MXPA97004381A - Carbon black products to color mining glands - Google Patents

Abstract

The present invention relates to a mineral binder composition having a carbon black product incorporated therein, comprising a carbon black having a bonded organic group containing an ionic group or an ionizable group.

Description

CARBON BLACK PRODUCTS FOR COLORING MINERAL AGGLUTINANTS TECHNICAL FIELD This invention relates to mineral binder systems containing a carbon black product as a colorant.

PREVIOUS TECHNIQUE Mineral binder systems used to form articles such as concrete, cement, mortar and exterior gypsum formulations are often colored to improve their aesthetic appearance. The coloration can be carried out either by applying an appropriate coating to the exposed surfaces or by adding small amounts of one or more pigments to the mineral binder system, to uniformly color the mixture. Because the surface coatings are exposed to peeling, fading and weathering, the latter method is preferred. The pigment or pigments can be added either to the dry mineral mixture for example, in the case of the concrete to the cement-sand mixture, or to the water used to prepare said mixture. The right pigments to color the P1.:62/97MX mineral binder systems that are exposed to outdoor conditions must: 1) be resistant to alkalis, 2) be resistant to light, 3) be resistant to industrial atmospheres, and 4) degrade to the weathering at a rate comparable to the body in which they are mixed, so that the appearance of the surface does not change substantially over time. In addition, to facilitate the application, the pigment should be relatively free of dust and should be easily dispersed in the mixture to achieve its maximum coloring ability. Black pigments are desirable colorants for use in mineral binder systems, because a great variety of colors and shades of color can be obtained by their use, either alone or in combination with other pigments. Oxides of black iron are the most preferred black pigment, but carbon blacks are also used to a limited degree. While carbon blacks exhibit excellent coloring properties, alkali resistance, light resistance and chemical stability, they are not preferred in systems exposed to weathering. Studies of weather degradation show that the appearance of the surface of bodies containing carbon black undergoes changes while carrying P1262 / 17MX carries out the degradation process outdoors. When the system contains only carbon black as the coloring pigment, the surface fades. When carbon black is used in combination with other dyes, the appearance of the other dyes becomes more pronounced. This change in mineral systems pigmented with carbon black has been attributed to the leaching and washing of carbon black pigment particles that are very small in relation to the other ingredients. This has limited its use in systems exposed to weathering. Additionally, depending on the physical form in which it is supplied, the carbon black can be either very dusty or very difficult to disperse. The process used to incorporate carbon black into a binder system depends both on the form in which the pigment is supplied and on the process equipment available to the user. In the way in which they are produced, carbon blacks are very dusty materials with volumetric densities that vary between approximately 0.02 and 0.1 gram / cc and are called spongy blacks. These blacks are very dusty. Due to its low densities and large surface areas, spongy products are cohesive, have very poor transportation properties and are therefore difficult to handle in bulk. For this reason, fluffy products have limited utility and, generally, are supplied in sacks. Fluffy blacks are, however, dispersible and can develop their full coloring potential by relatively simple grinding procedures. To improve the bulk handling properties of carbon blacks and reduce their dusty condition, spongy blacks are typically densified by various granulation processes to achieve a bulk density ranging from about 0.2 to 0.7 g / cc. For a given carbon black grade, the handling properties tend to improve as the degree of densification increases. The dispersion capacity, on the other hand, progressively degrades to the extent that the degree of densification increases. There is, therefore, a relationship between the improvement in bulk handling properties and the degradation in dispersion capacity. Due to the advantages of increased cleaning, however, granulated carbon blacks are frequently used to introduce carbon blacks into mineral binder systems. In such cases, however, the degree of grinding or grinding required to form a uniform intimate mixture will be greater than that employed with the spongy form of the product. Carbon black has been added to the P1 62 17MX mineral binder systems in a variety of ways. It can be ground by incorporating it into the dry cement-sand mixture, for example, and then the amount of water necessarily necessary to fix the mixture can be added. Alternatively, an aqueous dispersion of the carbon black, in all or in part of the necessarily required volume of water to fix the mixture, can be mixed uniformly in the cement-sand mixture. In any case, for a complete and uniform development of the color, the carbon black agglomerates must decompose to yield mainly individual aggregates (the smallest dispersible units of carbon black). This is achieved either by grinding the dry mix or by pre-dispersing, grinding the carbon black in the aqueous medium. Because carbon blacks tend to be hydrophobic, surfactants are frequently used to promote wetting. In addition, the presence of this agent in the aqueous medium can increase the dispersion process and help stabilize the dispersion. Attempts have been made to improve the properties of both dispersion and weathering of carbon blacks, used to pig mineral binder systems. Others, as described in European Patent No. 50354, have used l_f _ / 7M surfactant polymers which disperse the carbon black in the aqueous medium used to fix the mineral binder system and become inactive after drying. Benefits include better dispersion of black, resistance to weathering and decreased efflorescence. The disclosure of these patents is incorporated herein by reference. However, even in these prior art processes, carbon black, whether in granular or fluffy form, must be milled to achieve the required degree of pigment dispersion. In this way, a need persists for carbon blacks useful as colorants in mineral binder systems which can be used in granular form and which, however, are easily dispersed with a low shear agitation and which are less rapidly removed from the binder. system during weather degradation.

