Sulphur-bridged compounds, use thereof and process for production thereof

Abstract

The present invention relates to novel sulphur-bridged compounds, in which within the molecule there is at least one fatty acid bonded by way of at least one sulphur bridge to at least one polyalkylene glycol ester, the reaction product of a fatty acid with a polyalkylene glycol, and these have from 8 to 29% by weight sulphur content, to use of these as sulphur carrier and lubricant additive and to production of the said compounds.

Claims

1. Sulphur-bridged compounds comprising at least one fatty acid bonded by way of at least one sulphur bridge to at least one polyalkylene glycol ester, wherein the polyalkylene glycol ester is the reaction product of at least one fatty acid with a polyalkylene glycol, and the sulphur-bridged compounds have 8 to 29% by weight sulphur content.

2. The sulphur-bridged compounds according to claim 1, wherein the polyalkylene glycol ester is polyethylene glycol ester, polypropylene glycol ester, polybutylene glycol ester and/or polyalkylene glycol esters in which the ethylene oxide units, propylene oxide units and/or butylene oxide units are in random and/or blockwise arrangement.

3. The sulphur-bridged compounds according to claim 1 or 2, wherein the sulphur-bridged compounds have the following formulae: ##STR00005## where a, b, c, d, e, f, g, h, p, q, r, s, t, u, v and w correspond mutually independently to values of 3 to 29, n, k, j and y correspond mutually independently to values of 2 to 10, m=4 to 20, and x=1 to 10.

4. A mixture comprising at least one sulphur-bridged compound according to claim 3, and at least one of lubricant additives and carrier liquids.

5. A process for the production of the sulphur-bridged compounds according to claim 1, the process comprising: reacting the unsaturated fatty acid with sulphur and/or hydrogen sulphide to give the sulphur-bridged fatty acid, and reacting the sulphur-bridged fatty acid with the polyalkylene glycol in such a way that at least one carboxylic acid unit of the fatty acid is present within the sulphur-bridged compounds.

6. A process for the production of the sulphur-bridged compounds according to claim 1, the process comprising: reacting a molar excess of unsaturated fatty acid with polyalkylene glycol to give an intermediate product composed of unsaturated polyalkylene glycol ester and unsaturated fatty acid, and reacting the intermediate product with sulphur and/or hydrogen sulphide in such a way that at least one carboxylic acid unit of the fatty acid is present within the sulphur-bridged compounds.

7. A process for the production of the sulphur-bridged compounds according to claim 1, the process comprising: mixing the unsaturated fatty acid with at least one unsaturated fatty acid polyalkylene glycol ester, and reacting the mixture with sulphur and/or hydrogen sulphide in such a way that at least one carboxylic acid unit of the fatty acid is present within the sulphur-bridged compounds of the invention.

8. The process according to any of claims 5 to 7, wherein the unsaturated fatty acids are at least one of unsaturated monocarboxylic acids having a carbon-chain length of from 6 to 32 C atoms, and mixtures of unsaturated fatty acids.

9. The process according to any of claims 5 to 7, the sulphur is elemental sulphur.

10. The process according to any of claims 5 to 7, wherein the polyalkylene glycol comprises bifunctional polyethylene glycol.

11. The sulphur-bridged compounds according to claim 1, wherein the polyalkylene glycol ester is polyethylene glycol ester.

12. The sulphur-bridged compounds according to claim 3, wherein: a, b, c, d, e, f, g, h, p, q, r, s, t, u, v and w correspond mutually independently to values of 5 to 12, n, k, j and y correspond mutually independently to values of 4 to 8, m=8 to 16, and x=2 to 4.

13. A mixture comprising at least one of sulphur-bridged compound according to claim 1 or 2, and at least one of lubricant additives and carrier liquids.

14. The sulphur-bridged compounds according to claim 1, wherein the sulphur-bridged compounds have greater than 10% to 29% by weight sulphur content.

15. Sulphur-bridged compounds comprising at least one fatty acid bonded to at least one polyalkylene glycol ester via at least one sulphur bridge, wherein the sulphur-bridged compounds have at least 8% by weight sulphur content.

16. The sulphur-bridged compounds according to claim 15, wherein: the at least one fatty acid comprises unsaturated monocarboxylic acids having a carbon-chain length of from 6 to 32 C atoms; and the polyalkylene glycol ester is polyethylene glycol ester, polypropylene glycol ester, polybutylene glycol ester and/or polyalkylene glycol esters.

