FI56464C - FOOD FRAMEWORK FOR FOUNDATION - Google Patents

Description

Γηΐ ANNOUNCEMENT γλαγ. df & A ^ 1) UTLÄGGNINGSSKRIFT 56464 C (45) Patent granted 10 01 1930 Patent meddelat '(51) Kv.lk. * / lnt.CI. » H 05 B 5/26 ENGLISH - FI N LAN D (21) Ptt * nttlh »k * mui - P» t * r »tin * öknlnf 1059/70 (22) H * keml * pllvl - · AiwBknlnfidag l6. 0 ^ 4.70 ^ ^ (23) Alkupllvl — Glltlghetsdaf l6. O ^ t. 70 (41) Gotten stuck - Bllvlt offuntllg> j_q. 70

Patent and registration registers (44) Date of issue and date of issue. -

Patent and registration authorities AniBkan utltjd och uti. »Krtft * n pubitcend 28.09.79 (32) (33) (31) Privilege requested— Begird prloritet 18. Oi * .69 Ο6.Ο8.69 England-England (GB) 200i + l / 69, 39 ^ 80/69 - (71) The Research Association of British Paint, Color & Varnish Manufacturers,

The Paint Research Station, Waldegrave Road., Teddington, Middlesex,

England-England (GB) (72) John Allen Saunders, Teddington, Middlesex, England-England (GB) (7 ^) Oy Jalo Ant-Wuorinen Ab (5 * 0 Paint mixture and method for its preparation - Färgblandning och förfarande för dess framställning This The invention relates to an electrically conductive paint composition comprising electrically conductive carbon particles in an air-curable binder and having a paint-Neh consistency, which can be brushed or sprayed on a surface into a thin, uniform film with low electrical resistance, and the preparation of such a paint composition.

There have been many attempts to make electrically conductive coatings, and these have generally been of two different types. One of these is formed from a paint with pigments formed from metal particles, while the other type of coating is formed from mixtures containing carbon or graphite.

Paints containing metal particle pigments form coatings with very low resistivity and form coatings with high electrical conductivity.

Alloys containing carbon and graphite, on the other hand, have had a much higher resistivity. Thus, when formed into thin coatings, e.g., 0.0025 to 0.013 cm (0.001 to 0.005 ") thick, they have a very high resistivity, e.g., 100 ohms per square meter of surface area or much more. If they form thicker coatings, the films they crack over time, and these coatings could not be formed by painting alone.

C 09 D 5/214 2 56464

There is a need for electrically conductive coatings with a resistivity such that they can be used as heating elements, for example on the walls of a building. Thus, paints containing metal particle pigments are completely unsuitable due to their high electrical conductivity, as very strong electric currents would be required to achieve a reasonable thermal result. Alloys containing carbon or graphite, on the other hand, have too high a resistivity, so they require too high a voltage for safety in order to achieve a reasonable thermal result. Thus, if they are used in the walls of a building, the voltage as a whole should not exceed the limit of 40 volts, which according to the Institution of Electrical Engineers, United Kingdom, is defined as low voltage.

The paint composition of the present invention is characterized in that the amount of electrically conductive carbon particles has a pigment volume concentration of 25-75%, of which 14-80% are thin plate-like graphite particles formed by graphite wet grinding of graphite particles. the particle size is 20 to 60 nanometers, determined by electron microscopy, and that the resistivity of the dried paint film is 0.1 to 1 ohm per square meter of surface area.

The invention also provides a method for producing the above-mentioned electrically conductive paint, wherein the graphite is comminuted by wet grinding to reduce graphite to thin sheet-like particles by laminar cleavage, and the graphite is incorporated into an air-curing binder before, during or after grinding. is 20-60 nm.

By forming the paint in this way, it has been found that the dried films formed from the paint combination have a very low resistivity, e.g.

0.1 to 10 ohms per square meter of surface area. In practice, the resistivity of thin films, e.g. 0.0025 cm (0.001 ") thick, may well be less than 10 ohms per square meter and values as low as 1 ohm per square meter can be achieved. Thus, a film with a side length of 0.30 m (1 feet square) with a resistivity of 1 ohm per square gives a power of 25 watts at a voltage of 5. A larger surface, e.g. one with a side length of 2.44 m (8 feet square) has the same power (namely 25 watts ia / sq.ft,) at a voltage of 40 volts, this voltage being probably the highest voltage limit taking into account safety requirements.The paints of this invention are thus well suited for use on interior surfaces of buildings or in cases where large surface heating is desirable without high voltages.

