JPH02191716A - Conjugate fiber having latent crimpability and imparting method of high crimp to same conjugate fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber capable of smoothly treating by card without revealing of a natural crimp at the drying treatment and capable of revealing crimp at subsequent heating, being subjected to conjugate spinning of respectively a specific high-melting component and a low-melting component and satisfying a specific condition. CONSTITUTION:(A) A high-melting component composed of crystalline polypropylene and (B) a low-melting component composed of mixture of (i) high-density crystalline polyethylene having 0.94-0.97g/cm<3> density as a main component and (ii) low-density crystalline polyethylene having 0.915-0.93g/cm<3> density in an amount of 10-30wt.% of total of (A) and (B) are subjected to melt conjugate spinning to afford the aimed fiber as parallel-type or eccentric sheath-core type conjugate fiber comprising 4/6-6/4 fiber cross-section ratio of components A/B, and for the eccentric sheath-core type conjugate fiber, having >=10% eccentricity E given by the formula E=D/RX100 (D is distance between the center of the conjugate fiber and the center of core component; R is radius of a circle having same cross section as the cross section of the conjugate fiber).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a composite fiber having a latent crimp ability and a method for increasing the crimp of the composite fiber.

[Prior art] Composite fibers using polyolefin raw materials include parallel composite fibers in which a high melting point component such as crystalline polypropylene and a low melting point component such as high density polyethylene are bonded together;
Either one of the above high melting point component or low melting point component is used as a core component,
There are steel-core sheath-core composite fibers in which the other is a sheath component and the center of the core component is eccentric rather than coincident with the center of the composite fiber.In these composite fibers, the high melting point component is Natural crimp occurs due to the difference in shrinkage force between the fiber and the low melting point component, so it is used as a material for manufacturing bulky nonwoven fabrics.

In addition, it is being considered to increase the natural crimp force of the above-mentioned composite fibers and utilize its coiled elasticity to blend it into felts or the like, or to use it for stretchable nonwoven fabrics.

[Problems to be solved by the invention] However, by changing the melt index ratio and spinning temperature of the high-melting point polyolefin component and the low-melting point polyolefin component, a difference in shrinkage force is created between the two components after stretching, resulting in natural crimp. When producing stretchable nonwoven fabrics using conventional highly crimpable composite fibers, natural crimps with a number of 20 crimps/inch or more have already appeared during stretching and the drying process performed after stretching. , the carding process that is carried out after the drying process cannot be performed smoothly, and on the other hand, if an attempt is made to suppress the natural crimp in the above-mentioned drawing and drying process in order to perform the carding process smoothly, the resulting conjugate fiber will not be crimped. They had the disadvantage of being small in number and having poor elasticity.

Therefore, the first object of the present invention is to have the ability to prevent or suppress the appearance of natural crimp in the drying process after spinning, and to be able to smoothly carry out card processing after the drying process. The object of the present invention is to provide a composite fiber having a latent crimp ability that can manifest natural crimp through subsequent heat treatment.

A second object of the present invention is to provide a method for increasing the crimp of the composite fiber having potential crimp ability.

Means for Solving Problem U] The first object of the present invention is to provide a parallel type or eccentric sheath-core type composite fiber formed by melting composite spinning of a high melting point component and a low melting point component, and which is provided under the following conditions. (i), (ii) and (iii)
This was achieved by composite fibers with a potential crimp ability characterized by satisfying

(i) The high melting point component consists of crystalline polypropylene, while the low melting point component has a density of 09t10 to 0.
The main component is high-density crystalline polyethylene of 970 g/a (weight), and to this, low-density crystalline polyethylene with a density of 0915 to 0.930 g/at (10 to 30% by weight based on the total low melting point components) is added. consisting of an added mixture.

(Effect) The fiber cross-sectional area ratio of the high melting point component/'low melting point component is 4/6 to 6/4.

