GB2150581A - Silicone base artist's paints and their preparation - Google Patents

Abstract

The paints according to the invention contain 5 to 70% by weight of binder containing organic polysiloxane units and 30 to 95% by weight of pigment having a particle size of 5 mu or lower, said pigment having been optionally pre-treated with organic silicon hydrophobizing agents, such as hexamethyl-disilazane, methyl-chlorosilanes and the like. Variants described are 1) (a) RTV composition with cross-linking catalyst in a separate aerosol formulation (b) one component RTV composition 2) silicone-modified alkyd resin combined with air-drying vegetable oils 3) solution of an air-drying silicon resin varnish. w

Description

SPECIFICATION Silicone base artist's paints and their preparation The present invention relates to artist paints and to processes for preparing thereof. The artist paints according to the present invention contain organic polysiloxane polymers which may be varnish, resin or cold vulcanizing condensation or addition silicone rubber polymer binders.

The oil paints having widely been used for centuries are prepared from vegetable drying oils (linseed oil), appropriate pigments, additives (mastix) and diluents (turpentine) according to recipes worked out by the long practice (Kiplik: Maltechnik, Meuschel Edition, Berlin, 1934).

These known artist paints of organic base-besides their many advantages-possess disadvantages as well. The organic ingredients are aging due to oxidation processes taking place by the effect of heat, light, etc., the paint layer disintegrates, breakes and peals off the ground as a result of desctruction processes, or changes colour (Schramm: Historische Malmaterialien, Dresden, 1971).

Especially sensitive are the paintings made on linen or wooden ground, in the first line to heat and to the moisture content of air. These paintings, in case of non-sufficient storing can be damaged even irreversibly. Restoring and storing, resp., under appropriate circumstances causes big problems nowadays.

The present invention aims to dissolve the above problems by providing silicone base paints which are resistant against the above effects. The paints according to the present invention contain organic polysiloxanes as binders while the pigments are powder colours of mineral or synthetic origin, e.g. TiO2, Fe203, Cur2 02, CdS, CoO, ZnO, etc.

The paints according to the invention may have the following main ingredients: Variant 1: 20 to 80% by weight of silicone rubber binder having a viscosity of 1000 to 20000 mPa.s.

containing polysiloxanes built up by dimethyl- and in minor amount by methyl-vinyl-siloxy units and having the dimethyl-hydroxy-silyl or dimethyl-vinyl-silyl units as terminal groups; and preferably 80 to 20% by weight of pigment sufficient for artists' purposes.

Variant 2: Alkyd binder combined with air drying vegetable oils and this being modified by silicone resin intermediate and pigments.

Variant 3: Solution of air drying silicone varnishes, containing alkyl-, aryl- and/or alkenyl-siloxy units mainly in their trifunctional unit form-preferably methyl-, [methyi-, phenyl and [methyl-, phenyl-, vinyl-]siloxy units, resp., combined with pigment.

The above paints may also contain other auxiliaries generally used in the formulation of paints, such as plastifiers and the like.

According to the present invention the pigments may be mixed with the binders mentioned in the above Variants 1 to 3 according to well-known paint producing technologies (mechanical ways), or the artist may produce the desired colour by mixing the components when painting.

When producing the above paints the 20 to 80% by weight of pigment of particle size not higher than 5,u is mixed to the binder. The said pigment may be hydrophobized with different surface active silicone intermediates, e.g. hexamethyl-disilazane or the mixture of dimethyldichloro-silane and methyl-trichlorosilane and the like. Of course, the said pigment may be used without hydrophobizing as well. If desired, 1 to 5% by weight of cross linking catalyst and 0 to 40% by weight of filling agent or lubricant may be added, too.

By incorporating the pre-treated or non-treated pigments and lubricants and auxiliaries, resp., into the polysiloxane binder paint pastes of a consistence similar to the classic oil paints are prepared. The new inorganic plastic base paints may be used for coating different surfaces, e.g.

textile glass, linen, glass, wood, wood fibre, paper, concrete, as well as wall surfaces made of scratch coat, gypsum, and the like and thus for composing works of art.

