JP2003301327A - Polylactic acid fiber excellent in hydrolysis resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid fiber improved in hydrolysis resistance and having a good color tone, and a fibrous product consisting of the same. <P>SOLUTION: This polylactic acid fiber excellent in hydrolysis resistance obtained by blocking carboxylic terminals with a polycarbodiimide compound is characterized by exhibiting ≤7 b* value which is an indicator of the color tone. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polylactic acid fiber having improved hydrolysis resistance and a good color tone, and a fiber product comprising the same.

[0002]

2. Description of the Related Art Recently, development of a polymer material that decomposes in a natural environment has been earnestly desired for environmental problems on a global scale. Research and development of various polymers such as aliphatic polyester and practical use Attempts to realize this are becoming more active. Attention has been focused on polymers that are decomposed by microorganisms, that is, biodegradable polymers.

On the other hand, most conventional polymers use petroleum resources as raw materials, but it is possible that petroleum resources will be depleted in the future, and due to the large consumption of petroleum resources, they will be stored underground in the geological era. It is feared that the carbon dioxide that had been released will be released into the atmosphere, and that global warming will become more serious. However, if polymers can be synthesized from plant resources that take in carbon dioxide from the atmosphere and grow and grow, not only can we expect that global warming can be suppressed by the carbon dioxide cycle, but there is also the possibility that the problem of resource depletion can be solved at the same time. . Therefore, attention has been focused on polymers made from plant resources, that is, polymers using biomass.

From the above two points, biodegradable polymers utilizing biomass have attracted great attention and are expected to replace conventional polymers derived from petroleum resources. However, biodegradable polymers using biomass generally have the problems of low mechanical properties and low heat resistance and high cost. As a biodegradable polymer using biomass that can solve these problems, polylactic acid, which is a kind of aliphatic polyester, is currently receiving the most attention. Polylactic acid is a polymer using lactic acid as a raw material, which is obtained by fermenting starch extracted from plants, and has the best balance among mechanical properties, heat resistance and cost among biodegradable polymers using biomass. The development of resin products, fibers, films, sheets, etc. using these is being carried out at a rapid pace.

The development of polylactic acid fiber is preceded by agricultural materials and civil engineering materials which make use of biodegradability, but the following large-scale applications are clothing applications, interior applications such as curtains and carpets, and vehicle interior applications. It is also expected to be applied to industrial materials. In particular, the high hydrolyzability of polylactic acid becomes a bottleneck when applied to clothing and industrial materials. When polylactic acid fibers are used for clothing, most of them are dyed, but polylactic acid fibers have a lower dye exhaustion rate than general synthetic fibers such as polyethylene terephthalate (PET) and nylon. The dye remains at 110 ° C. or higher in many cases, because not only the dye remains but the environmental load due to the drainage is large and it is difficult to dye in a dark color. However, when dyed at a temperature of 110 ° C. or higher, there is a problem that hydrolysis of polylactic acid rapidly progresses and the tear strength of the fabric becomes less than a practical level. Further, since hydrolysis also progresses due to moisture in the environment, there is a problem that the product life is short especially when it is used for an industrial material application requiring high strength.

In order to solve this problem, Japanese Patent Laid-Open No. 2001-2001
Japanese Patent No. 261797 describes a polylactic acid fiber having a hydrolysis resistance improved by adding a monocarbodiimide compound. However, there is a problem that the monocarbodiimide compound is expensive. On the other hand, Japanese Patent Laid-Open No. 11-8
Japanese Patent No. 0522 describes a resin and a film to which a relatively inexpensive polycarbodiimide compound is added. However, as described in JP-A-2001-261797, the polycarbodiimide compound has low dispersibility in polylactic acid and is poor in heat resistance, so that gelation is likely to occur and hydrolysis resistance is not improved. In addition to being sufficient, the spinning stability became unstable, making it difficult to apply to industrial fiber production. Further, according to the study by the present inventors, due to poor heat resistance, the polylactic acid fiber to which the polycarbodiimide compound is added has a poor color tone (strong yellowness), and the b ^* value which is an index of the color tone is It was as high as 10 or more and could not be used for clothing.

From the above problems, the hydrolysis resistance of polylactic acid fiber has not been improved yet,
There was a great limitation in the application development. Therefore, a polylactic acid fiber having improved hydrolysis resistance and a good color tone and a fiber product made of the same have been desired.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a polylactic acid fiber having improved hydrolysis resistance and a good color tone, and a fiber product comprising the same.

