CA2560363A1 - Ultrafine polylactic acid fibers and fiber structure, and process for their production - Google Patents
Ultrafine polylactic acid fibers and fiber structure, and process for their production Download PDFInfo
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- CA2560363A1 CA2560363A1 CA002560363A CA2560363A CA2560363A1 CA 2560363 A1 CA2560363 A1 CA 2560363A1 CA 002560363 A CA002560363 A CA 002560363A CA 2560363 A CA2560363 A CA 2560363A CA 2560363 A1 CA2560363 A1 CA 2560363A1
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- fiber
- fiber structure
- lactic acid
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
- D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/0007—Electro-spinning
- D01D5/0015—Electro-spinning characterised by the initial state of the material
- D01D5/003—Electro-spinning characterised by the initial state of the material the material being a polymer solution or dispersion
- D01D5/0038—Electro-spinning characterised by the initial state of the material the material being a polymer solution or dispersion the fibre formed by solvent evaporation, i.e. dry electro-spinning
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
- D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
- D01F6/625—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters derived from hydroxy-carboxylic acids, e.g. lactones
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/78—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products
- D01F6/84—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products from copolyesters
-
- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
- D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
- D04H1/4326—Condensation or reaction polymers
- D04H1/435—Polyesters
-
- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
- D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
- D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
- D04H1/56—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving in association with fibre formation, e.g. immediately following extrusion of staple fibres
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2913—Rod, strand, filament or fiber
- Y10T428/2929—Bicomponent, conjugate, composite or collateral fibers or filaments [i.e., coextruded sheath-core or side-by-side type]
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- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Dispersion Chemistry (AREA)
- Artificial Filaments (AREA)
- Nonwoven Fabrics (AREA)
- Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
Abstract
A fibrous structure obtained by spinning a solution of L-lactic acid condensation product and D-lactic acid condensation product in accordance wi th an electrostatic spinning technique. There can be provided a fibrous structu re containing fibers that have an extremely small fiber diameter, exhibiting excellent heat resistance and biodegradability.
Description
DESCRIPTION
ULTRAFINE POLYLACTIC ACID FIBERS AND FIBER STRUCTURE, AND
PROCESS FOR THEIR PRODUCTION
Technical Field The present invention relates to fibers comprising biodegradable polylactic acid as a constituent component, and more specifically it relates to ultrafine polylactic acid fibers and a fiber structure, and to a process for their production.
Background Art Ultrafine fibers have a soft feel and are therefore used for such purposes as woven and knitted fabrics or artificial leather, for clothing or interior goods.
They are also used in the forms of sheets or nonwoven fabrics for such purposes as filters, insulating sheets, wipers, packing materials, sanitary goods and the like.
In recent years it has been desirable to reduce environmental load from the standpoint of preserving the earth environment. Yet because 6-nylon, polyethylene terephthalate, polypropylene and the like used for conventional ultrafine fibers do not decompose in soil or compost, they must be incinerated or buried after use and therefore create a major environmental load due to atmospheric pollution or prolonged durability after burial.
A demand therefore exists for ultrafine fibers that decompose in soil or compost. For example, there have been proposed ultrafine fibers composed of a biodegradable thermoplastic aliphatic polyester with a single fiber
ULTRAFINE POLYLACTIC ACID FIBERS AND FIBER STRUCTURE, AND
PROCESS FOR THEIR PRODUCTION
Technical Field The present invention relates to fibers comprising biodegradable polylactic acid as a constituent component, and more specifically it relates to ultrafine polylactic acid fibers and a fiber structure, and to a process for their production.
Background Art Ultrafine fibers have a soft feel and are therefore used for such purposes as woven and knitted fabrics or artificial leather, for clothing or interior goods.
They are also used in the forms of sheets or nonwoven fabrics for such purposes as filters, insulating sheets, wipers, packing materials, sanitary goods and the like.
In recent years it has been desirable to reduce environmental load from the standpoint of preserving the earth environment. Yet because 6-nylon, polyethylene terephthalate, polypropylene and the like used for conventional ultrafine fibers do not decompose in soil or compost, they must be incinerated or buried after use and therefore create a major environmental load due to atmospheric pollution or prolonged durability after burial.
A demand therefore exists for ultrafine fibers that decompose in soil or compost. For example, there have been proposed ultrafine fibers composed of a biodegradable thermoplastic aliphatic polyester with a single fiber
2 diameter of no greater than 0.5 decitex (for example, see Patent document 1). There have also been proposed fibers composed of poly(L-lactic acid) with a fiber diameter of 100 nm-4 um (for example, see Patent document 2).
However, the ultrafine fibers referred to above have poor heat resistance and their uses have therefore been limited.
A method for improving the heat resistance of polylactic acid that has been of note recently is stereo complex formation with poly(L-lactic acid) and poly(D
lactic acid) (for example, see Patent document 3).
It is known that blending poly(L-lactic acid) and poly(D-lactic acid) in equivalent amounts can yield racemic crystals with a higher melting point than polylactic acid.
However, hitherto obtained polylactic acid stereo complex fibers are mixtures of poly(L-lactic acid) single crystals and poly(D-lactic acid) single crystals, and their heat resistance has been insufficient. Such fibers have large fiber diameters and the fiber structures formed from the fibers have exhibited inadequate flexibility (for example, see Patent documents 3 and 4).
[Patent document 1) Japanese Unexamined Patent Publication No. 2001-192932 [Patent document 2] International Patent Publication No.
[Patent document 3] Japanese Unexamined Patent Publication No . 2002-30523 [Patent document 4) Japanese Unexamined Patent Publication No. 2003-138437 Disclosure of the Invention
However, the ultrafine fibers referred to above have poor heat resistance and their uses have therefore been limited.
A method for improving the heat resistance of polylactic acid that has been of note recently is stereo complex formation with poly(L-lactic acid) and poly(D
lactic acid) (for example, see Patent document 3).
It is known that blending poly(L-lactic acid) and poly(D-lactic acid) in equivalent amounts can yield racemic crystals with a higher melting point than polylactic acid.
However, hitherto obtained polylactic acid stereo complex fibers are mixtures of poly(L-lactic acid) single crystals and poly(D-lactic acid) single crystals, and their heat resistance has been insufficient. Such fibers have large fiber diameters and the fiber structures formed from the fibers have exhibited inadequate flexibility (for example, see Patent documents 3 and 4).
[Patent document 1) Japanese Unexamined Patent Publication No. 2001-192932 [Patent document 2] International Patent Publication No.
[Patent document 3] Japanese Unexamined Patent Publication No . 2002-30523 [Patent document 4) Japanese Unexamined Patent Publication No. 2003-138437 Disclosure of the Invention
3 It is an object of the present invention to overcome the aforementioned problems of the prior art by providing fibers with a very small fiber diameter, and excellent heat resistance and biodegradability.
It is another object of the invention to provide a fiber structure containing the fibers.
It is yet another object of the invention to provide a process for production of the fiber structure by a very convenient method.
Brief Explanation of the Drawings Fig. 1 is a schematic view showing an embodiment of the construction of an apparatus for production of a fiber structure of the invention.
Fig. 2 is a schematic view showing an embodiment of the construction of an apparatus for production of a fiber structure of the invention.
Fig. 3 is a photograph of the surface of the fiber structure obtained in Example 1, taken with a scanning electron microscope (2000x).
Fig. 4 is a photograph of the surface of the fiber structure obtained in Example l, taken with a scanning electron microscope (8000x).
Fig. 5 is a photograph of the surface of the fiber structure obtained in Example 2, taken with a scanning electron microscope (2000x).
Fig. 6 is a photograph of the surface of the fiber structure obtained in Example 2, taken with a scanning electron microscope (8000x).
Fig. 7 is a photograph of the surface of the fiber structure obtained in Comparative Example 1, taken with a
It is another object of the invention to provide a fiber structure containing the fibers.
It is yet another object of the invention to provide a process for production of the fiber structure by a very convenient method.
Brief Explanation of the Drawings Fig. 1 is a schematic view showing an embodiment of the construction of an apparatus for production of a fiber structure of the invention.
