JP4335987B2 - Method for producing polylactic acid-based multifilament - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polylactic acid-based multifilament having biodegradability, high strength, and excellent wear resistance.
[0002]
[Prior art]
Conventional synthetic fibers made of synthetic resin have a slow degradation rate in the natural environment and generate a large amount of heat during incineration, and therefore need to be reviewed from the standpoint of protecting the natural environment. For this reason, biodegradable fibers made of aliphatic polyester are being developed, and are expected to contribute to environmental protection.
[0003]
Some aliphatic polyesters are expected to be fiber materials with a certain level of fiber performance and new characteristics, but the strength and wear resistance of the fibers and their products are weak, and the quality of the surface touch, appearance, etc. There are many problems, and in particular, general-purpose deployment in fields requiring high strength is difficult.
[0004]
For this reason, high-strength fibers are being developed using polylactic acid polymers having a relatively high melting point among aliphatic polyesters. For example, JP-A-2-203729 and JP-A-8-222016 disclose high-strength monofilament fibers. However, the multifilament has a problem that it is difficult to obtain high-strength fibers due to a high production rate, and the abrasion resistance of the obtained fibers is extremely poor. In addition, the yarn diameter fluctuates between the fibers of the multifilament, the irregularities occur on the fiber surface, and those fluctuations easily occur in the length direction, which is a problem from the viewpoint of quality.
[0005]
[Problems to be solved by the invention]
The present invention provides a method for stably producing polylactic acid-based multifilaments , which solves the above-mentioned problems, has biodegradability, has high strength, wear resistance, and has a stable quality. It is a technical problem to provide.
[0006]
[Means for achieving the object]
The inventors of the present invention have reached the present invention as a result of intensive studies to solve the problem of steam. That is, the present invention has the following configuration.
(1) When a polylactic acid polymer having an optical purity of 95% or more and a melt flow rate value of 1 to 50 g / 10 min is melt-spun and then stretched, the moisture content of unstretched fibers is adjusted to 3% or less. After that, polylactic acid is characterized in that superheated air or superheated steam is applied in the first and / or second stretch zones, and the stretch point is located at the superheated air or superheated steam ejection point. -Based multifilament manufacturing method.
(2) As a polylactic acid polymer, a fiber spun using a polymer having an optical purity of 95% or more and a melt flow rate value of 1 to 50 g / 10 min is used (Tm-60) ° C. to (Tm-10). The method for producing a polylactic acid-based multifilament according to (1), wherein the multistage hot drawing is performed at a temperature of ° C.
Where Tm is the melting point (° C.) of the polylactic acid polymer.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. First, the polymer constituting the polylactic acid multifilament in the present invention will be described. Polylactic acid is mainly composed of a polymer of optical isomers of L-lactic acid and D-lactic acid or a blend thereof. Therefore, since different materials are not copolymerized but the same material, the yarn forming characteristics are extremely excellent. While the optical purity of L-lactic acid is 0 to 100%, the ratio of the D-form to the L-form is a factor affecting the heat resistance and biodegradability, and the purity of the L-form is low depending on the D-form. In addition, the crystallinity tends to decrease and the melting point drop tends to increase. In addition, it is possible to improve flexibility and elastic recovery, increase heat shrinkability, control decomposability and glass transition temperature, and improve adhesion with other components.
[0008]
On the other hand, while the optical purity of D-lactic acid is 0 to 100%, the ratio of L-form to D-form is a factor that similarly affects heat resistance and biodegradability, and the purity of D-form is L-form. When the purity is lowered, the crystallinity is lowered and the melting point drop tends to be increased. Furthermore, it is possible to improve flexibility and elastic recovery, increase heat shrinkage, control decomposability and glass transition temperature, and improve adhesion with other components. From such a point, when the blend ratio of L-form and D-form is 1: 1, the crystallinity is most lowered, the melting point is greatly lowered, and the biodegradation rate is simultaneously increased.
