JP2001123320A - Crimped fiber, fiber aggregate, web and absorbing article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide crimped fibers that a multi-layered film used as a raw material for the crimped fibers has had good interlayer adhesivity, good orientation property and high crimpability, and has not dusted, when slit into the fibers. SOLUTION: This invention relates to crimped fibers obtained by orienting a multi-layered film and then slitting the oriented film into the fibers. The multi-layered film comprises resins which form adjacent layers and comprise substantially the same systems of resins only whose physical properties such as MFRs, densities and melting points are different from each other. The crimped fibers can be used for fiber aggregates, webs, and absorbing articles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crimped fiber using a defibrated fiber obtained by defibrating a synthetic resin multilayer film, and a defibrated fiber aggregate for use in webs, absorbent articles and the like.

[0002]

2. Description of the Related Art It is known that fibers obtained by combining at least two kinds of synthetic resins having different properties, so-called composite fibers, have crimpability. As one of the methods for producing this composite fiber, conventionally, a composite synthetic resin film composed of two layers of raw materials having two different properties, for example, polypropylene and polyethylene, is drawn and slit to prepare a drawn tape. There has been a method of producing a conjugate fiber from a defibrated fiber obtained by defibrating a drawn tape (Japanese Patent Laid-Open No. 62-1).
No. 49905).

Further, as a composite synthetic resin film used for producing a defibrated fiber, Japanese Patent Application Laid-Open No. 1-2221507 (Japanese Patent No. 2613614) discloses a film of polypropylene 70-1 having a melt index of 0.5-10. Polyethylene 5 with 95% by weight and a melt index of 0.5 to 20
A polyethylene layer having a melt index of 0.5 to 20 and a polyethylene having a melt index of 0.5 to 20 and a melt index of 0.5 to 1.
Using a composite synthetic resin film, which is a polyethylene layer obtained by mixing 5 to 30% by weight of polypropylene with 0, and then slitting and stretching, or stretching and slitting to form a stretched tape, Is shown to obtain a defibrated fiber.

Japanese Patent Application Laid-Open No. Hei 8-267629 discloses a composite synthetic resin film used for producing a defibrated fiber. 40 to 95 parts by weight of a defibrated fiber (A) obtained by defibrating a composite resin film having a low-melting resin layer containing a thermoplastic resin having a melting point as a main component;
A dry nonwoven fabric containing 60 to 5 parts by weight of a fiber (B) made of a resin having a higher melting point than a polypropylene resin has been proposed.

However, the defibrated fiber obtained by defibrating a conventionally known composite synthetic resin film has a problem that delamination is apt to occur, and the composite synthetic resin film is liable to peel when stretched. There is a problem, for example, in a composite synthetic resin film composed of a polypropylene layer and a polyethylene layer, there is a problem that the polyethylene falls off at the time of defibration to cause so-called powder drop.

JP-A-3-220308 (Japanese Patent No. 2828757) describes a defibrated fiber obtained by defibrating a three-layer film of polyethylene layer / polypropylene layer / polyethylene layer and a defibrated fiber aggregate thereof. Have been. The defibrated fiber is mixed with pulp or the like in a diaper absorbent and heat-treated, for example, and is used to maintain the shape even after the diaper absorbent is wet. in this case,
The quality of the dispersibility when mixing the defibrated fibers with the pulp is important. Poor dispersibility may make it difficult to control the diaper's absorption capacity and shape retention.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems associated with the prior art described above, and to improve the interlayer adhesion of a multilayer film, improve the stretchability, and improve the powder quality during defibration. A crimped fiber having high crimpability without dropping is provided. In addition, a mesh-like fibrillated fiber aggregate using this crimped fiber is used as a sheet to improve the water absorption capacity required for a member of an absorbent article, and has a good shape retention and a good cushioning property during use. I will provide a.

[0008]

That is, the present invention is directed to a multilayer film composed of substantially the same resin except that the resins forming adjacent layers differ only in their physical properties. And crimped fibers obtained by defibration.