Fig. 2 is a schematic view showing an embodiment of the construction of an apparatus for production of a fiber structure of the invention.
Fig. 3 is a photograph of the surface of the fiber structure obtained in Example 1, taken with a scanning electron microscope (2000x).
Fig. 4 is a photograph of the surface of the fiber structure obtained in Example l, taken with a scanning electron microscope (8000x).
Fig. 5 is a photograph of the surface of the fiber structure obtained in Example 2, taken with a scanning electron microscope (2000x).
Fig. 6 is a photograph of the surface of the fiber structure obtained in Example 2, taken with a scanning electron microscope (8000x).
Fig. 7 is a photograph of the surface of the fiber structure obtained in Comparative Example 1, taken with a
4 scanning electron microscope (2000x).
Fig. 8 is a photograph of the surface of the fiber structure obtained in Comparative Example 1, taken with a scanning electron microscope (8000x).
Fig. 9 is a photograph of the surface of the fiber structure obtained in Comparative Example 2, taken with a scanning electron microscope (2000x).
Fig. 10 is a photograph of the surface of the fiber structure obtained in Comparative Example 2, taken with a scanning electron microscope (8000x).
Fig. 11 is a photograph of the surface of the fiber structure obtained in Comparative Example 3, taken with a scanning electron microscope (2000x).
Fig. 12 is a photograph of the surface of the fiber structure obtained in Comparative Example 3, taken with a scanning electron microscope (8000x).
Fig. 13 is a photograph of the surface of the fiber structure obtained in Example 3, taken with a scanning electron microscope (2000x).
Fig. 14 is a photograph of the surface of the fiber structure obtained in Example 3, taken with a scanning electron microscope (8000x).
Fig. 15 is a photograph of the surface of the fiber structure obtained in Example 4, taken with a scanning electron microscope (2000x).
Fig. 16 is a photograph of the surface of the fiber structure obtained in Example 4, taken with a scanning electron microscope (8000x).
Fig. 17 is a photograph of the surface of the fiber structure obtained in Comparative Example 4, taken with a scanning electron microscope (2000x).
Fig. 18 is a photograph of the surface of the fiber structure obtained in Comparative Example 4, taken with a scanning electron microscope (8000x).
Fig. 19 is a photograph of the surface of the fiber
Fig. 8 is a photograph of the surface of the fiber structure obtained in Comparative Example 1, taken with a scanning electron microscope (8000x).
Fig. 9 is a photograph of the surface of the fiber structure obtained in Comparative Example 2, taken with a scanning electron microscope (2000x).
Fig. 10 is a photograph of the surface of the fiber structure obtained in Comparative Example 2, taken with a scanning electron microscope (8000x).
Fig. 11 is a photograph of the surface of the fiber structure obtained in Comparative Example 3, taken with a scanning electron microscope (2000x).
Fig. 12 is a photograph of the surface of the fiber structure obtained in Comparative Example 3, taken with a scanning electron microscope (8000x).
Fig. 13 is a photograph of the surface of the fiber structure obtained in Example 3, taken with a scanning electron microscope (2000x).
Fig. 14 is a photograph of the surface of the fiber structure obtained in Example 3, taken with a scanning electron microscope (8000x).
Fig. 15 is a photograph of the surface of the fiber structure obtained in Example 4, taken with a scanning electron microscope (2000x).
Fig. 16 is a photograph of the surface of the fiber structure obtained in Example 4, taken with a scanning electron microscope (8000x).
Fig. 17 is a photograph of the surface of the fiber structure obtained in Comparative Example 4, taken with a scanning electron microscope (2000x).
Fig. 18 is a photograph of the surface of the fiber structure obtained in Comparative Example 4, taken with a scanning electron microscope (8000x).
Fig. 19 is a photograph of the surface of the fiber
5 structure obtained in Comparative Example 5, taken with a scanning electron microscope (2000x).
Fig. 20 is a photograph of the surface of the fiber structure obtained in Comparative Example 5, taken with a scanning electron microscope (8000x).
Fig. 21 is a photograph of the surface of the fiber structure obtained in Comparative Example 6, taken with a scanning electron microscope (2000x).
Fig. 22 is a photograph of the surface of the fiber structure obtained in Comparative Example 6, taken with a scanning electron microscope (8000x).
Best Mode for Carrying Out the Invention The invention will now be explained in greater detail.
The fibers of the invention must have a mean fiber diameter of no greater than 10 um. The mean fiber diameter of the fibers preferably does not exceed 10 ~m because the obtained fiber structure will lack flexibility. The mean fiber diameter of the fibers is preferably in the range of 0.01-5 um.
The fibers of the invention also must have fiber lengths of 20 um or greater. If the fiber lengths are less than 20 Vim, the dynamic strength of the obtained fiber structure will be insufficient. The fiber lengths are preferably at least 40 ~m and more preferably at least 1 mm .
The fibers of the invention must have as the main
Fig. 20 is a photograph of the surface of the fiber structure obtained in Comparative Example 5, taken with a scanning electron microscope (8000x).
Fig. 21 is a photograph of the surface of the fiber structure obtained in Comparative Example 6, taken with a scanning electron microscope (2000x).
Fig. 22 is a photograph of the surface of the fiber structure obtained in Comparative Example 6, taken with a scanning electron microscope (8000x).
Best Mode for Carrying Out the Invention The invention will now be explained in greater detail.
The fibers of the invention must have a mean fiber diameter of no greater than 10 um. The mean fiber diameter of the fibers preferably does not exceed 10 ~m because the obtained fiber structure will lack flexibility. The mean fiber diameter of the fibers is preferably in the range of 0.01-5 um.
The fibers of the invention also must have fiber lengths of 20 um or greater. If the fiber lengths are less than 20 Vim, the dynamic strength of the obtained fiber structure will be insufficient. The fiber lengths are preferably at least 40 ~m and more preferably at least 1 mm .
The fibers of the invention must have as the main
6 constituent component a polylactic acid component with a melting point of 190°C or higher, and they contain substantially no constituent component with a melting point of below 190°C.
Here, "contain substantially no constituent component with a melting point of below 190°C" means that no endothermic peak is exhibited at below 190°C in the melting endotherm (DSC curve) upon differential scanning calorimetric analysis of the obtained fibers.
Preferably no constituent component with a melting point of below 190°C is present because heat resistance will be lacking. The melting point of the fiber component is more preferably 195°C-250°C.
As mentioned above, the fibers of the invention have as the main constituent component a polylactic acid component with a melting point of 190°C or higher.
The fibers of the invention more preferably have surface depressions with diameters of 0.01-1 um, with the depressions constituting 10-950 of the fiber surfaces. This kind of surface structure will increase the surface area of fibers structures formed from the fibers, thereby improving the rate of decomposition in soil or compost. The diameters of the depressions are more preferably 0.02-0.5 um, and the proportion of depressions on the fiber surfaces is more preferably 40-950.
According to the invention, the polylactic acid component is a polymer comprising a condensate with at least 80 molo lactic acid based on the total repeating units, and it may be copolymerized with other components so long as the features of the invention are not prevented.
"Main constituent component" means that the component
Here, "contain substantially no constituent component with a melting point of below 190°C" means that no endothermic peak is exhibited at below 190°C in the melting endotherm (DSC curve) upon differential scanning calorimetric analysis of the obtained fibers.
Preferably no constituent component with a melting point of below 190°C is present because heat resistance will be lacking. The melting point of the fiber component is more preferably 195°C-250°C.
As mentioned above, the fibers of the invention have as the main constituent component a polylactic acid component with a melting point of 190°C or higher.
The fibers of the invention more preferably have surface depressions with diameters of 0.01-1 um, with the depressions constituting 10-950 of the fiber surfaces. This kind of surface structure will increase the surface area of fibers structures formed from the fibers, thereby improving the rate of decomposition in soil or compost. The diameters of the depressions are more preferably 0.02-0.5 um, and the proportion of depressions on the fiber surfaces is more preferably 40-950.
According to the invention, the polylactic acid component is a polymer comprising a condensate with at least 80 molo lactic acid based on the total repeating units, and it may be copolymerized with other components so long as the features of the invention are not prevented.
