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INVENTION
Patent of the Russian Federation RU2042694
ELECTRODUCING PAINT
Name of the applicant: Limited Liability Company "TIKO"
The name of the inventor: Titomir AK; Platonov Yu.M.
The name of the patent holder: Limited Liability Partnership "TIKO"
Address for correspondence:
Date of commencement of the patent: 1994.11.01
Use: for the production of artificial film conductive coatings (resistors).
Essence: the paint contains an epoxy binder of 8-20% filler mixture of graphite with soot at a weight ratio of 0.1: 1.0: 11-39% curing agent 0.5-1.5% organic solvent remaining. Characteristic properties: resistivity 10 3 -10 4 Ω · cm .
DESCRIPTION OF THE INVENTION
The invention relates to the production of paint and varnish materials based on polymeric film-forming binders and can be used in various fields of engineering for the production of artificial film conductive coatings (resistors) on large surface areas of products intended for electrical heating for the purpose of heating the environment, for example: basic and additional lightweight sources Heat of residential and industrial premises (warm walls, warm floors); Equipment for greenhouses; Dryers for agricultural products and household purposes; Medical heating pad; Warm seats for cars; Dry airfield runways and the like.
An electroconductive paint is known based on a polymer film-forming binder, which includes a polymer binder solvent and a fine dispersed conductive filler in the form of a mixture of silver (60-75% of the total weight of the components) and graphite ( 0.5-10% of the total weight of the components). The paint film of the known paint after drying has a specific volume resistance of the order of 10 3 -10 6 ohm cm ( see French Application No. 2662703, cl. C 09D 5/24, 1992 ). The high specific resistivity of the paint film is explained by the fact that despite the high percentage of silver (having an insignificant resistivity in pure form, of the order of 1.49 x 10 -6 ohm-cm ) in the paint coating, it is practically impossible to provide direct tight contact of finely dispersed adjacent silver particles With each other, because Said particles in the process of dispersing the components in the manufacture of the composition are encapsulated with a polymer binder, whereby the contact of adjacent silver particles in the dried coating is effected predominantly through a layer of binder material.
The presence of graphite particles in the composition contributes to a certain decrease in the resistivity of the paint film from the above composition, Fine particles of graphite, having a greater porosity than metals (in particular silver), are able to adsorb the binder and the solvent, thereby ensuring a close direct contact of the surfaces of adjacent graphite particles. However, in the presence of silver particles in the ink composition exceeding the pore size of the graphite particles, during the dispersing process, these pores will be filled with metal particles (silver). As a result, there will be no tight contact between all the graphite particles present in the paint film. That is, in this case, taking into account the fact that the total content of graphite particles is an insignificant part of the content of silver particles in the ink composition, the specific volume resistance of the coating film will be limited, mainly by the resistivity of the film-forming binder, which is several orders of magnitude higher than Graphite and silver.
Calculations show that when obtaining a paint film of this known composition on a substrate in the form of a square of dielectric with an area of 1 m 2 , with a coating thickness of 25 μm and applied to the respective sections of the coating with a voltage of 220 V (taking into account that the specific volume resistance of the coating film is 10 3 ohm cm ) on this sample will be allocated power of about 2 watts .
Comparing this power with the power, for example, of a standard household oil cooler (800-1200 W) having approximately the same area of the fuel surface, it can be concluded that the known paint is not applicable for its use in the manufacture of fuel-resisting electrical conducting surfaces of heating devices, in view of A very high specific volume resistivity (10 3 -10 6 ohm x cm) of a paint film of known composition. In addition, the electroconductive paint of a known composition is very expensive, which limits the field of its use, mainly by the space and aviation industries.
An electrically conductive paint based on a polymer film-forming binder is known, which includes a polymer binder solvent and a finely divided electrically conductive filler in a ratio of 40-80% of the total weight of the composition (composition). The electrically conductive filler can be made of particles of graphite or carbon with a content of 10-50% of the total weight of the composition (composition) ( see PCT Application No. 92-03509, class C 09 D 5/24, 1992 ).
