Title of Invention

FLAME RETARDANT POLYETHYLENE COMPOSITION COMPRISING POYPROPYLENE

Abstract The present invention relates to a flame retardant polymer composition comprising (A) a polyethylene, (B) a silicone-group containing compound, (C) an inorganic filler material, and (D) a polypropylene in an amount of 0.1 to 10 wt.% with respect to the total composition, to an article comprising said flame retardant polymer composition, in particular to a wire or cable comprising a layer made of said flame retardant composition and to the use of said flame retardant polymer composition for the production of a layer of a wire or cable. Furthermore, the invention relates to the use of a polypropylene in the production of a flame retardant layer for a wire or cable as a processing aid.
Full Text Flame Retardant Polyethylene Composition comprising Polypropylene
The present invention relates to a flame retardant polymer composition, to an
article, in particular a wire or cable, comprising said flame retardant polymer
composition, and to the use of said composition for the production of a layer
of a wire or cable.
For improving the flame retardancy of polymers, several approaches are
known in the art. First, it is known to include compounds containing halides
into the polymer. However, these materials have the disadvantage that by
burning hazardous and corrosives gases like hydrogen halides are
deliberated. This is also a disadvantage of flame retardant polymer
composition based on PVC.
In a further approach, flame retardant compositions include relatively large
amounts, typically 50 to 60 wt.%, of inorganic fillers such as e.g. hydrated
and hydroxy compounds, which during burning decompose endothermically
and deliberate inert gases at temperatures in the range of 200 to 600°C. Such
inorganic fillers e.g. include Al(OH)3 and Mg(OH)2. However, these flame
retardant materials suffer from the high costs of the inorganic fillers and the
deterioration of the processability and mechanical properties of the polymer
composition due to the high amount of filler.
A third approach as disclosed in EP 0 393 959 uses a silicon fluid or gum in
a composition together with an organic polymer comprising an ethylene
acrylate or acetate copolymer, and an inorganic filler. Although such a
composition has good flame retardant properties, the processability of the
composition may still be improved because often melt fracture occurs when

the composition is extruded as a cable layer. Furthermore, the surface quality
of extruded cable layers often is insufficient an may also be further
improved.
It is thus an object of the present invention to avoid the disadvantages of the
prior art materials and to provide a flame retardant polymer composition
which shows a combination of good flame retardancy, good processability,
such as extrudability, and good mechanical properties, such as improved
surface quality.
The present invention is based on the finding that the processability of a
polymer composition comprising an organic polymer, a silicone group
containing compound and an inorganic filler material can be improved by
the addition of a small amount of polypropylene, usually from 0.1 to 10
wt.%.
The invention therefore provides a flame retardant polymer composition
comprising
(A) a polyethylene,
(B) a silicone-group containing compound,
(C) an inorganic filler material, and
(D) a polypropylene in an amount of 0.1 to 10 wt.% with
respect to the total composition.
The composition of the invention shows improved processability as can be
seen by an improved extrusion behaviour when the composition is extruded
as a layer of a wire or cable. Furthermore, the extruded layers have
good/improved surface quality. Still further, the compositions show good
flame retardancy.

Preferably, the composition is free of halogen- and phosphorous-containing
compounds as flame retardancy aids, i.e. such compounds, if at all, are
present in the composition in an amount of below 3000 ppm.
More preferably, the composition is entirely free of halogen-containing
compounds. However, especially phosphorous containing-compounds may
be present in the composition as stabilizers, usually in an amount of below
2000 ppm, more preferably below 1000 ppm.
In the composition, components (A) to (D) may either consist of a single
chemical compound or a mixture of compounds of the required type.
Preferably, the amount of polypropylene (D) is 0.2 wt.% or more, more
preferably is 0.3 wt.% or more, and most preferably is 0.5 wt.% or more of
the total composition.
Furthermore, preferably the amount of polypropylene (D) is 8 wt.% or less,
more preferably is 4 wt.% or less, and most preferably is 3 wt.% or less of
the total composition.
Still further, preferably polypropylene (D) has a MFR2 measured according
to ISO 1133 at 230 °C and 2.16 kg of 0.1 to 15 g/10 min, more preferably of
0.5 to 10g/10min.
Polypropylene (D) preferably has a tensile modulus measured according to
ISO 527-2 of 400 to 2000 MPa, more preferably of 600 to 1600 MPa.
In a preferred embodiment, polypropylene (D) is a propylene heterophasic
copolymer comprising a polypropylene homo- or copolymer as matrix
polymer and an incorporated ethylene-propylene-rubber.
The heterophasic propylene copolymer may be produced by multistage
process polymerisation of propylene and ethylene and optionally alpha-

