Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PROCESS FOR PRODUCING MOLDINGS
Description
The present invention relates to a process for producing moldings comprising
(A) at least one
lactam, (B) at least one activator, and (C) at least one catalyst, where (A)
to (C) proceed
through treatments comprising a) mixing of (A), (B), and (C), b) metering of
(A), (B), and (C) into
an apparatus for producing mixture droplets, and producing mixture droplets,
and c) depositing
the mixture droplets comprising (A), (B), and (C) on a belt, and d) producing
moldings.
Polyamide moldings, in particular fiber-reinforced polyamide moldings, have in
recent years
increasingly been used as materials replacing metallic materials, for example
in automobile
construction, and can replace not only components in the engine compartment
but also
bodywork components made of metal. Production of a polyamide molding uses
monomer melts
of different degrees of polymerization, which depend on the application.
Lactams such as caprolactam, laurolactam, piperidone, and pyrrolidone, and
also lactones such
as caprolactone, can be polymerized with ring-opening in a base-catalyzed
anionic
polymerization reaction. The general method here polymerizes a melt made of
lactam and/or
lactone comprising an alkaline catalyst and what is known as an activator (or
co-catalyst or
initiator) at temperatures of about 150 C.
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DE-A 14 20 241 describes an anionic polymerization reaction of lactams in the
presence of
potassium hydroxide as catalyst and with use of 1,6-bis(N,N-
dibutylureido)hexane as activator.
The activated anionic lactam polymerization reaction with use of sodium
caprolactam is
described by way of example in Polyamide, Kunststoff Handbuch [Polyamides,
Plastics
Handbook], vol. 3/4, ISBN 3-446-16486-3, 1998, Carl Hanser Verlag, pp.49-52,
and
Macromolecules, Vol. 32, No.23 (1993), p. 7726.
It was an object of the present invention to provide a process which provides
moldings which
are composed of a monomer melt and of a polymer melt polymerized only as far
as a low
weight-average molar mass (Mw). Another object of the invention was to provide
a process
which can be conducted by using a system which requires little space. A
further intention was to
develop a process which provides a product which can be further processed
directly per se. In
particular, the process is intended to provide a product which enables
avoidance of a
complicated procedure which is otherwise conventional in anionic
polymerization and which is a
likely source of defects: admixture of additives prior to further shaping
processes.
For the purposes of the present invention, the term "molding" means a particle
which is solid at
a temperature of 25 C. It is preferable that the particle of the invention
remains solid even at
higher temperatures, e.g. at 50 C. The shape of an individual molding can be
spherical or
almost spherical. The shape of the moldings can also be that of pellets or of
flakes.
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In order to facilitate draw-off, transport, storage, and further processing in
an extruder, the
process should provide the moldings in a flowable form. The moldings are thus
intended to
facilitate further processing at a customer's premises.
Moldings which consist essentially of a monomer melt and of a polymer melt
polymerized only
as far as a low weight-average molar mass (Mw) are moldings which consist
essentially of
monomers and optionally polyamide with a weight-average molar mass (Mw) of
from 200 to
45 000 g/mol. The moldings of the invention, solid at 25 C, can comprise a
certain proportion of
polymer, but preferably comprise less than 50% by weight of polymer, based on
the total weight
of the polymer and of the monomer. The moldings can comprise catalyst,
activator, and
optionally at least one additive, alongside polyamide.
The object of the invention is achieved as described in the introduction.
Particularly suitable lactams (A) are caprolactam, piperidone, pyrrolidone,
laurolactam, and
mixtures of these.
Another possibility is to use a mixture of lactam and lactone as monomer
instead of a lactam.
Examples of lactones that can be used are caprolactone and butyrolactone. The
amount of
lactone as comonomer here should not exceed 40% by weight, based on entire
monomer. It is
preferable that the proportion of lactone as comonomer does not exceed 30% by
weight, and
particularly does not exceed 20% by weight, based on entire monomer.
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One preferred embodiment of the invention uses exclusively lactams as
monomers. In
particular, at least one monomer selected from the following group is used as
lactam (A):
caprolactone, piperidone, pyrrolidone, laurolactam, and mixtures of these.
