RU2462484C1 - Polymethyl(phenetyl)siloxanes for heat-resistant materials - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to polysiloxanes which can be used as heat-resistant materials in different industries. Polymethyl(phenetyl)siloxanes of general formula (I)

where n=100-1000, are disclosed. Said compounds are obtained via hydrolytic polycondensation of methyl(phenetyl)dichlorosilane with potassium hydroxide solution (KOH), followed by neutralisation of the hydrolysate and condensation thereof with hexamethylcyclotrisilazane at 100-150°C for 6-10 hours.

EFFECT: disclosed polymers have high heat resistance and good reproducibility of thermophysical properties.

1 cl, 1 tbl, 4 ex

Description

The invention relates to new compounds, namely to polymethyl (phenethyl) siloxanes of the formula 1:

where n = 100 ÷ 10000,

which can be used as the basis for heat-resistant materials intended for use in aviation and space technology, in special mechanical engineering and radio electronics. It should be noted that siloxane rubbers with a high content of phenylsiloxane units have high radiation resistance.

Known polydimethyldiphenylsiloxane polymer of the General formula:

where x = 1500 ÷ 2000. n / m = 1,

obtained by hydrolytic copolycondensation of a solution of dimethyldichlorosilane and diphenyldichlorosilane in toluene with a mixture of water and acetone, followed by condensation of the cohydrolyzate with heating. Merril D.F. Pat. U.S. 4085084, 1978 (Gen. El. Corp.).

Such a polymer has good heat resistance, but the temperature of the onset of decomposition is only 300 ° C. In addition, according to [Istvan Benedek "Pressure-sensitive adhesives and applications", Marcei Dekker, Inc., USA, 2nd edition, 2004, 170 pages, total 747 pages], the glass transition temperature of such polymers is -20 ° C , which significantly reduces the temperature range of operation of products based on them.

The closest analogue to the intended purpose is the polymethylphenylsiloxane polymer of the general formula:

where n = 300 ÷ 400 obtained by hydrolytic polycondensation of methylphenyl dichlorosilane followed by condensation of the resulting α, ω-hydroxyoligomethylphenylsiloxanes with α, ω-bis- (tripropylmethylphosphonium) methylphenylsiloxanolates (K. Andrianov, A.I., Nogaideli A.I. vol. 222, p. 1339-1342).

The temperature range of operation of products from this polymer is from -65 to 300 ° C.

According to the authors of this application, the temperature of the onset of decomposition of poly (methylphenyl) siloxane is 300 ° C, which limits their scope. In addition, poor reproducibility of properties is a serious drawback for the polydimethyl (methylphenyl) siloxane polymer. This is explained by the fact that methylphenyldichlorosilane, used as the initial monomer, as a rule, contains an impurity, for example phenyltrichlorosilane, which leads to the creation of rubbers with poor reproducibility of properties. The process of cleaning this impurity is technologically very complicated, small deviations lead to large losses of the product (CN 1880320, 12.20.2006. Hangzhow Teacher College).

The objective of this technical solution is the creation of polymers, which along with increased heat resistance have good reproducibility of properties.

The goal is solved by the synthesis of polymethyl (phenethyl) siloxanes of the general formula I:

where n = 100 ÷ 10000.

The specified compound is obtained by hydrolytic polycondensation of methyl (phenethyl) dichlorosilane with 20% ÷ 30% potassium alkali (KOH) solution, followed by neutralization and washing of the hydrolyzate, which is then condensed with hexamethylcyclotrisilazane at 100 ÷ 150 ° C for 6 ÷ 10 hours.

The number average molecular weight of the polymers is determined by gel chromatography. The structure and composition of the links are confirmed by the method. ¹ H NMR and ²⁹ Si.

Heat resistance is determined by thermogravimetric analysis on a GTA-6000 device from Perkin Elmer. The weight of the samples is 12-20 mg, the heating rate is 10 deg / min in the range from 40 ° to 600 ° C.

