BE504932A - - Google Patents

Description

       

   <Desc / Clms Page number 1>
 
 EMI1.1
 



  ACIDESO-RESISTANT BLUE PIGMENTS3 IMPROVEMENTS
The present invention relates to a novel ultramarine blue pigment which is highly resistant to acids and to the preparation of this pigment.
 EMI1.2
 



  More particularly. \) 1-'invention relates to a new pigment of blue d.9ou = tremer with modified surface, as well as methods for its production., More particularly still, the invention relates to a pigment of ultramarine blue , the particles of which have been reacted with a very dilute solution of a strong acid, then treated with a solution of an alkali metal silicate and finally calcined, as well as to the process used for this purpose and described below below.



   It has long been known that the clarity and brilliance of ultramarine blue are rapidly and seriously affected by weak acids, even extremely weak acids, which are normally present in the atmospheres of industrial centers and cities. Like blue
 EMI1.3
 ultramarine is generally applied with the aim of obtaining a permanent coloration and not a fleeting coloration, it is considered that the deterioration which it undergoes when exposed to atmospheric conditions for a short time, for example from six months, is fast.

   Another in-
 EMI1.4
 The notable advantage of ultramarine blue pigments is that the paint films subjected to atmospheric conditions do not appear blue, but have a whitish tint, which greatly reduces
 EMI1.5
 The intensity of the blue coloration of the underlying film was reduced. Tests were carried out to improve the resistance to atmospheric conditions and to dilute acids of out.emero blue In one of these tests the individual particles were enveloped in blue ultramarine in a coating of sodium silicate. This was done by putting the ultramarine blue into a paste with dilute sodium silicate, then
 EMI1.6
 while drying the product.

   This coating process only gave rise to a

 <Desc / Clms Page number 2>

 manages improvement, as the silicate coating is shown to be acid permeable and the sensitivity of the coated ultramarine blue to attack.
 EMI2.1
 that by acids was not modified. Further tests with a view to improving the quality of the silicate coating were carried out. In some of these tests chemicals were applied, which served to harden the silicate coating, while in other tests the ultramarine blue coated with silicate was calcined on cover granules.

   These tests were not satisfactory either in the sense that they did not make it possible to obtain ultramarine blue having satisfactory resistance to atmospheric conditions.
Since attempts to produce ultramarine blue particles coated with a sufficiently durable coating have not given the desired results, attempts have been made to modify the characteristics of the structure.
 EMI2.2
 crystalline ture itself of ultramarine blue.

   It was then discovered, not without surprise, that ultramarine blue has some of the properties of an artificial zeolite and that when ultramarine blue is reacted with a predetermined proportion of a very dilute solution of sulfuric acid. ., an ultramarine blue pigment is obtained which has lost very little of its original coloring and brilliance.

   This finding was most surprising, since it was believed that such an acid treatment would cause the same discoloration as known to be caused by the dilute acids present in the atmospheres of the cities.
 EMI2.3
 It was further found that this 1-acid reaction removed sodium from ultramarine blue and formed a surface of a totally different character in that the degree of crystallinity of the surface
 EMI2.4
 was reduced very markedly, as could be seen by the ability of said surface to diffract electron beams.



  This acid-treated ultramarine blue has been shown to be chemically active, in that it reacts easily in aqueous sodium silicate solution at elevated temperature to form an ultramarine blue which contains substantially the same proportion of sodium and
 EMI2.5
 little more silica than the original ultramarine blue By this silicatation reaction9 the acid resistance of ultramarine blue is greatly improvedo
We have also discovered, surprisingly.

   that the calcination of ultramarine blue described above, having undergone a treatment with
 EMI2.6
 The acid and silieatation, when said calcination is carried out under controlled conditions and to a controlled extent, results in the production of an ultramarine blue pigment exhibiting extraordinary acid resistance. The same calcination performed on a blue
 EMI2.7
 ultramarine silicate, but not having undergone any treatment with acid, does not make it possible to obtain such resistance to acids.



   Usually, the calcination of ultramarine blue attenuates some
 EMI2.8
 little its brilliance and alters its color. It was also discovered, not surprisingly, that., When acid-treated ultramarine blue, silicate and. calcined according to the present invention, is cooled in an atmosphere
 EMI2.9
 With water vapor, the tarnish or fading of gloss which has occurred during calcination is removed and in some cases the resulting product is even brighter than it was before calcination. The process according to the present invention does not necessarily require cooling in a steam atmosphere of the calcined ultramarine blue, but this cooling constitutes part of the preferred embodiment of the present invention.
 EMI2.10
 



  The new ultramarine blue treated with silicate and calcined acids according to the present invention can be used as a pigment in the main applications where ultramarine blue was used in the past, in particular for bleaching paper, leaching fabrics, laundering. preparation of paints and lacquers, coloring of natural and synthetic rubbers, pigmentation of synthetic plastics,

   1-Printing of wallpaper and dyeing of cover granules

 <Desc / Clms Page number 3>

 reo This new ultramarine blue is surprisingly more resistant to atmospheric conditions and acids than any of the ultramarine blue pigments known in the past and is the best pigment known for the last mentioned application. In addition, this pigment presents
 EMI3.1
 You have the new property of appearing as a blue pigment in paint films subjected to atmospheric conditions. All other known ultramarine blue pigments show a dirty whitish coloration in similar films.



