JP3129602B2 - Polyolefin-based conductive composite fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin-based conductive conjugate fiber suitable for a polyolefin nonwoven fabric used in a field in which troubles are easily caused by static electricity.

[0002]

2. Description of the Related Art Nonwoven fabrics made of a polyolefin such as polypropylene are widely used for various surface materials, filters, oil adsorbents, etc. because of their excellent chemical resistance, flexibility, oil absorption and low cost. However, since the nonwoven fabric is inherently hydrophobic, it tends to generate static electricity, and particularly when applied to a cover material of electronic equipment or dustproof clothing, high antistatic performance (antistatic performance) is required.

Generally, in order to prevent the non-woven fabric from being charged,
A method of mixing a small amount of conductive fibers such as carbon fibers (Japanese Patent Application Laid-Open No. 2-41453), metal fibers (Japanese Patent Application Laid-Open No. 63-315653), or conductive composite fibers containing conductive particles such as carbon black has been practiced. Have been done. The conductive fiber-mixed nonwoven fabric is produced by mixing ordinary nonwoven fabric fiber cotton and conductive fiber cotton, forming a card and forming a web, and performing a confounding treatment with a needle or a method such as heat and water flow. However, metal fibers and carbon fibers cannot be crimped and have poor thermal adhesiveness to ordinary synthetic fiber materials, and thus easily fall off the web during the above-described entanglement treatment. For these reasons, conductive composite fibers that can be processed similarly to ordinary synthetic fibers such as crimps are relatively frequently used. Further, among the conductive conjugate fibers, those in which the conductive component is continuously exposed in the fiber axis direction on the fiber surface (conductive component exposed type) are compared with the core-sheath type in which the conductive component is a core and the protective component is a sheath. It is used more frequently because of its excellent corona discharge property, that is, excellent antistatic property.

[0004]

However, in some cases, the conventional conductive composite fiber of the conductive component exposed type cannot be applied to a polyolefin nonwoven fabric. In particular, in the above-mentioned thermal bonding process such as embossing and calendering performed for bonding and entanglement of the constituent fibers of the nonwoven fabric or as a patterning of the nonwoven fabric, the conductive composite fiber of the polyolefin material has an adhesive property with the protective component. In view of this, since polyolefin is used as the conductive component, not only the protective component but also the conductive component may be melt-deformed or cut, often causing a significant decrease or loss of conductivity. In addition, conductive conjugate fibers made of materials other than polyolefins such as polyamides and polyesters do not have an affinity with polyolefins. Conductive fibers often fall off. As described above, a conductive composite fiber suitable for a polyolefin nonwoven fabric having a high adhesiveness with a polyolefin, a melting point and a softening point of a conductive component higher than that of the polyolefin, and having excellent antistatic properties has not yet been obtained. Is the current situation. An object of the present invention is to provide a polyolefin-based conductive conjugate fiber suitable for a polyolefin nonwoven fabric that can be industrially produced.

[0005]

That is, the present invention relates to a specific resistance of a thermoplastic polymer (P1) in which conductive particles are dispersed.
A mixture A of 50 to 90% by volume of the conductive composition (CP) of less than 0 ⁷ Ωcm and 10 to 50% by volume of the fiber-forming polyolefin (P2) is joined to the non-conductive fiber-forming polyolefin B, The conductive conjugate fiber is characterized in that at least a part of the component A is conjugated so as to be exposed on the fiber surface in the fiber axis direction.

The conductive composition (CP) according to the present invention comprises:
It is made of a thermoplastic polymer in which conductive particles are dispersed. The thermoplastic polymer (P1) is required not to be melted and deformed or cut by thermal processing of the above-mentioned nonwoven fabric of polyolefin, that is, to have a higher melting point and softening point than that of polyolefin. The temperature is preferably 200 ° C. or higher, and is not particularly limited. Examples of such thermoplastic polymers include polyamides such as nylon 6, nylon 66, nylon 10, nylon 12, and the like, and modified polyamide copolymers containing these as a main component, polyethylene terephthalate, and the like.
Known materials such as polyesters such as polybutylene terephthalate, polyethylene oxybenzoate, and modified polyester copolymers containing these as a main component can be used.

