JP2001032139A - Latently crimpable conjugate fiber and nonwoven fabric using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a latently crimpable conjugate fiber capable of providing a bulky nonwoven fabric good in touch feeling and a raw material therefor and good in card passableness. SOLUTION: This latently crimpable conjugate fiber conmprises a polypropylene having >=160 deg.C melting point as a first component and a propylene copolymer having a melting point within the range of 120-147 deg.C as a second component. The first component accounts for >=80% of the fiber surface of the conjugate fiber in (65/35) to (35/65) area ratio of the first component to the second component in the fiber cross section. The center of gravity of the fiber and the center of gravity of the second component are located in different positions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin-based conjugate fiber having latent crimping properties, in which crimps are developed by heat treatment, and a nonwoven fabric using the same.

[0002]

2. Description of the Related Art Conventionally, as one of the techniques for obtaining a bulky nonwoven fabric, a fiber in which a zigzag type crimp is mechanically applied by using a crimping means such as a crimper or a composite form of the fiber is arranged in a parallel type. There has been a method of using an eccentric sheath-core type fiber in which a three-dimensional helical crimp has been imparted by causing strain inside the fiber by means such as stretching.

For example, Japanese Patent Application Laid-Open No. 2-191720 proposes a sheath-core type composite fiber in which an ethylene-propylene random copolymer is mainly arranged as a sheath component and crystalline polypropylene is arranged as a core component. . This is achieved by applying a heat treatment to the web made of the fiber, utilizing the heat shrinkage characteristics of the ethylene-propylene random copolymer used as the sheath component, developing a latent crimp during nonwoven fabric processing, and forming a bulky nonwoven fabric. It is manufactured. However, the metal friction resistance of the ethylene-propylene random copolymer disposed in the sheath component is very high compared to other resins generally used for fibers (for example, high-density polyethylene), so that it is difficult to be discharged from the card machine, There is a problem that it is difficult to obtain a uniform web, and the obtained nonwoven fabric also has a unique slimy feeling and sticky feeling due to the properties of the resin of the sheath component. In addition, when the raw cotton is put into the card machine, in general, a means of opening the fiber mass by a fiber opening machine and transporting the raw cotton to the card machine by a blower pipe is employed,
Fibers having high metal friction resistance have a problem of poor transportability in which cotton adheres to the wall of the blower tube. Furthermore, even when these resins are combined and spun into a composite long fiber by a spun bond method that does not require a carding process, the fiber is opened due to high interfiber friction of the ethylene-propylene random copolymer covering the fiber surface. There was a problem that the fineness was poor and the formation of the web accumulated on the conveyor was disturbed. As described above, up to now, a bulky and well-formed nonwoven fabric using fibers having latent crimpability has not been obtained, but in recent years, with the intensifying competition in the market for disposable diapers and sanitary products, There has been an increasing demand for bulky nonwoven fabrics having a better texture.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a bulky nonwoven fabric having a good texture and a latent crimpable conjugate fiber as a raw material thereof.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found the following means, and have completed the present invention. The present invention has the following configurations. That is, (1) a conjugate fiber having a polypropylene having a melting point of 160 ° C. or higher as a first component and a propylene copolymer having a melting point Tm (° C.) of 120 ≦ Tm (° C.) ≦ 147 as a second component. The first component occupies 80% or more of the surface of the conjugate fiber, the area ratio of the first component to the second component in the fiber cross section is 65/35 to 35/65, and the center of gravity of the conjugate fiber and the A latently crimpable conjugate fiber characterized in that the positions of the centers of gravity of the two component parts are different. (2) The second component of the composite fiber has a propylene content of 90 to 9
The latently crimpable conjugate fiber according to the above (1), which is an ethylene-propylene-butene-1 terpolymer having 8% by weight, ethylene content of 1 to 7% by weight, and butene-1 content of 1 to 5% by weight. (3) The latently crimpable conjugate fiber according to the above (1) or (2), wherein the latently crimpable conjugate fiber is an eccentric sheath-core type conjugate fiber. (4) The above (1) to (1) to wherein the latently crimpable conjugate fiber is a long fiber.
The latently crimpable conjugate fiber according to any one of the above (3). (5) In a web in which the latently crimpable conjugate fiber contains the latently crimpable conjugate fiber, the heat shrinkage in the machine direction of the fiber is 60% or more, and the heat shrinkage in the direction perpendicular thereto is 40% or more. The latently crimpable conjugate fiber according to any one of the above items (1) to (4), comprising: (6) A nonwoven fabric comprising the latently crimpable conjugate fiber according to any one of the above (1) to (5).

