JP2002061021A - Method for producing polylactic acid fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a uniform polylactic acid fiber good in mechanical properties, highly uniform in fiber fineness and seldom causing dyeing defects including dyeing unevenness. SOLUTION: This method for producing a polylactic acid fiber comprises the following process: a highly oriented undrawn yarn of polylactic acid with L-lactic acid and/or D-lactic acid as the main recurring unit(s), having a birefrigence Δn of 0.008-0.020, is drawn by a factor of 1.1-2.5 between a feed roller rotating at a given rate and a draw roller rotating at a higher rate than the feed roller, and then heat-seat by a heat treatment means situated downstream of the feed roller; wherein the temperature T1 ( deg.C) of the feed roller and the temperature T2 ( deg.C) of the heat treatment means are characterized by meeting the relationship (1): 70<=T1<=100, and T1+10<=T2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polylactic acid fibers. More specifically, the present invention relates to a method for producing a polylactic acid fiber, characterized by obtaining a polylactic acid drawn yarn having good mechanical properties and fineness uniformity by stretching a highly oriented undrawn yarn using specific temperature conditions. .

[0002]

2. Description of the Related Art Polylactic acid fibers are attracting a great deal of attention as biodegradable fibers that degrade in the natural environment and as novel fibers having excellent coloring and tactile sensation.

[0003] Conventionally, polylactic acid fibers have been produced by a conventional method of spinning at a spinning speed of 2500 m / min or less and stretching the fiber by 2.5 times or more. However, in this case, since the molecular orientation of the undrawn yarn is extremely low, it is difficult to generate a uniform molecular orientation at the time of drawing, and as a result, only fibers having poor uniformity (U%) in fineness are obtained. I couldn't get it. In the case of using polylactic acid fibers for clothing, it is generally necessary to dye the fabric. With fibers having poor uniformity (U%) of fineness, dyeing irregularities such as spots occur, and Cannot be obtained.

[0004] JP-A-10-37020 and JP-A-Hei-1
Japanese Patent Application Publication No. 1-61561 discloses a method of spinning at a high speed to obtain an oriented crystallized fiber. Since these methods do not require a subsequent drawing step, they are efficient yarn production methods, and fibers with excellent uniformity of fineness can be obtained. It has a drawback of being inferior in high-order workability because it is low and the boiling water shrinkage rate is high.

[0005]

The problem to be solved by the present invention is to solve the above-mentioned problems, to have good mechanical properties, high uniformity of fineness, and to hardly cause dyeing defects such as spots. An object of the present invention is to provide a method for producing a homogeneous polylactic acid fiber.

[0006]

In order to achieve the above-mentioned object of the present invention, the present invention has the following constitution. (1) The birefringence Δn is 0.0, which is composed of polylactic acid having L-lactic acid and / or D-lactic acid as a main repeating unit.
A highly oriented undrawn yarn having a length of 08 to 0.020 is stretched 1.1 to 2.5 times between a supply roller rotating at a constant speed and a stretching roller rotating at a speed higher than the supply roller, When heat setting is performed by a heat treatment unit located downstream of the supply roller, the temperature T1 (° C.) of the supply roller and the temperature T2 (° C.) of the heat treatment unit satisfy a relationship represented by the following expression (1). A method for producing a polylactic acid fiber.

70 ≦ T1 ≦ 100, T1 + 10 ≦ T2 (1) (2) The method for producing a polylactic acid fiber according to the above (1), wherein the heat treatment means is a drawing roller. (3) The polylactic acid having L-lactic acid and / or D-lactic acid as a main repeating unit has a weight average molecular weight of 80,00.
(1) wherein the number is from 0 to 170,000.
Or the method for producing a polylactic acid fiber according to (2). (4) Worster normal% of highly oriented undrawn yarn (U1)
And (1) to (1), wherein the Worcester normal% (U2) of the drawn yarn satisfies the relationship of the following formula (2).
The method for producing a polylactic acid fiber according to any one of (3).

