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Патент USA US3069287

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306%,277
ttes
Patented Dec. 18, 1962
1
2
1955 (entitled Preparation of Mineral Fibers) now US.
3,069,277
Patent 2,908,545 and Serial No. 526,779, ?led August
5, 1955 (entitled Manufacturing Glass Fibers), now
abandoned. This application is a continuation-in-part of
.layanti Dharma 'll‘eja, Syosset, N.Y., assignor to Monte
catini-Societa Generale per l’lndustria li/iineraria e 5 said applications. The aqueous systems containing col
loidal ?brils of linear polysilicate are believed to have
Chimica, Milan, Htaly, a corporation of Italy
usefulness in the protective coating, adhesives, and other
No Drawing. Filed Dec. 18, 1959, Ser. No. 860,321
arts apart from their usefulness in preparing glass ?bers.
2 Claims. (Cl. 106-74)
As explained in ancestor applications, Serial Nos. 511,
AQ‘UZSG‘US DiSlPERSIONS ‘(BF HKGH MGLECULAR
WEIGHT FlBRilS 0F AMQRPHGUS SILICATES
This invention relates to the preparation of aqueous 10 132 and 526,779, molybdena is not in the group of glass
solutions of polymeric silicates.
This application is a continuation-in-part of my co
forming oxides recommended by glass technologists for
glass-making. Said Serial No. 526,779 explains that it
pending application Series No. 655,166, ?led April 26,
is sometimes preferable to select glass-forming oxides
1957, now U.S. Patent 2,919,996, assigned to the assignee
from the group consisting of boria, alumina, zirconia,
of the present application.
15 titania, zinc oxide, calcium oxide, barium oxide, arsenic
’ eretofore it has been known that monomeric silicic
oxide, germania, hafnia, phosphoric oxide, vanadia,
acid could undergo condensation in aqueous acid to form
antimo-nia, lead oxide, thoria, berryllia, and tungstic ox
ide. In the glass making technology, the term “metal
generally spherical colloidal particles of polysilicic acid.
Textbooks such as “The Colloidal Chemistry of Silica
and Silicates” by R. Iler (Cornell V.F., 1955), “Physical
Chemistry of Silicates” by Eitel (U. Chicago Press, 1952)
“Light-Scattering in Physical Chemistry” by Stacey
oxide” sometimes includes oxides of elements which some
chemists would not designate as metals. Although the
present invention is concerned with aqueous alkaline
silicates, the terminology and classi?cations have been
(Butterworth, 1956) “Silicic Science” by Hauser (Van
taken in part from some of the older classical textbooks
on glass technology.
>
Nostrand, 1955) and “Soluble silicates” by G. G. Vail
(Reinhold, 1952) each described data indicating that acid 25
The technical subject matter pertinent to the present
ic and neutral aqueous suspensions of polymeric silica con
sist of globular siliceous particles. The sodium silicates,
invention can be better understood by a consideration
of a series of sets of data, which are for convenience
designated as examples.
the akaline silicates, and share together a variety of
Because the prior art literature concerning aqueous
properties with which silicate chemists are familiar. 30 compositions of compounds of silicon connotes that the
Although the pH of an aqueous system might be above
larger particles resulting from polymerization in water
7, and hence alkaline, and although such a system might
are consistently of a globular structure, the persuasive
contain dispersions of insoluble siliceous minerals, such
ness of the evidence in support of the linear structure of
a system would not be an alkaline silicate system, be
the products of the present invention should be under
cause such term embraces only materials closely related 35 stood even before detailed consideration is given to the
to water glass. Although the possibility of linear poly—
methods by which such products are prepared.
merization of alkaline silicates has been recognized it
Colloidal polysilicic acid solutions in water have been
has been believed that only moderate molecular weights
studied by light scattering techniques to measure both
the turbidity molecular weights and the values of dis
were attainable, and that even these colloidal particles
7
were globular instead or" linear. Previous workers have 40 symmetry (Z).
potassium silicates and mixtures thereof are known as
described globular particles of 10,000 molecular weight
Consideration can be given to publications such as
in commercial alkaline silicate solutions but the average
molecular weights of such silicate solutions have gen
Naumann and Debye, J. Phys. Chem, 55, 1-8 (1951),
ller et al., J. Phys. Chem. 57, 932 (1953) and Edsall,
J.A.C.S. 75, 5058 (1953).
