JP2023131245A - Spun-bonded non-woven fabric - Google Patents

Abstract

To provide an environmentally friendly spun-bonded non-woven fabric having a sufficient strength for practical use, a good texture, excellent flexibility and touch, and excellent productivity and thermal adhesiveness.SOLUTION: A spun-bonded non-woven fabric comprising a core-sheath type composite fiber with a core component mainly composed of polylactic acid-based resin and a sheath component mainly composed of polyolefin-based resin has an apparent specific surface area of 250 cm2/cm3 or more and 3000 cm2/cm3 or less.SELECTED DRAWING: None

Description

The present invention relates to an environmentally friendly spunbond nonwoven fabric that has sufficient strength for practical use, has good texture, is excellent in flexibility and touch, and has excellent productivity and thermal adhesive properties. It is.

In recent years, efforts toward a sustainable society have been accelerating, with the adoption of SDGs (Sustainable Development Goals) at the United Nations Summit, and nonwoven fabrics used in disposable sanitary products such as disposable diapers and sanitary napkins are becoming more and more popular. Demand for materials that have a low impact on the natural environment is also increasing.

In general, nonwoven fabrics used in sanitary products are required to have good texture, flexibility, and high productivity. Nonwoven fabrics made of biodegradable long fibers containing specific amounts of , aliphatic bisamide, and/or alkyl-substituted aliphatic monoamide have been proposed.

Japanese Patent Application Publication No. 2006-291389

Indeed, according to the nonwoven fabric proposed in Patent Document 1, it is possible to obtain a nonwoven fabric that is more flexible than the nonwoven fabric made of biodegradable long fibers that was proposed before this nonwoven fabric was proposed. can. However, compared to spunbond nonwoven fabrics made of polypropylene resin that are commonly used for sanitary products such as disposable diapers and sanitary napkins, the nonwoven fabric proposed in Patent Document 1 does not have sufficient feel and flexibility. It's not satisfying. In addition, polylactic acid resin, which is commonly used as a biodegradable resin, has a higher melting temperature than polypropylene resin, and has poor thermal adhesion with other materials when molding sanitary products at high speed. It tends to be sufficient.

Therefore, the present invention has been made in view of the above circumstances, and its objects are to have sufficient strength for practical use, good texture, excellent flexibility and feel, and Our objective is to provide an environmentally friendly spunbond nonwoven fabric with excellent productivity and thermal adhesion.

As a result of extensive studies to achieve the above object, the present inventors have developed a spunbond nonwoven fabric whose main component is a polylactic acid resin, using a thermoplastic resin whose main component is a polyolefin resin as the sheath component. It was discovered that creating a core-sheath type composite fiber and controlling the apparent specific surface area significantly affects the feel of the fabric, and it is possible to significantly improve the flexibility and feel of environmentally friendly spunbond nonwoven fabrics. I gained knowledge. Furthermore, it has been found that this spunbond nonwoven fabric has excellent productivity and thermal adhesion.

The present invention has been completed based on these findings, and according to the present invention, the following inventions are provided.

The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric consisting of a core-sheath type composite fiber whose core component is a polylactic acid resin as a main component and whose sheath component is a polyolefin resin as a main component, and has an apparent specific surface area of It is 250 cm ² /cm ³ or more and 3000 cm ² /cm ³ or less.

According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the polyolefin resin is a polyethylene resin.

According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the polyethylene resin is a copolymer of ethylene and an α-olefin having 3 to 5 carbon atoms.

According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the α-olefin is 1-butene.

According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the content of the α-olefin is 0.1 to 10 mol% based on the polymerization component of the polyethylene resin.

According to a preferred embodiment of the spunbond nonwoven fabric of the present invention, the average single fiber diameter of the core-sheath type composite fiber is 7.6 μm or more and 15.2 μm or less.

Further, the sanitary product of the present invention is made using the spunbond nonwoven fabric described above.

According to the present invention, an environmentally friendly spunbond nonwoven fabric is provided which has sufficient strength for practical use, is excellent in flexibility and touch, and is also excellent in productivity and thermal adhesiveness. Due to these characteristics, the spunbond nonwoven fabric of the present invention can be particularly suitably used as a sanitary material.

The spunbond nonwoven fabric of the present invention is a spunbond nonwoven fabric consisting of a core-sheath type composite fiber whose core component is a polylactic acid resin as a main component and whose sheath component is a polyolefin resin as a main component, and has an apparent specific surface area of It is 250 cm ² /cm ³ or more and 3000 cm ² /cm ³ or less.

By doing so, it is possible to obtain an environmentally friendly spunbond nonwoven fabric that has sufficient strength for practical use, is excellent in flexibility and feel, and is also excellent in productivity and thermal adhesiveness.

The constituent elements of the present invention will be described in detail below, but the present invention is not limited to the scope described below unless it exceeds the gist thereof.

[Polylactic acid resin]
The spunbond nonwoven fabric of the present invention consists of a core-sheath type composite fiber whose core component is a polylactic acid resin as a main component. By doing so, an environmentally friendly spunbond nonwoven fabric having sufficient strength for practical use and excellent productivity can be obtained.

Examples of polylactic acid resins include poly(D-lactic acid), poly(L-lactic acid), copolymers of D-lactic acid and L-lactic acid, copolymers of D-lactic acid and hydroxycarboxylic acid, and L-lactic acid. and hydroxycarboxylic acid, a copolymer of D-lactic acid, L-lactic acid, and hydroxycarboxylic acid, or a blend of two or more of the above polymers. Among them, poly(L-lactic acid) or 60% or more of the constituent components is used as the core component of the core-sheath type composite fiber constituting the spunbond nonwoven fabric of the present invention because it has a melting point in a preferable range and has excellent spinnability. A copolymer of D-lactic acid and L-lactic acid in which L-lactic acid is L-lactic acid is preferably used.

When using a copolymer of lactic acid and hydroxycarboxylic acid, examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid, and hydroxyoctanoic acid. It will be done.

Polylactic acid resins have high biodegradability and high hydrolyzability, so they have the advantage of being easily decomposed in the natural environment. The weight average molecular weight of the polylactic acid resin is preferably 100,000 to 300,000, more preferably 100,000 to 200,000. By setting the weight average molecular weight to 100,000 or more, a decrease in single yarn strength can be prevented. Further, by setting the weight average molecular weight to 300,000 or less, spinnability can be improved and yarn breakage can be made less likely to occur even when the yarn spun from the die is pulled at high speed. As a result, even a small fiber diameter can be stably spun, and a spunbond nonwoven fabric with excellent texture, uniform texture, and strength can be obtained.

The polylactic acid resin used in the present invention includes commonly used antioxidants, weather stabilizers, light stabilizers, heat stabilizers, antistatic agents, charging aids, and spinning agents, as long as they do not impair the effects of the present invention. Additives such as a fogging agent, an antiblocking agent, a lubricant including a polyethylene wax, a crystal nucleating agent, and a pigment, or other polymers may be added as necessary.

The melting point of the polylactic acid resin used in the present invention is preferably 140°C to 200°C. By setting the melting point of the polylactic acid resin to preferably 140°C or higher, more preferably 150°C or higher, even more preferably 160°C or higher, it becomes easier to obtain heat resistance that can withstand practical use. In addition, by setting the melting point of the polylactic acid resin to preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower, the yarn discharged from the nozzle can be easily cooled, and the excessive Spunbond nonwoven fabrics with uniform texture, excellent flexibility and touch can be obtained by suppressing fusion and adhesion. Here, the melting point of the polylactic acid resin refers to the maximum melting peak temperature obtained by measuring the polylactic acid resin by differential scanning calorimetry (DSC).

