Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to smoke-retardant chlorinated
polymer compositions.
There is much art on flame-retardants, but little on
smoke-retarders or suppressants. A paper entitled SMOKE
GENERATION FROM THE BURNING OF SOME POLYMERIC MATERIALS BY
Brauman et al, given at the 32nd Annual Technical Conference
of the Society of Plastic Engineers held in San Francisco in
May 1974 discusses the problem and the effect of several smoke
deterrents, but does not suggest the invention. U.S. patent
No. 3,821rl51 ~L.C. Mitchell; June 28, 1974) suggests the use
of molybdenum oxide in conjunction with iron powder and copper
oxide as a smoke retardant in polyvinyl chloride, but no data
are given. Miscellaneous patents on smoke retardants for vinyl
chloride resins include, for example, U.S. Patents No. 3,725,313
(K.C. Frisch; April 3, 1973), No. 3,746,664 (H.P. Doerge et al;
July 17, 1963), No. 3,758,638 (H.P. Doerge et al; September 11,
1973), No. 3,819,577 (A.W. McRowe; June 25, 1974), No. 3,822,234
(A.W. McRowe; July 2, 1974), and No. 3,g00,441 (T.Y. King;
August 19, 1975); but these include no suggestion of the invention.
The present invention provides a polymer composition
ha~ing a reduced tendency to smoke under combustion conditions,
which consists essentially of (a) 100 parts by weight of at
least one polymer having a chlorine content of from about 5 to
about 70%, based on the weight of the polymer, (b) from 1 to 10
parts of at least one cobalt, zinc, iron or manganese salt of
a dicarboxylic aliphatic acid or a hydroxycarboxylic acid con-
taining 2 to 6 carbon atoms, and (c) from about 10 to about
150 parts by weight of hydrated aluminum hydroxide.
Cobalt, zinc, iron and manganese salts of dicarboxylic
and hydroxycarboxylic acids containing 2 to 6 carbon atoms are
very effective smoke suppressants when added to halogen-contai-
ning polymer~ or copolymers, including chlorinated polyethylene
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and propylene, chlorinated paraffins, oils and waxes, polyvinyl- -
idene chloride and preferably vinyl chloride polymers and
chlorinated vinyl chloride polymers and blends of the foregoing
polymers. The chlorine content of p_ y~i~y~
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chloride is about 57 percent. If copolymers of vinyl chloride
are used, the chlorine content is less if the comonomer (such
as vinyl acetate) does not contain chlorine, and is higher if
the comonomer contains chloride, (such as vinylidene chloride).
The chlorine content of chlorinated polyethylene, chlorinated
polypropylene, or other chlorinated paraffins can vary over a
wide range depending upon the physical properties desired in
the polymer composition. Generally, a range of from about 5 to
about 70 percent chlorine is present. The chlorine content of
a flexible polyvinyl chloride composition will ~enerally be less
than 57 percent unless chlorinated plasticizer is present. Thus,
the chlorine content of the polymer composition can range from
~ about 5 to about 70 percent. The incorporation of the above-
- named salts retards and lessens the smoke generated by the
burning polymer. One can use 1 to 10 parts by weight of the
salts, or more, if desired, per 100 parts by weight o~ the poly-
mer. Preferably there should be used 4 to 8 parts by weight of
the salts per 100 parts by weight of the halogenated polymer.
It has been found that the cobalt, zinc, iron, and
manganese salts of hydroxy- and dicarboxylic acids, besides being
excellent smoke retardants when used alone, have a particularly
excellent synergistic effect when used in combination with
hydrated aluminum hydroxide. Not only does there result a degree
of smoke suppression greater than is obtained with the use of the
individual materia~s, but also there is a substantial reduction
in flammability. This last is particularly surprising, since the
use of the fire retardant salts alone sometimes results in a slight
increase in flammability. To obtain this synergistic effect,
the hydrated aluminum oxide should be used in amounts of from
3Q about 10 to as high as 150 parts by weight of aluminum hydroxide
per 100 parts by weight
., .
