JPH06212550A - Ultra-fine polypropylene fiber nonwoven web and its production - Google Patents

Abstract

PURPOSE:To provide a raw material for ultra-fine polypropylene fiber nonwoven cloth having excellent mechanical properties, dimensional stability, flexibility and printability and useful as industrial material and clothes. CONSTITUTION:The nonwoven fabric web of ultra-fine polypropylene fiber is composed of ultra-fine fibers having an average fiber diameter of 0.1-10.0mum and a boiling water shrinkage of <=35% and composed of a mixture of 70-95wt.% of a crystalline polypropylene polymer and 30-5wt.% of an amorphous polyester polymer, wherein the core part of the fiber in the cross section of the single fiber is composed mainly of the polypropylene polymer and the sheath part is composed mainly of the polyester polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention obtains a polypropylene-based ultrafine fiber nonwoven fabric mainly composed of a polypropylene-based polymer, which has excellent mechanical properties, dimensional stability, flexibility and printability and is used for industrial materials and clothing materials. The present invention relates to a nonwoven web suitable for, and a method for efficiently producing the nonwoven web.

[0002]

2. Description of the Related Art A polypropylene-based ultrafine fiber nonwoven fabric manufactured by a melt blown method using a polypropylene-based polymer has been known. The melt-blown method is a method in which a melt-spinning die discharges a molten polymer and at the same time draws and thins a polymer stream melt-spun by a high-temperature high-pressure air stream to obtain ultrafine fibers. For example, Industrial and Engineering Chemistry No. 48 8th
No. 1342-1346 (1956) discloses a basic apparatus and method of the melt blown method. The melt blown method is applied to obtain various raw materials because extremely fine fibers can be obtained. There is. However, although the polypropylene-based ultrafine fiber nonwoven fabric obtained by the melt blown method is widely used as a material for various life-related materials and industrial materials, it has a problem of poor mechanical properties and printability. It was

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and obtains a polypropylene-based ultrafine fiber nonwoven fabric having excellent mechanical properties, dimensional stability, flexibility and printability, and for industrial materials and clothing materials. The present invention aims to provide a nonwoven web suitable for, and a method capable of efficiently producing the nonwoven web.

[0004]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above-mentioned problems. That is, the present invention relates to a crystalline polypropylene polymer 70-
The average fiber diameter composed of a mixture of 95% by weight and 30 to 5% by weight of the amorphous polyester polymer is 0.1 to 10.0.
that the polypropylene polymer constitutes a substantially core portion, the polyester polymer constitutes a substantially sheath portion, and the boiling water shrinkage ratio is 35% or less. The gist of the present invention is a polypropylene-based ultrafine fiber non-woven web. Also,
According to the present invention, when a polypropylene-based ultrafine fiber nonwoven fabric is manufactured by the melt blown method, the polypropylene-based polymer is 70 to 95% by weight and the relative viscosity is 1.20.
˜1.32 of a polyester polymer in an amount of 30 to 5 wt% and a ratio of the melt flow rate of the polyester polymer to the melt flow rate of the polypropylene polymer is 1.5 to
The polymer was melt-spun to 6.0, and the polymer stream melt-spun was drawn / thinned by a high-pressure air flow having a temperature higher than the melting temperature, cooled, and then collected / deposited on the moving collecting surface. The present invention is directed to a method for producing a polypropylene-based ultrafine fiber non-woven web, which is characterized in that a non-woven web is obtained.

