JP3056403B2 - Stretchable nonwoven fabric and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a stretchable nonwoven fabric having a high elongation recovery rate and a low modulus, and a method for producing the same.

[0002]

2. Description of the Related Art Various elastic members such as cataplasms, bandages, disposable diapers, and elastic nonwoven fabrics suitable for clothing have been proposed and put into practical use. As one of the general stretchable nonwoven fabrics, there can be mentioned one using a latent crimpable fiber which develops a crimp by heat.

For example, in Japanese Patent Application Laid-Open No. 3-69647, a fiber web made of a specific polyester-based composite fiber is subjected to needling by needle punch or water needling by water jet so that the fibers are entangled, and then heated. There has been proposed a stretchable nonwoven fabric which has been subjected to treatment to exhibit microcrimp. Also, Japanese Patent Laid-Open No. 1-2
No. 80058 discloses that a heat treatment is carried out at 5 / inch.
Nonwoven fabrics containing zero or more polyester-based composite fibers exhibiting a spiral crimp and being entangled by jetting water have been proposed.

[0004]

However, any of the nonwoven fabrics has room for improvement in stretchability.

[0005] One of the performances required for a stretchable nonwoven fabric is to satisfy two conditions of good return after stretching and good stretching with a small force. The former is expressed by the elongation recovery rate, and the latter is expressed by the elongation stress (modulus). The extension recovery rate is closely related to the fit to the body, and it is considered that the higher the recovery rate, the better the fit. Further, the magnitude of the modulus has a great effect on the wearing feeling of the wearer when the stretchable nonwoven fabric is used for an elastic member such as a pants-type diaper or for clothing. That is, when the elongation recovery rate is almost the same, the greater the modulus, the greater the tightening feeling and the worse the wearing feeling.

[0006] Conventional nonwoven fabrics do not satisfy the above two conditions, and have a high elongation recovery rate.
In fact, non-woven fabrics having a low modulus have not yet been obtained.

In view of such circumstances, the present invention has been made to provide a stretchable nonwoven fabric having a high elongation recovery rate and a low modulus in at least one direction.

[0008]

That is, the present invention relates to a nonwoven fabric comprising 80% by weight or more of latently crimpable fibers in which three-dimensional crimps have been developed, wherein the fibers are entangled by the action of a high-pressure water flow. A stretchable nonwoven fabric having a 50% elongation recovery rate of 75% or more in both the vertical and horizontal directions and a 50% modulus in at least one direction of 2 g / 5 cm or less per unit weight, and a method for producing the same. . Hereinafter, the contents will be described.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The term "latent crimpable fiber" used in the present invention refers to a fiber which develops a three-dimensional crimp when heated. Here, the three-dimensional crimp means not only a spiral crimp as shown in FIG. 1 but also a two-dimensionally bent one that draws a gentle curve as shown in FIG. It is intended to broadly include two-dimensional bending to which twist is added, and the like, and is a word used to distinguish it from mechanical crimping provided by a crimper or the like. In the present invention, it is preferable to use a fiber that undergoes a heat treatment in accordance with a manufacturing method described below so that 25 or more three-dimensional crimps are developed per inch. If the number of crimps is less than 25 pieces / inch, sufficient elasticity cannot be imparted to the nonwoven fabric.
More preferably, the number is 30 to 60.

[0010] As the latently crimpable fiber, specifically, fibers composed of two or more polymers having different heat shrinkage rates, for example, ethylene-propylene random copolymer / polypropylene, ethylene-butene-1-propylene It is composed of a combination of terpolymer / polypropylene, high-density polyethylene / polyethylene terephthalate, high-density polyethylene / polybutylene terephthalate, polyethylene terephthalate / modified polyester, polypropylene / polyethylene, polyolefin / polyamide, and the like. This has a side-by-side cross-sectional structure.

In order to realize a high elongation recovery rate and a low modulus, which are the characteristics of the stretchable nonwoven fabric of the present invention, the latently crimpable fiber must have a basis weight of 40 g / m2 consisting of only the fiber at its dry heat shrinkage initiation temperature. it is desirable areal shrinkage of the ^second nonwoven fabric has a property that is 10% or more. Here, the dry heat shrinkage starting temperature is defined as (100 ° A) fibers to be measured (A: fineness (d) of the fiber to be measured), and the bundle is made into a fiber bundle. Is a temperature at which the fiber bundle shrinks by 1% when the temperature is continuously raised at a rate of 1 ° C. per minute in a suspended state. Also,
The area shrinkage ratio of the nonwoven fabric is defined as a water pressure of 30 kg / m ² from a nozzle provided with orifices having a pore diameter of 0.13 mm at intervals of 1 mm on a parallel web having a basis weight of 40 g / m ² composed of only latently crimpable fibers to be used. When a water-entangled nonwoven fabric prepared by injecting a columnar water flow of cm ² onto the front and back surfaces of the web once at a processing speed of 5 m / min is subjected to a heat treatment at a predetermined temperature for 1 minute using a hot air penetration dryer. Refers to the area shrinkage of the nonwoven fabric.

