KR101112698B1 - Polypropylene staple with improved hot plate Weldability, manufacturing method thereof, and nonwoven fabric prepared from the same - Google Patents

Abstract

The present invention relates to a polypropylene short fiber with improved heat sealability, a method for manufacturing the same, and a nonwoven fabric prepared from the same and having a significantly improved strength. The polypropylene short fiber according to the present invention is melted, extruded, and delayed-cooled to a surface of a polypropylene resin. It is characterized in that the polypropylene short fibers oxidized chain cutting, the melt flow index is 2.5 or more compared to the melt flow index of the polypropylene resin.

Since the surface of the polypropylene short fibers according to the present invention is oxidized and cut in a predetermined range to have an elongation of 300% or more and at the same time have an improved heat fusion property, a non-woven fabric is manufactured by a thermal bonding method, in particular, a calender bonding method. Suitable. When the nonwoven fabric is manufactured by treating the short polypropylene fiber according to the present invention by a calender bonding method, it is possible to provide a nonwoven fabric having an elongation rate of about 100% and a markedly improved strength at the same time.

Polypropylene Short Fiber, Surface Oxidation Cutting, Heat Sealability, Lateral Cooling, Thermal Bond Index, Nonwoven Fabric

Description

Polypropylene staple fiber with improved thermal fusion, its manufacturing method and nonwoven fabric produced therefrom {Polypropylene staple with improved hot plate Weldability, manufacturing method, etc., and nonwoven fabric prepared from the same}

The present invention relates to a short polypropylene short fiber, improved manufacturing method thereof and a nonwoven fabric produced therefrom.

Polypropylene (polypropylene, PP) is light, strong and excellent wear resistance, relatively simple and inexpensive manufacturing process has been applied to a variety of applications, such as plastics, films, fibers. In the early days of polypropylene, its use was limited due to its weak thermal stability, UV stability, and difficulty in dyeing.However, the development of polypropylene polymerization process, heat stabilizer, UV stabilizer, etc. Due to the color impartment, the scope of application has gradually expanded to interior materials for automobiles and carpets for interior decoration.

On the other hand, polypropylene short fibers are applied to various types of non-woven fabric products because they have advantages such as low specific gravity, excellent chemical resistance, and low cost compared to other natural or synthetic fibers. In particular, the low melting point (about 165 ° C.) peculiar to polypropylene is best suited for thermal bonding nonwoven processes in which heat is used to bond the fibrous web, and is in fact most used. Thermal bonding nonwovens made from short polypropylene fibers are being used as coverstock for disposable hygiene products such as diapers, sanitary napkins and the like. In addition, polypropylene short fibers are manufactured into felt through needle punching process, and are used for automotive trim and carpet, civil drainage material, oil absorption cloth, filter substrate, and various spinning processes. It is manufactured as a spun yarn and is used for clothes, filters, etc.

As a method of manufacturing nonwoven fabric for hygiene (diaper, sanitary napkin, wet wipes, etc.) from polypropylene short fibers, the calender bonding method is most commonly used among thermal bonding methods. The calender-bonded nonwoven fabrics produced were often limited in weight reduction and use of nonwoven fabrics due to their poor thermal bondability (nonwoven fabric strength).

Therefore, in order to be competitive in calender-bonded nonwoven fabrics used for hygiene (diapers, sanitary napkins, wet wipes, etc.), a polypropylene stage for improving the thermal bonding property (nonwoven fabric strength) of the nonwoven fabric and concomitantly improving the covering property. The development of fibers is necessary.

The present invention is to solve the conventional problems, the present invention is to provide a polypropylene short fiber with improved heat sealability, a method for producing the same and a nonwoven fabric prepared therefrom, which has a remarkably improved strength and additionally improved cover properties. There is a purpose.

An object of the present invention is a polypropylene short fiber oxidatively cut the surface by melting, extruding and delayed cooling the polypropylene resin, the polypropylene stage characterized in that the melt flow index is 2.5 or more compared to the melt flow index of the polypropylene resin By providing the fibers. At this time, the polypropylene resin used to prepare the short polypropylene fiber is characterized in that the melt flow index is 5 to 30g / 10min, the isotactic index is 90% or more. In addition, the short polypropylene fiber is characterized in that the elongation is 300% or more, the fineness is 1.5 denier or less, or the cross-section of the tetralobal (Tetralobal) form.

