JP3692950B2 - Polylactic acid fiber and method for producing the same - Google Patents

Description

【００５９】
【表３】

【００６０】
【発明の効果】
本発明の繊維は適度な収縮率を有し、かつ１００℃における収縮応力が高いため、布帛構造を構成している場合にも繊維の収縮が可能である。そのため、精練や染色などの熱水処理によって、布帛は適度に収縮が可能であり、しぼ立てや糸長差発現などの風合い出し加工を行うことができる。
【図面の簡単な説明】
【図１】本発明の脂肪族ポリエステル繊維の製造方法の一例を示す工程概略図である。
【図２】本発明の脂肪族ポリエステル繊維の製造方法の他の一例を示す工程概略図である。
【符号の説明】
１：予熱ローラー
２：熱セットローラー
３：冷ローラー
４：ストレッチゾーン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polylactic acid fiber that can be appropriately contracted in hot water and a method for producing the same. More specifically, since the fiber can be shrunk even when a load is applied in the fabric structure, it is particularly useful as a woven or knitted fiber subjected to texture processing such as a fiber for squeezing or a fiber for shrinkage difference mixed yarn. It relates to a suitable polylactic acid fiber.
[0002]
[Prior art]
Polylactic acid fiber is attracting a great deal of attention as a biodegradable fiber that decomposes in the natural environment, and as a new fiber with excellent color development and tactile sensation. .
[0003]
Polylactic acid fibers used for clothing fibers are obtained by drawing undrawn yarns that have been spun once, for example, as described in JP-A-7-305227. Spinning and drawing methods are employed. In a normal stretching method, i.e., stretching using a heated roller or hot plate, and then applying a heat set and then cooling and winding, the roller speed for heat setting and the roller speed for cooling are almost the same. In this case, there was a problem that the resulting polylactic acid fiber had low shrinkage stress, and in particular, almost no shrinkage stress at 100 ° C. was generated.
[0004]
When used for woven or knitted fabrics as clothing fibers, the fabric structure may need to be shrunk by hot water treatment to create a texture such as relaxing scouring, squeezing and expression of yarn length difference. Since the polylactic acid fiber obtained by the above method has insufficient shrinkage stress, it cannot be shrunk almost due to the restraining force in the fabric structure, and has a drawback that it cannot be textured.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to overcome the above-described problems and provide a polylactic acid fiber that can be shrunk in hot water, particularly when viewed as a fabric structure, and a method for producing the same.
[0006]
[Means for Solving the Problems]
The problems of the present invention described above are that the shrinkage stress at 100 ° C. is 0.05 to 0.5 cN / dtex, the boiling water shrinkage rate S ₀ under no load and the boiling water shrinkage rate S under 0.01 cN / dtex load. _This can be solved by a polylactic acid fiber characterized in that 1 satisfies the following formulas 1 , 2 and 3 .
[0007]
5 <S ₁ <11.5 (Formula 1)
S ₀ × 0.7 <S ₁ (Formula 2)
S ₀ ≦ 12.5 (Expression 3)
In order to obtain such a polylactic acid fiber, after unwinding and drawing the undrawn yarn once or without drawing it once , the running yarn is brought into contact with the heated rotating roller and the heat set is performed. In the manufacturing method of the polylactic acid fiber to be performed, the temperature of the heat setting roller is set to 90 to 140 ° C., and the yarn that is heat set by the heat setting roller is cooled by a cold roller that rotates at a higher speed than the heat setting roller. A method for producing polylactic acid fibers characterized by stretching 1.05 to 2.0 times can be employed.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In general, the fibers in the fabric structure are constrained by adjacent fibers and are in a state in which free shrinkage is difficult. In particular, when it is intended to perform a textured process such as relaxation scouring, squeezing, and expression of a difference in yarn length, it is necessary that the fibers can overcome the restraint of adjacent fibers in the fabric structure and can shrink appropriately.
[0009]
In order to enable this appropriate shrinkage, it is important that the shrinkage stress of the fiber at 100 ° C. is 0.05 to 0.5 cN / dtex.