U2 ≦ 1.7 × U1 (2)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polylactic acid fiber of the present invention comprises polylactic acid having L-lactic acid and / or D-lactic acid as a main repeating unit. The method for producing polylactic acid includes a two-stage lactide method in which L-lactic acid and / or D-lactic acid is used as a raw material to once produce lactide as a cyclic dimer, followed by ring-opening polymerization, and L-lactic acid and / or Alternatively, a one-stage direct polymerization method in which D-lactic acid is used as a raw material to directly perform dehydration condensation in a solvent is known. The polylactic acid used in the present invention may be obtained by any production method.

The weight average molecular weight of polylactic acid is 80,00
It is preferably from 0 to 170,000. If the weight-average molecular weight is less than 80,000, the strength of the fiber becomes low, so that the yarn tends to be broken during spinning or drawing or the durability of the fabric tends to be poor, which is not preferable.
On the other hand, when the weight average molecular weight is higher than 170,000, the molecular orientation during spinning and stretching becomes difficult, so that unevenness is likely to occur. Becomes remarkable. The weight average molecular weight of the polylactic acid is preferably from 100,000 to 150,000, and most preferably from 110,000 to 130,000, from the viewpoint of good fiber properties and easy orientation.

Further, 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, 6
-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, Compounds containing a plurality of carboxylic acid groups in the molecule, such as adipic acid, sebacic acid, and fumaric acid, and derivatives thereof are included. It is desirable that the copolymer component does not contain an aromatic ring in the molecular structure. Further, in order to maintain good mechanical properties, it is desirable that 80 mol% or more is composed of L-lactic acid and / or D-lactic acid.

In order to reduce the melt viscosity, an aliphatic polyester polymer such as polycaprolactone, polybutylene succinate, polyethylene succinate and polyhydroxybutyric acid can be used as an internal plasticizer or as an external plasticizer.

Further, in order to improve the hydrolysis resistance, the carboxyl terminal group of polylactic acid is treated with a terminal blocking agent such as a carbodiimide compound, an epoxy compound, an oxazoline compound, an oxazine compound, an aziridine compound, a diol compound and a long-chain alcohol compound. Blocked polylactic acid may be used.

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.

In the method for producing a polylactic acid fiber of the present invention, the birefringence Δn of the highly oriented undrawn yarn to be drawn is
It is important that it is between 0.008 and 0.020. When the birefringence Δn is less than 0.008, the molecular orientation of the undrawn yarn is extremely low, so that the orientation is not smoothly performed during the drawing. That what fineness unevenness of very drawn yarn stretching conditions for the becomes a big thing,
In the case of dyeing a fabric made using such fibers, dyeing abnormalities such as spots may occur. In the case of an unstretched yarn having a birefringence Δn of higher than 0.020, the elongation of the unstretched yarn has already been reduced, so that a high draw ratio cannot be obtained and the strength does not improve. In addition, even during stretching, single yarn breakage is likely to occur, and the generation of fluff deteriorates the high-order processing passability, which is not preferable. From the viewpoint of good stretchability, the birefringence Δn of the polylactic acid highly oriented undrawn yarn is more preferably 0.02
10 to 0.015.

In the method for producing a polylactic acid fiber of the present invention, the highly oriented undrawn yarn is moved between a supply roller rotating at a constant speed and a drawing roller rotating at a higher speed than the supply roller. The film is stretched 5 times, and heat set is performed by a heat treatment unit located downstream of the supply roller.

When the stretching ratio is less than 1.1, the orientation crystallization during stretching does not sufficiently proceed, and the strength cannot be improved. On the other hand, when the draw ratio exceeds 2.5 times, the draw ratio is too high, and even when an undrawn yarn having an appropriate birefringence is used, the fineness unevenness tends to deteriorate, which is not preferable. In light of good mechanical properties and stretchability, the stretch ratio between the supply roller and the stretch roller is more preferably 1.2 to 2.0 times, and most preferably 1.3 to 1.7 times. is there. The strength of the drawn yarn is preferably 3.0 cN / dtex or more from the viewpoint of high-order processing passability.