[0009]

The above object is a polylactic acid fiber having a carboxyl group end blocked with a polycarbodiimide compound, which has a b ^* value of 7 or less as an index of color tone. This is achieved by the polylactic acid fiber having excellent hydrolyzability.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polylactic acid referred to in the present invention refers to a polymer obtained by polymerizing an oligomer such as lactic acid or lactide, and it is preferable that the optical purity of the L-form or D-form is 90% or more because the melting point is high. In the present invention, L-form or D-form having an optical purity of 97% or more is called homopolylactic acid. Further, components other than lactic acid may be copolymerized, or polymers other than polylactic acid, particles, additives such as flame retardants, antistatic agents and the like may be contained, as long as the properties of polylactic acid are not impaired. However, from the viewpoint of biomass utilization and biodegradability, it is important that the lactic acid monomer is 50% by weight or more as a polymer. The lactic acid monomer is preferably 75% by weight or more, more preferably 96% by weight or more. The molecular weight of the polylactic acid polymer is preferably 50,000 to 500,000 in terms of weight average molecular weight, because the balance between mechanical properties and moldability is good.

In the present invention, it is important to add a polycarbodiimide compound to polylactic acid and to block the carboxyl group terminal contained therein. The polycarbodiimide compound here is described in, for example, JP-A No. 11-80522. As described above, a polymer obtained by polymerizing a diisocyanate compound is preferably used, and among them, a polymer of 4,4′-dicyclohexylmethanecarbodiimide, a polymer of tetramethylxylylenecarbodiimide, or a polymer obtained by blocking the terminal thereof with polyethylene glycol or the like is preferable.

In the present invention, the reaction active end of the polylactic acid polymer and / or the oligomer contained therein is blocked with a polycarbodiimide compound to inactivate the reaction active end in the polymer and suppress the hydrolysis of polylactic acid. Is. This reaction active terminal has a hydroxyl group and a carboxyl group, but the carbodiimide compound is excellent in blocking the carboxyl group.

As a result of detailed investigation of the behavior of the polycarbodiimide compound in polylactic acid, the present inventors have found that the unreacted free polycarbodiimide compound which has not reacted with the reactive terminal has poor spinnability and color tone. I found that it was adversely affecting. More specifically, it has been found that the free polycarbodiimide compound causes the above problems due to rapid thermal deterioration at a temperature of 200 to 250 ° C., which is a temperature for molding and spinning polylactic acid. From this, in order to improve the spinnability and color tone of the polylactic acid fiber to which the polycarbodiimide compound has been added, it is important to select the addition amount of the polycarbodiimide compound and / or the temperature and the residence time during kneading or melt spinning. I found a thing.

First, regarding the amount of the polycarbodiimide compound added, it is more important to determine this with respect to the carboxyl group terminal than with respect to the weight of polylactic acid.
Furthermore, since residual oligomers such as lactide generate carboxyl group terminals by hydrolysis, the total carboxyl group terminal amount is important not only for the carboxyl group terminals of the polymer but also for those derived from residual oligomers and monomers. When the addition amount of the polycarbodiimide compound is equal to or less than twice the total carboxyl group terminal amount as the carbodiimide group equivalent, it is possible to reduce the amount of free polycarbodiimide compound and to carry out the carboxyl group terminal blocking at a high rate. . The addition amount of the polycarbodiimide compound is more preferably 1.5 times equivalent amount or less of the total carboxyl group terminal amount.

Further, it is preferable that the total carboxyl group terminal concentration of the polylactic acid fiber after addition of the polycarbodiimide compound is 10 equivalents / ton or less based on the whole polylactic acid fiber because the hydrolysis resistance can be remarkably improved. .

On the other hand, the residence time of the polycarbodiimide compound during kneading and melt spinning at 200 to 250 ° C. is 3
When it is 0 minutes or less, thermal deterioration of the polycarbodiimide compound can be suppressed, which is preferable. Where 200 to 25
The residence time at 0 ° C. is a time for passing through a portion substantially heated to 200 to 250 ° C., which is the temperature setting and piping size of the kneading machine and the melting portion, the size in the spinning pack. Etc. can be estimated.

Therefore, it is preferable to devise a method of adding the polycarbodiimide compound, and it is preferable to directly add the polycarbodiimide compound at the time of melt spinning, rather than preparing a polylactic acid chip to which the polycarbodiimide compound is added in advance. For example, there is a method in which a polycarbodiimide compound is added in the molten portion of polylactic acid, or the separately melted polycarbodiimide compound and polylactic acid are kneaded in a spinning pack by a static kneader or the like.

