阅读说明：本技术 卷曲纤维、纺粘无纺布、及它们的制造方法 (Crimped fiber, spun-bonded nonwoven fabric, and processes for producing these ) 是由 远藤雅纪 胜田大士 羽根亮一 船津义嗣 西村诚 于 2018-07-10 设计创作，主要内容包括：本发明的目的在于提供低成本、蓬松性优异的卷曲纤维及纺粘无纺布，以及可用工业上生产率和稳定性优异的方法制造所述卷曲纤维的卷曲纤维制造方法及纺粘无纺布的制造方法。为达到上述目的，本发明的卷曲纤维具有以下构成。即，卷曲纤维，其为以聚烯烃作为主要成分的纤维，上述卷曲纤维实质上由单一原料构成，在相对于纤维长度方向垂直的截面存在界面。(The invention aims to provide crimped fibers and spun-bonded nonwoven fabrics which are low in cost and excellent in bulkiness, and a crimped fiber production method and a spun-bonded nonwoven fabric production method which can produce the crimped fibers by a method excellent in industrial productivity and stability. In order to achieve the above object, the crimped fiber of the present invention has the following configuration. That is, crimped fibers are fibers mainly composed of polyolefin, and are substantially composed of a single raw material, and have an interface in a cross section perpendicular to the fiber longitudinal direction.)

1. Crimped fibers comprising a polyolefin as a main component, wherein the crimped fibers are substantially composed of a single raw material and have an interface in a cross section perpendicular to the fiber length direction.

2. A spunbonded nonwoven fabric comprising the crimped fiber according to claim 1.

3. A process for producing crimped fibers according to claim 1, wherein the polyolefin-based resin is discharged from two dumbbell-shaped nozzles having different circular discharge orifice areas.

4. A method for producing crimped fibers according to claim 3, wherein the value (area ratio) of large-pore-diameter area/small-pore-diameter area with respect to the two discharge-hole areas of the dumbbell nozzle is 1.2 or more.

5. A process for producing crimped fibers according to claim 3 or 4, wherein cooling is performed by blowing cooling air from two opposite directions or by blowing cooling air from three or more symmetrical directions against the side surfaces of the fiber group formed by discharging the polyolefin resin from the dumbbell nozzle.

6. A process for producing crimped fibers according to claim 3 or 4, wherein the fiber group formed by discharging the polyolefin-based resin from the dumbbell nozzle is naturally cooled.

7. A method for producing a spunbonded nonwoven fabric according to claim 2, wherein the crimped fibers obtained by the method for producing crimped fibers according to any one of claims 3 to 6 are collected immediately below the spinning line, and the fibers are crimped by a pair of rollers to form a sheet.

Technical Field

The present invention relates to crimped fibers, a spunbonded nonwoven fabric using crimped fibers, a method for producing crimped fibers, and a method for producing spunbonded nonwoven fabric.

Background

In general, nonwoven fabrics used for sanitary materials such as disposable diapers and sanitary napkins are required to have excellent bulkiness and softness for the texture when worn. Especially surface members that directly contact the skin are required to be bulky.

Conventionally, as a surface member of a sanitary material, a so-called air-laid nonwoven fabric is suitably used, which is obtained by converting short fibers represented by polyethylene terephthalate (PET)/Polyethylene (PE) composite materials into a sheet by carding and then subjecting the sheet to a hot air treatment to self-fusion. The air-laid nonwoven fabric has excellent bulkiness and softness, and thus is widely used for sanitary material applications and the like. However, there are problems that the manufacturing process of the air-laid nonwoven fabric is complicated and the production speed is slow.

On the other hand, a spunbond nonwoven fabric using polyolefin resin fibers represented by polypropylene (hereinafter, sometimes abbreviated as PP) as a raw material has a characteristic of high productivity and low cost in terms of process. However, the spunbond nonwoven fabric has a structure in which long fibers constituting the spunbond nonwoven fabric are oriented in the plane direction of the nonwoven fabric, and therefore has a problem of poor bulkiness.

