Note: Descriptions are shown in the official language in which they were submitted.
1 `
PROCESS FOR THE TREATMENT OF MIXTURES OF ALOGENATED_AND
NON-~ALOGENATED POLYMERS
The present invention relates to a process for treating
mixtures of halogenated and non-halogenated polymers in any
5 suitable thermoplastic processing eyuipment. The
halogenated component is subjected to controlled thermal
degradation to produce a stabilised useable thermoplastic
compound. The process results in no evolution of halogen
containing volatiles. The process can be carried out in
10 equipment such as a Banbury mixer, twin screw extruder,
single screw extruder, or the like.
On such process is already known from U.S. Patent No
4,643,861. According to this a composition of PP/PVdC
~polypropylene/polyvinylidene chloride) scrap plus hydrated
15 lime ~Ca(OH)2 ) and a metal carboxylate is subjected to a
densification process where the temperature is kept down to
20-100F (11-56C) below the melting point of the polymeric
film by the addition of water. A reaction is said to take
place durin~ this densification process lasting 5-15
20 minutes. This process differs from the present invention
in a number of respects. Firstly the present invention
requires a temperature above which the polymer is melted ~or
the reaction to take place.
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The present invention also specifically requires the use of
either a metal oxide or a metal aliphatic carboxylic acid
salt whereas in the above mentioned US patent, the process
requires the use of hydrated lime which is not the same as
calcium oxide.
A further distinction is the requirement of the patent that
water be added in an amount of 5 to 25~ by weight to
maintain the reaction temperature below the melting point of
the polymer, whereas in the present invention water or other
10 solvent is not added.
Also known in the prior art are Japanese Patent
Specification Nos. 51-3750, 53-21277 and 56-122894 wherein
waste plastics are thermally decomposed for subsequent
possible utility as fuels. The patents refer to reacting
15 the waste plastics in the presence of calcium compounds
including calcium oxide, calcium hydroxide or calcium
carbonate~ The purpose for addiny the calcium-containing
compounds is to react with any HC1 or other noxious gases
produced. Contrary to the Japanese patents, however, the
20 present invention is clearly directed to recovering useable
thermoplastic compositions from mixtures of halogenated and
non-halogenated polymers, including waste materials
thereof.
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The present process involves a controlled thermal
degradation to produce a stabilised halogenated polymeric
component, carried out in the presence of a specified
quantity of a metal oxide or metal aliphatic carboxylic acid
salt which results in the recovery of a material suita~le
for reuse.
Accordingly, it is an object of this invention to provide a
process enabling recovery of useable thermoplastic compounds
from mixtures of halogenated and non-halogenated polymers.
10 It is another object of this invention to provide a process
enabling recovery of useable thermoplastic compounds from
mixtures of halogenated and non-halogenated polymers,
wherein either or both of the polymers are derived from
waste materials.
15 It is yet another object of this invention to provide a
process enabling recovery of useable thermoplastic compounds
from mixtures of halogentated and non-halogenated polymers
wherein any conventional processing equipment may be
utilised.
20 It is yet another object of this invention to provide a
process enabling recovery of useable thermoplastic compounds
from mixtures of halogenated and non-halogenated polymers
whereby corrosion oE the p~ocessing equipment is minimised.
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The present invention relates to a non-solvented proce~s ~or
recovering a stabilised useable thermoplastic composition
from a mixture of at least one halogenated polymer and at
least one non-halogenated thermoplastic polymer, wherein the
5 halogenated polymer is subjected to controlled thermal
degradation while the non-halogenated thermoplastic polymer
is not substantially degraded, to produce a re-useable
thermoplastic composition. The mixture which may be, for
example, in the form of laminated film, coated bottles, and
10 the like is first made into a processable form by any
conventionally known means such as chopping, granulating or
agglomerating.
