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Патент USA US2117605

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, 7-75
._ Patented
May 17, 1938
‘v ‘tress Reference
Albert A. Fowler, North Hollywood, and Russell
M. Otis, Pasadena, Calif.
No Drawing. Application December 18, 1936,
A f .
Serial No. 116,644
7 Claims.
(01. 18-475)
This invention relates to a glass-like material
of light wei ht and to the me
0 ma ng
1a?‘e'._' " Vi"
In our patent, No. 2,038,034, we disclosed a
5 material composed of a solidi?ed silicate having
a spumiform structure, that is, a bubbled or in
tumesced solidi?ed material having a structure
similar to that of foam. This spumiform mate
rial is well adapted to heat insulation and we
have applied it to this use in several different
forms-pulverulent or granular, and also as solid
slabs. In the afore-mentioned patent, we‘
speci?cally disclosed the use of alkaline silicates
such as silicates of sodium and potassium. We
15 have found, however, that materials made from
these silicates alone are water-absorbent and are
in time dissolved in presence of water, which
properties, while not affecting their application
to many classes of work, ill-adapt them for many
20 other purposes.
An object of this invention, therefore, is to pro
vide a light-weight, glass-like material which
shall be comparatively insoluble in water.
Other objects are to provide light-weight glass
25 like materials in granular and slab form and
having an intumesced or spumiform structure.
Other objects are to provide e?icient methods
or other sui a le su s a'nce w
ch serves as a
source of boric oxide. We may add the boric
oxide or boric anh dride itself. Preferably we 5
add boric acid, or sodium tetraborate, in a hot
water solution, although they may be added in
solid form if desired, When the boric oxide con
taining substance is added to the alkaline silicate
solution, a white lump precipitate is formed there
in which is broken up by agitation. The com
position is heated at a temperature near boiling
and while‘u'ii'derming agitation until, with the
preferred compositions. all of the white precipi
tate has dissolved to make a thick viscous liquid.
In this stage, the liquid can be thinned some
what by addition of a limited amount of water.
In the next stage of the process, the thick
viscous liquid resulting from the above-described
steps is poured out into shallow pans or onto
a moving belt to be partially desiccated. In us
ing pans, the material is poured to a depth of
from 1A to 1/2 inch and the pans are placed in an
ovengwitha'temperature‘of about 320° F. In us- I
ing a belt, the material is poured“'in ‘a relatively 25
thin layer onto the belt and the belt is passed
through a heated oven space.
In any case, the
of making the afore-mentioned glass-like mate
drying is continued until a condition is reached
at which, when the material is cooled to atmos
pheric temperature, it is a hydrous solid, This 30
Our ?nished composition comprises as con
stituents, alkaline oxide, boric oxide (B203), and
silicon dioxide ($102). The alkaline oxide may
be, for example, sodium oxide (NazO), or potas
sium oxide (K20). The material of this com
35 position is glass-like in character and, due to the
manner of its preparation, may be made exceed
ingly light in weight, and almos
in water. The material of preferred composition,
[Min granular form, may weigh from 0.9 to 1.5 lbs.
near the boiling point. To this is added boric acid
(H3303) , or sodium tetraborate (Na-234m
er cu, ft. and is
cien y s rong at a density
of 1.5 lbs. per cu. ft. to support a load of about 150
lbs. per sq. ft. of surface area without further
de?ection. In slab igrm our material may be
made to weigh from about
45 greater than 12 lbs. er cu. ft. These materials
have'p'er'?aps the1r greatest utility in the ?eld of
heat insulation and sound absorption, although
they find application wherever their light weight,
comparatively high strength, resistance to water
50 solubility, and ?reproof character are of ad
We preferably prepare our glass-like material
in the fdifowing manner. Alkaline silicate, pref
condition generally corresponds to a water con
tent of from 15% to 25% of the material.
After this partially desiccated material has been
cooled, it is comminuted to a size of particle
which depen upon e
‘shed material which 35
it is desired to make. The material is very hard
and brittle and cracks very easily. When granu
lar material is to be the ?nished product, the
hydrous or partially desiccated composition is
preferably comminuted to from
mesh to 14 40
mesh in size, the larger particles making pr -
portionafely larger particles of the ?nished in
tumesced material. When molded bodies are to
be made, the partially desiccated material of
about 30 vmesh is preferably employed.
