Solid cyanoacrylate compositions

Abstract

A cyanoacrylate composition with thermoplastic polyurethane, formulated as a non-flowable soft solid or semi solid mass, for example in stick form, is reported.

Claims

1. A curable composition comprising: (i) a cyanoacrylate component, and (ii) a thermoplastic polyurethane (TPU) component, wherein the TPU component (ii) has a mass average molar mass M.sub.w from about 5000 to about 250000, and wherein said TPU component (ii) is soluble at a temperature of 65° C. in the cyanoacrylate component up to at least 40% by weight based on the total weight of the cyanoacrylate component, and wherein said TPU component (ii) is based on a polyol that is based on at least one of a diol or a dicarboxylic acid characterised in that at least one of said diol or dicarboxylic acid has greater than 10 carbon atoms (>C.sub.10) in the main chain, and wherein the TPU component (ii) has a glass transition temperature of from about −60° C. to about 0° C., and a melting point of from about 30° C. to about 100° C. as measured by differential scanning calorimetry in accordance with ISO11357, and wherein the TPU component (ii) is present in the curable composition in an amount from about 1 wt % to about 60 wt %, wherein the weight percentages are based on the total weight of the composition, and wherein the curable cyanoacrylate component (i) is selected from the group consisting of ethyl cyanoacrylate, butyl cyanoacrylate, β-methoxy cyanoacrylate and combinations thereof, and wherein the curable composition is solidified in a cylindrically shaped stick.

2. The curable composition according to claim 1, wherein the TPU component (ii) is present in the curable composition in an amount from about 5 wt % to about 40 wt %, wherein the weight percentages are based on the total weight of the composition.

3. The curable composition according to claim 1, wherein the TPU component (ii) has a glass transition temperature of from about −60° C. to about −5° C.

4. The curable composition according to claim 1, wherein the TPU component (ii) has a glass transition temperature of from about −55° C. to about −20° C.

5. The curable composition according to claim 1, wherein the TPU component (ii) comprises polyester segments.

6. The curable composition according to claim 1, wherein the TPU component (ii) comprises polyester segments, based on at least one of a greater than C.sub.10 diol or a greater than C.sub.10 dicarboxylic acid.

7. The curable composition according to claim 1 wherein the TPU component (ii) is based on a polyester polyol formed from 1,6-hexane diol and a greater than C.sub.10 dicarboxylic acid.

8. The curable composition according to claim 1, wherein the TPU component (ii) is based on a (co)polyester of dodecanedioic acid and 1,6-hexanediol, said (co)polyester having a melting point of about 70° C., and with an OH number from about 27 to about 34 mg KOH/g (as measured according to standard procedure DIN 53240-2).

9. The curable composition according to claim 1, further comprising a stabiliser of the cyanoacrylate component.

10. The curable composition according to claim 9, wherein the stabiliser is selected from the group consisting of boron trifluoride (BF.sub.3) and sulfur dioxide (SO.sub.2).

11. The method of preparing a solidified mass of the curable composition according to claim 1, comprising the steps of: (i) mixing a TPU component with a component comprising a curable cyanoacrylate at a temperature above the melting point of said TPU component, forming a mixture, (ii) casting the mixture of step (i) into a container to form the cast mixture into a cylindrically shaped stick, and (iii) allowing the cast mixture of step (ii) to cool, or cooling said cast mixture, sufficiently to solidify the composition, wherein said TPU component has a mass average molar mass M.sub.w from about 5000 to about 250000, and wherein said TPU component is soluble at a temperature of 65° C. in the curable cyanoacrylate up to at least 40% by weight based on total weight of the curable cyanoacrylate, and wherein said TPU component is based on a polyol that is based on at least one of a diol or a dicarboxylic acid characterised in that at least one of said diol or dicarboxylic acid has greater than 10 carbon atoms (>C.sub.10) in the main chain, and wherein said TPU component has a glass transition temperature, Tg, of from about −60° C. to about 0° C., and a melting point of from about 30° C. to about 100° C. as measured by differential scanning calorimetry in accordance with ISO11357, and wherein said TPU component is mixed in step (i) with a component comprising a curable cyanoacrylate such that said TPU component is present in the solidified mass of the curable composition in an amount from about 1 wt % to about 60 wt %, wherein the weight percentages are based on the total weight of the composition, and wherein the component comprising a curable cyanoacrylate comprises a curable cyanoacrylate selected from the group consisting of ethyl cyanoacrylate, butyl cyanoacrylate, and β-methoxy cyanoacrylate.

