Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a process for making
phosphorus pentasulfide (P2S5) of low reacttvity, wherein
molten P2S5 is caused to solidify in a cooling zone, the
solidified P2S5 is maintained for some time at temperatures
lower than its melting point t then cooled to temperatures
lower than 65C and ground. The invention also relates to
an apparatus for carrying out this process.
A feature of great importance in the processing of P2S5
is its "reactivity". An index of the reactivity of P2S5
is the reactio~ heat, expressed in C/h, which is set free
during the reaction of P2S5 with an alcohol~ e.g. ethyl
hexanol.
The various types of P2S5-material can be classified as
belonging to high an~ low reactivity P2S5, respectively.
High reactivity P2S5 is obtained by causing a P2S5-melt
to solidify rapidly at a temperature lower than its soli-
dification point, and low reactivity P2S5 is obtained by
allowing the melt to solidif~ gradually in a relatively
large container.
In a plurality of processes, it is obligatory to use
P2S5 of which the reactivity lies between that of highly
reactive P2S5 and that of low-reactive P2S5. Various pro-
cesses for making such P2S5 have already been disclosed
in the art.
U.S. Patent 3 146 069 discloses a proc2ss, wherein high
ly reactive P2S5 is heated to temperatures of 150 to 250~C
and annealed at that temperatures, the reactivity of the
resulting products decreasing with increasing annealing
temperatures. U.S. Patents 3 023 086 and 3 282 653 disclo-
r~
se processes, wherein use is made o~ various coolants or cooling
zones which make it possible for P2S5 to be passed throu~h the
liquid-solid phase transformation interval at temperatures within
the range 280 to 260C ~ithin controlled and predetermined periods
of time. P2S5 so made has a reactivity which is the lower the
longer the cooling periods selected for passing through the above
interval.
Another process has been described in United States
Patent 3,183,062, wherein solidified P2S5 is given a certain
reactivity by maintaining the P2S5 over a sufficient period of
time at a temperature between 190C and the melting point of
P2S5 by means of a heat-supplying heat exchanger material.
An adverse effect which has been found to be common to
all of the prior art processes just described resides in the fact
that it is necessary for solidified P2S5 to be supplied with con-
trolled quantities of heat or for controlled quantities of heat
to be abstracted during the solidification of P2S5 so as to obtain
final P2S5 of predetermined reactivity. Also, it is necessary in
the above prior processes to use expensive machinery for the
control of the reaction.
Applicants have now unexpec-tedly found that the high
reac-tivity which is typical of P2S5 obtained by causing it to
solidify rapidly in a cooling device, e.g. on a cooling cylinder,
can be reduced without the need to transmit additional energy to
solidified P2S5 and use expensive machinery.
In accordance with the presen-t invention therefore, there
is provided a process for makins phosphorus pentasulfide of low
reactivity, wherein molten phosphorus pentasulfide is caused to
solidify rapidly in a cooling zone, the soLidified phosphorus
pentasulfide is main-tained for some time a-t temperatures lower
than its melting point, cooled down to temperatures of less -than
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65C and ground, which comprises: introducing the solidified
phosphorus pentasulfide coming from the cooling zone with a
temperature of 150 to 220C into a heat-insulated tank and
abstracting therein the immanent heat by controlled cooling at
a rate of at most 30C/h with the resultant formation of final
phosphorus pentasulfide of which the reactivity is the lower the
lower the rate selected for cooling.
In another aspect, there is provided an apparatus for
making phosphorus pentasulfide of low reactivity from molten
phosphorus pentasulfide, which apparatus comprises a cooling
device for cooling molten phosphorus pentasulfide, said cooling
device being provided with a supply line for supplying molten
phosphorus pentasul~ide to a surface of the ~ooling device and
with a scraper for removing solidified phosphorus pen-tasulfide
from said surface, the cooling device being connected to a
sojourn tank communicating via locking means with a cooling tank
wherein the sojourn tank comprises a tank which is heat-insulated
to an amount sufficient for controlled cooling of contents there-
in at a rate of at most 30C/h.
