JP2000220035A - Heat-adhesive fiber and cushioning material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain heat-adhesive fibers suitable for cushioning materials, etc., having resistance to loss of resilience due to high temperature exhausting property and comfortableness by exposing an aliphatic polyester having a prescribed range of melting points at a part of the surface of fibers. SOLUTION: This heat-adhesive fiber is composed of an aliphatic polyester such as a polyester comprising L-lactic acid having 130-200 deg.C melting point as a main component and exposed on at least a part of the fiber surface and has <=40% dry heat shrinkage and <=330 mg shrinking force. Preferably, the heat-adhesive fiber is a core-sheath type composite fiber using an aliphatic polyester as the sheath component and having a multifoliate shape having more than three-foliate cross section and a matrix fiber of polyethylene terephthalate, etc., having more than 75 deg.C glass transition point is point joined by a heat- adhesive fiber to produce the objective cushioning material having more than 70% resistance to loss of resilience at 70 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat bonding fiber and a cushioning material using the same, and more particularly, the present invention relates to a method in which an aliphatic polyester having a specific melting point range is exposed on at least a part of the fiber surface. The present invention relates to a heat bonding fiber and a cushioning material using the heat bonding fiber at least in part. In particular, the present invention is intended to be used for applications that are frequently exposed to high temperatures, such as for vehicles, at least a heat-bonding fiber and a heat-bonding fiber suitably used for a cushion material having high heat resistance and comfort. It relates to a cushioning material used in part.

[0002]

2. Description of the Related Art Up to now, polyurethane foam has been mainly used as a cushioning material, but there is a problem in that it cannot be recycled, has poor air permeability, and has a problem in terms of comfort. In recent years, a fiber cushioning material mainly composed of polyester fiber has been proposed. Have been.

[0003] Conventionally, as a fiber cushion material,
JP-A-7-101018, JP-A-58-31150 and JP-A-3-220354 propose cushioning materials in which polyester fibers are melt-bonded. Since the crystalline low-melting-point adhesive component is used for the adhesive, the adhesive portion is brittle, and plastic deformation is severe in an atmosphere of 40 ° C. or more. For this reason, for example, high heat resistance under 70 ° C. condition is remarkably inferior, and residual strain is low, so that it cannot be generally used for vehicles.

For the purpose of improving the high heat resistance of cushioning materials for vehicles, Japanese Patent Application Laid-Open No.
JP-A-247724 and JP-A-5-247819 propose a heat-bonding fiber having a core-sheath structure and using a polyester elastomer for a sheath portion of a heat-bonding component, and a cushioning material using the heat-bonding fiber. However, since the heat resistance of the polyester elastomer used for the sheath portion is not taken into consideration, there is a disadvantage that when exposed to a relatively high temperature atmosphere for a long period of time, the bonded portion is deteriorated and the durability is poor.

Further, JP-A-6-165888 and JP-A-7-54253 disclose a glass transition temperature of 80.
Although polyester fiber having a melting point of 150 ° C. or higher and a polyester fiber having a melting point of 150 ° C. or higher is used as a base fiber and bonded with a copolyester thermal bonding fiber having a melting point of 80 ° C. or higher, a polyester solid cotton is disclosed. Is only described. In order to improve the set resistance to 70 ° C. of the cushion material, the glass transition temperature and the melting point of the base fiber constituting the cushion material also have an effect. However, the set resistance is controlled by the present inventors. According to various studies, when the thermal bonding fiber is an amorphous polymer, the relationship between the glass transition temperature and the melting point is important, and when the fiber is a crystalline polymer, the melting point range is important.

That is, a general amorphous polymer does not have a crystalline melting point, and begins to soften and melt at a glass transition temperature that is considerably lower than the melting point. Therefore, it is possible to improve the sag resistance at 70 ° C. for the first time with an amorphous polymer in which the relationship between the glass transition temperature and the melting point is more specified.