The melt flow rate (hereinafter sometimes abbreviated as MFR) of the polylactic acid resin used in the present invention is preferably 1 g/10 minutes to 100 g/10 minutes. By setting the MFR of the polylactic acid resin to preferably 1 g/10 minutes or more, more preferably 10 g/10 minutes or more, and still more preferably 20 g/10 minutes or more, stable spinning even with a small fiber diameter is possible. A spunbond nonwoven fabric with excellent texture, uniform texture, and strength can be obtained. On the other hand, by setting the MFR of the polylactic acid resin to preferably 100 g/10 minutes or less, more preferably 60 g/10 minutes or less, and even more preferably 40 g/10 minutes or less, the decrease in single yarn strength can be suppressed. I can do it.

For the MFR of this polyolefin resin, a value measured according to ASTM D1238 (Method A) is adopted. According to this standard, polylactic acid is specified to be measured at a load of 2.16 kg and a temperature of 230°C, and the polylactic acid resin according to the present invention is also measured at the same load and temperature. .

The polylactic acid resin used in the present invention includes commonly used antioxidants, weather stabilizers, light stabilizers, heat stabilizers, antistatic agents, charging aids, and spinning agents, as long as they do not impair the effects of the present invention. Additives such as a fogging agent, an antiblocking agent, a lubricant including a polyethylene wax, a crystal nucleating agent, and a pigment, or other polymers may be added as necessary.

[Polyolefin resin]
The spunbond nonwoven fabric of the present invention consists of a core-sheath type composite fiber whose sheath component is mainly composed of a polyolefin resin. By doing so, it is possible to obtain a spunbond nonwoven fabric that has sufficient strength for practical use, is excellent in flexibility and touch, and is also excellent in thermal adhesiveness.

Examples of the polyolefin resin used in the present invention include polyethylene resin, polypropylene resin, polybutene resin, and polymethylpentene resin. Among these, polyethylene resin or polypropylene resin is preferable, and polyethylene resin is more preferable. By using a polypropylene resin, a spunbond nonwoven fabric with excellent strength, flexibility, and touch can be obtained. Furthermore, by using a polyethylene resin, a spunbond nonwoven fabric with even better flexibility and feel can be obtained.

The polyethylene resin refers to a resin having an ethylene unit as a repeating unit, and includes an ethylene homopolymer or a copolymer of ethylene and various α-olefins. Among these, copolymers of ethylene and various α-olefins are preferred because they can improve flexibility and provide spunbond nonwoven fabrics with excellent texture.

As the copolymer of ethylene and various α-olefins, copolymers of ethylene and α-olefin having 3 to 5 carbon atoms are preferred. Examples of the α-olefin having 3 to 5 carbon atoms include propylene, 1-butene, and 1-pentene, with 1-butene being more preferred. By doing so, it is possible to suppress the entanglement of molecular chains during melting, suppress thread breakage, and prevent the fiber from becoming easily wrapped around a roll during thermal bonding due to an increase in the amorphous component. In addition, it is possible to prevent the side chains from changing the crystal structure of the polyethylene resin and impairing the smooth feel of the fiber surface.

The content of α-olefin is preferably 0.1 to 10 mol% based on the polymerization component of the polyethylene resin. By setting the α-olefin content to preferably 10 mol% or less, more preferably 7 mol% or less, and still more preferably 5 mol% or less, it is possible to prevent a decrease in spinning stability and to easily wrap around a roll during thermal bonding. This can be prevented. Furthermore, even small fiber diameters can be stably spun, resulting in a spunbond nonwoven fabric with excellent texture, uniform texture, and excellent strength. In addition, it is possible to prevent the dryness of the fiber surface from being impaired. On the other hand, by setting the content of α-olefin to preferably 0.1 mol% or more, more preferably 0.5 mol% or less, and still more preferably 1 mol% or less, the flexibility of the span can be improved and the texture can be improved. It can be a bonded nonwoven fabric.

The α-olefin species and the α-olefin content in the polymerization component of the polyethylene resin can be calculated from, for example, the peak position detected by a nuclear magnetic resonance apparatus (NMR) and the peak area ratio.

Examples of the polyethylene resin used in the present invention include medium density polyethylene, high density polyethylene (hereinafter sometimes abbreviated as HDPE), linear low density polyethylene (hereinafter sometimes abbreviated as LLDPE), etc. can be mentioned. Among these, HDPE or LLDPE is preferably used because of its excellent spinnability.

The melting point of the polyethylene resin used in the present invention is preferably 100°C to 150°C. By setting the melting point of the polyethylene resin to preferably 100°C or higher, more preferably 110°C or higher, still more preferably 120°C or higher, it becomes easier to obtain heat resistance that can withstand practical use. In addition, by setting the melting point to preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 135°C or lower, it becomes easier to cool the yarn discharged from the spinneret, and excessive fusion between fibers is suppressed. A spunbond nonwoven fabric with a uniform texture and excellent flexibility and feel can be obtained. Here, the melting point of the polyethylene resin refers to the maximum melting peak temperature obtained by measuring the polyethylene resin by differential scanning calorimetry (DSC).

The solid density of the polyethylene resin used in the present invention is preferably 0.935 g/cm ³ to 0.970 g/cm ³ . By setting the solid density of the polyethylene resin to preferably 0.935 g/cm ³ or more, more preferably 0.940 g/cm ³ or more, and even more preferably 0.945 g/cm ³ or more, excessive heat bonding can be avoided during thermal bonding. It is possible to prevent operational problems such as the material becoming easily softened and sticking to the hot roll. This enables sufficient thermal adhesion and provides a spunbond nonwoven fabric with excellent strength. Furthermore, by setting the solid density of the polyethylene resin to preferably 0.970 g/cm ³ or less, more preferably 0.965 g/cm ³ or less, and even more preferably 0.960 g/cm ³ or less, spinnability is improved. This allows for stable spinning even at fine fineness. As a result, even a small fiber diameter can be stably spun, and a spunbond nonwoven fabric with excellent texture, uniform texture, and strength can be obtained.

On the other hand, polypropylene resin refers to a resin having propylene units as repeating units, and includes propylene homopolymers, copolymers of propylene with ethylene, various α-olefins, and the like. Among these, a propylene homopolymer is preferred in order to prevent a decrease in spinning stability and strength.

When using a copolymer of propylene and various α-olefins, the copolymerization component is preferably ethylene or 1-butene, and more preferably ethylene, since it has excellent spinning stability. Further, in order to prevent a decrease in spinning stability and strength, the copolymerization ratio is preferably 15 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less.

The α-olefin species and the α-olefin content in the polymerization component of the polyethylene resin can be calculated from, for example, the peak position detected by a nuclear magnetic resonance apparatus (NMR) and the peak area ratio.

The melting point of the polypropylene resin used in the present invention is preferably 120°C to 180°C. By setting the melting point of the polypropylene resin to preferably 120°C or higher, more preferably 130°C or higher, still more preferably 140°C or higher, it becomes easier to obtain heat resistance that can withstand practical use. In addition, by setting the melting point to preferably 180°C or lower, more preferably 170°C or lower, and even more preferably 165°C or lower, it becomes easier to cool the yarn discharged from the spinneret, and excessive fusion between fibers is suppressed. A spunbond nonwoven fabric with a uniform texture and excellent flexibility and feel can be obtained. Here, the melting point of the polypropylene resin refers to the maximum melting peak temperature obtained by measuring the polypropylene resin by differential scanning calorimetry (DSC).

