KR20120002968A - Heat resisting conductive yarn and coating liquid thereof - Google Patents

Abstract

PURPOSE: A heat resistant conductive yarn and a coating solution are provided to ensure dispersion of load current and to prevent overheat. CONSTITUTION: A heat resistant conductive yarn contains silicon resin. The average number of organic groups in the silicon resin is 1.35-1.65. The volume resistivity of a conductive layer is 10-2 ohm cm to 103 ohm cm. The conductive layer is coated with a composite material of EPM(ethylene propylene copolymer) with 10-30 of viscosity.

Description

Heat resisting conductive yarn and coating liquid

The present invention relates to a heat-resistant conductive yarn coated with carbon nanotubes in order to ensure the safety, durability and heat resistance of the planar heating element.

The planar heating element refers to a thin sheet-like heating element that generates heat when power is applied.

Planar heating elements can be classified according to the material of the electrical resistance wire.

First, as a metal resistance wire, an alloy wire having a volume resistivity in the range of 10 × 10 ⁻⁶ Pa · cm to 200 × 10 ⁻⁶ Pa · cm and flattened in an “S” shape to apply power to both ends on one straight line. It is a structural way. However, since the load current flows only in one straight line, when chemical change or physical stress deformation occurs on the line surface, the distribution voltage is localized due to the increase in resistance, and thus there is a risk of overheating and fire.

Thus, in order to improve the problem of the tandem structure system, the volume resistivity of the electrical resistance wire is fabricated or filmed with carbon fiber or an electrically conductive composite material and the like in the range of 10 ^-4 Pa.cm to 10 ² Pa.cm, and the fabric Or it is a heating element which is a parallel structure system which forms an electrode wire in both ends of a film. That is, on the fabric heating element, film or fabric which is coated by weaving a composite material composed of conductive particles such as carbon black, carbon nanotubes, metal powder, etc., and a binder resin such as epoxy resin, urethane resin, polyester resin, etc. It consists of a film heating element to adhere | attach.

However, the carbon fiber is very weak against external forces such as abrasion, bending, distortion, and the like, and is prone to breakage when subjected to a force perpendicular to the fiber axis. The composite material has acid, alkali, moisture, Oil, a plasticizer, or the like penetrated or there was a problem in durability due to changes in the electrical resistivity over time due to thermal curing.

The present invention is to solve the problem of overheating due to the concentrated heat of the surface heating element and the change of the electrical resistance over time and the heat resistance.

In the present invention, the volume resistivity of the conductive layer coated on the heat-resistant fiber with a composite material of carbon nanotubes, silicone resins, and ethylene propylene copolymer (EPM) is 10 ^-2 kPa- 10 ³ kPa-cm. Glass fiber, fused silica fiber, high silica fiber, alumina-silica fiber, alumina fiber, zirconia fiber, aramid fiber, PBO (p-phentlene-2,6-benzobisoxazole) fiber, PBI (polybenzimidazole) fiber, polyimide fiber, Novo It is characterized in that any one or more than one of the Lloyd fibers.

The electrical parallel structure of the load according to the high electrical resistivity of the electric heating element, which does not cause overheating due to the dispersion effect of the load current, and the uniform temperature distribution of the surface heating and the heat-resistant fiber coated with carbon nanotubes. Hardening can be prevented.

In the heat-resistant conductive yarn, the volume resistivity of the conductive layer coated on the heat-resistant fiber with a composite material of carbon nanotube, silicone resin and EPM (Ethylene Propylene Copolymer) is 10 ^-2 Pa.cm to 10 ³ Pa.cm The heat resistant fiber is glass fiber, fused silica fiber, high silicic fiber, alumina-silica fiber, alumina fiber, zirconia fiber, aramid fiber, p-phentlene-2,6-benzobisoxazole (PBO) fiber, polybenzimidazole (PBI) fiber, It is characterized in that any one or at least one of polyimide fibers, novoroid fibers.

