JPH0921017A - Biodegradable fiber and nonwoven fabric using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable fiber consisting of polylactic acid specified in acid value, thus good in stability with the lapse of time at room temperature and useful in such areas as civil engineering/construction materials, fishery materials, agricultural materials, clothing use, etc. SOLUTION: The objective biodegradable fiber consists of polylactic acid and/or a copolymer predominant therein with an acid value (eq./10<3> kg) brought to <=60/(ηSP/C) prepared by ring opening polymerization of L-lactide singly or its combination with a comonomer in the presence of a catalyst. The ηSP/C is reduced specific viscosity (dl/g), being pref. 0.5-10 or so. It is preferable that the tensile tenacity, tensile elongation at break and knot tenacity of the fiber be >=3g/d, >=10% and >=1.5g/d, respectively.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable fiber,
In particular, the present invention relates to a biodegradable fiber having good stability over time at room temperature.

[0002]

2. Description of the Related Art Fibers that have hitherto been used for living materials, agricultural materials, fishery materials, and civil engineering materials include synthetic fibers such as polyester, polyolefin, and polyamide. When these fibers are left in the natural environment after use, they are not easily decomposed, which causes various problems. For example, since these living materials, agricultural materials, civil engineering materials, etc. are difficult to decompose,
After use, it was necessary to bury it in the soil, incinerate it, and so on, and if it was buried in the soil, its biodegradability was low, so there was a limit to how it could be used. In the case of fishery materials,
Often left in the water, there were problems such as polluting the ocean. In order to solve such a problem, it has been considered to use a material that is decomposed in soil or water, but a material that has been sufficiently decomposed has not been obtained.

Examples of conventional biodegradable polymers include cellulose, cellulose derivatives, polysaccharides such as chitin and chitosan, proteins, poly-3-hydroxybutyrate and 3-.
Polymers produced by microorganisms such as copolymers of hydroxybutyrate and 3-hydroxyvalerate, and aliphatic polyesters such as polyglycolide, polylactide and polycaprolactone are known. Cellulose-based cotton and regenerated cellulose, which are mainly used, are inexpensive, but require binders because they are not thermoplastic and use polyolefins, polyester fibers, etc. as the binder fibers, and thus have a problem of being difficult to biodegrade. . Since poly-3-hydroxybutyrate, a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate, etc. produced by a microorganism are expensive, their applications are limited, and their strength is low. Polycaprolactone is a relatively inexpensive biodegradable polymer, but its melting point is as low as about 60 ° C., which is a temperature that can occur in the distribution stage in summer in nature, and there was a problem in heat resistance. .

Further, as a cheap material, a material in which starch is mixed with polyethylene has been studied, but there is no satisfactory biodegradability and a fiber having uniform mechanical properties cannot be obtained. JP-A-4-108331 discloses a fishing line in which a hydrolyzable polyester fiber having glycolic acid and / or lactic acid as a structural unit is coated with a degradable polymer having a lower hydrolyzability than the fiber. There was a problem that requires post-processing. Although polylactic acid is a relatively stable polymer, it has a problem in stability over time (strength retention rate) at room temperature, and particularly has a problem that strength is lowered.

As described above, the prior art has strength and practical heat resistance and stability at room temperature with time (strength retention rate).
It was not possible to obtain a biodegradable fiber which is practical, and is relatively inexpensive, since there is no thermoplastic biodegradable fiber having good biodegradability and rapid biodegradability.

[0006] In view of such circumstances, the object of the present invention is to
It is an object of the present invention to provide a biodegradable fiber which has improved stability over time (strength retention rate) and has strength in a polylactic acid-based biodegradable fiber.

[0007]

Means for Solving the Problems As a result of intensive research to solve the above problems, the present inventors have found that biodegradable fibers are
The above problems have been solved by controlling the acid value and the like using a thermoplastic resin composed of polylactic acid and / or a copolymer mainly composed of polylactic acid.