olefin such as bulk polymerisation, gas phase polymerisation, slurry
polymerisation, solution polymerisation or combinations thereof using
conventional catalysts. The heterophasic copolymer can be made either in
loop reactors or in a combination of loop and gas phase reactor. Those
processes are well known to one skilled in the art.
A preferred process is a combination of a bulk slurry loop reactor(s) and gas
phase reactor(s). First, the propylene homo- or copolymer matrix is made
either in loop reactor(s) or in a combination of loop and gas phase reactor.
The polymer produced in this way is transferred into another reactor and the
disperse phase, the ethylene-propylene-rubber, is produced by
copolymerising a mixture of ethylene and propylene with the same catalyst
system, so obtaining a heterophasic system consisting of a semicrystalline
matrix with a nearly amorphous elastomeric component dispersed within it.
Preferably this polymerisation step is done in a gas phase polymerisation.
A suitable catalyst for the polymerisation of the heterophasic copolymer is
any stereospecific catalyst for propylene polymerisation which is capable of
polymerising and copolymerising propylene and comonomers at a
temperature of 40 to 110 °C and at a pressure from 10 to 100 bar. Ziegler-
Natta catalysts as well as metallocene catalysts are suitable catalysts.
Alternatively to producing the heterophasic copolymer in a sequential
multistage process as described above, it can be produced by polymerising
the matrix polymer and the ethylene-propylene-rubber in separate steps and
melt blending the two polymers.
"Rubber" and "elastomeric copolymer" are in this context used as synonyms.
An ethylene propylene elastomeric copolymer may be produced by known
polymerisation processes such as solution, suspension and gas-phase

polymerisation using conventional catalysts. Ziegler-Natta catalysts as well
as metallocene catalysts are suitable catalysts.
A widely used process is the solution polymerisation. Ethylene, propylene
and catalyst systems are polymerised in an excess of hydrocarbon solvent.
Stabilisers and oils, if used, are added directly after polymerisation. The
solvent and unreacted monomers are then flashed off with hot water or
steam, or with mechanical devolatilisation. The polymer, which is in crumb
form, is dried with dewatering in screens, mechanical presses or drying
ovens. The crumb is formed into wrapped bales or extruded into pellets.
The suspension polymerisation process is a modification of bulk
polymerisation. The monomers and catalyst system are injected into the
reactor filled with propylene. The polymerisation takes place immediately,
forming crumbs of polymer that are not soluble in the propylene. Flashing
off the propylene and comonomer completes the polymerisation process.
The gas-phase polymerisation technology consists of one or more vertical
fluidised beds. Monomers and nitrogen in gas form along with catalyst are
fed to the reactor and solid product is removed periodically. Heat of reaction
is removed through the use of the circulating gas that also serves to fluidise
the polymer bed. Solvents are not used, thereby eliminating the need for
solvent stripping, washing and drying.
The production of ethylene propylene elastomeric copolymers is also
described in detail in e.g. US 3,300,459, US 5,919,877, EP 0 060 090 A1 and
in a company publication by EniChem "DUTRAL, Ethylene-Propylene
Elastomers" , pages 1-4 (1991).
Alternatively, elastomeric ethylene-propylene copolymers, which are
commercially available and which fulfill the indicated requirements, can be
used.