Next, the present invention will be described in detail. The polypropylene-based polymer in the present invention is mainly a crystalline polypropylene polymer having an ordinary fiber-forming property. In addition to this, a polypropylene-based copolymer in which an ethylene component is copolymerized in an amount of 8% by weight or less, or a mixed polypropylene-based polymer It may be a mixture. When the copolymerization rate or mixing rate of the ethylene component exceeds 8% by weight, the melting point of the copolymer or the mixture is lowered, and when the nonwoven fabric product obtained using the nonwoven web is used under high temperature conditions, It is not preferable because the mechanical properties and dimensional stability are reduced. When such a polypropylene polymer is used, the degree of crystallization is higher than that of the polyester polymer when the melt blown method is applied. The polyester polymer in the present invention means an aromatic dicarboxylic acid such as phthalic acid, terephthalic acid, isophthalic acid, naphthalene-2,6 dicarboxylic acid or the like as an acid component, or an aliphatic dicarboxylic acid such as adipic acid, sebacic acid or the like. Esters of ethylene, ethylene glycol, diethylene glycol as diol component, 1
A homopolyester polymer or copolymer synthesized from a diol compound such as 4-butanediol, neopentyl glycol, cyclohexane-1-4-dimethanol, etc., and these polyester-based polymers include:
Paraoxybenzoic acid, 5-sodium sulfoisophthalic acid, polyalkylene glycol, pentaerythritol, bisphenol A and the like may be added or copolymerized. When such a melt-blown method is applied, such a polyester-based polymer has a lower degree of crystallization than a polypropylene-based polymer. In the present invention, the polypropylene-based polymer and / or the polyester-based polymer may be added with various additives such as a matting agent, a pigment, a light stabilizer, a heat stabilizer, and an antioxidant, if necessary. It can be added within a range that does not impair the effects of the present invention.

The ultrafine fibers in the present invention are composed of a mixture of 70 to 95% by weight of the polypropylene-based polymer and 30 to 5% by weight of the polyester-based polymer. It has a structure in which a core portion is formed and the polyester polymer forms a substantially sheath portion. In this ultrafine fiber, if the ratio of the polyester polymer to the total weight of the polypropylene polymer and the polyester polymer, that is, the mixing ratio is less than 5% by weight, the polyester polymer is not located on the outer periphery of the polypropylene polymer. Therefore, since the polypropylene-based polymer and the polyester-based polymer are incompatible with each other, they are fibrillated and the mechanical properties and printability are not improved. On the other hand, when this ratio exceeds 30% by weight, the polypropylene-based polymer is Since the peculiar flexibility is hindered, and the yarn formability and dimensional stability are impaired,
Neither is preferable. Therefore, in the present invention, the mixing ratio of both polymers is 70
To 95% by weight, preferably 75 to 92% by weight, more preferably 80 to 90% by weight, and 30% by weight of the polyester polymer.
-5 wt%, preferably 25-8 wt%, more preferably 20-10 wt%. As described above, this ultrafine fiber has a structure in which the polypropylene polymer constitutes a substantially core portion and the polyester polymer constitutes a substantially sheath portion in a single fiber cross section. It should be noted that the fact that the polypropylene-based polymer here constitutes the substantially core portion means that the polypropylene-based polymer is unevenly distributed in the vicinity of the central portion of the single fiber in excess of the mixing ratio of the polypropylene-based polymer and the polyester-based polymer. This means that the polyester polymer constitutes the core portion, while the polyester polymer substantially constitutes the sheath portion means that the polyester polymer exceeds the mixing ratio of the polypropylene polymer and the polyester polymer. It means that it is unevenly distributed in the vicinity of the surface layer of the monofilament to form a so-called sheath portion. In addition, in this ultrafine fiber obtained by applying the so-called melt blown method, the polypropylene polymer is easy to crystallize, while the polyester polymer is hard to crystallize, and thus relatively relatively. In the cross section of the single fiber, the substantially core portion formed by the polypropylene polymer is crystalline, and on the other hand, the substantially sheath portion formed by the polyester polymer in the single fiber cross section is amorphous. The term "crystalline" means that the degree of crystallization of the polypropylene polymer is higher than that of the polyester polymer, while the term "amorphous" means the degree of crystallization of the polyester polymer. Is lower than the polypropylene polymer.