The present invention provides different paints for different traditional painters' techniques, like oil painting, tempern colouring, aquarel and the like. The above silicone paint family meets the requirements of all the above painting techniques.

Thus, the silicone rubber binder base paint according to Variant 1, when painted on linen or textile glass provides paintings similar to or identical with those composed by traditional oil paintings. Similarly, using the alkyd resin combined with vegetable oil and modified by air drying silicone intermediates, i.e. paints of Variant 2 means in general terms a painting technique identical with that of oil paintings. This latter paint may be used for coating linen, wood, wood fibre, glass, metal and other carriers. The air drying silicone varnish according to Variant 3 may be used in the first line for composing paintings on porous surfaces, e.g. paper, wood, gypsum, cement, skratch coat. and the like.

In the following a more detailed discussion of the above variants is given.

Variant 1: The characteristics of the cold vulcanizing binder are as follows: In chemical aspects the polysiloxanes mentioned are built up by methyl-, or methyl-phenyl-, or methyl-vinyl-siloxy units, the said polysiloxane chains containing reactive groups at the terminal positions, like hydroxy or vinyl groups.

The polymerisation grade of the above polysiloxanes is 1 00 to 10000 and the viscosity thereof may be between 1000 and 200000 mPa.s., preferably 2000 to 100000 mPa.s.

In the above paints e.g. the following cold vulcanizing silicone rubbers may be used: One-component silicone rubbers which may be cross-linked by using catalyst hydrolizing by the moisture content of air and containing alkyl-acyloxy-, alkyl-amino groups and the like.

Two-component cold vulcanizing silicone rubbers which may be used along with any catalyst used for cross-linking cold vulcanizing rubbers chosen according to the desired vulcanizing time.

Two-component cold vulcanizing rubbers wherein one of the components is methyl-vinylpolysiloxane, and the other is methyl-hydrogen-polysiloxane and which may be cross-linked by addition reaction in the presence of appropriate catalyst, e.g. H2PtCI6 and the like.

The active filling agents in the paints according to Variant 1 are in the first line the untreated or surface treated aerosils of 100 to 400 m2/g specific surface (white carbon). The said filling agents may be present in the paint in a ratio of O to 36% by weight.

Inactive filling agents are quartz flour, Celite, diatomeous earth, kaolin it. alumina hydrate and the like. The ratio thereof in the paint is optimally 0 to 20% by weight.

The silicone oil plastifier is a methyl- and methyl-phenyl-silicon oil, resp., which has a viscosity of 10 to 1000 mPa.s., preferably 10 to 50 mPa.s.

As pigments preferably the well-known powder colours of mostly inorganic origin may be used which are resistent against heat (at least at 100 to 500"C), UV-ray. light and storm and do not react with the contaminations of air, e.g. CO, CO2, H2S, SO2, NO2 and the like.

The paint paste can be diluted with different non-polar organic solvents such as turpentine, benzene, toluene, xylene, chlorinated hydrocarbons and the like and methyl-oligosiloxane liquids, such as hexamethyl-disilazane, oktamethyl-cyclotetrasiloxane and the like. The amount of solvents may vary between 0 and 50% by weight. Most preferred solvent is the hexamethyldisiloxane.

The above cold vulcanizing silicone rubber paints can be applied on appropriately primed textile, wood, glass, metal surface and the like, under studio and open air conditions.

The painting technique is as herebelow: On the canvas which may be untreated or pre-treated with silicone hydrophobizing material a paint paste containing white pigment (TiO2) and appropriately diluted with hexamethyl-disiloxane is applied by the aid of a pasting apparatus and the layer is then cross-linked with catalyst.

The silicone paints of different colour according to the invention may be applied on this grounding and after application the layer is evenly oversprayed with an appropriate catalyst. By choosing the catalyst the vulcanizing time can be varied within broad ranges.

The application of paint may also be carried out by mixing the cross-linking catalyst in the paint before painting and use. The paint is diluted to the desired consistence during painting.