The process of the invention uses a catalyst (B). For the purposes of the
present invention, a
catalyst for the anionic polymerization reaction is a compound which enables
formation of
lactam anions. The lactam anions per se can also function as catalyst.
Catalysts (B) of this type are known to the person skilled in the art. For the
purposes of the
present invention, it is preferable to use a catalyst (B) selected from the
group consisting of
sodium caprolactamate, potassium caprolactamate, magnesium bromide
caprolactamate,
magnesium chloride caprolactamate, magnesium biscaprolactamate, sodium
hydride, sodium,
sodium hydroxide, sodium methanolate, sodium ethanolate, sodium propanolate,
sodium
butanolate, potassium hydride, potassium, potassium hydroxide, potassium
methanolate,
potassium ethanolate, potassium propanolate, potassium butanolate, and
mixtures of these,
preferably sodium caprolactamate, potassium caprolactamate, magnesium bromide
caprolactamate, magnesium chloride caprolactamate, magnesium
biscaprolactamate, sodium
hydride, sodium, sodium hydroxide, sodium methanolate, sodium methanolate,
sodium
propanolate, sodium butanolate, potassium hydride, potassium, potassium
hydroxide,
potassium methanolate, potassium ethanolate, potassium propanolate, potassium
butanolate,
and mixtures of these.
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It is particularly preferable to use a catalyst (B) selected from the group
consisting of sodium
hydride, sodium, and sodium caprolactamate; particular preference is given to
sodium
caprolactamate and/or a solution of sodium caprolactamate in caprolactam (e.g.
Bruggolen
(Bruggemann, DE) C10; 18% by weight of sodium caprolactamate in caprolactam).
The molar ratio of lactam (A) to catalyst (B) can vary widely, and is
generally from 1:1 to
10000:1, preferably from 5:1 to 1000:1, particularly preferably from 1:1 to
500:1.
Activator (C) used for the anionic polymerization reaction comprises a
compound selected from
the group of the lactams N-substituted by electrophilic moieties, the
aliphatic diisocyanates, the
aromatic diisocyanates, the polyisocyanates, the aliphatic diacyl halides, and
aromatic diacyl
halides.
Among the lactams N-substituted by electrophilic moieties are by way of
example acyllactams.
Activator (C) can also be precursors for these activated N-substituted
lactams, where these
form in situ, together with the lactam (A) an activated lactam.
Suitable compounds among the aliphatic diisocyanates as activator (C) are
those such as
butylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate,
decamethylene diisocyanate, undodecamethylene diisocyanate, dodecamethylene
diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), isophorone
diisocyanate, aromatic
diisocyanates such as tolyl diisocyanate, 4,4'-methylenebis(phenyl
isocyanate), and
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polyisocyanates (e.g. isocyanates of hexamethylene diisocyanate; Basonat HI
100/BASF SE),
and allophanates (e.g. ethyl allophanate). In particular, mixtures of the
compounds mentioned
can be used as activator (C).
Suitable aliphatic diacyl halides are compounds such as butylenedioyl
chloride, butylenedioyl
bromide, hexamethylenedioyl chloride, hexamethylenedioyl bromide,
octamethylenedioyl
chloride, octamethylenedioyl bromide, decamethylenedioyl chloride,
decamethylenedioyl
bromide, dodecamethylenedioyl chloride, dodecamethylenedioyl bromide, 4,4'-
methylenebis(cyclohexyloyl chloride), 4,4'-methylenebis(cyclohexyloyl
bromide),
isophoronedioyl chloride, isophoronedioyl bromide; and also aromatic diacyl
halides, such as
tolylmethylenedioyl chloride, 4,4'-methylenebis(phenyl) acyl chloride, and
4,4'-
methylenebis(phenyl) acyl bromide. In particular, mixtures of the compound
mentioned can be
used as activator (C). In one preferred embodiment, activator (C) used
comprises at least one
compound selected from the group comprising hexamethylene diisocyanate,
isophorone
diisocyanate, hexamethylenedioyl bromide, hexamethylenedioyl chloride, and
mixtures of these;
it is particularly preferable to use hexamethylene diisocyanate. An example of
a suitable
activator (C) is Bruggolen C20 (NCO content 17%) from Bruggemann, DE.
