JP2003201629A - Polylactic acid spontaneously crimped fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid spontaneously crimped fiber which exhibits biodegradability in soil and in the atmosphere and has excellent bulkiness, touch and elasticity suitable for uses such as a nonwoven fabric and a cushion. <P>SOLUTION: This polylactic acid spontaneously crimped fiber comprising a conjugated fiber obtained by eccentrically joining polylactic acid resins A and B having different mol.wts. and different optical purities, respectively, to each other in a single filament is characterized in that the polylactic acid resins A and B together have spontaneous crimpability and satisfy the following expressions: (1) 55,000≤MA, MB≤90,000, (2) RA, RB≥90, and (3) |1-(MA /MB)×(RB/RA)<SP>3</SP>|≥0.10, wherein, MA is the number-average mol.wt. of the polylactic acid resin A; MB is the number-average mol.wt. of the polylactic acid resin B; RA is the optical purity (%) of the polylactic acid resin A; RB is the optical purity (%) of the polylactic acid resin B. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polylactic acid self-crimped fiber which is biodegradable in soil or air and is suitable for non-woven fabric applications, spinning applications and the like.

[0002]

2. Description of the Related Art As fibers used in daily life materials, agricultural materials, fishery materials, civil engineering materials and the like, synthetic fibers such as polyester, polyolefin and polyamide are generally mentioned. After being used, these fibers are difficult to decompose even if they are left in the natural environment, which causes various problems. For example, since living materials, agricultural materials, civil engineering materials, etc. that use these fibers are difficult to decompose, it is necessary to bury them in the soil after use, incinerate them, etc. Due to its poor nature, its disposal was limited. In addition, fishery materials are sometimes left in the water, but there was a problem that these pollute the ocean. In order to solve such a problem, it has been considered to use a material that decomposes in soil or water, but a material that has been decomposed has not been obtained yet.

Examples of conventional biodegradable polymers include cellulose, cellulose derivatives, polysaccharides such as chitin and chitosan, proteins, poly-3-hydroxybutyrate and 3-.
Polymers produced by microorganisms such as copolymers of hydroxybutyrate and 3-hydroxyvalerate, and aliphatic polyesters such as polyglycolide, polylactic acid and polycaprolactone are known. Cellulose-based cotton and regenerated cellulose that are mainly used are inexpensive, but they require a binder because they are not thermoplastic, and there is a problem that they are difficult to biodegrade because polyolefin, polyester fibers, etc. are used as binder fibers. . In addition, poly-3-hydroxybutyrate produced by microorganisms, 3-
Copolymers and the like of hydroxybutyrate and 3-hydroxyvalerate are expensive and therefore have limited applications and low strength. Furthermore, although polycaprolactone and polybutylene succinate are melt-spinnable thermoplastic biodegradable polymers, they have a problem of low melting point and heat resistance.

On the other hand, polylactic acid, which is a thermoplastic resin like polycaprolactone, is easy to melt-spin and has heat resistance. However, even if a fiber is formed from a single component, the bulkiness, the texture, etc. There is an unsatisfactory point, and improvement is desired. In order to solve these problems of polylactic acid fiber, JP-A-9-209216 proposes a spontaneously crimped composite fiber in which aliphatic polyesters having different endothermic amounts during melting are eccentrically joined in a single fiber. Has been done. However, since this fiber uses a resin with low crystallinity, there is a problem in terms of heat resistance, and since polylactic acid is copolymerized with polyethylene glycol or the like, there are problems such as high polymerization cost. there were.

[0005]

The present invention solves the above problems, exhibits biodegradability in soil and air, and is excellent in bulkiness, texture and stretchability suitable for non-woven fabric applications, cushion applications and the like. It is a technical subject to provide polylactic acid self-crimped fibers.