The polylactic acid fiber of the present invention excellent in hydrolysis resistance
In Wei, an index of the yellow color tone, b ^*Value is less than 7
This is very important. As a result, the color tone for clothing
It can also be used for important applications. b^*Value is preferably 5
Or less, more preferably 3 or less.

For improving the b ^* value of polylactic acid fiber, see P.
It is of course possible to use a bluing compound such as cobalt acetate together as in ET etc., but if too much is used, the color will become cloudy at the time of dyeing and the clear color development characteristic of polylactic acid fiber will be impaired. Even if used in combination, the addition amount is preferably 500 ppm or less with respect to the weight of polylactic acid, because it may cause breakage or yarn breakage.

In the present invention, the hydrolysis resistance can be evaluated by the viscosity retention rate and strength retention rate of the fiber. In the present invention, 30 g of a sample and 300 g of water are put in a pressure vessel, and the viscosity retention rate of the fiber is preferably 75% or more before and after hot water treatment at 120 ° C. for 60 minutes. The viscosity retention rate is more preferably 85% or more. The strength retention of the fiber before and after the hot water treatment is preferably 70% or more. The strength retention is more preferably 85% or more.

The polylactic acid fiber excellent in hydrolysis resistance of the present invention preferably has a strength of 2.0 cN / dtex or more in order to keep the process passability and the mechanical strength of the product sufficiently high. The strength is preferably 3.5 cN / dtex or more. Further, it is preferable that the elongation of the fiber of the present invention is 15 to 70% because the process passability in forming a fiber product is improved. The elongation is more preferably 25 to 50%.

In the fiber of the present invention, when the boiling point is 0 to 20%, the dimensional stability of the fiber and the fiber product is good, which is preferable.
The boiling point is preferably 3 to 10%.

Regarding the cross-sectional shape of the polylactic acid fiber having excellent hydrolysis resistance of the present invention, it is possible to freely select a multi-lobed cross section such as a round cross section, a hollow cross section, and a trilobal cross section, and other modified cross sections. is there. The form of the fiber is not particularly limited, such as long fiber and short fiber, and in the case of long fiber, it may be multifilament or monofilament.

The method for producing the polylactic acid fiber excellent in hydrolysis resistance of the present invention is not particularly limited, but the following method can be adopted, for example.

First, a polycarbodiimide compound is produced as described in JP-A No. 11-80522. Also,
Although polylactic acid is synthesized by a known method, it is preferable that the color tone of polylactic acid itself is good and that residual oligomers and monomers such as lactide are reduced. As a specific method, for example, as described in JP-A-7-504939, it is preferable to use a metal deactivator, an antioxidant, etc., to lower the polymerization temperature, and to suppress the catalyst addition rate. In addition, the amount of residual oligomer and monomer can be significantly reduced by subjecting the polymer to reduced pressure treatment or extraction with chloroform or the like. Next, the total carboxyl group terminal concentration of the obtained polylactic acid was determined according to Japanese Patent Laid-Open No. 2001-2.
It is calculated as described in Japanese Patent No. 61797. That is, the weighed sample is dissolved in o-cresol adjusted to have a water content of 5%, an appropriate amount of dichloromethane is added, and then titrated with a 0.02N KOH methanol solution. At this time, since an oligomer such as lactide, which is a cyclic dimer of lactic acid, is hydrolyzed to generate a carboxyl group terminal, both the carboxyl group terminal of the polymer, the carboxyl group terminal derived from the monomer and the carboxyl group terminal derived from the oligomer are added together. The total carboxyl group terminal concentration can be obtained.

Next, the polylactic acid and the polycarbodiimide compound are kneaded. The first kneading method is to dry the polylactic acid and the polycarbodiimide compound, and then feed the mixture to a chisso-sealed extrusion kneader and use the extrusion kneader. This is a method in which a kneaded polymer melt of kneaded polylactic acid and a carbodiimide compound is introduced into a spinning machine, further finely kneaded by a static kneader installed in a spinning pack, and discharged from a spinneret for melt spinning. In the second kneading method, polylactic acid and polycarbodiimide compound are separately melted, the melt is guided to a spinning machine, finely kneaded by a static kneader installed in a spinning pack, and discharged from a spinneret and melted. This is a method of spinning. At this time, as described above, when the addition amount of the polycarbodiimide compound is equal to or less than twice the total carboxyl group terminal amount, it is possible to reduce the amount of free polycarbodiimide compound and to carry out the carboxyl group terminal blocking at a high rate. it can. Here, it is important to determine the addition amount based on the carboxyl group terminal amount, not on the total weight of polylactic acid. If the amount of the terminal group is small, the amount of free polycarbodiimide compound is increased to deteriorate the spinnability and color tone. On the other hand, if the amount of the terminal group of the carboxyl group is originally large, the end capping is insufficient and the hydrolysis resistance is not improved.

