A Method for Treating Textile Fibers of Different Lengths

Abstract

Textile fibers of different lengths are fractionated in a liquid medium at a predetermined consistency into at least two fractions on the grounds of the fiber length, the two fractions being a first accept and a second accept. The second accept, which has longer fibers than the first accept, is led to a refining step in the liquid medium, and the refined fibers are fractionated in the liquid medium into at least two fractions on the grounds of the fiber length.

Claims

1-9. (canceled)

10. A method for treating textile fibers of different lengths, the textile fibers comprising natural fibers and man-made fibers comprising synthetic fibers, the method comprising: fractionating the fibers in a liquid medium at a consistency of 0.2 to 4% into at least two fractions on the grounds of the fiber length, the two fractions being a first accept and a second accept; leading the second accept, which has longer fibers than the first accept, to a refining step in the liquid medium; and fractionating the refined fibers in the liquid medium at a consistency of 0.2 to 4% into at least two fractions on the grounds of the fiber length.

11. The method of claim 10, wherein the fibers are fractionated in the liquid medium at a consistency of 0.5 to 2%.

12. The method of claim 10 wherein the fibers are fractionated in the liquid medium at a consistency of 0.8 to 1.2%.

13. The method of claim 10 wherein the fractionating steps are carried out with a slotted screen basket or a hole screen basket.

14. The method of claim 10 further comprising leading the first accept into further processing.

15. The method of claim 14 further comprising a flotation step for separating synthetic fibers.

16. The method of claim 10 wherein textile fibers are derived from a recycled textile fiber pulp.

17. The method of claim 10 further comprising dispersing the textile fibers in the liquid medium prior to the fractionating step.

18. The method of claim 10 wherein the fractionating into the first accept and the second accept takes place before any refining step.

19. A method for treating textile fibers of different lengths, the textile fibers comprising natural fibers and man-made fibers comprising synthetic fibers, the method comprising: in a first phase fractionating the fibers in a liquid medium at a consistency of 0.2 to 4% into at least two fractions on the grounds of the fiber length, the two fractions being a first accept and a second accept, wherein the second accept has longer fibers than the first accept and wherein the liquid medium comprises water; leading the second accept to a refining step in the liquid medium to produce refined fibers; and fractionating the refined fibers in the liquid medium in the first phase at a consistency of 0.2 to 4% into at least two fractions on the grounds of the fiber length.

20. The method of claim 19 further comprising leading the first accept to a flotation step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings.

[0029] FIG. 1 shows a flow chart of the method.

[0030] FIG. 2 shows fiber distributions of one trial.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] FIG. 1 shows a flow chart of a method for fractionating textile fibers of different lengths. Recycled textile pulp may be dispersed in water in phase 1 in such a manner that the consistency is within 0.2 to 4%. After that the fibers may enter to a refining step, or to a fractionating step. Alternatively, the recycled textile fiber pulp may be fed directly to a refining step.

[0032] The recycled textile fiber pulp is fed into fractionation in phase 2 where the fibers of the pulp are fractionated into at least two fractions. The fraction comprising the short fibers, i.e. the first accept, may be led to further processing in phase 3. The further processing step may be e.g., flotation for separating the rest of the synthetic fibers from the fraction in question. The fraction of the short fibers may have fibers whose length is less than two millimeters. However, if there are more than two fractions more than one fraction may be led for further processing.

[0033] The fraction that has the long fibers, i.e. the second accept, is led for refining in phase 4. The fraction of the long fibers may have fibers whose length is at least two millimeters. The long fibers are refined in such a manner that their fiber length shortens. After the refining step the fibers return to the fractionating step at a consistency that is within 0.2 to 4%. The long fibers may cycle through the refining and fractionating steps as long as desired in order to achieve the desired fiber length.

Example

[0034] Table 1 shows a fiber distribution of a feed, i.e. a recycled textile fiber pulp that is fed into a fractionation process in order to produce a short fiber fraction and a long fiber fraction. Table 1 also shows a fiber distribution of the short fiber fraction and a fiber distribution of the long fiber fraction.

TABLE-US-00001 TABLE 1 Distribution Distribution of Distribution of of the feed Short fiber the short fiber Long fiber the long fiber Feed (mm) (%) fraction (mm) fraction (%) fraction (mm) fraction (%) 0.00-0.20 16.7 0.00-0.20 28.3 0.00-0.20 13.1 0.20-0.60 19.9 0.20-0.60 28.2 0.20-0.60 19.1 0.60-1.20 22.8 0.60-1.20 24.0 0.60-1.20 23.0 1.20-2.00 19.4 1.20-2.00 13.7 1.20-2.00 20.3 2.00-3.20 13.3 2.00-3.20 5.2 2.00-3.20 15.3 3.20- 7.9 3.20- 0.7 3.20- 9.2 L.sub.c (l) (mm) L.sub.c (l) (mm) L.sub.c (l) (mm) 1.386 0.832 1.476

[0035] The fiber length of the feed, short fiber and long fiber fractions can be analyzed and measured with the Valmet FS5 fiber analyzer or other similar apparatus. The fraction whose fiber length is 3.20 or more contains the longest fibers, i.e. the fraction may contain textile fibers whose length correspond to the original lengths of the textile fibers mentioned earlier in this text. The feed in this example was fibers that originate from recycled clothes and comprise both cotton and synthetic fibers.

[0036] FIG. 2 shows the results of table 1 graphically. One can see clearly that the recycled textile fiber pulp can be sorted efficiently into the short fiber fraction and the long fiber fraction. In other words, compared to the initial feed, i.e. the recycled textile fiber pulp, the fiber length of the short fiber fraction is weighted to the shorter fibers and the fiber length of the longer fiber fraction is weighted to the longer fibers. As one can see from Table 1, there is only a minimum amount of fibers of length 3.20 mm or more in the short fiber fraction.

[0037] Synthetic material is also separated efficiently from the short fiber fraction. It was noticed that the recycled textile fiber pulp initially included 8.0 wt.-% of synthetic fibers. After the fractionation and refining process the short fiber fraction had 2.6 wt.-% of synthetic fibers and the long fiber fraction had 10.3 wt-% of synthetic fibers.

[0038] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.