JP2980294B2 - Staple, nonwoven fabric and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a staple comprising crimped conjugate fiber, a method for producing the same, a nonwoven fabric produced from the staple, and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION It is known to produce nonwoven fabrics using staples of splittable conjugate fibers formed from two or more mutually incompatible thermoplastic polymers. The resulting nonwoven fabric is soft to the touch because each thermoplastic polymer part constituting the splittable conjugate fiber becomes fibrillated by splitting and exfoliation in the nonwoven fabric and becomes an ultrafine denier single fiber,
It is suitable as a sanitary article such as a disposable diaper, a sanitary napkin, a wiper, a filter, a mask, a disposable surgical gown, a synthetic leather base cloth, and the like.

However, in the prior art for producing a nonwoven fabric using staples of splittable conjugate fibers, excessive split fibrillation is liable to occur in the conjugate fibers in steps such as stretching, crimping, and cutting before manufacturing the nonwoven fabric. As a result, there are drawbacks in that the passability of the card becomes poor during the production of the nonwoven fabric, and that a web having a uniform thickness cannot be obtained due to the occurrence of neps in the card process. On the other hand, attempts have been made to make the composite fiber difficult to split fibrillated so as not to cause excessive split fibrillation before the carding process.In that case, although staples can be avoided in the carding process, troubles can be avoided. However, there is a drawback that split fibrillation after production of a web is difficult, and a soft nonwoven fabric made of ultrafine single fibers cannot be obtained.

[0004]

In view of the above, the present inventors have found that in the nonwoven fabric manufacturing process, prior to forming a web from staples, split fibrillation is unlikely to occur, so that permeability in the card process and the like is good, and the web After forming,
By an appropriate split fibrillating means such as high-pressure fluid injection, the individual single fibers constituting the conjugate fiber are easily split and peeled to produce fibrillation and entanglement, thereby forming an extremely flexible non-woven fabric composed of ultrafine single fibers. Research has been continued with the aim of obtaining conjugate fibers and staples that can be made, and with the aim of smoothly producing nonwoven fabrics from such staples.

As a result, the cross-sectional shape of the splittable conjugate fiber composed of two or more incompatible thermoplastic polymers is made circular or flat, and at least 80% of the lamination surface in the fiber cross-section is fiber. Across the long axis of the cross section, on average 3
Laminate and composite incompatible thermoplastic polymers in layers or more, and based on the total number of fibers constituting the staple, make the ratio of the flat cross-section fibers a certain ratio or more, and set the degree of fibrillation in the staple to a specific range. Then, the inventors have found that the above-mentioned object can be achieved and completed the present invention.

That is, according to the present invention, two or more types of incompatible thermoplastic polymers have a laminating surface of 8
A staple obtained by crimping a composite fiber having a circular or flat cross section, in which 0% or more traverses the major axis of the fiber cross section and averaging three or more layers in parallel. Assuming that the length of the major axis of the surface is a and the length of the minor axis is b, the ratio of the flat-section fibers satisfying a / b ≧ 1.1 is 80 based on the total number of fibers constituting the staple. % Or more, and the degree of fibrillation indicating the number of fibrillated fibers in the staple is 10 to 20%.
Is a staple.

Further, according to the present invention, two or more types of incompatible thermoplastic polymers are supplied to a spinning device so that 80% or more of the lamination surface of the incompatible thermoplastic polymers has a long axis of fiber cross section. After spinning, after spinning a laminated conjugate fiber having a circular or flat cross section laminated on average on three or more layers, stretching,
The present invention also includes a method for producing the above staple by performing crimping and cutting treatment, a method for producing a nonwoven fabric using the above staple, and a nonwoven fabric produced thereby.

First, the conjugate fiber constituting the staple of the present invention will be described.
The shape of the cross section cut at right angles to the length direction of the fiber is circular or flat. Here, the term "flat cross section" as used in the present invention means a fiber whose cross sectional shape deviates from a perfect circle and is flattened irrespective of its shape. When the length is a and the length of the minor axis is b, all fibers having a ratio a / b> 1 are treated as fibers having a flat cross section.

