JPH11293518A - Biodegradable staple fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable staple fiber having a dry-touch feeling, hardly causing environmental pollution, excellent in flexibility and useful for clothing, industrial material or the like by forming a polymer consisting essentially of an aliphatic polyester and having a melting point not less than a prescribed value into the fiber under a specified condition. SOLUTION: This biodegradable staple fiber is obtained by melt-spinning a polymer consisting essentially of an aliphatic polyester of a polylactic acid- based polymer such as a polymer selected from a poly(D-lactic acid), a poly(L- lactic acid), a poly(D/L-lactic acid), a copolymer of D-lactic acid and a hydroxycarboxylic acid and a copolymer of L-lactic acid and the hydroxycarboxylic acid, or a blend thereof, and having >=100 deg.C melting point, hot-drawing the spun fiber after winding the spun fiber or following the spinning, at a drawing ratio larger than the maximum elongation of the fiber at a temperature not less than the glass transition temperature and not higher than the softening temperature to manifest groove-like concavoconvexs on the fiber surface, and forming the drawn fiber into staple.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable composition,
The present invention also relates to a biodegradable short fiber having a dry touch feeling and flexibility, and a method for producing the same.

[0002]

2. Description of the Related Art Conventional synthetic fibers have a slow decomposition rate in a natural environment and generate a large amount of heat upon incineration. Therefore, it is necessary to review the synthetic fibers from the viewpoint of protecting the natural environment. For this reason, biodegradable fibers made of aliphatic polyesters are being developed and are expected to contribute to environmental protection. Some aliphatic polyesters have excellent fiber performance and are expected as fiber materials with new characteristics, but none have a dry touch texture and flexibility, and improvement thereof is desired.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, is biodegradable, and
An object of the present invention is to provide a biodegradable short fiber having a dry touch feeling and flexibility and a method for producing the same.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention. That is, the present invention has the following configuration. (1) Mainly aliphatic polyester, melting point 100 ℃
A biodegradable short fiber comprising the polymer described above and having at least fiber-like irregularities on the fiber surface. (2) Mainly aliphatic polyester, melting point 100 ° C
After the above polymer is melt-spun and the fiber is wound up, or continuously, the fiber is stretched at a draw ratio not less than the maximum elongation of the fiber, and not less than the glass transition temperature, and not more than the softening temperature. A method for producing a biodegradable short fiber, characterized in that short fibers are formed after the unevenness is developed.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Examples of the polymer mainly containing an aliphatic polyester in the present invention include (1) hydroxyalkyl carboxylic acids such as glycolic acid, lactic acid, and hydroxybutyl carboxylic acid; and (2) aliphatic lactones such as glycolide, lactide, and butyrolactone. (3) aliphatic diols such as ethylene glycol, propylene glycol, butanediol, hexanediol and the like; (4) oligomers such as polyalkylene ethers such as diethylene glycol and dihydroxyethylbutane; polyethylene glycol, polypropylene glycol and polybutylene Aliphatic polyesters such as polyalkylene glycols such as ethers, and (5) aliphatic carboxylic acids such as succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid. A component derived from a raw material as a main component, that is, 60% by weight or more, wherein a homopolymer of an aliphatic polyester, a block or random copolymer of an aliphatic polyester, and another component such as an aromatic polyester Group polyester, polyether, polycarbonate, polyamide, polyurea,
It includes all copolymers and / or mixtures of polyurethanes and the like in an amount of 40% by weight or less.

In the present invention, if necessary, for example, a crystal nucleating agent, a matting agent, a pigment, a light stabilizer, a weathering agent, an antioxidant, Various additives such as antibacterial agents and fragrances can be added as long as the effects of the present invention are not impaired.

The purpose of modifying the aliphatic polyester by copolymerization or mixing is to lower the crystallinity, lower the melting point, improve flexibility and elastic recovery, improve heat resistance and friction coefficient, heat shrinkage, decomposability and the like. Control of glass transition temperature, improvement of adhesiveness with multiple components and the like can be mentioned.

