JPH07100885B2 - Bulky composite fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a bulky conjugate fiber. The bulky heat-fusible conjugate fiber of the present invention is used for manufacturing nonwoven fabrics and the like.

(Prior Art and Problems Thereof) As is well known, staple fibers generate mechanical crimps by forcibly pushing a bundle of fibers into a crimper box in order to have fiber entanglement. This mechanical crimp is a zigzag crimp, and when manufacturing a nonwoven fabric, sufficient bulkiness cannot be obtained. In order to obtain a bulky nonwoven fabric, round omega-shaped or coil-shaped natural crimps are most preferable. As a bulky heat-bonding fiber that develops natural crimps, a bonding type composite fiber in which a low melting point component such as polyethylene and a high melting point component such as polypropylene are bonded is used. There was such a problem.

Small heat fusion strength. This is because in the case of the bonding type composite fiber 6 as shown in the cross-sectional shape in FIG. 3, the high melting point component 4 is not completely surrounded by the low melting point component 5 and the high melting point component 4 is partially exposed. Therefore, the surface area of the low melting point component 5 that contributes to the heat fusion is small, and as shown in the micrograph after the heat fusion in FIG. 4, the high melting point component and the low melting point component are separated after the heat fusion. This is because it is easy. The higher the bulkiness, the smaller the number of contacts between fibers, so it is important that the fusion strength of each contact is large.However, in the case of the bonded composite fiber, the fusion strength of each contact is small, which is a particular problem. Becomes

Since the low melting point component and the high melting point component are easily separated from each other, powder is likely to be generated.

 Compressive recovery is poor, probably because the bending rigidity of the fiber is low.

Spinnability is poor. That is, the bonded composite fiber is
Since both resins having different melting and crystallization characteristics are exposed on the surface, spinnability is poor and stable quality fibers cannot be obtained efficiently.

It is not possible to obtain stable bulkiness characteristics, because it is difficult to control crimps because the bonded composite fiber is very easy to crimp, and stable bulkiness and stable cardability are not available. Hard to get.

Therefore, an object of the present invention is to provide a bulky conjugate fiber which eliminates the above-mentioned drawbacks of the conventional bonding type conjugate fiber.

(Means for Solving the Problems) Therefore, as a result of intensive research, the present inventors have found that a sheath-core type composite fiber which satisfies the following conditions and in which the sheath component substantially covers the entire surface of the core component is obtained. It has been found that the fusion strength is high, no powder is generated due to the peeling of both components, the compression recovery property is excellent, the spinnability is also excellent, and stable bulkiness characteristics are given.

(I) The cross-sectional area ratio of the core component / the sheath component is 4/6 to 7/3.

(Ii) An equation where R is the radius of a circle having the same cross-sectional area as the composite fiber cross section and D is the distance between the center of the composite fiber and the center of gravity of the core component. The eccentricity A obtained by the above is 8 to 35%.

(Iii) Of the two polymers used for the core component and the sheath component, a polymer having a high MFR (meaning melt flow rate based on ASTM-D1238 (L). Polymers with high MFR values and low MFR values after spinning
When the FR value is displayed as low MFR, the ratio of high MFR / low MFR is 2 or less and the following formula is satisfied.

10 ≦ (High MFR / Low MFR ratio) × Eccentricity (A) ≦ 50 FIG. 1 shows a preferred specific example of the eccentric sheath-core type composite fiber of the present invention by its cross-sectional shape.

In the figure, 1 is a core component, 2 is a sheath component, and 3 is a sheath-core type composite fiber. In the figure, (A) has a circular cross section for both the core component and the composite fiber, and (B) has a circular cross section for the composite fiber, but the cross section of the core component has an oval shape and its major axis is Those extending in the vertical direction, (C) is the core component,
The composite fibers are both elliptical and their major axes extend in the same horizontal direction in the figure. (D) shows that the core component has a circular cross section, but the composite fiber has an oval cross section and its length Each axis has a horizontal axis. As is clear from FIGS. 7A to 7D, in the sheath-core type composite fiber of the present invention, the center of the composite fiber and the center of gravity of the core component are not coincident with each other and are eccentric.

In the sheath-core type composite fiber of the present invention, the melting point of the sheath component is preferably lower than the melting point of the core component by 20 ° C. or more, and the preferred polymer as the core component is polypropylene, particularly crystalline polypropylene, and the preferred polymer as the sheath component. Is polyethylene, especially high density polyethylene.

