Note: Descriptions are shown in the official language in which they were submitted.
:` ~L043~3~
' SPECIFICATION
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The present invention relates to improved flame retardant pro-
pylene-ethylene copolymeric compositions contaTning the following addit7ves:
' ' a halogen-conta7n7ng f7re retardaot,`an;antlmony compound, and a copper-lon' - -
stabi17zer. More part7cularly, the'Invention perta7ns to a flame retardant
- copolymeric composltion compr7slng a propylene-ethylene copolymer, a
chlorine-conta7nlng fire retardant, antimony tr70xide, and a minor amount
of oxalyl b7s(!2-denzylidene hydrazide). ~ ~
U. S. Patent No.'3,403,036, issued September 24,'1968, d7scloses'
" 10 render7ng polymer7c and copolymer7c res7ns of propylene flame retardant by
' 7ncorporat7ng therein a comb7nation o~ an ant7mony compound such as
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antlmony tr70xide with varlous halogenated cyclopentadiene adducts. One of
~' - the adducts taught in th7s patent 75, 1,4,7,10-d7methanocycloocta-1,2,3,4,
7,8,9,10,13-,13,14,14-dodecachloro-1 ,4?4a j5,6',6a,7,10l10a,11 912,12a-
dodecahydro (1,2,5,6)dibenzene wh7ch has a chlorine content of about 65~,
a meltlng polnt greater than 350C., and a density of 1.80 gm/cc.~ This
... . . .
compound 7s presently bejing~s~ld,bylthe Hooker~Chem7cal Corporation under "
req,s~Y~ d ~hr~ nnArk
the-e~h1~t~w~ Dechlorane Pluc and, for the purposes of convenience, w711 at
t7mes be referred to hereafte'r by 7ts tradename. One of the uses descr7bed
7n U. S. Patent No. 3,403,036 for these compositions is as wire coatings.
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U. 5. patent No. 3 576 784 issued April 27 1971 disc!oses
utlljzlng the same combinatlon of adclitlves for providlng flame retardancy
characterjst7cs to high molecular weight crystalline cGpolymers o~ propylene
: and ethylene without drastlcally affecting the high Impact strength of
: ~ 5 such.copolymers Thls patent teaches that the descrTbed composltions in
pellet form are suttable for the productlon of a~ticles by inJectlon
molding in a screw machine extrusion compression molding and the other
known methods of fabrication.
; Certaln dlfflcultles have arlsen when the aforementioned prior ~
'0 art flame retardant propylene-ethylene copolymertc compositions are employed :`
for the insulat70n of copper metal-containing wire and cable. It has been
found the existence of copper ions accelerates undesirable oxldative
. degradation of homopolymeric and copolymeric propylene resins. ~Severe
. ~ : . pitting of the copper wire..has also.been observed....Furthermore the large .~-
.- 15 amounts of the antimony compound I.e. antimony trloxide prescribed and
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.- ` shown in the prior art teachings substant7ally increases the cost of the
flame retardant compositions and tends to make them uneconomical compared
to other coating compositions that are commercially available. It would
- therefore be advantageous to have flame retardant propylene ethylene
copolymeric compositions that would avoid the oxidative degradation and
wire pitting problems that would be competitive with other compositions
`. and that would still have the desired low afterglow non-dripping.and other
;,
~ essential flame retardancy characteristics.
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:~ In accordance with the present invention these objectlves can
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be met by incorporating into the composition a minor amount of oxalyl
~: :. 6~n2 ~ n ~
: ~ ~ ~ . bis (2-~ ~r~f tn-hydrazide); by employTng less.than about.10% and pre-
ferably about 3 to 7~ by weTght based on the total weight of the flame
retardant composition .of the antimony compound; and ~ utilizing a weight
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ratio of the halogen-containing fire reta~dant to antimony compound of
at least 5 to 1, and preferably from ab~ut Sl~ to 7~1. When the'flame
retardant compositions of this invention are used to coat copper metal-
` containing wire and cable the coating wire or cable was found to exhibit
-5 excellent low afterglow and other flame.retardancy properties and to be
essen~ially free of the oxidative degradatlon and pltting problems dis-
cussed above,
The terms "propylene-ethylene copolymers" and "crystalline
.- . . . i, : , ....... .. . . .