"Main constituent component" means that the component
7 constitutes at least 75 wt%, preferably at least 80 wt%, more preferably at least 90 wt% and most preferably at least 95 wt% based on the total constituent components of the fibers of the invention.
According to the invention, the polylactic acid component preferably consists of a mixture of a condensate with at least 80 mol% L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units.
Here, a condensate with at least 80 mol% L-lactic acid based on the total repeating units means a content of 80-100 mol% L-lactic acid and 0-20 mol% of D-lactic acid or a copolymerizing component other than D-lactic acid. On the other hand, a condensate with at least 80 mol% D-lactic acid based on the total repeating units means a content of 80-100 mol% D-lactic acid and 0-20 mol% of L-lactic acid or a copolymerizing component other than L-lactic acid.
As copolymerizing components other than D-lactic acid and L-lactic acid there may be mentioned oxy acids, lactones, dicarboxylic acids and polyhydric alcohols.
There may also be mentioned various polyesters, polyethers and polycarbonates comprising such components and having ester bond-forming functional groups.
According to the invention, the polylactic acid component is preferably a mixture comprising a condensate with at least 80 mol% L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units, in a weight ratio of (6:4)-(4:6) .
More preferably, the condensate with at least 80 molo L-lactic acid based on the total repeating units and the condensate with at least 80 molo D-lactic acid based on the total repeating units are mixed in substantially a 5:5 ratio.
According to the invention, the weight-average molecular weight of the polylactic acid component is more preferably 100,000 or greater for improved dynamic strength of the obtained fiber structure.
The fiber structure of the invention includes at least the aforementioned ultrafine polylactic acid fibers, but a "fiber structure" according to the invention may be any three-dimensional structure formed by weaving, knitting or laminating the fibers, and a nonwoven fabric may be mentioned as a preferred example.
The content of the ultrafine polylactic acid fibers in the fiber structure of the invention is not particularly limited, but the features of the ultrafine polylactic acid fibers can be exhibited with a content of 50 wto or greater. The content is more preferably 80 wto or greater, and even more preferably the fiber structure is composed essentially of the polylactic acid fibers alone.
In particular, preferably the fibers forming the fiber structure have a mean diameter of no greater than 10 um and contain substantially no fibers with fiber lengths of less than 20 um.
Any process that yields the aforementioned fibers may be employed for production of a fiber structure of the invention, but there may be mentioned as a preferred mode of the production process one including a stage wherein a condensate with at least 80 molo L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units are combined in a weight ratio of (6:4)-(4:6) and then dissolved in a solvent to produce a solution, a stage wherein the solution is spun by an electrospinning method, and a stage wherein fibers are accumulated on a collecting plate by the spinning.
There may also be mentioned as a preferred mode of the invention a production process including a stage wherein a condensate with at least 80 mol% L-lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage wherein a condensate with at least 80 molo D-Lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage in which the two solutions are mixed in a weight ratio of (6:4)-(4:6), a stage wherein the mixed solution is spun by an electrospinning method, and a stage wherein fibers are accumulated on a collecting plate by the spinning.
An electrospinning method is a method in which a solution of a fiber-forming compound is discharged into an electrostatic field formed between two electrodes, the solution is drawn toward the electrodes, and the resulting filamentous substance is accumulated on a collecting plate to obtain a fiber structure, where the filamentous substance need not be free of the solvent used to dissolve the fiber-forming compound but may also include the solvent.
For production of fibers comprising a stereo complex of poly(L-lactic acid) and poly(D-lactic acid), either melt spinning is carried out after melt kneading, or dry spinning is carried out from a solution containing the L-lactic acid condensate and poly(D-lactic acid) condensate, but in either case it has not been hitherto possible to completely eliminate a melting point of below 190°C.
However, it was found surprisingly that fibers obtained by electrospinning have essentially no melting point below 190°C.
5 An apparatus used- in electrospinning for the production process of the invention will now be described.
The aforementioned electrodes may be of any type such as metal, inorganic or organic substances so long as they exhibit electrical conductivity, and they may also have 10 electrical conductive thin-films of metal, inorganic or organic substances on insulators.
The electrostatic field may be formed by a pair of or more electrodes, and a high voltage may be applied to any of the electrodes. This also includes cases of using, for example, a total of three electrodes where two are high-voltage electrodes with different voltage values (for example, 15 kV and 10 kV) and one is a grounded electrode, as well as cases of using more than three electrodes.
The steps in a procedure of producing fibers for a fiber structure of the invention by electrospinning will now be explained in order.
First, a solution containing the aforementioned polylactic acid components dissolved in a solvent is prepared, where the concentration of the polylactic acid components in the solution is preferably 1-30 wto. A low concentration of less than 1 wto is not preferred because it will be difficult to form a fiber structure. The concentration is also preferably not greater than 30 wt%
because the mean diameter of the obtained fibers will be increased. The preferred concentration range is 2-25 wt%.
The solvent used to dissolve the polylactic acid components is not particularly restricted so long as it is capable of dissolving the polylactic acid components and evaporating off during the spinning stage of the electrospinning to form fibers.
Using a volatile solvent as the solvent is preferred as it will facilitate formation of the aforementioned depressions on the fiber surfaces. A volatile solvent according to the invention is a substance which has a boiling point of no higher than 200°C at atmospheric pressure and is a liquid at room temperature (for example, 27°C). As examples of specific volatile solvents there may be mentioned methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane, bromoform, tetrahydrofuran, 1,4-dioxane, 1,1,1,3,3,3-hexafluoroisopropanol, toluene, xylene and dimethylformamide, among which methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane, bromoform, tetrahydrofuran and 1,4-dioxane are preferred and methylene chloride is most preferred.
These solvents may be used alone, or a plurality of solvents may be combined for use as a mixed solvent.
The stage of spinning the aforementioned solution by electrospinning will now be explained. Any desired method may be employed for discharge of the solution into the electrostatic field, and for example, the solution may be supplied to a nozzle for appropriate positioning of the solution in the electrostatic field, and the solution drawn from the nozzle by the electrical field for formation into a filament.
A preferred mode of production of a fiber structure of the invention will now be explained in greater detail with reference to Fig. 1.
An injection needle-shaped solution ejection nozzle (1 in Fig. 1) having a voltage applied by appropriate means such as a high-voltage generator (6 in Fig. 1) is fitted at the tip of the cylindrical solution-holder of a syringe (3 in Fig. 1), and the solution (2 in Fig. 1) is guided to the tip of the solution ejection nozzle. The tip of the solution ejection nozzle (1 in Fig. 1) is situated at an appropriate distance from a grounded filamentous substance-collecting electrode (5 in Fig. 1), and the solution (2 in Fig. 1) is ejected from the tip of the solution ejection nozzle (1 in Fig. 1) to form a filamentous substance between the nozzle tip solution and the filamentous substance-collecting electrode (5 in Fig. 1).
As a different mode, shown in Fig. 2, fine droplets of the solution (not shown) may be introduced into an electrostatic field, with the only condition being that the solution (2 in Fig. 2) is placed in the electrostatic field and held at a distance from the filamentous substance-collecting electrode (5 in Fig. 2) which allows formation into a filament. For example, an electrode (4 in Fig. 2) counter to the filamentous substance-collecting electrode may be inserted directly into the solution (2 in Fig. 2) in the holder (3 in Fig. 2) with the solution ejection nozzle (1 in Fig. 2).
When the solution is ejected through the nozzle into the electrostatic field, the filamentous substance production speed can be increased by using a plurality of nozzles in parallel. Also, the distance between electrodes will depend on the charge, nozzle dimensions, ejection volume of the solution from the nozzle and the solution concentration, but a distance of 5-20 cm has been found to be suitable for approximately 10 kV. The applied electrostatic potential will normally be 3-100 kV, preferably 5-50 kV and more preferably 5-30 kV. The desired potential can be produced by any appropriate method known in the prior art.
The two modes described above employ an electrode as the collecting plate, but a material serving as the collecting plate may also be placed between the electrodes, to provide a collecting plate separate from the electrodes for collection of a filament laminate. In this case, a belt-like substance, for example, is placed between the electrodes and used as the collecting plate to allow continuous production.
