DD246303A1 - METHOD FOR CONTINUOUS POLYMERIZATION OF VINYL GROUP-CONTAINING MONOMERERS - Google Patents

Abstract

Process for the continuous polymerization of monomers containing vinyl groups for the preparation of polymers in bulk or in the presence of solvents in one or more polymerization reactors with incomplete monomer conversion with condensation and continuous reuse of the monomers or monomer / solvent mixtures recovered from the polymerization reactors or degassing units in admixture with newly used, not yet included in the polymerization process monomers or monomer / solvent mixtures. The aim of the invention is to improve the economics of the preparation of homo-, co- or graft polymers by continuous bulk polymerization without deterioration of the quality of the polymers. In this case, until the steady state conditions are reached, the cycle ratio is the quotient of the monomers or monomer / solvent mixture amounts reused in the mass or bulk / solution polymerization process and the total recovered or monomer / reaction product (s) in process step (s). Solvent mixture amounts set in a defined range.

Description

Field of application of the invention

The invention relates to a process for the continuous polymerization of vinyl-containing monomers for the preparation of polymers in bulk or in the presence of solvents in one or more polymerization with incomplete monomer conversion with condensation and continuous reuse of the recovered from the polymerization or degassing monomers or monomer / solvent mixtures.

The invention is advantageously applicable for starting up continuous processes for the preparation of homo-, co- and graft polymers in a particularly economical procedure.

Characteristic of the known technical solutions

In the preparation of polymers by continuous polymerization in bulk or in the presence of solvents with incomplete monomer conversion are various methods for reuse of the recovered from the polymerization or degassing monomers or monomer / solvent mixtures together with newly used, not yet included in the polymerization process or monomers Monomer solvent mixtures known.

For this purpose, processes are known in which the recovered monomers or monomer / solvent mixtures are subjected to a cleaning operation before reuse (DE 1720304, DE 1770664, DE 3102780). Disadvantage of this method is that the total amount of the recovered monomers or monomer / solvent mixtures must be worked up by additional process steps. These process steps (e.g., distillation) are very energy intensive and often need to be repeated several times due to the composition of the mixtures.

Furthermore, processes are known in which the monomers or monomer / solvent mixtures recovered from the polymer are added directly to the starting monomer mixture after the condensation and intermediate storage (DE 2063602, DE 2240294, DE 2439341, DE 3026973, US 2745824). However, these methods have the disadvantage that due to the uncontrolled recycling of the recovered monomers or monomer / solvent mixtures, due to the thus caused constant enrichment of existing in the monomers or solvents in small amounts impurities, the quality of the polymers z. B. is negatively affected in terms of yellowing or molecular weight.

Furthermore, a process is known (WP C 08 F / 278656-2) in which the monomers or monomer / solvent mixtures recovered in the work-up process of the polymer are added to the newly used monomers or monomer / solvent mixtures in such a way that the amount of polymer used in the starting mixture Contaminants remain constant. A disadvantage of this method is that in the process of startup with reuse of the recovered monomers or monomer / solvent mixtures to reach the constancy of the concentration of impurities, a large amount of monomers or monomer / solvent mixtures by premature circling of the non-reusable fraction of Monomers or monomer / solvent mixtures is lost. This is particularly disadvantageous because this process requires very long setup times according to the method.

Object of the invention. , ,

The aim of the invention is to improve the economics of the preparation of homo-, co- or graft polymers by continuous bulk polymerization without deteriorating the quality of the polymers.

Explanation of the essence of the invention

- The technical task ',

The object of the invention is to develop a process for the continuous polymerization of monomers containing vinyl groups for the preparation of homopolymers, copolymers or graft polymers by reusing the recovered monomers or monomer / solvent mixtures with greatly improved economy without impairing the quality of the polymers.

Features of the invention

The object is achieved in that until the achievement of steady state conditions, the cycle ratio as a quotient of the in the process of mass or mass / solution polymerization reused monomers or monomer / solvent mixture amounts and in the (the) corresponding process stage e (η) total resulting recovered monomers or monomer / solvent mixture amounts in the range of 0.9 to 1 is set.

embodiments Example 1 (comparative example)

A mixture of the monomers styrene and acrylonitrile was reacted in the presence of ethylbenzene solvent from a continuous polymerization unit consisting of monomer-Z solvent mixture metering section, polymerization reactor, demonomerization unit and monomer-Z mixture mixture recoverer according to the conditions given in Tables 1 to 3 (Explanation and Ex Description of the symbols see page 12) at a temperature in the polymerization reactor of 446 K and a stirrer speed of 1.7s ^-1 and at a temperature in the Entmonomerisierungseinrichtung of 508K thermally polymerized while maintaining a polymer mass fraction at the outlet of the polymerization reactor of 0.6. It was dispensed with the re-use of recovered by condensation monomer ZLösungsmittelgemische. Styreneacrylonitrile copolymers whose most important properties are listed in Table 4 were obtained by this process.

Example 2 (comparative example)

In this example, the conditions described in Example 1 and in Tables 1 to 3 were carried out analogously. The objective was to add the recovered monomer / solvent mixtures to the monomers and solvents not yet used in the polymerization process so that the steady-state cycle ratio under steady-state operating conditions after the start-up phase of reuse of the monomer / solvent mixtures was reached.

is adjusted so that 12.5 mass% of the total recovered monomer-Z solvent mixture is removed. For this purpose, the conditions in the start-up phase were designed according to the usual procedure so that the circulation ratio in the start-up phase

X =

has already been set to the value of 0.875 from the beginning.

