Fabric Softener

Abstract

An improved fabric softener is disclosed comprising a mixture of a softener such as a quaternary ammonium compound or an imidazoline with an antiyellowing agent which is a complex of C.sub.12 to C.sub.22 alkyl alcohol and C.sub.12 to C.sub.19 alkylsulfate.

Description

This invention relates to an improved fabric softener formulation having antiyellowing properties.

It has been known for some time that the conventional cationic fabric softeners tend to cause yellowing of fabrics treated with them where the fabrics have been first washed using nonionic-based detergents. The reasons for the occurrence of yellowing are not fully understood. However, it is generally believed that yellowing involves an interaction between the cationic fabric softener, electronegative absorption sites on the part being treated, and color bodies contained in the rinse water, typically attributable to water hardness.

Yellowing may be mitigated by providing for an anionic surfactant in combination with the cationic fabric softener. The anionic surfactant forms a complex with the cationic fabric softener, which, under proper conditions, may be deposited on the fabric to be softened without causing yellowing. This approach to the control of the discoloration caused by fabric softeners, however, is not without difficulties. The principal disadvantage of it is that the presence of an anionic surfactant interferes with the softening efficiency of most cationic fabric softeners .

In accordance with the present invention it has been found that the complex between alkyl alcohols and alkyl sulfates may be used as an antiyellowing agent in combination with cationic fabric softeners. On a weight basis, a mixture in which the ratio of softener to complex is between about 1.4:1 and 10:1 is generally effective to reduce discoloration. Preferably the ratio of softener to complex is between 2:1 and 4:1. The use of the complex in excess of about 0.7 parts per part of softener continues to give still further improvement in reduction of discoloration. However, these higher levels of the complex tend to cause disproportionate losses in fabric softening efficiency.

The complex between alkyl alcohols and alkyl sulfates has previously been described in the art as having a ratio of alcohol to alkyl sulfate of either 1:1 or 1:2. It is generally assigned the formula 2ROSO.sub.3 Na.sup.. R'OH where an alkanol is employed. Similar complexes are believed to be formed also from alkanediols.

Alkanols suitable for use in the present invention usually contain from 12 to 22 carbon atoms. In general, linear alcohols may be used, whether of natural or synthetic origin, such as dodecyl alcohol, myristyl alcohol, stearyl alcohol, and mixed alcohols such as C.sub.16 to C.sub.18 alcohols prepared by Ziegler polymerization of ethylene. Alkane diols such as octadecane diol may also be used if desired.

Suitable alkyl sulfates for use in the present invention have from about 12 to about 18 carbons atoms. Typically, the alkyl group is linear, such as n-dodecyl, myristyl, stearyl, etc. The alkyl sulfates may be either substantially pure or mixed. The alkyl sulfate is used in the form of its alkali metal salt. For commercial convenience, the sodium or potassium salts are preferred, but other alkali metals may be substituted if desired.

Fabric softeners with which the antiyellowing agents of the present invention have been found effective include the quaternary ammonium compounds of the formula

in which R.sub.1 and R.sub.2 are each long chain, substantially linear groups from about 16 to 22 carbon atoms, R.sub.3 and R.sub.4 are each lower alkyl groups of from about one to three carbon atoms and X is a cation imparting water dispersibility such as chloride, bromide, iodide, sulfate, methosulfate, etc.

Another class of fabric softeners with which the antiyellowing agent of the present invention may be used are the imidazolines of the general formula

in which R.sub.5 and R.sub.6 are each substantially linear alkyl groups of about 15 to 21 carbon atoms, R.sub.7 is a divalent alkyl group of one to three carbon atoms, and R.sub.3 and X are as defined above.

In preparing fabric softener compositions in accordance with the present invention, the fabric softener, the alkyl alcohol and the alkyl sulfate may be combined in any convenient order. Thus, while the alkyl alcohol-alkyl sulfate complex may be formed prior to combination of these ingredients with the fabric softener if desired, it is not necessary to do so.

