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Патент USA US2410267

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Patented Oct. ‘29, 1946
' 2,410,267
, STATES- PATENT
GARBOTHERMIGMAGNESIA
l .,
’ I
’ - Altai CZ Byrns,'Lo's Altos, Cali?, as'signor to‘ The
‘
'Permanente
Metals
Corporation,
‘Oakland; .
‘ ‘ Gali?; ‘a’c'orporration of Delaware‘ "
No: Drawing,
Application November; 2%,.1944;
Serial No. 56534231.
.
..
8 Claims.‘ (01. 1657-406)‘
2\'_
advantageous-in-theworkingqup ofsynthetic elas
Thisr invention. relates to. al'product, and proc
tomers. and; of». they latter, exhibits peculiar ad
essfor preparing the; same?forruse in the manu
vantages-Vinthecase ofineoprene.
. factureof syntheticrubber, particularly neoprene.
araticn ottvnitrogen-treel, carbothermic magnesia
and; is an, improvement, ontthe copending' appli
magnesium- with; an. oxide of carboninthe vapor
state.- This proceedsiunder conditions whichprof
duce. rapid: formation and depositionof solid prod
cationeser. No. 527,347, ?ledtMarch 2Q, 1944, en
titled-1 “Product and process for»_manufacturing‘
ucts of reaction,- whereby extremely small par-v
rubbenff and. relating-_ tothe. preparation of car.—_
10 ticlesi; of MgO, are formed. These. particles have
bothermicimagnesia and its use in, compounding
rubben.
v
t
,i
'
’
Garbothermic magnesia. e?ective in the com-_
pounding; of rubbers can be produced vby reacting
Speci?cally the invention-relates to, the prep‘
‘
In... the. preparation of.. manufactured rubber,
orit'Imay‘be said, (if. manufactured~ rubber goods;
for example, tires-,. footwear, ‘or mechanical goods
a carbon». surface “deposition thereon, . the carbon
being bonded.- to; the- MgO,. or are at least co
deposited with carbon which, isv also in a very
highstateiof subdivision. In making‘ this prod
suchasins'ulation, gaskets. or'the like, it is nec 1,5 uct, magnesium inithle - vapor state is reacted with
essary“ to modify the properties of the starting I " an‘oxideoiqcarbonisuch/as carbon monoxide or
carbon. dioxide, For’ example, magnesium can
mate‘ri‘aL, which, may be ‘ rubber ‘or ‘ synthetic ‘elas
bevaporizedlandr while in the vapor state, treated‘
with-a/streamof. carbon monoxide or carbon, die‘
the'production of'rubbers'havingthe most dc‘
sirable' characteristics ‘for certain uses, it“ has ‘long 2o, oxidejtol yield the desiredproduct. ‘In the case‘
of, carbonv monoxide,_ the reaction may beex
been‘ ‘the practice“ to' add certain types of‘ car
bons', zinc oxides, magnesium oxi’d'es,‘organic'acj
pressed;as.follows:w
‘
celerat‘ors and'thellike in the compounding of ‘the
Mg+C0i->MgO+C
toiner,.or to impart new properties'thereto. In‘
rubber: The best“ methods“ for ‘ adding ' theseivari
ous ingredients and‘the‘ proper’ types of'ingredi 25 and in' the” caseoffcarb'on dioxideythe' reaction“
may‘ proceed stepwise; .?'rst reducing the" dioxide
ents for addition to ‘various rubbers have'b‘een
the .sub'j ect' of‘ considerable.investigation: As" one
to; the‘ monoxide‘ and" then to‘ carbon‘ or it may‘
amplei't has’ been theexperiencein the‘neoprene'
?eldtha-t it is‘ne'cessary, t'o'add; in‘- compounding,
In? thecarbothermic'process, magnesium oxide or:
other'suitableimagnesium compound and: a'carbo'-~
proceed’ more‘ directly; but the final product will
instance; ‘a ' great‘- deal" of vvattention has “been_ given:
contain magnesia and‘ carbon‘ ‘as' described.
