SU729200A1 - Method of inhibiting styrene thermal polymerization - Google Patents

Description

one

The invention relates to a method of inhibiting the thermal polymerization of styrene and is aimed at improving the technology for the isolation and purification of styrene, which is produced by multi-stage distillation.

Styrene is one of the most important monomers for the production of synthetic rubber and is widely used in the chemical industry, for example, jp for the production of polystyrene, styrene copolymers and styrene butadiene rubber.

The main industrial method for separating styrene from unreacted ethylbenzene, light by-products, 5 (benzene, toluene) and high-boiling impurities in the method of producing styrene used in the technique by catalytic dehydration of ethylbenzene at high temperatures is a multi-access method for rectification. However, this method, especially at the stage of separation of styrene and ethnylbenzene, components with a similar boiling point (145 and 136 C, respectively)

This has a significant disadvantage, which is the spontaneous (thermal) polymerization of the monomer, which leads to the precipitation of difficult-to-remove polymers in the heat exchange apparatus and on the plates of the distillation columns, and is -1s mn m loss of styrene.

There is a method of inhibiting the thermopolymerization of styrene when it is isolated by the method of rectification in the presence of hydroquinone 1.

However, at high temperatures, this inhibitor is not sufficiently effective and does not prevent the equipment from being driven by the polymer. Thus, in the process of distillation of styrene at the temperature of the bottom of the 8--90 90 column in the presence of O, 3-0.5% of the hydrolumine, 3% of the bottoms remain, which consist mainly of styrene polymers. In addition, hydroquinone is boundedly soluble in styrene, which causes an uneven distribution of the inhibitor in the reaction mass, complicates the technology and the achievement of the required inhibitor concentration.

The known method of inhibiting thermal polymerization of styrene by introducing into it, as an inhibitor, a mixture of peat wax and sodium nitrite with a weight ratio of 1; 0.01-1) 1: 0.1, respectively, taken in an amount of OD0, 5% by weight of monomer { ,

However, this mixture does not effectively inhibit the thermopolymerization of styrene.

The closest technical solution is the method of bending the thermal polymerization of styrene by introducing into it the cyclohexyl1 inhibitor and oxroxamum in an amount of 0.01 "OD% by weight

However, this inhibitor also has a relatively low inhibitory activity, which leads to clogging of equipment.

The purpose of the invention is to increase the efficiency of inhibition and prevent the clogging of equipment.

This is achieved by hem, that 0, O5-O, 5% by weight of styrene 2,4-dinitrophenylhydryzine or 1,3-diphenylcarbohydrazide is used as an inhibitor in the thermal polymerization of styrene, tab. Table 1 shows the comparative data of the proposed and known inhibitors, taken in an amount of 0.5 wt.%.

Table 1

Cyclohexylhydroxylamine A mixture of peat wax and nit- Example 1, In glass; Ampoules with a capacity of 5O ml, pre-washed with alcohol and dried with purified nitrogen, are introduced with 30 ml just before polymerization of distilled styrene with a concentration of the main substance of 99.7-99.8% and 0.0134 g ( monomer) hydroquinone, 2,4-di-nitrophenylhydrazine and diphenylcarbazide, respectively. The ampoules are sealed and shaken in a silicone bath, where they are kept at a temperature of 110 ° C for 15 hours. After tempering the polymer. Each vial is precipitated with methyl alcohol and centrifuged (2500 rpm) for 2O minutes. After decantation, the solvent is removed from the polymer by evacuating to constant weight. The amount of polymer per monomer loaded is 52.5% by weight with the use of hydroquinone and the average molecular weight of the resulting polymer No. 279900. the corresponding data is 21.15% and 82400; 25.48% and 207 Ltd.

