JPS6189329A - Production of stretch-broken doubled yarn - Google Patents

Abstract

PURPOSE:To enable uniform stretch-breaking of a yarn at a high stretching ratio, and to obtain the titled yarn having high uniformity, by spinning a polyester filament bundle having low orientation degree, aging for a specific days in the undrawn state, and drawing, stretch-breaking and doubling the yarn. CONSTITUTION:An undrawn polyester filament bundle having low orientation degree and having a birefringence (DELTAn) of <=0.02 is aged for >=5 days, preferably for >=10 days preferably at >=20 deg.C and a water-content of >=10%. The aged bundle is drawn at a draw ratio of >=2.3, and the obtained drawn filament bundle is subjected to the stretch-drawing and doubling at a draw ratio of >=4 to obtain the objective yarn. The drawing is carried out preferably at a low rate of drawing or using a thin bundle of the undrawn filaments compared with conventional drawing process because the drawability of the undrawn filament bundle is lowered by the aging process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an improvement in a method of cutting and tying polyester fibers together to form yarn.

(Prior Art) A method of stretching a continuous long fiber bundle to a value higher than its elongation at break and cutting it into a short fiber bundle, and imparting conjugation properties to the short fiber bundle to form a yarn is well known.

The key point of this method is how to uniformly chop the continuous long fiber bundle at a high magnification to obtain a short fiber bundle with less unevenness. In particular, polyester fibers are tougher than rayon fibers or acrylic fibers, so they are difficult to cut. This is generally true when cutting so-called tow into slivers, and for this purpose, the tow is cut little by little in multiple stages, or the stretched tow is cut into slivers before being cut. Efforts are being made to make it easier to cut by stretching it again until it is on the verge of breaking.

However, this also applies when making slivers,
If you want to make thin threads all at once without making them into slivers, you need to use a high cutting magnification of at least 4 times, preferably 10 times or more, or you will not be able to get the desired thinness, and you will not be able to make it evenly and constantly. It's getting harder and harder to stay focused. Furthermore, since it is wound into a thin thread, the processing speed must be fast for efficiency to increase, so it is preferable to process at a high speed of 100 m/min or more, preferably 200 m/min or more, and this is even more important. This is making this effort even more difficult.

(Problems to be Solved by the Invention) The present invention aims to resolve the problem that it is difficult to uniformly cut polyester fibers at a high magnification.

(Means for Solving the Problems) As a result of intensive studies on the problems of the prior art, the present inventors found that when producing polyester long fiber bundles as a raw material,
Uniform cutting at high magnification is possible by not stretching the undrawn fibers made by spinning a polymer immediately, but leaving them for 5 days or more to age, then drawing and cutting. I discovered that.

That is, in the present invention, a low-oriented undrawn polyester fiber bundle with a birefringence Δn of 0.02 or less is allowed to age for 5 days or more after spinning, and then stretched to 2.3 times or more to form a drawn fiber bundle. The method for producing a cut and conjugated yarn is characterized in that the fibers are further cut and conjugated at a magnification of 4 times or more to form a yarn.

The polyester fiber used in the present invention is not only pure polyester, but also polyester fiber that contains a so-called third component, or a mixture of both, as long as the undrawn fiber becomes brittle over time. Anything is fine.

In the present invention, it is necessary to allow the undrawn polyester fiber bundle to stand for at least 5 days after spinning before drawing. Normally, polyester fibers undergo rapid changes in their fine structure after spinning, resulting in poor drawability and generation of fuzz and lumps, so polyester fibers are drawn and used within 48 hours after spinning, but the present invention Then, the stretched material is not stretched immediately, but is allowed to stand for at least 5 days before being cut. At that time, the birefringence Δn of the undrawn polyester fiber bundle must be 0.02 or less. If it is oriented more than this, the structure is stable and there is little change over time.

Therefore, no embrittlement of the fibers is observed, and aging has little effect. Particularly when cutting at high magnification or cutting at high speed is desired, it is desirable to use a material with a birefringence Δn of 0°02 or less and to age it for 100 days or more. Moreover, it is effective to set the temperature during aging to 20° C. or higher. Further, if the moisture content of the undrawn polyester fiber bundle is set to 10% or more based on the weight of the fibers over time, the effect becomes even greater.

Since unstretched polyester fiber bundles aged in this manner tend to be unstretched during stretching, it is necessary to stretch the bundles at a stretching ratio of 2.3 times or more.

A stretching ratio of less than 2.3 times is unsuitable because unstretched portions remain.

Note that the undrawn polyester fiber bundle that has been aged as described above has reduced drawability, so when drawing, for example, the drawing speed is lowered (normally 200 to 300 m/rnil is drawn to 150 m/min or less). ), or make the fiber bundle thinner (normally, a fiber bundle with a thickness of 500,000 to 2,000,000 De is used after stretching, but it is changed to a fiber bundle with a thickness of 10,000,000 De or less after stretching), etc. Taking these considerations into consideration is effective in improving stretchability.

The reason why the method of the present invention improves the cutting properties of polyester fibers is not well understood, but by leaving undrawn polyester fibers, unoriented crystals (spherulites, etc.) are probably generated, and after drawing, This is thought to be due to the fibers becoming brittle.

(Example) Example 1.2, Comparative Example 1.2 Polyethylene terephthalate chips containing 0.2% titanium oxide and having an intrinsic viscosity of 0.64 were melt-spun to produce 1.00% titanium oxide.
Take off at a speed of 0 m/min and change to birefringence 〇=
A low-oriented undrawn fiber bundle (undrawn tow) of 50,000 De with an orientation of 0.008 was wetted with water to contain about 17% water and then heated at an average temperature of 24°C. The devices were aged for various days as shown in Table 1.

Next, each undrawn fiber bundle was drawn 3.0 times in hot water at 70°C to obtain a drawn long fiber bundle (drawn tow) of about 1,70,000 De.
After that, it was further cut at a magnification of 34 times and at a speed of 700 m/min, and was false-twisted and bound in a swirling flow using compressed air of 4 kg/cnf to obtain a yarn having a thickness of No. 10. .

The cutting conditions of each were as shown in Table 1.

Table 1 As is clear from the results, uniform cutting becomes possible when the undrawn fiber bundle is aged for 5 days or more.

Example 3, Comparative Example 3 In Example 2, the spinning speed was changed to obtain undrawn fiber bundles with different birefringence Δn as shown in Table 2, and the other conditions were the same as in Example 2. Aging, stretching, cutting, and conjugation were performed. The results were as shown in Table 2.

Table 2 As is clear from the results, uniform cutting is possible if the birefringence Δn of the undrawn fiber bundle is 0.02 or less, but if the orientation becomes too high, the effect of aging will be gone.

(Effects of the Invention) According to the present invention, it is possible to uniformly cut a polyester long fiber bundle even at high speed and high magnification.

Claims (3)

[Claims] (1) A low oriented undrawn polyester fiber bundle with a birefringence Δn of 0.02 or less is aged for 5 days or more after spinning, and then 2
．． A method for producing a cut conjugated yarn, which comprises stretching the fiber bundle by a factor of 3 times or more to form a drawn fiber bundle, and further cutting and conjugating the fiber bundle at a magnification of 4 times or more to obtain a yarn. (2) The method according to claim 1, wherein the low orientation undrawn polyester fiber bundle is aged for 10 days or more after spinning. (3) Contains low oriented unstretched polyester fiber bundles with moisture content of 1
0% or more and a temperature of 20° C. or more.