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BACKGROUND OF THE INVENTION
This invention generally relates to the heat and light stabilization of
halogenated vinyl polymer compositions containing a smoke retardant. More
particularly, the present invention relates to the use of organotin
stabilizers to provide improved heat and light stabilization of rigid
halogenated vinyl polymer compositions containing molybdenum smoke
retardants involving the use of mixtures of organotin compounds. In this
regard, an important aspect of this invention concerns the use of mixtures
of certain organotin compounds in halogen containing vinyl resin
compositions which contain molybdenum smoke retardants to provide improved
resistance of such polymer compositions to degradation caused by heat and
light without incurring discoloration or staining of the polymer
compositions.
In the absence of a smoke retardant, the burning of halogen containing
vinyl polymers, particularly vinyl chloride polymers, causes the formation
of large amounts of smoke. This smoke is extremely hazardous and its
prevention is desirable to meet environmental standards and to prevent
human injury caused by smoke inhalation.
Consequently smoke retardants are commonly added to halogenated vinyl
polymers. Among often used smoke retardants are molybdenum compounds.
Numerous molybdenum compounds are shown in the literature to be useful as
smoke retardants in vinyl polymers.
U.S. Pat. No. 4,053,455 to Kroenke discloses the use of amine molybdates as
retardants for smoke formed by the burning of vinyl chloride and
vinylidene chloride polymers. U.S. Pat. No. 4,161,466, also to Kroenke,
identifies amine molybdates as retarding smoke formation during the
burning of polyamides, polychloroprene, polymonoolefins and other
polymers; U.S. Pat. No. 3,870,679 to Mitchell et. al. shows the use of
molybdenum hexacarbonyl as a smoke retardant for polyvinyl halides: and
dodecyl-1,2-diammonium dimolybdate is proposed by U.S. Pat. No. 4,234,473
to Kroenke as a smoke retardant additive for vinyl chloride and vinylidene
chloride polymer compositions.
Also disclosed as being useful as flame retardants for vinyl chloride and
vinylidene chloride polymers are ammelinium beta-octamobybdate (U.S. Pat.
No. 4,235,770 to Kroenke) octadecylammonium alpha-octamolybdate (U.S. Pat.
No. 4,240,955 to Kroenke); didecylammonium beta-octamolybdate (U.S. Pat.
No. 4,248,766 to Kroenke); dodecylammonium alpha-octamolybdate (U.S. Pat.
No. 4,248,767 to Kroenke); methyltricaprylammonium molybdates (U.S. Pat.
No. 4,406,837 to Kroenke): trioctylammonium molybdates (U.S. Pat. No.
4,406,838 to Kroenke): tri (tridecyl) ammonium molybdates (U.S. Pat. No.
4,406,840 to Kroenke) and tridodecyl ammonium molybdates (U.S. Pat. No.
4,425,279 to Kroenke).
Also certain molybdenum compounds described in the literature are suitable
smoke suppressants when used in combination with other compounds. U.S.
Pat. No. 3,845,001 to Mitchell proposes a copper oxide-molybdenum oxide
mixture; U.S. Pat. No. 3,821,151 to Mitchell suggests cast iron powder
admixed with a molybdenum oxide; U.S. Pat. No. 4,053,452 to Kroenke
proposes mixtures of melamine molybdate or substituted melamine molybdate
with cobalt carbonate, cobalt oxide, colbalt acetylacetonate and hydrates
thereof and U.S. Pat. No. 4,053,453 to McRowe et al. proposes combinations
of copper oxalate and amine molybdates.
Also the literature contains numerous disclosures of organotin stabilizers
for halogen containing vinyl polymer. H. Verify Smith in his 1959
compilation, The Development of The Organotin Stabilizers, discusses the
early activity in the production of tin stabilizers and their function
particularly in vinyl chloride homopolymers in preventing
dehydrochlorination, oxidation, chain scission and cross-linkage.