By the way, it is preferable that the residence time of the polycarbodiimide compound in the spinning machine is within 20 minutes. Therefore, it is preferable to make the space in the spinning pack as small as possible. The kneading temperature and spinning temperature are preferably 210 to 250 ° C, more preferably 210 to 230 ° C.

After the yarn is cooled and solidified by the chimney, an oil agent for fibers mainly composed of a smoothing agent such as fatty acid ester or mineral oil is applied by an oiling guide or an oiling roller. After that, the yarn is taken up by a roller.

Then, in the case of long fibers, the drawn yarn is once wound up as a cheese package, and then this is drawn and heat treated. At this time, if the spinning speed, which is the peripheral speed of the first take-up roller, is 2500 to 7000 m / min,
Thread unevenness is reduced, which is preferable. The stretching temperature is 80 to 150.
When the temperature is set to ℃, yarn unevenness is reduced, which is preferable. The stretching temperature is more preferably 120 to 150 ° C. Further, it is preferable that the heat treatment temperature is 120 to 160 ° C. because the boiling point of the polylactic acid fiber is lowered and the thermal dimensional stability is improved. The heat treatment temperature is more preferably 130 to 150 ° C. In addition, when high strength is required as in industrial materials, multi-stage drawing may be performed. If necessary, the polylactic acid fiber may be crimped by false twisting, indenting, mechanical crimping, or the like.

On the other hand, in the case of short fibers, the taken-up yarns are combined and once received by a bunker, and then these are combined to form a tow, which is then stretched and mechanically crimped, and then subjected to the next step. Cut after applying a suitable oil. At the time of drawing, it is preferable to employ steam drawing or liquid bath drawing in consideration of thick tow and poor heat transfer. The temperature at this time is 75
It is preferable to set the temperature to -100 ° C.

When the nonwoven fabric is used, the above-mentioned short fibers may be used, or a method in which spinning and a nonwoven fabric forming process such as so-called spunbonding and melt blowing are continuous may be used.

The polylactic acid fiber excellent in hydrolysis resistance of the present invention can take various forms of fiber products such as woven fabrics, knitted fabrics, non-woven fabrics and molded products such as cups.

Further, the polylactic acid fiber having excellent hydrolysis resistance of the present invention may be mixed with a substance made of a plant-derived raw material. For example, a fiber mixed with a natural fiber such as silk or cotton or a regenerated fiber such as rayon or acetate, or mixed and woven can be used. Further, a non-woven fabric, a molded product, and the like, in which the polylactic acid fiber having excellent hydrolysis resistance of the present invention is used as a binder and mixed with pulp or the like, can also be mentioned.

The polylactic acid fiber excellent in hydrolysis resistance of the present invention is not only used for clothing such as shirts, blouson and pants, but also for clothing materials such as cups and pads, curtains, carpets, mats, wallpaper, furniture and the like. Interior applications and vehicle component applications, belts, nets, ropes, heavy cloth, bags,
It can be suitably used for industrial materials such as sewing thread, felt, non-woven fabric, filter, artificial grass and the like.

[0035]

EXAMPLES The present invention will be described in detail below with reference to examples. The following methods were used as the measuring methods in the examples.

A. Solution specific viscosity of polylactic acid (η _r ) A solution was prepared by dissolving 3 g of a sample weighed in 100 ml of o-chlorophenol. Next, the specific viscosity of this was measured using the Ostwald viscometer at 25 degreeC.

B. Total Carboxyl Group Terminal Concentration As described in JP 2001-261797 A, a weighed sample is dissolved in o-cresol adjusted to a water content of 5%, and an appropriate amount of dichloromethane is added, followed by a 0.02 N KOH methanol solution. It was determined by titrating with. At this time,
Since an oligomer such as lactide, which is a cyclic dimer of lactic acid, is hydrolyzed to generate a carboxyl group terminal, the carboxyl group terminal of the polymer and both the carboxyl group terminal derived from the monomer and the carboxyl group terminal derived from the oligomer are combined. The concentration can be obtained.

C. Eta _r retention before and after hot water treatment of (Rη _r) samples 30g and water 300g were placed in a pressure vessel, 120
Hot water treatment was performed at 60 ° C. for 60 minutes. Then, to measure this in eta _r, was determined Aruita _r by the following equation. When the sample was a fiber, tubular knitting was prepared and subjected to hot water treatment.