Another object of the invention, (a) melting the polypropylene resin in the temperature range of more than 280 ℃ to less than 310 ℃; (b) extruding the molten polypropylene resin through a spinneret at a rate of 1000 to 2500 m / min to provide an undrawn yarn; (c) oxidatively cutting the surface of the undrawn yarn by delay cooling the extruded undrawn yarn with cooling air supplied at a rate of 1 to 5 m / sec; (d) drawing the undrawn yarn whose surface is oxidatively cut; (e) attaching the spinning oil to the surface of the drawn yarn; And (f) cutting the drawn yarn with the spinning oil into short fibers of a predetermined length. At this time, the method for producing a short polypropylene fiber of the present invention may further include delayed cooling by passing the unstretched yarn extruded in the step (c) through the blocking area of the cooling air before delaying cooling with the cooling air.

Another object of the present invention can be achieved by providing a nonwoven fabric prepared by treating the short polypropylene fibers according to the present invention by a thermal bonding method. The nonwoven fabric thus prepared is characterized in that the thermal bond index is 2.0 or more.

Since the surface of the polypropylene short fibers according to the present invention is oxidized and cut in a predetermined range to have an elongation of 300% or more and at the same time have an improved heat fusion property, a non-woven fabric is manufactured by a thermal bonding method, in particular, a calender bonding method. Suitable. When the nonwoven fabric is manufactured by treating the short polypropylene fiber according to the present invention by a calender bonding method, it is possible to provide a nonwoven fabric having an elongation rate of about 100% and a markedly improved strength at the same time.

One aspect of the present invention relates to a polypropylene short fiber with improved heat sealability, the polypropylene short fiber of the present invention is prepared by melting, extruding and delay cooling polypropylene resin, the surface of which is oxidized chain cutting It is done.

When manufacturing nonwoven fabric by treating polypropylene short fibers with thermal bonding method, in order to improve the strength of nonwoven fabric, polypropylene short fibers should have excellent heat sealability. It is preferable that the oxidative chain cutting. According to the present invention, the range of oxidative chain cutting on the surface of polypropylene short fibers for excellent heat fusion is melt flow index (MFI) of polypripropylene resin and melting of polypropylene short fibers prepared from polypropylene resin. Indirectly, the ratio of the flow index (hereinafter referred to as "MFI-R" is the ratio of the melt flow index of the polypropylene resin to the melt flow index of the polypropylene short fibers produced from the polypropylene resin). , In order to improve the strength of the nonwoven fabric, the value of MFI-R should be 2.5 or more, and preferably 2.5 to 5.5.

Polypropylene short fibers with a MFI-R value of less than 2.5 do not sufficiently oxidize and cut the surface, and the nonwoven fabric produced therefrom has a thermal bond index (the longitudinal strength and the transverse strength of the nonwoven fabric). Combined exponential) value indicates less than 2.0, and improved strength cannot be expected.

Thermal Bondability Index of Nonwovens (hereinafter referred to as "TBI") =

(Longitudinal strength × transverse strength) ^1/2 × (Balance / 20)

Here, the longitudinal strength means the strength in the same direction as the roll direction when the nonwoven fabric is manufactured by the calender bonding method, and the transverse strength means the strength in the vertical direction and the longitudinal strength.

In addition, in order to manufacture polypropylene short fibers having a MFI-R value of more than 5.5, the hot molten polypropylene resin must be spun and then passed through a blocking area of cooling air for delayed cooling. Because of this, the productivity may be reduced and difficulty in controlling the value of MFI-R may occur.

The polypropylene resin used to prepare the polypropylene short fibers according to the present invention has a melt flow index of 5 to 30 g / 10 min measured according to ASTM D1238, and an isotactic index measured according to ISO 9113. Although it is preferable that it is 90% or more, the content of this invention is not limited only to the said range. The lower the melt index of polypropylene resin, the more rigidity, chemical resistance and low elongation of the fiber can be given, but the viscosity decreases, resulting in poor workability. If the melt index is too high, spinning is difficult because the melt index is too high. Having an index is most suitable for fiber spinning. In addition, the isotactic index should be 90% or more to obtain short fibers having excellent polypropylene crystallinity and rigidity, and polypropylene having more than 99% is practically difficult to commercialize.

