Polyols
| Polyols (selection) |
 |
 |
 Polyether -Polyol |
 Polyester -Polyol |
Polyols is the name of a group of organic compounds that contain several hydroxyl groups (-OH), so-called polyalcohols ( polyhydric alcohol with the simplest representatives monoethylene glycol and glycerine ). Polyols can be both linear (z. B. sorbitol ) and cyclic (eg. B. inositol ) constructed to be.
The number of hydroxyl groups in a chemical compound is indicated by the word ending: If a compound contains one, two or three hydroxyl groups, the ending “-ol”, “-diol” or “-triol” is added accordingly; four or more hydroxyl groups are generally referred to as a “polyol”.
The production of polyols, especially for the plastics industry, can be done both petrochemically (based on mineral oil ) and oleochemical (based on vegetable oil ).
properties
Since the umbrella term polyol is a purely chemical nomenclature and only indicates the presence of several hydroxyl groups, the polyols cannot be assigned any general properties. Polyols are mostly highly viscous (viscous) to solid at room temperature. This is due to the fact that hydrogen bonds form between the individual molecules.
Examples
Some commonly used polyols are:
- Polyols as tooth-friendly sugar substitutes in chewing gum and sweets: for example isomalt , sorbitol or mannitol
- Antifreeze : for example ethylene glycol ( 1,2-ethanediol ) or glycerine ( 1,2,3-propanetriol )
- Plastic components : Polyester polyols or polyether polyols are used in the manufacture of polyurethane .
- Dyes, fragrances, flavors and growth substances (for example essential oils ): various phenols with several hydroxyl groups
Biogenic polyols
As a rule, both the polyols and the polyisocyanates come from production from petrochemical raw materials, but polyols based on vegetable oils can also be used. Castor oil is particularly suitable for this because it itself has hydroxyl groups and can thus be reacted directly with isocyanates. Furthermore, derivatives used of castor oil. Furthermore, polyols based on vegetable oils can be produced on the one hand by epoxidation of the vegetable oils with subsequent ring opening and on the other hand via transesterification of vegetable oils with glycerine . Polyurethanes based on vegetable oils are also marketed as "bio-polyurethanes" due to the biogenic origin of some of the raw materials.
Biogenic polyols are currently priced above petrochemicals, which means that their use is restricted to specific purposes. Internationally, work is being done on polyols based on soy , rapeseed and sunflower oil , among other things as a basis for the production of mattress foams. Individual companies are working on the production of biogenic polyols from lignin . Large potential uses are u. a. for the production of polyurethanes as plastics, foams or synthetic resins as well as high-quality, light-resistant polyesters and polyurethanes for the paint raw materials industry.
literature
- W. Keim : Kunststoffe: Synthesis, Manufacturing Processes , Apparatus , 379 pages, Verlag Wiley-VCH Verlag GmbH & Co. KGaA, 1st edition (2006) ISBN 3527315829
Individual evidence
- ↑ Hans Kittel, Walter Krauß: Textbook of paints and coatings. Volume 2: Binders for solvent-based and solvent-free systems. 2nd edition Hirzel Verlag 1998, ISBN 3-7776-0886-6 .
- ^ A b Hans-Josef Endres, Andrea Siebert-Raths: Technical biopolymers. Hanser-Verlag, Munich 2009, pp. 113-114, ISBN 978-3-446-41683-3 .
- ↑ U. Buller, T. Hirth: From raw material to product - industrial biotechnology and material use of renewable raw materials as an example of process engineering research in the Fraunhofer Society. In: Chemical Engineer Technology - CIT. 81 (11); Pp. 1689-1696.