The melting point of these polymers is required to be 100 ° C. or higher from a practical point of view (problems occur in the summer management of fibers or products using the fibers or the materials are deteriorated by boiling water). The above is preferable, 120 ° C. or higher is more preferable, and 130 ° C. or higher is most preferable. As used herein, the term “melting point” refers to a condition of about 5 mg of a sample which has been sufficiently stretched, heat-treated, and dried using a scanning differential calorimeter (hereinafter, referred to as DSC), in nitrogen, and at a heating rate of 10 ° C./min. It was measured in.

The cross section of the biodegradable short fiber of the present invention includes:
The same or different combinations of round cross section, irregular cross section, hollow cross section, single type, core-sheath type, side-by-side type, multi-core type, multilayer type, and various split type composite cross sections are also possible.

In the present invention, when the fiber composed of a polymer mainly composed of an aliphatic polyester is a conjugate fiber, a low melting point component contributes as a heat bonding component when the difference in melting point is 10 ° C. to 80 ° C. In any case, it is possible to provide a crimping ability as a high-shrinkage component.

The single fiber fineness of the biodegradable short fibers of the present invention is preferably selected from 0.3 to 50 denier.
When it is less than 0.3 denier, problems such as control of solidification point, increase in accuracy of a die hole, decrease in productivity due to reduction in discharge amount, and occurrence of thread breakage when forming fibers are likely to occur. Therefore, it is not preferable. If it exceeds 50 denier, the flexibility is impaired, which is not preferable.

A feature of the biodegradable short fibers of the present invention is that they have streaky irregularities on at least the fiber surface. The streak-like irregularities are those having micro-streak-like irregularities particularly in a direction perpendicular to the fiber length direction. FIG. 1 is a photomicrograph taken at 200 × showing an example of the surface of the biodegradable short fiber of the present invention, which has micro-streak irregularities in a direction perpendicular to the fiber length direction. You can see that. The streak-like unevenness is obtained by, for example, uniformly expressing fiber strain (void) due to stretching. Therefore, the fiber density is lower than the original undrawn yarn density.

In particular, in order to uniformly develop micro-streak irregularities, it is preferable to use a polymer whose glass transition temperature is higher than room temperature. As a more preferable polymer, the main component of the aliphatic polyester described above is a polylactic acid-based polymer, and poly (D-lactic acid) and poly (L-lactic acid) are used.
-Lactic acid), poly (L / D-lactic acid), a copolymer of D-lactic acid and hydroxycarboxylic acid, and a polymer selected from the group of a copolymer of L-lactic acid and hydroxycarboxylic acid, or These are blends. Due to the appearance of the streaky irregularities, the fibers can be whitened to the extent that a matting agent is not added, and a dry feeling can be imparted. Also, there is an effect that the biodegradation speed is increased.

The strength of the biodegradable short fiber of the present invention is 1 g /
d or more is preferable. If the strength is less than 1 g / d, a problem occurs in practical use. The higher the fiber strength is, the wider the practical range is, which is preferable, but the upper limit is currently about 6 g / d. The elongation of the fiber is preferably 10 to 30%. Elongation is 1
If it is less than 0%, yarn breakage occurs, and the drawing operability tends to decrease. On the other hand, if the elongation exceeds 30%, it is difficult to develop microscopic irregularities on the fiber surface, which is not preferable. Therefore, the elongation is more preferably 12 to 28%,
15-25% is most preferred.

The biodegradable staple fiber of the present invention may be used alone or in combination with other fibers to form a spun yarn, a cord, a knitted fabric, a woven fabric or various nonwoven fabrics using them, that is, a thermal nonwoven fabric, an embossed nonwoven fabric, a needle punch. It can be used for nonwoven fabric, spunlace nonwoven fabric, wet nonwoven fabric, and the like, and can also be used for production of composite materials and other structures. When mixed with other fibers, natural fibers such as wool and silk and cellulose,
It is particularly preferable to use a mixture with a regenerated fiber such as rayon or a biodegradable fiber such as an aliphatic polyester fiber since a completely biodegradable product can be obtained. The biodegradable short fiber of the present invention is preferably obtained by a production method described later, but may be produced by another method.

Next, a method for producing the biodegradable short fiber of the present invention will be described. In order to produce the biodegradable short fiber of the present invention, basically, a spinning method and a drawing method using a known melt spinning apparatus can be applied.