On the other hand, in order to improve the above-mentioned drawbacks of the amorphous polymer, studies have been made using a polymer having a crystallinity or a copolymerized polyester. However, a material satisfying sufficient performance was not obtained.

Therefore, in the prior art, even if a heat-bonding fiber and a cushioning material used under a normal atmosphere are obtained, high heat sag resistance is satisfied particularly in the field of a cushioning material for a vehicle exposed to a high temperature. No cushioning material could be provided.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to provide a heat-bonding fiber and a heat-bonding fiber suitably used for a cushion material having high heat resistance and comfort, which could not be achieved by the above-mentioned prior art. It is intended to provide a cushion material used at least in part.

[0010]

Means for Solving the Problems The heat bonding fiber of the present invention comprises:
A heat-bonded fiber characterized in that an aliphatic polyester having a melting point of 130 ° C or more and 200 ° C or less is exposed on at least a part of the fiber surface.

[0011] In the cushioning material of the present invention, the base fiber is point-joined by the above-mentioned heat bonding fiber.
It is a cushion material having a set resistance of 70% or more at 0 ° C.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The heat bonding fiber of the present invention is characterized in that aliphatic polyester having a melting point of 130 ° C. or more and 200 ° C. or less is exposed on at least a part of the fiber surface.

In the heat-bonded fiber of the present invention, it is important that the polymer used by being exposed at least on a part of the fiber surface is an aliphatic polyester having a melting point of 130 ° C. or more and 200 ° C. or less. In general, aliphatic polyesters have a low melting point and a low crystallization rate, so that cooling properties during spinning are poor, yarn breakage and fusion of yarns are liable to occur, and there is a tendency that the spinnability is remarkably deteriorated. Therefore, even if a cushion material was molded using an aliphatic polyester having a temperature of less than 130 ° C., a material which was inferior in high heat sag resistance and could be used was not obtained.

On the other hand, the melting point range is from 130 ° C. to 200 ° C.
C. or less, the cushioning material can be easily formed due to the sharp melting point of the aliphatic polyester,
Even if a 0 ° C set resistance test is performed, no change occurs in the bonded portion, and the temperature is 70 ° C compared with other aromatic polyester polymers or polymers obtained by copolymerizing an aliphatic component with an aromatic polyester polymer. An improvement in sag resistance is observed. In the case of the aliphatic polyester having a melting point lower than 130 ° C., the fusion between the single yarns becomes remarkable at the time of spinning, particularly at the time of spinning, and the product quality is significantly impaired, such as poor drawability. Preferably, the melting point is at least 150 ° C. On the other hand, if the melting point exceeds 200 ° C., it is necessary to set a high molding temperature when producing a molded article such as a cushioning material, and as a result, the base material fibers such as the cushioning material are softened and melted, resulting in high heat resistance. The brittleness is reduced. Also, the texture of the cushioning material becomes hard.

Here, the melting point means a peak temperature of a melting peak obtained by DSC measurement.

In the present invention, the dry heat shrinkage of the heat bonding fiber is preferably 40% or less. Dry heat shrinkage of 40
%, The shrinkage in the case of thermoforming becomes large, making it difficult to widen the molded body, and the texture tends to be hardened. From the above point, the dry heat shrinkage is more preferably 15% or less.

The shrinkage stress of the heat bonding fiber is 330 mg.
/ D or less. The shrinkage of the fiber requires the shrinkage stress together with the dry heat shrinkage. If the shrinkage stress of the heat-bonding fiber exceeds 330 mg / d, it becomes difficult to make the molded product wider as described above, and the texture tends to be hardened. From the above point, the contraction stress is more preferably 200 mg or less.