R η _r (%) = (η _{r of the} sample after hot water treatment /
Η _r ) × 100 (%) before hot water treatment D. Strength retention rate (RT) before and after hot water treatment The sample was hot water treated in the same manner as C, and RT was calculated by the following formula. The strength of the polylactic acid fiber before the hot water treatment and the strength of the polylactic acid fiber after the hot water treatment were measured by loosening the yarn from the tubular knitting and measuring by the method shown in F.

RT (%) = (strength of sample after hot water treatment /
Strength before hot water treatment) x 100 (%) E. Color tone (b ^* value) A fiber sample is wrapped around a transparent plate so that the color of the base is almost negligible, and wrapped around it. MINOLTA SPECTROP
B ^* was measured with HOTOMETER CM-3700d. At this time, D ₆₅ (color temperature 6504K) was used as a light source, and measurement was performed in a 10 ° visual field.

F. Strength and Elongation At room temperature (25 ° C.), initial sample length = 200 mm, tensile speed = 200 mm / min, and a load-elongation curve was obtained under the conditions shown in JIS L1013. Next, the load value at break was divided by the initial fineness to obtain the strength, the elongation at break was divided by the initial sample length, and the strength / elongation curve was obtained as the elongation.

G. Evaporation boiling (%) = [(L0-L1) / L0)] x 100 (%) L0: Skein the drawn yarn and measure the original length L1: L0 of the skein measured under an initial load of 0.09 cN / dtex The skein is treated in boiling water for 15 minutes in a load-free condition, and after air-drying, the initial load is 0.09 cN / dte.
Skein length under x Crimping characteristics of the false twisted textured yarn, CR value The false twisted textured yarn was squeezed, treated in boiling water for 15 minutes in a substantially load-free state, and air dried for 24 hours. A load equivalent to 0.088 cN / dtex (0.1 gf / d) was applied to this sample and the sample was immersed in water to measure the skein length L′ 0 after 2 minutes. Next, the load equivalent to 0.088 cN / dtex was removed in water, and the load was replaced with a slight load equivalent to 0.0018 cN / dtex (2 mgf / d), and the skein length L′ 1 was measured after 2 minutes. Then, the CR value was calculated by the following formula.

CR (%) = [(L'0-L'1) / L'0]
× 100 (%) I. Number of crimps of crimped yarn The number of crimps was counted after shrinking the crimped yarn in hot water at 100 ° C in a substantially load-free state.

Reference Example 1 Lactide produced from L-lactic acid having an optical purity of 99.5% was
Polymerization was carried out at 180 ° C. for 140 minutes in a nitrogen atmosphere in the presence of a bis (2-ethylhexanoate) tin catalyst (lactide to catalyst molar ratio = 10000: 1). At this time, "Ultranox626" manufactured by GE Co. was used as a stabilizer in a ratio of 0.
2% by weight was added. The obtained polylactic acid had η _r of 7.5 and a carboxyl group terminal concentration of 35 equivalents / ton.

Reference Example 2 The polylactic acid obtained in Reference Example 1 was treated with ethanol to remove residual oligomers such as lactide to some extent. Η of this
_r is 7.5, and the carboxyl group terminal concentration is 15 equivalents / to
It was n.

Example 1 As a polycarbodiimide compound, a thermoplastic polycarbodiimide "Calbolitelite" HMV-8CA (1 equivalent of Calvoidimid / 278g of Calvodimide) manufactured by Nisshinbo Co., Ltd. was used.

The polylactic acid and the polycarbodiimide compound obtained in Reference Example 1 were separately melted at 220 ° C. and 120 ° C., respectively, and introduced into the spinning pack 4, and the static kneader 5 in the spinning pack 4 (Toray Engineering Co., Ltd.). Made "High Mixer" 10 steps)
Kneading was carried out and spinning was carried out as it was. At this time, the addition amount of the polycarbodiimide compound was 1.0 times equivalent to the carboxyl group terminal amount (1.0 wt% with respect to polylactic acid). The residence time of the polycarbodiimide compound in the spinning machine was 12 minutes, and the spinning temperature was 220 ° C.

Then, the spun yarn 8 is cooled and solidified by the chimney 7 with a cooling air of 25 ° C., a fiber oil agent mainly containing a fatty acid ester is applied by a focusing oil supply guide 9, and a yarn is drawn by a confounding guide 10. Was confounded (Fig. 1). There is no problem in the melt spinnability of this,
The yarn breakage during g winding was zero. Then the peripheral speed 3
After being taken up by the unheated first take-up roller 11 of 000 m / min, it was wound up by the non-heated second take-up roller 12. This yarn is first hot roller 15 temperature 90
After preheating at ℃, drawn to 1.45 times, heat set at 130 ℃ by the second hot roller 16 and wound through the cold roller 17 to obtain a drawn yarn 18 having 84 dtex, 36 filaments and a round cross section. (Figure 2). There was no problem in drawability at all, and the yarn breakage after winding 100 kg was zero.

