IL42898A - Method of complexing cations with 1:1 copolymers as complexing agents - Google Patents

Abstract

1438543 Softening water CONSORTIUM FUR ELECTROCHEMISCHE INDUSTRIE GmbH 3 Aug 1973 [4 Aug 1972] 36956/73 Heading C1C [Also in Divisions C3 and C5] In a water-softening process a cation is complexed by using a 1 : 1-copolymer comprising (i) units derived from an ester of a snuglyunsaturated primary alcohol having from 3 to 10 carbon atoms with a saturated carboxylic acid having up to 6 carbon atoms, and (ii) units derived from maleic anhydride or maleic acid, or a salt of such a copolymer. The term "1 : 1-copolymer" refers to copolymers wherein the components are used in a 1 : 1 molar ratio and copolymers wherein the deviation from this ratio is up to 10%. The copolymer or salt may be in admixture with a salt derived from a strong base and a weak acid. [GB1438543A]

Description

42898/a Method of complexing cations with 1 copolymers as complexing agents Consortium fur Blektrochemische Industrie GmbH C: 40785 - 2 - 42898/3 The present invention relates to the use of particular copolymers as agents for forming chemical complexes (chelates).

Although a large number of complexing agents are known only nitrilotriacetic acid, e thylenedianiinetetraacetic acid and, especially, polyphosphates have acquired industrial importance in this respect. These compounds are used in large quantities as water softeners in washing and cleaning agents and also as dyeing and printing auxiliaries. These complexing agent do, however, have various disadvantages: for example, they are corrosive, and especially the polyphosphates tend to hydrolyze o storage to give compounds of reduced activity, A further, very substantial, "disadvantage of these nitrogen-containing and phosphorus-containing compounds is their contribution to the eutrephication of waters.

For this reason, various nitrogen-free and phosphorus- free complexing agents have been suggested. Among such agents are monomeric hydroxy-acids and polyelectrolytes, for example, polyacr lates, polymethacrylates, polymaleates, and copolymers for example, pentasodium triphosphate. A further d sa van age is that these compounds are not readily biodegradable.

It has now been found that lsl-copolymers comprising (i) units from esters of singly-unsaturated primary alcohols having from 3 to 10, preferably 3 or 4, carbon atoms, with saturated straight-chain or branched-chain carboxylic acids having up to 6 carbon atoms, and (ii) units from maleic anhydride or maleic acid, and salts of such copolymers can be used as complexing agents, especially In water softening. ltl-copolymers of allyl acetate and maleic anhydride and the sakts of such copolymers are preferably used.

These nitrogen-free and phosphorus-free lil-copol mers surprisingly have very good complexing properties and are, additionally, biodegradable; thus no problems of eutrophication of waters arise when using these copolymers, furthermore, the complexing activity of these copolymers is better than that of the previously used complexing agents.

Singl -unsaturated primary alcohols having f om 3 to 10 carbon ajtoms that can be used as alcoholic components of the esters are, fo example, allyl alcohol, isopropenyl alcohol and butenyl alcohol. Examples of saturated straight-chain or branched-chain carboxylic acids having up to 6 carbon atoms that can be used as acid components of the esters are formi* acid, acetic acid, butyric acid, valeric acid, and caproic acid.

The manufacture of the l:l-copolymers has been described in various literature. For e»ample, the manufacture of allyl acetate-maleic acid copolymers is described by P.D. Bartlett and - 4 - 42898/2 K.Hezakl in J. Amer. Chen Soc. 66. 1495 (1946), and an improved procesa is described in German Qf enlengungsschrift No. 2,228,107. The polymerization of isopropenyl acetate and maleic anhydride is described by .C. de Wilde and G. Smets in J. Polymer Scl. 253 (1950). A alogo s procedure can be followed if other unsaturated esters are used in the copolymers.

The l:l-copolymers of allyl acetate and maleic anhydride, which are preferably used, are in most cases manufactured as described in German Offenlegungsschrift No. 2,223,107. They are white free-flowing readily-storable powders having a bulk density between 300 and 400 g/| {HIS 53,468). Their limiting viscosities in acetone at 20°C are generally from 1 to 25 dl/g.

The two components of the copolymer should be used in a lil molar ratio, but slight deviations from this ratio do not affect the completing properties of the copolymers.

As well as the lil-copolymers themselves, their salts may be used as complexing agents. The salts ca be obtained in a simple manner by reaction of the copolymers with bases. Preferably, the salts with alkali metal bases or ammonium bases are used, examples of which re the sodium, potassium, ammonium, tetraalkyl-ammonlum (for example, tetramethylammonlum and tetraethylammonlum) , and alky1-dlmethylbenzylammonium salts. In most cases, the salts have a better solubility than the copolymers themselves. Depending on the mode of the neutralization, the aqueous solutions of the salts are generally between weakly acid and alkaline.

