JP3311383B2 - Polymer network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer network having hydrolyzability. More specifically, the present invention relates to a hydrolyzable polymer network comprising a composition mainly composed of a lactic acid-based polymer that has hydrolyzability in a natural environment.

[0002]

2. Description of the Related Art Conventionally, an organic or inorganic foaming agent is blended with a general-purpose resin such as polyolefin, polyvinyl chloride or polyamide at a specific ratio, and then foamed and extruded by a melt extrusion method to obtain an extruded product. There is known a synthetic resin net formed by expanding the extruded product after foaming to expand the foam. For example, JP
Japanese Patent No. 47170 proposes a nonwoven fiber network obtained by melt-foaming and extruding a mixture of a thermoplastic resin such as polyolefin, polyurethane and polyester and a foaming agent, and opening the mixture. The nonwoven fiber network disclosed in this publication is useful as a nonwoven fabric, a bonding material, and the like. In addition, it is widely used as an absorbing material for oil and body fluid, a filtering material or a packaging material. Among these uses, particularly, absorbents such as oils and body fluids, filtration materials, and packaging materials are generally so-called disposable uses that are immediately discarded after use. However, the nonwoven fiber network formed from the resin, that is, the polymer network has a very low rate of hydrolysis in a natural environment, and therefore, remains semi-permanently in the ground when buried after use. It will be. In addition, when speculation is carried out offshore, the landscape is damaged or the living environment of marine life is destroyed.

Hitherto, a polymer network hydrolyzed in a natural environment has not been known. Polylactic acid and its copolymers are known as thermoplastic and hydrolyzable polymers. These lactic acid-based polymers are obtained by fermenting inexpensive raw materials such as corn starch and corn syrup, and also from petrochemical raw materials such as ethylene. U.S. Pat. No. 1,995,970 discloses a method for producing a lactic acid-based polymer for the polymerization of lactic acid, lactide or a mixture thereof. This lactic acid-based polymer is used as a suture for surgery and a sustained-release material for medicine due to its biocompatibility and hydrolyzability. However, since lactic acid-based polymers such as polylactic acid have a defect of lacking flexibility, it is difficult to open the fiber after melt-foaming the polymer, and the polylactic acid-based resin composition has a good network shape. A polymer network made of a material has not been known until now.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a polymer network having hydrolyzability.

[0005]

Means for Solving the Problems The present inventors have studied diligently to achieve the above object, and added a foaming agent to a polylactic acid-based resin composition containing a specific amount of a lactic acid-based polymer and a plasticizer, followed by melting. It has been found that a polymer network having appropriate softness and hydrolyzability can be obtained by foam extrusion and fiber opening, and the present invention has been completed.

That is, according to the present invention, a foaming agent is added to 100 parts by weight of a polylactic acid-based resin composition containing 80 to 100% by weight of a polylactic acid or a lactic acid-hydroxycarboxylic acid copolymer and 0 to 20% by weight of a plasticizer. A polymer network obtained by melt-foaming and extruding a mixture to which 2 to 10 parts by weight is added, and opening the mixture.

The polymer network of the present invention is a fibrous, porous, nonwoven fabric having a network structure composed of a resin composition mainly composed of a lactic acid-based polymer. The polymer network of the present invention is characterized in that it has a hydrolyzing property, and a foaming agent is added to a resin composition mainly composed of a lactic acid-based polymer, mixed with a ribbon blender or the like, and the mixture is uniaxially or biaxially mixed. It is melt-kneaded using a screw extruder or the like and discharged as a molten foam from the slit of an annular or linear die. Body. The obtained polymer network can be further stretched, heat-treated and the like.

Hereinafter, the present invention will be described in detail. The lactic acid-based polymer used in the present invention is polylactic acid or a copolymer of lactic acid and hydroxycarboxylic acid. Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, and hydroxyheptanoic acid. The preferred molecular structure of polylactic acid is L-lactic acid or D-lactic acid.
-It is composed of 85 to 100 mol% of any unit of lactic acid and 0 to 15 mol% of lactic acid unit of each enantiomer.
Also, a copolymer of lactic acid and hydroxycarboxylic acid is
It is composed of 85 to 100 mol% of either L-lactic acid or D-lactic acid units and 0 to 15 mol% of hydroxycarboxylic acid units. As preferred hydroxycarboxylic acids,
Glycolic acid and hydroxycaproic acid.

