LU84598A1 - PIGMENT EXPRESSING A BETTER COLOR HOLD FOR PAINTINGS OF WHICH THE VEHICLE IS A LATEX - Google Patents

Description

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1 -V

DESCRIPTIVE MEMORY

: FILED IN SUPPORT OF A REQUEST

OF

PATENT

FORMED BY

ELKEM METALS COMPANY for

Pigment showing better color fastness for paints whose vehicle is a latex.

The present invention relates generally to coatings in which the vehicle is an aqueous-based emulsion. More specifically, it relates to aqueous-based emulsion paints containing a new coloring agent whose improved properties accentuate the shade stability of these paints.

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Water-based emulsion paints of conventional type are obtained by dispersing one or more colored pigments in water containing appropriate additives, such as surfactants, stabilizers, dispersants and thickeners, then by incorporating agents film-forming agents such as acrylic polymers and copolymers and acrylic-based emulsions. An essential criterion which any pigment must satisfy is to confer, either alone or in conjunction with other pigments, a distinctive and pleasant coloring to the paint to which it is added. In addition, the pigment must be stable so as to retain its color for a long time. Another important condition is that the pigment must have a very fine particle size, generally less than about 10 µm. The fineness of the particles increases the ability of the pigment to disperse easily in the paint during manufacture and also ensures that the paint is distributed evenly in a thin layer without scratches or other imperfections when applied to a surface.

This last criterion is obviously of the utmost importance when the paint is to be applied by brush, roller or spray in the usual manner.

An important object of the invention is therefore to provide an improved pigment for water-based emulsion paints. Another more specific object of the invention is to provide an improved water-based emulsion paint having good coloring stability and a relatively high resistance to fading by exposure to sunlight.

The subject of the invention is an improved colored pigment for water-based emulsion paints which comprises manganomanganic oxide smoke (Mn ^ O ^) or a material containing manganomanganic oxide smoke as the main constituent. The smoke of Mn ^ C ^ *! i pigment color is first dispersed in water containing surfactants, dispersants, defoamers, thinners, thickeners, stabilizers, glycols etc., then incorporated into an aqueous-based emulsion containing polymers or copolymers acrylic. The smoke from pigmented colored Mn ^ O ^ can form about 5 to 50% by weight of the whole of the non-volatile fraction of the paint.

The invention is described in more detail below with reference to the accompanying drawing, the single figure of which is a diagram representing the particle size spectrum of a preferred material containing manganomanganic oxide smoke which is suitable as a pigment dye.

The invention is based on the discovery that manganomanganic oxide smoke or a material containing mainly manganomanganic oxide smoke in the finely divided state constitutes a new quality dye ideal for various water-based emulsion paints. In particular, the pigmented colored Mn ^ O ^ smoke is especially useful in applications where conventional iron oxide pigments have been used heretofore to prepare colored water-based emulsion paints. For example, the Applicant has observed that the fine manganomanganic oxide smoke used as a colored pigment confers a shade of dark brown or a close dark reddish brown, but very clearly distinguishable from the shade of a pigmentary brown imparted by various synthetic pigment iron oxides, for example yellow, brown or red iron oxide pigments. The Applicant has also observed that the pigmented Mn ^ O ^ smoke is stable at elevated temperatures reaching about 600 ° C. whereas the oxide pigments. classic yellow and brown iron turns red when CD.MJ - 3 - heated to about 177 ° C. The pigmented Mn ^ O ^ smoke can also be obtained in numerous particle sizes which differ little or no from the particle size of conventional iron oxide pigments. As indicated, it is advantageous for the pigment dye to have a very fine particle size so that the pigment can be distributed uniformly in the paint during its manufacture. As a general rule, the pigmented manganomanganic oxide smoke should have a particle size of less than about 10 µm.

As already specified, the pigment dye used for the purposes of the invention is manganomanganic oxide smoke, or else a material containing mainly manganomanganic oxide smoke, namely more than approximately 60% by weight.

