JP2002129459A - Biodegradable nonwoven fabric and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable nonwoven fabric with excellent softness, and further to provide a method for producing the nonwoven fabric. SOLUTION: This biodegradable nonwoven fabric is constituted of a thermoplastic aliphatic polyester. The constituent fibers are mutually integrated by thermobonding, and the nonwoven fabric has a wave shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a 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 polylactic acid-based polymers have been studied, and some of them are being put to 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 or industrial materials, agricultural materials and civil engineering materials. 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 excellent in bulkiness and flexibility is desired.

[0004]

DISCLOSURE OF THE INVENTION The present invention has both of flexibility and bulkiness as one of required performances of a nonwoven fabric,
An object of the present invention is to provide a biodegradable nonwoven fabric that can be used in various fields such as medical and hygiene materials, wipes and packaging materials, general living materials, agricultural materials, and the like.

[0005]

Means for Solving the Problems The present inventors have achieved the above-mentioned object, and have the following constitutions (1) and (2).

(1) A non-woven fabric composed of a thermoplastic aliphatic polyester, wherein the constituent fibers are integrated by thermal bonding, and the non-woven fabric has a corrugated shape. Nonwoven fabric.

(2) The thermoplastic aliphatic polyester is melted, melt-spun through a spinneret, the spun yarn spun from the spinneret is cooled, and taken up using an air sucker.
It is spread and deposited on a movable collecting surface such as a screen conveyor to form a long fiber web, and the long fiber web is heat-treated using a heat treatment apparatus to obtain a long-fiber nonwoven fabric in which constituent fibers are thermally bonded to each other. A method for producing a biodegradable nonwoven fabric, wherein the nonwoven fabric is subjected to a buckling process by a buckling machine to impart a wavy shape.

[0008]

Next, the present invention will be described in detail. The biodegradable nonwoven fabric of the present invention is composed of fibers made of a thermoplastic aliphatic polyester. Examples of the thermoplastic aliphatic polyester used in the present invention include poly (α-hydroxy acid) such as polyglycolic acid and polylactic acid, or a copolymer containing these polymer elements as a main repeating unit; Condensed polymers of dicarboxylic acids and the like can be mentioned.

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 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 30% by mass.
It is better to add 20% by mass.

[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, it is preferable to use polylactic acid having an optical purity of 90% or more.

In the case where 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.

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 properties to be obtained and the spinnability at the time of producing a nonwoven fabric.

Examples of the polyalkylene alkanoate which is a condensation polymer of glycol and dicarboxylic acid include polyalkylene alkanoates such as polyethylene oxalate, polybutylene succinate, polyethylene adipate, polyethylene azelate, polybutylene oxalate, and the like. Polybutylene succinate, polybutylene adipate, polybutylene sebagate, polyhexamethylene sebagate, polyneopentyl oxalate or a polyalkylene alkanoate copolymer containing a polymer element thereof as a main repeating unit, or a polymer thereof. One obtained by blending a plurality of coalesces is exemplified. 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 having 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 the copolymer of polybutylene succinate and polyethylene succinate, when the copolymerization ratio of butylene succinate is less than 70 mol%, the biodegradability is excellent, but the operability when obtaining a long-fiber nonwoven fabric is improved. It tends to be inferior. On the other hand, when the copolymerization ratio of butylene succinate is more than 90 mol%, the operability is excellent, but the biodegradability is inferior, which is not the object of the present invention.

[0015] Such a polyalkylene alkanoate preferably has a melting point of 100 ° C or higher. When these melting points are less than 100 ° C., the cooling property during spinning is reduced, and the heat resistance of the obtained nonwoven fabric is impaired,
The intended use is limited, which is not preferable.

Also, poly (ω-hydroxyalkanoate) such as poly (ε-caprolactone) and poly (β-propiolactone), furthermore, poly-3-hydroxypropionate, poly-3-hydroxybutyrate, Poly
Poly (β-hydroxyalkanoate) such as 3-hydroxycaprolate, poly-3-hydroxyheptanoate, poly-3-hydroxyoctanoate, and a repeating unit constituting the same; And a copolymer with a repeating unit constituting poly-4-hydroxybutyrate.

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.

In the present invention, the above-described single aliphatic polyester may be used, a plurality of types may be used in combination, or a plurality of types may be blended.

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 shape of the fiber used in the present invention may be either a short fiber or a long fiber. However, a long fiber is preferable because a corrugated shape can be remarkably imparted.

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 to 12 dtex.

