JPH03287848A - Bulky nonwoven fabric - Google Patents

Abstract

PURPOSE:To provide a bulky nonwoven fabric useful as a surface skin material for paper diapers, etc., and having excellent elastic recovery property, etc., by melt-fusing the sheath portions of conjugate fibers comprising two kinds of polymers having a specific melting point difference therebetween, the core portion of each fiber comprising the high melting point polymer and the sheath portion comprising the low melting point polymer. CONSTITUTION:The sheath portions of eccentric conjugate fibers are melt-fused to prepare the objective nonwoven fabric, the conjugate fibers comprising two kinds of polymer having a specific melting point difference therebetween, the core portion of each conjugate fiber being composed of the high melting point polymer (e.g. polypropylene) and having a hollow portion 2 with a hollow rate of 5-40% and the sheath portion 3 thereof being composed of the low melting point polymer (e.g. polyethylene), the conjugate fiber having a W2/r of 0.1-0.7 between the radius r of the core portion 1 and the distance W2 between the center O1 of the core portion 1 and the center O3 of the hollow portions 2 and the conjugate fiber also having a W1/r of 0.1-0.7 between the radius r of the core portion 1 and the distance W1 between the center O1 of the core portion 1 and the center O3 of the hollow portion 2.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a bulky nonwoven fabric obtained by heat-treating a web made of heat-adhesive eccentric composite fibers, and in particular to a bulky nonwoven fabric that has excellent bulk and elastic recovery properties and is suitable for use in paper diapers, etc. The present invention relates to a bulky nonwoven fabric suitable for skin materials, sanitary materials, medical products, etc.

(Prior Art) Conventionally, long-fiber nonwoven fabrics consisting of two components with different melting points have been widely used today, including in sanitary materials, and recently there has been an increasing demand especially for low basis weight fabrics.

For example, in the case of the long fiber nonwoven fabric described in Japanese Patent Publication No. 63-282351, since it is not hollow, it has the drawback that the bulk and elastic recovery properties are not necessarily satisfactory in the field of low basis weight.

(Problems to be Solved by the Invention) The present invention solves the drawbacks of conventional nonwoven fabrics, namely, lack of bulk.
It improves the poor feeling of wearing caused by the backflow of fluid in diapers, etc. due to lack of elastic recovery, and has a high bulk even in low basis weight fields without sacrificing the original characteristics of nonwoven fabrics such as flexibility, good texture, and flatness. The purpose of the present invention is to provide a bulky nonwoven fabric with high elastic recovery properties.

(Means for Solving the Problems) The present invention takes the following means to solve the problems described above. That is, the present invention provides a composite comprising two types of polymers having a difference in melting point of 20°C or more, in which the high melting point polymer constitutes a core portion having a hollow portion, and the low melting point polymer constitutes a sheath portion. A bulky nonwoven fabric composed of fibers and thermally bonded with the low melting point polymer, wherein the center of the core and the center of the hollow are eccentric with respect to the center of the sheath, and the hollow ratio is 5 to 40%. It is a bulky nonwoven fabric characterized by having.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

The composite fiber according to the present invention consists of a core part and a sheath part, the core part is made of a polymer with a high melting point, and has a hollow part, and the sheath part is 20° C. or higher than the core polymer. It consists of low melting point polymers with a melting point difference of .

In the present invention, polypropylene, polyethylene terephthalate, etc. are used as the high-melting point polymer constituting the core, and high-density, medium-density, and low-density polymers are used as the low-melting point polymers constituting the sheath. Polyethylene, polypropylene, ethylene/vinyl acetate copolymer, etc. are used. The high melting point polymer must be selected to have a melting point difference of 20°C or more in order to ensure thermal adhesion when made into a nonwoven fabric, and the sheath portion must be made of a low melting point polymer. must be configured. In this case, if the difference in melting point of the polymers used is less than 20°C, when the composite fibers are thermally bonded to produce a nonwoven fabric, not only will the core become soft and deformed, resulting in a decrease in flexibility and texture. , part of the hollow part is crushed, resulting in increased bulk and poor elastic recovery. However, if a polymer having a melting point difference of 20° C. or more is used, such problems will not occur, and a nonwoven fabric with excellent flexibility, texture, bulk, and elastic recovery can be obtained.

Next, the center of the core part 1 and the hollow part 2 existing in the core part
The center of the sheath 3 is eccentric with respect to the center of the sheath 3 (FIG. 1). This eccentricity promotes the development of crimp during heat setting,
It is necessary to make it bulky. In FIG. 1, the radius of the core is r, and the distance between the center 01 of the core 1 and the center 02 of the sheath 3 is W.

Then, the eccentricity ratio W,/r is preferably in the range of 0.1 to 0.7. In addition, the center 01 of the core part 1 and the hollow part 2
The eccentricity ratio W2/r is preferably in the range of 0.1 to 0.7, where W2 is the distance from the center 03. Eccentricity ratio W,
When 7r, W, /r is less than 0.1, crimp expression is insufficient and bulkiness is not achieved, which is not preferable. On the other hand, if the eccentricity ratio exceeds 0.7, the hollow portion may be exposed outside the core portion, which is not preferable.