This known electrically conductive paint can comprise an electrically conductive filler in the form of a mixture of finely divided metallic particles and graphite particles or only as a graphite-containing material.
Disadvantages of the known conductive paint, in which the electrically conductive filler is made as a mixture of metal and carbonaceous particles are described above. That is, in this case, the specific volume resistance of the coating film from this known composition will be limited by the resistivity of the polymer binder and have a value of the order of 10 3 -10 6 ohm x cm , which makes it impossible to use this film coating as a heat-releasing element for electric heating Devices and systems.
The implementation of this known composition of electrically conductive paint with electrically conductive filler in the form of carbon-containing fine particles and will not provide the desired result, since for a significant reduction in the specific volume resistance of a film of a known composition, it is required not only to increase the percentage of carbon-containing particles in a known paint, The percentage of pure carbon in said particles in combination with a certain specific adsorption surface of said carbonaceous particles, which is not provided for in the known technical solution. Therefore, it is practically impossible to obtain a film resistor with stable characteristics based on the known composition (for different voltages in the power supply circuit). In addition, the increased content of pure carbon in the known composition significantly reduces the mechanical strength of the film coating (resist) based on the known composition and, therefore, limits the field of application of the coating due to its low durability.
The closest technical solution is a composition for film resistances, which forms a resistive coating with stable physicomechanical properties under conditions of exposure to elevated temperatures at high humidity. The composition contains 20-70 wt. Coal powder, 30-80 wt. Binder epoxy-lanolin and 0.1-2 weight parts of hardener (imidazole) per 100 wt. H of the binder ( see Japanese Application No. 61-276868, cl., C 09 D 5/24, 1986 ) prototype .
A disadvantage of the known composition is that a high percentage of the carbon-containing filler in the form of carbon powder (carbon black) adversely affects the mechanical strength of the film resistances from the composition, which limits the field of use and reduces the durability.
The basis of the invention was the task of creating such a paint composition, a film coating (resist) of which on a dielectric substrate would have a high mechanical strength and a low value of the specific volume resistance ( from 10 -3 to 10 -4 ohm x cm ), allowing Use this electrically conductive coating as a heat-dissipating element of electric heating devices and systems at various voltages in the power supply circuit and under different operating conditions.
The object is achieved in that an electrically conductive paint comprising an epoxy binder, a carbon-containing filler, a curing agent and an organic solvent according to the invention contains as a carbon-containing filler a mixture of graphite and carbon black at a graphite-to-soot weight ratio of 0.1-1.0 with the following component ratio , Wt. Epoxy Binder 8-20
Carbon-containing filler 11-39 Hardener 0.5-1.5
Organic solvent Other
The combination of a certain percentage of the carbon-containing filler in combination with a certain ratio of pure carbon (carbon black) to graphite in said filler allows a tight contact of all carbon-containing filler particles in the film coating obtained from this paint with a specific paint-coat resistance of 10 -3 -10 -4 Ohm x cm , which is several orders of magnitude lower than in the known technical solutions. In addition, the proposed ratio of pure carbon (carbon black) and graphite in the carbon-containing filler allows to increase the mechanical strength of the coating based on the composition and to give it the necessary elasticity.
The method of obtaining an electrically conductive paint and varnish composition (paint) is carried out as follows.
All components (i.e., a film-forming binder, a finely dispersed electrically conductive filler, and an organic solvent) are loaded into a dispersing device in a suitable formulation ratio and dispersed in accordance with a technologically prescribed schedule. The contents are then discharged and a hardener solution in an amount of 0.5% to 1.5% by weight of the film-forming binder composition (ink) is introduced into the resulting composition immediately before application to the non-conductive substrate.
As a dispersing device, a ball or bead mill, a dissolver, a high-speed mixer can be used. The composition can be applied by brush, roller, or by pneumatic, electrostatic and airless spraying, by jetting, however, the aerosol technique of applying the formulation to the dielectric substrate is most preferable.
