JP2005048339A - Method and apparatus for producing polylactic acid filament nonwoven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain polylactic acid filament nonwoven fabric that has excellent heat shrinkage because the heat shrinkage of constituent filaments is extremely reduced by further refining the conventional technology and shows excellent fabric quality by reducing the defects. <P>SOLUTION: When polylactic acid polymer is melt-extruded into filaments and the filaments are piled up to produce filament nonwoven fabric according to the spun bonding process, a non-contact type heater 4 is arranged directly under the spinneret 2 to heat the extruded filament yarn 3, then the extruded yarn 3 is drawn with a drawing machine 7 at a speed of 6,000 to 8,000 m/min. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a production method and a production apparatus for a polylactic acid-based long fiber nonwoven fabric.

  Conventionally, as a long-fiber nonwoven fabric, what is manufactured by the spunbond method and thermocompression bonded is generally well known. That is, a thermoplastic polymer is heated and melted and discharged from a spinneret, and the obtained spun yarn is cooled using a cooling device such as a known horizontal spray or annular spray, and then a pulling device such as an air soccer Is pulled and thinned to obtain a desired single yarn fineness, and the web is deposited on the screen while being opened with a known opening device. The web is subjected to a partial thermocompression treatment through an embossing device to obtain a long fiber nonwoven fabric.

  In recent years, biodegradable long-fiber non-woven fabrics have been developed. Among them, long-fiber non-woven fabrics made of polylactic acid polymers are not only biodegradable but also have a relatively high melting point, so that they are practical. Therefore, it is expected to be suitable for various uses.

  As a method for producing a polylactic acid-based long fiber nonwoven fabric, there is one described in Patent Document 1. In this Patent Document 1, poly (D-lactic acid) and poly (L-lactic acid) having a melt flow rate measured at 210 ° C. according to ASTM-D-1238 at 10 to 100 g / 10 min. A copolymer of D-lactic acid and L-lactic acid, a copolymer of D-lactic acid and hydroxycarboxylic acid, a copolymer of L-lactic acid and hydroxycarboxylic acid, D-lactic acid and L- A polymer selected from the group consisting of lactic acid and a copolymer of hydroxycarboxylic acid having a melting point of 100 ° C. or higher, or a blend of polymers having a melting point of 100 ° C. or higher, and the melting point of these polymers or blends being Tm After being melted at a temperature of (Tm + 20) ° C. to (Tm + 80) ° C. and discharged from the die, the discharged yarn was pulled and thinned at a take-up speed of 3000 to 6500 m / min with a suction device. Mobile capture Depositing while opening on the surface to form a web, by heat treatment of the web, it is described that desired polylactic acid filament nonwoven fabric can be obtained.

The nonwoven fabric obtained by the manufacturing method of Patent Document 1 has a feature that the hot water shrinkage is 15% or less.
JP 2000-273750 A

  The present invention is intended to further improve the conventional technique described in Patent Document 1, and to obtain a nonwoven fabric comprising polylactic acid-based long fibers having further excellent heat shrinkage characteristics as constituent fibers. An object of the present invention is to obtain a polylactic acid-based long-fiber non-woven fabric that has very little heat shrinkage and is well formed (with few defects).

  In order to solve the above-described problems, the method for producing a polylactic acid-based long fiber nonwoven fabric according to the present invention comprises a spinneret for producing a long-fiber nonwoven fabric by depositing fibers obtained by melt spinning a polylactic acid polymer by a spunbond method. A non-contact type heater is disposed immediately below to heat the spun yarn, and then the spun yarn is pulled at 6000 m / min to 8000 m / min.

  In this way, by passing the spun yarn through a non-contact type heater immediately below the spinneret before the solidification point, crystallization of the polymer is suppressed between the spinneret and the pulling device, and the pulling device is used. Since it is pulled and stretched at once after being introduced, crystallization is not progressed when it is introduced into the traction device, which reduces the spinning stress and improves the suction and traction effect. Therefore, high-speed pulling becomes possible, and by pulling at 6000 m / min to 8000 m / min, the thinning deformation of the spun yarn proceeds smoothly, and the birefringence of the spun fiber, that is, the degree of orientation, compared to the conventional manufacturing method. Rise, thereby reducing the thermal shrinkage of the fiber.

  According to the present invention, in the production method described above, the heating conditions for the spun yarn include the heating temperature T1 (° C.) of the non-contact type heater with respect to the melting point Tm (° C.) of the polylactic acid polymer, It is preferable to use conditions where the residence time in the heater t (seconds) satisfies the following expressions (1) and (2).