In general, when the fibers are shrunk in a free state and when they are shrunk in a non-woven fabric state, even under the same conditions, the latter fibers are constrained by the entanglement of the fibers. Hard to do. It can be said that fibers having the above-mentioned properties show high shrinkage even in a restrained state, and this is considered to affect the elongation recovery rate and modulus of the nonwoven fabric. Also, it should be noted that even if the fibers are made of the same material, if the fineness is different, the dry heat shrinkage onset temperature measured by the above-described method is also different.

Fibers having such properties include side-by-side composite fibers (trade name: TC-79) made of modified polyester and polyethylene terephthalate manufactured by Teijin Limited, and modified polyesters and polyethylene manufactured by Kuraray Co., Ltd. Side-by-side conjugate fiber composed of terephthalate (trade name: N-780), side-by-side conjugate fiber composed of modified polyester manufactured by Nippon Ester Co., Ltd. and polyethylene terephthalate (trade name: C)
-81).

In the present invention, the latently crimpable fiber is preferably contained in an amount of 80% by weight or more, and more preferably, the nonwoven fabric is composed of only the latently crimpable fiber. If the content is less than 80% by weight, the nonwoven fabric cannot have sufficient elasticity.

The latently crimpable fibers may be used as a mixture of two or more latently crimpable fibers. Other fibers mixed with the latent crimpable fiber are not particularly limited. For example, if a water-absorbing fiber such as rayon or cotton (cotton) is mixed, the non-woven fabric can be given water absorbency and hygroscopicity. .

Next, the form of the nonwoven fabric of the present invention will be described together with the method for producing the same.

The nonwoven fabric of the present invention can be obtained by subjecting a web containing latently crimpable fibers to a high-pressure water treatment and then a heat treatment. The form of the web is not particularly limited, but in the present invention, it is particularly preferable to use a parallel web, a random web, a cross web or the like made of short fibers.
Here, the fineness of the fiber constituting the web is desirably 2 to 3 denier. The smaller the fineness is, the better the feel of the nonwoven fabric is, but the entanglement between the fibers is strengthened by the high-pressure water flow treatment described later, so that the high elongation recovery rate and the low modulus which are the objects of the present invention are hardly realized. . When a short fiber web is used, the fiber length is preferably 25 to 125 mm in consideration of card passing property. More preferably, it is 38 to 64 mm.

The basis weight of the web is not particularly limited and may be determined according to the intended use of the nonwoven fabric to be finally obtained. m ² is preferred.

The nonwoven fabric of the present invention contains latently crimpable fibers in which three-dimensional crimps have been developed, and the fibers are entangled by the action of high-pressure water flow. The 50% elongation recovery rate is 75% or more in both the vertical and horizontal directions. And at least 50 in one direction
% Modulus per unit weight is 2 g / 5 cm or less . In order to obtain such a nonwoven fabric, it is necessary to adjust the performance of the nonwoven fabric in a state before the three-dimensional crimping of the latently crimpable fiber (hereinafter referred to as a non-heat-treated nonwoven fabric).

In order to achieve the high elongation recovery rate and low modulus which are the objects of the present invention, it is necessary that the entanglement of the fibers in the nonwoven fabric before the heat treatment is not excessively strong. Specifically, it is preferable that the strength of the nonwoven fabric before the heat treatment is not excessively increased. For this purpose, it is desirable to perform the high-pressure water flow treatment under relatively mild conditions. Specific conditions are fiber type,
Depending on the fineness, the basis weight of the web, etc., for example, when a latently crimpable fiber having the specific properties as described above is used and a web of 30 to 50 g / m ² is processed, the pore size is 0.05 to 0. 0.5mm orifice 0.5 ~ 1.5mm
From nozzles provided at intervals, water pressure is 10 to 40 kg / cm ²
The columnar water stream is preferably injected from the front and back sides of the nonwoven fabric 1 to 5 times each.

Subsequently, the raw fabric is subjected to a heat treatment to cause the latently crimpable fiber to develop a three-dimensional crimp, thereby shrinking the raw fabric. In the heat treatment, the raw material shrinks by 30% or more in at least one direction,
In addition, it is preferable to perform the treatment under such a condition that the fibers do not adhere to each other. Specific conditions vary depending on the type of fiber and the like, but generally, when the heating temperature is too low, the expression of crimp is insufficient, and the nonwoven fabric does not have sufficient elasticity, and when the heating temperature is high, the crimping is not performed. Since the entanglement of the fibers with each other due to the occurrence of stiffness becomes strong, the modulus tends to increase. Specifically, assuming that the dry heat shrinkage initiation temperature T of the latently crimpable fiber is the heating temperature T _A
But better to be in the range of _{T <T A <T + 50} . The more preferred range is _{T + 20 <T A <T} + 40. The heating method is not particularly limited, but if a hot air penetration dryer is used, the treatment can be performed without disturbing the texture of the nonwoven fabric and without impairing the tactile sensation. Therefore, its use is particularly preferable in the present invention.