Further, the polyolefin resin according to the present invention may be a mixture of two or more types, and in addition to the main polyolefin resin (referring to the polyolefin that accounts for the largest mass % among polyolefin resins), polyolefin resin It is also possible to use resin compositions containing thermoplastic resins such as polyolefin resins such as , polypropylene and poly-4-methyl-1-pentene, thermoplastic elastomers, low melting point polyesters, and low melting point polyamides. However, in order to fully express the characteristics of the main polyolefin resin, the ratio of other thermoplastic resins to be mixed is preferably 20% by mass or less, more preferably 10% or less, and even more preferably 5% by mass or less. mass% or less.

The polyolefin resin used in the present invention includes commonly used antioxidants, weather-resistant stabilizers, light-resistant stabilizers, heat-resistant stabilizers, antistatic agents, charging aids, and fogging agents, as long as they do not impair the effects of the present invention. Additives such as anti-blocking agents, lubricants including polyethylene wax, crystal nucleating agents, and pigments, or other polymers may be added as necessary.

The melt flow rate (hereinafter sometimes abbreviated as MFR) of the polyolefin resin used in the present invention is preferably 1 g/10 minutes to 100 g/10 minutes. By setting the MFR of the polyolefin resin to preferably 1 g/10 minutes or more, more preferably 10 g/10 minutes or more, and still more preferably 20 g/10 minutes or more, even small fiber diameters can be stably spun. A spunbond nonwoven fabric with excellent feel, uniform texture, and excellent strength can be obtained. On the other hand, by setting the MFR of the polyolefin resin to preferably 100 g/10 minutes or less, more preferably 60 g/10 minutes or less, and even more preferably 40 g/10 minutes or less, decrease in single yarn strength is suppressed, It is possible to prevent operational problems such as excessive softening during thermal bonding and sticking to the hot roll. Furthermore, sufficient thermal adhesion becomes possible, and a spunbond nonwoven fabric with excellent strength can be obtained.

For the MFR of this polyolefin resin, a value measured according to ASTM D1238 (Method A) is adopted. According to this standard, it is specified that polyethylene is measured at a load of 2.16 kg and a temperature of 190°C, and polypropylene is measured at a load of 2.16 kg and a temperature of 230°C. The resin will also be measured under the same load and temperature.

Of course, the MFR of the polyolefin resin used in the present invention can also be adjusted by blending two or more types of resins with different MFRs in any ratio.

In a preferred embodiment, the polyolefin resin used in the present invention contains a fatty acid amide compound having 23 or more and 50 or less carbon atoms in order to improve the feel and flexibility.

By setting the carbon number of the fatty acid amide compound mixed in the polyolefin resin to preferably 23 or more, more preferably 30 or more, excessive exposure of the fatty acid amide compound to the fiber surface can be suppressed, improving spinnability and processing. It has excellent stability and can maintain high productivity. As a result, even a small fiber diameter can be stably spun, and a spunbond nonwoven fabric with excellent texture, uniform texture, and strength can be obtained. On the other hand, by setting the number of carbon atoms in the fatty acid amide compound to preferably 50 or less, more preferably 42 or less, the fatty acid amide compound can easily move to the fiber surface, thereby imparting slipperiness and flexibility to the spunbond nonwoven fabric. I can do it.

Examples of the fatty acid amide compound having 23 to 50 carbon atoms used in the present invention include saturated fatty acid monoamide compounds, saturated fatty acid diamide compounds, unsaturated fatty acid monoamide compounds, and unsaturated fatty acid diamide compounds. Among them, ethylene bisstearamide, which is a saturated fatty acid diamide compound, is preferably used because it can impart high slipperiness and flexibility and has excellent spinnability.

In the present invention, it is a preferred embodiment that the amount of the fatty acid amide compound added to the polyolefin resin is 0.01% by mass to 5% by mass. By setting the amount of the fatty acid amide compound to be preferably 0.01% to 5% by mass, more preferably 0.1% to 3% by mass, and even more preferably 0.1% to 1% by mass. , it is possible to impart appropriate slipperiness and flexibility while maintaining spinnability. The amount added here refers to the mass percent of the fatty acid amide compound added to the entire core-sheath composite fiber of the spunbond nonwoven fabric of the present invention. For example, even when the fatty acid amide compound is added only to the sheath component constituting the core-sheath type composite fiber, the addition ratio to the total amount of the core-sheath component is calculated.

As a method for measuring the amount of a fatty acid amide compound added to a fiber made of a polyolefin resin, for example, the additive is extracted from the fiber with a solvent and quantitatively analyzed using liquid chromatography mass spectrometry (LS/MS) or the like. There are several methods. At this time, the extraction solvent is appropriately selected depending on the type of fatty acid amide compound; for example, in the case of ethylene bisstearic acid amide, a method using a chloroform-methanol mixture can be cited.

As the polyolefin resin used in the present invention, a resin containing a petroleum-derived component or a resin containing a biomass-derived component can be used, but a resin containing a biomass-derived component is preferable. Further, the proportion of carbon derived from biomass preferably accounts for 20% or more, more preferably 50% or more, and even more preferably 90% or more of the total carbon constituting the polyolefin resin. By doing so, in combination with the core component polylactic acid resin made of biomass-derived components, a spunbond nonwoven fabric with a smaller environmental load can be obtained.

Furthermore, the polyolefin resin of the present invention includes not only polyolefin resins newly obtained by polymerizing biomass-derived components, but also recycled polyolefin resins containing biomass-derived polyolefin resins. It is something.

The proportion of carbon atoms derived from biomass is measured by the carbon-14 concentration measurement method using accelerator mass spectrometry (Method B) described in ASTM D6866. With this method, it can be determined whether the component in question is derived from biomass or petroleum from the amount of radioactive isotope of carbon atoms. When all carbon atoms are derived from biomass, the proportion of carbon atoms derived from biomass is 100%.

[Core-sheath type composite fiber]
The spunbond nonwoven fabric of the present invention is composed of a core-sheath type composite fiber whose core component is mainly composed of a polylactic acid resin and whose sheath component is mainly composed of a polyolefin resin.

By doing so, it is possible to obtain an environmentally friendly spunbond nonwoven fabric that has sufficient strength for practical use, is excellent in flexibility and feel, and is also excellent in productivity and thermal adhesiveness.

As the composite form of the core-sheath type composite fiber constituting the spunbond nonwoven fabric of the present invention, for example, composite forms such as a concentric core-sheath type, an eccentric core-sheath type, and an island-in-the-sea type can be used. Among these, a core-sheath type composite form is preferable, and a concentric core-sheath type composite form is more preferable, since it has excellent spinnability and fibers can be bonded uniformly to each other by thermal adhesion. .

The core-sheath type composite fibers constituting the spunbond nonwoven fabric of the present invention preferably have an average single fiber diameter of 7.6 to 15.2 μm. A spunbond nonwoven fabric that prevents deterioration in spinnability and has excellent production stability by setting the average single fiber diameter to preferably 7.6 μm or more, more preferably 9.6 μm or more, and even more preferably 10.8 μm or more. It can be done. On the other hand, by setting the average single fiber diameter to preferably 15.2 μm or less, more preferably 14.6 μm or less, and still more preferably 13.3 μm or less, the texture is excellent, the texture is uniform, and the It can be made into a spunbond nonwoven fabric having strength.

In addition, the average single fiber diameter (μm) of the core-sheath type composite fibers constituting the spunbond nonwoven fabric shall be a value calculated by the following procedure.
(1) Ten small samples (100 x 100 mm) are randomly taken from the spunbond nonwoven fabric.
(2) Photograph the surface at a magnification of 500 to 2000 times using a microscope (for example, "VW-9000" manufactured by Keyence Corporation) or a scanning electron microscope (SEM, such as "VHX-D500" manufactured by Keyence Corporation) , and measure the width (diameter) of 10 core-sheath type composite fibers in the unfused portion, 10 from each sample in total. If the cross-section of the core-sheath composite fiber is irregular, the cross-sectional area is measured, and the diameter of a perfect circle having the same cross-sectional area is determined. The non-fused portion is a portion where the fibers are not fused or deformed to each other.
(3) The diameter values of the 100 measured fibers are averaged and rounded to the second decimal place to obtain the average single fiber diameter (μm).

