WO2018092444A1

WO2018092444A1 - Spun-bonded nonwoven fabric and method for producing same

Info

Publication number: WO2018092444A1
Application number: PCT/JP2017/035941
Authority: WO
Inventors: 雅紀遠藤; 大士勝田; 拓史小林; 義嗣船津; 西村　誠
Original assignee: 東レ株式会社
Priority date: 2016-11-17
Filing date: 2017-10-03
Publication date: 2018-05-24
Also published as: JP6904260B2; TW201829868A; JPWO2018092444A1; TWI753968B

Abstract

The present invention provides a spun-bonded nonwoven fabric which is flexible, has excellent bulkiness, and which, in particular, can be suitably used as a hygienic material. The spun-bonded nonwoven fabric of the present invention is a nonwoven fabric having a polyolefin fiber as a main component, and in a cross-section of the olefin fiber, the value of the ratio, A1' A2'/B1' B2', between line segments A1' A2' and B1' B2' (where A1' A2'≧B1' B2'), which can be obtained by methods (1)-(4) below, is 1.05 or more. (1) The points of tangent at which the longest among line segments connecting two points on the circumference of a fiber cross-section meets with the circumference of the fiber cross-section are referred to as A and B. (2) The length of line segment AB is referred to as D, a point at a distance of D/4 from A is referred to as A', and likewise, a point at a distance of D/4 from B is referred to as B'. (3) The points of tangent between a straight line, which passes through A' and is perpendicular to line segment AB, and the fiber cross-section are referred to as A1' and A2'. (4) The points of tangent between a straight line, which passes through B' and is perpendicular to line segment AB, and the fiber cross-section are referred to as B1' and B2'.

Description

Spunbond nonwoven fabric and method for producing the same

The present invention relates to a spunbonded nonwoven fabric excellent in productivity and stability industrially, and particularly excellent in bulkiness at a satisfactory level when used as a sanitary material, and a method for producing the same.

Generally, non-woven fabrics for sanitary materials such as disposable diapers and sanitary napkins are required to have excellent bulkiness and flexibility due to the texture when worn. In particular, bulkiness is required for surface members that directly touch the skin.

Conventionally, as a surface member of a sanitary material, a so-called air-through nonwoven fabric in which short fibers represented by polyethylene terephthalate (PET) / polyethylene (PE) composite fibers are formed into a sheet by carding and then self-fused by hot air treatment is suitable. Is used.

This air-through non-woven fabric is widely used for hygiene materials because it has the characteristics of being bulky and flexible. However, the air-through nonwoven fabric has a problem that the manufacturing process is complicated and the production speed is slow.

On the other hand, a spunbonded nonwoven fabric using polyolefin resin fibers represented by polypropylene (hereinafter sometimes abbreviated as PP) as a raw material is characterized by high productivity and low cost. However, since this spunbonded nonwoven fabric has a structure in which the long fibers constituting the spunbonded nonwoven fabric are oriented in the surface direction of the nonwoven fabric, there is a problem that the bulkiness is inferior.

Therefore, as a method for imparting bulkiness to the spunbonded nonwoven fabric, a method of applying crimped fibers to the fibers constituting the nonwoven fabric has been proposed.

For example, a crimped composite fiber composed of two-component polymers having different melting points of 10 ° C. or more has been proposed (see Patent Document 1).

In addition, a method has been proposed in which crimping is expressed by performing asymmetric cooling on a deformed cross-section using a V-shaped cross-section nozzle from one side of the discharged fiber (see Patent Document 2).

Japanese Patent No. 5484564 JP 11-292159 A

However, in the case of the proposal of Patent Document 1, it is necessary to extrude different raw materials with different extruders and discharge them from the die, which causes a problem that the capital investment becomes high. In the proposal of Patent Document 1, it is necessary to select raw materials having melting points different by 10 ° C. or more, and a combination of ordinary PP (so-called homo PP) and copolymer PP (so-called random PP) is required. In general, random PP has a higher raw material price than homo PP, resulting in an increase in cost. Further, since the number of crimps of the obtained composite fiber is limited, bulkiness similar to an air-through nonwoven fabric is not obtained.

Further, in the proposal of Patent Document 2, there is a feature that even if the raw material is a single component, there is a feature that crimping occurs. However, when the cooling air speed is increased in this proposed method, the yarn sway and the yarn breakage occur. From the viewpoint of safety, the cooling air speed must be reduced, the number of crimps obtained is small, and the bulkiness that can be applied to the surface material of sanitary materials has not been obtained.

Therefore, conventionally, the crimped fiber and the spunbonded nonwoven fabric, which are low in cost and industrially excellent in productivity and stability, and have a satisfactory level of bulkiness when used suitably as a sanitary material, The current situation is that it has not been obtained.

Therefore, in view of the above problems, the object of the present invention is low in cost and industrially excellent in productivity and stability, and particularly excellent in bulkiness at a satisfactory level when used suitably as a sanitary material. An object of the present invention is to provide a spunbond nonwoven fabric and a method for producing the same.