The polymeric mixture is then combined with at least one
metal oxide or metal aliphatic carboxylic acid salt which
15 will yield a halogenated metal salt which is stable under
the conditions required to process and use the resultant
~hermoplastic composition. The metal oxide or metal aliphatic
carboxylic acid salt is utilised in an amount which is at
least the stoichiometric equivalent required to react with
20 all the halogen contained in the mixture. Preferably the
amounts of metal oxide or metal aliphatic carboxylic acid
salt range from at least l.0 to about 3.0 times the
stoichiometric amount necessary to prevent evolution of all
the halogen in the polymeric mixture. If insufficient
25 metal oxide o~ metal aliphatic carboxylic acid salt were to
be added then halogen in the polymeric mixture could be
evolved causing corrosion of the processing equipment.
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The metal oxide or metal aliphatic carboxylic acid sal~
should not be used in any amount which would result in
difficulties during processing of the polymeric material
and/or difficulties in utilising the resulting thermoplastic
compound. It is possible to utilise mixtures o~ metal
oxides, or mixtures of metal aliphatic carboxylic acid
salts, or mixtures of metal oxides and metal aliphatic
carboxylic acid salts.
The mixture o~ polymers and metal oxide or metal aliphatic
10 carboxylic acid salt is subjected to conditions of elevated
temperature such that the polymeric mixture is melted and
the halogen containing polymeric compound is thermally
degraded to evolve halogen acid gas which reacts with the
metal oxide and/or metal aliphatic carboxylic acid salt.
15 The mixture of polymers and metal oxide or metal aliphatic
carboxylic acid salt may be mixed by means of any apparatus
known to those skilled in the art. Moreoever it is not
critical whether the mixture of polymers and metal
oxide/metal aliphatic carboxylic acid salt is premixed prior
20 to being subjected to the conditions of elevated temperature.
The following are exemplary methods known for carrying out
the reaction.
2 ~ 8 5
Preferably suitable for use in processing the mixture of
polymers and metal oxide/metal aliphatic carboxyl~c acid
salt are Banbury mixers, extruders, two roll mills, or any
other devices utilised in the industry. The polymeric
mixture and metal oxide/metal aliphatic carboxylic acid salt
may be premixed or fed independently as long as the metal
oxide/metal aliphatic carboxylic acid salt is fed in prior
to the halogenated polymeric component liberating any
halogen acid gas.
10 The mixture of polymers and metal oxide/metal aliphatic
carboxylic acid salt is heated to a temperature such that
the polymeric mixture is melted and the halogen containing
polymeric compound is thermally degraded to evolve halogen
acid gas which reacts with the metal oxide/metal aliphatic
15 carboxylic acid salt. The temperatures utilised in the
processing of the polymeric mixture with the metal
oxide/metal aliphatic carboxylic acid salt reactants, will
depend upon the ingredients utilised in the reaction. The
temperature should not, however, be so high as to cause
20 either the metal oxide or metal aliphatic carboxylic acid
salt to decompose, or to cause the non-halogenated polymer
to significantl~ decompose. Where the metal-containing
compound utilised is a metal aliphatic carboxylic acid salt,
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the resulting stabilised polymeric compound, containing ~he
products of the reaction, is then recovered by any
conventional manner, for example, by forcing through a die
and forming pellets, by granulating, or the like. Where
5 the metal containing compound, however, is a metal oxide,
water is evolved during the reaction. This evolved water
is removed or captured by any suitable technique. For
example, the water may be captured by utilising an amount of
metal oxide in excess of that which is required for the
10 reaction. Alternatively, the water may be removed by vacuum
extraction, or any other technique which could be easily
applied for the removal of the water. Once the water has
been removed or captured the resulting stabilised polymeric
compound containing the product of the reaction is then
15 recovered utilising any conventional means.
Polymers suitable for use with the present invention are as
follows. The halogen containing polymer may be any halogen
containing polymer, preferably those where the halogen is
chlorine. In particular, polyvinyl chloride and
20 polyvinylidene chloride copolymers are most likely to be
used with the present process.