12. The method as claimed in claim 11, wherein the TPU component is present in the curable composition in an amount from about 5 wt % to about 40 wt %, wherein the weight percentages are based on the total weight of the composition.

13. The method as claimed in claim 11 wherein the TPU component comprises polyester segments.

14. A mass shaped in a stick form prepared by the method of claim 11.

15. A pack comprising: (i) a shaped mass of a curable composition according to claim 1; and (ii) a container for the composition, the container having a mechanism for expelling the shaped mass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 depicts the results of tensile shear tests on several substrates (GBMS, PC, Beechwood) using example soft solid form ethyl cyanoacrylate compositions according to the present invention, and provides results of comparative TPU-negative liquid form and solid form ethyl cyanoacrylate compositions. Tensile shear tests were performed using a lap-shear based test in accordance with ISO 4587.

(3) FIG. 2 depicts the results of side impact tests obtained using example soft-solid form ethyl cyanoacrylate compositions of the present invention when said tests were performed following 1 week of cure at room-temperature (25° C.).

(4) FIG. 3 depicts the results of side impact tests obtained using example soft solid form ethyl cyanoacrylate compositions of the present invention when said tests were performed following 3 days of cure at room-temperature (25° C.) and 1 day at 90° C.

(5) FIG. 4 depicts the results of fixture time tests obtained (22.2° C., 56.7% relative humidity) using example soft solid form ethyl cyanoacrylate compositions of the present invention when said tests were performed using polycarbonate as a substrate.

(6) FIG. 5 depicts the results of T-peel tests obtained using example soft solid form ethyl cyanoacrylate compositions of the present invention when said tests were performed on a substrate of mild steel, following cure at either 1 week at room temperature (25° C.), or 3 days at room-temperature followed by 1 day at 90° C.

(7) FIG. 6(A) [side view] and FIG. 6(B) [end view] depict a container suitable for holding A curable composition of the present invention, for example a shaped soft solid or semi-solid mass, the container having a mechanism for expelling the shaped mass.

DETAILED DESCRIPTION OF THE DRAWINGS

(8) FIG. 1 depicts bar charts showing the results of tensile shear tests obtained using unmelted soft solid form ethyl cyanoacrylate example compositions: Example 1 (‘Ex.1’), Example 2 (‘Ex.2’), Example 3 (‘Ex.3’), and Example 4 (‘Ex.4’). Results are also shown for commercially available liquid and solid form cyanoacrylate compositions that were included in the tests as TPU-negative comparative compositions. Said TPU-negative comparative compositions are LOCTITE 401 (‘401’, liquid), LOCTITE 454 (‘454’, liquid), LOCTITE 60 sec. (‘60 secs’, liquid), and SuperTape (‘SuperTape’, solid). Tensile shear is reported in MPa, and results were obtained in lap shear tests performed according to ISO 4587. The tensile shear strength was measured on following substrates: Grit blasted mild steel (GBMS), polycarbonate (PC), and beechwood.

(9) FIG. 2 depicts bar charts showing the results of side impacts tests performed after 1 week at room temperature (25° C.) in accordance with standard procedure GM9751P for soft solid form ethyl cyanoacrylate compositions Example 1 (‘Ex.1’), Example 2 (‘Ex.2’), Example 3 (‘Ex.3’), and Example 4 (‘Ex.4’), and for the comparative TPU-negative compositions: 401, 454, 60 secs, and SuperTape. As seen for Example 1, Example 2, Example 3, and Example 4, in a certain number of tests no breakage was observed; ‘% DNB’ in FIG. 2 and FIG. 3 refers to how often the tested compositions did not break during side impacts, expressed as a percentage of the total number of tests performed.

