Method for preparing frothing polystyrene

FIELD: polymers, chemical technology.

SUBSTANCE: invention describes a method for preparing frothing polystyrene by polymerization of styrene for two stages. At the first stage forpolymerization is carried out in the presence of antipyrene, a chain growth regulator, benzoyl peroxide as a polymerization initiating agent. At the second stage the suspension polymerization is carried out in aqueous medium in the presence of polyvinyl alcohol as a stabilizing agent, chain growth regulator, tert.-butylperbenzoate as initiating agent and frothing agent. The forpolymerization stage is carried out in the presence of water and dicumyl peroxide as antipyrene synergist is added additionally, and O,O-tert.-myl-O-(2-hexyl)-monoperoxycarbonate is used a additional initiating agent in the following ratio of components relatively to styrene mass, %: benzoyl peroxide : O,O-tert.-myl-O-(2-hexyl)-monoperoxycarbonate : tert.-butylperbenzoate = (0.24-0.25):(0.04-0.06):(0.04-0.10), respectively. Method provides intensification of the styrene polymerization process, improvement of granulometric composition of preparing polystyrene and reducing specific energy consumptions in manufacturing frothing polymer granules.

EFFECT: improved preparing method.

3 ex

 

The invention relates to petrochemistry, namely the production technology of polymeric materials, and can be used in the manufacture of expandable polystyrene used for the manufacture of foam for insulation boards, packaging, electronic equipment, etc.

A method of obtaining expandable polystyrene by multistage block-suspension polymerization, consisting of raw material preparation, terpolymerization of styrene in bulk, suspension of the prepolymer in the aqueous solution of the stabilizer - thin suspension of tricalcium phosphate, the final polymerization with the introduction of the blowing agent is isopentane, pressed pellet in the centrifuge, drying the pellets in a stream of hot air, sieving and packaging of the finished product [encyclopedia of polymers, vol with. 567-571, M., 1977].

The disadvantage of this method is the use of polymerization initiators at the stage of terpolymerization and final polymerization with substantially different temperature settings decomposition of peroxides, which in the conditions of the reactor even under vigorous stirring leads to local overheating of the reaction mixture with getting polydisperse by DFID polystyrene and the transition process in an unsupervised mode, may result in the formation of cross-linked polymer ("goat").

The closest in technical essence and the achievement of UEMOA effect is a method for expandable polystyrene by multistage block-suspension polymerization, consisting of raw material preparation, terpolymerization of styrene in bulk in the presence of the initiator is benzoyl peroxide, flame retardant - hexabromocyclododecane flame retardant synergist - peroxide of Dicumyl, growth regulator circuit - dimer of alpha-methylstyrene, suspension of the prepolymer in the aqueous solution of the stabilizer is polyvinyl alcohol, the final polymerization using as an initiator of tertbutylbenzene, growth regulator circuit - dimer of alpha-methylstyrene, calcium chloride, calcium carbonate, and with the introduction of the blowing agent is isopentane, pressed pellet in the centrifuge, drying the pellets in a stream of hot air, sieving and packaging of the finished product [Technology of plastics. Edited HAK, M., Chemistry, 1976, S].

The disadvantage of the prototype is a relatively large length of the process, relatively low production, which leads to increased energy costs, and unstable particle size distribution of the obtained polystyrene (high polydispersity of the polymer by DFID).

The aim of the invention is to improve particle size distribution of the obtained polystyrene, the intensification of the process of polymerization of the styrene and the decrease of specific energy consumption for the production of granules of expandable polymer.

This objective is achieved in that the act is both receiving expandable polystyrene by multistage block-suspension polymerization, consisting of raw material preparation, terpolymerization of styrene in bulk in the presence of a polymerization initiator, a flame retardant synergist of the flame retardant and growth regulator circuit, the suspension of the prepolymer in the aqueous solution of the stabilizer is polyvinyl alcohol, the final polymerization in the presence of a polymerization initiator and growth regulator circuit with the introduction of the blowing agent is isopentane, pressed pellet in the centrifuge, drying the granules, sieving and packaging of the finished product, the process of terpolymerization and final polymerization of styrene is carried out by using a three-component mixture of initiators, allowing to intensify the process with a simultaneous decrease in the amplitude of temperature fluctuations due to the smoothing of ekzotermicheskie process. The components of the initiator mixture of different temperature parameters of decomposition that allows you to gently raise the temperature of the reaction mixture. For this stage terpolymerization loaded the polymerization initiator is benzoyl peroxide, and optionally enter the initiator O,O-treamill-O-(2-hexyl)-nonoperational ("Luperox TAEC"); at the final stage of polymerization is loaded initiator of tertbutylbenzene. This somewhat reduces the consumption of the initiator of tertbutylbenzene, and the total consumption of the initiators in the polymerization process remains the I within the previous loading quantity and the cost. The proposed three-component mixture of peroxide polymerization initiators can significantly increase the rate of polymerization of styrene and avoid local overheating of the reaction mixture with simultaneous reduction of the spread of the mold, providing a more uniform particle size and a higher physical and mechanical properties of the obtained foam (Flexural strength, residual deformation and the like), without additional modernization of reactor-polymerizate, and as a result, significantly reduce the time of the polymerization process (about 5 hours).