(iii) In the case of eccentric sheath-core type composite fibers, the distance N (D) between the center of the composite fiber and the center of the core component is divided by the radius (R) of a circle with the same cross-sectional area as the cross-sectional area of the composite fiber. The eccentricity ratio (E=D/Rx1OO) obtained by this is 10% or more.

A second object of the present invention is to dry the composite fibers having the above-mentioned latent crimpability at a temperature below the melting point of low-density crystalline polyethylene so that the latent crimpability is not expressed. and then, after carding, the resulting web is heat treated at a temperature between the melting point of the high melting point component and the melting point of the low density crystalline polyethylene to achieve high crimp. This was achieved by a method of making highly crimped composite fibers with high crimping properties.

The present invention will be explained in detail below.

The conjugate fiber that is the object of the present invention is a parallel conjugate fiber in which a low melting point component and a high melting point component are bonded together, or one of the low melting point component and the high melting point component is a core component and the other is a sheath component,
This is a so-called eccentric sheath-core type conjugate fiber in which the center of the core component does not coincide with the center of the conjugate fiber and is eccentric.

Here, as an example of the above-mentioned parallel type composite fiber, Fig. 1 (a)
The low melting point component (L) and the high melting point component (F(
) and the parallel type composite fiber 1 whose cross section is almost semicircular, and the parallel type composite fiber 1 with a cross section of
Parallel type conjugate fibers 1 and the like shown in b) in which the cross-sectional area of the low-melting point component (L) is larger than the cross-sectional area of the high-melting point component (H) are exemplified.

Examples of eccentric sheath-core composite fibers are shown in Figure 1 (c).
Examples include those shown in (d), (e), and (f).

That is, in these figures, C indicates a core component, S indicates a sheath component, and 2 indicates an eccentric sheath-core type composite fiber, but in FIG. ,(
D) is a case in which the cross section of the composite fiber 2 is circular, but the cross section of the core component C is elliptical, with its long axis extending in the vertical direction of the figure, and (E) is a case in which the core component C1 is a composite fiber 2. Both are elliptical, with their long axes extending in the same horizontal direction in the figure, and (f) is a composite fiber 2 whose core component C has a circular cross section.
The cross-section of is elliptical, and each represents its long axis extending in the horizontal direction of the figure.

Next, the above conditions (i) and (ii) for the composite fiber of the present invention
and (iii) will be explained in order.

(1) Materials for high melting point component and low melting point component In the composite fiber of the present invention, the high melting point component consists of crystalline polypropylene, particularly crystalline polypropylene with a melting point of 160°C or higher, while the low melting point component has a density of 0. .940-0.97
The main component is high-density crystalline polyethylene with a weight of 0g/hundred,
In this, low-density crystalline polyethylene with a density of 0.915 to 0.930 g/cm3 is added to
It consists of a mixture containing 0 to 30% of royal weight.

By appropriately selecting the spinning and drawing conditions of the composite fiber, the difference in shrinkage force between the low-melting point component and the high-melting point component after drawing can be kept small, so self-crimping can be prevented in the drying process after drawing. This suppresses the occurrence of crimps, making it possible to adjust the number of crimps by mechanical crimping, and as a result, card processing after drying processing can be carried out smoothly.

In addition, in the low melting point component of the composite fiber of the present invention, the melting point is lower than the high density crystalline polyethylene, and the density is 0.91.
5 to 0.930 g/cm3 of low density crystalline polyethylene (including directly cast low density polyethylene) was added in an amount of 10 to 30% by weight based on the total low melting point components after card processing. When heat treated at a temperature higher than the melting point of polyethylene and lower than the melting point of the high-melting point component, the low-density polyethylene melts and the latent natural crimp becomes apparent, making it easier to increase the crimp of the composite fiber. Because there is nothing you can do. In addition, low density polyethylene is 1
If it is less than 0%, sufficient self-crimping cannot be achieved by heat treatment, and if it exceeds 35%, the cardability deteriorates, and in either case, the object of the present invention cannot be achieved. I can't.

