JP2541215B2 - Filiform heating element and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a filamentous heating element which is highly flexible and electrically heats up to withstand long-term use, and a method for producing the same.

[Prior Art] Conventionally, a flexible heating wire made of a thin metal wire has been used for keeping heat of equipment or heating, but it is particularly popular and widely used for consumer products such as electric blankets and electric carpets. Therefore, there is a trend that products will be more and more diversified in the future.

Conventionally, resistors made of thin metal wires such as stainless wire and nichrome wire were used for these heating elements, but when it is required that each of the above products is flexible, There are used those in which a very fine resistance wire is wound in a spiral shape on the core, and those in which carbon is fixed on a cloth with a resin binder.

However, none of them can satisfy the performance required in terms of bending resistance, abrasion resistance, etc.
It lacks flexibility and needs improvement.

As an attempt to obtain a highly flexible filamentous heating element, for example, a nylon conjugate filament is softened by heating or swelled with a swelling agent to fix carbon particles to the filament surface layer to form a filamentous heating element. Japanese Patent Laid-Open No. 51-109321 has been disclosed, but this heating element has a too high resistance value per length and is not suitable for use as a heating element. Also, after applying an adhesive such as an acrylic resin to the core yarn which is a reinforcing material, conductive particles are covered to form a filamentous heating element.
There is publication 0. According to these methods, it is difficult to fix the carbon particles uniformly, and therefore the resistance value varies greatly, and it is impossible to industrially stably supply the one having the required resistance value.

In addition, there is a Japanese Utility Model Publication No. 38-1470 in which a core thread is coated with a conductive resin in which conductive particles are mixed with rubber or plastic, but the volume specific resistance value (specific resistance) of the conductive resin described here is Not only is it considerably high at 20 Ωcm or more, but even if it is simply coated, the resistance value of the heating element varies greatly, and it was not possible to supply it stably in industry.

[Problems to be Solved by the Invention] The present invention solves the above conventional problems, is rich in flexibility, has a small variation in resistance value per length, can be used stably for a long time, and has low temperature heat generation. A filamentous heating element preferably used as a body and a method for producing the same.

[Means for Solving the Problem] The above-described object of the present invention is to provide a melt-coated conductive layer (hereinafter, simply referred to as a conductive layer) including a thermoplastic resin around the core yarn and conductive particles dispersed and blended in the resin. ), The eccentricity (e) defined by the following formula is 0.7 or less, and the weight variation CV in the yarn axis direction is 2.0% or less.

Of the above-mentioned constitutions, the core yarn is necessary for giving the filamentous heating element flexibility and durability against repeated folding and abrasion.

Further, by setting the weight variation CV in the yarn axis direction to 2.0% or less, the heat generation performance of the product satisfies the same level as the product made of the conventional fine metal wire. Especially, the weight variation CV is preferably 1.0% or less. Where the weight variation CV
(%) Is obtained by CV (%) when 40 weights of 25 cm each are continuously measured in the yarn axis direction, and is a constituent requirement required to bring the resistance variation to a practical level. Measurement
The continuous measurement at 25 cm intervals is an effective measurement method considering the size of the product because this length is almost equal to the one electrode interval in the case of a normal product.

Further, in the present invention, the eccentricity of the cross section of the product needs to be 0.7 or less. By setting the eccentricity to be 0.7 or less, that is, by approaching a perfect circle, not only does the process passability in producing a fabric heating element by weaving the filament heating element become good and no trouble occurs, but also the filament shape. The heating performance of the heating element, that is, the variation in the resistance value is also reduced.
It is considered that this is because the microscopic adhesion unevenness of the conductive layer is reduced. Those with an eccentricity of 0.5 or less are particularly preferably used.

A preferred method for producing the filamentous heating element of the present invention has the following constitution. That is, a thermoplastic conductive resin comprising a thermoplastic resin and conductive particles dispersed and blended in the resin is melt-measured under heating and flowing, and is defined by the following formula around a continuously running core yarn. The filamentous shape is characterized in that a conductive layer in which conductive particles are dispersed and blended is fused and continuously formed on the core yarn by extrusion-coating so that the draft ratio is 0.8 to 3.0 and then cooling and solidifying. It is a method of manufacturing a heating element.