The proposed method was implemented on an industrial reactor and it is illustrated by the following examples.

Obtaining foaming polystyrol PSV-NE-NM-15, 20, TG, MD, PSV-S.

Example 1. In the reactor container 11 m3download demineralized water in a quantity of 2500 l, styrene in the amount of 4900 l include a mixer (40 rpm) and load the polymerization initiator is benzoyl peroxide in the amount of 11.2 kg, calculated on the anhydrous initiator, the flame retardant hexabromocyclododecane (32.2 kg in two doses on 16,1 kg to avoid the formation of lumps), the synergist of the flame retardant - peroxide Dicumyl (9,0 kg) and growth regulator circuit - dimer α-methylstyrene (0.5 l), and 50 kg of dust polystyrene marks MD and the polymerization initiator - Oh,Oh-tratame Is-o-(2-hexyl)-nonoperational in the amount of 2.0 kg The mass is homogenized using a mixer for 20-30 minutes, after which the rotation speed of the agitator is reduced to 30 rpm and produce purging with nitrogen, and, at a residual pressure of 0.5 MPa, the reaction mass is heated to 84-86°C for 1-1 .5 hours. After 1.5-2 hours after the temperature specified and subsequently every 20 minutes determine the viscosity of the polymer and the conversion of monomer to achieve the degree of conversion ˜37-42% (2-2 .5 hours). After the desired degree of conversion of terpolymerization styrene complete, reduce speed of mixer until 26 rpm, load 0.5 l dimer α-methylstyrene and dosed 2600-2700 l of a solution of the stabilizer is polyvinyl alcohol (PVA) concentration of 0.33-0.34 percent PVA and a solution of calcium chloride in the solution of PVA concentration to 1.3-1.4% CaCl2in the amount of 10 kg and produce the dispersion of the mass. (The speed mixers vary to provide the necessary particle size distribution of beads in the range of 0.9-2.3 mm with a visual quality control breakdown.) After loading solution of PVA with a stable breakdown adds to align pH (not less than 5.5) up to 0.5 kg of calcium carbonate. Add initiator - tertbutylbenzene - 4.7 kg, the reactor sealed, provide positive pressure of nitrogen to a pressure of 2.5 MPa and 15 minutes for 0.5 hours injected foaming agent - isopen is in an amount of 500 l at a temperature of 50± 2°and the reaction mass is heated for 30-40 minutes until the 80±2°C and maintained at this temperature for 5 hours to implement the suspension polymerization. After this time the reaction mixture is heated to 85°C for 0.5 hour and incubated for 0.5 hour, after which the temperature was raised to 115°C and maintained at this temperature for 4.5 hours. Upon completion of the polymerization, the suspension is cooled to 40°and the pulp through the sieve is pumped into a buffer tank, after which the granules squeeze in a centrifuge and subjected to drying in a stream of air (up to 7000 m3/hour) in the fluidized bed apparatus with capacity up to 2 tons of pellets per hour for 0.5 hours at a temperature of supplied air 20°to a moisture content of granules from 0.6 to 1.5%, because when humidity <0.6% of the granules begin to accumulate static electricity.

