JP3146221B2 - Microbial degradable ultrafine fiber meltblown nonwoven fabric and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biodegradable product,
Microfibers with excellent bioavailability and microbial degradability that can be suitably used as a material for disposable general living materials represented by sanitary materials, wipes, packaging materials, etc.
The present invention relates to a melt blown nonwoven fabric and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, nonwoven fabrics have been widely used as materials for sanitary materials, general living materials, industrial materials and the like. Examples of the fiber material constituting the nonwoven fabric include polymers such as polyethylene, polypropylene, polyester, and polyamide. However, nonwoven fabrics made of these materials have no self-decomposability and are chemically very stable under ordinary natural environments. Accordingly, at present, disposable nonwoven fabrics are treated by incineration or landfill after use. Although incineration is widely practiced in Japan, it requires a great deal of cost and is causing pollution from waste plastics.How to solve this problem of disposal of waste plastics, It is a major social issue in terms of protection of the natural environment and living environment. On the other hand, with regard to landfill, there is a problem that the material remains chemically stable for a long time in soil because the material is chemically stable.

As a method for solving such a problem, a new nonwoven fabric which is naturally degraded in a short period of time by using a material having natural degradability (microbial degradability, biodegradability) is demanded. .

[0004] Generally, the fibers having microbial degradability include cellulosic fibers such as cotton and hemp, and protein fibers such as silk. However, because these so-called natural fibers are non-thermoplastic,
When producing a nonwoven fabric using these fibers, a so-called embossing method or a thermal bonding method in which the fibers are thermally bonded to form a nonwoven fabric cannot be employed. In addition, it is not decomposed in a short time, the nonwoven fabric form is maintained for a long time,
It is not preferable in terms of protection of the natural environment and living environment.

[0005] Microbial degradable polymers include polysaccharides such as chitin, proteins and polypeptides (polyamino acids) such as cut gut (intestinal tract) and regenerated collagen, and poly-3-hydroxybutyrate produced by microorganisms in nature. And microbial polyesters such as poly-3-hydroxyvalerate and poly-3-hydroxycaprolate; synthetic aliphatic polyesters such as polyglycolide and polylactide;
Etc. are well known. However, when producing fibers from these polymers, there is a restriction that it is necessary to use a wet spinning method. Also, due to the extremely high cost of the material, its application is limited to fields such as bioabsorbable sutures.

[0006] Recently, as a biodegradable film, a mixture of polyethylene and starch has been proposed, and the film is used as a material for shopping bags. However, since polyethylene will not be decomposed in the future, it cannot be said to be a biodegradable film in its original sense. Moreover, it is not easy to obtain fibers suitable for use in nonwoven fabrics, and at present, starch-containing fibers for nonwoven fabrics have not been obtained.

[0007]

SUMMARY OF THE INVENTION In view of the above background, the present invention provides an inexpensive nonwoven fabric which is easily decomposed by microorganisms, and which has high air permeability and flexibility, and a method for producing the same. .

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The melt-blown nonwoven fabric of the present invention has a polymer composed of only poly-.epsilon.-caprolactone, poly-.beta.-pro. A polymer consisting of only a piolactone alone or a mixture of a polymer consisting of only a poly-ε-caprolactone and a polymer consisting of only a poly-β-propiolactone, and having a single fiber fineness of 0.8 denier And less than ultrafine fibers.

Further, the biodegradable nonwoven fabric of the present invention comprises a polymer consisting of only poly-ε-caprolactone, poly-β-caprolactone.
A polymer consisting of only propiolactone, a mixture of a polymer consisting of only poly-ε-caprolactone and a polymer consisting of only poly-β-propiolactone, and having a single-fiber fineness of 0.8 10% by weight or more of a web composed of ultrafine fibers having a density of less than denier, a polymer composed of only poly-ε-caprolactone, a polymer composed of only poly-β-propiolactone, and a polymer composed of only poly-ε-caprolactone And 90% by weight or less of a web composed of fibers having a single-fiber fineness of 0.8 to 6 denier, which is made of any one of a mixture of a polymer consisting only of poly-β-propiolactone and poly-β-propiolactone. It becomes.