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. The first component constituting the latently crimpable conjugate fiber of the present invention
The polypropylene having a melting point of 160 ° C. or more used as a component is a crystalline polypropylene having excellent surface smoothness, and is a copolymer of propylene homopolymer or propylene with a small amount, usually 2% by weight or less, of an α-olefin. It is united. Examples of such polypropylene include crystalline polypropylene obtained from general-purpose Ziegler-Natta catalysts and metallocene catalysts. Among them, from the viewpoint of spinnability and latent crimpability, the Q value (weight average molecular weight / number average molecular weight) measured by the method described below is small, that is, the molecular weight distribution is preferably 4 or less, more preferably 3 or less. Narrow crystalline polypropylene can be suitably used in the present invention. If the effects of the present invention are not significantly impaired, a mixture of these crystalline polypropylenes, a crystalline polypropylene having a different molecular weight distribution, a melt flow rate (MFR), or the like, or another thermoplastic resin may be used as the first component. Those added may be used, or if necessary, inorganic materials such as titanium dioxide, calcium carbonate and magnesium hydroxide, or polypropylene added with a flame retardant, a pigment and other polymers may be used.

As the second component constituting the latently crimpable conjugate fiber of the present invention, the melting point Tm (° C.), which causes heat shrinkage at a relatively low temperature from the viewpoint of processability and has a fiber forming property, is 120 ≦ Tm. A propylene copolymer in the range of (° C.) ≦ 147 is used. Such a propylene copolymer can be obtained by mainly copolymerizing propylene with another α-olefin (including ethylene). Examples of such α-olefins include ethylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, and 4-methyl-pentene-1.
And the like, and two or more of these α-olefins can be used in combination. Specific examples of the propylene copolymer include ethylene-propylene binary copolymer, propylene-butene-1 binary copolymer, ethylene-propylene-butene-1 ternary copolymer, and propylene-hexene-
Examples thereof include 1 binary copolymer, propylene-octene-1 binary copolymer and the like, and a mixture thereof.
These copolymers are usually random copolymers, but may optionally be block copolymers.

Among the propylene copolymers which can be used as the second component of the latently crimpable fiber of the present invention and have a melting point Tm (° C.) within the above-mentioned range, the propylene content is 90 to 90%.
Ethylene-propylene-butene-1 terpolymer having 98% by weight, ethylene content of 1 to 7% by weight and butene-1 content of 1 to 5% by weight, propylene content of 93 to 99% by weight, ethylene content of 1 to 7% by weight % Of an ethylene-propylene binary copolymer is particularly preferred in terms of shrinkage, low-temperature processability, and cost.

Incidentally, a propylene copolymer having a melting point Tm (° C.) of less than 120 ° C. exhibits rubber elasticity, which may adversely affect the card processability of the obtained fiber. When a propylene copolymer having a melting point Tm (° C.) of more than 147 ° C. is used as the second component, the heat shrinkability of the obtained fiber is approximately equal to the heat shrinkage of a fiber comprising a single polypropylene component. Down to Therefore, by setting the melting point of the propylene copolymer in the above-described range, a latently crimpable fiber having both card processability and heat shrinkability can be obtained. In addition, as long as the heat shrinkability of the latently crimpable conjugate fiber of the present invention is not extremely reduced or the heat shrinkage is slightly suppressed, titanium dioxide and calcium carbonate may be added to the second component as necessary. And inorganic substances such as magnesium hydroxide, flame retardants, pigments and other thermoplastic resins may be added.