In the nonwoven fabric of the present invention, the constituent fibers are 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,
It is preferable that the nonwoven fabric has a partial thermocompression bonding part from the viewpoint 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 nonwoven fabric, that is, the thermocompression bonding area ratio is preferably 4 to 50%, and more preferably 10 to 20%. If the compression area ratio is less than 4%, the mechanical properties and dimensional stability of the nonwoven fabric will be poor. On the other hand, if the compression area ratio exceeds 50%, most of the fibers constituting the nonwoven fabric are thermally fused, and the resulting nonwoven fabric tends to be inferior in flexibility and feel.

The nonwoven fabric of the present invention has a corrugated shape.
The wavy shape may be either the longitudinal direction or the width direction of the nonwoven fabric. However, in order to obtain the nonwoven fabric of the present invention by the method described later, peaks and valleys appear alternately in the longitudinal direction (machine direction). It is preferable that the shape be a corrugated shape.

In the wave shape of the nonwoven fabric, the amplitude (the height of the wave, that is, the difference between the valley and the peak) is 1 to 5 m.
m is preferable. If the amplitude is less than 1 mm,
Since the corrugations are too fine, the fibers forming the peaks and valleys of the corrugations tend to be cut, and fiber breakage occurs at those portions, resulting in a non-woven fabric of inferior quality. When the amplitude exceeds 5 mm, the flexibility cannot be sufficiently imparted to the nonwoven fabric, so that the use is limited.

The wave number of the wave shape of the nonwoven fabric is 5 to 30.
It is preferable that the number is 25 / mm. If it is less than 5/25 mm, the flexibility of the nonwoven fabric tends to be inferior,
If the number exceeds 30 pieces / 2.5 cm, as in the case where the above amplitude is less than 1 mm, the wave shape is too fine, and the fibers constituting the peaks and valleys of the wave shape are easily cut,
The fiber breakage of that portion occurs, and the nonwoven fabric becomes inferior in quality.

The amplitude and wave number of the corrugated shape of the nonwoven fabric are controlled by the gap between the rolls, the processing speed between the rolls, the roll temperature, the relative angle of the letterer, and the surface roughness of the letterer in the buckling process described later. can do.

The basis weight of the nonwoven fabric may be appropriately selected according to the intended use, and is not particularly limited, but is 15 to 200 g / m ^2.
Degree.

Next, a preferred method for producing the biodegradable nonwoven fabric of the present invention will be described. The biodegradable nonwoven fabric of the present invention can be manufactured using a usual melt spinning device. First, the above-mentioned thermoplastic aliphatic polyester is weighed and then melt-spun through a spinneret, and the spun yarn is cooled by a known cooling device using a cooling air flow or the like.
Next, using a well-known take-off means such as air soccer, the material is drawn to a desired fineness and taken off. The drawn filaments are spread by a known spreader, and then spread and deposited on a movable collecting surface such as a screen conveyor to form a nonwoven web.

In the melt spinning, the spinning temperature is appropriately set in consideration of the melt flow rate of the aliphatic polyester to be used and the fiber forming property, that is, the spinning property. Usually, when the melting point of the polymer having the highest melting point among the polymers used is Tm ° C., it is preferable that the polymer melts in a temperature range of (Tm + 15) to (Tm + 50) ° C. When the melting temperature is lower than (Tm + 15) ° C., the spinnability and take-up property due to the high-speed airflow are poor. Conversely, when the melting temperature exceeds (Tm + 50) ° C., crystallization in the cooling process is delayed, and In addition, not only poor adhesion and inferior spreadability occurs, but also thermal decomposition of the polymer itself progresses, and it is difficult to obtain a nonwoven fabric which is soft and has good formation.

The traction speed is preferably at least 3000 m / min, more preferably at least 3500 m / min. By setting the towing speed to 3000m / min or more,
The dimensional stability of the nonwoven fabric is improved, and a nonwoven fabric with high heat stability can be obtained. If the drawing speed is less than 3000 m / min, not only is the spun yarn inferior in cooling performance, spinnability and spreadability, but also inferior in mechanical performance and dimensional stability of the obtained nonwoven fabric, which is not preferable.

Next, the obtained nonwoven web is subjected to a heat treatment using a heat treatment apparatus. As a heat treatment method, a method in which a polymer existing at the intersection of the fibers constituting the nonwoven web is melted or softened by a dry hot air circulation method, a suction band method, or the like, and a method of bonding the fiber intersection, heating is performed. A method in which a non-woven web is passed through an embossing device composed of a pair of embossing rolls or an embossing device composed of an embossing roll and a flat roll having a smooth surface to form a thermocompression bonding part on a nonwoven web. Can be

In the method using the embossing device, since the thermocompression bonding portion is formed on the nonwoven web at the portion in contact with the convex portion of the embossing roll,
An embossing roll having a size, density, and compression area ratio is used. The surface temperature of the roll, when the melting point of the polymer having the lowest melting point among the polymers constituting the fibers is TmL ° C, is set to a temperature lower than TmL ° C, and at least the polymer having the lowest melting point is melted or melted. It is softened to form a partial thermocompression bonding portion.

