JP2988818B2 - 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 where static electricity is liable to occur.

[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 easily generates static electricity. In particular, when the nonwoven fabric is applied to electronic equipment such as cover materials and dustproof clothing, high antistatic performance (antistatic performance) is required.

In general, carbon fibers (Japanese Patent Application Laid-Open No. 2-41453) and metal fibers (Japanese Patent Application Laid-Open No.
A method of mixing a small amount of conductive fibers such as conductive conjugate fibers containing conductive particles such as carbon black or the like has been used. The non-woven fabric of the conductive fiber is produced by mixing the cotton of the non-woven fabric constituting the non-woven fabric and the cotton of the conductive fiber, forming a card and forming a web, and performing a confounding treatment by 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. Among conductive conjugate fibers, those having a conductive component exposed on the fiber surface in the fiber axis direction as shown in FIG. 7 (conductive component exposed type) have a conductive component as a core and a protective component as a sheath as shown in FIG. Compared to the core-sheath type, it is more frequently used because of its excellent corona discharge property, that is, 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. Especially, in the case of thermal bonding such as embossing and calendering, which are performed for bonding and entanglement of the constituent fibers of the nonwoven fabric, or embossing and calendering of the nonwoven fabric, from the viewpoint of the adhesion to the protective component, the conductive composite fiber of the polyolefin material is used. Since polyolefin is also used as the conductive component, the conductive component, like the protective component, often undergoes melting deformation or cutting, resulting in 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. Thus, a conductive conjugate fiber suitable for a polyolefin nonwoven fabric, which is rich in adhesion to polyolefin, has a higher melting point and softening point of the conductive component than that of polyolefin, and has 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 that is easily produced industrially and is suitable for a polyolefin nonwoven fabric.

That is, the present invention provides a conductive component A comprising a polyamide or polyester containing conductive particles, an adhesive component B comprising a modified polyolefin obtained by graft-polymerizing an unsaturated carboxylic acid or a derivative thereof, and A three-component conjugate fiber comprising a protective component C comprising a fiber-forming polyolefin, wherein a B component is interposed between the A component and the C component, and at least a part of the A component is exposed on the fiber surface. The conductive composite fiber is characterized by the following.

The conductive component A in the present invention is composed of a thermoplastic polymer having a higher melting point and softening point than that of the polyolefin, and easily mixed with a modified polyolefin, and a conductive particle uniformly mixed according to a conventional method. Such thermoplastic polymers include nylon 6, nylon 66,
Polyamides such as nylon 10, nylon 12, etc. or polyamide copolymers containing these as main components, or polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene oxybenzoate or polyester copolymers containing these as main components are exemplified. . These are preferred because they easily adhere to a polyolefin grafted with an unsaturated carboxylic acid or a derivative thereof. Among them, those having a melting point or softening point of 170 ° C. or more, particularly 200 ° C. or more, are most preferable for preventing melting and deformation of the conductive component at the time of thermal processing of the polyolefin nonwoven fabric.

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 and indium. Conductive metal oxide particles doped with a small amount of a second component (impurity) such as tin oxide, aluminum, indium, germanium, and tin oxide doped with zinc, usually 50% or less, and often 25% or less. Can be 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 powder (50 kg /
resistivity in cm ² pressure) (volume resistivity) of 10 ⁴ .omega.c
m or less, particularly preferably about 10 ² Ωcm or less.
0 about ¹ [Omega] cm or less is most preferred. Actually 10 ² -1
Those having a conductivity of about 0 ^-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, most preferably 0.3 μm or less are used.

The mixing ratio of the conductive particles to the polyamide or polyester varies depending on the properties and crystallinity of the polymer to be mixed, the type of the conductive particles, the conductivity, the particle shape and the particle size, but in many cases about 10 to 85% by weight. And particularly preferably 15 to 80% by weight. If the amount is less than 10% by weight, conductivity often does not appear. On the other hand, if the content exceeds 85% by weight, it becomes 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 spinning is hindered.
The specific resistance of the conductive component A needs to be less than 10 ⁷ Ωcm, preferably 10 ⁴ Ωcm or less, and more preferably 10 ² Ωcm.
The following are particularly preferred.

As the protective component C of the conjugate fiber of the present invention, polyethylene, polypropylene, polybutene-1, and the like, and any of these copolymers can be used if they can be melt-spun.

In the present invention, it is important that a modified polyolefin is interposed between the amphoteric components as an adhesive (adhesive component) between the conductive component and the protective component. As the modified polyolefin, polyethylene, polypropylene, polybutene-1
Examples thereof include those obtained by graft-polymerizing an unsaturated carboxylic acid or a derivative thereof to a polyolefin such as the above. Examples of unsaturated carboxylic acids or derivatives thereof include acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid,
Unsaturated carboxylic acids such as silaraconic acid, crotonic acid and isocrotonic acid, or derivatives thereof such as acid halides,
Examples include amides, imides, anhydrides, and esters. Specific examples include maleic anhydride, monomethyl maleate, dimethyl maleic acid chloride, citraconic anhydride, and citraconic acid chloride. In particular, unsaturated dicarboxylic acids or anhydrides thereof are preferred.