The values covering the whole range of turbidity
erally been less than 2000.
In accordance with the present invention aqueous sys
terns containing linear polysilicates either having an
molecular weights and values of dissymmetry are shown
average molecular weight greater than about 5,000 or
in Table 1. It is to be noted that a (Z) value approach
containing signi?cant amounts of colloidal particles hav
ing 1.1 is necessary to estimate the value of a spherical
particle as equivalent to approximately Angstroms.
ing a molecular weight greater than 20,000 are prepared
by the application of, and control of, the catalysts and 50 Dissyrnrnetry (Z) values of 1.1 are extremely unreliable
polymerization conditions effective for achieving such
in terms of the accuracy of the method of determining
linear (as distinguished from globular) polymerization.
(Z), because a value of 1.1 may merely indicate that (Z)
is very nearly equal to 1.
One of the possible theories for explaining the bene
?cial results of the present invention is that speci?c dis
TABLE 1
tortion of the linear polysilicate unit favors the linear
Turbidity
Mol.
Weights
and (Z) Values for Colloidal
(as distinguished from globular) structure of silicate par~
Silica
ticles undergoing polymerization. By bringing about the
9’ polymerization of silicates in an alkaline aqueous system
in the presence of appropriate catalysts, linear ?brils of
polysilicate are formed. Some data relating to asbestos, 60
endellite and other naturally-occurring siliceous materials
possessing linearity, can be interpreted consistently with
such theory.
This discovery that aqueous systems containing col
loidal ?brils of linear polysilicate can be prepared clari
?es the explanation of the methods of preparing glass
?bers from aqueous systems as set forth in the applica
tions of I. D. Teja, Serial No. 511,132 ?led May 25,
Turbidity Particle
mol.
diameter
weight in
in
millions Angstrorns
3. 8
8.3
19. 5
54. 0
100.0
210.0
175
230
300
430
530
660
(Z) value
Approximately 1.
Approximately 1.
Approximately 1.
Approximately 1.1.
Approximately 1.1.
Approximately 1.15.
3,069,277
4
>
5.
In most light scattering work, carefully ?ltered solu
tions are employed. Such ?ltration of colloidal silica
solutions provides data on particles having molecular
weights in the range of approximately 4 million and a
particle size less than 200 A. and a (Z) value equal to 1.
The date on the 210,000,000 molecular weight 660 A. di
ameter particles of colloidal silica were obtained using
solutions puri?ed, not by ?ltration, but by centrifuging
techniques.
The diameter of such a particle of molecular weight
800,000 cannot be more than 530 Angstroms by compari
son with colloidal silica particles of density 2.2 and mo
lecular weight 100x106 and diameter 530 Angstroms.
The (Z) value for an aqueous system of such particles
should be approximately 1.1 and not as large as 5.2.
Such a high value for (Z) can only mean extended
molecules linear in nature, especially in view of the evalu<
ation of a polyelectrolyte system of high ionic strength.
Both the prior art literature and the experimental work‘ 10 Using the value of approximately 4 Angstroms for the
during the development of the present invention con?rmed
size of SHOE), unit in the systems, one obtains correla
the absence of dissymmetry and the existence of the globu
tion with observed (Z) values and hence particle sizes
lar shape of the particles in a colloidal silica solution.
if one theorises a rod particle of a small cross-section
Colloidal silica solutions are generally prepared under
containing, on the average, 4 or more silicon tetrahedra
slightly acidic conditions, but after being prepared may 15 linked together in the width and depth directions and
be converted to alkaline aqueous systems containing such
hundreds of silicon tetrahedra joined in the length direc
globular colloidal particles. In evaluating light scatter
tion.
ing data, consideration must be given to the effects of
Accordingly, it is necessary to postulate ?brillar mole
various amounts of ions in the system being investigated.
cules in the polysilicate systems prepared in accordance
Polyelectrolytes in ionizing solvents behave differently 20 with the present invention.
from non~electrolyte systems. In tests upon polyacrylic
Alkaline silicate material is converted to an aqueous
acid, the conversion of the material to a polyelectrolyte
system containing linear polymeric silicate by partially de
resulted in a reduction of the intensity of the 90° light
hydrating the aqueous system in the presence of an ap
scattering to about 2% of the intensity with the nonion~
propriate, expendable catalyst selected from the group
ized material. Under some conditions, there can be the 25 which excludes sodium oxide and potassium oxide, but
anomalous observation of (Z) values less than 1.
