JPH10237751A - Hot-melt nonwoven fabric and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide nonwoven fabric that shows excellent flexibility and touch even when hot-melt type fiber is mixed in a large proportion. SOLUTION: A fiber web consisting of 20-50wt.% of latently shrinkable conjugated fiber and 80-50wt.% of not hot-melt type fiber is mechanically interlaced to cause interlacing of fibers to each other. Then, the interlaced web is heat-treated so that the aerial shrinkage of the fiber web becomes <=10% to develop the three-dimensional shrinkage in the latently shrinkable conjugated fiber, and simultaneously, the fibers are thermally adhered to each other by the lower melting component in the latently shrinkable conjugated fiber thereby producing the objective nonwoven fabric.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-bondable nonwoven fabric using a latently crimpable conjugate fiber as a heat-bondable fiber.

[0002]

2. Description of the Related Art Generally, diaper members, wet tissues, wipers, and the like are required to have a good tactile sensation and a certain strength. Therefore, the nonwoven fabric used for them is
It is often a heat-bonded nonwoven fabric composed of a hydrophilic fiber such as rayon and a core-sheath type heat-bondable conjugate fiber of a core / sheath of polyester / polyethylene or polypropylene / polyethylene. In this nonwoven fabric, rayon or the like improves the feel of the nonwoven fabric, and the heat-adhesive conjugate fiber imparts strength to the nonwoven fabric. Therefore, when manufacturing a heat-bonded nonwoven fabric, flexibility,
It is necessary to determine the mixing ratio of the constituent fibers in consideration of the feel and strength.

[0003]

However, there is a case where a desired nonwoven fabric cannot be obtained only by adjusting the mixing ratio.
For example, if the ratio of the heat-adhesive fibers is reduced with emphasis on the tactile sensation, the number of bonding points is also reduced by that amount, so that fluff is likely to occur. If the proportion of the heat-adhesive fibers is small, sufficient heat sealing strength may not be obtained when the non-woven fabric is heat-sealed. In these cases, the mixing ratio of the heat-adhesive fibers must be increased to some extent.

[0004] In addition, the core-sheath type heat-adhesive conjugate fibers mentioned above can reduce the tactile sensation of the nonwoven fabric only by mixing a small amount.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a nonwoven fabric which exhibits excellent flexibility and touch even when the mixing ratio of the heat-adhesive fibers is increased.

[0006]

Means for Solving the Problems The heat-bonded nonwoven fabric of the present invention has a latent crimpable conjugate fiber 20 to 50 having a three-dimensional crimp.
A non-woven fabric consisting of 80% to 50% by weight of non-heat-adhesive fibers and being entangled with each other, wherein the fibers are heat-bonded by the low melting point component of the latently crimpable conjugate fiber. It is characterized by. By using a latently crimpable conjugate fiber as the heat bonding fiber, a nonwoven fabric excellent in flexibility and touch can be obtained even when the mixing ratio is increased.
In addition, the fibers are entangled to improve the strength.

The heat-bonded non-woven fabric is subjected to a mechanical entanglement treatment on the fiber web composed of the above-mentioned fibers, whereby the fibers are entangled with each other, and then heat-treated so that the area shrinkage of the fiber web becomes 10% or less. It is desirable that the latent crimpable conjugate fiber be formed into a non-woven fabric in which a three-dimensional crimp is developed and the fibers are thermally bonded to each other by a low melting point component. In general, when a latently crimpable conjugate fiber is used, the area shrinkage of the fibrous web after the heat treatment becomes large, but by reducing the area shrinkage, a uniform nonwoven fabric with a low basis weight can be obtained.

In the above-mentioned heat-bonded nonwoven fabric, the latently crimpable conjugate fiber is free from Tm−15 ≦ T <Tm (Tm
Is desirably a material which has a property of exhibiting a three-dimensional crimp of 30 pieces / inch or more when heated at a heat treatment temperature (T ° C.) of the low melting point component of the latently crimpable conjugate fiber. If the degree of crimping is small, the effect intended by the present invention cannot be obtained.