An important application of the present invention is in the formulation of multifunctional detergents. Because of the well-known cationic-anionic interaction, leading to a loss in both detergency and fabric softening efficiency, those skilled in the art of formulating multifunctional detergents conventionally choose to employ a nonionic detergent and a cationic fabric softener. This system, however, presents a most severe test of the yellowing characteristics of cationic fabric softeners in the presence of nonionic detergents. For this reason, antiyellowing agents will be particularly useful in the formulation of multifunctional detergents based upon nonionic detergent actives and cationic fabric softeners.

Typical multifunctional detergents employing the present invention will have the following composition:

% by weight __________________________________________________________________________ Nonionic detergent active 5% to 25% Builder 5% to 60% Fabric softener 1% to 10% Alkyl sulfate 0.05% to 6% Alkyl alcohol 0.02% to 3% __________________________________________________________________________

Preferred compositions generally are formulated with the proportions:

Preferred % by weight __________________________________________________________________________ Nonionic detergent active 10% to 20% Builder 25% to 50% Fabric Softener 2% to 6% Alkyl sulfate 0.2% to 4% Alkyl alcohol 0.1% to 2% __________________________________________________________________________

The nonionic detergent active contemplated is a conventional kind. Typically these are condensates of hydrophobic compounds having a reactive hydrogen with ethylene oxide, the amount of ethylene oxide in the condensate being sufficient to impart surface-active properties to it. Typical nonionic detergents which may be used include the ethylene oxide-polypropylene oxide block polymers commercially available as the so-called "Pluronic" series; ethylene oxide condensates of alkyl alcohols having from eight to 20 carbon atoms in the alkyl group and containing up to 80 percent ethylene oxide; ethylene oxide condensates of the fatty acids such as ethoxylated tall oil fatty acids, etc.; ethylene oxide condensates of the fatty amines; and many others. This class of detergents is well known to those skilled in the art.

As builders, the conventional alkaline builders may be employed such as the alkali metal phosphates, pyrophosphates, tripolyphosphates, hexametaphosphates, etc., as well as other alkali metal compounds such as alkali metal carbonates, etc. Organic builders are also known such as nitrilotriacetic acid. The amount of builder will be in the amounts conventionally employed. Normally, when builders are used in a detergent system, the amount used is in the order of 25 to 50 percent of the complete formulation.

The fabric softening actives, alkyl alcohols, and alkyl sulfates for use in the foregoing composition have already been described above.

While not specifically mentioned in the foregoing skeleton formulation, it will be obvious to those skilled in the art that many other materials may be included. Adjuvants may be provided such as suds boosters, such as fatty acid amides; soil suspending agents, such as carboxymethyl cellulose, hydroxyethyl cellulose; anticorrosion agents, such as sodium silicate; as well as optical brighteners, colorants, perfumes, fillers, germicides, enzymes etc.

Another important application of the present invention is in the formulation of rinse cycle fabric softeners. Because of carryover from the wash cycle to the rinse cycle, yellowing has been a persistent problem when detergent formulations are employed in the wash. The use of a mixture of a cationic fabric softener and a complex in accordance with the present invention mitigates this problem.

For a better understanding of the present invention, reference may be had to the following examples:

EXAMPLE 1

Antiyellowing agents in accordance with the present invention were tested in a multifunctional detergent composition composed of a conventionally built nonionic detergent employing and containing sodium tripolyphosphate builder, distearyldimethyl ammonium chloride as a fabric softener, sodium lauryl sulfate and various alkyl alcohols. Five 4.times.6 inch terry cloth swatches were treated in a Terg-O-Tometer pot for 15 minutes with 1,000 ml. of 90 p.p.m. hard water artificially hardened with calcium and magnesium in a 2:1 ratio and additionally containing 4 p.p.m. of Fe.sup.+.sup.3. The washing temperature was 120.degree. F. 1.94 grams of built nonionic detergent composition and 0.1 grams of distearyl dimethyl ammonium chloride were added. The amounts of sodium lauryl sulfate and alkyl alcohol were varied as set forth below.

