JP4912286B2 - Polylactic acid long fiber nonwoven fabric - Google Patents

Description

  The present invention relates to a polylactic acid-based long fiber nonwoven fabric.

  In recent years, synthetic fibers using petroleum as a raw material generate a large amount of heat at the time of disposal and incineration, and therefore need to be reviewed from the viewpoint of protecting the natural environment. In contrast, fibers made of aliphatic polyester that biodegrades in nature have been developed and are expected to contribute to environmental protection. Among aliphatic polyesters, polylactic acid polymers are expected to be used in a wide range of fields because they have a relatively high melting point. In addition, polylactic acid polymers have the best balance of mechanical properties, heat resistance, and cost among biodegradable polymers. And development of the fiber using this is performed at a rapid pitch.

  However, even the most promising polylactic acid-based polymers have the problem of poor high-temperature mechanical properties. Here, the poor high-temperature mechanical properties indicate that the polymer rapidly softens when the glass transition temperature (Tg) of the polylactic acid polymer exceeds 60 ° C. Actually, when a tensile test of a long-fiber non-woven fabric made of a polylactic acid polymer is performed at a different temperature, it has been found that the strength of the long-fiber non-woven fabric rapidly decreases at 70 ° C. or higher.

To compensate for the above-mentioned drawbacks of polylactic acid polymers,
(1) A method of blending poly (lactic acid) with polyethylene terephthalate copolymerized with alkylene diol or bisphenol A derivative,
(2) A method of blending polyethylene terephthalate copolymerized with a long-chain carboxylic acid into polylactic acid,
(3) A method using an oriented crystallization structure by high-speed spinning,
Etc. have been proposed.

Among these, in the method using the oriented crystallization structure by high speed spinning, for example, homopoly L lactic acid having a weight average molecular weight of 100,000 to 300,000 is discharged from the die at a spinning temperature of 210 to 250 ° C., and the yarn is cooled and solidified by cooling air. Let Then, the oil agent for fibers is applied, taken up at a high speed, and wound up as it is. At this time, a high take-up speed is set so that the crystal size in the (200) plane direction of the wound polylactic acid fiber is 6 nm or more. Then, the polylactic acid fiber oriented and crystallized by this high-speed spinning is further stretched at a stretching temperature of 100 ° C. or higher and is heat-set (Patent Document 1).
JP 2003-41433 A

  This invention makes it a subject to obtain the new method for providing heat resistance to the long-fiber nonwoven fabric formed with a polylactic acid-type polymer.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a resin in which a specific polymer is alloyed is a composite length in a nonwoven fabric comprising composite long fibers formed of a polylactic acid-based polymer. It has been found that heat resistance can be imparted to the nonwoven fabric by forming at least a part of the fiber surface of the fiber, and the present invention has been achieved.

That is, the means for solving the above problems are as follows.
1. A non-woven fabric formed by a spunbond method using a composite long fiber comprising a polylactic acid polymer (A) having a melting point of 150 ° C. or higher and a polymer alloy as constituent fibers,
The polymer alloy forms at least part of the fiber surface;
The polymer alloy contains the polylactic acid polymer (A), a polyester copolymer (B) having a melting point of 160 ° C. to 230 ° C., and a compatibilizing agent (C), The polylactic acid-based polymer (A) forms a sea component and the polyester copolymer (B) has a sea-island structure in which an island component is formed,
A polylactic acid-based long fiber nonwoven fabric, wherein the island component has a domain size in the range of 0.001 to 0.1 μm.

  2. 1. The polyester copolymer (B) is a crystalline resin and contains a terephthalic acid component, an ethylene glycol component, and a butanediol component. Polylactic acid long fiber nonwoven fabric.

  3. The composition ratio of the polylactic acid polymer (A) and the polyester copolymer (B) in the polymer alloy is (A) / (B) = 95/5 to 80/20 (mass%). 1. Or 2. Polylactic acid long fiber nonwoven fabric.

  4). The composite long fiber is a core-sheath type composite long fiber in which the polylactic acid polymer (A) forms a core and the polymer alloy forms a sheath. To 3. Any of the polylactic acid-based long fiber nonwoven fabrics.

  5. The compatibilizer (C) is one or more selected from an epoxy chain extender, an isocyanate chain extender, a carbodiimide chain extender, and a glycidyl ether chain extender. Features 1. To 4. Any of the polylactic acid-based long fiber nonwoven fabrics.

  6). The content of the compatibilizing agent (C) with respect to the total amount of the polylactic acid polymer (A), the polyester copolymer (B) and the compatibilizing agent (C) is 0.01 to 1% by mass. 1. To 5. Any of the polylactic acid-based long fiber nonwoven fabrics.

7). 1. It is integrated by having a partial thermocompression bonding part. To 6. Any of the polylactic acid-based long fiber nonwoven fabrics.
8). The constituent fibers are entangled three-dimensionally and integrated into a non-woven fabric. To 6. Any of the polylactic acid-based long fiber nonwoven fabrics.