(11) Cross-sectional area of high-melting point component/'low-melting point component In the composite fiber of the sunken wood invention, the cross-sectional area ratio of high-melting point component/low-melting point component is also an essential condition, and its range is 4 y' 6 to 6/
Limited to 4. The reason for this is that if the cross-sectional area ratio is less than 4/'6, card processing after stretching cannot be carried out smoothly, and if it exceeds -6/4, heat treatment after card processing is insufficient. In contrast, in the case of 4/6 to 6/'4, not only can card processing after stretching be carried out smoothly, but also the heat treatment after card processing This is because sufficient self-crimping can be caused.

(iii) Eccentricity in the case of eccentric sheath-core composite fibers Figure 1 (
In c), if R is the radius of a circle with the same cross-sectional area as the cross-sectional area of the composite fiber, 01 is the center of the composite fiber, and 02 is the center of the core component, then when the distance between ol and 02 is D, the eccentricity E is F
It is determined by the formula.

E=D/RX100 (%) If the eccentricity calculated by the above formula is less than 10%,
Sufficient natural crimp does not develop due to heat treatment after card processing. .

Therefore, the eccentricity of the eccentric sheath-core composite fiber of the present invention is limited to -E of 10% or more.

The composite fiber of the present invention that satisfies the above conditions (i), (port), and (iii) can be obtained by drying the composite fiber and then carding it. Since the ability is latent, card processing can be carried out smoothly, and by heat-treating the obtained web, it is possible to make the crimp that was hidden until then visible and increase the crimp. Therefore, it is preferably used as a stretchable nonwoven fabric material.

In the method for making composite fibers highly crimped according to the present invention, the drying treatment after spinning is carried out at a temperature below the melting point of low-density crystalline polyethylene (for example, about 100 °C It is necessary to carry out the process at a temperature above the melting point of high-density polyethylene. When the treatment is carried out, fusion occurs within the fibers before the natural crimp of the composite fibers has fully manifested.Therefore, the high crimp of the composite fibers (manifestation of latent crimp ability) is caused in advance. It is desirable to conduct the heat treatment at a temperature between the melting point of high density crystalline polyethylene and the melting point of low density crystalline polyethylene (eg, about 125°C) to ensure that the heat treatment is satisfactorily achieved.

[Example] The present invention will be further explained below with reference to Examples.

Example 1 Two single screw extruders and hole diameter 0.6+II! Using an eccentric sheath-core type composite fiber spinning equipment consisting of a circular nozzle for composite fibers, crystalline polypropylene (Ube Industries 8130MV> is used as the core component (high melting point component) and high density polypropylene (Ube Industries, Ltd. 8130MV) is used as the sheath component (low melting point component). Polyethylene (Asahi Kasei Santic J
310, density 0.962 g/cd), and 20% by weight based on all sheath components (all low melting point components) linear low density polyethylene (Japan Petrochemical Linilex, AJ6380,
density 0.919 g/ayi, melting point 120°C)
was added at a spinning temperature of 240°C at a ratio of 50:50.
The fibers were spun at a take-up speed of 666 m/l lin to obtain an eccentric sheath-core type composite fiber having a single yarn denier of 9 and an Ode and having a potential crimp ability.

The obtained composite fiber has a high melting point component (core component)/low melting point component (sheath component) cross-sectional area ratio of 515, and the distance between the center 01 of the composite fiber and the center 02 of the core component is the composite fiber cross-sectional area. The eccentricity E obtained by multiplying by the radius R of a circle with the same cross-sectional area as , was 17% (see Figure 1 (c)).

100 of these multifilaments were collected, with a total denier of approximately 400,000, and the first drawing roller was heated to 60°C. The second and third drawing rollers and the first and second drawing tanks were heated to 90°C. Stretched 4.0 times,
Oiling, mechanical crimping, cutting, and drying were performed to obtain a staple fiber with a cut length of 51 mm and a number of crimps per inch of mechanical crimping of 10.

