Composition containing benzimidazole derivatives for softening rinse

[57] ABSTRACT

Surface-active benzimidazole derivatives able to exist in either cationic or zwitterionic form and useful as textile treating agents are disclosed. The compounds are effective as textile softening agents substantive to fabrics as the ordinary pH of fabric rinsing operations and removable from fabrics in a zwitterionic form under succeeding alkaline washing conditions.

Claims, No Drawings

3,856,684

COMPOSITION CONTAINING BENZIMIDAZOLE DERIVATIVES FOR SOFTENING RINSE

This is a division of application Ser. No. 230,032, filed Feb. 28, 1972, now abandoned.

This invention relates to certain benzimidazole derivatives useful as textile treatment agents and able to exist in either cationic or zwitterionic form.

Quaternary ammonium compounds having at least one long chain (about C₈ upwards) hydrophobic radical in the molecule have long been known. They are useful as cationic surface active agents (so called, “invert soaps”), as textile softening agents and as bactericides. When intended for use as surface active agents, the long chain group usually has about 12 to 20 carbon atoms. When intended for use as textile softeners, long chain compounds, for instance having about 16 to 22 or more carbon atoms, are preferred, especially compounds with two long chain groups. Typical examples include dodecyldimethyl benzyl ammonium chloride, dodecyltrimethyl ammonium chloride, distearyl dimethyl ammonium chloride, the corresponding bromides, and many others of similar structure.

These compounds, particularly distearyl dimethyl ammonium chloride, have been used commercially in textile softening compositions intended to be added to the last rinse water after a conventional washing process, and attempts have been made to use them in detergent compositions intended to be combined washing and textile softening agents.

Being cationic, these substances ordinarily react with anionic detergents to form insoluble substances, and so their use in the presence of anionic detergents is not normally practicable. Furthermore, they have a strong affinity for fabrics, especially cotton and wools, a fact which plays an important part in their effectiveness as textile softeners, but also has the effect that they generally are not completely washed out of the fabric in a succeeding wash. They therefore tend to build up on repeatedly washed fabrics, where they may impair the re-wetting properties of the fabrics, and where they tend to cause discoloration, an unpleasing greasy feel, fiber snagging and even undesirable odors.

Other quaternary ammonium compounds constitute the known zwitterionic surface-active compounds, such as long chain carboxylic betaines, sulphobetaines, sulphato-betaines and sulphito-betaines. These compounds are valuable wetting agents and detergents. Being internal salts, they do not react with the metal ions present in hard water, especially calcium ions, and thus are almost unaffected by water hardness. For the same reason, they are compatible with anionic, cationic and nonionic detergents. Their affinity for and wetting effect upon certain highly hydrophobic fibers, such as polyamine and polyester fibers, renders them particularly valuable for removing certain types of soils, especially greasy soils, from these materials. They are also remarkably effective in cleaning cotton fabrics soiled with dirt which contains clay particles. However, they are not strongly substantive to fabrics and are not very effective textile softening agents. These known betaine and betaine-like compounds exist in zwitterionic form over a wide range of pH. In relatively strongly acid conditions they do become cationic, but the necessary acidity is outside the practical range for washing fabrics or the person.

The present invention is based on the discovery of a new class of detergents which are cationic under weakly acid conditions, and are zwitterionic under weakly alkaline conditions, relative to their pKa value as defined hereinafter. Thus, if present at the ordinary pH of a rinsing operation in an aqueous solution (which need not, of course, necessarily in fact constitute the rinse after a wash) they are largely in cationic form and are effective as textile softening agents substantive to fabrics. In the ordinarily alkaline conditions of a subsequent conventional washing operation, they convert to a zwitterionic form and, thus, are at least partially removed from the fabrics. When so removed, they are compatible with the detergent composition and may even enhance its effectiveness. Furthermore, the adsorbed cationic and/or zwitterionic layer on the textile fibers provides a surface which tends to repel important classes of soil and to promote their separation from the surface and their dispersion in a subsequent alkaline wash when the adsorbed layer is rendered nonsubstantive. Thus, these substances can act as soil release agents which are at least partly removed at each wash and can be re-applied before the surface is reexposed to soiling, as more fully described hereinafter. They may also provide antistatic properties for the surfaces treated with them.