[0006]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems. That is, the present invention has the following structures. (1) A polylactic acid resin A and a polylactic acid resin B, which have different molecular weights and optical purities, are eccentrically bonded in a single fiber, and are polylactic acid resin A and polylactic acid resin B.
And satisfying the following formulas 1 to 3 and having spontaneous crimping ability, a polylactic acid spontaneous crimping fiber. 55000 ≦ MA, MB ≦ 90000 (Formula 1) RA, RB ≧ 90 (Formula 2) | 1- (MA / MB) × (RB / RA) ³ | ≧ 0.10 (Formula 3) However, MA: polylactic acid Number average molecular weight of resin A MB: Number average molecular weight of polylactic acid resin B RA: Optical purity of polylactic acid resin A (%) RB: Optical purity of polylactic acid resin B (%) (2) Number of crimps 40 / The self-crimped polylactic acid fiber according to (1) above, which is 25 mm or more. (3) The polylactic acid spontaneous crimp fiber according to (1) or (2) above, wherein the fiber form is a short fiber.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polylactic acid spontaneously crimped fiber of the present invention will be described in detail below. The spontaneously crimped fiber of the present invention is formed by eccentrically joining a polylactic acid resin A and a polylactic acid resin B having different molecular weights and optical purities in a single fiber. Is a polylactic acid and / or a copolymer mainly composed of polylactic acid. The lactic acid for producing polylactic acid may be only the D-form, the L-form, or a mixture of the D-form and the L-form. Examples of the copolymer containing polylactic acid as a main component include lactic acid (either D form only, L form only, or a mixture of D form and L form), cyclic lactones such as ε-caprolactone, and α-hydroxy. Butyric acid, α-hydroxyisobutyric acid, α-hydroxy acids such as α-hydroxyvaleric acid, ethylene glycol, 1,4
-Copolymers with one or more monomers selected from glycols such as butanediol and dicarboxylic acids such as succinic acid and sebacic acid. As a copolymerization ratio, the amount of the monomer to be copolymerized is preferably 10 parts by mass or less, and more preferably 1 to 5 parts by mass with respect to 100 parts by mass of lactic acid.

In the present invention, it is necessary that the polylactic acid resins A and B satisfy the formula 1. That is, the polylactic acid resins A and B each have a number average molecular weight of 55,000 or more, 90 or more.
It is necessary to be 000 or less, preferably 60,000 or more and 85,000 or less. If the number average molecular weight of any one of the polylactic acid resins A and B is less than 55,000, the viscosity becomes low at the time of spinning, resulting in poor spinnability.
If it is larger than the above range, the viscosity is high at the time of spinning and the spinning becomes difficult.

The temperature of the polylactic acid resin at the time of melt spinning is preferably not lower than its melting point and not higher than 230 ° C, particularly preferably not lower than its melting point and not higher than 210 ° C. When the temperature of the polylactic acid resin during melt spinning exceeds 230 ° C., lactide is likely to be regenerated and heat deterioration is likely to occur.

The optical purity of the polylactic acid resin as referred to in the present invention is expressed by the content ratio of L-lactic acid in the total lactic acid when the lactic acid constituting the polylactic acid resin is mainly L-lactic acid.
When the lactic acid constituting the polylactic acid resin is mainly composed of D-lactic acid, it is represented by the content ratio of D-lactic acid in the total lactic acid. For example, when the polylactic acid is composed of 95% by mass of L-lactic acid and 5% by mass of D-lactic acid, the optical purity of this polylactic acid resin is 9%.
It will be 5%.

In the present invention, it is also necessary that the polylactic acid resins A and B satisfy the formula 2. That is, the polylactic acid resins A and B used in the present invention need to have an optical purity of 90% or more. The optical purity of polylactic acid resin is 90
If it is less than%, the melting point of the resin becomes low and sufficient heat resistance cannot be obtained.

Further, in the present invention, it is also necessary that the polylactic acid resin A and the lactic acid resin B satisfy the formula 3. | 1- (MA / MB) × (RB / RA) ³ | ≧ 0.10 (Formula 3) where MA and MB are the number average molecular weights of the polylactic acid resins A and B, and RA and RB Is polylactic acid resin A, B
Represents the optical purity (%). This formula is obtained by comparing the ratio of the number average molecular weights of polylactic acid resin A and polylactic acid resin B with that of polylactic acid resin B.
Is the absolute value of the product of 1 and the value obtained by multiplying the optical purity ratio of the polylactic acid resin A to the third power, and this value represents the difference in shrinkage between the polylactic acid resin A and the polylactic acid resin B. It is a parameter. That is, the higher the value, the greater the difference in contractility, and the smaller the value, the smaller the difference in contractility.

In the present invention, the value of the equation 3 is 0.1
It must be 0 or more. If this value is 0.10 or more, the difference in shrinkage between the polylactic acid resin A and the polylactic acid resin B is sufficient, and spontaneous crimping occurs by heat treatment, but 0.10
If it is less than the above range, the shrinkage difference between the polylactic acid resin A and the polylactic acid resin B is not sufficient, and it becomes difficult for the spontaneous crimping to occur, and the object of the present invention cannot be achieved.

The spontaneously crimped fibers of the present invention develop latent crimps when subjected to heat treatment. The heat treatment temperature can be arbitrarily set depending on the melting point of the polylactic acid resin used, the intended use, and the crimp development state, but a high temperature is desirable in order to improve the crimp performance. However, if the heat treatment temperature is close to the melting point of the polylactic acid resin exposed in the outer layer of the fibers, the fibers may be fused with each other. Therefore, it is necessary to set the temperature at which the fibers are not fused. Generally, in the case of polylactic acid fiber, the heat treatment temperature is the melting point of the polylactic acid resin exposed in the outer layer of the fiber (however, when both polylactic acid resins A and B are exposed in the outer layer of the fiber, the lower melting point is used). Melting point of polylactic acid resin)
20 ° C. or more lower temperature, more preferably 30 ° C. or more lower temperature.