The heat bonding fiber of the present invention is suitably used in the form of a single component fiber or a composite fiber. For composite fibers,
Examples of the cross-sectional shape include a side-by-side type and a core-sheath type (concentric, eccentric). The core-sheath type (concentric, eccentric) is preferable from the viewpoint of strengthening the adhesion. In the case of the core-sheath type (concentric or eccentric), it is preferable that the aliphatic polyester constitutes the sheath. In the case of a side-by-side type, an aliphatic polyester is used as at least one or both components.

The heat-bonded fiber of the present invention can be cut into a desired fiber length after spinning in the form of a conjugate fiber or the like, followed by drawing and crimping.

The aliphatic polyester used in the present invention has a melting peak peak temperature of 1 measured by DSC.
There is no particular limitation as long as the temperature is 30 ° C. or more and 200 ° C. or less, and polylactic acid, poly-3-hydroxypropionate, poly-
3-Hydroxybutyrate, poly-3-hydroxybutyrate valerate, and blends and modifications thereof can be used. In the present invention, by using such an aliphatic polyester, unlike the aromatic polyester fiber, a good soft feeling is exhibited. This good soft feeling is due to the fact that the Young's modulus of the aliphatic polyester fiber is clearly lower than the Young's modulus of the aromatic polyester fiber. In addition, since these aliphatic polyesters have high biodegradability or hydrolyzability, they have an advantage that they are easily decomposed in a natural environment.

The most desirable polymers from the viewpoint of melting point and glass transition temperature include polylactic acid which is a polyester mainly composed of L-lactic acid and polyglycolic acid which is a polyester mainly composed of glycolic acid. . L-lactic acid as a main component means that the component 6
It means that 0% by weight or more is composed of L-lactic acid, and a polyester containing D-lactic acid in a range not exceeding 40% by weight may be used.

The method for producing polylactic acid includes a two-stage lactide method in which lactide is used as a raw material to first produce lactide as a cyclic dimer, followed by ring-opening polymerization, or a direct dehydration condensation in a solvent using lactic acid as a raw material. Is known as a one-step direct polymerization method. The polylactic acid used in the present invention may be one obtained by any production method. In the case of the polymer obtained by the lactide method, since the cyclic dimer contained in the polymer is vaporized at the time of melt spinning and causes thread spots, the cyclic dimer contained in the polymer before the melt spinning is obtained. It is desirable that the body content be 0.1 wt% or less. In the case of the direct polymerization method, since there is substantially no problem caused by the cyclic dimer, it can be said that it is more preferable from the viewpoint of the spinning property.

The higher the average molecular weight of the polylactic acid, the better, usually at least 50,000, preferably at least 100,000.
More preferably, it is 100,000 to 300,000. If the average molecular weight is lower than 50,000, the strength physical properties of the fiber are undesirably reduced.

The polylactic acid in the present invention may be a copolymerized polylactic acid obtained by copolymerizing other components having an ester-forming ability in addition to L-lactic acid and D-lactic acid. The copolymerizable components include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid,
-Other than hydroxycarboxylic acids such as hydroxycaproic acid, ethylene glycol, propylene glycol, butanediol, neopentyl glycol, polyethylene glycol, glycerin, compounds containing a plurality of hydroxyl groups in the molecule such as pentaerythritol or derivatives thereof, Contains multiple carboxylic acid groups in the molecule such as adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, and 5-tetrabutylphosphonium isophthalic acid Compounds or their derivatives.

In order to reduce the melt viscosity, an aliphatic polyester polymer such as polycaprolactone, polybutylene succinate and polyethylene succinate can be used as an internal plasticizer or as an external plasticizer. Further, inorganic fine particles and organic compounds as a matting agent, a deodorant, a flame retardant, a yarn friction reducing agent, an antioxidant, a coloring pigment and the like can be added as required.

The cross-sectional shape of the heat-bonding fiber of the present invention may be circular or irregular, but it is preferably a fiber having three or more leaves. Since the surface area of the fibers is increased by forming fibers having three or more leaves with irregular cross-sections, thermoforming at the time of producing a molded body can be easily performed, and bonding can be performed more firmly by increasing the bonding area.