The short polypropylene fiber according to the present invention preferably has a MFI-R value of 2.5 or more and an elongation of 300% or more. Nonwoven fabric made of short polypropylene having the above range has a significantly improved strength and at the same time has a stretch of more than a certain standard, so that even when an external force is applied, it can be applied to various products without tearing.

The fineness of the short polypropylene fiber according to the present invention is not particularly limited, but preferably, it is an international unit used to express the thickness of 5.0 denier (fiber), and the standard length is 450 m and the unit weight is 0.05 g. .) Or less, More preferably, it is 1.5 denier or less, It is characterized by the above-mentioned. In the production of polypropylene short fibers, the fineness is mainly controlled by the diameter of the spinneret, and consequently, by the drawing ratio in the drawing process. The smaller the fineness is, the better the heat adhesion of the polypropylene short fibers is. Strength is improved. In addition, when the fineness of polypropylene short fibers exceeds 5.0 denier, the specific surface area (surface area per weight of the fiber) of the spun fiber surface is so small that the surface area oxidized and cut per fiber weight may be smaller than the desired level. Nonwoven fabric production by calendar bonding process treatment may not be smooth, or the strength of the nonwoven fabric may be less than the desired range.

The cross-section of the short polypropylene fiber according to the present invention generally has a spherical shape or near spherical shape as shown in FIG. 1, but may preferably have a modified shape so that the specific surface area of the fiber can be increased. As described in the previous fineness part, the larger the specific surface area of the fiber spun through the spinneret, the larger the surface area is oxidatively cut per fiber weight, and the nonwoven fabric is smoothly manufactured by the calender bonding method and the strength is significantly improved. Can be obtained.

Figure 2 is a photograph showing a polypropylene short fiber having a tetralobal cross-section (Tetralobal) cross-section in the form of increased specific surface area than the polypropylene short fiber having a spherical cross section. When the cross section of the fiber spun through the spinneret is in the form of tetralobal, the MFI-R value is increased by one or more than that of the polypropylene short fiber of the spherical cross section manufactured under the same conditions, and the nonwoven fabric manufactured by the calender bonding method treatment. The intensity of, or TBI, increases by about 0.4 to 0.6 or more, and the covering property is inversely proportional to that of the light transmissive warp. In addition, the manufacturing speed is reduced by improving the drying speed during the drying process of manufacturing the nonwoven fabric by calender bonding method.

Another aspect of the present invention relates to a method for producing polypropylene short fibers with improved heat sealability, wherein the method for preparing polypropylene short fibers of the present invention comprises (a) a polypropylene resin in a temperature range of 280 ° C. or higher to less than 310 ° C. Melting; (b) extruding the molten polypropylene resin through a spinneret at a rate of 1000 to 2500 m / min to provide an undrawn yarn; (c) oxidatively cutting the surface of the undrawn yarn by delay cooling the extruded undrawn yarn with cooling air supplied at a rate of 1 to 5 m / sec; (d) drawing the undrawn yarn whose surface is oxidatively cut; (e) attaching the spinning oil to the surface of the drawn yarn; And (f) cutting the drawn yarn to which the spinning oil is attached into short fibers of a predetermined length.

The manufacturing method relates to a method for producing polypropylene short fibers having a MFI-R value of 2.5 or more, and the important factors for determining the MFI-R value of polypropylene short fibers in the manufacturing method include a melting temperature of a polypropylene resin, Spinning speed, delayed cooling conditions, cross-sectional shape of the spinneret, etc. of the molten polypropylene resin. Hereinafter, the manufacturing method of the present invention will be described step by step using a melt spinning method using an extruder as an example, and the same parts as those described above will be omitted.

