JP7180761B2 - spunbond nonwoven fabric - Google Patents

Description

The present invention relates to spunbond nonwoven fabrics.

In general, nonwoven fabrics made of polyolefin are widely used for sanitary materials such as disposable diapers and sanitary napkins because of their lightness, low cost, softness, and the like.

In particular, the backsheets of paper diapers are often touched by hands, have a wide range of use, and have a large impact on the appearance of diapers. As for the appearance of paper diapers, those having characters on the surface are desired as an appearance that is preferred by babies, and the function of printability on the nonwoven fabric surface is one of the important functions. In terms of design, a highly glossy material having a silk-like appearance is especially preferred.

As a means for improving the feel and softness of nonwoven fabrics, it has been conventionally known that a method of controlling the fiber diameter of fibers constituting nonwoven fabrics is effective. For example, there has been proposed a spunbonded nonwoven fabric in which the bending softness of the fibers themselves is improved by setting the fineness and adsorption force of the fibers to specific ranges (see Patent Document 1).

JP 2013-159884 A

However, in the method disclosed in Patent Document 1, the unevenness of the nonwoven fabric surface is large, printing unevenness occurs, and it is difficult to obtain a good appearance.

In order to make the surface smooth, a method of contacting with a heat calender or the like is conceivable, but in this method, the surface of the nonwoven fabric is formed into a film, resulting in a hard texture.

Although there is a demand for nonwoven fabrics with reduced surface unevenness, the current situation is that no nonwoven fabrics with both practical printability and tactile feel have been obtained.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a spunbond nonwoven fabric that has good printability, excellent gloss, and flexibility.

The spunbonded nonwoven fabric of the present invention is a spunbonded nonwoven fabric made of a polyolefin resin, has an average fiber orientation degree of 0 to 30 degrees, and has a fiber ratio of 0 to 30 degrees fiber orientation of 50 to 80%. And the tensile strength in the reference direction is 3 to 6 times the tensile strength in the direction perpendicular to it.

According to a preferred aspect of the spunbond nonwoven fabric of the present invention, the average single fiber diameter of the fibers constituting the spunbond nonwoven fabric is 6.5 to 11.9 μm.

According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the ratio of the surface roughness SMD measured by the KES method in the reference direction on at least one side and the direction perpendicular thereto is 0.30 to 0.85.

According to a preferred aspect of the spunbond nonwoven fabric of the present invention, the polyolefin resin contains a fatty acid amide compound having 23 to 50 carbon atoms.

According to a preferred aspect of the spunbond nonwoven fabric of the present invention, the content of the fatty acid amide compound in the polyolefin resin is 0.01 to 5.0% by mass.

According to a preferred aspect of the spunbond nonwoven fabric of the present invention, the fatty acid amide contains ethylenebisstearic acid amide.

According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the bending resistance in the reference direction measured by the cantilever method is 10 to 80 mm.

According to a preferred aspect of the spunbond nonwoven fabric of the present invention, the spunbond nonwoven fabric further satisfies the following formula (1).

GL/100≧95 (1)
Here, G is the maximum value of glossiness and L is the average luminance.

ADVANTAGE OF THE INVENTION According to this invention, the spunbond nonwoven fabric which has good printability, is excellent in gloss, and is flexible can be obtained.

The spunbonded nonwoven fabric of the present invention is a spunbonded nonwoven fabric made of a polyolefin resin, has an average fiber orientation degree of 0 to 30 degrees, and contains 50 to 80% of fibers having a fiber orientation degree of 0 to 30 degrees, and The tensile strength in the reference direction is 3-6 times the tensile strength in the direction perpendicular to it.

By doing so, a spunbond nonwoven fabric having good printability, excellent gloss, and flexibility can be obtained.
Details of these will be described below.

[Polyolefin resin]
Polyolefin-based resins used in the present invention include, for example, polypropylene-based resins and polyethylene-based resins.

Examples of polypropylene-based resins include propylene homopolymers and copolymers of propylene and various α-olefins.

Polyethylene-based resins include homopolymers of ethylene and copolymers of ethylene and various α-olefins.

Among these, polypropylene-based resins are particularly preferably used because of their spinnability and strength characteristics.

The polyolefin-based resin used in the present invention may be a mixture of two or more types, or may be a resin composition containing other olefin-based resins, thermoplastic elastomers, and the like.

The polyolefin-based resin used in the present invention may be a composite fiber obtained by combining a plurality of polyolefin-based resins. Composite forms of composite fibers include, for example, concentric core-sheath, eccentric core-sheath and islands-in-the-sea types. Among them, a concentric core-sheath type composite form is a preferable embodiment because it has excellent spinnability and can be uniformly bonded to each other by heat bonding.

The polyolefin resin used in the present invention includes antioxidants, weather stabilizers, light stabilizers, antistatic agents, anti-fogging agents, anti-blocking agents, lubricants, nucleating agents, Additives such as pigments and other polymers can be added as necessary.

The melting point of the polyolefin resin used in the present invention is preferably 80 to 200.degree. C., more preferably 100 to 180.degree. C., still more preferably 120 to 180.degree. By setting the melting point to preferably 80° C. or higher, more preferably 100° C. or higher, and even more preferably 120° C. or higher, high heat resistance can be easily obtained. In addition, by setting the melting point to preferably 200° C. or lower, more preferably 180° C. or lower, the yarn extruded from the spinneret can be easily cooled, thereby suppressing fusion between fibers and facilitating stable spinning.

