Etherified starch is a starch substituent ether formed by the reaction of hydroxyl groups in starch molecules with reactive substances, including hydroxyalkyl starch, carboxymethyl starch, and cationic starch. Since the etherification of starch improves the viscosity stability and the ether bond is not easily hydrolyzed under strong alkaline conditions, etherified starch is used in many industrial fields. Carboxymethyl starch (CMS) is a denatured form of anionic natural products and a natural polymer polyelectrolyte ether soluble in cold water. At present, cMS has been widely used in food, medicine, petroleum, daily chemical, textile, papermaking, adhesives, and paint industries. the
In the food industry, CMS is non-toxic and harmless to the human body and can be used as a quality improver. The finished product has excellent shape, color and taste, making it smooth, thick and transparent; CMS can also be used as a food preservative. In the pharmaceutical industry, CMS is used as tablet disintegrant, plasma volume expander, thickener for cake-type preparations and drug dispersant for oral suspoemulsion. CMS is widely used in the oilfield industry as a mud fluid loss reducer. It has salt resistance, can resist salt to saturation, and has anti-slump effects and a certain anti-calcium ability. It is a high-quality fluid loss reducer. However, due to poor temperature resistance, it can only be used in shallow well operations. CMS is used for light yarn sizing, and has the characteristics of fast dispersion, good film-forming property, soft size film, and easy desizing. CMS can also be used as a tackifier and modifier in various printing and dyeing formulations. CMS is used as an adhesive in paper coating, which can make the coating have good leveling and viscosity stability. Its water retention properties control the penetration of the adhesive into the paper base, giving the coated paper good printing properties. In addition, CMS can also be used as a viscosity reducer for coal slurry and oil-coal mixed fuel slurry, so that it has good suspension emulsion stability and fluidity. It can also be used as a tackifier for water-based latex paint, a chelating agent for heavy metal sewage treatment, and a skin cleaner in cosmetics. Its physical properties are as follows:
PH value: Alkaline (5% aqueous solution) Solubility: Can be dissolved in cold water Fineness: Less than 500μm Viscosity: 400-1200mpas (5% aqueous solution) Compatibility with other materials: Good with other building material admixtures Compatibility
1. The main function
Very good rapid thickening ability: medium viscosity, high water retention;
The dosage is small, and a very low dosage can achieve a high effect;
Improve the anti-sag ability of the material itself;
It has good lubricity, which can improve the operating performance of the material and make the operation smoother. the
2. scope of use
Starch ether is suitable for all kinds of (cement, gypsum, lime-calcium) interior and exterior wall putty, and all kinds of facing mortar and plastering mortar. Recommended dosage: 0.05%-0.15% (measured in tons), the specific use is subject to the actual ratio. It can be used as an admixture for cement-based products, gypsum-based products and lime-calcium products. Starch ether has good compatibility with other construction and admixtures; it is especially suitable for construction dry mixes such as mortar, adhesives, plastering and rolling materials. Starch ethers and methyl cellulose ethers (Tylose MC grades) are used together in construction dry mixes to impart higher thickening, stronger structure, sag resistance and ease of handling. The viscosity of mortars, adhesives, plasters and roll renders containing higher methyl cellulose ethers can be reduced by the addition of starch ethers. the
3. Classification of starch ethers
Starch ethers used in mortars are modified from natural polymers of some polysaccharides. Such as potatoes, corn, cassava, guar beans and so on. the
General modified starch
Starch ether modified from potato, corn, cassava, etc. has significantly lower water retention than cellulose ether. Due to the different degree of modification, the stability to acid and alkali is different. Some products are suitable for use in gypsum-based mortars, while others can be used in cement-based mortars. The application of starch ether in mortar is mainly used as a thickener to improve the anti-sagging property of mortar, reduce the adhesion of wet mortar, and prolong the opening time. Starch ethers are often used together with cellulose, so that the properties and advantages of these two products complement each other. Since starch ether products are much cheaper than cellulose ether, the application of starch ether in mortar will bring about a significant reduction in the cost of mortar formulations. the
guar ether
Guar gum ether is a kind of starch ether with special properties, which is modified from natural guar beans. Mainly by the etherification reaction of guar gum and acrylic functional group, a structure containing 2-hydroxypropyl functional group is formed, which is a polygalactomannose structure.