That is, the present invention comprises (1) a thermoplastic resin composed of polylactic acid and / or a copolymer mainly composed of polylactic acid, and has an acid value (equivalent / 10 ³ kg) of (formula 1) Acid value ≦ 60 / (η _sp / C) (Formula 1) [wherein, η _sp / C is the reduced specific viscosity (dl / g)], biodegradable fiber, (2) melting point 120 ~ 200 ° C
Or the flow initiation temperature is in the range of 100 to 180 ° C. (1) The biodegradable fiber according to (1), wherein the thermoplastic resin is a carboxyl group in the thermoplastic resin due to a compound having a hydroxyl group. Is esterified with
(1) or (2) biodegradable fiber, (4) tensile strength 2.5
g / d or more and tensile elongation at break 10% or more (1) to (3)
Biodegradable fiber according to any one of (5) Tensile strength 2.5
g / d or more, tensile breaking elongation 10% or more, knot strength 1.5
The biodegradable fiber according to any one of (1) to (3), which is g / d or more, (6) in the form of multifilament (1) to
Biodegradable fiber according to any one of (5), (7) in the form of monofilaments (1) to biodegradable fiber according to any of (5), (8) in the form of short fibers ( 1) to (7), biodegradable fiber, (9) (8) biodegradable staple fiber non-woven fabric, (10) (1) to (3) The present invention relates to a long-fiber non-woven fabric using the biodegradable fiber described in 1.

Hereinafter, the present invention will be described in detail. The thermoplastic resin used in the present invention comprises polylactic acid and / or a copolymer mainly composed of polylactic acid. As lactic acid for producing polylactic acid, only D-form, L-form or D-form
It may be a mixture of body and L body. Examples of the copolymer containing polylactic acid as a main component include lactic acid [either D-form alone, L-form alone or a mixture of D-form and L-form], for example, ε-
Cyclic lactones such as caprolactone, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α-oxyacids such as α-hydroxyvaleric acid, glycols such as ethylene glycol and 1,4-butanediol, succinic acid, sebacic acid, etc. Examples thereof include those obtained by copolymerizing with one or more monomers selected from the above dicarboxylic acids. Of these, cyclic lactones and glycols are preferable from the viewpoint of polymer polymerizability. The proportion of copolymerization is not particularly limited, but 100 parts by weight or less of the monomer to be copolymerized is preferable, and 1 to 50 parts by weight is more preferable, relative to 100 parts by weight of lactic acid.

Further, the thermoplastic resin may be one obtained by esterifying a carboxyl group in the thermoplastic resin with a compound having a hydroxyl group. Examples of the compound having a hydroxyl group include higher alcohols having 6 or more carbon atoms such as octyl alcohol, lauryl alcohol and stearyl alcohol, and glycols such as ethylene glycol, diethylene glycol and 1,4-butanediol. By esterifying the carboxyl group at the molecular end of the thermoplastic resin with a compound having a hydroxyl group, the thermal stability during melt spinning and the temporal stability of the fiber after melt spinning can be improved. Among them, higher alcohols having 6 to 18 carbon atoms are preferable from the viewpoint of spinnability.

The thermoplastic resin may be synthesized by a method known per se, for example, ring-opening polymerization of L-lactide in the presence of a catalyst and, if necessary, reprecipitation purification to obtain a thermoplastic resin.
Further, a monomer or oligomer to be copolymerized and L-lactide are subjected to ring-opening polymerization in the presence of a catalyst, and if necessary, reprecipitation purification is carried out to obtain a copolymerized thermoplastic resin.

The thermoplastic resin used in the present invention preferably has a viscosity average molecular weight of 5 × 10 ³ or more, more preferably 1 × 10 ⁴ to 1 × 10 ⁶ . 5 x 10
^If it is less than ³ , sufficient fiber strength tends not to be obtained, and if it exceeds 1 × 10 ⁶ , the viscosity tends to be high during spinning and the spinnability tends to be poor.

The viscosity average molecular weight [MV] is η _sp /
C = 7.79 × 10 ⁻⁴ MV ^0.73 [wherein, η _sp / C is the reduced specific viscosity (dl / g) and MV is the viscosity average molecular weight].

The thermoplastic resin used in the present invention preferably has a reduced specific viscosity of 0.5 to 19 (dl / g), more preferably 1.0 to 6.0 (dl / g).
It is. The reduced specific viscosity of the thermoplastic resin is 0.4 (dl /
If it is less than g), the tensile strength tends to be insufficient,
If it exceeds 20 (dl / g), the viscosity during spinning tends to be high and the processability tends to be poor.