Therefore, as a method for imparting bulkiness to a spunbond nonwoven fabric, a method has been proposed in which crimped fibers are applied to fibers constituting a nonwoven fabric.

For example, patent document 1 proposes a crimped conjugated fiber composed of two-component polymers having melting points different by 10 ℃.

Further, patent document 2 proposes the following method: the discharged fiber is cooled from one side asymmetrically with respect to the irregularly shaped cross section using the V-shaped cross section nozzle, thereby realizing crimping.

Disclosure of Invention

Problems to be solved by the invention

However, in the case of the method of patent document 1, since it is necessary to extrude different raw materials by respective extruders and discharge the extruded raw materials from a spinneret, there is a problem that the equipment investment is increased. In addition, in the method of patent document 1, it is necessary to select raw materials having melting points different by 10 ℃ or more, and to combine ordinary PP (so-called homopolypp) with copolymeric PP (so-called random PP). In general, the random PP is expensive as a raw material compared to the homopolypropylene, and therefore, the cost is increased, and the bulkiness equivalent to that of the air-laid nonwoven fabric cannot be obtained because the number of crimps of the obtained composite fiber is limited.

In the case of the method of patent document 2, although the method is characterized in that curling can be achieved even if the raw material is a single component, the current situation is that: if the cooling air velocity is increased, yarn shakeout or yarn breakage occurs, and therefore, from the viewpoint of production stability, the cooling air velocity has to be decreased, the number of curls obtained is decreased, and bulkiness to such an extent that it can be applied to the surface material of sanitary materials cannot be obtained.

Therefore, the conventional cases are: crimped fibers and spunbond nonwoven fabrics having a low cost and excellent industrial productivity and stability and having an excellent and satisfactory level of bulkiness when used as sanitary materials cannot be obtained.

In view of the above problems, an object of the present invention is to provide crimped fibers and spunbond nonwoven fabrics which are low in cost and excellent in bulkiness. Another object of the present invention is to provide a method for producing crimped fibers and a method for producing spunbonded nonwoven fabrics, which are capable of producing crimped fibers according to the present invention by a method having excellent industrial productivity and stability.

Means for solving the problems

The crimped fiber of the present invention is a fiber mainly composed of polyolefin, and is substantially composed of a single raw material, and has an interface in a cross section perpendicular to the fiber longitudinal direction.

The spunbonded nonwoven fabric of the present invention is a spunbonded nonwoven fabric comprising the crimped fiber of the present invention.

The method for producing crimped fibers of the present invention is a method for producing crimped fibers of the present invention, wherein a polyolefin resin is discharged from two dumbbell-shaped nozzles having circular discharge openings with different areas.

The method for producing a spunbonded nonwoven fabric of the present invention is a method for producing a spunbonded nonwoven fabric of the present invention, and the method for producing a spunbonded nonwoven fabric comprises collecting crimped fibers obtained by the method for producing crimped fibers of the present invention immediately below a spinning line, and crimping the fibers using a pair of rollers to form a sheet.

Effects of the invention

According to the present invention, a crimped fiber and a spun-bonded nonwoven fabric which are low in cost and excellent in bulkiness can be obtained. The crimped fiber of the present invention and the spunbonded nonwoven fabric of the present invention can be produced by a method having excellent industrial productivity and stability.

Drawings

FIG. 1 is a photograph illustrating a cross section of a crimped fiber according to the present invention.

FIG. 2 is a schematic view of a photograph illustrating a cross section of a crimped fiber according to the present invention.

FIG. 3 is a schematic sectional view illustrating the discharge surface of a spinneret used for producing crimped fibers according to the present invention.

Detailed Description

The crimped fiber of the present invention is a fiber comprising polyolefin as a main component, and is substantially composed of a single raw material, and has an interface in a cross section perpendicular to the fiber length direction.