EXPOSITION OF THE INVENTION The present invention relates to a mineral binder composition having carbon black products incorporated therein, comprising a carbon black having an organic group containing an ionic group or an ionizable group. Carbon black products, when incorporated into a ri2ó2 / '* 7MX mineral binder system, offer superior weathering degradation properties in relation to conventional carbon black products.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mineral binder composition having carbon black products incorporated therein comprising: a carbon black bonded to an organic group containing an ionic group or an ionizable group. Carbon black products, when incorporated into a mineral binder system, offer superior weathering degradation properties than conventional carbon black products. Suitable mineral binder systems include concrete, cement, mortar, and exterior gypsum formulations. Other mineral binder systems are used here in a similar manner. Any additives conventionally known for mineral binder systems can be incorporated into the mineral binder systems of the present invention. The carbon black products can be prepared by reacting a carbon black with a diazonium salt in a liquid reaction medium to bind at least one organic group to the black surface of the carbon black. Diazonium may contain the organic group that is to be bonded to the carbon black., a diazonium salt is an organic compound having one or more diazonic groups. The preferred reaction medium includes water, any medium containing water and any medium containing alcohol. Water is the most preferred medium. These carbon black products and various methods for their preparation are described in a United States patent application entitled "Reaction of Carbon Black with Diazonium Salts, Resulting Carbon Black Products and Their Uses", filed on 15 December 1994, and incorporated herein by reference. To prepare the above-mentioned carbon black products, the diazonium salt alone needs to be sufficiently stable to allow reaction with the carbon black. In this way, that reaction can be carried out with only diazonium salts considered otherwise, unstable and subject to decomposition. Some decomposition processes can compete with the reaction between carbon black and diazonium salt and can reduce the total number of organic groups bound to carbon black. In addition, the reaction can be carried out at elevated temperatures where many of the diazonium salts may be susceptible to decomposition.

