JP2904966B2 - Thermally splittable composite fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-division conjugate fiber which is divided by heat treatment to form ultrafine fibers, and a method for producing a nonwoven fabric using the same.

[0002]

2. Description of the Related Art Nonwoven fabrics made of heat-adhesive conjugate fibers do not require the use of a binder in the production process, and have been used as surface materials for sanitary materials such as paper diapers and napkins. In order to produce these nonwoven fabrics, two kinds of polymers having different melting points are spun as a sheath-core type or side-by-side type composite fiber, and then drawn, crimped, cut and supplied to a card machine to form a uniform web. The web is fused with hot air or hot rolls at a temperature equal to or higher than the softening point of the low melting point component to form a nonwoven fabric. Many proposals have been made to improve the feel and feel of such a thermal bond type nonwoven fabric. However, the most effective denier (extremely fine) of the fiber itself, which is most effective, could only be dealt with up to 1 de with a single yarn due to the passability of a carding machine.

[0003]

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a heat-dividing conjugate fiber suitable for producing a nonwoven fabric having an excellent texture and touch. A second object of the present invention is to provide a method for producing a nonwoven fabric having excellent texture and touch from the heat-dividing fibers.

[0004]

The heat-splitting conjugate fiber of the present invention, which achieves the first object, is made of polyethylene terephthalate or polyethylene terephthalate.
High melting polymer segment composed of lamide and ethylene
・ Propylene random copolymer or ethylene pro
The low-melting polymer segments composed of pyrene-butene-1 random terpolymer have a cross-sectional shape joined to each other, and the difference in heat shrinkage between the high-melting polymer and the low-melting polymer at a temperature 10 ° C. lower than the melting point of the low-melting polymer is as follows. 50
~ 75%. The manufacturing method of the nonwoven fabric of the present invention to achieve the above second object, after forming a web by carding machine the heat dividable composite fibers, said
The web is heat-treated in a temperature range in which the difference in thermal shrinkage between the high-melting polymer and the low-melting polymer is 50% or more, so that the heat-dividing composite fiber is divided into fine fibers to form a web of ultrafine fibers. The non-woven fabric is obtained by mechanical entanglement means.

First, the heat-dividing conjugate fiber of the present invention will be described. The heat-dividing fiber of the present invention has a cross-sectional shape in which a high-melting polymer segment and a low-melting polymer segment are joined to each other. As such a sectional shape, FIG.
As shown in (a) to (g), the high-melting polymer segment A and the low-melting polymer segment B are bonded to each other, and at least one part of the high-melting polymer segment A and at least one part of the low-melting polymer segment B Are preferably exposed. It is preferable that a total of four or more high-melting polymer segments and low-melting polymer segments are joined. As the polymer constituting the high melting point polymer segment, polyethylene terephthalate (hereinafter referred to as PET), polyamide (hereinafter referred to as PA) or the like is used. On the other hand, as the polymer constituting the low melting point polymer segment, an ethylene / propylene random copolymer (hereinafter referred to as EP) is used. Random terpolymer (hereinafter referred to as EPB random terpolymer) and the like.

In the heat-splitting conjugate fiber of the present invention, the difference in heat shrinkage between the high-melting polymer and the low-melting polymer at a temperature 10 ° C. lower than the melting point of the low-melting polymer is 50 to 75.
% Is essential. The difference between the thermal shrinkage rates of the two polymers is evaluated at a temperature lower by 10 ° C. than the melting point of the low-melting polymer, because this temperature is the upper limit temperature at which the low-melting polymer fibers can be stably operated while retaining the form.

[0007] Difference in heat shrinkage of high-melting polymer and low-melting polymer at a temperature 10 ° C. lower than the melting point of low-melting polymer Δ
S is obtained by the following equation. ΔS (%) = S _lmp (%) − S _hmp (%) Here, S _lmp and S _hmp are temperatures lower by 10 ° C. than the melting points of the low-melting polymers (lmp) and the high-melting polymer (hmp), respectively. a thermal shrinkage at a fiber length of at unshrunk _{(L lmp1,} L _hmp1) and fiber length after heat shrinkage when heat-treated for 15 minutes at from 10 ° C. lower temperature of the low melting polymer melting _{(L LMP2,} L
_hmp2 ) by the following equation.