The Mn ^ O ^ smoke of the invention is most advantageously obtained by passing an oxygen current over or through the surface of a ferro-manganese molten bath. The usual ferro-manganese produced in the blast furnace, the electric furnace or in another metallurgical furnace at high temperatures reaching about 1200 ° C. or more may contain up to 6% of carbon, if not more. The carbon content is usually lowered, for example to about 1.5% by weight, by blowing oxygen or a mixture of air and oxygen onto or through the surface of a ferro bath -manganese in fusion. This operation is carried out in a separate enclosure containing a bath of molten ferro-manganese which has just been taken from the electric oven and which is at a temperature of approximately 1000 ° C. or more and preferably of approximately 1300 ° C. or more.

A process for lowering the carbon content of molten ferro-manganese is described in U.S. Patent No. 3,305,352 / (February 21, 1967). According to this preferred process for producing manganomanganic oxide smoke according to the invention, ferro-manganese is taken from the electric oven in which it is produced in a treatment enclosure, such as a ladle or an oven, at a temperature of about 1300 ° C or more. The slag, if any, is preferably evacuated, then oxygen is blown onto the surface of the molten ferro-manganese bath in any suitable manner, for example by means of one or more conventional oxygen lances maintained at a distance of approximately 25 mm above the surface of the bath so as to spray thereon one or more jets of oxygen under a pressure of approximately 7.7 to 10.5 bars. The oxygen flow rate is approximately 1.8 to 2.3 kg per minute for a 230 kg molten bath in a pocket with a depth of approximately 76 cm and an internal diameter of 50 cm. The operation can be carried out on a larger scale if the thing is desired.

The resulting burnt gases contain very finely divided particles of manganomanganic oxide of spherical shape which are easily isolated from the burnt gases using a conventional apparatus for this purpose.

If desired, the manganomanganic oxide smoke of the invention can be obtained as a by-product of the process specifically described in U.S. Patent No. 3,305,352 for lowering the carbon content d 'a ferro-manganese bath. When this is the case, the ferro-manganese bath must be brought to a temperature of approximately 1250 ° C. and the oxygen blowing rate must be sufficient to heat the bath to a temperature of approximately 1700 ° C before the carbon content of the molten metal has been lowered to 1.5%. The oxygen blowing is continued until the bath temperature reaches around 1750 ° C., as Γ described in the aforementioned patent. Conventionally, manganomanganic oxide smoke is separated from the burnt gases.

By "Mn ^ O ^ smoke or manganomanganic oxide smoke" is meant, for the purposes of the invention, the finely divided spherical particles of smoke produced by melt-blown ferro-manganese oxygen as described above.

The details below specify certain properties typical of manganomanganic oxide smoke produced as specified above for the application of the invention:

Chemical formula: substantially Mn ^ O ^. Nor mal 90 to 95% by weight or more of manganomanganic oxide, the remainder being a mixture comprising calcium oxide, magnesium oxide, potassium oxide and silica with less than about 1% by weight of free metallic manganese.

Chemical analysis (typical weight percentage): 65.2 7Mn; 2.03Fe; 0.029Al; 0.28 Si; 0.17C; 0.040 P; 0.045As; 0.46Ca; 1.43Mg; 0.072K; 0.023Cr; and 0.002Pb.

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Bulk density: 720 to 1440 kg / m

Humidity: normally 0.22% (1 hour at 107 ° C)

Grain size: 98% below lo ^ um (99% pass through the Tyler sieve with 0.044 mm mesh).

pH: 9 to 13 (50% Mn ^ O ^ in distilled water)

Shape: spherical 3

Density: 4600 to 4750 kg / m

Thermal stability: no effect up to 600 ° C.

Currently, in the field of coatings, preference is given to colored pigments of very fine particle size in order to improve the coloring efficiency (coloring power and covering power), the suspension properties and the uniformity of distribution of the pigment. in the bulk of the paint. It has been observed that when used as a pigment dye in accordance with the invention, the smoke of Mn ^ O ^ must have a particle size of less than about 10 µm. Normally, the smoke of Mn ^ O ^ described above contains about 1 to 2% of particles larger than about 10 µm. It can therefore sometimes be useful or necessary to remove these large particles from the smoke of Mn304. This operation can be carried out, for example, according to usual classification techniques or else by grinding, for example with balls. Manganese oxide smoke that has been classified or ground to a particle size of less than about 10 µm for 99.5% can be readily dispersed in paint using a medium shear device, such as a Cowles dissolver . Paints containing Mn ^ O ^ smoke of this size range can generally be applied to the desired surface without the appearance of scratches or other imperfections.