The spunbonded nonwoven fabric of the present invention is a nonwoven fabric mainly composed of polyolefin fibers, and the line segments A1′A2 ′ that can be obtained by the following methods (1) to (4) in the cross section of the polyolefin fibers. A spunbonded nonwoven fabric characterized in that the ratio A1′A2 ′ / B1′B2 ′ of the line segment B1′B2 ′ (assuming A1′A2 ′ ≧ B1′B2 ′) is 1.05 or more is there.
(1) The longest line segment is drawn among the line segments connecting the two points on the outer periphery of the fiber cross section, and the contact points between the line segment and the outer periphery of the fiber cross section are A and B.
(2) The length of the line segment AB is D, a point at a distance D / 4 from A is A ′, and a point at a distance D / 4 from B is B ′.
(3) Let A1 'and A2' be the contact points of the straight line passing through line A 'and perpendicular to line segment AB and the fiber cross section.
(4) Let B1 'and B2' be the contact points between the straight line passing through B 'and perpendicular to the line segment AB and the fiber cross section.

The spunbond nonwoven fabric of the present invention is a nonwoven fabric mainly composed of polyolefin fibers, and has the maximum orientation parameter obtained by measuring from the fiber side surface using Raman spectroscopy at four points equally divided in the fiber cross-section circumferential direction. The nonwoven fabric is characterized in that the difference between the value I _max and the minimum value I _min is 0.6 or more.

According to a preferred aspect of the spunbond nonwoven fabric of the present invention, the polyolefin fiber is composed of a single component.

The above-mentioned spunbonded nonwoven fabric of the present invention is manufactured by applying cooling air from two opposite directions to the side surfaces of a fiber group in which a polyolefin resin is discharged from a dumbbell-type nozzle.

Further, the spunbonded nonwoven fabric of the present invention is produced by naturally cooling a fiber group in which a polyolefin resin is discharged from a dumbbell-type nozzle.

According to the present invention, it is possible to obtain a spunbonded nonwoven fabric that is low in cost, industrially excellent in productivity and stability, and particularly excellent in bulkiness when used as a sanitary material.

Further, according to the present invention, the ratio A1′A2 ′ / B1′B2 ′ value of the line segment A1′A2 ′ and the line segment B1′B2 ′ (assuming A1′A2 ′ ≧ B1′B2 ′) of the fiber cross section. Is set to 1.05 or more, so that the crimp can be imparted to the fiber. Therefore, by controlling the value of the above A1′A2 ′ / B1′B2 ′, the degree of crimp imparted to the fiber is controlled. A spunbonded nonwoven fabric that can be controlled and has bulkiness according to applications and requirements is obtained.

On the other hand, according to the present invention, since the crimp can be imparted to the fiber by imparting a difference in the orientation parameter of the fiber cross section, it is imparted to the fiber by controlling the value of the difference in the orientation parameter of the fiber cross section. The degree of crimping can also be controlled, and a spunbonded nonwoven fabric having bulkiness according to the application and requirements can be obtained.

FIG. 1 is a drawing-substituting photograph of a schematic cross-sectional view illustrating a cross section of a polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention. FIG. 2 is a drawing-substituting photograph of a schematic cross-sectional view illustrating the cross-section of another polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention. FIG. 3 is a drawing-substituting photograph of a schematic cross-sectional view illustrating a cross section of a polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention. Moreover, the arrow in a figure shows the example of the measurement position in the Raman spectroscopy mentioned later. 3A and 3B show two examples with different orientation parameters in the present invention. FIG. 4 is a schematic cross-sectional view illustrating the discharge surface of the spinneret used for producing the fiber in the present invention.

The spunbonded nonwoven fabric of the present invention is a nonwoven fabric mainly composed of polyolefin fibers, and the line segments A1′A2 ′ that can be obtained by the following methods (1) to (4) in the cross section of the polyolefin fibers. And a line segment B1′B2 ′ (A1′A2 ′ ≧ B1′B2 ′) is a spunbonded nonwoven fabric having a ratio A1′A2 ′ / B1′B2 ′ of 1.05 or more.
(1) The longest line segment is drawn among the line segments connecting the two points on the outer periphery of the fiber cross section, and the contact points between the line segment and the outer periphery of the fiber cross section are A and B.
(2) The length of the line segment AB is D, a point at a distance D / 4 from A is A ′, and a point at a distance D / 4 from B is B ′.
(3) Let A1 'and A2' be the contact points of the straight line passing through line A 'and perpendicular to line segment AB and the fiber cross section.
(4) Let B1 'and B2' be the contact points between the straight line passing through B 'and perpendicular to the line segment AB and the fiber cross section.

The spunbond nonwoven fabric of the present invention is a nonwoven fabric mainly composed of polyolefin fibers, and has the maximum orientation parameter obtained by measuring from the fiber side surface using Raman spectroscopy at four points equally divided in the fiber cross-section circumferential direction. difference between the value _{I max} and the minimum value _{I min} is 0.6 or more spunbond nonwoven.

The spunbond nonwoven fabric of the present invention is a nonwoven fabric containing polyolefin fibers.

The shape of the cross section of the polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention is not a normal round cross section but a special modified cross section structure. More specifically, it is a symmetric structure with respect to the longest line segment among the line segments connecting the two points on the outer periphery of the fiber cross section, and an asymmetric structure with respect to a line segment perpendicular thereto. By adopting the structure as described above, there is a structural difference due to a difference in cooling in the fiber cross-sectional direction. Therefore, in the stress relaxation after stretching, a shrinkage difference occurs in the fiber cross-sectional direction. Can be granted.