   The product of the present invention will be described in more detail with reference to the accompanying drawings in which: Figure 1 shows a graph of the type of electrical diffraction.
 EMI3.2
 tronique d'lan sample of ordinary ultramarine blue (Graph 1-to), superimposed on a graph, with hatching, of the type of electron diffraction presented by a sample of ultramarine blue, which has been treated with acid according to the method of the present invention (Graph 1-B);

   - figure 2 shows a graph illustrating the type of dif-
 EMI3.3
 electron fraction of a sample of ordinary ultramarine blue (Graph 2-to), on which is superimposed a graph, with hatching, of the type of electron diffraction presented by a sample of the same ultramarine blue.
 EMI3.4
 mer, which has been treated with acid, silicate and calcined at 300'Og for 4 hours, according to the process according to the present invention (Graphi-
 EMI3.5
 as 2 B) and - Figure 3 shows a graph of the electron diffraction type of a 1xl sample of ordinary ultramarine blue (Graph 3-A). superimposed on a graph, with hatching, of the electron diffraction type of a sample of the same ultramarine blue, which has been processed
 EMI3.6
 with acid,

   silicate and calcined at 600 C for 1 hour, according to the method according to 1-'invention (Graph 3-B)
The type of electron diffraction of ordinary ultramarine blue is not materially changed when ultramarine blue is only pulped with the same dilute solution of sodium silicate as employed in the present invention, and dried. or when the ultramarine blue thus treated is calcined.

   In other words, neither of these two treatments, alone or in combination, causes a noticeable decrease in the total surface crystallinity of the blue particles.
 EMI3.7
 d 9 out erer In the drawings, the lines of the graphics relating to
 EMI3.8
 ultramarine blues -treated (Charts 1-B, 2-B and 3-B) are somewhat wider than the lines in the graphs relating to ordinary all-blue (Charts 1-A, 2- & and 3- &. ) o These differences in widths are used only to facilitate visual comparison of the pairs of graphics and do not represent the respective widths of the rings appearing on the photographic plates.
 EMI3.9
 



  The 1-aid treatments, silications and calcinations referred to in the description of the drawings, have all been carried out in a uniform manner and according to the embodiment.
 EMI3.10
 preferred of 1.9invention9 as described in the remainder of this Méwoire, except with regard to the graph z of FIG. 29 where the operation was carried out at a lower calcination temperature.



   For the preparation of the photographs of the electron diffraction types or patterns employed for the preparation of the graphs referred to above, a uniform procedure was followed.
 EMI3.11
 In each case an electronic potential of 60âo'o was applied, the same electron diffraction instrument was used the samples were mounted in the same manner and the exposure times were two seconds, so to obtain the best photographs under the same conditions.

   The photographs were obtained by reflection in
 EMI3.12
 pairs on glass plates, the diagram for ultramarine blue

 <Desc / Clms Page number 4>

 ordinary being produced on a different part of the same photo-
 EMI4.1
 graphic. The plates were then developed and rated in strictly the same way.



   With the diffraction by reflection method the depth of the vertical penetration is only 100 l, so that the resulting photographs show only the surface condition of the pigment particles.



   The three plates obtained presented the usual general appearance and allowed free intervals to appear between the concentric diffraction rings, the darkest rings appearing on the plates being those qualified, hereinafter as being those presenting the most intensity.
 EMI4.2
 When determining the relative intensity of each of the rings appearing in each pair of photographs, the intensity of the most intense 1-ring in the diagram of ordinary ultramarine blue, appearing on each plate, was taken as a standard. comparison for the whole plate.

   To this lines we have assigned the arbitrary value of 100 intensity units (ordinate). To the remaining rings of the plate, we have assigned numerical values proportional to their respective intensity.
 EMI4.3
 tive with respect to the arbitrary value. In other words, a ring having, for example, 30 units of intensity should be considered to have an intensity equal to 30% of that of the reference line or 1-ring.



   The relative intensities mentioned above were determined by visual comparisons. In the case of the most intense rings, these visual comparisons were checked for inaccuracy.
 EMI4.4
 by sensitometer readings. The values given by the visual comparisons were found to correspond well to the dental readings.
 EMI4.5
 sitometer.

   The densitometer was, however, found to be too insensitive for the determination of the relative intensities of the majority of the rings and visual comparisons must necessarily have been employed in these cases.
On the photographic plates, the rings corresponding to lattice or structure intervals (abscissa) of less than 1.5 A were not clearly defined, but were greatly enlarged and blurred. These rings were so indistinct that they appeared to lie at the side. limit or in the vicinity of the limit of sensitivity of the photographic plate. Rings this low and even rings with an intensity of about 10% or even 15% of the line la
 EMI4.6
 brighter than ordinary ultramarine blue could not always be detected.

   The combined experimental error recorded among the various observers varied by less than 10 units of intensity for the
 EMI4.7
 most intense rings at a maximum of about 15 units of intensity for the most pale lines, "exhibiting grating intervals less than 195 in. Examples of experimental error in the graphing of Figures 1 to 3 can be seen. first observed by comparing graph 2U with graph 340 The same ultramarine blue was used for the development of these two graphs and the same electron diffraction diagram photographs of this material were prepared, these photographs having, moreover, been appreciated. in the same way.

