GB1598154A - Manufacture of polyacrylic acid/iodine complexes - Google Patents

Description

(54) MANUFACTURE OF POLYACRYLIC ACID/IODINE COMPLEXES (71) We, BASF AKTIENGESELL SCHAFT, a German Joint Stock Company of 6700 Ludwigshafen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particuarly described in and by the following statement: The present invention relates to a novel process for the manufacture of polyacrylic acid/iodine complexes having a high content of active iodine, by mixing polyacrylic acid, iodine, iodide ions and water.

Such iodine complexes, generally referred to as "iodophores", render the iodine readily water-soluble, lower its vapor pressure and reduce its corrosive characteristics and its irritant action on the mucous membranes.

Iodophores based on water-soluble polymers, e.g. polyethylene oxide (D. E. Guttmann and T. Higuchi, J. Pharm. Assoc.

XLIV (1955), 668), polyvinyl alcohol (V. O.

Mokhnack and J. P. Zueva, Zh. Neorgan.

Khim. 8 (1963), 668) and polyvinylpyrrolidone (H. A. Shelanski et al, J. Internat. College of Surgeons, Chicago 25 (1956), 727) have long been known. It is true that these jodo- phores are good disinfectants, but they do not exhibit good dispersant properties. Iodophores based on surfactants have also been disclosed (for example in U.S. Patent 3,028,299), but because of their great tendency to foam they are unsuitable for use as disinfectant cleaning agents for numerous industrial cleaning purposes.

In addition, U.S. Patent 2,758,049 discloses compositions comprising aqueous solutions of polyacrylic acid, of from 10 to 50 per cent strength by weight, which contain from 1 to 10 per cent by weight of iodine in the form of a complex. These are obtained by mixing the polyacrylic acid solutions with the appropriate amount of iodine at from 20 to 400C over 24 hours as described in the Examples. The disadvantages is that the amount of active iodine is low and a substantial amount of time has to be expended on the preparation of the complexes.

According to German Laid-Open Application DOS 2 403 225 an attempt was made to achieve the object of higher active iodine contents by mixing from 10 to 30 per cent of elementary iodine and from 90 to 70 per cent by weight of an aqueous polycarboxylic add at above 500C, the aqueous solution containing from 7 to 30 per cent by weight of the acid, inter alia polyacrylic acid, from 0 to 20 per cent by weight of an alkali metal iodide and/or a monohydric aliphatic alcohol and from 0 to 20 per cent by weight of a polybasic mineral acid and/or hydroxycarboxylic acid.

The Examples given in that DOS show that the best results achieved, with or without addition of alkali metal iodide, are, in percentage terms, far below the percentage of free iodine. A further disadvantage of the said process is that too high temperatures, i.e. too much energy, are required and that the solutions obtained in every case contain constituents which have to be filtered off before the solutions are used.

The present invention seeks to provide a process for the manufacture of polyacrylic acid/iodine complexes which have a high content of active iodine, without the process necessarily suffering from the above disadvantages, above all the high energy consumption and the presence of undissolved residual iodine.

According to the invention there is provided a process for the manufacture of a polyacrylic acid/iodine complex in which from 14 to 80 of a polyacrylic acid having a K value of from 8 to 60, and from 86 to 20% of a mixture of iodine and iodide ions (derive from one or more iodine salts which provide iodide ions), in which mixture the ratio of iodine equivalents to iodide ion equivalents is from 0.2:1 to 1.1:1, the weight percentages being base on the total weight of solid polyacryilc acid, iodine and iodide ions, are allowed to interact at from 0 to 300C in an amount of water which is sufficient to produce complete dissolution.

Surprisingly, the measures provided by the present invention make it possible to work at a low temperature and to obtain an iodophore solution which is free from residues and has an active iodine content of from 15 to 30 per cent The polyacrylic acid required for the manufacture of the iodophore has a K value of from 8 to 60, preferably from 8 to 25.

The K values are measured by the method of H. Fikentscher, Cellulosechemie 13 (1932), 5844 ar.d 71-74, in 1 per cent strength aqueous solution at 250C; K = k.103.

The polyacrylic acid is in general in the form of an aqueous solution of from 20 to 60 per cent strength and is employed in an amount (expressed as solid) of from 14 to 80 per cent by weight, preferably from 20 to 50 per cent by weight, based on the total weight of solid polyacrylic acid, iodine and iodide ions. Only the iodide ion portion of the weight of the iodide is included in this total weight.

