CA1097216A - Germ killing composition and method - Google Patents

Abstract

GERM KILLING COMPOSITION AND METHOD

ABSTRACT OF THE DISCLOSURE
Germ-killing composition produced by contacting an acid material, preferably consisting of at least about 15% by weight of lactic acid, with sodium chlorite in aqueous media, the amount of acid being sufficient to lower the PH of the aqueous media to less than about 7. Methods of disinfecting and sanitizing include application of either the germ killing composition, or reactants providing in situ production thereof, to a germ carrier including substrates of various kinds as well as an enclosed air space.

Description

~97Z~6~
GERM KILLING CO~POSIT~ON AND M~THOD
BACICGROUND OF TEIE INVENTION FIELD OF THE INVENTION

This invention relates in general to germ-killing com-positions, methods of preparing and using same, and in particular to such compositions advantageously adapted ~or use in a wide variety of cleaning, sanitizing and disinfecking applications.

DESCRIPTION OF THE PRIOR ~RT

The use of chlorine compounds in various types of c]ean-ing, sanitizing, disinfecting, etc., compositions is of course well established. Chlorine compounds suggested for use in this regard include, for example, sodium hypochlorite, used in World War 1 as a wound irrigant, and chlorinated phenols such as m-chlorophenol, these compounds having increased bactericidal activity and reduc-ed toxicity, in some instances, when compared to non-chlorinated phenols. ~Thus, m-chlorophenol has a phenol coefficient of 7.4 (B.
typhosus), 5.8 (S. aureus). Other chlorine compounds found adv~an-tageous in some form of germ-killing utility include, without necessary limitation, chlorine gas itself, chlorine dioxide, chloramine T, mercuric chloride, calcium hypochlorite (a standard swimming pool disinfectant), chlora~icrin (an exterminator), chloroform (a fumiyant) chloradane (an insecticide) zinc chloride ~a preservative) and chloromycetin (an antlbiotic). ;
Chlorine dioxide in particular has been found to be an especially effective germ killer. This compound is quite veIsa-tile and has long been used as a bleaching agent such as in the oxidizLng of the natural colorant present in cotton, wood pulp and other cellulosic fibrous material. Thus~ the ch~orine di-oxide, thouyh performing an oxidizing function, is nevertheless non-injurious with respect to the fibrous material. Additiollally, chlorine dioxide has long been used in the treatment of water ~ g7~6 supplies and is currently available comme.rcially in powder form for use in swimming pools ~nd in li~uid form Eo:r household and industrial cleaning and disinfecting. In general, chlorine dioxide is superior to gaseous chlorine in the removal of odors, tastes and in destroying and removing algae or other organic material. ~oreover, chlorine dioxide is considered at least as effective if no-t superior to chlorine gas as a bac-tericide, viruside or sporicide chlorine dioxide is furt~er advantageous r in that its antiseptic properties are not as sensitive to PH ?
10 as chlorine i.e. chlorine dioxide retains its yerm killing capa-city to a significantly greater extent and over a wider PH range than does gaseous chlorine.
Despite the manifold advantages obtainable with the use :.
of chlorine dioxide Eor the aforedescribed and related purposes, :~
.certain difficulties are nevertheless encountered in practice.
Thus, chlorine dioxide as a concentrated gas is explosive and poisonous and accordingly is usually not shipped in the gaseous: r:
state to the medium or small user. It has thus become common ~:
practice to employ a chlorlne dioxide-liberatlng compound such~
20 as sodium ahlori~e powder which is much safer from the stand-points of storage, shipping and handling. Generat1on of the chlorine dioxide from the parent sodium chlorite is usually efected in one~of three ways as represented as follows~
(1~ addition of acid ~:
H+ + NaClO2 ~ HClO2 + Na+; 5 HClO2 ~ 4 C1O2 + HCl + ~ ~:

2 H2O ~ .
(2) addition o bleach (hypochlorite) 2 NaClO2 + NaClO + ~2 ~ 2 ClO2 -~ NaOH + ~aCl

(3) addition of chlorine 2 NaClO2 + C12 --- 2 C1O2 + 2 NaCl ~he generation of chlorine dioxide, hereinafter desig- i~
nated also as ClO2, according to reaction (1) is yenerally -- 2 -- .

