Method for separating volatile substances from material mixtures and device for producing polyarylene sulphides

Abstract

The present invention relates to a method for separating volatile substances, particularly iodine, diiodised aromatic compounds and/or mixtures thereof, from material mixtures containing said compounds. The invention further relates to a device for producing polyarylene sulphides, by means of which volatile substances, particularly iodine and diiodised aromatic compounds, can be separated from the polymers.

1 . A method for separating iodine of at least one di-iodized aromatic compound in accordance with the general formula II
   I-A-I  Formula II
   (where A represents a bivalent aromatic radical) and/or mixtures thereof from material mixtures comprising iodine and/or the at least one di-iodized aromatic compound in accordance with the general formula II characterized in that   a) a first part of the iodine, the at least one di-iodized aromatic compound in accordance with the general formula II, and/or the mixture thereof is/are separated at a pressure which is equal to or larger than the pressure which is present at the triple point of iodine; and   b) a second part of the iodine, the di-iodized aromatic compound in accordance with the general formula II, and/or the mixture thereof is/are separated at a pressure which is smaller than the pressure which is present at the triple point of iodine;   wherein in both steps a) and b) the material mixture respectively has temperatures at which at least iodine is present in a gaseous state at the said pressures.   
     
     
         2 . The method in accordance with  claim 1 , wherein the material mixture includes polyarylene sulfides including at least one repeat unit in accordance with the general formula I
   A-S  Formula I
   (where A represents a bivalent aromatic radical) and/or includes prepolymers thereof.   
     
     
         3 . The method in accordance with  claim 1 , wherein the separation is brought about by means of a condensation polymerization reaction in which a compound in accordance with formula II is transformed into a polyarylene sulfide in accordance with the general formula I using a sulfidation agent. 
     
     
         4 . The method in accordance with  claim 3 , wherein the condensation polymerization is carried out in two steps, wherein
 a) in a first step the compound in accordance with the general formula II is brought to a reaction using a sulfidation agent and a prepolymer of the polyarylene sulfide of the general formula I is produced by condensation polymerization; and   b) in a second step subsequent to the first step a condensation polymerization of the prepolymer is carried out,   wherein the separation from the first step takes place at pressures ≧126 mbar (absolute pressure) and from the second step takes place at pressures of <126 mbar (absolute pressure).   
     
     
         5 . The method in accordance with  claim 1 , wherein
 a) the first separated part is supplied to a distillation stage and/or condensation stage and the iodine is liquefied; and   b) the second part is supplied to a desublimation step and the iodine is desublimated.   
     
     
         6 . The method in accordance with  claim 1 , wherein the separation of the first part takes place at
 a) temperatures of the material mixture of 250 to 320° C., preferably of 260 to 285° C.; and/or   b) at pressures of ≧126 to 1200 mbar (absolute pressure) preferably of ≧126 to 500 mbar (absolute pressure), in particular of 130 to 335 mbar (absolute pressure).   
     
     
         7 . The method in accordance with  claim 1 , wherein the separation of the second part takes place at
 a) temperatures of the material mixture of 285 to 320° C., preferably of 290 to 300° C.; and/or   b) at pressures of 0.01 to <126 mbar (absolute pressure), preferably of 0.1 to 50 mbar, in particular of 0.2 to 10 mbar (absolute pressure).   
     
     
         8 . The method in accordance with  claim 1 , wherein
 a) the bivalent aromatic radical A is selected from the group comprising ortho radicals, meta radicals or paraphenyl radicals, biphenyl radicals, in particular p-p′-biphenyl radicals, diphenylether radicals, in particular p-p′-diphenylether radicals, naphthyl radicals and/or benzophenone radicals; and/or   b) the sulfidation agent is selected from the group comprising sulfur and/or alkali sulfides.   
     
     
         9 . An apparatus for producing polyarylene sulfides including at least one repeat unit in accordance with the general formula I
   ≡A-S  Formula I,
   (where A represents a bivalent aromatic radical) produced by condensation polymerization of a di-iodized aromatic compound in accordance with the general formula II
   I-A-I  Formula II
 
   using a sulfidation agent, comprising   a) a precondensation stage comprising an agitating tub or a cascade of agitating tubs composed of a plurality of agitating tubs connected one after the other, wherein the agitating tub and/or the first agitating tub of the cascade of agitating tubs has at least one input possibility for the reactants, and has an outlet for the prepolymer, and downstream of the agitating tub or the cascade of agitating tubs further comprising;   b) a condensation polymerization step comprising at least one condensation polymerization reactor or a cascade of a plurality of condensation polymerization reactors connected one after the other, wherein the condensation polymerization reactor and/or the first condensation polymerization reactor of the cascade of a plurality of condensation polymerization reactors has an input possibility for the prepolymers obtained from the first step and has a output possibility for the polycondensate,   wherein the precondensation stage is connected to the condensation polymerization step via a product line,   characterized in that   the agitating tub or at least one agitating tub of the cascade of agitating tubs has at least one drainage possibility for gaseous side products and/or non-reacted reactants, in particular iodine and/or the compound having the general formula II; and   the condensation polymerization reactor or at least one condensation polymerization reactor of the cascade of condensation polymerization reactors connected one after the other has at least one drainage possibility for gaseous side products and/or non-reacted reactants, in particular iodine and/or the compound of the general formula II.   
     