In the case where the heat treatment is continuously performed using a hot air penetration type dryer, the supply speed of the nonwoven fabric needs to be higher than the moving speed of the nonwoven fabric at the outlet of the dryer in consideration of the contraction in the vertical direction. Yes, and is usually expressed as an overfeed rate. When the nonwoven fabric is transported using a pin tenter, the width of the heat shrinkage in the width direction can be regulated by adjusting the width of the pin tenter at the inlet and the outlet. For example, the width of the exit pin tenter is 90% of the width of the entrance.
, The heat shrinkage in the width direction is about 10%.

The nonwoven fabric thus obtained has a high elongation recovery rate and a low modulus. The present invention requires that the low modulus be secured in at least one direction. This is because it is necessary to avoid a decrease in the modulus in one direction depending on the application. For example, when used as a poultice base fabric, it is not desirable that the modulus in the vertical direction is too low in order to improve the coatability of chemicals. Of course, when the modulus in the vertical direction may be low, for example, when used as an elastic member or disposable underwear for a diaper, both the vertical and horizontal lengths may be low.

In general, the modulus in the vertical direction tends to be smaller when a cross web or a random web is used than when a parallel web is used. Further, the modulus in the vertical direction tends to be higher as the overfeed rate at the time of performing the heat treatment is smaller.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described with reference to embodiments. In addition, the nonwoven fabric performance of each Example was measured according to the method described below.

[Thickness] The thickness was measured with a load of 3 g / cm ² applied to the nonwoven fabric.

[Strength, breaking length] JIS L 1096
5cm wide x 15cm long sample is gripped according to
With a constant speed elongation type tensile tester (trade name: Tensilon Orientec Co., Ltd.) at a tensile speed of 30 cm /
Minutes, and the load value at the time of cutting was made strong. The breaking length is
The breaking length (km) was calculated from the following formula: strength (kg / 0.05 m) / [sample width (m) × weight (g / m ² )].

[50% modulus] width 5 cm × length 15
cm sample is gripped at a spacing of 10 cm, and a constant speed elongation type tensile tester (trade name: Tensilon: Orientec Co., Ltd.)
15cm at a pulling speed of 30cm / min.
The value obtained by dividing the load value (g / 5 cm) when the sample was stretched until the weight per unit area by the basis weight of the sample was defined as a 50% modulus per unit basis weight (g / 5 cm / g / m ² ).

[50% elongation recovery rate] Width 5 cm x length 15
cm sample is gripped at a spacing of 10 cm, and a constant speed elongation type tensile tester (trade name: Tensilon Orientec Co., Ltd.)
) At a pulling speed of 10 cm / min and a gripping interval of 15 cm.
Then, the sample was relaxed at a rate of 10 cm / min until the sample slackened. Then, the sample was stretched again at a tensile speed of 10 cm / min, and the length (L) of the sample when the load value became non-zero was measured, and the following formula was used, and the stretch recovery rate (%) = [(1
5-L) / 5] × 100, and the elongation recovery rate was calculated.

[Preparation of Fibers] As latent crimpable fibers, seven types of side-by-side type composite fibers composed of modified polyester and polyethylene terephthalate were prepared. The product names and manufacturers are as follows.

Fiber A: trade name TC-79 Teijin Limited Fiber B: trade name N-780 Kuraray Fiber C: trade name C-81 Nippon Ester Co., Ltd. fiber D: trade name TYPE24 Toray Fiber E: trade name TF-7 Toyobo Co., Ltd. Fiber F: trade name N-780 Kuraray Co., Ltd. fiber G: trade name A-81 Nippon Ester Co., Ltd.

Table 1 shows the physical properties of the fibers A to G.

[0033]

[Table 1]

In Table 1, the area shrinkage was determined as follows. First, a square frame of 20 cm × 20 cm is raised on the surface of the nonwoven fabric before the heat treatment, and a mark corresponding to the midpoint (4) of each side of the square (3) is marked as shown in FIG. Then, after the heat treatment, the midpoints (4) facing each other are connected by a line, and as a result of the heat shrinkage, the square becomes a rectangle (5) in which those lines are the sides of the vertical (6) and the sides of the horizontal (7). And the area of the rectangle (5) was calculated. From these results, the area shrinkage was determined by the following equation.