The actual resistivity of the dried film formed from the paint composition of the invention depends on the thickness of the film and the paint films are generally 0.0025 to 0.013 cm (0.001 to 0.005 ") thick. A normal thin film has a thickness of about 0.0025 cm (25 microns) and Between 0.004 cm and 2 ...

the dry weight is about 50 to 60 g / m. Thicker end caps can be made by forming a thicker film, e.g., 0.0075 cm (75 microns, 0.003 "), or by forming multiple overlapping thin films.

It is not entirely clear why the paints according to the invention form coatings with such a low resistivity, but this is probably due to the fact that the graphite is ground wet. Due to this wet milling in suspension, the obtained ground graphite particles have a different shape compared to the dry ground particles, and also their particle size distribution is different. This wet grinding causes laminar cracking of the graphite particles, resulting in a large amount of formed particles, and this probably results in the ground particles packing together in a dry film, causing low resistivity. The graphite should preferably be of a type that readily forms flakes or plate-like particles.

Another advantage of the invention is that the films formed from the paint according to the invention can be heated intermittently, i.e. by repeatedly conducting an electric current through the film, and then cooled without cracking the film, while the film formed only by mixing fine carbon black and the same binder, cracks after only a few heat cycles.

The graphite content of the paint compositions according to the invention depends on the conductivity of the films formed from the combinations, so that the conductivity increases as the amount of graphite increases. However, a balance must be struck between high conductivity and a permanent paint combination with sufficient binder to achieve the desired paint properties. Thus, the ratio of graphite to binder should generally be 0.33: 1 to 4: 1 by weight of the nonvolatile material, or the pigment volume concentration (p.v.c.) should be 25-75%, preferably greater than 45%. It is clear that the carbon content of graphite also affects the conductivity and high carbon content is considered to be the best.

It has been found that wet grinding generally does not produce significant amounts of the very smallest, i.e., colloidal size particles. Thus, according to the present invention, colloidally sized carbon particles are preferably added to the paint compositions at a suitable stage in the manufacture of these paint compositions. It has been found that this measure further reduces the resistivity of the films formed from the paint compositions according to the invention.

In addition to the improvement of the electrical properties, the obtained paint compositions have improved brushability, i.e. they are easier to apply and form more uniform films.

According to the invention, there is thus provided a paint mixture which, when dispersed in an air-curable binder, contains a total of 25-75% (pvc) of conductive particles »of which 14-70% (pvc) are thin plate-like graphite particles and 2-35% (pvc) colloidal carbon particles with a particle size of 20%. -60 millimicrons as determined by an electron microscope with a combination of a surface-like consistency that can be brushed or sprayed onto a thin flat film with low resistivity.

The weight ratio of colloidal carbon to graphite can be as high as 0.8; preferably the weight ratio is 0.1 to 0.5, with a weight ratio of 0.4 giving the lowest specific resistance in the dried paints, and weight ratios between 0.2 and 0.3 giving optimal flow properties to the paint combinations. However, graphite particles cannot be completely replaced by colloidal carbon particles because, as mentioned above, the dried films obtained are unstable with respect to repeated thermal fluctuations, e.g., those formed by conducting an electric current in impulses through the film.

The size of the colloidal carbon particles is preferably 20 to 50 nanometers as determined by electron microscopy. Suitable colloidal carbon particles include imperfectly combusted carbon particles such as available fine carbon black pigments, e.g., Vulcan XXX or Vulcan XC-72, manufactured by Cabot Corporation, and acetylene black, e.g., a product marketed by Shawinigan Chemicals Limited.

As described above, thin sheet-like graphite particles can be prepared by wet milling. However, since it has been found that the electrical resistivity is significantly reduced in films made from paint compositions to which colloidal carbon particles have been added, graphite having a particle size smaller than it is if wet colloidal carbon particles are not added from the outset. This, of course, reduces the time and cost required for the grinding process, and prevents coarse particles from entering the final coating.

By "air-curable" binder is meant a binder that adheres, i.e. cures, to a dry film when the paint mixture is applied to a thin film that comes into contact with air at room or elevated temperature. This curing, or curing, can be accomplished in any suitable manner, for example, by evaporation of solvents, by reaction with another component of oxygen or the atmosphere, or by reaction with other components of the paint composition.

Films formed from the paint compositions of the invention can be used as a heat source by conducting current through them, so the binder should be stable at the temperatures reached by the film. The normal operating temperature of the inner wall or ceiling surface 5 56464 should be 30-50 ° C. Typical suitable binders are inorganic binders, such as alkali metal silicate, e.g. potassium or sodium silicate, aqueous binders, such as partially organic binders, e.g. silicates of quaternary organic bases, or fully organic binders, e.g. aqueous emulsion binders, and organic binders, and organic binders. The maximum operating temperature of the dried paint films depends on the binder used. Thus, for example, films made with silicate binders can be used at temperatures up to 40 ° C, while films made with aqueous emulsion paint can only be used at temperatures below 100 ° C.