The modified cross-section fiber used in the present invention can be produced by using a well-known melt spinning apparatus to make the holes for the corresponding modified cross section. For example, 3
When obtaining a fiber having a leaf cross section, a base having a known T-shaped or Y-shaped base hole may be used for the final discharge hole. Further, in order to increase the degree of irregularity, a method of reducing the base surface depth, a method of enhancing cooling, or the like can be used.

The above-mentioned heat bonding fiber of the present invention can be suitably used as a fiber constituting a fiber cushion material. The fiber cushion material is usually composed of a matrix fiber and a heat bonding fiber.

The fiber length of the heat bonding fiber may be a normal staple length of 30 to 100 mm, and the single fiber fineness may be usually 1 to 20 denier. When the heat bonding fiber is a conjugate fiber such as a core-sheath type, for example, polyethylene terephthalate can be used for the core and aliphatic polyester can be used for the sheath. The composite ratio of the heat bonding fiber is preferably 10/90 to 90/10, and more preferably 40/60 to 60/40.

The preferred content of the heat bonding fiber in the cushioning material of the present invention is from 5% by weight to 40% by weight,
More preferably, the content is 10% by weight or more and 30% by weight or less.
When the content is less than 5% by weight, the three-dimensional network structure formed as a thermal bonding point in the cushion material is small, and when a strain is applied, physical deformation occurs, and the settling resistance, durability, and cushioning property are significantly reduced. Is not preferred.
When the content exceeds 40% by weight, the number of heat bonding points increases. However, since less than 60% of the matrix fiber is responsible for sag resistance and durability against deformation when strain is applied, it is resistant to settling and durability against deformation when strain is applied. Properties tend to be significantly reduced.

Further, in the case of the conventional heat-bonded fiber, after drawing, it is necessary to perform crimping at room temperature because it adheres when applying mechanical crimp while performing steam treatment with a crimper. Could not be granted. In contrast,
The preferred heat-bonding fiber used in the present invention is different from the conventional one and has a high and sharp melting point range, so that the above-mentioned method can impart a mechanical crimp set by sufficient heat. .

That is, the conventional amorphous heat-bonded fiber has a low softening / melting range, so that it is difficult to impart sufficient crimp. Also, there was a disadvantage that the crimped form was easily deformed. Therefore, there is a limit in increasing the number of bonding points formed by entanglement of the base fiber and the heat bonding fiber.

In the present invention, the use of the heat-bonding fiber to which a strong crimp has been sufficiently imparted increases the number of heat-bonding points between the base fiber and the heat-bonding fiber, so that the bonding point can be further strengthened. . In addition, even when the fiber length is shortened as described below, the fiber hardly falls off.

As described above, when the heat bonding fiber of the present invention is used, the cushion material as a whole has a three-dimensional coil spring-like mesh structure, so that the coil of each fiber can be formed in any direction regardless of the large deformation. By deforming little by little, it can absorb force and strain and maintain high heat resistance.

The heat bonding fiber has a glass transition temperature of 75.
It is preferable to use fibers having a glass transition temperature of 75 ° C. or more as the matrix fibers, as in the case of using a polymer having a temperature of at least 70 ° C. Further, in order to obtain high heat and set resistance, the glass transition temperature is preferably 80 ° C. or higher, more preferably 10 ° C.
0 ° C. or higher.

The polymer constituting the base fiber in the present invention is preferably polyethylene terephthalate (PET).
EN), and polyesters having a high glass transition temperature, such as copolymers thereof, are preferably used.

Further, the cushioning material of the present invention has preferable characteristics of 70% or more sag resistance at 70 ° C. 70%
If it is less than 30, when the load is applied in a high-temperature atmosphere such as in summer, the cushion material is easily set and the strain is not recovered, so that the intended effect of the present invention may not be sufficiently obtained.