The stage of obtaining a fiber structure accumulated on the collecting plate will now be explained. According to the invention, a filamentous substance is formed by evaporation of the solvent, depending on the conditions, while the solution is drawn toward the collecting plate.
Although the solvent will usually evaporate completely during the period of collection on the collecting plate at room temperature, the drawing may be accomplished under reduced pressure conditions if the solvent evaporation is insufficient. A fiber structure satisfying at Least the fiber mean diameter and fiber length is formed upon collection on the collecting plate. The temperature for drawing may be adjusted according to the evaporation behavior of the solvent and the viscosity of the spinning solution, and will normally be in the range of 0-100°C.
A relative humidity of 20-80% RH is preferred between the nozzle and collecting plate where the filamentous substance is formed. If the relative humidity is outside of this range, it will be difficult to accomplish stable spinning for prolonged periods. A more preferred relative humidity range is 30-70o RH.
The fiber structure obtained by the production process of the invention may be used alone, but it may also be used in combination with other structural members depending on handleability and other essential factors. For example, a nonwoven fabric, woven fabric or film that can serve as a support material may be used as the collecting plate and the filament laminate formed thereover to allow fabrication of a member comprising a combination of the support material and the filament laminate.
The obtained fiber structure may also be subjected to heat treatment or chemical treatment, and the polylactic acid may be mixed with an emulsion or an organic or inorganic powder or filler at any stage prior to spinning.
For example, any of various catalysts may be supported on the fiber structure of the invention for use as a catalyst-supporting base material.
Examples The present invention will now be explained by examples, with the understanding that the invention is not limited to these examples. The evaluations of properties in the examples and comparative examples were carried out by the following methods.
Fiber mean diameter:
The fiber diameter was measured by selecting 20 random locations from a photograph taken of the surface of the obtained fiber structure (2000 magnification) using a scanning electron microscope (S-2400 by Hitachi, Ltd.), and the average value of the fiber diameters (n=20) was 5 determined and recorded as the fiber mean diameter.
Presence of fibers with fiber lengths of less than 20 pm:
A photograph taken of the surface of the obtained fiber structure (2000 magnification) using a scanning 10 electron microscope (S-2400 by Hitachi, Ltd.) was observed to confirm the presence of fibers with fiber lengths of less than 20 um.
Depressions in fiber surface structure:
15 An scanning electron microscope photograph (8000 magnification) was taken of the surface of the obtained fiber structure. General purpose image processing software (NanoHunter NS2K-Pro/Lt Ver. 5.2 by Nano System Corp.) was used to select the most clearly imaged fiber in the photograph, and after establishing an imaginary line A
running through the center axis of the selected fiber and imaginary lines B and B' along both outer edges of the selected fiber, two imaginary lines C and C' running between the centers between the imaginary line A and imaginary lines B, B' were established.
The section defined by the established imaginary lines C, C' and the edges of the photograph was extracted with the image processing software, and the area percentage of depressions in the region was determined.
The area percentage was measured for each of 10 arbitrary locations of the fiber structure in the electron microscope photograph, and the average was determined.
Weight-average molecular weight:
The weight-average molecular weight was measured with a GPC-11 by Showa Denko K.K. (Column: SHODEX LF-804, solvent: chloroform, detector: RI, styrene equivalent).
Melting point:
A DSC curve for the obtained fiber structure was measured using a differential scanning calorimeter (DSC TA-2920 by Texas Instruments), and the melting point was determined from the isothermal peak.
Example 1 After mixing 500 ppm of tin octylate with D-lactide, polymerization was conducted in a stirrer-equipped reactor at 200°C for 60 minutes under a nitrogen atmosphere, to obtain a poly(D-lactic acid) homopolymer with a weight-average molecular weight of 120,000.
There were prepared a solution of 1 part by weight of the obtained poly(D-lactic acid) in 9 parts by weight of methylene chloride and a solution of 1 part by weight of poly(L-lactic acid) (Lacty 9031TM by Shimadzu Corp., weight-average molecular weight: 168,000) in 9 parts by weight of methylene chloride, and both solutions were mixed at 5 parts by weight each.
Next, the apparatus shown in Fig. 2 was used for discharge of the solution for 5 minutes onto a filamentous substance-collecting electrode 5. The inner diameter of the ejection nozzle (1 in Fig. 2) was 0.8 mm, the voltage was 12 kV, the distance from the ejection nozzle (1 in Fig.
2) to the filamentous substance-collecting electrode (5 in Fig. 2) was 12 cm and the relative humidity was 35o RH.
Upon observing the obtained fiber structure with a scanning electron microscope (S-2400 by Hitachi, Ltd.), the mean fiber diameter was 3 um and no fibers were present with fiber lengths of less than 20 um. The mean diameter of the depressions on the fiber surfaces was 0.2 um, and the percentage of the fiber surface area occupied by the depressions was 230. Scanning electron microscope photographs of the fiber structure are shown in Figs. 3 and 4 .
As a result of, DSC measurement of the obtained fiber structure, the melting point was 216°C and no endothermic peak was observed below 190°C.
Example 2 There were mixed 6 parts by weight of a solution of 1 part by weight of the poly(D-lactic acid) in 9 parts by weight of methylene chloride and 4 parts by weight of a solution of 1 part by weight of poly(L-lactic acid) in 9 parts by weight of methylene chloride, and a fiber structure was obtained in the same manner as Example l, except that the distance from the ejection nozzle to the filamentous substance-collecting electrode was 10 cm.
The mean fiber diameter of the obtained fiber structure was 4 pm, and no fibers were present with fiber lengths of less than 20 um. The mean diameter of the depressions on the fiber surfaces was 0.2 dam, and the percentage of the fiber surface area occupied by the depressions was 220. Scanning electron microscope photographs of the fiber structure are shown in Figs. 5 and 6.
As a result of DSC measurement of the obtained fiber structure, the melting point was 218°C and no endothermic peak was observed below 190°C.
Comparative Example 1 A fiber structure was obtained in the same manner as Example 2, except for mixing 7 parts by weight of a solution of 1 part by weight of the poly(D-lactic acid) in 9 parts by weight of methylene chloride and 3 parts by weight of a solution of 1 part by weight of poly(L-lactic acid) in 9 parts by weight of methylene chloride.
The mean fiber diameter of the obtained fiber structure was 3 um, and no fibers were present with fiber lengths of less than 20 Vim. The mean diameter of the depressions on the fiber surfaces was 0.2 um, and the percentage of the fiber surface area occupied by the depressions was 31%. Scanning electron microscope photographs of the fiber structure are shown in Figs. 7 and
According to the invention, the polylactic acid component preferably consists of a mixture of a condensate with at least 80 mol% L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units.
Here, a condensate with at least 80 mol% L-lactic acid based on the total repeating units means a content of 80-100 mol% L-lactic acid and 0-20 mol% of D-lactic acid or a copolymerizing component other than D-lactic acid. On the other hand, a condensate with at least 80 mol% D-lactic acid based on the total repeating units means a content of 80-100 mol% D-lactic acid and 0-20 mol% of L-lactic acid or a copolymerizing component other than L-lactic acid.
As copolymerizing components other than D-lactic acid and L-lactic acid there may be mentioned oxy acids, lactones, dicarboxylic acids and polyhydric alcohols.
There may also be mentioned various polyesters, polyethers and polycarbonates comprising such components and having ester bond-forming functional groups.
According to the invention, the polylactic acid component is preferably a mixture comprising a condensate with at least 80 mol% L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units, in a weight ratio of (6:4)-(4:6) .
More preferably, the condensate with at least 80 molo L-lactic acid based on the total repeating units and the condensate with at least 80 molo D-lactic acid based on the total repeating units are mixed in substantially a 5:5 ratio.
According to the invention, the weight-average molecular weight of the polylactic acid component is more preferably 100,000 or greater for improved dynamic strength of the obtained fiber structure.
The fiber structure of the invention includes at least the aforementioned ultrafine polylactic acid fibers, but a "fiber structure" according to the invention may be any three-dimensional structure formed by weaving, knitting or laminating the fibers, and a nonwoven fabric may be mentioned as a preferred example.