The nonwoven web made of the ultrafine fibers in the present invention has a boiling water shrinkage of 35% or less. As described above, the non-woven web is composed of ultrafine fibers made of a mixture of a polypropylene-based polymer and a polyester-based polymer in a specific ratio. In the single fiber cross section, the crystalline polypropylene-based polymer, which is present in the amorphous polyester-based polymer that constitutes the substantially core portion and the substantially sheath portion in the single fiber cross section, inhibits the crystallization of the polyester-based polymer. Therefore, the shrinkage rate is suppressed, and the disadvantage of the polyester polymer having a high shrinkage rate is improved when the nonwoven web is prepared by applying the melt blown method, and the boiling water shrinkage rate is 35% or less. An excellent non-woven web can be obtained, and the obtained non-woven web is widely used as a non-woven web for obtaining nonwoven products for not only clothing materials but also industrial materials. It becomes possible to apply to. Further, in this non-woven web, since the polypropylene-based polymer forming the substantially core portion in the cross section of the single fiber is covered with the polyester-based polymer to form the substantially sheath portion, the non-woven web made of this fiber is formed. When used as a non-woven fabric product, a non-woven fabric product having improved mechanical properties and printability can be obtained.

The ultrafine fibers made of a mixture of the polypropylene polymer and the polyester polymer in the present invention have an average fiber diameter of 0.1 to 10.0 μm, and the average fiber diameter is 0.1 μm. When the average fiber diameter is more than 10.0 μm, the texture of the obtained nonwoven web becomes hard, and when the average fiber diameter exceeds 10.0 μm, the nonwoven fabric becomes soft when it is obtained. It is not preferable because a rich nonwoven fabric cannot be obtained.

The non-woven web composed of the ultrafine fibers in the present invention can be efficiently produced by a known so-called melt blown method. That is, using a mixture of 70 to 95% by weight of a polypropylene polymer and 30 to 5% by weight of a polyester polymer having a relative viscosity of 1.20 to 1.32 as a polymer, melt spinning is performed by a melt blown method,
This is a method in which a melt-spun polymer stream is drawn and thinned by a high-temperature, high-pressure air stream, cooled, and then collected and deposited on a moving collection surface to form a nonwoven web.

In the production method of the present invention, a polyester polymer having a relative viscosity of 1.20 to 1.32 is used. If the relative viscosity is less than 1.20, the degree of polymerization is too low, and it becomes difficult to pelletize the polymer during polymerization. On the other hand, if the relative viscosity exceeds 1.32, the degree of polymerization is too high, and thus in the spinning process. Polymer balls are generated on the surface of the melt-spinning die, so that the spinnability is deteriorated and it becomes difficult to form ultrafine fibers, and moreover, the energy required for fiber formation is large, which is not preferable. Therefore, in the present invention, the relative viscosity is 1.20 to 1.32, preferably 1.21 to 1.30, and more preferably 1.22 to 1.30.
Set to 1.28.

In the production method of the present invention, the ratio of the melt flow rate of the polyester polymer to the melt flow rate of the polypropylene polymer is 1.
It is necessary to carry out melt spinning so as to be 5 to 6.0. By setting the ratio of the melt flow rates to 1.5 to 6.0, when a mixture of polypropylene-based and polyester-based polymers which are incompatible with each other is supplied to the melt-spinning die, a polymer with a low degree of polymerization flows. The high flow resistance flows near the wall of the orifice, while the polymer with high degree of polymerization flows in the central part of the orifice with low flow resistance.
By the combination of these flows, a substantially core-sheath type structure is developed in the single fiber cross section. And
If the ratio of the melt flow rate is less than 1.5, the melt flow rate ratio is too small, so that the polyester polymer exhibits a so-called sea-island structure in which dots are located in the polypropylene polymer in the single fiber cross section. Does not develop a substantially core-sheath type structure, and thus the spinnability deteriorates, and even if a non-woven product is made using the non-woven web obtained, the non-woven product obtained is remarkably inferior in mechanical properties. When treated with boiling water, so-called wrinkling occurs and the quality deteriorates significantly. On the other hand, when the ratio of the melt flow rate exceeds 6.0, the polypropylene polymer develops a core-sheath structure in which the polypropylene polymer has a substantially core portion and the polyester polymer has a substantially sheath portion in the cross section of the single fiber. Since the ratio is too large, polymer balls on the surface of the melt-spinning spinner and twisting phenomenon of the discharge yarn may occur, resulting in extremely low spinnability and poor uniformity of the discharge yarn. . Therefore,
In the present invention, the ratio of the melt flow rates is 1.5 to 6.0, preferably 2.0 to 5.5, more preferably 2.5 to 5.0.
And