The amount (modified amount) of the unsaturated carboxylic acid or its derivative in the modified polyolefin is usually 0.1 to 10% by weight, preferably 0.1 to 10% by weight, based on the polyolefin.
It is 5 to 7% by weight, most preferably 1 to 5% by weight. If the amount of modification is less than 0.1% by weight, the adhesion to the polyamide or polyester forming the conductive component will be poor, and the conductive component and the protective component will peel off during spinning and stretching, making it difficult to form a yarn. On the other hand, when the amount of modification is 10% by weight or more, the thermal stability is deteriorated, and the composite spinning is often difficult, which is not preferable.

The conductive component, the protective component, and the adhesive component may include a dispersant (waxes, polyalkylene oxides, various surfactants, organic electrolytes, etc.), a coloring agent, and a heat stabilizer (antioxidant) as necessary. Agents, ultraviolet absorbers, etc.), flowability improvers and other additives.

The cross section (contour) of the conjugate fiber of the present invention may be circular or non-circular, and is not particularly limited, but the composite form of the conductive component A, the adhesive component B and the protective component C is important. That is, in the cross-sectional shape of the composite fiber, it is important that the adhesive component B is interposed between the conductive component A and the protective component C, and that at least a part of the conductive component A is exposed on the fiber surface in the fiber axis direction. . 1 to 5 are cross-sectional views of a composite fiber showing an example of a composite structure that can be used in the present invention. In the figure, A is a conductive component, C is a protective component, and B is an adhesive component. 1 and 2 are examples of a radiation type, FIG. 3 is an example of a keyhole type, FIG. 4 is an example of a multiplexed keyhole type, and FIG. 5 is an example of a parallel (side-by-side) type. Antistatic performance (antistatic property) by exposing conductive component to fiber surface
An electrically conductive composite fiber excellent in quality can be obtained. Further, by interposing an adhesive component that adheres to both the conductive component and the protective component that originally do not adhere to each other, it is possible to form a yarn.

With respect to the composite ratio (cross-sectional area occupancy) of the conductive component, a conductive component containing a large amount of conductive particles tends to have poor spinnability (spinnability) and high elongation.
It is preferably 0% or less, particularly preferably 30% or less, more preferably 20% or less. Although the composite ratio of the adhesive component varies depending on the single-fiber fineness of the fiber, the thickness L of the adhesive component in the fiber cross section is usually 0.3 μm or more, preferably 0.5 to 5 μm.
m is preferred. If the thickness L is too thin, there are many places where there is no adhesive component between the conductive component and the protective component due to uneven thickness,
Separation of the conductive component and the protective component is likely to occur, and in many cases, spinning becomes unstable. Conversely, if the thickness L is large, the composition ratio of the relatively expensive modified polyolefin in the fiber becomes high, which is disadvantageous in terms of cost. In addition, if the modified polyolefin has no fiber forming ability, yarn cannot be formed.

[0015]

The present invention will be specifically described below with reference to examples.

[0016]

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 referred to as CPI. Melt flow rate value (hereinafter,
The test method is ASTM D1238) 35 g / 10 min,
Conductive compound obtained by mixing and dispersing 35% by weight of conductive carbon black in polypropylene having a melting point of 152 ° C.
Let it be 2. A modified polypropylene having a melt flow rate of 17 g / 10 min and a melting point of 163 ° C. obtained by graft-polymerizing 2% by weight of maleic anhydride is referred to as AP1. Nylon 6 having a molecular weight of 16000 is designated as P1. A polypropylene having a melt flow rate of 23 g / 10 min and a melting point of 152 ° C. is designated as P2. CP1, CP2 is a conductive component A,
AP1 was used as an adhesive component B, P1 and P2 were used as protective components C, and these three or two components were compounded in a spinneret pack into a composite structure and a composite ratio shown in Table 1, and the temperature was 270.
Spinning from an orifice with a diameter of 0.25 mm and cooling at a speed of 700 m / min while cooling oiling 170
Denier / 24 filament undrawn yarn UDY1 to UD
Y6 was obtained.

[0017]

[Table 1]

Next, 85% of the undrawn yarns UDY1 to UDY6 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. DY5
In some cases, white spots appeared in the cup of the wound yarn. When this fiber was observed with an electron microscope, the thickness of the adhesive component varied from 0 to about 0.1 μm, and the conductive component and the protective component were separated in the white portion. on the other hand,
Similarly, DY1 was observed, but the thickness of the adhesive component was about 0.8.
It was stable at μm, and the conductive component and the protective component were sufficiently bonded. In the case of DY6, when the yarn was pulled out from the undrawn yarn bobbin, the fallout of the conductive component was scattered, and the wound yarn had a lot of fluff and thickness, and it was extremely difficult to draw.

