Degreasing processes

Surface prqiaiation of the joint area may be required to remove oxides, grease, moisture, etc. (prior to adhesive application) by mechanical, solvent, etching or degreasing processes to facilitate wetting. 

Surface preparation may be required to remove oxides, moisture, grease, etc. Prior to welding they are removed by mechanical, pickl or degreasing processes, the application of which canbe an addedsouree of variability. 

With few exceptions it is more efficient and economical to use at least two different pretreatments, i.e. degreasing processes which deal with a) and b), and pickling processes which remove oxide and corrosion films. Degreasing comes first, as pickling processes fail on hydrophobic surfaces. 

FIGURE 1.10 Schematic of the new degreasing process. (From Wang, L.K. et al. Case Studies of Cleaner Production and Site Remediation, Training Manual DTT-5-4-95, United Nations Industrial Development Organization, Industrial Sectors and Environment Division, Vienna, Austria, April 1995.)... 

Recalculate the time before breakthrough occurs, based on the following transient condition. The adsorber system is on line for one hour at the above normal design conditions when the inlet concentration of TCE rises to an average value of 2500 ppmv due to a malfunction in the degreaser process the efficiency also drops to 97.5% during this time. Assume the SAT remains the same. 

In contrast to alkyl phenol ethoxylates the class of fatty alcohol ethoxylates is biodegradable and eco-friendly. Efficient technical surfactants found in this class are Lutensol XL 700, Lutensol T08, Lutensol A07, Lutensol AO8 and Eusapon OD. The phase behaviour was characterised in systems of type H20/NaCl-suet-technical non-ionic surfactant. The salt mass fraction was kept constant at = 0.10 and the oil volume fraction at = 0.50. In view of the degreasing process, which is conducted at 30°C, the X-point of the optimal system should be located around 30°C and the formation of the highly viscous La-phase should be suppressed. Figure 10.5 presents the T-y cuts for the respective systems. 

However, the La-phase in both systems extends over a wide y -range below the lower phase boundary. The most suitable of the characterised surfactants regarding the degreasing process is Eusapon OD. Although less efficient than Lutensol A07 and Lutensol A08 no La-phase can be observed and the X-point is located near the degreasing temperature, T = 48.13°C. 

The results obtained from the characterisation of the phase behaviour and in the beam house imply that Eusapon OD is a suitable alternative allowing for an eco-friendly degreasing of animal skins. However, the understanding of the so far unidentified degreasing mechanism is the key goal for a continuous development of the degreasing process itself. In order to clarify the role of microemulsions in degreasing additional phase behaviour and interfacial tension measurements were conducted. 

Figure 10.12 Schematic of the variation of the phase behaviour during the degreasing process. In the short float the ultra-low interfacial tension between water and oil ensures efficient degreasing. Upon reducing the salt mass fraction the phase behaviour shifts to higher temperatures. At the degreasing temperature now an oil-in-water microemulsion coexists with an oil-excess phase. Shearing induces the formation of a stable macroemulsion that prevents the depositing of the fat on the skin and ensures the transport of the fat away from the skin. Note that only the Gibbs triangles correspond to the real experimental conditions. The T-y cuts are shown for clarity.

Guide to Cleaner Technologies—Cleaning and Degreasing Process Changes , U.S. EPA/625/R-93/017... 

Between 1914 and 1918, solvent and general chemical production had been geared to the needs of war. At war s end, the chemical surpluses included, in addition to phenol and cellulose acetate, the acetone and butanol from the Weizmann fermentation process and chlorine from poison gas production. The latter, made by electrolysis of sodium chloride solution, became the basis of the British chlorinated solvents industry. Here the outstanding firm was Albright Wilson, which began manufacture of carbon tetrachloride in 1925. Cleaning and degreasing processes led to production of trichloroethylene, for which demand increased dramatically between 1928 and 1936. The principal manufacturer was Weston Co., later taken over by ICl. 

Of the many factors in choosing a metal cleaning method, the degree of cleanliness required is perhaps the prime consideration. By selection of the proper solvent and cleaning equipment best suited to the shape of the work and the contaminants involved, the desired degree of cleanliness can usually be attained with the degreasing process. Solvent-soluble soils can be completely removed, and the insoluble soils flushed off. Because the final cycle in the process is a rinse in pure solvent vapors, no soluble residues will remain on the part nor will soil be redeposited. 

Appropriate characteristics for solvents to be used in the vapor degreasing process are as follows ... 

Figure 10.6 Metal degreasing process with SOLVSAFE solvents.

Uses Pesticide intermediate mfg. of phenol, chloronitrobenzene, aniline, DDT, silicone resins, dyes, perfumes, polysulfone solvent carrier for methylene diisocyanate solvent for paints, pesticides, degreasing processes, pharmaceuticals heat transfer medium adhesive rubbers and adhesives primer or adhesive additive for adhering elastomeric coatings to syn. fiber fabrics coated with syn. rubber surf, coating dry cleaning intermediate for halogen synthesis in food-pkg. adhesives adjuvant for PC food-pkg. resins solvent in food-contact polysulfone rGsins... 

Figure 14.8.17. Closed-loop batch vapor degreasing process.

Degreasing process can be conducted automatically in different ways by ... 

The concentration of substances emitted to the air during the degreasing processes reached the steady-state constant value ... 

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