OA16779A - Artificial hair fiber and hairpiece product. - Google Patents

Abstract

Provided is artificial hair with excellent curling properties. Fiber for artificial hair is generally shaped in a temperature range of 90 150°C. Artificial hair fiber for which the ratio of the storage elastic moduli E' in the shaping temperature region, that is, the ratio E'90/E'150 of the storage elastic modulus at 90°C, E'90, to the storage elastic modulus at 150°C, E'150, is a value of 3 - 20 maintains mechanical properties to the extent that melting does not occur while deforming adequately to form curls. Since shaping such as curling can be freely performed, hairpiece products that meet consumers' fashion needs are provided.

Description

The present invention relates to artificial hair fiber and a hairpiece product using the same.

Technical Background

Conventionally, to manufacture hairpiece products such as hair wigs, artificial hair made of synthetîc fibers has been used, Although most of the artificial hair is originally straight, there is an increasing demand for artificial hair fiber that can be processed into, for example, curled hair, due to an increase in the uses for fashion purposes.

As artificial hair fiber that easy to curl and set, there has been known, for example, flame résistant polyester artificial hair fiber (see Patent Document 1 ). This artificial hair fiber has high heat résistance, and therefore can be heated at a high température of a hair iron and the like, and can be well curled.

However, most of the manufacturera of the hairpiece products curl the fiber at a température from 90 to 150 °C that is lower than the température of the hair iron in order to prevent heat damage. Therefore, there has been a problem that the artificial hair fiber made of the above-described flame résistant polyester cannot be well curled.

Prior Art Document

Patent Document 1: Japanese Patent Application Publication No, 2009-235626

Summary of the Invention

It is therefore an object of the présent invention to provide artificial hair fiber that can be easily processed into, for example, curled hair.

The présent invention provides artificial hair fiber and a product manufactured by using the artificial hair fiber. The artificial hair fiber according to the présent invention has a storage elastic modulus E', a ratio (E'_eo/E’_ÎSo) of a storage elastic modulus E’ at a température of 90 °C to a storage elastic modulus E’ at a température of 150 °C is 3 to 20.

Here, a curve of the storage elastic modulus E' includes a glass state range in which the storage elastic modulus E’ is constant and a transition range in which a change rate in the storage elastic modulus E' becomes maximum, the transition range being on a higher température side than the glass state range. Preferably, a température coordinate of an intersection at which a tangent line of a curve of the storage elastic modulus E' passing through the glass state range intersects a tangent line of a curve of the storage elastic modulus E’ passing through the transition range is located between 180 to 240 °C.

More preferably, the artificial hair fiber is made of a resin composition primarily consisting of one or both of thermoplastic polyester resin and thermoplastic polyamide resin.

Further, the artificial hair fiber is manufactured by melting and discharging the resin composition from a nozzle hole to produce an un-stretched yarn, and applying a stretching process to the un-stretched yarn. Preferably, a ratio (Di/D₂)of a stretch Di while the un-stretched yarn is produced after the resin composition is melted and discharged to a stretch D₂ during the stretching process is 1.5 to 14.0.

It is possible to manufacture a hairpiece product by using the above-described artificial hair fiber,

According to the présent invention, it is possible to provide an artificial hair fiber that can be easily processed.

Brief Description of Drawings

Fig. 1 is a graph showing the relationship between storage elastic modulus and température;

Fig. 2 is a graph showing the viscoelasticity of artîficial hair fiber according to examples; and

Fig. 3 is a graph showing the viscoelasticity of artîficial hair fiber according to comparative examples.

Description of Embodiments

Hereinafter, although the présent invention will be described in detail, it is noted that the présent invention is not limited to the following embodiments.

The présent invention provides artîficial hair fiber that can be well curled (set, or styled). The artîficial hair fiber should not be limited to those described above, but may be, for example, synthetic fiber obtained by spinning resin composition, or fiber obtained by applying a processing agent to the synthetic fiber.

Formation and processing the artîficial hair fiber may be done by an artîficial hair fiber manufacturer, a person who processes the fiber into a hairpiece product and a user who bought the product. For example, a manufacturer of artîficial hair fiber or hairpiece product may form and process the artîficial hair fiber to hâve it curled before the artîficial hair fiber is put on sale. The formation and processing may be done any time, before, during or after the processing of the artificial hair fiber into a hairpiece product. Here, the formation and processing are not limited to curling (wavïng), but straightening the curled hair may also be applicable.