[0010]
The shrinkage ratio of polylactic acid fibers under no load increases as the shrinkage treatment temperature increases. On the other hand, after the peak value of the shrinkage stress reaches about 70 ° C, it gradually decreases with increasing temperature in the higher temperature range. Resulting in. For this reason, it is very important that the shrinkage stress is 0.05 cN / dtex or more at 100 ° C., which is the maximum temperature that can be taken by a normal pressure apparatus in which the texture processing is performed. When the shrinkage stress at 100 ° C. is less than 0.05 cN / dtex, the fibers cannot sufficiently shrink due to the restraining force of adjacent fibers. On the other hand, a fiber exhibiting a high shrinkage stress exceeding 0.5 cN / dtex is not desirable because it causes problems in the yarn production process such as winding of the package and concerns about the quality. From the viewpoint of better shrinkage characteristics, the shrinkage stress of the fiber at 100 ° C. is 0.07 to 0.15 cN / dtex.
[0011]
Further, polylactic acid fiber boiling water shrinkage _S 1 (%) satisfies the following formula 1 in the boiling water shrinkage _S 0 (%) and 0.01cN / dtex under a load under no load of the present invention, equations 2 and 3 It is important to satisfy this relationship.
[0012]
5 <S ₁ < 11.5 (Formula 1)
S ₀ × 0.7 <S ₁ (Formula 2)
S ₀ ≦ 12.5 (Expression 3)
The boiling water shrinkage ratio S ₁ under a load of 0.01 cN / dtex corresponds to the shrinkage ratio of the fibers in boiling water when the fibers exist as a fabric structure such as a woven fabric or a knitted fabric. If this S ₁ is 5% or less, it does not occur contracted as the fabric structure is not preferable because the texture out effects such as grain fresh and yarn length difference expression can not be obtained. On the other hand, if it is 11.5 % or more, the fabric may be cured by excessive shrinkage, which is not preferable.
[0013]
The boiling water shrinkage ratio S ₁ under a load of 0.01 cN / dtex is generally smaller than the shrinkage ratio S ₀ of the fiber under no load, but the polylactic acid fiber of the present invention has a sufficient shrinkage stress at 100 ° C. Since the value is high, S ₁ is larger than S ₀ × 0.7. From the viewpoint of better shrinkage characteristics, S ₁ is preferably a value larger than S ₀ × 0.8.
[0014]
The polylactic acid fiber of the present invention is composed of polylactic acid mainly composed of L-lactic acid and / or D-lactic acid, and the ratio of either L-lactic acid or D-lactic acid in the polylactic acid is 95 mol% or more. It is preferable to employ some. From the viewpoint of heat resistance, it is more preferable that the ratio of L-lactic acid or D-lactic acid in the polylactic acid is 98% or more.
[0015]
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 form lactide, which is a cyclic dimer, and then ring-opening polymerization is performed. Alternatively, a one-step direct polymerization method in which dehydration condensation is directly performed in a solvent using D-lactic acid as a raw material is known. The polylactic acid used in the present invention may be obtained by any method.
[0016]
The average weight molecular weight of polylactic acid is usually at least 50,000, preferably at least 100,000, preferably 100,000 to 300,000. If the average weight molecular weight is lower than 50,000, only fibers having low strength properties can be obtained.
[0017]
The melting point of polylactic acid is 100 ° C. or higher, preferably 140 ° C. or higher, and most preferably 160 ° C. or higher. If the melting point is less than 100 ° C, the product quality is extremely low, such as poor stretchability due to the occurrence of fusion between single yarns, and fusing defects during dyeing, heat setting, and friction heating. Therefore, it cannot be used for clothing. Here, the melting point means the peak temperature of the first run melting peak obtained by DSC measurement.
[0018]
The polylactic acid in the present invention may be a copolymerized polylactic acid obtained by copolymerizing other components having ester forming ability in addition to L-lactic acid and D-lactic acid. The copolymerizable component includes glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, hydroxycarboxylic acids such as 6-hydroxycaproic acid, ethylene glycol, propylene glycol, butanediol, neo Compounds containing a plurality of hydroxyl groups in the molecule such as pentyl glycol, polyethylene glycol, glycerin and pentaerythritol or derivatives thereof, compounds containing a plurality of carboxylic acid groups in the molecule such as adipic acid, sebacic acid and fumaric acid Or a derivative thereof.
[0019]
In order to reduce the melt viscosity, aliphatic polyester polymers such as polycaprolactone, polybutylene succinate, and polyethylene succinate can be used as an internal plasticizer or as an external plasticizer.
