Note: Descriptions are shown in the official language in which they were submitted.
-~~ 21 WC lg46
The significantly increased use of organic
hydrocarbon based polymeric compositions, such as
polyolefins, in many and diverse applications or products,
and the relatively high combustibility of such hydrocarbon
based polymeric ma-terials, and their propensity to spread ~ ;;
or propagate burning due to flow and dr.ipping at high
temperatures has greatly stimulated the investigation of
flame-proofing measures for such organic polymeric
compositions. Moreover, the high costs of fire damage
in lives and property, and the current trend of the
imposition of increasingly stringent safety requirements,
have substantially intensified the pursuit of more
effective and practical means of controlling or inhibiting
combustion and its spread or propagation in many products
and materials comprising organic polymers.
Notwithstanding prior developments of a
great number of flame-proofing measures or additives :
resulting from this expanding effort, there remains !;
a continuing need for improvements to meet current or
new requirements in this area. The magnitude and urgency
of this need for even greater improvements in this area ~.
and the proliferati.on of efforts and developments in
this field are best evidenced by the ever increasing
number of publications produced dealing with this
subject. -
This invention comprises the discovery that
effective resistance to flame or combustion, its spread
or propagation due to loss of physical integrity and
extensive volatilization, and other advantages, in hydro-
gen based polymers, such as polyolefins, can be attained
by the incorporation therein of the combination of a
polysiloxane gum and lead compound, without the presence .
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21 WC 1946
of a halogen. The invention thus relates to flame-
resistant hydrocarbon based polymer compounds, such as
polyolefin polymers, and i-t has particular application
or utility in flame-proofing electrical insulations such
as or wire and cable comprising dielectric ethylene-
containing polymer compounds, such as polyethylene,
which have been crosslink cured to a substantially
thermoset condition.
It is a primary object of this invention to
provide hydrocarbon based polymer compounds having
effective resistance to flame and combustion which do ~ ;
not require a halogen, and thereby avoid the disadvantages
and problems attributable to halogens.
It is also an object of this invention to
provide hydrocarbon based polymer compound, such as
polyolefins, having effective electrical and physical
properties, and chemical properties such as resistance
to heat aging as well, as a high degree of resistance
to flame and combustion and the spread or propagation
of ire due to loss of physical integrity and extensive
volatilization.
It is a further object of this invention to
provide flame resistant hydrocarbon based polymer
compounds such as polyolefins which are very flexible,
and which effectively and extensively char at flame or
com~ustion conditions and thereby resist loss of physical
integrity and excessive volatilization.
It is a still further object of this invention
to provide a new and improved electrical conductor
comprising a metallic conductive element having a
dielectric insulation thereabout of a crosslink cured
polyolefin polymer compound which is resistant to flame
- 2 ~
$~ 21 WC 1946
and combustion, chars and minimiæes volatilization and
loss of physical in-tegrity at flame temperatures, and
has superior electrical and physical properties.
In accordance with this inventiorl, hydrocarbon
based polymer compounds having an effective level of
resistance to flame and combustion, a high level of
physical integrity at high temperatures, among other
advantages and improved attributes, are provided by a
combination of such a hydrocarbon based polymer composition
with effective amounts of an organopolysiloxane gum or -~
elastomer and a lead compound, without the presence of
a halogen.
The hydrocarbon based polymeric materials
of this invention comprise polyolefins such as ethylene-
~efhy~e~
containing polymers, for example pollTe~ e~, both
high and low densi-ty, copolymers of ethylene and other
; polymerizable materials, and blends of such polymers
including copolymers. Typical copolymers o~ ethylene
i include, for example, ethylene-propylene copolymers
and ethylene copolymers and ethylene-propylene-dience ~
terpolymers, ethylene-vinyl acetate, ethylene-e-thyl ~-
acrylate and ethylene-methyl acrylate. Other hydrocarbon
based polymers within the scope of this invention includes ;;
polypropylene, ethylene butene copolymer, polybutylene,
polypentene, polystryrene, styrene maleic anhydride
copolymer, styrene acrylonitrile copolymer, acrylonitrile
butadiene styrene copolymer, methacrylate butadiene
styrene copolymer, polycarbonates, polyesters, and the
like. - ~r
The flame-resistant, hydrocarbon based polymers,
or compounds thereofl of this invention can additionally
comprise fillers, for example extendin~ or reinforcing
- 3 -
~ Y~ ~ 21 WC 1946
components such as silica, clay or fibers, pigments,
curing coagents, and other conventiona:L addltives including
preservatives, such as antioxidants, modifying agents
such as plasticizers, processing aids, mold rel.ease
ingredients or lubricants, and the like which are commonly
compounded with molding or insulating polymers, or
typical products formed therefrom such as, for example,
electrical insulations. Moreover, the polymer compounds
of this invention can also include auxiliary flame
retarding ingredients such as conventional flame
retarding agents, for example, phosphates, halogens,
borates, antimony oxides, and the like coImmon flame
retardants.
