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Патент USA US2100944

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Patented Nov. 36, 1&3?
-, '
united stares
EA'EENT
MAKING ALKALH spe
success or Smlg
'
Richard Lloyd Davies, Philadelphia, Pa, assignor
to Pennsylvania Salt Manufacturing @ompany,
‘Philadelphia, Pa". a corporation oil Pennsyl
vania
No Drawing. Application September 3, 1936
Serial No. 993%
'
20 Gimme.
My invention relates to‘ a novel process of man
ufacturing soluble alkali silicates and more par-é
ticularly it relates to an economic process for
,
(or. sci-no)
move the silicates therefrom by crystallization,
drying, and‘comminuting the crystals. In such
a. process, the plant and equipment are costly, the
the production of alkali sub-silicates with an al- , repair charges are high due to the slagging effect
“sell content not less than the silica content ‘by
the direct reaction of molten caustic alkali and
silica-containing material.
'
One object or‘ the present invention is to provide a method by which soluble alkali silicates
10 may be easily and economically manufactured
without resort to the expensive equipment and
‘laborious steps required in either the wet diges
tion or the furnace-‘process previously employed
in the production of these compounds.
'
on the furnace linings, and the fuel consumption
is high. ,In the wet digestion method, a solution
of water glass, or finely divided silica rendered
soluble by digestion with a concentrated solution
of caustic alkali, is evaporated and cooled to a 10
suitable crystallization temperature. It is then .
seeded,‘ agitated, and cooled to remove there
from theheat generated by the crystallization.
The crystals are removed, dried, and comminuted.
_When water glass is employed, it'is obtained by
A further object of the invention is to furnish
a process of making alkali sub-silicates by the
fusing silica with an. alkaline carbonate or an
reaction between molten caustic soda and solid
reactive silica-containing material in contradis
extraction process to render the silicate soluble.
tinction to the previous processes where the re
20 actions are carried out either in solution or by
fusion in a furnace“
alkali sulphate and carbon, followed by a special
It is obvious that in these digestion processes the
evaporation costs are high, a comparatively large
plant isrequired, and ‘the necessary digeste‘r
20
equipment is expensive. '
-~
Still another object is to provide a. process by
The process of the present invention is a marked
which granular or pulverulent soluble alkali sili- . departure from the previous processes, since
cates may be obtainedin one step at small ex
. pense for labor and with a small capital ‘invest
ment.
.
Still another object is to provide-a process for
the manufacture of high grade, free-?owing
stable alkali silicates of low hydration and of
30 variable ratios of Nazi) to SiOz; for example, it
is possible by this new method to manufacture the
sesquisilicate with a ratio of alkali to silica (No.20
to S102) oi’ 1.5 to 1 and increase this through the
2 to 1 ratio of the orthosilicate and up to 8, 10 or
even 40 to l in the case of detergents required in
Q Li
special cases, such as in bottle'washing or where
a. heavy duty‘ detergent is required. The sub
stantially anhydrous materials obtained by the
neither cry'stallizing tanks nor digesting appara
tus is necessary.‘ In accordance with the pro
25
visions of the present invention, the manufacture ’
of these sub-silicates is advantageously under
taken in connection with the manufacture of ‘
caustic soda or caustic potash, and themolten
caustic alkali from a caustic pot may be charged 30
into a mixing device and the solid, reactive silica
containing material added gradually with careful
stirring. The length of time of the reaction and
the'time required to produce the granular prod
uct will obviously depend on the temperature of 35
the caustic soda reacted. Preferably, caustic
soda of 100% purity is used at or above its melt
ing point, in which case the reaction is a violent.
process of the present invention may be con‘ 'one andis practically instantaneous. The re-'
40
40 trasted with the variety of silicates now available action is complete in one minute after the addi
on the market and which contain large and vary
tion of the last of the silica-containing material
ing percentages of ‘water of crystallization.
and in ?fteen to twenty minutes a free-?owing
granular material is discharged from the mixer.
, Other objects will be apparent from a consid
eration of the speci?cation and claims.
