MXPA00001726A - Process for the preparation of dithiophosphoricpolysulfide mixtures - Google Patents

Abstract

Stable dithiophosphoric acid polysulfide mixtures of formula (I) are prepared by heating the corresponding disulfide compounds (II) with sulfur optionally in the presence of a solvent. Process for preparing dithiophosphoric acid polysulfide mixtures of formula (I):R<1>- R<4>(same or different)=straight or branched 1-18 C alkyl, 1-18 C alkenyl, 5-28 C cycloalkyl, 5-28 C cycloalkenyl, 6-28 C aryl or 7-28 aralkyl n=2.5-3.5 are prepared by heating the dithiophosphoric acid disulfide compound (II):in which R<1>-R<4>are as above, with 0.5-1.5 mol sulfur at temperatures of 100-140 deg C, optionally in the presence of a solvent.

Description

PROCEDURE FOR THE OBTAINING OF MIXTURES OF DIESOPHOSPHORIC ACID POLYSULPHIDE. Field of the invention. The invention relates to a novel process for preparing dithiophosphoric acid polysulphide mixtures from dithiophosphoric acid disulfides. Description of the prior art. The dithiophosphoric acid polysulphides are known, as well as their use as vulcanizing agents or as accelerators for the vulcanization of rubber vulcanization (cf. DE 19 36 694, DE 22 49 090 and DE 44 31 727). The poly-sulphides of dithiophosphoric acid can be prepared from the corresponding dithiophosphoric acids or their alkali metal salts and sulfur chlorides, such as diazufre dichloride or sulfur dichloride. The disadvantage of the reaction of dithiophosphoric acid with sulfur chlorides lies in the high corrosivity of the sulfur chlorides and in their unpleasant odor, which leads to handling problems and makes corresponding, expensive apparatuses necessary. According to EP 0 383 102 Al, the sulfur dichloride is also disproportionate in a very easy manner so that this process does not allow direct access to the dithiophosphoric acid trisulfides. In addition, tetri sulphides of dithiophosphoric acid obtained according to the process described above have a tendency to dissociate sulfur due to their reduced stability. To avoid this, it is necessary to stabilize the tetrachlorides of dithiophosphoric acid against the precipitation of sulfur, as described for example in DE 44 31 727.

REF. : 32673 DETAILED DESCRIPTION OF THE INVENTION The task of the present invention is now to provide a process for the preparation of polysulfide mixtures of dithiophosphoric acid which avoids the use of sulfur chlorides and which leads to mixtures of dithiophosphoric acid polysulfides stable to The object of the invention is therefore a process for obtaining mixtures of polydisols of dithiophosphoric acid of the formula in which R1 to R4 are the same or different and represent an alkyl radical having 1 to 18 carbon atoms straight-chain or branched chain, an alkenyl radical having 1 to 18 carbon atoms, a cycloalkyl radical having 5 to 28 carbon atoms, cycloalkenyl radical with 5 to 28 carbon atoms as well as an aryl radical with 6 to 28 carbon atoms or an aralkyl radical with 7 to 28 carbon atoms and n means numbers of 2.5 to 3.5, characterized in that disulfides of the dithiophosphoric acid of the formula in which R1 to R4 have the meaning indicated above, with 0.5 to 1.5 moles of sulfur, if appropriate in the presence of a solvent, at temperatures of 100 to 140 ° C. The numerical values for n are obtained by means of the statistical determination, which corresponds to the distribution of the sulfur chains in the molecule.

The radicals R.sup.1 to R.sup.4 of the formulas mentioned above may be substituted by suitable radicals which are not detrimental to the subsequent application of the polysulphides, especially alkyl radicals and cycloalkyl radicals. Preference is given to the radicals R.sub.1 to R.sub.4, alkyl radicals having 6 to 12 carbon atoms, especially alkyl radicals having 8 to 12 carbon atoms, especially branched alkyl radicals such as 2-ethylhexyl. Preferably, according to the process of the invention, mixtures of dichlorophosphoric acid polysulphones will be obtained, in which n means numbers from 2.8 to 3.3. The disulfides of dithiophosphoric acid to be used in the process according to the invention are also known and are described, for example, in the Journal of Applied Polymer Science, Vol. 19, pages. 865-877 (1975). The disulfides are obtained, for example, by oxidation of dithiophosphoric acid with hydrogen peroxide or with HOC1 or with a mixture of potassium bromide and hydrogen peroxide. In the process according to the invention, the disulfides used preferably with 0 are reacted, 8 to 1.3 moles of elemental sulfur, with temperatures of 110 to 130 ° C, especially preferably of 120 to 130 ° C being preferred. In the case where the invention is carried out in solution, solvents, especially aliphatic solvents, for example benzine, aromatic solvents, for example toluene, or halogenated aromatic solvents such as chlorobenzene. The solvents can obviously also be used in admixture with one another. The amount of solvent can be easily determined by corresponding pre-tests. Usually amounts of solvent of 0.1 to 50% by weight are used, based on the amount by weight of the disulfide used. It is also possible to add hydrogen peroxide after the reaction according to the invention, in order to prevent any color changes that may occur. In this case, the hydrogen peroxide will be used in amounts of 0.1% to 5% by weight, based on the amount by weight of the disulfide used. Depending on the conditions used for the reaction, the reaction time is approximately 10 minutes to approximately 6 hours. Since the polysulphides of dithiophosphoric acid prepared according to the invention are particularly stable to sulfur, that is to say they have no tendency to form deposits of sulfur crystals, they are especially suitable for use as sulfur-containing agents for the vulcanization of natural rubber. and synthetic, as well as for the vulcanization of latex latex made of natural and synthetic rubber.