     
         10 . The apparatus in accordance with  claim 9 , wherein the at least one drainage possibility opens into a condensation apparatus and/or a distillation column for the separation by distillation of the gaseous side products and/or non-reacted reactants. 
     
     
         11 . The apparatus in accordance with  claim 10 , the distillation column has a feedback of non-reacted reactants into the agitation tub or into the first agitation tub of the cascade of agitation tubs respectively. 
     
     
         12 . The apparatus in accordance with  claim 10 , wherein the distillation column has a drain at the head side, the drain being connected to at least one condenser or desublimator via a supply. 
     
     
         13 . The apparatus in accordance with  claim 9 , wherein the at least one drainage possibility opens into at least one desublimator. 
     
     
         14 . The apparatus in accordance with  claim 13 , wherein at least one distillation column is connected downstream of the at least one desublimator, the distillation column being connected to the at least one desublimator via a line and having a head side drain and a sump side drain. 
     
     
         15 . The apparatus in accordance with  claim 14 , wherein the head side drain
 a) opens into the condenser or into the desublimator; or   b) is combined with the product flow stemming from the condenser.   
     
     
         16 . The apparatus in accordance with  claim 9 , wherein it comprises an apparatus for generating vacuum which
 a) is connected to the at least one desublimator via at least one connection line; and/or   b) is connected to the at least one condenser or to the desublimator via at least one connection line.   
     
     
         17 . A method for producing a polyarylene sulfide including at least one repeat unit of the following general formula I, the method comprising:
 performing a condensation of a di-iodized aromatic compound of the following general formula II using a sulfidation agent,   wherein a material mixture comprising iodine and/or the at least one di-iodized aromatic compound of the general formula II is separated during the condensation step by a method, characterized in that   a) a first part of the material mixture is separated at a pressure which is equal to or larger than the pressure which is present at the triple point of iodine; and   b) a second part of the material mixture is separated at a pressure which is smaller than the pressure which is present at the triple point of iodine;   wherein in both steps a) and b), the material mixture respectively has temperatures at which at least iodine is present in a gaseous state at the said pressures:
   A-S  Formula I
 
   I-A-I  Formula II
 
   In the Formulae I and II, A represents a bivalent aromatic radical.   
     
     
         18 . The method in accordance with  claim 17 , wherein the condensation step comprises:
 reacting the compound of the general formula II using the sulfidation agent to produce a prepolymer of the polyarylene sulfide of the general formula I; and   condensation polymerizing the prepolymer.   
     
     
         19 . The method in accordance with  claim 18 , wherein the separation of the material mixture is performed during each of the steps of producing the prepolymer and polymerizing the prepolymer. 
     
     
         20 . The method in accordance with  claim 19 , wherein the step of producing the prepolymer and the the separation of the first part therein takes place at
 a) the temperature of the material mixture of 250 to 320° C.; and/or   b) at the pressure of ≧126 mbar (absolute pressure).   
     
     
         21 . The method in accordance with  claim 19 , wherein the step of polymerizing the prepolymer and the the separation of the second part therein takes place at
 a) the temperature of the material mixture of 285 to 320° C.; and/or   b) at the pressure of <126 mbar (absolute pressure).   
     
     
         22 . The method in accordance with  claim 18 , wherein the steps of producing the prepolymer and polymerizing the prepolymer are continuously performed, and
 the separation of material mixture is performed during each of the steps of producing the prepolymer and polymerizing the prepolymer, thereby continuously separating and draining the first and the second parts of the material mixture, respectively.   
     
     
         23 . The method in accordance with  claim 18 , wherein the first and/or the second parts of the separated material mixture are recycled to and re-used in the step of the producing the prepolymer. 
     
     
         24 . The method in accordance with  claim 23 , wherein the di-iodized aromatic compound of the general formula II in the first parts of the separated material mixture is recycled to and re-used in the step of the producing the prepolymer. 
     
     
         25 . The method in accordance with  claim 17 , wherein the first part of the separated material mixture is distilled and condensed, and liquefied. 
     
     
         26 . The method in accordance with  claim 17 , wherein the second part of the separated material mixture is desublimated and distilled. 
     
     
         27 . The method in accordance with  claim 17 , wherein the condensation step including the separation of the iodine is performed in a reactor or an equipment comprising Hastelloy. 
     
     
         28 . The method in accordance with  claim 17 , wherein the di-iodized aromatic compound of the following general formula II has at least one bivalent aromatic radical A selected from the group consisting of ortho-phenylene radical, meta-phenylene radical, para-phenylene radical, biphenylene radical, diphenylether radical, naphthylene radical and benzophenone radical. 
     
     
         29 . The method in accordance with  claim 17 , wherein the sulfidation agent is sulfur or alkali sulfide. 
     
     
         30 . The method in accordance with  claim 18 , wherein the prepolymer and the polyarylene sulfide include the repeat units of the general formula I, and at least one end of the repeat units are terminated with hydrogen. 
     
     
         31 . The method in accordance with  claim 18 , wherein the prepolymer has a viscosity of 0.1 to 10 Pas and the polyarylene sulfide has a viscosity of 15 to 400 Pas.