One of the most preferred class of halogenated vinyl polymer stabilizers
are the organotin mercapto carboxylic acid esters. These materials are
discussed in U.S. Pat. Nos. 2,641,596 to Leistner et al. and 2,648,650 to
Weinberg et al. Organotin sulfide-containing mercapto carboxylic acid
esters are described in U.S. Pat. Nos. 3,565,930 to Kauder et al.,
3,565,931 to Brecker and 3,817,915, also to Kauder et al. U.S. Pat. No.
3,769,263 to Mayo et al. describes stabilizer compositions containing
alkyltin sulfides in admixture with alkytin mercaptocarboxylic acid
esters. While U.S. Pat. No. 4,255,320 to Brecker et al. describes
stabilizer compositions containing alkyltin sulfides in admixture with
mono-and dialkyltin 2-acyloxyethylmercaptides.
Several types of sulfur-free organotin compounds have been suggested in
which a hydrocarbon group is directly attached to tin through a carbon
atom, and an oxygen-containing group, such as an ester group, is attached
to tin through oxygen. Organotin compounds of this type, such as
dibutyltin dilaurate, are excellent light stabilizers but are relatively
poor heat stabilizers at the high temperatures, such as 350.degree. F. to
400.degree. F., commonly used today to process polyvinyl chloride
compositions for siding, and window and door profiles.
A number of organotin stabilizers have been proposed that include a
mercapto carboxylic acid ester moiety as well as a carboxylate moiety in a
single compound or in a combination of two or more compounds. For example,
U.S. Pat. No. 2,914,506 to Mack et al. discloses compounds broadly defined
by the formula RR'Sn(SX)(Z) wherein R and R' may be the same or different
monovalent hydrocarbon radicals, SX may be, among other things, an ester
of a mercapto acid, and Z may be, among other things, a carboxylic acid
linked through the oxygen of the carboxylic acid group to the tin atom.
According to U.S. Pat. No. 3,562,305 to Hoch the incorporation into an
organotin mercapto acid ester of a small amount of organotin carboxylate
yields products having a substantially reduced tendency to decompose on
standing and are at least as effective as the untreated organotin mercapto
acid esters as stabilizers for vinyl halide resin compositions.
United Kingdom Pat. No. 1,251,864 to M&T International N.V., discloses
compositions for stabilizing halogen-containing resins against the
deleterious effects of heat which compositions can comprise an organotin
mercapto acid ester, such as dibutyltin bis (iso-octyl) mercaptoacetate,
and an organotin carboxylate such as butyltin tris (laurate).
Additionally, U.S. Pat. No. 4,698,368 to Muller, discloses a stabilizer
composition that can include an organotin mercaptopropionate and organotin
carboxylate.
These patents as well as others, such as U.S. Pat. No. 3,810,868 to
Weisfeld et al., provide sufficient information to those skill-in-the-art
to produce these organotin mercapto acid esters and organotin
carboxylates.
It is also well known to those skilled-in-the-art to incorporate additives
such as phenolic antioxidants in the organotin stabilizer compositions for
enhanced performance. The art is replete with example of such additives
such as those disclosed in U.S. Pat. Nos. 3,398,114 to Pollock, 3,424,717
to Gottlieb et al and 4,418,169 to Gibbons et al.
Many of these stabilizers and additives have achieved some measure of
success at stabilizing halogen-containing resins against the degradative
action of heat and light, but there are many applications in which a
greater degree of heat and light stability is desired than has heretofore
been readily attainable. Additionally, not all of these stabilizers are
homogeneous liquid at room temperatures. Such homogenity is a
characteristic often desired by end users for handling and processing
ease. Those skilled-in-the-art recognize that although certain organotin
stabilizers exhibit different heat and light stability property there is
no definitive predictive rule for providing a stabilizer composition that
has all the features of liquid homogeneity, initial color control,
processing heat stability, light stability, and overall processability.
