An improved refractory composition especially adapted for use as a gunning mix is made of aggregate (for example, periclase) and a bonding material (for example, aluminum sulfate, boric acid, and citric acid) to which is added attapulgite. The composition may also contain other materials, as is known in the art.

BACKGROUND OF THE INVENTION 
This invention concerns refractory compositions and particularly such 
compositions adapted to placement by gunning. 
In gunning, refractory materials are placed, for example on a furnace wall, 
by projecting them through a gun or nozzle, the propelling force being, 
for example, compressed air. Water is added to the composition either 
before the gunning operation (as in slurry gunning, where sufficient water 
is added to the dry refractory composition to form a slurry, which is then 
projected through a nozzle into place) or during the gunning operation (as 
in nozzle gunning, where water is added to the dry refractory through a 
water ring placed just before the gun nozzle). This invention is concerned 
with refractory compositions which are particularly adapted for nozzle 
gunning. 
Among the characteristics desired in a gun mix are that it move smoothly 
through the gun, be projected onto the furnace wall or other target 
without undue dusting, have low rebound, adhere well to the wall, set 
relatively fast (so that a reasonable thickness of refractory can be 
placed without falling off), and have a relatively wide range of water 
contents within which it exhibits the above desired characteristics. In 
addition, it should have the usual characteristics desired of a 
refractory, for example good density, good strength, and ability to 
withstand the high temperature environment in which it will be used. 
Over the years, many different bonding systems have been suggested for gun 
mixes in an attempt to obtain the best balance of the desired 
characteristics mentioned above. For example, U.S. Pat. No. 4,001,029 
discloses a refractory composition suitable for nozzle gunning which is 
bonded with aluminum sulfate and hydrated lime (the bond disclosed and 
claimed in that patent being sometimes hereafter referred to in the 
specification and claims as the "aluminum sulfate and lime" bond); U.S. 
Pat. No. 4,244,744 discloses a refractory gun mix containing (as bond) 
sodium silicate and gypsum (the bond disclosed and claimed in that patent 
being sometimes hereafter referred to in the specification and claims as 
the "sodium silicate and gypsum" bond); and U.S. Pat. No. 4,276,091 
discloses a composition suitable for gunning with a bonding system of 
alkali metal phosphate and hydrated aluminum sulfate (the bond disclosed 
and claimed in that patent being sometimes hereafter referred to in the 
specification and claims as the "aluminum sulfate and phosphate" bond). As 
is common with gun mixes, the compositions described in the foregoing 
patents will often contain bentonite. 
Refractory compositions have also been suggested which attempt to combine 
in one composition the characteristics desired in a ramming mix, a 
castable, and a gun mix. For example, U.S. Pat. No. 3,879,208 discloses a 
refractory composition suitable for forming a monolithic structure by 
ramming, gunning, or casting containing (as bond) aluminum sulfate and an 
organic acid or salt thereof, with or without the addition of a boron 
compound (the bond disclosed and claimed in that patent being sometimes 
hereafter referred to in the specification and claims as the "aluminum 
sulfate and organic acid" bond); and U.S. Pat. No. 4,149,897 discloses a 
refractory composition suitable for ramming, casting, or gunning bonded 
with magnesium sulfate, sodium gluconate, and a soluble boron compound 
(the bond disclosed and claimed in that patent being sometimes hereafter 
referred to in the specification and claims as the "magnesium sulfate, 
sodium gluconate, and soluble boron" bond). 
The disclosures of the patents mentioned above are incorporated herein by 
reference. 
Unfortunately, it is often necessary to compromise between the properties 
desired in a gun mix and those desired in a castable (high density, for 
example) or a ramming mix (explosion resistance, for example). In other 
words, it may not be possible to obtain the highest density and strength 
in a composition which has good gunning characteristics. Similarly, it is 
often necessary to compromise between gunning characteristics and the 
desired refractory properties such as high temperature strength, erosion 
resistance, and the like. Accordingly, the refractories manufacturer is 
constantly seeking the best combination of properties he can achieve in a 
refractory composition. 