FIG. 1 is a drawing-substituting photograph of a schematic cross-sectional view illustrating a cross section of a polyolefin fiber constituting the spunbond nonwoven fabric of the present invention, and FIG. 2 is a cross-section of another polyolefin fiber constituting the spunbond nonwoven fabric of the present invention. It is a drawing substitute photograph of the schematic cross-sectional view illustrating the surface.

1 and 2, the contact points between the longest line segment connecting the two points on the outer periphery of the fiber cross section and the outer periphery of the fiber cross section are A and B. The length of the line segment AB is D, the point at a distance of D / 4 from A is A ′, the point at the distance of D / 4 from B is also B ′, and each is perpendicular to the line segment AB. A straight line is drawn, and the intersections with the outer circumference of the fiber cross section are set as A1 ′, A2 ′, B1 ′, and B2 ′ (A1′A2 ′ ≧ B1′B2 ′), respectively.

It is important that the polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention has a ratio A1′A2 ′ / B1′B2 ′ of the line segment A1′A2 ′ and line segment B1′B2 ′ of 1.05 or more. is there. The ratio A1'A2 '/ B1'B2' is more preferably 1.10 or more, and further preferably 1.20 or more. By setting the ratio A1′A2 ′ / B1′B2 ′ value to 1.05 or more, a structural difference can be made in the fiber cross-sectional direction, so that a structure in which crimps are easily developed after stretching is preferable.

The upper limit of the above ratio A1'A2 '/ B1'B2' value is likely to become unstable when the fiber is spun and discharged because the structural difference of the fiber cross section increases as the ratio increases. Therefore, the upper limit of this ratio is at most about 5.0 from the stability of spinning.

In the present invention, at four points equally divided in the fiber cross-sectional circumferential direction of the polyolefin fiber constituting the spunbond nonwoven fabric of the present invention, the maximum value I _max and the minimum value of the orientation parameter measured from the fiber side surface using Raman spectroscopy. It is important that the difference in I _min is 0.6 or more.

The orientation parameter in the present invention, in the Raman spectrum obtained by Raman spectroscopy, for example, in the case of PP, can be determined from the intensity of the Raman bands around 810 cm ^-1 and 840 cm ^-1. In the case of PP, it is known that Raman bands near 810 cm ⁻¹ and 840 cm ⁻¹ exhibit strong anisotropy with respect to the polarization of incident light. These are attributed to the coupling mode of CH ₂ bending vibration and CC stretching vibration and the CH ₂ bending vibration mode, respectively. Among these, for the Raman band at 810 cm ⁻¹ , the principal axis of the vibration mode Raman tensor is parallel to the main chain direction of the molecule, while it is orthogonal to the Raman band at 840 cm ⁻¹ . Therefore, the molecular chain orientation is obtained from the band intensity ratio of these Raman bands to the polarization direction.

The orientation parameter I as used in the present invention is determined as a value of I ₈₁₀ / I ₈₄₀ (I ₈₁₀ : Raman band intensity near ₈₁₀ cm ⁻¹ , I ₈₄₀ : Raman band intensity near ₈₄₀ cm ⁻¹ ).

In the case of PE, the Raman band around 1130 cm ⁻¹ is parallel to the main chain direction of the molecular tensor in the vibration mode, and the Raman band around 1060 cm ⁻¹ is orthogonal. Therefore, the orientation parameter I in the present invention is obtained as a value of I ₁₁₃₀ / I ₁₀₆₀ (Raman band intensity near I ₁₁₃₀ : ₁₁₃₀ cm ⁻¹ , Raman band intensity near I ₁₀₆₀ : ₁₀₆₀ cm ⁻¹ ).

In the case of general PP fiber, the difference between the maximum value and the minimum value of the orientation parameter is at most about 0.2. The difference between the maximum value and the minimum value of the orientation parameter in the case of PP-based side-by-side crimped composite fibers using different known two-component raw materials is about 0.4. By setting the difference between the maximum value and the minimum value of the orientation parameters of the fibers constituting the spunbonded nonwoven fabric to be 0.6 or more, a structure in which crimps are very easily developed can be obtained.

The difference between the maximum value and the minimum value of the orientation parameters of the fibers constituting the spunbonded nonwoven fabric of the present invention is preferably 0.6 or more, more preferably 0.8 or more, and further preferably 1.0 or more. It is. By setting the difference in the orientation parameters to 0.6 or more, it is possible to obtain a sufficient structural difference for the fibers to be crimped. In addition, the upper limit of the difference in the orientation parameters is at most about 7.0 as the limit that can be produced in the same fiber.

Examples of the polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention include fibers made of resins such as polyethylene, polypropylene, and copolymers of these monomers and other α-olefins. Among these, it is preferable to use polypropylene fibers because they are strong and difficult to break during use and are excellent in dimensional stability during production of sanitary materials.

The polypropylene resin may be a polymer synthesized by a general Ziegler Natta catalyst, or a polymer synthesized by a single site active catalyst typified by metallocene. Further, ethylene random copolymer polypropylene can also be used. The ethylene content is preferably less than 2% by mass, more preferably less than 1% by mass.

Other α-olefins are those having 3 to 10 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexane, 4-methyl-1-pentene, and 1-octene. Is mentioned. These can be used alone or in combination of two or more.

It is a particularly preferable aspect that the polypropylene resin is mainly composed of homopolypropylene from the viewpoints of strength and dimensional stability, and productivity and cost.