.~ .

72~

effected with the use of relati~ely ine~pensive inorganic acid eg: hydrochloric acid, sulfuric acid and the like. Eor home use, the use of phosphoric or acetic acid (vinegar) is sometimes indicated since they are comparatively saEe to handle and genex-ally readily available.
Acid induced generation of C102 Erom sodium chlorite as heretofore recommended and practiced has proved ineffective for the mosk part. Thus, it is often found that the acid material utiliæed tends to react with the C102 evolved thereby reducing the effective amount of active ingredients available for useful purposes. In addition, the compositibn resulting from acidi-fication of the sodium chlorite does not usually exhibit the r`~
desired germ-killing efficacyr and particularly from the stand~
point of rate of germ kill. To compensate for this deficiency, it becomes necessary to use increased concentration of sodium chlorite and acid which can lead to toxicity problems and particularly when the composition is used in an enclosed air space. Another problem stems from the fact that the composition obtained from the interaction of the sodium chlorite and acid 2b material does not provide a truly effective solvent medium for the active chlorine containing byproducts such as C102, chlorous acid and the like. Inhalation Oe these gaseous components to any significant extent can of course be injurious to health and thus the ris~ to personal safety becomes an important factor.
Significantly, the toxicity problem imposes severe limitation on the general utility of the disinfectant composition and particularly with respect to treatment of human beings.

SUMMARY OF THE INVENTION

Thus, a primary object of the invention is to provide ;-improved cleaning, sanitiæing and disinfecting compositions where- F
in the foregoing disadvantages are eliminated or at least miti-gated to a substantial extent.

",, ~

3~9~2~6 Another object of -the in~en-tion is to provide such com-positions haviny highly effective germ-killing properties with respect to diverse types of germs, germ-producing organisms etc., over a wide range of conditions.
Ya-t another object oE the invention is to provide such composltions wherein loss of active ingredierlts through fugitive side reaction is minimized.
Still another object of the invent:Lon is to provide such compositions having negligible toxicity under the conditions nor mally prescribed for use and thus highly useful in connection with the germicidal treatment of food receptables, and utensils, medical hardware, various types of wounds to the human anatomy and the like.
A further object of the invention is to ~rovide s~ich - compositions particularly advantageously adap-ted for use ln ultrasonic cleaning apparatus Yet a-further object of the invention is to provide such compositions having good stability over a relatively wide PH
range.
Still a further object of the invention is to provide -~
methods for disinfecting and sanitizing utilizing such composi-tions including application of either the germ killing composi- ~ -~
tion or reactants enabling in situ generation thereof to a germ carrier including substrates of various kinds as well as an en-closed air space.
Other objects and advantages of the invention will become more apparent hereinafter as the description proceecls. ~;

DETAILED DESCRIPTION OF THE INVENTION

The foregoing ~and related objects are attained in accordance with the present invention which in its broader ''''' ' ' :

jl\ 1. ' 72~1~

aspects provides a process for -the production of a composition having germicidal properties which comprises contaCtinCJ sodium chlorite wi-th a subs-tant~ally water soluble acid material selected from the group consisting of organic acids and mixtures thereof with inorganic acid, said acid material comprising at least about 15 % by weight of lactic aeid and wherein said contac~ g is caxried ou-t in aqueous media and in the presence of sufficient of said acid to lower the PH of the aqueous media to less than about 7.
In further embodiments, the invention provides a process of eleaning, sanitizing and disinfecting utilizing the aforedes-cribed composition including the application of either the germ killing composition per se, or reactan-ts enabling the in situ produetion thereof, to a germ carrier including substrates of various kinds as well as an enclosed air spaee.
The use of lactic acid in the compositions and process provided herein is essential. Thus 9 it is found that this parti- .
cular compound functions synergistically in combination with sodium ehlorite under the conditions hereinbefore prescribed to provide germ-killing compositions of exceptional efficacy. This result is somewhat surprising since ordinarily it would be ex-pected that the lactic acid, as is the casè with somewhat similar acid compounds, would react with the by-product chlorine di~xide thereby reducing the effeetive amount of lactic acid and chlorine dioxide which wou~d otherwise be available for useful purposes.
Also, the lactic acid salt produeed iD the reaction might ordinar-ily be considered an impurity in a bleaching operation or when disinfecting and removing organic material from a water supply. :
However, in the present invention, such undesired side reactions, .
30 as well as accompanying deleterious effects are evident, if at ~
all, to only a negligible extent. .

