This invention relates to liquid or powder laundry detergent compositions. More particularly, it relates to a mildly acidic laundry composition capable of providing improved protection of delicate fabrics during washing and enhanced removal of foam during rinsing in hand wash operation.
Detergent compositions which are specially formulated as fine fabric compositions to refresh the fabric and remove light soils are known in the art. They can be adapted for use over a wide range of pH and are generally formulated using mild nonionic surfactants sometimes in combination with anionic surfactants.
Anionic surfactants are known to generate large amounts of foam primarily upon mechanical agitation of the wash bath during laundering, either by machine or by hand washing. However, large amounts of foam are often considered undesirable in European washing machines where excessive amounts of foam may interfere with the mechanical operation of the machine, such as, by foam overflow and interference with outlet pumping. Reducing the amount of foam in the wash bath has a further benefit. It enables the detergent to be readily rinsed from the laundered fabrics. This is particularly useful for hand wash and hand rinse operations where the repetitive steps of rinsing washed fabrics with rinse water to effect the complete removal of detergent can be time-consuming and often tedious.
It has now been recognized that for purposes of protecting fine fabrics from fiber damage resulting from agitation in the wash bath, the presence of foam or suds may have a beneficial effect insofar as it creates a type of air cushion which surrounds the fabric and protects it from undue friction during laundering. For sensitive and delicate fabrics such as wool and silk, such fiber protection is particularly important. However, the elimination of a foam control agent from a fine fabric detergent composition, while useful for fabric protection in the wash bath, adversely affects the problem of foam removal during rinsing. Consequently, there is a need in the art for a detergent composition for fine fabrics which contains a foam control agent which is selective for rinsing but which is inoperative during laundering.
U.S. Pat. No. 4,894,177 describes a delayed release antifoaming laundry additive wherein a silicone based antifoaming agent such as polydimethyl siloxane is adsorbed on a water soluble carrier in granular form such as modified cellulose. The absence of a foam suppresser significantly increases the number of rinses required to provide a washed fabric rinsed free of detergent. It is theorized that under actual laundering conditions, the antifoam agent will be released toward the end of the wash cycle, providing antifoam activity in the rinse water.
In U.S. Pat. No. 4,637,890 suds control prills are described containing fatty acid soap, quaternary ammonium salt and a silicone suds suppresser. According to the patent, the prills dissolve in the relatively high pH wash water (from about 9 to about 10.5) but the antifoam components do not become active until exposed to lower pH solutions, namely the water of the rinse cycle.
EP 544 944 Al describes rinse-active foam control particles for inclusion in a detergent composition consisting essentially of a soap of fatty acids. The particles of soap are intended to be present in both the wash cycle and the rinse cycle, and a silicone suds suppresser is recommended for use in the wash cycle in conjunction with the soap particles under described washing conditions.