Process for bonding substrates or parts and system including cyanoacrylate adhesive and accelerator composition

1. An accelerator composition adhesive system comprising in one part a cyanoacrylate adhesive and in a second part an accelerator composition for curing cyanoacrylate adhesives comprising:

(a) one or more compounds selected from the group consisting of:

(i) unsubstituted pyrazine; or a pyrazine derivative; said pyrazine derivative being pyrazine substituted with at least one electron-releasing group which substituent causes a net increase in the base strength of the substituted compound as compared to the corresponding unsubstituted compound;

(ii) pyridine N oxides substituted with at least one electron-releasing group; and

(iii) 2,6 pyridines being pyridines substituted in the 2- and 6-positions by substituents, at least one of the substituents being electron-releasing provided that both substituents are not methyl;

(b) a volatile solvent carrier for the compound; and

(c) an organic compound containing the structural element, —N═C—S—S—or 5-nitro guinoline.

2. A system according to claim 1 wherein in a compound of group (iii) at least one of the substituents is more sterically hindering than a methyl group.

3. A system according to claim 1 wherein in a compound of group (i) the heterocycle is substituted on at least one of the carbon atoms directly bonded to the N heteroatom.

4. A system according to claim 3 wherein the heterocycle is substituted on at least two carbon atoms each carbon atom being directly bonded to one of the N heteroatoms.

5. A system according to claim 1 wherein the electron-releasing group(s) are selected from one or more of straight chain, branched chain or cyclic, optionally substituted, alkyl groups.

6. A system according to claim 5 wherein said electron-releasing groups are optionally substituted methyl, ethyl, propyl, butyl or pentyl.

7. A system according to claim 1 wherein component (b) the volatile organic solvent is a solvent mixture which comprises a volatile hydrocarbon and a cyclic ketone.

8. A system according to claim 7 wherein the volatile hydrocarbon is an aliphatic hydrocarbon.

9. A reaction product of the one part of the system of claim 1 and the second part of the system of claim 1 .

10. A bond formed between two surfaces by the reaction product of claim 9 .

11. A process to accelerate hardening of a cyanoacrylate adhesive, steps of which comprise:

(a) providing a cyanoacrylate adhesive according to claim 1 ,

(b) providing an accelerator composition according to claim 1 , and

(c) contacting the cyanoacrylate adhesive with the accelerator composition.

12. A process for the bonding of substrates or parts, characterised by either of the following series of steps:

(a) dispensing a composition from the second part of the system as according to claim 1 onto at least surface of the substrates or parts to be joined;

(b) optionally exposing solvent or other liquid vehicle in the accelerator composition to air, optionally with heating and/or with the aid of a fan;

(c) optionally holding the substrate or part having the accelerator composition thereon for a retention or shipping period,

(d) applying a cyanoacrylate adhesive from the one part of the system of claim 1 to at least one substrate or part;

(e) joining the substrates or parts, optionally with manual or mechanical fixing, and

(f) optionally subsequently dispensing the accelerator composition onto adhesive exposed from a joint gap; or

(i) applying a cyanoacrylate adhesive from the one part of the system according to claim 1 onto at least one surface of the substrates or parts to be joined;

(ii) joining the substrates or parts, optionally with manual or mechanical fixing;

(iii) dispensing an accelerator composition from the second part of the system as according to claim 1 onto the cyanoacrylate adhesive from the one part of the system according to claim 1 before or after the step of joining the substrates or parts, and

(iv) optionally exposing solvent or other liquid vehicle in the accelerator composition from the second part of the system according to claim 1 to air, optionally with heating and/or with the aid of a fan.

13. A bonded assembly of substrates or parts bonded by a process according to claim 12 .

14. An article of commerce comprising a substrate or part and the system according to claim 1 .

15. A process for the bonding of substrates or parts, characterised by the following series of steps:

(i) applying a cyanoacrylate adhesive from the one part of the system according to claim 1 onto at least one surface of the substrates or parts to be joined;

(ii) joining the substrates or parts, optionally with manual or mechanical fixing;

(iii) dispensing an accelerator composition from the second part of the system as according to claim 1 wherein component (b) is a solvent mixture which comprises a volatile hydrocarbon and a cyclic ketone, onto the adhesive before or after the step of joining the substrates or parts, and

(iv) optionally exposing the solvent mixture in the accelerator composition to air, optionally with heating or with the aid of a fan.

16. A bonded assembly formed by the process of claim 15 .