  9. The constituent fibers are bonded to each other at the contact portion with a binder resin. Polylactic acid long fiber nonwoven fabric.

  The polylactic acid-based long fiber nonwoven fabric of the present invention is composed of a composite long fiber composed of a plant-derived polymer and having a melting point of 150 ° C. or higher and a polymer alloy as components. The polymer alloy is formed by a bond method, and the polymer alloy forms at least a part of the fiber surface. The polymer alloy is composed of the polylactic acid polymer (A) and a polyester copolymer having a melting point of 160 ° C. to 230 ° C. It contains a coalescence (B) and a compatibilizer (C), and the polylactic acid polymer (A) forms a sea component and the polyester copolymer (B) forms an island component. Since the non-woven fabric has a sea-island structure and the domain size of the island component is 0.01 to 1 μm, the heat resistance when placed in a high temperature atmosphere is good. For this reason, it can be suitably used for applications requiring heat resistance such as automobile interior materials.

  The polylactic acid-based long fiber non-woven fabric of the present invention is a non-woven fabric formed by using, as constituent fibers, composite long fibers having a polylactic acid-based polymer (A) having a melting point of 150 ° C. or higher and a polymer alloy as components.

  First, the polylactic acid polymer (A) which is one component of the composite long fiber will be described.

  Examples of the polylactic acid polymer (A) used in the nonwoven fabric of the present invention include poly-D-lactic acid, poly-L-lactic acid, a copolymer of D-lactic acid and L-lactic acid, and D-lactic acid. A polymer selected from the group consisting of a copolymer of hydroxycarboxylic acid, a copolymer of L-lactic acid and hydroxycarboxylic acid, and a copolymer of D-lactic acid, L-lactic acid and hydroxycarboxylic acid, or These blends are mentioned. Examples of the hydroxycarboxylic acid for copolymerization include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid, hydroxyoctanoic acid, and the like. And glycolic acid are preferable from the viewpoint of decomposition performance and cost reduction.

  In the present invention, the polylactic acid polymer (A) needs to be a polymer having a melting point of 150 ° C. or higher or a blend thereof. Since the polylactic acid polymer (A) has a melting point of 150 ° C. or higher, the polylactic acid polymer (A) has high crystallinity, and thus can exhibit required heat resistance.

  The melting point of poly-L-lactic acid and poly-D-lactic acid, which are homopolymers of polylactic acid, is about 180 ° C. When a copolymer of L-lactic acid and D-lactic acid is used as the polylactic acid polymer, the copolymerization ratio of the monomer components is determined so that the melting point of the copolymer is 150 ° C. or higher. That is, the copolymerization ratio of L-lactic acid and D-lactic acid is (L-lactic acid) / (D-lactic acid) = 5/95 to 0/100, or (L-lactic acid) / (D- When lactic acid) = 95/5 to 100/0, the polylactic acid polymer (A) has a melting point of 150 ° C. or higher. When the copolymerization ratio is out of the above range, the melting point of the copolymer becomes less than 150 ° C., so that the amorphous property becomes high and the object of the present invention cannot be achieved.

The polymer alloy which is the other component of the composite long fiber will be described.
This polymer alloy forms at least a part of the fiber surface. And this polymer alloy includes the above-mentioned polylactic acid polymer (A) having a melting point of 150 ° C. or higher, a polyester copolymer (B) having a melting point of 160 ° C. to 230 ° C., a compatibilizing agent (C), The polylactic acid polymer (A) forms a sea component and the polyester copolymer (B) has an island-island structure in which an island component is formed. The island component needs to have a domain size in the range of 0.001 to 0.1 μm.

  As the polyester copolymer (B), one containing a terephthalic acid component, an ethylene glycol component, and a butanediol component can be used. Since the polyester copolymer (B) containing these as a component is crystalline, it has a clear crystal melting point (shows a clear melting point peak when a melting endothermic curve is drawn). For this reason, since the nonwoven fabric which uses the long fiber obtained by using this polyester copolymer (B) as a constituent fiber has high crystallinity when heat is applied, heat shrinkage hardly occurs. Therefore, a web or a nonwoven fabric comprising these long fibers as constituent fibers does not shrink when subjected to a thermal bonding treatment, and has good dimensional stability. Further, since there is little decrease in the strength and elongation of the fiber even in a high temperature atmosphere, the nonwoven fabric made of this fiber has good dimensional stability, little decrease in mechanical strength, and can maintain stable quality.

  The polyester copolymer (B) may be a copolymer obtained by further copolymerizing ε-caprolactone with an alkylene terephthalate unit containing the above three components. By copolymerizing ε-caprolactone, the melting point can be adjusted without impairing the crystallinity. The ε-caprolactone unit in the polyester copolymer (B) may be randomly copolymerized with other structural units or may be block copolymerized.