The polypropylene fiber constituting the spunbonded nonwoven fabric of the present invention may be composed of a single component polymer or a composite fiber composed of two or more different polymers, but from the viewpoint of productivity and cost. It is a particularly preferred embodiment that it is composed of a single component polymer. The phrase “consisting of a single component polymer” as used in the present invention means, for example, that the olefin species as the main raw material is one kind. Commonly used antioxidants, weathering stabilizers, light stabilizers, antistatic agents, antifogging agents, antiblocking agents, lubricants, nucleating agents, pigments, and other additives are not counted as polymer raw materials. That is, no matter how many kinds of these additives etc. are contained in a polymer having one kind of olefin species, the polymer is substantially a polymer composed of a single raw material.

Also, so-called blend spinning, in which a plurality of raw materials are mixed in the form of chips and then spun, is treated as a single component polymer in the present invention because the interface between the raw materials cannot be confirmed. In the present invention, “having polyolefin as a main component” means that the content of polyolefin in the fiber is 80% by 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.

The melt flow rate of the polypropylene resin used in the present invention (hereinafter sometimes referred to as MFR; ASTM D-1238 load; 2160 g, temperature; 230 ° C.) is preferably 1 to 1000 g / 10 min. More preferably, it is ˜500 g / 10 minutes, and more preferably 20 to 200 g / 10 minutes. By setting the melt flow rate in the range of 1 to 1000 g / 10 min, it becomes easy to perform stable spinning, and orientation crystallization easily proceeds, so that high-strength fibers can be easily obtained.

The melt flow rate (ASTM D-1238 load; 2160 g, temperature: 190 ° C.) of the polyethylene resin used in the present invention is preferably 1 to 1000 g / 10 minutes, more preferably 10 to 500 g / 10 minutes. More preferably 15 to 100 g / 10 min. By setting the melt flow rate in the range of 1 to 1000 g / 10 min, it becomes easy to perform stable spinning, and orientation crystallization easily proceeds, so that high-strength fibers can be easily obtained.

In the polypropylene resin and polyethylene resin used in the present invention, antioxidants, weathering stabilizers, light stabilizers, antistatic agents, antifogging agents, and antiblocking agents that are usually used are within the range that does not impair the effects of the present invention. Additives such as agents, lubricants, nucleating agents and pigments or other polymers can be added as necessary.

Examples of general nonwoven fabric production methods include needle punch nonwoven fabrics, wet nonwoven fabrics, spunlace nonwoven fabrics, spunbond nonwoven fabrics, melt blown nonwoven fabrics, resin bond nonwoven fabrics, chemical bond nonwoven fabrics, thermal bond nonwoven fabrics, tow spread nonwoven fabrics, and airlaid nonwoven fabrics. In the present invention, it is important that the nonwoven fabric is formed by the spunbond method. Spunbond nonwoven fabrics are excellent in productivity and mechanical strength, and are made of long fibers, so that they have a feature that they are less prone to fuzzing than short fiber nonwoven fabrics.

The average single fiber fineness of the polyolefin fibers constituting the spunbonded nonwoven fabric of the present invention is preferably 0.5 dtex or more and 3.5 dtex or less, more preferably 0.7 dtex or more and 3.2 dtex or less, further preferably 0. .9 dtex or more and 2.8 dtex or less. The average single fiber fineness is preferably 0.5 dtex or more from the viewpoint of spinning stability, and the finer the fineness, the higher the strength and flexibility of the nonwoven fabric because the number of bonding points of the yarn increases. Since the spunbond nonwoven fabric of the present invention is mainly used as a sanitary material, the average single fiber fineness is preferably 3.5 dtex or less from the viewpoint of the strength of the spunbond nonwoven fabric. The average single fiber fineness can be calculated from the fiber cross-sectional area A (m ² ) and the polymer density ρ (g / m ³ ) in the fiber cross-sectional photograph using the following formula.
Single fiber fineness (dtex) = A (m ² ) × ρ (g / m ³ ) × 10000 (m).

The spunbonded nonwoven fabric of the present invention is a preferred embodiment having a basis weight of 3 to 200 g / m ² . The basis weight is more preferably 5 to 150 g / m ² , and further preferably 10 to 100 g / m ² . By setting the basis weight within the above range, sufficient flexibility can be obtained particularly when used as a nonwoven fabric for sanitary materials.

Moreover, it is a preferable aspect that the apparent density of the spunbonded nonwoven fabric of the present invention is 0.130 g / cm ³ or less. The apparent density can be calculated by dividing the basis weight by the thickness. Apparent density is more preferably not more than 0.025 g / cm ³ or more 0.125 g / cm ^3, more preferably not more than 0.040 g / cm ³ or more 0.100 g / cm ^3. By setting the apparent density within the above range, sufficient bulkiness and physical properties can be obtained particularly when used as a nonwoven fabric for sanitary materials.

Next, an example of a method for producing the spunbonded nonwoven fabric of the present invention will be described.

In the spunbond method, the raw material resin is melted and spun from a spinneret, and then the cooled and solidified fiber group is pulled and drawn by an ejector and collected on a moving net to form a nonwoven web. This is a manufacturing method that requires a heat bonding step.

As the shape of the spinneret or the ejector, various shapes such as a round shape and a rectangular shape can be adopted. Among these, a combination of a rectangular die and a rectangular ejector is preferably used because the amount of compressed air used is relatively small and the fiber group is less likely to be fused or scratched.

