JP2002105829A - Method for softning processing of biodegradable nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable nonwoven fabric having excellent flexibility and to provide a method for producing the same. SOLUTION: This method for flexible processing of a biodegradable nonwoven fabric is characterized in that a filament nonwoven fabric composed of a thermoplastic aliphatic polyester is subjected to a flexural processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a long-fiber nonwoven fabric having biodegradability in a natural environment.

[0002]

2. Description of the Related Art In recent years, fibers and non-woven fabrics made of a biodegradable thermoplastic polymer which is decomposed by microorganisms in a natural environment have attracted attention from the viewpoint of environmental problems. Accordingly, research and development on biodegradable fibers and biodegradable nonwoven fabrics by a melt spinning method using a thermoplastic biodegradable polymer have been actively conducted. For example, long-fiber nonwoven fabrics made of a polylactic acid-based polymer have been studied, and some of them have been put into practical use.

[0003] In addition, such biodegradable fibers and nonwoven fabrics are required to be used in a wide range of fields such as medical and sanitary materials, general living materials, agricultural materials and the like. In recent years, in particular, various characteristics of nonwoven fabrics have been required with the expansion of these uses. As one of them, a nonwoven fabric having excellent flexibility is desired.

However, the above-mentioned long-fiber nonwoven fabric made of a polylactic acid-based polymer, which is being put into practical use, is rigid and inferior in flexibility. There is a problem that there is a hard feeling.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biodegradable nonwoven fabric which is soft and has a good touch and can be suitably used in applications such as touching the human body.

[0006]

According to the present invention, there is provided a method for flexibly processing a biodegradable nonwoven fabric, comprising bending a long-fiber nonwoven fabric made of a thermoplastic aliphatic polyester. It is the gist.

[0007]

Next, the present invention will be described in detail. As the thermoplastic aliphatic polyester constituting the biodegradable nonwoven fabric used in the present invention, for example, a poly (α-hydroxy acid) such as polyglycolic acid or polylactic acid or a polymer element containing these as a main repeating unit is used. Polymers. A polyalkylene alkanoate composed of a condensation polymer of glycol and dicarboxylic acid; and a poly (ω-hydroxyalkanoate) such as poly (ε-caprolactone) and poly (β-propiolactone);
Further, poly-3-hydroxypropionate, poly-3
-Hydroxybutyrate, poly-3-hydroxycaprolate, poly-3-hydroxyheptanoate, poly-
Poly (β-hydroxyalkanoate) such as 3-hydroxyoctanoate and a repeating unit constituting the same, and poly-3-hydroxyvalerate and poly-4
-A copolymer with a repeating unit constituting hydroxybutyrate.

The polylactic acid polymer used in the present invention includes poly (D-lactic acid), poly (L-lactic acid), a copolymer of D-lactic acid and L-lactic acid, and a copolymer of D-lactic acid and hydroxycarboxylic acid. Or a copolymer of L-lactic acid and hydroxycarboxylic acid, or a blend thereof.

In the case where poly (D-lactic acid) and a homopolymer such as poly (L-lactic acid) are used as the polylactic acid-based polymer, in particular, it is possible to improve the spinning property in the spinning step and obtain the fibers and It is desirable to add a plasticizer for the purpose of improving the flexibility of the long-fiber nonwoven fabric. As the plasticizer in this case, triacetylene, lactic acid oligomer, dioctyl phthalate, or the like is used, and 1 to 30% by mass, preferably 5 to 20% by mass is added.

[0010] The melting point of the polylactic acid-based polymer is preferably at least 100 ° C, more preferably at least 120 ° C. For example, poly (L-lactic acid) and poly (D-lactic acid), which are homopolymers of polylactic acid, have a melting point of about 180 ° C., but have a low optical purity and low crystallization.
The melting point drop tends to increase. Optical purity is a factor affecting heat resistance and biodegradability. Therefore, when using the copolymer as a polylactic acid-based polymer, it is preferable to determine the copolymerization ratio of the monomer components so that the melting point of the copolymer is 120 ° C. or higher. In the present invention, the optical purity is 90%. % Or more of polylactic acid is preferably used.

The number average molecular weight of the polylactic acid polymer used in the present invention is about 20,000 or more, preferably about 40,000.
It is preferable to use one having a value of 0 or more from the viewpoint of the fiber characteristics to be obtained and the spinnability at the time of producing a long-fiber nonwoven fabric.

When the polylactic acid-based polymer is a copolymer of lactic acid and hydroxycarboxylic acid, the hydroxycarboxylic acid may be glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxyheptanoic acid, Examples thereof include caprylic acid, and among these, hydroxycaproic acid or glycolic acid is particularly preferable from the viewpoint of decomposition performance and cost.