_ 5 _ ~97Z~6 In formulating the instant compositions, the lactic acid is contacted with the ~odium chlorite in a~ueous media, suEficient of the acid being used to reduce the PH of the composition below about 7. The water re~uirements are suppliecl ordinarlly by the acid and chlori-te which are available in varying concelltrations in aqueous solution. The rela-tive proportions of chlorite com-pound and lactic acid are selected so as to insure a PH in the aqueous medium below about 7. The necessary amount oE acid is of course determined in part by the strength of the acid reagen-t so-lution as well as the total dilution of the respective acid andchlorite compositions as mixed. However, the necessary ~uantities can readily be predetermined by standard technique. r~
The germ killing composition obtained upon contacting ~;
i.e., reacting, the chlorite and lactic acid comprises a mixture containing chlorine dioxide, chlorous acid, lactic acid and sodium lactate. The equilibrium mixture of the oregoing mater- ;
r-ials appears to be ln the form o a complex, analyses indicating the presence of at least the ingredients enumerated. The mixture or complex is relatively stable; however, for optimum~erm ~illing -results, the composition should be used within a period of up to about 48 hours following its formation. However, if the lactic acid and chlorite compounds are isolated from each other by se-parate packaging, which may be accomplished using a unitary~or common container, little in the way of limitation exists as re-gards shelf life provided contacting o the chlorite and lactic acid materials be prohibited until used.
Thus, the chlorite and lactic acid materials may be~
confined within separate chambers of an aerosol-type container provided with valve dispensing means actuatable by the application of slight finger pressure to permit substantially slmultaneous mixing and discharge of the chlorite and lactic acid components in the form of a fine ~pray. The necessary aerosol pressure can ~, 6 - : .. . , : :~

be supplied by -the use of we:L1 kno~n propellant gases including hydrocarbons and/or halogenated, eg: chlorinated, fluorinated, hydrocarbons. The amount of propellant gas used should be such r as to permit substantially complete expulsion or evacuation of the aerosol container contents. Container constructions useful in this regard are in any event well known in the art.
Alternatively, the chlorite and lactic acid may be separately packaged but sold as a unit bearing proper instructions for mixing and use by the home consumer.
The product composition is advantageous in a number of respects. The outstanding germ-killing properties of the composi tion as regards, for example, bacteria including wi-thout necessary -~
limitation, S. aureusj S. albus, Psuedomonas, E. coli, Protéus vulgaris, strep pyogenes, Candida albicans ~dried~ spores, B.
subtilus (dried) spores and the like ! proved particularly surpris-ing in view of the low temperature of the composition used for the kill (approximately 50C) as well as the low toxicity level of the composition. Moreover, complete kill of the microorganisms tested is obtained within a period of about 10 minutes when using 50C
20 tap water and in less than 5 minutes when using the composition in an ultrasonic cleaner.
Extensive testing establishes the instant compositions to be even less irritating and toxic than, Eor example, hypochlo-rite bleach, the latter having long been established to be rela-tively non-toxic, topically. In general, solutions of Clo~ are ` not considered to be hazardous and are discharged as a matter of course by textile processors into streams, rivers etc without harmful result; ln fact, such solutions are commonly used to puri-fy fish tanks in public and home aquariums. In addltion, C102 i5 30 used as a preservative for various foodstuffs including cottage cheese and to saniti~e food containers which do not require rinsing after such treatment. The instant compositions are even 7 - 7 ~

., :