The content of the ultrafine polylactic acid fibers in the fiber structure of the invention is not particularly limited, but the features of the ultrafine polylactic acid fibers can be exhibited with a content of 50 wto or greater. The content is more preferably 80 wto or greater, and even more preferably the fiber structure is composed essentially of the polylactic acid fibers alone.
In particular, preferably the fibers forming the fiber structure have a mean diameter of no greater than 10 um and contain substantially no fibers with fiber lengths of less than 20 um.
Any process that yields the aforementioned fibers may be employed for production of a fiber structure of the invention, but there may be mentioned as a preferred mode of the production process one including a stage wherein a condensate with at least 80 molo L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units are combined in a weight ratio of (6:4)-(4:6) and then dissolved in a solvent to produce a solution, a stage wherein the solution is spun by an electrospinning method, and a stage wherein fibers are accumulated on a collecting plate by the spinning.
There may also be mentioned as a preferred mode of the invention a production process including a stage wherein a condensate with at least 80 mol% L-lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage wherein a condensate with at least 80 molo D-Lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage in which the two solutions are mixed in a weight ratio of (6:4)-(4:6), a stage wherein the mixed solution is spun by an electrospinning method, and a stage wherein fibers are accumulated on a collecting plate by the spinning.
An electrospinning method is a method in which a solution of a fiber-forming compound is discharged into an electrostatic field formed between two electrodes, the solution is drawn toward the electrodes, and the resulting filamentous substance is accumulated on a collecting plate to obtain a fiber structure, where the filamentous substance need not be free of the solvent used to dissolve the fiber-forming compound but may also include the solvent.
For production of fibers comprising a stereo complex of poly(L-lactic acid) and poly(D-lactic acid), either melt spinning is carried out after melt kneading, or dry spinning is carried out from a solution containing the L-lactic acid condensate and poly(D-lactic acid) condensate, but in either case it has not been hitherto possible to completely eliminate a melting point of below 190°C.
However, it was found surprisingly that fibers obtained by electrospinning have essentially no melting point below 190°C.
5 An apparatus used- in electrospinning for the production process of the invention will now be described.
The aforementioned electrodes may be of any type such as metal, inorganic or organic substances so long as they exhibit electrical conductivity, and they may also have 10 electrical conductive thin-films of metal, inorganic or organic substances on insulators.
The electrostatic field may be formed by a pair of or more electrodes, and a high voltage may be applied to any of the electrodes. This also includes cases of using, for example, a total of three electrodes where two are high-voltage electrodes with different voltage values (for example, 15 kV and 10 kV) and one is a grounded electrode, as well as cases of using more than three electrodes.
The steps in a procedure of producing fibers for a fiber structure of the invention by electrospinning will now be explained in order.
First, a solution containing the aforementioned polylactic acid components dissolved in a solvent is prepared, where the concentration of the polylactic acid components in the solution is preferably 1-30 wto. A low concentration of less than 1 wto is not preferred because it will be difficult to form a fiber structure. The concentration is also preferably not greater than 30 wt%
because the mean diameter of the obtained fibers will be increased. The preferred concentration range is 2-25 wt%.
The solvent used to dissolve the polylactic acid components is not particularly restricted so long as it is capable of dissolving the polylactic acid components and evaporating off during the spinning stage of the electrospinning to form fibers.
Using a volatile solvent as the solvent is preferred as it will facilitate formation of the aforementioned depressions on the fiber surfaces. A volatile solvent according to the invention is a substance which has a boiling point of no higher than 200°C at atmospheric pressure and is a liquid at room temperature (for example, 27°C). As examples of specific volatile solvents there may be mentioned methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane, bromoform, tetrahydrofuran, 1,4-dioxane, 1,1,1,3,3,3-hexafluoroisopropanol, toluene, xylene and dimethylformamide, among which methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane, bromoform, tetrahydrofuran and 1,4-dioxane are preferred and methylene chloride is most preferred.
These solvents may be used alone, or a plurality of solvents may be combined for use as a mixed solvent.
The stage of spinning the aforementioned solution by electrospinning will now be explained. Any desired method may be employed for discharge of the solution into the electrostatic field, and for example, the solution may be supplied to a nozzle for appropriate positioning of the solution in the electrostatic field, and the solution drawn from the nozzle by the electrical field for formation into a filament.
A preferred mode of production of a fiber structure of the invention will now be explained in greater detail with reference to Fig. 1.
An injection needle-shaped solution ejection nozzle (1 in Fig. 1) having a voltage applied by appropriate means such as a high-voltage generator (6 in Fig. 1) is fitted at the tip of the cylindrical solution-holder of a syringe (3 in Fig. 1), and the solution (2 in Fig. 1) is guided to the tip of the solution ejection nozzle. The tip of the solution ejection nozzle (1 in Fig. 1) is situated at an appropriate distance from a grounded filamentous substance-collecting electrode (5 in Fig. 1), and the solution (2 in Fig. 1) is ejected from the tip of the solution ejection nozzle (1 in Fig. 1) to form a filamentous substance between the nozzle tip solution and the filamentous substance-collecting electrode (5 in Fig. 1).
As a different mode, shown in Fig. 2, fine droplets of the solution (not shown) may be introduced into an electrostatic field, with the only condition being that the solution (2 in Fig. 2) is placed in the electrostatic field and held at a distance from the filamentous substance-collecting electrode (5 in Fig. 2) which allows formation into a filament. For example, an electrode (4 in Fig. 2) counter to the filamentous substance-collecting electrode may be inserted directly into the solution (2 in Fig. 2) in the holder (3 in Fig. 2) with the solution ejection nozzle (1 in Fig. 2).
When the solution is ejected through the nozzle into the electrostatic field, the filamentous substance production speed can be increased by using a plurality of nozzles in parallel. Also, the distance between electrodes will depend on the charge, nozzle dimensions, ejection volume of the solution from the nozzle and the solution concentration, but a distance of 5-20 cm has been found to be suitable for approximately 10 kV. The applied electrostatic potential will normally be 3-100 kV, preferably 5-50 kV and more preferably 5-30 kV. The desired potential can be produced by any appropriate method known in the prior art.
The two modes described above employ an electrode as the collecting plate, but a material serving as the collecting plate may also be placed between the electrodes, to provide a collecting plate separate from the electrodes for collection of a filament laminate. In this case, a belt-like substance, for example, is placed between the electrodes and used as the collecting plate to allow continuous production.
The stage of obtaining a fiber structure accumulated on the collecting plate will now be explained. According to the invention, a filamentous substance is formed by evaporation of the solvent, depending on the conditions, while the solution is drawn toward the collecting plate.
Although the solvent will usually evaporate completely during the period of collection on the collecting plate at room temperature, the drawing may be accomplished under reduced pressure conditions if the solvent evaporation is insufficient. A fiber structure satisfying at Least the fiber mean diameter and fiber length is formed upon collection on the collecting plate. The temperature for drawing may be adjusted according to the evaporation behavior of the solvent and the viscosity of the spinning solution, and will normally be in the range of 0-100°C.
A relative humidity of 20-80% RH is preferred between the nozzle and collecting plate where the filamentous substance is formed. If the relative humidity is outside of this range, it will be difficult to accomplish stable spinning for prolonged periods. A more preferred relative humidity range is 30-70o RH.
The fiber structure obtained by the production process of the invention may be used alone, but it may also be used in combination with other structural members depending on handleability and other essential factors. For example, a nonwoven fabric, woven fabric or film that can serve as a support material may be used as the collecting plate and the filament laminate formed thereover to allow fabrication of a member comprising a combination of the support material and the filament laminate.
The obtained fiber structure may also be subjected to heat treatment or chemical treatment, and the polylactic acid may be mixed with an emulsion or an organic or inorganic powder or filler at any stage prior to spinning.
For example, any of various catalysts may be supported on the fiber structure of the invention for use as a catalyst-supporting base material.
Examples The present invention will now be explained by examples, with the understanding that the invention is not limited to these examples. The evaluations of properties in the examples and comparative examples were carried out by the following methods.