(10) FIG. 3 depicts bar charts showing the results of side impacts tests performed after 3 days cure at room (25° C.) followed by one day cure at 90° C. in accordance with standard procedure GM9751P for soft solid form ethyl cyanoacrylate compositions Example 1 (‘Ex.1’), Example 2 (‘Ex.2’), Example 3 (‘Ex.3’), and Example 4 (‘Ex.4’), and for the comparative TPU-negative compositions: 401, 454, 60 secs, and SuperTape.

(11) FIG. 4 depicts bar charts showing the results of fixture time tests on polycarbonate (PC) substrates for soft solid form ethyl cyanoacrylate compositions Example 1 (‘Ex.1’), Example 2 (‘Ex.2’), Example 3 (‘Ex.3’), and Example 4 (‘Ex.4’), and for the comparative TPU-negative compositions: 401, 454, 60 secs, and SuperTape (green strength only for SuperTape). The fixture time tests were performed at 22.2° C. and 56.7% relative humidity (RH). Fixture times were recorded in seconds. Fixture times were determined by stressing a single adhesive overlap joint with the application of a 3 kg tensile force parallel to the bond area and to the major axis of the PC test lap shear specimens. Clearly, fixture time will be modulated in part by the amount of stabiliser present; relevant to the fixture time results as depicted, Example 1 and Example 2 were formulated with 50 parts-per-million (ppm) of the stabiliser boron trifluoride (BF.sub.3), whereas Example 3, and Example 4 were formulated with 20 ppm BF.sub.3.

(12) FIG. 5 depicts bar charts showing the results of T-peel tests for soft solid form ethyl cyanoacrylate compositions Example 1 (‘Ex.1’), Example 2 (‘Ex.2’), Example 3 (‘Ex.3’), and Example 4 (‘Ex.4’), and for the comparative TPU-negative compositions: 401, 454, 60 secs, and SuperTape, as measured according to ASTM D903-04, on a mild steel (MS) substrate. The bar charts show results for compositions cured for 1 week at room temperature (25° C.) prior to testing, and for compositions cured for 3 days at room temperature (25° C.) followed by heating the coupons used in the test to 90° C. for 1 day (24 hours) prior to testing. Said coupons were prepared according to Federal Specification QQ-S-698.

(13) FIG. 6(A) shows a side view of a container 1 suitable for holding a curable composition of the present invention. The container is tubular being cylindrical in cross-section having cylindrical side walls 2. On the base of the container is a knurled wheel 3 which forms part of a propulsion mechanism for a (soft-solid or semi-solid) mass or stick 4 of the curable cyanoacrylate composition of the present invention. The mass 4 has been cast in a generally cylindrical shape. The container 10 further comprises a cap 5 which is snap-fit engageable over the top end 6 of the container 1 to protect the mass 4 of product. The top end 6 is of lesser diameter than the side walls 2 and has a rim 7 which engages in a corresponding recess on the underside of the cap 5 to secure the cap 5 in place. The knurled wheel 3 is attached to an elongate drive or winding shaft 8 which is centrally located within the housing formed by the side walls of the container. On the winding shaft 8 is located a moveable carrier 9. The carrier 9 is generally cylindrical (from an end view thereof, see for example FIG. 6(B)) and has a short peripheral upstanding wall 10 formed on its base 11. During the casting process the carrier 9 is positioned to secure itself to the lower end 12 of the mass 4 on solidification of the mass 4. Indeed the mass 4 may be cast also with the shaft 8 (and optionally the wheel 3) in place. The mass 4 can be considered to be in stick-form as that term is used in herein.