The latently crimpable conjugate fiber is an eccentric core-sheath having an ethylene-propylene copolymer as a first component, polypropylene as a second component, a first component as a sheath component, and a second component as a core component. It is desirable that the composite fiber be a type composite fiber or a composite fiber in which both components are joined in a side-by-side type. This fiber has a high crimpability. Further, heat treatment can be performed at a relatively low temperature.

[0010] In the heat-bonded nonwoven fabric, the non-heat-bondable fiber is desirably rayon fiber. Rayon fibers impart excellent flexibility and feel to the nonwoven.

A preferred method for producing the heat-bonded nonwoven fabric is as follows:
After subjecting the fibrous web composed of the latently crimpable conjugate fiber 20 to 50% by weight and the non-heat-adhesive fiber 80 to 50% by weight to high-pressure water flow treatment to entangle the fibers, the latently crimpable conjugate fiber A heat treatment is performed at a temperature higher than the temperature at which the low melting point component softens and lower than the melting point of the other components of the latently crimpable conjugate fiber so that the heat shrinkage of the fiber web becomes 10% or less. This is a method in which a three-dimensional crimp is developed in the conductive conjugate fiber and the fibers are thermally bonded together with a low melting point component. By performing a heat treatment so that the thermal shrinkage of the fiber web is 10% or less, a uniform nonwoven fabric with a low basis weight can be obtained, and the process control becomes easy. Hereinafter, the contents of the present invention will be described.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The latently crimpable conjugate fiber used in the present invention is a fiber composed of two or more different components and which develops a three-dimensional crimp when heat-treated in the state of a fibrous web or nonwoven fabric. . Here, the “three-dimensional crimp” refers to FIGS.
As shown in FIG. 3, not only a spiral crimp but also a two-dimensional bend with a gentle curve, or a three-dimensional bend with a two-dimensional bend And is a word used to distinguish it from a mechanical crimp given by a crimper or the like.

The latently crimpable conjugate fiber was heated in a free state at a heat treatment temperature (T ° C.) of Tm−15 ≦ T <Tm (Tm is the melting point of the low melting point component of the latently crimpable conjugate fiber). Sometimes it is desirable to have a property of expressing a three-dimensional crimp of 30 pieces / inch or more. A more preferable latent crimpable conjugate fiber is one that exhibits a three-dimensional crimp of 30 to 60 pieces / inch. Here, "heating in a free state" means heating in a state in which the fibers are not restrained, not in a state in which the fiber web is formed, and Tm is a melting point of the low melting point resin before fiberization. Point to. The melting point is represented by a melting peak temperature measured using a differential scanning calorimeter (DSC). A fiber having a small crimp ability is no different from the case of using a normal heat-adhesive fiber, and the object of the present invention cannot be achieved.

[0014] Latent crimpable conjugate fibers are often used for imparting elasticity to a nonwoven fabric, and various types are already known. In the present invention, a conventionally known latently crimpable conjugate fiber can be arbitrarily used.
However, in the present invention, since the latently crimpable conjugate fiber functions as a heat-adhesive fiber, at least one component constituting the fiber must be softened or melted by heat to bond the fibers.

Therefore, the latently crimpable conjugate fiber used in the present invention comprises a first component which is a high melting point component and a second component which is a low melting point component, wherein the first component is a core component and the second component is a second component. It is preferable that the core-sheath composite fiber having an eccentric core and a composite fiber in which both components are joined in a side-by-side configuration.

As the combination of the first component and the second component, ethylene-propylene copolymer / polypropylene,
Ethylene-butene-1-propylene terpolymer / polypropylene, high density polyethylene / polyethylene terephthalate, high density polyethylene / polybutylene terephthalate, polyethylene terephthalate / modified polyester, polypropylene / polyethylene, polyolefin /
Polyamide and the like can be mentioned.

In particular, the latently crimpable conjugate fiber composed of a combination of ethylene-propylene copolymer / polypropylene or ethylene-butene-1-propylene terpolymer / polypropylene has a relatively low temperature (130 ° C. to 1 ° C.).
(45 ° C.), and is preferably used because it has high crimpability.

