US3594113A - Bacteriostatic finish for cellulosic fabrics - Google Patents

Abstract

A FINE AQUEOUS DISPERSION OF A PHENOILIC BACTERIOSTATIC AGENT SUCH AS HEXACHLOROPHENE, WITH THE ADDITION OF ZIRCONIUM ACETATE AND A CELLULOSE CROSS-LINKING AGENT, IS CURED ONTO A CELLULOSIC FABRIC. THE RESULTING BACTERIOSTATIC FINISH IS DURABLE THROUGH TWICE AS MANY LAUDERINGS AS A FINISH OMITTING THE CROSS-LINKING AGENT.

Description

United States Patent 3,594,113 BACTERIOSTATIC FINISH FOR CELLULOSIC FABRICS Leonard Lifland, Wellesley Hills, Mass., and Leonard A. Stanley, Charlotte, N.C., assignors to The Kendall Company, Walpole, Mass.

No Drawing. Continuation-impart of application Ser. No. 774,509, Nov. 8, 1968, which is a continuation-impart of application Ser. No. 632,927, Apr. 24, 1967, which in turn is a continuation-in-part of application Ser. No. 457,437, May 20, 1965. This application Dec. 3, 1969, Ser. No. 881,843

Int. Cl. D06m 13/34, 13/02 US. Cl. 8115.6 Claims ABSTRACT OF THE DISCLOSURE A fine aqueous dispersion of a phenolic bacteriostatic agent such as hexachlorophene, with the addition of zirconium acetate and a cellulose cross-linking agent, is cured onto a cellulosic fabric. The resulting bacteriostatic finish is durable through twice as many launderings as a finish omitting the cross-linking agent.

This application is a continuation-in-part of our c0- pending application Ser. No. 774,509, filed Nov. 8, 1968, now abandoned, which is a continuation-in-part of our abandoned application Ser. No. 632,927, filed Apr. 24, 1967, which in turn is a continuation-in-part of our application Ser. No. 457,437, filed May 20, 1965, also abandoned.

The invention relates to a process for developing a durable non-toxic, non-irritating bacteriostatic finish on cellulosic textile fabrics, and to the products thereof. More particularly it relates to a bacteriostatic finish which is elfective even after repeated commercial or home launderings in suppressing the growth and proliferation of the skin bacteria which are responsible for the development of unpleasant odors in perspiration.

It is recognized that the skin of normal, healthy individuals has a resident bacterial flora estimated to run as high as 10,000 per square centimeter. This bacterial population resides chiefly on the surface of the skin, varies in number from place to place and is understood to be principally responsible for the development, by bacterial degradation, of unpleasant odors from perspiration, which as exuded by the normal body is sterile and odorless. It has, therefore, long been a goal of textile technologists to develop a safe and eifective bacteriostatic finish for garments to be worn in intimate contact With the human body.

Although literally hundreds of products are known to exert a bacteriostatic or even bactericidal action toward normal and pathogenic bacterial flora, the majority of them are unsuitable for use as a textile finish intended for use in contact with the body.

Many are irritants: others are so insoluble in Water as to be effective only in organic solvent solution: others, on the contrary, are so water soluble as to leach right out of the fabric and resist fixation thereto: still others, such as certain heavy metal salts, are definitely toxic to the human system.

One compound which is very effective as a bacteriostatic agent, and which shows no incidence per se of skin irritation, is hexachlorophene or 2,2-dihydroxy-3,5,6,- 3',5',6-hexachlorodiphenyl methane. This white crystalline powder, although soluble in a variety of organic solvents, is insoluble in water. When applied to fabrics from, for example, acetone solution, hexachlorophene residues on a carefully dried fabric will show bacteriostatic action. However, the hexachlorophene is merely 3,594,113 Patented July 20, 1971 "Ice physically present on the fabric, without even a superficial fixation thereto: mechanical manipulation of the fabric, and especially the agitation connected with laundering and the emulsifying, action of soaps or detergents, rapidly remove the insoluble and unfixed material and leave the fabric unprotected. This type of transient effect will often not even survive the rigors of laying-out, cutting, fabricating, packing, shipping and displaying garments treated with organic solutions of hexachlorophene, and no valid claims of durable eifects therefrom can be substantiated.

It is with a method of more durably complexing phenolic bacteriostatic agents such as hexachlorophene to certain fabric substrates that the present invention is concerned. It has been found that an effective and durable bacteriostatic finish can be developed on certain fabrics by complexing a small amount, generally not over 2% based on the fabric weight, of hexachlonophene to the fabric by means of a zirconium compound such as zirconium acetate or ammonium zirconyl carbonate, to gether with a finish of the cross-linking Wash-wear type. Surprisingly, the bacteriostatic efliciency of the phenolic compound is not masked or diminished by the crosslinking finish, but instead is rendered unexpectedly more durable. As little as 2% of a cross-linking reactant finish has been found to substantially double the number of launderings which a hexachlorophene treated fabric will survive and still show bacteriostatic activity.