The heterophasic copolymer is then produced by combining the matrix
polymer in the form of powder or granules and the elastomeric copolymer in
a melt mixing device.
In case a polypropylene random copolymer is used as matrix polymer for the
heterophasic copolymer, the comonomers preferably are linear alpha-olefins
or branched alpha-olefins like ethylene, butene, hexene etc. In the present
invention ethylene is most preferred.
The comonomer content is preferably equal to or below 10 wt.-%, more
preferably between 4 and 8 wt%, based on the total polypropylene random
copolymer.
However, preferably the matrix polymer is a polypropylene homopolymer.
Furthermore, the heterophasic copolymer contains an ethylene-propylene-
rubber preferably in a content of equal to or below 35 wt%, more preferably
from 10 to 20 wt%, based on the total weight of polymer (D).
The ethylene-propylene-rubber preferably has a propylene content of 40 to
80 wt.%, more preferably of from 45 to 60 wt.%, based on the total amount
of the ethylene-propylene-rubber.
The ethylene-propylene rubber apart from ethylene and propylene monomer
units may contain further alpha-olefin monomer units. However, it is
preferred that the ethylene-propylene rubber consists of ethylene and
propylene monomer units.
Preferably, in the composition of the invention the amount of polyethylene
(A) is from 30 to 70 wt.% of the total composition, more preferably from 40
to 60 wt% of the total composition.
In a preferred embodiment, polyethylene (A) comprises a polyethylene with

a molecular weight distribution Mw/Mn of > 20, more preferably of > 22, and
most preferably of > 25.
Preferably, polyethylene (A) is produced in a high pressure process, i.e.
typically under a pressure of 50 MPa and above, without the use of a
polymerisation catalyst.
Polyethylene (A) preferably has a g' value of 0.35 or less.
Preferably, the shear thinning index SHIeta0.05/eta300 of polyethylene (A) is at
least 70
In the composition of the invention, polyethylene (A) preferably comprises a
polyethylene with polar groups.
The polyethylene with polar copolymer preferably is produced by
copolymerisation of ethylene monomers with polar comonomers. However,
it may also be produced by grafting a polyethylene, for example by grafing
acrylic acid, methacrylic acid or maleic anhydride onto the polyethylene.
It is preferred that the polar groups are introduced into the polyethylene by
copolymerisation of ethylene monomers with appropriate comonomers
bearing polar groups.
It is further preferred that the polar copolymer comprises a copolymer of
ethylene, with one or more comonomers selected from C1 to C6-alkyl
acrylates, C1 to C6-alkyl methacrylates, acrylic acids, methacrylic acids and
vinyl acetate. The copolymer may also contain ionomeric structures (like in
e.g. DuPont's Surlyn types).
Still further preferred, the polar copolymer is an ethylene/acrylate, and/or
ethylene/acetate, copolymer.

Further preferred, the polar polymer comprises a copolymer of ethylene with
C1 to C4-alkyl, such as methyl, ethyl, propyl or butyl, acrylates or
vinylacetate.
In a particularly preferred embodiment, component (A) of the polymer
composition used for the flame retardant layer comprises, preferably makes
up at least 25 wt%, more preferably at least 35 wt% and most preferably
consists of, a copolymer or a mixture of copolymers of an olefin, preferably
ethylene, with one or more comonomers selected from the group of non-
substituted or substituted acrylic acids according to formula (I):

wherein R is H or an organic substituent, preferably R is H or a hydrocarbon
substituent.
More preferably, the type of comonomer is selected from the group of
acrylic acid according to formula (I) wherein R is H or an alkyl group, still
more preferably R is H or a C1- to C6-alkyl substituent.
It is particularly preferred that the polar polyethylene comprises a copolymer
of ethylene with an acrylic copolymer, such as ethylene acrylic acid or
methacrylic acid copolymer, and most preferred is ethylene methacrylic acid
copolymer.
Preferably, the amount of comonomer with polar groups in the ethylene
copolymer is from 2 to 40 wt.%, more preferably is from 4 to 20 wt.% and
most preferably is from 6 to 12 wt.%.
In addition to ethylene and the defined comonomers, the copolymers may
also contain further monomers. For example, terpolymers between acrylates

