JP2846675B2 - Composite fiber with excellent bulkiness - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an eccentric sheath-core conjugate fiber excellent in bulkiness. The conjugate fiber of the present invention is used for producing a nonwoven fabric having excellent bulkiness.

[Prior art] Composite fibers composed of two or more types of polyolefin polymers having different melting points can be bonded to each other without using an adhesive to form a nonwoven fabric, so that sanitary materials such as disposable diapers are used. Widely used for

Such non-woven fabrics are mainly made of composite spinning of a plurality of polyolefin polymers having different melting points, and are relaxed after stretching, thereby exhibiting natural crimp to form a composite fiber having excellent bulkiness. Processed into fiber,
It is manufactured by fibrillating with a carding machine to form a sheet-like web, and then heat-treating at a temperature between the melting points of the low-melting polymer and the high-melting polymer.

As a composite fiber composed of two or more kinds of polyolefin polymers having different melting points, a laminated composite fiber in which a low melting point polymer such as polyethylene and a high melting point polymer such as polypropylene are bonded, and a high melting point There is a sheath-core type composite fiber in which the outer periphery of the polymer is coated with a low melting point polymer. The sheath-core type composite fiber has advantages such as easy control of the expression of natural crimp and superior spinnability, as compared with the bonded type composite fiber. For this reason, sheath-core type composite fibers are mainly used as composite fibers composed of two or more kinds of polyolefin polymers having different melting points.

[Problems to be Solved by the Invention] However, today, there is a growing demand for a bulky nonwoven fabric having a better feel or a bulky nonwoven fabric having a more economical efficiency. It is preferable to use a conjugate fiber excellent in bulkiness as a material of the above, but there is a problem that conventional sheath-core type conjugate fibers cannot sufficiently meet these demands.

Therefore, an object of the present invention is to provide a conjugate fiber excellent in bulkiness, which can obtain a nonwoven fabric with further improved bulkiness.

Means for Solving the Problems The present invention has been made to achieve the above object, and the composite fiber having excellent bulkiness of the present invention comprises a low-melting polymer forming a sheath and a core. The composite yarn containing the high melting point polymer to be formed, the eccentric sheath-core composite fiber having excellent bulkiness obtained by expressing natural crimp, wherein the number of natural crimps is 6 to
At 20 particles / inch, the high melting point polymer is a crystalline polypropylene having a crystal grain size of 55 ° or more.

 Hereinafter, the present invention will be described in detail.

As described above, the composite fiber having excellent bulkiness of the present invention is an eccentric sheath-core composite fiber having a natural crimp number of 6 to 20 / inch. The reasons for limiting the natural crimp number are as follows. It is on the street.

That is, if the number of natural crimps is less than 6 / inch, the connection of the web when passing through a carding machine is reduced in forming a nonwoven fabric, and if it exceeds 20 / inch, a uniform web cannot be obtained, which is both undesirable. Because. In both cases, bulky composite fibers are not obtained.

The number of natural crimps is the cross-sectional area ratio between the sheath and the core, the eccentricity (in this specification, the fiber cross-section of the distance between the center of the fiber and the center of the core when the cross-section of the fiber is taken). Means the percentage with respect to the radius of a circle having the same area as described above), the take-up speed at the time of composite spinning, the preheating temperature at the time of stretching, and the like, so that the natural crimping number is 6 to 20 pieces / inch. Although it is difficult to stipulate the conditions for controlling in a unified manner, in the bulky composite fiber of the present invention, at least, the cross-sectional area ratio between the sheath and the core is set to 6/4 to 3/7. At the same time, the eccentricity is preferably set to 8 to 36%.

The reason why the cross-sectional area ratio of the sheath and the core is preferably 6/4 to 3/7 is that the natural cross-sectional ratio between the sheath and the core is out of the above range to develop a sufficient natural crimp. Because they cannot do it. A particularly preferable cross-sectional area ratio between the sheath portion and the core portion is 5/5 to 4/6.
It is. The reason why the eccentricity is preferably set to 8 to 36% is that if the eccentricity is less than 8%, sufficient natural crimp cannot be exhibited, and if the eccentricity exceeds 36%, the cross-sectional area ratio becomes 6/36. This is because it is physically impossible in the range of 4 to 3/7. A particularly preferred eccentricity is 13 to 36%.

The control of the cross-sectional area ratio and the eccentricity of the sheath portion and the core portion of the composite fiber having excellent bulkiness of the present invention is performed by a conventional method such as control of the discharge amount of an extruder or change of the eccentricity of a spinneret. Can be performed.