(14) As best seen from FIG. 6(B) the carrier 9 has a central threaded aperture 13 in which the threads 16 of the shaft 8 engage. The knurled wheel 3 and the shaft 8 are both mounted for relative rotation to the container body. When the wheel 3 is turned in the direction of the arrow it moves the carrier up or down the shaft 8 thus controlling the relative position of the mass and the container. In the position shown the carrier has travelled part way up the shaft, moving the mass to a position where it protrudes from the container. The mass can then be applied by rubbing against a substrate by manual force. Sufficient shearing of the mass takes place to allow it to rub off onto the substrate. No separate applicator/brush etc. is necessary. The composition can be applied with manual pressure.

(15) To prevent rotation of the carrier 9 with the shaft, elongate ribs 14 are provided on opposing sides of the internal wall of the container. The ribs 14 run from the base of the container to a position proximate to the mouth of the container. The ribs 14 each engage one of corresponding grooves 15 in the carrier 9 thus preventing relative rotation of the container and the carrier and ensuring that the carrier moves upwardly or downwardly when the shaft 8 turns. The carrier 9 and the mass 4 can be retracted by rotation of the wheel 3 in an opposing direction.

EXAMPLES

Synthesis of Example Thermoplastic Polyurethanes, Suitable for Practising the Present Invention

(16) Example TPU composition, ‘Example TPU-A’ was prepared as follows: Into a three necked resin kettle vessel was placed 370.33 g of polyol Dynacoll 7380 (Evonik), along with 2.15 g of Irganox 1010 (Ciba) antioxidant. Irganox is a registered trademark; Irganox 1010 is pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate). A 1-3 mbar vacuum was then applied to the vessel. The Dynacoll 7380 polyol, having a melting point of 70° C. and described as a solid highly crystalline saturated co-polyester, was melted at between 110-120° C. Melting under vacuum increases the efficiency of the degassing and moisture-removal procedure, while also reducing the possibility of depletion of the polyol due to deposition on the side walls of the vessel. Once melted (˜30-40 mins), the polyol was stirred for 30 mins at 100 revolutions-per-minute (rpm) under vacuum, allowing for further removal of unwanted moisture. The vacuum was then removed by introducing a slight flow of dinitrogen gas (N.sub.2). A 47.59 g flake of the isocyanate compound MDI was added through a wide-necked funnel, starting the reaction. The vessel was stoppered and the N.sub.2 flow removed. The reaction was maintained at 115° C. and the stirrer speed was increased to 250 rpm for 15 mins without vacuum. After this time the reaction vessel was again placed under vacuum (1-3 mbar) for 15 mins. Then, as a quality control step to ensure the reproducibility of the M.sub.w distributions, the vacuum was removed again and three 1 g samples were taken from the vessel to correctly determine the remaining amount of unreacted isocyanate groups using triplicate titrations. The vessel was then stoppered and placed under vacuum again, with continuous stirring for a further 30 mins. The vacuum was then removed by introducing a slight flow of N.sub.2 gas. The chain extender, in this case 1,4-butanediol, was now added (9.94 g) to the vessel under N.sub.2 via a dropping funnel to ensure full delivery. Once all of the 1,4-butanediol had been added to the vessel, the vessel was stoppered and the mixing speed was maintained at 250 rpm. The reaction proceeded for 15 mins without vacuum, and fora further 15 mins under vacuum; during this stage, the reaction, which is exothermic, was allowed to proceed at a temperature of 115° C., while ensuring that the temperature did not exceed 125° C. The TPU prepared this way is termed ‘Example TPU-A’. At the end of this time, the TPU that had formed was collected by filtration, and allowed to cool to room temperature. The glass transition temperature (Tg) of Example TPU-A is −32.3° C., and its melting point is 57.4° C., as determined by differential scanning calorimetry.

(17) The TPU was finely cut into small pieces and then rapidly mixed with the ethyl cyanoacrylate (comprising a desired final concentration of stabiliser), at 65° C., in the weight-percentages listed in the Table 3 (‘Example compositions of the present invention’). Once the mixture had been allowed to cool back down to room-temperature, a solid composition was obtained which is an embodiment of the current invention. The rate of cooling depends on several factors such as the M.sub.w and crystallisation rate of the TPU. For example, and without any intention of limiting the invention, the cooling rate can be from about 65° C. to room-temperature (25° C.) in 30 mins. Differential scanning calorimetry can be used to determine solidification rate and melting temperature, for example the solidification rate and melting temperature of a TPU, according to standard procedure ISO 11357.

