Doing without Phosgene, Hydrogen Cyanide, and FormaldehydePART II

Reducing Toxicity of Isocyanates

toluenediisocyanate

Isocyanates

- Associated with occupational asthma;

- Require a hood;

Ways to reduce toxicity:

-Increasing MW;

- Chemical conversion;

Chemical Conversion of Isocyanates

1. Conversion to carbodiimides

2. Reaction with polymeric diol

RNCO

Various HA Agents Can Add to Isocyanate Group

RNHCOAHARNCO

nRNHOCORNCOROCNOHRHO ))((

nRNHONHCRNCOROCNNHRNH ))((22

alchohol

isocyanate

isocyanate polyurethane

polyureaamine

• -used to inactivate isocyanate group

• -require thermal unblocking

• -volatile blocking agent

Blocked Prepolymer Mixtures

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

Methyl ethyl ketoxime

Thermally Reversible Polyurethane Polymers

Dissociation Temperature

Alcohol > Lactam > phenol > ketoxime >active methylene compound

1,4-butanediol

4,4-diphenyldiisocyanate

4,4’-isopropylidendipenol (bisphenol A, BPA)

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://www.bisphenol-a-europe.org/uploads/images/EN_Socio-economic-contribution_011013-2_08.png

http://atlasthermoforming.com.au/wp-content/gallery/poly-carb/polycarbonate_chair.png

http://www.metalandpolycarbonatesheets.com/durotuff/polycarbonate-sheet-1.jpg

http://gallinausa.com/wp-content/uploads/2012/02/547.photo_.c.jpg

PolycarbonatesTraditional polycarbonate synthesis involves phosgene

Solvent: methylene chlorideBase: pyridine, NaOH

Ester Exchange Method for Polycarbonate Synthesis

http://chem.chem.rochester.edu/~chem424/pcsynth.htm

No solvents, no salt by-productsNeeds:High temperatureVacuum/N2 flow to extract phenol

CO2 Can Be an Alternative to CO in Polycarbonates Synthesis

Summary for PhosgeneElimination of phosgene in PC production is getting commercialized (SABIC, Asahi, Mitsubishi)

Non-Phosgene Polycarbonate from CO2 - Industrialization of Green Chemical ProcessAuthors: 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 FormaldehydePhenol-formaldehyde and urea-formaldehyde adhesives for the plywood and particle board

Elimination of FormaldehydeCrease proofing resin for cottonBeing replaced by 1,2,3,4-butanetetracarboxylic acid and poly(maleic acid)

http://oecotextiles.wordpress.com/2011/01/04/formaldehyde-in-your-fabrics/