US2906664A

US2906664A - Maurice

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Publication number: US2906664A
Authority: US
Publication date: 1959-09-29
Anticipated expiration: 1976-09-29

Description

Sept. 29, 1959 P. MAURICE 2,996,654

GERMICIDAL COMPOSITIONS Filed Sept. 27, 1954 THE STER/L/SAT/ON TIME OF STAPHYLOCOCCUS AuREusM/aysm lso- FOLD 0 /1.u'r/o/v OFA' COMPOS/T/ON co/vml/w/vc emu/v OF THE SODlUM SALT OF D/CHLORO-M-XYLENOL AND VARY/NG AMOUNTS om soZw/v SOLUT/ON OF CASTOR 0/1. SOAP STER/L/SAT/ON T/ME (MINUTES) 7 %v/v orsoZw/v CASTOR O/L SOAP SOLUT/ON //v COMPOSITION Inventor United States Patent*() M GERMICIDAL COMPOSITIONS Philip Maurice, London, England, assignor to Monsanto Chemicals Limited, London, England, a British com- P y Applicafion September 27, 1954, Serial No. 458,567

Claims priority, application Great Britain October 8, 1953 7 Claims. (Cl. 167-31) This invention relates to germicidal compositions derived from dichloro-m-Xylenol.

When m-xylenol (3:5-dimethylphenol) is caused to react with about two molecular proportions of chlorine there is formed as the main product a compound of melting point about 95 C. This compound is believed to be 2:4-dichloro-3:S-dimethylphenol and is commonly spoken of as dichloro-m-xylenol; where dichloro-mxylenolis referred to in this specification it is to be understood that the reference is to the above dichloro-compound of melting point about 95 C.

Dichloro-m-xylenol is known to possess an effective germicidal activity against gram negative bacteria such as the organism Salmonella typhi, and considerable quantities of the compound are manufactured for use in the formulation of germicides. However, in order to make practical use of its germicidal effect it is necessary to ensure that when the dichloro-m-xylenol is bronght'into contact with the organisms to be destroyed it is in the form of an aqueous solution or dispersion. Like many other chlorinated phenols, however, dichloro-m-xylenol is almost insoluble in water (in fact it is soluble only to the extent of about 1 part in 25,000), and in practice it is normally formulated with a solubilise'r, particularly with a soap such as castor oil soap, which itself has a marked activity against gram negative bacteria. The usual method of formulation is to prepare a relatively concentrated aqueous solution of dichloro-m-xylenol.containing sufficient castor oil soap or coconut oil soap to ensure that when the composition has been diluted with a large excess of water, as the marketed composition normally will be immediately before use, the dichloro-rn-xylenol is still maintained in solution or dispersion. It is also customary to'add'an essential oil such as terpineol, and this, in addition to its capacity to confer on the formulation a pleasant odour, often has itself an appreciable solubilising action on the dichloro-m-xylenol. Thus a marketable aqueous solution might contain say 1.5% by weight of dichloro-m-xylenol, 2.5% by weight of castor oil soap and 4% by weight of terpineol, the remainder being water. Whether aqueous formulated compositions of'this and the foregoing type are true solutions or are on the other hand .colloidal in nature is debatable, but at any rate the dichloro-m-xylenol that they contain cannot-be removed by ordinary methods of filtration.

It is nevertheless a fact that dichloro-m-xylenol compositions as ordinarily formulated with a soap such as castor oil soap suffer from a serious disadvantage, namely their low activity against gram positive bacteria, for example Staphylococcus aureus strains, which are largely responsibe for blood infections. While castor oil soap enhances the activity of dichloro-m-xylenol against gram negative bacteria, so that as the proportion of soap in an aqueous composition containing a given quantity of dichloro-m-xylenol is increased so the germicidal activity of the composition againtst these organisms is increased (at least within ordinary limits), tests have shown that castor, oil soap exerts exactly the opposite effect on the Staphylococcus aureus.

activity of dichloro-m-xylenol compositions jagainst This phenomenon may possibly be due to the fundamental difierences in the cell wall structures of gram negative and gram positive bacteria, but whateverthe reason it is found in practicethat in order to prepare from dichloro-m-xylenol a germicidal composition having a usefully high degree of activity against such organisms as Salmonella typhi, there has to be used such a high proportion of soap that the activity of the composition against gram positive organisms such as Staphylococcus aureus is reduced to an undesirably low value. Such an ill-balanced germicidal activity against different types of organism, which may well be present together on a surface required to be sterilised, can be a practical disadvantage of considerable importance.