According to the findings of the present inventors, the cushioning material using the heat-bonding fiber according to the present invention at least 5% or more has a settling resistance at 70 ° C. of 70% or more, preferably 85% or more. , More preferably 90% or more.

The density of the cushion material is not particularly limited, but is preferably in the range of 0.02 to 0.06 (g / cc).

The cushioning material of the present invention is composed of a base fiber and a heat-bonding fiber. These fibers are mixed at a constant cotton mixing ratio, opened once with a carding machine, and then laminated with a web to have a constant density. , And then thermoformed with hot air at 200 ° C. for 30 minutes in a heat treatment machine, and then cooled.

The cushion material of the present invention is particularly suitable for use in vehicles exposed to high temperatures. As a vehicle application, a cushion material for a seat of a train, an automobile and the like is mainly used, but as another application, it can also be suitably used for a ceiling material, a dash insulator, a floor insulator, and the like of an automobile.

[0043]

EXAMPLES Each characteristic value defined in the present invention was determined by the following method.

(1) Glass transition temperature (Tg) Differential scanning calorimeter (DSC-
Using 7), the glass transition temperature (Tg) was determined by measuring at a heating temperature of 15 ° C./min under a nitrogen stream.

(2) Melting point (Tm) Differential scanning calorimeter (DSC-
Using 7), the temperature was measured at a temperature rise of 15 ° C./min under a nitrogen stream, and the peak temperature of the obtained melting peak was defined as the melting point.

(3) Dry heat shrinkage (%) Grasp both ends of the base fiber sample with clips, and a total of 300
An initial load of mg / d is applied to determine the original length L1 (cm). Loosen the gaps between the clips sufficiently and treat them in an oven at 180 ° C. for 15 minutes under no load.
An initial load of 00 mg / d is applied, and the length L2 after the treatment is applied.
Measure (cm). The dry heat shrinkage is determined by the following equation. The number of tests is 15 times, and the average value is obtained.

Dry heat shrinkage = {(L1−L2) / L1} × 100 (%) (4) Shrinkage stress (mg / d) A heat stress measuring device manufactured by Kanebo Engineering Co., Ltd., with a heating rate of 150 ° C./min. It was measured under the conditions. The sample is a loop of 10cm x 2 and the initial tension is fineness (denier) x (1/30)
gf.

(5) Melt Viscosity The relationship between the cutting speed at 260 ° C. and the melt viscosity was measured using a Capillograph manufactured by Toyo Seiki Co., Ltd. For the measurement, a die having L / D = 10/1 (mm) was used, and the viscosity at a cutting speed of 1000 sec ^-1 was defined as the melt viscosity of the sample.

(6) Resistance to sagging at 70 ° C. A cushion (10 × 10 10
× 10cm) and cut into parallel plane plates (vertical x horizontal = 1)
(5 × 15 cm).

In the method of cutting out from the cushion material, the direction in which the fibers are compressed at the time of forming the cushion is determined in view of the fiber arrangement inside the cushion material, and the compressed direction is substantially parallel to one surface of the cube. Cut out so that it becomes.
However, when the thickness or the like is less than 10 cm, the cube is made to have a thickness of 10 cm by stacking a plurality of pieces.

The compression in the set-off test is such that the web is compressed to a thickness of 50% under a surface direction having the same direction as the direction in which the web was compressed at the time of producing the molded body (the side surface is in a free state), After keeping it in dry heat at 70 ° C for 22 hours,
After removing the strain from the parallel flat plate to release the strain and stop the compression action, further transfer it to normal temperature (about 30 ° C.) and leave it as it is for one day (24 hours) (stand still) for thickness li.
(Cm) and the original thickness l0 (cm) before processing, ｛(l
i / 10) × 100)｝ (%).

The thickness was measured in units of 0.1 cm, and the number n was set to 5.