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'l'he non-halogen containing polymer suitable for use in the
present invention may be any non-halogen containing pol~mer
which will not thermally degrade prior to any substantial
thermal degradation of the halogen containing polymeric
5 component of the mixture. It is particularly preferred to
utilise as the non-halogen containing polymer, any
polyolefin, such as polyethylene, polypropylene; styrenics,
such `as polystyrene, and copolymers of olefins such as
copolymers of ethylene with vinyl acetate; and copolymers of
10 styrenics.
While any metal oxide may be used in the process of the
present invention provided it is one which will yield a
stable halogenated metal salt, it is preferred that the
metal oxide be one where the metal is selected from the
15 group consisting of calcium, magnesium and zinc. In the
case where a metal aliphatic carboxylic acid salt, which
will yield a stable halogenated metal salt, is to be used,
it is preferred that the metal be selected from the group
consisting of sodium, potassium, calcium, zinc, magnesium,
~ aluminium, tin and barium. It is preferred that the
aliphatic carboxylate contain a chain of 2-30 carbon atoms,
and more preferably 2-20 carbon atoms.
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Exemplary of the aliphatic carhoxylic acid radicals suitable
for use in the present invention are stearates, such as
calcium or zinc stearate, citrates, tartrates, adipates and
resinates.
~5 The stabilised thermoplastic polymeric eompound obtained as
a result of the process, can be mixed with additives of any
type known within the industry. The various additives are
incorporated into the polymeric compound in order to render
the polymeric compound suitable for given purposes. For
10 example, there may be mixed with the pol~meric compound,
antioxidants, antistatic agents, plasticisers, nucleating
agents, impact modifiers, pigments, fillers, reinforeements,
lubricants, processing aids, coupling agents, and the
like. Examples of materials which unetion for these
15 purposes are well known to those in the industry and are
generally comrnereially available.
The thermoplastie polymerie eompound o~tained as a result of
the process can also be mixed with other polymeric compounds.
In order to evaluate the physical properties of the
20 polymeric materials resulting from the proeess of the
present invention, there are u~ilised the following well
known test procedures:
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Melt flow index "MFI" ISO 1133
Ash content ISO 247
Izod notched impact strength ISO 180
Tensile strength ISO R527
Elongation ISO R527
Flexural modulus ISO 178
This invention is further illustrated by the following
examples wherein all parts are given by weight.
EXAMPLES 1-4.
Examples 1 - 4 of the present application demonstrate that
different metal oxides are e~ually suitable for use in
carrying out the present invention and also that mixtures of
metal oxides may be satisfactorily utilised. In carrying
15 out examples 1-4, the polymeric mixture contains 90% by
weight polypropylene and 10% by weight polyvinylidene
chloride copolymer, wherein the chlorine content is 50~ by
weight of the polyvinylidene chloride copolymer. In carrying
out examples 1-4 the procéssing conditions employed are the
20 same.
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In particular, the polymeric mixture and the metal oxide
utilised in examples l-4 as shown in the following Table l,
are premixed and then introduced into a Haake Rheocord 90
type mixer manufactured and sold by Fisons Instruments. The
5 polymeric mixture and metal oxide premix is then mixed for a
period of 8 minutes at a temperature of approximately 200C
at a mixer speed of 125 rpm. The resultant thermoplastic
polymer is recovered from the mixer and, as shown in Table
l, in each instance exhibits no odour of halogen.
10 From the conditions employed in carrying out examples 1-4
and the lack of any detectable odour of halogen, it can be
concluded that all of the halogen acid evolved from the
halogen containing polymer was reacted with the metal
oxide. Moreoever, there was no odour of halogen detected
15 during the processing of examples 1-4.
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Example No. l 2 3 4
PP/PVdC*, % 92 93 94 88
Calcium oxide, % 8 3.5 _ _
5 Magnesium oxide, % _ 3.5 6 _
Zinc oxide, % _ _ _ 12
Stoichiometric
equivalent of metal
oxide to halogen, % 3.63 3.06 2.65 5.02
10 Molar ratio of metal .
oxide to halogen ** 2.20 2.29 2.27 2.39
Halogen odour NO ~ NO NO
* polypropylene/polyvinylidene chloride copolymer.
