Method for Measuring Surface Potential of Yarn Containing Potential-Generating Fiber

Abstract

To provide a method for measuring surface potential of a yarn that generates a potential prescribed under predetermined conditions to exhibit desired effects such as antibacterial properties, static electrification and adsorption.SOLUTION: The method for measuring surface potential of a yarn including potential generating fiber of the present invention is performed under the following conditions (a) to (d). (a) The yarn is elongated to a specified value in an axial direction. (b) A core material made of conductive fiber is covered with the fiber. (c) The core material is connected to ground. (d) The surface potential of the yarn is measured by an electrical force microscope.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for measuring the surface potential of a thread and a cloth containing a potential generating fiber that generates electric charges.

Background Art

[0002] For example, Patent Document 1 discloses a thread and a cloth provided with a charge generating fiber that generates electric charges by external energy. The thread and the cloth of Patent Document 1 exhibit an antibacterial effect due to the generated electric charges.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, Patent Document 1 does not disclose the potential generated on the surface of the fiber. If the generated potential is too low, there is a possibility that the desired effect may not be produced.

[0005] Therefore, an object of the present invention is to provide a method for measuring the surface potential of a thread and a cloth that exhibit a desired effect.

Means for Solving the Problems

[0006] The method for measuring the surface potential of a thread containing the potential generating fiber of the present invention is characterized by measuring under the following conditions (a) to (d). (a) Stretch the thread by a predetermined amount in the uniaxial direction. (b) Cover the fiber on a core material made of a conductive fiber. (c) Ground the core material. (d) Measure the surface potential of the thread with an atomic force microscope.

[0007] Fibers that generate an electric potential on the surface by external energy include, for example, substances having a piezoelectric effect (such as polylactic acid), substances having a photovoltaic effect, substances having a pyroelectric effect (such as PVDF: Polyvinylidene Difluoride), or substances that generate electric charges by chemical changes, and the like. The thread of the present invention exhibits an antibacterial effect due to the generated electric potential. Further, the thread of the present invention can also charge a substance by generating an electric potential defined by the above conditions. Alternatively, the thread of the present invention can adsorb a substance by generating an electric potential defined by the above conditions.

Advantages of the Invention

[0008] According to this invention, by generating an electric potential defined under predetermined conditions, desired effects such as antibacterial, charging, or adsorption are exhibited.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described. FIG. 1(A) is a partial exploded view showing the configuration of thread 1, and FIG. 1(B) is a cross-sectional view taken along line A-A of FIG. 1(A).

[0011] The yarn 1 is a multifilament yarn formed by twisting a plurality of fibers 10. The fiber 10 is a fiber having a circular cross-section. The yarn 1 is a left-twisted yarn (hereinafter referred to as a Z-yarn) in which a plurality of fibers 10 are twisted in a left-handed direction.

[0012] The fiber 10 is made of, for example, a piezoelectric polymer. The fiber 10 is manufactured, for example, by a method of extruding and molding a piezoelectric polymer to form fibers. Alternatively, the fiber 10 can be manufactured by a method of melt-spinning and fiberizing a piezoelectric polymer (including, for example, a spinning-drawing method in which the spinning process and the drawing process are performed separately, a direct drawing method in which the spinning process and the drawing process are connected, a POY-DTY method in which a false-twisting process can also be performed simultaneously, or an ultra-high-speed spinning method for speeding up, etc.), a method of dry or wet spinning a piezoelectric polymer (including, for example, a phase separation method or a dry-wet spinning method in which a polymer as a raw material is dissolved in a solvent and extruded from a nozzle to form fibers, a gel spinning method in which fibers are uniformly formed in a gel state while containing a solvent, or a liquid crystal spinning method in which fibers are formed using a liquid crystal solution or a melt, etc.), or a method of fiberizing a piezoelectric polymer by electrospinning. Note that the cross-sectional shape of the fiber 10 is not limited to a circular shape.

[0013] There are piezoelectric polymers having pyroelectricity and those not having pyroelectricity, and either can be used. For example, PVDF has pyroelectricity, is polarized by a temperature change, and generates a potential on the surface of the fiber. Piezoelectrics having pyroelectricity such as PVDF are also polarized by the thermal energy of the human body. In this case, the thermal energy of the human body is external energy.