As the material of the core yarn used in the present invention, a yarn of natural fiber, regenerated fiber or synthetic fiber is used, but it is stable for a long period of time at a temperature usually used as a heating element, that is, a low temperature range of 20 to 100 ° C. Those that maintain performance are preferable. Here, the synthetic fibers are polyamide, polyester,
In addition to commonly known synthetic fibers such as polyolefin, polyacrylonitrile, polyvinyl alcohol, and polyvinyl chloride, glass fibers, inorganic fibers such as alumina and zirconia, and various metal fibers are included. Among them, thermoplastic synthetic fibers such as polyamide, polyester, and polyolefin are non-hygroscopic and chemical resistant, and have little heat deterioration in the above-mentioned operating temperature range of the heating element (20 to 100 ° C). This is preferable because it has a fuse function of fusing in the case of occurrence of. Also, aromatic polyamide,
When using a wholly aromatic polyester, polybenzimidazole, polyphenylenetriazole, polyoxadiazole, polyimide, heat resistant synthetic fiber such as thermosetting resin fiber, inorganic fiber or metal fiber, the usable temperature range is increased. This is preferable because it has the advantages that it can be used and that the product life can be significantly extended.

The form of the core yarn used in the present invention may be spun yarn multifilament, monofilament, or the like,
Those that have good adhesiveness to the conductive layer and are difficult to peel off, such as spun yarn, double structured yarn having monofilament in the surface layer, or bulked filament are preferable. Moreover, the cross-sectional shape of the single yarn may be modified.

In order to set the eccentricity, which is one of the constitutions of the present invention, to 0.7 or less, a particularly preferable form of the core yarn is to use one having a good bundling property. That is, in the case of the spun yarn filament, when the twisted yarn, especially the twin yarn or the triplet is melt-coated,
This is preferable not only because it can be formed by fusing a uniform conductive layer, but also because the cross-sectional shape of the coated yarn is close to a perfect circle and the process passability in post-processing is good.

It is also preferable to treat the core yarn with a substance having a high affinity for both the thermoplastic resin in which the conductive particles are dispersed and blended and the core yarn.

The thermoplastic resin in which the conductive particles used in the present invention are dispersed and mixed maintains stable electric resistance performance in the operating temperature range of the heating element (20 to 100 ° C.), and melts or softens at a temperature higher than the upper limit of the operating temperature. If so, there is no particular limitation,
A material that can be extruded at a commonly used extrusion molding temperature of 100 to 350 ° C is preferable. Of these, thermoplastic elastomers such as polyolefins, polyesters, polyurethanes, polyvinyl chlorides, polyvinyl alcohols, polystyrenes, etc. are preferably used in terms of flexibility and flexibility.

Here, the thermoplastic elastomer has rubber elasticity at room temperature and plasticity that can be extruded at high temperature.
The lower the A hardness of 6301 standard, the better the flexibility,
Not only can a larger amount of conductive particles be dispersed and blended,
When the resulting filamentous heating element is bent, cracking or cutting is unlikely to occur in the conductive layer fused and coated, which is preferable. Here, as the thermoplastic elastomer, JIS K6301 standard A
A hardness of 95 or less is preferable, a hardness of 90 or less is more preferable, and a hardness of 80 or less is more preferably used. These thermoplastic resins may be used as a blend of two or more kinds, and in that case, two or more kinds of resins may be reacted by being blocked or grafted.

Examples of the conductive particles used in the present invention include conductive carbon particles typified by carbon black and graphite, organic conductive particles, conductive metal particles, conductive metal oxide particles and particles having a coating film thereof. To be Here, the particles may have any shape as long as the maximum average particle diameter is 100 μm or less, and carbon fibers having a length of 100 μm or less are also included in the present invention. Further, two or more kinds of conductive particles may be mixed and used. Among the above-mentioned conductive particles, conductive carbon particles are particularly preferable because they can be easily dispersed and blended in a thermoplastic resin, and light and highly conductive particles can be obtained. Among them, carbon blacks having an average particle diameter of 10 to 100 mμ such as acetylene black, furnace black and ketching black are preferably used.

The thermoplastic conductive resin used in the present invention, the thermoplastic resin 30-75 wt%, preferably 35-70 wt%, more preferably 40-65 wt% and the conductive particles 70-25 wt% , Preferably 65 to 30% by weight, more preferably 60 to 35% by weight. When the thermoplastic resin is less than 30% by weight, the heating fluidity is poor, and it is difficult to coat the conductive resin evenly on the core yarn, and when the conductive particles are less than 25% by weight, sufficient heat conductivity is achieved as a heating element. It is difficult to maintain sex. Further, the conductive resin may contain various modifiers and additives depending on the purpose, provided that the mixing ratio of the thermoplastic resin and the conductive particles is within the above range.

In the present invention, a plurality of conductive layers may be provided if necessary. In this case, the composition and content of the conductive particles dispersed in the thermoplastic resin can be changed for each layer as necessary. For example, in order to enhance the surface smoothness of the filamentous heating element, the content in the outermost layer may be appropriately determined such that it is smaller than that in the inner layer.