The present invention is concerned with new germicidal compositions derived from dichloro-m-xylenol having 'a comparatively high activity against gram positive bacteria and a usefully high activity against gram negative bacteria also, and arises from the discovery that the germicidal activity against the gram positive organism Staphylococcus aureus of aqueous solutions of watersoluble salts of dichloro-m-xylenol, by which is meant salts having a solubility in water of more than 1 gram per 100 cc. of solution (usually abbreviated to 1% w./v.) at 20' C., is increased by including in the solutions a proportion of a soap or other anionic surface-active agent. i

That the activity of'these soluble salts against gram positive organisms should be increased in this manner was quite unexpected, and the mechanism by which the observed increase in germicidal activity is produced is in fact obscured. A soap or other anionic surface-active agent is, of course, added to an aqueous suspension of a germicidal phenol in order to solubilise the phenol and so to facilitate its access to the bacterial cell wall and hence its germicidal action against the bacteria. Since the germicidal compounds under consideration are watersoluble salts and not free phenols, however, it would appear that the increased activity is not associated with the solubilising effect of the surface-active agent. The proportion of a soap or other anionic surface-active agent that has in practice to be included to obtain the increased germicidal effect depends on a number of factors, as will appear later in this specification, but in general it can be determined by a process'of simple testing.

The invention is, therefore, a germicidal composition comprising as active ingredient a water-soluable salt of dichlo'ro-m-xylenol having a solubility of more than 1% w./v. in.water at 20 C. and a soap or other anionic surface-active agent in a proportion such that the germicidal activity of the composition against Staphylococcus aureus per unit weight of the above active ingredient is greater than that of the composition prepared in the absence of the soap or other anionic surface-active agent.

The water-soluble salts of dichloro-m-xylenol that are preferably used according to the invention are those having a solubility in water of more than 5% w./v. at 20 C., and the sodium salt, which has a solubility 'of about 40% w./v. at this temperature, and the potassium salt, which also has a high water-solubility, are especially preferred. These salts are easily obtained from dichlorom-xylenol itself by reacting the free phenol with the equivalent quantity of alkali metal hydroxide, and this can oftenvery conveniently be carried out by adding a solution. of the alkali to a solution of dichloro-m-xylenol in water containing the proportion of surface-active agent (and essential oil, if as will often be the case, it too is required to be present) that the final formulated product is required to contain. It has in practice been found advisable to formulate the compositions of the invention with a little free alkali so asto counteract any tendency for the slight acidity of water normally employedin Pat ented Sept. 29, 1959 their preparation and subsequent dilution for use to cause decomposition of the soluble salt of dichloro-m-xylenol. It has also been found advantageous to include a small proportion of an alkali metal sulphite, for instance sodium sulphite, suitably from about 0.05 to about 0.35% W./v., calculated on the anhydrous sulphite, in the compositions in order to reduce the tendency towards the formation of a slight precipitate and towards discolouration shown by the compositions on standing. The amount of the dichloro-m-xylenol salt which is incorporated in the formulated germicidal composition will depend on the type of composition it is desired to produce, and when preparing for instance an aqueous germicidal solution of the type intended for household use, an amount of the salt suflicient to give a concentration of from about 1 to 5% w./v. will in general be found satisfactory. However, if it is desired to prepare a highly concentrated composition, say in the form of a viscous liquid or a paste comprising the salt and surface-active agent with or Without essential oil, which can be economically transported and subsequently diluted with water to form an aqueous germicidal solution, then considerably more than 5% w./v., for instance up to about 40% by weight, or even more if the sodium or potassium salt is used, can be employed.

