JP4033712B2 - Latent crimped polylactic acid composite fiber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a latently crimpable polylactic acid composite fiber suitable for obtaining a woven or knitted fabric that is biodegradable in soil or air, has excellent crimpability, and has a feeling of swelling.
[0002]
[Prior art]
Polyester fibers are excellent in mechanical properties, thermal stability, washability and the like, and are used in a very wide range of fields such as clothing, industrial materials, and interiors. Among them, woven and knitted fabrics for general clothing and sports clothing are also required to have required performance such as stretchability and texture from the viewpoint of comfort during wearing. Various methods have been proposed.
[0003]
For example, as a method for obtaining a fabric having stretch properties, it is well known to use latent crimpable conjugate fibers obtained by joining two types of polyester polymers having different heat shrinkage behaviors in a side-by-side manner.
[0004]
However, synthetic fibers such as polyolefin and polyamide, including such polyester fibers, are difficult to be decomposed even after being used in the natural world, causing various problems from the viewpoint of protecting the global environment. For example, these daily apparel are difficult to disassemble and are partly recycled after use, but most of them require treatment such as incineration, so that their disposal is limited.
In order to solve such a problem, it has been considered to use a fabric that can be decomposed in soil or water, but a sufficient fabric has not yet been obtained.
[0005]
Conventional biodegradable polymers include microorganisms such as cellulose, cellulose derivatives, polysaccharides such as chitin and chitosan, proteins, poly 3-hydroxy propylate and copolymers of 3-hydroxy propylate and 3-hydroxy valerate. Polymers to be made, aliphatic polyesters such as polyglycolide, polylactic acid, polycaprolactone and the like are known.
[0006]
Among these, cellulose-based cotton and regenerated cellulose that are mainly used are inexpensive, but their use is limited because they are not thermoplastic. In addition, poly-3-hydroxy propylate, a copolymer of 3-hydroxy propylate and 3-hydroxy valerate produced by microorganisms are expensive, unsuitable for general use, and have low strength. . Furthermore, polycaprolactone and polybutylene succinate are thermoplastic biodegradable polymers that can be melt-spun, but have a problem of low melting point and poor heat resistance.
[0007]
Similarly, polylactic acid, which is a thermoplastic resin, is easy to melt-spin and has heat resistance, and is therefore used for general clothing applications including industrial materials. However, woven and knitted fabrics using polylactic acid are unsatisfactory in terms of stretchability, softness, texture and the like, and biodegradable fibers for woven and knitted fabrics suitable for such differentiated general clothing applications are It has not been proposed yet.
[0008]
[Problems to be solved by the invention]
The present invention is a latent crimpable polylactic acid composite fiber that solves the above-described problems, is biodegradable in soil and air, has excellent crimpability, and is suitable for obtaining a woven or knitted fabric having a feeling of swelling. It is a technical challenge to provide
[0009]
[Means for Solving the Problems]
The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the gist of the present invention is as follows.
(B) a different molecular weight polylactic acid resin A, a double synthetic fiber intervertebral which arranged B in a side-by-side type, crimp rate after boiling water treatment is 40% or more state, and are the modulus of elasticity 50% or more, and polylactic acid A latent crimpable polylactic acid composite fiber, wherein the resin A and the polylactic acid resin B satisfy the following formula (1):
5000 ≦ MA-MB ≦ 40000 (1)
However, MA: number average molecular weight of polylactic acid resin A
MB: The number average molecular weight of polylactic acid resin B (b) The latently crimpable polylactic acid composite fiber according to (a), wherein polylactic acid resin A and polylactic acid resin B satisfy the following formula (2) .
5 ≦ DA−DB ≦ 12 (2)
DA: Content (% by mass) of D-lactic acid in the total lactic acid in polylactic acid resin A
DB: D-lactic acid content (% by mass) in the total lactic acid in the polylactic acid resin B
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The latent crimpable polylactic acid conjugate fiber of the present invention is a conjugate fiber in which polylactic acid resins A and B having different molecular weights are arranged side by side.
