JP4598784B2 - Conductive composite fiber - Google Patents

Description

  The present invention relates to a conductive composite fiber in which polylactic acid containing conductive particles is a conductive component and a non-conductive component is a polyester resin, and is used for clothing such as antistatic work clothes and uniforms, and interiors such as curtains. The present invention relates to a conductive composite fiber that can be suitably used as a charging brush and a cleaner brush used in electrophotographic recording type dry copying machines, facsimiles, printers and the like as well as uses and industrial materials.

  Fibers made of hydrophobic polymers such as polyester, polyamide, and polyolefin have many advantages such as mechanical properties, chemical resistance, and weather resistance, and are widely used not only for clothing but also for industrial materials. However, these fibers generate significant static electricity due to friction, etc., which reduces the aesthetics by sucking in dust in the air, gives an electric shock to the human body, and gives discomfort to the human body. In addition, there are cases where problems such as flammable explosions to flammable substances may occur, and many studies have been made to impart conductivity to solve these problems.

  Patent Document 1 describes a core-sheath type composite fiber in which a conductive component containing conductive particles such as conductive carbon black and metal powder is wrapped with a nonconductive polymer. With such a core-sheath type composite fiber, the conductive particles are present only inside the fiber, so troubles during operation are unlikely to occur, and it is possible to obtain good operability. However, since the conductive particles exist only inside the fibers, the conductive performance is insufficient.

  On the other hand, Patent Document 2 describes a core-sheath type conductive composite fiber in which a conductive component containing conductive particles is arranged in a sheath part. Compared with the fiber described in Patent Document 1, such a conductive conjugate fiber was quite satisfactory in the conductive performance, but trouble during operation was likely to occur.

  However, synthetic fibers such as polyolefins and polyamides, including such aromatic polyester fibers, are difficult to be decomposed even after being used in the natural world, causing various problems in terms of protecting the global environment. . For example, these daily apparel are difficult to disassemble and are partly recycled after use, but most of them require treatment such as incineration, so that their disposal is limited.

  Furthermore, these synthetic fibers are made from petroleum, and as a result of mass consumption, the problem of depletion of fossil resources has been raised. Under such circumstances, the development of polymer materials that decompose in the natural environment is eagerly awaited, and research and development of various polymers such as aliphatic polyesters, and attempts to put them into practical use are active. Attention has been focused on polymers that are degraded by microorganisms, that is, biodegradable polymers.

  On the other hand, most of the conventional polymers are made from petroleum, but by consuming a large amount of petroleum resources, carbon dioxide that has been stored in the earth since the geological era is released into the atmosphere, which further increases global warming. There is a concern that it will become serious. However, if a polymer can be synthesized using plant resources that grow by taking in carbon dioxide from the atmosphere, it is possible not only to suppress global warming by carbon dioxide circulation, but also to solve the problem of resource depletion at the same time. . For this reason, attention has been focused on polymers made from plant resources, that is, biomass polymers.

  Based on the above, biodegradable polymers using biomass attract great attention and are expected to replace conventional polymers made from petroleum resources.

In particular, polylactic acid is currently the most popular polymer for biomass utilization. Polylactic acid is a polymer made from lactic acid obtained by fermenting starch extracted from plants, and has the best balance of mechanical properties, heat resistance, and cost among polymers using biomass. Has been used. However, there is a problem that mechanical properties and heat resistance are inferior to those of conventional synthetic fibers.
JP 09-143821 A WO2002 / 075030

  The present invention solves the above-mentioned problems and has sufficient conductivity performance and strength in spite of the use of polylactic acid in part, resulting in a decrease in strength under a high temperature atmosphere. It is suitable for clothing such as clean room and medical work uniforms, interior use and materials such as curtains, and charging used for electrophotographic recording type dry copying machines, facsimiles, printers, etc. An object of the present invention is to provide a conductive composite fiber that can be suitably used for brushes and cleaner brushes.

  The inventors of the present invention have arrived at the present invention as a result of studies to solve the above problems.