The b ^* value of the drawn yarn obtained was 4.2,
It had an excellent color tone that could be used for clothing. In addition, the carboxyl group terminal concentration is the detection limit of 5 equivalents / ton.
It was below and showed excellent hydrolysis resistance.

Example 2 Stretching was carried out in the same manner as in Example 1 except that the addition amount of polycarbodiimide was 1.8 times equivalent (1.8 wt% with respect to polylactic acid).

The obtained drawn yarn had ab ^* value of 5.7,
It had an excellent color tone that could be used for clothing. In addition, the carboxyl group terminal concentration is the detection limit of 5 equivalents / ton.
It was below and showed excellent hydrolysis resistance.

Example 3 A polycarbodiimide compound was added to the polylactic acid obtained in Reference Example 2 in the same manner as in Example 1 to carry out spinning and stretching.
A drawn yarn of dtex, 96 filaments was obtained. At this time,
The amount of polycarbodiimide compound added is 1.0 times equivalent to the amount of carboxyl end groups (0.4 wt% relative to polylactic acid)
And

The b ^* value of the obtained drawn yarn is 4.1,
It had an excellent color tone that could be used for clothing. In addition, the carboxyl group terminal concentration is the detection limit of 5 equivalents / ton.
It was below and showed excellent hydrolysis resistance.

Example 4 Spinning and drawing were carried out in the same manner as in Example 3 with the addition amount of the polycarbodiimide compound being 0.5 times equivalent (0.2 wt% with respect to polylactic acid).

The drawn yarn thus obtained had ab ^* value of 2.4,
It had an excellent color tone that could be used for clothing. Further, the carboxyl group terminal concentration was 8 equivalents / ton, showing excellent hydrolysis resistance.

Comparative Example 1 Example 1 without the addition of a polycarbodiimide compound
Spinning and drawing were carried out in the same manner as above to obtain a drawn yarn of 84 detx and 36 filaments.

The b ^* value of the obtained drawn yarn was 1.1,
It had an excellent color tone that could be used for clothing. But,
The carboxyl group terminal concentration was 40 equivalents / ton, and the hydrolysis resistance was extremely poor.

Comparative Example 2 Spinning and drawing were carried out in the same manner as in Example 3 with the addition amount of the polycarbodiimide compound being 3.0 times equivalent (1.2 wt% with respect to polylactic acid). However, due to thermal decomposition of the free polycarbodiimide compound, yarn breakage frequently occurred during spinning and drawing.

The drawn yarn thus obtained had ab ^* value of 10.2, which was a poor color tone unusable for clothing.

[0060]

[Table 1] Example 5 Spinning was performed in the same manner as in Example 3 at a spinning speed of 4500 m / min to obtain an undrawn yarn. Then, this was subjected to multi-stage drawing heat treatment with the apparatus shown in FIG. 3 to obtain high strength polylactic acid fiber.
At this time, the feed roller 19 temperature is 70 ° C., the first hot roller temperature 20 is 120 ° C., and the second hot roller 2
1 temperature is 145 ° C., third hot roller 22 temperature is 16
0 ° C., 0.7% stretch between feed roller 19 and first hot roller 20, first hot roller 2
0 / drawing ratio between the second hot rollers 21 is 1.80 times,
The draw ratio between the second hot roller 21 and the third hot roller 22 was 1.30, the ratio between the third hot roller 22 and the relax roller 23 was 2%, and the speed of the relax roller 23 was 800 m / min (FIG. 3). . The b ^* value of the drawn yarn of 560 dtex and 98 filaments was 4.2. The carboxyl group terminal concentration was 5 equivalents / ton or less, which is the detection limit, and showed excellent hydrolysis resistance.

Example 6 Spinning was performed in the same manner as in Example 3 at a spinning speed of 6000 m / min to obtain a highly oriented undrawn yarn. This was preheated at a temperature of 140 ° C. for the first hot roller 15 and drawn 1.65 times, and heat-set at 150 ° C. for the second hot roller 16 to obtain a drawn yarn of 56 dtex and 24 filaments. The b ^* value of this yarn was 4.0, which was an excellent color tone usable for clothing. The carboxyl group terminal concentration was 5 equivalents / ton or less, which is the detection limit, and showed excellent hydrolysis resistance.

