Methods for producing polyaspartic acids in the presence of methanesulfonic acid

Abstract

The present invention relates to methods for producing polyaspartic acids with a weight-average molecular weight (Mw) of from 6,000 to 15,000 g/mol. The invention also relates to polyaspartic acids which can be obtained by the method according to the invention, to a composition containing the polyaspartic acids, and to the use thereof as scale inhibitors, dispersants and as an additive in dishwashing agents, detergents or cleaning agents.

Claims

1. A method for producing polyaspartic acids with a weight-average molecular weight (Mw) of 6000 to 15 000 g/mol, comprising the following steps: (i) polycondensation of (a) aspartic acid in the presence of (b) 1 to 15 mol % of methanesulfonic acid, based on the amount of aspartic acid used in (a) at a temperature of 170? C. to 230? C. for a time period of 1 minute to 50 hours; (ii) subsequent hydrolysis of the polycondensates with addition of a base; and (iii) optional acidification of the salt of polyaspartic acid obtained in (ii) with mineral acids or acidic ion exchangers, and wherein the polycondensation step further comprises the addition of water.

2. The method according to claim 1, wherein 2 to 13 mol % of methanesulfonic acid are used in step (i) (b), based on the amount of aspartic acid used in (a).

3. The method according to claim 1, wherein 3 to 10 mol % of methanesulfonic acid are used in step (i) (b), based on the amount of aspartic acid used in (a).

4. The method according to claim 1, wherein the polycondensation in step (i) is carried out at a temperature of 190? C. to 220? C.

5. The method according to claim 1, wherein the quotient of weight-average molecular weight (Mw) to number-average molecular weight (Mn) of the polyaspartic acid produced is not greater than 3.

6. The method according to claim 5, wherein the quotient is not greater than 2.5.

7. The method according to claim 1, wherein the base used in step (ii) is selected from the group consisting of aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, calcium hydroxide, barium hydroxide, sodium carbonate, potassium carbonate, ammonia and ammonium hydroxide.

8. The method according to claim 1, wherein the mineral acid used in step (iii) is sulfuric acid or hydrochloric acid.

9. A polyaspartic acid obtainable by the method according to claim 1.

10. A composition comprising the polyaspartic acid according to claim 9.

11. The composition according to claim 10, wherein the composition is a dishwashing composition, a detergent composition or a cleaning composition.

12. A dishwashing composition comprising (a) 1-20% by weight polyaspartic acid according to claim 9; (b) 0-50% by weight complexing agents; (c) 0.1-80% by weight builders and/or co-builders; (d) 0.1-20% by weight non-ionic surfactants; (e) 0-30% by weight bleach, bleach activators and bleach catalysts; (f) 0-8% by weight enzymes; and (g) 0-50% by weight additives.

13. A solid detergent composition or cleaning composition comprising (A.sub.F) 0.1 to 20% by weight polyaspartic acid according to claim 9, (B.sub.F) 1 to 50% by weight surfactants, (C.sub.F) 0.1 to 70% by weight builders, co-builders and/or complexing agents, (D.sub.F) 0 to 30% by weight bleach system, and (E.sub.F) 0.1 to 70% by weight detergent or cleaning ingredients.

14. A liquid or gel-like detergent composition and cleaning composition comprising (A.sub.L) 0.1 to 20% by weight polyaspartic acid according to claim 9, (B.sub.L) 1 to 80% by weight surfactants, (C.sub.L) 0.1 to 50% by weight builders, co-builders and/or complexing agents, (D.sub.L) 0 to 20% by weight bleach system, (E.sub.L) 0.1 to 60% by weight detergent or cleaning ingredients, and (F.sub.L) 0 to 98.7% by weight water.

15. A scale inhibitor and/or dispersant which comprises the polyaspartic acid according to claim 9.

16. A scale inhibitor and/or dispersant in water-conducting systems which comprises the polyaspartic acid according to claim 9.

17. An additive in dishwashing agents, detergents or cleaning agents which comprises the polyaspartic acid according to claim 9.

18. The additive according to claim 17, wherein the dishwashing agent is for machine dishwashing.

19. The method according to claim 3, wherein the polycondensation in step (i) is carried out at a temperature of 200? C. to 220? C. for 1 hour to 15 hours.

20. The dishwashing composition as claimed in claim 12, wherein the composition comprises (a) 1-20% by weight said polyaspartic acid; (b) 3-50% by weight complexing agents; (c) 0.1-80% by weight builders and/or co-builders; (d) 0.5-10% by weight non-ionic surfactants; (e) 0.1-30% by weight bleach, bleach activators and bleach catalysts; (f) 0-8% by weight enzymes; and (g) 0-50% by weight additives.