(7) Cushioning property (softness, elasticity) The texture (softness, elasticity) when ten panelists pressed by hand was ranked very good (10 points).
Evaluated as good (8 points), normal (5 points), and poor (0 points), and when the average point exceeds 8 points, the texture of the cushioning material is very good. ○ 4 points or more to less than 7 points were evaluated as “normal”; less than 4 points were evaluated as “poor”.

Examples 1 to 7 and Comparative Example 1 260 ° C., 1000
A polylactic acid chip having a melt viscosity of 1200 poise in sec ^-1 and a melting point of 168 ° C. and having the composition shown in Tables 1 and 2 was vacuum-dried at 60 ° C. for 48 hours. And melted at a melter temperature of 250 ° C., and a polymer (polyethylene terephthalate; PET) used as another component (core component) was melted at 290 ° C. and spun from an ordinary spinning machine at a composite ratio of 50/50 by weight. Discharged from the spinneret at a temperature of 292 ° C, 1350m
/ Min speed. Subsequently, the obtained unstretched yarn was combined and stretched at a draw ratio of 3.0 in a warm bath at 80 ° C.
After applying the finishing oil and subsequently applying mechanical crimp, 5
It was cut to 1 mm. The thermal bonding fiber was obtained by changing the copolymerization ratio of L-lactic acid / D-lactic acid, melting point, dry heat shrinkage, shrinkage stress, cross-sectional shape and the like as shown in Tables 1 and 2.

Next, 6 denier fiber length and fiber length
Polyethylene tele having a hollow cross-section three-dimensional crimp of 64 mm
Using phthalate (PET), heat-bonded fiber obtained above
Weave cotton at 30% cotton blending rate, open with a card, and wrap the web.
4000g / m per layer ^TwoTonashi, up to 10cm in thickness
After compression with hot air of 200 ° C for 30 minutes, cool
To obtain cushioning material. Table of evaluation results for cushioning materials
1 and 2 are shown together.

[0056]

[Table 1]

[0057]

[Table 2] In Examples 1 to 3, cushioning materials were produced using heat-bonding fibers having a melting point of 130 ° C. or higher according to the present invention. These cushioning materials had good cushioning properties and 70 ° C. set resistance. Particularly, at a level above the melting point of 150 ° C. (Examples 1 and 2), there was a tendency that the set resistance at 70 ° C. was improved.

On the other hand, the cushion material using the heat-bonding fiber having a melting point of 110 ° C. in Comparative Example 1 had good cushioning properties, but had poor settling resistance at 70 ° C. and poor strain recovery. In addition, yarn breakage and fusion of the yarns occurred during the yarn production, and the yarn-producing properties tended to be significantly deteriorated.

The heat-bonded fibers of Examples 4 and 5 were obtained by
The shrinkage stress is high, the size of the cushion material after molding shrinks, it is difficult to extend the width, and the cushion feel tends to harden. Although the set resistance at 70 ° C. was good, the value of the set resistance at 70 ° C. tended to be low when the dry heat shrinkage and the shrinkage stress were high (Example 5).

In Examples 6 and 7, the cross-sectional shape was at the level of three leaves and five leaves, and the cushioning property was good and the value of sag resistance at 70 ° C. was also improved.

As is clear from the above results, the cushioning material using the heat-bonding fiber using the aliphatic polyester having the thermal characteristics specified in the present invention has both good cushioning property and resistance to settling at 70 ° C. However, it is clear that the cushioning material using the heat bonding fiber other than the present invention cannot satisfy both the cushioning property and the resistance to settling at 70 ° C.

