Liquid crystalline polyesters having a surprisingly good combination of a low melting point, a high heat distortion temperature, a low melt viscosity, and a high tensile elongation

Abstract

Disclosed is a select class of liquid crystalline polyesters and molding compositions comprising the polyesters and glass fiber. The liquid crystalline polyesters consist essentially of (1) diacid residues consisting essentially of (i) cyclohexanedicarboxylic acid residues and (ii) other diacid residues selected from terephthalic acid residues, 2,6-naphthalene-dicarboxylic acid residues, or a mixture thereof; (2) diol residues consisting essentially of hydroquinone residues, 4,4′-biphenol residues or a mixture thereof; and, optionally, (3) p-hydroxybenzoic acid residues. In the above definition, the moles of diol residues are equal to the moles of diacid residues and the total of the (1), (2) and (3) mole percentages is equal to 100. The liquid crystalline polyesters have melting points determined by differential scanning calorimetry equal to or less than 360° C.

We claim:  
     
         1 . A liquid crystalline polyester derived from: 
 (1) diacid residues consisting essentially of: 
 (a) about 3.8 to 20 mole percent terephthalic acid (T) residues, and  
 (b) about 15 to 31 mole percent 2,6-naphthalenedicarboxylic acid(N);  
   (2) diol residues consisting essentially of: 
 (c) about 25 to 40 mole percent hydroquinone (HQ) residues; and  
 (d) about 20 to 51 mole percent p-hydroxybenzoic acid (PHB) residues,  
   wherein the T/T+N molar ratio is from about 15:85 and 50.50, the moles of HQ are equal to the sum of the moles of T+N, and the total of the (a), (b), (c), and (d) mole percentages is equal to 100, and    the liquid crystalline polyester has a melting point determined by differential scanning calorimetry equal to or less than 360° C.    
     
     
         2 . A liquid crystalline polyester according to  claim 1  derived from: 
 (1) diacid residues consisting essentially of: 
 (a) about 6.9 to 20 mole percent terephthalic acid (T) residues, and  
 (b) about 15 to 30 mole percent 2,6-naphthalenedicarboxylic acid(N);  
 
 (2) diol residues consisting essentially of: 
 (c) about 27.5 to 40 mole percent hydroquinone (HQ) residues; and  
 (d) about 20 to 45 mole percent p-hydroxybenzoic acid (PHB) residues, and  
 
 wherein the moles of HQ are equal to the sum of the moles of T+N, and the total of the (a), (b), (c), and (d) mole percentages is equal to 100, and  
 the liquid crystalline polyester has a melting point determined by differential scanning calorimetry equal to or less than 360° C.  
 
     
     
         3 . A liquid crystalline polyester according to  claim 2  derived from: 
 (1) diacid residues consisting essentially of: 
 (a) about 9 to 16 mole percent terephthalic acid (T) residues, and  
 (b) about 18 to 28 mole percent 2,6-naphthalenedicarboxylic acid(N);  
 
 (2) diol residues consisting essentially of: 
 (c) about 30 to 40 mole percent hydroquinone (HQ) residues; and  
 (d) about 20 to 40 mole percent p-hydroxybenzoic acid (PHB) residues, and  
 
 wherein, the moles of HQ are equal to the sum of the moles of T+N, and the total of the (a), (b), (c), and (d) mole percentages is equal to 100, and  
 the liquid crystalline polyester has a melting point determined by differential scanning calorimetry equal to or less than 360° C.  
 
     
     
         4 . A liquid crystalline polyester according to  claim 1  having an inherent viscosity of about 3.0 to 11.0 dL/g measured at 25° C. in 60:40 by weight pentafluorophenol/1,2,4-trichlorobenzene at 0.1 g/l 00 mL in a Schott Gerate viscometer.  
     
     
         5 . A liquid crystalline polyester according to  claim 4  having an inherent viscosity of about 5.0 to 10.0 dL/g measured at 25° C. in 60:40 by weight pentafluorophenol/1,2,4-trichlorobenzene at 0.1g/100 mL in a Schott Gerate viscometer.  
     
     
         6 . A liquid crystalline polyester according to  claim 1  wherein said polyester has a tensile elongation at break of ≧1.8%.  
     
     
         7 . A liquid crystalline polyester according to  claim 1  wherein said polyester has a melt viscosity at 345° C. and 1 radian/second of ≦2500 poise at an inherent viscosity equaling from about 3.0 to 11.0 dL/g.  
     
     
         8 . A liquid crystalline polyester according to  claim 1  wherein said polyester has a heat distortion temperature at 264 psi of about ≧265° C.  
     