The conductive particles include metal powders such as conductive carbon black, silver, nickel, copper, iron and alloys thereof, metal compounds such as copper sulfide, copper iodide, zinc sulfide and cadmium sulfide, and antimony. Alternatively, conductive metal oxide particles doped with a small amount of a second component (impurity) such as tin oxide doped with indium, aluminum, indium, germanium, or tin oxide, usually 50% or less, and often 25% or less. Is mentioned. In addition, non-conductive inorganic particles such as titanium oxide, zinc oxide, magnesium oxide, tin oxide, iron oxide, silicon oxide, and aluminum oxide may also be formed by forming a conductive film of the above metal compound or conductive metal oxide on the surface of the particles. Used. Among these conductive particles, conductive tin oxide doped with conductive carbon black or antimony and titanium oxide coated with the same are particularly preferable because uniform particles having a small particle size can be easily obtained.

The conductivity of the conductive particles is in the form of a powder (50 kg
/ Cm ² under pressure) with a specific resistance (volume resistivity) of 10 ⁴ Ω
cm or less, particularly preferably about 10 ² Ωcm or less,
Most preferably, it is about 10 ¹ Ωcm or less. Actually 10 ² ~
Those having a conductivity of about 10 ⁻³ Ωcm can be suitably used for the purpose of the present invention, but those having more excellent conductivity are more preferable. In addition, the conductive particles must have a sufficiently small particle size. Although those having an average particle size of 1 to 2 μm are not unusable, coarse particles serve as nuclei and often cause yarn breakage during spinning and stretching. For this reason, those having an average particle size of usually 1 μm or less, particularly 0.5 μm or less, and most preferably 0.3 μm or less are used.

The mixing ratio of the conductive particles to the thermoplastic polymer (P1) varies depending on the properties and crystallinity of the polymer to be mixed, the type, the conductivity, the particle shape, the particle size, etc. of the conductive particles. In this case, the content is in the range of about 10 to 85% by weight, and particularly preferably 15 to 80% by weight. 10% by weight
If it is less than 5, the conductivity often does not appear, while 85
If the amount is more than 10% by weight, it is difficult to uniformly disperse the particles in the polymer, and even if the particles can be dispersed with great effort, the fluidity of the polymer is lowered, and the spinning is hindered. The specific resistance of the conductive component needs to be less than 10 ⁷ Ωcm, preferably 10 ⁴ Ωcm or less, and more preferably 10 ² Ωcm.
cm or less is particularly preferred.

As the fiber-forming polyolefin (P2) and B used in the present invention, polyethylene, polypropylene, polybutene-1, and the like, and all copolymers of these copolymers can be used if they can be melt-spun. .

The combination of P1 and P2 is not particularly limited, but a combination having high adhesiveness is preferable from the viewpoint that peeling due to stretching or the like can be further prevented. For example, P1 is polyamide or polyester, P
As No. 2, there may be mentioned a combination of an unsaturated dicarboxylic acid such as acrylic acid and maleic anhydride or a polyolefin modified with an anhydride thereof.

The conductive component and the protective component further include a dispersant (waxes, polyalkylene oxides, various surfactants, organic electrolytes, etc.), a coloring agent, a heat stabilizer (an antioxidant, an ultraviolet absorber). Etc.), a fluidity improver and other additives can be added.

The fiber of the present invention is a composite fiber in which a mixture A of a conductive composition (CP) and a fiber-forming polyolefin (P2) is bonded to a protective component of a fiber-forming polyolefin B, and a conductive mixture. It is important that component A is exposed on the fiber surface. By adopting such a composite structure, it is possible to produce a conductive composite fiber having excellent antistatic performance without causing P1 which originally does not adhere to B to be separated from the fiber by drawing or the like. The proportion of the conductive composition (CP) in the mixture A varies depending on the melt viscosity and compatibility of CP and P2, but is usually 50 to 90% by volume, preferably 60 to 80% by volume, and most preferably 65 to 90% by volume.
It needs to be ~ 75% by volume. At 50% by volume or less, CP having a melt viscosity higher than that of P2 generally becomes discontinuous in the fiber axis direction, or CP becomes a structure corresponding to an island having a sea-island structure in the mixture A, and is not exposed to the fiber surface. It tends to have poor conductivity and antistatic performance. On the other hand, if the content is 90% by volume or more, peeling between the component A and the component B is apt to occur in the spinning / drawing and processing steps, which is not preferable.

