JPH0748769A - Degradable nonwoven fabric and its production - Google Patents

Abstract

PURPOSE:To obtain a nonwoven fabric having excellent dimensional stability and disappearing by decomposing in natural environment when discarded after the use over a prescribed period and to provide a process for the production of the nonwoven fabric. CONSTITUTION:This decomposable nonwoven fabric is produced from a web formed out of a fiber of at least one kind of lactic acid-type polymer selected from among a poly(DL-lactic acid) containing >80mol% of L-lactic acid unit, a poly(DL-lactic acid) containing >80mol% of D-lactic acid unit, an (L-lactic acid)-hydroxycarboxylic acid copolymer containing >=70mol% of L-lactic acid unit and (D-lactic acid)-hydroxycarboxylic acid copolymer containing >=70mol% of D-lactic acid unit. The present invention also relates to a process for production of the nonwoven fabric.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a degradable nonwoven fabric and a method for producing the same. More specifically, the present invention relates to a degradable nonwoven fabric having excellent dimensional stability, which is obtained by binding or entanglement of a web composed of fibers containing a lactic acid-based polymer having a specific composition as a main component, and a method for producing the same.

[0002]

2. Description of the Related Art A non-woven fabric is a cloth-like material which is not made by knitting or weaving. More specifically, a cloth-like article formed by binding or entanglement of the constituent fibers of a so-called web in which fibrous substances form a lump but fibers are not bound or entangled with each other. It is a cloth-like material that is not knitted or woven.

Nonwoven fabrics have hitherto been widely used as clothing interlinings, carpets and other industrial materials. Fiber materials that make up the non-woven fabric include polyolefins such as polyethylene and polypropylene, aromatic polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), nylon 6, nylon 66,
Polyamides such as nylon 610 and celluloses such as rayon are used. Nonwoven fabrics using these polymers as raw materials and methods for producing the same are described in, for example, JP-A-59 / 59
It is described in JP-A-88961 and JP-A-59-94660.

However, all of these fiber materials hardly decompose in a natural environment or have a very low decomposition rate. Therefore, conventional non-woven fabrics made from these materials remain semi-permanently in the soil after use, for example, when they are buried. Also, when dumped in the ocean, it may damage the landscape and destroy the living environment of marine life, and waste treatment is a major social problem. In addition, incineration causes problems such as generation of toxic gas and destruction of the global environment, and also promotes deterioration of the incinerator, which causes a problem.

On the other hand, a non-woven fabric made of a bioabsorbable and hydrolyzable polymer as a fiber material has been developed.
For example, in JP-A-63-95041, a bioabsorbable polymer such as polyglycolic acid or glycolic acid-lactic acid copolymer is melt-spun to prepare a multifilament yarn, which is prepared from a random web obtained from the multifilamentary yarn. A medical pledget made of a non-woven fabric is disclosed. Then, as a production example of the non-woven fabric, a reduced viscosity (dissolved in a solvent mixed with 10 parts of phenol and 7 parts of trichlorophenol and heated at 190 ° C. for 3 minutes and then cooled to 30 ° C. (reduced viscosity ( Polyglycolic acid chips having η _SP / C) of 1.5 are melt-spun at 245 ° C. and drawn to make 12 denier 35 denier yarn, which is heat treated at 106 ° C. for 3 hours and A method is described in which a tube-shaped knit is formed, and a four-layered knit is needle-punched into a non-woven fabric whose stitches are hardly visible.

At present, one of the most popular methods for producing nonwoven fabrics is called the spunbond method, in which fibers obtained by melt-extruding a polymer are directly put on a screen belt or the like and made into a web. After that, it is a method of thermocompressing with a hot embossing roll to obtain a nonwoven fabric.

When a large amount of non-woven fabric is produced from polyglycolic acid by the spunbond method, the following problems occur. That is, the polyglycolic acid fiber melt-extruded from the extruder is an amorphous fiber having almost no crystal part, and the fiber is wound on a screen belt or the like and made into a web, and the web is pressed by a hot embossing roll. Sufficient crystallization does not occur by itself. Furthermore, if the polyglycolic acid fiber is left in an amorphous state for a long time, crystallization gradually progresses even at room temperature. Therefore, the nonwoven fabric obtained from the polyglycolic acid fiber produced by the spunbond method causes creases, wrinkles, and the like due to crystallization of polyglycolic acid during storage or use, which is a problem. Further, since polyglycolic acid has high rigidity, the nonwoven fabric obtained from the polyglycolic acid fiber is not necessarily a highly flexible nonwoven fabric, and its use is limited.

Similar to polyglycolic acid, polylactic acid is used as a degradable polymer. Nonwoven fabrics made from polylactic acid are improved in flexibility over nonwoven fabrics made from polyglycolic acid,
There are problems such as creases and wrinkles and dimensional stability.

Degradable surgical textiles derived from polylactic acid are known. For example, Japanese Examined Patent Publication No. 41-2734 discloses a filament of a lactic acid polymer having an intrinsic viscosity of at least 1.0 measured in a benzene solution of 0.1% by weight at 25 ° C.
Shrinkage rate of monofilament when soaked for 15 minutes is 15%
Disclosed is an absorbable surgical fiber product (filament) characterized by: Specifically, after poly (L-lactic acid) or poly (D-lactic acid) having the above-mentioned intrinsic viscosity is melt-spun, heat treatment is performed at 60 to 150 ° C. for 0.5 to 5 minutes under tension, and then under tension. A method for producing a filament suitable for a surgical suture having excellent tensile strength and a low shrinkage rate by cooling to room temperature is described. Since poly (L-lactic acid) or poly (D-lactic acid) has high crystallinity, heat treatment under tension is essential to improve dimensional stability and tensile strength of filaments obtained from them. It becomes the condition of.

On the other hand, the non-woven fabric does not require an extremely high tensile strength unlike the surgical suture, but rather requires excellent dimensional stability. Poly (L-lactic acid) or poly (D-lactic acid) for the purpose of improving the dimensional stability of the nonwoven fabric
When heat-treating a non-woven fabric manufactured from
Instead of heating the filaments in a one-dimensional manner under tension as in the method disclosed in Japanese Patent No. 2734, it is necessary to heat-treat the nonwoven fabric in a two-dimensionally even state. This is not a preferable method because it is complicated and requires a large scale. Even if the non-woven fabric is heat-treated without hesitation due to the technical complexity,
The problem of wrinkles and the like is unavoidable, and sometimes the nonwoven fabric is even broken, which is not preferable. In addition, poly (L-lactic acid)
Alternatively, since poly (D-lactic acid) has high crystallinity, it is difficult to add a plasticizer or the like to plasticize it and impart flexibility to the molded product.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a non-woven fabric which decomposes and disappears in a natural environment when it is discarded after being used for a predetermined period of time and a method for producing the same. Especially. Another object of the present invention is to provide a non-woven fabric which has good dimensional stability and is free from creases, wrinkles and the like, and a method for producing the same.