   Four of the weakest lines appearing on the
 EMI4.8
 photographic plate., from which the graph 2 = 1 was drawn were not detected by the majority of observers., who had to examine the photographic plate whose graph 3-A was
 EMI4.9
 derivative In this case, the experimental error was most likely an error of small magnitude and of human origin o Other minor errors can also be caused by variations in the quality of the extreme blue o The blue of the or

 <Desc / Clms Page number 5>

   ordinary commercial tremer constitutes a well standardized product, which is surprising if one considers the complex reactions, at elevated temperature, which are necessary for its synthesis,

   and the number of subsequent treatments, such as crushing, grading and flotation, to which this product is subjected. The variation which may be expected, from the standpoint of the apparent degree of surface crystallinity of these products.!) Is illustrated.
 EMI5.1
 by graphs 1-to and 2a For the elaboration of these graphs, two different dJ1 or tremer blues have been used. These two overseas blues were prepared by the ordinary process of commerce, but were obtained from different production batches.

   The same variation mid-
 EMI5.2
 nore that the graphs 2 = A and 3-4 are found between the following two graphs which were obtained from the same d90utremero blue LJ1efret of the experimental errors was reduced to a minimum, first of all by photographing the diagrams in pairs and by having these diagrams also in pairs, by the same group of observers, which allowed the elimination of some of his errors.
 EMI5.3
 experimental. The categorization process, described below, also minimized the effect of the inability or inability of the observers to discern the weaker lines.



   The drawings show that the surface of ordinary untreated commercial ultramarine blue is highly crystalline. In each of the graphs, more than six diffraction rings can be seen, the intensities of which ¯ are greater than 10% of
 EMI5.4
 Dominant Line Intensity at 3.70% The majority of observers also detected a large number of additional rings, exhibiting intensities equal to at least 10% of the dominant line intensity.

   
 EMI5.5
 h9eamoomparatz of graphs 1-to and 1-B of figure 1 shows that the acid treatment gives rise to the formation of an electron diffraction diagram revealing a stupefying decrease in surface crystallinity apparent ultramarine blue, the
 EMI5.6
 new surface having only about half of the total apparent crystallinity of the 19anoan surface. Only three of the more intense lines in Chart 1-to persist as strong lines in Chart 1-B.

   Two lines of marginal intensity were discerned on the photographic plate, from which graph 1a was drawn. As for the remaining lines of ultramarine blue o1'di =, nairep we have not come to hate them.



  Graph 2-B of FIG. 2 shows the electron differential diagram of ultramarine blue according to the present inventions obtained by calcining at 3000 0 for 4 hours acid-silicate treated ultramarine blue. The degree of apparent surface crystallinity to-
 EMI5.7
 The figure appearing in these graphs is only a fraction of that appearing in graph 1-B of Figure 1;
Graph 3-B of figure 3 shows the diagram of the
 EMI5.8
 blue gun electron diffraction d) typical ultramarine; prepared according to the preferred method of carrying out the invention. This ultramarine blue corresponds exactly to that used for the construction of graph 2 = B of FIG. 2s except that the calcination was carried out at 600 ° C. for 1 hour.

   Graph 3-B is much the same as Graph 2-B, the former being, however!) Of less intensity than the latter.



   For best results, acid treatment should be performed, so as to produce ultramarine blue with sensi =
 EMI5.9
 The total apparent surface crystallinity, indicated by graph 1-B in figure xi It goes without saying that d9ct eme blues with higher or lower degrees of apparent surface crystallinity can also be prepared) ) by varying the proportion
 EMI5.10
 acido

 <Desc / Clms Page number 6>

 
By making direct use of the graphs, one can appreciate the achievement of the optimum initial and final total decrease in apparent surface crystallinity. This decrease can be expressed by integrating the diagrams, as explained below.
 EMI6.1
 



  If we first consider figure i9 the intensity (length) of each of the lines of graph 1-A is determined on an initial scale
 EMI6.2
 and the values thus obtained are added to determine the total current of the diagram. This operation is hereinafter referred to as the "integration stage". The result in this case is approximately 29.5 intensity units.

   Integrating the lines of graph 1-B on the same initial scale gives a value of approximately 1238 intensity units o The total relative intensity of the diffraction pattern
 EMI6.3
 The electron of the treated material is therefore 12.9 seconds or substantially 44% of the intensity of the electron diffraction pattern of ordinary untreated ultramarine blue.



   In figure 2, 1-integration of the lines of graph 2-A gives
 EMI6.4
 a value of about 39.6 units of intensity. The corresponding value of the lines in Chart 2-B is approximately 6.4; The total relative intensity of the electron diffraction diagram of the material used for the construction of graph 2-B, compared to the intensity of the diagram
 EMI6.5
 ordinary otremer blue is therefore 6, Q .96a, or about 16%. -
A similar integration of the data in Figure 3 demonstrates that, thanks to the higher calcination temperature, a
 EMI6.6
 ultramarine blue exhibiting an electron diffraction pattern, the total relative intensity of which is 3e3 g 31 79, ie approximately 19%.

   In graph 3 = B, the value of the line corresponding to 2955 is doubtful and if this line is neglected the total apparent crystallinity becomes equal to approximately 9%.



   The total relative intensities of these patterns are a measure of the relative degree of electron beam diffraction, with the stronger patterns indicating a higher degree of total surface crystallinity. When establishing the relative intensities of the diagrams, only the intensities of the discernible lines can
 EMI6.7
 be taken into consideration and the general appearance of the photographic plate with its background is neglected. As has been pointed out, some observers are better able than others to discern a greater or lesser number of the most prominent lines. weaker.