It is therefore, an object of this invention to produce a bacteriostatic, wash-resistant finish on cellulosic textile fabrics wherein the bacteriostatic elfeot resides in a small amount of a phenolic bacteriostatic agent durably bonded to the fabric by means of a zirconium complex and a cross-linking agent for the cellulose.

Other objects of the invention will be more fully understood from the following description thereof.

Advantage is taken in this invention of the fact that certain salts of metals belonging to the fourth transition group of the Periodic Table, as typified by ammonium zirconyl carbonate and by the readily available zirconium acetate Zr(OAc) (OH) can form coordination complexes with hydroxy compounds such as phenols. The discussion and example in the following description of the invention will be illustrated by the use of zirconium acetate, a preferred complexing agent due to its stable nature and its ready availability commercially. Certain phenolic compounds have been reported to be complexed to cellulosic fabrics, by means of zirconium salts, to impart rot resistance to the fabrics (Gonzales et al, Textile Research Journal, vol. 33, No. 8, August 1963, pp. 600- 608). The rot resistance developed, however, was sensitive to alkaline conditions, such as are met with in laun dering, and the phenolic fraction of the complex, which was responsible for the activity, was reported to be removed. Hexachlorophene was not reported as one of the compounds tried. It has been our experience that by complexing a small percentage of a phenolic bacteriostatic agent such as hexachlorophene tocellulosic fabrics by means of zirconium salts and a wash-wear cross-linking agent, a bacteriostatic finish is developed which under standard test conditions remains effective after repeated exposure to alkaline conditions as typified by home or commercial laundering operations. In the case of hexachlorophine, the finish thus obtained is not harmed by bleaching or scouring, and provides a high level of bacteriostatic activity against a wide variety of Gram-positive organisms, and an apparently lower but still appreciable activity against Gram-negative organisms. In general, superior and more durable results are obtained by using bisphenols than with mono-functional phenolic compounds.

By cross-linking agents is meant here those reactants, whether resin-forming or not, which are used to produce a wash-wear effect on cellulosic fabrics when used at the level of to Included in this category are ureaformaldehyde, melamine formaldehyde, triazenes, tri azones, dimethylol ethylene urea, dihydroxy dimethylol ethylene urea, and the carbamate resins.

The durability of phenolic bacteriostatic agents complexed to a cellulosic fabric substrate by the process of this invention is determined in two ways: by the zone of inhibition shown by the fabric when grown on an agar plate containing common organisms such as escherichia coli and staphylococcus aureus, and by extraction. In the latter procedure, a sample of the fabric is extracted with 0.1 N KOH, which removes the bacteriostatic agent quantitatively. The UV absorbence of the aqueous extract is determined at 320 millimicrons, where hexachlorophene has a sharp peak. The magnitude of the peak is a quantitative measure of the amount of hexachlorophene present, when compared with standards of known strength. From this the percentage of hexachlorophene on the fabric can be calculated.

On a theoretical basis, one mole of zirconium acetate should be capable of complexing one mole of hexachlorophene to a fabric, through one of the hydroxy groups of the biphenolic hexachlorophene. By the same reasoning, one mole of zirconium acetate should be capable of complexing two moles of a monophenolic bacteriostatic agent to a fabric substrate containing groups with which the zirconium acetate will react.

It has been found that especially desirable and durable results are obtained if a theoretical excessi.e., two moles of zirconium acetate-is employed for each mole of hexachlorophene. The exact nature of this effect is not understood.

Even better results are obtained if the mole ratio of zirconium acetate to each phenolic group in the bacteriostatic agent is increased to 1.5 to 1: that is, 3 moles of zirconium acetate per mole of (bifunctional) hexachlorophene. Our effective limits are from two to ten moles of zirconium acetate per mole of hexachlorophene, With a preferred ratio of from three to six moles of zirconium acetate per mole of hexachlorophene.

We have also found that a pleasant, fresh and appealing odor, persistent after several launderings, may be imparted to cellulosic fabrics finished by the process of this invention by incorporating small traces, of the order of 0.01% or less, of odorous phenolic compounds such as Texodor 2 BIs and Resodor 21, products of Sindar Corporation.

Complex phenolic bodies with a pleasant odor have been developed for the reodorization of finished textiles, and are used to mask chemical odors and other offodors developed in storage of fabrics. As generally used, their influence is transient. By complexing such odorous phenolic bodies to a fabric substrate by means of zirconium acetate, however, their durability of odor persists through five or more washing cycles, prolonging the consumer appeal of fabrics thus treated.