SUMMARY OF THE INVENTION

According to the invention, there is provided a quaternary ammonium benzimidazole having the formula:

r λ N Ί + z/\Z \ χ/\ / A

NX N I L ii J or its corresponding zwitterionic form

<img file="US3856684A_D0001.tif" />

wherein either (i) R₄ is an alkyl group having from 14 to 22 carbon atoms or an alkylphenyl or alkylbenzyl group having from eight to 16 carbon atoms in the alkyl chain, and R₂ is alkyl of from one to 16 carbon atoms or a group (C₂H₄O)_mH where m is from one to 20; or (ii) each of R₄ and R₂ is an alkyl group of from 10 to 22 carbon atoms or an alkylphenyl or alkylbenzyl group as defined above; R₃ is alkyl of from one to six carbon atoms or a group (C₂H₄O)_mH where m is from one to 20; n is an integer from 1 to 4; and X is an anion.

In its composition aspect, the present invention provides textile softening compositions containing the benzimidazole derivatives and suited to use as presoaking or rinse-added compositions. Also provided are detergent compositions containing the benzimidazole derivatives herein and adapted to use as cleaning and softening compositions.

In its method aspect, the present invention provides a method of treating fabric materials whereby the fabrics are improved jri softness without undesirable buildup with succeeding washing treatments comprising the steps of treating the fabrics with a solution of a cationic compound described hereinbefore thereby to improve softness and, thereafter, washing the fabrics under alkaline conditions thereby to remove the softener in a

3,856,684 zwitterionic form. Also provided is a method whereby fabrics can be similtaneously cleaned and softened.

DETAILED DESCRIPTION OF THE INVENTION

As is apparent from the hereinbefore defined formulae, one or two long chain lipophilic groups are attached to the quaternary nitrogen atom. If only one is present, it can be an alkyl group of from 14 to 22, and preferably from 16 to 20, carbon atoms, or an alkylphenyl or alkylbenzyl group having from eight to 16, preferably 10 to 14, carbon atoms in the alkyl chain. If two are present and each independently can be an alkyl group of from 10 to 22, preferably 12 to 18, carbon atoms or an alkylphenyl or alkylbenzyl group as above. The latter group can be derived from a typical detergent alkylate. The one or two short-chain groups, R₂and R₃, can be short-chain alkyl groups, having from one to six carbon atoms; preferably, R₂ and R₃ are methyl or ethyl. The short-chain groups can also be the corresponding hydroxyalkyl groups, e.g., hydroxyethyl, or hydroxyalkyl groups can be ethoxylated, for instance with 1 to 20 ethylene oxide residues. In the hereinbefore defined formulae, the number n represents the number of methylene groups and is an integer of from 1 to 4; preferably n is from 1 to 3 and especially 1.

The anion X may be any water-soluble anion which is convenient. The most usual anions, especially in detergent, softening and like compositions, are halides, especially chloride or bromide, sulphate or methosulphate. Some others suitable, generally for other purposes, include bisulphate, nitrate, perchlorate, and fluoroborate.

Preferred compounds according to the invention are those which have a pKa value in the range from 5 to 10, especially in the range from 8 to 10. The optimum pKa value will depend to some extent upon the intended application. The pKa of a weak acid, such as the present compounds, in aqueous solution is defined as the pH of the solution when the compound is half neutralized, i.e., ii) the present instance, when it is 50 molar percent in zwitterionic form and 50 molar percent in cationic form. At pH values near to the pKa value both forms are present to a considerable degree.

The benzimidazole derivatives can be conveniently synthesized. For example, a 2-haloalkyl benzimidazole having the formula

<img file="US3856684A_D0002.tif" />

where X is chloro or bromo and n is an integer of from 1 to 4 can be prepared by the reaction of ophenylenediamine and a haloalkanoic acid. The preparation of 2-chloromethylbenzimidazole from 2-hydroxymethylbenzimidazole and thionyl chloride is disclosed by Hofmann in Imidazole and its Derivatives, Interscience Publishers, Inc., New York, Part I, pp. 303-304 (1953). The 2-haloalkyl benzimidazole, prepared in the manner described above, can be reacted with a tertiary amine having the formula NRiR₂R₃ where Ri, R₂and R₃ are defined as hereinbefore mentioned. The preparation of 2-monoalkyl and 2-dialkylaminomethylbenzimidazoles by reaction of 2chloromethylbenzimidazole with amines is disclosed by Hofmann, supra, at page 311.

