Flame-resistant polyamide, method for the production of said flame-resistant polyamide, and use of said flame-resistant polyamide.

Abstract

The invention relates to a flame-resistant polyamide as a product of the condensation of dicarboxylic acids with diamines and with a flame-retardant phosphorus compound, which flame-resistant polyamide is characterized in that the flame-resistant polyamide FR contains, in the main chain thereof, phosphinic acid amide structural units of formula (II) —PO(R 1 )—NH— (II) in addition to the amide structural units of formula (I) —CO—NH— (I), in which formula (II) R 1 means hydrogen or an organic group and can differ in the individual phosphinic acid amide structural units within the main chain, and that the polyamide FR achieves a relative viscosity, measured as a 1% solution in 96% sulfuric acid at 25° C., of at least 2.0 (in accordance with DIN 51562). The invention further relates to a method for producing said flame-resistant polyamide FR. In said method, one or more diamines are polycondensed with one or more dicarboxylic acids under pressure and at elevated temperature in the presence of water and with one or more diphosphinic acids and/or one or more phosphino-carboxylic acids by means of a polyamide synthesis. After the polycondensation, the pressure in the reaction chamber is reduced to less than 1 bar. The flame-resistant polyamide can be advantageously used to produce molded bodies, in particular films, components, and filaments or filament yarns.

1 . A flame-retardant polyamide as condensation product of dicarboxylic acids with diamines and also a flame-retardant phosphorus compound, characterized in that the flame-retardant polyamide FR contains in its main chain not only the amide structural units of the formula (I)
   —CO—NH—  (I)
   but also phosphinamide structural units of the formula (II)
   —PO(R 1 )—NH—  (II),
 
   R 1  being hydrogen or an organic group, and in which individual phosphinamide structural units within the main chain may be different, and in that the polyamide FR attains a relative viscosity, measured as a 1% strength solution in 96% strength sulfuric acid at 25° C., of at least 2.0 (according to DIN 51562).   
     
     
         2 . A flame-retardant polyamide according to  claim 1 , characterized in that the organic group R 1  is a linear, cyclic or branched C 1 -C 6  alkyl group, more especially a C 1 -C 3  alkyl group, an aryl group, more especially having up to three fused or unfused rings, more especially in the form of a phenyl, benzyl, naphthyl, phenanthryl, mesityl or tolyl group, an alkylaryl group, more especially a triphenylmethyl group, and/or an arylalkyl group, more especially an i-propylphenyl, t.butylphenyl or nonylphenyl group. 
     
     
         3 . A flame-retardant polyamide according to  claim 2 , characterized in that the C 1 -C 3  alkyl group is a methyl, ethyl, and/or a 2-propyl group. 
     
     
         4 . A flame-retardant polyamide according to  claim 1 , characterized in that on the basis of the phosphinamide structural units and relative to the flame-retardant polyamide FR, it contains at least 0.01 and/or not more than 10.0 wt % of phosphorus. 
     
     
         5 . A flame-retardant polyamide according to  claim 4 , characterized in that the polyamide FR contains 0.01 to 8 wt %, more especially 0.01 to 4.0 wt %, of phosphorus. 
     
     
         6 . A flame-retardant polyamide according to  claim 5 , characterized in that it contains 0.01 to 1.5 wt % of phosphorus. 
     
     
         7 . A flame-retardant polyamide according to  claim 1 , characterized in that it contains property-improving additives, more especially UV stabilizers, heat stabilizers and/or matting agents. 
     
     
         8 . A flame-retardant polyamide according to  claim 7 , characterized in that, based on the polyamide FR, it contains 0.01 to 1.0 wt % of additive. 
     
     
         9 . A flame-retardant polyamide according to  claim 8 , characterized in that, based on the polyamide FR, it contains 0.5 to 0.7 wt % of additive. 
     
     
         10 . A flame-retardant polyamide according to  claim 1 , characterized in that it has a nonflammability which meets the mandates of the UL 94 V-0 protocol. 
     
     
         11 . A flame-retardant polyamide according to  claim 1 , characterized in that the relative viscosity (measured according to DIN 51562) attains at least 2.4. 
     
     
         12 . A flame-retardant polyamide according to  claim 1 , characterized in that the relative viscosity (measured according to DIN 51562) attains at least 2.4 and/or not more than 4.0. 
     
     
         13 . A flame-retardant polyamide according to  claim 1 , characterized in that it is based on
 PA6.9 (hexamethylenediamine/azelaic acid),   PA6.12 (hexamethylenediamine/dodecanoic acid),   PA4.6 (tetramethylenediamine/adipic acid),   PA12.12 (dodecanediamine/dodecanedioic acid) or   PA6.6 (hexamethylenediamine/adipic acid),   in each case in a form modified in accordance with the invention.   
     
