DE2310450A1 - Phosphonocarboxylic acids as polyvalent metal ions complexants - esp. for softening water - Google Patents

Abstract

Title cpds. are of formula H2O3P-CRX-CO2H (where R is 1-4C alkyl and X is H or OH) and may be made by application of the Arbusor reaction to ethyl-alpha-bromo-alkane caroxylates.

Description

The invention relates to complexing agents for polyvalent metal ions is the use of certain 0 <-substituted phosphonocarboxylic acids as Complexing agent for polyvalent metal ions.

For many technical purposes it is desirable to prevent the precipitation of polyvalent To prevent metal ions. From the German patent specification 1 045 373 it is known that methylenediphosphonic acid is a good complexing agent for calcium.

However, it is disadvantageous when using methylenediphosphonic acid im With regard to eutrophy, the relatively high content of phosphorus. However, if methylenediphosphonic acid one of the geminal phosphonic acid groups through a carboxyl group substituted, so goes the complex-forming property of the corresponding phosphonocarboxylic acid considerably back. Surprisingly, it has been found that substitution of a proton of the methylene group by an alkyl radical with 1 to II carbon atoms can strengthen complex-forming properties quite considerably. A good complexing agent effect is also obtained if the second proton of the methylene group is passed through at the same time replaced a hydroxyl group.

The invention thus relates to the use of phosphonocarboxylic acids of the general formula where R is an alkyl radical having 1 to 4 carbon atoms and X is a hydrogen atom or a hydroxyl group as a complexing agent for polyvalent metal ions. Instead of the acids, the corresponding water-soluble salts such as potassium, sodium and ammonium salts or salts with organic bases can also be used for the same purposes. The latter are particularly alkanolamines such as monoethanolamine, diethanolamine or triethanolamine.

Preferably found because of their good effect, but also light ones Accessibility O (-phosphonopropionic acid and 0 <-phosphono-O (-hydroxypropionic acid or the water soluble salts of these compounds are used.

The production of the o <-phosphonoalkanecarboxylic acids used takes place by hydrolysis of 1-carboalkoxyalkane-1-phosphonic acid diethyl ester. the The last-mentioned compounds can be obtained by reacting ethyl o <-bromoalkanecarboxylate with triethyl phosphite (Arbusov reaction) (see also Houben-Weyl "Methods of organic chemistry "4th edition, Volume 12/1, p. 436).

QC-Phosphono - #### - hydroxypropionic acid is obtained by acid hydrolysis of the corresponding diethyl ester. The latter can be produced by implementing Pyruvic acid with diethyl phosphite. The reaction can be increased by adding smaller Amounts of diethylamine are accelerated. The ~ -phosphono- O <-hydroxyalkanecarboxylic acids can be obtained by hydrolysis of the corresponding esters will.

The esters, in turn, can be prepared using the method already described Ways using the appropriate ketocarboxylic acid as the starting product.

The free acids can be neutralized by complete or partial with inorganic or organic bases such as NaOH, KOH, NH40H or alkanolamines or alkali carbonates are produced.

The above compounds, including their alkali, ammonium or alkanolammonium salts, are good complexing agents Mr polyvalent, in particular 2- and 3-valent metal ions.

They can be used specifically for water softening processes. It is not necessary to work with stoichiometric amounts, but rather you can also use less than stoichiometric amounts of calcite precipitations considerably delay.

To determine the ability to complex calcium, the Often used in practice the Hampshire test. This test uses 1 g of the complexing agent dissolved in 100 ml of water and after adjusting the solution to a pH of 12 10 ml of 2 goat soda solution are added. Then under mechanical Stir and keep the alkalinity constant with a calcium salt solution until it remains Turbidity added dropwise.

The test value results from the amount of mg calcium carbonate per Grams of test substance are required until the cloudiness remains. This test value is when using the phosphonocarboxylic acid according to the invention about 7 to 10 times as high as with the use of phosphonoacetic acid.

The phosphonocarboxylic acids described above or their water-soluble ones Salts are therefore also used as corrosion and stone prevention agents for cooling water, especially in combination with additives known per se, such as divalent Zinc and / or cadmium salts, orthophosphates, chromates or hydrazine hydrate are well suited.

Which, depending on the compound used, is called stoichlometric The amount to be seen can easily be determined by a simple experiment. in the In general, the complexing agents are used in amounts of 1 mole per 2,000 moles of metal ions used up to six times the stoichiometric amount.

The phosphonocarboxylic acids according to the invention or their water-soluble ones Salts are also suitable for cleaning processes such as rigid objects especially metal or glass.

In particular, it is used as an additive to bottle washing agents into consideration.

The complex-forming ability can also be used in an advantageous manner Make use in systems where copper ions have an undesirable influence. As examples here are the avoidance of the decomposition of per compounds or also to mention the stabilization of fats and soaps.

