JPH0122365B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a conductive composite fiber and a method for manufacturing the same. Composite fibers in which a conductive layer made of a polymer mixed with conductive particles, such as metal particles or carbon black, and a non-conductive layer made of a fiber-forming polymer are bonded together are well known, and can be mixed with other fibers to provide antistatic properties. It is used for purposes such as giving. However, fibers mixed with carbon black have the disadvantage of being colored black or gray, and furthermore, if a large amount of carbon black is mixed into the spinning material (enough to impart conductivity), it exhibits structural viscosity and significantly reduces fluidity. In addition, carbon black is deposited inside the spinning device, making it difficult to perform stable spinning for a long period of time. On the other hand, it is very difficult to produce metal particles with a particle size of 1 μm or less, especially 0.5 μm or less, and ultrafine particles are extremely expensive and have little practical use. Furthermore, metal particles with smaller particle sizes tend to fuse (sinter) with each other due to high temperature and pressure during melt kneading and melt spinning, and become coarse or precipitate as metal lumps. Very difficult. An object of the present invention is to provide a conductive composite fiber that is less colored and relatively easy to manufacture. Another object is to provide a method for manufacturing such conductive composite fibers industrially easily and at low cost. That is, the present invention comprises a non-conductive layer made of a fiber-forming polymer, 50 to 15% by weight of a crystalline thermoplastic polymer having a melting point at least 30° C. lower than that of the polymer, and titanium oxide particles having a conductive coating. 50-85% by weight
and a conductive layer consisting of the above are bonded together, and the conductive film is formed of 50% by weight or more of a metal oxide and 50% by weight or less of a metal and/or an oxide of a metal different from the metal oxide. The conductive composite fiber is characterized by: The fiber of the present invention is characterized by the use of titanium oxide having a conductive film as the conductive particles. Metal films are also available as conductive films, but metal films have the drawback of being unstable and susceptible to deterioration and modification due to oxidation and the like. Some metal oxides are stable and conductive, such as copper oxide, silver oxide, zinc oxide, cadmium oxide, tin oxide, lead oxide, and manganese oxide. In particular, by using these metal oxides as the main component (50% or more, especially 75% or more) and adding a small amount (50% or less) of the second component, the conductivity can be significantly increased (for example, about 10 ³ Ω・cm). ) and is suitable for the purpose of the present invention. Examples of the second component include oxides of different metals and/or the same or different metals. For example, copper oxide/copper, zinc oxide/aluminum oxide, tin oxide/antimony oxide, zinc oxide/zinc/aluminum oxide/aluminum, tin oxide/
Suitable are those containing tin/antimony oxide/antimony and partially reduced oxides thereof. There are various methods and amounts of mixing the second component (conductivity improving component), but any other component other than the above may be used as long as it is effective and stable for improving conductivity. Titanium oxide with a conductive metal oxide film is
Specific resistance in powder form is approximately 10 ⁴ Ω・cm (order)
Below, it is particularly preferable to be about 10 ² Ω・cm or less, and 10 ¹
The most preferable value is approximately Ω·cm or less. Actually 10 ² Ω・
cm to ^{10 -2} Ω·cm have been obtained, and can be suitably applied to the purpose of the present invention. (Those with even better conductivity are even more preferred). The specific resistance of the powder is determined by placing 10 g of the sample in a cylinder with a diameter of 1 cm.
Measurement is performed by applying a pressure of 200 kg from the top of the r-packed tube with a piston and applying direct current (0.1 to 1000 V). It is desirable that the conductive particles have a small particle size from the viewpoint of spinnability and conductivity. For example, the average particle size is 1μm
Below, especially 0.7μm or less, most preferably 0.5μm or less
0.01 μm is used. Generally, the smaller the particle size, the better the conductivity of the mixture when mixed with a polymer. Particles with a particle size of 1 μm or more are not impossible to use, but their performance is significantly inferior. Normally, titanium oxide is commercially produced as a white pigment with a particle size of 0.2 μm or less, and a conductive coating is added to it to increase the particle size.
It is possible to obtain particles with a diameter of about 0.3 μm or less. The conductive film can be formed, for example, by vacuum evaporation, by depositing a metal compound (for example, an organic acid salt), baking it to form an oxide, or by partially reducing it. The conductive film preferably has sufficient conductivity and has little coloring, and is preferably one containing zinc oxide or tin oxide as a main component, and among them, one having zinc oxide as a main component is most preferable because it has little coloring. Any known thermoplastic polymer can be used as the polymer to be mixed with the conductive particles to form the conductive layer. Examples include polyamide, polyester, polyolefin, polyvinyl, polyether, polycarbonate, and many others. Although fiber-forming polymers are preferable from the viewpoint of spinnability, for the purpose of the present invention, polymers with poor spinnability may also be used (as long as composite spinning is possible).
