JP2009007727A - Method for producing polypropylene fiber excellent in heat resistance and strength - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene fiber excellent in heat resistance, strength and water holding capacity. <P>SOLUTION: The method for producing the polypropylene fiber includes preliminarily drawing an undrawn polypropylene fiber produced by carrying out melt spinning of polypropylene having an isotactic pentad fraction (IPF) of ≥94% and then cooling and solidifying the spun yarn at a draw ratio of 3-10 at 120-150°C, and then subsequently drawing the fiber at a draw ratio of 1.2-3.0 under conditions of 1.5-15 deformation rate/min and 1.0-2.5 cN/dtex draw tension at 170-190°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a polypropylene fiber having excellent strength, heat resistance and water retention.

  Polypropylene fiber has excellent chemical resistance, light weight, and other characteristics, can be easily melted, has excellent recyclability, and does not generate harmful gases such as halogen gas even when incinerated, making it easy to incinerate. It is widely used in a wide variety of applications. However, since the polypropylene fiber cannot be said to have sufficiently high heat resistance among the synthetic fibers, improvement in heat resistance is required.

For example, a polyolefin sheet reinforced with polypropylene fiber is known as a sheet having excellent recyclability and strength. In the production of this fiber reinforced sheet, improvement in productivity and adhesion between the polypropylene fiber and the polyolefin sheet substrate are known. From the standpoint of improving the properties, it is necessary to melt the polyolefin as high as possible to bond the polyolefin base material and the polypropylene fiber. However, the heat resistance of polypropylene fibers is insufficient, and polyolefin cannot be melted at a high temperature during the production of a fiber reinforced sheet, so that the production rate cannot be sufficiently increased. Insufficient adhesion was caused, resulting in a decrease in productivity and insufficient strength of the resulting fiber-reinforced polyolefin sheet.
Moreover, since the fabric made from a polypropylene fiber is used as a filter and the filter is sometimes used in a high temperature environment, improvement in heat resistance is required.

As a conventional technique for improving the heat resistance of polypropylene fiber, the isotactic pentad fraction is 96% or more and less than 98.5%, and the melt flow rate (230 ° C., 2.16 kg load) is 0.1. A polypropylene fiber having a heat shrinkage rate of 10% or less at 170 ° C. for 10 minutes and a melting peak temperature of 178 ° C. or higher obtained by stretching a homopolypropylene resin of ˜30 g / 10 minutes after melt molding is known. (See Patent Document 1).
However, since the endothermic peak shape of this polypropylene fiber is a broad double shape or a single shape and the crystals are not uniform, it cannot be said that the heat resistance is still sufficiently high.

As another prior art, there is a polypropylene fiber having two DSC endothermic peaks at 155 to 170 ° C., which is obtained by melt spinning or melt spinning a polypropylene homopolymer having an isotactic index of 90 to 99%. It is known (see Patent Document 2).
However, in this polypropylene fiber, the endothermic peak on the low temperature side of the two DSC endothermic peaks is an indicator of the heat resistance of the polypropylene fiber, and the endothermic peak shape is broad and the crystals are not uniform. Sex is not enough.

  Polypropylene fiber is a general-purpose synthetic fiber used for various industrial material applications, and its hydrophobicity is a problem in many applications. For example, in applications such as paper and non-woven fabric, high hydrophilicity is often required for the main fibers, and uniform dispersibility in the matrix and for fibers used as reinforcing materials for various matrix materials. Although hydrophilicity is required in terms of adhesive strength to the matrix, polypropylene fiber is hydrophobic and inferior in hydrophilicity, so it is used as it is for applications such as paper, nonwoven fabric, and reinforcing materials that require hydrophilicity. Hard to do.

  Thus, techniques for improving the hydrophilicity and water retention of polypropylene fibers have been proposed. For example, it is known to produce water-absorbing polypropylene fibers by melt spinning polypropylene in which a particulate water-absorbing resin is uniformly dispersed in a resin using polyethylene wax (Patent Document 3). However, according to this method, the polypropylene added with particles is spun and stretched, and the influence on spinnability and stretchability cannot be avoided, and polypropylene fibers having sufficient strength cannot be obtained.

In addition, by irradiating polypropylene fiber with ionizing radiation, by embossing / stretching the polypropylene fiber, or by drawing after changing the take-up speed of the polypropylene to melt spinning and then drawing it on the surface. It is known to produce polypropylene fibers having irregularities (references 4 to 6). However, these methods are carried out for polypropylene fibers having a single fiber fineness of 50 to 100,000 denier, and the fine fiber polypropylene fiber having a single fiber fineness of 10 dtex or less causes fiber damage. It is extremely difficult to apply.
In particular, Patent Document 4 describes a technique for obtaining monofilaments of 50 to 50000 denier, particularly 3000 to 12000 denier by irradiating ionizing radiation before and after stretching, and this technique is used for a single fiber fineness of 10 dtex. In the following, particularly when it is applied to polypropylene fibers of 3 dtex or less, strength reduction, frequent occurrence of fluff, uneven shape, etc. are severe, and there are problems in any of process passability, quality, and quality.

Also, a polypropylene having a single yarn strength of 9 cN / dtex or more produced by drawing an undrawn polypropylene yarn in a hot air bath at 125 to 155 ° C., and having a streaky rough structure along the curved surface of the fiber surface Fibers are known (Patent Document 7). However, in this polypropylene fiber, since the spacing and height of the streaky rough surface structure existing on the fiber surface are both small, the fiber does not have sufficient water retention and has insufficient affinity with the matrix. is there.
Furthermore, a method is known in which a polypropylene undrawn yarn is drawn in one stage with pressurized saturated steam of 3.0 to 5.0 kg / cm ² (temperature 133 to 151 ° C.) (patent) Reference 8). However, the drawn polypropylene yarn (polypropylene fiber) obtained by this method has insufficient formation of irregularities on the fiber surface, the interval and height of the irregularities are small, the fibers do not have sufficient water retention, and the matrix The affinity with is not enough.

JP 2002-302825 A JP 2001-20132 A JP-A-4-41710 Japanese Examined Patent Publication No. 61-26510 JP-A-56-9268 Japanese Patent Publication No.61-301 JP 2003-293216 A Japanese Patent No. 3130288 “Macromolecules”, Vol. 6, 1973, p925 "Macromolecules", Vol. 8, 1975, p687

An object of the present invention is to provide a method for producing a polypropylene fiber having a uniform crystal structure, excellent heat resistance, and excellent strength.
Another object of the present invention is to provide a method for producing polypropylene fibers having high water retention and excellent strength.
Furthermore, this invention is providing the manufacturing method of the polypropylene fiber which is excellent in water retention, intensity | strength, and heat resistance.

The inventor has intensively studied in order to achieve the above-described object. As a result, a polypropylene unstretched fiber is produced by melt-spinning using a polypropylene having a specific isotactic pentad fraction (IPF) and then cooled and solidified, and the resulting polypropylene unstretched fiber is subjected to specific conditions. When pre-stretched and post-stretched below, it shows specific endothermic / melting characteristics in differential scanning calorimetry (DSC), has a uniform crystal structure, excellent heat resistance, and excellent strength. Polypropylene fibers could be obtained.
Furthermore, when the present inventor adopts the above-described specific method to produce polypropylene fiber having a single fiber fineness of 3 dtex or less, particularly 0.1 to 3 dtex, a large-diameter bulge and a small-diameter non-bulge are formed on the fiber surface. The polypropylene fibers have irregularities with predetermined average intervals and average heights alternately present along the fiber axis, and are excellent in water retention and strength, and the scanning differential calorific value in the polypropylene fibers By making the endothermic / melting characteristics by measurement (DSC) specific, the crystal structure of polypropylene fiber becomes uniform, and in addition to the characteristics of high water retention and high strength, it also has excellent heat resistance. The present invention was completed based on these findings.

That is, the present invention
(1) A polypropylene unstretched fiber produced by melt spinning and cooling and solidifying a polypropylene having an isotactic pentad fraction (IPF) of 94% or more is heated at a temperature of 120 to 150 ° C. at a stretch ratio of 3 to 10 times. After stretching, after a stretching ratio of 1.2 to 3.0 times under conditions of a temperature of 170 to 190 ° C., a deformation rate of 1.5 to 15 times / min and a stretching tension of 1.0 to 2.5 cN / dtex. It is a manufacturing method of the polypropylene fiber characterized by extending | stretching.

And this invention,
(2) The production method of the above (1), wherein the total draw ratio of pre-stretching and post-stretching is 3.9 to 20 times; and
(3) The product (A × B) of the melt spinning speed A (m / min) during the production of polypropylene unstretched fibers and the total stretch ratio B (times) of pre-stretching and post-stretching is 3000 to 17000 (m (Times / min) The production method of (1) or (2) above;
It is.

Furthermore, the present invention provides
(4) The endothermic peak shape by scanning differential calorimetry (DSC) is a single shape having a half width of 10 ° C. or less, the amount of change in melting enthalpy (ΔH) is 125 J / g or more, and the fiber strength is 7 cN / a production method according to any one of the above (1) to (3), which is for producing a polypropylene fiber of dtex or more;
(5) An average interval in which the single fiber fineness is 0.1 to 3 dtex, the fiber strength is 7 cN / dtex or more, and a large-diameter raised portion and a small-diameter non-raised portion alternately exist along the fiber axis on the surface. The production method according to any one of the above (1) to (3), which is for producing polypropylene fibers having irregularities of 6.5 to 20 μm and an average height of 0.35 to 1 μm; and
(6) Single fiber fineness is 0.1-3 dtex, fiber strength is 7 cN / dtex or more, endothermic peak shape by scanning differential calorimetry (DSC) is a single shape having a half width of 10 ° C. or less, and change in melting enthalpy (ΔH) is 125 J / g or more, and an average height of 6.5 to 20 μm and an average height in which a large-diameter raised portion and a small-diameter non-raised portion alternately exist along the fiber axis on the surface. The production method according to any one of (1) to (3), which is for producing polypropylene fibers having irregularities of 0.35 to 1 μm;
It is.