Melting Polypropylene Resin

First, chips of polypropylene resin are placed in a hopper and melted in an extruder. At this time, the melting temperature range of the polypropylene resin is limited to more than 280 ℃ to less than 310 ℃, if the melting temperature is less than 280 ℃ MFI-R value of the polypropylene short fibers produced by the oxidized chain cutting is hardly made If it is less than 2.5 and the melting temperature is 310 ° C. or more, the polypropylene resin becomes excessively melted, so that the radioactivity is very poor and substantially no polypropylene short fibers can be produced.

The polypropylene resin used is not particularly limited but is characterized by a melt flow index of 5 to 30 g / 10 min and an isotactic index of 90% or more. In addition, the polypropylene resin may be melted by including a trace amount of one or more additives selected from the group consisting of antioxidants, ultraviolet stabilizers, process stabilizers, and colorants.

Fiber surface through extrusion and delayed cooling of molten polypropylene resin Oxidation Chain Cutting  step

The molten polypropylene resin is extruded through the spinneret, and the extruded unstretched yarn is delayed-cooled with cooling air to cause oxidative chain breakage of the surface. At this time, the spinning speed of the molten polypropylene resin is a value of 1000 to 2500m / min, the supply speed of the cooling air is limited to a value of 1 to 5m / sec, when the spinning speed is less than 1000m / min, the productivity of short fibers is reduced and 2500m If it exceeds / min, the spinning speed is too fast, so the delay cooling is not performed smoothly, and the oxidative chain cutting of the fiber surface is not made to the desired level, and at the same time, the cooling of the spun fiber is less than 1m / sec. This process is so slow that it is difficult to manufacture short polypropylene fibers in the process, and if it exceeds 5 m / sec, cooling of the spun fiber proceeds too fast, so that the oxidative chain cutting of the fiber surface is not made to the desired level. .

The temperature of the cooling air is not particularly limited within the range in which the extruded unstretched yarn can be cooled, and is preferably 15 to 20 ° C. If the temperature of the cooling air is less than 15 ° C., the orientation of the fiber and the crystallization of the fiber may be lowered due to the rapid temperature change, and the physical properties of the fiber may be lowered. If the temperature of the cooling air exceeds 20 ° C., the cooling of the spun fiber There is a fear that the progress of too slow to decrease the productivity of the polypropylene short fibers in the process.

In the manufacturing method of the present invention, the step of generating the oxidative chain cutting on the surface of the extruded undrawn yarn is additionally supplied to the cooling air by a delayed cooling method, before the delayed cooling of the extruded undrawn yarn into the cooling air. It may further comprise passing. When the extruded undrawn yarn is passed through the blocking area of the cooling air and then supplied with the cooling air, the degree of oxidative chain cutting can be easily controlled because the oxidized chain cutting on the surface of the undrawn yarn can be generated at a high temperature. The blocking area of the cooling air is preferably 10 cm or less, because if it exceeds 10 cm, the extruded unstretched yarn may be exposed to high temperature for a long time, resulting in deterioration in quality.

On the other hand, the fineness of the extruded undrawn yarn is mainly controlled by the size of the spinneret diameter, the cross-sectional shape is controlled by the cross-sectional shape of the spinneret. The size of the spinneret diameter is preferably adjusted such that the fineness of the polypropylene short fibers is 5.0 denier, preferably 1.5 denier or less, and the cross-sectional shape of the spinneret generally has a spherical shape or a shape close to a spherical shape, but preferably a fiber It may have a modified form so that the specific surface area of the may be increased, for example, there is a tetralobal form.

Oxidized chain  Undrawn Shrine Stretched Antiseptic  Attaching to the fiber surface

The unstretched yarn whose surface is oxidized and cut by the delay cooling is stretched at a draw ratio of 1.2 to 5.0, and then crimped in a crimper, and then the spinning oil is attached to the fiber surface. As a method of attaching the spinning emulsion, there is a method of impregnating or spraying the liquid resin containing the spinning emulsion. In the present invention, a hydrophilic or hydrophobic emulsion used in general polypropylene fiber production may be used as the spinning oil, and the amount of the spinning oil used is not particularly limited, but 0.3 to 0.5 parts by weight is preferable based on 100 parts by weight of the total fiber.

Drawing company Heat setting  And cutting to the desired length

The stretched yarn with the spinning oil attached is heat-set for about 8 to 12 minutes with hot air at a temperature of 60 to 100 ° C., and then cut to a length of about 3 to 100 mm to prepare polypropylene short fibers.