If films are used on the walls of buildings, it is desirable that they be refractory. This requirement can be met by using inorganic silicate binders.

Wet grinding of graphite can be aided by the addition of a surfactant to the mixture. Such substances improve the film-forming properties, as well as facilitate the use of the obtained paint combinations, in addition to increasing the efficiency of the grinding process, thus reducing the grinding time.

When using aqueous alkali silicates, anionic, cationic and nonionic surfactants can be used as binders. However, the sodium naphthenic sulfonic acid / formaldehyde condensate type (Dispersol T or Belloid TD) is preferred, but this cannot be used when the paint must be free of metal ions, e.g. when using organic ammonium silicate. In such cases, a nonionic agent such as Lissapol NX (nonylphenyl ethylene oxide condensate) is preferably used. This also improves the shelf life of the paints. In some silicate soils that readily form a gel upon contact with ceramic consumables from the mill, a cationic agent, e.g., fatty amine / ethylene oxide condensate (Ethomeen *), can be used to improve their shelf life.

Dispersol T is not suitable for use with some organic emulsion binders because it may turn the emulsion into a gel; Lissapol NX can be used instead with good results. Polymeric binders soluble in organic solvents are in some cases sufficiently dispersed without the specific addition of surfactant, but if necessary, one of the Rosaniline bases is used.

The surface can be coated with the paints according to the invention in the same way as when using ordinary paints, for example with a brush, roller, spraying or dipping.

The graphite must be ground wet, i.e. when ground, the graphite must be in suspension in a liquid which may be the binder itself or a liquid which is a solvent for the binder or compatible with the binder, such as water. When using organic latex binders as well as some silicate binders, it is better to grind the graphite, possibly together with colloid-sized carbon particles, for example in a small amount of water and dispersant, and then add the binder to the obtained ground paste. In other cases, the graphite may be ground together with a small amount of binder, after which the remaining major portion of the binder is added to the resulting ground mixture, while in cases where colloidal carbon particles are used, these colloidal particles may first be thoroughly ground with binder, then graphite is ground. still. The best relative order of the different steps can be found out by experiment in each case.

An excellent paint mixture according to the invention can be prepared from a potassium silicate solution with a molar ratio of SiOg / KgO of about 4, rather coarse-flake graphite, which of course fines during grinding, and an alkylaryl sulfonate, e.g. Belloid TD or Dispersol T (methylene) disodium salt of sulfonic acid) as a surfactant. Generally, such a combination is also diluted with water.

The manner in which the electrodes are attached to the films formed from the paints of the invention is not critical if the adhesion resistance of the formed joining point is low. In practice, it has been found that a particularly practical method is to coat the surface with the mixture according to the invention, and then to apply thin aluminum foils (e.g. 0.0008 cm thick) along opposite edges of the painted surface using a thin layer of paint as an adhesive. 18 B.G. contact bars formed of aluminum strip can be attached to the film along their entire length with screws or spring clips. Using such a system, currents of 3 to 6 amps per foot can be used without overheating the junctions.

The paint combinations of the invention are useful in many cases where an electrically conductive film is required. They can be used in the walls of buildings, e.g., houses, apartments, offices, factories, schools, and hospitals, and conduct electrical current through the formed membranes to heat the building. Alternatively, prefabricated heating sheets with a film of dried paint on a wide variety of substrates, e.g. insulated steel, insulated aluminum, hardboard, particle board and wood, can be used and can be attached to a building or used as a free-standing panel. Such panels have a wide range of applications in households and industries, e.g. as a special heating unit in cars, trains and airplanes.

7 56464

Not only can the paintwork be used in the wall panels of buildings, they can also be attached, for example, to concrete, which is covered with a plastic layer or floor brick, thus obtaining underfloor central heating.

Other uses for dried, electrically conductive paint films include, for example, heating livestock farms, hens, poultry incubators, greenhouses, seedlings, using separate heating panels or by painting the walls or floors of such units easily. coating the surfaces of the cathode ray tubes to form an electrostatic sieve, or their use as gas heating units, such as, for example, convector-type free-standing heating devices.