In this case the paint is fixed by the effect of the cross-linking catalyst. This latter method has the advantage that the paint mixed with the cross-linking catalyst may be used only within the vulcanizing time (pot time), thus composing the painting should be terminated within a pre-fixed time. This time may be varied, however, within broad ranges. On this painting, alterations may be performed by applying another layer only.

The aforesaid are the characteristics of the one-component embodiment of the silicone paints at the same time. This one-component system has the advantage, however, that the paint paste should not be fixed with the cross-linking catalyst. When pressing out the paint the catalyst present therein possesses the cross-linking effect as a result of the contact with the moisture content of the air and the final consistence is reached in about 24 hours.

As catalyst for the two-component system the mixture of tetraalkoxy- and alkyl-trialkoxysilanes, resp., and dialkyl-diacyloxy tin is used. An example of this catalyst is a mixture of tetraethoxy-silane and dibutyl-dilaurate tin.

For the one-component system methyl-triacetoxy-silane, methyl-trialkyl-amino-silanes and the like are used. As further catalysts boric acid esters and tetraalkoxy-titanium compounds may also be mentioned.

Variant 2: The characteristics of alkyd varnished combined with air drying vegetable oils and modified by silicone resin intermediates are as follows: In chemical aspects this paint is linseed oil, soybeen oil to other alkyd resin containing unsaturated groups which may be combined through its hydroxy functions by condensation with silicone resin intermediates of low molecular weight and possessing methoxy or hydroxy functions, e.g. Dow Corning Z-6018 or Z-6188 or Wacker SY-308 through the reactive hydroxy functions thereof thus providing a binder which is of high stability, waterproof and dries in the presence or absence of air drying siccatives.

Suitably, the binder contains a solvent of high boiling point in an amount of 10 to 40% by weight. These solvents include white spirit, xylene, tetraline, decaline and the like.

The pigment material is incorporated in the ready binder according to well-known paint producing methods.

The paint paste thus obtained can be diluted with solvents of high boiling point. If desired, drying may be promoted by siccatives, e.g. Co, Mn, Zn, and the like.

The paint as above can be applied on any surface on which traditional oil paint may also be used, such as textile, wood, glass, metal, wood fibre, wood fibre plates covered by plastic and the like.

The painting method corresponds to the traditional oil painting technique: On the surface which is primed or unprimed with paint cover prepared from the binder as above, paint is applied, If desired, the paint is diluted with solvent of high boiling point and siccated in given case. The ready painting gets powder-dry in one or two days.

Variant 3: In this variant the polysiloxanes may be those which dry on air and condense under the cleavage of water and contain methyl-, [methyl-, phenyl]- and/or [methyl-, phenyl-, vinyl]-siloxy units, generally [alkyl-, aryl-, alkenyl]-siloxy, preferably trisiloxy units which form varnish film when drying.

The silicone resin is preferred to be dissolved in solvents of high boiling point. The concentration of varnish may vary between 20 and 70% by weight. Suitable solvents are: butyl acetate, toluene, xylene, tetraline, decaline, and the like.

In the varnish solution thus obtained pigment material is dispersed according to methods known per se. The paint can be thus manufactured ready for use or prepared by the artist from the pigment powder and varnish solution when composing the painting. The painting method is similar to the traditional aquarel or tempern technics.

This variant is especially suitable for painting porous surfaces, such as concrete, scratch coat, paper, wood, gypsum and the like.

The dispersion aquarel paint prepared by using silicone varnish binder is especially suitable for composing paper base painting, as well as objects of fresco type.

After application, the dispersion paint is rapidly or slowly drying depending on the volatility of the solvent. The drying period may be regulated by chossing the appropriate solvent.

The advantages provided by the above silicone base paints according to variants 1, 2 and 3 are as follows: a) when using the two-component paint according to variant 1 the consistence of the paint paste is constant, no drying occures when exposed to air and the consistence does not change even when storing for longer period: b) in accordance with the painting technique the paint paste can be diluted with solvents to the desired extent. During painting the material can be applied in thin or thick layer according to the needs; c) when using the paint according to variant 1 the details of picture can be fixed by treating with the catalyst. As mentioned, the vulcanizing time at ambient temperature depends only on the quality and quantity of the catalyst and can be determined in an interval of a few minutes to 24 hours.