  The melting point of the polyester copolymer (B) needs to be 160 ° C. or higher and 180 ° C. or higher in consideration of heat resistance when the nonwoven fabric of the present invention is used in a high temperature atmosphere. preferable. The upper limit of the melting point is 230 ° C. The reason is to prevent the melting point difference from the polylactic acid polymer (A) from becoming large. When the temperature exceeds 230 ° C., the melting point difference between the polylactic acid polymer (A) and the polyester copolymer (B) increases, and the polylactic acid polymer (A) may be thermally decomposed in the melt spinning process. . For this reason, the preferable range of melting | fusing point of a polyester copolymer (B) is 180 to 200 degreeC. In addition, when a polyester copolymer (B) does not show clear melting | fusing point, the softening point is considered as melting | fusing point.

  The polyester copolymer (B) is selected so as to have a melting point in the above range, and can be obtained by polymerizing a terephthalic acid component, an ethylene glycol component, and a butanediol component.

  In the polymer alloy, it is important that the polylactic acid polymer (A) and the polyester copolymer (B) are uniformly blended. Here, being uniformly blended means the following states. That is, when the cross section of the long fiber constituting the long fiber nonwoven fabric is observed with a transmission electron microscope (TEM) (for example, 20,000 times), a so-called sea-island structure is adopted, and a polyester copolymer that forms an island component ( B) refers to a state in which the domain size is reduced to 0.001 to 0.1 μm in terms of diameter (diameter converted from the area of the domain assuming that the domain is a circle). The heat resistance of a nonwoven fabric can be improved by making the domain size of an island component into the said range. The smaller the domain size of the island component, the better the adhesion between the polylactic acid polymer (A) constituting the sea component and the polyester copolymer (B) constituting the island component. When this adhesiveness is good, it is possible to withstand the stretching tension during the production of the long-fiber nonwoven fabric that requires high-speed spinning.

  However, if the domain size of the island component is smaller than 0.001 μm, the heat resistance of the nonwoven fabric tends to be inferior. Further, when the domain size of the island component exceeds 0.1 μm, the domain size becomes too large with respect to the surface area of the fiber constituting the polylactic acid-based long fiber nonwoven fabric of the present invention. As a result, the yarn-making property deteriorates. Therefore, the size of the island domain is preferably 0.005 to 0.05 μm.

  In order to obtain such a domain size, in the polymer alloy chip comprising the polylactic acid polymer (A) and the polyester copolymer (B) used at the time of melt spinning, the polyester copolymer constituting the island component is used. It is preferable to use a polymer (B) having a domain size of less than 0.5 μm in average diameter and less than 1.0 μm in maximum diameter and finely dispersed in the polylactic acid polymer (A) which is a sea component. Thereby, high-speed spinning at a pulling speed of about 5000 m / min can be stably performed.

  The blend ratio of the polylactic acid polymer (A) and the polyester copolymer (B) in the polymer alloy is preferably (A) / (B) = 95/5 to 80/20. When the blend ratio of the polyester copolymer (B) is less than 5% by mass, the effect of blending the polyester copolymer (B) is hardly exhibited, and the heat resistance is hardly improved. On the other hand, when the blend ratio of the polyester copolymer (B) exceeds 20% by mass, the polyester copolymer (B) is difficult to be finely dispersed in the polylactic acid polymer (A). It tends to be inferior, and the strength of the obtained fiber tends to be inferior.

  The polylactic acid-based long-fiber nonwoven fabric of the present invention is a polymer alloy containing a polylactic acid-based polymer (A) and a polyester copolymer (B), and includes a sea-component polylactic acid-based polymer (A) and an island component polyester. It is important that the polymer (B) exists substantially independently. However, the polylactic acid-based polymer (A) and the polyester copolymer (B) are usually poorly compatible, and it is not only necessary to produce a long fiber nonwoven fabric as in the present invention by kneading the both, but a polymer alloy You can't even make a chip. Therefore, in the present invention, the polymer alloy used for the polylactic acid-based long fiber nonwoven fabric contains the compatibilizing agent (C). According to this, by dramatically improving the interfacial adhesion between the polylactic acid-based polymer (A) and the polyester copolymer (B), high-speed yarn production is possible, and the spunbond method is used to pull at high speed. A polylactic acid-based nonwoven fabric can be produced, and the heat resistance of the obtained nonwoven fabric can be improved.

  The compatibilizer (C) is not particularly limited as long as it improves the interfacial adhesion between the polylactic acid polymer (A) and the polyester copolymer (B), but is generally known. The chain extenders that are present can be applied most effectively. It is essential that the compatibilizing agent has reactivity with chain extension, such as an epoxy group, a carbodiimide group, an isocyanate group, and a maleic anhydride group.

Examples of such a compatibilizing agent include an epoxy chain extender, an isocyanate chain extender, a carbodiimide chain extender, and a glycidyl ether chain extender.
Specific examples of the epoxy chain extender include Joncryl ADR 4300, 4368 (manufactured by BASF).