Methods of forming the artificial hair fiber should not be limited. There are various methods, for example, a method of placing a heating device such as a hair iron in contact with the artificial hair fiber or pressing the artificial hair fiber with the hair iron; a method of exposing the artificial hair fiber wound around a core (métal cylinder) to heated air; and a method of heating the core around which the artificial hair fiber is wound. In general, it is usual to use a method of placing a core wound by the artificial hair fiber in a heating oven and heating the core.

A heating température (formation température) in the formation process should not be specifically limited. Although the heating température can be changed depending upon the raw materials of the artificial hair fiber, the formation température may be in a range from 90 to 150 ^DC in general.

Fig. 1 is a schematic diagram explaining the viscoelasticity of the artificial hair fiber. Both storage elastic modulus E' and loss elastic modulus E of synthetic fiber will drop upon being heated.

Here, a higher change rate in these elastic modulus will cause an easîer transformation (such as a curling) of the synthetic fiber. Therefore, a suitable synthetic fiber for manufacturing the artificial haïr fiber is the one whose elastic moduli significantly changes within its formation température range (température range for curling in an oven shown in Fig. 1) when curling.

Curve “c in Fig. 1 shows a change in the elastic moduli (E’, E”) of heat-resistant artificial hair that is commercially available. The change rate in the elastic moduli (E’, E) of the heat-resistant artificial hair is small within the formation température range due to its heat résistance, so that a formation such as curling is not acceptable. Meanwhile, as shown by curves “a and “b in Fig. 1, when the change rate in the elastic moduli (E¹, E”) is large within the formation température range, the artificial hair can be easrly transformed, thereby obtaining an acceptable formability.

It is possible to control a change in the elastic moduli (E’, E) within the formation température range by changing the blending ratio of the resin composition which is a raw material for manufacturing the artificial hair fiber. For example, if thermoplastic resin with a low glass-transition température is used as the main raw material, it is possible to significantly change the elastic moduli (E¹, E) within the formation température range, but the heat résistance is reduced.

After a forming process and purchased by a user, a hairpiece product may be processed by the user to satisfy the his or her taste (hereinafter referred to as “post-formation). Commercially available heating devices (e.g. a hair iron) are often used for the post-formation processing.

Although the heating températures of those heating devices are within a wide range from 60 to

240 °C, the température of the post-formation tends to be higher (180 to 240 °C) than the formation température before the product is sold in the market, since users preferto set the hairpiece product well in a short time.

As shown by curve “b, even if the change rate of the température within the formation température range is large, there is still a possibility that the fiber will be melted and transformed before the température reaches the post-formation température range (température range for curling with iron in Fig. 1). As a resuit, the fiber cannot tolerate the high température of the hair iron, and therefore is likely to significantly shrink, be damaged and broken.

Therefore, as shown by curve “a, it is most préférable that the fiber does not melt before the température reaches the post-formation température range and the rate of change is large in the formation température range and also in the post-formation température range. Here, the elastic moduli (E¹, E) significantly changes during the melting. Here, “a” and c in Fig. 1 melt in the post-formation température range, but b melts before the post-formation température range. In normal use, the artificial hair fiber is not heated at a high température above the post-formation température range. Therefore, if the rate of change is large in the post-formation température range, the fiber is allowed to melt in the post-formation température range, as shown by “a” and “c.

The formation température that is widely adopted in the artificial hair field is within 90 to

150 °C, while the post-formation température that the users prefer is within 180 to 240 °C.

Therefore, it is préférable that the elastic moduli significantly change in both these ranges.

When a change in the elastic moduli increases, the fiber can be well curled. However, if the change is too large, the fiber shrinks. For example, it is preferred that a ratio of a storage elastic modulus E’ at 90 °C to a storage elastic modulus E' at 150 °C E'go/E’iso be 3 to 20, and more preferably 4 to 10. If E'_eo/E'i5ois lower than 3, a change in the elastic moduli will be small in the formation température range (90 to 150 T3), and therefore it is difficult to curl the fiber well. On the other hand, if Ε'_θα/Ε’_15Ο is higher than 20, the fiber shrinks and therefore it is also difficult to curl the fiber well. If E’_eo/E'_1so is 4 to 10, it is possible to curl the fiber very well without shrinking, and therefore this température range is particularly préférable.

