SMOKE SUPPRESSED FLAME RETARDANT THERMOPLASTIC RESIN COMPOSITIONS

MELANGES DE RESINES THERMOPLASTIQUES RETARDANT LA PROPAGATION DE LA FLAMME ET REDUISANT LE DEGAGEMENT DE FUMEE

English Abstract

GL353.APP
ABSTRACT
Smoke suppressed flame retardant thermoplastic resin
compositions comprise bicyclic phosphate compound(s), flame
retardant(s) and polyvinyl halide, polyolefin or polystyrene
resins. These compositions exhibit a reduced tendency to smoke
under conditions of burning.

Claims

GL353.APP
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS°
1. A smoke suppressed thermoplastic resin composition
comprising a polyvinyl halide, polyolefin or polystyrene resin
and an effective amount of a mixture comprising;
at least one flame retardant agent; and
at least one bicyclic phosphate compound of the
formula:
<IMG>
where X is OH, OR', or OC(O)R'; R is H or a saturated or
unsaturated straight-chain or branched-chain C1-C17 alkyl; and R'
is a saturated or unsaturated straight-chain or branched-chain
C1-C17 alkyl.
2. A composition, as claimed in claim 1, wherein the flame
retardant agent is a member selected from the group consisting of
halogenated compounds, metal hydrates, metal borates, antimony
compounds, phosphorous compounds, and mixtures thereof.
3. A composition, as claimed in claim 1, wherein the
flame retardant agent is a member selected from the group
consisting of di-(2-ethylhexyl)tetrabromophthalate, alumina
trihydrate, magnesium hydroxide, antimony trioxide, zinc borate
and alkarylphosphates.
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GL353.APP
4. A composition, as claimed in claim 1, wherein the
bicyclic phosphate compound is 2,6,7-trioxa-phosphobicyclo
[2.2.2]-octane-4-methanol-1-oxide; or 2,6,7-trioxa-1-
phosphobicyclo[2.2.2]-octane-4-methanol, acetate, 1-oxide.
5. A composition, as claimed in claim 1, wherein the resin
is a member selected from the group consisting of polyvinyl
chloride, polystyrene and polyethylene, polypropylene and
polybutylene homo- and copolymers.
6. A composition, as claimed in claim 4, wherein the
member is polyvinyl chloride.
7. A composition, as claimed in claim 1, wherein the
weight ratio of bicyclic phosphate compound to flame retardant
agent lies in the range of about 1:25 to 20:1.
8. A composition, as claimed in claim 1, wherein the
mixture of bicyclic phosphate compound and flame retardant agent
is provided in the resin composition at a level lying in the
range of about 2 - 50 percent by weight of the overall
composition.
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GL353.APP
9. A method for suppressing the tendency of polyvinyl
halide, polyolefin or polystyrene resin compositions to smoke
under conditions of burning comprising the step of incorporating
therein an effective amount of a mixture comprising:
a flame retardant agent; and
a bicyclic phosphate compound of the formula:
<IMG>
where X is OH, OR', or OC(O)R'; R is H or a saturated or
unsaturated straight-chain or branched-chain C1-C17 alkyl; and R'
is a saturated or unsaturated straight-chain or branched-chain
C1-C17 alkyl.
10. A method, as claimed in claim 9, wherein the flame
retardant agent is a member selected from the group consisting of
halogenated compounds, metal hydrates, metal borates, antimony
compounds, phosphorous compounds, and mixtures thereof.
11. A method, as claimed in claim 9, wherein the flame
retardant agent is a member selected from the group consisting of
di-(2-ethylhexyl)tetrabromophthalate, alumina trihydrate,
magnesium hydroxide, antimony trioxide, zinc borate and
alkarylphosphates.
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GL353.APP
12. A method, as claimed in claim 9, wherein the bicyclic
phosphate compound is 2,6,7-trioxa-phosphobicyclo
[2.2.2]-octane-4-methanol-1-oxide; or 2,6,7-trioxa-1-
phosphobicylo[2.2.2]-octane-4-methanol, acetate, 1-oxide.