That is, the present invention provides a non-conductive component composed of polyethylene terephthalate obtained by copolymerizing 5 to 20 mol% of at least one component among isophthalic acid and cyclohexanedicarboxylic acid, and a conductive component composed of polylactic acid containing conductive particles. A conductive composite fiber having a shape in which the proportion of the conductive component is 10 to 60% by mass of the entire fiber, and at least a part of the conductive component is exposed on the fiber surface, The gist of the present invention is a conductive conjugate fiber having a resistance value of 1 × 10 ⁴ Ω / cm to 9 × 10 ¹² Ω / cm.

  Hereinafter, the present invention will be described in detail.

  The conductive conjugate fiber of the present invention is composed of a non-conductive component made of a polyester resin and a conductive component made of polylactic acid containing conductive particles.

  The polylactic acid referred to in the present invention includes poly-D-lactic acid, poly-L-lactic acid, poly-DL-lactic acid that is a copolymer of poly-D-lactic acid and poly-L-lactic acid, poly-D-lactic acid, and poly-L-lactic acid. (Stereo complex), poly D-lactic acid and hydroxycarboxylic acid copolymer, poly L-lactic acid and hydroxycarboxylic acid copolymer, poly D-lactic acid or poly L-lactic acid and aliphatic dicarboxylic acid, and Copolymers with aliphatic diols or blends thereof can be used.

  The polylactic acid is one in which L-lactic acid and D-lactic acid are used alone or in combination as described above, and among them, the melting point is preferably 150 ° C. or higher.

  The melting point of L-lactic acid and D-lactic acid, which are homopolymers of polylactic acid, is about 180 ° C., but in the case of a copolymer of D-lactic acid and L-lactic acid, the proportion of any component is about 10 mol%. Then, the melting point is about 130 ° C.

  Therefore, as polylactic acid, L / D or D / which is the content ratio (molar ratio) of L-lactic acid and D-lactic acid indicated by the content ratio of L-lactic acid or D-lactic acid when polymerizing using lactide as a raw material. L is preferably 90/10 or more, more preferably 95/5 or more, and even more preferably 97/3 or more.

  Among polylactic acids, a mixture (stereo complex) of poly D-lactic acid and poly L-lactic acid as described above is particularly preferable because it has a high melting point of 200 to 230 ° C. and high strength in a high temperature atmosphere. .

  The number average molecular weight (Mn) of the polylactic acid described above is not particularly limited, but is preferably 60000 or more and 90000 or less. When Mn of polylactic acid is smaller than 60000, the meltability is likely to deteriorate due to low viscosity at the time of melting. Moreover, when the number average molecular weight of polylactic acid is larger than 90,000, it will become high viscosity at the time of a melt | dissolution, and it will be easy to worsen a spinning property.

  Next, as the polyester resin of the non-conductive component, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene terephthalate (PPT), etc. can be used, and those singly or blended or copolymerized are also used. be able to.

  In the case of PET, the copolymer component is preferably PET obtained by copolymerizing at least one of isophthalic acid (IPA), cyclohexanedimethanol (CHDM), and cyclohexanedicarboxylic acid (CHDA).

  By using the copolymerized polyester as the copolymer component, not only the compatibility with the polylactic acid, which is a conductive component, is improved, but also the reaction temperature during the polycondensation reaction can be lowered. The temperature can also be lowered. Thus, since the thermal decomposition reaction of the polymer at the time of polycondensation reaction and spinning can be suppressed, it is possible to obtain a conductive composite fiber excellent in quality, heat resistance, and heat and humidity resistance.

  Especially, it is preferable to set it as the copolymerization PET which copolymerized 5-20 mol% of at least 1 component among IPA, CHDM, and CHDA. When the copolymerization amount is less than 5 mol%, the melting point does not drop much compared to ordinary polyester, so the polycondensation reaction temperature and spinning temperature cannot be lowered, and the effect of improving the heat and moisture resistance tends to be insufficient. When the copolymerization amount exceeds 20 mol%, the amorphous region in the fiber increases, so that not only the operability is deteriorated, but also a structure that is susceptible to hydrolysis reaction, so that the heat-and-moisture resistance performance tends to be lowered. .

  Among polyesters, PBT or PTT is preferably used. Since PBT and PTT are resins with very high crystallinity, they are not easily subjected to hydrolysis reaction, have high heat-and-moisture resistance, and have high strength retention in a high-temperature atmosphere.

