Modified, precipitated alumino silicate pigments

Abstract

Novel alkali aluminum silicate particulates, modified with and containing a chemically bound alkaline earth metal, are disclosed. The alumino silicate pigments contain an alkaline earth metal, preferably calcium or magnesium, in addition to an alkali metal, such as sodium. In chemical composition, the pigments contain oxides of the alkaline earth metal, the alkali metal, aluminum and silicon and are distinguishable from co-precipitates. The pigments are prepared by introducing dilute solutions of an alkali silicate and an aluminum salt of a mineral acid into an agitated aqueous receiving medium containing an alkaline earth salt or hydroxide. The pH of the fluid reaction medium may be controlled to form finely divided precipitated particulates having improved properties and which may be used as pigments in paper, paint, rubber, inks, plastics, and the like.

Description

REFERENCE TO COPENDING APPLICATIONS

The present application is a continuation-in-part of U.S. Ser. No. 198,022, filed Nov. 5, 1971, and is now allowed U.S. Pat. No. 3,798,046.

BACKGROUND OF THE INVENTION

The present invention relates to finely divided precipitated silicate pigments and, more particularly, to novel modified sodium alumino silicate pigments which are chemically analagous to zeolites but which have certain unique properties and characteristics.

As is well known in the art, natural alkali metal zeolites such as natrolite and analcine are known to possess water softening properties but have limited usefulness as pigments. In recent years a number of artificial or synthetic zeolites containing sodium, aluminum and silicon oxides, in various proportions, have been proposed and synthesized. Examples of synthetic zeolites are disclosed in U.S. Pat. Nos. 2,882,243; 2,962,335; 2,996,358; 3,010,789; 3,011,869; and 3,012,853. To a large extent, known synthetic zeolites lack the essential characteristics of pigments and have found limited use in this field.

In this regard, however, there has been developed novel precipitated sodium alumino silicates that have particular use as pigments in paper coatings, as fillers in rubber compounds, in inks, paints, plastics, and the like. Such pigments are commercially available and are manufactured and sold under the trademark "Zeolex" by J. M. Huber Corporation. While "Zeolex" pigments contain the essential oxide components of natural and synthetic products, these pigments are precipitated products of alumina and ph pH is reduced to between about 8 and 10∅ While the precipitation of the products of the invention can be executed by the simultaneous addition of the alkali silicate solution and the aluminum salt solution, it has been found to be particularly advantageous to add a portion of the solution of the alkali metal silicate (such as sodium meta or disilicate) to the receiving medium prior to the introduction of the solution of the aluminum salt. It is not understood how this affects the mechanics of the reaction or precipitating process other than perhaps affecting the nucleation effect of the alkaline earth metal salt. However products produced in accordance with this second method embodiment have further improved properties, particularly with regard to their brightness and their optical properties in paper. In practicing the latter embodiment, the sodium silicate solution is added to the reaction or receiving media until the pH of the aqueous mass is between 8 and 10. Thereafter the solutions of the sodium silicate and the aluminum salt are added simultaneously to the reaction mass until such time as the total amount of the aluminum salt solution has been added. After the aluminum salt solution has been added, the addition of the silicate solution is continued until the pH of the reaction mass is between about 8.0 to 10∅

Upon completion of the reaction procedure, the precipitated pigment is separated from the reaction liquid usually by filtration, but other means of separation, such as centrifuging, can be used. It is preferable to wash the separated pigment with water to remove water soluble salts and the like. The resulting filter cake is then dried in any suitable manner. The drying is preferably performed at elevated temperatures with the temperature of the drying step being used to control the percent of the water of the finished pigment. For example, when dried at about 105°C, the pigments usually contain from about 7 to 12 percent water.

It should also be understood that the amount of water remaining in the precipitated pigment depends upon the time, temperature, and other conditions of drying. It is not possible to express conditions which will be required for drying a particular pigment with any degree of exactness. This will vary to a large extend extent, depending e.g., upon the degree of air circulating through the pigment, the type of drying apparatus, etc. As recognized by those skilled in the art, there is a substantial difference in the manner in which "free water" and "bound water" are held in pigment compositions. Bound water appears to be chemically combined with the silicate pigment. For this reason bound water does not readily come off unless dried at temperatures on the order of about 300°C On the other hand, free water comes off readily upon drying at relatively moderate temperatures i.e., up to about 105° C.

As discussed above, the starting materials or reactants employed in producing the product of the present invention include alkali metal silicate, the alkaline earth salts or hydroxides and aluminum salts. As used herein, the term alkali metal silicates includes all the common forms of alkali metal silicates as, for example, metasilicates, disilicates, and water glass. Water soluble potassium silicates and sodium silicates are particularly advantageous. Because of their relatively low cost, sodium silicates are preferred. If employed, sodium silicates are effective in any composition in which the mol ratio of the SiO₂ to Na₂ O is from about 1 to 3.3:1.