In Wmmmwe W
rial rapidly by contacting it with a hot surface
maintained at a temperature preferably of from
650° F. to 1000" F. This heating may be con
heat the comminuted, partially desiccated mate
uc e
at work
nah eated drum in which an agitator is
6 hgniagiaiwwisiirasms:
sible and preferably continues until dessication
era-bly, sodium silicate of suitable compositio
of the particles is substantially complete. In
66 and in w'ater solution, is' brought to a tem
ture . this heati g operation, t e particles presumably 55
.. ,9
. 4:-..“
Dill, .I'l‘
q.» a .0, :1’
l‘r’ -* O5
~11 7
i 7
soften under the high temperature and the steam
which is formed in them, due to the contained
water, stretches and expands the particles until
the water has all left, when solidi?cation occurs
5 and expansion ceases. In this operation each
partially desiccated particle expands or explodes
into one
of gnmzn-mmmwggggggge.
is a granular materia
mg of
individual bubbled, intumesced, or spumiform
10 particles each comprising one or more small hol
low spherical shells of thin glass-like substance,
the cells, in most cases communicating with one
another because of the passages left by the rapid
ejection of the contained water by heat. Our
15 use of the word “granular” herein is meant to
describe a material in which distinct granules are
recognizable and is not meant to be restricted to
any size of particle, as these may be from the
size found in ?ne powder to that common in
20 what might more properly be termed chunks. In
applying the term spumiform to describe our ma
terial we do not intend that any limitation as to
size of the material shall be implied. Some
‘ urniform granules are so small that they con
2 I list 0 on y??gfébubble, while a molded spumi
fornTbb'd'yW?‘df millions of cells or
passages. This bubbled character, accompanied
by relatively thin bubble walls, is the distinguish
i‘hg feature of our material and is what we mean
by the term spumiform.
The thin walls, which
10 or 20 times their vo ume and retain a on
to 12
s par la y expande
lar intumescent m
orm so as to completely ?ll it.
There are several important advantages which
result from this preferred procedure. First, the
amount of water required to be removed from
the contents of the molding form is reduced and
the ?ring time is, therefore, lessened. Second,
the increased volume of the particles due to the
intumescing step makes it possible to completely
?ll the molding form with only a small weight of
material, and results in light-weight molded
bodies with sharp clean corners. When, instead,
the unexpanded hydrous particles are employed
and the form is ?lled, so much material is re
quired due to its comparatively high density that
the ?nished block is comparatively heavy. ‘In 25
order to
ke a light-weight slab, then, by using
unexpanded hydrous particles in the molding
form, one must resort to only partially ?lling the
form, and after the slab is ?nished it is generally
found that the material has not expanded to com
are generally of much less thickness than the en
pletely ?ll all corners as well as when the pre
closed bubble spaces, permit de?ection under
ferred method is followed. Third, the slab is of
?ner and more uniform structure because the
individual particles do not have to expand to ?ll
the form, for they already ?ll it and they need 35
pressure and thus cause a body of the granules to
be compressible and resilient.
hydrous or incompletely desiccated particles
which have been intumesced somewhat by heat.
Such particles are obtained by conducting the
process exactly as if ?nished granular spumiform
material were to be made but by conducting the
expanding operation only part way to completion
so that the particles are expanded to possibly only
In making molded bodies of our glass-like com
position we preferably place a multiplicity of par
tially desiccated particles of the intumescent com
position in a molding form of the shape desired,
close the form, and subject the form and contents
to a temperature preferably of from 750° F. to
1000° F. for a time su?icient to effect substantially
complete desiccation of the material. For a
ea mg
e place
for from 20 to 30 minutes. It is desirable to per
mit the escape of water vapor from the molding
form during heating without permitting any of
the solidifying material to escape, and for this
purpose a loose-?tting cover to the form is gener
ally satisfactory. As the contents of the form
50 are heated, the individual particles soften and
are expanded by the pressure of steam formed
within them. They expand against one another
while in the softened condition and unite to form
ne spumiform body which becomes solid when
lithe material has been completely desiccated.