  Examples of the isocyanate chain extender include aromatic diisocyanates having 6 to 20 carbon atoms (excluding carbon in the NCO group, the same shall apply hereinafter), aliphatic diisocyanates having 2 to 18 carbon atoms, and alicyclic diisocyanates having 4 to 15 carbon atoms. , Araliphatic diisocyanates having 8 to 15 carbon atoms, modified products of these diisocyanates, and mixtures of two or more thereof. Specific examples of the isocyanate include phenylene diisocyanate, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthylene diisocyanate, ethylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), Examples include lysine triisocyanate. Of these, lysine triisocyanate, TDI, HDI, and IPDI are preferable. Particularly preferred is lysine triisocyanate.

  Examples of the carbodiimide chain extender include diphenylcarbodiimide, di-cyclohexylcarbodiimide, di-2,6-dimethylphenylcarbodiimide, dioctyldecylcarbodiimide, diisopropylcarbodiimide, N, N′-di-p-aminophenylcarbodiimide, N, N ′. -Dioctyldecylcarbodiimide, N, N'-di-2,6-dimethylphenylcarbodiimide, N, N'-di-2,6-diisopropylphenylcarbodiimide, 2,6,2 ', 6'-tetraisopropyldiphenylcarbodiimide, N, N'-di-p-hydroxyphenylcarbodiimide, N, N'-di-cyclohexylcarbodiimide, N, N'benzylcarbodiimide, N, N'-di-p-ethylphenylcarbodiimide, N, N'- Di-o-isopropyl Phenylcarbodiimide, N, N′-di-2,6-diethylphenylcarbodiimide, N, N′-di-2-ethyl-6-isopropylphenylcarbodiimide, N, N′-di-2-isobutyl-6-isopropylphenyl Examples thereof include carbodiimide, N, N′-di-2,4,6-trimethylphenylcarbodiimide, N, N′-di-2-isobutyl-6-isopropylphenylcarbodiimide and the like. Of these, N, N′-di-2,6-diisopropylphenylcarbodiimide and 2,6,2 ′, 6′-tetraisopropyldiphenylcarbodiimide are preferable. Specific examples thereof include Stavacsol I (manufactured by Line Hemy), EN-160 (manufactured by Matsumoto Yushi Co., Ltd.), LA-1 (manufactured by Nisshinbo Co., Ltd.), and the like.

  Examples of glycidyl ether chain extenders include glycidyl methacrylate, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane polyglycidyl ether, polypropylene glycol diglycidyl ether. Examples include ether. Of these, polyglycerol polyglycidyl ether is particularly preferred.

  Polymers having these glycidyl group-containing compounds as monomer units, compounds in which a glycidyl group is graft-copolymerized to a polymer as a main chain, specifically, Modeler A4200 (manufactured by NOF Corporation) are also included. . In addition to these monomer units, a long-chain alkyl acrylate can be copolymerized to control the reactivity of the glycidyl group.

The compatibilizing agent (C) is preferably one that is arbitrarily selected from one or more compounds selected from the above.
The amount of the compatibilizer (C) added is the equivalent per unit mass of the reactive group of the compound used, the dispersibility and reactivity at the time of melting, the size of the island component domain, the polylactic acid polymer (A) It can be determined as appropriate depending on the blend ratio of the polyester copolymer (B). In terms of suppression of interfacial peeling, 0.01% by mass with respect to the total amount (100% by mass) of the polylactic acid polymer (A), the polyester copolymer (B), and the compatibilizer (C). % Or more is preferable. More preferably, it is 0.1 mass% or more. If the amount of the compatibilizer (C) added is too small, the diffusion and reaction amount at the interface between the polylactic acid polymer (A) and the polyester copolymer (B) are small, and the effect of improving the interfacial adhesion is limited. It becomes the target.

  On the other hand, in order for the compatibilizer (C) to exhibit the required performance without hindering the properties and yarn-forming properties of the polylactic acid polymer (A) and the polyester copolymer (B) that serve as the fiber base material The added amount is preferably 1% by mass or less, and more preferably 0.5% by mass or less.

  In the present invention, the polymer alloy forms at least a part of the surface of the composite fiber. As a fiber cross-sectional form for constituting such a fiber, for example, a side-by-side composite cross section in which a polylactic acid polymer (A) and a polymer alloy are bonded together, and the polylactic acid polymer (A) forms a core. And a core-sheath type composite cross section in which a polymer alloy forms a sheath, a split type composite cross section in which a polylactic acid polymer (A) and a polymer alloy are alternately present on the fiber surface, and a multi-leaf type composite cross section. It is done.

  When the polylactic acid-based polymer (A) has a core-sheath type composite cross section in which a core part is formed and a polymer alloy forms a sheath part, the composite ratio (mass ratio) of the core part and the sheath part is: The sheath portion is preferably 3/1 to 1/3. When the ratio of the core part exceeds 3/1, the ratio of the sheath part containing the polyester copolymer (B) becomes too small, and the physical properties of the nonwoven fabric in a high temperature atmosphere tend to be inferior. On the other hand, when the ratio of the core is less than 1/3, the resulting nonwoven fabric has insufficient mechanical strength.