FIG. 1 is a sectional view of the latently crimpable fiber of the present invention.
3 are shown. In the latently crimpable conjugate fiber of the present invention, the first
The composite form of the component and the second component is configured such that the first component occupies the surface of the composite fiber and the second component is enveloped in the first component, and the center of gravity of the fiber cross section and the center of gravity of the second component are combined. An eccentric sheath-core type structure arranged at different positions is most preferable. This is because, when the conjugate fiber has a concentric structure, even when heat treatment is performed, crimping that can sufficiently express bulkiness does not occur. The arrangement of the eccentric sheath-core type is generally a cross-sectional shape as shown in FIG. 1, but the degree of eccentricity is increased as shown in FIG. Because crimpability can be increased,
If the effect of the present invention is not hindered by the friction of the first component partially exposed on the fiber surface, it can be adopted. In this case, the first component is 80% of the fiber surface.
It is necessary to account for the above. Furthermore, as shown in FIG. 3, even when the cross-sectional shape of the core component is irregular (non-circular), the potential crimpability due to the difference in heat shrinkage can be increased.

Further, in order to impart latent crimpability to the conjugate fiber, the area ratio between the first component and the second component of the conjugate fiber (in the case of a sheath-core conjugate fiber, the fiber is oriented in a direction perpendicular to the axial direction). The area ratio of the sheath component and the core component on the cut surface is 65
/ 35 to 35/65, and 5
More preferably, it is in the range of 5/45 to 45/55. When the ratio of the area of the second component is much less than 35%,
At the time of heat treatment (at the time of shrinkage processing), the shrinkage force generated by the latent crimping property is reduced, and sufficient crimping is not developed in the fiber, so that a bulky nonwoven fabric cannot be obtained. 65%
When the value exceeds a large value, it is difficult to uniformly shrink the nonwoven fabric because the fibers cause excessive shrinkage. In an extreme case, a fiber mass may be generated, and the nonwoven fabric may not be obtained.

The latently crimpable conjugate fiber of the present invention preferably exhibits a heat shrinkage of at least 50% in the machine direction of the fiber (hereinafter abbreviated as MD) when processed into a web. Considering the case of using
60% or more in D, a direction orthogonal to this direction (hereinafter referred to as CD
) Is more preferably 40% or more. If the heat shrinkage in MD is significantly lower than 50%, the bulk of the obtained nonwoven fabric will be low.

As a method for producing the latently crimpable conjugate fiber of the present invention, various known spinning methods such as a melt spinning method, a spun bond method and a melt blow method can be exemplified, and by appropriately using these processing methods, Multifilaments, monofilaments, staple fibers, tows and nonwoven fabrics can be obtained.

When the latently crimpable fiber of the present invention is used as a staple fiber requiring a carding step, an appropriate number of crimps must be provided in order to impart good cardability to the fiber. Must. The number of crimps has an appropriate range depending on the fineness of the fiber.
Preferably, it is 25 peaks / 2.54 cm (1 inch). If the number of crimps is significantly below this range, the fibers may wrap around the cylinder or doffer during card processing,
Problems such as breakage of the web are likely to occur, and when the range is greatly exceeded, problems such as nep generation during card processing and difficulty in obtaining a uniform web arise. In order to obtain a bulky and well-formed nonwoven fabric, it is necessary to adjust the number of crimps within the above-mentioned range.

The fineness of the fiber is not particularly limited, and is appropriately selected according to the physical properties of the propylene copolymer to be used and the use of the fiber. For example, when used for sanitary materials such as absorbent articles such as disposable diapers and sanitary napkin surface materials, 0.1 to 10 dtex
When used for needle punch carpets and tufted carpets, etc., in the range of 8 to 80 dtex, when used for civil engineering materials such as monofilament,
A range of 50 to 7000 dtex is preferred.

In the melt spinning method, when the latently crimpable conjugate fiber of the present invention is a short fiber, the cut length of the fiber is not particularly limited, and may be appropriately selected depending on the processing method and application of the fiber to be used. do it. When a web such as a random web, a parallel web or a cross-wrap web is produced by a roller card machine or a random webber, the cut length is preferably 20 to 125 mm. , 2
A cut length of 5 to 75 mm is more preferred. In addition, when making a web by the air laid method or the papermaking method,
Preferably, the cut length is less than 20 mm.

