All fibers, whether natural or synthetic based, need to obtain a certain finish such as soft handle, smoothness or bulkiness, as well as hydrophilicity. This applies to terry towels, knitted and woven fabric as well as nonwovens.
Evonik offers a brought range of organic and organo-modified siloxanes (OMS), which might be used as synergistic blends to achive additional benefits.
Softeners are broadly used in textile finishing to provide the textile goods with a specific hand or softness (soft fluffy-dry, smooth or greasy). Negative effects of common softeners on fabric properties are mainly reduced water absorbency and yellowing. Hydrophilicity, non-yellowing and softness can be achieved by selection of specific surfactants whose performance is pre-determined by the chemical structure of its raw materials. Further beneficial properties for softeners are certain antistatic properties and the slip effect, based on lubrication which reduces fiber to fiber and fiber to metal friction. These properties are important for the processing in textile mills.
Softeners are applied by padding or the exhaust method, depending on the technology on the site. Softeners which are applied by padding are mainly non-substantive, while softeners applied by the exhaust method, per definition, must be substantive. Softeners are mainly applied from aqueous emulsions, microemulsions or dispersions. The particle size is crucial for the stability and performance of the finished textile auxiliaries.
Since it is almost impossible to cover all requirements with one type of surfactant (OMS or organic quaternary), premium softeners can be formulated by use of synergistic combinations of OMS, organic quaternaries and emulsifiers/ compatibilizers/ solvatropes.
Requirements for Softeners
- High softening performance (soft fluffy-dry, smooth or greasy hand)
- Hydrophilic or hydrophobic character
- Antistatic effect
- Substantivity or non-substantivity
- Emulsion stability
Softeners and preparation aids
We produce softeners based on organomodified siloxanes and oleochemical derivatives. Our product range covers a broad range of chemistries.
The softening performance is assessed by internal panel tests carried out by experienced persons using terry cotton fabric treated with softener. Two methods are established: APM 91-03 screening test and APM 91-04 pair-wise direct comparison test.
In both cases, the softest fabric sample gets the higher score. Points are given between 0 (worst, usually the untreated reference sample) and 5 (best result). The softness performance ranking is established accordingly. A comparison of results is valid only within the same panel test. Substantive softeners or cationic formulated products are applied by the exhaust method.
The rewetting performance is determined by the capillary rise of water (APM 91-02) on cotton fabric. The treated fabric is cut into stripes and, together with the untreated reference material, marked with a dye and suspended vertically with the lower end immersed into a water bath. The water migrates by capillary force vertically into the fabric stripes and the dye is carried to the height to which the water migrates. The reference stripe is quoted with 100 % rewetting and the rewetting ability of all treated samples is calculated with reference to the blank. The higher the rewetting ability in %, the more hydrophilic the tested softener is.
The non-yellowing performance is determined by APM 96-19 using a LUCI 100 spectrocolorimeter. The cotton fabric is treated with softener. The Berger whiteness index (Wb) is measured on untreated fabric, on treated fabric and on treated/untreated fabric which was exposed to 170 °C for 5 minutes. The lower the difference to the reference, the more resistant the softener is to yellowing caused by heat.
The following figure shows the performance evaluation of six single compounds for softening, rewetting and non-yellowing.
Advantages of synergistic blends
Microemulsions prepared from hydrophilic nonionic siloxanes and cationic siloxanes are stable and easy-to-handle low viscosity liquids, with good substantivity to textiles. They impart premium softness combined with good rewetting properties and excellent non-yellowing. By replacing the cationic siloxane by an organic quat the basic performance properties of the cationic formulations are comparable to the properties of the siloxane-based formulations, while the antistatic properties and substantivity are enhanced and the cost of the raw materials is reduced.
Preparation of aqueous emulsions
Since softeners basically are applied from aqueous dispersions, emulsions or microemulsions, the preparation procedure is very important in order to obtain stable emulsions with suitable particle size.