** includes at least 1. a mole equivalent of metal oxide
required to capture evolved water.
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In the following examples 5 and 6 there is demonstrated the
use of a combination of a metal oxide together with a metal
aliphatic carboxylic acid salt in carrying out the process
of the present invention. Utilised as the metal oxide is
.5 calcium oxide and as the metal aliphatic carboxylic acid
salt is zinc stearate.
EXAMPLES 5 & 6
Formulations at two different levels of metal oxideJmetal
aliphatic carboxylic acid salt concentrations are described
10in examples 5 and 6 in the processin~ of a polymeric
mixture containing 90% polypropylene and 10% polyvinylidene
chloride copolymer, wherein the chlorine content is 50% by
weight of the polyvinylidene chloride copolymer. Also
included in the formulation is waste polypropylene film.
15The formulations are shown in the following Table 2. In
processing the formulations of examples 5 and 6, each of the
ingredierlts of the formulation are weighed and separately
added to a Banbury mixer.
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The batch wei~ht of the formulation is llOOg and the mixing
is carried out at a temperature slightly above the melting
temperature of polypropylene for a period of 1.5 minutes
subsequent to fluxing OI the pol~ner, under a pressure of 40
,5 psi (2.8 bar). The material is removed from the Banbury
mixer and granulated prior to introduction into a Dolci
single screw extruder having a 45 mm. barrel wherein, at a
temperature exceeding 190C, the halogen acid gas is reacted
with the combination of oxide and stearate. The resulting
10stabilised thermoplastic pol~neric material obtained from
the extruder exhibits no odour of halogen.
Further characteristics of the resultant polymer obtained in
example 6 are described in Table 2. Moreoever, there was
no odour of halogen detected during the processing of
15examples 5 & 6.
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Table. 2
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Example number 5 6
_ . . _
PP/PVdC* % 73 78
Polypropylene % 10 10
5 Calcium oxide % 13 8
Zinc stearate % 4 4
Molar ratio of
metal oxide/metal aliphatic
carboxylic acid salt mixture to
halogen** 4.64 2O72
Stoichiometric equivalent of
metal oxide/metal aliphatic
carboxy~ic acid salt mixture
to halogen, % 3.66 4.41
15 Halogen odour NO NO
MFI, 2.16kg @ 230C, dg/min _ 5.2
Ash content, % _ 8.6
Izod notched impact
strength, KJ/m2 _ 2.7
20 Tensile strength at yield, MPa 24
Tensile strength at break, MPa _ 12
Elongation at break, % _ 43
Flexural modulus, GPa 1.18
* polypropylene/polyvinylidene chloride copolymer.
25 ** includes approximately 1.0 mole equivalent of me-tal
oxide required to capture evolved water.
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In the following examples 7 and 8 there is demonstrated the
use of a given metal oxide for the purpose of preventing the
evolution of the halogen acid gas, at two different
stoichiometric levels. As will be demonstrated hereinafter
5 it was established that both levels of metal oxide were
adequate to prevent the evolution of the evolved halogen
acid gas.
EXAMPLES 7 & 8
In examples 7 and 8 a polymeric mixture containing 90%
10 polypropylene and 10% polyvinylidene chloride, wherein the
chlorine content is 50% by weight of the polyvinylidene
chloride, is mixed with waste polypropylene film and calcium
oxide in the proportions shown in Table 3. In processing
the formulations, the ingredients specified in examples 7
15and 8, shown in Table 3, are séparately added into a Banbury
mixer. The batch weight of llOOg is introduced into the
Banbury mixer where mixing occurs at a temperature slightly
above the melting temperature of polypropylene under a
pressure of 40 psi ( 2.8 bar) for a period of l.5 minutes
20subsequent to fluxing of the polymer. The material is
removed from the Banbury mixer and granulated.
