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Патент USA US2111342

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Patented Mar. 15, 1938
' 2,111,342
' UNITED’ STATES PATENTv OFFICE
2,111,342
CAUSTIO RESISTANT MATERIAL
William F. Waldeck, Wadsworth, Ohio, assignor
,to Pittsburgh Plate Glass Company, a corpora
tion of Pennsylvania
No Drawing. Application October 2, 1938,
Serial No. 103.781
5Claims. (Cl. 23--240)
The present invention relates to the provision The concentrated material is then charged into.
of a material suitable for the coating of, or for tank cars or other containers for shipment.
In the manufacture of many products, such as
the manufacture ,of, containers and other appa
ratus employed in the manufacture, storage, soap and rayon, caustic of high purity and low
5 shipment, and use of chemical materials, and'it color is desirable or absolutely necessary. For 5
this reason, most of the hydrated caustic is sub
has particular relation to compositions for coat
ing containers and other apparatus employed in jected to careful purification prior to shipment in. >
order to eliminate such impurities as iron com
connection with the manufacture, storage, ship
pounds, manganese compounds, and the like. ment, or use of concentrated solutions of the hy
However, it is found that the caustic even of 50 10
10 droxides of the alkali metals.
One object of the invention is to provide a to 75 per cent concentration under the conditions
coating material which readily 'adheresto the
of storage, by shipment tends to absorb objection-V
surfaces of metals and other materials used in
the manufacture of ‘apparatus for storing or
15 otherwise treating concentrated caustic solutions
to form ?lms which are highly resistant to the
caustic even for relatively long periods of time.
' Av second object of the invention is to provide
a coating material of the above described char
able amounts of iron 'and manganese from the
20 acteristics, which is composed of inexpensive in
gredients and which may be applied to, or formed
into, various embodiments of apparatus adapted
for contact with caustic solutions, vby the simple
25
and inexpensive methods employed in connection
with paints, lacquers and various resinous'ma
terials;
'
"
‘ These and other objects will be apparent from
30
containers.
-
Heretofore no entirely satisfactory method of 15
eliminating this objectionable ‘attack upon the
iron of the containers has been available. ‘The
application of highly resistant coatings, of course,
suggests‘ itself, but vmost materials suitable for
coating purposes are inapplicable. Nickel linings 20
have been tried and are found successfully to
withstand corrosion. However, the cost of nick
el coating a_ single tank car amounts to several
thousand dollars andfor that reason is prohibi
tive. Ordinary coating materials, such ‘as natural 25
and arti?cial resins, rubber, and the like, are of
littleor no value because they do not withstand
consideration of the following speci?cations and
the attack 01’ caustic for any substantial period
the
of time. a In many instances,- they are within
appended
claims.
‘
‘
~
‘
'
The hydroxides of the alkali metals, notably
sodium hydroxide, are usually obtained by elec
troiysis of a salt, such as sodium'chloride, or by
causticization of a carbonate, such as sodium
carbonate, by contact with an aqueous'solution
35 or suspension of lime.‘ Such solutions of hydrox~
ides are normally of a concentration of about 8 to
12 per cent, which for most industrial applica
tions is so dilute as to necessitate further concen
tration. Further concentrationis also necessary
40 because the large percentage of water present in
the dilute solutions would render shipping costs
exorbitant. Accordingly, it is customary to evap
orate as much water as is practicable from the
solution. By ordinary methods of evaporation,
45 solutions of 50 to '70 per cent concentration may
be obtained withcomparative ease. However, as
the concentration further increases, the vapor
pressure is rapidly reduced and the heat require
ments for'the evaporation of water from the
50 solution becomes excessive. Furthermore, the
concentrated solutions ‘of caustic become ‘ ex
tremely corrosive and'no apparatus now avail
able -will satisfactorily withstand the action of
55 the caustic during the later stages of dehydra
tion;
.
'
For many purposes, caustic of 50 to '70 per
cent concentration is quite satisfactory and for
that reason, in many instances, the concentra
60 tion of the caustic is stopped within that range.
‘
themselves objectionable because they tend _fur- 3o
ther to contaminate the product.
The present invention involves the discovery
that certain cellulose ethers, notably ethyl cellu
lose, when applied as a coating material to con
tainers used to store or ship caustic, or when .,
otherwise employed to form the surface of appaé "
ratus, exhibits a remarkable degree of resistance
to the action even of highly concentrated solu
tions of caustic soda. In fact, in some instances,
it is observed that the higher concentration of the 40
caustic solution, the more resistant is the cellu
lose. ether in contact therewith.
"
The cellulose ethers are, within themselves, of
conventional character and the methods of man
ufacturing ‘and treating such materials are well 45
understood by those skilled in'the'art and do not
require discussion.
I‘
,
Cellulose ethers, such as ethyl cellulose, may
be employed without modi?cation in the coating
or formation of caustic resistant containers and 50‘
apparatus, but if desired, it may be modi?ed by
the addition of suitable plasticizers and ‘pigments
and the like. Care must be exercised in the se- ,
lection of the modi?ers because most of the mod-;
ifying agents conventionally employed in ordi- 55
nary lacquer forming resins are, within ,them
selves, susceptible to solution in, or decomposition
by, concentrated caustic solutions.
Practically any volatile solvent for ethyl cellu~
or the. other cellulose ethers which may be so
I
2
2,111,342
employed is applicable in the preparation of solu
obtained by the inclusion of from 10 to 25 per
tions suitable for most coating operations. The
following constitutes a speci?c example of one
such solvent composition.
Parts
cent of ground mica or asbestos or the like.
Alcohol
,
'
__
..