Here, the reduced specific viscosity means that a sample is precisely weighed,
The solution was dissolved in chloroform at 0.5 g / dl, and the solution was measured at 25 ° C. using an Ubbelohde viscometer.

The biodegradable fiber of the present invention can be obtained by subjecting the above-mentioned thermoplastic resin to a usual melt spinning method such as a spin draw method or a high speed spinning method.

The temperature of the thermoplastic resin during melt spinning is preferably above its melting point and below 230 ° C. More preferred is the range from the melting point to 210 ° C. If it exceeds 230 ° C, the thermoplastic resin tends to undergo thermal decomposition and depolymerization.

The melt-spun undrawn yarn is air-cooled or cooled in a water bath at 20 to 60 ° C. or in an oil bath, usually wound once, and then drawn in a one-step or two-step drawing process. It The total stretching ratio varies depending on the purpose of use and the required performance, but is usually 2 to 8 times, preferably 3 to 7 times.

The biodegradable fiber of the present invention has a temperature of 120 ° C. or higher,
It preferably has a melting point of 130 ° C. or higher. Thus, the temperature stability of the product in circulation, eg 80 in summer.
Can withstand storage at temperatures around ℃. From the viewpoint of the thermal stability of the thermoplastic resin during spinning, it is 200 ° C or lower, preferably 180 ° C or lower.

In the present invention, the melting point of the biodegradable fiber is measured by using a DSC-50 manufactured by Shimadzu Corp. at a rate of 10 ° C./min. However, if the biodegradable fiber is
When DSC does not show a crystal melting peak, the flow initiation temperature is preferably 100 to 180 ° C, more preferably 120 to 180 ° C. If the flow starting temperature is less than 100 ° C, the temperature stability of the product tends to deteriorate, and 1
If it exceeds 80 ° C, the thermal stability during spinning tends to deteriorate.

Here, the flow starting temperature is defined as a flow starting temperature by using a precision melting point measuring device manufactured by Yanaco Co., Ltd. to which shear stress is applied to indicate flow. The temperature rising temperature is 5 ° C./minute.

The flow initiation temperature of the biodegradable fiber can be adjusted by the copolymer and the copolymerization ratio.

The melting point of the biodegradable fiber is as follows:
It can be adjusted by copolymerizing glycols, dicarboxylic acid and the like. It can also be adjusted by changing the D / L ratio of lactic acid.

The acid value of the biodegradable fiber of the present invention is (formula 1) acid value ≦ 60 / (η _sp / C) (formula 1) [wherein η _sp / C is the reduced specific viscosity ( dl / g)], preferably acid value ≦ 40 / (η _sp /
C), and more preferably, the acid value ≦ 30 / (η _sp / C) is satisfied. If the acid value is outside the range of (Formula 1), the stability over time at room temperature becomes poor.

In the present invention, the acid value means the sample is precisely weighed,
It was dissolved in a mixed solvent of chloroform / methanol (volume ratio 1: 1), and this solution was titrated with a sodium methoxide / methanol solution, and measured, and it is represented by the equivalent amount of a carboxyl group per 10 ³ kg of a sample.

The acid value of the biodegradable fiber can be adjusted by controlling the polymer depolymerization.

In order to reduce the depolymerization of the polymer, esterification of terminal carboxyl groups in the polymer, the content of low molecular weight compounds such as oligomers are reduced, and the spinning temperature during spinning is lowered as much as possible (preferably 2).
00 ° C. or lower, more preferably 190 ° C. or lower),
In addition, it is carried out by adding an appropriate catalyst that suppresses depolymerization activity (for example, an aluminum-based catalyst is preferable to a tin-based catalyst), removing the catalyst in the polymer after polymerization, or eliminating the activity.

Here, the reduced specific viscosity of the biodegradable fiber of the present invention is preferably 0.5 to 10 (dl / g), and 1.0 to 6.0 (dl / g). Is more preferable. Reduced specific viscosity of biodegradable fiber is 0.5 (dl / g)
If it is less than 10%, the tensile strength is insufficient, and 10 (dl
If it exceeds / g), the productivity is lowered, which is not good.