[0012]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have found that a web is formed from fibers of a lactic acid-based polymer having a specific composition and the web is used as a material. Disintegrates in a natural environment,
Moreover, they have found that a non-woven fabric having excellent dimensional stability can be obtained, and arrived at the present invention.

That is, the present invention is a degradable nonwoven fabric obtained by forming a web from fibers of a lactic acid-based polymer, wherein the lactic acid-based polymer comprises L-lactic acid units 80
Poly (DL-lactic acid) having more than mol%, D-lactic acid unit having more than 80 mol%, poly (DL-lactic acid), having more than 70 mol% of L-lactic acid unit (L-lactic acid) -hydroxycarboxylic acid Copolymer and at least one lactic acid-based polymer (polymer A) selected from (D-lactic acid) -hydroxycarboxylic acid copolymer having D-lactic acid unit in an amount of 70 mol% or more, and a degradable non-woven fabric, and the same It is a manufacturing method.

In a preferred embodiment of the present invention, the lactic acid-based polymer fiber is a fiber obtained from the polymer A, and
The molar ratio of L-lactic acid unit to D-lactic acid unit is 1: 4 to 4:
1, poly (DL-lactic acid), (DL-lactic acid) -hydroxycarboxylic acid copolymer, (L-lactic acid) -hydroxycarboxylic acid copolymer having at least 30 mol% of hydroxycarboxylic acid units, and at least hydroxycarboxylic acid units. A degradable non-woven fabric, which is a mixed fiber with a fiber obtained from at least one low-temperature thermoplastic lactic acid-based polymer (polymer B) selected from (D-lactic acid) -hydroxycarboxylic acid copolymer having 30 mol% And its manufacturing method.

The degradable nonwoven fabric of the present invention is formed by spinning a lactic acid-based polymer having a specific composition to form a web, and the web is subjected to, for example, a thermal bond method, a needle punch method, a stitch bond method, a jet bond method, a resin bond. It can be obtained by combining by a method or the like. The thermal bond method is preferred.

The present invention will be described in detail below. In the present invention, the molecular weight of a polymer refers to the weight average molecular weight unless otherwise specified.

In the present invention, the lactic acid-based polymer used as the fiber material is poly (DL-lactic acid) having a specific amount of L-lactic acid unit and D-lactic acid unit as repeating units in the molecular structure, or in the molecular structure. Is a lactic acid-hydroxycarboxylic acid copolymer having a specific amount of lactic acid unit and another hydroxycarboxylic acid unit as a repeating unit. Further, in the present invention, poly (DL-lactic acid) used as a fiber material is polylactic acid having an L-lactic acid unit and a D-lactic acid unit as repeating units in its molecular structure, and L-lactic acid Poly (L-lactic acid) consisting only of units
And a polymer having a different structure from poly (D-lactic acid) consisting of D-lactic acid units only.

Specifically, as polylactic acid, poly (DL-lactic acid) having L-lactic acid units in excess of 80 mol%, poly (DL-lactic acid) having D-lactic acid units in excess of 80 mol%, and those A mixture may be mentioned. As a copolymer of lactic acid and other hydroxycarboxylic acid, L-lactic acid unit has 70 mol% or more (L-lactic acid) -hydroxycarboxylic acid copolymer, and D-lactic acid unit has 70 mol% or more (D-lactic acid). -Hydroxycarboxylic acid copolymers and mixtures thereof.

The lactic acid-based polymer having the above composition is L-
The crystallinity is lower than that of poly (L-lactic acid) consisting only of lactic acid units or poly (D-lactic acid) consisting only of D-lactic acid units,
The transition temperature from the amorphous region to the crystalline region is high by about 10 to 15 ° C. Therefore, the above-mentioned lactic acid-based polymer maintains its initial dimensions for a long period of time even when complicated operations such as heat treatment and annealing are performed when it is melt-spun and a nonwoven fabric is produced from the web, and it shrinks or wrinkles. The nonwoven fabric will not be deformed due to the occurrence of such as. Furthermore, since heat treatment can impart appropriate crystallinity, it is possible to improve the strength of the nonwoven fabric while minimizing the occurrence of wrinkles, creases, and the like. Further, since the lactic acid-based polymer having the above composition is easily plasticized by the plasticizer, it is easy to obtain a nonwoven fabric having a high flexibility. Moreover, since it is a polymer having a melting point, the fibers can be fused by heating and compression, which is suitable as a material for nonwoven fabric.

The hydroxycarboxylic acid which is a comonomer of the above-mentioned copolymer of lactic acid and other hydroxycarboxylic acid includes glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid,
Examples thereof include hydroxyheptanoic acid. Of these comonomers, glycolic acid and hydroxycaproic acid are preferred.

The lactic acid-based polymer used in the present invention is a method in which L-lactic acid and D-lactic acid or DL-lactic acid are dehydrated and polycondensed, or L-lactic acid, D-lactic acid or DL-lactic acid and other hydroxycarboxylic acid are dehydrated and co-dehydrated. A method of polycondensation, or
It is obtained by a method of ring-opening copolymerization of L-lactide, D-lactide or DL-lactide, which is a cyclic dimer of lactic acids, and a cyclic monomer or cyclic dimer of another hydroxycarboxylic acid.

In the case of dehydration polycondensation, the above-mentioned lactic acid or the above-mentioned lactic acid and another hydroxycarboxylic acid are preferably subjected to azeotropic dehydration polycondensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably distilled by azeotropic distillation. Polycondensation is carried out by a method of removing water from the solvent taken out and returning the solvent in a substantially anhydrous state to the reaction system.

In the case of ring-opening polymerization, L-lactide, which is a cyclic dimer of L-lactic acid, and D, which is a cyclic dimer of D-lactic acid.
-Lactide, DL-lactide which is an equimolar mixture of L-lactide and D-lactide, meso-lactide which is a cyclic dimer of DL-lactic acid, or these lactides and cyclic esters of other hydroxycarboxylic acids. Ring polymerize. Examples of other cyclic ester of hydroxycarboxylic acid include glycolide, which is a dimer of glycolic acid, and β-propiolactone, β-butyrolactone, δ-valerolactone, ε-caprolactone, and the like. Of these,
Glycolide and ε-caprolactone are preferred. When producing poly (DL-lactic acid), L-lactide and D-lactide are mixed in a specific ratio, DL-lactide is used, or L-lactide and / or D is used.
It is preferable to reduce the crystallinity of the obtained polylactic acid to some extent by, for example, mixing lactide and DL-lactide in a specific ratio.