[0010] Another biodegradable nonwoven fabric according to the present invention is a polymer comprising only poly-ε-caprolactone, poly-β-caprolactone.
A polymer consisting of only propiolactone, a mixture of a polymer consisting of only poly-ε-caprolactone and a polymer consisting of only poly-β-propiolactone, and having a single-fiber fineness of 0.8 It is formed by laminating 20% by weight or more of a web composed of ultrafine fibers of less than denier and 80% by weight or less of a web composed of natural fibers or cellulosic fibers.

The process for producing a microbial-degradable nonwoven fabric according to the present invention comprises a polymer comprising only poly-ε-caprolactone, a polymer comprising only poly-β-propiolactone,
After melt-discharging any one of a mixture of a polymer consisting only of ε-caprolactone and a polymer consisting only of poly-β-propiolactone by a melt blown method from a die, removing the traction air flow with a baffle plate, By blowing a cooling air from the side of the molten discharge body to cool, a fine fiber having a single-fiber fineness of less than 0.8 denier is formed, and a web made of this fine fiber is obtained.

Hereinafter, the present invention will be described in detail. The poly-ε-caprolactone (hereinafter, referred to as “PCL”) and / or poly-β-propiolactone (hereinafter, referred to as PPL) is ASTM-D-1238 (E).
The melt flow rate (g / 10 minutes) measured according to the above is suitably 70 or more and less than 300, preferably 100 or more and less than 200. If the melt flow rate is less than 70 or 300 or more, problems such as thread breakage and dropping of molten polymer (hereinafter referred to as “polymer balls”) occurring immediately after thread breakage, and difficulty in thinning fibers are caused. In some cases, it is difficult to stably produce ultrafine fibers, which is not preferable. In the following, "a polymer consisting only of poly-ε-caprolactone, a polymer consisting only of poly-β-propiolactone, a polymer consisting of only poly-ε-caprolactone and only poly-β-propiolactone Consisting of either a mixture with a polymer consisting of a polymer consisting of: (a) PCL and / or PPL.

The PCL and / or the nonwoven fabric of the present invention
Or, for PPL fibers, the single fiber fineness is limited to less than 0.8 denier, because disposable diapers, cover stocks for sanitary products, wipes, and particularly soft texture are required. It is for the purpose of obtaining a suitable material such as medical materials and hygiene materials,
This is because if the single-filament fineness is 0.8 denier or more, the texture becomes a coarse and hard nonwoven fabric, which is not preferable.

Since the nonwoven fabric of the present invention is made of PCL and / or PPL fibers, the rate of spontaneous decomposition of the nonwoven fabric in soil is increased, and the shape of the nonwoven fabric is not maintained for a long time.

If the nonwoven fabric of the present invention requires a certain level of strength, a plurality of webs composed of PCL and / or PPL fibers may be laminated,
And / or PPL fibers and webs of other fibers may be laminated. Other fiber materials include natural fibers or cellulosic fibers. As a form of lamination of fibers, for example, a method of spraying and laminating short fibers in a web forming step or a method of laminating webs can be used to obtain a laminated nonwoven fabric.

The reason that natural fibers or cellulosic fibers are suitable as other fiber materials is that when synthetic fibers are mixed, the synthetic fibers do not decompose, although they do not maintain the form of nonwoven fabric when buried in soil. That's why. For this reason, in the present invention, webs composed of PCL and / or PPL fibers are laminated, or PCL and / or PP are laminated.
A web made of L fibers and a web made of natural fibers or cellulosic fibers are laminated to form a nonwoven fabric. The natural fiber or cellulosic fiber used in the present invention is a material which is decomposed and decomposed and reduced to soil when buried in the soil, for example, natural fibers such as cotton and hemp, and wood. Cellulose fibers such as rayon obtained from pulp may be mentioned.