In order to produce a bulky nonwoven fabric using the latently crimpable conjugate fiber of the present invention, a web composed mainly of fibers is subjected to a heat treatment so that the latently crimped fiber is developed and simultaneously the web is produced. Need to be thermally shrunk to be integrated. For the heat treatment, a general-purpose hot air circulation device or a heat treatment device such as a floating drier can be used, but the use of a floating drier capable of more uniformly shrinking the web is more preferable. The feature of this device is that hot air is blown out from nozzles installed on the upper and lower surfaces of the web transport space, and the web is floated by the hot air, causing thermal shrinkage at the same time as air transport. Is to be done. However, in order to prevent the web from being cut or the fibers from being scattered when any of the devices is used, a known nonwoven fabric such as a needle punch method, an embossing roll method, an ultrasonic fusion method and / or a high-pressure water entanglement method is used. It is important to temporarily fix the web by using a processing method.

The basis weight of the nonwoven fabric comprising the latently crimpable conjugate fiber of the present invention is appropriately selected depending on the purpose of use. For example,
When used as a surface material for absorbent articles, 5 to 10
The range of 0 g / m ² is preferable, and the range of 50 to 2000 g / m ² is preferable when used for civil engineering materials such as drain materials. Further, the nonwoven fabric can be laminated according to the purpose, and a combination of spunbonded nonwoven fabric / nonwoven fabric of latently crimped conjugate fiber / spunbonded nonwoven fabric, nonwoven fabric of spunbonded nonwoven fabric / meltblown nonwoven fabric / latently crimped conjugate fiber Can be exemplified.

The latently crimpable conjugate fiber of the present invention is used not only alone, but also with other fibers, as long as the effects of the present invention are not impaired. By mixing the fibers, a primary fiber product such as a knitted fabric or a fiber molded product can be obtained. Further, since the latently crimpable conjugate fiber of the present invention has appropriate stretchability and good texture after the crimp becomes apparent, by further performing secondary processing, underwear, shirts, blouses, socks , Socks such as socks, cotton padding, futon side lining, sheets, bedspreads, pillowcases, beddings and other bedding fields, medical masks, surgical gowns, caps, medical gowns, gauze, bandages, etc. , Non-pharmaceutical fields such as pulp materials, sanitary products, disposable disposable diapers,
Sanitary materials such as incontinence pads, bedding interior such as carpets, curtains, wallpapers, etc., shoes linings, insoles, footwear materials, etc. It can be used in a wide range of fields such as materials, food packaging, furoshiki, towels, towels, scrubs, tablecloths, aprons, kitchen cloths, cosmetic puffs, tea packs, wiping cloths and other filter materials.

Other fibers used for cotton blending, blending, blending, interlacing, interlacing, etc. are not particularly limited. For example, polyamide fibers such as nylon 6 and nylon 66, polyester fibers such as polyethylene terephthalate and polybutylene terephthalate, and the like. Polypropylene, polyethylene and polyethylene /
Polyolefin fibers such as polypropylene composite fibers can be used according to the purpose.

[0021]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples. The definitions of the terms used in the examples and comparative examples and the measurement method are as follows.

(1) Melting point: (unit: ° C.) According to a differential scanning calorimeter DSC-10 manufactured by DuPont,
The temperature corresponding to the peak on the melting absorption curve obtained when the temperature of the raw resin was raised at 10 ° C./min was defined as the melting point of the raw resin.

(2) MFR: (unit: g / 10 min) JIS K7210 Condition 14 (230 ° C., 21.1)
8N). MFR (before spinning) is a value measured using a resin before spinning as a sample, and MFR (after spinning).
Is a value similarly measured for a resin sampled after melt extrusion by a spinning machine. The measurement of MFR was omitted for polyester.

(3) Q value: (weight average molecular weight / number average molecular weight) The Q value is determined by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the resin determined by gel permeation chromatography. Mw / Mn). Here, the values of the resin before spinning are shown.

(4) Fineness: (unit: dtex) The fibers were observed with a scanning electron microscope, the diameter of 100 fibers was measured from the obtained image, and the fineness was calculated from the average value.

(5) Number of crimps: (unit number of peaks / 2.54c)
m) For short fiber samples, 2.54 for 10 fibers
The number of crimps per cm was counted, and the average value was used as the number of crimps here.

(6) Heat shrinkage rate: (unit%) A web having a size of 25 × 25 cm and a basis weight of about 200 g / m ² is placed on a kraft paper, placed in a convection hot air dryer maintained at 145 ° C., and heated for 5 minutes. did. M of web before and after heat treatment
From the respective lengths of D and CD, the heat shrinkage was calculated by the following equation. Heat shrinkage (%) = (1−a / 25) × 100 where a is the length of the MD or CD of the web after heat treatment.