  The conductive particles contained in polylactic acid, which is a conductive component, include carbon black, metal powder (silver, nickel, copper, iron, tin, or alloys thereof), copper sulfide, copper iodide, zinc sulfide, sulfide Examples thereof include metal compounds such as cadmium. In addition, a small amount of antimony oxide may be added to tin oxide, or a small amount of aluminum oxide may be added to zinc oxide to form conductive particles.

  Furthermore, it is also possible to use a conductive particle obtained by coating the surface of titanium oxide with tin oxide and mixing and baking antimony oxide. Among these, carbon black (acetylene black, ketjen black, etc.) is preferable because it hardly inhibits polymer fluidity compared to other metal particles.

  The particle size of the conductive particles is not particularly limited, but it is preferable that the average particle size is 1 μm or less. When it exceeds 1 μm, the dispersibility of the conductive particles in the polymer tends to be deteriorated, and the fiber tends to have a deteriorated conductive performance and high elongation property.

  The content of the conductive particles in the conductive component may be appropriately selected depending on the type of conductive particles, conductive performance, particle diameter, particle chain-forming ability, and characteristics of the polymer used. It is preferable to set it as -70 mass%, More preferably, it is 10-30 mass%. If the content is less than 5% by mass, the conductive performance may be insufficient, and if it exceeds 70% by mass, it is difficult to uniformly disperse the conductive particles in the polymer.

  Further, in the conductive component and the non-conductive component, 1,3-propanediol, sebacic acid, dimer acid, dodecanedioic acid, xylylene are included as other copolymerization components as long as the effects of the present invention are not impaired. Glycol, polytetramethylene glycol, polyethylene glycol and the like may be contained.

  Depending on the purpose, waxes, polyalkylene oxides, various surfactants, organic electrolytes and other dispersants and antioxidants, UV absorbers and other stabilizers, matting agents, colorants, pigments, fluidity An improving agent and other additives can also be added.

  A terminal blocking agent may be added to both the conductive component and the non-conductive component in order to further improve the heat and moisture resistance. Specific examples of the end-capping agent include carbodiimide compounds such as N, N′-bis (2,6-diisopropylphenyl) carbodiimide, and epoxy compounds such as phenyl glycidyl ether.

  Next, the composite form of the conductive conjugate fiber of the present invention will be described with reference to the drawings. 1-3 is a schematic diagram showing a cross-sectional shape cut perpendicularly to the longitudinal direction of the fiber of the conductive conjugate fiber of the present invention.

  In the conductive conjugate fiber of the present invention, at least a part of the conductive component is exposed on the fiber surface. As shown in FIGS. 1 and 2, a part of the conductive component is exposed on the fiber surface, or as shown in FIG. 3, the conductive component covers the entire fiber surface, And a sheath-and-shell-shaped one in which the sheath is a conductive component and the core is a non-conductive component. In particular, in applications where heat resistance and heat-and-moisture resistance are required, it is preferable to use the shape shown in FIGS. In addition, these shapes are less likely to generate cracks or drop off.

  As shown in FIGS. 1 (a) to 1 (d), a part of the conductive component is exposed on the fiber surface, and a part of the fiber surface is covered with the conductive component. A conductive component is present in a non-conductive component, and a part of the conductive component (one side of a substantially triangular shape) is exposed on the fiber surface. The shape of the conductive component is not particularly limited, and may be quadrangular or semicircular.

  FIG. 1 (a) shows that the number of conductive components is one and the number of exposed portions on the fiber surface is one, and (b) shows that the number of conductive components is two and exposed on the fiber surface. There are two places, (c) is three places where the number of conductive components is exposed on the fiber surface, and (d) is four places where the number of conductive components is exposed on the fiber surface. This is an example where there are four locations.

  As for the location exposed to the fiber surface of an electroconductive component, 2-20 locations are preferable, and it is preferable that it is 3-8 locations especially. If there is only one spot exposed on the fiber surface of the conductive component, there are many parts where polylactic acid is exposed on the fiber surface, which is not only inferior to heat resistance and heat-resistant heat treatment, but also subjected to load due to wearing, etc. If a crack occurs, breaks, or falls off, the conductive performance becomes insufficient, and the original conductive performance may not be maintained.

