Adhesive compositions

Abstract

The present invention concerns a curable adhesive composition, wherein the composition is a two-component composition comprising: (A) an adhesive component comprising: (i) an aliphatic glycidyl ether; (ii) a cycloaliphatic epoxy and/or an aromatic glycidyl ether; and (iii) a silane reducing agent; and (B) a catalyst component comprising: (iv) a Group 9 or Group 10 noble metal catalyst, wherein the adhesive component (A) and/or the catalyst component (B) further comprises an initiator; articles coated by the composition or component compositions thereof; methods of bonding articles using the composition or component compositions thereof; and kits comprising the composition or component compositions thereof.

Claims

1. A contact curable adhesive composition, wherein the composition is a physically separated two-component composition that cures upon contact of the two components, the composition comprising: (A) an adhesive component comprising: (i) an aliphatic glycidyl ether; (ii) an aromatic glycidyl ether and optionally a cycloaliphatic epoxy; and (iii) a silane reducing agent; and (B) a catalyst component comprising: (iv) a Group 9 or Group 10 noble metal catalyst, wherein the adhesive component (A) and/or the catalyst component (B) further comprises an initiator.

2. The contact curable adhesive composition according to claim 1, wherein the aliphatic glycidyl ether is an aliphatic di- or tri-glycidyl ether.

3. The contact curable adhesive composition according to claim 1, wherein the cycloaliphatic epoxy is a dicycloalkyl epoxy.

4. The contact curable adhesive composition according to claim 1, wherein the aromatic glycidyl ether is an aromatic di- or tri-glycidyl ether.

5. The contact curable adhesive composition according to claim 1, wherein the initiator is an iodonium salt selected from (4-n-octyloxyphenyl)phenyliodonium hexafluoroantimonate (OPPI SbF.sub.6), (4-n-decyloxyphenyl)phenyliodonium hexafluorophosphate (DOPI PF.sub.6), di(t-butylphenyl)iodonium hexafluoroarsenate (DTBPI AsF.sub.6), and (4-methylphenyl)-(4-isopropylphenyl)iodonium tetrakis pentafluorophenylborate (Rhodorsil 2074).

6. The contact curable adhesive composition according to claim 1, wherein the silane reducing agent is of the formula (Ar).sub.2RSiH, wherein Ar is an optionally substituted 6-10-membered aryl or heteroaryl group, and R is an optionally substituted C.sub.1-6 alkyl group.

7. The contact curable adhesive composition according to claim 6, wherein Ar is an optionally substituted phenyl group.

8. The contact curable adhesive composition according to claim 6, wherein R is an optionally substituted methyl group.

9. The contact curable adhesive composition according to claim 1, wherein the Group 9 or Group 10 noble metal catalyst is a platinum or palladium catalyst.

10. The contact curable adhesive composition according to claim 1, wherein the Group 9 or Group 10 noble metal catalyst has an oxidation state of 0 or 2.

11. The contact curable adhesive composition according to claim 1, wherein the Group 9 or Group 10 noble metal catalyst is of the formula M(II)(X).sub.2(Y), wherein M is a metal selected from palladium and platinum, (II) represents the oxidation state of M, X is a monovalent ligand selected from halide, water, hydroxyl, cyanide, carbon monoxide, and ammonia, and Y is a bidentate ligand selected from a C.sub.1-6 alkylenediamine group, a C.sub.1-6 alkyl 1,3-dicarbonyl anion, a 1,2-dicarbonyl anion, a phenanthroline group, a bipyridyl group, and a cycloalkadienyl group.

12. The contact curable adhesive composition according to claim 11, wherein X is halide.

13. The contact curable adhesive composition according to claim 11, wherein Y is a cycloalkadienyl group.

14. The contact curable adhesive composition according to claim 1, wherein the catalyst component (B) further comprises a carrier selected from a solvent-based paint composition, a water-based paint composition, a VOC-free paint composition, a powder coat composition, an electro-coating composition, a polymeric film, a fibre-based film or resin, a thermoplastic polymer composition, and a thermosetting polymer composition, and the catalyst is provided at an outer surface of the carrier.