Examples Example 1. 999.0 g (2.6179 mol) of diethyl O, O-di-2-ethylhexyldithiophosphate (Cs-DTPS) with an acid number of 147 mg KOH / g and 1.0 g (0.084 g) are placed. moles) of potassium bromide in a flask arranged with an agitator, with dropping funnel, with introduction for gases and with reflux condenser and tempered to Then, 163.2 g (1.4399 moles) of hydrogen peroxide are added dropwise in such a way that the temperature does not increase above 40 ° C ± 5 ° C in this highly exothermic reaction. To accelerate the separation of the phases, 50 g of benzine (80-110) and 10 g of sodium chloride are added and the mixture is allowed to stand at 40 ° C ± 5 ° C, until a clean separation of the phases. The aqueous phase, which is in the lower part, is separated. The cloudy, yellow organic phase is heated to 70 ° C ± 5 ° C, and distilled in a vacuum (20 to 60 mbar). It is then filtered through 1% kieselguhr. For the second stage of the reaction, the charge is blown with nitrogen for 5 minutes. Then 46.1 g (1.4399 moles) of sulfur are added and the reaction mixture is heated to 122 ° C ± 2 ° C to concentrate the sulfur by boiling. The charge is stirred for 4 hours at this temperature. The yellow product can then be packaged without filtration. The product does not show any turbidity or precipitation after several months. The distribution of the chains in the mixture obtained from the polysulfides of dithiophosphoric acid was determined by high pressure liquid chromatography (HPLC) and is composed as follows: n = 1 0.8% n = 4 19.9% n = 7.25%, respectively referred to the surface of the HPLC signals. n = 2 29.2% n = 5 8.1% n = 3 35.5% n = 6 4.4%.

Comparative Example 1. 6,000 g (15 moles) of diethyl O, O-di-2-ethylhexyldithiophosphate (Cg-DTPS) with an acid number of 139.8 mg KOH / g and 300 g of benzene 80-100 are provided. at room temperature. In the course of 1.5 hours, 2,553.2 g of 23.5% sodium hydroxide solution (15.0 moles) were added, bringing the temperature to 45 ° C. Subsequently, it is heated to 55 ° C and then 1003 g (7.4 mol) of S2-CI2 are added dropwise over the course of 5 hours. To complete the reaction, stir for another 30 minutes. The load is then adjusted to pH 7 with approximately 600 g of 8% solution of NaHCOs. To obtain a good separation of the phases, it is heated to 65 ° C and 1,200 g of water are added. After separation of the aqueous phase the product is subjected to initial distillation for 3 hours at 70 ° C under vacuum of the water pump. It is then filtered through a heated pressure filtration nut using a reaction aid. After a few hours the product shows a yellow crystalline precipitation that turns out to be elemental sulfur. Comparative Example 2. 6,000 g (15 moles) of diethyl O.O-di-2-ethylhexyldithiophosphate (C8-DTPS) with an acid number of 139 are placed., 8 mg of KOH / g and 300 g of benzine 80-100 at room temperature. In the course of 1.5 hours, 2,553.2 g of 23.5% sodium hydroxide solution (15.0 moles) were added, bringing the temperature to 45 ° C. It is then heated to 55 ° C to then add, over the course of 5 hours, 1,003 g (7.4 moles) of S2-CI2. To complete the reaction, stirring is continued for another 30 minutes. The load is then adjusted to a pH value of 7 with approximately 600 g of an 8% solution of NaHCO 3. To achieve the separation of the phases, it is heated to 65 ° C and 1,200 g of water are added.

After separation of the phases, 282 g of 2-ethylhexanoic acid and 180 g of zinc oxide are metered in portions at 65 ° C for stabilization against the precipitation of the sulfur. Once the addition is complete, stir for another 2 hours at 70 ° C. For drying, an initial distillation of the product is carried out for 3 hours at 70 ° C under vacuum of the water pump. It is then filtered through a pressure filtration, heated, with the use of an auxiliary filtration agent. After a few days, the product has a yellow crystalline precipitation, which turns out to be elemental sulfur. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (3)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. - Procedure for obtaining mixtures of dithiophosphoric acid polysulfides of the formula wherein R1 to R4 are the same or different and mean an alkyl radical with 1 to 18 carbon atoms straight-chain or branched-chain, an alkenyl radical with 1 to 18 carbon atoms, a cycloalkyl radical with 5 to 28 carbon atoms carbon, a cycloalkenyl radical with 5 to 28 carbon atoms, and also an aryl radical with 6 to 28 carbon atoms or an aralkyl radical with 7 to 28 carbon atoms and n represents a number of 2.5 to 3.5, characterized in that they react disulfides of dithiophosphoric acid of the formula wherein R1 to R4 have the meaning indicated above, with 0.5 to 1.5 moles of sulfur, if appropriate in the presence of a solvent, at temperatures of 100 to 140 ° C.

2. Use of the dithiophosphoric acid polysulphide mixtures prepared according to claim 1, as sulfur dispensers for the vulcanization of natural and synthetic rubber.

3. Use of the dithiophosphoric acid polysulphide mixtures, prepared according to claim 1, as sulfur dispensers in the latex vulcanizate of natural and synthetic rubber latex.