Example 3

The conditions of the procedure were chosen according to Example 2 and Tables 1 to 3. However, the process of start-up was carried out so that the total amount of the recovered monomer-Z solvent mixture (X = 1) again together with new monomers and solvents in the polymerization process until reaching the target maximum amount of impurities (in Table 2 as ratio [Υν, ηΖΥ ?] ² ) was used. As from the table

2, a total of 20.0 kg of monomers and less solvent were required by this inventive method compared to the Betspiel 2. Furthermore, the desired stationary maximum amount of impurities could be achieved much faster. The properties of the resulting styrene-acrylonitrile copolymers were, as Table 4 shows, compared to those of Example 1 by the start-up process is not adversely affected.

Example 4 (Comparative Example)

In the polymerization unit given in Example, the monomers were used as described in Tables 1 to

3 reacted at a temperature of 452 K in the polymerization reactor at a stirrer speed of 1.7s ~ ¹ and a temperature of 468K in the Entmonomerisierungseinrichtung up to a polymer mass fraction of 0.6 at the exit of the polymerization reactor. The start-up process of the reuse of the recovered monomer-Z solvent mixtures was carried out analogously to Example 2 by immediately setting the final circulation ^ratio (X ^ISTATl ) of 0.8. The results are shown in Table 2.

Example 5

The polymerization was carried out analogously to the recipe and operating parameters of Example 4. The starting process was inventively designed so that only 2Ma ₁ - ⁰ A of the total recovered monomer ZLösungsmittelgemisches were removed. As shown by the results in Tables 1 to 3, this process of starting the reuse of the recovered monomer solvent mixtures over Example 4 saved 48.1 kg of monomers and solvents and the targeted steady state maximum amount of impurities much faster without degrading the properties the styrene-acrylonitrile copolymers are achieved.

Table 1 Mass flows of Examples 1 to 5 in the start-up phase.

example X (STAT). m ^E m ^p _m RM X m ^AK m ^K m ° kg / h kg / h kg / h kg / h kg / h kg / h 1 O 5.0 3.0 2.0 0 2.0 0 5.0 2 0.875 5.0 3.0 2.0 0.875 0.25 1.75 3.25 3 0.875 5.0 3.0 2.0 1 0 2.0 3.0 4 0.8 6.67 4.0 2.67 0.8 0.534 2,136 4,534 CJI 0.8 6.67 4.0 2.67 0.98 0.053 2,617 4,053

Table 2 Conditions for the start-up phase of Examples 1 to 5 (n-number of cycles, tn-time duration for one cycle)

example ri tn _m AK (n) [Υν.η / Υ?] ^Ζ Υξ, η / Υ? H kg 1 - "" - - - 2 8th 10 20.0 5.2 3.7 3 8th 10 0 5.2 5.2 4 5 20 53.4 3.4 2.5 5 5 20 5.3 3.4 3.38

Table 3 Composition of the mass flows of Examples 1 to 5

Example Yf ₇ Y _AN Y | _B Y§ ¥. ΥαΉ Y ^ YIt YXn YI

ib

1 0,665 0.285 0.05 0.612 0.263 0,125 0,665 0.285 0.05 2 0,665 0.285 0.05 0.612 0.263 0,125 0.693 0.297 0.01 3 0,665 0.285 0.05 ' 0.612 0,263 " 0,125 0.70 0.30 0 4 , 0.7125 0.2375 0.05 0.659 .0,216 0,125 0.738 0.247 0,015 5 0.7125 0.2375 0.05 0.659 0,216 0,125 0.749 0.25 0.01

Table 4 Properties of styrene-acrylonitrile copolymers

property

Unit of measurement

example 1

K value according to Fikent melt index; 473 K; 21.6 kp (TGL 25 244) Impact bending strength (TGL 14068) Notched impact strength (TGL 14068) Ball pressure hardness (TGL 20 924) Optical properties: Layer thickness

Light transmission (at 545 nm) yellowing (at 420 and 680 nm)

Example 3

60.0 60.9 g / 10min 15.0 14.7 kJ / m ² 30.1 28.8 kJ / m ² 1.6 1.7 N / mm ² 158 154 mm 2.1 1.9 ·% 88.0 85.8 % 18.4 15.7

Figure 1 cycle mode

TT ¹ IImI Eeaktor ! Y ^P * " V Y ⁰ ι \ γ * "

Explanations: m - mass flow Y - mass break Indices above: O - beginning E - entrance P - product RM - back monomer AK - Circled K - circulation Indices below: ST - styrene AN - acrylonitrile EB - Ethyibenzen V - pollution

Claims (1)

Invention claim: Process for the continuous polymerization of monomers containing vinyl groups for the preparation of polymers in bulk or in the presence of solvents in one or more polymerization reactors with incomplete monomer conversion under condensation and continuous reuse of the monomers or monomer / solvent mixtures recovered from the polymerization reactors or degassing units in admixture with newly used, monomers or monomer-Z solvent mixtures not yet included in the polymerization process, wherein the ratio of recovered monomers or monomer / solvent mixtures reused in the mass or bulk / solution polymerization process and the recovered monomers or monomer / solvent mixtures to be discharged remains constant, characterized by that until reaching steady state conditions, the cycle ratio as a quotient of the in the process of mass or Masse- / Lösungspol Ymerisation re-used monomers or monomer / Lösungsrnitte! Mixed amounts and in the (the) corresponding process step (s) total accumulating recovered monomers or monomer / solvent mixture amounts in the range of 0.9 to 1 is set.