   When the comparisons are
 EMI6.8
 made under uniform conditions, by the same groups of observers, and averaging these comparisons, remarkably consistent results are obtained and the effect of the inability or inability of observers to detect lines of weaker intensity tends to increase. disappear
 EMI6.9
 ra! be when the data from the graphs is integrated and the ratio of this data is calculated as indicated above.



  Ultramarine blues treated with silicates and caTines9 whose comparative electron diffraction patterns reveal total intensities exceeding about 25% of the intensity of the pattern.
 EMI6.10
 Ordinary ultramarine electron diffraction patterns are insufficiently acid resistant to be used satisfactorily in cover granules.

   The -bluei :. treated with 1-'a- aid, silicates and calcined., which give diagrams showing total relative intensities well below 11% of the total intensity
 EMI6.11
 of the diagram of ordinary ultramarine blue, can be prepared and usually show slightly better acid resistance., but are tinctorial weaker especially in the case
 EMI6.12
 ultramarine blues, the diagrams of which give intensities of the order of 6% of the total relative intensity.



   It has, moreover, been observed that the central part of the par-
 EMI6.13
 ultramarine blue particles are not affected by acid treatment,

 <Desc / Clms Page number 7>

 
 EMI7.1
 no more than by silication or calcination as far as we can judge. As noted above, the photographs of the electron diffraction patterns only show the condition
 EMI7.2
 prevailing on the surface of the ultramarine blue particle to a depth of about 100 A. These photographs therefore give no information as to the constitution of the interior of the particle.

   To obtain information on this last point, the diagrams have been prepared.
 EMI7.3
 diffraction analysis of ordinary ultramarine blue and the various ultramarine blues used for the preparation of the graphs shown in the accompanying drawings. The X-ray diffraction patterns thus obtained were substantially identical, in that all of them revealed the regular and intense diffraction characteristic of blue.
 EMI7.4
 ordinary ultramarine.



   The data given above demonstrates that an ultramarine blue composite pigment particle according to the present invention is constituted by an ultramarine blue particle having two areas substantially enveloped in a coating of an amorphous composition, composed of: predominantly silicon and oxygen as the dehydration product of hydrated silicic acids, this coating being substantially free of alkali metals. One of said areas is a central area of ordinary ultramarine blue, while the second area is a peri-
 EMI7.5
 Ripheric oxtremea blue with low apparent crystallinity.

   The nature of the peripheral zone and the nature of the coating are not precisely known and the Applicant does not wish, in this regard, to limit themselves to a particular formula or theory. The process according to the present invention, for the preparation of improved ultramarine blue,
 EMI7.6
 Starting from commercial ultramarine blue, scratching undergoes no reaction, can be carried out as follows, the example given hereinafter being only illustrative of one commercial embodiment of the invention and not in any way to be construed as limiting it. this.



   EXAMPLE
40 free English commercial ultramarine blue
 EMI7.7
 tee (dry base) are pulped with 67 pounds of water. In a separate container, 2 pounds of 93% sulfuric acid is dissolved in 175 pounds of water. The pellet of ultramarine blue is added to the acid solution without stirring, through a sedated line below the surface of the solution. acid reaction, at a temperature of 200 Co. The mixture is then stirred slowly. A substantially neutral or slightly acidic paste of a highly fluffy rough blue is obtained in less than a minute. This is the acid treatment specified above.



   The mixture is then stirred and heated by injection of va-
 EMI7.8
 fear of water at 90 C, appreciably Until the end of the evolution of hydrogen sulfide and until the pH of the solution becomes appreciably neutral at this temperature and during 1 1/2 hour, a solution of 17 English pounds of sodium silicate in 33 English pounds of water The mixture is stirred for half an hour ±) then left to stand. The sodium silicate solution used has a density of 42 Bé and a ratio of 1a0 to 81 2 of 1 g 3922 "'It contains approximately 1 liter of NaO and 0 3 pounds of Si 2 per pound of liquid and is Alkali in nature Almost all of this sodium silicate is consolidated when the silicate stage is specified above.



  The supernatant liquor is separated and the precipitate is repulped with water. Filter and dry at 0 = 90 @ 0. When using filter presses it is advantageous to add to the pulp sufficient aluminum sulphate. [A12 (S04) 3 18 112 to neutralize, to Yellow

 <Desc / Clms Page number 8>

 
 EMI8.1
 Brilliant alkalinity remaining. The silicate seawater blue thus prepared exhibits considerably greater resistance to acids and alums than the original ultramarine blue from which it was prepared.
 EMI8.2
 



  The final stage which leads to the production of overseas blue, whose resistance to acids and alums is the strongest known, consists in calcining the ultramarine blue treated with acid and silica. ,, this can be done in an indirectly heated clay calcination furnace of the ordinary rotary drum type con-
 EMI8.3
 holding spiral baffles.

   Thanks to the rotation of the drum and the 1-lac- tion of the baffles the load progresses slowly towards 1-forward, the speed of rotation of the drum and the temperature of the oven being regulated so that
 EMI8.4
 ultramarine blue reaches a temperature of about z 0, at the discharge end of the furnace, in a little less than half an hour, which corresponds to a calcination rate fast enough to prevent substantial deterioration by oxidation of the brilliance of the blue
 EMI8.5
 screen The ultramarine blue is maintained at this temperature .squ9à the end of the release of water vapor, that is to say approximately for 1 minute. The vapor which is given off as the temperature of the ultramarine blue increases escapes through the terminal openings in the oven.