The resin forming the one layer may be a blended resin containing 3 to 49% by weight of a main component resin of the resin of the adjacent other layer.

It is desirable that the above-mentioned different physical properties are differences in MFR. As a preferred embodiment, when two adjacent layers are an A layer and a B layer, and the MFR values of the resins forming these layers are MFR (a) and MFR (b), respectively, the MFR of each layer is in the following range. It is in. (1 / 1.5) × MFR (b) <MFR (a) <
1.5 x MFR (b)

[0011] An intermediate layer made of an adhesive resin may be further provided between adjacent layers of the multilayer film. Even if the intermediate layer is a blend resin obtained by blending the resins of both adjacent layers, or at least one selected from the group consisting of an SBS resin, an EVA resin, and a petroleum resin is added to the blend resin. May be added.

[0012] The present invention also relates to a fibrillated fiber aggregate comprising the above-mentioned crimped fiber, and an absorbent article comprising the fibrous fiber aggregate. Further, the present invention relates to a web obtained by widening the crimped fiber tow, and an absorbent article comprising the web.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to manufacture the crimped fiber according to the present invention, first, a resin for forming adjacent layers is made of a multilayer film composed of substantially the same resin except for the physical properties thereof. Prepare The multilayer film used in the present invention is composed of at least two layers, which will be described below.

As the resin forming the adjacent layers constituting the multilayer film of the present invention, substantially the same resin is used except that the physical properties are different from each other. Here, the physical properties of the resin include melt flow rate (MFR), melting point, density, crystallinity, molecular weight distribution, degree of branching, and the like. Among them, it is preferable to change the MFR.

In the present invention, the resin forming each layer is a resin of substantially the same system, wherein all resins in each layer are polymers of the same monomer such as polyethylene, and have MFR, melting point, This means that only the physical properties selected from the density, crystallinity, branching degree, molecular weight, and the like are different in the resin of each adjacent layer. Further, by describing ethylene as an example of an olefin, a copolymer of ethylene and an α-olefin using ethylene as a main monomer component and an α-olefin other than ethylene as a subcomponent is also used in the present invention. The polyethylene and the copolymer are treated as being in the same resin. Here, this copolymer also includes various kinds of resins having different physical properties such as MFR and melting point, and in the present invention, these resins are also assumed to be in the same resin.

Regarding the handling of the same resin as defined in the present invention, polyolefins such as polypropylene, polybutene and poly-4-methyl-1-pentene other than polyethylene are also used in the case of the polyethylene specifically shown above. Is the same as described above.

Regarding handling as the same resin,
Further, a copolymer of ethylene and α-olefin such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or propylene and ethylene, 1-butene, 1-pentene, 1-hexene, Α such as octene
Like the copolymer with an olefin, the case of a copolymer of an α-olefin and another α-olefin is the same as described for the case of polyethylene specifically shown above.

Further, polyethylene terephthalate (PE)
The same applies to polyesters such as T).

More specifically, the resin of the same type used in the present invention is, for example, a multilayer film having two or more layers composed of two kinds of resins, resin A and resin B. The types or combinations will be described below.

In the following description, the layer composed of resin A is represented as layer A, and the layer composed of resin B is represented as layer B. When the multilayer film is a two-layer film, it has an A layer / B layer, and when it is a three-layer film, it has a layer structure such as A layer / B layer / A layer. In the lower layer, a layer having a different layer thickness can be considered.

(1) Examples of combinations of the same resin when the resin of each layer is polyethylene:

(2) Examples of the combination of the same resin when the resin of each layer is a copolymer of polypropylene or propylene and another α-olefin (random or block copolymer):

The preparation of the above-mentioned multilayer film according to the present invention can be carried out according to a conventional method, and there is no particular limitation.
For example, it can be produced according to a melt extrusion method such as inflation extrusion molding, extrusion molding using a T-die, a calendering method, a casting method and the like.