  The nonwoven fabric of the present invention is a spunbonded nonwoven fabric on which the above-described composite fibers are deposited. As the form of the nonwoven fabric, it is preferable that the fibers are thermally bonded to each other by at least the fiber surface being melted or softened, but the constituent fibers may be held in a form by entanglement. As a form of thermal bonding, it may be one in which the fibers are thermally bonded at the contact points between the fibers through a polymer melted or softened on the surface of the fibers, or partially by passing the web through a heat embossing device. The heat-bonded part and the non-heat-bonded part are formed, and in the heat-bonded part, at least a part of the polymer constituting the fiber is melted or softened and held in the form of a nonwoven fabric. Also good.

  In addition, as the form of the nonwoven fabric of the present invention, it is also possible to adopt a form in which entanglement and integration are performed by a three-dimensional entanglement process such as a needle punch after a temporary thermocompression bonding process using a hot embossing device. When this three-dimensional entanglement treatment is performed, a part of or all of the fibers constituting the partial temporary press-bonded part are peeled off from the temporary press-bonded part to be in a free state. Will be entangled.

  Furthermore, if a desired amount of a binder resin is attached to the polylactic acid fibers entangled and integrated by the needle punching process as required, a nonwoven fabric in which the constituent fibers are firmly attached at the contact portions can be obtained.

  It is also a preferable condition in the present invention to select a polymer viscosity suitable for high speed spinning. That is, the viscosity of the polylactic acid-based polymer (A) and the polymer alloy was measured according to the method described in ASTM-D-1238 at a temperature of 210 ° C. and a load of 20.2 N (2160 gf) (hereinafter referred to as “melt flow rate”). (Abbreviated as “MFR”) is preferably 10 to 80 g / 10 minutes, more preferably 20 to 70 g / 10 minutes. When the MFR1 is less than 10 g / 10 minutes, the viscosity is too high, and the burden on the screw at the time of melting increases in the process for producing the non-woven constituent fibers. On the other hand, when the MFR exceeds 80 g / 10 min, the viscosity is too low, and yarn breakage tends to occur frequently in the spinning process, which tends to impair operability.

  The single yarn fineness of the composite fiber constituting the nonwoven fabric of the present invention is preferably 2 to 11 dtex. When the single yarn fineness of the composite fiber is less than 2 dtex, the spun yarn cannot withstand the drawing tension in the spinning process, and yarn breakage frequently occurs and the operability tends to deteriorate. On the other hand, when the single yarn fineness of the composite fiber exceeds 11 decitex, the spinning yarn tends to be inferior in cooling property, so that the yarn comes out from the opening device in a state of being in close contact with heat. As a result, the quality of the resulting nonwoven fabric is very poor. For these reasons, the single yarn fineness is more preferably 3 to 8 dtex.

The basis weight of the nonwoven fabric of the present invention may be appropriately selected depending on the use of the nonwoven fabric, and is not particularly limited, but is generally preferably in the range of 10 to 300 g / m ² . More preferably, it is the range of 15-200 g / m < ² >. When the basis weight is less than 10 g / m ² , the formation and mechanical strength are inferior, which is not practical. Conversely, if the basis weight exceeds 300 g / m ² , it is disadvantageous in terms of cost.

  In the polylactic acid-based polymer (A) and / or the polyester copolymer (B) for forming the conjugate fiber constituting the nonwoven fabric of the present invention, a crystal nucleating agent, Pigments, heat stabilizers, antioxidants, weathering agents, plasticizers, lubricants, mold release agents, antistatic agents, fillers, and the like can be added. For example, it is preferable to blend talc with the polylactic acid polymer (A) as a crystal nucleating agent, and blend a lubricant with the polyester copolymer (B) in order to further improve the openability.

Next, the preferable manufacturing method of the polylactic acid-type long fiber nonwoven fabric of this invention is demonstrated. The polylactic acid long fiber nonwoven fabric of the present invention is produced by a spunbond method.
That is, a twin-screw extrusion kneader at 220 to 230 ° C. while separately measuring a polylactic acid polymer (A), a polyester copolymer (B), and a compatibilizer (C) such as an epoxy chain extender. To produce a polymer alloy. As a method for reducing the island domain size, a lower kneading temperature in the above range is preferable, a higher shear rate is better, and a shorter residence time is better.

  Then, the polymer chip of the polylactic acid polymer (A) and the polymer chip of the polymer alloy obtained as described above are separately melt-metered, and the polymer alloy forms at least a part of the surface of the composite fiber. The melt spinning is performed through a composite spinneret that can be formed, and the spun yarn spun from the spinneret is cooled using a conventionally known cooling device such as a lateral spray or an annular spray, and then a suction device. Use the to pull and pull.