The cross section of the conjugate fiber of the present invention is exemplified by a circular cross section as shown in FIG. 1, an elliptical cross section as shown in FIG. 2, and a flat cross section having a high flatness as shown in FIG. Although the flat shape can be mentioned in FIGS. 2 and 3
Is not limited to Also, the fiber surface is shown in FIGS.
As shown in the above, it is preferable to make the surface smooth without any irregularities, because the card process passability in producing a web from staples is improved.

In the conjugate fiber used in the present invention, the ratio a / b of the length a of the long axis to the length b of the short axis is 1 to 1.
A value of 5 is preferred from the viewpoints of spinnability, ease of stretching and crimping, and split releasability. In the present invention, a / b
The proportion of the fibers having a flat cross section satisfying ≧ 1.1 needs to be 80% based on the total number of fibers constituting the staple, and is preferably about 85 to 100%.

In the above conjugate fiber, FIGS.
As exemplified in FIG. 3, 80% or more of the lamination surfaces of two or more incompatible thermoplastic polymer components 1 and 2 cross the long axis of the fiber cross section, and on average, three layers. It is necessary that they are stacked in parallel as described above. When the fiber has a circular cross section as shown in FIG. 1, a = b and the dimensions of the major axis and the minor axis are the same. The layers are laid in parallel or across the axis b.

As a splittable conjugate fiber composed of two or more incompatible thermoplastic polymers, for example, as shown in FIG. 4, a plurality of laminating two thermoplastic polymer components 1 and 2 are used. It is widely known that the surfaces have a structure in which the surfaces intersect radially. However, in the conjugate fiber used in the present invention, a plurality of lamination surfaces do not intersect as in FIG. Thus, it is necessary that they are arranged side by side, that is, juxtaposed across the long axis.

The laminating surface of the conjugate fiber may be such that the laminating surface of the two incompatible thermoplastic polymer components 1 and 2 is parallel to each other across the long axis as shown in FIG. They may be arranged side by side while being randomly involved. The number of laminations in the conjugate fiber is 3 on average as described above.
It is necessary that the number of layers is at least about 4 to 10 layers in terms of ease of production of conjugate fibers and fineness of single fibers in the obtained nonwoven fabric.

As the combination of two or more incompatible thermoplastic polymers in the conjugate fiber used in the present invention, any combination can be used as long as the combination can be easily separated and fibrillated when the web is formed. Polyester / polyolefin, polyester / polyamide, polyamide / polyolefin, polyester / polyamide / polyolefin, elastomer /
Combinations of polyester, elastomer / polyolefin and the like can be mentioned.

The thickness of the conjugate fiber is usually preferably about 1 to 10 denier per filament, and the denier of each single fiber formed by split fibrillation in the nonwoven fabric is about 0.1 denier. It is preferable to set it to about 1 to 1.0 denier. If the denier of the single fiber formed by the fibrillation exceeds about 1.0 denier, the skin becomes hard and it is not preferable.

At least 80% of the lamination surface traverses the major axis of the fiber cross section, and a circular or flat cross section composed of two or more incompatible thermoplastic polymers laminated in parallel on average in three or more layers. The above-mentioned conjugate fiber having a surface, for example, separately melts two or more incompatible thermoplastic polymers, and laminates the melt streams through one or more static kneading elements. After the composite stream is formed, it can be manufactured by melt-spinning from a plurality of spinnerets having a circular or flat shape.

The composite fiber bundle manufactured as described above has a composite state in the cross section composed of only one kind of fiber (filament) or the composite state in the cross section of the present invention described above. It may be a mixed fiber bundle composed of a plurality of fibers (filaments) which are variously different within the range. In the composite fiber bundle, the cross-sectional shapes (contours) of the fibers (filaments) constituting the bundle may be the same or different.

After the composite fiber is melt-spun to produce a composite fiber bundle as described above, the composite fiber bundle is further subjected to a stretching treatment, a crimping treatment such as a mechanical crimping treatment, and then cut into a predetermined length to obtain a nonwoven fabric. A staple of the present invention suitable for manufacturing can be manufactured.