21.5
Xylene __________________ __-__.._ _______ .__ 46.2
Acetate of monomethyl ether of ethylene
glycol-
,
‘
'
6.5
Toluene ____________________________ “s- 25.8
The ethyl cellulose is preferably dissolved in the
solvent mixture to form a solution containing
6 to 15 per cent of ethyl cellulose. The propor
15 tions of the ethyl cellulose may be varied over
a wide range, but in general, it is desirable to
add as much as is conveniently practicable with
out the viscosity of the resultant solution be
coming too high. The various components of
the solvent may likewise be subjected to various
Ethyl cellulose is highly suitable for coating
surfaces of iron or steel, such as those of tank
cars, to prevent corrosion by caustic soda solu
tions. However, it can also be applied to any
other common metal, such as copper, aluminum,
zinc, etc., which may be exposed to the action
of the solutions. Similarly, glass, porcelain, rub
ber, wood, and other materials may be coated to 10
obtain a resistance to caustic., In some instances,
it is desirable to give the metallic surfaces a pre
liminary treatment in order to improve adhesion
between the cellulose ether and the metaL- Proc
esses involving the application of a phosphate of
a metal, such as zinc, cadmium, or the like, are
‘quite suitable. Numerous methods of applying
such treatments are available and practically any
parent that the solvent does not constitute a per
of these which provide uniform phosphatic coat
ings may be employed. Excellent results are ob
tained by application of a zinc phosphate coat
ing by means of an alternating electrical cur
rent. Details 'of this process may be obtained
manent element in the caustic resistant ?lms, but
from British Patent No. 435,773.
instead it is eliminated by evaporation so that
Masses of ethyl cellulose, either 'alone or ad 25
mixed with plasticizers or pigments, may be
molded or otherwise shaped into apparatus for
modi?cations without departure from the scope
of the present invention. It‘ is, of course, ap
there is practically no restriction placed upon the
selection of a solvent. ‘Accordingly, any mate
rialvwhich is a volatile solvent for the cellulose
ether is applicable.
30
The modes of application of the cellulose ethers
treatment oi’ caustic.
‘
The use of ethyl cellulose in the coating or
formation of apparatus (for handling caustic so 30
. are conventional and involve brushing,» spraying,
lutions has been speci?cally discussed, however,
and dipping. In some instances, it may be de
ethyl cellulose may be replaced by other cellu
sirable‘ to pre-form suitable, ?lms of ethyl cellu
losic ethers, including methyl cellulose, butyl cel
lulose, benzyl cellulose, mixed cellulose ethers,
lose or the related cellulosic ethers and then to
apply the ?lms to the surfaces which are to be
‘protected by application of heat and pressure, or
by use of adhesives, or any other convenient
method.
‘
v
p‘
,
4
The ?lms are highly inert even to caustic so
40 lutions of 70 per cent or higher concentration at
temperatures up to or above 100 deg. C._, As pre
viously stated, ?lms ‘of yery high resistance to
attack even by the most concentrated solutions
of caustic may be prepared without the‘ use of
45 any permanent modi?er for the cellulose ethers.
such as ethyl-benzyl cellulose, and the like. Mix 35
tures of any two ‘or more of these latter ethers
witheach other and with ethyl cellulose may
I likewise be employed.
Coatings of cellulosic ethers will withstand the
action of caustic soda solutions over a long pe 40
riod of time. Upon eventual failure of the coat
ing material under the action of aqueous caustic,
the residual ?lms may be removed in any con
venient manner, for example, by solution, scrap
ing or by abrasion, and may then be replaced by 45
However, if desired, the plasticity ‘and water re
sistance may be increased by incorporation of
new ?lms.
suitable inert plasticizers. One convenient and
satisfactory plasticizer is obtained by the chlori
vention have been described, it will be apparent
to those skilled in the art that these are merely
50 nation of diphenyl.
Products suitable for the
purpose are sold under the trade name of “Arc
chlor". , These compounds are quite compatible
with ethyl cellulose and also exhibit a high de
gree of resistance to the action of concentrated
caustic. Practically any amount of chlorinated
diphenyl up to 30 or 40 per cent based upon the
content of ethyl cellulose may be employed. In
some cases where maximum resistance to the
action of caustic is not required, the ?lms of cel
lulose ether may bemodi?ed by the addition of
,a suitable natural or arti?cial resin.‘ Soluble
phenol-formaldehyde resins, known as “Am
berol" resins, may be added to the ethyl cellu
lose. The latter resin may be employed in
65 amounts up to 20 or 30 per cent or even higher.
These modifying resins within themselves do not
increase caustic resistance of the ?lms. How
ever, they do enhance certain desirable properties
of ethyl cellulose, notably adhesion and water
to ‘resistance.
Pigments, if inert, may likewise be incorporated
into the cellulose ether. Good results have been
‘
Although only the preferred forms of the in
exemplary and that numerous modi?cations may 60
be made therein without departure from the
spirit of the invention or scope of the appended
claims.
What'I claim is:
V
1. A‘ method of preserving caustic soda of .at 55
least 50% concentration, in metallic containers,
from contamination by the metallic surfaces,
which comprises applying to the surfaces ?lms
of a cellulose ether.
'
2. A method as de?ned in claim 1, in which
the cellulose ether is ethyl cellulose.
3. A process as de?ned in claim 1, in which
the cellulose ether is admixed with an inert pig
ment.
4. A method as de?ned in claim 1, in which 65
the cellulose ether 'is admixed with ?nely divided
mica.
.
5. A process as- de?ned in claim .1 in which
the metallic containers are composed essentially
of iron.
WHLIAM 1". WALDECK.
70
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