In addition, taking into account the post-formation (curling with an iron), it is préférable for the fiber to hâve a high heat résistance. However, if the heat résistance is too high, it is not possible to perform the post-formation with an iron, and therefore it is preferred that a transformation température at which a crystal glass state collapses is within 180 to 240 °C. Here, the transformation température may be defined as an intersection at which a tangent line passing through the glass state range having a constant storage elastic modulus is intersecting a tangent line passing through the transition range (or transition point) on a higher température side than the glass state range, which has a maximum change rate in storage elastic modulus.

The artificial hair fiber that meets the above-described requirements including the température and the viscoelasticity can be produced by appropriately adjusting the manufacturing conditions of the fiber and the blending ratio of the raw materials.

<Resin composition>

The resin composition consists primarily of thermoplastic resin (50% by mass or more) and contains additives such as a flame retardant, filler, a coloring agent and antioxidant. The viscoelasticity (such as E’ and E) can be adjusted by changing a mixing ratio of two or more kinds of thermoplastic resin, or a mixing ratio of thermoplastic resin and additives (a flame retardant, filler and the like). Particularly, by combining two or more kinds of thermoplastic resin having different glass-transition températures, il is possible to produce an artificial hair fiber whose elasticity significantly changes in both the formation température range and the post-formation température range.

In addition, it is possible to adjust the viscoelasticity by adjusting the manufacturing conditions of the fiber. For example, it is possible to control the viscoelasticity by changing the draw ratio and the stretch ratio appropriately. Here, the draw ratio means a ratio for the drawing of the fiber after being discharged from the nozzle hole until being cooled. Meanwhile, the stretch ratio means a ratio for the stretching of an un-stretched yarn (a magnification for a yarn to be stretched).

Hereinafter, the draw ratio and the stretch ratio will be described in detail below. The manufacturing process of the artificial hair fiber includes the steps of: heating and melting a composition containing thermoplastic resin; discharging the melted composition from the nozzle hole; (if necessary) passing the composition through a heating sieeve; and cooling it to obtain an un-stretched yarn. The draw ratio means a ratio for the drawing of the fiber after the fiber ïs discharged from the nozzle until being cooled and becoming an un-stretched yarn. Here, the ratio for the drawing can be calculated based on a ratio of a speed at which the un-stretched yarn is taken up to a speed at which the fiber is discharged from the nozzle.

The un-stretched yarn is subjected to a stretching process in order to improve the tensile strength of the fiber. In the stretching process, the un-stretched yarn once having been cooled is stretched while being heated at a lower température than the heating and melting température when the yarn is produced. Here, the stretch ratio means a ratio for the stretching of the un-stretched yarn (before being heated and stretched) until being stretched. This stretch ratio can be calculated based on a ratio of a speed at which the un-stretched yarn is wound off to a speed at which the stretched yarn is wound up.

<Themnoplastic resin>

The thermoplastic resin should not be limited in use, and it is possible to use vinyl chloride resin, acrylic resin, polypropylene resin, polylactic resin, polyester resin, polyamide resin and the like.

However, when only a resin with a low heat résistance, such as vinyl chloride resin, is used, the fiber will be damaged in the post-formation under a high température (180 °C or higher). Therefore, it is preferred that heat résistant resin such as polyamide resin and polyester resin is used independently or in combination.

Among the above-described resins, the present invention prefers to use a polyamide fiber primarily consisting of polyamide resin and a polyester fiber primarily consisting of polyester resin, since they are easy to process and hâve a desired strength.

It îs preferred that the polyamide fiber or the polyester fiber is made of a composition obtained by mixing 5 to 30 parts by weight of phosphorous or bromine flame retardant and 100 parts by weight of polyamide resin (or polyester resin) and melt-kneading them. In this case, the flame résistance can be significantly improved by combining the resin and a certain percentage of a phosphorous or bromine flame retardant.

The polyamide resin used for the polyamide fiber should not be limited, but it is préférable to use at least one kind of resin selected from a group consisting of, for example, nylon 6; nylon 6,6; nylon 4,6; nylon 12; nylon 6,10; and nylon 6,12, and among them, nylon 6,6 is most préférable. When the nylon 6,6 is employed, the texture is particularly acceptable. The weight-average molecular weight (Mw) of the polyamide may be a value within a range from ten thousands to two hundred thousands, and to be more spécifie, may be ten thousand, twenty thousand, forty thousand, sixty thousand, eighty thousand, one hundred thousand, one hundred fifty thousand and two hundred thousand.

The kind of the polyester resin used for the polyester fiber should not be limited, it is possible to use polyethylene terephthalate, polyphenylene ether, polypropylene terephthalate, and polybutylene terephthalate. Among them, the polyethylene terephthalate is most préférable in view of the heat résistance.