In the core-sheath type composite fiber constituting the spunbond nonwoven fabric of the present invention, the volume ratio of the core component is preferably 10% by volume to 90% by volume. By setting the volume ratio of the core component to preferably 10% by volume or more, more preferably 30% by volume or more, and even more preferably 50% by volume or more, the single yarn strength is improved and sufficient strength for practical use is imparted. At the same time, it is possible to suppress sticking to a heat roll or the like during thermal bonding. On the other hand, by setting the volume ratio of the core component to preferably 90% by volume or less, more preferably 80% by volume or less, and even more preferably 70% by volume or less, the sheath components can be firmly fused together during thermal bonding, making it practical. A spunbond nonwoven fabric having sufficient strength can be used.

The cross-sectional shape of the core-sheath composite fiber constituting the spunbond nonwoven fabric of the present invention may be a round cross-section, a flat cross-section, or a modified cross-section such as a Y-shape or a C-shape. Among these, a round cross section is preferable because it does not have the difficulty of bending due to a structure such as a flat cross section or an irregular cross section, and can be made into a spunbond nonwoven fabric that takes advantage of the flexibility of the polyolefin resin. Although a hollow cross-section can be used as the cross-sectional shape, a solid cross-section is preferred because it has excellent spinnability and can be stably spun even with a small fiber diameter.

[Spunbond nonwoven fabric]
The spunbond nonwoven fabric of the present invention has an apparent specific surface area of 250 cm ² /cm ³ or more and 3000 cm ² /cm ³ or less. Specifically, by setting the apparent specific surface area to 250 cm ² /cm ³ or more, preferably 270 cm ² /cm ³ or more, and more preferably 300 cm ² /cm ³ or more, it has sufficient strength for practical use. , it can be made into a spunbond nonwoven fabric with excellent flexibility and feel. In addition, it is possible to achieve excellent thermal adhesion and to suppress elongation and widening during processing. On the other hand, by setting the apparent specific surface area to 3000 cm ² /cm ³ or less, preferably 1500 cm ² /cm ³ or less, more preferably 1000 cm ² /cm ³ or less, the fibers are packed tightly and the flexibility of the spunbond nonwoven fabric is improved. It is possible to prevent deterioration of texture and texture.

In addition, in the present invention, the apparent specific surface area shall adopt the value measured as follows (1) Average single fiber diameter (μm) and solid density (g/cm) of the above-mentioned core-sheath type composite fiber ³ ), calculate the average single fiber fineness (dtex) using the following formula Average single fiber fineness (dtex) = π x ([average single fiber diameter (μm)]/2) ² x [solid density (g/cm) ³ )]/100
(2) Calculate ^{the specific surface area (cm 2 /g) from the average single fiber diameter (μm) and average single fiber fineness (dtex) of the core-sheath composite fiber using the following formula. Specific surface area (cm 2 /} g) = 100×π×[average single fiber diameter (μm)]/[average single fiber fineness (dtex)]
(3) From the specific surface area (cm ² /g) of the core-sheath type composite fiber and the apparent density (g/cm ³ ) of the spunbond nonwoven fabric described below, the apparent specific surface area (cm ² /cm ³ ) is calculated using the following formula. ) Apparent specific surface area (cm ² /cm ³ )=[specific surface area (cm ² /g)]×[apparent density (g/cm ³ )].

Note that the solid density (g/cm ³ ) of the core-sheath type composite fiber constituting the spunbond nonwoven fabric can be a value calculated by the following procedure.
(1) Five small pieces are randomly taken from the spunbond nonwoven fabric.
(2) Wash the small pieces by soaking them in ethanol and dry in the air.
(3) Determine the density of a small piece of spunbond nonwoven fabric by the float-sink method using a water-ethanol mixed liquid system.
(4) Perform similar measurements on five small pieces, average the measured density values (g/cm ³ ), and round to the fourth decimal place to obtain the solid density (g/cm 3 ) of the core-sheath type composite fiber. ³ ).

Further, the spunbond nonwoven fabric of the present invention preferably has a friction coefficient MIU of 0.01 to 0.20 according to the KES method. By having a friction coefficient MIU of preferably 0.20 or less, more preferably 0.18 or less, and even more preferably 0.16 or less, the slipperiness of the nonwoven fabric surface is improved and the entanglement of fibers during production is suppressed. It is possible to improve the uniformity of the formation and create a spunbond nonwoven fabric with excellent flexibility and feel. On the other hand, since the coefficient of friction MIU is preferably 0.01 or more, more preferably 0.05 or more, and still more preferably 0.10 or more, the yarns are able to be attached to each other when the spun yarns are collected on the collection conveyor. This can prevent slipping and deterioration of the uniformity of the ground.

In addition, in the present invention, the value measured as follows is adopted as the friction coefficient MIU by the KES method.
(1) Three test pieces with a width of 200 mm x 200 mm are taken from the spunbond nonwoven fabric at equal intervals in the width direction of the spunbond nonwoven fabric.
(2) Set the test piece on the sample stage.
(3) The surface of the test piece is scanned with a contact friction element (material: φ0.5 mm piano wire (20 wires in parallel), contact area: 1 cm ² ) to which a load of 50 gf is applied to measure the friction coefficient.
(4) Perform the above measurements in the longitudinal direction (longitudinal direction of the nonwoven fabric) and transverse direction (width direction of the nonwoven fabric) of all test pieces, and average the average deviation of these six points to the fourth decimal place. is rounded off to the nearest whole number to obtain the friction coefficient MIU.

The spunbond nonwoven fabric of the present invention preferably has a surface roughness SMD of 1 μm to 3 μm on at least one side by the KES method. If the surface roughness SMD by the KES method is preferably 1.0 μm or more, more preferably 1.3 μm or more, and even more preferably 1.5 μm or more, the spunbond nonwoven fabric may become excessively dense and its texture may deteriorate. This can prevent loss of flexibility. On the other hand, since the surface roughness SMD determined by the KES method is preferably 3.0 μm or less, more preferably 2.8 μm or less, and still more preferably 2.5 μm or less, the surface is smooth and has little roughness, and has an excellent texture. It can be a spunbond nonwoven fabric.

In addition, in the present invention, the surface roughness SMD by the KES method shall adopt a value measured as follows.
(1) Three test pieces with a width of 200 mm x 200 mm are taken from the spunbond nonwoven fabric at equal intervals in the width direction of the spunbond nonwoven fabric.
(2) Set the test piece 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 applied, and measure the average deviation of the uneven shape of the surface. do.
(4) Perform the above measurements in the longitudinal direction (longitudinal direction of the nonwoven fabric) and transverse direction (width direction of the nonwoven fabric) of all test pieces, and average the average deviation of these six points to the second decimal place. is rounded off to the nearest whole number to obtain the surface roughness SMD (μm).

The basis weight of the spunbond nonwoven fabric of the present invention is preferably 10 g/m ² 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, even more preferably 15 g/m ² or more, the spunbond nonwoven fabric can have sufficient strength for practical use. On the other hand, since 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, the span has flexibility suitable for use as a nonwoven fabric for sanitary materials. It can be a bonded nonwoven fabric.

In addition, in the present invention, the basis weight of the spunbond nonwoven fabric shall be the value measured by the following procedure in accordance with "6.2 Mass per unit area" of JIS L1913:2010 "General nonwoven fabric testing method". do.
(1) Take three test pieces of 20 cm x 25 cm per 1 m of sample width.
(2) Weigh the mass (g) of each in the standard state.
(3) The average value is expressed as mass per 1 m ² (g/m ² ).