FlCfc-V ^ M / The elevated temperatures can also advantageously increase the solubility of the diazonium salt in the reaction medium and improve its handling during the process. However, elevated temperatures may result in some loss of the diazonium salt due to other decomposition processes. The carbon black can be reacted with a diazonium salt when present as a dilute, aqueous, easily stirred paste, or preferably in the presence of a suitable amount of water for the formation of carbon black granules. A preferred group of organic groups that can be bonded to carbon black are organic groups substituted with an ionic group or an ionizable group, as a functional group. An ionizable group is one that is capable of forming an ionic group in the medium of use. The ionic group can be an anionic group or a cationic group and the ionizable group can form an anion or a cation. Ionizable functional groups that form anions include, for example, acidic groups or salts of acidic groups. The organic groups, therefore, include groups derived from organic acids. Preferably, when it contains an ionizable group forming an anion, such as an organic group, it has: a) an aromatic group or a C alquilo -Ci 2 alkyl group and b) at least P1 O2 / 17MX an acidic group having a pKa of less than 11, or at least one salt of an acidic group having a pKa of less than 11, or a mixture of at least one acidic group having a pKa of less than 11, and at least one salt of an acidic group having a pKa of less than 11. The pKa of the acidic group refers to the pKa of the organic group as a whole, not only to the acidic substituent. More preferably, the pKa is less than 10 and more preferably less than 9. Preferably, the aromatic group or the alkyl group of the organic group is directly bonded to the carbon black. The aromatic group may also be substituted or unsubstituted, for example, with alkyl groups. The C1-C12 alkyl group may be branched or unbranched and is preferably ethyl. More preferably, the organic group is a phenyl group or a naphthyl group and the acidic group is a sulfonic acid group, a sulfinic acid group, a phosphonic acid group, or a carboxylic acid group. Examples include -COOH, -SO3H and -PO3H2 and their salts, for example -COONa, -COOK, -COO-NR 4+, -S03Na, -HP03Na, -SO3-NR 4+, and P03Na2, wherein R is an alkyl or phenyl group. Particularly preferred ionizable substituents are -COOH and -SO3H and their potassium and sodium salts. More preferably, the organic group is a substituted or unsubstituted sulfophenyl group or a salt P1262 / 97MX thereof; a substituted or unsubstituted (polysulfo) phenyl group or a salt thereof; a substituted or unsubstituted sulfonaphthyl group or a salt thereof; a substituted or unsubstituted (polysulfo) naphthyl group or a salt thereof. A preferred substituted sulfophenyl group is the hydroxysulfophenyl group or a salt thereof. Specific organic groups having an ionizable functional group and forming an anion are p-sulfophenyl, 2-hydroxy-3-sulfophenyl and 2-sulfoethyl. The quaternary ammonium groups (-NR) and the quaternary phosphonium groups (-PR) represent examples of cationic groups and can be attached to the same organic groups as discussed above for ionizable groups that form anions. Preferably, the organic group contains an aromatic group, such as for example a phenyl group or a naphthyl group and a quaternary ammonium group or a quaternary phosphonium group. The aromatic group is preferably directly bonded to the carbon black. Quaternized cyclic amines and quaternized aromatic amines can also be used as the organic group. In this manner, N-substituted pyridinium compounds, such as N-methyl-pyridyl, can be used in this regard. An advantage of carbon black products that have a substituted organic group substituted with a group ? 12b2 / "'7MX ionic or an ionizable group is that carbon black products may have increased dispersion capacity in water with respect to untreated carbon black.In general, the dispersibility in water of black products of carbon increases with the number of organic groups bound to the carbon black having an ionizable group or the number of ionizable groups bound to a given organic group.Thus, by increasing the number of ionizable groups associated with the black products of The carbon should increase its dispersibility in water and allow the control of dispersibility in water to a desired level When the water-dispersible carbon black products of the present invention are prepared, it is preferred that the ionic or ionizable groups ionize in the water. reaction medium The solution or mixture of the resulting product can be used as is or in diluted form, before being used. to be made or processed in the form of granules or agglomerates, preferably by a conventional wet process, granulation or agglomeration operation. The carbon black products can be dried using techniques used for conventional carbon blacks. These techniques include, but are not limited to: drying in ovens and rotary kilns. ? 1 2 b2 / c > 7 X Overdrawn, however, can cause a loss in the degree of dispersibility in the water. In the event that the above carbon black products are not dispersed in the aqueous vehicle as quickly as desired, the carbon black products can be dispersed using conventional known techniques, such as ground or crushed. The carbon black products can be incorporated either in solid form or as a preformed liquid dispersion. The preferred addition of carbon black product is less than or equal to 5% by weight of the mineral binder. These mineral binder systems have improved the weathering properties, as shown in the following Examples.