In addition, the crimper that performs the above mechanical crimping process has a medium size of 25 m.
A stuffing box consisting of two metal rolls of 50 mm was used as in the case of applying normal mechanical crimping. The drying process was carried out for 10 minutes in hot air at 100°C, which is below the melting point of the linear low density polyethylene added as a low melting point component. The natural crimp caused by this drying process is small;
The number of crimps after drying was 14/inch.

Next, the staple fiber obtained above was added to 350+n
Pass it through a m-wide sample card machine and spread it thoroughly. The card quality was good and there were no problems at all. Next, heat treatment was performed for 10 minutes in hot air at 125°C, which is above the melting point of linear low-density polyethylene and below the melting point of high-density polyethylene, and the degree of natural crimp development was observed, and the number of crimp was 28/inch. A highly crimped composite fiber was obtained.

Example 2 A stable fiber with a cut I and length of 51 mTl+ and a number of crimps of 10 per inch during mechanical crimping was produced in the same manner as in Example 1 except that 30% by weight of linear low-density polyethylene was added. Obtained. It should be noted that the appearance of natural crimp due to the drying treatment was greater than in Example 1, but still smaller than in the conventional method, and the number of crimp after the drying treatment was 18/inch.

Next, the staple fiber obtained above is cut into 350mm
It was passed through a wide sample card machine and thoroughly opened. The card quality was good and there were no problems at all. Next, the fibers were heat-treated in hot air at 125° C. for 10 minutes, and the degree of natural crimping was observed. As a result, highly crimped composite fibers with a number of crimps of 31/inch were obtained.

Example 3 The same method as in Example 1 was used, except that a nozzle with a larger eccentricity was used and 10% by weight of linear low density polyethylene was added, the cut length was 51 m + n, and the crimping during mechanical crimping was reduced. Several ten staple fibers/inch and an eccentricity of 29% were obtained. The appearance of natural crimp due to the drying treatment was small, and the number of crimp after the drying treatment was 13 crimps/inch.

Next, the staple fibers obtained above were passed through a sample card machine with a width of 350 mm to fully open the fibers.

The card quality was good and there were no problems at all. Then 125℃
After heat treatment in hot air for 10 minutes and observing the degree of natural crimp, a highly crimp composite fiber with a number of crimp of 26/inch was obtained.

Example 4 Low density polyethylene (Ube Industries UBE Polyethylene J
2522, density 0.920 g/cJ, melting point 104°C) was added in an amount of 15% by weight, but the same method as in Example 1 was used to prepare staples with a cut length of 51 and a number of crimps of 10/inch during mechanical crimping. I got the fiber. Although the appearance of natural crimp due to the drying treatment was larger than that in Example 1, it was still smaller than that in the conventional method, and the number of crimp after the drying treatment was 16/inch.

Next, the staple fiber obtained above was passed through a sample card machine with a width of 350 m and thoroughly opened.

The card quality was good and there were no problems at all. Then 125℃
After heat treatment in hot air for 10 minutes and observing the degree of natural crimp, a highly crimp composite fiber with a number of crimp of 29/inch was obtained.

Comparative Example 1 Linear low density polyethylene 3 outside the range specified in the present invention
A staple fiber having a cut length of 51 prints and a number of crimps per inch of mechanical crimping of 10 was obtained in the same manner as in Example 1 except that 5% by weight was added. The natural crimp became more obvious due to the drying treatment, and the number of crimp after the drying treatment was 23/inch.

Next, when the staple fiber obtained above was passed through a sample card machine with a width of 350 mm and opened, it sank into the cylinder and did not come out from the card.

Comparative Example 2 Linear low density polyethylene 8 outside the range specified in the present invention
A staple fiber having a cut length of 51 mm and a number of crimps of 10 per inch during mechanical crimping was obtained by the same 5 methods as in Example 3 except that the weight percent was added.

Natural crimps hardly appeared during the drying process, and the number of crimps after the drying process was 11 crimps/inch.

Next, the staple fiber obtained above is cut into 350mm
The fibers were passed through a wide sample card machine, thoroughly opened, and heat treated in hot air at 125°C for 10 minutes. When the degree of natural crimp was observed, only 19 crimp per inch was obtained. There wasn't.

Comparative Example 3 Using the same spinning equipment as in Example 1, crystalline polypropylene (Ube Industries 3115M) was used as the core component (high melting point component).
), and high-density polyethylene (Showa Denko F
6200, density 0.952g/cn) using only
These were spun at a ratio of 50:50 at a spinning temperature of 220°C and a take-up speed of 666 m/min to obtain a single yarn denier of 9. Ode
An eccentric sheath-core composite fiber was obtained. The eccentricity of the obtained composite fiber was 17%.

100 of these multifilaments were collected to have a total denier of about 400,000, and the first, second, and third drawing rollers were heated at 30°C and the
The stretching tank was heated to 90°C, and stretched 40 times, oiled, mechanically crimped, cut, and dried, resulting in a cut length of 51 cylinders.
A staple fiber having a number of 10 crimps/inch during mechanical crimping was obtained. The natural crimps became very noticeable during the drying process, and the number of crimps after the drying process was 26/inch.

Next, 350rr of the above-obtained stay fiber
When I passed it through an n-width sample card machine, it sank into the cylinder and did not come out of the card.

Example 5 Using the same spinning equipment as in Example 1, the core component (high melting point component)
As crystalline polypropylene (Ube Industries 8115M
>, high-density polyethylene (Asahi Kasei Santic J320, density 0.962 g/a &
) with 30% by weight of linear low-density polyethylene (Japan Petrochemical Linyrex, AJ6381, density 0.921 g/a
H5 (melting point: 121°C) was added at a ratio of 60:40 at a spinning temperature of 250°C and a take-up speed of 666 m/min, resulting in a single yarn denier of 9. To obtain an eccentric sheath-core type composite fiber having the potential crimp ability of Ode. The obtained composite fiber is
The cross-sectional area ratio of the high melting point component (core component)/low melting point component (sheath component) was 6/4, and the eccentricity was 23%.

Next, the multifilament obtained above is applied to the first and second filaments.
, third stretching roller, first and second stretching tanks at 90°C, 4
．． 0x stretching, oiling, mechanical crimping, cutting, and drying to obtain a stable fiber with a cut length of 51 mm and a number of crimps per inch during mechanical crimping. The appearance of natural crimp due to drying was small, and the number of crimp after drying was 15/inch.

Next, the staple fiber obtained above was 3501T
Pass it through an IIT+ width sample card machine and spread it thoroughly.

The card quality was good and there were no problems at all. then 125°
After heat treatment in hot air of C for 10 minutes and observing the degree of natural crimp, a highly crimp composite fiber with a number of crimp of 27/inch was obtained.

Example 6 According to Example 5, the cross-sectional area ratio was 4/6 and the eccentricity was 10%.
A piece with a cut length of 51 points and a number of crimps per inch during mechanical crimping processing was obtained. Although the appearance of natural crimp due to the drying treatment was slightly larger than that in Example 5, it was still smaller than that in the conventional method, and the number of crimp after the drying treatment was 18 crimps/inch.

Next, the staple fiber obtained above is cut into 350mm
The fibers were passed through a wide sample card machine and the fibers were fully opened.The card properties were good and there were no problems at all. Next, the fibers were heat-treated in hot air at 125° C. for 10 minutes, and the degree of natural crimp was observed. As a result, highly crimped composite fibers with a number of crimps of 33 per inch were obtained.

