Shandong chuangyao talks about the influence on the application of dry mixed mortar from the product performance of cellulose ether

Cellulose ether, as the main admixture in building dry mixed mortar products, plays a key role in the performance and cost of dry mixed mortar. There are two types of cellulose ethers: one is ionic, For example, sodium carboxymethyl cellulose (CMC), the other is non-ionic, such as methyl cellulose (MC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPMC), etc. with the increasing popularity of the application of dry mixed mortar products, China will become the largest producer of dry mixed mortar in the world, the application of cellulose ether will further increase, and there will be more and more manufacturers and product varieties. Therefore, how to improve the product performance of cellulose ether used in dry mixed mortar has become the focus of manufacturers and users.

The most important property of cellulose ether is its water retention in building materials. If cellulose ether is not added, the thin layer of fresh mortar will dry out quickly, so that the cement cannot be hydrated in the normal way, resulting in the inability of the mortar to harden and obtain good adhesion. At the same time, the addition of cellulose ether makes the mortar have good plasticity and flexibility, and improves the bonding strength of the mortar. The influence of cellulose ether on the application of dry mixed mortar is discussed from the product performance of cellulose ether.

1. Fineness of cellulose

The fineness of cellulose ether reflects its solubility. For example, the lower the fineness of cellulose ether, the faster its dissolution rate in water and the improved water retention performance. Therefore, the fineness of cellulose ether should be included in one of its properties. Generally speaking, the sieve residue of cellulose ether with fineness over 0.212mm shall not be greater than 8.0%.

2. Loss on drying

The loss on drying rate refers to the percentage of the mass lost by drying cellulose ether at a certain temperature in the mass of the original sample. For a certain quality of cellulose ether, too high drying weight loss rate will reduce the content of effective components in cellulose ether, affect the application effect of downstream enterprises, and increase the purchase cost. Generally, the drying weight loss rate of cellulose ether is not more than 6.0%.

3. Sulfate ash of cellulose ether

For a certain quality of cellulose ether, if the ash content is too high, it will reduce the content of effective components in cellulose ether and affect the application effect of downstream enterprises. The sulfate ash content of cellulose ether is an important measure of its own performance. Combined with the production status of existing cellulose ether production enterprises in China, generally, the ash content of MC, HPMC and HEMC shall not be greater than 2.5%, and the ash content of HEC cellulose ether shall not be greater than 10.0%.

4. Viscosity of cellulose ether

The water retention and thickening effect of cellulose ether mainly depends on the viscosity and dosage of cellulose ether added to cement slurry.

5. PH value of cellulose ether

The viscosity of cellulose ether products decreases gradually at higher temperature or after storage for a long time. The performance of high viscosity products is particularly obvious. Therefore, it is necessary to limit the pH. It is generally required that the pH value range of cellulose ether should be controlled as 5-9.

6. Transmittance of cellulose ether

The transmittance of cellulose ether directly affects its application effect in building materials. The main factors affecting the transmittance of cellulose ether are: (1) the quality of raw materials; (2) the effect of alkalization; (3) process ratio; (4) solvent ratio; (5) the effect of neutralization. According to the application effect, the transmittance of cellulose ether shall not be less than 80%.

7. Gel temperature of cellulose ether

Cellulose ether is mainly used as tackifier, plasticizer and water retaining agent in cement products. Viscosity and gel temperature are important measures to characterize the quality of cellulose ether. Gel temperature is used to determine the degree of substitution of cellulose ether. In addition, salt and impurities also affect the gel temperature. When the solution temperature increases, the cellulose polymer gradually loses water and the solution viscosity decreases. When the gel point is reached, the polymer is completely dehydrated to form the gel. Therefore, cement products usually control the temperature below the initial gel temperature. Under this condition, the lower the temperature is, the higher the viscosity is, the more obvious the effect of viscosity increasing and water holding is.