The thickness of the spunbond nonwoven fabric of the present invention is preferably 0.05 mm to 1.5 mm. By having a thickness of preferably 0.05 to 1.5 mm, more preferably 0.08 to 1.0 mm, and even more preferably 0.10 to 0.8 mm, the sanitary material has flexibility and appropriate cushioning properties. The spunbond nonwoven fabric can be particularly suitable for use in disposable diapers.

In addition, in the present invention, the thickness (mm) of the spunbond nonwoven fabric is a value measured according to the following procedure in accordance with "5.1" of JIS L1906:2000 "General long fiber nonwoven fabric test method". shall be.
(1) Using a pressurizer with a diameter of 10 mm, the thickness is measured in units of 0.01 mm at 10 points per 1 m at equal intervals in the width direction of the nonwoven fabric under a load of 10 kPa.
(2) Round off the average value of the above 10 points to the third decimal place.

Further, the apparent density of the spunbond nonwoven fabric of the present invention is preferably 0.05 g/cm ³ to 0.70 g/cm ³ . By having an apparent density of preferably 0.70 g/cm ³ or less, more preferably 0.50 g/cm ³ or less, and even more preferably 0.30 g/cm ³ or less, the fibers can be packed tightly to form a spunbond nonwoven fabric. This can prevent loss of flexibility. On the other hand, the apparent density is preferably 0.05 g/cm ³ or more, more preferably 0.08 g/cm ³ or more, even more preferably 0.10 g/cm ³ or more, thereby suppressing the occurrence of fluffing and interlayer peeling. , it can be made into a spunbond nonwoven fabric with ease of handling.

In the present invention, the apparent density (g/cm ³ ) is calculated based on the following formula from the above-mentioned basis weight and thickness before rounding, and is rounded to the second decimal place. Apparent density (g/cm ³ )=[Weight (g/m ² )]/[Thickness (mm)]×10 ⁻³ .

The bending resistance of the spunbond nonwoven fabric of the present invention is preferably 60 mm or less. By having a bending resistance of preferably 60 mm or less, more preferably 50 mm or less, and even more preferably 40 mm or less, excellent flexibility is obtained that is particularly suitable for use as a spunbond nonwoven fabric for sanitary materials, especially in disposable diapers. I can do it. Furthermore, if the bending resistance is extremely low, the handling property will be poor, so the bending resistance is preferably 10 mm or more.

The tensile strength per basis weight of the spunbond nonwoven fabric of the present invention is preferably 1.0 (N/5 cm)/(g/m ² ) or more and 5.0 (N/5 cm)/(g/m ² ). . The tensile strength per area weight is preferably 1.0 (N/5cm)/(g/m ² ) or more, more preferably 1.2 (N/5cm)/(g/m 2 ) or more, and even more preferably 1.0 (N/5cm)/(g/m ² ) or more. 5 (N/5 cm)/(g/m ² ) or more, it is possible to obtain a spunbond nonwoven fabric that has sufficient strength for practical use and is flexible and feels good to the touch. On the other hand, the tensile strength per area weight is preferably 5.0 (N/5 cm)/(g/m ² ) or less, more preferably 4.0 (N/5 cm)/(g/m ² ) or less, and even more preferably By being 3.0 (N/5 cm)/(g/m ² ) or less, it is possible to prevent the flexibility of the spunbond nonwoven fabric from decreasing and the texture from being impaired. The tensile strength per fabric weight is determined by the volume ratio of the core component of the core-sheath composite fiber, the average single fiber diameter, the MFR of the spunbond nonwoven fabric, and/or the spinning speed and thermal bonding conditions (shape of the bonded part) described below. , crimping rate, temperature, linear pressure, etc.).

In addition, in the present invention, the tensile strength per unit weight of the spunbond nonwoven fabric is determined by the following procedure according to "6.3 Tensile strength and elongation (ISO method)" of JIS L1913: 2010 "General nonwoven fabric testing method". The measured value shall be adopted.
(1) Three test pieces of 50 mm x 300 mm are taken per meter of width of the nonwoven fabric, with the long side oriented in the longitudinal direction of the nonwoven fabric (longitudinal direction of the nonwoven fabric) and the horizontal direction (width direction of the nonwoven fabric).
(2) Grasp the test piece and set it in a tensile tester with an interval of 200 mm.
(3) Conduct a tensile test at a tensile speed of 100 mm/min and measure the maximum strength.
(4) Find the average value of the maximum strength measured for each test piece, calculate the tensile strength per area weight based on the following formula, and round to the second decimal place. Tensile strength per area weight ((N/5cm) )/(g/ ^m2 ))=[Average value of maximum strength (N/5cm)]/Weight (g/ ^m2 ).

The stress at 5% elongation per basis weight of the spunbond nonwoven fabric of the present invention is 0.1 (N/5 cm)/(g/m ² ) or more and 2.0 (N/5 cm)/(g/m ² ). is preferred. The stress at 5% elongation per area weight is preferably 0.1 (N/5 cm)/(g/m ² ) or more, more preferably 0.2 (N/5 cm)/(g/m ² ) or more, and even more preferably By having a value of 0.3 (N/5cm)/(g/m ² ) or more, it suppresses elongation due to tension during the production of spunbond nonwoven fabrics and processing for sanitary material applications, resulting in a stable and high yield. can be produced. In addition, the stress at 5% elongation per basis weight is preferably 2.0 (N/5 cm)/(g/m ² ) or less, more preferably 1.5 (N/5 cm)/(g/m ² ) or less, and Preferably, it is 1.0 (N/5 cm)/(g/m ² ) or less, so that a spunbond nonwoven fabric with excellent flexibility and touch can be obtained. The stress at 5% elongation per fabric weight can be determined by the volume ratio of the core component of the core-sheath type composite fiber, the average single fiber diameter, the MFR of the spunbond nonwoven fabric, and/or the spinning speed and thermal bonding conditions (described later). It can be controlled by appropriately adjusting the shape of the part, crimping rate, temperature, linear pressure, etc.).

In addition, in the present invention, the stress at 5% elongation per basis weight of spunbond nonwoven fabric is as follows in accordance with "6.3 Tensile strength and elongation rate (ISO method)" of JIS L1913: 2010 "General nonwoven fabric testing method" The value measured by the following procedure shall be adopted.
(1) Three test pieces of 50 mm x 200 mm are taken per meter of width of the nonwoven fabric, with the long side facing the longitudinal direction of the nonwoven fabric (longitudinal direction of the nonwoven fabric) and the horizontal direction (width direction of the nonwoven fabric).
(2) Grasp the test piece and set it in a tensile tester with an interval of 200 mm.
(3) A tensile test is carried out at a tensile speed of 100 mm/min, and the stress at 5% elongation (stress at 5% elongation) is measured.
(4) Find the average value of the stress at 5% elongation measured for each test piece, calculate the stress at 5% elongation in the longitudinal direction per fabric weight based on the following formula, and round to the second decimal place. Stress at 5% elongation in the vertical direction ((N/5cm)/(g/m ² )) = [Average value of stress at 5% elongation (N/5cm)]/Basic weight (g/m ² ).

[Method for manufacturing 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 a spunbond method. In addition to being excellent in productivity and mechanical strength, the spunbond method can suppress fuzzing and fiber shedding that tend to occur with short fiber nonwoven fabrics. In addition, by laminating multiple layers of the collected spunbond nonwoven fiber web or thermocompression bonded spunbond nonwoven fabric (both denoted as S) with SS, SSS, and SSSS, productivity and formation uniformity can be improved. This is a preferred embodiment because it improves.

