DE1132133B - Process for the preparation of dithiophosphinic acid esters - Google Patents

Description

Process for the preparation of dithiophosphinic acid esters The invention relates to a process for the preparation of dithiophosphinic acid esters.

According to the process of the invention, dithiophosphinic acid esters can be obtained Produce with high yields with little technical effort, since neither difficult The reaction conditions to be observed still require the use of a catalyst are.

In the process of the invention for the preparation of dithiophosphinic acid esters, a dithiophosphinic acid of the general formula is used in which R and R 'are optionally branched alkyl radicals with up to 8 carbon atoms or the phenyl radical, with monoolefins which may optionally be substituted by the carbalkoxy or hydroxyphenyl group, with pinenes or with quinone in approximately equimolar amounts, optionally in organic inert solvents at about 40 to 250 ° C, in particular at 100 to 110 ° C to.

The reaction components should be in such proportions and in such Temperatures are brought to act on each other that the reaction with sufficient Proceeds rapidly and without substantial decomposition of the esters formed; this is carried out until the acid value of the reaction mixture is significantly has decreased.

The esters of dithiophosphinic acids prepared by the process of the invention come in particular as quality-improving additives to oils, lubricants or Plasticizers into consideration.

It is known that monothiophosphinic acid esters are used as quality-improving Can use additives in lubricating oils. A small addition of these esters increases the resilience of the oil film. There is a disadvantage of these monothiophosphinic acid esters, which are particularly known from German patent specification 851237, in that the Oils mixed with these substances have only a low resistance to oxidation.

This leads to a relatively large increase in viscosity at higher operating temperatures.

In contrast, the use of the Invention produced dithiophosphinic acid esters the oxidation resistance of oils significantly increased, or the increase in viscosity is significantly slowed down, as has been found in comparative tests.

The dithiophosphinic acids to be used as starting materials according to the invention can be prepared by reacting a Grignard compound with phosphorus pentasulfide (cf. "Organophosphorus Compounds", G. M. Kosolopoff, p. 135, John Wiley & Sons, New York 1950). Another method of making these diorgano-dithiophosphinic acids is in U.S. patent application filed January 26, 1954 (Serial No. 406 323) treated.

In the method of the invention, the dithiophosphinic acid with a Monoolefin, especially with at least 4 carbon atoms, which is optionally replaced by the carbalkoxy or the hydroxyphenyl group can be substituted with a pinene or quinone initially mixed or dissolved at room temperature.

Since the stoichiometric conditions of the reaction are generally 1 Moles of dithiophosphinic acid per mole of the above-mentioned unsaturated organic Require compound, these molar ratios are preferred. However, it can also be a Excess of the one reaction component can be advantageous, so that a complete Course of the reaction is achieved.

The excess of a reaction component can be determined by known measures, for example by distillation, can be removed again and recovered. in the generally the reaction does not occur until the reaction mixture has reached about 40 up to 50 ° C has been heated. This does not preclude the reaction however, in certain cases it starts at room temperature. It can also be an essential higher temperatures up to 250 ° C can be used.

In general, the reaction proceeds at temperatures below Part of the range given above, for example at 100 to 110 ° C., is sufficient fast, so that higher temperatures do not need to be used here. The lower temperatures are preferred as they are lighter, more economical and are technically easier to reach, with a lower inclination of the resulting End products to decompose.

After the reaction mixture has been heated up to a temperature at which the reaction starts, the reaction proceeds as a function of the nature of the reaction components either endothermic or exothermic. When applied of a monoolefin, which contains activated double bonds, runs the Reaction generally exothermic; here it may be necessary to use the reaction mixture cools or brings the reaction components together so slowly that an excessive Heating the reaction mixture is avoided.

In such cases, it is generally appropriate that after If the main exothermic reaction subsides the reaction mass for a short time, generally at least about 1/2 hour to complete the reaction further heated. The reaction is complete when the reaction mixture has a constant and has reached low acidity.

