GB2437489A

GB2437489A - Disinfectant mixture of a donor of freely available chlorine (e.g. hypochlorite) and a buffering agent or acid, optionally in the form of an aqueous solution

Info

Publication number: GB2437489A
Application number: GB0608410A
Authority: GB
Inventors: David Robert Norton
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-04-28
Filing date: 2006-04-28
Publication date: 2007-10-31
Also published as: GB0608410D0

Abstract

A disinfectant chemical system consists of a mixture of: <SL> <LI>(i) a donor of freely available chlorine and <LI>(ii) one or more buffering agents or acids </SL> and may be dissolved in water to form an aqueous solution. The donor is preferably calcium hypochlorite [Ca(OCl)2] or sodium hypochlorite [NaOCl]. The acid is preferably selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, citric acid, hydrochloric acid, sulphuric acid and phosphoric acid. Components (i) and (ii) can be used in various proportions to produce predictable and controllable levels of active hypochlorous acid at pH of < 7.0 The system can be produced and used as either a dilute or concentrated aqueous solution or can be added, in the form of a blended powder, particulate, granule or tablet, to all forms of water to create a safe, stable, non-toxic, fast-acting and powerful oxidising aqueous solution.

Description

/ 2437489

CHEMICAL SYSTEM FOR USE AS A DISINFECTANT

The present invention is concerned with a chemical system that produces an effective broad-spectrum biocide that can successfully disinfect and sterilise diverse range of medical & dental, devices, instruments & equipment as well as dental unit water lines & the like.

It can also be used for the cleaning & sterilization of hospital & kitchen hard surfaces, food processing equipment, pharmaceutical manufacturing machinery as well as being suitable for complete room remediation. Other applications include disinfection & contamination control within swimming pools as well as domestic and commercial water systems, water tanks, cooling towers, & water distribution pipes. The invention can also be used for the emergency purification of contaminated drinking water.

Further applications include the cleaning & preservation of fresh produce such as salad foodstuffs, edible vegetables & cut-flowers whereby the invention can be added to produce cleaning water or product misting lines'.

The invention can also be used in its frozen state as a form of safe-ice' for use with, for example, fresh seafood produce, where it will aid preservation & odour control.

This chemical system herein described relies upon measured doses of powdered or granulated reagents and/or concentrated liquid reagents that are presented in the form of compressed solid tablets or dispersed within blister packs, sealed sachets, pouches, bottles or any other forms of hermetically sealed packaging.

For applications such as the cleaning of medical devices these reagents are simply added to either tap water or pre-treated water [such as de-ionised or distilled water] where the reagents rapidly dissolve to form a solution of a strong oxidant, or, where used in water purification applications such as swimming pools & water tanks can simply be added to the existing water present.

When correctly dosed & dissolved the solution oxidant consists predominantly of free available chlorine [FAC] in the form of hypochlorous acid in a mild acidic environment [pH 5 -7]. In the present invention, FAC formation does not rely on either organic chlorine, as in existing chioroisocyanurics based disinfectants, or on the electrolysis of brine, that can also be used to create a strong oxidant [known in the art as super-oxidised water].

Chlorine and chlorine-based disinfectants have been widely used in the medical field as early as the 18th century. Chlorine based chemicals, in particular sodium hypochlorite or bleach, were also used in water and sewage treatment.

Well-documented bacteriological studies have demonstrated that the effectiveness & efficacy of any chlorine solution depends chiefly on the concentration of hypochiorous acid present.

Importantly, the level, or relative content of hypochlorous acid present in any chlorine solution is controlled, not only by the amount & concentration of chlorine donor' chemical present but also by the pH of the final solution.

In effect, the more alkaline the chlorine solution, the less hypochlorous acid is present, the less effective it is as a sterilant. At near neutral pH [pH 7.5] only 5O% of the chlorine is present as hypochlorous acid [HOCI] and the remaining is present as the hypochlorite ion [OCl]. As the pH of the solution increases further [> pH 7.5], the relative concentration of hypochiorite ion increases, relative to hypochiorous acid content and the germicidal efficacy decreases still further.