In any of the polymerization methods, in order to obtain a lactic acid-based polymer having the above composition, a monomer having a composition substantially equal to the polymer composition may be used. In particular,
For example, in the case of producing poly (DL-lactic acid) having 80 mol% of L-lactic acid unit, a monomer obtained by mixing 80 mol% of L-lactic acid and 20 mol% of D-lactic acid is used, or
60 mol% of L-lactic acid and DL-lactic acid (D / L = 50/5
0) Dehydration polycondensation may be performed using a monomer in which 40 mol% is mixed. L-lactic acid is L-lactide, D-lactic acid is D-
Similar polymers can be obtained by ring-opening polymerization by replacing lactide and DL-lactic acid with DL-lactide. Further, in the case of producing a (L-lactic acid) -glycolic acid copolymer having 70 mol% of L-lactic acid unit, 70% of L-lactic acid is used.
Dehydration polycondensation may be performed using a monomer obtained by mixing mol% and glycolic acid 30 mol%. The same polymer can be obtained by ring-opening polymerization by replacing L-lactic acid with L-lactide and glycolic acid with glycolide.

100 L-lactic acid units or D-lactic acid units
%, The melting point of poly (L-lactic acid) or poly (D-lactic acid) is about 180 ° C., and the transition temperature (Tc) from the amorphous state to the crystalline state is about 90 ° C. The melting point of the poly (DL-lactic acid) obtained by the above ring-opening polymerization is in the range of about 3 to 5 ° C. per 1% content as the L-lactic acid unit or the D-lactic acid unit increases from zero to 20%. Drop,
Tc increases by about 1 to 3 ° C per 1% of content. Surprisingly, in particular, poly (DL-lactic acid) obtained by the dehydration polycondensation method contains only about 1% of L-lactic acid units (D-lactic acid).
Lactic acid unit is about 99%), or D-lactic acid unit is only 1
% (L-lactic acid unit is about 99%), the melting point is lower than that of poly (L-lactic acid) or poly (D-lactic acid) by about 10 to 20 ° C., and Tc is about 10%. 1
It increases by about 5 ° C. In addition, the highest ultimate crystallinity is about 30-
It stops at about 40%, and poly (L-lactic acid) or poly (D)
-Lactic acid) is lower than the highest achieved crystallinity of 50 to 60%. Therefore, the non-woven fabric manufactured from poly (DL-lactic acid) fiber has good dimensional stability over time without heat treatment or the like. In addition, it is suitable as a material for non-woven fabric because it can be improved in strength by heat treatment. The same applies to the lactic acid-based copolymer having the above composition.

L-lactic acid unit and D in poly (DL-lactic acid)
-The composition of lactic acid units can be determined by, for example, a method of measuring with an enzyme. That is, after hydrolyzing poly (DL-lactic acid) with an alkaline aqueous solution, L-lactic acid in the obtained solution is allowed to act with L-lactate dehydrogenase and nicotinamide adenine dinucleotide (hereinafter, referred to as NAD), and lactic acid causes pyruvin. The amount of NADH, which is a reduced product of NAD, generated when it was oxidized by acid was measured by L
-Lactic acid was quantified, while D-lactic acid was similarly measured by D-
In this method, lactate dehydrogenase is allowed to act on NAD to quantify the amount of D-lactic acid, and the ratio between L-lactic acid and D-lactic acid is studied to obtain the value. On the other hand, it is confirmed that L-lactic acid itself is not hydrolyzed in an alkaline aqueous solution to cause racemization. L-lactic acid units or D-lactic acid units in lactic acid-hydroxycarboxylic acid can be quantified in the same manner as above.

The molecular weight of the lactic acid-based polymer used in the degradable nonwoven fabric of the present invention is not particularly limited, but if the molecular weight is lowered, spinning becomes difficult, or even if spinning is possible, the strength of the obtained fiber is Is reduced. Further, if the molecular weight is high, the processability tends to be low, and spinning tends to be difficult.
Considering these points, the preferable molecular weight is selected from the range of 10,000 or more and 1,000,000 or less. A particularly preferable molecular weight range is 30,000 or more and 500,000 or less.

The lactic acid-based polymer that constitutes the degradable nonwoven fabric of the present invention is hydrolyzed not only in water or soil but also by moisture (humidity) in the air. Is also hydrolyzed by moisture in the air and rainwater. The rate of hydrolysis depends on the molecular weight of the polymer and the copolymer composition. Therefore, the optimum molecular weight and copolymer composition of the lactic acid-based polymer used for the degradable nonwoven fabric of the present invention is determined from the above range of composition based on the hydrolyzable data regarding the lactic acid-based polymer in accordance with the longest use period in the application of the nonwoven fabric. It is decided in consideration.

For example, based on the findings of the present inventors, poly (DL-lactic acid) of the above composition having a molecular weight of 150,000 or more is used as a material fiber when the usage period is six months or more. Is good. When the usage period is about one month, poly (DL-lactic acid) having the above-mentioned composition and having a molecular weight of 50,000 or more is preferably used.

As a spinning method for the raw material fibers, a known spinning method is applied. For example, a melt spinning method in which a lactic acid-based polymer is melt-spun using an extruder, a wet spinning method in which a lactic acid-based polymer is dissolved in a solvent to form a solution, and the solution is discharged from a nozzle into a poor solvent, the solution A dry spinning method or the like is used in which the is discharged from a nozzle into a dry gas. Examples of the solvent used in the wet spinning method or the dry spinning method include toluene, xylene, chloroform, methylene chloride and the like. Moreover, methanol, hexane, acetone, etc. can be illustrated as a poor solvent used for a wet spinning method.

For the melt spinning method, known extruders such as a single screw extruder and a twin screw extruder can be used. When the extrusion temperature is low, it is difficult to obtain extrusion stability, and overload tends to occur. If the extrusion temperature is high, the thermal decomposition of the polymer becomes severe, resulting in a decrease in molecular weight, a decrease in strength, coloration and the like. Considering these points, for example, the extrusion temperature of the lactic acid-based polymer is preferably in the range of 100 to 280 ° C., more preferably 1
It is in the range of 30 to 250 ° C. Extruder base (nozzle)
The caliber is appropriately determined depending on the relationship between the required fiber diameter (thread diameter) and the discharge speed or take-up speed of the extruder, but is preferably about 0.1 to 3.0 mm.

In any spinning method, it is not always necessary to stretch the fiber after spinning, but when it is stretched, it is stretched 1.1 to 10 times, preferably 2 to 8 times. The stretching temperature is selected from the range of 60 to 210 ° C. depending on the type of lactic acid polymer used. The preferable fiber diameter of the fiber is 0.5 to 40 denier. The preferred fiber length is 0.5 to 30 cm.

A mass of fibers called a web is formed from the fibers of the obtained lactic acid-based polymer. In the state of the web, the fibers are not bonded to each other, so it cannot be said to be a nonwoven fabric as it is. A known method can be used as the method for producing the web and is not particularly limited. For example, a card type using a flat card machine, a roller card machine, a garnet machine, or the like, and a melt blown type may be used. Further, when spinning a lactic acid-based polymer, a high-speed air may be blown when the fibers come out of a nozzle of a spinning machine, and a spun-bond type in which a web is formed by collecting on a perforated conveyor that is perpendicular to the air flow.

