Towels in linen fabrics, such as bath towels, pillow towels, face towels, etc., often need to be softened after acid neutralization. Therefore, softening agent is also a commonly used chemical material for linen fabric washing.
1. Main ingredients and use of softening agent
The main components of softening agents are mostly cationic surfactants. In the aqueous solution, the fabric fibers are generally negatively charged. During the softening process, the negatively charged fibers make the positively charged softening agent effectively adsorb on the surface of the fabric fibers, and the finely dispersed softening agent particles can penetrate deep into the fibers, so that the fiber fabric maintains a fluffy, soft and smooth feel.
Practice tells people that the use effect of softening agents is related to the type of cationic surfactant selected, the adsorption amount of active substances during softening, the temperature of softening, the action time, the pH value of the solution and many other factors.
Studies have shown that among several quaternary ammonium salt cationic surface actives with soft and antistatic effects, dialkyl quaternary ammonium salts have the best soft and antistatic effects.
Therefore, octadecyl dimethyl ammonium chloride (D1821) is the most commonly used softening antistatic agent. However, due to the low surface charge of chemical fibers in aqueous solutions, D1821 has less adsorption on chemical synthetic fibers, and its soft and antistatic effect on synthetic fibers is not as good as other fibers.
In order to make all kinds of fibers have good softening and antistatic effect, the method of compounding D1821 and quaternary ammonium salt ionic surfactants with different molecular structures is often used in the formulation of commercial softening agents.
2. The influence of the adsorption capacity of softening agent
Generally, the more the softening agent adsorbs on the fabric fibers, the better the softening effect. However, if the amount of softening agent adsorbed is too large, not only the re-wetting of the fabric will become poor, but also the repeated softening treatment of the fiber will cause the deposition of the softening agent to be too large, and it will also easily cause the fabric to turn yellow.
Tests have shown that, in general, when the active substance adsorption amount is 0.08% to 0.1% of the weight of the fabric, satisfactory results can be obtained.
When the fabric is softened, the treatment conditions also have a great influence on the softening effect of the fabric. The test points out that when the treatment temperature is 40~50℃, the pH value of the bath liquid is 5~6, and the time is controlled at 8~10min (the time can be shortened to 3~5min when the washing machine is rotating), the active adsorption capacity in the bath can reach more than 90%.