The invention is illustrated by the following examples:

Example 1:

An electrically conductive paint mixture was prepared by grinding the following components in a ball mill at said weight ratios for 10 hours in a ball mill: potassium silicate solution, 29.9% solids, molar ratio SiO 2 / K 2 O = 3.89,500

Kadagascar flake graphite (C content 85%) 222.5 anionic wetting agent (Belloid TD) 16.2 water 150

The formed paint mixture was applied in one layer by brushing to a rectangular asbestos sheet measuring 46 x 51 cm and the metal strips were fixed using the above-mentioned method. After the plate was dried, the aluminum mine contact bars, 3.17 x 51 cm in size, were attached to each of the longer edges of the plate using five clips on each contact bar. The total resistance of the plate coating was 0.90 ohms, and the JO ampere current through the membrane produced 0.04 · watts per cm (36 watts / sq.ft.) With a maximum power voltage of 0.2 volts / cm (6 volts / ft). .).

A decorative silicate paint containing a yellow inorganic pigment was sprayed on the front surface of the electrically conductive plate, and it was found that this operation did not substantially alter the heating properties of the film.

The membrane maintained its flatness during 16 months of daily use, during which time the plate was heated for 7 1/2 hours daily, switching on and off. The electrical properties also did not change during this time.

Example 2:

To compare different grades of graphite, a series of paint mixtures were prepared in a ball mill using potassium silicate solution (30% solids) as a binder, and Belloid TD as a dispersant. Different types of graphite were added to each combination as follows: 8 56464 A average particle size 5 μ B 98% passed through 300 mesh (53 μ)

C flake type substance, 20 mesh BS

In addition, the ratio of graphite to binder was varied.

Each paint mixture was then sprayed onto the asbestos sheets so that the coating had a dry weight of 0.00625 g / cm (film thickness about 0.0025 cm, 0.001 ") and the electrodes were attached in the same manner as above. After the films dried, their resistances were measured and the results are given. in the following table.

Graphite weight ratio Specific resistance to ohmic / nelic> j binder

Graphite A Graphite B. Graphite C

1.33 29.1 3.3 1.7 1.00 - 7.9 1.9 0.67 118.0 14.7 5.5 0.44 - HO, 2 26.0

It can be seen that the electrical conductivity increases as the amount of graphite increases. The best results were also obtained using flake-type graphite.

It is clear that by forming a second coating layer from each combination, the resistivity of the films can be halved.

Example 3:

Two paint combinations (A and B) were prepared by grinding for 8 hours in a ball mill together the following substances, expressed in parts by weight:

Haali A Maali B

Potassium silicate solution (molar ratio

SiO 2, 3.89, 29.9% solids 333.3 333.3

Madagascar flake graphite (coarse,> 85% carbon) 200.0 181.8 carbon black (Vulcan XC-72) - 18.2 dispersant (Belloid TD) 10.0 14.5 distilled water 231.8 231.8

Paint B contained about 10% colloidal carbon black out of the total amount of carbon particles as well as a larger amount of dispersant to promote dispersion of the colloidal particles.

It was then coated by brushing individual gypsum boards, measuring 30.5 x 35.6 cm (12 "x 14"), and after drying, 2.54 cm (1 ") wide aluminum foil terminals were bonded to give an electrically conductive coating with dimensions of 9,546,464. , 5 cm x 30.5 cm (12 "χ 12"). The electrical resistances were measured and the following results were obtained:

Paint A 5.5 ohms / square

Paint B 1.6 ohms / square

Example * 4:

Two paints (C and D) were prepared with the following compositions by weight:

Maali C Maali D

potassium silicate solution (molar ratio SiO 2 / K 2 O = 3.89, 29.9% solids 333.3 333.3

Ceylon graphite (<SO mesh powder 93-94 ·% carbon) 200.0 181.8 carbon black (Vulcan XC-72) - 18.2 dispersant (Belloid TD) 14.5 14.5 distilled water 231.8 231.8

The paints were tested as described in Example 3. The dried coatings obtained had the following resistances:

Paint C 7.6 ohms / square

Paint D 1.5 ohms / square

Example 5:

Two paints (E and F) were prepared as described in Example 3, the compositions in parts by weight of d.are the following:

Paint E Paint F

sodium silicate solution (molar ratio

SiO 2 / Na 2 O = 3.98, 28.0% solids) 357.0 357.0

Ceylon graphite (<S0 mesh powder, 93-94% carbon) 200.0 181.8 carbon black (Vulcan XC-72) - 18.2 dispersant (Dispersol T) 14.5 14.5 distilled water 208.0 208 , 0

Each paint was diluted with 75 ml of water before being removed from the mill, and the resulting paints were tested as described in Example 3. The dry coatings obtained had the following resistances:

Paint E 4.7 ohms / square

Paint F 1.3 ohms / square

As can be seen from Examples 3-5, paints A, C and E form films with low resistivity, however, paints B, D and F prepared by adding colloid-sized carbon particles formed films with even lower resistivity.