The kind of the phosphorous flame retardant should not be limited, and it is possible to employ a generally used phosphorous flame retardant. To be more spécifie, it is possible to use a phosphate compound, a phosphonate compound,a phosphinate compound, a phosphine oxide compound, a phosphonite compound,a phosphinite compound and a phosphine compound. These compounds may be independently used, or two or more kinds of the compounds may be used together.

In addition, the kinds of bromine flame retardant should not be limited, either. It is possible to employ a generally used bromine flame retardant. To be more spécifie, it is possible to use a brominë-containing phosphate ester flame retardant, such as pentabromotoluene, hexabromobenzene, decabromodiphenyl, decabromodiphenyl ether, bis(tribromophenoxy)ethane, tetrabromophtalic anhydride, ethylenebis(tetrabromophthalimide), ethylenebis (pentabromophenyl), octabromotrimethylphenylindane, and tris(tribromoneopentyl) phosphate; a brominated polystyrène flame retardant; a brominated poly(benzyl acrylate) flame retardant; a brominated epoxy flame retardant; a brominated phenoxy flame retardant; a brominated polycarbonate flame retardant; a bromine-containing triazine compound such as tetrabromobisphenol A, tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-bis(allylether), tetrabromobisphenol A-bis (hydroxyethyl ether), tetrabromobisphenol A dérivatives, and tris (tribromophenoxy)triazine; and isocyanuric acid compound such as tris (2,3-dibromopropyl) isocyanurate. They may be used alone, or in a combination of two or more of them.

It is preferred that the content of the above-described phosphorous or bromine flame retardant is 5 to 30 parts by weight for 100 parts by weight of polyamide (polyester), and more preferably is 5 to 20 parts by weight. Within these ranges, it is possible to ensure a sufficient flame résistance and to prevent various physical properties from deteriorating.

Moreover, 0.1 to 5 parts by weight of fine particles may be contained in 100 parts by weight of polyamide resin (or polyester resin). When the fine particles are contained in this ratio, the following advantageous can be provided. Namely, it is possible to improve the gloss or luster of the fiber surface by forming an uneven fiber surface, thereby increasing the fiber surface area and thus producing an improved hygroscopic property for the fiber. The ratio of the fine particles to 100 parts of the polyamide resin is preferably 0.2 to 3 parts by weight, and more preferably 0.2 to 2 parts by weight. This ratio can allow the above-described effect to be significant.

The average size ofthe fine particles is preferably 0.1 to 15 pm, more preferably 0.2 to 10 pm, and further more preferably 0.5 to 8 pm.

Within these ranges, it is possible to provide a sufficient effect of adjusting the gloss or luster and to prevent the fiber strength from decreasing, which is possibly caused due to the addition of the fine particles.

The above-described fine particles may be organic, or inorganic, or may include both organic and inorganic fine particles. The kinds of organic fine particles should not be limited as long as at least part of them is not compatible with the polyamide or polyester resin, and for example, fine particles made of cross-linked acrylic resin or cross-linked polyester resin are applicable.

The above-described cross-linked acrylic particles may be obtained by dispersing acrylic monomers and a crosslinking agent in water, followed by crosslinking and curing. Here, the acrylic monomer used herein may include an acrylic acid and its dérivatives, such as methyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, hydroxyethyl acrylate, acrylonitrile, acrylamide and N-methylolacrylamide. Alternatively, it is also possible to use a methacrylic acid and its dérivatives. The dérivatives may include methyl méthacrylate, butyl méthacrylate, hexyl méthacrylate, glycidyl méthacrylate, benzyl méthacrylate, cyclohexyl méthacrylate, N-vinyl-2-pyrrolidone méthacrylate, methacrylonitrile, methacrylamide, N-methylolmetacrylamide, 2-hydroxyethyl méthacrylate, with each molécule having one vinyl group, thus forming a vinyl monomer. These monomers may be used individually, or two or more kînds of these monomers may be used in combination.