As stated above, pronounced durability of bacteriostatic efficiency is shown when the zirconium acetate-hexachlorophene complexing is carried out in the presence of a wash-wear cross-linking finish applied to a cellulosic fabric. Particularly effective are the carbamate resins, represented by dimethylol methyl carbamate and dimethylol ethyl carbamate, which have been postulated to react with cellulose as follows, using the ethyl derivative as example:

C H OCON CH OH) Cellulose OH There is also the possibility that a certain amount of monomethylol ethyl carbamate, present in the dimethylol resin, will react with cellulose to give C H OCONHCH OCellu.

Alternatively, the dimethylol derivative may react with a single cellulose molecule to give C H OCON(CH OH) (CH OCellu), which hydrolyzes in laundering to give C H OCONH CH O Cellu) Whatever the route by which such a compound is formed, the amide hydrogen of this latter compound may be readily replaced by chlorine to form a chloramide of unusual stability, inasmuch as the chlorine does not degrade nor scorch the fabric during ironing, unlike the behavior of other nitrogen-containing wash-and-wear resins finished which form chloramides with available chlorine.

The invention will be illustrated by the following examples.

EXAMPLE 1 A cotton broadcloth was treated with the following dispersion:

3% Triton X- (Rohm and Haas brand of ethylene oxide nonyl phenol) heated above F.

0.5% hexachlorophene 4% Alkanol HCS (Du Pont brand of nonionic ethoxy alcohol) 1.5% zirconium acetate 10% dimethylol ethyl carbamate 3.5% magnesium chloride 4.0% of a 35% dispersion of a polyethylene softener 73.5% water In order to insure thorough dispersion, the hexachlorophene is dissolved in the wetting agents, and the water is then added, leaving the hexachlorophene in the form of a very fine, almost colloidal, dispersion. To promote maximum bath stability, the zirconium acetate is added just prior to processing the fabric.

The fabric was saturated with the above solution to 100% wet pickup in a conventional padder, dried at 225 R, cured for 5 minutes at 315 F., after washed and redried.

Samples of the fabric thus treated and the same fabric after 10 home launderings and after 10 commercial launderings were tested with a control sample of untreated base fabric against Staphylococcus aureus according to the AATCC test #100l96lT. Circular disks 1% inches in diameter were cut from each of the 4 samples, placed in cups and saturated with a culture of Staphylococcus aureus. After 24 hours incubation at 37 C., 100 milliliters of letheen broth was added to the test cups and an equal amount of sterile water to the test cups. The cups were shaken vigorously for one minute and aliquots of serial dilutions were plated in petri dishes, which were incubated at 37 C. for 24 hours and counted. The number of viable organisms on the samples treated according to this invention ranged from 75 to 367: on the parallel control samples of base fabric they ranged from 318,000 to 370,000. On a percentage basis, with three tests run on each of the three treated fabrics, the degree of control as compared with the base fabric was 99.98% for the unwashed treated fabric, 99.86% from the home-laundered treated fabric, and 99.76% from the commercially-laundered treated fabric.

Even after 50 commercial laundering cycles, which is beyond the life expectancy of wash-and-wear garments, fabrics treated as above with a combined carbamate resin finish and a cellulose-zirconium acetate-hexachlorophene complexing finish showed inhibitory action against Staphylococcus aureus and selected strains of Escherichia coli. Essentially identical results are obtained when any of the above-mentioned cross-linking agents for cellulose are substituted for the carbamate. By contrast, a parallel experi: ment omitting the carbamate cross-linking agent yielded a fabric which showed little or no bacteriostatic action after 25 launderings.

One reason. for rewashing after the curing operation set forth above is to remove traces of the nonionic wetting agents used in the bath formulation to assist in solubilizing the hexachlorophene. It is advisable to remove such nonionic stabilizers in a post-cure washing operation, since their presence on the fabric seems to inhibit or interfere with the bacteriostatic efficiency of the hexachlorophene. Alternatively, instead of a nonionic stabilizer, we have found that phenolic compounds effective against organisms, such as hexachlorophene and ortho phenyl phenol, can be dissolved in warm 50% solutions of cationic dispersing agents as represented by quaternary ammonium compounds such as alkyl dimethyl benzyl ammonium chloride, alkyl ethyl-benzyl dimethyl ammonium chloride, cetyl dimethyl benzyl ammonium chloride, and the like, to form stable baths which quite unexpectedly are infinitely dilutable and compatible with zirconium acetate solutions. By use of such quaternary compounds, not only is the deleterious effect of nonionic stabilizing agents avoided, but the quaternary ammonium compounds are themselves substantive on cellulose and display a bacteriostatic action of their own which broadens the spectrum of effectiveness of a treated cellulosic fabric.