In the case of the production method of the present invention, a polypropylene fiber excellent in heat resistance and strength can be produced smoothly.
In particular, in the case of the production method of the present invention, a half-value width having an endothermic peak shape in scanning differential calorimetry (DSC) of 10 ° C. or less using polypropylene having an isotactic pentad fraction (IPF) of 94% or more. Polypropylene which has a unique characteristic that its melting enthalpy change (ΔH) is 125 J / g or more, has a high crystallinity, has a uniform crystal structure, and is extremely excellent in heat resistance. A fiber can be manufactured smoothly.
Due to its high heat resistance, the above-described polypropylene fiber obtained by the production method of the present invention maintains good fiber shape and fiber strength without being easily melted even when exposed to high temperatures or subjected to friction. can do.

Furthermore, according to the production method of the present invention, it is possible to smoothly produce a polypropylene fiber having a fiber strength of 7 cN / dtex or more, excellent strength, and excellent water retention.
In particular, in the case of the production method of the present invention, the average distance between the large-diameter raised portions and the small-diameter non-raised portions alternately located along the fiber axis is 6.5 to 20 μm and the average height is on the surface. Polypropylene fibers having a high water retention of 10% or more can be produced smoothly by having irregularities of 0.35 to 1 μm and having the specific irregularities described above.
Further, in the case of the production method of the present invention, the single fiber fineness is 0.1 to 3 dtex, the fiber strength is 7 cN / dtex or more, and the endothermic peak shape by scanning differential calorimetry (DSC) has a half width of 10 ° C. or less. An unprecedented polypropylene fiber having a single shape, a melting enthalpy change amount (ΔH) of 125 J / g or more, and having the above-described specific irregularities on the surface, which has the characteristics of high heat resistance, high water retention and high strength. It can be manufactured smoothly.
Polypropylene fibers obtained by the production method of the present invention are in the form of short fibers, long fibers, fiber bundles, etc., or fiber structures such as woven and knitted fabrics, nonwoven fabrics, nets, and papers, taking advantage of the above-described excellent characteristics. It can be effectively used for various applications in the form.

The present invention is described in detail below.
In the production method of the present invention, it is necessary to use a polypropylene having an isotactic pentad fraction (IPF) (hereinafter sometimes simply referred to as “IPF”) of 94% or more as polypropylene as a raw material for producing fibers. It is preferable to use a polypropylene having an IPF of 95 to 99%, and more preferably a polypropylene having an IPF of 96 to 99%.
When the IPF of polypropylene is less than 94%, it becomes difficult to form a uniform crystal structure in the polypropylene fiber, and it becomes impossible to produce a polypropylene fiber having sufficient strength and heat resistance. On the other hand, polypropylene having an IPF of over 99% is difficult to industrially mass-produce, and therefore has low practicality in terms of cost.

In the present invention, as the polypropylene, one type of propylene homopolymer may be used as long as the IPF satisfies the above-mentioned value, or a propylene copolymer composed of propylene and another copolymerizable monomer. You may use only. Alternatively, as long as the IPF of the entire mixture satisfies the above-mentioned value, as polypropylene, a mixture of two or more propylene homopolymers, one or two or more propylene homopolymers and one or two or more A mixture of these propylene copolymers or a mixture of two or more types of propylene copolymers may be used.
In the present invention, two or more types of propylene homopolymers and / or propylene copolymers may be used as long as the IPF in the entire propylene-based polymer constituting the finally obtained polypropylene fiber satisfies the above-described values. May be used to produce a composite spun fiber or mixed spun fiber that is compounded or mixed in the form of core-sheath type, sea-island type, side-by-side type, etc., and polypropylene and other polymers are core-sheath type, sea-island type Alternatively, a composite fiber combined in a form such as a side-by-side type may be manufactured.

IPF in polypropylene is an index representing the stereoregularity, and affects the crystallinity when polypropylene is made into a fiber. In general, the higher the IPF, the higher the stereoregularity. The IPF in polypropylene can be determined from ¹³ C-NMR signals, and the IPF value of polypropylene in this specification refers to the value determined by the method described in the following examples.

  It is used in the production method of the present invention because the melt spinnability, stretchability, etc. when producing the polypropylene fiber are improved, and the polypropylene fiber having the above-mentioned specific characteristics defined in the present invention can be obtained smoothly. Polypropylene preferably has a melt flow rate (MFR) of 5 to 70 g, more preferably 10 to 50 g when measured under conditions of a temperature of 230 ° C., a load of 2.16 kg, and a time of 10 minutes in accordance with JIS K 7210. Preferably, it is 15-40 g.

In the present invention, polypropylene having an IPF of 94% or more is melt-spun to produce a polypropylene unstretched fiber (unstretched yarn). After cooling and solidifying it, the cooled and solidified unstretched polypropylene fiber is subjected to a specific condition. A polypropylene fiber is produced by pre-drawing and post-drawing.
In producing polypropylene unstretched fibers, a method in which a polypropylene having an IPF of 94% or more is melt-spun at a spinning speed of 200 to 3500 m / min, particularly 300 to 2000 m / min, and then cooled and solidified is preferably employed.
The melt spinning of polypropylene and the cooling and solidification of the melt-spun polypropylene fiber can be performed by a usual method. Generally, after polypropylene is melt-kneaded at 200 to 300 ° C., it is melted from a spinneret at 220 to 280 ° C. A method of cooling and solidifying by blowing a cooling gas (air or the like) at 5 to 50 ° C. is used.
The single fiber fineness of the unstretched polypropylene fiber is not particularly limited, and can be determined according to the draw ratio in the drawing process, the use of the finally obtained polypropylene fiber, etc., generally 0.3 to 90 dtex, especially It is preferable that it is 1-60 dtex from points, such as easiness of extending | stretching and intensity | strength.

In carrying out the present invention, when melt spinning is performed at a low spinning speed (generally when the spinning speed is about 200 to 1000 m / min), polypropylene unstretched fibers obtained by cooling and solidifying after melt spinning ( The unstretched yarn) is stretched at a high magnification in the next stretching step (generally a total stretching ratio of 5 to 20 times), so that the target polypropylene fiber having high heat resistance and high strength, particularly scanning differential calorimetry (DSC) ) Is produced in a single shape having a half-value width of 10 ° C. or less, a change in melting enthalpy (ΔH) of 125 J / g or more, and a fiber strength of 7 cN / dtex or more. be able to.
On the other hand, when melt spinning is performed at a high spinning speed (generally when the spinning speed is about 1000 to 3500 m / min), polypropylene unstretched fibers (unstretched yarn) obtained by cooling and solidifying after melt spinning are stretched. Even when the draw ratio at that time is low (generally, the total draw ratio is 3.9 to 7 times), the orientation at the stage of cooling and solidifying the melt-spun fiber becomes high, and as a result, by the above-mentioned scanning differential calorimetry (DSC) A polypropylene fiber excellent in heat resistance and strength having properties and fiber strength of 7 cN / dtex or more can be produced.

The cooled and solidified polypropylene unstretched fiber (unstretched yarn) may be continuously stretched without being wound, or may be subjected to the next stretching treatment while being unwound after winding. Among them, it is preferable to perform the next stretching process while winding after being wound up, from the viewpoint of easy control and management of the stretching conditions.
In the present invention, the cooled and solidified polypropylene unstretched fiber (unstretched yarn) has a total stretch ratio (total stretch ratio of pre-stretch and post-stretch) of 3.9 to 20 times, and a temperature of 120 to 150 ° C. The film was pre-stretched at a stretching ratio of 3 to 10 times, and then at a temperature of 170 to 190 ° C. under conditions of a deformation rate of 1.5 to 15 times / minute and a stretching tension of 1.0 to 2.5 cN / dtex. Post-stretching is performed at a ratio of 2 to 3.0 times to produce polypropylene fibers.

Pre-stretching and post-stretching are preferably performed using a hot stove or a hot plate from the viewpoint that the stretching process is performed smoothly. Both pre-stretching and post-stretching may be performed using a hot air furnace, both pre-stretching and post-stretching may be performed using a hot plate, or pre-stretching is performed using a hot air furnace, and post-stretching. A hot plate may be performed, or pre-stretching may be performed using a hot plate, and post-stretching may be performed using a hot air furnace.
When pre-stretching and / or post-stretching is performed using a hot air furnace, the above temperature at the time of pre-stretching and the above temperature at the time of post-stretching in the present invention refer to the atmospheric temperature of the hot air furnace, and pre-stretching and / or post-stretching. When performing using a hot plate, the said temperature at the time of pre-stretching in the present invention and the said temperature at the time of post-stretching refer to the temperature of a hot plate.

Pre-stretching of the polypropylene unstretched fiber (unstretched yarn) formed by cooling and solidification may be performed in one stage or in multiple stages, and is generally preferably performed in one to three stages. .
In addition, the post-drawing of the drawn polypropylene fiber (drawn yarn) that has been pre-drawn may be performed in one stage or may be performed in multiple stages, and is generally preferably performed in one to five stages.
In performing the stretching treatment, a method may be employed in which a polypropylene stretched fiber (stretched yarn) obtained by pre-stretching is continuously wound without being wound, or after-stretching, or a polypropylene stretched fiber obtained by pre-stretching. A method may be employed in which the (drawn yarn) is cooled (generally at about room temperature) and wound up and then unwound again and then drawn. Among them, the latter method in which a polypropylene drawn fiber (drawn yarn) obtained by pre-drawing is once wound and then rewound and then drawn is preferable from the viewpoint that the target polypropylene fiber can be obtained more smoothly.

