Softeners can be added in multiple processes of tanning. The main function is to improve the hand feel and softness, and to help absorb other tanning additives. It is an important auxiliary agent for the preparation of soft leather, high-grade top leather and cowhide two-layer film transfer leather. In the past, the tannery used more oil to increase the softness, but the oil in the leather will change its acid value, iodine value, and saponification value. Unbound oil will also migrate, making the leather greasy and the leather body hard. . With the development of the leather industry, softeners with surfactants and silicone polymers as the main components have attracted increasing attention.
The high-grade leather softener should have excellent emulsifying, dispersing, penetrating and binding abilities, and play a role of dispersing and isolating and shielding between leather fibers and fiber bundles, greatly reducing its surface and energy, and no or rarely migration, so that The softening effect is retained for a long time. The problem of the softness and smoothness of collagen fibers is also the problem of friction between fibers, and the friction of fibers is mainly evaluated by the coefficient of friction. The coefficient of friction is a parameter that expresses the surface performance of the friction body. Different types of surfactants have an effect on the friction coefficient of the fiber. Among them, the effect of reducing the static friction coefficient of the fiber surface is: cation>polyol type nonionic>anion>polyethylene glycol type nonionic>mineral oil.
For similar surfactants, due to the different chemical structure of the surfactant, the effect on the friction coefficient of the fiber is also different.
(1) The effect of anionic surfactants on the friction coefficient of fiber surface The main varieties of such surfactants are alkyl phosphate, alkyl sulfate, and alkyl sulfonate. Long alkyl chain, good smoothness and low friction coefficient. However, the sulfate esters of alkyl polyoxyethylene ethers are all anionic surfactants gradually showing non-ionic characteristics as the number of moles of ethylene oxide added to the ether increases. For the smoothness of phosphate esters, there are trialkyl phosphate> dialkyl phosphate> monoalkyl phosphate> polyoxyethylene ether phosphate.
(2) The effect of cationic surfactants on fiber friction coefficient. In addition to good antistatic properties, cationic surfactants also have good softness and smoothness. Therefore, they are widely used as softeners to reduce static friction between fibers. coefficient. Quaternary ammonium salt and amine salt surfactants are effective on the dynamic and static friction coefficients of fibers.
(3) The influence of nonionic surfactants on the friction coefficient of fibers The larger the alkyl group of the nonionic surfactants, the smaller the friction coefficient of the fibers.