The amount of activator (C) defines the number of growing chains, since each
activator
molecule represents the initial member of a polymer chain. The molar ratio of
lactam (A) to
activator (C) can vary widely and is generally from 1:1 to 10 000:1,
preferably from 5:1 to
2000:1, particularly preferably from 20:1 to 1000:1.
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At least one further component selected from fillers and/or fibrous
substances, polymers, and
further additives can be added as additional substance (D) to the moldings.
At least one polymer can be added to the moldings. By way of example, a
polymer and/or
oligomer which forms in situ via polymerization of the monomers comprised in
the composition
can be added to the moldings. The amount comprised of this optionally added
polymer is by
way of example from 0 to 40% by weight, preferably from 0 to 20% by weight,
particularly
preferably from 0 to 10% by weight.
It is moreover possible to add to the moldings at least one polymer, where
this is added in the
form of a polymer to the composition. These added polymers can by way of
example comprise
groups which are suitable for the formation of block copolymers and/or graft
copolymers with the
polymer formed from the lactam. Examples of these groups are epoxy, amine,
carboxy,
anhydride, oxazoline, carbodiimide, urethane, isocyanate, and lactam groups.
Another possibility for improving the properties of the product, the
compatibilities of the
components, and viscosity, is to add to the moldings at least one polymer (PM)
selected from
the group consisting of polystyrene, styrene copolymers, such as styrene-
acrylonitrile
copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS), or styrene-
butadiene
copolymers (SB), polyphenylene oxide ethers, polyolefins, such as polyethylene
(HTPE (high-
temperature polyethylene), LTPE (low-temperature polyethylene)),
polypropylene, or poly-1-
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butene, polytetrafluoroethylene; polyesters, such as polyethyleneterephthalate
(PET) or
polyamides; polyethers, e.g. polyethylene glycol (PEG), or polypropylene
glycol, or polyether
sulfones (PESU or PES); polymers of monomers comprising vinyl groups, e.g.
polyvinyl
chloride, polyvinylidene chlorides, polystyrene, impact-modified polystyrene,
polyvinylcarbazole,
polyvinyl acetate, polyvinyl alcohol, polyisobutylene, polybutadiene,
polysulfone, and
copolymers of the polymers mentioned.
It is moreover possible to add a crosslinking monomer to the moldings. A
crosslinking monomer
can be a compound which comprises more than one group which can be
copolymerized with
the lactam. Examples of these groups are epoxy, amine, carboxy, anhydride,
oxazoline,
carbodiimide, urethane, isocyanate, and lactam groups. Examples of suitable
crosslinking
monomers are amino-substituted lactams, such as aminocaprolactam,
aminopiperidone,
aminopyrrolidone, aminolaurolactam, and mixtures of these, preferably
aminocaprolactam,
aminopyrrolidone, and mixtures of these, particularly preferably
aminocaprolactam.
Filler and/or fibrous material that is added to the moldings can comprise an
organic or inorganic
filler and/or fibrous material. By way of example, it is possible to use an
inorganic filler, such as
kaolin, chalk, wollastonite, talc powder, calcium carbonate, silicates,
titanium dioxide, zinc oxide,
graphite, glass particles, e.g. glass beads, nanoscale filler, such as carbon
nanotubes, carbon
black, nanoscale phyllosilicates, nanoscale aluminum oxide (A1203), nanoscale
titanium dioxide
(Ti02), carbon nanotubes, graphene, phyllosilicates, and nanoscale silicon
dioxide (Si02).
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It is further preferable that the filler and/or fibrous material used
comprises fibrous materials. It is
possible here to use one or more fibrous materials selected from known
inorganic reinforcing
fibers, such as boron fibers, glass fibers, carbon fibers, silica fibers,
ceramic fibers, and basalt
fibers; organic reinforcing fibers, such as aramid fibers, polyester fibers,
nylon fibers,
polyethylene fibers, and natural fibers, such as wood fibers, flax fibers,
hemp fibers, and sisal
fibers.