Further, as described above, the high melting point polymer forming the core in the composite fiber having excellent bulkiness of the present invention is limited to crystalline polypropylene having a crystal grain size of 55 mm or more.

The reason is that if the crystal grain size of the crystalline polypropylene of the core component is less than 55 mm, a nonwoven fabric which is bulkier than the conventional nonwoven fabric using composite fibers can be obtained even if the natural crimp number is 6 to 20 / inch. Is not possible. By setting the size of the crystal grains of the crystalline polypropylene of the core to 55 mm or more, a change in the crimped form of natural crimp due to hot air when forming the nonwoven fabric is suppressed, that is, the crimp is hardly set. Therefore, it is possible to obtain a nonwoven fabric which is more excellent in bulkiness and good in feeling.

UBE Polypropylene S130M as crystalline polypropylene
V (Ube Industries, Ltd.) and UBE Polypro ZS1255 (Ube Industries, Ltd.) can be used. The crystallinity of the crystalline polypropylene is controlled by controlling the drawing conditions when the undrawn yarn is drawn, the heat treatment temperature when the drawn yarn is heat-treated into a composite fiber having excellent bulkiness, and the crystalline polypropylene. By appropriately selecting the melt flow rate (MFR) and the like.

The crystal grain size of the crystalline polypropylene forming the core is set to 55 mm or more, and the cross-sectional area ratio between the sheath and the core and the eccentricity are within the above-mentioned ranges and the natural crimp number is 6 to
By setting the number to 20 pieces / inch, a bulky conjugate fiber can be obtained, and by using this bulky conjugate fiber,
A nonwoven fabric having a further improved bulkiness than a conventional nonwoven fabric can be obtained.

In addition, since the low-melting-point polymer which forms a sheath part once melt | dissolves at the time of nonwoven-fabrication, the magnitude | size of the crystal grain of the sheath component in the eccentric sheath-core type composite fiber does not affect the bulkiness of a nonwoven fabric.

As the low melting point polymer forming the sheath in the bulky composite fiber of the present invention, it is preferable to use a polymer having a melting point 20 ° C. or more lower than the melting point of the above-mentioned crystalline polypropylene as the core. . Examples of such a polymer include low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer and the like, and it is particularly preferable to use high-density polyethylene.

A nonwoven fabric that is bulkier than a conventional nonwoven fabric can be obtained by using, for example, 30% or more of the composite fiber having excellent bulkiness of the present invention as a material.

[Examples] Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited to these Examples.

The methods for measuring various physical property values shown in the examples are shown in advance.

・ MFR: Based on ASTM D 1238, for polypropylene (PP) under (L) conditions (230 ° C), polyethylene (P)
E) and ethylene-vinyl acetate copolymer (EVA) were measured under the condition (E) (190 ° C.).

· Number of crimps: According to JIS L 1074.

-Crystal grain size: X-ray analysis.

(X-ray analysis: Bundling the fibers and setting the apparent thickness to about 2 mm to obtain a diffraction intensity curve on the equator, PP is 2θ = 14.2 degrees (11
0), PE was determined from the half width of the peak at 2θ = 21.4 degrees (110).

Analysis conditions: 30 kV, 30 mA, divergence slit: 1 mmφ, scattering slit: 1 mm width, detection slit: 0.3 mm width, goniometer scan speed: 1/2 degree, chart speed: 10 mm / min, time constant: 4 seconds, Baseline: 7.5 to 10 degrees) Bulk: 1.06 g / lambda in a laminate of 10 nonwoven fabrics cut to a size of 5 x 5 cm at a temperature of 25 ° C and a humidity of 65%.
added plane load of cm ² 30 seconds, to measure the height of the midpoint four part unloading to each side of the 30 seconds after leaving the addition of plane load of 0.26 g / cm ^2, the laminate The volume was calculated, and the specific volume obtained by dividing the volume by the weight of the test nonwoven fabric was defined as the bulk.

Example 1 Crystalline polypropylene (MFR = 17) was used as a high-melting polymer forming a core portion using an eccentric sheath-core type composite fiber spinning facility comprising two single-screw extruders and a circular nozzle for a composite fiber having a hole diameter of 0.6 mm. , A high-density polyethylene (MFR = 20) as a low-melting polymer forming a sheath at a spinning temperature of 50:50
Spin at 220 ° C, take-off speed 500m / min, single yarn denier 12.
An eccentric sheath-core composite fiber of 0 de was obtained.

The spinnability was good and even after continuous spinning for 1 hour, there was no spinning breakage and the spinning was stable.