In the present invention, the reduced specific viscosity means that the biodegradable fiber is precisely weighed in the same manner as that of the thermoplastic resin, and is 0.5 g /
The solution was dissolved in chloroform so as to have dl, and the solution was measured at 25 ° C. using an Ubbelohde viscometer.

The reduced specific viscosity of the biodegradable fiber can be adjusted by the molecular weight of the thermoplastic resin, the spinning temperature, and the water content in the thermoplastic resin during spinning.

The biodegradable fiber of the present invention preferably has a tensile strength of 3 g / d or more and a tensile elongation at break of 10% or more.

As described above, the tensile strength of the biodegradable fiber of the present invention is preferably 3 g / d or more, more preferably 4 g / d or more. If the tensile strength is less than 3 g / d, it can be used for civil engineering and construction materials, fishery materials, agricultural materials, other industrial materials, and clothing.
It is not preferable because the tensile strength is insufficient.

In the present invention, tensile strength means JIS L
It is measured according to 1013.

The tensile strength of the biodegradable fiber can be adjusted by spinning and drawing conditions.

Further, the biodegradable fiber of the present invention has a tensile elongation at break of preferably 10% or more, more preferably 20 to 100%, from the viewpoint of yarn physical properties.

In the present invention, the tensile elongation at break means JIS.
It is measured according to L1013.

The tensile elongation at break of the biodegradable fiber can be adjusted by spinning and drawing conditions.

The biodegradable fiber of the present invention preferably has a knot strength of 1.5 g / d or more, in addition to the tensile strength and the tensile elongation at break in the above ranges, and preferably 2.0 g.
/ D or more is more preferable. If the knot strength is less than 1.5 g / d, the yarn properties tend to be unsatisfactory for use in civil engineering / construction material applications, fishery material applications, agricultural material applications, other industrial material applications, and clothing applications.

In the present invention, knot strength means JIS L
It is measured according to 1013.

The biodegradable fiber of the present invention can be used in the form of multifilament or monofilament, or short fiber or long fiber nonwoven fabric.

The above-mentioned monofilament is a fiber composed of one fiber, and can be obtained by the spinning method.

The multifilament is a fiber having 3 to 100 monofilaments, and these can be obtained by the same method as the monofilaments.

The short fibers are fibers having a fiber length of about 2 to 80 mm and are used for spun yarn, wet non-woven fabric, dry non-woven fabric and the like. Normally, when used for spun yarn,
Fiber length is 20-80 mm, preferably 30-60 mm,
When used in a wet non-woven fabric, it is 2 to 10 mm, preferably 2
~ 6mm, 20-100m when used for dry non-woven fabric
m, preferably about 20 to 70 mm. The staple fiber of the present invention can be obtained, for example, after melt spinning, drawing, or high speed spinning.

The wet non-woven fabric is a non-woven fabric obtained by a papermaking method in which short fibers are dispersed in a liquid such as water, and the dry non-woven fabric is a random webber or a parallel webber, which is used as a cart web if necessary. It is a non-woven fabric that is fused or totally fused or entangled three-dimensionally.

The biodegradable short fibers can be crimped to improve the card opening property. The crimping method is not particularly limited, and a known method can be used, for example, a pushing gear method or a stuffing box method can be used.

The number of crimps is 5 to 50/25 mm, preferably 10 to 30/25 mm. If the number of crimps is less than 5/25 mm, unopened portions are likely to occur during opening, and if it exceeds 50/25 mm, uniform opening tends not to be obtained. Here, the number of crimps means JIS L
It is measured according to 1015.

The crimping rate is 5% or more, preferably 8% or more. When the crimping rate is less than 5%, it is difficult to obtain a uniform web when applied to a card, and a sparse and dense portion tends to occur. Here, the crimp ratio means JIS L101.
It was measured according to 5.

The short fiber non-woven fabric using the biodegradable fiber of the present invention may be produced by a method known per se using the above short fibers. For example, short fibers are carded with a roller card to form a web, If necessary, the physical properties of the non-woven fabric are obtained by interlacing or adhering by needle punching, calendering, embossing, or the like. If necessary, the fiber orientation can be changed by a random webber or the like.