In the pre-drawing, polypropylene undrawn fiber (undrawn yarn) formed by cooling and solidification is introduced into a hot air oven having a temperature (atmospheric temperature) of 120 to 150 ° C, particularly 125 to 140 ° C, or a temperature of 120 to 150. It is preferably carried out in contact with a heat plate at 125 [deg.] C., particularly 125-140 [deg.] C., in a single stage or multiple stages at a stretching ratio of 3 to 10 times, particularly 3 to 5 times.
In addition, the post-stretching is a polypropylene stretched fiber (drawn yarn) obtained by pre-stretching under the above-described conditions, and the temperature (atmosphere temperature) is 170 to 190 ° C, more preferably 170 to 185 ° C, particularly 170 to 180 ° C. It is introduced into a hot stove or brought into contact with a hot plate having a temperature of 170 to 190 ° C., further 170 to 185 ° C., particularly 170 to 180 ° C., and a draw ratio of 1.2 to 3.0 times in one or more stages. In particular, it is preferably performed at 1.3 to 2.5 times.
When post-stretching is performed using a hot air furnace or a stretching plate, the atmospheric temperature of the hot air furnace or the stretching plate temperature is set to a temperature higher than the endothermic start temperature + 10 ° C. in the DSC curve of the polypropylene fiber immediately before the post-stretching treatment. It is preferable to perform post-stretching.
The total draw ratio of pre-stretching and post-stretching is preferably 3.9 to 20 times, more preferably 4.5 to 11 times, and still more preferably 4.7 to 10.5 times.
Further, the melt spinning speed for producing polypropylene unstretched fibers (unstretched yarn) was A (m / min), and the total stretch ratio after the above-described pre-stretching and post-stretching was defined as B (times). Sometimes, the value of A × B is in the range of 3000 to 17000 (m · times / min), especially 3500 to 15000 (m · times / min), and the polypropylene is melt-spun and the above-mentioned pre-stretching and When the post-drawing is performed, the target polypropylene fiber can be produced smoothly.

Here, the above-mentioned draw ratio in the pre-drawing is obtained by dividing the length of the fiber (yarn) immediately after being discharged from the pre-drawing step by the length of the undrawn fiber (undrawn yarn) introduced in the pre-drawing step. The drawing ratio in the post-drawing is the value obtained by dividing the length of the fiber (yarn) immediately after being discharged from the post-drawing step by the length of the fiber (yarn) introduced in the post-drawing step. Say.
The total draw ratio of the above-mentioned pre-drawing and post-drawing is the length of the undrawn fiber (undrawn yarn) introduced into the pre-drawing step by the length of the fiber (yarn) immediately after being discharged from the post-drawing step. The value divided by the above.

The post-stretching employs the above-described temperature (170 to 190 ° C.) and stretch ratio (1.2 to 3.0 times), a deformation rate of 1.5 to 15 times / min, and a stretching tension of 1.0 to 2. Adopting the condition of 5 cN / dtex. By adopting such post-drawing conditions, the target polypropylene fiber can be obtained.
The deformation rate at the time of post-drawing is preferably 1.6 to 12 times / min, and more preferably 1.7 to 10 times / min.
The stretching tension during post-stretching is preferably 1.1 to 2.5 cN / dtex, more preferably 1.3 to 2.5 cN / dtex.

Here, the above-described deformation rate in post-stretching is the time (minutes) required for post-stretching the draw ratio (times) in post-stretching [in the case of post-stretching in a hot air furnace, the fiber (yarn) is in the hot air path. The time that was present, or when the fiber (yarn) was in contact with the stretch plate when post-stretching with a stretch plate, the value divided by], and when post-stretching was performed in multiple stages, A value obtained by dividing the final stretching ratio (total stretching ratio) by the total stretching time required for post-stretching.
The drawing tension in the post-drawing is measured by using a tensiometer for the yarn tension immediately after the final drawing in the post-drawing.

  A polypropylene unstretched fiber obtained by melt-spinning a polypropylene having an isotactic pentad fraction (IPF) of 94% or more and then cooled and solidified is pre-stretched under the above-mentioned conditions and then further stretched under the above-mentioned conditions. By the method of the present invention for producing polypropylene fiber, the polypropylene fiber excellent in heat resistance and strength, in particular, the endothermic peak shape by DSC is a single shape having a half width of 10 ° C. or less, and the amount of change in melting enthalpy (ΔH) Is 125 J / g or more, and the fiber strength is 7 cN / dtex or more, and the polypropylene fiber excellent in heat resistance and strength can be produced smoothly.

  Furthermore, polypropylene unstretched fiber obtained by melt-spinning polypropylene having an isotactic pentad fraction (IPF) of 94% or more and then cooled and solidified is pre-stretched under the above-described conditions, and further after the above-described conditions. In the method of the present invention for producing a polypropylene fiber by drawing, by adjusting the single fiber fineness of the polypropylene undrawn fiber supplied to the pre-drawing step, the draw ratio in the pre-drawing and / or the post-drawing, etc. When a polypropylene fiber having a fiber fineness of 3 dtex or less, particularly 0.1 to 3 dtex is obtained, the fiber strength of the above 7 cN / dtex or more, the above-mentioned specific DSC characteristics [the endothermic peak shape by DSC is 10 ° C. Single shape with the following half width, melting enthalpy change (ΔH) is 125 J / g or more And an average distance of 6.5 to 20 μm and an average height of 0.35 to 1 μm, in which a large-diameter raised portion and a small-diameter non-raised portion alternately exist along the fiber axis. It is possible to produce a polypropylene fiber having a specific concavo-convex structure of “having a concavo-convex structure”. This polypropylene fiber is excellent in heat resistance and strength and has excellent water retention by having the above-described specific irregularities on the surface, and usually has a high water retention rate of 10% or more.

Here, “endothermic peak shape by DSC measurement” and “half-value width” in this specification will be described.
First, FIG. 1 is a diagram schematically showing an endothermic peak shape by DSC measurement in polypropylene fiber.
In FIG. 1, (a) corresponds to a representative example of an endothermic peak curve of polypropylene fiber by the production method of the present invention, and has a single endothermic peak (single peak), which is sharp and has a large peak. The amount of change in melting enthalpy (ΔH) is also larger than that of conventional polypropylene fibers.
On the other hand, in FIG. 1, (b) is an example of an endothermic peak curve of a conventional polypropylene fiber, which has two endothermic peaks (double peak), a large peak width (half-value width), and a change in melting enthalpy. The amount (ΔH) is small.
Further, in FIG. 1, (c) is another example of the endothermic peak curve of the conventional polypropylene fiber. Although the endothermic peak is one (single peak), the amount of change in melting enthalpy (ΔH) is small.
Next, FIG. 2 is a diagram showing how to find the half width at the endothermic peak of the polypropylene fiber by DSC measurement.
FIG. 2 shows a representative example of endothermic characteristics (melting characteristics) by DSC measurement of the polypropylene fiber obtained by the production method of the present invention, which is lowered from the apex X of the only endothermic peak (single peak) to the temperature axis. When the intersection of the perpendicular line and the endothermic peak baseline is Y, the point that bisects the line segment XY is M, and the intersection of the straight line passing through M and the endothermic curve is parallel to the temperature axis. When N1 and N2, the length (temperature width) of the line segment N1-N2 corresponds to the “half-value width (° C.)” in this specification.

When the endothermic peak curve of the polypropylene fiber is a double peak having two endothermic peaks as shown in FIG. 1B, or when it has three or more endothermic peaks, the peak of the highest endothermic peak is X. , Y is the intersection of the perpendicular from the vertex X to the temperature axis and the baseline of the endothermic peak, M is the point that bisects the line segment XY, and a straight line passing through M and parallel to the temperature axis When the intersection having the lowest temperature is N1 and the intersection having the highest temperature is N2, the length (temperature width) of the line segment N1-N2 is referred to as “half” in this specification. It corresponds to “value width (° C.)”. In this case, the half width (° C.) is generally wide.
In the endothermic peak curve, the base line of the endothermic peak (see FIG. 2) and the area of the portion surrounded by the endothermic peak curve above the baseline are represented by the “melting enthalpy change amount (Δ H) ".

If the crystal formation in the polypropylene fiber is insufficient, an endothermic peak or an exothermic peak may newly appear due to the rearrangement of the crystal at the time of DSC measurement, resulting in a complicated DSC curve. Furthermore, if the crystal formation in the polypropylene fiber is insufficient, the endothermic peak curve changes due to the occurrence or disappearance of the endothermic peak or the exothermic peak even in the same sample due to the difference in the heating rate during DSC measurement. Sometimes.
On the other hand, the endothermic peak curve of the polypropylene fiber obtained by the production method of the present invention has a single endothermic curve even if the temperature rise rate is different in the range of the temperature rise rate of 1-50 ° C./min during DSC measurement. It has a sharp, large single peak shape with only a peak, and has a high amount of change in melting enthalpy (ΔH). This confirms that the polypropylene fiber obtained by the production method of the present invention has uniform and high crystallinity, and as a result, has high heat resistance.

In addition, as described above, the polypropylene fiber obtained by the production method of the present invention has a change in melting enthalpy (ΔH) by DSC measurement of 125 J / g or more.
When the amount of change in melting enthalpy (ΔH) of the polypropylene fiber is less than 125 J / g, the heat resistance becomes insufficient, and when used in various applications, it is likely to be melted and melted by friction and high-temperature heating, causing problems. .
For example, a polypropylene fiber having a change in melting enthalpy (ΔH) of less than 125 J / g is easily melted and cut by friction when used as a rope, and when used as sportswear, the fiber surface melts during friction. Trouble easily occurs. In addition, when used as a raw material for paper, problems such as adhesion to the fibers of the Yankee dryer for drying are likely to occur, and when using a needle punched nonwoven fabric as an air filter, melting problems due to high temperature air are likely to occur. Become.
The higher the amount of change in melting enthalpy (ΔH) of the polypropylene fiber, the higher the heat resistance. However, polypropylene fibers exceeding 165 J / g are difficult to produce unless the production rate is significantly reduced, and the IPF is 100%. Therefore, it is industrially ineffective.
From this point, in the polypropylene fiber obtained by the production method of the present invention, the amount of change in melting enthalpy (ΔH) is preferably 125 to 165 J / g, more preferably 128 to 165 J / g, 130 More preferably, it is -165 J / g, and it is still more preferable that it is 133-165 J / g.