A known method can be used to obtain the degradable nonwoven fabric of the present invention from a web made of lactic acid-based polymer fibers. For example, there are a needle punch method of entanglement with a needle, a stitch bond method of entanglement with a thread, a jet bond method of entanglement with a water stream, a thermal bond method of adhering by heat, and a resin bond method utilizing adhesion of a resin. Among these, the following methods (1) and (2) are preferred. (1) A method of compressing a web of lactic acid-based polymer fibers in a temperature range of 71 ° C to less than the melting point. The non-woven fabric obtained by this method has little deformation and shrinkage for a long period of time without being subjected to any particular heat treatment as described above. You may heat-process for the purpose of improving the strength of a nonwoven fabric. The heat treatment temperature is preferably 80 to 140 ° C. If the temperature is lower than 80 ° C, sufficient crystallization is unlikely to occur, and improvement in strength cannot be expected. 14
If the temperature exceeds 0 ° C, the non-woven fabric will soften or melt, causing deformation.
It is not preferable because it is easily damaged. It is particularly preferably 90 to 130 ° C. (2) A method in which a main web of lactic acid-based polymer fibers is mixed with a web of low-temperature thermoplastic lactic acid-based polymer fibers that melts or softens at a temperature of 70 ° C. or lower at a predetermined ratio and compressed in a temperature range of room temperature to 70 ° C. .

The web of lactic acid-based polymer fibers preferably used in the method (1) above and the main web of lactic acid-based polymer fibers preferably used in the method (2) above are:
Poly (DL-lactic acid) fiber having more than 80 mol% of L-lactic acid unit or D-lactic acid unit, (L-lactic acid) -hydroxycarboxylic acid copolymer fiber having at least 70 mol% of L-lactic acid unit, and D-lactic acid Have a unit of 70 mol% or more (D
A web made from at least one degradable fiber selected from (lactic acid) -hydroxycarboxylic acid copolymer fibers.

In the above method (2), a web of low-temperature thermoplastic lactic acid polymer fibers which melts or softens at a temperature of 70 ° C. or lower is added to and mixed with the main web of lactic acid polymer fibers used in the method (1). Then, the web of the low-temperature thermoplastic lactic acid-based polymer fibers is melted and softened in the temperature range of room temperature to 70 ° C. to bond the main webs together. As a preferable web of low-temperature thermoplastic lactic acid-based polymer fibers used in this method, poly (DL-lactic acid) and L-lactic acid unit in which the molar ratio of L-lactic acid unit and D-lactic acid unit is 1: 4 to 4: 1. (DL-lactic acid) -hydroxycarboxylic acid copolymer having an arbitrary molar ratio of OH to D-lactic acid unit, and having at least 30 mol% of hydroxycarboxylic acid units (D-lactic acid)
-Hydroxycarboxylic acid copolymers, (L-lactic acid) -hydroxycarboxylic acid copolymers having at least 30 mol% of hydroxycarboxylic acid units, and webs of fibers obtained from lactic acid-based polymers based on mixtures thereof. . As these (DL-lactic acid) -hydroxycarboxylic acid copolymers, (D-lactic acid) or (L-lactic acid) -hydroxycarboxylic acid copolymers having at least 30 mol% of hydroxycarboxylic acid units,
-Lactic acid), (L-lactic acid) or (D-lactic acid) with glycolic acid or hydroxycaproic acid are preferred.

The low-temperature thermoplastic lactic acid-based polymer, which is a material for the web of the low-temperature thermoplastic lactic acid-based polymer fibers, is obtained by dehydration polycondensation or ring-opening polymerization using monomers having compositions substantially equal to the respective polymer compositions. . For example, the molar ratio of L-lactic acid unit to D-lactic acid unit is 1: 4.
When poly (DL-lactic acid) is produced, L-lactic acid is mixed with 20 mol% and D-lactic acid is mixed with 80 mol% for dehydration polycondensation, or L-lactide is mixed with 20 mol%. D
It is obtained by ring-opening copolymerization by mixing 80 mol% of lactide. Further, in the case of producing a (D-lactic acid) -hydroxycaproic acid copolymer having 30 mol% of hydroxycaproic acid units, 70 mol% of (D-lactic acid) and 30 mol% of hydroxycaproic acid are mixed to perform dehydration polycondensation. Or 70 mol% of D-lactide and 30 mol% of ε-caprolactone are mixed and subjected to ring-opening polymerization.

In the case of the above method (2), it is preferable that the lactic acid-based polymer fiber as the main web is stretched and heat-treated before being mixed with the low temperature thermoplastic lactic acid-based polymer fiber. This makes it possible to melt only the low-temperature thermoplastic lactic acid-based polymer fibers within a compression temperature range of room temperature to 70 ° C. when the mixed web is thermally compressed.

In any of the above methods (1) and (2), when the compression temperature is low, the fusion property of the fibers is deteriorated, and when it is high, a hard sheet is formed, and a soft nonwoven fabric having an appropriate texture is obtained. It will be difficult. From this viewpoint, it is preferable to set the compression temperature in the above range. Further, in any method, the compression pressure is 1.1 to 200 kg /
It is selected from the range of cm ² .

By mixing and using this web of low-temperature thermoplastic lactic acid-based polymer fibers, it is possible to lower the heating compression temperature. In addition, since only the web of low-temperature thermoplastic lactic acid-based polymer fibers is melted and the main web is not melted, the resulting non-woven fabric is advantageous in that the non-woven fabric is rich in flexibility and the non-woven fabric feels good.

The low-temperature thermoplastic lactic acid polymer fiber web can be spun and made into a web in the same manner as the main web. When the amount of the low-temperature thermoplastic lactic acid-based polymer fiber web added is large, the resulting nonwoven fabric tends to be hard and the strength of the nonwoven fabric tends to be low. On the other hand, if the amount decreases, the adhesion of the main web becomes insufficient and it becomes difficult to obtain a good nonwoven fabric. From this viewpoint, the amount of the web of low-temperature thermoplastic lactic acid-based polymer fibers is 10 to 60% by weight based on the total weight of the entire web.
Is preferably selected from the range. More preferably, it is 20 to 40% by weight.

In the present invention, when the non-woven fabric is produced by the above method (2), the web may be mixed as described above, or the fiber used as the material for the main web may be made of the low temperature thermoplastic lactic acid polymer. After mixing the fibers, the mixed fibers may be made into a web, and the fibers may be bonded or entangled to form a nonwoven fabric.