Lithium silicates and mixtures of lithium silicate with sodium silicate and possibly potassium silicate are also good binders which can be used in the paint compositions according to the invention, as can be seen from Examples 6 and 7. Example 6:

Two countries (G and H) with the following compositions by weight:

Maali G Haali H

lithium silicate solution (molar ratio

SiO 2 / I 2 O = 6.0, 25% solids) 400 400

Ceylon graphite (50 mesh powder, 93-94% carbon) 200 181.8 carbon black (Cabot grade XC-72) to 18.2 dispersant (Dispersol T) 14.5 14.5 distilled water 165 165 were prepared and tested as follows: as shown in Example 3. The dry coatings obtained had the following resistances:

Paint G 10.0 ohms / square

Paint H 3.75 ohms / square

Example 7:

Two paints (I and J) with the following compositions by weight:

Maali I Haali J

sodium silicate solution (molar ratio SiO 2 / Na 2 O = 3.98, 28% solids) 155,155 lithium silicate solution (molar ratio SiO 2 / Li 2 O = 6.0, 25% solids) 226,226

Ceylon graphite (50 mesh powder, 93-94% carbon) 200 181.8 carbon black (Cabot grade XC-72) to 18.2 dispersant (Dispersol T) 14.5 14.5 distilled water 184 184 was prepared and tested as Example 3 is explained. The dry coatings obtained had the following resistances:

Paint I 7.9 ohms / square

Paint J 3.5 ohms / square

It can thus be seen from Examples 6 and 7 that satisfactory electrically conductive paint coatings can be prepared using lithium silicate as a binder, either alone or in admixture with sodium silicate, whether or not colloidal graphite is present. However, the use of lithium silicate (which is more expensive than sodium or potassium silicate) does not appear to reduce the resistivity, but it forms a binder that is more water resistant than sodium or potassium silicate * In addition, the use of lithium silicate alone or in combination with sodium silicate makes it possible to use n 56464 a silicate binder in which the molar ratio of silicate to alkali metal oxide is higher.

Example 8:

To demonstrate the effect of carbon black content, a series of paint mixtures were prepared using potassium silicate as a binder (molar ratio SiO 2 / O 2 = 3.89, 29.9% solids). The ratio of carbon black (XC 72) to graphite (Ceylon grade, <50-mesh B.S.) was varied. In each paint mixture, the dispersant was Dispersol T, and the mixtures were ground for 4 hours in a rotary mill; silicate binder was added after grinding.

The mixtures were prepared using the following ingredients, where 'x' stands for carbon black / graphite ratio:

Graphite powder 200 / x + 1 g

Carbon black 200x / x + 1 g

Dispersol T 14.5 g

Water 307.0 g

Potassium silicate 333.3 g 2 The gypsum boards were coated so that the dry weight of the coating became 50 g / m, giving the following resistances: x Specific resistance (ohms / square) 0 6.50 0.1 1.81 0.2 1.45 0.3 1.31 0.4 0.88 0.5 1.86 0.6 1.94 0.7 2.04 0.8 2.45

The lowest electrical resistivity was obtained with a carbon black / graphite ratio of 0.4. However, as the ratio increased to 0.8, even better results were obtained compared to a paint using only graphite. As the 'x' varied, the fluidity of the paint also changed, and at values greater than 0.4, the brushability deteriorated, while at best it was between 0.1 and 0.3.

Example 9:

Paints were prepared as in Example 8, using different types of carbon black and different values of 'x', with 'x * being defined in the same manner as above. The following table shows the specific resistances obtained using a coating weight of 2,50 g / m on gypsum board.

12 56464 --- 1 -; - 1--

Carbon black quality j Particle size (mp) j x Resistance (ohms / square)

Black Pearls 607 ^ 13 0.1 3.2 i Regal 330 '' 25 0.1 1.8

Sterling SO 41 0.1 1.7

Sterling SO 41 0.2 1.6

Sterling SO 41 0.3 1.5

Sterling MTFF 250 0.1 3.3 without - 0.0 7.8

In each of the above cases, improvements in electrical conductivity can be observed compared to a paint using graphite alone, and it is clear that the carbon black quality used is not very important when the particle size is of the same order of magnitude as "combustion grades" or other suitable carbon blacks with similar results, according to Cabot. «XXX and Cabot Regal SRF grades for sale. However, it is noted that higher resistances are obtained when the particle size of the carbon black is less than 20 mv or greater than 60 mv. (e.g. Sterling KTFF).