[0009]
The polylactic acid to be applied to the present invention is pure polylactic acid, preferably D-form or L-form as a main component, and preferably has a melting point of 120 ° C. or higher. Application of a material having a low optical purity is not preferable because it has a low melting point and thus it is difficult to heat stretch, a problem that a high-strength fiber is difficult to obtain, and heat resistance and wear resistance are lowered. Therefore, the optical purity needs to be 95% or more, more preferably 96% or more, and most preferably 97% or more.
[0010]
Next, the melt viscosity of the above-mentioned polylactic acid polymer, that is, the melt flow rate value (MFR) of the polymer constituting the fiber of the present invention is a value measured under 210 ° C. and 2160 g under the prescription of ASTM-D1238. Is required to be 1 g / 10 min or more and 50 g / 10 min or less. When the MFR is less than 1 g / 10 minutes, the melt viscosity is large and the fluidity of the polymer is lowered, so the spinnability is lowered. Further, if the spinning temperature is raised to improve the spinnability, the smoke generation property increases, the spinning environment is deteriorated, and the yarn breakage increases. On the other hand, if the MFR exceeds 50 g / 10 min, it is difficult to increase the strength, and the heat resistance and wear resistance also decrease. Accordingly, the MFR range needs to be 1 to 50 g / 10 minutes, more preferably 2 to 45 g / 10 minutes, and most preferably 3 to 40 g / 10 minutes.
[0011]
The polylactic acid-based multifilament obtained by the production method of the present invention needs to have a strength of 4.0 g / d or more. The higher the fiber strength, the wider the practical range may be. However, when the fiber strength is less than 4.0 g / d, application in fields requiring high strength such as industrial material use, civil engineering material use, and fishery material use is limited. Therefore, in the present invention, the strength needs to be 4.0 g / d or more, preferably 4.5 g / d or more, more preferably 5.0 g / d or more, and most preferably 5.5 g / d. Good thing.
[0012]
The elongation of the fiber is not particularly limited, but is preferably 20 to 60%. If the elongation is too small, fluffing occurs during fiber production, yarn breakage occurs, and operability tends to decrease. On the other hand, if the elongation is too large, it is not preferable because it stretches when knitting and weaving, and the dimensional stability tends to decrease.
[0013]
The polylactic acid-based multifilament obtained by the production method of the present invention needs to have a fiber / fiber (F / F) wear resistance of 5000 times or more. When the abrasion resistance is low, fibrillation occurs when weaving or weaving, fluffing is liable to occur, the strength tends to decrease, and the useful life of the product is too short, resulting in a decrease in practicality. In general, polylactic acid fibers are inferior in wear resistance to ordinary synthetic fibers, and it is difficult to make the F / F wear resistance 5000 times or more. The reason for this is presumed to be due to the difference in the fine crystal structure and the difference in the uniformity of the fiber surface, the friction coefficient, and the uniformity between the single fibers. On the contrary, the polylactic acid-based multifilament obtained by the production method of the present invention has an F / F wear resistance of 5000 times or more, preferably 6000 times or more, more preferably 7000 times or more, Most preferably, it is 8000 times or more.
[0014]
Moreover, it is preferable that the single fiber fineness of the polylactic acid-type multifilament obtained with the manufacturing method of this invention is 1-50 denier. If it is less than 1 denier, problems such as control of the solidification point when forming the fiber, increase in the accuracy of the cap hole, reduction in productivity due to reduction in the discharge amount, and occurrence of yarn breakage are likely to occur. Also, if it exceeds 50 deniers, in the process of producing long fibers by the usual melt spinning method, it becomes impossible to cool and solidify the yarn, making spinning and drawing difficult, and special production equipment is required. This is not preferable because of high cost.
[0015]
The cross-sectional shape of the single fiber in the present invention may be a round cross-section, an irregular cross-section, a hollow cross-section, or a composite cross-section such as a core-sheath type, sea-island type, split type, parallel type, and multilayer type with a composite form. Good.
[0016]
In the present invention, the above-described polylactic acid-based polymer may be added to the above-described polylactic acid-based polymer as necessary, for example, a heat stabilizer, a crystal nucleating agent, a matting agent, a pigment, a light-resistant agent, a weathering agent, an antioxidant, an antibacterial agent, and a fragrance. Various additives such as plasticizers, dyes, surfactants, surface modifiers, various inorganic and organic electrolytes, fine powders, flame retardants and the like can be added within a range not impairing the effects of the present invention.