The aluminum salts preferably include the water soluble acid salts of aluminum such as aluminum sulfate, aluminum chloride, aluminum nitrate and ammonium alum (aluminum ammonium sulfate). Additionally, the aluminum sulfate solution that is added to the reaction mass may comprise an aqueous slurry of a finely divided precipitated silica suspended in a dilute aqueous solution of the salt of aluminum and a mineral acid. In this regard, the aqueous reactant solution containing the pre-precipitated silica in suspension with the solution of the aluminum salt can be obtained by employing finely divided kaolin as a basic raw material and decomposing the kaolin in an aqueous suspension with sulfuric acid. The term "kaolin" is used herein to designate kaolin or like clays composed predominately of the mineral kaolinite. The decomposition of the kaolin may be carried out in an open vessel if the kaolin has been previously calcined or if uncalcined kaolin is used it should be reacted with the acid in a closed vessel at pressures on the order of about 150 to 160 psi as disclosed in U.S. Pat. No. 2,848,346. The product of this decomposition process is essentially a dilute solution of aluminum sulfate containing very finely divided free silica in suspension.

The alkaline earth salts or hydroxides that may be employed include the salts of hydroxides of metals from Group 2a of the Periodic Table such as magnesium, calcium and barium. Preferred salts are the water-soluble salts such as the sulfates, carbonates, nitrates, and chlorides. However others can be employed. it It has been found that the use of calcium sulfate and magnesium sulfate are particularly advantageous and thus are preferred.

As indicated above, the unique pigments of the present invention may be advantageously employed or used in paper, as reinforcing pigments in rubber compositions, in paints, inks, plastics and the like. Such pigments may, for example, be employed as reinforcing pigments in various rubber compositions including natural rubber and synthetic rubber compositions including butadiene 1,3-styrene copolymers, butadiene-acrylonitrile copolymers, butadiene-isobutylene copolymers and like synthetic elastomers. If employed as rubber pigments of the type described, the alkali silicates should contain from about 1 to about 3.3 molar equivalents of SiO₂ per molar equivalent of Na₂ O (when the sodium silicate is employed).

While the pigments of the invention may be employed in many applications, it has been unexpectedly discovered that the products are particularly and excellently suited for use in paper. In this regard, pigments produced for paper fillers as described herein should employ alkali silicates having SiO₂ in a molar ratio of from about 1.5 to about 3.3 to the content of the alkali oxide (Na₂ O). Again preferred results are obtained if the mol ratio (SiO₂ /Na₂ O) is from about 2.0 to 2.7.

The following Examples will serve to further illustrate the present invention but it is expressly understood that they are not intended to limit it thereto. The Tables which follow the Examples set forth specific properties and characteristics of the products of the Examples not otherwise included therein. References to Figures are those in U.S. Ser. No. 198,022. As used hereinafter the expression or letters "LOI" refers to loss on ignition, sometimes simply noted as ignition lost. As well known in the art, loss lost on ignition is determined by heating a sample of the pigment or product being tested in an oven until the sample maintains a constant weight, that is, no further water is driven off upon continued heating. A standard test loss procedure for establishing ignition loss is TAPPI T-618.

EXAMPLE 1

A dilute alkali silicate solution was prepared by dissolving 4,740 lbs. of sodium silicate (Na₂ O ·2.5 SiO₂) in 2,370 gallons of water. A separate dilute solution of aluminum sulfate was prepared by dissolving 2,500 lbs. Al₂ (SO₄)₃ ·14H₂ O in 1,000 gallons of water. A 7,500 gal. reaction vessel provided with a propellor type agitator blade was charged with 1,540 gallons of water to which was added 1,282 lbs. of MgSO₄ ·7 H₂ O, and the agitator was started. The sodium silicate solution was charged to the reaction vessel at a rate of 46.5 GPM as a thin stream directly into the vortex formed by the rotating agitator blade. The addition of the sodium silicate solution was continued for a period of 16 minutes at the end of which time the pH of the reaction mass was 9.9. Thereafter, and with the silicate solution still being introduced, the aluminum sulfate solution was introduced at a rate of 25.1 GPM for an additional period of 35 minutes. The pH, during the simultaneous addition of the silicate solution and the aluminum salt, was reduced to about 9.5. At the end of the 51 minute reaction period all the silicate solution had been added. Thereafter the addition of the aluminum sulfate solution was continued until the final pH of the reaction mass was 8.8. This required an additional 5.0 minutes. The temperature of the solutions of the reactants introduced into the reaction vessel as well as the receiving medium was maintained at about 65°C throughout the reaction. After the pH of the reaction mass was reduced to 8.8 and all of the aluminum salt had been added, agitation of the reaction mass was continued for an additional 15 minutes. The precipitate was then separated by filtration and thoroughly washed with water at ambient temperatures. The resulting filter cake was dried at 110°C The cake was pulverized in a hammer mill. The material so produced was a finely divided white particulate made up of particles less than 0.05 microns in diameter. The specific gravity of the product was 2.2. The pour density was 9.5 lbs. per cubic foot and the product had a BET surface area of 97m² /g. From a chemical analysis of the product the following formula was calculated:

1.3 Na₂ O·1.0 Al₂ O₃ ·1.2 MgO·14.3 SiO₂ ·4.3 H₂ O

EXAMPLE 2

The procedure of Example 1 was repeated except that the sodium silicate employed contained 1.4, 1.83, 2.34, 2.8, and 3.35 mols of SiO₂ per mol of Na₂ O respectively. The products obtained in this Example possessed properties similar to those of product of Example 1.