Example 7 Spinning was carried out in the same manner as in Example 3 at a spinning speed of 6000 m / min to obtain a highly oriented undrawn yarn. This was subjected to draw false twisting with the apparatus shown in FIG. At this time, a urethane disk triaxial twister is used as the rotor 28, and the stretching ratio between the feed roller 25 and the stretching roller 29 is 1.42 times.
Heater 26 temperature 130 ° C, stretching roller 29 speed 40
0 m / min, stretching roller 29 / relax roller 31
8% relaxed, second heater 30 temperature 15
It was set to 0 ° C. There was no problem in workability and no yarn breakage or fluff occurred. The obtained 160 dtex, 48 filament crimped yarn had ab ^* value of 4.1, which was an excellent color tone usable for clothing. The carboxyl group terminal concentration was 5 equivalents / ton or less, which is the detection limit, and showed excellent hydrolysis resistance. C, which is an index of crimp characteristics
The R value was 20%, which was sufficient crimp as a false twisted yarn. Further, the boiling point was 5%, which was sufficiently low.

Example 8 After melting a polycarbodiimide compound at 120 ° C., it was directly introduced into a twin-screw extrusion kneading machine 2 and kneaded with polylactic acid, spinning was carried out in the same manner as in Example 3, and the first take-up roller 11
At 1600 m / min, the undrawn yarn was taken out, combined and then received by the bunker 34 (FIG. 5). Then, the yarns received by the bunker were further combined into a tow of 150,000 dtex. This was stretched 3.2 times in a 90 ° C. water bath. After passing through the crimper, it was refueled and cut. The obtained cut fiber had a single yarn fineness of 7 dtex, a crimp number of 18 / m, and a fiber length of 51 mm. Further, the b ^* value was 4.2, which was an excellent color tone usable for clothing. The carboxyl group terminal concentration was 5 equivalents / ton or less, which is the detection limit, and showed excellent hydrolysis resistance. The fiber physical properties such as b ^* value and hydrolysis resistance were evaluated by sampling a part of the yarn between the crimper and the oil supply. Moreover, when the b ^* value of the cut fiber was measured using SM color computer SM-3 manufactured by Suga Test Co., Ltd., the b ^* value was 4.1. At this time, the cut fiber was pushed into a dedicated cell of the measuring instrument for measurement.

Example 9 Spinning was carried out in the same manner as in Example 8, the yarn was taken out by the air sucker 35, opened and collected in the net 38, and then calendered to give a nonwoven fabric (FIG. 6). The single yarn fineness of the fibers collected by air soccer is 1d.
tex, and the spinning speed calculated from the fineness is 5000 m /
It was worth a minute. The b ^* value of this yarn was 4.2. The carboxyl group terminal concentration is the detection limit of 5 equivalents /
It was not more than ton and showed excellent hydrolysis resistance. The fiber properties such as b ^* value and hydrolysis resistance were evaluated with the yarns taken. We have also measured the b ^* value of the resultant non-woven fabric, b ^* value was 4.1.

Example 10 Spinning was performed in the same manner as in Example 8 except that the spinneret discharge hole was Y-shaped. The spun yarn is drawn at 800 m / min, then drawn in two stages under the conditions of the first stage draw ratio of 1.4 times and the total draw ratio of 4.0 times, and further crimping using a jet nozzle. Then, a bulky processed yarn for carpet having 450 dtex and 90 filaments was wound up. The number of crimps was 15 / m, indicating a good crimp. The b ^* value was 4.2. The carboxyl group terminal concentration was 5 equivalents / ton or less, which is the detection limit. Note that b ^*
Evaluation of fiber physical properties such as values and hydrolysis resistance was performed on bulky processed yarn.

[0066]

[Table 2] Example 11 A plain weave was produced by using the yarns obtained in Examples 6 and 7 as warp yarns and weft yarns. The warp yarn was glued and dried at 110 ° C., but no fluff or yarn stretching problem occurred. The plain weave thus obtained was scoured at 60 ° C. according to a conventional method, and then intermediate set at 140 ° C. Further, it was dyed at 120 ° C. according to a conventional method. The obtained fabric has a squeaky feeling,
It had a soft feel, had an excellent texture for clothing, and showed vivid colors.

Comparative Example 3 A plain weave was produced in the same manner as in Example 11 using the yarn obtained in Comparative Example 1 as the warp yarn and the weft yarn, and dyeing was carried out at 120 ° C. The obtained fabric had almost no tear strength and was easily cut by hand.