The paintings composed by using the silicone paints according to the present invention possess the following preferred characteristics: a) resistance against chemical effects and environmental damages, such as 02, NO2, H2S, NH3, acidic as well as basic vapours and gases, b) no damaging effect of water vapour and water, c) due to the hydrophobic surface even the hydrophilic dusts do not adhere thus the painting has no affinity for dirt and can be cleaned by washing with water, d) resistance against photochemical effects as the siloxane bound does not absorb light quantums of a wave length higher than 100 nm, e) the layer applied is resistant to heat and cold.The vitrification point does not alter between - 60 and + 1 80 C. It has been found that the material can be stored at ambient conditions (between - 25 and + 50"C) for unlimited time as far as the powder paints used do not alter under these circumstances, f) due to the characteristics as mentioned above, storage of the art objects does not require any special measure, such as air conditioning and the like, g) the silicone paint may be applied en textile, paper, cement, scratch coat, glass, china and ceramic surfaces as the adhesion-if desired after appropriate pre-treating-is ensured. On the fixed coating the next layer may also be applied steadily, the adhesion is again good thus the picture may be further developed and altered, if desired.

The paint pastes according to the present invention can be produced according to processes well-known in the painting and varnish industry.

Preparation of the silicone paints according to the present invention Preparation of two-component pastes according to variants 1 and 2: The active and inactive filling materials as well as the necessary powdered pigment materials are incorporated in the ground material in mill, Z beater knife mixer or ball mill so that complete homogeneous greasy paint paste is obtained. The ready paint pastes are filled in tubes or pots.

The catalysts which are different in their hardening time and the cross-linking mechanism, resp., may be formulated to aerosols filled in bottles or in dropping containers or into pastes together with thickeners or filled in tubes.

Preparation of one-component pastes according to variant 1: When preparing one-component pastes the appropriate catalyst is mixed with the other component and tubulated in the absence of air in inert atmosphere or in vacuum filling apparatus.

Preparation of dispersion aquarel paint according to variant 3: The desired paint powder is dispersed in the concentrated solution of silicone varnish in fast mixing apparatus or the series of paint powders, the binders and solvents are separately made up or provided to the artists as unit packages.

The following examples give more detailed explanation of the embodiments according to the present invention.

Example 1 Preparation of two-component paint set 1.1 .a. Preparation of paint paste containing no additive: Component A (pigment + binder) As base dimethyl-polysiloxane-a,co-diol of viscosity of 10000 mPa.s. is used and when preparing the ground pastes of different colour the pigment materials described in the Table below are incorporated.

For providing a better incorporation of the pigments and the base silicone rubber, the surface of pigment powders should be pre-treated with silicones. This pre-treating may be carried out with a 10% by weight of benzene, toluene or carbon tetrachloride solution of the mixture of dimethyl-dichloro-silane and methyl-trichloro-silane or with a 10% by weight benzene solution of hexamethyl-disilazane.

The surface pre-treated, dried and optionally ground pigment is incorporated in the silicone rubber base by the aid of a suitable mill.

To the dense mass thus obtained the solvent for providing the optimal consistence of each paint paste (e.g. turpentine) is added in a suitable apparatus such as Z beater knife mixer. The amount of the solvent to be added is shown in the Table herebelow. The stirring is carried out until the paste is completely homogeneous.

For obtaining ease of handling the paste thus obtained is filled in tubes.

Component B (fixing material) This component is the catalyst formulated into aerosol for spraying fixing. As catalyst, any type of catalyst may be used which is good for cross-linking two-component cold vulcanizing silicone rubbers and which provides a vulcanizing time of 1 to 10 hours. As catalyst, a 67 to 33% by weight mixture of tetra-ethoxy-silane and dibutyl-dilaurate-tin is used (trademark "Szilorka K-1").

1.1 .b. Preparation of two-component paint paste containing lubricant (closed terminating silicone oil of viscosity of 20 mPa.s.).

Component A As binder dimethyl-polysiloxane-a--diol is used.