From the viewpoint of conductivity, crystallinity of 40% or more is used, preferably 50% or more, most preferably
60% or more is preferable. According to the findings of the present inventors, when mixing with low crystallinity (including non-crystalline) polymers, the mixing ratio (weight ratio) of conductive particles is extremely high, for example 80 to 95% ( In many cases, sufficient conductivity cannot be obtained unless the weight is reduced. On the other hand, when mixed with a highly crystalline polymer, sufficient conductivity is often obtained at a relatively small mixing ratio, for example, about 50 to 80%, particularly about 50 to 70%. Needless to say, the higher the mixing ratio of conductive particles, the lower the fluidity of the mixture and the difficulty of spinning, and the lower the drawability and the strength and elongation of the obtained fibers. The lower the better. That is, a polymer with high crystallinity is preferred. The reason why highly crystalline polymers have better conductivity is unknown, but when melted, the particles are uniformly dispersed in the polymer, but when it solidifies or is stretched, the polymer crystallizes. It is assumed that this is because, as the process progresses, particles are removed from the crystal parts, concentrated between the crystals, and come close to or in contact with each other to form a conductive structure. For example, conductive titanium oxide powder (specific resistance 12Ω cm) 75%, crystalline paraffin
A mixture consisting of 25% exhibits high resistance (specific resistance of 10 ⁸ Ω cm or more) close to that of an insulator when melted (the same applies to liquid paraffin), but when cooled and solidified (crystallized), it exhibits excellent conductivity (specific resistance). 10 ² to 10 ⁴ Ω・cm). (On the other hand, in the case of carbon black,
Excellent conductivity can be obtained even with amorphous polymers,
Conversely, highly crystalline polymers often have poor conductivity because the crystals break the chain of particles. ) As mentioned above, a structure in which the conductive particles are in contact with each other or in close proximity to each other is preferred in order to obtain high conductivity. However, such a structure may be destroyed or cut during the process of drawing the spun fibers. (On the other hand, stretching may cause the particles to align and grow a conductive structure.) One way to prevent the destruction of the conductive structure due to stretching is to make part or all of the polymer forming the conductive layer non-conductive. In this method, a crystalline polymer having a melting point lower than that of the layer polymer is used, and stretching is performed in a temperature range between that of the non-conductive layer polymer and the low melting point polymer. In this method, the low melting point polymer is molten during stretching, and is then cooled and solidified (crystallized) to grow the conductive structure. For example, a polymer with a melting point of 150°C or higher is used as the non-conductive layer polymer, and a polymer with a melting point of 30°C or higher (preferably 50°C or higher) than that of the non-conductive layer polymer is used as the conductive layer polymer.
℃ or higher, most preferably 80% or higher), and can be composited and stretched at a temperature between the melting points of both polymers, for example, 50 to 260℃, especially 80 to 200℃. The second method is to regrow the conductive structure destroyed by stretching by heating and cooling. For example, if the drawn yarn is above the melting point of the low melting point polymer,
The conductive structure can be regrown by heating under tension or relaxation to a temperature below the melting point of the non-conductive layer polymer, followed by cooling. In this case as well, the melting points of both polymers are within the above range, i.e. 30°C.
Composites are made by combining materials with the above differences, but it is preferable that the difference be 50° C. or more. Since the polymer must be solidified (crystallized) at the temperature at which the fiber is used, the melting point of a low melting point polymer is 40℃.
or more, preferably 80°C or more, most preferably 100°C or more
It is desirable that the heat treatment temperature is 50 to 260 °C, particularly 80 to 240 °C. Generally, undrawn yarn is heated to too high a temperature (150℃ or higher, especially 200℃)
(above)), it is often difficult to stretch the
The second method has a wider range of applications than the first method. The mixing ratio of conductive particles in the conductive layer varies depending on the conductivity, purity, structure, particle size, chain-forming ability of the particles, the nature and type of the polymer to be mixed, and the degree of crystallinity, but is between 50 and 85%. Weight%, preferably 60-80