_ __
Thus in a one-step process and with a small in
The processes‘ heretofore employed in the pro . vestment, it is possible to produce an excellent 45
duction of alkali silicates whose NazO content-is grade of a sub-silicate of soda and to discharge
from 'the -mixer, material that ‘goes directly to
not less than the silica content, known and're
ferred to herein as alkali sub-silicates, have been the consumer without further treatment. The
time consuming, laborious, and expensive and material is a substantially'anhydrous sub-silicate,
although it may contain a fraction oi. 1 molecule 50
have required a comparatively heavy plantin
vestment. As indicated above, the sub-silicates of water of crystallization. It will be seen that
have previously been manufactured by fusion
the process of the present invention largely elim
inates the dl?iculties and expense of both the wet
methods, or by'wet digestion methods or a com
bination of the two. In the fusion method, an , digestion and the furnace methods previously em
-
alkali carbonate and silica are heated together
to a high temperature substantially above the
fusion point of the system',‘and the fused product
after solidifying‘ is dissolved. in water ‘and cor
rected to the proper alkali-silicate ratio. It is
then necessary to concentrate the solution, re
ployed in the-manufacture of alkali sub-silicates. 56
The present process avoids the multiple adjust
ments and re-adjustments oi.’ composition, hyu
dration, and concentration, as well as the seeding,
crystallization, separation of the crystals, and
drying required in a wet digestion method. By 60
2
2,100,944
nically anhydrous sub-silicate, since water asso
ciated with the caustic soda is driven off by the
combined effect of the sensible heat and of the
making use of standard equipment, the process
obviates the need of special fusion furnaces of
complicated construction, of the high tempera
ture rotating reaction vessels provided with spe
cial mechanical agitators and of the special tur
nace linings required in the fusion process fur
heat of the reaction along with‘ chemically com- .
blned' water displaced from the caustic soda.
As previously indicated, the process of the present
' invention is advantageously carried out in con
nace.
I The process of the present invention is par
ticularly applicable for the production of alkali
nection with the manufacture of‘icaustic soda,
since the caustic pots provide the most economi
sesquisilicate or orthosilicate or mixtures of these - cal source
materials. If ‘the ratio of N‘aaO to S102 is 2 to 1,
. a silicate is formed directly in the mixture which
is from 99% to 100% soluble. The ratio of the
two oxides in the compound corresponds to the
15
orthosilicate
and is technically anhydrous.
When the ratio .of NazO to SiOz is 1.5 to 1, a com
pound is formed in the mixer in which the ratio
of NazO to vSiOi corresponds to the sesquisilicate.
If the ratios of NazO to $102 lies between the 2
of molten caustic soda. In the 10
preferred process, the molten caustic soda and
solid reactive silica-containing material are mixed
immediately after the removal of the desired
amount of water from the caustic soda, at which
point the temperature of the caustic soda is
sufficiently high to cause an immediate reaction.
Preferably the reaction is carried out at tem
peratures between approximately 300° C. and
approximately 500° C.
’
In a typical case, and to prepare sesquisilicate 20
20 to 1 and the 1.5 to 1, mixtures of the ortho- and‘ of soda, 60 parts of silica are added gradually
sesquisilicates will be obtained. If the ratio of
NazO to S102 is higher, then higher ratio silicates - to a revolving‘ mixer which contains 123 parts
or mixtures of caustic soda'and sodium silicate of molten caustic soda at a temperature of about
will be formed, which products,-as previously 400° C., the reaction is complete in about four
‘pointed out, are particularly applicable for use minutes, the mass becomes plastic during a fur 25
ther thirteen minutes and starts to crumble, and
as detergents.