The melt flow rate (hereinafter sometimes referred to as MFR) of the spunbond nonwoven fabric of the present invention is preferably 155 to 850 g/10 minutes. By setting the MFR to 155 to 850 g/10 minutes, preferably 155 to 600 g/10 minutes, and more preferably 155 to 400 g/10 minutes, even if drawing is performed at a high spinning speed to increase productivity, the viscosity is Since it is low, deformation can be easily followed, making it easier to perform stable spinning. Further, by drawing at a high spinning speed, the oriented crystallization of the fiber is promoted, and a fiber having high mechanical strength can be easily obtained.

The melt flow rate (MFR) of the spunbond nonwoven fabric is measured by the method described below.

The MFR of the polyolefin resin, which is the raw material of the spunbond nonwoven fabric of the present invention, is preferably 155 to 850 g/10 min, more preferably 155 to 600 g/10, for the same reason as the MFR of the spunbond nonwoven fabric. minutes, more preferably 155 to 400 g/10 minutes.

In the spunbonded nonwoven fabric of the present invention, two or more resins having different MFRs can be blended at any ratio to adjust the MFR of the polyolefin resin. In this case, the MFR of the resin blended with the polyolefin resin is preferably 10 to 1000 g/10 minutes, more preferably 20 to 800 g/10 minutes, still more preferably 30 to 600 g/10 minutes. By doing so, it is possible to prevent partial occurrence of uneven viscosity in the blended polyolefin-based resin, resulting in non-uniform fineness and deterioration in spinnability.

In addition, when spinning the fibers described later, in order to prevent the occurrence of partial viscosity unevenness, uniform the fineness of the fibers, and further reduce the fiber diameter as described later, the resin used is decomposed. It is also conceivable to adjust the MFR by However, it is preferred not to add free-radical agents such as, for example, peroxides, in particular dialkyl peroxides. When this method is used, uneven viscosity occurs partially and the fineness becomes non-uniform, making it difficult to sufficiently reduce the fiber diameter. There is also

In the spunbond nonwoven fabric of the present invention, the polyolefin resin preferably contains a fatty acid amide compound having 23 to 50 carbon atoms. By including a fatty acid amide compound having 23 to 50 carbon atoms, the orientation of the fibers and the flexibility of the nonwoven fabric are likely to be improved.

By setting the number of carbon atoms in the fatty acid amide compound to 23 or more, preferably 30 or more, excessive exposure of the fatty acid amide compound to the fiber surface is suppressed, excellent spinnability and processing stability are obtained, and high production is achieved. can retain their sexuality. On the other hand, when the number of carbon atoms in the fatty acid amide compound is 50 or less, preferably 42 or less, the fatty acid amide compound tends to move to the fiber surface, the fiber orientation tends to be uniform, and the flexibility of the spunbond nonwoven fabric is improved. can be improved.

Fatty acid amide compounds having 23 to 50 carbon atoms include saturated fatty acid monoamide compounds, saturated fatty acid diamide compounds, unsaturated fatty acid monoamide compounds, and unsaturated fatty acid diamide compounds.

Specifically, fatty acid amide compounds having 23 to 50 carbon atoms include tetradocosanoic acid amide, hexadocosanoic acid amide, octadocosanoic acid amide, nervonic acid amide, tetracosaentapenoic acid amide, nisic acid amide, ethylenebislauric acid amide, methylene Bislauric acid amide, ethylene bis stearic acid amide, ethylene bis hydroxy stearic acid amide, ethylene bis behenic acid amide, hexamethylene bis stearic acid amide, hexamethylene bis behenic acid amide, hexamethylene hydroxy stearic acid amide, distearyl adipic acid amide .

Among these fatty acid amide compounds, ethylenebisstearic acid amide, which is a saturated fatty acid diamide compound, is particularly preferably used. Ethylene bis-stearic acid amide is suitable for melt spinning due to its excellent thermal stability. Therefore, fibers made of a polyolefin-based resin containing ethylenebisstearic acid amide make it easier to obtain a spunbonded nonwoven fabric having excellent slipperiness and flexibility while maintaining high productivity.

In the spunbond nonwoven fabric of the present invention, the content of the fatty acid amide compound in the polyolefin resin is preferably 0.01 to 5.0% by mass. The content of the fatty acid amide compound is preferably 0.01 to 5.0% by mass, more preferably 0.1 to 3.0% by mass, still more preferably 0.1 to 1.5% by mass. , while maintaining the spinnability, it is possible to impart moderate slipperiness and higher flexibility.

The content here means the mass percentage of the fatty acid amide compound contained in the entire polyolefin resin constituting the spunbond nonwoven fabric of the present invention. For example, even when the fatty acid amide compound is contained only in the sheath component constituting the core-sheath type composite fiber, the content ratio with respect to the total amount of the core-sheath component is calculated.

As a method for measuring the content of the fatty acid amide compound in the polyolefin resin, for example, the additive is solvent-extracted from the fibers of the polyolefin resin and quantitatively analyzed using liquid chromatography mass spectrometry (LC/MS) or the like. method. At this time, the extraction solvent is appropriately selected according to the type of the fatty acid amide compound. For example, in the case of ethylenebisstearic acid amide, a method using a chloroform-methanol mixed solution can be mentioned as an example.