13. A method, as claimed in claim 9, wherein the weight
ratio of bicyclic phosphate compound to flame retardant agent
lies in the range of about 1:25 to 20:1.
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Description

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GL353.APP
CROSS-REFERENCE
This application is a continuation-in part of co-pending
application Serial No. 289,973, fil2d December 22, 19~8.
BACKGROUND OF THE INVENTION
Field of the Invention. This invention relates to flame
retardant thermoplastic resin compositions that exhibit a reduced
tendency to generate smoke under burning conditions. More
particularly, this invention relates to thermoplastic
compositions such as polyvinyl chloride ("PVC"), polystyrene and
polyolefins, comprising bicyclic phosphate compound(s); and flame
retardant agent(s). The compositions produced in accordance with
this invention exhibit a reduced tendency to smoke under burning
conditions.
DescriPtion of the Prior Art. It is known in the art that
the flammability of thermoplastics, such as polystyrene,
polyolefins, and polyvinyl halides, can be reduced by
incorporation of a flame retardant agent. Typical flame
retardant agents include reactive or additive haloganated organic
compounds, inorganic fillers, and special formulations ~ased on
phosphorous and ammonium salts.
Although efficient in suppressing the rate of combustion in
a resin system, most flame retardants tend to affect adversely
one or more key properties of the resin. For example, many flame
retardant additives are ineffective at producing low smoke
("smoke suppressed") formulations.
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GL353.APP
Recent public awareness about risk and hazard assessment
during fire situatiens, and technical limitations of conventional
flame retardant additives warrant a need for improved flame
retardant thermoplastic compositions. In particular, a need
exists for a thermoplastic composition that passes flammability
standards with low smoke and combustion by-product formation, and
does not detract from overall polymer performance.
Many prior art references describe the use of a variety of
smoke additives in polystyrene and polyolefins. Modern Pla~tics
EncvcloDedia, Vol. 63, No. lOA, McGraw-Hill, Inc., pp. 17~-180
(1986). However, the selection of a suitable smoke suppressant
for thermoplastic resins is not predictable. Selection is
particularly difficult when flame retardants are employed,
exacerbated by the complex interaction between the polymer and
the flame retardant agent.
Hechenbleikner, et al. describe in U.S. Patent No. 3,293,327
the production of bicyclic phosphites, phosphonates,
thiophosphates, and selenophosphates. These compositions are
said to be stabilizers for vinyl halide resins. They are alleged
to be useful as heat stabilizers for vinyl chloride resin, and as
antioxidants for fats and oils. The Hechenbleikner patent does
not specify the use of bicyclic phosphates to achieve low smoke
thermoplastic resin compositions, nor does it disclose that
cyclic phosphates of the present invention could be used with
flame retardant agents to produce smoke suppressed flame
retardant thermoplastic compositions.
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GL353.APP
British Patent No. 999,793 describes a process for producing
organic phosphates by subjecting organic phosphites to reaction
with peracetic acid. This patent shows a method for producing
the most preferred bicyclic phosphate of the present invention,
2,6,7-trioxa-1-phosphobicyclol2.2.2]-octane-4- methanol-l-oxide
and teaches the use of acetal ring-containing phosphates as
plasticizers or functional fluids. The British patent, however,
does not disclose the present invention. It does not mention
bicyclic phosphates as being useful for flame retardant
thermoplastic resins, nor that the most preferred bicyclic
phosphate of the present invention can be used with flame
retardant additives to yield improved smoke suppressed
thermoplastic compositions.
Hills, et al. describe in U.S. Patent No. 3,873,496 a flame
retardant polyester composition which contains 5 to 25 percent of
a hydroxymethyl bicyclic phosphate compound as a flame retardant
additive. Hills did not observe the ability for bicyclic phos-
phates to act as smoke suppressors for thermoplastic resin
compositions which employ halogenated compounds as the primary
flame retardant additive.
Halpern, et al. describe in U.5. Patent No. 4,341,694 a
composition comprising 2,6,7-trioxa-1-phosphobicyclo~2.2.2~-
octane-4-methanol-1-oxide and a nitrogen-containing co-additive,
which are intumescent and are adaptable to flame retard
polyolefins, polyvinylaromatic resins, polycarbonates, PVC and
blends thereof. Halpern did not observe any smoXe suppression o
the present invention.
