What Is Cellulose Ether?

Cellulose ether is the powdered cellulose ether generated with wood fiber or refined short cotton fiber as the primary raw materials, after chemical therapy and also by the reaction of etherifying agents such as chlorinated ethylene, chlorinated propylene and also oxidized ethylene.

The production procedure of cellulose ether is complex. It starts with the removal of cellulose from cotton or timber, which then changes right into alkaline cellulose after adding sodium hydroxide and also by chemical reaction (alkaline solution). Under the action of etherifying representatives (etherification response), cellulose ethers are produced from alkaline cellulose with such processes as washing with water, drying out and also grinding.

Various etherifying representatives can transform alkaline cellulose right into various sorts of cellulose ethers. The molecular structure of cellulose is composed of the molecular bonds of dried sugar systems. Each sugar unify contains three hydroxyl teams. Under specific problems, the hydroxyl groups will be replaced by methyl, hydroxyethyl, hydroxypropyl and the like groups, and also can create cellulose of various ranges (as an example, if substituted by methyl, then it is called methyl cellulose; if replaced by hydroxyethyl, after that it is called hydroxyethyl cellulose; if substituted by hydroxypropyl, after that it is called hydroxypropyl cellulose). Given that methyl cellulose is a blended ether created by the etherification response, with methyl as the main material however consisting of a small amount of hydroxyethyl or hydroxypropyl, it is called methyl hydroxyethyl cellulose ether or methyl hydroxypropyl cellulose ether. Because of the distinction in the substituents (such as methyl, hydroxyethyl and also hydroxypropyl) and also the distinction in the level of alternative (the quantity of replaced substance of responsive hydroxyl in each cellulose), cellulose ethers of various ranges and also qualities can be gotten. Different ranges can be widely made use of in building, food as well as pharmaceutical markets, in addition to various other different areas such as everyday chemical industry and also oil industry.
Cellulose ethers are water-soluble polymers produced by the chemical alteration of cellulose. Cellulose ethers work as stabilizers, thickeners, and viscosity modifiers in many industries.

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What Are The Functions Of Cellulose Ether In Cement Mortar?

 What Are The Functions Of Cellulose Ether In Cement Mortar?

In ready-mixed mortar, only a little bit of cellulose ether can significantly improve the performance of wet mortar. It can be seen that cellulose ether is a major additive that affects the construction performance of mortar. 

The selection of cellulose ethers with different varieties, different viscosities, different particle sizes, different degrees of viscosity and added amount will also have different effects on the improvement of the performance of dry mortar. At present, many masonry and plastering mortars have poor water retention performance, and water slurry separation occurs after a few minutes of standing still. Therefore, it is very important to add cellulose ether to cement mortar.

Cellulose ether-water retention

Water retention is an important performance of methyl cellulose ether, and it is also a performance that many domestic dry mortar manufacturers, especially those in areas with higher temperatures in the south, pay attention to.

In the production of building materials, especially dry mortar, cellulose ether plays an irreplaceable role, especially in the production of special mortar (modified mortar), it is an indispensable and important part.

The viscosity, dosage, environmental temperature and molecular structure of cellulose ether have a great influence on its water retention performance. Under the same conditions, the higher the viscosity of the cellulose ether, the better the water retention; the higher the content, the better the water retention. Usually, a small amount of cellulose ether can greatly increase the water retention of the mortar, and when the content reaches a certain level When the temperature is higher, the increasing trend of water retention rate slows down; as the ambient temperature rises, the water retention of cellulose ether usually decreases, but some modified cellulose ethers also have better water retention under high temperature conditions; fibers with lower substitution degree Plain ether has better water retention performance.

The hydroxyl group on the cellulose ether molecule and the oxygen atom on the ether bond will associate with the water molecule to form a hydrogen bond, so that the free water becomes bound water, thereby playing a good water retention effect; the water molecule and the cellulose ether molecular chain Interdiffusion allows water molecules to enter the macromolecular chain of cellulose ether and are subject to a strong binding force, thereby forming free water, entangles the water, and improves the water retention of cement slurry; cellulose ether improves the fresh cement slurry The rheological properties, porous network structure and osmotic pressure or film-forming properties of cellulose ether hinder the diffusion of water.