  On the other hand, when the number of places exposed on the fiber surface of the conductive component exceeds 20, cracks and dropping off after the wet heat treatment tend to occur.

  Furthermore, as the shape of the conductive conjugate fiber of the present invention, there are two or more portions exposed on the fiber surface of the conductive component, and the conductive component has a shape communicating with the vicinity of the fiber center portion. preferable. As an example, the ones shown in FIGS.

  In FIG. 2A, the conductive component is arranged in a straight line through the vicinity of the center of the fiber, and there are two portions exposed on the fiber surface. In (b), the conductive component is arranged in a cross shape through the vicinity of the center of the fiber, and there are four portions exposed on the fiber surface. In (c), the conductive component is arranged in a shape divided into three sides through the vicinity of the center of the fiber, and there are three portions exposed on the fiber surface.

  As described above, the conductive component communicates in the vicinity of the center of the fiber and is exposed at two or more positions on the fiber surface, so that there are a large number of conductive contacts on the fiber surface, and the center between the contacts is present. Since electrical flow is possible in multiple directions by conducting through the section, a fiber having excellent conductivity can be obtained. For this reason, it is preferable that the part exposed to the fiber surface of an electroconductive component shall be 3 or more places especially.

  Moreover, in the electroconductive composite fiber of this invention, the ratio of an electroconductive component is 10-60 mass% of the whole fiber, and it is preferable that it is 30-50 mass% especially. When the composite ratio of the conductive component is less than 10% by mass, not only the conductive performance may be insufficient, but also the heat resistance and heat and humidity resistance are inferior. On the other hand, when the composite ratio of the conductive components exceeds 60% by mass, the yarn quality performance such as the strength and elongation characteristics is inferior, and troubles during operation and cracks after sterilization are likely to occur.

The conductive conjugate fiber of the present invention has an electrical resistance value of 1 × 10 ⁴ Ω / cm to 9 × 10 ¹² Ω / cm as a conductive performance, and in particular, 1 × 10 ⁵ Ω / cm to 1 × 10 ^7. It is preferably Ω / cm. When the electrical resistance value of the composite fiber exceeds 9 × 10 ¹² Ω / cm, the conductive performance becomes insufficient depending on the application to be used. When the electrical resistance value of the conductive conjugate fiber is 9 × 10 ¹² Ω / cm or less, when the obtained woven or knitted fabric is used in a normal environment, the knitted or knitted fabric can be hardly charged.

On the other hand, if it is attempted to make it less than 1 × 10 ⁴ Ω / cm, it is necessary to contain a large amount of conductive particles in the polymer, which not only adversely affects the physical properties of the fiber but also easily causes troubles during spinning and stretching.

In addition, the electrical resistance value of the conductive conjugate fiber in the present invention is measured as follows according to the AATCC76 method. Conductive conjugate fiber (which may be either multifilament or single yarn) is cut to about 15 cm in the length direction, and 10 samples are collected. Apply keratin cream to the surface of both ends of this sample, connect this surface part to a metal terminal, apply a 50V direct current with a sample measurement length of 10 cm, and measure the current value. Is calculated. The arithmetic average value of the calculated electric resistance values of 10 samples is used.
Electric resistance value = E / (I × L)
E: Voltage (V) I: Measurement current (A) L: Measurement length (cm)

Next, the strength retention performance at high temperatures of the conductive conjugate fiber of the present invention will be described.
In the present invention, when the strength in the 25 ° C. atmosphere is 100%, the strength in the 120 ° C. atmosphere needs to be 40% or more of the strength in the 25 ° C. atmosphere. That is, the strength retention in an atmosphere at 120 ° C. is 40% or more.

The strength of the conductive conjugate fiber was measured at 25 ° C in a constant temperature layer set to surround the sample gripping part of the tensile tester with an orientec tensile tester. taking measurement. Thereafter, the temperature in the constant temperature layer is set to 120 ° C., and then the strength in an atmosphere at 120 ° C. is measured. At the time of measurement, after the temperature in the thermostatic layer reaches 25 ° C. or 120 ° C., the sample is measured after being held for 1 minute.
From the measured strength, the strength retention is calculated using the following formula.
Strength retention (%) = [(strength at 120 ° C. atmosphere) / (strength at 25 ° C. atmosphere)] × 100

  The conductive conjugate fiber of the present invention is a conjugate fiber composed of polylactic acid and a polyester resin, and has a shape in which at least a part of the conductive component is exposed on the fiber surface, so that the strength retention at a high temperature is 40. % Or more, and more preferably 50% or more.