Table Name of pigment Optimal amount of Amount of lubricant powder pigment part by w/100 part by w/100 part by w.

part by u.

rubber rubber 18.000 mPa.s.

Cadmium red 125 10 Titanium white 125 12,5 Burnt sienna 125 25 Ultra marine blue 125 25 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 13.000 mPa.s.

Titanium white 188 10 Cobalt blue 163 tO Cadmium yellow 160 50 }udder 63 12,5 Ultra marine blue 120 14 The pigments were not hydrophobized. The mass is thoroughly ground in mortar or mill and then filled in tubes.

Component B The catalyst used is the same as in Example 1.1 a.

1.1 .c. Preparation of two-component paint pastes containing filling materials: Component A The ingredients used in preparing the above component are as follows: 100 parts by weight of dimethyl-polysiloxane-a,diol (viscosity: 35 to 40000 mPa.s.) 50 parts by weight of celite (inactivated SiO2) 10 parts by weight of aerosil (Degussa R 972) 32 parts by weight of cadmium organge pigment (Cds).

As hydrophobizing material 10% benzene solution of hexamethyl-disilazane is used, thus impregnating the pigment, then the mass is dried at 80"C and ground.

Component A Another variant for the component A is prepared from a rubber base of lower viscosity and using the following ingredients: 100 parts by weight of dimethyl-polysiloxane-a,-diol (viscosity: 20 to 25.000 mPa.s.) 1 5 parts by weight of aerosil (Wacker HDK H-2000) 40 parts by weight of quartz flour 31 parts by weight of cadmium orange pigment (CdS).

For hydrophobizing the pigment 10% by weight solution of the 1:1 molar mixture of dimethyl-dichloro-silane and methyl-trichloro-silane in carbon tetrachloride is used.

The mixtures prepared in the composition as above are homogenized in a mill. If desired, the suitable consistence is set by the addition of a solvent, e.g. turpentine and the like. After homogenizing the product is filled in tubes.

When using, the paint may be diluted in the appropriate extent with a solvent, e.g. turpentine on the palette.

Component B The catalyst used may be the same as in Example 1.1.a.

1.1.d. Preparation of two-component paint paste containing filling material: Component A The ingredients used in preparing the above component are as follows: 30 parts by weight of dimethyl-polysiloxane-a,-diol (viscosity: 1 3000 mPa.s.) 7 parts by weight of aerosil (Wacker HDK H-2000) 2 parts by weight of hexamethyl-disilazane (hydrophobizing agent) 1 8 parts by weight of turpentine (solvent) 11 parts by weight of chromium oxide green pigment.

The above mixture is homogenized by using an appropriate mill. After homogenizing the product is filled in tubes. When using, the paint may be further diluted by mixing with a diluent, such as turpentine, on the palette.

Component B The catalyst used may be the same as in Example 1.1.a.

1.2. Preparation of one-component paint paste: The pastes according to examples 1.1 .a., 1.1 .b., 1.1 .c. and 1.1 .d. may be formulated in onecomponent form as well, by using non-acidic catalyst under exclusion of the moisture of air.

Suitable non-acidic catalysts are boric acid esters, tetraalkoxy-titanium-derivatives, silyl amines and the like.

A possible one component paint paste is made from the following ingredients: 98 parts by weight of paint paste containing chromium oxide green pigment, according to example 1.1.d., 2 parts by weight of boric acid triisopropyl-ester (catalyst).

In a closed homogenizing apparatus provided with stirrer and under nitrogen gas the absolute dry paint paste and catalyst are homogenized and filled in tubes by the aid of tubing apparatus attached to the equipment.

Care should be taken when using the one-component paint that the cross-linking of paint by the influence of the moisture content of air starts depending on the quantity and quality of catalyst. Thus, the use of one-component pastes is limited in time.

Example 2 Preparation of paints from alkyd varnishes combined with air drying vegetable oils and modified by silicone resin intermediates according to variant 2.

2.1. Binder prepared with soybean fatty acid: For preparing the above binder the following ingredients are used: 19,2 parts by vol. of Dow Corning Z-6018 intermediate 7,5 parts by vol. of pentaerythritol (mono) 1,4 parts by vol. of glycerol 9,8 parts by vol. of phtalic anhydride 26,7 parts by vol. of soybean fatty acid 35,4 parts by vol. of xylene.