In the present invention, PCL and / or P
When laminating webs made of PL fibers, one web has a single-fiber fineness of less than 0.8 denier as described above, and the other web has a single-fiber fineness of 0.8 to 6 denier. The reason for limiting the single-fiber fineness of the other web to 0.8 to 6 deniers is that the soft texture that can be applied to disposable diapers, cover stock for sanitary products, wipes, and the like and the strength of nonwoven fabric that can withstand practical use It is for the purpose of having both. When the single-fiber fineness exceeds 6 denier, the texture becomes a coarse non-woven fabric, which is not preferable. When the single-fiber fineness is less than 0.8 denier, the strength of the nonwoven fabric becomes lower than a required level, and the strength is required. It is not preferable because it becomes difficult to put it to practical use in the field.

The lamination ratio of a web having a single yarn fineness of less than 0.8 denier must be at least 10% by weight. The reason for this limitation is that if it is less than 10% by weight, a nonwoven fabric having high air permeability and flexibility can be obtained. It is not possible.

Regarding the lamination ratio of the web made of PCL and / or PPL fiber and the web made of natural fiber or cellulosic fiber (hereinafter referred to as “natural fiber etc.”), the web made of PCL and / or PPL fiber is 20%. 80% by weight or more of web made of natural fiber
The reason why the weight is limited to not more than% by weight is that a thermocompression bonding method and a heat fusion method can be adopted as a means for forming a nonwoven fabric. 20% by weight of PCL and / or PPL fiber
If it is less than 3, the binder effect with natural fibers and the like is reduced, the strength of the nonwoven fabric is low, and it is difficult to withstand practical use. In addition, when the high-pressure water entanglement method is adopted, PC
By laminating L and / or PPL fibers, the flexibility of the obtained nonwoven fabric is further improved, but the lamination ratio needs to be 20% by weight or more, and more preferably 30% by weight or more. .

The nonwoven fabric of the present invention has a basis weight of 5 to 50 g / m2.
Preferably it is ² . If the basis weight exceeds 50 g / m ² , a soft nonwoven fabric cannot be obtained. Further, a nonwoven fabric having a basis weight of less than 5 g / m ² is not only difficult to produce, but also has poor uniformity of the nonwoven fabric itself, which is not preferable.

The nonwoven fabric of the present invention is composed of ultrafine fibers obtained by the melt blown method using the above PCL and / or PPL. As is well known, the melt blown method is the simplest method for producing a nonwoven fabric made of ultrafine fibers, and a nonwoven fabric having a particularly soft texture can be obtained. The method for producing ultrafine fibers from a die by the melt blown method is not particularly limited in the present invention, and the production by the following conventional method is possible. That is, as in a die disclosed in JP-A-49-10258 or JP-A-49-48921, for example, a polymer is melt-discharged from a spinneret having a hole diameter of 0.1 to 1.0 mm, and the melt is discharged. At this time, the discharged melt is heated at a temperature 20 ° C. or more higher than the temperature of the spinneret,
It is possible to sharpen the ejected melt by applying an air stream ejected at a speed of 0 to 300 m / sec at an angle of 5 to 45 degrees with respect to the ejection direction.

Here, the temperature of the melt spinning is 170-31.
The range of 0 ° C. is preferable, and it may be appropriately selected according to the melt flow rate of PCL or PPL to be used. When using a mixture of PCL and PPL, the spinning temperature may be determined experimentally so that good spinnability is obtained from the melt flow rate and the mixing ratio of each of the above polymers. If the spinning temperature exceeds 310 ° C., decomposition of PCL and PPL becomes remarkable, and if it is lower than 170 ° C., it is difficult to extrude using a melt extruder and the number of polymer balls increases, which is not preferable.

