Spunbond nonwoven fabric

Abstract

Provided is a spunbond nonwoven fabric which is made of a polypropylene fiber and satisfies all of the following conditions A to E: A. the average single fiber diameter of the fiber is 6-17 μm; B. the degree of crystal orientation of the fiber as obtained by wide-angle X-ray diffraction is at least 0.91; C. the crystallite size of the (110) plane of the fiber as obtained by wide angle X-ray diffraction is at least 12 nm; D. the average orientation parameter of the fiber as obtained by Raman spectroscopy is at least 8.0; and E. the complex viscosity of the spunbond nonwoven fabric at a temperature of 230° C. is 20-100 Pa·sec at an angular frequency of 6.3 rad / sec.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This is the U.S. National Phase application of PCT / JP2018 / 035928, filed Sep. 27, 2018, which claims priority to Japanese Patent Application No. 2017-188004, filed Sep. 28, 2017 and Japanese Patent Application No, 2018-141053, filed Jul. 27, 2018, the disclosures of each of these applications being incorporated herein by reference in their entireties for all purposes.FIELD OF THE INVENTION[0002]The present invention relates to a spun-bonded nonwoven fabric which is soft and has excellent mechanical properties and higher-order processability.BACKGROUND OF THE INVENTION[0003]Spun-bonded nonwoven fabrics made of polyolefin, particularly polypropylene spun-bonded nonwoven fabrics, are low in cost and have excellent processability, and are hence widely used mainly in hygienic material applications.[0004]In recent years, as for polypropylene spun-bonded nonwoven fabrics used in hygienic material applications, further improvement in texture, touc...

AI Technical Summary

Benefits of technology

[0010]According to the method disclosed in Patent Literature 1, the softness of the nonwoven fabric can be reliably improved. However, since a melt flow rate of resin used therein is low, a softness improving effect thereof is not sufficient, and nonwoven fabrics exemplified in examples thereof are nonwoven fabrics containing low melting point polyolefin-based resin, hence the production efficiency may decrease due to occurrence of filament breakage. Further, there is also a problem that the resin used is substantially limited.

[0012]Therefore, an object of the present invention is to provide a spun-bonded nonwoven fabric which is soft and has excellent mechanical properties and higher-order processability.

[0013]As a result of studies performed by the present inventors, it has been found that the softness of the spun-bonded nonwoven fabric has a high correlation with complex viscosity thereof in a molten state. As the complex viscosity of the spun-bonded nonwoven fabric becomes lower, the softness is improved, while the mechanical properties and the higher-order processability are reduced. Therefore, as a result of intensive studies to solve the above problems, the present inventors have found that a spun-bonded nonwoven fabric, in which softness and excellent mechanical properties and higher-order processability are all achieved, is obtained by setting fineness, crystal orientation degree, crystallite size, and orientation parameter of the spun-bonded nonwoven fabric in specific ranges, and further by setting the complex viscosity of the spun-bonded nonwoven fabric in a specific range, hence the present invention was completed.

[0021]The fiber diameter of the fibers constituting the spun-bonded nonwoven fabric according to the present invention is low, and the complex viscosity thereof in the molten state is low, hence the spun-bonded nonwoven fabric has high softness. In addition, the crystal orientation thereof is high, the crystallite size thereof is large, and the orientation parameter thereof is high, hence the spun-bonded nonwoven fabric according to the present invention exhibits excellent mechanical properties and higher-order processability.

Problems solved by technology

However, since a melt flow rate of resin used therein is low, a softness improving effect thereof is not sufficient, and nonwoven fabrics exemplified in examples thereof are nonwoven fabrics containing low melting point polyolefin-based resin, hence the production efficiency may decrease due to occurrence of filament breakage.

Further, there is also a problem that the resin used is substantially limited.

In the method disclosed in Patent Literature 2, although the softness of the nonwoven fabric can be reliably improved, since the melt flow rate of the resin used therein is low, a softness improving effect thereof is not sufficient.

Moreover, a hole diameter of a spinneret exemplified in examples thereof is as large as 0.6 mmφ, hence spinneret pressure is difficult to be applied, spinning cannot be performed uniformly, and filament breakage and fiber diameter unevenness are generated, which makes it difficult to stably obtain uniform nonwoven fabrics.