It is important that the die for obtaining the cross-sectional shape of the polyolefin fiber used in the present invention has the shape of the discharge hole exemplified in FIG. 4 (in the present invention, it may be referred to as a dumbbell shape). . The discharge hole diameter of the dumbbell shape is a shape in which circles are arranged on both sides of the rectangle, and the hole diameters of the circles are different. FIG. 4 illustrates the discharge surface of the spinneret. Here, a discharge hole (large hole diameter side) 20 and a discharge hole (small hole diameter side) 30 are shown.

In order to obtain the polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention, it is important that there is a difference between the discharge hole areas of the two circles, and the value of the large pore diameter area / small pore diameter area (area ratio) is 1.2. It is preferable that it is above, More preferably, it is 1.5 or more, More preferably, it is 2.0 or more. By setting the area ratio to 1.2 or more, a structural difference can be imparted to the obtained fiber. The upper limit of the area ratio is 5.0 or less at most because the yarn bending immediately after discharge increases and spinning becomes unstable as the area ratio increases.

The cross section of the polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention can be obtained by appropriately adjusting the discharge shape of the die. By setting the value of the large pore diameter area / small pore diameter area to 1.2 or more, the line segment A1′A2 ′ and the line segment B1′B2 ′ (A1′A2 ′ ≧ B1′B2 ′) of the fiber cross section are obtained. ) Ratio A1′A2 ′ / B1′B2 ′ value of 1.05 or more can be obtained.

The spinning temperature at the time of melting and spinning is preferably 200 to 300 ° C, more preferably 210 to 280 ° C, and further preferably 220 to 260 ° C. By setting the spinning temperature within the above range, a stable molten state can be obtained, and excellent spinning stability can be obtained.

The polyolefin resin (raw material) is melted and measured by an extruder and spun from a nozzle discharge hole that is supplied to a spinneret.

Examples of the method for cooling the spun long fiber group include a method in which cold air is forcibly blown to the fiber group, a method of natural cooling at the ambient temperature around the fiber group, and a distance between the spinneret and the ejector. Adjustment methods and combinations thereof can be employed.

Further, it is preferable that the cooling is applied by cooling air from two directions opposite to the fiber group or is naturally cooled. In the case of so-called asymmetric cooling, in which cooling air is applied from one side, yarn breakage is likely to occur due to large fluctuations in the fiber group, and cooling unevenness occurs between the fibers. The cooling conditions can be appropriately adjusted and adopted in consideration of the discharge amount per single hole of the spinneret, the spinning temperature, the atmospheric temperature, and the like.

Next, the cooled and solidified fiber group is pulled and stretched by the compressed air jetted from the ejector. After being stretched, the stretched fiber is affected by stress relaxation because it is no longer restricted by compressed air. At this time, crimp is developed in the fiber due to the difference in shrinkage caused by the structural difference in the fiber cross section. Thereafter, the spunbonded nonwoven fabric can be obtained by collecting the long fibers on a moving net to form a nonwoven web, and integrating the obtained nonwoven web by thermal bonding.

As a method of thermal bonding, for example, a heat embossing roll in which engravings (uneven portions) are applied to a pair of upper and lower roll surfaces, a roll with one roll surface being flat (smooth) and an engraving (uneven portion on the other roll surface) ), A heat embossing roll formed of a combination with a roll provided with a), a heat calender roll formed of a combination of a pair of upper and lower flat (smooth) rolls, and thermocompression bonding with various rolls, and ultrasonic fusion.

Of these, thermal bonding using an embossing roll can be preferably employed from the viewpoint of strength and wear resistance. Moreover, it is a preferable aspect to use the roll by which the engraving (uneven | corrugated | grooved part) was given to any one of the upper and lower sides, since it becomes difficult to apply a pressure to the whole and the bulkiness by the crimped fiber is not impaired.

The embossed adhesive area ratio at the time of heat fusion is preferably 5 to 30%. By setting the embossed adhesion area ratio to 5% or more, more preferably 10% or more, it is possible to obtain a strength that can be practically used as a spunbonded nonwoven fabric. On the other hand, when the embossed adhesion area ratio is 30% or less, more preferably 20% or less, the bulkiness due to the crimped fibers can be maintained.

The embossed adhesion area ratio here refers to the entire nonwoven fabric of the portion where the convex part of the upper roll and the convex part of the lower roll are overlapped with each other to contact the non-woven web when thermally bonded by a roll having a pair of irregularities. This is the proportion of the total. Moreover, when heat-bonding by the roll which has an unevenness | corrugation, and the flat roll, the convex part of the roll which has an unevenness | corrugation means the ratio which occupies for the whole nonwoven fabric of the part which contact | abuts a nonwoven web.

As the shape of the engraving applied to the heat embossing roll, 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 ° C. with respect to the melting point of the lowest melting point resin (hereinafter, sometimes referred to as low melting point resin) among the resins used. By setting the surface temperature of the hot embossing roll to −50 ° C. or more, more preferably −30 ° C. or more, and further preferably −10 ° C. or more with respect to the melting point of the low melting point resin, the heat embossing roll can be sufficiently heat-bonded and given strength. Occurrence can be easily suppressed.