The above-described cross-linked polyester particles may be obtained by dispersing unsaturated polyester and vinyl monomers in water and crosslinking and curing them. The kind of unsaturated polyester used herein should not be lîmited. The unsaturated polyester may be obtained, for example, by polymerizing an α,β-unsaturated acid or the mixture of the α,β-unsaturated acid and a saturated acid with dihydric alcohol or triatomic alcohol. The unsaturated acid may include, for example, a fumaric acid, a maleic acid and an itaconic acid. Meanwhile, the saturated acid may include, for example, phthalic acid, terephthalic acid, succinic acid, glutaric acid, tetrahydrophthalic acid, adipic acid and sebacic acid. The dihydric alcohol and the triatomic alcohol may include, for example, ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1,3-propanediol, 1,6-hexanediol and trimethylolpropane. Meanwhile, the kind of vinyl monomer should not be lîmited, but may include, for example, styrene, chlorostyrene, vinyltoluene, divinylbenzene, acrylicacid, methylacrylate, acrylonitrile, ethylacrylate, and diallylphthalate.

The above-described crosslinking agent is not lîmited in use as long as it is a monomer that is a molécule having two or more vinyl groups, and more preferably, a monomer is a moiecule having two vinyl groups. A monomer used as a crosslinking agent should not be limited in use, but includes, for example, divinylbenzene, and a reaction product of glycol with methacrylic acid or acrylic acid, such as ethylene glycol dimethacrylate and neopentyl glycol dimethacrylate. It is preferred that an amount of the crosslinking agent is 0.02 to 5 parts by weight for 100 parts by weight of the acrylic monomer. As a polymerization initiator, it is préférable to use a peroxide radical polymerization initiator. For example, a peroxide radical polymerization initiator may include, a benzoyl peroxide, 2-ethylhexyl perbenzoic acid, di-tert-butyl peroxide, cumene hydroperoxide and methyl ethyl ketone peroxide. It is preferred that an amount of the radical polymerization initiator is 0.05 to 10 parts by weight for 100 parts by weight of the acrylic monomer.

As the above-described inorganic fine particles, it is préférable to hâve an index of refraction similar to that of polyamide and/ or a phosphorous-containing flame retardant, in view of an influence on the transparency and the color development of the fiber. For example, it is possible to use calcium carbonate, silicon oxide, titanium oxide, aluminium oxide, zinc oxide, talc, kaolin, «

montmorillonite, bentonite and mica.

In addition to the above-described fine particles and flame retardants, it is also possible to contain a flame retardant an auxiliary agent, a heat reststing agent, a light stabîlîzer, a fluorescent agent, an oxidation inhibitor, an antistatic agent, a plasticizer, a lubricant and a resin other than thermoplastic resin. By containing a coloring agent such as pigment, it is possible to produce pre-colored fiber (so-called spun-dyed fiber”).

<Manufacturing process>

Next, an explanation will be given to an exemplary process for manufacturing synthetic fiber.

However, the présent invention should not be limited by this.

The above-described additives such as a flame retardant and particles are dry-blended into thermoplastic resin such as polyamide or polyester resin in a predetermined proportion in advance, and then melt-kneaded by using a kneading machine. Various commonly used kneading machines may be employed as a melt-kneading apparatus. For example, it is possible to use a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, and a kneader as a melt-kneading apparatus. Among them, a twin-screw extruder is préférable, since it is easy to adjust a kneading degree and easy to operate. The kneaded material obtained by the melt-kneading is melt-spun to produce a spun yarn.

For example, the kneaded material is melted in a melt-spinning device such as an extruder, a gear pump and a pipe sleeve, under a température of 27 to 310 °C. Then, the kneaded material is passed through a heating sleeve, cooled to a glass-transition température or lower, and taken out at a speed of 50 to 5000 m/min, thereby producing a spun yarn. In addition, the yarn may be cooled with cooling water in a water tank to control the fineness. It is possible to appropriately control the température and the length of the heating sleeve, the température and the blast volume of a cooling air machine, the température of the cooling water tank, the cooling time and the take-up speed, according to the discharge quantity and the number of the holes of the pipe sleeve.

During the melt spinning, the cross-section of the artificial hair fiber may be formed into a cocoon shape, a Y-shape, an H-shape and an X-shape by using a spinning nozzle with a specially-shaped nozzle hole.

The obtained un-stretched yarn is subjected to a hot stretching process in order to improve the tensile strength of the fiber. The hot stretching process may be performed by a two-step method or a direct stretching method. The two-step method includes the steps of: winding an un-stretched yarn around a bobbin once; and stretching the yarn in a different step from a melt spinning step. The direct stretching method includes stretching the un-stretched yarn following the melt spinning step without winding the un-stretched yarn around the bobbin. In addition, the hot stretching process may be performed by a one-step stretching method or a multistep stretching method. In the one-step stretching method, the yarn is stretched to a desired stretch ratio in one step. In the multistep stretching method, the yarn is stretched two or more times to reach the desired stretch ratio. As heating means in the hot stretching process, it is possible to use a heating roller, a heat plate, a steam jet device and a warm water tank, alone or in combination.