The term “solid, reactive, silica-containing is discharged in a further three minutes as a
free-?owing, technically anhydrous, granular
material” employed herein includes silica and
'the solid water glasses where the ratio of S102
exceeds that of NaaO, for example the water
30
glasses where the ratio of NazO to SiOz is 1 to 3.32
material ready for the market. To prepare the
orthosilicate, 60 parts of silica are added 30
gradually to a mixer which contains 165 parts of
molten caustic soda under similar conditions to
the previous example, within one minute of the
and 1 to 2. It is to ‘be understood, however, that
other solid compounds of NazO and SiOz where
the ratio of the latter exceeds the former may addition of all of the silica the reaction is com
be employed. The silica may be of any desired plete and in less than a total time of twenty 35
purity and of any suitable ?neness to promote minutes a substantially anhydrous free-?owing
the reaction and may be anhydrous or a hydrated powder is discharged from the mixer, the mate
rial being ready for the market. To prepare the
silicon dioxide. The silica may be in an amor
phous form, such as opal or diatomaceous earth, detergents with the higher ratios of sodium oxide
or the natural crystalline formsjsuch as rock to silica, four examples are given, also it is some
crystal, sand, ?int, sandstone or any other variety times desirable in connection with this process
of quartz can be used. By-product amorphous to incorporate with the silicates other materials
possessing somewhat similar properties, for ex
or crystalline forms of silica hydrated or other
wise are also suitable sources of silica. Since in ample trisodium phosphate, disodium phosphate,
sodium .carbonate, and sodium bicarbonate. 45
general a high purity product is desired, a rela
45 tively pure silica will be used, but it the purity Such a mixture may be. employed, for example,
of the ?nished silicate is not a requisite, impure where water-softening properties are desired.
silica may be used, provided that the impurities
_do not react at the temperature and under the
- conditions of .the reaction to form insoluble
50 silicates.
I
The' term “molten caustic soda” refers to the
caustic soda which while molten at elevated tem
peratures is solid at ordinary temperatures.
Caustic soda of 100% purity may be used, as well
55 as molten caustic soda containing water, for
example as much as approximately 15% water.
Preferably, as previously stated, ‘the molten
caustic soda will possess suf?cient sensible heat,
as is the case when molten 100% caustic soda is
60 used at or above its melting point, to produce a
technically anhydrous product directly in, the
(1) Sodium oxide to silica-7 to .1 ratio.
_
(2) Sodium oxide to silica—20 to 1 ratio,
(3) Sodium oxide to silica-40 to 1 ratio
50
(4) Sodium oxide to silica-20 to 1 ratio in
which Na3PO412HzO was incorporated.
In Example (1) , 82 lbs. of molten caustic soda
and 8.6 lbs. of silica are used; in the 20 to 1
Example (2), '82 lbs. .of molten caustic and 3
lbs. of silica are used; in the 40 to 1 Example
(3), 82 lbs. of molten caustic-and 1.5 lbs of
silica' are used; and in Example (4), 3 lbs. of
silica are well mixed with 8 lbs of N83PO4(12H2O)
and the mixture added to 82 lbs. of. the molten
caustic. Each of. these mixtures is agitated from
?fteen to- twenty minutes and in each case a
mixing device. The reaction between the caustic , granular product is produced of excellent color
’ soda and the solid silica-containing material may and in a substantially anhydrous form. The
temperature of the molten ‘caustic used in these
' take place at any temperature between the melt
65 ing point of the caustic soda (about 318° C. for
100% caustic soda) the melting point of the re
action product. When molten' caustic soda of
less than 100% NaOH is employed, the tempera
ture and concentration thereof will determine the
70 reaction and granulation time, and the degree of
hydration of the product obtained from the mix
ing device. The higher the temperature and the
concentration 01' the molten caustic soda. the
75
more closely will the product approach the teeth
examples-varies from 335° to 370° C.
In the foregoing examples, silica has been em
ployed as the solid, reactive, silica-containing
material, but as stated the solid water glasses
may be used in-place of silica to form the same 70
detergents, and in this case the ratio of 8102
to Na'zO in the water glasses is figured in detera
mining the amount of caustic soda to be added 7
toform the sub-silicate desired.
To prepare the sesquisilicate using solid water
\
.