[0035]

(Equation 1)

[Examples 1 to 12] A parallel web was prepared using the fibers A to D described above, and subjected to a high-pressure water flow treatment to entangle the fibers. The high-pressure water flow treatment was performed by setting the processing speed to 5 m / min and injecting a high-pressure water flow from a nozzle provided with orifices having a hole diameter of 0.13 mm at intervals of 1 mm. There are three types of high pressure water treatment conditions, and the numbers 1 to 3 in the table indicate that the treatment was performed under the following conditions.

Condition 1: A columnar water stream with a water pressure of 30 kg / cm ²
It was sprayed once each from the front and back surfaces of the nonwoven fabric. Condition 2: A columnar water stream having a water pressure of 30 kg / cm ² was jetted twice from the front side and once from the back side of the nonwoven fabric. Condition 3: A columnar water stream having a water pressure of 30 kg / cm ² was jetted twice from the front and back surfaces of the nonwoven fabric.

Subsequently, the nonwoven fabric after the high-pressure water flow treatment was subjected to a heat treatment. Heat treatment is performed at a temperature shown in Table, and treated for 1 minute in a hot air penetration type dryer. Examples of this are, et al. 1
For Nos. 1 and 12, the heat treatment was continuously performed, and the nonwoven fabric was transported using a pin tenter. Therefore, the heat shrinkage in the vertical direction in the table is represented by the overfeed rate, and the heat shrinkage in the horizontal direction was [ Pin tenter width / entrance pin tenter width] × 100 (%). Tables 2 and 3 show the performance of the obtained nonwoven fabric.

[0039]

[Table 2]

[0040]

[Table 3]

Comparative Examples 1 to 6 Fibers E to G and Fiber A
Was used to prepare a nonwoven fabric in the same manner as in the example. Table 4 shows the performance of the obtained nonwoven fabric.

[0042]

[Table 4]

The Examples and Comparative Examples show that the use of latently crimpable fibers having specific properties affects the elongation recovery and modulus of the nonwoven fabric. Further, even when a latently crimpable fiber having specific properties is used, the nonwoven fabric before heat treatment has a large strength, and a nonwoven fabric set at a high heating temperature is inferior in elongation recovery and has a large modulus.

[0044]

The stretchable nonwoven fabric of the present invention is a nonwoven fabric having a high elongation recovery rate and a low modulus realized by using latently crimpable fibers having specific properties. Therefore, the stretchable nonwoven fabric of the present invention is particularly suitable for those in which the wearing feeling such as disposable underwear is important.

[Brief description of the drawings]

FIG. 1 is a side view of an example of a latently crimpable fiber in which a three-dimensional crimp has been developed.

FIG. 2 is a side view of an example of a latently crimpable fiber in which a three-dimensional crimp has been developed.

FIG. 3 is a side view of an example of a latently crimpable fiber in which a three-dimensional crimp has been developed.

FIG. 4 is a schematic view showing a method for measuring an area shrinkage of a nonwoven fabric.

[Explanation of symbols]

 1 latently crimpable fiber 2 dimensional crimp

Claims (4)

(57) [Claims] Claims 1. A latently crimpable fiber in which a three-dimensional crimp has been developed is
A nonwoven fabric containing 0% by weight or more and fibers entangled by the action of a high-pressure water flow, and has a 50% elongation recovery rate of 75% or more in both the vertical and horizontal directions, and a unit weight of 50% in at least one direction. Stretchable non-woven fabric characterized by being 2 g / 5 cm or less per piece. 2. The latently crimpable fiber in which the three-dimensional crimp has been expressed is 8
A nonwoven fabric containing 0% by weight or more, wherein fibers are entangled by the action of high-pressure water flow, and have a 50% elongation recovery rate of 75% or more in both the vertical and horizontal directions, and a unit of 50% modulus in the vertical and horizontal directions. A stretchable nonwoven fabric having a basis weight of 2 g / 5 cm or less. 3. The latently crimpable fiber has a property such that, at its dry heat shrinkage initiation temperature, the area shrinkage of a nonwoven fabric having a basis weight of 40 g / m ² is 10% or more. The stretchable nonwoven fabric according to claim 1 or 2. 4. An area shrinkage ratio of a nonwoven fabric having a basis weight of 40 g / m ² alone consisting of 10% at a dry heat shrinkage starting temperature.
The short fiber web containing the latent crimpable fiber having the properties described above is subjected to high pressure water flow treatment to entangle the fibers, and then subjected to a heat treatment at a temperature lower than the melting point of the latent crimpable fiber. The latently crimpable fibers exhibit a three-dimensional crimp and shrink the nonwoven fabric in at least one direction by 30% or more. The 50% elongation recovery rate is 75% or more in both the vertical and horizontal directions. 50 in one direction
A method for producing a stretchable nonwoven fabric having a% modulus of 2 g / 5 cm or less per unit weight.