includes all other metal oxides recommended by glass
Thus the molecular weight determinations of polyelec~
technologists for glass-making. The polymerization pro
trolytes by turbidity methods can lead to apparent mo
ceeds in part by a chain reaction of hydrogen ion transfer,
lecular weight determinations which are smaller than the
particularly in the more alkaline aqueous solutions and
real value. However, reliable measurements can be 30 is, further, catalyzed by the metal ions, which ?t Within
made by the turbidity methods in systems of high ionic
. the linear polymer in such a manner that the polysilicate
strength.
?brils partake of the nature of colloidally dispersed glass.
The linear polysilicate systems of the present invention
provide the high ionic strength necessary, and reliable,
erally as involving the following steps.
consistent data are obtained.
The method of polymerization can be described gen
The starting
35 solution is an aqueous solution of the silicate of an
Aqueous solutions of sodium silicate have previously
been studied by light scattering methods, as described for
alkali metal of the group consisting of sodium, potas
sium, and mixtures thereof in Which solution the ratio
example in the previously cited Naumann and Debye
of oxygen-containing compounds of the alkali metals to
article. They worked with pure sodium silicates and ob
the oxygen-containing compounds of silicon is within
40
tained generally only stoichiometric molecular weights
the range from 1:2 to 1:5. This aqueous solution of
e.g. approximately 76.1 for the ion SiO3. Only in ‘very
alkaline silicate is then modi?ed to prepare a mixture
dilute solutions of less than 0.05 gm./cc. concentration
by incorporating catalytic amounts of at least one oxygen-
of aged commercial tetrasilicate Na2O:SiO2::1:3.9
they found molecular weights up to 10,000. At higher
concentrations above 0.1 mg./cc., silicates more alkaline
than Na2O; 2.0 SiOz have turbidities similar to sucrose.
They detected no evidence of polymerization, The more
siliceous solutions as stated above in course of ageing de
containing compound of the group consisting of borcn,
aluminum, zirconium, titanium, zinc, calcium, barium,
arsenic, germanium, hafnium, phosphorus, vanadium,
antimony, lead, thorium, beryllium and tungsten. Heat
is applied to this mixture to cause Water to evaporate
from the surface thereof so as to concentrate the mix
velop larger particle sizes with molecular weights ap
ture. During this heating or concentrating step that
proaching 10,000. In all these cases studied (Z) values 50 portion of the body of the mixture closest to where the
were not expressed because they are almost equal to 1.
heat is applied is spaced somewhat from the surface of
Thus, prior art literature shows particles of sodium
the mixture at which the evaporation takes place and
silicate having a molecular weight as high as 10,000, in
maintained at a temperature signi?cantly higher than said
alkaline solution have a globular shope. Such prior art
surface so that a ?lm of heated mixture will thereby
?ndings are to be contrasted with the surprising results
diffuse through the balance of the mixture toward the
obtained by the present invention.
evaporative surface. The pH of the body of the mix;
Aqueous solutions prepared in accordance with the
ture is maintained above 7 during this heating of the
present invention were studied by light scattering methods,
mixture, and the heating is continued until at least 10%‘
which proved that these solution contained colloidal
of the initial water content of the mixture has been re
silicate particles of very high molecular weightand pos 60 moved and until the solids content of the remaining com
sessed such high (Z) values as to necessitate the conclu
position has become at least 40% by weight. At this
sion that the polymeric silicate was linear instead of
stage of the process the alkaline silicates in the mixture
globular. These data are shown in Table 2.
will have polymerized during the concentration of the
aqueous system. This polymerization is predominantly
TABLE 2
65 linear by reason of the catalytic in?uence of the oxygen
Turbidity mol. weights:
(Z) values
10,000
_______________________________ __
1.3
33,000
_______________________________ __
1.65
containing modi?ers, and consequently predominant
amounts of amorphous, glass~like, non-crystalline ?brils
100,000
_______________________________ __ 2.8
are formed as solids in the aqueous system, and these:
350,000
______________________________ .._ 4.7
70 solids have an average molecular Weight, as measured by
800,000
______________________________ __ 5.2
the light scattering method, of at least 10,000.