The present invention provides such an improved refractory composition 
suitable for nozzle gunning. More specifically, it provides a composition 
which combines good gunning properties such as good build-up and low 
rebound with good refractory properties such as high strength. 
BRIEF DESCRIPTION OF THE INVENTION 
It has now been found, according to this invention, that a refractory 
composition of superior properties and suitable for gunning by the method 
wherein water is admixed with the composition in a gun nozzle consists 
essentially of (1) from 1% to 10% by weight of bonding material and (2) 
from 0.1% to 5% by weight of attapulgite, the balance of the composition 
being (3) sized refractory aggregate, all percentages being by weight and 
based on the total weight of the composition. 
DETAILED DESCRIPTION 
The refractory aggregate used may be any such material having the requisite 
characteristics such as high softening point temperature, strength at high 
temperatures, erosion resistance, etc. The aggregate will be sized to 
promote good packing of the refractory particles and consequently achieve 
relatively high density. For example, all the aggregate will pass a half 
inch mesh screen (be smaller than 13 mm) and from 10% to 40% of it will 
pass a 100 mesh screen (be smaller than 0.15 mm). A preferred aggregate is 
one in which at least 10% is material passing a 100 mesh screen (smaller 
than 0.15 mm) and containing at least 50% MgO. An aggregate found 
particularly useful in the practice of this invention is periclase 
containing over 85% MgO. 
The bond material may be any such material that is compatible with the 
aggregate and other materials in the composition and with the environment 
in which the refractory composition is to be used. It has been found that 
this invention is particularly useful with the aluminum sulfate and 
organic acid bond mentioned above. Although that bond is at its best when 
used for a ramming or casting product, its use in the present invention 
produces an excellent gun mix, as will be shown by the examples which 
follow. The invention is also useful with the other bonds mentioned above 
and it has been found that when it is used with such bonds the customarily 
added bentonite is not necessary to obtain a good gun mix. 
Attapulgite is a material of commerce widely used in such products as 
paints, drilling muds, filter aids, animal litter, non-carbon copy papers, 
etc. It is a naturally occurring clay material found principally in the 
southeastern United States, although minor deposits occur in other parts 
of the world. It belongs to the category of clays known as fuller's earth. 
For a more detailed discussion of attapulgite, see the article 
"Attapulgite, Its Properties and Applications" by W. Linwood Haden, Jr., 
and Ira A. Schwint in Industrial and Engineering Chemistry, Vol. 59, 
September 1967, pages 58-69. 
The term "attapulgite" is used in three different senses: (1) to mean the 
mineral itself (a hydrated magnesium aluminum silicate with a unique chain 
structure that leads to a needle-like morphology), sometimes called 
palygorskite from the location where the mineral was first found; (2) to 
refer to the naturally occurring material (sometimes called Attapulgus 
clay from the location of its principal deposits in the United States), 
which contains, in addition to attapulgite mineral, such impurities as 
montmorillonite and other clays, quartz, calcite, dolomite, etc.; and (3) 
to refer to the material sold in commerce, which is a beneficiated and 
dried or calcined form of the naturally occurring material containing up 
to 85 to 90% of the mineral attapulgite. In the present specification and 
claims, the term "attapulgite" is used in the third sense, to mean the 
material of commerce which is incorporated in compositions according to 
the present invention. 
Two different types of attapulgite are recognized, colloidal (used for 
thickening, gelling, and stabilizing, as in paints nd drilling muds) and 
sorptive (used as decolorizing and clarifying agents, filter aids, floor 
adsorbents, animal litter, and in non-carbon copy papers, among other 
uses). The two different types have different properties. For example, the 
colloidal type has free moisture (% loss at 220.degree. F. or 105.degree. 
C.) of at least 8%, and typically from 10 to 17%, whereas the free 
moisture of the sorptive type is less, not over 7% and often 0%. 
Similarly, the BET surface area (m.sup.2 /g) of colloidal attapulgite is 
at least 150, and typically over 200, while that of sorptive attapulgite 
is about 130. These differences are primarily due to the different heat 
treatments given the two types, the sorptive type being calcined (for 
example, at temperatures over 200.degree. C. or 400.degree. F.), while the 
colloidal type is merely dried. 