In the staple of the present invention, the degree of fibrillation, which indicates the ratio of the number of fibrillated fibers, needs to be 10 to 20%. If the degree of fibrillation is less than 10%, the composite fibers constituting the staples are less likely to be divided into fibrils, and when formed into a web, the composite fibers are less likely to be divided into individual single fibers. On the other hand, if the degree of fibrillation exceeds 20%, fibrillation becomes excessive in the step before manufacturing the nonwoven web from staples, and nep occurs in the carding process,
Poor card processability.

Here, the fibrillation degree of the staple in the present invention was measured as follows. Measurement of fibrillation degree of staple Fifty fibers were randomly sampled from raw cotton, aligned, solidified with paraffin, cut with a microtome, and the cut surface was observed with an optical microscope. In, the number of fibers from which at least one lamination surface was completely peeled was counted, and the ratio (%) to 50 fibers was calculated to obtain the degree of fibrillation (%).

The staple has a fibrillation degree of 10 to 20.
%, Various methods are conceivable. Any method can be employed in the present invention as long as the fibrillation degree can be adjusted to 10 to 20%. Typically, the following two methods are used. Staples having a fibrillation degree of 10 to 20% can be obtained smoothly.

The spinning draft ratio (A) when spinning the conjugate fiber and the drawing draft ratio (B) when stretching.
A method of setting the spinning draft ratio and the drawing draft ratio so that the ratio (A / B) of the spinning draft is 15 to 45. A method in which the nip pressure (linear pressure) of the crimping machine is set to 70 to 120 kgf / cm, preferably 80 to 110 kgf / cm when applying mechanical crimping after stretching.

The above method will be described.
When spinning polyethylene terephthalate alone, for example, a spinning draft ratio of 50 times and a drawing draft ratio of 4
Spinning and drawing are performed at about twice (ie, at A / B = 12.5). To obtain the staple of the present invention, the spinning draft is adjusted so that A / B is in the range of 15 to 45. The spinning and drawing are performed by increasing the magnification to, for example, about 75 times and lowering the drawing draft ratio to, for example, 3.5 times. A /
When B is less than 15, the degree of fibrillation in staples exceeds 20%, and when A / B exceeds 45, the degree of fibrillation in staples becomes less than 10%, which is undesirable in any case.

In the above method, if the nip pressure is less than 70 kgf / cm, the degree of fibrillation of the staple becomes less than 10%, resulting in insufficient fibrillation, while if the nip pressure exceeds 120 kgf / cm. In addition, the degree of fibrillation of staples exceeds 20%, resulting in excessive fibrillation, which is not preferable. In producing the staple of the present invention, only one of the above methods and the above method may be employed, or both may be employed simultaneously.

In performing crimping such as mechanical crimping, it is desirable that the number of crimps be in the range of 8 to 18/25 mm. If the number of crimps is less than 8/25 mm, the staples will sink into the card, resulting in poor passability in the card process. In addition, the entanglement of the fibers in the nonwoven fabric is reduced, and the compression recovery of the nonwoven fabric is reduced. On the other hand, if the number of crimps exceeds 18/25 mm, nep or fibrillation occurs in the carding process, which also results in poor passability in the carding process and insufficient web bulk.

In the above-mentioned stretching treatment, crimping treatment, and cutting into staples, commonly used apparatuses and methods can be employed. The crimping treatment is preferably performed by mechanical crimping using a crimping box or the like, and an oil agent is preferably applied during the crimping treatment. In addition, it is preferable that the fiber length of the staple is usually about 30 to 70 mm from the viewpoint of the processability in producing the nonwoven web, the entangled state of the fibers in the nonwoven fabric, and the like.

In producing a web and a non-woven fabric from the staples of the present invention, a web is produced from the staples by a card process in a conventional manner, and the conjugate fibers in the web are divided and peeled on the laminating surface thereof by an appropriate method. This causes fibrillation, and the remaining undivided conjugate fibers and the single fibers produced by fibrillation are entangled with each other.