There are various speci?c modi?cations of this gen-.
eral method for polymerizing silicate, and the relative
For a spherical silicate particle in the system
effectiveness of these various techniques is indicated in
Na2O:3.75 SiO2_a density of 0.43 was estimated (Vail
‘and Will, vol. 1, page 100).
‘
7
75 Table 3 below.
3,069,277
6
TABLE 3
Solids content of
aqueous system
Treatment
Turbidity
mol. wt.
sisting essentially of water and colloidal silica in a con
centration of about 30%. Any of the several brands
of such solutions, which are sometimes brie?y desig
nated as 30% colloidal solutions, may be employed as
the ingredient first used in preparing a paste having a
(Z)
dissym
metry
Naz0.Si0i(1:3.4)_____ Re?uxing for 12 hrs.
with stirring; fol
lowed by rapid con
6, 000-8, 000
catalytic effectiveness similar to the catalysts described
in the ?fth and seventh procedures of Table 3. A solu
tion containing 30% colloidal silica was employed and
1. 3
centration in an
open vessel (CO2
present with
stirring in air) to
the amount of boria expressed as boric acid was slightly
To-360 g. of
the 30% silica solution, 37 g. of boria were added gradu
ally with stirring, thus forming an aqueous system con
taining both silica and boria. Possibly the boria was
in part absorbed-on the surface of the colloidal silica
10 more than half the amount of the silica.
45% solids.
N820.Si0g(123.4)_-.... Re?ux 12 hrs.; con-
<3,000
l. l
centrate in vacuum
NazO.SiOg(1:3.4),
5% colloidal silica.
to 45% solids.
Re?ux 12 hrs. with
stirring; and heat in
open vessel rapidly
with stirring. Con
centration to 45%
solids.
6, 000-8, 000
1. 35
NaiiO.Si0i(1:3.4),
_____do ______________ _- 18, 000-30, 000
1.6
NaiO.SiOg(l:3.4),
_____do ______________ __
3.0
5% colloidal silica
3% H38 03.
130,000
5% colloidal silica,
3% H3803, 2%
A1201, 2% ZnO,
1% MgO.
NagO.SiOz(1:3.4),
15 particles. Possibly the system included both dissolved
and absorbed boria. To the silica boria mixture, 174 g.
of alumina were added gradually with stirring, and 21 g.
of zinc oxide were introduced. ‘In this manner 592 g.
of a paste of uniform consistency was prepared contain
20 ing 108 g. of colloidal silica, 37 g. of boria, 174 g. of
alumina, 21 g. of zinc oxide (340 g. of solids) and 252
-____do ______________ ..
50,000
1.9
_____do ______________ -_
100,000
2. 8
g. of water. In preparing such a paste, the metal oxides
such as alumina and zinc oxide are in ?nely divided
113B 03, 3%
A1203, 2% h1g0
Na2O.SiOr(l:3 4),
3% HzBOx, 3%
1203, 2% MTgO,
form and may be in the anhydrous, partially hydrated,
25 or fully hydrated form inasmuch as the hydrated ?nely
divided silica makes it possible to mix a uniform catalytic
paste with any of such starting materials.
5% colloidal silica.
in a separate container, there was measured a sodium
In the above table the sodium silicate is a 34° Bé.
trisilicate solution which contain-ed 3.22 parts of silica
solution, and the colloidal silica solution is a 30% solu
tion. The data of Table 3 show: that the presence of 30 per part of sodium oxide, or about 8.5% sodium oxide,
about 27.5% silica, and about 64% water, and a density
air aids the attainment of higher molecular weights; that
designated as 38° Bé. (1.36 g./mi.). Some commercially
the presence of 5% boric acid (solids basis) catalyst can
available sodium trisilicate solutions corresponded exactly
bring about a ?vefold increase in the average molecular
to such speci?cations, but some samples contained 65%
weight; that a multi-component catalyst helps to attain
still higher molecular weights; and that the colloidal 35 Water (35% solids) instead of 64% water, and some
silica, although almost without effect by itself, promotes
the activity of the multi-component catalyst; and that
the higher molecular weight ?brils thus prepared have
dissymmetry values establishing the linearity of the sili
cate molecules.
samples contained signi?cant amounts of contaminants
such as calcium oxide and aluminum oxide.