The single figure in the accompanying drawing represents the typical particle size spectrum of a Mn ^ O ^ smoke. It can be deduced from the curve that in the particular case of classified Mn ^ O ^ smoke examined, the average particle size is about 0.68 µm.

Typical aqueous-based emulsion paints containing pigmented colored Mn ^ O ^ smoke according to the invention have the following constitution:

Ingredients% by weight

Latex 40-65

Thickener 0.5-12

Dispersant / stabilizer 0.2-2.0

Surfactants 0.2-2.0

Defoamers 0.1-1.0

Coalescing agent 0.3-6.0 CD.MJ - 7 - /

Preservative 0.1-1.5

Thinners 0.0-15.0

Smoke from Μη ^ 04 5.0-30

Ti02 0.0-25.0

Antifreeze 0.0-8.0 Alkyd resin or vegetable oil 0.0-10.0

Water remains „The water-based emulsion paints containing a pigmented manganornanganic oxide smoke in accordance with the invention can be obtained according to the usual methods. For example, the paint can be prepared by starting with the dispersion of additives such as dispersants, thickeners, protective colloids, defoamers, surfactants etc. in water. The colored pigment and any diluent are then dispersed in the aqueous solution using an apparatus which exerts an appropriate shear, for example a Cowles dissolver or a roller mill.

The fine particles of the pigment and of the diluent are thus placed in uniform suspension. The resulting pigmented aqueous solution is then added with a latex, a coalescing agent and the other constituents.

The physical properties and characteristics of the paint are checked and the surface tension, pH, viscosity and dispersion state of the pigment are corrected as necessary. Other methods and apparatuses can obviously be implemented with the same success, as is obvious to the specialist.

The latex or emulsion forming a vehicle for painting in accordance with the invention can be any one of the latexes of film-forming acrylic polymers and copolymers commonly used in the paint industry.

Rhoplex AC 507, Rhoplex MV9 and Rhoplex MV23, which are latex produced by the Company Rohm and Haas CD.MJ - 8 - f

Co., and UCAR 336, UCAR 515, UCAR 4341 and UCAR 4358, which are latexes produced by the Union Carbide Corporation, are typical examples of the many emulsions currently available which are useful for the purposes of the invention.

Protective thickeners and colloids are used in paints to give them the consistency and viscosity that are desired. The consistency and viscosity must be such that the paint can be easily applied in a uniform layer of the desired thickness on the surface to be treated. These additives also act as protective colloids which prevent the coagulation of pigments and diluents in the presence of electrolytes or during too sharp shearing. The thickeners, together with the surfactants, keep the pigments in suspension and stabilize the viscosity of the paint. The nature of the thickener chosen depends on various factors, such as the type of emulsion, the volume concentration of pigment and the rheology of the layer.

As a general rule, thickeners such as cellulose products or polyacrylic acid salts commonly used in the paint industry can be used in an aqueous-based emulsion paint containing Mn ^ O ^ smoke. Suitable thickeners are, for example, salts of polycarboxylic acids such as Acrysol G-110 (registered trademark of Rohm and Haas Co.) or cellulosic thickeners such as QP4400 (registered trademark of Union Carbide Corporation). Other thickeners are those sold under the registered trademarks Thickener 845, Thickener 4358 and Thickener E845 (registered trademarks of Rohm and Haas Co.).

A combined stabilizing dispersing agent can also be incorporated into the paint to ensure that CD.MJ - 9 - / all of the pigment and other constituents maintain uniform dispersion in the paint. Different dispersants of anionic, nonionic and polymeric type are suitable for this purpose, for example those sold under the registered trademarks Tamol 731 and Tamol 850 (Company Rohm and Haas Co.). Other suitable dispersants are Triton X-100 (alkylarylphenoxypoly-ethoxyethanol), Triton X-301 (alkylphenol ether sulfate) and Triton X-405 (alkylarylpolyether alcohol), which are registered trademarks of Rohm and Haas Co.