These lactic acid-based polymers include L-lactic acid and D-lactic acid.
-It can be obtained by selecting a required structure from lactic acid and hydroxycarboxylic acid as a raw material monomer, and subjecting it to dehydration polycondensation. Preferably, lactide, which is a cyclic dimer of lactic acid, glycolide, which is a cyclic dimer of glycolic acid, or caprolactone, is selected to have a required structure, followed by ring-opening polymerization. Lactide includes L-lactic acid, a cyclic dimer, L-lactic acid.
Lactide, D-lactide which is a cyclic dimer of D-lactic acid,
There are meso-lactide in which D-lactic acid and L-lactic acid are cyclically dimerized, and DL-lactide which is a racemic mixture of D-lactide and L-lactide. In the present invention, any lactide can be used. However, the main raw material is D
-Lactide, L-lactide, glycolide or caprolactone are preferred.

[0010] The lactic acid-based polymer preferably used in the present invention is composed of 85- 1 unit of either L-lactic acid or D-lactic acid.
A lactic acid-based polymer composed of 00 mol% and its enantiomer lactic acid unit or 0 to 15 mol% of the lactic acid unit and glycolic acid unit of the enantiomer.
Can be obtained. About 85 mol% or more of L-lactide and about 15 mol% or less of D-lactide and / or glycolide are copolymerized. About 85 mol% or more of D-lactide and about 15 mol% of L-lactide and / or glycolide are used.
L-lactide is copolymerized with about 70 mol% or more and DL-lactide and / or glycolide is about 30 mol% or less.
Lactide is copolymerized with about 70 mol% or more and meso-lactide and / or glycolide about 30 mol% or less.
L-lactide and / or glycolide are copolymerized with about 30 mol% or less.
More than 0 mol% and less than about 30 mol% of meso-lactide and / or glycolide are copolymerized.

These lactic acid-based polymers preferably have a high molecular weight, and the chloroform solution (25 ° C.) having a concentration of 0.5 g / dl preferably has an intrinsic solution viscosity of 1 to 10, and more preferably 3 to 7 It is. If the intrinsic solution viscosity is less than 1, the melt viscosity is too low to flow down from the die slit of the extruder, and it is not only difficult to mold, but also too brittle and difficult to handle. If it is too high, the melt extrudability deteriorates, which is not preferable.

In order to polymerize lactide or lactide and glycolide to obtain a high molecular weight polymer in a short time, it is preferable to use a catalyst. As such a polymerization catalyst, various catalysts having a catalytic effect on this polymerization reaction can be used. For example, as well-known substances, mainly polyvalent metals such as stannous octoate, tin tetrachloride, zinc chloride, titanium tetrachloride, iron chloride, boron trifluoride ether complex, aluminum chloride, antimony trifluoride, and lead oxide And a tin compound or a zinc compound is preferably used. Of the tin compounds, stannous octoate is particularly preferred. The amount used is preferably about 0.001 to 0.1% by weight based on the total amount of lactide or lactide and glycolide.

In the polymerization, a known chain-enhancing agent can be used. As the chain-enhancing agent, higher alcohols such as lauryl alcohol and hydroxy acids such as lactic acid and glycolic acid are preferably used. The coexistence of a chain-enhancing agent increases the polymerization rate, so that a polymer can be obtained in a short time. Also, the molecular weight of the polymer can be adjusted by adjusting the amount of the chain enhancer. However, if the amount of the chain-enhancing agent is too large, the molecular weight of the produced polymer tends to be small. Therefore, when the chain-enhancing agent is used, the amount is 0 to lactide or the total amount of lactide and glycolide. 0.1% by weight or less.

In the polymerization or copolymerization, a solvent may or may not be used. However, in order to obtain a high molecular weight polymer, it is preferable to carry out bulk polymerization in a molten state of lactide or glycolide.

In the case of melt polymerization, the polymerization temperature may be, in principle, a temperature higher than the melting point of lactide as a monomer or lactide and glycolide (around 90 ° C.). For example, in the case of solution polymerization using a solvent such as chloroform, it is possible to perform polymerization at a temperature lower than the melting point of lactide or lactide and glycolide. In any case, if the temperature exceeds 250 ° C., decomposition of the produced polymer occurs, which is not preferable.