Next, the significance of limiting the numerical values of each of the above conditions (i) to (iii) will be described with reference to FIG. .

(I) Cross-sectional area ratio of core component / sheath component If the cross-sectional ratio of core component 1 / sheath component 2 is less than 4/6, sufficient natural crimping will not occur and a bulky fiber will not be obtained. It is considered that this is because the difference in internal stress is too small, and even if it is eccentric, the bulkiness expression is not sufficient. On the other hand, when it exceeds 7/3, natural crimps do not develop and bulky fibers cannot be obtained. This seems to be because the internal stress of the sheath component is too small to cancel the eccentric effect. Further, in this case, it becomes difficult for the sheath component to cover the entire surface of the core component, which causes a decrease in heat fusion strength and generation of powder.
Therefore, the cross-sectional area ratio of the core component / the sheath component is limited to 4/6 to 7/3, and the case of 5/5 to 6/4 is particularly preferable.

(Ii) Eccentricity In Fig. 1, when R is the radius of a circle having the same cross-sectional area as the composite fiber cross section, O ₁ is the center of the composite fiber, and O ₂ is the center of gravity of the core component, the distance between O ₁ and O ₂ When A is D, the eccentricity A is calculated by the following equation.

If the eccentricity obtained by the above equation is less than 8% of the deformation R, sufficient natural crimps will not be expressed and bulky fibers will not be obtained. On the other hand, if it exceeds 35%, the natural crimps become too fine and bulky fibers cannot be obtained, and at the same time, the crimps change due to slight changes in external conditions such as manufacturing conditions, and stable natural crimps cannot be obtained. . Therefore, the eccentricity is limited to 8 to 35% and 10 to 25%
Is particularly preferable.

(Iii) High MFR / low MFR ratio and (high MFR / low MFR ratio) x eccentricity (A) It is preferable that the core component and the sheath component have similar melting characteristics during spinning, and high MFR / low MFR If the ratio of exceeds 2,
Spinnability is not good. When the ratio of high MFR / low MFR exceeds 2, the natural crimp becomes too fine and a bulky fiber cannot be obtained. Therefore, the ratio of high MFR / low MFR is limited to 2 or less.

When the product of high MFR / low MFR and eccentricity A is less than 10, sufficient natural crimping does not occur and a bulky fiber is not obtained. or,
If it exceeds 50, it will be pulled to the side with low MFR at the time of nozzle discharge, not only spinability will decrease, but also the natural crimp will not be too fine and bulky fiber will not be obtained, and at the same time stable natural crimp will be obtained. Absent. Therefore, their product is limited to 10-50.

From the viewpoint of bulky compression resistance, compression recovery and spinnability, the core component preferably has an MFR of 20 to 45.

In order to obtain a more appropriate natural crimp, when the eccentricity is large and the ratio of high MFR / low MFR is 2.0, which is the upper limit, the spinning temperature is rather high, the draft ratio is small, and the cooling condition is moderate. It is preferable to carry out the spinning, the stretching temperature is high, the stretching ratio is suppressed and the stretching is performed. At this time, it is better not to perform preheating before stretching, that is, it is preferable to manufacture in a direction in which internal strain is suppressed. On the other hand, when the eccentricity is small and the high MFR / low MFR ratio is 1.0, on the contrary, the spinning temperature is rather low, the draft rate is large, the cooling conditions are strong, the drawing temperature is low, and the drawing temperature is low. It is preferable to stretch to a higher magnification. That is, it is preferable to manufacture in the direction of increasing the internal strain. At this time, preheating before stretching may be performed.
If the temperature is higher than ℃, crystallization will proceed and the crimp will not be too fine and will not be bulky.

That is, within the range of the present invention, the natural crimp developing power can be controlled by spinning conditions and drawing conditions, but beyond the range of the present invention, the natural crimp developing power cannot be controlled.

The significance of limiting the numerical conditions of the sheath-core type conjugate fiber of the present invention has been described above. The sheath-core type conjugate fiber of the present invention satisfying these conditions is a bulky nonwoven fabric containing the conjugate fiber, for example, 30% or more. It is preferably used in production.