It is about % by weight. If it exceeds 85% by weight, the mixing operation will be difficult, and the fluidity of the resulting mixture will decrease, making spinning difficult. On the other hand, if it is less than 50% by weight, it becomes difficult to obtain sufficient conductivity. Moreover, if it exceeds 80% by weight, fluidity is insufficient, so it is often necessary to use a fluidity improver. In addition to the conductive titanium particles, different kinds of conductive particles can be used in combination for the purpose of improving the dispersibility, conductivity, spinnability, etc. of the particles. For example, metal oxides such as tin oxide, zinc oxide, zirconium oxide, indiram oxide, iron oxide, and bismuth oxide (preferably those with little coloring and high conductivity), copper, silver, nickel, iron, aluminum, and other metal particles. can be mixed. When used in combination, the mixing ratio of conductive titanium oxide may be lower than the above range, but the main component (50% or more) of the conductive particles is conductive titanium oxide. in any case,
The specific resistance of the conductive layer of the composite fiber must be approximately 10 ⁶ Ω·cm or less, particularly preferably 10 ⁴ Ω·cm or less, and most preferably 10 ² Ω·cm or less. The conductive layer further contains a dispersant (e.g. wax,
Polyalkylene oxides, various surfactants, organic electrolytes, etc.) colorants, pigments, stabilizers (antioxidants, ultraviolet absorbers, etc.), fluidity improvers, and other additives can be added. As the fiber-forming polymer forming the non-conductive layer (protective layer) of the composite fiber, any material that can be melt-spun may be used. For example, polyamides such as nylon 6, nylon 66, nylon 12, and nylon 610, polyesters such as polyethylene terephthalate, polyethylene oxybenzeate, and polybutylene terephthalate, polyolefins such as polypropylene and polyethylene, polyvinyl chloride,
Polyvinyl polymers such as polyvinylidene chloride and copolymers and modified products of these polymers are used. Additives such as pigments, colorants, stabilizers, antistatic agents (polyalkylene oxides, various surfactants, etc.) can be added to the fiber-forming polymer. Composite (joining) of conductive and non-conductive components
can be in any format. Figures 1 to 8 show typical composite types (shaded areas indicate conductive layers). Figure 1 is a core/sheath type (the sheath is also a conductive layer type), and Figure 2 is a side-by-side type. Type, 3rd
The figure shows an example of a three-layer type, FIG. 4 a radial type, FIG. 5 a multiple side-by-side type, FIG. 6 a multi-core type, FIG. 7 a multi-layer type, and FIG. 8 an example of a non-circular core type. Of course, any combination other than the above is possible, and the shape of the fibers may be circular or non-circular. The area ratio occupied by the conductive layer in the cross section of the composite fiber, that is, the composite ratio is arbitrary. This is because there is almost no need to consider the whiteness of the fibers. However, in general, a conductive layer mixed with a large amount of conductive particles tends to be inferior in strength, elongation, etc., so the composite ratio is often preferably about 3 to 80%, particularly about 5 to 60%. The fibers of the present invention can be easily manufactured to be white or nearly white, and are suitable for manufacturing white or light-colored textile products for which carbon black conductive threads are unsuitable. The fiber of the present invention is in the form of a continuous filament or stable and can be mixed with other chargeable fibers to impart antistatic properties to textile products. The mixing rate is usually about 0.1 to 10%, but depending on the purpose, a mixing rate of 10 to 100% or 0.1% or less may be applied. The mixing may be carried out by blending, doubling, twisting, blending, weaving, knitting, or any other known method. The present invention will be explained below with reference to Examples. Parts and percentages indicate weight ratios unless otherwise specified. Example 1 A zinc oxide coating (approximately 15% by weight) was formed on titanium oxide with an average particle size of 0.05 μm, and 4% aluminum oxide fine particles (particle size 0.02 μm) were mixed and fired to produce conductive powder A ₁ I got it. Powder _A1 has an average particle size of 0.06 μm, a specific resistance of 12 Ω·cm, and is almost white (slightly gray-blue). Polymer _P1 is a low-density polyethylene with a molecular weight of about 50000, a melting point of 102°C, and a crystallinity of 37%. Polymer _P2 is high-density polyethylene with a molecular weight of about 48000, a melting point of 130°C, and a crystallinity of 77%. Polyethylene oxide having a molecular weight of about 63,000, a crystallinity of about 55%, and a melting point of 55°C is used as polymer _P3 . 90 parts of a random copolymer with a molecular weight of approximately 20,000 consisting of 75 parts of ethylene oxide component/25 parts of propylene oxide component and 10 parts of bishydroxyethyl terephthalate.
245° C. for 6 hours under reduced pressure (0.5 Torr) using antimony trioxide (600 ppm) as a catalyst. Polyether ester with a molecular weight of approximately 75,000 is a high viscosity liquid (crystallinity 0%) at room temperature.
Let's say P ₄ . Polymer P5 is nylon ₆ with a molecular weight of about 16,000, a melting point of 215°C, and a crystallinity of 45%. A mixed polymer obtained by kneading powder A ₁ with polymers P ₁ to _{P 5} at a mixing ratio of 60% and 75%, respectively, was used for the core, and a mixture of polymer P ₅ and titanium oxide at 1% was used for the sheath. The structure shown in the figure is compounded at a compounding ratio of 1/10 (cross-sectional area ratio), spun at 270℃ from an orifice with a diameter of 0.3mm, cooled and oiled, wound at a speed of 1000m/min, and placed on a pin at 80℃. Stretch 3.1 times to 20
Drawn yarns Y ₁ to Y ₁₀ of denier/3 filaments were obtained. Table 1 shows the core polymer and conductive particle mixing ratio of each fiber and the electrical resistance per 1 cm of single yarn length.

