Web Coating Plastic Strips

Challenge

Recoup of precious metals that are deposited on plastic roll stock for use in architectural, electronics and window films. The production web coating substrates are rejected by the manufacturer because the:

(1) Roll stock is rejected as it does not meet coating or properties specifications,

(2) Cut-off sections from the width of coated roll stock that are beyond the sputtering target sweet spot,

(3) Roll is damaged and is typically scrapped.

 

Deposition

Gold, Silver and Indium

 

Substrate

PET Plastic Web Coating Rolls

 

Results

The final yield of all three metals turned out the same as the expected theoretical yield results from the Atomic Absorption Spectroscopy (AAS) analysis of the etching mix. Our novel technologies delivered metallic silver, indium and very pure gold bullions via a cost effective process that can be installed at customers site or remote locations with very little investment in necessary equipment.

 

The savings just coming from the savings of not running of silver and indium furnaces, along with not running three pieces of electrochemical equipment and the associated investments necessary to purchase these, more than justify the use of our new patented solution.

 

We were able to deliver metallic silver and indium in real modest conditions, together with our simple new solution to obtain very pure gold bullions. As far as we know, this is the only existing technology that delivers indium while bypassing electrochemistry and smelting. 

 

One of our clients, an European precision cleaning company, involved in cleaning precision parts, wanted to expand their market and was introduced by a German Sales team to web coatings and the potential of recouping precious metals from plastic films.

 

The client is skilled in cleaning precision parts with non-precious metal depositions.

 

There were in-house orders with precious metals deposited onto glass substrates that were cleaned by the weaker aqua regia (see our FAQs for more details) by the client. Once the deposition was dissolved by the weaker aqua regia, the client would send the solution to one of the major refineries. The glass substrates were trashed after cleaning.

 

While the weaker aqua regia is okay to be used for glass surfaces and substrates, it could not be applied for recouping precious metals deposited onto other surfaces, like PET.

 

That was the challenge from this new customer of our client, who was a producer of intelligent films to control areas of sun spectrum by reflecting, absorbing or transmitting various types of electromagnetic radiation (reflecting infrared heat, attenuating low frequency microwaves, and reducing surface glare of visible light).

 

The scrap they produce contains large amounts of indium, silver and gold on some types of films.

 

We were given the task to develop a technology that was QUANTITATIVE (see our FAQs) for the separation and purification of the three metals, and then smelting into solid form.

 

The client invested a few thousands of EUR in a simple furnace and some basic laboratory equipment to melt gold and filter solutions with fine gold particles.

 

Their suppliers incinerated the plastic, but they did not return any indium. Probably due to the fact that the melting point of indium is 157°C and that indium is highly susceptible to oxidation by air to create indium oxide which cannot be smelted. Since the indium content on the plastic film is the highest out of the three metals, our client’s new customer was interested in establishing a supplier who would be able to recoup the indium.

 

One has to bear in mind that the technology would need to be inexpensive, based on the current low price of indium and silver (the second highest content material in the coating).

 

Keep in mind that silver at 99.9% purity, delivered from precious metal refineries, is usually obtained by (1) smelting silver chloride with carbonates in a furnace, followed by (2) electrochemical purification of the crude silver.

 

Further, indium at 99.9% purity, delivered from indium refineries, is usually obtained by

(1) electrochemical separation of indium from liquid solutions, followed by

(2) electrochemical purification of the crude indium, then, followed by

(3) smelting of the indium in a vacuum furnace (because of the high susceptibility of indium to oxidize in air).

 

Our client did not have in-house electrochemical equipment to purify silver, or electrochemical equipment to separate and purify indium, no furnace to smelt silver chloride, or a vacuum furnace to smelt indium; in addition, the client did not wish to invest to acquire this equipment.

 

Having all of that in mind, we were ideally looking for a technology that would:

• dissolve the deposited metals in a way that all three metals are recovered;

• make the chemical compounds of the three metals simple to separate from each other preferably during dissolution;

• avoid the use of a furnace or electrochemical process to purify the silver;

• avoid using electrochemistry for (i) separation of indium, (ii) purification of indium and (iii) vacuum smelting of indium;

• it should be inexpensive due to current prices of silver and indium;

• and finally, be robust and simple enough to scale-up for use in remote locations and processed by unskilled labor.

 

When reviewed at length the technologies and processes that where known of available in the open market, we could not find one that would fulfill all of the requirements above.

 

This was a real challenge.

 

Originally, we did not want to use our new technology. Since majority of the plastic film substrate did not contain any gold, the costs of the license fees may make it economically less attractive when silver and indium are the only metals deposited and can be recouped.

 

Surprisingly, after a number of experiments with a variety of different etching/separation mixtures, it proved to be our new solution was in fact the best to fulfill all of the six requirements above.

 

The savings obtained from not investing in and running silver and indium furnaces, along with, no need for investing and running and additional three electrochemical equipment’s, more than justify the use of our technology.

 

Moreover – the novel sub-technologies developed to obtain metallic silver and indium in real modest conditions, together with our new solution to produce very pure gold bullions, make the overall Ag/Au/In technology very attractive and a cost effective process. The process can be performed in remote locations, with minimum chemical equipment and by unskilled labor.

 

The final yield of all three metals was the same as the expected theoretical yield obtained from Atomic Absorption Spectroscopy (AAS) analysis of the etching mix.

 

As far as we know, this is the only existing technology that delivers indium while bypassing electrochemistry and smelting.

 

The client’s new customer was extremely pleased with the results and now has the opportunity to recoup the indium, along with the silver and gold.