| 摘要 |
An unstretched shaped structure made from a linear polyester, e.g. a filament, thread or film, is rendered plastic at a temperature between the second order transition temperature and the apparent minimum crystallization temperature of the polyester by means of steam or water as the plasticizing medium, then subjected, while in the plastic state, in at least one direction to permanent plastic deformation without molecular orientation, reconverted into the non-plastic state by reducing the temperature or removing the structure from the plasticizing medium, and stretched in this non-plastic state with molecular orientation. The preferred temperature range for plastic deformation without orientation is 70-100 DEG C. The plastic deformation of the shaped structure may take the form of elongation, if desired in a direction deviating from the longitudinal, e.g. at right-angles thereto, and it may be assisted by mechanical means, e.g. by passage of the shaped structure between smooth, fluted or grooved rollers immersed in the plasticising medium. The shaped structure, while in the plastic state, may be subjected simultaneously or in either order to elongation without orientation in the longitudinal direction and to deformation without orientation in a different direction. If water is the plasticizing medium a wetting-agent may be added; if steam is the plasticizing medium the shaped structure may be previously treated with a wetting-agent. If desired, the path of the shaped structure through the plasticizing medium may be varied by use of an oscillating link-pin. The process may be applied to shaped structures several months old as well as to freshly-made structures. The final stretching with molecular orientation may be carried out with or without the application of heat. Specified polyesters are polymethylene terephthalates, particularly polyethylene terephthalate as such or modified by the replacement of a small proportion of glycol (used in its manufacture) by 1:4-butane diol or hexamethylene glycol or by the replacement of a part of the terephthalic acid by another dicarboxylic acid, e.g. adipic, sebacic, naphthalene-2:7-dicarboxylic, or isophthalic acid. Polyesters derived from hydroxy-carboxylic acids, e.g. para-o -hydroxybutoxybenzoic acid or hydroxypivalic acid, may also be treated. Examples are given. Specifications 695,567 and 831,961 are referred to. |