   Air access therein is limited as much as possible.
 EMI8.6
 



  The calcined ultramarine blue is cooled to about 100-150 C in an atmosphere of water vapor, which results in the absorption of a quantity of water appreciably equivalent to that which was expelled by the water. calcination and pro-doque, besides a noticeable improvement in the coloring of the pigment. When room temperature is reached, the ultramarine blue is 99% filtered through a 325 mesh sieve and is packaged.
A surprising advantage of the present invention lies in the fact that the aforementioned sieving can be carried out easily and that the formation of solid aggregates of "clinkers" does not occur during calcination.



   It goes without saying that the procedure described above is subject to variations.
 EMI8.7
 



  In the aid treatment described above, 5% sulfuric acid is used, based on the weight of the ultramarine blue. This proportion of diacid removes sufficient sodium from the crystal lattice and has been shown under many circumstances to give the best results.



  If the proportion of sulfuric acid is increased beyond 7%, a notable degradation of the product is observed from the point of view of its dyeing qualities. Less than 5% diacid can be used, but if the proportion of diacid is less than about 3 or 4%, the removal of sodium
 EMI8.8
 ultramarine blue does not occur to the extent desirable, nor does the reduction in surface crystallinity occur to a sufficient degree.
 EMI8.9
 The concentration of the acid in the initial paste is not critical and can vary within wide limits. It is not particularly advantageous to use an amount of water greater than 4 to 6 times the weight of ultramarine blue.

   When the total amount of water is less than about 3 times the weight of the oxygenxtrere blue, difficulty arises in oxidation. Sulfuric acid is preferred. However, a chemically equivalent proportion of another strong mineral acid can be used, such as hydrochloric acid, but this is less advantageous.
The process described above for combining the acid with ultramarine blue need not be followed exactly, but it is carried out primarily to cause all ultramarine blue to react rapidly.
 EMI8.10
 quickly and evenly with all the acido

 <Desc / Clms Page number 9>

 
 EMI9.1
 During the sillicatationg operation, the sodium silicate solution is added,

   when the ultramarine blue has been heated to a temperature well in excess of 50 ° C and preferably equal to about 900 because While the temperature of the paste rises to the desired value, the pigment reacts to a small extent with 19 water still slightly acidulated, which drives Sulfur out of the crystal lattice and causes the release
 EMI9.2
 out of solution, a very small amount of hydrogen sulfide Hydrogen sulfide has the undesirable property of lowering the pH of the bath and since sodium silicate solution should only be present under neutral or alkaline conditions ,

     intake of sodium silicate
 EMI9.3
 should be delayed until a sufficient quantity of hydrogen sulphide has evolved and a substantially neutral paste is obtained.
 EMI9.4
 



  Sodium silicate is alkaline and can therefore be added with the slurry when it is slightly acidic. However, if the degree of acidity of the paste is relatively high there will be precipitation of the silicate as a gel and inhibition of the desired reaction of the silicate with ultramarine blue.



  The amount of sodium silicate added should be sufficient to substantially satisfy the absorption capacity of the overseas blue for sodium ions. It is preferred to employ a slight excess of silicate. In the exemplary procedure described above, slight excess of sodium silicate was used.

   A larger excess of silicate can be used but the formation of a coating of sodium silicate should be avoided, because it does not increase the resistance to water.
 EMI9.5
 pigment acidic and decreases the dyeing capacity of the pigment. It is not necessary to use more silicate than necessary for the weight of SiO2 in the amorphous coating of the final pigment to exceed about 10 to 13% of the weight of the pigment. pigmenta according to the particle size thereof. Good pigments whose coating con-
 EMI9.6
 holds less than 8i02.9 can be prepared o The percentage of 3i02 can even be in the order of 69g in
The duration of the silication reaction is important and it should be prolonged until the capacity

  of so-
 EMI9.7
 dîum of ultramarine blue was noticeably reached. This seldom takes less half-uzre and often better results are obtained when the silioation reaction is continued for a longer period of time, ie for a period of up to about 2 hours.

   Absorb-
 EMI9.8
 tion of sodium ions in the crystals of ultramarine blue causes the formation of silicon and oxygen compounds of the type of silicon acid or of hydrated siliceous compounds, on the surface of the crystals.
 EMI9.9
 ultramarine blue The compounds thus formed have a brief existence and decompose on the surface of the ultramarine blue particles, so as to form an amorphous permeable coating previously formed.
 EMI9.10
 dominant by silicon and oxygen. It is very surprising that when we stick to the proportions given in the example given above, the coating in question is substantially free of sodium.



   Other sodium silicates of similar relative composition
 EMI9.11
 z, that ten silie shown in the above example and containing a substantial excess of SiO2 can be used. These silicates can be replaced, in whole or in part by similar solutions of si-
 EMI9.12
 potassium licate The product obtained is similar to that obtained above
The temperature of the silication reaction is not critical.
 EMI9.13
 tick. However, considerably better results are obtained by operating at 900 ° C. for a longer time than by operating at room temperature.



   At each calcination temperature, the ultramarine blue at-

 <Desc / Clms Page number 10>

 rapidly dyes a state of stability, so that prolonged heating at the same temperature does not cause further evolution of water and does not give rise to any significant increase in its resistance to acids. This stability is reached at 3000 C or 3500 0-in less than an hour, \! while at 8000 C the calcination should last only a few seconds.