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The granulated material is then introduced into a Betol
single screw extruder, Model 2520/J, having a barrel
diame-ter of 25 mm. wherein the calcium oxide reacts with the
halogen acid gas at a temperature exceeding l90~C. The
resulting stabilised thermoplastic polymeric mixtures
recovered from the extruder exhibit no odour of halogen.
Further physical properties of the resultant polymers
produced in examples 7 and 8 are shown in the following
Table 3. During the process for produciny the resulting
10 thermoplastic polymeric mixtures no odour of halogen was
detected.
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Table 3
.
Example number 7 8
PP/PVdC*, % 73 78
Polypropylene, % 14 14
5 Calcium oxide, % 13 8
Molar ratio of metal
oxide to halogen** 4.52 2.60
Stoichiometric equivalent
of metal oxide to halogen, % 2.88 3.08
10 Halogen odour NO NO
MFI, 2.16kg @ 230~C, dg/min 6.4 8.2
Ash content, % 12.6 8.2
Izod notched impact strength, KJ/m2 2.83.0
Tensile strength at yield, MPa 29 30
15 Tensile strength at break, MPa 16 25
Elongation at break, % 49
* polypropylene/polyvinylidene chloride copolymer.
** includes at least 1.0 mole equivalent of metal oxide
required to capture evolved water.
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19
In the following example 9 there is illustrated the process
of the present inventlon carried out in a twin screw
extruder.
EXAMPLE 9
5 In this example the pol~neric mixture contains 90%
polypropylene and 10% polyvinylidene chloride copolymer,
wherein the chlorine content is 50% by weight of the
polyvinylidene chloride copolymer. The polymeric mixture
and the calcium oxide are introduced as separate
10 ingredients directly into a Werner and Pfleiderer model
ZSK40 twin screw extruder having a barrel of 40 mm.
diameter. The extruder is operated at temperatures in
excess of 220C at a screw speed of 250 rpm and a pressure
of 14 bar. The resulting stabilised polymeric material
15 obtained from the extruder exhibits no odour of halogen.
Further properties of the resultant thermoplastic polymeric
material are found in the following Table 4.
Table 4
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Example number 9
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PP/PVdC* % 82
Calcium oxide % 18
Molar ratio of
metal oxide to halogen** 5.57
Stoichiome-tric equivalent of
metal oxide to halogen, % 3.23
Halogen odour NO
MFI, 2.16kg @ 230C, dg/min 5.0
Ash content, % 18.1
Izod notched impact strength, KJ/m~ 2.8
Tensile strength Q yield, MPa 26
Tensile strength ~ break, MPa 16
15 Elongation at break, % 71
Flexural modulus, GPa 1.2 .
_
* polypropylene/polyvinylidene chloride copolymer.
** i.ncludes at least 1.0 mole equivalent of metal oxide
reguired to capture evolved water.
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EXAMPLES lO-l9
Examples lO-l9 o~ the present application demonstrate that
different metal aliphatic carboxylic acid salts are
equally suitable for use in carrying out the present
invention and also that mixtures of metal aliphatic
carboxylic acid salts may be satisfactorily used. In
carrying out examples lO-l9, the polymeric mixture
contains 90% by weight polypropylene and 10% by weight
polyvinylidene chloride copolymer, wherein the chlorine
content is 50% by weight of the polyvinylidene chloride
copolymer. In carrying out examples lO-l9 the processing
conditions employed are the same. In particular, the
polymeric mixture and the metal aliphatic carboxylic acid
salt utilised in examples lO-l9 as shown in the following
Table 5, are premixed and then introduced into a Haake
Rheocord 90 type mixer as used in examples l-4. The
polymeric mixture and metal aliphatic carboxylic acid salt
premix is then mixed for a period of 5 minutes at a
temperature of 210C at a mixer speed of 50 rpm. During
processing, a glass rod dipped in a 5.0 N (normal)
solution of ammonium hydroxide is placed at the top of the
mixer where any evolved gas would escape. No white
clouds of ammonium chloride are formed indicating that no
halogen acid is evolved. The resultant stabilised
thermoplastic polymer is recovered from the mixer.
