Development trend of surfactant agents in metal cleaning industry
Date:2015-11-24 00:00 Source:http://www.chenhua.cc Click:
In metal processing, metal cleaning is an indispensable process, such as cutting, plating, painting and so on, which should be done cleaning process firstly, to remove rust, grease, scale, dust, etc. Metal detergent can be divided into two major categories: solvent-based and water-based, detergent with solvent based has oil solvent and halogen hydrocarbon solvent, etc. the oil solvent existent problems, like flammable, pollution, energy waste, etc, which largely limited the application, so in many cases, oil solvent have been gradually replaced by water-based detergent, water-based cleaning agent has become the main development direction of metal detergent industry. Water-based detergent is a hybrid system with main active component and other additives. Surfactant has big influence in cleaning process, e.g. firstly, surfactant can destroy the function of metal surface and dirt; secondly, surfactant can wet metal surface, so that the cleaning solution can surround dirty particles; thirdly, surfactant can emulsify animal and vegetable oil for small droplets, dispersed in solution; fourthly, surfactant can dissolve solid dirt particles; fifth, surfactant can disperse all kinds of dirt, prevent re-deposition. The difference of surfactant composition in detergent can change the function in cleaning process. As a detergent, the surfactant can destroy the interaction between dirt particles and metal surface, however, the wet, permeability and emulsifying ability of these surfactants not good enough, therefore, the formula of water-based detergent is often with several other kinds of surfactants. The choice of the surfactant is also related to the cleaning process, for example, in the process of spray washing, it require low foam detergent; In ultrasonic cleaning industry, it ask detergent with good resistance re-deposition, but in the pipeline cleaning process, high emulsification and high wet detergent is required.
After washed with water based detergent, surfactant is often adsorbed on the surface of a metal surface, which maybe influence the next process, in particular, the components of oxygen supply system are in danger of fire, therefore, the metal parts after cleaning must be cleaning with de-ionized water to absorbed surface active agent, and it should adopt surfactant that easy to remove for the cleaning of oxygen supply system.
The large of water-based cleaning agent is used, wastewater treatment has become a serious problem. Before, our focus on detergent is on the cleaning performance and service life, but now the formula of spray washing or ultrasonic cleaning agent is completely different from the past. It is not the best choice that emulsified completely the organic fouling into the cleaning liquid, on the contrary, the organic fouling can be released from the emulsion when the stirring is stopped or cooled, so when grease or dirt is separated, the cleaning agent can be regenerated. Membrane filtration technology can be used to separate cleaning agent and dirt, the filter can be divided according to the size, shape, and charge of the molecules.
In recent years, the characteristics of micro emulsion have also caused the attention, micro emulsion is exist in the phase region of multi system that is composed of water, oil, surfactant and the electrolyte, it with ultra low interfacial tension, high solubilizing capacity of lipophilic and hydrophilic substance, therefore, the solubilization of organic solvents in the process of fabric decontamination can be combined with traditional wet washing characteristics. Raney et al. has used to test the typical water/ surfactant/ assistant surfactant/ electrolyte by the multi-component system, they think that if the medium and oil pollution formed micro emulsion in the process of cleaning, and the washing temperature close to the phase transition temperature, the system decontamination force will achieve to maximum.