The compounds mentioned can also be used as additives to dye baths of textiles suitable to complex metal ions that form undesirable color nuances to tie.

Finally, the power of complexation can also be used for this purpose in order to supply plants with so-called trace elements. The good ability to form complexes of these compounds is also shown by the fact that the well-known red coloration does not occur, which otherwise when rhodanide is added to solutions containing trivalent iron, is observed. One can therefore also use these properties in an advantageous manner use to prevent the deposition of iron compounds, especially iron hydroxide to prevent when washing the bottle. The new connections can also be used instead of cyanides can be used in electroplating baths.

Example 1 Preparation of o <-phosphono - ## -hydroxypropionic acid 1 mol of pyruvic acid was mixed with 3 drops of diethylamine and kept at 40-50 ° C 1 mol of diethyl phosphite was added dropwise. The reaction mixture was taking a long time Leave stirring at this temperature. After cooling, diethylphosphonohydroxypropionic acid crystallized the end. The partial ester thus obtained was refluxed with 20% hydrochloric acid converted into the corresponding 3c-phosphonohydroxypropionic acid.

Analyzes S P found: 17.88 calculated: 18.23% C found: 21.21 Calculated: 21.20 Melting point: 178-1790C Molecular weight: By potentiometric titration determined: 171 calculated: 170 Example 2 Hampshire test for determination the ability of calcium complexing are 1 g of the complexing agent in approx. 100 ml of water dissolved. After adjusting the solution to pH = 12, 10 ml of 2% soda solution are added admitted. This is followed by mechanical stirring and keeping the alkalinity constant a calcium salt solution was added dropwise until it remained cloudy.

Complexing agent mg CaC03 g Complexing agent phosphonoacetic acid 50 0 < Phosphonopropionic acid 655 o (-Phosphono- # -hydroxypropionic acid 375 Example 3 Die The Hampshire test values given in the table below were analogous at pH 11 Example 1 determined.

Complexing agent mg CaC03 g Complexing agent Phosphonoacetic acid 65 o (-phosphonopropionic acid 635 di-phosphono- ### - hydroxy- 425 propionic acid Example 4 The complexing power to iron in a soda-alkaline solution of o <-phosphonopropionic acid or # -phosphono- γ-hydroxypropionic acid can be seen from the table below. Included the following experimental set-up was used.

In each case 10 ml of a 0.01 molar FeCl3 solution were mixed with 15 ml of a A solution containing 5 mmol of soda was added.

These solutions were given increasing amounts of the above-mentioned phosphonic acids added.

Table 1 Complexing agent mmol precipitation of o <-phosphonopropionic acid 0.2 yes no 0.6 no 0.8 no 1.0 no γ-phosphono-O <-hydroxy- 0.05 no propionic acid 0.10 none 0.125 none 0.15 none Example 5 The complexing power compared to copper in a soda-alkaline solution of O (-phosphonopropionic acid or O (-phosphono- γ-hydroxypropionic acid can be seen from the table below. Included the following experimental set-up was used: Each 10 ml one 0.01 molar CuCl2 solution was mixed with 15 ml of a solution, the 5 ml of soda contained.

Increasing amounts of the above-mentioned phosphonocarboxylic acids were added to these solutions added.

Table 2 Complexing agent mmol precipitation of γ-phosphonopropionic acid 0.10 yes 0.20 none 0.40 none 0.45 none 0.50 none o (-Phosphono-O <-hydroxy- 0.025 opaque propionic acid 0.05 none 0.075 none 0.10 none Example 6 As a bottle washing agent, which deposits fossilization even after prolonged use in the hot water zone (service water 150 i.e.) prevented a product of the following composition in one Concentration of 1 to 2% used: 78% caustic soda 4.5 S sodium silicate (Si02: Na20 = 3.35) 1.75% antifoam agent 5% γ-phosphonopropionic acid in the form of Sodium salt remainder sodium sulfate Example 7 For cleaning metal parts became a cleaning agent of the following composition at a concentration of 0.5 S used: 44 S trisodium monophosphate 49% sodium metasilicate 5.5% γ-phosphono-γ-hydroxypropionic acid in the form of the potassium salt 1.5 S non-ionic wetting agent

Claims (5)

Claims 1) Use of phosphonocarboxylic acids of the general formula (R = alkyl radical with 1-4 carbon atoms, X = H or OH), optionally in the form of the water-soluble salts as complexing agents for polyvalent metal ions. 2) Use of compounds according to claim as complexing agents for divalent and trivalent metal ions, preferably for the hardness components of water5. 3) Use of compounds according to claims 1 and 2 in substoichiometric Amounts based on the metal ions. 4) Use according to claim 1 to 3 of o (phosphonopropionic acid, optionally in the form of the water-soluble salts. 5) Use according to claim 1 to 3 of 0 (-Phosphono-O (-hydroxypropionic acid, optionally in the form of the water-soluble salts.