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GL353.APP
Parr, et al. describe in U.S. Patent No. 4,801,625 a flame
resist~nt composition having (1) an organic polymeric substance
in intimate contact with ~2) a bicyclic phosphorous compound, and
(3) a gas producing compound. Parr is silent on the use of
bicyclic compounds to attain smoke suppressed flame retardation
thermoplastic compositions.
Accordingly, a primary object of this invention is to
provide smoke suppressed flame retardant thermoplastic
compositions.
A related object is to provide flame retardant thermoplastic
polyvinyl chloride compositions with a reduced tendency to smoke
under burning conditions.
A further object is to provide polyvinyl chloride resin
compositions incorporating bicyclic phosphate compound and
flame retardants.
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GL353.APP
SUMMARY OF THE INVENTION
The foregoing and other objects, advantages and features of
the present invention may be achievable with smoke suppressed
thermoplastic polyvinyl halide, polyolefin or polystyrene resin
compositions incorporating an effective amount of an additive
mixture comprising a flame retardant agent and a bicyclic
phosphate compound of the following Formula (I):
O R
(I) O=P\ ~ CH
where X is OH, OR', or OC(O~R'; R is H or a saturated or
unsaturated straight-chain or branched-chain C1-C17 alkyl; and R'
is a saturated or unsaturated straight-chain or branched-chain
Cl-C17 alkyl. Compositions in accordance with this invention
exhibit a reduced tendency to smoke under burning conditions.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
This invention relates to smoke suppre6sed flame retardant
thermoplastic polyvinyl halide, polyolefin and polystyrene
compositions. In particular, the invention relates to
thermoplastic polyvinyl chloride, polyolefin and polystyrene
resin compositions which are flame retardant and which exhibit a
reduced tendency to smoke when burning. Compositions in
accordance with this invention incorporate an additive mixture
comprising one or more bicyclic phosphate compounds and one or
more flame retardant agents.
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~L353.APP
Preferred bicyclic phosphates in accordance with this
invention are compounds of Formula (I) where X is OH or OC(O)R'.
The most preferred bicyclic compounds are 2,6,7-trioxa-
phosphobicyclo[2.2.2]-octane-4-methanol-1-oxide (Compound BCP,
that is, Formula [I] when R is H and X is OH), and
2,6,7-trioxa-1-phosphobicyclo[2.2.2]-octane-4-methanol, acetate,
l-oxide (Compound BCP-A, that is, when R is H and X is OC(O)CH3).
The flame retardant agent employed in accordance with the
present invention may be any common flame retardant age~t which
can be used to reduce the flammability of thermopla6tic resins,
such as halogenated compounds containing bromine and/or chlorine,
or inorganic materials, such as metal hydrates, metal borates,
antimony-containing compounds, or phosphorous-containing
compounds.
Preferred halogen-containing compounds are
di-(2-ethylhexyl)tetrabromophthalate, hexabromocyclododecane,
tetrabromobisphenol h, tetrabromobisphenol A
bis-(dibromopropylether)~ dibromo(dibromoethyl)cyclohexane,
tetrabromocyclooctane, bis-(dibromonorbornane
dicarboximido)ethane, bis-(tetrabromophthalimido)ethane,
Diels-Alder adduct of chlorinated cyclopentadiene and an
unsaturated cycloaliphatic compound, bis-(tribromophenoxyethyl)
-tetrabromobisphenol A ether, pentabromodiphenyl ether,
octabromodiphenyl ether, decabromodiphenyl ether,
bis-(tribromophenoxy)ethane, bis-(pentabromophenoxy)ethane,
chloropentabromocyclohexane, (tribromophenoxy)-
(dibromononylphenoxy)ethane, pentabromoethylbenzene,
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GL353.APP
pentabromododecylbenzene, carbonate oligomers of
tetrabromobisphenol A, poly(bromostyrene), and brominated
polystyrene, poly(bromophenylene) ether, and mixtures thereof.
Particularly preferred is di-(2-ethylhexyl)tetrabromophthalate.