(1) Compared with cellulose ether, guar gum ether is more soluble in water. The pH value has basically no effect on the performance of guar ethers. the
(2) Under the conditions of low viscosity and low dosage, guar gum can replace cellulose ether in an equal amount, and has similar water retention. But the consistency, anti-sag, thixotropy and so on are obviously improved. (3) Under the conditions of high viscosity and high dosage, guar gum cannot replace cellulose ether, and the mixed use of the two will produce better performance.
(4) The application of guar gum in gypsum-based mortar can significantly reduce the adhesion during construction and make the construction smoother. It has no adverse effect on the setting time and strength of gypsum mortar. the
(5) When guar gum is used in cement-based masonry and plastering mortar, it can replace cellulose ether in an equal amount, and endow the mortar with better sagging resistance, thixotropy and smoothness of construction. the
(6) Guar gum can also be used in products such as tile adhesives, ground self-leveling agents, water-resistant putty, and polymer mortar for wall insulation. the
(7) Since the price of guar gum is significantly lower than that of cellulose ether, the use of guar gum in mortar will significantly reduce the cost of product formulation. the
Modified mineral water retention thickener
The water-retaining thickener made of natural minerals through modification and compounding has been applied in China. The main minerals used to prepare water-retaining thickeners are: sepiolite, bentonite, montmorillonite, kaolin, etc. These minerals have certain water-retaining and thickening properties through modification such as coupling agents. This kind of water-retaining thickener applied to mortar has the following characteristics. the
(1) It can significantly improve the performance of ordinary mortar, and solve the problems of poor operability of cement mortar, low strength of mixed mortar, and poor water resistance. the
(2) Mortar products with different strength levels for general industrial and civil buildings can be formulated. the
(3) The material cost is significantly lower than that of cellulose ether and starch ether.
(4) The water retention is lower than that of the organic water retention agent, the dry shrinkage value of the prepared mortar is larger, and the cohesiveness is reduced. the
4. Application of starch ether
Starch ether is mainly used in construction mortar, which can affect the consistency of mortar based on gypsum, cement and lime, and change the construction and sag resistance of mortar. Starch ethers are usually used in conjunction with non-modified and modified cellulose ethers. It is suitable for both neutral and alkaline systems, and is compatible with most additives in gypsum and cement products (such as surfactants, MC, starch and water-soluble polymers such as polyvinyl acetate).
Main features:
(1) Starch ether is usually used in combination with methyl cellulose ether, which shows a good synergistic effect between the two. Adding an appropriate amount of starch ether to methyl cellulose ether can significantly improve the sag resistance and slip resistance of the mortar , with a high yield value. the
(2) Adding an appropriate amount of starch ether to the mortar containing methyl cellulose ether can significantly increase the consistency of the mortar and improve the fluidity, making the construction smoother and the scraping smoother. (3) Adding an appropriate amount of starch ether to the mortar containing methyl cellulose ether can increase the water retention of the mortar and prolong the open time. the
(4) Starch ether is a chemically modified starch ether soluble in water, compatible with other additives in dry powder mortar, widely used in tile adhesives, repair mortars, plastering plasters, interior and exterior wall putty, gypsum-based embedded Joints and filling materials, interface agents, masonry mortar.
The characteristics of starch ether mainly lie in: ⑴ improving sag resistance; ⑵ improving construction; ⑶ increasing mortar yield, recommended dosage: 0.03% to 0.05%.
Post time: Feb-16-2023