Fiber mean diameter:
The fiber diameter was measured by selecting 20 random locations from a photograph taken of the surface of the obtained fiber structure (2000 magnification) using a scanning electron microscope (S-2400 by Hitachi, Ltd.), and the average value of the fiber diameters (n=20) was 5 determined and recorded as the fiber mean diameter.
Presence of fibers with fiber lengths of less than 20 pm:
A photograph taken of the surface of the obtained fiber structure (2000 magnification) using a scanning 10 electron microscope (S-2400 by Hitachi, Ltd.) was observed to confirm the presence of fibers with fiber lengths of less than 20 um.
Depressions in fiber surface structure:
15 An scanning electron microscope photograph (8000 magnification) was taken of the surface of the obtained fiber structure. General purpose image processing software (NanoHunter NS2K-Pro/Lt Ver. 5.2 by Nano System Corp.) was used to select the most clearly imaged fiber in the photograph, and after establishing an imaginary line A
running through the center axis of the selected fiber and imaginary lines B and B' along both outer edges of the selected fiber, two imaginary lines C and C' running between the centers between the imaginary line A and imaginary lines B, B' were established.
The section defined by the established imaginary lines C, C' and the edges of the photograph was extracted with the image processing software, and the area percentage of depressions in the region was determined.
The area percentage was measured for each of 10 arbitrary locations of the fiber structure in the electron microscope photograph, and the average was determined.
Weight-average molecular weight:
The weight-average molecular weight was measured with a GPC-11 by Showa Denko K.K. (Column: SHODEX LF-804, solvent: chloroform, detector: RI, styrene equivalent).
Melting point:
A DSC curve for the obtained fiber structure was measured using a differential scanning calorimeter (DSC TA-2920 by Texas Instruments), and the melting point was determined from the isothermal peak.
Example 1 After mixing 500 ppm of tin octylate with D-lactide, polymerization was conducted in a stirrer-equipped reactor at 200°C for 60 minutes under a nitrogen atmosphere, to obtain a poly(D-lactic acid) homopolymer with a weight-average molecular weight of 120,000.
There were prepared a solution of 1 part by weight of the obtained poly(D-lactic acid) in 9 parts by weight of methylene chloride and a solution of 1 part by weight of poly(L-lactic acid) (Lacty 9031TM by Shimadzu Corp., weight-average molecular weight: 168,000) in 9 parts by weight of methylene chloride, and both solutions were mixed at 5 parts by weight each.
Next, the apparatus shown in Fig. 2 was used for discharge of the solution for 5 minutes onto a filamentous substance-collecting electrode 5. The inner diameter of the ejection nozzle (1 in Fig. 2) was 0.8 mm, the voltage was 12 kV, the distance from the ejection nozzle (1 in Fig.
2) to the filamentous substance-collecting electrode (5 in Fig. 2) was 12 cm and the relative humidity was 35o RH.
Upon observing the obtained fiber structure with a scanning electron microscope (S-2400 by Hitachi, Ltd.), the mean fiber diameter was 3 um and no fibers were present with fiber lengths of less than 20 um. The mean diameter of the depressions on the fiber surfaces was 0.2 um, and the percentage of the fiber surface area occupied by the depressions was 230. Scanning electron microscope photographs of the fiber structure are shown in Figs. 3 and 4 .
As a result of, DSC measurement of the obtained fiber structure, the melting point was 216°C and no endothermic peak was observed below 190°C.
Example 2 There were mixed 6 parts by weight of a solution of 1 part by weight of the poly(D-lactic acid) in 9 parts by weight of methylene chloride and 4 parts by weight of a solution of 1 part by weight of poly(L-lactic acid) in 9 parts by weight of methylene chloride, and a fiber structure was obtained in the same manner as Example l, except that the distance from the ejection nozzle to the filamentous substance-collecting electrode was 10 cm.
The mean fiber diameter of the obtained fiber structure was 4 pm, and no fibers were present with fiber lengths of less than 20 um. The mean diameter of the depressions on the fiber surfaces was 0.2 dam, and the percentage of the fiber surface area occupied by the depressions was 220. Scanning electron microscope photographs of the fiber structure are shown in Figs. 5 and 6.
As a result of DSC measurement of the obtained fiber structure, the melting point was 218°C and no endothermic peak was observed below 190°C.
Comparative Example 1 A fiber structure was obtained in the same manner as Example 2, except for mixing 7 parts by weight of a solution of 1 part by weight of the poly(D-lactic acid) in 9 parts by weight of methylene chloride and 3 parts by weight of a solution of 1 part by weight of poly(L-lactic acid) in 9 parts by weight of methylene chloride.
The mean fiber diameter of the obtained fiber structure was 3 um, and no fibers were present with fiber lengths of less than 20 Vim. The mean diameter of the depressions on the fiber surfaces was 0.2 um, and the percentage of the fiber surface area occupied by the depressions was 31%. Scanning electron microscope photographs of the fiber structure are shown in Figs. 7 and
8.
As a result of DSC measurement of the obtained fiber structure, the main melting point was 219°C and a small endothermic peak was observed at 165°C.
Comparative Example 2 A fiber structure was obtained in the same manner as Example 2, except that only a solution of 1 part by weight of poly(D-lactic acid) in 9 parts by weight of methylene chloride was used.
The mean fiber diameter of the obtained fiber structure was 2 Vim, and no fibers were present with fiber lengths of less than 20 um. The mean diameter of the depressions on the fiber surfaces was 0.2 Vim, and the percentage of the fiber surface area occupied by the depressions was 210. Scanning electron microscope photographs of the fiber structure are shown in Figs. 9 and 10.
As a result of DSC measurement of the obtained fiber structure, the melting point was 174°C.
Comparative Example 3 A fiber structure was obtained in the same manner as Example 2, except that only a solution of 0.7 part by weight of poly(L-lactic acid) in 9.3 parts by weight of methylene chloride was used.
The mean fiber diameter of the obtained fiber structure was 3 Vim, and no fibers were present with fiber lengths of less than 20 um. The mean diameter of the depressions on the fiber surfaces was 0.2 um, and the percentage of the fiber surface area occupied by the Z5 depressions was 27%. Scanning electron microscope photographs of the fiber structure are shown in Figs. 11 and 12.
As a result of DSC measurement of the obtained fiber structure, the melting point was 172°C.
Example 3 A fiber structure was obtained in the same manner as Example 2, except that a methylene chloride/DMF mixed solvent (weight ratio: 8/2) was used instead of methylene chloride. The mean fiber diameter of the obtained fiber structure was 2 um, and no fibers were present with fiber lengths of less than 20 um. No fiber surface depressions were observed. Scanning electron microscope photographs of the fiber structure are shown in Figs. 13 and 14.
As a result of DSC measurement of the obtained fiber structure, the melting point was 220°C and no endothermic peak was observed below 190°C.
Example 4 A fiber structure was obtained in the same manner as Example 2, except for mixing 4 parts by weight of a solution of 1 part by weight of poly(D-lactic acid) in 9 5 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2) and 6 parts by weight of a solution of 1 part by weight of poly(L-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2).
10 The mean fiber diameter of the obtained fiber structure was 2 pm, and no fibers were present with fiber lengths of less than 20 um. No fiber surface depressions were observed. Scanning electron microscope photographs of the fiber structure are shown in Figs. 15 and 16.
15 As a result of DSC measurement of the obtained fiber structure, the melting point was 221°C and no endothermic peak was observed below 190°C.
Comparative Example 4 A fiber structure was obtained in the same manner as 20 Example 2, except for mixing 3 parts by weight of a solution of 1 part by weight of poly(D-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2) and 7 parts by weight of a solution of 1 part by weight of poly(L-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2).
The mean fiber diameter of the obtained fiber structure was 2 um, and no fibers were present with fiber lengths of less than 20 Vim. No fiber surface depressions were observed. Scanning electron microscope photographs of the fiber structure are shown in Figs. 17 and 18.
As a result of DSC measurement of the obtained fiber structure, the main melting point was 221°C and a small endothermic peak was observed at 156°C.
Comparative Example 5 A fiber structure was obtained in the same manner as Example 2, except that only a solution of 1 part by weight poly(D-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2) was used.