and acrylic acid or methacrylic acid, or acrylates with vinyl silanes, or
acrylates with siloxane, or acrylic acid with siloxane may be used.
These copolymers may be crosslinked after extrusion, e.g. by irradiation
Silane-crosslinkable polymers may also be used, i.e. polymers prepared
using unsaturated silane monomers having hydrolysable groups capable of
crosslinking by hydrolysis and condensation to form silanol groups in the
presence of water and, optionally, a silanol condensation catalyst.
It is further preferred that the polyethylene with polar groups makes up at
least 30 wt.%, more preferred at least 50 wt.%, and still more preferred at
least 70 wt.% of component (A). Most preferably, component (A) completely
consists of the polyethylene with polar groups.
The composition further comprises a silicone-group containing compound
(B).
In a preferred embodiment of the inventive composition, component (B) is a
silicone fluid or a gum, or an olefin, preferably ethylene, copolymer
comprising at least one silicone-group containing comonomer, or a mixture
of any of these compounds.
Preferably, said comonomer is a vinylpolysiloxane, as e.g. a vinyl
unsaturated polybishydrocarbylsiloxane.
Silicone fluids and gums suitable for use in the present inventions are known
and include for example organopolysiloxane polymers comprising
chemically combined siloxy units selected from the group consisting of
R3SiO0.5, R2SiO, R1SiO1.5, R1R2SiO0.5, RR1SiO, R12SiO, RSiO15 and SiO2
units and mixtures thereof in which each R represents independently a
saturated or unsaturated monovalent hydrocarbon radical and each R1
represents a radical such as R or a radical selected from the group consisting

of hydrogen, hydroxyl, alkoxy, aryl, vinyl or allyl radicals.
The organopolysiloxane preferably has a number average molecular weight
Mn of approximately 10 to 10,000,000. The molecular weight distribution
(MWD) measurements were performed using GPC. CHCl3 was used as a
solvent. Shodex-Mikrostyragel (105, 104, 103, 100 A) column set, RI-detector
and a NMWD polystyrene calibration were used. The GPC tests were
performed at room temperature.
The silicone fluid or gum can contain fumed silica fillers of the type
commonly used to stiffen silicone rubbers, e.g. up to 50% by weight
Copolymers of an olefin, preferably ethylene, and at least one silicone-group
containing comonomer preferably are a vinyl unsaturated polybis-
hydrocarbylsiloxane or an acrylate or methacrylate modified hydrocarbyl
siloxane according to formula (II) and (III):

wherein in both (II) and (III) n = 1 to 1000 and

R and R' independently are vinyl, alkyl branched or unbranched, with 1 to 10
carbon atoms; aryl with 6 or 10 carbon atoms; alkyl aryl with 7 to 10 carbon
atoms; or aryl alkyl with 7 to 10 carbon atoms. R" is hydrogen or an alkyl
chain.
Such compounds e.g. are disclosed in WO 98/12253 the contents of which is
herein enclosed by reference.
Preferably, component (B) is polydimethylsiloxane, preferably having a Mn
of approximately 1,000 to 1,000,000, more preferably of 200,000 to 400,000,
and/or a copolymer of ethylene and vinyl polydimethylsiloxane. These
components (B) are preferred due to commercial availability.
The term "copolymer" as used herein is meant to include copolymers
produced by copolymerization or by grafting of monomers onto a polymer
backbone.
It is preferred that silicone-group containing compound (B) is present in the
composition in an amount of 0.5 to 40 wt.%, more preferred 0.5 to 20 wt.%,
still more preferred from 0.5 to 10 wt.% and most preferred 1 to 5 wt.% of
the total composition.
It is, furthermore, preferred that the silicone-group containing compound is
added in such an amount that the amount of silicone-groups in the total
composition is from 1 to 20 wt.%, more preferably from 1 to 10 wt%.
It is preferred that inorganic filler (C) is present in the composition in an
amount of more than 10 wt%, more preferred of 20 wt% or more, still more
prefered of 30 wt% or more, and most preferred of 35 wt% or more.
It is further preferred that inorganic filler (C) is present in the composition in
an amount up to 70 wt%, more preferably of up to 60 wt% and most
preferably of up to 55 wt%.