Di?iculties
with such impurities can be avoided by employing a
freshly prepared sample of sodium trisilicate resulting
40 from the dispersion of fresh gelatinous silica in aqueous
sodium hydroxide or by dispersing puri?ed granular
Although the data from light scattering studies pro
sodium trisilicate in deionized water.
The sodium trisilicate solution was heated during about
are formed in accordance with the present invention, a
variety of other tests provide convincing con?rmation of 45 3 hours to evaporate water from the solution, and to
increase the solids content from about 35% to above
the result.
40%. Thus, 750 g. of such concentrated silicate was
The intrinsic viscosity of a solution of sodium sili
prepared. In concentrating the solution, colloidal silicate
cates is known to remain constant and independent of
was formed and dispersed within the concentrated sodium
the velocity gradient. The aqueous solutions of linear
polysilicates of the present invention exhibit an enormous 50 silicate solution.
vide the most persuasive evidence that linear polysilicates
The 592 g. of paste of boria, alumina, zinc oxide,
dependence on velocity gradient.
By a method employing velocity radient dependence,
employing various pressures and velocities and observing
time of ?ow through standard capillary viscometers and
colloidal silica and water was stirred into 750 g. of said
concentrated sodium silicate to form 1342 g. of a com
position, which was thoroughly mixed into 1500 g. of a
calculating back to zero rate of shear, the values of 55 liquid consisting of 900 g. of a 35% solution of a sodium
trisilicate (3.22 ratio) and 600 g. of a 17.4% solution
Table 4 were obtained for intrinsic viscosity (N) in stand
of pure sodium metasilicate (1.0 ratio). The 2842 grams
ard units.
TABLE 4
Sample
Turbidity
Intrinsic
nxéiecgggr
g
Viscosity
of mixture were heated to evaporate suflicient water to
concentrate the solution to a solids content of 40%
to prepare a viscous liquid designated as a drawing com
60 position. The mixture remains alkaline, i.e. at a pH
above 7, during this concentration thereof. Data relat
1
10,000
a
an
0 08
ing to this composition are set forth in Table 5.
4.
350.000
1 05 65
5-
800,000
1 85
TABLE 5
E20
The solutions studied undera polarizing microscope
and forced ?ow through a capillary exhibited ?ow birefringence similar to ?ne sodium bentonite suspensions.
450
tinguished from globular) polysilicate particles in the
Before contain?
23g
aqueous systems of the present invention.
Afttlé’rn-éb-?g-e-l?éj- 1,783
EXAMPLE 1
Several manufacturers market aqueous solutions con
SiOz
Colloidal silica
252
10s
éggétegfrsgge-dns-i?i -------------------- -cats____________ __
All such data con?rm the existence of linear (as dis
Naio
70
~-; 1' a
71
B203
37
ZnO
_____ __
21
A1203 Total
174
229 ___________________ __
360
232
750
288
197
63°
a as
37
21
174 2842
a
a 2;???
3,069,277
In the following table (Table 6) are illustrated by
some numerical examples, the possibilities of varying the
proportions (in parts by weight) of the individual com
ponents in the preparation of the dispersions, always
operating with the technique. described in Example 1.
By way of example, the “additives” of Example 1, as
tabulated in Table 5 may be replaced by the following
combinations (groups) With appropriate changes in other
components to'mal-Le up ‘a 100% composition:
(Parts by weight)
(a)
(b)
(c)
(:2)
(e)
(f)
(g)
(11)
(i)
(j)
(k)
Argo3 160, CaO 15, 13203 25, ZnO 5
A1203 200, P205 30
zro2 80, C210 10, ZnO 5, B203 30
"no, 100, A1203 10o, MgO 25, A1203 10
P150, 30, zro2 50, C00 15, M003 10
$1102 100, FeO 20, A5205 15
A1203 200, Bat) 20, B203 20
A1203 100, SrO 10, BeO 5, C00 5, Fe2O3 5
Ti02 50, W03 15
A1203 80, C00 5, NiO 5, FeO 5, 1912203 5, P205 10
13,03 27, ZnO 21, A1203 174
The quantities indicated are intended as quantities added
in the various stages prior to evaporating.