In the case of the crimped fiber of the present invention, it is important that an interface exists in a cross section perpendicular to the fiber length direction. Hereinafter, the "cross section perpendicular to the fiber longitudinal direction" may be simply referred to as "fiber cross section". The interface of the fiber section as referred to in the present invention means a portion where streaks are observed in the fiber section. Since a difference in molecular orientation occurs in the cross section of the fiber, even in a fiber substantially composed of a single raw material, a difference in refractive index occurs in the cross section of the fiber, and an interface can be observed. Therefore, the interface mentioned in the present invention divides the fiber section into 2 parts or more, and thus the starting point and the ending point of the interface exist on the outer circumference of the fiber section. Therefore, the case where the starting point and the ending point do not exist on the outer periphery of the fiber section is excluded from the interface mentioned in the present invention. This interface can be observed when the fibers are fixed with epoxy or the like and made into an extremely thin sample piece with a microtome. Since the interface mentioned in the present invention can be observed by the structural difference at the molecular chain level, the method of manufacturing the test piece is important. In order to produce a test piece, it is important to produce the test piece using a microtome which is generally used for microscopic observation such as TEM, instead of using a simple spatula or the like.

Fig. 1 shows a photograph illustrating a cross section of a crimped fiber of the present invention. Fig. 1(a) is a photograph of a cross section of a crimped fiber obtained in example 1 described later. Fig. 1 (b) is a photograph of a cross section of a crimped fiber of the present invention, which is different from fig. 1(a), obtained using a dumbbell-type nozzle. In any sectional photograph there is an interface 10 of the fiber section.

Fig. 2 (a) and (b) are schematic views of the sectional photographs of fig. 1(a) and (b), respectively.

It is important that the crimped fiber of the present invention consists essentially of a single raw material.

The term "consisting essentially of a single raw material" as used herein means that the kind of olefin as the main raw material is one, and not so-called a composite fiber consisting of raw materials of 2 or more components. Additives such as antioxidants, weather stabilizers, light stabilizers, antistatic agents, antifogging agents, antiblocking agents, lubricants, nucleating agents, and pigments which are generally used are not counted as raw materials of the polymer. That is, a polymer in which one kind of olefin is used is a polymer substantially composed of a single raw material, regardless of the presence of several kinds of the above-mentioned additives. In addition, so-called hybrid spinning, in which a plurality of raw materials are spun after being mixed in a chip state, is considered as a polymer composed of a single raw material in the present invention because it is melted by one extruder or the like and supplied to a spinneret.

In the present invention, "the polyolefin is used as a main component" means that the content of the polyolefin in the crimped fiber is 80 mass% or more. The content is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 100% by mass.

Examples of the polyolefin constituting the crimped fiber and nonwoven fabric of the present invention include polyethylene, polypropylene, and copolymers of these monomers with other α -olefin, among which polypropylene is preferably used in view of high strength, low tendency to break during use, and excellent dimensional stability during production of sanitary materials.

The polypropylene may be a polymer synthesized by a conventional Ziegler-Natta catalyst, or a polymer synthesized by a single-site active catalyst such as a metallocene catalyst. In addition, ethylene random copolymer polypropylene may also be used. The ethylene content is preferably less than 2 mass%, more preferably less than 1 mass%, with respect to 100 mass% of the entire mass of the ethylene random copolymer polypropylene.

As the other α -olefin, α -olefin having 3 to 10 carbon atoms is preferable, and specific examples thereof include propylene, 1-butene, 1-pentene, 1-hexane, 4-methyl-1-pentene, and 1-octene.

From the viewpoint of strength, dimensional stability, productivity and cost, a material containing homopolypropylene as a main component is particularly preferable.

The melt flow rate (hereinafter, occasionally referred to as MFR; ASTM D-1238A method, load: 2160g, temperature: 230 ℃) of the polypropylene used in the present invention is preferably 1 to 1000g/10 min, more preferably 10 to 500g/10 min, and still more preferably 20 to 200g/10 min. When the melt flow rate of the polypropylene is in the above range, stable spinning is facilitated, and oriented crystallization is facilitated, whereby a high-strength fiber can be easily obtained.