Similar results were obtained using these carbon black grades as well as a partially organic aqueous quaternary ammonium silicate type binder as a binder, e.g. sold under the trademark Quram, or a completely organic aqueous emulsion, as shown in the following example.

Example 10:

Four premixes I to IV were prepared by grinding together the following ingredients, expressed in parts by weight, in a rotary ball mill for four hours:

Ingredient _Premixture_

I II III IV

Graphite Avarc 202 200 166.7 200 166.7 carbon black (Vulcan XC-72) no 33.3 no 33.3

Dispersol T 14 14.5 no no

Dispersant (Lissapol NX) no no 12 12

Distilled water 357 357.0 357 357

Paint mixtures were then prepared by mixing certain of these premixes I to IV with certain binders V to XI.

13 56464 V Revinex 10 A 40 (carboxylated styrene / butadiene latex) VI Emultex F (non-plasticizable polyvinyl acetate latex) VII Vinamul 6825 (75/25 vinyl acetate / 2-ethylhexyl acrylate latex) VIII Revacryl 144 (styrene / acrylic latex) / 30 vinyl acetate / transport 911 latex) X Quram Expt. Well. 5 (quaternary ammonium silicate; SiO 2 = 45% by weight) XI Quram 220 (quaternary ammonium silicate, SiO 2 = 45% by weight).

Each paint was applied as a single coat to gypsum boards measuring 30.5 cm x 35.5 cm (12 "x 14"), and after drying, 2.54 cm (1 ") wide aluminum foil terminals were attached to each end to provide electrically conductive paint film with an area of 30.5 cm x 30.5 cm (12 ,: x 12 "). The electrical resistances were then measured.

The composition and resistivity of each paint are shown in the following table.

I -: - f --- I Premix Binder Resistance type (ohms / square) quality quantity by weight ---- --- 'i _l IV 110 17.0 II V Pleasure 3.3 II VI 106, 5 9.3 II VI 106.5 2.4 II VII 94 20.0 II VII 94 3.6 Ί

I I

! I X 117.5 12.3 I

I II X 117.5 3.6; i xi 122 10.4 II XI 122 3.5 III IX 101 10.3 IV IX 101 4.9 IV VIII 105 5.7 IV VI 106.5 4.5 III X 117.5 4.0 IV X 117, 5 3.0 IV XI 122 2.5

It can be seen that the addition of carbon black to the composition significantly reduced the resistivities.

Coating gypsum board panels with a second electrically conductive film 14 56464 reduced the resistivities of paint blacks containing carbon black to 1-2 ohms / square.

All paint films were stable to heat exchange conditions.

The temperature of the plates was raised to about 40 ° C by passing the required current (i.e., less than 5 amp.) Through the membrane to provide a power of 377 watts / m (35 watts / sq.ft.). The resistances of the hot paint films decreased by about 10-30%, but on cooling they returned to their original values. This stability also applied to sheets coated with a non-conductive emulsion.

The paint compositions of the invention can also be prepared using an organic solvent soluble resin as a binder to provide low resistivity films with coatings thickness of 0.0005 to 0.007 cm (0.002 to 0.003 "). Addition of Dispersant to Organic Solvent-Based Compositions in terms of appearance and flow properties, was not always necessary because the resins themselves can act as dispersants.

These paint compositions are illustrated by the following Example 11: Example 11:

Five paint mixtures K-0 were prepared by rotary grinding together different ingredients in different amounts using different long grinding times. In all cases, an epoxy ester binder was Synolac 400 W (80% resin in white spirit). To the formed paint mixtures, 2 g of a cobalt naphthenate drying solution (cobalt content 6%) was added, the gypsum boards were then coated with these paint mixtures, and the electrical resistances of the dried films were determined.

>. KaaJ iconic composition

Ingredient -; K L M N 0 | i --- 1 -----

Epoxy ester (g) 87.5; 87.5 87.5 87.5 87.5

Graphite (Avarc 202) (g) 166.7 166.7 166.7 166.7 166.7

Carbon black (XC-72) (g) 33.3 33.3 33.3! 33.3 and 33.3

White Spirit / xylene (ml) (50/50 mixture) 600 - 600 600

Copper oleate (g) - 11

Duomeen TDO. (g) - - 11 5 5

Cellosolve / xylene (3/1 mixture) (ml) 600 600

Grinding time (hours) 4 4455

Epoxy ester added before or after grinding graphite before before before after before Electrical resistivity 6.8 7.9 9.4 6.6 6.4 (ohms / square) _____! _______ 15 56464

Films with a specific resistance of aJhainen are obtained.

