measured on a teak substrate.

[0091] The T-peel performance of the tapes prepared with the compositions of Examples 1-3 were measured and compared with control composition DURO-TAK9640. T-peel testing was carried out in accordance with ASTM D 1876 (2010). Tests were performed on a substrate of grit blasted mild steel (GBMS) using T-peel coupons 25.4 mm wide and 150 mm long, following cure for either 24 h at room temperature (25° C.) or 24 h at room temperature followed by a further 20 minutes at 80° C. The results of the T-peel testing are shown in FIG. 4.

[0092] For both sets of cure conditions, all of the example compositions tested showed substantially improved performance over DURO-TAK9640. Excellent T-peel performance was exhibited by all of the example compositions. The highest T-peel values were achieved by Examples 1 and 2 when cured for 24 h at room temperature. For all compositions tested, T-peel performance was higher when cured at room temperature than when cured at room temperature followed by a 20-minute cure at 80° C. However, even the lowest T-peel value obtained for the example compositions tested was several times higher than either of the values observed for DURO-TAK9640.

[0093] The side impact performance of the tapes prepared with the compositions of Examples 1-3 were measured and compared with control composition DURO-TAK9640. Side impact testing was carried out in accordance with STM 812. Tests were performed on a substrate of mild steel, following cure for either 24 h at room temperature (25° C.) or 24 h at room temperature followed by a further 20 minutes at 80° C. The results of the side impact testing are shown in FIG. 5.

[0094] All of the example compositions tested showed excellent side impact performance, significantly outperforming control composition DURO-TAK9640. The results obtained with a 24 h cure at room temperature followed by a further 20 minutes at 80° C. were comparable to those achieved with the room temperature cure only.

[0095] The words “comprises/comprising” and the words “having/including” when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0096] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.