[0014] In addition, polylactic acid (PLA: Polylactic Acid) is a piezoelectric polymer that does not have pyroelectricity. Piezoelectricity is generated in polylactic acid when it is uniaxially stretched. As polylactic acid, depending on the crystal structure, there are poly-L-lactic acid formed by polymerizing L-lactic acid and L-lactide, poly-D-lactic acid formed by polymerizing D-lactic acid and D-lactide, and stereocomplex polylactic acid having a hybrid structure thereof, etc. Any of them can be used as long as it exhibits piezoelectricity. From the viewpoint of high piezoelectric constant, it is preferable to use poly-L-lactic acid or poly-D-lactic acid. Poly-L-lactic acid and poly-D-lactic acid have opposite polarities of polarization for the same deformation, respectively.

[0015] When polylactic acid is uniaxially stretched and the molecules are oriented, it exhibits piezoelectricity. The piezoelectric constant of polylactic acid can be increased by further applying heat treatment to increase the crystallinity. Since piezoelectricity is generated in polylactic acid by the orientation treatment of molecules by stretching, there is no need to perform a poling treatment like other piezoelectric polymers such as PVDF or piezoelectric ceramics.

[0016] The piezoelectric constant of uniaxially stretched polylactic acid is about 5 to 30 pC / N, which has a very high piezoelectric constant among polymers. Furthermore, the piezoelectric constant of polylactic acid does not vary over time and is extremely stable.

[0017] When the fiber 10 containing uniaxially stretched polylactic acid defines the thickness direction as the first axis, the stretching direction 900 as the third axis, and the direction orthogonal to both the first axis and the third axis as the second axis, as piezoelectric strain constants d 14 and d 25 has tensor components. Therefore, when shear deformation occurs in the direction intersecting the uniaxially stretched direction of the fiber 10 containing uniaxially stretched polylactic acid, a potential is generated.

[0018] In Fig. 1(A), the stretching direction 900 of each fiber 10 coincides with the axial direction of each fiber 10. By twisting a plurality of fibers 10, the stretching direction 900 of the fiber 10 is inclined with respect to the axial direction of the yarn 1.

[0019] When tension is applied to and the yarn 1 of such Z-yarn is stretched, strain occurs in the fiber 10 along the axial direction of the yarn 1, and shear deformation occurs along the axial direction of the yarn 1. Therefore, a positive potential is generated on the surface of the fiber 10, and a negative potential is generated inside. In the case of a right-twist yarn (hereinafter referred to as an S-yarn) in which the fiber 10 is twisted in a right-handed direction as shown in FIG. 2, when stretched, a negative potential is generated on the surface of the fiber 10, and a positive potential is generated inside.

[0020] Therefore, a positive potential is generated on the surface of the yarn 1, and a negative potential is generated inside. A negative potential is generated on the surface of the yarn 2, and a positive potential is generated inside. However, the twist angle of the fiber 10 varies depending on the part, and the thicknesses of the yarn 1 and the yarn 2 are not uniform as a whole. Therefore, the fiber 10 does not always generate a uniform surface potential.

[0021] FIG. 3 shows the simulation result of the potential when a 2% displacement is applied to the yarn 1 in the axial direction. However, in this simulation result, it is assumed that the respective fibers 10 slide when an axial displacement occurs in the yarn 1. In this simulation result, due to applying a 2% displacement in the axial direction, the average of the twist angles changes from 6.5° to 5.5°.

[0022] As shown in the simulation result of FIG. 3, the fiber 10 has a portion where a positive potential is generated and a portion where a negative potential is generated. The yarn 1 forms an electric field between the portion where a positive potential is generated and the portion where a negative potential is generated, respectively.

[0023] FIG. 4(A) shows the simulation result of the electric field in a certain cross-section in the yarn 1 which is a Z-yarn. FIG. 4(B) shows the simulation result of the electric field in a certain cross-section in the yarn 2 which is an S-yarn. As shown in these simulation results, it can be seen that the yarn 1 and the yarn 2 each have a portion where an electric field of several MV / m is generated even alone.