Mixtures of different copolymers, mixtures of different - 5 - 42898/2 complexing agents according to the invention.

The l:l-copolymers or their salts cam he used in admixture with salts of strong bases with weak acids.

This enables a particular pH of the aqueous solutions of the complexing agents to be achieved. Examples of suitable salts are alkali metal carbonates(for example sodium and potassium carbonates), and ammonium carbonate; sodium carbonate is preferred.

The l:l-copolymers and their salts have a very extensive complexing activity. Examples of cations that can be complexed with these compounds are magnesium, calcium, barium, cadmium, zinc, copper, manganese, nickel, lanthanum, iron-II and iroij-III cations. The nature of the anions with which the cations were originally associated Is Immaterial in thiv context* The complex-forming agents are ef ective even at as low a ratio as 3 molar units of the copolymer per mole of cation. A higher molar ratio than 10:1 is not generally used; preferably a ratio of 4:1 is used.

There are numerous fields of use fo the complexing agents. A preferred use is in washing and cleaning agents. In such agents, the customary formulations can be used with the polyphosphates, for example pentasodium triphosphate (about 30-50# by weight of the agent) replaced wholly ι or partially by the Itl-copolymers. Smaller amounts of the present complexing agents than of the polyphosphates suffice to achieve the same complexing effect.

Further fields of use of the complexing agents are as - 6 - , 42898/3 dyeing and printing auxiliaries and for the manufacture of heavy duty cleaning agents.

For use in washing and cleaning agents, the ability of the complexing agents to disperse calcium soaps is also of considerable importance. This ability can be determined according to DIN 55» 03· I is found that the complexing agents according to the invention are far superior to the customary phosphates in this respect (see Example 2 below). To prevent the precipitation of calcium soap from 1 litre of water of 40° dH (German degrees of hardness) containing 500 mg of sodium oleateT over 100#~by~ weight (relative to sodium oleate) of polyphosphates are required, whereas only 3 by weight of the l:l-copolymers (or" 3*6%~by weight- of the copolymer salts) are required. This is important since, even when using the* l:l-copolymer ; '-as ^such salts- are- produced as a result of the alkali content of the detergents. It is found that in the case of the complexing agents according to the inventio the difference between the activity of the copolymers and that of their salts is slight. On the other hand,, if citric acid is used as the complexing agent, a decrease in activity from 3»4 to more than 100 occurs if~the~acid~ is_ne tra^ize ^i3 ^ika±iv-~- A further important criterion of the activity of the complexing agents, especially if they are used~for~ ater soft--: ening, is the capacity to bind calcium. This is higher by a factor of 7 in the case of the complexing agents according to the invention, at a particular carbonate concentration, than in the case of a commercially available polyphosphate, and is also (see Example 3 below) .

The biodegradability of the 1 :1-copolymers can be demonstrated in the bottle test (BOD 5, biochemical oxygen requirement in 5 days) , by means of the oxygen consumption. Λ degradation of more than 80% was found after 5 days.

In the following Examples, the properties of the complexing agents of the invention are compared with those of known complexing agents.

In the Examples, a 1:l-copolymer of allyl acetate and maleic anhydride, which had an average limiting viscosity of about 10-12 dl/g in acetone at 20*C, was used as the complexing agent according to the invention.

Example 1 This example illustrates the formation of water-soluble complexes from allyl acetate/maleic anhydride 1:1-copolymers with metal ions in the presence of precipitants.

Various 0.1 molar salt solutions were prepared using, in turn, each of the following cations in the form of sulphates or chlorides: Fe , Fe , Hi , Mg , Mn , Cu , Ca J Ba , Co , Cd , Zn and La 5 ml portions of these salt solutions were added respectively to 20 ml portions of copolymer solutions which were 0.1 molar in respect of the basic recurrent unit (allyl acetate-maleic anhydride) . These solutions were then rendered alkaline with sodium hydroxide solution, and 10 ml portions of 0.2 molar ammonium carbonate solution were then added in each case. No precipitation occurred, showing that complexes were present and that these were water-soluble. - 8 - 42898/2 In. a further series of e xperiments, trlsodium phosphate was added (instead of ammoaium carbonate) to similar metal salt complex solutions. Again, no precipitation occurred.

Example 2 This Example shows the calcium soap dispersing capacity (determined according to DIH 53*903) of various complexing agents.