Component (C), i.e. the inorganic filler material suitable for use in the
composition, comprises all filler materials as known in the art. Component
(C) may also comprise a mixture of any such filler materials. Examples for
such filler materials are oxides, hydroxides and carbonates of aluminium,
magnesium, calcium and/or barium.
Preferably, component (C) comprises an inorganic compound of a metal of
groups 1 to 13, more preferred groups 1 to 3, still more preferred groups 1
and 2 and most preferred group 2, of the Periodic Table of Elements.
The numbering of chemical groups, as used herein, is in accordance with the
IUPAC system in which the groups of the periodic system of the elements
are numbered from 1 to 18.
Preferably, inorganic filler component (C) comprises, more preferably
consists of, a compound which is neither a hydroxide, nor a hydrated
compound, still more preferably comprises, more preferably consists of, a
compound selected from carbonates, oxides and sulphates, and most
preferably comprises, more preferably consists of, a carbonate.
Preferred examples of such compounds are calcium carbonate, magnesium
oxide and huntite Mg3Ca(CO3)4, with a particular preferred example being
calcium carbonate.
Although inorganic filler (C) preferably is not a hydroxide or hydrated
compound, it may contain small amounts of hydroxide typically less than 5%
by weight of the filler, preferably less than 3% by weight. For example there
may be small amounts of magnesium hydroxide in magnesium oxide.
Furthermore, although filler (C) is not a hydrated compound, it may contain
small amounts of water, usually less than 3% by weight of the filler,
preferably less than 1% by weight. However, it is most preferred that
component (C) is completely free of hydroxide and/or water.

Preferably, component (C) of the inventive flame retardant polymer
composition comprises 50 wt% or more of calcium carbonate and further
preferred consists of calcium carbonate.
The inorganic filler may comprise a filler which has been surface-treated
with an organosilane, a polymer, a carboxylic acid or salt etc. to aid
processing and provide better dispersion of the filler in the organic polymer.
Such coatings usually do not make up more than 3 wt.% of the filler.
Preferably, the compositions according to the present invention contain less
than 3 wt.% of organo-metallic salt or polymer coatings.
Furthermore, also other mineral fillers such as glass fibres may be part of the
composition.
The compositions according to the present invention may be cross-linkable.
It is well known to cross-link thermoplastic polymer compositions using
irradiation or cross-linking agents such as organic peroxides and thus the
compositions according to the present invention may contain a cross-linking
agent in a conventional amount. Silane cross-linkable polymers may contain
a silanol condensation catalyst.
In addition to components (A) to (D) the composition of the invention may
also contain additional conventional polymer ingredients such as, for
example, antioxidants or UV stabilizers in small amounts, usually below 10
wt.%, more preferably below 5 wt.%.
The flame retardant polymer composition of the invention may be prepared
by
a) preparation of a master batch comprising the silicone-group
containing compound, additives and polymer followed by
compounding with inorganic filler and matrix polymer or

b) one step compounding of all components.
For mixing, a conventional compounding or blending apparatus, e.g. a
Banbury mixer, a 2-roll rubber mill, Buss-co-kneader or a twin screw
extruder may be used.
Preferably, the composition will be prepared by blending them together at a
temperature which is sufficiently high to soften and plasticise the polymer,
typically a temperature in the range of 120 to 200 °C.
The flame retardant compositions of the invention can be used in many and
diverse applications and products. The compositions can for example be
moulded, extruded or otherwise formed into mouldings, sheets and fibers.
The present invention thus further relates to an article comprising the flame
retardant polymer composition in any of the above-described embodiments.
In particular, the invention relates to a wire or cable comprising a layer made
of the flame retardant composition in any of the above-described
embodiments and, accordingly, to the use of a flame retardant polymer
composition in any of the above-described embodiments for the production
of a layer of a wire or cable.
The polymer composition preferably is extruded to form a flame retardant
layer of a wire or cable. This is preferably done at a line speed of at least 20
m/min, more preferably at least 60 m/min and most preferably at least 100
m/min.
The pressure used for extrusion preferably is 50 to 500 bar.
Still further, the invention relates to the use of a polypropylene in the
production of a flame retardant layer for a wire or cable as a processing aid,
wherein the polypropylene is present in the composition used for the

production of the flame retardant layer in an amount of from 0.1 to 10 wt.%.
In the following the present invention is further illustrated by means of ex-
amples.
Examples
1. Measurement methods
a) Confocal Laser Scanning Microscopy
The improved surface smoothness and reduced melt fracture has been
evaluated by confocal laser scanning microscopy using a Leica TCS-SP. The
investigation area was 500 x 500 micrometer, and the wavelength of the
laser-beam was 488 nm. As the lens, a HC PL APO 20 x/0.70 was used, and
the resolution in xy-direction was 279 nm, and in xz-direction 768 nm. The
step size in the tests was 486 nm.
The resolution of the z-Table was 40 nm, the z-standard (for function control
and validation) was from Rommelwerke with Rmax of 0.97 micron.
b) Melt Flow Rate
The melt flow rate MFR2 was measured in accordance with ISO 1133 at
190°C and a load of 2.16 kg for polyethylene and at 230 °C and a load of
2.16 kg for polypropylene.
c) Tensile Modulus
Tensile modulus was determined according to IS0527-2.