[0024] Thus, the thread of the present invention includes a plurality of fibers 10 that generate a potential on the surface by external energy, and an electric field is generated between the plurality of fibers 10 when displacement is applied.

[0025] More specifically, the fiber 10 has a positive potential portion and a negative potential portion (portions with different potentials), and an electric field is generated between the positive and negative portions of the plurality of fibers 10.

[0026] Note that the stretching direction 900 of the fiber 10 only needs to intersect at least the axial direction of the thread. Preferably, the average of the twist angles is 10 to 50°. More preferably, the average of the twist angles is 20 to 40°.

[0027] Of course, an electric field is also generated between the thread 1 and another substance, between the thread 2 and another substance, or between the thread 1 and the thread 2. FIG. 5 is a cross-sectional view showing the state of the electric field when the threads 1 and 2 are close to each other. When the thread 1 is alone, the surface becomes a positive potential and the inside becomes a negative potential when an axial tension is applied. When the thread 2 is alone, the surface becomes a negative potential and the inside becomes a positive potential when an axial tension is applied.

[0028] When these threads 1 and 2 are close to each other, the adjacent portions (surfaces) tend to have the same potential. In this case, the adjacent portion between the thread 1 and the thread 2 becomes 0 V, and the negative potential inside the thread 1 becomes even lower so as to maintain the original potential difference. Similarly, the positive potential inside the thread 2 becomes even higher.

[0029] In the cross-section of the thread 1, an electric field mainly from the outside to the inside of the thread 1 is formed, and in the cross-section of the thread 2, an electric field mainly from the inside to the outside is formed. When the threads 1 and 2 are close to each other, these electric fields leak out into the air and are synthesized, and an electric field is formed between the threads 1 and 2 due to the potential difference between the threads 1 and 2.

[0030] Also, when the thread 1 is close to an object having a predetermined potential such as a human body, an electric field is generated between the thread 1 and the adjacent object. Also, when the thread 2 is close to an object having a predetermined potential such as a human body, an electric field is generated between the thread 2 and the adjacent object.

[0031] An electric field as described above exhibits an antibacterial effect that suppresses the growth of microorganisms such as viruses, bacteria, fungi, archaea, or mites and lice.

[0032] When moisture containing an electrolyte exists in Thread 1 or Thread 2, an electric current flows through the moisture. Thread 1 or Thread 2 may also directly exhibit an antibacterial or bactericidal effect due to this electric current. Alternatively, it may indirectly exhibit an antibacterial or bactericidal effect due to reactive oxygen species generated by the change of oxygen contained in the moisture by the action of an electric current or voltage, further due to radical species and other antibacterial chemical species (such as amine derivatives) generated by the interaction and catalytic action with additives contained in the fiber. Or, oxygen radicals may be generated inside the bacteria due to the stress environment caused by the presence of an electric field or electric current. As radicals, the generation of superoxide anion radicals (reactive oxygen) and hydroxyl radicals is considered.

[0033] Materials having antibacterial properties such as conventional drugs did not have a long-lasting effect. Also, conventional antibacterial materials may cause allergic reactions due to drugs or the like. In contrast, the antibacterial effect of the thread of this embodiment lasts longer than the antibacterial effect by drugs or the like. Also, with the thread of this embodiment, the possibility of an allergic reaction is lower than that of drugs. Furthermore, as described above, the piezoelectric constant of polylactic acid does not vary over time and is extremely stable, so the antibacterial effect of the thread is also stably exhibited for a long time.

[0034] Also, Thread 1 or Thread 2 can charge other substances due to the generated potential. Alternatively, Thread 1 or Thread 2 can adsorb substances due to the generated potential. For example, since a positive potential is generated on the surface of Thread 1, it can adsorb substances having a negative potential. Since a negative potential is generated on the surface of Thread 2, it can adsorb substances having a positive potential.