[0011]
The polylactic acid resin referred to in the present invention is a copolymer mainly composed of polylactic acid and / or polylactic acid. The lactic acid for producing polylactic acid may be only D-form, only L-form, or a mixture of D-form and L-form. Examples of the copolymer mainly composed of polylactic acid include lactic acid (D-form only, L-form alone, and a mixture of D-form and L-form), cyclic lactones such as ε-caprolactone, α-hydroxy, and the like. One or more monomers selected from butyric acid, α-hydroxyisobutyric acid, α-oxyacids such as α-hydroxypalate, glycols such as ethylene glycol and 1,4-butanediol, and dicarboxylic acids such as succinic acid and sebacic acid What copolymerized 2 or more types is mentioned. The proportion of copolymerization is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of lactic acid.
[0012]
The latent crimpable polylactic acid composite fiber of the present invention has a crimping performance of 40% or more, preferably 45% or more, and a modulus of elasticity of 50% or more, preferably 55% or more after boiling water treatment. It is necessary.
Here, the crimp rate and the elastic modulus after the boiling water treatment are measured by the following method. In other words, the yarn that has been squeezed five times with a measuring instrument is left for 30 minutes with a 1/6800 (cN / dtex) load applied, and then placed in boiling water for 30 minutes while maintaining this state. To do. Then, it is air-dried for 30 minutes, a 1/570 (cN / dtex) load is applied, and the length (b) is measured. Next, after removing the load of 1/570 (cN / dtex), the load of 1 / 22.5 (cN / dtex) is applied and the length (c) is measured. A load of 1/570 (cN / dtex) is again applied and the length (d) is measured. Then, the crimp rate and the elastic modulus are obtained by the following equations.
Crimp rate (%) = [(c−b) / c] × 100
Elastic modulus (%) = [(cd) / (c−b)] × 100.
[0013]
In the present invention, when the crimp rate of the composite fiber after boiling water treatment is less than 40%, the stretchability of the yarn after crimping is poor, and the stretchability of the woven or knitted fabric obtained from this yarn is also poor. , Good stretchability cannot be imparted to the woven or knitted fabric. In addition, when the elastic modulus of the composite fiber after boiling water treatment is less than 50%, the elongation recovery property of the yarn is low, the elongation recovery property of the resulting woven or knitted fabric is low, and the woven or knitted fabric has good stretchability and swelling. A feeling cannot be given.
[0014]
The composite fiber of the present invention is a fiber in which polylactic acid resins A and B having different molecular weights are arranged in a side-by-side manner, and uses a difference in heat shrinkage between both polylactic acid resins to develop spiral crimps. is there. The larger the difference in molecular weight between the polylactic acid resin A and the polylactic acid resin B, the more advantageous for crimp expression. However, if the difference in molecular weight is large, kneeling occurs immediately under the spinneret during spinning, resulting in poor spinning operability. On the other hand, when the difference in molecular weight is small, the expression of crimps decreases.
[0015]
In the present invention, in order to obtain a composite fiber having good spinnability and crimp development, having a crimping performance after boiling water treatment of 40% or more and an elastic modulus of 50% or more, a polylactic acid resin A , B preferably satisfies the above formula (1) , and further preferably satisfies the above formula (2) . That is, in order for the composite fiber to have good crimping performance, the difference between the number average molecular weight of the polylactic acid resin A and the number average molecular weight of the polylactic acid resin B is 5000 or more and 40000 or less, particularly 8000 or more and 32000 or less. It is preferable.
[0016]
The difference between the D-lactic acid content in the total lactic acid in the polylactic acid resin A and the D-lactic acid content in the polylactic acid B is preferably 5% by mass or more and 12% by mass or less. If the difference between the number average molecular weight of the polylactic acid resin A and the number average molecular weight of the polylactic acid resin B is less than 5,000, the difference in shrinkage when receiving heat between the respective resins becomes small, and the spiral crimp that appears is insufficient. . If the difference in the D-lactic acid content contained in the polylactic acid resin is less than 5% by mass, the difference in shrinkage during heat reception between the respective resins becomes small, and the spiral crimp that appears is insufficient, which is not preferable.
