Note: Descriptions are shown in the official language in which they were submitted.
10 ~ ~ O.Z. 31,453
MANUFACTURE OF FOAMED SULFUR
It is known that foamed sulfur, which may be used, for exam~e,
as insulating material in the building industry, may be prepared
by melting elementary sulfur and then blendlng the molten sulfur
with a stabillzing agent and a viscosity increaser. Bubbles are
then formed in the melt, for example by the passage of a gas there-
through, evaporation of a solvent or by means of a blowing agent,
whereupon the mixture is cooled to below the melting point of sul-
fur (U.S. Patent 3,3~7,355). Examples of agents used for increasing
the viscosity of the molten sulfur are phosphorus and arsenic or
sul~ides thereof, styrene and elastlc, rubbery and thermoplasti¢
plastlcs materlals of the alkyl polysulfide group such as those
which are known under the tradename of Thiokol and whlch are ob-
tained by the action of alkall metal polysulfides on alkyl dihalldes
and subsequent partlal ellmlnation of sulfur or by the reaction of
dlchlorodlethyl formal with sodium polysulfide. The stabilizing
agents used to stabilize the foams formed are partlculate inert
substances of plate-like form, for example mica, alumina, talc,
aluminum oxlde and slllcic acid, or organlc substances such as the
coupling product between diazotized p-nitroaniline and acetoacet-
anilide. Examples of blowing agents which can be used are carbonate/acld systems, for example CaCO~-H3P04, or sulfide/acid systems or
compounds giving off, say, nitrogen on heating, such as N,N'-di-
methyl-N,N'-dinitrosoterephthalamide, N,N'-dinitrosopentamethylene-
tetramine and diphenylsulfone-3,~'-disulfohydrazide, or physical
blowing agents such as chlorinated and fluorinated methanes or
ethanes~
German Published Application 2,324,185 describes a process for
the manufacture of foamed sulfurs, in which aromatic polysulfides
-1- ,~
: .
lOt~Z8SO
are Eoamed an~ cross-linked. In this process the viscosity
increasers ad~ed to the molten sulfur are aromatic hydroxyl-
containing compounds which forrn aromatic polysulfides with
slll rur . 13ubl)1es a~e formed in thc molten matcrial by the addi-
ti~n of proton donors, e.g. water or organic acids, and with
isocyanates or polyisocyanates.
Finally, German Published Application 2,340,927 des-
cribes a method of preparing foamed sulfur in 2 stages which,
however, does not differ from the aforementioned process as
regards the additives used.
However, the manufacture of foamed sulfur still
gives rise to considerable problems. If, as proposed in U.S.
Patent 3,337,355, the viscosity increasers used are inorganic
substances such as phosphorus and arsenic and/or their sulfides
and if acids are used as part of the expanding system, large
alllounts of poisonous hydrogen sulEide are formed. If the vis-
cosity is incre~ased by the use of styrenc, the said Thiokol poly-
sulfides or even phenols in conjunction with the described
isocyanate additives, evil-smelling products are again formed
by reaction with the molten sulfur, and the aliphatic and
aromatic compounds increase the cost of the foamed sulfur con-
siderably. For example, the foamed sulfurs described in
German Published Application 2,324,175 mostly contain from 20
to 30% by weight of organic compounds.
It is an object of the present invention to avoid the
above drawbacks in the manufacture of foamed sulfurs and to
filld a viscosiLy-increasilly <ubstallce wl-icll makes it possible
to avoid the occurrence of unpleasant odors and poisonous
gases.
We have found that this object is achieved in a process
for the manufacture o~ foamed sulfur by blending molten sulfur
with viscosity-increasillg and stabilizing compounds, foaming
2-
108~
the molten mixture by means of a blowing agent and solidifying
the foamed mixture by cooling thereof to temperatures below
the melting point of sulfur, wherein dicyclopentadiene is
added to the molten sulfur in an amount of 2 to 8~ at tempera-
tures of from 120 to 160C as viscosity increaser, the period
'
.
:. :
:. ~ . .
. . ~ ' .
lV~2850
o.z. 31,453
of lnteraction between the sulfur and dicyclopentadiene at the tem-
perature used being restricted by the values of the ordinates in the
accompanying figure at the points of intersection between the curves
A and D and a straight line parallel to the ordinate axis and lnter-
sectlng the abscissa axis at the temperature used.
The process of the inventlon may be carried out ln a variety
of ways. For example, the molten sulfur may be blended with from
2 to 8% and preferably rrOm 4 to 6%, by weight, of dicyclopenta-
diene, whereupon these two substances are allowed to interreact for
the relevant total reaction tlme depending on the temperature used
and given by the accompanying flgure and adding the other ingre-
dients, i.e. the stabilizer and blowing agent, during said reaction
tlme and immediately cooling the molten mlxture to temperatures
below the solidifying point at the end of said reaction period.