Tm−70 ≦ T1 (° C.) ≦ Tm + 100 (1)
0.07 ≦ t (seconds) ≦ 1.80 (2)

  According to the present invention, in the above production method, it is preferable that the melt flow rate of the polylactic acid polymer measured at a temperature of 210 ° C. according to ASTM-D-1238 is 20 to 80 g / 10 minutes.

  An apparatus for producing a long-fiber nonwoven fabric by depositing fibers obtained by melt spinning a polylactic acid polymer by a spunbond method according to the present invention is a non-contact type for heating a spun yarn directly under a spinneret. A heater is provided, and a pulling device that pulls the heated yarn at 6000 m / min to 8000 m / min is provided below the non-contact type heater.

  In the polylactic acid-based long fiber nonwoven fabric of the present invention produced by the above production method or production device, the long fibers constituting the nonwoven fabric have a single-phase cross section, and the long fibers have a hot water shrinkage of 15% or less. It is characterized by being.

  Moreover, in the polylactic acid-based long fiber nonwoven fabric of the present invention manufactured by the above-described manufacturing method or manufacturing apparatus, a plurality of types of polylactic acid-based polymers having a melting point difference form a composite cross section of the long fibers constituting the nonwoven fabric. And the hot water shrinkage rate is 20% or less.

  According to the method for producing a polylactic acid-based long-fiber nonwoven fabric of the present invention, a non-contact type heater is disposed directly below the spinneret and is pulled at 6000 to 8000 m / min. It is possible to suppress crystallization of the constituting polymer, and after introduction into the traction device, it is possible to crystallize at a high speed at a stretch, which can reduce the thermal shrinkage of the fibers constituting the web, so that the thermal stability Can be obtained. Moreover, since the obtained nonwoven fabric is comprised with the fiber which has such a thermal characteristic, a shrinkage | contraction is small in a thermocompression bonding process, Therefore The polylactic acid-type long fiber nonwoven fabric with few faults by a wrinkle etc. can be obtained.

  FIG. 1 shows a schematic configuration of an apparatus for producing a polylactic acid-based long fiber nonwoven fabric according to the present invention. Here, 1 is a spinning head and has a spinneret 2. The spinneret 2 can spin the yarn 3 downward. Below the spinning head 1, a non-contact type heater 4 is provided so as to surround the spun yarn 3 with no substantial gap between the spinning head 1. L is the length of the heating portion of the non-contact heater 4 along the traveling direction of the spun yarn 3. As the non-contact type heater 4, means such as an electric heater, a cast-in heater, a superheated steam heater, an infrared heater, and a laser beam can be adopted. Among them, it is preferable to employ an electric heater, a superheated steam heater or an infrared heater from the viewpoint of thermal efficiency and ease of handling.

  A cooling device 5 is provided at a position below the non-contact type heater 4. Although this cooling device 5 sprays the cooling air 6 with respect to the spinning yarn 3, it is comprised, for example so that a horizontal type spray structure and an annular spray structure may be exhibited. A traction device 7 such as an air soccer is provided at a position spaced downward from the cooling device 5. Reference numeral 8 denotes traction air.

Next, the manufacturing method of the polylactic acid type | system | group continuous nonwoven fabric using such an apparatus is demonstrated.
The polylactic acid polymer used as a raw material for production includes D-lactic acid, L-lactic acid, a copolymer of D-lactic acid and L-lactic acid, a copolymer of D-lactic acid and hydroxycarboxylic acid, and L Examples thereof include any polymer or blend selected from a copolymer of -lactic acid and hydroxycarboxylic acid, and a copolymer of D-lactic acid, L-lactic acid and hydroxycarboxylic acid.

  In the present invention, it is preferable to use a polylactic acid polymer having a melting point of 150 ° C. or higher or a blend of polymers having a melting point of 150 ° C. or higher. When the temperature is lower than 150 ° C., the polymer becomes amorphous, so that the cooling property at the time of spinning is lowered, and the melting point of the constituent fiber of the obtained nonwoven fabric is less than 150 ° C., and the heat resistance of the nonwoven fabric and Since the mechanical properties are impaired, the intended use is limited.