Ordinarily, the compounds of the invention are applied to fabrics from an aqueous solution, and conveniently at some atage in a washing process. They have surprisingly been found to have valuable textile softening properties when incorporated at any stage of a washing process. Thus they can be added, as are most conventional textile softening agents, at the rinse after a washing process. Provided that the rinse liquor has a pH in a range such that they are to a considerable degree in cationic form, they are substantive to most fabrics and are effective softeners.

Alternatively, the compounds can form part of the active detergent component of a washing composition formulated so that they are predominantly in zwitterionic form during the washing step. The proportion of the compound still present in the rinse liquor, when dilution with tap water or the like has reduced the alkalinity, is then available in cationic form to act as a substantive fabric softener.

The invention also provides textile treatment agents containing the quaternary ammonium benzimidazole in admixture with a diluent. The nature of the diluent will of course depend on the particular type of textile treatment agent. For example, a detergent composition will contain a detergent ingredient.

Suitable proportions of the benzimidazole in a detergent composition depend upon the nature of the composition. In most conventional heavy duty detergent compositions, a content of benzimidazole of 1 to 10 percent by weight, especially about 5 percent, gives good results.

A particularly effective method of employing these compounds as textile softening agents is to give fabrics which are to be washed a preliminary soaking or wetting in an aqueous solution of the cationic form of the compound. Thereafter, a detergent composition, such as a typical built heavy duty detergent composition, can be added to the same solution and washing and rinsing carried out normally. Alternatively, surplus solution can be separated from the fabrics, for instance by spin drying, and then they can be washed and rinsed in the ordinary way. Generally the former alternative is preferred.

In both these latter methods of applying the benzimidazole derivatives of the invention, it might be expected that the amount of adsorbed derivative would build up in repeated treatments, somewhat as in the case of the prior art cationic textile softeners, but it is surprisingly found that this does not occur. The reason for this is not known, although it may be postulated that the washing process always removes some of the entrapped, but non-substantive, zwitterionic form of the benzimidazole derivative, so that the amount remaining reaches a mazimum level after one or a few treatments and thereafter does not increase.

It is preferred that there should be from about 0.01 to 0.5 percent, especially about 0.1 percent of the cationic form of the benzimidazole derivatives, by dry weight of the fabric, present in the treatment solutions containing said cationic form, i.e., in presoak or rinse solutions.

The agents intended for use as rinse additives preferably contain pH buffers, of a type and in amount such that an aqueous solution of the agent (of concentration such that it contains 0.1 percent by weight of the benzimidazole) has a pH less than the pKa value of the benzimidazole, more preferably at least 2 units below

3,856,684 the pKa value. If the pH approaches the pKa value, it is advisable to have a further, preferably nonionic, surfactant present to solubilize that part of the benzimidazole derivative which is in zwitterionic form. Suitable buffering agents are known in the art, for example 5 phosphates, carbonates, borates, citrates and tartrates and the corresponding acids. The content of these components in the rinse additive compositions depends upon how they are intended to be employed. Effective and convenient compositions contain from about 1 to 10 20 percent by weight, for example about 5 percent, of the cationic form of the benzimidazole derivative, and can be used at a concentration of about 0.2 to 0.5 percent, by weight, in a rinsing or post-wash soaking solution, but these figures are not to be considered limiting. 15 When benzimidazole derivatives of the invention are employed which are poorly soluble in water even in their cationic form, they can be solubilized by including another surface active agent, preferably a nonionic agent, in the composition. 20