The spontaneously crimped fiber of the present invention can be heat-treated at the stage of raw cotton as a short fiber to be an actual crimped cotton. It can also be used as cotton wool. Also,
It can also be used as a long fiber of an actual crimp or a latent crimp.

The number of crimps developed by the heat treatment may be arbitrarily set according to the intended use, but in order to impart high stretchability to the nonwoven fabric as latent crimp cotton, the number of crimps after the heat treatment is required. Is preferably 40/25 mm or more. The number of crimps can be appropriately adjusted depending on the degree of eccentricity of the composite structure and the temperature during heat treatment.

When the spontaneously crimped fiber of the present invention is used as a latent crimped cotton, an ordinary press-type crimping machine is used so that no nep or unopened trouble occurs during the process of making a nonwoven fabric or the like. It is desirable to apply 8 to 20 pieces / 25 mm of mechanical crimps.

As described above, the spontaneously crimped fiber of the present invention is formed by eccentrically joining the polylactic acid resin A and the polylactic acid resin B having different molecular weights and optical purities in a single fiber. However, the cross section of a single fiber which is a specific example of a preferable composite structure is shown in FIGS. 1-3,
B indicates polylactic acid resin A, B indicates polylactic acid resin B, and C indicates a hollow portion. 1 is an example of a parallel type with high eccentricity, FIG. 2 is an eccentric core-sheath type, and FIG. 3 is a hollow parallel type. Any composite structure other than those shown in FIGS. 1 to 3 in which both components are eccentrically arranged can be applied to the present invention.

The composite ratio (cross-sectional area ratio) of polylactic acid resin A and polylactic acid resin B is not particularly limited and may be arbitrarily selected according to the purpose. Usually, the composite ratio is 1/10 to 10 /
1 range, especially 1/5 to 5/1 range is preferable, 1 /
The range of 3 to 3/1 is most widely used.

The cross section of the spontaneously crimped fiber of the present invention can be arbitrarily selected from circular, oval, gourd-shaped, polygonal, multilobal, alphabetical and other various non-circular (variant), hollow, etc. . Similarly, the fineness can be arbitrarily selected according to the purpose of use, but usually, the single yarn fineness is 0.1 to 50 dtex.
A range of about 0.5 to 30 dtex is preferably used. The fiber length when used as a short fiber can be arbitrarily selected according to the purpose of use, but is usually 20.
A range of -80 mm, especially 30-70 mm is preferably used.

The composite fiber of the present invention includes various pigments, dyes,
Mixing colorants, water repellents, water absorbing agents, flame retardants, stabilizers, antioxidants, UV absorbers, metal particles, inorganic compound particles, crystal nucleating agents, lubricants, plasticizers, antibacterial agents, fragrances and other additives. can do.

The spontaneously crimped fiber of the present invention can be used alone or in combination with other fibers for producing yarns, strings, ropes, knits, woven fabrics, nonwoven fabrics, papers, composite materials and other structures. . When used in combination with other fibers, it is particularly preferable to use it as a mixture with natural organic fibers such as cotton, wool and silk, and naturally degradable fibers such as aliphatic polyester fibers because a completely naturally degradable product can be obtained.

[0023]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these. In addition, the measuring method of the characteristic value etc. in an Example is as follows. (1) Relative Viscosity (ηR) Using an equal weight mixed solution of phenol / ethane tetrachloride as a solvent, the viscosity was measured at 20 ° C. using an Ubbelohde viscometer. (2) Single yarn fineness (dtex) It was measured by the method of JIS L-1015 7-5-1-1A. (3) Fiber strength (cN / dtex) It was measured by the method of JIS L-1015 7-7-1. (4) Number of crimps (pieces / 25 mm) It was measured by the method of JIS L-1015 7-12-1. (5) Number average molecular weight Tetrahydrofuran was used as a solvent and measured by gel permeation chromatography (GPC). Styragel H manufactured by waters as a filler
R # 54460 and # 44225, Ultrast
The measurement was carried out using a refractometer using three types of yragel # 10571. (6) Optical purity It was measured by a high performance liquid chromatography (HPLC) method using an equal weight mixed solution of ultrapure water and 1N sodium hydroxide in methanol as a solvent. Column is sumic
It was detected by a UV absorption measuring device using hiral OA6100.

