DEK0025732MA - - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

Registration date: May 5, 1955. Advertised on June 28, 1956

GERMAN PATENT OFFICE

PATENT APPLICATION

CLASS 39c GROUP 30 K 25732 IVb / 39c

Dr. Herbert Jenkner, Hanover-Wülfel

has been named as the inventor

Kali-Chemie Aktiengesellschaft, Hanover

Process for the alkylation of organopolysiloxanes

. It has been found that organopolysiloxanes can be alkylated with aluminum alkyl compounds by heating. In this way, high molecular weight organopolysiloxanes can be converted into lower molecular weight but more highly alkylated organopolysiloxanes. Compounds of the formula (RSiO ₁₁₆ ) ^ or (R ₂ SiO) _x or mixtures or copolymers thereof can be used as organopolysiloxanes, where R z. B. alkyl, aryl and aralkyl. Particularly suitable aluminum alkyl compounds are aluminum trialkyls, but also aluminum trialkyl etherates, aluminum alkyl halides, alkyl aluminum alcoholates, in short all compounds which contain at least one Al-alkyl bond. 15th

Schematically, this reaction can be expressed, for example, as follows:

(R ₂ SiO) _x + AIR'3 _n

-> R ₂ R'Si0 (R ₂ Si O) _X - ₁ A1R ' ₂ ^W

or ^ao

3 (R ₂ SiO) _x + A1R ' ₈ -> [R ₂ R'SiO (SiR ₂ 0) _x _j] ₃ Al

where R and R 'have the meanings given above and can be identical or different and χ 25 is an integer greater than 2. The organoaluminum

(2)

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K 25732 IVb / 39c

In general, the connection causes the otherwise stable Si - O - Si bond to be broken down, where Al - O- next to new Si - C bonds can be obtained.

In the first stage of the reaction, alkylaluminium silicoalkoxides are formed from which through further alkylation (i.e. by breaking Si - O - Si bonds) lower molecular weight, higher alkylated Organopolysiloxanes are obtained.

ίο If, for example, octamethylcyclotetrasiloxane (where χ = 4) is treated with aluminum trialkyl, the reaction initially preferably proceeds according to the following equation:

AlR ₃ + [Si (CH ₃ ) ₂ O] ₄ ..

¹ S → Al R ₂ O [Si (CH ₃ ) ₂ O] ₃ Si R (CH ₃ ) ₂ ^w;

wherein the corresponding alkyl aluminum silico alcoholate arises.

From the reaction product of equation (3) can by further addition of octamethylcyclotetrasiloxane the pure aluminum silico alcoholate of the formula

AL {O [Si (CH ₃ ) ₂ O] ₃ Si (CH ₃ ) ₂ R} ₃

can be obtained. Like all aluminum alcoholates, these alcoholates are easily hydrolytically cleavable, and siloxanes with twice the number of Si atoms per molecule _{are obtained (in addition to Al (OH) 8) by condensation of the silanols formed.} Organopolysiloxanes containing trialkylsilyl end groups have thus arisen from the cyclic organopolysiloxanes. If, on the other hand, you work with excess AlR ₃ according to equation (3), a further breakup of Si - O - Si bonds takes place, e.g. B. after the following

, Equation:

AlR ₂ O [Si (CH ₃ ) ₂ O] ₃ SiR (CH ₃ ) ₂ + AlR ₃

^ (AlR ₂ O) ₂ Si (CH ₃ ), (4)

+ SiR (CH ₃ ) ₂ OSi (CH ₃ ) ₂ OSi (CH ₃ ) ₂ R.

According to the above equation (4), the lower molecular weight, higher alkylated ones mentioned at the outset are obtained Organopolysiloxanes that can be distilled off while by hydrolysis of the residue remaining Alkylaluminiumsilicoalkoholates higher molecular weight polysiloxanes with the same degree of alkylation remain. By varying the ratio of organopolysiloxane to organoaluminum compound you have it in hand, the linear, cyclic or crosslinked organopolysiloxanes (or their Mixtures) contain Si - O - Si bonds predominantly or only partially blown open.

If organopolysiloxanes of the formula (RSiO ₁ , ^ are alkylated, the reactions via the stage of the diorganosubstituted polysiloxanes proceed in basically the same way.