[Fiber made of polyolefin resin]
In the spunbonded nonwoven fabric of the present invention, the average single fiber diameter of the fibers constituting the spunbonded nonwoven fabric is preferably 6.5 to 11.9 μm. To obtain a softer and more uniform nonwoven fabric by adjusting the average single fiber diameter to 6.5 to 11.9 μm, preferably 7.5 to 11.9 μm, more preferably 8.4 to 11.9 μm. can be done.

In addition, in the present invention, the average single fiber diameter (μm) of the fibers constituting the spunbond nonwoven fabric is measured by the method described later.

The fibers constituting the spunbond nonwoven fabric of the present invention preferably have a single fiber diameter coefficient of variation (CV value) of 7% or less. Here, the CV value of single fiber diameter is calculated by the following formula.
・ CV value of single fiber diameter = (standard deviation of single fiber diameter) / (average single fiber diameter) × 100
The CV value of the single fiber diameter is preferably 7% or less, more preferably 6% or less, and still more preferably 5% or less to prevent the surface from feeling rough and have high uniformity. becomes easier to obtain. The CV value of the single fiber diameter is dominated by the back pressure of the spinneret, the yarn cooling conditions, and the uniformity of the drawing conditions, and can be controlled, for example, by appropriately adjusting these.

[Spunbond nonwoven]
It is important that the spunbond nonwoven fabric of the present invention has an average fiber orientation of 0 to 30 degrees. By setting the average fiber orientation degree to 0 to 30 degrees, preferably 5 to 30 degrees, and more preferably 8 to 30 degrees, the fiber orientation becomes uniform and the uniformity and smoothness of the surface of the nonwoven fabric are improved. Coatability is improved.

In addition, it is important that the spunbond nonwoven fabric of the present invention has a fiber ratio of 0 to 30 degree fiber orientation of 50 to 80%. The ratio of fibers having a fiber orientation of 0 to 30 degrees is preferably 60 to 80%. By setting the ratio of fibers with a fiber orientation degree of 0 to 30 degrees to 50 to 80%, preferably 60 to 80%, the fibers are uniformly arranged, the texture is uniform, and the spunbond nonwoven fabric has good printability. can be given.

The degree of fiber orientation in the present invention refers to an acute angle formed between the reference direction of the nonwoven fabric and one arbitrarily selected fiber. Further, the average degree of fiber orientation in the present invention refers to the average degree of fiber orientation measured for a predetermined number of fibers. The method of determining the reference direction, the degree of fiber orientation, and the method of calculating the average degree of fiber orientation will be described later.

The average degree of fiber orientation and the ratio of fibers with a degree of fiber orientation of 0 to 30 degrees can be controlled by, for example, adjusting the fiber opening method, spinning speed, collection conditions, etc., or adding a lubricant to the polyolefin resin. can.

The spunbonded nonwoven fabric of the present invention preferably has a surface roughness SMD ratio of 0.30 to 0.85 according to the KES method measured in the reference direction on at least one side and in the direction perpendicular thereto. The ratio of the surface roughness SMD by the KES method measured in the reference direction and the direction perpendicular to it is 0.30 or more, preferably 0.35 or more, more preferably 0.40 or more. can be prevented from declining excessively. On the other hand, by setting the ratio of the surface roughness SMD by the KES method measured in the reference direction and the direction perpendicular thereto to 0.85 or less, high glossiness can be developed. The ratio of the surface roughness SMD by the KES method measured in the reference direction and the direction perpendicular thereto can be controlled by appropriately adjusting the degree of fiber orientation, for example.

In the present invention, the ratio of the surface roughness SMD by the KES method in the reference direction and in the direction perpendicular thereto is measured by the method described later.

It is important that the tensile strength in the reference direction of the spunbond nonwoven fabric of the present invention is 3 to 6 times, more preferably 3 to 4 times, the tensile strength in the direction perpendicular thereto. If the tensile strength ratio is less than 3 times, there is a concern that the nonwoven fabric will be widened during the molding process. On the other hand, if the tensile strength ratio is more than 6 times, the tensile strength in the direction orthogonal to the reference direction is not suitable for practical use. The tensile strength ratio can be controlled, for example, by adjusting the basis weight, average single fiber diameter and embossing roll (compression rate, temperature and linear pressure), or by adjusting the MFR of the polyolefin resin used.

The spunbond nonwoven fabric of the present invention preferably has a bending resistance of 10 to 80 mm in the reference direction measured by the cantilever method. To obtain sufficient softness particularly when used as a nonwoven fabric for sanitary materials by setting the bending resistance to preferably 80 mm or less, more preferably 70 mm or less, further preferably 67 mm or less, and particularly preferably 64 mm or less. can be done. In addition, the lower limit of the bending resistance is preferably 10 mm or more, and more preferably 20 mm or more, because if the bending resistance is too low, the handleability of the nonwoven fabric may be poor. Bending resistance can be adjusted by basis weight, average single fiber diameter and embossing roll (compression rate, temperature and linear pressure).

Preferably, the spunbond nonwoven fabric of the present invention further satisfies the following formula (1).