As the solution is acidified, in other words, the pH value drops {< pH 7.5], the relative concentration of hypochlorous acid increases and the germicidal efficacy increases dramatically. So that, at pH of 6.5 approximately 90% of the chlorine will be available as hypochlorous acid. It is in the pH range of 5- 6, that chlorine solutions are at their most potent as, at these pH values, hypochlorous acid constitutes >98% of the FAC.

Further, the germicidal efficacy of hypochlorous acid [from 5mg/I to >1000 mg/I FAC] has been researched extensively and it is now established that it is highly active against Mycobacterium tuberculosis, Mycobacterium a v/urn-in tracellulare, Mycobacteriurn chelonae, m eth ici lii n -resistant Staphylococcus aureus, Candida albicans, Escherichia coIl, Pseudomonas aeruginosa, Enterococcus faecails, Bacillus subtiis and human immunodeficiency virus HIV-1.

Accordingly, it could be assumed that chlorine solutions would be widely used, particularly in the medical field, as a potent germicide. However, this is not the case due to the following issues: * Chlorine solutions are generally, commercially available, but at relatively high pH [alkaline solutions at pH values 9-11]. This means they are not very effective as either a disinfecting or sterilising solution. In other words, although these solutions are stable their hypochlorous acid content is low.

* Also, at these relatively high pH values these chlorine solutions exhibit high levels of skin irritation & other corrosive effects.

* Because of the reasons eluded above, if used at a high pH, the FAC concentration required would be excessive [in excess of 1000 mg/I for some applications] in order to have a significant bactericidal effect. Consequently, materials incompatibility such as attack on metals, plastics and rubbers would be observed, as well as negative health and safety issues.

* Chlorine solutions at their most potent pH [pH 5-7 slightly acidic] have a very short life cycle [usually few days at most] and consequently cannot be stored for extended time periods.

* Attempts to "acidify" alkaline chlorine solutions is an extremely hazardous procedure, involving the handling of corrosive and irritant chemicals, requiring trained personnel, specialist equipment and could result in the release of dangerous chlorine vapour.

From the foregoing it can be deduced, therefore, that in existing systems, it is extremely difficult to control both the concentration of the free available chlorine & the pH of that solution.

Consequently, it would be most advantageous to have an easy to understand, safe, simple to dose chemical system, whereby both of these variables [pH & free available chlorine] could be predictably defined within an easily controlled & narrow range of values at a slightly acidic pH [5 -7].

It is one of the aims of the present invention to provide an effective chemical disinfectant system, which, when mixed with water [for example potable tap water, de-jonised water or distilled water], is both non-toxic and has no Irritation properties.

A further aim of the present invention is to provide an effective chemical disinfectant system, which, when mixed with water [for example potable tap water, de-ionised water or distilled water] is fast acting and has a very short application cycle [5-30 minutes] in other words, has high efficacy.

Another aim of the present invention is to provide an effective chemical disinfectant system, which, when mixed with water [for example potable tap water, de-jonised water or distilled water] is simple to use by untrained personnel and does not necessitate the use of special equipment for its preparation.

A further aim of the present invention is to provide an effective chemical disinfectant system, which, when mixed with water [for example potable tap water, de-ionised water or distilled water], can be used in any environment and does not necessitate special ventilation or disposal equipment.

Another complimentary aim of the present invention is to provide an effective chemical disinfectant system, which is not only easy to package & distribute but is also extremely & stable during storage and has a very long shelf life.

The present invention is based on the use of a mixture of solids comprising a free available chlorine donor such as, but not limited to, calcium hypochiorite [Ca (OCl)2] as the source of free available chlorine [the chlorine donor] together with various acids [the acid], particularly certain dicarboxylic & tricarboxylic acids, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, or citric acid etc.. It is a feature of the present invention that the reagent mixture could include the chlorine donor such as calcium hypochlorite with one, or two or even more of these acids. The use of other acids (for example hydrochloric acid, sulphuric acid, phosphoric acid and the like) or buffering agents to control the pH of the final solution can also be envisaged.

