JP2003064569A - Polylactic acid-based filament nonwoven fabric and polylactic acid-based filament - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid-based filament nonwoven fabric which can well be subjected to a partial thermocompression treatment, even when a polylactic acid-based polymer is used, and is hardly peeled in the thickness direction, and to provide polylactic acid-based filaments. SOLUTION: This nonwoven fabric comprises filaments which comprise a polylactic acid-based polymer, have single phase cross sections, respectively, and are partially thermocompression-bonded to each other. The filaments forming the nonwoven fabric have a temperature-falling crystallization temperature Tcc, when melted at a temperature-up speed of 10 deg.C/min and then measured with a differential thermal analyzer at a temperature-falling speed of 10 deg.C/min, have the temperature-falling crystallization temperature Tcc of 90 to 110 deg.C, and have a crystallization calorie ΔHexo of >=10 mJ/mg.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polylactic acid-based long fiber non-woven fabric and a polylactic acid-based long fiber, and more particularly to a polylactic acid-based long fiber non-woven fabric and a polylactic acid having excellent thermocompression bonding properties due to thermocompression bonding of constituent fibers. The present invention relates to long fibers.

[0002]

2. Description of the Related Art Conventionally, as a long-fiber non-woven fabric, one produced by a spunbond method and thermocompression-bonded is generally well known. That is, the thermoplastic polymer is heated and melted and discharged from the spinneret, and the obtained spun yarn is cooled by using a conventionally known cooling device such as horizontal spraying or annular spraying, and then suction such as air sucker. Using a device, the web is deposited on the screen while being pulled / thinned so as to obtain a desired single yarn fineness and being opened by a conventionally known opening device. Then, the web is passed through an embossing device and subjected to a partial thermocompression bonding treatment, whereby a long-fiber nonwoven fabric is obtained.

In recent years, biodegradable long fiber non-woven fabrics have been developed. Among them, long fiber non-woven fabrics made of polylactic acid type polymers are not only biodegradable but also have a relatively high melting point. It is expected to be highly practical and suitable for various purposes.

However, in order to obtain a non-woven fabric made of a polylactic acid-based polymer, a spunbonding process such as spinning, opening and web making, and a thermocompression bonding process are continuous processes, not an experimental device. In, a non-woven fabric made of a polylactic acid-based polymer obtained by subjecting a web manufactured by the spunbond method to partial thermocompression bonding seems to be partially thermocompression-appearing during use. In some cases, the partially thermocompression bonded portion was destroyed, the constituent fibers were unbonded, and the non-woven fabric was peeled in the thickness direction. In particular, when a long-fiber nonwoven fabric having a low basis weight is obtained, or when the web conveying speed is increased to increase the production efficiency, this phenomenon becomes more remarkable.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and uses a polylactic acid-based polymer as a constituent fiber,
It is an object of the present invention to provide a polylactic acid-based long fiber non-woven fabric and a polylactic acid-based long fiber, which can perform partial thermocompression bonding well and are less likely to peel in the thickness direction.

[0006]

Means for Solving the Problems The present inventors have conducted various studies to achieve this object. Polylactic acid, which is the same polyester as polyethylene terephthalate (hereinafter referred to as “PET”), which has high versatility, has a glass transition temperature (Tg) close to each other. Therefore, the fiber made of polylactic acid is also similar to PET fiber. It has mechanical properties as well as yarn quality properties. However, polylactic acid has a characteristic that it has a slower crystallization rate than PET and is less likely to be crystallized.

Usually, when a web made of thermoplastic fibers is partially subjected to thermocompression bonding, the fibers in the portion where the convex portion of the hot embossing roll abuts are once melted and then cooled and solidified, and the thermocompression bonding is performed. The part is a part where the thermoplastic polymer is melted and the fibers are firmly bonded to each other.

However, since polylactic acid has a slow crystallization rate, it takes time until it is sufficiently cooled and solidified once it is melted. In this production machine in which the spunbond process and the thermocompression bonding process are continuous processes, a process of forming a web by spinning and opening the fiber in the spunbond process, and a process of thermocompression bonding the web in the thermocompression bonding process. The web or nonwoven fabric is transported between the steps of winding the obtained nonwoven fabric, but tension is applied to the web or nonwoven fabric during the transport. Since polylactic acid has a characteristic that the crystallization rate is slow as described above, in this production machine consisting of such a continuous process, a web made of polylactic acid is passed through an embossing device in a thermocompression bonding process, While the molten thermo-compression bonding part is in the process of cooling and hardening, tension for transporting and winding is gradually applied to the web that has been subjected to thermo-compression bonding, and the tension causes the crimping part before cooling and hardening to come off, making it strong. It is considered that the thermocompression bonding portion cannot be formed.