The resistance value of the filamentous heating element of the present invention can be appropriately set depending on the content of the conductive particles dispersedly contained in the synthetic resin, the thickness of the layer to be coated, etc., but the resistance is 1 to 100 KΩ / m. A value is preferable. If the resistance value is less than 1 KΩ / m, the heat generation amount per unit length is too large, and if it exceeds 100 KΩ / m, the heat generation amount per unit length is too small, which is the main application of the heating element of the present invention. It is not preferable for use as a low temperature heating element capable of uniform heating.

The thread diameter of the filamentous heating element of the present invention can be appropriately selected according to the required conductivity and product form, but it is preferable that the filament diameter is as thin as possible, and in the state of the filamentous heating element coated with conductivity.
A diameter of 1 mm or less is preferable, and a diameter of 0.7 mm or less is more preferable.

The filamentous heating element of the present invention is manufactured by melt-extruding and coating a thermoplastic conductive resin around a core yarn that is continuously running using a melt coating device under heating and flow, and at that time. , The draft ratio defined by the following formula of coating resin
0.8 to 3.0, preferably 0.9 to 1.8, more preferably 0.95 to
It needs to be 1.5.

Here, the cross-sectional area of the core yarn and the cross-sectional area of the conductive layer of the filamentous heating element can be obtained by observing the sectional area of the filamentous heating element with a microscope.

When the draft ratio is greater than 3.0, when the running conductive core yarn is coated with a thermoplastic conductive resin, the resin is stretched and the adhesiveness (fusion property) between the conductive layer and the core yarn is poor. And there are voids between them. Therefore, the cross-sectional shape of the obtained filamentous heating element becomes flat and the eccentricity increases, so that not only the electric resistance value level of the heating element rises but also the resistance value variation CV (%) increases and it is stable as a heating element. You cannot get the performance you want. The reason for this is not clear, but by stretching the thermoplastic conductive resin, the structure of the conductive particles dispersed and blended in the resin is destroyed, voids are generated in the conductive layer, and / Alternatively, it is conceivable that microscopic adhesion unevenness of the conductive layer occurs in the yarn axis direction.

If the draft rate is less than 0.7, stable fusion bonding (adhesion) becomes difficult because part of the thermoplastic conductive resin adheres to the die hole outlet surface, and the obtained filamentous heating element is Not only increases the weight variation CV (%) of the heating element, but also increases the eccentricity of the cross-sectional shape of the heating element, which increases the variation CV (%) of the electric resistance value in the yarn axis direction.
A filamentous heating element with stable electric performance cannot be obtained. The draft rate can be controlled by changing the traveling speed of the core yarn, the supply speed of the thermoplastic resin, and the die hole diameter.

Next, a method for manufacturing the filamentous heating element of the present invention will be described with reference to an example.

FIG. 1 shows an example of an embodiment preferably used as the manufacturing method of the present invention. The core yarn 1 enters the die 5 while running continuously without being substantially stretched, while the thermoplastic conductive resin 2 in which conductive particles are dispersed and blended is heated and melted or fluidized by the melt extruder 3 to be weighed. It is continuously measured by the pump 4. The measured conductive resin enters the die 5 from a different port from the core thread 1 and has a draft rate of 0.8 to 3.0 on the core thread that has passed through the nipple in the die 5 as shown in FIG. It is fused and coated in a molten state. The core yarn fused and coated with the conductive resin, after exiting from the die hole 8 of the die 5, is water-cooled in an overflow type cooling water tank 6,
It is wound by the winder 7.

Thus, the filamentous heating element of the present invention is highly flexible, has excellent mechanical strength such as bending resistance and abrasion resistance, and has a uniform resistance value per unit length of the heating wire, so that the heat generation of various heating element products can be improved. It can be advantageously used as a material, especially as a low temperature heat generating material.

Hereinafter, the present invention will be specifically described with reference to examples. In the examples, the characteristics of the obtained filamentous heating element were measured by the following methods.

A. Electric resistance value: n is the resistance value per 25 cm using a tester
= 40, the average value and its CV (%) = standard deviation /
The average value was calculated.

B. Yarn diameter: The cross-sectional area of the yarn cross section was n =
It was measured by 10 and displayed by the diameter of a circle having an area equal to the average value.