Experimentation The carbon blacks used were characterized in relation to their structure using n-dibutyl phthalate absorption, DBP, using the method ASTM D 2414. The surface area was characterized by the adsorption of cetyltrimethylammonium bromide, C , using the ASTM method D 3765.

Granulation or agglomeration Granulation or agglomeration was carried out ri262 / r > 7MX using a continuous pilot scale as well as one. batch laboratory scale. The batch unit consisted of a cylinder 18 cm (7 inches) in diameter by 17 cm in length that contained a central arrow fastened with a plurality of pins extended almost to the wall of the cylinder. The arrow was rotated at approximately 500 RPM during the granulation or agglomerate operation. The continuous unit consisted of a cylindrical body of 25.5 cm (10 inches) in diameter by 155 cm (61 inches) in length mounted with a rotor running along its axis. The rotor, adapted with approximately 120 pins of a diameter of 1.27 cm (0.5 inches), extending almost to the walls of the unit, was rotated at a specified RPM to form granules or agglomerates.

Measurement of Aqueous Residue This procedure was used to obtain a measure of product dispersibility. The carbon black (5 g) was stirred vigorously with 45 g of water for 5 minutes. The resulting mixture was emptied through a 325 mesh screen (44 microns) and rinsed with water until the wash water no longer showed color. The dry weight of the residue in the screen was determined and expressed as a percentage of the carbon black used in the test. • i r,: / i7M? Product Dispersability A measure of the dispersibility of the product was obtained by dispersing several blacks in an aqueous medium having a pH of about 10, under low shear conditions, by means of a magnetic stirrer, for 30 minutes. For control, unmodified blacks, cetyltrimethylammonium bromide, a surfactant known to stabilize carbon black dispersions, were added to the medium. No surfactants were used in the case of carbon black products. The optical density (OD) of the mixture, at a low shear stress, was determined at a wavelength of 550 nm. Afterwards, the mixture was sonified (to reflect an intense grind) and the optical density of the mixture was determined, (OD) Bonded * The percentage change in optical density before and after sonification was calculated,? (OD) = [(OD) gonized- (OD) low shear stress] / (0D) sonified- A large change in the percentage at this value indicates poor dispersibility at low shear for the dispersion conditions employed.

Formulation of Colored Concrete The concrete was colored with a mixture of carbon black and a natural pigment of iron oxide red. Two procedures were used to introduce black P1262 / 17MX in the concrete mix. All quoted amounts are given based on parts by weight. In the first procedure, 90 parts of iron oxide red and 6 parts of carbon black or carbon black product were mixed vigorously in a mortar and pestle until further mixing did not change color. 1.4 parts of the mixed color was mixed with 60 parts of sand and 14 parts of cement, by means of a spatula. Then, approximately 10 parts of water were added and the mixture was worked with a spatula to form a paste. The dough was molded into channels (8.5 cm long x 1 cm wide x 1.5 cm deep) and allowed to dry slowly under ambient conditions. In the second procedure, all the amounts used to form the colored concrete were identical to those of the first procedure. In this case, however, carbon black or carbon black product, 0.0875 parts, was added to the water used to fix the concrete. Nothing was added to the iron oxide red. In all cases the blacks were dispersed in the water under low shear dispersion conditions by agitation for 30 minutes using a magnetic stirrer. The reflectance spectrum of the dry and colored concrete was determined. The reflectance values were used to calculate the values of the International P1262 / 97MX Commision on Illumination CIÉ 1976 L * a * y b *. L * represents the brightness coordinate that goes from 0 for a pure black to 100 for a pure white; a * represents the red-green coordinate whose value becomes larger as the degree of red tone increases; b * represents the blue-yellow coordinate whose value becomes larger as the yellow tone increases.