In the present invention, since the melting point and crystallization temperature of PCL or PPL are slightly higher than room temperature or near room temperature, nonwoven fabrics cannot be collected by ordinary methods. That is, usually, after discharging from a die, it is collected on a conveyor or a rotating drum as it is, but in the case of the polymer used in the present invention, if it is so, cooling is insufficient and a state close to a molten state is obtained. Can only get.

FIG. 1 shows the details of the device that takes measures against this point.
Will be explained. First, the melt flow 3 discharged from the die 1 is reduced by the heated air flow 2 jetted from both sides thereof. Thereafter, in order to remove this air flow, the baffle plate 4 is placed at a position several cm to several tens cm away from the die 1. After the air flow is removed by the baffle plate 4, cooling air controlled to a temperature equal to or lower than room temperature is blown from a cooling air device 5 installed on both sides at a position several cm away from the baffle plate 4 to melt the molten material. 3 is cooled and then collected. The ultrafine fibers thus obtained are then collected in a sheet shape by a net conveyor or the like, and become a fiber web 6 having a predetermined thickness and fiber arrangement. The arrows in the figure indicate the traveling direction of the air. Note that the present invention is not limited to the structure shown in FIG. 1, and the polymer may be melt-discharged in the lateral direction.

The average fiber diameter of the fiber thus obtained is about 0.5 to 10 μm. As a result, a soft texture is given, and when the microbial degradability is taken into account, the ratio of the fiber surface area is increased, so that there is an advantage that the microbial decomposition proceeds more quickly.

The nonwoven fabric of the present invention may be a single-layer nonwoven fabric obtained by the meltblown method as described above, or a multi-layered nonwoven fabric obtained by the above meltblown method. Good. Alternatively, for example, a PCL made by a method such as a spun bond method or a short fiber method,
A nonwoven fabric made of PPL, a natural fiber made by a method such as the short fiber method, or a nonwoven fabric made of cellulosic fiber may be used. At the time of lamination, confounding can be performed between the constituent fibers using a high-pressure water flow, or thermocompression bonding can be performed between the constituent fibers using an embossing roll or the like. For example, when performing high pressure water flow treatment, 0.05
A pore having a diameter of about 1.0 mm, a flat hole having a similar cross-sectional area, and a ratio of slit length to slit width of 10
A slit-shaped hole or the like having a shape of about 0 to 5000, preferably about 500 to 2000 and a slit width of 0.02 to 0.06 mm is arranged in one row or a plurality of rows.
A water stream or a hot water stream having a pressure of kg / cm ² may be injected. When performing the thermocompression bonding between the constituent fibers, a pair of embossing rolls or a pair of rolls including an embossing roll and a flat roll may be used.

The nonwoven fabric of the present invention has excellent microbial degradability,
When buried in the soil, it will be decomposed to such an extent that it will not remain in its original form in about two months. The nonwoven fabric of the present invention can also be obtained by laminating webs made of PCL and / or PPL fibers or webs made of PCL and / or PPL fibers and webs made of other natural fibers as described above. can get. As a method of lamination, for example, there is a method in which a web made of PCL and / or PPL ultrafine fibers and a web made of the other fibers are polymerized, and then entangled between constituent fibers by a high-pressure water flow to form a laminated nonwoven fabric. Alternatively, using an apparatus as shown in FIG.
In producing PCL and / or PPL microfibers,
There is a method of obtaining a laminated nonwoven fabric by collecting the above-mentioned other fibers toward the PCL and / or PPL fiber stream while spraying the fibers with a net.