Description

EXAMPLES

Example 1

Preparation of Polyaspartic Acids

(1) Polymers 1-6 and C2:

(2) 133.10 g of L-aspartic acid, 30 g of water and the amount of methanesulfonic acid specified in Table 1 were initially charged in a 2 l capacity reactor equipped with stirrer and temperature sensor. The reaction mixture was heated to the condensation temperature of 210? C. to 220? C. with stirring under a gentle stream of nitrogen and condensed at this temperature for 6 hours with simultaneous removal of water by distillation. After the reaction was complete, the polyaspartimide obtained was comminuted and cooled. In order to prepare the aqueous solution of polyaspartic acid sodium salt, 100 g of the polyaspartimide formed by the condensation step was dispersed in 100 g of water, the mixture was heated to 70? C. and sufficient 50% aqueous sodium hydroxide solution was added at this temperature so that the pH was in the range of 7-9. The powder dispersed in water dissolved gradually and a clear aqueous solution of the sodium salt of polyaspartic acid was obtained. The residual content of unreacted aspartic acid was determined by .sup.1H-NMR spectroscopy. This was <0.5% by weight based on the aspartic acid used.

(3) TABLE-US-00001 TABLE 1 Polyaspartic acids Molar MeSO.sub.3H ratio Mn Mw Polymer [g] L-Asp:MeSO.sub.3H [g/mol] [g/mol] Mw/Mn 1 2.4 40:1 2967 7323 2.5 2 4.81 20:1 3212 7713 2.4 3 7.21 13.3:1 4109 8492 2.1 4 9.61 10:1 4305 10630 2.5 5 12.01 8:1 4613 11430 2.5 6 13.9 6.9:1 4790 13750 2.5 C2 38.4 2.5:1 5450 19110 3.5
Polymer C1:

(4) 133.10 g of L-aspartic acid were polycondensed at a temperature of 210-220? C. for 2 h in a rotary evaporator. The resulting polyaspartimide was hydrolyzed to give an aqueous solution of polyaspartic acid sodium salt in a manner analogous to polymer 1-6 and C2. The weight-average molecular weight Mw was 5400 g/mol.

(5) Polymer C3:

(6) Polyaspartic acid was prepared according to the description of Example 5 from U.S. Pat. No. 5,457,176. The amount of MeSO.sub.3H (3 g) used was 15.4 mol % based on the amount of L-aspartic acid (27 g) used, the molar ratio L-Asp:MeSO.sub.3H was thus 6.5:1. The polycondensation was carried out at 240? C. as described in Example 5 of U.S. Pat. No. 5,457,176 and had to be interrupted repeatedly in order to comminute the solid mass formed. The resulting product was subjected to a CaCO.sub.3 inhibition test as described herein, see Table 2b.

Example 2

Determination of the Molecular Weight (Mw and Mn)

(7) The weight-average or number-average molecular weight (Mw and Mn) of the examples was determined by GPC (gel permeation chromatography) under the following conditions:

(8) TABLE-US-00002 Column PSS SUPREMA analytical linear M (Material: polyhydroxymethacrylate copolymer network Length: 300 mm, diameter 8 mm, particle size 10?) Eluent 0.08 mol/l TRIS buffer pH 7.0 in dist. water + 0.15 mol/l NaCl + 0.01 mol/l NaN.sub.3. Column temperature 35? C. Flow rate 0.8 ml/min Injection 100 ?L Concentration 1.5 mg/ml Detector DRI Agilent 1100UV GAT-LCD 503 (260 nm)

(9) To determine the molecular weight, a small amount of the polyaspartimide formed in the polycondensation step was taken and washed repeatedly with water in order to remove the methanesulfonic acid used. The washed powder was than hydrolyzed as described with aqueous sodium hydroxide solution (i.e. the washed powder was dispersed in water, the mixture was heated to 70? C. and sufficient 50% aqueous sodium hydroxide solution was added at this temperature so that the pH was in the range of 7-9. The powder dispersed in water dissolved gradually and a clear aqueous solution of the sodium salt of polyaspartic acid was obtained). Sample solutions were filtered through Sartorius Minisart RC 25 (0.2 ?m). Calibration was performed using narrowly distributed Na-PAA standards from Polymer Standard Service with molecular weights of M=1250 g/mol to M=130 500 g/mol. In addition, Na-acrylate having a molecular weight of M=96 and a PEG standard with M=620, which is synonymous with Na-PAA M=150, was used. Values outside this elution range were extrapolated. The evaluation limit was 122 g/mol.