It is particularly preferable to use glass fibers, in particular chopped glass
fibers, carbon fibers,
aramid fibers, boron fibers, metal fibers, or potassium titanate fibers. The
fibers mentioned can
be used in the form of short fibers or long fibers, or in the form of a
mixture of short and long
fibers. The average fiber length of the short fibers here is preferably in the
range from 0.1 to
1 mm. Preference is further given to fibers with an average fiber length in
the range from 0.5 to
1 mm. The average fiber length of the long fibers used is preferably above 1
mm, with
preference in the range from 1 to 50 mm.
In particular, it is also possible to add mixtures of the fillers and/or
fibrous materials mentioned.
The filler and/or fibrous material added particularly preferably comprises
glass fibers and/or
glass particles, in particular glass beads.
Examples of other additives that can be added are light stabilizers, PVC
stabilizers, or other
stabilizers, such as copper salts, dyes, antistatic agents, release agents,
antioxidants,
lubricants, flame retardants, blowing agents, impact modifiers, and nucleating
agents.
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Preference is given to addition of an impact modifier as additive, in
particular a polydiene
polymer (e.g. polybutadiene, polyisoprene) comprising anhydride and/or epoxy
groups. The
glass transition temperature of the polydiene polymer is in particular below 0
C, preferably
below -10 C, particularly preferably below -20 C. The polydiene polymer can be
one based on a
polydiene copolymer with polyacrylates, polyethylene acrylates, and/or
polysiloxanes, and can
be produced by means of the processes known to the person skilled in the art
(e.g. emulsion
polymerization, suspension polymerization, solution polymerization, gas-phase
polymerization).
In the process of the invention for producing moldings, a mixture comprising
(A) at least one lactam
(B) at least one catalyst
(C) at least one activator
(D) optionally at least one additional substance
proceeds through treatments comprising
a) mixing of (A), (B), and (C), and also optionally (D),
b) metering the mixture into an apparatus for producing mixture droplets
comprising (A), (B),
and (C), and also optionally (D), and producing mixture droplets,
c) depositing the mixture droplets on a belt, and
d) producing moldings.
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It is preferable that the proportions by weight of (A), (B), (C), and (D) in
the mixture give 100%
by weight.
It is generally advantageous to minimize contamination, e.g. water, carbon
dioxide, and oxygen.
In particular, the process steps of the invention are conducted with
substantial exclusion of
oxygen, carbon dioxide, and water. It is preferable that the steps a) to c),
and in particular a) to
d), take place in an inert gas atmosphere (e.g. under nitrogen). The inert gas
here can be
conducted cocurrently or countercurrently by way of example with respect to
the movement of
the belt, preferably cocurrently. After the gas has passed through the system
it is preferable that
at least to some extent, preferably to an extent of at least 50%, particularly
preferably to an
extent of 75%, it is returned to the reaction space in the form of circulated
gas. A portion of the
inert gas is usually discharged after each pass through the system, preferably
up to 10%,
particularly preferably up to 3%, very particularly preferably up to 1%.
In another embodiment, it is also possible to use dry air instead of inert
gas. The relative
humidity of this air is intended to be below 10%. The relative humidity of the
air can be
determined by using a hair hygrometer from Fischer, DE. Relative humidity
means the
percentage relationship between the present water vapor pressure and the
saturation water
vapor pressure (at the temperature of the air) over a clean and level water
surface.
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The reaction can be conducted at atmospheric pressure, at superatmospheric
pressure or at
subatmospheric pressure, preference being given to a superatmospheric pressure
of up to
300 mbar above ambient pressure, i.e. up to 1.3 atmospheres.
In one embodiment of the invention, steps a), b), and c) are conducted
independently of one
another at a temperature which is in the range from the melting point of the
highest-melting-
point lactam comprised in the mixture to 100 C above the melting point of the
highest-melting-
point lactam comprised in the mixture. For the purposes of the invention, the
expression
"independently of one another" means that the temperature during the steps a),
b), and c) does
not have to be identical but can be varied within the ranges mentioned.
