Process for the production of cyanuric chloride moldings

The invention relates to a process for the production of cyanuric chloride moldings, particularly in rod or flake form. Cyanuric chloride melt is cooled in a pressure cell equipped with a die capable of strand formation, wherein solidification takes place in the channel or channels of the die. The solidified cyanuric chloride is pressed out of the die in strand form at a temperature of 140.degree. C. or less, preferably 40 to 60.degree. C., and reduced in size as required. The process reduces the sublimation which is otherwise conventional during solidification and cooling.

FIELD OF THE INVENTION 
The invention relates to a process for the production of cyanuric chloride 
moldings, wherein the moldings are rod or flake-shaped, by cooling 
cyanuric chloride melt in a molding tool. 
BACKGROUND OF THE INVENTION 
It is known to convert cyanuric chloride in vapor form and obtained by 
trimerization of cyanogen chloride into solid fine-particle cyanuric 
chloride directly or via liquid cyanuric chloride: 
The precipitation of pulverulent cyanuric chloride by desublimation of 
cyanuric chloride in vapor form may take place in externally cooled 
chambers or by introducing the cyanuric chloride vapor into a 
precipitation chamber with an inert gas and/or an inert coolant which 
evaporates in the precipitation process--see for example DE-PS 12 66 308 
and U.S. Pat. No. 4,591,493. To obtain fine-particle cyanuric chloride 
from liquid cyanuric chloride the latter is sprayed into a precipitation 
chamber and cooled in the precipitation chamber with circulated inert 
cooling gases or by indirect cooling until the spray droplets precipitate 
in crystalline form--see for example DE 28 43 379. Considerable technical 
outlay for precipitation chambers and devices for recycling and cleaning 
process and waste gases is common to the processes. 
In the processes which have been appreciated in the past and are based on 
the same principles, cyanuric chloride is always obtained in fine-particle 
form, generally with a maximum particle diameter substantially below 250 
.mu.m. Although such fine-particle products are advantageous as regards 
their high reactivity they have a number of drawbacks which make another 
product form desirable for many purposes. 
The handling, such as feeding, storing and metering, of fine-particle 
cyanuric chloride poses particular problems because the corrosive and 
irritant properties accompany the conventional dust formation of 
fine-particle substances which requires extraction devices. Furthermore, 
cyanuric chloride is sensitive to hydrolysis, wherein hydrolysis products 
formed thereby can contaminate not only cyanuric chloride itself, but also 
subsequent products produced therefrom. Because of its high surface, 
cyanuric chloride is particularly accessible to hydrolysis. This also 
means that solid deposits in the dust removal devices and dust-carrying 
pipes can easily occur. Technically complex measures and/or fittings are 
required in order to prevent faults and eliminate those which have 
occurred. 
A further drawback of fine-particle cyanuric chloride is the unsatisfactory 
flowability. Although this can be improved by the addition of free-flow 
auxiliary substances, such as silicas, the free-flow auxiliary substance 
reduces the product purity of the cyanuric chloride and optionally also 
that of the products produced from it. According to EP-A 0 416 584 the 
flowability of solid cyanuric chloride produced by desublimation or spray 
crystallization may also be improved without the addition of a free-flow 
auxiliary substance, by a shear treatment thereof in a kneader or mixer, 
particularly at 60 to 120.degree. C.; the finely powdered nature of the 
cyanuric chloride is not, however, eliminated by this process as the 
average particle size of exemplary embodiments is in the range from 
approximately 10 .mu.m to 40 .mu.m. 
The as yet unpublished German patent application 196 42 449.6 discloses 
flake and pellet-shaped cyanuric chloride moldings. These moldings may be 
produced by applying molten cyanuric chloride in drop or strip form to a 
surface and removing the heat of fusion by cooling the surface or 
contacting the melt applied to the surface with a coolant gas. A drawback 
of this process is that the device with the cooling belt must be designed 
in enclosed form. Furthermore, because of the high sublimation vapor 
pressure of cyanuric chloride in the vicinity of the solidification point 
and also above 100.degree. C. considerable sublimation takes place and 
hence formation of fine-particle material. 
SUMMARY OF THE INVENTION 
Accordingly, the object of the present invention is to provide a further 
process for the production of cyanuric chloride moldings. The process 
should be simple to handle; furthermore it should also be possible to 
operate the process in such a way that no notable sublimation takes place. 
A process has been found for the production of cyanuric chloride moldings 
by cooling cyanuric chloride melt in a molding tool which is characterized 
in that a pressure cell equipped with a single or multi-channel die which 
is capable of strand formation is filled with cyanuric chloride melt. The 
wall of the pressure cell and/or the die is cooled in such a way that at 
the start of or within the channels of the die, the orifice cross-section 
of which is substantially constant over the channel length, the 
temperature is below the melting point of cyanuric chloride and a 
temperature of 140.degree. C. or less is reached at the outlet, solidified 
cyanuric chloride is pressed out of the die in strand form by the effect 
of force on the pressure cell and the strand is then reduced in size. 