Description

(1) The present invention further provides processes for the production of the sulphur-bridged compounds of the invention:

(2) Preference is given here to the 3 embodiments specified below. 1) The unsaturated fatty acid, preferably the unsaturated monocarboxylic acid, is first reacted with sulphur and/or hydrogen sulphide to give the sulphur-bridged fatty acid, preferably sulphur-bridged saturated fatty acid, and then this sulphur-bridged fatty acid is reacted with at least one polyalkylene glycol in such a way that at least one carboxylic acid unit of the fatty acid is present within the sulphur-bridged compounds of the invention. 2) A molar excess of unsaturated fatty acid, preferably of unsaturated monocarboxylic acid, is reacted with at least one polyalkylene glycol to give the intermediate product composed of unsaturated polyalkylene glycol ester and unesterified unsaturated fatty acid, and then this intermediate product is reacted with sulphur and/or hydrogen sulphide in such way that at least one carboxylic acid unit of the fatty acid is present within the sulphur-bridged compounds of the invention. 3) The unsaturated fatty acid, preferably the unsaturated monocarboxylic acid, is mixed with at least one unsaturated fatty acid polyalkylene glycol ester and then this mixture is reacted with sulphur and/or hydrogen sulphide in such a way that at least one carboxylic acid unit of the fatty acid is present within the sulphur-bridged compounds of the invention.

(3) The determination of the carboxylic acid unit takes place by way of the acid number according to ASTM D664 or DIN 53402. In the first and second embodiments of the process of the invention, the reaction of the fatty acid and/or sulphur-bridged fatty acid with the polyalkylene glycol is detected via the acid-number. The juncture at which the reaction is terminated is no later than that at which at least one carboxylic acid unit is still present.

(4) The first and second embodiment of the process of the invention preferably use the starting materials in the following ratios: a) Based on 1 g of unsaturated fatty acid, preferably unsaturated monocarboxylic acid, from 0.05 g to 1 g of polyalkylene glycol is used; and b) based on 1 g of unsaturated fatty acid, preferably unsaturated monocarboxylic acid, from 0.05 g to 0.5 g of sulphur is used.

(5) The third embodiment of the process of the invention preferably uses the starting materials in the following ratios: a) Based on 1 g of unsaturated fatty acid, preferably unsaturated monocarboxylic acid, from 0.2 g to 4 g of unsaturated fatty acid polyalkylene glycol ester is used; and b) based on 1 g of unsaturated fatty acid, preferably unsaturated monocarboxylic acid, from 0.05 g to 0.5 g of sulphur is used.

(6) In all of the embodiments of the processes of the invention, the reaction with sulphur and/or hydrogen sulphide (sulphurization) is preferably carried out at pressures from atmospheric pressure (i.e. in the range from 0.9 to 1.1 bar) to 15 bar and at temperatures of from 119 to 170 C. and with a reaction time of from 4 to 24 h.

(7) In the first and second embodiment of the process of the invention, it is preferable that the esterification is carried out at atmospheric pressure (i.e. in the range from 0.9 to 1.1 bar), with subsequent reduction to pressures extending as far as 10 mbar, the reaction being carried out at temperatures of from 120 to 200 C. and with a reaction time of from 4 to 24 h.

(8) In the third embodiment of the process of the invention, the mixing is preferably carried out at atmospheric pressure and at temperatures of from 15 to 100 C. and with a mixing time of from 5 to 30 min.

(9) In further embodiments of the present invention, preference is given to the reaction conditions specified below:

(10) In the first embodiment of the process of the invention, it is preferable that the unsaturated fatty acid, preferably the unsaturated monocarboxylic acid, is first reacted with sulphur and/or hydrogen sulphide and then with polyalkylene glycol, preferably polyethylene glycol, to give the sulphur-bridged compounds of the invention. In the first step, the unsaturated monocarboxylic acid is sulphurized with sulphur and/or hydrogen sulphide in a pressure reactor at from atmospheric pressure to 15 bar, preferably 4 bar, and at from 119 to 170 C., preferably 130 C. The sulphurization is preferably catalysed by amines, metal oxides or acids. In the second step, the intermediate product is esterified with polyalkylene glycol, preferably polyethylene glycol at from atmospheric pressure to 10 mbar and at from 120 to 200 C., preferably 180 C. The esterification is preferably continued until no further water is removed by distillation. The esterification is preferably catalysed by tin salts or by acids, preferably by phosphoric acid and/or p-toluenesulphonic acid.

