xxxxx
Hazard to Others
Posts: 116
Registered: 21-5-2004
Member Is Offline
Mood: No Mood
|
|
lycra spandex analog
i have observed that lycra spandex may depolymerize under certain conditions. i was wondering if a more durable fiber could be made by replacing
phosgene with 1,1 dichloroactone in the lycra spandex manufacturing process.
|
|
|
Nicodem
|
Thread Moved
29-7-2009 at 08:54 |
JohnWW
International Hazard
Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline
Mood: No Mood
|
|
COCl2 (the acid chloride of carbonic acid) is used to make polycarbonates, by reaction with diols or para-diphenols such as bisphenol A,
para-HO-C6H4-CH2-C6H4-OH, in the presence of pyridine (which forms the hydrochloride with the liberated HCl). A more recent "green" alternative is the
reaction of such substrates with CO2 (the anhydride of carbonic acid) under high pressure, with H2O being liberated and no need for pyridine. I
believe references about the new process involving CO2 have previously been posted on this forum, and there should be recent patent literature about
it. (Search on sites like http://www.patent2pdf.com and http://www.freepatentsonline.com ).
However, Lycra Spandex, which is produced as a highly elastic polyamide fiber, is NOT a polycarbonate, see http://www.lycraspandexlinks.com/ and http://en.wikipedia.org/wiki/Spandex , which do not seem to mention COCl2 used in the processes for making the stuff. Any depolymerization of it
would occur under conditions similar to those under which polyamides like nylons may depolymerize, e.g. hydrolysis by strong acids or alkalis.
Wikipedia says this about the chemistry involved:
Step 1: The first step is to produce the prepolymer. This is done by mixing a macroglycol with a diisocyanate monomer. The two compounds are mixed
together in a reaction vessel to produce a prepolymer. A typical ratio of glycol to diisocyanate is 1:2.
Step 2: The prepolymer is further reacted with an equal amount of diamine. This reaction is known as chain extension reaction. The resulting solution
is diluted with a solvent to produce the spinning solution. The solvent helps make the solution thinner and more easily handled, and then it can be
pumped into the fiber production cell.
Step 3: The spinning solution is pumped into a cylindrical spinning cell where it is cured and converted into fibers. In this cell, the polymer
solution is forced through a metal plate called a spinneret. This causes the solution to be aligned in strands of liquid polymer. As the strands pass
through the cell, they are heated in the presence of a nitrogen and solvent gas. This process causes the liquid polymer to react chemically and form
solid strands.
Substitution of 1,1-dichloroacetone for COCl2, not being an acid chloride unlike COCl2, in the polycarbonate process would result in no reaction at
all under ordinary conditions. The nearest acid chloride homologs would be para-dicarboxylic acid dichlorides, starting with oxalyl chloride,
ClC(=O)-C(=O)Cl, and including terephthalic acid dichloride, ClC(=O)-C6H4-C(=O)Cl , which, or alternatively the anhydride, is used to make PET
plastic. Reacting these with a diol or para-diphenol would result in a polyester (with liberation of HCl), not a polycarbonate. Polyesters, used as
clothing and other fibers and as sheets and bottles, are not as durable or resistant to UV light as polycarbonates. The main circumstances of any
depolymerization of polyesters would be hydrolysis with strong acids or alkalis, similarly to any ester.
[Edited on 29-7-09 by JohnWW]
|
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