[0008]

(Equation 1)

In the present invention, ΔS is set to 50 to 75%
The reason is that if ΔS is less than 50%, the heat-dividing conjugate fiber has a low splitting ratio, it is difficult to obtain ultrafine fibers by heating, and thus a nonwoven fabric with good texture and touch is not obtained. This is because there is no low-melting-point polymer that produces a difference in shrinkage of 75% or more at a temperature 10 ° C. lower than the melting point, which is close to the upper limit temperature at which the temperature is maintained.

The heat-splitting conjugate fiber of the present invention having the above-described structure is obtained by supplying a high-melting polymer and a low-melting polymer to a composite melt-spinning apparatus, and forming a composite melt-spun die having a cross section shown in FIG. It is obtained by drawing and crimping the obtained undrawn yarn. In the production of the heat-dividing conjugate fiber, various stresses are applied during mechanical processing such as drawing and crimping, but the high-melting polymer segment and the low-melting polymer segment are not substantially separated and separated, Single yarn denier must be kept at 1 de or more. Because both polymers are yarn protection, drawing,
This is because various troubles occur when peeling occurs during machining such as crimping. For example, in the stretching step, there are fluffing and winding around a roller, and in the crimping step, clogging at the crimper entrance occurs. Further, when the heat-dividing conjugate fiber is peeled, the ultrafine fiber peeled in the carding step for producing the web enters between the needles of the card machine and hinders the production of a uniform web. In order to suppress the occurrence of such troubles, to smoothly perform machining, and to obtain ultra-fine fibers by heat division, and to obtain a nonwoven fabric with a good feel and a sense of fusion, the ratio of the high-melting polymer to the low-melting polymer is It is necessary to select the content and MFR (melt flow rate) of components other than propylene of the EP random copolymer or EPB random terpolymer which is a low melting point polymer. That is, regarding the above, the cross-sectional area ratio of the high melting point polymer / low melting point polymer is preferably 3/7 to 7/3, more preferably 4/6 to 6/4, and particularly preferably 5/5 or its vicinity. With respect to the above, the EP random copolymer or EPB random terpolymer has a higher heat shrinkage as the content of components other than propylene increases, and is suitable for the present invention.
However, when the MFR is small, the strain during spinning or drawing is large, the peel strength at the interface between the two polymers is low, and the above-mentioned troubles during machining are frequent, which is not preferable. On the other hand, when the content of components other than propylene is low, or when the MFR is large, the distortion generated between the two components during spinning and drawing is small, and there is no problem in the drawing, crimping, and carding steps, but it is caused by heat treatment. The difference in shrinkage decreases, and the heat treatment at a temperature about 10 ° C. lower than the melting point of the low-melting polymer cannot be divided, and the processing temperature must be raised to a temperature equal to or higher than the melting point of the low-melting polymer. Then, the form of the fiber is broken and the texture becomes hard, which is not preferable. From such a viewpoint, the content of components other than propylene of the EP random copolymer or EPB random terpolymer is preferably 2.0 to 8.0 wt%, and the MFR is preferably 5 to 30%.

Next, a method for producing the nonwoven fabric of the present invention will be described. In the method for producing a nonwoven fabric according to the present invention, the heat-dividing conjugate fiber is formed on a web by a carding machine.
This carding step is performed by a conventional method, but since the heat-dividing conjugate fibers do not peel off at this stage, there is no trouble that the ultrafine fibers enter between the needles of the card machine. Next, the web is subjected to a heat treatment in a temperature range where the difference in thermal shrinkage between the high-melting polymer and the low-melting polymer is 50% or more. Obtain a fiber web. The heat-splitting conjugate fiber of the present invention has a difference ΔS
Since it is as large as ~ 75%, the above-mentioned divisional fineness is extremely smoothly performed. Next, the web is made into a nonwoven fabric by using a thermal or mechanical entanglement means. As thermal means, hot roll fusion at a temperature higher than the softening point of one of the components constituting the microfine fiber web, and hot air fusion to form a thermal bond type nonwoven fabric, and mechanical means as microfine fiber web Can be entangled with a needle punch or a water needle to form a nonwoven fabric.
Since the obtained nonwoven fabric is composed of ultrafine fibers, it has excellent texture and touch and is preferably used as a surface material of a sanitary material.