As the fineness of the synthetic fiber, 30 to 80 dtex, and preferably 35 to 75 dtex is suitable to be used for artificial hair.

Among synthetic fibers, a polyamide fiber is a non-crimped silk fiber, and its fineness is usually 10 to 100 dtex, preferably 30 to 80 dtex, and more preferably 35 to 75 dtex.

<Post-processing>

Although the produced synthetic fiber may be used as an artificial hair fiber as it is, its texture may be improved by coating it with a treatment agent containing an oil such as silicone oil. A coating with a treatment agent may be done at any time, before, during and after processing the synthetic fiber into a hairpiece product. Here, in view of a working efficiency for a uniform coating, a coating during the process for processing the synthetic fiber into a hairpiece product is most préférable.

The artificial hair fiber may not only be used alone for a hairpiece product (headdress product), but also used in combination with human hair or other artificial hairs.

The hairpiece product may include a wig, a hairpiece, a blade, a hair extension, doll's hair and the like. The use of the artificial hair fiber should not be limited. In addition to a hairpiece product, the artificial haïr fiber of the présent invention may also be used for false beard, false eyelash, false eyebrow and the like.

<Examples>

Now, although examples of the présent invention will be described in detail below, it is noted that the présent invention is not limited to the examples.

<Manufacturing process>

Hereinafter, a method of manufacturing a hair fiber bundle will be described in the following examples.

The polyamide (or polyester) fiber was produced by the following method. First, polyamide (or polyester) resin, phosphorous or bromine flame retardant and fine particles, ail used as raw materials here, were dried to reduce their moisture content to 100 ppm or lower.

The raw materials used were as follows.

Nylon 6: Ube Industries, Ltd. 1013B

Nylon 6, 6: Toray Industries, Inc. CM3001-N

Phosphorous flame retardant:

DAIHACHI CHEMICAL INDUSTRY CO., LTD. PX-200

Bromine flame retardant: ALBEMARLE JAPAN CORPORATION, HP-7010

Fine particles: cross-linked acrylic particles 1.8 pm, Soken Chemical & Engineering Co.,Ltd.

Polyester (PET): Mitsubishi Chemical Corporation, BK-2180

The blending ratios (mass ratio) of the materials are represented in the following table 1.

Table 1

	Ex 1	Ex 2	Ex 3	Ex 4	Comp. Ex 1	Comp. Ex 2
Nylon 6	-	-	-	80	-	-
Nylon 6,6	-	100	-	20	100	100
Polyester	100	-	100	-	-	-
Phosphorous flame retardant	-	-	-	-	-	-
Bromine flame retardant	15	15	15	15	15	15
Fine particles	1	1	1	1	1	1

Ex: Example

Com. Ex: Comparative example

Next, predetermined amounts of colored pellets were added to the above-described dried materials, and the materials were dry-blended in the percentages shown in table 1.

The dry-blended material was melt-kneaded at a température of 280 XL Then, the melt-kneaded material was formed into pellets.

The melt-kneading and the pellet-formation were performed by the twin-screw extruder.

These pellets were dried to reduce the moisture content to 100 ppm or lower, and then formed into an un-stretched yarn in a melt-spinning machine. To be more spécifie, the nozzle hole of the melt spinning machine has a circular cross section and is 0.5 mm in size. Melted polymer pellets were discharged from the nozzle hole of the melt spinning machine at a température of 280 Tl· Then, the discharged melted polymer was cooled in the water tank (located 30 mm below the nozzle hole) at a température of 50 °C, followed by being taken-up and wounded. In this way, an un-stretched yarn is produced. The draw ratio was controlled by changing the speed at which the un-stretched yarn was wounded.

Next, the produced un-stretched yarn was stretched to a length which is 4 times as long as the original length, and then is subjected to heat treatment. Then, the stretched yarn is wound at a speed of 30 m/min to produce a fiber primarily consisting of polyamide (or polyester). In the stretching and the heat treatment of the un-stretched yarn, a heat roller heated to 85 °C and 200 Tl· respectively, is used.

By this means, the fibers in examples 1 to 4 and comparative examples 1 to 2 were obtained. Here, the stretch ratio was controlled by changing the speed at which the un-stretched yarn was wound off.

The following tests were conducted to valuate the fibers obtained in examples 1 to 4 and comparative examples 1 and 2.