The mixing of the components in step a) can take place in a batch process or
continuous
process in apparatuses which are suitable and known to the person skilled in
the art. By way of
example, the components can be mixed continuously in a low-pressure mixing
machine and/or
batchwise in a stirred tank. It is preferable to mix the components
continuously in a low-pressure
or high-pressure mixing machine. Machines of this type are marketed by way of
example by the
companies Tartler, DE; Krauss-Maffei, DE; Unipre, DE, or ATP, CH.
In one particularly preferred embodiment of the process of the invention, the
separate melts
made of lactam, catalyst, and activator are respectively separately provided
at a temperature
just above the melting point thereof, they are then mixed, and are then cooled
to a temperature
just above the freezing point of the mixed melt, before the mixture is
introduced into step b).
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After the mixing process, the metering of the mixture takes place in step b)
in an apparatus for
producing mixture droplets comprising (A), (B), and (C), and also optionally
(D), and mixture
droplets are produced.
Mixture droplets can be produced via spraying by way of a nozzle or via
dropletization. The feed
systems and metering lines here have been heated to a temperature above the
melting point of
the lactam (A) used.
Process step b) for producing mixture droplets can use one or more spray
nozzles or casting
nozzles. The spray nozzles that can be used are not subject to any
restriction. The liquid to be
sprayed can be introduced under pressure into these nozzles. The liquid to be
sprayed can be
comminuted here by depressurization after reaching a certain minimum velocity
in the nozzle
aperture. It is also possible to use single-fluid nozzles for the purpose of
the invention, examples
being slot nozzles, or centrifugal chambers (solid-cone nozzles) (for example
from Dusen-
Schlick GmbH, DE, or from Spraying Systems Deutschland GmbH, DE).
Throughput per spray nozzle is advantageously from 0.1 to 10 m3/h, often from
0.5 to 5 m3/h.
It is equally possible to produce mixture droplets via laminar breakdown of a
jet, as described in
Rev. Sci. Instr. 38 (1966) 502.
The mixture droplets can also be produced by means of pneumatic drawing dies,
rotation,
section of a jet, or rapid-response microvalve dies.
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In a pneumatic drawing die, a jet of liquid is accelerated together with a gas
stream through an
aperture. The diameter of the jet of liquid, and thus the diameter of the
mixture droplets, can be
influenced by way of the amount of gas used.
When mixture droplets are produced via rotation, the liquid passes through the
openings in a
rotating disk. The centrifugal force acting on the liquid disentrains mixture
droplets of defined
size. Preferred apparatuses for rotation dropletization are described by way
of example in DE
43 08 842 Al.
However, it is also possible to use a rotating blade to chop the emerging
liquid jet into defined
segments. Each segment then forms a mixture droplet.
Use of microvalve dies directly produces mixture droplets with defined liquid
volume.
The metered mixture droplets are deposited on a belt in a step c). The belt is
preferably moved
with a velocity of from 1 to 20 m/min. The location of the belt is preferably
in a space to which an
inert gas is supplied.
In a step d), moldings are produced on the belt on which the mixture droplets
have been
deposited in step c). To this end, the belt on which the moldings were
deposited in step c) is
cooled to a temperature in the range from 100 C below the melting point of
(A), (B), and (C),
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and also optionally (D) to 20 C below the melting point of (A), (B), and (C),
and also optionally
(D). The effect of the cooling process can be to provide moldings which are
composed of a
monomer melt and/or polymer melt polymerized as far as a low weight-average
molar mass
(Mw).
The cooling of the moldings takes place as far as possible within a period in
the range from one
millisecond to ten minutes, preferably in the range from one millisecond to
five minutes,
particularly preferably in the range from one millisecond to one minute, very
particularly
preferably in the range from one millisecond to ten seconds. The cooling of
the molding can in
particular take place via cooling of the belt. It is also possible that
cooling of the molding takes
place via a cold stream of gas, for example a stream of nitrogen gas at 0 C.
The mixture droplets which in step d) become moldings on the belt have a
residence time of
from 20 sec to 20 min on the belt, in particular from 40 sec to 15 minutes,
preferably from
40 sec to 10 min.