,1
ly anhydrous, alkali sub-silicate product which
parts of water glass having a ratio of No.20 to
S102 of V1 to 3.32 are gradually added with stir-'
comprises adding molten caustic alkali, contain- ,
ring to 120 parts,oi molten caustic soda, the
reaction being complete in about two minutes.
anda solid, sub-divided, silica-containingmate
ing not more than approximately 15% water,
rial selected from the group consisting of silica CI
and alkali metal silicate having a molecular
ratio of $102 to alkali oxide greater than 1 to 1,
In six minutes, a free-?owing product is dis
7 charged from the mixer in powder form, more
. than 94% of which is soluble in water.
to a reaction vessel, the reactants‘ being present
in such molecular proportions that the alkali
oxide content is not less than the silicon dioxide 10
content, reacting the mixture while stirring it
at a temperature, below the melting point of
the reaction product, su?lcient to free the "mix
ture substantially of water, and to form a tech
To prepare the orthosilicate from a similar
10 grade of water glass and molten caustic soda,
100 parts of the water glass are added gradual
1y with stirring to 170 partsof molten caustic
"soda, the reaction is complete in less than two
minutes, and in ?ve and three-quarter minutes
a dry powdery material is discharged from the
nically anhydrous alkali sub-silicate product, and 15
converting the reaction mass into a solid state.
4. The processv of .claim 3 wherein a sodium
mixer, over 98% of which is soluble in water.
To prepare the sesquisilicate from another type
of water glass, for example one‘having a ratio
of NazO to S102 of l to 2, the following materials
20 are charged into the mixer: 91 parts of water
glass and 841/; parts of molten caustic soda. The
reaction is complete in less than a minute, an
sub-silicate product is formed by the reaction of
molten- caustic soda, containing not more than
approximately 15% water, and a solid, sub 20’
divided, silica-containing material selected from
the group consisting of silica anda sodium sili
excellent free-flowing product being discharged
cate having a molecular‘ratio of S102 to. No.20
from the mixer in about ?ve minutes;
The orthosilicate of soda is prepared from this
greater than 1 to _1.
second type of water glass by
91 parts
of water glass with 126%, parts'of molten caustic
silicate product which comprises adding molten
caustic soda, containing not more than approxi
mately 15% water, and a solid, sub-divided,silica
containing material selected from the group con
minute and a granular product in powder form
is produced in about ?ve minutes. '
.~
sisting of silica and sodium silicate having a 30
molecular ratio of S102 to NazQ greater than 1
to 1, to a reaction vessel, thereactants being‘
present in such molecular proportions that the
,
It is to be understood that products with a
higher ratio of NaaO to S102 than those given
may also be obtained by the use of the solid wa
ter glasses by a comparable process where the
35. ratio is increased as desired, In this case‘also,
other materials such as the phosphates and car
bonates mentioned may be incorporated in the
?nal product.
~
NazO content is not less than the S102’ content, " '
reacting the rnlxture while stirring it at a tem
perature between approximately 300° C. and ap
proximately 500" C. ‘to form a sodium sub-‘silicate
product, and converting the reaction mass into
-
In the foregoing examples, the
olten caustic
a solid state.‘
6. The process of preparing a solid, alkali sub 40
silicate product which comprises adding molten
caustic alkali, containing not more than approxi
mately 15% water; and a solid, sub-divided, silica
soda employedwas approximatel .100% caustic
soda, and it is to be understood that ii molten
caustic soda containing sometwater is used, the
weight .of caustic soda added will be increased
accordingly.
_
containing material selected .from the group con=
sisting of silica and alkali metal silicate‘ having 45
a molecular ratio of S102 to alkali oxide greater
than 1 to 1, to a reaction vessel, thereactants
being present in such molecular proportions that
the alkali oxide content, is not less than the
silicon dioxide content,- and the caustic alkali
‘
Considerable modi?cation is possible in the pro
portions of reactive silica material and water
glass employed, also the temperature of the mol
ten caustic can be varied without departing from
_-the essential features of the invention. ,
I
claim:
.
