JPH059805A - Polypropylene fiber and conjugate fiber - Google Patents

Abstract

PURPOSE:To provide the subject fiber useful for rope, short fibers for cement- reinforcement, conjugate yarn, etc., composed of a high-tenacity yarn having specific breakage strength, producible at a low cost and consisting of a specific drawn polypropylene yarn having high crystallinity. CONSTITUTION:The objective fiber having a breakage strength of >=8g/de (preferably >=9g/de) and a fineness (d) of 0.5<d<100 is produced by using a highly crystalline polypropylene having Q value (ratio of weight-average molecular weight to number-average molecular weight) of <5 (preferably <=4.5), a boiling n-heptane insoluble fraction (H>= wt.%) of 97<HI<100 (preferably 98<HI) and an isotactic pentad fraction (IPF mol%) of 94<IPF<100 (preferably 96<=IPF) and drawing the polypropylene e.g. by dry-drawing process at a high temperature not to cause the welding of the constituent components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention can be manufactured at low cost by a conventional manufacturing method and has higher strength than conventional polypropylene fibers, so that ropes, cement-reinforcing short fibers, non-woven fabrics, etc. for which strength improvement is required The present invention relates to a polypropylene fiber most suitable for, and a sheath-core type composite fiber having a structure in which the polypropylene fiber is used as a core, and the composite fiber has a higher strength than conventional fibers of the same kind.

[0002]

2. Description of the Related Art Conventional polypropylene fibers have boiling n-
Using crystalline polypropylene (PP) having a heptane insoluble content (HI) of 96 to 97% by weight and an isotactic pentad fraction (IPF; mol%) of 93 to 94 mol%,
The strength was usually 5 to 6 g / d. Further, there is also known a dry stretching method at about 150 ° C. by using PP having a low Q value of about 4 in order to improve the stretchability, but the maximum strength is about 7.5 g / d. Met.

Polypropylene fibers and composite fibers using highly crystalline PP are disclosed in JP-A-60-59113,
No. 62-41331 and Japanese Patent Publication No. 3-2050.
Although there is a publication such as Japanese Patent Laid-Open No. 5), the breaking strength similar to that of conventional polypropylene is only shown in the examples. Conventionally, high crystalline PP has been mainly used in the field of injection molding, and only polymers having a wide Q value of 6 or more have been distributed in the market in order to suppress heat shrinkage.

[0004]

However, polypropylene fibers produced by the conventional melt-spinning method have the advantages of low specific gravity, excellent chemical resistance, and low cost. However, since there is no demand for improvement in mechanical strength, the strength of ropes and cement-reinforcing staple fibers, which require strength, is reduced because relative strength with other fibers decreases. The demand for improvement has increased. Further, in the field of non-woven fabrics, there has been a strong demand for thermal contact fibers that can reduce the amount of fibers used and can improve the strength of non-woven fabrics in order to reduce the cost of final products.

In order to achieve the above-mentioned object, the present invention has a small Q value for high stretching and high strength, has a low crystalline component for improving orientation during stretching, and has extremely high stereoregularity. The purpose of the present invention is to obtain a high-strength yarn by using a highly crystalline PP and drawing at a high temperature in a range such that the constituent components do not fuse together, such as a dry drawing method, to increase the draw ratio.

[0006]

In order to achieve the above object,
The polypropylene fiber of the present invention has a Q value (Q; weight average molecular weight / number average molecular weight ratio) of less than 5, a boiling n-heptane insoluble matter (HI; weight%) of 97 <HL <100, and an isotactic pentad. Fraction (IPF; mol%) is 94 <
A drawn yarn of highly crystalline polypropylene having an IPF <100, having a constitution having a breaking strength of more than 8 g / denier.

In the above structure, the Q value is 4.5 or less,
It is preferable that the HI is 98 ≦ HI and the IPF is 96 ≦ IPF, which is made of highly crystalline polypropylene, the breaking strength is 9 g / denier or more, and the fineness d (denier) is 0.5 <d <100.

Further, in the constitution of the conjugate fiber of the present invention, the Q value (Q; ratio of weight average molecular weight / number average molecular weight) is less than 5, and boiling n-heptane insoluble matter (HI; weight%) is 9
A highly crystalline polypropylene having 7 <HL <100 and an isotactic pentad fraction (IPF; mol%) of 94 <IPF <100 is used as a core component, and a polyolefin or an olefin-based copolymer having a Q value of less than 5 is used. It is provided with a structure of a sheath component.

In the above structure, it is preferable to use poly-4-methylpentene-1 as the sheath component.