GL/100≧95 (1)
Here, G is the maximum value of glossiness and L is the average luminance. In addition, as will be described later, all of them are values without units. Methods for adjusting GL/100 to the above range include, for example, increasing the amount of lubricant added, decreasing the average single fiber diameter, decreasing the average fiber orientation degree, and increasing the ratio of fibers with a fiber orientation degree of 0 to 30 degrees. A method such as increasing the height is exemplified.

The value obtained by dividing the product of G and L in the above formula (1) by 100 (hereinafter simply referred to as "gloss intensity of appearance") indicates that the spunbond nonwoven fabric is difficult to see through and has gloss. It is an index that is expressed quantitatively, and when the gloss intensity of the appearance is 95 or more, more preferably 100 or more, it becomes a silk-like nonwoven fabric with excellent luxury design, whiteness and gloss. On the other hand, in the present invention, there is no particular upper limit for the glossiness of the appearance, but if the glossiness is excessively strong, it will glare and lose the sense of quality, so it is more preferably 200 or less.

In the present invention, G (maximum value of glossiness) and L (average luminance) used to calculate the gloss intensity of the appearance are values measured and calculated by the following methods.
(1) G (maximum value of glossiness)
In the present invention, the G (maximum value of glossiness) of the spunbond nonwoven fabric is the maximum value among the values (unitless) measured by rotating the sample from 0 to 360 ° using a variable angle photometer. point to For the measurement, for example, a three-dimensional goniophotometer (GONIOPHOTOMETER GP-200) can be used, and a 12V50W type halogen lamp or the like can be used as the light source, and a photomultiplier tube or the like can be used as the light receiver.
(2) L (average luminance)
In the present invention, the L (average brightness) of the spunbond nonwoven fabric adopts a value measured by the following procedure. For image scanning, for example, a color multifunction machine "DocuCentre-VI C4471 PFS" (Fuji Xerox Co., Ltd.) can be used.
(1) A spunbond nonwoven fabric is pasted on a black mount (AC card black #350).
(2) Using a color multifunction machine, scan in full color at 200 dpi to create a color scanned image of the spunbond nonwoven fabric and save it in JPG format.
(3) Crop a 6×6 inch (1200×1200 pixels) image from the color scan image.
(4) Divide into grid units of 0.1×0.1 inch (20×20 pixels).
(5) For each grid, the average value of the luminance (without unit) defined in the YUV color space for each pixel is defined as the average luminance using the following formula.

(Brightness of each pixel)=0.29891×R+0.58661×G+0.11448×B
Here, R, G, and B represent the luminance (unitless) of red, green, and blue in the RGB color model, respectively.

The spunbond nonwoven fabric of the present invention preferably has a water pressure resistance per basis weight of 7 mmH ₂ O/(g/m ² ) to 20 mmH ₂ O/(g/m ² ). By setting the water pressure resistance per basis weight within the above range, the smoothness of the surface, which is important for printability, can be further enhanced. The water pressure resistance can be adjusted by, for example, the fiber opening method, basis weight, average single fiber diameter and embossing roll (compression rate, temperature and linear pressure).

The spunbond nonwoven fabric of the present invention preferably has a basis weight of 10 to 100 g/m ² . By setting the basis weight to preferably 10 g/m ² or more, more preferably 13 g/m ² or more, it becomes easier to obtain a spunbond nonwoven fabric having good mechanical strength. On the other hand, when the nonwoven fabric is used as a sanitary material, the basis weight is preferably 100 g/m ² or less, more preferably 50 g/m ² or less, and even more preferably 30 g/m ² or less. It becomes easy to obtain a spunbonded nonwoven fabric having moderate flexibility.

[Method for producing spunbond nonwoven fabric]
Next, preferred embodiments of the method for producing the spunbond nonwoven fabric of the present invention will be specifically described.

The spunbond nonwoven fabric of the present invention is a long-fiber nonwoven fabric produced by the spunbond method. Methods for producing nonwoven fabrics generally include a spunbond method, a flash spinning method, a wet method, a card method, an airlaid method, and the like. Among these methods, the spunbond method is excellent in productivity and mechanical strength, and can suppress fluffing and fiber dropout, which tend to occur in short fiber nonwoven fabrics. In addition, by laminating the collected spunbond nonwoven fiber web or thermocompression spunbond nonwoven fabric (both of which are both denoted as S) with SS, SSS and SSSS in multiple layers, productivity and texture uniformity are improved. do.

In the spunbond method, first, a molten thermoplastic resin is spun from a spinneret as filaments, which are drawn by suction with compressed air using an ejector, and then collected on a moving net to obtain a nonwoven fibrous web. . Further, the obtained nonwoven fibrous web is subjected to heat bonding treatment to obtain a spunbond nonwoven fabric.

Various shapes such as a round shape and a rectangular shape can be adopted as the shape of the spinneret and the ejector. In particular, the combination of a rectangular nozzle and a rectangular ejector is recommended because it uses a relatively small amount of compressed air and is excellent in terms of energy cost, and because the yarns are less likely to fuse or rub against each other, and the yarns can be easily opened. It is preferably used.

