Note: Descriptions are shown in the official language in which they were submitted.
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,
A new blowing agent combination based on azodicarbon-
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aside, the production and use thereof for the foaming
of plastics
This invention relates to new blowing agent
combinations based on azodicarbonamide with the addition
of metal compounds, and the production and use thereof
for the production of cellular and porous articles,
such as foams of thermoplastic polymers.
As is known, it is possible to produce foamed
lo products from organic polymeric materials by decomposing
a blowing agent which is worked into the polymer or is
applied onto the surface of the plastics material.
These blowing agents decompose in a controlled manner
above a certain temperature with the release of a
blowing gas and the formation of a residue which remains
in the foam. The literature describes substances of the
most varied compound classes for this purpose, for
example ago compounds, horsehides, semicarbazides, in-
Azores, tetrazoles, Nutrias compounds and benzoxa-
zincs, inter aria (Kunststoffe 66 (1976) lo pages
698-701).
Aside derivatives of azodicarboxylic acid
generally meet these conditions. Azodicarbonamide is
particularly suitable owing to its outstanding stability,
its high decomposition temperature, its favorable
decomposition characteristics and the relatively large
volume of the gases which are released per unit weight.
Moreover, the gases which are released mostly consist
of nitrogen and the decomposition residues are sub Stan-
tidally colorless and odorless.
Depending on the polymer to be foamed, additives may be mixed with the azodicarbonamide which, for
example, lower the decomposition temperature or have a
favorable effect on the pore structure and on the
color of the resulting foam.
For example, different zinc salts on their
own or in admixture with other heavy metal salts, for
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example lead, tin and cadmium salts etc. and, in particular,
chromium compounds such as chromates or chromium salts may be used
very effectively as additives for the production of, for example
cross-linked polyethylene foams, foam rubber or polyvinyl chloride
foams (for example West German Auslegeschrift 1,936,098 published
March 29, 1973 (Tray Industries, ha.), West German Auslegeschri~t
2,653,748 published May 24, 1978 (Dynamite Nobel A), European
Patent Application No. 0 027 688 published April 29, 1981
(Bisons Limited)).
It is also known that the foaming operation may be
favorably influenced by the addition of, for example, magnesium
oxide (West German Auslegeschrift 2,852,287 published April 9, 1981
(~ynamit Nobel A), West German Offenlegungsschrift 2,351,515
published April 24, 1975 (Bayer A)). The addition of, for
example, zinc compounds combined with Al, Sun-, B- and Si-compounds
to the blowing agent has also been described (Japan Application
49-70931 filed June 20, 1974 (Ohtsuka, Kagako, Yakuhin OK
It has now been found that it is possible to dispense
with additives, for example chromates or chromium compounds come
brined with known zinc salts or other heavy metal salts, by adding
compounds such as boron molybdenum tungsten and/or titanium
compounds, individually or mixed together, to the azodicarbonamide.
According to the present invention, metal compounds are
added to the blowing agent. Compounds of boron, molybdenum,
tungsten and titanium are used. They may be used individually
or in mixtures.
The present invention is directed to a blowing agent
which comprises azodicarbonamide (ADO), doped with one or more
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metal compounds selected from the group consisting of boric acid,
boron trioxides sodium borate, calcium borate, perorates, molt-
bdenum oxide, sodium molybdate, ammonium molybdate, tungsten
oxide, tungstic acid, sodium tungstate, calcium tungstate,
ammonium tungstate, titanium dioxide, sodium titan ate, calcium
titan ate, titanium sulfite, titanium oxide sulfite, titanium
peroxide sulfite or titanium chloride, which metal compound is
present in an amount of from 0.05 to 0.6% by weight based on
the weight of azodicarbonamide.
Sodium perorate can be mentioned as one example of a
perorate.
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The blowing agent combination according to the
present invention consisting of azodicarbonamide (ADO) and metal
compound may be used, for example, in the foaming of polymers such
as thermoplastic polymers. It is preferably used in the foaming
of thermoplastic polymers which are processed in a temperature
range of from 140 to 350C, the processing temperature depending
on the thermoplast which is used in each case.
The following are mentioned as examples of thermoplasts:
polyvinyl chloride, polyethylene, polypropylene, copolymers of
VC/VAC, VC/EVAC, EVOKE, propylene/VC, EVOKE, ethylene, propylene
polystyrene, polyamides, polysulphones, PET, PUT, PRO, polyp
acrylates, rubbers, plastics based on cellulose esters, awry-
lonitrile-butadiene-styrene polymers (AS), mixtures of polyp
cellophane and styrene-acrylonitrile- or ABS-polymers, mixtures of
PVC and AS polymers or acrylonitrile polymers, polymeric
mixtures and mixtures of the polymers mentioned.