     
         9 . A liquid crystalline polyester according to  claim 1  wherein said polyester has a tensile elongation at break of about ≧1.8%, a melt viscosity at 345° C. and 1 radian/second of ≦2500 poise at an inherent viscosity equaling 3.0 to 11.0 dL/g, and a heat distortion temperature at 264 psi of ≧265°C.  
     
     
         10 . A liquid crystalline polyester according to  claim 9  wherein said polyester has a tensile elongation at break of ≧1.4%, a melt viscosity at 345°C. and 1 radian/second of ≦2500 poise at an inherent viscosity equaling 5.0 to 10.0 dL/g, and a heat distortion temperature at 264 psi of ≧265° C.  
     
     
         11 . A liquid crystalline polyester according to  claim 1  prepared using a catalyst selected from the group consisting of dialkyl metal oxide, diaryl metal oxide, titanium dioxide, alkoxy titanium silicates, titanium alkoxides, alkali metal and alkaline earth metal salts of carboxylic acids, gaseous acid catalysts and hydrogen halides.  
     
     
         12 . A liquid crystalline polyester composition of  claim 11  wherein said catalyst is utilized in the amount of about 50 to about 500 parts per million based on the total weight of starting materials.  
     
     
         13 . A liquid crystalline polyester of  claim 12  wherein said catalyst is utilized in the amount of 100 to about 300 parts per million based on the total weight of the starting materials.  
     
     
         14 . A liquid crystalline polyester of  claim 1  further comprising additives and/or fillers.  
     
     
         15 . A liquid crystalline polyester of  claim 14  wherein said additives and/or fillers are in fibrous, particulate, or flaky form.  
     
     
         16 . A liquid crystalline polyester of  claim 15  wherein said additives and/or fillers comprise antioxidants, titanium dioxide, carbon black, clay, flame retardants, drip suppressants and other pigments.  
     
     
         17 . A liquid crystalline polyester of  claim 15  wherein said fibrous fillers are selected from glass fiber, carbon fiber, silica fiber, silica/alumina fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and fibrous materials of stainless steel, aluminum, titanium, copper, and brass.  
     
     
         18 . A liquid crystalline polyester of  claim 15  wherein said particulate fillers are selected from carbon black, graphite, silica, quartz powder, glass beads, milled glass fiber, glass balloons, glass powder, calcium silicate, aluminate silicate, kaolin, talc, clay, diatomaceous earth, wollastonite, iron oxide, titanium oxide, zinc oxide, antimony trioxide, and alumina, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, ferrite, silicon carbide, silicon nitride and boron nitride.  
     
     
         19 . A liquid crystalline polyester of  claim 15  wherein said flaky fillers or additives are selected from mica, glass flake, and metallic foils.  
     
     
         20 . A liquid crystalline polyester of  claim 14  wherein said fillers include organic fillers selected from organic polyester fiber, liquid crystal polymer fiber, aromatic polyamide fiber and polyimide fiber.  
     
     
         21 . A liquid crystalline polyester of  claim 14  wherein said fillers may be used in a total amount of up to 60 weight percent based on the total weight of said fillers and said polyester.  
     
     
         22 . A molding composition comprising a blend of: 
 (1) a liquid crystalline polyester as defined in  claim 1;  and    (2) at least 20 weight percent glass fibers based on the total weight of the molding composition.    
     
     
         23 . A molding composition according to  claim 17  wherein said glass fibers are present in the amount of about 30 weight percent based on the total weight of the molding composition.  
     
     
         24 . A molding composition according to  claim 1  wherein the liquid crystalline polyester has an inherent viscosity of about 3.0 to 11.0 dL/g measured at 25° C. in 60:40 by weight pentafluorophenol/1 ,2,4-trichlorobenzene at 0.1 g/100 mL in a Schott Gerate viscometer and the molding composition contains about 25 to 40 weight percent glass fibers based on the total weight of the molding composition.  
     
     
         25 . A molding composition according to  claim 24  wherein the liquid crystalline polyester has an inherent viscosity of about 5.0 to 10.0 dL/g measured at 25° C. in 60:40 by weight pentafluorophenol/1,2,4-trichlorobenzene at 0.1 g/100 mL in a Schott Gerate viscometer and the molding composition contains about 25 to 45 weight percent glass fibers based on the total weight of the molding composition.  
     
     
         26 . A molding composition according to  claim 17  wherein the glass fiber has a thickness of about 9 to 15 microns and a length of about 0.8 to 26 mm.  
     
     
         27 . A molded article having a thickness of less than about 1.5 mm comprising the molding composition of claim  22 .