to, the; proper magnesia‘ addition~ and numerous‘
products‘ and‘ methods‘ have“ been"v devised‘v in" or” 30 Carbothermic magnesia" effective in- the com-'
pounding of‘ rubibers can‘ also be obtained‘;' for"
d'er‘t'o getfthe'desired‘degree‘oi dispersionsofmag=
nesia in rubbers and" toge?themaximum.bene'e' . example; as'a' result or‘ the manufacture v‘of mag
nesium“ by; the' so-called‘ carbothermic process.
?cia'l‘ effects from“ the" magnesia‘ added. - some
' naceous- reducing agent such'as coke arereactedi
a‘ magnesia‘ which" has‘ a; ‘high speci?c surface;
in an electric furnace at a suitably hig-h- tem
The disadvantage has also been encountered; how-J
perature; preferably‘ around- 2000" (3., to yield
ever; that" the" greater‘ the‘ degree of subdivision
magnesium and- CO; according‘to‘the following
of‘ the ‘magnesia; the‘ quicker ‘it will" hydrate‘ and
this undesirable" feature" has‘l‘edto- difficulties in 40
equation:
handling‘:
'
According" to; the- above-~ mentioned; c'opending
application it’has' beendiscovered-that the prop-1
vorablyaiTected‘by;compounding:thesstarting:ma_
products ‘known: 1 as ‘ ‘.‘carbothermictv . . magnesia.”
‘
‘
'
Mg-O'q-UéMeH-CO
This} process, has: been described by I-Iansgirg, in
erties- off‘the' rubb'erl starting-J: materials 1 are fa‘
teriali vwith a -_magnesia.\ and a carbon; containing
'
45,
U}, SLY 1,884,993?v and.1,943,'601',.and1by others. As
indicated; thisi‘reactionis. reversible. ,ItIis-dis
placed tow'ar'dlthe ri'glitb'y high temperatureslandv
thusis forwardedib'y, the-indicated high tempera
tureof. reaction... Asthe vaporous products of’
reacti'ompass, out of. thereactionzone they are.
which is obtained by the reaction of magnesium
chilled? as . rapidly,‘ aspossibl'e. in, a, stream of? an“
with; a carbon oxideto. give MgO: and, carbon or
asfa residue from the distillation-oi thes-crude, 50 inert quenchlgas'~ to condense. theMg as a solid"
magnesium; condensate produced in, the; carbo-,
andéto reducethe tendency of. the reaction. tore-v
verse towards the left; or to back-react“ Eyen
thermic processfor makingmagnesium as. will
withsuch precautions,.some of the M'gistback
be; described-'more' fully below. My process of.
compoundingibythe addition of. the aforesaid mag
reactedwith the'COto'giveMgO andcarbom v
nesia and? carbon. containing-product. is- especially 55 Thus, .‘the crude. condensate from, this ‘reaction
2,410,267
3
4
-
,
preparation of the raw carbothermic magnesia,
contains metallic magnesium, MgO, carbon, and
small amounts of other compounds such as car
or as in the case of the residue of the distillation
hides and nitrides, the latter arising from reaction
of the magnesium, for instance, with the nitrogen
used in cooling the glands at the site of exit from
the furnace, or reaction zone,’ or from traces of
step of the carbothermic process, by reaction with
the nitrogen which may comprise a substantial
amount of either the ?ushing gases or the cool
ing gases used in the furnace where the material
tobe distilled is prepared. The nitrogen com
nitrogen present in the quenching gas. The con-‘V
pounds generally comprise magnesium nitrides
densate also contains whatever concomitant ma;
which are hydrolyzed upon contact with the water
terials in the furnace feed are carried over in the _
reaction, such as unreacted MgO and C, CaO 10 present in the rubber mixes to be compounded
and the like. This crude condensate now goes to
a distillation zone where the Mg is vaporized off
' giving riseto ammonia.
