Impact-resistant polyoxymethylene moulding compounds with a low emission, the use thereof and moulded bodies produced therefrom

Abstract

The present invention relates to a polyoxymethylene molding composition comprising: (A) from 0.01 to 1.0% by weight of a cyclic stabilizer which contains at least one nitrogen atom in the ring (B) from 0.001 to 0.5% by weight of a salt of a carboxylic acid (C) from 5 to 50% by weight of an impact modifier (D) from 0.0 to 2.0% by weight of a sterically hindered phenol compound (E) from 0.0 to 1.0% by weight of at least one stabilizer from the group of the benzotriazole derivatives or benzophenone derivatives or aromatic benzoate derivatives (F) from 0.0 to 0.8% by weight of a sterically hindered amine as light stabilizer (HALS) (G) a polyoxymethylene polymer to 100% by weight. The molding compositions of the invention have substantially reduced formaldehyde emission, while the level of mechanical properties, particularly strength and impact strength, is retained.

1 . A polyoxymethylene molding composition comprising 
 Component (A) from 0.01 to 1.0% by weight of a cyclic stabilizer which contains at least one nitrogen atom in the ring    Component (B) from 0.001 to 0.5% by weight of a salt of a carboxylic acid    Component (C) from 5 to 50% by weight of an impact modifier    Component (D) from 0.0 to 2.0% by weight of a sterically hindered phenol compound    Component (E) from 0.0 to 1.0% by weight of at least one stabilizer from the group of the benzotriazole derivatives or benzophenone derivatives or aromatic benzoate derivatives    Component (F) from 0.0 to 0.8% by weight of a sterically hindered amine as light stabilizer (HALS)    Component (G) a polyoxymethylene homo- or copolymer to 100% by weight.    
     
     
         2 . A polyoxymethylene molding composition comprising 
 Component (A) from 0.03 to 0.3% by weight of a cyclic stabilizer which contains at least one nitrogen atom in the ring    Component (B) from 0.001 to 0.5% by weight of a salt of a carboxylic acid    Component (C) from 5 to 40% by weight of an impact modifier    Component (D) from 0.1 to 1.0% by weight of a sterically hindered phenol compound    Component (E) from 0.0 to 0.8% by weight of at least one stabilizer from the group of the benzotriazole derivatives or benzophenone derivatives or aromatic benzoate derivatives    Component (F) from 0.0 to 0.5% by weight of a sterically hindered amine as light stabilizer (HALS)    Component (G) a polyoxymethylene homo- or copolymer to 100% by weight.    
     
     
         3 . A polyoxymethylene molding composition comprising 
 Component (A) from 0.01 to 1.0% by weight of a cyclic stabilizer which contains at least one nitrogen atom in the ring    Component (B) from 0.001 to 0.5% by weight of a salt of a carboxylic acid    Component (C) from 7 to 30% by weight of an impact modifier    Component (D) from 0.2 to 1.0% by weight of a sterically hindered phenol compound    Component (E) from 0.0 to 1.0% by weight of at least one stabilizer from the group of the benzotriazole derivatives or benzophenone derivatives or aromatic benzoate derivatives    Component (F) 0.4% by weight of a sterically hindered amine as light stabilizer (HALS)    Component (G) a polyoxymethylene homo- or copolymer to 100% by weight.    
     
     
         4 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  3 , where the component (A) used comprises aminopyridines, 2,6-diaminopyridine, substituted and dimeric aminopyridines, pyrrolidone, imidazolidinone, hydantoin, allantoin, triamino-1,3,5-triazine(melamine), melamine-formaldehyde condensates, methylolmelamine, individually or as a mixture.  
     
     
         5 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  4 , where the component (B) used comprises carboxylates of an alkali metal and/or of an alkaliene earth metal having from 10 to 32 carbon atoms.  
     
     
         6 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  5 , where the component (B) used comprises magnesium stearate.  
     
     
         7 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  6 , where the component (C) comprises a polyurethane, a 2-phase mixture made from polybutadiene and styrene-acrylonitrile (ABS), modified polysiloxanes or, respectively, silicone rubbers, or graft copolymers made from an elastomeric, single-phase core based on polydiene and from a hard outer graft layer, with fine distribution.  
     
     
         8 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  7 , where component (C) comprises graft copolymers made from an elastomeric, single-phase core based on polydiene and from a hard outer graft layer, and where the outer layer of the particles has a single- or dual-shell structure, and in the case of single-shell particles is composed of poly(meth)acrylate and poly(meth)acrylonitrile, and where in the case of dual-shell particles the inner shell is composed of crosslinked polystyrene and the outer shell is composed of crosslinked polymethacrylate.  
     
     
         9 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  8 , where component (D) comprises pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and/or triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)proprionate] and/or 3,3′-bis[3-(3,5,-di-tert-butyl-4-hydroxyphenyl)propiono] hydrazide and/or hexamethylene glycol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and/or 3,5-di-tert-butyl-4-hydroxytoluene.  
     
     
         10 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  9 , where the component (E) used comprises 2-[2′-hydroxy-3′,5′-bis(1,1-dimethylbenzyl)phenyl]benzotriazole.  
     
     
         11 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  10 , where component (F) comprises 2,2,6,6-tetramethyl-4-piperidyl compounds, bis-(2,2,6,6-tetramethyl-4-piperidyl) sebacate, and/or the polymer made from dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tertamethyl-4-piperidine.  
     
     
         12 . The polyoxymethylene molding composition as claimed in one or more of  claims 1  to  11 , where component (G), the polyoxymethylene, has been prepared using trifluoromethanesulfonic acid as initiator.  
     
     
         13 . The use of the thermoplastic molding composition as claimed in one or more of  claims 1  to  12  for producing moldings or films.  
     
     
         14 . A molding produced from a thermoplastic molding composition as claimed in one or more of  claims 1  to  12 .