The of carbamate resin used in the above example will impart a Wash-wear finish to the fabric. However, as little as 1% resin will result in enhanced durability of the bacteriostatic finish (up to 50 launderings or more). The fabric hand, at such low resin levels, is scarcely aflected, with no crease-resistance or wash-wear effect noticeable. Our preferred limits of cross-linking agent are from 1% to on the weight of the fabric, depending on whether a wash-wear finish is desired or not.

Although hexachlorophene is our reagent of choice in the bacteriostat-resin finish combination of this invention, other phenolic bacteriostatic agents may be used, such as ortho phenyl phenol, halogenated phenolics such as tribromophenol, bithionol, and the like, the chief requirement being that the bacteriostatic agents contains at least one phenolic hydroxyl group capable of complexing with cellulose through the intermediary of the bifunctional zirconium acetate, and that in the concentration used, the phenolic compound should be nonirritating and non-toxic when in contact with the human skin.

An additional phenolic bacteriostatic agent, with a broader activity spectrum than hexachlorophene, is 5-chloro-2-(2,4-dichlorophenoxy) phenol, produced by the Geigy Company and known as Irgasan CH-3565. It may be used alone, or in combination with hexachlorophene, as illustrated in the following example.

EXAMPLE 2 A cotton broadcloth was treated with the following dispersion:

10% Iegal CO-850 (General Anilines trademark for a nonyl phenoxy polyoxyethylene ethanol wetting agent).

0.5% hexachlorophene 5% zirconium acetate 5% Protorez AA (Proctor Chemicals trademark for a 50% solution of a dimethylene propyleneurea resin) 0.9% of a 40% zinc chloride solution 78.1% water The fabric was padded with the above to 70% wet pickup, dried at 250 F., cured for 90 seconds at 340 F.,

afterwashed and redried. Even after 40 commercial launderings, the fabric showed antibacterial activity against Staphylococcus aureus according to the AATCC #-1965 Agar Plate Streak Test. Essentially identical results were obtained when the CH3S65 hexachlorophene combination was replaced by tribromophenol.

In general, we prefer to fix onto the fabric an amount of phenolic bacteriostatic agent not in excess of about 2% on the Weight of the dry fabric, to avoid discoloration and boardiness associated with excessive fabric loading with reagents of this type. The amount of zirconium acetate employed will vary with the molecular weight of particular phenolic compound chosen, and is, therefore, best expressed on a mole basis. In case an additional, odor-bearing phenolic compound is also complexed to the cellulose, the amount of zirconium acetate employed may be increased slightly. The extra amount of zirconium acetate needed can be calculated from the molecular weight of the odor-bearing phenolic compound, but in general will not exceed about 0.2%.

Having thus described our invention, we claim:

1. The process for producing a durable laundry-resistant bacteriostatic finish on a cellulosic fabric which comprises preparing an aqueous dispersion comprising a phenolic bacteriostatic agent, a wetting agent selected from the class consisting of non-ionic and cationic wetting agents, zirconium acetate, about 1% to 15%, based on the dry weight of the fabric of an aminoplast; cross-linking agent for the cellulose and a catalyst for promoting cross-linking,

impregnating said fabric with said aqueous dispersion,

and drying, and curing the impregnated fabric.

2. The process according to claim 1 wherein the phenolic bacteriostatic agent is selected from the class consisting of hexachlorophene, tribromophenol, 5-chloro- 2-(2,4-dichlorophenoxy) phenol and mixtures thereof.

3. A product prepared by the process of claim 1 in which not more than 2% of the phenolic bacteriostatic agent is complexed to the cellulose by between 1.5 and 3 mole equivalents of zirconium acetate for each phenolic hydroxy group on the bacteriostatic agent, said percentage being based on the dry weight of the fabric.

4. A cellulose fabric prepared by the process of claim 1.

5. A cellulose fabric prepared by the process of claim 2.

References Cited UNITED STATES PATENTS 3,183,149 2,850,407 8/1958 Zurawie et a1 117l39.4 2,774,746 12/1956 Shelly et al. 260---29.4

FOREIGN PATENTS 760,344 9/ 1954 Great Britain.

OTHER REFERENCES Gonzales et a1., Textile Research Journal, vol. 33, No. 8, August 1963, pp. 600-608.

GEORGE F. LESMES, Primary Examiner B. BE'IIIS, Assistant Examiner U.S. Cl. X.R. 8-116, 116.2

5/1965 Gonzales 16738.7