In the present invention, if necessary, an intermediate layer made of an adhesive resin may be provided between the layers of the multilayer film. As the adhesive resin in this case, a resin having rubber-like properties or tackiness such as SBS resin, EVA resin, or petroleum resin is used as a blend resin obtained by blending the resins of adjacent layers. The added blend resin can be illustrated.

In order to produce a defibrated fiber from the multilayer film, the multilayer film is subjected to slitting and then stretched, or stretched and then slit to form a stretched tape and then defibrated. Slit processing is a process of cutting a multilayer film into a thin band shape using a device such as a cutter.

The stretching of the multilayer film can be carried out according to a conventional method such as a method using a nip roll, a clover roll or the like, or a continuous stretching method using an air oven, a hot plate or the like. This stretching is usually performed at a temperature of about 90 to 150 ° C.,
The stretching is performed at a draw ratio of about 0 times.

In the present invention, the drawn tape obtained by drawing and slitting can be defibrated to form a defibrated fiber having a fine network structure. This defibration treatment can be performed by a porcupine machine having a knife edge formed in a sawtooth shape or a roll having a needle implanted on the outer peripheral surface. Moreover, the obtained defibrated fiber can be cut to a required length as required.

In the present invention, as described above, the crimped fiber of the present invention is produced by defibrating a stretched film of a multilayer film composed of substantially the same resin. FIG. 1 shows a schematic diagram of a process for producing a compressed fiber.

The crimped fiber obtained by defibrating the multilayer film of the present invention usually has a crimp ratio of 40 to 75%. Here, the crimp rate is a value defined by the following.

Crimp ratio: A fiber sample obtained by defibrating a multilayer film immediately after molding is cut into 1 m lengths, and an initial load (0.18 mN × tex (2 mgf × display denier)) is applied to the sample. And the length (bmm) when a load (4.41 mN × tex (50 mgf × display denier)) is applied thereto is measured. Next, remove all loads, leave for 2 minutes, apply initial load, read length,
The crimp rate (%) of the fiber is calculated by the following equation. The number of tests is 20 times, and the average value is obtained. Crimp rate (%) = {(ba) / b} × 100

Usually, the thickness of the crimped fiber of the opened fiber according to the present invention usually comprises a trunk fiber having a fineness of about 6,000 to 10,000 denier and a branch fiber having a fineness of 0.5 denier or less. In addition, the defibrated fiber usually has a fibril structure having a fine network structure while having a stem fiber and a branch fiber.

In the present invention, using the crimped defibrated fiber, a defibrated fiber aggregate is prepared, and from this, industrial products such as disposable diapers, absorbents for napkins and sanitary materials for second sheets, cloths, wipers, oil-absorbing materials, etc. Materials and absorbent articles can be manufactured.

Further, in the present invention, a web obtained by widening a tow of a crimped defibrated yarn obtained by defibrating a stretched film of a multilayer film is used to form a sanitary material for a paper diaper, an absorbent for a napkin or a second sheet, a cloth, Industrial materials such as wipers and oil-adsorbing materials, and absorbent articles can be manufactured.

[0034]

The present invention will be described below with reference to examples. The melt flow rate (MFR) was measured using ASTM D1238 for polyethylene, 190 ° C., 2.16 kg load, and ASTM D for polypropylene.
It is a value measured under the conditions of 1238, 230 ° C., and a load of 2.16 kg.

The crimped fiber of the present invention can be prepared by, for example, an extrusion / film-forming step 1, a drawing step 2, a defibration step 3, and a winding step 4 shown in FIG.
In each of the following examples of the present invention, an inflation film composed of two layers, an outer layer and an inner layer, is prepared by an inflation method using two kinds of the same resin shown in Table 1, and The crimped fibers obtained by defibrating this film were evaluated. Here, with respect to the two-layer film obtained by the inflation method, the inner layer is formed into a bag-like shape, inflated and extruded.
Refers to the inner layer of the layer film bag. The outer layer refers to the outer layer of the bag. Next, each step of FIG. 1 will be described.

