Subject: I need your HELP on nucleophilic substitution rxn
From: abangi@mail.clemson.edu (Audimar P. Bangi)
Date: Sat, 16 Nov 1996 00:27:05 -0800
Greetings.
I'm currently working on the reaction of wood, a ligno-cellulosic material,
with acetic anhydride, (CH3CO)2O. There is considerable evidence that
after reaction (--which is carried out at 120 degrees centigrade without
any catalyst), the wood's hydroxyl groups (-OH) are replaced by a more
bulky acetyl group (-COCH3). Most references point to a nucleophilic
substitution reaction. While I understand that a carbonyl-containing
carboxylic acid derivative such as acetic anhydride is susceptible to
nucleophilic attack on its carbonyl carbon, I can't exactly figure out if,
by application of heat at 120 degrees C, wood-OH will undergo
homolytic-type fission to produce a nucleophile fragment; and which one:
(1) wood-O: (-) + H (+)
or
(2) wood (+) + :OH (-) ???
[It might help to point out that C-H has higher bond energy compared to an
O-H bond. But does it mean that (1) is more likely to occur?]
The basic repeat unit of the cellulosic component of wood is cellubiose,
which consists of 2 glucose units (C6H12O6).
Thank you for your kind help.
All the best,
Audimar P. Bangi
Clemson University
Subject: Re: Desperately needing information re: polymers
From: Skip Thacker
Date: 16 Nov 1996 04:04:18 GMT
Hi Todd,
The application you describe, namely pouring a polymer into a mold to
obtain a 70-90A hardness 2" thick by 15" diam. part that will be tough,
abrasion resistant, U.V. resistant, and resistant to most chemicals (except
aromatic and polar solvents) sounds ideal for a PVC Plastisol. Plastisols are
liquid, or paste, at ambient temperatures and can be fused or cured by
heating to 350-400 deg. F depending on their formulation (choice of
plasticiser, etc.). A good starting point for plastisol technology would be
the Geon Co., in Avon Lake, Ohio. I also have formulation and compounding
background in PVC, but unless you want to "mix your own", I'd suggest
contacting a producer. Modern Plastics Magazine, the January issue, is a
good scource for this type of info.
Regards, Skip
Subject: Polyacrylimides
From: eric.larson@shockwave.metronj.org (eric larson)
Date: 15 Nov 96 22:16:06
Acylamide is a very versatile monomer; it can be copolymerized with a wide
variety of other materials that add various functionality and topological
variations. For soil erosion topology is likely to be more important than in
most other PAM applications. It is unlikely that the same type of PAM would be
desirable for erosion control and flocculation of solids in run-offs. The amide
group also allows for various post polymerization modification. In addition, it
is possible to graft polyacrylamide onto other polymer backbones eg. starch.
Thus you have endless possibilities for polymer design. The major PAM
manufacturers are Allied Colliods, SNF-Floeger, Nalco and Cytek. Of that group
Cytec and Nalco are more interested in supporting R&D; in the US on PAM
applications. Aquatic toxicity varies tremendously with polymer structure; you
cannot just ask for PAM aquatic tox data; you have to know a bit more first.
Inhibitors and catalysts? PAM is always polymerized using a free radical
process; azo type initiators and redox pair systems are most commonly used.
Catalysts aren't used in PAM polymerization - some people call initiators
catalysts, which is not correct. Acrylamide monomer is produced by hydrolysis
of acrylonitrile over a Raney copper catalyst. The inhibitors used in
acrylamide monomer are usually copper sulfate or MEHQ. Dosing generally means
dissolving the PAM in water and squirting or injecting the solution somewhere.
If you want more information a good starting point is the chapter on acrylamide
in the most recent Kirk-Othmer Encyclopedia of Chemical Technology.
There is probably already a substantial body of literature on soil applications
- PAMs have been used for seedling dips, erosion control, water retention (some
types of PAM are even deliquescent).
By the way, there is a BIG difference between polyacrylamide and
polyacrylimide. The second is generally the result of abuse of the first, and
is quite useless for the applications you are considering.
m> We are starting to investigate the effectiveness of
m> polyacrylimides (PAM) as erosion control agents at
m> construction sites and ancillary benefits as a
m> flocculant for enhancing precipitation of solids in
m> stormwater runoff. The agricultural world is
m> doing backflips over the effectiveness of PAM
m> as a soil erosion inhibitor. I called a
m> company called Allied Colloids and they said
m> there is about 200 different varieties of PAM. Does
m> anybody know any good information sources and/or
m> quality research on: 1) aquatic toxicity, 2)
m> catalysts, 3) inhibitors, 4) effective dosing
m> ranges, 5) dosing mechanisms, etc. for PAM. Any
m> help would be greatly appreciated.
--
|Fidonet: eric larson 1:107/407
|Internet: eric.larson@shockwave.metronj.org
| Standard disclaimer: The views of this user are strictly his/her own.
Subject: Re: Polyacrylimides
From: deherrin
Date: Sat, 16 Nov 1996 16:03:52 -0500
John Spevacek wrote:
>
> Ed Molash wrote:
> >We are starting to investigate the effectiveness of
> >polyacrylimides (PAM) as erosion control agents at
> >construction sites and ancillary benefits as a
> >flocculant for enhancing precipitation of solids in
> >stormwater runoff. The agricultural world is
> >doing backflips over the effectiveness of PAM
> >as a soil erosion inhibitor. I called a
> >company called Allied Colloids and they said
> >there is about 200 different varieties of PAM. Does
> >anybody know any good information sources and/or
> >quality research on: 1) aquatic toxicity, 2)
> >catalysts, 3) inhibitors, 4) effective dosing
> >ranges, 5) dosing mechanisms, etc. for PAM. Any
> >help would be greatly appreciated.
> >
> I'm guessing that you mean polyacryl **a*mides, not **i** mides. Cytec
> (nee American Cyanamide) also is a supplier, although with a lot fewer
> grades. I know that beyond a certain molecular weight, the toxicity drops
> to zero (it can be used as a flocculant in water treatment facilities).
> You might try giving them a call, as they do make it there.
>
> John
The largest user and perhaps, now, the largest manufacturer of
polyacrylamides is SNF Floerger. The North American corporate
headquarters for SNF Holding Company is located in Riceboro, GA. If you
can't find them listed under SNF Holding Company, you can surely find
them under Chemtall, Inc.
Subject: Re: Coilcoating?
From: Dante Ferrari
Date: Sat, 16 Nov 1996 16:27:05 -0500
Although I am somewhat familiar with your process of interest, coating
metals with a chemical- or weather-resistant plastic covering, I know of
no formal name for such a process. There are several recent patents
which take advantage of maleic anhydride (or derivatives thereof) or
organosilane monomer grafts onto a polymeric substrate, and use these to
"stick" the polymer to a metal surface. Unfortunately, I have never seen
an article published on this process. Check the Chem Abstracts over the
past ten years, particularly under "maleic anhydride", "maleic acid",
"maleic ester" or organosilanes such as "triethyl vinylsilane", etc.
The problem with the Chem Abs is that they tend to use proper IUPAC names
for these compounds, so you will probably not find them listed as such.
Particularly in Japan, there are a tonne of patents available, if you
have access to such information.
Good luck,
Dante
