hydroxypropyl methylcellulose HPMC in Plastering MortarFebruary 2nd 2023
Redispersible latex powder is the main additive of the new material cement dry powder mortar. It has been widely used in exterior wall insulation, coatings, floor mortars, polymer cement-based waterproof coatings and various building materials. As redispersible latex powder is a process in which emulsion is dried to produce latex powder, and then the latex powder is converted into emulsion during use, it is required that the produced latex powder should not be agglomerated during transportation and storage, in order to facilitate the latex powder in The redispersion in the mortar ensures that the application performance of the rubber powder in the mortar is close to the performance of the emulsion. At present, various inorganic mineral powders such as talc, diatomite, calcium carbonate, kaolin, etc. are mainly used as anti-caking agents. These inorganic mineral powders have played a very good role in the production of redispersible latex powders. However, due to the environmental, transportation, preservation and other natural environmental and human influences, the latex powders produced with the above-mentioned mineral powders are affected during transportation. After being pressed or stored for a long period of time, there are different degrees of agglomeration, which affects the performance of rubber powder in cement mortar and the shelf life of rubber powder.
The preparation method of the redispersible latex powder modified anti-caking agent includes the following steps: heating anhydrite to 75 to 90°C, adding molten fatty acid, stirring at 40 to 60 rpm for 20 to 40 minutes, and then adding The ethanol solution of the phthalate coupling agent is continuously stirred for 20 40 minutes, and finally the cationic etherifying agent is added and stirred for 50 70 minutes to obtain the finished product; in the ethanol solution containing the phthalate coupling agent, the The weight content is 40 to 60%; the redispersible latex powder modified anti-caking agent of this process can be used for redispersible latex powder to play an anti-caking effect. The weight amount is generally the total weight of the redispersible latex powder 1 3%. Redispersible latex powders include acrylic latex powder, vinyl acetate homopolymer latex powder, styrene and butadiene copolymer rubber powder or vinyl acetate and ethylene copolymer rubber powder.
In this process, the gypsum powder is composite modified with fatty acid and titanate coupling agent. The surface charge effect of the modified gypsum powder makes the powders mutually exclusive. When the redispersible latex powder is spray-dried, the modified gypsum powder and When other anti-caking agents are adsorbed on the surface of the rubber powder particles, air is introduced due to the repulsive effect between the gypsum powders, which makes the gaps between the latex powders larger, and the bulk density becomes smaller. They are compressed during transportation or the product is stored. During the period, it is not easy to agglomerate and agglomerate again; when the rubber powder is redispersed in the cement mortar, because the cationic etherifying agent is a surfactant that is easily soluble in water, it promotes the modified gypsum to become hydrophilic again. Under the action of the strong alkali of the cement mortar The cationic etherifying agent is decomposed and loses its surface activity, so that the redispersibility of the latex powder in the cement mortar is not affected, the anti-caking ability of the latex powder is improved, and the product quality is stabilized