In the present invention, a polyolefin resin is melted in an extruder, weighed, supplied to a spinneret, and spun as long fibers. The spinning temperature at which the polyolefin resin is melted and spun is preferably 200 to 270°C, more preferably 210 to 260°C, still more preferably 220 to 250°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 spinneret back pressure is preferably 0.1 to 6.0 MPa. By setting the back pressure to preferably 0.1 to 6.0 MPa, more preferably 0.3 to 6.0 MPa, and even more preferably 0.5 to 6.0 MPa, the uniformity of ejection deteriorates and the fiber diameter increases. It is possible to prevent the occurrence of variations and the increase in the size of the mouthpiece for increasing the pressure resistance. The back pressure of the spinneret can be adjusted by adjusting the ejection hole diameter, ejection hole depth, spinning temperature, etc.
Above all, the contribution of the diameter of the discharge hole is large.

The spun yarn of long fibers is then cooled. Methods for cooling the spun yarn include, for example, a method of forcibly blowing cold air onto the yarn, a method of natural cooling at the ambient temperature around the yarn, and a method of adjusting the distance between the spinneret and the ejector. etc., or a method combining these methods can be adopted. Also, the cooling conditions can be appropriately adjusted in consideration of the discharge rate per single hole of the spinneret, the spinning temperature, the ambient temperature, and the like.

Next, the cooled and solidified yarn is pulled and stretched by compressed air jetted from an ejector.

The spinning speed is preferably 3500-6500 m/min, more preferably 4000-6500 m/min, and even more preferably 4500-6500 m/min. By setting the spinning speed to 3500 to 6500 m/min, a high productivity can be obtained, and the oriented crystallization of the fibers can be promoted to obtain high-strength long fibers.

Normally, as the spinning speed is increased, the spinnability deteriorates and it becomes difficult to stably produce filaments. It can be made stable and easy to spin.

Subsequently, the obtained long fibers are collected on a moving net to obtain a nonwoven fibrous web. Here, when drawing at a high spinning speed, the fibers coming out of the ejector are collected by the net in a state controlled by a high-speed air flow, which makes it easier to obtain a nonwoven fabric with less fiber entanglement and high uniformity. .

At this time, it is preferable that the spinning speed/line speed ratio is 18 or more. By setting the spinning speed/line speed ratio to preferably 18 or more, more preferably 20 or more, the fibers can be collected on the moving net in a vertical orientation. As a method of uniformly aligning, there is a method in which a flat plate with an angle is installed between the ejector and the net to guide the yarn, and by providing a plurality of grooves with different angles in the above flat plate, A method of separating falling yarns and yarns falling along grooves and dispersing them in the direction of flow of a nonwoven fiber web to open the fibers, and a method of arranging a plurality of flat plates with different angles in a comb-like shape at the ejector exit, For example, the fibers are dispersed in the direction of flow of the nonwoven fiber web by dropping the strips along each flat plate, and the fibers are opened.

Among them, a method in which a plurality of flat plates with different angles are arranged in a comb shape at the exit of the ejector and the yarn is dropped along each flat plate to spread the yarn efficiently produces a non-woven yarn with a fine fiber diameter. This is a preferable mode for aligning the orientation directions of the fibers because the fibers can be dispersed in the flow direction of the fiber web and the fibers can be opened in a controlled state without deceleration as much as possible.

In addition, it is also a preferred embodiment to temporarily bond the nonwoven fibrous web by contacting a heated flat roll from one side thereof on the net. By doing so, it is possible to prevent the surface layer of the non-woven fiber web from being turned up or blown away during transportation on the net and the formation to deteriorate, and the transportation from collecting the yarn to thermocompression bonding can be prevented. can improve sexuality.

Subsequently, the intended spunbond nonwoven fabric can be obtained by integrating the obtained nonwoven fibrous webs by heat bonding.

As a method for heat-bonding non-woven fiber webs, thermal embossing rolls with engraving (unevenness) on the surface of a pair of upper and lower rolls, a roll with a flat (smooth) surface on one roll and engraving on the surface of the other roll are used. A method of heat bonding with various rolls, such as a heat embossing roll consisting of a combination of a roll with unevenness and a heat calendering roll consisting of a pair of upper and lower flat (smooth) rolls, and ultrasonic vibration of a horn A method such as ultrasonic bonding, which is heat-sealed by means of Above all, it has excellent productivity, provides strength in the partial heat-bonded part, and easily maintains the unique texture and feel of non-woven fabric in the non-bonded part. or a combination of a roll with a flat (smooth) surface on one roll and a roll with an engraved (uneven portion) on the surface of the other roll. is.

As for the surface material of the hot embossing rolls, in order to obtain a sufficient thermocompression effect and to prevent the engraving (unevenness) of one embossing roll from being transferred to the surface of the other roll, a metal roll and a metal roll are used. Pairing is a preferred embodiment.

The adhesion area ratio by the hot embossing roll is preferably 5 to 30%. By setting the bonded area ratio to preferably 5% or more, more preferably 8% or more, and even more preferably 10% or more, it becomes easy to obtain sufficient strength as a spunbond nonwoven fabric. On the other hand, by setting the bonded area ratio to preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less, the spunbond nonwoven fabric for sanitary materials is particularly suitable for use in disposable diapers. Appropriate flexibility can be easily obtained. Even when ultrasonic bonding is used, the bonding area ratio is preferably within the same range.