The mean fiber diameter of the obtained fiber structure was 1 um, and no fibers were present with fiber lengths of less than 20 Vim. No fiber surface depressions were observed. Scanning electron microscope photographs of the fiber structure are shown in Figs. 19 and 20.
As a result of DSC measurement of the obtained fiber I5 structure, the melting point was 172°C.
Comparative Example 6 A fiber structure was obtained in the same manner as Example 2, except that only a solution of 1 part by weight poly(L-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2) was used.
The mean fiber diameter of the obtained fiber structure was 3 um, and no fibers were present with fiber lengths of less than 20 um. Some corrugation of the fiber surfaces was seen, but no depressions were observed.
Scanning electron microscope photographs of the fiber structure are shown in Figs. 21 and 22.
As a result of DSC measurement of the obtained fiber structure, the melting point was 170°C.
As a result of DSC measurement of the obtained fiber structure, the main melting point was 219°C and a small endothermic peak was observed at 165°C.
Comparative Example 2 A fiber structure was obtained in the same manner as Example 2, except that only a solution of 1 part by weight of poly(D-lactic acid) in 9 parts by weight of methylene chloride was used.
The mean fiber diameter of the obtained fiber structure was 2 Vim, and no fibers were present with fiber lengths of less than 20 um. The mean diameter of the depressions on the fiber surfaces was 0.2 Vim, and the percentage of the fiber surface area occupied by the depressions was 210. Scanning electron microscope photographs of the fiber structure are shown in Figs. 9 and 10.
As a result of DSC measurement of the obtained fiber structure, the melting point was 174°C.
Comparative Example 3 A fiber structure was obtained in the same manner as Example 2, except that only a solution of 0.7 part by weight of poly(L-lactic acid) in 9.3 parts by weight of methylene chloride was used.
The mean fiber diameter of the obtained fiber structure was 3 Vim, and no fibers were present with fiber lengths of less than 20 um. The mean diameter of the depressions on the fiber surfaces was 0.2 um, and the percentage of the fiber surface area occupied by the Z5 depressions was 27%. Scanning electron microscope photographs of the fiber structure are shown in Figs. 11 and 12.
As a result of DSC measurement of the obtained fiber structure, the melting point was 172°C.
Example 3 A fiber structure was obtained in the same manner as Example 2, except that a methylene chloride/DMF mixed solvent (weight ratio: 8/2) was used instead of methylene chloride. The mean fiber diameter of the obtained fiber structure was 2 um, and no fibers were present with fiber lengths of less than 20 um. No fiber surface depressions were observed. Scanning electron microscope photographs of the fiber structure are shown in Figs. 13 and 14.
As a result of DSC measurement of the obtained fiber structure, the melting point was 220°C and no endothermic peak was observed below 190°C.
Example 4 A fiber structure was obtained in the same manner as Example 2, except for mixing 4 parts by weight of a solution of 1 part by weight of poly(D-lactic acid) in 9 5 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2) and 6 parts by weight of a solution of 1 part by weight of poly(L-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2).
10 The mean fiber diameter of the obtained fiber structure was 2 pm, and no fibers were present with fiber lengths of less than 20 um. No fiber surface depressions were observed. Scanning electron microscope photographs of the fiber structure are shown in Figs. 15 and 16.
15 As a result of DSC measurement of the obtained fiber structure, the melting point was 221°C and no endothermic peak was observed below 190°C.
Comparative Example 4 A fiber structure was obtained in the same manner as 20 Example 2, except for mixing 3 parts by weight of a solution of 1 part by weight of poly(D-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2) and 7 parts by weight of a solution of 1 part by weight of poly(L-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2).
The mean fiber diameter of the obtained fiber structure was 2 um, and no fibers were present with fiber lengths of less than 20 Vim. No fiber surface depressions were observed. Scanning electron microscope photographs of the fiber structure are shown in Figs. 17 and 18.
As a result of DSC measurement of the obtained fiber structure, the main melting point was 221°C and a small endothermic peak was observed at 156°C.
Comparative Example 5 A fiber structure was obtained in the same manner as Example 2, except that only a solution of 1 part by weight poly(D-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2) was used.
The mean fiber diameter of the obtained fiber structure was 1 um, and no fibers were present with fiber lengths of less than 20 Vim. No fiber surface depressions were observed. Scanning electron microscope photographs of the fiber structure are shown in Figs. 19 and 20.
As a result of DSC measurement of the obtained fiber I5 structure, the melting point was 172°C.
Comparative Example 6 A fiber structure was obtained in the same manner as Example 2, except that only a solution of 1 part by weight poly(L-lactic acid) in 9 parts by weight of a methylene chloride/DMF mixed solvent (weight ratio: 8/2) was used.
The mean fiber diameter of the obtained fiber structure was 3 um, and no fibers were present with fiber lengths of less than 20 um. Some corrugation of the fiber surfaces was seen, but no depressions were observed.
Scanning electron microscope photographs of the fiber structure are shown in Figs. 21 and 22.
As a result of DSC measurement of the obtained fiber structure, the melting point was 170°C.
Claims (14)
1. Ultrafine polylactic acid fibers comprising as the main constituent component a polylactic acid component with a melting point of 190°C or higher, with a mean fiber diameter of no greater than 10 µm and fiber lengths of 20 µm or greater, and containing substantially no constituent component with a melting point of below 190°C.
2. (deleted)
3. Fibers according to claim 1, having depressions with diameters of 0.01-1 µm on the fiber surfaces, the depressions constituting 10-95% of the fiber surfaces.
4. Fibers according to claim 1, wherein the polylactic acid component is a blend of a condensate with at least 80 mol% L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units.
5. Fibers according to clam 4, wherein the weight ratio of the L-lactic acid condensate and the D-lactic acid condensate is (6:4)-(4:6).
6. A fiber structure comprising at least ultrafine polylactic acid fibers according to claim 1.
7. A fiber structure according to claim 6, wherein the fibers forming the fiber structure have a mean diameter of no greater than 10 µm and contain substantially no fibers with fiber lengths of less than 20 µm.
8. A production process for a fiber structure, which includes a stage wherein a condensate with at least 80 mol%
L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units are combined in a weight ratio of (6:4)-(4:6) and then dissolved in a solvent to produce a solution, a stage wherein said solution is spun by an electrospinning method, and a stage wherein a fiber structure is accumulated on a collecting plate by said spinning.
L-lactic acid based on the total repeating units and a condensate with at least 80 mol% D-lactic acid based on the total repeating units are combined in a weight ratio of (6:4)-(4:6) and then dissolved in a solvent to produce a solution, a stage wherein said solution is spun by an electrospinning method, and a stage wherein a fiber structure is accumulated on a collecting plate by said spinning.
9. A production process according to claim 8, wherein the solvent is a volatile solvent.
10. A production process according to claim 8, wherein the relative humidity is in the range of 20-80% RH between the nozzle and collecting plate where the filamentous substance is formed in the stage of spinning by electrospinning.
11. A production process for a fiber structure which includes a stage wherein a condensate with at least 80 mol%
L-lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage wherein a condensate with at least 80 mol% D-lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage in which the two solutions are mixed in a weight ratio of (6:4)-(4:6), a stage wherein said mixed solution is spun by an electrospinning method, and a stage wherein a fiber structure is accumulated on a collecting board by said spinning.
L-lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage wherein a condensate with at least 80 mol% D-lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage in which the two solutions are mixed in a weight ratio of (6:4)-(4:6), a stage wherein said mixed solution is spun by an electrospinning method, and a stage wherein a fiber structure is accumulated on a collecting board by said spinning.
12. A production process according to claim 11, wherein the solvent is a volatile solvent.
13. A production process according to claim 12, wherein the volatile solvent is at least one selected from the group consisting of methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane, bromoform, tetrahydrofuran and 1,4-dioxane.