Said examples
are indicative. Other formulations falling under the
ranges stated above can be employed.
10
TABLE 6
Dispersions
I
15
Colloidal silica _____________________ _Additives ___________ _.
Other examples are possible, provided the proportions are
500
II
III
IV
1, 000
23'
2, 100
232
______ __
232
H2O _ _ _ _
Concentrated s1l1cate__
in the ranges stated to be admissible.
Trisilic
e ___________ __
Metasilicate _______________________ -_
The viscous liquid resulting from the polymerization
40% sod ‘1
820
_
of the silicate can be used for any purpose for which
Total ________________________ __
aqueous dispersals of linear polysilicate ?bril-type colloidal
2,902
particles are useful such as in the protective coating,
adhesive, and/or other industrial arts employing sodium
silicate.
It should be noted that the combination of metallic
The dispersions I, II, III,’ 717V“ tabulated, as prepared by
25 the method of Example 1, should be successively evapo
rated in the warm state until the ?nal weight of 40% min.
solids is achieved so as to correspond to the ?nal com
anion such as borate with a metallic cation such as
position'of the dispersion of Example 1, namely:
aluminum is particularly effective for catalyzing the linear
polymerization. The polymerization is brought about
Percent
Percent
by heating one portion of the alkaline silicate solution 30 H2O ____________ __ 60> BiOs ____________ __ 1.5
while evaporating water from a surface thereof.
Na2O ___________ __
7.4
ZnO _____________ __ 0.8
During such concentration of the solution, the dehy
Si02 ____________ __ 23.8
A1203 ____________ __ 6.5
dration of the silicate aggregates to form larger aggre
gates occurs predominantly in a portion of the liquid
EXAMPLE 3
near the surface of evaporation. This is accomplished 35
For the preparation of the solution of Example 3, the
by maintaining that portion of the body of the liquid at
same operative conditions of Example 1 are followed, but
which heat is applied at a distance from and at a sig
the quantities added of colloidal silica and of alkali
ni?cantly higher temperature than the temperature of
silicates are conveniently varied in such a way that the
the surface of water removal, and thus a ?lm of heated 0 ratio SiO2:Na2O is varied, but always between 2 and 5.
liquid can diffuse through the balance of the liquid toward
In Tables 7 and 8 are indicated some compositions
the evaporative surface to form such larger aggregates.‘
suitable for the latter purpose.
Such polymerization occurs linearly instead of globularly
because of the catalytic effect of the hydroxyl ions, the
TABLE 7
sodium ions, the borate ions, the aluminum ions, and
particularly the combination of all of the catalytic
H2O N320 SiOz
components.
EXAMPLE 2
In the preparation of the solution as described in the
above Example 1 and following the same procedure and
operating technique, there may be prepared solutions hav
ing the same ?nal compositions, with the variation within
wide limits of the relative quantities of colloidal silica,
concentrated and diluted trisilicate, metasilicate.
Metasilicate _____ __
Total before con
centrating ______ -_
2, 710
Total after con
Generally speaking it is possible to employ in the
preparation of the aqueous dispersions the following 55
quantities of the various ingredients:
30% colloidal silica: from 0% to 100% of the silica
contained in the system;
40% conc. trisilicate: from 0% to 100% of the total silica;
35% trisilicate: from 0% to 100% of the total silica;
17% metasilicate: the amount needed to make the ?nal
centrating _____ __
1, 518
Percent by weight-
60
SiO; to NazO ratio. ..... _
TABLE 8
H2O
Colloidal silica
NazO
600
SiOz
B203
ZnO
37
21
260
860
Additives _____________________________ __
1120---, _________ -_
dispersion have the desired siOgzNazO ratio between
Gone.
Metasilicate .
_
232
800
_ . _ . __
1, 600
_ _ _ _ .
200
640
___________________ __
_ . _ _ _ _ _
Total before con-
,
centrating _____ __ 3,000
persion have the desired SiO2:Na2O ratio between 2_‘
174
_________________________________ __
silicate _ _ . . _ _
Trisilicate _______ __
2 and 5;
50% soda: the amount needed to make the ?nal dis
s00
A1203 Total
2, 440
_ _ _ _ __
V
,
,
200
900
37
21
174
centrating _____ __
2,000
200
900
37
21
174
Percent by weight;
60. 0
. 0
SiOg to NaiO ratio-
4. 5
4, 332
Total after con-
and 5.