Substantially any suitable metal hydrates and oxides may be
employed as flame retardant agents, including hydrates and oxides
of aluminum, iron, inc, magnesium, tin, molybdenum and antimony.
Alumina trih ~ rate, magnesium hydroxide, and antimony trioxide
are the preferred compounds in this class.
Suitable metal boron-containing flame retardant compounds
include zinc, barium, calcium, magnesium, cadmium and mercury.
Zinc borate is the preferred compound in this class.
Substantially any suitable phosphorus-containing compound
may be used as a flame retardant agent, including ammonium
polyphosphate, arylphosphates, alkarylphosphates and
alXylphosphates. Particularly preferred are phenyl
isopropylphenyl phosphate and isodecyldiphenyl phosphate
commercially available from FMC Corporation under the trademarks
Kronit.ex lOO and Santicizer 148.
The foregoing flame retardant compounds are added to thermo-
plastic resins at effective levels such that the resultant resin
composition may be rendered flame retardant.
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GL353.APP
Thermoplastic resins which may be treated in accordance with
the invention include thermoplastics such as polyvinyl halides,
polystyrene, and homopolymers and copolymers of polypropylene,
polyethylene, and polybutylene. Polyvinyl chloride is most
preferred in accordance with this invention.
The scope of the present invention also includes the
incorporation of other additives in the composition so far as to
produce a particular end result. Such additives incll~de, without
limitation, blowing agents, heat stabilizers, light stabilizers,
plasticizers, pi~ments, preservatives, ultraviolet light stabi-
lizers, fillers, antioxidants, antistatic agents and other
materials well known to those skilled in the art, for example, as
described in Modern Plastics EncYclopedia, Vol. 63, No. lOA,
McGraw-Hill, Inc. (1986).
The bicyclic phosphates of the present invention may be used
alone or as mixtures of any such compounds. When mixtures of
bicyclic phosphates are employed, substantially any combinations
of amounts and proportions of the individual compounds may be
used. The use of Compound BCP and Compound BCP A is especially
preferred in accordance with this invention.
The bicyclic phosphate may be employed at substantially any
level because even very low levels are believed to assist in
smoke ~uppression. Preferably it is present at a level of at
least 2 percent and preferably about 3 percent up to about 20
percent by weight of the composition.
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GL353.APP
The flame retardant agents of the present invention may be
used alone or as mixtures of any such compounds. When mixtures
of flame agents are employed, substantially any combinations of
amounts and proportions of the individual compounds may be used.
The use of di-(2-ethylhexyl)- tetrabromophthalate, alumina
trihydrate, magnesium hydroxide, zinc borate, antimony trioxide,
and alkylaryl phosphates are especially preferred in accordance
with this invention.
Desirably, flame retardants are employed at a level of about
2 to 50 percent by weight of the composition, preferably about 3
to 20 percent, depending on the specific flame retardant and
thermoplastic resin employed. Operative and preferred ranges for
various flame retardants in accordance with this invention are
given in the Table I.
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TABLE I
:: OPERATING RANGES
-
` MATERIAL OPERATIVE RANGE PREFERRED RANGE
:. BrFr 2-50 3-20
~" AAP 2-50 3-20
ATH 2-50 5-20
;~~ MgOH 2-50 5-10
;~ ZnBor 2-50 5-10
SbOx 1-15 5-10
BrFr - di-(2-ethylhexyl)tetrabromophthalides brominated flame
retardant
AAP - alkylarylphosphate (Kronitex 100 - FMC Corp.)
ATH - alumina trihydrate
. MgOH - magnesium hydroxide
2nBor - zinc borate
- SbOx - antimony oxide
Desirably, the bicyclic phosphate compound and flame
; retardant are provided as a mixture useful as an additive which
may be added to polystyrene or polyolefin resin compositions.
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The additive mixture utilizes bicyclic phosphate and flame
retardant in a weight ratio lying in the range of about 1:25 to
20:1, most preferably, about 3:20 to 20:3.