[0020]
In addition, in order to improve hydrolysis resistance, polylactic acid having a carboxyl terminal group blocked 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, or a long-chain alcohol compound. Lactic acid may be used. In this case, if the terminal carboxyl group concentration of the polylactic acid is 0 to 10 eq / t, it is possible to suppress a decrease in strength during the hot water treatment, so that sufficient processing for texture creation such as relaxing scouring and dyeing is sufficient. To be able to do that.
[0021]
Furthermore, inorganic fine particles and organic compounds can be added as necessary as a matting agent, deodorant, flame retardant, yarn friction reducing agent, antioxidant, coloring pigment, and the like.
[0022]
The polylactic acid fiber in the present invention desirably has a fiber strength of 2 cN / dtex or more. When the strength is less than 2 cN / dtex, it is not preferable because a yarn breakage stop at the time of weaving or weaving occurs or the strength of the fabric or knitted fabric is reduced, resulting in a decrease in product strength. More preferably, it is 3 cN / dtex or more, and most preferably 4 cN / dtex or more.
[0023]
Polylactic acid fiber of the present invention, after winding the undrawn yarn once, or after the stretching without once winding, polylactic acid fibers for performing a heated heat-set by contacting the running yarn to the rotating roller was In the production method, the temperature of the heat setting roller is 90 to 140 ° C., and the yarn that has been heat set by the heat setting roller is 1.05 to a cold roller that rotates at a higher speed than the heat setting roller. It can be produced by a method for producing polylactic acid fiber characterized by stretching 2.0 times.
[0024]
When the temperature of the heat setting roller is less than 90 ° C, the shrinkage rate of the obtained fiber may be too high, which is not preferable. The higher the temperature of the heated rotating roller, the lower the shrinkage rate S _{0 of the} fiber. However, at a temperature exceeding 140 ° C., the value of the shrinkage rate itself becomes too small and the fabric structure, which is the effect of the present invention, is moderate. This is not preferable because it may not be possible to shrink. In addition, fiber fusion may occur at a temperature higher than this. The temperature of the heated rotating roller is more preferably 110 to 130 ° C.
[0025]
As for the method of contacting the running yarn to the rotating roller, the fiber may be in contact with a part of the circumference of the roller, or the heated rotating roller and the separating roller are used in combination, or the heated rotation is performed. You may make it rotate in multiple times using a roller and another heated rotating roller. A part or all of the heated rotating roller may be a mirror surface, or a satin roller having a rougher surface than the mirror surface.
[0026]
Further, it is important that the yarn that has been heat set by the heat setting roller is stretched 1.05 to 2.0 times by a cold roller that rotates at a higher speed than the heat setting roller. The temperature of the cold roller only needs to be lower than the temperature of the heating roller that performs heat setting, and may be maintained at room temperature without actively heating. When the temperature of the cold roller is the same as or higher than that of the heat setting roller, the fibers have a very low shrinkage stress due to orientation relaxation.
[0027]
In addition, unlike general aromatic polyester fibers such as polyethylene terephthalate, polylactic acid fibers, when the stretch rate after heat setting is less than 1.05 times, causes orientation relaxation abruptly and hardly causes shrinkage stress. Become fiber. This is a phenomenon that is very specific to polylactic acid fibers. On the other hand, when the stretch rate is larger than 2.0 times, the strain remaining in the obtained fiber becomes too large, and process troubles such as winding tightening and package foam abnormality may occur.
The stretch rate is preferably 1.1 to 1.8 times, and most preferably 1.15 to 1.5 times from the viewpoint of good shrinkage characteristics and process passability.
[0028]
FIG. 1 is a process diagram showing an example of a method for producing a polylactic acid fiber of the present invention. In FIG. 1, an undrawn yarn that has been melt-spun and once wound is preheated by a preheating roller 1 and then drawn in a drawing zone with a heat setting roller 2 that is a heated rotating roller. The preheating temperature can be appropriately set so that the stretching tension does not become too high. The running yarn that has left the heat setting roller 2 is stretched 1.05 to 2.0 times in the stretch zone 4 that is between the next cold roller 3.
[0029]
FIG. 2 is a process diagram showing another example of the method for producing polylactic acid fiber of the present invention. In FIG. 2, the melt-spun running yarn is once taken up by the preheating roller 1 without being wound up and preheated, and is drawn between the heat setting roller 2 that is a heated rotating roller. The running yarn that has left the heat setting roller 2 is stretched 1.05 to 2.0 times with the cold roller 4 that rotates at a higher speed than the heat setting roller. A winder roller bale may be substituted for this cold roller.