The term "bonded area ratio" as used herein refers to the area ratio of the bonded portion to the entire spunbond nonwoven fabric. Specifically, when thermal bonding is performed using a pair of rolls having unevenness, the spunbond nonwoven fabric at the portion (bonded portion) where the convex portion of the upper roll and the convex portion of the lower roll overlap and contact the nonwoven fiber web It refers to the percentage of the whole. In the case of heat-bonding with a roll having unevenness and a flat roll, it refers to the area ratio of the portion (bonded portion) where the convex portion of the roll having unevenness abuts the nonwoven fiber web to the entire spunbond nonwoven fabric. In the case of ultrasonic bonding, it refers to the area ratio of the portion (bonded portion) thermally bonded by ultrasonic processing to the entire spunbond nonwoven fabric.

As the shape of the bonded portion by the heat embossing roll or ultrasonic bonding, circular, elliptical, square, rectangular, parallelogram, rhombus, regular hexagon, regular octagon, and the like can be used. Moreover, it is preferable that the bonded portions are uniformly present at regular intervals in the longitudinal direction (conveyance direction) and the width direction of the spunbond nonwoven fabric. By doing so, variations in the strength of the spunbond nonwoven fabric can be reduced.

In a preferred embodiment, the surface temperature of the thermal embossing roll during thermal adhesion is -50 to -15°C relative to the melting point of the polyolefin resin used. To obtain a spunbonded nonwoven fabric having a suitable thermal bonding strength for practical use by setting the surface temperature of a hot roll to preferably −50° C. or higher, more preferably −45° C. or higher with respect to the melting point of the polyolefin resin. can be done. Further, the surface temperature of the heat embossing roll is preferably −15° C. or less, more preferably −20° C. or less, relative to the melting point of the polyolefin resin, thereby suppressing excessive heat adhesion and producing a spunbond for sanitary materials. As a nonwoven fabric, it is possible to obtain moderate softness particularly suitable for use in disposable diapers.

The linear pressure of the thermal embossing roll during thermal adhesion is preferably 50 to 500 N/cm. The linear pressure of the roll is preferably 50 N/cm or more, more preferably 100 N/cm or more, and still more preferably 150 N/cm or more, so that the spunbond nonwoven fabric can be appropriately heat-bonded and has sufficient strength. easier to obtain. On the other hand, the linear pressure of the heat embossing roll is preferably 500 N/cm or less, more preferably 400 N/cm or less, and still more preferably 300 N/cm or less, so that the spunbond nonwoven fabric for sanitary materials, especially Appropriate flexibility suitable for use in disposable diapers can be easily obtained.

Also, for the purpose of adjusting the thickness of the spunbond nonwoven fabric, it is possible to subject the spunbond nonwoven fabric to thermal compression by a thermal calender roll consisting of a pair of upper and lower flat rolls before and/or after thermal bonding by the thermal embossing roll. A pair of upper and lower flat rolls is a metal roll or elastic roll that does not have unevenness on the surface of the roll. can be used. In addition, the elastic roll is a roll made of a material having elasticity as compared with a metal roll. Examples of elastic rolls include so-called paper rolls such as paper, cotton and aramid paper, and resin rolls made of urethane-based resins, epoxy-based resins, silicon-based resins, polyester-based resins, hard rubbers, and mixtures thereof. be done.

Next, the present invention will be specifically described based on examples. However, the present invention is not limited only to these examples.

[1] Melt flow rate (MFR) of polyolefin resin:
The melt flow rate of the polyolefin resin was measured according to ASTM D-1238 under conditions of a load of 2160 g and a temperature of 230.degree.

[2] Average single fiber diameter (μm):
After being pulled by an ejector and stretched, 10 small piece samples were randomly collected from the nonwoven web collected on the net, photographed with a microscope at 500 to 1000 times the surface, 10 pieces from each sample, The width of a total of 100 fibers was measured, and the average value was defined as the average single fiber diameter (μm).

[3] Spinning speed (m/min):
The mass per 10,000 m of length was calculated as the single fiber fineness from the above average single fiber diameter and the solid density of the resin used, and the single fiber fineness was rounded off to the second decimal place. Based on the single fiber fineness (dtex) and the discharge amount of the resin discharged from the spinneret single hole set under each condition (hereinafter abbreviated as the single hole discharge amount) (g/min), based on the following formula: The spinning speed was calculated.
- Spinning speed = (10000 x single hole discharge rate)/single fiber fineness.

[4] Metsuke:
JIS L1913: 2010 "General nonwoven fabric test method" 6.2 "Weight per unit area" Based on the test piece of 20 cm × 25 cm, 3 samples per 1 m width of the sample, the mass of each in the standard state (g ) were weighed, and the average value was expressed as the mass per 1 m ² (g/m ² ).

[5] Average fiber orientation and ratio of fibers with a fiber orientation of 0 to 30 degrees:
Values measured as follows were adopted. In the measurement, a scanning electron microscope "VHX-D500" manufactured by Keyence Corporation was used as the scanning electron microscope.
(1) Ten test pieces each having a width of 20 mm×20 mm were taken from the spunbond nonwoven fabric at equal intervals in the width direction (horizontal direction) of the spunbond nonwoven fabric.
(2) Using a scanning electron microscope, the inclination of 20 fibers with respect to the longitudinal direction of each sample was measured.
(3) The average value of the inclination angles of a total of 200 fibers was taken as the average degree of fiber orientation.
(4) The number of fibers with a fiber orientation degree of 0 to 30 degrees out of a total of 200 fibers was taken as the fiber ratio of a fiber orientation degree of 0 to 30 degrees.