  The melting point of poly (L-lactic acid) and poly (D-lactic acid), which are homopolymers of polylactic acid, is about 180 ° C. When the copolymer is used as the polylactic acid polymer, it is important to determine the copolymerization ratio of the monomer components so that the melting point of the copolymer is 150 ° C. or higher. For this purpose, in the copolymer of L-lactic acid and D-lactic acid, the copolymerization amount ratio of L-lactic acid and D-lactic acid is a molar ratio, and one of L-lactic acid and D-lactic acid is It is necessary to be more than 0% and 5% or less, and the other is less than 100% and 95% or more. A polymer in the case where the long fibers constituting the polylactic acid-based long fiber nonwoven fabric of the present invention have a single-phase cross section, or a high melting point polymer in the case of a composite cross section composed of a plurality of types of polymers having a melting point difference, The copolymerization amount ratio of L-lactic acid and D-lactic acid is a molar ratio, and one of L-lactic acid and D-lactic acid is more than 0% and 2% or less, and the other is less than 100% and 98% or more. Is preferred. When the molar ratio of L-lactic acid or D-lactic acid having a lower copolymerization ratio exceeds 2%, the crystallinity of the polylactic acid polymer itself deteriorates, and the spunbond is performed simultaneously with the traction and thinning process. According to the method, even if a non-contact type heater 4 is provided immediately below the spinneret 2 in accordance with the present invention and pulled and thinned at once, the birefringence, that is, the degree of orientation of the spun yarn 3 does not increase. Therefore, in this case, it is difficult to obtain a heat shrinkage characteristic that is the object of the present invention, and the thermal water shrinkage of the fibers constituting the long-fiber nonwoven fabric exceeds 15%, so that heat shrinkage occurs in the thermocompression bonding process. There is a fear. For this reason, the copolymerization amount ratio of L-lactic acid and D-lactic acid is a molar ratio, and one of L-lactic acid and D-lactic acid exceeds 0% and is 1.5% or less, and the other is less than 100% and 98 More preferably, it is 5% or more.

  As the polylactic acid polymer in the present invention, a blend of the polylactic acid polymer and a biodegradable aliphatic-aromatic copolymer polyester may be used. When such a blend is used, effects such as imparting flexibility and impact resistance to polylactic acid having properties of being hard and brittle at room temperature can be obtained. As the biodegradable aliphatic-aromatic copolymer polyester, those obtained by condensation polymerization of an aliphatic diol, an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid can be used. Examples of the aliphatic diol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the aromatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanoic acid and the like. By selecting and polycondensing one or more of these, the desired biodegradable aliphatic-aromatic copolymer polyester can be obtained. In addition, it can also bridge | crosslink with a polyfunctional isocyanate compound as needed.

  The melt viscosity of the polylactic acid polymer used in the present invention is 20 to 80 g of melt flow rate (hereinafter abbreviated as “MFR”) measured at a temperature of 210 ° C. according to the method described in ASTM-1238 (E). / 10 minutes is preferable. Especially, when the long fiber which comprises a polylactic acid-type long fiber nonwoven fabric is a single phase cross section, it is preferable that MFR is 30-80 g / 10min. Furthermore, it is more preferable that it is the range of 35-75 g / 10min. If the MFR is lower than 20 g / 10 min, the polymer viscosity is high, so that the spinning stress increases, it is difficult to make the material thin by pulling, and the spinnability is lowered. Moreover, since the viscosity of the polymer is high in the thermocompression bonding step, the thermocompression bonding is not sufficient, and the obtained nonwoven fabric is not preferable because delamination occurs. On the other hand, if the MFR exceeds 80 g / min, the melt viscosity is too low, so that the spinnability is inferior, the mechanical properties of the obtained fiber are inferior, the fiber spots become large, and stable operation becomes difficult.

  Moreover, when the long fiber which comprises the nonwoven fabric of this invention is a composite cross section, MFR can be suitably selected according to cross-sectional shape. For example, in the case of a core-sheath composite cross section, the MFR of the core component is preferably in the range of 20 to 70 g / 10 minutes, and the MFR of the sheath component is preferably higher than the MFR of the core component by 10 g / 10 minutes or more.

  In the case of a multileaf composite cross section, the core component MFR is preferably in the range of 30 to 80 g / 10. The leaf component has a lower MFR value than the core component MFR, and the difference between the two is 10 g / 10 min or more. It is preferable.

  If necessary, for example, various additives such as a matting agent, a pigment, and a crystal nucleating agent may be added to the polymer applied in the present invention as long as the effects of the present invention are not impaired. In particular, the addition of crystal nucleating agents such as talc, titanium oxide, calcium carbonate, and magnesium carbonate can effectively prevent fusing (blocking) between yarns in the spinning and cooling process. Is useful when used in the range of 0.1 to 3% by weight.