Example 1 Optical purity was 98.8% and number average molecular weight was 8120.
0, a polylactic acid resin A mainly composed of L-lactic acid having [ηR] = 1.850, an optical purity of 98.9%, a number average molecular weight of 70100, and L− having [ηR] = 1.670.
A polylactic acid resin B containing lactic acid as a main component and a discharge amount of 240 using an ordinary nozzle for composite fibers having 443 holes.
Composite spinning was carried out in a parallel type (composite ratio 1/1) at a temperature of 220 ° C. in g / min and was taken up at a take-up speed of 1000 m / min to obtain an undrawn yarn. At this time, there was no spinning breakage and the process condition was extremely good.

The undrawn yarns thus obtained were collected so that the fineness of the tow was 64 ktex, and the draw ratio was 2.92 in the first step.
Second stage 1.20, stretched at a stretching temperature of 60 ° C., subjected to tension heat treatment at 125 ° C., and then fed to a push-type crimper,
After crimping with 12 crimps / 25 mm, it was dried at 70 ° C. and cut into 51 mm to obtain a polylactic acid composite fiber having a fineness of 1.7 dtex and a strength of 3.5 cN / dtex. The number of crimp occurrences of this polylactic acid conjugate fiber at the time of heat treatment under no load at 140 ° C. for 5 minutes was 50.6 pieces / 25 mm.

Examples 2 to 7 and Comparative Examples 1 to 6 Polylactic acid composite fibers were obtained in the same manner as in Example 1 except that the optical purity and the molecular weight of the polylactic acid resin were variously changed. However, the heat treatment temperature for crimp performance evaluation was the highest temperature in the range where the resin did not fuse, and the number of crimps after heat treatment under no load was 40 pieces / 25 mm or more. Table 1 shows the evaluation results of the composite fiber and the combination of the polylactic acid resins in Examples 1 to 7 and Comparative Examples 1 to 6.

[0027]

[Table 1]

As is clear from Table 1, the polylactic acid composite fibers obtained in Examples 1 to 7 have good spinnability and heat resistance, and the number of crimps developed after heat treatment is excellent at 45/25 mm or more. It was crimped fiber.

On the other hand, in Comparative Example 1, the number average molecular weight of the polylactic acid resin A was small and the melt viscosity at the time of melt spinning was low, so that spinning was impossible. In Comparative Example 2, the polylactic acid resin A had a large number average molecular weight and a high melt viscosity during melt spinning, so that the spinning pressure of the spin pack was high and stable production was difficult. In Comparative Example 3, since the optical purity of the polylactic acid resin B was low and the melting point was low, fusion of fibers occurred in the drawing step and the drying step, and the obtained fibers had poor heat resistance. Further, in Comparative Examples 4 to 6, since the polylactic acid resin did not satisfy the formula 3, the spinnability and the heat resistance of the fiber were good, but the spontaneous crimping property was insufficient.

[0030]

EFFECTS OF THE INVENTION According to the present invention, the properties which could not be obtained by the conventional polylactic acid fiber, that is, the biodegradability in the soil or the air, is exhibited, but the bulkiness, the texture and the elasticity are excellent. Provided is a polylactic acid spontaneously crimped fiber which has characteristics and can be applied to non-woven fabric applications, patch materials, sanitary materials, cushions and other application fields.

[Brief description of drawings]

FIG. 1 is a transverse cross-sectional view showing a side-by-side composite structure of single fibers constituting a polylactic acid self-crimped fiber of the present invention.

FIG. 2 is a cross-sectional view showing an eccentric core-sheath type composite structure of single fibers constituting the polylactic acid self-crimped fiber of the present invention.

FIG. 3 is a transverse cross-sectional view showing a hollow parallel type composite structure of single fibers constituting the polylactic acid self-crimped fiber of the present invention.

[Explanation of symbols]

B Polylactic acid resin A B Polylactic acid resin B C Hollow part

Claims (3)

[Claims] 1. A composite fiber in which a polylactic acid resin A and a polylactic acid resin B having different molecular weights and optical purities are eccentrically bonded in a single fiber, and the polylactic acid resin A and the polylactic acid resin B are combined. Satisfying the following formulas 1 to 3 and having spontaneous crimping ability, a polylactic acid spontaneous crimping fiber. 55000 ≦ MA, MB ≦ 90000 (Formula 1) RA, RB ≧ 90 (Formula 2) | 1- (MA / MB) × (RB / RA) ³ | ≧ 0.10 (Formula 3) However, MA: polylactic acid Number average molecular weight of resin A MB: number average molecular weight of polylactic acid resin B RA: optical purity of polylactic acid resin A (%) RB: optical purity of polylactic acid resin B (%) 2. The polylactic acid spontaneous crimp fiber according to claim 1, wherein the number of crimps is 40/25 mm or more. 3. The fiber form according to claim 1, wherein the fiber form is a short fiber.
The spontaneously crimped polylactic acid fiber described.