Attapulgite should be distinguished from other clays such as kaolin, in 
which the principal clay mineral is kaolinite, and bentonite, in which the 
principal clay mineral is montmorillonite. Whereas the crystal structure 
of these later two minerals is of a sheet type, that of attapulgite is a 
chain structure. This leads to particles of flake and plate shape in the 
case of bentonite and kaolin, respectively, while particles of attapulgite 
are of needle form. Also, the properties of the three clays are quite 
different. The surface area, sorptivity, and decolorizing power of 
attapulgite are high, while for bentonite these are medium and for kaolin 
they are low. In other words, one would not expect to use attapulgite as a 
substitute for either bentonite or kaolin. 
There are many patents pertaining to the processing and use of attapulgite. 
For example, U.S. Pat. No. 3,197,317 discloses a low density oil well 
cement of portland cement and attapulgite, but the point of the use of 
attapulgite is that this material reduces the setting time of the cement 
less than does the use of bentonite. Also, U.S. Pat. No. 3,203,813 
discloses a relatively low temperature (less than 1000.degree. C.) thermal 
insulating material; while attapulgite is mentioned as one possible 
ingredient (as an equivalent to kaolin, among other clays), there is no 
example of such use. Finally, U.S. Pat. No. 3,509,066 discloses a method 
of deflocculating attapulgite (so as to be able to degrit it by settling) 
and contains a discussion of the material itself. 
Those skilled in the art will appreciate that the addition of a magnesium 
silicate material to a predominantly MgO composition will impair the 
refractoriness of the composition less than would the addition of an 
aluminum silicate. 
It will be understood that compositions according to this invention may 
also contain other materials, for example a carbonaceous material such a 
graphite or pitch, as is well known in this art. 
While is is not desired to be bound by any specific theory, it is believed 
that the following may be the reason for the very good gunning properties 
of compositions according to this invention. As mentioned above, it is 
necessary that the bond in a gun mix set up relatively rapidly so that the 
gunned material will adhere to the furnace wall or other surface on which 
it is placed. It is also desirable that the bond have a relatively high 
strength at operating temperatures. In the past, it has been necessary to 
rely on a single bond system to provide both these properties. In the 
present invention, it is believed, the attapulgite provides the initial 
adherence to the wall or other surface and the bond component can be 
chosen to provide other properties, e.g., strength at high temperatures. 
In other words, it is not necessary, in compositions according to the 
present invention, that the bond provide the initial adherence and set of 
the gunned material, that function being carried out by the attapulgite. 
Compositions according to this invention can be used wherever gun mixes are 
used, for example to repair holes in furnaces such as BOF furnaces, to 
repair slag line cutting in electric furnaces, and such similar uses, as 
are well known in this art. Usually, compositions according to this 
invention will be made by a refractories manufacturer, the dry ingredients 
being mixed together (for example, in a rotating drum mixer with internal 
paddles or in a Muller mixer without wheels), and placed in bags or other 
containers for shipment to a customer, who will apply the material, mixing 
water with it, for example in a nozzle gun as described above.

EXAMPLES 
Table I gives the compositions of several mixes made to demonstrate the 
effectiveness of this invention. Some of the compositions (B, C, D, E, F, 
G, H, J, K, M, P, R, and T) are within the scope of the invention and some 
(A, L, N, Q, and S) are comparison compositions. The amounts of the 
different ingredients shown in Table I are in parts by weight and the 
properties in the units indicated. 
The aggregate used was a synthetic periclase made by reacting seawater with 
calcined dolomite, as is well known. It had the following typical chemical 
composition: 2.1% SiO.sub.2, 0.9% CaO, 0.4% Fe , 0.2% 0.2% B.sub.2 
O.sub.3, and (by difference) 96.2% MgO; the Cr.sub.2 O.sub.3 content was 
less than 0.01%. 