In addition, the conductive coating liquid on which the conductive layer is coated on the heat-resistant fiber has a continuous chain structure space in carbon nanotubes, silicone resins, and solutions, and has a Mooney viscosity of 10 to 30 ML _{1 + 4} (100 ° C.). Phosphorus EPM (Ethylene Propylene Copolymer) and toluene, which is a solvent, are composed of 50 to 1000 parts by weight of silicone resin, 2 to 100 parts by weight of EPM, and 1000 to 5000 parts by weight of solvent based on 100 parts by weight of carbon nanotubes. It is characterized in that the configuration.

Hereinafter, preferred embodiments of the present invention will be described in detail.

In the conductive coating liquid for forming a uniform electrical resistor on the heat-resistant conductive yarn imparting a conductive function on the heat-resistant fiber, carbon nanotubes, EPM, and solvent are first dispersed in a high speed mixer, roll mill, pressurized kneader or half-barrier mixer. (Banbury Mixer) and the like kneading process (dispersion → uniform dispensing sequence) and the addition of the solvent and the silicone resin to the kneaded kneaded material by the high-speed mixer or the like to finish the conductive coating solution to prepare a conductive coating solution It features.

Alternatively, the conductive carbon black may be formed of carbon black and carbon nanotubes having different particle diameters and shape ratios, thereby maximizing contact surfaces between particles and controlling capacitance.

In order to have excellent conductivity, it is necessary to be within about 5 nm in order for electrons to move due to the tunnel effect between the electrically conductive particles, carbon black or carbon nanotubes.

The shear force for crushing the aggregates of the conductive particles is preferably in the range of 0.5 to 10.0 kgf / cm 2.

When the shearing force of the pressurized kneader, the Banbury Mixer, or the roll mill exceeds 10.0 kgf / cm 2, the electrically conductive particles, which are electrical properties, are crushed to lower the conductivity.

If the shear force is less than 0.5 kgf / cm 2, the aggregates of the electrically conductive particles are not broken, and thus the dispersion mixing effect cannot be exhibited.

Since carbon nanotubes or carbon black, which are electrically conductive particles, have a large surface tension, when the particles become fine particles and have a large surface area, agglomeration tends to be strong, and they tend to reaggregate even after crushing and dispersing during mixing.

Even the conductive coating liquid having good dispersion and distribution mixing in the above step cannot pursue dispersion stability due to reaggregation of the conductive particles after a certain time.

Accordingly, the surface of the electrically conductive particles is subjected to chemical and physical treatment such as ultrasonic treatment, plasma treatment, acid treatment, and the like to form functional groups such as hydroxyl group (-OH) and carboxyl group (-COOH) on the surface of the carbon nanotubes. The dispersion stability can be pursued by introducing, but it is also a factor that deteriorates the electrical properties of carbon nanotubes.

It is also possible to reduce the surface tension by coating the surface of the carbon nanotubes with a material having a low surface tension.

In other words, when the polymer is grafted on the surface of the carbon nanotubes, the repulsive force between the particles increases, and the polymer increases the affinity with the medium and improves the dispersion and dispersion stability during mixing, but has a trade-off that inhibits the original conductive function. Have

Therefore, when the polymer is grafted between the electrically conductive particles and the polar thin film is interposed, the contact resistance between the conductive particles increases.

Ultimately, it is most desirable to form a conductive passageway in a continuous phase with only carbon nanotube particles.

In addition, with respect to stabilization of the coating liquid dispersion, there is a tendency to flocculate with time.

The present invention seeks to resolve such tradeoffs with polymer solution theory.

The spontaneous polymer solution must have a negative value for the Gibbs free energy change.

Polymer arrangements are highly dependent on the nature of the solvent. A good solvent is a strong attraction between the solvent and the polymer, the polymer chain is stretched, the coil is released.

In the process of making a polymer into a solution, a solvent penetrates into the polymer to block the attraction between the polymer chains and destroy the cohesion of the polymer so that a swelling process occurs. The crosslinked polymer only has this swelling process in contact with the solvent. However, the polymer without crosslinking gradually diffuses the polymer into the solvent phase and finally forms a uniform solution phase.

The present invention is to make a polymer solution using a polymer of EPM and a solvent of toluene, and to disperse carbon nanotubes into the prepared polymer solution.

The following shows the main properties of EPM and toluene.

The solubility index of toluene is about 8.9 (cal / cm 3) ^1/2 and the specific gravity is about 0.86.