r
'
5. The process of preparing 'a ‘solid, sodium sub 25
soda, the reaction is complete in less than a
I so
45
.3
2,100,044
glass, the following example may be given: 100
v
containing su?lcient sensible heat to cause a re
1. The process of preparing a solid, alkali sub
action/ between said reactants to form‘ a sub-sili
cate‘ product without the application of further
heat but being at a temperature below the melt
ing point of the reaction product, during said re
action ,stirring the mixture to produce said prod
uct, and converting the reaction mass into a solid
silicate product which comprises adding molten
caustic alkali, containing not more than approxi
mately_15% water, and a solid, sub-divided, silica
containing material selectedfrom the group con
sisting of silica and alkali metal silicate having
a molecular ratio of $102 to alkali‘ 'oxide greater
qthan 1 to 1, to a reaction vessel, the reactants
being present in such molecular proportions that v '7. The process of claim 6~wherein a sodium sub~
the alkali oxide content is not less than the silicon silicate product is formed by the reaction of
molten caustic soda, containing not more than
dioxide content, reacting the mixture while stir
ring it at a temperature, below the melting point approximately 15% water, and‘ a solid, sub
divided, silica-containing material selected from
I of the reaction product, sufficient to form an al
kali sub-silicate product, and converting the re vthe group consisting of silica and a sodium sili
cate having a molecular ratio of- $102 to NazO
action mass into a solid state.
_
state.
greater than 1 to l.
2. The process of _ claim 1 wherein a sodium
'
»
’
8. The process of preparing a solid, technically
anhydrous alkali sub-silicate product which com
sub-silicate product is formed by the reaction
of molten caustic soda, containing not more than
70 approximately 15% water, and a solid, .sub-di
prises adding molten caustic alkali, containing
vided, silica-containing material selected from ' not more than approximately 15% water, and
the group'gconsisting of silica and a sodium sili-‘
cate having a molecular ratio of SiOz to NazO
greater than 1 to 1.
75
,
3. The process of preparing a solid, technical
'
‘a solid, sub-divided, silica-containing material
selected from the group consisting of silica and
alkali metal silicate having a molecular ratio of
Si02 to alkali oxide greater than 1 to 1, to a re 75
2,100,044
, 4
action vessel, the reactants being present in such
molecular proportions that the alkali oxide
content is v‘not less than the silicon dioxide con
tent and the caustic alkali containing sumcient
sensible heat to cause a reaction between said
reactants and to free the mixture substantially
of_ water to form a sub-silicate product without
the application of further heat but being at a a
temperature below the melting point of the re
10 action product, during said reaction stirring the
mixture to produce said technically anhydrous
product, and converting the reaction mass into a
solid state.
sumcient sensible heat to cause a reaction between
said reactants to i'orm'a sub-silicate product with
out the application of further heat but being at a
temperature below the melting point of the re
action product; and during said reaction stirring
the mixture to produce said product in granular
form.
-
16. The process ,of preparing a solid, ‘techni
cally anhydrous, sodium silicate product which
comprises_adding molten caustic soda, containing 10
approximately 100% 119.011 and solid, sub-divided,
sodium silicate having a'molecular ratio 01-810:
to NazO greater than 1 to 1, to a reaction vessel,
'
9. The process of claim 8 wherein a sodium sub- ‘ the reactants being present in such molecular pro
silicate product is formed by the reaction of portions that the NazO content is'not less than the .
molten caustic soda, containing approximately. SiOa content and the caustic soda containing sui
100% NaOH and a solid, sub-divided, silica-con ‘?cient sensible heat to cause a reaction between
said reactants and to free the mixturesubstan
taining material selected from the group consist
,tially
of water to form a sub-silicate product
ing of silica and a sodium silicate having a
20
molecular ratio of SiO: to NazO greater than 1 without the application or iurther heat but being
at a temperature below the melting point of the
to 1.
.
-
,
.10. The process of preparing 'a solidrsodium
sub-silicate product which comprises adding
molten caustic soda, containing not more than
approximately 15% water, and sub-divided silica '
to a reaction vessel, the reactants being present
in such molecular proportions that the HMO con
tent is not less than the S10: content, and the
caustic soda containing su?icient sensible heat to
30 cause a reaction between said reactants to form
a sub-silicate product without the application of
' further heat but being at a temperature below the
melting point 0! the reaction product, and-dur
ing said reaction stirring the mixture to produce
reaction product, and during said reaction stir
ring the mixture to produce said technically an
hydrous product‘ in granular form.
v
17. The process of claim 16 wherein a techni
25
cally anhydrous, sodium sesquisilicate is formed
.by having the reactants present‘in the approxi- ’ '
mate molecular ratio of 1.5 119.20 to 1 SiO:'.-
.