d) Molecular weight distribution and long chain branching
The following procedure is used to determine g'. This procedure should be
followed when determining the branching parameter g' in accordance with
the present invention.
Gel Permeation Chromatography is used for determination of molecular
weight (M), molecular weight distribution (Mw/Mn), intrinsic viscosity [η]
and contents of long chain branching (LCB) g'.
Gel Permeation Chromatography (GPC), which is also known as Size
Exclusion Chromatography (SEC), is an analytical technique where the
molecules are separated after their size. Large molecules elutes first and the
smaller ones later.
Molecules elute after decreasing hydrodynamic volume Vh. This can be
described as a product of the molecules molecular weight (M) and its
intrinsic viscosity [η].
The principal of universal calibration in GPC states that for given sets of
solvent and temperature conditions in which a polymer sample is separated
by pure size mechanism (no adsorption or other effects), the logarithm of the
hydrodynamic volume of a polymer molecule as a function of its elution
volume (or time) is identical for all polymers, linear or branched. See the
equation:
Vh = [η] x M or logVh = log ([η] x M)
The hydrodynamic volume is defined as a product of intrinsic viscosity [η]
and molecular weight M.
Universal calibration is independent of the polymer type and possible
branched polymers.

A serial of small standard is used to find the relation between retention time
and molecular weight.
Mark-Houwink-Sakurade equation relates a polymer intrinsic viscosity to its
viscosity average molecular weight Mv.

[η] is the intrinsic viscosity.
Mv is the viscosity average molecular weight.
K and a are Mark-Houwink constants. These constants are dependent of the
polymer type, solution and the temperature.
By taking the logarithm on both sides of the equation we will get:

A plot of log [n] versus log [Mv] (narrow standards) gives slope and the
intercept K.
If K and a are known for both standards and samples, the molecular weights
can be decided by mean of the relation to their respective constants.
GPC uses a Universal Calibration for quantitative evaluation of the
molecular weight distribution.
The calibration is based on narrow standards to calculate a universal
calibration curve. The retention time for each standard (the RI peak) is
calculated. These values, together with the appurtenant molecular weight are
used to make a universal calibration curve.
The software is able to produce a plot of Log Viscosity versus Log
Molecular Weight for both the RI- and the viscosity-detector. Each detector

produces a universal calibration for each fraction within the polymer
chromatogram.
A universal calibration gives genuine molecular weight results.
The software can decide K and a for the standards.
The following values are recommended to be used.

The equipment used was a Waters 150CVplus Gel Permeation
Chromatograph no. W-4412 (cf. Waters 150CVplus Viscometer Supplement)
having a differential Refractive Index (dRI) detector and a single capillary
viscometer detector, and three HT6E Styragel (porous styrene-
divinylbenzene) columns from Waters. Calibration was made with narrow
molecular weight distribution polystyrene standards with different molecular
weights (a1116_05002). The mobile phase was 1,2,4-trichlorobenzene
(purity 98.5 %) with 0.25 g/l BHT, 2-tert-butyl-4-methylphenol added as an
antioxidant. Millennium32 Version 4 software from Waters was used for
calculation of g' (LCB).
Viscosity Low Plots are determined for the polystyrene standards which
have no long chain branching and therefore represent linear (unbranched)
polymers, and for the branched polyethylene composition of the invention.
The branching parameter is thereafter calculated from the equation:


where [η]branched is the intrinsic viscosity of the branched polymer in question
and [η]linear is the intrinsic viscosity of an linear (unbranched) standard
polymer.
e) Shear Thinning Index
The shear thinning index SHI(eta0.05/eta300) was determined by dynamic
rheology in a plate/plate rheometer.
This property can be measured as a ratio of the viscosity at two different
shear stresses. In the present invention the shear stresses (or G*) at 0.05 kPa
and 300 kPa are used for calculating the SHI(eta0.05/eta300) as a measure of the
broadness of the molecular weight distribution.

wherein

It was measured in a Physica MCR300 in oscillating — frequency sweep.
Temperature was 170°C and frequency range was 0.1-500 rad/s. Strain was
set to 5%.
2. Compounding of compositions
Flame retardant polymer compositions were produced by compounding
together the components in a Busskneader, 200 mm.