_ ~ _
~L~ 3 9 6 5 Z~
of chlorine-containing polymer; the upper limit selected for
said aluminum hydroxide is one based on practicality.
The acid moieties of the salts of cobalt, zinc, iron
or manganese can be those of any aliphatic organic hydroxy-
carboxylic or dicarboxylic acid containing 2-6 carbon atoms;
mixtures can be utilized. Examples of such acids include
oxalic, malonic, succinic, glutaric, adipic and similar di-
carboxylic acids; hydroxyacetic, tartaric, ascorbic, citric,
- hydroxypropionic and similar hydroxy acids.
Before referring to the results, it is advantageous
to know the meaning of the terms utilized. Definitions follow.
NATIONAL BUREAU OF STANDARDS SMOKE DENSITY CHAMBER
- Evaluations for the density of visible smoke were
made using a commercial smoke density chamber modeled after
one developed at the National Bureau of Standards by the Fire
Research Group (see D. Gross, J.J. Loftus and A.F. Robertson,
ASTM Special Technical Plublication 422 pages 1~6-204 (1969~.
This chamber contains a radiant heater producing 2.5 W/cm2 of
heat at the surface o~ a 3" x 3" sample, a propane-air pilot
burner and a vertical beam of light with a photomultiplier
tube detector and microphotometer to record the attenuation of
light by smoke developing in the chamber. During smoke testing,
the chamber is sealed to enclose the combustion products and
smoke~ The smoke developed is measured as Specific Optical
Density, Ds, where
S AL logl0 o = 132 logl0 To
V = volume of chamber
~ = area of test specimen
L = Length of light path
To = initial light transmittance through the chamber
T = transmittance of light during test
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At the peak of smoke build-up DS = Dm~ and for purposes of the
report, corrected maximum smoke is recorded as DmC = Dm ~ Dc
where Dc is the clear beam specific optical density occurring
after the smoke test, when the chamber has been exhausted of
smoke. Lower values of DmC indicate less obscuration of light
, . ~ .
due to smoke.
Several other quantities measured include the time in
minutes to 90 percent of Dm (t.9D~) and the time (in minutes~
to DS = 16 (t D16), which are indicative of the rate of smoke
development (higher numbers signify slower rates), as well as
the smoke obscuration number for the first four minutes of test,
SON4, where.
SON4 = DS (1 min.) + DS (2 min.) + DS (3 min.) + DS ~4 min,)
which also represents the early rate of smoke development (lower
numbers mean less smoke). The definitions of terms are summarized
below.
DmC = Specific optical density at maximum smoke
- intensity, corrected for fogging of lens seals.
DmC ~ 25, light; 25~75, moderate; 100-400, dense,
> 400 very dense.
t.9 Dm = time (minutes) to reach 90 percent of maximum
optical density.
tD16 = time (minutes) to D = 16, corresponds to early
visibility obscuration. tD16 < 1, very fast;
1-3 fast; 4-6 moderate; 7-10 510w; > 10, Yery
slow smoker.
SON4 = Smoke obscuration number over first four
minutes of test, indicates amount of smoke
vs. rate of build-up early in the test.
SON4 < 3, very low; 4-10, low; 10-S0, moderate;
50-100, high; > 200, very high.
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LOI is the abbreviation for Limiting Oxygen Index
which is defined as the minimum volume percent oxygen content
required in an oxygen/nitrogen mixture to maintain combustion
of a vertical, top-lighted test specimen. The value is
expressed in mathematical terms as follows :
LOI = ~ G2~7 x 100
~ 2 7 ~ ~ N2 ~
where ~02_7 is the volume of oxygen and ~N2 J is the volume
of nitrogen. The LOI is considered to be an accurate, reproduc-
ible determination of the flammability of materials. From a
practical standpoint, an LOI value of greater than 25 generally
means that the test specimen will be self-extinguishing. For
a more detailed discussiom of the LOI and method of determination,
C.P. Fenimore and F. R. Martin's article in COMBUSTION AND
FLAME 10 No. 2, page 135 (1966), should be consulted.
