Cellulose ether (CelluloseEther) is made from cellulose through the etherification reaction of one or several etherification agents and dry grinding. According to the different chemical structures of ether substituents, cellulose ethers can be divided into anionic, cationic and nonionic ethers. Ionic cellulose ethers mainly include carboxymethyl cellulose (CMC); non-ionic cellulose ethers mainly include methyl cellulose ether (MC), hydroxypropyl methyl cellulose ether (HPMC) and hydroxyethyl cellulose Ether (HC), etc. Non-ionic ethers are divided into water-soluble ethers and oil-soluble ethers, and non-ionic water-soluble ethers are mainly used in mortar products. In the presence of calcium ions, ionic cellulose ether is unstable, so it is rarely used in dry-mixed mortar products that use cement, slaked lime, etc. as cementing materials. Nonionic water-soluble cellulose ethers are widely used in the building materials industry because of their suspension stability and water retention.
01. Chemical properties of cellulose ether
Each cellulose ether has the basic structure of cellulose – anhydroglucose structure. In the process of producing cellulose ether, the cellulose fiber is first heated in an alkaline solution, and then treated with an etherifying agent. The fibrous reaction product is purified and pulverized to form a uniform powder with a certain fineness.
Propylene oxide is used to obtain hydroxypropyl substituents in addition to methane chloride in the production of HPMC. Various cellulose ethers have different methyl and hydroxypropyl substitution ratios, which affect the organic compatibility and thermal gelation temperature of cellulose ether solutions.
In the production process of MC, only methyl chloride is used as etherification agent
02. Application scenarios of cellulose ether:
Cellulose ether is a non-ionic semi-synthetic high molecular polymer, which is water-soluble and solvent-soluble. It has different effects in different industries. For example, in chemical building materials, it has the following composite effects:
①Water retaining agent ②Thickener ③Leveling property ④Film forming property ⑤Binder
In the polyvinyl chloride industry, it is an emulsifier and dispersant; in the pharmaceutical industry, it is a binder and a slow and controlled release framework material, etc. Because cellulose has a variety of composite effects, its application The field is also the most extensive. The following focuses on the use and function of cellulose ether in various building materials.
(1) In wall scraping putty:
At present, in most cities in my country, the water-resistant and scrub-resistant environment-friendly putty has been basically valued by people. It is produced by acetal reaction of vinyl alcohol and formaldehyde. Therefore, this material is gradually eliminated by people, and the cellulose ether series products are used to replace this material. That is to say, for the development of environmentally friendly building materials, cellulose is currently the only material.
In the water-resistant putty, it is divided into two types: dry powder putty and putty paste. Among these two kinds of putty, modified methyl cellulose and hydroxypropyl methyl should be selected. The viscosity specification is generally between 30000-60000cps. The main functions of cellulose in putty are water retention, bonding and lubrication. Since the putty formulas of various manufacturers are different, some are gray calcium, light calcium, white cement, etc., and some are gypsum powder, gray calcium, light calcium, etc., so the specifications, viscosity and penetration of cellulose in the two formulas are also different. The amount added is about 2‰-3‰. In the construction of wall scraping putty, since the base surface of the wall has a certain degree of water absorption (the water absorption rate of the brick wall is 13%, and the water absorption rate of the concrete is 3-5%), coupled with the evaporation of the outside world, if the putty loses water too quickly , It will lead to cracks or powder removal, which will weaken the strength of the putty. Therefore, adding cellulose ether will solve this problem. But the quality of the filler, especially the quality of ash calcium is also extremely important.
Due to the high viscosity of cellulose, the buoyancy of the putty is also enhanced, and the sagging phenomenon during construction is also avoided, and it is more comfortable and labor-saving after scraping. It is necessary to add more cellulose ether in the powder putty. Its production and use are more convenient. The filler and additives can be evenly mixed in dry powder.
(2) Concrete mortar:
In concrete mortar, to achieve the ultimate strength, the cement must be fully hydrated. Especially in summer construction, the concrete mortar loses water too quickly, and the measures of complete hydration are used to maintain and sprinkle water. Waste of resources and inconvenient operation, the key is that the water is only on the surface, and the internal hydration is still incomplete, so the solution to this problem is to add water-retaining agent cellulose to the mortar concrete, generally choose hydroxypropyl methyl or methyl fiber The viscosity specification is between 20000–60000cps, and the addition amount is 2%–3%. The water retention rate can be increased to more than 85%. The method of use in mortar concrete is to mix the dry powder evenly and put it in water.
(3) In plastering gypsum, bonded gypsum, and caulking gypsum:
With the rapid development of the construction industry, people’s demand for new building materials is also increasing. Due to the increase in people’s awareness of environmental protection and the continuous improvement of construction efficiency, cementitious gypsum products have developed rapidly. At present, the most common gypsum products are plastering gypsum, bonded gypsum, inlaid gypsum, and tile adhesive. Plastering gypsum is a high-quality plastering material for interior walls and ceilings. The wall surface plastered with it is fine and smooth. A new type of building light board adhesive is a sticky material made of gypsum as the base material and adding various additives. It is suitable for bonding between various inorganic building wall materials. It is non-toxic, tasteless, and fast setting. It is a supporting material for building boards and block construction; gypsum caulking agent is a gap filler between gypsum boards and a repair filler for walls and cracks.
These gypsum products have a series of different functions. In addition to the role of gypsum and related fillers, the key issue is that the added cellulose ether additives play a leading role. Since gypsum is divided into anhydrous gypsum and hemihydrate gypsum, different gypsum has different effects on the performance of the product, so thickening, water retention and retardation determine the quality of gypsum building materials. The common problem of these materials is hollowing and cracking, and the initial strength cannot be reached. To solve this problem, it is to choose the type of cellulose and the compound utilization method of the retarder. In this regard, methyl or hydroxypropyl methyl 30000 is generally selected. –60000cps, the addition amount is 1.5%–2%. Among them, cellulose focuses on water retention and retarding lubrication. However, it is impossible to rely on cellulose ether as a retarder, and it is necessary to add a citric acid retarder to mix and use without affecting the initial strength.
Water retention generally refers to how much water will be lost naturally without external water absorption. If the wall is too dry, water absorption and natural evaporation on the base surface will make the material lose water too quickly, and hollowing and cracking will also occur. This method of use is mixed with dry powder. If you prepare a solution, please refer to the preparation method of the solution.
(4) Thermal insulation mortar
Insulation mortar is a new type of interior wall insulation material in the northern region. It is a wall material synthesized by insulation material, mortar and binder. In this material, cellulose plays a key role in bonding and increasing strength. Generally choose methyl cellulose with high viscosity (about 10000cps), the dosage is generally between 2‰-3‰), and the method of use is dry powder mixing.
(5) interface agent
Choose HPNC 20000cps for the interface agent, choose 60000cps or more for the tile adhesive, and focus on the thickener in the interface agent, which can improve the tensile strength and anti-arrow strength. Used as a water-retaining agent in the bonding of tiles to prevent tiles from dehydrating too quickly and falling off.