The additive mixture is incorporated into the polymer
composition at an effective level such thzt the resulting resin
composition i8 rendered flame retardant. In general, the
additive mixture is provided in the flame retardant at a level of
about 2 - 50 percent by weight of the resin composition,
preferably about 3 - 30 percent by weight.
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Practice of the present invention is illustrated by the
following examples, which are given to illustrate the invention
and should not be construed as limiting its scope.
EXAMPLES
Preparation of Polwinylchloride Resin Svstems. A general
purpos~ polyvinylchloride ("PVC") resin was u~ed in the study.
PVC resin, powdered additive~ and flame retardant were blended in
a mixing bowl and warmed to 90C. Liguid plasticizer was ~dded,
~ and the admixture was compounded on a two-roll mill at 160C.
`; The compounded PVC material was compression molded at 180C.
Table II shows examples of the use of Compound BCP in flexible
PVC formulations. The general formulation used is as follows:
. Material /~by weiqht
. PVC Resin varied
Compound BCP varied (see Table)
Flame Retardant varied (see Table)
Dioctylphthalate Plasticizer varied (see below~
Epoxidized Soya Plasticizer 5
Stabilizer 3
The amount of dioctyl phthalate ("DOP") plastici~er wa adjusted
to give compositlonR with comparable physical properties (i.e.,
approximately 90 Shore A hardness) and flammability
(approximately 30 OI) performance.
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GL353.APP
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Flammabilit~ Test Procedures. The following flammability
tests were used throughout the study:
- Test Method Description
ASTM D-2863 Limiting Measurement of the minimum oxygen
Oxygen Index necessary to ~ustain burning of a
vertically supported sample for
- thrse minutes. High values indicate
improved re~istance to burning.
NBS Smoke Chamber Smoke density determinations
ASTM -662 under smolderinq conditions. Low
values indicate low smoke evolution.
~' A series of experimental and comparative studies were
performed using the foregoing techniques. The data are given in
Table II.
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GL353 . APP
i
TABLE II
` FLAMMABILITY AND PHYSICAL PROPERTY PERFORMANCE
FLEXIBLE POLYVINYLCHLORIDE COMPOSITIONS
~` E.YAMPLE AMOUNT OF FLAME RETARDANT NBS SMOKE OXYGEN HARDNESS
NUMBER BCP TYPE AMOUNT SMOLDERING INDEX SHORE A
wt % wt % ASTM ~662 ASTM ASTM
-. D-2863
CONTROL5.0 ----- 0.0 170 30 90
- 1 5.0 BrFr10.0 165 30 90
COMP 2 0.0 BrFr10.0 210 30 90
2 5.0 AAP 15.0 160 30 90
COMP 3 0.O AAP 15.0 200 30 90
3 5.0 ATH 15.0 145 30 90
COMP 4 0.0 ATH 15.0 160 30 gO
4 5.0 MgOH15.0 140 30 90
- COMP 5 0.0 MgOHlS.O 165 30 90
5.0 ZnBor15.0 130 30 90
COMP 6 0.0 ZnBor15.0 155 30 90
.
BCP - Preferxed bicyclic phosphate
BrFr - di-(2-ethylhexyl)tetrabromophthalates
AAP - alkylarylphosphate (Kronitex 100 - FMC Corp.)
ATH - alumina trihydrate
MgOH - magnesium hydroxide
ZnBor - zinc borate
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.
These data demonstrate the patentability of the subject
invention as follows. The Control Example shows the effect of
5.0% BCP alone on the smoke performance of a 30 OI flexible PVC
composition. Comparative Examples 2-6 show the effect of various
flame retardants on smoke performance when Compound BCP is not
present.
Example 1 illustrates the invention when the flame retardant
is a bromine-containing flame retardant. Example 2 illustrates
the invention when the flame retardant is phosphate-containing
flame retardant (an alkarylphosphate). Example 3-5 illustrate
the invention when the flame retardant i5 an inorganic flame
retardant.
In the case of each invention composition, compositions
comprising a bicyclic phosphate (Compound BCP) and a flame
retardant had lower smoke than the Control ~i.e., a system
without any additional flame retardant a~ent) or the
corresponding Comparative Examples 2-6 ~i.e., a system without
bicyclic phosphate).
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