In addition, when the vertical direction is unknown due to cut samples, etc., it was determined as follows.
(1) 10 nonwoven fabric samples oriented in one direction were collected.
(2) For each sample, the inclination of 20 fibers was measured with the given direction set to 0 degrees, and the average value was rounded off to the first decimal place.
(3) The inclination of the fiber in each direction of 30, 60, and 90 degrees with respect to 0 degree in (2) was measured in the same manner, and the average value was rounded off to the first decimal place.
(4) The direction in which the average of the tilt angles obtained for the above four directions is the smallest is taken as the reference direction.

[6] Surface roughness SMD of spunbond nonwoven fabric by KES method:
A value measured by the following method was adopted. For the measurement, an automated surface tester "KES-FB4-AUTO-A" manufactured by Kato Tech Co., Ltd. was used.
(1) Three test pieces each having a width of 200 mm×200 mm were taken from the spunbond nonwoven fabric at regular intervals in the width direction of the spunbond nonwoven fabric.
(2) The test piece was set on the sample stage.
(3) Scan the surface of the test piece with a surface roughness measuring contact (material: φ0.5 mm piano wire, contact length: 5 mm) with a load of 10 gf, and measure the average deviation of the uneven shape of the surface. did.
(4) The above measurements were carried out at three points each in the reference direction (determined by the method described above) and in the direction perpendicular thereto for all test pieces. For 9 points in the reference direction and 9 points in the direction perpendicular to the reference direction, the values obtained by averaging the average deviations and rounding off to the second decimal place are the surface roughness SMD (μm) in the reference direction and in the direction perpendicular to the reference direction. The value of surface roughness SMD (μm) in the reference direction/surface roughness SMD (μm) in the direction perpendicular to the reference direction was defined as the surface roughness SMD ratio.

[7] Tensile strength:
The tensile strength was measured by the following method according to JIS L1913:2010 "Testing methods for general nonwoven fabrics", 6.3 "Tensile strength and elongation", 6.3.1 "Standard time". Ten test pieces each having a length of 200 mm and a width of 25 mm were sampled in the vertical and horizontal directions of the nonwoven fabric. The test piece is subjected to a tensile test with a constant speed elongation type tensile tester at a grip interval of 100 mm and a tensile speed of 100 ± 10 mm / min, and the strength (N) at the maximum load until breakage is about 0.1N. This was taken as the tensile strength (N/2.5 cm).

[8] Bending resistance:
In accordance with JIS L1913: 2010 "General nonwoven fabric test method" (Section 6.7.3), collect 5 test pieces with a width of 25 mm × 150 mm and place the test piece on a horizontal table with a slope of 45 °. The short side of was aligned with the scale baseline. The test piece was manually slid in the direction of the slope, and when the center point of one end of the test piece touched the slope, the length of movement of the position of the other end was read on the scale. The front and back surfaces of five test pieces were measured, and the average value was calculated.

[9] Maximum glossiness (G):
Measurements were made according to the method described above. A three-dimensional goniophotometer (GONIOPHOTOMETER GP-200) was used for the measurement. A 12 V 50 W type halogen lamp was used as the light source, and a photomultiplier tube was used as the light receiver.

[10] Average luminance (L):
Measurements were made according to the method described above. For image scanning, a color multifunction machine "DocuCentre-VI C4471 PFS" (Fuji Xerox Co., Ltd.) was used.

[11] Water pressure resistance per basis weight:
According to JIS-L1092:2009 "Waterproof test method for textile products", "7.1.1A method (low water pressure method)", the water pressure resistance per basis weight of the nonwoven fabric was measured. Five test pieces with a width of 150 mm × 150 mm are collected at equal intervals in the width direction of the nonwoven fabric, and the test piece is clamped (the test piece is The part that hits the water has a size of 100 cm ² ), and the water level device filled with water is raised at a speed of 600 mm / min ± 30 mm / min, and water is poured from three places on the back side of the test piece. The water level at exit was measured in mm. This measurement was performed on five test pieces, and the average value was obtained as the water pressure resistance per basis weight.

[12] Printability Oil-based stamp ink was applied to the entire surface of a 10 cm x 10 cm rubber plate, and the ink-coated surface of the rubber plate was pressed against a spunbond nonwoven fabric and held for 10 seconds. The rubber plate was removed, and the printability was determined with the naked eye. The printability was judged as A when there was no printing unevenness or fading, and B when there was printing unevenness or fading.

(Example 1)
A polypropylene resin having an MFR of 200 g/10 min, to which 5.0% by mass of ethylenebisstearic acid amide was added as a fatty acid amide compound, was melted by an extruder for a sheath component. On the other hand, a polypropylene resin having an MFR of 200 g/10 min, to which no ethylenebisstearic acid amide was added, was melted in an extruder for the sheath component. These were weighed so that the mass ratio of the core component and the sheath component was 50:50, the amount of ethylene bis stearic acid amide in the whole fiber was 2.5%, the spinning temperature was 235 ° C., and the hole diameter φ was 0. A yarn spun from a 40 mm rectangular core-sheath spinneret at a single hole discharge rate of 0.30 g/min was cooled and solidified, and then pulled by a rectangular ejector with compressed air at an ejector pressure of 0.55 MPa. Stretched. Subsequently, this was collected on a moving net to obtain a nonwoven fibrous web made of polypropylene long fibers. The properties of the obtained polypropylene long fibers were that the fineness was 0.71 dtex, and the spinning speed converted from this was 4225 m/min. The spinnability was good, with no yarn breakage in 1 hour of spinning.

