WO1996015204A1

WO1996015204A1 - Epoxy adhesive formulation

Info

Publication number: WO1996015204A1
Application number: PCT/AU1995/000750
Authority: WO
Inventors: William James Burge Derham; Stephen William Burge Derham
Original assignee: Derham Investments Pty. Ltd.
Priority date: 1994-11-14
Filing date: 1995-11-14
Publication date: 1996-05-23
Also published as: AUPM940894A0

Abstract

An adhesive formulation including an epoxy adhesive and a chemically inert fine particulate filler additive, and a process for the preparation thereof.

Description

EPOXY ADHESIVE FORMULATION

This invention relates to a new and improved adhesive formulation.

The range of modern adhesives is immense and includes natural and synthetic adhesives such as polyurethanes, polyamides, polyesters and epoxies.

One of the most successful and useful class of adhesives is the class of epoxy adhesives. The epoxy adhesives include generally monomers or pre-polymers that further react with curing agents to yield high performance thermosetting plastics which in the curing process adhere adjoining surfaces. Epoxy resins are characterised in that they contain a three membered ring or epoxy group. Depending on the precise formulation used, including the base epoxy resin and the curing agent, the properties of the epoxy adhesive can vary widely. It is a characteristic of epoxy resins generally that they demonstrate good mechanical strength and adhesive ability. These properties make epoxy resins useful in a very wide range of applications in particular for adhering materials for which many other adhesives are inadequate. For example, epoxy adhesives are regarded as pre ng good adhesion between plastics, glass, metal, ceramics, wood and oth materials. However, notwithstanding the variability available and the often imprt sive adhesive qualities of epoxies, those adhesive properties are often inadequate for a number of potential uses. Accordingly, there is a need for adhesive formulations having increased adhesive characteristics over the known epoxy resins.

It has now been found that the adhesive qualities of known epoxies may be significantly improved simply by mixing with them a small amount of one or more chemically inert fine particulate filler materials, particularly silicates. Preferably the additive is an alkaline earth metal silicate more preferably magnesium silicate. Moε preferred is an hydrated magnesium silicate for example talc. Preferably the filler will consist of fine but uneven sized particles. A preferred filler is commercial talc of 200 mesh or greater (finer). Whilst not wishing to be bound by any theory the applicant believes that the particles of a neutral filler such as hydrated magnesium silicate provide in effect a reinforcement structure to the epoxy. The fine but variable sized particles provide a large surface bonding area, able to pack together without large particle interstices. In addition to providing an increase in strength, the addition of such particulate filler material also increases the capacity of the adhesive to absorb heat.

As will be apparent to the person skilled in the art the amount of additive to be used will depend on the particular epoxy and the filler concerned. The person skilled will appreciate that the ratio of epoxy to additive must be sufficiently high for there to be adequate epoxy to bond the particles of the additive.

An improvement in the adhesive properties of the epoxy adhesive is achievable by use of a relatively small amount of additive in comparison with the amount of adhesive. It has been found that by use of as little as 0.1 % by weight of additive to weight of adhesive satisfactory results are obtained with significantly increased bond strength compared with the adhesive without the additive of the invention. It has been found that amounts of 1% and 5% and even greater produce good results.

As stated above this invention relates to adhesives falling within the general class of epoxy. A preferred adhesive is that formed from epoxy resin including bisphenol A diglycidyl ether, with a curing agent including tertiary amines N,N- dimethyldipropylenetriamine and tri(dimethylaminomethyl)phenol, for example the rapid set adhesive ARALDITE® K219 manufactured by Ciba-Geigy Australia Limited.

Another preferred adhesive is that formed from epoxy resin including Bisphenol A diglycidylether and dibutyl phthalate with a curing agent including triethylenetetramine, for example the adhesive ARALDITE® 2019 manufactured by Ciba-Geigy Australia Limited.

A preferred formulation is 0.1% by weight hydrated magnesium silicate (talc) mixed with "rapid set" ARALDITE K219. Preferably the additive is included in the liquid epoxy resin component before the tertiary amine curing agent is added. However, the additive may be included with the tertiary amine curing agent if desired.

Formulations according to this invention can be used in relation to any use for which the adhesive is otherwise applicable. In particular they are useful to provide improved strength for glass, metal, ceramics, plastics, wood and the like and combinations of these materials. It is particularly applicable for ceramic to ceramic bonding such as in attaching bathroom fittings such as ceramic bases to wall tiles and in bonding stainless steel to stainless steel.

