Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Patent
1996-04-19
1997-12-23
Howard, Jacqueline V.
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
508513, C10M13306, C10M17302
Patent
active
057007667
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the use of an amphoteric surfactant in a water-base system for reducing the flow resistance between a solid surface and the water-base liquid system.
It is well-known that the flow resistance of a liquid in a conduit is largely due to the turbulence that arises at the conduit wall. Surfactants with the ability to form extremely long, cylindrical micelles have, in recent years, attracted a great interest as friction-reducing additives to systems with circulating water, especially those destined for heat distribution. An important reason for this interest is that, although one desires to maintain a laminar flow in the conduits, one wishes at the same time to have turbulence in the heat exchangers to achieve therein a high heat transfer per unit area.
The rod-shaped micelles are distinguished by operating in a fairly disorderly fashion at low Reynold's numbers (below 10.sup.4), and having no or only a very slight effect on the flow resistance. At higher Reynold's numbers (above 10.sup.4), the micelles are paralleled and result in a friction reduction very close to that which is theoretically possible. At even higher Reynold's numbers (e.g. above 10.sup.5), the shear forces in the liquid become so high that the micelles start to get torn and the friction-reducing effect rapidly decreases as the Reynold's numbers increase.
The range of Reynold's numbers within which the surface-active agents have a maximum friction-reducing effect is among others dependent on the concentration, the range increasing with the concentration.
By choosing the right concentration of surface-active agents and suitable flow rates in tubings and heat exchangers, it is thus possible to establish a laminar flow in the tubes and turbulence in the heat exchangers. Thus, the dimensions of both the tubes and the exchangers can be kept at a low level, or the number of pump stations, and consequently the pump work, can alternatively be reduced while retaining the same tubular dimensions.
Most of the surface-active agents hitherto used as friction-reducing additives to circulating water system--mainly destined for heat distribution, see for example WO 85/03083--are cationic surfactants like C-.sub.16-18 -alkyltrimetyl ammonium salicylate. However, this type of surface-active agent is slowly degraded, both aerobically and anaerobically, and is highly toxic to marine organisms. Since heat-distribution systems usually suffer from important leaks (it is estimated that in one year 60-100% of the water leaks out), it follows that the added chemicals end up in the ground water and in various fresh-water recipients. This combination of low biodegradability and high toxicity is a fundamental criterion for a product injurious to the environment.
In the Swedish Patent publication No 467 826 it is disclosed that nonionic, alkoxylated alkanolamides may be used as friction-reducing agents. These nonionic surfactants have an excellent friction reducing effect at low or moderate temperatures but at higher temperatures the friction reducing effect is less satisfactory and may even be lost.
It has now surprisingly been found that a water-soluble amphoteric surfactant containing preferably hydrocarbon groups, forming a hydrophobic portion containing 10-36 carbon atoms, groups and molecular weight of less than 1400, preferably less than 800, or a salt thereof has the ability to form long cylindrical micelles. The amphoteric surfactant may also contain one or more nonionic, hydrophilic groups, such as hydroxyl groups and ether groups. This type of amphoteric surfactant has an excellent friction-reducing effect well adapted for aqueous heat transfer systems. Furthermore, the effect of the amphoteric surfactant on the environment is low, especially in comparison with the previous used cationic friction-reducing agents. The amount of the amphoteric friction-reducing agent may vary within wide limits depending on the conditions but generally is 100-10.000 g/m.sup.3 of the aqueous heat transfer liquid.
Suitable amphoteric surfactants to b
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Harwigsson Ian
Hellsten Martin
Berol Nobel AB
Howard Jacqueline V.
Mancini Ralph J.
Morris Louis A.
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