Suspension rate and viscosity of bentonite in water based casting coating

　　The effects of sodium bentonite, sodium carboxymethyl cellulose (CMC), white latex and Sodium Tripolyphosphate on the suspension rate and viscosity of water-based casting coatings were studied.
　　The results show that: sodium bentonite and CMC can significantly improve the suspension rate and viscosity of the coating; white emulsion adhesive can reduce the suspension rate of the coating, but increase its viscosity; sodium tripolyphosphate can reduce the suspension rate and viscosity of the coating. It is found that there is an interaction between them on the suspension rate of the coating, but no interaction on its viscosity.
　　Water based casting coating is cheap, safe and reliable, stable performance, convenient transportation, clean and pollution-free. It is widely used in sand casting, metal mold casting, centrifugal casting, lost foam casting and so on. It is one of the development directions of casting coatings in the future. In the production of water-based casting coating, the most commonly used inorganic suspending agent is sodium bentonite, the organic suspending agent is sodium carboxymethyl cellulose (CMC), the thickener is white latex, and the binder is sodium tripolyphosphate. However, the influence of these additives on the most important technical indexes of coatings, suspension rate and viscosity, and their interaction are studied. In this paper, neutral bauxite was selected as the aggregate of water-based coating. The effects of additives such as sodium bentonite, CMC, white latex and Sodium Tripolyphosphate on the suspension rate and viscosity of the coating were studied, providing reference for the research of water-based casting coating.
　　Materials and methods: bauxite, 320 mesh; sodium bentonite; CMC; sodium tripolyphosphate; white latex; wetting agent: OP-10; defoamer: JFC.
　　The suspension rate of the coating was 100 ml cylinder, which was clarified by standing for 6 and 24 h, and its viscosity was determined by flow cup method of 100 ml and quasi 6 mm. Sodium bentonite, white latex, CMC and sodium tripolyphosphate were used to initiate and dissolve before use, and then the slurry was prepared and used 72 hours later.
　　Conclusion：
　　1. The results show that white latex can significantly improve the viscosity of the coating, but reduce the suspension rate of the coating; sodium bentonite and CMC can improve the suspension rate and viscosity of the coating; sodium tripolyphosphate can reduce the suspension rate and viscosity of the coating.
　　2. According to the influence of the four additives on the suspension rate and viscosity of the coating, there is no corresponding relationship between the suspension rate and viscosity of the coating.
　　3. There is interaction between sodium tripolyphosphate and sodium bentonite, sodium tripolyphosphate and white latex, sodium bentonite and CMC, but no interaction on its viscosity.
　　4. The interaction between CMC and Na bentonite is strengthened when the suspension rate of coating is investigated for 6h. The interaction between sodium tripolyphosphate and sodium bentonite,sodium　tripolyphosphate and white latex is weakened in Tongling bentonite production and sales.