copolymer of propylene and ethylene~''are used herein In the same sense
that these terms are commonly employed in the art and as specifically
defined in U.S. Patent No. 3,576,784. Thus, these .terms are Intended to
mean the homogeneous product of polymerization resulting from the sequen-
tial polymerization of (1) propylene and (2) a mixture of propylene and
ethylene in the presence of a stereospecif~lc polymerization catalyst. ! The
most convenlent method for making such compositions is to homopolymerize
propylene tn a liquid diluent to form a homopolymer and then introducing
ethylene while there remains some unpolymerized propylene. At this point
the polymerization continues as a copolymerization, and tf the introduction
of ethylene in continued past the stage at which the first monomer is
'. ~ 20 -exhausted, some homopolymerization of the ethylene will occu'r. In theory
the product of such a process is'intended to be composed of macromolecules
In which one or more segments of the homopolymer of propylene (A) alterhate
with one or more segments of a copolymer of the propylene and ethylene
(B), viz:
.. 25 (AAAAAA-ABABAB)
where n equals an integer of one or more depending on the number of poly-
merization sequences. If polymerization of the second monomer is continued
after the exhaustion of the first monomer, the theoretical repeating unit
will have the structure
: ';;. 30 (AAAAAA-ABABAB-BBBBBB)n
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~L043(~3~
However, there is substantial evidenc:e'that the so-called "copolymer" iS
actually an intimate mixture of a homopolymer of propylene and a copolymer
of propylene wlth ethylene and, optimally, homopolymer of ethylene, the
mixture being homogeneous tn the sense that there èx~sts a uniform disper-
~ 5 sion of the component polymers thraughout the product. Hence, In uslng
.~' the term ~'copolymer" it Is not intended to restrlct the inventton to poly-
merlc composition of true block copolymer structure, but it is intended to
include the compositions commonly referred to as "block" copolymers e~en
~;- though such may not actually be the case.
Processes of producing the crystalline copolymers emp10yed in
this invention are descrlbed in, for example, British Pat. 970,478/~im~-
-.ekserhefe,- Teh crystalline copolymers employed in the invention are those
;~ in wh~ch 75'to 93~ by weight Is derlved from propylene, and 7 to 25~ by -~
weight is derlved from ethylene.'' Moreover, the crystalline copolymers
employed in the invention have a high molecular weight as delineated by a
melt flow rate less than 3 according to ASTM D-1238 employing a 2 kg.
~~ weight at a temperature of 230C. ~ -
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-~ The particular halogen-containlng fire retardant employed in
~ formulating the composltions of this invention is as mentioned above
;~ 20 Dechlorane Plus whlch is an adduct of 2 moles of hexachorocyclopen~adiene
with 1 mole of cyclooctadiene. The resultlng adduct has the followlng ~. '
structural formula~
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~ ~ . C~Cl~
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In accordance wlth another feature of the present 7nventlon, It has been
found advantageous for some applicatTons to employ Dechlorane Plus having
an average partlcle size of from about 2 to 5 microns. It will be under-
stood, however, that the average partlcle size may vary wldely, although
~ 5 the preferred particle slze may range from about 2 to 15 microns or mQre.
; In general, the amount of the Dechlorane employed in the formulations wlll `;
range from about 20 to 35~, and preferably from about 25 to 30% by weight
based on the total weight of the flame retardant composition.
An~imony trioxide is the preferred antlmony compound, although
many other ant7mony compounds may be utlllzed. Su7table 7norgan7c antimony
compounds 7nclude ant7mony sulf7de, sod7um ant7mon7te, potasslum ant7monate,
and the llke. Many organ7c ant7mony compounds are also su7table such as
the antimony salts of organlc aclds and thetr pentavalent der7vat7ves, as
:
s ~ ; d7sclosed 7n U. S. Patent No.i2,996,528,~ Compounds of thls~c!ass-lnclude ;
-~ 15 antimony butyrate, ant7mony valerate, antimony caproate, antimony heptylate,
....
` antlmony caprylate, ant7mony pelargonate, ant7mony caprate, ant7mony
c7nnamate, anttmony anisate and their pentavalent dihalide derivatives.
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; The copper meta~ stabil7zer or Inh7b7tor9 oxalyl b7s(2-benzl7dene
~- hydraz7de) 7s currently being sold by the Eastman Kodak Company and has the
follow7ng structural formula:
For conven7ence, th7s compound may be re-ferred to hereafter by its init7als
-- OABH. As prevlouslj d7sclosed, only minor amounts of thls compound, at
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least sufficlent In amount to produce the deslred stab7lizatlon or 7nhibi-
t70n, need be employed 7n the formulat70ns of th7s 7nvent70n. ~ore spe-
c7fically, however, the amount OABH may range from about 0.05 to 1 0~,
preferably from about 0 1 to 0.5~ by weight, based on the total ~wdight of
the flame retardant composition.