EXAMPLE 3

The general procedure of Example 1 was repeated except that magnesium chloride, magnesium hydroxide, and magnesium nitrate, were substituted for the magnesium sulfate of Example 1. The products obtained were substantially the same as that in Example 1.

EXAMPLE 4

The general procedure of Example 1 was repeated except that the aluminum sulfate and sodium silicate solutions were added simultaneously at the outset of the reaction or precipitation process. In addition the pH of the reaction mass was maintained constant (8.0) by adjusting the rate of addition of the two solutions. At the end of the reaction period, which required 51 minutes, the final pH of the slurry was increased to 9.5 by the addition of a dilute solution of the silicate. This required an additional 3 minutes. The product produced in this Example was substantially the same as the product of Example 1.

EXAMPLE 5

The general procedure of Example 1 was repeated except that aluminum chloride, aluminum nitrate and ammonium alum were substitued for the aluminum sulfate employed in Example 1. The products produced were substantially the same as that of Example 1.

EXAMPLE 6

The general procedure of Example 1 was repeated except that in a series of two test runs the reaction vessel was charged with 1,480 gallons of water to which was added 1,081 lbs. of calcium sulfate and 1,053 lbs. of calcium carbonate, respectively. After the precipitate was recovered by filtration, washed and dried, the product from test run No. 2 was reslurried and treated with sufficient HCl to reduce the pH of the slurry to about 3.5. Thereafter sufficient NaOH was added to the pigment slurry to increase the slurry pH to 8.8. The products obtained both prior to and after the additional treatment with NaOH possessed properties similar to that of the products of Example 1. In a series of further tests the above general procedure was repeated except that the amount of the calcium salt was varied and sodium silicate was substituted for the NaOH. (See Table 3 below).

EXAMPLE 7

The procedure of Example 1 was repeated except that the aluminum sulfate solution consisted of a slurry of finely divided precipitated silica in a solution of aluminum sulfate that was prepared by reacting 3250 lbs. of commercial kaolin with 4000 lbs. of 95% sulfuric acid in 1,000 gallons of water. The slurry was formed by agitating the kaolin with the sulfuric acid in a lead line lined autoclave at a temperature of 185°C for 10 hours. This reaction mass as cooled, discharged and made up to volume of 3,000 gallons by the addition of water. In examination, the finely divided precipitated silica particles suspended in the aqueous solution of aluminum sulfate showed that almost all the precipitated silica particles were less than 0.2 microns in its greatest dimension. The separate dilute solution of the sodium silicate and the aluminum sulfate solution containing the finely divided precipitate silica was then charged to the reaction vessel in the manner of Example 1. The precipitate was recovered by filtration with water and dried at 110°C The filter cake was obtained in the form of soft lumps. On passing these lumps through the hammer mill a white powder was obtained, substantially all the particles of which were smaller than 0.5 microns in their greatest diameter.

EXAMPLE 8

The procedure of Example 1 was repeated except that the reaction vessel was charged with 1,500 gallons of water to which was added 1,085 lbs. of barium sulfate. The product produced in this Example was substantially the same as that of Example 1.

EXAMPLE 9

The procedure of Example 1 was repeated except that a mixture of MgSO₄ ·7 H₂ O and CaCO₃ (641 lbs. each or a total of 1,282 lbs.) was charged to the reaction vessel containing 1,540 gallons of water. The general properties of the product produced in this Example (e.g., particle size, surface area, density, etc.) were similar to those of the product of Example 1. Further properties of the pigment are shown in the Table set forth hereinbelow.

EXAMPLE 10

The general procedure of Example 1 as used to prepare 7 batches under varied reaction pH ranges. FIG. 5 shows the reaction pH ranges under which these batches were precipitated. These Examples clearly establish the flexibility of the method of the invention to produce a given product consistently. Table 4 shows the effect of these variations on the physical properties of the product. Table 5 illustrates the fine paper properties of the products produced in accordance with this Example.

EXAMPLE 11

The general procedure of Example 1 was repeated except that the amount of the MgSO₄ added to the receiving medium was varied (See Table 2 below) such that the final product contained varying amounts of magnesium based on the dry weight of the product.

EXAMPLE 12

In this Example, the procedure of Example 2 of U.S. Pat. No. 2,739,073 was duplicated and the resulting pigment recovered. Comparative data of the properties of this pigment (fine paper properties) and that of the pigment produced in accordance with Examples 1-11, is shown in Tables 2 and 3 (with the pigment produced by way of Example 2 of the patent being identified as "Zeolex 23").

EXAMPLE 13

In this Example, the procedure of Example 3 of U.S. Pat. No. 2,739,073 was duplicated. The resulting pigment product was recovered. Comparative data of the properties of this pigment and that of the pigment produced in accordance with Examples 1-11 is shown in the following Tables with the product of Example 3 of the said patent being identified as "Zeolex 20."