Moreover, the fiber strength (single fiber fineness strength) of the polypropylene fiber in this specification refers to the fiber strength measured by the method described in the following examples.
As described above, the fiber strength of the polypropylene fiber obtained by the production method of the present invention is 7 cN / dtex or more, preferably 7 to 13 cN / dtex, more preferably 8 to 13 cN / dtex, more preferably 9 to It is more preferably 13 cN / dtex, and further preferably 10 to 13 cN / dtex.
The polypropylene fiber obtained by the production method of the present invention can be effectively used for various applications by having the above-described fiber strength. If the fiber strength of the polypropylene fiber is less than 7 cN / dtex, it may be difficult to produce various products having excellent strength using the polypropylene fiber, or a large amount of polypropylene fiber may be used to obtain a predetermined strength. It becomes necessary, and the characteristic that the polypropylene fiber originally has is not able to be utilized. For example, when a rope is manufactured from polypropylene fiber having a fiber strength of less than 7 cN / dtex, it becomes difficult to obtain a strong rope, and in order to obtain a sufficiently strong rope, it is necessary to use a large amount of polypropylene fiber to make a rope with a large fineness. It is not obtained and lightness is impaired. Further, when the fiber strength of the polypropylene fiber is less than 7 cN / dtex, a sufficient reinforcing effect may not be exhibited when used for reinforcing various matrices such as cement.
On the other hand, a polypropylene fiber having a fiber strength exceeding 13 cN / dtex is difficult in practical use because it is necessary to adopt conditions with low mass productivity in the production.

Further, in this specification, “polypropylene fiber has irregularities in which a large-diameter raised portion and a small-diameter non-raised portion are alternately positioned along the fiber axis on the surface” in the schematic diagram of FIG. As shown, the polypropylene fiber does not have a uniform diameter along the length direction, and has a large diameter raised portion (convex portion) (A1, A2, A3, A4,... In FIG. 3) and , Non-protruding portions (concave portions) having a smaller diameter (B1, B2, B3, B4,... In FIG. 3) are alternately formed along the fiber axis (fiber length direction). This means that the fiber surface is uneven.
In the present specification, the “average interval” refers to an interval between two adjacent ridges (projections) among a large number of projections and depressions (bumps and non-bumps) formed along the fiber axis. It means the average value of (distance) (the length of A1-A2, A2-A3, A3-A4,... In FIG. 1).
The “average height” is an imaginary straight line that connects the minimum diameter portions of two adjacent non-protruding portions (concave portions) among a large number of irregularities (protruding portions and non-protruding portions) formed along the fiber axis. (A straight line connecting B1 and B2 in FIG. 3, a straight line connecting B2 and B3, a straight line connecting B3 and B4,...) Between the two adjacent non-protruding parts (concave portions) ( It means the average value of the lengths of the vertical lines (h1, h2, h3, h4,... In FIG. 3) from the apex of the convex portion.
The average interval and the average height of the irregularities formed along the fiber axis of the polypropylene fiber can be determined from a photograph of the polypropylene fiber taken using a scanning electron microscope or the like, and the average of the irregularities in the present specification The interval and the average height are values obtained by the method described in the following examples.

As described above, by producing polypropylene fibers according to the method of the present invention such that the final single fiber fineness of the polypropylene fibers is 0.1 to 3 dtex, the average spacing is 6.5 on the surface. It is possible to smoothly obtain a polypropylene fiber having the above-described irregularities along the fiber axis with an average height of ˜20 μm and an average height of 0.35 to 1 μm. The polypropylene fiber having the above-described specific irregularities along the fiber axis obtained by the production method of the present invention has high water retention due to the presence of the irregularities (generally a water retention rate of 10% or more). For example, cement When it is blended with other matrix materials, it has a high affinity with the matrix and can be effectively used for other applications requiring water retention.
If the average interval between the irregularities is less than 6.5 μm and / or the average height is less than 0.35 μm, the irregularities on the fiber surface become too fine, and the water retention decreases. On the other hand, polypropylene fibers with an average irregularity interval of more than 20 μm and / or an average height of more than 1 μm cannot be produced unless the production speed of the polypropylene fiber is significantly reduced, and polypropylene with an IPF close to 100% is used. Because it is necessary to do so, it is not practical.
Among the polypropylene fibers obtained by the production method of the present invention, in the polypropylene fibers having the unevenness on the surface, the average interval of the unevenness formed along the fiber axis direction is 6.6 to 20 μm, particularly 6.8 to 20 μm. The average height is preferably 0.40 to 1 μm, particularly preferably 0.45 to 1 μm.
Moreover, in the said polypropylene fiber which has an unevenness | corrugation along the surface obtained by the manufacturing method of this invention, it is preferable that the water retention is 10.5% or more, It is more preferable that it is 11-50%, 12- More preferably, it is 50%. Polypropylene fibers having a water retention rate exceeding 50% must have very large irregularities on the fiber surface, and in reality, it is difficult to produce them with high productivity.
In addition, the water retention rate of the polypropylene fiber in this specification says the water retention rate measured by the method described in an Example below.

In the production method of the present invention, the fineness (single fiber fineness) of the polypropylene fiber finally obtained by pre-stretching and post-stretching is not particularly limited, and can be determined according to the use of the polypropylene fiber. From the viewpoints of ease of production (especially ease of stretching), applicability to various uses, durability, and the like when producing polypropylene fibers, the fineness (single fiber fineness) of polypropylene fibers is generally 0.00. It is preferably 01 to 500 dtex, more preferably 0.05 to 50 dtex, and still more preferably 0.1 to 5 dtex.
In particular, fiber strength of 7 cN / dtex or more, specific DSC characteristics as described above [endothermic peak shape by DSC is a single shape having a half width of 10 ° C. or less, and the amount of change in melting enthalpy (ΔH) is 125 J / g or more. In the case of producing a polypropylene fiber having the above-mentioned specific irregularities on the surface together with the characteristic that there is, the single fiber fineness of the finally obtained polypropylene fiber is 0.1 to 3 dtex, and further 0.2 to 2. Polypropylene fibers are preferably produced so as to be 5 dtex, particularly 0.3 to 2.4 dtex.
If the fineness (single fiber fineness) of the polypropylene fiber is too small, it may melt and break due to wear when used in a structure or the like, leading to deterioration of the structure. On the other hand, if it is too large, a polypropylene fiber is obtained. For this reason, the stretched physical properties may be lowered, and high strength and highly crystallized polypropylene fibers may not be obtained.

  In the production method of the present invention, the shape (transverse cross-sectional shape) of the polypropylene fiber finally obtained is not particularly limited, and may be a solid circular cross-sectional shape or other irregular cross-sectional shape. Either may be sufficient. Specific examples of the case where the cross section of the fiber has an irregular cross section include a flat shape, a cross shape, a Y shape, a T shape, a V shape, a star shape, a multi-leaf shape, an array shape, and a hollow shape. . When polypropylene fiber is used as a reinforcing material, if it has an irregular cross-sectional shape with a large surface area, especially a multi-leaf shape, the adhesive strength with the matrix is increased, and a fiber-reinforced molded body with high strength can be obtained.

  In the polypropylene used as a raw material within a range not hindering the object of the present invention, for example, one kind of heat stabilizer, ultraviolet absorber, antioxidant, colorant, lubricant, mold release agent, filler, antistatic agent, etc. Or 2 or more types can be contained. Polypropylene fiber generally has a specific gravity smaller than water and floats in water as it is, so when dispersing polypropylene fiber in water, calcium carbonate, barium sulfate, titanium oxide, zinc oxide, alumina, Specific gravity can be appropriately adjusted by including silica, potassium methacrylate, and the like in the fiber.

  The polypropylene fiber obtained by the production method of the present invention may be used as it is without performing surface treatment, or for the purpose of improving affinity with various substances, antistatic, stabilizing the treatment agent, etc. You may surface-treat with arbitrary surface treating agents. Specific examples of the surface treatment agent that can be used for the polypropylene fiber obtained by the production method of the present invention include, but are not limited to, polyoxyethylene softanol, fatty acid potassium soap, alkyl phosphate potassium salt, dialkylthiodipropionate. , Di-2-ethylhexylsulfosuccinate sodium salt, polyethylene glycol fatty acid ester, polyoxyethylene decyl ether phosphate potassium salt, polyoxyethylene castor oil ether, alkansulfonate sodium salt, isooctyl palmitate, isooctyl stearate, Isocetyl phosphate potassium salt, coconut fatty acid amide, oleyl alcohol, polyoxyethylene alkyl ether, dioctyl flusuccinate sodium salt, polyoxyethyl Emissions decyl ether phosphate amine salts, and the like polyethylene glycol coconut fatty acid ester.

The polypropylene fiber obtained by the production method of the present invention can be used in the form of monofilament, multifilament, sliver, short fiber, twisted yarn (spun yarn), false twisted yarn, entangled yarn, and other processed yarn.
Moreover, the polypropylene fiber obtained by the production method of the present invention can be used as a fiber structure such as a woven or knitted fabric, a nonwoven fabric, a net-like material, or paper. Further, the polypropylene fiber obtained by the present invention or a fiber structure using the fiber is made of a fiber-reinforced plastic molded body, a fiber-reinforced rubber molded body, a fiber-reinforced hydraulic material molded body (concrete, mortar, slate, roof tile, etc.), etc. Can be used as a fiber reinforcing material. Further, since the polypropylene fiber obtained in the present invention is excellent in heat resistance, it can be used for cords and ropes. Using the cords and ropes, sling ropes, fishing nets, and curing nets that are excellent in wear resistance and light weight. Golf ball nets can be manufactured.

  When the polypropylene fibers obtained by the production method of the present invention are used for the production of woven or knitted fabrics, various woven or knitted fabrics can be used by using a jet loom, a sulzer loom, a lapia loom, a circular knitting machine, a warp knitting machine, a flat knitting machine, a tricot machine, etc. Can be manufactured. The woven or knitted fabric may be produced only from the polypropylene fiber obtained in the present invention, and if necessary, natural fibers such as cotton, silk, wool, hemp, etc., polyester fibers, nylon fibers, acrylic fibers, polyvinyl alcohol fibers It may be produced in combination with one or more of other fibers such as synthetic fibers such as viscose and semi-synthetic fibers such as rayon. For example, when a knitted fabric (knit) is produced by combining the polypropylene fiber excellent in heat resistance obtained in the present invention and cotton, it will not melt even if it rubs against the floor of a gymnasium, etc., and it is lightweight and excellent in sweat absorption. A knitted fabric (knit) suitable for sports clothing can be obtained.