Weather Degradation Weather degradation was simulated by contacting the concrete, for 30 seconds, with the undiluted SURE CLEAN® 600 detergent provided by ProSoco, Inc., Kansas City, Kansas. The product is a mixture of organic and inorganic acids combined with moisture agents and is usually diluted with water and used to clean the new masonry. The concrete was then washed with large quantities of distilled water, dried and then its surface reflectance was determined again. The pure, undiluted product vigorously attacks the alkaline concrete so that some of the surface layers are washed off. Changes in L *, a * and b * (? L *,? A * and? B *) before and after treatment give a measure of preferential leaching. ri "62 / '> 7MX EXAMPLES Example 1 This example illustrates the preparation of a carbon black product having a P-C6H4SO3-bonded group, a sponge carbon black (200 g) having a CTAB surface area of 350 m 2 / g and a DBP of 120 c / 100 g of carbon and 42.4 g of sulphanilic acid were placed in the batch of the granulator or agglomerator After mixing for 40 seconds by means of the rotor, a solution of 20.7 g of sodium nitrite , NaN02, in 150 g of water was added to the granulator or agglomerator.The internal salt of 4-sulfobenzenediazonium hydroxide was formed in situ making it react with the carbon black.After mixing for 45 seconds by means of the rotor, the product of carbon black was transformed into granules, which were dried in an oven at 120 ° C. The granulated product had handling properties comparable to at least conventionally granulated carbon blacks and was dispersible. resid or 325 mesh of 0.6% compared to 97% for untreated spongy black. A sample of the product was subjected to Soxhlet extraction overnight with tetrahydrofuran. The analysis of the extracted sample showed that it contained 3.47% of sulfur, compared with 0.5% of sulfur for the black of P1262 / 97MX untreated sponge carbon. Therefore, the carbon black product has 0.93 mmol / g of p-C6H4S03-linked groups.

Example 2 This example illustrates the preparation of a carbon black product having a P-C6H4CO2-linked group. The concentrated solutions A and B were formed as follows: Concentrated solution A: 19 g of concentrated hydrochloric acid (approximately 36% HCl) and 20 g of water. Concentrated solution B: 8.0 g of NaN 2 and 39.2 g of water. The concentrated solutions were cooled to 5 ° C. 1.58 g of anthranilic acid (o-amino benzoic acid) was added to 10.3 g of concentrated solution A. Then 10.5 g of concentrated solution B were slowly added while ensuring that the temperature did not exceed 10 ° C. The resulting solution, preserved in an ice bath, was stirred for 15 minutes. A mixture of 20 g of spongy black used in Example 1 in 350 ml of water was then achieved. The resulting mixture was stirred for 15 minutes and then filtered. The filtered cake was washed twice with water then dried in an oven at 110 ° C.

FI - ^ - V? MX While this product was not granulated, the dried cake had a density that was comparable to that of the granulated or agglomerated product and had much better handling properties than the spongy black precursor.

Dispersability The dispersion properties of the products of Examples 1 and 2 were evaluated using the optical density method. The controls used were untreated spongy carbon black, and its counterpart granulated or agglomerated in a conventional drying drum. The change in optical density in percentage is presented in Table 1.

Table 1 Percentage of Change of the Optical Densities in a Suspension and in Sonification.

The values? (0D) in the table show that the products of Example 1 and of Example 2 have more dispersibility than the granulated product P1 b2 / r, 7MX conventional drying drum, under conditions of low shear dispersion. In spite of its very large volumetric densities, the dispersibility of the product of Example 2 is comparable to that of the non-densified spongy black and the dispersibility of Example 1 is substantially higher than that of the non-densified spongy black.

Evaluation of Colored Concrete Samples with Carbon Black. The products of Examples 1 and 2 as well as the fluffy control blacks and dry granules were used to form colored concrete using the mortar and pestle mixing process, Procedure I, and the low shear aqueous dispersion process, Procedure II . The values L *, a * and b * found are given in Table 2.