Next, the heat-treated nonwoven fabric is subjected to a buckling process to impart a corrugated shape. Further, it is preferable that after the buckling process is performed, a heat treatment is continuously performed to thermally fix the imparted wave shape. As the buckling process, a buckling compression method in which a nonwoven fabric is pushed into a narrow gap to bend the nonwoven fabric to give a corrugated shape is applied.

A method for performing the processing by buckling compression will be described in detail with reference to FIG. The non-woven fabric 5 subjected to the heat treatment is passed between a pair of supply rolls 1 and 2 and pressed into the letterers 3 and 4 to impart a corrugated shape. At this time,
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, the amplitude and wave number of the wave shape given to the nonwoven fabric can be adjusted. Can be determined.

That is, the larger the gap between the rolls, the larger the amplitude of the wave shape. On the other hand, the smaller the gap between the rolls, the smaller the amplitude of the wave shape. The gap between the rolls is appropriately selected according to the basis weight and thickness of the nonwoven fabric. In addition, since the fibers constituting the nonwoven fabric to be treated are softened by increasing the roll temperature, a wave shape is easily provided, and the wave number tends to increase. 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. With respect to the relative angle of the letter, the larger the angle, the larger the amplitude and the wave number tends to decrease, while the smaller the angle, the smaller the amplitude and the wave number tends to increase. The relative angle of the letterer is preferably about 15 to 30 degrees. Regarding the surface roughness of the letterer, as the roughness increases, the frictional resistance between the nonwoven fabric and the letterer decreases, so that the nonwoven fabric tends to be discharged, and the amplitude and wave number tend to decrease. On the other hand, when the roughness is small, the frictional resistance between the nonwoven fabric and the letterer increases, so that the nonwoven fabric is difficult to be discharged, and the amplitude and the wave number tend to increase.

After the buckling treatment, the corrugated nonwoven fabric may be subsequently subjected to a heat treatment in the heat treatment device 6. By this heat treatment, the corrugated shape given by the buckling process has excellent recoverability when repeatedly stretched. This heat treatment is performed without applying pressure and tension, that is, in a relaxed state. As the heat treatment temperature at this time,
The temperature is lower than the melting point of the polymer having the lowest melting point in the polymer constituting the fiber. At this time, if the treatment is performed at a temperature equal to or higher than the melting point of the low-melting polymer, the low-melting polymer is melted and the fibers are fused to each other, thereby significantly impairing workability.

[0039]

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
-The temperature was adjusted to 2 according to the method described in D-1238 (E).
The measurement was performed at 10 ° C.

(2) Melting point (° C.): Using a differential scanning calorimeter DSC-7 manufactured by PerkinElmer, and weighing a sample of 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 measuring with a sample mass of 5 mg and a heating rate of 20 ° C./min using a differential scanning calorimeter DSC-7 manufactured by Perkin Elmer. The temperature giving the maximum value of the curve was defined as the crystallization temperature (° C.).

(4) Amplitude of wave shape (mm), wave number (pieces /
25 mm); arbitrarily select 20 non-woven fabrics with a magnifying projector, measure the amplitude and wave number of the wave shape given to the non-woven fabric, and average the average values of the wave shape (mm) and the wave number (pieces / 25 mm).

(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 the water content was equilibrated. Is weighed, the obtained value is converted per unit area, and the basis weight (g
/ M ² ).

(6) Tensile strength of nonwoven fabric (N / 5 cm
Width): Measured according to the method described in JIS-L-1096A. That is, 10 points of a sample having a sample length of 20 cm and a sample width of 5 cm were prepared, and a constant-speed elongation type tensile tester (Tensilon UTM-4-1-100 manufactured by Orientec) was prepared for each sample in the longitudinal direction of the nonwoven fabric. ) And the pulling speed 2
The film was stretched at 0 cm / min at a grip interval of 10 cm, and the average value of the obtained load values at cutting was defined as tensile strength (N / 5 cm width). The tensile strength was measured in both the MD direction (machine direction) and the CD direction (direction perpendicular to the machine direction) of the nonwoven fabric.

(7) 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.

Example 1 As an aliphatic polyester, a polylactic acid polymer having a melting point of 170 ° C. and a crystallization temperature of 70 ° C. at a melt flow rate of 30 g / 10 min.
A nonwoven fabric was manufactured using [L-lactic acid / D-lactic acid = 99/1 (copolymer molar ratio)].