[0012]

Next, the present invention will be described specifically with reference to examples. In addition, the evaluation method of the fiber and nonwoven fabric performed in the Example is as follows.

(1) Difference in heat shrinkage (ΔS) Difference in heat shrinkage between high-melting polymer and low-melting polymer ΔS
The fiber obtained by spinning and drawing both polymers separately under the same conditions is heated at a temperature 10 ° C. lower than the melting point of the low melting point polymer at 1 ° C.
It was determined from the shrinkage ratio after heat treatment for 5 minutes. The calculation formula is as described above. (2) Division ratio About 100 yarns were measured under a microscope, and the number X divided into single component single yarns was divided by the single component single yarn number Y, and expressed as a percentage. Division ratio = X ÷ Y × 100% (3) Peel strength The peel strength of both polymers was determined by peeling one end of the sample in advance by about 2 cm, sandwiching both ends with clips, attaching the clips to a tensile tester, and setting the clips at 5 mm / min. At that time, the load: W (g) was measured, and the fiber diameter measured by a microscope: divided by D (μm) Peel strength: P (g / μ)
m). P = W / D (4) Breaking length: means the length of breaking by its own weight, length 10
A sample having a width of 0 mm and a width of 25 mm was pulled at a pulling speed of 100 mm / min. (5) Tactile sensation (sensory test) It was evaluated by a sensory test by five adult women. That is, the sample is pressed against the inside of one forearm with the other hand, and rubs in multiple directions. The contact feeling was evaluated by five panelists. On average, those having good contact feeling were indicated by 、, those having bad contact feeling were indicated by x, and those having extremely bad contact feeling were indicated by XX.

Example 1 A high melting point polymer having a relative viscosity of 0.6 [equivalent weight mixture of phenol and ethane tetrachloride was used as a solvent, and the solution concentration was adjusted to 0.1.
5 g / 100 ml, measured at a temperature of 20 ° C.] (K101 manufactured by Kanebo Co., Ltd.), 4.0 wt% of ethylene content as a low melting point polymer, MFR of 24, melting point of 135 ° C.
Of a random EP copolymer (Idemitsu Polypropylene Y2035G, manufactured by Idemitsu Petrochemical Co., Ltd.) in a composite melt spinning apparatus at a volume ratio of high-melting polymer to low-melting polymer of 1: 1 at a spinning temperature of 280 ° C. and a winding speed 1200m /
Wound with min. The obtained undrawn yarn is subjected to 3.5 at 90 ° C.
It is stretched twice, crimped at 14 pieces / inch by a press-type crimper, and cut into 51 mm to obtain a joint type bicomponent fiber I having a cross section shown in FIG. Was.
The performance of this fiber is shown in Table 1. The difference in thermal shrinkage between the two polymers at 125 ° C., which is 10 ° C. lower than the melting point of the low melting polymer, was 65.2%. This fiber was applied to a carding machine to obtain a web of 20 g / m @ 2. However, the fiber was not peeled off in the carding machine, the permeability was good, and a uniform web was obtained. This web was heat treated for 10 seconds in a hot blast stove set at 125 ° C. As a result, the high-melting-point polymer segment and the low-melting-point polymer segment constituting the fiber were peeled off due to the difference in heat shrinkage, resulting in a web of ultrafine fibers. At this time, the fiber splitting ratio was 100%.
Photomicrographs of the heat-splitting fibers before and after heat treatment are shown in FIG.
(A) and (b) show. Then wind speed 2m / sec, 140
The above-mentioned web was supplied to a hot-air fusion device adjusted to ° C. and heat-treated for 5 seconds to obtain a hot-air fusion nonwoven fabric. As shown in Table 2, the obtained nonwoven fabric had a soft texture and a high strength.