Further, by setting the surface temperature of the hot embossing roll to −1 ° C. or less with respect to the melting point of the low melting point resin, it is possible to easily prevent the separation of the resins due to the melting of the fibers.

The linear pressure of the hot embossing roll during thermal bonding is preferably 5 to 50 kgf / cm. When the linear pressure is 5 kgf / cm or more, more preferably 10 kgf / cm or more, and still more preferably 15 kgf / cm or more, sufficient thermal bonding can be achieved. On the other hand, by setting the linear pressure to 50 kgf / cm or less, more preferably 40 kgf / cm or less, and even more preferably 30 kgf / cm or less, the bulkiness due to the crimped fibers is maintained by not applying excessive stress to the roll. Can do.

Since the spunbonded nonwoven fabric of the present invention is very bulky, it can be suitably used for sanitary material applications such as disposable paper diapers and napkins. Among hygienic materials, it can be suitably used particularly for surface materials (top sheets) and the like. Moreover, it can be used suitably for any of various uses requiring bulkiness and flexibility, such as bandages, medical gauze, towels, and sanitary masks.

Next, based on the examples, the spunbonded nonwoven fabric of the present invention and the production method thereof will be specifically described.

(1) Calculation of ratio A1′A2 ′ / B1′B2 ′ value in fiber cross section:
The cross section of the fiber constituting the spunbonded nonwoven fabric was photographed with a scanning electron microscope (model number: VE7800) manufactured by Keyence Corporation, and line segments A1′A2 ′ and line segment B1 ′ were followed according to the following procedures (A) to (D). The length of B2 ′ (A1′A2 ′ ≧ B1′B2 ′) was measured, and the ratio A1′A2 ′ / B1′B2 ′ value was calculated. The measurement of various line segments at this ratio was calculated using a measurement function attached to the microscope software used for image capturing. Measurement was performed on three fibers collected from different positions of the nonwoven fabric, and the average was obtained.
(A) The longest line segment is drawn out of the line segments connecting two points on the outer periphery of the fiber cross section, and the contact points between the line segment and the outer periphery of the fiber cross section are designated as A and B.
(B) The length of the line segment AB is D, a point at a distance of D / 4 from A is A ′, and a point at a distance of B / 4 from D / 4 is also B ′.
(C) Let A1 'and A2' be the contact points of the straight line passing through the above A 'and perpendicular to the line segment AB and the fiber cross section.
(D) Let B1 'and B2' be the contact points of the straight line passing through B 'and perpendicular to the line segment AB and the fiber cross section.

(2) Orientation parameter difference (I _max −I _min ) in the fiber cross section:
As a measuring device, a triple Raman spectroscopic device T-64000 manufactured by Ehime Bussan was used. The measurement conditions were as follows.
・ Measurement mode: Micro Raman (polarization measurement)
Objective lens: Long focal length 90 times (NA = 0.90)
Beam diameter: 51 μm, light source: Ar ⁺ laser / 514.5 nm
・ Laser power: 100mW
Diffraction grating: Single 1800 gr / mm
・ Slit: 100 μm
・ Cross slit: 200μm
Detector: CCD / Jobin Yvon 1024 × 256
-Integration time: 120 seconds One fiber was taken out from the spunbond nonwoven fabric, and the Raman spectrum was measured from the fiber side surface at four points equally divided in the fiber cross-section circumferential direction. For PP, it calculates the intensity _{I 810} and _{I 840} of the Raman bands of 810 cm ^-1 and 840 cm ^-1 at each measurement point, the ratio _I 810 _{/ I 840,} was calculated as the orientation parameter I. In the case of PE, Raman band intensities I ₁₁₃₀ and I ₁₀₆₀ at ₁₁₃₀ cm ⁻¹ and 1060 cm ⁻¹ were calculated and calculated as the ratio I ₁₁₃₀ / I ₁₀₆₀ orientation parameter I. The maximum value I _max and the minimum value I _min of the orientation parameters at each measurement point were determined, and the difference (I _max −I _min ) was calculated. It measured similarly about one fiber extract | collected from the different position of a spun bond nonwoven fabric, calculated | required the average of 2 points | pieces, and made it the difference of the orientation parameter.

The measurement position of the orientation parameter in the present invention will be described. FIG. 3 illustrates a cross section of the polyolefin fiber constituting the spunbonded nonwoven fabric of the present invention, and shows an example of the orientation parameter measurement position 10. FIGS. 3A and 3B show two different specific examples in the present invention. The alignment parameter measurement position 10 shown in FIG. 3 is an example showing the positions of four points at which the alignment parameter of the present invention is measured, and the measurement position can be appropriately selected according to the form of the invention. It is important that the measurement positions indicated by the alignment parameter measurement positions 10 are four points at equal intervals on the fiber circumference. By using such measurement positions, the difference in the alignment parameters in the present invention can be calculated. It becomes.

(3) Number of crimps of fiber:
The number of crimps of the fiber was measured from the image of the fiber taken with a microscope. The total number of peaks and troughs of fibers per unit length was counted, the total was divided by 2, and the number per 25 mm was the number of crimps. Ten fibers were measured and the average was determined. The number of crimps is 50/25 mm or more as the degree of crimp (◎), the number of crimps is 25/25 mm or more and less than 50/25 mm is the degree of crimp (◯), and the number of crimps is 0/25 mm ( Crimps (x) are from those not crimped) to less than 25 pieces / 25 mm. Those having a number of crimps of 25 pieces / 25 mm or more (◎ and ○) were accepted.