Cellulose ether-thickening and thixotropy

Cellulose ether gives the wet mortar excellent viscosity, can significantly increase the bonding ability of the wet mortar and the base layer, and improve the sag resistance of the mortar. It is widely used in plastering mortar, tile bonding mortar and external wall insulation system. The thickening effect of cellulose ether can also increase the anti-dispersion ability and homogeneity of freshly mixed materials, prevent material delamination, segregation and bleeding, and can be used in fiber concrete, underwater concrete and self-compacting concrete.

The thickening effect of cellulose ether on cement-based materials comes from the viscosity of the cellulose ether solution. Under the same conditions, the higher the viscosity of the cellulose ether, the better the viscosity of the modified cement-based material, but if the viscosity is too large, it will affect the fluidity and operability of the material (such as sticky plaster knife). Self-leveling mortar and self-compacting concrete, which require high fluidity, require low viscosity of cellulose ether. In addition, the thickening effect of cellulose ether will increase the water demand of cement-based materials and increase the output of mortar.

The high viscosity cellulose ether aqueous solution has high thixotropy, which is also a major characteristic of cellulose ether. The aqueous solution of methyl cellulose usually has pseudoplasticity and non-thixotropic fluidity below its gel temperature, but exhibits Newtonian flow properties at low shear rates. Pseudoplasticity increases with the increase of the molecular weight or concentration of cellulose ether, regardless of the type of substituent and the degree of substitution. Therefore, cellulose ethers of the same viscosity grade, whether it is MC, HPMC, or HEMC, always exhibit the same rheological properties as long as the concentration and temperature remain constant. When the temperature increases, a structured gel is formed, and a high thixotropic flow occurs.

High-concentration and low-viscosity cellulose ethers exhibit thixotropy even below the gel temperature. This property is very beneficial to the construction of building mortar to adjust its leveling and sagging properties. It should be noted here that the higher the viscosity of the cellulose ether, the better the water retention, but the higher the viscosity, the higher the relative molecular weight of the cellulose ether, and the corresponding reduction in its solubility, which will have a negative impact on the mortar concentration and construction performance.

Cellulose ether-entraining effect

Cellulose ether has obvious air-entraining effect on fresh cement-based materials. Cellulose ether has both hydrophilic group (hydroxyl group, ether group) and hydrophobic group (methyl group, glucose ring). It is a surfactant with surface activity and air-entraining effect. The air-entraining effect of cellulose ether will produce a "ball" effect, which can improve the working performance of freshly mixed materials, such as increasing the plasticity and smoothness of the mortar during operation, which is conducive to the paving of mortar; it will also increase the output of mortar. , Reduce the production cost of mortar; but it will increase the porosity of the hardened material, reduce its strength and elastic modulus and other mechanical properties.

As a surfactant, cellulose ether also has a wetting or lubricating effect on cement particles, which together with its air-entraining effect increases the fluidity of cement-based materials, but its thickening effect will reduce fluidity. Cellulose ether has an effect on cement-based materials. The influence of fluidity is a combination of plasticizing and thickening effects. Generally speaking, when the content of cellulose ether is very low, it is mainly manifested as plasticizing or water-reducing effect; when the content is high, the thickening effect of cellulose ether increases rapidly, and its air-entraining effect tends to become saturated. Therefore, it has a thickening effect or an increase in water demand.

Cellulose ether-retarding effect

Cellulose ether will prolong the setting time of cement paste or mortar and delay the hydration kinetics of cement. This will help increase the operating time of fresh materials and improve the consistency of mortar and the loss of concrete slump over time, but it may also delay the construction progress.

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The Properties Of Cellulose Ether

In the ready-mixed mortar, the amount of cellulose ether added is very low, but it can significantly improve the performance of the wet mortar and is a major additive that affects the construction performance of the mortar. Reasonable selection of cellulose ethers of different varieties, different viscosities, different particle sizes, different degrees of viscosity and added amount will have a positive effect on the improvement of the performance of dry mortar. Currently, many masonry and plastering mortars have poor water retention properties, and water slurry separation occurs after a few minutes of standing still. Water retention is an important performance of methyl cellulose ether, and it is also a performance that many domestic dry mortar manufacturers, especially those in areas with higher temperatures in the south, pay attention to. The factors that affect the water retention effect of dry mortar include the amount of MC added, the viscosity of MC, the fineness of particles and the temperature of the environment in which it is used.