The tendency is always to expand to ?ll out all of
the space in the form, so that molded bodies of
all shapes may be made. The weight of a ?nished
molded body may be controlled by putting more
60 or less hydrous material into the form. It will
be noted that since the steam from the inside of
the body must get out through the outer portions,
passages are formed from one bubble to the next
so as to form intercommunicating cells. This
" type of structure is advantageous from the stand
point of sound absorption, while it is of no prac
tical disadvantage for heat insulation due to the
smallness of the communicating passages and the
non-importance of this type of convection in
‘i0 affecting thermal conductivity in a body of this
We may put into the molding form the com
minuted partially desiccated material above de
scribed just as it e’ol'ries from_ the comminuting
75 operation, but‘we' prefer to place into the form
only exert pressure on one another and unite in
The composition above-mentioned as employed
in making these materials has very superior prop
erties compared to sodium silicate, for example. 40
The most important advantage of the alkaline
oxide-boric oxide-silica glass~like material is its
relative insolubilit in water. This is an exceed
ma material to be em-;
ployed as insulation. By the employment of the; 45
proper relative amounts of alkaline oxide, boricg
oxide, and silicon dioxide in the material it is
possible to secure a solubilit in boiling water
which is only a small fraction of that o alkaline
silicate, for '
er importan
erty of our composition in the form of spumiform
granules is that the granules are rounder and
more uniform than is the case with granules made
from alkaline silicate. The highest thermal in
sulation value per unit weight, other things be 55
ing equal, will be found in a structure comprising
a multitude of minute, hollow, round shells with
t ,I
. I o
sition substantial] match t "s description.
tion is that we can secure over alkaline silicate,
for instance, the great reduction in water solubil
ity without any increase in the density of the ?n
ished spumiform material, and in fact in most of
our preferred compositions the density of our 65
?nished material is less than the alkaline silicate
which we may employ as the source of our alka
line oxide and silicon dioxide. This is a very
important» feature because the heat insulation
value is least for low density material as is also
the cost per cubic foot.
The chemical action between the~several com
ponents of our glass-like composition is di’l?cult
to determine as is the case with all glass compo
sitions; and we offer no theory as to the exact
""106. '* COMPOSITIONS,”
tress Reiercnce
pound compositions which lie in a range of lower
manner in which these components are combined,
but content ourselves with de?ning the compo
sitions, as is common in glass technology, by the
relative proportions of oxides going to make up
5 the total. And where we de?ne our compositions
in this manner, it is understood that we do so
for convenience and that compositions having the
solubility than it '
This is because w en s
In.‘ using the
um e ra
rate is add
ed as a source of boric oxide, one necessarily in- 5
creases also the amount of sodium oxide in the
composition by the amount" of sodium oxide con
tained in the sodium tetraborate.
speci?ed components in the speci?ed proportions
Since there
is no sodium oxide contained in boric acid or the
shall be considered to be included within our de?
10 nition regardless of the exact manner in which
anhydride, this situation is avoided by their use. 10
It is understood that our glass-like composi
tion may be employed together with other mate
they may actually be combined.
Compositions of alkaline oxide, boric oxide, and
rials such as ,?ife?grFsgof one sort or another, etc.,
silicon dioxide may advantageously be made hav
ing a mol. fraction of boric oxide greater than
15 .03. A lesser proportion than this is without
and we desire
our invention shall be consid
not wish to be restricted to the proportions here
in speci?ed, we prefer to employ mol. fractions of
boric oxide less than (2A-.35), where A is the
20 mol. fraction of the alkaline oxide, for we ?nd
that it is not practical to form a desirably homo
geneous composition with mol. fractions of boric
oxide greater than these values. Moreover, in
ered to extend to all such applications wherever 15
our composition shall be employed for its intu
mescent e?ect or shall be part of a spumirorm
structure. It is further understood that various
equivalent substances and processes may be em
ployed by those skilled in the art to arrive at the 20
material of our invention without departing from
the spirit of the invention de?ned in the appended
order to secure a satisfactory degree of water in
25 solubility of the composition, we prefer to em
ploy 2. mol. fraction of boric oxide less than .15 but
greater than (2A-—.46). Thus, we ?nd the range
1. The method of making a light-weight mold- 25
ed body which comprises heating particles of a
hydrous intumescent solid to create in them a
practical e?ect in our material.
While we do
spumiform structure, compressing said spumi
of compositions combining the greatest advan
form particles into a molding form and con?n
ing them therein, heating said form and contents 30
at a temperature su?iciently high to unite said
tages in a spumiform material to be those con
30 taining alkaline oxide, boric oxide, and silicon di
oxide, these three being in proportions de?ned
by the condition that the mol. fraction of boric
oxide is greater than .03 and greater than
(2A-.46) but less than .15 and less than
particles, and continuing said heating until des
iccation is substantially complete.
