Note: Descriptions are shown in the official language in which they were submitted.
~5'~69
mis lnvention relates to a method for reducing
the amount of dripping that occurs when thermoplastic com-
positlons are unrestrained and in molten condition, and to
thermoplastic compositions prepared by this method and ;
having nondrip characteristics when said materials are sub-
jected to temperatures above the melting point of the ori-
ginal thermoplastic material~
It is an object of the present invention to pro-
vide a method to reduce or prevent dripping which usually
accompanies melting of thermoplastic materials when s~lch
~ materials are exposed to combustion conditions such as those
- in ASTM D-635 flammability test. It is a further ob~ect of
~ the present invention to provide a method to prevent the
. ~ ~
spread of fire which usually accompanies such dripping.
, 15 Other objects will become apparent as the description pro-
ceeds.
When suspended thermoplastics burn, molten polymer
~`~ drips carrying flame with it and spreading the fire. Such
,,~
;~ thermoplastics can not meet the requirement set up as indus-
( 20 try's standards such as those of ASTM D-635 and Underwrite~s
Laboratory UL-9~ for a self-extinguishing rating (SE-O).
~ For example, the UL-9~ test requires that a 5"xl/2"xl/8" bar
:,a; of the material tested b0 supported vertically at one end. ~ ~
~' The free end is exposed to a specified gas ~lame for two 10- ~ ~-
;, 25 second ignitions. Thermoplastics which drip and ignite dry
1 absorbent surgical cotton placed 12 inches beneath the bar
at any time longer than 10 seconds after the second removal
~ of the specified gas flame fail to earn the SE-O rating.
-1, It has been discovered according to this inven-
~' 30 tion that a thermoplastic polymer containing flame
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retardant agents, a nonflammable fibrous material and poly-
tetrafluoroethylene is nondripping when subjected to com-
~` bustion temperatures as described in ASTM D-63~ and UL-94.
The amounts of both polytetrafluoroethylene and the non-
flammable fibrous material used can be varied~ usually
between about .1 and 5.0 percent of each by weight of the
.,
total composition. Generally the amounts used will be
varied with changes in the flame retardant agents used in
,.
; the base resin
...
. ,,.
Representative examples of nonflammable fibrous
material useful in this invention are potassium titanate
(DuPont's FybexTh), fiberglass, asbestos, graphite fiber and
carbon fiber.
Materials such as octabromobiphenyl, decabromobi-
phenyl oxide~ hexabromobenzene, triphenyl phosphate~ bis(2,
6-tribromophenyl)carbanate, ethoxylated tetrabromobiphenol-
3 A, 2,5-dibromoterephthalic acid, tris(2,3-dibromopropyl)
phosphate and antimony oxide can be used to impart flame
~ retarding properties to the resin. These materials can be
.,,~
used alone or in mixtures with the resins.
The polytetrafluoroethylene and nonflammable
, ~ .
`~ fibrous material can be added to the thermoplastic resin by
methods well known to those skilled in this art.
Representative examples of thermoplastic resins
useful in the practice of this invention are thermoplastic
polyesters such as poly(ethylene terephthalate), poly
(tetramethylene terephthalate), 80/20 poly(tetramethylene
terephthalate/isophthalate), 70/10/20 poly(tetramethylene/
isophthalate~sebacate); polyamides such as Nylon 6/6, Nylo~
6, Nylon 6/10, Nylon 6/12 and polyolefins such as high
.,
.,
~ j -2-
.~ ,
lV~5269
density polyethylene~ low density polyethylene, polypro-
pylene. Other thermoplastic resins useful in the practice
of this invention are polyphenylene oxide, acrylonitrile/
butadiene/styrene (~BS) resins, polyacetals (polyoxymethy-
lene), polystyrene and polycarbonates such as poly(4,~'-
dihydroxy-diphenyl-2,2-propane)-carbonate and poly(4,4'-
dihydroxy-diphenyl-methyl-phenyl-methane)-carbonate.
The products of the invention are useful as flame re-
sistant and drip resistant molding compositions.
, . . .