1. Concept

Cellulose ethers are a synthetic high molecular polymer made from natural cellulose through chemical modification. Cellulose ether is a derivative of natural cellulose. The production of cellulose ether is different from synthetic polymers. Its most basic material is cellulose, a natural polymer compound. Due to the special structure of natural cellulose, cellulose itself has no ability to react with etherifying agents. However, after the treatment of the swelling agent, the strong hydrogen bonds between the molecular chains and within the chain are destroyed, and the active release of the hydroxyl group becomes alkali cellulose with reactive ability. After the reaction of the etherifying agent, the -OH group is converted into the -OR group. Obtain cellulose ether.

The properties of cellulose ether depend on the type, quantity and distribution of substituents. The classification of cellulose ethers is also based on the types of substituents, the degree of etherification, solubility and related applications. According to the type of substituents on the molecular chain, it can be divided into monoethers and mixed ethers. The MC we usually use is monoether, and Cellulose Ether HPMC is mixed ether.

In terms of solubility, it can be divided into ionic and non-ionic. Water-soluble non-ionic cellulose ethers are mainly composed of two series of alkyl ethers and hydroxyalkyl ethers. Ionic CMC is mainly used in synthetic detergent textile printing and dyeing food and petroleum exploitation. Non-ionic MC, HPMC, HEMC, etc. are mainly used in building materials, latex coatings, medicine, daily chemistry, etc. Used as a thickener, water-retaining agent, stabilizer, dispersant, and film-forming agent.

2.Water retention of cellulose ether

Water retention of cellulose ether: in the production of building materials, especially dry mortar, cellulose ether plays an irreplaceable role, especially in the production of special mortar (modified mortar), it is an indispensable and important part .

The important role of water-soluble cellulose ether in mortar is mainly in three aspects, one is excellent water retention capacity, the other is the influence on the consistency and thixotropy of mortar, and the third is the interaction with cement. The water retention effect of cellulose ether depends on the water absorption of the base layer, the composition of the mortar, the layer thickness of the mortar, the water demand of the mortar, and the setting time of the coagulating material. The water retention of cellulose ether itself comes from its solubility and dehydration. It is well known that although the cellulose molecular chain contains a large number of highly hydratable OH groups, it is not soluble in water itself. This is because the cellulose structure has a high degree of crystallinity.

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 ground to form a uniform powder with a certain fineness.

In the production of MC, only methyl chloride is used as an etherifying agent; in addition to methyl chloride, propylene oxide is also used to obtain hydroxypropyl substituents in the production of HPMC. Various cellulose ethers have different methyl and hydroxypropyl substitution rates, which affect the organic compatibility and thermal gel temperature of the cellulose ether solution.

Cellulose Ether Hpmc

Development Trend of Cellulose Ether HPMC

Due to the structural differences in market demand for cellulose ethers, a situation in which companies with different strengths can coexist has been formed. In view of the obvious characteristics of structural differentiation of market demand, domestic cellulose ether manufacturers adopt a differentiated competition strategy based on their own strengths, and at the same time, they are also able to grasp the development trend and direction of the market.

(1) Ensuring product quality stability will still be the core competitiveness of cellulose ether companies

Cellulose ether accounts for a relatively small part of the production costs of most downstream companies in this industry, but it has a greater impact on product quality. Mid-to-high-end customer groups must go through formulation experiments before using a certain brand of cellulose ether. After forming a stable formula, it is usually not easy to replace other brands of products, and at the same time put forward higher requirements for the quality stability of cellulose ether. This phenomenon is more prominent in high-end fields such as large domestic and foreign building materials manufacturers, pharmaceutical excipients, food additives, and PVC. In order to improve the competitiveness of products, manufacturers must ensure that the different batches of cellulose ether supplied can maintain quality stability for a long time in order to form a better market reputation.

(2) Improving the level of product application technology is the development direction of domestic cellulose ether enterprises

With the increasing maturity of cellulose ether production technology, a higher level of application technology is conducive to enterprises to enhance their comprehensive competitiveness and form stable customer relationships. The well-known cellulose ether companies in developed countries mainly adopt the competitive strategy of "facing large-scale high-end customers + developing downstream uses and usage", develop cellulose ether uses and use formulas, and configure series of products according to different sub-application areas to facilitate customer use , And to cultivate downstream market demand. The competition of cellulose ether enterprises in developed countries has moved from product to application technology competition.