The lactic acid-based polymer having the above composition used in the present invention is easily plasticized by a plasticizer. Therefore, it is preferable to add a plasticizer to the lactic acid-based polymer in order to obtain a non-woven fabric having an improved texture and flexibility. As a plasticizer, phthalic acid derivatives such as di-n-octyl phthalate, di-2-ethylhexyl phthalate, dibenzyl phthalate, diisodecyl phthalate, ditridecyl phthalate, diundecyl phthalate, isophthalic acid derivatives such as diisooctyl phthalate, di- adipic acid derivatives such as n-butyl adipate and dioctyl adipate,
Maleic acid derivatives such as di-n-butyl maleate, tri-
Citric acid derivatives such as n-butyl citrate, itaconic acid derivatives such as monobutyl itaconate, oleic acid derivatives such as butyl oleate, ricinoleic acid derivatives such as glycerin monoricinoleate, tricresyl phosphate, trixylenyl phosphate Examples thereof include low molecular weight compounds such as phosphoric acid esters, acetic acid derivatives such as triacetin (glycerin triacetate), lactic acid oligomers having a degree of polymerization of about 2 to 10, polymeric plasticizers such as polyethylene adipate and polyacrylate. Among the above plasticizers, preferred plasticizers include triacetin and lactic acid oligomers having a degree of polymerization of about 2 to 10. The content of the plasticizer is preferably 1 to 35% by weight, and particularly preferably 5 to 15% by weight, based on the lactic acid polymer.

Further, according to the knowledge of the present inventors, when the lactic acid-based polymer is used outdoors, the strength of the lactic acid-based polymer decreases obviously faster than when it is used indoors, in a dark place, or in vivo. It is known that phenomena such as embrittlement and destruction can occur earlier than expected. In order to suppress or prevent this undesired phenomenon, the base fiber of the degradable nonwoven fabric of the present invention is preferably a lactic acid-based polymer as a main component to which an ultraviolet absorber or a light stabilizer is added and mixed.

The ultraviolet absorber absorbs ultraviolet rays having a destructive high energy in the wavelength range of 250 to 380 nm, changes to a non-destructive wavelength and re-radiates, and the light stabilizer is not always required. It does not absorb ultraviolet rays,
Photodegradation of a material is suppressed by some mechanism by decomposing hydroperoxide, which is a photodegradation initiator, in a non-radical manner, trapping and removing radicals generated by photodecomposition. The distinction between UV absorbers and light stabilizers may not be clear.

The ultraviolet absorbers and light stabilizers that can be used in the present invention include salicylic acid derivatives such as phenyl salicylate and p-tert-butylphenyl salicylate,

2,4-dihydroxybenzophenone, 2
-Hydroxy-4-methoxybenzophenone, 2,2 '
-Benzophenones such as dihydroxy-4-methoxybenzophenone,

2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'- Hydroxy-3'-ter
t-Butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'
-Di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5'-ter
benzotriazoles such as t-octylphenyl) benzotriazole,

Nickel-containing organic light stabilizers, barium, sodium, phosphorus-containing organic / inorganic composites, semicarbazone light stabilizers, zinc oxide UV stabilizers and synergists known under the trade name Sanshade, etc.

Bis (2,2,6,6-tetramethyl-4
-Piperidyl) sebacate, bis (1,2,2,6,6)
-Pentamethyl-4-piperidyl) sebacate, dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate of succinate,

Poly [6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-
Diyl] [(2,2,6,6-tetramethyl-4-piperidyl) imino] hexamethylene [(2,2,6,6-
Tetramethyl-4-piperidyl) imino], 1, 2,
3,4-butanetetracarboxylic acid and 1,2,2,6,6
-Condensate of pentamethyl-4-piperidinol and tridecyl alcohol, condensate of 1,2,3,4-butanetetracarboxylic acid and 2,2,6,6-tetramethyl-4-piperidinol and tridecyl alcohol , 1, 2,
3,4-butanetetracarboxylic acid, 2,2,6,6-tetramethyl-4-piperidinol and β, β, β ′, β ′
-Condensation product with tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (5,5) undecane] diethanol, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, Hindered amines such as 2,2,6,6-tetramethyl-4-piperidyl methacrylate may be mentioned.

When the amount of the ultraviolet absorber and / or the light stabilizer used in the present invention is decreased, the effect of suppressing the promotion of decomposition when the nonwoven fabric is used outdoors is decreased, and when it is increased, the lactic acid-based polymer is originally added. It tends to impair the physical properties of. From this viewpoint, the amount of the ultraviolet absorber and / or the light stabilizer added is 0.00 with respect to the lactic acid-based polymer.
1-5% by weight is preferred. More preferably 0.01-
It is 2% by weight.

As a method of mixing the ultraviolet absorber and / or the light stabilizer with the lactic acid-based polymer, the lactic acid-based polymer is mixed with chloroform, methylene chloride, benzene, toluene,
Dissolve in a solvent such as xylene, dimethylformamide, dimethylsulfoxide, dimethylimidazolidinone,
Alternatively, a method of heating and melting a lactic acid-based polymer at 100 to 280 ° C. and adding and mixing a predetermined amount of an ultraviolet absorber or a light stabilizer can be mentioned.

The lactic acid-based polymer fiber used in the present invention is not only a fiber made of a lactic acid-based polymer alone, a fiber of a lactic acid-based polymer composition obtained by mixing a lactic acid-based polymer with a plasticizer, an ultraviolet absorber and a light stabilizer, It may be a fiber of a lactic acid-based polymer in which a heat stabilizer, a lubricant, an antioxidant and the like are blended if necessary.

[0055]

EXAMPLES The present invention will be described in more detail below with reference to examples. In addition, L-lactic acid unit and D- in polylactic acid
The composition ratio with the lactic acid unit and the composition ratio between the lactic acid unit in the lactic acid-hydroxycarboxylic acid copolymer and the hydroxycarboxylic acid unit other than lactic acid were measured by the following methods.

<Measurement Method of Composition Ratio of L-Lactic Acid Unit and D-Lactic Acid Unit in Polylactic Acid> The polymer was hydrolyzed by keeping it in a 5N aqueous solution of sodium hydroxide at 60 ° C. for 10 hours, and in the resulting solution. L-lactic acid is reacted with L-lactate dehydrogenase and nicotinamide adenine dinucleotide (hereinafter abbreviated as NAD), and the amount of NADH, which is a reduced form of NAD produced when lactic acid is oxidized to pyruvate, is measured by absorption spectrometry. To determine the amount of L-lactic acid. On the other hand, with respect to D-lactic acid, similarly, D-lactic acid dehydrogenase and NAD are allowed to act to determine the amount of D-lactic acid, and the ratio of L-lactic acid and D-lactic acid is calculated. Also, L-lactic acid itself is held in a 5N sodium hydroxide aqueous solution for 10 hours to confirm that racemization of lactic acid does not occur under hydrolysis conditions.

<Measurement Method of Composition Ratio of Lactic Acid Unit in Lactic Acid-Hydroxycarboxylic Acid Copolymer and Hydroxycarboxylic Acid Unit Other Than Lactic Acid> The copolymer was dissolved in deuterated chloroform to measure nuclear magnetic resonance (NMR) spectrum. It is determined by the intensity ratio of peaks derived from the structures of both units.