Another aspect of the present invention relates to a nonwoven fabric having a markedly improved strength and improved incidental cover, wherein the nonwoven fabric of the present invention is prepared by treating the polypropylene short fibers according to the present invention by a thermal bonding method.

Thermal bonding processing methods for producing a nonwoven fabric from polypropylene short fibers include a calendar bonding method and an air-through bonding method, and the nonwoven fabric according to the present invention can be produced by applying all of the above methods, but more commonly used calendar The bonding method will be described.

The calender bonding method is a method of manufacturing a nonwoven fabric by carding short fibers and then heat-sealing the fibers while passing webs stacked on a conveyor between two hot rolls set at 140 to 170 ° C. In the present invention, the thermal bonding non-woven fabric was manufactured through a pilot calender bonding facility, and the hot roll temperature of hot roll was the most favorable for the non-woven fabric production speed, the shape of the embossed pattern of the roll, the difference between the roll setting temperature and the surface temperature, and the like. This is a relative result, not an absolute result, as it may vary depending on the production, equipment conditions and fineness of the short fibers used as raw materials.

The nonwoven fabric according to the present invention has a significantly improved strength of thermal bond index of 2.0 or more, and has an additionally improved covering property when made of polypropylene short fibers having a cross-sectional shape of tetralobal (Tetralobal).

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the scope of the present invention is not limited to the Examples described later.

1. Description of Analysis Method

(1) Melt Flow Index (MFI): Measured according to ASTM D1238. For homopolypropylene and random copolymer series, load conditions of 230 ° C. and 2.16 kg were used.

(2) Isotactic Index (II): Measured according to ISO 9113. After boiling normal heptane to dissolve the atactic component, the remaining isotactic component is weighed and expressed as wt%. Is called isotactic index.

(3) Short fiber fineness: It measured based on ASTMD1577.

(4) Short Fiber Strength and Elongation: Fiber tensile properties were measured according to ASTM D3822.

(5) Optimal hot roll temperature: A nonwoven fabric was produced while changing the temperature of the hot roll to 140-170 degreeC, and the temperature of the hot roll which shows the highest TBI was selected as the optimal hot roll temperature.

(6) Basis weight: weight of nonwoven

(7) Nonwoven fabric tensile strength and elongation: longitudinal strength of the nonwoven fabric (hereinafter referred to as "MD strength") based on the cut-strip method (sample width 5cm, length 14cm) of JIS L 1096, transverse direction of the nonwoven fabric The strength (hereinafter referred to as "CD strength") and the transverse elongation of the nonwoven fabric (hereinafter referred to as "CD elongation") were measured.

(8) MIF-R: A value obtained by dividing the melt flow index of the polypropylene short fibers (hereinafter referred to as "MFI-f") by the melt flow index of the polypropylene resin (hereinafter referred to as "MFI-p").

(9) Thermal Bondability Index (TBI) of nonwoven fabric =

(CD strength × MD strength) ^1/2 × (base weight / 20)

(10) Battle Transition: Measured using NDH 2000 (Haze meter) and light source D65.

(11) Drying speed of nonwoven fabric: Measured according to KS K0815 6.28.1.A.

2. Polypropylene Short fibers  And manufacturing of nonwovens

Polypropylene resins having an isotactic index ranging from 95 to 99% were melted and extruded through a spinneret. The extruded unstretched yarn was delayed-cooled by supplying cooling air at 18 ° C. or additionally passing through a blocking area of the cooling air. The unstretched yarn, in which the oxidative chain was cut on the surface by delayed cooling, was adjusted to a draw ratio of 1.4 and stretched to a preheating temperature of 70 ° C. to crimp the crimp. Silicone spinning oil is used as the spinning oil, and the spinning oil is attached to the fiber surface by dipping or spraying the liquid resin containing the hydrophobic spinning oil emulsion to 0.45% by weight of the total short fiber weight. After heat-setting at 100 ° C. for 10 minutes, the fibers were cut to 40 mm in length to prepare polypropylene short fibers. The polypropylene short fibers obtained by the above method were carded with a carding machine at a speed of 80 m / min, a nonwoven web was produced, and passed through two hot rolls, where the basis weight (nonwoven fabric weight) was about 20 g / m 2. An in calender bonded nonwoven fabric was prepared.