In the laminating apparatus shown in FIG. 2, a Ricken roll 7 arranged beside the die 1 of the melt blowing apparatus is used to introduce the fibers to be laminated into the microfine fiber stream 3.
The web 8 can be produced, for example, on a garnet machine or a land webber, which is propelled along a table 10 arranged in the vicinity of a drive roll 9, the leading end of which engages the Ricken roll 7. The Ricken roll 7 rotates in the direction of the arrow to scrape the fibers from the leading end of the web 8. The scraped fibers are carried by a stream of air through a conduit 12 and merged into a stream of ultrafine fibers into which the melt stream 3 has been turned into ultrafine fibers. The merged material is deposited on the net conveyor 13, and the scraped fibers and the ultrafine fibers are laminated to form a laminated web 14. The air flow described above can be generated by rotation of the Ricken roll 7, or can be generated by blowing air from a blow port 11 as shown.

For lamination, PCL and / or PPL
The ratio of the ultrafine fibers is preferably 20% by weight or more. 20
When the amount is less than the weight%, the texture of the nonwoven fabric decreases when laminating by the high-pressure water entanglement method. Alternatively, when a laminated non-woven fabric is obtained by spraying, the inter-fiber adhesion effect of PCL and / or PPL ultrafine fibers is inferior, and as a result, disadvantages such as low strength of the non-woven fabric occur, which is not preferable.

[0030]

The nonwoven fabric of the present invention thus obtained has good microbial degradability, good air permeability, and a soft texture, and is particularly suitable for soft materials such as sanitary materials, wipes, and packaging materials. Although texture is required, it can be suitably used as a material.

[0031]

The present invention will be described below in detail with reference to examples. In the examples, the measurement method and measurement conditions for each item are as follows.

The melt flow rate (hereinafter referred to as “MFR”) was determined according to ASTM-D-1238 (E). The melting point was measured at a heating rate of 20 ° C./min using a DSC-7 type device manufactured by PerkinElmer. The tensile strength of the nonwoven fabric was determined by measuring the maximum tensile strength from a test piece having a width of 3 cm and a length of 10 cm according to the strip method described in JIS-L-1096.

Regarding the evaluation of the biodegradability, the nonwoven fabric was taken out after burying it in the soil for three months, and it was checked whether or not the nonwoven fabric maintained its shape, or even if it was maintained, the tensile strength was reduced to 50% or less of the initial value. Was judged to be good in microbial degradability. In order to convert the initial tensile strength shown in the examples into a basis weight of 30 g / m ² for comparison, the basis weight was measured, and the initial tensile strength was determined by the following formula.

Initial tensile strength (g / 3 cm) = 30 × tensile strength (g) / weight (g / m ² ) The thickness of the nonwoven fabric is 100 g per sample according to the method described in JIS-L-1096. / Cm ² pressure,
After standing for 10 seconds, the measurement was performed.

The bulk density of the nonwoven fabric was calculated from the basis weight and thickness of the nonwoven fabric by the following equation. The higher the bulk density, the higher the density of the nonwoven fabric. In the evaluation, the bulk density was 0.1.
Those with a density of 150 g / cm ³ or more were regarded as having good denseness.

Bulk density (g / cm ³ ) = weight (g / m ² )
/ [Thickness (mm) × 1000] The air permeability of the nonwoven fabric was measured according to the Frazier method described in JIS-L-1096. At the time of evaluation, those having an air permeability of 5 cc / cm ² / sec or more were evaluated as good. Example 1 Using PCL having a melting point of 59 ° C. and an MFR of 200, using an extruder-type melt spinning apparatus at a spinning temperature of 230 ° C., a discharge rate of 80 g / min from a die having a hole diameter of 0.15 mm and 200 holes was used. And melt extruded. At this time, an air flow at a temperature 30 ° C. higher than the die temperature was applied to the melt flow at a speed of 170 m / sec and at an angle of 25 ° to the discharge direction.

At this time, a baffle for removing the air flow was attached at a position 15 cm below the die, and a cooling air having a temperature of 10 ° C. was blown from the lateral direction at a position 5 cm below the baffle. Then, a web was formed by collection on a net conveyor provided 40 cm below the die. At this time, the web was adjusted so that the basis weight was 30 g / m ² .