[0030]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. In addition, each characteristic value in an Example was calculated | required with the following method.
[0031]
A. From a room temperature to 200 ° C. using a thermal stress measuring machine TYPE KE-2S manufactured by Kanebo Engineering under conditions of an initial load of 0.03 cN / dtex and a heating rate of 150 ° C./min. Obtain a heat-shrinkage stress curve with elevated temperature. The shrinkage stress at 100 ° C. was read from this heat shrinkage stress curve and used as the fiber shrinkage stress (cN / dtex).
[0032]
B. Strength Using a tensile tester (Tensilon UCT-100 type) manufactured by Orientec Co., Ltd., a tensile test was conducted under the conditions of a sample length of 20 cm and a tensile speed of 20 cm / min, and the stress at the breaking point was determined as the fiber strength (cN / dtex). did.
[0033]
C. Boiling water shrinkage under no load (S ₀ )
The sample is scraped 10 times, and the original length L ₀ is measured under a load of 0.1 cN / dtex. After removing the load to make it unloaded, the sample soot is removed for 15 minutes in a boiling water bath adjusted to 100 ° C. After air-drying this, the post-treatment length L ₁ is measured under a load of 0.1 cN / dtex. The value obtained by the following equation was used as the boiling water shrinkage under no load.
[0034]
S ₀ (%) = {(L ₀ −L ₁ ) / L ₀ } × 100
D. Boiling water shrinkage under load of 0.01 cN / dtex (S ₁ )
The sample is scraped 10 times, and the original length L ₀ is measured under a load of 0.1 cN / dtex. After removing the load, the load is attached so as to be 0.01 cN / dtex, and the soot of the sample is removed for 15 minutes in a boiling water bath adjusted to 100 ° C. After removing the load and air-drying it, the post-treatment length L ₁ is measured under a load of 0.1 cN / dtex. The value obtained by the following formula was defined as the boiling water shrinkage under a load of 0.01 cN / dtex.
[0035]
S ₁ (%) = {(L ₀ −L ₁ ) / L ₀ } × 100
E. A plain woven fabric (taffeta) having a warp yarn density of 40 yarns / cm and a weft yarn density of 40 yarns / cm is produced using fibers for measuring the shrinkage of the fabric. A 10 cm line is drawn in the weft direction of the woven fabric, and both ends are marked with a marker, followed by hot water treatment at 100 ° C. × 1 hr. After air drying, the distance L ₁ (cm) between the markers was measured, and the value obtained by the following formula was used as the shrinkage of the fabric.
[0036]
Fabric shrinkage (%) = {(10−L ₁ ) / 10} × 100
Example 1
A poly-L-lactic acid chip having a melting point of 168 ° C., a weight average molecular weight of 120,000 and an L-form ratio of 98 mol% was 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, introduced into a melt spinning pack having a spinning temperature of 220 ° C., and spun from a die hole of 0.23 mmφ−0.30 mmL. The spun yarn was cooled by a chimney wind at 20 ° C. and 30 m / min, and after converging by applying an oil agent, the spun yarn was taken up at 3000 m / min to obtain an undrawn yarn. The type of undrawn yarn obtained was 122 dtex-36f.
[0037]
This undrawn yarn is preheated with a preheating roller 1 (temperature 90 ° C.) using a hot roller / hot roller drawing machine shown in FIG. 1, and the draw ratio is 1 between the preheating roller 1 and the heat setting roller 2. The film was stretched so as to be doubled. The stretched running yarn was heat set at a temperature of 130 ° C. with the heat setting roller 2 and then stretched so as to be 1.2 times between the cold roller 3 at room temperature (stretch zone). The stretching speed was 800 m / min, and each roller was set to 6 revolutions. The obtained fiber was 84 dtex-36f.
[0038]
As shown in Table 1, the fiber was excellent in mechanical properties and did not cause a handling problem. Shrinkage _{S 0} under no load of the fibers was 11.0%. The shrinkage stress at 100 ° C. was a sufficiently high value of 0.08 cN / dtex, and the shrinkage rate S ₁ under load was 9.4 %, which was as high as 0.85 times S ₀ .
[0039]
When the shrinkage rate of the fabric produced using this fiber was measured, it was a sufficiently high value of 8.5 %, and it was found that the fabric can be textured.
[0040]
Example 2 , 3
A fiber of 84 dtex-36f was obtained in the same manner as in Example 1 except that the temperature of the heating roller 2 and the stretch ratio between the heating roller 2 and the cold roller 3 were set to the values described in Table 1.