(Examples) Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

Example 1 An eccentric sheath-core type composite fiber spinning equipment consisting of two single-screw extruders and a circular nozzle for composite fibers having a hole diameter of 0.6 mm was used, and crystalline polypropylene (Ube Kosan J109G) was used as the core component and high-density polyethylene was used as the sheath component. (Showa Denko F6200) at 60:40
At a spinning temperature of 250 ° C. and a take-up speed of 1200 m / min, to obtain an eccentric sheath-core type composite fiber having a single yarn denier of 6.0 de.
The spinnability was good, and the spinning was stable for 1 hour without any breakage. At this time, the cooling air temperature was cooled to 20 ° C under relatively gentle conditions, and the maximum take-up speed was 1450
It was m / min.

The obtained composite fiber has a core component / sheath component cross-sectional area ratio of 6/4.
The eccentricity was A13%. In addition, the MFR of the core component and the sheath component after spinning under the same spinning conditions are 26 and 42, respectively, which is high MFR /
The low MFR ratio was 1.62, and the product of the high MFR / low MFR ratio and the eccentricity A was 21.1.

300 multifilaments were collected to make total denier about 400,000 and staple fiber trial production facility at 90 ℃
3.5 times stretch, oiling, crimping, cutting, drying,
Heat treatment was performed to obtain a staple fiber having a single yarn denier of 2 de, a cut length of 51 mm, and a crimp number of 12 pieces / inch.

The crimper used for crimping consists of two metal rolls with a width of 25 mm. The stuffing box normally used for applying mechanical crimps is not used and natural crimps are developed only by pulling the crimper rolls. It was When stretching,
Sufficient natural crimps can be obtained without preheating, and the obtained staples are round and extremely bulky fibers, unlike the zigzag type of mechanical crimps.

This staple fiber was passed through a sample card machine having a width of 350 mm to prepare a uniform web having a basis weight of 25 g / m ² . At this time, a very bulky web was obtained with no problem of card passing property. This web was placed on a wire mesh belt having a width of 350 mm and a speed of 5 m / min, and hot air having a wind temperature of 140 ° C. and a wind speed of 2.2 m / sec was blown for 5 seconds to prepare a hot-air-bonded nonwoven fabric. When the obtained non-woven fabric was observed with an electron microscope (magnification: 1000), it was completely fused as shown in FIG. As shown in Table 1, the uniformity, tear length, initial bulk, compression resistance, and compression recovery of this nonwoven fabric were all good.

Example 2 Using a nozzle with an increased eccentricity, a core component / sheath component cross-sectional area ratio was 4/6 and an eccentricity was 27% and a high MFR / low MFR × eccentricity was 43.7 in the same manner as in Example 1. (The ratio of high MFR / low MFR is
A sheath-core type composite fiber was produced at 1.62 (the same as in Example 1), and a nonwoven fabric was prepared in the same manner as in Example 1, and then the performance was evaluated. The results were all good as shown in Table 1.

Example 3 In the same manner as in Example 1, crystalline polypropylene (Ube Industries J130G) was used as the core component, and high-density polyethylene (Asahi Kasei J310) was used as the sheath component at a spinning temperature of 50:50.
The eccentric sheath-core type composite fiber having a single yarn of 6.0 de was obtained by spinning at ℃ and a take-up speed of 1300 m / min. At this time, the cooling air temperature was 10 ° C., and spinning was performed under relatively strong cooling conditions, but there was no problem in spinnability.

The cross-sectional area ratio of core component / sheath component of the obtained composite fiber is 5/5.
The eccentricity is 20%, the MFR of the core component and the sheath component after spinning under the same spinning conditions is 37 and 38, respectively, and the high MFR / low MFR ratio is 1.03. The product of the rates was 20.6.

Staple fibers were obtained from this filament in the same manner as in Example 1, but the preheating before stretching was 60 ° C.
It was done in. The number of crimps in the obtained staple fiber
It was a bulky fiber having a natural crimp of 10 pieces / inch.
A non-woven fabric was obtained from this staple fiber in the same manner as in Example 1. The non-woven fabric was good in all physical properties as shown in Table 1.

Example 4 Crystalline polypropylene (Ube Industries J130
G), high-density polyethylene as a sheath component (Asahi Kasei J320)
Was spun in the same manner as in Example 3 at a ratio of 50:50 and stretched to obtain a bulky composite fiber. In the same manner as in Example 3, the obtained composite fiber had a core component / sheath component cross-sectional area ratio of 5/5 and an eccentricity of 20%. The MFR of the core component and the sheath component after spinning under the same conditions are 37 and 20, respectively, and the ratio of high MFR / low MFR is
It was 1.85, and the product of the high MFR / low MFR ratio and the eccentricity was 37.0.