This invention also specifically applies to
and includes any of the above-reference hydrocarbon
polymers which can be crosslink cured and thermoset,
when effected by means of high energy irradiation such
as by electrons or chemical means such as a heat-
ac~ivatable organic peroxide crosslinking agent such
as disclosed in U.S. patents 2,888,424 - issued May 26,
1959; 3,079,360 - issued February 26, 1963; 3,086,966
issued April 23, 1963 and 3,214,422 issued October 26, 1965.
Suitable peroxide crosslink curing agents comprise
organic tertiary peroxides characterized by at least
one unit of -the structure:
:` Ic f
C _ C--O--O--C _ ~
C C
which decompose at a temperature above about 1~6C
(295F) and thereby provides free radicals. Preferred
,~
. peroxides for curing polyolefins are a di~ cumyl
peroxide, and other apt peroxides comprising the ter~iary
4 -
:
21 WC 1946
diperoxides such as 2,5-dimethyl-2,4-di(t-butyl peroxy)
hexane, and 2,5-dimethyl-2,4-di(t-butyl peroxy) hexyne-3,
and the like diperoxy and polyperoxide compounds.
The organopolysiloxane gum or elastomer of
this invention, for use incombination with a lead
compound, among o-ther preferred or optional ingredients,
and the hydrocarbon polymer, comprises gums or organo-
polysiloxanes which have been condensed to a high
molecular weight polymer of a gummy elastic, substantially
semi-solid state. For example a typical silicone
elastomer for use in the composition of this invention ~.
is a class of dimethylpolysiloxanes having the following
repeating units:
CEI3
- r ~ o-- ~
~H ;,:~
: : L 3
....
Other classes of silicone elastomers for :~
use in this invention are the methyl-phenyl polysiloxanes,
dimethyl-diphenyl copolymers, and all such silicones
containing minor amounts of vinyl groups. Further
examples of the type of silicone elas~omer gums usable
in obtaining the compositions of this invention --
comprise the organopolysiloxanes referred to in U~S.
patents 2,888,424 and 2,888,419 issued May 26, 1959, and
.
identified in detail in U. S. patents 2,448,556 issued
September 7, 1948; 2,448,756 - issued September 7, 1948;
2,457,688 - issued December 26, 1948; 2,484,595 -
issued Oc~ober 11, 1949; 2,490,357 - issued December 6,
1949; 2,521,528 - issued September 5, 1950;
:
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21 WC 1946
2,541,137 - issued February 13, 1951; 3,098,836 -
issued July 23, 1963 and 3,341,489 - issued September
12, 1967. Such high molecular weight sllicone polymers
normally have Brookfield viscosities of in excess of
about 100,000 centipoise at 25C.
The lead compound comprises dibasic lead
phthalate, lead stearate, lead sebacate, tribasic
lead maleate, basic lead silicate sulfate, and comperable
lead compounds. -
It is highly preferred that the compositions
of this invention also include effective amounts
of conven-tional antioxidants, such as polymerized 1,2-
dihydro-2,2,4 tri-methylquinoline, which in combination
with the other essential ingredients, provides a high
degree of resistance in the compound to flow or dripping
when exposed to flame or combustion temperatures.
Fumed silica fillers also comprise a pre-
ferred ingredient which enhances the overall resistance
to flame and other desired attributes in some embodiments
of the hydrocarbon polymer compounds of this invention.
Also fumed silica can be employed as an aid to improve
disperson of the silicone gum with the other ingredients.
Fumed silica comprises a form of silica described in
U. S. Patent 2,888,~24 and a type which is sold under
the trade designation of Carbosil MS7 o~ Godfrey L.
Cabot, Inc., of Boston, MassachusettsO
The essential combination of organopolysiloxane
`! gum, with the lead compound, and preferred ingredients
such as an antioxidant and fumed silica, can be mixed
and combined w.ith a hydrocarbon based polymer material
or compound thereo~, by means of any conventional
compounding method or apparatus, such as working in a
-- 6 --
- 21 WC 1946
Banbury mixer or on a two roll rubber mill~
I the polymer compound is to be cured with
a heat activatable curing agen-ts such as an organic
peroxide, it .is preferred that all ingredients of
the compound Eormulation, except the heat decomposable
organic peroxide curing agent or any o-ther ingredients
which are sensitive to the relatively moderate mixing
temperatures of about 150C (300F) to about 205C
(400F), are combined and initially admixed together
at a temperature sufficient to sof-ten and plasticize
the particular polyolefin polymer ingredients.