(11) In the second embodiment of the process of the invention, it is preferable that a molar excess of unsaturated fatty acid, preferably the unsaturated monocarboxylic acid, is first reacted with polyalkylene glycol, preferably polyethylene glycol, and then with sulphur and/or hydrogen sulphide to give the sulphur-bridged compounds of the invention. In the first step, the unsaturated monocarboxylic acid is esterified with polyalkylene glycol, preferably polyethylene glycol, at from atmospheric pressure to 10 mbar and at from 120 to 200 C., preferably 180*C. The esterification is preferably continued until no further water is removed by distillation. The esterification is preferably catalysed by tin salts or by acids, preferably by phosphoric acid or p-toluenesulphonic acid. In the second step, the intermediate product which comprises unsaturated polyalkylene glycol ester and unesterified unsaturated fatty acid is sulphurized with sulphur and/or hydrogen sulphide in a pressure reactor at from atmospheric pressure to 15 bar, preferably 4 bar, and at from 119 to 170 C., preferably 130 C. The sulphurization is preferably catalysed by amines, metal oxides or acids.

(12) In the third embodiment of the process of the invention, the unsaturated fatty acid, preferably the unsaturated monocarboxylic acid, is first mixed with the unsaturated fatty acid polyalkylene glycol ester and then reacted with sulphur and/or hydrogen sulphide to give the sulphur-bridged compounds of the invention. In the first step, the unsaturated monocarboxylic acid is mixed with the unsaturated fatty acid polyalkylene glycol esters at atmospheric pressure and from 15 to 100 C., preferably 40 C. In the second step, the mixture is sulphurized with sulphur and/or hydrogen sulphide in a pressure reactor at from atmospheric pressure to 15 bar, preferably 4 bar, and at from 120 to 170 C., preferably 130 C. The sulphurization is preferably catalysed by amines, metal oxides or acids.

(13) The present invention further provides a process for the production of a mixture according to which lubricant additives and carrier liquids are additionally added before, during or after the production of the sulphur-bridged compounds of the invention.

(14) The addition process can use commercially available mixing assemblies, preferably stirred tanks.

(15) The present invention further provides the use of the sulphur-bridged compounds of the invention as sulphur carrier and/or as lubricant additive in all lubricants according to ISO 6743, for example preferably lubricants for metalworking or lubricants for machinery.

(16) The sulphur-bridged compounds of the invention are preferably used as lubricant additive in water-miscible or water-mixed cutting fluids. These are described in DIN 51385.

(17) The scope of the invention encompasses combinations of all of the moiety definitions, indices, parameters and explanations provided above and listed below in general terms or in preferred ranges, i.e. also encompasses any desired combination between the respective ranges and preferred ranges.

(18) The examples below serve to illustrate the invention without any resultant limiting effect.

INVENTIVE EXAMPLES

(19) In the Example that follows, the percentages relate to % by weight.

(20) Reagents:

(21) Additin RC 5250, sulphur-bridged fatty acids based on a vegetable fatty acid mixture (composed of: >90% by weight of unsaturated fatty acids, main constituents oleic acid and linoleic acid), with sulphur content about 15% by weight; producer: Rhein Chemie Rheinau GmbH.

(22) Pluriol E 600, linear bifunctional polyethylene glycol, average molar mass: about 600 g/mol; producer: BASF SE.

(23) The following components were mixed by means of a magnetic stirrer at about 25 C. (Mixture A1):

(24) 20.00 g of Additin RC 5250

(25) 10.00 g of Pluriol E 600

(26) 0.03 g of phosphoric acid, 75% by weight

(27) The acid number was 115.9 mg of KOH/g.

(28) The Method for the Examples was as Follows:

(29) 5 drops were taken from the Mixture A1 and added to about 50 ml of drinking water of hardness 20 dH (sample A1) at about 25 C. After sample A1 had been mixed by stirring, insoluble droplets remained in the water.