Calcium hypochlorite, Ca(OCI)2 dissolves readily in water according to the reactions below: Ca(OCI)2 +2 H20 Ca(OH)2 + 2 HOCI (1) Ca(OH) -* Ca + 2 Oft (2) Reactions (1) and (2) would result in a chlorine solution with the free available chlorine supplied by the HOd, but in a highly alkaline environment due to the formation of the hydroxyl ion (OF-i). The pH of such a solution would be alkaline & would vary, depending on the amount of calcium hypochiorite [Ca(QCJ)2] added, the initial pH and the buffer capacity of the water used [which is dependent upon total alkalinity of the water]. The germicidal efficacy of such a solution would be low.

The germicidal efficacy of this alkaline solution can be significantly improved without Increasing the amount of free available chlorine. To do this a measured quantity of acid is added to the calcium hypochlorite [Ca(OCI)2] so 400g of succinic acid would be added to 230 -250 mg of calcium hypochlorite [Ca (00)2] to achieve a final pH of 6.0.

Because of the compatibility of the chemical reagents in the present invention it is also possible to achieve a similar effect on the pH level of an alkaline solution by adding two [or more] acids together in lower concentrations, say, approximately 160 -180 mg of adipic acid, or approximately 160 -200g of succinic acid. This would also achieve a final pH of 6.0.

Similarly, for the same type of water, for final free available chlorine of 50 mg/I, approximately 150 mg of adipic acid or approximately 180 mg of succinic acid would be added to approximately 50 -60 mg of calcium hypochlorite [Ca (OCI)2] to achieve a final pH of 6.0.

It can easily be understood, therefore, that the final pH of the aqueous solution & its free available chlorine level in the form of hypochiorous acid can be closely controlled by combining calcium hypochlorite & acid [or several acids] together in specific ratios relative to the volume of aqueous solution required.

This close control & modification of pH that the present invention permits enables the chlorine solution to always be in the most advantageous pH range, maximizing the concentration of free available chlorine in the form of hypochiorous acid, to enable the chemical system thus produced, to be both fast acting & active for extended periods of time.

Furthermore, the simplicity of the chemical system enables both the pH & free available chlorine level to be predictably controlled within narrow, specified ranges making it possible to produce any number of different concentrations of solutions that will be suitable for a vast range of commercial applications.

Some results relating to the chemical system that comprises the current invention will now be described by way of numerous examples: g An amount of 240mg of Calcium Hypochiorite & 240 mg of adipic acid was pre-mixed & then added to one litre of potable tap water. After one minute of continuous stirring the Free Available Chlorine [FAC] was measured to be 205 mg/I. The solution had a measured pH of 6.3. The same solution was measured after 3 days; the Free Available Chlorine [FAC] was still 205 mg/I whilst the pH of the solution was now 6.75 An amount of 250mg of Calcium Hypochlorite & 500 mg of adipic acid was pre-mixed & then added to one litre of potable tap water. After one minute of continuous stirring the measured Free Available Chlorine [FAC] was 210 mg/I whilst the pH of the solution was 4.8. After 3 days the measured Free Available Chlorine [FAC] was still 210 mg/I whilst the pH of the solution was now 5.42. After 6 days the measured Free Available Chlorine [FAC] was still 210 mg/I whilst the pH of the solution was now 5.40.

A powdered mixture of 300mg of Calcium Hypochlorite, 150 mg of adipic acid & 150 mg of succinic acid was added separately to one litre of potable tap water. After one minute of continuous stirring the measured Free Available Chlorine [FAC] was 250 mg/I whilst the pH of the solution was 6.3. After 3 days the measured Free Available Chlorine [FAC] was still 250 mg/I whilst the pH of the solution was now 6.74. After 6 days the measured Free Available Chlorine [FAC] was now 240 mg/I whilst the pH of the solution was now 7.00.