The alkyd resin is prepared according to methods known per se and subsequently boiled with Z-601 8 intermediate at a temperature of 1 65 to 170"C in an apparatus provided with Markusson equipment, until the dissoiution is complete.

2.2. Dow Corning E1-3044 copolymer: silicon content 30% (Z-6018 or Wacker SY-308) phtalic anhydride 1 6,1 % soybean oil 43,8% Hydroxy content in the resin: 2,2%.

Solvent: white spirit, xylene or tetraline.

The extract content is preferred to be adjusted to 60 to 80%.

2.3. Dow Corning E1-3046 copolymer: Z-6018 or SY-308 content 25% phtalic anhydride 17,4% linseed oil 43,6% Solvent: white spirit, xylene or tetraline.

The extract content is preferred to be adjusted to 60 to 90%.

2.4. The following preparation is carried out in a 1 liter round bottom flask provided with Markusson equipment, cooler, gas inlet and thermometer. In the process the following ingredients are used: A 200,0 9 of soybean fatty acid B 73,5 g of phtalic anhydride C 56,2 g of pentaerythrite D 12,0 g of glycerol (87%) E 43,4 g of xylene F 98,5 g of xylene G 143,8 9 of SY-308 silicon intermediate H 167,5 9 of xylene.

The components A, B, C, D, and E are placed into the flask. The temperature is slowly elevated to 220 to 230"C. The water obtained during the reaction is removed by azeotropic distillation. By controlling the amount of the xylene distilling off with the water, the temperature of the flask content is maintained at 220 and 230"C under continuous refluxing.

Samples are taken in every 30 minutes for determining the acid value. The alkyd component is perfect if the acid value is under 1 0. Subsequently, the mixture is cooled to the temperature of 1 30 to 140"C and the xylene F is added. While further cooling, the silicon intermediate G is added at a temperature of 80 to 100"C. The mixture is heated to 160"C when the condensation of intermediate and alkyd polymer takes place. The water obtained is removed by azeotropic distillation as above.

During the reaction the co-condensation is followed by taking drop samples. When the sample dropped on glass plate of the temperature of 1 50 to 160"C is transparent, the reaction is regarded as complete.

The co-condensation takes place in about 1 hour.

After finishing the reaction the system is cooled and diluted with the xylene H. The reaction is preferably carried out in CO2 or nitrogen atmosphere. The extract content of the product obtained is 60 to 70%.

To the alkyd resin prepared according to examples 2.1., 2.2. and 2.3., resp., more preferably according to example 2.4. prepared by using soybean oil and Z-601 8 or Wacker SY-308 the following powder paints are flushed (the amount thereof is given to 100 g of resin): 112,0 9 titanium white (tit2) 125,0 9 iron oxide red 33,0 g chromium oxide green 100,0 g cadmium red 1 25,0 g cadmium yellow 125,0 g Thenard's blue 1 25,0 g Berlin blue 125,0 g cobalt blue 33,0 g krapp 33,0 g acetylene black 100,0 g nickel titanium yellow 66,0 9 ultra marine blue 114,0 g burnt sienna.

When painting the canvas is preferably primed with titanium white as above.

The paint may be diluted, if desired, with tetraline or decaline or siccatived with cobalt or manganese containing materials. The amount of siccatives is preferably 0,00001 to 0,01%.

Example 3 Preparation of air drying paints prepared from alkyl-alkenyl-aryl-polysiloxane resin: As binders the following commercially available resins may be mentioned, without limiting the scope of protection on these materials: Wacker Silikonharz MK Wacker Silikonharz-Lösung RF6 Wacker Silikonharz H 44.