15. A method of curing a contact curable adhesive composition, wherein the composition is a physically separated two-component composition that cures upon contact of the two components, the method comprising: bringing an adhesive component (A) into contact with a catalyst component (B), wherein the adhesive component (A) comprises: (i) an aliphatic glycidyl ether; (ii) an aromatic glycidyl ether and optionally a cycloaliphatic epoxy; and (iii) a silane reducing agent; wherein the catalyst component (B) comprises: (iv) a Group 9 or Group 10 noble metal catalyst; and wherein the adhesive component (A) and/or the catalyst component (B) further comprises an initiator.

16. The method according to claim 15, further comprising heating the contact curable adhesive composition at a temperature of up to 180 C.

17. The method according to claim 16, wherein the contact curable adhesive composition is heated for a period of time of up to 60 minutes.

18. A cured composition obtained by the method of claim 15.

Description

(1) FIG. 1 shows the individual reactivity of an aliphatic glycidyl epoxy (A), a cycloaliphatic epoxy (B), and an aromatic glycidyl epoxy (based on Bisphenol A; C). The results show that the aliphatic glycidyl epoxy is reactive at room temperature, the cycloaliphatic epoxy is reactive at temperatures between 100 and 200 C., and the aromatic glycidyl epoxy has a medium level of reactivity between 200 and 250 C.

(2) FIG. 2 shows the reactivity of certain mixtures of an aliphatic glycidyl epoxy (1,6-hexandiol-diglycidether) and an aromatic glycidyl epoxy (based on Bisphenol A). The results show that mixtures of these components (A-C) also react at temperatures below 100 C., whereas the aromatic glycidyl epoxy alone (D) requires much higher temperatures for curing.

(3) FIG. 3 shows the influence of the amount of catalyst on the reaction rate for a mixture of an aliphatic glycidyl epoxy (1,6-hexandiol-diglycidether) and an aromatic glycidyl epoxy (based on Bisphenol A-epichlorohydrin). The results show that a contact cure is possible with this mixture. Furthermore, the rate of reaction increases as the amount of catalyst on the contact surface is increased.

(4) FIG. 4 shows the reactivity of the adhesive formulations according to Table 2, as measured by differential scanning calorimetry (DSC) measurements. The results show that each composition has an optimum reactivity at below 100 C. for curing.

(5) FIG. 5 shows a dynamic mechanical thermal analysis (DMTA) trace showing the network development of the adhesive formulations according to Table 2, by monitoring the increase in elastic modulus (G) with time. The results suggest that each formulation provides a comparable bond, but that formulations comprising an aliphatic glycidyl ether (i.e. 1.6-hexane diglycidyl ether), a further aliphatic glycidyl ether, and an aromatic glycidyl ether (i.e. bisphenol-A-epichlorohydrin resin) have a slightly longer induction time.

(6) FIG. 6 shows the results of a T peel test on the adhesive formulation of Example 4. Powder coated panels were prepared and cured at various temperatures: 100 C., 120 C., 140 C., 160 C. and 180 C. for both textured (NW36/2; left-hand bar) and smooth (NW35/2; right-hand bar) surfaces. The results show that the bond strength is improved when the powder coated catalyst component is first cured to the substrate panel at higher temperatures, i.e. 140 to 160 C.

(7) FIG. 7 shows the lap shear strengths of a number of carbon fibre (CF) panels, which have been powder coated with a catalyst component composition and cured with an adhesive component composition according to the invention to another panel of carbon fibre (CF) or aluminium (AR14). The results are also shown in Table 4, where samples 1-9 correspond with lines A-I, respectively.

(8) FIG. 8 shows the lap shear strengths of steel panels, which have been powder coated with a catalyst component composition and cured with an adhesive component composition according to the invention to another panel of steel.