Therefore, the inventors of the present invention can form a strong partial thermocompression bonding portion by cooling and solidifying the melted thermocompression bonding portion even if tension is gradually applied to the web after the thermocompression bonding treatment. In other words, by conducting research on polylactic acid-based fibers that tend to cool and solidify after being melted, and by imparting certain characteristics to the polylactic acid-based fibers, it is possible to produce with this production machine consisting of continuous processes, and production efficiency is not reduced. It was found that partial thermocompression bonding can be satisfactorily applied to the non-woven fabric, and a partial thermocompression bonding part that does not separate in the thickness direction of the nonwoven fabric can be formed.
The present invention has been reached.

That is, the present invention is a non-woven fabric composed of long fibers having a single-phase cross section made of a polylactic acid-based polymer, wherein the long fibers are partially thermocompressed with each other, and the fibers constituting the non-woven fabric are After melting at a temperature rising rate of 10 ° C./min and then performing a differential thermal analysis at a temperature lowering rate of 10 ° C./min, there is a lowering temperature crystallization temperature Tcc, and this lowering crystallization temperature Tcc is 90 ° C.
Above 110 ° C and the heat of crystallization ΔHexo is 10 m
The gist of the present invention is a polylactic acid-based long-fiber non-woven fabric characterized by being J / mg or more.

The present invention also relates to a single-phase cross-section filament made of a polylactic acid-based polymer, which is melted at a heating rate of 10 ° C./min and then subjected to a differential thermal analysis at a cooling rate of 10 ° C./min. Has a cooling crystallization temperature Tcc, and this cooling crystallization temperature Tcc is 90 ° C. or more and 110 ° C. or less, and the heat of crystallization ΔH
The gist is a polylactic acid-based long fiber characterized by having exo of 10 mJ / mg or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The polylactic acid-based long fiber non-woven fabric of the present invention is a non-woven fabric composed of long fibers having a single-phase cross section made of a polylactic acid-based polymer, and the long fibers are partially thermocompression-bonded to each other.

The polylactic acid-based polymer includes poly (D-lactic acid), poly (L-lactic acid), a copolymer of D-lactic acid and L-lactic acid, and D-lactic acid and hydroxycarboxylic acid. Examples thereof include any polymer or blend selected from a copolymer, a copolymer of L-lactic acid and hydroxycarboxylic acid, and a copolymer of D-lactic acid, L-lactic acid and hydroxycarboxylic acid. . Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid, and hydroxyoctanoic acid. Among them, hydroxycaproic acid or glycolic acid is a microorganism. It is preferable from the viewpoint of having decomposition performance and cost reduction.

The fibers constituting the non-woven fabric must have the following characteristics when the differential thermal analysis is performed. Figure 1
(A) and (b) are D at the time of temperature rising and at the time of temperature lowering when fibers made of the polylactic acid-based polymer of the present invention are subjected to differential thermal analysis.
The SC curve is shown. As shown in the DSC curve a1 of FIG. 1 (a), after the fibers were melted at a heating rate of 10 ° C./min,
As shown in the DSC curve b1 in (b), the cooling rate is 10 ° C /
Perform differential thermal analysis in minutes.

In the present invention, the DSC curve b when the temperature is lowered
It is necessary that the temperature-falling crystallization temperature Tcc exists at 1. The cooling crystallization temperature Tcc is a temperature at which the melted fiber is cooled and crystallized, and is represented by a temperature at an exothermic peak existing in the DSC curve b1. The long fibers having the temperature-reduced crystallization temperature Tcc in the DSC curve b1 when the temperature is lowered have a high ability to be crystallized after being once melted, and can be crystallized and solidified in a short time.

The long fibers having the temperature-lowering crystallization temperature Tcc are cooled and reach the temperature of the temperature-lowering crystallization temperature Tcc after melting or softening of the long fibers contacting the convex portions of the hot embossing roll in the thermocompression bonding process. At times, crystallization solidifies to form thermocompression bonding points to form a non-woven fabric, but in order to perform this partial thermocompression bonding sufficiently, the cooling crystallization temperature Tcc is 90 ° C or higher and 110 ° C or higher.
It must be within the following range. Falling crystallization temperature Tcc is 9
If the temperature is lower than 0 ° C., it takes time for the fibers once melted by the thermocompression bonding to cool and reach the temperature falling crystallization temperature Tcc, and during that time, tension is applied to the web to make it difficult to form a strong thermocompression bonding point. On the other hand, the falling crystallization temperature Tcc is 11
If it exceeds 0 ° C, the time until the once melted fiber cools and reaches the temperature-lowering crystallization temperature Tcc becomes shorter, so it is theoretically preferable. If it is attempted to be obtained, a fairly rapid quenching is required immediately below the spinning, and the fiber breaks frequently, making it difficult to obtain the nonwoven fabric itself.