The melt flow rate (ASTM D-1238A, load: 2160g, temperature: 190 ℃) of the polyethylene used in the present invention is preferably 1 to 1000g/10 min, more preferably 10 to 500g/10 min, and still more preferably 15 to 200g/10 min. When the melt flow rate of the polyethylene is in the above range, stable spinning is facilitated, and oriented crystallization is facilitated, so that a high-strength fiber can be easily obtained.

Additives such as an antioxidant, a weather resistant stabilizer, a light stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a lubricant, a nucleating agent, and a pigment, which are generally used, or other polymers may be added to the polypropylene and the polyethylene used in the present invention as necessary within a range not to impair the effects of the present invention.

The spunbonded nonwoven fabric of the invention is formed by containing the crimped fiber of the invention. As a method for producing a general nonwoven fabric, there are various methods such as a needle punched nonwoven fabric, a wet nonwoven fabric, a spunlaced nonwoven fabric, a spunbonded nonwoven fabric, a meltblown nonwoven fabric, a resin-bonded nonwoven fabric, a chemically-bonded nonwoven fabric, a thermally-bonded nonwoven fabric, a tow-open nonwoven fabric, and an air-laid nonwoven fabric. The spunbond nonwoven fabric is excellent in productivity and mechanical strength, and is formed of long fibers, so that it is less likely to have fluff than a short fiber nonwoven fabric.

In the present invention, the average single fiber fineness of the fibers mainly composed of polyolefin is preferably 0.5dtex or more and 3.5dtex or less, and more preferably 0.5dtex or more and 3.5dtex or lessIs 0.7dtex or more and 3.2dtex or less, and more preferably 0.9dtex or more and 2.8dtex or less. From the viewpoint of spinning stability, the average single fiber fineness is preferably 0.5dtex or more. On the other hand, the smaller the fineness, the more the number of bonding points of the filaments increases in the spun-bonded nonwoven fabric, so that the strength tends to be high and the flexibility tends to be good. In order to use the spunbonded nonwoven fabric as a sanitary material, it is preferable that the average single fiber fineness is 3.5dtex or less from the viewpoint of the strength of the spunbonded nonwoven fabric. The average single fiber fineness can be determined by the fiber cross-sectional area A (m) in the photograph of the fiber cross-section²) And polymer density ρ (g/m)³) And is calculated by the following formula.

Single fiber fineness (dtex) a (m)²)×ρ(g/m³)×10000(m)。

The spun-bonded nonwoven fabric of the present invention preferably has a weight per unit area of 3 to 200g/m². The weight per unit area is more preferably 5 to 150g/m²More preferably 10 to 100g/m². By setting the unit area weight within the above range, sufficient flexibility can be easily obtained particularly when used as a nonwoven fabric for sanitary materials.

The apparent density of the tacky nonwoven fabric of the present invention is preferably 0.130g/cm³The following. The above apparent density can be calculated by dividing the weight per unit area by the thickness. More preferably 0.125g/cm in terms of apparent density³Hereinafter, more preferably 0.100g/cm³The following. By setting the apparent density within the above range, sufficient bulkiness can be easily obtained particularly in the case of using as nonwoven fabric for sanitary materials.

The spinneret and the ejector may have various shapes such as a circular shape and a rectangular shape. Among them, a combination of a rectangular spinneret and a rectangular ejector is preferably used in view of a small amount of compressed air and difficulty in fusion and friction between fibers.

The method for producing crimped fibers of the present invention is a method for producing crimped fibers of the present invention, wherein a polyolefin resin is discharged from two dumbbell-shaped nozzles having different circular discharge orifice areas. In the two discharge hole areas of the dumbbell nozzle, the value (area ratio) of the large hole area/the small hole area is preferably 1.2 or more, more preferably 1.5 or more, and still more preferably 2.0 or more. By making the area ratio within the above range, structural differences can be imparted to the resulting fibers. The upper limit of the area ratio value is not particularly limited, and since the degree of bending of the yarn immediately after discharge increases with an increase in the area ratio, the spinning becomes unstable, and therefore the area ratio is at most 5.0 or less.