<Extrusion / Film Forming Step 1> An extruder 11 (cylinder inner diameter 65 mm) for supplying a resin forming the inner layer side,
Another extruder (cylinder inner diameter 65 mm) for supplying the resin forming the outer layer side, and an annular two-layer die (die inner diameter 3
00 mm), a resin having a low MFR is supplied to the inner layer side, and a resin having a high MFR is supplied to the outer layer side. The cylindrical molten film extruded from the annular die is cooled by an air ring. The tube in which the inside of the bag-like inflation film 51 is pressurized with air is then pressed by the pinch roll 13 and taken off.

<Stretching Step 2> Slitter 21: Metal or ceramic cutter blade or blue blade. Heating device 23: A shape formed by combining a pair of upper and lower metal-made bumpers, and is heated through steam therein. The surface is coated with a fluororesin in the flow direction so that the slit film can be easily stretched. Tube 5 folded by pinch roll 13
2 is slit at a certain interval using a slitter 21, and is fed through a feed roll 22 to a stretching roll 24 along the surface of a heating device 23. At this time, when two films are stacked, the heating device 23 is placed on the upper surface. The heating device 23 can heat the film to an arbitrary temperature using steam. In the present embodiment, the heating temperature was 120 to 125 ° C. The stretching ratio is determined by the speed ratio between the feed roll 22 and the stretching roll 24.

<Fibrillation Step 3> Fibrillation cutter 31: A roll having a shape in which a number of special metal needles are embedded in a metal shaft was used. Stretching roll 2
4 and film 53 stretched by F (Fiu) roll 32
And defibrate through the defibration cutter 31.
The defibration state is determined by adjusting the installation depth and the rotation speed of the defibration cutter 31. If the assembling depth is too deep, defibration occurs, and if it is shallow, it becomes unfibrillated. On the other hand, if the rotation speed is high, the needle does not bite into the stretched film 53 and the fiber is not defibrated.

<Winding Step 4> The defibrated yarn 54 or tow coming out of the F (fiu) roll 32 is pinched by the final roll 41, applied to a winder 42, and wound into a paper tube and a coil by traverse to produce a product. .

Example 1 Experiment No. 1 in Table 1 1,2,3
A film made of a propylene homopolymer (abbreviated as h-PP) having an MFR of 0.5 g / 10 min was used as an inner layer,
R is 2.4 g / 10 min propylene homopolymer (h-
As shown in Table 1, the thickness of the inner layer / outer layer (μm)
= 20/20, 30/10, 10/30 for two layers of blown film, stretching temperature 120 ° C
The film was stretched under the conditions of two-stage stretching shown in Table 1. Next, the stretched multilayer film was defibrated with a film slit width of 75 mm, and the resulting defibrated fibers were evaluated for crimping effect and the like. The results are shown in Table 1.

<Evaluation of Fibrillation> Evaluation was made by the following method. The defibrated tow was visually and surface photographed to observe the stem and branches of the defibrated yarn and evaluated by the following method. The symbols ◎, △, and Δ shown in Table 1 mean the following contents. The thickness (diameter) of the stem portion of the defibrated yarn is d1, and the thickness (diameter) of the branch portion is d2.
◎: a defibrated yarn comprising a fiber having a ratio of d1 / d2 of 3 to 7 and a trunk portion thicker than that of a branch ○: a ratio of d1 / d2 of approximately 1 and a fiber of a branch and a trunk portion Defibrated yarn consisting of fibers having the same thickness of △: defibrated yarn having a ratio of d1 / d2 of about 1 or less

<Evaluation of crimpability> A sample of the defibrated fiber was measured according to the crimping ratio measuring method described above, and evaluated by the following method. The symbols ◎, △, Δ, and X shown in Table 1 mean the following contents. ◎: Crimp rate of 65% or more ：: Crimp rate of 60 to 65% △: Crimp rate of 45 to 60% X: Crimp rate of 45% or less

<Evaluation of Interlayer Adhesion> The interlayer adhesion of the multilayer film was evaluated by measuring the interlayer adhesion by a 180 ° peel test according to JIS K6781. ◎ shown in Table 1,
The symbols ○, Δ, and X mean the following contents. ◎: Interlayer adhesive strength of 500 g / 25 mm width or more ：: Interlayer adhesive strength of 300 to 500 g / 25 mm width. C: Interlayer adhesive strength of 150 to 300 g / 25 mm width. X: Those having an interlayer adhesion of 150 g / 25 mm width or less.

