RU2082720C1 - Process for preparing low-molecular weight polybutadiene - Google Patents

Abstract

FIELD: synthetic rubber industry. SUBSTANCE: polymer serves as substrate for manufacturing electroinsulating, anticorrosive coatings as plasticizing additive in the manufacture of tyres and industrial rubber products. Process of polymerization of butadiene-3 is carried out at temperature of 20-80 C by successively adding to toluene 10-50 wt % butadiene - 1.3 in amount of 15-60 moles of 2-ethylhexyl magnesium per 1 ton of monomer and sodium and/or hydrofurfurylate potassium at magnesium to sodium and/or potassium molar ratio from 0.25 to 2.0. Invention makes it possible to prepare low molecular weight polybutadiene having high content of vinyl units within wide range of molecular weights at low amounts of catalytic system components without using organolithium compounds. EFFECT: more efficient preparation process. 1 tbl

Description

 The invention relates to the polymerization of butadiene-1,3 and can be used in the synthetic rubber industry, and the resulting polymer serves as the basis for the manufacture of electrical insulating, anti-corrosion coatings, as a plasticizing additive in the manufacture of tires, rubber products.

Known methods for producing 1,2-polybutadiene by polymerization of butadiene-1,3 in a hydrocarbon medium (including toluene) under the action of combined catalytic systems of n-butyl lithium tetrahydrofurfurylate sodium [1] or potassium [2]
A disadvantage of the known methods is the use of lithium-containing compounds, which determines the need for special local extraction of lithium from water obtained after washing the polymer from the catalyst residues.

Known methods for producing polybutadiene by polymerization of butadiene-1,3 in a hydrocarbon medium in the presence of catalytic systems consisting of alkaline earth metal compounds and alkali metal compounds, for example R ₂ Mg RMgJ or Ba (AlR ₄ ) ₂ ROLi [3]
However, the resulting polybutadiene in the presence of such systems has a predominant 1,4-structure of polymer chains (or 1,4-trans, or 1,4-cis). The content of 1,2 units in this case does not exceed 25% in the case of the use of non-polar solvents.

The closest to the proposed invention in technical essence and the achieved results is a method for producing polybutadiene by polymerization of butadiene-1,3 in an aliphatic or cycloaliphatic hydrocarbon at a temperature of from -30 ^o C to +50 ^o C in the presence of a catalyst containing potassium alcoholate and organomagnesium compound MgR ₂ , where RC ₁ -C ₂₀ with a molar ratio of potassium magnesium 1 1 5 1 and the amount of MgR ₂ in the range of 0.1-20 mol per 100 g of butadiene [4]
The disadvantages of this known method include the production of polybutadiene with a content of 1,4-trans units from 80 to 98% i.e. 1,2 units less than 10% and low system activity.

The aim of the invention is a method for producing polybutadiene having a molecular weight of up to 50 • 10 ³ , containing more than 50% vinyl units without components based on lithium compounds at a high process speed and low catalyst costs.

The essence of the proposed technical solution lies in the fact that the polymerization of butadiene-1,3 is carried out at a temperature of 20-80 ^o C by sequentially introducing butadiene-1,3 in toluene in an amount of 10-50 wt. 2-ethylhexylmagnesium based on 15-60 mol per 1.0 ton of sodium and / or potassium monomer and tetrahydrofurfurylurite based on a molar ratio of magnesium sodium (and / or potassium) from 0.25 to 2.0.

When the polymerization temperature is below 20 ^o C there is a drop in the process speed (quantitative polymer yield is achieved in a few days), and polymerization at a temperature of more than 80 ^o C requires special safety requirements and equipment.

 Limitations on the monomer concentration are associated with environmental feasibility (lower) and process safety conditions, as well as the possibility of secondary gelation reactions (upper).

 When the concentration of organomagnesium compounds is less than 15 mol per 1.0 ton of monomer, the process speed drops sharply. The introduction of more than 60 mol per 1.0 ton of monomer does not lead to significant changes in the properties of the polymer and the efficiency of the system, but requires special washing from the catalyst residues.

 Both the upper and lower limits for the molar ratio of magnesium sodium (and / or potassium) are associated with a sharp decrease in the process speed.

 After the polymerization of butadiene-1,3, an alcohol solution of the antioxidant (agidol-2) in the amount of 0.2-0.4 wt. and then the polymer is isolated by known methods (water degassing, followed by drying in an oven or on hot rollers, a rotary film evaporator, etc.).