Detergent compositions containing the benzimidazole derivatives include built detergent compositions, and can contain any detergency builder, such as the water-soluble (usually sodium or potassium) phosphates and polyphosphates, carboxylates, silicates, bo- 25 rates, etc., and chelating agents such as nitiloctriacetates, polycarboxylates such as those described in U.S. Pat. No. 3,308,067 (Mar. 7, 1967), citrates and gluconates. Neutral salts such as alkali metal sulphates and chlorides, and bleaching agents such as sodium perbo- ³⁰rate, percarbonates or perphosphates can also be present. The organic surfactant component can comprise anionic, nonionic or zwitterionic surfactants. Preferably, the major part of the surfactant component is anionic. Suitable surfactants are known in the art. Suitable ³⁵anionic surfactants include the sulphonic and sulphuric acid derivatives, such as alkyl aryl sulphonates, alkyl sulphates and alkyl ether sulphates, the nonionic surfactants include the sulphonic and sulphuric acid derivatives, such as alkyl aryl sulphonates, alkyl sulphates ⁴⁰and alkyl ether sulphates; the nonionic surfactants include polyethoxy- alcohols, polyethoxy -alkyl phenols, polyethoxy -fatty acids, polyethoxy-amines, polyethoxy polypropylenoxy condensates, polyethoxy sorbitan esters and many others, and can include tertiary amine ⁴⁵oxides and phosphine oxides; zwitterionic surfactants include quaternary ammonium carboxylates (betaines) and sulphonates (sulphobetaines) and the like, some of which have been mentioned above. Examples of suitable detergents are provided in U.S. Pat. No. 3,213,030, issued Oct. 19, 1965, lines 53-75 of col. 3 lines 1 to 75 of col. 4 and lines 1 to 30 of col. 5, which disclosure is incorporated herein by reference. Normally, the built detergent compositions of the invention ₅₅will comprise the benzimidazole of the invention and an admixture of detergent active and builder salt as described above in a ratio of detergent to builder of from about 2:1 to about 1:10 by weight.

Agents intended for use as pre-soak additives, i.e., for ₆θ soaking fabrics before they are washed, can consist solely of the cationic form, for instance the hydrochloride, of the benzimidazole derivative, but preferably they contain a diluent which can be or include a component to make them convenient to handle or aestheti- ₆₅cally attractive. When benzimidazole derivates which are poorly soluble in water even the cationic form, for instance some of those wherein both Rj and R₂ are hy drophobic groups, are used, they can be solubilized by including another surface active agent, for instance a nonionic, in the composition.

The agents of the invention can of course contain as appropriate in each case, the usual minor components such as suds controlling agents, bleaching agents, bactericides, enzymes and activators or stabilizers therefore, dust inhibitors, soil suspending agents, tarnish or corrosion inhibitors, opacifiers, dyes, perfume and the like.

The following Examples illustrate the invention:

EXAMPLE I

PREPARATION OF

DIMETHYL-HEXADECYL-(2BENZIMIDAZOLYLMETHYL) AMMONIUM CHLORIDE

Five grams 1-chloromethylbenzimidazole (0.03 mole) and 8.1 grams dimethylhexadecylamine (0.03 mole) in acetone (100 ml) were heated under reflux (1 hour) and allowed to cool. The product (11.1 g.) was removed by filtration and had a melting point of 93°-95°C. This was converted to the relatively insoluble zwitterionic form upon basification (melting point, 131°-134°C.)

The corresponding n-dimethyl docosyl compound (melting point, 50°-55°C.; zwitterion, 19Γ- 193°C.) was prepared using the procedure of Example I above but employing dimethyldocosylamine in place of dimethylhexadecylamine.

EXAMPLE II

Solutions were prepared consisting of

a. water acidified to pH 4.

b. 1 percent by weight solution of the compound having the structure:

<img file="US3856684A_D0003.tif" />

in water, and acidified to pH 4. This compound has a pKa value in the range 8.5 to 9.5.

Test pieces of cotton Terry Towelling were dipped in the solutions (at about 20°C) rinsed in water of pH about 4 and dried.

The test pieces treated in solution (b) had softer feel than those treated in solution (a).

Some of the test pieces from solution (b) were stirred in water (at about 20°C) rendered alkaline, to pH 10. The solution became visibly cloudy as the poorly soluble and non-substantive zwitterionic form of B became detached from the fabric.

Other test pieces which has been treated in each solution (a) and (b), were soiled with a mixture of motor engine oil and soot. They were stirred in aqueous alkaline solutions as above, and it could be clearly seen that more soil was transferred into the solution from the test pieces treated in solution (b) than from the others, and correspondingly the test pieces were visibly cleaner.