In the spunbond method, first, a molten thermoplastic resin is spun into long fibers from a spinneret, and after this is drawn by suction with compressed air using an ejector, the fibers are collected on a moving net to obtain a nonwoven fiber web. . Furthermore, the obtained nonwoven fiber web is subjected to thermal bonding treatment to obtain a spunbond nonwoven fabric.

The shape of the spinneret and ejector is not particularly limited, but various shapes such as round or rectangular can be used. Among these, the combination of a rectangular nozzle and a rectangular ejector is preferred because it uses relatively little compressed air and is superior in energy costs, is less likely to cause fusion or abrasion between yarns, and is easy to open the yarns. Preferably used.

In the present invention, a polylactic acid resin and a polyolefin resin are each melted in separate extruders, weighed and fed to a single spinneret, and spun as a core-sheath composite fiber. The spinning temperature when spinning the core-sheath composite fiber is preferably 200°C to 250°C, more preferably 210°C to 240°C, even more preferably 220°C to 230°C. By controlling the spinning temperature within the above range, thermal deterioration of the polylactic acid resin or polyolefin resin can be suppressed, a stable molten state can be obtained, and excellent spinning stability can be obtained.

The spun filament yarn 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. methods, etc., or a combination of these methods can be adopted. Further, 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 ambient temperature, and the like.

Next, the cooled and solidified yarn is drawn and drawn by compressed air injected from an ejector.

The spinning speed is preferably 3000 m/min to 6000 m/min, more preferably 3500 m/min to 5500 m/min, and even more preferably 4000 m/min to 5000 m/min. By setting the spinning speed to 3,000 m/min to 6,000 m/min, high productivity can be achieved, and the oriented crystallization of the fibers can proceed, making it possible to obtain long fibers with high strength. As described above, the composite fiber containing polyethylene resin as a main component of the present invention has excellent spinning stability and can be stably produced even at high spinning speeds.

Subsequently, the obtained long fibers are collected on a moving net to obtain a nonwoven fibrous web.

In the present invention, it is also a preferred embodiment to temporarily bond the nonwoven fiber web by contacting the nonwoven fiber web with a hot flat roll from one side on the net. By doing this, it is possible to prevent the surface layer of the nonwoven fiber web from being turned up or blown away during conveyance on the net and deteriorating the formation, and also to prevent the surface layer of the nonwoven fiber web from being turned up or blown away while being conveyed on the net, and to prevent the formation from deteriorating. Transportability can be improved.

Subsequently, the obtained nonwoven fiber web is fused to form a fused portion to obtain the intended spunbond nonwoven fabric.

The method of fusing the nonwoven fiber web is not particularly limited, but for example, a pair of heat-embossed rolls each having an upper and lower roll surface engraved (irregularities), or a roll with one roll surface flat (smooth) and the other roll surface. A method of heat fusing using various rolls, such as a heat embossing roll, which is a combination of a roll with an engraved surface (irregularities), and a heat calendar roll, which is a combination of a pair of upper and lower flat (smooth) rolls. , a method of heat-sealing by ultrasonic vibration of a horn, and a method of passing hot air through a nonwoven fiber web to soften or melt the surface of the composite fibers and heat-seal the fiber intersection points.

Among these, a pair of heat-embossed rolls with engravings (uneven parts) on the surfaces of a pair of upper and lower rolls, or rolls with one roll surface that is flat (smooth) and one with engravings (uneven parts) on the surface of the other roll. It is preferable to use a heat embossing roll consisting of a combination of rolls. By doing so, it is possible to provide a fused portion that improves the strength of the spunbond nonwoven fabric and a non-fused portion that improves the texture and feel of the spunbond nonwoven fabric with good productivity.

The surface material of the hot embossing roll is a metal roll and a metal roll in order to obtain a sufficient thermocompression bonding effect and to prevent the engraving (unevenness) of one embossing roll from being transferred to the surface of the other roll. A preferred embodiment is to pair them.

The emboss bonding area ratio by such a hot embossing roll is preferably 5% to 30%. By setting the bonding area to preferably 5% or more, more preferably 8% or more, and still more preferably 10% or more, it is possible to obtain a strength that can be used practically as a spunbond nonwoven fabric. On the other hand, by setting the adhesion area to preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less, it can be used as a spunbond nonwoven fabric for sanitary materials, with moderate flexibility, especially suitable for use in disposable diapers. You can get sex. Even when ultrasonic bonding is used, the bonding area ratio is preferably within the same range.

The bonded area here refers to the ratio of the bonded portion to the entire spunbond nonwoven fabric. Specifically, in the case of thermal bonding using a pair of uneven rolls, the spunbond nonwoven fabric is bonded at the part (bonded part) where the convex part of the upper roll and the convex part of the lower roll overlap and contact the nonwoven fiber web. Refers to the percentage of the total. In addition, when heat bonding is performed using a roll having unevenness and a flat roll, it refers to the proportion of the part (adhesion part) where the convex part of the uneven roll comes into contact with the nonwoven fiber web to the entire spunbond nonwoven fabric. Furthermore, when ultrasonic bonding is used, it refers to the proportion of the part (bonded part) to be thermally welded by ultrasonic processing to the entire spunbond nonwoven fabric. If sufficient heat is applied to the bonded portion during thermal bonding and the entire conjugate fibers in the bonded portion are fused, the areas of the bonded portion and the fused portion can be considered to be equal.

The shape of the bonded part by hot embossing roll or ultrasonic bonding is not particularly limited, but for example, a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, a regular octagon, etc. can be used. Further, it is preferable that the bonded portions are uniformly present at regular intervals in the longitudinal direction (conveyance direction) and width direction of the spunbond nonwoven fabric. By doing so, variations in the strength of the spunbond nonwoven fabric can be reduced.

The surface temperature of the hot embossing roll during thermal bonding ranges from 30°C lower to 10°C higher than the melting point (hereinafter sometimes referred to as Tm (°C)) of the polyolefin resin used as the sheath component. That is, it is a preferred embodiment that the temperature range is from (Tm-30°C) to (Tm+10°C). The surface temperature of the heating roll is preferably -30°C (i.e. (Tm - 30°C), the same applies hereinafter) or higher than the melting point of the polyolefin resin, more preferably -20°C (Tm - 20°C) or higher, and Preferably, by setting the temperature to -10°C (Tm -10°C) or higher, it is possible to obtain a spunbond nonwoven fabric having a strength that can be firmly thermally bonded and used for practical use. In addition, the surface temperature of the hot embossing roll is preferably set to below +10°C (Tm+10°C), more preferably below +5°C (Tm+5°C), and even more preferably below +0°C (Tm+0°C) relative to the melting point of the polyolefin resin. By doing so, it is possible to suppress excessive thermal adhesion and obtain appropriate flexibility suitable for use as a spunbond nonwoven fabric for sanitary materials, particularly for disposable diapers and masks.

The linear pressure of the hot embossing roll during thermal bonding is preferably 50 N/cm to 500 N/cm. By setting the linear pressure of the roll to preferably 50 N/cm or more, more preferably 100 N/cm or more, and still more preferably 150 N/cm or more, a spunbond nonwoven fabric with a strength that can be firmly thermally bonded and used in practical use can be obtained. be able to. On the other hand, by setting the linear pressure of the hot embossing roll to preferably 500 N/cm or less, more preferably 400 N/cm or less, and still more preferably 300 N/cm or less, it can be used as a spunbond nonwoven fabric for sanitary materials, especially for disposable diapers. Provides appropriate flexibility suitable for use in

Further, in the present invention, in order to adjust the thickness of the spunbond nonwoven fabric, thermocompression bonding is performed using a thermal calendar roll consisting of a pair of upper and lower flat rolls before and/or after the thermal bonding using the above-mentioned hot embossing roll. I can do it. A pair of upper and lower flat rolls refers to metal rolls or elastic rolls with no unevenness on the surface of the rolls. Can be used.