~72~
.r~

less toxic than conventional ClO2 germicidal solutions and accordingl~ can be eEfect.ively applied to the aforemen-tioned pur-poses as well as in the treatment of an open wound, the scrubbing of surgeon's hands etc. When used as a wound irrigant, the use of buf~ering agent to insure maintenance of a compatible PH of.ten proves advantageous.
Without intending to be found by any theory, the follow~
ing is postu].ated in explanation of the truly outstanding germ-killing properties obtainable with the compositions-of the present ~
10 invention. Thus, C1O2 is about five times as water soluble as .:~.
. .
chlorine and thus much less likely to be lost through volatiliza- : .
tion. Moreover, the chlorite ion is signlficantly less corrosive than the hypochlorite ion to the extent that, in the bleaching of .
cloth, for example, the presence of C1O2 serves to protect the cloth from the degradative action of the hypochloritè. The bactericidal power of bleach is generally attributed to its abil~
ity to diffuse through cell walls and reach vital parts of the ~:
bacteria, the killing action resulting from the reaction of hypo- ~ .
chlorous acid with the enz~me, :triosephosphate dehydrogenase.
Other authority holds that the ClO2 accelerates the metabolism of a bacterial cell to the detriment of cell growth. Yet.other credible authority asserts that the chlorine ion in ClO2 goes ~ .
through as many as 8 possible oxidation states in passing through a spore wall. As an algaecide, ClO2 destroys the chlorophyll, breaks down the cell until water is lost from the protoplasm,.and thereater completely destroys or oxldizes the cell so there is no slimy residue on water ilters. The presence o the lactic :
: : acid appears to enhance or:augment the aforedescribed mechanisms. ~.

For example, lactic acid, being a natural by-product of muscular exertion, and the frementation of a wide variety of bacteria is not : :

"~ a ~'fo~eign" body in a bacterl~ env~ronment as are other and closely related acids. ~o this extent, the lactic acid i5 much more able to .`` ' ,. 8 ."
_, ,.
:

3L~31~7Z~L~
penetrate the wall oE a bacte~i~ cell without "rejection" and in so doing carry with it the C1O2 and/or chlorous acid molecule.
Having penetrated the bacteria cell, it is quite possible that the lactic acid and salts thereof affect the cell's metabolic activity resulting in the ormation o~ in-termediate compouncls particularly suscep~ible to the germicidal action of the ClO2 or products derived therefrom. In addition, the formation of other semi-stable chlorine intermediates may be facilitated and these or the ClO2 could inactivate enzymes in critical metabolic pro-, cesses. Furthermore, it is probable that the oxidi~ing action ofthe chlorite ion additionally present on the outside portion of the cell wall is enhanced by the lactic acid which coats the cell wall.
The foregoing explanations notwithstanding, it has in any event been determined in accordance with the invention~that the addition of lactic acid in particular to the sodium chlorite material results in a germ-killing composition of ou-tstanding efficacy.
The instant germ killing compositions are particularly effective for use in ultrasonic cleaner devices. The germ-killing properties of ultrasonics alone or cavitation has been ; studied for years. If intensities are high enough, e.g., over 100 watts per square centimeterr cavitation will not only kill all cells but break thèm open. Howeverl in an ordinary ultra-sonic cleaner, the intensities are far smaller being on the ord~r of 1 watt per square centimeter. }lowever, at this intensity level, the bacteria may well culture at a faster rate than if not sonicated due to separation of bacterial dumps and partlcles.
However, the use of the instant germ-killing compositions in ultrasonic cleaning equipment at reduced or ordinary intensity levels proves markedly more effective than germ killing composi-tions heretobefore provided. Thus, the instant compositions are A

97;2~;

