Conductive adhesive for wet electrostatic precipitator panel

Abstract

A conductive adhesive is provided useful for providing electrically conductive joints in joins between panels, particularly conductive carbon composite panels in a WESP, is prepared from a corrosion resistant resin and particulate carbon black which is uniformly dispersed in the resin.

Claims

1. A method of assembly of a wet electrostatic precipitator (WESP) conductive carbon composite panel comprising corrugated strips of conductive carbon composite panels adhesively bonded together using an electrically-conductive adhesive composition, the composition comprising a polyunsaturated resin which, following polymerization, exhibits resistance to corrosion and heat distortion, and a carbon black filler uniformly dispersed in the resin, the method comprises: molding conductive carbon composite material into corrugated form; abrading mating surfaces of adjacent panels to expose carbon fibres; and adhering adjacent corrugated strips at their abutting corrugations to form a hexagonal tube bundle.

2. The method of claim 1 wherein the polyunsaturated resin is a polyunsaturated vinyl ester resin.

3. The method of claim 2 wherein said polyunsaturated vinyl ester resin is an epoxy novolac vinyl ester resin.

4. The method of claim 1 wherein said carbon black filler is present in an amount of about 10 to about 30 wt %.

5. The method of claim 1 wherein the composition further comprises at least one cross-linking agent for said polyunsaturated resin.

6. The method of claim 5 wherein the cross-linking agent is cumyl hydroperoxide.

7. The method of claim 1 wherein the composition further comprises at least one curing accelerator.

8. The method of claim 7 wherein said curing accelerator is cobalt naphthalate.

9. The method of claim 1 wherein the composition further comprises a solution of paraffin wax and styrene.

10. The method of claim 1 wherein the electrically conductive adhesive composition is formed by a method comprising: mixing a paste of finely divided carbon black filler with a polyunsaturated resin which, following polymerization, exhibits resistance to corrosion and heat distortion, along with other optional additives other than a cross-linking agent for said resin under high shear to fully disperse the carbon black filler and optional additives in the resin to form a homogenous mixture.

Description

GENERAL DESCRIPTION OF THE INVENTION

(1) The polyunsaturated resin of the present invention should be resistant to the corrosion and heat distortion conditions often encountered in a WESP. A number of commercial vinyl ester resins are available which are suitable for use herein, including the Vipel F085 series of epoxy novolac vinyl ester resins. These resins have a backbone chemistry which provides resistance to acids and bases and has superior resistance to many organic solvents. Vipel F085 series resins generally are resistant to liquids and vapors at higher temperatures than conventional bisphenol-A epoxy vinyl ester resins.

(2) Other commercially-available polyunsaturated vinyl ester resins for use herein include Ashland Hetron 970, Ashland Durakane 470, Interplastic CoREZYN 8730 and Reichhold Dion 9480. In addition, polyunsaturated epoxy resin exhibiting corrosion resistance and heat distortion resistance may be employed, including Epon 828, Epon 815 and Epon 9504. Further, polyunsaturated urethane resin having corrosion resistance and heat distortion resistance may be employed, including Bayer Baypreg F, Bayer Blendur TP PU 90IK28.

(3) The carbon black filler component of the conductive adhesive, usually added in the form of a paste, is one which permits a high loading of carbon black into the composition with the polyunsaturated vinyl ester resin. One such commercially-available product is Plasticolors HC-21109. Alternative commercially-available carbon black products include Degussa/Evonik Printex XE2, and Timcal Ensaco 350G. In general, the quantity of carbon black filler employed in the composition is about 10 to about 30 wt %.

(4) To form the adhesive composition of the present invention, the carbon black filler is mixed with the polyunsaturated vinyl ester resin along with other additives other than the cross-linking agent, under high shear to fully and uniformly disperse the carbon black filler and other ingredients in the resin base to provide a homogenous mixture.

(5) In addition to the base resin and the carbon black paste, the conductive adhesive of the present invention may include a number of additives which are useful in the curing of the polyunsaturated vinyl ester resin. Such materials include the main cross-linking agent, such as cumyl hydroperoxide, and polymerization accelerators, such as cobalt naphthalate and dimethylmethacrylate.

(6) A further process additive which may be present includes a solution of paraffin wax and styrene, which serves to prevent air occlusion during curing of the adhesive corrugation.

(7) The homogenous mixture of polyunsaturated vinyl ester resin and carbon black can be stored for future use without separation of components thereof. At the time of application of the adhesive composition for achieving adhesion between surfaces, the cross-linking agent, such as cumyl hydroperoxide, is added and dispersed therein and the formulation applied to the surfaces to be adhered together by any convenient means, such as manually, such as by roller, brush or squeegee, and the polyunsaturated vinyl ester resin cured with the surfaces to be adhered together abutting other. Such time-dependent catalysis system may be replaced by a temperature activated catalysis.

EXAMPLE

(8) This Example illustrates an adhesive composition provided in accordance with the invention.

(9) A formulation was prepared from the following components:

(10) 100 phr AOC Vipel-F085-ASA-DO

(11) 15 phr Plasticolors HC-21109

(12) 0.4 phr cobalt naphthalate

(13) 0.2 phr DMA

(14) To the Vipel-F085 resin was added, in order, the cobalt naphthalate, DMA and Plasticolors HC-21109, and the composition mixed for 20 minutes using a polybladed impeller. During the mixing, the impeller was continuously raised and lowered to prevent overheating of pockets of material. The temperature of the composition was maintained below 30° C. during the mixing operation.

(15) When this composition was used, 2.0 phr of NOVOX CHP (cumyl hydroperoxide) was added.

SUMMARY OF THE DISCLOSURE

(16) In summary of this disclosure, the present invention provides an electrically conductive adhesive useful for adhering elements of wet electrostatic precipitator tube bundles formed from conductive carbon composites. Modifications are possible within the scope of this invention