[0017]
Also, if the difference between the number average molecular weight of the polylactic acid resin A and the number average molecular weight of the polylactic acid resin B is greater than 40,000, the difference in viscosity at the time of melting will increase, increasing the kneeling that occurs immediately below the spinneret and increasing the spinning operability. Since it gets worse, it is not preferable. Alternatively, when the difference in the D-lactic acid content contained in the polylactic acid resin exceeds 12% by mass, the amount of D-lactic acid in the total lactic acid in the polylactic acid resin A will increase. This is not preferred because it decreases and is hard to develop crimping due to agglutination and melting during the heat treatment of the composite fiber and hardens the texture of the woven or knitted fabric.
[0018]
The cross-sectional form of the latently crimpable polylactic acid composite fiber of the present invention is arbitrarily selected from a circular shape, an oval shape, a gourd shape, a polygonal shape, a multi-leaf shape, and other various non-circular shapes (atypical shapes), a hollow shape, Can do. Similarly, the fineness may be arbitrarily selected according to the purpose of use, but in a normal apparel application, a range of single yarn fineness of about 1.0 to 20 dtex, particularly 2 to 10 dtex is preferably used.
[0019]
The composite fiber of the present invention includes various pigments, dyes, colorants, water repellents, water absorbents, flame retardants, stabilizers, antioxidants, ultraviolet absorbers, metal particles, inorganic compound particles, crystal nucleating agents, lubricants, Plasticizers, antibacterial agents, fragrances and other additives can be mixed depending on the intended use.
[0020]
Next, an example of manufacturing the latent crimpable polylactic acid composite fiber of the present invention will be described.
First, using a compound spinning device for a normal side-by-side type composite fiber, the polylactic acid resin A and the polylactic acid resin B are melted and weighed in separate measuring holes, and merged to be side-by-side on the back of the base. The yarn is discharged from the same discharge hole, and the spun yarn is cooled by blowing air using a known cooling device such as a horizontal spraying device or an annular spraying device. Pick up the machine. Considering the spinnability, the take-up roller speed is preferably 800 to 3500 m / min.
[0021]
Next, the obtained undrawn yarn is drawn and heat-treated between groups of rollers having different peripheral speeds by a known drawing machine to obtain a target latent crimpable polylactic acid composite fiber.
In the above production method, the temperature of the polylactic acid resin during melt spinning is not particularly limited, but is not lower than the melting point of the polylactic acid resin and not higher than 230 ° C., particularly not lower than the melting point of the polylactic acid resin and not higher than 210 ° C. It is desirable that When the temperature of the polylactic acid resin at the time of melt spinning exceeds 230 ° C., lactide is regenerated and heat deterioration is likely to occur.
[0022]
【Example】
EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these.
In addition, the measuring methods, such as a characteristic value in an Example, are as follows.
(1) Relative viscosity [ηR]
An equimass mixed solution of phenol / ethane tetrachloride was used as a solvent, and measurement was performed at a temperature of 20 ° C. using an Ubbelohde viscometer.
(2) Number average molecular weight Measured by gel permeation chromatography (GPC) method using tetrahydrofuran as a solvent. Three types of fillers, Styragel HR # 54460 and # 44225, and Ultrastyragel # 10571, manufactured by waters, were used, and measurement was performed using a refractometer.
(3) L / D-lactic acid content (mass%)
It measured by the high performance liquid chromatography (HPLC) method by using the equal mass mixed solution of the pure water and the methanol solution of 1N sodium hydroxide as a solvent. The column used was sumichiralO A6100 and was detected by a UV absorption measuring device.
(4) Spinnability
48 spindles were spun and the following evaluation was performed from the number of yarn breakage per 24 hours.
The evaluations ◎ and ○ were regarded as passing points.
(5) Crimp rate, elastic modulus (%)
It was measured by the method described in the text.
(6) Texture evaluation (stretching and swelling)
The composite fiber was knitted into a cylinder, scoured, and boiled at 100 ° C. for 30 minutes. The cylinder knitted fabric was subjected to a sensory test based on the tactile sensation of 10 panelists, and was scored according to the following five-level evaluation.
1 point: poor texture 2 points: slightly bad texture 3 points: normal texture 4 points: good texture 5 points: very good texture, the evaluation is based on the total score of 10 panelists, the total of the texture evaluation is 35 points The above was regarded as a passing score.