The heat of crystallization ΔHexo is the amount of heat generated at the exothermic peak, and is calculated from the area S2 of the exothermic peak. In the present invention, the heat of crystallization ΔHexo needs to be 10 mJ / mg or more. Heat of crystallization ΔHexo is 10mJ /
If the amount is less than mg, it takes time for the fibers melted in the thermocompression bonding step to cool and crystallize in the thermocompression bonding step, and the thermocompression bonding points cannot be formed sufficiently.

The non-woven fabric composed of long fibers constructed as described above is sufficiently thermo-compressed even if the non-woven fabric has a low basis weight or is produced by high-speed production, and the thickness direction due to the destruction of the thermo-compression bonding portion It becomes a good long-fiber non-woven fabric in which the occurrence of peeling into the fabric is suppressed.

The long fibers having the above thermal characteristics are
Select and mix inert particles to promote crystallization,
It can be obtained by combining three conditions of rapidly cooling the yarn spun from the nozzle and selecting the viscosity of the polylactic acid polymer.

As the inert particles (crystal nucleating agent) for promoting crystallization, talc, calcium carbonate, titanium oxide and the like can be preferably used. The amount of inert particles added is 0.1
It is preferable to be in the range of 2.0 mass%. If the addition amount of the inert fine particles is less than 0.1% by mass, a sufficient crystallization accelerating effect cannot be obtained, and if the addition amount of the inert fine particles exceeds 2.0% by mass, the crystallinity is poor and terrible. Sometimes thread breaks occur frequently.

[0021] The yarn spun from the nozzle can be rapidly cooled by setting the cooling start position within 70 cm below the nozzle surface and selecting the cooling temperature, the cooling air volume and the like as appropriate. The polylactic acid polymer viscosity is 50 MFR (g / 10 minutes) measured at a temperature of 210 ° C. according to the method described in ASTM-D-1238.
It is preferably 100 or more and less than 100, more preferably 60 to 85. If the MFR is less than 50, the viscosity of the polymer is too high, and the point (solidification point) at which the yarn discharged from the nozzle cools and solidifies separates from the nozzle surface. Since such a yarn is hard to cool and is a slow-cooling type, the distance from the solidification point to the take-up jet is short, and it is difficult to perform sufficient drawing, and as a result, it is not sufficiently crystallized. Conversely, M
When FR exceeds 100 g / 10 minutes, the melt viscosity is too low and thus the spinnability is poor and the mechanical properties of the resulting fiber are poor, and the fineness unevenness becomes large, making stable operation difficult.

The fibers constituting the nonwoven fabric of the present invention are
In addition to the above configuration, it is preferable that the melting point Tm is 160 ° C. or more and the heat of fusion ΔHendo is 20 mJ / mg or more when the differential thermal analysis is performed at a temperature rising rate of 10 ° C./min.

The melting point Tm is the temperature at the endothermic peak due to the crystal melting of the polymer in the DSC curve a1 shown in FIG. 1 (a). By setting the melting point Tm to 160 ° C. or higher, the thermal stability is good. A non-woven fabric can be obtained. In order for the polylactic acid polymer to have a melting point of 160 ° C. or higher, it is necessary to determine the copolymerization ratio of the monomer components. That is, the melting point of poly (L-lactic acid) or poly (D-lactic acid), which is a homopolymer of polylactic acid, is about 180 ° C., but when the copolymer is used as the polylactic acid-based polymer, the melting point of the copolymer is It is important to determine the copolymerization amount ratio of the monomer components so as to be 160 ° C or higher. L-lactic acid and D
-In the copolymer with lactic acid, the copolymerization amount ratio of L-lactic acid and D-lactic acid is (L-lactic acid) / (D-lactic acid) = 3/97 to 0/100, or (L -Lactic acid) /
(D-lactic acid) = 97 / 3-100 / 0 is used. If it is out of this range, the melting point of the polymer, and thus the melting point of the constituent fibers of the non-woven fabric, becomes less than 160 ° C., the polymer becomes amorphous, and the cooling property during spinning is lowered, resulting in the thermal stability of the obtained non-woven fabric. Is impaired, and its intended use tends to be limited.