Soaps such as coconut oil soap are in general very suitable and economical to use in the germicidal compositions of the invention, and particularly good results have been obtained using castor oil soap. However, other anionic surface-active agents can be used if desired. Thus an alkylaryl sulphonate, for instance a sodium dodecylbenzene sulphonate, can very conveniently be em ployed. Other very suitable agents are the salts of primary and secondary long-chain alkyl hydrogen sulphates (for example sodium lauryl sulphate and the product sold under the name Teepol) and the sulphosuccinates (for example a sodium dioctyl sulphosuccinate such as Aerosol OT). Mixtures of a soap and another anionic surface-active agent, for instance an alkylaryl sulphonate, can be used in formulating the compositions of the invention if desired. Anionic surface-active agents of the above type can often be used with particular advantage in the preparation of detergent compositions having germicidal properties for use, for example, in dish-washing. It will, of course, be appreciated that the anionic surfaceactive agent employed should not contain any appreciable proportion of unneutralised acidic groupings for these (in common with acids generally) would have the effect of converting the soluble salt of dichloro-m-xylenol to the free phenol itself.

In preparing the germicidal compositions of the invention some care is necessary in selecting the proportion of the soap or other anionic surface-active agent that is included, since in some instances the inclusion of large amounts of the surface-active agent will actually decrease the activity of the composition against Staphylococcus aureus organisms. It has for instance been found that by increasing the proportion of castor oil soap in an aqueous solution containing 1.67% w./v. of the sodium salt of dichloro-m-xylenol there is at first obtained a progressive increase in the germicidal activity of the solution against Staphylococcus aureus until, when the solution contains about 1% w./v. of castor oil soap, the germicidal activity is a maximum. Thereafter, however, any further increase in the proportion of castor oil soap results in a progressive decrease in the germicidal activity of the solution, and when the solution contains about 6.5% w./v. of castor oil soap its germicidal activity is less than that of the original solution containing the sodium salt alone. This is illustrated in the accompanying drawing. However, to determine what proportion of any given soap or other anionic surface-active agent should be included in a composition containing the soluble salt of dichloro-m-xylenol to produce a composition of increased germicidal activity against Staphylococ-- cus aureus is a simple matter, and Example 1 describes a procedure which can very suitably be followed in the determination; from this example it will be seen that a proportion of castor oil soap to sodium salt of dichlorom-xylenol of about 0.15-2.4 to l by weight is effective in increasing germicidal activity against Staphylococcus aureous.

As has already been mentioned, it is very desirable that a germicidal composition should have a balanced activity, that is to say its germicidal activity against each type of organism (gram positive or gram negative) should be roughly of the same order, and the invention provides compositions having a usefully high activity against both types. It will, of course, be appreciated that a composition in which the proportion of surfaceactive agent to soluble salt of dichloro-m-xylenol is such that the composition has maximum activity against Staphylococcus aureus will not in general possess maximum or even near-maximum activity against gram negative bacteria such as Salmonella typhi. In practice a compromise will usually be sought by adjusting the proportion of surface-active agent to soluble salt of dichlorom-xylenol so that the resulting composition, while not possessing maximum activity against either organism, yet has a comparatively high activity against both. Again it is a fairly simple matter to determine what proportion of surface-active agent to use in order to achieve this result, and very satisfactory compositions have for example been obtained using castor oil soap and the sodium salt of dichloro-m-xylenol in the proportion 0.5-2 to l, and particularly 0.7-1.1 to l, by weight.

As mentioned earlier, it is often the practice to incorporate an essential oil in germicidal compositions, especially those aqueous solutions intended for household or surgical use, and any essential oil of the type and in the proportion commonly used may be employed in formulating compositions according to the invention. It will, of course. usually be preferred to use an essential oil whose presence in the aqueous solution does not result in appreciable clouding, and a quantity of terpineol amounting to about 4% w./v. of the aqueous composition has been found to give very satisfactory results.

