Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to fire and smoke retardant
vinyl chloride polymer compositions
Presently there is need for improved plastic products
which are safer in fire situations, even for vinyl chloride
polymers which generally are considered to be flame resistant,
While rigid vinyl chloride products have many structural
applications useful in buildings and transportation vehicles,
many uses are also made of plasticized vinyl chloride polymers
as in fabrics, upholstery, wall coverings and the like where
flame resistance and smoke formation could be a problem. Govern-
ment and safety regulations relating to such materials are now
in effect. Not only is flame resistance to be reduced in such
materials as vinyl chloride plastic products, but smoke
generated by vinyl chloride polymer products in fires also must
be reduced. The NBS smoke chamber is accepted as a measure of
smoke generated. A number of materials have been proposed and
used in vinyl chloride for this purpose, but very few have been
found to be completely satisfactory. Many are not compatible
or readily mixed with vinyl chloride polymers, many are colored
or form colored products in vinyl chloride polymer compositions
and many have adverse effects on the physical properties of
vinyl chloride polymers.
U.S. Patent 3,845,001, issued June 28, 1974, Lawrence
C, Mitchell, discloses the use of copper compounds alone, such
as Cu20 or mixtures of MoO3 and Cu20 that reduce smoke pro-
duction during combustion. This patent also states that "the
applicability of such oxides suggests the use of other com~
pounds" such as acetyl acetonylacetates and copper salts of
carboxylic acids such as the acetates and butyrates. While
cuprous oxide is satisfactory in reducing the smoke produced
during the combustion of polyvinyl chloride, it results in an
undesirable red color in the compounds. This coloration
problem is particularly
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acute with the tin sulfur stabilizers used widely throughout
the industry. The copper carboxylates suggested are generally
unsatisfactory from other viewpoints than smoke reduction,
for example, cupric formate during milling into polyvinyl
ch:Loride cause~ discoloration and black spots. Copper
acetylacetonate causes discoloration during processing, which
discoloration continues to develop undesirably on heating.
SUMMARY OF THE INVENTION
Copper oxalate is a very effective fire and smoke
retardant in vinyl chloride polymer composition. The copper
oxalate is compatible and easily mixed with vinyl chloride
polymers in both rigid and flexible forms, does not form
objectionable color products in vinyl chloride polymers and
has no adverse effects on the physical properties or pro-
cessing of compounds containing it.
DETAILED DESCRIPTION
The copper oxalate is normally used in powder form
in amounts greater than about 0.01 part per 100 weight parts
of vinyl chloride polymer, more preferably from about 0.1
to about 20 weight parts per 100 weight parts of vinyl
chloride polymer. From about 1 to about 10 weight parts is
a very practical range providing a good balance of desirable
properties in the compounds. The copper oxalate is readily
mixed with the vinyl chloride polymers in powder form as is
any other powder ingredient mixed with vinyl chloride polymers
as is well known to those skilled in the art.
Cupric oxalate is readily prepared by mixing
stoichiometric amounts of hot concentrated solutions of
cupric sulfate and oxalic acid. The precipitate is filtered
and may be dried in vacuum or at 100C. and atmospheric
pressure.
The vinyl chloride polymers include those vinyl
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108598~7
chloride polymers that are homopolymers, that is, polyvinyl
chloride, as well as those copolymers containing vinyl
chloride and up to about 50%, more usually about 30% by weight
of at least one other vinylidene monomer containing at least
one terminal CH2=C~ group such as vinylidene chloride, alkyl
acrylates and methacrylates wherein the alkyl group contains
l to lO carbon atoms, acrylic acids, amides and nitriles
thereof such as acrylic acid, ethacrylic acid, acrylamides,
N-methylol methacrylamide, acrylonitrile, methacrylonitrile
and the like, ~-olefins containing 2 to 6 carbon atoms such
as ethylene and propylene, vinyl esters such as vinyl acetate,
vinyl butyrate, vinyl benzoate, vinyl aromatics such as
styrene, chlorostyrene, ethyl styrene, vinyl naphthalene,
vinyl alkyl ethers, vinyl ketones, chlorinated vinyl chloride
polymers; and blends of vinyl chloride polymers with other
polymers, both plastics and elastomers, for example, with
ABS resins, with 10 to 40~ of copolymers of styrene and
acrylonitrile or styrene and methyl methacrylate wherein
` styrene is the major component, elastomers containing about
equal amounts of styrene and acrylonitrile with butadiene,
polyurethanes, nitrile elastomers, both liquid and solid con-
: taining from about 15 to 40% acrylonitrile with the remainder
butadiene, polyolefins and the like. These vinyl chloride
polymers normally are high molecular weight polymers having
a specific viscosity greater than 0.4 measured as a 0.4% solu-
: tion in nitrobenzene.
