RU2472825C1 - Electroconductive paint for radar-absorbent filler - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used to produce artificial film-type electroconductive coatings (resists) for making radar-absorbent filler. The electroconductive paint for radar-absorbent filler contains polyvinyl acetate binder, colloidal graphite, water and OP-10 emulsifying agent.

EFFECT: invention enables to obtain and control resistivity of a current-conducting coating in the range of 150-800 ohm·cm.

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Description

The invention relates to the manufacture of paints and varnishes based on polymer film-forming binders and can be used to obtain artificial film conductive coatings (resistes) intended for the manufacture of radar absorbing aggregates. Elements of dielectric materials (paper, ceramics, plastics, etc.) with a conductive (resistive) layer deposited on the surface are widely used as a radar absorbing aggregate. To achieve maximum absorption efficiency of electromagnetic waves of the microwave range, the resistivity of the conductive layer should lie within 150 - 800 Ohm · cm and be uniform in all directions.

A known method of manufacturing a conductive fabric for the manufacture of electric heaters (US Pat. RF - RU 2074519, IPC Н05В 3/14, Н05В 3/28, published. 02.27.1997). The fabric is impregnated with a conductive composition, which is a 30-60% alcohol solution of phenol-formaldehyde resin, filled with a mixture of carbon (soot) and graphite (in a ratio of 4: 1 to 6: 1) in a total amount of 40 wt.% (On the dry residue of the resin part) . At the same time, depending on the number of impregnations (1-3 times), a conductive fabric with a square resistance (100 × 100) of fabric from 30 to 160 Ohms is obtained. This composition contains an organic solvent, requires a high curing temperature (more than 100 ° C) and is not suitable for thin coatings with a specific resistance in the range of 150-800 Ohm · cm.

The closest in technical essence to the proposed claimed technical solution is the composition (US Pat. RF - RU 2042694, IPC C09D 167/00, C09D 5/24, published. 1995) for electric heaters, including (wt.%):

Epoxy binder 8-20 Carbon filler 11-39 (mixture of graphite with soot in mass graphite to soot ratio 0.1 1.0) Hardener 0.5-1.5 Organic solvent Rest.

The proposed composition of the paint allows to obtain on its basis a film conductive coating on a dielectric substrate with a resistivity of 10 ^-3 to 10 ^-4 Ohm · cm.

By the greatest number of similar features and achieved by using the result, this invention is selected as a prototype.

The disadvantages of the prototype, which does not allow us to achieve our goal, is that the specific resistance of the resulting coating is less than 10 ^-3 Ohm · cm, which is noticeably less than the required values of 150-800 Ohm · cm. An attempt to reduce the specific resistance of the coating by reducing its thickness leads to a decrease in the uniformity of the resistance value over the surface, and it is impossible to obtain a continuous coating on porous substrates (paper, ceramic, etc.) with a roughness of more than 5 μm. The conductive filler included in the composition - a mixture of graphite with soot, fundamentally does not allow to obtain a coating with uniform electrical microconductivity due to the significant difference in the particle sizes of graphite and soot.

In addition, the organic filler included in the composition increases the environmental and fire hazard of the claimed composition.

Also a disadvantage of the known composition is its two-pack, i.e. the hardener included in the composition is introduced immediately before painting, which creates inconveniences in work and limitations in use, and in some cases unproductive losses of material due to incorrect estimation of the required amount of paint for work.

The purpose of the claimed technical solution is to create a paintwork composition (paint), which allows to obtain and adjust the resistivity of the conductive coating on its basis within 150-800 Ohm · cm, used for the manufacture of radio-absorbing fillers of electromagnetic waves of the microwave range.

This goal is achieved in that the electrically conductive paint, including a polymer binder, a carbon-containing filler, an emulsifier and a solvent, contains a polyvinyl acetate resin as a binder and contains colloidal graphite as a carbon-containing filler in the following ratio, wt.%

Polyvinyl acetate binder 18.5-20.3 Colloidal graphite 22.3-23.9 Emulsifier OP-10 0.02-0.03 Water Rest

The proposed paint can be made from materials known in the industry on known equipment. This allows us to conclude that the claimed technical solution meets the criterion of "industrial applicability".

Paint preparation technology

To prepare the emulsifier solution, 99.95 wt.% Softened water is poured into the mixer, 0.05 wt.% Emulsifier (OP-10) is added and mixed thoroughly.