The invention is illustrated by the following examples. In the examples, where reference is made to castor oil soap it is to be understood that the sodium soap is intended.

EXAMPLE I This example illustrates the effect on germicidal activity against Staphylococcus aureus produced by including varying proportions of castor oil soap in a solution of the sodium salt of dichloro-m-xylenol.

Dichloro-m-xylenol (1.5 g.) was dissolved in 6 cc. of aqueous sodium hydroxide solution (2 N, 1.5 moles), and a known volume (x cc.) of an aqueous solution containing 50% w./v. of castor oil soap, added with stirring. This solution was then diluted to cc. with distilled water, and a portion of the resulting germicidal composition was further diluted under aseptic conditions with 149 volumes of distilled water. To 5 cc. of this test solution maintained at 17-l8 C. was added 0.2 cc. of a 24-hour culture of Staphylococcus aureus (4163) grown in Rideal-Walker broth at 37 C. and containing approximately 10 organisms per cc. Samples (loopfuls) were take at 3 minute intervals after the addition of the culture, and each sample was sub-cultured into a 5 cc. portion of sterile nutrient broth, which was then incubated at 37 C. for 48 hours.

The germicidal activity of the solution containing the sodium salt alone (i.e. without included soap) was determined under the same conditions. In this and subsequent experiments the pH of the material in the medication tubes was 7.5.

The mean results of duplicate (in some instances, triplicate) determinations of the sterilisation times are 5 shown in the following table, in which the first column shows the volume (x cc.) ofsoap solution containing 50%fw./v. of castor oil soap used in the preparation of the germicidal composition.

These results are shown graphically in the accompanying drawing. The germicidal activity (which is inversely proportional to the sterilisation time) against Staphylococcus aureus of the solution containing 1.67% w./v. of the sodium salt of dichloro-m-vylenol is thus seen to be markedly increased by the inclusion of certain proportions of castor oil soap, particularly a proportion of from 0.15 (based on the weight of puresoap as distinct from the volume of 50% w./v. solution) to 2.4:1 (sodium salt) by weight.

The compositions produced as described above which include 1, 2, and 8 cc. of the castor oil soap solution exemplify the germicidal compositions of the invention.

, EXAMPLE II This example illustrates the effect produced by including varying proportions of an anionic surface-active agent and aiportion of the resulting germicidal composition was further. diluted under aseptic conditions with 99 volumes of distilled water. r a

The germicidal activities against Staphylococcus aureus of this test solution and a test solution containing the potassium salt alone (i.e. without added surface-active agent) were then determined following the procedure of Example I. The results are shown in the following table:

Table 2 Sterilisation time (to Ice: nearest minute), minutes 0 More than 21 0.5 More than 21 1 t More than 21 5 I Less than 3 From the above figures it is clear that the germicidal activity against Staphylococcus aureus of the solution con taining 1.8% w./v. of the potassium salt of dichloro-mxylenol is considerably increased by theinclusion of certain proportions of the sodium alkyl sulphate, especially a proportion of from 0.28 to 1.411 (potassium salt) by weight.

The compositions produced as described above which include 2, 5 and 10cc. of Teepol 530 are examples of the germicidal compositions of the invention.

, 6 EXAMPLE III This example illustrates the effect produced by including varying proportions of an anionic surface-active agent of the alkylaryl sulphonate type in a solution of the sodium salt of dichloro-m-xylenol.

Dichloro-m-xylenol (1.5 g.) was dissolved in 6 cc. of aqueous sodium hydroxide solution (2 N, 1.5 moles) and a known volume (x cc.) of a solution containing 31% w./v. of a mixture of 4 parts by weight of sodium dodecylbenzene sulphonate, and 1 part by weight of anhydrous sodium sulphate was added with stirring. This solution was then diluted to cc. with distilled water and a portion of the resulting germicidal composition was further diluted under aseptic conditions with 149 volumes of distilled water.