The time of commencement of foamlng must be selected such that
foamlng ls oomplete at the end of the total reactlon tlme, slnce
the foamed melt ls then cooled to below the melting point.
Accordlng to a particularly preferred embodiment of the pro-
cess of the invention, a mixture of sulfur and dicyclopentadiene is
prepared and these components are allowed to interact for only from
80 to 99% of the time required at the temperature used. In this first
stage it is preferred to use higher temperatures, for example tem-
peratures of from 130 to 145C, in order to accelerate the reaction
between sulfur and dicyclopentadiene. In the second stage, which
may be separated from the first stage in space and time, lower tem-
peratures of from 120 to 130C are preferred, since ~ust a small dif-
~erence in temperature between the liquid and solidifying melt gives
greater uniformity in the size of the foam pores formed. In this
second stage, the stabilizing agent, iOe. talcg and the blowing
agent, e.g. calcite, are stirred into the melt and finally the foam
is produced by stirring in concentrated phosphoric acid, these ope-
rations being carried out in the remainder of the reaction time as
determined by the different temperature used.
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~oez~
o,Z. ~1,453
The Table 1 below llsts some points on the curves A and D and
on curves B and C determining the pre~erred interaction times.
TAELE 1
Temperature (C) Total reactlon tlme (hours)
A B C D
120 ll,oo 15.00 23.0~ 29.00
125 4.70 6s60 11.50 14.00
130 2.35 ~.~0 6.oo 8.oo
135 1.25 1 r 80 ~.40 4.70
140 7 1O05 2015 2.90
145 0.4~ 0067 1.40 l.90
150 0027 0.44 o.g5 1-35
155 0.18 0.31 0.67 1.00
160 0.12 0.22 0.50 0.75
The process o~ the lnvention ls preferably carried out at tem-
peratures Or from 120 to 145C.
As ln the prlor art processes, suitable stabilizers are fine-
ly powdered substances havlng particles of plate-like structure
and inert to the molten sulfur and other additives, examples bein8
mica, alumina, aluminium oxide and talc. The stablllzers are added
to the melt ln amounts of froml 0 to 50~ by weight, based on the
sulfur.
Particularly suitable blowing agents are, again as in the
prior art processes, carbonate-containing substances such as cal-
clte, sodium carbonate and sodium bicarbonate in con~unction with
aclds such as phosphoric acid and sul~urlc acid. It wlll be appre-
ciated that any other blowing agent known to be suitable for thls
purpose may be used, for example the said nitrogen-eliminating
blowing agents or physical blowing agents based on chlorinated and
fluorinated hydrocarbons, e.g. monofluorotrlchloromethane, difluoro-
dlchloromethane, trifluoromonochloromethane, difluoromonochloro-
methane, tri~luorotrichloroethane, tetrafluorodlchloroethane, octa-
- 1082~S0
o,z. 31,453
fluorocyclobutane, and trlfluoromonobromomethane.
The amounts of blowing agent used depend on the desired densi-
ty of the foamed sulfur to be manufactured and on the blowing agent
ltselr .
EXAMPLE
(a) 648 parts by welght of sulfur are blended wlth 32 parts by
welght of dicyclopentadiene at a temperature of 135C and the mlx-
ture ls held at this temperature for 135 mlnutes (90% of the average
total reactlon tlme requlred at thls temperature). The temperature
is reduced to 125C and 257 parts by weight of talc and 36 parts by
weight of F-calcite are stirred into the mixture and stirring is
continued for a total of 54 minutes (10% of the average total re-
action time required at this temperature). At the end of this re-
actlon period, the melt is blended with 27 parts by weight of con-
centrated phosphoric acid (93% H3P04), whereupon the mixture foams.
It ls then poured into molds to set.
The ~oamed sulfur prepared ln thls manner has the followlng
propertles:
density (g/cm3) o,30
compressive strength (kg/cm3) 12.0
flexural strength (kg/cm3) 7.6
heat conductivlty ( kcal ) 0.09
mhr C
water absorption after 28 days 13.5/48.4
coefficient of impermeability to water520
vapor/u
proportion of closed cells (~) 46.
The above combination of properties makes this foamed sulfur
a rigid foam which may be used, for example, as an antifreeze ma-
terlal for road constructlon.
(b) This test is commenced as in Example (a), but the mixture
of sulfur and dlcyclopentadiene ls held at 135C for 360 minutes.
The melt ls so viscous that neither talc nor blowing agent can be
incorporated.
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o.z. ~1,45
(c) This test is commenced as in Example (a), but the mixture
is held at 1~5C for, say, only 40 minutes. When the test ls then
continued as ln Example (a), a foam is obtalned whlch forms volds
prlor to solldirication and usually collapses completely.