Comparative Example 4 Same as Example 5, except that the cross-sectional area ratio was set to 6.5/3.5, which is outside the range specified in the present invention, with an eccentricity of 19%, a cut length of 51 nm, and a winding during mechanical crimping. A composite fiber with a reduction number of 10 mm/inch was obtained. Natural crimps hardly appeared due to the drying process, and the number of crimps after the drying process was 12 crimps/inch.

Next, the stable fiber obtained above was 35011
I! Pass it through the sample card machine in TI and fully open it for 12 minutes.
When heat-treated in hot air at 5° C. for 10 minutes and observing the degree of natural crimp, only 18 crimp/inch was obtained.

Comparative Example 5 The same procedure as Example 5 was carried out except that the cross-sectional area ratio was set to 3.5/6.5, which is outside the range specified in the present invention. Obtain a composite m-fiber with a reduction number of 10 pieces/inch. The natural crimps became very noticeable during the drying process, and the number of crimps after the drying process was 23/inch.

Next, 350ff of the staple fiber obtained above was
l! When I passed it through a +1 width sample card machine, it sank into the cylinder and did not come out of the card.

Example 7 Using the same spinning equipment as in Example 1, crystalline polypropylene (Ube Industries R3L2) was used as the core component (high melting point component).
38>, high-density polyethylene (Showa Denko F6200, density 0.952 g/hu) as a sheath component (low melting point component)
20% by weight of linear low density polyethylene (Japan Petrochemical Linyrex AJ5410, density 0.924g/cr#
, melting point 123°C) was spun at a ratio of 50:50 at a spinning temperature of 240°C and a take-up speed of 666 m/min, and the single yarn denier was 9. An eccentric sheath-core type composite fiber having a potential crimp ability of Ode was obtained. The obtained composite fiber had a high melting point component/low melting point component cross-sectional area ratio of 515 and an eccentricity of 13%.

This multifilament was heated at 30°C by the first Nobeoki roller.
, the second and third stretching rollers, and the first and second stretching tanks at 90°C.
The fiber was then stretched 4.0 times, oiled, mechanically crimped, cut, and dried to obtain a stable fiber with a cut length of 51 rTn and a number of crimps per inch during mechanical crimping. The appearance of natural crimp due to drying treatment is small;
The number of crimps after drying was 13 crimps/inch.

Next, the stable fiber obtained above was cut into a 350 mm
It was passed through a wide sample card machine and thoroughly opened. The card properties were good and there were no problems at all.

Next, the fibers were heat-treated in hot air at 125° C. for 10 minutes, and the degree of natural crimping was observed. As a result, highly crimped composite fibers with a number of crimps of 26/inch were obtained.

Example 8 The same method as Example 7 was used except that a nozzle with a slightly reduced eccentricity was used and 30% by weight of linear low density polyethylene was added, with a cut length of 51 mm and mechanical crimping. A stable fiber with 10 crimps/inch was obtained. The eccentricity of the obtained conjugate fiber was 10%, and the number of natural crimps that appeared due to drying was small at 14 crimps/inch.

Next, the stable fiber obtained above was
It was passed through a 1 m wide sample card machine and thoroughly opened. The card quality was good and there were no problems at all. Next, the fibers were heat-treated in hot air at 125° C. for 10 minutes, and the degree of natural crimping was observed. As a result, highly crimped composite fibers with a number of crimps of 28/inch were obtained.

Comparative Example 6 Example 8 except that a nozzle with a smaller eccentricity was used
Using the same method as above, obtain a stable fiber with a cut length of 51 mm and a crimping count of 10 crimps/inch. The eccentricity of the obtained composite fiber was 8%, and the number of crimps after drying was 12/1, with almost no natural crimps appearing during the drying process.
It was inches.

Next, the stable fiber obtained above was
The fibers were passed through a wide sample card machine, fully opened, and heat treated in hot air at 125° C. for 10 minutes. When the degree of natural crimp was observed, only 21 crimp/inch was obtained.

The conditions and results of Examples 1 to 8 and Comparative Examples 1 to 6 are summarized in Table 1.