The germicidal activities against Staphylococcus aureus of this test solution and of a test solution containing the-sodium salt alone (i.e. without added surface-active agent) were then determined following the procedure of Example I. The results are shown in the following table:

Table 3 sterilisation time (to x cc.: nearest minute), minutes 0 More than 21 0.5 More than 21 1 More than 21 2 7 5 4 10 More than 21 This example illustrates the germicidal activity against Staphylococcus aureus of germicidal aqueous solutions prepared from the sodium salt of dichloro-m-xylenol, castor oil soap, and terpineol.

Dichloro-m-xylenol (1.5 g.) and terpineol (4 g.) were dissolved in a known volume(x cc.) of an aqueous solution containing 50% w./v. of castor oil soap. 3 cc. of 4 N-sodium hydroxide solution were added with stirring and the solution was diluted to 100 cc. with distilled water.-

The germicidal activity of the resulting germicidal com position against Staphylococcus aureus (4163) was determined in a manner similar to that described in Example 1 except that the test solution was formed by diluting the germicidal composition with 199 volumes of distilled water. The results were-as follows:

Table 4 x cc. sterilisation time, minutes 1 I 6 Again the inclusion of certain proportions of castor oil soap is seen to have a marked effect on germicidal activity.

7 EXAMPLE v This example illustrates the preparation according to the invention of an aqueous germicidal composition of balanced activity suitable for household or surgical use, and compares the activity of the composition with that of similar compositions containing an equivalent quantity of dichloro-m-xylenol (i.e. the free phenol) itself.

Dichloro-m-xylenol (1.5 g.) and terpineol (4 g.) were dissolved in 5 cc. of an aqueous solution containing 50% w./v. of castor oil soap, and sodium hydroxide solution (4 N, 3 cc.) was added with stirring. The composition was diluted to 100 cc. with distilled water to obtain the aqueous germicidal solution (referred to as A) of the invention.

The phenol coefficients of this solution against various organisms were then determined by a modified Rideal- Walker procedure as follows, and are shown below compared with those of a solution prepared as above but to which no sodium hydroxide had been added (referred to as B"), and a solution (referred to as C) prepared as above but to which no sodium hydroxide had been added and in whose preparation 12 cc. of the 50% w./v. castor oil soap solution were used. (This soap to dichloro-m-xylenol proportion is often utilised by commercial formulators).

0.2 cc. of a 24-hour nutrient broth culture of the test organism was added to 5 cc. of the appropriately diluted aqueous germicidal solution. Subcultures (loopfuls) were made into sterile nutrient broth after 2 /2, 5, 7 /2 and 10 minute intervals and the concentration which sterilised in 7V2 but not in 5 minutes was compared with the corresponding concentration of phenol (C H OH). The inverse ratio of these concentrations gave the phenol coefiicient of the formulated aqueouse germicidal composition, which is taken as a measure of the germicidal activity of the composition under test against the particular organism employed.

Table 5 Coetfieients Composition Test organism:

Salmonella lupin (786) 3. 3 3.8 4.2

Staphylococcus aureus (4163) 2.0 1.0 0.

Staphylococcus aureus (6571) 2. 5 0.3

Bacterium colt (8333) 2. 5 2. 0

It can be seen that although the activity of solution A against Salmonella typhi is slightly inferior to that of solutions B and C, its activity against Staphylococcus aureus is very much superior to the activity of these other solutions against this organism; the composition A clearly has a desirably balanced activity.

The pH value of the aqueous germicidal composition A was fairly high, but repeated application of it to a tender part of the arm produced no irritation.

EXAMPLE VI 8 Table Again, the pH value of the germicidal composition was fairly high but the composition showed no irritant action on the skin.

EXAMPLE VII This example illustrates the preparation of an aqueous germicidal composition suitable for household or surgical use and containing a small amount of sodium sulphite as stabilising agent.

Dichloro-m-xylenol (1.5 g.) Teepol 530 (5 cc.) (an aqueous solution containing 25% w./v. of the sodium salt of a long chain secondary alkyl sulphate), terpineol (4 g.), sodium hydroxide (0.32 g.) and hydrated sodium sulphite (0.5 g.) were dissolved in a small amount of water and the solution thus formed was diluted to 100 cc. with distilled water to form the germicidal composition of the invention.