  When manufacturing the nonwoven fabric, as described above, the non-contact type heater 4 is disposed under the spinneret 2 shown in FIG. 1, a specific MFR polymer is selected, and the spun yarn 3 is solidified. Crystallization is suppressed by passing through the non-contact type heater 4 before the point, and after cooling with the cooling device 5, the traction device 7 such as an air soccer is pulled and stretched. Thereby, since crystallization is not progressing compared with what spins a thread | yarn in the atmosphere of room temperature conventionally, a spinning stress falls and the attraction | suction and the traction effect by the traction apparatus 7 improve. Accordingly, high-speed pulling becomes possible, the thinning deformation of the spun yarn 3 proceeds smoothly, the birefringence of the spun fiber, that is, the degree of orientation, is higher than that of the conventional manufacturing method, and the heat shrinkage rate of the fiber is reduced.

  What is important here is that there is no substantial gap between the spinning head (lock to which the base 2 is attached) 1 and the heater 4. If there is a gap, air is sucked in from that portion and the inside of the heater 4 becomes turbulent, so that not only high-speed traction is possible, but also the degree of uniformity of the obtained yarn is poor.

  In the present invention, the heating temperature T 1 (° C.) of the non-contact type heater 4, that is, the temperature of the running portion of the yarn 3 in the non-contact type heater 4 is the yarn 3 regardless of the discharge amount from the spinneret 2. It is preferable that the formula (1) is satisfied with respect to the melting point Tm (° C.) of the polylactic acid polymer constituting

Tm−70 ≦ T1 (° C.) ≦ Tm + 100 (1)
The melting point Tm (° C.) of the polylactic acid polymer in this case is the melting point of the polymer in the case of a single-phase fiber form, and the highest melting point of the polymers constituting the composite form in the case of a composite fiber form. The melting point of the low polymer is Tm (° C.). The heating temperature T1 (° C.) of the non-contact type heater 4 is controlled as a set temperature of the heater 4.

  If the heating temperature T1 (° C.) is less than [Tm-70] (° C.), the crystallization suppression in the heater 4 becomes insufficient, and the thermal shrinkage of the obtained fiber is large, and the non-woven fabric is formed. Therefore, the problem of heat shrinkage of the fiber web in the hot pressing process tends to occur. On the other hand, when the heating temperature T1 (° C.) exceeds [Tm + 100] (° C.), the amount of heat supplied by the heater 4 is too much, and the cooling property of the spun yarn 3 is deteriorated.

  In the present invention, as described later, the pulling speed in the pulling device 7 is set to 6000 to 8000 m / min, and the residence time t (second) in the heater 4 of the spun yarn 3 is expressed by the formula (2 ) Is preferably satisfied.

0.07 ≦ t (seconds) ≦ 1.80 (2)
If the residence time t is less than 0.07 seconds, the heating efficiency with respect to the spun yarn 3 is lowered, so that the effect of suppressing the crystallization of the polymer between the spinneret 2 and the traction device 7 becomes insufficient. The effect of promoting the orientation and crystallization of the spun yarn 3 after being introduced into the pulling device 7 tends to decrease, which is not preferable. On the other hand, if the residence time t exceeds 1.80 seconds, the change in physical properties of the spun yarn 3 due to heating has already reached saturation in this region, and an unnecessary excess amount of heat is applied to the spun yarn 3. Not only is it supplied, it becomes uneconomical, but it also induces thread wobble. Therefore, in the present invention, the residence time t is more preferably 0.15 to 1.80 seconds.

  The length of the heater 4 along the traveling direction of the spun yarn 3, that is, the length of the portion of the heater 4 that is actually heating the yarn 3 is 50 to 300 mm. It is preferable for sufficiently stretching the fiber within the range of temperature and residence time.

  The high speed traction speed in the present invention is in the range of 6000 to 8000 m / min. When the pulling speed is less than 6000 m / min, the hydrothermal shrinkage rate as a heat shrinkage characteristic of the obtained fiber exceeds 15% when the fiber cross section is a single phase, and 20% when the fiber cross section is composite. Therefore, the shrinkage of the fibers constituting the web is increased in a process such as hot pressing, which tends to be a defect that impairs the appearance of the sheet after the hot pressing process. On the other hand, when it exceeds 8000 m / min, yarn breakage tends to occur, and the operability tends to deteriorate.