Example 3

Calcium Carbonate Inhibition Test

(10) A solution of NaHCO.sub.3, MgSO.sub.4, CaCl.sub.2 and polymer was shaken at 70? C. for 2 h in a water bath. After filtration of the still warm solution through a 0.45 ?m Milexfilter, the Ca content of the filtrate was determined complexometrically or by means of a Ca.sup.2+ selective electrode and determined as % by comparison before/after the CaCO.sub.3 inhibition (see formula 1).

(11) TABLE-US-00003 Ca.sup.2+ 215 mg/l Mg.sup.2+ 43 mg/l HCO.sub.3.sup.? 1220 mg/l Na.sup.+ 460 mg/l Cl.sup.? 380 mg/l SO.sub.4.sup.2? 170 mg/l Polymer 3 mg/l (cf. Table 2a) or 1.5 mg/l (cf. Table 2b) Temperature 70? C. Time 2 hours pH 8.0-8.5
CaCO.sub.3 inhibition (%)=[(mg(Ca.sup.2+) after 24 h?mg(Ca.sup.2+)blank value after 24 h)/(mg(Ca.sup.2+)zero value?mg(Ca.sup.2+)blank value after 24 h)]?100Formula 1

(12) TABLE-US-00004 TABLE 2a CaCO.sub.3 inhibition at 3 mg/l polymer Example Inhibition [%] 2 61.2 4 59.2 C2 43.9

(13) TABLE-US-00005 TABLE 2b CaCO.sub.3 inhibition at 1.5 mg/l polymer Example Inhibition [%] 2 50.9 C3 40.8

Example 4

Dishwashing Machine Test

(14) The polymers were tested in the following phosphate-free formulation PF1.

(15) TABLE-US-00006 TABLE 3 Dishwashing agent test formulation 1 (PF1) Constituent PF 1 Protease 2.5 Amylase 1.0 Non-ionic surfactant 5 Polymer 10 Sodium percarbonate 10.2 Tetraacetylethylenediamine 4 Sodium disilicate 2 Sodium carbonate 19.5 Sodium citrate dihydrate 35 Methylglycinediacetic acid, 10 Na salt Hydroxyethane-(1,1- 0.8 diphosphonic acid) Values in % by weight based on the total amount of all components

(16) The following experimental conditions were observed:

(17) TABLE-US-00007 Dishwasher: Miele G 1222 SCL Program: 65? C. (with pre-rinse) Crockery: 3 knives (nickel chrome knives Karina, Solex Germany GmbH, D-75239 Eisingen) 3 drinking glasses Amsterdam 0.2 | 3 BREAKFAST DISHES OCEAN BLUE (MELAMINE) 3 porcelain dishes FLAT RIMMED PLATES 19 CM Arrangement: Knives in the cutlery rack, glasses in the upper basket, plates in the lower basket Dishwashing agent: 18 g Soil addition: 50 g of ballast soiling is thawed with the formulation added after the prerinse, composition see below Wash temperature: 65? C. Water hardness: 21? dH (Ca/Mg):HCO3 (3:1):1.35 Wash cycles 15; 1 h pause between each cycle (10 min door closed, 50 min door open) Evaluation: Visually after 15 cycles

(18) The crockery was evaluated after 15 cycles in a darkened chamber with light behind an aperture plate using a grading scale from 10 (very good) to 1 (very poor). Ratings were awarded of 1-10 for spotting (very many, intensive spots=1 to no spots=10) and for scaling (1=very intense scaling, 10=no scaling)

(19) Composition of the Ballast Soil:

(20) Starch: 0.5% potato starch, 2.5% gravy Fat: 10.2% margarine Protein: 5.1% egg yolk, 5.1% milk Others: 2.5% tomato ketchup, 2.5% mustard, 0.1% benzoic acid, 71.5% water
Result:

(21) The formulations with polyaspartic acid modified in accordance with the invention were characterized particularly by their very high scale-inhibiting effect with respect to inorganic and organic deposits on glass and knives. Furthermore, they increased the cleaning power of the dishwashing agent and favored the draining of water from the crockery such that particularly clear glasses and shiny metal cutlery items were obtained.

(22) In Table 4 below, the added gradings for scale formation (B) and spotting (S) on knives and drinking glasses are listed.

(23) TABLE-US-00008 TABLE 4 Test result for dishwashing test formulation 1 (PF1) Example Knives (B + S) Glasses (B + S) without polymer 7.3 7.2 2 16.3 15.3 4 13.0 14.0 C1 11.4 9.0