<Degree of Curling in Oven>

To evaluate the degree of curling in oven, a fiber bundle (length: 50 cm) was wound around an aluminum cylinder (diameter: 20mm(p); each end of the fiber bundle was fixed to the aluminum cylinder; and the fiber bundle was put in an air-circulated oven at a température of 100 °C and heated for 30 minutes.

Next, the aluminum cylinder around which the fiber bundle was wound was left in a thermostatic chamber for 24 hours. Here, the température in the thermostatic chamber is 23 °C and the relative humidity is 50 %.

After that, the fiber bundle was removed from the aluminum cylinder and suspended, with its one end fixed.

The degree of curling was evaluated based on a value obtained by dividing the curled fiber length from its root to the tip with the entire length (50 cm) of the un-curled fiber. The smaller the value, the greater the degree of curling.

Evaluation criteria were as follows, and A and B were acceptable values in the évaluation.

A: lower than 0.75

B: 0.75 or higher and lower than 0.85

C: 0.85 or higher <Processability>

To evaluate processability, the frequency of the yarn break during the fiber manufacturing process (spinning and stretching) was checked, and evaluated by the following criteria,

A and B are acceptable values in the évaluation.

A: no yarn break;

B: yarn break occurs about every 30 minutes, but there is no problem on the quality of the product; and

C: there is a lot of yarn break and it is difficult to manufacture a product.

<Physical property>

In accordance with JIS-L1069, ten pièces of the fiber were randomly selected and subjected to a tensile test to calculate an average tensile strength value. The test was conducted under the following conditions: test température is 23 “C; relative humidity is 50 %; tensile speed 200 mm/min; and an clearance (distance between chucks)is 20 mm.

Evaluation criteria were as follows:

A: tensile strength (cN/dtex) was 1.0 or higher and 2.0 or lower

B: tensile strength (cN /dtex) was 0.5 or higher and 3.0 or lower

C: tensile strength (cN /dtex) was lower than 0.5 or higher than 3.0

A: quite acceptable

B: acceptable

C: not acceptable <Dynamic viscoelasticity>

Dynamic viscoelasticity (stretch modulus) was measured under the following conditions: frequency îs 1.0 Hz; initial température is 30 °C; final température is 260 °C; and rate of température increase is 2 ‘C/min. The measuring equipment used in the measurement was DMS6100, which was available from Sll Nanotechnology Inc. During the measurement, a bundle of forty pièces of fiber was sandwiched between the chucks with the chuck distance being 3 mm.

The results of the measurement are shown in table 2 together with manufacturing conditions such as kinds of resin, draw ratio, stretch ratio and the like.

Table 2

	Ex	Comp. Ex
1	2	3	4	5	6	1	2
Storage elastic modulus ratio (Ego/Eieo)	8.2	3.8	10.4	5.3	3.6	18.5	2.0	34
Resin	PET	PA66	PET	PA66/PA6	PET	PA66	PA66	PA66
Nozzle hole diameter (mm)	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
Draw ratio (times)	9	9	12	9	6	18	5	25
Stretch ratio (times)	3	3	2	3	4	1.5	5	1.5
Draw ratio/stretch ratio	3	3	6	3	1.5	12	1	16.7
Fineness (dtex)	70	70	80	70	80	70	76	58
Degree of curling in oven	A	B	B	A	B	B	C	C
Processability	A	A	A	A	B	A	B	B

Physical property (tensile strength)

A

A

B

A

A

B

B

C

In examples 1 to 4, the ratio of draw ratio D1 to stretch ratio D2 was 1.5 to 14.0, and the storage elastic modulus ratio (E'₀o/E'i5o) was 3 to 20. Here, not only the degree of curling in oven and the processability, but also strength was excellent. Among them, examples 1 and 4 in which the storage elastic modulus ratios (Ε’_θο/Ε'₁₅ο) were 4 to 10 yield good results of the degree of curling 10 in oven.

When the ratio (D,/D₂) of the draw ratio Di to the stretch ratio D₂ was smaller than 1.5, the un-stretched yarn will be excessively stretched and therefore likely to be broken during the stretching, so that the processability tended to be worse. On the other hand, when the ratio (ϋ,/D^ of the draw ratio D, to the stretch ratio D₂ was greater than 14.0, the un-stretched yarn will not be 15 sufficiently stretched, so that the tensile strength was likely to decrease.