Comparative Example 4 A plain weave was prepared in the same manner as in Example 11 using the yarn obtained in Comparative Example 2 as the warp and the weft, and dyeing was carried out at 120 ° C. The resulting fabric was turbid in color and could not provide clear color development.

Example 12 A mixed filament yarn obtained by bundling the bronze ammonia rayon “Cupula” (83 dtex, 45 filaments) of Asahi Kasei Kogyo Co., Ltd., which is a cellulosic fiber, as warp and the yarn obtained in Example 5 at 300 T / m. Was used as the warp, and the yarn obtained in Example 7 was used as the weft to prepare a plain weave. The plain weave thus obtained was scoured at 60 ° C. according to a conventional method, and then intermediate set at 140 ° C. Further, it was dyed at 100 ° C. according to a conventional method. The obtained cloth had a squeaky feeling and a soft feeling, had an excellent texture for clothing and showed a vivid color. Further, not only a high dry feeling due to a large contact cooling sensation peculiar to copper-ammonium rayon fiber was developed, but also excellent hygroscopicity was obtained, which was an excellent texture not obtainable only by polylactic acid fiber.

Example 12 In the same manner as in Example 8, a polylactic acid cut fiber having a single yarn fineness of 2.5 dtex, a fiber length of 51 mm, ab ^* value of 4.2, and a carboxyl group terminal concentration of 5 equivalent / ton or less was obtained. This and cotton were sliver blended to obtain a 36th polylactic acid / cotton blend yarn having a cotton blend ratio of 50%. Then, a Z twist of 800 turns / m was applied to this. Then, using this as a warp and a weft, a plain weave was prepared in the same manner as in Example 9, and 120
Staining was performed at ° C. The obtained fabric had a soft feel and a span feel, had an excellent texture for clothing and showed vivid color. Furthermore, it has an excellent hygroscopicity, and has an excellent texture that cannot be obtained by only polylactic acid fiber.

[0071]

EFFECTS OF THE INVENTION The polylactic acid fiber of the present invention having improved hydrolysis resistance and good color tone can greatly expand the application of polylactic acid fiber.

[Brief description of drawings]

FIG. 1 is a diagram showing a spinning device.

FIG. 2 is a diagram showing a stretching device.

FIG. 3 is a diagram showing a stretching device.

FIG. 4 is a diagram showing a drawing false twisting device.

FIG. 5 is a view showing a spinning device.

FIG. 6 is a view showing a spinning device.

[Explanation of symbols]

1: Hopper 2: Twin-screw extruder 3: Melting device 4: Spin pack 5: Static kneader 6: Base 7: Chimney 8: Thread 9: Focused refueling guide 10: Confounding guide 11: First take-up roller 12: Second take-up roller 13: Undrawn yarn 14: Feed roller 15: 1st hot roller 16: Second hot roller 17: Cold roller 18: Stretched yarn 19: Feed roller 20: First hot roller 21: Second hot roller 22: Third hot roller 23: Relax roller 24: High strength polylactic acid fiber 25: Feed roller 26: Heater 27: Cooling plate 28: Rotor 29: Stretching roller 30: Second heater 31: Relax roller 32: crimped yarn 33: Synthetic yarn 34: Bunker 35: Air soccer 36: Opening device 37: open yarn 38: Net

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4J029 AA01 AA02 AB02 AC01 AC02                       AD02 AD10 AE02 EA05 JC143                       JE243 KH01                 4J200 AA06 AA28 BA14 CA06 DA00                       DA01 DA12 EA04 EA21                 4L035 BB31 BB89 BB91 DD19 EE20                       FF01 FF08 GG08 HH10                 4L036 MA05 MA33 MA35 PA05 RA04                       UA12 UA25

Claims (6)

[Claims] 1. A polylactic acid fiber having a carboxyl group terminal blocked with a polycarbodiimide compound and having a b ^* value of 7 or less as an index of color tone, which is excellent in hydrolysis resistance. fiber. 2. The polylactic acid fiber excellent in hydrolysis resistance according to claim 1, wherein the total carboxyl group terminal concentration is 10 equivalents / ton or less. 3. The polylactic acid fiber having excellent hydrolysis resistance according to claim 1, wherein the polylactic acid fiber is a long fiber. 4. The polylactic acid fiber having excellent hydrolysis resistance according to claim 1 or 2, wherein the polylactic acid fiber is a short fiber. 5. The polylactic acid fiber having excellent hydrolysis resistance according to claim 1, wherein the polylactic acid fiber is a crimped yarn. 6. A fiber product in which the polylactic acid fiber excellent in hydrolysis resistance according to any one of claims 1 to 5 is used at least in part.