Example 2 Experiment No. 1 in Table 1 For 4 and 5
A film composed of a propylene homopolymer (h-PP) having an MFR of 0.5 g / 10 min is used as an inner layer, and a film composed of a propylene and ethylene block polymer (b-PP) having an MFR of 5.0 g / 10 min. With the film as the outer layer, as shown in Table 1, the thickness of the inner layer and the outer layer was as shown in Table 1, and the thickness (μm) of the inner layer / outer layer was changed to 20/20, 30/10. The film was stretched at 2 ° C. under the conditions of two-stage stretching shown in Table 1. Next, the stretched multilayer film was defibrated with a film slit width of 75 mm, and the resulting defibrated fibers were evaluated for crimping effect and the like. The results are shown in Table 1.

Example 3 Experiment No. 1 in Table 1 For 6,7
A film made of a block copolymer of propylene and ethylene having an MFR of 0.5 g / 10 min (abbreviated as b-PP) is used as an inner layer, and a block copolymer of propylene and ethylene having an MFR of 5.0 g / 10 min. As shown in Table 1, the thickness of the inner layer and the outer layer was as shown in Table 1, and the thickness of the inner layer and the outer layer (μm) was 20/20, 3
With respect to the two-layer and three-layer multilayer film which was changed to 0/10, it was stretched at a stretching temperature of 120 ° C. under the conditions of two-stage stretching shown in Table 1. Next, the stretched multilayer film was defibrated with a film slit width of 75 mm, and the resulting defibrated fibers were evaluated for crimping effect and the like. The results are shown in Table 1.

Example 4 Experiment No. 1 in Table 1 8 and 9
A film made of a propylene homopolymer (h-PP) having an MFR of 0.5 g / 10 min was used as an inner layer, and a propylene homopolymer (h-PP) having an MFR of 6.5 g / 10 min was used.
The thickness of the inner layer / outer layer (μm) =
The two-layer and three-layer multilayer films changed to 20/20 and 30/10 were stretched at a stretching temperature of 120 ° C. under the conditions of two-stage stretching shown in Table 1. Next, the stretched multilayer film was defibrated with a film slit width of 75 mm, and the resulting defibrated fibers were evaluated for crimping effect and the like. The results are shown in Table 1.

Example 5 Experiment No. 1 in Table 1 10,1
A film composed of a propylene homopolymer (h-PP) having an MFR of 2.4 g / 10 min corresponding to 1, 12 was used as an inner layer, and a propylene homopolymer (h-P) having an MFR of 6.5 g / 10 min.
The thickness of the inner layer / outer layer (μm) =
The two-layer and three-layer multilayer films changed to 20/20 and 30/10 were stretched at a stretching temperature of 120 ° C. under the conditions of two-stage stretching shown in Table 1. Next, the stretched multilayer film was defibrated with a film slit width of 75 mm, and the resulting defibrated fibers were evaluated for crimping effect and the like. The results are shown in Table 1.

Example 6 Experiment No. 1 in Table 1 13,14
A film composed of a blend of a propylene homopolymer (h-PP) having an MFR of 0.5 g / 10 min and a high-density polyethylene (HDPE) having an MFR of 13 g / 10 min at a weight ratio of 90/10. With an MFR of 13g
As shown in Table 1, the thickness of the inner layer and the outer layer was 20/20, 3 as shown in Table 1.
With respect to the two-layer and three-layer multilayer film which was changed to 0/10, it was stretched at a stretching temperature of 120 ° C. under the conditions of two-stage stretching shown in Table 1. Next, the stretched multilayer film was defibrated with a film slit width of 75 mm, and the resulting defibrated fibers were evaluated for crimping effect and the like. The results are shown in Table 1.