<Production Example of Lactic Acid Polymer> Production Example 1 L-lactide, lauryl alcohol as a molecular weight modifier, and stannous octoate as a catalyst are added to a glass reaction vessel whose surface is treated with silane, as shown in Table 1. The container was charged in the amount shown, and the inside of the container was degassed under reduced pressure and dried overnight. The reaction vessel was sealed under reduced pressure, heated to the temperature shown in [Table 1], and polymerized for a predetermined time. After completion of the reaction, the contents of the reaction vessel were dissolved in 20 volumes of chloroform, and the solution was poured into 5 volumes of hexane. The precipitated polymer was recovered and dried to obtain polylactic acid. The obtained polylactic acid is called P-1. The molecular weight of the obtained P-1 was measured using a gel permeation chromatography method (hereinafter referred to as GPC) using chloroform as a solvent, and calculated in terms of polystyrene. In addition, the melting point and glass transition point (Tg) of P-1 were measured using a differential scanning calorimeter (DSC). P-1 polymerization conditions, and
Table 1 shows the molecular weight of P-1, the composition ratio of the L-lactic acid unit and the D-lactic acid unit (hereinafter referred to as the copolymer composition), the melting point and the glass transition point (Tg).

Production Examples 2 to 7 L-lactide, DL-lactide (molar ratio of D-form / L-form; 50/50) and / or caprolactone, lauryl alcohol as a molecular weight regulator, and octanoic acid primary catalyst Lactic acid-based polymers P-2 to P-2 were prepared in the same manner as in Production Example 1 except that tin was charged in the amounts shown in [Table 1] and reacted at the polymerization temperature shown in [Table 1] for the time shown in [Table 1]. P-7 was obtained. The molecular weight of the obtained lactic acid-based polymer, the composition ratio of L-lactic acid unit, D-lactic acid unit and hydroxycarboxylic acid unit (hereinafter, referred to as copolymer composition), melting point and Tg were measured in the same manner as in Production Example 1. . The polymerization conditions and measurement results of the lactic acid-based polymer are shown in [Table 1].

[0060]

[Table 1]

Production Example 8 L-lactic acid in the amount shown in [Table 2] was placed in a reactor and heated to 150 ° C.
/ 50mmHg After distilling water while stirring for 3 hours, 0.06 parts by weight of tin powder was added, and 150 ° C / 30mmH
The mixture was stirred at g for a further 2 hours for oligomerization. 0.29 parts by weight of tin powder and diphenyl ether 21 were added to this oligomer.
1 part by weight was added to carry out an azeotropic dehydration reaction at 150 ° C./35 mmHg, the distilled water and the solvent were separated by a water separator, and only the solvent was returned to the reactor. After 2 hours, the organic solvent returned to the reactor was passed through a column packed with 46 parts by weight of molecular sieve 3A and then returned to the reactor at 150 ° C. /
The reaction was carried out at 35 mmHg for 40 hours to obtain a polylactic acid solution. After 440 parts by weight of dehydrated diphenyl ether was added to this solution to dilute it, the solution was cooled to 40 ° C., and the precipitated crystals were filtered, washed with 100 parts by weight of n-hexane three times, and dried at 60 ° C./50 mmHg. 0.5 of this powder
120 parts by weight of N-hydrochloric acid and 120 parts by weight of ethanol were added, and the mixture was stirred at 35 ° C for 1 hour and then filtered, 60 ° C / 50m.
It was dried at mHg to obtain a lactic acid-based polymer P-8. The molecular weight, copolymer composition, melting point and Tg of the obtained lactic acid-based polymer were measured in the same manner as in Production Example 1, and the measurement results are shown in [Table 2]. Although only L-lactic acid was used as the raw material, the polymer produced contained 1% D-lactic acid units.

Production Examples 9 to 10 L-lactic acid and DL-lactic acid (D-form / L) in the amounts shown in Table 2
-Mole ratio of isomer: 50/50) and / or lactic acid-based polymers P-9 and P-10 were obtained in the same manner as in Production Example 8 except that glycolic acid was used. The molecular weight, copolymer composition, melting point and Tg of the obtained lactic acid-based polymer were measured in the same manner as in Production Example 1, and the results are shown in [Table 2].

[0063]

[Table 2]

<Production Example of Plasticizer> Production Example 11 1.0 kg of an aqueous lactic acid solution (concentration 87% by weight) was added to 1.8 kg of L-lactide placed in a reactor, and heated at 100 ° C. for 2 hours. When cooled, a viscous transparent liquid was obtained at room temperature. The oligomer was dissolved in chloroform and the degree of polymerization distribution was measured by gel permeation chromatography. As a result, lactic acid and a lactic acid oligomer were contained. The average degree of polymerization was 2.8. Hereinafter referred to as LA oligomer.

Examples 1 to 7, Comparative Examples 1 to 6 The lactic acid polymers P-1 to P-6 and P-8 to P-10 obtained in Production Examples 1 to 6 and 8 to 10 were used as plasticizers. Commercially available triacetin or LA obtained in Production Example 11
2- (2'-hydroxy-5'-methylphenyl) benzotriazole as an ultraviolet absorber was added as an ultraviolet absorber in the amounts shown in [Table 3] and [Table 4], respectively, and mixed, and then a small screw type extruder was used. Melt-extruded and spun under the conditions shown in [Table 3] and [Table 4]. Comparative Example 1
Then, spinning was tried under the same conditions as in Example 1, but the polymer was clogged in the screw, and extrusion was impossible. The obtained lactic acid-based polymer fiber was scraped on a screen to form a random web, which was compressed with a hot roll under the conditions shown in [Table 3] and [Table 4] to obtain a degradable nonwoven fabric. The resulting degradable non-woven fabric still retains the shape of the fiber, and retains a cloth-like form that is distinctly different from the film formed by melting, grasping the front and back of the non-woven fabric with the fingers of both hands, and in the direction perpendicular to the cloth surface. Even if I pulled it to, it didn't come loose or lose its shape.

Examples 1-2, 5-7 and Comparative Example 2-
The nonwoven fabric (10 × 10 cm) obtained in Nos. 3 and 5 to 6 was sandwiched between two iron plates having a thickness of 5 mm, and heat-treated at the temperature shown in [Table 3] for 10 minutes. As a result, the non-woven fabrics obtained in the examples were not observed creases and deformations, whereas the non-woven fabrics obtained in the comparative examples were creases and deformations observed, and further softening and structural change due to melting were observed. Admitted.
1 x 1 non-heat treated and heat treated non-woven
It was cut to 0 cm, and the breaking strength was measured at room temperature using a tensile tester at a chuck distance of 4 cm and a pulling speed of 10 mm / min. The strength improvement rate (%) was calculated by dividing the breaking strength of the heat-treated nonwoven fabric by the breaking strength of the non-heat treated nonwoven fabric. The obtained results are shown in [Table 3] and [Table 4].