The long-fiber nonwoven fabric using the biodegradable fiber of the present invention may be manufactured by a method known per se, for example, a spunbond method or a melt blow method. Here, the spunbond method is a method in which a thermoplastic resin is heated and melted at a temperature equal to or higher than its melting point, spun from a spinneret, and the spun long fibers are cooled and solidified to draw air suckers or the like installed in the lower part. 20 by the taking means
It is pulled at a take-up speed of 00 m / min or more, then opened and collected on the endless collection surface that is moving at a constant speed to form a web, which is wholly or partially heated by embossing or calendering. It is a method that can be entangled by pressure bonding, needle punching, or hydroentanglement.

In the melt-blowing method, a thermoplastic resin is heated and melted to a temperature equal to or higher than its melting point, discharged from a spinneret having spinning holes arranged in a straight line, and high-temperature high-pressure air jetted at high speed from both sides of a spinning nozzle. Convert to microfiber. After that, it is collected on the endless collecting surface that is moving at a constant speed to form a non-woven fabric. Emboss this,
Thermocompression bonding is carried out entirely or partially by calendering,
Alternatively, it is a method that can be entangled by needle punching or hydroentanglement.

The biodegradable fiber of the present invention has an antistatic property,
Considering the focusing property, anionic surfactants such as lauryl phosphate potassium salt, cationic surfactants such as quaternary ammonium salt, nonionic surfactants such as ethylene oxide adducts of higher aliphatic alcohols and higher fatty acids. One or more kinds of silicone oils such as polyalkylene glycols such as polyethylene glycol and polyethylene glycol / polypropylene glycol block copolymers, dimethylpolysiloxane, polyether modified silicone oil, higher alkoxy modified silicone oil, etc. it can.

The biodegradable fiber of the present invention is a thermoplastic resin,
One or two kinds of other aliphatic polyesters such as polycaprolactone, polymers such as polyvinyl alcohol, polyalkylene glycol and polyamino acid, inorganic substances such as talc, calcium carbonate, calcium sulfate and calcium chloride, starch, protein and food additives. As described above, it is possible to mix an appropriate amount and variously change the mechanical properties, biodegradation properties and the like.

In addition to the above, the biodegradable fiber of the present invention may be mixed with known additives such as an antioxidant, an ultraviolet absorber and a plasticizer, if necessary.

[0054]

The present invention will be further described with reference to the following examples. Moreover, each measuring method is demonstrated below.

The acid value was measured by precisely weighing a sample, dissolving it in a chloroform / methanol (volume ratio 1: 1) mixed solvent, and titrating this solution with a sodium methoxide / methanol solution.

The reduced specific viscosity is 0.5 g /
It was dissolved in chloroform so as to have a dl, and the solution was measured at 25 ° C. using an Ubbelohde viscometer.

The tensile strength and the tensile elongation at break are JIS
It measured based on L1013.

The knot strength was measured according to JIS L1013.

The melting point was measured by using DSC-50 manufactured by Shimadzu Corp. while raising the temperature at a rate of 10 ° C./min.

The strength retention is the initial tensile strength of the fiber,
The tensile strength of the fiber after standing for 12 months in a room temperature of 25 ° C. and a relative humidity of 60% was measured and determined by (Equation 2). Strength retention rate (%) = (T / T ₀ ) × 100 (Equation 2) [In the equation, T is the tensile strength (g / d) of the fiber after standing for 12 months at room temperature of 25 ° C. and relative humidity of 60%, T ₀ is the initial tensile strength (g / d) of the fiber]

Regarding the biodegradability, the fiber was buried in the soil and the state of degradation after 6 months was examined by a scanning electron microscope (SE).
M: Scanning Electron Microscope). When the shape was lost (for example, when the surface had irregularities or was broken), the biodegradability was considered to be good.