As a method of dividing the composite fibers constituting the web into divided fibrils, a high-pressure fluid injection method, a needle punching method, a heat treatment, a chemical treatment, or the like can be employed. It can be carried out. Among them, the high-pressure fluid injection method is preferable because the fibrillation and entanglement of the composite fiber can be uniformly performed over the entire web. In this case, it is preferable that the high pressure fluid injection nozzle has a hole diameter of about 0.2 to ² mm, the injection pressure is about 30 to 100 kg / cm ² , and the basis weight of the nonwoven fabric is about 30 to 500 g / m ^2. .

[0029]

According to the present invention, a flat cross-section fiber having a / b ≧ 1.1
%, When the web is manufactured from the staple of the present invention containing at least 10% by weight, as shown in FIG. 5, for example, as shown in FIG.
Is more likely to be arranged such that the major axis in the cross section of the fiber is the same as or approximate to the plane of the web 3, that is, lying horizontally in the web without standing. As a result, in the cross section of the conjugate fiber, most of the lamination surfaces of the incompatible thermoplastic polymers arranged side by side across the long axis of the conjugate fiber stand up with respect to the web plane, that is, injection of the high-pressure fluid for division. When the high-pressure fluid is ejected from the high-pressure fluid nozzle 5 in a state in which the fibers are oriented in the same direction as the direction, the composite fibers are very easily and sufficiently divided into fibrils on the laminating surface thereof, and entanglement occurs, and It is possible to obtain a nonwoven fabric having good flexibility and good touch.

On the other hand, as shown in FIG. 6, a nonwoven web 6 other than the present invention formed by using a composite fiber staple having a circular cross section having a radial division surface as shown in FIG. 4, for example. In the case of the above, the split surfaces of the conjugate fiber 7 are radially oriented in various directions, and the number of the split surfaces oriented in the same direction as the ejection direction of the high-pressure fluid from the high-pressure fluid nozzle 5 is small. In comparison with the present invention, the proportion of undivided conjugate fibers in the final nonwoven fabric is increased due to a lower ratio of splitting fibrils of the conjugate fibers by high-pressure fluid injection, and the nonwoven fabric has lower flexibility than the present invention. Becomes

Further, in the present invention, by setting the degree of fibrillation in the staple to 10 to 20%, the conjugate fibers constituting the staple are not excessively fibrillated in the step before the web is manufactured, and the staples are not fibrillated. In the carding process, it is possible to prevent the occurrence of a nep and to improve the carding process passability. Nevertheless, when the web is formed and then divided by a high-pressure fluid, the separation and separation can be easily performed. .

[0032]

【Example】

<< Examples 1-2 and Comparative Examples 1-2 >> Polyethylene terephthalate (PET) was melted at 290 ° C.
(N-6) was melted at 250 ° C., and a PET melt flow and N-
And 6 (Example 1), 8 (Example 2) and 2 (Comparative Example 2) static kneading elements, respectively, between the inlets of both melt streams and the spinning nozzle. The kneaded laminar flow was supplied to the installed die device to form a kneaded laminar flow, and the kneaded laminar flow was melt-spun from a spinning nozzle to produce a composite fiber bundle.

Example 3 A composite fiber bundle was manufactured in the same manner as in Example 1, except that the nozzle shape was rectangular (long side / short side = 1.3).

In the above Examples 1 to 3 and Comparative Examples 1 and 2, the supply ratio (weight ratio) of PET and N-6 to the die, spinning temperature, spinning draft ratio, denier of the obtained composite fiber bundle, and composite fiber bundle The cross-sectional shapes of the composite fibers and the ratios (%) thereof, and the average value of the total number of laminated layers of the PET layer and the N-6 layer in the composite fibers were as shown in Table 1 below. The above composite fiber bundle is stretched at a stretching temperature and a draft ratio shown in Table 1 and then supplied to a crimp box at a nip pressure (linear pressure) of a crimping machine shown in Table 1. ,
After mechanical crimping and heat treatment at 100 ° C. for 10 minutes, the resultant was cut into staples having a fiber length of 38 mm.

The staples obtained above were passed through a carding process according to a conventional method to produce a web having a basis weight shown in Table 1. The jet pressure of the water stream is 60 k from the high pressure water jet nozzle (nozzle hole diameter 0.5 mm).
A high-pressure water stream was sprayed at g / cm ² to split the composite fibers into fibrils and entangled, and then dried to obtain a nonwoven fabric.