EXAMPLES

Example 1Improved Lap Shear Strength

(9) Lap shear tests were conducted according to DIN EN 1465 at room temperature. The expression lap shear strength is synonymous with the expression half lap bond strength.

(10) Substrates: 1 mm thick Aluminium 2024 panel.

(11) Lap shear strengths were measured using an Instron 5967 Instrument.

(12) Lap shear strengths were prepared using coupons either cut from aluminium QUV Test panels (150 mm100 mm) as supplied by Q-Panel or using coupons pre-cut to the correct length, usually 100 mm25 mm in size.

(13) Where appropriate, the panels/coupons were either coated with the adhesive component composition or powder coated with a powder coat catalyst component composition prior to testing or left uncoated (i.e. the adhesive component composition was applied directly to the catalyst component composition).

(14) Types of Joints Prepared: 1) Powder coated coupon to Powder coated coupon, with adhesive component applied between the two coupons to one of the powder coated coupons, or 2) Powder coated coupon to blank coupon, with adhesive component applied between the two coupons to either the powder coated coupon or the blank coupon.

(15) The powder coatings were prepared by adding the desired amount of catalyst to the premix of the powder coating (EPDXYPOL BT ULTRA, 30686, by Valspar), high speed mixing the dry mix, compounding in a twin screw extruder and grinding on an air classifying mill, followed by post sieving.

(16) Test Parameters:

(17) Bond Area: 25 mm12.5 mm

(18) Preload: 10N

(19) Rate of Extension: 10.0 mm/min

(20) End of Test Criteria: 5.0 mm

(21) The testing of different resin mixtures after 3 h and after 24 hours curing at room temperature is shown in Table 1 below.

(22) TABLE-US-00008 TABLE 1 Lap shear strength [MPa] parts of after 3 hours aliphatic parts of Bisphenol-A- room after 24 h room glycidyl epoxy epichlorhydrin resin temperature temperature 100 0 1.3 100 100 4.5 7.2 50 150 1.5 7.8 0 100 did not cure did not cure

(23) The adhesive composition was prepared by mixing the aliphatic glycidyl epoxy (1,6-hexandiol-diglycidether) with the Bisphenol-A-epichlorhydrin in their respective amounts, along with at least an initiator (OPPI) and a silane (diphenylmethylsilane). The catalyst was contained in a catalyst component composition comprising Pt (II) Cl.sub.2 (cod) catalyst and a thermosetting epoxy polyester resin (EPDXYPOL BT ULTRA, 30686, by Valspar). The results show that mixtures of aliphatic glycidyl epoxy with Bisphenol-A-epichlorhydrin resin increases the lap shear strength. Lap shear strengths of 7-8 N/mm.sup.2 were achieved

Example 2Adhesive Mixtures

(24) A number of different adhesive component mixtures were prepared, as set out in Table 2. These compositions also contained an initiator (OPPI) and a silane (diphenylmethylsilane), and a Pt catalyst (Pt (II) Cl.sub.2 (cod)) was added to activate the polymerisation/curing process.

(25) TABLE-US-00009 TABLE 2 1,6- Bisphenol-A- Hexandiol- epichlrohydrin diglycidether resin aliphatic glycidether A 1000 parts 1000 parts B 500 parts 1000 parts 500 parts Glycerintriglycidether C 500 parts 1000 parts 500 parts Pentaerythriolpolyglycidether D 500 parts 1000 parts 500 parts Trimethylolpropanetriglycidether

(26) DSC measurements are shown in FIG. 4 and cure rates are shown in FIG. 5. Each formulation has an optimum reactivity at below 100 C. for curing, and provide comparable bonding, but formulations comprising an aliphatic glycidyl ether (i.e. 1.6-hexane diglycidyl ether), a further aliphatic glycidyl ether, and an aromatic glycidyl ether (i.e. bisphenol-A-epichlorohydrin resin) take slightly longer to achieve the same results.

Example 3Substrates

(27) Substrates which have been successfully bonded with the two-component adhesive composition of the invention include:

(28) Aluminium: NG5754, A46, AL46, and AR14.