The amount of iodine and iodide required to make up to 100 per cent is added, in the form of a solution or preferably as the solid, to the polyacrylic acid solution. The ratio of equivalents of iodine to equivalents of iodide must not exceed 1.1: 1, since there is otherwise a danger that iodine will separate out on dilution and/or storage. In principle, there is no lower limit to the same ratio, but a value of less than 0.2:1 is of no interest industrially or, above all, economically and is therefore excluded on purely practical grounds. Preferably, the ratio, in terms of equivalents, of I:Ia is from 0.8:1 to 1.1:1.

Advantageously, an alkali metal salt, e.g. sodium iodide and/or potassium iodide, is used as the iodine salt which provides iodide ions. Ammonium iodide, and other ionic iodides, can of course also be used. The process is carried out at from 0 to 300C, preferably from 10 to 250C; the dissolution process, during which interaction takes place, generally requires from 30 minutes to 4 hours. For this length of time, the mixture is advantageously kept agitated by stirring, shaking or tumbling.

The solution can be of any concentration within the limits of solubility. Depending on the composition, the solids content may be as much as 75 or 80 per cent.

The iodophores obtained as described above can be kept indefinitely without forming a precipitate and can be diluted with water in any ratio without causing phase separation.

The iodophores may be used for making up surfactant-free non-foaming disinfectants which are used, above all, in breweries, dairies, agriculture and hospitals. Such formulations above all contain phosphoric acid and/or water soluble lower alcohols of up to, say, 6 carbon atoms, e.g. isopropanol, and/or glycols, e.g. butyldiglycol, and in general comprise from 25 to 150 ppm of active ingredient.

The following properties were tested: the absence of foam in accordance with DIN 53,902, sheet 1, the shelf life over prolonged periods by titrating the active iodine with Na2S2O3, the calcium-binding capacity and the dilutability with water.

In addition, iodophores in which the I : I- ratio was greater than 1.1:1 were prepared for comparison.

The Examples which follow describe the process of manufacture and the use of the products in conventional formulations, as well as the test results.

In the Examples, parts and percentages are by weight, unless stated otherwise, and parts by volume bear the same relation to parts by weight as the liter to the kilogram.

EXAMPLE 1.

The following were introduced successively, at 20at, into a vessel having a capacity of 1,000 parts by volume, and provided with a blade stirrer; 215 parts of a 35 per cent strength aqueous solution of a polyacrylic acid having a K value of 19, 165 parts of potassium iodide and 120 parts of elementary iodine (in the form of flakes). The mixture was stirred at 100 rpm for 3 hours at room temperature. A deep brown solution containing 24 per cent by weight of active iodine was obtained. The active iodine content remained constant for several weeks. It proved possible to dilute the iodophore solution in the ratio of 1/2, 1/20 or 1/200, without causing iodine to separate out.

The ratio, in equivalents, of iodine:iodide is 0.95:1.

EXAMPLE 2.

The following were introduced successively, at 200C, into a vessel having a capacity of 1,000 parts by volume, and provided with a blade stirrer: 500 parts of a 35 per cent strength aqueous solution of a polyacrylic acid having a K value of 19, 175 parts of potassium iodide and 125 parts of elementary iodine (in the form of flakes). The mixture was treated as described in Example 1. A homogeneous, deep brown solution containing 15.6 per cent by weight of active iodine was obtained. The active iodine content remained constant for several weeks: It proved possible to dilute the iodophore solution in the ratio of 1/2, 1/20 or 1/200, without causing iodine to separate out.

The molar ratio of iodine: iodide is 0.93: 1.

EXAMPLE 3.

The following were introduced successively, at 200C, into an enamelled tumbler mixer having a capacity of 200 parts by volume: 56.45 parts of a 30 per cent strength aqueous solution of a polyacrylic acid having a K value of 11, 23.55 parts of potassium iodide and 20.0 parts of elementary iodine (in the form of flakes). After a mixing time of four hours at room temperature, a homogeneous iodophore solution which contained 20 per cent by weight of active iodine and was free from solids was obtained. The active iodine content remained constant for several weeks.

It proved possible to dilute the iodophore solution in the ratio of 1/2, 1/20 or 1/200, without causing iodine to separate out.

The ratio, in equivalents, of iodine:iodide is 1.1:1.

COMPARATIVE EXPERIMENT 1.

The following were introduced successively, at 200C, into a vessel having a capacity of 1,000 parts by volume, and provided with a blade stirrer: 315 parts of a 30 per cent strength aqueous solution of a polyacrylic acid having a K value of 11, 97.3 parts of potassium iodide and 87.5 parts of elementary iodine (in the form of flakes). The mixture was treated as described in Example 1. A deep brown solution containing 17.5 per cent of active iodine was obtained. On diluting in the ratio of i/20 with water, solid spangles of iodine separated out.

