Liquid-crystalline polyester resin and method for producing it
View Patent ↗The present invention provides a liquid-crystalline polyester obtainable by a method comprising the steps of: (1) preparing a prepolymer consisting of the repeating units represented by formulae (I), (II), (III) and (IV): wherein, p, q, r and s represent relative molar proportions (mol %) of the repeating units in the liquid-crystalline polyester resin and satisfy the following formulae: 60≦p≦80, 10≦r≦20, 10≦q+s≦20, 0.05≦s/(q+s)≦0.3, p+q+r+s=100; and (2) heating the prepolymer in substantially solid state at 250-350° C., provided that the liquid crystalline polyester has a deflection temperature under load of 280-340° C., and a melt viscosity of 10-60 Pa·s.
1. A liquid-crystalline polyester obtainable by a method comprising the steps of:
preparing a prepolymer consisting of the repeating units represented by formulae (I), (II), (III) and (IV):
wherein, p, q, r and s represent relative molar proportions (mol %) of the repeating units in the liquid-crystalline polyester resin and satisfy the following formulae:
60 ≦p≦ 80
10 ≦r≦ 20
10 ≦q+s≦ 20
0.05 ≦s /( q+s )≦0.3
p+q+r+s= 100; and
heating the prepolymer in solid state at 250-350° C.,
provided that the liquid crystalline polyester has a deflection temperature under load of 280-340° C., and a melt viscosity of 10-60 Pa·s,
wherein the melt viscosity is determined at a temperature 30° C. higher than the crystalline melting temperature of the resin, which is determined by differential scanning calorimetry, and a shear rate of 1000 sec-1.
2. The liquid-crystalline polyester resin according to claim 1 , which has a crystalline melting temperature determined by differential scanning calorimetry of 340-400° C.
3. A liquid-crystalline polyester resin composition comprising 100 parts by weight of the liquid-crystalline polyester of claim 1 and 0.1-200 parts by weight of a fibrous, lamellar or particulate filler and/or reinforcement.
4. The liquid-crystalline polyester resin composition according to claim 3 , wherein said filler and/or reinforcement is glass fiber.
5. The liquid-crystalline polyester resin composition according to claim 3 , wherein a 0.3-0.8 mm thick plate of the liquid-crystalline polyester resin composition exhibits V-0 grade flame retardancy according to UL-94 standard.
6. A molded article obtained by molding the liquid-crystalline polyester resin according to claim 1 .
7. A molded article obtained by molding the liquid-crystalline polyester resin composition according to claim 3 .
8. Method for producing a liquid-crystalline polyester resin which comprises the steps of:
preparing a pellet of prepolymer consisting of the repeating units represented by formulae (I), (II), (III) and (IV):
wherein, p, q, r and s represent relative molar proportions (mol %) of the repeating units in the liquid-crystalline polyester resin and satisfy the following formulae:
60 ≦p≦ 80
10 ≦r≦ 20
10 ≦q+s≦ 20
0.05 ≦s /( q+s )≦0.3
p+q+r+s= 100; and
heating the pellet of prepolymer in solid state at 250-350° C.
9. The method according to claim 8 , wherein said pellet is columnar with circular or elliptic cross section with cross section diameter (when cross section is elliptic, major axis of cross section) of 2.5-4.0 mm and with pellet length of 2.5-5.0 mm.