(29) Steel: S275.

(30) Magnesium: AZ31.

(31) Plastics: PA6, PA6/ABS, and PP (the substrate surface was first functionalised using either a flame or corona treatment, and every test showed failure of the polypropylene material before the bond strength could be determined, i.e. the bond was stronger than the substrate material).

(32) Composites: Carbon fibre composite.

(33) Where magnesium substrates were employed, it was found that the magnesium could lead to poisoning of the catalyst. Thus, a coating on the magnesium surface may be required to prevent this from occurring. Surprisingly, it was found that a coating of the catalyst component composition (e.g. powder coat) of the invention, particularly at a thickness of 40 to 80 m, prevented the catalyst from being poisoned.

Example 4T-Peel Tests

(34) T-Peel Strengths were measured using the Zwick Universal Testing System.

(35) TABLE-US-00010 Device UTS from Zwick Serial number 801240/99 temperature room temperature rate 100 mm/min

(36) Powder coated panels of catalyst component (comprising Pt (II) Cl.sub.2 (cod) catalyst (0.3% by weight, 52 wt % platinum) and a thermosetting epoxy polyester resin) were prepared and cured at various temperatures: 100 C., 120 C., 140 C., 160 C. and 180 C. for both textured (NW36/2) and smooth (NW35/2) surfaces (this cured the powder coating to the panel and allowed it to be stored for subsequent use with the adhesive). The adhesive (composition shown below) was pre-cured at room temperature for 24 hours, and then the adhesive and powder coated catalyst were cured at 70 C. for 1 hour. Similar results can also be obtained without pre-curing of the adhesive.

(37) The adhesive component composition (liquid composition) was as follows:

(38) TABLE-US-00011 ADEKA resin ED 503 (1,6-hexanediol diglycidyl ether) 1000 parts Epikote resin 862 (BFDGE; based on bisphenol-F) 1000 parts OPPI hexafluoroantimonate 10 parts Diphenylmethylsilane 34 parts Deolink Epoxy TM-100 2 parts Genioperl P52 360 parts

(39) The powder coatings were electro-statically applied to the earthed substrate using a Wagner hand gun with the following parameters and subsequently cured in an electric or gas oven.

(40) TABLE-US-00012 Powder Coat Settings Program P01 P02 Kv 100 50 A 80 20 Cloud Volume, % 50 40 Oven Temp 100-180 C. 100-180 C. Time 30 mins. 30 mins.

(41) The results of the T peel test are shown in FIG. 6.

Example 5Catalyst Studies

(42) In order to evaluate the amount of platinum catalyst required to achieve the required fixture bond strength after 45 minutes, aluminium substrates were prepared with different amounts of platinum catalyst. These were tested by DSC measurements and by simple tests to determine the time to achieve a fixture bond. The adhesive component formulation was applied onto one aluminium substrate (i.e. without catalyst), and then a second substrate having a coating containing the platinum catalyst was placed on top. The results are shown in Table 3.

(43) TABLE-US-00013 TABLE 3 observation after 45 minutes amount of Pt (II) Cl.sub.2 (cod) with adhesive catalyst/area (aliphatic/aromatic glycidyl mg/cm.sup.2 g/m.sup.2 ether) 0.03 0.31 Fixture bond 0.06 0.56 Fixture bond 0.09 0.85 Fixture bond 0.11 1.05 Fixture bond 0.13 1.34 Fixture bond 0.16 1.62 Fixture bond 0.19 1.94 Fixture bond 0.21 2.12 Fixture bond

(44) It was found that the Pt (II) Cl.sub.2 (cod) catalyst reacts very rapidly, and at lower concentrations of catalyst on the surface than for other catalysts. All samples tested achieved fixture bond for handling after 45 minutes. Also, an adhesive component composition containing both an aliphatic and aromatic glycidyl epoxy was found to react more rapidly than that with just an aliphatic glycidyl epoxy resin. It was also noted that a concentration of 0.3 g/m.sup.2 is sufficient to achieve the required fixture bond strength after 45 minutes.