[0035] The thread 1 or thread 2 can also be used to form a filter, thereby efficiently adsorbing substances. Such a filter is suitable for a mask or air purifier. Furthermore, by using thread 1 or thread 2 as a pre-filter in the preceding stage to charge substances positively or negatively, and using thread 1 or thread 2 that generates a potential of the opposite polarity as a subsequent filter, substances can be more efficiently adsorbed. Alternatively, the thread 1 or thread 2 can be used as a pre-filter in the preceding stage to charge substances positively or negatively, and an electret filter with a potential of the opposite polarity can be used as a subsequent filter.

[0036] Here, if the potential generated on the surface of yarn 1 or yarn 2 is too low, the various desired effects described above may not be achieved. However, the yarn of the present invention is characterized by including fibers that generate a potential on their surface when exposed to external energy, and by generating a potential of 0.1 V or more on the yarn surface when measured under the following conditions (a) to (d). The yarn of the present invention can achieve the desired effects by generating a potential specified under these conditions. (a) The yarn is stretched in one axial direction by a predetermined amount. (b) A core material made of conductive fibers is covered with the fibers. (c) grounding the core material; (d) Measuring the surface potential of the yarn with an electric force microscope.

[0037] The predetermined amount (a) is preferably a yarn distortion of 0.1% or more, more preferably 0.5% or more, and the surface potential is preferably 0.3 V or more, more preferably 1.0 V or more.

[0038] The thickness of the yarn (single fiber fineness) is preferably 0.005 to 10 dtex. If the single fiber fineness is small, the number of filaments becomes too large, making the yarn more susceptible to fluffing. On the other hand, if the single fiber fineness is large and the number of filaments is too small, the texture will be impaired. Note that the single fiber fineness referred to here is the single fiber fineness of a single twisted yarn. Even if twisted yarns are further combined, it means the single fiber fineness of a single twisted yarn before being combined.

[0039] Furthermore, the fiber strength of the yarn is preferably 1 to 5 cN / dtex. Thereby, even if the yarn undergoes a greater deformation to generate a high potential, it can withstand without breaking. The fiber strength is more preferably 2 to 10 cN / dtex, still more preferably 3 to 10 cN / dtex, and most preferably 3.5 to 10 cN / dtex. For the same reason, the elongation of the yarn is preferably 10 to 50%.

[0040] Also, the crystallinity of polylactic acid is preferably 15 to 55%. Thereby, the piezoelectricity derived from the polylactic acid crystals is increased, and the polarization due to the piezoelectricity of polylactic acid can be more effectively generated.

[0041] Hereinafter, examples will be described. The yarns of Examples 1 to 3 are twisted yarns using polylactic acid with a crystallinity of 45%, a crystal size of 12 nm, and an orientation degree of 79%, and 84 dtex - 24 filaments. The yarns of Examples 1 to 3 are formed by covering a core material made of conductive fiber with polylactic acid filaments. Also, the core material is grounded. Therefore, the inside of the yarns of Examples 1 to 3 has a potential of 0 V.

[0042] In Example 1, the twist number is 500 T / m, in Example 2, the twist number is 1150 T / m, and in Example 3, the twist number is 3000 T / m. When the twist number is 500 T / m, the average twist angle is 10°, when the twist number is 1150 T / m, the average twist angle is 28°, and when the twist number is 3000 T / m, the average twist angle is 47°.

[0043] Table 1 shows the results of measuring the surface potential of the yarns of Examples 1 to 3. After sandwiching both ends of the yarns with rigid jigs, stretching the 40 mm yarn to 40.2 mm and discharging it with an ionizer, then stretching it axially by 0.5% (from 40.2 mm to 40.4 mm) and measuring the surface potential of the yarn with an electron force microscope. The potential values shown in Table 1 are positive or negative peak values. <(

[0044] [Table 1]

[0045] As shown in Table 1, the S yarn of Example 1 generates a potential of -0.15 V. The Z yarn of Example 1 generates a potential of 0.12 V. The S yarn of Example 2 generates a potential of -1.22 V. The Z yarn of Example 2 generates a potential of 0.96 V. The S yarn of Example 3 generates a potential of -0.35 V. The Z yarn of Example 3 generates a potential of 0.40 V.