18. The process of claim 16 wherein a techni
cally anhydrous, sodium orthosilicate is formed
by having the reactants present in the approxi
mate molecular ratio of .2 NaaO t0 1 $102.
19. The process of preparing a solid sodium
sub-silicate product which comprises adding
molten caustic soda, containing not more than
15% water, and a solid, sub-dividé
11. The process of preparing a solid, technically approximately
ed, silica-containing material selected from the
anhydrous, sodium silicate product which com ‘ group consisting oi’ silica and sodium silicate hav
prises adding molten caustic soda, containing ap
ing a molecular ratio of $102 to NazO greater than
proximately 100% NaOH and subidivided silica 1' to 1, to a reaction vessel, the reactants being 40
to a reaction vessel, the reactants being present present in such molecular proportions that the
in such molecular proportions that the N320 con
NazO content is not less than the SiO: content,
- tent is not less than the SiO: content and the and reacting the mixture while stirring it in the
caustic soda containing su?lcient sensible heat to . presence of a compound selected from‘ the group
cause a reaction between said reactants and to 0f:.a sodium carbonate, a sodium phosphate, at a
45 free the mixture substantially of water to form temperature, below the melting point of the re-_
. a sub-silicate product without the application of action product,‘ su?lcient to form a granular
further heat but being at a temperature below the sodium silicate product.
_
said product in granular form.
-.
‘
. melting point of the reaction product‘, and during
20. The process or preparing a solid sodium
'said reaction stirring the mixture to produce said sub-silicate product‘ which comprises adding.
technically anhydrous product in granular form. ‘molten caustic soda, containing not more than
' 12. The process of claim 11 wherein a techni
approximately 15% water, and a solid, sub-divid
cally anhydrous, sodium sesquisilicate is formed ed, silica-containing material selected from the
by having the reactants present in the approxi
group consisting or silica and sodium silicate hav
mate molecular ratio of 1.5 NazO to 1 SiO:.
13. The process of claim 11 wherein a techni
cally anhydrous, ‘sodium orthosilicate~ is formed
by having the reactants present in the approxi
mate molecular ratio of 2 NazO to 1 S102.‘
'
14. The process of claim 11 wherein a techni
cally anhydrous sub-silicate product is formed by
having the reactants present in the molecular
’ , ratio or 2 to 40 Naomi $102.
15. The process of preparing a solid, sodium
sub-silicate product which comprises adding
molten caustic soda, containing not more than
approximately 15% water, and solid, sub-divided,
ing a molecular ratio of $102 to NaaO greater than 55
1 to 1, and a material selected from the group
consisting of : a sodium carbonate, a sodium phos
phate, to a reaction vessel, the "caustic soda and
silica-containing material being present in mo
lecular proportions to form a sub-silicate having
a molecular ratio of N820 to $10: not less than
1 to 1, and the caustic soda containing su?icient
sensible heat to cause a reaction between the
caustic soda and the silica-containing material
to form a sub-silicate product'without the ap
plication of further heat but being at a tempera‘
sodium silicate having a molecular ratio of S10:
ture below the melting point of the reaction prod
the reactants being present in such molecular
to produce said'product in granular form.
to Na-.~O greater than 1 to 1, to a reaction ‘vessel, ‘ uct, and during said reaction stirring the mixture
70 proportions that the No.20 content is not less than.
the S10: content, and thecaustic' soda containing
' RICHARD LLOYD DAVIES.
70
, CERTIFICATE _0F' ‘CORRECTION.
Patent No. 2,100,91411,
v
-
,
-
November 50 ,
RICHARD LLOYD DAVIES. -
*
1937 a
'
It ishereby certified that verror appears in the printed specification
of the above numbered patent requiring correction as follows :‘ Pagev 2, first
i‘colmnn; line 12, for‘the word "mixture" read-mixer; page 14., first column, I
- line 67, claim 15, for “8102'” read S102; and that the said Letters Patent
_should be read with these corrections therein that the same may conform
to the record .of the case in the Patent Office.
\
‘Signed and sealed this 26th day of April, A. D. 1938.
.
(Seal)
_
I
Henry Van Arsdale, _
Acting Commissioner of Patents.
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