Example 1 Polylactic acid obtained by esterifying a carboxyl group at the molecular end with lauryl alcohol, which has a reduced specific viscosity of 1.58,
Melt spinning was performed at a spinning speed of 500 m / min from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at a spinning temperature of 190 ° C. The unstretched yarn is once wound and then stretched 4.5 times at 140 ° C. to obtain a fiber having a single yarn fineness of 2.0 d, a reduced specific viscosity of 1.56 and an acid value of 18 (equivalent / 10 ³ kg). It was

Example 2 Polylactic acid having a reduced specific viscosity of 1.93 and a carboxyl group at the molecular end esterified with lauryl alcohol
Melt spinning was performed at a spinning speed of 500 m / min from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at a spinning temperature of 200 ° C. The unstretched yarn is once wound and then stretched 4.5 times at 140 ° C. to obtain a fiber having a single yarn fineness of 2.2 d, a reduced specific viscosity of 1.86 and an acid value of 12 (equivalent / 10 ³ kg). It was

Example 3 Polylactic acid having a reduced specific viscosity of 1.52 was spun at a spinning temperature of 19
Melt spinning was carried out at a spinning speed of 500 m / min from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at 0 ° C. After unwinding the undrawn yarn, it was drawn 4.5 times at 140 ° C., the single yarn fineness was 2.0d, the reduced specific viscosity was 1.47, and the acid value was 30.
(Equivalent / 10 ³ kg) of fibers were obtained.

Example 4 Polylactic acid having a reduced specific viscosity of 1.73 was added at a spinning temperature of 19
A spinning nozzle having one spinning hole with a diameter of 1.0 mm at 0 ° C
Melt spinning from the solution, solidify in a water bath (30 ° C), and spin 2
It was spun at 0 m / min. After winding the undrawn yarn once,
Stretched 5.3 times at 140 ° C, fineness 380d, reduced specific viscosity
Degree 1.69, acid value = 28 (equivalent / 10 ^Threekg) fiber
I got

Comparative Example 1 Polylactic acid having a reduced specific viscosity of 1.62 was added at a spinning temperature of 19
Melt spinning was carried out at a spinning speed of 500 m / min from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at 0 ° C. After unwinding the undrawn yarn, it was drawn 4.5 times at 140 ° C., the single yarn fineness was 2.0d, the reduced specific viscosity was 1.58, and the acid value was 65.
(Equivalent / 10 ³ kg) of fibers were obtained.

Comparative Example 2 Polylactic acid having a reduced specific viscosity of 1.56 was used at a spinning temperature of 19
Melt spinning was carried out at a spinning speed of 500 m / min from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at 0 ° C. After unwinding the undrawn yarn, it was drawn 4.5 times at 140 ° C., the single yarn fineness was 2.1d, the reduced specific viscosity was 1.53, and the acid value was 45.
(Equivalent / 10 ³ kg) of fibers were obtained.

Comparative Example 3 Polylactic acid having a reduced specific viscosity of 1.64 was used at a spinning temperature of 19
Melt spinning was carried out at a spinning speed of 500 m / min from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at 0 ° C. After unwinding the undrawn yarn, it was drawn 4.5 times at 140 ° C., the single yarn fineness was 2.1d, the reduced specific viscosity was 1.57, and the acid value was 43.
(Equivalent / 10 ³ kg) of fibers were obtained.

Comparative Example 4 Polylactic acid having a reduced specific viscosity of 1.78 was added at a spinning temperature of 19
A spinning nozzle having one spinning hole with a diameter of 1.0 mm at 0 ° C
Melt spinning from the solution, solidify in a water bath (30 ° C), and spin 2
It was spun at 0 m / min. After winding the undrawn yarn once,
Stretched 5.3 times at 140 ° C, fineness 380d, reduced specific viscosity
The degree is 1.73, the acid value is 55 (equivalent / 10 ^Threekg) fiber
I got

Comparative Example 5 Polylactic acid having a reduced specific viscosity of 3.53 was used at a spinning temperature of 19
Melt spinning was carried out at a spinning speed of 500 m / min from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at 0 ° C. After unwinding the undrawn yarn, it was drawn 4.5 times at 140 ° C., the single yarn fineness was 2.2d, the reduced specific viscosity was 3.25, and the acid value was 29.
(Equivalent / 10 ³ kg) of fibers were obtained.

Comparative Example 6 Polylactic acid having a reduced specific viscosity of 4.82 was prepared at a spinning temperature of 21.
Melt spinning was carried out at a spinning speed of 500 m / min from a spinning nozzle having 20 spinning holes with a diameter of 0.3 mm at 0 ° C. After unwinding the undrawn yarn, it was drawn 4.5 times at 140 ° C., the single yarn fineness was 2.3d, the reduced specific viscosity was 4.62, and the acid value was 30.
(Equivalent / 10 ³ kg) of fibers were obtained.