Table 1 shows the results of the physical property test of the nonwoven fabric obtained from this composite fiber.
However, all of them showed good values.

Example 5 Crystalline polypropylene as a core component (Mitsui Toatsu Chemicals J2H
-G), high density polyethylene as a sheath component (Showa Denko 51
Using 10) at a ratio of 60:40, a composite fiber having a core component / sheath component cross-sectional area ratio of 6/4 and an eccentricity of 13% was obtained in the same manner as in Example 1. At this time, the core MFR was 18 and the sheath MFR was 27, the high MFR / low MFR ratio was 1.50, and the product of the high MFR / low MFR ratio and the eccentricity ratio was 19.5. As shown in Table 1, the obtained non-woven fabric was excellent in various physical properties such as bulkiness.

Example 6 Crystalline polypropylene as a core component (RS153, Ube Industries)
8), high density polyethylene (Asahi Kasei J130G) was used at a ratio of 50:50, and a composite fiber having a core component / sheath component cross-sectional area ratio of 5/5 and an eccentricity of 20% was obtained in the same manner as in Example 3. . At this time, the core component has an MFR of 50, and the sheath component has an MFR of 38, which is high MFR / low MF.
The R ratio is 1.32, and the product of high MFR / low MFR ratio and eccentricity is 2
It became 6.4. The non-woven fabric obtained from this composite fiber is shown in Table 1.
It was excellent in various properties such as bulkiness as shown in.

Comparative Example 1 Using a circular nozzle for bonding type composite fiber having a hole diameter of 0.6 mm, crystalline polypropylene (Ube Industries
J109G), high density polyethylene (Showa Denko H6200) as a low melting point component was spun at a ratio of 50:50 at a spinning temperature of 250 ° C and a cooling air temperature of 20 ° C and a single yarn of 6.0de, but the spinnability was poor. , The maximum take-up speed can only be increased to 860m / min, 80
Spinning was performed at 0 m / min. The obtained composite fiber had a core component / sheath component cross-sectional area ratio of 5/5, and as shown in FIG.
The high melting point component is exposed at 0%. Also, the MFR of the high melting point component and the low melting point component after spinning under the same spinning conditions were 28 and 40, respectively, and the ratio of high MFR / low MFR was 1.43. In the same manner as in Example 1, A staple fiber was made from this filament, but the number of crimps is 14 even if the crimps tend to become finer and the internal strain is less likely to occur.
Natural crimps of inches or less were not obtained, and the crimps were also non-uniform. When this staple fiber was applied to a sample card, fine powder falling was observed when the card speed was increased, and the card passing property was poor, and a uniform web was obtained unless it was passed through the card machine several times.

Furthermore, when a nonwoven fabric was prepared and the breaking length and the like were measured, it was inferior to that of the example. When the non-woven fabric obtained from this composite fiber was observed with an electron microscope (magnification: 1000), peeling of the low melting point component was found everywhere as shown in FIG.
The bulkiness characteristics were also inferior to those of the examples.

Comparative Example 2 By the same method as in Example 2, the eccentricity was out of the range of the present invention.
% (The product of the ratio of high MFR / low MFR and the eccentricity is 64.0, which is outside the scope of the present invention), the sheath component could not cover the whole fiber, and the core component was partially exposed. As a result, the same phenomenon as in Comparative Example 1 was found, although the degree of difference was small.

Comparative Example 3 By the same method as in Example 3, the eccentricity was set to 7 outside the range of the present invention.
%, A sufficient natural crimp was not obtained, so a staffin box was used at a low pressure, and a mechanical crimp was added a little to obtain a bulky fiber having 10 crimps / inch. When the nonwoven fabric obtained from this bulky fiber was evaluated,
The bulkiness and the like were inferior to those of the examples.

Comparative Examples 4 and 5 In the same manner as in Example 1, the cross-sectional area ratio of the core component / the sheath component was 3/7 (Comparative Example 4) and 8/2 (Comparative Example 5) out of the range of the present invention.
However, none of them had sufficient bulkiness. Further, in the case of the cross-sectional area ratio of 8/2 in Comparative Example 5, the spinnability was poor, the powder fell off, and the nonwoven fabric lacked uniformity, probably because the sheath component did not easily cover the entire surface of the core component.

