Filled polyamide molding materials showing a reduced water absorption

Abstract

The present invention relates to filled polyamide molding materials, in particular polyamide molding materials with medium filler content, which are producible from a polyamide blend and for example by compounding with chopped or endless fibers on two-screw extruders, and have a combination of reduced water absorption and good mechanical properties, which results in very good dimensional stability and reduced variation of the electrical properties of the produced molded part, such as an antenna housings of stationary or mobile communication devices. The thermoplastic polyamide molding materials according to the present invention are suitable for manufacturing molded parts and other semi-finished or finished parts, for example by extrusion, injection molding, pressing, direct process or direct compounding, respectively, wherein the compounded polyamide molding material is directly processed by injection molding or other shaping methods.

1 . Filled polyamide molding materials with low water absorption and good mechanical properties based on polyamide 613, polyamide 614, polyamide 615, polyamide 616, polyamide 617, polyamide 618, of a blend, consisting essentially of the following components:
 (A) at least one aliphatic polyamide from the group consisting of polyamide 613, polyamide 614, polyamide 615, polyamide 616, polyamide 617, polyamide 618, or mixtures thereof,   (B) polyamide, build up from
 (b 1 ) 60 to 100 wt.-parts units, preferably 60 to 80 wt.-parts units, more preferably 67 wt.-parts units, derived from isophtalic acid (I) in combination with hexamethylene diamine (6) in almost equimolar ratio, 
 (b 2 ) 0 to 40 wt.-parts units, preferably 20 to 40 wt.-parts units, more preferably 33 wt.-parts units, derived from terephthalic acid (T) in combination with hexamethylene diamine (6) in almost equimolar ratio, 
 wherein the wt.-parts of the components (b 1 ) and (b 2 ) totals 100 wt.-parts, and at least one filler component (C): 
   (C) selected from the group consisting of glass fibers, carbon fibers, metal fibers, aramid fibers, whiskers, talc, mica, silicates, quartz, titanium dioxide, wollastonite, kaolin, silicic acids, magnesium carbonate, magnesium hydroxide, chalk, grounded or precipitated calcium carbonate, lime, feldspar, barium sulfate, permanent magnetic or magnetizable metals or alloys, glass balls, hollow glass balls, hollow spheroidal silicate fillers, natural layered silicates, synthetic layered silicates and mixtures thereof,   wherein the weight percents of the components (A) to (C) total 100%, and   wherein the components (A), (B) and (C) fulfill the following conditions:   
       
         
           
                 
                 
               
                     
                 
                   (A) + (B): 
                   80 to 20 wt.-%, 
                 
                   weight ratio (A)/(B): 
                   60/40 to 90/10, preferably 70/30 to 85/15, more 
                 
                     
                   preferably 70/30 to 80/20, most preferably 75/25, 
                 
                   (C): 
                   20 to 80 wt.-%, preferably 21 to 70 wt-.%, more 
                 
                     
                   preferably 31 to 64 wt.-%, 
                 
                     
                 
             
                
               
               
                
                
                
                
                
                
               
            
           
         
         wherein the polyamide molding materials optionally comprise usual additives (D) in addition to the components (A) to (C), and wherein their amount is in addition to the sum of the components (A) to (C). 
       
     
     
         2 . Polyamide molding materials according to  claim 1 , characterized in that the aliphatic polyamide has a solution viscosity, measured in m-cresol (0.5 wt.-% at 20° C.) of η ref  between 1.4 and 2.5, preferably between 1.5 and 2.1. 
     
     
         3 . Polyamide molding materials according to one of the preceding  claims 1  and  2 , characterized by a water absorption (23° C., 50% relative humidity) of <1% and of <2.8%, respectively (23° C., 100% relative humidity). 
     
     
         4 . Polyamide molding materials according to one of the preceding  claims 1  to  3 , characterized by a tensile modulus of elasticity (measured according to ISO 527) of at least 8000 MPa (dry) at a glass fiber content of 30 wt.-%. 
     
     
         5 . Polyamide molding materials according to one of the preceding  claims 1  to  4 , characterized in that the molding materials have elongations at break of 3.5% or more (measured according to ISO 527) at a glass fiber content of at least 30 wt.-%. 
     
     
         6 . Polyamide molding materials according to one of the preceding  claims 1  to  5 , characterized in that additives (D) are contained in the molding materials, which are selected from the group, consisting of the inorganic stabilizers, organic stabilizers, lubricants, dyes, metallic pigments, metal spangle, metal coated particles, halogenated flame retardants, halogen-free flame retardants, impact modifiers, antistatics, conductivity additives, in particular carbon black and/or carbon nanotubes, demolding agents, optical brighteners, or mixtures of the above additives. 
     
     
         7 . Polyamide molding materials according to one of the preceding  claims 1  to  6 , characterized in that glass fibers with a diameter of 5 to 20 μm, preferably 5-15 μm, more preferably from 5 to 10 μm are used as filler component (C), wherein the cross-section of the glass fibers is especially circular, oval, elliptical or angular, and wherein E glass fibers are particularly preferably used. 
     
     
         8 . Polyamide molding materials according to one of the preceding  claims 1  to  7 , characterized in that the aliphatic polyamide is particularly polyamide 614 or polyamide 618 or their mixture. 
     
     
         9 . Method for producing polyamide molding materials according to one of the  claims 1  to  8  on conventional compounding machines at cylinder temperatures of 260° C. to 320° C., wherein the polymeric portion is melted first and then the fillers, particularly the glass fibers and/or other fillers, are dosed. 
     
     
         10 . Method for producing polyamide molding materials according to any of the previous  claim 1  to  9 , characterized in that firstly a compound in granular form is made from the first components (A) and (B) and the fillers (C) and optionally the additives (D), respectively, and these granules are subsequently mixed and optionally additional granular quantities of the components (A) and optionally (B) are added, and then the granules are processed. 
     
     
         11 . Use of the molding materials according to one of the  claims 1  to  10  with water absorptions below 1% (23° C., 50% relative humidity) and below 2.8% (23° C., 100% relative humidity), respectively, for producing of molded parts, preferably injection molded parts, more preferably antenna housings for stationary or mobile communication devices. 
     
     
         12 . Method for producing molded parts from polyamide molding materials according to one of the  claims 1  to  8  by injection molding, extrusion, blow molding, direct compounding and other shaping methods. 
     
     
         13 . Molded part, obtainable from the polyamide molding materials according to one of the  claims 1  to  8 . 
     
     
         14 . Molded part according to  claim 13 , characterized in that it is an antenna housing for stationary or mobile communications devices.