[0046] Table 2 shows the results of measuring the surface potential of the yarn by an electric force microscope when it is further stretched and contracted by 0.25% in the axial direction (stretched and contracted between 40.4 mm and 40.5 mm) after measuring under the conditions of Table 1 above. For the S yarn, a negative potential is generated on the surface when it is stretched, and a positive potential is generated on the surface when it is contracted. For the Z yarn, a positive potential is generated on the surface when it is stretched, and a negative potential is generated on the surface when it is contracted. Therefore, when the yarn is stretched and contracted, positive and negative potentials are generated alternately. The surface potential values shown in Table 2 are the difference between the minimum value and the maximum value (the difference between the values from peak to peak).

[0047]

Table 2

[0048] As shown in Table 1, the S yarn of Example 1 generates a potential of 0.28 V. The Z yarn of Example 1 generates a potential of 0.33 V. The S yarn of Example 2 generates a potential of 2.83 V. The Z yarn of Example 2 generates a potential of 2.42 V. The S yarn of Example 3 generates a potential of 0.80 V. The Z yarn of Example 3 generates a potential of 0.75 V.

[0049] From the results of Table 1 and Table 2, it was confirmed that when the twist number is 500 - 3000 Tm, a potential of about 0.1 V or more is generated on the surface of the yarn. It has been confirmed that all of these examples produce an antibacterial effect. Therefore, the yarn of the present invention can exhibit a desired effect by generating a potential (0.1 V or more) defined under the above conditions (a) to (d).

[0050] From the measurement results of these examples, it can be said that the average twist angle is preferably 10 to 50°. Further, in the above measurement results, since the highest potential is generated when the twist angle is 30°, it can be said that more preferably, the average twist angle is 20 to 40°.

[0051] The yarn of the present invention can be used by combining multiple types of twisted yarns as needed. For example, an S-twisted yarn mainly made of poly-L-lactic acid and a Z-twisted yarn mainly made of poly-L-lactic acid can be used. When these yarns are brought close to each other, the electric field between the fibers increases and the antibacterial property becomes higher.

[0052] The same applies to the case of using an S-twisted yarn mainly made of poly-L-lactic acid and an S-twisted yarn mainly made of poly-D-lactic acid, and the case of using a Z-twisted yarn mainly made of poly-L-lactic acid and a Z-twisted yarn mainly made of poly-D-lactic acid, and the case of using an S-twisted yarn made of poly-D-lactic acid and a Z-twisted yarn mainly made of poly-D-lactic acid.

[0053] These twisted yarns may be used by combining them, or any two of the above-mentioned twisted yarns may be used in combination as the yarns constituting the fabric. The fabric of the present invention is composed of, for example, the above-mentioned yarn 1 or yarn 2. In the present invention, the fabric refers to fiber products such as woven fabrics, knitted fabrics, braided fabrics, non-woven fabrics, and lace.

[0054] Each of the yarns constituting the fabric may generate a potential of 0.1 V or more on the surface under the above-mentioned conditions (a) to (d), but the fabric of the present invention itself may also generate a potential of 0.1 V or more on the surface of the fabric when measured under the following conditions (a) to (d). The fabric of the present invention can also exhibit a desired effect by generating a potential defined under such conditions. (a) Stretch the fabric by a predetermined amount in the uniaxial direction. (b) Cover the fiber on a core material made of conductive fiber. (c) Ground the core material. (d) Measure the surface potential of the fabric with an atomic force microscope.

[0055] Similar to the case of the thread, as the predetermined amount in the above (a), it is preferable that the strain of the fabric is 0.1% or more. More preferably, the strain is 0.5% or more. The surface potential is preferably 0.3 V or more, and more preferably 1.0 V or more.

[0056] The parameters of the fibers constituting the fabric are the same as those of the above-mentioned thread. That is, the thickness (single fiber fineness) of the fiber is preferably 0.005 to 10 dtex. Further, the fiber strength is preferably 1 to 5 cN / dtex. The fiber strength is more preferably 2 to 10 cN / dtex, still more preferably 3 to 10 cN / dtex, and most preferably 3.5 to 10 cN / dtex. The elongation of the fiber is preferably 10 to 50%. The crystallinity of polylactic acid is preferably 15 to 55%.