(4) Fabric weight of spunbond nonwoven fabric:
Based on 6.2 "mass per unit area" of JIS L1913 (2010), three pieces of 20 cm x 25 cm test pieces were collected per 1 m width of the sample, and the basis weight of the spunbond nonwoven fabric was measured. The mass (g) was measured, and the average value was expressed in terms of mass per 1 m ² (g / m ² ).

(5) Thickness of spunbond nonwoven fabric:
Based on JIS L 1908 (2010), the thickness of the spunbonded nonwoven fabric was measured. A presser foot having an area of 2500 mm ² is prepared. For a test piece having a size of 1.75 times the diameter of the presser foot, a pressure of 2 kPa is applied for a certain time, and then the thickness is measured. The average value for 10 test pieces was calculated, and the value was taken as the thickness. It was evaluated that the higher this value, the better the bulkiness.

(6) Apparent density of spunbond nonwoven fabric:
The apparent density of the spunbonded nonwoven fabric was calculated from the measured basis weight and thickness of the spunbonded nonwoven fabric. The lower this value, the better the bulkiness.

Example 1
A polypropylene (PP) resin having a melt flow rate (MFR) of 60 g / 10 min (load: 2160 g, temperature: 230 ° C.) and a melting point of 162 ° C. was melted with an extruder, and a spinning temperature of 235 was used. As shown in FIG. 1, a single hole discharge rate is 0.6 g / min from a spinneret (dumbbell type nozzle) having a shape with a hole diameter of φ0.38 mm and φ0.27 mm and a center distance between both holes of 0.8 mm. Long fibers with different cross-sectional shapes were spun.

After cooling the sides of the spun long fiber group by applying cooling air from two opposite directions, the compressed air is injected from the ejector at an ejector pressure of 0.17 MPa through the ejector, and the fiber group is pulled and stretched. Crimp was expressed. Thereafter, the filament was collected on a moving net to form a nonwoven web. Subsequently, using an upper roll engraved with a metal polka dot pattern and a pair of upper and lower embossed rolls made of metal and a flat lower roll, a linear pressure of 20 kgf / cm and thermal bonding are used. A heat bonding treatment was performed at a temperature of 135 ° C. to obtain a spunbonded nonwoven fabric having a basis weight of 20 g / m ² . Ratio of fiber cross-section ratio A1′A2 ′ / B1′B2 ′ constituting the obtained spunbond nonwoven fabric, difference in orientation parameters (I _max −I _min ) in the fiber cross-section of fibers constituting the spunbond nonwoven fabric, crimp The number, the basis weight of the nonwoven fabric, the thickness, and the apparent density were measured. The obtained evaluation results are shown in Table 1.

(Example 2)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 1 except that a polypropylene (PP) resin having an MFR of 35 g / 10 min (load; 2160 g, temperature: 230 ° C.) and a melting point of 162 ° C. was used as a raw material. It was. The obtained evaluation results are shown in Table 1.

(Example 3)
Spunbond was carried out in the same manner as in Example 1 except that a copolymer polypropylene (copolymer PP) resin having an MFR of 33 g / 10 min (load; 2160 g, temperature: 230 ° C.) and a melting point of 149 ° C. was used as the raw material. A nonwoven fabric was obtained. The obtained evaluation results are shown in Table 1.

Example 4
A high-density polyethylene (HDPE) resin having an MFR of 18 g / 10 min (load; 2160 g, temperature: 190 ° C.) and a melting point of 130 ° C. was used as the raw material, and the heat bonding temperature of the embossing roll was set to 90 ° C. A spunbonded nonwoven fabric was obtained in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

(Example 5)
The first component of the raw material has an MFR of 60 g / 10 min (load; 2160 g, temperature: 230 ° C.) and a melting point of 162 ° C., and the second component has an MFR of 35 g / 10 min (load; 2160 g, temperature: 230 ° C.), a polypropylene resin having a melting point of 162 ° C., melted in different extruders, weighed so that the mass ratio of each component was 50:50, and the first component was discharged A spunbonded nonwoven fabric was obtained in the same manner as in Example 1 except that the second component was introduced into the discharge hole diameter φ0.27 mm side and spun on the φ0.38 mm side. The obtained evaluation results are shown in Table 1.

(Example 6)
A polypropylene (PP) resin having an MFR of 60 g / 10 minutes (load; 2160 g, temperature: 230 ° C.) and a melting point of 162 ° C. is used as the first component of the raw material, and an MFR of 33 g / 10 is used as the second component. A spunbonded nonwoven fabric was obtained in the same manner as in Example 5 except that a copolymer polypropylene (copolymerized PP) resin having a melting point of 149 ° C. was used for a minute (load; 2160 g, temperature: 230 ° C.). The obtained evaluation results are shown in Table 1.

(Example 7)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 1 except that the spinneret used had a discharge diameter of φ0.35 mm and φ0.32 mm, and the center distance between both holes was 0.8 mm. . The obtained results are shown in Table 1.

(Example 8)
The raw material has a MFR of 35 g / 10 min (load: 2160 g, temperature: 230 ° C.) and a melting point of 162 ° C. polypropylene (PP) resin and MFR of 25 g / 10 min (load: 2160 g, temperature: 230 ° C.). A spunbonded nonwoven fabric was obtained in the same manner as in Example 1 except that a mixed raw material in which a polymerized polypropylene (PP) resin was blended so that the mass ratio of each raw material was 88:12 was used. The obtained results are shown in Table 2.