The following compositions were prepared:
Composition 1:
- 56 wt.% ethylene butylacrylate (BA) copolymer with BA content of
8.7 wt.%, MFR2 = 0.45 g/10min, Mw/Mn = 50, g' = 0.24,
SHI(eta0.05/eta300) = 102.9;
- 2 wt.% heterophasic propylene copolymer with 85 wt.% propylene
homopolymer as matrix and 15 wt.% of ethylene propylene rubber, of
which 7 wt.% are ethylene units, as dispersed phase, MFR2 = 1.3
g/10min, d = 0.908 g/cm3, tensile modulus =1300 MPa;
- 12 wt % of silicone masterbatch with 40 wt % of polysiloxane;
- 30 wt% chalk;
the composition had ad= 1.153 g/cm3 and a MFR2 of 0.46 g/10min (190 °C,
2.16 kg).
Composition 2:
- 56 wt.% ethylene butylacrylate (BA) copolymer with BA content of
8.1 wt.%, MFR2 = 0.45 g/10min, Mw/Mn = 14, g' = 0.41,
SHI(eta0.05/eta300) = 92.6;
- 2 wt.% heterophasic propylene copolymer with 85 wt.% propylene
homopolymer as matrix and 15 wt.% of ethylene propylene rubber, of
which 7 wt.% are ethylene units, as dispersed phase, MFR2 = 1.3
g/10min, d = 0.908 g/cm3, tensile modulus = 1300 MPa;
- 12 wt % of silicone masterbatch with 40 wt % of polysiloxane;
- 30 wt% chalk;

the composition had a d = 1.148 g/cm3 and a MFR2 of 0.46 g/10min (190 °C,
2.16 kg).
Composition 3 (Comparative):
- 58 wt.% ethylene butylacrylate (BA) copolymer with BA content of
8.1 wt.%, MFR2 = 0.45 g/10min, Mw/Mn = 17, g' = 0.41,
SHI(eta0.05/eta300) = 92.6;
- 12 wt % of silicone masterbatch with 40 wt % of polysiloxane;
- 30 wt% chalk;
the composition had a d = 1.140 g/cm3 and a MFR2 of 0.39 g/10min (190 °C,
2.16 kg).
Cables were made on a laboratory extrusion line. The compositions were
extruded onto a 7 mm nylon rope and the insulation thickness was 1 mm. A
tube-on die was used and the line speed was 25 and 50 meter per minute. The
laboratory extrusion line was equipped with seven temperature zones (120,
140, 150, 160, 170, 170, 170°C).
The following table 1 shows, the ratio of surface (3D) to area (2D) which is a
measure for the surface quality, i.e. he lower the ratio, the better is the
surface quality. The surface areas have also been inspected visually and by
touch. The values from ratio of surface (3D) to area (2D) is corresponding to
visual and manual inspection.


A high ratio of surface (3D) to area (2D) means that the surface is rough.
Thus, the surface of the inventive compositions is significantly better than
the surface of the comparative example.

Claims
A flame retardant polymer composition comprising
(A) a polyethylene,
(B) a silicone-group containing compound,
(C) an inorganic filler material, and
(D) a polypropylene in an amount of 0.1 to 4 wt.% with respect to
the total composition.
Flame retardant polymer composition according to claim 1, wherein the
amount of component (D) is from 0.3 to 4 wt.%.
Flame retardant polymer composition according to claim 1 or claim 2,
wherein component (D) has a MFR2 measured according to ISO 1133 at
230 oC and 2.16 kg of 0.1 to 15g/10min.
Flame retardant polymer composition according to any of the preceding
claims, wherein polypropylene (D) is a propylene heterophasic copolymer
comprising a polypropylene homo- or copolymer as matrix polymer and
an incorporated ethylene-propylene-rubber.
Flame retardant polymer composition according to any of the preceding
claims, wherein component (D) has a tensile modulus measured according
to ISO 527-2 of 400 to 2000 MPa.
Flame retardant composition according to any of the preceding claims
wherein the amount of polyethylene (A) is from 30 to 70 wt.% of the total
polymer composition.
Flame retardant composition according to any of the preceding claims
wherein polyethylene (A) comprises a polyethylene with a molecular
weight distribution Mw/Mn of > 20.