EXAMPLE 14

The procedure of Example 3 of U.S. Pat. No. 2,739,073 was duplicated except that MgSO₄ was substituted for the calcium hydroxide. It was found that this product had properties substantially the same as the product produced by Example 3 of U.S. Pat. No. 2,739,073 (see Example 13 above) with comparative data for the two pigments with that of the product produced in accordance with Examples 1-11 also being substantially the same. At this point it may be noted that in Example 3 of U.S. Pat. No. 2,739,073, the percent of the calcium hydroxide employed therein is 5% Ca (7.5% CaO). In a series of further tests, the procedures of Example 3 of this patent (see Example 13 above) was repeated except that the amount of the calcium hydroxide employed was varied so that the amount of calcium oxide present in the product was

TABLE 1
__________________________________________________________________________
CHEMICAL-PHYSICAL PROPERTIES OF PIGMENTS MODIFIED WITH MAGNESIUM AND
CALCIUM
Pigment          Valley
Oil    lbs./ft3
6         BET
(Elrepho) 20%
% 325
Abrasion
Absorption
Density, No./ft3
Surface
Pigment         Brightness
% LOI
pH Residue
mg loss
cc/100 g
Pour Pack Area
__________________________________________________________________________
Example 1
MgSO4
90.8  7.0 11.3
4.4 6.2  132   10.0 20.9  97
Example 2
MgSO4
91.6  8.1 10.9
3.7 2.7  140   8.6  18.3 114
Example 2
MgSO4
91.6  8.1 11.4
5.1 5.5  156   10.0 21.6 106
Example 2
MgSO4
91.0  7.6 11.2
3.6 10.9 135   10.4 22.4 102
Example 2
MgSO4
91.1  7.5 11.3
4.8 7.5  140   10.0 17.5 122
Example 2
MgSO4
91.7  8.0 11.3
0.9 8.0  136   10.8 22.0 105
Example 3
MgCl2
90.4  9.7 10.6
0.8 4.3  138   10.2 20.1 142
Example 3
Mg(OH)2
90.8  9.2 10.4
2.4 7.8  131   10.2 22.3 142
Example 3
MgNO3
91.0  9.6 10.1
1.8 6.8  135   12.0 25.0 176
Example 4
MgSO4
91.3  8.1 11.0
5.3 6.6  148   9.2  20.1 119
Example 6
CaSO4
90.8  8.5 11.3
1.25
6.0  132   10.1 20.8 105
Example 6
CaCO3
91.0  9.3 10.9
0.81
8.0  170   9.9  22.0 111
Example 8
BaSO4
91.2  9.0 11.3
1.01
6.5  160   10.2 23.2 112
Example 9
MgSO4 & CaCO3
91.4  8.9 11.0
1.04
7.5  156   10.4 20.4 130
__________________________________________________________________________
from about 0.1 to 8% based on the dry weight of the composition. The
resulting pigments had substantially the same properties as the pigment
produced in accordance with Example 3 of the said patent. This was also
found to be true when varying the amounts of MgSO4 substituted for
the calcium salt as set forth in this Example.

TABLE 2
__________________________________________________________________________
FINE PAPER PROPERTIES OF PIGMENTS MODIFIED WITH MAGNESIUM
% Solids
% F
% Mg in
of Wet
I  % Pigment
TAPPI TAPPI
Pigment       Pigment
Cake L  Retention
Brightness
Opacity
__________________________________________________________________________
Unfilled                -- --    87.0  80.0
Zeolex 23-Control
Example 11    None 28.4 3  56    88.0  81.2
6  52    88.3  82.1
9  50    88.9  83.0
Example 11    0.43 26.4 3  49    88.0  81.6
6  53    88.6  82.9
9  50    89.3  83.8
Example 11    0.49 27.5 3  48    87.9  81.6
6  45    88.5  83.0
9  42    88.9  83.9
Example 11    0.43 29.3 3  48    88.0  81.6
6  53    88.8  83.1
9  50    89.0  84.1
Example 11    0.55 26.4 3  57    88.0  81.5
6  52    88.6  82.7
9  49    89.0  83.6
Example 11    0.56 29.7 3  51    88.2  81.6
6  47    88.9  82.9
9  44    89.3  83.9
-- --    88.4  79.3
Example 11    1.5  28.7 3  53    88.9  81.6
6  51    89.3  83.2
9  52    89.5  84.0
Example 11    3.3  24.0 3  48    88.9  81.7
6  46    89.3  83.6
9  48    89.5  84.9
Example 11    2.7  26.0 3  48    89.0  81.2
6  47    89.5  82.8
9  47    89.8  83.8
Example 11    2.7  24.1 3  44    89.0  81.5
6  42    89.5  82.9
9  47    89.7  83.5
Example 11    1.8  27.3 3  44    89.2  81.0
(Note: in this test, pigment
6  44    89.8  83.3
reslurried and treated in
9  42    90.2  84.2
accordance with Example 6)
Example 11    8.0  26.6 83
45    89.2  81.7
6  44    89.6  83.7
9  42    90.0  84.9
__________________________________________________________________________

