Silicone oils

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The repeating unit of the siloxane - polymer

Silicone oils (actually diorganopolysiloxanes; polymerized siloxanes with organic side chains ) come from the group of silicones and are synthetic silicon-based oils which, in contrast to mineral oils or vegetable oils , do not have organic, i.e. carbon-based , but siloxane-based chain molecules as their basic structure. This is characterized by the periodically alternating arrangement of silicon and oxygen atoms with the general empirical formula [R 1 R 2 SiO] n . Residues R , which are mostly organic residues , but can also be halogens, hang on the free outer electrons of the silicon . So silicone oils have both an organic and an inorganic part.

properties

Silicone oils are clear, colorless, non-toxic, neutral, odorless, tasteless, chemically inert , hydrophobic liquids that are temperature- stable over a wide range and have a molecular weight of 162 to 150,000 g / mol, a density of 0.76 to 1.07 g / cm 3 and viscosities from 0.6 to 1,000,000 mPa · s. They are also excellent electrical insulators . Silicone fluids have a low surface tension of 21.5 mN / m (at 25 ° C) or less. They are permanently heat-resistant up to approx. 180 ° C in air. Depending on the viscosity, their pour point is −80 to −40 ° C. Silicone fluids have between -60 ° C and to 200 ° C lubricating properties on. The lubricity is lower than that of mineral oils and other lubricants. They do not tend to gum up. Silicone fluids are soluble in benzene , toluene , aliphatic and chlorinated hydrocarbons . They are not very resistant to strong inorganic acids and bases . Like all silicones, they are very gas-permeable.

The representative with the simplest structure is the polydimethylsiloxane in which R 1 and R 2 (see structural formula above) are each a methyl group .

Industrial and technical use

There are many uses for silicone oils. Some of the most important are:

  • In the refrigeration in the freeze-drying silicone oils are used as a refrigerant, and because of their non-combustibility in heat baths , used as a heat transfer medium of laboratories, so-called oil baths.
  • Due to their low surface tension, some silicone oils have a foam-inhibiting effect and are accordingly typically used in industrial plants such as fermenters or distillation plants , where foaming can have critical consequences.
  • Silicone oil is also a great propellant in oil diffusion pumps .
  • Silicone fluids play an important role as electrical insulating materials (dielectrics) (e.g. in transformers).
  • Specific plasticine , as silly putty consist half of silicone oil, while the other half of boric acid exists.
  • In vehicle construction, silicone fluids of higher viscosity are used than fluids for torque transmission with automatic speed compensation in viscous clutches as axle and / or (in connection with a) central differential.

In addition, silicone oils can be used as hydraulic fluids , as mold release agents, as an ingredient for special printing inks, for hydrophobing glass (e.g. in pharmaceuticals), ceramics, textiles, leather etc., cleaning and polishing additives for car paints, metals, leather and furniture, to prevent pigments from floating out in pigmented paints, as pressure gauges, collectors in flotation processes, dampening agents.

Silicone grease

Silicone grease is a waterproof grease. It is made by combining a silicone oil with a thickener.

Technical applications

Silicone grease is often used for the lubrication and preservation of rubber parts that are sensitive to contact with mineral oils . It also acts as a corrosion inhibitor and lubricant for purposes that require thicker lubricants. When fitting grease or hot water fat , it is also used for lubrication of drinking water - taps used.

Use in the chemical laboratory

Silicone grease is widely used as a temporary sealant and lubricant for joint joints such as those typically used on laboratory glassware . Although silicones are considered to be chemically inert, some historically significant compounds were created through unintended reactions with silicones.

Medical and cosmetic applications

Due to the properties of silicone oil, medical products and cosmetics are also made from silicone oils. The area of ​​application is very broad.

In addition, silicone oils serve as a component of cosmetics , detergents and cleaning agents , skin protection ointments , ointment bases , massage oils , implants and agents for hairstyle stabilization and as a carrier for fragrances.

food industry

The defoaming effect also plays an important role in the food industry . For example, silicone oils are added in the production of jams and, outside of Europe, fruit juices in order to suppress the formation of undesirable foams . Additions to deep-frying oils also make the foam formation during deep-frying processes much more controllable.