Table 1 shows the fiber physical property values obtained in Examples 1 to 4 and Comparative Examples 1 to 6 and the results of evaluation of biodegradability.

[0073]

[Table 1]

From Table 1, it was found that the biodegradable fiber of the present invention has excellent biodegradability and good physical properties, has a good room temperature storage strength retention rate, and is excellent in heat resistance.

Example 5 The biodegradable fiber obtained in Example 1 was crimped by the stuffing box method and then cut into 64 mm to obtain short fibers for cards. The short fibers were made into a web having a basis weight of 100 g / m ² by a random webber and then needle punched to obtain a short fiber non-woven fabric. The reduced specific viscosity of the short fiber non-woven fabric was 1.57 and the acid value was 19 (equivalents / 10 ³ kg).

Example 6 A polylactic acid obtained by esterifying a terminal carboxyl group of a molecule having a reduced specific viscosity of 1.58 with lauryl alcohol was obtained by a spunbond method to obtain a long fiber nonwoven fabric having a basis weight of 100 g / cm ² . The spinning condition is that the spinning temperature is 200 ° C., and the discharge rate is 0.8 g / min from a spinning nozzle having a spinning hole with a diameter of 0.3 mm.
The holes had a pulling speed of 3500 g / min. The reduced specific viscosity of the long fiber non-woven fabric is 1.42, the acid value = 17 (equivalent / 10 ³
kg).

Example 7 Polylactic acid having a reduced specific viscosity of 1.13 was prepared at a spinning temperature of 210 ° C.
The average fiber diameter was 3.2 μm and the basis weight was 50 by the melt-blowing method under the conditions of an air temperature of 210 ° C. and a discharge rate of 0.1 g / min.
A long-fiber nonwoven fabric having a g / cm ² was obtained. The reduced specific viscosity of the long fiber non-woven fabric was 1.01, and the acid value was 52 (equivalent / 10 ³ kg).

When the biodegradability of the nonwoven fabrics obtained in Examples 5, 6 and 7 was evaluated, the biodegradability was good.

[0079]

Industrial Applicability The biodegradable fiber of the present invention is a polylactic acid type biodegradable fiber, and has stability over time (strength retention rate).
It is a biodegradable fiber that has excellent properties, strength, and practical heat resistance, is practical, and is relatively inexpensive. Moreover, the biodegradable fiber of the present invention is suitable for daily life materials, agricultural materials, fishery materials, civil engineering and construction materials, clothing, and has excellent biodegradability in the natural world.

Claims (10)

[Claims] 1. A thermoplastic resin comprising polylactic acid and / or a copolymer mainly composed of polylactic acid, wherein the acid value (equivalent / 10 ³ kg) is (formula 1) acid value ≦ 60 / (η _sp / C) (Formula 1) [In formula, (eta) _sp / C is reduced specific viscosity (dl / g)] The biodegradable fiber in the range. 2. The biodegradable fiber according to claim 1, which has a melting point in the range of 120 to 200 ° C. or a flow starting temperature in the range of 100 to 180 ° C. 3. The biodegradable fiber according to claim 1, wherein the thermoplastic resin is obtained by esterifying a carboxyl group in the thermoplastic resin with a compound having a hydroxyl group. 4. The biodegradable fiber according to claim 1, which has a tensile strength of 2.5 g / d or more and a tensile elongation at break of 10% or more. 5. The biodegradable fiber according to claim 1, which has a tensile strength of 2.5 g / d or more, a tensile elongation at break of 10% or more, and a knot strength of 1.5 g / d or more. 6. The biodegradable fiber according to claim 1, which is in the form of a multifilament. 7. A monofilament form.
6. The biodegradable fiber according to any one of to 5. 8. The biodegradable fiber according to claim 1, which is in the form of short fibers. 9. A short fiber non-woven fabric comprising the biodegradable fiber according to claim 8. 10. A long-fiber nonwoven fabric comprising the biodegradable fiber according to any one of claims 1 to 3.