Abstract: This invention provides an oil well pipe which is resistant to fracturing caused by ground subsidence by providing a sliding layer on the outside of the oil well pipe to reduce the frictional force acting on the oil well pipe. Furthermore, by constituting the sliding layer by a material and a thickness so that the residual negative frictional force becomes 2×103 N/m2 or less after 1 year of deformation at the operating temperature of the oil well pipe, or by the sliding layer comprising a material of which the stiffness factor S(t) after 1 year of deformation is in the range from 10−5 N/m2 to 103 N/m2 at the operating temperature of the oil well pipe and providing an adhesive layer between the pipe body and the sliding layer, thereby reducing the sliding phenomenon upon construction which restricts the properties of the sliding layer.

Abstract: The present invention relates to a polyethylene-2,6-naphthalate film comprising a resin composed mainly of polyethylene-2,6-naphthalate and having an intrinsic viscosity .eta. in the range of from 0.31 to 0.6, said film having stretch ratios of 1 to 3 times and 1 to 3 times or 3 to 6 times and 1 to 1.8 times respectively in substantially mutually perpendicular directions and a thickness in the range of from 5 to 150 .mu.m;a polyethylene-2,6-naphthalate resin comprising a blend composed mainly of two components of: a polyethylene-2,6-naphthalate resin having an intrinsic viscosity in the range of from 0.3 to 0.5 dl/g and prepared by an esterification reaction of a dicarboxylic acid having a 2,6-naphthalenedicarboxylic acid content of not less than 90% by mole with a glycol having an ethylene glycol content of not less than 90% by mole, or a transesterification and a polyethylene-2,6-naphthalate resin having an intrinsic viscosity in the range of from 0.5 to 0.

Abstract: Packaging films for press-through packaging comprise a polyethylene-2,6-naphthalate film having an intrinsic viscosity .eta. of 0.31 to 0.6 wherein the film is: (1) stretched in mutually perpendicular directions each with draw ratios of 1 to 3 times; or (2) stretched in the longitudinal direction at draw ratios of 3 to 6 times and in the transverse direction at draw ratios of 1 to 1.8 times. The films have a thickness of 5-150 .mu.m and may be incorporated into multi-layer cover films comprising the polyethylene-2,6-naphthalate film, a barrier layer, a reinforcing layer, and a sealing or adhesive layer.

Abstract: 1. An ester copolymer resin having a general formula ?I!.HO.paren open-st.COArCOORO.paren close-st..sub.n H ?I!wherein Ar represents 2,6-naphthalene group or phenylene group, R represents ethylene group or 1,4-cyclohexylene group, and n is a number of 100 to 1000 and a polymer alloy having a solubility parameter of 10.8 to 11.9 consisting essentialy of the ester copolymer and a polycarbonate resin are provided. The ester resin and the alloy are transparent and has a heat resistance and a hot water resistance (resistance to whitening) resisting sterilization of food, a good heat sealebility to aluminum closure, and recycling ability with PET resin.

Abstract: 1. An ester copolymer resin having a general formula ?I!. ##STR1## wherein Ar represents 2,6-naphthalene group or phenylene group, R represents ethylene group or 1,4-cyclohexylene group, and n is a number of 100 to 1000 and a polymer alloy having a solubility parameter of 10.8 to 11.9 consisting essentialy of the ester copolymer and a polycarbonate resin are provided. The ester resin and the alloy are transparent and has a beat resistance and a hot water resistance (resistance to whitening) resisting sterilization of food, a good heat sealability to aluminum closure, and recycling ability with PET resin.