^ 10 ~he term "thermoplastic resin" as employed in this
disclosure is understood to include base thermoplastic
resin as well as those thermoplastic resins compounded l~th
..
- lubricating and nucleating agents or other additives. The
thermoplastic resins are crystalline in form. The crystal-
line thermoplastic resins employed in this invention have a
melting point at or abore 100 C. me melting point is the
maximum useful service temperature of a crystalline solid
- i .
and is the temperature at which a highly ordered crystalline
solid is transformed into a liquid.
, 20 ~he term "polyester" as employed in this disclo-
;'!
sure is intended to include both homopolyester and copoly- ~;
`~ ester.
,
These polyesters are conveniently prepared by
-; reacting aromatic dicarboxylic acids or ester forming
derivatives thereof with a glycol of the formula HO(C ~ )nOH
~ where n is an integer ranging from 2 to 10 to form the
-~ corresponding glycol ester and then polycondensing the
glycol ester with-elimination of glycol under conditions of
elevated temperatures and reduced pressures to form high
molecular weight linear polyester or copolyester resins.
Representative examples of such polycondensation
. polyester resins include resins derived from dicarboxylic
. _ 3 _
lV45Z69
acids such as terephthalic acid, aliphatic dicarboxylic
' acids such as adipic acid~ sebacic acid, azelaic acid and
`Y- aromatic dicarboxylic acids such as orthophthalic acid,isophthalic acid, terephthalic acid~ bibenzoic acid~ naph-
.
~^ 5 thalic acid and the like. The resins can be made from
various glycols such as those of the formula HO(CH2)IlOH
where n is an integer ranging from 2 to 10 and including
ethylene glycol, propylene glycol, tetramethylene glycol,
~ pentamethylene glycol~ hexamethylene glycol, decamethylene
`~ 10 glycol and the like~ alkyl substituted polymethylens gly-
~;, cols such as neopentyl glycol and 2-methyl-2-ethylene and
cyclic glycols such as cyclohexanedimethanol and 2,274,4-
tetramethyl-1,3-cyclobutene diol. Ethylene glycol is a
preferred glycol because of its low cost and ready avail-
-~j 15 ability.
i The examples below illustrate the invention. me
resin used is an .80 Intrinsic Viscosity (IV) poly(tetra-
methylene terephthalate). In this application intrinsic
~i viscosity was measured in a Cannon-Ubbelhode viscometer
using a 60 phenol/40 tetrachloroethane solvent at 30 C.
PHR in the examples is parts by weight per hundred parts of
.
resin by weight. All parts and percentages are by weight
unless otherwise specified. Examples 1 to 3 and a portion
of 6 are comparative examples. Examples 4~ 5 and a portion
, 25 of 6 illustrate the invention. ~ ;
Example 1
Poly(tetramethylene terephthalate) (PTMT) was
produced in a stirred tank reactor by reacting one mole of
dimethylterephthalate (DMT) with 1.2 moles of tetramethyl-
ene glycol at 190 C. and at atmospheric pressure until
,,
.
-: ~
1045269
85 percent of the theoretical amount of methanol had evolved
then the oligomers were polymerized under reduced pressure
' at 2500 C. At the polymerization stage 8 PHR of octabromo- -
~- biphenyl and ~ PHR of antimony trioxide were added. An o.80
. . ,
'~ 5 IV PTMT containing these flame retardants was obtained.
'~ ~nis was molded into a bar of 5" x 1/2" x 1/8" at 250~ C.
by injection molding prQcess. The bar was tested for flam-
mability according to AS~M D-635 and UL-9~ flammability test
''~ methods. The polymer started dripping five seconds after
~ 10 the application of flame. me droplets carrying the flame
::;
" ` ignited cotton placed one foot b'elow the bar. me polymer
~ . ~
~-~ thus failed to meet the requirements to earn an SE-0 rating.