The polymer for producing the biodegradable staple fiber in the present invention may be appropriately selected from the above-mentioned polymers. Particularly, the main component of the aliphatic polyester is a polylactic acid-based polymer. , Poly (D-lactic acid) and poly (L
-Lactic acid), poly (D / L-lactic acid), a copolymer of D-lactic acid and hydroxycarboxylic acid, and a polymer selected from the group of a copolymer of L-lactic acid and hydroxycarboxylic acid, or When these blends have a melting point of 100 ° C. or higher, the desired short fibers are easily obtained. This is because the glass transition temperature is equal to or higher than room temperature.

Next, the polymer is melted and weighed, and a fiber is spun out from a spinneret, cooled, wound up, or continuously without winding at a draw ratio not less than the maximum elongation of the fiber. In addition, it can be obtained by hot stretching at a temperature not lower than the glass transition temperature of the fiber and not higher than the softening temperature, and then crimping it by a conventional method and cutting it into a predetermined fiber length. When spinning the fiber, using an apparatus for compound spinning of different components, the individual components may take different composite forms in the spinneret, or the individual components may be spun from individual holes. It may take a mixed fiber form by simple co-spinning.

When the obtained fiber is hot-drawn, a temperature not lower than the glass transition temperature and not higher than the softening temperature is generally applied for uniform drawing. The fiber of the present invention can be obtained only by giving a draw ratio. In other words, this causes uniform stretching unevenness, and it is particularly preferable to apply hot pin stretching because uniform micro unevenness can be exhibited on the fiber surface.

In the hot pin drawing, a pin of a heatable specification is set in a drawing zone, and the fiber is swung around the pin to promote fixing of a drawing point. In the drawing zone, by applying a draw ratio equal to or more than the maximum elongation of the fiber, excessive strain is caused in the fiber, and furthermore, by controlling the fiber slipping with a hot pin, the fiber surface is uniform microscopic. An uneven fiber is obtained. The maximum elongation of the fiber means that the fiber (undrawn yarn) melt-spun and wound is gripped at a room temperature of 20 ° C. at a room temperature of 20 ° C. at a holding interval of 10 cm and a pulling speed of 20 cm / min. It refers to the maximum elongation (ME) when pulled under conditions.

Preferred stretching ratio (DR) in the present invention
Depends on the molecular weight level of the polymer, the spinning temperature, and the drawing speed, but ME / 100 + 1 ≦ DR ≦ ME / 100
It is about +1.5. A more preferred range is ME / 10
0 + 1.1 ≦ DR ≦ ME / 100 + 1.4. If the draw ratio is less than the maximum elongation, the fiber is less likely to be strained, so that micro unevenness is less likely to appear. On the other hand, the stretching ratio (ME / 100 + 1.
In the case of 5), yarn breakage occurs, and the operability tends to be reduced.

On the other hand, as another method for uniformly generating excessive strain in the fiber without using a hot pin, a method in which the drawing step is performed in two steps and the draw ratio is apart from 1: 1, for example, 1: Control is also possible with the 4 or 4: 1 method.

The melt spinning in the present invention has a winding speed of 30.
Low speed spinning from 0 to 2000 m / min, winding speed from 2000 to 2000
High-speed spinning at 5000 m / min and ultra-high-speed spinning at a take-up speed of 5000 m / min or more are possible, and a so-called spin draw method in which spinning and drawing are continuously performed is also preferably applicable.

[0024]

Next, the present invention will be described in detail with reference to examples. In Examples,% is a weight ratio unless otherwise specified. Each characteristic value was measured by the following method. (1) Molecular weight of aliphatic polyester This is the number average value of the dispersion of the high molecular weight component excluding components having a molecular weight of 1,000 or less in a GPC analysis using a 0.4% chloroform solution as a sample and polystyrene as a standard substance. (2) MFR (g / 10 min) This is a value measured at 210 ° C. under a load of 2160 g according to ASTM D1238. (3) Strength and elongation of short fiber According to JIS L-1015, the maximum tensile strength when the fiber is pulled under the conditions of a gripping interval of 2 cm and a pulling speed of 2 cm / min divided by the fineness is defined as the strength. The elongation was determined from the elongation of the sample. (4) Hot water shrinkage (%) It was determined according to JIS L-1015.