Thus, an enormous array of organotin stabilizers have been shown and
patented in attempts to resolve various problems encountered during the
processing and use of the products encountered during the processing and
use of the products made from the halogenated vinyl polymers. Some offer
more effective protection from heat during the compounding of the vinyl
polymer, while others afford protection against light during the use of
the fabricated objects. Some prevent degradation during the early heating
of the vinyl polymer while other stabilizers are more effective at higher
temperatures.
Without the use of heat and light stabilizers, particularly organotin
stabilizers the use of halogenated vinyl polymers would not be practical
due to the degradation that would occur during processing and use of the
halogenated vinyl polymers. For this purpose there is now available a wide
variety of organotin stabilizers.
The selection of the proper organotin stabilizer is further complicated by
the presence of other additives in the halogenated vinyl polymer. Thus,
for example, the presence of a molybdenum containing smoke retardant in
the halogenated vinyl polymer can cause difficulty with the use of
organotin stabilizers due to the formation of molybdenum reaction
products. These undesired by-products can cause discoloration and staining
of the polymer.
Accordingly, it is an object of the present invention to provide a method
of stabilizing halogenated vinyl polymers containing smoke retardants.
Another object of the present invention is to provide stain-free
halogenated vinyl polymers compositions that are stabilized against
degradation by light and heat and also are capable of suppressing smoke
formed by the burning of vinyl polymers.
Still another object of the present invention is to provide stable
halogenated vinyl polymer compositions containing molybdenum smoke
retardants.
Still another object of the present invention is to provide polymer
compositions that are stain-free.
Other objects will become apparent from the ensuing description.
SUMMARY OF THE INVENTION
The present invention provides a stabilized halogenated vinyl polymer which
contains a suppressant for smoke formed during the burning of the polymer
composition. These halogenated vinyl polymer compositions comprise a
halogenated vinyl polymer, a molybdenum smoke retardant and an organotin
stabilizer having an overall an overall ratio of sulfur to tin of not more
than 1.7 gram atoms of sulphur per gram atom of tin. Also the present
invention provides a method for stabilizing halogenated vinyl polymer
compositions containing smoke retardants.
DETAILED DESCRIPTION OF THE INVENTION
Due to their need for stabilization the present invention is particularly
directed to chlorinated polyvinyl polymers The most important of these
polymers are vinyl chloride and vinylidene chloride polymers, including
homopolymers, copolymers and blends of homopolymers and/or copolymers. The
vinyl chloride and vinylidene chloride polymers may contain from 0 to
about 50 percent by weight of at least one other olefinically unsaturated
monomer. Suitable monomers include 1-olefins containing from 2 to 12
carbon atoms such as ethylene, propylene, 1-butene, isobutylene, 1-hexene,
4-methyl-l-pene, and the like; dienes containing from 4 to 10 carbon
atoms, including conjugated dienes such as butadiene, isoprene,
piperylene, and the like; ethylidene norbornene and dicyclopentadiene;
vinyl esters and allyl esters such as vinyl acetate, vinyl chloroacetate,
vinyl propionate; vinyl laurate, alkyl acetate, and the like; vinyl
aromatics such as styrene, a-methyl styrene, chlorostyrene, vinyl toluene,
vinyl naphthalene, and the like; vinyl and allyl ethers and ketones such
as vinyl methyl ether, allyl methyl ether, vinyl isobutyl ether, vinyl
n-butyl ether, vinyl chloroethyl ether, methylvinylketone, and the like;
vinyl nitriles such as acrylonitrile, methacrylonitrile, and the like;
cyanoalkyl acrylates such as a-cyanomethyl acrylate, the .alpha. and
.beta.-cyanopropyl acrylates, and the like olefinically unsaturated
carboxylic acids and esters thereof, including olefinically unsaturated
acids and esters thereof such as methyl acrylate, ethyl acrylate,
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