EPM (Ethylene Propylene Copolymer) is composed of ethylene and propylene copolymer, solubility index is about 7.9 (cal / cm3) ^1/2 and specific gravity is about 0.86 ~ 0.89.

The Mooney viscosity of the EPM according to the present invention is preferably 10-30 ML _{1 + 4} (100 ° C.).

Since the value of the Mooney viscosity has a certain relation with the molecular weight, it is measured by the Mooney viscosity. It is the viscosity of the unvulcanized rubber measured by a Mooney viscometer. In other words, using the rotor at 100 ° C, measure and read the value 4 minutes after the start of the rotor at 1 minute of preheating, and mark it as ML _{1 + 4} (100 ° C).

When the Mooney viscosity is greater than 30, the molecular weight is large so that it does not dissolve well in the solvent. If the Mooney viscosity is less than 10, the polymer chain is short and the internal space is small so that stability after dispersion cannot be pursued.

As in the main physical properties, the polymer solution is well formed because the specific gravity and solubility index of toluene and EPM are similar.

Since the two properties correspond to good solvents, the solvent is absorbed and the chain size is increased by increasing the contact between the polymer and the solvent. In addition, a strong attraction force between the toluene and the EPM acts to increase the polymer chain, and the coil is released to form an internal space between the EPM chains.

The mixing ratio of the EPM is preferably 2 to 100 parts by weight based on 100 parts by weight of carbon nanotubes. Less than 2 parts by weight of the inner space between the polymer chain is insufficient to pursue the stability after the coating liquid dispersion and the continuous phase of the conductive passages, if more than 100 parts by weight, the stability after dispersion is good but the conductive function is reduced.

That is, the polymer solution according to the present invention is composed of EPM and toluene, which is a solvent, to form a conductive coating solution, and EPM in the liquid phase pursues dispersion and dispersion stability of carbon nanotubes, and the conductive coating solution is impregnated on the fiber to dry and Through the curing process, a conductive layer is formed, and the EPM present in the conductive layer is dispersed in the independent phases of the polymer EPM chains as the solvent toluene is volatilized.

Therefore, the EPM is characterized in that it does not degrade the electrical conductivity function while pursuing dispersion and dispersion stability.

The solution dispersion causes carbon nanotubes to be mixed in the polymer solution, causes the sawtooth disc impeller to rotate at a high speed with a high speed mixer, and causes shock and shearing action by the sawtooth turbine-shaped sawtooth.

In the solution dispersion, the shear rate is preferably 100-300 s ^-1 with a diameter of the tooth disc-shaped impeller in the open drum, the size of 200 ~ 250φ. If less than 100s ^-1 can not homogenize the conductive coating solution, when it exceeds 300s ^-1 it is difficult to disperse the dispersion of the conductive coating solution due to the dispersion of the conductive coating solution.

Solution dispersion of the conductive coating solution according to the present invention is characterized in that the composition consisting of carbon nanotubes, EPM, toluene has a pretreatment process of dispersion in a high speed mixer or the like.

Since the maximum shear force of solution dispersion | distribution by the said sawtooth-shaped impeller is only 0.03 kgf / cm <2>, the dispersion | distribution and distribution mixing of the said kneading process cannot be exhibited by the said solution dispersion process.

Therefore, the solution dispersion according to the present invention is characterized in that the solution is made into the EPM and toluene in the open drum, and the carbon nanotubes are mixed to form the solution in a high speed mixer.

Next, a kneading process is carried out in a rolling mill, pressurized kneader, Banbury mixer, or the like, followed by mixing, dispersing, and uniform dispensing.

Finally, the silicone resin and the remaining toluene are added to disperse with a stirrer to prepare a conductive coating solution.

Carbon nanotubes have a very large specific surface area, a ratio of length to diameter, excellent elastic strength, excellent electrical properties and excellent heat transfer characteristics, and thus can secure a safe conductive path as an electric heating element.

Carbon nanotubes have a graphite sheet circularly rolled to a nano-sized diameter, and exhibit the characteristics of electrically metallic and semiconducting materials according to the angle and shape of the graphite sheet. Nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. The structure of the carbon nanotubes is divided into armchair, zigzag and chiral forms according to the angle of rolling up the graphite plate. Multi-walled carbon nanotubes have electrical conductivity similar to copper. In addition, the hexagonal structure has a cylindrical tube shape, which has about 100 times stronger strength and flexibility than steel.

