Packing yarn of graphite and plastic sheet

摘要

The packing yarn is composed of layered ribbons with alternating layers of at least one flexible graphite and a reinforcement layer. The ribbons (9) of layered materials (10) have a width of not more than 5 mm. The flexible graphite (1) has a thickness of not more than 1 mm and a bulk density of 0.7-1.8 g/cm<3>. Other layers (3) are of plastics film with a tensile strength of at least 25 MPa and an elasticity of at least 0.4 GPa. The packing yarn (15,17) is composed of at least two ribbons (9), where at least one is twisted into a yarn before working into the packing yarn (15,17). The ribbons (9) can be of layers (10) with a width of not more than 3 mm or 2 mm, containing a graphite film (1) with a thickness of not more than 0.5 mm or 0.35 mm. The reinforcement plastics film (3) has a tensile strength of at least 50 MPa or 140 MPa and an elasticity of at least 1 GPa or 2.5 GPa, and a thickness of not more than 50 mu m. The flexible graphite film (1) has a graphite content or at least 96 wt% or 99 wt%. The plastics film (3) is bonded to the graphite film (1) with or without an adhesive, and they can be welded together at a high temp. such as 240-270 degrees C or 350-380 degrees C using a pressure of at least 0.1 MPa, using a non-adhesive bonding process as described in EP 0 616 884 B1. The ribbons (9), twisted together, contain up to six or not more than 12 layers of flexible graphite film (1), each bonded to a reinforcement plastics film layer (3). The packing yarn (15,17) has a round, oval, elliptical or rectangular cross section. An Independent claim is included for a prodn. process, where a flexible graphite film (1) is bonded to a reinforcement plastics film (3), and the bonded layers (10) are cut into ribbons (9). At least two ribbons (9) are twisted together in a textile yarn twisting process to give a twisted packing yarn (15), which is shaped (16) into the required cross section for the final packing yarn (17). Preferred Features: The operation is a continuous process to bond the graphite (1) and plastic (3) layers together in strips. At least three ribbons (9) are braided into a yarn (15), or at least two ribbons (9) are twisted into a yarn (15). At least one of the bonded ribbons (9) from the bonded web (10) can be twisted into a yarn.