Next, the above drawn yarns DY1 to DY4 are
The staples Y1 to Y4 were obtained by knitting the yarns to a denier of 100,000, crimping them by a stuffer-type crimping machine at about 15 pieces / 25 mm, and cutting them to a length of 51 mm. Staple Y1
The electric resistance value of Y4 is 3.3 × 10 ⁷ , 2.7 × 10
⁷ , 5.9 × 10 ⁷ , 1.4 × 10 ⁷ Ω / cm,
All had good conductive performance. Staple Y1
~ Y4, 15 single yarn 1.5 denier separately prepared / 25
mm crimp, 51mm cut length polypropylene (melt flow rate value 23g / 10min) staple cotton, blended at 10% by weight, carded, and weighed 50g / m
^Two webs were prepared, and these webs were heated to 160 ° C.
Roller pattern, cotton pressure 30Kg / cm, grid pattern (5mm
The corners) were embossed to produce nonwoven fabrics F1 to F4. 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.

[0020]

[Table 2]

The surface resistivity of the nonwoven fabric F1 is 2.3 × 10 ⁷
Ω is excellent in conductivity, but in the nonwoven fabric of F2 to F4,
In each case, the conductivity was inferior at 10 ¹⁰ Ω or more. Non-woven fabric F
For No. 3, a large number of conductive fibers came off when the surface was rubbed with flannel cloth. When the surface of the nonwoven fabric F2 was observed with a scanning electron microscope, the conductive component of the conductive conjugate fiber was cut and deformed into a droplet.

[0022]

Example 2 Polyethylene terephthalate having a molecular weight of 15000 and a melting point of 257 ° C., and a tin oxide film on the surface of 15%
And 1.5% antimony oxide mixed and fired with titanium oxide particles having
A conductive compound obtained by mixing and dispersing 65% by weight of conductive particles of 5 μm and specific resistance of 4.0 Ωcm is referred to as CP3. C
P3 is a conductive component A, AP1 of Example 1 is an adhesive component B, P
2 as a protective component C, a composite ratio A / B / C = 10/1
A staple Y7 was prepared under the same conditions as in Example 1 except that the composite was formed into a side-by-side type as shown in FIG. Y7 had a good electrical conductivity of 3.2 × 10 ⁷ Ω / cm.
Y7 was mixed with the polypropylene cotton of Example 1 at a mixing ratio of 10% and carded to prepare a web. Next, this web was embossed into a lattice shape at a linear pressure of 30 Kg / cm with a roller at 160 ° C. to produce a nonwoven fabric. The surface resistivity of this nonwoven fabric was 5.4 × 10 ⁸ Ω, which was excellent in conductivity.

[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 a non-crimped state or in a crimped state, it can be mixed with a nonwoven fabric of a polyolefin material by a known method, and antistatic properties can be imparted to a product. Of course, it can be mixed with fiber products of other materials other than polyolefin, and the mixing ratio to fiber products is usually 0.1 to
About 5% by weight, 5 to 100% by weight or 0.1% depending on the purpose.
In some cases, an incorporation ratio of less than 1% by weight is applied.

[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 specific example of a composite structure of the conductive composite fiber of the present invention.

FIG. 6 is a comparative example of a composite structure of a two-component conductive composite fiber used to show the superiority of the present invention.

FIG. 7 is a comparative example of a composite structure of a two-component conductive composite fiber used to show the superiority of the present invention.

[Explanation of symbols]

 A Conductive component of conductive composite fiber B Conductive component of conductive composite fiber C Conductive component of conductive composite fiber

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-2808 (JP, A) JP-A-57-191324 (JP, A) JP-A-6-272113 (JP, A) JP-A 62-1982 21819 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) D01F 8/00-8/16

Claims (3)

(57) [Claims] 1. A conductive component A comprising a thermoplastic polyamide or polyester containing conductive particles, an adhesive component B comprising a modified polyolefin obtained by graft polymerization of an unsaturated carboxylic acid or a derivative thereof, and a protective component comprising a fiber-forming polyolefin. A ternary composite fiber comprising C, wherein a B component having a thickness of 0.3 μm or more is interposed between the A component and the C component, and at least a part of the A component is exposed on the fiber surface. Characteristic conductive composite fiber. 2. The graft polymerization amount of the unsaturated carboxylic acid or its derivative as the component B is 0.1 to 0.1 with respect to the polyolefin.
The conductive conjugate fiber according to claim 1, wherein the amount is 10 to 10% by weight. 3. An unsaturated carboxylic acid or a derivative thereof,
The conductive conjugate fiber according to claim 1, which is an unsaturated dicarboxylic acid or an anhydride thereof.