In example 5, the storage elastic modulus ratio (EVE¹,®) was 3.6 and the degree of curling in oven and the processability were not A, but B. This resuit was within an acceptable range.

Further, in example 5, the ratio (D^D?) of the draw ratio D, to the stretch ratio D₂ was 1.5, and the processability was B. This resuit was also within an acceptable range.

In example 6, the storage elastic modulus ratio (E’9o/E’_1So) was 18.5 and the degree of curling in oven and the physical property (tensile strength) was not A, but B. This resuit was also within an acceptable range. In addition, in example 6, the ratio (Di/D₂)of the draw ratio D_t to the stretch ratio D₂ was 12, and the tensile strength (physical property) was B. This resuit was also within an acceptable range.

In contrast, in comparative example 1 the storage elastic modulus ratio (E’₉o/E'₁₅o) was smaller than 3 and the degree of curling in oven was C, and, in comparative example 2 in which the storage elastic modulus ratio (E'go/E^so) was greater than 20, not only the degree of curling in oven but also the tensile strength was C.

Fig .2 shows the resuit of the measurement of the dynamic viscoelasticity in example 1,

Fig. 3 shows the resuit of the measurement of the dynamic viscoelasticity in comparative example 1. As seen from Fig. 3, it was found that the artîficial hair fiber of comparative example 1 was not melted even at a high température of 240 °C, and the storage elastic modulus E' was maintained, exhibiting a high heat résistance. However, since the heat résistance was too high, the artîficial hair fiber was not melted in the formation température range (90 to 150 °C), nor in the post-formation température range (180 to 240 °C), and both the storage elastic modulus E' and the loss elastic modulus E changed little. In contrast, with the artîficial hair fiber of example 1, it was found that the storage elastic modulus E’ and the loss elastic modulus E signifîcantly changed in both the formation température range and in the post-formation température range, and the formability is excellent.

M, shown in Figs. 2 and 3 is a tangent line of the curve of the storage elastic modulus E', which passes through the glass state range in which the curve is fiat. M₂ is a tangent line of the curve of the storage elastic modulus E', which passes through a transition range in a higher température side than the glass state range. Here, the change rate of the storage elastic modulus is maximized in the transition range. The crystal state is lost at intersection P at which the tangent line Mf of the curve of the storage elastic modulus E’ passing through the glass state range intersects the tangent line M₂ of the curve of the storage elastic modulus E' passing through the transition range, thereby starting the melting. As seen in Fig. 2, the artificial hair fiber of example 1 has the température at the intersection P within 180 to 240 'C, and therefore can be processed with a commercially available hair iron (with a heating température of 240 Ό or lower). In contrast, the artificial hair fiber of the comparative example 1 has the température at the intersection P higher than 240 “C, and therefore it is not likely to be transformed by the heat of a commercially available hair iron.

Industrial Applicability

The use of the artificial hair fiber of the présent invention should not be limited, and the présent invention is applicable to various hairpiece products for a headdress such as a wig, a hairpiece, a blade, and a hair extension, or for a doll’s hair.

Claims (5)

1. What is claimed is:

   1. An artificial hair fiber having a storage elastic modulus E', wherein a ratio (EWE'iso) of a storage elastic modulus E’ at a température of 90 °C to a storage elastic modulus E' at a température of 150 Ύ3 is 3 to 20.
2. 2. The artificial hair fiber according to claim 1, wherein:

   a curve of the storage elastic modulus E' includes a glass state range in which the storage elastic modulus E' is constant and a transition range in which a change rate in the storage elastic modulus E' becomes maximum, the transition range being on a higher température side than the

   15 glass state range; and a température coordinate of an intersection at which a tangent line of a curve of the storage elastic modulus E' passing through the glass state range intersects a tangent line of a curve of the storage elastic modulus E’ passing through the transition range is located between 180 to 240 °C.
3. 3. The artificial hair fiber according to claim 1 or 2, wherein said artificial hair fiber is made of a resin composition primarily consisting of one or both of thermoplastic polyester resin and thermoplastic polyamide resin.
4. 4. The artificial hair fiber according to claim 3, wherein:

   said artificial hair fiber is manufactured by melting and discharging the resin composition from a nozzle hole to produce an un-stretched yarn, and applying a stretching process to the un-stretched yarn, a ratio (D₁/D₂)of a stretch D) while the un-stretched yarn is produced after the resin composition is melted and discharged to a stretch D₂ during the stretching process is 1.5 to 14.0.
5. 5. A hairpiece product produced by using the artificial hair fiber according to any one of claims