The blowing agent combination according to the present
invention is preferably used in the production of cross-linked
polyolefin foams, in which case polyethylene is particularly pro-
furred.
The blowing agent combination of the present inventions added in conventional quantities to the polymer to be foamed.
The polymer to be foamed preferably contains from 0.1 to 35% by
weight, more preferably from 1 to 20~ by weight, of the blowing
agent combination according to the present invention which
consists of azodicarbonamide DO and one or more metal coup-
wounds.
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The cross-linked polyethylene foams which are prefer-
ably produced therewith are generally light in color and odor-
less, they exhibit a very wine, regular pore form at a low volt
use weight and have a
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smooth, pale surface. Another advantage of the
blowing agent combination according to the present
invention is seen in the fact that the foaming operation
is accelerated. This advance is particularly visible
in the case of high production speeds, because in such
a case, the desired volume weight of the respective
foam is achieved in a shorter time or at a lower
temperature. The use of the blowing agent combination
of the present invention improves the economy
of the foam production, and a higher space-time yield
is achieved thereby.
The azodicarbonamide may be doped with metal
compounds in any phase of production, for example before
oxidation of the hydrazodicarbonamide with a conventional
oxidizing agent, such as chlorine, bromide, iodine,
hydrogen peroxide or sodium chlorate etc., during
oxidation or after oxidation. It is also possible to
add the substances during isolation through a
conventional filter unit, for example a pressure suction
filter a rotary filter, a box suction filter or a
filter press etc., while the solid is being washed or
after washing. The metal compounds may also be
charged before drying in a conventional conveying
or mixing unit, during the drying procedure or after
drying in a generally conventional mixing or grinding
unit. The components which have been mentioned may be
added separately or combined in a solution. If they
are added separately, it is possible to add them to
the azodicarbonamide as a solid, a paste or a liquid.
This may be carried out in a finely-divided form for
example as a mist, as a vapor or as droplets, or as
a compact mass. Suitable measures are used to
distribute the material regularly over the surface of
the azodicarbonamide.
The plastics to be foamed may be mixed,
according to requirements and depending on the area of
use, with additives such as fillers, pigments, flame-
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proofing agents, plasticizers, thermostabilisers,
peroxides, anti-agers, and cross-linking and vulcanizing
agents.
Example 1
300 g (2.54 mows) of hydrazodicarbonamide in
1,200 ml of water are introduced into a stirrer-equipped
apparatus. 3 g of molybdenum trioxides are then added
and the suspension is oxidized with chlorine. After 3
hours, oxidation of the hydrazodicarbonamide is complete
with a chlorine consumption of 249 g. The yellow solid
is filtered off on a suction filter, washed with water
and dried in a vacuum drying chamber.
Yield : 284 g (96.3 % based on
hydrazodicarbonamide
(HDC)
Amount of molybdenum in the
ADC1) : 0.45 %
0 grain ADO (~) : 32
(ADO - Azodicarbonamide)
Example 2
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Instead of molybdenum trioxides 3.0 g of boric
acid are introduced, with otherwise identical conditions.
248 g of chlorine have been consumed after the same
reaction time.
Yield : 280 g - 94.9 % based on
HDC
Amount of boron in ADO : 0.0075 %
0 grain ADO (~) : 29
Example 3
_..
The reaction was carried out analogously with
3 g of titanium dioxide instead of molybdenum trioxides
Chlorine consumption 241 g, time 4 hours.
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Yield : 290 g -I 98.3 based on HO
Amount of titanium in ADO : 0.7 %
0 grain (~) : 25
Example 4
_
3 g of tungsten trioxides were used as the
metal compound in an analogous reaction. Reaction
time 4 hours, chlorine consumption 253 g.
Yield : 283 g - 95.9 % based on HDC
lo Amount of tungsten : 1.6 %
0 grain ADO (~) : 33
Example 5
I_ . .
The following were introduced into a stirrer-
equipped apparatus:
1,200 ml of water,
300 g of hydrazodicarbonamide,
and
3 g of titanium dioxide.
The mixture is oxidized using chlorine, with a
chlorine consumption of 241 g.
Yield : 280 g - 94.9 % based on HDC
Amount of titanium in ADO : 0.7 %
0 grain (~) : 12
Example 6
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A solution of 0.2 g of boric acid in 200 ml of
water is added to 222 g of moist ADO and stirred regularly.
The suspension is freed from water. Yield about 200 g
of dry product.
0 grain ADO (~) : 15.5.
Example 7
As in Example 6, with an ADO product of an average
grain size of 27 and with 0.2 g of boric acid in 200 ml
of water.
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Example 8
As in Example 6, but the ADO is treated with
a suspension of 1 g of tungstic acid in 200 ml of water,
a regular distribution being achieved by evaporation.
0 grain ADO I 15.5.
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