[0010]

According to the above-mentioned constitution of the present invention, there are few low crystalline components which hinder the crystal orientation by stretching, the boiling n-heptane insoluble matter (HI) is larger than that of the conventional polypropylene (PP), and the crystal by stretching is high. It has excellent stereoregularity to promote orientation, that is, it has a larger isotactic pentad fraction (IPF) than conventional PP, and in order to improve the stretchability, it has a weight average molecular weight / number average molecular weight ratio ( Since the Q value) was made much lower than that of the conventional high crystalline PP, the draw ratio could be increased and a high tenacity yarn could be obtained.
Further, it is characterized by using PP that is more easily oriented crystallized than conventional PP, and preferably melt-spun at a relatively low temperature to avoid entanglement and breakage of molecules like conventional polypropylene fiber, Stretched at as high a temperature as possible with a high draw ratio to obtain highly oriented crystallized fibers as compared to conventional polypropylene fibers. At least a single fiber has a breaking strength that could not be achieved by mass production with ordinary PP of 8 g / It is possible to obtain polypropylene having a denier exceeding.

If the above-mentioned preferred drawing conditions are used, it is possible to easily set the breaking strength of single fiber to 9 g / denier or more, and even in the case of the composite fiber, restrictions such as melting point and softening point of the sheath component are large. Even if the conventional PP is used, the breaking strength can be increased, and the known conventional P can be used.
If the stretching conditions are selected in the same manner as P, the breaking strength can be improved by at least 30% as compared with the conventional one. When used as a cement-reinforcing short fiber that is steam-cured at 170 ° C or higher, poly-4-methylpentene-1
Even in the case of a composite fiber having a sheath as a sheath and a shape-fixing component during steam curing and polypropylene as a core component, the breaking strength can be improved in the same manner as described above.

[0012]

EXAMPLES The polypropylene used in the present invention has a Q value of less than 5, more preferably 4 or less in terms of stretchability, and has a HI of 97 <HI <100, more preferably 98 or more in terms of ensuring high orientation. , IPF 94 <IPF <100, and more preferably 95 ≦ IPF with high crystallinity PP. In addition, the melt flowability is a melt flow rate (MFR, g / 10 minutes, JIS K7210, weight 21) for the convenience of melt spinning.
69g, same as measurement temperature of 230 ° C) 1 <MFR <10
The density is 0, more preferably 5 <MFR <30, most preferably 10 to 20, and the density is about 0.905 in the raw material pellet state, which is not different from ordinary PP. In addition, IPF refers to “insoluble components of n-heptane” in “Macromolecules 6 , 925 (197).
3) and 8 , 687 (1975).

In the composite fiber of the present invention, the thermoplastic resin used as the sheath component preferably has excellent stretchability,
For this reason, the Q value is generally preferably less than 5, but a smaller value may be desirable depending on the type of resin. The thermoplastic resin used in the present invention, linear low density,
Medium and high density polyethylene (PE), poly 4-
Homopolymer or copolymer polyolefin such as methylpentene-1 and ethylene-vinyl alcohol copolymer (EVHO), ethylene-vinyl acetate copolymer (EVA) or ethylene-acrylic acid ester copolymer (EMA, EEA) , Ethylene-acrylic acid ester-acrylic acid copolymer (E-MA-A), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid ester copolymer (EMMA), methylene-methacrylic acid copolymer An ethylene-unsaturated carboxylic acid-based copolymer such as a polymer (EMAA) or a polyolefin-based copolymer such as an ethylene-propylene-α-olefin copolymer such as butene-1 and a graft modified product thereof are conveniently used. be able to.

The melt-spinning temperature may be a temperature in the range that does not impair the stereoregularity, but it is preferably a relatively low temperature in order to reduce the entanglement of the molecule and rounding, for example, 260 to 280 ° C. for a single fiber. The stretching temperature is 140 to 15 in a single case in order to improve the stretchability as much as possible.
In the case of a composite fiber at 0 ° C., it is desirable to highly draw at a temperature close to the melting point of the low melting point component. In addition, in the case of composite fibers, it is desirable to consider this point when selecting the sheath component,
It is desirable for the purpose of the present invention to increase the core component / sheath component composite ratio as well. Further, the area composite ratio in the fiber cross section is not particularly limited for the purpose of merely making the fiber stronger than the conventional fiber, but a range of 70:30 to 40:60 is preferable.

Although the thickness of the fiber is not particularly limited, there is an optimum denier (d) range for each application, for example, 0.5 to 30 d as a cement reinforcing short fiber, and 50 to 100 d when used as a multifilament. Is appropriate. However, in the case of a monofilament having an extremely large fiber thickness of 1000 d or more, the fiber temperature may not sufficiently rise during drawing and the drawability may be poor, and the thickness limit at which the high-strength fiber of the present invention cannot be obtained is limited. is there.