(5) Biodegradability A short fiber sample was buried in soil for 18 months, taken out after standing, washed, measured for single fiber strength, and the difference from the single fiber strength immediately after production was measured. The strength was determined as the strength retention (%) according to the following formula, and the degradability was evaluated. DW = 100T ₁₈ / T ₀ where DW: strength retention, W ₀ : fiber strength immediately after production, T ₁₈ : fiber strength after standing in soil for 18 months.

Example 1 The MFR was 25 g / 10 min and the number average molecular weight was 7100.
Glass transition temperature 69 ° C, crystallization temperature 136 ° C, melting point 1
Melt spinning was performed using a poly D / L lactic acid resin having a density of 1.262 g / cm ³ at 70 ° C. That is, using a single-screw extruder-type melt extruder, a temperature of 200 ° C.
At a single hole discharge rate of 0.58 g / min from a nozzle having a diameter of 0.3 mm and a number of holes of 180, cooled by an air cooling device, and spun at a spinning speed of 1,000 m / min.
The yarn was wound at a speed of 1 minute to obtain an undrawn yarn. The maximum elongation of this undrawn yarn was 140%.

Using this undrawn yarn, drawing can be carried out using a hot drawing machine which is capable of performing two-stage drawing, which is generally used, and has a 30 mm diameter hot pin between one and two rollers. Was. That is, the ratio of the first-stage draw ratio to the second-stage draw ratio is 2: 1, the first roller temperature is 60 ° C., the hot pin temperature is 75 ° C., the second roller temperature is 90 ° C., and the yarn is connected to the hot pin. The strip was turned once, and the drawing was performed at a total draw ratio of 2.6 times.

Next, the long fiber is re-wound to 10
Form a 10,000 denier tow, push it into a stuffing box to give crimp, and then apply a finishing oil,
After drying, it was cut into a cut length of 51 mm to obtain short fibers. The obtained short fibers had a strength of 4.0 g / d and an elongation of 30.
%, Hot water shrinkage 14%, fiber density 1.235g / cm
^As shown in FIG. 1, the fiber had micro unevenness perpendicular to the fiber length direction.

Example 2 The MFR was 10 g / 10 min and the number average molecular weight was 1,000.
Using a poly D / L lactic acid resin having a glass transition temperature of 70 ° C., a crystallization temperature of 136 ° C., a melting point of 170 ° C., and a density of 1.263 g / cm ³ , a temperature of 220 ° C. and a single hole discharge amount of 0.75 g
An undrawn yarn was obtained in the same manner as in Example 1 except that the melt spinning was performed at a rate of / min. The maximum elongation of the obtained undrawn yarn was 87%.

Rewinding is performed by using the undrawn yarn, and 2
After forming a 40,000-denier undrawn yarn tow, the ratio of the first-stage drawing ratio to the second-stage drawing ratio was set to 4: 1 using a commonly used short-fiber three-stage drawing machine. The temperature of the first roller is set to 72 ° C., the temperature of the second roller is set to 90 ° C., and the drawing is performed at a total draw ratio of 2.4 without using a hot pin. Was done.

The obtained short fiber had a single fiber fineness of 3.0 denier, a strength of 4.8 g / d, an elongation of 23%, and a hot water shrinkage of 15%.
%, Fiber density is 1.237 g / cm ³ ,
As shown in FIG. 1, micro unevenness was perpendicular to the fiber length direction.

Example 3 The MFR was 21 g / 10 min and the number average molecular weight was 8500.
Glass transition temperature 63 ° C, crystallization temperature 132 ° C, melting point 1
An undrawn yarn was obtained in the same manner as in Example 1 except that melt spinning was performed using a copolymer lactic acid resin of poly L-lactic acid and hydroxycarboxylic acid having a density of 1.255 g / cm ³ at 65 ° C. . The maximum elongation of the obtained undrawn yarn was 152%.

A rewind is performed using the undrawn yarn,
After forming a 100,000-denier undrawn yarn tow, the ratio of the first stage draw ratio to the second stage draw ratio is 2: 3, the first roller temperature is 65 ° C., the hot pin temperature is 70 ° C., and the second roller Temperature 8
The stretching was performed at 5 ° C. and the total stretching ratio was 2.9 times. Thereafter, the fiber was shortened in the same manner as in Example 1.