2. The method of making a molded body which
comprises heating particles of a hydrous in- 35
35 (2A—.35) where A is the mol. fraction of the al
tumescent composition containing alkaline ox
kaline oxide. It will be noted that this de?nition
restricts the proportions of all three components
because since the sum of the mol. fractions of the
three components equals 1.0 it is sumcient to de
40 ?ne the relations between two of the components
as done above and these relations automatically
determine the proportions of the third compo
As examples of the method of forming compo
45 sitions within this range, we offer the following.
Proceeding in the manner previously described,
we may add to 100 parts by weight of a sodium
ide, boric oxide, and silicon dioxide, to create
in them a spumiform structure, compressing said
spumiiorm particles into a molding form and
con?ning them therein, heating said form and 40
contents at a temperature su?iciently high to
unite said particles, and continuing said heating
until desiccation is substantially complete.
3. The method of making a molded body which _
silicate solution having a 37% solid content com-'
rising a so rum silicate with a mol. ratio of sili
50 con dioxide to sodium oxide of 3.15, 13.5 parts b
weight of commercial sodium tetraborate of 55 a
solid content, which is usual. The 5;;
borate may be separated into NazO '0 for pur
‘ poses of computation.
The complete composi
structure while still retaining some water, com- 65
55 tion, then, will be found to consist of approxi
mately .255 mol. fraction of NazO, .103 mol. frac
tion of B26: and .6101. fraction of gl‘Uz. Ur
to 100 par s '0
we may a
above mentioned of 3.15 ratio, 4.5 parts of boric
60 acid (H3303). From the boric acid is derived
boric oxide by the reaction 2H3BO3=B2O3+3H2O.
This composition then has the proportions: .227
mol. fraction of NazO, .056
o .
rac ll’l
By employ:
1 a -
65 kaline smcates of other ratios and by proportion
ing the amount of sodium tetraborate or boric
acid or a suitable quantity of each, it is possible
to construct compositions containing any desired
e use
in making our intumes
cent compositions has important advantages over
using sodium tetraborate. If one employs com
mercial sodium silicates as a convenient source of
sodium oxide and silicon dioxide, it is possible by
75 using boric acid or the boric anhydride to com
comprises forming a water solution containing 45
alkaline oxide, boric oxide, and silicon dioxide,
the mol. fraction of boric oxide in the composi
tion being greater than .03 and greater than
(2A—.46) and less than .15 and less than
(2A--.35) where A is the mol. fraction of the 50
alkaline oxide, partially desiccating said solution
to form a hydrous solid, comminuting said solid,
heating said comminuted material at a temper
ature su?iciently high to create in it a spumiform
pressing the particles of said spumiform ma
terial into a molding form and con?ning them
therein, heating said form and contents at a
temperature suf?ciently high to unite said par
ticles, and continuing the heating until desicca- 60
tion is substantially complete.
4. The method of making a lighti-weight mold
ed body which comprises heating a hydrous in
tumescent material to create therein a spumi
form structure, placing hydrous spumiform par- 65
ticles of said material into a molding form and
con?ning them therein, heating said form and
contents at a temperature su?iciently high to
unite said particles, and continuing said heat
ing until desiccation is substantially complete. 70
5. The method of making a light-weight mold
ed body which comprises heating a hydrous in
tumescent composition containing alkaline oxide,
boric oxide, and silicon dioxide, to create therein
a spumiform structure, placing $hydrous spumi- 76
form particles of said material into a molding
form and con?ning them therein, heating said
form and contents at a temperature sufficiently
ed body which comprises heating a hydrous in
tumescent compositon containing alkaline 0x
high to unite said particles, and continuing said
heating until desiccation is substantially com
0. The method of making a light-weight mold
ed body which comprises heating a hydrous in
tumescent material to create therein a spumi
10 form structure, ?lling a molding form with hy
drous spumiform particles of said material and
con?ning them therein, heating said form and
contents at a temperature su?iciently high to
unite said particles, and continuing said heating
7. The method of making a. light-weight mold
ide, boric oxide, and silicon dioxide, to create
therein a spumiform structure, ?lling a molding
form with hydrous spumiiorm particles of said
composition and con?ning them therein, heating
said form and contents at a temperature su?i
ciently high to unite said particles, and con
tinuing said heating until desiccation is sub
stantially complete.
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