What is a dispersant?
A dispersant is a surfactant that has two opposite properties, lipophilicity and hydrophilicity, in its molecule. It can evenly disperse the solid and liquid particles of inorganic and organic pigments that are difficult to dissolve in liquids, and at the same time prevent the sedimentation and agglomeration of particles, forming an amphiphilic agent required for a stable suspension.
The role of a dispersant is to use a wetting dispersant to reduce the time and energy required to complete the dispersion process, stabilize the dispersed pigment dispersion, modify the surface properties of the pigment particles, and adjust the mobility of the pigment particles.
A dispersant is a chemical substance that can disperse chemicals or particles so that they are evenly dispersed in a liquid. In many industrial fields, the use of dispersants is crucial to the stability, quality and efficiency of the products produced. Among them, in the papermaking industry, dispersants are widely used in pulping and papermaking processes to improve the stability and product quality of pulping and papermaking.
Structural types and characteristics of dispersants
Classification 1: Anionic dispersants. Most anionic types are composed of non-polar negatively charged lipophilic hydrocarbon chain parts and polar hydrophilic groups. The two groups are located at the two ends of the molecule, forming an asymmetric hydrophilic and lipophilic molecular structure. Anionic dispersants have good compatibility and are widely used.
Category 2: Cationic dispersants. Cationic is a non-polar compound with a positive charge. Cationic surfactants have strong adsorption and have good dispersing effects on carbon black, various iron oxides, and organic pigments, but it should be noted that it reacts chemically with the carboxyl group in the base material, and it should be noted that it should not be used at the same time as anionic dispersants. It should be used with caution.
Category 3: Nonionic dispersants. Nonionics cannot be ionized and have no charge. They are weakly adsorbed on the pigment surface and are mainly used in water-based coatings. Their function is to reduce surface tension and improve wettability.
What kind of stability does a papermaking dispersant have?
Papermaking dispersants can disperse solid particles so that they are well dispersed in water, making the production process more convenient and reasonable. The main functions of papermaking dispersants are degumming, whitening, uniform dyeing, wettability, antifouling, waterproofing and other aspects. Due to the complexity of the papermaking process and the long production cycle, manufacturers must consider the stability of the product when selecting dispersants. The stability of the dispersant ensures the quality of the paper and maintains the production efficiency of the papermaking plant.
The basic principle of dispersants is to reduce the cross-linking force and the charge force. The molecular structure of papermaking dispersants enables them to reduce the cross-linking force and electrostatic interaction between particles, so that the particles in the pulp are easy to disperse. In dispersants, anionic, nonionic and cationic polymers are usually used. These polymers are dissolved when mixed with water and pulp, and the molecular chains are extended to release the surface charge of the particles. When the suspended matter is dissolved in water, the molecular chains will deform the particles and aggregate into larger particles. These particles are dispersed and supplemented to form a suspension in water, which is the key to achieving stability.
The key to achieving stability of dispersants is to prevent particle aggregation. If too much dispersant is added to the pulp, it will hinder the cooperation between the pulp particles. Conversely, if the amount of dispersant is insufficient, the particles will regroup and the hardness and strength of the paper will be weakened. The selection and use of dispersants must be precisely the right amount to achieve the desired effect.