Limiting Oxygen Indices were obtained using the
Michigan Chemical LOI apparatus. An Aminco-NBS smoke density
chamber was used to obtain data on the rate of smoke generation
as well as intensity of visible smoke.
EXPERIMENTAL RESULTS
_ . _
Polyvinyl Chloride Resin 100 grams
.. ,.. ", ~ .. .. ...
~"FPC-965" a product of
The Firestone Tire &
Rubber Company)
Calcium Stearate 2 grams
Dilauryl Tin Mercaptide 3~75 grams
Smoke Suppressant 5 grams
(per-Table I)
3U A series of pla~ues was prepared in accordance with
the foregoing recipe, using different smoke suppressants in
the several runs as set forth in Table I. In each case, the
- 6 -
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..
ingredients in the recipe were compounded, in the order in
which they are listed, on a laboratory roll mill heated at
350F. (177C.). The compounded material was then pressed
into sheets 0.030" ~0.762 mm.) thick in a laboratory press,
' ~ the platens of which were heated at 345F. (174C). Specimens
from each sheet were submitted to NBS smoke density tests
as de~cribed above. Also, specimens were pressed out at
345F. (174C.) with dimensions 0.25" x 5" x 1.0" (6.35 mm.
x 127 mm. x 25.4 mm) and subjected to oxygen index measurements
as described above. Set ~orth herewith in Table I are the
results of these experiments.
TABLE I
: .
~- Smoke tColor of TEST RESULTS
Used Specimen LOI DmC t-9Dm tD16 SON~ No.
None light 45.1 357 2.67 0.42 272
(Control)yellow
Cobalt light 43.4 273 2.43 0.45 214 2
oxalate blue
Zinc light 48.9 294 2.47 0.40 256 3
Tartrateyellow
Ferric dark 40.9 283 2.93 0.38 223 4
Tartratebrown
Manganese light tan- 43.0 317 2.16 0.39 265 5
Tartrate yellow
Barium light 39.9 432 3.16 0.37 342 6
Tartrateyellow
TABLE II
SmokeitC 1 of TEST RESULTS
Used o or LOI mc ~ NRuOn.
None cream 49.0 284 3.20 0.48 206 7
Cobalt light 57.4 216 3.34 0.56 145 8
Oxalate blue
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.. . .
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TABLE I I ( su i te)
Inhibitor Color of TEST RESULTS
Used Speclmen LOI Dmc t.9Dm tD16 14 No
Zinc pale 59.4 206 2.81 0.56 142 9
Tartrate yellow
Ferric brown 52.1 177 3.~8 0.74 110 10
Tartrate
_
Runs Nos. 1-6 show the different eff~cts of the
various compounds added. Thus cobalt oxalate, zinc tartrate,
ferric tartrate, and manganese tartrate of the present invention
(Runs Nos. 2-5) decreased the smoke in relation to the control
tRun No. 1). Barium tartrate increased the smoke.
Runs Nos. 7-10 of Table II illustrate the synergistic
effect of the smoke suppressants of the present invention when
used in connection with aluminum hydroxide, which itself is
used as a flame retardant and smoke suppressant for a variety
of resins.
The compositions of Table II contained, in addition
- to the ingredients of the foregoing recipe and the indicated
smske inhibitors, 30 grams of hydrated aluminum oxide (aluminum
.,,,"~.. " ,.,,~,. ,
hydroxide, Al(OH3) ). Comparing the control Run No. 1 of Table
I with the other runs, in Run No. 7 of Table II, the aluminum
hydroxide alone cuts down thevisible smoke (DmC) by 20%, and
at the same time, increases LOI by 9% (decreased flammability).
In contrast, ferric tartrate alone (Run No. 4) cuts down visible
smoke (D~c) by 20%, but decreases LOI by 10% (increased
flammability). However, when both are used together (Run No.
10), the visible smoke (DmC) is reduced by 50% and the LOI
(inverse to flammability) is increased by 15%.
It is understood that the preceding examples are
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representative and that they can be varied within the context
of my total specification, as it would be understood by one
skilled in the art, to achieve substantially the same results.
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