The maximum concentrations for the silicone oil polydimethylsiloxane ( food additive E900) are:

  • Jam , jam , jelly (max. 10 mg / kg)
  • Frying oils and fats (max. 10 mg / kg)
  • Canned fruit and vegetables (max. 10 mg / kg)
  • Chewing gum (max. 100 mg / kg)

Individual evidence

  1. ↑ a b W. Kaiser, R. Riedle: Silicones. In: H. Harnisch, R. Steiner, K. Winnacker (eds.): Winnacker-Küchler: Chemische Technik , Organic Technologie II. 4th edition. Volume 6, Carl Hanser Verlag, Munich 1982, p. 838.
  2. ↑ H. Miyahara, A. Nakajima, J. Wada, S. Yanabu: Breakdown Characteristics of Combined Insulation in Silicone Oil for Electric Power Apparatus. In: "2006 IEEE 8th International Conference on Properties and Applications of Dielectric Materials", Properties and applications of Dielectric Materials, 8th International Conference. 2006, pp. 661-664. doi: 10.1109 / ICPADM.2006.284264 . ISBN 1-4244-0190-9 .
  3. ↑ MG Voronkov, WP Mileshewitsch, Yu. A. Yuzhelewski: The Siloxane Bond, Physical Properties and Chemical Transformations. In: Studies in Soviet Science. New York / London 1978, p. 6 ff.
  4. ^ A. Brulls, M. Johan: Method of monitoring a freeze drying process. AstraZeneca UK, London 2001, p. 3.
  5. ↑ W. Thimm: Silicone oil as a working fluid for a thermostat and such a thermostat. Offenlegungsschrift DE 10 2004 042 829.8 , Karlsruhe 2004, p. 2.
  6. ↑ K. Klein, J. Maluzi: Process for activating defoamer liquids . German gold u. Silber-Scheideanstalt, Offenlegungsschrift DE 1 544 001 , Frankfurt 1966, pp. 1-6.
  7. ↑ M. Takahashi et al.: Electrically insulating oil. Kureha Kagako Kogyo KK, Offenlegungsschrift DE 24 46 591 A1 , Tokyo 1974, pp. 1-14.
  8. ↑ N. Horiuchi: Mold release agents. Daikin Kogyo Co. Ltd., laid- open specification DE 26 41 898 A1 , Osaka (Japan) 1976, pp. 1-49.
  9. ^ Y. Ogawa et al .: Magnetic Toner. Offenlegungsschrift DE602004001025T2 , Tokyo 2006, p. 26 ff.
  10. ↑ P. Ehlenz: Protective agent for the formation of a protective coating of an organosilicon compound on glass and ceramic surfaces. Collo GmbH, Offenlegungsschrift DE 28 43 234 , Bornheim-Hersel 1978, pp. 1-15.
  11. ↑ G. Bauernfeind ao: paint care, cleaning and preservation agents. VEB Petrolchemisches Kombinat Schwedt, Offenlegungsschrift DD 220 321 B1 , Schwedt (Oder) 1985, pp. 1-3.
  12. ↑ S. Betlej: Dynamic torsional vibration damper especially for power machines. Offenlegungsschrift DE 1 292 451 A , Budapest, pp. 1-4.
  13. ↑ Thorsten Bartels et al: Lubricants and Lubrication. In: Ullmann's Encyclopedia of Industrial Chemistry. Weinheim 2005. doi : 10.1002 / 14356007.a15_423
  14. ^ I. Haiduc: Silicone Grease: A Serendipitous Reagent for the Synthesis of Exotic Molecular and Supramolecular Compounds. In: Organometallics. volume 23, 2004, pp. 3–8. doi: 10.1021 / om034176w
  15. ↑ Lucian C. Pop, M. Saito: Serendipitous Reactions Involving a Silicone Grease . In: Coordination Chemistry Reviews . 2015, doi : 10.1016 / j.ccr.2015.07.005 .
  16. ^ RD Blackledge, M. Vincenti: Identification of Polydimethylsiloxane Lubricant Traces From Latex Condoms in Cases of Sexual Assault. In: Journal of the Forensic Science Society. Vol. 34, 1994, pp. 245-256.
  17. ↑ H. Gnad et al.: Temporary silicone oil implantation after vitrectomy for proliferative diabetic retinopathy in Klin Monatsbl Augenheilkd 189 (11), 1986, pp. 388-390.
  18. ^ IF Burgess, CM Brown, PN Lee: Treatment of head louse infestation with 4% dimeticone lotion: randomized controlled equivalence trial. (PDF; 75 kB). In: BMJ . Vol. 330, 2005, p. 1423 ff.
  19. ↑ SM Barry et al.: Portioned detergent and cleaning agent preparation containing silicone oil. Procter & Gamble Company, laid- open specification EP 1 595 939 B1 , The Cincinnati, Ohio, US pp. 1-15.
  20. ↑ W. Schalk et al.: Skin protection ointment containing silicone. Offenlegungsschrift DE 1 134 478 , Schenley Industries Inc., New York 1960, pp. 1-5.
  21. ↑ n.v . : clear water-in-silicone oil hair conditioning agent. Wella AG, Offenlegungsschrift WO 10/28506 A1 , Darmstadt 2001, pp. 1-30.
  22. ↑ Frank Massholder: Dimethylpolysiloxan, E 900: Foam inhibitor: definition, product knowledge, food science: food lexikon.de. In: www.lebensmittellexikon.de. Retrieved January 30, 2016 .
  23. ↑ Zusatzstoff-Online.de: E 900: Dimethylpolysiloxane