The size of the moldings from the process of the invention can be selected
freely, but generally
depends on practical factors. Moldings which are either very small or else
very large are often
difficult to handle during packaging or further processing. By way of example,
they are difficult to
input into the processing machine, or are difficult to meter. The moldings can
be elongate to
round. Preference is given to moldings of which the longest axis is in the
range from 0.05 to
15 mm, preferably in the range from 0.1 to 11 mm, particularly preferably in
the range from 1 to
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9 mm, for example from 3 to 8 mm, and of which the shortest axis is in the
range from 0.05 to
15 mm, preferably in the range from 0.1 to 11 mm, particularly preferably in
the range from 1 to
9 mm, for example from 3 to 8 mm.
The size and the shape of the moldings can by way of example be influenced by
way of the size
of the nozzle through which the polymer melt is forced, but can also be
influenced via the
throughput, the viscosity of the polymer melt, and the velocity at which this
is comminuted. The
person skilled in the art is aware of these measures or can implement them by
using methods
known per se (e.g. Granulieren von Thermoplasten: Systeme im Vergleich
[Granulation of
thermoplastics: comparison of systems], annual conference on compounding
technology,
Baden-Baden, 24./25.11.99, VDI Verlag pp. 327 to 401).
The shape and size of the moldings obtained via the process of the invention
are particularly
suitable for storage, for transport, and for further processing. Specifically
the flowability and the
uniform product size of the moldings permit easy further processing by using
commercially
available extruders and/or injection-molding machines.
The moldings obtained, solid at 25 C, can be stored for a number of months and
used for
polyamide production at a later juncture. The moldings can be polymerized via
use of processes
known to the person skilled in the art, for example injection molding,
casting, vacuum injection,
or extrusion, generally at temperatures in the range from 100 to 250 C.
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The moldings of the invention, solid at 25 C, can comprise a certain
proportion of polymer, but
preferably comprise less than 50% by weight of polymer, based on the total
weight of the
polymer and of the monomer. According to variant I, it is particularly
preferable that the
moldings of the invention, solid at 25 C, comprise less than 30% by weight of
polymer, based
on the total weight of the polymer and of the monomer.
The molding described, solid at 25 C, is a valuable intermediate which can per
se be stored,
transported, and handled.
The moldings of the invention, solid at 25 C, are mechanically stable. They
can be stored
without undergoing chemical reaction or becoming discolored. The moldings
feature high
colorfastness and long shelf life, and also high purity.
The process of the invention for producing moldings for polyamide production
via activated
anionic polymerization of lactam (A) is characterized by the advantage that it
is possible to
achieve exact adjustment of the stoichiometric ratio between lactam (A),
catalyst (B), and
activator (C), and additional substances (D).
The examples below provide further explanation of the invention. These
examples illustrate
some aspects of the present invention but are in no way to be considered as
restricting the
scope of protection of said invention.
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Comparative example 1
E-Caprolactam was continuously mixed in a static mixer at 85 C at a conveying
rate of 8.44 kg/h
with a solution composed of 95.2% by weight of E-caprolactam and 4.8% by
weight of sodium
caprolactamate, the conveying rate at which the solution was added being 4.25
kg/h. The
temperature of said mixture was controlled to 80 C. After continuous addition
of 0.55 kg/h of a
solution composed of 80% by weight of N,N'-hexamethylenebis(carbamoyl-E-
caprolactam) and
20% by weight of caprolactam, the resultant mixture was sprayed into a
nitrogen-inertized spray
tower (also termed prilling tower) by means of a two-fluid nozzle. The
temperature of the gas
phase in the spray tower was 25 C. Measurement of ten randomly selected
particles under a
microscope showed that the number-average longest axis of the particles was
160 pm, and the
number-average shortest axis was 159 pm.
Comparative example 2
E-Caprolactam was continuously mixed in a static mixer at 95 C at a conveying
rate of 8.44 kg/h
with a solution composed of 95.2% by weight of 6-caprolactam and 4.8% by
weight of sodium
caprolactamate, the conveying rate at which the solution was added being 4.25
kg/h. The
temperature of said mixture was controlled to 90 C. After continuous addition
of 0.55 kg/h of a
solution composed of 80% by weight of N,N'-hexamethylenebis(carbamoyl-E-
caprolactam) and
20% by weight of caprolactam, the resultant mixture was sprayed into a
nitrogen-inertized spray
tower by means of a two-fluid nozzle. The temperature of the gas phase in the
spray tower was
35 C. Measurement of ten randomly selected particles under a microscope showed
that the
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number-average longest axis of the particles was 118 pm, and the number-
average shortest
axis was 123 pm.