C. Flexibility: Displayed as the flexibility level when the filamentous heating element was bent by hand.

Example 1 In the apparatus of FIG. 1, melting point 260 continuously running at a speed of 70 m / min through a nipple having a nipple hole diameter of 0.35 mmφ.
Thermoplastic conductive resin consisting of 60% by weight of various thermoplastic resins and 40% by weight of conductive carbon black having an average particle diameter of 40 mμ is added to spun yarn (470 denier) of polyester twin yarn at ℃
It was heated and fluidized (melted) at 200 to 230 ° C., continuously weighed with a metering pump at a rate of 10 g / min, and melt-extruded and coated through a die having a die hole diameter of 0.45 mm. The results are shown in Table 1.

As is clear from Table 1, the thermoplastic conductive resin is uniformly attached in the yarn axis direction by the method of the present invention, and its cross-sectional shape is close to a perfect circle, and microscopic unevenness of adhesion is small. The variation in resistance was extremely small.
Further, although the flexibility of the obtained filamentous heating element depends on the hardness of the thermoplastic resin used, it was at a considerably good level as compared with the metal nichrome wire.

A cloth-shaped heating element obtained by using the filament heating element will be described with reference to FIG. The cloth-like heating element 12 shown in the figure is composed of a copper wire tin-plated electrode wire 13 and a polyester thread.
No. 1 was used as the weft yarn, and the polyester yarn 15 for adjusting the calorific value was used as the weft yarn to obtain a cloth-like heat generating element by a normal loom. Further, for the purpose of insulating coating, a polyethylene film was laminated on both sides of the cloth using a polyethylene melt as a binder. Further, when a lead wire 16 that conducts a current to the electrode wire 13 is connected by soldering 17, this cloth-like heating element is sewn to the lining of the vest, and electricity is supplied from the Ni-Cd battery, a local There was no temperature unevenness and it was extremely flexible, and was well received by the person trying it on.

Example 2 A filamentous heating element was manufactured in the same manner as in No. 1 of Example 1 by changing the running speed of the core yarn, the feeding speed of the thermoplastic conductive resin and the die hole diameter. The results are shown in Table 2.

As is clear from Table 2, Nos. 6 to 8 in which the draft ratio is within the range of the present invention have eccentricity and weight variation CV (%) within the range of the present invention, and resistance value variation CV (%) is 5 % Or less, showing stable performance equivalent to that of a nichrome wire or a commercial cord heater.

In No. 5, the draft rate was too small, so unevenness was generated on the surface of the obtained filamentous heating element, and the eccentricity varied greatly,
The weight variation CV (%) also became very large. As a result, the resistance variation CV (%) was large.

In addition, since No. 9 had a large draft rate, the resistance value variation CV (%) was large.

[Advantages of the Invention] The present invention is formed by melt-coating a conductive layer and fusion-bonding it to a core yarn, so that it is highly flexible and has a small variation in resistance value per length for a long period of time. It is a filamentous heating element that can be used stably and is preferably used as a low-temperature heating element. With this, it is possible to knit and weave, and it can be applied to various applications such as clothing field, construction field, agriculture, fisheries, civil engineering field. It was the one that provided the body. Of course, it can be suitably applied to all vehicles such as vehicles such as automobiles and trains, airplanes, ships, and space rockets.

[Brief description of drawings]

FIG. 1 shows an example of a filamentous heating element manufacturing apparatus of the present invention.
FIG. 2 shows a sectional view of the die therein. Further, FIG. 3 is an explanatory view of a cloth-like heating element obtained by weaving a filament heating element. 1: Core yarn 2: Thermoplastic conductive resin 3: Melt extruder 4: Metering pump 5: Die 6: Cooling water tank 7: Winder 8: Die hole 9: Nipple 10: Nipple hole

Claims (5)

(57) [Claims] 1. A melt-coated conductive layer comprising a thermoplastic resin and conductive particles dispersed and blended in the resin, which is fused around a core yarn, and the eccentricity defined by the following formula: e is
0.7 or less, and weight variation CV in the yarn axis direction is 2.0%
A filamentous heating element characterized in that: 2. The thermoplastic resin has an A hardness according to JIS K6301.
The filamentous heating element according to claim 1, which is a thermoplastic elastomer of 95 or less. 3. A thermoplastic conductive resin comprising a thermoplastic resin and conductive particles dispersed and blended in the resin is melt-measured under heating and flowing, and the following formula is provided around a continuously running core yarn. After extrusion coating so that the draft rate defined by the above is 0.8 to 3.0, by cooling and solidifying, the conductive layer in which the conductive particles are dispersed and blended is fused and continuously formed on the core yarn. A feature of the present invention is a method for producing a filamentous heating element. 4. The thermoplastic resin has an A hardness according to JIS K6301.
The method for producing a filamentous heating element according to claim 3, which is a thermoplastic elastomer of 95 or less. 5. The method for producing a filamentous heating element according to claim 3, wherein the draft rate is 0.9 to 1.8.