The polylactic acid-based resin composition of the present invention comprises:
80 to 100% by weight of the lactic acid-based polymer and 0 to plasticizer
It is a resin composition containing 20% by weight. 20 plasticizers
Exceeding the weight percentage is not preferred because the composition is melt-extruded and the formability during foam opening deteriorates, and the strength of the obtained molded product decreases.

The plasticizer used in the present invention is, for example, di-n
Phthalic acid derivatives such as -octyl phthalate, di-2-ethylhexyl phthalate and dibenzyl phthalate; isophthalic acid derivatives such as diisooctyl phthalate; di-n
-Adipic acid derivatives such as -butyl adipate and dioctyl adipate; maleic acid derivatives such as di-n-butyl malate; citric acid derivatives such as tri-n-butyl citrate; itaconic acid derivatives such as monobutyl itaconate; Examples include oleic acid derivatives, ricinoleic acid derivatives such as glycerin monoricinoleate, phosphate plasticizers such as tricresyl phosphate and trixylenyl phosphate, lactic acid, linear lactic acid oligomers, cyclic lactic acid oligomers, and lactide. it can. These plasticizers may be used alone or in combination of two or more.

Of the above plasticizers, lactic acid, linear lactic acid oligomers, cyclic lactic acid oligomers or lactide are preferably used in view of the plasticizing effect. The above-mentioned lactic acid oligomer can be easily prepared by heating and dehydrating and condensing lactic acid at 50 to 280 ° C. Usually, the degree of polymerization of the oligomer obtained by this method is about 1 to 30. It can also be prepared by heating glycolide or lactide to 50 to 280 ° C. in the presence of water and glycolic acid or lactic acid. The oligomer referred to in the present invention also includes lactide (a cyclic dimer of lactic acid) used as a monomer during the synthesis of the lactic acid-based polymer.

By adding the above plasticizer to the lactic acid-based polymer, the lactic acid-based polymer is effectively plasticized, and the resulting resin composition becomes flexible. When the amount of the plasticizer in the resin composition is 5% by weight or more, flexibility becomes apparent, and when it exceeds 20% by weight, the moldability at the time of melt-extrusion and foaming of the composition deteriorates. In addition, the strength of the obtained molded article is weakened, which is not preferable.

As a method of mixing a plasticizer with a lactic acid-based polymer, chloroform, methylene chloride,
Examples thereof include a method of dissolving in a solvent such as toluene and xylene, or a method of heating and melting a lactic acid-based polymer at 100 to 280 ° C., and adding and mixing a predetermined amount of a plasticizer.

In the case of using lactic acid or lactic acid oligomer (including lactide) as a preferable plasticizer, the following two methods can be mentioned as a mixing method. (A) a method in which lactide or lactide and glycolide are polymerized to leave unreacted lactide without completing the reaction, and (b) after lactide or polymerization of lactide and glycolide is completed.
There is a method of adding and mixing a predetermined amount of lactic acid or lactic acid oligomer (including lactide). Further, the methods (a) and (b) may be used in combination. In the method (a), the unreacted lactide is microscopically mixed well with the lactic acid-based polymer,
Shows good plasticizing effect. The monomer (lactide) is heated in the presence of a catalyst, possibly in the presence of a chain-enhancing agent, to start the reaction, and then, when the desired residual monomer concentration is reached, the heating is stopped to stop the reaction. The amount of residual monomer in the resulting lactic acid-based polymer can be determined by gas chromatography analysis and thermogravimetric analysis.
In the method (b), after the polymerization reaction is completed, the obtained lactic acid-based polymer is dissolved in a solvent such as chloroform, methylene chloride, toluene and xylene, or the lactic acid-based polymer is heated and melted at 100 to 280 ° C, A predetermined amount of lactic acid or lactic acid oligomer is added and mixed. This method has the advantage that the amount of lactic acid or lactic acid oligomer in the composition can be easily adjusted.

The polylactic acid resin composition obtained by the above method is formed at 180 to 280 ° C. by compression molding, melt extrusion molding or the like to form a film, sheet, rod or the like, which is then dried ice-methanol or the like. After cooling to about −20 ° C. using a pulverizer, pulverizing using a hammer mill or the like,
Alternatively, it may be pelletized by melt extrusion or the like.