  After towing, the fibers are deposited to form a long fiber nonwoven fabric. As a means for forming a nonwoven fabric, for example, a thermocompression bonding is performed partially on a web on which fibers are deposited by a thermocompression bonding apparatus. Partial thermocompression bonding of the web refers to the formation of a point-bonded area by embossing. Specifically, a point-like shape is formed between long fibers through the web between an embossing roll and a metal roll with a smooth surface. The formation of a thermocompression bonding area. As the crimping temperature, it is preferable to apply a temperature lower than the melting point (Tm) of the polymer constituting the fiber and not lower than [Tm-35] ° C.

In addition, as a partial thermocompression bonding condition, each thermocompression bonding area, which is a specific partial area of the web, has an area of 0.2 to 15 mm ² , and the area is round, oval, rhombus, triangular. The shape is preferably an arbitrary shape such as a mold, T-shape, or well, and the distribution density of the region, that is, the pressure-bonding point density is preferably 4 to 100 points / cm ² . Further, the ratio of the total thermocompression bonding area to the total surface area of the web, that is, the compression bonding area ratio is preferably 3 to 50%.

The single yarn fineness of the long fibers constituting the polylactic acid-based long fiber nonwoven fabric of the present invention prepared as described above is not particularly limited, and is about 1 to 8 dtex.
Moreover, when the long fiber which comprises this nonwoven fabric is a single phase cross section, it is preferable that the obtained nonwoven fabric has a hot-water shrinkage rate of 15% or less. Furthermore, when the same long fiber has a composite cross section that tends to shrink by itself, the hot water shrinkage rate is preferably 20% or less. When the hot water shrinkage rate is within the range of these values, the shrinkage of the fibers constituting the web does not increase in the process such as hot press bonding, so that the defects that impair the appearance of the sheet after the hot press process are less likely to occur. Become.

  Hereinafter, the present invention will be described specifically by way of examples. In addition, this invention is not limited only to these Examples. In the following Examples and Comparative Examples, each physical property value was determined as follows.

(1) MFR (g / 10 min): Measured according to the method described in ASTM-D-1238 at a temperature of 210 ° C. and a load of 20.2 N (2.16 kgf).

(2) Melting point Tm (° C.) of polymer: melting endotherm obtained by using a differential scanning calorimeter DSC-7 manufactured by Perkin Elma Co., Ltd. and measuring a sample mass of 5 mg and a heating rate of 10 ° C./min. The temperature giving the extreme value of the endothermic peak of the curve was defined as the melting point Tm (° C.).

(3) Fineness (Decitex, hereinafter abbreviated as “dtex”): The fiber diameter in a web state was measured with 50 optical microscopes, and the average value obtained by density correction was defined as the fineness.

(4) Yarn breakage: The spun yarn was pulled by air soccer and evaluated in the following three stages.
○: Thread breakage 0 times / (per spindle weight / hour)
Δ: Less than 3 yarn breaks / (per spindle of spindle / hour)
X: Thread breakage 3 times or more / (per spindle weight / hour)

(5) Hot water shrinkage rate (%) of fiber: It was determined according to JIS L1013 hot water shrinkage rate “filament shrinkage rate (Method B)” as follows. That is, the fiber that has been pulled and thinned is taken out from the web, the initial load described in JIS L1013 is applied to the fiber, and the initial load is calculated by measuring the distance of 200 mm in the length direction of the fiber. It was unwound and immersed in hot water at 85 ° C. for 15 minutes, taken out, air-dried and then subjected to the initial load again, the length (Amm) between the two points was measured, and the hot water shrinkage (%) was calculated by the following formula. The number of tests was five, and the average value was evaluated as the hot water shrinkage.

    Hot water shrinkage (%) = {(200−A) / 200} × 100 (3)

(6) Birefringence: measured using a polarizing microscope equipped with a Belek compensator and using tricresyl phosphate as the immersion liquid.

(7) Appearance of non-woven fabric: Sheet inspection of a 1000 m roll was carried out, and the number of defects caused by web shrinkage was evaluated as follows.