TABLE 3
______________________________________
FINE PAPER PROPERTIES OF
PIGMENTS MODIFIED WITH CALCIUM AND BARIUM
%       %   %
Solids  F   Pigment
TAPPI
% Ca in  of Wet  I   Reten- Bright-
TAPPI
Pigment Pigment  Cake    L   tion   ness  Opacity
______________________________________
Un-                      --  --     88.0  80.3
filled
Zeolex 23
None     28.6    3   55     88.7  82.0
(Control)                6   53     89.0  82.5
9   52     89.2  84.3
Example 0.4      24.3    3   52     88.7  82.2
(CaSO4)             6   57     89.1  83.7
9   56     89.4  84.7
Example  0.55    23.6    3   47     88.9  82.1
6
(CaSO4)             6   49     89.1  83.6
9   46     89.4  84.7
Example 4.1      25.4    3   47     89.2  82.0
6
(CaSO4)             6   49     89.4  83.4
9   47     89.7  84.6
Example 4.3      25.2    3   47     89.2  82.0
6
(CaCO3)             6   49     89.4  83.3
9   47     89.7  84.4
Example 4.6      28.8    3   47     89.6  82.4
6
(CaSO4)             6   49     89.9  84.1
9   46     89.9  85.5
Example 3.9      29.0    3   47     89.1  82.2
6
(CaCO3)             6   47     89.4  83.8
9   46     89.6  85.1
% Ba in
Pigment
Example 4.0      28.7    3   46     89.1  82.2
8
(BaSO4)             6   49     89.4  84.0
9   46     89.6  86.3
______________________________________

TABLE 4
__________________________________________________________________________
PHYSICAL PROPERTIES AND REACTION CONDITIONS OF PIGMENTS MODIFIED
WITH MAGNESIUM IN ACCORDANCE WITH EXAMPLE 10
Min.           Valley
% 325
BET Sur
Oil
Run
Excess
Prec. pH
Final
%  Abrasion
screen
face area
Absorption
Pigment
No.
Silicate
Range
pH LOI
mg-loss
residue
m2 /g
cc/100 g
Brightness
__________________________________________________________________________
1  16  10.0-10.0
8.8
6.52
4.5  0.24
110   112  93.3
2  16  10.0-9.0
8.8
6.81
5.6  0.16
101  110   93.5
3  16  10.0-9.0
8.8
6.53
6.5  0.12
71  108   93.3
4  20  10.5-10.5
8.8
6.42
5.6  0.48
124  118   92.7
5  20  10.5-9.5
8.8
6.43
4.2  0.12
108  120   93.3
6  20  10.5-9.5
8.8
6.55
2.9  0.14
82  110   93.5
7   6  8.0-8.0
9.8
7.06
4.1  0.06
75  137   94.5
8   6  8.0-9.0
9.8
6.38
2.9  0.04
59  127   94.1
9   6  8.0-9.8
9.8
6.56
1.5  0.10
61  136   93.2
__________________________________________________________________________

TABLE 5
__________________________________________________________________________
FINE PAPER PROPERTIES OF DRIED AND MILLED MAGNESIUM MODIFIED SILICATE
PIGMENTS PRODUCED IN ACCORDANCE WITH EXAMPLE 10
Minutes                        Pigments
Run  Excess
Prec. pH
Final
%    % Pigments
Tappi Tappi
No.  Silicate
Range
pH Filler
Retention
Brightness
Opacity
__________________________________________________________________________
Control           unfilled    85.6  82.0
1    16   10.0-10.0
8.8
3    50     87.1  85.0
6    49     87.9  87.0
9    48     88.5  88.3
2    16   10.0-9.0
8.8
3    51     87.1  85.0
6    51     87.9  87.2
9    50     88.5  88.5
3    16   10.0-9.0
8.8
3    51     87.1  85.0
6    52     87.9  87.2
9    52     88.6  88.6
4    20   10.5-10.5
8.8
3    50     87.1  84.8
6    50     87.9  86.9
9    47     88.5  88.2
5    20   10.5-9.5
8.8
3    50     87.1  84.8
6    50     87.9  86.9
9    48     88.5  88.1
6    20   10.5-9.5
8.8
3    48     87.1  85.0
6    47     88.0  87.1
9    50     88.6  88.5
7    6    8.0-8.0
9.8
3    50     87.3  85.4
6    49     88.3  87.6
9    50     89.1  89.0
8    6    8.0-9.0
9.8
3    50     87.3  85.4
6    48     88.3  87.6
9    50     89.0  89.0
9    6    8.0-9.8
9.8
3    49     87.1  85.2
6    48     88.0  87.3
9    49     88.6  88.7
__________________________________________________________________________

TABLE 6
______________________________________
PHYSICAL PROPERTIES OF THE PRODUCT OF THE
INVENTION AND THE PRIOR ART
Product of Invention  Prior Art
Product of
Prior Art
Invention
(Zeolex 20)
(Example 10.
(Example
Properties          (Run 2)    13)
______________________________________
20% pH              9.9        10.4
% LOI               7.7-8.5    12.6
Alkalinity meg/100 g
44         148
Oil AbsorptionAdsorption cc/100g
126        140
BET Surface Area M2 /g
54         72
% 325 Screen Residue
0.02-0.06  8.0-10.0
______________________________________
NOTE:
From further tests it was found that the product of the invention (as per
Examples 1-11) had the following range of properties: 20% pH  8.5 to 10;%
LOI  6 to 8.5; alkalinity (meg/100 g)  40 to 60; oil adsorption (cc/100 g
100 to 145; BET surface area(M2 /g)  50 to 120; and
%325 screen Residue  .02 to .06. This combination of properties is unique
and could not be reproduced following the teachings and examples of U.S.
2,739,073. The product of the invention has a lower pH and alkalinity.
This is believed to be due to the manner in which the alkaline earth meta
is bound to the pigment. The LOI shows, e.g. a difference in the amount o
bound water.