Solutions of 500 g of sodium oleate per litre of water of 40° dH were treated with increasing amounts of various complexing agents until the precipitation of calcium soap was just prevented.

The amount of auxiliary, in % by weight relative tc the sodium oleate, at which precipitation is just prevented is given below: Complexing agent : by weight Allyl acetate/malelc anhydride copolymer 3.0 All l acetate/maleic anhydride copolymer neutralized (to phenolphthalein) by HaOH 3.6 Commercially-available polyphosphate (Oalgon Trademark of Messrs. Bencklser, Ludwigsha en, Germany) more than 100 Citric acid 3.4 Citric acid neutralized (to phenolphthalein) by NaOH more than 100 Example In this Example the calcium binding capacity of various complexing agents was determined (see German Offenlegungsschridt No. 1,942,556). 2 g of complexing agent were dissolved in approx. 50 ml of distilled water and neutralized, and 10 ml of a 2 by weight sodium carbonate solution of pH 11-12 were added. The solution was diluted to 100 ml and titrated with 0.5 molar calcium acetate solution until a distinct and persistent turbidity occurred. The calcium binding capacity of the complexing agent was calculated from the following formula: ml of calcium acetate solution x 0«5 x 40 = ' m Ca g of complexing agent The results are listed : mg Ca bound Complexing agent g of complex agent Allyl acetate/maleic anhydride copolymer 568 Commercially-available polyphosphate (Calgon) 74 Citric acid 140 Various polyaldehydocarboxylic acids 106 - 250 (German Offenlegungschrift Nos. 1,942,556) Example 4 A detergent containing an allyl acetate/maleic anhydride copolymer (instead of pentasodium triphosphate) an which therefore does not exert a eutrophicating action on waters, was manufactured according to the following formulat (parts are by weight): 20 parts of sodium dodecylbenzenesulphonate , 5 parts of sodium laurate, 20 parts of allyl acetate/maleic anhydride copolymer, , 20_par_ts_l_Qf_sodium_car_boiiate-, 30 parts of sodium perborate, 4 parts of"sodium sulphate, 0.5 part of sodium chloride, and .5 part of carboxymethylcellulose.

This washing agent had the same washing action as a washing agent manufactured with about 40 by weight pentasodium phosphateβ .

The formulation given above is only one of numerous possibilities. It is possible to use further suitable detergent compounds and additives, for example, optical brighteners, reviving agents (avivage) , foam regulators and enzymes, in various amounts.

Claims (14)

- 11 42898/4 CLAIMS 4 1— 1:1

1. Method of complexing a cation, wherein a/copolymer comprising (i) units from an ester of a single-unsaturated primary alcohol having from 3 to 10 carbon atoms with a saturated carboxylic acid having up to 6 carbon atoms, and (ii) units from maleic anhydride or maleic acid, or a salt of such a copolymer, is applied in aqueous solution for complexing cations.

2. Method as claimed in Claim 1, wherein the alcohol has 3 or 4 carbon atoms.

3. Method as claimed in Claim 1, wherein the alcohol is allyl alcohol, isopropenyl alcohol, or butenyl alcohol.

4. Method as claimed in any one of Claims 1 to 3, wherein the acid is formic acid, acetic acid, butyric acid, valeric acid, or caproic acid.

5. Method as claimed in Claim 1, wherein the copolymer comprises units from allyl acetate and units from maleic anhydride.

6. Method as.claimed in Claim 5, wherein the copolymer has a bulk density of from 300 to 400 g/1, determined according to DIN 53,468.

7. Method as claimed in Claim 6, wherein the copolymer has a limiting viscosity of from 1 to 25 dl/g, determined in acetone at 20eC.

8. Method as claimed in any* one of Claims 1 to 7, wherein the salt of the copolymer is an alkali metal or ammonium salt.

9. Method as claimed in any one of Claims 1 to 7, wherein the salt of the copolymer is a sodium, potassium, ammonium, tetraalkylaims nium, or alk ldimethylbenzylammonium salt. 42898/3 -

10. Method as claimed in any one of Claims 1 to 9, wherein the copolymer or salt is in admixture with a strong base and a weak acid.

11. Method as claimed in any one of Claims 1 to 9, wherein the copolymer or salt is in admixture with an alkali metal carbonate or ammonium carbonate.

12. Method as claimed in any one of Claims 1 to 9, wherein the copolymer or salt is in admixture with sodium carbonate or potassium carbonate.

13. Method as claimed in any one of Claims 1 to 12, wherein the copolymer or salt is used in a washing or cleaaing agent.

14. Method as claimed in any one of Claims 1 to 13, wherein complexing is for the purposes of water-softening. HE:mr