The ratio, in equivalents, of I: Iz is 1.2:1.

COMPARATIVE EXPERIMENT 2.

The following were introduced successively, at 200C, into a vessel having a capacity of 1,000 parts by volume, and provided with a blade stirrer: 315 parts of a 30 per cent strength aqueous solution of a polyacrylic acid having a K value of 11, of1.25 parts of potassium iodide, 87.5 parts of elementary iodine (in the form of flakes), and, in addition, 16 parts of water in order to bring the polyacrylic acid concentration and iodine concentration in the total solution to the same values as in Comparative Experiment 1. The mixture was treated as described in Example 1. A deep brown solution containing 17.5 per cent of active iodine was obtained. On diluting in the ratio of 1/20 with water, solid spangles of iodine separated out.

The ratio, in equivalents, of I : I is 1.4:1.

COMPARATIVE EXPERIMENT 3.

The following were introduced successively, at 200C, into a vessel having a capacity of 1,000 parts by volume, and provided with a blade stirrer: 315 parts of a 30 per cent strength aqueous solution of a polyacrylic acid having a K value of 11, 71.5 parts of potassium iodide, 87.5 parts of elementary iodine (in the form of flakes), and, in addition, 26 parts of water in order to bring the polyacrylic acid concentration and iodine concentration in the total solution to the same values as in Comparative Experiments 1 and 2. The mixture was treated as described in Example 1. A deep brown solution containing 17.5 per cent of active iodine was obtained.

On diluting in the ratio of 1/2, 1/20 and 1/200 with water, solid iodine separated out.

The ratio of I: Is is 16:1.

TABLE Dilutability of the iodophore formulations with water

Dilutability with water Comparative Weight ratio of 1/2 1/20 1/200 Example Experiment iodine/iodide 1 - 0.95 : 1 + + + 2 - 0.93 : 1 + + + 3 - 1.1 : 1 + + + - 1 1.2 : 1 + iodine spangles + separate out - 2 1.4 : 1 + iodine spangles + separate out - 3 1.6 : 1 iodine spangles iodine spangles iodine spangles separate out separate out separate out The following formulations were prepared with an iodophore as described in Example 3: 1. 10% of iodophore 20% of phosphoric acid 70% of water 2. 10% of iodophore 20% of isopropanol 15 e; of phosphoric acid 55' of water 3. 20% of iodophore 15% of butyldiglycol 20% of phosphoric acid 45% of water These three formulations were also dilutable with water, without causing iodine to precipitate.

Claims (10)

WHAT WE CLAIM IS:-

1. A process for the manufacture of a polyacrylic acid/iodine complex wherein (a) from 14 to 80 ', by weight of a polyacrylic acid having a K value of from 8 to 60, and (b) from 86 to 20 or by weight of a mixture of iodine and iodide ions (derived from one or more iodine salts which provide iodide ions), in which mixture the ratio of iodine equivalents to iodide ion equivalents is from 0.2:1 to 1.1:1, the weight percentages being based on the total weight of solid polyacrylic acid, iodine and iodide ions, are allowed to interact at from 0 to 300C in an amount of water which is sufficient to produce complete dissolution.

2. A process as claimed in claim 1, wherein the interaction temperature is from 10 to 250C.

3. A process as claimed in claim 1 or 2, wherein sodium iodide, potassium iodide or ammonium iodide is employed as iodine salt providing iodide ions.

4. A process as claimed in any of claims 1 to 3, wherein the ratio of equivalents of iodine to equivalents of iodide ion is from 0.8:1 to 1.1:1.

5. A process as claimed in any of claims 1 to 4, wherein the mixture in water is agitated for from 30 minutes to 4 hours for interaction.

6. A process as claimed in any of claims 1 to 5, wherein the polyacrylic acid has a K value of from 8 to 25.

7. A process as claimed in any of claims 1 to 6 carried out substantially as described in any of the foregoing Examples 1 to 3.

8. An aqueous solution of an acrylic acid/ iodine complex, when obtained by the process as claimed in any of claims 1 to 7.

9. Surfactant-free non-foaming disinfectants containing an aqueous solution as claimed in claim 8.

10. Disinfectants as claimed in claim 9 containing from 25 to 150 ppm of active ingredients and containing phosphoric acid and/or a water-soluble alcohol or glycol.