Sodium lignosulfonate is an organic substance with a chemical formula of C20H24Na2O10S2. Lignin is a natural polymer with a content second only to cellulose and chitin in nature. One of its most extensive uses is to convert it into Lignosulfonate, including sodium lignosulfonate. Sodium lignosulfonate can be used as an admixture for polymers and concrete with the advantages of low cost and environmental friendliness.
Sodium Lignosulphonate is a type of lignosulfonate. Lignin is a natural macromolecular polymer with a content second only to cellulose and chitin in nature. It can produce about 6 × 1014t every year in the world. As a filling and binding material, it can strengthen the interaction between plant cellulose and also The components that must be removed for the utilization of plant cellulose are extracted on a large scale. Lignin is a high molecular weight polyphenol three-dimensional network space structure composed of guaiacyl, syringyl and p-hydroxyphenylpropane three basic structural units connected in the form of C-C bonds, C-O-C bonds, etc. polymer.
In the process of paper pulping and bioethanol production, lignin remains in the waste liquid to form a large amount of industrial lignin. One of its most extensive uses is to convert it into lignosulfonate through sulfonation modification, sulfonic acid The group determines that it has good water solubility and can be widely used in construction, agriculture and light industry as an auxiliary agent.
The lignin molecule is a network of molecules connected by its basic structural units. The molecule contains functional groups such as methoxy, hydroxyl, carbonyl, and phenolic hydroxyl groups. Therefore, lignin can undergo various chemical reactions such as sulfonation, oxidation, Phenolization, polycondensation and graft copolymerization, etc. These reaction pathways are the theoretical basis for lignin modification, development and utilization.
Sodium lignosulfonate is tan powder or liquid. No special odor. Non-toxic, easily soluble in water and lye, precipitated by acid, with strong dispersing ability
Lignosulfonate is derived from sulfite pulping in the acid pulping process. This process is widely used and is currently the dominant process in the papermaking process. Lignosulfonate is due to the sulfonic acid group in the molecule. The introduction makes it have good water solubility, which greatly improves its reactivity. Therefore, sodium lignosulfonate is a rich source of industrial lignin with a wide range of applications.
According to the different plant sources of lignin, lignin can be divided into hardwood lignin, softwood lignin and grass lignin. Logignin is a white or nearly colorless substance, but the color of the lignin obtained by separation has changed, so the color of commercial lignin is between light fawn to dark brown. Woody lignin is generally an amorphous powder with a relative density of 1.3-1.5g/cm3. There is no asymmetric carbon atom in the lignin structure, so lignin has no optical activity, and log lignin is insoluble in water.
The properties of lignosulfonates from different sources are quite different. The weight-average relative molecular weights of wood sodium and bamboo wood sodium are larger, and the weight-average relative molecular weights of wheat grass wood sodium and bagasse wood sodium are lower; the sulfonic acid group content of wheat grass wood sodium and bamboo wood sodium are higher, and bagasse wood sodium The content of carboxyl group is relatively low; the carboxyl group content of four kinds of wood sodium is not much different; the content of phenolic hydroxyl group of wood wood sodium is higher. Even if lignosulfonates from the same source have different relative molecular weights, their structural properties and surface activities are different. From the perspective of surface activity, it seems that the larger the relative molecular mass, the better. However, from the perspective of dispersion, after the dispersed phase adsorbs the surface active substances, the electrostatic repulsion caused by its charge is dominant in the dispersed system, indicating that with the lignosulfonic acid The increase of the relative molecular mass of the acid salt reduces the ionizable charged hydrophilic groups such as sulfonic acid and carboxyl groups, resulting in poor dispersion performance. Therefore, in order to make lignosulfonates have good dispersibility, appropriate relative molecular mass and charged group content are required.
Applications of lignosulfonates:
At present, there are more than 200 kinds of lignin products, and new products are constantly being developed. The output and quality of products have also been greatly improved, and there are more and more application fields. The applications of lignin and its modified products are mainly in the following aspects:
(1) Water reducing agent for cement and concrete: Lignosulfonate is the most widely used water reducing agent at present. In 1935, American E.W. SeriPture successfully developed a water-reducing agent with lignosulfonate as the main component. Since then, humans have begun to study the lignosulfonate water-reducing agent. The use of lignosulfonate as a cement and concrete water reducing agent can not only greatly improve its fluidity and plasticity, but also greatly reduce harmful pores and significantly enhance compressive strength.
(2) Dispersant, flocculant and corrosion and scale inhibitor: lignosulfonate is an anionic surfactant with excellent performance, which can be used as dispersant, flocculant, etc.
(3) Oilfield chemicals: Lignosulfonate has a special molecular structure and is widely used in oilfield chemicals. It is often used as a surfactant for tertiary oil recovery, a drilling fluid treatment agent, and a water blocking agent.
(4) Synthetic resin: Since the 1990s, lignin has often been used as a basic renewable material for synthetic polymer materials, resins and adhesives.
(5) Polymer materials: lignin and its derivatives can be blended with polyvinyl chloride (PVC), polyethylene (PE), polyvinyl alcohol (PVA) and other olefin polymer materials to improve the stability, strength and stability of the material. Anti-photolysis and other properties. Liu Chunfang et al. added lignosulfonate to rubber as a rubber reinforcing agent, which can improve the mechanical properties of rubber. Li Haijiang et al. compounded hydrolyzed lignin with natural rubber to form an interpenetrating network structure, and then obtained a lignin-natural rubber compound by co-precipitation method.
(6) Agricultural adjuvants: Sodium lignosulfonate can not only be used as a pesticide dispersant, but also as a wetting agent, complexing agent and fertilizer, and is widely used in all aspects of agriculture.