much less to~ic, less pollutin~, moxe effective at lower tempexa-tures as well as being non-odorous. The use o~ the instant compo-sitions in ultrasonic cleaning equipment enables the surgeon, dentist, food processor, etc~to both clean and disinfect an instru-ment or device quickly in a single operation. It appears accord-ing to such use -that bacteria agglomerates are broken up and separated or bacteria is removed from -the ins-trument or device resulting in complete exposure of the bacteria to the solution and thus, its germ killing effects. Microscopic bubbles which 10 often surround or otherwise protect the bacteria are broken up.
These bubbles as well as the bubbles produced from cavita-tion become filled with C1O2. The bubbles, which are very small, often attach to scratches, small cracks and other imperfections ln the instrument or-device being cleaned enabling t~orou~h disinfecting.
In addition, cavitation causes the disinfectant composition to ; bombard the bacteria cell walls which facititates diffusion of the germ killing composition to the ~nternal portions of the bacteria. ~ ~;
Thus, in accordance with the invention, the combination 20 of the advantages inherent in an ultrasonic cleaner device and the superior germ killing properties of the instant compositions ; provides exceptional means for cleaning, sanitizing and disinfect~
ing a wide variety of substrates providing a locus for the ~ .
; accumulation of bac~eria, virus, spores, and the like.
The use of lactic acid alone in combination with the chlorite material constitutes a particularly preferred embodime~nt of the invention. However, it is also effective to use the lactic acid in combination with other acids including organic and/or inorganic acids. Suitable organic acids include water soluble or 30 dispersible monocarboxylicant poly-carboxylic acids containing g from 2 to about 16 carbon atoms including by way of e~ample, acetic, citric, sorbic, fumaric, tannic, acid, etc. Suitable I ~

72~i inorganic acids include, for e~ample, sulfuric, hydrochlorie, phosphorie aeid and the like. ~hen usincJ aeid mixt~res, it is required that the lactie acid eomprise at least abou-t 15 % and preferably at least about 45% by weight of the total mi~ture in order to insure efEeetive results.
Although the use oE sodium ehloxite is preferred as the ClO2-liberating material, other water solubilizing ea-tions may be used in plaee of the sodium including other alkali metals sueh as r potassium and alkaline earth metals, the former, however, being partieularly preferred.
The terms "substrate" and "germ earrier" as used herein are intended to eover any type of hard surface or earrier whieh `
eould provide a locus for the aeeumulation of germs, virus, spores, bacteria, fungi i.e., all types of parasitic miero~
organisms. Obvious examples~inelude surgical and dental instru-ments, food containers, human tissue, swimming pools, household sinks, garbage containers, bathroom applieances etc. Cleaning - action can be enhanced by the addition of wetting agent, the latter being eompatible with and devoid of any tendency to react with C1O2. Partieularly efeetive wetting agents for sueh use are the fluorocarbon surfactants commereially available from Du Pont. The instant compositions in aerosol form can be effectively used to destroy airborne or atmospheric germs sueh as carried within an enclosed~air space. The term "germ carrier" as uscd herein is intended to cover sueh atmospheric or gaseous carriers.
~In some instanees, sueh as the application of the germ killing composition to the human tissue as a wound irrigant, it may be advisable to include a buffering agent capable of maintain-ing a PH level compatible with sueh tissue. Conventional buffers such as alkali metal biearbonates may be used in this regard. ~ ~

' :

'`

~72~ :
.
The instant compos:it.ions may be used in a relatively wide concentration range, the essential requirement being that at least a small but e~Eective germ-killing amount be used. The upper limitation on the amount used is in most cases determined by the point beyond which no urther benefi.cial effect is obtain-ed. The necessary eEfective amount in a particular instance is also affected by such factors as temperature, certain types of spectral radiation which can cause loss of C1O2 from the solution.
In general however, it is found that the use of the chlorite com-pound in amount ranging from about 100 to 5000 ppm in tbe reactantsolution with concentrations on the order of about 2700 ~o 3300 ppm being preerred, provides effective germ killing results. ~;
The following examples are given for purposes of lllu-stration only and are not to be considered as limiting the inven-tion; All parts and percentages are by weight unless otherwise speci~ied.

EX~MPLE l ., ~
... . .
To an aqueous solution of sodlum chlorite containing 3,000 ppm sodium chlorite is added sufEicient of an aqueous lactic acld solution to reduce the PH of the resultant solution to about _ three ~ A portion of the solution-thus formed is taken and by analysis found to consist of chlorine dioxide, chlorous acid, lactic acid and sodium lactate. The germ killing effects of the composition were tested~ using warm tap water ~about 50C~ against the followlng:
a) S. aureus b) S. albus c) Psuedomonas d) E. Coli -30 e) Proteus vulgaris f) Strep Pyogenes ~.
.,;
:? ~
~, .