The amount of heat of fusion ΔHendo is 10
It is the amount of heat required to melt all the crystals when the temperature is raised at ° C / min, and as shown in Fig. 1 (a), the DSC curve a1
In S.1, the area S1 of the endothermic peak due to crystal melting that appears near the crystal melting point of the polymer is obtained. This heat of fusion Δ
Hendo mainly depends on the crystallinity of the fiber itself, and when the crystallinity is large, this value becomes large. The heat of fusion ΔHendo is preferably 20 mJ / mg or more. Heat of fusion Δ
When Hendo is less than 20 mJ / mg, the crystallinity of the fiber becomes insufficient, and the nonwoven fabric made of this fiber tends to be poor in dimensional stability and mechanical properties and in practical use. Also,
Since it lacks heat stability, the nonwoven fabric tends to shrink when used at high temperatures, and its application is likely to be limited.

A long fiber made of a polylactic acid type polymer which does not have the above-mentioned characteristics, that is, as shown in FIG. 2 (a), the DSC curve a2 at the time of heating shows the same tendency as that of the present invention. As shown in FIG. 2B, the DSC at the time of temperature decrease is shown.
A long fiber made of a polylactic acid-based polymer in which the exothermic peak does not appear in the curve b2 and the falling crystallization temperature Tcc does not exist, and sufficient thermocompression bonding cannot be obtained in the thermocompression bonding process. This is because it is difficult to crystallize the softened long fibers in a short time in the thermocompression bonding step because the crystallization ability of the fibers is low, and the crystals are sufficiently crystallized unless they are cooled to the glass transition temperature Tg (58 ° C). It is considered that it takes a long time to solidify, that is, to solidify the crystal.

Therefore, in the case of such a fiber, in the production process in which the tension is gradually applied after the thermocompression bonding process in the continuous process as in the present production machine, or in order to obtain a long-fiber nonwoven fabric having a low basis weight, When the transfer speed is increased to increase the production efficiency and the time from the processing in the thermocompression bonding process to the winding becomes short, the melted or softened thermocompression bonding part cools and crystallizes in the thermocompression bonding process. Before forming a strong thermocompression-bonding point, the thermocompression-bonding point is removed by tension, or a problem such as the thermocompression-bonding step ends, and a sufficient partial thermocompression-bonding point is not formed, The obtained nonwoven fabric is peeled off in the thickness direction.

Next, a method for producing the polylactic acid-based long fibers and the nonwoven fabric made of the same according to the present invention will be described.
First, a polylactic acid-based polymer having a specific MFR, to which the above-mentioned crystal nucleating agent is added, is melt-spun, and the spun filament is drawn and thinned, and then deposited on the movable collecting surface while being opened. A web is formed and the web is partially thermocompressed.

When the spun yarn is towed and thinned by using a suction device, it is preferable that the take-up speed be 2500 to 6000 m / min. This take-up speed depends on the MF of the polymer
It can be appropriately selected according to R, but by setting it in this range,
The melting point Tm measured by differential thermal analysis at a temperature rising rate of 10 ° C./min, which is the object of the present invention, is 160 ° C. or higher, and the heat of fusion is 20 m.
Fibers of J / mg or more can be obtained. When the take-up speed is less than 2500 m / min, it is difficult to obtain sufficient molecular orientation, and the residual elongation tends to be high. Therefore, the obtained non-woven fabric tends to be inferior in dimensional stability, mechanical properties, and thermal stability. The take-off speed is 6000m.
If it exceeds / min, the spinnability tends to be poor, and the uniformity of the fiber diameter tends to be poor. Further, although the crystallinity is improved, the spinning stress is increased, and the strain caused thereby disturbs the crystal structure and tends to generate microvoids in the crystal structure, making it difficult to obtain a practical fiber.
In addition, the mechanical properties of fibers and nonwoven fabrics tend to be inferior.

In summary, in producing the polylactic acid-based long-fiber nonwoven fabric of the present invention, for example, as the first step, a polylactic acid-based polymer, preferably L-lactic acid and D-lactic acid, is used.
The molar ratio of copolymerization with lactic acid is (L-lactic acid) / (D-
Lactic acid) = 3/97 to 0/100, or (L-lactic acid)
/ (D-lactic acid) = 97 / 3-100 / 0 and MFR is 50
Melt spinning of polylactic acid at -100 g / 10 min and addition of crystal nucleating agent, and as the second step, when the yarn spun from the spinneret is subjected to high-speed spinning with air sucker, the spun yarn is used as the nozzle surface. The target long fiber can be obtained by cooling the mixture within 70 cm or less and then performing high speed spinning as much as possible, preferably 2500 m / min or more, and more preferably 3000 m / min or more.