     
         14 . A flame-retardant polyamide according to  claim 1 , characterized in that it is mixed in a mixture with a further polyamide in the form of a non flame-retardant polyamide, more especially with polyamide 6 (polycaprolactam), the phosphorus content of the mixture being adjusted via the flame-retardant polyamide FR included to at least 0.01 wt % and/or not more than 10.0 wt %, more especially not more than 8.0 wt %. 
     
     
         15 . A flame-retardant polyamide according to  claim 14 , characterized in that the phosphorus content is adjusted to 0.01 to 4.0 wt %, more especially 0.01 to 1.5 wt %. 
     
     
         16 . A flame-retardant polyamide according to  claim 14 , characterized in that the mixture of flame-retardant polyamide FR and the non flame-retardant polyamide attains a relative viscosity (measured according to DIN 51562) of at least 2.0, more especially of at least 2.4 and/or not more than 4.0. 
     
     
         17 . A process for producing the flame-retardant polyamide according to  claim 1 , characterized in that in a polyamide synthesis one or more diamines are subjected to polycondensation with one or more dicarboxylic acids under a pressure of at least 16 bar, more especially a pressure from 20.0 bar to 25 bar, and at elevated temperature, more especially a temperature of less than 295° C., more especially from 230° C. to 280° C., in the presence of water, the amount of water more especially being not more than 25 wt % and/or more especially at least 10 wt %, based on the reaction mixture, in order to build up the pressure in the reactor that is required at the selected reaction temperature, and with one or more diphosphinic acids of the formula (III) 
       
         
           
           
               
               
           
         
         and/or with one or more carboxy-phosphinic acids of the formula (IV), 
       
       
         
           
           
               
               
           
         
         the dicarboxylic acid being replaced in part, under the stoichiometric conditions on which the polycondensation is based, by the diphosphinic acid (III) and/or by the carboxy-phosphinic acid (IV), the dicarboxylic acid, the diphosphinic acid, and the carboxy-phosphinic acid being subjected to the polycondensation in the form of the AH salts with the diamines used, the pressure in the reaction space after the polycondensation being lowered to less than 250 mbar, more especially less than 100 mbar, and 
         the following definitions applying to the formulae (III) and (IV): 
         R 2  and R 3 , independently of one another, are a linear, cyclic or branched C 1 -C 6  alkyl group, more especially a C 1 -C 3  alkyl group, an aryl group, more especially having up to three fused or unfused rings, more especially in the form of a phenyl, benzyl, naphthyl, phenanthryl, mesityl or tolyl group, an alkylaryl group, more especially a triphenylmethyl group, and/or an arylalkyl group, more especially an i-propylphenyl, t.butylphenyl or nonylphenyl group, and 
         R 4  is a divalent organic group, more especially in the form of a linear, cyclic or branched C 1 -C 10  alkylene, more especially C 1 -C 4  alkylene group, a C 1 -C 10  alkenylene, more especially a C 1 -C 6  alkenylene group, or a C 6 -C 10  arylene, more especially a 1,4-phenylene group. 
       
     
     
         18 . A process according to  claim 17 , characterized in that the pressure is lowered to 1 to 100 mbar, more especially 1 to 50 mbar. 
     
     
         19 . A process according to  claim 18 , characterized in that the pressure is lowered to less than 100 mbar, more especially 1 to 10 mbar. 
     
     
         20 . A process according to  claim 17 , characterized in that the proportion of the reactants in the form of the diamines, dicarboxylic acids, diphosphinic acids, and the carboxy-phosphinic acids is adjusted such that the phosphorus content of the flame-retardant polyamide process product obtained, based on the polyamide FR, is at least 0.01 wt % and/or not more than 10.0 wt %. 
     
     
         21 . A process according to  claim 17 , characterized in that the flame-retardant polyamides produced from an AH salt of the diphosphinic acid of the formula (III) and/or of the carboxy-phosphinic acid of the formula (IV) are mixed without blending or in a blend with a further, non phosphorus-containing, non flame-retardant polyamide and are passed on for further use. 
     
     
         22 . A shaped article formed by an extrusion process for producing films, components, monofilament yarns, multifilament yarns or staple fibre yarns, said article comprised of the polyamide of  claim 1 . 
     
     
         23 . The use of the article of  claim 22 , characterized in that extrusion processes are employed in the form of the blow-moulding, injection-moulding or melting process.