1. Field of the Invention
This invention relates to an improved liquid detergent having added softener and brightener for use in laundering fabrics. In particular, it relates to a storage stable, single-phase laundry detergent-softener-brightener composition free from phosphates and possessing enhanced softening and brightening properties.
2. Description of the Prior Art
In the recent past, laundry was washed by simply placing it in a machine filled with detergent, running the machine through a wash cycle and then through a rinse cycle.
Later, cationic fabric softeners were added to the rinse cycle to improve the feel of the laundry and reduce the static charges built up on fabrics during drying. These cationic fabric softeners were not blended with liquid detergents, since they became unstable in the presence of the detergents and tended to form distinct phases during storage. The softeners were not successfully employed in the wash cycle, since they tended to deposit on the clothing as a yellow film. This film also tended to coat fabrics with a water-repellent finish after repeated use. In fabrics, particularly those which needed to breathe or absorb water, this was a serious defect. Fine fabrics were recognized to be particularly susceptible to yellowing, clinging and filming from detergent washing with softening treatment.
In an attempt to correct these defects, anionic detergents and phosphate builders were added to detergents to complex the softeners and prevent their yellowing and filming of fabrics. However, these attempts proved unsuccessful, since the softening effect of the fabric softeners, notably the quaternary ammonium salts of "quats", was seriously reduced. In addition, it has been recognized, recently, that phosphates can adversely effect the ecology. Consequently, there has been much clamor for detergents, which are free from phosphates.
Modern fabrics, including nylons, polyesters, cotton and blends thereof and particularly fine fabrics, are expected to be bright in appearance after washing. Commonly used detergent fluorescent brighteners, such as DASC brighteners (DASC-ASTM designation--those derived from diaminostilbene disulfonic acid-cyanuric chloride) have two sulfonic acid groups per molecule. These brighteners have been suggested for use with detergents and softeners. However the disulfonate brighteners tend to form unstable opaque products with very poor brightening properties, when combined with laundry detergents and cationic softeners. Monosulfonate, NTS-type stilbenesulfonic acid brighteners have been proposed, but provide very poor brightening when employed with detergents and softeners. Diaminostilbene hexa-sulfonate brighteners are used in coatings in the paper industry, but are not recommended for use as brighteners with standard detergents owing to their high level of water solubility. Such hexa-sulfonate brighteners and cationic softeners. Monosulfonate, NTS-type stilbenesulfonic acid brighteners have been proposed, but provide very poor brightening when employed with detergents include those disclosed in British Pat. No. 941,993 which utilize detergents and DASC brighteners, but no fabric softeners. These compositions are merely powder mixtures, not liquid compositions.
In U.S. Pat. No. 3,625,891, a blend of three different quaternary ammonium ("quats") fabric softeners were employed to overcome detergent compatibility problems. The softener and detergent were added separately to the wash.
In U.S. Pat. No. 3,644,203 a minor amount of anionic surfactant was employed with a cationic fabric softener together with a nonionic surfactant and a conventional phosphate builder, forming a multifunctional detergent, in which the anionic surfactant served to neutralize the cationic softener. Optical brighteners were optionally disclosed, but not those employed in this invention.
A nonphosphate softener-detergent composition is set forth in U.S. Pat. No. 3,959,157. A DASC brightener is employed having only two sulfonate groups. To stabilize the "quat" softeners, up to 20% of an alcohol is disclosed to be necessary. This adds to the expense of the composition. Further, the level of "quat" softeners employed in the patent is from about 3% to 15% by weight of the composition. It is most desirable to reduce this level, while maintaining softening properties, to reduce the costs of the product to the consumer and reduce yellowing and filming tendencies.