Cure of anaerobic compositions

Abstract

A bonding system for bonding a plastic substrate to another substrate, the bonding system comprising a plastic substrate wherein the plastic substrate is impregnated with a transition metal; and an anaerobically curable composition. Cure of the anaerobically curable composition is initiatable by the transition metal when the anaerobically curable composition is contacted with the plastic substrate under anaerobic conditions.

Claims

1. A bonding system for bonding a plastic substrate to another substrate, the bonding system comprising: (a) a plastic substrate wherein the plastic substrate is impregnated with a transition metal; and (b) an anaerobically curable composition, wherein cure of the anaerobically curable composition is initiatable by the transition metal when the anaerobically curable composition is contacted with the plastic substrate under anaerobic conditions.

2. A bonding system according to claim 1 wherein the transition metal is present in the form of a salt.

3. A bonding system according to claim 1 wherein the transition metal is selected from the group consisting of copper, iron, vanadium, cobalt, chromium, silver, manganese, and combinations thereof.

4. A bonding system according to claim 1 wherein the transition metal is in salt form and is selected from the group consisting of: cobalt (II) naphthenate; copper carbonate; copper (II) acetylacetonate; silver nitrate; vanadium (III) acetylacetonate and combinations thereof.

5. A bonding system according to claim 1 wherein the plastic substrate is impregnated with a transition metal when the plastic is in molten form.

6. A bonding system according to claim 1 wherein the plastic substrate is PCABS (Polycarbonate/Acrylonitrile Butadiene Styrene); polycarbonate; polyarylamides; polyamides, acrylic plastics, said substrate being optionally transparent and/or being optionally reinforced with fibres.

7. A bonding system according to claim 1 wherein the anaerobically curable component is present in an amount of from 50% to 99% by weight of the total composition.

8. A bonding system according to claim 1 wherein a curing component within the anaerobically curable composition is present in an amount of from 0.1 to 10% by weight based on the total weight of the composition.

9. A bonding system according to claim 1 wherein the anaerobically curable composition includes a rubber component, which is optionally present in an amount of from 5 to 35% based on the total weight of the composition.

10. A bonding system according to claim 1 wherein the transition metal is present in an amount up to about 1% by weight of the composition that forms the plastic component.

11. A bonding system according to claim 1 wherein the anaerobic composition is a one-part composition.

12. A method of bonding a plastic substrate to another substrate, the method comprising: (a) providing a plastic substrate wherein the plastic substrate is impregnated with a transition metal; and (b) providing an anaerobically curable composition; and (c) initiating cure of the anaerobically curable composition by contacting the transition metal with the anaerobically curable composition by contacting the anaerobically curable composition with the plastic substrate under anaerobic conditions.

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 an exploded view of various component layers of a hand held consumer electronic display device, and in which the bonding system of the invention may be used to bond a plastic part to one or more other parts.

DETAILED DESCRIPTION

(3) An example of one or more articles that may be formed using a bonding system of the invention may be seen with reference to FIG. 1. There, several articles that are used in the assembly of hand held consumer electronic devices are highlighted as benefiting from the bonding system of the invention. Articles that may be bonded with the bonding system of the invention: include: 1. touch panel window 11 and cover 12; 2. speaker 21 and camera lens 22; 3. cover 31, metal trim 32 and subframe 33; and 4. touch panel 41, plastic bezel 42 and metal trim 43. In accordance with the present invention at least one plastic part to be bonded to another part is impregnated with a transition metal and an anaerobically curable composition activated by the transition metal is used to bond the parts together. It will be appreciated in all aspects of the invention that suitable anaerobic conditions may be achieved when parts to be bonded are brought together in a way that creates the anaerobic conditions, for example when the anaerobic composition is sufficiently isolated from ambient air (oxygen) by the bringing of the parts to be bonded together.

Experimental

(4) The following experimental work was carried out to exemplify the present invention. It demonstrates the impregnation of plastic substrates with transition metals to facilitate bonding with an anaerobic adhesive.

(5) The following anaerobic adhesive was prepared (all amounts are 10%):

(6) TABLE-US-00001 TABLE 1 Amount (% weight based on the Component total weight of the composition) Methyl Methacrylate 57.62 Methacrylate functional polybutadiene 15.54 rubber (Hypro VTBX LC 2000 Liquid Rubber) Linear copolymer of styrene and 11.89 polybutadiene (Kraton D1155) Methacrylic acid 4.57 Polyethylene glycol 200 dimethacrylate 0.171 1,4 Naphthoquinone 0.009 Propanediol 1,2 0.669 Deionised water 0.209 EDTA tetrasodium salt 4H.sub.2O 0.032 Acetyl Phenylhydrazine 0.14 Saccharin 1.83 Cumene Hydroperoxide 1.83 Hydrophobic silica 5.49

(7) As a control experiment standard off the shelf PCABS lapshears were bonded with the anaerobic adhesive set out above in Table 1 under anaerobic conditions under the following curing conditions 20 minutes at 80 C. followed by 24 h at room temperature. Low bond strengths were achieved and the bonds were easily pulled apart by hand.

(8) In the following tests all bonding was carried out using the composition in Table 1 above.

(9) Pin to Lapshear Tests

(10) 700 ppm of copper(II)-acetylacetonate 97% powder was added to pellets of PCABS. The pellets were then moulded into pins for bonding with the adhesive of Table 1. The plastic discolours slightly when moulded.

(11) The pins were bonded to lapshears as set out in Table 2 below following standard test method DIN EN 15870 for 20 minutes at 80 C. followed by 24 h at room temperature and then tested for tensile strength. (So two substrates are bonded together for tensile bond strength testingthe pin and the lapshears.)

(12) TABLE-US-00002 TABLE 2 Pin to lapshear bonding Pin used Lapshear used Tensile strength PCABS copper added to pin standard anodised 3.39 1.75 MPa aluminium lapshear PCABS copper added to pin standard PCABS 4.22 0.48 MPa lapshear PCABS No copper added to standard anodised Al *5.39 2.1 MPa pin PCABS No copper added to standard PCABS **No Cure pin lapshear PCABS No copper added to PCABS lapshear no **No Cure pin copper added *Control using one Aluminium substrate - good bond strength expected as industrial grades of aluminium contain amounts of copper which facilitate anaerobic cure. **Control where both substrates are plastic
Tensile Shear test Lapshears

(13) 700 ppm of copper(II)-acetylacetonate 97% powder was added to pellets of PCABS. The pellets were then moulded into lap shears for bonding with the adhesive of Table 3. The plastic discolours slightly when moulded.

(14) Lapshears were bonded to lapshears as set out in Table 3 below following standard test ISO 4587 for 20 minutes at 80 C. followed by 24 h at room temperature and then tested for tensile shear strength. (So two substrates are bonded together for tensile shear strength testingfirst and second lapshears.)

(15) TABLE-US-00003 TABLE 3 Lapshears Used Tensile Shear strength PCABS standard lapshears - PCABS No cure standard lapshears PCABS no copper added lapshears - 4.19 0.31 MPa standard anodised aluminium lapshears PCABS copper added lapshears - >5 Mpa - SF PCABS copper added lapshears PCABS copper added lapshears - 3.93 .49 MPa - SF standard anodised aluminium lapshears

(16) All lapshears were moulded in house except where indicated as standard.

(17) SF indicates substrate failure i.e. the substrate failed before the bond shear strength was reached.

(18) The results above demonstrate that including a transition metal component within a plastics substrate, for example during moulding thereof, results in much better bonding with an anaerobically curable adhesive.

(19) 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.

(20) 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.