  The pulling speed at the time of pulling is preferably set to 3000 to 6000 m / min, and more preferably 4000 to 5000 m / min. If the pulling speed is less than 3000 m / min, the molecular orientation is not sufficiently promoted in the yarn, and the dimensional stability of the resulting nonwoven fabric tends to be poor. On the other hand, if the pulling speed exceeds 6000 m / min, the pulling tension cannot be withstood and yarn breakage is likely to occur.

  After opening the taken yarn, it is deposited on a movable collection surface such as a screen conveyor to form a nonwoven web. Then, what is necessary is just to make it a nonwoven fabric by a well-known nonwoven-fabrication means, for example, heat-treating this nonwoven web, and heat-bonding fibers by softening or melt | dissolving the polyester copolymer (B) of the fiber surface at least. As a thermal bonding method, it is preferable to perform partial thermocompression bonding using a thermocompression bonding apparatus such as a heat embossing apparatus.

  The temperature of the roll in the heat embossing device, that is, the surface temperature of the roll may be set to a temperature at which the low-melting point polyester copolymer (B) is melted or softened. To do. Specifically, the surface temperature of the roll is preferably set in a range from a temperature 20 ° C. lower than the melting point of the low-melting polyester copolymer (B) to a temperature 20 ° C. higher. However, the surface temperature of the roll is 30 ° C. higher than the melting point of the polylactic acid polymer so that the polylactic acid polymer (A) as a fiber-forming component does not melt or soften and lose its original function. It is preferably lower, more preferably 40 ° C. or lower.

  When the temperature of the roll in the heat embossing apparatus is set to a temperature lower than the melting point of the low-melting point polyester copolymer (B) by 20 ° C., the polyester polymer (B) as the heat bonding component is sufficiently melted or Since it does not soften, it cannot be sufficiently bonded, and the strength is likely to decrease, and it becomes easy to fluff. On the other hand, if the temperature is set higher than 20 ° C. higher than the melting point of the polyester copolymer (B), the polylactic acid polymer (A) is easily affected by heat and heat shrinkage occurs. It becomes a nonwoven fabric with poor mechanical strength.

  By heat-treating under the above temperature conditions, the polylactic acid polymer (A) as a fiber-forming component can be heat-treated at a temperature that is not affected by heat such as heat shrinkage. The flexibility of the resulting nonwoven fabric can be improved.

  Next, based on an Example, this invention is demonstrated concretely. However, the present invention is not limited only to these examples. In addition, the measurement of the various physical-property values in the following examples and comparative examples was implemented with the following method.

(1) Melting point (° C)
A differential scanning calorimeter (manufactured by Perkin Elma, DSC-2 type) was used to measure the sample mass at 5 mg and the heating rate at 10 ° C./min. The temperature giving the maximum value of the obtained endothermic curve was defined as the melting point (° C.).

(2) Melt flow rate of polylactic acid polymer (A) and polymer alloy (g / 10 min)
According to the method described in ASTM-D-1238 (E), the temperature was 210 ° C. and the load was 20.2 N (2160 gf).

(3) Relative viscosity of polyester copolymer (B) 0.5 g of a sample was dissolved in 100 cc of a mixed solvent of phenol and ethane tetrachloride and measured using an Ostwald viscometer.

(4) Fineness (decitex)
The diameter of 50 fibers in the web state was measured with an optical microscope, and the average value obtained by correcting the density was defined as the fineness.

(5) Weight per unit area (g / m ² )
Ten sample pieces having a length of 10 cm and a width of 5 cm were prepared from a sample in a standard state, the mass (g) of each sample piece was weighed, and the average value of the obtained values was converted per unit area to obtain a basis weight ( g / m ² ).

(6) Size of island domain in synthetic fiber Cut out an ultra-thin slice in the direction perpendicular to the fiber axis of the fiber constituting the long-fiber nonwoven fabric, soak it in visible curable resin (epoxy embedding material) for several hours, and then cure it. Sections were collected. Using the slice, a photograph was taken (20,000 times) by transmission measurement with an acceleration voltage of 100 kV, a current of 58 μA, and an irradiation aperture 3 using a JEM-1230 TEM apparatus manufactured by JEOL. The length of 100 island domains at that time was measured, and the average value was defined as the domain size.

(7) Tensile strength (N / 5 cm width) and elongation (%)
It measured according to JIS-L-1906. That is, for each of the vertical direction (MD) and the horizontal direction (CD) of the nonwoven fabric, 10 sample pieces having a length of 20 cm and a width of 5 cm were prepared, and a constant-speed extension type tensile tester (Orientec Corp., Tensilon UTM- 4-1-100), stretching at a grip interval of 10 cm and a tensile speed of 20 cm / min, and setting the average value of the obtained breaking load at break (N / 5 cm width) as the tensile strength (N / 5 cm width). The average value of breaking elongation at that time was defined as elongation (%).