, It is an object of the present invention to pro
vide a substantially. nitrogen-freev carbothermic
and the other materials are left behind as va'prode
magnesiaand'a process of preparing the same.
not containing magnesia (MgO) [carbon and small
'
amounts of other substances as described above.
It is a characteristic of the product obtained by,»
It ‘is another object of the invention to provide
. aproduct which is suitable for use as an acceler
the back-reaction of Mg and CO that the particle ‘ u .i
ator or pigment in rubber, particularly neoprene
size thereof is extremely small, and. it further-.
grades.
‘
In the practice of the present invention the
more appears that the particles consist of "an MgO
nucleus upon which a carbon surface deposition 20 nitrogen compounds of" the, raw carbothermic
magnesia are substantially completely removed
is rather ?rmly bonded. Microscopic investiga-I
by hydration of the magnesia ‘contained- therein,‘
tion has shown that the predominant particle
size is below one micron in diameter in the back
drying and calcining the resultant material, and‘:
then grinding, all under controlled conditions.
reacted materiah However, since, larger particles
of unreacted MgO and C, as well as other sub
The hydration step may be carried out in sev
stances in larger particles, are also found in the
crude condensate and therefore in the distillation
residue, it is usually found to be advantageous to
grind the distillation residue and air classify the
ground material so that it preferably passes
eral ways. Effective‘methods comprise submer
sion in water, or spraying with water, or treating
with water vapor. However, regardless of the
methodemployed, the treatmentshouldlbe con
ducted in such a manner and for such a length
through a 325 mesh screen. This sizing, of course,
of time until the magnesia is substantially com
relates onlyito the largest particles of anyftype
found in the distillation residue. The character
istics of the particles formed by the back-reac
tion are not changed or lost by the operations, 35
pletely hydrated and the ammonia producing
such as pelleting or‘ impasting, incidental to the
distillation of the magnesium from the crude con
densate.v The grinding and air classi?cation are
compounds are completely reacted.
Obviously,
the concentration of the ammonia'producing sub
stances controls the length of the water treat
ment. The amount of water used in effecting hy-'
dration by the submersion method should be in‘
excess of that stoichiometrically required, and
effective in breaking up grit,‘ oraccompanying . the amount .used in the spray method‘i's prefer
materialsjas described above',,and in breaking 40 ably 50 to 1001 per cent of the quantity of carbo
down the extraneous bonding effect which vhad
thermic magnesia treated. Considerable heat of
been produced in the pelleting‘ or impasting;
reaction,is"'developed' in ‘this hydration step and
thereby restoring the discrete particles to their
in any event the quantity of water added should
be sufficient t'ocompensate for the resultant vva
original state. , The product is black in color.
7 It’ is believed that the compounding of rubbers
porization.
with carbothermic magnesia owes its advantages
in-some measure to the "extremely small particle
size of the magnesia, not obtainable by the usual
'
,
'
‘x
‘
'
'
Raw carbothermic magnesia, particularly asv
produced in the distillation step'lof the carbo
thermic process, is generally contaminated with
methodsnof milling, grinding or the like. Carbo
traces of calcium carbide and magnesium carbide
thermicr magnesia tends to be less hygroscopic, 50 as well as sulfur. The'acetylene which is pro
and is more effective than other known magnesiai
products when compared by weight in the com
pounding of rubbers. Furthermore, it is believed
that the carbon present is important in promot
ing dispersion and in reducing the tendency to
hydrate.
duced from’ the reaction of the carbides, and
the sulfur odors are both objectionable in rubber
compounding. However, the hydration step of
the invention is effective in removing these con
55 stituents as 'well as the nitrogen-containing com
T
pounds.