   It is therefore not necessary to use the oven described above. For the said calcination of ultramarine, use may be made of any type of furnace, provided that it permits constant and rapid uniform heating to 600 or 8000 ° C., with the escape of the evolved water vapor. Also, a fixed horizontal cylinder type furnace containing a rotary horizontal worm rotating around a hollow shaft has been successfully employed. When a furnace of this type is used, the heating gases are admitted into the central shaft of the worm and the load is pushed forward by the rotation of the latter.

     When using a calcining furnace
 EMI10.1
 conventional type operating at C00 0s the calcination takes place in much less than five minutes.
 EMI10.2
 It is also possible to perform the calcination continuously and this is, in fact, the usual laboratory method.
 EMI10.3
 In the batch calcination, crucibles of ultramarine blue are placed in a retort heated to 600 G, where they remain for about 1 hour. It is advantageous to maintain a sensitive atmosphere-
 EMI10.4
 ment inert above ultramarine blue. The crucibles are cooled in a humid atmosphere, as described above.



   During calcination the presence of air must be avoided
 EMI10.5
 as much as possible and it is preferable to exclude the air completely.



  However, the presence of the quantities of air which normally diffuse into the furnace at the loading and unloading openings thereof does not constitute a serious drawback. The extent of the damage caused by air is greater the higher the temperature.



  In the following description of the effect of the calcination temperature.!)
 EMI10.6
 it is assumed that there is a small amount of air present, which is difficult to exclude.



   To obtain good results, it is sufficient to calcine the blue
 EMI10.7
 ultramarine above 3500 c, until the silica coating, which acts as a continuous permeable membrane is dehydrated and converted
 EMI10.8
 to a substantially and generally impermeable coating, that is, until the release of water from the treated seawater blue ceases or until additional heating results in a substantial improvement in the acid resistance of the treated seawater. this last. During calcination, small cracks may form in the coating, but this is not harmful. The most economical calcination temperature can be determined by subjecting the pigment to the 1-acid test described below.



   In practice the improvement begins to be evident, when the acid-treated silicate ultramarine blue has been calcined at a low temperature.
 EMI10.9
 temperature of about 300 or 3500 Co The improvement in alum resistance of ultramarine blue becomes progressively stronger as the calcination temperature increases. At around 500 to 700 C, and particularly at 600 C, the improvement appears to reach its maximum. The highest temperature found to be practical
 EMI10.10
 to heat the pigment is 0 gas. However, the application of such a high temperature leads to disadvantages.

   Ultramarine blue si-
 EMI10.11
 licate cannot be heated above z00 C for longer than this, otherwise it seriously loses its strength. If heated to 7000 C9 the maximum exposure time may be a little less, but should not greatly exceed five minutes, otherwise a similar loss of strength will occur. If the temperature of 60 010 C constitutes

 <Desc / Clms Page number 11>

 the highest temperature to which ultramarine blue is subjected. \! it can be maintained at this temperature for about 1 hour without appreciable loss of strength. The temperature can be easily adjusted according to the duration of the calcination by observing the appearance of the stream of ultramarine blue coming out of the furnace.

   Any substantial alteration in the appearance of the ultramarine blue indicates that the drum rotational speed of the continuous calcining furnace must be increased or the temperature thereof must be moderate. These conditions must be controlled
 EMI11.1
 These can compensate for the effects due to variabJ.es, 9 such as the water content of each batch, the particular dimensions of the pigment., the amount of silicate used and must be adjusted in such a way as to
 EMI11.2
 evoke the least drawbacks As .gméi3atien of the resistance to alums caused by heating the ultramarine blue d.9 to 6000 0 is substantially the same as that obtained. when one heats it to 700 or 800 Ce but the danger of deterioration of ultramarine blue is much less.!)

     it is preferred to regard the temperature of 600 ° C. or, preferably, the area ranging from 500 to 7000 ° C., as the optimum working temperature.



   When the calcination is carried out in a completely inert atmosphere, the damage is very greatly reduced. When we exclude
 EMI11.3
 Completely air-free, the silicate treated ultramarine blue can be kept at 600 ° C for several hours without damage.



  Not only is the product not damaged, it is darker, stronger and more acid resistant than a similar product obtained by heating the same starting material for one hour at 6000 C, presence of a limited amount of air.
 EMI11.4
 



  It can be noticed that the silicatation of the acid-treated d9o.ta.em blue seems to give it resistance to high temperatures.
 EMI11.5
 vées9 in the presence of 1-'air, qax931 Would not know *? there had been no silisation. Non-silicate ultramarine blue cannot be heated up to 3 C9 and, in particular, up to 9 to 600 C, without suffering severe loss of quality, presumably for the reasons stated in the patent. UoSoA. n 2ad ,, 1o951o The enhancement caused by silication appears to be due, in part, to the protective coating of silica, which prevents harmful access to ozidizing gases, such as air and furnace gases.



   The process according to the invention can be applied successfully to any of the commercial ultramarine blue pigments. The
 EMI11.6
 Particle size of the chosen ultramarine blue is, however, of some interest. Thus!) ultramarine blues composed mostly of coarse particles (for example, particles larger than 2 to 3 uderons) make it possible to obtain a pigment which has the widest range of use and shows the most resistance to alum
 EMI11.7
 high.

   However, the ultramarine blues ±), whose particles are the largest and which are commonly obtained by commercial classification methods, are regularly the weakest in terms of
 EMI11.8
 Tinctorial view However, when the acid treatment is followed by silication and calcination it has been surprising to find that it is not necessary to separate the coarse particles and use them separately.