When producing a nonwoven fabric, the yarn-forming property is good.
The obtained non-woven fabric has an initial tensile strength of 750 (g / 3c).
m), bulk density 0.200 g / cm^Three, Air permeability is 15c
c / cm ^TwoPer second, the biodegradability was excellent. Example 2 Using PPL having a melting point of 101 ° C. and an MFR of 160,
Spinning at 270 ° C using a melter spinning machine
At the yarn temperature, discharge from a die with a hole diameter of 0.15 mm and 200 holes
It was melt extruded at an output of 80 g / min. At that time, die temperature
Air flow at a temperature 30 ° C. higher than the speed of 170 m / sec.
To the melt flow at an angle of 25 degrees to the discharge direction.
Was.

At this time, as in the case of the first embodiment, 15
Attach a baffle for removing airflow
A cooling air having a temperature of 10 ° C. was blown from a lateral direction at a position 5 cm below the cooling air. Then, a web was formed by collection on a net conveyor provided 45 cm below the die. At this time, the web was adjusted so that the basis weight was 30 g / m ² .

When producing a nonwoven fabric, the yarn-making properties are good.
The obtained nonwoven fabric has an initial tensile strength of 870 (g / 3c).
m), the bulk density is 0.231 g / cm^Three, Air permeability is 12c
c / cm ^TwoPer second, the biodegradability was excellent. Example 3 50 parts by weight of PCL having an MFR of 200 and an MFR of 160
And 50 parts by weight of PPL in a chip form
Spinning temperature of 255 ° C. using a melter type spinning machine
And a discharge amount of 8 from a die having a hole diameter of 0.15 mm and 200 holes.
It was melt extruded at 0 g / min. At that time,
An air stream of 30 ° C higher temperature is discharged at a speed of 170 m / sec.
The melt flow was applied at an angle of 25 degrees to the exit direction.

Thereafter, the web was cooled in the same manner as in Example 1, and then collected on a net conveyor provided 40 cm below the die to form a web. At this time, the web was adjusted so that the basis weight was 30 g / m ² .

When producing a nonwoven fabric, the yarn-forming properties are good.
The obtained non-woven fabric has an initial tensile strength of 810 (g / 3c).
m), bulk density is 0.188 g / cm^Three, Air permeability is 10c
c / cm ^TwoPer second, the biodegradability was excellent. Example 4 Using a PCL having an MFR of 25, a hole diameter of 0.35 mm and the number of holes
Using a plurality of spinneret packs having a spinning temperature of 230
It was melt spun at ℃. Place 150cm below the spinneret
Using the established air soccer, suck the spun filament fibers
Pulling / taking off at 3500m / min drawing / taking speed, single yarn fineness
Adjust the polymer discharge rate so that it becomes 2 denier long fiber
did. Opening on a moving net conveyor
40g / m weight by collection and deposition^TwoWeb.
Then, on this web, PCL fiber with MFR of 200
Were spray-laminated by the melt blown method. Melt
The conditions of the blown method were the same as in Example 1, and the basis weight of the web was
Is 10 g / m^TwoAnd Then the heated metal emboss
Rolls and metal flat rolls.
The line pressure is 40 kg / cm, the contact area ratio is 17%,
Heat treatment is performed under the condition of a treatment temperature of 57 ° C. and a basis weight of 50 g / m
^TwoWas obtained.

The obtained laminated nonwoven fabric has an initial tensile strength of 2
It was 400 g / 3 cm, the bulk density was 0.185 g / cm ³ , the air permeability was 16 cc / cm ² / sec, and the microbial degradability was excellent. Example 5 A PCL web having a basis weight of 15 g / m ² was produced in the same manner as in Example 1 using PCL having an MFR of 200 g / 10 min. Next, a parallel card web made of rayon short fiber having a single yarn fineness of 2 denier and a fiber length of 51 mm and having a basis weight of 35 g / m ² was laminated to form a laminated web. Furthermore, the pore size is 0.
Using a discharge hole arranged at an interval of 1 mm and a pitch of 2.5 mm, treatment was performed with a high-pressure water flow of a water pressure of 40 kg / cm ² to obtain a nonwoven fabric having a basis weight of 50 g / m ² . The obtained nonwoven fabric had an initial tensile strength of 1800 g / 3 cm, a bulk density of 0.190 g / cm ³ , a permeability of 50 cc / cm ² / sec, and was excellent in microbial degradability.