The resulting composite fiber has a sheath / core cross-sectional area ratio of 5/5.
And the eccentricity was 20%.

A total of 100 multifilaments were collected to give a total denier of about 600,000 denier.
One-stage stretching at a stretching ratio of 5 times is performed between the first and second rollers at 45 ° C., a second and third stretching roller temperature of 50 ° C., and a first and second stretching bath temperature of 90 ° C., and subsequently oiling and crimping After performing processing and heat treatment (110 ° C), it becomes an eccentric sheath-core composite fiber with excellent bulkiness with a natural crimp number of 12.0 pieces / inch.
The fiber was cut to a fiber length of 45 mm to obtain a naturally crimped staple fiber of 3 denier single yarn.

The crimper that performs the crimping process consists of two metal rolls with a width of 25 mm, and does not use a stuffing box that is usually used when applying mechanical crimping, and exhibits natural crimping only by taking up the crimper roll. I let it.

The obtained naturally crimped staple fiber was analyzed by X-ray to measure the size of crystal grains of the crystalline polypropylene in the core.

Thereafter, the obtained staple fiber was passed through a roller card machine having a width of 350 mm to produce a uniform web having a basis weight of 20 g / m ² . At this time, there was no problem in the card passing property, and a very bulky web was obtained. The web is then
A hot air-fused nonwoven fabric was prepared by placing the device on a wire mesh belt at 350 mm and a speed of 5 m / min and blowing hot air at an air temperature of 140 ° C. and an air speed of 2.7 m / sec for 5 seconds.

The bulk of the obtained nonwoven fabric was 140 cm / g as shown in Table 1.
And excellent in bulkiness.

Examples 2 to 11 The same polymers as in Example 1 were used as the low-melting polymer for forming the sheath and the high-melting polymer for forming the core.
Under the conditions shown in 1, the number of natural crimps is 6 to 20 pieces / inch, and the size of crystal grains of the crystalline polypropylene forming the core is
An eccentric sheath-core composite fiber having an excellent bulkiness of 59.0 to 67.0 ° was obtained. The composite fiber was formed into a naturally crimped staple fiber, and a nonwoven fabric was obtained in the same manner as in Example 1.

The bulk of each nonwoven fabric was 130 to 145 cm / g as shown in Table 1, and all the nonwoven fabrics were excellent in bulkiness.

Examples 12 to 16 The same polymer as in Example 1 was used as the low-melting polymer for forming the sheath, and MFR was used as the high-melting polymer for forming the core.
Is 27, the natural crimping number is 10 to 14 / inch, and the crystal grain size of the crystalline polypropylene forming the core is 55 to 73 ° under the conditions shown in Table 1. An eccentric sheath-core type composite fiber having excellent bulkiness was obtained. The composite fiber was made into a naturally crimped staple fiber, and a nonwoven fabric was obtained in the same manner as in Example 1.

The bulk of each nonwoven fabric is 130 to 140 cm / g as shown in Table 1.
All nonwoven fabrics were excellent in bulkiness.

Examples 17 to 18 The same polymer as in Example 1 was used as the low-melting polymer for forming the sheath, and MFR was used as the high-melting polymer for forming the core.
Is 5 and the natural crimping number is 8 to 10 pieces / inch, and the size of the crystal grains of the crystalline polypropylene forming the core is 56.0 to 58.0 mm under the conditions shown in Table 1.
An eccentric sheath-core type composite fiber having excellent bulkiness was obtained, and this composite fiber was made into a naturally crimped staple fiber, and a nonwoven fabric was obtained in the same manner as in Example 1.

The bulk of each nonwoven fabric was 130 to 131 cm / g as shown in Table 1, and all the nonwoven fabrics were excellent in bulkiness.

Examples 19 to 20 As the low-melting polymer forming the sheath, low-density polyethylene having an MFR of 20 (Example 18) and EVA having an MFR of 20 (Example 19) were used. Using the same crystalline polypropylene as in Example 1 as a united product, under the conditions shown in Table 1, the natural crimp number was 11.0 to 12.0, and the size of the crystalline polypropylene crystal forming the core was 59 to An eccentric sheath-core type composite fiber having an excellent bulkiness of 62 ° was obtained. The composite fiber was made into a naturally crimped staple fiber, and a nonwoven fabric was obtained in the same manner as in Example 1.

The bulk of each nonwoven fabric was 131 to 132 cm / g as shown in Table 1, and all the nonwoven fabrics were excellent in bulkiness.

