EP0277463A2

EP0277463A2 - Process to obtain yarns for making crepe type and particularly crepon type fabrics by using synthetic yarns

Info

Publication number: EP0277463A2
Application number: EP87810788A
Authority: EP
Inventors: Arturo Ratti; Olimpio Brovelli
Original assignee: Michele Ratti SpA
Current assignee: Michele Ratti SpA
Priority date: 1987-01-16
Filing date: 1987-12-31
Publication date: 1988-08-10
Also published as: CN88100121A; TR25203A; IT1205706B; IT8747535A0; EP0277463A3; CN1026252C

Abstract

The process provides a successive operation of twisting and false twist (hot set) and vice versa in which in one or the other operation the direction of real or false twist is opposite; the whole is followed by a steam heat treatment to attenuate the torsional reaction force during unwinding the yarn from the bobbin.

The operations of false twist and twisting can be without a break in continuity or distinct.

Description

It is known that in recent years processes have been developed on synthetic yarns to obtain, when making fabrics, effects similar to those obtained by standard natural (silk) or artificial (rayon, viscose, etc.) crepe yarns.
Standard crepe yarns are those with a twist value per meter, as a function of the total count of the yarn, around 2000 + 2500.
The high degree of twist serves to impart high torsional forces to the yarn which, during the finishing phase of the fabric, move the weft yarns and warp yarns, obtaining surface effects that distinguish the fabrics by various names, of which the main ones are: crepe de chine, georgette crepe, crepon. The high degree of twist further imparts a characteristic luminous effect to the fabric.
The cost of natural or artificial yarns, clearly greater than that of synthetic yarns, has caused study and research on synthetic yarns to give silk characteristics to the latter to be able to make crepe type fabrics.
These processes, which use synthetic yarns, are based on a flow chart that provides:
-- the operation of twisting with medium high twist (600 + 1200 twists per meter) for a range of counts of 30 + 167 dtex.
-- a subsequent operation of false twist with thermosetting, characterized by having the direction of false twist the same as that of the first of real twist.
These same processes were successively developed by combining the two consecutive phases of twisting and false twist, quite different from one another, into a single phase by use of a single machine equipped for the purpose.
The crepe fabrics thus obtained have an orange peel surface aspect, i.e., slightly corrugated and have become a particular article that is not totally a substitute for that of standard crepe fabrics: this article can replace that of crepe de chine.
Yarns are already marketed for making georgette crepe type fabrics by using a production chart on a machine equipped for contemporaneousness of the twisting phase and falst twist phase (i.e., without a break in continuity between the two phases), which provides a definitely high twist range (1800 + 3000 twists per meter) still on counts of 30 to 167 dtex. In this process also, the twisting and false twist phase is characterized by having the direction of the false twist the same as that of the first phase of real twist.
Both the yarns used for crepe de chine and those used for georgette crepe have not given valid results in making crepon fabrics characterized by a tree bark aspect.
Said crepon fabric is formed by a warp comprising synthetic yarns with any degree of twist and a weft comprising highly twisted yarns with very high torsional reaction.
In the applicant's laboratories two preferred embodiments were found (fig. 1 and 2) for obtaining synthetic yarns suitable for making crepe type fabrics and in particular of the crepon type, according to the invention.
Example: A synthetic yarn is elasticized where a preferred embodiment is that of figure 1:
-- a synthetic yarn (2) coming from a spinning bobbin (1) goes over a feeder (3), then goes through a furnace (4), an optional cooler (5), any false twist spindle (6), a feeder (7), an optional oiling device (8) and finally it is gathered on a bobbin (9).
This elasticized yarn, wound on a suitably shaped bobbin, undergoes a second twisting operation where a preferred embodiment is that of figure. 2.
Fig.2: The bobbin of elasticized yarn (9) is placed on a twisting spindle (10) where twisted yarn (11) goes through a yarn guide (12), then over a feeder (13), over an optional oiling device (14) and finally is gathered on a bobbin (15).
These two false twist and twisting operations are characterized in that in one or the other operation the direction of real or false twist is opposite.
A second preferred embodiment is the following (see fig. 3).
Fig. 3: On a machine suitably equipped to have the two phases of twisting and false twist without break in continuity, a synthetic yarn undergoes the two phases in the following sequence:
from a twist spindle (16) yarn (17) goes through a yarn guide (18) and after a feeder (19) goes through a setting furnace (20), then over an optional cooler (21) and through a false twist spindle (22), then over a feeder (23), an oiling device (24) and is gathered on a bobbin (25).
The amount of false twist inside furnace (20) must be such as to distort completely the real twist and to accumulate on the yarn during the setting phase in said furnace (20) a determined amount of false twist in the opposite direction with respect to the real twist.

Claims

1. Process to obtain yarns for making fabrics of crepe yarn and in particular of the crepon type by use of synthetic yarns characterized by a successive operation of twisting and false twist (hot set) and vice versa in which in one or the other operation the direction of real or false twist is opposite; the whole is followed by a steam heat treatment to attenuate the torsional reaction force during unwinding the yarn from the bobbin.

2. Process according to claim 1, wherein the false twist and twisting operations are performed on two different machines, where the false twist is made by passing in a single elasticizing furnace and the single or double twisting phase is performed in a known normal way.

3. Process according to claim 1, wherein on a single machine, the false twist operation follows that of twisting without a break in continuity and the amount of false twist is such as to distort completely the real twist and at the same time to accumulate a determined amount of false twist in the opposite direction with respect to the real twist.

4. Yarn obtained with the process according to claims 1, 2, 3 for production of crepe fabrics and in particular of the crepon type so as:
-- to have thermodynamic and mechanical torsional forces that impart to it a high torsional elastic force which causes a movement of the yarn during the fabric finishing phase causing regular crinkling of the crepe and in particular of the crepon or tree bark type, said torsional force being characterized by the sum of a thermodynamic torsional force obtained in false twist and of a mechanical torsional force obtained in the twist operation;
-- to have a low residual return obtained during thermosetting to facilitate the formation of the crinkling in the fabric.