Example 9
A spunbonded nonwoven fabric in the same manner as in Example 4 except that linear low density polyethylene (LLDPE) having an MFR of 30 g / 10 min (load; 2160 g, temperature: 190 ° C.) and a melting point of 130 ° C. was used as a raw material. Got. The results obtained are shown in Table 2.

(Example 10)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 1 except that the cooling of the fiber group was natural cooling. The results obtained are shown in Table 2.

(Comparative Example 1)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 5 except that the discharge hole diameter of the die used was changed to a conventionally known round shape (discharge hole diameter φ0.5 mm). The evaluation results obtained are shown in Table 2.

(Comparative Example 2)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 6 except that the discharge hole diameter of the die used was changed to a conventionally known round shape (discharge hole diameter φ0.5 mm). The evaluation results obtained are shown in Table 2.

(Comparative Example 3)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 1 except that the discharge shape was discharged from a conventionally known V-shaped base. The evaluation results obtained are shown in Table 2.

In Examples 1 to 4 and 8 to 10 of the present invention, the ratio A1′A2 ′ / B1′B2 ′ value is 1.05 or more even though the raw material is a single component. Due to the difference, the fibers were crimped, and the obtained spunbonded nonwoven fabric was very excellent in bulkiness and was very suitably used as a surface member of a sanitary material. In addition, the difference in the orientation parameters of the fiber cross section is 0.6 or more and a sufficient structural difference is made, and the spunbond nonwoven fabric obtained by crimping the fiber is very bulky and is a surface member of a sanitary material. It was very suitably used as.

In addition, Examples 5 and 6 of the present invention have a larger number of crimps due to structural differences in the fiber cross section compared to Comparative Examples 1 and 2, and the bulkiness of the spunbonded nonwoven fabric is excellent, and the hygienic material It was used very suitably as a surface member. Further, the difference in orientation parameters is large, the number of crimps is large, the bulkiness of the nonwoven fabric is excellent, and it is very suitably used as a surface member for sanitary materials.

Example 7 in Table 1 has a small ratio A1′A2 ′ / B1′B2 ′ value in comparison with Example 1, and the surface of the sanitary material although the number of crimps of the obtained fiber and the bulkiness of the nonwoven fabric are inferior. It was used suitably as a member. Moreover, Example 7 is suitably used as a surface member of a sanitary material, although the difference in the orientation parameter is small compared to Example 1, and the number of crimps of the obtained fiber and the bulkiness of the spunbonded nonwoven fabric are inferior. It was a thing.

On the other hand, although Comparative Example 3 had a deformed cross section, there was no difference in fiber cross-sectional structure, no crimp was developed, and the bulkiness of the nonwoven fabric was inferior. Further, there was almost no difference in the orientation parameters, and no crimp was developed in the fiber, and the bulkiness of the spunbonded nonwoven fabric was inferior.

A, B: The contact point between the longest line segment connecting the two points on the outer periphery of the fiber cross section and the outer periphery of the fiber cross section D: Length of the line segment AB A ′: A distance from A to D / 4 Point B ′: Points A1 ′, A2 ′: A line passing through A ′ at a distance of D / 4 from B and straight line perpendicular to line segment AB and contact points B1 ′, B2 ′: B ′ passing through line cross section AB Straight line and contact point of fiber cross section 10: Orientation parameter measurement position 20: Discharge hole (large hole diameter side)
30: Discharge hole (small hole diameter side)

Claims

A non-woven fabric mainly composed of polyolefin fibers, wherein a line segment A1'A2 'and a line segment B1'B2' (A1) that can be obtained by the following methods (1) to (4) in the cross section of the polyolefin fiber: The ratio A1′A2 ′ / B1′B2 ′ of “A2” ≧ B1′B2 ′) is 1.05 or more.
(1) The longest line segment is drawn among the line segments connecting the two points on the outer periphery of the fiber cross section, and the contact points between the line segment and the outer periphery of the fiber cross section are A and B.
(2) The length of the line segment AB is D, a point at a distance D / 4 from A is A ′, and a point at a distance D / 4 from B is B ′.
(3) Let A1 'and A2' be the contact points of the straight line passing through line A 'and perpendicular to line segment AB and the fiber cross section.
(4) Let B1 'and B2' be the contact points between the straight line passing through B 'and perpendicular to the line segment AB and the fiber cross section.
A non-woven fabric mainly composed of polyolefin fibers, and at four points equally divided in the fiber cross-section circumferential direction, the maximum value I max and the minimum value I min of orientation parameters obtained by measuring from the fiber side surface using Raman spectroscopy A spunbonded nonwoven fabric characterized by having a difference of 0.6 or more.
3. The spunbonded nonwoven fabric according to claim 1 or 2, wherein the polyolefin fiber is composed of a single component.
The method for producing a spunbonded nonwoven fabric according to any one of claims 1 to 3, wherein the side surface of the fiber group discharged from the dumbbell-shaped nozzle is cooled by applying cooling air from two opposite directions. .
The method for producing a spunbonded nonwoven fabric according to any one of claims 1 to 3, wherein the fiber group in which the polyolefin resin is discharged from the dumbbell nozzle is naturally cooled.