TABLE 7
__________________________________________________________________________
COMPARATIVE DATA-FINE PAPER PROPERTIES
TAPPI TAPPI
% Alkaline
%    % Pigment
BRIGHT-
OPACI-
Pigment      EARTH FILLER
RETAINED
NESS  TY
__________________________________________________________________________
Unfilled     0     --   --     85.9  82.1
Zeolex 23 (Control)
0     3    40     87.1  85.3
Example 2-U.S. 2,739,073
6    40     87.9  87.4
9    39     88.6  88.2
Zeolex 20    5% Ca 3    53     86.5  83.4
Example 3-U.S. 2,739,073
6    50     86.9  84.4
9    47     87.1  85.0
Zeolex 20 (Mg)
5% Mg 3    50     86.6  83.1
Example 14 of Application
6    50     87.0  83.8
9    49     87.3  84.3
Product of Example 10
3%    3    47     87.6  87.6
(Run 8)            6    46     88.7  88.7
9    48     89.5  89.5
Product of Example 6
3%    3    47     87.4  85.2
6    48     88.1  87.0
9    49     89.0  88.2
Product of Example 8
3%    3    48     87.2  85.4
6    48     87.9  87.3
9    49     88.8  88.5
__________________________________________________________________________

To further illustrate the uniqueness of the pigment of the invention with that of the prior art, the pigment of the invention was tested in a rubber formulation, shown in Table 8 below, and compared with an identical formulation except that the pigment employed was that produced in accordance with Example 3 of U.S. Pat. No. 2,739,073 (see Example 13 above).

Tests on the rubber formulation included the following: A. Hardness Data--Olsen Test pieces 8-12 at 320° F.; B. Abrasion Data--NBS 8-12 at 320° F.; C. Olsen Stiffness on Unaged Ross Flex pieces, 8 inch lbs., 4 inch Span, 8-12 at 320° F.; and D. Rheometer Data: (1) 320° F. (2) Hi Speed. (3) 30 foot minute Chart Motor. (4) Range 100. (5) Preheat 60 Secs. (6) 3° Arc.

TABLE 8
______________________________________
Ingredients      Parts/100 RHC
______________________________________
SBR 1502         100.0
Pliolite S6B     20.0
Zinc Oxide       3.0
Stearic Acid     2.0
Cumar MH 21/2    7.5
Pigment (Ex. 11, 1.5% Mg)
66.5
Santocure        2.0
DOTG             1.0
Sulfur           2.5
Total            204.5        Sp.Gr. 1.215
______________________________________

The results of the test established when the pigment produced as per Example 3 of U.S. Pat. No. 2,739,037 was employed, the rubber formulation cured too fast resulting in a hard, stiff rubber with poor abrasion resistance. On the other hand, the pigment of the invention produced good rubber reinforcing with high abrasion resistance, increased modulus, tensile strength and elongation. The Olsen stiffness was 100 (8 inch minute cure) for the pigment of the invention vs. 187 and 191 (6 foot minute and 8 foot minute respectively) for the pigment of the prior art. The NBS abrasion was 100 vs 67 and 65 for the same cure rates. A further summary of the tests is shown in Table 9.

TABLE 9
__________________________________________________________________________
Cure
200% 300% Tear Data
Pigment
Min.
Modulus
Modulus
Tensile
Elongation
Longitudinal
Transverse
Average
__________________________________________________________________________
Example 11
6  950  1275 2033
500   267    279   273
(1.5% Mg)
8  1008 1342 1950
467   278    266   272
12 983  1317 1883
467   270    273   272
Example 3 of
4  858  1092 1717
477   266    285   276
U.S. 2,739,073
6  850  1075 1675
567   263    270   267
(Prior Art)
10 892  1150 1642
433   265    265   265
__________________________________________________________________________
Note:
Test pieces employing pigment of Example 3 (U.S. 2,739,073) were cured fo
6 and 10 minutes to achieve the same degree of cure as 8 and 12 minute
cures when pigment of invention is employed.

Claims

1. A finely divided, precipitated, white powdery composition comprising chemically bound oxides of magnesium, sodium, aluminum, and silicon in a uniform matrix substantially all of the particles of which are less than 1 micron in diameter, the molar ratio of SiO₂ to Na₂ O being at least about 4 to 1 and the molar ratio of Na₂ O to Al₂ O₃ being from about 0.8 to 1.4:1, said magnesium oxide being present in an amount of from about 0.1 to 8 percent based on the dry weight of the composition; said composition having a specific gravity of 2.0 to 2.4; said composition further having an alkalinity in the range of from about 40-60 meg/100 g; a loi in the range of from about 6-8.5% by weight; an oil absorption in the range of from about 110 to 145 cc/100 g and a surface area in the range of from about 50 to 120 M² /g.