TABLE I 
__________________________________________________________________________ 
Composition 
A B C D E F G H J K L M N P Q R S T 
__________________________________________________________________________ 
Aggregate 
Total 98 96 96 96 96 96 96 96 96 95 98 96 95 95 95 95 95 95 
Amount - 100 
31 29 29 26 21 21 20 21 21 21 30 22 20 20 20 20 20 20 
mesh 
Bond 
Aluminum Sulfate 
0.8 
0.8 
0.8 
0.8 
0.8 
0.8 
0.8 
0.8 
0.8 
0.8 
-- -- -- -- 1.3 
1.3 
2.2 
2.2 
(Hydrated) 
Boric Acid 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
-- 0.7 
0.7 
-- -- -- -- -- -- 
Citric Acid 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
0.7 
-- -- -- -- -- -- -- -- 
(Food Grade) 
Gypsum -- -- -- -- -- -- -- -- -- -- -- -- 1.1 
1.1 
-- -- -- -- 
(Dihydrate) 
Lime (Hydrated) 
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 0.8 
0.8 
Magnesium 
-- -- -- -- -- -- -- -- -- -- 0.8 
0.8 
-- -- -- -- -- -- 
Sulfate (Calcined) 
Sodium -- -- -- -- -- -- -- -- -- -- 0.6 
0.6 
-- -- -- -- -- -- 
Gluconate 
Sodium Silicate 
-- -- -- -- -- -- -- -- -- -- -- -- 1.9 
1.9 
-- -- -- -- 
(Na:Si ratio 1:2) 
Sodium -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1.7 
1.7 
-- -- 
Tripolyphosphate 
Attapulgite 
Min-U-Gel FG 
-- 2.0 
-- -- 2.0 
-- -- 1.0 
1.0 
-- -- 2.0 
-- 2.0 
-- 2.0 
-- 2.0 
Min-U-Gel 400 
-- -- -- -- -- 2.0 
2.0 
-- -- 2.0 
-- -- -- -- -- -- -- -- 
Min-U-Gel 500 
-- -- 2.0 
2.0 
-- -- -- -- -- -- -- -- -- -- -- -- -- -- 
Other Materials 
Bentonite 
-- -- -- -- -- -- -- -- -- -- -- -- 2.0 
-- 2.0 
-- 2.0 
-- 
(Volclay 200) 
Flour (White 
-- -- -- -- -- -- -- -- 1.0 
-- -- -- -- -- -- -- -- -- 
Enriched Food 
Grade) 
Frit -- -- -- -- -- -- -- -- -- 1.0 
-- -- -- -- -- -- -- -- 
Methocel F4M 
-- -- -- -- -- -- -- 0.5 
-- -- -- -- -- -- -- -- -- -- 
Properties 
Build-up (inches) 
3-4 
4-5 
6 4-5 
4-5 
4-5 
4-5 
4-5 
4-5 
5 3 4 4.5 
5.5 
5 4 5 4.5 
Density (lb/ft.sup.3) 
144 
150 
149 
146 
145 
147 
146 
142 
145 
146 
159 
151 
144 
138 
150 
145 
147 
141 
Rebound (%) 
43 24 19 22 21 16 18 26 22 16 49 21 18 11 21 19 24 14 
__________________________________________________________________________ 
It was sized so that substantially all passed a 4 mesh screen (was smaller 
than 4.7 mm); the compositions contained the amount of -100 mesh (smaller 
than 0.15 mm) aggregate indicated in Table I. 
The bond components are standard articles of commerce and all passed a 10 
mesh screen (were smaller than 1.6 mm). Further details of these materials 
are included in the disclosures of the patents cited in the "Background of 
the Invention." 
"Min-U-Gel" is a trademark of the Floridin Company, Berkeley Springs, W. 
Va., and the terms FG, 400, and 500 are grade designations of different 
attapulgites they supply. Each is of the gelling type and contains about 
11% free moisture. They different mainly in their fineness, the 400 and 
500 grades being finer (and also somewhat more expensive). 
The other ingredients used are also standard articles of commerce. The 
Lo-Sil frit (manufactured by the Ferro Corporation) is a low silica frit 
containing lime, alumina, and boron oxide. It was added as an insoluble 
form of boron addition to enhance sintering. 
