LAUNDRY RINSES AND DRYER SHEETS

Abstract: An N-alkyl-N,N-dimethylamine oxide is used together with N,N-dihydrogenated-tallow-N,N-dimethylammonium chloride to provide an improved fabric softener product which has synergistic properties and which is (1) a laundry rinse which comprises an aqueous solution of a mixture of 25-80 % by weight of the quaternary ammonium chloride and 75-20 % by weight of N-octadecyl-N,N-dimethylamine oxide or (2) a laundry dryer sheet which comprises a flexible absorbent substrate impregnated with a mixture of 10-80 % by weight of the quaternary ammonium chloride and 90-20 % by weight of an N-alkyl-N,N-dimethylamine oxide wherein the alkyl is octadecyl when the amine oxide constitutes 20-40 % of the mixture and otherwise may be any primary alkyl group containing 8-24 carbons.

Description: LAUNDRY RINSES AND DRYER SHEETS Field of Invention This invention relates to laundry rinses and dryer sheets containing N,N- dihydrogenatedtallow-N,N-dimethylammonium chloride and an amine oxide. Background When fabrics are laundered, it is frequently desirable to treat them with fabric softeners, not only to soften them, but to give them greater bulk, make them easier to iron, decrease fabric drying time, and reduce static charge. A fabric softener that is commonly used is N,N-dihydrogenatedtallow-N,N-dimethylammonium chloride (DTMAC), which is both inexpensive and effective as a softener but, on the other hand, has certain deficiencies, such as its yellowing and reducing the washability of the softened fabrics, having inefficient antistatic activity on polyesters, and decreasing the rewettability of the treated fabrics. Amine oxides, such as N-alkyl-N,N-dimethylamine oxides, are also effective fabric softeners; and they sometimes have advantages over DTMAC in this regard. However, when used together with DTMAC, they have either failed to improve the results obtained with DTMAC alone or have provided results intermediate to those obtained with either component of the fabric softener alone. Summary of Invention It has now been found that the use of an N-alkyl-N,N-dimethylamine oxide together with N,N-dihydrogenatedtallow-N,N-dimemylammmoniιιm chloride can provide an improved fabric softener product when the fabric softener product is (1) a laundry rinse which comprises an aqueous solution of a mixture of 25-80% by weight of the quaternary ammonium chloride and 75-20% by weight of N-octadecyl-N,N-dimethylam- ine oxide or (2) a laundry dryer sheet which comprises a flexible absorbent substrate impregnated with a mixture of 10-80% by weight of the quaternary ammonium chloride and 90-20% by weight of an N-alkyl-N,N-dimethylamine oxide wherein the alkyl is octadecyl when the amine oxide constitutes 20-40% of the mixture and otherwise may be any primary alkyl group containing 8-24 carbons. Detailed Description As already mentioned, the quaternary ammonium chloride component of the fabric softener mixture is the known N,N-dihydrogenatedtallow-N,N-dimethyIammonium chloride (DTMAC). The DTMAC used in preparing the mixture is generally the material that is most commonly available, i.e., a 75% paste in an alcohol. The amine oxide component of the mixture is N-octadecyl-N,N-dimethylamine oxide or other N-alkyl-N,N-dimethylamine oxide in which the alkyl is a primary alkyl group containing 8-24 carbons, preferably 12-18 carbons. The primary alkyl group may be a straight- or branched-chain group, but the preferred oxides are those in which the primary alkyl group in at least most of the molecules has a straight chain. Exemplary of these oxides are the N-octyl-, N-decyl-, N-dodecyl-, N-tetradecyl-, N- hexadecyl-, N-octadecyl-, N-eicosyl-, N-docosyl-, and N-tetracosyl-N,N-dimethylamine oxides. Although the amine oxide used in preparing any of the products of the invention may be a conventional aqueous solution or a solid amine oxide, such as the amine oxide dihydrates described in European Patent Application 0401503 and British Patent Application 2,240,791, it is apt to be preferred to employ an amine oxide in solution form when the mixture is to be utilized as an aqueous solution and otherwise to employ a solid amine oxide. Except for the fabric softener mixture used, a laundry rinse of the invention is a conventional rinse which has water as its major ingredient (generally comprising 70-90% by weight of water) and may contain any of the other ingredients typically used in laundry rinses, e.g., minor amounts of materials such as dyes and perfumes and sometimes an alcohol, such as ethanol, to prevent phase separation, as well as the novel fabric softener mixture. Moreover, the rinse may be prepared as such rinses are normally prepared except for the use of the novel mixture as the fabric softener; and conventional techniques are also suitable for rinsing laundry therewith. All of the laundry rinses of the invention, regardless of the particular proportion- ation of DTMAC and N-octadecyl-N,N-dimethylamine oxide within the specified ranges, have the advantage of providing laundered fabrics, such as cotton, with better rewettability than laundry rinses containing only one component of the fabric softener mixture; but optimum rewettability is obtained when the fabric softener is a mixture of about 75% by weight of the quaternary ammonium chloride and about 25% by weight of the amine oxide. This advantage of the mixtures is