In the present invention, after the foaming agent is mixed with the polylactic acid-based resin composition, the mixture is melt-kneaded using a single-screw or twin-screw extruder or the like, and the molten foam is melted from a circular or linear die. Extrude as

As the blowing agent used in the present invention, an organic blowing agent represented by dinitrile azoisobutyrate, diazoaminobenzene, 1,3-bis (p-xenyl) triazine, azodicarboxylic acid amide, or ammonium oxalate Inorganic blowing agents represented by oxalic acid, sodium bicarbonate and oxalic acid, ammonium bicarbonate, and a mixture of ammonium carbonate and sodium nitrite are exemplified. Any of these organic foaming agents and inorganic foaming agents may be used as long as they decompose at a temperature lower than the extrusion temperature. In addition, volatile liquids such as acetone, methyl ethyl ketone, ethyl acetate, methyl chloride, ethyl chloride, chloroform, methylene chloride, methylene bromide, and nitrogen, carbon dioxide, ammonia, methane, ethane, propane, ethylene, propylene, and gaseous halogens Compounds which are gaseous at room temperature, such as hydrogenated hydrocarbons, are also exemplified.

The amount of the foaming agent varies depending on the desired network and the type of the foaming agent, but it is 0.2 to 10 parts by weight based on 100 parts by weight of the polylactic acid resin composition.
Parts by weight. If the amount is less than 0.2 part by weight, the foaming becomes low and it is difficult to defibrate. If the amount exceeds 10 parts by weight, extrudability is deteriorated and uneconomical. The mixing of the polylactic acid-based resin composition and the foaming agent may be performed by a usual mixing method using a ribbon blender, a conical blender, or the like. The mixing conditions may be such that the lactic acid-based resin composition and the foaming agent are well mixed, but preferably at room temperature for 5 to 30 minutes.

For melt-extrusion of the mixture of the polylactic acid-based resin composition and the foaming agent, a usual single-screw or twin-screw extruder or the like is used. The extrusion temperature is preferably from 100 to
It is in the range of 270 ° C, more preferably in the range of 130 to 250 ° C. If the temperature is lower than 100 ° C., it is difficult to obtain extrusion stability,
In addition, if the temperature exceeds 270 ° C., the decomposition of the lactic acid-based polymer becomes severe, which is not preferable.

The die of the extruder used in the present invention may have an annular or linear slit. The temperature of the die may be as high as the extrusion temperature range.

In the present invention, the polylactic acid resin composition and foam
The mixture of the agents is discharged from the extruder die as a molten foam.
Immediately after, a gas such as air at 10 to 50 ° C is blown to cool
While stretching to remove air bubbles in the molten foam.
Destroy and open to form a mesh. 10-
Solidified on a take-off roll having a surface temperature of 50 ° C.Was
Later, take up. The take-up speed by the take-up roll is
The ratio is set to 10 to 500. Outside this range
Is not preferable because it does not result in a good spread state. Use
Air is the most suitable cooling gas from the viewpoint of economy and handling.
Although suitable, other gases such as nitrogen and carbon dioxide may be used. cold
The amount of gas used for rejection is affected by temperature.
If the mesh is lm^TwoHit0.1~ 15m^Three / MinIs preferred
No.0.1m^Three / MinIf less, the cooling effect is insufficient and good
It does not spread. Also, 15m^Three / MinCooling over
Increases velocity and solidifies generated bubbles before they break
It is not preferable because it may occur.

If the melted foam of the polylactic acid-based resin composition is not stretched while being cooled to the above-mentioned temperature range using a gas such as air, it is difficult to open the fiber because it has a property of dripping easily. Even if the die temperature is lowered and the melt viscosity of the composition is increased, the spread is not uniform. When it is desired to increase the degree of foaming, the amount of the foaming agent added may be increased, or the timing of cooling the molten foam discharged from the guy may be delayed. If it is desired to reduce the degree of foaming, the opposite is recommended. The degree of opening is adjusted depending on the degree of stretching of the molten foam discharged from the guy, but is usually stretched to 1.5 to 5 times the length immediately after extrusion.

The polylactic acid-based resin composition used in the present invention may contain a coloring agent, a filler, a reinforcing agent and the like, in addition to the foaming agent, as long as the object of the present invention is not impaired. Further, the obtained polymer network can be further subjected to stretching, heat treatment and the like.