(18) A similar TPU (‘Example TPU-B’), differing compositionally only in the weight percentages of the relevant components, was also prepared according to an identical method (Table 2). The glass transition temperature (Tg) of Example TPU-B is −35.7° C., and its melting point is 52.2° C., as determined by differential scanning calorimetry. Tables 1-3 provided below summarise the TPU compositions, and detail formulations of cyanoacrylate compositions comprising said Example TPUs. Freshly prepared stock Stabiliser Solution is used to mix in BF.sub.3 (a stabiliser of the curable cyanoacrylate component) to a pure ECA component of the formulations (forming thereby a ‘stabilised ECA component’), prior to the addition of the given TPU, to ensure that the desired final concentration of stabiliser can be conveniently achieved (for example, 50 ppm BF.sub.3, or for example, 20 ppm BF.sub.3). Stabiliser Solution comprises curable ethyl cyanoacrylate (ECA); therefore the total amount of curable ethyl cyanoacrylate (ECA) reported the Example Compositions described in Table 3 includes the contribution from both the pure ECA solution and the Stabiliser Solution. By way of example, the composition Example 1 comprises a stabiliser, BF.sub.3, at a final concentration of 50 ppm by weight, said BF.sub.3 content being adjusted/determined by the addition of Stabiliser Solution; accordingly composition Example 1 comprises a total of 89.995 wt % ECA (ECA from the initially pure ECA solution and yet further ECA from the stock Stabiliser Solution comprising 1000 ppm BF.sub.3), wherein the wt %'s are based on the total weight of the composition.

(19) TABLE-US-00001 TABLE 1 Components used for synthesis of TPU-A Mass (g) Percentage by weight Dynacoll 7380 (polyol) 370.33 86.12 MDI 47.59 11.07 1,4-Butanediol 9.94 2.31 Irganox 1010 2.15 0.50 Total 430.01 100

(20) TABLE-US-00002 TABLE 2 Components used for synthesis of TPU-B Mass (g) Percentage by weight Dynacoll 7380 (polyol) 370.03 85.99 MDI 47.55 11.05 1,4-Butanediol 10.27 2.39 Irganox 1010 2.15 0.50 Total 430.00 100

(21) TABLE-US-00003 TABLE 3 Example Compositions of the present invention Example Compositions Component Example 1 Example 2 Example 3 Example 4 Total Ethyl 89.995 wt % 89.995 wt % 84.998 wt % 84.998 wt % cyanoacrylate (ECA) Boron  0.005 wt %  0.005 wt %  0.002 wt %  0.002 wt % trifluoride That is: a final That is: a final That is: a final That is: a final (BF.sub.3); [From concentration concentration concentration concentration fresh stock of 50 ppm of 50 ppm of 20 ppm of 20 ppm Stabiliser Solution comprising 1000 ppm BF.sub.3 in ECA] Example  10.0 wt % — —  15.0 wt % TPU-A Example —  10.0 wt %  15.0 wt % — TPU-B Physical form Two phase Two phase Two phase Soft solid, at 25° C. liquid/crystalline; liquid/crystalline; liquid/crystalline; non-flowable non-flowable non-flowable non-flowable (stick) soft solid (stick) soft solid (stick) soft solid (stick)

(22) By way of example, and with no intention of limiting the invention, the following compositions are embodiments of the invention.