Carbothermic magnesia, particularly that ob
tained as a residue ofv the distillation step for
. the production of metallic magnesium as ac
cording to the above enumerated Hansgirg pat
ents contains certain nitrogen compounds, such
as' magnesium nitride, which yield‘ ammonia in‘
the compounding operation and whichmay be
of advantage under certain conditions. ‘On the
other ‘hand, nitrides and other nitrogen yielding
compounds are disadvantageous in certain oper
ations because uponthe formation of ammonia
'
‘
.
‘
'
The hydrated carbothermic magnesia is dried
and calcined to remove the combinedwater. This
treatment;v may be carried out in air or in an in
60
art atmosphere, although a reducing atmosphere
is preferred for calcining. The‘ pressure. is not
critical and atmospheric pressure is preferable.
The temperature, of the drying and, calcining
treatment may vary within the range of 1000 to
150051“. Obviously, the time required for drying
and calcining willbe less atv the elevatedtempera
premature aging or curing of the milled rubber
> The carbothermic magnesia that has been thus
stock sets in'necessitating,immediate fabrication
and preventing storage of portions of milled 70 treated, i. e. hydrated‘ followed by drying and cal
cining, is next cooled by ‘dry air or inertgases"
batches of any substantial’ period of time with
to a temperature at which it may be safely ground
out curing.
'
'
(450° F. or under); The material may then be
' The objectionable nitrogen compoundsare gen?
ground and air classi?ed until less than one per
erally formed from the nitrogen which occurs as
an impurity in the oxide ‘of carbon used in the 75 cent remains on a 325 mesh screen. The latter
tures.
I
3
'
'
_
'
>
'
v
6
treating. the canbothermicimagnesia with; a war;
terkrepelr'lantvagemi 'oiiitlr saturated’ fatty acid
such as stearic
_ '
y Mgsrln-imraw‘ arb'o'tlier
assrecoverecli-fromitheir
"
.
Having now described the invention: w-haétris
' imagines-ta
Iu'e ofithef ‘still'ation
claimed".is‘:v
'
'
l
~l ll. Th‘ei process. oficlaim
‘step; ‘of, the carbothermic‘ process‘ for ithef-produc
tionwolfg ( ,talli‘cnmagnesium varies, butii’slgeneré
ally‘ on‘ theorder of approximately 0.5 per cent
..
I
" 7-.
91
wherein: the‘:- drying
' " 'aIciniing-is. carrije ' out; in an atmosphere.‘ of
ij'§_i'.. ~ .. "1
..f;!.'
"
:f f}.
I.
'5112t-1Eh6i'processof'claimi i’iwhereini'the drying
calculated as equivalent NH3. On the other hand
the product obtained by the process of the inven 10 and calcining is carried out in a reducing. at
mosphere.
tion is substantially completely free of nitrogen
3. A process for the removal of nitrogen from
compounds, and'if any is present the amount
will be insu?icient to be objectionable in rubber
carbothermic magnesia including magnesium ni
tride as impurity, said magnesia being obtained
.01 to .03%.
15 in the carbothermic process for making magne
sium metal wherein nitrogen gas is present and
Having described the product of the invention
available for reaction with the condensing mag-.
and methods for its preparation, an example
nesium, which comprisestreating said carbother
thereof and an illustration of the improved
compounding, that is on the order of less than
mic magnesia with water until the magnesium
results obtained by compounding in rubber will
now be described.
20 nitride contained therein is substantially com
-
pletely hydrolyzed to produce ammonia, drying
A 13.2 lb. sample of raw carbothermic magne
and driving off ammonia, and calcining the so
sia occurring as a residue of the carbothermic
treated material.
process for the production of metallic magnesium
4. A process for removing nitrogen from car
and having an ammonia content of 0.54 per cent
was soaked in an equal weight of water until the 25 bothermic magnesia including magnesium ni
tride as impurity, said magnesia being obtained
magnesia thereof became completely reacted.
