In recent years, with increased demand for high-performance plastics, lots of polymers of various novel properties have been developed and come on the market. Liquid crystalline resins having characteristic parallel arrangement of molecular chains and showing optical anisotropy, such as liquid crystalline polyester, have received particular attention, because of their excellent moldability and mechanical properties, and their applications have been expanded to mechanical components and electric and electronic components. In particular, the liquid crystalline resins are favorably used for electric and electronic components requiring the high flowability, such as connectors.
With downsizing and refining the mechanical components and the electric and electronic components, molded products have ultra-thin wall thickness. Liquid crystalline polyester compositions filled with fibrous inorganic fillers have been used with an aim to improve the strength of the product and reduce the anisotropy.
With the aim of improving the weld strength and the surface smoothness of the molded product, for example, the following liquid crystalline resin composition has been proposed (e.g., see JP 2009-215530A). This liquid crystalline resin composition contains 20 to 80 parts by weight of a fibrous filler having the maximum fiber length of not greater than 1000 μm and the weight-average fiber length of not less than 200 μm and not greater than 450 μm, relative to 100 parts by weight of liquid crystalline resin.
With the aim of preventing blister and reducing protrusion of glass fibers from the gate and from the fluid terminals, the following liquid crystalline resin composition has been proposed (e.g., see JP 2009-191088A). This liquid crystalline resin composition contains: (i) 5 to 50 percent by weight of glass fiber having the number-average fiber length of 50 to 120 μm and the content of the fiber length of 20 to 150 μm to be not lower than 80%; and (ii) 95 to 5 percent by weight of liquid crystalline polymer.
To produce favorable mechanical properties and reduce the warpage deformation for asymmetric electronic components, the following liquid crystalline polymer composition has been proposed (e.g., see WO 2008-023839). This liquid crystalline polymer composition is prepared by mixing: (i) a fibrous filler having the average fiber diameter of 5 to 30 μm, the weight-average fiber length of 250 to 350 μm excluding the fiber length of not greater than 10 μm, and the content of the fiber length of not less than 700 μm to be not higher than 5 percent by weight; and (ii) a plate-like filler having the average particle diameter of 0.5 to 200 μm.
Many mechanical components and electric and electronic components include snap-fit elements and screw structures. Recent size reduction and refinement of components requires the high snap-fit property and self-tapping property for materials. The resin compositions disclosed in JP 2009-215530A and JP 2009-191088A, however, have the small content of the glass fiber of long fiber length, which results in the low weld strength, the poor toughness and the insufficient snap-fit property required for components with joints. The resin composition disclosed in WO 2008-023839, on the other hand, has the high degree of breakage of glass fiber, which results in the insufficient self-tapping property, weld strength and snap-fit property required for molded products with screw structures.
It could therefore be helpful to provide a liquid crystalline polyester composition having less variation in flowability that gives a molded product having high snap-fit property, self-tapping property and weld strength.