(8) Tensile strength (N / 5 cm width) and elongation (%) under high temperature atmosphere
Tensile strength (N / 5 cm width) and elongation (%) were determined by the same method as in (6) above at a high temperature atmosphere of 90 ° C. and 130 ° C.

Example 1
L-lactic acid / D-lactic acid = 98.4 / 1.6 mol% L-lactic acid / D-lactic acid copolymer (hereinafter abbreviated as “P1”) having a melting point of 168 ° C. and an MFR of 20 g / 10 min. ) Was prepared as a core component.

  The polymer alloy of the sheath component was obtained as follows. That is, a polyester copolymer (hereinafter abbreviated as “P2”) manufactured by Nippon Ester Co., Ltd. having a relative viscosity of 1.49 and a melting point of 180 ° C. containing a terephthalic acid component, ethylene glycol and 1,4-butanediol component Used). And this P2, the above-mentioned P1, and an epoxy chain extender manufactured by BASF as a compatibilizing agent, ADR4300 (hereinafter abbreviated as “C1”), P1: P2: C1 = 89.9: The mixture was blended at 10: 0.1 (mass%) and supplied to a twin-screw kneader (manufactured by Ikegai Co., Ltd., PCM-30) set at a temperature of 230 ° C. Then, the strand was extruded from a 0.4 mm diameter × 3 hole die. Subsequently, the strand was cooled in a cooling bath, and then cut with a pelletizer, and a sheath component polymer alloy (hereinafter abbreviated as “P3”) was collected. MFR of the obtained polymer alloy was 16 g / 10min.

Furthermore, a masterbatch containing 20% by mass of talc (TA) as a crystal nucleating agent based on P1 was prepared.
And, the composite ratio of P1 and P3 is P1: P3 = 1: 1 by mass ratio, and 0.5% by mass of talc is contained in the molten polymer of P1 and P3, respectively. After weighing individually, each is melted at a temperature of 230 ° C. using an individual extruder-type extruder so that a cross section of the sheath-core-sheath composite fiber in which P1 is arranged in the core and P3 is arranged in the sheath Then, melt spinning was performed under the condition of a single hole discharge rate of 1.5 g / min.

  After cooling the spun yarn with a known cooling device, it is subsequently pulverized at a traction speed of 5000 m / min with an air soccer provided below the spinneret, and opened using a known opening device, It was collected and deposited as a web on a moving screen conveyor. The single yarn fineness of the deposited composite long fiber was 3.0 dtex.

Next, this web was passed through a hot embossing device consisting of an embossing roll and a smooth metal roll, and heat treated to obtain a polylactic acid-based long fiber nonwoven fabric having a basis weight of 100 g / m ² . As heat embossing conditions, the surface temperature of both rolls is set to 135 ° C., and the embossing roll is a circular sculpture pattern with an individual area of 0.6 mm ² , the pressure contact density is 20 pieces / cm ² , and the pressure contact area ratio is 15 % Was used.

  Table 1 shows the performance of the obtained nonwoven fabric. In addition, in the cross section of the fiber which comprises the obtained nonwoven fabric, the island component of the domain size of the range of 0.001-0.1 micrometer existed.

(Example 2)
The composite ratio of P1 and P3 was set to be P1: P3 = 1: 2 in mass ratio. Otherwise in the same manner as in Example 1, a polylactic acid-based long fiber nonwoven fabric was obtained.

  Table 1 shows the performance of the obtained nonwoven fabric.

(Example 3)
A polymer alloy polyester copolymer (B) constituting a sheath component, comprising a terephthalic acid component, an ethylene glycol and a 1,4-butanediol component, having a relative viscosity of 1.44 and a melting point of 200 ° C., Japan A polyester copolymer (hereinafter abbreviated as “P4”) manufactured by Ester Co. was used. Moreover, the addition amount of the compatibilizing agent was changed to P1: P4: C1 = 89.8: 10: 0.2 (mass%). Otherwise, a polymer alloy (hereinafter abbreviated as “P5”) was obtained under the same conditions as in Example 1.

And other than that was carried out similarly to Example 1, and obtained the polylactic acid-type long fiber nonwoven fabric.
Table 1 shows the performance of the obtained nonwoven fabric.
Example 4
Compared to Example 1, the basis weight when collecting and depositing as a long fiber web was 126 g / m ² . Moreover, as conditions for carrying out the hot embossing of the obtained web, the surface temperature of both rolls was 95 degreeC, and the linear pressure was 30 kg / cm. Other than that was carried out similarly to Example 1, and obtained the polylactic acid-type long fiber nonwoven fabric.

Thereafter, the nonwoven fabric was passed through a needle punch machine in which a needle needle of RPD40 # was implanted, and needle punching was performed at a needle density of 45 times / cm ² to mechanically entangle the constituent fibers of the nonwoven fabric. Next, an acrylic binder resin solution was adhered so that the amount of adhesion (solid content) of the binder was 10% by mass with respect to the mass of the long fiber nonwoven fabric. Thereby, the polylactic acid-based long fiber nonwoven fabric of Example 4 was obtained. The basis weight of the obtained long fiber nonwoven fabric was 140 g / m ² .