(7) Spinnability When spun by the melt spinning method, the number of occurrences of yarn breakage per 10 hours was measured, and the spinnability was evaluated in the following three stages. Good: No yarn breakage, most preferable for production. Good: One or more times less than three times the number of thread breaks. Defective: Thread breakage occurs 4 times or more, and there is a problem in production efficiency.

(8) Card Suitability A short fiber sample (50 g) was put into a miniature card machine, and the state of the web discharged from the miniature card machine and the state of the fibers in the miniature card machine were visually judged according to the following criteria. Suitable: Uniform web with good formation and good discharge. Inappropriate: Raw cotton wraps around the cylinder or doffer inside the card machine, causing problems in processing.

(9) Formation A web having a basis weight of about 20 g / m ² was subjected to a heat treatment for 1 minute in a hot air circulation device heated to 145 ° C., and the formation of the obtained nonwoven fabric was visually observed according to the following three-step criteria. Judged. Good: A non-woven fabric having a uniform heat shrinkage and a good texture was obtained. Good: Thermal shrinkage occurs almost uniformly, and although formation disorder is slightly observed, it is considered that there is no practical problem. Defective: Heat shrinkage does not occur uniformly and the formation is disordered, or shrinkage is small

(10) Texture A web having a basis weight of about 20 g / m ² was subjected to a heat treatment for 1 minute in a hot air circulation apparatus heated to 145 ° C. The touch of the obtained nonwoven fabric was evaluated by a sensory test by 10 panelists based on the following criteria, and the texture was scored in four stages, and the average value was rounded off for evaluation. 4: Non-woven fabric is bulky, showing elasticity and softness 3: Non-woven fabric is bulky, soft but slightly lacking in stretchability 2: Non-woven fabric is not bulky, feels hard and lacks stretchability 1: Almost Practically problematic because it breaks when pulled lightly without shrinking

(11) Spreadability The fibers spun by the spunbond spinning apparatus are collected on an endless net-shaped conveyor, and the spread state of the collected long-fiber web is visually evaluated according to the following three grades. . Good: those that are uniformly spread Good: those that are spread almost uniformly, and that are slightly dense and poor Poor: those that are disturbed in the spread state and cannot be used as a product

Examples 1-5, Comparative Examples 1-4 Polypropylene, polyester (IV value 0.6)
7) Any one of ethylene-propylene-butene-1 terpolymer, ethylene-propylene-butene-1 terpolymer, ethylene-propylene binary copolymer, and polypropylene as the first component As a second component, an extruder, an eccentric sheath-core spinneret having a hole diameter of 0.8 mm, any one of a parallel spinneret or a concentric sheath-core spinneret, and a spinning device including a winding device, Using a drawing device equipped with a multi-stage heating roll and a stuffer box type crimper, a conjugate fiber was manufactured, and the heat shrinkage of the obtained fiber was measured.

With respect to the data of each conjugate fiber and nonwoven fabric, Examples 1 to 5 are shown in Table 1 and Comparative Examples 1 to 4 are shown in Table 2.
It was shown to.

[0035]

[Table 1]

[0036]

[Table 2]

In Comparative Example 1, since the propylene copolymer used as the second component had poor heat shrinkability, even if the produced conjugate fiber was subjected to heat treatment, sufficient crimp was not developed and the heat shrinkage was extremely low. Was lower. In Comparative Example 2, the same second component was used as in Example 2. However, since the rigidity of the polyester used as the sheath component was high, heat shrinkage did not occur, and a bulky nonwoven fabric was not obtained. . In Comparative Example 3, since the center of gravity of the fiber and the center of gravity of the second component were the same, the heat shrinkage was small. In Comparative Example 4, ethylene-propylene-
When the butene-1 terpolymer was used as the first component, it was effective in heat shrinkage, but had problems in workability such as card suitability.