In the manufacturing method of the present invention, it is necessary to set the temperature of the high-pressure air stream for drawing and thinning the melt-spun polymer stream to a temperature higher than the melting temperature of the polymer stream.
If this temperature is lower than the melting temperature of the polymer flow, the spinnability deteriorates and it becomes difficult to form ultrafine fibers, which is not preferable.

In the present invention, the non-woven web obtained as described above can be subjected to a partial hot-pressing treatment if necessary to retain its shape. A publicly known method can be applied when performing the partial hot-pressing treatment. For example, there is a method in which the obtained nonwoven web is passed between both rollers, which are a heated embossing roller and a metal roller having a smooth surface, or a method using an ultrasonic fusing device.
When a heated embossing roller is used, the pressure contact area ratio is 5 to 50%. If the pressure contact area ratio is less than 5%, the number of spot fusion areas is small and the mechanical properties of the non-woven fabric are deteriorated. Stability cannot be obtained, and on the other hand, if the pressure contact area ratio exceeds 50%, the nonwoven fabric becomes rigid and the flexibility is impaired, so both are not preferable. Also, the roller temperature is preferably 150 to 220 ° C., and this temperature is 1
If the temperature is lower than 50 ° C, the fusion strength between fibers in the fusion zone becomes low, so that the mechanical properties of the nonwoven fabric are deteriorated and good dimensional stability cannot be obtained.
If the temperature exceeds 0 ° C, the non-woven fabric becomes rigid and the flexibility is impaired. The embossing pattern when using the hot embossing roller has a pressing area ratio of 5 to 5
The shape is not particularly limited as long as it is within the range of 0%, and may be any shape such as a round shape, an elliptical shape, a rhombus shape, a triangular shape, a T shape, and a well shape. The partial thermal pressure welding process using this hot embossing roller or ultrasonic fusing device may be a continuous process or a separate process.

In the present invention, the non-woven web obtained as described above may be subjected to a high-pressure liquid flow treatment to cause a three-dimensional entanglement between the fibers to maintain the shape.
A well-known method can be applied when performing this high-pressure liquid flow treatment. For example, the pore size is 0.05-1.0m
m There is a method of ejecting a high-pressure liquid having an ejection pressure of 5 to 150 kg / cm ² G from the ejection holes by using a device in which a large number of ejection holes of 0.1 to 0.4 mm are arranged. The injection holes are arranged in rows in a direction orthogonal to the direction of travel of the web. This treatment may be performed on one side or both sides of the web. In particular, in the case of one-side treatment, the injection holes are arranged in a plurality of rows and the injection pressure is lowered in the front stage and increased in the rear stage. As a result, it is possible to obtain a non-woven fabric having a uniform and dense entangled form and a uniform texture. As a high pressure liquid,
It is common to use water or warm water. The distance between the injection hole and the web is preferably 1 to 15 cm. When this distance is less than 1 cm, the texture of the web is disturbed, while when this distance exceeds 15 cm, the impact force when the liquid flow collides with the web is reduced and the three-dimensional entanglement is not sufficiently performed. Is also not preferable. This high pressure liquid flow treatment
It may be either a continuous process or a separate process. When performing the high-pressure liquid flow treatment, the structure or handle of the non-woven fabric can be changed by appropriately changing the mesh or woven structure of the screen carrying the web. After the high pressure liquid stream treatment, excess moisture is removed from the web. A known method can be applied to remove the excess water. For example, a squeezing device such as a mangle roll is used to remove excess water to some extent, and then a drying device such as a continuous hot air dryer is used to remove the remaining water.