[0031]

The present invention will be described in more detail with reference to the following examples. The evaluation method used in this example is as follows. Residual monomer amount After the completion of the polymerization reaction, the reaction mixture was dissolved in hexafluoroisopropanol (hereinafter referred to as HFIP) or methylene chloride to obtain a solution having a known concentration, and the amount of the residual monomer was quantified by gas chromatography. Solution viscosity Dissolve lactic acid-based polymer in chloroform (concentration 0.5g
/ Dl), 25 ± 0.05 using an Ubbelohde viscometer.
The solution viscosity was measured at ℃, and the intrinsic viscosity η was calculated by the following equation. η = log _e (T ₁ / T ₀ ) / C T ₀ : measurement time of solvent (sec) T ₁ : measurement time of sample solution (sec) C: concentration of sample solution (g / dl) Spreading state A state in which the fiber was opened into a fine fibrous mesh structure was regarded as a good state, and a fiber opening of 5 mm or more and a portion which was not opened was 100c.
A state in which there were three or more places in m ² , or in which there was a fiber opening of 30 mm or more, and there were five or more places in 1 m ² that were not opened was regarded as defective. Basis weight The weight of a sample having a size of 5 cm square was measured, converted to the weight per 1 m ² , and defined as the basis weight (g / m ² ). A sample having a stiffness ratio of 20 mm in width was set in a tensile tester so as to have a measurement length (gripping interval) of 50 mm, and the sample was pulled in a winding direction at a pulling speed of 50 mm / min to obtain a load-strain curve. The load at the time of 100% tension was obtained by extrapolating the tangent at the initial rising portion of this curve, and was calculated by the following equation.

Rigidity (kgf · m / g) = 100 × R ×
1 / W × 1 / M Here, R: load at the time of 100% tension (kgf), W: sample width (cm), M: basis weight (g / m 2). Degree of polymerization of oligomer The oligomer is dissolved in tetrahydrofuran or chlororum, and gel permeation chromatography (G
PC), and the degree of polymerization distribution was measured and calculated.

Preparation Example 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. Upon cooling, a viscous transparent liquid was obtained at room temperature. As a result of measurement by GPC, this liquid contained lactic acid and lactic acid oligomer. The average degree of polymerization was 2.8. Hereinafter, it is referred to as LA oligomer.

Examples 1 to 15, Comparative Examples 1 to 4 Commercially available L-lactide (hereinafter referred to as L-LTD), D-lactide
Lactide (hereinafter referred to as D-LTD), DL-lactide (hereinafter referred to as DL-LTD) and glycolide (hereinafter referred to as GLD) were each recrystallized four times using ethyl acetate and purified. After drying ε-caprolactone (hereinafter referred to as CL) on calcium hydride,
Purified by distillation. The amounts of the above L-LTD and D-LT shown in Table 1 were placed in a glass reaction vessel whose surface was treated with silane.
D, DL-LTD, GLD, CL and stannous octoate as a catalyst were charged, and the inside of the vessel was degassed under reduced pressure and dried for one day. The reaction vessel was heated to a predetermined temperature shown in Table 1 and polymerized for a predetermined time. After the reaction is completed,
The reaction product was taken out. The obtained lactic acid-based polymer is
Called P1 to P6. The intrinsic viscosity and residual monomer amount of these lactic acid-based polymers were measured, and the results are shown in [Table 1].

[0035]

[Table 1] Next, after adding L-LTD or the LA oligomer obtained in the preparation example at a ratio shown in [Table 2] to these lactic acid-based polymers, they were mixed at a temperature shown in [Table 2] using a plastomill to obtain polylactic acid. The system resin compositions C1 to C8 were obtained.
Further, these resin compositions were heated at a temperature shown in [Table 2].
The sheet was pressed at 00 kg / cm ² to form a sheet having a thickness of 1 mm.

[0036]

[Table 2] After cooling the polylactic acid-based resin composition shown in [Table 3] using liquid nitrogen and pulverizing it using a hammer mill pulverizer, a blowing agent (azodicarboxylic acid amide) was added at a ratio shown in [Table 3]. And mixed at room temperature using a ribbon blender.
The mixture was melt-kneaded using a single-screw extruder having a diameter of 19 mm at an extrusion temperature shown in [Table 3], and a discharge amount of 30 g was obtained through a 150 mm wide T-die slit at the temperature shown in [Table 3].
/ Min as a molten foam or a non-foam.
Immediately after discharge, the molten foam is stretched while being cooled by blowing air at room temperature at the air volume shown in Table 3, and wound up at a stretching speed of 10 m / min while spreading to obtain a polymer network. Was. The obtained polymer network was evaluated for the open state, basis weight, and rigidity as a measure of flexibility, and the results are shown in [Table 3].