When heat-treating the web made of long fibers, a partial thermocompression bonding apparatus is used to partially thermocompress the web at a temperature lower than the melting point of the polymer constituting the fiber. Partial thermocompression bonding of a web means forming a point-shaped pressure bonding area by embossing. Specifically, the web is passed between an embossing roll and a metal roll with a smooth surface to form a point pressure bonding between long fibers. The method of forming the area is adopted. As the pressure-bonding temperature, it is preferable to apply a temperature lower than the melting point of the polymer constituting the fiber, particularly (melting point of polymer constituting the fiber −35) ° C. to a temperature lower than the melting point.

Each thermocompression bonding area, which is a specific partial area of the web, has an area of 0.2 to 15 mm ² , and the area is round, elliptical, rhombic, triangular, T-shaped, or well-shaped. And the like, and the distribution density of the region, that is, the density of pressure-bonding points is preferably ⁴ to 100 points / cm ² . If the density of crimping points is less than 4 points / cm ² , the mechanical strength and shape retention of the resulting nonwoven fabric are not improved, and conversely, if the density of crimping points exceeds 100 points / cm ² , the resulting nonwoven fabric is sparse Tend to be lost and the flexibility is impaired, which is not preferable. The ratio of the area of the total thermocompression bonding area to the total surface area of the web, that is, the pressure bonding area ratio depends on the area of each pressure bonding point, but is preferably 3 to 50%. If this crimping area ratio is less than 3%, the mechanical strength and shape retention of the resulting nonwoven fabric will not improve, and conversely, if the crimping area ratio exceeds 50%, the resulting nonwoven fabric will become coarsely rigid and flexible. This tends to impair the sex and is not preferable.

The single-filament fineness of the long fibers constituting the polylactic acid-based long-fiber non-woven fabric of the present invention produced as described above is not particularly limited and is about 1 to 12 decitex. The basis weight of the polylactic acid-based long-fiber nonwoven fabric in the present invention is not particularly limited, but is about 10 to ²⁰⁰ g / m ² .

[0033]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In addition, measurement of each physical property value in the following Examples and Comparative Examples was performed by the following methods. (1) Melting point (° C.): using a differential scanning calorimeter DSC-7 type manufactured by Perkin Elma Co., Ltd., measured with a sample mass of 5 mg and a heating rate of 10 ° C./min. The temperature giving the value was defined as the melting point Tm (° C). (2) Heat of fusion and heat of crystallization (mJ / mg): measured using a differential scanning calorimeter DSC-7 type manufactured by Perkin Elma Co., with a sample mass of 10 mg and a heating rate of 10 ° C./min. The area of the endothermic peak of the obtained melting endothermic curve was defined as the heat of fusion (mJ / mg). Similarly, the temperature decrease rate is set to 1
The area of the exothermic peak of the crystallization exothermic curve obtained by measuring 0 ° C./min was defined as the heat of crystallization (mJ / mg). (3) Falling temperature crystallization temperature (° C.): using a differential scanning calorimeter DSC-7 type manufactured by Perkin Elma Co., Ltd., and a sample mass of 10 m
g, the temperature that gives the extreme value of the exothermic peak of the crystallization exothermic curve obtained by measuring the temperature decreasing rate at 10 ° C./min was defined as the temperature decreasing crystallization temperature Tcc (° C.). (4) Melt flow rate (g / 10 minutes): ASTM-
It measured at the temperature of 210 degreeC according to the method of D-1238. (Hereinafter, the melt flow rate is referred to as MFR.) (5) Yarn breakability: When the spun yarn is taken out by air sucker, no yarn breakage occurs per 10 minutes, and good yarn breakability. It was judged that it was, and it was represented by ○. In addition, when the yarn breakage occurred around 10 minutes, it was determined that the yarn breakage property was poor and was represented by x. (6) Thermocompression bonding state: The pressure contact state of the thermocompression bonded sheet was observed. In the entire sheet, the pressure contact of the sheet is not effective and the long fiber non-woven fabric is peeled in the thickness direction. × is the pressure contact state of the sheet, Δ is the pressure contact state of the sheet in which the peeling in the thickness direction occurs, and peeling in the thickness direction occurs. The pressure contact state of the non-existent sheet was marked as ◯. (7) Unit weight (g / m ² ): Vertical 10 from the standard sample
After making 10 sample pieces of cm × width 10 cm and reaching equilibrium water content, the mass (g) of each sample piece was weighed, and the average value of the obtained values was converted to per unit area, Basis weight (g
/ M ² ). (8) Tensile strength (N / 5 cm width): JIS-L-109
The measurement was performed according to the strip method described in 6. That is, each of the sample pieces having a sample length of 20 cm and a sample width of 5 cm
Points were prepared, and the warp and weft directions of the non-woven fabric were measured for each sample piece by using a constant-speed extension type tensile tester (Tensilon UTM-4-1-100, manufactured by Orientec Co., Ltd.) and a gripping interval of 10 cm and a pulling speed. It was stretched at 20 cm / min, and the average value of the maximum tensile strength was defined as the tensile strength (N / 5 cm width). (9) Shrinkage rate of boiling water (%): The area (X) cm after a sample of 20 cm × 20 cm was left for 15 minutes in boiling water was measured and calculated by the following formula. In the present invention, those having a boiling water shrinkage of 10% or less are considered to have a small thermal shrinkage and be good.

