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Off Topic - Wet suits

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Does any one have/heard any thing about Henderson's new "GreenPreem" wet suits made from a non- rubber based material?

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I've seen the ads, but nothing more.  I am also curious about them.

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These suits are advertised as being made from Limestone - this is in reality quite a stretch.  I have a background in process industries and I can tell you that there is no actual limestone in the neoprene material.   A long story follows for those interested.

The process starts with limestone and a source of carbon I believe the Japanese made one uses old tyres.  

Limestone is calcium carbonate and it first reacts to make lime - calcium oxide,  releasing the CO2 that is bound with the calcium.  The calcium oxide reacts with the carbon source at very high temperatures - 2200°C.  The reaction makes calcium carbide:  CaO + 3 C → CaC2 + CO .  The CO would need to be combusted to CO2 or used in another process.

Next step is to react the Calcium Carbide (CaC2 ) with water to make Acetylene and Calcium hydroxide.  The Calcium hydroxide is a waste product but could be used for agricultural lime for example - I don't know if it is or not it is a low value product.  If they recycled the lime that I think would be a positive step from a green perspective.

Once you have the acetylene - this is the gas used in oxy-acetylene welding and cutting - you can then react it with chlorine to make chloroprene which is polymerised to make neoprene.

Conventional neoprene is also made from chloroprene but the chloroprene is made from butadiene which is manufactured from petroleum - a by-product of the refining of petroleum and chlorine or hydrochloric acid.  In fact when it was invented in the 1930's neoprene was made via the acetylene process but had odor problems that were easier to overcome making via the petroleum route.

Effectively what happens is two acetylene molecules react to make a compund similar to butadiene that can be reacted to make chlorprene.

So both types of neoprene start from the same building blocks:  you see claims that the "limestone" product has superior properties but if they both start from the same building block -that is chlorprene- oil based neoprene could use the same reactions. 

So where does this leave us?? - both processes are energy intensive I don't have the numbers but my educated guess is that the limestone product has higher energy input to achieve the same product - but the raw material is in fact old tyres and this is probably a better use for them than landfill or burning them - it is a form of recycling. 

I would say that if you like the properties of the suits over conventional suits - use them.  But don't claim they are made of limestone and are somehow magically a lot greener. They in fact are made of old tyres which is a good thing but maybe not as marketable perhaps as trying to claim they are not made from petroleum.  I have not been able to find any analysis on the greenhouse footprint differences in the new technologies but my gut feel is that the limestone process is more energy intensive.  If they made it in a solar furnace that would be a clear advantage  I think and definitely tip the scales in favour of the new product.

There is also Yulex, which is a  made from natural rubber (85%) which is a renewable resource, but utilises agricultural land to grow rubber trees.  It is certainly less energy intensive.

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Posted (edited)

Thanks Chris, that is a great and useful analysis.

Edited by SwiftFF5

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Chris:

Nice write up. One point is that I don't think the limestone needs to be replaced.

I think it goes like (from an old paper in J Chem. Soc (1957)

Ca(OH)2 + Heat (500+C) -->CaO + water

CaO + C +Heat (2000C) --> CaC2 +CO

CaC2 + H20 --> C2H2 + Ca(OH)2

It is the carbon that is replaced. In my remembrance in the US they used charcoal as the carbon source, probably cleaner than tires but not as eco friendly.

 

I think all the stories about more closed cell and warmer are all marketing BS. Once you have chloroprene then you can process it however you like

 

Bill

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6 hours ago, bvanant said:

Chris:

Nice write up. One point is that I don't think the limestone needs to be replaced.

I think it goes like (from an old paper in J Chem. Soc (1957)

Ca(OH)2 + Heat (500+C) -->CaO + water

CaO + C +Heat (2000C) --> CaC2 +CO

CaC2 + H20 --> C2H2 + Ca(OH)2

It is the carbon that is replaced. In my remembrance in the US they used charcoal as the carbon source, probably cleaner than tires but not as eco friendly.

 

I think all the stories about more closed cell and warmer are all marketing BS. Once you have chloroprene then you can process it however you like

 

Bill

Hi Bill, agree, I don't have direct knowledge about the calcium cycle - the CaOH2 from step 3 is probably a finely divided suspension mixed with all the stuff in the Calcium carbide which is not carbide - I think the carbide comes out as about 80-90% carbide - the rest must be something else- probably silica and alumina?.  So whether it is recyled or not depends on how difficult it is filter out the CaOH2 from what is left - it may be more cost effective to sell the slurry as agricultural lime?  There may also be some nasty by-products from the acetylene mixed in  - that is an extremely reactive molecule.  I found an article on a study on the CO2 footprint of using carbide sludge in cement kilns vs fresh limestone which tends to indicate it is a waste product - it reduces CO2 emissions compared to mining limestone as you don't get the CO2 emission from the limestone and you don't mine and crush it, but you do have to dry it.

I agree about the chloroprene - there may be better processes you can use and you can use that process whatever the source of chloroprene.   A lot of marketing for wetsuit material is dubious - take all these claims of reflective layers reducing radiant heat loss - radiant heat loss is not a thing for underwater - I could go into a lot of detail why not - suffice it to say that the temperature difference of the radiating body - you in your wetsuit - to the environment is very low so the driving force for radiant heat loss is minimal.  Convective and conductive heat loss dominate.  The point is don't believe the marketing all you can go on is reviews about how people like the product - compared to what they had before.

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The whole wetsuit story is getting more interesting. It turns out (I think) that the Yamamoto guys actually use the tires by burning them to make the heat to convert the acetylene into chloroprene. Waste heat then supposedly goes to an eel farm. In any case what isn't clear is why polychloroprene from chloroprene from acetylene is any different than from butadiene. Marketing is a wonderful thing.  

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12 hours ago, bvanant said:

The whole wetsuit story is getting more interesting. It turns out (I think) that the Yamamoto guys actually use the tires by burning them to make the heat to convert the acetylene into chloroprene. Waste heat then supposedly goes to an eel farm. In any case what isn't clear is why polychloroprene from chloroprene from acetylene is any different than from butadiene. Marketing is a wonderful thing.  

well whatever they do they need to get to 2200 deg C or so.  Classic way to achieve that is an electric arc furnace.  I wouldn't think you'd need a lot of heat to dimerise acetylene then add HCl unless the reaction is particularly endothermic? 

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In fact the dimerization  it is done at 80C in a reaction tower with lots of cooling. The chlorine addition is done at 60C or so (at least according to my very old o-chem text.

BVA

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