○: Less than 10 defects / per roll ×: 10 defects / per roll (Example 1)

  L-lactic acid / D-lactic acid copolymer having a melting point Tm of 168 ° C., MFR of 60 g / 10 min, and L-lactic acid / D-lactic acid = 98.7 / 1.3 mol% as a polylactic acid polymer And 0.5% by mass of talc was added as an additive to this polymer. This mixture was melt-spun from a spinneret 2 having a round hole diameter of 0.3 mmφ shown in FIG. 1 at a spinning temperature of 210 ° C. and a single hole discharge rate of 1.67 g / min. A cylindrical non-contact type heater 4 composed of an electric heater is provided immediately below the spinneret 2, and the yarn 3 spun from the spinneret 2 has an effective heating length of 50 mm and a heating temperature T1 of 150 ° C. ([Tm-18] ° C.) was passed through the inside of the cylindrical heater 4. The residence time t of the yarn 3 inside the heater 4 was 0.16 seconds.

Further, after cooling air 6 at 20 ° C. is blown by the cooling device 5, it is taken up at 7000 m / min by an air soccer as the traction device 7, opened, and deposited on the collecting surface of the moving conveyor. A web was formed. Next, it is passed through a partial thermocompression bonding machine composed of embossed rollers, and partially thermocompression bonded under the conditions of a roll temperature of 130 ° C., a crimping area ratio of 14.9%, a crimping point density of 21.9 pieces / cm ² , and a linear pressure of 60 kg / cm. Thus, a long fiber nonwoven fabric having a basis weight of 50 g / m ² made of 2.4 dtex long fibers was obtained. Table 1 shows the measurement results such as hot water shrinkage, yarn breakage (operability), and nonwoven fabric appearance of the obtained web.

（実施例２）

(Example 2)

The length of the cylindrical heater 4 was 150 mm, and the spinning speed was 7500 m / min. In this case, the residence time t of the yarn 3 inside the heater 4 was 0.48 seconds. And otherwise, it carried out similarly to Example 1, and obtained the long fiber nonwoven fabric which consists of a 2.2 dtex long fiber. Details of Example 2 are shown in Table 1.
(Example 3)

The length of the cylindrical heater 4 was 300 mm, and the spinning speed was 8000 m / min. In this case, the residence time t of the yarn 3 inside the heater 4 was 0.95 seconds. And otherwise, it carried out similarly to Example 1, and obtained the long fiber nonwoven fabric which consists of a 2.1 dtex long fiber. Details of Example 3 are shown in Table 1.
(Example 4)

The heating temperature T1 was 120 ° C. ([Tm−48] ° C.), and the traction speed was 7000 m / min. In this case, the residence time t of the yarn 3 inside the heater 4 was 0.48 seconds. And otherwise, it carried out similarly to Example 2, and obtained the long-fiber nonwoven fabric which consists of a 2.4-dtex long fiber. Details of Example 4 are shown in Table 1.
(Example 5)

The length of the cylindrical heater 4 was 150 mm, the heating temperature T1 was 200 ° C. ([Tm + 32] ° C.), and the traction speed was 7500 m / min. In this case, the residence time t of the yarn 3 inside the heater 4 was 0.48 seconds. And otherwise, it carried out similarly to Example 1, and obtained the long-fiber nonwoven fabric which consists of a 2.2-dtex long fiber. Details of Example 5 are shown in Table 1.
(Example 6)

In FIG. 1, a spinneret 2 with a round hole diameter of 0.6 mmφ was used, and the single hole discharge rate was 4.00 g / min. Moreover, the length of the cylindrical heater 4 was 300 mm, and the traction speed was 6000 m / min. In this case, the residence time t of the yarn 3 inside the heater 4 was 1.59 seconds. Other than that, a long-fiber nonwoven fabric composed of 6.6 dtex long fibers was obtained in the same manner as in Example 1. Details of Example 6 are shown in Table 1.
(Example 7)

  The MFR was 50 g / 10 min and the traction speed was 7000 m / min. In this case, the residence time t of the yarn 3 inside the heater 4 was 0.48 seconds. And otherwise, it carried out similarly to Example 2, and obtained the long-fiber nonwoven fabric which consists of a 2.4-dtex long fiber. Details of Example 7 are shown in Table 2.