The ratio of the latently crimpable conjugate fiber to the nonwoven fabric is desirably 20% by weight or more and 50% by weight or less. If the amount is less than 20% by weight, the strength of the nonwoven fabric is reduced. 5
If the content exceeds 0% by weight, not only the flexibility and touch feeling of the nonwoven fabric are reduced, but also the area shrinkage of the nonwoven fabric after the heat treatment due to the development of three-dimensional crimp becomes large.

The nonwoven fabric of the present invention comprises a latently crimpable conjugate fiber and a non-heat-adhesive fiber. Here, the non-heat-bonding fiber is
A fiber that does not substantially soften or melt when subjected to the heat treatment described below and does not exhibit thermal adhesion. In the present invention, it is used to improve the feel and water absorption of the nonwoven fabric. The material is not particularly limited as long as this condition is satisfied. Regenerated fibers such as rayon, natural fibers such as cotton and wool, semi-synthetic fibers such as acetate, polyamide fibers such as nylon 6, nylon 66, polyethylene terephthalate, and poly One or more selected from polyester fibers such as butylene terephthalate and polyolefin fibers such as polyethylene and polypropylene may be used.

Among them, rayon fiber improves the feel of the nonwoven fabric.
It is preferably used when it touches the human body. Further, if a nonwoven fabric containing rayon fibers is used for the backsheet (outermost layer) of the diaper, a diaper that is comfortable to the mother and caregiver can be provided. If hydrophilic fibers such as rayon fibers and cotton are used, water absorption is imparted to the nonwoven fabric, so that a nonwoven fabric suitable for wet tissues and wipers can be obtained.

The nonwoven fabric composed of the latent crimpable conjugate fiber composed of the above-described ethylene-propylene copolymer / polypropylene combination and rayon fiber exhibits high heat sealing strength when they are heat-sealed to each other. Although the reason is not clear, it is considered that both fibers are likely to adhere to each other particularly under heat and pressure for some reason.

The ratio of the non-thermo-bonding fiber to the nonwoven fabric is as follows:
It is desirable that the content be 50% by weight or more and 80% by weight or less. If the content is less than 50% by weight, the softness and feel of the nonwoven fabric are reduced, and the content is 80% by weight.
If it exceeds, the strength of the nonwoven fabric is reduced.

The fineness and fiber length of both the latently crimpable conjugate fiber and the non-heat-bondable fiber described above can be arbitrarily selected according to the finally obtained nonwoven fabric.
When the fibers are entangled by the high-pressure water flow treatment as described below, the fineness is 1 to 6 denier and the fiber length is 38 to
Desirably, it is 64 mm.

Next, the structure of the nonwoven fabric of the present invention will be described together with the method for producing the nonwoven fabric. Although the nonwoven fabric of the present invention is formed by entanglement of the constituent fibers, it is necessary to mix fibers to be used and to form a fibrous web in advance before entanglement of the fibers. The form of the web is not particularly limited, and may be any of a parallel web, a cross web, a semi-random web, a random web, and the like. The basis weight of the web can be determined according to the use of the nonwoven fabric to be finally obtained. For example, when the nonwoven fabric of the present invention is used as a diaper backsheet, a wet tissue, or a wiper, it is preferable that the nonwoven fabric be 20 to 50 g / m ² .

The fibers can be entangled by needle punching or high-pressure water flow treatment. In the present invention, it is desirable to employ high-pressure water flow treatment. According to the high-pressure water flow treatment, a nonwoven fabric which is flexible and has a good touch can be obtained. High-pressure water flow treatment is also suitable for treating low-weight fiber webs.

The high-pressure water flow treatment may be performed by any known method, and the conditions may be set according to the basis weight of the fiber web. For example, when treating a fibrous web having a basis weight of 20 to 50 g / m ² , a pore size of 0.05 to 0.5
A columnar water stream having a water pressure of 20 to 80 kg / cm ² may be sprayed from the front and back sides of the web one to four times from nozzles provided with 0.5 mm orifices at intervals of 0.5 to 1.5 mm.