(30) 20 g of the Mixture A1 were then heated in an open glass beaker at 120 C. with the use of a magnetic stirrer. After a reaction time of 6 hours, the reaction product, i.e. a mixture of the sulphur-bridged compounds of the invention, and where appropriate of unreacted starting materials and by-products, was cooled to room temperature (Mixture A2). 5 drops were likewise taken from the Mixture A2 and added to about 50 ml of drinking water of hardness 20 dH (sample A2). After the sample A2 had been mixed by stirring, the droplets were emulsified in water and formed an emulsion with coarse disperse phase.

(31) Finally, a few drops of aqueous potassium hydroxide solution were added to each of the samples A1 and A2 until a pH>10 had been reached. In the neutralized sample A1, voluminous precipitate formed, and in the neutralized sample A2 an emulsion with fine disperse phase formed and exhibited a slight, fine sediment only after some days.

(32) The table below collates the results of the Examples:

(33) TABLE-US-00002 Mixture A1 Mixture A2 (Comparison) (Of the invention) Solubility in drinking Insoluble Emulsion with coarse water disperse phase Solubility in drinking Voluminous Emulsion with fine water after neutralization precipitate disperse phase Acid number measured 115.9 mg of KOH/g 85.4 mg of KOH/g after 6 hours Corrected acid number 114.6 mg of KOH/g 84.1 mg of KOH/g (= measured acid number after deduction of the calculated acid number of the phosphoric acid content) Measured sulphur content 10.3% by weight 10.3% by weight

(34) The Mixture A1 had reacted after a reaction time of 6 hours to give the product of the invention (Mixture A2). The sulphur-bridged compounds of the invention have 10.3% by weight sulphur content. The acid number of the product of the invention is 85.4 mg of KOH/g. The reduced acid number proves that within the sulphur-bridged compounds there are not only unesterified fatty acids but also polyethylene-glycol-esterified fatty acids (polyethylene glycol esters). The value for the Mixture A1 (Comparison) remained unchanged.

(35) Quantitative studies were moreover carried out to determine soap scum deposit. To this end, each of the Mixtures A1 and A2 was dissolved at 0.3% by weight at about 25 C. in water according to DIN 51367 with a defined total hardness of 3.58 mmol/liter, corresponding to 20 dH. Aqueous potassium hydroxide solution (45% by weight) was admixed with each of these solutions until a pH of 11.00.2 had been achieved. In order to facilitate dissolution of the Mixtures A1 and A2 in water, most of the aqueous potassium hydroxide solution required was first dissolved in water. Each of the Mixtures A1 and A2 was then slowly added dropwise during constant stirring. Finally, a pH of 11.00.2 was established with the aqueous potassium hydroxide solution.

(36) The 0.3 percent by weight solution of the Mixture A1 is termed Solution A1, and the 0.3 percent by weight solution of the Mixture A2 is termed Solution A2. The pH of the Solutions A1 and A2 was 11.0.

(37) The freshly mixed Solution A1 comprised voluminous suspended precipitate; after 24 h the precipitate sunk to the bottom, and above the sediment there was an emulsion visible with fine disperse phase. The freshly mixed Solution A2 was an emulsion with fine disperse phase; after 24 h the emulsion still had a fine disperse phase, but a slight, fine sediment was apparent.

(38) After 24 h, the matured Solutions A1 and A2 were filtered by using prepleated filters (Macherey-Nagel 615 ). The residues (soap scum) in the filter were dried at 105 C. for 2 b and analysed gravimetrically.

(39) TABLE-US-00003 Mixture A1 Mixture A2 (Comparison) (Of the invention) Mass of residue (scum) 0.89 g 0.36 g Input weight of mixture 1.50 g 1.50 g Ratio of mass of residue to 59% by weight 24% by weight input weight of mixture

(40) In the case of the Mixture A1 the mass of the residue was 0.89 g. In the case of the Mixture A2 of the invention the mass of the residue was only 0.36 g.

SUMMARY

(41) With the Inventive Examples it was possible to show clearly that when the product of the invention (Mixture A2) is used there was significantly less soap scum deposit.

(42) Experiments have shown that the object of the present invention has been achieved. After adequate reaction time, the Mixture A1 was modified in such a way as to provide a product (Mixture A2) which is water-miscible without addition of emulsifier, and has high polarity, has no, or no significant, tendency towards formation of soap scum deposit in hard water, and has high sulphur content.