Table 1 below shows the physical properties of the polypropylene resin, spinning conditions, the optimum hot roll temperature of the nonwoven fabric according to the Examples and Comparative Examples of the present invention. In Table 1, the spinneret denoted by "R" means 0.4 mm in diameter and spherical in shape, and "T" denoted by Lobe width of 0.15 mm and Lobe length of 0.42. It means that it is ㎜ and the cross-sectional shape (Tetralobal).

division Polypropylene Short Fiber Manufacturing Conditions Non-woven fabric manufacturing conditions Polypropylene resin Radiation conditions MFI-p
(g / 10 min) Melting temperature
(℃) Spinneret Spinning speed
(m / mim) Cooling air blocking area
(Cm) Cooling Air Supply Speed
(m / sec) Optimum hot roll temperature
(℃) Example 1 8 290 R 1600 5 2 160 Example 2 8 300 R 1600 5 2 158 Example 3 12 280 R 1600 5 2 162 Example 4 12 290 R 1600 5 2 159 Example 5 12 300 R 1600 5 2 157 Example 6 25 280 R 1600 5 2 161 Example 7 8 290 R 1600 0 2 162 Example 8 12 290 R 1600 5 2 157 Example 9 8 290 T 1600 5 2 156 Example 10 12 290 T 1600 5 2 155 Comparative Example 1 8 260 R 1600 5 2 164 Comparative Example 2 8 310 R 1600 5 2 - Comparative Example 3 12 260 R 1600 5 2 164 Comparative Example 4 12 310 R 1600 5 2 - Comparative Example 5 25 260 R 1600 5 2 164 Comparative Example 6 25 260 R 70 0 30 166 Comparative Example 7 25 280 R 70 0 30 164 Comparative Example 8 12 260 T 1600 0 2 164 Comparative Example 9 12 260 T 1600 5 2 163

3. Polypropylene Short fibers  And nonwoven fabric properties

The physical properties of the polypropylene short fibers and nonwoven fabrics prepared in Examples 1 to 10 and Comparative Examples 1 to 9 were measured, and the results are shown in Table 2 below.

As shown in Table 2, the MFI-R value was less than 2.5 and the TBI value was less than 2.0 when the melting temperature was less than 280 ° C. Did. In addition, even if the melting temperature is 280 ℃ from Comparative Example 7, it can be seen that the MFI-R value and the TBI value is still low when the spinning speed is 70 m / min and the cooling air feed rate is 30 m / sec. From this, it can be seen that the MFI-R value and the TBI value are complexly dependent on factors such as melting temperature, spinning speed and cooling air feed rate.

division Polypropylene Short Fiber Properties Nonwovens Properties Island
(Denier) MFI-f
(g / 10 min) MFI-R burglar
(g / denier) Elongation
(%) Basis weight
(g / m ² ) MD strength
(Kg / 5cm) CD strength
(Kg / 5cm) CD elongation
(%) TBI Battle
(%) Drying time
(min) Example 1 2.2 32 4.0 2.4 392 20 4.15 1.54 113 2.528 Example 2 2.2 38 4.8 2.3 395 21 4.20 1.52 108 2.406 Example 3 2.1 30 2.5 2.3 385 20 3.75 1.30 116 2.208 Example 4 2.2 38 3.2 2.2 382 20 4.10 1.42 128 2.413 89.8 105 Example 5 2.2 46 3.8 2.1 388 20 4.06 1.38 122 2.367 Example 6 2.1 62 2.5 1.9 345 20 3.30 1.25 106 2.031 Example 7 2.2 22 2.8 2.4 388 20 3.82 1.36 118 2.072 Example 8 1.5 52 4.3 2.0 368 20 4.35 1.75 118 2.759 Example 9 2.3 42 5.3 2.2 405 20 4.70 2.10 110 3.142 Example 10 2.2 55 4.6 2.1 401 21 4.60 1.92 115 2.830 82.6 75 Comparative Example 1 2.1 13 1.6 2.4 384 20 3.09 0.80 105 1.572 Comparative Example 2 No radiation Comparative Example 3 2.2 17 1.4 2.3 380 20 3.02 0.75 107 1.505 Comparative Example 4 No radiation Comparative Example 5 2.3 29 1.2 2.0 371 21 2.95 0.70 - 1.369 Comparative Example 6 2.1 29 1.2 1.8 370 20 2.81 0.69 94 1.392 Comparative Example 7 2.2 34 1.4 1.6 355 20 2.95 0.76 102 1.497 Comparative Example 8 2.2 21 1.8 2.3 382 20 3.04 0.76 106 1.520 Comparative Example 9 2.2 23 1.9 2.3 383 21 3.22 0.85 105 1.576