Shrinkage rate of boiling water (%) = (400−X) × 100/400 (10) Biodegradability: A non-woven fabric was embedded in an aged compost maintained at about 58 ° C. and taken out after one month. The case where the morphology is not retained is indicated by ◯, and the case where the nonwoven fabric retains the morphology is indicated by x. Example 1 A polylactic acid-based polymer having a melting point of 171 ° C. and an MFR of 7
0 g / 10 minutes, L-lactic acid / D-lactic acid = 99/1 mol% L-lactic acid / D-lactic acid copolymer was used, and 0.5% by mass of talc was added to this polymer as an additive. . This mixture was melt-spun from a round spinneret at a spinning temperature of 210 ° C. and a single hole discharge rate of 1.67 g / min. The yarn spun from the nozzle is cooled rapidly and then air sucked for 500
It was taken out at 0 m / min, opened, and deposited on the collecting surface of a moving conveyor to form a web. Then, pass this web through a partial thermocompression bonding device consisting of an embossing roll,
Long fibers with a single yarn fineness of 3.3 decitex, which are partially thermocompressed under the conditions of a roll temperature of 135 ° C., a crimping area ratio of 14.9%, a crimping point density of 21.9 pieces / cm ² , and a linear pressure of 60 kg / cm. A long-fiber nonwoven fabric having a basis weight of 50 g / m ² was obtained.

Table 1 shows the performance and the like of the obtained non-woven fabric.

[0036]

[Table 1]

Example 2 A polylactic acid-based polymer having a melting point of 166 ° C. and an MFR of 7
The roll temperature of the embossing roll was set to 130 ° C., using 0 g / min of L-lactic acid / D-lactic acid = 98/2 mol% L-lactic acid / D-lactic acid copolymer. A long fiber nonwoven fabric was obtained in the same manner as in Example 1 except for the above.

Table 1 shows the performance of the obtained non-woven fabric. Example 3 A polylactic acid-based polymer having a melting point of 162 ° C. and an MFR of 7
The roll temperature of the embossing roll was 127 ° C., using 0 g / min L-lactic acid / D-lactic acid = 97/3 mol% L-lactic acid / D-lactic acid copolymer. A long fiber nonwoven fabric was obtained in the same manner as in Example 1 except for the above.

Table 1 shows the performance of the obtained non-woven fabric. Examples 4 and 5 The MFR, single hole discharge rate, and traction speed were changed as shown in Table 1. Then, a long fiber nonwoven fabric was obtained in the same manner as in Example 1 except for the above.

Table 1 shows the performance and the like of the obtained non-woven fabric. Examples 6 and 7 The single hole discharge amount and the pulling speed were changed as shown in Table 1. Then, a long fiber nonwoven fabric was obtained in the same manner as in Example 1 except for the above.

Table 1 shows the performance of the obtained non-woven fabric. Examples 8 and 9 The single hole discharge amount, the pulling speed, and the single yarn fineness were changed as shown in Table 1. Then, a long fiber nonwoven fabric was obtained in the same manner as in Example 1 except for the above.

Table 1 shows the performance of the obtained non-woven fabric. Example 10 The additive was changed to titanium oxide (TiO ₂ ). A long fiber nonwoven fabric was obtained in the same manner as in Example 1 except for the above.