Moreover, the elastic roll here refers to a roll made of a material that has more elasticity than a metal roll. Examples of elastic rolls include so-called paper rolls such as paper, cotton, and aramid paper, urethane resins, epoxy resins, silicone resins, polyester resins, hard rubber, and mixtures thereof. Examples include resin rolls.

[Hygiene materials]
The spunbond nonwoven fabric of the present invention has sufficient strength for practical use, good texture, excellent flexibility and feel, and is also excellent in productivity and thermal adhesion, so it can be used as a sanitary material, It can be widely used for medical materials, daily life materials, industrial materials, etc. In particular, it can be suitably used for sanitary materials such as disposable diapers, sanitary products and poultice materials, and medical materials such as protective clothing and surgical gowns.

Further, since the spunbond nonwoven fabric of the present invention has excellent thermal adhesiveness, it can be easily laminated with other spunbond nonwoven fabrics, meltblown nonwoven fabrics, films, and the like. In the side gathers of disposable diapers, which are one of the sanitary material applications, a laminate of spunbond nonwoven fabric and meltblown nonwoven fabric is generally used because water resistance is required. The spunbond nonwoven fabric of the present invention can also be laminated with a meltblown nonwoven fabric and suitably used for side gathers.

Next, the spunbond nonwoven fabric of the present invention will be specifically described based on Examples. However, the present invention is not limited only to these examples. In addition, in the measurement of each physical property, unless otherwise specified, the measurement was performed based on the method described above.

[Measuring method]
(1) Average single fiber diameter (μm) of core-sheath type composite fiber:
The average single fiber diameter of the core-sheath composite fiber was measured by the method described above using an electron microscope "VHX-D500" manufactured by Keyence Corporation.

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

(3) Friction coefficient MIU (no unit) of spunbond nonwoven fabric by KES method
The friction coefficient MIU of the spunbond nonwoven fabric by the KES method was measured using "KES-SE Friction Feel Tester" manufactured by Kato Tech Co., Ltd.

(4) Tensile strength per unit weight of spunbond nonwoven fabric ((N/5cm)/(g/m ² )):
The measuring device used was "RTG-1250" manufactured by A&D Co., Ltd., and the measurement was carried out according to the method described above.

(5) Longitudinal stiffness of spunbond nonwoven fabric (mm):
The bending resistance of spunbond nonwoven fabrics is determined by the method described in ``6.7.4 Gurley method'' of ``6.7 Bending resistance (JIS method and ISO method)'' of JIS L1913:2010 ``General nonwoven fabric test methods.'' Accordingly, the longitudinal direction (longitudinal direction) of the nonwoven fabric was measured. In addition, the bending resistance in the longitudinal direction (longitudinal direction) of each spunbond nonwoven fabric was greater than the bending resistance in the transverse direction (width direction). A bending resistance in the longitudinal direction of 60 mm or less was considered acceptable.

(6) Uniformity of formation of spunbond nonwoven fabric (points):
A sample with a size of 100 mm x 100 mm was taken, placed on a black mount (AC card black #350), and 20 panelists evaluated the uniformity of the texture of the spunbond nonwoven fabric using the following five criteria. Subsequently, the scores determined by each panelist were totaled to determine the uniformity of formation of the spunbond nonwoven fabric, and a score of 80 or more was considered to be a pass. The uniformity of the formation is preferably 85 points or higher, more preferably 90 points or higher.
・5 points: Very good (fibers are uniformly dispersed, and there is almost no shading (black and white).)
・4 points: Good (between 5 points and 3 points)
・3 points: Normal (There is little tangle of fibers (strands), but shading (black and white) can be seen.)
・2 points: Bad (between 3 points and 1 point)
・1 point: Very poor (many fibers are tangled (strands), and strong shading (black and white) is seen.)

(7) Texture of spunbond nonwoven fabric (points):
A sample with a size of 100 mm x 100 mm was taken, and 20 panelists touched the sample and each evaluated the feel of the spunbond nonwoven fabric using the following 5-level criteria. Subsequently, the scores determined by each panelist were totaled to determine the feel of the spunbond nonwoven fabric, and a score of 80 or more was considered to be a pass. The texture score is preferably 85 points or higher, more preferably 90 points or higher.
・5 points: Very good (Flexibility, smooth feel, and excellent comfort.)
・4 points: Good (between 5 points and 3 points)
・3 points: Average (Feels flexible and smooth.)
・2 points: Bad (between 3 points and 1 point)
- 1 point: Very poor (feels like it lacks at least one of flexibility and smoothness).

(8) Heat seal adhesiveness (grade):
Three test pieces with a size of 100 mm x 100 mm were taken, and each test piece was layered with a linear low-density polyethylene (LLDPE) film (thickness 0.02 mm) and placed in a hot plate heating type heat seal test device. Then, heat seal bonding was performed under the conditions of a hot plate temperature of 120° C., a heat seal contact pressure of 4.9 MPa (50 kgf/cm ² ), and a bonding time of 1 second. Next, the adhesion of the test pieces was graded in the following five grades, and the average value of the grades of the three test pieces was rounded to the second decimal place to obtain the heat seal adhesion (grade). Heat-seal adhesion of grade 3.5 or higher was considered a pass. Heat seal adhesiveness is preferably 4.0 grade or higher, more preferably 4.5 grade or higher.
・Grade 5: Very good (strongly adhered and difficult to peel off)
・Grade 4: Good (adhered, but can be partially peeled off)
・Grade 3: Normal (Although it is glued, it can be easily peeled off.)
・Grade 2: Poor (partially not adhered)
- Grade 1: Very poor (the entire surface is not adhered).

[Example 1]
(Core-sheath type composite fiber)
The core component is a polylactic acid resin with a melt flow rate (MFR) of 30 g/10 min, a melting point of 170°C, and a solid density of 1.240 g/cm ³ , an MFR of 20 g/10 min, a melting point of 130°C, and a solid density of 0. Plant-derived high-density polyethylene (CoHDPE) resin made of ethylene-1-butene copolymer with 950 g/cm ³ and a 1-butene content of 2.0 mol% in the polymerization component was used as a sheath component, and an extruder was used for each. The spinning temperature was 230°C, the single-hole discharge rate was 0.55 g/min, and the volume ratio of the core component was 40% by volume. A core-sheath composite fiber was spun. After the spun yarn was cooled and solidified, it was pulled and stretched by compressed air in an ejector and collected on a moving net to form a spunbond nonwoven fiber web. The characteristics of the core-sheath type composite fibers constituting the formed non-woven fiber web are that the average single fiber diameter is 11.9 μm and the solid density is 1.066 g/ ^cm3 , and the spinning speed converted from this is 4640 m/min. Met. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good.

(Spunbond nonwoven fabric)
Subsequently, the formed nonwoven fiber web was thermally bonded using a pair of upper and lower heat embossing rolls consisting of the following upper roll and lower roll under the conditions of linear pressure: 500 N/cm and thermal bonding temperature: 130 ° C. A spunbond nonwoven fabric with a basis weight of 20 g/m ² was obtained.
(Top roll): Embossed roll made of metal and engraved with a polka dot pattern, with an adhesion area ratio of 16% (referred to as "embossed" in Tables 1 and 2)
(Lower roll): Metal flat roll (written as "flat" in Tables 1 and 2)
The resulting spunbond nonwoven fabric had a uniform texture score of 85 points. The evaluation results are shown in Table 1.