Example

To test its adhesive qualities, the adhesive formulation, was used to adhere a ceramic soap holder to a wall tile. The tile was a ceramic wall tile 8.2mm thick of class 5 standard. The surfaces of both the ceramic tile and the back surface of the soap holder were prepared by first wiping with facial tissues and then cleaning by applying an aerosol degreasing agent (CRC Lectra-clean), and then again wiping with facial tissues. The adhesive formulation was prepared by thoroughly mixing 0.2% by weight of hydrated magnesium sulphate (talc T45B from Commercial Minerals Limited ACN 000 971 844) with the base epoxy resin component of Araldite® K219 rapid set epoxy adhesive, manufactured by Ciba- Geigy Australia Limited and then mixing an equal quantity of hardener to base resin, thus providing an overall 0.1% ratio of talc to epoxy. The resultant adhesive mixture was then applied both to the back surface of the soap dish and the tile and the soap dish pressed against the tile, and the bond was allowed to cure. 6 soap holders were bonded, 3 each to 2 separate tiles. The tiles were then clamped to a steel angle plate and fixed vertically in the compressive force area of a universal testing machine [Mohr and Federhof]. Force was then transmitted from the hydraulic activator to the front edge of each of the soap holders in turn, to failure point. In each case tested, failure occurred either in the tile or the body of the soap holder. In all cases there was no failure of the bond between the tile and the soap holder. The results of the tests are shown in below.

Test Failure Failure Description Number Load kα

1 86.6 tile broken; bond to sample (soap holder) remaining intact

2 94.8 as above

3 66.3 as above

4 76.5 as above

5 71.4 fracture across front edge of soap holder

6 113.1 fracture across base of soap holder

The adhesive was also found most suitable for adhering glass to glass and to metal, and metal to metal. The availability of such an adhesive makes it possible to design a new and improved range of bathroom and similar items, such as soap holders, for example.

It will be appreciated that while the present invention has been described with reference to a particular liquid epoxy resin, amine setting agent and magnesium silicate additive, the principles of the invention are applicable to other composition components of the same class.

Claims

1. An adhesive formulation including an epoxy adhesive and a chemically inert fine particulate filler additive.

2. An adhesive formulation according to claim 1 wherein the additive includes a silicate.

3. An adhesive formulation according to claim 2 wherein the additive includes an alkaline earth metal silicate.

4. An adhesive formulation according to claim 1 or claim 2 wherein the additive includes magnesium silicate.

5. An adhesive formulation according to any one of the preceding claims wherein the additive includes an hydrated magnesium silicate.

6. An adhesive formulation according to any one of the preceding claims wherein the amount of the additive is up to about 5 parts by weight per 100 parts by weight epoxy adhesive.

7. An adhesive formulation according to any one of the preceding claims wherein the amount of the additive is up to about 1 part by weight per 100 parts by weight epoxy adhesive.

8. An adhesive formulation according to any one of the preceding claims wherein the amount of additive is up to about 0.1 parts by weight per 100 parts epoxy adhesive.

9. An adhesive formulation according to any one of the preceding claims including additive of 200 mesh grade or finer.

10. An adhesive formulation according to any one of the preceding claims wherein the epoxy adhesive includes a curing agent.

11. An adhesive formulation according to claim 10 wherein the curing agent includes tertiary amine.

12. An adhesive formulation according to any one of the preceding claims wherein the epoxy adhesive is a quick setting epoxy adhesive.

13. An adhesive formulation according to any one of the preceding claims wherein the epoxy adhesive is a two part formulation including a base epoxy resin and a separate curing agent.

14. An adhesive formulation according to claim 13 wherein the additive is included with the base epoxy resin component or the curing agent component or both components.

15. An adhesive formulation according to claim 13 or claim 14 wherein the additive is included with the base epoxy resin component.

16. An adhesive formulation according to claim 13 or claim 14 wherein the additive is included with the curing agent component.

17. A process for the preparation of an adhesive formulation including combining a small amount of a chemically inert fine particulate filler additive with an epoxy adhesive.

18. A process according to claim 17 wherein the additive includes an alkaline earth metal silicate.

19. A process according to claim 17 or claim 18 wherein the silicate includes magnesium silicate.

20. A process according to any one of claims 17 to 19 wherein the silicate includes an hydrated magnesium silicate.

21. A process according to any one of claims 17 to 20 wherein the amount of silicate is less than about 5 parts by weight per 100 parts by weight of epoxy adhesive.

22. A process according to any one of claims 17 to 21 wherein the amount of silicate is less than about 1 part by weight per 100 parts by weight epoxy adhesive.

23. A process according to any one of claims 17 to 22 wherein the amount of silicate is less than about 0.1 part by weight per 100 parts by weight epoxy adhesive.

24. A process according to any one of claims 17 to 23 including a two part epoxy adhesive wherein one of the set parts is a base epoxy resin and the other of the set parts is a separate curing agent.

25. A process according to claim 24 wherein the silicate is added to one or both parts followed by combination of the two parts.

26. A process according to claim 25 wherein the silicate is mixed with the base epoxy resin and the resultant mixture then added to the curing agent.

27. A method of bonding two surfaces including application of an adhesive formulation according to any one of claims 1 to 16 to one or both of the surfaces to be bonded.