[0015]

EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the examples, each characteristic value was measured by the following method. Melting point (℃): Differential scanning calorimeter DS manufactured by Perkin Elma
Using a C-2 type, the measurement is performed at a temperature rising rate of 20 ° C./min,
The temperature that gives the extreme value in the obtained melting endothermic curve was taken as the melting point. Relative viscosity: 0.5 g of a sample was dissolved in 100 cc of a mixed solvent of phenol and ethane tetrachloride in an equal weight ratio, and the temperature was 20 ° C.
It was measured by a conventional method under the conditions of. Melt flow rate (g): Using a melt indexer melt flow rate measuring device, orifice diameter 0.4 mm, orifice length 1.2 m
The discharge amount of the molten polymer per 10 minutes was measured under the conditions of m and a load of 2160 g. The measurement temperature was the same as the melt spinning temperature. Average fiber diameter (μm): Obtained by taking an electron micrograph of the sample. Tensile strength (kg / 5cm width) and tensile elongation (%): JI
It was measured according to the method described in S-L-1096A. That is, a sample piece 1 having a sample length of 10 cm and a sample width of 5 cm
Create 0 points, and for each sample piece, regarding the warp direction of the nonwoven fabric,
Tensile speed 10c using a constant speed extension type tensile tester (Tensilon UTM-4-1-100 manufactured by Toyo Baldwin Co., Ltd.)
The load value at the time of cutting obtained by stretching at m / min (kg / 5cm
The average value of the width was taken as the tensile strength (kg / 5 cm width), and the average value of the elongation at break (%) was taken as the tensile elongation (%). Boiling water shrinkage ratio (%): A plurality of sample pieces each having a sample length and a sample width of 25 cm were prepared, and each sample piece was subjected to boiling water treatment using boiling water under a treatment time of 3 minutes. At this time, the area S1 of the sample piece before the boiling water treatment and the area S2 of the sample piece after the boiling water treatment were obtained, and the average value of the values calculated by the following equation (1) from the obtained S1 and S2 was taken as the boiling water shrinkage rate (%). did. Shrinkage rate of boiling water (%) = [1- (S2 / S1)] × 100 (1) Flexibility: According to the handle odometer method described in JIS-L-1096, the slit width is 1 cm. It was measured under the conditions. Printability: A sample was printed using both oil-based and water-based inks, and the sharpness and durability of the print were obtained, and each was evaluated in the following three grades. ◎: Very good, ○: Good, ×: Poor

Example 1 A nonwoven web was prepared by a melt blown method using a mixture of 95% by weight of a polypropylene polymer having a melting point of 160 ° C. and 5% by weight of a polyethylene terephthalate polymer having a melting point of 259 ° C. and a relative viscosity of 1.22. Manufactured. That is, a mixture of both the above polymers is melted, and the mixture is spun at a spinning temperature of
The polymer stream was spun at 40 ° C. with a single hole discharge rate of 0.2 g / min, and the polymer stream melt-spun was pulled and thinned by a high-pressure air stream. At this time, the ratio of the melt flow rate of the polyethylene terephthalate polymer to the melt flow rate of the polypropylene polymer was 3.2. This high-pressure air flow has a temperature of 370 ° C. and a pressure of 1.
2 kg / cm ² of heated air was used. Following traction / thinning, the polymer stream was cooled and formed into fibers, and then 5 from the die.
A non-woven web was obtained by collecting and depositing it on a wire mesh belt arranged at a position separated by cm and moving at a speed of 6.7 m / min. The spinnability was good. When the cross section of the constituent fibers of the obtained non-woven web was observed with an electron microscope at a magnification of 5000 times, it had a substantially core-sheath structure in which the periphery of the polypropylene polymer was covered with a polyethylene terephthalate polymer in a thin film form. It was confirmed that The properties of the resulting nonwoven web are shown in Table 1. As is apparent from Table 1, the nonwoven web of the present invention had excellent mechanical properties, dimensional stability, flexibility and printability.