After the fibers are entangled with each other, a heat treatment is applied to soften or melt the low melting point component of the latently crimpable conjugate fiber, and at the same time, develop the three-dimensional crimp in the latently crimpable conjugate fiber. The heat treatment temperature is higher than the temperature at which the low melting point component of the latently crimpable fiber softens or melts, and lower than the temperature at which the other components of the latently crimpable fiber, that is, components other than the low melting point component, melt. Further, when a fiber made of a thermoplastic resin is used as the non-thermo-bonding fiber, it is necessary to perform the treatment at a temperature lower than the temperature at which the non-thermo-bonding fiber melts. Even when such a condition is satisfied, if the heat treatment temperature is too high, three-dimensional crimping proceeds excessively, and the area shrinkage of the nonwoven fabric increases. On the other hand, when the heat treatment temperature is lower than the temperature at which the low melting point component is softened, only the three-dimensional crimp is developed and the heat bonding is not performed, and the strength of the nonwoven fabric is reduced.

Further, it is important in the present invention to suppress the area shrinkage of the nonwoven fabric which occurs during the heat treatment.
Since the area shrinkage is caused by the appearance of the three-dimensional crimp, a certain degree of shrinkage inevitably occurs also in the present invention. However, if it is too large, it is necessary to determine the basis weight of the web in consideration of the area shrinkage, so that the process management becomes complicated. Also, when producing a nonwoven fabric having a low basis weight, a web having a fairly low basis weight must be prepared. However, the lower the web weight, the less uniform the web becomes and the resulting nonwoven fabric also becomes less uniform. Therefore, it is desirable to avoid setting the web weight low. Therefore, in the present invention, it is desirable to perform the heat treatment under the condition that the area shrinkage of the nonwoven fabric after the heat treatment is 10% or less.

In order to satisfy this condition, it is necessary to set the temperature, time and the like according to the type of the latently crimpable conjugate fiber. For example, when using the latent crimpable conjugate fiber composed of the above-mentioned ethylene-propylene copolymer / polypropylene, it is preferable to use a hot air penetration type drier at a heat treatment temperature of 130 to 145 ° C for 5 to 20 seconds.

The thus obtained nonwoven fabric of the present invention is a non-woven fabric in which latently crimped conjugate fibers exhibit three-dimensional crimp, and the fibers are thermally bonded to each other by the low melting point component of the latently crimpable conjugate fibers. is there. This nonwoven fabric has sufficient strength to withstand practical use, and exhibits excellent flexibility and touch.
In addition, even when the proportion of the latently crimpable conjugate fiber is increased,
The degree of decrease in flexibility and tactile sensation is smaller than in the case of using normal heat-adhesive conjugate fibers.

Further, the non-woven fabric of the present invention has an advantage that the fluff is reduced compared to a non-woven fabric mixed with ordinary thermo-adhesive conjugate fibers. Although the reason is not clear, it is presumed that the three-dimensional crimp on the surface of the nonwoven fabric contributes in some way to preventing fluff.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described with reference to embodiments. The properties of the obtained heat-bonded nonwoven fabric were evaluated by the following methods.