A powdered mixture of 250mg of Calcium Hypochlorite & 500 mg of adipic acid was added separately to one litre of de-ionised water. After one minute of continuous stirring the measured Free Available Chlorine [FAC] was 210 mg/I whilst the pH of the solution pH was 4.8. After 3 days the measured Free Available Chlorine [FAC] was still 210 mg/I whilst the pH of the solution was now 5.42. After 6 days the measured Free Available Chlorine [FAC] was still 210 mg/I whilst the pH of the solution was now 5.45.

A powdered mixture of 80mg of Calcium Hypochlorite & 80 mg of adipic acid was added to one litre of potable tap water. After one minute of stirring the measured Free Available Chlorine [FAC] was 100 mg/I whilst the pH of the solution was 5.8. After 3 days the measured Free Available Chlorine [FAC] was still 100 mg/I whilst the pH of the solution was now 6.39. After 6 days the measured Free Available Chlorine [FAC] was now 92 mg/I whilst the pH of the solution was now 6.89.

A powdered mixture of 50mg of Calcium Hypochlorite & 100 mg of adipic acid was added to one litre of potable tap water. After one minute of stirring the measured Free Available Chlorine [FAC] was 50 mg/I whilst the solutions' pH was 6.6. After 3 days the measured Free Available Chlorine [FAC] was still 50 mg/I whilst the solutions' pH was now 6.90. After 6 days the measured Free Available Chlorine [FAC] was now 46 mg/I whilst the pH of the solution was now 7.00.

A powdered mixture of 80mg of Calcium Hypochlorite & 80 mg of adipic acid was added separately to one litre of potable tap water. After one minute of continuous stirring the measured Free Available Chlorine [FAC] was 100 mg/I whilst the pH of the solution was 5.8. After 3 days the measured Free Available Chlorine [FAC] was still 100 mg/I whilst the pH of the solution was now 6.39. After 6 days the measured Free Available Chlorine [FAC] was now 92 mg/I whilst the pH of the solution was now 6.89.

A powdered mixture of 7.5g of Calcium Hypochiorite, 3.75g of adipic acid & 3.75g of succinic acid was added to 25 litres of potable tap water. After three minutes of continuous stirring the measured Free Available Chlorine [FAC] was 250 parts per million [mg/I] whilst the pH of the solution was 6.5. After 3 days the measured Free Available Chlorine [FAC] was still 250 parts per million [mg/I] whilst the pH of the solution was now 6.65. After 6 days the measured Free Available Chlorine [FAC] was still 250 parts per million [mg/I] whilst the pH of the solution was now 6.80. I0

A powdered mixture of 2.0 g of Calcium Hypochlorite, 1.25g of adipic acid & 1.25g of succinic acid was added separately to 25 litres of de-ionised water.

After three minutes of continuous stirring the measured Free Available Chlorine [FAC] was 98 mg/I whilst the pH of the solution was 5.78. After 3 days the measured Free Available Chlorine [FAC] was now 96 mg/I whilst the pH of the solution was now 6.26. After 6 days the measured Free Available Chlorine [FAC] was now 94 mg/I whilst the pH of the solution was now 6.72.

A powdered mixture of 300mg of Calcium Hypochlorite, 150 mg of adipic acid, 150 mg of succinic acid & 50 mg of citric acid was added to one litre of potable tap water. After one minute of continuous stirring the measured Free Available Chlorine [FAC] was 250 mg/I whilst the pH of the solution was 6.20. After 3 days the measured Free Available Chlorine [FAC] was now 200 mg/I whilst the pH of the solution was now 6.55. After 6 days the measured Free Available Chlorine [FAC] was now 150 mg/I whilst the pH of the solution was now 6.8.

A small 480 mg tablet comprising 240mg of Calcium Hypochlorite & 350 mg of adipic acid was crushed & then added to one litre of potable tap water.

After two minutes of continuous stirring the measured Free Available Chlorine [FAC] was 200 mg/I whilst the pH of the solution was 5.0. After 3 days the measured Free Available Chlorine [FAC] was still 200 mg/I whilst the pH of the solution was now 5.62. After 6 days the measured Free Available Chlorine [FAC] was still 200 mg/I whilst the pH of the solution was now 5.75.