Example 2 A mixture of 85% by weight of a polypropylene polymer having a melting point of 160 ° C. and 15% by weight of a polyethylene terephthalate polymer having a melting point of 259 ° C. and a relative viscosity of 1.22 was used.
A nonwoven web was obtained in the same manner as in Example 1 except that the pressure of the high pressure air flow was 1.4 kg / cm ² . The spinnability was good. When the cross section of the constituent fibers of the obtained nonwoven web was observed, it was confirmed that the polypropylene web had a substantially core-sheath structure in which the periphery of the polypropylene polymer was covered with a polyethylene terephthalate polymer in a thin film form. The properties of the resulting nonwoven web are shown in Table 1. The non-woven web of the present invention has mechanical properties, dimensional stability,
It had excellent flexibility and printability.

Example 3 A mixture of 75% by weight of a polypropylene polymer having a melting point of 160 ° C. and 25% by weight of a polyethylene terephthalate polymer having a melting point of 259 ° C. and a relative viscosity of 1.22 was used.
A non-woven web was obtained in the same manner as in Example 1 except that the pressure of the high pressure air flow was 1.5 kg / cm ² . The spinnability was good. When the cross section of the constituent fibers of the obtained nonwoven web was observed, it was confirmed that the polypropylene web had a substantially core-sheath structure in which the periphery of the polypropylene polymer was covered with a polyethylene terephthalate polymer in a thin film form. The properties of the resulting nonwoven web are shown in Table 1. The non-woven web of the present invention has mechanical properties, dimensional stability,
It had excellent flexibility and printability.

Example 4 A mixture of 85% by weight of a polypropylene polymer having a melting point of 160 ° C. and 15% by weight of a polyethylene terephthalate polymer having a melting point of 259 ° C. and a relative viscosity of 1.22 was used.
In the same manner as in Example 1 except that the ratio of the melt flow rate of the polyethylene terephthalate polymer to the melt flow rate of the polypropylene polymer was 4.0, and the pressure of the high-pressure air flow was 1.2 kg / cm ² . A non-woven web was obtained.
The spinnability was good. When the cross section of the constituent fibers of the obtained nonwoven web was observed, it was confirmed that the polypropylene web had a substantially core-sheath structure in which the periphery of the polypropylene polymer was covered with a polyethylene terephthalate polymer in a thin film form. The properties of the resulting nonwoven web are shown in Table 1. As is apparent from Table 1, the nonwoven web of the present invention had excellent mechanical properties, dimensional stability, flexibility and printability.

Comparative Example 1 A mixture of 50% by weight of a polypropylene polymer having a melting point of 160 ° C. and 50% by weight of a polyethylene terephthalate polymer having a melting point of 259 ° C. and a relative viscosity of 1.22 was used.
A nonwoven web was obtained in the same manner as in Example 1 except that the pressure of the high-pressure air flow was 0.8 kg / cm ² . Regarding the spinnability, polymer balls were generated on the surface of the melt-spinning spinneret after the start of melt-spinning, and it was unsatisfactory. The cross section of the constituent fibers of the obtained non-woven web was observed, and it was found that the polyethylene terephthalate polymer had a substantially core-sheath structure in which the polyethylene terephthalate polymer was coated in a thin film around the polypropylene polymer. It was confirmed that the united body also had a so-called sea-island structure scattered in the polypropylene polymer. The properties of the resulting nonwoven web are shown in Table 1. As is clear from Table 1, this nonwoven web was excellent in dimensional stability and printability, but was inferior in both mechanical properties and flexibility and was not practical.