The vinyl chloride polymers will be mixed withstandard compounding ingredients known to those skilled in
the art, plasticizers, lubricants, stabilizers, fillers,
colorants, processing aids, other flame and smoke retardants,
and the like. While these compounds are most effective in
vinyl chloride polymers substantially free of plasticizers
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subject to burning, they provide improved compositions as to
flame propagation and smoke when plasticizers are present,
In the following Examples, there is reported the
D ~g, maximum optical density/gram of sample observed with a
vertical light path in the Nation Bureau of Smoke Chamber (NBS)
and ~/0 smoke reduction, Dm iq maximum optical density according
to Gross, The NBS smoke chamber and its use are described by
Gros~ et al in fire test methods ASTM STP 422, 1967, Pages 166-
206. The NBS Dm/g. smoke numbers reported are in the flaming
mode.
EXAMPLE I
A vinyl chloride polymer compound was prepared by mix-
ing 100 weight parts of polyvinyl chloride having a specific
viscosity of 0.38-0.42 in nitrobenzene at 30C, with 2 weight
parts of polyethylene having a specific gravity of 0.924 g/cc
and melt index of 5 g/10 minuteQ, and the amounts of copper oxa-
late shown in the data table below as Phr of polyvinyl chloride,
The ingredients were all dry blended, milled at 325F,, press
molded at 350F. for 3 minutes to 25 mil sheets, 3X3 inch
samples were tested in the flaming mode in the NBS smoke
chamber.
Parts CuC 0 .1/2 H 0 D ~ g % Smoke
2 4 2 Reductlon
0 65
0.5 37.8 42
2.0 16.2 75
5.0 12.0 82
_XAMPLE II
In another composition, to demonstrate the unex-
pected advantages of copper oxalate in polyvinyl chloride
compounds, compounds containing 100 weight parts of the poly-
vinyl chloride of Example I, 2 weight parts of dibutyltin-
bis isooctyldithioglycolate, 4 weight parts of methyl
methacrylate processing aid having a Brookfield viscosity in
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10% toluene solution of 200-1000 cps.,3 weight parts of
titanium dioxide, 1 weight part of calcium stearate, and
1 weight part of ethylenebisstearamide were mixed with from
0.5 to 10 weight parts of copper oxalate by milling and
molding as described above to produce 6" X 6" X 0.025" test
sheets. There was no discoloration observed up to about the
5 weight parts level, and at 5 to 10 weight parts there was
only a pale bluish-green cast to the compounds. In contrast,
cupric hexanoate and cupric acetate gave very strong dark
discoloration at levels as low as 1 weight part. Cupric
stearate could not be incorporated into the compound at levels
above 2.5 weight parts because of excessive lubrication and
even at 1 weight part level the compound turned a dark tan
as compared to no discoloration with 2.5 weight parts of
copper oxalate. In NBS smoke chamber tests the cupric oxalate
was more effective on an equal weight basis than many of these
carboxylates as is shown in the data below and did not have
the disadvantage of discoloration. Further, other processing
problems are introduced when these copper carboxylates are
used in addition to loss of physical properties of the re-
sulting polyvinyl chloride compound.
Flaming Mode NBS Smoke Chamber Data
Cupric Oxalate No. of Mea- ~ Smoke
phr Dm/g Dm surements Reduction
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25-0- control 55.5 290 8 -0-
; 0.5 38.3 191 6 31.0
1.0 33.4 184 6 39.8
2.5 29.3 145 6 47.2
5.0 27.6 152 6 50.3
3010.0 19.9 117 6 64.1
`~ 1.0 cupric stearate 42.1 6 24.1
1.0 cupric acetate 42.3 6 23.8
2.5 34.7 6 37.5
5.0 30.2 6 45.6
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