In the method for producing a polylactic acid fiber of the present invention, it is important that the temperature T1 (° C.) of the supply roller and the temperature T2 (° C.) of the heat treatment unit satisfy the following equation (1).

70 ≦ T1 ≦ 100, T1 + 10 ≦ T2 (1) When the temperature T1 of the supply roller is less than 70 ° C.,
Preheating becomes insufficient, so that thermal deformation during stretching is not performed uniformly, and unevenness of fineness is generated. On the other hand, if the temperature exceeds 100 ° C., the yarn sway on the roller becomes severe and the stretching point cannot be fixed, so that fineness unevenness occurs. for that reason,
The temperature T1 of the supply roller is 70 ° C. or more and 100 ° C. or less, more preferably 80 ° C. or more and 95 ° C. or less, and most preferably 82 ° C. or more and 90 ° C. or less.

Further, the temperature T2 of the heat treatment means is set to be higher than the temperature of the supply roller by 10 ° C. or more.
When the temperature T2 of the heat treatment means is not higher than the temperature T1 of the supply roller by 10 ° C. or more, the heat setting of the fiber is not sufficiently performed, and the obtained drawn yarn has a high boiling water shrinkage and a poor stability. . The boiling water shrinkage of the drawn yarn is desirably 15% or less from the viewpoint of handleability of the fabric.

Here, the heat treatment means is provided downstream of the supply roller, and is not particularly limited as long as it can directly or indirectly heat the running yarn. As a specific heat treatment means, a heat roller,
Examples include a hot plate, a steam generator, a hot tube, and a slit heater. It is preferable to use a heat roller as a heat treatment means from the viewpoint of reducing heating efficiency and running friction against the fiber. In this case, it is most efficient that the drawing roller 2 is heated and also serves as the heat treatment means 3, as shown in FIG. It is. In FIG. 1, reference numeral 5 denotes a highly oriented undrawn yarn, which is drawn in a drawing zone 4 between the supply roller 1 and the drawing roller 2. Further, as shown in FIG. 2, a stretching method in which a heat treatment is performed between the supply roller 1 and the heated or unheated stretching roller 2 under tension or relaxation by a heat treatment means 3 such as a hot plate.

In the drawing of the present invention, the highly oriented undrawn yarn may be once wound in the spinning step and then drawn, or a method of continuous drawing from the spinning step may be employed.

In the above-described method for producing a polylactic acid fiber according to the present invention, in the highly oriented undrawn yarn, Worcester normal% (U1) and drawn yarn, Worcester normal% (U2)
Preferably satisfies the relationship of the following expression (2).

U2 ≦ 1.7 × U1 (2) A highly oriented undrawn yarn in which the Wooster Normal% (U2) of the drawn yarn that is drawn and subjected to a heat treatment is a fiber before drawing. It is an important matter to obtain a drawn yarn excellent in uniformity of fineness that it is 1.7 times or less of Worcester Normal% (U1). U2 is more preferably not more than 1.5 times U1 and most preferably not more than 1.3 times.

[0025]

The present invention will be described in more detail with reference to the following examples. Each characteristic value in the examples is obtained by the following method. A. Birefringence (Δn) The birefringence was determined from the retardation and the fiber diameter by a compensator method using a BH-2 polarizing microscope manufactured by OLYMPUS. B. Fineness unevenness (Worcester normal%) Measurement was carried out using a Wooster unevenness tester manufactured by Zellbeger Worcester Co., Ltd. under conditions of a yarn speed of 25 m / min, a measurement type normal and a measurement time of 3 minutes, and the obtained value was defined as U%. . C. Boiling water shrinkage (boiling) The sample is wound into 10 skeins, and 0.1 cN / dte
The original length (L ₀ ) is measured under a load of x. 98 ° C
After treatment in a boiling water bath with no load for 15 minutes, take it out, air-dry, and measure the post-treatment length (L ₁ ) under a load of 0.1 cN / dtex. The value obtained by the following equation was defined as the boiling water shrinkage (boiling yield).