Further, in FIG. 1, assuming that the cross-sectional area of the core portion 1 is 0 and the cross-sectional area of the hollow portion is E, the hollow ratio S needs to be in the range of 5 to 40%. If it is less than 5%, it is not preferable because it will not be bulky due to a decrease in the constituent volume, it will not be possible to increase the bending moment of the fiber due to eccentric hollowing, and the elastic recovery will be insufficient.

On the other hand, if the hollowness ratio S exceeds 40%, the hollow portion will easily collapse under high loads, resulting in loss of bulk and elastic recovery, which is not preferable.

In the present invention, since the center of the core and the hollow part in the core is eccentric from the center of the sheath, the eccentricity of the sheath and the core and the center of the core and the hollow part in the core can be prevented during thermal bonding. Due to the synergistic effect of the eccentricity of the fibers, nonwoven fabrics formed from the fibers with high crimp development properties are bulky, have excellent elastic recovery properties, and are highly durable even in the field of low basis weight.

Since there is a hollow part in the core, even if the sheath part melts during thermal bonding, the presence of the hollow part increases the bending moment of the fiber, improving bulk and elastic recovery. On the other hand, because the centers of the sheath and core are eccentric during thermal bonding, the sheath melts while crimping occurs, and after melting, the hollow part is eccentric with respect to the core, so the sheath The core released from constraints exhibits three-dimensional crimp due to structural anisotropy due to the eccentricity of the hollow part.

As a result, a bulky nonwoven fabric is obtained.

In addition, the bulky nonwoven fabric has a stable form as a fiber bundle due to the adhesive bonding between the fibers, and exhibits high elasticity and good recovery properties in combination with the elastic recovery properties of the fibers themselves.

Furthermore, even in the field of low basis weight, the bulk of the nonwoven fabric after thermal bonding is 25 cc/g or more.

(Example) Example 1.2, Comparative Example 1 The core was made of polyethylene terephthalate with a melting point of 266°C and an intrinsic viscosity of 0.63, and the sheath part was made of polyethylene terephthalate with a melting point of 132°C and a melt index of 28.8 g/10 m1n 1 density 0.9.
53g/ca high density polyethylene at 290℃
, melt extrusion was carried out at 245°C, spinning temperature was 290°C, and continuous spinning was carried out at a discharge rate ratio of 1:1. After stretching under specified conditions, the fibers were collected on a net to form a web, which was then heated under no load with hot air (
120° C.) treatment to obtain a predetermined long fiber nonwoven fabric.

At this time, the fibers were spun with different cross-sectional shapes. The results are shown in Table 1.

Table 1 Melting point refers to the temperature at the peak of the melting endothermic curve measured by DSC measurement method, and the value measured by DSC (heating rate 20℃/
IQin), the intrinsic viscosity is the value measured with an Ubbelohde viscometer, the density is the value measured with a density gradient tube, the melt index is the value measured with a melt indexer, and the thickness of the nonwoven fabric is A( ml) is the value measured under a load of 3 g/cl, and the thickness B (, TI) is 35 g/cl.
After applying a load of cJ and leaving it for 5 days, apply a load of 3 g/cJ again.
This is the value measured under a load of The elastic recovery rate (%) is a value obtained by dividing the thickness B (,,) by the thickness A (,,) and expressed as a percentage. Tensile strength (kg15cm) is
This is the value measured by Tensilon, and the tear strength (kg)
is the value measured in tensilon.

As is clear from Table 1, the nonwoven fabric of Example 1.2 satisfied the hollowness ratio and was eccentric, so the nonwoven fabric was bulky and had excellent elastic recovery properties.

Since the material of Comparative Example 1 was not eccentric, it had poor elastic recovery properties and poor bulk.

(Effects of the Invention) According to the present invention, the following exceptional effects can be obtained.

(1) Since the core and the center of the hollow part in the core are eccentric from the center of the sheath, it has a synergistic effect during thermal bonding, resulting in a high degree of crimp development, and a highly durable nonwoven fabric. becomes.

■ During thermal bonding, the sheath melts while producing crimp due to the eccentricity of the sheath and core, and after melting, the hollow part is eccentric with respect to the core, creating a three-dimensional crimp. do. In addition, the presence of hollow parts increases elastic recovery,
The result is a bulky nonwoven fabric with high elastic recovery.

(3) Nonwoven fabrics, which are bulky and have elastic recovery properties, are ideal for impact materials, and particularly have the effect of preventing backflow of liquid in the absorbent core material.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a core-sheath structure fiber having a hollow portion according to the present invention.

Claims (1)

[Claims] Consisting of two types of polymers with a melting point difference of 20°C or more,
A bulky nonwoven fabric comprising composite fibers in which a high melting point polymer constitutes a core having a hollow portion and a low melting point polymer constitutes a sheath, the low melting point polymer being thermally bonded, The bulky nonwoven fabric is characterized in that the center of the core portion and the center of the hollow portion are eccentric with respect to the center of the sheath portion, and have a hollowness ratio of 5 to 40%.