Example 2 (the prototype). In the reactor container 11 m3download demineralized water in a quantity of 2500 l, styrene in the amount of 5000 l include a mixer (40 rpm) and load the polymerization initiator is benzoyl peroxide in the amount of 11.5 kg, calculated on the anhydrous initiator, the flame retardant hexabromocyclododecane (32.2 kg in two doses on 16,1 kg to avoid the formation of lumps), the synergist of the flame retardant - peroxide Dicumyl (9,0 kg) and growth regulator circuit - dimer α-methylstyrene - 0,5 L. MA is su homogenized using a mixer for 20-30 minutes, then the rotation speed of the agitator is reduced to 30 rpm and produce purging with nitrogen, and, at a residual pressure of 0.5 MPa, the reaction mass is heated to 85±2°C for 1-1 .5 hours. After 1.5-2 hours after the temperature specified and subsequently every 20 minutes determine the viscosity of the polymer and the conversion of monomer to achieve the degree of conversion ˜37-42% (2-2 .5 hours). If agreed conversion and viscosity of 10-15 is loaded with 0.5 l of dimer α-methylstyrene, reduce speed of mixer until 26 rpm, and dosed 2600-2700 l of a solution of the stabilizer is polyvinyl alcohol (PVA) concentration of 0.33-0.34 percent PVA and a solution of calcium chloride in the solution of PVA concentration to 1.3-1.4% CaCl2in the amount of 10 kg and produce the dispersion of the mass. (The speed mixers vary to provide the necessary particle size distribution of beads in the range of 0.9-2.3 mm with a visual quality control breakdown.) After loading solution of PVA with a stable breakdown adds to align pH (not less than 5.5) up to 0.5 kg of calcium carbonate. Add the initiator of tertbutylbenzene in the amount of 7.9 kg, the reactor sealed, provide positive pressure of nitrogen to a pressure of 2.5 MPa and 15 minutes for 0.5 hours injected foaming agent is isopentane in the amount of 500 liters at a temperature of 50±2°and the reaction mass is heated for 30-40 mi the ut up to 80± 2°C and maintained at this temperature for 5 hours to implement the suspension polymerization. After this time the reaction mixture is heated to 85°C for 0.5 hour and incubated for 0.5 hour, after which the temperature was raised to 115°C and maintained at this temperature for 4.5 hours. Upon completion of the polymerization, the suspension is cooled to 40°and the pulp through the sieve is pumped into a buffer tank, after which the granules squeeze in a centrifuge and subjected to drying in a stream of air (up to 7000 m3/hour) in the fluidized bed apparatus with capacity up to 2 tons of pellets per hour for 0.5 hours at a temperature of supplied air 20°to a moisture content of granules from 0.6 to 1.5%, because when humidity <0.6% of the granules begin to accumulate static electricity.

Analysis of temperature-time dependence of the polymerization process under the terms of the prototype (dashed curve) shows that the use of two-component system of the initiators of the prototype restricts access to the process temperature 80°C, resulting in a longer time of polymerization on the current stage of the process up to 5 hours and, in order to avoid transfer polymerization process in unmanaged mode, allows to achieve a 0.5-hour exposure at a temperature of 85°only after these 5 hours before increasing the tempo of atory process to 115° When comes the stage of maturation of the polymer (the duration of which is 4.5 hours). Carrying out suspension polymerization in two stages at lower temperatures 80 and 115°With (unlike 85 and 120°when the three-component mixture of initiators) to achieve the required characteristics of the polymer leads to an overall lengthening of the polymerization process to 25.5 hours, i.e. for 4.5 hours.

Example 3. Perform all operations as in example 1 with the difference that at the stage of terpolymerization download benzoyl peroxide in the amount of 11.5 kg, and O-treamill-O-(2-hexyl)-nonoperational in the amount of 3.0 kg; suspension polymerization initiator, tertbutylbenzene load in the amount of 2.0 kg

The total curing time is 21 hours.

Granulometric composition obtained by the proposed method polystyrene has a high uniformity and getting after sieving the main fraction of granules with a size of 0.4-2.8 mm with the release of 96-100%.

Thus, the application of the proposed system of peroxide initiators consisting of three components: benzoyl peroxide, O-treamill-O-(2-hexyl)-monoperoxyphthalate and tertbutylbenzene, different temperature intervals decomposition, can improve the controllability of the polymerization of styrene to intensify this breadboard is th process and reduce the time to obtain pellets of expandable polystyrene 4.5 hours, to improve the particle size distribution of the obtained polymer.

Thus, the application of the proposed system of peroxide initiators consisting of three components: benzoyl peroxide, O-treamill-O-(2-hexyl)-monoperoxyphthalate and tertbutylbenzene, different temperature intervals decomposition allows to:

1) to optimize the MMD obtained polymer;

2) to improve the controllability of the polymerization of styrene;

3) to intensify this process;

4) reduce the time to obtain pellets of expandable polystyrene 4.5 hours;

5) to improve the particle size distribution of the obtained polymer.

The proposed method is introduced in production in the shop polystyrene JSC ASP and allows only by increasing the intensity of production to increase the production of expandable polystyrene in 2 tonnes/year, which will provide additional income in current prices in the range of 10 million/year.

The method of obtaining expandable polystyrene by the polymerization of styrene in two stages, first perform terpolymerization in the presence of a flame retardant, a growth regulator circuit, benzoyl peroxide as a polymerization initiator, and subsequent suspension polymerization in the second stage in an aqueous medium in the presence of the stabilizer of polyvinyl alcohol, reg is the centre of growth of the chain, tertbutylbenzene as an initiator, a blowing agent, characterized in that the stage of terpolymerization carried out in the presence of water, optionally enter a synergist anticrossing - peroxide Dicumyl and as an additional initiator O,O-Trammel-O-(2-hexyl)-nonoperational in the following ratios by weight of styrene, %: benzoyl peroxide : O,O-Trammel-O-(2-hexyl)-nonoperational : tertbutylbenzene equal 0,24-0,25 : 0,04-0,06 : 0,04-0,10 respectively.



 

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3 ex

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