[0037]

[Table 3] As a result of practical evaluation of these polymer networks, they were successfully used for wiping edible oil. Also, wrap cotton and feathers,
Combining was possible without impairing the air permeability. It could be suitably used as a good garbage bag for draining kitchen garbage at home. When used as an underlay for packing meat, fish sashimi, etc., liquids such as blood could be absorbed. It was also suitable for wrapping plant roots and as a light-shielding material for sunlight.
It could be suitably used also as a filter of a ventilation part.

Next, the polymer network obtained in Examples 1, 2 and 5 and the polymer network obtained from the polyolefin resin (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name: Neunetz U) were mixed with 37. It was immersed in distilled water at ℃ and the weight loss rate after 120 days was measured. As a result, the weight reduction rates were 9%, 17%, 27% and 0%, respectively.

[0039]

The hydrolyzable polymer network of the present invention is characterized in that it has hydrolyzability and, in addition, has a moderate softness. Therefore, it is useful as a material for absorbing oil, body fluids, etc., a light shielding material, a heat insulating material, a filtering material, a packaging material, and the like. When discarded after use, it is hydrolyzed in nature and accumulated as industrial waste. Never be. In addition, in the case of ocean speculation, the living environment of marine life is not destroyed.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08L 67/04 C08L 67/04 D01D 5/00 D01D 5/00 D04H 3/02 D04H 3/02 13/00 13/00 // B29K 67: 00 B29K 67:00 105: 04 105: 04 B29L 28:00 B29L 28:00 (56) References JP-A-51-47170 (JP, A) JP-A-1-104635 (JP, A) JP-A-5 -39381 (JP, A) JP-A-6-240037 (JP, A) JP-A-61-42531 (JP, A) JP-T-6-504799 (JP, A) International Publication No. 92/1737 (WO, A1) (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 47/00-47/96 B29D 28/00 C08G 63/00-63/91 D01D 5/00-5/42 D04H 3/00-3 / 16 D04H 13/00-13/02

Claims (8)

(57) [Claims] 1. A polylactic acid or a lactic acid-hydroxycarboxylic acid copolymer of 80 to 100% by weight and a plasticizer 0
A polymer network obtained by melt-foaming and extruding a mixture obtained by adding 0.2 to 10 parts by weight of a foaming agent to 100 parts by weight of a polylactic acid-based resin composition containing 20 to 20% by weight. 2. The method according to claim 1, wherein the polylactic acid has an L-lactic acid unit of 85 to 100.
Mol% and 0 to 15 mol% of D-lactic acid unit, or D
-85 to 100 mol% of lactic acid units and 0 to L-lactic acid units
The polymer network according to claim 1, which is a polylactic acid containing 15 mol%. 3. A lactic acid-hydroxycarboxylic acid copolymer comprising 85 to 100 mol% of L-lactic acid units and 0 to 15 mol% of glycolic acid units, or 85 to 1 mol of D-lactic acid units.
The polymer network according to claim 1, which is a copolymer containing 00 mol% and 0 to 15 mol% of glycolic acid units. 4. The polymer network according to claim 1, wherein the plasticizer is lactic acid, lactic acid oligomer or lactide. 5. The polylactic acid (A) has an L-lactic acid unit of 85-1.
The lactic acid-hydroxycarboxylic acid copolymer (B) contains L-lactic acid-hydroxycarboxylic acid copolymer (B) containing 00 mol% and 0 to 15 mol% of D-lactic acid units or 85 to 100 mol% of D-lactic acid units and 0 to 15 mol% of L-lactic acid units. 85-100 mol% of lactic acid units,
Or a plasticizer (C) containing 85 to 100 mol% of D-lactic acid units and 0 to 15 mol% of glycolic acid units
Is lactic acid, lactic acid oligomer or lactide.
The polymer network according to the above. 6. The polymer network according to claim 1, wherein the blowing agent is azodicarboxylic amide. 7. The polymer network according to claim 1, wherein the melt foaming extrusion temperature is in the range of 100 to 270 ° C. 8. The amount of gas for cooling at the time of fiber opening is 0.1 to 15 m.
The polymer network according to claim 1, wherein the polymer network is ³ / min · m ^2.