Transcript Doing Without Phosgene, Hydrogen Cyanide, and Formaldehyde

Doing without Phosgene,
Hydrogen Cyanide, and
Formaldehyde
PART II
Reducing Toxicity of Isocyanates
Isocyanates
- Associated with occupational asthma;
- Require a hood;
toluenediisocyanate
Ways to reduce toxicity:
-Increasing MW;
- Chemical conversion;
Chemical Conversion of Isocyanates
1. Conversion to carbodiimides
RNCO
2. Reaction with polymeric diol
Various HA Agents Can Add to
Isocyanate Group
RNCO  HA  RNHCOA
HO  R  OH  OCN  R  NCO  ( R  O  C (O)  NH  R) n 
alchohol
isocyanate
polyurethane
H 2 N  R  NH 2  OCN  R  NCO  ( R  NHC(O)  NH  R)n 
amine
isocyanate
polyurea
• -used to inactivate isocyanate group
• -require thermal unblocking
• -volatile blocking agent
Blocked Prepolymer Mixtures
Methyl ethyl ketoxime
Tengfei Shen, Mangeng Lu, Liyan Liang; Synthesis and properties of biodegradable
polyurethane crosslinkers from methyl ethyl ketoxime-blocked diisocyanate.
Macromolecular Research, August 2012, Volume 20, Issue 8, pp 827-834
Thermally Reversible Polyurethane
Polymers
Dissociation Temperature
Alcohol > Lactam > phenol > ketoxime >active methylene compound
1,4-butanediol
4,4’-isopropylidendipenol (bisphenol A, BPA)
4,4-diphenyldiisocyanate
4,4’-Isopropylidendipenol (bisphenol A, BPA)
http://www.edf.org/health/four-reasons-bpa-free-wont-protect-you?s_src=ggad&s_subsrc=bpa&gclid=CM_c2IT1wsACFaTm7Aodo1cA2Q
Polymerization of Isocyanate
Monomers
Polymers Made without Isocyanates: Reactions
of Cyclic Carbonates with Diamines
Contras: low MW (9350 and 5345)
Possible solution: use chain extension agents
Reactions of Cyclic Carbonates with Diamines
Applications of Polycarbonate Polymers
http://atlasthermoforming.com.au/wp-content/gallery/poly-carb/polycarbonate_chair.png
http://www.metalandpolycarbonatesheets.com/durotuff/polycarbonate-sheet-1.jpg
http://www.bisphenol-a-europe.org/uploads/images/EN_Socio-economic-contribution_011013-2_08.png
http://gallinausa.com/wp-content/uploads/2012/02/547.photo_.c.jpg
Polycarbonates
Traditional polycarbonate synthesis involves phosgene
Solvent: methylene chloride
Base: pyridine, NaOH
Ester Exchange Method for Polycarbonate Synthesis
No solvents, no salt by-products
Needs:
High temperature
Vacuum/N2 flow to extract phenol
http://chem.chem.rochester.edu/~chem424/pcsynth.htm
CO2 Can Be an Alternative to CO in
Polycarbonates Synthesis
Summary for Phosgene
Elimination of phosgene in PC production is getting commercialized
(SABIC, Asahi, Mitsubishi)
Non-Phosgene Polycarbonate from CO2 - Industrialization of Green Chemical Process
Authors: Shinsuke Fukuoka (Asahi Kasei Chemicals Corporation)
Chapter 1. Introduction: Society And Chemical Industry
Chapter 2. Background Of Polycarbonate
Chapter 3. General Method For Synthesis Of Polycarbonate
Chapter 4. Technological Aspects Of The Industrial Processes For Producing Aromatic
Polycarbonates Using Carbon Monoxide (Co) As A Starting Material
Part 1. Interfacial Polycondensation Phosgene Process
Chapter 5. Technological Aspects Of The Industrial Processes For Producing Aromatic
Polycarbonates Using Carbon Monoxide (Co) As A Starting Material
Part 2. Non-phosgene Process
Chapter 6. General Aspect Of Non-Phosgene Polycarbonate Process From Co2 (Asahi
Kasei Process)
Chapter 7. Monomer Production Technology From Co2 (Asahi Kasei Process)
Chapter 8. Melt Polymerization Technology Of Asahi Kasei Process
Chapter 9. Excellent Features Of Polycarbonate Produced By Asahi Kasei Non-Phosgene
Process
Chapter 10. Economical Features Of Asahi Kasei Non-Phosgene Polycarbonate Process
Chapter 11. Contribution Of Asahi Kasei Non-Phosgene Polycarbonate Process To Society
Chapter 12. Other Approach 1 – Outline Of Chemical Fixation Of Co2 Into Polymer
Chapter 13. Other Approach 2 – Development Of Non-Phosgene Mdi Process
Summary for Phosgene
Polyurethane Synthesis
- Elimination of phosgene from isocyanate synthesis
- Methyl isocyanate synthesis on demand (DuPont)
- Advances in pest management to eliminate carbamates
Challenge:
- On demand production of other isocyanates
- Create similar products synthetized from less harmful materials
General Toxicity Rules for Safer
Substitutions
• CO2 is less toxic than CO
• Ethanol is less toxic than methanol
• Aliphatic amines are less toxic than aromatic and nitro aromatic compaunds
• Routs to amines through diols are less toxic than through nitriles
• Higher MW substance is less toxic that low MW substance
• Roots via carboxylic acid are less toxic than via nitro compounds
• Solids give less problems than liquids
Replacements for HCN
1. Replacements in gold ore extraction
- Thiourea (can be reused)/ thiourea + Fe(III) sulfate in ionic liquid
- Chloride on activated carbon
2. Replacements in adipic acid synthesis
- Renewable raw materials (petroselenic acid, cis-muconic acid
Elimination of Formaldehyde
Phenol-formaldehyde and urea-formaldehyde adhesives for the plywood and particle board
Elimination of Formaldehyde
Crease proofing resin for cotton
Being replaced by 1,2,3,4-butanetetracarboxylic acid and poly(maleic acid)
http://oecotextiles.wordpress.com/2011/01/04/formaldehyde-in-your-fabrics/