Comparative Example 3 A drawing process was performed in the same manner as in Example 1 except that a composite fiber in which PET and N-6 were radially compounded in an eight-split type as shown in FIG. 4 was used. A crimping process, cutting, and production of a nonwoven fabric were performed to produce a nonwoven fabric. Table 1 shows the results of Examples 1 to 3 and Comparative Examples 1 to 3.
Shown in

[0038]

[Table 1]

From the results shown in Table 1 above, when the staple of the present invention was used, the conjugate fibers constituting the staple did not excessively fibrillate in the process until the web was manufactured, and the card process in the web manufacturing was not affected. It can be seen that no NEP was generated and the card processability was good.

The above Examples 1 to 3 and Comparative Examples 1 to
When the nonwoven fabric after split fibrillation obtained in 3 was cut in the thickness direction and its cross section was observed with an optical microscope, most of the flat composite fibers were found in the nonwoven fabrics of Examples 1 to 3 and Comparative Example 1. Comparative Examples 2 and 3
In this case, the composite fiber in which the lamination surface of the two polymers was not divided was conspicuous.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a cross section of a conjugate fiber constituting a staple of the present invention.

FIG. 2 is a schematic diagram showing an example of a cross section of a flat conjugate fiber constituting the staple of the present invention.

FIG. 3 is a schematic view showing another example of the cross section of the flat conjugate fiber constituting the staple of the present invention.

FIG. 4 is a schematic view showing an example of a cross section of a conjugate fiber that is not suitable for use in the staple of the present invention.

FIG. 5 is a cross-sectional view showing an arrangement state of conjugate fibers in a web obtained from the staple of the present invention.

FIG. 6 is a cross-sectional view showing an arrangement state of conjugate fibers in a nonwoven web other than the present invention obtained by using the staples of conjugate fibers shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 One incompatible thermoplastic polymer component 2 The other incompatible thermoplastic polymer component 3 Nonwoven web 4 Composite fiber 5 High-pressure fluid ejection device 6 Nonwoven web 7 Composite fiber

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-28467 (JP, A) JP-A-4-119112 (JP, A) JP-A-2-160964 (JP, A) JP-A-54-1979 96181 (JP, A) JP-A-49-132377 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) D04H 1/00-5/08 D01F 8/00-8/18

Claims (7)

(57) [Claims] 1. In a fiber cross section, two or more incompatible thermoplastic polymers are laminated in parallel with three or more layers on average, with 80% or more of the lamination surface crossing the major axis of the fiber cross section. A staple obtained by crimping a composite fiber having a circular or flat cross section, wherein the length of the long axis of the fiber cross section is a, and the length of the short axis is b, a / b
The ratio of the fibers having a flat cross section of ≧ 1.1 is 80% or more based on the total number of the fibers constituting the staple, and the degree of fibrillation indicating the number of the fibrillated fibers in the staple is 10 to 20%. Staples. 2. The staple according to claim 1, wherein the staples are composed of two or more incompatible thermoplastic polymers in which the laminating surfaces are randomly and side-by-side laminated in a direction crossing the major axis of the fiber cross section. 3. Feeding two or more incompatible thermoplastic polymers to a spinning apparatus so that at least 80% of the laminating surface of the thermoplastic polymers crosses the major axis of the fiber cross section and averages. After spinning a laminated composite fiber having a circular or flat cross section, which is laminated in parallel with three or more layers, drawing,
The method for producing staples according to claim 1, wherein crimping and cutting are performed. 4. The method according to claim 3, wherein the ratio (A / B) of the spinning draft (A) to the drawing draft (B) is 15 to 45. 5. The method according to claim 3, wherein the crimp is a mechanical crimp and the nip pressure (linear pressure) during the mechanical crimp is 70 to 120 kgf / cm. 6. A method for producing a nonwoven fabric, comprising forming a web from the staples of claim 1, and then performing fibrillation and entanglement of the fibers. 7. A nonwoven fabric produced by the method of claim 6.