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Minor amounts of other additives may also be utillzed in the
flame retardant compositions. Conventional antioxidants such as the
hindered phenols and thio esters ~re often used in flame retardant poly-
meric and copolymeric compos7tions. Addttional ingredlents that may be
included are plastTcizers, d,yes, plgments, heat and ltght stablllzers,
antistatlc agents, and the llke.
The flame retardant copolymerlc compositions of this invention
are particularly sultable as coa~ings for copper wtre useful as elevator
cable and the like. The copper wire coatlng will generally vary ln thlck-
ness from at least about 10 mlls or more.
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The flame retardant compositions of this invention are prepared
by utilizing conventional methods !ntsrnal mixers such as Banburys, contin- -
~ uous mixers, mixlng extruders,~and t~o-roll mills. Conventional procedures
-; and apparatus can also be empioyed in extruding the flame retardant com-
;~ 15 positions of this tnvent70n on to the copper metal-containing electrical
wires.
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The invention will be more fully understood by reference to the
following specific embodiments which are not to be construed as limiting
the scope of the invention but only for the purposes of illustration.
Unless otherwise indicated, all of the amounts of ingredtents are expressed
tn parts by weight.
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EXAMPLE
The formulations set forth in Table A were prepared by admixing
the ingredients in a two-roll mill at a temperature above the melting point
of the propylene-ethylene copoiymeric resin. Plaques were formed from a
portion of the resulting compositionsj while another portion were extruded
on to copper wire. The physical and electrical tests set forth in Tables B
and C.
TABLE A
FORMULATIONS
t ! l~ 2 `
- Pro-fax-7823~ 64.30 62.30
Dechlorane Plus T ~ 30.00 30.00
-~r~ Antimony Trioxide 5 00 5.00
; - Irganox lOlO** ~ 0.10 0.10
DLTDP*** ~ -3 ~3
OABH ` ;- ~0.30 0,30 ' ! '`~
Carbon Black ~ 2.00
~Propylene-ethylene copolymeric rèsin sold by Hercules under this
~ ~ trademark and having a flow rate (g/lO min) of 0.4, a density of
:- 20 0.901, and an ethylene content of less than lO~
-.
.~ **Tetrakis [methylene 3-(31,51-di-t-bu~yl-4l-hydroxyphenol) propionate]
` methane
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***Dilaury1thiodipropionate ''~
Trn- r ~g is~ered JG~mar/c
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: TABLE B
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FORMULATIONS
PROPERTIES 1 2
:- Tensile Strength (psi~ . 3100 3000
' ~ 5 Dens;ty (g/cc) ~; ~ l.l ~ ,l.l , ,,
Maximum Elongation (%) 450-500 450-500 ' '
- Fl:ame Resistance
- (0 .1 2 5" thickness) SE-l~ SE-l*
' UL Subject 94
. iO AST~ D635 ~ ; Non-burning Non-burning
Afterglow (sec.) ; : ' ~ ' O to 5 ,' 0 to 5 , ,
Afterglow (am't) : Very slight Very slight
~ ~ Oxygen index 25 25
-' Dielectric Constant 2 . 45 2 . 45
~' 15~ ~ Factor .oO07 ,ooo7
- : Oxidative Degradation of
, Copolymer~ None None
; Pitting of Copper W~ire ~ -` None ~ ~; None
*Non-dripping
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20 ` In order to further demonstrate the stability of the compositions
- : : of this invent:ion in the presence of copper metal, the following formulations
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'"~ . were prepared: :
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"~ : . : A - Formulation l f romiTable A
;-,' B - Formulation l ~ithout OABH : ,~
C - Formulation l with 1.5~ by weight ~f copper dust
' D r Formulation l with 1.5% by weight of copper-dust but without
OA8H
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`,~These`formulations were pressed into slabs,and~dumbbel1s prepared therefrom
were aged in:an oven at 140C. and,tested for elongation. The results are
'3~ reported below in TABLE C:
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TABLE C
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FORMULATIONS
DAYS A B C D
`` o 475% ~ 550% 475% 575% ,
^ . 5 5 280% 325% 325~ 300%
; `7` 325% ~ 300% 285% 250%
11 325% 275% 250% 300%
~ - 21 250% 282% 282% -0-
:: ~ The above data show that the propylene-ethylene copolymeric
compositions of this invention retain excellent flame retardency and
other properties important wire and cable applications despite the use
of-substantially higher fire retardant additive to antimony trioxide
weight ratios than previously employed and.the use cf oxalyl bis (2~ q
-benzylidene hydrazide) as a s~abalizer. for the copper.~ n~
~ . . . .
While particular embodiments of the invention have been set. ~:
~- : : forth above, it will be understood tha~ the invention is obviously
subject to modifications and variations without departing from its
: broader aspects.
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