Leather Chemists: Changing Reactivity to avoid contardictio

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Topic: Changing Reactivity to avoid contardictio

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zercas
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Posted: 22 March 2010 at 11:23pm \| IP Logged

Well, what do you know , we are getting there!!!

http://www.chinaleather.org/download/2-1/2-25.pdf

Regards

Zercas

DavidR
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Posted: 22 March 2010 at 11:48pm \| IP Logged

Nevertheless the chromium ion is electrostatically associated with a carboxyl side group residing in the component chains of the triple helix. that remains intact and definable. and by reacting with a carboxyl will displace a cationic amino sidegroup previously making a saline link, that can either be reactive as such in retannage with anionic chemicals, or can be made neutral to then react with an aldehyde, for instance!

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zercas
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Posted: 23 March 2010 at 12:27am \| IP Logged

Of course, you have daid that over and over, but dimentionally it does not go inside the pentafibril, AKA 5 triple helix, it bounds to the carboxililcs that happens to be in the outside of that structure in their "twist" but not the one inside. So, it is something to analize how Cr react at at one unipoint site and the other is how it does it in the whole structure. Not to mention the 20 some different sizes the Ramasami mentions due to different levels of basification, oleations and all those agregations mechanisms.

Regards

Zercas

DavidR
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Posted: 19 April 2010 at 12:07am \| IP Logged

As mentioned in an other posting, in then two bath chrome tanning, the "agregation" processes do not start until Cr2O7= anion is reduced, presumably after complete penetration by a single ion has occurred. Hence if penetration of trivalent chromium is so complicated and difficult, there should be tremendous differences in properties from two bath chrome tannage and the modern one bath process. I have handled two-bath wet-blue in Russia, and frankly no great difference in properties, including retannage properties is easily percieved! Thus I believe penetration of ordinary chrome three pre-tannins are no different from the two bath process! Only after elaborate changes occurring upon "demasking" and basification, are chrome three tannins begun to be locked inside collagen, and anionic sulphate masked chrome penetrates just as deeply as anionic dichromate, and the restrictions postulated by the Zercas-Ramasami team are not important at all!

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zercas
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Posted: 22 April 2010 at 12:52pm \| IP Logged

The Zercas-Ramasami Team, WOW !!! Do you know the mexican expression? " Hazmela buena compadre. ( Translation= I wish )

What do you mean by pre- tannins, PLS ? The only way to have a small molecule of Cr 3+ is to have 0 basicity. It is still done in some calf skin tanneries due to the " even tighter" collagen structure of the young skin.

By the way how long ago where you in Russia doing such anachronic tanning system ?

Regards

Zercas

zercas
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Posted: 22 April 2010 at 1:05pm \| IP Logged

Another Time Capsule, this one 73 years from the old ages of tanning I think the first page of this paper ends in "cero"

Regards

Zercas

http://pubs.acs.org/doi/abs/10.1021/j150385a006

zercas
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Posted: 22 April 2010 at 2:40pm \| IP Logged

And we have really come a long way baby ( like that Viginia Slims cigarette comercial goes )

As you can see it is a continious steping on some elses foot prints.

Regards

Zercas

http://pubs.acs.org/doi/abs/10.1021/ja01971a016

Edited by zercas on 22 April 2010 at 3:04pm

zercas
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Posted: 08 May 2010 at 3:56pm \| IP Logged

http://www.chinaleather.org/download/2-2/2-93.pdf

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Edited by zercas on 08 May 2010 at 6:34pm

zercas
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Posted: 08 May 2010 at 4:09pm \| IP Logged

I have found Atzet's work presented at the XXX IULTCS in China.

We have talked about it before, but I think as a matter of fact of recording it , this topic is the place to have it.

Drying and having a fluffy substrate is ideal for penetration, but I think it will remain as a curiosity and I do not see hords of tanners rushing to do three acetone degreasing and dehydration treatments. Maybe I am mistaken, time will tell. Acetone is a difiucult product to store and have around.

Regards

Zercas.

http://www.chinaleather.org/download/2-2/2-93.pdf

I have been having problems with some chinese links, maybe is my PC.

If you can not open the above link use this frase in Google Search

FAST CHROME TANNING BY IMMERSION OF BCD

Edited by zercas on 08 May 2010 at 6:32pm

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