Rinse-added softeners

Because of the static electricity imparted to synthetic fabrics by tumble drying, and the increasing proportion of synthetic fabrics in the U.S., the sales of dryer-sheet fabric softener rose much more in the U.S. than in the rest of the world. By 1983, these products accounted for 40% of all household fabric softener sales. Today, tumble dryer sheets and liquid softener sales are of the same order of magnitude [5,6,16], In contrast, rinse-added softeners had a much larger impact in Europe, where 100% cotton items have always been dominant and line drying is still standard practice hence, the softener effect is more noticeable to consumers. 

The first softergents appeared on the market in the early 1970s. They were quite popular in the U.S. between 1981 and 1989 or so, but their popularity declined in the 1990s as a result of the increased softening efficacy of rinse-added softeners and the stronger cleaning efficacy of detergents [10]. 

Ester quaternaries have been known since the 1930s, but found limited commercial use in earlier years. However, their commercial relevance took a quantum leap forward in 1991, when European detergent manufacturers reformulated their rinse-added softeners because of pressure from environmental authorities in some European Union member states. A major benefit or feature of the ester quat structure is its decomposition into nonsurface-active fragments upon hydrolysis. However, this benefit, i.e. hydrolytic instability, also posed a challenge to the formulator. Ester quaternaries are stable in aqueous solutions only over a narrow pH range, unlike the traditional alkyl quaternaries. Softener dispersions based on ester quaternaries are typically adjusted to pH < 4 to maintain hydrolytic stability. 

Due to the chemical nature of HEUR rheology modifiers, no neutralization is required to induce thickening. These materials are therefore compatible with anionic, nonionic, and cationic surfactant matrices, and are effective across a wide range of pH (3 to 13) [22], HEUR rheology modifiers are used in cationic systems such as rinse-added fabric softeners (where anionic thickeners have... 

This section briefly describes the anionic and nonionic surfactants commonly used in commercial HDLD formulations. Cationic surfactants, although used on a large scale, are found predominantly in rinse-added fabric softener products. LAS, alcohol ethoxylates, and alkyl ether sulfates are three of the most widely used surfactants in liquid laundry detergents [44], Recently, various external considerations, such as environmental pressures, have prompted manufacturers to change their surfactant mix to include newer natural-based surfactants [45-47], including alkyl polyglucosides (Henkel) [48],... 

U.S. 6696405 02/2004 Mooney/Unilever Improved crease recovery of fabrics utilizing C20-C40 saturated or unsaturated aliphatic hydrocarbons. For use in fabric conditioning formulations used in the dryer cycle (sheets, liquids for rinse-added fabric softeners)... 

U.S. 5854200 12/1998 Severns et al.l Procter Gamble Rinse-added fabric softeners containing antioxidants for sun fade protection of fabrics. Nonfabric-staining, light-stable antioxidant compounds comprising C8-C22 hydrocarbon fatty organic moieties... 

From a softening standpoint, dryer sheets are less efficient than rinse-added products but slightly more efficient than wash cycle fabric softeners. Besides the lower amount of solids delivered, the deposition in the dryer is much less uniform than in the rinse [9,34,37],... 

Household fabric softeners have been formulated to be utilized by the consumer in either a rinse-added, dryer-added, or wash-added (softergent = detergent plus softener) application. It must be noted that there have been many cationic compounds developed since the introduction of DHTDMAC to meet the needs of for-mulators. 

Of the four forms, rinse cycle softeners provide the most effective softening [4]. These are added to the laundry during the last rinse cycle, after the soil and the detergent residues are ranoved. Rinse cycle softeners are most effective because their addition after the main wash prevents... 

Levinson, M. I., Rinse-added fabric softener technology at the close of the twentieth century, J. Surf. Det., 2(2), 223, 1999. 

Uses Good hand, exc. rewet and antistatic props, for household and commercial rinse-added fabric softeners textile processing aid for natural and syn. libers Properties Gardner 3 paste dens. 8.07 Ib/gal (50 C) vise. 1200 cps (105 F) pour pt. 97 F pH 3 (10% aq. IPA) 90% solids STEPANTEX NA-90 [Stepan]... 

The reactor needs to be kept clean to keep the heat transfer optimal and to prevent solid material in the prepolymer. The method employed is to use an appropriate solvent such as methyl ethyl ketone (MEK), methylene chloride, or m-pyrol (NMP). To prevent an explosive vapor mixture from being formed when the solvent is added to the reactor, the air must be replaced by nitrogen gas. The solvent needs to be heated to just above its boiling point and kept there until the solid material has been softened and removed from the metal. A second rinse with clean solvent may be needed. 

Fabric softeners are cationic surfactants and these are often added to the final rinse of the laundry and dispensed to the rinse water via a special compartment in the washing machine. How can a surfactant... 

Nonionic and even anionic surfactants have also been added in small amounts to DHTDMAC to boost a product s softening efficacy. For example, it was shown in the late 1970s that the performance of a 6% DHTDMAC composition is matched by a mixture of 4.4% DHTDMAC and 0.6% anionic [56] 1.6% DHTDMAC could then be replaced by 0.6% anionic, which is less expensive. That was quite unexpected, as it was generally accepted that fabric softeners must be introduced in the last rinse of the laundering process to avoid their neutralization by the anionic detergent residues on the fabric, which causes the formation of insoluble species. 

Concentrates are dilute-before-use products. They must be first dispersed in three or four times the amount of tap water and shaken vigorously to regenerate the 5 to 8% concentrate dispersion and avoid clogging the fabric softener dispenser [3,35], This is not necessary with ultras, which can be added directly in the rinse without preliminary dilution. 

---