Multifunctional Additives For Metalworking Fluids
Metalworking fluids provide many advantages and benefits to their users. However, they are subject to stringent requirements with regard to their technical characteristics and environmental properties. In order to adjust the performance and ancillary properties of metalworking fluids, the formulator needs high quality additives. Most of these additives are surface/interface active molecules or formulations.
Goldschmidt Chemical Corporation, a wholly owned subsidiary of Degussa Corporation, and its Industrial Specialties business line have a long history in the development and production of surface/interface active products using organic chemistry or organomodified polysiloxanes (OMS). As a result, Goldschmidt has a unique molecular construction set available that enables us to offer additives to meet the specific requirements of the metalworking fluid formulator. Further, our products are developed to ensure ease of formulation while eliminating in-use issues such as metal and process incompatibility.
The following overview provides a summary of the product classes Goldschmidt’s Industrial Specialties business line can provide.
GOLDSCHMIDT EMULSIFIERS
For water miscible metalworking fluids it is essential to use good emulsifiers in order to maintain stable dilutions in water. Due to the fact that metalworking fluid emulsions are typically formed without specific mixing equipment, the concentrates must be selfemulsifiable in waten In addition to being self-emulsifiable, good emulsifiers should also be readily soluble in base oils, demonstrate lubricating properties and prevent dermatologicai and toxicological issues.
Although Goldschmidt has a complete line of emulsifiers based on natural raw materials like fatty acid amides, fatty alcohol ethoxylates and vegetable oil-based polyglycolesters, our focus is on specialty emulsifiers based on glycerol fatty acid esters and sorbitan fatty acid esters see Figure 5 (page 25).
In addition to providing excellent emulsifying properties in the base oils typically used in metalworking fluids, emulsifiers based on glycerol fatty acid esters demonstrate excellent toxicological, ecological and dermatologicai properties. Goldschmidt emulsifiers based on glycerol fatty acid esters, such as TAGAT® V 20 have especially good solubility in vegetable oils and synthetic esters. Therefore, they are particularly recommended for the formulation of environmentally-friendly metalworking fluids based on renewable resources.
Goldschmidt emulsifiers can be used alone or in combination with other emulsifiers to optimize the performance of a wide variety of metalworking fluids. Goldschmidt emulsifiers ensure the spontaneous formation of finely dispersed, stable oil-in-water emulsions. Additionally, Goldschmidt can provide custom-made products for specific applications based on our customer’s requirements.
GOLDSCHMIDT ANTIFOAMS
The main requirement of a metalworking fluid antifoam is high efficiency with regard to foam suppression and foam knock down. The negative consequences of foam in a metalworking fluid operation are numerous, including poor lubrication, inadequate cooling and diminished ability to visually inspect parts during the metalworking operation.
In addition to high efficiency, other critical success factors must be considered when selecting an antifoam. The antifoam must be stable in the metalworking fluid concentrate and should not separate during storage. Stability can especially be a problem in metalworking fluids with high water content. Not only the water content, but the overall composition of the metalworking fluid is crucial for the stability of the antifoam. For example, certain antifoams are very effective in soluble oils and not in synthetics. Other antifoams are best chosen on the basis of the operating conditions to which the formulated metalworking fluid will be subjected. Considerations include in-use water quality and system filtration. Furthermore, the antifoam should not negatively influence subsequent treatments of processed metal parts, such as painting, electro plating and gas nitrating or gas carbonization.
All antifoam classes are characterized by different properties. Organic oil antifoams have a high surface tension (> 30 mN/m), making them comparatively less efficient than silicone antifoams. However, they offer the advantage of good process compatibility.
Silicone oil antifoams are characterized by a very high efficiency due to their low surface tension (~21 mN/m). However, they can not be used in many critical applications since unmodified silicone oil is hydrophobic and oleophobic at the same time. Due to this incompatibility, silicone oil antifoams can cause problems during subsequent plating and painting operations.
Antifoams based on organo-modified siloxanes combine the high compatibility of organic oil antifoams with the high efficiency of the silicone oil antifoams. Organo-modified siloxanes, like silicone oils, are based on a polysiloxane backbone to ensure low surface tension which is essential for efficient defoaming activity. Additionally, substantial physical and physico chemical characteristics are achieved by organic side chains which are not present in silicone oils. By careful selection of organic substituents, it is possible to adjust antifoams based on organo-modified siloxanes to meet demanding performance requirements. Goldschmidt applies this approach to tailor make anitfoams for specific applications.