The invention is illustrated by the following examples.

Example 1

Stage 7. In a three-necked flask with a capacity of 1 l, equipped with a mechanical stirrer, dropping funnel and reflux condenser, place 228.3 g of a separately prepared 30% potassium hydroxide solution and start supplying 97.2 ml of methyl (phenethyl) dichlorosilane so so that the temperature of the reaction mixture does not exceed 50 ° C. At the end of the feed, the layers are separated, the organic layer is diluted with chloroform, washed with water, a 3% hydrochloric acid solution, again with water until the pH of the aqueous extract of the neutral reaction is reached.

The chloroform solution of α, ω-hydroxyoligomethyl (phenethyl) siloxane is transferred to the distillation system and chloroform is first distilled off at atmospheric pressure, then vacuum is turned on and volatiles are distilled off at a temperature of 200 ° C and a pressure of 2 mm Hg. Art.

Stage 2. In a three-necked flask with a capacity of 0.5 l, equipped with a mechanical stirrer and reflux condenser, place 27 g of the obtained α, ω-hydroxyoligomethyl (phenethyl) siloxane and 1 ml of hexamethylcyclotrisilazane and the oligomers are condensed for 6 hours at a temperature of 150 ° C until polymer. At the end of the polymerization, the polymer is evacuated for 2 hours at 230 ° C and a pressure of 15 mm Hg. Obtain 26 g of polymethyl (phenethyl) siloxane, which according to NMR ¹ H and ²⁹ Si corresponds to the formula I, where m = 100. Yield 94%.

Example 2. According to the method described in example 1, from 250.0 g of a separately prepared 20% solution of potassium hydroxide and 95 ml of methyl (phenethyl) dichlorosilane using 0.8 ml of hexamethylcyclotrisilazane at 140 ° C. for 10 hours, 26 , 1 g of polymethyl (phenethyl) siloxane, which according to NMR ¹ H and ²⁹ Si corresponds to the formula I, where m = 1000. Yield 93.4%.

Example 3 According to the procedure described in example 1, from 245.0 g of a separately prepared 25% solution of potassium hydroxide and 92.0 ml of methyl (phenethyl) dichlorosilane using 0.6 ml of hexamethylcyclotrisilazane at 100 ° C for 7 hours receive 26.2 g of polymethyl (phenethyl) siloxane, which according to NMR ¹ H and ²⁹ Si corresponds to the formula I, where m = 5000. Yield 92.8%.

Example 4. According to the method described in example 1, from 228.0 g of a separately prepared 25% solution of potassium hydroxide and 97.0 ml of methyl (phenethyl) dichlorosilane using 0.4 ml of hexamethylcyclotrisilazane at 150 ° C for 8 hours 26.1 g of polymethyl (phenethyl) siloxane are obtained, which according to NMR ¹ H and ²⁹ Si corresponds to formula I, where m = 10000. Yield 93%.

Example No. 1 was reproduced 10 times. The prototype example was reproduced ten times. The properties of the obtained polymers are shown in table 1.

As can be seen from the data in table 1, the proposed polymers have not only high heat resistance, but also good reproducibility of thermophysical properties.

Table 1 Polymethyl (phenethyl) -siloxane τ ₀ τ ₁₀ Polymethyl-phenylsiloxane τ ₀ τ ₁₀ 10-1 379 433 10-1 313 353 10-2 382 430 10-2 300 320 10-3 377 435 10-3 270 340 10-4 380 436 10-4 291 335 10-5 385 435 10-5 283 341 10-6 382 436 10-6 320 358 10-7 377 431 10-7 302 337 10-8 379 438 10-8 260 318 10-9 384 429 10-9 304 321 10-10 376 428 10-10 316 364 τ ₀ - temperature of the beginning of decomposition, ° С. τ ₁₀ - temperature loss of 10% of the mass, ° C.

Claims (1)

Polymethyl (phenethyl) siloxanes of the formula

where n = 100 ÷ 10000, for heat-resistant materials.