That is, the polylactic acid-based polymer was melted at a temperature of 200 ° C. using an extruder-type melt extruder, and a spinneret having a circular fiber cross section was used. The single hole discharge rate was 1.64 g / min. It was melt spun. After cooling the spun yarn using a known cooling device, the drawing speed is 4300 m / h using an air sucker installed below the die.
The fiber was spread by a known fiber opening device, and the yarn was spread and deposited on a moving screen conveyor. The nonwoven web was hot-pressed with an embossing device composed of an embossing roll and a flat roll to obtain a nonwoven fabric having a basis weight of 50 g / m ^{2 and} a filament length of 3.85 dtex. The heat treatment conditions were as follows: the shape of the embossed portion serving as the thermocompression bonding portion was circular, the area was 0.7 mm ² , and the density of the thermocompression bonding portion was 20 pieces /
cm ^2, the embossing roll and the surface thermocompression bonding area ratio is 15% with a smooth flat roll, the roll temperature 12
Set to 5 ° C.

The obtained nonwoven fabric was subjected to buckling using a buckling machine as shown in FIG. 1 to obtain a biodegradable nonwoven fabric of the present invention. That is, as a buckling machine, a buckling machine (microcreper) manufactured by Micrex Corp. was used and passed between a pair of rolls (roll surface temperature was set to 50 ° C.) moving at 10 m / min. Roll gap 0.8m
m, linear pressure of roll 6 kg / cm, relative angle of letterer 20 degrees, upper letter pressure 3 kg / cm ² , lower letter pressure 5 kg / cm ² , distance between contact point center between rolls and upper letter 5 mm, The buckling treatment was performed with the distance between the center point of the contact pressure between the rolls and the lower letterer being 10 mm, to obtain the nonwoven fabric having the wavy shape of the present invention.

Example 2 A nonwoven fabric having a corrugated shape according to the present invention was obtained in the same manner as in Example 1 except that the relative angle of the letterer was changed to 25 degrees.

Example 3 A nonwoven fabric having a corrugated shape according to the present invention was obtained in the same manner as in Example 1 except that the relative angle of the letterer was changed to 30 degrees.

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

Table 1 shows the physical properties of the obtained nonwoven fabrics of Examples 1 to 3 and Comparative Example 1.

[0054]

[Table 1]

As is clear from Table 1, the buckled biodegradable nonwoven fabric of the present invention has excellent flexibility as compared with the nonbuckled nonwoven fabric. Was bulky.

[0056]

According to the present invention, there is provided a biodegradable nonwoven fabric comprising a biodegradable aliphatic polyester, which is excellent in flexibility and bulkiness because the nonwoven fabric has a corrugated shape. It is obtained.

The biodegradable nonwoven fabric of the present invention includes diapers, sanitary products and other medical and sanitary materials, wiping cloths such as disposable towels and wiping cloths, bags such as disposable warmers, disposable packaging materials, household and commercial products. It can be suitably used as a living related material such as a garbage collection bag or other waste disposal material, or as an industrial material represented by agriculture, horticulture or civil engineering. Besides, this non-woven fabric
Because it is biodegradable, it completely decomposes and disappears after its use, which is not only beneficial from the standpoint of protecting nature, but also makes it possible to recycle it as fertilizer by composting it. It is an ecological nonwoven fabric that is also useful from the viewpoint of.

[0058]

[Brief description of the drawings]

[0059]

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

[0060]

[Explanation of symbols]

 1, 2 Supply roll 3 Letterer (upper) 4 Letterer (lower) 5 Non-woven fabric subjected to heat treatment 6 Heat treatment device 7 Non-woven fabric of the present invention

Continued on the front page F term (reference) 3B074 AA02 AA08 AB01 AC00 3E023 BA03 BA20 4L047 AA21 AB03 BA08 BB06 CA12 CA19 CB02 CB10 CC03 CC04 CC05 CC15 DA00 EA10

Claims (4)

[Claims] A biodegradable non-woven fabric comprising a thermoplastic aliphatic polyester, wherein constituent fibers are integrated by thermal bonding, and the non-woven fabric has a corrugated shape. Non-woven fabric. 2. The biodegradable nonwoven fabric according to claim 1, wherein an amplitude (wave height) of a wave shape of the nonwoven fabric is 1 to 5 mm, and a wave number is 5 to 30/25 mm. 3. The biodegradable nonwoven fabric according to claim 1, wherein the thermoplastic aliphatic polyester is a polylactic acid-based polymer. 4. Melting the thermoplastic aliphatic polyester,
The spun yarn spun through the spinneret is cooled, the spun yarn spun from the spinneret is cooled, taken up using an air sacker, and spread and deposited on a movable collecting surface such as a screen conveyor to form a long fiber web. The long fiber web is heat-treated using a heat treatment apparatus to obtain a long-fiber nonwoven fabric in which constituent fibers are thermally bonded to each other, and the long-fiber nonwoven fabric is subjected to buckling with a buckling machine to impart a corrugated shape. A method for producing a biodegradable nonwoven fabric, comprising: