Softeners are not just silicone oil

In order to make fabrics soft, smooth or plump, in addition to mechanical finishing, most fabrics need to be finished with softeners.

1. The role of softeners

1. Supplement the natural oils lost by natural fibers in the processes of refining and bleaching to make the feel more ideal.

2. Attach to natural or synthetic fibers to improve smoothness and strength and improve the feel.

3. Improve the wearing performance of fabrics through certain characteristics of softeners.

In order to achieve some of the above effects, softeners are generally substances with the smoothness and feel of oils and fats. Attaching to the fiber surface can reduce the friction resistance between fibers and make the fibers lubricated and soft. Some softeners can also cross-link with some reactive groups on the fibers to achieve the purpose of washability.

2. Requirements for softeners

1. Under various softening processing conditions, the working fluid must be very stable.

2. Do not reduce the whiteness and dyeing fastness of fibers or fabrics.

3. The softened fibers or fabrics are not easily discolored by heat, and should not change in color, feel, or smell during storage.

4. If the softener is an emulsion, the emulsion stability should be good.

5. According to different processing requirements, it can have appropriate water absorption or water repellency, antistatic properties and other properties (should be selected according to the different requirements of the fabric). It has water washing or dry cleaning resistance.

6. There is no adverse effect after contact with human skin.

Due to the wide variety of textiles, different fibers used, different fabric specifications, different fabric uses, and different finishing requirements, the selection of softeners cannot be generalized. Based on the softening mechanism and function of various softeners, the softener that meets the requirements should be selected. In addition, the performance of each softener is always limited. To obtain multiple good performance effects, two or more softeners can be used in combination (or compounded into a new softener product). For example, the compound application of silicone softener and long-chain aliphatic softener can achieve a good effect of soft, plump and smooth hand feel. It can also combine the application of softener with mechanical softening finishing, which can often achieve good results.

3. Types of softeners

Softeners are the most diverse and largest type of auxiliaries in dyeing and finishing auxiliaries. According to reports, among the 920 domestic and foreign auxiliary samples collected by Shanghai Printing and Dyeing Technology Research Institute from 1990 to 1999, there were 350 softeners, accounting for 38%. Such a large number of softener varieties, according to their chemical structure, are basically two categories: long-chain aliphatic or high molecular polymer. The long hydrocarbon chains in the molecular structure of long-chain aliphatic softeners can be arranged in an irregular curling state, forming the flexibility of the molecules. The flexible molecules are adsorbed on the fiber surface to play a lubricating role, reducing the dynamic and static friction coefficients between fibers.

Therefore, long-chain aliphatic structures generally have a good softening effect. Among softeners, there are not only many varieties, but also a large amount. This type of softener can be divided into anionic, cationic, nonionic and amphoteric types according to its ionicity. In addition, natural oils and paraffin softeners can also be classified as a separate category because they are all natural lubricating substances, but they are also classified into different ionic categories according to the different ionicity of the emulsifiers used. There are two main types of polymer softeners: polyethylene and silicone. The varieties of polyethylene softeners are relatively simple, and the dosage is also small. The main use is silicone softeners. Since the main chain of polysiloxane is a very flexible helical straight chain structure, it can rotate 360 degrees freely, and the energy required for rotation is almost zero. Therefore, the molecular structure of polysiloxane alone conforms to the softening mechanism of textiles. It can not only reduce the static and dynamic friction coefficients between fibers, but also has very small intermolecular forces, and reduces the surface tension of fibers. It is an ideal material for textile softening finishing agents. Silicone softener is the fastest growing softener variety in recent years.

4. Anionic softener

In addition to soap, sulfonated oil, etc., the main components of anionic softeners are cationic compounds with long-chain alkanes such as sodium octadecyl sulfonate and octadecyl sulfate, or anionic and nonionic compounds. Generally, it has good wettability and thermal stability, can be used in the same bath with fluorescent brighteners, and can be used as a softener for extra-white fabrics. It is also more suitable for cellulose fibers and can give fabrics better water absorption, but its adsorption on fibers is similar to direct dyes, which is relatively weak, so the softening effect is poor and easy to be washed off. In addition, because it has a softening effect in the bath, it can be used for silk refining to prevent abrasions (ash damage).

5. Nonionic softener

Nonionic softeners are generally polyoxyethylene esters (or ethers) of decacarboxylic acid (or alcohol), fatty esters of pentaerythritol or dehydrated sorbitan. Since nonionic softeners have poorer adsorption on fibers than ionic softeners, they can only play a smoothing role. However, it can be used with ionic softeners, has good compatibility with other agents, good electrolyte stability, and does not cause fabric yellowing. It can be used as a non-durable softening finishing agent, and can also be used as an important component of synthetic fiber spinning oil. Some of its products can be used as a silk-like finishing agent for fabric "silky sound".

6. Cationic softener

This type of softener has many varieties and is the most commonly used softener at present.

Mainly because most fibers carry negative charges in water, cationic softeners are easily adsorbed on the fiber surface, have strong binding ability, are resistant to high temperatures and washing, and the fabric is plump and smooth after finishing, which can improve the wear resistance and tear strength of the fabric, and also has a certain antistatic effect on synthetic fibers. Therefore, it is widely used in fabrics such as cotton, nylon, acrylic, etc., and this variety is also suitable for silk. However, some cationic softeners are prone to yellowing at high temperatures, accompanied by a decrease in light fastness.

Cationic softeners are generally derivatives of octadecylamine or dimethyloctadecylamine or condensates of stearic acid and polyethylene polyamine. According to its structure, it can be divided into tertiary amine softeners, quaternary ammonium salt softeners, imidazoline quaternary ammonium salt softeners, dialkyl dimethyl quaternary ammonium salt softeners, etc.

7.Amphoteric softeners

Amphoteric softeners are a type of softener developed to improve cationic softeners. It has a strong affinity for synthetic fibers and does not have the disadvantages of yellowing and discoloration of dyes. It can also be used in the re-scouring process of silk to make the silk feel better. Amphoteric softeners can also be used together with cationic softeners to play a synergistic role. This type of softener is generally an alkylamine lactone structure.

8. Low molecular weight polyethylene emulsion

This type of softener is a product of low molecular weight polyethylene after oxidation treatment and emulsification. It has a certain affinity for fibers, giving the fabric a smooth feel. It can be used in the same bath with resins, and can improve the tear strength and wear resistance reduced by resin finishing. It is a cheap fabric softening and smoothing additive before the promotion and application of silicone softeners. At present, this type of softener is generally not used alone. It can be used as a compound component of various softeners, and can also be used as a stabilizer in hydroxy silicone emulsion.