In general, the reaction can be carried out at temperatures up to about 250 ^° C. without solvents, without catalysts and at normal pressure. In some cases it can be advantageous to use higher pressure, solvents and catalysts such as e.g. B.

Boron alkyls, zinc alkyls, cadmium alkyls, zinc haloalkyls, to be used in the reaction.

If the alkyl aluminum compound contains other bonds in addition to Al - C bonds, such as B. halogen bonds in the alkylaluminum halides, in addition to new Si - C- also arise Si-halogen bonds, so that a variety of Variation results.

example 1

978 parts by weight of a dimethylpolysiloxane having a boiling. _{0, 01} over 200 ° (oil bath) were mixed with a total of 464 parts by weight of aluminum triethyl. After 5 hours of heating at 170 ° was 45 ° / _0, 77% of the overflowed Aluminiumtriäthyls used in the reaction for further 8 hours to 190 ^0th

The reaction mixture was then poured into dilute HCl, extracted with ether, the ethereal layer washed, then dried with sodium sulfate and distilled. After removal of the ether, the following fractions were obtained: bp ₂₁ to 93 ⁰ 34%, bp ₂₁ 95 to 115 ⁰ 17%, bp ₁₇ 115 to 150 ⁰ 32 _{%, bp 17} 150 to 18o ° 10%, Kp. ₁₇ 180 to .205 ° 5% ,. Residue 2%.

Total yield 960 parts by weight. 98% of the used High molecular weight dimethylpolysiloxanes were thus converted into lower molecular weight ethylmethylpolysiloxanes (or silanols) transferred.

Example 2

465 parts by weight of a mixture of hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane (bp. ₁₂ 60 to 70 ^{0 ) were heated to 220 to 250 0 for} 7 hours with a total of 240 parts by weight of aluminum triethyl. About 84% of the Aluminiumtriäthyls used were reacted after this time, approximately 6 ° / ₀ of the Aluminiumtriäthyls used were thermally decomposed during this time.

The reaction mixture was then distilled without hydrolyzing. 32 parts by weight passed between bp ₁₂ 50 to 115 ⁰ ; the residue contained the aluminum silico alcoholates formed (35 parts by weight) which, at room temperature, were a light yellow, easily hydrolytically cleavable resin.

Example 3

105

48.5 parts by weight of methylpolysiloxane (R Si O ₁₁ J) _9., Made of Natriummethylsiliconatlösung) of 2 hours, then _ mixed with a total of 190 parts by weight of triethylaluminum with stirring at 200 ⁰ in vacuo and dried. At 140 to 110.160 °, the J emerged within 35 minutes

initially viscous pulp an easily mobile, still cloudy liquid. To complete the reaction, the mixture was heated ^{to 170 to 175 0 for a further 12 hours.} Work-up was carried out as in Example 1. 55 parts by weight of liquid polysiloxane were obtained, which passed over at bp ₁₄ between 60 and 80 °.

Example 4

A total of 20 parts by weight of aluminum triethyl were added dropwise to 36 parts by weight of an infusible, elastic dimethylpolysiloxane gel at 150 ^{° (oil bath).} After 30 minutes the gel was already completely liquefied. It was still heated to 160 ° for 6 hours. The conversion, based on the aluminum triethyl used, was after

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6 hours more than 85 ° / _o ig. Working up was carried according to example I. Obtained was the following groups:. ₁₈ Kp below 35 ⁰ 14%, 35 to 45% ⁰ 15, ⁰ 65 to 95 24% 95-140 ⁰ 47 ° / _0.

Claims (3)

PATENT CLAIMS: i. A process for the alkylation of organopolysiloxanes, characterized in that aluminum alkyls are reacted with linear, cyclic or crosslinked organopolysiloxanes by heating at temperatures up to about 250 ⁰ C. 2. The method according to claim i, characterized in that that the reaction product with water and / or acids or water and / or alkalis is decomposed and the resulting organopolysiloxanes extracted with organic solvents will. 3. The method according to claim 1 and 2, characterized in that the reaction is in the presence is carried out by catalysts and / or solvents or at elevated pressure. © 609 547/558 6.56