  If the strength retention rate is less than 40%, the decrease in strength increases during exposure to high temperatures and high humidity during washing, ironing, and industrial materials for clothing, and the fibers are cut. Or poor quality. Furthermore, due to this, the conductive performance is also lowered.

  In addition, in the fiber which consists only of normal polylactic acid, the intensity | strength retention in a high temperature atmosphere will be 10% or less.

  Furthermore, in the conductive conjugate fiber of the present invention, it is preferable to add a terminal blocking agent to both the non-conductive component and the conductive component so that the carboxyl end group is 25 grams equivalent / ton or less.

  By using a resin having a carboxyl end group of 25 gram equivalent / ton or less, hydrolysis is suppressed when exposed to high temperature and high humidity, and as a result, the strength of the fiber can be sufficiently maintained, and the strength retention rate is increased. Can be improved.

  In addition, about the technique which makes a carboxyl terminal group 25 gram equivalent / ton or less, the addition of a terminal blocker, the optimization of a solid phase polymerization method or a melt polymerization method etc. are mentioned.

  The conductive conjugate fiber of the present invention may be a multifilament composed of a plurality of fibers, a monofilament used only with a single yarn, or may be a long fiber or a short fiber.

Next, the manufacturing method of the electroconductive composite fiber of this invention is demonstrated.
Polylactic acid is used as the conductive component, and a polyester resin obtained by conducting a normal polycondensation reaction is used as the nonconductive component. Both polymers are each subjected to a treatment such as drying to form a chip, and composite spinning is performed using an ordinary two-component composite melt spinning apparatus. At this time, about the shape and arrangement position of a nonelectroconductive component or a conductive component, it is set as the composite fiber of desired cross-sectional shape by changing a spinneret shape variously. And the electroconductive composite fiber of this invention can be obtained by extending | stretching and heat-processing the obtained thread | yarn.

  In addition, as a method for obtaining the conductive component, there are a method of adding conductive particles at the polymerization stage of the polymer as a base, and a method of adding conductive particles at the time of melt kneading of the polymer. Is preferred.

  The conductive conjugate fiber of the present invention has a low electrical resistance value, sufficient conductive performance and strength, and little reduction in strength under a high temperature atmosphere. For this reason, it is suitable for use in clothing such as clean room and medical work uniforms that require antistatic effects and repeated wet heat treatment such as sterilization, interior use such as curtains, and materials. be able to.

Next, the present invention will be described specifically by way of examples. In addition, measurement and evaluation of various values in the examples were performed as follows.
1. Electrical resistance value of conductive conjugate fiber Measured and calculated according to the method described above.
2. Strength and strength retention under 25 ° C. atmosphere and 120 ° C. atmosphere Measurement and calculation according to the method described above.
3. Spinning operability
Spinning was performed continuously for 24 hours, and the following three stages were evaluated according to the number of cut yarns during this period.
○: No cutting thread △: Cutting thread count 1 to 2 ×: Cutting thread count 3 or more

Example 1
As a non-conductive component, PET having a relative viscosity (measured at a temperature of 20 ° C. using an equal mass mixture of phenol and ethane tetrachloride as a solvent) of 1.48 and a melting point of 230 ° C. was used. Chips were made by conventional methods. As a conductive component, L / D, which is the content ratio of L-lactic acid and D-lactic acid, is 98.7 / 1.3, polylactic acid having a number average molecular weight of 88200, a relative viscosity of 1.87, and a melting point of 170 ° C. A carbon black having a particle size of 0.2 μm (20% by mass in the conductive component) melted and kneaded was used. Using a spinneret designed to supply a conductive component and a non-conductive component to an ordinary composite spinning apparatus, and the cross-sectional shape of the fiber is as shown in FIG. 1 (c), a spinning temperature of 250 ° C., a conductive component The melt spinning was carried out so that the composite ratio was 20% by mass. The spun yarn was cooled and wound at a speed of 3000 m / min while oiling to obtain 42 dtex / 2f undrawn yarn.
This undrawn yarn is drawn 1.50 times through a 90 ° C. heat roller, further heat treated with a 140 ° C. heat plate, and wound up to give 28 dtex / 2f having the cross-sectional shape of FIG. The conductive conjugate fiber was obtained.