The addition of soda is carried out under stirring as
'
.
.
.
3, 332
____ __
the last operation of the aqueous dispersion before
evaporating.
H2O: The amount needed to make the dispersion have a
70
EXAMPLE 4
Operation is as in Example 1 but the sodium silicates
are replaced wholly or partly by the corresponding sili
solids content not higher than 37%, before evaporation.
cates of potassium or of the other alkali metals of group
The addition of water is effected initially during the
75 I of the periodic classi?cation of elements.
mixing of the’additives.
8,069,277
to
EXAMPLE 5
To summarize, the invention includes:
By operating under the same conditons of Example 1
it is possible to prepare other dispersions by varying the
The preparation of an alkaline aqueous system contain
ing silicates according to Example 1;
The preparation of aqueous dispersions having a Slog
formulation of the additives added.
Besides the oxides (A1203, ZnO) and the anhydride
(B203) cited in the preceding examples, it is possible to
to alkali oxide ratio of from 2 to 5 and containing a cata
lyst as above de?ned;
The preparation of ‘aqueous dispersions of alkali sili
cates containing non-alkaline oxygenated derivatives
employ a considerable number of other additives.
Said additives or catalyst have the purpose of causing
the linear polymerization of the silica in aqueous basic
medium. Such additives are the non-alkaline compounds
containing oxygen and are components in conventional
known per se to be components in conventional glasses
and acting ‘as catalysts for the formation of silicates hav
ing prevailingly linear character.
compositions of glass as made by melting. They may be
divided into three categories:
As above stated, said components may belong to 3
classes:
Oxides of groups 11 and VIII of the periodic chart;
(1) catalysts basic in character (oxides);
(2) catalysts acid in character (anhydrides);
(3) catalysts amphoteric in character.
15 Oxides of groups III and IV of the periodic chart;
Anhydrides of groups 111 and V of the periodic chart;
and these .can be employed in the ranges de?ned in Ex
The catalytic action may be exerted by one single
ample 5.
catalyst but generally it is preferred to utilize the con
In the manufacture of glass from fused siliceous sys
temporaneous action of a number of catalysts and in 20 tems, data ihas been accumulated relating to the relative
particular the combination of a catalyst having basic char
attractiveness of various metal oxides as components for
acter, of one having acid character and of one having
soda glasses. By a series of tests, it is established that the
amphoteric character.
relative attractiveness of metal oxides as catalysts for
To the ?rst category belong the oxides of groups II
25 linear polysilicates is approximately the same as the order
and VIII of the periodic system, such as those of Ca, Mg,
of attractiveness of metal oxides as components for soda
Ba, Sr, Be, Co, Ni, Fe, etc.; these can be employed alone
glasses. Thus boria and alumina (especially combina
or in admixture with one another in such amounts as not
tions thereof) are superior to tungstia. In the oxide-com
to surpass the oxide to alkali oxide ratio=0.2.
taining paste of the present invention, one or more of
To the second category belong the anhydrides of groups 30 such various metal oxides, commonly known as “glass—
III, V and VI of the periodic system, such as: B203,
forming oxides” or “halogenic” compounds, may be em
P205, W03, AS203, AS205, Sb2O5, etc.: these can be em
ployed. The preferred glass-forming oxides are those
ployed alone or in admixture With one another in such
selected from the group consisting of oxygen-containing
roportions as not to exceed the anhydride to alkali oxide
compounds of the group consisting of compounds of
ratio=0.3. The latter may also be employed in the
boron, aluminum, zirconium, titanium, zinc, calcium,
form of salts: NaBO3, H3BO3 Na3AsO4; K2HPO4,
(NHg)2NIOO4, (Etc.
barium, arsenic, germanium, hafnium, phosphorus, vana
dium, antimony, lead, thorium, beryllium, and tungsten.
To the third category belong the oxides of metals of
Obviously various modi?cations of the illustrative ex
groups III and IV such as A1203, ZrOz, TiO2, P1302,
amples are possible without departing from the full scope
SnOZ, etc. Said oxides may be employed (each taken 40 of the invention as de?ned in the appended claims.
alone) in such proportions as to come within the follow
ing ranges of the oxide to alkali oxideratio:
AlgoszAlkali oxide ratio from 0 to 1.25;
ZrOzzAlkali oxide ratio from 0 to 1.000;
TiO2:Alkali oxide ratio from 0 to 0.70;
PbOzzAlkali oxide ratio from 0 to 0.25;
SnO2:Alkali oxide ratio from 0 to 0.25.