[0067]

[Table 3]

[0068]

[Table 4]

<Evaluation of Appearance of Nonwoven Fabric> Immediately after production and after being left outdoors for one month, the same appearance inspection as above is carried out. The front and back of the nonwoven fabric are grasped by fingers of both hands and pulled in a direction perpendicular to the cloth surface. Even if it was not distorted or the shape was not broken, it was evaluated as good, and the results are shown in [Table 3] and [Table 4].
Shown inside.

<Evaluation of Degradability of Nonwoven Fabric> The obtained degradable nonwoven fabric was buried in soil for 18 months, allowed to stand and then dissolved in chloroform, and the molecular weight in terms of polystyrene was measured by GPC method. Was calculated, the molecular weight retention rate was calculated by the following formula, and the degradability was evaluated. The obtained results are shown in [Table 3]. DW (%) = 100 W ₁ / W _{0 In the} above formula, DW: molecular weight retention rate (%) W ₀ : molecular weight immediately before production W ₁ : molecular weight after leaving in soil for 18 months after production The mark * in 3] indicates that the decomposition of the non-woven fabric is remarkable and the measurement of the molecular weight is difficult.

Preparation Examples 1 to 6 Lactic acid-based polymers P-2 obtained in Production Examples 2 and 5 to 9
And P-5 to P-9, as an ultraviolet absorber 2-
(2'-Hydroxy-5'-methylphenyl) benzotriazole was added in the amounts shown in [Table 5], and melt extrusion was performed using a screw type small extruder under the conditions shown in [Table 5]. Polymer fibers F-1 to F-6 were obtained. In Preparation Examples 1 to 3, stretching was performed using a continuous stretching machine, and then heat treatment was performed by continuously passing between hot plates having a predetermined temperature. The stretching conditions and heat treatment conditions are shown in [Table 5].

[0072]

[Table 5]

Examples 8 to 10 Lactic acid-based polymer fibers F-1 to F obtained in Preparation Examples 1 to 3
-3 cut into short fibers having a length of about 5 cm, and lactic acid-based polymer fibers F-4 to F-6 obtained in Preparation Examples 4 to 6 cut into short fibers having a length of about 4 cm. After mixing and stirring at a weight ratio shown in [Table 6] to form a random web, hot pressing was performed under the conditions shown in [Table 6] to obtain a degradable nonwoven fabric. The properties of the obtained degradable nonwoven fabric were evaluated in the same manner as in Example 1, and the results are shown in [Table 6]. The mark * in Table 6 indicates that the nonwoven fabric is significantly decomposed and it is difficult to measure the molecular weight.

[0074]

[Table 6]

Example 11 The lactic acid-based polymer fiber F-2 obtained in Preparation Example 2 was cut into short fibers having a length of about 4 cm and stirred to form a random web, which then had a surface temperature of 100 ° C. It was lightly pressed by an embossing roll with a textured engraving and wound up. The wound non-woven fabric was joined by needle punching with a needle depth of 11 mm30 P / cm ² by alternating 6 times on both sides. The resulting decomposable non-woven fabric was a good non-woven fabric in which the fibers were entangled, and it did not deform even when left outdoors for one month without wrinkles. Also, when left in the soil for 18 months, it was effectively decomposed. The molecular weight retention was 72%.

Comparative Example 7 A commercially available needle punch type non-woven fabric (manufactured by Mitsui Petrochemical Industry Co., Ltd., trade name: Tufnel PA-4021) was
After left in the soil for 8 months, it was dissolved in dichlorobenzene and the molecular weight retention was determined in the same manner as in Example 1. The molecular weight retention was 98%, and it was hardly decomposed.

[0077]

The degradable nonwoven fabric of the present invention maintains a certain shape as a nonwoven fabric for a predetermined period of time, and when it is discarded after use, it is hydrolyzed in a natural environment. Therefore, it does not accumulate as waste. Further, since the degradable nonwoven fabric of the present invention is made of a lactic acid-based polymer having a specific composition as a raw material, it has appropriate crystallinity and is excellent in dimensional stability.

Front page continuation (72) Inventor Shigeru Imuro 2-1-1 Tangodori, Minami-ku, Aichi Prefecture Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Keiko Taniguchi 2-1-1 Tangodori, Minami-ku, Aichi Prefecture Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Shinobu Moriya, 2-chome, Tango-dori, Minami-ku, Nagoya, Aichi Prefecture Mitsui Toatsu Chemical Co., Ltd. (72) Masahiro Washino 2-chome, Tango-dori, Minami-ku, Aichi Prefecture Address Mitsui Toatsu Chemical Co., Ltd.

Claims (24)