3.1. Preparation of dispersion paint binder: 5000 g of methyl-trichloro-silane and 6250 g of phenyl-trichlorosilane are dissolved in 80 l of butyl acetate and the mixture is added to the mixture of 200 1 of water and 147 l of butyl acetate under cooling during a period of 3,5 to 4 hours. The stirring is continued for a further 0,5 to 1 hour and then washed four times with each 200 1 of water to acid free, while after the stirring and each washing the water is separated after 2 hours' settling.The separated butyl acetate resin solution is azeotropically dried to about 110 to 125"C. Then the solution is evaporated to 60 to 70% of the original volume at 450 to 650 Hgmm and 11 5 to 120"C. After evaporation the residue is dissolved in xylene to obtain a 60% solution.

For preparing dispersion paints the above methyl-phenyl varnish proved to be the best.

3.2. To the xylene solution of the methyl-phenyl silicon resin described in 3.1. pigment (titanium white, iron oxide white, chromium oxide green, cadmium red, Thenard's blue, Berlin blue, cobalt blue, krapp, burnt sienna and the like) is mixed until a dense paste is obtained which is diluted with xylene, if desired, and painted on the corresponding surface (paper, wood, gypsum, cement, etc.).

If desired, the ready painting may be glazed with the colourless varnish solution.

3.3. Painting is carried out with the 30% solution of the varnish solution as described in 3.1.

from tablets of paint similarly to the technique with watercolour. The advantage is that after drying the paint cannot be washed away by the water.

3.4. Into 100 ml of 30% solution of Wacker MK, RF-6 or H 44 and the silicon varnish according to 3.1., resp., 30 to 40 g of powdered colour is dispersed and filled and stored in wide-necked paint containers. When painting, the dispersion paint is stirred or shaked and the painting is carried out by using brush.

Claims (17)

1. Artist paint comprising 5 to 70% by weight of binder containing organic polysiloxane units and 30 to 95% by weight of pigment having a particle size of 5,u or lower, said pigment having been optionally pre-treated with organic silicon hydrophobizing agents, such as hexamethyl-disilazane, methyl-chlorosilanes and the like.

2. Artists paint according to claim 1, wherein the binder is polymeric silicon rubber having a viscosity of 1000 to 20000 mPa.s. containing polysiloxanes built up by dimethyl- and in minor amount by methyl-vinyl-siloxy units and having dimethyl-hydroxy-silyl or dimethyl-vinyl-silyl units as terminal groups.

3. Artist paint according to claim 1, wherein the binder is the concentrated organic solvent solution of an alkyd resin combined with air drying vegetable oils and modified with silicon resin intermediates.

4. Artist paint according to claim 1, wherein the binder is the organic solution of an air drying, i.e. polycondensation hardening silicon varnish containing alkyl-, aryl- and/or alkenylsiloxy units, mainly in their trifunction unit form.

5. Artist paint according to claim 2, wherein the polysiloxane possesses reactive terminal groups which are cross-linking to the binder according to one or two-component polycondensation or addition mechanism.

6. Artist paint according to claim 2, wherein the polymerisation grade of the polysiloxane is 100 to 10000.

7. Artist paint according to claim 2, wherein the viscosity of the polysiloxane is 2000 to 100000 mPa.s.

8. Artist paint according to claim 2, wherein the paint contains the cross-linking catalyst.

9. Artist paint according to claim 2, wherein the polysiloxane is one-component or twocomponent cold vulcanizing silicon rubber.

10. Artist paint according to claim 2, wherein the binder is dimethyl-polysiloxane-a,co-dioi.

11. Artist paint according to claim 3, wherein the alkyd resin contains unsaturated groups and may be combined with the silicon resin intermediates by condensation through the reactive hydroxy functions thereof.

12. Artist paint according to claim 3, wherein the vegetable oil is linseed oil or soybean oil.

1 3. Artist paint according to claim 3, wherein the silicon resin intermediate is Dow Corning Z-6O18, U-6188 or Wacker SY-308.

14. Artist paint according to claim 3, wherein the binder contains a solvent.

1 5. Artist paint according to claim 4, wherein the silicon varnish contains [methyl-,][methyl-, phenyl]- and/or [methyl-, phenyl-, vinyl]-siloxy units in their trifunctional form.

16. Preparation of artist paints according to any of claims 1 to 1 5.

17. Process for preparing artist paints according to any of claims 1 to 1 5 substantially as described in the specification and examples.