The fiber of the present invention is produced by a melt spinning method (composite). The conductive composition (CP) and the fiber-forming polyolefin P2 can be mixed by any method. For example, a method of mechanically kneading in a single-screw or twin-screw extruder, a method of mixing with a static kneader provided in a polymer flow path, or a relatively small static type of about 3 to 5 pieces in a spinning pack A method of providing a kneading element and mixing, or a combination thereof can be used.

The cross section (contour) of the conjugate fiber of the present invention may be circular or non-circular, and is not particularly limited. However, a mixture of the conductive composition (CP) and the polyolefin (P2) may be formed on the cross section of the conjugate fiber. It is important that at least a part of A is exposed on the fiber surface. 1 to 4 are cross-sectional views of a conjugate fiber showing an example of a conjugate structure that can be used in the present invention. In the figure, A is a conductive composition (CP)
And shows a mixture of the polyolefin (P2), B is a protective component of the non-conductive fiber-forming polyolefin B.
1 is an example of a three-layer type, FIG. 2 is an example of a radiation type, FIG. 3 is an example of a keyhole type, and FIG. 4 is an example of a multiplexed keyhole type. By exposing the mixture A, that is, the conductive composition (P1), to the fiber surface, a conductive composite fiber having excellent antistatic performance (antistatic property) is obtained, and a conductive composition which does not originally adhere to B Can be formed without peeling off from the protective component of the polyolefin. Regarding the composite ratio (cross-sectional area occupancy) of the conductive composition A, a conductive composition in which a large amount of conductive particles are mixed tends to be inferior in spinnability (spinnability) and high elongation. It is preferably at most 50%, particularly preferably at most 30%, more preferably at most 20%.

Hereinafter, the present invention will be described in detail with reference to examples.

[0017]

Example 1 A conductive compound obtained by mixing and dispersing 35% by weight of conductive carbon black in nylon 6 having a molecular weight of 14,000 is designated as CP1. Melt flow rate value 36g /
A conductive compound obtained by mixing and dispersing 35% by weight of conductive carbon black in polypropylene having a melting point of 152 ° C. for 10 minutes is referred to as CP2. Nylon 6 with a molecular weight of 20,000
Is P1. Melt flow rate value is 23g / 10m
In, polypropylene having a melting point of 152 ° C. is designated as PO1.
In addition, modified polypropylene having a melt flow rate (test method ASTM D1238) of 17 g / 10 min and a melting point of 163 ° C., which is obtained by graft polymerization of maleic anhydride at 2% by weight, is designated as PO2. CP1, CP2, P1, PO1, P
Using O2, composite spinning was performed at the composite structure and composite ratio (volume ratio) shown in Table 1. 0.25 diameter at 270 ° C
mm (L / D = 1) orifice, and wound up at a speed of 700 m / min while cooling oiling.
0 denier / 24 filament undrawn yarn UDY1 to UDY
DY7 was obtained. In addition, the conductive composition forming the conductive component and the polyolefin B were chip-blended at a predetermined mixing ratio, and charged from a hopper port of a single-screw melt extruder.

[0018]

[Table 1]

Next, the undrawn yarns UDY1 to UDY5 are
The film is stretched 2.36 times on a stretching roller at 120 ° C., heat-treated on a hot plate at 120 ° C. and wound up, and 72 denier / 24
Filament drawn yarns DY1 to DY6 were obtained. Also, U
In the case of DY7, when the yarn was pulled out from the undrawn yarn bobbin, the fallout of the conductive component was scattered, and the wound yarn was so fuzzy and thick that it could not be drawn.