Boiling yield (%) = {(L ₀ −L ₁ ) / L ₀ } × 100 Dyed spots A wefted fabric was prepared using the drawn yarn to be measured, dyed under the following conditions, and visually determined for dyed spots. That is, ◎ indicates no dyeing spots, ○ indicates almost no dyeing spots, 斑 indicates dyeing spots but has an acceptable level, and × indicates marked dyeing spots (10 each). , 15, 30, 50 points).

Disperse dyes, etc .: Sumikaron Navy Blue S-2GL: 0.6% owf Tetrosin Pen: 5.0% owf Sun salt # 1200: 1.0% owf Dyeing conditions: 98 ° C. × 60 minutes Bath ratio: 1: 50E. Strength After leaving the sample in a temperature control room at 20 ° C. and 65% RH for 24 hours or more, an SS curve was obtained using a Tensilon tensile tester manufactured by Orientec Co., Ltd. at a test length of 25 cm and a take-up speed of 30 cm / min. Calculated and divided by fineness to obtain strength (cN / te
x) was calculated.

Examples 1-4 Chips of poly-L-lactic acid having a weight average molecular weight of 120,000 were dried for 12 hours in a vacuum dryer set at 105 ° C. The dried chips were melted at a melter temperature of 220 ° C. by a pressure melter type spinning machine, and a spinning temperature of 22 ° C.
0.30mmφ-
It was spun from a 0.50 mmL die hole. This spun yarn is
After cooling at 0 ° C. with a 30 m / min chimney wind, applying an oil agent and converging, the mixture was taken out at 3000 m / min to obtain a 120 dtex-36f highly oriented undrawn yarn.
When Δn of this highly oriented undrawn yarn was measured,
2, and Worcester Normal% (U1) was 0.68.

The undrawn yarn is subjected to 1 HR temperature T1 (° C.), 2
Stretching was performed under the conditions of HR temperature T2 (° C.) and the stretching ratio shown in Table 1, and a stretching speed of 800 m / min (see FIG. 1).

As shown in Table 1, U2 of the obtained drawn yarn was 1.7 times or less of U1 of the highly oriented undrawn yarn, and it was found that a uniform fiber having a small fineness unevenness was obtained. Was. Example 2 where T1 was 85 ° C. and T1 was 10
In Example 3 at 0 ° C., U2 was a slightly higher value. Dyeing spots were scarcely recognized at all levels, showing good appearance quality. In addition, the boiling points of all the fibers were within 15%, indicating that the fibers had excellent thermal stability.

Examples 5 to 7 Stretching was performed in the same manner as in Examples 1 to 4, except that the weight average molecular weight of the poly L-lactic acid polymer used was changed as shown in Table 1. The obtained drawn yarn had good fineness uniformity and heat setting property as shown in Table 1.

However, in Example 6 in which polylactic acid having a molecular weight of 62,000 was used, breakage of a single yarn was sometimes caused at the time of stretching, and the yarn forming property was not good. In Example 7 using polylactic acid having a molecular weight of 198,000, the drawn yarn had a high Worcester Normal% (U2), and dyed spots were observed.

Example 8 The poly L-lactic acid polymer used had a molecular weight of 150,
The stretching was carried out in the same manner as in Example 1 except that D-lactic acid copolymerized poly L-lactic acid having a D-lactic acid copolymerization ratio of 5% was used. The obtained drawn yarn had good fineness uniformity and heat setting property as shown in Table 1.