(1) Thickness: thickness measuring machine (trade name: THICKN
Using an ESS GAUGE model CR-60A (manufactured by Daiei Kagaku Seiki Seisaku-Sho, Ltd.), the measurement was performed with a load of 3 g / cm ² applied to the nonwoven fabric. (2) Strength, elongation: width 5c according to JIS L1096
m, a sample with a length of 15 cm is gripped at a spacing of 10 cm, and is stretched at a speed of 30 cm / min using a constant-speed stretching type tensile tester. did. (3) Area shrinkage after heat treatment: A square frame of 20 cm × 20 cm is placed on the surface of the non-woven fabric before heat treatment, and a mark corresponding to the midpoint of each side is marked. Then, after the heat treatment, the midpoints facing each other are connected by a line, and the heat treatment is performed to calculate the area of the rectangle assuming that the square has become a rectangle in which the line is vertical and horizontal, and the area shrinkage rate (%) = ｛(40
The area shrinkage was determined from the equation: 0−area of rectangle (cm ² )) / 400 ° × 100. (4) Bending length (flexibility): Cantilever method (JIS
L 1096.6.9.1A method). (5) Tactile sensation: A sensory test was conducted by 10 panelists. Three, two, and one points were assigned in the order of good tactile sensation, and the points with the highest total score were represented by ○, Δ, and ×. (6) Fluff removal: A sample was attached to a jig of a flooring wiper mop having a wiping surface of 11 cm x 26 cm, and the width was 3 mm.
It was reciprocated 30 times on a plain fabric (33 mesh / 25 mm) of a polyester monofilament 2 cm long and 92 cm long. After the reciprocating motion, a 2 cm wide and 10 cm long mending tape (manufactured by Sumitomo 3M Limited) was applied to the center of the friction surface of the sample, and a 500 g weight was passed twice over it. The mending tape was peeled off and affixed to black paper, and the degree of fluff removal was visually observed. (7) Heat seal strength: Two samples of 20 cm width and 10 cm length are stacked and bonded at 1 cm from the top at a heat seal width of 2 mm, a heating temperature of 140 ° C., a pressure of 2 kg / cm ² , and a heat seal time of 1 second. I let it. This is cut to a width of 3 cm so that the heat-sealed portion is in the width direction. The cut sample is gripped at a grip interval of 10 cm so that the heat-sealed portion is located at the center, and pulled at a speed of 30 cm / min using a constant-speed elongation type tensile tester. did.

Example 1 As a latently crimpable conjugate fiber,
An eccentric core-sheath composite fiber having a fineness of 2 denier and a fiber length of 51 mm (trade name: CPP, Daiwa Spinning Co., Ltd.) having an ethylene-propylene copolymer having a melting point of 142 ° C. as a sheath component and polypropylene having a melting point of 162 ° C. as a core component. )) Was prepared. The fibers exhibited a three-dimensional crimp of 40 pieces / inch within 12 seconds when freely placed in an atmosphere at 130 ° C.

40% by weight of the latent crimpable conjugate fiber and 60% by weight of rayon fiber (trade name: Corona Daiwabo Rayon Co., Ltd.) having a denier of 1.5 denier and a fiber length of 40 mm.
And 35 g / m ² using a parallel card.
A fiber web was prepared.

Next, an orifice having a hole diameter of 0.12 mm is used.
From a nozzle provided at 6mm intervals, on the surface side of the fibrous web columnar water flow pressure ^{40kg / cm 2, 60kg / cm} 2 was injected twice, on the back side of the fibrous web columnar water flow pressure 40 kg / cm ² One time, a columnar water stream with a water pressure of 50 kg / cm ² was jetted twice to entangle the fibers.

Subsequently, this is subjected to a heat treatment to cause the latently crimpable conjugate fiber to exhibit three-dimensional crimp, and at the same time, soften the ethylene-propylene copolymer of the latently crimpable conjugate fiber to bond the fibers to each other. An adhesive nonwoven was obtained. Heat treatment is 13
This was performed for 12 seconds in a hot air penetration type dryer set at 5 ° C.

Comparative Example 1 A heat-bonded nonwoven fabric was obtained in exactly the same manner as in Example 1, except that the proportion of the latent crimpable conjugate fiber was 60% by weight and the proportion of the rayon fiber was 40% by weight.

Comparative Example 2 A core-sheath type composite fiber having a fineness of 2 denier and a fiber length of 51 mm (trade name: NBF (H ) (Manufactured by Daiwa Spinning Co., Ltd.) was prepared as a heat-adhesive fiber. Then, 40% by weight of the heat-adhesive fiber and 60% by weight of the same rayon fiber used in Example 1 were mixed, and a heat-bonded nonwoven fabric was obtained in exactly the same manner as in Example 1.

Table 1 shows the physical properties of the heat-bonded nonwoven fabric obtained in Example 1 and Comparative Examples 1 and 2, and Table 2 shows the heat seal strength of Example 1 and Comparative Example 2.