[0041]
As shown in Table 1, the fiber was excellent in mechanical properties and did not cause a handling problem. The shrinkage stress of the fiber at 100 ° C. is a sufficiently high value of 0.06 to 0.10 cN / dtex, the shrinkage rate S1 under load is 7.4 to 11.5 %, and the S ₀ is 0.90 to The value was 0.92 times as high.
[0042]
When the shrinkage rate of the fabric produced using this fiber was measured, it was found to be a sufficiently high value of 6.6 to 10.4 %, and it was found that the fabric can be textured.
[0049]
Comparative Example 1
Example 1 except that the stretch ratio between the preheating roller 1 and the heat setting roller 2 is 1.44 times, and the stretch ratio between the heat setting roller 2 and the cold roller 3 (stretch zone) is 1.007 times. Similarly, a drawn yarn of 84 dtex-36f was obtained.
[0050]
As shown in Table 3, the shrinkage stress of this drawn yarn at 100 ° C. was an extremely low value of 0.01 cN / dtex, and the shrinkage rate S ₀ under no load was an appropriate value of 5.2%. The shrinkage ratio S ₁ under load was as extremely low as 2.0%. Therefore, the shrinkage rate of the fabric was almost 1.2%, and it was found that the fabric cannot be textured.
[0051]
Comparative Example 2
A stretched yarn of 84 dtex-36f was obtained in the same manner as in Comparative Example 1 except that the temperature of the heat setting roller 2 was 100 ° C.
[0052]
As shown in Table 3, the shrinkage stress of this drawn yarn at 100 ° C. was an extremely low value of 0.02 cN / dtex, and the shrinkage rate S ₀ under no load was an appropriate value of 9.0%. The shrinkage ratio S ₁ under load was a very low value of 4.8%. Therefore, the shrinkage rate of the fabric was almost 2.2%, and it was found that the fabric was not able to be textured.
[0053]
Comparative Example 3
A stretched yarn of 84 dtex-36f was obtained in the same manner as in Example 1 except that the temperature of the heat setting roller 2 was 30 ° C.
[0054]
As shown in Table 3, the shrinkage stress of this fiber at 100 ° C. was an appropriate value of 0.06 cN / dtex, but the shrinkage ratio S ₀ under no load was as extremely large as 82.5%, and the shrinkage under load was small. The rate S ₁ was too high at 60.8%. For this reason, the shrinkage rate of the fabric was 55.2%, and it was found that the fabric was significantly shrunk and could not be used for extremely coarse clothes.
[0055]
Comparative Example 4
Stretching was attempted in the same manner as in Example 1 except that the temperature of the heat setting roller 2 was set to 160 ° C. However, fusion occurred on the heat setting roller, and stretching was not possible.
[0056]
Comparative Example 5
Stretching was performed in the same manner as in Example 4 except that the stretch ratio between the heat setting roller 2 and the cold roller 3 was 2.5 times, but the single winding on the heat setting roller was severe and the stretchability was extremely poor. Therefore, further evaluation could not be performed.
[0057]
[Table 1]

[0059]
[Table 3]

[0060]
【The invention's effect】
Since the fiber of the present invention has an appropriate shrinkage rate and a high shrinkage stress at 100 ° C., the fiber can be shrunk even when a fabric structure is formed. Therefore, the fabric can be appropriately shrunk by hot water treatment such as scouring and dyeing, and textured processing such as squeezing and expression of yarn length difference can be performed.
[Brief description of the drawings]
FIG. 1 is a process schematic diagram showing an example of a method for producing an aliphatic polyester fiber of the present invention.
FIG. 2 is a process schematic diagram showing another example of the method for producing an aliphatic polyester fiber of the present invention.
[Explanation of symbols]
1: Preheating roller 2: Heat setting roller 3: Cold roller 4: Stretch zone

Claims (1)

The shrinkage stress at 100 ° C. is 0.05 to 0.5 cN / dtex, and the boiling water shrinkage S0 (%) under no load and the boiling water shrinkage S ₁ (%) under 0.01 cN / dtex load are as follows. A polylactic acid fiber characterized by satisfying the relations of Formula 1, Formula 2 and Formula 3.
5 <S ₁ <11.5 (Formula 1)
S ₀ × 0.7 <S ₁ (Formula 2)
S ₀ ≦ 12.5 (Expression 3 )

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