unexpected, since such synergism is not obtained when other amine oxides, such as N-octyl-N,N-dimethylamine oxide, are used instead of the N-octadecyl-N,N-dimethylamine oxide. A laundry dryer sheet of the invention may be prepared by the conventional technique of soaking an absorbent flexible substrate with an aqueous mixture of the fabric softener mixture, pressing the resultant soaked sheet to remove any excess surfactant, and then drying it. However, it is preferably prepared by coating an absorbent flexible substrate with a molten mixture of the fabric softener components and then solidifying the mixture. In preparing a laundry dryer sheet from a molten fabric softener mixture, it is convenient to conduct the process by soaking the absorbent flexible substrate in a molten mixture of the fabric softener components, thus coating and inherently impregnating it with the surfactants; passing the soaked sheet between two rollers, as in a roller press, to remove any excess surfactant; and allowing the remaining surfactant to solidify. The absorbent flexible substrate used in preparing the dryer sheets may be any of the substrates typically employed in making such sheets, since the only requirement for the substrate is that it be an absorbent material in sheet form. For example, it may be a sponge, paper, or woven or non-woven cloth, especially a non-woven cloth made from fibers or filaments of a material such as wool, silk, jute, hemp, cotton, linen, sisal, ramie, rayon, cellulose esters, vinyl polymers, polyamides, and polyesters. A particularly desirable substrate is a sheet of non-woven polyethylene terephthalate cloth. All of the laundry dryer sheets of the invention in which the fabric softener is a mixture of 50-80% by weight of DTMAC and 50-20% by weight of N-octadecyl- N.N-dimethylamine oxide have the advantage of being able to impart greater softness to laundered fabrics, such as cotton, than can be achieved when either component of the mixture is used alone as the fabric softener. However, optimum reults are achieved when the fabric softener is a mixture of about 75% by weight of DTMAC and about 25% by weight of the amine oxide. The laundry dryer sheets in which the fabric softener is a mixture of 10-60% by weight of DTMAC and 9040% by weight of any of the aforementioned N-alkyl-N,N- dimethylami ^ e oxides have the advantage of leading to the reduction of static charge buildup on laundered polyester fabrics or laundry batches comprising at least some polyester fabric when they are used in the drying step. In this case, optimum results are obtained when the fabric softener is a mixture of about 50% by weight of DTMAC and about 50% by weight of the amine oxide. The following examples are given to illustrate the invention and are not intended as a limitation thereof. Unless otherwise specified, quantities mentioned in the examples are quantities by weight. EXAMPLE I Five medium-grade cotton terrycloth towels were subjected to f our wash/rinse/- dryer cycles in which the rinses were aqueous solutions of N-octadecyl-N,N-dimethylam- ine oxide (AO-18) and/or N,N-dihydrogenatedtaUow-N,N-dimethylammonium chloride (DTMAC). The treated towels were then tested for rewettability in accordance with CSMA test protocol Method D-13D by cutting the towels into strips measuring 5 x 6 inches (12.7 x 15.2 cm), marking each of the strips one centimeter from the narrow edge and lowering it into a 0.01% Rhodamine B dye bath for six minutes, and recording the distance of dye movement at the end of that time in centimeters. The amounts of AO-18 and DTMAC used in the fabric softener and the results of the rewettability tests are shown in the Table following the examples. EXAMPLE II Fifty cotton hand-towels were washed on medium loading for 30 minutes in the presence of 37.5g of an anionic laundry detergent and divided into five groups of ten towels, each group then being loaded into an automatic dryer and dried for 60 minutes on "normal" at about 65 ° C in the presence of a polyester dryer sheet having a lg loading of softener comprising AO-18 and/or DTMAC. The softness of the dried towels was then evaluated by a panel of evaluators who ranked them from 5 (softest) to 1 (least soft). The amounts of AO-18 and DTMAC used in the fabric softener and the results of the softness test are shown in the Table following the examples. EXAMPLE III A laundry batch composed of 23% polyester fabric, 46% cotton/polyester fabric, and 31% cotton fabric was washed on medium loading for 30 minutes in the presence of an anionic laundry detergent and then separated into five identical sub-batches. Each sub-batch was loaded into an automatic dryer, a polyester dryer sheet having a lg loading of AO-18 and/or DTMAC fabric softener was placed into each of the automatic dryers on top of the sub-batch, and the sub-batch was then dried for 60 minutes on "normal" at about 65 ° C. The antistatic activity of the fabric softener in each dryer sheet was then determined in accordance with CSMA test protocol Method D-13F by removing the separate pieces of laundered fabric from the dryer, dropping them into a Faraday cage, and recording the initial voltage - the test being performed on a day when the relative humidity was 50% at 22 * C. The amounts of AO-18 and DTMAC used in the fabric softener and the results of the softness test are shown in the Table following the examples.