Formulation of Composition Example 1

(23) A composition was formulated to comprise a total of 89.995 wt % curable ethyl cyanoacrylate, 0.005 wt % of the stabiliser BF.sub.3 (i.e. 50 ppm by weight), and then 10 wt % of Example TPU-A, wherein the weight-percentages (wt %) are based on the total weight of the composition. Stabiliser Solution (1000 ppm BF.sub.3 in ECA) was used to adjust the amount of BF.sub.3 in the curable ethyl cyanoacrylate component to the desired concentration of 50 ppm (forming a stabilised ECA component); then, the Example TPU-A was finely sliced and rapidly mixed with the stabilised ECA component at 65° C. for a time sufficient dissolve the TPU component (melting point=57.4° C.) into the stabilised ECA component. The resulting composition was cast directly in to a tubular stick cartridge of the type shown in FIG. 6(A, B), and as described in the description of FIG. 6, and allowed to cool to 25° C. The resulting curable cyanoacrylate composition, Example 1, was a non-flowable soft solid in stick-form at 25° C.

Formulation of Composition Example 2

(24) A composition was formulated to comprise a total of 89.995 wt % curable ethyl cyanoacrylate, 0.005 wt % of the stabiliser BF.sub.3 (i.e. 50 ppm by weight), and then 10 wt % of Example TPU-B, wherein the weight-percentages (wt %) are based on the total weight of the composition. Stabiliser Solution (1000 ppm BF.sub.3 in ECA) was used to adjust the amount of BF.sub.3 in the curable ethyl cyanoacrylate component to the desired concentration of 50 ppm (forming a stabilised ECA component); then, the Example TPU-B was finely sliced and rapidly mixed with the stabilised ECA component at 65° C. for a time sufficient dissolve the TPU component (melting point=52.2° C.) into the stabilised ECA component. The resulting composition was cast directly in to a tubular stick cartridge of the type shown in FIG. 6(A, B), and as described in the description of FIG. 6, and allowed to cool to 25° C. The resulting curable cyanoacrylate composition, Example 2, was a non-flowable soft solid in stick-form at 25° C.

Formulation of Composition Example 3

(25) A composition was formulated to comprise a total of 84.998 wt % ethyl cyanoacrylate, 0.002 wt % of the stabiliser BF.sub.3 (i.e. 20 ppm by weight), and then 15 wt % of Example TPU-B, wherein the weight-percentages (wt %) are based on the total weight of the composition. Stabiliser Solution (1000 ppm BF.sub.3 in ECA) was used to adjust the amount of BF.sub.3 in the curable ethyl cyanoacrylate component to desired concentration of 20 ppm (forming a stabilised ECA component); then, the Example TPU-B was finely sliced and rapidly mixed with the stabilised ECA component at 65° C. for a time sufficient dissolve the TPU component (melting point=52.2° C.) into the stabilised ECA component. The resulting composition was cast directly in to a tubular stick cartridge of the type shown in FIG. 6(A, B), and as described in the description of FIG. 6, and allowed to cool to 25° C. The resulting curable cyanoacrylate composition, Example 3, was a non-flowable soft solid in stick-form at 25° C.

Formulation of Composition Example 4

(26) A composition was formulated to comprise a total of 84.998 wt % ethyl cyanoacrylate, 0.002 wt % of the stabiliser BF.sub.3 (i.e. 20 ppm by weight), and then 15 wt % of Example TPU-A, wherein the weight-percentages (wt %) are based on the total weight of the composition. Stabiliser Solution (1000 ppm BF.sub.3 in ECA) was used to adjust the amount of BF.sub.3 in the curable ethyl cyanoacrylate component to the desired concentration of 20 ppm (forming a stabilised ECA component); then, the Example TPU-A was finely sliced and rapidly mixed with the stabilised ECA component at 65° C. for a time sufficient dissolve the TPU component (melting point=57.4° C.) into the stabilised ECA component. The resulting composition was cast directly in to a tubular stick cartridge of the type shown in FIG. 6(A, B), and as described in the description of FIG. 6, and allowed to cool to 25° C. The resulting curable cyanoacrylate composition, Example 4, was a non-flowable soft solid in stick-form at 25° C.

(27) Soft-solid stick-form ethyl cyanoacrylate compositions Examples 1-4, formulated as described, were subject to a range of comparative tests versus commercially available ethyl cyanoacrylate control compositions containing no TPU (i.e. TPU-negative compositions): LOCTITE 401 (401; liquid form), LOCTITE 454 (454; liquid form), LOCTITE 60 Sec. glue (60 secs; liquid form), and solid-form Super Tape (FIGS. 1-5). LOCTITE and Super Tape are registered trademarks.