A 23.3 wt.% Colloidal graphite (KG) weighed was loaded into another mixer, 38.3 wt.% Of the prepared emulsifier solution was added and stirred for 30 minutes. 38.4 wt.% Polyvinyl acetate (PVA) dispersion (dry residue 50%) is added to the graphite paste and mixed for 60-90 minutes until a homogeneous composition is formed. Then the mixer switches to low revolutions and samples are taken to determine the solids and resistivity. If necessary, adjustments are made by adding KG paste or PVA dispersion.

As colloidal graphite, a colloidal-graphite preparation of the brand KGP-S TU 113-08-48-63-90 is used.

As the polyvinyl acetate binder, a PVA dispersion GOST 18992-80 is used. The solids content of 50%.

As an emulsifier, products of processing a mixture of mono- and dialkylphenols with ethylene oxide - OP-10 GOST 8433-81 are used.

Paint composition adjustment

To obtain the required technological and electrical properties, the ratio of the mass of KG powder to the mass of PVA binder in the cured coating is important. The value of the mass ratio of KG: binder PVA should be in the range of 1.10 ÷ 1.30. The optimal ratio value is 1.22. With an increase in the content of KG, the coating begins to grind (when wiping, dirty with graphite). With a decrease in the content of colloidal graphite, the coating resistance sharply increases.

The amount of PVA dispersion introduced is adjusted after determining the solids content (i.e., polyvinyl acetate binder) in it.

Paint is applied by brush, roller, dipping, filling, pneumatic spraying. To obtain the necessary viscosity during application, the paint can be diluted with softened water.

The compositions of the specific electrically conductive paints are presented in table 1.

Table 1 Component The composition according to the example, wt.% Prototype one 2 3 Polyvinyl acetate binder - from PVA dispersion (GOST 18992-80) 20.3 19,2 18.5 Epoxy Diane resin E-41 (TU 6-10-3342-4-90) twenty Colloidal graphite KGP-S (TU 113-08-48-63-90) 22.3 23.3 23.9 Carbon (soot) P 268-E (TU 38.41579-83) fourteen GOST 23463-79 graphite eleven Amine hardener No. 1 (TU 6-10-12663-77) one Emulsifier OP-10 (GOST 8433-81) 0.02 0,025 0,03 Water Rest Rest Rest Solvent (acetone: ethyl acetate: toluene - 3: 1: 5) Rest

The value of the specific resistance of the resulting coating in the range of 150-800 Ohm · cm is easily adjusted by changing its thickness (changing the number of layers). Ease of regulation is provided by a convenient interval of thickness variation of 30-100 microns. The resistivity values for the examples are presented in table 2.

table 2 Indicator Composition No. 2 Prototype Number of layers one 2 3 one Coating thickness, microns thirty 70 one hundred thirty The specific resistance of the coating, Ohm · cm 800 240 150 Less than 1 · 10 ^-3

For comparison, the selected composition according to example 3 of the prototype. This composition is the closest to the proposed claimed technical solution, because has the smallest ratio of the mass of the carbon-containing filler to the mass of the polymer binder and, accordingly, the lowest resistivity.

The proposed composition in comparison with the prototype allows to obtain and adjust the resistivity of the conductive coating in the range of 150-800 Ohm · cm and, in addition, is characterized by:

- less environmental and fire hazard, because does not contain organic solvents;

- homogeneous electrical microconductivity, as colloidal graphite has a narrower dispersed distribution than a mixture of graphite with soot;

- better adaptability, as It is one-pack and does not contain hardener.

Thus, the new qualitative and quantitative composition of the claimed composition provides new properties of coatings based on it.

Comparison of the proposed composition with the known allows us to conclude a new qualitative composition of the composition, characterized by a certain quantitative ratio of its ingredients. This allows us to conclude that the claimed technical solution meets the criteria of novelty, inventive step, industrial applicability.

Claims (1)

Electrically conductive paint for radar absorbing aggregates, including a polymeric binder, a carbon-containing filler, a solvent, characterized in that it contains a polyvinyl acetate binder as a binder, colloidal graphite as a carbon-containing filler, and water as a solvent, and additionally contains an OP-10 emulsifier in the following ratio components, wt.%:
Polyvinyl acetate binder 18.5-20.3 Colloidal graphite 22.3-23.9 Emulsifier OP-10 0.02-0.03 Water Rest