Flame retardant composition according to any of the preceding claims
wherein polyethylene (A) comprises a polyethylene with polar groups.
Flame retardant composition according to claim 8 wherein the
polyethylene with polar groups comprises a copolymer of ethylene with
one or more co-monomers selected from C1- to C6- alkylacrylates, C1- to
C6- alkyl methacrylates, acrylic acid, methacrylic acid and vinyl acetate
including ionomers thereof.
Flame retardant composition according to claim 8 or 9 wherein the
polyethylene with polar groups is present in an amount of at least 50 wt.%
of the total weight of component (A).
Flame retardant composition according to any of the preceding claims
wherein the amount of component (B) is from 1 to 20 wt.% of the total
polymer composition
Flame retardant composition according to any of the preceding claims
wherein component (B) is a silicone fluid and/or gum, and/or a copolymer
of ethylene and at least one other co-monomer which comprises a silicone
group.
Flame retardant composition according to any of the preceding claims
wherein component (B) comprises polydimethylsiloxane and/or a
copolymer of ethylene and vinyl-polymethylsiloxane.
Flame retardant polymer composition according to any of the preceding
claims wherein the amount of inorganic filler (C) is from 20 to 60 wt.% of
the total polymer composition.
Flame retardant polymer composition according to any of the preceding
claims, wherein inorganic filler (C) is neither a hydroxide nor a hydrated
compound.

Flame retardant polymer composition according to any of the preceding
claims wherein inorganic filler (C) comprises a carbonate, oxide and/or
sulphate of an element of groups 1 to 13 of the Periodic System of the
Elements.
Flame retardant composition according any of the preceding claims
wherein component (C) comprises a metal carbonate.
Articles comprising the flame retardant polymer composition according to
any of the preceding claims.
Wire or cable comprising a layer made of the flame retardant composition
according to any of claims 1 to 17.
Use of a flame retardant polymer composition according to any of claims
1 to 17 for the production of a layer of a wire or cable.
Use of a polypropylene in the production of a flame retardant layer for a
wire or cable as a processing aid wherein the polypropylene is present in
the composition used for the production of the flame retardant layer in an
amount of from 0.1 to 4 wt.%.
Use of polypropylene in the production of a flame retardant layer for a
wire or cable as a processing aid wherein a composition is used as in
claim 1 to 17.

The present invention relates to a flame retardant polymer composition comprising (A) a polyethylene, (B) a silicone-group
containing compound, (C) an inorganic filler material, and (D) a polypropylene in an amount of 0.1 to 10 wt.% with
respect to the total composition, to an article comprising said flame retardant polymer composition, in particular to a wire or cable
comprising a layer made of said flame retardant composition and to the use of said flame retardant polymer composition for the
production of a layer of a wire or cable. Furthermore, the invention relates to the use of a polypropylene in the production of a flame
retardant layer for a wire or cable as a processing aid.

Documents:


Patent Number 257882
Indian Patent Application Number 4555/KOLNP/2008
PG Journal Number 47/2013
Publication Date 22-Nov-2013
Grant Date 14-Nov-2013
Date of Filing 10-Nov-2008
Name of Patentee BOREALIS TECHNOLOGY OY
Applicant Address P. O. BOX 330, FIN-06101 PORVOO
Inventors:
# Inventor's Name Inventor's Address
1 ROBINSON, JAMES ELLIOT RUE COLONEL MONTEGNIE 85A, B-1332 GENVAL
PCT International Classification Number C08K 3/00,C08L 23/08
PCT International Application Number PCT/EP2007/004396
PCT International Filing date 2007-05-16
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 06011269.5 2006-05-31 EUROPEAN UNION