In the work-up and precipitation of the reacted reaction mixture with solvents, a solvent layer is obtained which consists of a mixture of the solvent originally used, also for example for the Working up of the methanol used as a solvent and any unreacted methanol Dithiophosphinic acid consists. This solvent layer is peeled off and the acid number of the product. Provided the acid number is the presence of substantial amounts Indicates dithiphosphinic acid, the product is dissolved in the chosen solvent and again in the manner mentioned, for example with methanol, precipitated. at in practice it is very difficult to remove the last traces of dithiophosphinic acid to remove. For most purposes that of the method of the invention produced new substances is however a detrimental effect of this proportionately small amounts of residual dithiophosphinic acid not observed.

The product obtained in this way is in turn in the chosen solvent dissolved and then worked up according to one of the following working methods.

I. The solution can be placed in a still and heated until the volume has reduced to about half that proportion.

The distillate represents a mixture of the selected solvent and essentially all of the lower boiling point impurities in the solvent which were originally present in the liquid mixture to be distilled.

The end product that remains consists of a solution of the process product in the chosen solvent.

2. The solution can also be placed in a distillation vessel and heated under reduced pressure until the solvent is removed.

The remaining liquid consists essentially of the solvent-free Process product.

Depending on the particular application for which the Process product to be used is one of the working methods explained above to obey. If the process product is used, for example, as an additive to heating oils, Lubricants and plasticizers or plasticizers are to be used, the first mode is preferred. If you look at the process product in this Wisely processed, it usually exhibits its maximum solubility in organic Substances on.

The invention is illustrated in more detail below with the aid of a few examples.

Example 1 Preparation of carbomethoxyheptadecyl ester of diphenyldithiophosphinic acid 1 mole (330 g) of essentially pure diphenyldithiophosphinic acid with the following analysis values: Calculated Found sulfur .............. 25.6 ° / o 24.9 ° / o phosphorus ............. 12, 4 ° / o 12.2 ° / o acid number ............. 223 173 was heated with 1 mol (296 g) of methyl oleate with continued stirring at 90 to 100 ° C for 10 hours. The acid number of the mixture decreased from 87.5 to 35 during this time. After cooling, the whole thing was washed once with approximately the same volume of a 5% aqueous sodium carbonate solution, a small amount of benzene and n-butanol being added. to facilitate separation. Then the organic layer was washed three times with water and distilled as in the previous step to remove the solvents. The dark colored liquid ice left in the distillation flask weighed 501 g. It consisted essentially of pure dithiophosphinic acid ester.

Analysis: Calculated Found sulfur .............. 10.2 ° / 0 10.9 ° / 0 phosphorus ............. 4.95 ° / 0 5.08% acid number 8.7 Example 2 Preparation of dihydroxyphenyl ester of diphenyldithiophosphinic acid Diphenyldithiophosphinic acid (428 g, 1.3 mol of the same acid as used in Example 1) was dissolved in 500 ml of benzene, and a solution of p-quinone (140.4 g, 1.3 Mol) in 750 ml of warm benzene that the reaction mixture was kept at about 50 ° C (exothermic reaction). After everything had been added, the mixture was stirred at 45 to 50 ° C. for 11/2 hours. After cooling, it was then washed with a 5% sodium bicarbonate solution and water. The organic layer was extracted with 800 g of a 20% aqueous sodium hydroxide solution, and the aqueous extract was acidified with hydrochloric acid. The acidified extract was then extracted by shaking with benzene, and the benzene layer was washed and distilled to remove volatile substances.

The pale yellow colored semi-solid distillation residue weighed 425 g and consisted of pure dihydroxyphenyl ester of diphenyldithiophosphinic acid.

Analysis: Calculated Found sulfur .............. 17.88 ° / 0 17.15 ° / o phosphorus ............. 8.66 ° / o 8.63% hydroxyl groups ...... 9.5 ° / 0 8, 74 ° / 0 Example 3 Preparation of the dihydroxyphenyl ester of di (2-ethylhexyl) dithiophosphinic acid It was prepared in a known manner from 2-ethylhexyl chloride (594 g, 4 mol), magnesium turnings (97.2 g, 4 mol) and a catalytically active amount (5 g) of ethyl bromide in anhydrous ether.