No substantial colouration or precipitate formed in the composition even after it had been allowed to stand for 2 months.

EXAMPLE VIH This example illustrates the preparation of a relatively highly concentrated composition suitable for dilution with water to form a germicidal solution of the type intended for household use.

Dichloro-m-xylenol (1.5 g.) and sodium hydroxide (0.32 g.) were warmed with 4 cc. of an aqueous solution containing 25 w./v. of castor oil soap to form a clear solution having a Rideal-Walker coefiicient of about 50 and a phenol coeflicient (Staphylococcus aureus) of about 30.

EXAMPLE 1);

A composition in the form of a clear solution similar to that of Example VIII was prepared by warming dichloro-m-xylenol (1.5 g.) and sodium hydroxide (0.32 g.) with 5 cc. of Teepol 530.

What is claimed is:

1. A germicidal composition comprising castor oil soap and as active ingredient the sodium salt of dicholorom-xylenol in the proportion of 0.15 to 2.4 parts of the former to one part of the latter by weight.

2. A germicidal composition comprising the potassium salt of a mixed long chain secondary alkyl sulfate possessing an average chain length of C and, as active ingredient the potassium salt of dichloro-m-xylenol in the proportion of 0.28 to 1.4 parts of the former to one part of the latter by weight.

3. A germicidal composition comprising the sodium salt of dodecylbenzene sulfonate and as active ingredient the sodium salt of dichloro-m-xylenol in the proportion of 0.3 to 0.75 part of the former to one part of the latter by weight.

4. A germicidal composition comprising castor oil soap and as active ingredient the sodium salt of dichlorom-xylenol in the proportion of 0.5 to 2 parts of the former to one part of the latter, by weight.

5. A composition according to claim 4 in the form of an aqueous solution.

6. A composition according to claim 5, containing in addition a small proportion of sodium sulphite.

7. A composition according to claim 6, containing in addillOQ a mall proportion of terpineol.

(References on following page) References Cited in the file of this patent Schimmel: Briefs, No. 22, January 1937 (1 p.).

UNITED STATES PATENTS Gammel: Mfg. (1101111511., February 1952, V01. 23, N0.

2,614,060 Rogers 1952 McCulloch: Disinfection and Sterilization, 2nd ed., FOREIGN PATENTS 5 1945, Lea and Febiger, Philadelphia, Pa., pp. 316-317.

Nat. Inst. of Health Bull. N0. 190, 1949, p. 208.

1383 Canada 1949 Gershenfeld at 9.1., vol. 45, 1951, pp. 5767-8.

OTHER REFERENCES Reddish: Antisep., Disinf., Fung. and Chem. and Phy. Fisher: Am. J. Pub. Health, v01. 32, April 1942, Sterilization, 19 4,11 Leaand Febiger, Philadelphia, 389-394. 10

Marfindale: The Extra Pharmaca, -vol. 1, London, 1952, pp. 842-843, The Pharmaceutical Press.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No; 2,906,664 5 September '29, 1959 Philip Maurice It is hereby certified that error appears in the printed specification 9 of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Golumn 1, line 69, for. "againtst" read against column 2, line 32, for "obscured" read obscure line 46, for "water-soluable" read water-soluble column 22,; line '7 for "aureous", in italics" read aureus in italics; lines and 49, for "examples" read "Examples column 5, line 23;for "dichloro-m-vylenol" read dichloromaxylenol same column-5, line 34, column 6, lines 3 and 45, column '7,' lines 2-, 8-, lines 14 and 32, for "example", each occurrence, read Example a; column 7, line 35, for "aqu'eouse" read aqueous. column 8, lines 50 and 51, for "dicholoro-zn xylenol" read dichloro-m- Xylenol Signed and sealed this 24th day of May 1960. SEAL) .Attest: KARL H AJCLINE ROBERT C. WATSON Atte-sting O ficer Commissioner-oi Patents