   The mixture of coarse and fine particles, obtained by the usual wet grinding, can be silicate and calcined and the product obtained has substantially the same degree of resistance to alums as the coarse particles alone treated in the same manner. Since the finer particles are the best from a tinc-
 EMI11.9
 torial, this means that the calcination process results in ultramarine blue not only more resistant to alums, but also a more resistant coloring.



   In the present specification, the expression "resistance to alums !!
 EMI11.10
 is used synonymously with 1-the expression "acid resistance". tan-

 <Desc / Clms Page number 12>

 say that the term "resistance to atmospheric conditions" means the resistance of ultramarine blue to bleaching in the presence of a solution
 EMI12.1
 boiling aqueous aluminum sulfate L A12 (SO4) 301SH2 -1 also known as "papermaker's alum" referred to herein as "alum". In order to assess the value of the acid-treated, silicate and calcined ultramarine blue according to the present invention, it has obviously been impossible to make real tests of resistance to atmospheric conditions.

   for such tests would have taken at least several years. It has long been known that alum solutions are particularly deleterious to ultramarine blue and that they cause the same kind of deterioration as the atmospheric conditions themselves. An alum solution is simply a suitable means of preparing a buffered solution of a given pH. It is the pH value of an alum solution which determines the inactivity of its attack.



   Such solutions have long been common practice for testing the comparative acid resistance of different blues.
 EMI12.2
 d90utremerj / because they constitute a rapid, simple, reproducible and very drastic means of recognizing even the ultramarine blues which are most resistant to acids. As a result, we have
 EMI12.3
 made use of this test at 19alun. The test in question is performed as follows
A solution is prepared by dissolving 100 grams of
 EMI12.4
 Ai (304) 30 l8 H20 in water, up to a total volume of 1000 eco 100 cc of this solution are placed in a test tube in which 1.0 gr of ultramarine blue is then introduced. To try.

   The test tube is then immersed for 30 minutes in a boiling water bath. At
 EMI12.5
 after these 30 minutes, the sample is filtered, washed until the end of acidity and dried. The loss of resistance is evaluated by determining the resistance of the 1-untreated sample by visual comparison with a series of ultramarine blues of predetermined resistance9 by determining
 EMI12.6
 the same way, the resistance of 1,9 sample treated, and by calculating the residual resistance as a percentage of the original resistance of the pigmento
Five tests were performed to illustrate the resistance
 EMI12.7
 with ultramarine blue alums obtained above.

   In Test 1, ordinary, commercial, untreated OXtremer blue was used, which corresponds to the ordinary ultramarine blue used for the plotting of Figures 1, 2 and 3. The other four tests were carried out on pigments prepared, by subjecting respective portions of this overseas blue to one or more of the operational steps required by the following process
 EMI12.8
 the invention
In addition, two tests were carried out on pigments, the preparation of which is described in U.S. Patent No. 2029606830 In the first of these last two tests, a sample of ultramarine blue
 EMI12.9
 untreated tressai No. 1 is pulped first with sulfuric acid and then with sodium silicate, according to the procedure of Example 1 of the U.S.A. patent.

   nc 20260639 modified by the remark in lines 63 to 66 of column 2, page 3 of the latter patent.



   The second test (test 7) is carried out on the material pre-
 EMI12.10
 ready for test no â9 which was heated at 300 ° C for 4 hours.

 <Desc / Clms Page number 13>

 
 EMI13.1
 
<tb> Test <SEP> no <SEP> Ultramarine blue <SEP> <SEP> used <SEP> Appearance <SEP> after <SEP> test <SEP> colora =
<tb>
<tb> resistance <SEP> tiono
<tb> tinctorial
<tb>
<tb> 1
<tb>
 
 EMI13.2
 a = ooooooeoooeooemeamomoeoo ooooooaomommomomomomoaom 1 blue d9.t ere ordi- bleached in 5 minutes nary untreated 2 2 ncl, acid treated2 bleached in 5 Il 3 n19 silicate bleached in 5 '' 4 n1, treated with 19acid
 EMI13.3
 
<tb> and <SEP> silicate <SEP> 2 <SEP> 12 <SEP>% <SEP> very <SEP> slightly
<tb>
<tb>
<tb>
<tb>
<tb> bluish <SEP> gray
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 5 <SEP> nol,

   <SEP> treated <SEP> to <SEP> acid
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> silicate <SEP> and <SEP> calcined <SEP> 2 <SEP> 48 <SEP>% <SEP> blue <SEP> dark
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 6 <SEP> nol, <SEP> treated <SEP> according to <SEP> cleared <SEP> in <SEP> 5 <SEP> minutes
<tb>
<tb>
<tb>
<tb> the <SEP> 1 <SEP> example of the <SEP> patent
<tb>
 
 EMI13.4
 ILS.A. n2o6063 mo-
 EMI13.5
 
<tb> defined <SEP> by <SEP> lines <SEP> 63-66
<tb> solo <SEP> 2, <SEP> page <SEP> 3
<tb>
 
 EMI13.6
 7 n6n calcined at 3000G bleached in 5 minutes laying 1 h \ 92 ------------------------------------ ------------------------------ 1 percentage resistance of the pigment before test 2 according to the process described in example if -above.