In the case of producing a nonwoven fabric using the polypropylene fiber obtained in the present invention, for example, crimping can be applied to the polypropylene fiber of the present invention, and a needle punch can be applied after carding to form a felted nonwoven fabric. A bulky dry nonwoven fabric can be obtained by blending polyolefin binder fibers during carding and heat-treating them. In addition, the nonwoven fabric (paper) can be obtained by cutting the polypropylene fiber of the present invention into a short fiber, mixing a polyolefin-based binder fiber to prepare a water-dispersed slurry, and papermaking and drying treatment. . In producing a nonwoven fabric using the polypropylene fiber of the present invention, the polypropylene fiber has high heat resistance, and since the treatment process such as the adhesion treatment process and the drying treatment process can be performed at a high temperature, the nonwoven fabric is high. Can be manufactured at production speed.
Since the nonwoven fabric and paper obtained by using the polypropylene fiber obtained by the present invention are excellent in heat resistance and chemical resistance, they can be effectively used as industrial filters.

A multiaxial mesh or a multiaxial prepreg can also be produced using the polypropylene fiber obtained by the present invention. For example, by producing biaxial mesh using polypropylene fiber obtained by the present invention, laminating with polyolefin sheet and thermocompression bonding, high production of polypropylene fiber reinforced polyolefin sheet with dramatically improved tensile strength and tear strength And can be manufactured smoothly. That is, since the biaxial mesh produced using the polypropylene fiber obtained by the present invention is superior in heat resistance compared to the conventional biaxial mesh made of polypropylene fiber, the polyolefin sheet is melted at a higher temperature than before. Along with this, the production rate can be increased sufficiently, and the polypropylene fiber biaxial mesh and the polyolefin sheet are sufficiently bonded to produce a high strength polypropylene fiber reinforced polyolefin sheet. It can be manufactured with good performance.
When the polypropylene fiber obtained according to the present invention is used for reinforcing a polymer sheet such as polyolefin, the strength utilization factor of the polypropylene fiber is obtained when the polypropylene fiber is used in a unidirectional prepreg shape rather than being used as a woven or knitted fabric. Can be high.

Moreover, the fiber reinforced molded object which is excellent in intensity | strength can be obtained by making the polypropylene fiber obtained by this invention into a short fiber, mix | blending with an olefin type polymer, melt-kneading, and shaping | molding. The polypropylene fiber obtained by the present invention is excellent in heat resistance, and can maintain its fiber shape without melting even when exposed to a considerably high temperature. The coalescence can be melt-kneaded, whereby an olefin polymer molded body reinforced with polypropylene fibers can be obtained at a high production rate.
And since the polypropylene fiber reinforced olefin polymer molding obtained thereby is excellent in light weight and recyclability, it can be widely used for automobile parts, electrical / electronic parts, sanitary goods, and other uses.

  In reinforcing the resin using the polypropylene fiber obtained by the present invention or a fiber structure comprising the polypropylene fiber, the reaction heat during curing of the thermosetting resin or the temperature of the molding process of the thermoplastic resin As long as the properties are not impaired, it can be used for both thermosetting resins and thermoplastic resins. Examples of the resin that can be reinforced by using the polypropylene fiber obtained by the present invention or a fiber structure comprising the same include thermosetting resins such as epoxy resins, unsaturated polyester resins, and vinyl ester resins, polypropylene, polyethylene, and the like. Examples thereof include olefin resins, polylactic acid, modified polyester, and modified polyamide.

Further, when the polypropylene fiber obtained by the production method of the present invention is used for reinforcement of concrete, mortar, etc., the proportion of polypropylene fiber used is 0.01 to the total volume of concrete or mortar raw materials other than polypropylene fiber. The amount is preferably about 10 to 10% by volume, particularly about 0.03 to 5% by volume.
Mixing of polypropylene fibers into raw materials for concrete and mortar can be performed using various mixers such as a bread mixer, an Eirich mixer, a tilting mixer, a forced biaxial mixer, an omni mixer, a Hobart mixer, and a hand mixer. . Examples of raw materials in this case include hydraulic materials, aggregates, fillers, polypropylene fibers, other reinforcing fibers, and other admixtures. As the hydraulic material, one or more of ordinary Portland cement, early-strength cement, intermediate cement, blast furnace cement, silica fume, fly ash, and the like can be used. Examples of the aggregate include gravel, crushed sand, river sand, sea sand, mountain sand, powdered silica sand, various lightweight aggregates, and examples of the filler include calcium carbonate and kaolin. One or two of these may be used. The above can be used. Examples of the other admixture described above include water reducing agents, thickeners, foaming agents, swelling agents, shrinkage reducing agents, and the like.
The mixing method, the order of addition, the stirring time, and the like of the raw materials for concrete or mortar are not particularly limited and can be appropriately adjusted. In addition, as a molding method for forming concrete or mortar, conventionally used molding methods such as casting, vibration molding, centrifugal molding, suction molding, extrusion molding, and press molding can be employed. Also, the curing method is not particularly limited, and for example, air curing, underwater curing, poultice curing, autoclave curing, a method of combining two or more thereof, and the like can be employed.

  Moreover, when manufacturing slate using the polypropylene fiber obtained by this invention, slate can be manufactured by systems, such as a circular net | network, a long net | network, and a flow-on. Examples of slate materials include hydraulic materials, reinforcing fibers (polypropylene fibers of the present invention and other reinforcing fibers as required), pulp, flocculants, and other additives (such as inorganic substances). it can. When using the polypropylene fiber obtained by this invention for reinforcement of a slate, the usage-amount of a polypropylene fiber is 0.1-7 mass% with respect to the total mass of the raw materials for slate other than a polypropylene fiber, especially 1-5 mass. It is preferable that the amount is about%.

As the hydraulic material used for the production of slate, ordinary portland cement is preferably used, but is not limited thereto. In addition, a wide range of pulp can be used, and specific examples include conifers, hardwoods, manila hemp, mitsumata, kouzo, ganpi, sarago, mulberry, straw, bamboo, reed, sabai, lalan grass, esparto, bagasse, sisal , Kenaf, linter, banana, waste paper, etc., and it may contain one or more of the above-mentioned pulps that have been exposed or unexposed, and the degree of beating and the amount added should be controlled appropriately. To use. Examples of the coniferous tree include conifers such as cedar family, pine family, cypress family, and cedar family, and examples of the broad-leaved tree include elmaceae, beech family, myrtaceae family, wig family family, citrus family family, citrus family, birch family. The family includes the family, maple family, walnut family, linaceae family, araceae family, categoraceae family, asteraceae family, oleander family, oleander family, machinaceae family, blue family family. Examples of the other additives include inorganic substances such as blast furnace slag, fly ash, calcium carbonate, silica fume, sepiolite, bentonite, attapulgite, mica, and wollastonite. These additives have the effect of improving the physical properties of the cured product, for example, improvement of freeze-thaw resistance, suppression of invasion of corrosive substances (various acids such as chlorine and sulfuric acid), improvement of adhesion between the reinforcing fiber and the matrix, It has the effect of improving the papermaking efficiency by appropriately adjusting the viscosity of the suspension, the effect of controlling the drying shrinkage of the papermaking body, the effect of improving the strength of the cured body, etc. It is used within a range that does not impair the process passability, moldability, and mechanical properties of the slate.
The order of addition and stirring time when preparing the raw slurry for producing the slate can be appropriately adjusted. In addition, the curing method for producing the slate is not particularly limited, and as in the case of concrete and mortar molded bodies, for example, air curing, underwater curing, poultry curing, autoclave curing, a method of combining two or more of them Etc. can be adopted.

  In addition, among the polypropylene fibers obtained by the production method of the present invention, the polypropylene fibers having the above-described specific irregularities on the surface are superior in water retention compared to conventional polypropylene fibers, and in some cases are further excellent in heat resistance. ing. Therefore, for example, when used in the production of concrete, mortar, slate, etc., it has high affinity with the water-curing material (matrix) and adheres to the matrix with high adhesive strength, and is cured at a high temperature such as autoclave curing. Polypropylene fiber does not melt, and good fiber morphology and fiber properties can be maintained. Therefore, while shortening the curing time, it can be produced with good productivity of compacts such as concrete, mortar, and slate with excellent strength. be able to.

  Since the polypropylene fiber obtained by the production method of the present invention is superior in heat resistance as compared with the conventional polypropylene fiber, the use temperature range can be increased in any application. For example, concrete, mortar When used for the production of slate, etc., the polypropylene fiber does not melt even if it is cured at a high temperature such as autoclave curing, and good fiber morphology and fiber properties can be maintained, so the curing time can be shortened. As a result, the productivity of compacts such as concrete, mortar, and slate can be improved.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. In the following examples and the like, the isotactic pentad fraction (IPF) of polypropylene, the stretching tension at the time of stretching, the DSC of the polypropylene fiber, the single fiber fineness, the fiber strength, the average spacing and the average height of the irregularities on the fiber surface, Friction-proof property and water retention were measured as follows.

(1) Isotactic pentad fraction (IPF) of polypropylene:
Using a superconducting nuclear magnetic resonance apparatus (“Lambda500” manufactured by JEOL Ltd.), the IPF of polypropylene was determined according to “ ¹³ C-NMR spectrum method” described in Non-Patent Document 1. Specifically, the content ratio (fraction) of propylene units (isotactic pentad units) in which five propylene monomer units are continuously isotactically bonded in a ¹³ C-NMR spectrum in polypropylene (%) ) To obtain IPF. At that time, the peak assignment in the ¹³ C-NMR spectrum was determined according to the method described in Non-Patent Document 2.

(2) Stretch tension during stretching:
Using a load tension measuring instrument ("DTMX-5B" manufactured by Nidec Simpo Co., Ltd.), measure the tension of the yarn immediately after coming out of the drawing furnace (hot air furnace) or just after leaving the drawing plate. It was set as the stretching tension (cN / dtex).