Comparative Examples 1 to 5 The same polymers as in Example 1 were used as the low melting point polymer forming the sheath portion and the high melting point polymer forming the core portion.
An eccentric sheath core in which the number of natural crimps is 4.0 to 5.0 pcs / inch, which is outside the limited range of the present invention, and the crystal grain size of the crystalline polypropylene forming the core is 56 to 66 ° under the conditions shown in 1. After obtaining a composite fiber of a mold and using the composite fiber as a naturally crimped staple fiber, a nonwoven fabric was attempted in the same manner as in Example 1.

However, these composite fibers have a natural crimp number of 4 to
Since it was as low as 5 pieces / inch, the connection of the web when passing through the card machine was poor, and it could not be formed into a nonwoven fabric. In the conjugate fibers of Comparative Examples 3 and 4 in which the cross-sectional area ratio between the sheath and the core was 2/8, the low-melting-point polymer forming the sheath could not cover the entire fiber, and the crystal formed the core. A part of the extruded polypropylene became a fiber which was exposed, and fine powder falling was observed when passing through a carding machine.

Comparative Example 6 Crystalline polypropylene having an MFR of 12 was used as the high-melting polymer forming the core portion, and the other conditions were the same as in Example 7, except that the natural crimp number was 23.0 pieces outside the limited range of the present invention. / Inch, crystalline polypropylene with a grain size of 68 mm
After obtaining an eccentric sheath-core type conjugate fiber, and making this conjugate fiber a naturally crimped staple fiber, a nonwoven fabric was attempted in the same manner as in Example 1.

However, since this composite fiber had a high natural crimping number of 23 pieces / inch, it had poor carding machine passability and could not be formed into a nonwoven fabric.

Comparative Examples 7 and 8 The same polymer as in Example 1 was used as a low-melting polymer forming a sheath portion and a high-melting polymer forming a core portion.
The eccentric sheath core of 48 to 51 ° in which the number of natural crimps is 11.0 to 11.5 pieces / inch and the size of the crystal grains of the crystalline polypropylene forming the core is out of the limited range of the present invention under the conditions shown in 1. After the composite fiber was made into a naturally crimped staple fiber, a nonwoven fabric was obtained in the same manner as in Example 1.

The bulk of each nonwoven fabric was 120 to 121 cm / g as shown in Table 1, and was inferior in bulkiness to the nonwoven fabrics of Examples 1 to 21.

Comparative Examples 9 to 11 The same polymer as in Example 13 was used as a low-melting polymer for forming a sheath portion and a high-melting polymer for forming a core portion.
Under the conditions shown in FIG. 1, an eccentric sheath core type having a natural crimp number of 9.0 to 12.0 pieces / inch and a crystal grain size of the crystalline polypropylene forming the core of 40 to 48 ° which is out of the limit of the present invention. After obtaining the conjugate fiber of the above and using the conjugate fiber as a naturally crimped staple fiber, a nonwoven fabric was obtained in the same manner as in Example 12.

The bulk of each nonwoven fabric was 90 to 110 cm / g, as shown in Table 1, and was inferior in bulkiness to the nonwoven fabrics of Examples 1 to 20.

Comparative Example 12 The same polymer as in Example 18 was used as the low-melting polymer forming the sheath portion and the high-melting polymer forming the core portion.
Under the conditions shown in No. 1, the natural crimping number is 5.0 / inch, which is out of the range of the present invention, and the crystal grain size of the crystalline polypropylene forming the core is also out of the range of the present invention.
After obtaining the eccentric sheath-core type conjugate fiber of this example and using the conjugate fiber as a naturally crimped staple fiber, a nonwoven fabric was tried in the same manner as in Example 13, but passed through a carding machine as in Comparative Examples 1 to 5. Due to poor web connectivity at the time, it was not possible to make a nonwoven fabric.

[Effects of the Invention] As described above, by using the eccentric sheath-core type conjugate fiber of the present invention, a nonwoven fabric with further improved bulkiness can be obtained, and a nonwoven fabric with a better feeling and a more economical nonwoven fabric can be obtained. It is possible to obtain a bulky nonwoven fabric having excellent properties.

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Claims (1)

(57) [Claims] 1. An eccentric sheath-core composite having excellent bulkiness by exhibiting a natural crimp to a composite yarn containing a low melting point polymer forming a sheath portion and a high melting point polymer forming a core portion. In the fiber, the number of the natural crimps is 6 to 20 / inch, and the high melting point polymer is a crystalline polypropylene having a crystal grain size of 55 ° or more, and is excellent in bulkiness. Sheath-core type composite fiber.