Claims: WHAT IS CLAIMED IS: 1. A fabric softener product containing N,N-dihydrogenatedtallow-N,N- dimethylammonium chloride and an N-alkyl-N,N-dimethylamine oxide, characterized in that it is (1) a laundry rinse which comprises an aqueous solution of a mixture of 25-80% by weight of the N,N-dihydrogenatedtallow-N,N-dimethylammonium chloride and 75-20% by weight of N-octadecyl-N,N-dimethylamine oxide or (2) a laundry dryer sheet which comprises a flexible absorbent substrate impregnated with a fabric softener that is a mixture of 10-80% by weight of N,N-dihydrogenatedtaUow-N,N- _imethylammo- πium chloride and 90-20% by weight of an N-alkyl-N,N-dimethylamine oxide wherein the alkyl is octadecyl when the amine oxide constitutes 20-40% of the mixture and otherwise is any primary alkyl group containing 8-24 carbons. 2. The fabric softener product of claim 1 which is a laundry rinse that provides improved rewettability of laundered fabrics. 3. The fabric softener product of claim 1 which is a laundry dryer sheet comprising a flexible absorbent substrate impregnated with a mixture of 50-80% by weight of N,N-dihydrogenatedtallow-N,N-dimethylammonium chloride and 50-20% by weight of N-octadecyl-N,N-dimethylamine oxide as a fabric softener. 4. The fabric softener product of claim 2 or 3 wherein the fabric softener isamixtureofabout75%byweightofN,N-dihydrogenatedtallow-N,N-dimethylammo- nium chloride and about 25% by weight of N-octadecyl-N,N-dimethylamine oxide. 5. The fabric softener product of claim 1 which is a laundry dryer sheet comprising a flexible absorbent substrate impregnated with a fabric softener that is a mixture of 10-60% by weight of N,N-dihydrogenatedtallow-N,N-dimethylammonium chloride and 90-40% by weight of an N-alkyl-N,N-dimethylamine oxide wherein the alkyl is a primary alkyl group containing 8-24 carbons. 6. The fabric softener product of claim 5 wherein the primary alkyl group contains 12-18 carbons. 7. The fabric softener product of claim 6 wherein the N-alkyl-N,N- dimethylamine oxide is N-octadecyl-N,N-dimethylamine oxide. 8. The fabric softener product of any of claims 5-7 wherein the fabric softener is a mixture of about 50% by weight of the substituted ammonium chloride and about 50% by weight of the amine oxide. 9. A process for providing softened laundered fabrics having improved rewettability which comprises rinsing the laundered fabrics with a laundry rinse of claim 1. 10. The process of claim 9 wherein the fabric is cotton and the fabric softener of the laundry rinse is a mixture of about 75% by weight of the substituted ammonium chloride and about 25% by weight of the amine oxide. 11. A process for improving the softness of a laundered fabric which comprises drying the laundered fabric in an automatic dryer contaimng a laundry dryer sheet of claim 3. 12. The process of claim 11 wherein the fabric is cotton and the fabric softener in the dryer sheet is a mixture of about 75% by weight of the substituted ammonium chloride and about 25% by weight of the amine oxide. 13. A process for reducing static charge buildup on a laundry batch comprising at least some polyester fabric which comprises drying the laundry batch in an automatic dryer containing a laundry dryer sheet of any of claims 5-8. 14. The process of claim 13 wherein the laundry batch is composed entirely of polyester fabric.

Inventors: BORLAND JAMES E, CRUTCHER TERRY, PERINE JEFFREY W, SAUER JOE D, SMITH KIM R, BORLAND, JAMES, E., CRUTCHER, TERRY, PERINE, JEFFREY, W., SAUER, JOE, D., SMITH, KIM, R.
Applicants: ETHYL CORP, ETHYL CORPORATION
Application year: 1991
Main classification: C11D17
IPC codes: C11D1, C11D3, C11D17, D06M13, D06M23, D06M101