[0017]
The polylactic acid-based multifilament obtained by the production method of the present invention may be used alone or mixed with other fibers to produce knitted fabrics, woven fabrics and nonwoven fabrics, and composite materials and other structures. Can do. When mixed with other fibers, synthetic fibers made of fiber-forming polymers such as polyester fibers, nylon fibers, acrylic fibers, vinylon fibers, polypropylene fibers, and polyethylene fibers, regenerated fibers such as rayon, and half fibers such as acetate Synthetic fibers and natural fibers such as wool, silk, cotton and hemp are used. Among them, it is preferable to mix with biodegradable fibers such as recycled fibers, semi-synthetic fibers, natural fibers, or fibers made of aliphatic polyester, since a completely biodegradable product can be obtained.
[0018]
Next, a method for producing the polylactic acid multifilament of the present invention will be described. In order to produce the polylactic acid-based multifilament of the present invention, basically, a spinning method using a known melt spinning apparatus can be applied. If the above-mentioned polylactic acid-based polymer is selected and used as the polymer, Good. Next, this polymer is melted and weighed, the fiber is spun from a spinneret device, cooled and solidified, and after applying an oil agent, taken up with a roller, wound up, and then hot stretched or not taken up. Subsequently, the film is wound and then rolled to obtain the desired polylactic acid-based multifilament .
[0019]
A spinning temperature at the time of melt spinning the polylactic acid-based polymer is preferably 190 ° C to 250 ° C. If the spinning temperature is too low, the fluidity of the polymer is lowered, so that the spinnability is lowered. On the other hand, if the spinning temperature is too high, the polymer is liable to be thermally decomposed and smoke is generated, which deteriorates the spinning environment. Accordingly, the spinning temperature is preferably 190 to 250 ° C, more preferably 200 to 240 ° C, and most preferably 210 to 230 ° C.
[0020]
As the spinneret, a die having an appropriate hole diameter and shape may be used depending on the fineness and cross-sectional shape of the target fiber. Although any spinning speed can be applied, in order to obtain a high-strength fiber, it is preferable to use an undrawn yarn fiber in which the total draw ratio is as large as possible. From the viewpoint of property, it is usually preferable to apply from 100 m / min to 1500 m / min.
[0021]
The most important point in the production method of the present invention is to perform hot drawing after adjusting the moisture of the undrawn fiber after melt spinning the polylactic acid polymer to 3% or less. As mentioned above, in general, polylactic acid fiber is due to the difference in fine crystal structure and the degree of uniformity of the fiber surface, the coefficient of friction and the degree of uniformity between single fibers, compared to ordinary synthetic fibers, Since the wear resistance is inferior, it is difficult to make the F / F wear resistance 5000 times or more. Therefore, in order to improve the abrasion resistance of the polylactic acid fiber and increase the F / F abrasion resistance to 5000 times or more, how to control the fine crystal structure, increase the uniformity of the fiber, and reduce the frictional resistance. Is an important point.
[0022]
Therefore, in the present invention, after adjusting the moisture of the unstretched fiber to 3% or less, more preferably 2% or less, and most preferably 1% or less, the fine crystal structure is controlled by performing heat stretching, and the fiber This increases the uniformity of the fiber to reduce the frictional resistance, and the fiber has an F / F wear resistance of 5000 times or more. That is, when hot drawing with a lot of moisture attached, the fiber surface is partially hydrolyzed before the undrawn fiber is drawn and deformed by the latent heat of vaporization of the water, and then the drawing tension is applied to make the fiber finer. Uneven shape appears on the surface. If even a part of the fiber has an uneven shape, the strength and wear resistance are totally reduced. Therefore, in the present invention, by adjusting the moisture of the unstretched fiber to 3% or less and stretching, the occurrence of the uneven shape on the fiber surface is suppressed, and the fiber has excellent strength and wear resistance.