Comparative Example 7 The same procedure as in Example 1 was carried out except that the additive low-density polyolefin was not used and a nozzle with an eccentricity of 0% was used during crimping with an additive of 0% and an eccentricity of 0%. Number of crimps: 17
Staple fibers with a cut length of 51 pieces/inch and a cut length of 51 bars were obtained. There were no crimps after drying of ioo"c or after heat treatment at 125°C after card processing, and the number of crimps was 17 per inch, the same as during mechanical crimping. The morphology was a zigzag mechanical crimp.

Example 9 The stable fibers obtained in Example 1 and Comparative Example 2.7 were passed through a sample card machine, and the resulting web was
After being heat-treated at ℃ to make it highly crimped, it was hot-air fused in a test hot-air fusion equipment to give it a fabric weight of about 30 to 32 g/tr?
'A nonwoven fabric was produced. Next, Tensilon (UTM-n-
20), measure the 20% elongation stress and 20% elongation modulus.

The method for measuring 20% elongation stress and 20% elongation elastic modulus is as follows.

(1) 20% elongation stress In the elongation modulus measurement test, the stress at an elongation rate of 20% was measured and defined as 20% elongation stress.

(2) 20% elongation modulus It was carried out according to the J　15-L1096A method.

That is, the sample width was 50! using a constant speed extension type tensile tester.
lTm, sample length 20Trrm, tensile speed 20mm/mi
Measurement was made at an elongation rate of 20%.

Apply an initial load, measure the length of 1-m when the elongation rate is 20%, leave it for 1 minute, then remove the weight, leave it for 3 minutes, apply the same load as the initial load again, and stretch it to an elongation rate of 20%. The residual elongation length Llmm was measured and calculated using the following formula.

20% elongation modulus (%) = xio.

The measurement results are shown in Table 2. As shown in Table 2, Example 1
The results showed that the nonwoven fabric obtained using the composite fibers of Comparative Example 2.7 was easier to stretch with a small force, and the elastic modulus of 20% elongation was 80% at the 10th time, indicating excellent elasticity. Obtained.

(The following is a blank space) [Effects of the Invention] As detailed above, according to the present invention, card processing after drying processing can be carried out smoothly, and heat treatment after card processing can prevent latent A composite fiber having latent crimp ability that can manifest natural crimp, and a method for increasing the crimp of the composite fiber have been provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the cross-sectional structure of the composite fiber of the present invention.

Claims (2)

[Claims] (1) A parallel type or eccentric sheath-core type composite fiber made by melt-spinning a high melting point component and a low melting point component, and is characterized by satisfying the following conditions (i), (ii) and (iii). Composite fiber with potential crimp ability. (i) The high melting point component consists of crystalline polypropylene, while the low melting point component has a density of 0.940 to 0.9.
The main component is high-density crystalline polyethylene with a density of 70 g/cm^3, and a density of 0.915 to 0.930 g/cm.
It consists of a mixture in which 10 to 30% by weight of low-density crystalline polyethylene of ^3 is added based on the total low melting point components. (ii) The fiber cross-sectional area ratio of the high melting point component/low melting point component is 4/6 to 6/4. (iii) In the case of eccentric sheath-core type composite fibers, the distance (D) between the center of the composite fiber and the center of the core component is divided by the radius (R) of a circle with the same cross-sectional area as the cross-sectional area of the composite fiber. The eccentricity ratio (E=D/R×100) obtained is 10% or more. (2) The composite fiber having a latent crimp ability according to claim (1) is treated so that the latent crimp ability is not expressed.
After drying at a temperature below the melting point of low density crystalline polyethylene and then carding, the resulting web is heat treated at a temperature between the melting point of the high melting point component and the melting point of the low density crystalline polyethylene for high winding. 1. A method for increasing the crimp of a composite fiber having a potential crimp ability, the method comprising crimping the composite fiber.