These soil mixtures were relatively flowable and were found to improve their flow properties by reducing the volume ratio from 65% to 47%, increasing the ratio of carbon to graphite and adding Rosaniline base as a dispersant. This is illustrated by the following Example 12. Example 12:

Two paint mixtures (P and Q) were prepared from the following ingredients:

Epoxy ester (Synolac 400W) 87.5 g

White spirit / xylene (50/50 mixture) 350 mj.

Carbon black (XC-72) 33.3 g

Dispersant (Rosaniline base) 1.0 g.

These were rotationally ground for one hour, then 66.7 g of Avarc 202 graphite was added to both paints, followed by further grinding for 3 hours.

Both paint mixtures produced were flowable, thin paints with similar performance characteristics to water-based paints.

This was probably mainly due to the dispersant, Rosaniline Base, which is one of the best dispersants of colloidal carbon particles and graphite v organic solvents.

Rosaniline was used in two different ways. For the earth mixture P, rosaniline was heated to 190 ° C with the epoxy ester 15 minutes before grinding, whereby a chemical reaction probably occurs because the base changes color and its dispersing efficiency is improved. In paint mixture Q, the rosaniline base was dissolved in the resin only at 100 ° C before grinding, and this combination was found to be thicker than combination P.

Gypsum boards were treated with paint mixtures as above and the weight of the coating was determined. The electrical resistivity was determined and the results were calculated for a coating weight of 2,100 g / m, which corresponds to a film thickness of 0.005 cm (0.002 "). The electrical properties were: (-; - r

Paint Resistance, 100 g coating /) nr (ohms / square)! P 7.4 Q 6.9

Example 13:

8 paint mixtures were prepared by R-Y rotary grinding together with the various ingredients listed in the table below. When using carbon black (XC-72), this was predispersed 2 hours before the addition of graphite (Avarc 202). After the addition of graphite 16 56464, all paint mixtures were ground for 4 hours. Gypsum boards were coated with the finished paint mixture, after which the electrical resistances of the dried films were determined and the results were calculated per 100 g / m baling weight. Using an alkyd / melamine binder, the films were cured by heating in an oven at 125 ° C for 1/2 hour.

. Paint

Component ---— —-f-r-f -—---

R S T U | V W X Y

_____ j --------

Polymethacrylic ester I

40% solution (Bedacryl 122X) - (g)

Xylene (ml) 500 500 500 500 -

Carbon black (g) 33.3 16.7 - - 33.3 16.7 '-

Graphite (g) 166.7 83.3 200 100 166.7 83.3 200 100 non-drying castor oil 1 alkyd resin (60% solids (g) - 65 65 65 65

Butylated melamine-formaldehyde resin - - - - 21.8 21.8 21.8 21.8 (60% solids) (g)

Xylene-n-butanol (3/1 mixture) (ml) - 600 600 600 600 p.V.c; (%) 65 47 65 47 65 47 65 47 carbon black / graphite 0.2 0.2 no no 0.2 0.2 no no resistivity (ohms / square) 3.0 2.4 9.5 18.0 3, 9 3.0 6.8 6.1 1 I τ. -I__J_

As can be seen from the table, the addition of carbon black to the composition significantly reduces the resistivities and using a reduced volume ratio provides a film with an ohmic vasfus of low levels.

Example 14: A 25.4 cm x 20.3 cm (10 "x 8") asbestos surface was provided with two abundant coatings of partially hydrolyzed ethyl silicate, the surface being hardened and glossy after drying. It was then coated with a thick film of the paint mixture W of Example 13, and the solvents were allowed to evaporate at room temperature. Aluminum foil was attached and the electrical resistance was measured before heating and found to be 6 ohms.

j7 56464

An electric current was passed through the membrane, and when the surface temperature reached about 125 ° C, a constant temperature was maintained by conducting a 4 amp current from a 13 V source for two hours.

The final resistance of the cold films was 3.2 ohms. The advantage of this method is that such fuel paint combinations can be cured electrically by heating in. in situ, without the use of conventional incinerators.

Example 15:

Electrically conductive paint combinations based on hydrolyzed ethyl silicate binder were prepared in which the binder solution used was Stauffer

Chemical Co.'s Silbond H6 grade with a SiO content of 18%.

11 ^

Paint combinations A and B were prepared by grinding the following ingredients in a rotary mill for four hours:

Ingredient A ^ "'-' ~ ——--- * ........ ....... '. ... 1- I— -> I .1'».

Graphite powder (<50 mesh B.S.) (g); 200 166.7

Carbon black (Cabot XC72) (g) -, 33.3

Isopropanol (ml) ‘300’ 300

Silbond H6 (g) 100 100 followed by the addition of a second batch of 455 g Silbond H6.