For the production of an electrically conductive paint and varnish (paint), bicomponent systems are most preferable as a binder, in which epoxy oligomers of the dianium group, the so-called binder, are used as a binder. Diane resins with a molecular mass of 400-3000. Most preferably, epoxy oligomers with a molecular weight of 400-1000 are used . For example, the brands ED-20 and ED-22 (GOST 10587-93) E-40 (TU 6-21-48-90), E-41 (TU 6-10-3342-4-87) .
As a solvent, aromatic hydrocarbons, ketones, ethers and chlorinated hydrocarbons are used. However, it is more preferable to use acetone (GOST 2768-84) , ethyl and butyl acetate (GOST 8991-78) , ethyl cellosolve (GOST 8313-88) , toluene (GOST 9880-76) , xylene (GOST 9410-78), and mixtures thereof.
As hardeners, aromatic polyamines, polyamides, diisocyanates and their modifications are used, as well as boron trifluoride, acid and their anhydride complexes. However, it is more preferable to use imidazolines and primary, secondary and tertiary amines. For example, polyethylene polyamide brand PEPA (TU 6-17-12742-74) or amine curing agent N 1 (TU 6-10-12663-77) .
Carbon (carbon black) and graphite are used as an electrically conductive carbon-containing filler. It is most preferable to use, for example, carbon grade P 268-E (TU 38.41579-83) , or carbon grade P 803 (GOST 7885-86) , or low-ash graphite (GOST 18191-78E) , or powder graphite of special purity (GOST 23463- 79) .
Carbon is obtained by thermo-oxidative destruction of liquid hydrocarbon feedstock, such as, for example, gasoline, toluene, naphthalene at a temperature equal to or greater than 1000 ° C.
It is possible to replace liquid raw materials with gaseous hydrocarbons, such as, for example, ethylene, propylene, propane, methane or carbon monoxide CO . It is desirable that the content of pure carbon in the electrically conductive carbon-containing filler is not less than 97 wt. And the specific adsorption surface is more than 230 m 3 / g .
The graphite particles have a branched shape (structure), their preferential sizes are 0.3-30 nm , which increases the elasticity of the film coating on the basis of the proposed composition (paint).
Compositions of compositions of specific electrically conductive paints are presented in the table.
1-st example (see Table) composition of the composition for producing a film electrically conductive coating used with a voltage of 12 V applied.
2-nd example (see Table) composition of the composition for producing a film electrically conductive coating used with a voltage of 110 V applied.
The third example (see Table) is the composition of the composition for the production of a film electrically conductive coating used with a voltage of 220 V applied.
It has been experimentally verified that in each of the above examples, the corresponding qualitative and quantitative composition of the conductive paints at a given value of the applied voltage provides the temperature of heating of the film coating (formed by this composition) in the range of 30 to 100 ° C.
Thus, the main advantages of the proposed paint composition is that the resulting film-based electrically conductive coating on the dielectric substrate has the following properties:
Low resistivity ( from 10 -3 to 10 -4 ohm x cm ), which allows using both safe ( 12-36 V ) and industrial ( 127-220 V ) voltage values when using a paint film coating as a heat-dissipating (resistive) Element of electric heating devices and systems;
High adhesion ability, allowing the use of a wide range of substrates, including glass, laminates, rubber;
The possibility of creating heating surfaces of a large area;
The possibility to produce in the manufacturing process electro-heat-releasing films with a specified output temperature parameter in the temperature range 30 о С-300 о С ;
Economy;
The possibility of making electrical heat-emitting films with a thermal load from 150 to 1600 W / m 2 ;
Optimal conditions for the heat transfer of the resulting electrothermal-emitting films.
CLAIM
ELECTRODUCING PAINT comprising an epoxy binder, a carbon-containing filler, a curing agent and an organic solvent, characterized in that it contains as a carbon-containing filler a mixture of graphite and carbon black at a graphite-to-soot ratio of 0.1: 1.0 , with the following component ratio,
- Epoxy Binder 8-20
- Carbonaceous filler 11-39
- Hardener 0.5-1.5
- Organic solvent Other
print version
Date of publication 12.11.2006гг
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