2. A finely divided precipitated, white powdery composition comprising chemically bound oxides of calcium, sodium, aluminum, and silicon in a uniform matrix substantially all of the particles of which are less than 1 micron in diameter, the molar ratio of SiO₂ to Na₂ O being at least about 4 to 1 and the molar ratio of Na₂ O to Al₂ O₃ being from about 0.8 to 1.4:1, said calcium being present in an amount of from about 0.1 to 8 percent based on the dry weight of the composition having a specific gravity of 2.0 to 2.4; said composition further having an alkalinity in the range of from about 40-60 meg/100 g; a loi in the range of from about 6-8.5% by weight; an oil absorption in the range of from about 110 to 145 cc/100 g and a surface area in the range of from about 50 to 120 M² /g.

3. A finely divided, precipitated, white powdery composition comprising chemically bound oxides of barium, sodium, aluminum, and silicon in a uniform matrix substantially all of the particles of which are less than 1 micron in diameter, the molar ratio of SiO₂ to Na₂ O being at least about 4 to 1 and the molar ratio of Na₂ O to Al₂ O₃ being from about 0.8 to 1.4:1, said barium being present in an amount of from about 0.1 to 8 percent based on the dry weight of the composition having a specific gravity of 2.0 to 2.4; said composition further having an alkalinity in the range of from about 40-60 meg/100 g; a loi in the range of from about 6-8.5% by weight; an oil absorption in the range of from about 110 to 145 cc/100 g and a surface area in the range of from about 50 to 120 M² /g.

4. The composition in accordance with claim 1, said composition further comprising the oxides of magnesium, sodium, aluminum, and silicon precipitated in intimate association with finely divided particles of precipitated silica.

5. The composition in accordance with claim 2, said composition further comprising the oxides of calcium, sodium, aluminum, and silicon precipitated in intimate association with finely divided particles of pre-precipitated silica.

6. The composition in accordance with claim 3, said composition further comprising the oxides of barium, sodium, aluminum, and silicon precipitated in intimate association with finely divided particles of pre-precipitated silica.

7. A finely divided precipitated, white powdery composition comprising chemically bound oxides of an alkaline earth metal selected from the group consisting of magnesium, calcium, barium, or combinations thereof; sodium; aluminum; and silicon in a uniform matrix substantially all of the particles of which are less than 1 micron in diameter, the molar ratio of SiO₂ to Na₂ 78 O being at least about 4 to 1 and the molar ratio of Na₂ O to Al₂ O₃ being from about 0.8 to 1.4:1, said alkaline earth metal oxide being present in an amount of from about 0.1 to 8 percent based on the dry weight of the composition having a specific gravity of 2.0 to 2.4; said composition further having a loi in the range of from about 6.38 to 9.7% by weight; an oil absorption in the range of from about 108 to 170 cc/100 g and a surface area in the range of from about 59 to 176 M² /g.

8. The composition in accordance with claim 7, said composition further comprising the oxides of an alkaline earth metal, sodium, aluminum, and silicon precipitated in intimate association with finely divided particles of pre-precipitated silicate. 9. The composition of claim 7 wherein said alkaline earth metal is magnesium.

10. The composition of claim 9 wherein said composition has an oil absorption in the range of from about 108 to 156 cc/100 g.

11. The composition of claim 7 wherein said alkaline earth metal is calcium.

12. The composition of claim 11 wherein said composition has a loi in the range of about 8.5 to 9.3% by weight. 13. The composition of claim 12 wherein said composition has an oil absorption in the range of from about 132 to 170 cc/100 g.

14. The composition of claim 13 wherein said composition has a surface area in the range of from about 105 to 111 M² /g.

15. The composition of claim 7 wherein said alkaline earth metal is barium.

16. The composition of claim 15 wherein said composition has a loi of about 9.0% by weight.

17. The composition of claim 16 wherein said composition has an oil absorption in the range of about 160 cc/100 g.

18. The composition of claim 17 wherein said composition has a surface area of about 112 M² /g.

19. The composition of claim 7 wherein said alkaline earth metal is a combination of magnesium and calcium.

20. The composition of claim 19 wherein said composition has a loi of about 8.9% by weight.

21. The composition of claim 20 wherein said composition has an oil absorption of about 156 cc/100 g.

22. The composition of claim 21 wherein said composition has a surface area of about 130 M² /g.

23. A finely divided precipitated, white powdery composition comprising chemically bound oxides of an alkaline earth metal selected from the group consisting of magnesium, calcium, barium, or combinations thereof; sodium; aluminum; and silicon in a uniform matrix substantially all of the particles of which are less than 1 micron in diameter, the molar ratio of SiO₂ to Na₂ O being at least about 4 to 1 and the molar ratio of Na₂ O to Al₂ O₃ being from about 0.8 to 1.4:1, said alkaline earth metal oxide being present in an amount of from about 0.1 to 8 percent based on the dry weight of the composition having a specific gravity of 2.0 to 2.4.