On the other hand, when the non-drawn yarn extruded from Example 1 and Example 7 is passed through the blocking area of the cooling air and delayed cooling before delayed cooling with the cooling air, the MFI-R value is about 1.0 or more and the TBI value is about 0.5. It can be seen.

In addition, when changing the cross-sectional shape of the spinneret from Example 1 and 9 or Example 4 and Example 10 from the shape of the sphere to the shape of the tetralobal (that is, the cross-sectional shape of the short polypropylene fiber in the shape of the sphere In case of changing into tetra-global form, MFI-R and TBI values are significantly increased, and concomitantly decreases the combat transients, which improves the covering properties.

1 to 2 are photographs showing the cross-section and side surfaces of the short polypropylene fiber according to the present invention. FIG. 1 is a spherical cross section, and FIG. 2 is a tetralobal form.

Claims (15)

A polypropylene short fiber in which the surface of the polypropylene resin is oxidatively cut by melting, extruding, delayed cooling, and having a melt flow index of 2.5 or more and an elongation of 300% or more relative to the melt flow index of the polypropylene resin. Short fibers. The polypropylene short fiber according to claim 1, wherein the polypropylene resin has a melt flow index of 5 to 30 g / 10 min and an isotactic index of 90% or more. delete The polypropylene short fiber according to claim 1, wherein the fineness of the short polypropylene fiber is 1.5 denier or less. The polypropylene short fiber according to claim 1, wherein the cross section of the short polypropylene fiber is tetralobal. A method for producing the polypropylene short fibers of any one of claims 1, 2, 4 or 5, (a) melting the polypropylene resin in a temperature range of at least 280 ° C and less than 310 ° C; (b) extruding the molten polypropylene resin through a spinneret at a rate of 1000 to 2500 m / min to provide an undrawn yarn; (c) oxidatively cutting the surface of the undrawn yarn by delay cooling the extruded undrawn yarn with cooling air supplied at a rate of 1 to 5 m / sec; (d) drawing the undrawn yarn whose surface is oxidatively cut; (e) attaching the spinning oil to the surface of the drawn yarn; And (f) cutting the drawn yarn to which the spinning oil is attached into short fibers of a predetermined length. 7. The method of claim 6, wherein the step (c) further comprises delayed cooling by passing the extruded undrawn yarn through a blocking area of the cooling air before delaying the cooling of the extruded undrawn yarn with the cooling air. . 8. The method of claim 7, wherein the blocking area of the cooling air is 10 cm or less. The method of claim 6, wherein the polypropylene resin of step (a) has a melt flow index of 5 to 30 g / 10 min and an isotactic index of 90% or more. 7. The method of claim 6, wherein the spinneret of step (b) has a cross section through which the molten polypropylene resin passes in a tetralobal form. The method of claim 6, wherein the draw ratio of the step (d) is a method for producing polypropylene short fibers, characterized in that 1.2 to 5.0. The method of claim 6, wherein the fineness of the polypropylene short fibers is 1.5 denier or less, and the fineness is controlled by the diameter or the stretching ratio of the spinneret. A nonwoven fabric prepared by treating the polypropylene short fibers of any one of claims 1, 2, 4 or 5 by a thermal bonding method. The nonwoven fabric according to claim 13, wherein the thermal bonding method is a calendar bonding method. The nonwoven fabric of claim 13 wherein the thermal bond index of the nonwoven fabric is 2.0 or greater.

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