Patent GB-1196307-A (GB)
Title: Process for the Production of Polyester Fibre Materials with a Very Low Pilling Formation
Inventor: GERNHART SIEGMUND
IPC: D02J1/22
Filed: 1967-07-28
Abstract: 1,196,307. Polyester filaments. INSTITUT FUR TEXTILTECHNOLOGIE DER CHEMIEFASERN. 28 July, 1967, No. 34726/67. Heading B5B. Polyester fibre materials with a very low pilling formation are made by subjecting the fibre material in filamentary form to at least one stretching step and during one such stretching step the material is treated for not more than 10 seconds in the presence of at least one organic liquid or vapours thereof which, in the liquid phase, possesses a coefficient of thermal conductivity of less than 7 x 10<SP>-4</SP> cal. cm.<SP>-1</SP> sec.<SP>-1</SP> ‹C.<SP>-1</SP> and furthermore, has a crystallization temperature (as defined below) for the unstretched fibre material which lies above the stretching temperature used and in which the unstretched fibre material is not dissolved or chemically attacked, the treatment with the organic liquid or vapour being carried out at a temperature at least 40‹ C. below the second order transistion temperature of the fibre material. The crystallization temperature is defined as the temperature at which the unstretched fibre material undergoes crystallization when treated with a solvent but without stretching, and thus varies from one solvent to another. The method of determination is given. In the case of polyethylene terephthalate the treatment temperature amounts to about 30‹ C., preferably 20‹ to 25‹ C. Preferably, treatment with the organic liquid or vapour thereof takes place during the first stretching step after winding of the filaments of the fibre material when more than one stretching step is employed, and the organic liquid used has a crystallization temperature for the unstretched fibre material which lies above the second order transition temperature of the fibre material. The organic liquid may be used in the form of an aqueous solution or emulsion, containing the organic liquid suitably in a proportion greater than 60% by volume. A solution or emulsion of at least two organic liquids may be used, at least one of said liquids fulfilling the requirements as to thermal conductivity and crystallization temperature. Desirably, the treated fibre material in filamentary form, is subjected to a second stretching at a temperature which lies 50‹ to 10‹ C. below the second order transition temperature of the fibre material. Specified organic liquids include carbon tetrachloride, ethanol, methanol, propanol, ethanolamine, n-heptane, cyclohexane and ethylene glycol. Methylene chloride, benzene, chloroform and acetone are specifically stated to be unsuitable. In Example 1, a fibre hank of polyethylene terephthalate is passed in a first stretching step, through a bath containing a mixture of 60% by volume ethylene glycol and 40% by volume water at 25‹ C. During the residence time of about 5 seconds, the fibre is stretched to a ratio of 1 : 2. After leaving the bath, the remaining liquid is squeezed off and the fibre hank washed with warm water at 30‹C., and the pre-stretched fibres are then passed through a water bath at 60‹ C., and stretched in a ratio 1 : 2, so that a total stretch of 1 : 4 is obtained. After complete removal of residual water, the fibre is crimped, cut, fixed and baled. Fibre so treated shows per millimetre of fibre length, more than 20 protuberances transverse to the axis of the fibre, and the fibre is substantially resistant to pilling. In a second example, an organic liquid is used comprising a solvent mixture consisting of 70% by volume ethylene glycol and 30% by volume ethanol, and the treatment temperature in the first stretching step is 30‹ C. Similar results are obtained to those of the first example.