In both paint combinations, the weight ratio of total carbon pigments to silica was 2: 1. The paints obtained were flowable and had a low viscosity. "

The gypsum test panels were coated with paint films, and after drying 2, their electrical resistances were determined and corrected to correspond to a coating weight of 100 g / m 2. The following values were obtained:

Haali Resistance (ohms / square) A1 17.6 B1 8.8 [_ * _

Although these combinations were based on organic solvents, the final binder after complete curing is silica only. In this way, heat-resistant coatings comparable to those formed by aqueous silicate binders are obtained.

Oil-modified alkyd resins can act as binders as shown in the following example.

Example 16:

Four paint mixtures were prepared by pre-dispersing in a rotary mill a carbon black (XC-72) binder for one hour, followed by the addition of graphite (Avarc 202) and further grinding for three hours. In all combinations, the ratio of carbon to graphite was 0.5, with a volume ratio of 47%.

After grinding, 2 g of a cobalt naphthenate drying solution (6% cobalt content) was added and the gypsum boards were coated with a paint mixture. The electrical resistances of the dried 2 films were measured and corrected to correspond to a coating weight of JOO g / m.

,

Substance Paint

C1 D1 E1 FJ

toy seed / pentaethritritol, long oil alkyd binder (Paralac 10) (g) 52.5 52.5 carbon black (g) 33.3 33.3 33.3 33.3 white spirit / xylene (50/50 mixture) (ml) 400 350

Rosaniline base preheated with resin to 190 ° C 1.0 to 1.0

Rosaniline base (dissolved in resin at 100 ° C) (g) - 1.0 to 1.0

Graphite (g) 66.7 66.7 66.7 66.7 Medium Oil Flaxseed / Tung Glycerol Alkyd Binder (Paralac N18X) (g) 87.5 87.5

Xylol (ml) - - 450 300 Electrical resistivity (ohms / square) 7.3 4.9 6.4 4.1 These four paint mixtures were similar to those shown in Example 12.

Claims (16)

19 56464 An electrically conductive paint composition comprising electrically conductive carbon particles in an air-curable binder and having a paint-like consistency and which can be brushed or sprayed onto a thin, uniform film with low electrical resistance, characterized in that the number of electrically conductive carbon particles has a pigment volume concentration of % of which are pigmented graphite particles with a pigment volume concentration of 14 to 70%, formed by wet grinding of graphite and pigmented carbon particles with a pigment volume concentration of 2 to 35%, with a particle size of 20 to 60 nanometers, determined by electron microscopy, determined by electron microscopy is 0.1 to 1 ohm per square meter of surface area. Paint mixture according to Claim 1, characterized in that the weight ratio between colloidal carbon and graphite is 0.1 to 0.5. Paint mixture according to Claim 1 or 2, characterized in that it contains colloidal carbon particles with a particle size of 20 to 50 nanometers, determined by electron microscopy. Paint mixture according to one of Claims 1 to 3, characterized in that the air-curable binder is an inorganic silicate binder. Paint mixture according to Claim 3, characterized in that it contains sodium naphthenic sulphonic acid / formaldehyde condensate as dispersant. Paint mixture according to one of Claims 1 to 3, characterized in that the air-curable binder is an organic ammonium silicate binder. Paint mixture according to one of Claims 1 to 3, characterized in that the air-curable binder is an aqueous emulsion binder. Paint mixture according to Claim 6 or 7, characterized in that it contains nonylphenylethylene oxide condensate as dispersant. Paint mixture according to one of Claims 1 to 3, characterized in that the air-curable binder is a plastic binder soluble in an organic solvent. Paint mixture according to Claim 9, characterized in that it contains rosaniline base as dispersant. A method for producing an electrically conductive paint composition according to any one of the preceding claims having a paint-like consistency and which can be brushed or sprayed onto a thin flat film with low electrical resistance, characterized in that the graphite is comminuted by wet grinding into thin lamellar particles. and the graphite is incorporated into the air-curable binder before, during or after grinding, and colloidal carbon particles having a size of 20 to 60 nm are added to the mixture. Process according to Claim 11, characterized in that the graphite is ground wet in the presence of a surfactant. A method according to claim 11, characterized in that the colloidal carbon particles are mixed with the binder before the latter is mixed with the graphite. Process according to Claim 13, characterized in that the colloidal carbon particles are ground with a binder, graphite is added and wet-milled in the binder. Process according to Claim 11, characterized in that the graphite is wet-milled in a binder solvent together with colloidal-sized carbon particles, after which the binder is added to the ground mixture. Method according to Claim 11 or 12, characterized in that the graphite is wet-milled in at least part of the binder. claim;