What are Defoamers?
Defoamers are chemical additives that reduce and/or prevent the formation of foam in industrial process liquids such as paints, inks, adhesives and even construction products. The terms antifoam agent and defoamer are often used interchangeably, however, antifoam agents more accurately refer to materials that inhibit the generation and formation of bubbles. Dependent upon the application and performance requirements, they consist of polydimethylsiloxanes and other silicones, insoluble oils, stearates and glycols, as well as inorganics, such as silicates and talc.
What is Foam?
Foam is a coarse dispersion of a gas in a liquid, where the volume fraction of gas is greater than that of the liquid. The bubbles will migrate to the surface, as their density is less than that of the liquid. As the bubbles coalesce and collect at the air/surface interface, the bubble walls thin and break. Silicone defoamers accelerate the process and break the smaller bubbles as well. Generally, a defoamer is insoluble in the foaming medium and has surface-active properties. An essential feature of a polyether defoamer is the ability to spread rapidly on foamy surfaces.
In industrial processes, foams pose serious problems. They cause defects on surface coatings. They prevent the efficient filling of containers. Some of the sources of foam formation include:
Inclusion of air through agitation during production, filling, mixing of two-pack systems (often high-viscosity (epoxies, adhesives);
Air inclusion on the pigment surface, resulting in poor wetting of pigments;
Application: roller, spraying, brushing;
Filtration through a sieve or anything with air on the surface;
Generation/liberation of gases during chemical curing processes; e.g. polyisocyanates;
Introduction of air through substrate wetting (wood coatings, other highly porous substrates).
In the papermaking process, fibers, fillers and some additives are not water-insoluble, so they are easy to accumulate in an aqueous solution. Moreover between the different materials as far as possible from the incompatibility away, so it is difficult to get uniform performance and ideal strengthen paper. In order to solve the long fiber in the process of this problem, the use of polyacrylamide has the following advantages:
to improve the retention rate of fillers, pigments and so on. To reduce the loss of raw materials and environmental pollution.
to improve the strength of the paper (including dry and wet strength).
to improve the tear resistance and porosity to improve visual and printing performance.
The advantages of using polyacrylamide as a paper dispersant are also manifested in the fact that the product is soluble in water and forms a high viscosity liquid which promotes good dispersion of papermaking fibers and excellent paper forming effect at low added levels to improve pulp consistency And the softness of the paper, but also to improve the strength of the paper performance.
Adipic acid is one of the most commercially important aliphatic dicarboxylic acids. It is produced on a large scale primarily to supply the nylon 6,6 production chain. Other applications include the manufacture of coatings, synthetic lubricants, fibers, plastics, plasticizers and polyurethane resins. Adipic acid production has been predominantly based on cyclohexane and, to a lesser extent, phenol. Shifts in the hydrocarbon market and growing environmental concerns have resulted in the development of alternative production routes for adipic acid from renewable resources, such as sugar and fatty acids.
Epoxy propanol (EP), also known as glycidol, is an organic compound used in the manufacture of a range of products, such as detergents, industrial paints and coatings, and healthcare products. It is primarily manufactured in Japan and, to a much lesser degree, in the United States. Traditionally, EP is produced by one of two methods: epoxidation of allyl alcohol with hydrogen peroxide, or the reaction of epichlorohydrin with a caustic agent. However, allyl alcohol is extremely toxic and epichlorohydrin is made from hydrocarbon feedstocks, such as propylene. Both methods generate toxic by-products, such as hydrochloric acid, requiring costly purification processes to prevent the acid residues from entering the environment.
- ایجاد شده: 21/09/13
- آخرین ورود: 21/09/13