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From the conditions employed in carrying out examples
10-19 and the lack of any detectable halogen, it is
evident that all of the halogen acid evolved from the
halogen containing polymer was reacted with the metal
aliphatic carboxylic acid salt. Moreover there was no
halogen detected while carrying out examples 10-19.
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In the following examples 20-22 there is demonstrated
another manner for producing granulate from the polymeric
composition of the invention and, further, the production
of in~ection moulded specimens from the granulates. Also,
these examples demonstrate three metal aliphatic
oarboxylic acid salts utilised to react with halogen acid
gas.
EXAMPLES 20-22
. . _
In examples 20-22 a polymeric mixture containing 90
polypropylene and 10% polyvinylidene chloride copolymer,
wherein the chlorine content is 50% by weight of the
polyvinylidene chloride copolymer, is mixed with various
metal aliphatic carboxylic acid salts as shown in Table
6. In processing the formulations, the ingredients
specified in examples 20 22 and shown in Table 6 are
separately added into a Banbury mixer. In each case the
batch weight of 1200g is introduced into the Banbury mixer
where mixing occurs at a temperature slightly above the
melting temperature of polypropylene under a pressure of
psi (2.8 bar). Mixing is for a period of between 5 and
10 minutes subsequent to fluxing of the polymer, for
examples 20 and 21; and for a period of 1.5 minutes
subsequent to fluxing of the polymer, for example 22.
The material is removed from the Banbury mixer and
granulated.
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The granulated material is then introduced into a
Battenfeld injection moulding machine, Model BA300 CD
plus, having a barrel diameter of 3Omm wherein the
reaction of the halogen acid gas with the metal aliphatic
,5 carboxylic acid salt occurs at 230C.
The resulting moulded test pieces of polymers produced
exhibited no odour of halogen. Physical properties of
the resultant polymers produced in examples 20-22 are
shown in the following Table 6.
.
.
26
Table 6
Example ~o. 20 21 = _
PP/PVdC*, % 65 65 75
Sodium stearate, % 35 _
.5 Aluminium stearate, % _ 35 _
Sodium hydrogen tartrate, % _ _ 25 ~;
Stoichiometric equivalent of metal
oxide to halogen, % 30.129.1 19.5
Molar ratio of metal aliphatic
10 carboxylic acid salt to halogen, % 1.25 1.31 1.38
Halogen odour NO NO NO
MFI, 2.16kg Q 230C, dg/min _ 34.3 4.9
Ash content, % 3.2 4.1 8.8
Izod notched impact strength, kJ/m2 1.7 2.9 2.6
15 Tensile strength at break, MPa 20 17 _
Elongation at break, % 6 10
Flexural modulus, GPa 2.09 1 0 6a
* polypropylene/polyvinylidene chloride copolymer
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From a review of the data shown in the foregoing tables 1-6,
it will be readily observed that the stabilised
thermoplastic polymeric materials obtained ky means of the
process of the present invention are characterised by having
~5 physical properties comparable to those of standard
commercially available grades of polypropylene having melt
flow index (MFI~ properties of approximately the range shown
in the examples of the invention. When drawing a
comparison with the standard grades of polypropylene, the
10 thermoplastic polymeric materials of the present invention
exhibit comparable values for tensile strength~ flexural
modulus and Izod notched impact strength. Accordingly, the
thermoplastic polymeric materials of the present invention
would be suitable as starting materials for the production
15 of polymeric compounds.
While the present invention has been disclosed in connection
with the embodiments hereof~ it should ~e understood that
there are other embodiments which fall within the spirit and
scope of the invention and that the invention is susceptible
20 to modification, variation and change without departing from
the proper scope or fair meaning of the following claims.
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