A large 12 g tablet comprising 6.0 g of Calcium Hypochlorite & 6.0 g of adipic acid was crushed & then added to twenty-five litres of de-ionised water. After 3 minutes of continuous stirring the measured Free Available Chlorine [FAC] was 205 mg/I whilst the pH of the solution was 4.80. After 3 days the measured Free Available Chlorine [FAC] was now 200 mg/I whilst the pH of the solution was now 5.45. After 6 days the measured Free Available Chlorine [FAC] was now 192 mg/I whilst the pH of the solution was now 5.70.

II

To a Sodium Hypochlorite solution that had measured Free Available Chlorine [FAC] of 100 mg/I & a measured pH of 7.32 was added an amount of 800 mg of succinic acid. After 5 minutes of continuous stirring the measured pH was 6.90 & the measured Free Available Chlorine [FAC] was 105. After 3 days the measured Free Available Chlorine [FAC] was now 60 mg/I whilst the pH of the solution was now 6.95.

To a Sodium Hypochlorite solution that had measured Free Available Chlorine [FAC] of 200 mg/I & a measured pH of 7.36 was added an amount of 1 g of adipic acid. After 5 minutes of continuous stirring the measured pH was 6.95 & the measured Free Available Chlorine [FAC] was 188. After 3 days the measured Free Available Chlorine [FAC] was now 130 mg/I whilst the pH of the solution was now 7.00.

To a Sodium Hypochlorite solution that had measured Free Available Chlorine [FAC] of 100 mg/I & a measured pH of 7.32 was added an amount of 800 mg of adipic acid & 800 mg of succinic acid. After 5 minutes of continuous stirring the measured pH was 6.58 & the measured Free Available Chlorine [FAC] was 98. After 3 days the measured Free Available Chlorine [FAC] was now 72 mg/I whilst the pH of the solution was now 6.50.

To a Sodium Hypochiorite solution that had measured Free Available Chlorine [FAC] of 50 mg/I & a measured pH of 7.20 was added an amount of 500 mg of adipic acid & 500 mg of succinic acid. After 5 minutes of continuous stirring the measured pH was 6.70 & the measured Free Available Chlorine [FAC] was 48. After 3 days the measured Free Available Chlorine [FAC] was now 32 mg/I whilst the pH of the solution was now 6.75

Claims

CLAIMS

1. A chemical system consisting of a mixture, in various proportions, of a free available chlorine donor such as calcium hypochiorite or sodium hypochiorite in combination with one or a number of buffering agents or acids, including, but not limited to, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, & citric acid, for use in combination with all forms of water.

2. A chemical system in the form of a dissolved aqueous solution, either dilute or concentrate, consisting of a free available chlorine donor, for example calcium hypochlorite [Ca (OCI)2] or sodium hypochlorite [NaOCl] mixed in various proportions with one or a number of acids, including, but not limited to, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, & citric acid.

3. A chemical system as claimed in claim 1 where the mixture of available free chlorine donor such as calcium hypochiorite & the acid [or acids] is in the form of a solid, powder or granules & can be dispensed, for example, from various forms of commercially available, hermetically sealed, protective packaging such as peel-pouches, tear-pouches, soluble-pouches, sachets or blister packs 4. A chemical system as claimed in claim 1 where the mixture of available free chlorine donor, for example calcium hypochlorite & the acid [or acids] are presented in various commercial dispensing forms, such as a tablet, a capsule or a caplet & can be dispensed, for example, from various forms of hermetically sealed packaging such as blister packs or bottles & the like. /3

5. A chemical system as claimed in claim 2 where the mixture of chlorine donor chemicals such as sodium hypochlorite & the acid [or acids] are produced in liquid form & packed into various commercially available, re-sealable liquid packaging containers, such as bottles & vials, trigger & pump dispensers & other similar packaging forms manufactured from polymer or glass materials.

6. A chemical system substantially as herein described above & explained

in the accompanying description & examples.