[Table] Yarns Y ₁ to _{Y 10} are each drawn nylon 6 yarn (2600d/
144f) and crimping, and the combined yarn is
A tufted carpet (loop) was manufactured by using one thread for one course and using nylon 6-wrap crimped yarn (2600d/144f) for the other three courses. The electrostatic potential of the human body when walking on the resulting carpet with leather shoes (25°C, 20% RH) was as shown in Table 2. For comparison, the voltage charged on the human body when walking on a carpet made of only 6-wrap nylon crimped yarn is also shown.

[Table] The yarns Y ₁ to Y ₄ were heat-treated by relaxing them by 3% at 150° C. and are designated as HY ₁ to HY ₄ , respectively. _HY1〜
The electrical resistance of HY ₄ is shown in Table 3, and a considerable improvement in conductivity was observed.

[Table] Example 2 Titanium oxide particles with an average particle size of 0.04 μm formed with a tin oxide film (approximately 12% by weight) were mixed with 5% antimony oxide particles (particle size 0.02 μm) and fired. Let the conductive powder be _A2 . Powder A ₂ had an average particle size of 0.05 μm, a specific resistance of 9 Ω·cm, and was almost white (slightly gray-blue). 60% of powder A ₂ using polymer P ₅ of Example 1;
A conductive layer was prepared by mixing 70% of titanium oxide with polymer _P5 , and a protective layer was prepared by mixing 2% of titanium oxide with Polymer P5.They were combined as shown in Fig. 3 (composite ratio 1/8), and the yarn Y of Example 1 was prepared as follows. Spun and drawn the same way as in step ₉ to make each yarn.
Y ₁₁ and Y ₁₂ were obtained. The electrical resistance of yarn Y ₁₁ and Y ₁₂ is
They were 1.1×10 ¹¹ and 8.5×10 ⁹ Ω/cm. Example 3 Consisting of particles A ₁ of Example 1 and polymer P ₂ ,
The core is a mixture of particles with a mixing ratio of 70%, and the molecular weight is approx.
18000 polyethylene terephthalate was used as a sheath and composited at a composite ratio of 1/9 into a cross section as shown in Figure 8.
Spun from an orifice with a diameter of 0.25 mm at 278°C, oiled, wound at a speed of 1500 m/min, and heated at 80°C.
The yarn was drawn 3.15 times and further heat-treated at 180° C. under tension to obtain drawn yarn Y ₁₃ of 30 denier/6 filaments. The electric resistance of a single yarn of yarn Y ₁₃ was 1.0×10 ¹⁰ Ω/cm. In addition, when the composite fiber in which the conductive part of the core is placed is near a charged object, the sheath breaks down and eliminates the charge by corona discharge, but as shown in Figure 8, if the core has one or more When the shape has a pointed tip, the above-mentioned dielectric breakdown occurs easily and the antistatic property is excellent. In order to form such a tip, it is preferable that the conductive particles have a smaller particle size, and those having a particle size of 0.1 μm or less are most preferable. Even if the conductive layer is exposed on the fiber surface, for example, those with pointed ends as shown in Figures 3 and 4 tend to cause corona discharge and have excellent antistatic properties, and the same applies to these as well. It is desirable that the particle size is small.

[Brief explanation of drawings]

FIGS. 1 to 8 show specific examples of cross sections of the composite fibers of the present invention, and the shaded areas in the figures indicate conductive layers.

Claims (1)

[Scope of Claims] 1. A non-conductive layer consisting of a fiber-forming polymer, 50 to 15% by weight of a crystalline thermoplastic polymer having a melting point at least 30°C lower than that of the polymer, and an oxidized layer comprising a conductive coating. and a conductive layer consisting of 50 to 85% by weight of titanium particles, and the conductive film is
1. A conductive composite fiber comprising 50% by weight or more of a metal oxide and 50% by weight or less of a metal and/or an oxide of a metal different from the metal oxide. 2. Claim 1 in which the titanium oxide conductive film contains zinc oxide or tin oxide as a main component.
Scope stated in section. 3. The fiber according to claim 1, wherein the fiber-forming polymer is polyamide, polyester, polyether, vinyl polymer or polyolefin.