Table 1 shows the performance of the obtained non-woven fabric. Example 11 L-lactic acid / having a melting point of 177 ° C. and an MFR of 70 g / min.
D-lactic acid = 99/1 mol% L-lactic acid / D-lactic acid copolymer as the first component, melting point 162 ° C., MFR 70 g
/ Min L-lactic acid / D-lactic acid = 97/3 mol% L-
Using lactic acid / D-lactic acid copolymer as the second component, the respective components were mixed at a ratio of the first component / second component = 1/1 (mass ratio), and the spinning temperature was 210 ° C. from the spinneret. Melt spinning was performed at a single hole discharge rate of 1.67 g / min. The spun yarn is cooled with a cooling air flow and then 500 times with an air sucker.
A web was formed by taking it out at 0 m / min, opening the fiber, and depositing it on the collecting surface of the moving conveyor. Then, this web is passed through a partial thermocompression bonding device consisting of an embossing roll, and the roll temperature is 132 ° C., the bonding area ratio is 14.9%, the bonding point density is 21.9 pieces / cm ² , and the linear pressure is 60 kg / cm. By thermocompression bonding to obtain a long fiber nonwoven fabric having a unit weight of 50 g / m ^{2 and} made of long fibers having a single yarn fineness of 3.3 dtex.

Table 1 shows the performance of the obtained non-woven fabric. Example 12 The single hole discharge rate and the pulling speed were changed as shown in Table 1. Then, a long fiber nonwoven fabric was obtained in the same manner as in Example 1 except for the above.

Table 1 shows the performance and the like of the obtained non-woven fabric.
As is clear from Table 1, the long fibers obtained in Examples 1 to 12 have a falling temperature crystallization temperature Tcc, the Tcc is 90 ° C or higher and 110 ° C or lower, and the heat of crystallization ΔHexo is 10 mJ / Since it was at least mg, the crystallinity was high, sufficient thermocompression bonding was obtained in the thermocompression bonding step, and a nonwoven fabric that did not peel in the thickness direction was obtained. Also, the melting point Tm is 160 ° C.
Since the heat of fusion ΔHendo was 20 mJ / mg or more, the dimensional stability and mechanical properties were excellent, the boiling water shrinkage of the nonwoven fabric was small, and it was practical and thermally stable. Further, these non-woven fabrics are also very good in biodegradability, and when they were taken out after a predetermined period passed after being embedded in a compost, all the non-woven fabrics had a large mass reduction rate and a large morphological change, and had a strong retention rate. Was also significantly lower. Comparative Example 1 The polylactic acid-based polymer had an MFR of 30 g / min. A long-fiber nonwoven fabric was prepared in the same manner as in Example 1 except for the above.

Table 2 shows the performance and the like of the obtained long-fiber nonwoven fabric.

[0047]

[Table 2]

Comparative Example 2 The polylactic acid-based polymer had an MFR of 150 g / min. Other than that, it was attempted to prepare a long-fiber non-woven fabric in the same manner as in Example 1, but the viscosity was too low and the spinnability was poor, and the non-woven fabric could not be prepared. Comparative Examples 3 and 4 A polylactic acid-based polymer having a copolymerization ratio of D-lactic acid and L-lactic acid shown in Table 2 was used, and the embossing temperature was changed to the temperature shown in Table 2. A long-fiber nonwoven fabric was prepared in the same manner as in Example 1 except for the above.

Table 2 shows the performance and the like of the obtained long-fiber nonwoven fabric. Comparative Example 5 No additive was added to the polylactic acid polymer. A long-fiber nonwoven fabric was prepared in the same manner as in Example 1 except for the above.

Table 2 shows the performance of the obtained long-fiber nonwoven fabric. In Comparative Example 1, since the MFR of the polylactic acid-based polymer was smaller than the range of the present invention, the temperature-lowering crystallization temperature Tcc did not exist. As a result, in the thermocompression bonding step, sufficient thermocompression bonding was not obtained, and the obtained nonwoven fabric peeled in the thickness direction.

In Comparative Example 2, the viscosity of the polylactic acid-based polymer was too low to allow high-speed spinning, and a non-woven fabric could not be formed. In Comparative Example 3, although the temperature falling crystallization temperature Tcc exists in the long fibers constituting the nonwoven fabric,
The temperature was lower than 90 ° C., which is the range of the present invention, and the heat of crystallization ΔHexo was also lower than 10 mJ / mg.
Peeling occurred in the thickness direction at the thermocompression bonding portion. Further, since the heat of fusion ΔHendo is lower than 20 mJ / mg and the crystallinity is low, the heat shrinkage is large and the thermal stability is poor.