[0023]
As a method of adjusting the moisture of unstretched fibers after cooling and solidification to 3% or less, a method of regulating the amount of moisture adhering to the fiber surface by increasing the concentration of the emulsion oil agent, giving warm air below the glass transition temperature of the fibers Thus, a method of reducing the moisture content, a method of heating the take-up roller temperature at the time of spinning below the glass transition temperature of the fiber, a method of applying a non-aqueous oil agent, and the like can be suitably used.
[0024]
The temperature at the time of hot stretching is preferably in the range of (Tm-60) ° C to (Tm-10) ° C, particularly (Tm-50) ° C to (Tm-20) ° C. When performing multistage stretching, it is more preferable to provide a temperature gradient between the rollers so that the final roller temperature becomes the highest. When the roller temperature is less than (Tm-60) ° C, the total draw ratio cannot be increased, and as a result, it becomes difficult to obtain high-strength fibers. On the other hand, when the roller temperature exceeds (Tm−10) ° C., the fibers are brought into close contact with each other, or the operability is liable to be lowered by winding around the roller. The draw ratio when drawing in multiple stages following spinning is such that about 80% of the total draw ratio is given in the first stage, the remaining 20% is drawn in the second and subsequent stages, and then a relaxing heat treatment is applied. Good.
[0025]
In addition, when the unstretched fiber that has been wound up is stretched after spinning, the first stage is stretched as a preliminary stretch at a slight stretch ratio, and then the second stage is 80% to the total stretch ratio. About 100% may be applied, and then the remainder may be stretched after the third stage or relaxed heat treatment may be performed.
[0026]
When hot stretching is performed using heated air or superheated steam, the total stretching ratio can be further increased and fibers having high strength can be obtained. The position for applying superheated air or superheated steam needs to be applied to the first and / or second drawing zones. The temperature of the superheated air or superheated steam applied to the fiber is preferably (Tm-40) ° C. to (Tm-10) ° C., particularly preferably (Tm-30) ° C. to (Tm-15) ° C. When the temperature of superheated air or superheated steam is less than (Tm-40) ° C., the effect of increasing the total draw ratio tends to be reduced. Moreover, when it exceeds (Tm-10) degreeC, a fiber will adhere | attach and it will become easy to adhere.
[0027]
Note that when superheated air or superheated steam is used during hot stretching, the rollers also usually superheat, but the temperature of the superheated air or superheated steam is made higher than the roller temperature, and the stretch point is ejected from the superheated air or superheated steam. Positioning at a point is necessary because the stretching ratio is high and the film can be stretched with good operability.
[0028]
【Example】
Next, the present invention will be specifically described based on reference examples and examples. In addition, the measurement and evaluation of various characteristics in the reference examples and examples were performed by the following methods.
(1) Melting point of polymer (℃)
Using a differential scanning calorimeter DSC-2 manufactured by Perkin Elma Co., Ltd., a polymer sample of about 5 mg, held in nitrogen, heated at a rate of 10 ° C./min, held at 200 ° C. for 5 minutes, and cooled at a rate of 10 ° C./min of 20 The maximum melting exothermic peak temperature when the temperature was lowered to 200 ° C. and again raised to 200 ° C. at a heating rate of 10 ° C./min was defined as the melting point (Tm).
(2) Glass transition temperature (℃)
The initial exothermic peak temperature obtained when the melting point was measured was defined as the glass transition temperature (Tg).
(3) Crystallization temperature (℃)
The endothermic peak temperature obtained when measuring the melting point was defined as the crystallization temperature (Tc).
(4) MFR (g / 10 min)
It is the value measured under 210 ° C. and 2160 g load according to ASTM D1238.
(5) Strength and elongation of fiber According to JIS L-1013, the strength (g / d) obtained by dividing the maximum tensile strength when pulled under the conditions of a grip interval of 25 cm and a tensile speed of 30 cm / min by the fineness The elongation (%) was determined from the elongation at that time.
(6) Dry heat shrinkage rate of fiber According to JIS L-1013, heat treatment was performed at a dry heat temperature of 120 ° C. for 15 minutes to obtain a dry heat shrinkage rate.
(7) F / F wear resistance of fiber Using a cylindrical rotating plate with a diameter of 100 mm and a rubbing device in which the shaft part is given a constant load of 140 g and moves in the horizontal direction, the fiber swirls around the outer periphery of the cylindrical rotating plate After that, the cloth was crossed twice and the cross angle was fixed at 50 degrees, the stroke length was 3 cm, the stroke speed was 30 times / minute, and the number of strokes until cutting by fiber / fiber (F / F) abrasion was measured. Abrasive. A larger value means better wear resistance.
(8) A sample of a biodegradable long fiber fiber is buried in the soil and taken out two years later. If the fiber form is not retained, or is retained, but the tensile strength is When it decreased to 50% or less, it was evaluated that the decomposability was good.
Reference example 1
Poly L-lactic acid resin having an optical purity of 99%, MFR of 20 g / 10 min, a glass transition temperature (Tg) of 60 ° C. by DSC, a crystallization temperature (Tc) of 136 ° C., and a melting point (Tm) of 170 ° C. Used as melt spinning. First, using a spinning machine with a single-screw extruder-type melt extruder, melted at a temperature of 220 ° C., spun from a nozzle die with a hole diameter of 0.4 mm and a number of holes of 96, and discharged at a rate of 128 g / min. While cooling with an apparatus and applying a non-aqueous oil agent, the film was taken up at a spinning speed of 300 m / min, and subsequently spin-draw type hot drawing capable of four-stage drawing was performed.
[0029]
In the heat stretching, the stretch ratio of the first stage / 2nd stage / 3rd stage was 8/1/1, and the fourth stage was given a stretching ratio of 0.98. The first roller temperature is 110 ° C., the second roller temperature is 120 ° C., the third roller temperature is 130 ° C., the fourth roll temperature is 140 ° C., the fifth roll temperature is 150 ° C., and the total draw ratio is 7.1. Drawing was performed as a double to obtain 500 denier / 96 filament long fibers. The unstretched fiber taken from the first roller was continuously wound up at 300 m / min by preparing another winder, and the moisture content of the fiber was measured to be 0%.
[0030]
The obtained long fibers had no adhesion, all the single fibers were in a smooth state, the strength was 5.3 g / d, the elongation was 25%, and the dry heat shrinkage rate at 120 ° C. was 8%. The F / F wear resistance of this fiber was 6500 times, and it was a fiber having excellent wear resistance. Moreover, when this long fiber was embed | buried in soil and the biodegradability was evaluated, it has confirmed that it was favorable.
Reference example 2
A poly L-lactic acid resin having an optical purity of 99.5%, MFR of 10 g / 10 min, a glass transition temperature by DSC of 63 (Tg) ° C., a crystallization temperature (Tc) of 139 ° C., and a melting point (Tm) of 175 ° C. A 500 denier / 96 filament long fiber was produced in the same manner as in Reference Example 1 except that the polymer was used and the discharge rate was 96.7 g / min and the total draw ratio was 5.8. The moisture content of the unstretched fiber before stretching was 0%.
[0031]
The obtained long fibers had no adhesion, all the single fibers were in a smooth state, the strength was 5.6 g / d, the elongation was 27%, and the dry heat shrinkage rate at 120 ° C. was 8%. The F / F wear resistance of this fiber was 7400 times, and it was a fiber having excellent wear resistance. Moreover, when this long fiber was embed | buried in soil and the biodegradability was evaluated, it has confirmed that it was favorable.
Reference example 3
Poly L-lactic acid resin having an optical purity of 95%, MFR of 18 g / 10 min, glass transition temperature (Tg) in DSC of 56 ° C., crystallization temperature (Tc) of 130 ° C., melting point (Tm) of 152 ° C. Spinning was carried out in the same manner as in Reference Example 1 except that the polymer was used, the discharge rate was set to 108 g / min, and an emulsion oil agent having an oil concentration of 20% was used instead of the non-aqueous oil agent. .
[0032]
In addition, the heat drawing was performed by applying 500 denier / 96 filament long fibers in the same manner as in Reference Example 1 except that the temperature of each roller was decreased by 15 ° C. and the total draw ratio was 6.5 times. Obtained. The undrawn fiber taken up from the first roller was continuously wound up at 300 m / min by preparing another winder, and the moisture content of the fiber was measured to be 3.0%.
[0033]
The obtained long fibers had no adhesion, and fine irregularities were observed on a part of single fibers on the fiber surface, but the strength was 4.8 g / d, the elongation was 28%, and the dry heat shrinkage at 120 ° C. 10%. The F / F wear resistance of this fiber was 5000 times, and it was a fiber having practical wear resistance. When this long fiber was embedded in the soil and its biodegradability was evaluated, it was confirmed that it was good.
Reference example 4
Poly L-lactic acid resin having an optical purity of 99%, MFR of 50 g / 10 min, glass transition temperature by DSC of 60 (Tg) ° C., crystallization temperature (Tc) of 136 ° C., melting point (Tm) of 170 ° C. 500 denier / 96 filament long fiber in the same manner as in Reference Example 1 except that melt spinning was performed at a spinning temperature of 210 ° C. and a discharge rate of 137 g / min as the coalescence and stretching was performed at a total draw ratio of 8.2 times. Got. The moisture content of the unstretched fiber before stretching was 0%.
[0034]
The obtained long fibers had no adhesion, all the single fibers were in a smooth state, the strength was 5.8 g / d, the elongation was 26%, and the dry heat shrinkage rate at 120 ° C. was 8%. This fiber had an F / F wear resistance of 6400 times, and was a fiber having excellent wear resistance. Moreover, when this long fiber was embed | buried in soil and the biodegradability was evaluated, it has confirmed that it was favorable.
Reference Example 5
Poly L-lactic acid resin with an optical purity of 99%, MFR of 4 g / 10 min, glass transition temperature by DSC of 60 (Tg) ° C., crystallization temperature (Tc) of 136 ° C., melting point (Tm) of 170 ° C. As a coalescence, 500 denier / 96 filament length was obtained in the same manner as in Reference Example 1 except that melt spinning was performed at a spinning temperature of 230 ° C. and a discharge rate of 86.7 g / min and stretching was performed at a total draw ratio of 5.2 times. Fiber was obtained. The moisture content of the unstretched fiber before stretching was 0%.
[0035]
The obtained long fibers had no adhesion, all the single fibers were in a smooth state, the strength was 6.5 g / d, the elongation was 26%, and the dry heat shrinkage at 120 ° C. was 8%. The F / F wear resistance of this fiber was 8600 times, and it was a fiber having excellent wear resistance. Moreover, when this long fiber was embed | buried in soil and the biodegradability was evaluated, it has confirmed that it was favorable.
Example 1
A device that can be heated and stretched with superheated air at 140 ° C. between the second and third rollers with a discharge rate of 108 g / min (the diameter of the yarn inlet is 2.5 mm, and the superheated air is +30 degrees with respect to the running yarn. And -30 degrees, and the flow rate is 1,200 m / min), and the stretch ratio of the first stage / 2nd stage / 3rd stage is 7.5 / 2 / 0.5, and the total draw ratio A 500 denier / 96 filament long fiber was obtained in the same manner as in Reference Example 1 except that stretching was performed at 6.5 times. The moisture content of the unstretched fiber before stretching was 0%.
[0036]
The obtained long fibers had no adhesion, all the single fibers were in a smooth state, the strength was 6.8 g / d, the elongation was 27%, and the dry heat shrinkage rate at 120 ° C. was 8%. The F / F wear resistance of this fiber was 9100 times, and it was a fiber having excellent wear resistance. Moreover, when this long fiber was embed | buried in soil and the biodegradability was evaluated, it has confirmed that it was favorable.
Comparative Example 1
Poly L-lactic acid resin having an optical purity of 93%, MFR of 25 g / 10 min, glass transition temperature (Tg) in DSC of 49 ° C., and no crystallization temperature (Tc) or melting point (Tm) (actual melting) Melt spinning was carried out using a temperature of 125 ° C. as the polymer. First, using a spinning machine with a single-screw extruder-type melt extruder, the melt was performed at a temperature of 220 ° C., and it was spun at a discharge rate of 63 g / min from a nozzle base having a hole diameter of 0.4 mm and a number of holes of 96. The system was cooled by an apparatus, and the emulsion-based oil was applied with an oiling roller, and was taken up at a spinning speed of 560 m / min. The moisture content of this unstretched fiber was 4%.
[0037]
Next, this unstretched fiber was stretched using a heat stretcher capable of two-stage stretching. The first roller temperature is 25 ° C., the second roller temperature is 80 ° C., the third roller temperature is 25 ° C., the heater temperature between the second roller and the third roller is 120 ° C., and the first stage draw ratio is 1.01. Drawing was performed at a draw ratio of 3.76 in the second stage to obtain 500 denier / 96 filament long fibers.
[0038]
Although the obtained long fibers did not adhere, some single fibers had irregularities in the longitudinal direction. The fiber performance was a strength of 3.6 g / d, an elongation of 30%, and a dry heat shrinkage at 120 ° C. of 28%. The F / F wear resistance of this fiber was 3600 times, and the fiber was inferior in wear resistance. Moreover, when this long fiber was embed | buried in soil and the biodegradability was evaluated, it has confirmed that it was favorable.
Comparative Example 2
Instead of the emulsion-based oil agent having an oil agent concentration of 20%, spinning and drawing were performed under the same conditions as in Reference Example 3 except that the oil agent concentration was 10% and the oiling rotation speed was doubled, to obtain a 500 denier / 96 filament long fiber. It was.
[0039]
Although the obtained long fibers did not adhere, more than half of all the single fibers had irregularities in the length direction on the fiber surface. When the moisture content of the undrawn fiber before drawing was measured, it was 7%, and it was found that this moisture was caused by irregularities on the fiber surface. The obtained fiber had a strength of 4.2 g / d, an elongation of 28%, and a dry heat shrinkage of 9% at 120 ° C. The F / F wear resistance of this fiber was 1900 times, and the fiber was inferior in wear resistance.
[0040]
【The invention's effect】
According to the present invention, less likely to pollute the environment because biodegradable, has high strength, and polylactic acid having excellent wear resistance high uniformity between single fibers constituting the fiber A method for producing a multifilament is provided. Since the polylactic acid-based multifilament obtained by the production method of the present invention is also excellent in dimensional stability, products that can be applied to knitted fabrics, woven fabrics, other various fiber structures, composite structures, etc. are obtained. , Industrial materials, household goods, civil engineering materials, agricultural materials, forestry materials, etc. In particular, since the fabric using this polylactic acid fiber is excellent in strength and abrasion resistance, it is excellent in filters, vegetation sheets, slope greening, landslide prevention sheets, fishing nets, tents, sleeping bags, kitchen draining bags, garbage bags. , Wipers, wood boards, automobile interior materials and the like. In addition, this fiber is completely decomposed and lost when it is left in an environment where many microorganisms are present after use or in an environment such as seawater or fresh water, for example, in soil or water. It is also useful from the viewpoint of resource reuse because it can be reused, for example, composted into fertilizer.

Claims (2)

After melt spinning a polylactic acid polymer having an optical purity of 95% or more and a melt flow rate value of 1 to 50 g / 10 min, and then stretching, after adjusting the moisture content of unstretched fibers to 3% or less, A polylactic acid-based multifilament characterized in that superheated air or superheated steam is applied in the first and / or second drawing zones, and the drawing point is located at the point of ejection of the superheated air or superheated steam. Manufacturing method . Using a polymer having an optical purity of 95% or more and a melt flow rate value of 1 to 50 g / 10 min as a polylactic acid polymer, a spun fiber is heated at a temperature of (Tm-60) ° C. to (Tm-10) ° C. The method for producing a polylactic acid-based multifilament according to claim 1, wherein the multi-stage heat stretching is carried out at a step .
Where Tm is the melting point (° C.) of the polylactic acid polymer .