[0041]

[Table 1]

[0042]

[Table 2]

The nonwoven fabric of Example 1 is superior in flexibility and touch to each of the comparative examples, and has less fluff. Although the strength is rather small, it is enough for practical use. In addition, the area shrinkage rate of Example 1 is 10% or less. The fiber of Comparative Example 1 has a small amount of fluff, but is slightly inferior in flexibility and has a high area shrinkage due to a large proportion of the latently crimpable conjugate fiber. Comparative Example 2 was inferior in flexibility, tactile sensation, and fluff removal. In Comparative Example 2, although the nonwoven fabric strength was high, the heat seal strength was smaller than that in Example 1.

[0044]

The heat-bonded nonwoven fabric according to the present invention comprises 20 to 50% by weight of a latently crimpable conjugate fiber exhibiting three-dimensional crimp and 80 to 50% by weight of a non-heat-bondable fiber. Wherein the fibers are thermally bonded to each other by a low melting point component of the latently crimpable conjugate fiber. By using a latently crimpable conjugate fiber as the heat-adhesive fiber, excellent flexibility and tactile sensation are imparted to the nonwoven fabric, and fluff is prevented. Further, by suppressing the shrinkage of the nonwoven fabric caused by the appearance of crimp during the heat treatment to a certain rate or less, it becomes possible to obtain a nonwoven fabric having a low basis weight. Due to such properties, the heat-bonded nonwoven fabric of the present invention can be advantageously used as a diaper top sheet, back sheet, wet tissue, wiper, and the like.

[Brief description of the drawings]

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

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

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

Claims (8)

[Claims] Claims 1. A latently crimpable conjugate fiber exhibiting a three-dimensional crimp, 20 to 50% by weight, and a non-heat-adhesive fiber, 80 to 50% by weight.
In a non-woven fabric consisting of fibers entangled with each other,
A thermally bonded nonwoven fabric, wherein the fibers are thermally bonded to each other by a low melting point component of the latently crimpable conjugate fiber. 2. A latently crimpable conjugate fiber of 20 to 50% by weight.
And a fibrous web consisting of 80 to 50% by weight of the non-heat-adhesive fiber is subjected to a mechanical entanglement treatment so that the fibers are entangled and integrated, and then subjected to a heat treatment to give a three-dimensionally crimped conjugate fiber. A nonwoven fabric in which fibers are thermally bonded to each other with a low melting point component of a latently crimpable conjugate fiber at the same time as exhibiting crimping, wherein the heat treatment is performed so that the area shrinkage of the fiber web is 10% or less. A heat-bonded non-woven fabric. 3. The latently crimpable conjugate fiber is freely T
When heated at a heat treatment temperature (T ° C.) of m−15 ≦ T <Tm (Tm is the melting point of the low melting point component of the latently crimpable conjugate fiber), a three-dimensional crimp of 30 / inch or more is developed. The heat-bonded nonwoven fabric according to claim 1 or 2, which is a fiber having properties. 4. An eccentric core comprising a latent crimpable conjugate fiber comprising an ethylene-propylene copolymer as a first component, polypropylene as a second component, a first component as a sheath component, and a second component as a core component. The heat-bonded nonwoven fabric according to claim 3, which is a sheath-type composite fiber or a composite fiber in which both components are joined in a side-by-side type. 5. The heat-bonded nonwoven fabric according to claim 1, wherein the non-heat-bondable fiber is rayon fiber. 6. The heat-bonded nonwoven fabric according to claim 1, wherein the mechanical entanglement treatment is a high-pressure water flow treatment. 7. The heat-bonded nonwoven fabric according to claim 1, wherein the basis weight is 20 to 50 g / m ² . 8. A latently crimpable conjugate fiber of 20 to 50% by weight.
And after applying a high-pressure water-flow treatment to a fibrous web composed of 80 to 50% by weight of the non-heat-adhesive fibers to entangle the fibers,
At a temperature higher than the temperature at which the low melting point component of the latently crimpable conjugate fiber softens and lower than the melting point of the other components of the latently crimpable conjugate fiber, the heat shrinkage of the fiber web is 10% or less. A method for producing a heat-bonded nonwoven fabric, comprising heat-treating a latently-crimpable conjugate fiber to develop a three-dimensional crimp and simultaneously heat-bonding the fibers by a low-melting-point component.