[0057] When the fiber constituting the fabric is a twisted yarn, the average of the twist angles of the twisted yarn is preferably 10 to 50°, and more preferably, the average of the twist angles is 20 to 40°.

[0058] The basis weight of the fabric is 20 to 200 g / m 2 , and the porosity is preferably 50 to 95%. Further, when the fabric is used as a filter, in order to improve the collection performance and collection stability, it is preferable to use a filter having a fine particle collection rate of 40% or more for 0.3 μm at a wind speed of 5.1 cm / sec or more and a pressure loss of less than 250 Pa.

[0059] The fabric of the present invention is applicable to various products such as clothing, medical members, etc. For example, the fabric of the present invention can be used for underwear (especially socks), towels, linings for shoes and boots, sports wear in general, hats, bedding (including futons, mattresses, sheets, pillows, pillow covers, etc.), toothbrushes, dental floss, various filters (such as filters for water purifiers, air conditioners or air purifiers), stuffed toys, pet-related products (pet mats, pet clothes, inners for pet clothes), various mat products (for feet, hands, or toilet seats, etc.), curtains, kitchen supplies (such as sponges or dishcloths), seats (seats in cars, trains or airplanes), cushioning materials and outer covering materials for motorcycle helmets, sofas, bandages, gauze, masks, sewing threads, clothes for doctors and patients, supporters, sanitary supplies, sports supplies (inners for wear and gloves, or hand guards used in martial arts), or packaging materials, etc.

[0060] Among clothing, especially socks (or supporters), due to movements such as walking, stretching and contraction always occur along the joints, resulting in polarization frequently. Also, socks absorb moisture such as sweat and become a breeding ground for bacteria, but with the fabric of the present invention, the growth of bacteria can be suppressed, so it has a remarkable effect as a measure against bacteria.

[0061] Note that the thread of the present invention may be an untwisted thread or a false-twisted thread. The thread constituting the fabric of the present invention may also be an untwisted thread or a false-twisted thread. As long as it is provided with fibers that generate a potential on the surface by external energy and generates a potential of 0.1 V or more under the above conditions, various desired effects such as antibacterial effects can be exerted.

[0062] The description of this embodiment should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the claims. Furthermore, it is intended that the scope of the present invention includes all modifications within the meaning and scope equivalent to the claims.

Explanation of Reference Numerals

[0063] 1, 2... threads 10…fiber 900…elongation direction

Claims

1. A method for measuring the surface potential of a yarn containing potential - generating fibers, characterized by measuring under the following conditions (a) - (d). (a) Cover the core material made of conductive fibers with the potential - generating fibers. (b) Ground the core material. (c) Stretch the yarn by a predetermined amount in the uniaxial direction. (d) Measure the surface potential of the yarn with an atomic force microscope.

2. The measuring method according to Claim 1, wherein the predetermined amount is such that the strain of the yarn is 0.1% or more. The measuring method according to Claim 1.

3. The measuring method according to Claim 1 or Claim 2, wherein the thickness of the potential - generating fibers is 0.005 - 10 dtex.

4. The measuring method according to any one of Claims 1 to 3, wherein the potential - generating fibers contain polylactic acid.

5. The measuring method according to any one of Claims 1 to 4, wherein the potential - generating fibers are twisted.

6. The measuring method according to Claim 5, wherein the average twist angle of the yarn is 10 - 50°.

7. The measuring method according to any one of Claims 1 to 6, wherein the potential - generating fibers satisfy the following requirements (A) - (C). (A) The fiber strength is 1 - 5 cN / dtex. (B) The elongation is 10 - 50%. (C) The crystallinity is 15 - 55%.

8. A method for measuring the surface potential of a fabric containing potential - generating fibers, characterized by measuring under the following conditions (a) - (d). (a) Cover the core material made of conductive fibers with the potential - generating fibers. (b) Ground the core material. (c) Stretch the fabric by a predetermined amount in the uniaxial direction. (d) Measure the surface potential of the fabric with an atomic force microscope.

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