The ingredients of each composition were mixed for 5 minutes in a 
V-Blender. 
Each of the compositions was gunned through a "de-tuned" nozzle mix gun, 
that is to say, a gun which had been designed for less than optimum 
performanoe. For example, the air line was connected directly to the 
air/material mixing chamber, rather than just below the material butterfly 
valve, where it helps to prevent bridging and other feeding problems. 
Also, the material was fed to the nozzle through a short (25 feet or about 
8 meters), old, very stiff 1.5 inch (38 mm) ID hose, which acentuated any 
tendency of the mix toward surging, and the water ring was attached using 
a 1.25 inch (3.2 cm) pipe nipple, thus providing an internal restriction 
which could cause flow problems. In other words, the equipment was 
designed to simulate the below average type of gunning equipment sometimes 
found in actual use in the field and not the optimally designed and 
maintained equipment which might be used in a research laboratory. 
Compositions A to G demonstrate the effect of various attapulgite additions 
to a refractory bonded with a "universal" bond, that is to say, a bond 
that can be used in a ramming, casting, or gunning mix. As can be seem by 
comparing Composition A with Compositions B through G, the compositions 
with attapulgite show better build-up during cold gunning onto a 
substantially vertical surface, have generally better density, and show 
very greatly reduced rebound. Compositions substantially the same as A, B, 
and C were hot gunned onto a furnace wall at 1300.degree. C.; comparison 
Composition A showed a great deal of dusting (impairing visibility for the 
gun operator) and the small amount of material built up on the wall fell 
off before completion of gunning. In contrast, the two compositions 
according to this invention showed vastly improved visibility and very 
good build-up. 
Compositions H, J, and K demonstrate the use of other materials in 
compositions according to this invention. Again, they show the increased 
build-up and vastly reduced rebound of the previously discussed 
compositions, and their densities were comparable. 
The remaining compositions demonstrate the benefits of this invention with 
other bonds, the pairs of compositions (L,M), (N,P), (Q,R), and (S,T) 
showing the effect of attapulgite additions on four different bond 
systems. The bond of Compositions L and M is another "universal" bond, the 
remaining three being bonds especially adapted for use in gun mixes. It 
can be seen that the attapulgite addition of this invention is beneficial 
even in the case of state-of-the-art gun mixes, and that when attapulgite 
is used, it is not necessary to use bentonite in the mix. Again, 
Compositions L through T were also hot gunned; those compositions 
containing attapulgite again showed excellent visibility and build-up, 
even better in many cases than that of the prior art gun mixes. 
In summary, while the present invention makes a composition with a 
"universal" bond into an excellent gun mix, it also enhances the 
properties of compositions designed as gun mixes. 
The superior results with compositions according to this invention are all 
the more surprising when it is considered that, when subjected to a 
gelling test that has been used in the refractories industry for over 30 
years, the attapulgite used herein was indicated to be vastly inferior in 
gelling properties to bentonite, for example. The gelling test referred to 
consists of adding about 7 grams of the material to be tested to 100 ml of 
water in a test tube, shaking the mixture, letting it stand for up to 24 
hours, and then inverting the test tube. A good gelling agent (for 
example, bentonite) will show no flow when inverted after standing for as 
little as 6 hours and certainly after 24 hours. However, in this test 
attapulgite (Min-U-Gel FG) flowed when inverted even after standing for 48 
hours. 
In the specification and claims, percentages and parts are by weight unless 
otherwise indicated. Mesh sizes referred to herein are Tyler standard 
screen sizes which are defined in Chemical Engineers' Handbook, John H. 
Perry, Editor-in-Chief, Third Edition, 1950, published by McGraw Hill 
Company, at page 963. For example, a 100 mesh screen opening corresponds 
to 147 microns or 0.147 mm. Analyses of mineral components are reported in 
the usual manner, expressed as simple oxides, e.g., MgO and SiO.sub.2, 
although the components may actually be present in various combinations, 
e.g., as a magnesium silicate.