Comparative Examples 2 to 5 PHT shown in Table 3 as one component (sheath component) of the composite fiber
(Polyhexamethylene terephthalate), PBT (polybutylene terephthalate), PBS (polybutylene succinate), PCL (polycaprolactone), and a polymer used as another component (core component) in a Brescher melter type spinning machine ( Polyethylene terephthalate; PE
The mixture was melted together with T), discharged from a spinneret at a spinning temperature of 292 ° C. from a normal spinning machine at a weight ratio of a composite ratio = 50/50, and wound at a speed of 1350 m / min. continue,
The obtained unstretched yarn was ligated, stretched in a 80 ° C. warm bath at a stretch ratio of 3.0 times, subsequently applied with a finishing oil, mechanically crimped, and cut into 51 mm. Table 3 shows the melting point, dry heat shrinkage, shrinkage stress, cross-sectional shape and the like.

Next, polyethylene terephthalate (PET) having a three-dimensional crimp with a hollow cross section of 6 denier and a fiber length of 64 mm was used as a base material fiber, and the obtained heat-bonded fiber was mixed at a mixing ratio of 30%. After opening, the web was laminated to give a basis weight of 4000 g / m ² , compressed to a thickness of 10 cm, thermoformed with hot air at 200 ° C. for 30 minutes, and cooled to obtain a cushion material. Table 3 also shows the evaluation results of the cushioning material.

[0064]

[Table 3] Comparative Example 2 is a heat bonding fiber having PHT (polyhexamethylene terephthalate), which is an aromatic polyester having a melting point of 146 ° C., as a sheath component. Although the cushioning property of the molded cushioning material was good, the value of the settling resistance at 70 ° C. was low, and a cushioning material satisfying the performance was not obtained. Comparative Example 3 is a heat bonding fiber having PBT (polybutylene terephthalate) as a sheath component. The molded cushion material was too soft, and was in a state of so-called insufficient adhesive strength. Comparative Example 4 is a heat-bonded fiber having PBS (polybutylene succinate) as a sheath component. The cushioning property of the molded cushioning material was good, but the value of the settling resistance at 70 ° C. was low as in Comparative Example 2, and a cushioning material satisfying the performance was not obtained. In Comparative Example 5, spinning was performed using PCL (polycaprolactone) as a sheath component. However, yarn breakage due to fusion occurred frequently and spinning was not possible.

As is clear from the above results, the cushioning material using the heat-bonding fiber fiber using the aliphatic polyester having the melting point range specified in the present invention has both the cushioning property and the settling resistance at 70 ° C. Although good, it is clear that a cushioning material using a heat-bonding fiber other than those specified in the present invention cannot satisfy both the cushioning property and the resistance to settling at 70 ° C.

[0066]

According to the present invention, a heat-bonding fiber and a heat-bonding fiber which are preferably used for a cushioning material having high heat resistance and comfort, especially for applications frequently exposed to high temperatures such as for vehicles. A cushioning material using at least a part of the heat bonding fiber is obtained. In particular, by using the heat bonding fiber of the present invention in combination with a suitable base fiber, a cushion material having 70% or more set resistance at 70 ° C. can be obtained.

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Claims (8)

[Claims] 1. A heat-bonded fiber wherein an aliphatic polyester having a melting point of 130 ° C. or more and 200 ° C. or less is exposed at least on a part of the fiber surface. 2. The heat-bonded fiber according to claim 1, having a dry heat shrinkage of 40% or less and a shrinkage stress of 330 mg / d or less. 3. The heat-bonded fiber according to claim 1, which is a core-sheath type composite fiber using an aliphatic polyester as a sheath component. 4. The heat-bonded fiber according to claim 1, wherein the aliphatic polyester contains L-lactic acid as a main component. 5. The heat-bonded fiber according to claim 1, wherein the cross-sectional shape is a multi-leaf cross-sectional shape of three or more leaves. 6. A cushion material in which a base material fiber is point-joined by the heat bonding fiber according to any one of claims 1 to 5. 7. The cushion material according to claim 6, wherein the glass transition temperature of the base fiber is 75 ° C. or higher. 8. The cushion material according to claim 6, wherein the cushion material is integrally formed by thermoforming, and has a sag resistance at 70 ° C. of 70% or more.