(3) DSC measurement of polypropylene fiber:
Polypropylene fibers were allowed to stand for 5 days in an atmosphere at a temperature of 20 ° C. and a relative humidity of 65%, and then the humidity was adjusted. Then, the polypropylene fibers were cut to a length of 1 mm, and 5 mg was weighed to obtain an aluminum pan (capacity 100 μL) (made by METTTLER TOLEDO No. 51119872), sealed using an aluminum pan cover (Meteller Toledo "No. 51119871"), and in a nitrogen atmosphere using a scanning differential calorimeter (TA Instruments "DSC2010"). From the 1 st run DSC curve measured at a heating rate of 10 ° C./min, the half-value width (° C.) of the endothermic peak and the amount of change in melting enthalpy (ΔH) (J / g) are shown in FIG. 1 and FIG. In particular, it was determined by the method described above with reference to FIG.

(4) Fineness of polypropylene fiber (single fiber fineness):
The polypropylene fiber was left to stand for 5 days in an atmosphere at a temperature of 20 ° C. and a relative humidity of 65%, and then the humidity was adjusted. Then, a fixed length (900 mm) of the conditioned polypropylene fiber (monofilament) was taken and its mass was measured. The fineness was calculated. About the same humidity control polypropylene fiber, the same measurement operation as the above was performed 10 times, and the average value was taken as the fineness (single fiber fineness) of the polypropylene fiber. In addition, when the fineness was not able to be measured by mass measurement of a fixed length because the fiber was thin, the fineness was measured using the fineness measuring device (“VIBROMAT M” manufactured by Texttechno) for the same humidity control fiber.

(5) Fiber strength of polypropylene fiber:
The polypropylene fiber is left to stand for 5 days in an atmosphere of a temperature of 20 ° C. and a relative humidity of 65%, and then the humidity is adjusted. Then, the polypropylene fiber (single fiber) is cut to a length of 60 mm to obtain a sample. A single fiber is gripped at both ends (gripping from both ends to 10 mm), and using a fiber strength measuring device (“FAFEGRAPH M” manufactured by Texttechno) under an environment of a temperature of 20 ° C. and a relative humidity of 65%, a tensile speed of 60 mm The tensile strength at the time of cutting was measured, and the fiber strength (cN / dtex) was determined by dividing the value by the fineness of the polypropylene single fiber. In addition, the same operation was performed 10 times about the same polypropylene fiber, fiber strength was calculated | required, the average value was taken, and it was set as the fiber strength of polypropylene fiber (polypropylene single fiber).

(6) Average spacing and average height of the irregularities on the fiber surface of the polypropylene fiber:
Using a scanning electron microscope ("S-510" manufactured by HITACHI), polypropylene fibers (single fibers) were photographed at a magnification of 1000 times from the direction perpendicular to the fiber axis. According to the method described above based on No. 3, the average spacing and average height of the irregularities on the fiber surface were determined. In calculating the average interval and the average height, for ten polypropylene fibers (single fibers), five locations (interval of 10 cm between each measurement location) were selected for each fiber, and the uneven spacing at each location and The height was measured (total of 50 locations), and the average value thereof was taken as the average interval (μm) and the average height (μm).

(7) Friction resistance:
(I) Polypropylene fibers obtained in the following Examples or Comparative Examples are bundled into a 1000 dtex multifilament yarn, and using the multifilament yarn, the base fabric density is 30 warps / 25.4 mm and 30 wefts / A 25.4 mm plain weave fabric was prepared.
(Ii) A specimen (width × length = 3.5 cm × 8.5 cm) was cut out from the plain weave fabric obtained in (i) above, and the specimen was 1134 g on a roller (material: Sakuragi) rotating at 1800 rpm. The test piece was pressed with a load of (2.5 pounds), and the length of time from the start of the test to the start of melting of the test piece was measured. In the measurement, the moment when the frictional sound became large was set as the melting start point of the test piece. The same test was performed three times on the same sample (plain woven fabric), and the average value was taken as an index of frictional fusion resistance. It shows that it is excellent in heat resistance, so that the time until a test piece starts melting by friction is long.

(8) Water retention rate of polypropylene fiber:
After drying 1 g of polypropylene fibers at 105 ° C. for 5 hours, the mass (M1) is measured. The dried polypropylene fiber was immersed in 30 ml of ion-exchanged water and allowed to stand at 20 ° C. for 10 minutes, then taken out and left in an exposed state (without wrapping with other materials), a tabletop centrifuge (“H-made by KOKUSAN”) 27F "), and spin-dehydrated at a temperature of 20 ° C for 5 minutes at a rotational speed of 3000 rpm, the mass (M2) thereof was measured, and the water retention rate (%) was determined from the following formula (1).

Water retention of polypropylene fiber (%) = {(M2-M1) / M1} × 100 (1)

Example 1
(1) Polypropylene [“Y2000GV” manufactured by Prime Polymer Co., Ltd., IPF = 97%, MFR = 18 g / 10 min (230 ° C., load 2.16 kg)] is put into an extruder of a melt spinning apparatus and melt kneaded at 240 ° C. Then, from a spinneret attached to the spinning head at a temperature of 245 ° C. [24 holes (circular holes), hole diameter 0.2 mm], 22.3 g / min is discharged and polypropylene is unstretched at a take-up speed of 800 m / min. A yarn was produced, wound on a bobbin, and stored at room temperature (total fineness of polypropylene undrawn yarn = 288 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 128 ° C., and pre-drawn 4.6 times in two stages to obtain a polypropylene pre-drawn yarn. It was manufactured, wound on a bobbin and stored at room temperature (total fineness of polypropylene predrawn yarn = 63 dtex / 24 filament, endothermic onset temperature = 153.5 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 172 ° C., and the deformation rate was 1.7 times / minute and the draw tension was 1.18 cN / dtex. Under the conditions, a polypropylene drawn yarn (total fineness = 48 dtex / 24 filament) having a total draw ratio of 6.0 times was produced by post-drawing by 1.3 times in three stages.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 1 below.
Moreover, when the polypropylene drawn yarn (polypropylene fiber) obtained in the above (3) was photographed using a scanning electron microscope (“S-510” manufactured by HITACHI) (magnification 1000 times), as shown in FIG. Met.

Example 2
(1) A polypropylene undrawn yarn was produced in the same manner as in (1) of Example 1 except that the undrawn yarn take-up speed was changed to 3000 m / min in (1) of Example 1, and a bobbin was produced. And wound at room temperature (total fineness of polypropylene undrawn yarn = 214 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in (1) above is unwound from a bobbin, introduced into a hot air oven at a temperature of 128 ° C., pre-drawn 3.1 times in two steps, and a polypropylene pre-drawn yarn Was wound around a bobbin and stored at room temperature (total fineness of polypropylene predrawn yarn = 69 dtex / 24 filament, endothermic onset temperature = 155.3 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 172 ° C., and the deformation rate was 1.8 times / min and the draw tension was 1.34 cN / dtex. Under the conditions, a polypropylene drawn yarn (total fineness = 46 dtex / 24 filament) having a total draw ratio of 4.7 times was produced by post-drawing by 1.5 times in three stages.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 1 below.

Example 3
(1) The same polypropylene used in (1) of Example 1 was put into an extruder of a melt spinning apparatus, melted and kneaded at 240 ° C., and a spinneret with a temperature of 245 ° C. attached to the spinning head [number of holes 48 Each piece (cross-shaped hole) was discharged at a rate of 20.2 g / min from a hole diameter of 0.2 mm], and undrawn polypropylene yarn was produced at a take-up speed of 800 m / min, wound on a bobbin and stored at room temperature (polypropylene). Total fineness of undrawn yarn = 436 dtex / 48 filament).
(2) The polypropylene undrawn yarn obtained in (1) above is unwound from a bobbin, introduced into a hot air oven at a temperature of 138 ° C., pre-drawn 3.9 times in two stages, and a polypropylene pre-drawn yarn Was wound around a bobbin and stored at room temperature (total fineness of polypropylene pre-drawn yarn = 112 dtex / 48 filament, endothermic temperature = 155.2 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 172 ° C., and the deformation rate was 2.1 times / minute and the draw tension was 1.12 cN / dtex. Under the conditions, the film was post-stretched 1.3 times in one stage to produce a polypropylene stretched yarn (total fineness = 86 dtex / 48 filament) having a total draw ratio of 5.1 times.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 1 below.

Example 4
(1) Using the same polypropylene as used in (1) of Example 1, the same conditions as in (1) of Example 1 were adopted to produce a polypropylene unstretched yarn and wound around a bobbin.
(2) The polypropylene unstretched yarn obtained in (1) above is unwound from the bobbin, pre-stretched using the same conditions as in (2) of Example 1 to produce a polypropylene pre-stretched yarn, I wound it on a bobbin.
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 180 ° C., and the deformation rate was 1.7 times / min and the drawing tension was 1.06 cN / dtex. Under the conditions, a polypropylene drawn yarn (total fineness = 50 dtex / 24 filament) having a total draw ratio of 6.0 times was produced by post-drawing by 1.3 times in three stages.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 1 below.

Example 5
(1) The same melt spinning conditions as (1) of Example 1 using polypropylene [“ZS1337A” manufactured by Prime Polymer Co., Ltd., IPF = 96%, MFR = 20 g / 10 min (230 ° C., load 2.16 kg)] Was used to produce a polypropylene undrawn yarn and wound around a bobbin (total fineness of polypropylene undrawn yarn = 288 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 135 ° C., pre-drawn 4.8 times in two stages, and a polypropylene pre-drawn yarn Was wound around a bobbin and stored at room temperature (total fineness of polypropylene predrawn yarn = 60 dtex / 24 filament, endothermic onset temperature = 152.0 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above is unwound from a bobbin and introduced into a hot air oven at a temperature of 172 ° C., and the deformation rate is 1.6 times / minute and the drawing tension is 1.33 cN / dtex. Under the conditions, the film was post-stretched 1.8 times in three stages to produce a polypropylene stretched yarn (total fineness = 50 dtex / 24 filament) having a total draw ratio of 8.6 times.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 1 below.

