Polyurethane dispersion

Polyurethane Dispersion, or PUD, is understood to be a polyurethane polymer resin dispersed in water, rather than a solvent. Its manufacture involves the synthesis of polyurethanes having carboxylic acid functionality or nonionic hydrophiles like PEG incorporated into, or pendant from, the polymer backbone.[1]

Background

There has been a general trend towards converting existing resin systems to waterborne resins, for ease of use and environmental considerations.[2] Particularly, their development was driven by increased demand for solventless systems since the manufacture of coatings and adhesives entailed the increasing release of solvents into the atmosphere from numerous sources.[3]

The problem has always been that polyurethanes in water are not stable, reacting to produce a urea and carbon dioxide. Many papers have been published on the subject.[4][5] For environmental reasons there is even a push to have PUD available both water-based and bio-based.[6][7][8] PUDs are used because of the general desire to formulate coatings, adhesives, sealants and elastomers based on water rather than solvent, and because of the perceived or assumed benefits to the environment.

Synthesis

The techniques and manufacturing processes have changed over the years from those described in the first papers, journal articles and patents that were published. There are a number of techniques available depending on what type of species is required. An ion may be formed which can be an anion thus forming an anionic PUD or a cation may be formed forming a cationic PUD. Also, it is possible to synthesize a non-ionic PUD.[9] This involves using materials that will produce an ethylene oxide backbone, or similar, or a chain pendant from the main polymer backbone. Anionic PUDs are by far the most common available commercially. To produce these, initially a polyurethane prepolymer is manufactured in the usual way but instead of just using isocyanate and polyol, a modifier is included in the polymer Backbone chain or pendant from the main backbone. This modifier is/was mainly dimethylol propionic acid (DMPA).[10] This molecule contains two Hydroxy group and a carboxylic acid group.[11] The OH groups react with the isocyanate groups to produce an NCO terminated prepolymer but with a pendant COOH group. This is now dispersed under shear in water with a suitable neutralizing agent such as Triethylamine. This reacts with the carboxylic acid forming a salt which is water soluble. Usually diamine chain extender is then added to produce a polyurethane dispersed in water with no free NCO groups.[12] Various papers and patents show that an amine chain extender with more than two functionalities such as a triamine may be used too.[13] There is also a push to have a synthesis strategy that is non-isocyanate based.[14]

Uses

Uses include industrial coatings,[15] UV coating resins,[16] floor coatings,[17] hygiene coatings,[18] wood coatings,[19] adhesives,[20] concrete coatings,[21] automotive coatings,[22][23] clear coatings[24] and anticorrosive applications.[25] They are also used in the design and manufacture of medical devices such as the polyurethane dressing, a liquid bandage based on polyurethane dispersion.[26]