The paint according to the invention can comprise various other constituents of usual use in the paint industry. For example, an antifoam such as Nopco NDW sold by the Nopco Chemical Company can also be used. Usual driers can also be used when the paint contains an alkyd resin. Such driers are, for example, those with cobalt and zirconium. A coalescing agent can also be added, for example the 2,2,4-trimethyl-1,3-pentanediol monoiso-butyrate sold under the trade name Texanol by the company Eastman Kodak. Other known constituents, such as antioxidants, preservatives, antifreezes (e.g. ethylene glycol) and modifiers can be added to the paints, as is obvious to the specialist.

Some experiments have revealed that the smoke of Mn ^ O ^ can be combined with usual pigments such as titanium dioxide (TiC ^) to achieve different shades. For example, during such an experiment, different shades were obtained by means of a smoke of Μη ^ 04 mixed with different amounts of TiC> 2. For this experiment, controls containing 100% smoke of Μη30 ^ and 100% Ti02 respectively made it possible to establish the comparison. La Deman CD.MJ - 10 - / deresse observed that the emulsion layer in the case of 100% of T1O2 (0% of Mn ^ O ^) has the nuance "£> basic launch", in the case of 10% smoke of Mn ^ O ^ (90% of T1O2) the shade "light brown" or "beige", in the case 40% of smoke of Mn ^ O ^ (60% of T1O2) the shade "medium brown" and in in the case of 100% Mn ^ O ^ smoke (0% T1O2) the shade "dark brown" or "dark reddish brown".

The color of the emulsion layer observed during the experiment described above can be specified by reference to the Munsell Book of Color, Munsell Color Company, Baltimore, Maryland. The shade, the intensity and the chromatic parameter are determined for each emulsion layer in accordance with the operating mode specified in the Munsell Color Book and are listed in Table I below. In the column entitled "Munsell Scale", the first numerical value and the letter or letters denote the shade, the numerical value succeeding the letter denotes the intensity and the last numerical value indicates the chromatic coefficient.

TABLE I

Definition of the coloring Ti02% Smoke of Mn ^ O ^% Munsell scale 100 0 N 9.5 / 90 10 5 YR 8/2 60 40 7.5 YR 5/2 0 100 5 YR 3/4

It can be deduced from the Munsell indices of Table I that the manganomanganic oxide smoke which is the subject of the invention exerts a coloring and modifying effect on other pigments such as titanium dioxide and leads to defined shades such as oxide yellow iron, Hansa yellow, chromium oxide green, phthalocyanine blue and phthalocyanine green.

The application of the invention is further illustrated by the following examples. CD.MJ - 11 -

EXAMPLE 1 An aqueous-based emulsion paint is prepared using a white pigmentary titanium dioxide of rutile type for general application. The paint is prepared by first mixing together 60.0 g of titanium dioxide of the rutile variety, 70.0 g of thickener (pH 9.7), namely a 20% aqueous solution of Thickener 745 (Rohm and Haas Co. ), 2.0 g of a dispersant / stabilizer, namely Tamol 850 (Rohm and Haas Co.); 10.0 g of alkylarylphenoxypolyetho-xy ethanol, namely Triton 100 (Rohm and Haas Co.); 1.5 g of Hevi-Duty A.F. Agent antifoam (Interstab Chemicals Inc.), 2.0 g of polypropylene glycol; 20.0 g of a coalescing agent, namely Butyl Carbitol (Union Carbide Corp.); 2, Ο g of 28% ammonium hydroxide and 87.5 g of water. After intimate incorporation, 622 g of latex, namely UCAR 4358 (Union Carbide Corp.), are added to this mixture.