This Grignard solution slowly became a suspension with stirring of phosphorus pentasulfide (222 g, 1 mole) in absolute ether, so that the mixture was kept at a low boil by the heat of reaction. After everything is added the mixture was refluxed for 1 hour and at room temperature for 4 hours stirred further and then extracted with an ice-water-ammonium chloride solution, which was acidified with hydrochloric acid after a short time. The organic layer was separated, washed with water, dried over anhydrous magnesium sulfate and filtered. Part of the ether was reduced from the filtrate at room temperature Pressure (about 100 mm Hg) removed, allowing a gentle stream of nitrogen through the solution was passed through to promote the removal of the ether. The back in the piston permanent Liquid weighed 1200 g, had an acid number of 98, and was essentially pure Di- (2-ethylhexyl) dithiophosphinic acid (2.1 mol) in ethereal solution.

The dithiophosphinic acid thus produced slowly became p-quinone (226 g, 2.1 mol) added so that the reaction mixture without external heat supply simmered slightly. When the addition was complete, the mixture became 1/2 hour at approximately 50 ° C stirred.

The purification by washing and extraction with sodium hydroxide solution was made then carried out in the same manner as in Example 2.

The brown viscous liquid that remained in the still weighed 260 g and consisted essentially of pure dihydroxyphenyl ester of di- (2-ethylhexyl) dithiophosphinic acid, as the analysis shows: Analysis: Calculated Found sulfur .............. 14.87 ° / o 13.0 ° / o phosphorus ............. 7.21% 7.31 "/.

Hydroxyl groups ...... 7.91 "/ o 6.18 ° / 0 Example 4 Preparation of sec-octyl ester of di- (4-methylsec-amyl) dithiophosphinic acid 4-Methyl-sec-amylmagnesium chloride was prepared in a known manner from (CH3) 2CHCH2CHCICH3 (723 g, 6 mol), magnesium turnings (145 g, 6 mol) and a catalytically active amount (5 ml) of ethyl bromide in absolute ether.

This Grignard reagent slowly became a suspension with stirring of phosphorus pentasulfide (333 g, 1.5 mol) was added in absolute atlier so that the Mixture boiled moderately due to the heat of reaction. After everything was added the mixture was gently refluxed for 21/2 hours and then extracted with an aqueous solution of ammonium chloride, which after a short time with Hydrochloric acid was acidified. The organic layer was separated with water washed, dried over anhydrous magnesium sulfate and filtered. The ethereal Solvent was removed from the filtrate by distillation at 100 ° C and 30 mm Hg pressure removed. The substance remaining in the flask was taken up in benzene, washed with dilute hydrochloric acid and then with water and at 95 ° C and Distilled 45 mm Hg pressure to remove the benzene.

The greasy green liquid that was left in the still weighed 440 g, had an acid number of 207 and was essentially pure di- (4-methylsec-amyl) dithiophosphinic acid.

A portion of the acid so produced (200 g, 0.75 mol) was with a Excess of n-octene-1 (169 g, 1.5 mol) mixed and the mixture under reflux (125 to 132 ° C) stirred until the acid number is essentially constant Value had declined.

This took 12 hours; during this time the acid number fell from an initial value of 112 to a final value of 62.

The reaction mixture was washed with an aqueous solution of sodium bicarbonate washed to remove unreacted dithiophosphinic acid. The organic Layer was then separated and distilled at 100 ° C and 25 mm Hg pressure to remove unreacted n-octene-1.

The greasy brown liquid that remained in the still weighed 95 g. It was essentially pure octyl ester of di- (4-methyl-sec-amyl) -dithiophosphinic acid.

Analysis: Calculated Found sulfur .............. 16.9% 15.6% phosphorus ............. 8s2% 7 , 77% acid number 12 Example 5 Preparation of the tert-butyl ester of diphenyldithiophosphinic acid A solution of 50 g of diphenyldithiophosphinic acid in 200 ml of benzene was prepared and this was heated to reflux. Gaseous isobutylene was passed into this boiling solution for 10 hours; after this time the acid number was reduced to 11.

The solution was then concentrated and the remaining liquid Poured into 10% aqueous sodium bicarbonate solution. The precipitate was filtered off and the solid substance is recrystallized from naphtha, whereby 30 g of a compound with a melting point of 90 to 92 ° C were obtained. The mixed melting point of this Product with an authentic sample of tert-butyl diphenyldithiophosphinate was 91 to 92 ° C.