In Comparative Example 4, since the cooling crystallization temperature Tcc does not exist and the crystallization heat amount ΔHexo does not exist, a sufficient thermocompression bonding portion is not formed, and the obtained nonwoven fabric peels in the thickness direction. became. In addition, the heat of fusion ΔH of the polylactic acid fiber
Since endo was lower than 20 mJ / mg and crystallinity was low, shrinkage due to heat was large and thermal stability was poor.

In Comparative Example 5, although the temperature-lowering crystallization temperature Tcc exists in the long fibers constituting the non-woven fabric, the temperature is lower than 90 ° C. which is the range of the present invention, and the heat of crystallization ΔHexo is also 1.
Since it was lower than 0 mJ / mg, peeling occurred in the thickness direction in the thermocompression bonded portion. In addition, the heat of fusion ΔHendo of the polylactic acid-based fiber was lower than 20 mJ / mg and the crystallinity was low, so that the shrinkage due to heat was large and the thermal stability was poor.

[0054]

As described above, according to the polylactic acid-based long-fiber nonwoven fabric of the present invention, the fibers constituting the nonwoven fabric are heated at a heating rate of 10%.
After melting at ℃ / min, when the differential thermal analysis at a temperature decrease rate of 10 ℃ / min, there is a cooling crystallization temperature Tcc, and this cooling crystallization temperature Tcc is 90 ℃ or more and 110 ℃ or less, crystallization By setting the heat quantity ΔHexo to be 10 mJ / mg or more, the crystallization rate of the fiber is increased, and the time from once melting to cooling and hardening can be shortened, and the spunbonding step and thermocompression bonding step can be performed continuously. It is possible to perform production with such a production machine as described above, and it is possible to favorably perform partial thermocompression bonding at high speed without lowering production efficiency, and to form a partial thermocompression bonding portion that does not separate in the thickness direction of the nonwoven fabric.

Further, the polylactic acid-based long fiber of the present invention has a temperature-falling crystallization temperature Tcc when it is melted at a temperature-rising rate of 10 ° C./min and then subjected to a differential thermal analysis at a temperature-falling rate of 10 ° C./min, and By setting the temperature falling crystallization temperature Tcc to 90 ° C. or more and 110 ° C. or less and the heat of crystallization ΔHexo to 10 mJ / mg or more, a polylactic acid-based continuous fiber which is easily melted after cooling once is obtained. A lactic acid-based long-fiber nonwoven fabric can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a DSC curve of a polylactic acid-based polymer according to an embodiment of the present invention when the temperature is raised and when the temperature is lowered.

FIG. 2 is a diagram showing DSC curves of a polylactic acid-based polymer at the time of temperature increase and the temperature decrease, for comparison with FIG.

[Explanation of symbols]

a1, a2 DSC curve at temperature rise b1, b2 DSC curve when the temperature is lowered

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4L035 BB31 BB40 BB54 EE20 FF05                 4L047 AA21 AB03 AB10 BA08 BA23                       EA05

Claims (4)

[Claims] 1. A non-woven fabric comprising long fibers having a single-phase cross-section made of a polylactic acid-based polymer, wherein the long fibers are partially thermocompression-bonded to each other, and the fibers constituting the non-woven fabric have a heating rate. After melting at 10 ° C./min, a temperature-decreasing crystallization temperature Tcc exists when performing differential thermal analysis at a temperature-decreasing rate of 10 ° C./min, and the temperature-decreasing crystallization temperature Tcc is 90 ° C. or more and 110 ° C. or less, and crystallization is performed. A polylactic acid-based long-fiber nonwoven fabric having a calorific value ΔHexo of 10 mJ / mg or more. 2. The fibers constituting the non-woven fabric have a melting point Tm of 160 ° C. or more and a heat of fusion ΔHendo of 20 mJ / mg or more as measured by differential thermal analysis at a heating rate of 10 ° C./min. Item 1. A polylactic acid-based long-fiber nonwoven fabric according to item 1. 3. A long fiber having a single-phase cross-section made of a polylactic acid polymer, which is melted at a temperature rising rate of 10 ° C./minute and then crystallized at a temperature lowering rate of 10 ° C./minute by differential thermal analysis. There is a temperature Tcc, the temperature falling crystallization temperature Tcc is 90 ° C. or higher and 110 ° C. or lower, and the heat of crystallization ΔHexo is 10 mJ.
/ Mg or more, a polylactic acid-based long fiber. 4. The melting point Tm measured by differential thermal analysis at a heating rate of 10 ° C./min is 160 ° C. or higher, and the heat of fusion ΔHendo is 20.
The polylactic acid-based long fiber according to claim 3, which has a content of mJ / mg or more.