The obtained short fiber had a single fiber fineness of 3.0 denier, a strength of 3.8 g / d, an elongation of 32%, and a hot water shrinkage of 15%.
%, The fiber density is 1.239 g / cm ³ ,
As shown in FIG. 1, micro unevenness was perpendicular to the fiber length direction.

Comparative Example 1 Using the undrawn yarn obtained in Example 1, the draw ratio of the first stage was 2
The draw ratio of the first stage is 1: 1, the first roller temperature is 60 ° C.,
After the second roller temperature was set to 85 ° C. and the drawing was performed at a total draw ratio of 2.2 without using a hot pin, short fibers were obtained in the same manner as in Example 1. The obtained short fibers had a single fiber fineness of 3.0 denier, a strength of 3.2 g / d, an elongation of 32%, a hot water shrinkage of 25%, and a fiber density of 1.255 g / cm ^3. It did not have micro unevenness perpendicular to the fiber length direction.

A spun yarn was prepared using the short fibers obtained in Examples 1 to 3 and Comparative Example 1. That is, each staple was passed through an opener, a flat card machine, a pin drafter, a reducer, and a rover, and a sliver obtained was passed through a ring spinning machine to obtain a spun yarn of 60th count. After one warp of this spun yarn was warped by a warper, the spun yarn was woven into a plain weave structure as a weft using an air jet type loom. Examples 1-3
Was a soft and dry touch texture, but the fabric of Comparative Example 1 had only a coarse
It did not have a dry touch texture. Next, the short fibers obtained in Examples 1 to 3 and Comparative Example 1 were buried in the soil and their biodegradability was evaluated. It was found that decomposition was promoted. In particular, the short fiber of Example 3 hardly kept its original shape, and could not even measure.

[0037]

[Table 1]

[0038]

According to the present invention, there is provided a short fiber which is biodegradable, has little environmental pollution, and has a microscopic unevenness on the fiber surface. And this short fiber is
When applied to knits, woven fabrics, non-woven fabrics and other various fiber structures, composite structures, etc., soft and dry-touched products can be obtained, which can be suitably used for clothing, industrial materials, household goods and the like.

In general, aliphatic polyester fibers only decompose in a natural environment and have no dry feeling. However, as in the present invention, voids are uniformly expressed in fibers including irregularities on the fiber surface. As a result, a matte effect is exhibited together with a dry feeling, the decomposition performance is accelerated, and the flexibility is also increased.

The biodegradable staple fiber of the present invention has practical fiber strength and, when used in an environment in which a large number of microorganisms are present, for example, when left in the soil or water, it is completely decomposed. It is useful from the viewpoint of protection of the natural environment because it disappears, or it can be reused, for example, by composting it into fertilizer, so it is also useful from the viewpoint of resource reuse.

[Brief description of the drawings]

FIG. 1 shows one example of the surface of a biodegradable short fiber of the present invention.
It is an optical microscope photograph taken at 0 magnification.

Claims (4)

[Claims] 1. A biodegradable short fiber comprising an aliphatic polyester as a main component, a polymer having a melting point of 100 ° C. or more, and having streaky irregularities on at least the fiber surface. 2. The main component of the aliphatic polyester is a polylactic acid-based polymer, wherein poly (D-lactic acid) and poly (L-lactic acid) are used.
Lactic acid), poly (D / L-lactic acid), a copolymer of D-lactic acid and hydroxycarboxylic acid, and a polymer selected from the group of a copolymer of L-lactic acid and hydroxycarboxylic acid, or a polymer thereof. The biodegradable short fiber according to claim 1, which is a blend of: 3. A fiber containing an aliphatic polyester as a main component and having a melting point of 100 ° C. or higher is melt-spun to wind up the fiber, or continuously, at a draw ratio of at least the maximum elongation of the fiber and glass. A method for producing a biodegradable short fiber, characterized in that the fiber is heat-drawn at a transition temperature or higher and a softening temperature or lower to develop streaky irregularities on the fiber surface, and then converted into a short fiber. 4. The aliphatic polyester is a polylactic acid-based polymer, wherein poly (D-lactic acid), poly (L-lactic acid),
A polymer selected from the group consisting of poly (D / L-lactic acid), a copolymer of D-lactic acid and hydroxycarboxylic acid, and a copolymer of L-lactic acid and hydroxycarboxylic acid, or a blend thereof. A method for producing a biodegradable short fiber according to claim 3.