Example 6 Preparation of the p-hydroxyphenylisopropyl ester of diphenyldithiophosphinic acid To prepare this ester, 67 g (0.5 mol) of p-allylphenol and 125 g (0.5 mol) of diphenyldithiophosphinic acid were stirred together at 100 ° C. for 8 hours. The result was a brown viscous liquid which had the following analytical values: Calculated Found sulfur .............. 16.7% / 0 15.8% phosphorus ........ ..... 8.1 ° / o 7.7 ° / 0 Example 7 Preparation of the oc-pinene ester of diphenyldithiophosphinic acid There were 272 g (2.0 mol) -pinene and 125 g (0.5 mol) diphenyldithiophosphinic acid for 5 hours stirred together for a long time at 110 to 167 ° C. The product obtained was then heated to 200 ° C. at 20 mm Hg pressure in order to remove excess pinene. The distillation residue weighed 200 g.

He presented an oily liquid with the following analytical values dar: Calculated Found sulfur .............. 16.5 ° / o 16.7 ° / o phosphorus ............. 8.0 ° / o 7.4 ° / o saponification number ........ 145 145 The advantages, which are in the Technique in applying the new ones made by the method of the invention Products are obtained from the comparative comparison of known dithiophosphoric acids and the dithiophosphinic acid esters can be seen according to the process of the invention.

The investigation was based on the following products: 1. Dithiophosphinic acid ester according to the method of the invention: 2. Phosphoric dithiophosphate Both products were heated to temperatures between 200 and 250 ° C to check their respective thermal stability. The dithiophosphoric acid ester decomposed almost instantaneously, while the dithiophosphinic acid ester remained unchanged after 18 hours at the same temperature. Due to the similarly shifting rates of decomposition of these products at lower temperatures, it can be seen that the compounds which can be prepared by the process of the invention are particularly thermally stable, which is the case with lubricant additives A copper strip was then placed in each of the two samples in order to promote oxidation; the samples were then held at a temperature of 149 ° C. for 231 hours. After 96, 120, 144, 160, 190 and 231 hours, the viscosities of the two samples were measured according to the USA standard, ie in Saybolt seconds at 37.8 ° C. (SUS / 100 ° F), and compared with one another. The result of these measurements is summarized in the following table: Encore Time sample 1 sample 2 lao ester 11% ester II Hour viscosity viscosity (SUS 37.8 ° C) (SUS 37.8 ° C) 0 448452 96 535 539 120 623 614 144 700 647 160 818 639 190 1065 656 231 1715 694 The comparison shows that the viscosity of the oil to which the known dithiophosphinic ester I had been added had increased by 290% after 231 hours, while the increase in the same oil to which the dithiophosphinic ester II prepared according to the invention had been added in the at the same time and under the same conditions was only 54%.

It can be seen that the decrease in viscosity increase and the increase in resistance to oxidation, as is the case with the corresponding oils Application of the according to the method of the invention and also with plasticizers, for example in weldable plastics, is essential.

Others using those made by the method of the invention New compounds achievable advantages are from the following comparative tests evident.

Of two samples of a mineral oil of 300 g each, the first was mixed with 3 g of a diphenyldithiophosphinic acid ester of the formula I and the second with likewise 3 g of a diphenylthiolphosphinic acid ester of the formula II. produced novel connections is possible, brings significant advantages in technology. The very strong increase in viscosity when the known ester I is used as a lubricant additive under the same test conditions shows that the lubricant has undergone substantial degradation with the formation of oxidation products. Such disadvantages are eliminated by using the new products as produced by the process of the invention.

Claims (1)

PATENT CLAIM: Process for the preparation of dithiophosphinic acid esters, characterized in that a dithiophosphinic acid of the general formula is used in which R and R 'are optionally branched alkyl radicals with up to 8 carbon atoms or the phenyl radical, with monoolefins which may optionally be substituted by the carbalkoxy or hydroxyphenyl group, with pinenes or with quinone in approximately equimolar amounts, optionally in organic inert solvents at about 40 to 250 ° C, in particular at 100 to 110 ° C, is reacted. Publications considered: German Patent No. 851 237; Chemisches Zentralblatt, 1953, I, p. 1792; Journal of the American chemical Society, 74, 1952, pp. 161 to 163.