Example 7 Experiment No. 1 in Table 1 15,1
6 and 17 to the corresponding MFR of 0.7g / 10 minutes of high-density polyethylene (HD
PE) as the inner layer, and the MFR is 1.6 g.
As shown in Table 1, the thickness of the inner layer and the outer layer was 20/20, 3 as shown in Table 1.
The two-layer and three-layer multilayer films, which were changed to 0/10 and 10/30, were stretched at a stretching temperature of 120 ° C. under the conditions of two-stage stretching shown in Table 1. Next, the stretched multilayer film was defibrated with a film slit width of 75 mm, and the resulting defibrated fibers were evaluated for crimping effect and the like. The results are shown in Table 1.

[0050]

[Table 1]

The crimped fiber of the present invention can be obtained by widening multiple lamination,
The defibrated fiber aggregate of the present invention can be obtained by a laminating method such as dating lamination or a processing method such as heat setting, hot embossing, or ultrasonic shielding. Similarly, the web of the present invention can be obtained by widening the tow of the present invention. Furthermore, an absorbent article can be processed from these by a known method.

[0052]

The crimped fiber obtained by defibrating the multilayer film of the present invention has good interlayer adhesion of the multilayer film, has improved stretchability, and has no powder drop during defibration. Is good and has high crimpability. Therefore, the crimped fiber can be used to produce a sanitary material and an absorbent article having more excellent qualities such as flexibility, elastic recovery, absorption performance (absorption speed, rewet, and permanence).

[Brief description of the drawings]

FIG. 1 is a schematic view showing a production process of a crimped fiber according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extrusion and film-forming process 2 Stretching process 3 Fibrillation process 4 Winding process 11 Extruder 12 Die 13 Pinch roll 21 Slitter 22 Feed roll 23 Heating device 24 Stretch roll 31 Fibrillation cutter 32 F roll 41 Final roll 42 Winder 51 blown film 52 folded tube 53 stretched film 54 defibrated yarn

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D01F 6/06 F term (Reference) 4C003 AA16 4G066 AC13B BA03 BA05 BA16 BA25 BA38 BA42 EA05 FA37 4L035 FF08 4L045 AA05 BA36 BA39 BA50 BA55 BA60 BB02 BB12 BB22 DA42

Claims (11)

[Claims] 1. A resin forming adjacent layers is a multilayer film composed of resins of substantially the same system except that the physical properties are different from each other, and a crimp obtained by stretching and fibrillating the multilayer film. fiber. 2. The crimped fiber according to claim 1, wherein the resin forming the one layer contains 3 to 49% by weight of a main component resin of the resin of the adjacent other layer. 3. The crimped fiber according to claim 1, wherein the different physical properties are different in MFR. 4. The multilayer film according to claim 1, wherein
The MFR of each layer is in the following range when the MFR values of the resin forming these layers are MFR (a) and MFR (b), respectively, where the three layers are an A layer and a B layer. The crimped fiber according to any one of the above. (1 / 1.5) × MFR (b) <MFR (a) <
1.5 x MFR (b) 5. The crimped fiber according to claim 1, wherein an intermediate layer made of an adhesive resin is further provided between adjacent layers of the multilayer film. 6. The crimped fiber according to claim 5, wherein the intermediate layer made of the adhesive resin is a blend resin obtained by blending the resins of both adjacent layers. 7. The crimped fiber according to claim 6, wherein at least one resin selected from the group consisting of an SBS resin, an EVA resin and a petroleum resin is further added to the blend resin. 8. A fibrillated fiber aggregate comprising the crimped fiber according to claim 1. 9. An absorbent article comprising the defibrated fiber aggregate according to claim 8. 10. A web obtained by widening the tow of the crimped fiber according to claim 1. 11. An absorbent article comprising the web according to claim 10.