(Comparative Example 1)
L-lactic acid / D-lactic acid = 98.6 / 1.4 mol% L-lactic acid / D-lactic acid copolymer having a melting point of 168 ° C. and MFR1 of 70 g / 10 min were weighed, and then an individual extruder. Melting was performed using a mold extruder, and spinning was performed at a spinning temperature of 210 ° C. under a single-hole discharge rate of 1.7 g / min so as to obtain a single-phase fiber cross section. After cooling the spun yarn with a known cooling device, it is subsequently pulverized at a traction speed of 5000 m / min with an air soccer installed under the spinneret, opened with a known fiber opening device, and moved. It was collected and deposited as a long fiber web on a screw conveyor. The single yarn fineness of the long fibers was 3.3 dtex. Next, this web was partially heat-welded through a partial heat-welding apparatus composed of an embossing roll having a roll temperature of 135 ° C. to obtain a polylactic acid-based long fiber nonwoven fabric having a basis weight of 100 g / m ² .
Table 1 shows the performance of the obtained nonwoven fabric.

(Comparative Example 2)
Compared to Comparative Example 1, the basis weight when collecting and depositing as a long fiber web was 126 g / m ² . Moreover, as conditions when carrying out the hot embossing of the obtained web, the surface temperature of both rolls was 100 degreeC, and the linear pressure was 30 kg / cm. Other than that was the same as Comparative Example 1 to obtain a polylactic acid-based long fiber nonwoven fabric.

Thereafter, the nonwoven fabric was passed through a needle punch machine in which a needle needle of RPD40 # was implanted, and needle punching was performed at a needle density of 45 times / cm ² to mechanically entangle the constituent fibers of the nonwoven fabric. Next, an acrylic binder resin solution was adhered so that the amount of adhesion (solid content) of the binder was 10% by mass with respect to the mass of the long fiber nonwoven fabric. Thereby, the polylactic acid-based long fiber nonwoven fabric of Comparative Example 2 was obtained. The basis weight of the obtained long fiber nonwoven fabric was 140 g / m ² .

  The long-fiber nonwoven fabrics obtained in Examples 1 to 4 were provided with practical mechanical strength and had a good strength retention at high temperatures as compared with Comparative Examples 1 and 2. In particular, since the elongation at high temperature is high, it can be expected to be used for molding into a specific shape by thermoforming, such as a primary base fabric of thermoforming carpet.

Claims (9)

A non-woven fabric formed by a spunbond method using a composite long fiber comprising a polylactic acid polymer (A) having a melting point of 150 ° C. or higher and a polymer alloy as constituent fibers,
The polymer alloy forms at least part of the fiber surface;
The polymer alloy contains the polylactic acid polymer (A), a polyester copolymer (B) having a melting point of 160 ° C. to 230 ° C., and a compatibilizing agent (C), The polylactic acid-based polymer (A) forms a sea component and the polyester copolymer (B) has a sea-island structure in which an island component is formed,
A polylactic acid-based long fiber nonwoven fabric, wherein the island component has a domain size in the range of 0.001 to 0.1 μm.   2. The polylactic acid-based length according to claim 1, wherein the polyester copolymer (B) is a crystalline resin and includes a terephthalic acid component, an ethylene glycol component, and a butanediol component. Fiber nonwoven fabric.   The composition ratio of the polylactic acid polymer (A) and the polyester copolymer (B) in the polymer alloy is (A) / (B) = 95/5 to 80/20 (mass%). The polylactic acid-based long fiber nonwoven fabric according to claim 1 or 2.   The composite long fiber is a core-sheath type composite long fiber in which the polylactic acid polymer (A) forms a core and the polymer alloy forms a sheath. The polylactic acid-based long fiber nonwoven fabric according to claim 1.   The compatibilizer (C) is one or more selected from an epoxy chain extender, an isocyanate chain extender, a carbodiimide chain extender, and a glycidyl ether chain extender. The polylactic acid-based long fiber nonwoven fabric according to any one of claims 1 to 4, characterized in that it is characterized in that   The content of the compatibilizing agent (C) with respect to the total amount of the polylactic acid polymer (A), the polyester copolymer (B) and the compatibilizing agent (C) is 0.01 to 1% by mass. The polylactic acid-based long fiber nonwoven fabric according to any one of claims 1 to 5.   The polylactic acid-based long fiber nonwoven fabric according to any one of claims 1 to 6, wherein the nonwoven fabrics are integrated by having a partial thermocompression bonding portion.   The polylactic acid-based long-fiber nonwoven fabric according to any one of claims 1 to 6, wherein the constituent fibers are entangled three-dimensionally and integrated to form a nonwoven fabric.   The polylactic acid-based long fiber nonwoven fabric according to claim 8, wherein the constituent fibers are bonded to each other at the contact portion with a binder resin.