Example 6
(1) Using polypropylene [IPF = 98%, MFR = 16 g / 10 min (230 ° C., load 2.16 kg)], adopting the same melt spinning conditions as in (1) of Example 1 and unstretched polypropylene A yarn was produced and wound on a bobbin (total fineness of undrawn yarn = 293 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 128 ° C., and pre-drawn 4.6 times in two stages to obtain a polypropylene pre-drawn yarn. It was manufactured and wound on a bobbin and stored at room temperature (total fineness of polypropylene predrawn yarn = 64 dtex / 24 filament, endothermic onset temperature = 156.4 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 178 ° C., and the deformation rate was 2.8 times / min and the drawing tension was 1.54 cN / dtex. Under the conditions, it was post-drawn 2.2 times in 4 stages to produce a polypropylene drawn yarn (total fineness = 29 dtex / 24 filament) having a total draw ratio of 10.1 times.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 2 below.

Example 7
(1) Polypropylene [IPF = 98%, MFR = 16 g / 10 min (230 ° C., load 2.16 kg)] and polypropylene [“Y3002G” manufactured by Prime Polymer, IPF = 93%, MFR = 30 g / 10 min (230 The same melt spinning conditions as in (1) of Example 1 were employed using a mixture (IPF of the mixture = 95.5%) mixed at a mass ratio of 1: 1 at a temperature of 2.16 kg at a temperature of 2.degree. A polypropylene undrawn yarn was produced and wound on a bobbin (total fineness of polypropylene undrawn yarn = 288 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 128 ° C., and pre-drawn 4.6 times in two stages, and the polypropylene pre-drawn yarn Was wound around a bobbin and stored at room temperature (total fineness of polypropylene predrawn yarn = 63 dtex / 24 filament, endothermic onset temperature = 152.5 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 172 ° C., and the deformation rate was 1.7 times / min and the draw tension was 1.20 cN / dtex. Under the conditions, a polypropylene drawn yarn (total fineness = 48 dtex / 24 filament) having a total draw ratio of 6.0 times was produced by post-drawing by 1.3 times in three stages.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 2 below.

Example 8
(1) A spinneret [24 holes (circular holes), hole diameter 0.2 mm] for producing core-sheath composite fibers is attached to a spinning head of a melt spinning apparatus, and polypropylene ("Y3002G" manufactured by Prime Polymer Co., IPF = 93%) using a core component and polypropylene [IPF = 98%, MFR = 16 g / 10 min (230 ° C., load 2.16 kg)] as a sheath component, and a mass ratio of core component: sheath component = 1: 2. , Melt-kneaded at 240 ° C., discharged from the spinneret (die temperature: 245 ° C.) at an amount of 22.3 g / min, and wound on a bobbin at a take-up speed of 800 m / min to produce a core-sheath type polypropylene undrawn yarn And stored at room temperature (total fineness of polypropylene undrawn yarn = 287 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 128 ° C., and pre-drawn 4.6 times in two stages to obtain a polypropylene pre-drawn yarn. It was manufactured and wound on a bobbin and stored at room temperature (total fineness of polypropylene predrawn yarn = 62 dtex / 24 filament, endothermic onset temperature = 152.2 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 172 ° C., and the deformation rate was 1.7 times / min and the draw tension was 1.25 cN / dtex. Under the conditions, a polypropylene drawn yarn (total fineness = 48 dtex / 24 filament) having a total draw ratio of 6.0 times was produced by post-drawing by 1.3 times in three stages.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 2 below.

Example 9
(1) Using the same polypropylene as used in (1) of Example 1, the same conditions as in (1) of Example 1 were adopted to produce a polypropylene unstretched yarn and wound around a bobbin.
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 128 ° C., pre-drawn 4.6 times in one stage, and a polypropylene pre-drawn yarn Was wound around a bobbin and stored at room temperature (total fineness of polypropylene pre-drawn yarn = 63 dtex / 24 filament).
(3) The polypropylene pre-drawn yarn obtained in (2) above is unwound from a bobbin and brought into contact with a hot plate at a temperature of 172 ° C., with a deformation rate of 13.8 times / min and a draw tension of 1.43 cN / dtex. Under the conditions, a polypropylene stretched yarn (total fineness = 39 dtex / 24 filament) having a total draw ratio of 7.4 times was stretched 1.6 times in one stage (contact time to the heat plate = 15 seconds). Manufactured.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 2 below.

Example 10
(1) Using the same polypropylene as used in (1) of Example 1, the same conditions as in (1) of Example 1 were adopted to produce a polypropylene unstretched yarn and wound around a bobbin.
(2) The polypropylene unstretched yarn obtained in (1) above is unwound from the bobbin, pre-stretched using the same conditions as in (2) of Example 1 to produce a polypropylene pre-stretched yarn, I wound it on a bobbin.
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from the bobbin, and the same condition as (3) of Example 1 was adopted to produce a polypropylene drawn yarn, which was wound around the bobbin.
(4) The polypropylene drawn yarn obtained in the above (3) was unwound from a bobbin, introduced into a hot air oven at a temperature of 168 ° C., and contracted by 2% to produce a polypropylene yarn.
(5) About the polypropylene yarn obtained in the above (4), DSC measurement [measurement of endothermic peak shape, half width, amount of change in melting enthalpy (ΔH)], fiber strength, surface unevenness dimension (average of unevenness) The distance and average height) and the water retention rate were measured by the methods described above, and the results were as shown in Table 2 below.

Example 11
(1) A spinneret [24 holes (circular holes), hole diameter 0.2 mm] for producing core-sheath composite fibers is attached to the spinning head of the melt spinning apparatus, and polyethylene (“HJ490” manufactured by Mitsubishi Kasei, MFR = 20 g) / 10 min) is used as the sheath component and the core component and polypropylene [IPF = 98%, MFR = 16 g / 10 min (230 ° C., load 2.16 kg)], the mass ratio of core component: sheath component = 1: 1 And melt-kneaded at 240 ° C., discharged from the spinneret (die temperature: 245 ° C.) in an amount of 22.3 g / min, wound on a bobbin at a take-up speed of 800 m / min, and a core-sheath type polypropylene undrawn yarn was obtained. Manufactured and stored at room temperature (total fineness of polypropylene undrawn yarn = 282 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 128 ° C., and pre-drawn 4.6 times in two stages to obtain a polypropylene pre-drawn yarn. Produced, wound on a bobbin and stored at room temperature (total fineness of polypropylene predrawn yarn = 61 dtex / 24 filament, endothermic onset temperature = 148.7 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 172 ° C., and the deformation rate was 1.7 times / min and the draw tension was 1.24 cN / dtex. Under the conditions, a polypropylene drawn yarn (total fineness = 47 dtex / 24 filament) having a total draw ratio of 6.0 times was produced by post-drawing 1.3 times in three stages.
(4) For the drawn polypropylene yarn obtained in (3) above, DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, surface unevenness dimensions (unevenness of unevenness) Measurement of the average interval and average height) and the water retention rate were carried out by the methods described above, and the results were as shown in Table 2 below.

<< Comparative Example 1 >>
(1) Using polypropylene (“Y3002G” manufactured by Prime Polymer Co., Ltd., IPF = 93%) and adopting the same melt spinning conditions as in (1) of Example 1, a polypropylene undrawn yarn was produced and wound on a bobbin And stored at room temperature (total fineness of polypropylene undrawn yarn = 288 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 128 ° C., and pre-drawn 4.6 times in two stages, and the polypropylene pre-drawn yarn Was wound around a bobbin and stored at room temperature (total fineness of polypropylene predrawn yarn = 68 dtex / 24 filament, endothermic onset temperature = 151.8 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above was unwound from a bobbin and introduced into a hot air oven at a temperature of 172 ° C., and the deformation rate was 1.7 times / min and the draw tension was 0.96 cN / dtex. Under the conditions, a polypropylene drawn yarn (total fineness = 48 dtex / 24 filament) having a total draw ratio of 6.0 times was produced by post-drawing by 1.3 times in three stages.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the property and the water retention rate were measured by the method described above, the results were as shown in Table 3 below. The polypropylene fiber obtained in Comparative Example 1 did not have irregularities on the surface.

<< Comparative Example 2 >>
About the polypropylene predrawn yarn (polypropylene fiber) obtained in (2) of Example 1, DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, friction prevention When the meltability and water retention were measured by the methods described above, the results were as shown in Table 3 below. The polypropylene fiber obtained in Comparative Example 2 did not have irregularities on the surface.

<< Comparative Example 3 >>
(1) Using the same polypropylene as used in (1) of Example 1 (“Y2000GV” manufactured by Prime Polymer, IPF = 97%), the same melt spinning conditions as in (1) of Example 1 were adopted. A polypropylene undrawn yarn was produced and wound on a bobbin.
(2) The polypropylene undrawn yarn obtained in (1) above is unwound from a bobbin, introduced into a hot air oven at a temperature of 143 ° C., drawn 6.9 times in one stage, and drawn polypropylene yarn (total Fineness = 42 dtex / 24 filament) was produced.
(3) About the polypropylene drawn yarn (polypropylene fiber) obtained in the above (2), DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 3 below.

<< Comparative Example 4 >>
(1) Using the same polypropylene as used in (1) of Example 1 (“Y2000GV” manufactured by Prime Polymer, IPF = 97%), the same melt spinning conditions as in (1) of Example 1 were adopted. A polypropylene undrawn yarn was produced and wound on a bobbin.
(2) After unwinding the polypropylene unstretched yarn obtained in (1) above from the bobbin, introducing it into a hot water tank at a temperature of 90 ° C., and pre-stretching 3.7 times in one step, without winding Subsequently, it was introduced into a hot air oven at a temperature of 138 ° C. and post-drawn by 1.2 times to produce a drawn yarn having a total draw ratio of 4.4 times (total fineness = 65 dtex / 24 filament).
(3) About the polypropylene drawn yarn (polypropylene fiber) obtained in the above (2), DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 3 below.

<< Comparative Example 5 >>
(1) Using the same polypropylene as used in (1) of Example 1 (“Y2000GV” manufactured by Prime Polymer, IPF = 97%), the same melt spinning conditions as in (1) of Example 1 were adopted. A polypropylene undrawn yarn was produced and wound on a bobbin.
(2) After unwinding the polypropylene unstretched yarn obtained in (1) above from the bobbin, introducing it into a hot water tank at a temperature of 90 ° C., and pre-stretching 3.7 times in one step, without winding Subsequently, it was introduced into a hot air oven at a temperature of 172 ° C. and post-drawn by 1.2 times to produce a drawn yarn having a total draw ratio of 4.4 times (total fineness = 65 dtex / 24 filament).
(3) Since the polypropylene drawn yarn (polypropylene fiber) obtained in the above (2) has a lot of fluff and could not be used, DSC measurement, fiber strength, friction-fusibility, surface unevenness dimensions and water retention rate Measurement was not performed.