Example 6Lap Shear Strengths Carbon Fibre Joints

(45) Carbon fibre reinforced polymer (CFRP), smooth side (NW35/2) was applied with a powder coating of Pt (II) Cl.sub.2 (cod) catalyst (0.3% by weight catalyst, 52 wt % platinum) and the powder coat cured for 20 minutes at 140 C. Lap shear joints were prepared, and then bonded with adhesive for 24 hrs ambient cure and 1 hr post cure at 70 C. The lap shear results are shown in Table 4 and FIG. 7. For uncoated materials, the adhesive was applied on top of the powder coating immediately prior to bonding.

(46) TABLE-US-00014 TABLE 4 Extension Load Maximum at Max at Break Elong at Break Stress at Break Strain at Load [N] Load [mm] [N] [mm] [N/mm.sup.2] Break [%] Failure Mode Sample 1 - CF (NW35/2(0.3%) + 8195.88 2.58 8195.88 2.57755 25.41 25775.46 50% Adhesive, CF (NW35/2(0.3%)) 50% Cohesive Sample 2 - CF (NW35/2(0.3%) + 7763.25 2.03 7763.25 2.03254 24.07 20325.38 50% Adhesive, AR14 (NW35/1(0%)) 50% Cohesive Sample 3 - CF (NW35/2(0.3%) + 6728.18 1.80 6728.18 1.80457 20.86 18045.69 50% Adhesive, AR14 (NW35/1(0%)) 50% Cohesive Sample 4 - CF (NW35/2(0.3%) + 7145.15 2.01 7093.23 2.02670 21.99 20266.99 50% Adhesive, AR14 (NW35/2(0.3%)) 50% Cohesive Sample 5 - CF (NW35/2(0.3%) + 7312.68 1.94 7312.68 1.93807 22.67 19380.73 50% Adhesive, AR14 (NW35/2(0.3%)) 50% Cohesive Sample 6 - CF (NW35/2(0.3%) + 2006.00 0.45 1916.36 0.46953 5.94 4695.28 50% Adhesive, AR14 (Uncoated, Treated)) 50% Cohesive Sample 7 - CF (NW35/2(0.3%) + 2926.73 0.70 2816.77 0.71881 8.73 7188.12 50% Adhesive, AR14 (Uncoated, Treated)) 50% Cohesive Sample 8 - CF (NW35/2(0.3%) + 1701.63 0.42 1701.63 0.42413 5.28 4241.25 70% Adhesive, CF (Uncoated) 30% Cohesive Sample 9 - CF (NW35/2(0.3%) + 1179.47 0.20 1094.69 0.21486 3.39 2148.60 40% Adhesive, CF (Uncoated) 60% Cohesive

(47) In samples 1, 3 and 4, the carbon fibre panel was cured to a second carbon fibre panel, where both were powder coated with the catalyst composition and the adhesive was applied to one of the panels before curing. In samples 2 and 3, the aluminium panel was coated with the powder coating, but no catalyst was present therein. In samples 6 to 9, the aluminium or carbon fibre second panel was uncoated.

Example 7Lap Shear Strengths for Steel Joints

(48) Steel (S275, NW35/2) was applied with a powder coating of Pt (II) Cl.sub.2 (cod) catalyst (0.3% by weight catalyst, 52 wt % platinum) and the powder coat cured for 15 minutes at 140 C. Lap shear joints were prepared, and then bonded with adhesive for 24 hrs ambient cure and 1 hr post cure at 70 C. The lap shear results are shown in Table 5 and FIG. 8.

(49) TABLE-US-00015 TABLE 5 Maximum Extension at Max Load at Elong at Stress at Strain at Load Load Break Break Break Break Failure [N] [mm] [N] [mm] [N/mm.sup.2] [%] Mode 1 6152.41 0.67 6152.41 0.66865 19.07 6686.48 Cohesive 2 6761.97 0.75 6741.52 0.76449 20.90 7644.93 Cohesive 3 7063.87 0.79 6910.71 0.80621 21.42 8062.12 Cohesive

(50) In sample 1, the steel panel was cured to a second steel panel, where both were powder coated with the catalyst composition and the adhesive was applied to one of the panels before curing. In samples 2 and 3, the second steel panel was coated with the powder coating, but no catalyst was present therein.