. ~1,.~3972~

g) Candida Albicans (d.ried~ Spores h~ B. Subtilus (dried~ Spores Testin~ in each instance is carried out by impregnating a peni cylinder and surgical knot with the bacteria specimen iden-tified until saturated. The test specimens were -then immersed in the germicidal composition prepared as described. In each case, ; complete kill of the microorganism is obtained in a period of about 10 minutesO

; EXAMPLE 2 Example 1 is repeated except that testing is carried out in an ultrasonic cleaner device at an intensity of 1 watt per s~uare centimeter and at room temperature. In this case, complete kill of the microorganisms tested is obtained in less than 5 minutes.
The foregoing results are particula~ly surprising in - view of the low temperature prevailing during the testing and the r relatively low toxicity levels of the germ~killing composition.
When the foregoing examples are repeated but wholly replacing the lactic acid with respectively ~a~ phosphoric acid,~
(b) acetic acid, (c) sorbic acid, (d) fumaric acid, (e) sulfamic acid, (f) succinic acid, (g) boric acid, (h) tannic acidj and (i) citric acid, the results obtained in terms of rate of kill and ~` completeness of kill are markedly inferior when compared to the results obtained with lactic acid. Again, this result is somewhat surprising in view of the close relationship of some of the acids . ~:
tested to lactic acid. `~
When examples 1 and 2 are repeated but partly replacing the lactic acid with up to about 80 % respectively of phosphoric acid, acetic acid, sorbic acid etc~, it is found that effective germ killing compositions are obtained although the improved germ killing effects are not as pronounced as those characterizing the compositions of ~xamples 1 and 2.

.

i ~L~39~2~

A lati-tude of m~diflcation, substi-tution and change is intended in the foregoing disclosure, and.in some instances some ~eatures of the lnvention wlll be employed without a corresponding r use of other Eeatures.

::

~, : ~
.
r~

~ ~.; : :
~ ~ ' : ' ' ' ., .
:: ' : :
r :: : ':, ~: ~ ~. : ' .' ., . :

-~: - 14 -

Claims (12)

WHAT IS CLAIMED IS:

1. Process for the production of a composition having germicidal properties comprising contacting sodium chlorite with a substantially water soluble acid material selected from the group consisting of organic acids and mixtures thereof with in-organic acid, said acid material comprising at least about 15 %
by weight of lactic acid, and wherein said contacting is carried out in aqueous media and in the presence of sufficient of said acid to lower the PH of said aqueous media to less than about 7.

2. Process according to claim 1 wherein said acid material consists solely of lactic acid.

3. Process according to claim 2 wherein said contacting is carried out in ultrasonic cleaner means.

4. Process for disinfecting and sterilizing which comprises contacting a germ carrier with at least a small but effective germ-killing amount of a germicidal composition obtained by reacting sodium chlorite with a substantially water soluble acid material selected from the group consisting of organic acid and mixtures thereof with inorganic acid, said acid material comprising at least about 15 % by weight of lactic acid and wherein said contacting is carried out in aqueous media and in the presence of sufficient of said acid to lower the PH of said aqueous media to less than about 7.

5. Process according to claim 4 wherein contacting said germ carrier is effected by dispensing said germicidal composition from pressurized, aerosol container means equipped with valve dis-pensing means.

6. Process according to claim 4 wherein said acid material consists solely of lactic acid.

7. Germicidal composition obtained in accordance with the process of claim 1, claim 2 or claim 3.

8. Process according to claim 1 wherein said con-tacting is carried out in ultrasonic cleaner means.

9. Process according to claim 4 wherein contacting said germ carrier is effected by dispensing said germicidal composition from ultrasonic spray producing means.

10. Process for the production of a composition having germicidal properties comprising contacting sodium chlorite with lactic acid and in an aqueous media and in the presence of sufficient of said lactic acid to lower the PH
of said aqueous media to less than about 7.

11. Process for disinfecting and sterilizing which comprises contacting a germ carrier with at least a small but effective germ-killing amount of a germicidal composition obtained by reacting sodium chlorite with lactic acid in an aqueous media and in the presence of sufficient of said lactic acid to lower the PH of said aqueous media to less than about 7.

12. Germicidal composition obtained in accordance with the process of claim 10 .