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References
  1. Ducheyne, Paul; Healy, Kevin; Hutmacher, Dietmar W.; Grainger, David W.; Kirkpatrick, C. James (2015). Comprehensive Biomaterials. Amsterdam: Elsevier. pp. 447. ISBN 9780080553023.
  2. "Water Based Polyurethanes Dispersions(PUDs)-An Overview". 2015-01-30. Retrieved 2018-08-21.
  3. Tant, M. R.; Mauritz, K. A.; Wilkes, G. L. (1997). Ionomers: Synthesis, structure, properties and applications. London: Blackie Academic Professional. p. 447. ISBN 9780751403923.
  4. Dieterich, D (1981-11-13). "Aqueous emulsions, dispersions and solutions of polyurethanes; synthesis and properties". Progress in Organic Coatings. 9 (3): 281–340. doi:10.1016/0033-0655(81)80002-7. ISSN 0300-9440.
  5. "US Patent US3491050" (PDF).
  6. Patel, Chintankumar J; Mannari, Vijay (2014-05-01). "Air-drying bio-based polyurethane dispersion from cardanol: Synthesis and characterization of coatings". Progress in Organic Coatings. 77 (5): 997–1006. Bibcode:1992POrCo..20....1B. doi:10.1016/j.porgcoat.2014.02.006. ISSN 0300-9440.
  7. Gurunathan, T; Arukula, Ravi (2018-04-01). "High performance polyurethane dispersion synthesized from plant oil renewable resources: A challenge in the green materials". Polymer Degradation and Stability. 150: 122–132. doi:10.1016/j.polymdegradstab.2018.02.014. ISSN 0141-3910.
  8. Li, Yingyuan; Noordover, Bart A. J.; van Benthem, Rolf A. T. M.; Koning, Cor E. (2014-01-02). "Reactivity and Regio-Selectivity of Renewable Building Blocks for the Synthesis of Water-Dispersible Polyurethane Prepolymers". ACS Sustainable Chemistry & Engineering. 2 (4): 788–797. doi:10.1021/sc400459q. ISSN 2168-0485.
  9. "NON-IONIC POLYURETHANE DISPERSIONS HAVING SDE CHANS OF POLYOXYETHYLENE" (PDF).
  10. "GEO Specialties Use of DMPA for PUDs" (PDF).
  11. Pubchem. "Dimethylolpropionic acid". pubchem.ncbi.nlm.nih.gov. Retrieved 2018-08-21.
  12. Jang, JY; Jhon, YK; Cheong, IW; Kim, JH (2002-01-01). "Colloids and Surfaces A: Physicochem". Eng. Aspects. 196: 135–143.
  13. Sun, DC; Chen, Q (2010-12-01). "Effect of chain extender and chain extension on properties of high solid content polyurethane dispersion and its film". Gaofenzi Cailiao Kexue Yu Gongcheng/Polymeric Materials Science and Engineering. 26: 69–72.
  14. Ma, S; Chen, C; Sablong, RJ; Koning, CE; Benthem, R (2018). "Non-isocyanate strategy for anionically stabilized water-borne polyurea dispersions and coatings". Journal of Polymer Science Part A: Polymer Chemistry. 56 (10): 1078–1090. doi:10.1002/pola.28986. ISSN 1099-0518.
  15. Blank, Werner. "FORMULATING POLYURETHANE DISPERSIONS" (PDF).
  16. Asif, Anila; Huang, Chengyu; Shi, Wenfang (2003). "UV curing behaviors and hydrophilic characteristics of UV curable waterborne hyperbranched aliphatic polyesters". Polymers for Advanced Technologies. 14 (9): 609–615. doi:10.1002/pat.380. ISSN 1099-1581.
  17. "Floor Coatings with PUD" (PDF).
  18. Howarth, G A; Manock, H L (July 1997). "Water-borne polyurethane dispersions and their use in functional coatings". Surface Coatings International. 80 (7): 324–328. doi:10.1007/bf02692680. ISSN 1356-0751.
  19. "Waterborne Floor Coatings for Wood Floors" (PDF).
  20. "PUD - Polymers - Adhesive Raw Materials - Adhesives - Markets & Industries - BASF Dispersions & Pigments". www.dispersions-pigments.basf.com. Retrieved 2019-04-11.
  21. Howarth, GA (2003). "Polyurethanes, polyurethane dispersions and polyureas: Past, present and future". Surface Coatings International Part B: Coatings Transactions. 86 (2): 111–118. doi:10.1007/BF02699621.
  22. "Patent US5071904A" (PDF).
  23. Communications, Covestro AG. "Automotive OEM Metal Metal Basecoat". www.coatings.covestro.com. Retrieved 2019-04-22.
  24. "URESEAL - Water-Based High-Gloss Polyurethane Coating | Polygem Epoxy". www.polygem.com. Retrieved 2019-04-26.
  25. Christopher, Gnanaprakasam; Anbu Kulandainathan, Manickam; Harichandran, Gurusamy (2015-07-01). "Highly dispersive waterborne polyurethane/ZnO nanocomposites for corrosion protection". Journal of Coatings Technology and Research. 12 (4): 657–667. doi:10.1007/s11998-015-9674-3. ISSN 1935-3804.
  26. Davim, J. Paulo (2012-10-16). The Design and Manufacture of Medical Devices. Cambridge, UK: Woodhead Publishing. p. 135. ISBN 9781907568725.
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