Examples 6 to 9, Comparative Examples 5 to 6 As shown in Tables 3 and 4, crystalline polypropylene and an ethylene-propylene binary copolymer were used as the first component, and ethylene-propylene-butene-1 was used. Using a ternary copolymer or another polymer as the second component, composite spinning was performed with a spunbond spinning apparatus, and the physical properties of the resulting spunbond long-fiber nonwoven fabric were measured and evaluated. Using a spinneret corresponding to the fiber cross section, the composite fiber group discharged from the spinneret is introduced into an air soccer and drawn and stretched to obtain a composite filament, and then the filament group discharged from the air soccer is charged with a charging device. After applying the same charge and charging, the fiber is made to impinge on a reflection plate and spread, and the spread long fiber group is collected as a long fiber web on an endless net-shaped conveyor provided with a suction device on the back surface.

Data on the long-fiber nonwoven fabrics are shown in Table 3 for Examples 6 to 9 and Table 4 for Comparative Examples 5 to 6.

[0040]

[Table 3]

[0041]

[Table 4]

In Comparative Example 5, since the composite form was a concentric sheath core, no crimping occurred even when the produced nonwoven fabric was subjected to heat treatment. In Comparative Example 6, the propylene copolymer was used as the first component, so that the nonwoven fabric was opened. There was a problem in workability such as fineness.

[0043]

According to the latently crimpable conjugate fiber of the present invention, a polypropylene having a low friction resistance to metal is disposed on the fiber surface and a propylene copolymer having a high friction resistance to metal is disposed inside the fiber. , The workability such as card passability is good, and the following excellent effects are obtained. (1) Since the fibers in the web are crimped by the heat treatment, a bulky nonwoven fabric is obtained. In particular, a crimp can be easily applied to a long fiber spun by a spun bond method or a melt blow method in which mechanical crimping means cannot be used, and a bulky nonwoven fabric can be obtained. (2) In the case of short fibers, a uniform web can be obtained during card processing by reducing the friction on the fiber surface. In addition, by performing heat treatment on the web to develop crimp, a bulky and well-formed nonwoven fabric can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an eccentric sheath-core composite fiber.

FIG. 2 is a cross-sectional view of an eccentric sheath-core type composite fiber (with a higher degree of eccentricity).

FIG. 3 is a cross-sectional view of a sheath-core composite fiber having an irregularly shaped core.

[Explanation of symbols]

 Reference Signs List 1 First component constituting eccentric sheath-core composite fiber 2 Second component constituting eccentric sheath-core composite fiber 3 First component constituting parallel-type composite fiber 4 Second component constituting parallel-type composite fiber 5 Composite First component constituting fiber 6 Second component constituting composite fiber

Continued on the front page F term (reference) 4L041 BA02 BA05 BA09 BA22 BA24 BA60 BC04 BD11 CA38 CA42 CA43 DD01 DD05 DD10 DD15 4L047 AA14 AA27 AB09 AB10 BB02 CB10

Claims (6)

[Claims] 1. A polypropylene having a melting point of 160 ° C. or higher as a first component, and a melting point Tm (° C.) of 120 ≦ Tm (° C.) ≦
147. A conjugate fiber comprising a propylene copolymer in the range of 147 as a second component, wherein the first component is 80% of the surface of the conjugate fiber.
The first component and the second component in the fiber cross section
A latently crimpable conjugate fiber characterized in that the component has an area ratio of 65/35 to 35/65, and the center of gravity of the conjugate fiber is different from the center of gravity of the second component part. 2. A ternary copolymer of ethylene-propylene-butene-1 having a propylene content of 90 to 98% by weight, an ethylene content of 1 to 7% by weight, and a butene-1 content of 1 to 5% by weight. 2. The latently crimpable conjugate fiber according to claim 1, which is a union. 3. The latently crimpable conjugate fiber according to claim 1, wherein the latently crimpable conjugate fiber is an eccentric sheath-core conjugate fiber. 4. The latently crimpable conjugate fiber according to claim 1, wherein the latently crimpable conjugate fiber is a long fiber. 5. The latent crimpable conjugate fiber in a web containing the latent crimpable conjugate fiber has a heat shrinkage of 60% or more in the machine direction of the fiber and a heat shrinkage of 40% or more in a direction perpendicular thereto. The latently crimpable conjugate fiber according to any one of claims 1 to 4, having the following characteristics. 6. A nonwoven fabric comprising the latently crimpable conjugate fiber according to any one of claims 1 to 5.