Table 2 Color Values Obtained in Concrete The results in Table 2 show that when the coal products of this invention are incorporated into the concrete by Process I, pigmented concretes have darker colors than spongy carbon blacks or dried granules, as shown. by its smaller L * values. With method II, where the blacks are dispersed under conditions of low shear stress in water, the product of Example 1, being the most dispersible (see Table 1), gives the darker color. The product of Example 2 forms the next darker color. Surprisingly, spongy black, which is more dispersible than the dried drum granulate product, provided a pigmented concrete with the lightest surface color. This is attributed to the segregation of the pigment away from the surface layers because, as will be shown, a darker color is obtained when the surface is washed with the SURE CLEAN® detergent.

Weathering of Colored Concrete Samples The simulated weathering degradation was conducted by washing the surfaces of the samples characterized in Table 2 with SURE CLEAN® 600 detergent and water. The acidic detergent, in all cases, attacked the surfaces of the samples. The? 62 / a7MX values L *, a * and b * of the washed surfaces were presented in Table 3. The aggressive washing procedure employed, in all cases, resulted in some change in the appearance of the surface. The change in appearance, however, was the lowest for the carbon products of the present invention.

Table 3 Washing Concrete Color Values Changes in wash color values are shown in Table 4.

Table 4 Change in Wash Color For each procedure used to form the P12Ó2 / 97MX, the magnitude of the value? L * is smaller for the carbon products of the present invention. In addition to the sample formed with the spongy black using Process II, where some color segregation occurred and the change in? L * is very large, the magnitude of the values? A * is smaller for the products of the present invention . Finally, the values of? B * are reasonably comparable for all samples. Accordingly, the results show that the color changes are smaller with the black products of the present invention.

Example 3 The present example shows that the carbon black products can be formed in a continuous granulation operation. A sponge carbon black having a surface area of 133 m / g and a DBP of 190 cc / 100 g of carbon was introduced into a granulator or pin agglomerator operating continuously at a rate of 100 parts by weight per hour. Simultaneously, a 30% solution of sodium nitrite and a suspension containing 5.43% concentrated nitric acid, 8.72% sulphanilic acid and 85.9% water was introduced to the granulator or agglomerator. The sodium nitrite solution and the suspension were introduced at speeds of 16 and 112 parts by weight per P1262 / "'7 X hour, respectively The internal salt of 4-sulfobenzenediazonium hydroxide was generated in situ and reacted with the carbon black in the granulator or agglomerator The material existing in the granulator or agglomerator is the treated black , in granular or agglomerated form, and dried at 125 ° C. These materials can also be used in mineral binder systems to obtain superior weathering properties Other embodiments of the invention will be apparent to those skilled in the art. from the consideration of the specification and practice of the invention disclosed herein, it is intended that the specification and the examples have an exemplifying character.

P1262 / 97MX

Claims (11)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMSt 1 is claimed as property. A mineral binder composition having a carbon black product incorporated therein. , which comprises a carbon black having a bonded organic group containing an ionic group or an ionizable group.
2. 2. A composition according to claim 1, wherein the carbon black product is a water-dispersible carbon black product.
3. 3. A composition according to claim 2, wherein the carbon black product is dispersible in the mineral binder composition by means of low shear stirring or mixing.
4. 4. A composition according to claim 1, wherein the carbon black product is present in an amount less than or equal to 5% by weight of the mineral binder.
5. 5. A composition according to claim 1, wherein the carbon black product is in the form of granulate.
6. 6. A composition according to claim 1, P12o2 / "'7MX wherein the mineral binder is selected from concrete, cement, mortar and gypsum 7.
7. A composition according to claim 1, wherein the ionic group or the ionizable group is a carboxylic acid or a salt thereof.
8. A composition according to claim 1, wherein the ionic group or the ionizable group is a sulfonic acid or a salt thereof
9. 9. A composition according to claim 1, wherein the organic group is a sulfophenyl group or a salt thereof
10. 10. A composition according to claim 1, wherein the organic group is p-sulfophenyl or a salt thereof
11. 11. A composition according to claim 1, wherein the organic group is a carboxyphenyl group or a salt thereof. F1262 / ^ 7MX