Example 8Viscosity Modification

(51) Viscosity modification was tested as a means to improve the viscosity characteristics of the adhesive component composition of Example 4. In particular, Aerosil particles (fumed silica) were added into the adhesive component composition in order to determine whether a composition could be obtained which does not flow on a substrate placed in a vertical orientation.

(52) Adhesive component compositions were obtained by adding Aerosil R8200 or 104 particles into the composition of Example 4 at a level of 4.4 wt % or 5.7 wt % of the composition. The resulting viscosities were then measured at two different shear rates at 23 C. Some of the results are presented in Table 6 below.

(53) TABLE-US-00016 TABLE 6 Adhesive Component Viscosity Composition of Example 4 at 0.1 1/s [Pas] Viscosity at 150 1/s [Pas] +4.4 wt % Aerosil R8200 143 1.5 +5.7 wt % Aerosil R8200 269 3.1

(54) The results showed that adding between 4.4 wt % and 5.7 wt % Aerosil particles provided a composition with suitable wetting properties, but which did not flow on the substrate when it was placed in a vertical orientation, thereby improving the viscosity profile of the composition and allowing it to be used in a number of different applications.

Example 9Catalyst Film

(55) Equipment

(56) Cast film line consisting of a single screw extruder, a Dr. Collin Slot Die Machine type 250 mm, and a Dr. Collin Chill Roll Machine type 136/350.

(57) Method

(58) Preparation of the Catalyst Film

(59) The ingredients were volumetrically weighed and hand shaken in a polyethylene bag. The compositions of three catalyst films are shown in Table 7 in terms of the relative proportions (%) of each component.

(60) A measuring jug was used to dose the correct volume of pellet into the bag. For NWPT4/5, 250 ml of Dowlex, 250 ml Amplify and 5 g of catalyst was shaken in the bag.

(61) TABLE-US-00017 TABLE 7 Material NWPT4/1 NWPT4/4 NWPT4/5 Dowlex 2107 GC 100 50 49 Amplify GR204 0 50 50 Pt catalyst** 0 0 1.0 Dowlex 2107 GC LLDPE (linear low density polyethylene) MFI (melt flow index) 2.3 g/10 min Amplify GR204 >1% MAH (maleic anhydride) grafted HDPE (high density polyethylene) MFI 12 g/10 min **Strem Chemicals product number 78-0430, Dichloro(1,5-cyclooctadiene)platinum II The catalyst was employed in an excess in these tests in order to be certain that enough catalyst was present to initiate curing; less catalyst is actually required to achieve curing.

(62) The line was then started using NWPT4/1 material to produce an approximately 50 m film. Once the film had stabilised, NWPT4/4 (no catalyst) was added to the hopper and the line re-stabilised. NWPT4/5 was then added to the hopper, the line stabilised and the film collected.

(63) The line was set up to produce a self-supporting sheet of NWPT4/1. Once stable, NWPT4/5 film was fed onto the molten film to laminate the two films together. Pressure was applied using the nip roller on the chill roll. This produced a film with a catalysed surface on one side only.

(64) NWPT4/1 ran very well at 290/210/210/200 extruder, die all zones 200 C., 60 rpm, 20% torque.

(65) To add functionality to aid wetting of the adhesive, NWPT4/4 contained Amplify GR204. A good film was produced.

(66) Catalyst was added to make NWPT4/5. The line was run as with NWPT4/4 and a good film produced with 50 m thickness. NWPT4/5 film ran sufficiently well, but was improved by reducing the line speed in order to prevent breakage of the film. No significant change in extruder torque was noted between NWPT4/4 and NWPT4/5.

