Compositions – Oxidative bleachant – oxidant containing – or generative – Plural oxidants
Reexamination Certificate
1999-03-23
2001-07-03
Lovering, Richard D. (Department: 1712)
Compositions
Oxidative bleachant, oxidant containing, or generative
Plural oxidants
C252S186210, C252S186260, C510S318000
Reexamination Certificate
active
06254801
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
The application is based on German application No. 198 12 588.7, filed Mar. 23, 1998, the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to hardness-stabilizing percarboxylic acid solutions containing one or more percarboxylic acids from the group performic acid, peracetic acid and perpropionic acid which contain the carboxylic acids from which these acids are derived, hydrogen peroxide, water and a hardness stabilizer. The invention also provides a process for preparing hardness-stabilizing percarboxylic acid solutions and their use.
BACKGROUND OF THE INVENTION
Percarboxylic acids (peroxycarboxylic acids) such as in particular peracetic acid and performic acid are highly effective microbiocides which are used in a very wide range of different water systems for controlling microorganisms, reference being made, by way of example, to WO 97/08100 and EP 0 688 302. The percarboxylic acids mentioned are especially effective in the form of a so-called aqueous equilibrium percarboxylic acid solution which consists substantially of a percarboxylic acid, the carboxylic acid from which it is derived, hydrogen peroxide and water and may also contain a mineral acid catalyst and conventional active oxygen stabilizers in effective amounts.
In order to satisfy specific application-oriented requirements, additives are added to the percarboxylic acid solutions mentioned, such as wetting agents, emulsifiers, corrosion inhibitors and buffers. Microbiocidal compositions in accordance with WO 93/10088 or WO 94/14321 are based on an equilibrium percarboxylic acid and non-ionic surfactants. A similar composition, but with an anionic surfactant selected from the group alkylbenzene sulfonates, alkyl sulfates and alkane sulfonates instead of the non-ionic surfactant, is disclosed in FR 2 321 301 and DE 26 16 049, wherein the composition in the last-named document also contains a phosphonic acid. A stabilised aqueous peracetic acid solution with increased antimicrobial effect and a reduced corrosive effect contains, according to DD 96833, a buffering agent, wetting agents or emulsifiers, such as alkali metal salts of sulfonated fatty acids, fatty alcohol sulfonates, alkane sulfonates and alkylaryl sulfonates, and organic sequestering agents such as dipicolinic acid and ethylenediamine tetraacetic acid. Finally, thickened percarboxylic acid solutions are known, such as those in accordance with EP 0 421 974 B1, which contain a cross-linked acrylic acid polymer and also a sequestering agent from the group of phosphonic acids and nitrogen-containing carboxylic acids.
In water-circulating systems, there is often the need to simultaneously avoid or reduce problems due to the presence of microorganisms and the production of solid coatings of hardness-producing components. Hitherto, a hardness stabilizer, in particular one from the group of phosphonocarboxylic acids, and an equilibrium peracetic acid have been added, separately, to the circulating system for this purpose. This addition process is costly. Although a solution of an equilibrium peracetic acid and a phosphonocarboxylic acid exhibit the required microbiocidal and hardness-stabilizing effect, the storage stability is inadequate.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide an agent which combines both a microbiocidal effect and also a hardness-stabilizing and scale-preventing effect in one agent. At the same time, the agent should have high storage stability.
A hardness-stabilizing percarboxylic acid solution containing one or more percarboxylic acids from the group performic acid, peracetic acid and perpropionic acid, the carboxylic acid(s) from which the peracid(s) is/are derived, hydrogen peroxide, water and a hardness stabilizer from the group comprising (i) polymers prepared by the oxidative polymerization of acrolein or of acrolein and acrylic acid, (ii) polyacrylic acid and(iii)copolymers of acrylic acid and another unsaturated carboxylic acid, in particular maleic acid, and(iv) polymaleic acid, wherein the hardness-stabilizer is not cross-linked, the average molecular weight M
w
, of the hardness stabilizer is in the range 500 to 25000, in particular 1000 to 15000, and some of the carboxyl groups in the hardness stabilizer may have been converted into percarboxyl groups, has been found.
Preferred hardness-stabilizing percarboxylic acid solutions contain peracetic acid or a combination of peracetic acid and performic acid in a total amount of 0.1 to 15 wt. %, in particular 0.5 to 6 wt. %, as the percarboxylic acid. Since the hardness stabilizers also contain carboxyl groups, some of these may have been converted into percarboxylic acid groups by the hydrogen peroxide which is present. Expediently, the solution is aqueous and has a water content of more than 40 wt. %. The percarboxylic acid, the carboxylic acid from which it is derived, hydrogen peroxide and water are preferably present in the equilibrium state or in the vicinity thereof. The solution according to the invention generally contains 0.01 to 10 wt. % of hardness stabilizer (calculated as 100% strength), preferably 0.5 to 5 wt. %. In addition, other additives which adjust certain additives relating to the particular application, may be present. The following additives may be mentioned, by way of example: surfactants, in particular anionic and non-ionic surfactants with wetting, emulsifying and/or dispersing effects, corrosion prevention agents, buffers, conventional active oxygen stabilizers such as phosphonic acid derivatives, pryridinocarboxylic acids, aminocarboxylic and hydroxycarboxylic acids, tin compounds and free-radical scavengers, and mineral acids for adjusting the equilibrium such as sulfuric acid, phosphoric acid, pyrophosphoric acid and polyphosphoric acid.
The use of aminocarboxylic acids such as ethylenediamine tetraacetic acid (EDTA)and aminophosphonic acids as sequestering agents for trapping heavy metals contained in percarboxylic acid solutions and which reduce the storage stability of active oxygen compound is known per se, but these types of substances are, on the one hand, undesirable in large amounts from an ecotoxicological point of view and/or their hardness-stabilizing effect is inadequate. Moreover, these types of substances are not really suitable as scale-preventers; and a scale-preventer is definitely required in aqueous circulating systems. Hitherto a phosphonocarboxylic acid, in particular 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), has been used separately in water-circulating systems in order to control microorganisms and lower forms of plant and animal life and to prevent scaling. The addition of PBTC to an equilibrium peracetic acid leads, however, as shown in comparative tests, to solutions with unsatisfactory storage stability and which are thus not commercially viable. The solutions according to the invention, in contrast, are characterised by high storage stability.
It was also found that equilibrium peracetic acid solutions containing anionic surfactants became very cloudy when diluted with tap water due to the precipitation of lime soaps. This problem can be largely reduced if the solution also contains a hardness stabilizer according to the invention in an effective amount, in addition to the anionic surfactant. These types of percarboxylic acid solutions preferably contain 0.5 to 6 wt. % of peracetic acid or a combination of peracetic acid and performic acid, 1 to 10 wt. %, in particular 1 to 7.5 wt. % of hardness stabilizer according to the invention (calculated as 100% strength), in particular those in accordance with (i) above, and 0 to 5 wt. % of surfactants, in particular anionic surfactants based on sulfonic acid and sulfate esters.
The hardness stabilizers according to the invention contained in the percarboxylic acid solutions act both as hardness stabilizers and also as scale-preventers. Products with M
w
less than 500 and greater than 25000 are less suitable because either the e
Reinold Andreas
Walzer Egon
Degussa - AG
Lovering Richard D.
Pillsbury & Winthrop LLP
LandOfFree
Hardness-stabilizing percarboxylic acid solutions, a process... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hardness-stabilizing percarboxylic acid solutions, a process..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hardness-stabilizing percarboxylic acid solutions, a process... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2498139