[Claims] 1. A degradable nonwoven fabric obtained by forming a web from fibers of a lactic acid-based polymer, wherein the lactic acid-based polymer has a poly (DL-) content of more than 80 mol% L-lactic acid units. Lactic acid), poly (DL-lactic acid) having more than 80 mol% of D-lactic acid units, (L-lactic acid) -hydroxycarboxylic acid copolymer having at least 70 mol% of L-lactic acid units, and 70 D-lactic acid units. Holds more than mol% (D-
A degradable non-woven fabric, which is at least one lactic acid-based polymer (polymer A) selected from a lactic acid) -hydroxycarboxylic acid copolymer. 2. Fibers of a lactic acid-based polymer are fibers obtained from the polymer A and poly (DL-) in which the molar ratio of L-lactic acid units to D-lactic acid units is 1: 4 to 4: 1. Lactic acid), (DL-lactic acid) -hydroxycarboxylic acid copolymer, at least 30 mol% of hydroxycarboxylic acid units
Mochi (L-lactic acid) -hydroxycarboxylic acid copolymer,
And a fiber mixed with a fiber obtained from at least one low temperature thermoplastic lactic acid-based polymer (polymer B) selected from (D-lactic acid) -hydroxycarboxylic acid copolymer having at least 30 mol% of hydroxycarboxylic acid units. The degradable nonwoven fabric according to claim 1, which is characterized in that 3. The polymer A has 7 L-lactic acid units.
The (L-lactic acid) -hydroxycarboxylic acid copolymer having 0 mol% or more is at least one lactic acid-based copolymer selected from (L-lactic acid) -glycolic acid copolymer, (L-lactic acid) -hydroxycaproic acid copolymer and mixtures thereof. (D-lactic acid) -hydroxycarboxylic acid copolymer having a D-lactic acid unit content of 70 mol% or more is a polymer,
(D-lactic acid) -glycolic acid copolymer, (D-lactic acid)
Degradable nonwoven fabric according to claim 1 or 2, characterized in that it is at least one lactic acid-based polymer selected from hydroxycaproic acid copolymers and mixtures thereof. 4. In the polymer B, (DL-lactic acid)-
The hydroxycarboxylic acid copolymer is (DL-lactic acid)-
At least one lactic acid-based polymer selected from glycolic acid copolymers, (DL-lactic acid) -hydroxycaproic acid copolymers, and mixtures thereof, and having at least 30 mol% of hydroxycarboxylic acid units (L-lactic acid) -hydroxycarboxylic acid The copolymer is at least one lactic acid-based polymer selected from (L-lactic acid) -glycolic acid copolymer, (L-lactic acid) -hydroxycaproic acid copolymer and mixtures thereof, and has at least 30 mol% of hydroxycarboxylic acid units. (D-
The lactic acid) -hydroxycarboxylic acid copolymer is at least one lactic acid-based polymer selected from (D-lactic acid) -glycolic acid copolymer, (D-lactic acid) -hydroxycaproic acid copolymer and mixtures thereof. The degradable nonwoven fabric according to claim 2. 5. The degradable nonwoven fabric according to claim 2, wherein the content of the fibers obtained from the polymer B is 10 to 60% by weight based on the total weight of the fibers. 6. The degradable nonwoven fabric according to claim 2, wherein the fiber obtained from the polymer A is heat-sealed with the fiber obtained from the polymer B. 7. The heat fusion is performed at room temperature to 70 ° C. at 1.1.
~ 200kg / cm ²By heat compression under the pressure of
The component according to claim 6, characterized in that it has been made.
Degradable nonwoven fabric. 8. The molecular weight of the lactic acid-based polymer is 10,000 to 100.
The degradable non-woven fabric according to claim 1, wherein 9. The degradable nonwoven fabric according to claim 1, wherein the lactic acid-based polymer is a lactic acid-based polymer obtained by a direct polymerization method. 10. The degradable non-woven fabric according to claim 1, wherein the fiber obtained from the polymer A contains at least one selected from a plasticizer, an ultraviolet absorber and a light stabilizer. 11. The degradable nonwoven fabric according to claim 2, wherein the fiber obtained from the polymer B contains at least one selected from a plasticizer, an ultraviolet absorber and a light stabilizer. 12. A method for forming a web from fibers of a lactic acid-based polymer and producing a degradable nonwoven fabric from the web, wherein the lactic acid-based polymer has L-lactic acid units in an amount of more than 80 mol%. -Lactic acid), D-lactic acid unit 80 mol%
Poly (DL-lactic acid) and L-lactic acid units with a maximum of 70
At least one lactic acid-based polymer selected from (L-lactic acid) -hydroxycarboxylic acid copolymer having a mol% or more and (D-lactic acid) -hydroxycarboxylic acid copolymer having a D-lactic acid unit of 70 mol% or more (polymer A )
A method for producing a degradable nonwoven fabric, characterized in that 13. A fiber of a lactic acid-based polymer, a fiber obtained from the polymer A, and poly (DL-) in which a molar ratio of L-lactic acid unit to D-lactic acid unit is 1: 4 to 4: 1.
Lactic acid), (DL-lactic acid) -hydroxycarboxylic acid copolymer, (L-lactic acid) -hydroxycarboxylic acid copolymer having at least 30 mol% of hydroxycarboxylic acid units, and at least 3 hydroxycarboxylic acid units.
13. A mixed fiber with a fiber obtained from at least one low-temperature thermoplastic lactic acid-based polymer (polymer B) selected from (D-lactic acid) -hydroxycarboxylic acid copolymer having 0 mol%. A method for producing the degradable nonwoven fabric described. 14. A polymer (A), wherein the (L-lactic acid) -hydroxycarboxylic acid copolymer having L-lactic acid units in an amount of 70 mol% or more is (L-lactic acid) -glycolic acid copolymer, (L-lactic acid) -hydroxycaproic acid. A (D-lactic acid) -hydroxycarboxylic acid copolymer, which is at least one lactic acid-based polymer selected from a copolymer and a mixture thereof, and has a D-lactic acid unit of 70 mol% or more,
(D-lactic acid) -glycolic acid copolymer, (D-lactic acid)
A method for producing a degradable nonwoven fabric according to claim 12 or 13, characterized in that it is at least one lactic acid-based polymer selected from a hydroxycaproic acid copolymer and a mixture thereof. 15. In the polymer B, (DL-lactic acid)
-Hydroxycarboxylic acid copolymer (DL-lactic acid)
At least one lactic acid-based polymer selected from glycolic acid copolymers, (DL-lactic acid) -hydroxycaproic acid copolymers and mixtures thereof, and having at least 30 mol% of hydroxycarboxylic acid units (L-lactic acid) -hydroxycarboxylic acid The acid copolymer is at least one lactic acid-based polymer selected from (L-lactic acid) -glycolic acid copolymer, (L-lactic acid) -hydroxycaproic acid copolymer and a mixture thereof, and contains at least 30 mol% of hydroxycarboxylic acid units. Hold (D-
The lactic acid) -hydroxycarboxylic acid copolymer is at least one lactic acid-based polymer selected from (D-lactic acid) -glycolic acid copolymer, (D-lactic acid) -hydroxycaproic acid copolymer and mixtures thereof. The method for producing a degradable nonwoven fabric according to claim 13, which is characterized in that. 16. The degradable nonwoven fabric according to claim 2, wherein the content of the fibers obtained from the polymer B is 10 to 60% by weight based on the total weight of the fibers. 13. The method for producing a degradable nonwoven fabric according to 13. 17. The method for producing a degradable nonwoven fabric according to claim 13, wherein the fiber obtained from the polymer A is heat-sealed with the fiber obtained from the polymer B. 18. The heat fusion is performed at a temperature of room temperature to 70 ° C.
The method for producing a degradable non-woven fabric according to claim 17, which is produced by heat compression under a pressure of 1 to 200 kg / cm ² . 19. A lactic acid-based polymer having a molecular weight of 10,000 to 10
It is 0,000, The manufacturing method of the degradable nonwoven fabric of Claim 12 characterized by the above-mentioned. 20. The lactic acid-based polymer is a lactic acid-based polymer obtained by a direct polymerization method.
A method for producing the degradable nonwoven fabric described. 21. The method for producing a degradable nonwoven fabric according to claim 12, wherein the fiber obtained from the polymer A is stretched and heat-treated. 22. The production of a degradable nonwoven fabric according to claim 12 or 13, wherein the fiber obtained from the polymer A contains at least one selected from a plasticizer, an ultraviolet absorber and a light stabilizer. Method. 23. The method for producing a degradable nonwoven fabric according to claim 13, wherein the fiber obtained from the polymer B contains at least one selected from a plasticizer, an ultraviolet absorber and a light stabilizer. 24. The method for producing a degradable nonwoven fabric according to claim 13, wherein the fiber obtained from the polymer A is stretched and heat-treated and then mixed with the fiber obtained from the polymer B.