Examples of polyalkylene alkanoates comprising a condensation polymer of glycol and dicarboxylic acid include, for example,
Polyethylene oxalate, polybutylene succinate, polyethylene adipate, polyethylene azelate, polybutylene oxalate, polybutylene succinate, polybutylene adipate, polybutylene sebacate, polyhexamethylene sebacate, polyneopentyl oxalate or a mixture thereof Polyalkylene alkanoate copolymer having a main unit as a united element,
Alternatively, those obtained by blending a plurality of these polymers may be used. Among them, a copolymerized polyester having a main repeating unit of polyethylene succinate, polybutylene succinate, polybutylene adipate, or polybutylene sebacate is suitably used because of its excellent thread-forming properties and biodegradability.

In particular, a copolymer containing butylene succinate as a main repeating unit, a copolymerization molar ratio of polybutylene succinate and polyethylene succinate is (polybutylene succinate) / (polyethylene succinate) = 9
A copolymer in the range of 0/10 to 70/30 mol% can be suitably used. In a copolymer of polybutylene succinate and polyethylene succinate, when the copolymerization ratio of butylene succinate is less than 70% by mole, the biodegradability is excellent, but the operability in obtaining a long-fiber nonwoven fabric Tend to be inferior. On the other hand, when the copolymerization ratio of butylene succinate is more than 90% by mole, the operability is excellent, but the biodegradability is inferior, which is not the object of the present invention.

Such a polyalkylene alkanoate preferably has a melting point of 70 ° C. or higher. If the melting point is lower than 70 ° C., the cooling property during the spinning is reduced, and the heat resistance of the obtained nonwoven fabric is impaired, and the usage is limited, which is not preferable.

In the present invention, a polylactic acid-based polymer is preferable among the above-mentioned aliphatic polyesters from the viewpoint of biodegradability and spinning properties. In addition, long fibers made of a polylactic acid-based polymer have relatively low elongation and are rigid, so that the bending effect of bending is high. Can be.

The polymer used in the present invention may optionally contain
Antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, pigments, colorants, lubricants, antistatic agents, crystal nucleating agents and other known additives and fillers impair the performance of the biodegradable nonwoven fabric of the present invention. It can be blended and mixed to an extent not to a degree.

The cross-sectional shape of the fiber may be any shape as long as it can be melt-spun, and may be appropriately selected depending on the intended use. For example, circular, elliptical, polygonal, multi-lobal, hollow, well-shaped and the like can be mentioned. Further, the fiber form may be a single-phase form made of a single polymer or a composite form made of a plurality of polymers such as a core-sheath type, a side-by-side type, a split type and the like.

The fineness of the single fiber of the fiber may be appropriately selected according to the intended use, and is generally about 1.0 to 12 dtex.

In the long-fiber nonwoven fabric of the present invention, the constituent fibers are preferably integrated by thermal bonding. As the thermal bonding, the constituent fibers are bonded at their intersections by melting or softening of the polymer constituting the fibers. One in which the constituent fibers are bonded and integrated with each other by melting or softening the polymer forming the fibers in the pressure-bonded portion is exemplified. The method of thermal bonding may be appropriately selected depending on the application, but is preferably a long-fiber nonwoven fabric having a partial thermocompression bonding portion in terms of flexibility.

The shape of each thermocompression bonding portion of the thermocompression bonding portion does not necessarily have to be circular, but may be elliptical, cross, rhombic, triangular,
Any of T type, well shape and the like may be used, and each thermocompression bonding portion has an area of 0.1 to 1.2 mm ² , and its density, that is, the compression point density is ² to 80 pieces / cm ² . Preferably, it is 4 to 60 particles / cm ² . Further, the ratio of the area of the entire thermocompression bonding area to the total surface area of the long-fiber nonwoven fabric, that is, the thermocompression bonding area ratio is preferably 4 to 50%, more preferably 10 to 20%. When the compression area ratio is less than 4%, the mechanical properties and dimensional stability of the long-fiber nonwoven fabric are inferior. On the other hand, if the compression area ratio exceeds 50%, most of the fibers constituting the long-fiber nonwoven fabric are thermally fused, and the obtained long-fiber nonwoven fabric tends to be inferior in flexibility and touch.

The basis weight of the long-fiber nonwoven fabric may be appropriately selected according to the intended use, and is not particularly limited.
/ M ² .

The long-fiber nonwoven fabric comprising the above polymer used in the present invention can be obtained by a usual spunbonding method. The long fiber web obtained by the spun bond method is preferably subjected to a heat treatment to integrate the constituent fibers.