It is important that the discharge orifices (nozzles) of the spinneret for obtaining the cross-sectional shape of the crimped fibers of the present invention have the shape of the discharge orifices shown in fig. 3 (in the present invention, referred to as a dumbbell-type nozzle). The discharge shape of the dumbbell nozzle is a shape in which circles are arranged on both sides of a rectangle and the diameters of the circles are different from each other. In the exhaust holes exemplified in fig. 3, an exhaust hole (large pore diameter side) 20 and an exhaust hole (small pore diameter side) 30 are shown.

The spinning temperature in the melt spinning is preferably 200 to 300 ℃, more preferably 210 to 280 ℃, and further preferably 220 to 260 ℃. By setting the spinning temperature within the above range, a stable molten state is achieved, and excellent spinning stability can be obtained. A polyolefin resin (raw material) is melted by an extruder, and is supplied to a spinneret after being measured, and spun from a discharge hole of the spinneret.

As a method of cooling the fiber bundle of the spun long fibers, for example, there can be adopted: a method of forcibly blowing cold air to the fiber group; a method of naturally cooling the fiber group by using the temperature of the atmosphere around the fiber group; a method of adjusting the distance between the spinneret and the ejector; and combinations of the above.

In terms of cooling, it is preferable to blow cooling air from two opposite directions to the side surfaces of the fiber group, blow cooling air from three or more symmetrical directions to the side surfaces of the fiber group, or naturally cool the fiber group.

That is, in the first preferred embodiment of the method for producing crimped fibers according to the present invention, it is preferable that the cooling air is blown from the side surfaces of the fiber group in which the polyolefin-based resin is discharged from the dumbbell nozzle from two opposite directions or from three or more symmetrical directions to cool the fiber group. In the present invention, the "side surface" of the fiber group means a virtual surface parallel to the traveling direction of the fiber group discharged from the dumbbell nozzle and surrounding the fiber group along the outermost fibers of the fiber group. Further, "cooling air is blown from three or more symmetrical directions" means that cooling air is blown from n directions at an angle of about 360/n degrees formed by the wind directions of the adjacent cooling air in an imaginary cross section perpendicular to the traveling direction of the fiber group. For example, when n is 3, the cooling air is blown in three directions in which angles formed by the wind directions of the adjacent cooling air are about 360/3 degrees to 120 degrees in an imaginary cross section perpendicular to the traveling direction of the fiber group.

By blowing cooling air to the side surfaces of the fiber group from two opposite directions or blowing cooling air to the side surfaces of the fiber group from three or more symmetrical directions, the wobbling of the fiber group can be suppressed and stable spinning performance can be obtained. In addition, the fiber group can be cooled in a shorter time than in a second preferred embodiment of the method for producing crimped fibers of the present invention described later.

In the case of blowing cooling air from one side, so-called asymmetric cooling, the fiber group is likely to be broken due to large fluctuation, and uneven cooling between fibers is likely to occur.

In the second preferred embodiment of the method for producing crimped fibers according to the present invention, it is preferred that the fiber group in which the polyolefin resin is discharged from the dumbbell-shaped nozzle is naturally cooled. By performing natural cooling, as in the case of the first preferred embodiment of the method for producing crimped fibers according to the present invention, stable spinnability can be obtained while suppressing the wobbling of the fiber group.

The cooling conditions may be appropriately adjusted in consideration of the discharge amount per one hole of the spinneret, the spinning temperature, the atmospheric temperature, and the like.

Next, in the case of the fiber group solidified by cooling, it is preferable to draw with compressed air ejected from an ejector. The drawn fiber is not restrained by the compressed air after being drawn, and therefore, the drawn fiber is affected by stress relaxation. At this time, a crimp is easily generated in the fiber due to a difference in shrinkage caused by a difference in structure of the cross section of the fiber.