(67) To test the catalytic activity of the film, the film was cut into small strips and fastened to Al LSS bars with clips, as discussed below. The adhesive thickness was controlled by making a K bar out of a spreading knife with calibrated thickness wire wrapped around the edge.

(68) Verification of Catalyst Surface Activation

(69) Three separate AC600 Type 6000 aluminium alloy sheets were prepared, two with a Powderbond powder coating (as described in Example 1) and one without, and were coated in a 100 m film of the adhesive component composition of Example 4. The compositions were then cured in a gas oven at 100 C. for 45 minutes.

(70) Rubbing a blade over the adhesive surface showed that the adhesive had hardened on the samples coated in the Powderbond powder coating (containing catalyst) but was still liquid on the sample that was not uncoated (i.e. did not have any catalyst to initiate adhesive cure). This was a control test to verify the quality of the adhesive being used in the study.

(71) Three separate AC600 Type 6000 aluminium alloy sheets were prepared by clipping the following films to the surface: NWPT4/1 (no catalyst), NWPT4/4 (no catalyst), and NWPT4/5 (catalyst). Each substrate was coated in a 100 m film of the adhesive component composition of Example 4. The compositions were then cured in a gas oven at 100 C. for 45 minutes.

(72) The cure of the adhesive was checked by running a blade across the surface to verify the material state. The adhesive was liquid on films NWPT4/1 and NWPT4/4, but had changed to a hard solid on film NWPT4/5. A colour change and shrinkage of film sample NWPT4/5 could be seen as the adhesive cured during the baking cycle.

(73) To test the bonding of two separate substrates, cross bars of AC600 Type 6000 aluminium alloy sheets were prepared: (i) AC600 Powderbond powder coated aluminium (as described in Example 1, i.e. containing catalyst), (ii) NWPT4/4 film (no catalyst), and (iii) NWPT4/5 film (containing catalyst). A 200 m layer of the adhesive component composition of Example 4 was applied at each intersection where the cross bars meet.

(74) After cooling, hand pressure was applied to the joint to try to break the bond. The AC600 Powderbond powder coated sample and the NWPT4/5 film could not be easily pulled apart. The sample containing NWPT4/4 came apart with light pressure and the adhesive was seen to be in a liquid state.

(75) In another bonding test, NWPT4/4 film and NWPT4/5 film, which were each attached to AC600 Type 6000 aluminium alloy panels, were covered with a 200 um layer of the adhesive component composition of Example 4. The thickness was controlled using spacer wires. Following curing, the adhesive in contact with the NWPT4/4 film remained in a liquid state with no adhesion to either surface; the panels were easily separated. The panels containing the NWPT4/5 film were well bonded and had to be prised apart with a screwdriver. The film was very well bonded to the adhesive, which in turn was strongly bound to the aluminium panel.

(76) Table 8 shows the activity of the catalyst from the catalysed surface. Surface 1 and surface 2 describe the surfaces in contact with the adhesive.

(77) TABLE-US-00018 TABLE 8 Surface 1 Surface 2 Result NWPT4/1 None Adhesive remained liquid, no cure NWPT4/4 None Adhesive remained liquid, no cure NWPT4/5 None Adhesive became solid, cured AC600 None Adhesive became solid, cured Powderbond coated sheet NWPT4/5 NWPT4/5 Adhesive became solid, cured NWPT4/4 NWPT4/4 Adhesive remained liquid, no cure AC600 AC600 Powderbond Adhesive became solid, cured Powderbond coated sheet coated sheet NWPT4/4 Aluminium Adhesive remained liquid, no cure NWPT4/5 Aluminium Adhesive became solid, cured

(78) Accordingly, the catalyst was successfully incorporated into a polyethylene film and processed using standard cast film equipment. The catalyst remained active following processing and cured the adhesive component composition of Example 4 on contact. Good bonds were achieved against aluminium substrates and the film using the adhesive. The adhesive was shown not to cure when the catalyst was absent. A bilayer film was produced with good adhesion between the bonding film and the LLDPE.