I claim:
1. The method of polymerizing alkaline silicates in an
aqueous system to form an aqueous dispersion of linear
polysilicate ?brils which includes the steps of evaporating
45 water from an aqueous silicate solution to concentrate it
and to form colloidal silicate dispersed therein, said aque
ous silicate solution containing the silicate of at least one
alkali metal of group I of the periodic classi?cation of
Hence for the preparation of aqueous dispersions many
elements, the ratio of alkali metal oxides in said aqueous
formulations can be employed which take into account 50 silicate solution to the silica therein being Within the range
the principles set forth hereinabove.
from 1:2 to 1:5, modifying the concentrated aqueous
By Way of examples of various additives, in the follow
ing table some formulations (in parts by Weight) are
indicated which may be substituted for the additives of
Tables 5—6—7—8 of Examples l-2-3.
55
TABLE 9
Additives (parts by weight)
_
prepared by adding to an aqueous solution of approxi
mately 30% colloidal silica an amount of at least one
additive suf?cient to catalyze the linear polymerization of
said alkaline silicate, said additive being selected from
the three groups ‘consisting of: ?rst, an oxide of the ele
ments calcium, magnesium, barium, strontium, beryllium,
A1203, 160_-_ C210, l5_____ BaO, 5 ____ __ B203, 25.
A1203, 250.“ NnBOs, 20
A1203, 200.-.
_
silicate solution by incorporating therein a catalytic paste
cobalt, nickel and iron in such amounts as not to surpass
60 an oxide to alkali oxide ratio of about 0.2; second, a com
Zl‘oz, 80".“
pound selected from the group P205, W03, AS205, Sb2O5,
Na3AsO4, K2I-IPO4, (NH4)2MoO4, in such proportions as,
Th0, 100""
PbOz, 30.“.
5110;, l00___
not to exceed the ratio of the anhydride equivalent of
said compound to alkali oxide of about 0.3; third, an
A1203, 200.A1203, 100-.-
SIO, I0 .... __
B210, 5 ____ __
C00, 5.
65 oxide of the metals aluminum, zirconium, titanium, lead,
germanium, tin, hafnium, vanadium and thorium in such
proportion as not to exceed the values of 0.25, 0.25, 0.70,
It is thus evident that a considerable number of pos
sibilities can derive from the combination of the various
y.
1.00 and 1.25 respectively for SnOZ, PbO2, TiO2, ZrOa
‘and A1203; the sum of the non-alkaline oxygenated com
oxygenated compounds above mentioned, in the prepara 70 pounds in said additive being Within the range necessary
tion of the aqueous dispersions.
to make the ratio of said sum to alkali oxide within the
It should be noted that the sum of the non-alkaline
range of 0.1 to 2.0; thereafter applying heat to a body
oxygenated compounds should be such as to be kept
of the mixture of concentrated silicate solution and cata
within the limits of the 0.1 to 2 range of the non-alkaline
lytic paste to evaporate water from the surface thereof
oxygenated compound to alkali oxide ratio.
75 and to form aggregates of material therein, maintaining
3,069,277
11
said mixture at alkaline conditions above pH 7 during
the evaporation of water from the mixture, continuing the
heating of said body of mixture until the water evapo
2. A composition prepared in accordance with claim 1,
and consisting of Water containing at least 40% high
molecular weight, predominantly over 10,000 molecular
rated therefrom is at least 10% of the initial water con
weight, linear, amorphous, non-crystalline, glass-like alka
tent and until the solids content of the remaining compo
line silicate ?brils having the modifying content of said
additive.
sition is increased to at least 40% by weight, whereby the
alkaline silicate molecules polymerize under the in?uence
of said :catalytic paste and incorporate the oxygen-con
taining compounds of said paste in the polymer to form
a predominant amount of amorphous glass-like non-crys 1°
talline ?brils.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,886,404
2,919,996
Teja ________________ __ May 12, 1959
Teja _________________ __ Jan. 5, 1960
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