The pressure cell to be used may be designed in any way, as a pressurized 
feed container for example or a coolable cell connected to such a 
container and with a die integrated therein or fitted thereto. The 
pressure cell is equipped with a coolable die with one or more straight 
channels located therein, the orifice cross-section of which is 
substantially identical over the length of the channels. The term 
"substantially" means that the channel may be wider in the inlet region, 
e.g. to avoid edge abrasion or to facilitate the insertion of a ram. The 
die is coolable via the external wall and/or cooling channels located in 
the die, so as to remove the heat of fusion and latent heat of the 
cyanuric chloride. A feature of the process essential to the invention is 
the fact that the solidification of the cyanuric chloride takes place only 
in the channel or channels of the die, i.e. after final forming, and the 
material solidified in this way is pressed out of the die accompanied by 
further cooling. The channels must be uniformly designed from the inlet on 
the pressure cell side to the outlet of the strands because a plastic 
forming after the solidification of the cyanuric chloride proved not to be 
possible. Because of the lack of plastic formability of the solidified 
cyanuric chloride on the one hand and low viscosity of the cyanuric 
chloride melt and hence insufficient pressure build-up on the other hand 
the use of an extruder proved to be unsuitable. 
The length of the die and/or the intensity of the cooling thereof are 
responsible for the temperature of the emerging strand(s). A lower outlet 
temperature and hence a lower sublimation vapor pressure of the solidified 
material is achieved by prolonging and/or intensifying the cooling. The 
sublimation vapor pressure falls from approx. 27 kPa at 150.degree. C. to, 
for example, 6.3 kPa at 120.degree. C. and 0.27 kPa at 60.degree. C. 
Preferably the outlet temperature is below 140.degree. C., particularly 
below 100.degree. C. and particularly preferably in the range from 40 to 
60.degree. C. The compressive force required for discharge increases as 
the length increases. Although the compressive force decreases as the feed 
speed increases, the outlet temperature rises. 
The one or more channels in the die may have any cross section, but a 
round, oval or rectangular cross section is preferred. Where the cross 
section is round, the diameter is generally in the range from 1 to 5 mm; 
channels with a rectangular cross section, i.e. slit-shaped channels in 
particular, are preferably 5 to 30 mm wide and 1 to 5 mm high.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In diagrammatic form, FIG. 1 shows a cross section of a particularly 
appropriate embodiment of the lower part of a pressure cell with a 
5-channel die: the die 2 with the channels 3.1 to 3.5 is arranged at the 
bottom of the pressure cell 1. The die comprises a cooling zone with 
cooling channels 4.1 to 4.6. A ram plate 5 with needles 6.1 to 6.5 which 
fit into the channels and are fixed to the ram plate is arranged in the 
pressure cell so that it can move vertically (lifting gear not shown). In 
the lowest position of the ram 5 the needles 6.1 to 6.5 extend only 
partially into the channels 3.1 to 3.5--with solidified cyanuric chloride 
strands 7.1 to 7.5 the lower part of the channels remains closed so that 
the cyanuric chloride melt 8 cannot escape from the pressure cell. 
The person skilled in the art may build up the pressure required for 
discharge in any way. Examples which may be considered are high pressure 
piston pumps and diaphragm pumps. It is also possible to effect the 
pressure build-up and hence the discharge of the strand(s) by introducing 
a plunger by means of a screw press into a corresponding cylinder or 
directly into the channel or channels of the die. The use of a pressurized 
feed container to which the actual cell with the die is connected is 
preferred. The compression process may be continuous or intermittent. 
Depending on the length of the die and the desired feed speed the 
discharge pressure is generally in the range from 1 MPa to 100 MPa, 
particularly 1 MPa to 20 MPa and particularly preferably 1 to 5 MPa. 
The reduction of the strands or strips emerging from the die into pieces, 
particularly ones with a length in the range from 5 to 30 mm, may take 
place using conventional crushing or cutting tools. 
Cyanuric chloride moldings produced according to the invention are fully 
crystallized, stable in storage and transportable and largely dustless. 
The process according to the invention is distinguished in that the 
solidification of the cyanuric chloride melt and further cooling of the 
solid take place in a closed channel, by which means problems, such as 
formation of desublimate during solidification and cooling, are largely 
prevented. 
EXAMPLES 
Cyanuric chloride extrudates were produced in laboratory equipment. The 
device used for the purpose comprised a coolable cylindrical pressure cell 
of abrasion-resistant material with a capillary-shaped die integrated into 
the lower part. The capillary diameter was 5 mm. The cell was located in a 
pressure cell base with a chamber to receive the discharged strand. For 
discharge purposes a pressure needle was inserted into the cell by means 
of a screw press. The feed speed and length of the capillary were varied. 
The discharge pressure was recorded. 
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Length of the capillary Maximum pressure on 
(mm) Feed (mm/min) discharge (MPa) 
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20 5 3 
30 5 14 
40 5 62 
50 5 170 
20 60 11 
20 1000 2.5 
20 1600 2.5 
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In all cases the temperature of the discharged strand was around/below 
60.degree. C.