(28) The tensile shear performance of compositions Example 1, Example 2, Example 3, and Example 4 was compared against the control compositions on three substrates: Grit-blasted Mild Steel (GBMS), Polycarbonate (PC), and Beechwood (See FIG. 1). The overall performance of the compositions Example 1, Example 2, Example 3, and Example 4 was comparable to that of the liquid form TPU-negative compositions (401, 454, 60 secs), and exhibited improved performance on these substrates over the solid format Super Tape control. The greatest tensile shear values measured for the compositions Example 1, Example 2, Example 3, and Example 4 were on GBMS substrate.

(29) The side impact performance of the compositions Example 1, Example 2, Example 3, and Example 4, as measured according to standard test method GM9751P, was compared to that of the control compositions. In one set of tests the compositions were cured for 1 week at room temperature prior to side impact testing (FIG. 2), and in another set of tests the compositions were cured for 3 days at room temperature followed by 1 day at 90° C. prior to side impact testing (FIG. 3). The compositions Example 1, Example 2, Example 3, and Example 4 showed excellent impact resistance, outperforming all of the TPU-negative control compositions in both sets of tests (FIG. 2 and FIG. 3); evidencing that desirable toughening of the compositions had been achieved. When tests were performed as described for FIG. 2, in 100% of tests the compositions Example 2, Example 3 and Example 4 did not break (% DNB) following side impact; in 33% of tests the composition Example 1 did not break following side impact. When tests were performed as described for FIG. 3, in 100% of tests the composition Example 1 did not break; in 66% of tests the composition Example 2 did not break; and in 33% of tests the composition Example 3 did not break. Taken as a whole the results for these Example compositions indicate that the compositions containing TPU solidifying agents exhibit remarkable side impact resistance, representing a considerable improvement over the TPU-negative comparative compositions.

(30) Fixture times of the compositions Example 1, Example 2, Example 3, and Example 4, were measured at 22.2° C., and a relative humidity 56.7%, by stressing a single adhesive overlap joint with the application of a 3 kg tensile force parallel to the bond area and to the major axis of the polycarbonate test lap shear specimens. Fixture time tests were performed by applying a small quantity of curable composition to the surface of one polycarbonate lap shear (time=0 s), spreading the composition evenly using a clean applicator stick so as to ensure that when the mating polycarbonate lap shear specimen was subsequently placed on top of the lap shear to which curable cyanoacrylate composition had been applied, a 323 mm.sup.2 (0.5 inch.sup.2) overlap bond area was completely covered. In these tests, the composition was only applied to one of the two lap shears that mate, the completed assembly resting on a flat surface. The mated lap shears were then clamped with a clamp load of 45 N using spring clamps, positioned at 6 mm (0.25 inches) from the edge of the lap, taking care to ensure the correct alignment of the lap shears. At a schedule of tested cure time intervals, in separate repeated tests, the clamps were carefully removed, the lap shear assembly was gently lifted off a surface, and a 3 kg weight block was carefully placed on the lower lap shear. Fixture was considered to have occurred if, in three consecutive tests at a given cure time interval post-application, the lap shear assembly supported the 3 kg block for at least 5 seconds. Cure time intervals assessed in these fixture time tests (relative to t=0 s) were: 5 s, 10 s, 20 s, 25 s, 30 s, 45 s, 60 s, 75 s, 90 s, 105 s, 120 s, 150 s, and 180 s. The fixture times of the compositions Example 1, Example 2, Example 3, and Example 4 were compared to those of the TPU-negative control compositions (FIG. 4). The TPU-negative control compositions all exhibit fixture times of around 60 seconds or less. In contrast, it was found that in the presence of 20-50 ppm of the Lewis acid stabiliser BF.sub.3, the fixture time of the soft solid TPU-positive compositions was slower, and had been extended out to from about 100 seconds to about 120 seconds (FIG. 4).