   
 EMI13.7
 Of the samples tested, those from runs # 1, 2e 3, 6 and 7 whitened very quickly in the hot alum solution and after 5 minutes his samples were all dirty white in color when these tests were stopped. In tressai no 4, after 30 minutes, the sample had acquired a slightly gray = bluish color and had only one ninth of the tinctorial resistance that it exhibits.
 EMI13.8
 was before 19assai.

   The braided material No. 5 corresponds to the ordinary product manufactured on a commercial scale by the following process
 EMI13.9
 19 invention This sternum, subjected to the drastic tern test, loses about half of its strength and is therefore four times as strong as the tressai product # 4. The tressai product # 5 is dark blue and
 EMI13.10
 does not have 19greyish appearance of 19g sample having been braided: 0.0 4.



  In the laboratory, was prepared by the method according to the invention,
 EMI13.11
 ultramarine blues, which exhibit considerably better acid resistance than the commercial pigment used in Tressai No. 5 and have residual strengths of up to about 60%.



   In the event that they must be exposed to atmospheric conditions
 EMI13.12
 pherical9 ultramarine blues, which have a dye fastness of about 25%, are sufficiently resistant to acids to be applied as paint pigments and paint films remain blue even after being subjected to severe atmospheric conditions. To be used on roofing granules, the blue

 <Desc / Clms Page number 14>

 sea must be more resistant to acids. In the latter case, use is preferably made of ultramarine blues, the tinctorial strength of which is about 40%.



   The aforementioned tests demonstrate the astonishing degree of resistance to alums offered by the product according to the present invention. These tests also demonstrate that the improvement brought about by the combination of the operating stages according to the invention is greater than the sum of the improvements provided by each of said stages in isolation.



    CLAIMS.



   1. As a novel composition of matter, the ultramarine blue pigment particles enveloped in a composition insoluble in water, substantially free of alkali metals and amorphous of dehydrated silicic acids. , these particles revealing, when exposed to an X-ray beam in an X-ray diffraction apparatus, the type of diffraction characteristic of ordinary ultramarine blue and also revealing, when exposed to a beam of electrons in an electronic diffraction apparatus the residue of the type of diffraction exhibited by said ordinary ultramarine blue under the same conditions, the aforementioned pigment being characterized, in addition,

   by the fact that when part of this pigment is heated in 100 parts of a 10% aqueous solution of Al2 (SO4) 3.18 H2O at 100 C, for 30 minutes, the residual dye fastness of the ultramarine blue thus treated is greater than about 25%.


    

Claims (1)

2. The pigment of claim 1 wherein the relative intensity of the residual pattern is about 6-25%. 3. The pigment of claim 1 wherein the relative intensity of the residual pattern is about 14%. 4. A pigment according to claim 1, wherein the residual dye solidity is about 40%. 5. The pigment of claim 1 wherein the relative intensity of the residual pattern is about 6-25% and the residual dye fastness is about 40%. 6. The pigment of claim 1 wherein the relative intensity of the residual pattern is about 14% and the residual dye fastness is about 40%. 7. A process for preparing an ultramarine blue with improved acid resistance, in which (1) the ultramarine blue is reacted with a very dilute solution of a strong mineral acid to form a paste. aqueous acid treated ultramarine blue, the proportion of mineral acid in said solution being the stoichiometric equivalent of 2 to 7% sulfuric acid, \) based on the weight of the ultramarine blue , 9 (2) the acid-treated ultramarine blue is heated in aqueous medium to a temperature not lower than 600 ° C., until the evolution of hydrogen sulphide substantially ceases. 9 (3 ) the resulting ultramarine blue is reacted with a solution of an alkali metal silicate.!} until the absorption capacity of the ultramarine blue in ions of the alkali metal is substantially satisfied, (4) the silicate ultramarine blue is calcined between 350 and 800 C, until the release of water appreciably ceases. 9 and (5) the ultramarine blue referral is cooled. 8. The method of claim 7, wherein the mineral acid is sulfuric acid. 9. The method of claim 8, wherein the proportion of sulfuric acid is about 5%. <Desc / Clms Page number 15> 10. The method of claim 9, wherein the aloaline metal silicate is sodium silicate. - - 11. The method of claim 10, wherein the ratio EMI15.1 The IVaO to S'O2 is about 1 g 3D20 120 The process of claim 11 wherein the temperature of the silicate is about 90 °. 130 The method of claim 129 wherein the calcination temperature is about 500-7000 0. 14. The method of claim 13, wherein the temperature EMI15.2 calcination rature is degenvion 600 0. 15. The method of claim 14, wherein the blue EMI15.3 the calcined ultramarine is cooled slowly in a humid atmosphere. 160 A process for the preparation of an acid-enhanced seawater blue pigment in which (1) an aqueous paste is mixed. EMI15.4 containing 40 parts of ultramarine blue with approximately 2 parts by weight of approximately 93% sulfuric acid, (2) the acid-treated ultramarine blue is heated in aqueous medium at approximately 90 C., until the pH of the acid is obtained. medium in question is substantially neutral, - (3) mixing the paste of EMI15.5 substantially neutral ultramarine blue with about 17 parts sodium silicate in aqueous solution, until substantially all of the silica- EMI15.6 your sodium is absorbed by the blue d9ot eme $ (4) the ultramarine blue silicate is calcined at approximately 500-70000 until the release of water from the ultramarine blue silioate oeeee- eena.bleme.t9 and (5) the calcined ultramarine blue is cooled in a humid atmosphere.