[0023]
Example 1
A polylactic acid resin A mainly composed of L monolactic acid having a number average molecular weight of 74500 and a D-lactic acid content of 7.0% by mass, a number average molecular weight of 52000 and a D-lactic acid content of 1.2% by mass. A polylactic acid resin B mainly composed of a certain L-lactic acid is melted at a spinning temperature of 210 ° C., the mass ratio of each polymer is 50:50, the discharge rate is 30.6 g / min, and a normal side-by-side type with 24 holes Using a spinning nozzle for forming a high-oriented undrawn yarn was drawn at a take-up speed of 2800 m / min. At this time, spinning was performed with 48 spindles, and the yarn breakage per 24 hours was as good as once.
The obtained highly oriented undrawn yarn was preheated at 70 ° C. and then drawn at a draw ratio of 1.25, a heat setting temperature of 150 ° C. and a drawing speed of 500 m / min to obtain a composite fiber.
[0024]
The physical properties of the obtained composite fiber were a fineness of 108 dtex, a strength of 2.4 cN / dtex, and an elongation of 18.5%. Moreover, the performance of the composite fiber was 58.4% crimp rate and 56.5% elastic modulus after boiling water treatment. When the texture of this composite fiber was evaluated, it had very good stretchability and swell.
[0025]
Examples 2 to 4 and Comparative Examples 1 to 4
A polylactic acid composite fiber was obtained in the same manner as in Example 1 except that the number average molecular weights of the polylactic acid resins A and B and the content of D-lactic acid were changed as shown in Table 1. The evaluation results of the obtained composite fiber are also shown in Table 1.
This is not preferable because the texture of the woven or knitted fabric is hardened.
[0026]
[Table 1]
[0027]
As apparent from Table 1, the composite fibers obtained in Examples 1 to 4 had a crimp rate of 40% or more after boiling water treatment and an elastic modulus of 50% or more. It had a feeling of swelling.
[0028]
On the other hand, Comparative Example 1 has a small number average molecular weight difference between the used polylactic acid resins A and B and a difference in the content of D-lactic acid, and the spinnability is good, but the values of crimp rate and elastic modulus are low. It became a thing. Therefore, the texture of the obtained composite fiber has poor stretchability.
In Comparative Example 2, since the number average molecular weight of polylactic acid A is larger than that of polylactic acid resin B, the values of crimp rate and elastic modulus are low, and the texture of the obtained composite fiber is poor in elasticity and hard. there were.
Next, in Comparative Example 3, since the difference in number average molecular weight between the polylactic acid resins A and B was small, the fiber had a low crimp rate, and the texture of the obtained composite fiber was poor in extensibility.
[0029]
In Comparative Example 4, since the number average molecular weight difference between the polylactic acid resins A and B was too large, the kneeling just under the nozzle during spinning was so great that the spinning condition was remarkably deteriorated, and a composite fiber could not be obtained.
[0030]
【The invention's effect】
According to the present invention, it is suitable for obtaining a woven or knitted fabric having biodegradability in soil and air, having good yarn-making properties, easy to manufacture, excellent in crimpability, and having a feeling of swelling. A polylactic acid latent crimpable composite fiber is provided.

Claims (2)

Polylactic acid different molecular weight resin A, a double synthetic fiber intervertebral which arranged B in a side-by-side type, crimp rate after boiling water treatment is 40% or more state, and are the modulus of elasticity 50% or more, and a polylactic acid resin A A latently crimpable polylactic acid composite fiber, characterized in that the polylactic acid resin B satisfies the following formula (1):
5000 ≦ MA-MB ≦ 40000 (1)
However, MA: number average molecular weight of polylactic acid resin A
MB: Number average molecular weight of polylactic acid resin B The latent crimpable polylactic acid composite fiber according to claim 1, wherein the polylactic acid resin A and the polylactic acid resin B satisfy the following formula (2) .
5 ≦ DA−DB ≦ 12 (2)
DA: Content (% by mass) of D-lactic acid in the total lactic acid in polylactic acid resin A
DB: D-lactic acid content (% by mass) in the total lactic acid in the polylactic acid resin B