The resulting paint is spread over the surface of various bare aluminum specimens of about 76 mm x 229 mm using a filmograph to achieve a thickness of about 25.4 µm. The coated test pieces are then left to dry for about 1 week at room temperature, then subjected to a discoloration or discoloration test in the laboratory under ultraviolet light. To this end, the test pieces are placed on shelves and exposed continuously to a constant source of ultraviolet light in accordance with the so-called Fadometer ASTM G 25-70 test. For a period of up to 1000 hours, the color stability and the fading of the test pieces are observed periodically. The discoloration of the test pieces is assessed according to the scale below: CD.MJ - 12 -, 1

Rating scale 10 - No alteration 9 - Very slight alteration 8 - Low alteration 7 - Average + 6 - Average 5 - Average -4 - Quite bad 3 - Bad 2 - Very bad 1 - Partial failure 0 - Failure

The results of the discoloration tests are shown in Table II. Each dimension of the table is preceded by the letter "D" indicating that it is a bleaching test, except when the pigment is T1O2 · The pigment of TiC> 2 produces an essentially white pigmentation which, by a long exposure to ultraviolet light, becomes washed out.

Consequently, in Table II the abbreviation "del" indicates that the paint in the example takes on a washed-out appearance. EXAMPLE 2 -

An aqueous-based emulsion paint is prepared using the same constituents as those of the paint of Example 1, but replacing the 60.0 g of TiO2 with 57.0 g of leached Mn ^ O ^ smoke . The smoke of Mn ^ O ^ is li-xivie by treating it in hydrochloric acid. In the present example, 73.0 g of a thickening polycarboxylic acid, namely Thickener 485 (Rohm and Haas Co.) and 480.0 g of latex, namely UCAR 4358 (Union Carbide Corp.) are used instead of of the 622.0 g of latex used in Example 1. The paint is applied to test tubes as in Example 1 and subjected to the same bleaching tests. The . layer color is "dark brown" or "reddish brown OTi MT _ 1 ^ _ dark".

EXAMPLE 3 -

An emulsion paint is prepared by dispersing diluents and pigments in an emulsion which is prepared by mixing a long oil alkyd resin, namely Aroplaz 1271 (Spencer Kellog Co.) containing cobalt and zirconium driers. with water. To 350 g of the alkyd resin emulsion, 4.0 g of cellulosic thickener, namely QP 4400 (Union Carbide Corp.), are added; 8.0 g of anionic dispersant, namely Tamol 850 (Rohm and Haas Co.); 5.0 g of nonionic surfactant, namely Triton CF-10 (Rohm and Haas Co.) which is of alkyl phenol ether type, 5.0 g of an anti-foaming agent, namely Hevi-Duty AF Agent and 20.0 g ethylene glycol. 150.0 g of synthetic red iron oxide, 35.0 g of dilution pigment, namely Mica 325 from the English Mica Company, 75.0 g of CaCO 4, 50.0 g, are incorporated into the resulting vehicle. rust inhibiting pigment, which is modified barium metaborate, namely Busan 11-Ml (registered trademark of the company Buckman Labs, Inc.) which is dispersed using a Cowles dissolver. After intimate mixing, 500 g of a latex of styrene-acrylic copolymer, namely UCAR 4341 (Union Carbide Corp.) and a coalescing agent, are added.

As in the previous examples, the paint is applied to bare test pieces of aluminum sheet of approximately 76 mm × 229 mm using a filmograph formed from a metallic wire wound on a rod (Meyers) to achieve a layer thickness 25.4yum dry.

The paint layer is then left to dry at room temperature. The test pieces are placed on the shelf and subjected to the same discoloration tests. EXAMPLE 4 -