динамической вязкости при 50^oC по Хепплеру, микроструктурой.The polymer is characterized by molecular parameters

dynamic viscosity at 50 ^o C according to Heppler, microstructure.

 The absolute values of the process conditions are calculated based on the data presented in the table, which also shows the properties of polybutadiene.

Example 1 (prototype)
0.28 mmol of di-n-butyl magnesium, 0.56 mmol of potassium tert-amylate are added to a solution of 64 g of butadiene in 196 g of n-hexane and polymerization is carried out at 5 ^° C. for 18 hours. The polymer yield is 50%
Example 2 (and further according to the invention)
1045.2 g (1201.4 ml) of toluene and 120 g (193.5 ml) of butadiene are introduced into a metal laboratory reactor with a capacity of 3 l, equipped with devices for loading and unloading reagents, measuring temperature and pressure, a stirrer and a jacket for thermostating. 1,3, toluene solutions of 2-ethylhexyl magnesium (MgR ₂ ) (concentration 0.24 mol / L) at the rate of 60 mol per 1.0 t of monomer and potassium tetrahydrofurfurylate (concentration 0.36 mol / L) based on the molar ratio of magnesium potassium 2.0. The concentration of the mixture is calculated taking into account the solvent supplied with the catalysts (as in other examples).

The process is carried out at a temperature of 20 ± 1 ^o C for 6 hours, the polymer yield is 84 wt.

 Example 3

465.2 g (534.7 ml) of toluene and 500 g (806.5 ml) of butadiene-1.3, toluene solutions of MgR ₂ (concentration 0.75 mol / l) are added to the reactor at the rate of 15 mol per 1.0 t of monomer and sodium tetrahydrofurfurylate (concentration 0.25 mol / l) based on the molar ratio of magnesium sodium 1.0.

The process is carried out at a temperature of 40 ^o C for 5 hours and the polymer yield is 90 wt.

 Example 4

 693.4 g (797.0 ml) of toluene and 300 g (483.9 ml) of butadiene-1.3, toluene solutions of sodium tetrahydrofurfurylate (concentration 0.21 mol / l) and potassium tetrahydrofurfurylate (concentration 0.42) are introduced into the reactor mol / l) with their molar ratio of 1 1, and then 2-ethylhexyl magnesium (concentration of 0.12 mol / l) at the rate of 35 mol per 1.0 t of monomer and the molar ratio of magnesium (sodium + potassium) 0.25.

The process is carried out at a temperature of 80 ^o C for 1 h and the polymer yield is 89 wt.

 Example 5

 878.2 g (1009.4 ml) of toluene and 200 g (322.6 ml) of butadiene-1.3, 2-ethylhexylmagnesium toluene solutions (concentration of 0.2 mol / l) are calculated at a rate of 40 mol per 1, 0 t of monomer and sodium tetrahydrofurfurylate (concentration 0.11 mol / L) based on a molar ratio of magnesium sodium 0.75.

The process is carried out at a temperature of 35 ^o C for 3.5 hours and the polymer yield is 98 wt.

References
1. Aksenov V.I. Zolotareva I.V. Arrest-Yakubovich A.A. Synthesis of low molecular weight 1,2-polybutadiene under the action of the catalytic system of sodium n-butyllithium tetrahydrofurfurylate. Production and use of elastomers. M. TsNIITEneftekhim, 1990, N 3, p. 5-8.

 2. Patent of Russia N 1758042 from 07.19.93, cl. C 08 F 136/06.

 3. Arest-Yakubovich A. A. Alkaline earth metals and their compounds as initiators of anionic polymerization of unsaturated monomers. Advances in Chemistry, 1981, v. 50, No. 6, p. 1141-1165.

 4. US patent N 4225690, CL. C 08 F 4/54, publ. 09/30/80, declared 11/13/78 N 960514 (RZhKhim, 1981, N 9, p. 242P.)

Claims (1)

A method of producing low molecular weight polybutadiene by polymerization of butadiene-1,3 in a hydrocarbon solvent in the presence of a catalytic system consisting of an organic compound of magnesium and an alkali metal alkoxide, characterized in that 2-ethylhexyl magnesium is used as an organic magnesium compound in an amount of 15-60 moles per ton of monomer, as an alkali metal alkoxide used is sodium tetragidrofurfurilat and / or potassium, polymerization is carried out in toluene at 20 80 ^o C by sequentially adding a toluene Utada-10 concentration of 1.3 to 50 wt. 2-ethylhexyl magnesium and alkali metal alkoxide with a molar ratio of magnesium to alkali metal equal to 0.25 2.0.

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