DE1208890B - Process for the preparation of organosiloxanes or halogenorganosiloxanes - Google Patents

Description

Process for the preparation of organosiloxanes or halogenorganosiloxanes When organosiloxanes are produced from halosilanes by hydrolysis as a by-product of hydrogen halide, which is split off in the presence of water of acid-sensitive groups, for example phenyl residues. These Appearance is extremely undesirable in the production of high polymer organosiloxanes, such as B. in the production of phenylmethylsiloxanes. Because then it arises some monomethylsiloxane units, which are already in a concentration of 0.04 to 0.08 mole percent (cf.

"Analytical Chemistry", Vol. 20, p. 706) leads to undesired gel formation being able to lead.

It is recommended according to British Patent Specification 606 301 been, alkylhalosilanes under anhydrous conditions with a metal oxide the I. or II. Group of the periodic table, optionally in the presence of an inert To implement solvent. However, it has been shown that when using the in this patent specified solvents, namely diethyl ether and petroleum ether, in a completely dry state and with the use of hydrogen halide-free silanes aliphatic radicals the yields of organosiloxanes are very unsatisfactory.

What is claimed is a process for the production of organosiloxanes or halogenorganosiloxanes by reacting silanes or mixtures of silanes of the formula RnSiX4-n RnSIX4-n (R = alkyl, aryl, alkaryl or halogenated aryl radical or hydrogen; X = halogen; n = 1 to 3) with lead, calcium, magnesium, zinc or copper oxide using liquid, saturated aliphatic or aromatic Nitriles or liquid saturated aliphatic or aromatic nitro compounds in an amount of at least 1 percent by weight (based on the silane) as inert Solvents, which is characterized in that all reagents used are free from hydrogen chloride and water.

Because water and hydrogen chloride cause the conversion of silanes to siloxanes able to catalyze even in traces, are those by the inventive method advances made over that of British Patent Specification 606 301 surprised. These advances consist of shorter response times and better ones Exploit.

The inventive method also allows the production of Organosiloxanes, which are normally difficult to obtain by mixed hydrolysis.

If the halosilane is reacted with such an amount of metal oxide that there is at least 1 equivalent of metal oxide for 1 equivalent of halogen in the silane, organosiloxanes are obtained as reaction products. However, if less than 1 equivalent of metal oxide per equivalent of silicon-bonded halogen is used, and n has a value of less than 3, a haloorganosiloxane is obtained, e.g. B. a connection of the basic structure: So if the formation of a haloorganosiloxane is desired, one sets z. B. 1 mole of R2SiX2 with less than 1 mole of CaO, or 1 mole of RSiX3 with less than 11/2 moles of CaO.

But if a non-chlorinated organosiloxane is to be obtained, then becomes 1 mole R2SiX2 with at least 1 mole metal oxide and 1 mole R3SiX with at least 1/2 mole of metal oxide implemented. It is useful here that the amount of metal oxide 1 to 10% larger than the theoretical amount. A considerable excess of oxide does not affect the reaction, but has no particular advantage either.

Any silane can be used for the reaction, at least a radical (R) and a halogen atom, both on silicon. R can be a hydrogen atom, any alkyl or Aryl radical or a halogenated aryl hydrocarbon radical be. Suitable silanes are, for example: trichlorosilane, dichlorosilane, methyldichlorosilane, Dimethylfluorosilane, octadecyldichlorosilane, trifluorotolyltrichlorosilane, bis - trifluorotolyldichlorosilane, Chlorophenylmethyldichlorosilane, xenylitrichlorosilane and bromoxenyltrichlorosilane.

Any saturated aliphatic or aromatic nitrile and any saturated aliphatic or aromatic nitro compound that is liquid is favored the reaction between the halosilanes and - the metal oxides mentioned and can accordingly can be used as a solvent. Any in excess of 1 percent by weight Amount of solvent can be used without adversely affecting the reaction will. However, there is generally no benefit if more than a twofold Excess weight of solvents is used.

Solvents which can be used for the reaction are, for. B. acetonitrile, Propionitrile, butyronitrile, valeronitrile, benzonitrile, cyclohexyl nitrile, capronitrile, Nitromethane, nitroethane, nitropropane, nitrooctane, nitrobenzene, nitrotoluene and nitrocyclohexane.

The process according to the invention can not only be used for production of polymeric uniform organosiloxanes, but also for the production of Use copolymers. So you get z. B. by reacting bis-trifluoromethylphenyldichlorosilane with. Dimethyldichlorosilane is a copolymer made from these substances. Such copolymers are very difficult to produce by hydrolysis.