12O4D Example 2, Raw styrene containing 18.6% ethylbenzene is fed to a continuous distillation column. Productivity of a column is 1,0 l / hour. The residual pressure of the top of the column is not more than 15 mm Hg "Art. The temperature of the bottom of the column is 90-95 ° C. The reflux number is 10 ° C. The upper part of the column is taken off by ethyl benzene vapor pairs, and the styrene pairs are taken off as a side fraction. In order to prevent the polymer from rectifying the distillation column, styrene distillation is carried out in the presence of 2,4-dinitrophenylhydrazine, which is introduced with food in the form of a monomer solution at a rate of 0.5% of the total mass of styrene fed to the rectification. The content of 2,4-dinitrophenylhydrazine is monitored by its concentration in the bottom of the column. Opening the column after 52OO hours of continuous operation showed that the apparatus was not filled with polymers and styrene products. Example 3. The distillation of styrene was carried out analogously to example 2, with the only difference being that the release of monomer was carried out in the presence of 1,5-diphenyl carbohydraend in an amount of 0.3% relative to styrene. Polymer ester does not occur. By virtue of its highly effective inhibitory action against radical chain reactions 2,4-dinitroph 1 ILGidraein and diphenyl Hydroquinone

2,4-Dinitrophenylhydrazine 1,5-D and phenylcarbohydrazide

The possibility of avoiding the clogging of the processing equipment with a polymer in the presence of styrene in the presence of 2,4-di-nitrophenylhydrazine or 1,5-diphenylcarbohydrazide is due to the fact that these inhibitors, together with the manifestation of high inhibitory efficiency, form the molecular weight regulators of the polymer and in their presence VII thermal polymerization of styrene

Hydroquinone

2,4-.Dinitrophenylhydrazine

1,5-Diphenylcarbohydrazide

The use of 2,4-dinitrophenylhydrazine and diphenylcarbazide as an inhibitor of the thermopolymerization of styrene when it is isolated by distillation makes it possible to reduce the losses of styrene to form poorly soluble polymeric compounds by 1.5 to 2 times, to prevent clogging of the equipment and thereby improve the equipment utilization rate, and also to improve economic indicators of styrene production in general.

Thus, the invention makes it possible to affectively inhibit the thermal polymerization process of styrene and prevent equipment clogging. 72

3.99 25.69 67.9 O 29.99 134.3 183.2 1.05 1.21 3.45 7.57 11.61 14.93 0.43 9.75 23.27 21.16 89.74 125 ,9

proceeds with the formation of low molecular weight oligomeric reaction products, which, by virtue of their good solubility, are removed together with the bottom residue (Table 3).

; in tab. 3 shows the dependence of the mole, in, lIoLicidal concentration and the nature of the inhibitor during 15 hours.

Table 3

279.90 201.50 183.2О 134.30 128.5О

82.41 19.72 18.24 11.61 15.24

207.00 145.90 99.31 89.74 9.84

DETAILED DESCRIPTION OF THE INVENTION The method is inhibited by thermally polymeric lnmervacin styrene by introducing an inhibitor thereto, characterized in that, in order to increase the effectiveness of inhibiting equipment prevention, the O, 05-O, 5% by weight of styrene 2,4-dinitrophenylhydrazine is used as an inhibitor or 1,5-Aifen Sharbargdraz Ida.

Sources of information taken into account in the examination

1. Production of styrene and inhibition. its spontaneous polymerization, M., ShIITEneftekhim, 1974, p. 45-47, 006 to rbazide, significantly suppress the development of the process of thermal polymerization of styrene even with prolonged tempering. Dependence of the amount of the formed polymer and its mol. at. on the nature of the inhibitor in tempering styrene at llOtC, the inhibitor concentration is 0.3% veCo%) "Table 2

: 77292008

2. USSR author's certificate3. US Patent No. 3287430,

No. 569581, cl. C 08 F 2/42, Cl, 26O-666.5, published. 1966 (proto 1974. Type).

Claims (2)

SUMMARY OF THE INVENTION A method for inhibiting the thermal polymerization of styrene by introducing an inhibitor into it, characterized in that, in order to increase the efficiency of inhibition and prevent clogging of equipment, 0.05-0.5% by weight of styrene is used as an inhibitor 2,4-dinitrophenidhydrazine or 1,5-diphenylcarbohydrazide.