Next, the above drawn yarns DY1 to DY6 are
Threaded to 00000 denier, crimped about 15 pieces / 25mm by stuffer type crimping machine, 51mm
It was cut into long pieces to obtain staples Y1 to Y6. The electric resistance values of the staples Y1 to Y5 are 5.3 × 10 ⁷ and 5.7.
× 10 ⁷ , 3.9 × 10 ⁷ , 4.4 × 10 ⁷ , 1.6 ×
The conductivity was 10 ⁸ Ω / cm, and all had good conductivity. However, Y6 was 7.8 × 10 ¹¹ Ω / cm, and the conductivity was poor. These staples Y1 to Y5 were separately prepared, and a single yarn 1.5 denier, 15 pieces / 25 mm crimp,
1mm cut length polypropylene (melt flow rate value 23g / 10min) staple cotton and 10% by weight
The mixture was mixed with cotton and carded to prepare a web having a basis weight of 50 g / m ^2.
The lattice pattern (5 mm square) was embossed at 0 Kg / cm to form nonwoven fabrics F1 to F5. Table 2 shows the measurement results of the surface resistivity of these nonwoven fabrics under the conditions of temperature and humidity of 20 ° C. and 23% RH.

[0021]

[Table 2]

The surface resistivity of the nonwoven fabrics F1, F2 and F4 is 1
In 0 ⁹ Omega orders less it was excellent in conductivity but, F3, F
All of the nonwoven fabrics of No. 5 were inferior in conductivity at 10 ¹¹ Ω or more. Observation of the surface of the nonwoven fabric F5 with an optical microscope revealed that the nonwoven fabric F5 was melt-cut into an embossed lattice pattern provided with the conductive component of the conductive conjugate fiber. Next, the nonwoven fabric F
Friction test was performed on 1, F2 and F4 according to JISL-0823 (1971). The friction conditions were as follows:
Friction element: white cotton cloth, load: 300 g, number of friction: 500 times. The surface resistivity of the nonwoven fabric after the test was F1, F2,
5.7 × 10 ⁸ , 7.6 × 10 ⁸ , 8.6 × 10 in F4
¹² Ω, and the conductivity of F4 was significantly reduced. Also,
In F4, many conductive fibers were found on the white cotton cloth of the friction element after the test.

[0023]

According to the present invention, a polyolefin-based conductive conjugate fiber having excellent antistatic performance and excellent adhesion to polyolefin can be easily produced. The conjugate fiber obtained here can be handled in the same manner as ordinary synthetic and natural fibers,
In a continuous filament or staple form, in an uncrimped state or in a crimped state, it can be mixed with a nonwoven fabric of a polyolefin material by a known method, and it is possible to impart antistatic properties to a product. Of course, it can be mixed with fiber products of materials other than polyolefin, and the mixing ratio to fiber products is usually 0.1.
A mixing ratio of about 1 to 5% by weight, 5 to 100% by weight or less than 0.1% by weight may be applied depending on the purpose.

[Brief description of the drawings]

FIG. 1 is a specific example of a composite structure of a conductive composite fiber of the present invention.

FIG. 2 is a specific example of a composite structure of the conductive composite fiber of the present invention.

FIG. 3 is a specific example of a composite structure of the conductive composite fiber of the present invention.

FIG. 4 is a specific example of a composite structure of the conductive composite fiber of the present invention.

FIG. 5 is a comparative example of a composite structure of a conductive composite fiber used to show the superiority of the present invention.

[Explanation of symbols]

A Conductive component of conjugate fiber composed of a mixture of conductive composition and polyolefin B Protective component of conductive conjugate fiber composed of polyolefin

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-148811 (JP, A) JP-A-63-235526 (JP, A) JP-A-63-190017 (JP, A) 40211 (JP, A) JP-A-60-110920 (JP, A) JP-A-2-289108 (JP, A) JP-A-55-6540 (JP, A) JP-A-61-174469 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) D01F 8/06 D01F 1/09

Claims (1)

(57) [Claims] 1. A mixture A of 50 to 90% by volume of a conductive composition having a specific resistance of less than 10 ⁷ Ωcm, in which conductive particles are dispersed in a thermoplastic polymer, and 10 to 50% by volume of a fiber-forming polyolefin, The conductive conjugate fiber is bonded to the fiber-forming polyolefin B, and is compounded so that at least a part of the component A is exposed on the fiber surface in the fiber axis direction.