（実施例８）

(Example 8)

The MFR was 80 g / 10 min and the traction speed was 7000 m / min. In this case, the residence time t of the yarn 3 inside the heater 4 was 0.48 seconds. And otherwise, it carried out similarly to Example 2, and obtained the long-fiber nonwoven fabric which consists of a 2.4-dtex long fiber. The details of Example 8 are shown in Table 2.
Example 9

The MFR was 30 g / 10 min, the round hole diameter of the spinneret 2 was 0.4 mmφ, and the traction speed was 6000 m / min. The residence time t of the yarn 3 inside the heater 4 was 0.85 seconds. Other than that, a long-fiber nonwoven fabric composed of 2.7 dtex long fibers was obtained in the same manner as in Example 2. Details of Example 9 are shown in Table 2.
(Example 10)

The fiber cross section was flattened. The length of the tube heater 4 was 150 mm, and the traction speed was 7000 m / min. In this case, the residence time t of the yarn 3 inside the heater 4 was 1.14 seconds. Other than that, a long-fiber nonwoven fabric composed of 2.7 dtex long fibers was obtained in the same manner as in Example 2. Details of Example 10 are shown in Table 2.
(Example 11)

  As a core component, an L-lactic acid / D-lactic acid copolymer having a melting point Tm of 168 ° C., an MFR of 30 g / 10 min, and L-lactic acid / D-lactic acid = 98.7 / 1.3 mol% was prepared. . On the other hand, as a sheath component, an L-lactic acid / D-lactic acid copolymer having a melting point Tm of 155 ° C., an MFR of 60 g / 10 min, and L-lactic acid / D-lactic acid = 95.5 / 4.5 mol%. Prepared.

The two kinds of polymers were individually weighed so that the core / sheath = 1/1 (mass ratio), and then melted at a spinning temperature of 210 ° C. using an individual extruder type extruder, and the pore diameter was 0.4 mmφ. The spinneret 2 was melt-spun at a single-hole discharge rate of 1.38 g / min so as to have a core-sheath fiber cross section. A cylindrical heater 4 having an effective heating length of 50 mm and a heating temperature of 150 ° C. is provided immediately below the spinneret 2 in FIG. Then, the yarn 3 spun from the spinneret 2 is retained in the heater 4 for 0.34 seconds, and further the cooling air 5 is blown by the cooling device 5, and then the air soccer as the traction device 7. Was taken up at 6000 m / min, and was opened and deposited on the collecting surface of the moving conveyor to form a web. Next, it was passed through a partial thermocompression bonding device comprising an embossed roller, and partially heated under the conditions of a roll temperature of 130 ° C., a crimping area ratio of 14.9%, a crimping point density of 21.9 pieces / cm ² , and a linear pressure of 60 kg / cm. Crimping was performed to obtain a long-fiber non-woven fabric having a basis weight of 50 g / m ² made of 2.3 dtex long fibers. Table 2 shows the measurement results of the obtained web, such as the thermal shrinkage rate, thread breakage (operability), and nonwoven fabric appearance.
(Example 12)

  L-lactic acid / D-lactic acid = 98.7 / 1.3 mol% L-lactic acid / D-lactic acid copolymer (hereinafter abbreviated as “P1”) having a melting point Tm of 168 ° C. and an MFR of 50 g / min. ) Was prepared. On the other hand, L-lactic acid / D-lactic acid = 95.5 / 4.5 mol% L-lactic acid / D-lactic acid copolymer (hereinafter referred to as “P2”) having a melting point Tm of 155 ° C. and MFR of 60 g / min. And a polybutylene adipate terephthalate copolymer having a melting point of 110 ° C. and an MFR of 50 g / min (trade name: Easter Bio GP; hereinafter abbreviated as “P3”) manufactured by Eastman Chemical Co., Ltd. A blend (hereinafter abbreviated as “P4”) prepared by blending so that P3 = 90/10 (mass ratio) was prepared.

Two polymers P1 and P4 were weighed separately so that P1 was a core component, P4 was a sheath component, and core / sheath = 1/1 (mass ratio), and then an individual extruder extruder was used. Used, melted at a spinning temperature of 210 ° C., and melt-spun at a single-hole discharge rate of 1.38 g / min using a spinneret 2 (FIG. 1) having a hole diameter of 0.4 mmφ so as to have a core-sheath fiber cross section. did. A cylindrical heater 4 having an effective heating length of 50 mm and a heating temperature T1 of 150 ° C. was provided immediately below the spinneret 2, and the yarn 3 spun from the spinneret 2 was retained for 1.02 seconds. Further, after cooling air 6 at 20 ° C. is blown onto the yarn 3 in the cooling device 5, the air soccer as the traction device 7 is taken up at 6000 m / min, and is opened on the collecting surface of the moving conveyor. Deposited to form a web. Next, it is passed through a partial thermocompression bonding machine composed of embossed rollers, and partially thermocompression bonded under the conditions of a roll temperature of 130 ° C., a crimping area ratio of 14.9%, a crimping point density of 21.9 pieces / cm ² , and a linear pressure of 60 kg / cm. Thus, a non-woven fabric having a basis weight of 50 g / m ^{2 made} of a long fiber of 2.3 dtex was obtained. Table 2 shows the measurement results of the obtained web, such as the thermal shrinkage rate, thread breakage (operability), and nonwoven fabric appearance.
(Comparative Example 1)