In each test conducted, improvements in softness and yellowing were measured relative to the softness and yellowness observed on swatches washed in nonionic detergent only. By recording the differences in softness (.DELTA.S) and yellowing (.DELTA.b), more meaningful comparisons may be made between successive experiments. In the data reproduced below, an increase in the value of .DELTA.S indicates an improved softness in the final product relative to the softness of the control. An increase in the value of .DELTA.b indicates a deterioration in whiteness or an increase in yellowness of the washed swatches. ##SPC1##

EXAMPLE 2

The test described in Example 1 was repeated substituting the fabric softener 1-methyl-1-alkylamido-ethyl-2-alkylimidazolinium methosulfate as the fabric softener for distearyldimethyl ammonium chloride previously described. The following results were obtained: ##SPC2##

In like manner a series of complexes were prepared from alkyl sulfates having from 12 to 18 carbon atoms and alkyl alcohols having from 12 to 22 carbon atoms and tested as antiyellowing additives.

Complexes found to be effective were the following:

Alkyl Sulfate, ROSO.sub.3 Na Alkyl Alcohol, R'OH R R' __________________________________________________________________________ nC.sub.12 H.sub.25 nC.sub.12 H.sub.25 nC.sub.14 H.sub.29 nC.sub.16 H.sub.33 mixed nC.sub.16 -C.sub.18 fatty alcohol nC.sub.18 H.sub.37 nC.sub.20 H.sub.41 nC.sub.22 H.sub.45 nC.sub.14 H.sub.29 nC.sub.12 H.sub.25 nC.sub.14 H.sub.29 nC.sub.16 H.sub.33 nC.sub.18 H.sub.37 nC.sub.16 H.sub.33 nC.sub.12 H.sub.25 nC.sub.14 H.sub.29 nC.sub.16 H.sub.33 nC.sub.18 H.sub.37 nC.sub.18 H.sub.37 nC.sub.18 H.sub.37 __________________________________________________________________________

Claims

we claim:

1. A fabric softening composition having a reduced tendency to cause yellowing, consisting essentially of a complex of (a) an alcohol selected from the group consisting of alkanols and alkane diols of 12 to 22 carbon atoms and an alkali metal alkyl sulfate of 12 to 18 carbon atoms in combination with (b) a cationic fabric softener selected from the group consisting of ##SPC3##

wherein R.sub.1 and R.sub.2 are each substantially linear alkyl groups of about 16 to 22 carbon atoms, R.sub.3 and R.sub.4 are each alkyl groups of about one to three carbon atoms, R.sub.5 and R.sub.6 are each substantially linear alkyl groups of about 15 to 21 carbon atoms, R.sub.7 is a divalent alkylene group of about one to three carbon atoms, and X is an anion imparting water dispersibility to said fabric softener; the weight ratio of said fabric softener (b) to said complex (a) being between about 1.4:1 and 10:1, and the molar ratio of the alcohol to the alkali metal-alkyl sulfate in the complex (a) being from between about 1:1 and 1:2.

2. A composition according to claim 1 wherein the weight ratio of said fabric softener (b) relative to the amount of said complex (a) is between about 2:1 and 4:1.

3. A composition according to claim 1 wherein said complex is formed from a linear alkanol having from 12 to 22 carbon atoms and an alkali metal alkyl sulfate having from 12 to 18 carbon atoms and in which the alkali metal is selected from the group consisting of sodium and potassium.

4. A composition according to claim 3 wherein said complex is formed from octadecanol and lauryl sulfate.

5. A composition according to claim 3 wherein said complex is formed from hexadecanediol and lauryl sulfate. ##SPC4##