Comparative Examples 1 to 4 1HR temperature T1 (° C.) during stretching and 2HR temperature T2 (° C.)
The stretching was performed in the same manner as in Example 1 except that the stretching ratio was changed to the temperature shown in Table 1. Comparative Example 1
Since T1 was as low as 60 ° C., unevenness of fineness of the obtained drawn yarn was large, and marked dyeing unevenness was observed in the dyed fabric.
In Comparative Example 2, since T2 was low at room temperature (about 30 ° C.), the boiling water shrinkage ratio was as high as 40.2%, and the fabric was significantly shrunk during dyeing, making it difficult to handle high-order processing. It was something with In Comparative Example 3, the draw ratio was too high, and a single winding and a broken yarn due to a single yarn break occurred during stretching. Fluff was also observed in the fabric, and the quality was problematic.

Comparative Example 4 A poly L-lactic acid highly oriented undrawn yarn obtained in the same manner as in Example 1 except that the spinning speed was 1300 m / min, and this undrawn yarn was drawn by a hot roller-hot roller system. 1HR temperature T1 is 90 (° C) and 2HR temperature T
2 was stretched at a stretching ratio of 3.0 under the conditions of 120 (° C.) and a stretching speed of 800 m / min. Δn of highly oriented undrawn yarn
Was 0.004 and Worcester Normal% (U1) was 0.48. The obtained drawn yarn was a fiber having an extremely large fineness unevenness.

Comparative Example 5 A poly-L-lactic acid highly oriented undrawn yarn was obtained in the same manner as in Example 1 except that the spinning speed was changed to 6000 m / min. Δn of the obtained fiber was 0.022, and U1% was 0.82. The boiling point is as high as 20.8% and the strength is 2.4 cN.
/ Dtex was low.

[0037] A wefted fabric was prepared without stretching this fiber and dyed. As a result, weaving sink occurred and marked spots were observed.

[0038]

[Table 1]

[0039]

By using the method for producing polylactic acid fiber of the present invention, a thermally stable drawn yarn having excellent mechanical properties and a low shrinkage rate can be obtained, and a polylactic acid fiber without unevenness of fineness can be produced. Can be manufactured. As a result, it is possible to obtain a high-quality polylactic acid fiber structure having a high strength and free from abnormal dyeing such as spotting.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a method for producing a polylactic acid fiber of the present invention.

FIG. 2 is a process chart showing another example of the method for producing a polylactic acid fiber of the present invention.

[Explanation of symbols]

 1: Supply roller 2: Drawing roller 3: Heat treatment means 4: Drawing zone 5: Highly oriented undrawn yarn

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4L035 BB33 BB56 BB77 BB89 BB91 DD20 EE20 4L036 MA05 MA26 MA33 PA01 PA03 PA17 UA25

Claims (4)

[Claims] 1. A highly oriented undrawn yarn comprising a polylactic acid having L-lactic acid and / or D-lactic acid as a main repeating unit and having a birefringence index Δn of 0.008 to 0.020 is produced at a constant speed. 1.1 to 2.5 between a rotating supply roller and a stretching roller rotating at a higher speed than the supply roller.
When performing heat setting by a heat treatment unit located downstream of the supply roller, the temperature T1 (° C.) of the supply roller and the temperature T2 of the heat treatment unit
(C) which satisfies the relationship of the following formula (1). 70 ≦ T1 ≦ 100, T1 + 10 ≦ T2 (1) 2. The method for producing polylactic acid fiber according to claim 1, wherein the heat treatment means is a drawing roller. 3. A polylactic acid having L-lactic acid and / or D-lactic acid as a main repeating unit has a weight average molecular weight of 8%.
The method for producing a polylactic acid fiber according to claim 1 or 2, wherein the number is from 000 to 170,000. 4. Worcester normal% of highly oriented undrawn yarn
2. The method according to claim 1, wherein (U1) and the wool normal% (U2) of the drawn yarn satisfy the relationship of the following expression (2).
The method for producing a polylactic acid fiber according to any one of claims 3 to 3. U2 ≦ 1.7 × U1 (2)