Examples 2 to 8 and Comparative Examples 1 to 2 The heat splittable conjugate fibers II, III, IV, V, VI and Comparative Examples of the present invention were prepared in the same manner as in the actual traveling example 1 using the combinations of raw materials shown in Table 1. Of composite fiber VII was obtained. The performance of each fiber is as shown in Table 1. Each web made of each fiber was heat-treated at a temperature 10 ° C. lower than the melting point of the low-melting polymer for 10 seconds in the same manner as in Example 1, and then made into a nonwoven fabric under the conditions shown in Table 2 to obtain strength and tactile sensation. It was measured. Table 2
As is clear, Examples 1 to 4 in which the low-melting point polymer was a web composed of composite fibers I to VI each of which was an EP random copolymer having an ethylene content of 3 to 5 wt%.
In the case of No. 8, a high-strength nonwoven fabric with a good tactile sensation was proposed by a hot air fusion method, a hot roll fusion method, or a needle punch method. On the other hand, in Comparative Example 1 in which the low-melting-point polymer used a web made of the conjugated fiber VII, which is a propylene homopolymer containing no ethylene, the fiber was not split before being entangled, so that only a normal nonwoven fabric was obtained. Further, in Comparative Example 2 in which the temperature of the hot air was increased to 170 ° C., which is a temperature higher than the melting point of polypropylene, in an attempt to increase the difference in shrinkage from PET, the form of the fibers was broken and a nonwoven fabric was not obtained.

Example 9, Comparative Example 3 Relative viscosity of Ube Kosan Co., Ltd.
Fibers VIII and IX were prepared using a combination of the raw materials shown in Table 1 by using nylon 66 of 0 [equivalent weight mixture of phenol and ethane tetrachloride as a solvent, solution concentration of 0.5 g / 100 ml, measured at a temperature of 20 ° C.] Obtained. The web composed of the fibers VIII and IX was formed into a nonwoven fabric in the same manner as in Example 1. Table 2 shows the performance of the nonwoven fabric. From Table 2, Example 9
Although the nonwoven fabric of Example 3 had high strength and excellent tactile sensation, that of Comparative Example 3 was inferior in both strength and tactile sensation.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

By using the heat-division conjugate fiber of the present invention, a thermal bond type nonwoven fabric having a good tactile sensation, which cannot be obtained with conventional adhesive fibers, can be obtained. When this nonwoven fabric is used for sanitary materials such as napkins and disposable diapers, it has good touch and can greatly increase added value. If the fiber of the present invention is used, as in the water needle method,
An expensive device for generating a high pressure in the fluid is not required, and a nonwoven fabric made of ultrafine fibers can be manufactured with a device having a relatively simple structure such as a hot blast stove, and energy saving can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional shape of a heat-dividing conjugate fiber of the present invention.

FIGS. 2 (a) and (b) show a state before heat treatment in Example 1. FIG.
It is a microscope picture of a pyrolytic conjugate fiber after that.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) D01D 5/36 D01F 8/06-8/14 D04H 1/54

Claims (3)

(57) [Claims] (1) Polyethylene terephthalate or poly
High melting point polymer segment composed of amide and ethylene
Propylene random copolymer or ethylene propylene
Low-melting-point polymer segments composed of len-butene-1 random terpolymer have a cross-sectional shape joined to each other,
The difference in heat shrinkage between the high melting point polymer and the low melting point polymer at a temperature 10 ° C. lower than the melting point of the low melting point polymer is 50 to 7
A heat-dividing conjugate fiber, which is 5%. 2. A high melting polymer segment and a low melting poly.
Mer segments are joined together in a total of four or more
The thermally splittable conjugate fiber according to claim 1 . 3. After forming the web by a carding machine to heat dividable composite fiber according to claim 1 or claim 2, wherein
The web is heat-treated in a temperature range in which the difference in thermal shrinkage between the high-melting polymer and the low-melting polymer is 50% or more, so that the heat-dividing composite fiber is divided into fine fibers to form a web of ultrafine fibers. A method for producing a nonwoven fabric, wherein the nonwoven fabric is obtained by mechanical entanglement means.