Comparative Example 2 A mixture of 85% by weight of a polypropylene polymer having a melting point of 160 ° C. and 15% by weight of a polyethylene terephthalate polymer having a melting point of 259 ° C. and a relative viscosity of 1.22 was used.
In the same manner as in Example 1 except that the ratio of the melt flow rate of the polyethylene terephthalate polymer to the melt flow rate of the polypropylene polymer was 1.0, and the pressure of the high pressure air flow was 0.6 kg / cm ² . A non-woven web was obtained.
Since the ratio of the melt flow rate was too small, yarn breakage occurred frequently and the spinnability was extremely deteriorated. By observing the cross section of the constituent fibers of the obtained non-woven web, it was confirmed that the non-woven web had a so-called sea-island structure in which polyethylene terephthalate polymer was scattered in polypropylene polymer. The properties of the resulting nonwoven web are shown in Table 1. This nonwoven web is shown in Table 1.
As is clear from the results, mechanical properties, dimensional stability, flexibility and printability were all extremely inferior. In addition, the non-woven product obtained by subjecting this nonwoven web to boiling water shrinkage treatment is
So-called wrinkling occurred and the quality was inferior.

Comparative Example 3 A mixture of 85% by weight of a polypropylene polymer having a melting point of 160 ° C. and 15% by weight of a polyethylene terephthalate polymer having a melting point of 259 ° C. and a relative viscosity of 1.22 was used.
Melt spinning was performed in the same manner as in Example 1 except that the ratio of the melt flow rate of the polyethylene terephthalate polymer to the melt flow rate of the polypropylene polymer was 7.1 and the pressure of the high-pressure air flow was variously changed. Since the ratio of the melt flow rate was too large, the twisting phenomenon of the polymer balls and the discharge yarns frequently occurred on the surface of the melt spinneret, and the nonwoven web could not be obtained. The cross section of the fiber obtained in a small amount was observed with an electron microscope at a magnification of 5000 times. As a result, it was found that the polymer had a substantially core-sheath structure in which a polyethylene terephthalate polymer was coated in a thin film around the polypropylene polymer. Although this was confirmed, the degree of uniformity was inferior and a large variation was found in the single fiber diameter.

[0023]

[Table 1]

[0024]

The polypropylene-based ultrafine fiber non-woven web of the present invention has an average fiber diameter of 70-95% by weight of a crystalline polypropylene-based polymer and 30-5% by weight of an amorphous polyester-based polymer. It is composed of ultrafine fibers of 0.1 to 10.0 μm, and in the single fiber cross section, the polypropylene polymer constitutes a substantially core portion, the polyester polymer constitutes a substantially sheath portion, and the boiling water shrinkage ratio is 35.
% Or less, it has excellent mechanical properties, dimensional stability, flexibility, and printability, and is suitable as a polypropylene-based ultrafine fiber nonwoven material for industrial materials and clothing materials. Further, according to the method for producing a polypropylene-based ultrafine fiber non-woven web of the present invention, the non-woven web can be efficiently produced.

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Claims (2)

[Claims] 1. A crystalline polypropylene polymer 70-9.
The average fiber diameter made of a mixture of 5% by weight and 30 to 5% by weight of the amorphous polyester polymer is 0.1 to 10.0 μm.
that the polypropylene-based polymer constitutes a substantially core portion, the polyester-based polymer constitutes a substantially sheath portion, and the boiling water shrinkage ratio is 35% or less. Characteristic polypropylene-based ultrafine fiber non-woven web. 2. When producing a polypropylene-based ultrafine fiber non-woven fabric by the melt blown method, the polypropylene-based polymer is 70 to 95% by weight and the relative viscosity is 1.
20 to 1.32 polyester polymer 30 to 5% by weight
And the ratio of the melt flow rate of the polyester polymer to the melt flow rate of the polypropylene polymer is 1.5.
The melt-spun polymer stream is drawn to ˜6.0, and the polymer stream melt-spun is drawn / thinned by a high-pressure air stream having a temperature higher than the melting temperature, cooled, and then collected on a moving collection surface. A method for producing a polypropylene-based ultrafine fiber nonwoven web, which comprises depositing the nonwoven web.