It is often useful to use a small amount of CuC12 or To use HgCI2 in the implementation in order to accelerate the reaction.

As a result, the same yield can be obtained in a shorter time. In general, the amount of catalyst is 0.1 to 2 g per mole of halosilane, however, it can be varied as desired.

Example 1 There were four three-necked flasks with stirrers and reflux condensers used and designated as pistons A, B, C and D. Flasks B and D were with Thermometers fitted with heating jackets to flasks A and C. The flasks were as follows filled: I. Flasks A and B according to the invention: 70 g redistilled acetonitrile, 62 g technical zinc oxide, dried overnight at 150 "C in the oven 60 g dimethyldichlorosilane (CH3) 2SiC12, 40 g (N31 mole percent) methylphenyldichlorosilane CH3 (C6H5) SiCl2.

II. Operation according to British patent specification 606 301 piston C and D: 70 g petroleum ether, dried with CaH2, boiling range 45 to 50 "C, 62 g technical Zinc oxide, dried in the oven at 150 "C overnight, 60 g dimethyldichlorosilane (CH3) 2SiC12, 40 g methylphenyldichlorosilane CH3 (C6H5) SiC12.

The addition of the chlorosilanes to flasks A and B had to be done during one A period of 15 minutes must be carried out, since when touching the chlorosilanes and the mixture of acetonitrile and zinc oxide in the flask reacted immediately.

Flasks B and D were not heated, but the temperature of the reaction mixture was recorded for approximately 21/4 hours. The following temperature table resulted for pistons B and D: Time temperature temperature Hours iMin. Piston B piston D ° C ° C 0 25 25 (All Silane added) 107 73 27 / 15 75 32 (All Silane added) / 30 75 ~ 34 / 45 45 33.5 1/15 31.5 28 1/30 30 27 2/00 27 25 2/15 27 25 It turns out that the reaction in flask B was exothermic and so violent that a gradual addition of the chlorosilanes was necessary. Flask D barely noticeable conversion took place, and the temperature rise was a maximum of about 9 "C compared to about 50" C in flask B.

The reactants in flasks A and C were simultaneously Stirring heated under reflux for 41/4 hours. The piston C had to have a significantly larger one Amount of heat can be supplied to maintain the reflux.

The contents of flasks A, B, C and D were at room temperature (approx 25 "C) stored overnight (15.5 hours). The samples were continued with petroleum ether diluted that was dried over C2H2 to allow filtration. The reaction mass was filtered in each case, the flasks were rinsed with petroleum ether, and the for Rinsing petroleum ether was used to wash the solids in the suction filters used. Samples A, B, C and D were then placed in 500 cc stills, which were connected to simple stills, condensers and templates. The temperature each flask was brought to 165 "C, leaving solvent and unreacted Dimethyldichlorosilane (boiling point 69.6 "C) were removed. Any unreacted Methylphenyldichlorosilane does not go over because - it only boils at 205 "C. That reaction product remaining after distillation was weighed. There were get the following values: piston A ... 51.3 g piston C ... 34.7 g piston B. . 61.0 g flask. . 41.0 g portions of the samples were then titrated with alcoholic KOH to determine the amount of the existing not to determine converted methylphenyldichlorosilane. The percentage of chlorine found was as follows: Flask A. practically OO / o Piston B. . .. 1; 370/0 piston C .. .320 / 0 piston. . ..29.50 / 0 The chlorine content of the sample provides the following for the amount of unreacted methylphenyldichlorosilane Values: piston A ..... practically OO / o piston B. . .. 3,690 / 0 piston C .. .86,20 / 0 Piston D. . .. 79.50 / o The yield of siloxane copolymers was: Flask A ... 81.50 / o piston C ... 7.60 / o piston B. . 93.5 ° / o piston D. . 13,3 ° / o each one of the samples was a real mixed polymer, which is evident from the homogeneity of the product was recognizable. Separately prepared methylphenylsiloxane is with dimethylsiloxane incompatible, and if there were no interpolymer, a cloudy-looking or get multiphase product.

The comparative tests clearly demonstrate that when used acetonitrile converts silanes into siloxanes in high yields, regardless of whether the process is carried out without heating or under reflux conditions.

When using petroleum ether, however, is both at room temperature as well as under reflux, the yield is completely unsatisfactory.

Example 2 In a three-necked flask with a reflux condenser, thermometer, The dropping funnel and stirrer were made from 122 g (1.5 mol) of zinc oxide (technical; 5 days at 150C oven dried) and 300 g of redistilled acetonitrile a slurry prepares.