Carbon nanotubes according to the present invention is not limited, but considering the electrical properties, the armchair structure and multi-walled carbon nanotubes exhibiting metallicity are preferred.

Accordingly, the present invention enables the formation of a three-dimensional network-shaped conductive layer on the heat resistant fiber surface with high electrical conductivity and aspect ratio of carbon nanotubes.

The average diameter of the carbon nanotubes can be selected, for example, from about 0.5 to 1 micrometer, in particular about 1 to 100 nanometers, and the average length is, for example, about 1 to 1500 micrometers, in particular, about 5 to 1000 micrometers. You can choose from.

In addition, since the ratio of the silicone resin allows the carbon nanotubes to adhere smoothly to the heat resistant fiber surface without completely covering the surface of the carbon nanotubes, for example, from 50 to 100 parts by weight of the carbon nanotubes, 1000 parts by weight is preferred.

The silicone resin is also referred to as silicon resin. In general plastics, carbon is often composed of the skeleton of the composition, but the molecular structure of the silicone resin is composed of silicon in the form of siloxane bonds (Si-O) in which silicon and oxygen are alternately formed, and an organic group is a methyl group. , Phenyl group, hydroxyl group, fluorine group, vinyl group and the like are added. In general, chlorosilane can be used as a raw material and can be obtained by hydrolysis. The organic groups bonded to the silicon atoms described above are not limited, but are generally methyl (-CH ₃ ), phenyl (-C ₆ H ₅ ), and vinyl groups. (-CH ₂ = CH), a hydroxyl group, a fluorine group, or a combination thereof may be included. The properties of the silicone resin can be expressed by the crosslinking density of the siloxane and the ratio of the methyl group and the phenyl group in the organic group. The crosslinking density of the siloxanes is represented by R / Si. Here, R / Si shows the average number of organic groups bonded to one silicon atom, and the smaller it is, the higher the degree of crosslinking.

Silicone is changed from oil to rubber and resin by various chemical structural formulas, and various kinds of materials are changed. The thermosetting resin having a network structure by crosslinking in silicone is called silicone resin. It is excellent in heat resistance, moisture resistance, weather resistance and chemical resistance, and its electrical properties are not degraded even at high temperature for a long time.

R / Si of the silicone resin according to the present invention is preferably in the range of 1.30 to 1.65. The property of silicone resin is that as R / Si becomes smaller, the hardenability becomes faster, the film becomes harder and becomes thermosetting. Therefore, the R / Si of the silicone resin composed of heat resistant conductive yarn is preferably 1.30 or more.

 If R / Si exceeds 1.65, the property becomes closer to oil, making it harder to cure, weakening mechanical strength, and vulnerable to oil resistance such as silicone rubber.

In addition, the advantage of the silicone resin is the three-dimensional crosslink density and siloxane bond structure has the advantage of excellent heat resistance and oil resistance.

The method for treating the carbon nanotubes coated with the conductive coating liquid with the above-mentioned conductive coating liquid is not particularly limited. For example, a method of immersing the heat resistant fiber in the conductive coating liquid, a sizing device using a touch roller, a doctor, a pad, and a spray And a method of treating with a conductive coating liquid using a coating apparatus such as an apparatus or a seal printing apparatus.

The coating treatment using the conductive coating liquid may be repeated once or a plurality of times.

In the drying and curing process, a composite material layer of carbon nanotubes and a silicone resin is formed on a heat-resistant fiber treated with a conductive coating solution, and a plurality of conductive passages are formed on the heat-resistant fiber surface with a uniformly thin layer of carbon nanotubes. It is characterized by.

The drying and curing process may be divided into two stages, and the first stage is preferably a drying process of volatilizing a solvent in the conductive coating solution. The curing step of two steps is preferably a curing step of the silicone resin 150 ℃ to 250 ℃.

The carbon nanotube coated fiber according to the present invention is characterized in that the volume resistivity of the coated conductive layer is 10 ⁻² to 10 ³ Pa · cm.