‘in the carbothermic process for making mag
Thereafter, the material was heated gently for
nesium metal wherein nitrogen gas is present and
several hours to remove most of the excess mois- '
available for reaction with the condensing mag
ture present. The partially dried hydrated sam
ple was calcined in a retort at a temperature of 30 nesium», which comprises soaking said magnesia
in water until the magnesium nitride contained
1000° F. for a period of one and one-half hours
therein is substantially completely hydrolyzed to
after having been gradually brought up to that
produce ammonia, and drying and driving o?
temperature. The calcined product was cooled
‘ ammonia, and calcining said carbothermic mag
in dried air, pulverized, in a disc pulverizer,
ground in a hammer mill, and air separated. 35 nesia.
5. A process for removing nitrogen from car
The recovered material had an ammonia con
bothermic magnesia including magnesium ni
tent of less than 0.01 per cent.
tride as impurity to render it suitable for use in
> The table below illustrates the marked differ
compounding synthetic rubber, said magnesia
ence in curing time between neoprene stock con
taining raw carbothermic magnesia (sample A) 40 being obtained in the carbothermic process for
making magnesium metal wherein nitrogen gas
and neoprene stock similar in all respects except
is present and available for reaction with the
that it contains carbothermic magnesia '(sample'
condensing magnesium, which comprises treat
B) treated in accordance with the invention.
ing said magnesia with water until the magnesi
Table
45
Min.
U21
um nitride contained therein is substantially
completely hydrolyzed to produce ammonia,
drying and driving off ammonia, and calcining
said dried material, and thereafter grinding said
dried and calcined carbothermic magnesia until
O! o a majority of the particles thereof will pass
through a 325 mesh screen.
6. A process for making nitrogen-free carbo
thermic magnesia of lowered hygroscopicity and
for use in compounding synthetic rubber from
carbothermic magnesiaincluding magnesium ni
tride as impurity, said starting magnesia being
obtained in the carbothermic process for making
magnesium metal wherein nitrogen gas is pres
ent and available for reaction with the condens
133 min.
2 61 min.
ing magnesium, which comprises treating said
60
starting magnesia with water until the magnes
The ?gures in the table were recorded in a
ium nitride contained therein is substantially
Mooney plastometer where the temperature of
completely hydrolyzed to produce ammonia, dry
the plastometer was 220° F. and the ?rst read
ing was taken after a one minute warmup.
ing and driving o? ammonia, and calcining said
It has also been demonstrated that neoprene 65 treated magnesia, grinding said dried and calcined
carbothermic magnesia until a majority of the
stocks similar to sample B identi?ed in the table
particles thereof will pass through a 325 mesh
give improved tensile strength at break and
screen, and surface treating said carbothermic
elongation at break while hardness is satisfac
magnesia with a saturated fatty acid.
tory, as compared with sample A. i v
'7. As a new composition of matter, carbother
The surface activity of the product of the in 70
mic magnesia, said magnesia having been ob
vention may be rather high due to the extreme
tained in the carbothermic process for making
ly small particle size. One evidence of this sur
magnesium metal wherein nitrogen gas is present
face activity is that the product tends to hydrate
and available for reaction with the condensing
rapidly in a moist atmosphere. The rate of hy
dration may be greatly decreased by surface 75 magnesium to form magnesium nitride, which
2,410,267
8
7
has been treatedto substantially completely hy
drolyze the magnesium nitride contained therein
to produce ammonia, dried to drive of! ammonia,
and'c'alcined.
-
-
8. As a new composition of matter, carbother
mic“ magnesia, said magnesia having been ob
tained‘ in the carbothermic process for making
magnesium metal wherein nitrogen gas is present
and available for reaction with the condensing
magnesium to form. magnesium nitride, which
has been treatednto substantially completely by
drolyze the magnesium nitride contained therein
to produce ammonia, dried to drive o? ammonia,
and calcined, said dried and calcined magnesia
having a surface-protective coating of saturated
fatty acid.
I
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,
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ALVA C. BYRNSL
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