Comparative example 3
E-Caprolactam was continuously mixed in a static mixer at 95 C at a conveying
rate of 8.44 kg/h
with a solution composed of 95.2% by weight of E-caprolactam and 4.8% by
weight of sodium
caprolactamate, the conveying rate at which the solution was added being 4.25
kg/h. The
temperature of said mixture was controlled to 95 C. After continuous addition
of 0.55 kg/h of a
solution composed of 80% by weight of N,N'-hexamethylenebis(carbamoyl-E-
caprolactam) and
20% by weight of caprolactam, the resultant mixture was sprayed into a
nitrogen-inertized spray
tower by means of a two-fluid nozzle. The temperature of the gas phase in the
spray tower was
50 C. Measurement of ten randomly selected particles under a microscope showed
that the
number-average longest axis of the particles was 80 pm, and the number-average
shortest axis
was 81 pm.
Inventive example 4
E-Caprolactam was continuously mixed in a static mixer at 85 C at a conveying
rate of 8.44 kg/h
with a solution composed of 95.2% by weight of E-caprolactam and 4.8% by
weight of sodium
caprolactamate, the conveying rate at which the solution was added being 4.25
kg/h. The
temperature of said mixture was controlled to 80 C. After continuous addition
of 0.55 kg/h of a
solution composed of 80% by weight of N,N'-hexamethylenebis(carbamoyl-E-
caprolactam) and
20% by weight of caprolactam, the resultant mixture was deposited onto a belt
cooled to 25 C
CA 02850640 2014-04-01
under 1.2 bar (atmospheres) by way of a die based on a plate with a plurality
of perforations,
with die-face cutter. The temperature of the gas phase above the belt was 25
C. Measurement
of ten randomly selected particles under a microscope showed that the number-
average longest
axis of the moldings was 6 mm, and the number-average shortest axis was 3 mm.
The moldings
are therefore flat.
Inventive example 5
c-Caprolactam was continuously mixed in a static mixer at 85 C at a conveying
rate of 8.44 kg/h
with a solution composed of 95.2% by weight of E-caprolactam and 4.8% by
weight of sodium
caprolactamate, the conveying rate at which the solution was added being 4.25
kg/h. The
temperature of said mixture was controlled to 80 C. After continuous addition
of 0.55 kg/h of a
solution composed of 80% by weight of N,N'-hexamethylenebis(carbamoyl-c-
caprolactam) and
20% by weight of caprolactam, the resultant mixture was deposited onto a belt
cooled to 25 C
under 1.2 atmospheres by way of a perforated drum die. The temperature of the
gas phase
above the belt was 25 C. The belt speed here was 2 m/min. Measurement of ten
randomly
selected moldings under a microscope showed that the number-average longest
axis of the
moldings was 8 mm, and the number-average shortest axis was 7 mm.
Inventive example 6
E-Caprolactam was continuously mixed in a static mixer at 85 C at a conveying
rate of 8.44 kg/h
with a solution composed of 95.2% by weight of c-caprolactam and 4.8% by
weight of sodium
caprolactamate, the conveying rate at which the solution was added being 4.25
kg/h. The
CA 02850640 2014-04-01
21
temperature of said mixture was controlled to 80 C. After continuous addition
of 0.55 kg/h of a
solution composed of 80% by weight of N,N'-hexamethylenebis(carbamoyl-c-
caprolactam) and
20% by weight of caprolactam, the resultant mixture was deposited onto a belt
cooled to 25 C
under 1.2 atmospheres by way of a perforated drum die. The belt speed was 3
m/min. The
temperature of the gas phase above the belt was 25 C. Measurement of ten
randomly selected
particles under a microscope showed that the number-average longest axis of
the moldings was
mm, and the number-average shortest axis was 3 mm.