A similar result was observed when the soiled treated test pieces were washed at 60°C in a 0.5 percent by weight solution of a typical conventional heavy duty built detergent, having pH in this solution of about 10.

3,856,684

EXAMPLE III

A composition was prepared consisting of 5 parts of the compound

<img file="US3856684A_D0004.tif" />

and 95 parts of a commercial granular built detergent composition comprising as essential components:

9.3 percent mixed dodecylbenzene sulphonate and tallow alkyl sulphate,

2.5 percent soap, percent sodium tripolyphosphate, percent sodium silicate, percent sodium sulphate, percent sodium perborate tetrahydrate, percent moisture, with minor components including enzymes, suds stabilizer, optical brightener, perfume and the like constituting the balance.

Test pieces of cotton terry towelling and cotton towelling were washed in a 0.5 percent by weight solution of this composition in tap water (hardness 170 ppm as CaCo₃) at 50°C for 5 minutes, and rinsed thoroughly and dried. Corresponding test pieces were washed similarly in a 0.5 percent by weight solution of said detergent composition without the benzimidazole derivative.

In each case 60 g of fabric were treated in 1 liter of detergent solution, corresponding to 0.4 percent of benzimidazole derivative by weight of the fabric.

The treatment was carried out 5 times and the fabrics were then compared by a panel of six judges, blindfolded to avoid any confusion resulting from visual impression. All six judges found the fabrics treated with the composition of the invention softer than the control fabrics.

EXAMPLE IV

0.25 g of the benzimidazole derivative of Example III were dissolved in 1 liter of tap water at 50°C, and 60 g of test fabrics, similar to those treated in Example III, were soaked for 2 to 5 minutes in this solution. Then there were added to the solution 5 g of the detergent composition of Example III, and the fabrics were washed for 5 minutes, and rinsed and dried normally. They were compared as in Example III with fabrics washed similarly, but employing only water for the presoak. After only one such treatment the judges all found the fabrics pretreated in the solution of benzimidazole softer than the control fabrics.

EXAMPLE V

Test fabrics were washed with the detergent composition alone as in Example III and rinsed once.

They were then given a second rinse in 1 liter of a. tap water, or

b. a solution containing 250 parts per million of the benzimidazole derivative of Example III, or

c. a solution as (b) but also containing an equal weight of a mixture of 2 parts sodium citrate and 3 parts citric acid to adjust the pH to 5.

The fabrics were then spin dried and dried fully.

After only one treatment the fabrics rinsed in solutions (b) and (c) were adjudged softer than those rinsed in water only.

EXAMPLE VI

Similar results were obtained in the treatments of Examples IV and V when the benzimidazole derivative was replaced by one having the formula:

<img file="US3856684A_D0005.tif" />

I It and by one having the formula: r a N

<img file="US3856684A_D0006.tif" />

<img file="US3856684A_D0007.tif" />

N I it

C-Clb—N-Cislb;

together with twice its weight of a nonionic surfactant, viz., coconut fatty alcohol condensed with six molar proportions of ethylene oxide. In the absence of the nonionic surfactant, some softening effect was observed with the latter compound, but less than that with the other compounds alone, or with the said mixture.

EXAMPLE VII

Test pieces of cotton shirt fabric were treated as in Example V(b). By comparison similar test pieces were given their second rinse in a solution containing 250 parts per million of ditallowyldimethyl ammonium chloride, added in the form of a commercial fabric softener composition.

After one cycle the pieces rinsed with the benzimidazole derivative were judged slightly softer than those rinsed in the conventional softener. After 3-6 cycles there was no consistent difference, after 9 and 12 cycles the pieces rinsed in the conventional softener were adjudged softer. However, they had a more “greasy” feel and had become more discolored than the pieces rinsed in the benzimidazole composition.

EXAMPLE VIII

Example IV was repeated using 240 g of test fabrics, corresponding to 0.1 percent of benzimidazole derivative by dry weight of fabric. After one such treatment the judges all found the fabrics pretreated in the solution of benzimidazole derivative softer than the control fabrics.