SU422258A1 - Method of obtaining thermoelastic plastics - Google Patents

Abstract

METHOD OF OBTAINING THERMOELAS TOPLASTES by sequential polymerization of vinyl aromatic. and diene monomers, for example, styrene, butadiene and again styrene in their hydrocarbon solutions in the presence of lithium ororganic initiators, in a few minutes, in order to improve the physical and mechanical properties and working properties of the final products, initiators use a mixture of mono- and di-lithium-organic compounds, taken in the ratio 9: 1-7: 3.

Description

one . The invention relates to the synthesis of thermoplastic elastomers, in particular, to the process of producing block copolymers of diene and hydroxy aromatic hydrocarbons, in which the blocks formed by vinyl aromatic hydrocarbons are located at the ends of the polymer chain. Block copolymers of this type, called thermoplastic elastomers, possessing a number of technically valuable properties (high strength in the unvulcanized state, elasticity of frost resistance, and the ability to multiple processing without compromising the original properties) are widely used in manufacturing. rubber technical, electrical insulation and other products, as well as in the production of consumer goods (shoes, toys, etc.). There is a known method for the synthesis of thermal elastomers for the sequential polymerization of vinyl aromatic and diene monomers in their hydrocarbon solutions in the presence of organolithium compounds. According to this method, the copolymerization of divgnyl and styrene is carried out in hydrocarbon solvents in the presence of organolithium compounds of the type RLi, where R is alkyl or aryl, by feeding the monomers in the following sequence; styrene, divinyl, styrene. Thus, the synthesis of block copolymers of type A-B-A (A-styrene 5 B-divinyl) is carried out. However, the thermoplastic elastomers synthesized in a known manner have finer working properties, which make it difficult to process them on the equipment of rubber and plastic plants. The working properties of thermoplastic elastomers should be evaluated by the melt index. The poor working properties of thermoplastic toplasts are mainly associated with their narrow mole; sullary-weight distribution (MBRO, which is generally characteristic of any polymers 5 synthesized in solutions in the presence of organolithium initiators. Conventional ways of improving the working properties by reducing molecular weight or adding low molecular weight in this case, the fractions are unsuitable, since better working properties are accompanied by a decrease in the strength of thermoelastomas and an increase in residual deformation. 8 The purpose of the invention is to develop According to the invention, this goal is achieved by copolymerizing diene and vinyl aromatic hydrocarbons in the presence and initiator, which is a mixture of mono- and dilithium-organic compounds. The use of this initiator allows the formation of materials with good working properties and high physical and mechanical properties. It is not possible to obtain thermoplastic elastomers containing both three- and five-block molecules. The ratio of these structures in the final product is determined by the ratio of mono- and dilithium compounds in the initiator and ranges from 9: 1 to 7: 3. Thus, according to the proposed method, while maintaining the molecular weight, the sizes of the individual blocks are reduced, which leads to an improvement in the working properties. Example 1 In a steel reactor with a capacity of 6 liters, equipped with a stirrer, heating or cooling jacket, pieces: centers for loading components and illuminated with instrumentation, are fed a solution of 100 g of styrene to 4 liters of toluene (in this and in all subsequent examples the solvent and monomers after purification by conventional methods, it is subjected to fine purification by precontact with organolithium compounds). Then, 29 ml of a 0.20 solution of vnestiliutyl in hexane and 9 ml of a 0.22 N solution fall into the reactor. dilithiistilbene. The polymerization of the first portion of styrene is completed in 10 minutes at 35 ° C. After cooling the reactor, 400 g of divinyl is added to it, which is polymerized on the long-lived chains of mono- and dilithium polystyrene. The second stage ends in 2.5-3 hours at 35-45 ° C. At the end of the divinyl polymerization, a second portion of styrene (100 g) is fed to the reactor. 60 minutes after the styrene is supplied, the polymerization is completed and the polymer solution is squeezed through the bottom fitting of the reactor into a container containing 8.0 liters of isopropyl alcohol. The precipitated polymer is washed three times with fresh portions (O5 L) of isopropyl alcohol. The washed polymer for separating traces of the solvent and alcohol rolls 342 s on laboratory fingers heated to 110 ° C and, at the same time, is charged with 1.5% ionol. Polymer yield 590 g. Polymer tests are performed according to test methods according to VTU-38-3 No. A-16-68 for divinyl styrene thermoplastic elastomers. Example 2 The polymerization was carried out under the conditions of Example 1, but as an initiator, 30 ml of 0.2 N solution of v-lithium butyl in hexane and 11 ml of dilithium naphthalene (as a thin suspension in toluene) were introduced into the reactor. Polymer yield 580 g. To obtain experimental data used to compare the properties of thermoplastic elastomers synthesized by the proposed method with the properties of thermoplastic elastomers obtained in a known manner, experiments 3 and 4 were performed under the conditions of examples 1 and 2, but only monolithium were used as the initiator organometallic compounds. Example 3, out of 400 g of divinyl and 200 g of styrene in the presence of 26 ml 0.2 n. 59.5 g of polymer was obtained as a solution of sputyl butyl. Example 4. From 400 g of divinyl and 200 g of styrene in the presence of 37.5 ml of 0.2 N solution of repetid butyl, 599 g of polymer were obtained. The isolation and testing of thermoplastic elastomers is carried out under the conditions of examples 1 and 2. The test results of all four samples of thermoplastic elastomers are tabulated.

Intrinsic viscosity, in benzene at, dl / g

The styrene content, wt.%

Strength at break, kgf / cm

at

at 50 ° C Relative lengthening

1.20 1.17 0.76 1.25 31.5 30.0 32.0 30.5

260

314

300 120 133

Zb

Claims (1)

METHOD FOR PRODUCING THERMOELAS- TOPOLASTS sequential polymerization of vinyl aromatic. and diene monomers, for example, styrene, butadiene and again styrene in their hydrocarbon solutions in the presence of organolithium initiators, which is due to the fact that, in order to improve the physicomechanical properties and working properties of the final products, as initiators, a mixture of mono- and dilithium-organic compounds taken in the ratio 9: 1-7: 3 is used.