Subsequently, the obtained non-woven fiber web was subjected to a pair of upper and lower heat rollers, using an embossing roll made of metal engraved with a polka dot pattern and having a bonding area ratio of 11% as the upper roll, and a metal flat roll as the lower roll. Using an embossing roll, thermal bonding was performed at a linear pressure of 300 N/cm and a thermal bonding temperature of 145° C. to obtain a spunbond nonwoven fabric having a basis weight of 25 g/m ² . The obtained spunbond nonwoven fabric was evaluated. Table 1 shows the results.

(Example 2)
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that the basis weight was 15 g/m ² and the line speed was 160 m/min. The obtained spunbond nonwoven fabric was evaluated. Table 1 shows the results.

(Example 3)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 1, except that the amount of ethylenebisstearic acid amide as a sheath component added was 3.0% by mass. The characteristics of the obtained polypropylene long fibers were that the fineness was 0.73 detx, and the spinning speed converted from this was 4109 m/min. The spinnability was good, with no yarn breakage in 1 hour of spinning. The obtained spunbond nonwoven fabric was evaluated. Table 1 shows the results.

(Example 4)
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that ethylenebisstearic acid amide was not added to the sheath component. The characteristics of the obtained polypropylene long fibers were that the fineness was 0.74 dtex, and the spinning speed converted from this was 4054 m/min. The spinnability was good, with no yarn breakage in 1 hour of spinning. The obtained spunbond nonwoven fabric was evaluated. Table 1 shows the results.

(Example 5)
The addition amount of ethylene bis stearic acid amide as a sheath component was set to 0.5% by mass, the single hole discharge amount was set to 0.40 g/min, the basis weight was set to 15 g/m ² , and the line speed was set to 200 m/min. A spunbond nonwoven fabric was obtained in the same manner as in Example 1. The properties of the obtained polypropylene long fibers were that the fineness was 0.85 dtex, and the spinning speed converted from this was 4705 m/min. The spinnability was good, with no yarn breakage in 1 hour of spinning. The obtained spunbond nonwoven fabric was evaluated. Table 1 shows the results.

(Comparative example 1)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 4, except that the discharge rate per hole was 0.40 g/min, the basis weight was 10 g/m ² , and the line speed was 300 m/min. The characteristics of the obtained polypropylene long fibers were that the fineness was 0.91 dtex, and the spinning speed converted from this was 3823 m/min. The spinnability was good, with no yarn breakage in 1 hour of spinning. The obtained spunbond nonwoven fabric was evaluated. Table 1 shows the results.

(Comparative example 2)
A spunbonded nonwoven fabric was obtained in the same manner as in Example 5, except that a polypropylene resin having an MFR of 40 g/10 min was used for both the core component and the sheath component, and the pressure of the ejector was set to 0.30 MPa. The characteristics of the obtained polypropylene long fibers were that the fineness was 1.30 dtex and the spinning speed converted from this was 3076 m/min. The spinnability was good, with no yarn breakage in 1 hour of spinning. The obtained spunbond nonwoven fabric was evaluated. Table 1 shows the results.

Examples 1 to 5 were excellent in surface smoothness and had good printability. In addition, the average single fiber diameter of the fiber is 9.97 to 10.9 μm, and the ratio of the surface roughness measured by the KES method in the reference direction and the direction perpendicular to it is 0.53 to 0.66. , the softness and luster of the non-woven fabric were excellent. On the other hand, as shown in Comparative Examples 1 and 2, when the numerical value of the average fiber orientation degree is relatively high, the average single fiber diameter exceeds 11.9 μm, and the surface roughness ratio is greater than 0.85, the nonwoven fabric surface As a result, the unevenness was increased, resulting in poor printability and glossiness.

Claims (8)

A spunbond nonwoven fabric made of a polyolefin resin, having an average fiber orientation degree of 0 to 30 degrees, a fiber ratio of 0 to 30 degrees fiber orientation of 50 to 80%, and a tensile strength in the reference direction. A spunbond nonwoven that is 3 to 6 times the tensile strength in the orthogonal directions. The spunbond nonwoven fabric according to claim 1, wherein the average single fiber diameter of fibers constituting the spunbond nonwoven fabric is 6.5 to 11.9 µm. 3. The spunbond nonwoven fabric according to claim 1, wherein the ratio of the surface roughness SMD measured by the KES method in the reference direction on at least one side and the direction perpendicular thereto is 0.30 to 0.85. The spunbond nonwoven fabric according to any one of claims 1 to 3, wherein the polyolefin resin contains a fatty acid amide compound having 23 to 50 carbon atoms. The spunbond nonwoven fabric according to claim 4, wherein the content of the fatty acid amide compound in the polyolefin resin is 0.01 to 5.0% by mass. 6. The spunbond nonwoven fabric of Claim 5, wherein said fatty acid amide comprises ethylene bis stearamide. The spunbond nonwoven fabric according to any one of claims 1 to 6, which has a bending resistance in the reference direction of 10 to 80 mm as measured by the cantilever method. The spunbond nonwoven fabric according to any one of claims 1 to 7, further satisfying the following formula (1).
GL/100≧95 (1)
Here, G is the maximum value of glossiness and L is the average luminance.