The fibers of the present invention are short cut staples,
Examples include multifilaments, monofilaments and spunbonds using stretch techniques. Next, a measurement example of each factor defined in the present invention will be described. (1) The weight average molecular weight is determined by the following formula 1 using, for example, a light scattering method, a viscosity method, and an ultracentrifugation method.

[0017]

[Equation 1]

(2) The number average molecular weight is determined by the following formula 2 using, for example, the end group quantitative method, the freezing point depression method, the boiling point elevation method, and the osmotic pressure method.

[0019]

[Equation 2]

Generally, the weight average molecular weight / number average molecular weight is used as a measure of polydispersity, and the larger this value is 1 (monodisperse), the wider the molecular weight distribution curve is (broad). In addition, polymers with many branches also have high values. (3) For boiling n-heptane insoluble matter (HI), 5 g of polypropylene sample was completely dissolved in 500 ml of boiling xylene, and these were poured into 5 liters of methanol to collect and dry the precipitate. After that, the extract is the rest of the Soxhlet extracted with boiling n-heptane for 6 hours. (4) Isotactic pentad fraction (IPF) is n
-About heptane insoluble matter "Macromoleculars"
(Measured according to Macromolecules, 6,925 (1973) and 8,687 (1975). (5) Melt flow rate (MFR) is 190 ° C temperature, the amount of nozzle passage (unit: g / 10 minutes, JIS K7210, load weight 2 .169 Kg).

Specific examples will be described below. Examples 1 to 10 Comparative Examples 1 to 8 Using the polypropylene and the polyolefins or olefin copolymers shown in Tables 1 and 2, single fiber or a sheath-core type in which the area composite ratio in the fiber cross section is 1: 1 polypropylene The composite fiber is melt-spun and drawn in a hot roll or hot water to form a drawn yarn, and the strength and elongation of the fiber are measured. The results are shown in Tables 1 and 2.

[0022]

[Table 1]

[0023]

[Table 2]

As described in the above Examples and Comparative Examples, according to this Example, since the ratio of the weight average molecular weight / number average molecular weight (Q value) is small because of high stretching and high tenacity, To improve the orientation, there are few low-crystalline components and extremely high stereoregularity. Highly crystalline PP is used, and it is stretched at a high temperature within the range where it does not fuse with the constituent components such as the dry stretching method. It was confirmed that a high tenacity yarn can be obtained by increasing the value.

Further, when the single fiber of the present invention is used for a rope, the strength can be greatly improved as compared with the conventional product, and it is used as a short fiber for cement reinforcement and is naturally cured or steam-cured at 160 ° C. for 10 hours. When made, the impact Charpy value (K
gf-cm) could be improved to about 6 Kgf-cm, which is more than double. Further, when used as a heat-bondable composite fiber, the direction of the fiber orientation was stronger than that of the conventional non-woven fabric, for example, the non-woven fabric using the parallel roller card could improve the non-woven fabric in the longitudinal direction.

[0026]

According to the present invention described above, there are few low crystalline components that hinder the crystal orientation due to stretching, and the boiling n-
Heptane insoluble matter (HI) is a conventional polypropylene (P
P) and is superior in stereoregularity because it promotes crystal orientation by stretching, that is, the isotactic pentad fraction (IPF) is larger than that of conventional PP and the stretchability is improved. Since the ratio (Q value) of average molecular weight / number average molecular weight was made much lower than that of the conventional high crystalline PP, it was possible to increase the draw ratio and obtain a high tenacity yarn.

Claims (4)

[Claims] 1. A Q value (Q; weight average molecular weight / number average molecular weight ratio) of less than 5, a boiling n-heptane insoluble matter (HI; weight%) of 97 <HL <100, and an isotactic pentad fraction. (IPF; mol%) is a drawn yarn of highly crystalline polypropylene having 94 <IPF <100, and has a breaking strength of more than 8 g / denier. 2. A Q value of 4.5 or less, an HI of 98 ≦ HI,
The polypropylene fiber according to claim 1, wherein the polypropylene fiber is made of highly crystalline polypropylene having an IPF of 96 ≦ IPF, a breaking strength of 9 g / denier or more, and a fineness d (denier) of 0.5 <d <100. 3. A Q value (Q; weight average molecular weight / number average molecular weight ratio) of less than 5, boiling n-heptane insoluble matter (HI; weight%) of 97 <HL <100, isotactic pentad fraction. (IPF; mol%) is a composite fiber comprising a highly crystalline polypropylene having a 94 <IPF <100 as a core component and a polyolefin or an olefin copolymer having a Q value of less than 5 as a sheath component. 4. The composite fiber according to claim 3, which comprises poly-4-methylpentene-1 as a sheath component.