Following the attainment of substantial uniformi.ty of l:
the initially admlxed ingredients, the tempe~ature
of the a~nixed batch is reduced below the decomposition :
level of the particular peroxide curing agent used,
or other heat sensitive ingredients to be added, and
the curing agent or other heat sensi-tive ingredients
are then introduced and dispersed preferably uniformly
throughout the mix.
The proportions of the essential ingredients
of the combination of this invention, as well as the :
optional ingredien-ts and/or conventional additives or
: compounding agents can be varied and depend primarily
upon the level or degree of resistance to flame and
combus-tion, or charring, of the polymer, or compound
thereof, and the relative flammability or combustibility
of the polymer or compound ingredients and their ratios.
~; ~Ioweverl effective resistance to flame or combustion,
~:~ and effective charring, in many typical polym~ric
compounds can be achieved with ratios of the respective
ingredients in the following approximate relative parts
;~ by weight of:
-- 7
21 WC 1946
Hydrocarbon based polymer 100
Organopolysiloxane gum 2 - 20
Lead compound 2 - 15
Fumed silica 0 - 10
Antioxidant 0 - 10
Filler 0 - 50
Organic peroxide curing agent 0 - 10
In a preferred embodiment of this invention
for a highly effective electrical insulation hav.ing a
high degree of resistance to flame and combustion, and
substantial charring at flame temperature, -the ingre-
dients and their proportions comprise the following in
the approximate relative parts by weight of: :
Polyolefin 100
Organopolysiloxane 3 - 10
Dibasic lead phthalate l - 5
: Fumed silica 2 - 6
Antioxidant l - 6
Antimony oxide 0 - 15
~ 20 Filler 0 - 30
; Curing coagent 0O5 - 2
~; Organic tertiary peroxide curing
agent l - 5
The following examples of the compositions
of this invention and data derived therefrom demonstrate
the resistance to flame or combustion, and charring,
as well as other beneficial and improved attributes, of
~;; the halogen-fr~e, novel compositions of the inven~ion,
with respec-t to similar compositions for standards of
comparison. The pol~mer composition formulations of
the examples of this i.nvention and also of the standards
21 WC 1946
are all given in parts by weight, and the compositions ~
of the examples of this invention and o their respective . ~ :
standards were each prepared, crosslink cured where `;
indicated, and tested or evaluated under identical ~ :
.. . :
condikions..
The relative degress of resistance to flame
and combustion of the various compositions of the
examples of this invention and of the standards were `.
all determined in accordance with the Oxygen Index :
: 10 Test procedure prescribed in ASTM Test Method D-2863-70,
and as described in U. S. patents 3,755,214 issued
August 28, 1973 and 2,787,356 issued April 2, 1957
As is known, this test designates the fraction of ~.
oxygen by volume in nitrogen required to just maintain ;:
flaming of the material of the test sample. Thus,
the higher the oxygen index for a composition,
the better its resistance to flame and combustion.
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EXAMPLE V
INGREDIENTS PARTS PERCENT
Polyethylene 100 82.82
Polysiloxane gum* 5 4.14
Dibasic lead phthalate 4 3.31
(25% polybutene)
Octamethylcyclotetra siloxane 3 2.48
Antioxidants
Flectol-H 1.5 1.24
Santowhi-te Crystals 0.25 0.21
Pigment - titanium dioxide 2 1.66
triallyl cyanurate 1.5 1.24
Dicumyl peroxide 3.5 2.90
* Vinyl containing polysiloxane, containing minor amounts .
of siloxane treated fumed silica and diatomaceous earth ..
Flectol-H is a Monsanto Co. trademark for polymerized :
1,2-dihydro-2,2,4-trimethylquinoli.ne, a rubber antioxidant.
When crosslink cured at 182C (360F) for 45 minutes, the
polymer compound of Example 3 exhibited the following
prop~rties~
Toluene extraction: 10% based on polymer
Tensile strength: 2779 psi -~
Elongation: 318%
; After heat aging 7 days at 121C ~ ~:
Tensile strength: 2832 psi (102~ ret.)
Elongation: 336 (106% ret.)
Oxygen Index~ percent: 30.2
Char (UL - 94 - NB?: Yes
Drip: Slightly
The composition of Example V ex-truded on #14 copper wire
in a wall thickness of each 0.Q30 inch and 0.045 inch
passed the UL - 44 - XHHW and RHH - RHW Horizontal Flame
- 14 -
-~3
21 WC 19~6
Test and did not drip, while comperable crosslink cured,
unfilled polyethylene compositions without the flame
retardant system of this invention both failed thls test
and dripped.
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