The method for producing a spunbonded nonwoven fabric of the present invention is a method for producing a spunbonded nonwoven fabric of the present invention, wherein crimped fibers obtained by the method for producing crimped fibers of the present invention are collected directly under a spinning line, and the fibers are crimped by a pair of rollers to form a sheet.

In the present invention, the nonwoven fabric is produced by the spunbond method as described above. The spunbond method is a manufacturing method requiring the following steps: after melting the raw material resin and spinning from a spinneret, the cooled and solidified fiber group is drawn and stretched by an ejector, collected on a moving web to be nonwoven web-formed, and then thermally bonded.

The nonwoven fabric can be obtained by collecting the long fibers (drawn fibers) drawn in the above-described steps on a web moving directly below the web, forming a nonwoven web, and integrating the obtained nonwoven web by thermal bonding. In the present invention, "collection is performed directly under spinning" means collection immediately after cooling and solidification in the case where drawing is not performed, and means collection immediately after drawing in the case where drawing is performed.

As a method of thermal bonding, for example, there can be used: thermal compression bonding of various rollers such as a thermal embossing roller in which engraved (uneven) portions are formed on the surface of each of a pair of rollers, a thermal embossing roller in which a roller having a flat (smooth) surface is combined with a roller having an engraved (uneven) surface is formed on the surface of the other roller, and a thermal embossing roller in which a pair of flat (smooth) rollers are combined; or ultrasonic based welding.

Among them, from the viewpoint of strength and abrasion resistance, thermal bonding using an emboss roller is preferable. Further, it is preferable to use a pair of rolls engraved (uneven portion) on either one of them, because it is difficult to apply pressure on the whole and the bulkiness of the crimped fibers is not impaired.

The embossing bonding area ratio at the time of heat-sealing is preferably 5 to 30%. By setting the embossed bond area ratio to 5% or more, more preferably 10% or more, the strength of the nonwoven fabric can be obtained. On the other hand, by setting the embossed bond area ratio to 30% or less, more preferably 20% or less, the bulkiness of the crimped fibers can be maintained.

The embossed bond area ratio referred to herein means a ratio of a portion in which the convex portion of one roll overlaps with the convex portion of the other roll to be in contact with the nonwoven web in the entire nonwoven fabric when the thermal bonding is performed by a pair of rolls having concave and convex portions. In the case of thermal bonding between a roll having irregularities and a flat roll, the ratio of the portion of the roll having irregularities in contact with the nonwoven web to the whole nonwoven fabric is referred to.

As the shape of the engravings applied to the heat embossing roller, shapes such as a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, and a regular octagon can be used.

The surface temperature of the hot embossing roll is preferably-50 to-1 ℃ with respect to the melting point of the resin used. By setting the surface temperature of the heat-embossing roll to-50 ℃ or higher, more preferably-30 ℃ or higher, and still more preferably-10 ℃ or higher, with respect to the melting point of the resin used, it is possible to sufficiently heat-bond the resin and impart strength thereto, and it is possible to easily suppress the occurrence of fuzz.

Further, by setting the surface temperature of the heat embossing roll to-1 ℃ or lower with respect to the melting point of the resin, it is possible to easily prevent the resins from peeling off from each other due to the melting of the fibers.

The linear pressure of the hot embossing roller during thermal bonding is preferably 5 to 50 kgf/cm. The above-mentioned linear pressure is preferably 5kgf/cm or more, more preferably 10kgf/cm or more, and further preferably 15kgf/cm or more, whereby the thermal bonding can be sufficiently performed. On the other hand, when the linear pressure is 50kgf/cm or less, more preferably 40kgf/cm or less, and still more preferably 30kgf/cm or less, excessive stress is not applied to the roll, and the bulkiness of the crimped fiber can be maintained.

The spunbonded nonwoven fabric using the crimped fiber of the present invention has very excellent bulkiness and can be suitably used for sanitary materials such as disposable diapers and napkins. In sanitary material applications, it is particularly suitable for surface materials.