| Abstrakt: |
Whiteness retention results obtained with a soil 'deposition' type test, in which soil material as such is added to the detergent bath, are found to be in contradiction to those obtained with soil 'redeposition' tests, in which clean and soiled cloth are washed together. A carbon soil deposition test shows polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) to be superior to sodium carboxymethyl cellulose (CMC), and a polyethylene glycol (PEG) equal to CMC in improving whiteness retention results with a built anionic detergent, with pronounced synergistic effects for PVA-CMC and PEG-CMC combination. In contrast, the redeposition tests, employing either carbon black or tagged clay soil, show only the CMC to be effective, the nonionic polymers being ineffective alone and in combinations with CMC. Further, in evaluating the effect of tripolyphosphate builder with an alkylbenzene sulfonate, the deposition and redeposition tests give quite contradictory results. The observed contradictions cast considerable doubt on the validity of the usual carbon soil deposition tests, and emphasize the need for further study of whiteness retention test methods. [ABSTRACT FROM AUTHOR] |
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