~ - - - Example_2
,'`~ m e process, polymer composition, and testing are
the same as those in Example 1 except that 10 PHR of octa~
bromobiphenyl were used in place of 8 PHR octabromobiphenyl
'~'Y~ ' and one percent by weight polytetrafluoroethylene (DuPont's
;~ ' TeflonTM)was added. The polymer failed to pass the flamma-
bility-test because of dripping.
. .. -~ .
~ 20 ~3~EL~
. ,~.~ . - .
lhe product of Example 1 was dry blended with one
weight percent of potassium titanate fibers (DuPont's FybexTM)
~ ~ .
`~ and injection molded into a test bar~ which ~ras tested using ~' '
`~ the AS~M and UL test methods. The compounded polymer again '
failed to pass the test because of dripping. ~ -
.~ ExamPle L~ ' -,
The product in Example 1 was dry blended with one '~
weight percent of potassium titanate fibers (DuPont's Fybex~M)
and one weight percent of polytetrafluoroethylene (DuPont's
' 30 Teflon~)and injection molded into a 5" x 1/2" x 1/8" test '
. . .
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. , .. , , . . .. ~ ,. .
11~)45Z69
1 bar. The compounded poly~er bar was tested in the flamma-
bility test and did not drip during thirty seconds of flame
application time. The poly(tetramethylene terephthalate)
thus compounded passed both ASTM and UL tests and was rated
, ; .
as SE-0.
,! Exam~le 5
At the polymerization stage of the preparation of
polyttetramethylene terepht,halate) 8 PHR o~ decabromobi-
~A, phenyl oxide (DBBP0)~ 4 PHR of antimo~y oxide~ .5 weight
;, 10 perce~t of polytetrafluoroethylene (DuPont~s Teflon) and
~..
.5 weight percent of potassium titanate ~DuPont's Fybex)
were added to the reactor and mixed with the polymer under
~, condensation conditions. The compounded resin t.80 IV) was
injection molded into a 5" x 1/2" x l/8" test bar. The test
bar was tested for flammability and started to drip slowly
after 24 seconds of flame application. me droplets did not
spread the fire. me bar passed both ASTM and UL test re-
., ,. ~ .
, quirements and was rated SE-0. This result indicates ~hat
.5 weight percent of Fybex and .~ weight percent o~ Teflon
l . .
- 20 are the minimum levels for retarding flame spreading.
^ Example 6
; Dechlorane plus 515, plus 25 and 603(chlorinated
, organic flame retarding agent~ from Hooker Chemical Cor-
l poration containing 65 percent by weight of chlorine was
. ~
used to impart self-extinguishing properties to polyester
polymer rendering the poly (tetramethylene terephthalate)
polymer self-extinguishing. At least 16 PHR of the
' Dechlorane and 5 PHR of the antimony trioxide Sb20~ are
required. Dechlorane inherently induced less dripping
--6--
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1045Z69
of the polymer during burning. Poly (tetramethylene tere-
phthalate) polymer with the above composition dripped after
20 seconds of burning. In con-trast the same polymer with
one-half PHR of Teflon and one-half PHR of Fybex did not
drip.
. .
The amount of polytetrafluoroethylene used will
generally be in the range of from about 0.1 percent by
: .
~ weight to about 5.0 percent by weight of the total composi-
. '!
tion, more preferred from about .5 percent by weight to
about 1.0 percent by weight of the total composition. The
; nonflammable fibrous material used will be in a concentra-
~ tion of from about 0.1 percent by weight to about 5.0 per-
, 1 :
~`;`3~ cent by weight of the total composition, more preferred from
about .5 percent to about 1.0 percent by weight of the total ~ ~
1 15 composition. me amount of flame retardant used will be in ~-
i the concentration sufficient to render the polymer self-
extinguishing. When the polymer contains these ingredients
in these amounts it becomes nondripping during the 30 second
'?~' test burning in accordance with ASTM D~635 flammability
tests and UL-94 flammability test, and the polymer is rated
self-extinguishing.
While certain representative embodiments and
details have been shown for the purpose of illustrating
the invention, it will be apparent to those skilled in ~
this art that various changes and modifications may be ~ ;
made herein without departing from the spirit or scope of ~ ;
this invention.
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