The long-fiber nonwoven fabric made of the above-mentioned thermoplastic aliphatic polyester is bent. In the present invention,
As a bending process, a long-fiber nonwoven fabric is pushed into a narrow gap through a buckling machine, that is, a pair of rolls, and the long-fiber nonwoven fabric is bent by buckling.The long-fiber nonwoven fabric is bent by passing the long-fiber nonwoven fabric through a pair of gear rolls. How to make
A method in which the long fiber nonwoven fabric is passed through a plurality of guides to bend and bend, and a method in which the long fiber nonwoven fabric is immersed in a liquid and bent by a liquid flow are exemplified. In the present invention, it is preferable to perform a buckling process performed by a buckling machine in consideration of a high effect of improving flexibility, productivity, and the like.

Regarding the method of processing in the buckling machine,
This will be described more specifically with reference to FIG. Long-fiber nonwoven fabric 5 to be treated
Is passed between a pair of supply rolls 1 and 2, and a letter
4 to bend the long-fiber nonwoven fabric. At this time,
The bending degree of the long-fiber nonwoven fabric is determined by appropriately selecting the processing speed between the rolls (supply speed and discharge speed), the gap between the rolls, the roll temperature, the relative angle of the letterer, and the surface roughness of the letterer. Roll gap is 1.5m
m is preferable. The roll temperature is preferably from room temperature to a temperature lower by at least 20 ° C. than the melting point of the polymer having the lowest melting point among the polymers constituting the fibers. Regarding the relative angle of the letterer, if the angle is too large, the effect of buckling is reduced, so the relative angle is preferably about 15 to 30 degrees. Regarding the surface roughness of the letterer, if the roughness is too large,
Since the frictional resistance between the long-fiber nonwoven fabric and the letterer decreases, the long-fiber nonwoven fabric tends to be discharged, and the buckling effect tends to be reduced.

The biodegradable nonwoven fabric obtained by the bending process has a softness of 500 g in terms of a basis weight of 100 g / m ^2.
It is preferably not more than cN, more preferably 40
0 cN or less. When the bending resistance is 500 cN or less, it can be suitably used for applications that have good touch and directly touch the human body.

[0027]

EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the examples, various physical property values were measured by the following methods. (1) Melt flow rate (g / 10 minutes); ASTM-D-123
The temperature was measured at 190 ° C. according to the method described in 8 (E).

(2) Melting point (° C.): A differential scanning calorimeter DSC-7 manufactured by PerkinElmer Co., Ltd. was used, and the sample mass was 5 m.
g, the temperature giving the maximum value of the melting endothermic curve obtained by measuring the temperature rising rate at 20 ° C./min was defined as the melting point (° C.).

(3) Crystallization temperature (° C.): solidification exotherm obtained by using a differential scanning calorimeter DSC-7 manufactured by Perkin Elmer Co., Ltd. and measuring the sample weight at 5 mg and the heating rate at 20 ° C./min. The temperature giving the maximum value of the curve was defined as the crystallization temperature (° C.).

(4) Flexural softness (cN); sample length is 10
Five specimens each having a width of 5 cm and a specimen width of 5 cm were prepared, and each specimen was bent in the lateral direction to form a cylindrical body. Then, for each measurement sample, in the axial direction, a constant-speed elongation type tensile tester (Tensilon UTM-4-1-100 manufactured by Orientec)
, And the average value of the obtained maximum load (cN) was taken as the compression stiffness (cN). In addition, this compression bending softness means that the smaller the value, the better the flexibility.

(5) Weight (g / m ² ): Ten pieces of a sample having a sample length of 20 cm and a sample width of 5 cm were prepared from a sample in a standard state, and 10 pieces were prepared. Is weighed, the obtained value is converted per unit area, and the basis weight (g
/ M ² ).

(6) Nonwoven fabric strength (N / 5 cm width); JI
The measurement was carried out according to the method described in SL-1096A. That is, a sample piece having a sample length of 20 cm and a sample width of 5 cm
A zero point was created, and a constant-speed elongation type tensile tester (Tensilon U manufactured by Orientec Co., Ltd.) was used for each sample piece in the longitudinal direction of the nonwoven fabric.
TM-4-1-100) and a pulling speed of 20 cm /
The grip was stretched at a grip interval of 10 cm, and the average value of the resulting load values at cutting was defined as the strength (N / 5 cm width). In addition, it measured about MD direction (machine direction) and CD direction (direction orthogonal to a machine direction) of the nonwoven fabric.