A mixture of 116.1 g (0.9 mole) dimethyldichlorosilane and 19.1 g (0.1 mol) phenylmethyldichlorosilane was added dropwise from a dropping funnel during is introduced into the flask over a period of 1.25 hours. The addition of the chlorosilanes had to be done slowly as the reaction with the slurry of zinc oxide and acetonitrile is exothermic.

The reaction mixture was refluxed for about 5 hours and then left to stand overnight at room temperature. By subsequent filtration The reaction mass of solid zinc chloride, unreacted, was above the suction filter Zinc oxide and part of the acetonitrile-zinc chloride complex freed. With four times The flask was rinsed out 50 ml of toluene and the solid was washed. From the The filtrate was not acetonitrile for 8 hours in a water pump vacuum converted dimethyldichlorosilane and most of the toluene present expelled and collected in a cold trap. This resulted in 276 g of solvent, the 0.20 / o Contained unreacted chlorosilanes. The residue was diluted again with toluene, filtered and freed from solvent in a high vacuum.

The latter stages are required to remove the Acetonitrile zinc chloride complex, which is somewhat soluble in acetonitrile.

The product became commercially available under the name "Super Cel" Filter aid sucked and thereby by removing the last traces of cyclic Phenylmethylsiloxane and / or acetonitrile zinc chloride complex clarified.

The yield consisted of 57.5 g (71.8% of theory) of copolymer Organosiloxane of 159cSt / 25 "C with less than 0.050 / 0 unreacted chlorosilanes.

Example 3 The procedure described in Example 2 was repeated without reflux, but the acetonitrile was replaced by 300 g of redistilled nitroethane (a further 100 g were added during the reaction). The following time-temperature relationships resulted: Time, minutes temperature; ° C 28 3 34 5 39 8 49 (Silane dropping funnel closed and 100 g of nitroethane added) 18 42 25 51 30th 35 62 40 69 45 78 50 79 60 79 70 79 (Addition finished) 75 75 100 51 115 42 220 29 The reaction product was freed from volatile constituents. The solvent that had passed over did not contain any unreacted chlorosilanes.

There were 43 g of product (53.70 / 0) of a copolymer of one viscosity of 88.9 cSt / 25 "C, which was free of unreacted chlorosilanes.

Example 4 To a. Mixture of 0.1 mol refluxed Bis-trifluorotolyldichlorosilane, (FsCCsH4) 2SiCl2, and 20 cc of acetonitrile are added a mixture of 0.103 mol of PbO and 0.1 g of CuC12 in portions. The reaction mixture is then refluxed for 3 days, then filtered and heated to 320 "C at 1 mm heated. After removing the solvent, a viscous, non-volatile one is obtained Residue representing bis-trifluorotolylsiloxane [(F3CC6H4) 2SiO] z.

1 mol of PbO is covered with acetonitrile and 1 g of CuC12 is added. This The mixture is heated to reflux. A mixture of 0.44 mol of bis-trifluorotolyldichlorosilane is then left and 0.24 mol of dimethyldichlorosilane slowly drop onto the oxide. The addition of the chlorides takes place in the course of 2 hours. The mixture is then taken for a further 4 hours Maintained reflux, then filtered and the filtrate at a temperature up to 262 "C at less than 1 mm pressure. The distillate obtained is cyclic Organosiloxanes, the copolymers3 or bis-trifluorotolylsiloxane and dimethylsiloxane represent.

All reagents used according to the above examples were used according to methods known per se are carefully dried or of hydrogen chloride before they are used freed. So was z. B. acetonitrile, as in "Organic Syntheses, Collective Volume 2, New York, 1950, p. 523, Note 2 ", indicated, each distilled over phosphorus pentoxide. The silanes were obtained by distillation from columns of strong reflux of hydrogen chloride freed.

Claims (1)

Claim: Process for the production of organosiloxanes or Halogenorganosiloxanes by reacting silanes or mixtures of silanes Formula R, SiX4-n Rn SiX4-n (R = alkyl, aryl, alkaryl or halogenated aryl radical or hydrogen; X = halogen; n = 1 to 3) with lead, calcium, magnesium, or zinc Copper oxide using liquid, saturated aliphatic or aromatic Nitriles or liquid saturated aliphatic or aromatic nitro compounds in an amount of at least 1 percent by weight (based on the silane) as inert Solvents that do not indicate that all are used Reagents are free from hydrogen chloride and water. ~~~~~~~ Considered References: British Patent No. 606 301.