  When operated without a heater just below the spinneret, the traction speed could not be increased and the speed was set at 5000 m / min. And otherwise, it carried out similarly to Example 1, and obtained the long-fiber nonwoven fabric. Table 2 shows the measurement results of the obtained web, such as the thermal shrinkage rate, thread breakage (operability), and nonwoven fabric appearance.

  Since the nonwoven fabrics of Examples 1 to 12 were all formed by the spun yarn 3 heat-treated by the heater 4 provided immediately below the spinneret 2 as shown in FIG. As shown in Tables 1 and 2, it was possible to keep the hot water shrinkage low. In particular, as shown in Examples 1 to 3, the longer the residence time of the yarn 3 in the heater 4 is, the more the crystallization of the polymer constituting the yarn 3 is reduced until it is introduced into the traction device 7. Since the effect could be achieved, the orientation and crystallization at the time of high-speed traction in the traction device 7 could be improved, and the hot water shrinkage rate could be kept low. Further, as shown in Examples 4 to 5, the higher the heating temperature T1 in the heater 4, the more the crystallization of the polymer constituting the yarn 3 until the introduction into the traction device 4 could be suppressed. The orientation crystallization during high-speed traction can be improved, and the hot water shrinkage rate can be kept low.

  On the other hand, the nonwoven fabric of Comparative Example 1 was not provided with the heater 4 and was immediately cooled by the cooling device without heating the spun yarn, and thus constituted the yarn before being introduced into the traction device 7. The crystallization of the polymer progressed, and thus the hot water shrinkage ratio was 15% or more.

It is a figure which shows schematic structure of the manufacturing apparatus of the polylactic acid-type long fiber nonwoven fabric of embodiment of this invention.

Explanation of symbols

2 Spinneret 3 Spinning yarn 4 Non-contact heater 7 Pulling device L Length of heated part

Claims (6)

A method for producing a non-woven fabric composed of long fibers made of a polylactic acid-based polymer, in producing a long-fiber non-woven fabric by depositing fibers obtained by melt spinning the polylactic acid-based polymer by a spunbond method, A non-contact type heater disposed immediately below the spinneret to heat the spun yarn, and then tow the spun yarn at 6000 m / min to 8000 m / min. Manufacturing method. As heating conditions for the spun yarn, the heating temperature T1 (° C.) of the non-contact type heater with respect to the melting point Tm (° C.) of the polylactic acid polymer, and the residence time t (second) of the spun yarn in the heater Using the conditions which satisfy | fill following formula (1) and (2), respectively, The manufacturing method of the polylactic acid-type long fiber nonwoven fabric of Claim 1 characterized by the above-mentioned.
Tm−70 ≦ T1 (° C.) ≦ Tm + 100 (1)
0.07 ≦ t (seconds) ≦ 1.80 (2) The polylactic acid-based length according to claim 1 or 2, wherein the polylactic acid-based polymer has a melt flow rate measured at 210 ° C in accordance with ASTM-D-1238 at 20 to 80 g / 10 minutes. A method for producing a fiber nonwoven fabric. A non-contact type heater for heating a spun yarn directly under a spinneret for producing a long-fiber nonwoven fabric by depositing fibers obtained by melt-spinning a polylactic acid polymer by a spunbond method And a pulling device for pulling the heated yarn at a speed of 6000 m / min to 8000 m / min is provided below the non-contact type heater. A long fiber nonwoven fabric produced by the production method according to any one of claims 1 to 3 or the production apparatus according to claim 4, wherein the long fibers constituting the nonwoven fabric have a single-phase cross section, A polylactic acid-based long fiber nonwoven fabric having a hot water shrinkage of 15% or less. A long-fiber non-woven fabric manufactured by the manufacturing method according to any one of claims 1 to 3 or the manufacturing apparatus according to claim 4, wherein the long fibers constituting the non-woven fabric are a plurality of types having a melting point difference. A polylactic acid-based long-fiber nonwoven fabric characterized in that a polylactic acid-based polymer forms a composite cross section and has a hot water shrinkage rate of 20% or less.

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