Thus the present invention relates to a process for
making phosphorus pentasulfide of low reacti-
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vity9 wherein molten phosphorus pentasulfide is caused
to solidify rapidly in a cooling zone, the solidified
P2S5 is maintained ~or some time at temperatures lower
thar, its melting point, cooled down to temperatures of
less than 65C and ground, which comprises: introducing
the rapidly solified P2S5 coming from the cooling zone
with a temperature of 150 to 220C into a heat-insulated
tank and abstracting therein the immanent heat ~y con-
trolled cooling at a rate of at most 30C per hour.
Next, the product is delivered to a reservoir, which
is kept in thermal eauilibrium with the atmosphere, and
allowed to cool therein do~m to temperatures of less than
65C, then ground and packed. P2S5 which is so produced
has a reactivity which is the lower the lower the cooling
ve ocity inside the heat-insulated tanX.
Considering the prior art, the skilled artisan would
not have expected the immanent heat of P2S5 at temperatures
considerably lower than the solidification in-terval of
P2S5 to be sufficient for effecting the crystallization
of P2S5, whereby its reactivity is ultimately reduced
and this without any use o~ additional energy.
The invention also relates -to an apparatus for carrying
out the present process~ which is shown diagrammatically
and by way of example in the accompanying drawing.
As can be seen, this is an apparatus of the kind wherein
a device 1 for cooling molten P2S5, preferably a cooling
cylinder, is provided with a line 2 supplying molten P2S5
to, and with a scraper ~ removing solidified P2S5 from,
the surface of the cooling device 1 which is connected
to a sojourn tank 4 communicating via a locking means 5
'7rd
with a cooling ta~k 6 kept in thermal equilibrium with the
atmosphere.
Our present inve~tion pro~ides for the sojourn tank 4 to
comprise a heat-insulat~d tank, which preferably is a Dewar
5 vessel~ or for it to be lined wi~h heat-retaining material.
Dependi~g on the velocity selected ~or cooli~g the phos
phorus pentasulfide, use is made of a more or less ef~ectiJ
~ely heat-i~sulated so~our~ ~essel 4.
The following Examples illustrate the invention. In the
10 Examples, the reactivity was determined as the gradient of
the temperature~time-straight lin~, which was produced by
placing 50 g o~ pul~erulent P2S~ in a calorimeter which
had 100 g of ethyl hexanol at 30C placed therein.
EXAMPLE 1: (Comparative Example)
By means of a scraper, scaly P2S5 was removed from a coo-
ling cylinder at a temperature o~ 208C, cooled down to
about 80C within 2 hours in a customary tank, and groundO
The ground P2S5 had a reactivity o~ 47C/h.
EXAMPLE 2:
By means of a craper, scaly P2S5 was removed ~rom a coo-
ling cylinder at a temperature of 207C and placed for 2
hours in a Dewar vess~l; the temperature dropped dow~ to
160Co Next, the P2S5 was cooled within 1 hour down to 50C
and pul~erized. The pulverulent P2~ had a reactivity o~12~hh
EXAMPLE ~:
By mean~ of a ~craper,scaly P2S5 was removed from a coo-
li~g cylinder a~ 207~C and placed for 2 hours in a contai~
he~t insulated with heat-retaining plates;the temperature
dropped down to about 15~C.Next,the P2S5 was cooled do~n to
30 6d~ within 2 hours and ground.The ground P2~ had a reæ~ity
of 22C/h
EXAMPLE 4:
By means of a scraper~ scaly P2S5 was removed from a
cooling cylinder at 167C and placed for two hours in a
Dewar vessel; the temperature dropped down to 110C. Next,
the P2S5 was cooled down to 50C and pulverized. The pul-
verulent P2S5 had a reactivity of 26C¦h.
EXAMPLE 5:
By means of a scraper, scaly P2S5 was removed from a
cooling cylinder at 205C and placed for 1 hour in a Dewar
vessel; the temperature dropped to 180C. Next, the P2S5
was cooled within 2 hours down to 60C and ground. The
ground P2S5 had a reactivity of 15C/h.
EXAMPLE 6:
By mea~s o~ a scraper, scaly P2S5 was removed from a
cooling cylinder at 167C and placed in a Dewar v~ssel over
4 hours;the temperature dropped to 85~C. Next, the P2S5 was
cooled within 1 hour down to 50C and ground. The ground
P~S5 had a reactivity of 23C/h.