Reference example 1
The same procedure as in Example 1 was performed, except that PBT having a relative viscosity of 1.58 and a melting point of 230 ° C. (substantially having a butylene terephthalate repeating unit of 100 mol%) was used as the nonconductive component.

Reference example 2
The same procedure as in Example 1 was conducted except that PPT having a relative viscosity of 1.58 and a melting point of 225 ° C. (substantially having a propylene terephthalate repeating unit of 100 mol%) was used as the non-conductive component.

Examples 5-6, Comparative Examples 3-4
The same procedure as in Example 1 was carried out except that the content of the conductive component carbon black, the composite ratio of the conductive component, and the cross-sectional shape were changed as shown in Table 1.

Comparative Example 1
As a non-conductive component, L / D, which is the content ratio of L-lactic acid and D-lactic acid, is 98.7 / 1.3, melt-spun using polylactic acid having a number average molecular weight of 88200, a relative viscosity of 1.87, and a melting point of 170 ° C., The spun yarn is cooled and wound at a speed of 3000 m / min while oiling to obtain an undrawn yarn of 36 dtex / 2f. The undrawn yarn is drawn 1.3 times through a 90 ° C. heat roller. The procedure was the same as in Example 1 except that.

Comparative Example 2
The same procedure as in Example 1 was performed except that PET having a relative viscosity of 1.35 obtained by copolymerization of 30 mol% of CHDM and a flow initiation temperature of 135 ° C. was used as the non-conductive component.

Table 1 shows the characteristic values and operability results of the conductive conjugate fibers obtained in Examples 1 and 5 to 6, Reference Examples 1 and 2, and Comparative Examples 1 to 4.

As is clear from Table 1 , the conductive composite fibers of Examples 1 and 5 to 6 had low electrical resistance values and good strength retention in a high temperature atmosphere.
On the other hand, since the conductive composite fiber of Comparative Example 1 was polylactic acid for both the conductive component and the nonconductive component, the conductive composite fiber of Comparative Example 2 had a high copolymerization amount of CHDM as the nonconductive component. Therefore, in the conductive conjugate fiber of Comparative Example 4, since the composite ratio of the conductive component was too large, the decrease in strength under a high temperature atmosphere was too large, and measurement was not possible. Moreover, it was inferior to the spinning operability. The conductive conjugate fiber of Comparative Example 3 had a high electrical resistance because the content of the conductive particles of the conductive component was small.

It is the cross-sectional schematic diagram cut | disconnected perpendicularly | vertically with respect to the longitudinal direction of the fiber which shows one embodiment of the electroconductive composite fiber of this invention. It is the cross-sectional schematic diagram cut | disconnected perpendicularly | vertically with respect to the longitudinal direction of the fiber which shows the other embodiment of the electroconductive composite fiber of this invention. It is the cross-sectional schematic diagram cut | disconnected perpendicularly | vertically with respect to the longitudinal direction of the fiber which shows the other embodiment of the electroconductive composite fiber of this invention.

Claims (2)

Consists of a non-conductive component made of polyethylene terephthalate copolymerized with 5 to 20 mol% of at least one component of isophthalic acid and cyclohexanedicarboxylic acid, and a conductive component made of polylactic acid containing conductive particles, The ratio of the component is 10 to 60% by mass of the entire fiber, and the conductive composite fiber has a shape in which at least a part of the conductive component is exposed on the fiber surface, and the electrical resistance value is 1 × 10 ^4. Conductive conjugate fiber characterized by being ⁴ Ω / cm to 9 × 10 ¹² Ω / cm. The conductive conjugate fiber according to claim 1, wherein the strength measured in an atmosphere of 120 ° C is 40% or more of the strength measured in an atmosphere of 25 ° C (strength retention rate of 40% or more).