Comparative Example 6 A composite fiber was obtained in the same manner as in Example 2 except that high density polyethylene (Chisso M693) was used as the sheath component. The MFR of the sheath component after spinning under the same spinning conditions was 65. Therefore, the high MFR / low MFR ratio at this time is 2.50, which is outside the range of the present invention, and the product of the high MFR / low MFR ratio and the eccentricity is also outside the range of the present invention.
It was 7.5. The bulkiness was not sufficient, the spinnability of this composite fiber was inferior, and the fusion strength was low because the molecular weight of the sheath component was small.

Comparative Example 7 Crystalline polypropylene (Mitsui Toatsu Chemicals J2H
A composite fiber was obtained in the same manner as in Example 3 except that -G) was used. The MFR of the above core component after spinning under the same spinning conditions is 15
And high MFR / low MFR ratio is 2.53, high MFR outside the scope of the present invention.
The FR / low MFR ratio times the eccentricity product was also 50.6, which is outside the scope of the invention. This composite fiber had insufficient bulkiness and poor spinnability.

Comparative Example 8 High density polyethylene (Japan Petrochemical E750-
A composite fiber was obtained in the same manner as in Example 3 except that C) was used. The MFR of the sheath component after spinning under the same spinning conditions is 17, the high MFR / low MFR ratio is 2.18, which is outside the scope of the present invention, and the high MFR / low MFR ratio and the eccentricity product are 43.6. there were. This composite fiber had insufficient bulkiness and poor spinnability.

The methods for measuring various physical properties in Table 1 are as follows.

Spinnability: Evaluation was made at the maximum take-up speed at which stable spinning was possible without spinning breakage for 5 minutes.

Breaking length; breaking strength (g) x {1 / sample width (m)} x {1 / unit weight (g / m ² )} That is, the breaking length is equal to the breaking length by its own weight.

Initial bulk: Cut non-woven fabric into 5 x 5 cm and stack 8 sheets.
Apply a flat load of 1.0 g / cm ² for 1 minute and unload 1 part to 0.25 g / cm ^2.
The volume of the nonwoven fabric is calculated by measuring four intermediate points on each side while applying a plane load of cm ² .

The specific volume was obtained by dividing this volume by the weight of the tested nonwoven fabric.

Compression resistance: After measuring the initial bulk, an average load of 8.0 g / cm ² was applied, the specific volume after 24 hours was measured, and the compression resistance was evaluated from the decrease in bulk.

Compression recovery: After measuring the compression resistance, the weight was removed, an average load of 0.25 g / cm ² was applied, the specific volume after a predetermined time was measured, and the compression recovery was evaluated by the recovery of bulk.

(Effect of the invention) The eccentric sheath-core type composite fiber of the present invention has a large fusion strength, does not generate powder due to peeling of the sheath component and the core component, and is excellent in compression recovery property by satisfying the above numerical conditions. There are advantages such as providing stable and bulky characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the sheath-core type composite fiber of the present invention, FIG. 2 is an electron micrograph of a heat-sealing nonwoven fabric obtained by using the sheath-core type composite fiber of the present invention, and FIG. FIG. 4 is a cross-sectional view of the bonding type composite fiber, and FIG. 4 is an electron micrograph of a heat-bonded nonwoven fabric obtained by using the conventional bonding type composite fiber. 1 ... core component, 2 ... sheath component, 3 ... sheath-core type composite fiber,
4 ... High melting point component, 5 ... Low melting point component, 6 ... Bonding type composite fiber.

Claims (1)

[Claims] 1. A sheath-core type composite fiber which satisfies the following conditions (i), (ii) and (iii) and in which the sheath component substantially covers the entire surface of the core component. (I) The cross-sectional area ratio of the core component / the sheath component is 4/6 to 7/3. (Ii) An equation where R is the radius of a circle having the same cross-sectional area as the composite fiber cross section and D is the distance between the center of the composite fiber and the center of gravity of the core component. The eccentricity A obtained by the above is 8 to 35%. (Iii) Among the two polymers used for the core component and the sheath component, the polymer having a high MFR value after spinning has a high MF.
When the MFR value of a polymer having a low R and a low MFR value after spinning is expressed as low MFR, the ratio of high MFR / low MFR is 2 or less and the following formula is satisfied. 10 ≦ (High MFR / Low MFR ratio) × Eccentricity (A) ≦ 50