(31) Toughness of the compositions was assessed, in part by, performing T-peel tests on a substrate of Mild Steel (MS) according to standard test method ASTM D903-04 (FIG. 5). Coupons for use in the T-peel tests were prepared according to Federal Specification QQ-S-698. Prior to T-peel testing, said coupons of the test method were cured either for 1 week at room temperature (25° C.), or for 3 days at 25° C. followed by heating to 90° C. for 24 hours. The compositions Example 1, Example 2, and Example 3 outperformed the control compositions. The compositions Example 1, Example 2, Example 3, and Example 4 exhibited remarkably enhanced toughness when the compositions had been heat treated to 90° C. for 1 day prior to T-peel testing. Heat treatment produced no improvement in the T-peel performance of the TPU-negative comparative compositions.

Comparative Examples

(32) Not every TPU will impart solidity to a curable cyanoacrylate composition. To illustrate this the following are comparative examples in which TPUs not according to the claims were tested for their ability to impart solidity on curable ethyl cyanoacrylate. A range of compositions were prepared by mixing uncured liquid ethyl cyanoacrylate with TPUs that are not based on polyols based on diol units with greater 10 carbon atoms in the main chain (>C.sub.10), nor based on dicarboxylic acid units with greater 10 carbon atoms in the main chain (>C.sub.10). Such TPUs include Pearlstick® 48-60/03 (‘48-60/03’), Pearlstick® 48-60/30 (‘48-60/30’), Pearlbond® DAP 893 (‘DAP 893’), and Pearlbond® D1160/L (‘D1169L’) (commercially available from Merquinsa/Lubrizol, Carrer del Gran Vial, 17, 08160 Montmelo, Barcelona, Spain). DAP 893 is a linear polycaprolactone-copolyester thermoplastic polyurethane, while D1169L, 48-60/03, and 28-60/30 are all linear aromatic thermoplastic polyurethanes. The TPUs were finely sliced and then separately dissolved by rapid mixing at 65° C. in separate batches of ethyl cyanoacrylate. Each TPU was added at 5 wt %, 10 wt % or 15 wt % based on the total weight of the resulting TPU-ECA mixture. The mixture was allowed to cool back to room temperature (25° C.). Unlike the compositions claimed in the present invention, in no case did the addition of these particular TPUs at these comparable weight percentages (5-15 wt %) result in soft-solid form curable cyanoacrylate compositions at 25° C. All of the resulting compositions were in liquid form at 25° C., with varying viscosity, and thus could clearly not be formed as sticks. Viscosity was measured at 25° C. using a Brookfield LVT 4 viscometer. The results of these comparative tests are summarised in Table 4 below:

(33) TABLE-US-00004 TABLE 4 Comparative compositions-TPUs tested to see whether they were capable of imparting solidity to ethyl cyanoacrylate at 25° C. 5 wt % 10 wt % 15 wt % TPU TPU in ECA, TPU in ECA, TPU in ECA, tested Viscosity and Form Viscosity and Form Viscosity and Form ‘48-60/03’ 206 mPa .Math. s, Liquid 8410 mPa .Math. s, Liquid 18000 mPa .Math. s, Liquid ‘48-60/30’ 1200 mPa .Math. s, Liquid 13800 mPa .Math. s, Liquid >20000 mPa .Math. s, Liquid ‘D1160L’ 325 mPa .Math. s, Liquid 8970 mPa .Math. s, Liquid >20000 mPa .Math. s, Liquid ‘DAP 893’ 19.0 mPa .Math. s, Liquid 126 mPa .Math. s, Liquid 470 mPa .Math. s, Liquid

(34) These Comparative Examples strikingly demonstrate that—without foreknowledge of the claimed compositions—it is not at all trivial or straightforward to identify TPUs that can simultaneously impart solidity to curable cyanoacrylate compositions, and that are chemically compatible with the cyanoacrylate component (i.e. that do not destabilise the cyanoacrylate). Furthermore, it is not straightforward to identify such TPUs and that also do not adversely impact on T-peel shear strength.

(35) 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.

(36) 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.