An emulsion paint is prepared in melan-CD.MJ - 14 -. "/ Giant acrylic emulsion, namely Rhoplex MV 23 (Rohm and Haas Co.) with Mn ^ O ^ smoke. The constitution is as follows: 59 g of water, 25.0 g of poly-acrylate thickener with a concentration of 20%, namely Thickener E84b (Rohm and Haas Co.), 17.6 g of dispersant of concentration from 40%, namely from QR-681 to 40% (Rohm and Haas Co.), 2.0 g of surfactant which is the benzyl ether of the product of addition of ethylene oxide to octylphenol, namely Triton CF-10 (Rohm and Haas Co.), 28.0 g of ethylene glycol, 5.7 g of antifoam, namely of Foamaster NDW (Diamond Shamrock Co.), 12.0 g of pigmentary zinc oxide, namely AZO 77 (American Zinc Co.), 53.0 g of CaCO ^, 2.1 g of Skane M-8 (Rohm and Haas Co.), which is a biocide (2- n-octyl-4-iso-thiazolin-3-one) and 151 g of Mn ^ O ^ smoke. After intimate mixing, 667.0 g of acrylic latex, namely Rhoplex MV 23 (Rohm and Haas Co.), 7.0 g of ammonium hydroxide (28%) and 5.7 g are added to the mixture. coalescing agent, which is 2,2,4-tri-methyl-1,3-pentane-diol monoisobutyrate, namely Texanol (Eastman Kodak Co.). The paint is applied to aluminum sheet test tubes as in the previous examples and the layer is left to dry at room temperature. The resulting layer is again "dark brown" or "dark reddish brown". There is no fundamental difference in coloring between the smoke of Mn ^ O ^ before and after leaching. The test pieces are then subjected to the same discoloration tests. The results of the discoloration tests on the various paints described in Examples 1 to 4 are shown in Table II below.

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It appears from the results of Table II that the aqueous-based emulsion paints containing Mn ^ O ^ pigmentary smoke in accordance with the invention have a coloration stability and a resistance to discoloration which are equal to or greater than those of paints containing conventional pigments. In particular, the paints of Examples 2 and 4 which contain Mn ^ O ^ smoke as a pigment dye show only slight discoloration, while the paint of Example 3 containing red pigment oxide undergoes a much greater discoloration (i.e. from D-10 after 50 hours to D-3 after 1000 hours). The comparison of the results in Table II also shows that the paints prepared using titanium dioxide as the "white" pigment become washed out (Example 1) after barely 50 hours of exposure to ultraviolet light. The results of Table II also show that the pigmentary Mn ^ O ^ smoke is suitable for many paints containing different constituents such as thickeners, dispersants, stabilizers, defoamers, preservatives etc. without any adverse effect on the applied layer. The tests further show that paints containing leached Mn ^ O ^ smoke as a pigmentary dye are not as stable as paints containing unmixed Mn ^ O ^ smoke. However, the smoke from Mn ^ O ^ used as a dye after leaching is more resistant to discoloration than synthetic red iron oxide.

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Claims (5)

1. Improved aqueous emulsion paint which contains a mainly acrylic emulsion, a thickener, dispersants and a colored pigment and which shows an improvement in the stability of the coloration and in the resistance to discoloration, characterized in that it is added of a colored pigment formed from finely divided particles of manganomanganic oxide smoke. 2. An aqueous-based emulsion paint according to claim 1, characterized in that the colored pigmented manganomanganese oxide is Mn ^ O ^ smoke having the following properties: (a) a chemical composition such that it comprises at least about 90% by weight of manganomanganic oxide, the remainder being a mixture comprising calcium oxide, magnesium oxide, potassium oxide and silica with less than about 1% by weight of free metallic manganese, and (b) a particle size falling below about 10 µm to 98%. 3. Water-based emulsion paint, characterized in that it comprises approximately 40 to 65% by weight of a latex; about 0.5 to 12% by weight of a thickener; about 0.2 to 2.0% by weight of a dispersant; about 0.2 to 2.0% by weight of a surfactant; about 0.1 to 1.0% by weight of an antifoam; about 0.3 to 6.0% by weight of a coalescing agent; about 0.1 to 1.5% by weight of a preservative; about 0.0 to 15.0% by: weight of a diluent; about 5.0 to 30% by weight of Mn ^ O ^ smoke; about 0.0 to 25% by weight of TXO2; and water for the rest. 4. Water-based emulsion paint following CD.MJ - 18 -! 4 "ν’ T vant claim 3, characterized in that it further comprises about 0 to 8.0% by weight of an antifreeze. 5. An aqueous-based emulsion paint according to claim 3, characterized in that it also comprises approximately 0 to 10.0% by weight of an alkyd resin.