<< Comparative Example 6 >>
(1) The same polypropylene (“Y2000GV” manufactured by Prime Polymer Co., Ltd., IPF = 97%) used in (1) of Example 1 was put into an extruder of a melt spinning apparatus, melted and kneaded at 270 ° C., and spinning. From the spinneret attached to the head at a temperature of 295 ° C. [24 holes (circular holes), hole diameter 0.2 mm], discharge at an amount of 9.5 g / min and take it up at 1500 m / min to produce a polypropylene undrawn yarn. And wound around a bobbin and stored at room temperature (total fineness of polypropylene undrawn yarn = 65 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin, introduced into a hot air oven at a temperature of 130 ° C., drawn 1.5 times in one stage, and drawn polypropylene yarn (total Fineness = 44 dtex / 24 filament) was produced.
(3) About the polypropylene drawn yarn (polypropylene fiber) obtained in the above (2), DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 4 below.

<< Comparative Example 7 >>
(1) The same polypropylene (“Y2000GV” manufactured by Prime Polymer Co., Ltd., IPF = 97%) as used in (1) of Example 1 was put into an extruder of a melt spinning apparatus, melted and kneaded at 230 ° C., and spun From the spinneret attached to the head at a temperature of 300 ° C. [number of holes 30 (circular holes), hole diameter 0.8 mm], discharge at an amount of 20 g / min, and take up at 300 m / min to produce polypropylene undrawn yarn, bobbin And wound up at room temperature (total fineness of polypropylene undrawn yarn = 535 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in (1) above is unwound from a bobbin and drawn 3.7 times in a single stage with a heat roller at a temperature of 110 ° C. to obtain a polypropylene drawn yarn (total fineness = 145 dtex). / 24 filament).
(3) After fixing both ends of the polypropylene drawn yarn obtained in (2) above, heat treatment was performed by placing it in an air oven at 165 ° C. for 30 minutes.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 4 below.

<< Comparative Example 8 >>
(1) Polypropylene [“ZS1337A” manufactured by Prime Polymer Co., Ltd., IPF = 96%, MFR = 20 g / 10 min (230 ° C., load 2.16 kg)] is charged into an extruder of a melt spinning apparatus and melt kneaded at 300 ° C. Then, from the spinneret attached to the spinning head at a temperature of 320 ° C. [24 holes (circular holes), hole diameter 0.2 mm], 22.3 g / min is discharged and polypropylene is unstretched at a take-up speed of 600 m / min. A yarn was produced, wound on a bobbin, and stored at room temperature (“total fineness of polypropylene undrawn yarn = 304 dtex / 24 filament).
(2) The polypropylene unstretched yarn obtained in (1) above is unwound from the bobbin, pre-stretched 1.5 times in a single step with a heating roll at a temperature of 90 ° C., wound on the bobbin and stored at room temperature. (Total fineness of polypropylene pre-drawn yarn = 203 dtex / 24 filament, endothermic start temperature = 150.8 ° C.).
(3) The polypropylene pre-drawn yarn obtained in (2) above is unwound from a bobbin, introduced into a hot air oven at a temperature of 138 ° C., and post-drawn in a single step to 4.9 times, and the total draw ratio is A 7.4 times drawn polypropylene yarn (total fineness = 40.8 dtex / 24 filament) was produced.
(4) DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance of the drawn polypropylene yarn (polypropylene fiber) obtained in (3) above. When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 4 below.

<< Comparative Example 9 >>
(1) Melt spinning of the same polypropylene used in (1) of Example 1 [“Y2000Gv” manufactured by Prime Polymer, IPF = 97%, MFR = 18 g / 10 min (230 ° C., load 2.16 kg)] The amount is 35.4 g / min from a spinneret (24 holes (circular holes), hole diameter 0.2 mm) having a temperature of 260 ° C. attached to the spinning head and charged into an extruder of the apparatus at 255 ° C. The polypropylene undrawn yarn was produced at a take-off speed of 600 m / min, wound on a bobbin and stored at room temperature (“total fineness of polypropylene undrawn yarn = 635 dtex / 24 filament).
(2) The polypropylene undrawn yarn obtained in the above (1) is unwound from a bobbin and drawn 11.5 times in a single stage by a steam tank at a temperature of 145 ° C. to obtain a polypropylene drawn yarn (total fineness = 55. 2 dtex / 24 filament).
(3) About the polypropylene drawn yarn (polypropylene fiber) obtained in the above (2), DSC measurement [measurement of endothermic peak shape, half-value width, amount of change in melting enthalpy (ΔH)], fiber strength, and friction resistance When the properties, surface irregularities (average interval and average height of irregularities) and water retention were measured by the methods described above, the results were as shown in Table 4 below.

As seen in Tables 1 and 2 above, in Examples 1 to 10, the conditions specified in the present invention were obtained by using polypropylene unstretched fibers produced by melt-spinning polypropylene having an IPF of 94% or more and then melted by cooling. Is used to produce a polypropylene fiber having a single fiber fineness of 3 dtex or less, that is, after pre-drawing at a temperature of 120 to 150 ° C. and a draw ratio of 3 to 10 times, then a temperature of 170 to 190 The fiber was post-drawn at a draw ratio of 1.2 to 3.0 times under the conditions of a deformation rate of 1.5 to 15 times / min and a draw tension of 1.0 to 2.5 cN / dtex at a temperature of 1 ° C., and the single fiber fineness was 3 dtex. By producing the following polypropylene fibers, the endothermic peak shape by DSC measurement is a single shape having a half width of 10 ° C. or less, and the amount of change in melting enthalpy (ΔH) is 125 J. g, and the friction melting start time in the friction-fusibility test is long as 6.8 to 8.0 seconds, which is excellent in heat resistance, the fiber strength is 7 cN / dtex or more, and the fiber strength is high. The surface has irregularities with an average interval of 6.5 to 20 μm and an average height of 0.35 to 1 μm, in which large-diameter bulges and small-diameter non-bulges are alternately present along the fiber axis. A polypropylene fiber having a high water retention rate of 10% or more is obtained smoothly.
Further, in Example 11, the fiber strength is 7 cN / dtex or more, the fiber strength is high, and the average distance between the large-diameter bulges and the small-diameter non-bulges on the surface alternately along the fiber axis Of polypropylene fibers (core-sheath type polypropylene fibers) having an unevenness of 6.5 to 20 μm and an average height of 0.35 to 1 μm and a high water retention of 10% or more.

  On the other hand, in Comparative Examples 1-9, the polypropylene fibers obtained in Comparative Examples 1-9 have high fiber strength, high heat resistance and high water retention by adopting conditions outside the range specified in the present invention. They are not combined, and at least one of fiber strength, heat resistance and water retention, most of them are inferior in two or more.

  By the production method of the present invention, it is possible to smoothly produce polypropylene fibers having high crystallinity, having a uniform crystal structure, extremely excellent heat resistance, further high fiber strength, and excellent water retention, Polypropylene fibers obtained by the production method of the present invention, taking advantage of their properties, are in the form of short fibers, long fibers, fiber bundles, etc., or in the form of fiber structures such as woven and knitted fabrics, nonwoven fabrics, nets, and papers. It can be used effectively for various purposes.

It is the figure which showed typically the endothermic peak shape by DSC measurement in a polypropylene fiber. It is the figure which showed how to obtain | require the half value width in the endothermic peak by DSC measurement of a polypropylene fiber. It is the figure which showed how to obtain | require the average space | interval and average height of an unevenness | corrugation typically while showing the uneven | corrugated shape of the polypropylene fiber obtained by the manufacturing method of this invention. 2 is a photograph taken with a scanning electron microscope of the polypropylene fiber obtained in Example 1. FIG.

Claims (6)

  After pre-stretching polypropylene unstretched fibers produced by melt-spinning polypropylene having an isotactic pentad fraction (IPF) of 94% or more and then cooling and solidifying at a temperature of 120 to 150 ° C. and a stretching ratio of 3 to 10 times The film is post-stretched at a stretching ratio of 1.2 to 3.0 times at a temperature of 170 to 190 ° C. under conditions of a deformation rate of 1.5 to 15 times / minute and a stretching tension of 1.0 to 2.5 cN / dtex. A process for producing polypropylene fibers characterized by   The production method according to claim 1, wherein the total draw ratio of the pre-stretching and the post-stretching is 3.9 to 20 times.   The product (A × B) of the melt spinning speed A (m / min) during the production of polypropylene unstretched fibers and the total stretch ratio B (times) of the pre-stretch and post-stretch is 3000 to 17000 (m · times / The production method according to claim 1 or 2, wherein:   The endothermic peak shape by scanning differential calorimetry (DSC) is a single shape having a half width of 10 ° C. or less, the amount of change in melting enthalpy (ΔH) is 125 J / g or more, and the fiber strength is 7 cN / dtex or more. The production method according to any one of claims 1 to 3, wherein a certain polypropylene fiber is produced.   The average distance between the single fiber fineness is 0.1 to 3 dtex, the fiber strength is 7 cN / dtex or more, and a large-diameter raised portion and a small-diameter non-raised portion alternately exist along the fiber axis on the surface is 6.5. The production method according to any one of claims 1 to 3, wherein polypropylene fibers having irregularities with a mean height of 0.35 to 1 µm and a mean height of ~ 20 µm are produced.   The single fiber fineness is 0.1 to 3 dtex, the fiber strength is 7 cN / dtex or more, the endothermic peak shape by scanning differential calorimetry (DSC) is a single shape having a half width of 10 ° C. or less, and the change in melting enthalpy (ΔH ) Is 125 J / g or more, the average distance between the large-diameter bulges and the small-diameter non-bulges along the fiber axis is 6.5 to 20 μm, and the average height is 0.35. The production method according to any one of claims 1 to 3, wherein a polypropylene fiber having irregularities of -1 µm is produced.