What kinds of thickeners are commonly used?
The common thickeners are cellulose ether and its derivatives, associative alkali swelling thickener and polyurethane thickener.
(1) Cellulose ether and its derivatives: Cellulose ether and its derivatives are mainly hydroxyethyl cellulose, methyl hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose and so on. Hydrophobically modified cellulose is an associative thickener by introducing a small amount of long-chain hydrophobic alkyl groups into the hydrophilic framework of cellulose. Its thickening effect is comparable to that of cellulose ether thickeners with much larger molecular weight.
(2) Alkali swelling thickeners: Alkali swelling thickeners are divided into two categories: non-associative alkali swelling thickeners and associative alkali swelling thickeners.
(3) Polyurethane thickener and hydrophobic modified non-polyurethane thickener: polyurethane thickener is a hydrophobic group modified ethoxy polyurethane water-soluble polymer, which belongs to non-ionic associative thickener. The development of environmentally friendly associative polyurethane thickeners has attracted widespread attention. In addition to the linear associative polyurethane thickeners described above, there are comb associative polyurethane thickeners. Thickening agent has a specific rheological property, and the acid resistance is the first to promote alginate propylene glycol. The guar gum is the first choice of the modified guar gum. The pseudoplasticity of the solution and the strongest solubility in cold water are xanthan gum. The emulsion adhesive is the best in Arabia gum; gel agar is stronger than other gum, but the transparency of the gel is especially carrageenan; carrageenan is also superior to other adhesives in the stability of milk.
Thickening agent is also called gelling agent. It is also called paste or food glue when used in food. It can increase the viscosity of the system and keep the system in a uniform stable suspension state or opacification state, or form a gel. Widely used in food, paint, adhesives, cosmetics, detergents, printing and dyeing, rubber, medicine and other fields. In re-coating printing, the shear force occurs under the action of the printing mechanical force of the pigment printing paste, which consists of thickener, water, binder and paint paste. The shear force reduces the viscosity of the printing paste greatly in an instant. When the shear force disappears, the paste returns to its original high viscosity and the printing outline of the fabric is clear. This viscosity change with the change of shear force is mainly realized by the thickener. Thickener plays a coordinated role in the thickening, stability and rheological properties of re-latex paint. In the process of latex polymerization, it can be used as a protective colloid to improve the stability of the emulsion. When the pigment and filler are dispersed, the viscosity of the dispersed material will be increased and dispersed. During the storage and transportation process, the stability and the freeze-thaw resistance of the coating will be improved, and the pigments and fillers will be prevented from caking. Then the viscosity of the latex paint will be adjusted and the thixotropy will be good. Adding several thousandth of food thickeners in food has the functions of gelation, film formation, water holding, suspension, emulsification, foam stabilization and lubrication. It plays an important role in the color, aroma, taste, structure and relative stability of fluidized food or gelatin food.
Thickeners are mostly hydrophilic macromolecule compounds, which can be classified as animal, plant, mineral, synthetic or semi-synthetic according to their sources. It can be divided into two categories: natural and synthetic. Natural products are mostly made from plants and algae containing polysaccharide viscous substances, such as starch, pectin, agar, gelatin, alginate, keratin, dextrin, Jasmine gum, polysaccharide derivatives, etc. Synthetic products include cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, starch derivatives, casein, sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, poly. Ethylene alcohol, low molecular weight polyethylene wax, polyacrylamide, etc.