14. A production process according to claim 11, wherein the relative humidity is in the range of 20-80% RH
between the nozzle and collecting plate where the filamentous substance is formed in the stage of spinning by electrospinning.
between the nozzle and collecting plate where the filamentous substance is formed in the stage of spinning by electrospinning.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004074011 | 2004-03-16 | ||
| JP2004-074011 | 2004-03-16 | ||
| PCT/JP2005/004165 WO2005087988A1 (en) | 2004-03-16 | 2005-03-03 | Extremely fine polylactic acid fiber, fibrous structure and process for producing these |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2560363A1 true CA2560363A1 (en) | 2005-09-22 |
Family
ID=34975614
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002560363A Abandoned CA2560363A1 (en) | 2004-03-16 | 2005-03-03 | Ultrafine polylactic acid fibers and fiber structure, and process for their production |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US20070172651A1 (en) |
| EP (1) | EP1731633A4 (en) |
| JP (1) | JP4243292B2 (en) |
| KR (1) | KR20060130732A (en) |
| CN (1) | CN1985032A (en) |
| CA (1) | CA2560363A1 (en) |
| WO (1) | WO2005087988A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007231480A (en) * | 2006-03-03 | 2007-09-13 | Institute Of Physical & Chemical Research | Polylactic acid fiber having stereo complex structure and method for producing the same |
| JP4848224B2 (en) * | 2006-08-03 | 2011-12-28 | 太陽化学株式会社 | Nanofiber assembly |
| JP5028047B2 (en) * | 2006-08-08 | 2012-09-19 | 倉敷繊維加工株式会社 | Laminated sheet having excellent windproof and waterproof moisture permeability, fabric using the same, and production method thereof |
| JP4903595B2 (en) * | 2007-02-09 | 2012-03-28 | パナソニック株式会社 | Nanofiber manufacturing method and nanofiber manufacturing apparatus |
| JP2009006135A (en) * | 2007-05-31 | 2009-01-15 | Teijin Ltd | Favorite beverage extract filter and favorite beverage extract bag formed using it |
| WO2009010443A2 (en) * | 2007-07-18 | 2009-01-22 | Basf Se | Method for producing nanofibres and mesofibres by electrospinning colloidal dispersions containing at least one essentially water-insoluble polymer |
| CN101878330B (en) * | 2007-09-28 | 2014-07-23 | 自然工作有限责任公司 | Methods for making polylactic acid stereocomplex fibers |
| CN101970527A (en) * | 2007-09-28 | 2011-02-09 | 自然工作有限责任公司 | Method for making polyactic acid ( pla) stereocomplexes |
| ATE531839T1 (en) | 2007-09-28 | 2011-11-15 | Natureworks Llc | STEREOCOMPLEX CONJUGATE FIBERS MADE OF POLYLACTIC ACID |
| PL2135887T3 (en) | 2008-06-18 | 2011-05-31 | Inst Biopolimerow I Wlokien Chemicznych | Process for producing a polylactic acid stereocomplex powder |
| US8242073B2 (en) * | 2008-07-10 | 2012-08-14 | The Hong Kong Polytechnic University | Biodegradable and bioabsorbable biomaterials and keratin fibrous articles for medical applications |
| CN101831762A (en) * | 2010-04-08 | 2010-09-15 | 苏州大学 | Composite fiber porous membrane composited by ornithoctonus huwena threads and polylactic acid and method for producing same |
| AR091031A1 (en) | 2012-05-14 | 2014-12-30 | Teijin Ltd | IRONED PRODUCT AND HEMOSTATIC MATERIAL |
| CN104018294B (en) * | 2014-04-10 | 2016-06-22 | 中国科学院宁波材料技术与工程研究所 | A kind of polylactic acid nano fiber film and preparation method thereof |
| CN105274728B (en) * | 2014-05-28 | 2018-10-16 | 福建赛特新材股份有限公司 | A kind of biosoluble fibres felt and preparation method thereof and vacuum heat-insulating plate using the felt |
| CN104029443B (en) * | 2014-05-28 | 2016-04-13 | 中原工学院 | A kind of preparation method of PM2.5 protective mask PLA multi-layer fiber film |
| JP6119863B2 (en) * | 2014-06-18 | 2017-04-26 | 東レ株式会社 | Laminated body and method for producing the same |
| JP6718159B2 (en) * | 2015-05-28 | 2020-07-08 | 国立大学法人京都工芸繊維大学 | Plastic nanofiber, optical fiber, and method for producing plastic nanofiber |
| KR101747825B1 (en) | 2015-12-22 | 2017-06-15 | 경희대학교 산학협력단 | Piezoelectric material comprising Poly(D-lactic acid)/Poly(L-lactic acid) stereocomplex crystals |
| CN108754832B (en) * | 2018-04-10 | 2021-08-10 | 何炽斌 | Biodegradable disposable mopping cloth and production method thereof |
| US11361893B2 (en) * | 2018-11-27 | 2022-06-14 | City University Of Hong Kong | Soft body robotic device |
| CN115467084B (en) * | 2022-09-05 | 2023-08-08 | 南通大学 | Hydrophilic PLA oil-water separation film and preparation method thereof |
| CN116791233A (en) * | 2023-03-17 | 2023-09-22 | 东华大学 | Porous polylactic acid antibacterial nanofiber and preparation method thereof |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2181207B (en) * | 1985-10-04 | 1990-05-23 | Ethicon Inc | Improvements in electrostatically produced structures and methods of manufacturing thereof |
| JPH0781204B2 (en) * | 1987-04-21 | 1995-08-30 | 株式会社バイオマテリアルユニバ−ス | Polylactic acid fiber |
| JPH03220305A (en) * | 1989-11-21 | 1991-09-27 | I C I Japan Kk | Production of antistatic spun yarn |
| US5338822A (en) * | 1992-10-02 | 1994-08-16 | Cargill, Incorporated | Melt-stable lactide polymer composition and process for manufacture thereof |
| FR2709500B1 (en) * | 1993-08-02 | 1996-02-16 | Fiberweb Sodoca Sarl | Nonwoven based on polymers derived from lactic acid, process for manufacturing and using such a nonwoven. |
| JP3316306B2 (en) * | 1994-05-06 | 2002-08-19 | カネボウ株式会社 | Method for producing high molecular weight polylactic acid molded article |
| JP2002030523A (en) * | 2000-07-14 | 2002-01-31 | Toray Ind Inc | Polylactic acid fiber |
| KR20020063020A (en) * | 2001-01-26 | 2002-08-01 | 한국과학기술연구원 | Method for Preparing Thin Fiber -Structured Polymer Webs |
| US6713011B2 (en) * | 2001-05-16 | 2004-03-30 | The Research Foundation At State University Of New York | Apparatus and methods for electrospinning polymeric fibers and membranes |
| JP4056361B2 (en) * | 2002-11-14 | 2008-03-05 | 帝人株式会社 | Polyglycolic acid fiber structure and method for producing the same |
| JP2004256974A (en) * | 2003-02-27 | 2004-09-16 | Japan Vilene Co Ltd | Method for electrospinning and device for electrospinning |
| JP4383763B2 (en) * | 2003-03-28 | 2009-12-16 | 帝人株式会社 | Cell culture substrate and method for producing the same |
-
2005
- 2005-03-03 US US10/592,760 patent/US20070172651A1/en not_active Abandoned
- 2005-03-03 CN CNA2005800156860A patent/CN1985032A/en active Pending
- 2005-03-03 EP EP05720436A patent/EP1731633A4/en not_active Withdrawn
- 2005-03-03 KR KR1020067021160A patent/KR20060130732A/en not_active Application Discontinuation
- 2005-03-03 WO PCT/JP2005/004165 patent/WO2005087988A1/en active Application Filing
- 2005-03-03 JP JP2006510973A patent/JP4243292B2/en not_active Expired - Fee Related
- 2005-03-03 CA CA002560363A patent/CA2560363A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP1731633A1 (en) | 2006-12-13 |
| JP4243292B2 (en) | 2009-03-25 |
| CN1985032A (en) | 2007-06-20 |
| KR20060130732A (en) | 2006-12-19 |
| JPWO2005087988A1 (en) | 2008-01-31 |
| EP1731633A4 (en) | 2007-12-19 |
| WO2005087988A1 (en) | 2005-09-22 |
| US20070172651A1 (en) | 2007-07-26 |
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