24. The composition of claim 23 wherein said alkaline earth metal is magnesium.

25. The composition of claim 23 wherein said alkaline earth metal is calcium. 26. The composition of claim 23 wherein said alkaline earth metal is barium.

27. The composition of claim 23 wherein said alkaline earth metal is a combination of magnesium and calcium. 28. The composition of claim 23 wherein said composition has a loi in the range of from about 6.38 to 9.7% by weight.

29. The composition of claim 25 wherein said composition has a loi in the range of about 8.5 to 9.3% by weight.

30. The composition of claim 23 wherein said composition has an oil absorption in the range of from about 108 to 170 cc/100 g.

31. The composition of claim 24 wherein said composition has an oil absorption in the range of from about 108 to 156 cc/100 g.

32. The composition of claim 25 wherein said composition has an oil absorption in the range of from about 132 to 170 cc/100 g.

33. The composition of claim 23 wherein said composition has a surface area of from about 59 to 176 M² /g.

34. The composition of claim 25 wherein said composition has a surface area in the range of from about 105 to 111 M² /g.

35. The composition of claim 23 wherein said composition has a pigment (Elrepho) brightness of from about 90.4 to 94.5.

36. The composition of claim 23 wherein said composition has a 20% pH of from about 10.1 to 11.3.

37. The composition of claim 23 wherein said composition has a 325 screen residue of from about 0.04 to 5.3%.

38. The composition of claim 23 wherein said composition has a Valley Abrasion of from about 1.5 to 10.9 mg. loss.

39. The composition of claim 23 wherein said composition has a pour density of from about 8.6 to 12.0 lb./ft³.

40. The composition of claim 23 wherein said composition has a pack density of from about 17.5 to 25.0 lb./ft³.

41. The composition of claim 23 wherein said composition has a percentage retention in fine paper of from about 42 to 57%.

42. The composition of claim 23 wherein said composition has a percentage of solids in its wet cake of from about 23.6 to 29.7% solids.

43. The composition of claim 23 wherein said composition has a TAPPI Brightness in fine paper of from about 87.1 to 90.2.

44. The composition of claim 23 wherein said composition has a TAPPI Opacity in fine paper of from about 79.3 to 89∅

45. The composition of claim 23 wherein said composition consists essentially of particles substantially all of which are less than 0.5 microns in diameter after milling.

46. The composition of claim 23 wherein said composition consists essentially of particles at least about 97 percent of which are less than 0.05 microns in diameter after milling.

47. The composition of claim 23 wherein said composition may be represented by the following formula:

1.3 Na₂ O.1.0 Al₂ O₃.1.2 MgO.14.3 SiO₂.4.3 H₂ O.

48. The composition of claim 23 wherein said composition has a loi in the range of from about 6.38 to 9.7% by weight; an oil absorption in the range of from about 108 to 170 cc/100 g; a surface area in the range of from about 59 to 176 M² g; and a pigment (Elrepho) brightness of from about 90.4 to 94.5.

49. The composition of claim 48 wherein said composition has a 325 screen residue of from about 0.04 to 5.3%.

50. The composition of claim 49 wherein said composition has a Valley Abrasion of from about 1.5 to 10.9 mg. loss.

51. The composition of claim 50 wherein said composition has a pour density of from about 8.6 to 12.0 lb./ft³.

52. The composition of claim 51 wherein said composition has a pack density of from about 17.5 to 25.0 lb./ft³.

53. The composition of claim 52 wherein said composition consists essentially of particles substantially all of which are less than 0.5 microns in diameter after milling.

54. The composition of claim 53 wherein said composition consists essentially of particles at least about 97 percent of which are less than 0.05 microns in diameter after milling.

55. The composition of claim 54 wherein said composition has a TAPPI Brightness in fine paper of from about 87.1 to 90.2.

56. The composition of claim 55 wherein said composition has a TAPPI Opacity in fine paper of from about 79.3 to 89∅

57. The composition of claim 56 wherein said composition has a percentage retention in fine paper of from about 42 to 57%.

58. The composition of claim 57 wherein said composition has a 20% pH of from about 10.1 to 11.3. 59. The composition of claim 58 wherein said composition has a percentage of solids in its wet cake of from about 23.6 to 29.7% solids.

60. The composition of claim 59 wherein said alkaline earth metal is magnesium.

61. The composition of claim 60 wherein said composition has an oil absorption in the range of from about 108 to 156 cc/100 g.

62. The composition of claim 61 wherein said composition may be represented by the following formula:

1.3 Na₂ O.1.0 Al₂ O₃.1.2 MgO.14.3 SiO₂.4.3 H₂ O.

63. The product of claim 23 wherein the product is produced by introducing a dilute aqueous solution of an alkali silicate and a dilute aqueous solution of an aluminum salt into an agitated aqueous receiving medium containing an alkaline earth metal salt or hydroxide, with at least some of the alkali silicate and aluminum salt solutions being simultaneously introduced into said receiving medium.

64. The product of claim 63 wherein said aqueous receiving medium contains an alkaline earth metal salt and the pH of the reaction solution is maintained between about 8 and 12.