Example 1 As a thermoplastic aliphatic polyester, a melt flow rate of 40 g /
A nonwoven fabric was produced using a polylactic acid-based polymer [L-lactic acid / D-lactic acid = 99/1 (copolymer molar ratio)] having a melting point of 170 ° C. and a crystallization temperature of 70 ° C. in 10 minutes.

That is, the polylactic acid-based polymer is melted at a temperature of 200 ° C. by using an extruder-type melt extruder, and a spinneret having a circular fiber cross section is used. It was melt spun. After cooling the spun yarn using a known cooling device, the drawing speed is 4200 m / h using an air sucker installed below the die.
The yarn was spread by a known opening device, and the opened yarn was deposited on a moving screen conveyor.
This long fiber nonwoven web was partially hot-pressed with an embossing device composed of an embossing roll and a flat roll, and the basis weight consisting of a long fiber of 3.2 dtex was 50 g / m2.
^Two long-fiber nonwoven fabrics were obtained. The conditions of the hot pressing were as follows: an embossing roll having a surface area of 0.7 mm ² , a density of the hot pressing portion of 20 pieces / cm ² , and a thermocompression bonding area ratio of 15%, and a flat roll having a smooth surface. And the roll temperature was set to 125 ° C.

Next, the obtained long-fiber nonwoven fabric was bent using the buckling machine shown in FIG. 1 to obtain the biodegradable nonwoven fabric of the present invention. That is, as a buckling machine,
Using a micro-craper made by Mike Flex,
The long-fiber nonwoven fabric was passed between a pair of supply rolls (roll surface temperature was 50 ° C.) moving at 10 m / min, and the roll gap was 1.5 mm and the relative angle of the letterer was 20 degrees.

Example 2 A biodegradable nonwoven fabric was obtained in the same manner as in Example 1, except that the liquid flow treatment was performed as buckling.
That is, using a circular type liquid jet dyeing machine manufactured by Hisaka Seisakusho Co., Ltd. as a buckling machine, the liquid was subjected to a liquid jet treatment at 100 ° C. × 60 minutes, and then dried by a known drying device.

Comparative Example 1 A biodegradable nonwoven fabric was obtained in the same manner as in Example 1 except that buckling was not performed.

The physical properties of the obtained nonwoven fabrics of Examples 1 and 2 and Comparative Example 1 are shown in Table 1.

[0039]

[Table 1]

As is apparent from Table 1, the buckled biodegradable nonwoven fabric of the present invention is 200% less in Example 1 than the non-buckled nonwoven fabric.
In Example 2, the flexibility was increased by 180%.

[0041]

According to the present invention, a long-fiber nonwoven fabric made of a thermoplastic aliphatic polyester is subjected to a bending process,
By bending and kneading a rigid long-fiber nonwoven fabric,
A long-fiber nonwoven fabric provided with flexibility can be obtained.

[0042] The biodegradable long-fiber nonwoven fabric obtained by the processing method of the present invention has an improved texture and feel, and is used in the field of touching the human body, ie,
Diaper and sanitary products and other medical and sanitary materials, wiping cloths such as disposable towels and wiping cloths, bags such as disposable warmers, etc., can be suitably used, and living-related materials that require flexibility, or It can be suitably used as each material in the field of agricultural and horticultural materials. In addition, the long-fiber nonwoven fabric of the present invention is made of aliphatic polyester and has biodegradability, so that it completely decomposes and disappears after its use. It is an ecological nonwoven fabric that is useful from the viewpoint of resource recycling because it can be composted and reused as fertilizer.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing an example of a buckling process in the present invention.

[Explanation of symbols]

 1, 2 supply roll 3 letterer (upper part) 4 letterer (lower part) 5 long-fiber nonwoven fabric 6 flexible nonwoven fabric

Claims (5)

[Claims] 1. A flexible processing method for a biodegradable nonwoven fabric, comprising bending a long-fiber nonwoven fabric made of a thermoplastic aliphatic polyester. 2. The flexible processing method for a biodegradable nonwoven fabric according to claim 1, wherein the bending is buckling performed by a buckling machine. 3. The method for flexible processing of a biodegradable nonwoven fabric according to claim 1, wherein the thermoplastic aliphatic polyester is a polylactic acid-based polymer. 4. The method for flexible processing of a biodegradable nonwoven fabric according to claim 1, wherein the constituent fibers of the long-fiber nonwoven fabric are thermally bonded to each other. 5. A biodegradable nonwoven fabric obtained by the flexible processing method according to any one of claims 1 to 4, wherein the nonwoven fabric has a rigidity of 500 cN or less in terms of a basis weight of 100 g / m ^2. Biodegradable nonwoven fabric.