The volume resistivity is a value measured in blocks of the conductive coating solution dried in a volume of 1 cubic centimeter.

When the volume resistivity is exceeded, the capacitance increases, and output stabilization as an electric heating element cannot be expected.

 If the volume resistivity is lower than the above, it is impossible to have an electrical parallel structure that produces a dispersion effect of the load current of the electric heating element at a commercial voltage.

The heat-resistant fiber is a glass fiber, fused silica fiber, high silicic fiber, alumina-silica fiber, alumina fiber, zirconia fiber, aramid fiber, PBO (p-phentlene-2,6-benzobisoxazole) fiber, PBI (polybenzimidazole) fiber, Polyimide fiber, novoroid fiber, etc. are preferable.

The heat-resistant conductive yarn for a heating element according to the present invention can provide a uniform temperature distribution and heat-resistant heating element of the surface heating by the distribution effect of the load current in the electrical parallel structure of the load according to the higher electrical resistivity than the metal resistance wire.

That is, a large difference between the series and parallel, which are the load structures of the electric heating element, depends on the load length between the electrode terminals, and as the load length becomes longer, the voltage distribution becomes uneven. Since the series structure has a long load length and a current flows only on one line, heat collection by external stress may occur.

Therefore, a uniform temperature distribution can be realized by voltage distribution with a short load length as well as a load current distribution effect by the parallel structure.

<Example>

The solution dispersion is a high speed mixer with a toothed disc-shaped impeller of 200 pies in an open drum and 200g of EPM (Kumho Polychem's product, KEP-020P) and 40,000g of toluene are mixed to produce a polymer solution at 1500 RPM. In the polymer solution, 2,000 g of carbon nanotubes (multi-walled carbon nanotubes of CM Hanwha, CM-95) are mixed and dispersed at 2600 RPM for 30 minutes.

Next, as a kneading process, the solution dispersion is dispersed in three roll mills. The intervals between the rolls were maintained at 5 micrometers and a rotational speed of 150 rpm, respectively, and repeated five times at 25 ° C. conditions of the mixture.

As a final dispersion process, 2,000 g of silicon resin (MOSRIVE, TSR116) and 20,000 toluene were added, and a conductive coating solution was prepared at a speed of 1500 RPM using a high speed mixer.

The conductive coating solution was impregnated onto a glass fiber (fineness 67tex, manufactured by Fiber Korea, ECG 75 1/0), which was a heat resistant fiber, and dried and cured to 200 ° C. to prepare a heat resistant conductive yarn coated with carbon nanotubes. As a result, the electrical resistance of the heat resistant conductive yarn was measured at about 1500 mW / cm.

Although described in detail with respect to preferred embodiments of the present invention as described above, those of ordinary skill in the art, without departing from the spirit and scope of the invention as defined in the appended claims Various modifications may be made to the invention. Therefore, changes in the future embodiments of the present invention will not depart from the technology of the present invention.

Claims (2)

In the heat-resistant conductive yarn, the silicone resin having an average number of organic groups bonded to one carbon atom and one silicon atom on the heat-resistant fiber is 1.35 to 1.65, and an EPM having a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 10 to 30. The volume resistivity of the conductive layer coated with the composite material of (Ethylene Propylene Copolymer) is 10 ^-2 Ω · cm to 10 ³ Ω · cm, and the heat resistant fiber is glass fiber, molten silica fiber, high silica fiber, alumina-silica fiber Heat-resistant conductive yarn, characterized in that any one or more of alumina fiber, zirconia fiber, aramid fiber, PBO (p-phentlene-2,6-benzobisoxazole) fiber, PBI (polybenzimidazole) fiber, polyimide fiber, novoroid fiber . In the conductive coating solution, a silicone resin having an average number of organic groups bonded to a carbon nanotube and one silicon atom of 1.35 to 1.65, and EPM (Ethylene Propylene Copolymer) having a Mooney viscosity of 10 to 30 ML _{1 + 4} (100 ° C). , And a solvent, and the composition ratio of the materials is 50 to 1000 parts by weight of silicone resin, 2 to 100 parts by weight of EPM, and 1000 to 5000 parts by weight of solvent based on 100 parts by weight of carbon nanotubes.