[0044]

As described above, according to the present invention, a nonwoven fabric having microbial decomposability, having tensile strength enough to withstand practical use, good air permeability, and soft feel, can be obtained at low cost. . In particular, the nonwoven fabric of the present invention can be suitably used as a material for a medical mask or the like that requires a soft texture.
Further, the nonwoven fabric of the present invention is also suitable as a material for general living materials such as sanitary materials, wipes, packaging materials, etc. It does not require waste disposal and is extremely useful from the global environmental conservation point of view.

[Brief description of the drawings]

FIG. 1 is a diagram showing a die and its vicinity in an apparatus for producing a nonwoven fabric of the present invention.

FIG. 2 is a view showing a schematic overall configuration of an apparatus for producing a nonwoven fabric of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die 2 Heated air flow 3 Melt flow 4 Baffle plate 5 Cooling device 6 Microfiber web 14 Laminated web

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takashi Inoue 222-1203 Imai Nishimachi, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture (56) References JP-A-2-119866 (JP, A) JP-A-3-146754 ( JP, A) JP-A-4-50353 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D04H 1/00-18/00 EPAT (QUESTEL) WPI / L (QUESTEL)

Claims (4)

(57) [Claims] 1. A polymer consisting only of poly-.epsilon.-caprolactone, a polymer consisting only of poly-.beta.-propiolactone, a polymer consisting of only poly-.epsilon.-caprolactone and only consisting of poly-.beta.-propiolactone. A microbial-degradable ultrafine fiber meltblown nonwoven fabric, which is made of any one of a mixture with a polymer and has an ultrafine fiber having a single yarn fineness of less than 0.8 denier. 2. A polymer consisting only of poly-.epsilon.-caprolactone, a polymer consisting only of poly-.beta.-propiolactone, a polymer consisting only of poly-.epsilon.-caprolactone and only consisting of poly-.beta.-propiolactone. 10% by weight or more of a web composed of ultrafine fibers having a single-fiber fineness of less than 0.8 denier and a polymer comprising only poly-ε-caprolactone;
Polymer consisting of only β-propiolactone, poly-ε-
90% by weight of a web consisting of a mixture of a polymer consisting of only caprolactone and a polymer consisting of only poly-β-propiolactone, and having a single fiber fineness of 0.8 to 6 denier A microbial degradable nonwoven fabric characterized by laminating: 3. A polymer consisting only of poly-.epsilon.-caprolactone, a polymer consisting only of poly-.beta.-propiolactone, a polymer consisting only of poly-.epsilon.-caprolactone and only consisting of poly-.beta.-propiolactone. 20% by weight or more of a web composed of ultrafine fibers having a single-fiber fineness of less than 0.8 denier, and 80% by weight of a web composed of natural fibers or cellulosic fibers A microbial degradable nonwoven fabric characterized by laminating: 4. A polymer comprising only poly-.epsilon.-caprolactone, a polymer comprising only poly-.beta.-propiolactone, a polymer comprising only poly-.epsilon.-caprolactone and only comprising poly-.beta.-propiolactone. After any one of the mixture with the polymer is melt-discharged from the die by the melt blown method, the traction air flow is removed with a baffle plate, and then cooled by blowing cooling air from the side of the melt-discharged body. A method for producing a microbial-degradable ultrafine fiber melt-blown nonwoven fabric, comprising forming ultrafine fibers having a yarn fineness of less than 0.8 denier and obtaining a web comprising the ultrafine fibers.