[Example 2]
(Core-sheath type composite fiber) was made using the same method as in Example 1, except that the volume ratio of the core component was 70% by volume and the concentric core-sheath composite fiber was used, and the flow rate of the compressed air of the ejector was increased. A spunbond nonwoven fabric was obtained. The characteristics of the fibers constituting the formed spunbond nonwoven fiber web were that the average single fiber diameter was 10.5 μm, the solid density was 1.153 g/cm ³ , and the spinning speed calculated from these was 5510 m/min. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good. The resulting spunbond nonwoven fabric had a uniform texture score of 88 points. The evaluation results are shown in Table 1.

[Example 3]
(core-sheath type composite fiber), a spunbond nonwoven fabric was obtained in the same manner as in Example 2, except that the single hole discharge rate was 0.75 g/min and the flow rate of compressed air of the ejector was reduced. The characteristics of the fibers constituting the formed spunbond nonwoven fiber web were that the average single fiber diameter was 14.1 μm, the solid density was 1.153 g/cm ³ , and the spinning speed calculated from these was 4170 m/min. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good. The resulting spunbond nonwoven fabric had a texture uniformity of 80 points, which was slightly inferior to that of Example 1. The evaluation results are shown in Table 1.

[Example 4]
In (core-sheath type composite fiber), the single hole discharge rate was set to 0.30 g/min, and the flow rate of compressed air of the ejector was reduced, and in (spunbond nonwoven fabric), (upper roll) was changed to a metal flat roll. A spunbond nonwoven fabric was obtained by the same method as in Example 2 except that the method was changed to . The characteristics of the fibers constituting the formed spunbond nonwoven fiber web were that the average single fiber diameter was 8.8 μm, the solid density was 1.153 g/cm ³ , and the spinning speed calculated from these was 4280 m/min. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good. The resulting spunbond nonwoven fabric had an excellent texture uniformity of 95 points. The evaluation results are shown in Table 1.

[Example 5]
(core-sheath composite fiber), high-density polyethylene (HDPE) resin consisting only of ethylene polymer units with an MFR of 20 g/10 min, a melting point of 130°C, and a solid density of 0.955 g/cm ³ was used as the sheath component. A spunbond nonwoven fabric was obtained in the same manner as in Example 2 except for this. The characteristics of the fibers constituting the formed spunbond nonwoven fiber web were that the average single fiber diameter was 10.6 μm, the solid density was 1.155 g/cm ³ , and the spinning speed calculated from these was 5500 m/min. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good. The resulting spunbond nonwoven fabric had a uniform texture score of 87 points. The evaluation results are shown in Table 1.

[Example 6]
(core-sheath type composite fiber), polypropylene resin (PP) consisting only of propylene polymerized units with an MFR of 25 g/10 min, a melting point of 148°C, and a solid density of 0.910 g/ ^cm3 was used as a sheath component. A spunbond nonwoven fabric was obtained in the same manner as in Example 2, except that the hole discharge rate was 0.30 g/min and the thermal bonding temperature was changed to 135° C. (spunbond nonwoven fabric). The characteristics of the fibers constituting the formed spunbond nonwoven fiber web were that the average single fiber diameter was 8.9 μm, the solid density was 1.141 g/cm ³ , and the spinning speed calculated from these was 4230 m/min. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good. The resulting spunbond nonwoven fabric had an extremely excellent texture uniformity of 97 points. The evaluation results are shown in Table 1.

[Comparative example 1]
(core-sheath type composite fiber), the core component is a polylactic acid resin with an MFR of 20 g/10 min, a melting point of 168 °C, and a solid density of 1.240 g/cm ³ , an MFR of 25 g/10 min, a melting point of 129 °C, High-density polyethylene (HDPE) resin consisting only of ethylene polymer units with a solid density of 0.950 g/ ^cm3 was used as the sheath component, the single-hole discharge rate was 1.40 g/min, and the flow rate of the compressed air of the ejector was A spunbond nonwoven fabric was obtained by the same method as in Example 1, except that the . The characteristics of the fibers constituting the formed spunbond nonwoven fiber web were that the average single fiber diameter was 19.2 μm, the solid density was 1.066 g/cm ³ , and the spinning speed calculated from these was 4540 m/min. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good. The resulting spunbond nonwoven fabric had a uniformity of 37 points, which was inferior to Examples 1 to 6. Table 2 shows the results of evaluating the obtained spunbond nonwoven fabric.

[Comparative example 2]
(core-sheath type composite fiber), a spunbond nonwoven fabric was obtained in the same manner as in Comparative Example 1, except that the single hole discharge rate was 1.10 g/min and the flow rate of compressed air from the ejector was increased. The characteristics of the fibers constituting the formed spunbond nonwoven fiber web were that the average single fiber diameter was 16.3 μm, the solid density was 1.066 g/cm ³ , and the spinning speed calculated from these was 4950 m/min. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good. The resulting spunbond nonwoven fabric had a uniformity of 56 points, which was inferior to Examples 1 to 6. Table 2 shows the results of evaluating the obtained spunbond nonwoven fabric.

[Comparative example 3]
(core-sheath type composite fiber), which used a core-sheath type composite fiber, was replaced with a single component consisting only of polylactic acid resin with an MFR of 30 g/10 minutes, a melting point of 170°C, and a solid density of 1.240 g/ ^cm3 . A spunbond nonwoven fabric was obtained in the same manner as in Comparative Example 2, except that fibers were used. The characteristics of the fibers constituting the formed spunbond nonwoven fiber web were that the average single fiber diameter was 14.3 μm, the solid density was 1.240 g/cm ³ , and the spinning speed calculated from these was 5520 m/min. Regarding the spinnability, no yarn breakage was observed after spinning for 1 hour, and the result was good. The resulting spunbond nonwoven fabric had a texture uniformity of 72 points, which was slightly inferior to that of Examples 1 to 6. Table 2 shows the results of evaluating the obtained spunbond nonwoven fabric.

Examples 1 to 6 are made of core-sheath composite fibers in which the core component is mainly composed of polylactic acid resin and the sheath component is mainly composed of polyolefin resin, and the apparent specific surface area is 250 cm ² /cm ³ or more and 3000 cm ² / ^cm3 or less, spunbond nonwoven fabrics have sufficient strength for practical use, good texture, excellent flexibility and feel, and excellent productivity and thermal adhesion. Met.

On the other hand, the spunbond nonwoven fabrics shown in Comparative Examples 1 and 2 with an apparent specific surface area smaller than 250 cm ² /cm ³ and the spunbond nonwoven fabrics made of monocomponent fibers whose main component is polylactic acid resin shown in Comparative Example 3 , the flexibility was low, and the feel and thermal adhesion were also poor.

Claims (7)

A spunbond nonwoven fabric made of a core-sheath type composite fiber whose core component is a polylactic acid resin as a main component and whose sheath component is a polyolefin resin as a main component, and has an apparent specific surface area of 250 cm ² /cm ³ or more and 3000 cm ² / ^cm3 or less, a spunbond nonwoven fabric. The spunbond nonwoven fabric according to claim 1, wherein the polyolefin resin is a polyethylene resin. The spunbond nonwoven fabric according to claim 2, wherein the polyethylene resin is a copolymer of ethylene and an α-olefin having 3 to 5 carbon atoms. The spunbond nonwoven fabric according to claim 3, wherein the α-olefin is 1-butene. The spunbond nonwoven fabric according to claim 3 or 4, wherein the content of the α-olefin is 0.1 to 10 mol% based on the polymerization component of the polyethylene resin. The spunbond nonwoven fabric according to any one of claims 1 to 5, wherein the average single fiber diameter of the core-sheath type composite fiber is 7.6 μm or more and 15.2 μm or less. A sanitary product using the spunbond nonwoven fabric according to any one of claims 1 to 6.